JP6128163B2 - Mobile crane and mobile crane boom raising method - Google Patents

Description

  The present invention relates to a mobile crane and a method for raising a boom of a mobile crane, and particularly relates to a luffing specification in which both a boom and a jib are provided so as to be raised and lowered.

  Conventionally, as a mobile crane of luffing specifications, for example, as described in Patent Document 1, an upper swing body that is turnably provided on a lower traveling body, and a base end that is raised and lowered at the front portion of the upper swing body A boom that can be connected, a jib whose base end is connected to the tip of the boom so as to be raised and lowered, and a suspension hook that is suspended from a jib point sheave provided at the tip of the jib via a hoisting rope Or what is equipped with the hoisting drum to wind down, the boom raising / lowering apparatus which consists of the raising / lowering drum etc. which raises / lowers the said boom, and the jib raising / lowering apparatus which consists of the raising / lowering drum etc. which raise / lower the said jib is known.

  In this type of mobile crane, when the boom and the jib are erected by themselves from the state where the boom and the jib are lying on the ground, first, the wheel attached to the tip of the jib is moved along the ground. The boom is raised to a predetermined angle while being moved toward the lower traveling body. Subsequently, the boom is raised above the predetermined angle and the jib is raised while the hoisting rope is extended while the hoisting hook is placed on the ground while a certain load is applied to the hoisting rope. . And after the said boom stood to the working posture, the said hoisting rope was wound up and the said hanging hook was wound up.

  Here, the tip of the jib is usually provided with a roll-off preventing roller for restricting the hoisting rope from coming off the jib point sheave. The boom is raised by the conventional self-standing method. In this case, since the boom stands up to the working posture and the suspension hook is not loaded on the escape prevention roller, the suspension hook is wound up. .

JP 2012-116607 A

  However, in the case of a large mobile crane, the hoisting rope becomes thicker and heavier. Therefore, when the boom is raised while the hoisting rope is extended, the hoisting rope is not smoothly delivered, and the hoisting rope is near the hoisting drum. Has a problem that it causes slack and causes turbulence during winding.

  On the other hand, if the boom is raised while the hoisting rope is suspended from the jib point sheave via the hoisting rope without feeding the hoisting rope, the hoisting hook is passed through the hoisting rope to the escape prevention roller. There is a problem in that the load of the cable is applied, the escape preventing roller is broken, or the hoisting rope is damaged.

  The present invention has been made in view of such a point, and the problem is that the boom is raised in a state where the suspension hook is suspended from the jib point sheave through the winding rope without feeding the winding rope. It is an object of the present invention to provide a mobile crane and a mobile crane boom erecting method capable of raising the boom smoothly and quickly without causing breakage of the escape prevention roller and damage of the hoisting rope.

  In order to solve the above-described problems, the present invention provides a mobile crane that includes an upper swing body that is turnable on a lower traveling body, and a base end that is connected to the front portion of the upper swing body so as to be raised and lowered. A boom, a jib whose base end is connected to the tip of the boom so as to be raised and lowered, and a hoisting drum that winds or unwinds a hanging hook suspended from a sheave provided at the tip of the jib via a hoisting rope It is assumed that a boom hoisting device for hoisting the boom and a jib hoisting device for hoisting the jib are provided. The tip of the jib is provided with an escape prevention roller for restricting the hoisting rope from coming off the sheave, and when the boom and the jib are erected by themselves, the hoisting rope A protective roller that prevents contact with the prevention roller is provided.

  In such a configuration, even when the boom is raised with the suspension hook suspended from the sheave via the hoisting rope without feeding the hoisting rope, the protective roller provided at the tip of the jib Since the hoisting rope is prevented from coming into contact with the unwinding prevention roller, the hoisting prevention roller does not come into contact with the hoisting rope and the load of the hanging hook is not applied. Damage to the hoisting rope can be prevented.

  Here, it is preferable that an attachment member for attaching an auxiliary sheave is provided at the tip of the jib, and the protection roller is attached to a position near the sheave of the attachment member. In this case, since the auxiliary sheave side (that is, the mounting member side) has a space margin compared to the jib side, even when the protective roller is set to a large diameter, the space for the protective roller can be easily secured. This is advantageous for implementation.

  The protective roller may include a support shaft extending in the axial direction by the width of the tip of the jib, and a plurality of roller bodies that are rotatably and laterally fitted to the outer periphery of the support shaft. preferable. In particular, the width of each roller body is preferably set smaller than the diameter of the hoisting rope. In this case, when the boom stands up, the protection roller reliably prevents the hoisting rope from coming into contact with the escape prevention roller, so that the operation reliability can be improved.

  Furthermore, it is preferable that the diameter of the protective roller is set to 5 times or more the diameter of the hoisting rope. In this case, even when the protective roller comes into contact with the hoisting rope, the hoisting rope is not bent, and damage to the hoisting rope can be prevented.

  The boom standing method of the crawler crane of the present invention is based on the above-described mobile crane of the present invention. Then, after the boom and the jib have fallen on the ground, the boom is raised up to a predetermined angle while moving the wheel attached to the tip of the jib to the lower traveling body side along the ground, and then the jib When the boom is lifted from the sheave through the hoisting rope without extending the hoisting rope when the boom is raised above the predetermined angle by separating the tip of the boom from the ground, Make it upright.

  In such a configuration, after the boom and the jib are lying on the ground, the boom attached to the tip of the jib is moved to the lower traveling body side along the ground, and the boom is raised to a predetermined angle, and then the hoisting rope Without lifting the boom, the boom is raised while the suspension hook is suspended from the sheave via the hoisting rope, so that the hoisting rope can be omitted, and the boom can be raised smoothly and quickly. It can be carried out. In addition, the winding rope does not become slack in the vicinity of the winding drum due to the unwinding of the winding rope.

  In addition, the protective roller provided at the tip of the jib prevents the hoisting rope from coming into contact with the hoisting prevention roller. It is not hung, and it is possible to prevent breakage of the escape preventing roller and damage to the hoisting rope.

  According to the mobile crane and the boom raising / lowering method of the mobile crane of the present invention, when the boom is raised with the hanging hook suspended from the sheave through the hoisting rope without feeding the hoisting rope. However, the protection roller provided at the tip of the jib prevents the hoisting rope from coming into contact with the escapement prevention roller, so that the escapement prevention roller comes into contact with the hoisting rope and loads the suspension hook. No breakage of the escape prevention roller and damage to the hoisting rope can be prevented.

  In addition, the operation of extending the hoisting rope can be omitted, and the boom can be raised smoothly and quickly accordingly. Further, since the winding rope does not become slack in the vicinity of the winding drum due to the winding failure of the winding rope, implementation can be facilitated.

FIG. 1 is a side view showing a state of the crawler crane according to the embodiment of the present invention during operation. FIG. 2 is a side view showing a state in the middle of raising the boom of the crawler crane. FIG. 3 is an enlarged view of a region X in FIG. FIG. 4 is a side view showing the structure of the jib tip of the crawler crane. FIG. 5 is an arrow view seen from the Y direction of FIG. 6 is a cross-sectional view taken along line ZZ in FIG. FIG. 7 is a perspective view showing the structure of the tip of the jib. FIG. 8 is an enlarged view of region D in FIG. FIG. 9 is a side view showing the crawler crane boom and jib lying on the ground. FIG. 10 is a side view showing a state where the boom is slightly raised from the state shown in FIG.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments that are modes for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows an overall configuration of a crawler crane 1 as a mobile crane according to an embodiment of the present invention. The crawler crane 1 includes a lower traveling body 2 traveling by a crawler, an upper revolving body 4 provided on the lower traveling body 2 with a swivel device 3 interposed therebetween, and a boom 5 and a jib 6 as attachments. .

  The base end of the boom 5 is connected to the front portion of the upper swing body 4 so as to be able to undulate (rotate) around the boom foot pin 7. The base end of the jib 6 is connected to the tip of the boom 5 so as to be able to undulate around the jib foot pin 8.

  A jib point sheave 10, an auxiliary sheave 11, and an idler sheave 12 are provided at the tip of the jib 6, and a main hook 14 as a hanging hook is suspended from the jib point sheave 10 via a main winding rope 13. ing. One end of the main hoisting rope 13 is connected to the tip of the jib 6, while the other end side of the main hoisting rope 13 passes through the idler sheave 12 along the rear side of the jib 6 and the rear side of the boom 5. In addition to being wired, it is wound around a main winding drum 15 as a hoisting drum provided at the front portion of the upper swing body 4. The main hook 14 is wound up or down by forward and reverse rotation of the main winding drum 15.

  Further, an auxiliary hook 17 is suspended from the auxiliary sheave 11 via an auxiliary winding upper rope 16. One end of the auxiliary winding upper rope 16 is coupled to the auxiliary hook 17, while the other end side of the auxiliary winding upper rope 16 passes through the idler sheave 12 in the same manner as the other end side of the main winding upper rope 13. This is wired along the side and the back side of the boom 5, and is wound around the auxiliary winding drum 18 provided at the front portion of the upper swing body 4. The auxiliary hook 17 is wound up or down by forward / reverse rotation of the auxiliary winding drum 18.

  In addition to the base end of the jib 6, the base end of the front strut 21 and the base end of the rear strut 22 are connected to the tip of the boom 5 so as to be rotatable around pins. The front end of the front strut 21 and the front end of the jib 6 are connected via a first jib guy link 23 formed by connecting a plurality of link members. The front end of the rear strut 22 and the base end portion of the boom 5 are connected via a second jib guy link 24 having the same configuration as the first jib guy link 23.

  Further, a jib spreader 25 is attached to the front end of the front strut 21, and a jib spreader 26 is attached to the front end of the rear strut 22. ing. One end of the jib hoisting rope 27 is coupled to one of the jib spreaders 25 and 26, while the other end of the jib hoisting rope 27 is provided from the jib spreader 26 to the rear side of the tip of the boom 5. In addition, it is wired along the back side of the boom 5 through the idler sheave 28 and wound around a jib undulation drum 29 provided at the base end of the boom 5. Then, when the jib hoisting rope 27 is wound or fed out by the jib hoisting drum 29, the distance between the two jib spreaders 25, 26 changes, and the jib 6 is raised and lowered. Accordingly, the jib hoisting drum 29, the jib hoisting rope 27, and the jib spreaders 25, 26 constitute a jib hoisting device 30 for hoisting the jib 6.

  The crawler crane 1 further includes a mast 31 whose base end is connected to the front portion of the upper swing body 4 so as to be raised and lowered, a gantry 32 provided at the rear portion of the upper swing body 4, and a rear portion of the upper swing body 4. And a counterweight trailer 35 connected to the rear end of the upper swing body 4 via a connecting arm 34.

  The tip of the mast 31 is connected to the tip of the boom 5 via a boom guy link 36 and a boom hoisting rope 37. The boom guy link 36 is formed by connecting a plurality of link members, and one end of the boom guy link 36 is coupled to the tip of the boom 5. A boom spreader 38 is attached to the other end of the boom guy link 36, and a boom spreader 39 is attached to the tip of the mast 31. A boom hoisting rope 37 is wound around the boom spreaders 38, 39. . One end of the boom hoisting rope 37 is coupled to one of the boom spreaders 38 and 39, while the other end of the boom hoisting rope 37 is connected to the rear surface of the mast 31 through a sheave 40 provided at the tip of the mast 31. It is wired along the side and is wound around a boom hoisting drum 41 provided at the base end of the mast 31. Then, by winding or unwinding the boom hoisting rope 37 by the boom hoisting drum 41, the distance between the boom spreaders 38, 39 is changed, and the boom 5 is hoisted. Therefore, the boom raising and lowering device 42 for raising and lowering the boom 5 is configured by the boom raising and lowering drum 41, the boom raising and lowering rope 37, the boom spreaders 38 and 39, and the mast 31.

  The top of the gantry 32 is connected to the tip of the mast 31 via a mast guy link 43 and a mast hoisting rope 44. The counterweight trailer 35 is supported from the tip of the mast 31 via a suspension link 45. Both the mast guy link 43 and the suspension link 45 are formed by connecting a plurality of link members.

  Here, FIG. 1 is a side view showing a state of the crawler crane 1 during operation, and FIG. 2 is a side view showing a state in the middle of the boom 5 of the crawler crane 1 standing up. That is, FIG. 2 shows a state in which the boom 5 is raised to a predetermined angle from the horizontal plane with the wheel 82 attached to the tip of the jib 6 being in contact with the ground. As shown in detail in FIG. 3, the tip portion of the jib 6 includes a jib top 50 constituting the tip main portion of the jib 6 and an attachment member 70 for attaching the auxiliary sheave 11 to the jib top 50.

  As shown in FIGS. 4 to 7, the jib top 50 has two left and right frame plates 51 and 51, and a base end portion and a distal end portion on the abdominal surface side extending in the left and right directions between the two frame plates 51 and 51, respectively. Two pipe-like horizontal members 52a, 52b installed, and two pipe-like members installed between the frame plates 51, 51 extending in the left-right direction at the base end portion and the distal end portion on the back side. Of the horizontal members 52c, 52d, and a plurality of pipe-shaped connecting members 53, 53,... That connect the horizontal members 52a to 52d.

  One end of the first jib guy link 23 is coupled to the back side of each frame plate 51 of the jib top 50 via a bracket 54 or the like (see FIG. 3). In addition, three idler sheaves 12 a, 12 b, and 12 c are provided side by side at the central portion in the lateral width direction on the back side of the jib top 50, and these idler sheaves 12 a to 12 c are interposed via a support shaft 55 and a bearing member 56. It is supported rotatably. The bearing member 56 is formed in a bifurcated shape, and the support shaft 55 passes through an intermediate portion thereof. Both ends of the bearing member 56 are fixed to the two lateral members 52c and 52d on the back side of the jib top 50, respectively. ing. Of the three idler sheaves 12a to 12c, the diameter of the central idler sheave 12b is set larger than that of the other idler sheaves 12a and 12c. An auxiliary winding upper rope 16 is wound around the center idler sheave 12b, and a main winding upper rope 13 is wound around the other idler sheaves 12a and 12c. An escape prevention roller 57 that restricts the auxiliary winding upper rope 16 from coming off the idler sheave 12 b is disposed opposite to the center idler sheave 12 b, and the escape prevention roller 57 is attached to the bearing member 56. It is supported by a fixed support lever 58. For the three idle sheaves, apart from the reference numeral 12, the reference numerals 12a to 12c are used to distinguish the three.

  A plurality of jib point sheaves 10, 10,... Are supported side by side between the left and right frames 51 and 51 so as to be rotatable around the same spindle 59, respectively. The support shaft 59 has a plurality of (four in the figure) partition plates 60, 60,... So as to partition the axial direction into three or four jib point sheaves 10, 10,. Each partition plate 60 has a substantially triangular shape, and its two apexes are fixed to the two horizontal members 52a and 52b on the abdominal surface side of the jib top 50, and the support shaft 59 penetrates the remaining one apex. doing. A main winding upper rope 13 is wound a plurality of times between the jib point sheave 10 and a sheave (not shown) on the main hook 14 side. Opposing each jib point sheave 10, a plurality of escape prevention rollers 61 that restrict the main hoisting rope 13 from coming off the jib point sheave 10 are arranged. As shown in an enlarged detail in FIG. 8, the escape prevention rollers 61 are supported by the frame plate 51 or the partition plate 60 via the holding members 62 every three or four. In the holding member 62, a plurality of support plate portions 62b, 62b,... Protrude from the base portion 62a at a predetermined interval in the lateral width direction of the jib top 50 and prevent escape between the tip portions of the adjacent support plate portions 62b, 62b. A roller 61 is rotatably installed.

  The attachment member 70 has two left and right leg portions 71, 71. Each leg portion 71 has two pipe-shaped main materials 72, 73 arranged in a V shape, and the main materials 72, 73. These are joined together by a plurality of sub-materials 74. One end of the main material 72 is connected to a lateral member 52 b on the abdominal surface side of the jib top 50 via a bracket 75. One end of the main material 73 is coupled to the extending portions 60a formed on the two partition plates 60 at the center in the lateral width direction of the jib top 50 among the plurality of partition plates 60, 60,. The other ends of the main materials 72 and 73 are coupled to the coupling plate 76. Note that the two left and right leg portions 71 and 71 are integrally configured by joining the corresponding main members 72 and 72 (or 73 and 73) with a sub-material 77.

  A cylindrical support shaft 78 is installed between the connecting plates 76 of the left and right leg portions 71, 71, and the auxiliary sheave 11 is rotatably supported at the axial central portion of the support shaft 78. An auxiliary winding upper rope 16 is wound around the auxiliary sheave 11. Opposing to the auxiliary sheave 11, an escape prevention roller 79 that restricts the auxiliary winding upper rope 16 from coming off the auxiliary sheave 11 is disposed, and both ends of the escape prevention roller 79 are connected to the coupling plate 76. It is supported by a support lever 80 fixed to. An axle 81 having a shaft length longer than the shaft length of the support shaft 78 is rotatably inserted into the support shaft 78, and wheels 82 for assembly / disassembly are attached to both ends of the axle 81.

  In addition, both ends of a bifurcated bearing member 83 are fixed to one main material 72 of each leg 71. An idler sheave 84 is rotatably supported at a middle portion of the bearing member 83 of each leg portion 71 via a support shaft (not shown). The auxiliary winding upper rope 16 is wound around the idler sheave 84 at a portion between the auxiliary sheave 11 and the idler sheave 12 (see FIG. 1). Opposite the idler sheave 84, an escape prevention roller 85 that restricts the auxiliary winding upper rope 16 from coming off from the idler sheave 84 is disposed, and both ends of the escape prevention roller 85 are respectively bearing members 83. It is supported by a support lever 86 fixed to.

  Further, a protective roller 90 is attached to each end 71 of the other main member 73 on the jib top 50 side (that is, a position near the jib point sheave 10 of the attachment member 70) via an attachment plate 87. When the boom 5 and the jib 6 are erected, the protective roller 90 comes into contact with the main hoisting rope 13 before the main hoisting rope 13 comes into contact with the escape prevention roller 61 so that the main hoisting rope 13 This is to prevent contact with the escape prevention roller 61. The protective roller 90 includes a pipe-shaped support shaft 91 made of metal such as steel extending in the axial direction corresponding to the width of the jib top 50, and a resin that is rotatably fitted side by side on the outer periphery of the support shaft 91. A plurality of ring-shaped roller bodies 92, 92,. The diameter of the protection roller 90 is set to be five times or more the diameter of the main winding upper rope 13, and the width of each roller body 92 is set to be smaller than the diameter of the main winding upper rope 13.

  Next, a method for raising the boom of the crawler crane 1 will be described with reference to FIGS. 1 to 4, 9, and 10. Now, as shown in FIG. 9, the boom 5 and the jib 6 have fallen on the ground and the crawler crane 1 has been assembled. In this state, the mast 31 is in the same state as when the crawler crane 1 shown in FIG. 1 is working.

  When raising the boom 5 and the jib 6 from such a state, first, the boom 5 is raised by the boom hoisting device 42 until the tip of the boom 5 is slightly lifted from the ground (see FIG. 10).

  Subsequently, the boom 5 is raised to a predetermined angle while the wheel 82 attached to the tip of the jib 6 is moved toward the lower traveling body 2 along the ground (see FIG. 2). At this time, as shown in FIG. 3, the main hook 14 is on the ground, and the main hoisting rope 13 is wound around the main hook 14 side sheave and the jib point sheave 10 with the main hoisting rope 13 slightly bent. It has been.

  Thereafter, the tip of the jib 6 (the wheel 82 in this embodiment) is separated from the ground, and the boom 5 is erected at a predetermined angle or more. At this time, the boom 5 is raised in a state where the main hook 14 is suspended from the jib point sheave 10 via the main hoisting rope 13 without feeding the main hoisting rope 13.

  At that time, when the main hook 14 is separated from the ground, the main hook 14 moves vertically below the jib point sheave 10 and the main hoisting rope 13 comes close to the escape prevention roller 61, but from the escape prevention roller 61. Since the protective roller 90 located on the lower traveling body 2 side of the tip of the jib 6 is in contact with the main hoisting rope 13, the main hoisting rope 13 is not in contact with the escapement prevention roller 61, and the escapement prevention The roller 61 is positioned below the oblique portion 13a between the jib point sheave 10 of the main winding upper rope 13 and the protective roller 90 (see FIG. 4). As a result, the load on the main hook 14 is not applied to the unwinding prevention roller 61 via the main hoisting rope 13, and the breakage preventing roller 61 is prevented from being damaged and the main hoisting rope 13 from being damaged. it can. The rigidity of the protective roller 90 is set so that the protective roller 90 can sufficiently withstand even when the main roller 14 is loaded by the protective roller 90 coming into contact with the main hoisting rope 13.

  In addition, the operation of extending the main hoisting rope 13 can be omitted, and the boom 5 can be raised smoothly and quickly accordingly. Further, since the main winding rope 13 is not loosened in the vicinity of the main winding drum 15 due to a feeding failure of the main winding rope 13, implementation can be easily achieved.

  In particular, in the case of this embodiment, an attachment member 70 for attaching the auxiliary sheave 11 is provided at the tip end portion (jib top 50) of the jib 6, and the protection roller 90 is located at a position near the jib point sheave 10 of the attachment member 70. It is attached. In this case, since the auxiliary sheave 11 side (that is, the mounting member 70 side) has a space margin compared to the jib top 50 side, even when the protective roller 90 is set to a large diameter, the space for the protective roller 90 is easily secured. This is advantageous for implementation.

  Further, the protection roller 90 includes a support shaft 91 extending in the axial direction corresponding to the width of the jib top 50, and a plurality of roller bodies 92, 92,... The width of each roller body 92 is set to be smaller than the diameter of the main winding upper rope 13. For this reason, even when the main hoisting rope 13 comes close to the escape prevention roller 61 at a plurality of positions in the width direction of the jib top 50 when the boom 5 stands, the main hoisting rope 13 and the escape prevention roller 61 are in contact with each other. Is reliably prevented by the protective roller 90, and the reliability of the operation can be improved.

  Furthermore, since the diameter of the protection roller 90 is set to be five times or more the major axis of the main winding upper rope 13, the main winding rope 13 can be bent even when the protection roller 90 comes into contact with the main winding upper rope 13. No, damage to the main winding upper rope 13 can be prevented.

  In addition, this invention is not limited to the said embodiment, A various other form is included. For example, in the above-described embodiment, the crawler crane 1 is described in which the wheel 82 for assembly / disassembly is mounted on the same axis as the auxiliary sheave 11 and the wheel 82 remains attached even during work. It can be applied to a crawler crane that attaches a wheel to the tip of a jib only occasionally, and the same effect can be achieved.

  In the above embodiment, the crawler crane has been described in which the auxiliary sheave 11 is attached to the tip of the jib 6 and the auxiliary hook 17 is suspended from the auxiliary sheave 11 via the auxiliary winding rope 16. The present invention can be similarly applied to a crawler crane in which the auxiliary sheave 11 and the auxiliary hook 17 are not provided at the tip end of 6 or a crawler crane provided with the auxiliary sheave and the auxiliary hook at the tip of the boom.

  Furthermore, the present invention can be applied not only to a crawler crane but also to a wheel crane.

1 Crawler crane (mobile crane)
2 Lower traveling body 4 Upper rotating body 5 Boom 6 Jib 10 Jib point sheave (sheave)
11 Auxiliary sheave 13 Main winding rope (winding rope)
14 Main hook (hanging hook)
15 Main winding upper drum (winding drum)
30 Jib hoisting device 42 Boom hoisting device 61 Roll-out prevention roller 70 Mounting member 82 Wheel 90 Protection roller 91 Support shaft 92 Roller body

Claims (6)

An upper swing body provided on the lower traveling body so as to be able to swivel, a boom having a base end connected to the front of the upper swing body so as to be raised and lowered, and a base end connected to the front end of the boom so as to be raised and lowered A jib, a hoisting drum for hoisting or lowering a hoisting hook suspended from a sheave provided at the tip of the jib via a hoisting rope, a boom hoisting device for hoisting the boom, and a jib for hoisting the jib In a mobile crane with a hoisting device,
The tip of the jib is provided with an escape prevention roller that restricts the hoisting rope from coming off the sheave, and when the boom and the jib are raised by themselves, the hoisting rope A mobile crane characterized in that a protective roller is provided to prevent contact with the escape prevention roller.   The mobile crane according to claim 1, wherein an attachment member for attaching an auxiliary sheave is provided at a tip portion of the jib, and the protection roller is attached to a position of the attachment member near the sheave.   The protective roller has a support shaft extending in the axial direction by the width of the tip of the jib, and a plurality of roller bodies that are rotatably and laterally fitted to the outer periphery of the support shaft. Item 3. The mobile crane according to Item 1 or 2.   The mobile crane according to claim 3, wherein a width of each roller body is set to be smaller than a diameter of the hoisting rope.   The diameter of the said protection roller is a mobile crane as described in any one of Claim 1 thru | or 4 currently set to 5 times or more of the diameter of the said hoisting rope. A method for raising a boom of a mobile crane according to any one of claims 1 to 5,
After the boom and the jib are lying on the ground, the boom attached to the tip of the jib is moved to the lower traveling body side along the ground while the boom is raised to a predetermined angle, and then the tip of the jib The boom is lifted from the jib point sheave via the hoisting rope without extending the hoisting rope while the boom is raised from the ground. A method for raising a boom of a mobile crane, wherein the boom is raised.

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