Method for dripless liquid color delivery using a dripless liquid color feed throat adaptor

Abstract

Apparatus and methods for converting resin into colored finished or semi-finished plastic parts include a process machine having a barrel, a rotatable screw inside the barrel, and a color feed conduit assembly extending into the barrel for passage of liquid color through the color feed conduit assembly into proximity with the screw.

Description

CROSS REFERENCE TO RELATED PATENT APPLICATIONS[0001]This patent application is a 35 USC 120 division of co-pending U.S. patent application Ser. No. 14 / 105,958 filed 13 Dec. 2013 in the name of Stephen B. Maguire and entitled “Dripless Liquid Color Feed Throat Adaptor and Method for Dripless Liquid Color Delivery.”BACKGROUND OF THE INVENTIONField of the Invention[0002]This invention relates to molding and extrusion of plastic resin pellets to produce finished and semi-finished plastic products, and more particularly relates to using liquid color to color those finished and semi-finished plastic parts as the parts are being molded or extruded.Description of the Prior Art[0003]In the plastics industry, injection molding machines and extruders (herein collectively referred to as “process machines”) include a screw inside a barrel for melting the plastic resin pellets by working it by action of the screw against the resin as the screw rotates and driving the melted plastic forward throug...

AI Technical Summary

Benefits of technology

The patent text describes a design for a color delivery system in a machine. The system uses a small diameter Teflon tube that is fixed in place, eliminating the risk of dripping during color changes. The tube stays in the machine and is positioned to ensure that the inlet is higher than the outlet, so that any excess color is pushed out of the machine. Overall, this design allows for quick and safe color changes in the machine.

Problems solved by technology

Problems can arise if the liquid color contacts any portion of the feed throat as the liquid color is being fed to the screw.

Liquid color for coloring plastics is extremely viscous, somewhat like tar, and hence is very difficult to handle!

If the liquid color touches even the sides of the feed throat, this can present a problem due to the difficulty of clean up and the possibility of contamination of one color with another when color changeover is effectuated.

In the prior art, the most accepted way to introduce liquid color into the screw barrel and adjacent to the rotatable screw is to introduce the liquid color through a guide tube that passes through the feed throat and has its outlet end positioned close to the screw, so the liquid color does not exit the guide tube until it is well past the surfaces of the feed throat and other components, where spillage of the liquid color on to those surfaces could cause a problem.

A problem with current liquid color delivery systems as described immediately above is that when a color delivery tube is withdrawn, liquid color will drip from the open outlet end of the color delivery tube.

Any dripping of the liquid color creates a mess that is difficult to clean up due to the high viscosity, staining and other properties of liquid color.

Typically, the mess only gets worse and worse as time passes using current liquid color delivery techniques.

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