Marine propulsion – Screw propeller – Propeller arrangement
Reexamination Certificate
1999-12-24
2001-09-11
Morano, S. Joseph (Department: 3617)
Marine propulsion
Screw propeller
Propeller arrangement
C440S042000, C440S083000
Reexamination Certificate
active
06287162
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 mechanisms for transmitting motive power from an inboard marine engine to a water jet apparatus.
BACKGROUND OF THE INVENTION
The powerhead of a boat or any other watercraft can be placed either inside (inboard) or outside (outboard) the hull of the boat. In both cases, a water jet apparatus can be mounted outside the boat at a certain depth below the waterline.
For example, it is well-known to retrofit a water jet on an outboard motor in place of a propeller. In such a system, a rotor or impeller is mounted (e.g., spline fitted) directly on the propeller output shaft in place of the propeller. There are typically no modifications to the drive train, cooling or sealing components. A housing having a water inlet and a water outlet surrounds the rotor.
A water jet system has the advantages of protecting the rotating elements from interference with and damage by foreign objects in the water, and improving some aspects of performance of the propulsion system. Another benefit inherent with the water jet is a directed jet of water that results in greater steering response at speed.
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.
Alternatively, some water jets are designed with an inlet housing which is built into the hull such that the inlet lies in the plane of the hull bottom. In a typical design, an inlet housing which rotatably supports a first shaft is mounted to the boat hull, and then a stator housing which rotatably supports a second shaft is attached to the inlet housing. The impeller is securely mounted on the forward end of the second shaft and has a splined bore for receiving a splined end of the first shaft when the inlet and stator housing are coupled. This conventional arrangement requires two sets of bearings: one set installed in the inlet housing for rotatably supporting the first shaft at two axial positions therealong and another set installed in the stator housing for rotatably supporting the second shaft at two axial positions therealong.
There is a need for a water jet apparatus having a simplified design which is relatively easier to mount onto a boat hull.
SUMMARY OF THE INVENTION
The present invention is directed to a water jet apparatus which has a single drive shaft rotatably supported by a pair of bearings installed in an inlet housing. The impeller is securely mounted on a splined end of the drive shaft which extends out of the inlet housing in the aft direction. The drive shaft is not supported by the stator housing, thereby eliminating the need for bearings inside the stator housing.
In accordance with the preferred embodiment of the invention, the inlet housing comprises a vertical strut having an axial bore which houses a portion of the drive shaft, both ends of the drive shaft projecting out of the bore. Toward the forward end of the drive shaft, the drive shaft is rotatably supported by a forward bearing installed in an annular space between the drive shaft and a bearing housing. The bearing housing in turn has a generally annular portion which extends into an annular cavity formed between the inlet housing and the bearing, and a generally radial flange with holes for screwing the bearing housing to the inlet housing. At a position to the rear of the forward bearing, an aft bearing is installed in an annular space formed between the drive shaft and the inlet housing. The inlet housing comprises a generally annular projection which extends in the aft direction into a cavity formed in the forward section of the impeller hub. Oil seals are installed between the generally annular projection of the inlet housing and the drive shaft. The impeller is held securely on the drive shaft by a lock nut.
Thus, in accordance with the preferred embodiment of the invention, the impeller is mounted on a distal section of a drive shaft having no bearing support aft of the impeller. As a result, the second shaft of the conventional drive shaft arrangement is eliminated. Moreover, the assembly of the water jet apparatus is simplified since no bearing assemblies need to be installed in the stator housing.
REFERENCES:
Outboard Marine Corporation Turbojet, exploded view of housings and drive shaft, commercially available product, 3 sheets.
Polaris PWC, exploded views of driveshaft/coupler and pump assembly, commercially available product, 2 sheets.
Mercury Sportjet, exploded views of pinion & impeller shaft and hozzle rudder components, commercially available product, 2 sheets.
Freitag Michael W.
McChesney Richard M.
Westhoff Paul E.
Bombardier Motor Corporation of America
Flaherty Dennis M.
Morano S. Joseph
Vasudeva Ajay
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