GB560285A - Improved electro-mechanical switch suitable for use on telegraphic transmission apparatus - Google Patents

Abstract

560,285. Telegraphic apparatus; electric switches. BRAIN, H. E., and AUTOMATIC TELEGRAPH & RADIOTRANSCEIVER CO., Ltd. Aug. 26, 1942, No. 16779/41. [Class 40 (iii)] [Also in Group XXXVII] A switching device, suitable for controlling the paper feed of a recording telegraph instrument by stopping it after a predetermined time has elapsed since the receipt of a signal, comprises a lever 27 operating switch contacts 25 and carrying a pivoted disc 28 having a part cylindrical periphery 28a which, when the lever is rocked by a spring 27c, is brought into contact with a disc 29 rotated by a motor. The disc 28 is thereby rotated until at the end of the cylindrical part of the periphery a recess 28b comes opposite the disc 29, upon which the lever 27 is further rocked and allows the contacts 25 to open. The lever 27 is rocked against the action of the spring 27c, to a position in which the contacts 25 are closed and the disc 28 is out of contact with the disc 29, by the energization of an electro-magnet 26. In the form shown, the disc 28 is formed with two part cylindrical peripheral portions and two recesses, and each time it is withdrawn from contact with the disc 29 (by de-energization of the magnet 26) a flat spring 31 engaging a cam formed with two flat surfaces turns it so that the leading end of one of the cylindrical portions is presented to the disc 29 at the next contact. In the application to a recording telegraph instrument, the motor driving the disc 29 also drives the paper feed mechanism through a magnetic clutch in the circuit of which are the contacts 25. The magnet 26 is energized when a signal is received, resulting in the closure of the contacts 25 and consequent operation of the paper feed until the interval after a signal is sufficiently long for a recess on the disc 28 to be brought opposite the disc 29, when the contacts 25 are opened to de-energize the magnetic clutch, so stopping the paper feed. The device shown is provided also with means to open the motor circuit after a still longer period in which no signal is received. For this purpose, at each revolution of the disc 29 a pin 29a on it rocks an arm 38 carrying a pawl 36 which rotates clockwise a ratchet wheel 35 frictionally mounted on the same shaft 30 as the disc 29. Return movement of the wheel 35 is prevented by a second pawl 36a. After substantially one revolution a pin 40 on the wheel 35 engages a spring-mounted cam nose 41 and thereby opens contacts 24 in the motor circuit. When a signal is again received the solenoid 26 rocks the lever 27 and an arm 37 carried by the lever lowers both the.pawls from engagement with the wheel 35, which can now rotate anticlockwise, so that the cam nose 41 pushes the pin 40 back and returns to the position shown in which the contacts 24 are closed to start the motor. The subsequent rotation of the shaft 30 carries the ratchet wheel 35 back to the initial position in which it is shown, owing to the frictional connection between it and the shaft.