GB497490A - Selective tuning mechanism for radio receivers - Google Patents

Abstract

497,490. Electric selective signalling systems. TRIGGS, W. W. (Operadio Manufacturing Co.) June 24, 1937, No. 17579. [Class 40 (i)] A wireless receiver is tuned automatically by means of a shading coil motor, all the coils being energized to brake and stop the drive when the required tuning position has been reached. The invention is described as applied to a receiver which is tuned to different stations at various times of the day, the units which determine the station selected being rotatable cam shafts mounted around the clock dial and any one of five different stations can be selected at any quarter hour of the day. The selecting shafts 92 arranged in apertures 90 around the dial in positions corresponding to the times at which they are effective are turned until the number of the station required at the corresponding time is visible. This rotation moves the station cam 96 into the path of the rotating wipers 100 so that at the appropriate time the cam 96 and the wiper 100 make contact. At the exact quarterhour period spring-set 119 drops into a notch 118 in cam 117, and a circuit is completed for the one pair of shading coils 145, 146 or 147 and 148 of motor A, Fig. 2, so that the motor is energized and drives the condenser shaft of the radio set (through shaft 12) and the sleeve 35 carrying cams 60-65, Fig. 6. These cams have been so set that when each cam engages plunger 20, the receiver is tuned to a wanted station. When the cam 60-65 relating to the wiper 100 engaged by cam 96 engages the plunger 20, a circuit is completed for the other pair of windings of the motor and as the two pairs of windings create opposing torques the movement stops. The circuit of the motor is opened when spring-set 119 is restored by the continuously rotating cam 117. The tuning action is repeated at each quarter hour interval, no movement taking place if the station required is that to which the set is tuned. The sixth cam provides an off position. Switch 49 enables the clock control to be removed so that the set remains tuned to a particular station whilst the motor can be started independently of the clock control by push button 50.