Marine propulsion – Inboard engine mount
Reexamination Certificate
2003-01-09
2004-05-25
Basinger, Sherman (Department: 3617)
Marine propulsion
Inboard engine mount
C440S112000, C440S083000
Reexamination Certificate
active
06739923
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an engine alignment jig assembly for positioning the output shaft of an engine to a correct position when the engine is installed in the hull of a small watercraft, and a method of positioning the engine using such engine alignment jig assembly.
BACKGROUND OF THE INVENTION
Various types of planing watercrafts are known. One such known planing watercraft is a jet propulsion watercraft, in which a jet pump installed in a rear part of a hull is driven by an engine to rotate an impeller thereof so that water is pumped up from the bottom of the hull and a pressurized stream of water is ejected backward of the hull to thereby propel the watercraft. Since the impeller of the jet pump is designed to rotate at high speeds within the stator, the stator needs to be correctly positioned with respect to the impeller.
Japanese Patent Laid-open Publication No. 2000-62688 (JP 2000-62688 A) discloses a jet propulsion unit mounting structure of a small boat, in which for correct positioning of a stator relative to an impeller, a vertical positioning first claw and a horizontal positioning second claw are provided on a hull of the boat so that they are in abutment with a first stopper portion and a second stopper portion, respectively, of a stator thereby to position the stator in both vertical and horizontal directions.
Additional to the positioning of the stator relative to the impeller, it is also important that a rotating shaft of the impeller is aligned with the output shaft of an engine to secure transmission of power from the engine to the impeller. To this end, when the engine is installed in the hull, the output shaft of the engine is aligned with the rotating shaft of the impeller. A conventional engine output-shaft alignment operation will be described with reference to FIG.
25
.
As shown in
FIG. 25
, a small planing watercraft includes an engine
152
installed in a hull
150
of the watercraft via four engine mounts
151
(two being shown). The engine mounts
150
are attached to the hull
150
. The engine
152
has an output shaft
153
connected via a coupling assembly
154
a
,
154
b
to a drive axle or shaft
155
. The drive shaft
155
has a rear end spline-connected to a rotating shaft
157
of an impeller
156
. Rotation of the engine output shaft
153
can thus be transmitted to the impeller
156
. To secure smooth connection of the engine output shaft
153
and the impeller rotating shaft
157
via the drive shaft
155
, the engine output shaft
153
must be aligned with the rotating shaft
157
of the impeller
156
.
To this end, in the process of installing the engine
152
in the hull
150
, the impeller
156
is assembled within a stator
158
, and the drive shaft
155
is spline-connected to the rotating shaft
157
of the impeller
156
. Then, the engine
152
while being lifted by a crane (not shown) is moved up and down, left and right or forward and backward until the output shaft
153
of the engine
152
is correctly aligned with the drive shaft
155
During that time, in order to secure correct alignment between the engine output shaft
153
and the drive shaft
155
, a fine positional adjustment of the engine
152
is needed wherein the engine
152
is moved bit by bit in almost all directions. At the same time, the engine
152
must be also positioned relative to the engine mounts
151
. However, since the engine
152
is a heavy component, the foregoing engine positioning operation requires a dexterous crane work, which will impose a great burden on the operator. Thus, the conventional engine installation work requires a relatively long time, and the productivity of the small planing watercraft is relatively low.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide an engine alignment jig assembly for a small watercraft, which enables the operator to position an engine correctly in a relatively short time without requiring dexterity, thereby reducing the necessary engine installation time.
Another object of the present invention is to provide a method of positioning an engine using such jig assembly.
According to a first aspect of the present invention, there is provided an engine alignment jig assembly used for installing an engine in a hull of a small watercraft via four engine mounts in such a manner that an output shaft of the engine is in alignment with a rotating shaft of a propulsion unit of the watercraft. The engine alignment jig assembly comprises an engine positioning jig for positioning the engine mounts relative to the rotating shaft of the propulsion unit, the engine positioning jig including an engine lower part dummy constructed to resemble a lower half of the engine. The engine lower part dummy includes a generally rectangular skeleton frame having substantially the same size in plan view as the lower half of the engine, four screws each provided at a respective corner of the rectangular skeleton frame and adapted to be threaded in a corresponding one of the engine mounts to attach the engine lower part dummy to the engine mounts, wherein two adjacent ones of the screws that are disposed on a bow side of the watercraft form left and right front screws, and the remaining two screws that are disposed on a stern side of the watercraft opposite the bow side form left and right rear screws, a front through-hole formed in the skeleton frame with a center thereof disposed between the left and right front screws and aligned with an axis of the rotating shaft of the propulsion unit, and a rear through-hole formed in the skeleton frame with a center thereof disposed between the left and right rear screws and aligned with the axis of the rotating shaft of the propulsion unit.
Since the engine lower part dummy is much smaller in weight than a real engine, so that positioning of the engine mounts can be achieved easily in a relatively short time without requiring a dexterous crane work. A subsequent engine mount work does not require adjustment of the position between the engine and the engine mounts, so that the watercraft can be manufactured with improved productivity and at a relatively low cost.
Preferably, the engine positioning jig further includes a centering shaft adapted to be inserted through the front and rear through-holes of the engine lower part dummy while assuming a position of the rotating shaft of the propulsion unit, so as to position the engine mounts with respect to a vertical direction, a widthwise direction and a lengthwise direction of the watercraft through displacements of the engine lower part dummy in the respective directions relative to the centering shaft.
In one preferred form of the invention, the front through-hole of the engine lower part dummy has an inside diameter smaller than an inside diameter of the rear through-hole, the centering shaft includes a first portion and a second portion coaxial with each other and adapted to be simultaneously received in the front and rear through-holes, respectively, such that a loose fit is formed between each of the through-holes and a corresponding one of the shaft portions, and the engine positioning jig further includes means for determining an offset in the vertical direction of the center of each through-hole from an axis of the corresponding shaft portion. The means for determining an offset comprises a gauge block having a series of steps formed on one side thereof and adapted to be inserted between each through-hole and the corresponding shaft portion. The skeleton frame may have a groove extending radially outward in a vertical direction from each of the front and rear through-holes for receiving part of the gauge block. Alternatively, the means for determining an offset may comprise an ultrasonic depth indicator provided on the skeleton frame adjacent each of the front and rear through-holes for measuring a vertical thickness of a clearance between each through-hole and the corresponding shaft portion.
The centering shaft may further include a third portion and a fourth portion
Basinger Sherman
Honda Giken Kogyo Kabushiki Kaisha
Rankin, Hill Porter & Clark LLP
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