Worm Single Screw Extruder
Single screw extruder for mixing viscous materials by dividing material in only the forward flow direction in an irregular sequence into a plurality of communicating flow paths which are subjected to constant change between being divided and rejoined. Extruder design can be varied by removable and interchangeable partial arcuate twin screw extruder sections which are affixed to the body of the screw in the space between selected threads of a continuous screw thread.
A single worm extruder for the mixing and processing of rubber consists of two sections, an intake section and a mixing section. The mixing section has lands countercurrent to those of the intake section for partially back-feeding the rubber on to the intake section to provide a turbulent current of material. The countercurrent lands are interrupted by gaps which collectively have the same total area as the cross-sectional area of the intake section. The material is divided into a number of back-feed flows which thereafter recombine. Such extruders are disclosed in Menges et al., U.S. Pat. application Ser. No. 55,542, filed July 16, 1970, now U.S. Pat. No. 3,680,844, and Lehnen et al., U.S. Pat. application Ser. No. 808,543, filed Mar. 19, 1969, and now abandoned, both of which applications are assigned to same assignee as the present application.
The sheet production extruder, according to the invention is a multi-threaded screw with a continuous main screw thread having a constant pitch. Intermediate adjacent threads of the main screw is an appreciable portion of the body of the screw which does not have any threads. In this thread-free portion, the material mixture recombines into a single flow path resulting in a reduction of the material flow through the extruder and an accompanying increase in the apparent density of the material.
While there has been described what is at present considered to be the preferred embodiment of this twin screw extruder, various changes and modifications may be made therein without departing from the spirit of the invention and it is intended to cover all such changes which may come within the scope of the single screw extruder.