JP2003090060A - Boom of construction machinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To locally increase the strength of a boom foot part, which requires the high strength, without especially increasing the size and weight of a boom. SOLUTION: A bent part T is formed in an upper plate 22a in a position near the boom foot part of a boom body 22 so as to increase the strength of the boom foot part which serves as a part for coupling the boom 20 to a mounting bracket 21a. In the upper plate 22a with the bent part T, a surface of a part for coupling the upper plate 22a to a boss part 23 is taken as P1; a surface of a part for a shift to an intermediate bent part B is taken as P2; and a surface in a position of the bent part T is taken as P3. In this case, an angle, which a lower plate 22b forms with a line which connects P1 with P2, is taken as θ1, an angle which the lower plate 22b forms with a line which connects P1 with P3, that is, an opening angle between the upper plate 22a and the lower plate 22b on the side of the boom foot part is taken as θ2 and made greater than the angle θ1; and an angle, which the upper plate 22a forms with the lower plate 22b, is made smaller than the angle θ1 in a part from the position of the bent part T to a part provided to continue into the bent part B.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydraulic excavator, etc.
The present invention relates to a boom structure of a construction machine having a front working machine, and particularly to a boom structure in which a boom foot portion has high strength.

[0002]

2. Description of the Related Art FIG. 5 shows the overall construction of a hydraulic excavator as an example of construction machinery. In the figure, reference numeral 1 denotes a lower traveling body. The lower traveling body 1 is usually constituted by a crawler type traveling means having a crawler belt, and the traveling means are provided on both left and right sides of a traveling body frame. The lower traveling body 1 can be configured not only by a crawler type traveling means but also by a so-called wheel type having wheels.

An upper revolving structure 3 is rotatably provided on the lower traveling structure 1 via a revolving device 2. A driver's cab 4 is installed on the upper swing body 3, and the driver's cab 4
The front working machine 5 is provided so as to line up with.
The front working machine 5 has a boom 6 operably connected to the frame of the upper swing body 3, an arm 7 rotatably connected to the tip of the boom 6, and a link mechanism 8 at the tip of the arm 7. It is composed of a front attachment that is detachably connected. As a typical front attachment, there is a bucket 9 for work such as excavation of earth and sand. The boom 6, arm 7 and bucket 9 are driven by a boom cylinder 6C, an arm cylinder 7C and a bucket cylinder 9C, respectively.

Both ends of the boom 6 are connected to the frame of the upper swing body 3 and the arm 7 so as to be relatively rotatable. For this reason, the boom 6 is configured as shown in FIG. In the figure, 10 is a boom body, and this boom body 10 includes an upper plate 10a and a lower plate 10b.
And the left and right side plates 10c and 10d (the one side plate 10
(d is not shown in the drawing) is a box-shaped structure. The boom body 10 is not straight, and the upper plate 10a and the lower plate 10b have a structure having an intermediate bent portion B that is bent to have a curved shape at an intermediate portion. In addition, the upper plate 10a and the lower plate 10b are continuously increased in distance from both ends thereof toward the intermediate bending portion B, and therefore, the cross-sectional area of the boom body 10 is the largest at the position of the intermediate bending portion B and is large at both end portions. Has a structure that is continuously flattened so as to be the smallest.

A boss portion 11 is formed at the lower end of the boom body 10, and an arm connecting portion 12 is provided at the upper end. Here, the boss portion 11 is usually fixed by welding means. The arm connecting portion 12 on the upper side of the boom body 10 constitutes a connecting portion to the arm 7. The arm connecting portion 12 and the base end portion of the arm 7 are connected by a connecting pin so as to be relatively rotatable. Has been done. On the other hand, the boom body 10
The lower side of the above constitutes a boom foot portion, and the boss portion 11 provided on this lower side is connected to the frame of the upper swing body 3 so as to be rotatable relative thereto. For this purpose, the upper revolving structure 3 is provided with a pair of left and right mounting brackets, and the boss portion 11 is disposed between the pair of left and right mounting brackets provided on the upper revolving structure 3 and connected by connecting pins. ing.

[0006]

By the way, the front working machine 5 is a means for carrying out work such as excavation of earth and sand, and an extremely large load acts at the time of work. Boom body 10
The box shape is used to effectively receive this work load. Here, in the boom body 10,
Compared to the tip, the boom foot has a bucket 9
In addition to the arm 7 and the entire load of the boom 6, a larger load than the arm connecting portion 12 side acts. However, in the structure of the boom 6, the cross-sectional area of the box structure portion of the boom body 10 is from the connecting portion of the upper plate 10a and the lower plate 10b to the boss portion 11 to the intermediate bending portion B.
Depends on the opening angle towards. Therefore, the boom body 1
The cross-sectional area of 0 is the outer diameter of the boss portion 11 and the intermediate bent portion B.
It depends on the length to the transition portion to and the size of the intermediate bending portion B. As long as this shape is not broken, in order to improve the strength of the boom foot portion of the boom body 10,
The thickness of each plate must be increased. Therefore, if the boom foot side has a structure that can receive a sufficient load,
As a result, the entire boom 6 becomes heavier.

The present invention has been made in view of the above points, and it is an object of the present invention to locally increase the strength of a boom foot portion that requires high strength without increasing the size and weight of the boom. It is to be able to improve.

[0008]

In order to achieve the above-mentioned object, the present invention is a box which comprises an upper plate, a lower plate and left and right side plates, and in which an intermediate bent portion is formed by bending the intermediate portion into a substantially curved shape. A boom body having a shape and a boss portion, which is attached to a lower end portion of the boom body, for inserting a connecting pin that is connected to the frame of the upper swing body so as to be rotatable relative to the frame, A boom constituting a front working machine to be mounted on a body, wherein an opening angle in a direction of the intermediate bending portion from a connecting portion of an upper plate and a lower plate of the boom main body to a boss portion on the frame side is increased. The angle between the line connecting the position of the connecting portion to the boss portion of the plate and the lower plate and the position of the transition portion to the intermediate bending portion, and at least one of the upper plate and the lower plate, the boss portion of In the direction where the opening angle decreases in the vicinity It is an its features that it has a structure to form a folded portion.

In short, in the boom main body, the opening angle between the upper plate and the lower plate is not constant at the boom foot part, with the intermediate bending part as a boundary, as in the connecting part side to the arm. The opening angle with the plate is changed to increase the cross-sectional shape at the boom foot position. For this reason, the opening angle between the upper plate and the lower plate is increased on the boom foot side, that is, from the boss part forming the connecting part to the upper swing body to the middle. That is, the opening angle of the line connecting the position of the connecting portion of the upper plate and the lower plate to the boss portion and the position of the transition portion to the intermediate bent portion is set to a predetermined position from the side of connection to the boss portion. However, if it is extended in this state, the cross section of the intermediate bent portion becomes extremely large. Therefore, a bent portion is provided at an intermediate position on at least one of the upper plate and the lower plate so that the opening angle from the bent portion becomes smaller. Moreover, this bent portion is provided near the boom foot portion. As a result, the strength of only the boom foot portion can be made higher than others, and the shape and weight of the boom main body do not increase so much. When the bent portion is provided on the lower plate, it is preferable to form the bent portion on the upper plate side because it may interfere with the lower traveling body.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. First, in FIGS. 1 and 2, reference numeral 20 denotes a boom, and one end side of the boom 20 is a mounting bracket 21 provided on a frame 21 of an upper swing body.
The arm is connected to the other end. Therefore, the connecting portion of the boom 20 to the mounting bracket 21a is the boom foot portion, and the tip end side is the arm connecting portion.
As shown in FIG. 3, the boom 20 has a box-shaped boom body 22 in which an upper plate 22a, a lower plate 22b, and left and right side plates 22c and 22d are interconnected by welding means,
The base end of the boom body 22 is connected to the boss 23. The mounting bracket 21 is attached to the boss portion 23.
The connecting pin inserted through a is inserted, whereby the boom 20 is connected to the mounting bracket 21a so as to be vertically rotatable. An intermediate bent portion B is formed at an intermediate position of the boom main body 22, and the overall shape of the boom main body 22 is substantially V-shaped. In addition, the boom body 2
An arm connecting portion 24, which is connected to the arm so as to be rotatable relative to the arm, is provided at the tip of the arm 2.

A bent portion T is formed on the upper plate 22a at a position near the boom foot portion of the boom body 22. As shown in FIG. 1, the bent portion T causes the upper plate 22a to have a surface P1 at the connecting portion to the boss 23 and a surface P2 at the transition portion to the intermediate bending portion B. When the surface at the position of the portion T is P3, the angle formed by the line connecting the lower plate 22b and P1-P2 is θ1,
The angle formed by the line connecting the lower plate 22b and P1-P3, that is, the opening angle between the upper plates 22a and 22b on the boom foot side is θ2, which is larger than the angle θ1. Further, between the position of the bent portion T and the continuous portion to the intermediate bent portion B, the angle formed by the upper plate 22a and the lower plate 22b is the angle θ.
It is smaller than 1.

By configuring as described above, the lower plate,
When the left and right side plates have the same shape, as compared with the case where the upper plate is extended straight up to the intermediate bent portion as in the conventional technique, the bent portion T like the upper plate 22a is formed.
Is provided to the upper plate 22a and the lower plate 22 on the boom foot side.
By increasing the opening angle with respect to b, the cross-sectional shape increases by the amount shown by the diagonal lines in FIG. Therefore, the upper plate 2
The bent portion T of 2a is formed at a position near the boss portion 23, that is, at a position close to the boom foot portion, and the opening angle θ2 is made as large as possible to include the position of the boss portion 23 and the boom main body 22 in the vicinity position. The cross-sectional area can be larger than in the prior art. As a result, only the strength of the boom foot portion of the boom body 22 that receives the load of the entire front working machine locally increases.

Moreover, since the bent portion T of the upper plate 22a is provided at a position close to the boom foot portion, even if the opening angle θ2 is increased, the bent portion T does not largely project from the upper surface of the boom body 22. On the other hand, since the portion from the intermediate bending portion B to the arm connecting portion does not require as high strength as the boom foot portion side, the opening angle of the upper plates 22a and 22b from the arm connecting portion 24 to the intermediate bending portion B is as shown in FIG. It is substantially the same as the boom body 10 of the prior art shown in FIG. This makes it possible to secure high strength in the boom foot portion, which requires the most strength, without making the boom body 22 heavy. In addition, since there is no large protruding portion on the upper portion of the boom 20, there is no sense of discomfort in appearance.

Further, as shown in FIG. 4, the space between the left and right side plates 22c and 22d is wide at the position of the boom foot portion, and the width becomes narrower toward the intermediate bent portion B. Is provided. The side bent portion D is formed so that the side plates 22c and 22d are substantially parallel to each other at a position beyond the bent portion T of the upper plate 22a. Frame 21 of upper swing body and boom side plates 22c, 2
A pair of boom cylinders 25 are connected between the 2d, and the boom 20 is raised and lowered by extending and contracting the boom cylinders 25 provided on the left and right of the boom 20. Here, the side plate 2 described above
The positions of the side bent portions D in 2c and 22d are located at the tip end side with respect to the thickest part of the boom cylinder 25, that is, the position of the rod guide 25b connected to the cylinder tube 25a.

By forming the side bent portions D on the left and right side plates 22c and 22d of the boom body 22 as described above, when the boom 20 is driven by the boom cylinder 25, the locus of movement of the boom 20 Since the range in which the boom cylinder 25 does not interfere with the side plates 22c and 22d becomes large, the depression and elevation angle of the boom 20 can be made large. In particular, the range of movement of the boom 20 during the raising operation can be increased, which is advantageous in terms of the upward work and the turning radius when turning. Moreover, since the strength of the boom foot portion of the boom body 22 is increased and the bent portion T of the upper plate 22a and the side bent portion D of the side plates 22c and 22d are displaced from each other, the strength of the entire boom 20 is sufficiently increased. Can be maintained.

[0016]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is possible to locally improve the strength of the boom foot portion that requires high strength without increasing the size and weight of the boom.

[Brief description of drawings]

FIG. 1 is a front view of a boom body showing an embodiment of the present invention.

FIG. 2 is a front view showing a state in which the boom is mounted on the upper swing body.

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

FIG. 4 is a right side view of FIG.

FIG. 5 is an external view of a hydraulic excavator as an example of a construction machine.

FIG. 6 is a front view of a boom body according to the related art.

[Explanation of symbols]

20 boom 21 mounting bracket 22 Boom body 22a Upper plate 22b Lower plate 22c, 22d Side plate 23 Boss 25 boom cylinder

Claims (3)

[Claims] 1. A box-shaped boom main body comprising an upper plate, a lower plate, and left and right side plates, and an intermediate bending portion formed by bending an intermediate portion into a substantially curved shape, and a boom main body attached to a lower end portion of the boom main body. A boom comprising a boss portion for inserting a connecting pin that is rotatably connected to a frame of the upper swing body and configured as a front working machine mounted on the upper swing body of a construction machine, wherein the boom body The opening angle in the direction of the intermediate bending portion from the connecting portion of the upper plate and the lower plate to the boss portion on the frame side,
The angle between the line connecting the position of the connecting portion of the upper plate and the lower plate to the boss portion and the position of the transition portion to the intermediate bending portion is made larger, and the boss portion is formed on at least one of the upper plate and the lower plate. A boom for a construction machine, characterized in that a bent portion is formed at a position in the vicinity of, in a direction in which the opening angle becomes smaller. 2. The boom for a construction machine according to claim 1, wherein the bent portion is formed on the upper plate. 3. The left and right side plates are formed with side bent portions that are bent in directions separating from each other at a position between the bent portion and the intermediate bent portion. The boom of a construction machine according to claim 1.