Patent GB-490404-A (GB)
Title: Improvements in or relating to transmitters for step-by-step telegraph systems
IPC: H04L19/00
Filed: 1937-01-12
Abstract: 490,404. Type printing telegraphy; constant-torque spring device. CREED & CO., Ltd., THOMPSON, A. E., and SALMON, R. D. Jan. 12, 1937, No. 15545. Divided out of 490,361. [Class 40 (iii)] [Also in Group XXVI] In a step-by-step transmitter in which the number of impulses sent is dependent on the previous key actuated, the actuated key is locked in the actuated position and the other keys in the unactuated position, the number of impulses transmitted being preferably determined by a shaft carrying a helical series of projections coacting with individual key levers and driven through a reduction gearing from the transmitting shaft. Drive. A spring 8, Fig. 1 is wound up by means of a handle 1 on an arm 2 and drives through gear 10 pinions 11 and 12. A clutch 12a, 52 is engaged on, and during, the depression of a key and, on rotation by the pinion 12, a cam 54 and lever mechanism 55, 56 allows the engagement of a clutch 16, 17 driven by the pinion 11. The driven part 17 of this clutch operates the transmitting contact cams 22, 23 and also drives, through gearing 20, 21, 28, 29 a shaft 30 on which are helically arranged a series of arms 32, The transmitting cams 22, 23 have either one or two humps so that they may send either two or four impulses per revolution. Keyboard locking device. A bell-crank 39, 40, Fig. 2, is supported on each key lever 34 and on depression of a key the lower arm 40 tilts a frame 41 about an axis 42 which is linked by a spring arrangement, Fig. 7 (not shown), to a rod 70 bearing a common retaining arm 43. This passes over an extension of the key depressed and under similar extensions on the remaining keys so locking the whole keyboard. Rotation of the shaft 30 causes the appropriate arm 32, by raising the depressed lever 39, to release the retaining mechanism. An arrangement of rollers forced aside between stops by a depressed key renders it impossible to depress two keys simultaneously. Clutch operation. Shaft 42, tilted by the depression of a key causes, through links 45, 46, Figs. 4, 5, the release of the clutch 12a, 52 allowing engagement and, on rotation, a cam 54 raises a detent 57, allowing the engagement of the clutch 16, 17. This detent 57 is held raised by an arm 60 until the depressed key is released whereupon both clutches are thrown out of engagement and the contact cams cease to rotate. Spring tension indicator. The operating handle 1 rotates, through a friction clutch 3, a shaft 4 on which is mounted a gear-wheel 6 and a drum 7 to which is attached one end of a coil spring 8, the other end of the spring being connected to the shaft 9 which drives the transmitter and on which is mounted a gear-wheel 85. By means of a differential gear 92, 93, 94, 95, a shaft 91 is made to rotate at the difference in the speeds of the wheels 6 and 9 and this shaft drives, through gearing 97, 98, 99, 100 a cam 102, Fig. 9. When the tension in the spring is too low the cam 102 rotates to a position in which it closes contacts 105 to light a warning lamp. As the tension is increased, the cam 102 moves to a position in which it causes a detent 104 to hold the shaft 4 by means of a cam 5, so preventing the tension being taken beyond safe limits. If the transmitter is electrically instead of hand driven, the detent 104 holds the shaft 4 against rotation except when the tension in the spring falls below the desired limit.