Patent GB-474852-A (GB)
Title: Improvements in or relating to electric circuit breakers with automatic releasing means
IPC: H01H71/40
Filed: 1936-08-14
Abstract: 474,852. Automatic circuit-breakers; switchboards. SQUARE D CO. Aug. 14, 1936, Nos. 22450, 22451, and 22452. Convention dates, Aug. 15, 1935, April 1, 1936, and May 2, 1936. [Class 38 (v)] Bases contacts ; indicators ; springs, arrangement of; arc-rupturing devices.-An automatic circuit-breaker comprises a fixed contact and a movable member having a contact-surface adjacent one end, current-responsive latching- means for the opposite end of the member, and means biassing the member against the contact and latching-means. A pivotal axis is provided for said member between the biassing- means and contact-surface, together with manual means for moving the axis against the biassing-means to move the contact-surface to open position. The movable contact-carrying member 6 carries a contact surface at one end engageable with a fixed contact 23 on a plate 5, and at the other end is engageable with a bimetal latch 7 to which it is connected by lead 19. The latch 7 is supported on the pushed-out centre part 10 of a support 8, the outer limbs of which are turned over at 11 to receive a bridge 12 into which is threaded an adjusting screw 13 for the latch. Member 6 is notched at 15, 16 to co-operate with slots in a U-shaped member 18 which is guided for vertical reciprocation in the base 4 when an operating member 37 is manually rotated about its pivot 35. The right-hand side of Fig. 2 shows the closed position, in which a spring 14 maintains member 6 in engagement with the contact 23 and latch 7, and a spring 45 in a recess 46 in member 37 maintains the latter in contact with member 18 and the latter in turn in contact with the member 6. To open the breaker manually, member 37 is rotated anticlockwise into the position shown for another breaker on the left-hand side of Fig. 2, the member 6 pivoting about the latch 7 as the member 18 is depressed. A locking action is imparted by a projection 40 engaging the bevel 42, and when, in closing, these parts are disengaged, the spring 14 imparts a rapid closure. The automatically-opened position, reached bv deflection of latch 7, is shown in Fig. 3, in which slot 16 engages the top of the slot in the shorter limb of member 18 and the handle 37 is moved right over, so indicating the tripped condition. Reclosure from this position is effected by first moving the handle right over beyond the " off " position until a projection 41 -engages the member 18, in reaching which position the member 6 is caused to rotate at the contact end about the base 4 until its free end moves below the latch 7. On release of the handle, the spring 14 restores the parts to the normal " off " position, whereupon closure may be effected by the normal " on " movement of the handle. In a modification, Fig. 11 (not shown), the handle is arranged so that the manual " off " and reset positions are the same. Figs. 14 and 17 show the manual " on " and " off " positions of a further form of handle, which comprises an L-shaped member 53 slotted at 55 to co-operate with a guiding projection 54 on the member 18, and having a spring 59 to replace the spring 45 of Fig. 2. When the breaker is tripped from the Fig. 14 position, it moves rectilinearly upwards, and in order to reset, the handle is depressed as far as it will go and then released, whereupon spring 14 restores it to the Fig. 14 position. When the handle is rotated to the Fig. 17 " off " position, an abutment 60 prevents its complete detachment. Fig. 1 shows a structure comprising two units 1, 2, each comprising four breakers and being secured by screws 47. By removing the latter and sliding a unit sideways, an operating member 48 having pins 49 may be applied to two juxtaposed breakers for conjoint operation, the fit being such as to allow one to be tripped independently of the other, as shown at the top of Fig. 1. The handles 53 of Fig. 14 are slotted at 56 to admit the pins 57 of a similar operating member 58. The fixed contacts 23 of each unit are disposed at the corners of a rectangular plate 5, and may be the distributing point of four sub-circuits, or alternatively, one breaker may control the main feed to the plate 5, the other three breakers then serving for sub-circuit control. Plate 5 is disposed in a cut-out part of a longitudinal barrier 20 from which it is separated by a fibre liner 21, further fibre liners 25 being provided on either side of the wall 20, as shown in Fig. 5, to provide arc chambers which are separated from the mechanism by transverse barriers 26. The latter are slotted at 27 to pass the members 6 and to straddle wall 20, and H-shaped plates 28, Figs. 2 and 7, serve to restrict the arc chambers. Arc gases escape through openings 24 in the plate 5, and a fibre sheet 30 fits closely round the handles 37 to minimize escape of gases thereat. A steel cover 31 and fibre shield 33 for the terminals 32 are provided. The Specification as open to inspection under Sect. 91 describes also the use of wavy bimetal strips, but this subject-matter does not appear in the Specification as accepted.