Manual precompression pump

A manual precompression pump for spraying or dispensing a fluid substance contained in a receptacle, said pump comprising:

• a hollow cylindrical pump body (1) provided with an admission orifice (1b) in communication with the receptacle;
• a hollow piston (2) sliding inside said pump body and extended by a hollow actuation rod (3) to a top end, said hollow actuation rod including a valve seat (7a);
• a valve member (6) for closing said hollow rod (3);
• resilient means (10) urging said valve member (6) towards said hollow rod (3) in such a manner as to press said valve member (6) against said valve seat (7a) in a sealed manner, and in such a manner as to urge said valve member (6) and said piston (2) towards a rest position;
• a pump chamber (12) delimited by the pump body (1), the piston (2), and the valve member (6), said pump chamber communicating with the receptacle via the admission orifice (1b) when the valve member and the piston are in their rest position, said pump chamber (12) being capable of being isolated from the receptacle by sealed engagement between a first cylinder (8) integral with the valve member (6) and a second cylinder (4) integral with the pump body, each of said cylinders having a first end that is close to the other cylinder;
• and
• a valve member rod (7b) extending the valve member (6) through the hollow rod (3) to a first distance H1 beyond an outside end of the hollow rod such that, starting from the rest position of the valve member, the cylinder (8) integral with the valve member can be moved towards the cylinder (4) integral with the pump body through a second distance H2 greater than H1 without any sealing engagement between said cylinders, thereby enabling fluid to be introduced into or evacuated from the receptacle.