JPS6335356B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an upper revolving body mounted on a lower traveling body, a boom mounted on the upper revolving body so as to be able to be lifted up,
The present invention particularly relates to a new method for manufacturing the boom in a hydraulic excavator, in which an arm is provided at the tip of the boom so that it can be lifted up and down, and a bucket belt is pivotably attached to the tip of the arm.

As is well known, the entire boom has a dogleg shape when viewed from the side, and is made by assembling and welding four members (steel plates) into a box-shaped cross section: upper and lower flanges, and left and right webs. In order to resist the strong bending load and torsional load movement that are applied when the boom is used, a configuration is generally adopted in which a plurality of bulkheads are arranged inside the boom along its longitudinal direction. ing.

The above structure is adopted to withstand high loads despite its light weight, but the partition wall in particular always has an important function to achieve uniformity of stress, and its design and manufacturing are important. This is an area that requires careful consideration. Particularly important is the bulkhead provided on the foot side of the boom, since that part is under severe stress. Therefore, it is desirable that these bulkheads, especially the bulkhead on the boom foot side, are all welded to the inner surfaces of the four members. However, it is difficult to insert a partition wall after forming the four members into a closed cross-sectional shape, or to weld the entire circumference, so various proposals have been made to solve these inconveniences. Typical examples include the systems shown in Figures 2 to 7 and the systems shown in Figures 8 to 10 of JP-A-53-31539.

However, in the case of the above-mentioned former method (shown in Figures 2 to 7), although the manufacturing work is certainly easy, stress analysis of the finished product revealed that because plug welding was used, the bulkhead It is thought that the cause is that sufficient welding line length is not secured between the lower flange and the lower flange, and that there is a sudden cross-sectional change in the lower flange due to the hole being drilled in the lower flange for plug welding. , the stress in this part of the lower flange is larger than in other parts, and there is still a need for practical improvement. On the other hand, in the latter method (shown in Figures 8 to 10), the welding between the bulkhead and the lower flange is more sufficient than in the former method, and it is considered to be a preferable method for equalizing stress. However, it is quite difficult to weld the bulkhead inside the four members through the holes in the web, and it is practically impossible, especially for small booms. Since this requires a separate reinforcing member and increases welding work, there is still a need for improvement in terms of cost.

In view of the above background, the present invention has been made with the object of providing a method for manufacturing a boom, which allows the bulkhead, especially the bulkhead on the boom foot side, to be welded to four members reliably and easily. The method includes manufacturing a boom in which a main body having a box-shaped cross section is formed by upper and lower flanges and left and right webs, and a plurality of partition walls are provided in the main body in a distributed arrangement along the longitudinal direction of the main body. a step of assembling and welding three members of the upper and lower flanges and left and right webs to form a gutter-like object; a step of arranging the webs and flanges in a T-shape and welding to prepare a partition; a step of fitting the partition wall into at least a portion corresponding to the boom foot of the gutter-like object so that the three side edges of its web are in contact with the inner surfaces of the three members of the gutter-like object, and fillet welding at both contact edges, the partition wall; The upper and lower flanges are cut at locations corresponding to the flanges of
preparing the remaining one member of the left and right webs, arranging the one member in a box-shaped cross-section with respect to the three members with the cut edge overlapping the flange of the partition; The method is characterized in that it includes the step of welding a member to two of the three members and simultaneously welding the three members including the flange of the partition wall along the cut edge of the one member. .

The method of the present invention will be explained in detail below using the drawings.

left and right webs 1 cut out in a dogleg shape;
2. An upper flange 3 bent into a dogleg shape is prepared, and the upper flange 3 and the left and right webs 1 and 2 are connected to the second
As shown in the figure, the left and right webs 1,
2 along the upper abutting edge and welded at both corners to form a gutter.

On the other hand, the width W corresponding to the distance between the left and right webs 1 and 2 and the height of the left and right webs 1 and 2 approximately correspond to the width W and the height of the left and right webs 1 and 2 in the part of the bulkhead where the method of the present invention is applied, that is, in the illustrated example, the part of the bulkhead A that exists on the boom foot side. A partition wall 6 is separately prepared in which a web 4 having a height H and a flange 5 having a width W corresponding to the same width W are arranged in a T-shape and welded at both corners. (see figure).

As shown in Figure 2, the partition wall 6 is installed inside the already assembled upper flange 3 and left and right webs 1 and 2 so that the top and left and right side edges of the web 4 are in contact with the inner surfaces of the upper flange and left and right webs. It is fitted so that the flange 5 is located on the open side, and is fillet welded to the upper flange 3 and the left and right webs 1 and 2 at the corners of both sides on the top and left and right side edges of the web 4, and as necessary. Fillet welding is performed at the corners of the left and right upper edges of the flange 5 and the left and right webs 1 and 2. Here, when the method of the present invention is applied to the other partition walls 7, 8, 9, and 10, the same steps as above are used. In the illustrated example, the other partition wall parts have a different structure because the stress conditions are not as severe as the partition wall 6 part. That is, the partition walls 7, 8, and 10 adopt the method shown in Figures 2 to 7 of Japanese Patent Application Laid-open No. 53-31539, and in the partition wall 9, only the upper and left and right three side edges are connected to the upper flange 3 and the left and right edges. A method of fillet welding the webs 1 and 2 is adopted. The lower flange is made up of two members 1 cut at corresponding parts of the partition wall 6.
1 and 12, both members 11 and 1
2 abuts the cut edges and connects the abutting portion to the flange 5
It is located above and placed against the lower edges of the left and right webs 1, 2 from below, and fillet welded at the corners of the outer lower edges of the left and right webs 1, 2 and the upper surfaces of the members 11, 12. Further, at the abutting edge of the member 11 and the member 12, the flange 5 is used as a backing metal, and the flanges 5 of both the members 11 and 12 are welded together over the entire width in the open working position.

Since the present invention is as described above, welding between the partition wall 6 and the lower flanges 11 and 12 can be carried out in an open state, which not only makes the work easy but also ensures that a defect-free welded part can be obtained. Together with,
The partition wall 6 and the lower flanges 11 and 12 are the lower flange 1
1 and 12 are welded with a long welding line that spans the entire width of the boom. Therefore, there is no stress concentration due to cross-sectional changes, etc., resulting in a highly strong welded part, and the boom can be made with uniform stress as a whole at a low cost. There are benefits to be gained.

[Brief explanation of the drawing]

The drawings are for explaining the method of the present invention, and Fig. 1 is a side view of the completed boom, Fig. 2 is a perspective view of the portion of the boom shown in Fig. 1 A during manufacture, and Fig. 3 is a view of the bulkhead. FIG. 3: Upper flange, 11, 12: Lower flange,
1: left web, 2: right web, 6: bulkhead, 4: web of bulkhead, 5: same flange.

Claims (1)

[Claims] 1. When manufacturing a boom that has a main body with a box-shaped cross section formed by upper and lower flanges and left and right webs, and a plurality of partition walls are provided in the main body in a distributed manner along the longitudinal direction of the main body, a step of assembling and welding three members of the upper and lower flanges and left and right webs to form a gutter-like object; a step of arranging the webs and flanges in a T-shape and welding to prepare a partition; a step of fitting the partition wall into at least a portion corresponding to the boom foot of the object such that the three side edges of the web are in contact with the inner surfaces of the three members of the gutter-like object, and fillet welding at both contact edges, the flange of the partition wall; a step of preparing the remaining one of the upper and lower flanges and the left and right webs that have been cut at the portions corresponding to the above, the one member is shaped into a box-shaped cross-section with respect to the three members, and the cut edge is disposed overlapping the flange of the bulkhead, welding the one member to two of the three members, and simultaneously welding the three members including the flange of the bulkhead along the cut edge of the one member; A method for manufacturing a boom for a hydraulic excavator, the method comprising a welding step.