US4031846A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Anti-cavitation shroud and rudder
Assignee: Individual
•
Filing: 1975-10-09
•
Granted: 1977-06-28
•
Expires: 1995-10-09
Abstract
Abstract An anti-cavitation semi-cylindrical shroud and rudder combination is described which attaches to the transom of a boat so as to partly enclose a propeller which extends rearwardly of the boat. The axis of the propeller is selected to provide a line of thrust which intersects the approximate center of hull resistance to provide more stable running characteristics. The shroud itself encompasses about 37% of the periphery of the propeller and the lower edges of its side skirt portions lie in a plane which is parallel to the keel of the boat. The configuration of the shroud is such that it conforms to the bottom hull configuration at the front end and shrouds the propeller at the rear end. The shroud itself is configured to provide minimal flow resistance to the water. Yoke-mounted flanking rudders are pivoted ahead of the center of area of the rudder with the center of area of the rudders lying approximately in the fore and aft plane of the propeller. This facilitates turning particularly at low speeds. Finally, a planing plate extends rearwardly of the shroud and is configured to the contour of the shroud such that it may be pivoted in a vertical plane to change the attack angle of the water flowing from the propeller.
Inventors
- 👤 John W. Tone
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 12:00
CPC Classifications
B; B63; B63H; B63H5/00; B63H5/07; B63H5/16
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
85 words
A shroud adapted to be mounted at the rear transom of a boat having a propeller, said propeller defining a propeller disc and a plane of revolution, a propeller shaft extending through said transom, a keel, and a hull having a planing center of resistance; said shroud extending rearwardly of said boat and being of expanding arcuate shape encompassing only the upper portion of said propeller disc and extending forwardly of said plane of revolution to said transom and rearwardly of said plane of revolution.
Claim 2
Dependent Claim
85 words
A shroud adapted to be mounted at the rear transom of a boat having a propeller, said propeller defining a propeller disc and a plane of revolution, a propeller shaft extending through said transom, a keel, and a hull having a planing center of resistance; said shroud extending rearwardly of said boat and being of expanding arcuate shape encompassing only the upper portion of said propeller disc and extending forwardly of said plane of revolution to said transom and rearwardly of said plane of revolution.
Claim 3
Dependent Claim
24 words
An apparatus according to claim 1 wherein the axis of said propeller shaft extends about through the planing center of resistance of said hull.
Claim 4
Dependent Claim
22 words
Apparatus according to claim 2 wherein said shroud has depending skirts whose lower edges lie in a plane parallel to said keel.
Claim 5
Dependent Claim
42 words
An apparatus according to claim 3 wherein said shroud substantially conforms to the transverse bottom contour of said hull at the front portion thereof and rises to shroud less than 50% of the periphery of said propeller at the rear portion thereof.
Claim 6
Dependent Claim
37 words
An apparatus according to claim 4 wherein said shroud has an innerwall whose intersections with planes parallel to a vertical plane through the axis of said propeller shaft are straight lines, thereby to reduce turbulence in water.
Claim 7
Dependent Claim
22 words
An apparatus according to claim 5 wherein the axis of the propeller shaft forms about an 8° angle with said hull's keel.
Claim 8
Dependent Claim
23 words
An apparatus according to claim 6 wherein said shroud has a rear portion which encompasses about 37% of the periphery of said propeller.
Claim 9
Dependent Claim
63 words
An apparatus according to claim 5 wherein said shroud has an upper portion and which also includes a yoke pivoted on the upper portion of said shroud about a vertical axis intersecting the axis of said propeller shaft, a pair of aft flanking rudders secured to either end of said yoke on opposite sides of said shroud, and means to manipulate said yoke.
Claim 10
Dependent Claim
24 words
An apparatus according to claim 8 wherein the center of area of said rudders is aft of the plane of revolution of said propeller.
Claim 11
Dependent Claim
39 words
An apparatus according to claim 9 wherein said yoke is pivoted ahead of the center of area of said rudders, whereby either rudder is permitted to swing behind said propeller without the other rudder impeding flow to said propeller.
Claim 12
Dependent Claim
51 words
An apparatus according to claim 10 which also includes a horizontally disposed planing plate having substantially the same contour as the rear contour of said shroud and pivotally secured to the rear portion of said shroud to pivot in a vertical plane, and means to adjust the position of said plate.
Claim 13
Dependent Claim
23 words
An apparatus according to claim 1 wherein said shroud has depending skirts whose lower edges lie in a plane parallel to said keel.
Claim 14
Dependent Claim
40 words
An apparatus according to claim 1 wherein said shroud substantially conforms to the bottom contour of said hull at the front portion thereof and rises to shroud about 37% of the periphery of said propeller at the rear portion thereof.
Claim 15
Dependent Claim
37 words
An apparatus according to claim 13 wherein said shroud has an innerwall whose intersections with planes parallel to a vertical plane through the axis of said propeller shaft are straight lines, thereby to reduce turbulence in water.
Claim 16
Dependent Claim
63 words
An apparatus according to claim 1 wherein said shroud has an upper portion and which also includes a yoke pivoted on the upper portion of said shroud about a vertical axis intersecting the axis of said propeller shaft, a pair of aft flanking rudders secured to either end of said yoke on opposite sides of said shroud, and means to manipulate said yoke.
Claim 17
Dependent Claim
24 words
An apparatus according to claim 15 wherein the center of area of said rudders is aft of the plane of revolution of said propeller.
Claim 18
Dependent Claim
39 words
An apparatus according to claim 15 wherein said yoke is pivoted ahead of the center of area of said rudders, whereby either rudder is permitted to swing behind said propeller without the other rudder impeding flow to said propeller.
Claim 19
Dependent Claim
47 words
An apparatus according to claim 1 which also includes a horizontally disposed planing plate having substantially the same contour as said shroud and pivotally secured to the rear portion of said shroud to pivot in a vertical plane, and means to adjust the position of said plate.
Claim 20
Dependent Claim
47 words
An apparatus according to claim 8 which also includes a horizontally disposed planing plate having substantially the same contour as said shroud and pivotally secured to the rear portion of said shroud to pivot in a vertical plane, and means to adjust the position of said plate.
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) | 1980-06-27 | 1980-12-27 | 1981-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-06-27 | 1984-12-27 | 1985-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-06-27 | 1988-12-27 | 1989-06-28 | $7700.00 | Window Closed / Lapsed |