Abstract: A pump including at least three rotors each being provided with a generally helical screw thread, the rotors being mounted for rotation in a housing such that the screw threads of the rotors mesh and rotation of one rotor causes rotation of the other rotor, wherein the pitch of the threads is less than 1.6 times the outer diameter of the rotors or where one of the rotors has a larger outer diameter than the other rotors the outer diameter of the larger diameter rotor.

Abstract: A pump e.g. a screw pump, includes a main pumping element and a generally parallel auxiliary pumping element, and a pump housing, the main and auxiliary pumping elements interacting with each other and with an internal wall of an elongate pumping chamber of the housing as they relatively rotate to pump fluid from a first axial inlet end of the elongate chamber towards a second axial outlet end of the elongate chamber, and wherein the internal wall of the elongate pumping chamber includes at least one recess which extends along at least a substantial portion of the axial extent of the chamber between the inlet and outlet ends of the chamber, an adjacent pumping element being contactable with the chamber wall at discrete contact edges either side of the recess.

Abstract: A pump including a power rotor and an idler rotor, the rotors each being provided with a generally helical screw thread and being mounted for rotation in a housing such that the screw threads of the rotors mesh and rotation of one rotor causes rotation of the other rotor, the power rotor being connected to a driving means operation of which causes rotation of the power rotor, wherein the pitch of the threads is less than 1.6 times the outer diameter of the power rotor, the depth of the threads is less than or equal to 0.2 times the outer diameter of the power rotor, and the root diameter of the idler rotor is less than 0.31 times the outer diameter of the power rotor.

Abstract: A pump including at least three rotors each being provided with a generally helical screw thread, the rotors being mounted for rotation in a housing such that the screw threads of the rotors mesh and rotation of one rotor causes rotation of the other rotor, wherein the pitch of the threads is less than 1.6 times the outer diameter of the rotors or where one of the rotors has a larger outer diameter than the other rotors the outer diameter of the larger diameter rotor.

Abstract: A pump assembly including a pump, a pump frame and a motor, the pump including a pumping member which is mounted in a pump housing, relative rotation of the pumping member with respect to the pump housing causing pumping of fluid, and the motor including a rotor and a stator, operation of the motor causing rotation of the pumping member relative to the pump housing, wherein one or two of the stator, pumping member and pump housing is fixed relative to the pump frame, a resilient support part being provided between the pump frame and each of the other two or one of the stator, pumping member, and the pump housing, the resilient support part or parts permitting movement of the stator, pumping member or pump housing with respect to the pump frame.

Abstract: A pump including at least three rotors each being provided with a generally helical screw thread, the rotors being mounted for rotation in a housing such that the screw threads of the rotors mesh and rotation of one rotor causes rotation of the other rotor, wherein the pitch of the threads is less than 1.6 times the outer diameter of the rotors or where one of the rotors has a larger outer diameter than the other rotors the outer diameter of the larger diameter rotor.

Abstract: A pump assembly including a pump, a pump frame and a motor, the pump including a pumping member which is mounted in a pump housing, relative rotation of the pumping member with respect to the pump housing causing pumping of fluid, and the motor including a rotor and a stator, operation of the motor causing rotation of the pumping member relative to the pump housing, wherein one or two of the stator, pumping member and pump housing is fixed relative to the pump frame, a resilient support part being provided between the pump frame and each of the other two or one of the stator, pumping member, and the pump housing, the resilient support part or parts permitting movement of the stator, pumping member or pump housing with respect to the pump frame.

Abstract: A pump e.g. a screw pump, includes a main pumping element and a generally parallel auxiliary pumping element, and a pump housing, the main and auxiliary pumping elements interacting with each other and with an internal wall of an elongate pumping chamber of the housing as they relatively rotate to pump fluid from a first axial inlet end of the elongate chamber towards a second axial outlet end of the elongate chamber, and wherein the internal wall of the elongate pumping chamber includes at least one recess which extends along at least a substantial portion of the axial extent of the chamber between the inlet and outlet ends of the chamber, an adjacent pumping element being contactable with the chamber wall at discrete contact edges either side of the recess.

Abstract: A motor driven pump comprises a motor stator (30), a motor rotor (10) operable to rotate around the outside of the stator (30) and a pump mechanism (40, 50) driven by the motor rotor (10) and disposed at least partly inside the motor stator (30).