Patent GB-190426295-A (GB)
Title: Improvements in Electric Control Systems
Filed: 1904-12-02
Granted: 1905-11-09
Abstract: 26,295. British Thomson-Houston Co., [General Electric Co.]. Dec. 2. Motors, controlling.-A motor used to operate valves, elevators, steering-gear, and bulkhead or other doors is controlled by the movement of a bar between two normally balanced electromagnets. The motor 4 is shown geared to the nut 3 on the stem 2 of a gate valve 1 and in circuit with a reversing-switch 5 operated by solenoids 6,7. Two electromagnets 15, 16 have a common armature 17 on a lever 11, which carries at its other end a bridging-piece which can complete the circuits of the solenoids 6, 7 through the contacts 14, 13. The coils 25, 26 of the differential volt-meter or am-meter 24 are connected in shunt or series with the electromagnets 15, 16. A rheostat 18 at the controlling - station is connected in series with a rheostat 19 across the mains 8, 9. The arm 21 of the rheostat 19 is geared to the valve stem, preferably by a toothed sector 22 and a rack 23 on the stem. While the arms 20, 21 rest on corresponding studs, the resistances shunting the electromagnets 15, 16 are equal, and the switch 10 remains open. If the arm 20 be moved, the balance between the magnets 15, 16 will be disturbed and the armature 17 will move, thus forcing the bridging- piece 10 against the contacts 13 or 14. One of the solenoids 7, 6 is energized, and operates the switch 5 closing the motor circuit. The motor then raises or lowers the valve until the arm 21 has changed the resistance 19 in the circuit to restore the balance between the magnets 15, 16. In a modification, Fig. 2, the rheostats 18<1>, 19<1> are arranged under one handle 29, and are connected to the main 8, and by means of the strips 27, 28 to the electromagnets 15', 16', which have a common armature 17<1> normally midway between them. This armature can complete the motor circuit through the contacts 13<1> or 14<1>, The coils 15', 16<1> are connected at opposite ends of a rheostat 32 and to two solenoids 36, 37 with a common core 35, which carries an arm 34 in contact with the strip 33 and the studs of the rheostat. The other terminals of the solenoids 36, 37 are connected to the strips 38, 39, which are connected to the studs of the rheostats 40, 41 by two insulated arms 42, 43 carried by the stem of the valve. When the switch arms are arranged as in Fig. 2, the two current paths through the rheostats 18<1>, 19', 32, and the solenoids 15<1>, 16<1> balance each other. To close the valve, the handle 29 is moved to the extreme left. The coil 15<1> then has a stronger current than the coil 16', and the armature 17<1> is moved to close the motor circuit across the contacts 13'. As the valve falls, the arms 42, 43 insert more of the resistance 40 in circuit with solenoid 36, and cut out resistance 41 from the circuit of the solenoid 37. This disturbs the balance between the two solenoids, and the core 35 moves downwards, changing the resistance until the valve is closed and the arm 34 is at the bottom of the rheostat 32. The current in the coil 15<1> then balances that in the coil 16', and the armature 17<1> breaks the motor circuit in moving to its central position. The arm 32 acts as an indicator showing the position of the valve, elevator, &c. The rheostats are preferably of a continuous kind, so that the circuit is not broken when the arms pass from one stud to another.