design and fabrication of film frame1
TRANSCRIPT
DESIGN AND FABRICATION OF FILM FRAME BY
GENEVA MECHANISM
PROJECT REPORT
Submitted by
M.Krishnakumar 51608114017
A.Prabakaran 51608114025
K.Sudhakar 51608114304
R.Senthilkumar 51608114401
In partial fulfilment for the award of the degree
Of
BACHELOR OF ENGINEERING
In
MECHANICAL ENGINEERING
THANTHAI PERIYAR GOVERNMENT INSTITUTE OF
TECHNOLOGY, VELLORE-632 002.
ANNA UNIVERSITY: CHENNAI 600 025
APRIL 2011
1
ANNA UNIVERSITY:: CHENNAI 600 025
BONAFIDE CERTIFICATE
Certified that this project report “DESIGN AND FABRICATION
OF FILM FRAME BY GENEVA MECHANISM” is the bonafide work
of ______________________________ who carried out the project work
under my supervision.
HEAD OF THE DEPARTMENT
Thanthai Periyar Government Institute
Of Technology
Vellore -02
SUPERVISOR
Tmt.M.KANTHASHOBA.M.E,
Asst.prof in Mechanical Engineering,
Thanthai Periyar Government Institute
Of Technology
Vellore -02
Project Viva-Voce examination held on…………………….
Internal Examiner External Examiner
ACKNOWLEDGEMENT
2
We are honoured to express thanks to our principal
Dr. R.ELANGOVAN, M.E, Ph.D., who always served as a source of
inspiration and encouraged us throughout the project.
We express our heartfelt thanks to our beloved Head of
the Department Prof.S.RAJKUMAR.M.E., who has contributed
his valuable suggestions, instruction and encouragement in
doing this project.
We have no words to express our thanks to our project
supervisor and faculty advisor Tmt.M.KANTHASHOBA,
M.E.,Assistant Professor for her keen interest, guidance, inspir-
ation and valuable suggestion during the course of our project.
We express our profound gratitude to the Non-teaching
staff of Mechanical Engineering Department for their valuable
suggestions.
TABLE OF CONTENTS
CHAPTER NO.
TITLE PAGE NO.
3
ABSTRACT v
LIST OF FIGURES vi
LIST OF SYMBOLS vii
1 INTRODUCTION 81.1 Geneva Mechanism 81.2 Classification of Geneva mechanism 91.3 Advantages of Geneva Mechanism 111.4 Disadvantages of Geneva Mechanism 11
2 GEOMETRY OF FILM FRAME BY GENEVA MECHANISM
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2.1 Components of Geneva 132.2 Materials 14
3 WORKINF OF FILM FRAME 16
4 DESIGN CALCULATION 194.1 Specifications 194.2 Design Calculation for Cam Drive 194.3 Design calculation For Bearing & Geneva Cross 20
5 FABRICATION PROCEDURE 21
6 CONCLUSION 26
BILL OF MATERIALPHOTOGRAPHS
2728
BIBILIOGRAPHY 33
ABSTRACT
4
Geneva drive or Maltese cross is a indexing mechanism that converts the
continuous motion into intermittent motion. By means of this mechanism the
rotary motion of the driver wheel is converting into intermittent rotary motion
of sprocket. The film passed over the sprocket. Due to the intermittent motion,
the film advanced frame by frame in front of lens for 1/24th second in frequency
of 48 Hz.
LIST OF FIGURES
5
FIGURE NO. TITLE PAGE NO.
1 Geneva Mechanism 8
2 External Geneva Mechanism 9
3 Internal Geneva Mechanism 10
4 Spherical Geneva Mechanism 10
5 Moving Of Film Frame By Geneva Mechanism
12
6 Working Stages Of Geneva Mechan-ism
12
7 Dwell Period 15
8 Working Process 15
9 Intermittent Mechanism 17
10 Ball Bearing 20
11 Project Model 22
LIST OF SYMBOLS
6
Z No. Of Slots R Radius of Geneva Wheel rD Radius of driving wheel r Radius of cam rp radius of pin a Centre distance between Geneva cross & the
centre of cam disc ds Diameter Of Shaft t Slot Width l Slot Length L Shaft Length γ Angle Of Locking Section α Semi Indexing Angle (Driven) β Semi Indexing Angle (Driver) € Gear ratio v Indexing Time Ratio T Time ω1 angular velocity of cam ω2 angular velocity of driven disc
CHAPTER 1
INTRODUCTION
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Geneva mechanism is commonly used indexing mechanism where an
intermittent motion is required.
The Inverse Geneva mechanism, which is a variation of the Geneva
mechanism, is used where the wheel has to rotate in the same Direction as crank. It
requires less radial space and the locking device can be a circular segment attached
to the crank that locks by wiping against a built up rim on the periphery of the
wheel.
The design and fabricating of a conventional Geneva mechanism is gen-
erally simple and inexpensive because there is no specially curved profile on any
of the components except straight lines and circular arcs. However, due to the dis-
continuity of the acceleration at the beginning and ending positions, the shortcom-
ing of using conventional Geneva mechanism is the large impact when the driving
crank engages and disengages with the wheel slot.
1.1 GENEVA MECHANISM
Fig.1. GENEVA MECHANISM In this mechanism, for every turn of the driver wheel A, the driven
wheel B makes a quarter turn. The pin, attached to driver wheel A, moves in the
slots causing the motion of wheel B. The contact between the lower parts of
driver A with the corresponding hollow part of wheel B retains it in position
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when the pin is out of the slot. Wheel A is cut away near the pin as shown, in
order to provide clearance for wheel B as it moves. If one of the slots is closed,
A can make less than one revolution in either direction before the pin strikes the
closed slot and, stopping the motion.
1.2 CLASSIFICATION OF GENEVA MECHANISM
1.2.1 EXTERNAL GENEVA MECHANISM: In this type of mechanism,
the Geneva cross is connected with cam drive externally which is the
most popular and which is represented by the device below fig.
FIG.2. EXTERNAL GENEVA MECHANISM
1.2.2 INTERNAL GENEVA MECHANISM: In this type of mechanism, the
Geneva cross and cam drive are connected internally in the closed
box, which is also common and is illustrated by below fig.
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Fig.3. INTERNAL GENEVA MECHANISM
1.2.3 SPHERICAL GENEVA MECHANISM: In this type of mechanism
the Geneva cross is in spherical shape and cam drive are connected in
externally, which is extremely rare and is illustrated in below fig
Fig.4. SPHERICAL GENEVA MECHANISM
1.3 ADVANTAGES OF GENEVA MECHANISM
i. Geneva mechanism may be the simplest and least Expensive of all intermittent motion mechanisms.
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ii. They come in a wide variety of sizes, ranging from those used in instruments, to those used in machine tools to index spindle carriers weighing several tons.
iii. They have good motion curves characteristics compared to ratchets, but exhibit more “jerk” or instantaneous change in acceleration, than better cam systems
iv. Geneva maintains good control of its load at all Times, since it is provided with locking ring surfaces.
1.4 DISADVANTAGES OF GENEVA MECHANISM
i. The Geneva is not a versatile mechanism.
ii. The ratio of dwell period to motion is also established Once the no of dwells per revolution has been selected.
iii. All Geneva acceleration curves start and end With finite ac-celeration & deceleration.
iv. This means they produce jerk.
CHAPTER 2
GEOMETRY OF FILM FRAME
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Fig.5. GEOMETRY OF FILM FRAME
In the most common arrangement, the driven wheel has four slots and thus ad-
vances for each rotation of the driver wheel by one step of 90° If the driven
wheel has n slots, it advances by 360°/n per full rotation of the drive wheel.
Fig.6. WORKING STAGES OF GENEVA MECHANISM
2.1 COMPONENTS
DRIVER GEARThe input is given manually by handle through this
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Driver gear. It’s a one type of continuous motion.
CAM & PINIt’s main part of this mechanism. Because it converts
The continuous rotary motion into intermittent motion by guiding the Geneva cross along its circular path. Then it converts this motion as require for the movement of film frame.
GENEVA GEAR OR MALTESE CROSSIt’s also take part as vital role in this mechanism.
Because the rotary intermittent motion produced in this part only. Geneva cross has 4 slots in it, pin goes into along circular movement of cam.
SHAFTShaft holds the all parts of mechanism by horizontally
On its threaded portion. There are 2 shafts are provided in this mech-anism.
SPROCKETIt is provided for hold the film frame according to the
rotary intermittent motion of the Geneva cross. Pressure rollers also provided for perfect movement of film frame.
FILM FRAMEIt’s the component which carries the picture on it and to
slide on the sprockets regularly according to the motion.
2.2 MATERIALS
Geneva wheel ---------> M S plate
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Shaft --------------------> M S rod
Bearings ----------------> deep groove ball bearing
Cam drive --------------> aluminium alloy plate
Geneva cross ----------> steel plate
Sprockets ---------------> acrylic fibre
Pressure roller ----------> polymers
Base, stand --------------> steel
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CHAPTER 3
WORKING PRINCIPLE OF FILM FRAME
According to the principle of Geneva mechanism, the input is given
by motor to the driver gear of the arrangement. In the most common arrange-
ment, the driven wheel has four slots and thus advances for each rotation of the
drive wheel by one step of 90°. If the driven wheel has n `slot.
ELEMENTS
I. Film frame
A commonly-held misconception is that film projection is simply
a series of individual frames dragged very quickly past the projector's intense
light source. If a roll of film were merely passed between the light source and
the lens of the projector, all that would be visible on screen would be a continu-
ous blurred series of images sliding from one edge to the other. It is the shutter
that gives the illusion of one full frame being replaced exactly on top of another
full frame.
A rotating petal or gated cylindrical shutter interrupts the emitted light during
the time the film is advanced to the next frame. The viewer does not see the
transition, thus tricking the brain into believing a moving image is on screen.
Modern shutters are designed with a flicker-rate of two times (48 Hz) or even
sometimes three times (72 Hz) the frame rate of the film, so as to reduce the
perception of screen flickering. Higher rate shutters are less light efficient, re-
quiring more powerful light sources for the same light on screen.
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Fig.8.WORKING PROCESSES OF MOVING OF FILM FRAME
Mechanical sequence when image is shown twice and then advanced.
Outer sprockets rotate continuously while the frame advance sprockets are con-
trolled by the mechanism shown.
II. Feed & extraction of sprockets
Smooth wheels with triangular pins called sprockets engage per-
forations punched into one or both edges of the film stock. These serve to set
the pace of film movement through the projector and any associated sound play-
back system
III. Film loop
As with motion picture cameras, the intermittent motion of the
gate requires that there be loops above and below the gate in order to serve as a
buffer between the constant speed enforced by the sprockets above and below
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the gate and the intermittent motion enforced at the gate. Some projectors also
have a sensitive trip pin above the gate to guard against the upper loop becom-
ing too big.
IV. Film gate pressure plate
A spring loaded pressure plate functions to align the film in a
consistent image plane, both flat and perpendicular to the optical axis. It also
provides sufficient drag to prevent film motion during the frame display, while
still allowing free motion under control of the intermittent mechanism. The
plate also has spring-loaded runners to help hold film while in place and ad-
vance it during motion.
V. Intermittent mechanism
Fig.9. INTERMITTENT MECHANISM
The intermittent mechanism can be constructed in different ways. For
smaller gauge projectors (8 mm and 16 mm), a pawl mechanism engages the
film's sprocket hole one side, or holes on each side. This pawl advances only
when the film is to be moved to the next image. As the pawl retreats for the next
cycle it is drawn back and does not engage the film. This is similar to the claw
mechanism in a motion picture camera.
17
In 35 mm and 70 mm projectors, there usually is a special sprocket im-
mediately underneath the pressure plate, known as the intermittent sprocket.
Unlike all the other sprockets in the projector, which run continuously, the inter-
mittent sprocket operates in tandem with the shutter, and only moves while the
shutter is blocking the lamp, so that the motion of the film cannot be seen. The
intermittent movement in these projectors is usually provided by a Geneva
drive, also known as the Maltese cross mechanism.
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Fig. 7. DWELL PERIOD FOR MECHANISM
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CHAPTER 4
DESIGN CALCULATION4.1 SPECIFICATIONS
o Number of Slots, Z= 4
o Radius of Geneva wheel, R = 40 mm
o Distance between centres of Geneva Wheel &driven
wheel, a= 56.5 mm
o Radius of driving Wheel, rd= 60 mm
o Radius of cam, r= 40mm
o Radius of pin, rp=2.5mm
4.2 DESIGN CALCULATION FOR CAM DRIVE
o Angle of locking section, γ= π/2 (Z+2) =270˚
o Semi-indexing angle(driven) α= π/Z = 45˚
o Semi-indexing angle (driver) β= π(Z-2)/(2Z) =45˚
o Gear ratio є=1 for Z=4
o Radius ratio, µ= R/r =1.000
o Indexing time ratio, ν= β/π =0.2500
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4.3 DESIGN CALCULATION FOR BEARING & GENEVA CROSS
FOR GENEVA CROSS:o Slot width, t = 5 mm
o Length of Slot, l= 25 mm
o Shaft diameter, ds= 15 mm
o Thickness, b = 5m
FOR BEARINGS:
Fig.10
Here we used ball bearings.o Bearing of basic design no. (SKF) = 6000
o Inner diameter of bearing, d = 10 mm
o Outer diameter of bearing, D = 26 mm
o Static capacity, Co= 19 KN
o Dynamic capacity, C = 36 KN
o Assume :
Time T=0.166 sec
Speed N=360 rpm (N=60/T)
Angular velocity of driving crank ω1= 2πN/60 =37.7rad/sec Angular velocity of driven disc
ω2 =λ/ (1-λ) ω =91.012rad/sec
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CHAPTER 5
FABRICATING PROCEDURE
GENEVA WHEEL DESIGN The basic design criteria of a Geneva wheel is that the centrelines of the
slot and crank are mutually perpendicular at engagement and at Disengagement.
The crank, which usually rotates at a uniform angular Velocity carries a roller to
engage with the slots. During one revolution of the crank the Geneva wheel ro-
tates a fractional part of the revolution, the amount of which is dependent upon
the number of slots. The Circular segment attached to the crank effectively
locks the wheel Against rotation when the roller is not in engagement and also
positions the wheel for correct engagement of the roller with the next slot.
The design of the Geneva mechanism is initiated by specifying the Crank
radius, the roller diameter and the number of slots. At least 3 slots Are neces-
sary but most problems can be solved with wheels having from 4 to 12 slots.
The angle (β) is half the angle subtended by adjacent slots I.e. where n is the
number of slots in the wheel. Then, defining r2 as the crank radius we have,
Where c is the centre distance. Note that the actual Geneva wheel radius is more
than that which would be obtained by a zero-diameter roller. This is due to the
difference between the sin and the tangent of the angle subtended by the roller,
measured from the wheel centre.
The final step in the design process is to choose a convenient radius for
the circular pert of the Geneva wheel, which meshes with the input wheel lock-
ing the Geneva wheel.
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Fig.11. GENEVA WHEEL DESIGN
A ball bearing used for fix the shaft on stand on base. The bearing se-
lected according to the diameter of the shaft. The shaft was threaded on its both
ends. The driver gear And cam are inserted to the shaft on threaded end. Then
the Maltese cross also fitted with sprockets on its end. Sprockets are designed
according to the film frame width. Pressure rollers are provided for regular
movement of film frame. A handle is fitted to the driver gear manual input. Fi-
nally all these arrangements are fit on the base.
Fabricating process
The Geneva Wheel Mechanism, which was manufactured, had 9 parts.
They were the two Geneva wheel pieces, two circular locking slots, a Crank
Pin, a spacer plate, two Shaft Pins to carry the Geneva wheel and the input shaft
and a Base plate.
The Geneva wheel was manufactured by turning a 10 mm thick MS Plate
to the external dimensions. Then the profile was punch marked on the plate. The
plate was put in a indexing milling machine and the Profile was milled to the re-
quired dimensions including the cutting of slots.
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The locking wheel was also punch marked and milled to the required di-
mensions. The crank pin was made by gas cutting the required shape and the
roller pin was fitted at the required distance of 50 mm from the crank centre. All
the other components were turned to the required dimensions. The Base plate
as cut out of a 4 mm thick transparent acrylic plate. The holes for carrying the
shafts were then drilled by using a 16mm drill taking care of the distance
between the centres.
Geneva wheel analysis
The Analysis of Geneva wheel is done by drawing the position of the pin
and the Geneva wheel at the required position. The position of the Geneva
wheel is given by, Differentiating this with respect to time we get, Differentiat-
ing again with respect time we get, These equations are valid only in the region
– (90-b) to (90-b) of the input crank angle. At all other angles the Geneva wheel
is stationary and hence both angular velocity and acceleration are zero. Both the
angular and acceleration are plotted as a function of input angle in the accompa-
nying plot for an input angular velocity of 1 rad/sec.
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APPLICATIONS & USES
STEPPER MECHANICAL WATCHES PLOTTERS CNC MACHINE IRON RING CLOCK
Modern film projectors may also use an electronically controlled index-
ing mechanism or stepper motor, which allows for fast-forwarding the
film.
Geneva wheels having the form of the driven wheel were also used in
mechanical watches, but not in a drive, rather to limit the tension of the
spring, such that it would operate only in the range where its elastic force
is nearly linear.
Geneva drive include the pen change mechanism in plotters, automated
sampling devices
Indexing tables in assembly lines, tool changers for CNC machines, and
so on.
The Iron Ring Clock uses a Geneva mechanism to provide intermittent
motion to one of its rings.
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MERITS
o The sequence of slides can be altered to meet specific needs.
o May be adopted to group or to individual user
o One can control the length of time each one is shown to allow for explan-
ation, questions from the audience, or discussion of the problem at hand.
The audience will focus its attention on the one slide being shown.
o Easily handled, stored and rearranged for various uses.
o The room need not be extremely dark for projection.
DEMERITS
o The fixed sequence does not permit easy flexibility.
o Can get out of sequence and be projected incorrectly if slides are handled
individually use of the never automatic projectors will alleviate this prob-
lem as the sequence can be worked out and loaded into the special car
bridge before presentation.
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CHAPTER 6
CONCLUSION
Geneva drive indexing mechanism converts the continuous motion of
the driver wheel into intermittent rotary motion of the sprocket. According to
the film length, the cam wheel diameter was chosen. Cam with pin
arrangement integrated with Geneva drive. Input shaft having driver wheel at
one end and cam drive at the other end. Geneva drive and sprocket are mounted
on the output shaft. By cam with Geneva drive arrangement the continuous
motion of the driver wheel converts into intermittent motion of sprocket. Due to
sprocket rotation the film advances frame by frame in front of the lens. Thus the
slide show of the film was obtained successfully.
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BILL OF MATERIALS:
Driver wheel ---------------------> ₨ 150/-
Cam drive ---------------------> ₨ 250/-
Geneva cross --------------------> ₨ 200/-
Sprockets ------------------------> ₨ 150/-
Shafts ----------------------------> ₨ 200/-
Bearings -------------------------> ₨ 100/-
Base & stand --------------------> ₨ 300/-
Bolts & nuts ---------------------> ₨ 50/-
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PHOTOGRAPHS
29
MOVIE PROJECTOR
KODAK 35mm SLIDEPROJECTOR
AUTOMATED SLIDEPROJECTOR
30
FILM SLIDE PROJECTOR
SLIDE PROJECTOR
31
LCD PROJECTOR
32
KODAK FILM PROJECTOR
33
BIBLIOGRAPHY
C.Y. Cheng, Y. Lin, Improving dynamic performance of the Geneva mechanism using non-linear spring elements, Mechan-ism and Machine Theory 30(1995) 119–129.
E.A. Dijksman, Jerk-free Geneva wheel driving, Journal of Mechanisms 1 (1966) 235–283.
E.A. Fenton, Geneva mechanisms connected in series, ASME Journal of Engineering for Industry 97 (1975) 603–608.
E.A. Sadek, J.L. Lloyd, M.R. Smith, A new design of Geneva drive to reduce shock loading, Mechanism and Machine Theory 25 (1990) 589–595.
F.L. Litvinov, Gear Geometry and Applied Theory, Prentice-Hall, New Jersey, 1994.Fig. 12. Embodiment of the design and operation sequence.
F.L. Litvinov, Theory of Gearing, NASA, Washington, DC, 1989.
G. Figliolini, J. Angeles, Synthesis of conjugate Geneva mech-anisms with curved slots, Mechanism and Machine Theory 37 (2002) 1043–1061.
H.P. Lee, Design of a Geneva mechanism with curved slots us-ing parametric polynomials, Mechanism and Machine Theory 33 (3) (1998) 321–329.
34
J.J. Lee, K.F. Huang, Geometry analysis and optimal design of Geneva mechanisms with curved slots, Journal of Mechanical Engineering Science, Proceedings of the Institution of Mechan-ical Engineers, Part C 218 (4) (2004) 449–4540–45.
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