Extrusion Adapter

This invention relates to an extruder and more particularly to an adapter for a die head of an extruder which splits the melt from the extruder into separate flow paths for movement to separate die heads.

Materials which are plasticized by an extruder such as polyvinyl chloride wherein the solid granular materials are heated and plasticized to issue as cylindrical shaped extrudate is very sensitive to overheating and subject to degradation. The improvements have been principally directed to extruder screw design and die head design to improve the homogeneous viscosity of the melt to assure a smooth flow of the plasticized material. It is also desirable to maintain this smooth flow of material in the die head adapter which splits the main flow from the extruder to into at least a pair of extrudates for extrusion from their respective die heads. The physical properties such as viscosity and velocity of flow are adversely affected by pronounced changes in the direction of flow as by movement past crevices or dead corners which tend to stagnate the flow of materials at such areas causing them to harden and tends to cause degradation in the material and adversely affects the end product. Through applicant's invention, there is a significant improvement in the unobstructed flow for the extrudate from the extruder through the adapter to the plural die heads. This is accomplished by having the respective conduits of the mating adapters and its associated parts with the die heads being circles presenting a perfect sealing between joints and surfaces. With the use of such adapters, the overall weight is reduced in the ratio of 3 to 1 in the case of small adapters and in ratio of 5 to 1 in the case of larger adapters thereby making it easier to handle and change as well as to facilitate the efficient dissipation of heat.

The present invention contemplates an adapter apparatus having an adapter block that splits the single flow channel from an extruder into at least a pair of separate flow channels. The adapter block is connected to die means via gooseneck. All of the openings between the extruder, adapter block, adapter means or gooseneck and the die heads are circle to circle connections to provide perfect sealing surfaces at all joints to eliminate dead corners at such junctures.

FIG. 1 is a schematic side elevational view of an extruder with adapter and die head.

FIG. 2 is a plan view of the extruder, adapter and die head.

Referring to the drawings wherein like reference characters designate like or corresponding parts throughout several views, there is shown in FIG. 1 an extruder which includes a casing 10 suitably mounted on a base not shown. Casing 10 has a longitudinally extending bore co-axial with an opening 11 on the one end thereof to provide communication with the passageway of an adapter apparatus to be described. An extruder screw 12 of suitable design is closely received by the bore of the extruder for plasticizing material therein. A feed hopper 13 is operatively connected to the bore of the extruder to supply thermoplastic material thereto. The one end of the extruder screw 12 is suitably keyed to a gear 15 which meshes with a spur gear 16 that receives its input from transmission means 17 which in turn is connected to motor 18. The one end of the extruder has a planar annular surface 20 which is adapted to abuttingly engage the adapter apparatus 21. The opening 11 makes a circle on the planar surface 20. The adapter apparatus 21 is a one piece adapter block 22 which has a first planar surface 23 which abuttingly engages the planar surface 20 of the extruder. The adapter block 22 has a pair of coverging planar surfaces 24 and 25 which in the example shown form an acute angle relative to each other. A first bore 26 extends into the adapter block 21 forming a perfect circle with the first planar surface 23 and mating with the circle that opening 11 makes with the planar surface 20. A pair of diverging passageways 27 and 28 extend from the junction with passageway 26 outwardly to form a perfect circle with respective planar surfaces 24 and 25. Connected to respective planar surfaces 24 and 25 are adapter means or goosenecks 30 and 31. Goosenecks 30 and 31 are constructed or molded as a linearly extending pipe that is curved sufficiently to provide a non-linear pipe without distorting the central passageway 32 therein so that cylindrical cross-sectioned extrudes passing therethrough passes un-interrupted, thereby providing a conduit means that facilitates the flow of melt therealong. Each gooseneck has a flange 33 and 34 at the respective end portions thereof to provide means for connecting them to the adapter block and their respective die means. Such passageways 32 form a circle on their respective end flanges. The flanges 33 and 34 have planar outer surfaces which form an annular planar surface for connection to the respective planar surfaces 24 and 25 of the adapter block 21 with the circles of the passageways 32 aligning with the respective passageways 27 and 28 of the adaptor block 21. The respective flanges 33 and 34 of goosenecks 30 and 31 are suitably connected to die means 36 for shaping the extrudate to the desired configuration or form. The die means indicated as 36 includes a spider which contours the cylindrical melt into an annular extrudate.

In the operation of the apparatus described, the material to be plasticized is fed into the extruder via hopper 13 and after being worked is extruded therefrom through opening 11 into bore 26 of adapter block 21. The melt is split into two portions for passage via passageways 27 and 28 in goosenecks or adapter means 30 and 31 to the spider portion of die means 36 for shaping into annular forms. The melt is then extruded from the die means 36. The respective mating bores and passageways of the extruder, adapter block, adapter means and die means are all perfect circles to eliminate crevices and assure a smooth mating of the parts. In addition, with the adapter means or gooseneck 30 and 31 being of slender construction, makes the adapter apparatus very compact and light providing excellent dissipation of heat.

Various modifications are contemplated and may obviously be resorted to by those skilled in the art without departing from the described invention, as hereinafter defined by the appended claims, as only a preferred embodiment thereof has been disclosed.