Patent GB-636291-A (GB)
Title: Remote control or indication of the angular position of a motor driven shaft
IPC: H03J1/22
Filed: 1948-01-22
Abstract: 636,291. Electric selective signalling systems. STANDARD TELEPHONES & CABLES, Ltd., MALTBY, R. C., BROWN, F. LORIMER-, and PATRICK, B. W. Jan. 22, 1948, No. 2001. [Class 40 (i)] A rotating shaft is stopped at a predetermined position by relays which operate when a first set of contacts, which counts the rotations of the shaft in a binary scale, is in agreement with a second set of contacts set by a selecting switch. Preferably the initial direction of rotation of the shaft is such as to bring the shaft to the desired position after the minimum number of revolutions, and the final direction of rotation is the same independently of the initial direction of motion, so that for one direction, the shaft over-runs and then reverses to reach the desired position. The system is described for local and remote operation of the selecting switch. Local operation of selecting switch.-The shaft 5, Fig. 1, has keyed to it a wheel 3 which carries teeth on one half only which co-operate with a loose gear 4 to drive a wheel 1, loose on shaft 5 ; the wheels 3, 1 are cams opening and closing contacts TCA, TCB so that contacts TCA open for the 1st, 3rd &c. halfrotations of 5, close for the 2nd, 4th &c. halfrotations of 5, while contacts TCB close for the 2nd, 4th &c. rotations, but open for the 1st, 3rd, &c. rotations of shaft 5 ; similarly actuated cams operate switches TCC ... TCH to the accuracy desired. A selecting switch, Fig. 2, comprises a drum having projections 8 cooperating with contacts DCA ... DCG so that a desired setting of contacts DCA .. DCG can be obtained by rotation of the shaft 7. The contacts TCA .... TCH and DCA ... DCG are connected as shown in Fig. 3. When it is desired to re-set shaft 5, shaft 7 is set manually to the corresponding code and switch K, Fig. 3, operated to the position shown. Relay B energizes to close contact b2 so that relay C is energized or not depending on whether the setting on the switch of Fig. 2 is less than the setting of the contacts TCA ... TCH ; relay C controls contacts c1, c2 determining the direction of rotation of the motor M driving the shaft 5, so that the shaft will be rotated in the direction corresponding to the minimum number of rotations necessary to take it from the present to the desired position ; relay B also changes over contact b1 to actuate MC2 to clutch shaft 5 to the motor M. Key PL is then closed to actuate relay A which locks over a1 and energizes the motor M over a2, the shaft 5 then rotating to sequentially alter the setting of contacts TCA ... TCH. Assuming that the initial direction of rotation of motor M is'also the desired final direction, when the setting of contacts TCA ... TCG agrees with contacts DCA ... DCG, a circuit will be completed for relay D to open contacts d1, d2 to stop the motor and de-energize the clutch MC2. If the initial direction of rotation is not that of the desired final rotation, i.e. if the setting of contacts DCA ... DCG is higher than that of TCA ... TCG, when the contacts have reached the same setting, relay C will not be operated and relay D cannot operate ; the shaft will continue to run until contacts TCA ... TCH record a higher number than contacts DCA ... DCG, when relay C will be actuated to reverse the motor M which will then run back and stop as described above. Remote control of selecting switch.-The selector switch SR at the remote point is set manually, and with key K in the up position, key PR is closed. Motor M is thus energized and drives the shaft 7, Fig. 2, of the selecting switch over clutch MC1, relay B being unenergized and its contact b1 being as shown ; selector switch SL is driven with shaft 7 until it reaches the position to which switch SR is set, when relay B is energized to change over contacts b1, thus de-energizing the clutch MC1. The selecting switch of Fig. 2 is now set to the position determined by switch SR, and the setting of shaft 5, Fig. 1, proceeds as 'described above. The invention is applicable to the tuning of a radio-transmitter.