Propulsion system for a ship or seagoing vessel

Abstract

A marine drive is engaged with and is driven by a vessel's engine drive shaft. The drive includes: a universal joint secured to the vessel's hull; a first screw shaft supporting a first screw; a first gear set driven by the first screw shaft; a second screw shaft driven by the first gear set; a second gear set driven by the second screw shaft; a third screw shaft driven by the second gear set and supporting a second screw; and a third screw supported by the second screw shaft at its terminal end. The first and second gear sets are enclosed within a water-tight enclosure enabling rotational speed differentiation between the first and second screw shafts and enabling rotational sense reversal between the second and third screw shafts. An actuator provides changes in angle of attack of the second and third screws.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]Not applicable.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not applicable.THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT[0003]Not applicable.INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC[0004]Not applicable.REFERENCE TO A “MICROFICHE APPENDIX”[0005]Not applicable.BACKGROUND OF THE INVENTION[0006]1. Field of the Present Disclosure[0007]This disclosure relates generally to marine drives, and more particularly to a marine drive capable of efficiently converting the output of powerful marine engines to forward thrust, to provide rotational speed differentials between plural screws driven by a single engine shaft, and to provide variable thrust vector angle of attack.[0008]2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98[0009]Kirin, U.S. Pat. No. 1,595,949, discloses a boat comprising a hull having a cylindrical portion and keel supported centrally up...

AI Technical Summary

Benefits of technology

[0032]Engines for small ships and yachts are able to generate significant thrust. However, prior art marine drives for ships and yachts are relatively inefficient with low speed and high fuel consumption. Such ships and yachts are most efficient at lower speeds where the hull is plowing. Incremental increases in screw RPM are not matched by equivalent incremental hull speeds. This is because, when plowing, a ship's hull must displace ever greater bow wave mass as speed increases and such mass increases non-linearly with hull speed. The present invention provides a solution to this problem enabling larger craft to move more quickly through the water while using relatively less fuel to do so.

[0033]By changing the angle of attack of a ship's drive screws the hull may be raised in the water so that it displaces less water and produces a smaller bow wave. To achieve greater screw thrust, dual in-line screws are used with counter-rotation to provide a significant improvement in thrust without producing undesirable screw steering effects. However, because a change in angle of attack of a ship's screws to provide hull lift is sub-optimal in producing forward thrust, the first effect tends to be negated by the second effect. To overcome this problem, the screws used for lift are able to be placed at an optimal angle for doing so, while a third screw is positioned for maximum forward thrust. To provide for simplicity and economy of enabling this capability, all three screws are driven by a single drive shaft. The present invention reduces fuel consumption while permitting relatively higher speeds in larger boats and yachts.

Problems solved by technology

However, prior art marine drives for ships and yachts are relatively inefficient with low speed and high fuel consumption.

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