Compact valve with rolling diaphragm poppet

A valve apparatus comprises a valve body, a piston disposed within the valve body, and a rolling diaphragm poppet that is attached the piston to regulates fluid flow through the valve via interaction with a valve seat within the valve body. The valve body has a chamber extending therethrough that includes a valve seat at one chamber end that defines a fluid inlet passage into chamber. The piston disposed within the chamber and is adapted for axial displacement therein by an actuating means. The rolling diaphragm poppet is attached to an end of the piston and is of a one-piece construction. The poppet includes a head that has a circular radial cross section, and that has a frontside surface that is adapted to interface with the valve seat in the chamber to control fluid flow therethrough. The head also has a backside surface that is adapted to accommodate attachment with an end of the piston. The poppet includes a cylindrical sleeve that extends axially away from a peripheral edge of the head and that has a non-bellowed configuration. A flange extends radially from the sleeve to define a peripheral edge of the poppet. The flange including means for providing a leak-tight seal with the valve body. Axial displacement of the poppet head within the chamber, in response to the axial movement of the piston, is provided by a rolling movement of the sleeve in an axial direction between a piston wall surface and a concentric wall surface within the valve body.