Patent GB-965789-A (GB)
Title: Electric circuit breakers
IPC: H01H71/74
Filed: 1961-01-09
Abstract: 965,789. Electrically-tripped switches. CUTLER-HAMMER Inc. Jan. 9, 1961 [Jan. 7, 1960], No. 910/61. Heading H2B. A circuit-breaker is held closed by the engagement of a latch carried by the operating handle with a catch on part of the operating mechanism, the engagement being maintained by a biased latch retainer movable by a thermal or electromagnetic trip to release the latch and open the breaker. The circuit-breaker comprises a pivoted handle 8 whose portions 8d pivotally support a movable contact member 26 and a latch 18, member 26 being connected by a tension spring 28 to a latch lever 20, which is pivoted at 48, controlled by a spring 22 and has a catch 20d engageable by the yoke 18b of the latch 18. The movable contact 26b co-operates with a fixed contact 30a and is connected by conductors 32 to a bi-metal strip 34 whose upper end is secured to an adjustable terminal bracket 36 and whose lower end 34a is received in the slot 44c of a plate 44 slidable in grooves in the housing and having notches 44a engageable with a compression spring 46. Plate 44 also has a slot 44b receiving the lower end 40b of an armature 40 pivoted at 66 and carrying a bi-metal strip 42 providing ambient temperature compensation, the armature 40 co-operating with the poles of a magnetic member 38 pivoted at 64 to have limited lateral movement, its rotational movement being limited by the engagement of its projection 38d with a stop 78. Anti-clockwise movement of handle 8 produces, through members 26, 28, clockwise motion of lever 20 until members 18b, 20b engage, whereupon the lever movement is reversed and subsequent handle movement brings the spring 28 over centre to close the contacts, the pressure therebetween being maintained by stretching of the spring 28 during the final movement of lever 20, and the mechanism being held closed by the pressure of strip 42 on the latch 18, Fig. 2 (not shown). Prolonged overload flexes strip 34 anti-clockwise to move plate 44 to the right and permit anticlockwise movement of armature 40 to release latch 18, such release also occurring when armature 40 is pulled towards member 38 upon sudden high overload. Disengagement of members 18b, 20d allows spring 28 to rotate lever 20 clockwise to engage a stop 56, and to rotate member 26 anti-clockwise to engage a projection 62b, Fig. 7 (not shown), this engagement enabling the remaining stress in spring 28 to fully restore the handle 8, after which spring 22 restores members 20, 26, 28 to the position shown in Fig. 3. The position of strip 34 may be adjusted by a screw 36f and strip 42 may be non-bimetallic. The breaker is trip-free and has grooves 68 in its arcing chamber which is vented through a channel 70. The breaker may be modified by including a trip lever 112, Fig. 9, pivoted adjacent the plate 44 and having a projection 122f and a face 122d engageable respectively with the strip 42 and the end of lever 20, two such breakers being mounted side by side with their trip levers connected by a member 116 and their operating handles 8 connected by a tie engaging the apertures 14, Figs. 8 and 10 (not shown). Tripping of one breaker causes the lever 20 to rotate the lever 112, Fig. 11 (not shown), which turns its fellow to move the corresponding strip 42 and so trip that breaker. Alternatively, two breakers of the construction shown in Fig. 3, may have their operating handles linked by a " lost motion " connection, so that tripping of one breaker opens the other by movement of its handle, Figs. 12 and 13 (not shown).