Patent US4529564A successfully refreshed from Google Patents.
US4529564A
Expired / Lapsed
US
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Manufacture of low density sintered polytetrafluoroethylene insulated cable
Assignee: Carlisle Corp
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Filing: 1983-11-17
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Granted: 1985-07-16
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Expires: 2003-11-17
Abstract
Abstract A method for extruding, stretching and sintering polytetrafluoroethylene in a single pass operation to form articles of low density sintered polytetrafluoroethylene and articles such as electric cable (C) having low density, sintered polytetrafluoroethylene insulation (F) applied about a conductor (W) by such method.
Inventors
- 👤 Norman R. Harlow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:59
CPC Classifications
H; H01; H01B; H01B13/00; H01B13/06; H01B13/14; B; B29; B29C; B29C48/00; B29C48/022; B29C48/03; B29C48/06; B29C48/15; B29C48/25; B29C48/88; B29C48/885; B29C48/91; B29C48/92; D; D01; D01F; D01F6/00; D01F6/02; D01F6/08; D01F6/12; H01B3/00; H01B3/18; H01B3/30; H01B3/44; H01B3/443; H01B3/445; B29C2948/00; B29C2948/92; B29C2948/92504; B29C2948/92571; B29C2948/9258; B29C2948/92819; B29C2948/92857; B29C2948/92904; B29K; B29K2027/00; B29K2027/12; B29K2027/18
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
236 words
A method of forming an elongated product of low density sintered polytetrafluoroethylene having a central core of inextensible material which comprises: A. forcing an extrusible mixture of unsintered polytetrafluoroethylene and extrusion aid through a die, while substantially reducing the cross-section of said mixture and forming a central opening in said mixture to extrude an elongated continuous tube formed of said extrusible mixture; B. passing an indefinite length of inextensible material through said central opening in said mixture and through said die into said tube; C. controlling the linear speed of said tube exiting from said die to hold the volumetric rate thereof at approximately the volumetric rate of said mixture passing through said die; D. thereafter passing said tube with said inextensible material therein in sequence through an extrusion aid removal zone, a stretching zone and a sintering zone; E. drawing said tube together with said inextensible material through said sintering zone at the same linear speed, said speed being in excess of the linear speed of said mixture exiting from said die; F. maintaining conditions in said extrusion aid removal zone effective to remove the extrusion aid in said mixture as said tube is passed through said extrusion aid removal zone; G. heating said tube in said stretching zone to a temperature above that in said extrusion aid removal zone but less than sintering temperature; and H. maintaining sintering temperature conditions in said sintering zone.
Claim 2
Independent Claim
236 words
A method of forming an elongated product of low density sintered polytetrafluoroethylene having a central core of inextensible material which comprises: A. forcing an extrusible mixture of unsintered polytetrafluoroethylene and extrusion aid through a die, while substantially reducing the cross-section of said mixture and forming a central opening in said mixture to extrude an elongated continuous tube formed of said extrusible mixture; B. passing an indefinite length of inextensible material through said central opening in said mixture and through said die into said tube; C. controlling the linear speed of said tube exiting from said die to hold the volumetric rate thereof at approximately the volumetric rate of said mixture passing through said die; D. thereafter passing said tube with said inextensible material therein in sequence through an extrusion aid removal zone, a stretching zone and a sintering zone; E. drawing said tube together with said inextensible material through said sintering zone at the same linear speed, said speed being in excess of the linear speed of said mixture exiting from said die; F. maintaining conditions in said extrusion aid removal zone effective to remove the extrusion aid in said mixture as said tube is passed through said extrusion aid removal zone; G. heating said tube in said stretching zone to a temperature above that in said extrusion aid removal zone but less than sintering temperature; and H. maintaining sintering temperature conditions in said sintering zone.
Claim 3
Dependent Claim
33 words
A method according to claim 1 which further includes controlling the linear speed of said tube entering said sintering zone at the same speed as that of said tube exiting said sintering zone.
Claim 4
Dependent Claim
34 words
A method according to claim 2 in which said linear speed of said tube exiting said die is controlled by passage between a pair of pinch rolls in peripheral rolling contact with said tube.
Claim 5
Dependent Claim
67 words
A method according to any of claim 1, claim 2 or claim 3 in which said extrusion aid is a volatile substance and said conditions in said extrusion aid removal zone include a temperature sufficient to volatilize said extrusion aid as said tube passes through said extrusion aid removal zone, and said temperature of said tube in said stretching zone is between 250° F. and 450° F.
Claim 6
Dependent Claim
16 words
A method according to claim 4 in which said extrusion aid is V.M. & P. naphtha.
Claim 7
Dependent Claim
15 words
A method according to claim 3 in which said inextensible material is an electric conductor.
References Cited (Backward Citations)
US3260774A
Cited
US4225547A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-07-15 | 1989-01-14 | 1989-07-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-07-15 | 1993-01-14 | 1993-07-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-07-15 | 1997-01-14 | 1997-07-16 | $7700.00 | Window Closed / Lapsed |