Patent GB-615410-A (GB)
Title: Apparatus for controlling the position of a useful load
IPC: G05D3/12
Filed: 1944-11-14
Abstract: 615,410. Control apparatus. YARDENY, M. N. Nov. 14, 1944, No. 22469. [Class 40 (i)] Control apparatus comprises a number of pairs of control elements (selectors) and a load arranged in series. Each controlled element is driven, under electrical control, to bring it into a selected one of a number of possible positions in relation to the controlling element of the same selector. Each controlled element is mechanically connected to the succeeding controlling element, but there is no intrainment between the two elements of a selector. The mechanical connection between a controlled member and a succeeding controlling member is not limited to a one transmission ratio. The load is driven entirely by the motor driving the controlled element of the final selector of the series. Succeeding selectors provide progressively fine adjustments corresponding for example to the hundreds, tens and units figure of a complete setting. A selector I, Figs. 1, 2, comprises a number of contact elements 17, 18, 19, a selected one of which is connected through a switch contact arm 28 to a source of power 30. One or the other of the field windings 9, 10 of a reversible motor 11, Fig. 2, is energized to drive the selected contact element 17, 18 or 19 towards the gap 5 between conducting members 3 and 4 of the controlling member 1. The motor stops when the chosen contact element bridges the gap 5 and energizes both windings of the motor. The contact elements 17, 18, 19 comprising the controlled element are mounted on a tube 13 which carries the controlling element 36 of the selector II. Similarly the controlled member of selector II and the controlling member of selector III are mounted on a tube 14 and the load 79 is mounted on a rod 78 carrying the controlled member of selector III. A control switch 28, 49, 71 is provided for each selector I, II, III. The lamps 92 indicate the condition of each selector. Short supplementary conducting segments 186, 187, Fig. 12, connected to tappings of the motor windings may be provided adjacent the gap 5 so as to reduce the speed of the motor as the gap is approached and to avoid hunting. Alternatively the connections can be arranged so as to increase the motor speed and to produce a buzzing effect on the completion of the operation of a selector. Modifications. Various modifications are described. In one modification, Fig. 6, each contact element 142 in a selector 153 is provided with a separate set of semi-cylindrical conducting members 139, 140. All the contact elements 142 of a selector are energized together and the switches 166 provided for each selector enable the appropriate set of conducting members 139, 140 to be connected. When the contact element 142 bridges a gap 161 both relays 124, 125 operate and short-circuit the armature of motor 120 to stop it. The setting controlled by each contact element and pair of conducting members can be adjusted by means of a friction pinion 150. In a second modification, the contact element 224 wipes a variable resistance 218. This resistance forms the fourth arm of a Wheatstone bridge, the test relay 213 of which short-circuits the armature and stops the motor 227 by releasing both relays 124, 125 when the bridge is balanced. Resistances 222, 223 form the fixed arms and a switch 240 controls a variable resistance 228, the third arm, to balance which the contact 224 and resistance 218 are automatically set by the motor 227. In a third modification (Fig. 5, not shown), all the selectors are driven by a single motor to which they are connected, as necessary, by clutches. In a fourth modification, linear movements are substituted for the rotational movement of previous examples. Switches. The separate switches for each selector can be combined in a single rotary switch, Fig. 14. The first, second and third selectors offer respectively four, three and two settings and the corresponding contacts 450, 452 and 455 are so arranged that the switch can be operated for any combination of selector settings by one motion of the arm 460.