Patent GB-601024-A (GB)
Title: Electrical control apparatus for placing a useful load in any desired position
IPC: G05D3/12
Filed: 1945-05-03
Abstract: 601,024. Electric follow-up systems. YARDENY, M. N. May 3, 1945, No. 11256. [Class 40 (i)] In a system for controlling a motor determining the position of a load, the motor is energized whenever a second motor is energized by the displacement of the primary member of a follow-up switch, the secondary member of which is driven by the second motor. Fig. 1 shows an arrangement in which displacement of an energized switch arm 48 from the position shown, i.e. occupying the gap between segments 45 and 46 in the case of Fig. 1, and bridging it in the case of later figures, causes one or other of relays 30 and 31 to lift one of arms 22, 23, whereupon motor 52 runs to drive the switch 42 round arm 48 until the switch arm is in its original relative position. If switch 19 has been closed during this operation, motor 1, driving load 5 through electromagnetic clutch 2,will have been actuated for a period determined by the displacement of arm 48. Indicators 60-62, consisting of meters associated with potentiometers suitably geared to the shaft to indicate digits, indicate the position of the load when switch 93 is closed. Load 5<SP>1</SP> is similarly controlled when switches 19<SP>1</SP> and 93<SP>1</SP> are closed. Fig. 2 (not shown) shows an arrangement in which two follow-up switches and motors are used to control the load motor from separate points, the relay arms being arranged to short the armatures of the motors which are of the permanent magnet type when arm 48 bridges the gap energizing them both to effect dynamic braking when the arm of the switch arrives at its original relative position. Fig. 8 (not shown) shows an arrangement in which separate relays are used to control the load and follow-up motors. In the arrangement of Fig. 9 (not shown) ratchet electromagnetic motors are employed, one being provided for each direction of rotation, an interruptor device driven from the switch shaft giving the necessary periodic interruption of the current to the motors. In Fig. 10 (not shown) a suitable circuit for using a squirrel cage induction motor is shown, dynamic braking being effected when both the relays are energized. Fig. 11 (not shown) shows a somewhat similar arrangement using single phase motors with shading poles. An additional motor and follow-up switch being interposed between the " load " motor and the load. Figs. 12, 13 and 16 (not shown) show similar arrangements. In the arrangement of Fig. 32 the angular motion of the load motor shaft is translated into linear motion by causing it to rotate tube 102 carrying a nut 1011 which causes screw rod 1010 and hence member 1002 to move up and down. Limit switches 1070 and 1062 are provided. In Fig. 34 (not shown) the screw rod is driven by the motor and engages a nut carried by member 1002. In this case the limit switch is additionally arranged to reverse the load motor in the event' of over-running, due to inertia. The arrangement may control a variable stroke pump as in Fig. 35 (not shown). Alternative indicating systems. The indicating system of Fig. 1 may be modified as in Fig. 22 (not shown) by replacing the potentiometers by a single potentiometer having independently movable arms, or as in Fig. 24 (not shown) by replacing the meters with one multiscale meter which can be connected to any one of the potentiometers by means of a multipolar switch. Alternatively resultant A.C. field devices may replace the potentiometer and meters. In the arrangement of Fig. 28 a rotary switch 827 lights one of lamps 810-812 to indicate coarsely the load position, while a similar switch 704 is geared up to give fine indications, the potentiometer and the lamp systems may be used together as in Fig. 25 (not shown). Optical projection means may be employed to magnify the movement of the load shaft, as in Fig. 30 (not shown). A neon stabilizer may be employed to stabilize the potentiometer supply voltage. Follow-up switch construction and mounting. The follow-up switch arm may have a ball contact as shown in Fig. 3, so that it tends to remain in the gap if over-shooting occurs. To equalize the thrust on the contact bearing disc, extra insulatingly mounted arm 291 (Fig. 4) may be provided. Provision may be made for stopping the motors at any instant by connecting both contact segments to the supply by giving an axial movement to the follow-up switch rotor, as in Fig. 14 (not shown).