JPH0511278Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a jib structure for a mobile crane.

[Prior Art] Some mobile cranes include an inner jib and an outer jib, and the outer jib can be folded next to the inner jib during transportation to shorten the overall length of the jib. In recent years, mobile cranes have tended to have longer jibs.

[Problems to be solved by the invention] However, when the jib becomes longer like this, the torsional moment when the outer jib is folded relative to the inner jib increases.
There was a risk that buckling would occur in the diagonal members of the truss structure that constituted the inner jib.

Therefore, it has been considered to increase the diameter of the diagonal members, but in this case, there was a problem that the weight would increase significantly.

In view of these circumstances, the present invention attempts to increase the strength of the inner jib against torsional moments without significantly increasing the weight.

[Means for solving the problem] The present invention consists of four main members arranged at predetermined intervals, one end of which is fixed to one of the adjacent main members, and the other end of which is fixed to the other main member. In the jib structure of a mobile crane, an outer jib is connected to the tip of an inner jib having a truss structure and a diagonal member so that the outer jib can be folded to the side of the inner jib. When the time comes,
Adjacent diagonal members that receive compressive force due to torsional moment are fixed to each other by gussets.

[Operation] Therefore, in the diagonal member that receives compressive force, the length of the portion that substantially receives compressive force is shortened, making it difficult to buckle. This increases the strength of the inner jib.

[Example] Hereinafter, an example of the present invention will be described based on the drawings.

4 and 5 schematically show a mobile crane, in which a rotating body 2 is provided on a traveling body 1, and a jib 3 is attached to the rotating body 2 so as to be able to raise and lower. The jib 3 includes a main member 4 and each main member 4 arranged in a rectangular shape.
An inner jib 6 and an outer jib 7, which are mainly composed of a diagonal member 5 connecting four parts in a truss structure, are connected so that the outer jib 7 can be folded to the side of the inner jib 6. 8 is a folding support shaft.

In the present invention, as shown in FIGS. 1 to 3, in the inner jib 6, among the diagonal members 5, the diagonal members 5 are adjacent to each other in the horizontal and vertical planes of the inner jib 6 and compressed by the torsional moment M. The ends of the diagonals 5 and 5 (the corners of the diagonals 5 and 5) that receive the force (shown downward to the right in Figure 1 and upward to the right in Figure 2) are connected by gussets 9 as reinforcing materials. The structure is as follows.

In such a configuration, the outer jib 7 of the jib 3
When the inner jib 6 is rotated around the spindle 8 from the state shown by the imaginary line to the state shown by the solid line in FIG. A torsional moment M acts in the direction shown in FIGS. At this time, compressive force and tensile force alternately act on each diagonal member 5 of the inner jib 6 in the longitudinal direction (this has already been solved theoretically, computationally, and experimentally). As is well known, bars are generally weaker against compressive forces than tensile forces and are more likely to buckle.

However, in the present invention, the strength of each diagonal member 5 is reinforced by providing gussets 9 between adjacent diagonal members 5, 5 which are subjected to compressive force. , since the buckling length of the compression diagonal member 5 that bears the torsional moment M is shortened (L
>L'), the strength of the inner jib 6 has been improved,
It is possible to resist the torsional moment M when the outer jib 7 is folded.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention.

[Effect of the invention] As explained above, according to the invention, the diagonals that bear the torsional moment are connected by the reinforcing material, so the strength of the inner jib against the torsional moment is improved without significantly increasing the weight. It can have an excellent effect of increasing the number of students.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the jib structure of the mobile crane of the present invention, Fig. 2 is a - arrow view of Fig. 1, Fig. 3 is a - arrow view of Fig. 1, and Fig. 4 is a mobile crane. A schematic side view of the crane, FIG. 5 is a plan view of FIG. 4. 3 is a jib, 4 is a main member, 5 is a diagonal member, 6 is an inner jib, 7 is an outer jib, and 9 is a gusset.

Claims (1)

[Scope of utility model registration request] The tip of an inner jib having a truss structure, which has four main members arranged at predetermined intervals and a diagonal member whose one end is fixed to one of the adjacent main members and the other end is fixed to the other main member. In the jib structure of a mobile crane in which the outer jib is foldably connected to the side of the inner jib, when the outer jib is folded to the side of the inner jib, an adjacent inclined plane receives a compressive force due to a torsional moment. A mobile crane jib structure characterized by materials that are fixed together using gussets.