Marine propulsion – Jet drive – Having means to prevent clogging
Reexamination Certificate
1999-06-09
2001-02-06
Swinehart, Ed (Department: 3617)
Marine propulsion
Jet drive
Having means to prevent clogging
Reexamination Certificate
active
06183319
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a blockage preventing apparatus for a water jet propulsion unit used in a hull.
BACKGROUND ART
Since a water jet propulsion unit for a hull draws and injects water in the neighborhood of the water surface, it is blocked in a short time when pulling floating matter or pieces. Due to this, a screen is provided at an intake to prevent large floating pieces from being drawn into a suction casing.
However, floating matter or pieces cling to the screen in the water where many other or pieces are floating so that cavitations and the like occur in the water jet propulsion unit, thereby reducing propulsion force. There are some cases where a vessel cannot continue running when the floating matter clinging to the screen increases. In particular, when the screen is of a fixed type navigating the vessel becomes impossible in quite a short time.
To eliminate the floating matter or pieces clinging to the fixed screen, there has been proposed an apparatus in which a movable screen is combined with a fixed screen as disclosed in, for example, Japanese Patent Application Publication No. 54-18475 or Japanese Patent Application Laid-Open No. 6-32288.
Even with a movable screen, once floating matter strongly clings to the screen, it is difficult to remove it and the navigation of the vessel might become impossible.
Furthermore, when floating matter or pieces pass through the screen, are drawn into the suction casing and deposited, the water jet propulsion unit is blocked. To remove the deposited matter or pieces, it is necessary to provide a hand hole in the water jet propulsion unit and to remove the deposited matters manually while the vessel is stopped.
DISCLOSURE OF THE INVENTION
The present invention has been made in consideration of the conventional problems stated above. It is therefore an object of the present invention to provide a blockage preventing apparatus capable of ensuring the elimination of floating matter strongly clinging to a screen.
It is another object of the present invention to provide blockage preventing apparatus capable of preventing dust from passing through the screen and being deposited in a water jet propulsion unit.
To attain the above object, a first aspect of the present invention is a blockage preventing apparatus used for a water jet propulsion unit provided with a casing member including a lower opening at a front end, a lateral opening at a rear end and an internal space between the lower opening and the lateral opening, and vanes arranged within the internal space and rotated for drawing water from the lower opening to inject the water from the lateral opening, the blockage preventing apparatus comprising:
a screen rotatably supported with respect to a front end edge of the lower opening and moving between a closed position at which the screen covers the lower opening and an open position shifted downward from the lower opening;
an urging member urging the screen to the closed position;
a first engagement portion moving together with the screen; and
a second engagement portion moving from a first position beyond a second position, wherein
when the second engagement portion moves from the first position to the second position, the second engagement is engaged with and presses the first engagement portion to move the screen from the closed position to the open position, and
when the second engagement portion moves beyond the second position, the first engagement portion is disengaged from the second engagement portion and the screen is returned from the open position back to the closed position by the urging member.
The blockage preventing apparatus may further comprise an open/close driving machine for moving the second engagement portion, and the second engagement portion may be set such that a movement region of the second engagement portion from the first position to the second position overlaps a movement region of the first engagement portion and the movement region of the second engagement portion beyond the second position is out of the movement region of the first engagement portion.
The open/close driving machine may include a piston moved forward and backward by oil pressure, and the second engagement portion may be provided at the piston.
When the vessel sails in a location where much floating matter, such as floating pieces or materials exist, there is a high possibility that the floating matter may cling to the screen. For this reason, the second engagement portion is appropriately moved from the first position toward the second position. Thereby, the second engagement portion is engaged with and presses the first engagement portion and the screen is moved from the closed position to the open position against the urging force of the urging member, thereby opening the lower opening. At this time, the screen opens. When the second engagement portion moves beyond the second position, the second engagement portion is disengaged from the first engagement portion so that the screen is momentarily moved to the closed position by the urging force of the urging member. When the second engagement portion is moved to the second position again after returned to the first position, the screen opens the lower opening again. In this way, the screen slowly opens the lower opening and then to quickly moves to the closed position.
Therefore, while the screen slowly moves to the open position, the floating matter, such as floating pieces or materials, clinging to the screen is driven out by water flow to thereby clean the screen. Since the screen quickly returns from the open position to the closed position, it is difficult for floating matter to flow into the suction port while the screen is moving to the open position. In addition, appropriate vibration and impact are applied to the screen by the quick return of the screen from the closed position to the open position. Thus, the effect of removing the floating matter clinging to the screen increases, thereby cleaning the screen more effectively. It is, therefore, possible to ensure eliminating the floating matter strongly clinging to the screen. Additionally, by repeating the opening/closing operation a plurality of times, the effect of cleaning the screen further improves.
A second aspect of the present invention is the blockage preventing apparatus according to the first aspect, further comprising open/close controlling means for intermittently actuating the open/close driving machine at predetermined time intervals.
The intervals at which the open/close control means actuate the open/close driving machine may be set according to the quantity of floating matter. The appropriate setting range is, preferably, not less than 10 seconds and not more than 120 seconds.
With the above constitution, since the screen is opened and closed at predetermined time intervals, the screen is cleaned before the quantity of the floating matters clinging to the screen becomes excessive. This facilitates removing the floating matter from the screen and enhances the effect of cleaning the screen.
A third aspect of the present invention is a blockage preventing apparatus according to the first aspect, further comprising:
rotating speed detecting means for detecting a rotating speed of the vane;
hull speed detecting means for detecting a speed of a hull; and
control means for estimating a design speed of the hull corresponding to the detected rotating speed of the vane and for actuating the open/close driving machine in accordance with a reduction rate of the hull speed with respect to the design speed.
With the above constitution, when the quantity of floating matter clinging to the screen increases and the hull speed is reduced, then the hydraulic cylinder is actuated in accordance with the reduction rate. It is, therefore, possible to clean the screen before the quantity of floating matter clinging to the screen becomes excessive. This facilitates removing the floating matter from the screen and thereby enhances the cleaning effect for the screen.
The fourth aspect of the present in
Howard & Howard
Ishigaki Company Limited
Swinehart Ed
LandOfFree
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