US4676720A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bearingless hub structure for rotary-wing aircrafts
Assignee: Technical Research and Development Institute of Japan Defence Agency
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Filing: 1985-07-09
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Granted: 1987-06-30
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Expires: 2005-07-09
Abstract
Abstract A bearingless hub structure for rotary-wing aircrafts comprising a hub bodyecured to a rotor shaft, a plurality of radially extending flexbeams integrally formed with the hub body, and pitch housings enclosing each of the flexbeams in spaced relationship, the pitch housing having a radially outer end portion rigidly secured to an inboard end of a rotor blade and a radially inner end portion supported by a spherical bearing in the vicinity of a root end of said flexbeam. The flexbeam consists of a flexible element of low lead-lag stiffness and a torsion element of low torsional stiffness located radially outside the flexible element. The flexible element consists of two beam-like members having radially inner ends spaced in the lead-lag direction and extending radially outward with narrowing the distance between them, the beam-like member having radially outer end connected to a radially inner end of the torsion element.
Inventors
- 👤 Yoshiyuki Niwa
- 👤 Masahiro Kashiwagi
- 👤 Masahiro Yasue
- 👤 Shunichi Bandoh
- 👤 Asao Kakinuma
- 👤 Tadashi Wakatsuki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 08:40
CPC Classifications
B; B64; B64C; B64C27/00; B64C27/32; B64C27/33; B64C27/51
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
165 words
A bearingless hub structure for rotary-wing aircraft comprising: a hub body secured to a rotor shaft, a plurality of radially extending flexbeams integrally formed with said hub body, pitch housings enclosing respective ones of said flexbeams in spaced relationship, each of said pitch housings having a radially outer end portion rigidly secured to an inboard end of a rotor blade and a radially inner end portion supported by spherical bearing means in the vicinity of a root end of said flexbeam, each of said flexbeams including first flexible means of low lead-lag stiffness and second flexible means of low torsional stiffness located radially outside said first flexible means, said first flexible means comprising two beam-like members which extend radially outward, said beam-like members having radially inner ends spaced in the lead-lag direction, and the distance between said beam-like members decreasing in the radially outward direction, said first flexible means having a radially outer end connected to a radially inner end of said second flexible means.
Claim 2
Dependent Claim
165 words
A bearingless hub structure for rotary-wing aircraft comprising: a hub body secured to a rotor shaft, a plurality of radially extending flexbeams integrally formed with said hub body, pitch housings enclosing respective ones of said flexbeams in spaced relationship, each of said pitch housings having a radially outer end portion rigidly secured to an inboard end of a rotor blade and a radially inner end portion supported by spherical bearing means in the vicinity of a root end of said flexbeam, each of said flexbeams including first flexible means of low lead-lag stiffness and second flexible means of low torsional stiffness located radially outside said first flexible means, said first flexible means comprising two beam-like members which extend radially outward, said beam-like members having radially inner ends spaced in the lead-lag direction, and the distance between said beam-like members decreasing in the radially outward direction, said first flexible means having a radially outer end connected to a radially inner end of said second flexible means.
Claim 3
Dependent Claim
32 words
A hub structure in accordance with claim 1 in which a space of triangular configuration is defined between said beam-like members, ending at the radially inner end of said second flexible portion.
Claim 4
Dependent Claim
202 words
A bearingless hub structure for rotary-wing aircraft comprising: a hub body secured to a rotor shaft; a plurality of radially extending flexbeams integrally formed with said hub body; pitch housings enclosing respective ones of said flexbeams in spaced relationship; each pitch housing having a radially outer end portion rigidly secured to an inboard end of a rotor blade and a radially inner end portion supported in the vicinity of a root end of said flexbeam by spherical bearing means; each of said flexbeams including a first flexible portion having a low lead-lag stiffness and a second flexible portion located radially outside said first flexible portion and having a low torsional stiffness; said first flexible portion including a pair of beams which extend radially outward, said beams having radially inner ends spaced in the lead-lag direction, and the distance between said beams decreasing in the radially outward direction; said beams having radially outer ends connected to a radially inner end of said second flexible portion; and stopper means provided for cooperation with said first flexible portion for preventing said flexbeam from further deflection with respect to the pitch housing when a deflection in the lead-lag direction of the flexbeam reaches a predetermined value.
Claim 5
Dependent Claim
202 words
A bearingless hub structure for rotary-wing aircraft comprising: a hub body secured to a rotor shaft; a plurality of radially extending flexbeams integrally formed with said hub body; pitch housings enclosing respective ones of said flexbeams in spaced relationship; each pitch housing having a radially outer end portion rigidly secured to an inboard end of a rotor blade and a radially inner end portion supported in the vicinity of a root end of said flexbeam by spherical bearing means; each of said flexbeams including a first flexible portion having a low lead-lag stiffness and a second flexible portion located radially outside said first flexible portion and having a low torsional stiffness; said first flexible portion including a pair of beams which extend radially outward, said beams having radially inner ends spaced in the lead-lag direction, and the distance between said beams decreasing in the radially outward direction; said beams having radially outer ends connected to a radially inner end of said second flexible portion; and stopper means provided for cooperation with said first flexible portion for preventing said flexbeam from further deflection with respect to the pitch housing when a deflection in the lead-lag direction of the flexbeam reaches a predetermined value.
Claim 6
Dependent Claim
30 words
A bearingless hub structure as claimed in claim 3, wherein said flexbeams have a spring-like portion of generally rectangular cross section allowing a flapping motion radially inside said flexible element.
Claim 7
Dependent Claim
41 words
A bearingless hub structure in accordance with claim 3 in which said stopper means includes stopper members which are positioned to provide a gap sized such that said flexbeam does not come in contact with said pitch housing during normal flight.
Claim 8
Dependent Claim
29 words
A bearingless hub structure in accordance with claim 3 in which said flexbeam tapers its cordwise width to a narrow portion by which said first flexible means is formed.
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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) | 1990-06-29 | 1990-12-29 | 1991-06-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-06-29 | 1994-12-29 | 1995-06-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-06-29 | 1998-12-29 | 1999-06-30 | $7700.00 | Window Closed / Lapsed |