Strut-mounted marine propulsion unit

Details Strut-mounted marine propulsion unit Strut-mounted marine propulsion unit

2000-03-20

2001-06-12

Avila, Stephen (Department: 3617)

Marine propulsion

Electric drive for propelling means

C440S067000, C440S080000

Reexamination Certificate

active

06244912

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to propulsion units for marine vessels and, more particularly, to propulsion units for marine vessels which are supported by a strut extending from a hull of a vessel.
Conventional propulsion arrangements for surface ships are generally internally powered shaft-driven propeller-type systems in which the propeller shaft passes through the ship's hull at an angle to facilitate the layout of the propulsion plant equipment within the ship due to the typical hull geometry. Such angled shafting reduces propeller efficiency. Moreover, the typical geometry of the hull of a marine vessel does not provide uniform inflow to such a propeller which also reduces propeller efficiency.
The patents to Kirin U.S. Pat. No. 1,595,949, Pierce U.S. Pat. No. 1,910,561, Billing U.S. Pat. No. 2,372,247 and Waterval U.S. Pat. No. 2,691,356 disclose coaxial dual propeller drives for ships. The Waterval patent describes a coaxial dual propeller drive arrangement in an offset pod supported by a strut through which a mechanical drive connection is provided. The patents to Clark U.S. Pat. No. 3,528,383, Lemont U.S Pat. No. 5,292,088, Lashman U.S Pat. No. 5,634,423 and Itima et al. U.S. Pat. No. 5,848,922 disclose shrouded propeller arrangements for marine vessels arranged to produce a desired flow of water to the propeller. The Tank et al. U.S. Pat. No. 1,691,593 discloses an aircraft propulsion pod supported by struts from an aircraft wing powering a pusher propeller and containing an internal fan to pump air to the cylinders of the drive motor. The Niemi U.S. Pat. No. 5,679,045 discloses a propulsion device supported by a strut in spaced relation to a ship's hull in which electrical power is transmitted through the strut to an electric motor in the pod which drives a propeller.
SUMMARY OF THE INVENTION
Accordingly, it is an object to the present invention to provide a strut-mounted marine propulsion unit which overcomes disadvantages of the prior art.
Another object of the invention is to provide a strut-mounted marine propulsion unit which does not require engine room disruption or hull cuts for maintenance and/or replacement of a propulsion motor and which produces a more efficient propulsive force for a marine vessel.
A further object to the invention is to provide a strut-mounted marine propulsion unit arranged to utilize the boundary layer flow along the housing for the unit to improve propulsion efficiency and to provide improved cavitation performance, thereby permitting an increase in the time interval between scheduled maintenanee-operations.
These and other objects to the invention are attained by providing a propulsion unit for marine vessels which contains an electric motor within a housing, a forward propeller driven by the electric motor and having a diameter larger than the housing for the electric motor, and an aft section with a shrouded propulsion unit positioned to take in the boundary layer flowing along the housing and containing at least one row of blades driven by the electric motor. The motor housing is supported in spaced relation from the hull of the marine vessel by a strut in such a way as to insure that a uniform flow velocity profile is generated by the forward propeller for fluid directed around the housing and toward the inlet to the aft section. If appropriate, hydrodynamic vanes are mounted on the housing and project into the flow produced by the forward propeller to reduce tangential forces resulting from the propeller rotation. Further, hydrodynamic vanes are provided at the inlet to the aft section and, if desired, counter-rotating blade sections can be provided within the aft section. In addition, the shroud for the aft section may include flow-reversing clamshells of the like to reduce stopping distances for the vessel or assist in maneuvering the vessel. The strut mounting for the propulsion unit facilitates removal of the propulsion unit for replacement, maintenance and servicing.


REFERENCES:
patent: 2974628 (1961-03-01), Erlbacher
patent: 3137265 (1964-06-01), Meyerhoff
patent: 3266733 (1966-08-01), Goehler
patent: 4074652 (1978-02-01), Jackson
patent: 5101128 (1992-03-01), Veronesi et al.
patent: 5445545 (1995-08-01), Draper

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