Patent GB-1098617-A (GB)
Title: Apparatus for operating door
IPC: E05F15/14
Filed: 1965-06-29
Abstract: 1,098,617. Automatic speed control. WESTINGHOUSE ELECTRIC CORPORATION. June 29, 1965 [July 22, 1964], No.27521/65. Heading G3R. [Also in Division E2] In a door-operating mechanism in which the door is powered by a D. C. electric motor M1, the speed of the door is precisely controlled, a Pattern Generator producing a Command signal to dictate the speed of the door at all positions thereof, further means producing a signal proportional to the actual speed of the door, the two signals being compared and the error signal used to control the flow of current to the motor. Pattern Generator. The reluctances of transformers T4, T5 are varied according to door position by suitably shaped iron cams rotating in synchronism with the motor. The current flowing in the secondary circuits T45, T55 are rectified by bridges D1-D4, D7-D10 to produce voltages L+ and L-. According to whether switch SW is connected to DO for opening the door or to DC for closing the door, transistor Q3 causes either Q5 or Q2 to conduct and connect either L- or L+ to line LP. The current in LP (i.e. the Command signal) therefore flows in one or the other direction and is dependent in magnitude on either L- or L+ (i.e. the door position whilst opening or the door position whilst closing). Speed proportional signal. The armature of D. C. motor M1 is connected in a balanced bridge having arms M1, R21 and Ll, R22, R24. The bridge is unbalanced by the back-E. M. F. of the motor when running, and a signal proportional to this E. M. F. and hence the motor speed appears at J2. Motor Control. The current flowing into the base of transistor Q9 is the difference between the Command signal and the speed-proportional signal. Condensers C4, C5 are charged in circuits V B , R26, C4, TIP, ground and V B , R29, C5, T2P, ground at rates too slow to cause substantial current in secondaries T15, T25 of transformers T1, T2, and to potentials too low to cause discharge through uni-junctions Q6, Q7, which are biased by the output, rectified by bridge D13-D16, of transformer T3. The motor is supplied from A. C. source 110, 111 via controlled rectifier SCR2 for opening or via SCR1 for closing. If the door is initially closed, switch SW is on DO but the motor supply is cut-off by limit switch CL. Switch SW is then connected to DO for opening the door, and a Command signal current flows from J2 and through Q5. This reduces the current through transistor Q9, correspondingly increasing that through transistor Q8. The potential on condenser C5 is so raised that it discharges early during each half-wave impressed on SCR2, thus causing SCR2 to conduct and deliver pulses of power to motor M1 The current flowing in LP (i.e. the error signal of the Command signal and the speed-proportional signal) determines the charge on C5 and the proportion of each half-wave applied to SCR2 that SCR2 conducts. Should the current in LP be reversed, by the motor running faster than the command potential dictates, the conduction of transistor Q9 increases at the expense of the conduction of Q8, the potential of condenser C4 increases and that of C5 decreases, so that SCR1 is switched on in place of SCR2 to regeneratively brake the motor. The motor is similarly controlled during door closing, SCR1 being the normally conducting of the two controlled rectifiers. Limit switches OL, CL stop the motor as the door reaches its closed and open positions respectively.