Piston seal

In an assembly comprising a piston slidably disposed within a cylinder, the cylinder comprises a resiliently deformable lining and the piston comprises a substantially rigid sealing portion which engages the lining and resiliently deforms it in the region of contact.

A fluid pump comprising a housing having an internal displacement chamber, an inlet, an outlet and a displacement rod which passes reciprocally into the displacement chamber through an aperture in the wall of the pump housing, wherein the displacement rod comprises a resiliently deformable sleeve or coating and the housing comprises a sealing member having a substantially rigid sealing portion which engages the sleeve or coating and resiliently deforms it in the region of contact.

A fluid pump comprising a housing having an internal displacement chamber, an inlet, an outlet and a displacement rod which is reciprocable sealingly within the displacement chamber, the displacement chamber comprising a resiliently deformable lining and the piston comprising a substantially rigid sealing portion which engages the lining and resiliently deforms it in the region of contact.

A fluid pump comprising a housing having an internal displacement chamber, an inlet, an outlet and a displacement rod which passes reciprocally into the displacement chamber through an aperture in the wall of the pump housing, the pump further comprising inner and outer spaced-apart seal means which engage the outer surface of the displacement rod and means for applying fluid to the surface of that portion of the displacement rod between the inner and outer seal means.

A fluid pump comprising a housing having an internal displacement chamber, an inlet, an outlet, a displacement rod which passes reciprocally into the displacement chamber through an aperture in the wall of the pump housing and a seal means which engage the outer surface of the displacement rod and define a boundary of the displacement chamber, the pump further comprising guide means to ensure that fluid displaced by the displacement rod passes over the inner portion of the seal means before being discharged through the outlet.

A fluid pump comprising a housing having an internal displacement chamber, an inlet, an outlet, a displacement rod which passes reciprocally into the displacement chamber and seal means which engage the outer surface of the displacement rod and define a boundary of the displacement chamber, the displacement rod comprising a resiliently deformable sleeve or coating and the seal means being substantially rigid, the pump further comprising a scraper means outwardly of the seal means which comprises one or more edges for scraping unwanted deposits off the resiliently deformable sleeve or coating of the displacement rod.