Marine propulsion – Jet drive
Reexamination Certificate
1999-12-24
2001-05-01
Avila, Stephen (Department: 3617)
Marine propulsion
Jet drive
C440S046000
Reexamination Certificate
active
06224435
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to water jet apparatus for propelling boats and other watercraft. In particular, the invention relates to inlet structures for guiding water into a water jet apparatus.
BACKGROUND OF THE INVENTION
It is known to propel a boat or other watercraft using a water jet apparatus mounted to the hull, with the powerhead being placed inside (inboard) the hull. The drive shaft of the water jet apparatus is coupled to the output shaft of the inboard motor. The impeller is mounted on the drive shaft and housed in a jet propulsion duct or water tunnel.
To facilitate use of water jet-propelled boats in shallow water, it is known to mount the water jet at an elevation such that the water jet does not project below the bottom of the boat hull. This can be accomplished, for example, by installing a duct in the stern of the boat, the duct being arranged to connect one or more inlet holes formed in the bottom of the hull with an outlet hole formed in the transom. The water jet is then installed outside the hull in a position such that the water jet inlet is in flow communication with the duct outlet at the transom. Such a system is shown in Australian Patent Specification No. 262306, published in 1963. Alternatively, the water jet can be installed inside the duct built into the hull, as shown in U.S. Pat. No. 5,181,868.
In another type of design, a water jet apparatus is installed inside the hull and penetrates the transom. An inlet housing of the water jet has a horizontal opening and an inclined water tunnel for guiding water to the impeller. The horizontal opening of the inlet housing is mounted in a hole in the bottom or near the bottom of the hull. A similar design is disclosed in Swiss Patent No. 481788.
There is a need for a boat design in which a water jet apparatus can be easily installed in a cavity formed in the hull, and in which the water tunnel of the water jet is elevated above the hull bottom.
SUMMARY OF THE INVENTION
The present invention is directed to a marine craft (e.g., a boat) propelled by water impelled through a duct, the inlet of which is situated below the boat waterline. A first portion of the duct comprises an inlet ramp formed in a hull of the boat, while a second portion of the duct is formed in an inlet housing of the propulsion apparatus, the inlet housing being installed in a hull cavity. The second portion of the duct is in flow communication with the first duct portion. The propulsion apparatus comprises an impeller rotatably mounted inside a third portion of the duct for impelling water rearward toward the duct outlet. The third portion of the duct is in flow communication with the second duct portion. The duct inlet is formed in part by a lower boundary of the inlet ramp formed in the hull and in part by a lower boundary of the inlet housing. In accordance with the preferred embodiment, each lower boundary has a U-shape. Preferably, the hull is made of non-metallic material (e.g., fiberglass) and the inlet housing is made of metal (e.g., aluminum alloy).
In accordance with a further aspect of the invention, a marine craft comprises a hull having a first plurality of hull sections defining an inlet ramp which increases in height as the inlet ramp extends rearward, and a second plurality of hull sections defining a cavity which communicates at its front with the rear of the inlet ramp. The cavity is open at its bottom and its rear. The marine craft further comprises a jet pump apparatus comprising an inlet housing installed in the aforementioned cavity in the hull. The inlet housing defines an inlet volume in flow communication with the inlet ramp and a water tunnel in flow communication with the inlet volume. The inlet volume has a height which increases as it extends rearward. In accordance with a preferred embodiment, the first plurality of hull sections comprise a first set of boundaries which form a first lower boundary and the inlet housing comprises a second lower boundary. The first and second lower boundaries define the water inlet.
In accordance with a further aspect, the invention is directed toward a water jet apparatus comprising a housing having a duct with an inlet and an outlet, and an impeller rotatably mounted to said housing and comprising a plurality of blades extending across respective portions of the duct. The duct inlet is formed by a first U-shaped boundary of the housing lying in a first plane and connected at endpoints to a second U-shaped boundary of the housing lying in a second plane. The first and second planes are not mutually parallel. Preferably, the first and second planes are generally mutually perpendicular. The housing may comprise an inlet housing, a stator housing in flow communication with the inlet housing and an exit nozzle in flow communication with the stator housing.
In accordance with another aspect, a boat hull comprises a first plurality of hull sections defining an inlet ramp which increases in height as it extends rearward from a beginning to an end, and a second plurality of hull sections defining a cavity which communicates at its front with the end of the inlet ramp. The cavity is open at its bottom and its rear, and has a width greater than the width of the inlet ramp and a height greater than the height of the inlet ramp at its end.
REFERENCES:
patent: 3109407 (1963-11-01), Dorst
patent: 3572281 (1971-03-01), Becker
patent: 5700169 (1997-12-01), Jones
patent: 5713768 (1998-02-01), Jones
patent: 5752864 (1998-05-01), Jones et al.
patent: 262306 (1963-05-01), None
patent: 481788 (1970-01-01), None
patent: 1321564 (1963-02-01), None
patent: 724662 (1966-11-01), None
Freitag Michael W.
Westhoff Paul E.
Avila Stephen
Bombardier Motor Corporation of America
Flaherty Dennis M.
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