JP7086454B2 - Telescopic boom - Google Patents

Description

The present invention relates to a telescopic boom provided on a vehicle body such as an aerial work platform.

An aerial work platform is generally configured to have a workbench for worker boarding at the tip of a telescopic boom provided on the vehicle body so as to be able to move up and down, expand and contract, and turn. By operating the operating device provided on the workbench, the on-board worker can operate the telescopic boom to move the workbench to a desired high position and perform work (). For example, see Patent Document 1).

The telescopic boom described in the above patent document is configured as a three-stage telescopic boom in which a base end boom, an intermediate boom, and a tip end boom are nestedly combined. This telescopic boom is equipped with a telescopic cylinder that expands and contracts the intermediate boom with respect to the base end boom, and a telescopic mechanism that expands and contracts the tip boom with respect to the intermediate boom in conjunction with the expansion and contraction of the intermediate boom. There is. The expansion / contraction mechanism consists of an extension mechanism part and a reduction mechanism part, and each mechanism part hangs a wire around a sheave rotatably provided on the intermediate boom, and connects the wire to the base end boom and the tip end boom, respectively. By transmitting the expansion / contraction movement of the expansion / contraction cylinder to the wire via the sheave, the tip boom can be expanded / contracted with respect to the intermediate boom.

Japanese Unexamined Patent Publication No. 8-2892

In the telescopic boom described in the above patent document, the sheave mounting structure of the extension mechanism portion is configured to directly fix the sheave pin, which is the axis of rotation of the sheave, to the side wall of the intermediate boom. At this time, since a part of the sheave pin protrudes to the outside of the side wall of the intermediate boom, the intermediate boom cannot be stored in the proximal boom beyond this protruding portion, and the expansion / contraction boom cannot be accommodated when the telescopic boom is reduced. There is a problem that the protruding amount (protruding amount) of the intermediate boom increases by that amount, and the total length of the telescopic boom in the fully contracted state cannot be suppressed to a small size. In order to reduce the amount of protrusion of the intermediate boom, it is conceivable to move the sheave further to the tip side of the intermediate boom, but there is a slider at the tip of the intermediate boom to guide the expansion and contraction of the tip boom. Since a plurality of sheaves are arranged, there is a problem that if the sheaves are relocated, they interfere with the slider and the sheave arrangement space cannot be secured.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a telescopic boom capable of keeping the total length of the boom in a fully contracted state small.

In order to solve the above problems, the telescopic boom according to the present invention has a hollow first boom and a hollow first boom that is inserted into the first boom and stretches with respect to the first boom. A second boom that is movably provided, a third boom that is inserted into the second boom and is movably provided with respect to the second boom, and a second boom that expands and contracts with respect to the first boom. It is provided with a telescopic cylinder to be moved and a telescopic mechanism for expanding and contracting the third boom with respect to the second boom in response to the telescopic movement of the second boom with respect to the first boom by the telescopic cylinder. A telescopic boom in which a first boom, a second boom, and a third boom are combined in a nested manner in order from the tip side to the tip side, and the telescopic mechanism is provided on the inner surface side of the second boom. The base member is provided with a base member, a sheave rotatably provided on the base member, a wire rod whose intermediate portion is hung around the sheave, and a fixing member attached from the outer surface side of the second boom. It has a fixing means for fixing to the inner surface side of the second boom, and the fixing means is provided at a position offset to the tip end side of the second boom with respect to the rotation center of the sheave. ..

In the expansion / contraction boom having the above configuration, the expansion / contraction mechanism includes a rotation shaft member that is fixed to the base member and rotatably supports the sheave, and the rotation shaft member and the fixing member are separately configured. Is preferable.

Further, in the expansion / contraction boom having the above configuration, a pair of guide members for guiding the expansion / contraction movement of the third boom with respect to the second boom are provided on the inner surface on the tip end side of the second boom in the expansion / contraction direction and the rotation center of the sheave. It is preferably provided at a predetermined interval in a direction substantially orthogonal to the axial direction, and the fixing means is preferably arranged between the pair of guide members.

According to the telescopic boom according to the present invention, since the fixing means of the sheave mounting structure is provided at a position offset to the tip end side of the second boom with respect to the rotation center of the sheave, the telescopic boom is corresponding to the offset amount. It is possible to reduce the amount of protrusion (protrusion amount) of the second boom with respect to the first boom when is in the fully contracted state (the most contracted state). Therefore, it is possible to shorten the length of the telescopic boom in the fully contracted state, and it is possible to reduce the size of the entire vehicle. On the other hand, while the length of the telescopic boom in the fully contracted state is the same as the conventional one, the length of the first boom can be extended by the above offset amount from the conventional one (only by the above offset amount). (Because both booms do not interfere with each other even if extended), in that case, the lap length (the part where both booms overlap) when the second boom is extended with respect to the first boom can be increased. For example, the guide members arranged between the outer surface of the first boom and the inner surface of the second boom (the guide members arranged on the inner surface on the tip side of the first boom and the outer surface on the rear end side of the second boom). It is possible to reduce the load reaction force (load) acting on the guide member).

Further, in the telescopic boom having the above configuration, the single sheave pin, which has conventionally been used as both the rotary shaft member and the fixing member, is configured as a separate body by the first sheave pin (rotary shaft member) and the second sheave pin (fixing member). As a result, the sheave (first sheave pin) can be placed between the pair of guide members by offsetting only the fixing member (second sheave pin) toward the tip end side of the second boom while keeping the conventional mounting position. Therefore, it is possible to efficiently lay out the sheave mounting structure by effectively utilizing the limited space near the tip opening of the second boom.

It is a side view of the aerial work platform provided with the telescopic boom which concerns on this embodiment. It is a schematic diagram for demonstrating the expansion / contraction mechanism provided in the expansion / contraction boom. It is a perspective view which looked at the intermediate boom (the state which the slider is attached) which constitutes the telescopic boom from the tip side. It is a perspective view which looked at the said intermediate boom (the state which a slider was removed) from the tip side. It is an exploded perspective view of the sheave mounting structure provided in the said intermediate boom.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the aerial work platform 1 provided with the telescopic boom 30 according to the present embodiment. First, the overall configuration of the aerial work platform 1 will be outlined with reference to this figure.

The aerial work platform 1 includes a vehicle body 10 of a truck-type vehicle provided with tire wheels 11 for traveling and capable of driving operation from a driving cab 12, a swivel table 20 provided on the vehicle body 10, and the swivel table. A telescopic boom 30 whose base end is supported via a foot pin 22 on the upper part of a support column 21 extending upward from the 20 and a workbench 40 for worker boarding attached to the tip of the telescopic boom 30. It is composed of and.

The swivel base 20 is attached to the rear portion of the vehicle body 10 so as to be rotatable 360 degrees around the vertical axis. A swivel motor 23 is provided inside the vehicle body 10, and by rotationally driving the swivel motor 23, the swivel base 20 can be swiveled horizontally via a gear (not shown).

The telescopic boom 30 has a configuration in which the base end boom 31, the intermediate boom 32, and the tip end boom 33 are assembled in a nested manner in order from the swivel base 20 side, and the telescopic drive of the telescopic cylinder 38 provided inside the telescopic boom 30. Therefore, the intermediate boom 32 and the tip boom 33 can be relatively moved with respect to the base end boom 31, and the telescopic boom 30 can be expanded and contracted in the axial direction. Further, an undulating cylinder 24 is straddled between the base end boom 31 and the support column 21 of the swivel base 20, and the entire telescopic boom 30 is undulated in the upper and lower surfaces by telescopically driving the undulating cylinder 24. be able to.

A boom head 34 is attached to the tip of the tip boom 33. A vertical post 36 is pivotally supported on the boom head 34 via a swing pin 35 so as to be swingable in the vertical direction. The vertical post 36 is swing-controlled by a leveling device (not shown) arranged between the vertical post 36 and the tip boom 33, and the vertical post 36 is always held in a vertical posture regardless of the undulations of the telescopic boom 30. It is configured to be.

The workbench 40 includes a workbench main body 41 having a substantially box shape on which an operator is boarded, and a workbench bracket 42 provided so as to project outward from the workbench main body 41. The workbench bracket 42 is rotatably attached to the upper end of the vertical post 36. A swing motor 43 is provided inside the workbench bracket 42, and by rotationally driving the swing motor 43, the entire workbench 40 is swung (horizontally swiveled) around the vertical post 36. Can be done. Here, since the vertical post 36 is always maintained in a vertical posture as described above, as a result, the floor surface of the workbench 40 is always held horizontally regardless of the undulation angle of the telescopic boom 30. Further, the workbench 40 is provided with an upper operation device 44 operated by a worker who is on board the workbench 40. Therefore, the worker on the workbench 40 operates the upper operation device 44 to expand / contract the undulating cylinder 24, expand / contract the telescopic cylinder 38, rotate the swivel motor 23, and rotate the swing motor 43. Each operation such as operation can be performed.

Four outrigger jacks 13 are provided on the front, rear, left and right sides of the vehicle body 10 to stably support the vehicle when working at a high place using the telescopic boom 30 or the like. Each outer trigger jack 13 includes an outer jack 13a extending in the vertical direction, an inner jack 13b provided in the outer jack 13a that can be expanded and contracted in the vertical direction, and a jack that is swingably attached to the lower end of the inner jack 13b. It is configured to have a pad 13c. Each outrigger jack 13 lifts and supports the vehicle body 10 by driving a jack cylinder (not shown) provided inside the outrigger jack 13 and extending it downward to stabilize the vehicle. The vehicle body 10 is provided with a jack operating device 14 for operating each outrigger jack 13.

Next, the structure of the telescopic boom 30 according to the present embodiment will be described in detail with reference to FIG.

The telescopic boom 30 has a proximal boom 31 pivotally connected to the upper part of the support column 21, an intermediate boom 32 movably inserted into the proximal boom 31, and a telescopic boom 32 inserted into the intermediate boom 32. The tip boom 33 and the tip boom 33 are combined in a nested manner. Each boom 31, 32, 33 is formed in a rectangular cylinder shape having a hollow space, and in the hollow space communicating the inside of these members in the axial direction, the above-mentioned telescopic cylinder 38 and the telescopic cylinder 38 are formed. A pair of expansion / contraction mechanisms 50 that operate in conjunction with the above are arranged.

The telescopic cylinder 38 is configured by assembling a cylinder tube 38a and a piston rod 38b so as to be relatively movable in the axial direction. In this telescopic cylinder 38, the end portion of the cylinder tube 38a is pivotally connected to the proximal end portion of the intermediate boom 32 via the support shaft 39a, and the end portion of the piston rod 38b is the support shaft 39b to the proximal end portion of the proximal boom 31. It is pivoted through. By hydraulically driving the telescopic cylinder 38, the intermediate boom 32 can be expanded and contracted with respect to the base end boom 31.

The expansion / contraction mechanism 50 expands / contracts the tip boom 33 with respect to the intermediate boom 32 in conjunction with the expansion / contraction movement of the intermediate boom 32 with respect to the base end boom 31 by the expansion / contraction cylinder 38. The expansion / contraction mechanism 50 has an extension mechanism portion 51 that extends the tip boom 33 with respect to the intermediate boom 32, and a reduction mechanism portion 55 that contracts the tip boom 33 with respect to the intermediate boom 32.

The extension mechanism portion 51 includes an extension sheave 52 rotatably provided inside the tip of the intermediate boom 32, and an extension wire 53 hung around the extension sheave 52. One end of the stretched wire 53 is connected to a first stretched wire connecting portion 54a formed on the rear end side of the base end boom 31, and the other end of the stretched wire 53 is formed on the rear end side of the tip boom 33. It is connected to the connection portion 54b. In this embodiment, the mounting structure of the extended sheave 52 (sheave mounting structure) is characteristic, which will be described later.

The shrinking mechanism portion 55 includes a shrinking sheave 56 rotatably provided on the rear end side of the intermediate boom 32 and a shrinking wire 57 hung around the shrinking sheave 56. One end of the shrink wire 57 is connected to a first shrink wire connecting portion 58a formed on the tip end side of the base end boom 31, and the other end is connected to a second shrink wire connection portion formed on the rear end side of the tip boom 33. It is connected to the portion 58b.

In the expansion / contraction boom 30 of the present embodiment, when the expansion / contraction cylinder 38 is extended, the intermediate boom 32 moves forward (extension direction) with respect to the proximal boom 31, and the extension sheave 52 provided in the intermediate boom 32 thereof. By pushing the stretched wire 53 wound around the wire 53 forward, the tip boom 33 connected to the other end of the stretched wire 53 (second stretched wire connecting portion 54b) is pulled forward. Moving. At this time, the relative movement amount (extension amount) of the tip boom 33 with respect to the base end boom 31 is the relative movement amount of the intermediate boom 32 with reference to the base end boom 31 based on the principle of the moving pulley. It is twice as much as (elongation amount). Therefore, in the extension operation of the expansion / contraction boom 30, the intermediate boom 32 extends and moves forward by the same length with respect to the base end boom 31 and the tip boom 33 with respect to the intermediate boom 32.

On the other hand, when the telescopic cylinder 38 is reduced, the intermediate boom 32 moves rearward (in the reduction direction) with respect to the base end boom 31, and the contracted sheave 56 provided on the intermediate boom 32 is wound around the contracted wire. By pushing the 57 backward, the tip boom 33 connected to the other end of the shrink wire 57 (second shrink wire connecting portion 58b) is pulled and moves backward. At this time, the relative movement amount (reduction amount) of the tip boom 33 with respect to the base end boom 31 is the relative movement amount of the intermediate boom 32 with reference to the base end boom 31 based on the principle of the moving pulley. It is twice as much as (reduction amount). Therefore, in the reduction operation of the telescopic boom 30, the intermediate boom 32 is reduced and moved rearward by the same length with respect to the base boom 31 and the tip boom 33 with respect to the intermediate boom 32. ..

Subsequently, the sheave mounting structure (mounting structure of the extended sheave 52) of the present embodiment will be described in detail with reference to FIGS. 3 to 5. In the following, for convenience of explanation, the up-down, left-right, and front-back directions are defined with reference to the arrow directions shown in FIGS. 3 to 5. In the present embodiment, the sheave mounting structure is applied to the intermediate boom 32 among the three-stage booms 31, 32, 33 described above. The intermediate boom 32 includes a pair of side walls 321 facing left and right, an upper wall 322 connecting the upper ends of the left and right side walls 321 and a lower wall 323 connecting the lower ends of the left and right side walls 321. It is formed in the shape of a rectangular cylinder having a hollow space 324 open to the public.

The sheave mounting structure mainly includes the above-mentioned extended sheave 52, a bracket 60 that rotatably supports the extended sheave 52, and a fixing mechanism 70 that fixes the bracket 60 to the side wall 321 of the intermediate boom 32.

The bracket 60 is formed in a flat plate shape using, for example, a metal steel plate, and is fixed to the inner surface side of the side wall 321 of the intermediate boom 32 by a fixing mechanism 70 described later. The bracket 60 is provided with a first sheave pin 61 which is a rotation axis of the extension sheave 52.

The first sheave pin 61 is composed of a cylindrical outer rotating shaft portion 61a fixed to the bracket 60 and a cylindrical inner rotating shaft portion 61b coaxially connected to the rotating shaft portion 61a with a bolt (not shown). Become. The outer peripheral surfaces of the rotating shaft portions 61a and 61b are inserted into the central hole 52a of the extension sheave 52 and formed so as to be slidable with the inner peripheral surface of the central hole 52a. The extension sheave 52 is rotatably supported in both directions while being sandwiched between the flanges of both rotation shaft portions 61a and 61b, and the extension wire 53 is hung around the outer peripheral surface thereof. It has become. Above and below the stretched sheave 52, a retaining protrusion 62 acting as a retaining protrusion of the stretched wire 53 hung around the stretched sheave 52 is fixedly fixed on the bracket 60.

The fixing mechanism 70 includes a rectangular block-shaped pin holding portion 71 fixed to the bracket 60, a cylindrical second sheave pin 72 inserted into the pin holding portion 71, and a rectangular shape recessed in the pin holding portion 71. It includes a plate-shaped plate nut 73 that is locked to the groove 71b, and a plurality of fixing bolts 74 that are screwed into the plate nut 73 to fasten the second sheave pin 72 to the pin holding portion 71. The fixing mechanism 70 is mounted on the side wall 321 of the intermediate boom 32 at a position offset to the front side (the tip end side of the intermediate boom 32) from the rotation center of the extension sheave 52.

A pin insertion hole 71a having a circular cross section is formed through the pin holding portion 71 in the left-right direction. The pin insertion hole 71a is position-aligned with the pin insertion opening 321a having a circular cross section formed through the side wall 321 of the intermediate boom 32, and extends continuously in the left-right direction in cooperation with the pin insertion opening 321a. It forms a cylindrical receiving space (a space for receiving the second sheave pin 72). The pin insertion hole 71a is formed to have substantially the same hole diameter as the pin insertion opening 321a. Then, the second sheave pin 72, which is a fixed shaft, is inserted across the pin insertion hole 71a and the pin insertion opening 321a. Here, the pin holding portion 71 and the extension sheave 52 are arranged so as to be offset in the axial direction (front-back direction), and a predetermined gap is provided between the outer peripheral surface of the pin holding portion 71 and the outer peripheral surface of the extension sheave 52. It is formed. By setting this predetermined gap to the size of the gap between the extension sheave 52 and the retaining protrusion 62, the pin holding portion 71 may function as a retaining wire 53.

The second sheave pin 72 is a member that receives the tension of the extension wire 53 hung around the extension sheave 52 (in other words, the shearing force acting on the mounting mechanism 70 by the tension). The second sheave pin 72 has a cylindrical pin body portion 72a inserted into the pin insertion hole 71a and a disk-shaped pin collar portion 72b locked to the outer surface of the side wall 321 of the intermediate boom 32 as a whole. It is formed in a stepped cylinder extending in the left-right direction. A pair of bolt insertion holes 72c penetrated in the left-right direction is formed in the second sheave pin 72, and the fixing bolt 74 can be inserted into the bolt insertion holes 72c. The end surface of the pin body portion 72a is substantially flush with the inner surface of the rectangular groove 71b in a state of being inserted into the pin insertion hole 71a of the pin holding portion 71.

The nut plate 73 is formed in a horizontally long flat plate shape extending in the front-rear direction, and has a pair of screw holes 73a that penetrate in the plate thickness direction (left-right direction) and screw into the fixing bolt 74. The pair of screw holes 73a formed in the nut plate 73 are arranged at the same pitch as the pair of bolt insertion holes 72c formed in the second sheave pin 72. The nut plate 73 is receptively formed in a rectangular groove 71b recessed in the pin holding portion 71, and two fixing bolts inserted into the second sheave pin 72 are screwed together. By fastening the second sheave pin 72 and the nut plate 73 with the fixing bolt 74 in this way, the side wall 321 of the intermediate boom 32 and the bracket 60 are between the pin flange portion 72b of the second sheave pin 72 and the nut plate 73. And are sandwiched so that the bracket 60 is fixed to the side wall 321 of the intermediate boom 32.

In the vicinity of the tip opening of the intermediate boom 32, a slider group for guiding the expansion / contraction movement of the tip boom 33 with respect to the intermediate boom 32 is attached. This group of sliders includes side sliders 81 provided above and below the inner surface side of each side wall 321, an upper surface slider 82 provided on the inner surface side of the upper wall 322, and a lower surface slider 83 provided on the inner surface side of the lower wall 323. And have. Each slider 81 to 83 is formed in a substantially rectangular parallelepiped shape extending in the front-rear direction using a synthetic resin material. Further, each of the sliders 81 to 83 is formed so as to be slidable with the outer surface of the tip boom 33, and guides the front-back movement (straight line movement) of the tip boom 33. Here, there is not enough empty space between the upper and lower side sliders 81 to attach the extension sheave 52, but there is enough empty space to attach the fixing mechanism 70. Therefore, by arranging the fixing mechanism 70 between the upper and lower side sliders 81, the fixing mechanism 70 is offset to the tip end side of the intermediate boom 32 with respect to the rotation center (first sheave pin 61) of the extension sheave 52. It is possible.

Next, as the operation of the sheave mounting structure in the present embodiment, the mounting procedure of the extended sheave 52 will be described. The mounting work of the extension sheave 52 is carried out in a state where the intermediate boom 32 and the tip boom 33 are combined in a nested manner.

First, the extension wire 53 is hung around the outer peripheral surface of the extension sheave 52. Next, the outer rotating shaft portion 61a and the inner rotating shaft portion 61b are inserted into the center hole 52a of the extension sheave 52 from the left and right, and both the rotating shaft portions 61a and 61b are fastened with bolts (not shown) to form the first sheave pin. The extension sheave 52 is attached to the bracket 60 via 61 (61a, 61b). Subsequently, the bracket 60 is inserted through the gap between the inner surface of the intermediate boom 32 and the outer surface of the tip boom 33, and is addressed to the side wall 321 of the intermediate boom 32. Then, after inserting the knock bolt 63 into the through hole of the side wall 321 from the left and right outside, the bracket 60 is further inserted into the through hole of the bracket 60 and screwed into the nut 64, so that the bracket 60 is used. Temporarily fixed (positioned) to the side wall 321. Next, the bracket 60 is swung up and down around the knock bolt 63 to align the pin insertion hole 71a formed in the bracket 60 with the pin insertion opening 321a formed in the side wall 321 of the intermediate boom 32.

Subsequently, the second sheave pin 72 is inserted into the pin insertion opening 321a of the side wall 321 from the left and right outside, and then further inserted into the pin insertion hole 71a of the pin holding portion 71. After inserting the second sheave pin 72 in this way, the nut plate 73 is inserted through the gap between the inner surface of the intermediate boom 32 and the outer surface of the tip boom 33, and is locked in the rectangular groove 71b of the pin holding portion 71. With the nut plate 73 locked in the rectangular groove 71b, the fixing bolt 74 is inserted into the bolt insertion hole 72c of the second sheave pin 72 through the spring washer 75 and the flat washer 76 and screwed into the nut plate 73. , The side wall 321 of the intermediate boom 32 and the bracket 60 are sandwiched between the pin flange portion 72b of the second sheave pin 72 and the nut plate 73 to fix both. As a result, the extension sheave 52 is attached to the side wall 321 of the intermediate boom 32 via the bracket 60, and is arranged at a predetermined position near the tip opening of the intermediate boom 32.

Here, among the components of the fixing mechanism 70, the flange portion 72b of the second sheave pin 72 and the head of the fixing bolt 74 protrude outward from the side wall 321 of the intermediate boom 32. However, since this fixing mechanism 70 is mounted at a position offset forward from the mounting position (rotation center) of the extension sheave 52, the telescopic boom 30 is fully contracted (most reduced) by the amount of the offset. The protrusion amount (protrusion amount) of the intermediate boom 32 with respect to the base end boom 31 can be reduced. Further, since the fixing mechanism 70 is arranged near the tip opening of the intermediate boom 32 in this way, a finger is inserted into the gap between the inner surface of the intermediate boom 32 and the outer surface of the tip boom 33 from the tip opening to fix the fixing mechanism 70. The mechanism 70 can be easily attached (workability is improved).

After the extension sheave 52 is attached to the intermediate boom 32 in this way, the vertical and horizontal sliders 81 to 83 are attached to the tip opening of the intermediate boom 32 with bolts (not shown). Although not shown, a sweeper is attached to the most advanced portion of the intermediate boom 32 to prevent foreign matter or the like from entering the gap between the inner surface of the intermediate boom 32 and the outer surface of the tip boom 33. As a result, the safe and reliable expansion / contraction movement of the expansion / contraction boom 30 is ensured.

The knock bolt 63 not only functions for positioning the bracket 60 with respect to the intermediate boom 32, but also functions as a detent (rotation preventing means) for the bracket 60. That is, when the bracket 60 is fixed only by the second sheave pin 72, the bracket 60 may rotate around the second sheave pin 72 due to the tension of the extension wire 53 or the like, but the knock bolt 63 is also a bracket. By fastening to 60 and fixing at two points, the bracket 60 is prevented from rotating. However, since the tension of the extension wire 53 basically acts in the axial direction (front-back direction), if the axis of the extension sheave 52 and the axis of the second sheave pin 72 are set at the same height position. , No detent is required.

As described above, according to the telescopic boom 30 according to the present embodiment, since the fixing mechanism of the sheave mounting structure is provided at a position offset to the tip end side of the intermediate boom 32 with respect to the rotation center of the extended sheave 52, the offset amount thereof. It is possible to reduce the amount of protrusion (protrusion amount) of the intermediate boom 32 with respect to the base end boom 31 when the telescopic boom 30 is in the fully contracted state (the most contracted state). Therefore, it is possible to shorten the length of the telescopic boom 30 in the fully contracted state, and it is possible to reduce the size of the entire vehicle. On the other hand, while the length of the telescopic boom 30 in the fully contracted state is the same as the conventional one, the length of the base end boom 31 can be extended by the above offset amount (of the above offset amount). (Because both booms do not interfere even if they are extended by the amount), in that case, the lap length (the part where both booms overlap) when the intermediate boom 32 is extended with respect to the base end boom 31 can be increased. According to it, a slider arranged between the outer surface of the base end boom 31 and the inner surface of the intermediate boom 32 (slider arranged on the inner surface on the distal end side of the proximal boom 31 and the outer surface on the rear end side of the intermediate boom 32). It is possible to reduce the load reaction force (load) acting on the arranged sliders).

In addition, the single sheave pin, which was conventionally used as both the rotating shaft and the fixed shaft, is configured as a separate body by the first sheave pin (rotating shaft) 61 and the second sheave pin (fixed shaft) 72, so that the extended sheave 52 (1st sheave pin 61) can be placed between the pair of sliders 81 by offsetting only the fixing mechanism 70 (second sheave pin 72) to the tip end side of the intermediate boom 32 while keeping the conventional mounting position. The sheave mounting structure can be efficiently laid out by effectively utilizing the limited space near the tip opening of the intermediate boom 32.

The present invention is not limited to the above embodiment, and can be appropriately improved as long as it does not deviate from the gist of the present invention.

In the above embodiment, the telescopic boom 30 is configured as a three-stage telescopic type including a first boom (base end boom 31), a second boom (intermediate boom 32), and a third boom (tip boom 33), but four or more stages. It may be configured as a multi-stage telescopic type. For example, when configured as a four-stage telescopic telescopic boom composed of a first boom, a second boom, a third boom, and a fourth boom in order from the base end side to the tip end side, the second boom and the third boom A sheave mounting structure may be applied to at least one of the above. That is, the sheave mounting structure can be applied to all the booms arranged in the middle except the boom on the most advanced side and the boom on the most basic end side among the booms in a plurality of stages.

Further, in the above embodiment, the case where the extended sheave 52 is applied as the target sheave of the sheave mounting structure has been described as an example, but the present invention is not limited to this configuration, and the contracted sheave 56 is used as the target sheave of the sheave mounting structure. May be applied.

In the above embodiment, the bracket 60 on which the extension sheave 52 is pivotally supported is fixed to the intermediate boom 32 by the second sheave pin 72, and the tension of the extension wire 53 wound around the extension sheave 52 is received by the second sheave pin 72. However, the present invention is not limited to this configuration, and the bracket 60 may be fixed by using another fixing means instead of the second sheave pin 72. The cross-sectional shape of the second sheave pin 72 is not limited to a circular shape, and other shapes such as a rectangular shape and a cam shape may be adopted.

In the above embodiment, as the telescopic boom type work vehicle, an aerial work platform provided with a work platform for worker boarding at the tip of the telescopic boom has been described as an example, but the present invention is not limited to this configuration. For example, on a crane vehicle equipped with a suspension device at the tip of the telescopic boom, a digging pillar vehicle equipped with an earth auger device at the tip of the telescopic boom, or on a work platform provided at the tip of the telescopic boom. It may be applied to other work vehicles such as a self-propelled aerial work platform capable of traveling operation and boom operation, and a road-rail vehicle equipped with a telescopic boom and capable of traveling on a road and on a track.

1 Aerial work platform 30 Telescopic boom 31 Base boom (1st boom)
32 Intermediate boom (second boom)
33 Tip boom (3rd boom)
39 Telescopic cylinder 40 Workbench 50 Telescopic mechanism 51 Extension mechanism 52 Extension sheave (sheave)
53 Stretched wire (wire)
55 Reduction mechanism 60 Bracket (base member)
61 First sheave pin (rotary shaft member)
70 Fixing mechanism (fixing means)
71 Pin holding part 72 Second sheave pin (fixing member)
73 Nut plate 74 Fixing bolt 81 Side slider (guide member)
82 Top slider (guide member)
83 Bottom slider (guide member)
321 Side wall 322 Upper wall 323 Lower wall 324 Hollow space

Claims (3)

The first boom formed in a hollow shape and
A second boom formed in a hollow shape, inserted into the first boom, and flexibly provided with respect to the first boom, and a second boom.
A third boom that is inserted into the second boom and is provided so as to be able to expand and contract with respect to the second boom.
A telescopic cylinder that expands and contracts the second boom with respect to the first boom,
It is provided with an expansion / contraction mechanism that expands / contracts the third boom with respect to the second boom in response to the expansion / contraction movement of the second boom with respect to the first boom by the expansion / contraction cylinder.
A telescopic boom in which the first boom, the second boom, and the third boom are nestedly combined in order from the proximal end side to the distal end side.
The expansion / contraction mechanism includes a base member provided on the inner surface side of the second boom, a sheave rotatably provided on the base member, a wire rod whose intermediate portion is hung around the sheave, and an outer surface of the second boom. It has a fixing member attached from the side and is provided with a fixing means for fixing the base member to the inner surface side of the second boom.
The telescopic boom is characterized in that the fixing means is provided at a position offset to the tip end side of the second boom with respect to the rotation center of the sheave. The telescopic mechanism includes a rotary shaft member that is fixed to the base member and rotatably supports the sheave .
The telescopic boom according to claim 1, wherein the rotary shaft member and the fixing member are formed as separate bodies. On the inner surface on the tip end side of the second boom, a pair of guide members for guiding the expansion / contraction movement of the third boom with respect to the second boom are predetermined in a direction substantially orthogonal to the expansion / contraction direction and the rotation center axis direction of the sheave. It is provided at intervals of
The telescopic boom according to claim 1 or 2, wherein the fixing means is arranged between the pair of guide members.

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