Indretning til stempelnulstilling i dispenser forflydbart materiale

An adjustable dose dispenser having a measuring chamber of constant cross-section defined in a housing wherein an end of the chamber is selectively placed in communication with a reservoir containing flowable material to fill the chamber and with a passage to discharge material from the dispenser, and including a piston movably mounted in the housing and having an end face located in the measuring chamber so as to define the measuring volume between the piston end face and the end of the chamber. A manually operable drive mechanism is movably carried by the housing and has formations thereon operatively engaging formations on the piston so that upon movement of the drive mechanism the piston end face is moved along the measuring chamber to vary the volume thereof and so that dimensional control of the volume of the measuring chamber is determined by tolerance associated with misalignment of the formations on the piston and drive mechanism. The formations preferably are fine pitch gear teeth, and the piston and drive mechanism are installed in the dispenser in a manner such that the total tolerance associated with the volume of the measuring chamber is defined as the circular pitch of the gear tooth, i.e., the maximum misalignment between the gear teeth on the piston and on the drive mechanism.