Marine propulsion – Jet drive
Reexamination Certificate
1999-10-14
2001-05-22
Basinger, Sherman (Department: 3617)
Marine propulsion
Jet drive
C416S24400R, C416S24500R, C440S049000
Reexamination Certificate
active
06234852
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an impeller for a water jet pump of a watercraft, and more particularly to an attaching structure of a pump shaft side of the impeller and a propeller shaft side thereof.
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”) is configured to suck water (including sea water) through a water intake hole provided on a bottom of a hull. The water jet pump pressurizes the water and ejects the water rearward from the hull through an outlet port of the water jet pump, thereby advancing the PWC.
The water jet pump structure includes an impeller, which is rotatably provided in a pump casing, the inner periphery of which is circular-shaped. The impeller has a base portion shaped rather like a cone with its tip cut off (a frustum of a cone), that is, a “bullet shape,” with blades provided on the outer periphery of the base portion. That is to say, the outer shape of the base portion is smaller on a tip side (upstream, or propeller shaft, side) and gradually becomes larger toward a more rearward portion. The blades (fins) are projected with a pitch angle to forcibly discharge water rearward on an outer peripheral portion of the base portion.
The tip portion of the base of the impeller is connected to a rear end of the propeller shaft on the engine (upstream) side so as to be rotated integrally with the propeller shaft. A rear (downstream) end of the impeller is connected to a tip portion of a pump shaft, so as to be rotated with the propeller shaft and the pump shaft.
The water sucking (front, or upstream) side of the water jet pump is connected to a water sucking (intake) passage having a water intake formed on the bottom of the hull. A pump nozzle, incorporating an outlet port of the water jet pump, has a cross-sectional area gradually reduced rearward. Consequently, water pressurized by the impeller is discharged at a high speed through the outlet port of the pump nozzle positioned at the rear end of the watercraft. Thus, the watercraft can advance by means of a water jet reaction force.
The portion of the impeller connecting to the propeller shaft comprises a spline hole formed in the tip portion of the impeller, and accommodates spline teeth formed on a rear-end portion of the propeller shaft such that the propeller shaft can be spline-connected to the spline hole. A connecting portion of the impeller to the pump shaft comprises a female screw-threaded hole formed in a rear end portion of the impeller. A male screw-threaded portion provided on a tip portion of the pump shaft is provided such that it can be screwed to the female screw hole.
In the prior art, the following techniques, described with reference to
FIGS. 5 and 6
, are known for providing connecting portions of the propeller shaft (upstream) side, and the pump shaft (downstream) side of an impeller.
More specifically, an impeller
1
shown in
FIG. 5
which has been described in Japanese Utility Model No. 2513811, has a spline hole
1
b
and a female screw hole
1
d
provided on an impeller
1
itself, respectively. The spline hole
1
b
is provided by forming spline grooves one by one at predetermined intervals on the inner peripheral face of a prepared hole that is drilled before, by using a machine tool which is referred to as a “slotter.” The female screw hole
1
d
is provided by forming a female screw
1
m
on the inner peripheral face of a prepared hole that is drilled, by using a machine tool which is referred to as a “tapper” or the like. An impeller manufactured by such a technique requires considerable working time. A special jig having a complicated shape, or the like, for setting (holding) is required. Consequently, the manufacturing cost of an impeller has increased.
With a structure such as is shown in
FIG. 6
, a spline hole
1
b
is formed beforehand in a cylindrical member
1
Y by using a “broaching machine”. A fitting hole
1
y
for fitting the cylindrical member
1
Y therein is formed on the tip side portion of the impeller
1
and a prepared hole for a female screw is formed in the rear end of the impeller. A female screw-thread
1
m
is applied to the prepared hole for forming the female screw by means of the “tapper”, and the cylindrical member
1
Y is then fitted in the fitting hole
1
y
on the tip side portion of the impeller
1
.
The impeller manufactured by such a technique is made with greater working efficiency than the impeller shown in FIG.
5
. However, an outside diameter d
1
of the tip portion of the impeller is increased, so that the pump efficiency of the impeller is reduced.
SUMMARY OF THE INVENTION
In consideration of the foregoing circumstances it is an object of the invention to provide an impeller for a water jet pump of a watercraft having a structure such that the pump has a high efficiency, and also so that manufacturing work can be performed easily, and the manufacturing cost can be reduced.
A first aspect of the invention is directed to an impeller for a water jet pump of a watercraft, having a tip portion configured to be affixed to a propeller shaft extending from the engine to a water jet pump upstream side, for rotating integrally with the propeller shaft, and a rear end portion configured to be fixed to a pump shaft rotatable in a pump casing, comprising:
splines disposed in a spline hole formed in a tip portion of the impeller, configured for being coupled to a spline shaft portion of the propeller shaft;
structure defining a fitting hole formed in a rear end portion of the impeller, configured for fitting a cylindrical member therein; and
a cylindrical member having an outer periphery, configured to be fitted into the fitting hole, defining a female screw thread on an inner peripheral face, configured for coupling to the pump shaft.
In a more detailed aspect in accordance with the impeller for a water jet pump of a watercraft having such a structure, a prepared hole for forming the spline hole is provided in the tip portion of the impeller and the fitting hole for fitting the cylindrical member therein. The spline hole is directly formed in the impeller itself. Therefore, the outside diameter of the tip portion of the impeller can be reduced, and a high pump efficiency obtained. The spline hole can be formed in the prepared hole easily and efficiently in a short amount of time by means of a broaching machine.
In the impeller for the water jet pump, it is preferable that the fitting hole is provided concentrically (coaxially) with the spline hole, and that the fitting hole and the spline hole communicate with each other. The fitting hole has a larger diameter than that of the spline hole, so that an inner peripheral wall of the fitting hole is positioned on an outer periphery of the spline hole in a portion where these holes communicate. In accordance with this configuration, a structure suitable for forming the spline hole by broaching is obtained.
In another more detailed aspect, in an impeller for the water jet pump in accordance with principles of the invention, furthermore, it is preferable that a buffer member configured for elastically abutting against an end (a rear end) of the propeller shaft is provided between the spline hole and the fitting hole. According to this structure, axial positioning (setting) for coupling of a crankshaft of an engine and the propeller shaft can be performed accurately and elastically.
In a further more detailed aspect, in the impeller for the water jet pump, moreover, it is preferable that provision be made for a connecting (transitioning) grommet for connecting (transitioning) an outer peripheral face surface of the propeller shaft to an outer peripheral face surface on a tip of the impeller to form a continuous face at the tip (upstream) end of the impeller. In accordance with this structure, it is possible to obtain a preferable structure with functions to cause water to smoothly flow in the water jet pump, and to enhance the pump efficiency.
T
Basinger Sherman
Kawasaki Jukogyo Kabushiki Kaisha
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