Patent ID: 8157547

Claim:
A peristaltic pump for circulating a medium comprising: a pump housing defining an interior space; an elastically deformable hose having a part in contact with a pressing surface and having a medium inlet and a medium outlet; a pressing means comprising a plurality of equally spaced pressing elements and a central axis, an angular pitch between the pressing elements remaining constant over one revolution of the pressing means; wherein the pressing means are drivable such that the pressing elements move along the hose; wherein the pressing elements press the part of the hose in contact with the pressing surface during operation thereby locally compressing and closing the part of the hose so that a medium under pressure is drawn in via the medium inlet and discharged via the medium outlet; the pressing surface comprising: an infeed part connected to the medium inlet having a radial distance from the central axis of the pressing means that decreases from a first value at which the part of the hose in contact with the pressing elements is substantially open even when a pressing element is present, to a second value at which the part of the hose in contact with the pressing elements is substantially closed even when a pressing element is present; an intermediate part with a radial distance from the central axis of the pressing means which is substantially equal to the second value; and an outfeed part having a radial distance from the central axis of the pressing means that increases from the second value to the first value; wherein an angle of at least one of the following: the outfeed part or the infeed part, is greater than one and smaller than two times an angular pitch between the pressing elements.