GB568952A - Improvements in and relating to electrical remote control systems - Google Patents

Abstract

568,952. Signalling over power circuits. PRICE, D. R., and METROPOLITANVICKERS ELECTRICAL CO., Ltd. Sept. 4, 1943, No. 14472. [Class 40 (i)] [Also in Group XXXVII] In a system for controlling switching operations over a power circuit in which each receiver is arranged to respond to a characteristic number of impulses of current of a control frequency, which is high compared with the supply frequency, the moving member of the receiver is controlled by a shaded-pole induction motor. As shown, the control frequency operates a tuned relay 4 of the kind described in Specification 517,971, [Group XXXVII], which is coupled to the power circuit by a transformer 7, and may be protected against surges by means of a metal filament lamp 5 and a resistance 11 having a negative voltage characteristic and by the provision of an opposing winding 12, as described in Specification 543,794, [Group XXXVII]. The stator 15 of the induction motor carries an energizing winding 16 connected to the supply, and its poles are provided with shading rings 17 and also with winding 18 connected in series with a winding 19 and normally closed contacts 3 of the relay 4. In the absence of control current, the windings 18 are energized by induction between the windings 16, 19 and the motor tends to drive its shaft and a gear-wheel 32, Fig. 2, in the direction of the arrow, so that a pin 34 on the gear-wheel normally presses against a lever 54 thereby withdrawing a detent 50 from a ratchet 38. The latter is, therefore, urged by a spring 49 into an initial position with a pin 55 against a back-stop 56. When the relay 4 is operated by a control impulse, however, the shading rings 17 become effective to drive the gear-wheel 32 in the reverse direction, and the pin 34 disengages the lever 54 and eventually moves an arm 36 from a fixed stop 43 until it strikes a second fixed stop 44. During this movement of the arm 36, a pawl 47 pivoted thereon slides over a finger 48 and advances the ratchet 38, which is now held against backward rotation by the detent 50. At the end of the impulse the gear-wheel 32 again moves in the direction of the arrow, but the interval between impulses is insufficient for the pin 34 to reach its initial position against the lever 54. The ratchet 38 is, therefore, advanced one step for each impulse until an arm 39 integral therewith closes a pair of contacts 21, which make a circuit for a thermal relay 22. At the end of the series of impulses, the gear-wheel 32 returns to its initial position and the ratchet is released. The final impulse is prolonged sufficiently to allow the thermal relay 22 to operate. Specifications 522,419, 523,360, [Group XXXVII], 535,634 and 536,284 also are referred to.