Patent GB-547154-A (GB)
Title: Improvements in transmitters and receivers for facsimile telegraphy
IPC: H04N1/06
Filed: 1940-12-13
Abstract: 547,154. Facsimile telegraphy; local copying. FINCH, W. G. H. Dec. 13, 1940, No. 17652. Convention date, Feb. 10, 1940. [Class 40 (iii)] A combined transmitter and receiver for facsimile telegraphy comprises transmitter and receiver drums 20, 21, Fig. 1, situated outside a casing 22 and driven by a single motor disposed within said casing. The transmitting and receiving drums and their scanning devices are driven by a motor 26, Fig. 2, connected by a clutch 35 to a main shaft 36. A worm gear 48 transmits the drive from main shaft 36 to shaft 43, which drives transmitting drum 20 and is connected by another worm gear to another shaft 217 itself connected by worm gear 121 to screw shaft 211 for driving the scanning device of the transmitting drum. Similarly, a worm gear 49 transmits the drive from main shaft 36 to hollow shaft 45, which drives receiving drum 21 through a friction clutch 162 ; and spur gearing 340, 341, 342 transmits drive from shaft 45 tn screw shaft 344 for driving the scanning device of the receiving drum. The transmitting drum 20, Fig. 2, is detachably mounted between tail stocks 74, 90 and is keyed to the shaft 43 by means of a hob in its inner end engaged by a pin 76 on a disc 75 fast with the shaft 43. The outer tail stock 90 is carried by a lever 95 pivoted at 96 and forked at its other end 99 for engagement with a latch 100 provided with a spring controlled knob, which normally bears on the forked end 99 of the lever 95. The knob may be lifted by hand and the latch swung out to allow the lever 95 in its turn to be swung out to release the transmitting drum. For securing the message sheet around the transmitting drum, a bar 700, is disposed alongside the drum and is urged against the drum by tension springs 701, Fig. 7, extending through holes in the drum and anchored to a rod 702 within the drum. The edges of the message sheet are successively brought under the edges of the bar 700 and are clamped thereby. To facilitate this operation, the bar 700 is fitted with pins 705 which pass loosely through holes in the drum and fit between pins 710, 711 on cranks 712 on the rod 702, which extends through the end of the drum and is fitted with a handle. This handle when rocked one way causes one edge of the bar 700 to rise to permit the insertion of one edge of the message sheet between the drum and the raised edge of the bar 700. The message sheet may then be wrapped round the drum, after which the handle is rocked the other way to lift the other edge of the bar 700 to permit the insertion and clamping of the second edge of the message sheet. The receiving drum 21 may be similar to the transmitting drum; but, as shown, it is permanently mounted on its shaft, and the message sheet is secured on the drum by resilient garters 721. The drive of the transmitting drum is continuous ; but the drive of the receiving drum is stopped and started again for each revolution. For this purpose, the clutch member fast with the shaft of the receiving drum is provided with a lug which is arrested by a pawl at the end of each revolution. Then a synchronizing signal received by an electromagnet deflects the pawl and allows the next revolution to be performed and so on. The clutch 162 being a friction clutch slips when the drum stops. The synchronizing signal is sent by the transmitter and the message signals are simultaneously interrupted by a change-over switch operated by cams once at every revolution of the transmitting drum. The shaft of the receiving drum is also provided with a cam for operating a change-over switch once at every revolution. To enable initial adjustments of the drums, the main shaft 36 is extended through the housing and provided with a hand wheel 38, Fig. 1. The scanning device of the transmitting drum comprises a lamp 312, Fig. 2, a photo-electric cell 122, and suitable optical systems therefor, all carried on a platform 221 guided on a rod 226 in front and by adjustable rollers on a rail 235 at the back. The platform is gradually moved along the drum by the engagement of a half-nut 320 with the screw shaft 211 driven as described above. The half-nut 320 is pivoted at 312 and is normally held in mesh by a spring ; but it may be depressed by a push-button 330 to enable the scanning device to be moved my hand to any desired position or to end positions beyond the screw part of the shaft 211 when transmitting operation is not required. The stem of the push-button 330 rides in a slot in the housing, so that the push-button can be operated from outside. The lamp 312 is enclosed in a hood formed with a slot allow-' ing a narrow light beam to pass to the optical system 302. The lamp 312 is detachably fitted in a socket which can be screwed up and down in a base plate to adjust the vertical position of the lamp, a hand grip being provided on the socket to facilitate this adjustment. The base plate can be moved by a screw for adjusting the lamp horizontally. The scanning device for the recording drum 21 comprises a carriage adapted to be brought by a spring into engagement with a screw to drive the carriage along a guiding rod. A stylus is adjustably clamped in the fork end of a member pivoted on the carriage 350 and urged against the drum by a spring. The same or different messages may be transmitted and received simultaneously.