Patent GB-191204073-A (GB)
Title: Improvements in and relating to Electrical Installations for Lighting, Heating and Ventilating Railway Carriages and for similar purposes.
IPC: H01H35/12
Filed: 1912-02-17
Granted: 1913-02-17
Abstract: 4073. Stone & Co., J., and Darker, A. H. Feb. 17. Lighting systems ; systems of charging and discharging galvanic batteries. - The reversible dynamo of a lighting-system is provided with a rocking-switch which is initially moved by the friction between the commutator brushes and the commutator to complete the circuit of the shunt field winding and the winding of an electro-magnet, which, when sufficiently energized, causes a further movement of the switch to connect the dynamo to the load circuit. The rocking switch may also. be employed to charge the battery connexions of a two-battery system, and, when the dynamo is provided with a demagnetizing series field winding, the movement of the brushes may be varied to provide an additional means of self-regulation. The rocking switch may be employed in addition to the usual connecting-switch, and an over-charge preventing switch for the battery is employed. In the arrangement shown in Figs. 1 and 2, the brushes b are mounted on a revoluble ring a, which also carries two iron projections c and at two diametrically opposite points, axially directed projections h, j which carry the brushes b. A pair of contact brushes m are placed on one side of the diameter passing through the projections h j, and two pairs of brushes r, s are similarly arranged on the other side of this diameter. The brushes m are connected to negative main n, Fig. 5, and the brushes r to a terminal of the shunt field winding p through a wire t and the winding z of an electromagnet d. The brushes s are connected to the positive main of the system through wires v, w. When the dynamo armature rotates in one direction or the other, the friction between the brushes b and the commutator causes the rocker a to turn through a small angle until the projections h, j are arrested, a member of the pair of brushes m and a member of the pair of brushes r thereby closing the circuit of the shunt field winding p and coil z of the electromagnet d. Further movement of the rocker a is resisted by the spring action of the brushes m, r until the dynamo has attained a predetermined voltage, when the electromagnet d attracts one of the projections c, which has been brought near it by the initial movement of the rocker, to produce a further movement of the rocker a, thereby causing one of the brushes s to contact with the projection h or j, to connect the dynamo to the positive main u. When the dynamo slows down, the diminished action of the magnet d allows the armature to be disconnected from the main u. If necessary, a second main circuit closer 7 may be provided, and the iron projections may be polarized. The dynamo may also be provided with a de-energizing series field winding 18 adapted to be short-circuited by means of a plug 22; when this winding is in use, the amplitude of the oscillation of the brushes b is increased by varying the thickness of the liners h', j<1> on the projections h, j, Fig. 1, in order that certain of the armature windings may assist the series field winding 18 in regulating the dynamo. The winding 29 of the battery over-charge preventer P is energized only when the load circuit is ' off,' by providing the main switch S with a pair of additional contacts 33, 34, which are bridged when the load 14 is disconnected. The switch P is arranged to disconnect the battery from the dynamo, or to insert a resistance 28 in the shunt field circuit of the latter. To reverse the battery connexions when the direction of rotation of the dynamo is reversed, the brushes s, s<1>, Fig. 6, are insulated from one another and connected respectively to the positive terminals of the batteries x, x<1>, a resistance 62 being inserted between the dynamo and the lamps 14. In the modification shown in Fig. 7, an extra brush 63 is provided, and the magnet d is provided with a series winding. The brush 63 is connected to a point in the shunt winding z of the magnet d, so that, when the brush 63 engages either of the projections h, j, a portion or the whole of the winding z is short-circuited, thereby decreasing the resistance in the shunt field winding p of the dynamo,