Patent GB-501420-A (GB)
Title: Improvements in or relating to printing telegraph apparatus
IPC: H04L19/00
Filed: 1937-08-27
Abstract: 501,420. Type - printing telegraphy. CREED & CO., Ltd., THOMPSON, A. E., and SALMON; R. D. Aug. 27, 1937, Nos. 18778/38 (divided out of 490,361), and 16779/38 (divided out of 490,404). [Class 40 (iii)] For setting a step-by-step telegraph transmitter and receiver in unison, means are provided to set both instruments in a position corresponding to a predetermined character. The transmitter is provided with a synchronizing key for sending a number of impulses greater than that required for the transmission of any character and means for bringing the transmitter to rest in a position corresponding to a predetermined character. The receiver is provided with means responsive to a number of impulses greater than that corresponding to any character and for positioning the type wheel in a predetermined position. The invention is described as applied to a transmitter, of the type described in specification 490,404 in which the depression of a key lever releases for rotation a shaft carrying a helical series of projections which, co-operating with the depressed key, cause stoppage of the shaft after a fraction of a revolution characteristic of the key depressed. A synchronizing key 106, Fig. 1 (18779/38), pivoted on a spindle 35, carries a projection 107 which causes the depression of a predetermined character key, e.g. key T, whenever the key 106 is depressed. In common with all the other key levers, it carries, a two-armed lever 39a, 40a, the lower arm 40s of which, by coacting with a common bar 41, releases for rotation a shaft 30 carrying the helical series of projections 32. The arm 40a associated with the key 106 is slightly longer than those of the remaining keys. A continuation of-the key 106 carries a link 113 operating a bell-crank 114 pivoted at 115 whose upper end forms a detent engaging a stud 117 on a toothed wheel 110. When the key is depressed, this detent is removed and the wheel 110 is free to rotate, the detent being almost immediately reset by a spring 116. By means of a spring 118, Fig. 2 (16779/38), connected to a radius arm 109, the wheel 110, which has a gap 111 in its teeth, Fig. 3 (16779/38), is pulled round until its teeth engage a pinion 112 on the shaft 30 which has been released for rotation by the depression of the common bar 41. The shaft 30 then makes a number of revolutions, during which impulses are transmitted, until the gap 111 again reaches the pinion 112. The spring.'118 pulls the wheel 110 round until the stud 117 again engages its detent and an extension of the arm 109 operates a bell-crank 119 to disengage the lever 40a from the common bar 41. This, therefore, rises until held by the lever 40a of the key lever T which remains depressed until the appropriate arm 32 engages its projection 39a to release it and stop the machine in the corresponding position. The second part of the invention is described with reference to a receiver of the type disclosed in Specification 490,361 in which the receipt of impulses releases for appropriate rotation a type shaft, and the cessation of the impulses releases a shaft to effect the printing operation. The type shaft 107, Fig. 1 (16778/38), is driven through a differential gearing, the planetary pinions of which are normally held by a detent 109, Fig. 2 (16778/38), engaging a toothed wheel 100 on which they are mounted, so providing a positive drive. The type shaft 107 carries a pinion 86 which, through gearing 85, 87 rotates a segment 88 pivoted on an arm of a bell-crank 90, 91 whose other arm follows a cam 94 mounted on a shaft 35. During normal working, the shaft 35 is rotated before a whole revolution of the shaft 107 is completed and the crank 90 is then rotated counterclockwise by the cam 94 to disengage the sector 88 from the pinion 87 and allow it to return to its initial position under the action of a spring 89. When a number of impulses greater than that corresponding to any character is received, the crank 90 is not so operated and the sector 88 rotates until a stud 115, carried by it, engages a crank 101 and removes its upper arm from a projection on a pivoted arm 102. A disc 103 is meanwhile rotated with the type wheel until a slot 117 in it, at a position corresponding to the predetermined character T, is engaged by a projection 114 on the lever 102, this being moved counterclockwise by a spring 118. The movement of the lever 102 in entering the slot 117 causes its upper projection to rotate a pivoted lever 111 to remove the detent 109 from the wheel 100. Thus, the type wheel is held in the predetermined position while the planet pinions of the differential are free to rotate on receipt of the remaining impulses. As soon as the impulses cease, the shaft 35 is released for rotation with consequent counterclockwise movement of the crank 90. The engaging of the upper end of the crank 90 with a stud 120 on the lever 102 removes the latter from engagement with the slot 117 and allows the detent 109 to re-engage the wheel 100. In addition, the sector 88 is removed from the wheel 87 and allowed to return to its initial position. Specification 490,413 also is referred to.