JP2001048475A - Multiple boom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep lateral displacement from being increased during operation by disposing each one longer portion of folding members alternately on right and left extending from the base end part to the forward end part. SOLUTION: This boom is manufactured by welding bilateral folding members, and the right and left longer members forming the side of the boom are alternately arranged extending from the base end part to the forward end part. The right and left welding positions are alternately high and low to cancel lateral asymmetry, so that during operation, bending of the boom, and lateral deviation due to torsion are hardly caused. Thus, the asymmetry of the welding part can be relaxed, residual stress of welding and lateral bending or torsion are kept from being increased, run-out of the boom tip position in operation can be lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage boom using an asymmetrical bending member.

[0002]

2. Description of the Related Art FIG.
As shown in (a) and (b), there is a method in which a plate material is bent at two places to form a symmetrical member, and this member is welded. However, as shown in FIG. 6 (c), if the vertical length of the boom is much larger than the horizontal length, the corners cannot be bent twice with a normal bending tool, and FIGS. As shown in FIG. 6), a method of bending the central portion of the plate material from the outside to the inside, bending the corner portion, and then returning the central portion to the original position, or FIG.
It is necessary to use a specially shaped bending tool as shown in (d). Therefore, when the aspect ratio of the boom is large, FIG.
As shown in (1), a method is often used in which an ordinary bending tool is used to bend left and right asymmetrically, and the left and right non-paired members are alternately combined up and down and welded.

[0003]

However, in a multi-stage boom using such a left-right asymmetrical member, since the welded portion is left-right asymmetrical, the horizontal bending and torsion are in the same direction during operation due to residual stress of the welded portion. May be amplified. Therefore, an object of the present invention is to provide a multi-stage boom that does not increase left and right displacement during operation.

[0004]

In order to solve the above-mentioned problems, the present invention employs the following multistage boom. That is, the multi-stage boom according to claim 1 is a multi-stage boom composed of all or a part of each of the booms formed by welding the members which are bent asymmetrically left and right alternately up and down, and wherein the asymmetric bending is performed. In each of the booms made of a member, the longer one of the left and right lengths of the bending member is arranged so as to be alternately left and right from the base end to the front end. Next, the multi-stage boom according to claim 2 is a multi-stage boom composed of respective booms formed by combining members which are bent asymmetrically left and right alternately up and down and welded,
The longer part of one of the left and right sides of the member is arranged so as to be alternately left and right from the base end boom to the distal end boom.

[0005]

In the multistage boom according to the present invention, the asymmetrical portions are arranged so as to be alternately left and right from the base end to the tip end, so that the asymmetry of the welded portion is canceled out and the lateral force caused by the welding residual stress is eliminated. Bending and twisting do not increase. It should be noted that “boom” in this specification has a broad meaning including “jib”.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-stage boom according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing one embodiment of a boom according to the present invention. As shown in FIG. 1, each boom is manufactured by welding left and right asymmetric bending members (FIG. 1 (a)), and long left and right members forming the side surface of the boom are from the base end to the tip end. They are arranged so that they are alternately left and right. FIG. 1B is a perspective view when the boom is extended, and FIG. 1C is a cross-sectional view of the boom. As can be seen from these figures, the heights of the left and right welding positions are alternated to cancel the left-right asymmetry, so that the left and right deviations due to the bending and twisting of the boom during operation are less likely to occur.

Next, another embodiment is shown in FIG. The multi-stage boom shown in FIG. 2 is a combination of a boom made of a left-right asymmetric bending member and a boom made of a left-right asymmetric bending member. Are arranged so that left and right members alternate with each other.

When a bilaterally asymmetric bending member is used for the base end boom, the displacement of the boom caused by the bilateral asymmetry is
Although not so large at the distal end of the proximal boom, the displacement of the distal end boom is considerably enlarged at the distal end of the distal boom because the length of each boom ahead is long. That is, in order to reduce the displacement of the distal end boom tip, it is necessary to eliminate the left-right asymmetry, especially near the base end. Another embodiment based on such a concept is shown in FIG. In this manner, in the base end portion and the next two booms, the left and right asymmetric portions may be alternately provided, and the left and right asymmetric portions may not be alternately provided thereafter.

The lower side of the boom receives a compressive force during operation and may buckle, so it is necessary to increase the strength from the upper side. Therefore, as shown in FIG. 4, the boom may be formed by changing the plate thickness of the asymmetrical bending member so that the upper side is thinner and the lower side is thicker. Further, the cross-sectional shape of the boom is not limited to a rectangular cross-section as shown in FIG. 5, but may be a rectangular cross-section having bent corners, an arc-shaped corner, or a polygonal cross-section.

[0010]

In the multistage boom according to the present invention,
The left and right asymmetrical portions of the bent members are alternately arranged left and right from the base end to the front end, so that the asymmetry of the welded part is alleviated and the lateral bending and torsion due to residual stress of welding are not amplified, and the boom during operation Less deviation of the tip position.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a multistage boom according to the present invention.

FIG. 2 is a view showing another embodiment of the multistage boom according to the present invention.

FIG. 3 is a view showing another embodiment of the multistage boom according to the present invention.

FIG. 4 is a diagram illustrating a boom including bending members having different thicknesses.

FIG. 5 is a diagram showing a cross-sectional shape of the multi-stage boom according to the present invention.

FIG. 6 is a diagram illustrating a method of bending a plate material forming a boom.

FIG. 7 is a diagram illustrating a method of forming a boom with left-right asymmetric members by bending a plate material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plate material 2 Welding beam 10 Bending tool

Claims (2)

[Claims] 1. A multi-stage boom composed of all or a part of each boom formed by welding a combination of vertically and horizontally asymmetrically bent members, wherein each of the booms includes the asymmetrically bent member. A multi-stage boom, wherein the longer one of the left and right lengths of the bending member is arranged so as to be alternately left and right from a base end to a front end. 2. A multi-stage boom comprising a plurality of booms formed by welding members which are bent asymmetrically left and right alternately up and down, and a longer portion of one of the left and right sides of the member is a base end. A multi-stage boom, which is arranged so as to be alternately left and right from the boom to the tip boom.