US4075268A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of making dual wall pipe with foam insulation between pipe walls
Assignee: Individual
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Filing: 1976-09-20
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Granted: 1978-02-21
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Expires: 1996-09-20
Abstract
Abstract A section of conduit is insulated by a thermoplastic outer pipe and an insulating layer of foamed or beaded insulating material disposed in the annular space between the outer pipe and the conduit. The annular layer is preformed to substantially the size of the annular space, then the outer pipe is heated to cause expansion of its diameter and facilitate insertion of the annular layer within the outer pipe. The inner pipe, or the conduit, may also be thermoplastic and may be cooled to cause contraction to facilitate insertion of the annular layer over it. After the outer pipe and inner pipe have returned to ambient temperature, the annular layer is retained within by a shrink fit, without chemical bonding between the annular layer and the pipes. Sections of the pipe are joined by simultaneously heating the ends of the inner pipe, annular layer, and outer pipe, placing the ends of one section against the ends of the other section, and allowing them to fuse while cooling.
Inventors
- 👤 Harold L. Nolan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:14
CPC Classifications
F; F16; F16L; F16L59/00; F16L59/14; F16L59/143; B; B29; B29C; B29C44/00; B29C44/34; B29C44/56; B29C63/00; B29C63/38; B29C63/42; B29C63/46; B29C65/00; B29C65/02; B29C65/18; B29C65/20; B29C66/00; B29C66/01; B29C66/05; B29C66/10; B29C66/11; B29C66/114; B29C66/1142; B29C66/50; B29C66/51; B29C66/52; B29C66/522; B29C66/5221; B29C66/70; B29C66/72; B29C66/723; B29C66/727; B29C66/73; B29C66/739; B29C66/7392; B29C66/73921; B29C66/71; B29C66/7234; B29C66/72341; B29C66/80; B29C66/81; B29C66/812; B29C66/8122; B29K; B29K2105/00; B29K2105/04; B29L; B29L2009/00; B29L2023/00; B29L2023/22; B29L2023/225; Y; Y10; Y10T; Y10T156/00; Y10T156/10; Y10T156/1052; Y10T156/1062; Y10T156/1066
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
100 words
A method of insulating a conduit comprising: heating a thermoplastic pipe to cause expansion of its diameter; the thermoplastic pipe being larger in diameter than the conduit, forming an annular space between the thermoplastic pipe and the conduit when the conduit is carried concentrically within the thermoplastic pipe; forming an annular layer of insulating material of a size substantially equal to the annular space when the thermoplastic pipe is at ambient temperature; inserting the conduit into the annular layer; and inserting the annular layer into the thermoplastic pipe while the thermoplastic pipe is at an elevated temperature, to facilitate insertion.
Claim 2
Independent Claim
100 words
A method of insulating a conduit comprising: heating a thermoplastic pipe to cause expansion of its diameter; the thermoplastic pipe being larger in diameter than the conduit, forming an annular space between the thermoplastic pipe and the conduit when the conduit is carried concentrically within the thermoplastic pipe; forming an annular layer of insulating material of a size substantially equal to the annular space when the thermoplastic pipe is at ambient temperature; inserting the conduit into the annular layer; and inserting the annular layer into the thermoplastic pipe while the thermoplastic pipe is at an elevated temperature, to facilitate insertion.
Claim 3
Dependent Claim
23 words
The method according to claim 1 wherein the thermoplastic pipe is heated to a temperature within the range of 145° - 174° F.
Claim 4
Dependent Claim
12 words
The method according to claim 1 wherein the annular layer is urethane.
Claim 5
Dependent Claim
15 words
The apparatus according to claim 1 wherein the thermoplastic pipe is heated in an oven.
Claim 6
Dependent Claim
21 words
The method of claim 1 wherein said forcing step causes formation of a bead about both said inner and outer pipes.
Claim 7
Dependent Claim
30 words
The method according to claim 1 wherein the linear thermal expansion coefficient is greater than 4 × 10 -5 inch/inch ° F, for the temperature range 25° - 175° F.
Claim 8
Dependent Claim
12 words
The method according to claim 6 wherein the thermoplastic pipe is polyethelene.
Claim 9
Independent Claim
94 words
A method of constructing a section of insulated conduit having inner and outer concentric polyethelene pipes and an annular layer of insulating material carried between, comprising: heating the outer pipe to cause expansion of its diameter to facilitate insertion of the annular layer; forming the annular layer to a size substantially equal to the annular space between the inner and outer pipes when at room temperature; and inserting the inner pipe into the annular layer and inserting the annular layer into the outer pipe while the outer pipe is maintained at an elevated temperature.
Claim 10
Independent Claim
94 words
A method of constructing a section of insulated conduit having inner and outer concentric polyethelene pipes and an annular layer of insulating material carried between, comprising: heating the outer pipe to cause expansion of its diameter to facilitate insertion of the annular layer; forming the annular layer to a size substantially equal to the annular space between the inner and outer pipes when at room temperature; and inserting the inner pipe into the annular layer and inserting the annular layer into the outer pipe while the outer pipe is maintained at an elevated temperature.
Claim 11
Dependent Claim
95 words
The method according to claim 8 further including the steps of joining two sections of the insulated conduit, comprising: squaring off the ends of each section of insulated conduit so that the ends of the inner pipe, outer pipe, and annular layer are flush; heating the ends of the inner pipe, outer pipe, and annular layer of each conduit simultaneously with a heater plate until the edges of the inner and outer pipes soften; removing the heater plate and forcing the ends of each section of the conduit together under pressure while allowing to cool.
Claim 12
Independent Claim
139 words
A method of constructing and joining sections of insulated conduit having inner and outer concentric polyethelene pipes and an annular layer of insulating material carried between, comprising: forming the annular layer to a size substantially equal to the annular space between the inner and outer pipes; inserting the inner pipe into the annular layer and inserting the annular layer into the outer pipe; squaring off the ends of each section of insulated conduit so that the ends of the inner pipe, outer pipe, and annular layer are flush; heating the ends of the inner pipe, outer pipe, and annular layer of each conduit simultaneously with a heater plate until the edges of the inner and outer pipes soften; removing the heater plate and forcing the ends of each section of the conduit together under pressure while allowing to cool.
Claim 13
Independent Claim
139 words
A method of constructing and joining sections of insulated conduit having inner and outer concentric polyethelene pipes and an annular layer of insulating material carried between, comprising: forming the annular layer to a size substantially equal to the annular space between the inner and outer pipes; inserting the inner pipe into the annular layer and inserting the annular layer into the outer pipe; squaring off the ends of each section of insulated conduit so that the ends of the inner pipe, outer pipe, and annular layer are flush; heating the ends of the inner pipe, outer pipe, and annular layer of each conduit simultaneously with a heater plate until the edges of the inner and outer pipes soften; removing the heater plate and forcing the ends of each section of the conduit together under pressure while allowing to cool.
Claim 14
Independent Claim
110 words
A method of constructing a section of insulated conduit having inner and outer concentric polyethelene pipes and a foamed urethane annular layer carried between, comprising: heating the outer pipe to cause expansion of its diameter to facilitate insertion of the annular layer; cooling the inner pipe to cause contraction of its diameter to facilitate insertion of the annular layer; forming the annular layer to a size substantially equal to the annular space between the inner and outer pipes when at ambient temperatures; and inserting the inner pipe into the annular layer while at a cool temperature and inserting the annular layer into the outer pipe while at an elevated temperature.
Claim 15
Independent Claim
110 words
A method of constructing a section of insulated conduit having inner and outer concentric polyethelene pipes and a foamed urethane annular layer carried between, comprising: heating the outer pipe to cause expansion of its diameter to facilitate insertion of the annular layer; cooling the inner pipe to cause contraction of its diameter to facilitate insertion of the annular layer; forming the annular layer to a size substantially equal to the annular space between the inner and outer pipes when at ambient temperatures; and inserting the inner pipe into the annular layer while at a cool temperature and inserting the annular layer into the outer pipe while at an elevated temperature.
Claim 16
Dependent Claim
46 words
The method according to claim 11 wherein the step of heating the outer pipe includes: placing the outer pipe in an oven maintained at a temperature within the range 145° to 174° F, for heating until the outer pipe temperature equals the temperature of the oven.
Claim 17
Dependent Claim
51 words
The method according to claim 12 wherein the step of cooling the inner pipe includes the step of placing the inner pipe in a chamber cooled to a temperature within the range of 25° - 45° F, for cooling until the inner pipe temperature equals the temperature of the cooling chamber.
Claim 18
Dependent Claim
49 words
The method according to claim 13 wherein the steps of inserting the inner pipe into the annular layer and the annular layer into the outer pipe are performed in normal room temperatures, but while the inner and outer pipes are still substantially at their cooled and elevated temperatures respectively.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-02-20 | 1981-08-22 | 1982-02-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-02-20 | 1985-08-22 | 1986-02-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-02-20 | 1989-08-22 | 1990-02-21 | $7700.00 | Window Closed / Lapsed |