Proportional volumetric dosing unit

Abstract

A proportional volumetric dosing unit (1) is described, comprising: a motor (20) provided with an output shaft (31) movable along a respective sliding axis (X) between an upper dead centre position and a lower dead centre position, and a pump (25) fixed to the motor and adapted to be driven by said output shaft. Said pump comprising: a pump piston (362) fixed to an end of the output shaft, and a tubular body (300) coaxial with the output shaft and provided with an inner tubular surface (305), which comprises at least one contact section on which the pump piston slides in contact. Said tubular body (300), at least at the contact section, comprises a first annular portion (301) at least partially lined by a second annular portion (302), which second annular portion provides the inner tubular surface (305) at the contact section. Where the second annular portion is made of a polymeric material which is chemically more resistant to corrosion, against a predetermined corrosive agent, with respect to a polymeric or composite material of which the first annular portion is made, and/or the first annular portion is made of a polymeric or composite material which is mechanically more resistant than a polymeric material in which the second annular portion is made.

Dependencies are inferred from the claim text.