JP6536145B2 - Tension rod storage structure - Google Patents

Description

  The present invention relates to a storage structure of a tension rod which is stretched between an upper end of a boom and an appropriate end of a jib.

  Traditionally, mobile cranes have a telescopically configured boom. A boom head is provided at the tip of the tip boom of the boom (main jib), and a jib (auxiliary jib) is often attached to the boom head. Generally, the jib is such that the proximal end engages the lower end of the distal boom.

  By the way, in the case of work which does not use jib, it is necessary to store jib. As a method of storing the jib, a lower holding method in which the jib is arranged on the lower surface of the boom in the storing state and a horizontal holding method in which the jib is arranged on the side of the boom are representative.

  Among them, as a mobile crane of the lower storage type, for example, the one disclosed in Patent Document 1 is known. In the mobile crane of Patent Document 1, as shown in FIG. 1, the lower surface of the boom is stored with the jib base end directed to the boom tip and the jib tip directed to the boom base end. There is. At that time, a bracket-like rod support device is installed on the lower surface of the jib to hold the middle portion of the tension rod (see FIG. 7 of Patent Document 1). More specifically, the rod support device has a fixed bracket integrally provided with the lower surface of the jib, and a movable bracket rotatably attached to the fixed bracket.

JP, 2009-40601, A

  However, the rod support device described in the above-mentioned Patent Document 1 is complicated in structure, and when extending the jib from the jib storage position, the rod support device holding the middle portion of the tension rod is manually operated. The step of removing it was necessary. Furthermore, there is also a problem in that it vibrates during traveling to generate a contact noise because it is configured to only support its own weight.

  Therefore, an object of the present invention is to provide a retractable structure of a tension rod which has a simple configuration and does not require an operation at an intermediate portion of the tension rod when the jib is extended.

  In order to achieve the above object, the retractable structure of the tension rod of the present invention is a retractable structure of a tension rod stretched between the upper end of the boom and the proper position of the distal end of the jib in the jib working posture. A tensioning rod having a rod tip end coupled to the tip end in place and a rod proximal end coupled to the proximal end of the jib in the jib storage position; a jib tip connected to the rod tip end A jib having a connecting portion, a U-shaped guide member for receiving the middle portion of the tension rod in the jib storage posture, and a jib proximal end coupled to the rod proximal end, the jib comprising In the storage posture, the rod end connection portion is connected to the jib end connection portion, and the rod base end connection portion is connected to the jib base end connection portion. By the restoring force due to the elastic deformation of the emission Deployment rod, an intermediate portion of the tension rod is adapted to be pressed against the U-shaped guide member.

  As described above, the storage structure of the tension rod according to the present invention includes the tension rod having the rod distal end connecting portion and the rod proximal end connecting portion, the jib distal end connecting portion, the U-shaped guide member and the jib proximal end connecting portion. And in a state where the rod end connection portion is connected to the jib end connection portion and the rod base end connection portion is connected to the jib base end connection portion in the jib storage posture, the elastic deformation of the tension rod is caused. By the restoring force, the middle portion of the tension rod is pressed against the U-shaped guide member. For this reason, it is a simple structure, and when extending a jib, it becomes the storing structure of the tension rod which does not require the operation | work in the intermediate part of a tension rod. Furthermore, it is possible to suppress the generation of contact noise due to vibration during traveling.

It is a side view of a rough terrain crane. FIG. 7 is a side view of the jib storage posture of the jib of the first embodiment. FIG. 5 is a plan view of the jib storage posture of the jib of the first embodiment. It is a sectional view of a guide member. It is a side view of a guide member. It is explanatory drawing of the procedure of jib storage. (A) is a tension rod removal step, and (b) is a boom raising / retracting step. It is explanatory drawing of the procedure of jib storage. (C) is an auxiliary rope installation step, (d) is a boom down / jib removal step, and (e) is a jib side up step. It is sectional drawing of a holding posture. FIG. FIG. 14 is a side view of the jib storage posture of the jib of the second embodiment. It is a side view of the jib working posture of the jib of Example 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the constituent elements described in the following embodiments are exemplifications, and the technical scope of the present invention is not limited to them. In the following embodiments, the rough terrain crane 1 will be described as an example, but the present invention is not limited to this and can be widely applied to mobile cranes such as all terrain cranes.

(Constitution)
First, the overall configuration of the rough terrain crane 1 will be described. As shown in FIG. 1, the rough terrain crane 1 can horizontally turn on the vehicle body 10 as a main body of a vehicle having a traveling function, outriggers 11 provided at four corners of the vehicle body 10,. It has a swivel base 12 attached thereto, and a boom 14 attached to a bracket 13 provided upright on the swivel base 12.

  The boom 14 is configured to be telescopic by a distal boom 143, a proximal boom 141, and an intermediate boom 142 between them. A relief cylinder 15 is bridged between the lower portion of the proximal boom 141 and the bracket 13 so that the entire boom 14 can be undulated. Furthermore, in the present embodiment, the jib 30 and the tension rod 20 are stored on the side surface of the base end boom 141 in a lying position.

  2 and 3 show the tension rod 20 and the jib 30 in the jib storage posture in which the jib 30 is stored. However, in the following description, “upper direction / lower direction” is defined as the direction in the jib work posture unless otherwise mentioned.

  The tension rod 20 is formed in a long rod shape as a whole. The tension rod 20 is disposed at the tip end side of the length adjustment portion 24 having a plurality of attachment holes, the main body portion 25 formed of a hollow steel pipe, and the distal end side of the main body portion 25 and connected to the jib tip coupling portion 31 of the jib 30. The rod end connection portion 21, the rod base end connection portion 22 disposed on the base end side of the main body portion 25 and connected to the jib base end connection portion 32 of the jib 30 in the jib storage posture, and the base end of the tension rod 20 And a grip 23 for gripping the vicinity.

  The rod end connection portion 21 is rotatably attached by communicating the pin to the jib end connection portion 31. The rod end connection portion may be slidably supported in the elongated hole as the jib end connection portion as described later, and may be configured to slide by extending and retracting the tilt cylinder (see Example 2). ).

  The jib 30 is formed in a substantially Y shape as a whole. The proximal end of the jib 30 (during the jib operation) is bifurcated so as to engage with the engagement portions (not shown) on the lower side of the boom head 144 (see FIG. 1) at the distal end of the tip boom 143 A U-shaped engaging portion 33 is attached to the forked tip. The front end side of the jib 30 has a box-like structure, and two plates are attached at the front end thereof, and the sheave is rotatably held.

  The jib 30 according to the present embodiment includes a jib distal end coupling portion 31 coupled to the rod distal end coupling portion 21, a U-shaped guide member 40 for receiving an intermediate portion of the tension rod 20 in the jib storage posture, and a rod proximal end And a jib proximal end connecting portion 32 connected with the connecting portion 22.

  As shown in FIGS. 2 and 3, the jib tip connection portion 31 is disposed at the upper end of the tip of the jib 30 and is connected to the rod tip connection portion 21 of the tension rod 20 by a pin. In addition, as the jib tip connection portion, as described later, it is possible to form a long hole slidably supporting the rod tip connection portion in the axial direction of the jib (see Embodiment 2).

  The jib proximal end connection portion 32 is disposed on the proximal end upper portion of the jib 30, as shown in FIGS. 2 and 3, and is connected to the rod proximal end connection portion 22 of the tension rod 20 by a pin. As will be described later, in order to connect the rod proximal end connecting portion 22 to the jib proximal end connecting portion 32, the operator holds and depresses the grip 23 of the tension rod 20 by hand. However, since the tension rod 20 is bent downward by its own weight in a state in which the middle portion is supported by the guide member 40, the force of pushing down is sufficiently large manually.

  The guide member 40 is formed in an arm shape projecting upward and outward from the jib 30 as a whole, as shown in FIGS. The guide member 40 has a U-shaped portion 41 receiving the tension rod 20, an arm portion 42 supporting the U-shaped portion 41, and a reinforcing portion 43 supporting the U-shaped portion 41 and the arm portion 42 from below. .

  The U-shaped portion 41 is formed to open upward in the jib working posture, in other words, to open in the opposite direction of the jib 30. The position in the width direction of the jib 30 of the U-shaped portion 41 is set so that the center in the width direction of the U-shaped portion 41 is positioned on a straight line connecting the jib tip coupling portion 31 and the jib base end coupling portion 32.

  The height of the U-shaped portion 41 of the guide member 40 from the upper surface of the jib 30 is a predetermined distance above the straight line connecting the jib tip coupling portion 31 and the jib proximal end coupling portion 32 (jib working posture) It is considered to be a distant position. That is, in the inverted posture in which the tension rod 20 is positioned below the jib 30, the height of the U-shaped portion 41 is on the bottom of the U-shaped portion 41 even if the tension rod 20 is bent by its own weight. It is set to be pressed and fixed. In other words, the deflection amount (shape) of the full length of the tension rod 20 at the guide member 40 position in the reverse posture is calculated beforehand, and at least above the calculated deflection amount (downward in the use posture and reverse posture) The U-shaped portion 41 may be arranged. Therefore, when connecting the tension rod proximal end connecting portion 22 to the jib proximal end connecting portion 32 in the middle of the storing operation, since the middle portion is supported by the guide member 40, it is bent. It is necessary to manually apply a force corresponding to the difference in deflection amount.

  The height of the guide member 40 adds a predetermined margin height to the height calculated based on the above-mentioned deflection amount in consideration of vibration and the like when traveling in a model in which the storage posture is the lower posture. Is preferred. However, the height of the guide member 40 needs to be within a range in which the pipe-shaped main body 25 of the tension rod 20 is elastically deformed and can be pressed and connected by hand.

(Action)
Next, the operation of the storage structure S of the tension rod of this embodiment will be described with reference to FIGS. First, the overall procedure for storing the jib 30 will be described with reference to FIGS. 6 (a) and 6 (b) and FIGS. 7 (c), 7 (d) and 7 (e). The procedure for shifting the jib 30 from the storage posture to the use posture (projected posture) is generally in the reverse order of the following procedure.

  First, as shown in FIG. 6A, the boom 14 is lowered to a substantially horizontal state, and the tension rod 20 is removed from the boom head 144. That is, while the rod distal end connecting portion 21 is connected to the jib distal end connecting portion 31 by the pin, the rod proximal end connecting portion 22 removes the pin and removes it from the boom head 144. Then, in the present embodiment, in a state where the middle portion of the tension rod 20 is placed in the guide member 40, the grip 23 of the tension rod 20 is gripped and pushed downward by hand to align the position. Is connected to the jib proximal end connection 32 by a pin.

  Conversely, when projecting the jib 30, while pulling the grip 23 and pushing it down with the hand, the pin is pulled out and the tension rod is removed by removing the rod proximal end connection portion 22 from the jib proximal end connection portion 32. Fixation of 20 is released. That is, since the guide member 40 is open at the top, in the middle portion of the tension rod 20, there is no need to release the conventional catch member.

  Next, as shown in FIG. 6 (b), the boom 14 is raised while the boom 14 is being contracted. Then, the jib 30 is pivoted by its own weight and stands approximately vertically.

  Next, as shown in FIG. 7C, the auxiliary wire 50 is hung on the jib 30 (and the tension rods 20, 20) and wound up with a winch, thereby drawing the jib 30 to the lower surface of the boom 14.

  Next, as shown in FIG. 7 (d), the boom 14 is again lowered to a substantially horizontal state, and the jib 30 is removed from the boom head 144. That is, in a state where the boom 14 is turned over, the pin is removed from the engagement portion 33 of the jib 30 and the boom 14 is temporarily extended to disengage the jib 30 and the boom head 144 from each other. Furthermore, a side up cylinder (not shown) disposed on the side of the proximal boom 141 is connected to the jib 30 by a pin.

  Finally, as shown in FIG. 7E, the jib 30 is pulled up from the lower surface of the proximal boom 141 to the side surface of the proximal boom 141 by retracting the side-up cylinder. Then, the proper position of the jib 30 is fixed to the proximal boom 141 and the storage of the jib 30 is completed.

  As described above, in the process of FIG. 6A, the jib 30 is swung out to the front of the boom head 144. In this state, the tension rod 20 is located above the jib 30. Then, in this state, the intermediate portion of the tension rod 20 is placed in the guide member 40, and while holding down the grip 23 (while elastically deforming), the proximal end connection portion 22 of the tension rod 20 is the base of the jib 30. It is connected by the end connection part 32 and a pin.

  In the processes of FIG. 6 (b) to FIG. 7 (c), the jib 30 is suspended and stands below the boom head 144. In this state, since gravity acts in the longitudinal direction of the tension rod 20, the tension rod 20 does not deviate from the guide member 40.

  In the process of FIG. 7D, the jib 30 is drawn to the lower surface of the boom 14, and the tension rod 20 is at the bottom and the jib 30 is at the top. In this state, gravity acts in the direction in which the tension rod 20 deviates from the guide member 40. Therefore, this state is a state in which the tension rod 20 is most easily deviated. However, in the present embodiment, the height of the guide member 40 is set so as to exceed the amount of deflection due to its own weight, so even in this state, the intermediate portion of the tension rod 20 is It is pressed against the bottom. In the model in which the storage posture is the lower posture, the load relationship between the tension rod 20 and the jib 30 is the same as that shown in FIG. 9, although there is a difference in the process.

  Next, in the process of FIG. 7E, the jib 30 is drawn to the side of the boom 14 so that the tension rod 20 is outside and the jib 30 is inside. Then, this state is the storage posture of the jib 30 and the tension rod 20 in the horizontal posture. In this state, as shown in FIG. 8, the restoring force of the tension rod 20 acts to push the bottom wall of the U-shaped portion 41 horizontally inward, and the weight of the tension rod 20 is the side wall of the U-shaped portion 41 Act in the direction to push vertically downward. That is, the acting direction of the restoring force and the acting direction of its own weight are substantially orthogonal. The own weight is received by the side wall of the U-shaped portion 41, and the restoring force is received by the bottom wall of the U-shaped portion 41. That is, no force acts in the direction in which the tension rod 20 deviates from the U-shaped portion 41. Rather, a force acts in a direction that prevents the tension rod 20 from deviating from the U-shaped portion 41.

(effect)
Next, the effects of the storage structure S of the tension rod of this embodiment will be listed and described.

(1) As described above, the storage structure S of the tension rod of the present embodiment is a storage structure S of the tension rod stretched between the upper end of the boom 14 and the appropriate end of the jib 30 in the jib working posture. is there. The storage structure S of the tension rod has a rod end connection 21 connected to the tip end of the jib 30 and a rod base end connection 22 connected to the base end of the jib 30 in the jib storage posture. A tension rod 20; a jib tip coupling portion 31 coupled to the rod tip coupling portion 21; a U-shaped guide member 40 for receiving an intermediate portion of the tension rod 20 in the jib storage posture; and a rod proximal end coupling portion 22 coupling And a jib 30 having a jib proximal end connection portion 32; Then, in the jib storage posture, the rod distal end coupling portion 21 is coupled to the jib distal end coupling portion 31, and the rod proximal end coupling portion 22 is coupled to the jib proximal end coupling portion 32, the elastic deformation of the tension rod 20 is performed. The middle portion of the tension rod 20 is pressed against the U-shaped guide member 40 by the restoring force due to the force. Therefore, the storage structure S of the tension rod which does not require the work at the middle portion of the tension rod 20 at the time of the extension work of the jib 30 is a simple configuration.

  That is, by utilizing the deflection of the tension rod 20, the tension rod 20 can be stored and held by the guide member 40 having a simple structure. Furthermore, since the guide member 40 has an open upper structure, it is not necessary to release the catch member as in the prior art when the jib 30 is extended.

(2) Also, in the reverse posture in which the tension rod 20 is positioned below the jib 30, the bottom surface portion of the U-shaped guide member 40 does not cause the tension rod 20 to deviate from the guide member 40 by its own weight. The height of the guide member 40 from the jib 30 is set so as to be pressed against and fixed. That is, in the storing operation, the posture of the jib 30 changes with each process. And in each process, the load state of the inversion posture in which the tension rod 20 is positioned below the jib 30 is the load state in which the tension rod 20 is most likely to deviate from the guide member 40. Therefore, if the height of the guide member 40 is set so that the tension rod 20 does not go out of the guide member 40 even in the reverse posture in which the most easily deviated load state, the tension rod 20 can be obtained in all steps. The guide member 40 can be prevented from coming off. Specifically, the bottom surface portion of the guide member 40 may be disposed at a position higher in the working posture than the deflection amount due to its own weight in the reverse posture.

(3) Furthermore, in the jib storage posture, the jib 30 can be configured to be held in a lying posture in which the lower surface of the jib 30 in the jib working posture is drawn to the side surface of the proximal boom 141. In this lying position, the weight of the tension rod 20 is supported by the side wall of the guide member 40, and at the same time, the restoring force due to the elastic deformation of the tension rod 20 acts in the direction to push the bottom of the guide member 40. That is, in the lying position, since the restoring force due to the elastic deformation of the tension rod 20 acts in the direction to prevent the deviation from the guide member 40, the tension rod 20 does not deviate from the guide member 40. Furthermore, the generation of contact noise due to traveling vibration can be suppressed by bending the tension rod 20 to suppress rattling.

(4) Also, in the jib storage orientation, the jib 30 can be configured to be held in the lower position in which the lower surface of the jib 30 in the jib working orientation is drawn closer to the lower surface of the base boom 141. In this posture, the weight of the tension rod 20 acts in a direction opposite to the restoring force of the elastic deformation of the tension rod 20. However, by giving a restoring force that allows the middle portion of the tension rod 20 to be pressed against the U-shaped guide member 40, deviation of the tension rod 20 from the guide member 40 can be prevented even in the lower posture.

  Hereinafter, the storage structure S of the tension rod different from that of the first embodiment will be described with reference to FIGS. The same or equivalent parts as the contents described in the above embodiment will be described with the same reference numerals.

(Constitution)
The configuration will be described first. As shown in FIGS. 10 and 11, the storage structure S of the tension rod of the present embodiment is constituted by the tension rod 20 and the jib 60 as in the first embodiment. However, unlike the first embodiment, the tilt rod 20 has a base end connected to the tension rod connection link 145 in the working posture, and a tip cylinder slidably supported by the support member 61 in the working posture and the storage posture. Connected to 63.

  The tension rod 20 is connected to the main end 25, a rod end connecting portion 21 slidably supported by the support member 61 as the jib end connecting portion 31, and the jib base end connecting portion 62 in the jib storage posture. And a rod proximal end connecting portion 22 connected to the tension rod connecting link 145 in the working posture. The two rod end connection portions 21 of the present embodiment are connected to each other via a sliding shaft 26 which is inserted into the support member 61 and slidably supported.

  The jib 60 supports the sliding shaft 26 connecting the rod tip couplings 21 in the axial direction of the jib 60 in a sliding manner, and the support member 61 as a jib tip coupling and the tension rod 20 in the jib storage position. A U-shaped guide member 40 for receiving the middle portion, a jib proximal end connection portion 62 coupled to the rod proximal end connection portion 22 in the jib storage posture, and a rod distal end connection portion 21 extending and contracting in the axial direction of the jib 60 And a tilt cylinder 63 for sliding the sliding shaft 26 to be connected. The support member 61 has an elongated hole on the side, and slidably supports the slide shaft 26 in the elongated hole.

(Action)
Next, the operation of the storage structure S of the tension rod of this embodiment will be described. In the jib storage orientation, as shown in FIG. 10, the slide shaft 26 connecting the rod tip connecting portions 21 is disposed at a position near the base end in the support member 61, and the rod base end connecting portion 22 is the jib base end. The middle portion of the tension rod 20 is pressed against the U-shaped guide member 40 in connection with the connection portion 62. Furthermore, as shown in FIG. 11, in the jib working posture, the slide shaft 26 connecting the rod end connecting portions 21 is moved to a position close to the end by the tilt cylinder 63 in the support member 61, and the rod base end connecting portion 22 is connected to a tension rod connecting link 145, and the middle portion of the tension rod 20 moves upward out of the guide member 40.

  When the jib storage posture is the lower posture, gravity acts in the direction in which the tension rod 20 deviates from the guide member 40 as shown in FIG. In the present embodiment, the height of the guide member 40 is set to exceed the amount of deflection due to its own weight, so even in this state, the middle portion of the tension rod 20 is the bottom portion of the guide member 40 by the restoring force of the tension rod 20. It is pressed against. Further, when the jib storage posture is the lying posture, as shown in FIG. 8, the restoring force of the tension rod 20 acts to push the bottom wall of the U-shaped portion 41 horizontally inward, and the tension rod 20 The weight acts on the side wall of the U-shaped portion 41 in the direction of pushing vertically downward. In this state, the restoring force of the tension rod 20 acts in a direction that prevents the tension rod 20 from deviating from the U-shaped portion 41.

(effect)
Next, the effect of the storage structure S of the tension rod of this embodiment will be described.

(1) As described above, the storage structure S of the tension rod of the present embodiment includes the tension rod 20 and the jib 60 as in the first embodiment, and in the jib storage posture, the rod tip connecting portion 21 is the jib While being connected with the support member 61 as the distal end connecting portion and in a state where the rod proximal end connecting portion 22 is connected with the jib proximal end connecting portion 62, the middle of the tension rod 20 is restored by the restoring force by the elastic deformation of the tension rod 20. The portion is pressed against the U-shaped guide member 40. For this reason, the storage structure S of the tension rod which does not require the operation at the middle part of the tension rod 20 at the time of the extension work of the jib 60 is a simple configuration.

(2) In the tension rod storage structure S of the present embodiment, the tension rod connection link 145 connected to the rod proximal end connection portion 22 in the working posture is attached to the boom head 145 at the tip of the boom 14 . The jib 60 slidably supports the rod end connection portion 21 in the axial direction of the jib 60. The support member 61 as a jib end connection portion and the rod end connection portion 21 extend and contract in the axial direction of the jib 60. And a tilt cylinder 63 for moving. Then, in the jib storage posture, the rod distal end connecting portion 21 is disposed at a position near the proximal end in the support member 61, and in a state where the rod proximal end connecting portion 22 is coupled with the jib proximal end connecting portion 62 By the restoring force of the elastic deformation of the rod 20, the middle portion of the tension rod 20 is pressed against the U-shaped guide member 40. Furthermore, in the jib working posture, the rod tip connecting portion 21 is slidingly moved within the support member 61 by extending and retracting the tilt cylinder 63 and disposed at a predetermined position, and the rod proximal end connecting portion 22 is a tension rod connecting link It is connected with 145. Thus, the storage structure S of the tension rod of the present embodiment can be applied to the tension rod 20 and the jib 60 in a form different from that of the first embodiment. At this time, similarly to the first embodiment, by utilizing the deflection of the tension rod 20, the tension rod 20 can be stored and held by the guide member 40 having a simple structure. Furthermore, since the guide member 40 has an open upper structure, it is not necessary to release the catch member as in the prior art when the jib 60 is extended. Furthermore, there is also an effect of preventing damage to the tension rod 20 due to forgetting to release the catch member at the time of jib extension.

  And, with the above-mentioned configuration, the tension rod connection on the upper side of the boom becomes unnecessary in the jib extension operation, the height operation can be eliminated and the safe operation at the low position can be realized, and the extension in space saving is possible. Thus, the effect of greatly reducing the overhang and storage time can be achieved.

  The other configurations and operational effects are substantially the same as those of the above-described embodiment, and hence the description thereof is omitted.

  Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes to the extent not departing from the scope of the present invention are included in the present invention. included.

  For example, in the embodiment, the “U-shaped” guide member 40 has a U-shape in which the bottom wall and the side wall are substantially orthogonal to each other, but the present invention is not limited thereto. It may be U-shaped or U-shaped with a curved bottom wall. In other words, the "U-shaped" in the present invention is intended to be an open shape with one side open at the top in the jib working posture, and in a strict sense, the "U" shape should be used. It is not intended.

  Moreover, although the case where the guide member 40 was arrange | positioned only at one place in the length direction of the tension rod 20 was demonstrated in the Example, it is not limited to this. The guide members 40 can also be arranged at a plurality of positions, for example, two places.

S Tension rod storage structure 1 Rough terrain crane 14 Boom 141 Base end boom 143 Tip boom 144 Boom head 145 Tension rod connection link 20 Tension rod 21 Rod end connection part 22 Rod base end connection part 23 Grip 26 Sliding shaft 30 Jib 31 Jib end connection portion 32 Jib base end connection portion 40 Guide member 41 U-shaped portion 42 Arm portion 43 Reinforcement portion 60 Jib 61 Support member (Jib end connection portion)
62 Jib base end connection part 63 tilt cylinder

Claims (5)

A retractable structure of a tension rod which is stretched between a top end of a boom and a proper position of a tip of the jib in a jib working posture,
A tensioning rod having a rod end connection portion connected to the tip end of the jib and a rod end connection portion connected to the base end of the jib in the jib storage position;
A jib distal end coupling portion coupled to the rod distal end coupling portion, a U-shaped guide member for receiving an intermediate portion of the tension rod in a jib storage posture, and a jib proximal end coupling portion coupled to the rod proximal end coupling portion And a jib having
In the jib storage posture, the rod distal end coupling portion is coupled with the jib distal end coupling portion, and the rod proximal end coupling portion is coupled with the jib proximal end coupling portion, and restoration by elastic deformation of the tension rod is performed. A retractable structure of a tension rod, wherein the middle portion of the tension rod is pressed against the U-shaped guide member by force.   The tension rod according to claim 1, wherein the tension rod is pressed and fixed to the bottom surface portion of the U-shaped guide member in a reverse posture in which the tension rod is positioned lower than the jib. Storage structure.   The tension rod according to claim 1 or 2, wherein the jib is held in a horizontal holding posture in which the lower surface of the jib in the jib working posture is drawn close to the side surface of the boom in the jib storage posture. Construction.   The tension rod according to claim 1 or 2, wherein the jib is held in a holding posture in which the lower surface of the jib in the jib working posture is drawn closer to the lower surface of the boom in the jib storage posture. Construction. Attached to the distal end of the boom is a tension rod connecting link connected to the rod proximal end connecting portion;
The jib slidably supports the rod end connection portion in the axial direction of the jib, supports the support member as the jib end connection portion, and extends and retracts the rod end connection portion in the axial direction of the jib. And a tilt cylinder for moving
In the jib storage posture, the rod distal end connecting portion is disposed near the proximal end in the support member, and the rod proximal end connecting portion is coupled to the jib proximal end connecting portion, the tension rod The middle portion of the tension rod is pressed against the U-shaped guide member by the restoring force due to the elastic deformation of
In the jib working posture, the rod tip connecting portion is slidably moved in the support member by extending and retracting the tilt cylinder and is disposed at a predetermined position, and the rod base end connecting portion is the tension rod connecting link The storage structure of a tension rod according to any one of claims 1 to 4, which is adapted to be coupled.