Pumps for transferring small quantities of dosed liquids

A pump for transferring small quantities of dosed liquids, comprising a cylinder, an axial inlet bore in said cylinder for alternately receiving and discharging dosed liquid, a valve being provided at one end of said bore controlling the suction of liquid in said bore, the other end of said bore being in communication with a space for another liquid or gas at a higher pressure than the first mentioned liquid, a plunger being disposed above the other end of said inlet bore and in said space, said plunger being provided with an axial bore and a valve housing with valve for controlling the evacuation of the dosed liquid out of the inlet bore of said cylinder when the plunger penetrates in the bore of said cylinder, means for obtaining the axial displacement between said plunger and said cylinder and for bringing said plunger alternately within and without said cylinder, whereby in the latter mentioned position of said plunger the liquid which has been fed into said inlet bore of said cylinder is brought up to the same pressure as that which prevails in said space.