Arm extending through a work pan of a wire EDM permitting improved arm movement

Claim 1

A wire cutting type electrical discharge machining system for removing metal by means of an electrical discharge energy between an electrically conductive workpiece and a wire electrode which is continuously fed lengthwise relative to the workpiece, comprising: a work pan for supporting the workpiece therein, said work pan including a side wall which has an elongate aperture extending substantially horizontally; a lower arm extending laterally through said elongate aperture inwardly into said work pan to a position below the workpiece, and carrying a lower electrode guide for guiding said wire electrode, said lower arm being movable relative to said work pan in a longitudinal direction thereof and in a longitudinal direction of said elongate aperture; a closure strip disposed along said elongate aperture to close the elongate aperture substantially fluid-tightly, said closure strip being slidable in said longitudinal direction of the elongate aperture and having a hole in a longitudinal central portion thereof; feed means for feeding said work pan and said lower arm relative to each other in any direction in a horizontal direction, thereby to feed said workpiece supported by the work pan in any desired direction in said horizontal plane; a pair of reels rotatably supported by said work pan, opposite end portions of the closure strip being wound on said reels; and annular sealing means disposed on said closure strip adjacent to said hole, said lower arm fluid tightly and slidably extending through said annular sealing means, whereby said closure strip provides a fluid tight sealing between said work pan and said lower arm while allowing relative movements thereof in said two longitudinal directions.