EP0267719A2
Expired / Lapsed
EP
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Method for extruding and expanding polytetrafluoroethylene tubing and the products produced thereby
Assignee: W.L. Gore and Associates Inc
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Filing: 1987-11-02
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Granted: —
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Expires: 2007-11-02
Abstract
Abstract Apparatus, and a method, for extruding and expanding tubular products of polytetrafluoroethylene (PTFE), and the products produced thereby, are provided. In the apparatus, at least one helical groove (26 or 28) is placed in the wall of the extruder tip or die. Preferably, at least one groove (28) is machined in the tip (18) having a pitch angle of 135 degrees and at least one groove (26) is machined in the die (24) having a pitch opposite that (45 degrees) of the tip groove. In the expanded tube, at at least one radial position within the wall of the tube, substantially all of the longitudinal axes of the nodes are oriented at an angle between 85 degrees and 15 degrees with respect to the longitudinal axis of the tube. In a preferred embodiment, substantially all of the longitudinal axes of the nodes located adjacent the inside wall of the tube are oriented at an angle between 85 degrees and 15 degrees with respect to the longitudinal axis of the tube, and substantially all of the longitudinal axes of the nodes which are located adjacent the outside wall of the tube are oriented at an angle between 15 degrees and 165 degrees with respect to the longitudinal axis of the tube. The grooved extrusion tip and die give the finished tube increased hoop strength.
Inventors
- 👤 Charles Edward Biggerstaff
- 👤 Michael Lee Campbell
- 👤 Rob Gordon Riffle
- 👤 Benjamin Griffith Williams
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 10:56
CPC Classifications
B; B29; B29C; B29C55/00; B29C55/005; A; A61; A61F; A61F2/00; A61F2/02; A61F2/04; A61F2/06; B29C48/00; B29C48/022; B29C48/03; B29C48/09; B29C48/13; B29C48/25; B29C48/30; B29C48/32; B29K; B29K2027/00; B29K2027/12; B29K2027/18; Y; Y10; Y10S; Y10S138/00; Y10S138/03; Y10T; Y10T428/00; Y10T428/13; Y10T428/1352; Y10T428/1376; Y10T428/31504; Y10T428/3154; Y10T428/31544
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
91 words
An extruded and expanded tube of a porous material consisting essentially of polytetrafluoroethylene (PTFE) said tube having a longitudinal axis and tube wall, which PTFE material has a microstructure consisting of elongated nodes, each node having a longitudinal axis and a transverse axis, which nodes are interconnected by fine fibrils, characterised by substantially all of the longitudinal axes of said nodes at at least one radial position within said tube wall being oriented at an angle between 85 degrees and 15 degrees with respect to said longitudinal axis of said tube.
Claim 2
Dependent Claim
91 words
An extruded and expanded tube of a porous material consisting essentially of polytetrafluoroethylene (PTFE) said tube having a longitudinal axis and tube wall, which PTFE material has a microstructure consisting of elongated nodes, each node having a longitudinal axis and a transverse axis, which nodes are interconnected by fine fibrils, characterised by substantially all of the longitudinal axes of said nodes at at least one radial position within said tube wall being oriented at an angle between 85 degrees and 15 degrees with respect to said longitudinal axis of said tube.
Claim 3
Dependent Claim
50 words
A tube according to claim 1 characterised in that it has not been heated to a temperature above its crystalline melt point, that said material has a crystallinity greater than 95%, and that said material has a matrix tensile strength in at least one direction above 7,300 psi (50,735 kPa).
Claim 4
Dependent Claim
87 words
A tube according to claim 1 characterised in that substantially all the longitudinal axes of said nodes which are located adjacent the inside radius of said tube are oriented at an angle between 85 degrees and 15 degrees with respect to said longitudinal axis of said tube, and substantially all of the longitudinal axes of said nodes which are located adjacent the outside radius of said tube are oriented at an angle between 15 degrees and 165 degrees with respect to said longitudinal axis of said tube.
Claim 5
Dependent Claim
89 words
A tube according to any preceding claim characterised in that substantially all of the longitudinal axes of said nodes which are located adjacent the inside radius of said tube are oriented at an angle of 30 degrees to 60 degrees with respect to said longitudinal axis of said tube, and substantially all of said longitudinal axes of said nodes which are located adjacent said outside radius of said tube are oriented at an angle of 30 degrees to 150 degrees with respect to said longitudinal axis of said tube.
Claim 6
Dependent Claim
55 words
A tube according to claim 1, characterised in that the PTFE material has been heated to a temperature above the crystalline melt point, and has a matrix tensile strength in at least one direction above about 9,290 psi (64,055 kPa) and a hoop stress exceeding 250 psi (1724 kPa), or exceeding 450 psi (3103 kPa).
Claim 7
Dependent Claim
160 words
Apparatus for extruding tubing of PTFE characterised by a hollow, cylindrical barrel containing a mandrel centrally positioned within said barrel, said barrel having a resin supply region, a tapered region leading from said supply region to an annular outflow region comprising an external, hollow, circular cylindrical die having positioned centrally therein the circularly cylindrical tip of said mandrel, the tip and die forming an annulus, at least one of said tip and die having at least one groove in the surface thereof, said groove being oriented helically with respect to the longitudinal axis of said tip and die, a ram capable of reciprocation within said barrel and surrounding said mandrel, and means providing said ram with reciprocating movement whereby, when a preformed, tubular billet of lubricated PTFE is placed in said barrel and said ram is activated to force said PTFE through said annulus, tubing is produced having at least one helically oriented ridge on at least one surface thereof.
Claim 8
Dependent Claim
160 words
Apparatus for extruding tubing of PTFE characterised by a hollow, cylindrical barrel containing a mandrel centrally positioned within said barrel, said barrel having a resin supply region, a tapered region leading from said supply region to an annular outflow region comprising an external, hollow, circular cylindrical die having positioned centrally therein the circularly cylindrical tip of said mandrel, the tip and die forming an annulus, at least one of said tip and die having at least one groove in the surface thereof, said groove being oriented helically with respect to the longitudinal axis of said tip and die, a ram capable of reciprocation within said barrel and surrounding said mandrel, and means providing said ram with reciprocating movement whereby, when a preformed, tubular billet of lubricated PTFE is placed in said barrel and said ram is activated to force said PTFE through said annulus, tubing is produced having at least one helically oriented ridge on at least one surface thereof.
Claim 9
Dependent Claim
72 words
Apparatus according to claim 8 characterised in that both the tip and the die have at least one groove in the surface thereof, the groove or grooves being oriented helically with respect to the longitudinal axis of said tip and die, at least one groove being pitched at an angle between 15 degrees and 85 degrees, or between 95 degrees and 165 degrees with respect to the longitudinal axis of said tip.
Claim 10
Dependent Claim
58 words
Apparatus according to claim 6 or claim 7 characterised in that both said tip and said die contain a groove and said groove in said tip is of opposite pitch to said groove in said die, and said groove in said tip has a pitch angle of between 30 and 60 degrees, or between 120 and 150 degrees.
Claim 11
Dependent Claim
57 words
Apparatus according to claim 6 characterised in that said tip has at least one groove in the surface thereof which gradually decreases in depth longitudinally along said tip, said depth approaching zero at the exit end of said annulus between said tip and said die, whereby an extruded tube exiting said apparatus has a smooth-surfaced inner bore.
Claim 12
Dependent Claim
36 words
Apparatus according to claim 6 characterised in that said die has at least one groove therein and including means for smoothing the external surface of said tubing subsequent to extrusion thereby substantially eliminating any ridges thereon.
Claim 13
Dependent Claim
157 words
A process for extrusion of PTFE tubing characterised by extruding a preformed billet of a mixture of coagulated dispersion of PTFE and liquid lubricant through an extruder comprising a hollow, cylindrical barrel containing a mandrel centrally positioned within said barrel, said barrel having a resin supply region, a tapered region leading from said supply region to an annular outflow region comprising an external, hollow, circular cylindrical die having positioned centrally therein the circularly cylindrical tip of said mandrel, the tip and die forming an annulus, at least one of said tip and die having at least one groove in the surface thereof, said groove being oriented helically with respect to the longitudinal axis of said tip and die, the apparatus including a ram capable of reciprocation within said barrel and surrounding said mandrel, forcing said PTFE through said annulus, thereby producing extruded, unsintered tubing having at least one helically oriented ridge on at least one surface thereof.
Claim 14
Dependent Claim
157 words
A process for extrusion of PTFE tubing characterised by extruding a preformed billet of a mixture of coagulated dispersion of PTFE and liquid lubricant through an extruder comprising a hollow, cylindrical barrel containing a mandrel centrally positioned within said barrel, said barrel having a resin supply region, a tapered region leading from said supply region to an annular outflow region comprising an external, hollow, circular cylindrical die having positioned centrally therein the circularly cylindrical tip of said mandrel, the tip and die forming an annulus, at least one of said tip and die having at least one groove in the surface thereof, said groove being oriented helically with respect to the longitudinal axis of said tip and die, the apparatus including a ram capable of reciprocation within said barrel and surrounding said mandrel, forcing said PTFE through said annulus, thereby producing extruded, unsintered tubing having at least one helically oriented ridge on at least one surface thereof.
Claim 15
Dependent Claim
58 words
A process according to claim 11 characterised by expanding said extruded tubing, after removal of liquid lubricant, by stretching said unsintered tubing longitudinally and maintaining said tubing at a temperature between 35°C and the crystalline melt point of said PTFE during said stretching, and wherein the rate of stretch exceeds 10% per second, or exceeds 100% per second.
Claim 16
Dependent Claim
84 words
A process according to claim 12 characterised in that the tubing is expanded such that its final length in the direction of expansion is greater than four times its original length, or is greater than seven times its original length, including the subsequent step of heating the stretched tubing to a temperature above the crystalline melting temperature of PTFE, and including the subsequent step of slitting said tubing along its length, or rolling down the tubing without slitting, thereby producing a sheet of PTFE.
References Cited (Backward Citations)
No citation records indexed.
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