JP2006021877A - Telescopic boom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a telescopic boom, capable of improving resistance to buckling at a lower section of a boom without causing problems in conventional devices such as a larger change ratio of boom cross sectional size when combined in a case of addition of a reinforcement member to the lower section of the boom, and increase in manufacturing manhours or cost due to longer welding required. <P>SOLUTION: The lower section 22 of a boom 20 for each stage for composing a telescopic boom has a cross section in a roughly U-shaped form by use of a continuous plate member. On the part of the roughly U-shaped form of the lower section 22, a small sectional part 27 is formed in a separate form from the roughly U-shaped form. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a telescopic boom used for a work vehicle such as a mobile crane or an aerial work vehicle, and particularly to a telescopic boom having a cross-sectional shape with excellent buckling strength.

  Work vehicles such as mobile cranes and aerial work platforms tend to increase the length of the telescopic boom when it is fully extended in order to respond to the desire to increase the workable height. On the other hand, since the total weight of the work vehicle is suppressed to a predetermined weight or less by a law or the like that regulates a vehicle traveling on a public road, the weight of the entire telescopic boom cannot be increased. Therefore, the booms of the respective stages constituting the telescopic boom must be lengthened when the telescopic boom is fully extended while reducing the weight per unit length in the longitudinal direction.

  In order to meet the above requirements, a high-tensile steel sheet that can reduce the thickness of the steel sheet used for the boom and can use the material to a higher stress than before has been adopted. Therefore, the strength against buckling on the side where the compressive stress of the boom section is generated has been a problem.

  In order to solve the above-described problem, in recent years, a material in which a section of a lower section of each stage boom constituting the telescopic boom is formed into a substantially U-shape by a continuous plate material has appeared (for example, see Patent Document 1). . FIG. 1 explains the cross-sectional shape of one boom from the telescopic boom described in Patent Document 1. FIG. The lower section 2 of the boom 1 is composed of large arc-shaped portions 3 and 5 and a linear portion 4 sandwiched between the arc-shaped portions 3 and 5. By adopting the shape of the lower section, since the arc-shaped portions 3 and 5 of the lower section 2 where compressive stress is generated are difficult to buckle, the buckling strength of the entire lower section 2 is also high. Yes.

Furthermore, what was described in patent document 2 shown in FIG. 2 as what makes the cross-sectional shape of the lower section of each step boom into a substantially U shape is also proposed. The lower section 11 of the boom 10 has an elliptical shape with a small diameter portion serving as the lowest point portion 12 of the lower section 11. That is, the curvature R1 of the lowest point portion 12 is the smallest, and the curvature of the cross section of the lower section gradually increases as R2 and R3 as the distance from the lowest point portion 12 increases. For buckling, the smaller the curvature is, the greater the strength of the portion is. Therefore, the cross-sectional shape of Patent Document 2 in which the curvature of the lowest point of the lower section 11 at which the compressive stress is maximum is minimal is very reasonable. It is a thing.
Japanese Patent No. 28287979 (FIG. 7) EP 0499208B1 (Fig. 2)

  However, in recent years, because of the demand for further boom lengthening and weight reduction, it has come to be used at a higher stress by a steel plate having a higher tension than before, so even with the cross-sectional shape described in Patent Document 1 or Patent Document 2 described above. The buckling strength is no longer sufficient.

  In the boom 1 (FIG. 1) described in Patent Document 1, the lower section 2 is formed by forming a cross-sectional shape by adding a U-shaped reinforcing member 6 along the longitudinal direction to the straight portion 4 as shown in FIG. It is conceivable to improve the buckling strength of the steel. However, this boom cross-sectional shape requires a large space for avoiding the U-shaped reinforcing member 6 when combined with the outer boom, and as a result, the ratio of change in the cross-sectional dimensions of each stage of the telescopic boom becomes large. End up. This is a particularly serious problem when the number of boom stages is increased as a method of increasing the boom length when fully extended. In addition, a very long welding for attaching the long U-shaped reinforcing member is required, which causes a problem in terms of manufacturing man-hours or cost.

  Also in the boom 10 (FIG. 2) described in Patent Document 2, the buckling strength is insufficient for use at a higher stress, and thus the addition of a reinforcing member as described above is necessary. In this case, the same problem occurs. Therefore, the present invention seeks to provide an extendable boom that can improve the buckling strength of the lower section of the boom without causing the above-described problems.

  The telescopic boom described in claim 1 of the present application is a telescopic boom in which an intermediate boom and a top boom are respectively telescopically incorporated in a base boom, and a cross section of a lower section of each stage boom constituting the telescopic boom is provided. It is formed in a substantially U shape by a continuous plate material, and further, a small partition portion having a shape independent of the substantially U shape is formed in a substantially U shape portion of the lower section.

  Furthermore, in the telescopic boom described in claim 2 of the present application, in the telescopic boom described in claim 1, the small partition portion is formed to protrude outward from the substantially U-shaped portion. Features.

  Moreover, the telescopic boom described in claim 3 of the present application is the telescopic boom according to claim 1, wherein the small partition portion is one trapezoid protruding downward from a central portion of the substantially U-shaped portion. It is formed in a shape.

  In the telescopic boom according to claim 1, since the small section portion having a shape independent of the substantially U shape of the substantially U-shaped portion of the lower section has high buckling strength, The buckling strength of the entire character-shaped part is improved. In addition, a small section made up of an independent U-shaped part formed by a continuous plate material is formed without adding another reinforcing member, so there is no increase in weight and welding work. Is also unnecessary. Moreover, it is not necessary to increase the space | interval at the time of combining with the outside boom by providing the shape of the said small division part in each step boom in the same position and shape. Therefore, as a result, the change rate of the cross-sectional dimensions of each stage of the telescopic boom can be reduced.

  In the telescopic boom according to the second aspect, in addition to the configuration of the telescopic boom according to the first aspect, the small partition portion protrudes outward, so that the strength of the entire boom against bending is reduced. The buckling strength of the lower section is improved.

  In the telescopic boom according to the third aspect, in addition to the configuration of the telescopic boom according to the first aspect, since one small partition portion is formed in the central portion of the lower section where the compressive stress is maximized, The strength against bending can be increased efficiently. Furthermore, since the shape of the small partition portion is a simple trapezoidal shape, the small partition portion can be easily formed.

  The best mode for carrying out the invention will be described in the case where the present invention is applied to the above-described boom section of Patent Document 1 (FIG. 1) and boom section of Patent Document 2 (FIG. 2).

  FIG. 4 shows a boom 20 of the telescopic boom according to the embodiment of the present invention. The cross section of the boom 20 is composed of an upper section 21 made of continuous plate material and a lower section 22 made of continuous plate material.

  The thickness of the plate material of the upper section 21 is t1, and the whole is substantially U-shaped. The upper section 21 is bent at two right angles by R4, which is a relatively large bending radius. Both end portions 23 and 24 of the cross section of the upper section 21 are parallel to each other.

  The lower section 22 is made of a plate material having a thickness t2 that is slightly thicker than the thickness t1 of the upper section. The overall shape of the lower section 22 is substantially U-shaped. Both end portions 25 and 26 of the cross section of the lower section 22 are parallel to each other, and the inner space is the same as the distance between the both end portions 23 and 24 of the upper section 21. The upper section 21 and the lower section 22 are joined to each other at both ends 23 and 25 and 24 and 26 in the cross section to form a cross section of the boom 20 as a whole.

  One small partition portion 27 having a trapezoidal shape protruding downward is formed at the center of the lower section 22. FIG. 5 is a detailed view of the small section 27. As shown in FIG. 5, the small partition portion 27 is formed in a trapezoidal shape that protrudes downward as a whole by providing four bent portions of R6 that are small bends R. The dimensions L1 and L2 and the height dimension H of the upper and lower sides of the trapezoid are selected according to the relationship with the plate thickness t2 of the lower section 22. As a method of bending the small section 27, the boom 20 may be bent at once by placing the boom 20 on a long die and pressing it with a long punch, or by bending the roll. You may make it bend | fold in the trapezoid shape of the small division part 27, sending 20 to a longitudinal direction.

  Since the bend R6 for forming the small section 27 shown in FIG. 5 is much smaller than the bend R5 for forming the substantially U-shape of the lower section 22, the local portion of the small section 27 portion is shown. The buckling strength is very large. And since the center part of the lower section 22 in which the small division part 27 is formed is a part with the highest compressive stress in the lower section 22, it is a part that becomes a starting point when buckling occurs. By improving the local buckling strength, the buckling strength of the entire lower section 22 can be improved.

  FIG. 6 shows a cross section when the boom 20 is combined with the outer boom 30. The cross section of the outer boom 30 is composed of an upper section 31 made of a continuous plate material and a lower section 32 made of a continuous plate material. Reference numeral 33 denotes one small partition portion having a trapezoidal shape protruding downward at the center of the lower section of the outer boom 30. The cross-sectional shape of the boom 30 is similar to the cross-sectional shape of the boom 20, and the small partition portion 27 of the boom 20 and the small partition portion 33 of the boom 30 according to the present invention are also similar trapezoidal shapes. Therefore, as in the case where the conventional U-shaped reinforcing member shown in FIG. 3 is added, the change in cross-sectional dimension between adjacent booms does not increase, and the similarity ratio between adjacent booms is very close. can do. Therefore, even if the number of boom stages of the telescopic boom is increased, the cross-sectional dimension of the top boom with respect to the base boom does not become too small. In other words, since the boom cross-sectional dimension at the distal end side of the telescopic boom can be increased, it is only necessary to configure the boom cross section with a thinner plate thickness to give the same strength, and as a result, the overall telescopic boom can be reduced in weight. be able to.

  FIG. 7 shows a boom 40 in which the present invention is applied to the boom cross-sectional shape described in Patent Document 2 (FIG. 2). The lower section 41 of the boom 40 is formed in a substantially U shape by a plate material having a continuous cross section. Further, the substantially U-shaped portion of the lower section 41 has three shapes that are independent of the substantially U shape. Small partition portions (42, 43, 44) are formed to protrude outward from the substantially U-shaped portion. All of the three small sections are formed in a small arc shape having a curvature R8 that is sufficiently smaller than the curvatures (R1, R2, R3) of the substantially U-shaped section. The first small section 42 is disposed at the center of the substantially U-shaped portion, and the second small section 43 and the third small section 44 are adjacent to the first small section 42. It is arranged in a symmetrical position.

  The lower section 41 of the boom 40 has three small partition portions (42, 43, formed in a small arc shape having a curvature R8 that is sufficiently smaller than the curvature (R1, R2, R3) of the substantially U-shaped portion. 44), the strength against buckling of the lower section 11 of the conventional boom 10 can be improved.

It is a boom section indicated in patent documents 1. It is a boom section indicated in patent documents 2. A U-shaped reinforcing member 6 is added to the boom cross section described in Patent Document 1. It is the boom 20 of the telescopic boom which concerns on Example 1 of this invention. FIG. 5 is a detailed view of a small section 27 in FIG. 4. The cross section when the boom 20 is combined with the outer boom 30 is shown. It is the boom 40 of the telescopic boom which concerns on Example 2 of this invention.

Explanation of symbols

20: Boom 22: Lower section 27: Small section 40: Boom 41: Lower sections 42, 43, 44: Small section

Claims (3)

A telescopic boom in which an intermediate boom and a top boom are each telescopically incorporated in a base boom,
The section of the lower section of each step boom constituting the telescopic boom is formed in a substantially U shape by a continuous plate material, and the substantially U shape portion of the lower section is independent of the substantially U shape. A telescopic boom, characterized in that a small section having a shape is formed. The telescopic boom according to claim 1,
The telescopic boom, wherein the small partition portion is formed to protrude outward from the substantially U-shaped portion. The telescopic boom according to claim 1,
The telescoping boom is characterized in that the small partition part is formed in one trapezoidal shape projecting downward at a central part of the substantially U-shaped part.

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