Bi-directional pressure relief valve

DETAILED DESCRIPTION The present invention provides an improved bi-directional pressure relief valve which utilizes a single valve opening, yet eliminates the necessity of separate coil springs, axial movement of the entire valve for reverse flow around the valve body, and permits overpressure relief or reverse flow through the hollow, cylindrical main body portion of the valve.
Specifically, the valve includes a hollow, cylindrical main body portion made of an elastomeric material and terminating in a radially asymmetrical lip portion having a curved contour about an axis of curvature extending perpendicularly to the flow path through the main body portion and a substantially linear contour which is substantially normal to the curved contour.
The lip portion defines a normally closed slit formed through it.
The valve is shaped such that, if the forward flow pressure within the body portion is increased above a first predetermined pressure level, the lip portion expands to open the slit, permitting forward flow from the body portion through the lip portion.
A reverse flow pressure at a second predetermined pressure level, preferably greater than the first predetermined pressure level, does not distort the lip portion sufficiently to open the slit and permit reverse flow through the lip portion so there is no flow through the valve under these conditions.
At a reverse flow pressure greater than the second predetermined pressure level, the lip portion collapses, thereby opening the slit and permitting reverse flow.
Thus, the valve responds to flow pressure in both a forward and a reverse direction at predetermined pressure levels.
The lip portion collapses in response to reverse flow pressures to permit reverse flow through the slit, yet will regain its uncollapsed shape throughout repeated cycles of use.
Due to the asymmetric shape of the lip portion, the center of the lip portion is less able to bear the pressure exerted against the outer surface of the lip portion than the sides adjacent the wall of the main body portion