Marine propulsion – Jet drive
Reexamination Certificate
1999-02-17
2001-02-27
Swinehart, Ed (Department: 3617)
Marine propulsion
Jet drive
Reexamination Certificate
active
06193570
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a water jet propulsion system for vessels, and more particularly, it relates to a water jet propulsion system for vessels of a displacement type which has streams of water taken in from a bottom of a vessel and changed at an impeller into water jets, and ejects the water jets at a stern of the vessel substantially in parallel with a surface of water, to thereby travel.
BACKGROUND ART
Such a water jet propulsion system for vessels typically has an arrangement in which a single ejection nozzle is fixed to a transversely central part at a stern of a vessel, and water jets to be ejected from the nozzle have an ejection quantity changed, as a rotation speed of an impeller is changed, and an ejection velocity controlled, as a bore diameter of the nozzle is controlled.
The changed ejection quantity of water jets shifts propulsive power of the vessel, and the controlled ejection quantity provides a controlled travel speed.
Accordingly, the ejection quantity and the ejection velocity of water jets are adequately varied in accordance with a weight of loads on the vessel, to thereby enable a saved fuel consumption at a drive for the impeller, allowing an economical travel.
However, the load weight of a vessel has an inseparable relationship to a drafting state of the vessel, such that a lighter load weight provides a shallower draft level, and a heavier load weight provides a deeper draft level.
If the draft is deep, a hull of the vessel has an increased fluid resistance, and besides, water jets hit waves, having a fraction of propulsive power killed, whereas a compensation therefor would cause an inflexible controllability of water jet ejection quantity and ejection velocity.
As a result, the economical travel has conventionally been allowed within a relatively narrow range of load weight.
To this point, there has been proposed an arrangement, which had a pair of ejection nozzles arranged side by side.
This arrangement allowed a sufficient ejection quantity to be secured, with a postponed problem of water jets hitting waves when with a heavy load.
There has been proposed another arrangement, which had a pair of ejection nozzles vertically arranged for a concurrent use, with a wave-hitting problem still left on a lower nozzle.
DISCLOSURE OF INVENTION
The present invention has been achieved with such points in view. It therefore is an object of the invention to provide a water jet propulsion system for vessels, allowing an economical travel, whether the load is much or little.
To achieve the object, according to the invention, there is provided a water jet propulsion system for vessels, comprising jet stream supply means for changing streams of water taken in from a bottom of a vessel into jet streams to supply jet streams in a flow rate variable manner, and water jet ejection means for ejecting supplied jet streams, rearwadly of a stern of the vessel, as velocity-variable water jets along an ejection axis having a variable vertical position.
According to the water jet propulsion system for vessels, the ejection axis of water jets can be vertically shifted in accordance with a varying draft level of the vessel, and the ejection quantity of water jets as well as the ejection velocity is controllable at a shifted position, thus allowing an economical travel, whether the load is much or little.
The water jet ejection means may preferably comprise a plurality of ejection nozzles arranged in a vertically spacing manner, a plurality of valve members provided in fluid paths connected to the plurality of ejection nozzles, and control means adapted to individually control the plurality of valve members, thereby permitting a selective use of an ejection nozzle having an adequate vertical position in accordance with a varying draft level of the vessel.
The plurality of ejection nozzles may preferably include an arbitrary first ejection nozzle, and a second ejection nozzle lower in position than the first ejection nozzle and having a smaller ejection bore diameter than the first ejection nozzle, thereby allowing for an upper ejection nozzle to have a relatively large ejection bore diameter, permitting a relatively large ejection quantity of water jets to be used when the vessel has a deep draft with a heavy load.
The water jet ejection means may preferably further comprise bore diameter control means adapted to control an ejection bore diameter individually of the plurality of ejection nozzles, thereby permitting the water jet ejection velocity to be controlled in a voluntary manner.
The plurality of ejection nozzles may preferably be arranged in a plurality of upper and lower rows, thereby allowing the ejection quantity of water jets to have a relatively large variation at a respective position, and adaptive to a large-scale vessel to be large in variation of load weight.
The water jet ejection means may preferably comprise an ejection nozzle having a controllable ejection bore diameter, and drive means for vertically driving the ejection nozzle, thereby allowing an economical travel of the vessel, whether the load is much or little, in addition to a reduced weight, a reduced construction cost and an improved appearance of the vessel to be expected.
REFERENCES:
patent: 1749087 (1930-03-01), Riley
patent: 3279704 (1966-10-01), Englehart et al.
patent: 3985094 (1976-10-01), Stricker
patent: 22222 (1882-10-01), None
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patent: 4-133895 (1992-05-01), None
patent: 4-283196 (1992-10-01), None
patent: 5-294284 (1993-11-01), None
patent: 7-101392 (1995-04-01), None
patent: 9-39888 (1997-02-01), None
Ishigaki Company Limited
McDonnell & Boehnen Hulbert & Berghoff
Swinehart Ed
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