Note: Descriptions are shown in the official language in which they were submitted.
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HYDRAULIC STEERING APPARATUS FOR AN OUTBOARD ENGINE
FIELD OF THE INVENTION
The present invention relates to a hydraulic steering apparatus for the
outboard engine mainly of a small vessel such as a fishing boat, a motorboat
or
a yacht. The engine is supported by a swivel bracket and can turn right and
left on a steering axis. The steering apparatus is fixed to the swivel
bracket.
The swivel bracket is supported tiltably on a horizontal tilt axis by one or
more
clamp brackets, which are fixed to the transom of the stern of the vessel. In
particular, the invention relates to a structure for mounting the steering
apparatus.
BACKGROUND OF THE INVENTION
In general, an outboard engine of this type is supported by a swivel
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bracket and can be turned right and left on a roughly vertical steering axis
to
steer the vessel. The swivel bracket is positioned between a pair of clamp
brackets. It is possible to steer the vessel by turning the steering wheel of
a
steering apparatus, which includes either a mechanical device or a hydraulic
device of the cantilever type or both-end support type.
The mechanical device has a push-pull cable, which includes an outer
cable and an inner cable. The outer cable is connected to one end of a guide
tube, which extends along a horizontal tilting axis through the clamp and
swivel
brackets. The inner cable extends through the guide tube, protrudes from its
other end is connected through a link to a steering lever, which is fixed to
the
engine housing. Because the pushing force and pulling force transmitted by
the inner cable are limited, the mechanical device is used for an outboard
engine having relatively low horsepower.
The hydraulic device of the cantilever type has a hydraulic cylinder and
a horizontal piston rod. One end of the hydraulic cylinder is fitted to one
end of
a guide tube, which extends along a horizontal tilting axis through the clamp
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and swivel brackets. One end of the piston rod is connected through a link to
a
steering lever, which is fixed to the engine housing. Because the moment
exerted on the link is limited, this hydraulic device as well is used for an
outboard engine having relatively low horsepower.
As stated above, a push-pull cable is connected to only one end of the
guide tube, or one end of a hydraulic cylinder is fixed to only one end of the
tube. This causes no inconvenience because the thread of one end of the
guide tube is standardized in outer diameter.
The hydraulic device of the both-end support type is used for an
outboard engine having high horsepower. This hydraulic device as well has a
hydraulic cylinder and a horizontal piston rod. Both ends of the piston rod
are
supported by a pair of arms, which is fitted to a guide tube. The guide tube
extends along a horizontal tilting axis through the clamp and swivel brackets.
The hydraulic cylinder slides along the piston rod to steer the vessel.
Against such a background, the outboard engines made by different
makers are so standardized that one end (generally the starboard end) of each
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guide tube has an external thread that is 7I8 inch in outer diameter. Each
maker sets its own outer diameter of the external thread of other end, which
may be 7/8 inch or 20 mm.
One end of the guide tube is fitted with a cylindrical nut fit for the 7/8
inch thread. The cylindrical nut makes it possible to fit the push-pull cable
or
the hydraulic cylinder of the cantilever device smoothly to this end of the
guide
tube.
One arm of the hydraulic device of the both-end support type is fitted
to one end of the guide tube by fittings including a cylindrical nut fit for
the 7/8
inch thread. However, before the other arm is fitted to the other end of the
guide tube, it is necessary to buy fittings fit for this tube. It is
inconvenient and
may take a long time to buy the fittings. Even if fittings are bought, they
may
not be fit for the guide tube.
Fig. 7 of the accompanying drawings shows a steering apparatus
including a hydraulic device of the both-end support type. This hydraulic
device has a horizontal hydraulic cylinder 26, through which a piston rod 25
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slides. Each end of the piston rod 25 is supported by the front end of an arm
23, the rear end of which is supported turnably by one end of a guide tube 48.
The guide tube 48 extends along a horizontal tilting axis through a pair of
clamp
brackets 42 and a swivel bracket 41. The clamp brackets 42 are fixed to the
hull (stern) of a boat. The swivel bracket 41 is positioned between the clamp
brackets 42 and has a central recess 43 formed in its front end. The hydraulic
cylinder 26 is connected through a steering link 47 to the front end of a
steering
lever 46, which is fixed to the housing of an outboard engine 40.
The guide tube 48 has external threads 48a and 48b cut in both its
ends, which engage with cylindrical nuts 31. Each cylindrical nut 31 includes
a
sleeve 32. Each arm 23 has a bearing hole 23a cut through its rear end,
through which the associated sleeve 32 extends so that the arms 23 can pivot
on the tilting axis. A nut 34 engages with the outer end of each sleeve 32.
A similar steering apparatus is disclosed in Japanese unexamined
patent publication No. 2002-331997 (paragraphs 0017 - 0019 and Figs. 1 - 3).
As stated above, an arm is fitted to each end of the guide tube. In
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this case, each of the makers of outboard engines sets its own outer diameter
of the thread of one end of the guide tube. This makes it necessary to order
exclusive fittings after knowing the maker of the outboard engine for which
the
steering apparatus is to be used. It may take a long time to buy the fittings,
and wrong fittings may be bought.
The arms extend from the guide tube on the tilting axis backward and
toward the hull. The rear ends of the arms support the piston rod, which
supports the hydraulic cylinder. As a result, great moments are exerted on the
arms. For this reason, the arms and other parts need to have high strength.
This makes the steering apparatus complex in structure and heavy.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a hydraulic steering
apparatus that is simple in structure, compact, small and light, that can be
produced at a low cost, and that includes a piston rod supported by a frame
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which can be fixed directly to the swivel bracket of an outboard engine of any
type, and on which a low load is exerted.
According to the present invention, a hydraulic steering apparatus is
provided for a vessel having an outboard engine supported by the stern of the
vessel hull. A pair of clamp brackets is fixed to the stern. A swivel bracket
is
positioned between the clamp brackets and supported by them tiltably on a
tilting axis, which extends horizontally across the vessel. The outboard
engine
is supported by the swivel bracket turnably on a steering axis, which is
perpendicular to the tilting axis. The steering apparatus has a substantially
bow-shaped horizontal frame, which includes a middle portion and a pair of end
portions bent forward. The middle portion has bolt holes cut through it. Bolts
extend through the bolt holes and engage with the front end of the swivel
bracket to fix the frame to this end. The end portions support a piston rod,
which extends in parallel with the tilting axis. The piston rod supports a
hydraulic cylinder, which can slide along it. A steering lever is fixed to the
outboard engine and has a front end, which can move around the steering axis
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to turn the engine on this axis. The front end of the steering lever is linked
to
the hydraulic cylinder by a steering link.
The middle portion of the frame can be fixed directly to the swivel
bracket of the outboard engine by the bolts. This makes it easy to fit the
steering apparatus to the swivel bracket and shortens the end portions of the
frame so that the frame is loaded lower.
The bolt holes of the frame may be adapted for the swivel brackets of
outboard engines made by different makers. This makes it possible to fit the
frame to any one of the different engines, so that the frame can be used
widely.
While the hydraulic cylinder slides along the piston rod, the angle
between the steering lever and link changes.
The swivel bracket may include a pair of side portions formed at its
front end, which define a recess between them. A guide plate may be fitted in
the recess. The guide plate includes a pair of end portions bent at right
angles.
These end portions engage with the inner sides of the side portions of the
swivel bracket. The guide plate has a tapped hole cut in its middle. The
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frame further has a middle bolt hole cut through its middle. A bolt extends
through the middle bolt hole of the frame, engages with the tapped hole of the
guide plate and is tightened.
When the hydraulic cylinder slides, shearing forces are exerted on the
bolts fixing the frame to the swivel bracket. The shearing forces are reduced
greatly by the guide plate, so that the bolts are not liable to bend or break
even
if the apparatus is used for a long time.
The middle portion of the frame may have a pair of projections formed
on its rear side and spaced from each other. The middle portion may have a
pair of inner bolt holes cut through it. Each of the projections has an outer
sloping side and an inner sloping side. The steering apparatus may be fitted
with a pair of nuts, each of which has a flat side in contact with the inner
side of
one of the side portions of the swivel bracket and an inclined side in contact
with the outer sloping side of one of the projections. Each of the nuts
further
has a tapped hole cut in it. Bolts extend through the inner bolt holes of the
frame, engage with the tapped holes of the nuts and are tightened.
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As is the case with the guide plate, the projections of the frame greatly
reduce the shearing forces exerted on the bolts fixing the frame to the swivel
bracket.
Each of the end portions of the frame may have an end hole cut
through it, which has a hemispherical surface. The piston rod extends through
the end holes of the frame. The piston rod may have a pair of screw stocks
each extending from its one end. Each of the screw stocks protrudes outward
from the adjacent end hole. A nut engages with one of the screw stocks and is
tightened. A washer is interposed between the nut and the adjacent end
portion of the frame. The washer has a hemispherical surface in contact with
the hemispherical surface of the adjacent end hole of the frame.
When the frame is fitted to the swivel bracket of the outboard engine,
the frame may be distorted. Even if the frame is distorted, the hemispherical
washer (spherical nut) absorbs the distortion of the piston rod, which is
supported by the end portions of the frame. Accordingly, the piston rod is not
liable to be distorted. This enables the hydraulic cylinder to slide smoothly
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along the piston rod.
The steering apparatus achieves the following outstanding effects.
The steering apparatus is easy to fit. The frame is not liable to be
high loaded. The bolt holes of the frame may be adapted for the swivel
brackets of outboard engines made by different makers. This makes it
possible to fit the frame to any one of the different engines. The steering
apparatus is simple in structure, durable and small in size, and can be
produced
at a low cost.
The frame can be fixed to the swivel bracket of any one of the
outboard engines of different makers easily and securely by bolts.
The frame can be fixed in a very short time as compared with the
conventional case where the user orders fittings after knowing the maker or
type of the outboard engine for which the steering apparatus is to be used.
The maker of the steering apparatus does not need to provide different
types of fittings. This prevents purchase of wrong fittings, makes it possible
to
efficiently fix the frame etc., and reduces costs.
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BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention are shown in the
accompanying drawings, in which:
Fig. 1 is top plan of a hydraulic steering apparatus embodying the
present invention;
Fig. 2a is an enlarged top plan of part of Fig. 1; Fig. 2b is an enlarged
front view of a middle portion of the arm of the hydraulic steering apparatus;
Fig. 3 is a side view of the hydraulic steering apparatus as seen in
direction A in Fig. 1;
Fig. 4 is a perspective view of the hydraulic steering apparatus as fixed
to the swivel bracket of an outboard engine;
Fig. 5 is an enlarged sectional view of end portions of the arm and the
piston rod of the hydraulic steering apparatus, showing how they are
connected;
Figs. 6a and 6b are views similar to Figs. 2a and 2b, respectively, but
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showing another hydraulic steering apparatus embodying the present invention;
Fig. 7 is a top plan of a conventional hydraulic steering apparatus.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to Figs. 3 and 4, a pair of clamp brackets 42 is fixed to
the transom 50 of the stern of a boat. A swivel bracket 41 is positioned
between the clamp brackets 42, which so support its front end that the swivel
bracket 41 can tilt on a horizontal tilting axis t parallel with the transom
50. The
swivel bracket 41 so supports an outboard engine 40 that the engine can turn
right and left on a steering axis s.
With reference to Figs. 1 and 2a, the swivel bracket 41 has a central
U-shaped recess 43 formed through a front portion of it. Both sides of the
recess 43 are defined by a pair of side portions 41a of the swivel bracket 41.
Each side portion 41a has two tapped holes 44 cut in its front end, one of
which
is positioned over the other. Each side portion 41 a also has a grease hole 45
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cut in its front end and on the outer side of the tapped holes 44. The recess
43
might be shallower as shown in Fig. 7.
A hydraulic steering apparatus 1 embodying the present invention has
a roughly bow-shaped frame 2, which may be either a die-cast molding or a
press molding that is a bent metal plate having a constant width. The frame 2
has a pair of end portions 2a bent forward at right angles. The front ends of
the end portions 2a support a piston rod 3, which is parallel with the tilting
axis t.
As shown in Fig. 5, the front end of each end portion 2a of the frame 2
has a cylindrical hole 2b cut on its inner side and a hemispherical hole 2c
cut on
its outer side. The holes 2b and 2c communicate with each other. Each end
3a of the piston rod 3 is positioned in one of the cylindrical holes 2b, with
clearance allowed between the rod 3 and frame 2. The piston rod 3 has a pair
of screw stocks 3b extending from its ends 3a and having a slightly smaller
diameter. A washer 4 has a hemispherical surface and a central bore 4a.
The hemispherical surface is in engagement with the hemispherical hole 2c of
each end portion 2a of the frame 2. Each screw stock 3b extends through the
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associated washer bore 4a. A nut 4b is in engagement with each screw stock
3b and tightened to fix the piston rod 3 to the frame 2. Under this condition,
the piston rod 3 is supported without being deformed by torsion or other
slight
deformation of the frame 2. Torsion or deformation of the piston rod 3 is
prevented even if the frame 2 is deformed by a great external force exerted on
the outboard engine 40 or swivel bracket 41 while the boat is running.
The piston rod 3 extends through a hydraulic cylinder 5, which can
slide along it. The hydraulic cylinder 5 has inlet/outlet ports (not shown)
formed in both its ends. A helm pump (not shown) pumps hydraulic oil from a
hydraulic tank through a hydraulic hose to one of the inlet/outlet ports, and
back
from the other port through another hydraulic hose into the tank. This moves
the hydraulic cylinder 5 in one direction along the piston rod 3. In general,
the
helm pump is operated when the steering wheel (not shown) of the boat is
turned.
The frame 2 includes a middle portion 2A recessed or offset backward.
As best shown in Fig. 2b, the middle portion 2A has three pairs of bolt holes
2B
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cut through it. One pair of bolt holes 2B is positioned in the middle of the
middle portion 2A, and the other pairs are on both its sides. One of the bolt
holes 2B of each pair is positioned over the other hole. Bolts 11 extend
through the outer pairs of bolt holes 2B and engage with the tapped holes 44
of
the swivel bracket 41 to fix the frame 2 to the front end of this bracket.
The middle portion 2A of the frame 2 also has two slightly larger holes
2C cut through it on the outer sides of the outer pairs of bolt holes 2B.
Grease
can be applied through these holes 2C.
The middle pair of bolt holes 2B of the frame 2 is used to fix a guide
plate 6 as an anti-shearing member to the frame 2. The guide plate 6 has a
pair of end portions 6a bent backward at right angles and a middle portion 6b
recessed gently backward. The middle portion 6b has two tapped holes 6c cut
through its middle. One of the tapped holes 6c is positioned over the other.
The guide plate 6 is positioned in the recess 43 of the swivel bracket 41,
with its
end portions 6a in contact with the inner sides 43a of the side portions 41 a
of
this bracket. Bolts 12 extend through the middle pair of bolt holes 2B and
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engage with the tapped holes 6c. The bolts 12 are tightened to force the
recessed portion 6b of the guide plate 6 toward the frame 2, thereby bringing
the end portions 6a of this plate into compressive contact with the side
portions
41 a of the swivel bracket 41.
Thus, the steering apparatus 1 is fixed to the front end of the swivel
bracket 41 of the outboard engine 40.
The outboard engine 40 is fitted with a steering lever 46, the rear end
of which is fixed to its bottom. The steering lever 46 has a tapped hole 46a
cut
through its front end. A steering link 7 has a bolt hole 7c cut through its
one
end. A bolt 9 extends loosely through the bolt hole 7c and engages with the
tapped hole 46a so that the steering link 7 can pivot on an axis parallel with
the
steering axis s. The steering link 7 also has a pin 7a extending downward from
its other end and in parallel with the steering axis s. The hydraulic cylinder
5
has a pin hole 5a cut through it near its one end. The link pin 7a extends
loosely through the pin hole 5a and has a thread 7b cut at its bottom. A nut 8
engages with the pin thread 7b.
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Fig. 1 shows the hydraulic cylinder 5 as being in its neutral position,
where the link pin 7a is at point b.
With the hydraulic cylinder 5 in its neutral position, when the steering
wheel is turned counterclockwise, hydraulic oil is supplied to the left (right
in Fig.
1 ) inlet/outlet port of the cylinder. This slides the hydraulic cylinder 5 to
the
right (left in Fig. 1) along the piston rod 3, moving the link pin 7a from
point b
toward point a. Consequently, the steering lever 46 turns clockwise with the
outboard engine 40, so that the angle between the lever and the steering link
7
approaches 180 degrees. As a result, the boat steers to the left.
With the hydraulic cylinder 5 in its neutral position, when the steering
wheel is turned clockwise, hydraulic oil is supplied to the right (left in
Fig. 1 )
inlet/outlet port of the cylinder. This slides the hydraulic cylinder 5 to the
left
(right in Fig. 1 ) along the piston rod 3, moving the link pin 7a from point b
toward
point c. Consequently, the steering lever 46 turns counterclockwise with the
outboard engine 40, so that the angle between the lever and the steering link
7
approaches 90 degrees. As a result, the boat steers to the right.
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When the hydraulic cylinder 5 slides along the piston rod 3, shearing
forces are exerted mainly on portions of the frame 2 that surround the outer
bolts 11. Whichever direction the hydraulic cylinder 5 slides in, the shearing
forces are resisted by the guide plate 6, which is fixed to the middle portion
2A
of the frame 2 and in compressive contact with the inner sides 43a of the side
portions 41a of the swivel bracket 41. Consequently, little shearing force is
exerted on the bolts 11 and 12. The moment exerted on the six bolts 11 and
12 is dispersed by them. The moment exerted on the frame 2 is small
because the frame is fixed directly to the front end of the swivel bracket 41,
and
because, as shown in Fig. 3, the distance L between this bracket end and the
front ends of the frame end portions 2a, which support the piston rod 3 and
hydraulic cylinder 5, is short.
Figs. 6a and 6b show another hydraulic steering apparatus 1'
embodying the present invention. The steering apparatus 1' has a frame 2',
which is bolted to the front end of a swivel bracket 41 identical with that
shown
in Figs. 1, 2a, 3 and 4. The frame 2' includes a middle portion 2A recessed or
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offset backward.
The middle portion 2A of the frame 2' has a pair of projections 13
formed on its rear side. Each projection 13 is spaced inward from the inner
side 43a of the adjacent side portion 41 a of the swivel bracket 41. Each
projection 13 has an outer side 13a and an inner side 13b, which slope at
angles of about 30 and 45 degrees, respectively, to the inner sides 43a of the
bracket portions 41 a. The middle portion 2A also has two pairs of bolt holes
2B cut through it. One of the bolt holes 2B of each pair is positioned over
the
other hole. The middle portion 2A further has two pairs of bolt holes 2D cut
through it. Each pair of bolt holes 2D is positioned on the inner side of one
pair
of bolt holes 2B. One of the bolt holes 2D of each pair is positioned over the
other hole.
Bolts 11 extend through the bolt holes 2B and engage with the tapped
holes 44 of the swivel bracket 41.
The steering apparatus 1' has a pair of nuts 14 in place of the guide
plate 6. Each nut 14 has a flat side 14a for engaging with the inner side 43a
of
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one of the bracket portions 41 a and an inclined side 14b for engaging with
the
outer side 13a of one of the nuts 13. Each nut 14 also has two tapped holes
14c cut through it. Bolts 15 extend through the bolt holes 2D of the frame 2'
and engage with the tapped holes 14c of the nuts 14. The bolts 15 are
tightened to fix the frame 2' securely to the front end of the swivel bracket
41.
Thus, the steering apparatus 1' is fixed to the swivel bracket 41
without extending greatly from the front end of this bracket. This makes the
steering apparatus 1' compact.
With reference to Figs. 1 and 5, the piston rod 3 could be fixed to the
frame 2 only by the nuts 4b, without the washers 4 interposed. Alternatively,
a
spherical nut including a hemispherical washer might fix the piston rod 3 to
the
frame 2.
2l
