Patent ID: 6881330

Claim:
A two-stage retrofit filter adapted for use with an electrical discharge machine (EDM) of the type wherein a one-stage filter is placed in a tank over an apertured standpipe such that a fluid being filtered flows through the apertured standpipe and filter, the retrofit EDM filter comprising: a plurality of nested filter elements, including an inner element and an outer element, the physical configuration of the elements being such that the retrofit filter may be placed in the same tank and over the apertured standpipe used for the one-stage filter, so that the fluid to be filtered flows through the apertured standpipe and each of the filter elements; an aperture extending through the inner filter from an upstream side to a downstream side of the inner filter; and a reproducibly rupturable diaphragm covering the aperture, the diaphragm being designed to rupture when subjected to a predetermined pressure.