A conical screw compressor or pump comprises an inner element configured to rotate around a first axis and an outer element configured to rotate around a second axis. An outer surface of the inner element and an inner surface of the outer element comprise cooperating grooves and teeth that intermesh on rotation. The first axis and the second axis are each stationary and the first axis is inclined relative to the second axis. The inner element and the outer element are configured to be, in operation, synchronously rotated, thereby to reduce or eliminate force exerted by the inner element on the outer element or vice versa.

An eccentric screw pump for pumping fluids or flowing conveying media from a suction side to a pressure side, which includes a rotor and a stator, the stator being flexible and is connected to the pump housing on one side, in particular on the suction side. The rotor is connected to the drive shaft by means of an articulation. When the eccentric screw pump is in the idle state, there is no sealing contact at least in areas between the rotor and the stator in the sealing areas. When the eccentric screw pump is in the operating state, the stator is surrounded, at least in sections and/or, essentially, on the periphery by the conveying medium. The rotor and the stator are brought into contact with each other in the operating state along the sealing area.

Rotary positive displacement machines based on trochoidal geometry and including a helical rotor that undergoes planetary motion relative to a helical stator can be designed and configured so that the axial load or rotor pressure force is positive, negative, or neutral. In some embodiments, a change in axial load, caused by a change in differential pressure across the machine, can be used to trigger a change in a mechanical configuration of the machine.

Cylindrical symmetric volumetric machine (1), which machine (1) includes two cooperating rotors (6a, 6b), namely an outer rotor (6a) which is rotatably mounted in the machine (1) and an inner rotor (6b) which is rotatably mounted in the outer rotor (6a), whereby the machine (1) is provided with an electric motor (15) with a motor rotor (16) and a motor stator (17) to drive the outer and inner rotor (6a, 6b), characterised in that the electric motor (15) is mounted around the outer rotor (6a), whereby the motor stator (17) is directly driving the outer rotor (6a), and whereby the electric motor (15) extends along only a part of the length (L) of the outer rotor (6a) and the inner rotor (6b), whereby the motor (15) is located at an end (9b) of the inner rotor (6b) with a smallest diameter (D).

A rotor for a mud motor includes a core having a first outer shape, and a shell positioned around the core, the shell having a second outer shape that is different from the first outer shape, the second outer shape defining one or more lobes and one or more cavities that are configured to engage a bore of a stator during rotation of the rotor relative to the stator. A thickness of the shell varies as proceeding around the core, from a non-zero minimum thickness to a maximum thickness.

Rotary positive displacement machines based on trochoidal geometry that includes a helical rotor that undergoes planetary motion relative to a helical stator are described. The rotor can have a hypotrochoidal-based cross-sectional shape, with the corresponding stator cavity cross-sectional shape being the outer envelope of the rotor cross-sectional shape as it undergoes planetary motion, or the stator cavity can have an epitrochoidal-based cross-sectional shape with the corresponding rotor cross-sectional shape being the inner envelope of the stator cross-sectional shape as it undergoes planetary motion. Such machines can be configured so that the stator axis is spaced from the rotor axis, the rotor is configured to spin about its axis and the stator is configured to spin about its axis, and/or the rotor and the stator are held at a fixed eccentricity so that the rotor undergoes planetary motion relative to the stator, but does not orbit.

Rotary positive displacement machines based on trochoidal geometry and including a helical rotor that undergoes planetary motion relative to a helical stator can be designed and configured so that the axial load or rotor pressure force is positive, negative, or neutral. In some embodiments, a change in axial load, caused by a change in differential pressure across the machine, can be used to trigger a change in a mechanical configuration of the machine.

A cylindrical symmetric volumetric machine, includes a housing (2) with two co-operating rotors (6a, 6b) therein, namely an outer rotor (6a) mounted rotatably in the housing (2) and an inner rotor (6b) mounted rotatably in the outer rotor (6a), whereby a compression chamber (8) is located between the rotors (6a, 6b), which will move by rotation of the rotors (6a, 6b) from the inlet side (9a) of the rotors (6a, 6b) to the outlet side (9b) of the rotors (6a, 6b), wherein the inlet side (9a) of the outer rotor (6a) is provided with a ventilator (12), to supply air to the compression chamber (8).

The present invention aims to provide a long-life stator and a uniaxial eccentric screw pump provided with the stator, which enable a comparatively extended period of use by preventing damage of the stator due to repeating of attachment and removal to/from the uniaxial eccentric screw pump. A stator 20 includes an outer cylinder 30, and a stator main body 42 having flange-shaped gasket parts 46 and 47. The stator 20 includes fixing areas 24 and 25 to which the gasket parts 46 and 47 and the outer cylinder 30 are adhered. One or both of the outer cylinder 30 and the gasket parts 46 and 47 has a derricking part penetrating or being dented in axial directions X and made into such a shape where at least part of one of the outer cylinder and the gasket parts is fitted into the other.

Improved solids handling in rotary positive displacement machines, where the machines are based on trochoidal geometry, can be achieved through the use of solids-handling features on the surface of the rotor and/or stator and/or by the use of modified seals mounted on the rotor or stator. In at least some embodiments the rotary machines comprise a helical rotor that undergoes planetary motion relative to a helical stator.