Marine propulsion – Jet drive – Direction control for fluid jet
Reexamination Certificate
2000-03-14
2001-05-08
Swinehart, Ed (Department: 3617)
Marine propulsion
Jet drive
Direction control for fluid jet
Reexamination Certificate
active
06227919
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 shifting a water jet apparatus to selectively propel a craft in the forward or reverse direction.
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 installed in a housing, the interior surface of which defines a water tunnel. The impeller is designed such that during motor operation, the rotating impeller impels water rearward through the water tunnel. The reaction force propels the boat forward.
In addition, it is known to provide a mechanism for diverting the exiting water flow to one side or the other of a water jet mid-plane, thereby enabling the boat operator to steer the boat to the left or right during forward propulsion. One such mechanism is a steering nozzle pivotably mounted to the housing and in flow communication with the housing outlet. Preferably the pivot axis of the steering nozzle lies in the water jet mid-plane. As the steering nozzle is pivoted to the left of a central position, the water flow out of the housing is diverted leftward, producing a reaction force which pushes the water jet apparatus and the boat stern to the right, thereby causing the bow of the boat to turn to the left. Similarly, the boat bow turns to the right when the steering nozzle is pivoted to the right of the central position.
It is also known to provide a mechanism for reversing the direction of the water flow exiting the steering nozzle. The reverse gate can be pivotably mounted to the steering nozzle, its pivot axis being generally perpendicular to the pivot axis of the steering nozzle. In the up position, the reverse gate is clear of the water flow exiting the steering nozzle. In the down position, the reverse gate is disposed in the path of the exiting water flow. In its simplest embodiment, the reverse gate has a U-shaped channel which reverses the water flow exiting the steering nozzle. When the steering nozzle is turned to the left, the resulting water flow having rearward and leftward velocity components is redirected by the reverse gate to have forward and rightward components. This produces a reaction force which pulls the boat rearward and propels the water jet apparatus and boat stern to the left, causing the boat to turn left during rearward movement. Similarly, the boat turns to the right during rearward movement when the steering nozzle is turned to the right. The provision of a steerable reverse gate allows the boat operator to steer in forward and reverse in the same manner that an automobile can be steered.
A conventional reverse gate mounted to the steering nozzle does not provide enhanced control and maneuverability of a boat in reverse. In particular, there is a need for an arrangement whereby additional lateral thrust can be applied during reverse motion of a boat.
SUMMARY OF THE INVENTION
The present invention is directed to a water jet apparatus having means for providing additional lateral thrust when a boat is moving in reverse. In accordance with the preferred embodiment, a water jet propulsion unit comprises a steering nozzle pivotably mounted at and in flow communication with the outlet of a flow-through housing, and having a pair of opposing side thrust nozzles. The preferred embodiment further comprises means for reversing the water flow exiting the steering nozzle. For example, the reversing means may comprise a reverse gate for covering the outlet of the steering nozzle and a reverse nozzle incorporated as part of the steering nozzle. The reversed flow exits the steering nozzle via the reverse nozzle.
In accordance with the preferred embodiment of the invention, when the steering nozzle is turned a predetermined angle, e.g., 30 degrees, to one side, the side thrust nozzle on the opposing side is swung into the path of water flow exiting the housing outlet. In this position, the side thrust nozzle directs a portion of the flow exiting the housing outlet in a direction approximately at a right angle relative to the centerline of the turned steering nozzle. This provides a lateral thrust directed toward the one side. In addition, when the reverse gate is lowered into a position where the reverse gate closes the steering nozzle outlet, the flow inside the steering nozzle is reversed. Some portion of the reversed flow then exits the steering nozzle via the reverse nozzle, causing a thrust for pulling the boat in a direction collinear with the centerline of the turned steering nozzle, i.e., the thrust vector has a reverse thrust component and a lateral thrust component, the latter also being in the direction toward the one side.
In accordance with the preferred embodiment of the invention, the left side thrust nozzle provides a rightward lateral thrust, in addition to the rightward lateral thrust provided by the reverse gate and reverse nozzle, when the steering nozzle is turned to the right by a predetermined angle. Similarly, the right side thrust nozzle will provide a leftward lateral thrust, in addition to the leftward lateral thrust provided by the reverse gate and reverse nozzle, when the steering nozzle is turned to the left by a predetermined angle. The reverse gate is pivotable between open and closed positions. In the open position, the reverse gate is clear of the flow exiting the steering nozzle. With the reverse gate in the open position and the steering nozzle in a central position, i.e., symmetrically disposed relative to a mid-plane of the water jet housing, the exit flow is rearward during water jet operation and the boat is propelled forward. In the closed position, the reverse gate obstructs the flow in the steering nozzle and changes the rearward directional flow component into a predominantly forward directional flow component, which exits the steering nozzle via the reverse nozzle. If the steering nozzle is in the central position, then the forward flow out of the reverse nozzle propels the boat rearward along a straight line. Alternatively, if the steering nozzle is in an off-center position, then the boat is propelled along an arcuate path, i.e., the boat will turn. Whether the boat is being propelled forward or rearward, turning the steering nozzle to the right of the mid-plane causes the boat to turn right; turning the steering nozzle to the left of the mid-plane causes the boat to turn left. However, the side thrust nozzles on the steering nozzle provide increased lateral thrust when the boat is in reverse and the steering nozzle is turned to a pre-determined angle. The result is enhanced control and maneuverability when the boat is in reverse.
REFERENCES:
patent: 3030909 (1962-04-01), Barnes
patent: 3258916 (1966-07-01), Lehman
patent: 3842787 (1974-10-01), Giacosa
patent: 3937172 (1976-02-01), Castoldi
patent: 4031844 (1977-06-01), Onal
patent: 4252075 (1981-02-01), Kobayashi
Bombardier Motor Corporation of America
Flaherty Dennis M.
Swinehart Ed
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