Patent GB-264552-A (GB)
Title: Improvements in and relating to electric switches
IPC: H01H71/56
Filed: 1925-09-12
Abstract: 264,552. Cox, F. B. Sept. 12, 1925. Automatic circuit-breakers; electrically tripped and released switches. - Electric switchgear which may be used as an automatic circuit-breaker, motor controller &c. is provided with a primary or operating part, a secondary part constituting a switch which is positively moved to its closed position by the operating member and a spring or gravity operated percussive member or striker also positively moved to its set position by the operating member in which it is potential to effect or permit the opening of the said switch when released or actuated from its set position by a novolt overload or time-limit device. As shown in Fig. 1, the operating handle A1 carries a pin a4 engaging a lateral extension c4 of the striker c1 the portion c4 in turn engaging a pin b4 on the switch arm B1. When the operating handle is moved to the position shown against its spring a3 the parts assume the positions shown, the blade B1 engaging the fixed contact b1 and the striker C1 carrying an armature which is held magnetically against the no-volt electromagnet E1. On release of the handle it moves to the dotted position so that on de-energization of the magnet E1 the striker C1 is moved by its spring D1 to engage the switch arm B1 with a hammer blow forcing it quickly away from the fixed contacts to the position shown in Fig. 2. In the modification shown in Fig. 1<1>, the striker is moved across a dead-centre position on release by an overload magnet M fitted with an adjustable dashpot T. The spring D1 may alternatively be connected between levers C1 and A1 and the operating member may in one or both of its extreme positions close switch contacts. This form of switch may be employed as a loose-handle circuitbreaker as shown in Fig. 19, the contacts b1 completing the circuit of the no-volt magnet E3 when engaged by the blade B3 and the main circuit being completed at contacts a1 is series with contacts b1 on the return movement of the operating handle. Other modifications are described in which the primary or operating member instead of itself carrying contacts operates an independent contact arm which may be operated positively and latched in its operated position, the latch being released by the return movement of the operating member. The secondary switch member may also be latched against a return spring, the retaining detent being released by impact of the striker arm, which may itself be held in the set position by a detent controlled by the no-volt magnet. The circuit of the no-volt magnet may be controlled by overload devices. In the further modification shown in Fig. 15, the primary or operating member A15 in its return movement wipes over contacts a12 connected to sections of a motor starting resistance. The primary or operating member may be manually or electromagnetically controlled. The switchgear described may be embodied in stardelta motor starters which are constructed in the manner described in Specification 254,776, the contacts of the main and connection-changing switches being mounted on coaxially pivoted spindles and sleeves which extend through the switch casings and are provided outside the casings with operating and releasing mechanisms of the type described.