Patent GB-280271-A (GB)
Title: Improvements in electric switchgear
IPC: H01H83/12
Filed: 1926-08-09
Abstract: 280,271. Cox, F. S. Aug. 9, 1926. Automatic circuit-breakers.-Electric switches which may be employed as automatic circuitbreakers, electric motor starters, &c. have a primary or operating member which in one of its extreme positions is held by a detent and effects directly or through a secondary or switch members the closing of switch contacts against the action of a spring or gravity ; a percussive member is moved by the primary member into a set position in which it is in operative relationship with a no-volt electromagnet, the percussive member being retained in its set position against a spring or gravity by a retaining device which is disengaged on the primary member moving to the circuit-closing position so that on failure of the voltage the percussive member may be released to effect the unlatching of the primary retaining detent. As shown in Fig. 1, the primary member A<1> when moved against a spring a<3> to engage contacts a' is held closed (Fig. 1A) by a spring-controlled detent D'. In moving to its closed position the tail-piece a<2> of the member A<1> releases a detent G<1> from engagement with the percussive member F<1> so that this member although normally attracted to the no-volt magnet H<1 >may on release be moved by the spring C<1> to the dotted position in which its tail piece f<1> draws aside the primary retaining detent D<1>. The consequent circuit-opening movement of the arm A' restores the parts to the position shown in Fig. 1 in which the percussive member is. automatically relatched in its set position. The spring C<1> may alternatively be connected between the primary and percussive members. In the modification shown in Fig. 3 the switch contacts are controlled by a secondary switch blade B<3> which has a pin b<4> engaged by a detent E on the primary member A<3>, the two members moving together in closing and the secondary member being released to open by the percussive member F<3> drawing aside the latch E. Auxiliary contacts b<3> are provided which are engaged by the blade B<3> slightly in advance of the main contacts b<1> so that the energization of the novolt magnet H<3> occurs slightly before the unlatching of the percussive member F<3>. In Fig. 4 the switch blade B<4> has a tail portion b<6> which when in the off position releases the detent D<4> so that the switch may not be moved to break the circuit slowly. The operating handle A<4>, by engaging the detent G<4>, effects the unlatching of the percussive member F<4> in the switch closing movement. The unlatching of the percussive member may alternatively be effected by a detent controlled by an electromagnet the circuit of which is completed at contacts controlled by the primary member. In its closing movement the switch blade may be arranged to wipe over a series of contacts connected to sections of a motor starting resistance. The modification shown in Fig. 6 shows a switch arranged as a star-delta starter the switch arm A<6> being biassed' to a central or " off " position bv a spring a<3>. When the handle is moved upwardly to the starting position it engages the contacts a<1> and latches the percussive member in its set position and when subsequently it is moved downwardly to the running position the switch arm is latched in engagement with contacts a<2> by the detent D<6> the latch g<1> on the percussive member F<6> being at the same time automatically released. In further modifications the primary and percussive members are arranged on different axes and the switch may be operated through a collapsable toggle. The switch shown diagrammatically in Fig. 4 may be constructed as shown in Fig. 10, the movable contacts B<4> for the three phases being mounted on a sleeve b<10> surrounding the operating shaft a and journaled in the sides of the casing K (Fig. 14). The sleeve b<10> carries also the contact member B<4a> engaging theauxiliary contacts b<3>.