Method and pump for low-flow proportional metering

A proportional dosing pump comprising a hydraulic machine having an inlet and an outlet, the hydraulic machine extending along a longitudinal axis and enclosing a member configured to reciprocate along the longitudinal axis, wherein supplying a main liquid to the inlet of the hydraulic machine triggers a reciprocating translational motion of the member along the longitudinal axis, and wherein the proportional dosing pump comprises:

• a displacement pump, provided with an axis of rotation, an inlet intended to be placed in fluid communication with an additive reservoir, and an outlet in fluid communication with the outlet of the hydraulic machine, and
• a motion converter provided to transform the reciprocating translational motion of the member of the hydraulic machine into a rotational motion, said rotational motion being transmitted directly or indirectly to the displacement pump so that supplying the main liquid to the inlet of the hydraulic machine actuates the displacement pump which thus supplies additive from the additive reservoir to the outlet of the hydraulic machine, causing the additive to mix with the main liquid at the outlet of the hydraulic machine.