PUMP MODULE, DISCHARGE HEAD AND FLUID DISPENSER

From the prior art pump modules (10) for liquid dispensers (100) are known. A specific type of such pump modules (10) comprises a pump cylinder (14) having a fluid inlet (16) at one end and an inlet valve (18), a stem (40) and a piston (44) which is attached to the stem (40), the piston (44) being located within the pump cylinder (14) and defining a pump chamber (30) together with the pump cylinder (14), the stem (40) extending out of the pump cylinder (14) and comprising an outlet channel (46) of the pump module (10).The pump module (10) comprises a return spring in the form of a bellows spring (50) or a dome-shaped spring (51) by which the stem (40) and the piston (44) are pressed in the direction of the unactuated end position, the bellows spring (50) or the dome-shaped spring (51) being supported with a first end surface (56) by the stem (40) or a support collar fixedly attached to the stem and being supported with a second end surface (58) by the pump cylinder or a support collar (20) fixedly attached to the pump cylinder (14).It is proposed that a ventilation path (4) is provided, through which an interior space (52) of the bellows spring (50) or the dome-shaped spring (51) is connected to a surrounding atmosphere, said ventilation path (4) running at least partially through at least one ventilation aperture (64) or at least one end-side recess (62) in the bellows spring (50) or the dome-shaped spring (51) and/or through at least one ventilation channel (24) or at least one ventilation groove (26) in the support collar (20) attached to the pump cylinder (14).