Patent GB-954523-A (GB)
Title: Improvements in or relating to photo-telegraphic apparatus
Inventor: HOER KENNETH GEORGE
IPC: H04N1/06
Filed: 1962-03-12
Abstract: 954,523. Picture telegraphy. MUIRHEAD & CO. Ltd. Feb. 8, 1963 [March 12, 1962], No. 9447/62. Heading H4F. In a photo - telegraph apparatus comprising a drum 1 adapted to be rotated by a motor 6 and scanning means 32 arranged to traverse the drum in a longitudinal direction, the drum, the motor and the means 10 for transmitting the drive from the motor to the drum form a subassembly detachable from the body of the apparatus as a single and complete unit. The invention is primarily intended for use with high-speed apparatus where, although the drum requires to be removable for loading, the drum bearings are of such constriction that the drum alone cannot be detached. The sub-assembly is arranged to register exactly at fixed points on the main body of the apparatus by means of buffers and stops (of which only three, 13, 13<SP>1</SP>, 14, 14<SP>1</SP> and 15, 15<SP>1</SP> are visible in Figs. 1 and 2), the buffers on the underside of the subassembly being located in U-shaped plastic channels 19, 20 which engage chamfered grooves 17, 18 and function as runners when the sub-assembly is placed in position. Locking lever assemblies 27-30, one at each end of the apparatus, which are manipulated by a common hand control 21, engage pins 31 extending from the sub-assembly and exert both horizontal and vertical pressure to hold the sub-assembly in intimate contact with the stops. Spring-loaded locking arms (of which only one, 54, is visible in Fig. 1), which have slots (not shown) intended to engage lugs (not shown) on the underside of the sub-assembly, prevent the sub-assembly being fitted to or withdrawn from the apparatus except when the scanning means is in the " start " position where a thrust pin engages an inclined part of a lever and rotates a shaft to displace the arms. The drum bearings are air bearings, an air supply being obtained through a pneumatic socket, Fig. 7 (not shown), which is engaged by a plug when the sub-assembly is placed in position. A valve 67 operated by an extension 68 on hand control 21 cuts off the air supply to the pneumatic socket when control 21 is depressed to disengage the locking lever assemblies to permit the sub-assembly to be removed. The invention may be applied to a transmitter or receiver, but is only described as applied to a receiver where the drum carries photo-sensitive recording material which is exposed to a modulated light-source member 36 carried by scanning means 32. The sub-assembly is enclosed within a light-tight case 2 provided with a slot 37 which is surrounded by a hood 50 and closed by an opaque flexible blind 38 extending between drums 39, 40. The blind has a circular aperture 45 which is surrounded by a hood 46 and is normally closed by spring-urged flaps 47, 48. When the sub-assembly is fitted to the apparatus, the member 36 enters hood 46 and forces flaps 47, 48 open to allow exposure of the record material on the drum. A cup-shaped part 49 on member 36 surrounds hood 46 to provide a light seal. As the scanning means 10 moves to traverse the drum, the motion is communicated via member 36 to blind 38 which winds off one of drums 39, 40 on to the other. The blind is locked in the " start " position when the subassembly is removed from the apparatus by a spring-loaded plunger 69 which engages a hole in the lower flange of drum 39. The plunger is withdrawn when the sub-assembly is fitted to the apparatus by engagement of a conical head 71 on the plunger with a part 61 (the pneumatic valve) of the main apparatus.