Abstract: A volumetric pump comprises at least one piston inside a cylindrical housing and means to cause a relative to-and-fro linear movement between the cylindrical housing and the piston in order to produce a stroke of the volumetric pump. This pump further comprises a bi-directional angular rotatable disc acting as a valve which connects alternately at least one inlet port and at least one outlet port to a least one pump chamber located inside the housing, and a driving mechanism arranged to dissociate at least partially the bi-directional angular movement of the rotatable disc with the to-and-fro linear movement of the housing. This driving mechanism is arranged such that the rotatable disc reaches an angular position at which it opens and/or closes the inlet and/or outlet ports when there is no relative to-and-fro linear movement between the cylindrical housing and the piston.