Abstract: A multi-purpose flow apparatus of the type which operates on the principle of volumetric displacement, has an internally helicoidal chamber rotatable about its center of gravity and having one of a constant or variable pitch and z.sub.k thread starts and an externally helicoidal spindle rotatable about an axis disposed at its center of gravity. The spindle has z.sub.o =z.sub.k +1 thread starts, the thread division thereof is z.sub.o /z.sub.k times the pitch of the chamber and the angular velocity of rotation of the spindle is z.sub.k /z.sub.o times that of the chamber.

Abstract: There is disclosed an hydraulic drilling motor for well drilling. The motor is of the push-down axial flow type. It is of vibration-free rotary chamber-type construction functioning with high torque wherein the r.p.m. and capacity of the drilling tool are in proportion with the velocity and pressure of the flowing medium. The motor consists of an internally threaded chamber with an arch parallel with the flow direction of an externally threaded spindle of z.sub.o =z.sub.k (arch or thread)+1, or z.sub.o =z.sub.k -1 thread, of identical course with the chamber, arranged in the chamber. The cross section of the spindle or chamber is prolate, peaked or curate cycloid. When the spindle is cycloid cross sectional, the cross section of the chamber is in the same plane, and when the chamber is in cycloid cross sectional the cross section of the spindle is in the same plane. This is limited by the external or internal envelope curve of the surface touched by the cycloid during relative motion.