Patent GB-744900-A (GB)
Title: Improvements in synchronizing means in electric remote control systems of the so-called stepless type
Inventor: SAXON-SNELL MAURICE
IPC: G05D3/14
Filed: 1952-10-22
Abstract: 744.900. Electric follow-up systems. DOWTY EQUIPMENT, Ltd. Jan. 21, 1954 [Oct. 22, 1952], No. 26543/52. Class 40(1) The invention relates to positional control systems of the balanced bridge type in which a plurality of follow-up members are positioned through respective bridges by a single control member, unbalance in each bridge being sensed by a polarized relay. According to the invention the normally "fixed" contacts of all the polarized relays are mounted on a rigid displaceable member so that, during operation, the movable relay contact of a faster moving follow-up member will separate from its "fixed" contact, to retard movement of that member so that synchronism of the followup members is substantially achieved. As shown, two follow-up members 11, 12 are positioned by a single control member 27 through respective. br:dge circuits 24- 25, 124-125. Unbalance of the bridges is detected by respective polarized relays 23, 123 the cranked arms 29, 129 of which rotate in one direction or the other so that the main movable contacts 30, 130, 30<SP>1</SP>, 130<SP>1</SP>, carried by these arms engage the "fixed" contacts 32, 132 or 32', 132<SP>1</SP> according to the sense of the unbalance. Solenoids 17- 117 or 18-118 are thereby selectively actuated to control hydraulic jacks 15, 115 through selector valves 16, 116 to drive the respect members 25. 125 in the followup sense. The' relay arms carry auxiliary contacts 31. 31', 13<SP>1</SP>, 131' co-operating with respective "fixed" contacts 33. 33', 133. 133<SP>1</SP> so arranged that co-operating auxiliary contacts close after and open before the corresponding main contacts. The auxiliary contacts control through soleno'ds 22, 122 respective restrictor valves 21, 121 acting in the hydraulic return lines 20, 21. The hydraulic jacks 15, 115 are thereby restricted in their speed of operation except when the appropriate subsidiary contacts are closed so that the follow-up members 25, 125 are driven at full speed only for deviations greater than a predetermined minimum and are braked as coincidence is approached. The "fixed" contacts 32-33-132-133. 32<SP>1</SP>-33<SP>1</SP>-132<SP>1</SP>-133<SP>1</SP>. are carried resiliently an rigid members 34. 34<SP>1</SP> normally biased by respective springs to rest against a stop 35, the rigid members being pivotally moved against the action of their biasing springs by the relay arms 29. 129 proportionally to the amount of unbalance of the bridges. During rebalancing, should either follower member 25, 125 move faster than the other then the corresponding auxiliary and main relay contacts open in turn to slow down and then stop the faster moving follower until synchronism is substantially restored (Fig. 3, not shown). Modifications The arms 29, 129 may be mechanically linked through a lost motion which is not taken up during normal working. but which functions, when an electrical fault in one bridge arises, so that both follow-up members are operated although to some degree out-of-step.