GB1564331A - Motion picture projector - Google Patents

Description

(54) MOTION PICTURE PROJECTOR (71) I, JAYADEWA MAHODERA SWAY- THEN MUTHUKUDA, a citizen of Sri Lanka, at No. 11, Galle Face Terrace, Colombo 3, Sri Lanka, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to motion picture projectors and in particular to the film advancing means for use in them. Primarily this invention is directed towards improvement of the mechanism controlling the advancement of film in cinematograph projectors and enables the user to operate the apparatus at low rates of speed whenever "slow motion" effect is required, i.e. at low rates of frames per second. Various studies of activity such as work motion studies, scientific movement analyses, checking the progress of various processes and experiments, investagations on athletic events, fault finding & c., may be accomplished without using much valuable long lengths of film.

Still scenes, landscapes and the like may be exposed for very brief periods using only a fraction of the film customarily wasted for this purpose and the duration of time can be extended by shifting the projector in to any desired slow speed when the still scene appears on screen.

Conventional movie projectors have a minimum frames per second projection rate below which the picture projected on a screen is of inferior quality because it becomes the subject of the phenomenon commonly known as the "flicker". In the intermittent advancement of exposed photographic film through a projector, a shutter blade blacks out the projected light beam and thus the projection screen gets dark during the time the film advances past the gate through which the light beam travels on to screen. These black outs are hardly noticeable by the human eye at speeds of or above 16 frames per second (the usual amateur speed) because, the viewers perceptive image of the projected picture continues for a short time interval approximately 1/14th of a second after the screen is darkened. During this short time this perceptive image gradually decays to a total darkness.

Hence the poor quality of the flicker effect entirely depends on the rate of interruptions or blacking out of the screen. The present invention improves this effect by having a constant interruption rate for example of 96 per second irrespective of the film advancement rate. This particular rate brings down the time of screen darkness to a mere 1/96 of a second and avoids the flicker effect almost completely. The usual time at which the flicker gets minimised is about 1/48 second commonly used in amateur equipment.

A motion picture projector according to the present invention incorporates a mechanism for forward or reverse movement of a cine film through a projection gate wherein said mechanism comprises a film aperture engaging finger carried by a shuttle member acted upon by (a) a rotary cam rotating at constant speed in synchronism with a rotary shutter to produce the longitudinal reciprocation of the shuttle member and (b) a lever to produce the in & out transverse reciprocation of the shuttle member, the lever amplifying the movement of a cam follower which makes contact with a selected track of a multi-track cam belt moving in synchronism with the rotary shutter, each track corresponding to a desired film movement rate.

An apparatus incorporating the film advancing mechanism of the present invention is capable of advancing films at preprogrammed extremely low frames per second rates absolutely without any noticeable flicker effect, such as a single frame per second or even lower down to still projection, both in forward as well as in reverse directions. Also this invention allows a very wide range of speeds or rates of projection including a maximum 96 frames per second to be used for special scientific or biological growth investigations, to get over a lull section of film to the viewer in double quick time while viewing is in progress and for fast rewind of the film. This wide range of speeds are obtainable with this machine without any undesriable change of operating hum of the machine.

Hence this projector achieves slow or fast motion projection in forward or reverse directions at any preprogrammed rate, as described with a film in conventional uniform start stop cycles, but which includes means for interruping in a regular pattern the intermittent film advancement during the stop portion of the predetermined cycles.

The time period that the film is stopped and the image projected on the screen is lengthened while the time period of the film advancement, during which the screen is darkened remains the same.

A motion picture projector in accordance with the present invention will now be described fully with reference to Figs. 1 - 3 accompanying this complete specification and Figs. 4 - 8 accompanying the provisional specification, wherein:-- Fig. 1 shows a side elevation of the projector which embodies the present invention; Fig. 2 is a fragmentary section along lines 3-3 in Fig. 3; Fig.

3 is a plan of the interior mechanism of the projector with the belt cam employed from the pulleys; Fig. 4 is a detailed rear view of the aperture plate and the connected framer mechanism to adjust aperture size and position to suit different types of films e.g., super 8 or normal 8 m.m films; Fig. 5 is a section about line 5-5 in Fig. 4; Fig.

6 is a sectional plan about line 4-4 in Fig.

4; Fig. 7 gives a fragmentary plan of the belt cam surface showing details or recesses and projections; and Fig. 8 is a line diagram of the arrangement of the fixed and adjustable pulleys and belt drive.

A typical embodiment of the improved intermittent film advance mechanism of this invention is now described with reference to a projector 6 shown in Fig. 1 which has a film gate assembly 7, and a lens system 8. The path of the film 9 is shown in broken line in Fig. 1. The film gate 7 swings open about a pivot 15 in Fig. 6. The aperture plate 10 is provided with adjustable projection aperture 11 and film moving finger slot 12. This arrangement allows the gate to be cleaned conveniently. A lamp 13 inside the projector housing as shown in Fig. 3 projects a beam of light, through the aperture plate 10, the film 9 and the system of lenses 8, to give a clear image of the film frame on the screen. The film 9 is held against the aperture plate 10 by the pressure plate 14 attached to the lens system pivotally mounted at 15. The pressure plate 14 is suitably apertured to coincide with aperture 11 and slot 12.

This projector provides no drive sprockets and falls within amateur projection equipment commonly known as sprocketless projectors where the film is pulled directly from the supply spool and fed in to the take up spool by means of the pulldown finger. If this pulldown mechanism were to be used in a conventional sprocket type projector, however, means should be provided to change the sprocket feed rate in exact synchronism with that of the change in the pulldown rate in order to avoid a loss of film loop above the pulldown finger. This type of mechanism to drive the sprockets will be complicated and expensive. Besides, a sprocket is not essential as the type of film used in an amateur equipment is so light, it does not essentially require an extra sprocket feeder. However, if such an expensive system is to be adopted in this projector it will fall outside the price range of amateur projection equipment.

In Fig. 3 the film engaging finger 16 extending through the slot 12 engages in the sprocket holes of the film 9 to advance the film, frame by frame in front of the projection aperture 11. This finger 16 projects from an extending arm 17 of a shuttle plate 18. The rotating cam 19 together with the belt surface cam 20 in Fig. 2 and the associated mechanism described below cooperate to move the plate and the attached finger 16, in film advancing movement.

A shutter 21 rotates about an axis perpendicular to the main drive shaft 22 on the same plane by means of a suitable pair of metre gear wheels 23 as shown in Fig. 3.

The cam 19, a driven pulley 24, a shuttle plate guide wheel 25 and the shutter driving gear 23 are mounted on a shaft 22 supported on bearings 28 and 29. This shaft 22 has a splined end which carries a shifter sleeve 30. The shifter 30 in turn has a crank extention piece fitted on it. This has two projecting pins 31 and 31a to engage with a shaft 33 through a circular slanted groove 32b and a hole 32a in a wheel 32 fitted on the same. The shifter has two operative positions along the axis of the shaft 22. In one position the pin 31 engages in the hole 32a radially spaced in the circular slanted groove 32b to lead pin 31 in to same instantaneously and causes shaft 33 to rotate at the same speed as shaft 22. In the next position the pin 31a spaced 180 degrees from pin 31 engages with the hole 32a similarly after sliding in the slanted groove and causes the shaft 33 to rotate at the same speed as shaft 22 on bearing 34 & 35. Hence this arrangement allows the shaft 22 to be advanced by 180 degrees with respect to the shaft 33 and this effect is used to reverse the film flow across the gate 10 instantaneously. The 180 degree turn gets the cam 19 to a position such that the finger 16 is engaged with the film perforations at the end of the pull down stroke of the same and is disengaged with the film perforations at the end of the upward stroke of the finger instead of vice versa as in the case for forward projection. The shifter sleeve 30 effecting this change is moved to either of the two positions by a bar 75 fitted in a groove 76 in the shifter and carried on a cranked and hinged rod 77, the end of which carries the speed direction change knob 77a for the convenient operation of reverse and forward film movement. As this is quite independent of the shuttle movements this invention allows the same series of speeds of projection on both forward as well as in reverse directions.

The shafts 33 & 22 turn in bearings on the supports 36, 37 & 38 attached to the projector housing as shown in Fig. 3. The pulley 24 is suitably aligned and connected by a rubber belt 41 fitted on the driving pulley 39 of the motor 40. The motor 40 can be of a conventional type such as a two pole or a shaded pole motor. The normal operating speed of commercially available small motors is approximately 3250 r.p.m, or 50 cycles per second under normal load conditions. As such the diameter ratios of the two pulleys 39 & 24 are so selected in order to get a rate of 96 revolutions per second to the shaft 22 or any other suitable rate on which the dimensions of the belt surface cam are programmed. For this high speed shaft helical gears are not essentially required as all gear wheels will have a pitch line speed of only around 600 feet per minute.

The shuttle plate 18 follows cams 19 and 20. It co-operates with cam 19 to reciprocate the finger up and down in the slot 12 in Fig. 4, or in other words along the line of sprocket holes in film 9 lying against the finger in to the sprocket holes and out of them systematically. The shuttle plate 18 is slidably pivotted at its rear end to the shaft 42 which is only free to move horizontally on the rectangular sleeves 43 & 44 fixed on the projector housing. The plate 18 has an interior recess 45 at its front end as seen in Fig. 2, in which the cam 19 is eccentrically mounted and disposed. Thin plates 46 & 47 bent at right angles from the top and bottom of the recess 45 from the cam engaging surfaces. The single disc circular arc, positive return cam 19 with a peripheral camming surface that is constantly engaged with both plates 46 & 47 through-out its period of rotation is ideally suited for this application. This cam 19 provides the plate 18 to move upwards during 120 degrees of its rotation followed by a dwell for the next 60 degrees, then a downward movement during another 120 degree followed by a further dwell for the final 60 degrees. The belt cam surface 20 is so designed and programmed such that the in and out movement is imparted to the shuttle 18 only during these 60 degree dwells of the cam 19.

The shutter 21 which turns at the same speed as the cam 19 through metre gears on shaft 91 in bearings 92 & 93 has a single blade which blacks out the screen during the fingers downward frame advancing movements. This shutter is made to black out the screen at the rate at which the cam 19 rotates irrespective of the film advance rate.

As such it gives a picture interruption rate of 96 per second which is the speed of shaft 22. This is double the rate of 48 interruptions per second at which the human eye hardly notices the phenomenon of flicker through persistence of vision. The metre gears could be replaced with a suitable pair of spirals if one desires. The shaft 91 also carries a coolin fan 19 for the integral reflector lamp 13.

Because of the constantly run high speed shutter this system completely avoids "flicker" irrespective of the rate of film advancement whether fast, slow or even still.

This leads to a sharply defined picture image clearness on the screen or a high degree of picture quality.

A novel feature of this invention is the process of obtaining the in & out movement of the finger at the preprogrammed rates by means of the synchronous belt surface cam 20 clearly shown in Fig. 7. This cam has a series of programmed recesses and projections spaced in such a way so as to allow the follower 48 in Fig. 2 pivotally mounted at 48a on the vertical member 49 slidably pivotted on the shaft 50 to impart a preprogrammed horizontal, amplified in & out reciprocation to the shuttle plate 18 through shaft 42, slidably connected to the member 49 at its wide upper end. These recesses on the belt cam are systematically elongated leaving projections on the surface on several parallel planes spaced across the width of the surface as shown in Fig. 7, so as to impart an in & out reciprocation through its follower 48 and connected lever mechanism to the shuttle plate 18, at 1/2(n-1) times the speed rate of cam 19, where 'n' is an integer greater than 1. That is, the camming effect of 20 is programmed on several parallel planes across the belt cam so that at each plane the follower is skipping (2n-1) rotations of the rotating cam 19.

Hence the film can be advanced at a fast speed of 96 frames per second, being the full speed of cam 19 when the follower 48 is made to act on every rotation of the same.

This type of a high speed is quite useful to get over any unwanted section of the film in double quick time or for quick rewind of the film in reverse direction. The length of a recess or a projection depends on the gear ratio between rotating cam 19 and the pulleys 51 & 52 and their peripheral speeds i.e, speed of belt cam. Also the linear dimension and the spacings of the recesses is in direct proportion to the moving and dwell periods of the rotary cam action on the shuttle member. The pulleys 51 & 52 are synchronous belt drives and have teeth to move the belt 20 at a constant ratio such as 1:20 with the shaft 22. By this means it is possible to achieve any desired rate from a maximum down to still projection with a pre-programmed series of recesses on the belt cam. It has been found that a number of ten differently programmed speeds per belt to be a convenient system to be adopted on a single belt of approximate width of 3 centimetres. This belt is positioned in the projector as shown in Figs. 3 & 8 clear of other mechanisms such that it could be con veniently changed even by an unskilled per son with another belt having a different series of speed programmes to suit his investi gation work or the like.

This novel invention allows the film spools to be driven by means of the same belt cam passing over suitably spaced pulleys 53, 54, 55 & 56 as shown in Fig. 8. The system allows convenient fitting of belt cams of different lengths for the required film speed programmes by having the adjustable floater pulley 53 (smooth faced) to take up any shortening or lengthening effects of the belt owing to change of programmes. The pulley 53 is a smooth surfaced one as it bears the smooth camming side and not the toothed side of the belt 20. This floater pulley 53 is mounted in a long narrow slot 57 on the rear side of the projector housing, as shown in Fig. 8, so that its position can be slidably adjusted with suitable means conveniently.

The recesses on the belt surface as shown in Fig. 7 are so shaped and edges curved in order to allow the ball ended follower 48 to be shifted horizontally from one plane to another without much resistence. Also in order to make belt replacement convenient, the follower 48 is pivoted in a groove 48b in Fig. 2 such that it can be turned upwards about the pivot 48a to release the belt from pulley 51.

The belt cam 20 is made with glass fibre chords instead of rayon or polyester in order to achieve stretchlessness and an excellent flex life. The belt is protected from friction by means of a thin layer of Neoprene backing. The teeth of the belt is of Neoprene of a harder construction and is accurately spaced and formed to engage correctly with mating groves of the pulleys 51, 52, 54. 55 & 56. In addition a coat of nylon fabric of low coefficient of friction to cover both the contact surfaces of the cam surface and teeth is provided to avoid wear. As a belt constructed to this specification is very flexible and capable of running on small pulleys, it can be very safely used on this projector at the required speeds. The floater pulleys 53 & 56 are so spaced and aligned in this projector such that at least six or more teeth are always in mesh with the pulleys 51 & 52 which drive the belt cam. This type of synchronous drive does not impart a chordal rise and fall in the pitch line of the belt giving rise to a quite, vibrationless drive transmitting the reciprocations to its follower 48 with a high degree of accuracy and precision expected from it.

The pulleys 51 & 52 have flanges in order to disallow any possible side shift of the belt cam during its motion. The follower is positioned on top of the pulley 51 giving a radial contact and thus a maximum effect of the micro cam action amplified by lever member 49 can be obtained. The pulleys 51 & 52 in Fig. 2 are connected through gears 65 & 66 to floater compound gears 57 & 58 mounted on fixed shafts 59 & 60 respectively, and through floater gears 61 & 62 on fixed shafts 63 & 64. This system rotates the pulleys 51 and 52 at the same speed in synchronism. The compound floater gear 58 is connected to gear 67 fixed on the driving shaft 33 run on bearings 34 & 35 in Fig. 3. A ratio of speed 1:9 between shaft 68 in Fig. 3 and main driving shaft 22 together with a belt pitch diameter of 33 m.m produces a good linear dimension for the recesses on the belt cam.

The smooth horizontal shift of the follower 48 is obtained by means of a drum 69 carried on a smooth surfaced worm gear 69a having two spiral teeth 69b diametrically opposite to each other on its periphery as shown in Fig. 2. The drum slidably fitting on the worm 69a carries two spiral grooves on its inner surface on which the worm spiral teeth act to move the drum 69 horizontally. The outer surface of the drum 69 carries two brackets 70 fitted on to it.

These brackets 70 have holes to go into the axle 50 just on either side of the member 49 slidable on same. This arrangement allows the horiontal movement of the member 49 on shaft 50. The worm is mounted on a shaft 71, which is directly taken out of the projector housing through sleeves 72 & 73, fixed on same. The shaft 71 can be turned to shift drum 69 which carries with it the follower 48, by means of a speed selector knob 74 at the front control panel. The spiral groove on the drum 69 is so designed in order to shift the follower 48 associated with it, fully across the width of the belt cam touching upon all cam programmes on same. This enables the operator to touch upon all the programmed speeds of the machine with a single turn of the knob 74.

The different speed positions corresponding to the various programme planes can be marked on the housing below and around the control knob 74.

The novel spool drives of this machine are operated by the same belt cam running through synchronous pulleys 54 & 55 as shown in Fig. 8. The details of this mechanism is as shown in Fig. 3. The pulley 54 for front spool drive and the pulley 55 for rear spool drive fitted on shafts 78 & 79 turn on racers 784, 78b, and 79a and 79b provided on suitable brackets 80, 80 fixed on the projector housing. As the drive mechanism is common to both front and rear spools, their operation is explained be low only in respect of the front spool drive means. The shaft 78 has a wheel 81 fitted at its end. The spool shaft 83 is mounted on racers 85 and 84 fitted on a bracket 86 and the projector housing respectively. The two shafts 78 & 83 are aligned on the same axis and can be connected together slidably through clutch action of the spring 82 fitted on the face of a shifter sleeve 88 against wheel 81. The shifter 88 is slidably mounted on the shaft 83 about a key 87 engaged in a groove provided in same. It can be operated at two positions on the shaft 83 by a cranked and a pivoted lever 89 which is rotatable in an axis perpendicular to shaft 83 about the pivot 89a. This lever 89 is connected to a projecting arm of the lever 77 used for reversing the film movement.

The other end of the lever 89 is also cranked in order to move the shifter for the rear spool drive mechanism in a similar manner but in opposite direction, as the idea is to impart clutch action to one spool while releasing the other spool and vice versa.

At the position shown in Fig. 3, the clutch at front spool drive is engaged so that the shaft 83 and the front spool turns through clutch action or through the friction developed by the spring 82 on the face of the wheel 81. This turning effect is used to wind up the film on the front spool when the machine runs in the reverse direction of projection. When the pivoted lever 89 is shifted by the lever arm 77 to its forward direction of projection position the friction at the shifter sleeve 88 gets relieved by disengagement of the spring 82. At the same time the spring at the rear spool drive gets engaged with its friction shifter causing the rear spool shaft to turn through gear 79d and wind up the film release by the film advancing finger 16. By this means and the arrangement of levers it is possible to control all these three functions with a single control lever arm and knob 774 connected to the pivoted bar 77 and taken out of the projector housing to the outer control panel.

As such this invention allows front or rear take up spools to be actively driven only when film winding is required on them, leav ing either of them released to feed the film freely to the finger 16 at the time it requires to pull the film from them. This is particularly important as this system is meant for amateur sprocketless projectors.

The optical system of this projector as shown in Fig. 3 consists of the lens system 8 fitted along the axis of the light beam from lamp 13 through the film gate. The lamp 13 is of the integral reflector type with ellipsoidal reflector surfaces avoiding the re quirement of a light condenser. The film gate 11 is spaced at the second focus of the ellipsoidal reflector of the lamp 13. This lamp is cooled by means of a fan 90 fitted on the shaft 91 carrying the shutter 21 and metre gear 23. The draught of air thrown out of this fan 90 at 96 revelutions per second is adequate to circulate around lamp 13 and cool it. The current of air from the fan 90 also runs past slots 944 & 94b in Fig. 3 to cool the film at the gate exposed to the heat and light from the lamp 13. The plate 94 of the projector housing acts as an air current deflector making the air currents to spiral round the lamp 13 before its way out of the housing from the top. During very slow or still projection of the film this cooling effect on film is insufficient to avoid buckling of the film. Therefore this invention provides a heat filter glass 95 fitted on plate 94, in the path of the beam of light before it reaches the film. The unavoidable small fraction of light loss due to this heat filter is disregarded for the safety of the film. Hence this invention allows adequate means for protecting the film against overheating.

This invention also allows operation of two types of film with different film perforations (e.g. Super 8/ Normal 8). This effect was not taken up before as it could have led to a confusion in the explanation. This effect is achieved by having an additional set of shuttle 18 and cam 19 parallel to the first, on the same shaft, position axially shifted. The additional cam required forms a single unit with cam 19. It has slightly a smaller eccentricity to give a vertical reciprocation to a finger 16s of different dimensions, shown in Fig. 4 placed in a suitable position which is two frames beyond the picture aperture 11, in the direction of the film travel. This provides two different positions for the fingers 16 & 164 as the perforations with respect to the picture frame in the two types of film differs. The angular positions of the two cams of the double cam 19 with respect to the shaft 22 is same. The guide wheel 25a keeps the plate 18 containing additional camming surfaces shown in Fig. 3 in one plane while it moves. The in and out movement of the fingers will be given to either of these at a time by the shifter sleeve 96 carrying fixed pulleys 97a and 97b fitted on to it. This shifter is slidably mounted on shaft 42 carrying a key 98 slidably fitting to the groove 99. The plates 18 & 18a have rectangular openings 100v and lOOb in the blocks 100 fitted at their ends so that the plates do not get any action transmitted on them by the horizontal reciprocation of the shaft 42 unless the shifter engages the key 97a or 97b in the openings 100u or 100 b respectively for the in & out movement of either of them. By this means either the plate 18 or plate 1 8a is given the in & out movement at a time, by a shift of the shifter sleeve 96. This shift is carried out by means of the cranked lever 101 acting in the shifter groove 102 about a pivot 103.

This cranked lever is taken out of the housing so that the operator can manupulate same conveniently by the knob 104. In addition this cranked lever prevents the finger 16 or 1 6a from engaging in the film perforations by means of the extending cranked bars 105 & 106 by successively acting on the end vertical projections 107 & 107s in Fig. 2 of the plates 18 & 18Q respectively. They hold either of the vertical projections 107 or 107a back, when the other operates in the in & out movements.

The smooth faced wheel 108 fitted on the shaft 42 acts as a guide to the plate 18a. The wheels 42a fixes the position of shaft 42 allowing adjustment.

The picture frame size of the super 8 film is wider than that of the normal 8 film frame. Therefore a gate mask for the normal 8 should be narrower. This is achieved in this invention by a cranked and pivoted lever mechanism 109 pivotally connected to arm 119 of lever 101 at one end as shown in Fig. 3. This system is so arranged to slide the gate mask 110, sandwiched and slid ably fitted in a narrow groove within aperture plate 10 and free to move only horizontally as shown in Fig. 4. By this means the vertical arm 111 of the gate mask covers the extra amount not required by the normal 8 film at the film gate avoiding any possible projection of its perforations. All this activity is done with a single movement of the lever knob 104 by the operator. Hence this invention provides means for accommodating two different types of films yet making all available and above explained variation of speeds possible on both types equally well.

The framing or the adjustment of the film gate position vertically involving a shift of 0.64 m.m upwards or downwards according to the B.S 3475 is achieved as shown in the Figs. 4, 5 & 6 of the provisional drawings read in conjunction with this specification, by a suitable circular cam means 112 with the required micro-eccentricity, acting on two camming surfaces 113 & 114 connected to a plate 115 consisting correctly spaced two horizontal and one vertical sharp edges 116, 117, & 118 respectively forming the rectangular opening of the gate mask slidably fitted within the aperture plate 10.

The cam 112 is directly turned from outside the housing to effect any vertical movement or shift of the aperture required with respect to the position of the film and accomplishes the process of framing. The edges 116, 117, 118 & 111 of the two plates forming the gate mask are chamfered as shown in Fig. 6 to give a sharp edge to the resu

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. carrying fixed pulleys 97a and 97b fitted on to it. This shifter is slidably mounted on shaft 42 carrying a key 98 slidably fitting to the groove 99. The plates 18 & 18a have rectangular openings 100v and lOOb in the blocks 100 fitted at their ends so that the plates do not get any action transmitted on them by the horizontal reciprocation of the shaft 42 unless the shifter engages the key 97a or 97b in the openings 100u or 100 b respectively for the in & out movement of either of them. By this means either the plate 18 or plate 1 8a is given the in & out movement at a time, by a shift of the shifter sleeve 96. This shift is carried out by means of the cranked lever 101 acting in the shifter groove 102 about a pivot 103. This cranked lever is taken out of the housing so that the operator can manupulate same conveniently by the knob 104. In addition this cranked lever prevents the finger 16 or 1 6a from engaging in the film perforations by means of the extending cranked bars 105 & 106 by successively acting on the end vertical projections 107 & 107s in Fig. 2 of the plates 18 & 18Q respectively. They hold either of the vertical projections 107 or 107a back, when the other operates in the in & out movements. The smooth faced wheel 108 fitted on the shaft 42 acts as a guide to the plate 18a. The wheels 42a fixes the position of shaft 42 allowing adjustment. The picture frame size of the super 8 film is wider than that of the normal 8 film frame. Therefore a gate mask for the normal 8 should be narrower. This is achieved in this invention by a cranked and pivoted lever mechanism 109 pivotally connected to arm 119 of lever 101 at one end as shown in Fig. 3. This system is so arranged to slide the gate mask 110, sandwiched and slid ably fitted in a narrow groove within aperture plate 10 and free to move only horizontally as shown in Fig. 4. By this means the vertical arm 111 of the gate mask covers the extra amount not required by the normal 8 film at the film gate avoiding any possible projection of its perforations. All this activity is done with a single movement of the lever knob 104 by the operator. Hence this invention provides means for accommodating two different types of films yet making all available and above explained variation of speeds possible on both types equally well. The framing or the adjustment of the film gate position vertically involving a shift of 0.64 m.m upwards or downwards according to the B.S 3475 is achieved as shown in the Figs. 4, 5 & 6 of the provisional drawings read in conjunction with this specification, by a suitable circular cam means 112 with the required micro-eccentricity, acting on two camming surfaces 113 & 114 connected to a plate 115 consisting correctly spaced two horizontal and one vertical sharp edges 116, 117, & 118 respectively forming the rectangular opening of the gate mask slidably fitted within the aperture plate 10. The cam 112 is directly turned from outside the housing to effect any vertical movement or shift of the aperture required with respect to the position of the film and accomplishes the process of framing. The edges 116, 117, 118 & 111 of the two plates forming the gate mask are chamfered as shown in Fig. 6 to give a sharp edge to the resulting gate mask in a single plane. This is important as the gate mask aperture defines the area of the film depicted on screen. WHAT I CLAIM IS:

1. A motion picture projector incorporating a mechanism for forward or reverse movement of a cine film through a projector gate wherein said mechanism comprises a film aperture engaging finger carried by a shuttle member acted upon by (a) a rotary cam rotating at constant speed in synchronism with a rotary shutter to produce the longitudinal reciprocation of the shuttle member and (b) a lever to produce the in & out transverse reciprocation of the shuttle member, the lever amplifying the movement of a cam follower which makes contact with a selected track of a multi-track cam belt moving in synchronism with the rotary shutter, each track corresponding to a desired film movement rate.

2. A cine projector as in Claim 1, wherein the mechanism comprises two shuttle members and film fingers for alternative use with two different types of film.

3. A cine projector as claimed in Claim 1 or 2 wherein a synchronous belt cam for the movement of film fingers runs on fixed and adjustable pulleys located clear of other mechanisms for convenient replacement with similar belts to achieve many other sets of speed programmes.

4. A cine projector as claimed in Claim 1, 2, or 3 wherein the synchronous belt cam drives the front and rear film spools.

5. A cine projector as claimed in Claim 1, 2, 3, or 4 wherein the belt cam contains surfacial recesses whose linear dimensions and spacings are in direct proportion to the moving and dwell periods of the single disc circular are positive return rotary cam action on the shuttle member.

6. A cine projector as claimed in Claim 5 wherein the equi-spaced recesses on the belt cam are arranged on tracks parallel to each other and the belt cam is located on a plane parallel to the optical axis of the provector.

7. A cine projector as claimed in Claim 1 or any Claim appended thereto wherein the belt cam follower is pivoted on a lever

slidable on a horizontal shaft amplifying the frequency transmitted, and is manipulated with a suitably arranged circular drum with internal spiral grooves to engage on suitable gear teeth on a worm to produce micro-movements whereby the said lever causes the cam follower to engage selectively on different tracks on belt cam.

8. A cine projector as in Claim 7 wherein the belt cam follower means makes contact with the belt cam radially and over a belt cam supporter or a driver pulley.

9. A cine projector as in Claim 7 wherein a synchronous belt cam together with a single disc circular arc positive return rotary cam produces an intermittent motion to the film through suitable film fingers associated with them.

10. A cine projector as claimed in Claim 9 wherein the drive shaft for the rotary cam is made to engage in two angular positions 180 degrees apart relative to the driven shaft of the belt cam drive gear train effecting reverse of the direction of film travel through the gate.

I 1. A cine projector as claimed in Claim 10 wherein the means for adjusting the rotary cam between two angular positions comprises a radial arm on an axially displaceable shifter sleeve on the drive shaft, carrying two pins angularly spaced at 180 degrees to engage in a hole on a disc fitted to the driven shaft, from either side, whereby the drive shaft can be drivingly connected relative to the driven shaft in either of the two angular positions.

12. A cine projector substantially as hereinbefore described with reference to and as illustrated in Figs. 1, 2, 3, 4, 5, 6, 7 & 8.