Patent GB-765214-A (GB)
Title: Improvements in or relating to withdrawable electric switchgear such as circuit breakers
IPC: H02B11/133
Filed: 1953-07-02
Abstract: 765,214. Switchgear structure. WHIPP & BOURNE, Ltd., and WHIPP, C. L. Sept. 30, 1954 [July 2, 1953], No. 18308/53. Class 38(5) A circuit breaker 4 carrying isolating contacts 5 is mounted in a cubicle 1 on a framework 3 pivoted at 6 to a moveable carriage 7 so that the breaker can be moved out of the cubicle and then tilted for easy access to the breaker connections. Screwed shafts 9 connected together by a chain and sprocket mechanism pass through sleeves 8 formed on carriage 7, a handle 14 being used to rotate a shaft manually to move the carriage, a wheel 15 on each sleeve 8 running on a flange of a frame 11. The framework 3 is then tilted relatively to the carriage 7 by means of a screwed rod 50. In order to prevent rotation of framework 3 when the carriage is not in the withdrawn position, a pin 16 (Fig. 3) projecting from the framework 3 co-operates with a surface 19 of a member 17 fixed to the cubicle, a surface 20 of the member preventing return movement of carriage 7 if the framework 3 is still tilted. anually operable tripping means are provided for the breaker which must be tripped before the carriage can be moved, and comprise a' spindle 60 provided with a trip lever 24, anticlockwise rotation of the spindle 60 (Fig. 6) causing the tripping of the breaker. In order to prevent the spindle 60 being impeded during withdrawal of the breaker, a trip lever 22 is pivoted to the cubicle and carries a pin 23 for engagement with lever 24 the end of lever 22 being connected to a trip rod 61 which terminates in a trip knob 21 outside the cubicle, which knob can be locked in its operated position by a pin 25 and slot 26. To prevent movement of the carriage 7 unless the breaker is tripped, a shutter 29 is secured to the knob 21 and normally obscures an opening 30 in the cubicle door 2 over one shaft 9, and is only moved aside when the breaker is tripped. When the handle 14 is inserted in the opening 30 to move the carriage engagement of the shutter 29 and the handle prevents release of the trip knob. As the pin 23 only engages with lever'24 when the carriage is in the fully operative position, additional interlock means are provided to ensure that the breaker remains tripped until the isolating contacts are separated, and comprise a lever 31 pivoted to the cubicle at 32 and carrying a cam plate 33 to engage with a pin 34 projecting from trip lever 24. During the first part of the withdrawal movement of the carriage, pin 34 is engaged by plate 33 causing the spindle 60 to remain displaced in an anticlockwise direction (Fig. 6), and to prevent return of spindle 60 to its normal position until the carriage is back in its operative position. Interlocking means are further provided so that the door 2 cannot be opened until carriage 7 is in an intermediate position in which the breaker is isolated, so that the carriage cannot be fully withdrawn from the latter position unless the 'door is open, and so that the carriage cannot be moved to an operative position until the door is closed. A pin 38 on the frame 3 is received in slots 35, 36 in the lever 31 a stud 39 of which is received in a cam slot 40 of an interlock lever 41 pivoted to' the cubicle at 42. A bracket 43 on the door 2 carries a stud 44 which is received in a slot 45 in a lever 46 pivoted at 47 to the cubicle, a tie rod 48 interconnecting the levers 46, 41. With the door and breaker in their closed positions, (Fig. 4), the door cannot be opened as the lever 41 is prevented from rotating in an anticlockwise direction by engagement of stud 39 with slot 40 since rotation of lever 31 is prevented by engagement of pin 38 in slot 35. As the carriage is moved out, pin 38 moves down slot 35 until it abuts the end of this slot in the intermediate position, and opening of the door causes lever 46 to rotate clockwise under influence of spring 49 causing anticlockwise rotation of lever 41, the co-operation of stud 39 and slot 40 causing lever 31 to descend, thus transferring pin 38 to slot 36. Cam plate 33 now comes out of engagement with pin 34 to permit spindle 60 to return to its normal position so that the breaker can be operated normally for testing.