Patent GB-618663-A (GB)
Title: Improvements in oil-immersed electric fuse-switches and circuit breakers
IPC: H01H71/12
Filed: 1946-11-11
Abstract: 618,663. Automatic circuit-breakers. LONG & CRAWFORD, Ltd., LONG, E., and TAYLOR, E. Nov. 11, 1946, No. 33416. [Class 38 (v)] Opening of the cover of a three-phase oilimmersed fusibly tripped circuit-breaker raises the fuses above the oil level to permit their renewal and re-setting after blowing. For each phase there is a pair of side cheeks 1 through which pass supporting bars 2 fixed to an end plate 3 having a pivot pin 4, each pair of cheeks 1 forming a carrier for a fuse constructed as disclosed in Specification 618,664. The plate 3 is urged counter-clockwise by springs 12 connected to a member 11 pivoted to it at 6a; a hook 6 also pivoted at 6a is held by a link 7, pivoted to it, whereby it normally engages a roller 22 on a triangular plate 21, freely pivoted on the pin 4. The link 7 is also pivoted to a part 8 fixed to a shaft 9 which passes through the side cheeks 1 and end plate 3, the shaft 9 being torsion spring- loaded by a spring (not shown). A link 20 pivoted at 20a to the plate 21 is pivoted to a plate 18 to form an overset toggle. The plate 18 is freely mounted on the handle-shaft 15 and has a lug 19 normally engaging an adjusting screw 65 in a fixed bracket 66. Fixed on the shaft 15 is a plate 16 having a hook 17 spring- urged anti-clockwise about a pin 17a, the hook 17 normally engages the bracket 66, whereby it is held clear of the lug 19. Movement of the handle 14 to the " off " dotted position, rotates the shaft 15 clockwise, and the hook 17 moves without engaging, past the lug 19, and the pin 17a comes against the plate 18, thereby breaking the toggle. The springs 12 then rotate the plates 3, 21 and hence the fuse carriers 1 anticlockwise about the pivot 4 and break the circuit between the fixed contacts 25, 26 and the movable contacts 23, 24 on the carriers. During this action the lug 19 overtakes and is latched by the hook 17. The opening movement is arrested by a pin 27 on the plate 16 engaging at the point P in the jaw of a plate 28 pivoted at 31. The plate 28 is also pivoted to a link 30 pivoted to the cover 29, whereby raising the cover rotates the plate 28 anti-clockwise and a point Q in the jaw engages the pin 27 rotating the plate 16 further clockwise. Since the lug 19 is engaged by the hook 17, the carrier frames 1 are further rotated and the fuses are brought above the oil level for renewal. The fuse tripping mechanism comprises for each phase, an insulating carriage 34 having rollers 33 slidable in grooves 32 formed in the cheeks 1. The carriage has a trip lever 36 pivoted at R and having fuse end clamps 37 which normally prevent anti-clockwise rotation of the lever 36 under the action of a spring 39. Pivoted at S to the carriage is a hook 38 held in engagement with a roller 41, fixed to the cheeks 1, by a spring 40. Blowing of a fuse releases the clamps 37 enabling the lever 36 to strike the hook 38 at T, whereby it disengages the roller 41, and the carriage 34 moves rapidly to the left, opening a wide gap between the fixed and movable ends of the fuse. In this movement the carriage 34 strikes the appropriate one of three trip arms 10 fixed to the shaft 9 between the side cheeks, so rotating the shaft 9 and causing the link 7 to disengage the hook 6 from the roller 22. The springs 12 then rotate the carriers 1 and open the breaker. The breaker cannot be reclosed until each blown fuse is renewed and the carriage reset. Usual interlocks are provided between the cover and handle. A shutter 60 pivoted at 61 and connected by a link 62 to the plate 28, prevents access to the live contacts beyond a fixed baffle 63, when the cover 29 is raised. An " off " and " on " indicator shows the switch position.