Marine propulsion – Jet drive – Direction control for fluid jet
Reexamination Certificate
1999-12-24
2001-05-01
Swinehart, Ed (Department: 3617)
Marine propulsion
Jet drive
Direction control for fluid jet
Reexamination Certificate
active
06224436
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 housed in a water jet 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 thrust 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 midplane, 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 water jet housing and in flow communication with the housing outlet. Preferably the pivot axis of the steering nozzle lies in the water jet midplane. 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 thrust 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. In other words, when the steering nozzle is turned to the left, the resulting water flow having rearward and leftward flow components is redirected by the reverse gate to have forward and rightward components. This produces a thrust 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.
In accordance with another known design, the reverse gate is not steerable, i.e., the reverse gate is pivotably mounted to the water jet housing. In the up position, the reverse gate is clear of the water flow exiting the steering nozzle; in the down position, the reverse gate obstructs the water flow exiting the steering nozzle and reverses the rearward flow component, but does not reverse the lateral flow component. As a result, when the steering nozzle is turned to the left, the resulting water flow having rearward and leftward flow components is redirected by the reverse gate to have forward and leftward components. This produces a thrust which pulls the boat rearward and propels the water jet apparatus and boat stern to the right, causing the boat to turn to right during rearward movement. Similarly, the boat turns to the left during rearward movement when the steering nozzle is turned to the right. Thus there is a need for a non-steerable reverse gate design which would cause the rearward-moving boat to turn left when the steering nozzle is turned to the left and to turn right when the steering nozzle is turned to the right.
SUMMARY OF THE INVENTION
The present invention is a water jet apparatus comprising a non-steerable reverse gate which redirects the steered pump discharge to the opposite side of the boat. In effect, to steer to the port side in reverse, the thrust is discharged to starboard (and vice versa). The additional desired effect is to discharge the reverse steering thrust as close to 90 degrees relative to the water jet longitudinal centerline as possible. The reason for this characteristic is that the boat is steered most efficiently with a 90-degree vector. This allows a boat or other marine craft to be steered in reverse in the same manner as an automobile.
The reverse gate in accordance with the preferred embodiments accomplishes the foregoing by reversing the flow exiting the steering nozzle. When the steering nozzle is positioned to the left, causing the rearward exit flow to be directed to the left side of a midplane of the water jet apparatus, the reverse gate redirects that leftward and rearward flow so that it flows predominantly rightward and forward. Conversely, when the steering nozzle is positioned to the right, causing the rearward exit flow to be directed to the right side of the midplane, the reverse gate redirects that rightward and rearward flow so that it flows predominantly leftward and forward.
In accordance with the preferred embodiments of the invention, the water jet apparatus comprises a housing having a water tunnel, a steering nozzle pivotably mounted to the housing and in flow communication with the outlet of the housing outlet, and a reverse gate pivotably mounted to the housing. The reverse gate is pivotable between forward and reverse positions. In the forward position, the reverse gate is clear of the flow exiting the steering nozzle. With the reverse gate in the forward position and the steering nozzle in a central position, i.e., symmetrically disposed relative to a midplane of the water jet housing, the exit flow is rearward during water jet operation and the boat is propelled forward. In the reverse position, the reverse gate obstructs the flow exiting the steering nozzle and changes the rearward directional flow component into a predominantly forward directional flow component, which forward flow propels the boat rearward. If the steering nozzle is in the central position, then the boat is propelled along a straight line. 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. When the boat is being propelled forward, turning the steering nozzle to the right of the midplane causes the boat to turn right; turning the steering nozzle to the left of the midplane causes the boat to turn left.
The reverse gate of the invention deflects the flow exiting the steering nozzle to achieve the desired steering response when the boat is moving in reverse. In particular, when the steering nozzle is pivoted to the left side of the midplane during reverse operation, so that the water flow exiting the steering nozzle has predominantly leftward and rearward flow components, the reverse gate is designed to redirect that water flow so that it has predominantly rightward and forward flow components. Conversely, when the steering nozzle is pivoted to the right side of the midplane, so that the water exiting the steering nozzle has predominantly rightward and rearward flow components, the reverse gate redirects that water flow so that it has predominantly leftward and forward flow components. Thus when the boat operator shifts the boat into reverse and turns the steering wheel to the right, the stern of the boat will turn right as the boat backs up. Similarly, when the boat operator shifts the boat into reverse and turns the steering wheel to the left, the stern of the boat will turn left as the boat backs up.
In accordance with one preferred embodiment of the invention, a water jet apparatus comprises a housing comprising a water tunnel having an inlet and an outlet; and a reverse gate pivotably mounted to
Jones James R.
Westhoff Paul E.
Bombardier Motor Corporation of America
Flaherty Dennis M.
Swinehart Ed
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