Injection molding process utilizing low shear screw
US4299792A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 22, 1980 |
| Grant date | Nov 10, 1981 |
| Priority date | — |
| Expiry date | May 22, 2000 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C45/60
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A method for the injection molding of plastics material wherein the forward portion of the screw is designed such that mixing and shear of the material is minimized. This is advantageous when processing materials having diverse colorations so as to produce a mottled product, and also for processing glass reinforced materials wherein high shear processing would break the fibers thereby resulting in a lower quality product. Low shear processing of the material in the forward portion of the barrel is accomplished by providing a screw having a fully flighted rear portion, but a forward portion which is flightless so that a generally unobstructed, annular flow passage is formed between the cylindrical outer periphery of the flighted portion and the inner wall of the barrel. In a mottling application of the apparatus, materials of diverse coloration are softened by the flighted rear portion of the screw but not yet fully mixed so that distinct color patterns are present. When the material reaches the unflighted portion, it will be forced forwardly by the forward pressure developed as the screw continues to pump material forwardly, but the only shear imparted thereto is the gentle wiping …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.