Patent GB-925475-A (GB)
Title: Improvements relating to electro-acoustic control systems
IPC: B66B1/34
Filed: 1961-10-16
Abstract: 925,475. Electro-acoustic control systems. PEELLE CO. Oct. 16, 1961 [Dec. 30, 1960], No. 37015/61. Class 40 (7). In a system for controlling the movement of a movable element (constrained to move along a predetermined path) in dependence upon its position relative to a fixed position, a primary station transmits pulses of ultrasonic energy towards both the movable element and the fixed position at each of which means are positioned which transmits back to the primary station, in response to reception of the pulses from the latter, respective distinguishable reply pulses (also of ultrasonic energy) and at the primary station a control signal for controlling the movement of the element is produced the magnitude of which is dependant on the time interval between the reception of the two distinguishable reply pulses and the sign of which is dependent on which of the two latter pulses is first received. The invention is described in connection with the control of a lift carriage C (Figs. 1 and 2) in the vicinity of one or more floor stations B, the arrangement comprising a primary station A at the bottom of the lift shaft transmitting pulses of ultrasonic energy of frequency f1, a reflector 18 on the carriage C and a transponder B transmitting reply pulses on frequency f2. As shown in Fig. 2, the station A comprises a master pulse generator 11 producing pulses of 10 microsecond duration with (for a 100-ft. shaft) a repetition frequency of about 5 c.p.s. These pulses trigger an oscillator 12 (operating at a frequency f1 of 15 to 100 kc./s.) which controls via a T/R device 13 an ultrasonic transducer 14, the pulses transmitted by which are reflected directly by reflector 18 (frequency f1) whilst at a floor station such as B, apparatus comprising a transducer 17, T/R device 20, detector 21, adjustable delay 22 (to compensate for distance d), lift call switch 23, oscillator of frequency f2, 24 and amplifier 25, operates (when switch 23 is closed) in response to reception of the pulses from 14 to transmit reply pulses of ultrasonic energy of frequency f2. At station A the received pulses of frequency f1,f2 are detected by respective receivers 27, 28 and supplied, inter alia, to an error sign register 30 which is set to the " 0 " state (indicative of " lift too high ") by the commencement of f2 pulses and to the " 1 " state (indicator of " lift too low ") by the commencement of f1 pulses. The output of receiver 28 is also supplied to a circuit 35 (details of which are given with refence to Fig. 4, not shown) which after the reception of about 3 or 4 pulses of frequency f2, is conditioned by the next pulse from generator 11 to supply an output signal to an " AND " gate 37 a second input to which is derived from an " OR " gate 36 having as input, the outputs of receivers 27, 28. In operation, when gate 37 conducts it supplies signals to a switch 38 which operates in response to each input signal to reverse the state of a register 31, the latter being set in the " 1 " state at the commencement of each cycle of operation by a pulse from generator 11. When the register 31 is set in the " 0 " state it opens a gate 40 which passes a control potential from the register 30. This potential, which is a D.C. signal, the polarity of which depends on the setting of the register 30, is supplied over lead 45 to conventional lift control devices including magnetic amplifiers 50 which operate to move the lift car in the appropriate direction until the f1 and f2 pulses occur simultaneously. In the latter condition, the lift car is correctly positioned with respect to the floor station and further movement is stopped. A modified form of the circuit in rectangle 33 (Fig. 2) and which ensures that the operation of gate 40 is independent of the interval between the reception of f1 and f2 pulses (which is important when such interval is very small, i.e. when the lift car is almost correctly positioned) is described with reference to Fig. 5 (not shown). Conventional electronic interlock and memory arrangements are employed to prevent simultaneous operation of two or more of the switches 23 which may also be operated by remote radio control from switches in the lift car.