(under subclass 253) Rotary piston meters, having at least two pistons mounted in a common cylinder and having interengaging portions so that each may act as an abutment for the other.
(1) Note. This subclass includes meters of the "Roots blower" or lobed impeller type.
SEE OR SEARCH CLASS
418, Rotary Expansible Chamber Devices,
166+, for rotary expansible chamber devices of the moving cylinder type having intermeshing peripheral surfaces; subclasses 172+, for such devices of the moving cylinder type having interengaging peripheral surfaces and subclasses 191+, for such devices having interengaging rotating members.
