US3764641A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of forming irregularly shaped hollow articles using a variable stiffness mandrel
Assignee: Individual
•
Filing: 1971-01-08
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Granted: 1973-10-09
•
Expires: 1991-01-08
Abstract
Abstract A structure of flexible foam material covered by an elastomeric casing which is subjected to increased internal air pressure to make the structure rigid. Creating a vacuum within the structure causes it to collapse. The structure is used as a mandrel in a process for fabricating plastic conduits. The structure includes flexible tubes embedded in the foam material inflated to improve structural strength.
Inventors
- 👤 A Ash
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 04:59
CPC Classifications
B; B29; B29C; B29C33/00; B29C33/44; B29C33/48; B29C33/50; B29C33/505; Y; Y10; Y10T; Y10T428/00; Y10T428/24; Y10T428/24942; Y10T428/249921; Y10T428/249953; Y10T428/24996
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
277 words
A method of forming irregularly shaped hollow articles having at least one open end without requiring the use of a female mold about the exterior of the article during formation which includes: forming a mandrel core of flexible open cell, foam material having an exterior shape substantially duplicating the desired interior shape of the hollow article to be Formed which foam material will become rigid and will maintain a fixed size and shape substantially identical with the exterior size and shape of the foam material as formed when subjected to any level of internal fluid pressure which is in excess of the exterior pressure level but which is below an upper pressure level at which the core will begin to expand, said upper pressure level being measurably greater than the exterior pressure level and which foam material will collapse when subjected to a fluid pressure level below the pressure level on the exterior of the core, bonding a layer of elastomeric fluid impermeable material to the entire outer surface of said core to form a gas tight flexible mandrel, connecting a fluid pressure valve means with said mandrel in communication with said mandrel core through said layer of elastomeric fluid impermeable material, injecting a fluid into the foam material to create a fluid pressure therein sufficient to substantially increase the rigidity of the mandrel without reaching said upper pressure, forming said article about said mandrel by applying material capable of being rigidified to the exterior of the mandrel while the mandrel is pressurized, and causing said article to become rigid, decreasing said fluid pressure so as to collapse the mandrel, and removing the mandrel from the article.
Claim 2
Independent Claim
277 words
A method of forming irregularly shaped hollow articles having at least one open end without requiring the use of a female mold about the exterior of the article during formation which includes: forming a mandrel core of flexible open cell, foam material having an exterior shape substantially duplicating the desired interior shape of the hollow article to be Formed which foam material will become rigid and will maintain a fixed size and shape substantially identical with the exterior size and shape of the foam material as formed when subjected to any level of internal fluid pressure which is in excess of the exterior pressure level but which is below an upper pressure level at which the core will begin to expand, said upper pressure level being measurably greater than the exterior pressure level and which foam material will collapse when subjected to a fluid pressure level below the pressure level on the exterior of the core, bonding a layer of elastomeric fluid impermeable material to the entire outer surface of said core to form a gas tight flexible mandrel, connecting a fluid pressure valve means with said mandrel in communication with said mandrel core through said layer of elastomeric fluid impermeable material, injecting a fluid into the foam material to create a fluid pressure therein sufficient to substantially increase the rigidity of the mandrel without reaching said upper pressure, forming said article about said mandrel by applying material capable of being rigidified to the exterior of the mandrel while the mandrel is pressurized, and causing said article to become rigid, decreasing said fluid pressure so as to collapse the mandrel, and removing the mandrel from the article.
Claim 3
Dependent Claim
73 words
The method according to claim 1 wherein the steps of forming the mandrel include; forming said foam material of said mandrel core in a female mold defining said shaped outer surface, and then coating the surface of the foam material with a curable liquid material and curing said liquid material to bond and embed the same in the surface of said foam material to form said elastomeric, fluid impermeable shaped outer surface layer.
Claim 4
Dependent Claim
47 words
The method according to claim 6 wherein the step of forming the article about the pressurized mandrel includes the steps of; wrapping uncured plastic about the mandrel and then curing the plastic; imparting to the interior of the plastic a shape corresponding to said shaped outer surface.
Claim 5
Dependent Claim
154 words
The method of claim 1 wherein said fluid pressure valve means constitutes a first fluid pressure means, wherein the steps of forming said mandrel include locating at least one inflatable chamber means of limited expanded cross section and having a second fluid pressure valve means communicating with the interior of the chamber in a female mold defining said shaped outer surface of said mandrel, forming said foam material in said mold about said inflatable chamber means while the chamber means is inflated to said expanded cross-section so as to form a tight bond between the walls of the chamber means and the foam, and wherein the step of forming the article includes maintaining an equal or greater fluid pressure in said inflatable chamber than said foam material during fabrication of said article to reinforce said foam, the pressure in said chamber means being released to enable removal of the mandrel from the finished article.
Claim 6
Independent Claim
256 words
A method of forming irregularly shaped hollow articles including the steps of providing a flexible mandrel having a fluid permeable core, pressurizing the mandrel by injecting fluid under pressure into the mandrel to cause the mandrel to hold a desired size and shape, applying hardenable article forming material about the mandrel, causing the article forming material to harden and withdrawing fluid from the mandrel to collapse the mandrel so that the mandrel can be removed from the article wherein the improvement comprises the steps of forming a core of flexible open-cell collapsible foam material having an exterior shape substantially duplicating the desired interior shape of the hollow article to be formed which foam material will become rigid and will maintain a fixed size and shape substantially identical with the exterior size and shape of the foam material as formed when subjected to any level of internal fluid pressure which is in excess of the exterior pressure level but which is below an upper pressure level at which the core will begin to expand, said upper pressure level being measurably greater than the exterior pressure level and which material will collapse when subjected to an internal fluid pressure level below the external pressure level; and bonding a layer of flexible, fluid impermeable material to the entire outer surface of said core to form a gas tight flexible mandrel, whereby the mandrel can be used repeatedly to form articles of identical internal size and shape in spite of variations in the pressure level used during the pressurization step.
Claim 7
Independent Claim
256 words
A method of forming irregularly shaped hollow articles including the steps of providing a flexible mandrel having a fluid permeable core, pressurizing the mandrel by injecting fluid under pressure into the mandrel to cause the mandrel to hold a desired size and shape, applying hardenable article forming material about the mandrel, causing the article forming material to harden and withdrawing fluid from the mandrel to collapse the mandrel so that the mandrel can be removed from the article wherein the improvement comprises the steps of forming a core of flexible open-cell collapsible foam material having an exterior shape substantially duplicating the desired interior shape of the hollow article to be formed which foam material will become rigid and will maintain a fixed size and shape substantially identical with the exterior size and shape of the foam material as formed when subjected to any level of internal fluid pressure which is in excess of the exterior pressure level but which is below an upper pressure level at which the core will begin to expand, said upper pressure level being measurably greater than the exterior pressure level and which material will collapse when subjected to an internal fluid pressure level below the external pressure level; and bonding a layer of flexible, fluid impermeable material to the entire outer surface of said core to form a gas tight flexible mandrel, whereby the mandrel can be used repeatedly to form articles of identical internal size and shape in spite of variations in the pressure level used during the pressurization step.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-08 | 1977-04-09 | 1977-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-08 | 1981-04-09 | 1981-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-08 | 1985-04-09 | 1985-10-09 | $7700.00 | Window Closed / Lapsed |