JP3631371B2 - Telescopic boom - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a telescopic boom, and more particularly, to a telescopic boom equipped with a telescopic cylinder.
[0002]
[Prior art]
Some aerial work vehicles are configured by pivotally supporting a telescopic boom that can be freely expanded and contracted on a swivel provided on a vehicle body, and by providing a work platform at the tip of the telescopic boom. This work at a high altitude is performed by an operator by moving the work table to a desired high altitude work position by raising and lowering and extending the telescopic boom during work.
[0003]
As the telescopic boom of such an aerial work vehicle, for example, as shown in FIG. 8, a base end boom 9a provided on a vehicle body (not shown) of the aerial work vehicle so as to be raised and lowered, and the base end boom There is an intermediate boom 9b that is telescopically inserted into 9a and a tip boom 9c that is telescopically inserted into the intermediate boom 9b. The telescopic boom 9 includes a telescopic cylinder 21 that extends and retracts the intermediate boom 9b relative to the proximal boom 9a. The distal end portion of the cylinder rod 21b of the telescopic cylinder 21 is attached to the inner side of the proximal end portion of the proximal boom 9a, and the cylinder tube 21a is placed on the inner side of the proximal end portion of the intermediate boom 9b via a fixed shaft 23 protruding to the side. It is attached.
[0004]
The fixed shaft 23 is provided with a contraction sheave 25 which is rotatable at a position having a certain distance from the cylinder tube 9a. A contraction wire 41 is wound around the contraction sheave 25 and one end of the contraction sheave 25 is connected to the tip boom 9c. The other end is fixed to the inner side of the distal end portion of the proximal end boom 9a. Two extending sheaves 31 that are rotatable are provided at the tip of the cylinder tube 21 a, and these extending sheaves 31 are arranged inside the contracted sheave 25. An extension wire 43 is wound around the extension sheave 31 and one end thereof is fixed to the inner side of the base end portion of the base end boom 9a, and the other end is fixed to the inner side of the base end portion of the distal end boom 9c.
[0005]
A work table (not shown) is provided at the front end of the tip boom 9c. The work table is provided with a winch that is operated by hydraulic pressure and an operating device that receives a power supply and sends a control signal to the vehicle body. . For this reason, a hydraulic hose and an electric cable (hereinafter referred to as “hose etc.”) for connecting the vehicle body and the work table are provided in the telescopic boom 9. As shown in FIG. 9, one end of the hose 65 is held on the upper surface of the proximal end portion of the proximal boom 9a, and extends in the distal direction of the telescopic boom 9 along the upper surface of the proximal boom 9a. Then, the hose 65 or the like is wound around a sheave 61 attached to the distal end portion of the proximal boom 9a and reversed in the proximal direction, and passes through the gap between the proximal boom 9a and the intermediate boom 9b. It extends to the end portion, is wound around a hose sheave 63 attached to the proximal end portion of the intermediate boom 9b, and is reversed again in the distal direction. The tip of the hose 65 extends through the inside of the tip boom 9c to the tip of the tip boom 9c. By drawing the hose and the like 65 in this way, the hose and the like 65 can be expanded and contracted with the expansion and contraction operation of the telescopic boom 9.
[0006]
[Problems to be solved by the invention]
However, the hose sheave requires a hose separator for separating the hose and the like so that the hose does not get entangled, and a detachment prevention for preventing the hose and the like from coming off the hose sheave. In addition, as the telescopic boom is extended and retracted, the hose is subjected to repeated operations such as tension and deflection, so the hose repeatedly contacts the hose separator and the hose is worn or damaged. There is a case to do. Moreover, since tension cannot be applied to the electric cable, there is a risk that the wire may be broken if excessive tension is applied thereto. Furthermore, there has been a problem that the stretched wire hung around the stretched sheave may break, or the stretched wire may come off from the stretched sheave and the tip boom may drop and move to the proximal end side of the telescopic boom.
[0007]
The present invention has been made in view of such a problem, and there is no possibility that the tip boom will fall and move to the base end side of the telescopic boom even if the extension wire is broken, so that the hose and the like are not detached from the hose sheave. An object of the present invention is to provide a telescopic boom that eliminates the need for auxiliary parts.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the telescopic boom of the present invention is a first boom (for example, a proximal boom 9a in the embodiment) provided in a vehicle (for example, an aerial work vehicle 1 in the embodiment) so as to be raised and lowered. And a second boom (for example, the intermediate boom 9b in the embodiment) inserted in the first boom so as to be extendable and a third boom (for example, in the embodiment) inserted in the second boom so as to be extendable. The tip boom 9c) is nested. Therefore, the front-end | tip part of an expansion-contraction boom can be moved to a desired position by expanding-contracting and turning the expansion-contraction boom.
[0009]
The telescopic boom has a telescopic cylinder that is fixed to the inner base end of the first boom and a cylinder body that is fixed to the inner base end of the second boom, and is capable of protruding into the third boom. A contraction sheave provided on at least one of the left and right side walls on the base end side of the first boom in the cylinder body of the telescopic cylinder; and at least one of the left and right sides on the tip end side of the first boom in the cylinder body. A stretched sheave provided on the side wall of the first boom, and a rod-shaped member disposed above or below the telescopic cylinder, with one end secured to the base end of the first boom and the other end disposed between the contracted sheave and the stretched sheave (for example, implementation Guide pipe 35), one end fixed to the distal end of the rod-shaped member and wound around the contraction sheave, the other end fixed to the base end of the third boom, and one end to the distal end of the rod-shaped member Fixation Then, the extension wire is hung around the extension sheave and the other end is fixed to the proximal end portion of the third boom, and the one end is fixed to the distal end portion of the rod-like member so that the proximal end of the first boom is interposed via the rod-like member. Connected to the section, extends in the distal direction of the telescopic boom, reverses around the distal end of the cylinder body, extends to a position facing the rod-like member with the cylinder body as a boundary, extends in the proximal direction of the telescopic boom, The other end is connected to the base end of the third boom to bend oil / power transmission protection means (for example, the protective tube 47 in the embodiment), and one end is fixed to the base end of the first boom. And an oil transmission / power transmission means (for example, a hose 45 in the embodiment) that is inserted into the oil transmission / power transmission protection means that communicates therewith and the other end is fixed to the tip of the third boom. .
[0010]
When the telescopic cylinder is operated and extended from the fully contracted state, the second boom extends with respect to the first boom. At the same time, since the extension wire is wound around the extension sheave provided in the telescopic cylinder, the third boom is pulled up by the extension of the extension sheave. That is, by extending the telescopic cylinder, the entire telescopic boom extends at the same rate and at the same rate. Further, when the cylinder body moves to the distal end side of the telescopic cylinder, the third boom extends. At the same time, the extension sheave and the oil transmission / power transmission protection means connected to the base end of the third boom are connected to the telescopic cylinder. Since it moves to the front end side, the bending position of the oil transmission / power transmission protection means that bends around the tip of the cylinder body moves to the oil transmission / power transmission protection means side connected to the base end of the third boom.
[0011]
On the other hand, in order to reduce the extended telescopic boom, the telescopic cylinder is reduced. When the telescopic cylinder is reduced, the second boom is reduced with respect to the first boom. At the same time, a contraction wire is wound around the contraction sheave provided in the telescopic cylinder, so that the third boom is pulled back when the contraction sheave is lowered. That is, by reducing the telescopic cylinder, the entire extension boom is simultaneously reduced at the same rate. Further, when the cylinder body moves to the cylinder rod side, the first boom contracts. At the same time, the extension sheave and the oil transmission / power transmission protection means connected to the base end portion of the third boom are connected to the base end side of the telescopic cylinder. Therefore, the bending position of the oil transmission / power transmission protection means bent around the tip of the cylinder body moves to the oil transmission / power transmission protection means connected to the tip of the rod-like member.
[0012]
In the telescopic boom of the present invention, the tip end portion of the cylinder rod is fixed to the inner base end portion of the first boom, the cylinder body is fixed to the inner base end portion of the second boom, and protrudes into the third boom. A flexible telescopic cylinder, a contracted sheave provided on at least one of the left and right side walls of the base end of the first boom in the cylinder main body of the telescopic cylinder, and the left and right of the front end of the first boom in the cylinder main body An extension sheave provided on at least one of the side walls and an upper or lower side of the telescopic cylinder, one end fixed to the base end of the first boom, and the other end disposed between the contraction sheave and the extension sheave The rod-shaped member, one end fixed to the tip of the rod-shaped member and wound around the contraction sheave, the other end fixed to the base end of the third boom, and one end fixed to the tip of the rod-shaped member To stretch sheave One end is connected to the distal end of the rod-like member, and the other end is fixed to the proximal end of the third boom, and the other end extends in the distal direction of the telescopic boom and reverses around the end of the cylinder body. And a fall prevention wire that extends to a position facing the rod-like member with the cylinder body as a boundary, extends in the proximal direction of the telescopic boom, and has the other end connected to the proximal end portion of the third boom. Is preferred.
[0013]
When the extension wire breaks or disengages from the extension sheave and the third boom falls and moves to the proximal end side of the telescopic boom, the fall prevention wire is caught by the end of the cylinder body on the distal end side of the telescopic boom, and the third boom is moved into the telescopic boom. Can be stopped. The length of the fall prevention wire is preferably such that the third boom can be stopped in the telescopic boom.
[0014]
Further, the cylinder body is provided with a rotating shaft that passes through the left and right directions on the distal end side of the telescopic boom and protrudes to the outside of the left and right side walls of the cylinder main body. The extension sheave is pivotally supported at both ends of the rotating shaft, and when the third boom drops and moves to the base end side of the telescopic boom, the fall prevention wire is caught by the exposed intermediate portion of the rotating shaft, and the third boom expands and contracts. You may make it stop within a boom. It is preferable that both ends of the rotating shaft are supported, and the intermediate portion is exposed so that the fall prevention wire is caught.
[0015]
Furthermore, it is preferable that the fall prevention wire is extended in the oil transmission / power transmission protection means. When the telescopic boom is operating normally, the fall prevention wire is idle, and there is a risk that it will get entangled with the rotating shaft as the third boom moves. Therefore, by extending the fall prevention wire in the oil feeding / power transmission protection means, it is possible to prevent play of the fall prevention wire and eliminate the possibility of entanglement with the rotating shaft.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. This embodiment shows an aspect of an aerial work vehicle having a telescopic boom having a work table on which a person who works at a high altitude rides at the tip.
[0017]
[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an aerial work vehicle equipped with a telescopic boom according to a first embodiment of the present invention. First, an aerial work vehicle will be described before describing the telescopic boom of the present invention. As shown in the figure, an aerial work vehicle 1 includes an outrigger jack 5 that supports the vehicle body 3 at four locations on the front, rear, left, and right sides of the vehicle body 3 and a turntable that can be turned on the vehicle body 3 by a hydraulic motor (not shown). 7. A base end portion of the telescopic boom 9 is pivotally supported on the upper part of the swivel base 7 so as to be movable up and down. The telescopic boom 9 is raised and lowered by a telescopic action of a boom hoisting cylinder 11 provided between the swivel base 7 and the telescopic boom 9.
[0018]
A vertical post 13 is provided at the tip of the telescopic boom 9, and the vertical post 13 is always kept vertical by a leveling cylinder (not shown) that performs an expansion / contraction operation according to the undulation angle of the telescopic boom 9. A swing arm 15 is provided on the vertical post 13 and is formed so as to be horizontally swivelable with respect to the vertical post 13 by a hydraulic motor (not shown). A work table 17 is provided at the tip of the swivel arm 15. The work table 17 is provided with a winch device 19 for lifting a work object or the like.
[0019]
FIG. 2 shows a front view of the telescopic boom 9, and FIG. 3 shows a plan view of the telescopic boom 9. As shown in FIGS. 2 and 3, the telescopic boom 9 is composed of three boom members, ie, a proximal boom 9a, an intermediate boom 9b, and a distal boom 9c from the outside, and is configured to be telescopically telescopic. The proximal boom 9a and the intermediate boom 9b are metallic, and the distal boom 9c is formed of an insulating member such as FRP in order to ensure electrical insulation between the workbench 17 and the vehicle body 3. The telescopic boom 9 includes a telescopic cylinder 21 for extending and retracting the intermediate boom 9b with respect to the proximal boom 9a. The telescopic cylinder 21 has a cylinder tube 21a and a cylinder rod 21b provided so as to protrude into the telescopic boom. ing. The distal end of the cylinder rod 21b is attached to the inner side of the proximal end of the proximal boom 9a, and the cylinder tube 21a is connected to the proximal end of the intermediate boom 9b via a fixed shaft 23 that protrudes outward from the left and right side walls on the cylinder rod 21b side. It is attached inside the unit.
[0020]
On the fixed shaft 23, a contracted sheave 25 is pivotally supported at a portion having a constant separation dimension A in a direction away from the left and right side walls of the cylinder tube 21a. Further, a protruding portion 27 that protrudes toward the distal end side of the telescopic cylinder 21 and has an inverted U-shaped cross section is provided at the end portion of the cylinder tube 21a on the distal end side of the telescopic boom 9. A rotation shaft 29 that is inserted in a direction perpendicular to the center axis J of the telescopic cylinder 21 is provided at the center of the projecting portion 27. Both end portions of the rotating shaft 29 protrude to a portion having a certain distance from both side walls of the projecting portion 27, and the both end portions of the rotating shaft 29 have a certain spacing dimension A in a direction away from each side wall of the projecting portion 27. The extending sheave 31 is pivotally supported at the site.
[0021]
A rod-shaped guide pipe 35 having a through hole 33 in the axis J direction is provided above the telescopic cylinder 21 and inside the tip boom 9c. The guide pipe 35 has a base end portion fixed to the inner side of the base end portion of the base end boom 9 a and a tip end portion disposed between the front end boom 9 c and the cylinder tube 21 a and between the contracted sheave 25 and the extended sheave 31. ing. A first wire connecting portion 37 is provided at the distal end portion of the guide pipe 35 so as to project to the left and right sides. A second wire connecting portion 39 is provided below the cylinder tube 21a and at the base end portion of the tip boom 9c.
[0022]
One end portion of the contracted wire 41 is connected to the first wire connecting portion 37 of the guide pipe 35, and the other end is connected to the second wire connecting portion 39 while being wound around the contracted sheave 25. Further, one end portion of the extension wire 43 is connected to the first wire connection portion 37, and the other end is connected to the second wire connection portion 39 while being wound around the extension sheave 31. More specifically, the contraction wire 41 that is hung around the contraction sheave 25, the contraction wire 41 that extends from the contraction sheave 25, the extension wire 43 that extends around the extension sheave 31, and the extension that extends from the extension sheave 31. The wire 43 is stretched in the same plane (in a plane perpendicular to the plane of FIG. 3). Therefore, the contraction sheave 25 and the extension sheave 31 do not receive the thrust load from the contraction wire 41 or the extension wire 43.
[0023]
At the tip of the guide pipe 35, a hydraulic hose and an electric cable (hereinafter collectively referred to as "hose 45") for connecting the vehicle body 3 and the workbench 17 are held and a flexible protective tube is provided. (Oil transmission / power transmission protection means) 47 is connected to one end of the telescopic boom 9 with respect to the rotating shaft 29, and is inverted around the tip of the protrusion 27 to extend below the protrusion 27. The other end portion is connected to the second wire connection portion 33. As shown in FIG. 4, the protective tube 47 is configured by fitting a plurality of convex molds 47 a and concave molds 47 b each having a rectangular cross section. Therefore, the protective tube 47 can freely swing in the vertical direction as indicated by an arrow IV.
[0024]
2 and 3, a hose 45 is inserted into the protective tube 47, and one end of the hose 45 is inserted into the guide pipe 35 and fixed to the base of the proximal boom 9a. Is inverted at the second wire connecting portion 39 and extended to the inner wall surface of the tip boom 9c and fixed to the tip portion of the tip boom 9c. Therefore, even if the telescopic cylinder 9 is expanded and contracted and the tip boom 9c is expanded or contracted, the hose 45 is provided in the protective tube 47, so that the hose 45 does not protrude outside the protective tube 47. , Never get tangled or scattered.
[0025]
Next, the operation of the first embodiment of the present invention will be described with reference to FIG. In order to extend the telescopic boom 9 from the contracted state, hydraulic pressure is supplied to the telescopic cylinder 21 to extend the cylinder rod 21b. When the cylinder rod 21b extends, the cylinder tube 21a moves to the distal end side of the telescopic boom 9. At the same time, the intermediate boom 9b to which the cylinder tube 21a is fixed extends. Further, when the cylinder tube 21 a moves to the distal end side of the telescopic cylinder 9, the stretch wire 43 wound around the stretch sheave 31 pulls the distal boom 9 c to the distal end side of the telescopic boom 9 through the second wire connecting portion 39. Therefore, the tip boom 9 extends.
[0026]
Further, when the cylinder tube 21a moves to the distal end side of the telescopic cylinder 9, the distal end boom 9 expands. At the same time, the second tube connecting portion 39 moves to the distal end side of the telescopic cylinder 9, and as a result, the cylinder tube 21a. The bent position of the protective tube 47 that is bent around the tip end of the wire moves toward the protective tube 47 connected to the second wire connecting portion 39. Therefore, even if the tip boom 9c is extended, the bending position of the protective tube 47 only moves, and the bending state hardly changes. Therefore, the hose 45 provided in the protective tube 47 may be entangled or scattered. Absent.
[0027]
On the other hand, in order to reduce the telescopic boom 9 from the extended state, the hydraulic pressure of the telescopic cylinder 21 is released. When the hydraulic pressure of the telescopic cylinder 21 is released, the cylinder tube 21a is reduced by the dead weight of the intermediate boom 9b fixed to the cylinder tube 21a and the tip boom 9c suspended via the extension wire 43, and the intermediate boom 9b is reduced. To do. At the same time, the contracted wire 41 wound around the contracted sheave 25 pulls the distal end boom 9 c back to the proximal end side of the telescopic boom 9 via the second wire connecting portion 39. Accordingly, the tip boom 9 is reduced.
[0028]
Further, when the cylinder tube 21a moves to the cylinder rod 21b side, the distal end boom 9c shrinks. At the same time, as the second wire connecting portion 39 moves to the proximal end side of the telescopic cylinder 9, the cylinder tube 21a The bent position of the protective tube 47 that is bent around the distal end portion moves to the protective tube 47 connected to the first wire connecting portion 37. Therefore, even if the tip boom 9c is reduced, the bent position of the protective tube 47 only moves and the bent state hardly changes. Therefore, the hose 45 provided in the protective tube 47 may be entangled or scattered. Absent.
[0029]
[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, only the differences from the first embodiment will be described, and the same reference numerals will be given to the same aspects as those in the first embodiment, and the description thereof will be omitted. FIG. 6 is a front view of the telescopic boom 9, and FIG. 7 is a plan view of the telescopic boom 9. As shown in these figures, one end of a fall prevention wire 49 for preventing the tip boom 9c from dropping in the telescopic boom 9 is connected to the tip of the guide pipe 35, and the other end is inserted through the protective tube 47. The end is connected to the proximal end portion of the distal end boom 9c.
[0030]
Accordingly, when the extension wire 43 is broken or the extension wire 43 is detached from the extension sheave 31 in a state where the telescopic boom 9 is extended, and the tip boom 9c falls and moves in the telescopic boom 9, it is connected to the tip boom 9c. The end portion of the fall prevention wire 49 moved downward, and the fall prevention wire 49 provided in the protection tube 47 jumps out to the cylinder tube 21 a side of the protection tube 47 and is caught by the rotary shaft 29. Therefore, the fall movement of the tip boom 9c is blocked by the fall prevention wire 49, and the fall movement of the tip boom 9c is stopped.
[0031]
【The invention's effect】
As described above, according to the present invention, one end of the oil transmission / power transmission protection means is fixed to the distal end portion of the rod-like member, extends in the distal end direction of the telescopic boom, and is reversed around the end portion of the cylinder body. Extending to the position opposite to the rod-shaped member with the cylinder body as a boundary, extending in the base end direction of the telescopic boom, and connecting the other end to the base end portion of the third boom so that it can be bent freely. The oil supply / power transmission protection means changes the bending position while protecting the oil transmission / power transmission means even if the oil is telescopically operated, does not apply excessive tension to the oil transmission / power transmission means, and does not interfere with other members. In addition, the oil transmission / power transmission means can be disposed at a desired position. In addition, since auxiliary parts for reversing the oil transmission / power transmission means that have been necessary in the past are not required, the configuration of the telescopic boom can be simplified and the product cost can be reduced.
[0032]
Further, when one end of the fall prevention wire is connected to the distal end portion of the rod-shaped member and the other end is connected to the proximal end portion of the third boom member, the extension wire is broken and the third boom is the base of the telescopic boom. Even if it falls and moves to the end side, the third boom can be stopped in the telescopic boom by the fall prevention wire being hooked on the end of the cylinder body on the distal end side of the telescopic boom.
[0033]
Furthermore, the cylinder body is provided with a rotating shaft that passes through the left and right directions on the distal end side of the telescopic boom and protrudes outside the left and right side walls of the cylinder body. Thus, even if the third boom drops and moves to the base end side of the telescopic boom, the third boom can be stopped in the telescopic boom by being caught by the intermediate portion of the rotating shaft where the fall prevention wire is exposed.
[0034]
In addition, when the fall prevention wire is extended in the oil feeding / power transmission protection means, when the telescopic boom is operating normally, the rotating shaft or oil feeding / power transmission protection means by play of the fall prevention wire Can be prevented.
[Brief description of the drawings]
FIG. 1 is a front view of an aerial work vehicle having a telescopic boom according to a first embodiment of the present invention.
FIG. 2 is a front view of the telescopic boom according to the first embodiment of the present invention.
FIG. 3 is a plan view of the telescopic boom according to the first embodiment of the present invention.
FIG. 4 is a perspective view of a protective tube in the telescopic boom according to the first embodiment of the present invention.
FIG. 5 is a view for explaining the operation of the telescopic boom according to the first embodiment of the present invention.
FIG. 6 is a front view of a telescopic boom according to a second embodiment of the present invention.
FIG. 7 is a plan view of a telescopic boom according to a second embodiment of the present invention.
FIG. 8 shows a plan view of a telescopic boom in the prior art.
FIG. 9 is a front view showing the routing of the hydraulic hose and electric cable of the telescopic boom in the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Aerial work vehicle 9 Telescopic boom 9a Base end boom 9b Middle boom 9c End boom 21 Telescopic cylinder 21a Cylinder tube 21b Cylinder rod 25 Shrinking sheave 29 Rotating shaft 31 Extending sheave 35 Guide pipe 41 Contracting wire 43 Extending wire 45 Hose etc. 47 Protection Tube 49 Fall prevention wire

Claims (4)

A first boom that is provided in a vehicle so as to be raised and swiveled, a second boom that is inserted into the first boom in a telescopic manner, and a third boom that is inserted into the second boom in a telescopic manner are nested. A telescopic boom constructed in a formula,
A distal end of a cylinder rod fixed to the inner base end of the first boom, a cylinder main body fixed to the inner base end of the second boom, and a telescopic cylinder that can freely protrude into the third boom;
A contracted sheave provided on at least one of the left and right side walls of the first boom in the cylinder body of the telescopic cylinder;
An extension sheave provided on at least one of the left and right side walls of the cylinder body at the tip end side of the first boom;
A rod-like member disposed above or below the telescopic cylinder, one end fixed to the base end of the first boom, and the other end disposed between the contracted sheave and the expanded sheave;
A crimped wire having one end secured to the distal end of the rod-shaped member and wound around the contracted sheave; the other end secured to the proximal end of the third boom;
An extension wire having one end fixed to the distal end of the rod-shaped member and wound around the extension sheave, and the other end fixed to the proximal end of the third boom;
One end of the rod- like member is fixed to the distal end portion of the rod- like member so that the rod- like member is connected to the base end portion of the first boom , extends in the distal end direction of the telescopic boom, and is reversed around the tip portion of the cylinder body. Then, it extends to a position opposite to the rod-like member with the cylinder body as a boundary, extends in the base end direction of the telescopic boom, and has the other end connected to the base end portion of the third boom. Oil and power transmission protection means,
One end fixed to the base end of the first boom, the rod-shaped member and the oil transmission / power transmission protection means communicating therewith, and the other end fixed to the tip of the third boom. A telescopic boom characterized by comprising oil and power transmission means. A first boom provided in a vehicle so as to be raised and swiveled, a second boom inserted into the first boom so as to be extendable and a third boom inserted into the second boom so as to be extendable are nested. Telescopic boom constructed in a formula,
A distal end of a cylinder rod fixed to the inner base end of the first boom, a cylinder main body fixed to the inner base end of the second boom, and a telescopic cylinder that can freely protrude into the third boom;
A contraction sheave provided on at least one of the left and right side walls of the first boom in the cylinder body of the telescopic cylinder;
An extension sheave provided on at least one of the left and right side walls on the tip end side of the first boom in the cylinder body;
A rod-like member disposed above or below the telescopic cylinder, one end fixed to the base end of the first boom and the other end disposed between the contracted sheave and the expanded sheave;
A crimped wire having one end secured to the distal end of the rod-shaped member and wound around the contracted sheave; the other end secured to the proximal end of the third boom;
An extension wire having one end fixed to the distal end of the rod-shaped member and wound around the extension sheave, and the other end fixed to the proximal end of the third boom;
One end is connected to the tip of the rod-like member, extends in the direction of the tip of the telescopic boom, reverses around the end of the cylinder body, and extends to a position facing the rod-like member with the cylinder body as a boundary. A telescopic boom, characterized in that the telescopic boom comprises a fall prevention wire extending in the base end direction of the telescopic boom and having the other end connected to the base end of the third boom. The cylinder body is provided with a rotating shaft that passes through the left-right direction of the distal end side of the telescopic boom and protrudes outside the left and right side walls of the cylinder main body. When the third boom is dropped and moved to the base end side of the telescopic boom, the fall prevention wire is exposed to an intermediate portion of the rotary shaft that is exposed. The telescopic boom according to claim 2, wherein the telescopic boom is caught and stopped in the telescopic boom. The telescopic boom according to claim 1, wherein the fall prevention wire according to claim 2 is extended in the oil transmission / power transmission protection means of the telescopic boom according to claim 1.

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