Marine propulsion – Jet drive – Direction control for fluid jet
Reexamination Certificate
1999-12-22
2001-02-06
Sotelo, Jesus D. (Department: 3617)
Marine propulsion
Jet drive
Direction control for fluid jet
C440S038000
Reexamination Certificate
active
06183318
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a reverser for a watercraft which allows the watercraft to go astern.
2. Description of the Related Art
A watercraft which is propelled by a water jet pump, for example, a personal watercraft (which is also referred to as a “PWC”) has such a structure as to suck water (including sea water) through a water intake hole provided on the bottom of a hull, to pressurize the water by the water jet pump and to eject the water rearward from the hull through an outlet port of the water jet pump, thereby advancing the PWC.
To go in reverse, a deflector liftably (movably) provided behind the steering nozzle is positioned in a portion behind the steering nozzle (brought down), thereby changing the direction of the water flow ejected rearward from the steering nozzle into a forward direction. Thus, the watercraft can go in reverse.
As described in Japanese Utility Model Publication No. Hei 5-13677 (U.S. Pat. No. 4,708,671), a reverser for a watercraft according to the prior art comprises a deflector having a lower end which can be positioned below the bottom in a reverse state and having a semibowl-shaped inner face. By the shape of the inner face and the position of the lower end of the deflector, the direction of the water flow discharged rearward from the pump nozzle is changed such that the water flow is ejected forward in a region under the bottom.
With such a structure, if the reverser is to function effectively, it is necessary that the water flow should be smoothly ejected forward from the lower end of the deflector along the bottom face of a rear end of the watercraft body which is hollowed out slightly upward.
However, the bottom face of the rear end of the body is significant in enhancing planing performance when the watercraft is going forward. It is desirable that this portion should form a rectilinear bottom face as continuously as possible from a forward region thereof.
SUMMARY OF THE INVENTION
In consideration of the forgoing circumstances, it is an object of the invention to provide a reverser for a watercraft which has a high reverse efficiency and can function as a side thruster and additionally has high planing performance.
A first aspect of the invention is directed to a reverser for a watercraft in which a deflector is movably provided behind a pump nozzle of a water jet pump to change the direction of water flow ejected rearward from the pump nozzle, thereby moving the watercraft rearward, wherein a discharge port opened in a transverse direction is provided on both side portions of the deflector, thereby feeding the water flow from the discharge ports along a transom of the body of the watercraft.
According to the reverser for a watercraft of the invention which has the above-mentioned structure, the water positioned adjacent to a transom portion of the body flows toward the side end of the body along the transom of the body by the water flow ejected from the discharge port. By the movement of the water, the water pressure is lowered in a region behind the body (behind the transom). Consequently, the body can move sternway. More specifically, while the conventional reverser positively discharges the water forward to move the body rearward, the reverser according to the invention moves the water positioned behind the body toward the side end of the body to form a portion having a low water pressure, thereby moving the body rearward. According to the invention, it is possible to provide a reverser having a good rearward moving efficiency while maintaining planing performance.
In the reverser for a watercraft, if an inner face of the deflector includes a wall portion vertically extended in the center thereof, and a deflecting curved face is provided on both sides of the wall portion for deflecting the water flow ejected rearward into a transverse direction, it is possible to obtain an excellent structure in that the water flow is directed smoothly and uniformly toward both sides in reverse.
Furthermore, the reverser is provided with steering means such as a steering nozzle for being swung to the right and left sides which will be described below. Consequently, left side or right side steering of the watercraft can effectively be performed while going in reverse.
In the reverser for a watercraft, furthermore, if a guide face for smoothly leading the water flow to the discharge port is formed on the inner face of the deflector from the deflecting curved face toward the discharge port turned in the transverse direction, the water flow can smoothly be directed from the wall portion to the discharge port.
In the reverser for a watercraft, moreover, if the discharge port is turned toward a transom side of the body at an angle of about 5 to about 30 degrees as seen in a plane view, it is possible to obtain an effective structure for forming water flow along the transom.
In the reverser for a watercraft, furthermore, if a lower end of the deflector has a partially circular shape as seen from a side and the discharge port is provided in a position from middle portions of both side portions of the deflector toward the lower end thereof, the water flow discharged from the discharge port is pressed downward by the upper water and is discharged (ejected) toward the side (in a transverse direction) because the discharge port fully sinks into the water. Therefore, the discharged energy is not directed toward the water surface but effectively flows along the transom.
In the reverser for a watercraft, moreover, if a fairing fin horizontally extended in reverse state is projected onto the inner face of the deflector, the water flow ejected from the steering nozzle is prevented from being deflected into a vertical direction and is smoothly directed toward a discharge port side:
In the reverser for a watercraft, furthermore, if a steering nozzle capable of being moved in a transverse direction is provided between the pump nozzle of the water jet pump and the deflector, an optional amount of the water flow can be discharged from an optional discharge port provided on both sides of the deflector, thereby performing steering while in reverse. In addition, the reverser can also be caused to function as a side thruster.
In the reverser for a watercraft, moreover, if both comer portions of a rear end of the watercraft provided with the deflector are round-shaped as seen in a plane view, the water flow fed toward the side along the transom can positively form a water flow to be fed from the transom to the forward portion of the body along side face of the body. Consequently, a reverser having high reverse efficiency is obtained.
These objects as well as other objects, features and advantages of the present invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings.
REFERENCES:
patent: 5752864 (1998-05-01), Jones et al.
patent: 5934954 (1999-08-01), Schott et al.
Japanese Publication Number JP HEI 1-273785 Dated Nov. 1, 1989, Patent Abstracts of Japan.
Japanese Publication Number JP UM HEI 5-13677 Dated Dec. 4, 1993.
Ikeyama Masafumi
Kanazawa Tomohiro
Nakagawa Kenichi
Tsumiyama Yoshinori
Kawasaki Jukogyo Kaisha
Sotelo Jesus D.
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