Patent GB-1292030-A (GB)
Title: Improvements in or relating to a control device and a method of controlling thereby
Inventor: VARGA JOHN MAXIMILLIAN JULES
IPC: G05B19/16
Filed: 1968-12-24
Abstract: 1292030 Programmed control of machines CARDING SPECIALISTS (CANADA) Ltd 22 Dec 1969 [24 Dec 1968] 61244/68 Heading G3N A machine, having a member to be moved in accordance with a predetermined programme, is controlled by information sensed by a pick-up adjacent to a programmed surface which is moved relative to the pick-up, the pick-up being moved in accordance with movement of the movable member, and the pick-up and surface are moved concurrently. As shown, a magnetic tape passes at constant speed from a delivery spool 11 to a take-up spool 12 and bears wavelength modulated waveforms sensed by pick-ups y, y, a reference waveform sensed by a pick-up x, a velocity controlling waveforms sensed by pick-ups w, w and a viscosity related waveform sensed by a pick-up z. The pick-ups y, y are positioned by an hydraulic ram 15 coupled to a movable member of a machine tool, (not shown). The frequencymodulated signals from the pick-ups yy are fed to converters 16 from which are derived D.C. voltages which are compared in a comparator 18 and the error, through a servo-amplifier 19, controls a servovalve 22 determining the supply of fluid to the ram 15 from a pump 23. The signal from the pick-up x is fed to a converter 33 and the resultant D.C. signal fed through an amplifier 33 to a logic circuit box 34. The programme, produced by operating movements of the member coupled to ram 15 or prerecorded, contains breaks in the signal whereby the arm is maintained in step. During play-back a positioning break is sensed by the pick-up x and the logic circuit box opens a switch 30 between a speed control amplifier 31 and an electric motor 29 driving the spool 12. A unique identification of the coincidence between pick-ups yy and x is effected by ratcheting the spool 12 through a clutch 36 and a solenoid 37 and, when the pick-ups yy are moving in the same direction as the tape; actuating a freeze-valve actuator 35 locking servovalve 22. When the heads yy reach the break the logic circuit box 34 causes the tape to re-start. The pair of pick-ups ww detect waveforms on the tape for accelerating or decelerating the device and the signals derived are fed to frequency-voltage converters 39 and the resultant D.C. signals compared in a comparator 40. The resultant signal is amplified in an amplifier 41 and used to control the delivery of the pump 23 and the speed of the motor 29 by control of amplifier 31. A pick-up z is used to compensate for changes in the viscosity of the hydraulic fluid, the detected signal being fed through a converter 42, a comparator 43 to control the pump 23. A reference generator 44 is connected to the comparator 43 and amplifier 31 to keep a reference voltage v kept in step with programmed changes in the general speed of the work-cycle. Two or three dimensional movement is effected by providing two or three different programmed tapes all having fixed and movable heads which are synchronized by positioning breaks. It is stated that an additional pair of tracks can be used to maintain tape speed slightly faster than that of the moving member. In an alternative arrangement for effecting tape synchronization the movable head positions a belt which through selectively operated electromagnetic clutches drives the tape take-up spool. In an alternative embodiment, a separate track is employed for each direction of travel and the output from a pick-up is arranged to operate a change-over valve.