Control valve with axial sealing

A three-way, two-position control valve arrangement for controlling flow of gas within a gas drying system having at least one desiccant containing chamber such that a stream of unpurified gas is passed through the desiccant containing chamber to filter and remove moisture therefrom, and a portion of the filtered and dried gas is passed back through the desiccant containing chamber in the reverse direction to purge moisture from the desiccant with such purge gas being discarded to atmosphere, said control valve arrangement comprising:

• (A) a housing structure having a valve body opening, said valve body opening having sidewall portions and a base portion, and including;
• (a) a first passageway interconnecting said desiccant containing chamber with said valve body opening emerging through one of said sidewall portions adjacent to said base portion,
• (b) a second passageway interconnecting the atmosphere with said valve body opening emerging through one of said sidewall portions displaced from said base portion, and
• (c) a third passageway interconnecting a source of unpurified gas with said valve body opening emerging through said base portion;
• (B) a valve body secured within said valve body opening, said valve body having an internal end disposed between said first passageway and said second passageway and a middle portion around which is defined an annular channel, said internal end of said valve body defining a plurality of slots therethrough;
• (C) a piston reciprocally disposed within a piston cylinder extending axially through said valve body, said piston cylinder, at one end thereof, being in communication with said third passageway and, at the other end thereof, having a control chamber in which a control pressure is received to move said piston reciprocally within said piston cylinder;
• (D) at least one radial port extending through a wall of said valve body adapted to provide communication between said second passageway and an intermediate cylindrical portion of said piston cylinder via said annular channel in said valve body;
• and
• (E) a plunger disposed at an inner end of said piston adjacent to said base portion, adapted to bias against said internal end of said valve body, closing said slots and thus said piston cylinder and said second passageway from said first passageway, thereby opening said third passageway to said first passageway, when said piston is reciprocated outwardly with respect to said piston cylinder, and further adapted to bias against said base portion, closing said third passageway from said first passageway, thereby opening said slots and thus said piston cylinder and said second passageway to said first passageway, when said piston is reciprocated inwardly with respect to said piston cylinder.