Pumps

A pump, comprising:

• a housing having a fluid inlet and a fluid outlet, the housing containing a rotor having chamber-forming surfaces that are radially inward of the housing, the chamber-forming surfaces forming chambers with the housing such that, on rotation of the rotor about an axis, the chambers convey fluid from the fluid inlet to the fluid outlet to pump the fluid to the fluid outlet at an outlet pressure:
• and
• a seal assembly comprising a seal and being arranged between the fluid outlet and the fluid inlet such that, on rotation of the rotor, the seal moves radially inward and outward relative to the axis of rotation of the rotor to maintain contact with the chamber-forming surfaces of the rotor and apply a sealing force along an axial length of the rotor to prevent the fluid passing from the fluid outlet to the fluid inlet in the direction of rotation of the rotor, and
• wherein the seal assembly includes a spring member of flexible resilient material that generates the scaling force,
• wherein the spring member has respective opposite side edges that are fixed relative to the housing and extend generally parallel to the rotation axis of the rotor,
• wherein the spring member applies the sealing force to the rotor between the opposite side edges and flexes resiliently between the opposite side edges as the rotor rotates,
• wherein the spring member is formed as a hollow tube, a generally U-section member, or another arcuate member, or a member conformable into a U-section member, and
• wherein the seal assembly is configured to apply a force per unit distance of movement that does not vary by more than plus or minus ten percent throughout travel of the seal assembly to minimise the scaling force applied by the seal assembly to the rotor for a given output pressure.