Abstract: The invention concerns a volumetric device with reciprocating piston to deliver defined quantities of liquid and includes a piston valve pump and a valve block with intake and discharge valves affixed to a reservoir. The nullify the pressure difference generated upon withdrawing liquid from the hermetically sealed reservoir between this reservoir and the ambient atmosphere, the valve head additionally is provided with a ventilation valve allowing on one hand the inflow of ambient air into the reservoir and on the other hand preventing the escape of the tiniest amounts of liquids even after lengthy standing.

Abstract: A dispenser for precisely dispensing fluid from a storage vessel into a recipient vessel includes a housing formed with a connector portion having a valve chamber with a suction valve and a discharge valve therein. A cylinder is mounted on the connector portion. The valve chamber contains a suction valve and a discharge valve. The piston is slidably and rotatably guided in the cylinder and carries an operating button at one end thereof remote from the valve chamber. A counter stop is fixed to the housing and an end portion remote from the valve chamber to cooperate with an adjustable stop. A bush having an exterior thread is slidably and rotatably microscopically mounted on the outer surface of the cylinder. The bush carries the adjustable stop in threaded engagement while being coupled to the operating button in a axially fixed and freely rotatable manner.

Abstract: A piston for a precision dosing instrument includes a cylindrical core which may be made of glass, ceramic or metal, and a precision ground sleeve of polytetrafluorethylene disposed over the core. One end of the sleeve is closed while the core is open at both ends.

Abstract: A piston for a precision dosing instrument includes a cylindrical core which may be made of glass, ceramic or metal, and a precision ground sleeve of polytetrafluorethylene disposed over the core. One end of the sleeve is closed while the core is open at both ends but the openings may have different diameters.

Abstract: A piston for a metering device with a glass cylinder which comprises a cylindrical core of glass, ceramic or metal and a casing of poly(tetrafluoroethylene) reinforced with 10 to 60 weight percent glass fibers.