U.S. patent application number 10/842745 was filed with the patent office on 2004-11-18 for axle beam for industrial vehicle, method of manufacturing the same and rear steering apparatus.
Invention is credited to Katae, Kenichi.
Application Number | 20040227395 10/842745 |
Document ID | / |
Family ID | 33028385 |
Filed Date | 2004-11-18 |
United States Patent
Application |
20040227395 |
Kind Code |
A1 |
Katae, Kenichi |
November 18, 2004 |
Axle beam for industrial vehicle, method of manufacturing the same
and rear steering apparatus
Abstract
An axle beam for an industrial vehicle has a beam and a boss.
The beam is supported on a vehicle body. The boss is provided at
opposite ends of the beam for supporting a kingpin. The beam
includes at a longitudinally middle thereof a portion having a
closed cross-section perpendicular to a longitudinal direction of
the beam and is shaped at the portion to form a space which is
surrounded by a front and rear and a top and bottom of the beam.
The portion is formed by welding two members or by one tube
member.
Inventors: |
Katae, Kenichi; (Kariya-shi,
JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
3 WORLD FINANCIAL CENTER
NEW YORK
NY
10281-2101
US
|
Family ID: |
33028385 |
Appl. No.: |
10/842745 |
Filed: |
May 11, 2004 |
Current U.S.
Class: |
301/124.1 |
Current CPC
Class: |
B60B 35/08 20130101;
B60G 2200/322 20130101; B60G 17/005 20130101; B60G 9/02 20130101;
B60G 2206/32 20130101; B60G 2300/022 20130101; B60G 2206/30
20130101; B66F 9/07568 20130101; B60G 2204/129 20130101; B60G
2206/31 20130101 |
Class at
Publication: |
301/124.1 |
International
Class: |
B60B 035/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 15, 2003 |
JP |
2003-136916 |
Claims
What is claimed is:
1. An axle beam for an industrial vehicle comprising: a beam
supported on a vehicle body; and a boss provided at opposite ends
of the beam for supporting a kingpin, wherein the beam includes at
a longitudinally middle thereof a portion having a closed
cross-section perpendicular to a longitudinal direction of the beam
and is shaped at the portion to form a space which is surrounded by
a front and rear and a top and bottom of the beam, the portion
being formed by welding two members or by one tube member.
2. The axle beam according to claim 1, wherein the number of welded
portions that appear in the cross-section ranging from 0 to 2.
3. The axle beam according to claim 2, wherein the number of welded
portions is 0.
4. The axle beam according to claim 1, wherein the beam is tapered
at the opposite ends.
5. The axle beam according to claim 1, wherein the beam is formed
by fusing a tube material.
6. The axle beam according to claim 5, wherein the tube material is
seamless.
7. The axle beam according to claim 1, wherein the beam is at least
formed by two members welded to each other, whereby the space being
surrounded by the front and rear and the top and bottom of the
beam.
8. The axle beam according to claim 7, wherein one of the two
members has a U-shaped cross-section perpendicular to the
longitudinal direction of the beam.
9. The axle beam according to claim 7, wherein the two members each
have an L-shaped cross-section perpendicular to the longitudinal
direction of the beam.
10. A rear steering device for an industrial vehicle comprising the
axle beam as set forth in claim 1, further comprising: a cylinder
located in the space for power steering.
11. A method of manufacturing an axle beam for an industrial
vehicle having a beam and a boss, the beam including a tube portion
while being supported on a vehicle body, the boss being connected
to opposite ends of the beam in a longitudinal direction of the
beam for supporting a kingpin, comprising the steps of: fusing a
tube material to form the beam in a first manufacturing process;
and connecting the boss to the beam in a second manufacturing
process.
12. The method of manufacturing the axle beam according to claim
11, wherein the first manufacturing process includes: forming the
beam having the tube portion at a middle portion thereof in the
longitudinal direction; and shaping the opposite ends of the beam
thinner than the tube portion.
13. The method of manufacturing the axle beam according to claim
12, wherein the first manufacturing process includes: producing a
plurality of identical beams from one tube material; and
determining a cutting line in staggered arrangement of the
identical beams for fusing the tube material.
14. The method of manufacturing the axle beam according to claim
11, wherein the first manufacturing process includes fusing the
tube material by using a three dimensional plasma fusing apparatus
or a three dimensional laser fusing apparatus.
15. The method of manufacturing the axle beam according to claim
11, wherein the first manufacturing step includes utilizing the
tube material of a seamless type.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an axle beam in a wheel
suspension system for an industrial vehicle and a method of
manufacturing the same.
[0002] Conventionally, a rear axle beam for supporting rear wheels
in an industrial vehicle such as forklift truck is pivotally
connected to a vehicle frame for supporting a rear wheel for the
sake of traveling stability of the vehicle and comfort of riding.
For example, as disclosed in FIG. 8 of Unexamined Japanese Patent
Publication No. 2000-16107, a rear axle beam (31) includes an axle
beam body (34) having a first plate 32 and a pair of second plates
(33a, 33b) and also includes two pairs of bosses (35a, 35b) for
supporting kingpins (not shown). Each pair of the bosses (35a, 35b)
is welded on each side of the axle beam body (34) in such a manner
that the bosses (35a, 35b) are vertically arranged on the upper
side and the lower side, respectively. The rear axle beam (31) is
pivotally supported with respect to a rear frame of a vehicle body
(not shown) through a pair of center pins (36) which is formed at
the middle portion of the axle beam body (34) as seen in the
direction of the vehicle width.
[0003] Referring to FIG. 8 of Unexamined Japanese Patent
Publication No. 2000-16107, one of the center pins (36) is fixedly
connected to the first plate (32) that interconnects a pair of the
second plates (33a, 33b). Though it is not directly apparent from
the above FIG. 8, in view of the arrangement that the center pins
(36) are fixedly connected on both front and rear sides of the rear
axle beam (31), it is assumed that the paired second plates (33a,
33b) are also interconnected by a plate member 40 on the opposite
side relative to the side interconnected by the first plate (32),
as shown in FIG. 9A. Then, the other center pin (36) is presumably
fixedly connected to the plate member 40. It is noted that FIG. 9A
is a perspective view as seen from the opposite side as shown in
FIG. 8 of Unexamined Japanese Patent Publication No. 2000-16107.
The bosses (35a, 35b) are not shown in FIG. 9A.
[0004] The above four plates, that is, the first plate (32), the
second plates (33a, 33b) and the plate member 40, cooperate to form
a space R surrounded by the front and rear and the top and bottom
walls, as shown in FIG. 9B. Thus, the axle beam body (34) forms a
tube having a hollow space inside. The shape of the axle beam body
(34) increases the rigidity of the axle beam body (34) and ensures
the strength thereof.
[0005] In the structure disclosed in Unexamined Japanese Patent
Publication No. 2000-16107, however, the number of manufacturing
processes undesirably increases due to the multiple number (four)
of plates to be welded. As indicated by the filled triangles in
FIG. 9B, there are as many as four welded portions and the strength
tends to be weakened by such relatively large number (four parts)
of welded portions. Additionally, it is difficult to ensure
stability of strength for an axle beam having many welded portions.
To compensate for the insufficient strength due to of the welded
portions and to achieve the required strength, the four plates
themselves need be made thicker, which only causes increased
manufacturing cost.
[0006] The four plates prepared, for example, by means of gas
fusing may lead to undesired dimensional accuracy and, therefore,
the yield rate of material may be reduced to 60% to 70%, thereby
increasing manufacturing cost. Additionally, the quality of the
welded portions of the bosses (35a, 35b) fixed to the axle beam
body (34) by welding tends to be lowered due to poor dimensional
accuracy of each component plate of the axle beam body.
[0007] Moreover, according to the structure disclosed in Unexamined
Japanese Patent] Publication No. 2000-16107, since the four plates
are used to form the axle beam body (34), the number of components
increases, thereby increasing the trouble in controlling such
components. Therefore, there is a need for providing an axle beam
for an industrial vehicle which reduces the number of components
and also reduces the number of manufacturing processes by reducing
welded portions.
SUMMARY OF THE INVENTION
[0008] In accordance with the present invention, an axle beam for
an industrial vehicle has a beam and a boss. The beam is supported
on a vehicle body. The boss is provided at opposite ends of the
beam for supporting a kingpin. The beam includes at a
longitudinally middle thereof a portion having a closed
cross-section perpendicular to a longitudinal direction of the beam
and is shaped at the portion to form a space which is surrounded by
a front and rear and a top and bottom of the beam. The portion is
formed by welding two members or by one tube member.
[0009] Other aspects and advantages of the invention will become
apparent from the following description, taken in conjunction with
the accompanying drawings, illustrating by way of example the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The features of the present invention that are believed to
be novel are set forth with particularity in the appended claims.
The invention together with objects and advantages thereof, may
best be understood by reference to the following description of the
presently preferred embodiments together with the accompanying
drawings in which:
[0011] FIG. 1 is a plan view of a whole rear axle device having an
axle beam according to a preferred embodiment of the present
invention;
[0012] FIG. 2 is a partially cross-sectional rear end view of the
rear axle device according to the preferred embodiment of the
present invention;
[0013] FIG. 3 is a perspective view of the axle beam according to
the preferred embodiment of the present invention;
[0014] FIG. 4 is a cross-sectional view that is taken along the
line I-I in FIG. 3;
[0015] FIG. 5 is a perspective view illustrating a process for
carving a beam out of a square pipe according to the preferred
embodiment of the present invention;
[0016] FIG. 6 is a perspective view of a process for fixedly
connecting a boss and the like to the beam according to the
preferred embodiment of the present invention;
[0017] FIG. 7A is a perspective view of the axle beam according to
a first alternative embodiment of the present invention;
[0018] FIG. 7B is a cross-sectional view of a middle portion as
seen in the longitudinal direction of the axle beam according to
the first alternative embodiment of the present invention;
[0019] FIG. 8A is a perspective view of the axle beam according to
a second alternative embodiment of the present invention;
[0020] FIG. 8B is a cross-sectional view of a middle portion as
seen in the longitudinal direction of the axle beam according to
the second alternative embodiment of the present invention;
[0021] FIG. 9A is an exploded perspective view of an axle beam
according to a prior art; and
[0022] FIG. 9B is a cross-sectional view of a middle portion as
seen in the longitudinal direction of the axle beam according to
the prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] A preferred embodiment of the present invention will now be
described with reference to FIGS. 1 through 3.
[0024] Now referring to FIG. 1, the drawing illustrates a plan view
of an entire rear axle device 100 provided on the rear side of a
forklift truck according to the first preferred embodiment of the
present invention. The rear axle device 100 has an axle beam 110
and a pair of right and left steering knuckles 2R, 2L which are
pivotally supported on opposite sides of the axle beam 110.
[0025] The axle beam 110 includes a beam 1 extending laterally
relative to the vehicle body and two pairs of upper and lower
bosses 9 provided at the opposite ends of the beam 1, as best seen
in FIG. 3. The paired bosses 9 on each side are located one above
the other. Center pins 20 are welded to the front and rear surfaces
of the beam 1, respectively, and are located at the middle portion
in the longitudinal direction (the longitudinally middle portion)
of the beam 1 between the opposite ends. The axle beam 110 is
pivotally supported by a rear frame (not shown) of the vehicle body
through the center pins 20.
[0026] As shown in FIG. 2, a bracket 15 is fixedly connected to the
top surface of the beam 1 adjacent to one end of the beam 1 in the
longitudinal direction. A damper device 14 is pivotally coupled at
one end thereof to the bracket 15 and at the other end thereof to
the rear frame of the vehicle body.
[0027] The paired steering knuckles 2R, 2L are shaped and provided
symmetrically with respect to the middle of the axle beam 110.
Referring to FIG. 2 showing a cross-sectional rear end view of the
rear axle device 100, each of the steering knuckles 2R, 2L has a
kingpin 6 and a wheel spindle 8. Each of the kingpins 6 extends in
the vertical direction (the upper and lower direction in FIG. 2) of
the vehicle body. Each of the wheel spindles 8 protrudes from its
associated kingpin 6 outward in the lateral direction of the
vehicle body. The kingpins 6 of the steering knuckles 2R, 2L are
rotatably supported in the paired upper and lower bosses 9 disposed
at the opposite ends of the axle beam 110, respectively.
[0028] The wheel spindles 8 of the steering knuckles 2R, 2L
rotatably support rear wheels or steerable wheels 13R, 13L,
respectively. As shown in FIGS. 1 and 2, a knuckle arm 7 extends
rearward from each of the kingpins 6.
[0029] A double acting hydraulic cylinder 4 of a full hydraulic
power steering device 3 is mounted on the longitudinally middle
portion (the laterally middle portion in FIG. 1) of the axle beam
110. The hydraulic cylinder 4 has a cylinder rod 5 which is
operable to be displaced in the lateral direction of the vehicle
body.
[0030] Clevises (or connecting members) 10R, 10L are formed on the
opposite ends of the cylinder rod 5, respectively. Tie rods 12R,
12L are pivotally coupled at the inner ends thereof to the devises
10R, 10L and at the outer ends thereof to the knuckle arms 7 of the
steering knuckles 2R, respectively.
[0031] The structure of the full hydraulic power steering device 3,
which is known in the art, is operable to displace the cylinder rod
5 in the axial direction thereof by charging and discharging oil
under pressure into and out of the double acting hydraulic cylinder
4 in response to the operation of a steering wheel (not shown)
provided at operator's seat. As the cylinder rod 5 is displaced in
either direction, one of the tie rods 12R, 12L connected to the
cylinder rod 5 through the respective devises 10R, 10L pushes one
knuckle arm 7, and the other tie rod pulls the other knuckle arm 7.
As a result, the steering knuckles 2R, 2L pivot to change the
direction of the rear wheels 13R, 13L, so that the forklift truck
is operable to turn in the steered direction.
[0032] Thus, the axle beam 110, the hydraulic cylinder 4, the
devises 10R, 10L, the tie rods 12R, 12L and the steering knuckles
2R, 2L cooperate to make the rear steering device for changing the
direction of the rear wheels.
[0033] Now referring to FIG. 4 showing a cross-section of the beam
1 taken perpendicularly to the longitudinal direction of the beam 1
of the axle beam 110 along the line I-I of FIG. 3, the beam 1 of
the axle beam 110 forms a closed rectangular shape at the middle
thereof where the center pins 20 are fixed. That is, as shown in
FIG. 4, the beam 1 is shaped at its middle to form a space R which
is surrounded by the front and rear and the top and bottom of the
beam 1. Thus, the tube structure of the beam 1 increases the
rigidity and hence ensures the strength required for the beam
1.
[0034] In the preferred embodiment, the above described hydraulic
cylinder 4 is located in the space R which is surrounded by the
beam 1, as shown in FIG. 4. Consequently, the front and rear and
the top and bottom of the hydraulic cylinder 4 is surrounded by the
beam 1, so that the hydraulic cylinder 4 is protected against
breakage due to hitting from outside by a rock and the like.
[0035] Now referring to FIG. 5 illustrating the process of
manufacturing the beam 1 of the axle beam 110, the beam 1 is made
by cutting from an elongated square tube material 21 as a base
material having a closed rectangular cross-section that is taken
perpendicularly to the longitudinal direction of the beam 1. The
square tube material 21 is cut into beams 1 by fusion using a three
dimensional plasma fusing apparatus (first manufacturing process).
A three dimensional laser fusing apparatus is also applicable for
fusing the square tube material 21.
[0036] The square tube material or the base material 21 is made of
metal and formed by extruding a bar material called billet. It is
noted that the square tube material 21 may be made by bending a
flat plate material and then welding the ends thereof to form a
square tube. In this case, the beam 1 has one welded portion in the
cross-section thereof taken perpendicularly to the longitudinal
direction of the beam 1. For enhancing dimensional accuracy by
reducing the number of welded portions, however, it is desirable to
form a seamless tube by extrusion molding.
[0037] Thus forming a seamless tube by extrusion molding, the beam
1 can be made free of welded portion which are relatively weak in
strength as shown in FIG. 4, with the result that the strength of
the beam 1 is improved. In other words, even if the square tube
material 21 is made relatively thin, the strength required for the
beam 1 is ensured, so that material cost, as well as manufacturing
cost, is reduced.
[0038] As most clearly seen in FIG. 3, the beam 1 is formed in such
a way that only its middle portion between the opposite ends
thereof is closed by four top, bottom, front and rear walls thereby
to form the space R, while the remaining end portions are open on
the rear side and taper-shaped toward the ends as seen from the
top.
[0039] The tapered ends of the beam 1 allow the rear wheels 13L,
13R to be turned over a wider range, as indicated by the chain
lines in FIG. 1, so that turning radius of the forklift truck is
advantageously reduced. Additionally, the tapered ends help reduce
the manufacturing cost and also the weight of the axle beam 110,
while ensuring the strength required for the axle beam 110.
[0040] Furthermore, since the beam 1 is tapered at the opposite
ends where the beam 1 is shaped thin, a plurality of identical
beams 1 can be cut from a single elongated square tube material or
a base material 21 with as little waste as possible by cutting
along the cutting lines indicated by bold lines in FIG. 5, that is,
a plurality of the identical beams 1 is in staggered arrangement on
the elongated square tube material 21 for fusing. That is, the
cutting lines (indicated by the bold line in FIG. 5) for fusing are
determined in such a manner that the tapered ends of the coadjacent
beams 1 are arranged to vertically overlap relative to the
longitudinal direction of the square tube. Thus, more number of the
beams 1 is manufactured from a bar of the square tube material 21,
so that waste produced from the square pipe 21 is reduced.
[0041] By using the three dimensional plasma fusing apparatus (or
the three dimensional laser fusing apparatus) as in the preferred
embodiment, dimensional accuracy of the resulting beam 1 is much
improved over that obtainable by gas fusing and the like. The
improved dimensional accuracy helps increase yield rate and hence
reduce the manufacturing cost.
[0042] Now referring to FIG. 6 illustrating the second
manufacturing process, the center pins 20, the bracket 15 and the
bosses 9 are welded to the cut out beam 1. Thus, the axle beam 110
shown in FIG. 3 is completed.
[0043] It is noted that, as shown in FIG. 6, cutout portions 1g are
formed on opposite sides of the rear center pin 20 in such a manner
that the beam 1 is recessed in the lateral direction for a
predetermined length. The formation of such cutout portions 1g
helps relieve the stress concentration which tends to occur during
vehicle operation at positions of the beam 1 which are indicated by
dotted bold circles in FIG. 6.
[0044] The present invention is not limited to the embodiments
described above but may be modified into the following alternative
embodiments.
[0045] Referring to FIG. 7A showing a first alternative embodiment,
the beam 1 includes a first member 91 having a U-shaped
cross-section perpendicular to the longitudinal direction of the
beam 1 and a second plate member 92 which is welded to the first
member 91. In other words, the beam 1 is formed by two members. The
first U-shaped member 91 and the second plate member 92 are welded
together in such a way that a space R surrounded by four walls as
shown in FIG. 7B which is a cross-sectional view of FIG. 7A is
formed in the resulting beam 1. In this case, as shown in FIG. 7B,
the resulting beam 1 has two welded portions in the cross-section
of the longitudinally middle portion thereof as indicated by two
arrows. In this first alternative embodiment, the number of welded
portions is two that is fewer than four welded portions of the
prior art, so that the yield rate of material and dimensional
accuracy are improved.
[0046] Referring to FIG. 8A showing a second alternative
embodiment, the beam 1 is formed in such a manner that a first
member 93 having an L-shaped cross-section perpendicular to the
longitudinal direction of the beam 1 is welded to a second member
94 having a similar L-shaped cross-section perpendicular to the
longitudinal direction of the beam 1. In other words, the beam 1 is
formed by two members. The L-shaped members 93, 94 are welded to
each other so as to form a space R at the center of the resulting
beam 1 which is surrounded by four walls as shown in FIG. 8B which
is a cross-sectional view of FIG. 8A. In this case, as shown in
FIG. 8B, there are two welded portions in the cross-section of the
longitudinally middle portion of the resulting beam 1. In the
second alternative embodiment, the number of welded portions is two
that is fewer than four welded portions of the prior art, so that
the yield rate of material and dimensional accuracy are
improved.
[0047] As mentioned above, the number of welded portions is not
limited to 0 but may range from 0 to 2 that is fewer than four
welded portions of the prior art.
[0048] In the preferred embodiment, the present invention has been
described by way of a rear axle beam of a forklift truck. As a
matter of course, the present invention is also applicable to a
front axle beam of a front steering vehicle. In addition, the
present invention is not limited to application to a forklift
truck, but it is applicable to other types of industrial
vehicles.
[0049] Therefore, the present examples and embodiments are to be
considered as illustrative and not restrictive, and the invention
is not to be limited to the details given herein but may be
modified within the scope of the appended claims.
* * * * *