GB390151A - Method of cleaning the contact members and other metal parts in electric switches operating in evacuated containers - Google Patents

Abstract

390,151. Switch contacts. BIRKA REGULATOR GES., 40, Konigstrasse, Wannsee, and ROZUMEK, E., 10, Marsschnerstrasse, Lichterfelde, both in Berlin. Sept. 17, 1931, No. 26096. Convention date, Sept. 17, 1930. [Class 38 (v).] The contacts of switches in evacuated containers are cleaned and freed from impurities during the evacuation of the container by being included in a circuit of relatively low voltage containing an inductance and carrying a current of the same order of magnitude as the normal working current so that a discharge from the inductance occurs repeatedly across the contacts and produces a series of sparks therebetween. As shown in the Figure, a number of thermal switches in containers 1 are disposed within an evacuating stove 4 and have their contact members 2 connected to a low voltage battery 6 in a circuit containing a large inductance 5. The thermal elements 3 are connected to brushes bearing on a rotary drum 7, the drum contact also passing to a control circuit 9, and as each brush 8 is engaged by the contact, the corresponding thermal element closes the switch contacts. Thus the opening of the contacts in turn by the thermal element as the drum contact leaves the brushes causes the discharge of the inductance to pass across the contacts 2 in turn and remove impurities, oxides, &c., therefrom during the evacuating process. In a modified arrangement, Fig. 2 (not shown), the contacts of the treated switches are arranged to be separated by a small gap across which the discharge of the inductance is arranged to be produced by an auxiliary thermal switch the switching movements of which are controlled by a drum switch in a manner similar to that already described in connection with the Figure. The battery 6 may be replaced by any other suitable source of current.