Patent GB-881539-A (GB)
Title: Improvements in or relating to film transport mechanism
Inventor: NUTTALL THOMAS CAYTON
IPC: G03B1/22
Filed: 1959-03-10
Abstract: 881,539. Television. BUSH & RANK CINTEL Ltd. March 10, 1960 [March 10, 1959], No. 8227/59. Class 40(3). [Also in Group XX] A film feeding mechanism designed to take account of film shrinkages comprises a plurality of transport members, each of which performs a cyclic movement and is arranged to engage the film in turn to control its movement through a predetermined distance. The cyclic movements of the members are so phased that immediately after one member has moved the film through the fixed distance it is caused to move at a slower rate than the next operative member, so that the distance between the two members is reduced to the perforation pitch of the film in use. The mechanism is described as applied to a kinematograph-television apparatus, Fig. 1, in which a picture film 1 is scanned by a cathode ray tube 2, presenting a raster of two interlaced fields 3, continuous images of which displayed in the direction of film travel by one-half the height of a frame are formed in succession in each film frame by lenses 4, 5 in the light path of which is arranged a shutter plate 6. The light from the film is collected by a lens 7 and cast upon a photomultiplier 8 providing the required television signals. During the scanning of each complete film frame the,film is moved at a constant speed, but during the transition period between two scans the film speed is retarded by an amount depending on the film shrinkage. As shown in Fig. 4, the film is moved by claws 42, 43 on claw levers 44, 45 which are moved in a plane perpendicular to the film by bell-crank levers 46, 47 having followers 48, 49 in contact with edge cams 50, 51 and which are reciprocated in the direction of the film feed by links 52, 53 pivoted to bell-cranks 54, 55 having followers 56, 57 in engagement with edge cams 58, 59. The movements of the claws 42, 43 are so phased that just before the end of a scanning period the next claw to operate enters the succeeding film perforation but does not engage the edges thereof. At the end of this film scanning period, the operative claw slows down so that the distance between the two claws decreases by a value depending upon the film shrinkage until the next operative claw engages the edge of its film perforation and takes up the film drive so that the film moves at a uniform rate during the succeeding scanning period. In the further embodiment shown in Fig. 6. claw levers 144 and 145 are provided with two sets of claws 142, 142<SP>1</SP>, 143, 143<SP>1</SP>, of which the claws 142<SP>1</SP> and 143<SP>1</SP> do not come into operative engagement with the edge of the film perforation unless the perforation entered by the main claw 142 or 143 is damaged. The claw levers 144 and 145 are provided with guiding shoes 161, 163 and 165 and 162, 164, 166 respectively. Of these, the shoes 161, 163 and 162, 164 slide on opposite surfaces of a fixed plate disposed between the claw levers, while the shoes 165 and 166 ride on surfaces disposed outside the claw levers and parallel to the guide plate 160. The claw levers 144, 145 are, as shown in Fig. 9 for the lever 144 coupled by bell-cranks 146 and 154 to edge cams 150, 158. The cam 150 and bell-crank 146 provide for reciprocation of the claw lever 144 perpendicular to the film path, whereas the cam 158 and the bell-crank 154, which is linked at 152 to the claw lever provide for movement of the lever 144 in the direction of the film feed. Preferably, the cams operating the two claw levers 144, 145 are mounted on a common cam shaft 190 which is provided also with a cam and follower arrangement designed to ensure that the centre of the mass of the mechanism remains substantially stationary as the cam shaft rotates.