JPH079887U - boom - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce weight without lowering the strength of booms such as cranes, and to reduce manufacturing costs and improve durability. [Structure] Upper plate 19 and side plate 16 of inner boom 15,
The plate 20, at an angle of about 45 degrees with respect to the 16 mating surfaces,
20 is provided. The plates 20, 20 are provided with arcuate recesses 20a, 20a along the longitudinal direction. Further, it has convex portions 24a, 24a that are loosely fitted in the concave portions 20a, 20a, and the outer surface thereof is the upper plate 22 of the outer boom 21.
And slide shoes 24, 24 that are in surface contact with the inner surfaces of the side plates 23, 23.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a boom, and more particularly to a boom in which an inner boom is loosely inserted inside an outer boom so that the boom can expand and contract.

[0002]

[Prior art]

 FIG. 1 shows a crane truck as an example of a construction machine, and a telescopic boom 2 is attached to a machine body 1 so as to be able to rise and fall. The boom 2 generally has a rectangular cross section, and FIG. 4 shows a cross section of the boom 2 at the lower end position of the inner boom 3.

The inner boom 3 is composed of an upper plate 4, a lower plate 5, and both side plates 6 and 6, and the vicinity of the left and right corners of the upper plate 4 and the lower plate 5 and the upper and lower corners of the side plates 6 and 6. Slide shoes 7a, 7a ..., 7b, 7b ... are provided near the respective parts, and the inner shoe 3 is supported on the outer boom 8 by the slide shoes 7a, 7a ..., 7b, 7b. The movement is smooth.

Since the suspension load and the own weight of the boom 2 act on the slide shoes 7a, 7a, ... Of the upper plate 4 of the inner boom 3, the outer boom 8 is pressed by the slide shoes 7a, 7a ,. A bending moment is generated in the upper plate 9 and the side plates 10 and 10. Further, when the boom 2 is turned, the boom 2 swings to the left and right due to the swinging of the load, so that the slide shoes 7b, 7b of the side plates 6 and 6 of the inner boom 3 press the side plates 10 and 10 of the outer boom 8. A bending moment is generated in the outer boom 8.

Therefore, the upper plate 9 and the side plates 10, 10 of the outer boom 8 are required to have reinforcing plates 11a, 11a and 11b, 11b.

[0006]

[Problems to be solved by the device]

 As described above, in the conventional boom, since the slide shoe of the inner boom presses the upper plate and the side plate of the outer boom due to the suspension load and the self-weight, a bending moment is generated in the upper plate and the side plate of the outer boom. Further, the surface pressure of the slide shoe of the inner boom, which presses the outer boom, becomes high at the rear end portion, so that the rear end portion of the slide shoe is largely worn.

On the other hand, a gap δ is required in the boom assembly between the slide shoe provided on the side plate of the inner boom and the side plate of the outer boom. Therefore, the left and right load swings increase, which causes the bending moment of the outer boom to increase. Therefore, a reinforcing material is welded to the upper plate and the side plate of the outer boom to secure the strength against the bending moment. However, since the weight of the boom increases due to the welding of the reinforcing material, and the corrugation phenomenon occurs due to welding heat and the appearance is impaired, this repair requires a lot of man-hours. Further, with the occurrence of the waving phenomenon, the boom may be deformed and the gap between the inner boom and the outer boom may not be constant, which may cause a trouble in the expansion and contraction operation of the boom.

Therefore, there is a technical problem to be solved in order to reduce the weight without lowering the strength, reduce the manufacturing cost, and improve the durability, and the present invention solves this problem. The purpose is to resolve.

[0009]

[Means for Solving the Problems]

 The present invention has been proposed in order to achieve the above-mentioned object, and in a construction machine such as a crane truck equipped with a telescopic boom, a longitudinal direction is formed at a joint portion between an upper plate and a side plate at a lower end of an inner boom. A boom having a plate having an arcuate recess is fixedly attached to the upper plate and a side plate of the outer boom, and a slide shoe having a projection loosely fitted in the recess of the plate is provided. It is provided.

[0010]

[Action]

 When the boom is subjected to a hanging load, its own weight, and a load in the left-right direction due to load swing, the outer surface of the slide shoe of the inner boom presses the upper plate and side plates of the outer boom. In that case, a reaction force proportional to the pressing force of the slide shoe is generated in the outer boom and presses the outer surface of the slide shoe. Therefore, the slide shoe is pressed against the inner surface corner of the outer boom by the reaction force of the outer boom, and is held in a state of being pressed against the corner.

Further, in the longitudinal direction of the boom, even if the distance between the inner boom and the outer boom is not uniform and there is a slight inclination, the convex portion provided on the inner side surface of the slide shoe is inside the arcuate concave portion of the plate. The outer surface of the slide shoe makes surface contact with the outer boom substantially evenly. Therefore, the inner boom slides smoothly with respect to the outer boom.

[0012]

【Example】

 Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 shows a crane truck as an example of a construction machine, and a telescopic boom 2 is attached to a machine body 1 so as to be capable of hoisting. A sheave 12 is pivotally attached to the tip of the telescopic boom 2, a wire rope 13 is wound around it, and a hook 14 is suspended.

FIG. 2 is a cross section taken along the line AA of the boom 2 shown in FIG. 1, and FIG. 3 is a cross section taken along the line BB of FIG. Similar to the conventional type, the lower part of the inner boom 15 is provided with slide shoes 18a, 18a near the lower corners of the side plates 16, 16 of the inner boom 15, and is slid near the left and right corners of the lower plate 17. Install the shoes 18b, 18b.

On the other hand, at the joint between the upper plate 19 and the side plates 16 and 16 of the inner boom 15, the plates 20 and 20 are fixed at an angle of about 45 degrees with respect to the upper plate 19 and the side plates 16 and 16. Set up. The outer surface of each plate 20 is provided with a concave portion 20a which is arcuate in the longitudinal direction along the ridge lines of the upper plate 19 and the side plates 16 and 16. Then, slide shoes 24, 24 having a convex portion 24a loosely fitted in the concave portion 20a of the plate 20 and inscribed in the upper plate 22 and the side plates 23, 23 of the outer boom 21 are provided. Each of the slide shoes 24 can swing in the recess 20a of the plate 20 by the projection 24a provided on the inner surface thereof, and the outer surface of the slide shoe 24 has the upper plate 22 and the side plates 23, 23 of the outer boom 21. It is formed so as to come into surface contact with each inner surface.

The bending moment generated when the boom 2 is subjected to a load such as a suspension load and its own weight is received by the slide shoes 24, 24. At that time, a reaction force F is generated from the upper plate 22 of the outer boom 21 and a reaction force F is also generated from the side plate 23 on each of the slide shoes 24, and the two are balanced and the slide shoes 24 are orthogonal to each other. The outer side surface and the inner side surfaces of the upper plate 22 and the side plate 23 are in close contact with each other. Therefore, no bending moment is generated in the upper plate 22 and the side plates 23, 23, and the resultant force FF is applied in the direction of the joint (45 degree direction) between the upper plate 22 and the side plates 23, 23 of the outer boom 21 to generate a boom. The deformation of No. 2 does not occur, and the reinforcement that was necessary in the conventional type is unnecessary.

Further, since the outer side surfaces of the slide shoes 24, 24 orthogonal to each other and the inner side surfaces of the upper plate 22 and the side plates 23, 23 are in close contact with each other, the gap δ shown in FIG. 4 is always 0. It becomes the state of. Therefore, the rolling of the boom 2 is reduced, the operability of the boom 2 is improved, and the wear of the contact surface is reduced, so that the durability is also improved. The present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified version.

[0017]

[Effect of device]

 In the present invention, as described in detail in the above-described embodiment, the convex portion of the slide shoe is loosely fitted in the arcuate concave portion provided on the plate of the inner boom, and the load in either the pushing direction or the left-right direction is set. Since the load is evenly distributed, it is not necessary to reinforce the boom, and the weight can be reduced without lowering the strength. In addition, since the outer surface of the slide shoe is always in surface contact with the inner surface of the outer boom, lateral vibration is also small, and wear of the contact surface is reduced.

[0018] Thus, the invention has various practical values such as reduction of manufacturing cost and improvement of durability.

[Brief description of drawings]

FIG. 1 is a front view of a mobile crane as an example of a construction machine.

FIG. 2 is a sectional view taken along the line AA of FIG. 1 of the present invention.

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

FIG. 4 is a sectional view taken along line AA in FIG. 1 of the conventional type.

[Explanation of symbols]

 15 Inner Boom 16 Inner Boom Side Plate 19 Inner Boom Top Plate 20 Plate 21 Outer Boom 22 Outer Boom Top Plate 23 Outer Boom Side Plate 24 Slide Shoe

Claims (1)

[Scope of utility model registration request] 1. In a construction machine such as a crane truck equipped with a telescopic boom, a plate having an arcuate recess in the longitudinal direction is fixed to a joint portion between an upper plate and a side plate at a lower end of the inner boom. A boom which is inscribed in the upper plate and the side plate of the outer boom and has a slide shoe having a convex portion loosely fitted in the concave portion of the plate.