Patent US5124109A successfully refreshed from Google Patents.
US5124109A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for producing a double wall pipe
Assignee: Contech Engineered Solutions LLC
•
Filing: 1990-11-29
•
Granted: 1992-06-23
•
Expires: 2010-11-29
Abstract
Abstract Pipe made from thermoplastic polymeric material and including a transversely corrugated outer wall and a smooth inner wall of constant diameter fusion welded to the inner crests of the corrugations of the outer wall is produced by an improved method involving simultaneous extrusion of two tubes, blow molding of the outer wall and fusion of the two walls while the inner wall is supported by an internal shaping and cooling mandrel. Even when the polymeric material is polyvinyl chloride, good fusion welds and lack of brittleness are achieved by the manner in which extrusion is carried out, control of the location at which the fusion welds are established, and the extrusion formulation. The finished pipe is characterized by the fact that, when the fusion welded areas have been cut for inspection, no line of demarcation between the materials of the two walls can be observed.
Inventors
- 👤 Hubert M. Drossbach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 19:34
CPC Classifications
B; B29; B29D; B29D23/00; B29D23/001; B29C; B29C48/00; B29C48/001; B29C48/0013; B29C48/0014; B29C48/0015; B29C48/03; B29C48/09; B29C48/11; B29C48/13; B29C48/16; B29C48/18; B29C48/21; B29C48/25; B29C48/30; B29C48/303; B29C48/32; B29C48/325; B29C48/327; B29C48/36; B29C48/50; B29C48/695; B29C48/88; B29C48/89; B29C48/90; B29C48/901; B29C48/902; B29C48/911; B29C48/9115; B29C48/912; B29C49/00; B29C49/0015; B29C49/0029; B29D23/18; B29C33/00; B29C33/0022; B29K; B29K2027/00; B29K2027/06; B29L; B29L2016/00; B29L2023/00; B29L2023/18; B29L2023/186; B29L2024/00; B29L2024/003; B29L2031/00; B29L2031/60; B29L2031/601; Y; Y10; Y10T; Y10T156/00; Y10T156/10; Y10T156/1002; Y10T156/1007; Y10T156/1016
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
244 words
The method of producing a double wall PVC pipe comprising the continuous steps of extruding concentric outer and inner tubes of PVS from respective inner and outer die orifices, said inner die orifice spaced from said outer die orifice in the extrusion direction by a distance form 0 to 2.5 inches, inflating by pressurized gas the outer PVC tube while in a state of thermal fusion against a surrounding annular transversely corrugated mold surface which is traveling in the extrusion direction to form a corrugated outer tube having inner crests, expanding by pressurized gas the inner PVC tube to fuse it to said outer tube crests while advancing said inner PVC tube onto a coaxial shaping and cooling mandrel which commences at an upstream tip spaced from the inner die orifice and tapers smoothly outwardly to a point of larger transverse dimension substantially equal to an inner diameter of the PVC pipe to be produced, said point being spaced from the outer die orifice in the extrusion direction by a distance which is less than the PVC pipe diameter such that the temperature of both the inner and outer PVC tubes at said point is at least equal to the fusion temperature of the PVC and cooling the resulting double wall PVC pipe to a solid state such that scanning electron micrographs of an enlargement at 20 times exhibits no line of demarcation at the fused joint between the outer and inner PVC tubes.
Claim 2
Independent Claim
244 words
The method of producing a double wall PVC pipe comprising the continuous steps of extruding concentric outer and inner tubes of PVS from respective inner and outer die orifices, said inner die orifice spaced from said outer die orifice in the extrusion direction by a distance form 0 to 2.5 inches, inflating by pressurized gas the outer PVC tube while in a state of thermal fusion against a surrounding annular transversely corrugated mold surface which is traveling in the extrusion direction to form a corrugated outer tube having inner crests, expanding by pressurized gas the inner PVC tube to fuse it to said outer tube crests while advancing said inner PVC tube onto a coaxial shaping and cooling mandrel which commences at an upstream tip spaced from the inner die orifice and tapers smoothly outwardly to a point of larger transverse dimension substantially equal to an inner diameter of the PVC pipe to be produced, said point being spaced from the outer die orifice in the extrusion direction by a distance which is less than the PVC pipe diameter such that the temperature of both the inner and outer PVC tubes at said point is at least equal to the fusion temperature of the PVC and cooling the resulting double wall PVC pipe to a solid state such that scanning electron micrographs of an enlargement at 20 times exhibits no line of demarcation at the fused joint between the outer and inner PVC tubes.
Claim 3
Dependent Claim
40 words
The method according to claim 1, wherein the PVC comprises at least 85% by weight of polyvinyl chloride, and at least one impact modifier selected from the group consisting of chlorinated polyethylene, acrylic polymers and copolymers, acrylonitrile-butadiene-styrene copolymers and polyalphamethylstyrene.
Claim 4
Dependent Claim
22 words
The method according to claim 2, wherein the impact modifier is chlorinated polyethylene and constitutes at least 1% of the formulation weight.
Claim 5
Dependent Claim
24 words
The method according to claim 2, wherein the PVC further comprises at least 0.1% by weight of at least one wax as a lubricant.
Claim 6
Dependent Claim
17 words
The method according to claim 2, wherein the temperature is maintained at about 360-420° F. (188-216° C.).
Claim 7
Dependent Claim
18 words
The method according to claim 5, wherein the temperature is maintained at about 370° F. to 390° F.
Claim 8
Dependent Claim
17 words
The method according to claim 5, wherein the temperature is maintained at about 377-379° F. (192-193° C.).
Claim 9
Dependent Claim
52 words
The method according to claim 2, wherein the inner die orifice is spaced form the outer die orifice in the extrusion direction by a distance such that the ratio of that distance to the inner diameter of the outer die orifice is in the range of from about 1:8 to about 1:22.
Claim 10
Dependent Claim
18 words
The method according to claim 1, wherein the gas supplied under pressure is heated by the die structure.
References Cited (Backward Citations)
US3412189A
Cited
US3280430A
Cited
US3538209A
Cited
US3677676A
Cited
US3743456A
Cited
US4021169A
Cited
US3872893A
Cited
US3994646A
Cited
US3996323A
Cited
US4303104A
Cited
USRE30338E
Cited
US4305703A
Cited
US4487232A
Cited
US4510013A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-06-23 | 1995-12-23 | 1996-06-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-06-23 | 1999-12-23 | 2000-06-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-06-23 | 2003-12-23 | 2004-06-23 | $7700.00 | Window Closed / Lapsed |