Electronically controlled linear pump drive

摘要

Electronically controlled linear pump drive actuator for a dispensing pump has a servo motor unit having a stator with front and rear faces and a central hollow cavity, a rotor coaxially in the hollow cavity with a front portion having a front end with an open central bore and a shaft with a stepped diameter forming a rear extension, front and rear support members respectively for the front and rear faces, a support bearing in the rear member, a front bearing, and a position sensor; a ball screw drive mechanism having a nut connected with the rotor and a screw shaft having a front end section; a hollow cylinder attached to the front member's front end; an actuator member axially moveable in the hollow cylinder with a central rear part fixed to the front end section, and a hollow front part; and a pump plunger adaptor.

主权项

1. An electronically controlled linear pump drive actuator for operating a fluid dispensing pump with precision and stability within a wide range of dispensing volumes and loads, comprising:
a servo motor unit that comprises: a stator (30) with a central hollow cavity defining a longitudinal axis, and front and rear faces; a rotor (31) extending coaxially in the hollow cavity of said stator (30) for rotation around said longitudinal axis, the rotor (31) having a front portion (32) that has a front end, a central bore open at the front end, and a predetermined length, both said front end and said front portion (32) of the rotor (31) extending in a frontal direction beyond said front face of said stator (30); and a rear shaft (33) with a stepped diameter forming a rear extension of said front portion (32), said rear shaft (33) extending in a rearward direction beyond said rear face of the stator (30); respective front and rear support members (41; 42, 43, 44) supporting and being attached to respective front and rear faces of said stator (30) to form a single stable mechanical assembly therewith; at least one support bearing (34, 35) inside of said rear support member (42) and situated beyond said rear face of the stator in the rearward direction, the at least one support bearing having its inner ring fixed on said stepped rear shaft (33) of said rotor (31), wherein said at least one support bearing is able to take and resist axial loads; a front bearing (48) placed directly between said front support member (41) and said front portion (32) of said rotor (31); and a position sensor with an encoder (40) sensing the actual angular position of said rear shaft (33) of said rotor (31); a ball screw drive mechanism having a ball screw nut (36) and a ball screw shaft (37) guided in said ball screw nut (36), said ball screw nut (36) being arranged in said central bore and attached to said front portion (32) of said rotor (31); said ball screw shaft (37) has a threaded rear portion, extendable to different lengths in said central bore behind said screw nut (36) depending on the momentary angular position of the rotor (31); a stationary hollow cylinder (45) attached to a front end of said front support member (41) that extends in the frontal direction around said longitudinal axis; an actuator member (39) guided exclusively for axial movement in said hollow cylinder (45) and having a central rear part fixed to a front end section of said ball screw shaft (37) to prevent any angular displacement of said shaft (37) and said actuator member (39) having a hollow front part; a pump plunger adaptor (22) fixed in said hollow front part of said actuator member (39) for releasable attachment of a plunger element (50) of said dispensing pump; and wherein, rotation of said rotor (31) in either direction causes the frontal or rearward linear movement of said ball screw shaft (37) together with said actuator member (39), and during reciprocation movement the rear end of said ball screw shaft (37) moves in and out of said central bore of said rotor (31).