(under subclass 545) Apparatus in which the valve comprises a rigid member which is mechanically interconnected with the piston in a manner which constrains said member for movement about an axis.
(1) Note. A movable rigid valve member which is connected to the piston by means of a flexible element (e.g., resilient material hinge) which flexes upon movement of the valve to constrain movement of the valve member about an axis is not classified under this definition, such subject matter being provided for in subclass 550, above.
