Spool valve for connecting an output to one of two inputs

Abstract

A valve has a tubular housing with two inlets spaced apart along its length, and a single outlet intermediate the inlets on the opposite side of the housing. One end of the housing is closed, its other end being open. The first inlet, close to the open end, is connected to a source of reduced pressure; the second inlet opening, close to the closed end, is connected to a source of raised pressure. A valve member is displaceable along the housing, being urged to the open end by a spring. First, second and third dished flanges are mounted coaxially on the valve member. The three flanges are spaced such that the outlet is connected to the second inlet when the first flange is located between the outlet and the first inlet, and the other two flanges are located between the open end of the housing and the second inlet. The outlet is connected to the first inlet when the valve member is positioned with the second flange between the second inlet and the outlet, and the first flange between the first inlet and the closed end of the housing. The valve member can be positioned such that the outlet is isolated from both inlets, when the second flange is located between the outlet and the second inlet, and the first flange is located between the outlet and the first inlet. The orientation of the flanges is such that pressure within the valve improves the seal of the flanges with the housing.