Patent DE-10051101-A1 (DE)
Title: Drive system for the injection screw of a plastics injection molding machine has separate electromotors and gearing for the rotary and axial movements with a rack and pinion transmission
Inventor: WEINMANN ROBERT
IPC: B29C45/50
Filed: 2000-10-14
Abstract: The drive for the injection screw (4), for a plastics injection molding machine, has separate electromotors (A1,A2) for the rotary and axial screw movements. A rack overdrive has at least one double rack for the axial movements of the injection screw. The rotary and axial movements are combined in a drive unit (100).  The drive for the injection screw at an injection molding machine can have two double racks as the overdrive, spaced apart and parallel to the rotary axis of the injection screw. The rack overdrive has angled teeth, on both sides of each double rack, pitched against each other in a mirror image to equalize the tooth forces and the inertia. The teeth profiles of the double racks and the toothed pinions are on a common plane. The pinions can be adjusted to equalize the forces in the direction of their rotary axes. The gearing for the rotary and axial movements are integrated into a single component group. The rotating and sliding mechanisms form a compact group, moving in a guide tube coaxial to the injection axis (41). The racks, at the drive side, are mounted at the bearing bushes of the screw coupling, which has two axial radial bearings and the bearing bush slides through a guide tube. The racks are linked to a guide strip by a closure flange, at the ends away from the injection screw, to pass through the guide tube. The racks have their teeth aligned outwards, so that the common working line of the rack drive is an extension of the injection screw. The rack drive motor has a gearing (45) with two outputs, or it is operated by two motors with vertically upright drive axes in relation to the injection screw drive. The rotary drive is through a wedge projection and a splined shaft for a sliding mounting linked to the drive motor. The splined shaft is mounted with a gearing (40) at the drive side, and rides with the wedge projection for the stroke length to transmit the rotary movement through a sleeve with the screw coupling. The wedge projection with a sleeve extends over the rack length when retracted. The splined shaft is flush with the screw shaft axis, with symmetrical or coaxial racks and sleeve. The racks are at a quadrilateral profile with teeth on two sides. At least one rack drive is used for the axial movements of the injection screw, as a twin-axis gearing. The working axis of the rack matches the rotary drive axis to rotate the injection screw in an advance action. The gearing for the rotary and axial movements of the injection screw have their own gear housings. The rotary drive gearing has the wedge projection and the splined shaft. The rack of the double-rack overdrive is mounted to the gear housing at the drive take-off side for the rotary movement. The gear housing, for the axial movement, is bonded to a frame of the injection assembly and the rotary drive gearing has additionally a sliding movement in relation to the injection unit. The rotary and axial drive gearing are on a powered injection unit with a sliding movement in relation to the machine columns, with a third drive (A3). The electromotor (A1) for the rotary movement is an asynchronous servo motor or a hollow motor. The electromotor (A2) for the axial movement is an alternating current synchronous servo motor, with electronic power control.