JPH11269908A - Work equipment boom - Google Patents

Abstract

(57) [Problem] To disperse stress applied to a lower wall of a boom to avoid local stress concentration and improve durability.
Enables cost reduction and weight reduction. SOLUTION: A halfway part 20 is bent in a shape like a side view, and a lower wall 21, an upper wall 22, a vertical wall 23, and a halfway bent part 2 are provided.
There is a reinforcing member 24 connecting the lower wall 21 and the upper wall 22 at least on the front side before and after zero. The reinforcing member 24 is inclined with respect to the lower wall 21 so as to be attached to the lower wall 21 at a mounting position A.
Is positioned closer to the halfway bent portion 20 than the mounting position B with the upper wall 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boom for a working machine such as a backhoe.

[0002]

2. Description of the Related Art A conventional working machine boom is disclosed in
As disclosed in Japanese Patent Publication No. 20882, a boom cylinder connecting portion and a work implement side cylinder are provided at a halfway bent in a box shape in a side view in a box shape having a lower wall, an upper wall, and right and left vertical walls. A connecting portion, and a rear portion is pivotally connected to the swivel table, and an arm for connecting a work tool such as a bucket to the front portion or the work tool itself is connected to perform excavation work. Have been.

In such a boom of a working machine, a load is applied during excavation work so as to bend and stretch a halfway bent portion, and one of the lower wall and the upper wall receives a tensile stress and the other receives a compressive stress. Therefore, it is required to secure the strength of the halfway bent portion.

[0004]

Therefore, it has been considered that reinforcing ribs for connecting the lower wall and the upper wall are provided at the front and rear portions of the halfway bent portion to reinforce the reinforcing member. There is a case where a partition wall plate is provided and used as a reinforcing rib. However, such a partition-like plate is provided substantially at right angles to the lower wall and the upper wall, and effective dispersion of stress is not considered. Particularly, a large tensile stress is locally applied to the lower wall. Therefore, it is necessary to make the strength strong enough to withstand the concentrated stress, which leads to waste and weight of the material.

[0005] That is, as shown by a two-dot chain line in FIG. At this time, the stress applied to the mid-bent portion 20 of the boom 11 and the vicinity thereof is, as shown in FIG. 6, as shown in FIG.
On the lower wall 21, a concentrated portion where the tensile stress is extremely large occurs on the front side of the boom cylinder connecting portion 26 and on the rear side of the reinforcing rib 30.

FIG. 6 shows the stress distribution in eight stages from the maximum tensile stress to the maximum compressive stress. The white portion b of the lower wall 21 is the second tensile stress portion, which is surrounded by the white portion b. It is clear that the minimum black portion a is the maximum tensile stress concentration portion and is concentrated on the front side of the boom cylinder connecting portion 26 and on the rear side of the reinforcing rib 36, and these portions have sufficient durability. So that
The wall thickness, in particular, the thickness of the lower wall 21 and the like are determined. In addition,
In FIG. 6, reference symbol c indicates a stress-neutral portion, and portions where the compressive stresses e and f increase in order.

As described above, since excessive stress is locally concentrated, it is necessary to design a strength such as a plate thickness on the basis of the concentration, which leads to an increase in cost and weight. In view of such various problems, the present invention disperses the stress applied to the lower wall of the boom so that local stress concentration can be avoided and durability can be improved. It is an object of the present invention to provide a boom of a working machine capable of performing measurement or the like.

[0008]

A first concrete means for solving the problem in the present invention is that the middle portion 20 is bent in a shape as viewed from the side, and the lower wall 21 and the upper wall 22 are vertically connected. Wall 23
And a reinforcing member 24 for connecting the lower wall 21 and the upper wall 22 at least at the front side before and after the halfway bent portion 20, wherein the reinforcing member 24 is inclined with respect to the lower wall 21. The position A of attachment to the lower wall 21 is located closer to the halfway bent portion 20 than the position B of attachment to the upper wall 22.

Accordingly, when a load is applied to the lower wall 21 of the boom 11 during the excavation operation, the inclined reinforcing member 24 effectively releases the stress to the upper wall 22 side, and disperses the stress acting on the lower wall 21. Second solution for solving the problem in the present invention
Is a box-shaped cross section having a lower wall 21, an upper wall 22, and left and right vertical walls 23, and a boom cylinder connecting portion 26 and a work implement side cylinder A boom of a working machine having a connecting portion 27 and a reinforcing member 24 connecting the lower wall 21 and the upper wall 22 at least at the front side before and after the boom cylinder connecting portion 26, wherein the reinforcing member 24 is connected to the lower wall. That is, the mounting position to the lower wall 21 is located closer to the boom cylinder connecting portion 26 than the mounting position to the upper wall 22 by being inclined with respect to the upper wall 22.

Thus, the boom 11 can be used during excavation work.
Although a large load is applied to the lower wall 21 on the front side of the boom cylinder connecting portion 26, the inclined reinforcing member 24 effectively releases the stress to the upper wall 22 side and disperses the stress of the lower wall 21.
A third specific means for solving the problem in the present invention is:
In addition to the first or second specific means, the reinforcing member 24 is located on or substantially parallel to a radiation 29 substantially passing through the center of curvature 28 of the halfway bent portion 20.

As a result, the stress applied to the lower wall 21 is more effectively dispersed throughout the boom 11.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 5, reference numeral 1 denotes a backhoe used for civil engineering, construction, and the like, and a swivel 4 is rotatably supported on a traveling body 3 having a crawler traveling portion 2 around a vertical axis. , A sunshade device 6, a steering device 7, and the like, and a backhoe device 8 is mounted on a front portion of the swivel 4.

In the backhoe device 8, a swing bracket 10 is pivotally supported by a bracket 9 at a front portion of the swivel base 4 so as to be swingable about a vertical axis. Pivoted freely,
An arm 14 driven by an arm cylinder 13 is pivotally connected to the tip of the boom 11, and a working tool 16 such as a bucket driven by a working tool cylinder 15 is pivotally connected to the tip of the arm 14.

In the embodiment shown in FIGS. 1 to 4, the boom 11 has a halfway portion 20 bent in the shape of a letter when viewed from the side, and a base end (rear end) pivotally connected to the revolving bracket 10. The coupling body 17 has a distal end coupling body 18 that pivotally connects to the arm 14 at the distal end (front end). Boom 1
1 has a box (square tube) shape having a rectangular cross section having a lower wall 21, an upper wall 22, and right and left vertical walls 23. A pair of left and right plate members 26A is fixed to the wall 21 and a boom cylinder connecting portion 26 for connecting the boom cylinder 12 via a pin is formed. A working tool side cylinder connecting portion 27 for connecting the arm cylinder 13 is formed.

Further, reinforcing ribs (reinforcing members) 24 for connecting the lower wall 21 and the upper wall 22 are provided before and after the mid-bent portion 20 inside the boom 11, and the reinforcing ribs 24 are formed of a plate material. The left and right vertical walls 23 are also fixed. The reinforcing ribs 24 are not perpendicular but inclined with respect to the lower wall 21 and the upper wall 22.
Is located closer to the halfway bent portion 20 than the mounting position B. The reinforcing rib 24 is located on or substantially parallel to the radiation 29 substantially passing through the center of curvature 28 of the halfway bent portion 20, and is preferably in an inclined state close thereto.

The reinforcing ribs 24 may be blind plates without holes,
As shown in FIG. 1, it is preferable to reduce the weight while forming the burring holes 30 to reinforce the reinforcing ribs 24. A plurality of strips or bars connecting the lower wall 21 and the upper wall 22 may be used. . When the boom 11 performs excavation work with the bucket 16, a force that extends the V-shape to the halfway bent portion 20 by pulling the boom cylinder 12 acts on the lower wall 21, particularly from the boom cylinder connecting portion 26. A large tensile stress is generated on the front side, and the stress is applied to the lower wall 21.
Is propagated to the reinforcing ribs 24.

If the inclination angle K of the reinforcing rib 24 is larger than a right angle, the reinforcing rib 24 is actuated by a stick-like action.
, The load is more strongly supported and the stress is dispersed than in the case of a right angle. That is, when the state of sharing of stress in each member of the boom 11 during the excavation work is analyzed, when the reinforcing ribs 24 are substantially perpendicular to the lower wall 21, the stress is dispersed as shown in FIG. Instead of being concentrated near the front reinforcing ribs 24,
Are inclined with respect to the lower wall 21, as shown in FIG. 2, the white portion b (second tensile stress portion) and the minimum black portion a (maximum tensile stress concentration portion) disappear, and the portion having small compressive stress is removed. e, a portion f having the next slightly larger compressive stress is generated, and a portion g having a moderate compressive stress is formed in the mounting portion of the front reinforcing rib 24, and the stress distribution state is reduced and leveled, It has been found that the reinforcement can be optimized.

In order to determine the mounting position A of the reinforcing rib 24 with respect to the lower wall 21, the relationship between the displacement T from the mounting position of the reinforcing rib 24 and the maximum concentrated stress at a substantially right angle is analyzed. As shown in FIG. 4, it was found that the maximum concentrated stress decreases as the mounting position A moves away from the right-angled mounting position.
The reinforcing rib 24 had an inclination angle close to the radiation 29.

In FIG. 4, the displacement T = 1.0 is about 80 to 90 mm, and a necessary and sufficient decrease in stress is obtained at T = 1.0. Preferably, the displacement T is about 0.5 or more. Since stress concentrates near the front reinforcing ribs 24, the rear reinforcing ribs 24 may be fixed at a substantially right angle to the lower wall 21 or may be inclined.

When the soil is pressed by a bucket, a compressive stress may act on the lower wall 21 and a tensile stress may act on the upper wall 22. However, the compressive stress has a relatively low concentration. If there is sufficient strength against the tensile stress, the compressive stress can be cleared, and even if the reinforcing rib 24 is inclined, the tensile stress applied to the upper wall 22 can be dispersed more than the substantially right angle state, and the durability is improved. Can be improved.

Therefore, the upper wall 22 and the left and right vertical walls 23 are formed by bending a plate material into a U-shaped cross section to have the same thickness.
Only the lower wall 21 is formed of a thicker plate, but the tensile stress applied to the lower wall 21 is reduced, so that the lower wall 21 can be made thinner than before. The present invention is not limited to the above-described embodiment and specific examples, and can be variously modified. For example, the boom 11 can be applied to a boom such as a front loader and the like, and the band-shaped lower wall 2 can be used.
Although the upper wall 22 and the left and right vertical walls 23 are integrally formed on the base member 1 by welding, a U-shaped member in cross section is formed. The upper wall 22 and 1
It may be connected by two vertical walls 23 to form an I shape.

The boom 11 is formed by bending a single wide plate into a quadrangular or octagonal cross section by press working to form a cylindrical member, and connecting the two cylindrical members directly or via a joint plate. Alternatively, it may be formed in a shape like a side view.

[0023]

According to the present invention described in detail above, the stress applied to the lower wall 21 of the boom 11 during operation is effectively released by the inclined reinforcing member 24 to the upper wall 22 side, and the stress at the lower wall 21 is reduced. The concentration can be dispersed, and the reinforcement by the reinforcing member 24 can be optimized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional side view showing a vicinity of a bent portion of a boom according to an embodiment of the present invention.

FIG. 2 is a stress distribution diagram near a bent portion of a boom.

FIG. 3 is a sectional view taken along line XX of FIG. 1;

FIG. 4 is a graph showing a relationship between a displacement amount of a mounting position A of a reinforcing member and a maximum tensile stress.

FIG. 5 is an overall side view of the backhoe.

FIG. 6 is a stress distribution diagram in the vicinity of a bent portion of a boom in which a reinforcing member is disposed at a substantially right angle.

[Explanation of symbols]

 Reference Signs List 8 backhoe device 11 boom 12 boom cylinder 13 arm cylinder (work tool side cylinder) 21 lower wall 22 upper wall 23 vertical wall 24 reinforcing rib (reinforcement member) 26 boom cylinder connecting part 27 work tool side cylinder connecting part 28 center of curvature 29 radiation A Lower wall side mounting position B Upper wall side mounting position

Claims (3)

[Claims] A reinforcing member connecting the lower wall and the upper wall at least in front of the lower wall, the upper wall, the vertical wall, and the front and rear of the halfway bent portion; Wherein the reinforcing member is tilted with respect to the lower wall, and a mounting position with the lower wall is positioned closer to the mid-bent portion than a mounting position with the upper wall. And the working machine boom. 2. A boom cylinder connecting part and a work implement side cylinder connecting part in a middle part bent in a rectangular shape when viewed from the side, having a box-shaped cross section having a lower wall, an upper wall, and right and left vertical walls. A boom of a working machine having a reinforcing member that connects a lower wall and an upper wall at least at a front side before and after a boom cylinder connecting portion, wherein the reinforcing member is inclined with respect to the lower wall and the upper wall, and A boom for a working machine, wherein a mounting position with respect to a wall is located closer to a boom cylinder connecting portion than a mounting position with respect to an upper wall. 3. The boom of a working machine according to claim 1, wherein the reinforcing member is located on or substantially parallel to radiation passing substantially through the center of curvature of the halfway bent portion.