Liquid-level valving device particularly useful as automatic relief valve

Claim 1

A liquid-level responsive valving device comprising: a housing defining a first chamber and including an end wall having a central opening therethrough; an annular support circumscribing said opening externally of said first chamber; a cap including an inner annular wall and an outer annular wall coaxial therewith, said outer annular wall being internally threaded and threadedly received on said annular support with the inner annular wall constituting an open cylinder facing and in alignment with said opening in the housing end wall; a control member axially movable in said opening and having a first end disposed within said first chamber and an opposite end carrying a piston movable within said cylinder and defining a second chamber therewith; said second chamber having a small vent opening in a wall thereof; said control member being formed with a bore extending axially therethrough and establishing communication between the two chambers; the cross-sectional area of said first end of the control member in the first chamber being less than that of said opposite end thereof in the second chamber, and the mouth of the bore at said one end of the control member in the first chamber being of larger diameter than that of the vent opening in the second chamber, such that upon an increase in pressure in the first chamber, the pressure in the second chamber is likewise increased which pressure, by virtue of the larger surface area in the second chamber, causes the control member to be moved further into the first chamber; a float in the first chamber coaxial with and axially spaced from the control member; a pilot valve element fixed to the end of the float facing said first end of the control member; said float being movable towards and away from said first end of the control member according to the quantity of liquid in the first chamber to bring the pilot valve element into engagement therewith to close the mouth of said bore whereupon the pressure in the first chamber moves the control member away from the float and further into said second chamber, or in disengagement therefrom to open the mouth of the bore whereupon the pressure in the second chamber moves the control member towards the float and further into said first chamber, guiding means in the first chamber guiding the movement of the float towards and away from the control member; and a main valve communicating with the first chamber and operated by the control member such as to be opened upon the movement of the control member further into the first chamber and to be closed upon the movement of the control member further into the second chamber.