(under the class definition) Dispensers having a chamber containing a piston impelled successively in opposite directions by material entering under pressure, the material in the contracting side being expelled by the piston movement.
SEE OR SEARCH THIS CLASS, SUBCLASS:
253, for material operated differential piston.
SEE OR SEARCH CLASS
73, Measuring and Testing,
239+, for reciprocating piston meters. A device as defined in this subclass (249) having means controlled by piston movement, material pressure, etc., for reversing the flow control means to admit the material to the contracted chamber and thus be continuously operated so long as material flows, is considered a meter.
417, Pumps,
392+, for pumps having a single piston common to motor and pump chambers.
