Patent GB-462790-A (GB)
Title: Improvements in and relating to electric circuit breakers
IPC: H01H71/02
Filed: 1936-04-27
Abstract: 462,790. Automatic circuit-breakers ; snap-action switches. BRITISH THOMSONHOUSTON CO., Ltd. April 27, 1936, No. 11936. Convention date, April 25,1935. [Class 38 (v)] Arc-rupturing devices ; cases.-The base 10 of moulded insulation has side walls 11 and intermediate walls 12 . . . 14 which extend to bearing blocks 15, the trip device 16, and lowermost end of the base, respectively, so as to form a number of compartments corresponding to the poles of the switch. A cross-wall 19 is also provided, Fig. 2. Extending between each terminal 20 and the cross-wall 19 is a conductor 22 and from each terminal 21 a conductor 25 extends to the cross-wall, this circuit including also conductors 27, 28 between which is a heater element 116 forming part of the trip device 16. The adjacent ends of bars 22, 25 have contacts 30 adapted to be bridged by contacts 32 of silver on a bridge 31, which is mounted within a carrier 33 and controlled by springs 36. A strip 38 carrying an arcing tip 37 is riveted in a slot in the carrier and connected to bar 25, to form a shunt to bridge 31. These are shunted by an arc-extinguishing device comprising a cylindrical compression chamber 41 with a fibre liner 45 surrounding fixed and movable contacts 46, 47. Contact 46 is connected to bar 22 by a bar 48, and is insulated from 41 by bushings 49, 50 and a washer 51 which, with a soft copper washer 55, make a gas-tight closure. A cap 56 with intervening gasket is threaded into the lower end of 41 to make a gas-tight closure for the movable contact 47, and a plug 58 with leather sealing washers 60 has a skirt 59 for directing such gases as escape along the contact 47 away from the bridge 31. In the open position, the sealing is aided by the shoulder 61 engaging the seat 62. An extension 63 on the contact 47 is connected to bar 25 and is slotted at 66 to receive a pin 65 on an operating lever 34 which carries the bridge 31, a spring 67 being provided for ensuring that contacts 46, 47 open after, and close before, the arcing tips 37. The levers 34 of all the poles are clamped at 69 to a common bar 68 for conjoint operation. Manual operation. The handle 74 is pivoted to a pin 72 in a U-frame 71 mounted on the bar 25 and has a pair of extensions 77 to which are pivoted the yokes 80 each carrying the rods 81 and plate 82. A U -member 79 pivoted to a pin 78, which engages in slots 86 in frame 71, serves as upper abutment to springs 83, Fig. 8. Pin 78 also engages a slot in a triangular plate 88 which is pivoted to frame 71 at 89 and to a link 87, which is pivoted to one of the levers 34. A further pair of levers 84 with cross-bar 85 are pivoted at 72 and carry the pin 78. When the handle 74 is moved downwards from the position shown in Fig. 2, the extensions 77 move the springs 83 and associated parts past the deadcentre position corresponding to pin 72, so moving the pin 78 in a direction to break the toggle 87, 88 and open the circuit. The reverse happens on reversely moving the handle, the toggle being extended to provide good contactpressure. Automatic tripping. The pin 72 carries a further lever 91, the free end of which carries a member 94 co-operating with a latch 93. Pivoted at 95 to lever 91 are a pair of pins 98 which are guided in the bar 25 and base 10 and surrounded by springs 92 bearing on surfaces 96 on the pins 98. When the latch 93 is deflected on overload, the springs 92 rotate lever 91 clockwise so that an arm 100 thereon bearing on the member 85 moves the levers 84 to open the circuit. Resetting is effected by lowering the handle so that a part 101 thereon engages a part 102 on lever 91 to restore it to the latched position, whereupon reverse movement of the handle recloses the switch. Electromagnetic and thermal trip devices. Latch 93 is carried on a member 104 pivoted at 105 and is adapted to be moved by impact from a surface 106a of a member 106 which is pivoted at 107, is under control of spring 121, and is held set by a part 114 thereon engaging a part 112a on a trip bar 112 controlled by springs 113 and common to all the poles. Bar 112 can be acted on either by the common armature 119 of U-shaped cores 118 partially surrounding the bars 28, or by means of insulating pins 117 moved by the flexure of bimetal elements 115 heated by the elements 116. When bar 91 is released, it releases a U-shaped, spring-urged reset member 108 which is pivoted at 109. Each limb of member 108 carries a pin 110 which engages a cam finger 111 on the member 106 to reset the latter behind the projecting part 112a. Thus, the latch system is reset ready for manual reclosure of the switch.