Manual pump with a free sleeve piston

摘要

The manual pump body defines a pump chamber with an inlet valve. A hollow activating rod which moves between rest and pushed positions is assisted into its rest position by a return spring. The rod has an internal return pumping channel. A free piston slides in the pump body on the activating rod. The rod has a stop surface (223) with which the piston engages during sliding upwards in order to create a seal at this point. An oversleeve (30) surrounding the activating rod has a lower end (32) in sealed contact at rest with the rod to form the outlet valve and an upper end engaging the rod stop surface during upwards sliding. The friction forces exerted between the piston and the pump body are greater than the friction forces exerted between the piston and the activating rod.