Improvements in or relating to the electrical control of the tuning mechanism of radio-receiving apparatus

摘要

509,750. Electric control systems. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Feb, 6, 1939, No. 3896. Convention date, Feb. 8, 1938. [Class 40 (i)] In a motor-operated tuning system for radio receivers, the tuning member is operated at a high speed which is reduced just before the desired tuning position is reached, the reduction being brought about by opening or closing a switch which is mechanically coupled to the tuning member. Upon key T1 being depressed, the previously operated key T2 is released, magnet M de-energising to allow contacts m to close, whereupon the motor Mt runs and through gearing 16, 17 rotates condenser 27. A lug 20 on disc 19 fast on shaft 18 engages lug 21 on the loose disc 22 but is normally held by spring 42 in the position shown in Fig. 3, so that almost a complete revolution of shaft 18 is necessary to take up the drive, a further lug 23 on disc 22 engaging a lug 24 on a disc 25 fast on the condenser shaft. Contacts k arranged on the lugs 20, 21 close as the drive is taken up to maintain the motor circuit when contacts m open as brush I mounted on the condenser shaft passes on to the marked contact, magnet M being strongly energised to hold the ring 13, Fig. 2, stationary so that the drive from shaft 11 is transmitted to the ball-bearing cage 15 fastened to shaft 10, thus rotating lever 34 which displaces the bush 36 to complete the gear train 37, 38, 39, 41. Lugs 23, 24 disengage, whereupon disc 22 rotates rapidly, opening contacts k, the motor circuit being maintained due to contacts h having closed when lever 34 was displaced. The condenser shaft rotates at the slower speed until brush II engages the marked contact, magnet M now being only energised, sufficiently to maintain open contacts m, the lever 34 being moved back by spring 35 to. open contacts h, any rotation of shaft 18 consequent upon disc 25 moving back is not transmitted to the condenser shaft due to the spring coupling between discs 22 and 25. In a modification, Figs. 4 and 5, the condenser shaft carries cams S, engaged by feelers 48 attached to contact discs 50, and upon a key T being depressed the feeler will generally be upon one of the circular parts 45, 46 so that a circuit will be completed over contacts 52, 53 to cause the motor Mt to rotate in one or other direction, the circuit being opened as the feeler passes on to the surface 47, a flywheel causing it to continue to rotate at approximately the same speed. The motor is of the type in which the rotor is normally held off-centre by a spring and when energised is displaced to a symmetrical position with respect to the stator, engaging gears 80, 81 to rotate the condenser rapidly, and when de-energised is spring-urged to the position shown in Fig. 5 where gears 77, 78 engage to rotate shaft 79 slowly. Upon contact 54 engaging contact 55, brake magnet 70 is energised to stop the condenser shaft 44. To provide for the selection of an adjacent station whencontact 55 may fall on the insulation between contacts 52, 53, upon the key T being depressed, the switch 65 is reversed and locked over, its release being effected when the rotor 73 moves to the left.