Barrier type screw designs are the most widely used screw designs in the extrusion industry. The first barrier screw design was by Maillefer (Swiss patent # 82,535/59, filed 12/3/1959). The second and currently the most widely used barrier design is by R.F.Dray (Patent # 3,650,652, filed 5/5/1970). There are many different names for versions of this design by virtually all manufacturers and designers, although the basic part of the patent (see figure 1) is common in all of these versions. In figure one you will note that the primary channel width is maintained allowing the barrier flight and auxiliary channel to be formed with the remaining width. Although these various versions incorporate the original technology, they do not include new innovations by the original inventor. These new innovations allow R.Dray Mfg. to maintain its competitive advantage.
The advantages derived from properly designed barrier screws are improved rate, lower melt temperature, and improved melt quality. To fully enjoy these benefits, barrier screw designs normally incorporate a downstream mixing device. R.Dray Mfg. offers both distributive and dispersive mixer types.
For over thirty years R.Dray has provided advanced screw design technology and leading screw manufacturing techniques to the extrusion industry. Applications include virtually all resins and all types of compounding and processing. We have manufactured screws of all configurations and sizes. Diameters up to 26 in. and lengths up to 40 ft.
R.Dray was the first to guarantee performance in the Extrusion Industry. Other companies may claim to be the performance leader in screw design technology, we go a step further - we guarantee that our designs will out perform all others - and have guaranteed this for thirty years. Screws purchased from R.Dray Mfg. are designed and manufactured by R.Dray Mfg., therefore we can provide the service and reliability of a single source supplier.

R.Dray Mfg. Inc. of Texas
Pennsylvania Sales Office
Route 1 Box 343
West Middlesex, PA 16159
Phone (724) 964-0703 Fax (724) 964-8174

R.Dray Mfg. Inc. of Texas
Texas Office
P.O. Box 671326
Dallas, TX 75367
Phone (214) 368-5424
Fax (214) 363-9787

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