Patent ID: 6291791
Filing Date: 2001-09-18
Classification: B23H,H01H

Abstract:
A switch for changing a connection between an electric discharge power supply circuit and a machining gap formed between a tool electrode and a workpiece, comprising:a movable contact having a piston and a piston rod attached to a first surface of the piston;a housing having a cylindrical hole, said piston being positioned for reciprocal movement in said cylindrical hole;a first fixed contact fitted to the housing in a generally water-tight relationship, said first fixed contact having a hole through which the piston rod is adapted to slide;a second fixed contact fitted to the housing in a generally water-tight relationship, said second fixed contact having a planar surface extending parallel to and opposite to a second planar surface of the piston;a first terminal attached to the first fixed contact and at least partially exposed to the exterior of the housing;a second terminal attached to the second fixed contact and at least partially exposed to the exterior of the housing;a driver for moving the movable contact to selectively contact the second fixed contact; anda third fixed contact fitted to the housing in a generally water-tight relationship and having a planar surface extending generally parallel to and opposite to the first planar surface of the piston, and a third terminal attached to the third fixed contact, said third terminal being at least partially exposed to the exterior of the housing.