Metering system

A metering system for metering a liquid, comprising:

• an electric motor (32) for establishing a desired liquid feeding rate by modifying a rotation speed of the electric motor;
• an eccentric drive (52, 56), drivable by said electric motor (32), for a pump (53) that has two delivery directions;
• a stationary ring (70);
• a pump ring (62) made of an elastomeric material;
• the pump ring (62) is located within said stationary ring and is nonrotatable relative to the stationary ring (70);
• the stationary ring (70) being arranged, relative to the pump ring (62) and to the eccentric drive (52, 56), in such a way that a pump chamber (120) extending in a circumferential direction, viewed in a section extending perpendicular to the rotation axis (74) of the pump (53), is defined between the stationary ring (70) and pump ring (62), said chamber changing shape upon rotation of the electric motor (32) in order to deliver the liquid to be metered through the pump chamber (120), a stationary seal (142) being formed in said pump chamber (120) at an angular position between a suction connector (124;
• 122) and a discharge connector (122;
• 124);
• a first transverse stationary element (151) and a second transverse stationary element (152) sandwich said pump ring (62) therebetween, said elements each being formed with a respective hole (125), and wherein
• the pump ring (62) is formed near its radially outer surface with a transverse internal bore (141) at a circumferential location angularly between the suction connector (124;
• 122) and the discharge connector (122;
• 124);
• a wedge (140) is mounted through said holes (125) in said first and second transverse stationary elements (151, 152) and extends through said transverse internal bore (141), thereby pegging said pump ring (62) against possible rotation,
• said wedge also distending a transverse linear portion of said pump ring outer surface radially outward against the stationary ring (70), thereby producing said stationary seal (142) in the pump chamber (120).