Contaminant resistant valve

Claim 1

A contaminant resistant valve comprising: a housing having a cavity therein and first and second ports communicating with the cavity; a valve seat surrounding the first port; a guide shaft, having a cylindrical surface, secured to the housing and extending into the cavity; a valve element, having a recess therein with a cylindrical surface, positioned in the cavity for axial movement between seated and unseated positions such that the respective cylindrical surfaces are in sliding engagement whereby movement of the valve element is guided by the shaft, such that the guide shaft is axially spaced from the base of the recess when the valve element is seated to thereby define a first chamber and such that the valve element is in spaced relationship to the wall of the cavity whereby it does not slide therealong during movement between the seated and unseated positions; a diaphragm extending across the recess and fixedly secured to the wall thereof and the shaft to seal at least a portion of the recess from the cavity, the diaphragm being spaced from the cylindrical surface of the recess which slidingly engages the guide shaft to define a second chamber separated from the first chamber by the area of cylindrical surface engagement; hydraulic oil in The first and second chambers for damping and lubricating the sliding engagement between the valve element and the guide shaft; passage means to fluidly interconnect the first and second chambers for enabling oil trapped in the first and second chambers to be displaced during valve element movement; and whereby contaminants in the fluid entering the cavity via the first port and leaving the cavity via the second port will not hinder movement of the valve element.