Patent GB-1417634-A (GB)
Title: Tuning assembly
IPC: H04B1/08
Filed: 1973-01-29
Abstract: 1417634 Tuning selector arrangements GENERAL INSTRUMENT CORP 29 Jan 1973 [17 July 1972] 4475/73 Heading H3Q [Also in Division F2] In a tuning assembly comprising an input member A, an output member E and a tuning element B coupled to the output member E, a transmission means C is coupled between the members A, E and comprises index means F coupled to the output member E having a plurality of stop surfaces 28a, 28b each corresponding to a different one of a plurality of tuning positions of the tuning element B, an actuator G, H is coupled to the input member A to engage successive stop surfaces 28a, 28b and biasing means 10 is coupled to the index means F for urging the index means F in a direction to cause each stop surface 28a, 28b to engage the actuator H. Rotation of channel selector knob 40 and a sleeve 38 drives gears 36 and 34 so as to rotate a shaft 30. The first part of rotation (Fig. 12, not shown) of the shaft 30 causes a crank arm 34a to remain against a stop surface S, Fig. 4, of a recess 28a in a plate 22 of the index means F. On further rotation of the sleeve 38 and shaft 30 the crank arm 34a moves out of recess 28a and a crank arm 34b moves into engagement with the stop surface S of a recess 28b in a plate 24 of the index means F. The biasing means I formed by a spring 10 causes rotation of the index means F between these stop surfaces so as to precisely locate the control shaft D of the tuning element B. Further rotation of the sleeve 38 and shaft 30 allowed by a detent K, having a ball 44 and recesses (42, Fig. 6, not shown) in a gear 36, does not alter the tuning setting of the index means F since the crank arm 34b still engages the stop surfaces of the recess 28b. The output from the index means F is coupled at 80 by a gear 20 to an internal gear 4 which drives the tuning element control shaft D. The recesses 28a, 28b are offset and allow 70 preset channel positions to be selected. Since the precise preset tuning positions are determined by the index means F and not the detent K an electric motor may be used to drive the tuning assembly via a gear 40. The recesses 28a, 28b of the index plates 22, 24 may be formed by bendable tabs (90a, 90b, Fig. 13, not shown) on the periphery of the plates 24<SP>1</SP>, 22<SP>1</SP>) so that adjustments may be made to obtain non-linear or arbitrary relationships between frequency tuning and channel selection. Alternative cross-sectional shapes for the crank arms 34a, 34b are disclosed (Fig. 14, not shown) and the recesses 28 need not be circular and can be ellipse or oval in shape. A digital indicator may be provided having the "unit" indicator of a counter driven from the sleeve 38. A pinion 52 is rotated one step for each full rotation of the gear 36 by a lock 48 and key 50 and a gear 56 and sleeve 58 are rotated by the pinion 52 so that the gear 56 drives the 'tens' indicator of the counter. End stops are provided by a cam 88 on the gear 56 which engages a pin 86 carried by the gear 36 so as to move the pin 86 against the action of a spring (85, Fig. 8A, not shown) into contact with a tab 82 on a support panel 32. Fine tuning knob 60 is coupled via a shaft 14 to a fine tuning device in the index means F. The shaft 14 is coupled to a cam (62, Figs. 10 and 11, not shown) which on rotation of the shaft 14 moves an arm (66) which is pivoted at (68) to the plates 22, 24. Fine movement of the arm (66) is coupled by a finger (74) and a sleeve (76) to the gear 20 for fine adjustment of the tuning element B. Specification 1,417,635 is referred to.