GB632642A - Improvements in electric high-frequency vibrator - Google Patents

Abstract

632,642. Electromagnetic interrupters. PLESSEY CO., Ltd. Feb. 21, 1946, No. 5475. Convention date, Feb. 22, 1945. [Class 38 (v)] A vibrating armature 35 secured in a stack 12 passes through a driver coil 29 supported on an iron bracket 31 attached to an iron frame 10. The free end of the armature 35 co-operates with the end 11 of the frame 10 which forms a pole-piece of the magnet system. The armature carries two moving interrupter contact arms 36, 39 and two moving rectifier contact arms 37, 38, all of which engage stationary contacts supported in the stack 12. The two stationary contacts on each side of the armature are insulated from one another and situated side-by-side, being shaped as shown at 24 in Figs. 2 and 5 to enable them to be secured to the single bolt which holds the stack together. In order to avoid the use of heavy contact pieces on the moving arms the connections are so made that current always passes from the fixed contacts to the moving contacts as metal tends to be transferred from the positive to negative contacts. Heavy contact pieces are therefore used on the stationary contact arms, the moving arms being provided with a thin layer of contact metal by spraying or other means. The moving arms may for example consist of spring steel. coated with silver or platinum, the fixed contacts being of silver alloy or discs of tungsten. Only the interrupter contacts need be made in this way as the rectifier contacts are alternatively positive and negative and no transfer of metal takes place. Fig. 4 shows a modification of the moving contact arms in which free oscillations of the arms are damped. A phosphor bronze or beryllium copper spring 52 carrying a thin layer of contact metal 53 is engaged by a steel spring 51, the two springs being separated at their lower ends. When the springs are in vibration the friction between their upper engaging ends tends to damp free oscillations. Specification 594,862 is referred to.