Patent GB-664678-A (GB)
Title: Improvements in and relating to television apparatus for scanning cinematograph film
IPC: H04N3/40
Filed: 1947-12-31
Abstract: 664,678. Television. BRITISH THOMSONHOUSTON CO., Ltd. Dec. 31, 1947 [Feb. 2, 1945], No. 35376/47. Class 40 (iii). [Also in Group XX] Television film scanning apparatus wherein the film image is projected into the television camera during the frame fly-back period includes a film sprocket driven by a variablespeed motor at a speed not exceeding that required to feed the film at frame scanning frequency, a motor synchronized with the frame scanning frequency, means for deriving from the latter motor an intermittent drive for a Maltese Cross driving a second film sprocket to move the film through the gate, the latter means including a servo-mechanism to bring the Maltese Cross into, or out of, engagement with the synchronous motor drive in dependence upon the tension of a film portion between the two sprockets to regulate the average speed of the intermittent movement through-the gate to equal the speed determined by the variablespeed motor. In the form shown, the film from the spool 102 is taken up on the spool 116 driven, together with the continuously-running sprockets 103, 115, by the variable-speed motor 117. In its passage through the gate 104 the film is illuminated by a light source 108 and an image is thrown by the lens 146 through an aperture in the shutter 145 into the television camera 109. The motor 147 driving the shutter, and the motor 123 derive their supply from the unit 110 forming part of the television apparatus and are thereby synchronized with the camera. The motor 123 drives a shaft 124 to which is secured a disc 125 having an aperture in which is axially slidable the striker pin 127 for the Maltese Cross 126 of the intermittent sprocket 105. The striker pin is secured to a disc 128, slidable on the shaft and having a groove engaged by a pin on a crank 129 on the same shaft as a double-armed crank 130. Rods 131, 132 supported by links 133, 134 are pivoted to the ends of the crank 130. A rod 135 is continuously reciprocated by a crank 137, driven from the shaft 124, and, by vertical movement of the supporting link 139, can be brought into line with, to push on the end of, the rod 131 or the rod 132 to disengage, or engage, respectively, the striker-pin from the Maltese Cross. The link 139 is connected to a system of levers including an arm 141 with pins 142 and 143, respectively, above and below the film in the loop 106 so that the size of this loop controls the engagement of the striker pin. A toggle spring arrangement may be included to retain the crank 130 in one or other of its extreme positions of movement. A system of levers coupled to the crank may also be provided to lock the Maltese Cross when the striker pin is disengaged since the locking disc 149 is ineffective during what is normally the driving part of the cycle. To prevent accidental operation of the apparatus while a film is being threaded a cam 144 may be operated by hand to retain the arm 141 in the position corresponding to disengagement of the intermittent drive. The cam movement may be interlocked with the movable gate member and a switch in the circuit of the motor 117. Also, the movable member of the gate may be coupled with the link 134 so that when it is opened the rod 132 is lowered out of the path of the rod 135. The sound-reproducing mechanism is indicated at 113, 114. Specification 657,294 is referred to.