GB244058A - Improvements in electric knife switches - Google Patents

Abstract

244,058. Akt.-Ges. Brown, Boveri, et Cie. Dec. 8, 1924, [Convention date]. Mechanical switches with contacts reinforced electromagnetically. The electromagnetic action of a heavy current flowing through a knife switch prevents the switch from opening by increasing the frictional pressure between the knife blade and the fixed contact. According to the construction shown in Fig. 1, a slot d in the knife blade b engages a pin c on the fixed contact a and one or both of the insulators f, g are mounted so as to be slightly movable. A heavy current tends to force the insulators f, g apart and hence causes the pin c to press with great force against the side of the slot. In a modification, the slot d is inclined, and in another modification a pin on the knife blade engages the outer edge of the contact a. According to the construction shown in Fig. 3, the fixed contact consists of two U- shaped springs. The outer arms of the springs are held fast by a member e and the current flowing through the springs causes their inner arms to squeeze the knife blade b. Instead of the member e a bolt passing through the springs may be used, which also co-operates with a slot in the knife blade as in Fig. 1. In a further modification, two knife blades connected by a pin embrace a double U-shaped fixed contact.