GB940439A - Improvements in push-button incremental tuners - Google Patents

Abstract

940,439. Radio receiver push-button tuning mechanism. SYDNEY S. BIRD & SONS Ltd. Feb. 12, 1962 [March 9, 1961], No. 8704/61. Heading H3Q. In a push-button tuner a number of channels may be selected individually by means of preselectors of helical form, and mounted on the shaft of each push-button such that when one of the push-buttons is operated the angular setting of its helical preselector about the pushbutton shaft determines the position of a contact assembly along a track over a series of inductance elements and their associated fixed contacts. As shown in Fig. 1, helical preselectors 25 are mounted on shafts 17 of push-buttons 16 which are biased away from the tuner wall 12 by springs 23 and arranged to be rotatably and axially movable. When one of the buttons is pushed inwardly the helical preselector 25 comes into contact with abutment 26 on a rod 27, arranged to rotate about its longitudinal axis and connected by levers 28 and pins 29 to a contact assembly 13 slidable in slots 11, Fig. 3, such that the rod rotates and the contact assembly moves over the fixed contacts of a circuit board 14. Each shaft 17 is further provided with a flange 31 which when the pushbutton 16 is pushed inwardly forces down a bar 32 biased by spring 33 and passes over it, the bar 32 returning to its position and locking the shaft in its operating position. The shafts 17 are splined to toothed collars 21 which cooperate with three 120 degrees spaced projections in the holes through the tuner wall through which the shafts pass, whereby both the axial movement of the shaft 17 is limited and the final position of the preselector 25 and hence the contact assembly 13 may be determined by angularly rotating the shaft 17. Thus, once each preselector has been set to a predetermined angular displacement one of four channels may be obtained by pressing the appropriate button 16. One of the shafts, Fig. 1, has no preselector 25 and acts as a trip to release the push-buttons. The hollow shafts 17 are also provided with rods 42 which thread into the ends of inserts 40 and are arranged when the push-button is operated to engage a tongue 44 formed on a hinged plate 45 to cause a plunger attached to the plate to move axially in the direction of the shaft 17 and vary the capacitance of two trimmer capacitors. When the shaft is in its locked position the capacitances are varied by rotating the insert 40, thus causing the threaded rod 42 to move along the axis of the shaft and thereby alter the distance the rod protrudes from the shaft. In the embodiment of Fig. 3, the push-button on the extreme left has no helical preselector but is provided with a cylindrical abutment on its shaft which engages a projection 26 to move the contact assembly to the distance determined by the dimensions of the push-button. In addition this push-button carries a switching arm 33 of a switch, Figs. 4, 5 (not shown), and is operated whenever the tuner is required to select F.M. signals.