(under subclass 279) Apparatus comprising a pump of the nonrotary expansible chamber type having plural pumping chambers, one of which is caused to expand simultaneously with the contraction of another, and the fluid flow control means comprises valve means which controls the flow of fluid directly from the contracting chamber to the expanding chamber.
(1) Note. The passage connecting the chambers may do so by branching from another flow line, but if it does so, the branching must be between the chamber and any pump distributor valve located in the other flow line.
