Bypass reverse flow valve

Claim 1

In a filter assembly having a housing including a fluid inlet and outlet, a tubular filter element seated within said housing for filtering fluid under pressure flowing from said inlet to said outlet, the improvement for providing bypass and reverse flow capability through flow paths other than said filter element comprising: ring valve means including first and second ring members telescopically received one within the other and having first and second surfaces and an opening disposed coaxially with said filter element and including fluid sealing means, the first surface being exposed to fluid under pressure before filtering thereof and the second surface being exposed to said fluid after filtering thereof; spring means biasing said ring members in opposite directions and sealing means into sealing engagement during normal operation of said filter assembly; said sealing means opening against said spring bias responsive to said filter element becoming plugged and generating a first differential pressure thereacross which is applied across said first and second surfaces to allow unfiltered fluid to flow from said inlet to said outlet without passing through sasid filter element; and reverse flow check valve means disposed to close said opening to prevent fluid flow from said outlet to said inlet through said filter element, said check valve means, responsive to said fluid flow from said outlet toward said inlet generating a second differential pressure, opening said sealing means to allow fluid to flow freely from said outlet to said inlet, said second differential pressure being less than said first differential pressure.