Abstract: A portable step stool assembly including a step stool having a bottom surface adapted to be supported on a generally horizontal support surface and having a top surface adapted to be stepped on by a person. The assembly further includes an elongate resiliently flexible handle which is sufficiently stiff to remain straight when supported from one of its end portions. One end portion of the handle is attached to the step stool with the handle normally projecting upwardly past its top surface to a position where its opposite end portion can be grasped by a user of the step stool assembly. The handle is resiliently flexible in any direction normal to its longitudinal axis which restricts injury should a person fall against the handle and facilitates storage of the step stool assembly.

Abstract: Centrifugal pumps (10) are disclosed having nonrotatable membranes (21) to rotate fluid in a pumping chamber having at least a first open passage inlet (71) and an open passage outlet (91). Specifically, the membrane (21) is deflected into a nonconcentric shape to the fluid rotation, with the nonconcentric shape being rotated to function as a centrifugal pump impeller by deformers (41, 42, 43) separated from the pumped fluid by the membrane (21). As the membrane (21) does not rotate, rotary shaft seals, bearings, or small gaps between moving, sliding, and/or rubbing pump surfaces and to which the pumped fluid is accessible are not required in the pumps (10). In preferred forms, the deformers (41, 42) can be located inside the membrane (21) and inside the pumping chamber or the deformer (43) can be located outside the membrane (21) and outside the pumping chamber.