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: An electric motor including a rotor mounted on a motor shaft for rotation around a stator, the rotor including a generally cylindrical wall and a rotor top generally closing the cylinder of the rotor wall, the rotor being connected to the motor shaft by a connecting device, the connecting device being received within an opening in the rotor top and having an aperture for receiving the motor shaft as an interference fit which prevents of rotation of the shaft with respect to the connecting device, the connecting device including a first radially outwardly extending formation at a first side of the rotor top, and a second radially outwardly extending formation at a second side of the rotor top such that the rotor top is received between the first and second radially outwardly extending formations, and there being a spacer between the first radially outwardly extending formation and the first side of the rotor top, the spacer including teeth which dig into the first side of the rotor top and the first radially o

Abstract: An electric motor including a rotor with a generally cylindrical rotor wall and a plurality of magnetic field producing elements mounted on an inside surface of the rotor wall, the rotor being mounted for rotation around a central stator, wherein the magnetic field producing elements are mounted on the rotor wall by means of a plurality of resilient retaining members, at least one resilient retaining member being located between and engaging with edges of two adjacent magnetic field producing elements, the edges of the magnetic field producing elements extending generally parallel to an axis of rotation of the rotor, the resilient retaining member being elastically deformed so as to exert a retaining force on the magnetic field producing elements.

Abstract: A brushless DC motor comprises a rotor (20) and a stator (22) having confronting surfaces. Permanent magnets (M) are provided at one of the confronting surfaces, the magnets being equally angularly spaced around an axis (A--A) of rotation of the rotor such that each magnet occupies part of a respective pole arc (PA) of a first circle (C1) centred on the axis (A--A), the pole arcs each subtending a common pole angle .alpha. to the axis. Teeth (Tm) are provided at the other of the confronting surfaces, the teeth being angularly spaced from one another around the axis (A--A) such that each tooth occupies part of a respective tooth arc (TA) of a second circle (C2) centred on the axis, the tooth arcs each subtending a common tooth angle .beta. to the axis. Windings (40) are wound around the teeth (Tm) whereby energisation of the windings with electrical currents at respective phases will produce a torque that will rotate the rotor (20). The tooth angle .beta. is substantially equal to the pole angle .alpha..