Coextrusion block, especially for the coextrusion of generally flat PVC articles, such as siding

• US 4,856,975 A
• Filed: 08/26/1988
• Issued: 08/15/1989
• Est. Priority Date: 08/26/1988
• Status: Expired due to Fees

• Current Assignee: National Canada Finance Corp.
• Original Assignee: American Maplan Corp. (BC Extrusion Holding GmbH)
• Inventors: Gearhart, Kenton
• Primary Examiner(s): Woo, Jay H.
• Assistant Examiner(s): Heitbrink, Timothy W.
• Application Number:
  US07/237,211
• Time in Patent Office: 354 Days
• Field of Search: 425/130, 425/131.1, 425/133.1, 425/133.5, 425/DIG. 243, 425/462, 264/177.1, 264/177.17
• US Class Current: 425/131.1
• CPC Class Codes: B29C 48/07 Flat, e.g. panels
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/09 Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• CPC Class Codes: B29C 48/21 the layers being joined at their surfaces
• CPC Class Codes: B29C 48/307 specially adapted for bringing together components, e.g. melts within the die

Abstract

A coextrusion block for siding communicates through respective separate circular inlets with two extruders at the inlet side of the coextrusion block while, at the outlet side, a curved kidney-shaped outlet is disposed about an inlet of acorn shape so that the outlets have boundaries lying along the common circle which corresponds to the circular inlet of the broad-mouth die.

Claims

1. A coextrusion assembly for the extrusion of wide generally flat workpieces in the form of extruded siding, said assembly comprising:

a first extruder for supplying a synthetic resin capstock material;

a second extruder for supplying a synthetic resin substrate material;

a coextrusion block having an upstream side and a downstream side, said block being formed at said upstream side with spaced apart first and second circular inlets opening on a common face of said block and connected respectively to said first and second extruders for receiving said capstock material and said substrate material, respectively, said block being formed at said downstream side with a first outlet for said capstock material and a second outlet for said substrate material, said first outlet having generally an elongated arcuate kidney shape with terminal lobes connected by an arcuate region extending arcuately around and strangling said second outlet, said second outlet having a generally acorn-shaped outline with opposite rounded segments of different radii of curvature having S-shaped transitions between them, said first and second outlets having diametrically opposite margins lying along a common circle, said coextrusion block being further formed with respective passages smoothly connecting said first inlet with said first outlet and said second inlet with said second outlet whereby flow from said first outlet wraps around flow from said second outlet; and

a die having a circular inlet coaxially with said common circle and registering with both sides outlets, a wide mouth from which a flat workpiece consisting of said materials in respective layers emerges, and a passage flaring from said circular inlet of the die to said mouth.

2. The coextrusion assembly defined in claim 1 wherein said outlets are symmetrical with respect to a plane of symmetry including centers of said first and second inlets and said common circle.

3. The coextrusion assembly defined in claim 2 wherein said first outlet has rounded ends terminating substantially at a plane through said center of said common circle and perpendicular to said plane of symmetry.

4. The coextrusion assembly defined in claim 2 wherein said first outlet has rounded ends terminating short of a plane through said center of said common circle and perpendicular to said plane of symmetry.

5. The coextrusion assembly defined in claim 2 wherein said first outlet has rounded ends passing through and terminating beyond a plane through said center of said common circle and perpendicular to said plane of symmetry.

6. A coextrusion block for use with two extruders and an extrusion die for producing generally flat workpieces in the form of extruded siding by the coextrusion of two polyvinylchloride materials, said coextrusion block comprising a body having an upstream side and a downstream side, said body being formed at said upstream side with spaced apart first and second circular inlets opening on a common face of said block and connected respectively to first and second ones of said extruders for receiving a capstock polyvinylchloride material and a substrate polyvinylchloride material, respectively, said block being formed at said downstream side with a first outlet for said capstock material and a second outlet for said substrate material, said first outlet having generally an elongated arcuate kidney shape with terminal lobes connected by an arcuate region extending arcuately around and straddling said second outlet, said second outlet having a generally acorn-shaped outline with opposite rounded segments of different radii of curvature having S-shaped transitions between them, said first and second outlets having diametrically opposite margins lying along a common circle so as to communicate with an inlet of said die registering with said common circle, said body being further formed with respective passages smoothly connecting said first inlet with said first outlet and smoothly connecting said second inlet with said second outlet whereby flow from said first outlet wraps around flow from said second outlet.

7. The coextrusion block defined in claim 6 wherein said outlets are symmetrical with respect to a plane of symmetry including centers of said first and second inlets and said common circle.

8. The coextrusion block defined in claim 7 wherein said first outlet has rounded ends terminating substantially at a plane through said center of said common circle and perpendicular to said plane of symmetry.

9. The coextrusion block defined in claim 7 wherein said first outlet has rounded ends terminating short of a plane through said center of said common circle and perpendicular to said plane of symmetry.

10. The coextrusion block defined in claim 7 wherein said first outlet has rounded ends passing through and terminating beyond a plane through said center of said common circle and perpendicular to said plane of symmetry.