Patent US3972646A successfully refreshed from Google Patents.
US3972646A
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Propeller blade structures and methods particularly adapted for marine ducted reversible thrusters and the like for minimizing cavitation and related noise
Assignee: RTX BBN Technologies Corp
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Filing: 1974-04-12
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Granted: 1976-08-03
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Expires: 1994-04-12
Abstract
Abstract This disclosure is concerned with reducing blade-generated cavitation and accompanying noise in systems such as marine ducted reversible thrusters and the like, by novel techniques including a skew-forward blade configuration at the outer radii and particular blade thickness/chord length ratios associated therewith.
Inventors
- 👤 Neal A. Brown
- 👤 John A. Norton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 22:55
CPC Classifications
B; B63; B63H; B63H1/00; B63H1/02; B63H1/12; B63H1/14; B63H1/26; B63H1/18
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
167 words
A fully immersed propeller blade structure for providing reduced cavitation and noise in marine and related applications, said structure having a substantially circular cylindrical blunt tip edge with a surface connecting opposite faces of said blade structure, a leading edge with at least a forwardly skewed radially outer region on one side of the blade structure axis, and a trailing edge of the same general outline as the leading edge but unsymmetrically disposed on the other side of said axis, the blade structure being substantially flat and untwisted and having sections of hydrofoil shape and the minimum blade section thickness-to-chord ratio being at least about 6%, the thickness of said blade structure at said tip edge surface being substantially the same as the thickness at adjacent sections of said blade structure, to provide angle of attack tolerance for avoidance of leading edge cavitation, the forward skew of said leading edge region relieving inherent blade tip overloading while permitting blade section thickness appropriate for avoidance of thickness cavitation.
Claim 2
Dependent Claim
167 words
A fully immersed propeller blade structure for providing reduced cavitation and noise in marine and related applications, said structure having a substantially circular cylindrical blunt tip edge with a surface connecting opposite faces of said blade structure, a leading edge with at least a forwardly skewed radially outer region on one side of the blade structure axis, and a trailing edge of the same general outline as the leading edge but unsymmetrically disposed on the other side of said axis, the blade structure being substantially flat and untwisted and having sections of hydrofoil shape and the minimum blade section thickness-to-chord ratio being at least about 6%, the thickness of said blade structure at said tip edge surface being substantially the same as the thickness at adjacent sections of said blade structure, to provide angle of attack tolerance for avoidance of leading edge cavitation, the forward skew of said leading edge region relieving inherent blade tip overloading while permitting blade section thickness appropriate for avoidance of thickness cavitation.
Claim 3
Dependent Claim
25 words
A propeller blade structure as claimed in claim 1 and in which the said axis passes through substantially the midchord position of the tip edge.
Claim 4
Dependent Claim
28 words
A propeller blade structure as claimed in claim 1 and in which the intersection of the said tip edge with the leading edge is substantially ellipsoidal in shape.
Claim 5
Dependent Claim
13 words
A propeller blade structure as claimed in claim 1 disposed with duct means.
Claim 6
Dependent Claim
31 words
A propeller blade structure as claimed in claim 4 and in which means is provided for operating said blade structure within said duct means as a reversible thruster while rotating unidirectionally.
Claim 7
Dependent Claim
38 words
A propeller blade structure as claimed in claim 1 and in which the leading edge region radially inward of said outer region curves in a smooth transition to a radial condition, and then to a backwardly skewed condition.
Claim 8
Dependent Claim
27 words
A propeller blade structure as claimed in claim 6 and in which said forwardly skewed region is skewed at an acute angle of approximately 35° to 45°.
Claim 9
Dependent Claim
34 words
A propeller blade structure as claimed in claim 1 connected with hub means at the inner end and with further similar propeller blade structure means extending from said hub means to constitute a propeller.
Claim 10
Dependent Claim
43 words
A propeller blade structure as claimed in claim 8 having an associated duct and in which said propeller is disposed in the duct and the blade area is at least of the order of about 50% of the duct area at the propeller.
Claim 11
Dependent Claim
48 words
A propeller blade structure as claimed in claim 1 and in which the ratios of the blade section thickness t to tip radius R for blade sections at different percentages of the radius R are as follows:% R t/R______________________________________100 0.064695 0.065690 0.068080 0.073575 0.076170 0.079260 0.082650 0.085040 0.0865.______________________________________
Claim 12
Dependent Claim
57 words
A propeller blade structure as claimed in claim 1 and in which the ratios of blade section thickness t to chord length c at different percentages of the tip radius R are as follows: % R t/c
______________________________________
100 0.070
95 0.075
90 0.082
80 0.100
75 0.111
70 0.124
60 0.150
50 0.185
40 0.236.
______________________________________
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) | 1979-08-03 | 1980-02-02 | 1980-08-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-03 | 1984-02-02 | 1984-08-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-03 | 1988-02-02 | 1988-08-03 | $7700.00 | Window Closed / Lapsed |