(under subclass 474) Apparatus comprising two or more distinct isolated relatively long pumping chambers, each of said pump chambers having one of its walls formed of flexible material, and means for progressively or sequentially collapsing each of said flexible walls.
(1) Note. A single elongated flexible wall member which is collapsed by plural engagement elements at spaced locations along its length to divide the chamber formed by said flexible wall into progressively formed chamber portions is not considered to constitute plural chambers under this definition. Also, excluded under this definition, are devices in which a secondary pump chamber is provided which has the sole function of enhancing the operation of another collapsible wall chamber (e.g., vacuum producing pump for restoring the shape of a flexible wall pump after deformation thereof).
