Patent GB-474747-A (GB)
Abstract: 474,747. Automatic regulators; automatic control systems. BRITISH THOMSON-HOUSTON CO., Ltd. April 6, 1936, No. 10152. Convention date, April 9, 1935. [Class 38 (iv)] An electric regulator for effecting variation of resistance in a circuit and of the kind in which a main control element provided with a movable coil is maintained in alignment by a parallel motion linkwork, is constructed so as to provide a closed magnetic circuit with an annular gap in which the coil moves. This apparatus may be employed to regulate automatically the voltage of a D.C. generator as used for example on vehicles. In the construction shown in Figs. 1 and 2, the magnet core consists of a central member 4 surrounded by a stationary exciting coil 10 and two return bars 6, 7 connected to the member 4 and to one another at their lower ends by a transverse bar 8 and at their upper ends by a ring 5. Arranged in the air gap between the member 4 and the ring 5 is a movable coil 11 mounted on an insulating member 12 and a copper or other metal cup member 13 having a damping effect. The movable coil assembly is supported by tension springs 29, 30 and is guided vertically by steel spring blades 23, 24, 25. The lower blades 23, 24 also serve as leads for the current flowing through coil 11. To the upper end of the coil assembly is connected a steel plate 15 supporting insulation 16 on which is mounted a contact bar 17 electrically connected to the blade 25 and co-operating with a double row of spring contacts 38 mounted on insulating strips 35. As the coil assembly including bar 17 rises or falls in response to variation of current in the coil 11, contact is made or broken between the bar 17 and contacts 38 in succession whereby resistances associated with the contacts 38 may be cut in or out of a circuit. As the assembly moves downwards in response to current increase in coil 11, the additional tension of the springs 29, 30 and the variation in pressure of the spring contacts 38, is largely counteracted by the increasing magnetic forces acting on the steel plate 15. Excessive magnetic force on the plate 15 towards its lowermost position is counteracted by the reverse pull on the steel disc 15<1> where it passes the edge of the recess 4<1> in the core member 4. In a modification, the lower transverse bar 8 is replaced by a magnetic ring similar to the upper ring 5 and a coil similar to the coil 12 moves vertically in the air gap between the core member 4 and the ring. This coil co-operates with the upper coil 12 by acting on the lower ends of the springs 29, 30. The apparatus described above may be used as shown in Fig. 3, to control automatically a generator 44 adapted to charge a battery 49 and supply lamps on a vehicle. The shunt field winding 45 is supplied through a series of resistances 51 which may be switched in or out in succession by vertical adjustment of the bar 17 in response to variations in the generator output. The fixed and movable coils 11, and 10 are in parallel and are connected to the generator positive pole through a relatively large resistance 52. The coils 11, 10 are connected to the negative pole of the generator through the load resistance 54, and the compensating resistance 56 respectively. Resistances 57, 58, 59 are also. introduced to give an increased dashpot action, to prevent hunting and to increase sensitiveness. In a modification, the resistance 56 is dispensed with and the field winding 45 is connected to the negative pole of the generator through an additional fixed coil on the core member 4 supplementing coil 11. In the modified construction of apparatus, the additional lower coil is connected across the series field winding of the generator and the fixed and movable coils 11, 10 are arranged in series. A temperature responsive winding may be connected across the coil 11.