JP2008087886A - Boom of crane and manufacturing method for boom of crane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boom of a crane and a manufacturing method for the boom of the crane for preventing a boom on a tip side from being buckled in a side wall part while reducing its weight. <P>SOLUTION: This boom 1 of the crane is extended and contracted by moving the unit boom 2 on the tip side in the axial direction for a unit boom 2 on a terminal side. Each of the unit booms 2 includes a lower side member 6 formed by a plate material bent to open onto an upper side and an upper side member 4 formed by a plate material bent to open onto a lower side. The lower side member 6 and the upper side member 4 are mutually joined on opening part 6a, 4a sides of them. The lower side member 6 has a pair of right and left side wall parts 6c, 6c like flat plates provided on the opening part 6a side and constituting side walls 2a, 2a of the unit boom 2 and a reinforcing part 6d having a shape for improving buckling strength of the side walls 2a of the unit booms 2 for compression load in the axial direction of the unit boom 2 and formed continuously with an end part on the opening part 6a side of the side wall part 6c. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crane boom and a method for manufacturing a crane boom.

  Conventionally, in the prior art section of Patent Document 1 below, a boom for a crane having a box-type structure in which the ends of four flat plates are joined together is disclosed. In this boom, a reinforcing plate is attached to its side surface to compensate for the buckling strength of the boom side wall against the compressive load in the axial direction of the boom. However, in this boom, since stress concentrates on the joint portion of each flat plate when a suspension load is applied, the fatigue strength of the joint portion is likely to be reduced.

  Therefore, Patent Document 2 below discloses a boom structure capable of improving the fatigue strength of the joint. In Patent Document 2, a cylindrical boom is formed by joining an opening end portion of a lower member opened upward and an opening end portion of an upper member opened downward. In this boom, since the joining position of both members is close to the neutral plane for bending deformation due to the suspension load, that is, the plane where the bending stress associated with the bending deformation is zero, the joining position is compared to the structure of the boom described in Patent Document 1. Stress concentration on the part can be reduced. For this reason, it is possible to improve the fatigue strength of a junction part.

Moreover, the boom by patent document 2 has a substantially flat side wall, and the bottom wall part formed so that the cross section perpendicular | vertical to an axial direction might be circular arc shape or polygonal shape. In this bottom wall portion, since the width of the flat plate portion is small, the buckling strength against the compressive stress due to the hanging load is improved.
Japanese Utility Model Publication No. 2-11431 JP-A-2005-112514

  However, the side wall of the boom according to Patent Document 2 is formed in a substantially flat plate shape, and the buckling strength against the compressive stress due to the suspension load is not improved. In the boom of Patent Document 2, as a method for improving the buckling strength against the compressive stress caused by the hanging load on the side wall, a method of sticking the reinforcing plate according to Patent Document 1 on the side wall can be considered. However, in this method, since the reinforcing plate is joined to the side wall of the boom, there arises a problem that the number of joints to be concerned about fatigue strength increases.

  The present invention has been made in order to solve the above-described problems. The object of the present invention is to suppress the boom side wall seat against the compressive stress caused by a suspended load while suppressing an increase in the number of joints to be concerned about fatigue strength. It is to improve the bending strength and improve the fatigue strength of the joint.

  To achieve the above object, a boom of a crane according to the present invention includes a plurality of unit booms, the unit booms on the distal end side are inserted into the unit booms on the proximal end side, and the distal end side The booms of the crane extend and contract when the unit booms move in the axial direction with respect to the base unit side booms, and each unit boom is a bottom made of a plate material bent so as to open upward. Each of which includes a side member and an upper member made of a plate material that is bent so as to open downward, and the lower member and the upper member are joined to each other on the opening side, and the lower member And at least one of the upper member is provided on the opening side and a pair of left and right flat side walls constituting the side wall of the unit boom, and a compressed load in the axial direction of the unit boom. And a said reinforcing portion formed continuously to the end of the opening side of the shape to improve the buckling strength of the side wall of the unit booms the sidewall portion against.

  In this crane boom, the lower member that opens upward and the upper member that opens downward are joined at the opening side of each other to form a unit boom. Near the neutral plane for bending deformation. For this reason, the fatigue strength of the junction part of a lower member and an upper member can be improved. Further, in the boom of this crane, the reinforcing portion is formed in at least one of the lower member and the upper member in a shape that improves the buckling strength of the side wall of the unit boom against the compressive load in the axial direction of the unit boom. Therefore, the buckling strength of the boom sidewall against the compressive stress caused by the suspension load can be improved. Furthermore, in the boom of this crane, since the reinforcing portion is formed continuously at the opening side end of the side wall portion of at least one of the lower member and the upper member, Unlike the case where the reinforcing plate and the reinforcing member are joined to the side wall of the unit boom, it is possible to suppress the formation of a joint portion where the reinforcing plate and the reinforcing member are joined to the side wall of the unit boom. Thereby, it can suppress that the junction part which should be anxious about fatigue strength increases. Therefore, the boom of this crane improves the buckling strength of the side wall of the unit boom against the compressive stress caused by the suspension load while suppressing the increase of the joint where the fatigue strength is a concern. Can be improved.

  In the boom of the crane, a sliding pad is provided on the inner peripheral surface of the base end unit boom, and the outer peripheral surface of the lower member of the unit boom on the distal end side slides on the sliding pad. The reinforcing portion moves in the axial direction while in contact, and the distal end unit boom is in a specific range including a position where the distal end unit boom is in contact with the sliding pad in a state in which the distal end unit boom projects most from the proximal end unit boom. It is provided continuously along the axial direction of the boom, and has a shape that improves the buckling strength of the side wall of the unit boom on the distal end side against the push-up load acting from the sliding pad when a suspension load is applied. Is preferred. When the lifting load is applied to the distal end unit boom in the state where it protrudes the most from the proximal end unit boom, a local thrust load is received from the sliding pad, and the sidewall of the distal unit boom is seated by the thrust load. You may succumb. In this case, by configuring the reinforcing portion as described above, the unit boom on the distal end side is pushed up from the sliding pad in a specific range including the position where the unit boom is in contact with the sliding pad in the state where the unit boom projects most from the base end side unit boom. Since the buckling strength of the side wall of the unit boom on the front end side with respect to the load can be improved, the buckling of the side wall of the unit boom on the front end side due to the push-up load from the sliding pad can be suppressed.

  In the boom of the crane, the reinforcing portion may extend from an end portion of the side wall portion on the opening portion side to the inside of the opening portion. If comprised in this way, since a reinforcement part can be provided so that it may extend inside a unit boom, the buckling strength of the side wall of a unit boom can be improved, without affecting the outer surface shape of a unit boom.

  In this case, it is preferable that the reinforcing portion is formed by bending a plate material continuous from an end portion of the side wall portion on the opening portion side to the inside of the opening portion. If comprised in this way, the structure where a reinforcement part is continuously extended from the edge part by the side of the opening part of the said side wall part to the inner side of the opening part can be comprised easily.

  In the boom of the crane, the end portion on the opening portion side of the side wall portion of the lower member and the end portion on the opening portion side of the side wall portion of the upper member are joined in a state of abutting in the vertical direction. It is preferable. If comprised in this way, when the compression load of an up-down direction is applied to a unit boom, it can mutually support in the part which the lower side member and the upper side member faced. For this reason, unlike the structure in which the region in the vicinity of the opening end of the lower member and the region in the vicinity of the opening end of the upper member are overlapped in the vertical direction, the lower member is Since it can suppress that a shearing force is applied to the junction part of an upper member, the fall of the fatigue strength of the junction part can be suppressed.

  In this case, the reinforcing portion is provided in a partial region of the unit boom in the longitudinal direction, and the reinforcing portion is provided at the vertical position of the end portion of the side wall portion on the opening side. The remaining area may be substantially equal to the other area. If comprised in this way, even when a reinforcement part is provided in the partial area | region of the longitudinal direction of a unit boom, the edge part of the opening part side of the side wall part of a lower member and the opening part side of the side wall part of an upper member When joining in the state which faced | matched the edge part in the up-down direction, it can suppress that the area | region in which the reinforcement part of the side wall part of one member was provided interferes with the edge part of the other side wall part. Thereby, even when the reinforcing portion is provided in a partial region in the longitudinal direction of the unit boom, it is easy to make the end of the side wall of the lower member and the end of the side of the upper member abut each other in the vertical direction. Can be joined.

  In the configuration in which the end portion of the side wall portion of the lower member and the end portion of the side wall portion of the upper member are joined in a state in which they are abutted in the vertical direction, the reinforcing portion includes the lower member and the upper member. On one side, the unit boom is provided in a part of the longitudinal direction of the unit boom, and the other side wall of the lower member and the upper member has an interference with the reinforcing portion at the end on the opening side. A notch for avoiding the above may be provided. If comprised in this way, even when a reinforcement part is provided in the partial area | region of the longitudinal direction of a unit boom, the edge part of the opening part side of the side wall part of a lower member and the opening part side of the side wall part of an upper member When joining in the state which faced | matched the edge part in the up-down direction, it can suppress that the area | region in which the reinforcement part of the side wall part of one member was provided interferes with the edge part of the other side wall part. Thereby, even when the reinforcing portion is provided in a partial region in the longitudinal direction of the unit boom, it is easy to make the end of the side wall of the lower member and the end of the side of the upper member abut each other in the vertical direction. Can be joined.

  In the boom of the crane, the reinforcing portion may be provided on both the lower member and the upper member. If comprised in this way, the buckling strength with respect to the compressive stress by the suspension load of the side wall of a unit boom can be improved more.

  The present invention includes a step of forming the lower member opening upward by bending a flat plate, a step of forming the upper member opening downward by bending the flat plate, and the lower member And the step of forming the unit boom by joining the upper member and the upper member on the opening side of each other, and at least one of the step of forming the lower member and the step of forming the upper member is a pair of left and right Forming the flat plate portion, and forming the side wall portion and the reinforcing portion continuous therewith by bending an area in the vicinity of the opening side end portion of the flat plate portion to the inside of the opening portion. The manufacturing method of the boom of a crane including these.

  In this crane boom manufacturing method, at least one of the step of forming the lower member and the step of forming the upper member is performed by bending a region in the vicinity of the end portion of the flat plate portion toward the inside of the opening portion. Since the step of forming the side wall portion and the reinforcing portion continuous therewith is included, at least one of the lower member and the upper member may constitute a structure in which the reinforcing portion is continuous with the end portion on the opening side of the side wall portion. it can. This suppresses the formation of a joint where the reinforcing plate and the reinforcing member are joined to the side wall of the unit boom, unlike when the reinforcing plate and the reinforcing member separate from the unit boom are joined to the side wall of the unit boom. can do. Thereby, it can suppress that the junction part which should be anxious about fatigue strength increases. Furthermore, in this manufacturing method, since the reinforcing portion can be formed only by bending a flat plate, an effective reinforcing portion can be formed by a simple manufacturing process.

  As described above, according to the present invention, the buckling strength of the side wall of the unit boom with respect to the compressive stress due to the suspension load is improved while suppressing the increase in the number of joints to be concerned about fatigue strength. It is possible to improve the fatigue strength.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing a crane to which a boom 1 according to an embodiment of the present invention is applied, and FIG. 2 is perpendicular to the axial direction of a unit boom 2 constituting the boom 1 according to an embodiment of the present invention. It is sectional drawing of a direction. First, with reference to FIG.1 and FIG.2, the structure of the boom 1 of the crane by one Embodiment of this invention is demonstrated.

  As shown in FIG. 1, the boom 1 of the crane according to the present embodiment is attached to the crane body 100 so as to be raised and lowered. The boom 1 includes a plurality of unit booms 2. Each unit boom 2 is formed in a cylindrical shape, and the unit boom 2 on the distal end side is inserted into the unit boom 2 on the proximal end side. Then, the boom 1 is configured to expand and contract when the unit boom 2 on the distal end side moves in the axial direction with respect to the unit boom 2 on the proximal end side.

  The cross section perpendicular to the axial direction of each unit boom 2 has a similar shape. A sliding pad (not shown) is provided on the inner peripheral surface of the unit boom 2 on the proximal end side, and the sliding pad and the outer peripheral surface of the unit boom 2 on the distal end side are in contact with each other. The unit boom 2 on the front end side slides while sliding on the sliding pad.

  Each unit boom 2 includes an upper member 4 and a lower member 6 as shown in FIG. The upper member 4 is made of a single plate material that is bent so as to open downward, while the lower member 6 is made of a single plate material that is bent so as to open upward. The upper unit 4 and the lower member 6 are joined to each other on the side of the openings 4a and 6a, so that a cylindrical unit boom 2 is formed.

  The upper member 4 is formed so that a cross section perpendicular to the axial direction of the unit boom 2 is substantially U-shaped. The upper member 4 integrally includes a top wall portion 4b and a pair of left and right side wall portions 4c, 4c. The top wall portion 4b is located at the upper end of the unit boom 2, and is formed in a shape in which both end portions in the left-right direction of the flat plate are rounded and bent downward. Each side wall 4c is formed in a flat plate shape, and continuously extends downward from the left and right lower ends of the top wall 4b. And a pair of side wall part 4c, 4c is mutually arrange | positioned in parallel. The opening 4a is located between the lower ends of the pair of side walls 4c, 4c. The upper member 4 is formed using a plate material having a smaller plate thickness than the lower member 6. The upper member 4 may be formed using a plate material having a plate thickness equivalent to that of the lower member 6.

  The lower member 6 integrally includes a bottom wall portion 6b, a pair of left and right side wall portions 6c and 6c, and a pair of left and right reinforcing portions 6d and 6d. The bottom wall portion 6b is formed such that a cross section perpendicular to the axial direction of the unit boom 2 has an arc shape. By forming the bottom wall part 6b in such a shape, the buckling strength of the bottom wall part 6b with respect to the compressive load along the axial direction of the unit boom 2 is improved. Thereby, it is suppressed that buckling arises in the bottom wall part 6b by the compressive stress which acts by suspension load. Further, the outer peripheral surface of the lower member 6 of the unit boom 2 on the distal end side is in contact with the sliding pad provided on the inner peripheral surface of the lower member 6 of the unit boom 2 on the proximal end side, When a suspension load is applied to the unit boom 2, the unit boom 2 on the distal end side is supported by the unit boom 2 on the proximal end side at the position of the sliding pad.

  Each side wall 6c is formed in a flat plate shape, and continuously extends upward from the left and right upper ends of the bottom wall 6b. And a pair of side wall part 6c, 6c is mutually arrange | positioned in parallel. The opening 6a is located on the upper end side of the pair of side wall portions 6c. And the edge part by the side of the opening 4a of the side wall part 4c of the upper side member 4 and the edge part by the side of the opening part 6a of the side wall part 6c of the lower side member 6 are joined in the state faced | matched by the up-down direction. This joining is performed by welding from the outside of the unit boom 2 to the abutting portion between the end of the side wall 4c on the opening 4a side and the end of the side wall 6c on the opening 6a side. The joint 7 formed by this welding extends in the axial direction of the unit boom 2. The side wall 2c of the upper member 4 and the side wall 6c of the lower member 6 joined together constitute a substantially flat side wall 2a of the unit boom 2.

  Each reinforcing portion 6d of the lower member 6 is formed continuously with the end of the side wall portion 6c on the opening 6a side so as to improve the buckling strength of the side wall 2a against the compressive load in the axial direction of the unit boom 2. ing. Specifically, each reinforcement part 6d is each extended inside the opening part 6a from the edge part by the side of the opening part 6a of the side wall parts 6c and 6c. Each reinforcing portion 6d is arranged substantially perpendicular to the side wall portion 6c. Each reinforcing portion 6 d is continuously provided along the axial direction of the unit boom 2, and extends over the entire longitudinal range of the unit boom 2. And the reinforcement part 6d is formed by bending the board | plate material which continues from the edge part by the side of the opening part 6a of the side wall part 6c inside the opening part 6a. By providing the reinforcing portion 6d, the buckling strength of the side wall 2a against the compressive load in the axial direction of the unit boom 2 acting by the suspension load is improved.

  The shape of each reinforcing portion 6d is that the unit boom 2 on the distal end side with respect to the push-up load that acts from the sliding pad provided on the unit boom 2 on the proximal end side when a suspension load is applied to the unit boom 2 on the distal end side. It is also a shape which improves the buckling strength of the side wall 2a. The range in which the reinforcing portion 6d is provided in the distal unit boom 2 includes a position where the distal unit boom 2 comes into contact with the sliding pad in the state where the distal unit boom 2 projects most from the proximal unit boom 2. Yes. For this reason, even if the unit boom 2 on the distal end side receives a pushing-up load from the sliding pad when a suspension load is applied, the buckling of the side wall 2a in the vicinity thereof is suppressed.

  3 and 4 are diagrams for explaining a manufacturing process of the unit boom 2 according to the present embodiment. Next, with reference to these drawings, a process for manufacturing each unit boom 2 in the method for manufacturing the crane boom 1 according to the present embodiment will be described.

  First, the lower member 6 is produced. In the step of manufacturing the lower member 6, as shown in FIG. 3, by bending a metal flat plate, the member 10 that opens upward and has a U-shaped cross section perpendicular to the axial direction is formed. Form. The member 10 having a U-shaped cross section integrally includes a bottom wall portion 6b having an arc-shaped cross section perpendicular to the axial direction and flat plate portions 10c and 10c extending upward from left and right upper ends of the bottom wall portion 6b. Formed as follows. And the area | region of the upper end part of each flat plate part 10c is bend | folded at a substantially right angle inside the opening part of the said member 10. FIG. Thereby, as shown in FIG. 4, the flat side wall part 6c and the reinforcement part 6d which follows the upper end part of the side wall part 6c are formed. In this way, the lower member 6 is formed.

  Further, by bending another flat plate made of metal, the upper member 4 having an opening in the lower side and a substantially U-shaped cross section perpendicular to the axial direction is formed. At this time, the upper member 4 is formed using a flat plate having a smaller thickness than that of the lower member 6. In addition, you may form the upper member 4 using the flat plate which has the board thickness equivalent to the flat plate used for the said lower side member 6. FIG.

  Finally, the end on the opening 6a side of the side wall 6c of the lower member 6 and the end on the opening 4a side of the side wall 4c of the upper member 4 are butted against each other in the vertical direction, and the butted portion is outside. Weld from. Thus, the unit boom 2 by this embodiment shown in FIG. 2 is produced.

  As described above, in the boom 1 of the crane according to the present embodiment, the lower member 6 that opens to the upper side and the upper member 4 that opens to the lower side are welded to each other on the side of the openings 6a and 4a, and the unit boom 2 Therefore, the joining position of the lower member 6 and the upper member 4 is close to the neutral plane with respect to the bending deformation caused by the suspended load. For this reason, the fatigue strength of the joint part 7 of the lower member 6 and the upper member 4 can be improved. Moreover, since the reinforcement part 6d is formed in the lower member 6 in the shape which improves the buckling strength of the side wall 2a with respect to the compressive load about the axial direction of the unit boom 2, the side wall of the unit boom 2 with respect to the compressive stress by the suspension load The buckling strength of 2a can be improved. Further, in the lower member 6, the reinforcing portion 6 d is formed continuously at the end of the side wall portion 6 c on the opening 6 a side, so that a reinforcing plate and a reinforcing member that are separate from the unit boom 2 are attached to the unit boom 2. Unlike the case where it joins to the side wall 2a, it can suppress that the junction part in which these reinforcement boards and reinforcement members are joined to the side wall 2a of the unit boom 2 is formed. Thereby, it can suppress that the junction part which should be anxious about fatigue strength increases. Therefore, in the boom 1 of the crane according to the present embodiment, the buckling strength of the side wall 2a of the unit boom 2 with respect to the compressive stress due to the suspension load is improved while suppressing an increase in the number of joint portions that are concerned about fatigue strength. The fatigue strength of the joint 7 can be improved.

  Further, in the unit boom 2 on the distal end side, when a lifting load is applied in a state where it protrudes most from the unit boom 2 on the proximal end side, a local thrust load is received from the sliding pad, and the unit boom on the distal end side is received by the thrust load. 2 side wall 2a may buckle. On the other hand, in the boom 1 of the crane according to the present embodiment, the reinforcing portion 6d is provided over the entire range in the longitudinal direction along the axial direction of the unit boom 2 on the distal end side, and a suspension load is applied. Since it has a shape that improves the buckling strength of the side wall 2a of the unit boom 2 on the front end side against the push-up load acting from the sliding pad sometimes, the unit boom on the front end side caused by the local push-up load from the sliding pad The buckling of the side wall 2a of 2 can be suppressed.

  Further, in the boom 1 of the crane according to the present embodiment, the reinforcing portion 6d extends from the end of the side wall portion 6c on the opening 6a side to the inside of the opening 6a. A portion 6d can be provided. Thereby, the buckling strength of the side wall 2a of the unit boom 2 can be improved without affecting the outer surface shape of the unit boom 2.

  Moreover, in the boom 1 of the crane by this embodiment, the edge part by the side of the opening part 6a of the side wall part 6c of the lower side member 6 and the edge part by the side of the opening part 4a of the side wall part 4c of the upper side member 4 protrude in the up-down direction. They are joined together. Thereby, when the compressive load of an up-down direction is applied to the unit boom 2, it can mutually support in the part where the lower member 6 and the upper member 4 were faced | matched.

  Generally, as a joining structure of the lower member and the upper member, the region in the vicinity of the opening end portion of the side wall portion of the lower member and the region in the vicinity of the opening end portion of the side wall portion of the upper member are joined to each other with overlapping in the vertical direction. However, in this structure, when a vertical compressive load is applied to the unit boom, a shearing force acts on the joint between the upper member and the lower member. For this reason, in this structure, the fatigue strength of the said joint part falls easily. On the other hand, in the structure according to the present embodiment, when the unit boom 2 is subjected to a vertical compressive load as described above, the lower member 6 and the upper member 4 support each other at the abutted portion. It is possible to suppress a shearing force from being applied to the joint 7 between the side member 6 and the upper member 4. As a result, it is possible to suppress a decrease in fatigue strength of the joint portion 7.

  Further, in the method for manufacturing the boom 1 of the crane according to the present embodiment, the step of forming the lower member 6 of the unit boom 2 is a region in the vicinity of the end portion on the opening side of the flat plate portion 10c in the member 10 having a U-shaped cross section. Is formed inside the opening to form the side wall portion 6c and the reinforcing portion 6d continuous therewith, so that the lower member 6 has an end portion on the opening 6a side of the side wall portion 6c. A structure in which the reinforcing portion 6d is continuous can be configured. Thus, unlike the case where the reinforcing plate and the reinforcing member that are separate from the unit boom 2 are joined to the side wall 2a, it is possible to suppress the formation of a joint portion where the reinforcing plate and the reinforcing member are joined to the side wall 2a. it can. Thereby, it can suppress that the junction part which should be anxious about fatigue strength increases. Furthermore, in this manufacturing method, since the reinforcement part 6d can be formed only by bending a flat plate, the effective reinforcement part 6d can be formed by a simple manufacturing process.

  The scope of the present invention is not limited to the above embodiment, and includes various modifications without departing from the scope of the present invention. The structure of the unit boom by an example of each of these modifications is each shown by FIGS.

  In the above embodiment, the lower member 6 is provided with the reinforcing portion 6d. However, like the unit boom 12 of the first modified example shown in FIG. 5, the end portion on the opening 4a side of the side wall portion 4c of the upper member 14 is provided. The reinforcing portion 4d may be formed so as to be continuous. Similarly to the reinforcing portion 6d according to the above embodiment, the reinforcing portion 4d is formed by bending a plate material extending continuously from the end portion on the opening portion 4a side of the side wall portion 4c to the inside of the opening portion 4a at a substantially right angle. Is. In the first modification, the lower member 16 is not provided with a reinforcing portion.

  Moreover, like the unit boom 22 of the 2nd modification shown in FIG. 6, while providing the upper part 14 with the reinforcement part 4d, you may provide the lower part 16 with the reinforcement part 6d. These reinforcing portions 4d and 6d are arranged to overlap each other. If comprised in this way, the buckling strength with respect to the compressive stress by the suspension load of the side wall 2a of the unit boom 22 can be improved more.

  Further, like the unit boom 32 of the third modified example shown in FIG. 7, the bottom wall portion 36b of the lower member 36 is formed in a shape in which the left and right ends of the flat plate are bent with roundness on the upper side. Also good. In this configuration, the roundness of the left and right end portions of the bottom wall portion 36b can be variously changed. Moreover, the magnitude | size of the roundness of the right-and-left both ends of the top wall part 4b in the upper member 4 can be changed similarly.

  Further, like the unit boom 42 of the fourth modified example shown in FIG. 8, the bottom wall portion 46b of the lower member 46 may be formed in a polygonal shape having a plurality of corners in a cross section perpendicular to the axial direction. . In this configuration, the number of corners can be variously changed. In the unit boom according to the present invention, the bottom wall portion of the lower member and the top wall portion of the upper member can be formed in various shapes, not limited to the third modification and the fourth modification. .

  Moreover, like the unit boom 52 of the fifth modification shown in FIG. 9, the corner between the side wall 6c and the reinforcement 6d of the lower member 56 may be rounded. Further, like the unit boom 62 of the sixth modification shown in FIG. 10, the corner between the side wall 4c and the reinforcing portion 4d of the upper member 64 may be rounded. The roundness of these corners is often formed when the plate material is bent to form the reinforcing portions 6d and 4d. Note that the roundness of the corner can be variously changed.

  Moreover, you may form so that the reinforcement part 76d of the lower side member 76 may be wound inside the opening part 6a like the unit boom 72 of the 7th modification shown in FIG. Further, like the unit boom 82 of the eighth modification shown in FIG. 12, the reinforcing portion 86d of the lower member 86 may be bent downward. Further, like the unit boom 92 of the ninth modification shown in FIG. 13, the portion from the side wall portion 6c of the lower member 96 to the reinforcing portion 96d is bent in a crank shape in a cross section perpendicular to the axial direction. A reinforcing portion 96d may be formed on the substrate. The upper member 4 may also be provided with a reinforcing portion to which the shapes of the reinforcing portions 76d, 86d, and 96d according to the seventh to ninth modifications are applied. Moreover, you may provide the reinforcement part which has shapes other than these 7th-9th modifications in a lower member and / or an upper member.

  Further, like the unit boom 112 of the tenth modification shown in FIG. 14, the reinforcing portion 116 d of the lower member 116 may be provided in a partial region in the length direction of the unit boom 112. In this case, it is preferable that the reinforcing portion 116d is provided in a region where the compressive stress acting on the unit boom 112 is increased by the suspension load. Specifically, when a hanging load is applied, a large compressive stress is applied in the vicinity of the portion in contact with the sliding pad 118 on the inner peripheral surface of the unit boom 112 on the proximal end side. It is preferable to provide the reinforcing portion 116d in a region that covers the length range of the portion that is in contact with 118.

  In this case, for example, as in the unit boom 122 of the eleventh modification shown in FIG. 15, the rectangular portion for avoiding the interference with the reinforcing portion 116d at the end of the side wall 4c of the upper member 124 on the opening 4a side. It is preferable that a notch 124e having a shape is provided. In this configuration, the joint between the side wall 4c of the upper member 124 and the side wall 6c of the lower member 116 is U-shaped at the notch 124e. Further, as another form, like the unit boom 132 of the twelfth modification shown in FIG. 16, the reinforcing portion 136d is provided at the vertical position of the end portion on the opening 6a side of the side wall portion 6c of the lower member 136. You may comprise so that it may become substantially equal in the area | region made and the area | region other than that. Specifically, a pair of cut portions 136e and 136e extending vertically are provided at the end of the side wall portion 6c of the lower member 136 on the opening 6a side. The length of the notch 136e is set to a length corresponding to the plate thickness of the lower member 136. And the board | plate material between the notch parts 136e and 136 is bend | folded inside the opening part 6a from the position of the lower end of the notch parts 136e and 136e, and the reinforcement part 136d is formed. As a result, the vertical position of the end of the side wall 6c on the opening 6a side is substantially equal between the region where the reinforcing portion 136d is provided and the other regions. In this configuration, the joint between the side wall 4c of the upper member 4 and the side wall 6c of the lower member 136 is linear along the axial direction of the unit boom 132.

  According to the configurations of the eleventh and twelfth modified examples, even when the reinforcing portion 116d (136d) is provided in a partial region in the longitudinal direction of the unit boom 122 (132), the side wall of the lower member 116 (136). When the end portion of the portion 6c and the end portion of the side wall portion 4c of the upper member 124 (4) are joined in a state of abutting in the vertical direction, the reinforcing portion 116d of the end portion of the side wall portion 6c of the lower member 116 (136). It can suppress that the area | region in which (136d) was provided interferes with the edge part of the side wall part 4c of the upper side member 124 (4). As a result, even when the reinforcing portion 116d (136d) is provided in a partial region in the longitudinal direction of the unit boom 122 (132), the end portion of the side wall portion 6c of the lower member 116 (136) and the upper member 124 (4). ) Can be easily joined in a state in which the end of the side wall 4c is butted in the vertical direction.

  Moreover, the installation positions of the above-described reinforcing portions 6d, 76d, 86d, 96d, 116d, 136d and the reinforcing portion 4d can be variously changed in the vertical direction.

  Next, various simulations performed in order to confirm the effect of the unit boom according to the embodiment and each of the modifications will be described.

  First, in the first simulation, it was examined how the buckling generated in the side wall of the unit boom differs depending on the presence or absence of the reinforcing portion. This simulation was performed assuming a unit boom located at the forefront of the crane boom. Specifically, as shown in FIG. 17, the simulation was performed under the condition that the base boom is restrained at two locations on the base end side where the sliding pad abuts and a suspension load is applied to the tip of the unit boom. And this simulation was performed about the unit boom in which the reinforcement part was provided, and the unit boom in which the reinforcement part was not provided.

  18 and 19 show the result of the first simulation. FIG. 18 shows the result for the unit boom not provided with the reinforcing portion, and FIG. 19 shows the result for the unit boom provided with the reinforcing portion. 18 and FIG. 19, in the unit boom provided with the reinforcing portion, the buckling amount on the side wall is small and the buckling occurs compared to the unit boom not provided with the reinforcing portion. You can see that the range is small. Therefore, it has been found that the buckling of the side wall of the unit boom can be suppressed by providing the reinforcing portion on the unit boom.

  Next, in the second simulation, the difference in the maximum suspension load of the unit boom depending on the presence or absence of the reinforcing portion and the difference in the ratio of the maximum suspension load to the weight of the unit boom due to the presence or absence of the reinforcement portion were examined. The result is shown in FIG. In the unit boom according to the present invention, when a suspension load exceeding the maximum suspension load is applied, the side wall buckles. That is, the maximum suspension load of the unit boom and the maximum suspension load with respect to the weight of the unit boom can be used as an index representing the magnitude of the buckling strength of the side wall of the unit boom.

  From the result of FIG. 20, it can be seen that the maximum suspension load is increased by about 15% in the unit boom having the reinforcing portion compared to the unit boom not having the reinforcing portion. From this result, it has been found that the buckling strength of the side wall of the unit boom can be improved by providing the reinforcing portion on the unit boom. Further, it can be seen from FIG. 20 that the ratio of the maximum suspension load to the weight of the unit boom having the reinforcing portion is about 15% larger than that of the unit boom not having the reinforcing portion. From this result, it was found that the buckling strength of the side wall can be effectively improved while suppressing an increase in the weight of the unit boom by providing the reinforcing portion on the unit boom.

  Next, in the third simulation, the influence of the vertical position of the reinforcing portion on the buckling strength of the side wall of the unit boom was examined. Specifically, in this simulation, the weight of the unit boom in the case where the reinforcing portion is provided 24 mm above the upper end of the bottom wall portion of the lower member, 48 mm above, and 73 mm above. The ratio of the maximum suspension load with respect to was respectively examined. The result is shown in FIG. From FIG. 21, it can be seen that the ratio of the maximum suspension load to the weight of the unit boom decreases as the position of the reinforcing portion moves away from the upper end of the bottom wall portion. This result can be attributed to the following reasons. That is, as shown in FIGS. 18 and 19, the buckling of the side wall of the unit boom occurs near the upper end of the bottom wall portion of the lower member (near the boundary between the bottom wall portion and the side wall portion). For this reason, it is considered that the buckling strength of the side wall of the unit boom is improved when the reinforcing portion is provided at a position closer to the upper end of the bottom wall portion. Accordingly, it has been found that the position where the reinforcing portion is provided is more effective for reinforcing the side wall of the unit boom as the position closer to the buckling position of the side wall of the unit boom.

  Next, in the fourth simulation, the influence of the length of the reinforcing portion along the axial direction of the unit boom on the buckling strength of the side wall of the unit boom was examined. Specifically, the ratio of the maximum suspension load to the weight of the unit boom was examined while changing the length of the reinforcing portion along the axial direction of the unit boom. The result is shown in FIG. It can be seen from FIG. 22 that the ratio of the maximum suspension load to the weight of the unit boom increases as the length of the reinforcing portion along the axial direction of the unit boom increases. From this result, it has been found that the buckling strength of the side wall of the unit boom improves as the length of the reinforcing portion along the axial direction of the unit boom increases. However, since it is considered that the reinforcement effect of the reinforcing part is not improved even if the reinforcing part is expanded to the area where the buckling does not occur in the side wall of the unit boom, the area where the buckling of the side wall of the unit boom is sufficiently covered. It is considered that the length of the degree is appropriate as the length of the reinforcing portion.

  Next, in the fifth simulation, the influence of the width of the reinforcing portion on the buckling strength of the side wall of the unit boom was examined. Specifically, the ratio of the maximum suspension load to the weight of the unit boom was examined while changing the ratio of the width of the reinforcing portion to the width in the left-right direction of the unit boom. The result is shown in FIG. From FIG. 23, in the range where the ratio of the width of the reinforcing part to the width in the left-right direction of the unit boom is about 30% or less, the ratio of the maximum suspension load to the weight of the unit boom increases as the width of the reinforcing part increases. I understand. Furthermore, from FIG. 23, when the ratio of the width of the reinforcing portion to the width in the left-right direction of the unit boom exceeds about 30%, the ratio of the maximum suspension load to the weight of the unit boom hardly increases even when the width of the reinforcing portion increases. I understand that. From these results, the buckling strength of the side wall of the unit boom can be improved as the width of the reinforcing portion is increased in a range where the ratio of the width of the reinforcing portion to the width in the left-right direction of the unit boom is about 30% or less. It has been found. Further, it has been found that when the ratio of the width of the reinforcing portion to the width in the left-right direction of the unit boom exceeds 30%, the buckling strength of the side wall of the unit boom can hardly be improved even if the width of the reinforcing portion is increased.

  It should be noted that the reinforcing effect of the side wall of the unit boom can be sufficiently expected from the result of FIG. 23 even if the reinforcing portion has a relatively small width in which the ratio of the width of the reinforcing portion to the width in the left-right direction of the unit boom is about 10%. I understand. From this result, it was found that the buckling strength of the side wall of the unit boom can be effectively improved while reducing the width of the reinforcing portion and suppressing the increase in weight.

It is the figure which showed the crane with which the boom by one Embodiment of this invention is applied. It is sectional drawing of the direction perpendicular | vertical to the axial direction of the unit boom which comprises the boom of the crane by one Embodiment of this invention. It is a figure for demonstrating the manufacturing process of the unit boom by one Embodiment of this invention. It is a figure for demonstrating the manufacturing process of the unit boom by one Embodiment of this invention. It is sectional drawing of the unit boom by the 1st modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 2nd modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 3rd modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 4th modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 5th modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 6th modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 7th modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 8th modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 9th modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 10th modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 11th modification of one Embodiment of this invention. It is sectional drawing of the unit boom by the 12th modification of one Embodiment of this invention. It is a figure for demonstrating the setting conditions of the 1st simulation which investigated how buckling which arises in the side wall of a unit boom changes with the presence or absence of a reinforcement part. It is the figure which showed the result of the 1st simulation about the unit boom in which the reinforcement part is not provided. It is the figure which showed the result of the 1st simulation about the unit boom provided with the reinforcement part. It is the figure which showed the result of the 2nd simulation which investigated the difference of the maximum suspension load of a unit boom by the presence or absence of a reinforcement part, and the difference of the ratio of the maximum suspension load with respect to the weight of a unit boom by the presence or absence of a reinforcement part. It is the figure which showed the result of the 3rd simulation investigated about the influence which the position of the up-down direction of a reinforcement part has on the buckling strength of the side wall of a unit boom. It is the figure which showed the result of the 4th simulation which investigated the influence which the length of the reinforcement part along the axial direction of a unit boom has on the buckling strength of the side wall of a unit boom. It is the figure which showed the result of the 5th simulation investigated about the influence which the width | variety of a reinforcement part has on the buckling strength of the side wall of a unit boom.

Explanation of symbols

1 Boom 2 Unit boom 2a Side wall 4, 14, 64, 124 Upper member 4a, 6a Opening 4c, 6c Side wall 4d, 6d, 76d, 86d, 96d, 116d, 136d Reinforcing part 6, 16, 36, 46, 56 , 76, 86, 96, 116, 136 Lower member 10c Flat plate portion 124e Notch

Claims (9)

A plurality of unit booms are provided, and the unit boom on the distal end side is inserted into the unit boom on the proximal end side, and the unit boom on the distal end side is axial with respect to the unit boom on the proximal end side A boom of a crane that expands and contracts by moving to
Each unit boom includes a lower member made of a plate material bent so as to open upward, and an upper member made of a plate material bent so as to open downward, and the lower member, The upper member is joined to each other on the opening side;
At least one of the lower member and the upper member is provided on the opening side and a pair of left and right flat side wall portions constituting the side wall of the unit boom, and a compressive load in the axial direction of the unit boom. A boom for a crane, comprising: a reinforcing portion continuously formed at an end of the side wall portion on the opening side in a shape that improves the buckling strength of the side wall of the unit boom. A sliding pad is provided on the inner peripheral surface of the base boom on the base end side,
The unit boom on the distal end side moves in the axial direction while the outer peripheral surface of the lower member slides on the sliding pad,
The reinforcing portion is continuous along the axial direction of the unit boom on the distal end side in a specific range including a position where the unit boom on the distal end side contacts the sliding pad in a state where the unit boom projects most from the unit boom on the proximal end side. 2. The crane according to claim 1, wherein the crane has a shape that improves the buckling strength of the side wall of the unit boom on the distal end side against a push-up load acting from the sliding pad when a suspension load is applied. Boom.   The crane boom according to claim 1 or 2, wherein the reinforcing portion extends from an end portion of the side wall portion on the opening portion side to the inside of the opening portion.   The boom of a crane according to claim 3, wherein the reinforcing portion is formed by bending a plate material continuous from an end portion of the side wall portion on the opening portion side to the inside of the opening portion. .   The end portion on the opening portion side of the side wall portion of the lower member and the end portion on the opening portion side of the side wall portion of the upper member are joined in a state of abutting in the vertical direction, The boom of the crane of any one of Claims 1-4. The reinforcing portion is provided in a partial region in the longitudinal direction of the unit boom,
The vertical position of the end of the side wall portion on the opening side is substantially equal in the region where the reinforcing portion is provided and the other region. Crane boom as described. The reinforcing portion is provided in a partial region in the longitudinal direction of the unit boom in one of the lower member and the upper member,
The end of the other side wall of the lower member and the upper member on the opening side is provided with a notch for avoiding interference with the reinforcing portion. Item 6. The crane boom according to item 5.   The crane boom according to any one of claims 1 to 6, wherein the reinforcing portion is provided on both the lower member and the upper member. A crane boom manufacturing method according to any one of claims 5 to 8,
Forming the lower member that opens upward by bending a flat plate;
Forming the upper member that opens downward by bending a flat plate; and
A step of producing the unit boom by joining the lower member and the upper member on the opening side of each other,
At least one of the step of forming the lower member and the step of forming the upper member includes a step of forming a pair of left and right flat plate portions, and a region in the vicinity of the end portion of the flat plate portion on the opening portion side. A method of manufacturing a boom for a crane, comprising the step of forming the side wall portion and the reinforcing portion continuous therewith by bending the inside of the crane.

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