Shampoo dispensing pump with anti=drip mechanism - has back suction phase using pump chamber negative pressure to draw back fluid in exit after discharge phase

摘要

The pump chamber contains a reciprocating piston (4) which creates positive and negative pressure in the chamber, and a check valve at each end of the chamber. The first check valve permits a return flow of fluid before closing fully, while the second valve remains closed until a specified threshold negative pressure exists in the chamber. The positive pressure is used to discharge fluid, while the negative pressure creates the back suction phase and a following suction phase straight after the back suction. The suction phase uses the negative pressure in the pump chamber to pull fluid up from the main fluid container and into the pump chamber ready for the next discharge phase. The suction valve (7) is held closed until after discharge and back suction to prevent dripping.