Patent GB-819703-A (GB)
Title: Improvements in or relating to mechanical scanning systems for facsimile recording apparatus
Inventor: FARR GERALD
IPC: H04N1/16
Filed: 1957-07-05
Abstract: 819,703. Facsimile records. MUIRHEAD & CO. Ltd. April 16, 1958 [July 5, 1957], No. 21312/57. Class 40 (3). Facsimile recording apparatus comprises a plurality of scanning elements each of which, in turn, effects a line scan on the record sheet. In the described embodiment, which is concerned with two scanning elements, the latter consist of semicircular blades 11 and 12 (Fig. 1) the former being mounted for translatory movement along guides 17, 18 and the latter for similar movement along guides 19, 20 (see Fig. 3). The four guides are attached to end plates 21, 22 the whole forming a carrier which is rotated about axis 25 via a hollow shaft 24, gears 32, 35, 34 and a shaft 37 the speed of which is synchronized to the scanning at the transmitter by known means. Also mounted for rotation about axis 25, via shaft 27, gears 33, 36 and shaft 37, and inside the carrier is a drum 26 the surface of which is provided with two helical grooves 41, 42 of left-hand and righthand progression respectively the start ends of which merge smoothly into each other and each of which (in the case of two scanning elements) consists of one and one half turns extending over a distance equal to the length of a scanning line. Each scanning element is provided with means 27a, 28 which engage the grooves so that relative motion between the drum and the carrier causes the scanning elements to slide along the guides the gearing being such that during the period of one line scan the carrier and scanning elements make one half revolution, in one direction, whilst the drum makes a complete revolution in the opposite direction. In operation the received signals are supplied between the scanning elements (the edges of which are provided with a suitable facing material when an electrolytic recording is to be made) and a transverse electrode (writing bar) 38 spring urged towards the elements which, initially, are positioned at opposite ends of the carrier. The record sheet is fed by known means between electrode 38 and the scanning elements so that, whilst one of the latter is effecting a line scan by rotatory and translatory movement, the other element is being returned to the start preparatory to commencing the scanning of the next line. The scanning elements although substantially semicircular are however of such arcuate length that there is just sufficient clearance to allow them to pass each other when moving in opposite directions and, to prevent the electrode 38 from moving forward (due to its spring urging) and jamming the mechanism when one element is breaking contact and the other about to make contact, the end plates 21, 22 are provided with ramps 39, 40 of sufficient height to limit such movement. Instead of effecting an electrolytic recording the apparatus may be employed for producing a recording by indenting the record sheet the scanning elements in this case forming anvils and the electrode 38 acting as a hammer. More than two scanning elements may be employed the peripheral length of each of the latter and the length of the grooves being suitably proportioned.