Abstract: A worm press extruder or the like includes a worm shaft which conveys a flow medium within a housing cylinder. In order to provide the medium with an appropriate pressure and temperature the worm shaft cooperates with a constriction plate so as to define a gap therebetween. The gap is controlled by heat responsive unit e.g. a bolt of high thermal expansion coefficient which is connected to a stationary portion of the housing as well as to another housing portion which is movable with respect to the stationary housing portion by lever means. Consequently, when the temperature of the bolt is changed its length is altered thus causing the other housing portion which is associated with the constriction plate to shift towards the stationary housing portion. Since the worm shaft is supported by the stationary housing portion and cannot move axially with respect to the latter, the movement of the constriction plate causes a modification of the gap.