PUMPE

A pump comprising a body having at least one chamber and preferably two axially spaced and aligned pumping chambers, each such pumping chamber communicating at opposite ends respectively with a pump inlet and a pump outlet and containing an actuator reciprocable longitudinally of the pumping chamber by drive means, the actuator having a rigid main central portion and a peripherally extending elastic sealing ring in non-sliding fluid-tight engagement with a lateral wall of the pumping chamber and having mounted thereon actuator valve means controlling the flow of fluid from the inlet to the outlet of the pump, the pumping chambers communicating at their outlet ends with manifold passageways in the body of the pump which in turn communicate with respective passageways in an outlet duct situated on opposite sides of a longitudinally extending web therein terminating at a position spaced from the downstream end of the outlet duct to provide for cyclic flow of the pump fluid out of one pumping chamber and into the other around the downstream end of said web when shut off occurs at the pump outlet, fluid inductance means and fluid capacitance means with the latter operative throughout the pumping cycle being provided to limit the internal pressure to a safe value under shut off conditions.