US3771922A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Stabilized rotary blades
Assignee: McDonnell Douglas Corp
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Filing: 1972-10-30
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Granted: 1973-11-13
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Expires: 1992-10-30
Abstract
Abstract Projections near the tips of high speed rotary blades are actuated by centrifugal force to ensure uniform spacing between the blade tips as a means of reducing buzz-saw noise.
Inventors
- 👤 A Tracy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 18:07
CPC Classifications
F; F01; F01D; F01D5/00; F01D5/12; F01D5/22
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
151 words
In combination with a turbofan engine having a plurality of blades attached to a rotor hub and a housing having a circumferential inner surface in close radial proximity to the tips of said blades, means for reducing noise caused by irregular spacing of said blade tips and thus varying the frequency of blade tip passage over a point on the inner surface of the housing about the periphery within which said blade tips rotate, said means comprising side arms extending laterally outwardly from the surfaces of said blades and radially inwardly toward said hub, said arms having outer edge surfaces positioned radially inwardly from the connection of said arms to said blades, said arms deflecting radially outwardly due to centrifugal force when said blades are rotated at a preselected frequency, the outer edge surfaces of adjacent arms on adjacent blades abutting each other when said blades rotate at said preselected frequency.
Claim 2
Dependent Claim
151 words
In combination with a turbofan engine having a plurality of blades attached to a rotor hub and a housing having a circumferential inner surface in close radial proximity to the tips of said blades, means for reducing noise caused by irregular spacing of said blade tips and thus varying the frequency of blade tip passage over a point on the inner surface of the housing about the periphery within which said blade tips rotate, said means comprising side arms extending laterally outwardly from the surfaces of said blades and radially inwardly toward said hub, said arms having outer edge surfaces positioned radially inwardly from the connection of said arms to said blades, said arms deflecting radially outwardly due to centrifugal force when said blades are rotated at a preselected frequency, the outer edge surfaces of adjacent arms on adjacent blades abutting each other when said blades rotate at said preselected frequency.
Claim 3
Dependent Claim
31 words
The combination as in claim 1 wherein said arms are of equal length thereby to cause equal spacing of said blade tips when said blades are rotated at said preselected frequency.
Claim 4
Dependent Claim
40 words
The combination as in claim 1 wherein said outer edge surfaces are substantially parallel to the surfaces of said blades in the arm thickness direction and in the arm length direction to define abutting planes parallel to said blade surfaces.
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) | 1976-11-12 | 1977-05-14 | 1977-11-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-12 | 1981-05-14 | 1981-11-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-12 | 1985-05-14 | 1985-11-13 | $7700.00 | Window Closed / Lapsed |