Patent GB-539029-A (GB)
Title: Push-button operating mechanism for adjusting variable inductance tuning devices
IPC: H03J5/12
Filed: 1940-02-20
Abstract: 539,029. Push-button devices for tuning inductances. JOHNSON LABORATORIES, Inc. Feb. 20, 1940, No. 3195. Convention date, Feb. 20, 1939. [Class 37] A push-button device for adjusting tuning inductances comprises tuning inductances 34, Figs. 2 and 4, supported on one side of a mounting plate 10 in a plane parallel with said plate and with cores 35 movable within said plane, operating key devices 13 supported on the other side of the mounting plate 10 in a second parallel plane with said plate for rectilinear movement within said plane, and a motion transfer mechanism between the keys and the inductance cores including a shaft 25 extending transversely through the mounting plate 10. Preferably the motion transfer mechanism has a multiplying action so that a short movement of the keys is sufficient to produce the comparatively longer movements of the cores. As shown, the inductance cores 35 are connected by slender rods 36 to a yoke 38 jointed by a pivot 46 to one end of a lever 45 jointed by a pivot 47 at its other end to an arm 48 pivoted at 49 to the frame. The centre 44 of the lever is pivoted to a crank 43 on one end of the shaft 25, the length of the crank being equal to half the length of the lever 45, the pivot 47 being directly above the centre of the shaft 25, and the mean position of the arm 48 being substantially horizontal, so that for movements of the crank 43 between stops 50, 51 produce substantially horizontal magnified movements of the cores 35. Springs 52, 53, 53<1> are provided to prevent backlash at the pivots. The slender rods 36 are screw-threaded into insulating sleeves 37 clamped to the yoke 38, this permitting preliminary adjustments of the cores for aligning or tracking purposes. The other end of the shaft 25 carries three cranks 27a, 27b, 27c, Fig. 1 ; another transverse shaft 26 is similarly provided with three cranks 28a, 28b, 28c ; and these two sets of cranks are connected by parallel links 29, 30, 31, so that the two shafts rotate simultaneously and the links 29, 30 move in opposite directions. Each operating key device comprises a vertically sliding key-bar 13 provided with a key-rod 16 fitted with a button 17 and normally held up by a spring 21. A sector 14 is pivoted at 15 to the key bar 13 and is clamped thereto in the desired position by an angle-piece 19, Fig. 6, tightened by rotation of key-rod 16 with which it has a screw-thread engagement. The upper parts of the key-bars 13 with the sectors 14 are turned through a small angle so that the several key-bars may be placed close together with the sectors in overlapping formation as shown in Fig. 4. A front lug 14a on each sector is above parallel link 29 and a rear lug 14b above link 30. If a button 17 is depressed, one of the lugs 14a, 14b drives its corresponding link downward until the other lug abuts against its corresponding link. The throw is determined by the angular position to which the sector has been set and is transmitted to the cores 35. When the button is released, it is raised to the normal position by the corresponding spring 21 ; but the motion transfer mechanism and the cores remain in their set position until another key is depressed. A knob 54 is provided on the shaft 25 for manual operation when desired. In a modification, instead of a double acting sector, a single lug member 56, Fig. 10, is provided on each key-bar 13a. This lug member is slidable along the key-bar and is set in desired position by the rotation of a key-rod 16a having a screw-thread in engagement with a U-shaped spring nut member 55 secured by a rivet 57 to the member 56. Each key device is normally urged up by a spring 64 ; and the whole set of keys is also held up by a spring controlled latch-bar 60 pivoted at 61, Fig. 11, and engaging bottom notches 13b in the key-bars 13a. Another notch 13c in each key-bar is adapted to be engaged by the latch-bar when the key-bar is depressed. Moreover the motion transfer mechanism is normally urged by a spring 59 on the shaft 25 to the end position in which the cores 35 are fully in. With this arrangement, when a button is depressed, the latch-bar 60 is deflected and releases any key-bar previously held down by it; and the depressed key-bar is held down by the engagement of its notch 13c by the latch-bar. The depression of the key-bar causes its lug member 56 to bear on the parallel link 29 and thereby to operate the mechanism. To adjust the cores 35 in accordance with the setting of the lug member on the key-bar ; and the cores remain in the adjusted position against the action of the spring 59 so long as the key-bar is held depressed by the latch-bar, i.e. until another button is depressed.