Pressure balanced three-way transfer valve

Claim 1

A pressure-balanced three-way transfer valve for controlling fluid flow into one of two fluid lines, comprising, in combination: (1) a housing; (2) a valve chamber in the housing; (3) first, second and third fluid flow ports in the housing; (4) first, second and third fluid flow passages in the housing, intercommunicating the valve chamber with the first, second and third fluid flow ports; (5) a first valve member in the valve chamber movable between open and closed positions across the first fluid flow passage, and controlling flow through the first fluid flow port; (6) a second valve member in the valve chamber movable between open and closed positions across the second fluid flow passage, and controlling flow through the second fluid flow port; (7) first cam-following valve-actuating means in the valve chamber operatively connected to the first valve member; (8) second cam-following valve-actuating means in the valve chamber operatively connected to the second valve member; (9) a cam in the housing separated from the valve chamber and exposed to a pressure lower than fluid pressure; movable between first and second positions and operatively connected with the first and second cam-following valve-actuating means in a manner such that (a) with the cam in the first position, the first valve member is open and the second valve member is closed; (b) with the cam in the second position, the second valve member is open and the first valve member is closed; and (c) with the cam in intermediate positions, both the first and second valve members are open at least partially; (10) means for moving the cam between the first and second positions, thereby opening and closing the valves; (11) a first pressure-equalizing chamber defined by the first cam-following valve-actuating means and the first valve member; (12) a second pressure-equalizing chamber defined by the second cam-following valve-actuating means and the second valve member; (13) a first fluid passage through the first cam-following valve-actuating means intercommunicating the pressure lower than fluid pressure with the first pressure-equalizing chamber; (14) a second fluid passage through the second cam-following valve-actuating means intercommunicating the pressure lower than fluid pressure with the second pressure-equalizing chamber; (15) the first and second valve members each having pressure-receiving surfaces exposed to fluid pressure in the valve chamber and opposed pressure-receiving surfaces exposed to a pressure lower than fluid pressure in the pressure-equalizing chamber; (16) the first and second cam-following valve-actuating means each having pressure-receiving surfaces exposed to fluid pressure in the valve chamber and opposed pressure-receiving surfaces exposed to pressure lower than fluid pressure; and (17) the opposed pressure-receiving surfaces of the first and second valve members and first and second cam-following valve-actuating means being of such surface areas that the fluid pressure and lower pressure acting on the opposing pressure-receiving surfaces of the cam-following valve actuating means and valve members are substantially balanced; whereby such fluid pressures do not interfere with movement of the first and second valve members.