US3830190A

US3830190A - Variable geometry marine propulsor

Info

Publication number: US3830190A
Application number: US00363447A
Authority: US
Inventors: P Mantle
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1973-05-24
Filing date: 1973-05-24
Publication date: 1974-08-20
Anticipated expiration: 1991-08-20

Abstract

A marine propulsive apparatus and a device and method for increasing the apparatus'' efficiency by controlling the amount of wetting of the apparatus over a range of speeds. A housing, mounted in a cavity formed in the stern of a ship, encloses a drive shaft connected to a propeller. A control surface is pivotally connected to the hull of the ship ahead of the propeller and in a raised position contacts the stern portion of the hull to form the upper wall of the cavity. A hydraulic device is used to raise and lower the control surface, the latter directing the flow of water across the propulsive apparatus. As the speed of the ship increases wetting of the propulsive apparatus is decreased.

Description

United States Patent 1 Mantle Aug. 20, 1974 VARIABLE GEOMETRY MARINE PROPULSOR [75] inventor: Peter J. Mantle, Tacoma, Wash.

[22] Filed: May 24, 1973 [21] Appl. No.: 363,447

' [52] US. Cl 115/34 R, 114/66.5 P

[51] Int. Cl B63h 5/06. [58] Field of Search 115/34, 39, 41 R, 14;

[56] References Cited UNITED STATES PATENTS 130,110 8/1872 Dodge 115/41 R 2,135,907 ll/1938 Miller 115/41 R 2,265,079 12/1941 Mettair 115/41 R 2,377,442 6/1945 Osterhoudt.... 114/235 2,928,365 3/1960 Moon 114/66.5 P 2,929,346 3/1960 Perce ll4/66.5 P

Carter, Jr. 114/665 P Shields 115/14 Primary Examiner-Robert G. Sheridan Assistant Examiner-Donald W. Underwood Attorney, Agent, or Firm-R. S. Sciascia; P. Schneider; R. B. Rothman [57] ABSTRACT A marine propulsive apparatus and a device and method for increasing the apparatus efficiency by controlling the amount of wetting of the apparatus over a range of speeds. A housing, mounted in a cavity formed in the stern of a ship, encloses a drive shaft connected to a propeller. A control surface is pivotally connected to the hull of the ship ahead of the propeller and in a raised position contacts the stern portion of the hull to form the upper wall of the cavity. A hydraulic device is used to raise and lower the control surface, the latter directing the flow of water across the propulsive apparatus. As the speed of the ship increases wetting of the propulsive apparatus is decreased.

7 Claims, 4 Drawing Figures VARIABLE GEOMETRY MARINE PROPULSOR BACKGROUND OF THE INVENTION The present invention relates generally to marine propulsion devices and more particularly to a method and apparatus for increasing the efficiency of a propulsion device.

Top speeds of high-speed, marine craft have heretofore been limited by the drag of the propulsion appendages required to support the propeller. Partially submerged propellers are not capable along of solving this problem, because such propellers lack thrust at low speeds. Low speeds require more submergence to absorb the thrust and torque of the propeller and maintain maximum efficiency. The problem is intensified on craft required to operate at both low and high speeds at high thrust levels, as for example, air cushion vehicles and surface effect ships which have high hump drag and high design speed drag.

Variable geometry hulls employed in the past have not been addressed to this problem, since the speed of large marine craft until relatively recently did not necessitate its solution. Propulsion devices in the past have actually varied hull geometry, generally to ensure complete wetting of the propeller.

SUMMARY OF THE INVENTION The present invention recognizes that at high speeds the propulsive force, thrust less drag,-of apropulsion system is severely affected by the drag of the submerged propeller and appendages required to support the propeller. The invention solves this problem by providings system which controls wetting of both the propeller and its support structure as the speed of the craft varies.

OBJECTS OF THE INVENTION An object of the present invention is to optimize the efficiency of a propulsion system over the entire speed range of a ship.

Another object is to control the wetting of a propeller and its supporting structure as the speed of 'a ship var- 1es.

A further object is to provide fully submerged propeller performance at high speed.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic of the stern position of a hull section partially in cross section illustrating the variable geometry marine propulsor in raised position;

FIG. 2 is a view of the rear of a preferred hull incorporating the present invention;

FIG. 3 is a schematic similar to FIG. 1 showing the control surface in its fully lowered position; and

FIG. 4 is another view of the rear of a preferred hull incorporating the present invention with the control surface in the lowered position.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1, which illustrates a preferred embodiment of the variable geometry propulsor, shows a propeller 2 mounted on a housing 4 which is connected to the stern portion 8 of the hull of a ship. The housing 4 encloses drive shafts (not shown) which are connected to the propeller and serves as a propeller mounting. A control surface 10 is pivotally connected at 12 to the hull ahead of the propeller. The pivotal connection may be made using any suitable hinge.

A hydraulic actuator 16, of any suitable type, is connected via shaft 18 to appendage I4. Appendage 14 is rigidly affixed to control surface 10 by, for example, welding. The actuator deploys the control surface in selected positions depending on the speed of the ship. At low speeds, for example Froude Number less than 1.0, a fully submerged propeller with percent disc wetting provides the maximum propulsion force. At high speeds,,Froude Number greater than 1.0, the advantage of 100 percent disc wetting is lost by the drag of the housing structure 4 or other appendages (not shown) required to support the propeller. At low speed the control surface 10 is in the raised position as shown in FIG. 1 and the water level just behind the hull 8 is indicated by the numeral 6.

FIG. 2 is a view of the rear of a preferred hull incorporating the propulsor. As can be seen in FIG. 2, the housing 4 is within a cavity in the stern portion of the hull. The cavity is in the form of a triangular prism. The disc 20 illustrates the area covered by propeller 2. The interior of the disc 20 is completely filled with dotted lines to indicate that when the control surface is in the raised position as shown in FIG. 2, 100 percent of propeller 2 and housing 4 is submerged.

FIGS. 3 and 4, in which like numerals indicate like structure, depict the control surface 10 in its lowered position. As can be seen in the Figures, at least 50 percent of the propeller and housing 4 are no longer submerged. This control surface position is used for running at high speeds. One can also see that the propeller 2 in the preferred embodiment is just outside the cavity formed in the stern portion of the hull 8. In addition, the upper face of control surface 10 is shaped complementary with respect to the hull surface that forms the upper wall of the cavity. In the raised position of the control surface 10, therefore, its upper face smoothly overlaps and contacts the hull 8.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim:

1. A ship comprising:

a hull having a stern portion, said stern portion having a cavity therein, said cavity being formed between depending sides of the hull at the stern portion of the hull;

a housing rigidly affixed to said stern portion and depending into said cavity, said housing being immovable with respect to said hull;

a drive shaft within said housing, immovable vertically and horizontally with respect to said hull;

a propeller connected to said drive shaft;

control surface means pivotally mounted on said hull within the cavity ahead of said propeller for directing the flow of water over said propeller to change the degree of submergence of the propeller without a substantial change in position or attitude of the hull relative to the water surface; and

raised position.

4. The ship of claim 3 wherein the propeller is outside the cavity formed in the stern portion of said hull.

5. The ship of claim 3 wherein the upper face of said control surface is flat.

6. The ship of claim 5 wherein the cavity formed in said stem is in the shape of a triangular prism.

7. The ship of claim 6 wherein the propeller is outside the cavity formed in the stern portion of said hull.

Claims

1. A ship comprising: a hull having a stern portion, said stern portion having a cavity therein, said cavity being formed between depending sides of the hull at the stern portion of the hull; a housing rigidly affixed to said stern portion and depending into said cavity, said housing being immovable with respect to said hull; a drive shaft within said housing, immovable vertically and horizontally with respect to said hull; a propeller connected to said drive shaft; control surface means pivotally mounted on said hull within the cavity ahead of said propeller for directing the flow of water over said propeller to change the degree of submergence of the propeller without a substantial change in position or attitude of the hull relative to the water surface; and deployment means for moving said control surface means into and out of contact with the stern portion of said hull.

2. The ship of claim 1 wherein said cOntrol surface means comprises a control surface whose bottom face is planar.

3. The ship of claim 2 wherein the control surface has an upper face contacting the stern portion of said hull when said control surface is in a raised position, said upper face being shaped complementary to said stern portion to fit smoothly against said stern portion in said raised position.

5. The ship of claim 3 wherein the upper face of said control surface is flat.

6. The ship of claim 5 wherein the cavity formed in said stern is in the shape of a triangular prism.