Patent GB-626751-A (GB)
Title: Improvements in or relating to power-operated follow-up controls
IPC: G05G19/00
Filed: 1947-03-10
Abstract: 626,751. Jack-like actuators. WATSON, C. D., and MANSELL, R. C. S. March 10, 1947, No. 6692. [Class 78 (iii)] [Also in Group XXIV] A power-operated follow-up control has means under the control of an input member for effecting a driving connection between a source of power and an output member, the drive being transmitted through a member oscillated by the source of power, and follow up means for breaking the driving connection. Linear displacement of the input member 10, Figs. 1 and 2, rotates a nut 12, rotatably carried thereby, on the associated threaded portion of a shaft 14, which nut rotates a tubular member 26, connected therewith by a pin 28 and a slot 27, on which tubular member is carried a cam plate 25 the lobe portions 125 of which selectively engage oscillating pawls 18 with a toothed ratchet wheel 16, having a number of teeth differing by one from a number divisible by three and being keyed to the shaft 14, so that the wheel and shaft are rotated and effect a linear displacement of the output member 11 carry a nut 13, guided by pin 29 engaging with a slot 30 in a fixed sleeve 31, and at the same time rotate the nut 12, member 26 and cam 25 in a direction to return the cam plate to a position which prevents driving engagement between the pawls and the wheel 16 by either engaging or disengaging both of each pair of pawls with said wheel. A motor 22, controlled by a micro switch 32 actuated by an abutment 33 on the tubular member 26, and a reduction gearing 23 oscillate through cranks 21, 24 and pin 19, an annular member 17 to which are pivotally attached the three pairs of pawls 18, set 120 degrees apart, the arrangement being such that the cam plate can regulate engagement of the pawls with the wheel 16 to give six mean follow up rates in either direction. As the pawls engage the wheel 16 for only half of each oscillation thereof energy which is stored in the moving parts of the mechanism during the no load half cycles allows a small power source to be used, but in a modification (not shown) this feature is sacrificed to obtain a smoother follow up which is effected by the provision of a second ratchet wheel and pawl assembly which is driven by the motor through a reversing gear during the no load half cycles. In a modification, Figs. 3 and 4, movement of the cam plate 25, in addition to controlling the sequence of operation of the pawls, also controls both the amplitude and frequency of the oscillations, the latter being effected by the operation of a micro switch 39 by an abutment carried on an extension of said cam plate, which switch controls the speed of the motor, and the amplitude control being effected by dispensing with the wrist pin connection between the annular member 17 and the crank 21 which instead is slidably connected to a pin 34 pivotally mounted on the member 17 by means of a hole therethrough, and above and below said pin the crank passes through holes in the limbs 35, 36 of a cross head which slides up and down the crank 21 in response to movement of a roller 37, attached thereto, by a slot 38 in a further extension of the cam plate 25, the arrangement being such that when the axes of the pin 34 and roller 37 are aligned member 17 will remain stationary, but when these axes are out of alignment the amplitude of oscillation of the member 17 will be proportional to the degree of misalignment.