Patent US3874816A successfully refreshed from Google Patents.
US3874816A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Windmill blade
Assignee: Individual
•
Filing: 1973-10-23
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Granted: 1975-04-01
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Expires: 1993-10-23
Abstract
Abstract A windmill blade that has a rigid leading edge, a rigid root portion and a movable blade tip. Control of the geometric twist of the windmill blade is accomplished through proper selection of the axis of rotation for the movable blade tip and by controlling the position of the windmill blade tip with a servo motor or by controlling the position of the windmill blade tip with a spring and a weight. The ability to vary the geometric twist of the blade enables the frequency of rotation of the blade to be controlled to reduce wind drags upon the blade. This improved windmill blade eliminates the need for current complicated and expensive rotor hubs which are used to vary the blade pitch angle at the root end of the blade to reduce wind drag upon the blade.
Inventors
- 👤 Thomas E Sweeney
- 👤 Walter B Nixon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 18:06
CPC Classifications
F; F03; F03D; F03D7/00; F03D7/02; F03D7/04; F03D7/041; F03D7/022; F03D7/0224; F05; F05B; F05B2240/00; F05B2240/20; F05B2240/30; F05B2240/307; F05B2260/00; F05B2260/70; F05B2260/74; F05B2260/77; F05B2260/90; F05B2260/901; F05B2260/9011; Y; Y02; Y02E; Y02E10/00; Y02E10/70; Y02E10/72
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
133 words
A windmill blade comprising a rigid leading edge portion, a rigid root portion connected to said rigid leading edge portion, a rotatable tip member rotatably connected to the outer end portion of said rigid leading edge portion, said rotatable tip member being rotatable about an axis of rotation so positioned that a straight line extension thereof in a direction toward said rigid root portion intercepts said rigid root portion at a point located forward of the aft end thereof, an elongated flexible member having one end thereof connected to said rotatable tip member and the other end thereof connected to the aft end of said rigid root portion and weight means operatively connected to said rotatable tip member for controlling the position of said tip member and the consequent twist of said blade.
Claim 2
Dependent Claim
133 words
A windmill blade comprising a rigid leading edge portion, a rigid root portion connected to said rigid leading edge portion, a rotatable tip member rotatably connected to the outer end portion of said rigid leading edge portion, said rotatable tip member being rotatable about an axis of rotation so positioned that a straight line extension thereof in a direction toward said rigid root portion intercepts said rigid root portion at a point located forward of the aft end thereof, an elongated flexible member having one end thereof connected to said rotatable tip member and the other end thereof connected to the aft end of said rigid root portion and weight means operatively connected to said rotatable tip member for controlling the position of said tip member and the consequent twist of said blade.
Claim 3
Dependent Claim
52 words
The windmill blade of claim 1 wherein said intercept point is located substantially no further forward from the aft end of said root portion than a point at which said axis of rotation and the straight line extension thereof would be substantially parallel to the long axis of said rigid leading edge.
Claim 4
Dependent Claim
30 words
The windmill blade of claim 1 wherein said weight means is operatively connected to the side of the rotatable tip member which faces the plane of rotation of said blade.
Claim 5
Dependent Claim
21 words
The windmill blade of claim 3 further comprising weight extension means extending from said rotatable tip member to said weight means.
Claim 6
Dependent Claim
33 words
The windmill blade of claim 4 further comprising resilient means connected to said weight extension means for biasing said rotatable tip member in a direction toward the plane of rotation of said blade.
Claim 7
Dependent Claim
34 words
The windmill blade of claim 1 further comprising resilient means operatively connected to said rotatable tip member for biasing said movable tip member in a direction toward the plane of rotation of said blade.
Claim 8
Dependent Claim
13 words
The windmill blade of claim 6 wherein said resilient means comprises a spring.
Claim 9
Dependent Claim
13 words
The windmill blade of claim 1 further comprising a covering for said blade.
Claim 10
Dependent Claim
16 words
The windmill blade of claim 8 further comprising a rotor hub member connected to said blade.
Claim 11
Dependent Claim
24 words
The windmill blade of claim 9 further comprising a windmill body and wherein said rotor hub member is rotatably mounted on said windmill body.
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) | 1978-03-31 | 1978-09-30 | 1979-04-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-31 | 1982-09-30 | 1983-04-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-31 | 1986-09-30 | 1987-04-01 | $7700.00 | Window Closed / Lapsed |