Fluid dispenser with a piston sealingly movable in a dosing chamber but only in sealing contact with a narrower first section during a part of the stroke.

摘要

A fluid dispenser (110) is disclosed comprising a dosing chamber (120), a fluid outlet and a piston member (114) which is arranged to sealingly stroke in the dosing chamber (120). Piston movement in a first direction fills the dosing chamber (120) with fluid from the supply and in a second direction dispenses fluid from the dosing chamber (120) towards the outlet. The dosing chamber (120) has a first section which is narrower than a second section and located in the second direction. The piston member (114) is in constant sealing contact with the second section but only in sealing contact with the first section during a portion of the piston strokes in the first and second directions.