부산대학교 도서관

A valveless positive displacement pump including a closed end cylinder having two fluid inlet and outlet ports adjacent the closed end. A piston reciprocably and rotatably driven in the cylinder and including a reduced area portion on one free end which communicates cyclically with the inlet and outlet ports to pump fluid through the positive displacement pump. The piston reduced area is a reduced radius portion to minimize air bubble buildup and to minimize fluid volume at the end of the piston stroke. The piston also has a gland area formed in the piston which cyclically communicates with a pair of ports to clean the piston and cylinder and prevent the buildup of solids. The piston and cylinder can be formed from a hard ceramic material for accuracy and wear resistance. The cylinder is closed by a resilient end cap to relieve pressures caused by piston movement when the inlet and outlet ports are closed. The piston is driven by a compliant ball support including a ball and socket biased between the piston and drive shaft to self adjust and compensate for misalignment of the pump. The angle between the drive shaft and the piston is variable to vary the fluid volume and aligned so that the end clearance between the piston and cylinder does not change as the angle is changed.