ingenious mechanisms, vol. 4

INGENIOUS MECHANISMS;

FOR DESIGNERS' AN'-O INVENTORSVOLUME IV

Mechanisms and Mechanical Movements Selectedfrom Automatic Machines and Various Other Forms,of Mechanical Apparatus as Outstanding Examplesof Ingenious Design Embodying Ideas or PrinciplesApplicable in Designing Machines or Devices Re-quiring Automatic Features or Mechanical Control

Edited byJOHN A. NEWELL

and

HOLBROOK l. HORTON

INDUSTRIAL PRESS INC.200 MADISON AVENUE, NEW YORK 10016

Ii______________________________IIIIIIiiII ~~=.=.=.. _~.=,.."~..~~~

Industrial Press Inc.200 Madison Avenue

New York, New York 10016-4078

INGENIOUS MECHANISMSFOR DESIGNERS AND INVENTORS-VOLUME IV

Copyright 1967 by Industrial Press Inc., New York, N.Y. Printed in theUnited States of America. All rights reserved. This book or parts thereof may

not be reproduced in any form without permission of the publishers.

20 19 18 17 16

I

II

FOURTH VOLUME OF INGENIOUS MECHANISMS

A considerable period of time has elapsed since the pti,blica-tion of the third volume of Ingenious Mechanisms. During thisperiod we have received many inquiries about the possible publi-cation of a fourth volume in the series, indicating a continuinginterest in this area.

This fourth volume follows the same pattern as its predeces-sors. The mechanisms described have been developed for appli-cation in a wide variety of fields. Rather than classify them byapplication, however, they have been grouped by type of me-chanical movement. Thus, the reader is quickly guided to thosemechanisms which may provide a possible solution to his prob-lem.

Furthermore, the grouping is closely similar to, if not exactlythe same as, that in the previous volumes so that the entire setmaybe used as an integrated reference library on the subject ofmechanisms.

v

L

CONTENTS

CHAPTER PAGE

Preface __ -__ __ __ ________ ____ __ __ ___ ___ v

1. Cam Applications and Special Cam Designs 1

2. Intermittent Motions from Gears and Cams____________________ 27

3. Iniermittent Motions from Ratchet and Geneva Mech-anisms __ ~ _____ __ _________ ___ __ ___ _ ___ 47

4. Overload, Tripping, and Stop Mechanisms ~ 94

5. Locking, Clamping, and Locating Devices 119

6. Reversing Mechanisms of Special Design 145

7. Reciprocating Motions Derived from Cams, Gears, andLevers __ __ _____ __ ________ ____ _____ ___ ___ ___ __ __ _ __ 166

8. Crank Actuated Reciprocating Mechanisms . 199

9. Variable Stroke Reciprocating Mechanisms :_____ 215

10. Mechanisms Which Provide Oscillating Motion 245

11. Mechanisms Providing Combined Rotary and Linear Mo-tions _____ _ _____ ___ _________ __ 265

12. Speed Changing Mechanisms 279

13. Speed Regulating Mechanisms 299

14. Feed Regulating, Shifting, and Stopping Mechanisms 313

15. Automatic Work Feeding and Transfer Mechanisms 327

16. Feeding and Ejecting Mechanisms for Power Presses 356

17. Hoppers and Hopper Selector Mechanisms for AutomaticMachines _ __ 371

18. Varying_Continuously Rotating Output 401:

19. Clutch and Disconnecting Devices .____ 420

20. Miscellaneous Mechanisms . .______ 435

Index ---__ __ __ ___ ____ __ __ _ 473:

vii

CHAPTER 1

(am Applications and Special (am Designs

In the design of mechanisms to obtain irregular movements ofvarious kinds, cams are frequently employed. Those which aredescribed or illustrated in connection with the mechanisms cov-ered by this chapter are notable for some ingenious arrangementor design. Other applications of cams and cam-operated mecha-nisms will be found in Chapter 1, Volume I; Chapter 1, VolumeII; and Chapter I, Volume III of "Ingenious Mechanisms for De-signers and Inventors."

Cam Produces Motion onAlternate Revolutions

A conventional plate-cam was used on a machine producing awire product to operate a forming press. The press had to beactuated once during each revolution of the driving shaft. A sub-sequent product change necessitated an alteration in the operat-ing cycle of the cam - it was now required to operate the presstwice during one revolution, then to remain at rest during thenext revolution. Figures 1 and 2 show the design and operationof a cam which produced the desired movements with no altera-tions being required on the machine.

Cam body A, Fig. 1, is in the shape of a disc having an integralhub on its front face. The cam is keyed to shaft B and rotates inthe direction indicated by the arrow. Two studs C pass throughthe disc and are free to rotate. Welded to them are curved bars Dwhich act as cam lobes. Compression springs E apply sufficientfrictional resistance to the studs to prevent movement by cen-trifugal force. Lever F, which operates the forming press, carries

1

2 CAM APPLICATIONS AND SPECIAL CAM DESIGNS CAM APPLICATIONS AND SPECIAL CAM DESIGNS 3

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FIG. 2. During the active revolution, follower G rises along the cam-bar D,view W, then forces it to pivot for the downward movement, view X.On the next trip around, the upended cam-bar passes over the follower

and is returned to its original position, views Y and Z.

movements of lever F, followed by a rest period of 540 degrees.There may appear to be an undesirable feature in the design

of this cam in that there would be a rapid drop of roller G on thefalling side of bar D (view X, Fig. 2). This, however, does notoccur, due to the fact that the outer surface of the cam-bar is ona rising angle (view W). Thus, downward movement takes placealmost immediately after the center of stud C passes the centerof roller G.

Outer surfaces of the cam-bars may be contoured to produce

1

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follower-roller G and is held against the cam by a spring (notshown).

Operation of the cam is illustrated in Fig. 2. At W, cam-bar Dis in the same position as in Fig. 1, but the entire cam has ro-tated 90 degrees. Stud C and roller G are now on the samecenter line, bar D having caused the roller to rise and operate thepress through lever F. The cam continues to rotate, as at X, andspring tension on lever F overcomes the frictional resistance ofstud C, forcing bar D into the position shown. When the otherlobe of the cam comes into position this action is repeated, so thattwo movements'of the lever are produced, 180 degrees apart, inone revolution of shaft B.

No movement of lever F is produced during the next revolu-tion of the shaft. This is because the leading ends of the cam-barshave been lifted from the hub of disc A and now pass over rollerG, as shown at Y. As (the cam rotates further, and the rollerpasses the center line of stud C, cam-bar D is forced to pivot asat Z - thus being returned to its original position (Fig. 1). Inthis manner, each two-revolution cycle of the cam produces two

FIG. 1. Cam body A carries two moving cam-bars D. This design impartstwo movements to lever F during one revolution, followed by one revolu-

tion at rest.


*'

almost any conventional rise and fall pattern. Their inner sur-faces must be so dimensioned that there will be sufficient clear-ance for the passage of roller G, and that full closing of the lead-ing ends will be assured when the roller exits from beneath them.

Four-Lobed Cam TransmitsVariable Motion to Follower

On a machine for fabricating a formed wire part, a revision inthe product design required a change in a cam which operated apress. Previously, there had been a uniform oscillating motionof the follower with each revolution of the operating shaft. Forthe new design, it became necessary to transmit a motion of vary-ing magnitude and varying timing for each of four revolutions ofthe shaft, without any major changes in the machine. The draw-ing shows the cam that was made to meet the requirements.

In Fig. 3, operating shaft A, rotating in the direction indicated,carries arm B, which is keyed to it. On the arm is pawl C, which

F

D

A

F

8

FIG. 3. As long as pawl C remains in contact with angle-plate G, camD rotates. When the pawl leaves the angle-plate, the cam stops.

I'

III

IrI!rI;b

can swing on its stud. Four-Iob~d cam D is free on the extendedhub of the arm, and is ~etained by collar E. Projecting from theface of the cam are fout pins F, equally spaced around the centerof rotation. Angle-plate G is machined to a true arc of a circle onits upper edge, and is attached to a stationary part of the ma-chine. '

The shaft, arm, and pawl rotate as a unit. No motion is trans-mitted to the cam until the pawl contacts the upper edge of theangle plate, when the pawl is brought into position to engage oneof the pins. The drawing shows the position of the componentsat about the midpoint of the cam movement.

Having engaged one of the pins, the pawl carries the cam withit, until it no longer contacts the angle-plate. At this point, dueto the angularity of the contact. surface of the pawl, it disengagesautomatically, and the cam stops. (The position of the pawl atthe time of disengagement is shown in broken lines on the left sideof the drawing.) Stop H limits the swing of the pawl so that itwill be in position to engage the next pin upon rotating to theright side of the angle-plate. Thus, the cam rotates 90 degreesfor each revolution of the shaft, and the four lobes of the camare brought consecutively into position to actuate cam followerJ as required. .

Intermittent Rotary Motion from aUniform Reciprocating Drive

Two devices on a machine had to be rotated intermittently,with a rest period at each of eight stations in each cycle. Al-though the loading devices were widely separated, they could beplaced in axial alignment and, be carried on the same shaft. Therequired movement, shown in Fig. 4, was obtained from a barrel-cam driven by a reciprocating part.

Shaft A, on which the loading devices are mounted, is sUP-rported in bearings and carries a barrel-cam B with an irregulargroove. Roller C operates in this groove and is carried on a slide..bar D mounted on a stationary part of the machine by gibs E,Member D is given a uniform reciprocating motion by a cam(not shown). Since there are eight stations, eight axial follower


FIG. 4. Cam mechanism for converting uniform reciprocating motion tointermittent rotary motion.

grooves are machined on opposite sides of the cam barrel. Theseare connected by other grooves milled in the periphery at an angleof about 45 degrees with the axis of the cam. The vertex of theangle formed by any two of the angular grooves is approximatelyin line with one side of the axial grooves, as indicated byline W.

The assembly is shown with slide-bar D at the extreme leftposition. To demonstrate the action, three positions of the rollerin the center groove are seen at X, Y, and Z. Roller C, in movingfrom the extreme right position, acts against the angular side ofthe groove, causing the cam B to rotate in the direction indicatedby the arrow. When roller C reaches position Y, rotation of thecam ceases, and it remains at rest during the continued movementof the roller to the extreme left position X.

On the return movement, no rotation of cam B is produceduntil roller C again contacts the angular groove at position Z.Since the vertex of the angular groove surfaces are not alignedwith the centers of the axial grooves, the roller cannot return tothe groove previously traversed, but must enter the next one.Continued movement of roller C causes cam B and shaft A torotate to the next station, and the cycle is repeated.

Cylindrical Cam PositionsWire Guide

Figures 5 and 6 show two views of a mechanism designedto guide a strand of wire through an irregular path in a ma-chine which produces a woven wire product. The purpose of'this mechanism is to create a continuously varying pattern inthe weave. Position of the wire strand W in the weave patternmust bear a given relationship to other parts of the weave overa required length of the fabric, and then repeat. Figure 5 is aplain view of the mechanism, and Fig. 6 is a front view.

The driving shaft A carries the worm B, which meshes withthe worm-gear C on shaft D. Shaft D carries the cylindrical camE, which imparts a transverse guiding movement to wire W. Thetwo rounded grooves in cam E are identical, although the axesof the grooves are offset from the shaft axis and are 180 degreesapart.

Shaft G receives motion from worm B through worm-gear Fand carries the disc H, which is connected to block J by the pit~man I. Block J is attached to the dovetailed slide K, which is

FIG.~. PIa? view o~ wire-gui~e ~echanism for a metal textile weavingmachme deSIgned to Impart an mtrIcate transverse motion pattern to wire

strand W.


FIG. 6. Sixty turns of shaft A are required to completely cycle follower Mthrough a single out-and-back traverse of rotating cam E.

given a reciprocating motion by the rotation of crank disc H.Slide K carries the dovetailed slide L, which in turn mounts theroller follower M. The follower roll is held in contact with cam Eby the spring N attached to a pin in slide L and a pin in bracketo attached to slide K.

In operation, the rotation of worm B transmits rotary motionto cam E through worm-gear C and shaft D,. and reciprocatingmotion to slide K through worm-gear F and disc H. As slide Kmoves, roller M traverses axially along cam E, following thegrooves which are constantly varying in width and depth as aresult of the rotation of cam E. The position of slide L in slide Kis continually changing except when roller M is in contact withthe cylindrical periphery of cam E. As the strand of wire W feedsthrough a hole in the leg of slide L, its position is guided by themovement of slide L.

In the diagrams, which show the position of the mechanismat the beginning of the cycle, wire W is guided in a straight pathuntil roller M begins to follow the right-hand groove in cam E.Thus the wire is moved from start position. It returns to its start-ing position when roller M returns to the periphery of cam E.After a short period of rest, slide L again moves as roller M enters

the second groove. This is followed by a period of rest as roller Magain reaches the periphery of cam E. Worm-gears C and F are ofdifferent pitch diametei-s. G has thirty teeth and F has twentyteeth. Therefore, the rotation of cam E and the movement ofslide K are not synchronized. Thus the path followed by roller Mvaries as the varying contours of the cam are presented to it. This,action results in varying rest periods at the ends of the movementof slide K, as well as a varying timing pattern and positioningof slide L at different points of the cycle, setting up an intricatepattern in the positioning of wire W. '

While the diagrams indicate the starting point of the cycle,the completion of the cycle is accomplished only when all of themoving members of the mechanism are returned to this start posi-tion. As stated, worm-gears C and F have thirty and twentyteeth, respectively, having a ratio of 3 to 2. Therefore, for acomplete cycle, gear F must complete three revolutions, and gearC must complete two revolutions. The complete cycle, therefore,requires sixty revolutions of drive-shaft A.

Combination Cam ControlsStock Feed of Wire-Forming Machine

A combination end and radial cam is the heart of a stock feedfor a multiple-slide wire-forming machine. Figure 7 shows thearrangement of the parts.

The combination cam A is carried by the machine's shaft sys-tem. I t is basically a two-diameter plug, the shoulder havingbeen modified to form an axial cam, and the small diameter toform a radial cam. Follower B in lever C rides on both cam sur-faces.

This lever fulcrums at its center on stud D. By being joinedto the stud by cross-pin E, the lever can swing both left to right(to follow the end cam surface) and in and out (to follow theradial cam surface).

DirectlYA.behind the lower end of the lever is a dovetail slide Fcontaining quill G. The quill has two parts. One part fits thedovetail, and the other has a pin carrying bushing J which fits aslot in the lower end of the lever. There is a semicircular section


o

spring M operates, pulling the ,lever to the left, and the feedcycle is completed. \

Stop-block assembly b provides'-stroke-Iength adjustment bycontrolling the point to which the lever can return. A simpleway to prevent the wire from tending to move backon the returnstroke is to add a pair of non-reversing rolls P. Or, a springcheck Q can be used.

Mechanism Loops andTwists Wire Ends

Completion of a certain job necessitated the production ofwire components having a twisted loop at each end. The softsteel wire parts were required in lengths of 16 inches andlonger. A typical twisted loop is shown at X in Fig. 8.

Hollow shaft A has a running fit on drive shaft B, and iscoupled to it by means of a clutch, a portion. of which may be

FIG. 8. Device loops and clamps wire component, then transfers it on arotary disc to a point where the loop is twisted into the form shown at x.

z

~22222222~X

L

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K in the mating surfaces of the two parts of the quill, throughwhich the stock advances. (The section can be modified to acceptwhatever stock size or shape is used.) The outer part of thequill is held in position by loose-fitting pin L.

The drawing shows the lever position at a point in the feedstroke. At the start of the stroke, spring M pulls the bottom ofthe lever to the left. As the cam starts to rotate, the lobe on itssmall diameter bears against the follower, causing the bottom ofthe lever to swing in and thus force the quill to close tightly overthe wire. At the same time, the end cam forces the bottom ofthe lever to the right, thus advancing the wire.

When the lever reaches the end of the forward stroke, thefollower no longer has any thrust on it from either cam surface.Spring N, contained in a hole extending into both parts of thequill, then allows the quill to release its grip on the wire. Next,

FIG. 7. Cam A controls the feed of the wire by having its motion trans-lated to quill G through lever C.

seen at C. This clutch allows shaft A, shown at Y, to rotateone-half revolution for each complete revolution made by shaftB. During the remaining one-half revolution of the drive shaft,shaft A dwells. Keyed to the left-hand end of thehollow shaftis mounting disc D.

Disc cam E, having two notches, Fland F2, is keyed directlyto the drive shaft. The purpose of the cam is to actuate followerrollers Gl and G2 which, in turn, pivot levers H l and H 2 Thisaction either causes the jaws of clamps J land J 2 to close orpermits them to open under the influence of springs K 1 and K 2 The two clamps, together with their actuating levers, aremounted on disc D. There is a second complete unit (notshown), identical to the one illustrated, at the left-h~nd end ofshaft B to twist a loop in the opposite end of the WIre part.

In operation, the wire L to be formed is fed through guidenozzle M, as shown at Z, between two cutting blades Nandthen between two pins 0 and P of looping head Q. When thecorrect developed length of wire has been fed out, clamp J 1moves up from below to nest it. At this point clutch C releases,with the result that the clamp remains stationary while cam Econtinues to rotate.

As this occurs, follower G1 leaves notch F 1 and rides up onthe high portion of the cam, forcing the clamp jaws to close onwire L. Cutting blades N now shear the wire, and looping headQ rotates, thus forming a loop in the wire end around pin 0 bythe action of pin P. The wire end comes to rest in the V-shapedentrance to the clamping jaws and is held in this position bythe pin P. .

As cam notch F 2 arrives under follower Gl , the clamp Jawsare permitted to open a sufficient amount to allow the wire endto drop in place. The passing of the notch once again closesthe jaws, locking the looped wire securely in place while thelooping head is retracted.

By this time, cam notch F 1 has arrived under follower G2 ,allowing the jaws of clamp J 2 to open wide. At this instantclutch C engages, causing disc D and cam E to once again rotatein unison for one-half revolution. During this movement,

FIG. 9. Cardboard web layout showing die-cut carton blanks and theattached scrap material.

13

WEB. CARTON BLANK .sCRAP TAB

i

CAM APPLICATIONS AND SPECIAL CAM DESIGNS

clamp J 2 moves up into contact with a newly fed length ofwire, which begins the next cycle.

While in this position, with clampJl dwelling at a location180 degrees away from its starting point, a twisting headengages the clamped wire loop. This head, not shown, completesthe twist as shown in the illustrated example of the workpiece.Following the twisting operation, cam notch F 1 moves beneathfollower Gb allowing the clamp jaws to open and to drop thefinished wire components clear of the machine. The cycle ofoperation then continues.

Rotary Scrap-Stripping Device

One step in the manufacture of cardboard cartons is the diecutting of the developed form. Each printed carton blank isjoined to the adjacent carton and to the scrap material sur",rounding the end flaps by means of small tabs. A typical lay-out, Fig. 9, shows the arrangement of the die-cut shapes on theweb, or continuous cardboard strip; the scrap material, depicted'by shading; and the tabs, indicated by two parallel lines.

Upon completion of the die-cutting operation, the scrappieces mustftbe removed from the web. This procedure, known'as stripping, is frequently carried out by hand. However, therotary scrap stripper shown in Fig. 10 has been designed toreplace this manual operation.

CAM APPLICATIONS AND SPECIAL CAM DESIGNS12

14 CAM APPLICATIONS AND SPECIAL CAM DESIGNSCAM APPLICATIONS AND SPECIAL CAM DESIGNS 15

FIG. 10. A rotating unit strips scrap material from a die-cut web on aproduction line handling cardboard cartons.

The main member of the device is a cylindrical housing A.This housingis driven at the same surface speed and is the samediameter as the printing cylinders that are located ahead of thecutting dies. Cam B is stationary, being mounted on a fixedportion of the machine by means of bracket C. An arcuate slotin the.bracket permits adjustment of the cam position.

Scrap pieces. are picked out by a hook attached to followerarm D. This arm pivots on shaft E which fits into a bearinghole bored through an integral housing lug. On the other endof the arm is a cam-follower F. Because arm D and its associ-ated parts rotate with the cylindrical housing, tension springs Gare necessary to overcome the centrifugal force developed duringnormal operation and maintain the cam-followers in contact withthe cam surface. A clearance opening H is provided for each

hook.It is apparent from the lay-out of the carton blanks on the

weh that there is a periodic repetition of the scrap pieces and,

therefore, that they will always contact the same area on hous-ing A. Because of th~s, one o'r more hooks are located withineach contact area. i

During normal operation, follower G rides up on the camlobe as the leading edge of the scrap piece contacts the housing.Follower arm D is raised just enough to allow the hook to punc~ture the scrap piece an curvedhooks. This division in paths of travel causes the tabs to break,thus effecting a separation between the carton blanks and theunwanted trimmings. After the cam-followers leave the camlobe, the hooks are withdrawn, and the scrap is free to fall intodisposal cans.

Single Closed-Track CamDrives Glue-Transfer Mechanism

One station of a large machine for packaging material inpaper sacks is devoted to the application of glue before the finalfold is made to seal the container. An interesting mechanicalarrangement is employed to accomplish the various motionsrequired.

At this station of the machine, the package carrier A isbrought to a momentary halt (see Fig. 11). During this interval,an applicator B (carried by slide C) must pick up glue fromcylinder D, turn through an arc of 180 degrees (by means ofastationary cam, not shown), and move to the package fold todeposit a strip of the adhesive.

All movements necessary to advance and retract the appli-cator slide, rotate the glue cylinder between packages, aqdsynchronize these functions are furnished basically by just oneclosed-track cam E. Follower-roller F is carried by follower-lever G, which is integral with short lever H. The roller ridesin cam track J.

Long lever K pivots freely about the same shaft used by Gand H. However, it is coupled to them as shown in the auxiliary


Glue

FIG. 11. All movements necessary to the proper functioning of this glue-transfer mechanism are under the control of one closed-track cam.

sketch so that there is over 90 degrees of play between them.The coupling is designed so that lever G will drive lever K tothe left only. G and K are shown in their closest position.

As the cam rotates, follower-roller F is forced to the right.Because the coupling does not provide positive drive in thisdirection, a spring L, attached to levers G and K, causes thelatter to follow the movement of the former.

In this way, both desired end motions are achieved. First,lever K, through connecting-rod M, advances and retracts slideC and, in turn, applicator B. Second, lever H, through connect-ing-rod N, raises and lowers the pivoting support arm 0 thatpermits ratchet and pawl P to function, thus rotating the gluecylinder in glue tray Qduring each reciprocation of slide C. On

the return movement of lever G the coupling engages and leverK is forced back to its original position under direct drive.

The cam is designed to yield ...a 180-degree rise and a 180-degree return motion. Although this high-speed mechanism iscapable of transferring large forces, its capacity can be increasedby cutting a close-tolerance cam groove and by replacing theline-contact follower-roller with a plane-contact sliding piece.

Indexing Attachment thatControls Ratchet Operation

On a machine for producing ornamental wire screening, it isnecessary for the movement of the screening through the ma-chine to be interrupted at certain times, depending on the screen~attern. During the idle period of the feeding mechanism, work~s performed on the screening. In its movements, the screeningIS fed by a ratchet mechanism. How this mechanism was de-signed is shown in Fig. 12.

Drive-shaft A carries a worm C and disc B which rotate withthe shaft in a clockwise direction. Disc B is provided with aslide-bar M which operates in a groove against light frictionalresistance that is provided by two springs. The. ends of bar Mare shaped to serve as cam surfaces, .and contact roller L whichis carried on follower bar K. This latter bar is provided with areturn spring, not shown.

Worm C meshes with worm-gear D on shaft E. This shaft alsocarries disc F, which has twelve holes into which cylindrical but-tons are pressed, in various positions, as required by the specifiedscreen pattern. These buttons periodically actuate the swinginglever G as disc F revolves. The worm-gear has twelve teeth sothat there is one rotation of shaft E to twelve turns of shaf~ A.A cylindrical plunger H mounted in block N carries a roller Iat its upper end. A pin extends through vertical slots in plungerH and the wall of block N, and into a horizontal slot in lever G.This lever is mounted to swivel freely on a stud at its left-handend.

In Fig. 12 slide-bar M is in a position to permit roller L to passfreely between disc B and the contoured offset end of bar M. At

19

8


FIG. 13. Position of the various components of the mechanism whetiscreening is being fed;


FIG. 12. Mechanism designed to periodically interrupt a feed movementas required for an operation.

18


this point, motion is not transmitted to follower bar K, as rollerL remains in contact with the periphery of disc B. The contactlug on the underside of lever G lies between two of the buttonson disc F, and cylinder H is in its lower position. The cylinderremains in this position until one of the buttons on disc F con-tacts the lug on lever G. Bar M remains in this relative positionwith disc B as long as cylinder H remains in its lower position,the roller L passing through the opening between the contouredend of bar M and the periphery of disc B.

In Fig. 13, shaft Ehas rotated sufficiently to cause one of thebuttons on disc F to raise cylinder H, through lever G. At thispoint, roller H lies in the path of the oncoming cam surface onthe end of bar M. Continued rotation of disc B causes bar Mto be moved. so that the offset angular end of bar M coincideswith the periphery of disc B, causing the opposite end of barM to protrude.

As the angular end of bar M passes roller L it causes thefollower bar to be moved, thus actuating the ratchet mechanismand feeding the screening to its next position. Continued rota-tion of disc F causes the button to lose contact with the lug onlever G, and cylinder H again falls to its low position. Furtherrotation of disc B will bring the protruding end of bar Mintocontact with roller L, but the spring tension on bar K is sufficientto overcome the frictional resistance of bar M so that it is re-turned to the position shown in Fig. 12. Bar M remains in thisposition until cylinder H rises to return it to the position shownin Fig. 13.

Gear Mechanism forVarying Cam Timing

On a machine thatmanufactures a woven-wire product, it wasnecessary to provide for varied spacing in the weave. This wasaccomplished by means of a cam-actuated mechanism which isshown in Fig. 14. The cycle of. the mechanism is controlled byshaft A to which gear B is keyed. Gear C is fixed to the hub ofcam D which rotates freely on the shaft and is retained by collar

FIG. 14. A cam action which produces varied spacing in a woven product.

E. Cam D operates the follower bar F which actuates the spac-ing mechanism. Pinion G is supported to rotate freely onbearing bracket H and mesh with gears Band C. Gear B is ofstandard pitch and has fifty teeth. Gear C has fifty:..one teethbut the same outside and pitch diameters as gear B. The addi-tional tooth, however, decreases the circular pitch since thewidth of the teeth must be narrower than standard.

In operation, shaft A rotates gear B, the motion being trans-mitted to gear C through pinion G. Since gear C rotates slowerthan gear B, due to the difference in the number of teeth cam D, . ,actuated by gear C, will turn less than one revolution in relationto gear B. In the situation described, the loss in radial mov~ment would be approximately 7 degrees, and shaft A wouldrequire fifty-one turns to produce a complete timing cycle of camE. The modification of gear C is restricted by its relation topinion G. Since the teeth of gears Band C must remain in align-ment as they mesh with the pinion gear, the reduction in thethickness of the teeth of gear C must be sufficient to prevent anybinding action.

FIG. 15. Arrangement that incorporates a cam to prevent excessive shockin an intermittent, reciprocating rack movement.

23CAM APPLICATIONS AND SPECIAL CAM DESIGNS

and the position of existing meplbers were major considerationsgoverning design of th,e device.

A face-cam C is key~d to' a drive-shaft D which existed priorto the modification of the machine. Roller follower E is free torotate on a stud secured to a slider guide F. One 'end of theslider guide is turned 'and threaded for assembly to a rack G.A lock-nut secures the assembly in the proper position. RackG is restrained to a vertical linear motion by a pinion H, guide J,and a stationary slider K, the drive-shaft D having a 'runningfit in the slider. The pinion H is in m~sh with rack G, and isfree to rotate on a shaft L.

A disc integral with pinion H carries drive-pin A which islocated in a 120-degree circular slot in an adjacent disc M. DiscM and a pinion N, which is in mesh with the guided horizontalrack B, are keyed to shaft L. Thus, if pinion H is rotatedcounterclockwise, pin A will traverse the circular slot and contactdisc M. Further motion in the same direction will be transmittedthrough disc M, shaftL, and pinion N to drive rack B. Reversalof rotation of pinion H will again cause the drive-pin to traversethe circular slot before contacting disc M to drive the load in theother direction.

The rotational speed of pin A at impact with disc M is con-trolled by the path of the slot in cam C. If the rotation is notred~c:d to ~ minimum at the moment of contact, the resultingad~I.tlOnal . Impact. loadi~g could cause breakage of the pin.MInImum Impact IS obtaIned by making the incremental radialrise of the cam-slot as small as possible in the areas of points Pand Q which are traversed by the follower at the two momentsof contact. In addition, cam C is designed to impart the move-mentnecessary for rack B 'to complete its function in the ma-chine.

In operation, cam C is rotated counterclockwise. The riseimpa~ted to the vertical rack during the first 90 degrees ofrotat,lOn .of ihe cam traverses pin A through the 120-degreeslot In' dISC M, rack B remaining stationary. When the centerof the follower coincides with point P on the cam, pin A is incontact with disc M. For the next 120 degrees of cam rotation

SECTION x-x

M 8

CAM APPLICATIONS AND SPECIAL' CAM DESIGNS

Cam Eliminates Shockin Rack Movement

An arrangement that imparts a rapid intermittent and recip-rocating movement to a rack employed in an aluminum foil bag-making machine is shown in Fig. 15. The interesting feature ofthe mechanism is a cam which slows the motion of a drive-pin Aeach time it is about to contact a disc and move the load. Thisdeceleration prevents undue impact loading and possible break-age of the pin. Since the load, rack B, and its drive were addedsubsequent to the construction of the machine, limited space

22


..

SectionYY

pin A moves to the horizontal rack to the left. Reversal in therotation of the pin occurs when point R of the cam coincideswith the center of the follower. Again, rack B is stationary asthe pin traverses the slot in disc M clockwise during the follow-ing 60-degree movement of the cam. Pin A contacts the discwhen the follower is at point Q and returns rack B to its initialposition in the final 90 degrees of cam rotation. At both pointsP and Q the rate of rise or fall of the follower is at a minimumto prevent impact damage to the pin.

Wheel-Dressing Attachment for aGear-Grinding Screw

A patented attachment for dressing a continuous helical ribon the abrasive wheel of a gear-grinding machine is shown inthe accompanying drawing. The attachment, see Fig. 16, ismounted on the compound slide of the machine. During dress-ing, it is traversed parallel with the axis of the wheel-spindle bya screw driven from the spindle through pick-off gears.

Dressing is carried out simultaneously on both flanks of thehelical rib by separate diamonds mounted in holders A and B.The holders are set to correspond with the pressure angle of thegear to be ground. At the end of the dressing stroke, the cross-slide and attachment are moved away from the spindle byhand, so that the diamonds clear the wheel.

Then, the longitudinal slide is returned to the starting positionby power traverse. Next, the cross-slide is brought to the dress-ing position, and the diamond holders are adjusted lengthwiseby means of screws C and D for applying another cut. In thisway, the rib on the grinding wheel is dressed to its full depth inseveral passes.

The housing for the left-hand diamond holder A is fixed tobase E, which is secured to the compound slide of the grinder. Aslide F is provided for the right-hand diamond holder B. Withthis arrangement, the right-hand holder can be moved towardor away from the left-hand holder by means of a screw, for set-ting the distance between the diamonds in accordance with therequired width of the helical rib to be dressed.

FIG. 16. .Attachment for diamond dressing a continuous helical rib onthe abraSIve wheel of a gear-grinding machi~e. By changing cam N, the

wheel may be dressed to varIOUS profiles.

Since both diamond-holder assemblies are of similar design,only the right-hand unit will be described. This unit can bepivoted about pin G. The diamond holder B is set to the re-quired angle by means of gage-blocks, which are placed betweenthe periphery of reference pin H and the machined surface J.The unit is then secured to slide F by nuts on the threadedupper ends of pins G and K. The enlarged-diameter lower endof pin K engagEls aT-slot in the slide.

An.eccentric ring L is keyed to a sleeve surrounding the pinK. DIamond holder B is held in close contact with this ring anda sleeve surrounding pin G by a tension spring M. When a wheel

26 CAM APPLICATIONS AND SPECIAL CAM DESIGNS

for grinding gear teeth of modified involute form is to be dressed,a plate type cam N is attached to the diamond holder. Thiscam is engaged by a follower-arm P, which is also keyed to thesleeve surrounding pin K.

When the diamond holder is adjusted lengthwise at the endof each dressing stroke, the action between the cam and fol-lower-arm causes the eccentric ring L to be rotated through asmall angle. As a result, the diamond holder is set in differentangular positions during the dressing operation so that a rib withcurved flanks is formed on the wheel. By using cams of differentshapes, the wheel may be dressed to grind gears having modifiedprofiles over part or full tooth depth.

CHAPTER 2

Intermittent Motions from Gears and (oms

The term "intermittent motion" is applied to me,chanisms forobtaining a "dwell" or possibly a series of dwells or movingand stationary periods of equal or unequal lengths. Many dif-ferent designs of intermittent motions are in use because theyare required on so many different types of automatic and semi-automatic machines. The intermittent motions illustrated anddescribed in this and the following chapter supplement thosepresented in Volumes I, II and III 'of "Ingenious Mechanismsfor Designers and Inventors."

Intermittent Worm-Gear Train

The worm-gear drive shown in Fig. 1 was designed to provideintermittent motion. It consists of a worm-wheel A having teethin sectors X, Y, and Z; worms Band C, mounted on and keyedto shaft D; and a plunger E. Worm B is firmly attached tothe shaft; Worm C is free to slide. The helices of these wormsshould be continuous.

In order to hold worm C to the right, out of engagement withthe worm-wheel, a spring F is located in a longitudinal hole inshaft D. A cross-pin G, extending through a slot in the shaft andengaging a seat in worm C, transmits the spring pressure to thisworm. A similar seat is provided in worm B for this pin. Thespring is suitably secured at its left end.

The device o{?erates as follows: as shaft D rotates in the direc-tionshownby.the arrow, there will be no rotation of the worm-wheel A in the position illustrated, as worm B is rotating in aplain sector of the worm-gear. In order to produce rotation of

27

28 INTERMITTENT MOTIONS - GEARS AND CAMS INTERMITTENT MOTIONS - GEARS AND CAMS 29

FIG. 1. Worm-gear train for producing intermittent motion. The worm-wheel A is rotated one-third of a revolution, followed by a stationary

period, through the action of the two worm-gears Band C.

the worm gear - in this case one-third a complete revolution_ plunger E (timed by other parts not shown) rises into en-gagement with the worm thread. Upon engagement, the rotat-ing worm C moves to the left, as its thread moves past theplunger until the worm engages the last tooth in sector X of theworm-wheel. The plunger must be withdrawn before worm Creaches worm B.

When the end of worm C comes in contact with the end ofworm B, the worm-wheel A is rotated in the direction of thearrow, both worms operating as a single unit. After worm-wheel A has rotated sufficiently to bring the last tooth of sectorX out of engagement with worm C, spring F pushes the wormto the extreme right, where it cannot engage the teeth of sectorY. When the last tooth in sector Y is disengaged from worm B,worm-wheel A will stop, having made one-third of a revolutionabout its axis.

Indexing Movement thatStarts without Shock

Most indexing mechanisms incorporate either cams, Genevamovements, or other components which present machining prob-lems. An indexing mechanism made up of easily machined com-ponents and accurate gears that can be obtained from gearspecialists is shown in Fig. 2.

The mechanism, illustrated in the top view of Fig. 2,. is aplanetary gear device incorporating two eccentrically loc~tedspur gears. The bore of each of these gears is machined offcenter by an amount equal to 20 per cent of its pitch radius.The desired dwell period is realized when the ratio of the num-ber of turns of arm C to the number of turns of sun gear H is3 to 1; that is, the arm must rotate three times faster than thesun gear, but in the opposite direction.

FIG. 2. (Top) Planetary gear type indexing device that provides fixeddwell periods in the movement of follower-shaft M. (Bottom) Alternate

gear arrangement permits the elimination of internal gear G.

31

G~~~'8:---::c~I,-+ ---

II 'Ht.1

N~l

0-----1~ _,M, . ~ I J F

l.'

INTERMITTENT MOTIONS - GEARS AND CAMS

ried on the slide-bar. A spring I serves to resist any movementof the slide-bar to the right, and maintains the follower roller incontact with the cam. The driven shaft H has a sprocket Gkeyed to it which, like the sprocket on the driving shaft, is inmesh with a chain N.

In order to explain the operation of the mechanism, let it beassumed that the cam and lever were omitted. The rotationof shafts A and H would then be in the ratio of the number ofteeth on sprockets Band G, the idler sprockets D serving >merelyto direct the chain over the required path. The two idler sprock-etsE carried on the slide-bar do not affect the motion of sprocketG, provided the slide-bar remains stationary. But if there is achange in the position of the slide-bar, there will also be a changein the relative positions of sprockets Band G. This is becausethe movement})f the slide-bar causes the chain to be let out onone side and taken up on the other side, this action producing apartial rotation of sprocket G.

By referring to the drawing, it can be seen that the cam

FIG. 3. Practical design for producing intermittent rotation in a drivenshaft H from a uniformly rotating driving shaft A.

INTERMITTENT MOTIONS-GEARS AND CAMS

Chain Driven IntermittentRotary Movement

On a wire fabricating machine, a driven shaft was to be givenan intermittent rotary movement through a roller chain from auniformly rotating driving shaft. Both shafts had to begin andcomplete each revolution together. However, because the drivenshaft was to move intermittently, it had to rotate at a higherspeed than the driving shaft. The drawing illustrates the mech-anism that was designed to obtain the required motion.

Keyed to the driving shaft A, (see Fig. 3), are a sprocket Band a cam C. A bracket L supports a lever J. At its lower end,lever J carries a follower roller K which contacts the cam. Theupper end of the lever is joined by a link M to a slide-bar Fdovetailed to the frame of the machine. Four idler sprockets Dare mounted on the machine, and two idler sprockets E are car-

Drive-shaft A, which carries a 20-tooth pinion B, is keyed toarm C. Frame member D supports two pinions E and F, eachhaving 20 teeth, which mesh with pinion B and also with internalgear G. This internal gear has 60 teeth and is integral with aneccentrically located, 40-tooth sun gear H. Gears G and H re-volve around shaft A.

Meshing with the sun gear is another eccentrically located,40-tooth gear J. Mounted on the same shaft with gear J is a20-tooth pinion K. This gear meshes with a 60-tooth gear Lthat is mounted on follower-shaft M.

In operation, drive-shaft A turns clockwise as indicated bythe arrow; pinions E and F, internal gear G, and sun gear H turncounterclockwise, while gear J and pinion K turn clockwise.Since gear L is driven in a counterclockwise direction, follower-shaft M receives this motion. One full revolution of the drive-shaft results in several fixed dwell periods in the follower-shaft

rotation.An adaptation of the gear train to the left of sun gear H is

shown in the lower view of Fig. 2. In this alternate arrangementonly external spur gears are used, thus eliminating internal gearG. The gear ratio, however, remains the same (3 to 1).

30

FIG. 4. Lever A is permitted to function only once for each five revolu-tions of camshaft E. This intermittent movement is controlled by the

action of cams C1 and C2.

During this rotation of the camshaft, follower-roller B 2 is dis-engaged from the surface of cam C2 This permits roller B1 totrack along the entire surface of cam C1 , thus causing lever Ato pivot. For the next four rotations of the camshaft, follower-roller B 2 will ride along cam C2 , thereby preventing roll~r B1from being affected by the contour of cam C1 , and causing leverA to remain motionless.

33INTERMITTENT MOTIONS - GEARS AND CAMS

Intermittent Rotary Movementwith End-Cycle Reversal

On a machine for forming a product of flat wire, the materialis fed intermittently through a twisting clamp. During thecycle, a shaft rotates one revolution, dwells, then rotates an-other revolution in the same direction. After several such revo-lutions, the shaft rotates in the reverse direction for a numberof revolutions equal to the number of forward, separate revolu-tions, then stops to end the cycle.

In Fig. 5, tubular spindle shaft A, which carries the twistingclamp, is supported by bearing brackets B. Pinion gear C, brake-drum D, and counterweight drum E are keyed to shaft A. Fric-tion is applied to the brake-drum by leather band F which is

Intermittent Motion fromTwo Synchronized Cams

Packaging machines often require mechanisms to transmit aparticular motion during each fifth revolution of.. the main cam-shaft. Such a need might arise where five packages are to begrouped, then pushed from the machine at the same ti~e. Amechanism that has been arranged to satisfy these partIcularrequirements is shown in Fig. 4.

The principal operating elements of this mechanism are twosynchronized cams and one follower-lever. The upper end ofsingle, L-shaped lever A drives the package-ejector unit (notshown). At the opposite end of the lever are two follower-rollersB

1and B2 which are held in contact with cams C1 and C2 , re-

spectively, by a spring D (attached to the upright lev~r arm).Cam C1 is pinned directly to the constantly rotatIng cam-

shaft E, while the motion for cam C2 is obtained indirectly froma gear F, also pinned to the camshaft. By means of gears G an.dH - the latter being keyed to cam C2 - movement of gear F ISreduced to one-fifth by the time it reaches the second cam. Thus,the speed of cam C2 is only one-fifth that of the camshaft andC

balthough the rotational movement of both of the cams is in

the same direction.Bearing this in mind, and noting the cam configurations and

positions in the right-hand view, it can be seen that in one r~volution of cam C1 cam C2 will rotate a distance equal to the WIdthof its cutout J. This cutout occupies approximately one-fifth ofthe otherwise circular cam.

rotates in the direction indicated by the arrow, and is aboutto make the lever swing on its fulcrum and move the slide-bar tothe right. As a result of this action, the chain is let out on t~eleft side and taken up on the right side. If the take-up speed ISequal to the linear speed of the chain, no. rotativ~ ~otion ~inbe transmitted to sprocket G while the slIde-bar IS In motIon.The linear speed of the slide-bar must equal one-half the speedof the chain to produce this condition, because the chain is letout and taken up on both sides of sprockets E.

32 INTERMITTENT MOTIONS - GEARS AND CAMS

FIG. 5. Mechanism that provides intermittent rotary movement from arotating drive-shaft, and which has provision for automatic reversal upon

completion of operating cycle.


arrow, is in contact with the geat teeth on the under side ofrack K. This causes the ra

FIG. 6. Index-plate mechanism incorporates locating device and one-directional driving dog to provide fool-proof operation by eliminating

the possibility of faulty indexing.


Escapement ProvidesRegular Intermittent Drive

An escapement mechanism in which a pendulum is applied tocontrol the timing of an intermittently rotating shaft was in-corporated in a wire weaving machine to advance strands ofwire a required distance at regulated time intervals. It resemblesthe pin-pallet, or Brocot, escapements used in French and pendu-lum clocks.

Drive-shaft A, see Fig. 7, has gear B keyed to it. This gearmeshes with gear C, which is carried free on driven shaft E. GearC carries a series of spring-loaded plungers which contact discD, keyed to shaft E, see Fig. 8. Shaft E carries, at its outer end,a disc G, which is provided with a series of pins. A ring of fric-tion material F is carried on the hub of disc G where it transmitsrotary motion from gear C to disc G due to the pressure appliedby the spring~plungers. Bracket H, bolted to a stationary parto{ the machine, carries a pivot stud which supports a pallet Iand a. pendulum J, which are locked togetherby two screws in

At the same time that these :p:1ovements are taking place,spring-loaded dog C free~heels over the dog teeth that are in-tegral with ratchet wheel 13 and drop's into position after havingmoved a distance equal to one dog tooth. The ratchet wheel,which has the same number of dog teeth as ratchet teeth, is pre-vented from turning by pawl E.

Lever A is now moved back to its original position. In doingso, dog C drives ratchet wheel B one tooth which, in turn, movesthe index-plate to the next position. During the first part ofthis stroke, spring-loaded ball J retains locating plunger G, al-lowing the index-plate to move unrestricted. Toward the end ofthe stroke an adjustable screw K, which is threaded through apad on the lever, contacts the pin connecting slotted lever F withthe plunger. This drives the plunger forward causing the locat-ing tongue to enter a tooth slot on the index plate, thus lockingit firmly in place. The plunger is held in this position by coilspring L.

y

:--;-----! II i

o~ ii ii ii i! !


plunger slides in a guide block fastened to the base of the in-dexing table. A locating tongue on the plunger end is accuratelyground to fit within the tooth spaces around index-plate D.This tongue is partially relieved on the face parallel to the hori-zontal center line to clear any burrs that may have been raisedin the tooth spaces on index-plate D by the action of ratchetwheelB.

To move the index-plate from one position to the next, leverA is moved from the position shown at X to that shown at Y.During the initial part of this motion, pin H, pressed in the shortleg of the lever, moves freely in an arc until it contacts slottedlever F. The pin, during the remainder of the stroke, forces theslotted lever to pivot around the common spindle, thereby dis-engaging locating plunger G from the index-plate. At the end ofthe stroke, spring-loaded ball J rides into a cone-shaped recessin the top plunger face. The plunger is thus held in the retractedposition.

36

1

38 INTERMITTENT MOTIONS- GEARS AND CAMS INTERMITTENT MOTIONS - GEARS AND CAMS 39

FIG. 8. Driven shaft E is turned intermittently under control of pendu-lum escapement, receiving power from shaft A.

G. In Fig. 7, the positions of penqulum J and pallet I are suchthat the upper foot of pall~t I contacting a pin of disc G preventsits rotation. As pendulumiJ swings to the other end of its arc, asshown dotted, the contacting pallet foot slides off the pin, allow-ing disc G to rotate. But before the upper foot has completelylost contact with its pin,the lower pallet foot carries into posi-tion to catch the succeeding pin. Thus, at the end of the arc

I,,'.:

-+)E

A

i),\

: "-Y

the side plates attached to pallet 1. These screws provide ameans of adjusting the position of the pallet relative to thependulum.

In operation, the continuously rotating shaft A transmitsmotion to the shaft E through gears B and C, friction ring F,and disc G, where there is no restriction to the movement of disc

FIG. 7. Pendulum escapement gives disc G intermittent clockwise motionby means of the pin pallet 1 alternately releasing the pins in the disc as

pendulum J swings from side to side.

40 INTERMITTENT MOTIONS - GEARS AND CAMSINTERMITTENT MOTIONS - GEARS AND CAMS 41

to the right the pallet I will be in the position shown by thedotted outline, the succeeding pin having moved to contact thelower foot of pallet I. If the pallet feet are correctly located,the angular movement of shaft E will equal one-half the angularspacing between any two consecutive pins on disc G. Therefore,the number of angular movements of shaft E per revolution willequal twice the number of pins in disc G.

The number of movements per minute of shaft E is controlledby the swing of the pendulum regardless of the number of pinson disc G. But in all cases the rotative speed of disc G must besuch that the time required for any 'pin to arrive at the lockingposition must be less than the time required for the pendulumto swing. The angularity of the feet of pallet I relative to theline of movement of the pins provides an impulse to producecontinued motion of pendulum J. However, this angularity isregulated by operating conditions. If the angle is too small,there will be insufficient impulse applied to the pendulum to keepit swinging. But if the angle is too large, free movement of thependulum will be restricted, particularly when a heavy load isapplied by the pins. With a light load and a large angle, therewill be a noticeable jerk of disc G as the pallet feet slide off thepins. If this is objectionable, the contact surfaces of the palletfeet must be curved, with the center of the pivot as the centerof the arc of curvature. In the latter case, an angle on the lead-ing side of the pallet feet must deliver the impulse. In general,it is advisable to locate the pallet feet at the lowest angle withthe line of movement of the pins which provides the necessary

impulse.To determine the length of the pendulum needed to produce

the required timing, the formulas applied to a free-swingingweight suspended on a length of cord are applicable. For deter-mining the time of swing, the accepted formula is

in which: t = time, in seconds; l= length of pendulum in feet;and g = the force of gravity in feet per second2 The generallyapplied value of g is 32.2.

To determine the length of pendulum required to produce aspecified rate of swing, t~e foregoing formula is transposed, thus:

J

In the formulas, the'8ymbol l is the distance from the pivotpoint to the center of the suspended weight. However, thisformula is based on a weight suspended on a cord in which thereis no friction influence and negligible weight of the cord. Qn theother hand, an accurate determination of the length of pendulumby this formula for the escapement application is not accuratebecause the combined weight of the rod and its fastening producea distribution of weight which is not easily pinpointed. For allpractical purposes, the calculated length is determined by thecenter of the suspended weight which is provided with a nut foradjustment, as shown. The pound value of the suspended weightin no way controls the timing of the swing. Its value lies inincreasing momentum and providing the steadying influence ofinertia when the impulse is applied. The lightest weight whichwill serve this purpose is recommended.

Rotary Work-Table with Mechanismfor Automatic Indexing

An indexing work-table that can be used in conjunctionwith independent cutter-heads to form an automatic multiple-spindle machine is shown in Fig. 9. The table is intended toreceive several work-holding fixtures according to the numberof indexing stations provided. A variety of machining opera-tions may be performed automatically while the work-pieces arelocated at these stations.

Referring to sectional view W-W, annular table A rotates onsteel balls which surround fixed central disc B. Indexing iscarried out by means of gear segment C (section X-X) whichis secured to spindle D. The latter component is mounted inball bearings which are housed in disc B and in the base.

Motion from gear segment C is transmitted by pinion E,which engages gear teeth in the bore of the table. The indexingaction is controlled by compound cam F (section W-W) which

42 INTERMITTENT MOTIONS - GEARS AND CAMS INTERMITTENT MOTIONS - GEARS AND CAMS 43

w

LSection W-W

FIG. 9. Sectional views of work-table that can be set up for automaticindexing. Limit switch M stops indexing cycle and switch N starts

machining cycle.

engages follower rollers housed in recesses in the gear segmentC and is driven through bevel gears by shaft G. This shaft isdriven by a motor, through V-belts, an electromagnetic clutch,and brake units. This driving equipment is not shown in theillustration.

At the beginning of the cycle, segment C dwells for a period,and the indexing motion is then completed during a 210-degreeangular movement of cam F. Subsequently, segment C is againcaused to dwell before it is returned to its original position. Thisis done in preparation for the next indexing cycle in the courseof the final 90-degree angular movement of cam F.

During the dwell periods of the segment C before and afterthe indexing movement, pinion E and plunger H (section Y-Y)are moved vertically in opposite directions by lever J. At thebeginning of the cycle, the plunger is withdrawn from one of anumber of holes provided in the under side of the table at theindexing positions. Simultaneously pinion E is brought intoengagement with the gear teeth in the table for the indexingmovement. After indexing has been completed, the plunger isinserted into the next hole in the table. The latter is, therefore,positively located while the machining operations are being car-

ried out on the work-piece. At the same time, the pinion iswithdrawn from the geB.;r tee~h in. the table in preparation forthe return movement or the segment. At certain points in thecycle, the pinion and the plunger are in simultaneous engage-ment with the table, so that the latter is positively locatedduring the entire indexing operation.

MQvement is transmitted to the pinion and the plunger bybevel gear teeth on lever J and on pivoted segment K (sectionZ-Z) . The segment carries two follower rollers which ~r1gagesimultaneously with compound L. This cam is keyed to thelower end of the shaft which carries cam F. The arrangementmay be seen in section W-W of the illustration.

The indexing cycle is started by means of a switch (notshown) which activates the electromagnetic clutch to engagethe drive with shaft G. At the end of the indexing cycle, limitswitch M (section Z-Z) is operated by means of a detent on thelower end of spindle D, with the result that the clutch and con-sequently the drive to the shaft G are disengaged. Concurrently,an arm attached to the pivot spindle for the lever J actuates thelimit switch N to start the cycle of the cutterheads.

Intermittent and PressureApplying Mechanism

The gluing of paper watch dials to their metal backings orig-inally required the use of four presses and four operators. Inorder to reduce labor and equipment costs, a gluing device in-corporating an ingenious operating mechanism was developed todo this work. The new device required only one operator, elim-inated scrap, and enabled the work to be done with greatersafety.

In designing this device, it was necessary to incorporatemeans for holding and pressing the paper dials and their metalbackings together for a sufficient period of time to allow theglue to set. 'Phis requirement was met by providing the fixturewith eight cam-operated pressing spindles mounted in an inter-mittently indexed eight-position spindle-carrier, with one positionreserved for loading and unloading the work. The spindle-car-

45

\SECTION x-x

K-~""''''


G

F

FIG. 10. Mech~nism used to glue paper dials to metal discs by applyingsufficIent pressure for a predetermined length of time.


rier is operated slowly enough to permit proper setting of thegluein one complete revolution of the carrier. A glued dial andits backing is removed from the loading and unloading stationdesignated "0" and replaced by new pieces during the dwellperiod following each indexing of the spindle-carrier. Thus eightglued dials are completed in one revolution of the spindle-carrier, each dial and its backing being under pressure duringone revolution of the carrier.

The essential features of the mechanism designed to operatethe gluing device are shown in Fig. 10. The mechanism is drivenby a motor through a belt passing over the friction pulley Handa clutch operated by lever J. When the clutch is engaged, wormK on shaft F turns the worm-wheel L. The upper portion of theworm-wheel carries the indexing pin of a Geneva mechanism.At each revolution of the worm-wheel, the indexing disc M, whichis fastened rigidly to vertical shaft N, is rotated one-eighthrevolution. Since the spindle-carrier A is keyed to the verticalshaft, it also rotates.

The eight equally spaced pressure spindles C are mounted inthe carrier A as shown. Directly above, and in axial alignmentwith each pressure spindle C, is a spring-backed spindle B. It isbetween the work supporting disc P on the upper end of spin-dle C and the disc at the end of spindle B that the watch dialand its backing are pressed together to complete the gluing oper-ation. Both spindles C and B are provided with keys that slidein keyways to prevent them from turning in the carrier A. Slotsat the bottom ends of spindles C accommodate rollers, whichare in constant contact with a circular cam-ring D.

The cam-ring has a raised portion throughout 246 degrees ofits circumference, sloping portions throughout 47 and 44 degrees,and a flat portion throughout 23 degrees, which is located be-tween the sloping portions. The flat portion at the positionmarked "0" is directly in front of the operator, and it is at thislocation that a pair of spindles is loaded and unloaded.

Bed E, besides acting as a support for cam-ring D, houses theGeneva motion and worm-wheel and serves as a support bracketfor the worm-shaft F. The driving pulley G engages the spring-

44

46 INTERMITTENT MOTIONS-GEARS AND CAMS

loaded friction pulley H when the clutch lever J is in the raisedposition, imparting rotation to shaft F, worm K, and worm-wheel L.

In operation, the parts to be glued are placed by the operatoron the disc P of the spindle that is in the "0" position. The cor-rect positioning of the paper dial and metal backing on disc P isfacilitated by means of locating pins (not shown). The operatorthen releases the flat-hooked spring Q, which allows spring-loadedclutch lever J to move upward. This, in turn, releases driven pul-ley H and engages the train of members that drive the spindle-carrier A.

As the spindle-carrier rotates, the pressure spindle C is movedupward by the action of its roller on the circular cam-ring D.The pressure exerted on this member by the spring-loaded spin-dle B is sufficient, both in magnitude and duration, to permitsetting of the glue. As one spindle is loaded and moved into theposition where pressure is exerted, the pressure on the spindleimmediately following is relieved. Its roller then follows thedescent in the cam-ring under the influence of gravity in movinginto position "0." Once in this position, the bottom spindle isquickly unloaded and reloaded.

The mechanism is stopped by depressing lever J, which dis-engages the driving pulley G. The clutch lever also .acts as afriction brake. It is locked in the depressed position by meansof flat hooked springQ.

CHAPTER 3

Intermittent Motions from Ratchet and Geneva Mechanisms

Two methods of producing intermittent motion in which theperiods of rest are evenly spaced and of equal length are bymeans of ratchet gearing and by using some modification of theGeneva motion. In its basic form this motion is obtained bymeans of a Geneva wheel, acting as a driven member, which hasfour radial slots located 90 degrees apart that successively en-gage a roller or pin on the driving member. The Geneva wheelthus turns with the driving member through one-quarter of arevolution and is idle for the remainder of the revolution of thedriving member.

A number of ingenious mechanisms in which a ratchet a~rangement or a Geneva motion playa prominent part are described inthis chapter. For other mechanisms of a similar type, the readeris referred to Volumes I, II, and III of "Ingenious Mechanismsfor Designers and Inventors."

Adiustable IntermittentRatchet Mechanism

The device shown in Fig. 1 was used to give intermittentdrive to a mechanism by means of a ratchet. The number ofteeth per cycle was to be adjustable, as well as the location ofthe teeth in the cycle.

The device itself consists of two ratchets of the same diameteralldnumber of teeth. Ratchet A is keyed to shaft B, and trans-mits the desired motion to this shaft. Ratchet C is free to turnon shaft B. On the extended hub of ratchet C is carried, on onesidethe pawl arm D, and on the other side the masks E and F.

47

--------------~-

48 INTERMITTENT MOTIONS - RATCHET AND GENEVAINTERMITTENT MOTIONS - RATCHET AND GENEVA 49

FIG. 1. Pawl G rotates ratchet C and attached masks E and F with everystroke. Masks E and F are capable of lifting pawl J and H, through pin

K, thus controlling the rotation of ratchet A.

These masks have stepped diameters, the major equal to thatof the ratchets, and the minor slightly less than the root diameterof the ratchet teeth. There is a series of arcuate slots in themasks, and tapped holes in ratchets C are so arranged that avariable number of teeth can be uncovered, and the position ofthese teeth located anywhere on the circumference of the ratchet.It is obvious that a modification of the profile of these maskswill provide for an infinite number of conditions.

On the upper end of the pawl arm are carried two pawls, G,and H, and a pawl-like lever, J. These are carried on a pivot pinK, pawl H, and leverJ being pinned on pin K. Pawl G is free onpin K.

Motion is transmitted to the pawl arm D by the connectingrod M by means not shown.

The operation of this device is as follows: As shown, themechanism is set up to move four teeth per cycle, one tooth

having been moved already. The next three movements of thepawl arm will move a tooth each, the whole mechanism rotatingas a unit. The fourth baakward movement of the pawl arm willcause lever J to ride up on the major diameter of mask F. Bothlever J and pawl H being pinned to pivot pin K, this movementoutward of lever J will, lift pawl H out of engagement withratchet A. Pawl H will remain out of engagement as long as Jremains on the major periphery of the masks F and E. Pawl G,however, will engage ratchet C, moving it forward with it~ at-tached masks. This will continue until the lever J will be "per-mitted to move down to the minor radius of the masks, whenpawl H will re-engage ratchet A and the next movements of thepawl arm will carry the driven mechanism forward, in this case,four teeth.

Ratchet-Tripping MechanismContro.ls Cut-off Length of Sheets

A mechanism employing a feed-ratchet tripped indirectly bya roller chain for pre-setting cut-off lengths was designed for anexpanded-metal fabricating machine. The ram type machine hastoothed blades attached to a slide that reciprocates across thesheet between strokes. The blades punch and expand openingsin a solid steel sheet.

During the first stroke, the slide is laterally situated in one ex-treme position. Then, after the material has been fed forwarda distance equal to one row of perforations, the blade slide movesto the opposite extreme position for a second stroke. Thus therows of expanded openings are staggered on the sheet. The ex-panded metal is cut off from the solid sheet each time that thefeed mechanism is prevented from functioning by the ratchet-tripping device here described.

The adjustable ratchet arrangement employed for feeding themetal, sheets is shown in Fig. 2. Ratchet wheel A is intermit-tently rotated by feed-pawl B. The feed rate may be controlledby the adjustment of knob C to change the radial location of thedriver that imparts motion to the feed pawl.

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50 INTERMITTENT MOTIONS-RATCHET AND GENEVA INTERMITTENT MOTIONS-RATCHET AND GENEVA 51

FIG. 2. Ratchet-tripping mechanism for interrupting a press feed at pre-set points, shown in feeding position at X, and non-feeding position at Y.

Slide D, which is retained between two guides E, trips thefeed-pawl B directly. The slide is shown in its extreme right-hand position at X, held there by' spring F. The left-hand endof the slide is an arc of approximately the same radius as ratchetwheel A. Roller G, attached to the feed-pawl, rides on thisrounded end when the slide is shifted to the left.

Slide D is actuated by the ratchet-driven roller chain mech-anism at the right in view X. A nonadjustable eccentric H,mounted on the drive-shaft, actuates pawl J. In tum, pawl J

Positive Ratchet MechanismsDesigned for Silent Operation

Silent-operating positive-drive ratchet mechanisms are not toowell known. By substituting a brake for the conventional spring,

imparts intermittent motion to the ratchet wheel K. The eccen-tricity of member H was calculated to advance the ratchet wheelone tooth for each revohhion of the drive-shaft.

A chain sprocket L is mounted on the same shaft as theratchet wheel. The sprocket carries a roller chain M which isheld in tension by idler sprocket N. Ratchet wheel K andsprocket L have the same. number of teeth so that each feedmovement of the pawl will advance the chain a distance of onelink. Cam 0, bolted to one of the chain links, pushes sli

S2 INTERMITTENT MOTIONS - RATCHET AND GENEVA INTERMITTENT MOTIONS - RATCHET AND GENEVA 53

the pawl or finger member is lifted off the ratchet teeth on theidle stroke and made to engage the teeth again on the returnstroke. Thus, although still being a positive intermittent mech-anism, it works without the usual clicking noise made by thefinger in riding or jumping over the teeth on the idle stroke,and therefore reduces the wear on the finger as well as on theteeth.

Referring to Fig. 3, the finger F is pivoted on an arm A whichis, in turn, pivoted on the shaft S. The connecting-rod C pivotson the finger F. A spring-loaded brake B - prevented fromrotating by a stud in the body of the machine - acts as a brakeon a drum which is part of arm A. The toothed ratchet wheel Wis keyed to the shaft S.

On the idle stroke (indicated by dotted-line arrow), the con-necting-rod C will first pivot the finger F, thus lifting its pointoff the tooth on the ratchet wheel W. The arm A will not turnon the shaft at that time, as it is being restrained by the brakeB and so offers more resistance to movement than the finger.This finger will pivot only through a certain angle until its shortfinger hits the stop T on the arm. It will then force the arm Ato turn on the shaft, overcoming the friction of the brake andcausing the finger and the arm to pivot on the shaft as one part.

FIG. 4. Alternate design of silent, positive ratchet mechanism with con-necting-rod and pawl pivoted on same pin.

On the return stroke, the finger will first pivot to engage a newtooth, and then the whole mechanism will turn as one piece,including the ratchet wheel and the shaft.

Another design of silent ratchet, in which the connecting-rodand the finger are both pivoted on the same pin, is shown inFig. 4. The arm A and the brake arm B are arranged on oppositesides of the ratchet wheel. A pin P fixed in the finger provides

FIG. 5. Front and side views of ratchet designed for use on small-sizedmechanisms.

FIG. 3. Silent-operating, positive-drive mechanism with the ratchet pawlpivoted on the oscillating driving arm.

S4 INTERMITTENT MOTIONS - RATCHET AND GENEVA INTERMITTENT MOTIONS - RATCHET AND GENEVA SS

FIG. 6. Reversible ratchet with,double-ended pawl.

the necessary stop by engaging an elongated slot in the brakearm on one side and a circular slot in the arm A on the otherside.

A design that is suitable for small-size mechanisms, and whichis similar to the one illustrated in Fig. 4, is shown in Fig. 5. Thebrake is made of a piece of spring wire. The big disc replaces thearm. The designs shown in Figs. 4 and 5 have the brakes operat-ing on a drum which is attached to the shaft and ratchet wheel.This arrangement calls for a stationary finger to prevent theshaft from reversing on the idle stroke, or else the shaft with allthe elements driven by it should offer enough resistance to pre-vent reversal on the idle stroke--resulting from the grip of thebrake. Obviously, this arrangement is not absolutely necessaryfor the design, and the brake drum can be attached to the bodyof the machine, as in the design shown in Fig. 3.

A reversible silent ratchet mechanism is seen in Fig. 6. Theteeth on the wheel are made "square" to. have two radial sides,for forward and reverse driving. The finger is made double-pointed. To change the direction of drive, pin R on the brakearm should be shifted to position Q, and stop-pin P on the fingershould be shifted to position S.

Silent Ratchet Mechanismfor Over-Running Drive

Ratchet mechanisms used on over-run drives frequently pre-sent problems of noise and wear. Shown in Fig. 7 is a ratchet

mechanism designed to operate silently, with a minimum of wearon its working parts. .

Consisting principally Of a gear A -.and a ratchet B, the over-drive assembly is driven either by shaft C, to which the ratchetis keyed, or by the gear. The driving gear is mounted on thehub of the ratchet, and is free to turn on the hub, being retainedby collar D. A recess is pro:yided in the gear member to accom-modate pawl E. Although the pawl pivots on pin F, it fits thepin loosely, and the actual pressure transmitted by thepa\yl isborne by the right-hand end of the recess in the gear.

When the shaft is driven by the gear, which revolves counter-clockwise, the pawl drives the ratchet in the usual manner. Butwhen the shaft, which also rotates counter-clockwise, becomesthe driver, the gear is stationary, and the pawl over-rides theratchet. One of the functions of the mechanism at this time isto prevent the pawl from sliding over the ratchet teeth.

This is accomplished in the following manner: When theratchet rotates counter-clockwise, a brass cam-plate G moveswith it due to the friction developed by four cork-tipped springplungers H in the ratchet as they ride on the cam-plate. Themovement of the cam-plate lifts the pawl from the ratchet as pinJ, which projects from the pawl, slides up slot K in the cam-plate.

When the gear drives the shaft, the ratchet remains stationaryuntil the pawl is engaged. Since the friction generated by the

FIG. 7. Ratchet mechanism on an over-run assembly which operatessilently and with minimum wear on the parts.


spring plungers in this case will retard the rotation of the cam-plate, pawl pin J is forced down to the left in slot K. Therefore,the pawl engages the ratchet teeth and the entire assembly re-volves as a unit.

Spring plungers H are contained in four blind holes bored inthe side of the ratchet. Outward pressure of each plunger isexerted by a spring L against a cork friction button M, fittedinto a hole bored in the plunger. Covering the ratchet mech-anism is a protective plate N, which is relieved to avoid a largearea of contact with the cam-plate. To assure the frictionalmovement of the cam-plate only under the desired circum-stances, the area of contact is reduced to a minimum. There isalso clearance between the cover plate and the shaft for the samereason.

Additive and SubtractiveRatchet Mechanism

In the operation of a ratchet-driven device it was found de-sirable to automatically, and frequently, add extra tooth move-ments. Occasionally, all movement must stop.

The device illustrated in Fig. 8 includes ratchet wheel Awhich is keyed to the driven shaft B. Mounted on an extendedhub of the ratchet is a bushed push-pawl arm C. Push pawl Dis pivotally mounted on arm C. The pawl is provided with aprojecting pin E that rides on the periphery of mask K. ArmC is provided with gear teeth cut around a portion of its hub forengagement with mating teeth cut on the left end of hook-pawlarmF.

The hook-pawl arm is pivotally mounted on bracket G. Thelocation of this pivot point must be such that the movement ofthe pawl H on the outer end of arm F is equal to that of pawl D.The hook pawl is provided with a pin J which also rides on maskK. Mask K is bushed and is mounted freely on shaft B. Con-necting-rod L has one end attached to the mask. Pawl arm Cis reciprocated by another connecting-rod M.

In the operation of this device pawl D does all the driving,ordinarily moving a distance of one tooth on ratchet wheel A

H

D

FIG. 8. Ratchet mechanism has a mask that allows automatic changes inratchet stroke or complete temporary stoppage.

for each reciprocation of arm C, as a simple ratchet movement.In such movement pin J on hook pawl H rests on the lobe of,mask K so that pawl H is held out of engagement with theratchet.

When conditions arise that require increased movement ofshaft B, the control mechanism, through connecting-rod L,moves mask K clockwise so as to permit pawl H to function.The mask holds the new setting until changed.

Conversely, if stoppage of shaft B is called for, the mask movescounterclockwi.e until pawl D is lifted out of engagement. Thisoccurs when pin E rises on the lobe of mask K. Size of the lobeon mask K for pin J permits sufficient counterclockwise move-ment to hold both pawls out of engagement with ratchet wheelA.

FIG. 9. The design of the teeth of pilot wheel D keeps. pawl E out ofengagement with ratchet wheel B on alternate oscillations of levers C.

59INTERMITTENT MOTIONS-RATCHET AND GENEVA

and D coincide, and since the pawl is wide enough to engageboth wheels, they have b~n rotated in unison.

The pawl is shown in btokel1line at the end of the subsequentreturn stroke. Here, it is in contact with one tooth of pilotwheel D, but is raised out of contact with the ratchet wheel B.On the next power stroke, the pilot wheel is rotated, but nomotion is transmitted to the ratchet wheel, and therefore nomotion to the driven shaft. At the end of this power stroke,the pilot wheel will come to rest so that the contact face ofthe tooth will coincide with the contact face of one of the teethin the ratchet wheel.

Then, at the end of the next return stroke, the pawl willagain be in position to fall into contact with one tooth on bothwheels. In this way, the required shaft rotation on alternatereciprocations of the drive lever is obtained~ on one powerstroke, both wheels are rotated in unison, and the motion istransmitted to the driven shaft; but on the subsequent powerstroke, the ratchet wheel is not rotated, since the pawl is heldup.

Two spring-loaded plungers G are contained in the ratchetwheel, bearing against the adjacent face of the pilot wheel. Byapplying a l~ght frictional resistance to the pilot wheel, theyprevent any backward rotation due to the drag of the pawl onthe return stroke.

The mechanism will operate regardless of the angular oscilla-tion of levers C, with the limitation that the pawl always mustmove an uneven number of teeth, such as one, three, or five.If the pawl were to move an even number of teeth, such as two,four, or six, the ratchet wheel would be rotated on each oscilla-tion, rather than on alternate oscillations as required. This,in. itself, may be an advantage, in some instances, in that it ispossible to vary the driven-shaft rotation from alternate to con-secutiveaction merely by changing the range of oscillation ofthe levers, to increase or decrease the movement of the ratchetwheel. There must, of course, be an even number of teeth orcontact faces on both the ratchet wheel and the pilot wheel ofthis mechanism.

A

INTERMITTENT MOTIONS - RATCHET AND GENEVA

Ratchet Operates onAlternate Strokes

A dual ratchet-wheel system provides the required rotationof a shaft only on alternate strokes of a reciprocating drive lever.Figure 9 shows the mechanism at the end of a power stroke.

Driven shaft A and ratchet wheel B are k~yed together. Thiswheel has a hub on each side; one side carries one lever C, andthe other side, pilot wheel D and a second lever C. Both leversand the pilot wheel are free on the hubs. Pawl E is pinnedbetween levers C, and is wide enough to engage the teeth ofboth wheels. Reciprocating drive lever F transmits motion toboth levers C.

Teeth of ratchet wheel B are the usual shape, except thatthere is somewhat greater spacing between them. On the otherhand, the teeth of pilot wheel D are a special shape, as shown.

With the levers in the position illustrated, at the end of apower stroke, the pawl has engaged one tooth of ratchetwheel B and rotated it to the limit of lever movement. It willbe noted that the radial contact faces of the teeth of wheels B

58

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Intermittent Motion Derivedfrom Continuously Rotating Shaft

On a wire-forming machine, it was necessary to interrupt thefeed of the wire at certain intervals in the cycle. To accomplishthis, the shaft operating the feeding mechanism was cut at onepoint, and the mechanism illustrated was then installed.

As indicated in Fig. 11, shaft A, the driving member, trans-mits its motion to shaft B, which operates the feeding mech-anism. Keyed to shaft A and rotating with it is a disc C. Thedisc carries a pawl D that is normally held in contact with aratchet E by a spring F. Ratchet E is attached to shaft B.There are eight teeth spaced around the ratchet. A ring G,which is mounted on a stationary part of the machine, is slottedat eight equally spaced points to receive studs carrying rollersH, which contact the tail of the pawl.

For purpose of explanation, the rollers H are numbered 1 to5. As shaft A and disc C rotate in the direction indicated by thearrow, the pawl engages one of the teeth of the ratchet, causingshaft B to rotate in unison until the tail of the pawl contacts

screw M. Driving pin N is pressed into the pawl and passesthrough a short elongated hole in lever G. The purpose of thisconnection is to control tIle swinging movement of the pawl.

As driving gear A rotates in the direction indicated by thearrow, ratchet wheel J is forced to revolve in the same directiondue to the engagement of pawl L. Because driving pin N isconnected with eccentrically mounted lever G, the pin movesin a circular path that is not concentric with shaft B. Thus, asgear A rotates, the pawl is successively drawn closer to, t~enfarther away from, the teeth of the ratchet wheel. In this way,an intermittent motion is imparted to output shaft K.

With slide E located so as to provide an offset equal to dis-tance Z, the ratchet wheel will rotate approximately 45 degreesduring each revolution of gear A. The length of engagementbetw~en the pawl and the ratchet wheel is denoted by numbers1 and 2 in the left-hand view. By adjusting.the position of slideE, the distance traveled by the ratchet wheel can be varied.

Variable Intermittent MovementDerived from Gear Drive

An unusual mechanism which provides intermittent move-ment from a standard gear drive is shown in Fig. 10. Theamount of movement of the driven member is variable withinwide limits and is easily adjusted to any degree of arc.

In this mechanism, driving gear A revolves freely on station-ary shaft B and is retained in position by collar C. Three con-centric bores in gear A contain the elements of the intermittentmovement device. A rectangular flange D, mounted integrallyon shaftB, provides a mounting surface for slide E. Two screwsF, passing through elongated holes in the slide, fasten it to thebase of a deep slot machined across the flange face. Theseholes permit the degree of intermittent movement obtained fromthe mechanism to be varied.

A lever G pivots freely on shoulder-screw H. The screw isthreaded into slide E at a point below the center of gear A asindicated by dimension Z. Ratchet wheel J is keyed to a shoul-der on the end of output shaft K.

Motion is transmitted between gear A and ratchet wheel Jby means of pawl L. The pawl is secured to gear A by shoulder-

FIG. 10. Drive mechanism designed to convert constant rotary motioninto variable intermittent rotary motion.

_________~ ~~~ .....................iiiiiiilliiiiiiililiililiiliiiiiiiiiiiiiiiiiiiliiliiiiii_......


FIG. 11. The pawl D is disengaged from ratchet E by contact with oneof the rollers H.

roller No. 1. The pawl at this and subsequent locations is rep-resented in broken line. In contacting the roller, the pawl isreleased from the ratchet and the motion of shaft B is inter-rupted until the pawl again engages a ratchet tooth.

Assuming for the present that roller No.2 has been removed,the movement of the ratchet again begins when the pawl engagesratchet tooth adjacent to roller No.3. Thus far, shaft A hasrotated 90 degrees, but shaft B has rotated only 45 degrees, theother 45 degrees having been lost by the pawl passing over onetooth of the ratchet. Continued movement of the disc causesthe ratchet to again be rotated until the tail of the pawl contactsroller No.3, when movement is once more interrupted. Withrollers Nos. 1, 3, 4, and 5 positioned as shown, there are four

movements of shaft B and four res~ periods of 45 degrees eachin every rotation of shaft, A. On the machine involved, thiswas the particular intermittent motioh required.

The design,moreover, lends itself to other variations. Assum-ing, for example, that roller No.2 is placed as shown, the pawlis prevented from engaging the ratchet tooth. It will be notedthat this roller has been moved to the upper end of its slot, thepurpose being to operate the pawl before tooth engagement." Ifroller No. 3 were moved to the upper end of its slot, diseng'age-ment would continue until the tooth adjacent to roller No.4is reached, thus producing a rest period of 135

ingenious mechanisms, vol. 4

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