Patent GB-543128-A (GB)
Title: System and apparatus for facsimile telegraphy
IPC: H04N1/06
Filed: 1940-08-31
Abstract: 543,128. Facsimile telegraphy. CREED & CO., Ltd. Aug. 31, 1940, No. 13675. Convention date, Sept. 2, 1939. [Class 40 (iii)] The copyholding drum 12, Fig. 2, of a facsimile telegraph apparatus is given a longitudinal scanning movement from a lead screw 22 by means of an arm 42 rotatably mounted with friction on the drum, so that when the drum rotates the arm 42 tends to follow the rotation and is thus urged towards the lead screw, causing the engagement therewith of a halfnut 41 at the end of the arm. The drum comprises end pieces 29, 31, Fig. 8, clamped to the cylindrical part 28 by longitudinal bolts 33, 34. One end piece 31 has an annular recess 37 to overlap the edge of the message sheet, which is held on the drum by a spring garter 39. The longitudinal edges of the sheets are situated along the line marked on the drum. The drum is rotated by a shaft 14 driven through gearing 21 by a motor 18. The rotation is transmitted from the shaft 14 to the drum by means of a finger 40, Fig. 5, on the shaft 14 adapted to engage the bolt 34 of the drum ; this enables the drum to be rotated by hand as is required for resetting the drum to starting position. The arm 42, which carries the half-nut 41, is rotatably mounted on a boss 43, Fig. 8, on the end piece 31 of the drum, and is frictionally clamped to the drum by means of friction discs 46, 47 and a spring garter 48. The lead screw 22 is driven from the drum shaft 14 through gearing 26, 27. Assuming a message sheet on the drum and the drum in starting position on the right as in Fig. 2, operation is started by pulling a rod 68 by its handle 77 towards the right, until a spring 83 snaps over a flange 81 on the rod and holds said rod in its pulled position as in Fig. 2. In this position, the inner end of the rod releases the operating lever 67 of a switch 65, which closes and starts the motor 18. Then, when a start signal is received, this signal operates an electro-magnet 58, Fig. 7, which attracts its armature 57 and thereby removes a bail 45 from a notch 55 in the arm 42. The arm 42, by virtue of its friction mounting on the drum, is turned round to engage the half-nut 41 with the lead screw 22, and the recording operation starts during which the bail 45 is kept down by the arm 42. During the recording operation, the garter 39 is gradually moved along the drum by a finger 106 on the handle 77. Near the end of the operation, the tip of the arm 42 comes against a lug 85 on the rod 68 and pushes that rod to the left. At the end of the operation, the rod 68 reaches the switch lever 67 and opens the switch thereby stopping the motor. Near the end of the operation, the arm 42 also comes in the range of a notch 60 in the upper edge of the bail 45, which thereupon is raised by the spring 59, Fig. 7, the electromagnet 58 being by now de-energized. This prevents direct or accidental return of the arm 42 to the right. To return the parts to the starting position on the right, the drum is rotated slightly forward and then back to the driving finger 40. During this forward movement of the drum, the arm 42 remaining stationary against the lead screw slips back relatively to the drum, so that, when the drum is turned back, the arm 42 is'turned away from the lead screw, and the notch 55 in the arm comes in line with the bail 45 and allows the arm 42 with the drum to be moved to the right. Additional notches may be provided along the length of the bail 45 for shorter messages. The operations described above proceed in the same way for receiving and transmitting ; but for receiving, a stylus device is used, and for transmitting a photoelectric device, these devices being selected by a switch 142, Fig. 1. In a modification, Fig. 11 (not shown), the length of the drum is divided into two sections separated by a flange ; one section is used for transmitting and the other for receiving. The receiving section can thus be in readiness while a message is being sent from the other section. The recording stylus 91, Fig. 5, is attached to the end of an arm 92 on a crank 93 adjustably clamped to a shaft 96 by a screw 94. Another crank 104, Fig. 6, also adjustably clamped to the shaft 96 by a screw 105 is connected by a link 103 to the armature 101 of an electro-magnet 99. The stylus is normally held away from the drum and is moved to operative position by the energization of the electromagnet 99. The photoelectric scanning device for message transmission comprises a lamp 107, Fig. 3, rotatably adjustable and clamped by a set-screw and lock-nut combination 117, 118 to a bracket 116 rotatably adjustable on a pillar 114 and clamped thereto by a set screw 115. The light from the lamp passes through an aperture in a shield 119 and through a lens tube 108 to the drum 12 ; and the light from the drum passes through a lens tube 109 with an aperture and through a light chopper 111 to a photo-electric cell 110. The light chopper is driven by a motor 126 to generate a carrier frequency. A separate device may be provided to produce the carrier frequency, instead of the light chopper. The casing of the apparatus is made with an open space 78, Fig. 1, in which the drum 19 is accessible when in the starting position. An internal panel 128, Fig. 2, of channelshape is provided to support various instruments. Fumes or gases, which may be evolved during recording, are expelled by a fan 134, Fig. 3, on the shaft of the motor 18 through a channel 133 and through a filter 129, Fig. 2, which retains any deleterious matter. The Specification as open to inspection under Sect. 91 comprises also the following : (1) a transmission system between central and local offices connected by a line comprising two conductors bridged at their ends by centre tapped transformers to permit the message signals and the control signals to be transmitted on the same line by A.C. and D.C. respectively. When a local office desires to transmit, a switch there is placed at " send " and the circuits switched on. When current from a rectifier attains a given value a signal goes through to the central office and lights a signal lamp there. A receiver at the central office is then connected to a jack belonging to the calling office. After this, a phasing signal generated at the transmitting office causes the transmitting and recording operations to start and proceed until the transmitter is automatically switched off at the end of the message. The recording circuit includes a signal inverter comprising a pair of valves heavily biased for Class C operation. (2) A modification of the transmission system including an alternating current relay device at the local transmitter for preventing operation if the " sendreceive " switch is not in correct position for the operation desired, and a signal lamp device to indicate misplacement of the switch. And (3) a recording apparatus including a supply of drums in a magazine and means for removing and discharging a drum from the recording apparatus and replacing it by a fresh one from the magazine. This subject-matter does not appear in the Specification as accepted.