Patent GB-802547-A (GB)
Title: Multiturn shaft positioning means
IPC: G05D3/12
Filed: 1956-10-09
Abstract: 802,547. Angular control of shafts. COLLINS RADIO CO. Oct. 9, 1956 [Jan. 16, 1956], No. 30780/56. Class 40 (1). A shaft positioning means in which the shaft controlled may make a number of turns comprises a first and second single seeking switch system, each system having a control switch, a rotary seeking switch attached to a shaft, gearing between the shafts of the two seeking switches to reduce the rotation of the shaft of the second system by a ratio of M : 1, where M is the number of possible positions of the second seeking switch, and driving means actuated by either system and coupled to one of the shafts so that the shaft of the first system makes a number of turns in response to the settings of the control switches of both systems. The seeking switch systems operate, as described in Specification 660,939, a combination of lines being energized by a rotary switch 19 at the transmitting end and a similar switch 26 at the other being rotated by the driving motor 27 through shaft 30 until the switch 26 arrives at a position corresponding to the switch 19, in which position the solenoid 31 is de-energized and the contact 36 opens to switch off the driving motor. A shaft positioning stop-wheel 29 is also fixed to the output shaft 11 with switch 26 and the de-energization of solenoid 31 allows pawl 32 to engage one of ten notches therein to locate the shaft in the final position. The angular position in tenths of a revolution is set by a control knob 13 connected to switch 19 by shaft 18. The number of complete rotations to be performed by the shaft 11 is set by knob 14 governing switch 39 through shaft 38. There are three control lines 63, 64, 66 from switch 39 of which lines 63, 64 are applied to contacts 67, 68 of a cycling switch 46 and line 66 and earth to contacts 69 and 71 of a cycling switch 44. Each cycling switch comprises two separate switches and they are mounted to rotate with shaft 11. These cycling switches serve to connect the control wires and earth to a seeking switch 41a for one half revolution of shaft 11 and to a similar seeking switch 41b for the other half revolution. Each seeking switch 41a, 41b has eight possible positions and gearing 59 causes their control shaft to rotate at one-eighth of the speed of shaft 11. The seeking switches 41a, 41b are displaced by an angle of 22¢ degrees relative to one another (or a whole number of eighths of a revolution plus this angle) this representing half the angle which corresponds to a complete rotation of output shaft 11 Because of the cycling switches 44, 46 the seeking switches 41a, 41b become operative alternately during alternate halves of a revolution of the shaft 11. This allows the contacts on the seeking switches to overlap somewhat in angle of effect between the two seeking switches, interference being prevented by the cycling switches. The solenoid 31 controlling the driving motor is also energized by connections through the two seeking switches 41a, 41b over line 34. When these, or the one operative at the time, has reached the position corresponding to the setting of switch 39, line 34 is de-energized and the control is taken over by the seeking switch 26 for the fine adjustment.