The present invention relates to an axle beam in a wheel suspension system for an industrial vehicle and a method of manufacturing the same.
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.
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
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
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
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.
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.
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.
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.
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:
A preferred embodiment of the present invention will now be described with reference to
Now referring to
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
As shown in
The paired steering knuckles 2R, 2L are shaped and provided symmetrically with respect to the middle of the axle beam 110. Referring to
The wheel spindles 8 of the steering knuckles 2R, 2L rotatably support rear wheels or steerable wheels 13R, 13L, respectively. As shown in
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
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.
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.
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.
Now referring to
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
Now referring to
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.
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
As most clearly seen in
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
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
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.
Now referring to
It is noted that, as shown in
The present invention is not limited to the embodiments described above but may be modified into the following alternative embodiments.
Referring to
Referring to
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.
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.
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.
Number | Date | Country | Kind |
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2003-136916 | May 2003 | JP | national |
This application is a divisional of pending U.S. patent application Ser. No. 10/843,745 filed May 11, 2004 under 35 U.S.C. § 120, which claims priority to Japanese Patent Application No, 2003-136916 filed on May 15, 2003 under 35 U.S.C. §119, the entirety of all of which are incorporated herein by reference as if fully set forth herein.
Number | Date | Country | |
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Parent | 10843745 | May 2004 | US |
Child | 12031205 | US |