GB655491A - Improvements relating to contact arrangements of electric circuit breakers - Google Patents

Abstract

655,491. Switch contacts. REYROLLE & CO., Ltd., A., ALLAN, A., and SMALL, J. F. S. June 18, 1948, No. 16448. [Class 38(v)] In a self-aligning butt contact arrangement for a circuitbreaker, either the fixed or the moving contact comprises a contact member mechanically connected to its supporting member through a part spherical surface on one member engaging a part cylindrical surface on the other member to permit tilting and bodily movement of the contact member against spring action. In Fig. 1, the fixed contact comprises a fixed part B, a supporting member C, an inner housing D slit longitudinally to provide contact fingers, and the part spherical tilting member A which engages the contact fingers and is biassed towards the moving contact E by a spring G and thrust cap F. The cap F has a part spherical surface F<SP>1</SP> engaging a bore A<SP>1</SP> in the member A: When the contacts are closed, the moving contact E may move the tilting contact member A a short distance vertically in the housing D and the member A may tilt within the housing so as to bring its lower surface into correct alignment with the contact E. The outward movement of the member A under the bias of the spring is limited by the inturned flange C<SP>1</SP> of the support C, though in modifications, the extent of this movement may be determined by a screw or screws on the member A engaging in a slot or slots in the housing D (Fig. 2, not shown), by ball headed studs extending through springs G into recesses in the member A (Fig. 4, not shown), by slotted links Q, Q<SP>1</SP> connected between the members A, B, Fig. 6, or by securing the spring G to both members A, B (Fig. 7, not shown). In all these modifications and as shown in Fig. 6 the arrangement may be such that as the contacts separate the member A is tilted, so that the separation always occurs between the same points on the contact surfaces. Both contact members A, E may be provided with erosionresisting inserts A<SP>5</SP>, E<SP>1</SP> at these points, slots A<SP>3</SP>, E<SP>2</SP> being provided to confine the arc to these inserts. In Fig. 4 (not shown). the housing D is formed by hairpin-shaped fingers so that the electrodynamic forces set up by the current in the fingers tend to maintain the fingers in firm contact with the contact member A. The contact member A may be formed with a slot in a lateral plane to cause the current in the contact to flow in a loop which tends to blow out the arc in a transverse direction. Fig. 5 shows a modified arrangement in which the fixed member B is provided with a part spherical surface B<SP>1</SP> and the tilting contact member is formed by a cup N with an inner housing N<SP>1</SP> having fingers engaging the surface B'. A chain P limits the movement of the cup N.