.~ Radially expansible piston portion controls pump and motor chamber intercommunication
DEFINITION
Classification: 417/59
(under subclass 56) Apparatus in which at least a portion of the piston is capable of expansion and contraction in a direction perpendicular to its axis of reciprocation to thereby provide a valving action with the chamber in which it reciprocates to allow or interrupt fluid communication between the pump and motor chambers.
SEE OR SEARCH THIS CLASS, SUBCLASS:
555.1+, and see the search notes therein, for other fields of search for radially expansible and contractible pistons.