GB548507A - Improvements in and relating to fluid-actuated electric circuit breakers - Google Patents

Abstract

548,507. Regulating fluid flow. BRITISH THOMSON-HOUSTON CO., Ltd. Aug. 20, 1941. Convention date, Aug. 22, 1940. [Class 135] [Also in Group XXXVII] An automatic circuit-breaker or other switch adapted to be closed, against the action of a throw-off spring, by a pneumatic motor, has means for increasing the flow of operating fluid to the motor during the closing stroke so as to overcome the increasing spring-strain. The contacts may be separable in an arc-chute to which an arc-extinguishing cross-blast may be supplied from the pneumatic source, as in Specification 544,017, [Group XXXVII]. The contact-carrying rod 19 is opened by spring 18 and held in closed position by a linkage-system which is held, in turn, by a lever 36 and latch 44 trippable by coil 46. A toggle 33, 34 is pivoted to the lever 36 and also to a lever 39 which is pivoted at 40 and linked at 41 to a further lever 24 pivoted at 25 and connected to a lever 20. In the opening movement the latter is moved away from stop 23 and a cross-head 21 slides in a guide 22 so rotating 24 clockwise and 39 anti-clockwise. In the closing movement, a rod 29 acts on the toggle-roller 35, and, provided the lever 36 is latched, moves the toggle over-centre against abutment 48. A link 26 is connected to lever 24 for simultaneous operation of the other phases. The rod 29 is formed on a piston 28 in a cylinder having a port 32 and return-spring 30, the fluid being admitted behind the piston through a solenoid-operated valve 50. Interposed between the two is a flow-varying device 51, Fig. 2, comprising a displaceable rod 53 which is urged by a spring 54 to follow the piston 28 and has a tip 55 of reduced diameter providing an annular space 56 in the inlet 271 initially restricting the flow. As the closing stroke proceeds, the spring 54 initially, and then the fluid itself, urges the rod so as to bring flutes 561 into the inlet 271. Instead of reducing the tip-diameter a slot may be cut in the tip, Fig. 3 (not shown). In Fig. 5, a device 59 interposed between valve 50 and inlet 271 comprises a pair of members 63 forming a housing for a plate 60 which has small and large orifices 62, 61 for the initial and final parts of the stroke, respectively, and is linked to the lever 39 so as to be operated thereby.