US4470188A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of mechanically prestressing a tubular apparatus
Assignee: Babcock and Wilcox Co
•
Filing: 1982-08-31
•
Granted: 1984-09-11
•
Expires: 2002-08-31
Abstract
Abstract A method of prestressing a tubular apparatus having coaxial inner and outer tubes which are connected to each other at axially spaced locations comprises, after the inner and outer walls are connected to each other and the tube is heat-treated or otherwise processed, reducing the diameter of the outer wall so that the outer wall is elongated. The elongation of the outer wall establishes a prestressed condition between the inner and outer walls, with the inner wall under tension and the outer wall under compression. The reduction in diameter of the outer wall can be accomplished by using a roll extrusion machine, a tube reducer or a draw bench.
Inventors
- 👤 Richard L. Holbrook
- 👤 Dean L. Mayer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 04:52
CPC Classifications
B; B21; B21D; B21D41/00; B21D41/04; E; E21; E21B; E21B17/00; B21C; B21C37/00; B21C37/06; B21C37/15; B21C37/151; B21C37/154; E21B36/00; E21B36/003; F; F16; F16L; F16L9/00; F16L9/18; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49826; Y10T29/49861; Y10T29/49863; Y10T29/49879; Y10T29/49908; Y10T29/49925; Y10T29/49927; Y10T29/49934
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
115 words
A method of prestressing a tubular apparatus having at least one inner metal tube positioned within and spaced from an outer metal tube comprising connecting the inner tube to the outer tube at at least two spaced locations along the length of the tubular apparatus with the walls thereof spaced from each other, and, while said tubes are connected, reducing the diameter of the outer tube so as to permanently elongate the outer tube while elastically stressing the inner tube whereby a tensile prestress is applied to the inner tube and a compressive prestress is applied to the outer tube and with the walls of the inner and outer tubes remaining spaced from each other.
Claim 2
Independent Claim
115 words
A method of prestressing a tubular apparatus having at least one inner metal tube positioned within and spaced from an outer metal tube comprising connecting the inner tube to the outer tube at at least two spaced locations along the length of the tubular apparatus with the walls thereof spaced from each other, and, while said tubes are connected, reducing the diameter of the outer tube so as to permanently elongate the outer tube while elastically stressing the inner tube whereby a tensile prestress is applied to the inner tube and a compressive prestress is applied to the outer tube and with the walls of the inner and outer tubes remaining spaced from each other.
Claim 3
Independent Claim
121 words
A method of manufacturing a tubular apparatus having prestressed inner and outer metal tubes comprising: positioning the inner tube within and spaced from the outer tube; connecting the inner tube to the outer tube at at least two spaced locations along the length of the inner and outer tubes with the walls of the inner and outer tubes spaced from each other; and while said tubes are connected, mechanically reducing an outer diameter of the outer tube as to permanently elongate the outer tube while elastically stressing the inner tube in tension whereby the inner tube is prestressed in tension with respect to the outer tube and with the walls of the inner and outer tubes remaining spaced from each other.
Claim 4
Independent Claim
121 words
A method of manufacturing a tubular apparatus having prestressed inner and outer metal tubes comprising: positioning the inner tube within and spaced from the outer tube; connecting the inner tube to the outer tube at at least two spaced locations along the length of the inner and outer tubes with the walls of the inner and outer tubes spaced from each other; and while said tubes are connected, mechanically reducing an outer diameter of the outer tube as to permanently elongate the outer tube while elastically stressing the inner tube in tension whereby the inner tube is prestressed in tension with respect to the outer tube and with the walls of the inner and outer tubes remaining spaced from each other.
Claim 5
Dependent Claim
46 words
A method according to claim 1 or 2, including reducing the diameter of the outer tube by cold working the outer wall using one of the group consisting of a drawbench, a roll extrusion machine, a swaging means, a roll sinking means, and a tube reducer.
Claim 6
Dependent Claim
73 words
A method according to claim 1, including reducing the diameter of the outer tube by applying stress in a radially inwardly direction to said outer tube to exceed the yield point of said outer tube to thereby permanently reduce the diameter of and elongate said outer tube while elastically stressing said inner tube whereby a tensile prestress is applied to the inner tube and a compressive prestress is applied to the outer tube.
Claim 7
Independent Claim
113 words
A method of manufacturing a prestressed tubular apparatus having at least one inner metal tube positioned within and spaced from an outer metal tube comprising connecting the inner tube to the outer tube at at least two locations spaced along the length of the tubes with the walls of the inner and outer tubes spaced from each other, and, while said tubes are connected, permanently elongating one of said tubes while elastically stressing the other of said tubes whereby a compressive prestress is applied to said one tube and a tensile prestress is applied to said other tube and with the walls of the inner and outer tubes remaining spaced from each other.
Claim 8
Independent Claim
113 words
A method of manufacturing a prestressed tubular apparatus having at least one inner metal tube positioned within and spaced from an outer metal tube comprising connecting the inner tube to the outer tube at at least two locations spaced along the length of the tubes with the walls of the inner and outer tubes spaced from each other, and, while said tubes are connected, permanently elongating one of said tubes while elastically stressing the other of said tubes whereby a compressive prestress is applied to said one tube and a tensile prestress is applied to said other tube and with the walls of the inner and outer tubes remaining spaced from each other.
References Cited (Backward Citations)
US2289401A
Cited
US2693026A
Cited
US2828537A
Cited
US3149513A
Cited
US2924245A
Cited
US3246394A
Cited
US3608640A
Cited
US3693665A
Cited
US3863328A
Cited
US4125924A
Cited
US4375843A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-09-11 | 1988-03-12 | 1988-09-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-09-11 | 1992-03-12 | 1992-09-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-09-11 | 1996-03-12 | 1996-09-11 | $7700.00 | Window Closed / Lapsed |