Multiple-disc filter

Claim 1

A filter including: a housing having an inlet and an outlet; a stack of filter elements within said housing for filtering the fluid flowing therethrough from the housing inlet to the housing outlet; said stack of filter elements having an upstream surface facing the housing inlet and a downstream surface facing the housing outlet; a pressure member located within the housing in the path of the inletted fluid upstream of the filter elements such as to be impinged by the fluid introduced into the housing via its inlet, to constrain the fluid to flow to the upstream surface of the stack of filter elements and therethrough to the housing outlet, and to press the filter elements together by the force of the inletted fluid to tighten the stack when the fluid flows from the housing inlet to the housing outlet; and a spring acting against said pressure member such that: (a) when the fluid is introduced into the housing in a forward direction via said inlet, the force of the spring adds to the force of the fluid to cause the pressure member to constrain the fluid to flow in the forward direction to the upstream surface of the stack and to press the filter elements together to tighten the stack, for a normal filtering operation during which solid particles are separated from the fluid and accumulate on the upstream surface of the stack and between the filter elements of the stack; (b) and when the fluid is introduced into the housing via said outlet so as to flow in the reverse direction first to the downstream surface of the stack and then through the stack, the force of the fluid causes the pressure member to move against the force of the spring to loosen the stack and thereby to permit the fluid to flush out the solid particles accumulated between the filter elements of the stack and on the upstream surface of the stack.