Patent GB-841446-A (GB)
Title: Improvements in function control systems
IPC: G08B21/00
Filed: 1958-04-01
Abstract: 841,446. Remote control circuits. SHAND & JURS CO. April 1, 1958 [April 26, 1957], No. 10485/58. Class 40 (1). In a remote-control system for controlling a valve, door or other movable device, the remote station 10 has a first relay M for effecting the desired control and, controlling the operation of the first relay M, a second relay V operable by a strong current and inoperable by a weak current, a line 98 from a control station 9 and a resistance connected to a power source in the control station which normally sends a weak current and is by-passed to send a strong current. The source T1, T2 is connected to the primary of a transformer 11, the secondary having one end earthed at T4 and connected at the other through a resistor R1 to rectifiers 14, 23. These are connected through relay coils A, B and CA and line 18 to terminal T3, relays A and CA being shunted by push-button 19 and relays B and CA by push-button 28. A push-button 31 earths terminal T3. The secondary winding is also connected to a line 37 which connects through rectifier 36 and relay contacts B6 or rectifier 42 and relay contacts A6 to line 39. This passes through coil CB, and resistors R2, R3 to earth T4. Between line 37 and earth are connected lamp L1 and relay contacts A1, lamp L2 and contacts C1 or contacts A3 and B1 and lamp L3 and contacts B3. The remote station 10 connected by terminal T5 to the other end of transmission line 98 consists of a rectifier 61 connected through relay coil V and switch 63 to earth point T6. A parallel circuit consists of rectifier 74, relay coil U and switch 77. Switches 63 and 77 are limit switches which open when the controlled device reaches the end of its movement. Input terminal T5 is also connected through resistance R4 and relay contacts M1, N1 and parallel rectifiers 68, 79, from the other sides of which are connections through line 69 and the primary winding of transformer 66 to earth. Contacts M1, N1 are connected by condensers 83, 87 to earth. Secondary winding of transformer 66 connects to power source terminals 77, 78 and is shunted by parallel circuits consisting of contact Ul, relay coil M and contact V2 and contact U3, coil N and contact V4. If the controlled member is a door, switch 63 remains closed until the door is fully open and switch 77 closed until it is fully closed. Operation.-When the door is closed a weak current consisting of positive pulses passes through rectifier 14, coils A and CA, terminal T3, line 98, terminal T5, rectifier 61, relay coil V, switch 63 and terminal 76 to earth. This current is insufficient to operate relay V but it operates relay A, contacts A1 of which open to switch off lamp L1. Contacts A6 close and negative pulses pass through coil CB, opposing the current in coil CA to prevent operation of relay C. Lamp L2 remains until lamp L3 remains lit. To open the door push-button 19 is pressed to by-pass coils A and CA and apply the strong positive pulses to the line so as to operate relay V. Closing of contacts V2 energizes relay M adapted to control the moving of the door and closing of contacts M1 provides a steady D.C. voltage from rectifier 68, smoothed by condenser 83, to hold relay V and, returning along line 98, flows through coils B and CA to operate both relays B and C. This causes lamps L1 and L2 to light, indicating that the door is being moved towards an open position, and lamp L3 goes out. If it is desired to stop the movement of the door before it is fully open, button 31 is pressed to connect line 98 to earth, thereby dropping out relay V, opening contacts V2 and de-energizing control relay M. Switch 77 is now closed so that when button 31 is released, weak currents of both polarities pass over line 98 and operate relays A and B, causing lamp L1 to go out and leave L2 lit. Had it been desired to move the door to the fully-opened position button 31 would not have been pressed. At the fully open-position switch 63 opens to de-energize relay V which, in turn, drops out relay M. A path over line 98 now exists for negative pulses from rectifier 23 through rectifier 74 and relay coil U. Relay U is not operated by weak currents but relay B picks up to cause lamp L3 to go out. Lamp L1 lights and lamp L2 remains out. Pressing push-button 28 applies strong negative currents to line 98 from rectifier 23. This energizes relay U, and through contacts U3 energizes relay N to drive the door in the other direction. This causes a steady negative voltage to be applied to line 98 which operates relays A and C as before, the lamps responding to changes in contacts. The closing movement of the door can be stopped when required by pressing button 31 as before and the process may be recontinued by pressing button 28 again. At the fully closed position switch 77 opens to de-energize relay U and stop further movement of the door. If line 98 fails the weak current is interrupted and neither of relays A or B is operated. Lamps L1 and L3 light to indicate the fault.