Marine propulsion – Jet drive – Having means to increase fluid drive means efficiency
Reexamination Certificate
2000-03-27
2001-09-25
Morano, S. Joseph (Department: 3617)
Marine propulsion
Jet drive
Having means to increase fluid drive means efficiency
C440S038000
Reexamination Certificate
active
06293836
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 varying the outlet area of the exit nozzle of 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) or outside (outboard) the hull. The drive shaft of the water jet apparatus is coupled to the output shaft of the 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.
The overall performance of a water jet propulsion system is highly dependent on the size, i.e., area, of the exit nozzle outlet. A relatively large opening is required to provide initial thrust, whereas a relatively small opening is desirable for high speed. A smaller opening is also desirable for low-speed maneuvering, as it would result in a higher velocity of the exiting water flow at low engine rpm. Consequently, an adjustable exit nozzle outlet would be desirable to provide improved overall performance.
Some conventional adjustable exit nozzles for water jet propulsion systems have been designed using the iris method for opening or closing down the exit nozzle outlet, thereby increasing or decreasing the diameter of the outlet. While these means produce the desired results, an iris-type structure has a tendency to clog with silt or debris present in the water being pumped through the water jet propulsion system. This clogging eventually causes the adjustment mechanism to become inoperable.
Another technique for providing an adjustable exit nozzle outlet area is disclosed in U.S. Pat. No. 5,244,425 to Tasaki et al. An arrangement is provided for variably adjusting the effective flow area along a region within a water jet propulsion system. A bullet-shaped adjusting cone is moveable in and out of the outlet region, thereby adjusting the area of the outlet region. The adjusting cone is housed with a hub of the impeller assembly. A front portion of the cone member is flanged and forms an actuator. A spring is also housed within the hub, around a shaft connecting the cone portion and the actuator, and provides a forward biasing force against the actuator, thereby positioning the adjusting cone out of the outlet region and maximizing the outlet region's area. A rod and lever assembly is used to overcome the spring force, thereby moving the adjusting cone rearwardly and into the outlet region in order to reduce the area of that region.
Another type of variable nozzle employs a resilient or elastic member which can be expanded and contracted by the supply and withdrawal of a fluid from a chamber formed by the elastic member. For example, U.S. Pat. No. 3,279,704 to Englehart et al. discloses a water jet device which incorporates a control element which is moveable in and out of the outlet region and an annular flexible member made of rubber or like material which is installed in the outlet region. The flexible member and the outlet region form an internal hollow portion within which fluid pressure can be varied to adjust the position of the flexible member, thereby adjusting the thickness of the annular flow of water between the control element and the flexible member.
There is a need for a means by which the area of the exit nozzle outlet of a water jet propulsion system can be adjusted without the possibility of clogging, without use of a complicated linkage system and without redesigning the exit nozzle itself.
SUMMARY OF THE INVENTION
The present invention is directed to a water jet apparatus having means for adjusting the size of the outlet of the exit nozzle. The size of the outlet is increased to provide initial thrust and decreased for high speed. A smaller opening is also desirable for low-speed maneuvering.
In accordance with the preferred embodiment of the invention, means for adjusting the size of the outlet of the exit nozzle are mounted to the inner stator hub of a water jet propulsion system. The adjusting means comprise a bullet-shaped tail cone made of resilient or elastic material, e.g., molded rubber, and a hollow piston which is axially slidable relative to the inner stator hub. The piston is slidably mounted on an axial cylinder, the piston and cylinder forming a chamber between the distal end of the cylinder and the inner wall of the hollow piston. That chamber is in flow communication with a source of fluid via a conduit which penetrates the cylinder. The piston is hydraulically activated by supplying pressurized fluid to the chamber. The axial pressure exerted by the fluid in the chamber causes the piston to slide axially to an extended position. During rearward axial travel of the piston from its retracted position to its extended position, the tip of the piston bears against the internal surface of the resilient tail cone and carries the tip of the tail cone with it. This causes the resilient cone to elongate as the tip of the tail cone travels axially rearward while the base of the tail cone remains stationary. The piston and tail cone are configured, sized and positioned so that in an elongated position, the tail cone protrudes into the exit nozzle outlet, thereby efficiently reducing the area of the nozzle outlet. The elastic nature of the tail cone material will cause the cone to return to its unelongated configuration when the hydraulic pressure is relieved, e.g., by opening a hydraulic valve, thereby increasing the area of the nozzle outlet.
The preferred embodiment of the invention will be disclosed in the context of water jet propulsion system which is driven by an inboard motor. However, the person skilled in the art will readily appreciate that the adjustable nozzle disclosed herein has application beyond water jet propulsion systems driven by an inboard motor. For example, the adjustable nozzle disclosed herein has application in a water jet propulsion system driven by an outboard motor.
REFERENCES:
patent: 3214903 (1965-11-01), Cochran
patent: 3279704 (1966-10-01), Englehart et al.
patent: 3286641 (1966-11-01), Delao et al.
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patent: 3637140 (1972-01-01), Palovchik
patent: 3650110 (1972-03-01), Ghougasian
patent: 3834626 (1974-09-01), Sevik et al.
patent: 4331173 (1982-05-01), Culaud
patent: 4479507 (1984-10-01), Nichols
patent: 5244425 (1993-09-01), Tasaki et al.
patent: 5679035 (1997-10-01), Jordan
patent: 576223 (1959-05-01), None
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patent: 406001288 (1994-01-01), None
patent: 406001289 (1994-01-01), None
Bombardier Motor Corporation of America
Flaherty Dennis M.
Morano S. Joseph
Vasudeva Ajay
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