US3580693A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Boundary layer control devices
Assignee: TECHNOLOGY UK
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Filing: 1969-03-17
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Granted: 1971-05-25
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Expires: 1989-03-17
Abstract
Abstract A rotor blade on which lift is induced by circulation control is provided with a chordwise extending slot at the blade tip formed by a plate spaced from the tip by a distance piece extending around part of the blade periphery towards the rear of the blade, i.e., the slot extends around the front and under part of the blade for about 240*. Air blown from the interior of the blade into the slot is discharged radially as a sheet which forms a pneumatic fence and thus modifies flow over the blade tip. The normal tip vortex can be moved radially outwards relative to the blade root and an appreciable drag reduction obtained. In a variation, air is discharged spanwise relative to the blade.
Inventors
- 👤 Ian Clifford Cheeseman
- 👤 Michael Charles George Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 23:06
CPC Classifications
B; B64; B64C; B64C23/00
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
78 words
A blade for helicopters and the like, having means for controlling fluid flow lengthwise of the blade comprising slotted means formed in the surface of said blade and extending in a chordwise direction around part of said surface and embracing at least a significant portion of the under part of said blade, a source of gaseous fluid, and a connection therefrom for leading fluid to said slotted means for discharge as a sheet therefrom externally of said surface.
Claim 2
Dependent Claim
78 words
A blade for helicopters and the like, having means for controlling fluid flow lengthwise of the blade comprising slotted means formed in the surface of said blade and extending in a chordwise direction around part of said surface and embracing at least a significant portion of the under part of said blade, a source of gaseous fluid, and a connection therefrom for leading fluid to said slotted means for discharge as a sheet therefrom externally of said surface.
Claim 3
Dependent Claim
27 words
A blade according to claim 1, wherein said slotted means discharges a sheet of gaseous fluid substantially radially relative to an axis extending lengthwise of said blade.
Claim 4
Dependent Claim
25 words
A blade according to claim 1, wherein said slotted means discharges a sheet of gaseous fluid in a substantially spanwise direction relative to the blade.
Claim 5
Dependent Claim
31 words
A blade according to claim 3, wherein said slotted means is located adjacent to one end of said blade and discharges a sheet of gaseous fluid inwardly relative to said end.
Claim 6
Dependent Claim
47 words
A blade according to claim 3, comprising further slotted means extending around a further part of said blade in substantially the same transverse plane as said slotted means to discharge a sheet of gaseous fluid in a substantially opposite direction to that discharged by said slotted means.
Claim 7
Dependent Claim
12 words
A blade according to claim 1 having a substantially circular cross section.
Claim 8
Dependent Claim
125 words
A hollow blade for helicopter and like rotors of substantially circular cross section having aperture means extending along its length connected to discharge a stream of gaseous fluid tangentially over the surface of the blade to induce lift thereon, comprising a plate spaced from the tip of the blade to define therewith a slot extending peripherally relative to the blade surface, blanking means closing off a portion of said slot, a connection between said slot and the interior of the blade, and a connection between the interior of the blade and a source of pressurized gaseous fluid whereby the plate is arranged so that fluid introduced into the blade will be discharged from the slot, substantially radially relative to the lengthwise axis of the blade.
Claim 9
Dependent Claim
125 words
A hollow blade for helicopter and like rotors of substantially circular cross section having aperture means extending along its length connected to discharge a stream of gaseous fluid tangentially over the surface of the blade to induce lift thereon, comprising a plate spaced from the tip of the blade to define therewith a slot extending peripherally relative to the blade surface, blanking means closing off a portion of said slot, a connection between said slot and the interior of the blade, and a connection between the interior of the blade and a source of pressurized gaseous fluid whereby the plate is arranged so that fluid introduced into the blade will be discharged from the slot, substantially radially relative to the lengthwise axis of the blade.
Claim 10
Dependent Claim
36 words
A blade according to claim 7 in which the blanking means closes off a portion of the slot which extends substantially around the rear upper quadrant of the blade relative to normal airflow around the blade.
Claim 11
Dependent Claim
27 words
A blade according to claim 7 in which the closed off portion of the slot subtends an angle at the blade axis of the order of 120*.
Claim 12
Dependent Claim
39 words
A blade according to claim 8 in which the blanking means has a trailing edge which is positioned within an angle in the range 80* to 90* subtended at the blade axis from the vertical centerline of the blade.
References Cited (Backward Citations)
US2333555A
Cited
US2759548A
Cited
US3109494A
Cited
US3109499A
Cited
US3139936A
Cited
US3348618A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-05-24 | 1974-11-23 | 1975-05-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-05-24 | 1978-11-23 | 1979-05-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-05-24 | 1982-11-23 | 1983-05-25 | $7700.00 | Window Closed / Lapsed |