Abstract: A pump for conveying a viscous medium, comprising a feed hose in the pump housing, a support wall extending along the feed hose and supporting the feed hose in the housing, pressure rolls mounted for movement along the feed hose diametrically opposite the support wall and arranged to compress the feed hose between the support wall and a respective pressure roll as the pressure roll moves along the feed hose whereby the feed hose is successively deformed from a normal, expanded shape to a compressed, flattened shape and the viscous medium therein is conveyed from a suction to the output end of the feed hose, and a centering device engaging the feed hose at its periphery for holding the feed hose in alignment with the support wall and for returning the feed hose from the compressed to the normal shape after the pressure roll has passed, the centering device including resiliently yielding support elements mounted in the housing and arranged at both sides of the feed hose, the support wall and the pressure roll d