Patent GB-691009-A (GB)
Title: Improvements in or relating to impact-operated electric switches for alternating current mains
IPC: H01H1/50
Filed: 1950-10-31
Abstract: 691,009. Impact-operated switches; electromagnetic switches; distortable-container switches; protective cutout arrangements. SIEMENS-SCHUCKERTWERK EAKT.-GES. Oct. 31, 1950 [Oct. 31, 1949], No. 26566/50. Class 38 (v) A switch comprises a number of elastic bodies, e.g. metal balls, arranged in-line, two adjacent ones of the bodies forming the contacts, whereby an impact given to one end of the line causes the circuit to be opened, and an impact given to the other end causes the circuit to be closed. The arrangement, by reducing the number, and consequently the weight, of the movable parts, permits high-speed contact operation. An impact given to the fixed contact ball 2 by the ball 1 is transmitted to the contact ball 3 which is thereby moved against ball 4 to open the circuit connected to metal troughs 6, 7. A spring plunger 10 serves to maintain the ball 3 in the switch positions. To close the switch, the ball 4 is given an impact by the ball 5. In Fig. 3, the fixed and movable contacts 21, 22, respectively, are provided with an arc-chute 25, 26 having a blow-out magnet 27, the contact 21 being resiliently connected to the arc horn 23 and the contact 22 being slidable in the horn 24. In Fig. 4 (not shown), the movable contact is mounted at the centre of a coil spring held under compression which moves over-centre and thereby maintains the contact in its switch positions. An evacuated container, Fig. 5, is formed by a stiff diaphragm 43, flexible diaphragm 41, and insulating member 44, and encloses fixed and movable contacts 42, 40, the contact 42 being integral with the diaphragm 43 and contact 40 being carried by the diaphragm 41. The external air-pressure which tends to hold the contacts 40, 42 together is partly counterbalanced by a spring 47 acting on an extension 45 of the contact 40 and abutting a fixed body 50 on a diaphragm 51. An impact imparted by a ball 53 is transmitted by contact 42 to the contact 40 which is thus moved to break the circuit connected to diaphragms 43, 51 and retained by a spring-plunger 48 which engages a groove 46 in the extension 45. To close the switch a cylindrical body 52 abutting the body 50 transmits an impact to the flattened rear surface of the contact 40, the impact causing release of the plunger 48. According to another construction, a further evacuated enclosure formed by a stiff diaphragm 66, Fig. 6, shields the flexible diaphragm 61 from atmospheric pressure. The movable contact 60 is controlled by an over-centre arrangement comprising a stressed steel band 67 which embraces rigid members 68 and pivotally engages the contact 60 and resilient bars 69 which are stressed towards each other. The opening impact is imparted by an armature 71 urged by a spring 74 but normally retained by the flux across an annular gap between pole shoes 77, 78 of a permanent ring or electromagnet 76. The current to be controlled passes through holes 79 in the pole-shoes and when it exceeds a determined value the retaining flux is eliminated and the contact 60 thereby opened. Manual opening may be effected by pressing the extension 73. The switch closure is effected in a similar manner, a bell-crank lever 82 and rod 83 serving for manual closing. The switch may be opened at zero current by obtaining the current for eliminating the magnet flux from the secondary of a saturable transformer whose primary is traversed by the current to be broken. Two switches may be connected in series, one switch being shunted by a resister. On overload, the said one switch is first opened, as described above in connection with Fig. 6, and the reduced current through the other switch is then broken at zero value.