US3889506A
Expired / Lapsed
US
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Method and apparatus for forming a tubular billet about a mandrel using multi-directional stress
Assignee: AT&T Inc
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Filing: 1974-03-25
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Granted: 1975-06-17
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Expires: 1994-03-25
Abstract
Abstract In the manufacture of a tubular member which is to be concave inward as viewed in longitudinal section and precisely symmetrical on opposite sides of its transverse centerline, such as a hi-pass millimeter waveguide filter, a tubular billet initially is fabricated with temporary end flanges having circumferential grooves for receiving hydrostatic seals during a stress-forming operation. Next, the tubular billet is positioned in a hydrostatic forming device and a split mandrel is positioned within the billet and retained against movement. Hydrostatic pressure then is applied to the tubular billet to stress the billet longitudinally in tension while compressively stressing the billet inward into formed engagement with the mandrel, to reduce the hydrostatic pressure required in the stress-forming operation and to achieve the desired symmetry in the formed billet. The hydrostatic stress-forming of the billet preferably is accomplished in successive steps, with intermediate annealing, using mandrels of progressively decreasing size, and the billet may be stretched longitudinally while being formed inward. When the hydrostatic stress-forming of the billet has been completed, portions of the temporary end flanges which define the seal receiving grooves are removed from each end flange and the end flanges are formed to a final desired configuration.
Inventors
- 👤 John Richard Shaffer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 13:06
CPC Classifications
B; B21; B21D; B21D26/00; B21D26/02; B21D26/033; B21D26/045; B21D26/043; B21D26/047
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
408 words
A method of forming a tubular metal member to a configuration in which internal and external surfaces of the member are concave inward as viewed in longitudinal section and at least the internal surfaces are symmetrical on opposite sides of the transverse centerline of the member, which comprises: forming a tubular metal billet having an external surface of uniform diameter and an internal surface of uniform diameter; forming the tubular metal billet with substantially identical temporary integral end flanges having an external diameter greater than the external diameter of the billet between the end flanges and substantially corresponding to a diameter of cylindrical interior surfaces of a hydrostatic forming device, and having opposed annular bearing surfaces intersecting the external surface of the billet to provide hydrostatic seals at their respective intersections and of sufficient crosssectional area such that when the bearing surfaces and the peripheral portion of the billet therebetween subsequently are subjected to hydrostatic pressure in a forming operation, the end flanges are retained against any substantial inward longitudinal movement and the billet is stressed longitudinally in tension; forming each temporary integral end flange of the tubular billet with a circumferential seal-receiving portion; positioning annular hydroStatic seals in engagement with the circumferential seal-receiving portions; positioning the tubular billet in the hydrostatic forming device with the temporary integral end flanges confined against transverse movement by the cylindrical interior surfaces of the forming device, and with the seals in sealing engagement with the cylindrical interior surfaces; positioning a split mandrel having an external configuration conforming to the desired internal concave configuration of the tubular member, within the tubular billet with opposed inner ends of the mandrel in aligned engagement and spaced relationship to the interior of the billet; subjecting the opposite outer ends of the split mandrel to opposing forces to preclude longitudinal movement of the mandrel and separation of the engaged inner ends of the mandrel during the forming of the billet inwardly about the mandrel; simultaneously applying hydrostatic pressure to the opposed annular bearing surfaces of the temporary integral end flanges and to the peripheral portion of the tubular billet therebetween, to retain the end flanges against any substantial inward longitudinal movement and to stress the billet longitudinally in tension, while compressively stressing the billet inward into inwardly concave symmetrical engagement with the mandrel; and removing selected portions of the temporary integral end flanges not required in the tubular metal member after the stressforming of the billet.
Claim 2
Independent Claim
408 words
A method of forming a tubular metal member to a configuration in which internal and external surfaces of the member are concave inward as viewed in longitudinal section and at least the internal surfaces are symmetrical on opposite sides of the transverse centerline of the member, which comprises: forming a tubular metal billet having an external surface of uniform diameter and an internal surface of uniform diameter; forming the tubular metal billet with substantially identical temporary integral end flanges having an external diameter greater than the external diameter of the billet between the end flanges and substantially corresponding to a diameter of cylindrical interior surfaces of a hydrostatic forming device, and having opposed annular bearing surfaces intersecting the external surface of the billet to provide hydrostatic seals at their respective intersections and of sufficient crosssectional area such that when the bearing surfaces and the peripheral portion of the billet therebetween subsequently are subjected to hydrostatic pressure in a forming operation, the end flanges are retained against any substantial inward longitudinal movement and the billet is stressed longitudinally in tension; forming each temporary integral end flange of the tubular billet with a circumferential seal-receiving portion; positioning annular hydroStatic seals in engagement with the circumferential seal-receiving portions; positioning the tubular billet in the hydrostatic forming device with the temporary integral end flanges confined against transverse movement by the cylindrical interior surfaces of the forming device, and with the seals in sealing engagement with the cylindrical interior surfaces; positioning a split mandrel having an external configuration conforming to the desired internal concave configuration of the tubular member, within the tubular billet with opposed inner ends of the mandrel in aligned engagement and spaced relationship to the interior of the billet; subjecting the opposite outer ends of the split mandrel to opposing forces to preclude longitudinal movement of the mandrel and separation of the engaged inner ends of the mandrel during the forming of the billet inwardly about the mandrel; simultaneously applying hydrostatic pressure to the opposed annular bearing surfaces of the temporary integral end flanges and to the peripheral portion of the tubular billet therebetween, to retain the end flanges against any substantial inward longitudinal movement and to stress the billet longitudinally in tension, while compressively stressing the billet inward into inwardly concave symmetrical engagement with the mandrel; and removing selected portions of the temporary integral end flanges not required in the tubular metal member after the stressforming of the billet.
Claim 3
Dependent Claim
41 words
A method as recited in claim 1, wherein: the forming of the tubular billet is accomplished in a series of separate hydrostatic forming steps utilizing mandrels of progressively decreasing size; and the tubular billet is annealed between each hydrostatic forming step.
Claim 4
Dependent Claim
37 words
A method as recited in claim 1, in which: the portions of the temporary integral end flanges which are removed after the stress-forming of the billet include the opposed annular bearing surfaces and the seal receiving portions.
Claim 5
Dependent Claim
52 words
A method as recited in claim 1, in which: the seal-receiving portion in each temporary integral end flange is formed as a groove with an undercut seal-entrapping portion; and the portions of each end flange which are removed after the stress-forming of the billet include the groove and the undercut entrapping portion.
Claim 6
Dependent Claim
67 words
A method as recited in claim 1, which further comprises: applying the hydrostatic pressure to the billet so as to stretch the billet longitudinally and uniformly on opposite sides of its transverse centerline relative to the mandrel while compressively stressing the billet inward about the mandrel; and positively limiting the stretching of the billet longitudinally relative to the mandrel to produce a formed billet of precise length.
Claim 7
Dependent Claim
113 words
A method as recited in claim 5, which further comprises: exerting equal yieldable biasing and centering forces on opposite ends of the tubular billet in the hydrostatic forming device; and applying the hydrostatic pressure to the opposed annular bearing surfaces of the end flanges to stretch the tubular billet longitudinally and uniformly on opposite sides of its transverse centerline against the yieldable biasing action of the centering forces and relative to the mandrel and the interior cylindrical surfaces of the hydrostatic forming device, while simultaneously applying the hydrostatic pressure to the peripheral portion of the tubular billet between the bearing surfaces to compressively stress the billet inward into formed engagement with the mandrel.
Claim 8
Dependent Claim
63 words
A method as recited in claim 6, which further comprises: diverting a portion of a hydrostatic liquid for applying the hydrostatic pressure to the tubular billet, to produce one of the forces exerted on one of the outer ends of the split mandrel to retain the split mandrel in a desired position against separation and longitudinal movement during the stress-forming of the billet.
Claim 9
Dependent Claim
274 words
A hydrostatic method of forming a tubulAr metal member to a configuration in which internal and external surfaces of the member are concave inward as viewed in longitudinal section and at least the internal surfaces are symmetrical on opposite sides of the transverse centerline of the member, which comprises: forming a tubular metal billet having an external surface of uniform diameter and an internal surface of uniform diameter; positioning the tubular billet and a hydrostatic forming device with both of the opposite ends of the billet capable of longitudinal movement but confined against transverse movement; positioning a split mandrel having an external surface which is concave inward as viewed in longitudinal section and which corresponds to a desired internal configuration of the metal member, within the billet with opposed inner ends of the mandrel in aligned engagement and in spaced relationship to the interior of the billet; subjecting the opposite outer ends of the split mandrel to opposing forces to preclude longitudinal movement of the mandrel and separation of the engaged inner ends of the mandrel during the hydrostatic forming of the billet inwardly about the mandrel; exerting equal yieldable biasing and centering forces on opposite ends of the billet; and simultaneously applying hydrostatic pressure to opposed annular bearing surfaces on opposite ends of the billet and to the peripheral portion of the billet between the bearing surfaces to stretch the billet longitudinally against the yieldable biasing action of the centering forces and uniformly on opposite sides of the transverse centerline of the billet relative to the split mandrel, while compressively forming the billet inward into inwardly concave symmetrical engagement with the split mandrel.
Claim 10
Dependent Claim
274 words
A hydrostatic method of forming a tubulAr metal member to a configuration in which internal and external surfaces of the member are concave inward as viewed in longitudinal section and at least the internal surfaces are symmetrical on opposite sides of the transverse centerline of the member, which comprises: forming a tubular metal billet having an external surface of uniform diameter and an internal surface of uniform diameter; positioning the tubular billet and a hydrostatic forming device with both of the opposite ends of the billet capable of longitudinal movement but confined against transverse movement; positioning a split mandrel having an external surface which is concave inward as viewed in longitudinal section and which corresponds to a desired internal configuration of the metal member, within the billet with opposed inner ends of the mandrel in aligned engagement and in spaced relationship to the interior of the billet; subjecting the opposite outer ends of the split mandrel to opposing forces to preclude longitudinal movement of the mandrel and separation of the engaged inner ends of the mandrel during the hydrostatic forming of the billet inwardly about the mandrel; exerting equal yieldable biasing and centering forces on opposite ends of the billet; and simultaneously applying hydrostatic pressure to opposed annular bearing surfaces on opposite ends of the billet and to the peripheral portion of the billet between the bearing surfaces to stretch the billet longitudinally against the yieldable biasing action of the centering forces and uniformly on opposite sides of the transverse centerline of the billet relative to the split mandrel, while compressively forming the billet inward into inwardly concave symmetrical engagement with the split mandrel.
Claim 11
Dependent Claim
59 words
A method as recited in claim 8, which further comprises: diverting a portion of a hydrostatic liquid for applying the hydrostatic pressure to the tubular billet to produce one of the forces exerted on one of the outer ends of the split mandrel to retain the split mandrel against separation and longitudinal movement during the stress-forming of the billet.
Claim 12
Dependent Claim
360 words
Hydrostatic apparatus for forming a tubular metal billet having end flanges and of uniform internal and external diameter between the end flanges, into a member having internal and external surfaces which are concave inward as viewed in longitudinal section, with at least the internal surfaces being symmetrical in configuration on opposite sides of the transverse centerline of the member, which comprises: a housing having a cylindrical hydrostatic forming chamber for receiving the billet and including cylindrical interior surface portions engageable with the end flanges on the billet to permit longitudinal movement of both end flanges while confining the end flanges against transverse movement; a split mandrel having an inwardly concave external configuration which corresponds to the desired internal configuration of the billet, said mandrel being positionable in the billet with inner opposed ends thereof in aligned engagement and spaced relationship to the interior of the billet; retaining means engageable with the opposite outer ends of the split mandrel for precluding longitudinal movement of the mandrel and separation of the engaged inner ends of the mandrel during the forming of the billet; a pair of rigid cylindrical members slidably positionable on respective parts of the split mandrel and engageable with opposite ends of the billet; means engageable by said rigid cylindrical members for positively limiting stretching of the billet so as to produce a formed billet of precise length; first and second resilient means between said limiting means and said cylindrical members for exerting equal, yieldable biasing and centering forces on said cylindrical members and thus on the opposite ends of the billet; and means for applying hydrostatic pressure to the end flanges on the billet to stretch the billet uniFormly on opposite sides of its transverse centerline relative to the split mandrel and the interior surfaces of the cylindrical chamber in said housing and to move said slidable members on said mandrel against the biasing and centering action of said first and second resilient means into engagement with said limiting means, while simultaneously applying hydrostatic pressure to the exterior of the billet between the end flanges to compressively stress the billet into inwardly concave symmetrical engagement with the split mandrel.
Claim 13
Dependent Claim
360 words
Hydrostatic apparatus for forming a tubular metal billet having end flanges and of uniform internal and external diameter between the end flanges, into a member having internal and external surfaces which are concave inward as viewed in longitudinal section, with at least the internal surfaces being symmetrical in configuration on opposite sides of the transverse centerline of the member, which comprises: a housing having a cylindrical hydrostatic forming chamber for receiving the billet and including cylindrical interior surface portions engageable with the end flanges on the billet to permit longitudinal movement of both end flanges while confining the end flanges against transverse movement; a split mandrel having an inwardly concave external configuration which corresponds to the desired internal configuration of the billet, said mandrel being positionable in the billet with inner opposed ends thereof in aligned engagement and spaced relationship to the interior of the billet; retaining means engageable with the opposite outer ends of the split mandrel for precluding longitudinal movement of the mandrel and separation of the engaged inner ends of the mandrel during the forming of the billet; a pair of rigid cylindrical members slidably positionable on respective parts of the split mandrel and engageable with opposite ends of the billet; means engageable by said rigid cylindrical members for positively limiting stretching of the billet so as to produce a formed billet of precise length; first and second resilient means between said limiting means and said cylindrical members for exerting equal, yieldable biasing and centering forces on said cylindrical members and thus on the opposite ends of the billet; and means for applying hydrostatic pressure to the end flanges on the billet to stretch the billet uniFormly on opposite sides of its transverse centerline relative to the split mandrel and the interior surfaces of the cylindrical chamber in said housing and to move said slidable members on said mandrel against the biasing and centering action of said first and second resilient means into engagement with said limiting means, while simultaneously applying hydrostatic pressure to the exterior of the billet between the end flanges to compressively stress the billet into inwardly concave symmetrical engagement with the split mandrel.
Claim 14
Dependent Claim
74 words
Hydrostatic apparatus for forming a tubular metal billet, as recited in claim 10, in which: said mandrel retaining means includes at least one slidably-mounted mandrel retaining member; and said housing includes a hydrostatically sealed passageway for directing a portion of a hydrostatic liquid which is pressurized by said hydrostatic pressure applying means, against said slidable mandrel retaining member to retain the split mandrel against separation and longitudinal movement during the stress-forming of the billet.
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) | 1978-06-16 | 1978-12-16 | 1979-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-16 | 1982-12-16 | 1983-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-16 | 1986-12-16 | 1987-06-17 | $7700.00 | Window Closed / Lapsed |