Duplex filter assembly

Abstract

Duplex filter apparatus suitable for pressure or suction applications includes dual filter housings and a central valve housing having dual, cylindrical, three-way plug valves. Four glass-filled Teflon sleeve seals, each having an inner cylindrical cut edge conform to the valve periphery and seal the valve openings in either a pressure or suction configuration. A wave spring biases each sleeve seal against the plug valve and further o-ring seals utilize the pressure or suction condition to enhance the effectiveness of the sleeve seals. In the pressure configuration a tubular support is used in conjunction with the sleeve seal with the wave spring acting either directly on the sleeve seal or indirectly through an intermediate metal ring which houses the o-ring seals and which minimizes thermal expansion effects. Interlock mechanisms are associated with a handle which rotates the plug valve between off-duty and on-duty filter housings to assure that the filter housing cover cannot be opened while on-duty, nor that the valve can be turned without the off-duty housing prepared for fluid. The interlock mechanisms comprise mechanical detents and levers interconnected with the handle and the filter housing covers.