Patent GB-751342-A (GB)
Title: Improvements in or relating to shaft-positioning mechanisms for adjusting two interconnected rotary shafts
IPC: G05D3/12
Filed: 1954-10-11
Abstract: 751,342. Stopping shafts in predetermined postions; escapements. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Oct. 11, 1954 [March 19, 1954], No. 29299/54. Classes 80(2) and 80(4) Relates to mechanism for positioning two or more rotary shafts, e.g. in radio tune apparatus, wherein one main shaft 3, setting e.g. a capacitor 4, positioned by one selector-disc 2, controlling a number of stop-pawls (not shown) engaging lockrings 6 on the shaft, which latter is turned through an overload-release clutch 5, of the spring type, whilst another and secondary shaft 7, which operates e.g. a switch 11 for resistors, fixed capacitors or inductances for range-changing, is controlled by a secondary selector disc 8, stop-pawls, lock-rings 10 and overload-release clutch 9. Such mechanism is characterized in that only one driving mechanism for the main shaft 3 is provided, the secondary selector disc 8 being driven from the main shaft 3, and the secondary shaft 7 being driven by the main shaft drive independently of the movement of the main shaft and having a number of stopping positions which is a factor of that of the main shaft. In Figs. 1 and 2, coupled wheels 12, 13, driven by a motor 1, are freely mounted on main and secondary shafts 3, 7 respectively, which they drive through overload release clutches 5, 9. The primary selector disc 2, driven directly by the motor 1, controls the stopping of the main shaft 3 in any of twelve positions distributed through 360 degrees, by means of twelve primary stop-pawls, whilst the secondary shaft 7 is required to be stopped in the same number or a sub-multiple, e.g. two, three, four or six positions by a like number of secondary stop-pawls under control of the secondary selector disc 8. Thus with twelve primary stop-pawls and four secondaries, the secondary shaft 7 will be repositioned after each of a cycle of three successive positionings of the main shaft 3. In Fig. 3, not shown, the additional load on the springs of the primary overload release clutch 5 due to its driving also the secondary selector disc 8, is reduced by providing a reducing gear train between the wheels 14, 8, the train ratio being equal to the multiplying factor between the number of stopping positions of the main and secondary shafts. The number of secondary stop-pawls is the same as that, e.g. twelve, of the main shaft, but successive sub-multiples of secondary pawls repeat the stopping positions of the secondary shaft for each of a corresponding number of successive revolutions of the main shaft. Thus with twelve stop-pawls in main and secondary, and a three-to-one gear ratio, successive groups of four secondary pawls will give four secondary stop positions as before. In Fig. 4, not shown, the main-shaft wheel 14 is connected with the secondary selector-disc 8 through a Maltese Cross movement which retains the secondary selector-disc 8 locked until it is actually required to move. In Fig. 6 the gear train connecting the main shaft wheel 14 with the secondary selector disc 8 includes an escapement comprising a spiral spring 50, the inner end of which is connected to a plate 54, connected by gearing 53, 55, 56 with the secondary selector disc 8, and carrying a pawl 47 which, by engaging a stationary ratchet plate 44, holds back the secondary selector disc 8 until the driving main shaft 3 has wound up the spring 50 through a predetermined angle by an input disc 21 connected to the outer end of the spring. At this point a peg 48 on the input disc 21 trips the tail of the pawl 47 and permits the spring 50, to advance the secondary selector-disc 8 through an angle corresponding to one tooth of the ratchet-plate 44.