Patent ID: 8388324

Claim:
A device for metering a flowable mass comprising: a pump comprising a housing defining a chamber having an inlet and an outlet, a rotary piston having a passage and a surface, said rotary piston being positioned in the chamber for rotary movement about an axis A in the chamber between (1) a first position wherein the inlet communicates with the chamber through the passage in the rotary piston and the outlet is closed to the chamber by the surface of the rotary piston and (2) a second position wherein the inlet is closed to the chamber by the surface of the rotary piston and the outlet communicates with the chamber through the passage in the rotary piston, a plunger mounted in the chamber in opposition to the rotary piston and defining with the housing and the rotary piston a pump chamber, a lifting bar movable in a direction along axis A toward and away from the rotary piston for moving the flowable mass from the inlet to the outlet, the passage comprises a recess configured in an open slot, the housing forms in an interior an annular edge against which a front edge of the rotary piston bears, the rotary piston has an external diameter d 1 corresponding to an internal diameter of the chamber in the housing upstream of the annular edge, and the plunger has an external diameter d 2 corresonding to the internal diameter of the chamber in the housing downstream of the annular edge, the annular edge is formed by a sleeve, the front edge of the rotary piston lies opposite the plunger and is curved in the shape of a horseshoe, the front edge is adjoined by a conchoidal inner vault which is followed by a cylindrical portion, and the conchoidal inner vault has side edges which run linearly and horizontally away from the front edge.