Viscous liquid dispensing pump

摘要

A dispensing pump ( 12 ) for a viscous liquid comprises a cylinder ( 16 ), a piston ( 24 ) mounted for reciprocation within said cylinder ( 16 ), an inlet ( 50 ) for admitting liquid to be dispensed into said cylinder ( 16 ) and a ball check valve ( 52 ) arranged selectively to open and close said inlet opening. The ball valve ( 52 ) is retained in position by a spring ( 58 ) having a variable diameter. The piston ( 24 ) has a dispensing passage ( 40 ) in fluid communication with said cylinder ( 16 ) and with a self sealing dispensing valve ( 38 ). The pump ( 12 ) further comprises a sliding cut-off valve ( 70 ) arranged selectively to open and close fluid communication between the piston dispensing passage ( 40 ) and the cylinder ( 16 ) as the piston ( 24 ) reciprocates within the cylinder ( 16 ).