Pump unit comprising an outer part, an inner part, and a top part with a piston, wherein the piston extends into the inner part and the top part is arranged to perform a scrolling movement whereby the inner part is caused to slide in a first direction relative to the outer part

A pump unit comprising an outer part and an inner part arranged so as to form a cavity, the cavity having a cavity opening formed by the outer part and the inner part, the pump unit further comprising a top element, said top element sealing the cavity opening and further comprising a piston wall extending through the cavity opening and into the cavity such that the cavity is divided into a first chamber and a second chamber separated by the piston wall, the piston wall sealing the first chamber and the second chamber from each other at a first end stop of the inner part and a second end stop of the inner part at opposite ends of the cavity, the outer part being fixed relative to the inner part and the top element and further comprising at least one inlet and at least one outlet, the top element being arranged to perform a scrolling movement whereby the inner part is caused to slide back and forth in a first direction relative to the outer part and the piston wall is caused to slide in a second direction relative to the inner part, wherein the second direction is perpendicular to the first direction, the first chamber fluidly coupled with the at least one inlet and the at least one outlet in such a way that the sliding of the inner part will cause the first inlet and the first outlet to be alternatingly closed and exposed by the inner part to achieve a pumping effect from the first inlet to the first outlet.