Patent GB-555242-A (GB)
Title: Improvements in and relating to electric circuit breakers
IPC: H01H3/30
Filed: 1942-01-06
Abstract: 555,242. Automatic circuit-breakers; fluid-blast switches, actuation of switches; switch contacts. FOSTER TRANSFORMERS & SWITCHGEAR, Ltd., and LOWE, R. G. Jan. 6, 1942, No. 181. [Class 38 (v)] A circuit-breaker comprises a pair of contact arms 15a, 15b pivoted at 14 and carrying contacts 16a, 16b which co-operate with fixed contacts 12a, 12b and are interconnected by a fuse, overload coil, current transformer or flexible connection 17. Downward extensions 15c, 15d of the arms are shaped as cam surfaces co-operating with cam members 27 on an arm 28 which is rotatable by a rack and pinion 45, 46 from a rod 47 passing through apertures 50, 48 in the plates 10, 13, and guided by a toggle-roller arrangement 55 .. 58. The rod 47 is lifted to close the breaker by means of a handle 53 and pivoted pawl 51 and retained by a spring-catch 54. The toggle 55 .. 57 can be broken by an overload-operated cam 64, or if the closing effort is relaxed, so that a downward pressure is imparted to the roller 58, so freeing the rack from the pinion and allowing the switch to open. The cam 27 is preferably moved slightly over-centre in the fully-closed position so that it continues its rotation in the same direction when tripped, the opening being accelerated by a pair of springs 24 and rods 22 pivoted on shaft 23. Each fixed contact comprises a main part 39, and arcing tip 40 and the end of each movable arm is cleft to receive the "flick" contact 16a or 16b which is slotted at 33, Fig. 4, to engage the pivot pin 32 and is acted upon by a blade spring 36 engaging a recess 37. In opening, the arcing lip a lags and rotates the contact 16a anti-clockwise, straining spring 36, until stopped by pin 38, thus causing the contact to spring clear, when it finally leaves the tip 40. The making occurs at surface b away from the main contact surface c. A modified form of fixed contact is also described, Fig. 6 (not shown). In Fig. 7 a pair of "solid" movable contacts 16b, 16b' are interconnected by a blow-out coil 70 surrounding a magnetic core 73 connected to cheeks 72 and plates forming an arc chute 71. In the open position a transverse barrier 74 comes between the fixed contacts. Since the contacts are " solid " a spring-connection is interposed in the cam actuating-means, Fig 9 (not shown). Alternatively, a fixed arc chute comprises, Fig. 12, a transverse radiator plate 80, which is corrugated to give a large cooling surface and apertured to allow escape of gases. and a reflector plate 81, the space between them leading to an outlet 132. The lift rod of 86, Fig. 11, may be manually operated or connected to an electromagnet 92, and has a cam 87 co-operating with the long arms 85a of a star wheel 85 on the shaft 28. When cams 27 move over-centre, the short arm 85b engages the cam 87 to retain the breaker closed. The rod 86 is guided by pins 88 and a roller 94 on a lever 95 having slots 96 engaging pins 97. The lever is positioned by springs 133 and a roller 98 engaged by a trippable roller 99, this providing release on overload and faulty closing movement, as in Fig. 1. A fluid-blast switch (gas, air, or liquid) comprises a nozzle 109 communicating with the hollow shaft 14 and by way of a valve and pipe 102 with a reservoir 101. the valve having an operating rod 105 operated by a pivoted hand lever 106. The reservoir communicates also through a manual or mechanical valve 113 with a pipe 111 and cylinder 112 containing a piston 116 which, when actuated is pressed to the left against spring 117 and by means of a wing 118 engages the arm 85 of the star wheel to close the switch. The piston 116 is latched, and the switch retained by a recess 120 and roller 119 on a lever pivoted at 122. This lever is connected by a lever system 124, 125 127 to the lever 106 so that operation of the latter trips the switch as well as supplying the arcing blast. The lever 127 can also be operated by the armature 129 of electromagnet 128 to trip the breaker.