GB282074A - Improvements in and relating to combined automatic and manual electric circuit controllers - Google Patents

Abstract

282,074. British Thomson-Houston Co., Ltd., (Assignees of Hutt, L. P.). Dec. 13, 1926, [Convention date]. Automatic circuit-breakers; thermal switches; switches, quick-action.-A switch for controlling the electric motor of a refrigerator is opened and closed manually, and if closed manually is opened and closed automatically according to temperature variations in the refrigerator, and should the motor be stalled is tripped open due to the excess current. The member 13, Fig. 5, is moved to the left to press against an extension 33 and so turn a cradle 23 about a pivot 24 until a shoulder 28 catches under the hooked end of a bimetallic strip 26. This action causes mercury in a tube 14, carried by the cradle 23, to bridge the contact terminals 34 and so complete the circuit. Decrease of temperature causes bellows 16 to contact under the action of a spring 20 and thereby lower the pivot 24 which is carried by a lever 18 pivoted at 19. The cradle 23 thereupon turns counter clockwise about the hooked end of the element 26 as fulcrum and the circuit is broken. Successive rise of temperature causes expansion of the bellows and clockwise rotation of the cradle and reclosure of the circuit. Movement of the strip 26 to the right, due either to excess current in a heater 29 or to movement of the member 13 to the right, causes the hooked part to disengage the shoulder 28 and allow the cradle to turn to the open circuit position. In a modification the mercury tube is replaced by snap action contacts 61, 62, Fig. 9. Movement to the " on " position of a handle, not shown in this Figure, lifts a bell crank lever 64 about a pivot 63 until its end catches under the hooked end of the bimetallic strip 26. This movement brings the contact 62 into engagement with the contact 61. Decrease of temperature causes the bellows 10 to contract and move the lever 18 to the right.. The lefthand leaf spring 66 carried by the lever 18 bears against a pin 67 carried by a lever 65 pivoted at 63 and is strained until a pin 75, attached to the lever 18 by an arm 76, moves a latching-arm 72 Sufficiently to allow a notched arm 73 also carried by the lever 65 to move upwards, whereupon the member 65 moves with a snap action to carry the contact 61 to the left and break the circuit. Successive rise of temperature causes expansion of the bellows and straining of the right hand leaf spring 66 until another latching-arm 71 is moved sufficiently to allow the notched arm 73 to move downwards, whereupon the contact 61 moves to the right with a snap action to complete the circuit again. Movement of the strip 26 to the right, as in the first construction, releases the member 64 which falls and opens the contact 62. Specification 214,768, [Class 29, Cooling &c.], is referred to.