JPH0211431Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an improvement of a box-shaped boom used in self-propelled cranes such as hydraulic truck cranes.

(Prior art) Box-shaped booms for self-propelled cranes generally have a fourth
As shown in the figure, it is formed into a rectangular cross-sectional shape by left and right side plates a ₁ and a ₂ , an upper plate b, and a lower plate c. Bending moment, shearing force, axial force, etc. are applied to this boom, but when looking at each member, particularly high stress acts on the upper plate b and the lower plate c. For this reason, thick plates are usually used for the upper plate b and lower plate c, and thinner plates are used for the left and right side plates a ₁ and a ₂ , which have lower stress than these, in order to reduce the weight of the boom. However, as a result, the buckling strength of the side plates a ₁ and a ₂ becomes a problem.

Conventionally, as a countermeasure against buckling of the side plates a ₁ and a ₂ , reinforcing plates d ₁ and d ₂ were attached to the outer surfaces of both the upper and lower sides of the side plates a ₁ and a ₂ over the entire length, as shown in Fig. 4. I am trying to increase the bending strength. However, this not only increases the number of man-hours for manufacturing the boom by welding the reinforcing plates, but also causes distortion in welding when welding the reinforcing plates _{d 1} , _{d 2 to} the thin side plates a ₁ , a 2 . ₂ exhibits a so-called wavy shape, which adversely affects the strength of the boom.
As a solution to this point, we installed reinforcing plates on the side plates a ₁ and a ₂ in advance.
After welding d ₁ and d ₂ and correcting the welding distortion with rollers, etc., weld the side plates a ₁ and a ₂ to the upper plate b and the lower plate c. The number of manufacturing steps increases, productivity decreases, and costs increase.

On the other hand, in the case of a box-shaped boom, particularly high stress acts on the four corners, but in conventional booms, members a ₁ , a ₂ , b, and c are welded together at these four corners. This was very disadvantageous in terms of the strength of the welded portion.

(Purpose of the invention) In view of the above circumstances, the present invention satisfies the two prerequisites of securing side plate buckling strength and reducing the weight of the boom, while omitting the conventional reinforcing plate, thereby improving boom manufacturability. It is an object of the present invention to provide a box-shaped boom for a self-propelled crane that can realize cost reduction and is advantageous in terms of member welding strength.

(Structure of the invention) The present invention is a box-shaped boom for a self-propelled crane that is composed of four members: left and right side plates, and an upper plate and a lower plate that are thicker than the left and right side plates. The plate and the lower plate are formed into a U-shaped cross section that integrally has rising parts on both sides in the width direction, and the rising part of at least one member of the upper plate and the lower plate has a height that increases from the boom tip side to the boom base side. It is formed into a shape that becomes higher in the direction, and the raised portions of the upper and lower plates are welded to the upper and lower end portions of the left and right side plates.

(Embodiment) An embodiment of the present invention is shown in FIGS. 1 to 3. 1 and 1 are left and right side plates, 2 is an upper plate, and 3 is a lower plate. The upper plate 2 and the lower plate 3, which are subject to high stress, are made of thick plates, and the side plates 1 and 1 are made of thick plates to reduce the weight of the boom. Therefore, it is made of thin plate.

The upper plate 2 and the lower plate 3 have vertical rising parts 21, 21 and 31, 31 on both sides in the width direction, respectively.
This upper plate 2 is formed into a U-shaped cross section integrally equipped with
A box-shaped boom with a rectangular cross section according to the present invention is constructed by butt welding the end surfaces of the rising portions 21, 31 on both sides of the lower plate 3 and the upper and lower end surfaces of the left and right side plates 1, 1. There is. 4... is a welded part. Although FIG. 1 shows a case in which welding is performed on the inside and outside of the abutting portion, welding may be performed only on the outside.

According to this boom configuration, the upper plate 2 and the lower plate 3
The rising portions 21, 31 on both sides of the side plates 1, 1 are extended portions of the upper and lower sides of the side plates 1, 1 to form boom side plate portions, and the thick rising portions 21, 31
As a result, sufficient buckling strength is ensured for the boom side plate portion as a whole, which is the same as that of the side plates a ₁ and a ₂ with reinforcing plates shown in FIG. 4. In addition, since the side plates 1, 1, which are the intermediate portions of the boom side plates excluding the upper and lower sides (rising portions 21, 31), are thin plates,
Another prerequisite of reducing the weight of the boom will also be satisfied as before.

By the way, since the side plate buckling load is normally larger on the boom base side than on the boom tip side, it is necessary to increase the buckling strength on the boom base side. Therefore, in this boom, as shown in FIGS. 2 and 3, the rising portions 31 and 31 on both sides of the lower plate 3 are sloped so that the height H ₁ on the boom base side is higher than the height H ₂ on the boom tip side. (unequal height) formed like a wall. By doing this, while ensuring a large buckling strength on the boom base side, compared to the case where the lower plate rising parts 31, 31 are made into a uniform wall shape with a height H ₁ on the boom base side over the entire length. The entire boom is lightweight.

Note that the same effect can be obtained when the rising portions 21, 21 of the upper plate 2 are formed into the above-mentioned inclined wall shape. Alternatively, the rising portions 21, 21 and 31, 31 of both the upper plate 2 and the lower plate 3 may be formed into inclined wall shapes.

(Effect of the invention) As described above, when using the box-shaped boom for a self-propelled crane of the invention, the rising portions 21 and 31 are formed on both sides of the thick upper plate 2 and lower plate 3 in the width direction.
are integrally connected, and these rising parts 21, 31
Since the boom side plates are constructed by welding and joining the side plates 1 and 1 made of thin plates, the two prerequisites of securing sufficient buckling strength of the side plates and reducing the weight of the boom are satisfied. Conventional reinforcing plates can be omitted. Therefore, the step of welding the reinforcing plate and the step of correcting the welding distortion are not necessary, so that the boom manufacturing efficiency can be improved and the boom manufacturing cost including welding cost can be reduced.

Moreover, because the rising portions of one or both of the upper and lower plates are formed in a shape that increases in height from the tip of the boom toward the base, the base of the boom is subject to the largest buckling load among the side plates. Large buckling strength can be ensured. In other words, it is possible to most effectively achieve the basic objectives of reducing the weight of the boom and ensuring buckling strength.

In addition, since the welded portions 4 are located at the tips of the rising portions 21 and 31, rather than at the four corners as in conventional booms, the strength of these welded portions is It will be very advantageous.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a side view of the same part, FIG. 3 is a partially cutaway perspective view of the lower plate, and FIG. 4 is a sectional view of a conventional boom. 1, 1...Both left and right plates, 2...Top plate, 21,2
1...Both rising parts, 3...Lower plate, 31,3
1...Rising portions on both sides.

Claims (1)

[Scope of utility model registration request] In a box-shaped boom for a self-propelled crane, which is composed of four members: left and right side plates, and an upper plate and a lower plate that are thicker than the left and right side plates, the upper plate and the lower plate are attached to both sides in the width direction. The boom is formed to have a U-shaped cross section integrally having a rising part, and the rising part of at least one of the upper plate and the lower plate is formed in a shape in which the height increases from the tip side to the base side of the boom, A box-shaped boom for a self-propelled crane, characterized in that the raised portions of the upper and lower plates are welded to the upper and lower ends of the left and right side plates.