Patent GB-752567-A (GB)
Title: Improvements in electric relays of the conducting liquid type
IPC: H01H87/00
Filed: 1954-01-26
Abstract: 752,567. Thermal switches. BENCHEMOUL N. R. Jan. 26. 1954 [Jan. 29, 1953], No. 2386/54. Class 38(5) An electric relay comprises a tank 4 containing a conducting liquid 13 communicating through small holes 39, 40 with liquid 3 in an outside container 1 and with a small chamber having a movable wall 14, so that when current passing through the liquid in tank 4 exceeds a predetermined value its effect on the liquid, as for example increasing its vapour pressure, results in movement of the wall 14 and consequent operation of contacts. These contacts may be in the circuit of the. current traversing the liquid or another circuit. The two electrodes are tank 4 and a metal cylinder 7 inside it. The liquid may be an electrolyte or mercury according as the current passing through it is A.C. or D.C. Tank 4 is mounted on a support 5 welded to the outer metal container 1 to which one terminal 37 is fixed. Electrode 7, which is retained in position by insulating ring 6, is connected through bolt 21, fixed contact 19, moving contacts 24, 25 on resilient blade 23, and fixed contact 20 to conductor 22. The moving wall 14 is a plunger which moves upwards against spring 15 when pressure is generated by the liquid so that stem 16 engaging rod 28 moves this up together with the moving contacts 24, 25 and button 26a. This button' 26a is depressed to close the switch, which may ibe opened manually by rotation of lever 34 when button 36 is depressed. The button 26a and with it the moving contacts, are located by the engagement of spring-pressed ball 29 in one or other of grooves 32; 33 in button 26a. The moving switch parts are mounted in an insulating block 18 carried by an insulating plate 8 forming with the help of flexible member 9 a lid for the hermetically-sealed container 1. The plunger 14 may be replaced by a bellows and the communicating holes between the liquid inside and outside tank 4 may be closed by valves when there is pressure inside, or the escape of liquid may be reduced by aerodynamic action, (Fig. 5, not shown). So that it may be evident whether the switch has been opened manually or by the liquid, in the arrangement of Fig. 2, the contact member 45 pivoted at 43 is operated manually by on-off buttons 54, 55 so that its lower end moves over spring-pressed ball 53, and by the fluid pressure through lever 44 which moves over spring-pressed ball 52 carried by contact member 45. While fluid pressure can open the switch at any time, once it has been so opened, it cannot be closed by depression of button 55 until lever 44 has been moved by depression of reset button 56. For three-phase operation, three switches with their separate inner tanks 4 may be immersed in common liquid in an outer tank, and there may be a common operating rotatable bar carrying contact levers, a handle, a cam cooperating with a spring-pressed ball, and levers operated by the pistons moved by the fluid pressure (Figs. 6, 7, not shown). Such a rotatable bar may be moved in opposite directions by two fluid pressure arrangements operated by current through them controlled by separate switches (Fig. 8, not shown).