Patent GB-190902754-A (GB)
Title: Improvements in or relating to Switches for Electrical Purposes.
Inventor: RORKE THOMAS JOSEPH
IPC: H01H50/30
Filed: 1909-02-04
Granted: 1910-02-04
Abstract: 2754. Rorke, T. J., and Rorke, E. Feb. 4. E l e c t r o - m a g n e t i c switches; mercury switches. - Electric switches are actuated by imparting a rocking movement to an armature provided with a coil or coils arranged in a magnetic field, and carrying a mercury-contact tube which is adapted to short-circuit or break the circuit of the armature coil or coils which has been closed to bring about the rocking movement of the switch. In the form shown in Fig. 1, the switch comprises two or more pairs of permanent magnets or electro-magnets a', between the pole pieces a<6> of which the armature is rotatably mounted on stationary spindles b<1>. The armature comprises a cylinder of copper wound with a coil b<4>, Fig. 5, and provided with an extension piece to which are secured a cradle b<7> for the mercury contact tubes c, c' and an insulated switch arm b<8>, carrying a fork b<9> dipping into mercury pots c<2>. The arrangement of the armature is such that the field set up by the current in the coil b<4> produces a rotary movement and inserts or withdraws the fork b<9> from the mercury pots according to the direction of the current, the movement being assisted by the weight of the arm b<8> and by a counterbalance arm b<10> carrying an adjustable weight b<11>. The main terminals d<4> are connected to the mercury pots. The connexions for the switch are shown in Fig. 5, in which e' is a battery and e<5> a two-way switch. The mercury contact tubes c, c' are each provided with two pairs of contacts e, e<1> and e<2>, e<3>. Assuming that the main switch and two way switch are in the positions shown in Figs. 1 and 5 current flows from the lattery to the coil b<4> through the contacts e, e<1> which are connected by the mercury ; the main switch then moves into the " on " position and at the same time the mercury leaves the contacts e, e<1> and connects the contacts e<2>, e<3>, thus preparing a circuit ready to send the current through the coil b<4> in the opposite direction and to open the main switch when the switch e<5> is moved into its other position. The two-way switch e<5> may be operated manually or automatically, or may be replaced by a maximum and minimum thermometer with contacts, or by similar apparatus. In a modification, two batteries are used and one of the contact tubes c, c' is dispensed with. In another modification, Figs. 9 and 10, especially applicable for use in charging accumulators, the armature is provided with a coarse winding f<1> and a fine winding f; the fine winding is always in circuit with the dynamo and accumulators but is so arranged as to be short-circuited as long as the electromotive force of the dynamo is greater than that of the accumulators. In the form of this device shown in Fig. 9, the fork b<9> and mercury pots c<2> are replaced by a contact tube h<4> provided with contacts f<5Î>, g<6Î> to which the fine winding f is connected. The connexions for this form of switch are shown in Fig. 10, in which the fine winding f is short-circuited by the mercury in the tube h<4> when the latter is horizontal. Should the current be reversed, the armature is rotated, and the contact is broken in the tube h<4>. For controlling the lights in a building the form shown in Fig. 11 is employed, in which the fork b<9> is connected to the terminals f<4>, f<5> of the coarse winding, ard a single contact tube c with a constriction is used ; g<5>, g<6> are the terminals of the fine winding. Assuming the switch to be in the " off " position as shown, on closing the switch or switches g<4>, a current is sent through the fine winding, thus causing the armature to tilt the tube c and break the contacts e<1>, e<2>. Before this has time to take place (owing to the constriction in the tube c) the prongs of the fork b<9> enter the mercury pots c<2>, c<3>, thus sending the main current through the coarse winding in such a direction as to hold the switch in its closed position. When all the switches g' are opened, the flow of current through the coil f ceases, and the armature moves to the " off " position under the action of gravity, the mercury being prevented by the constriction in the tube from reaching the contacts e', e' until the main circuit is broken at the mercury pots.