JP2017057025A - crane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crane capable of easily suppressing bending of a boom.SOLUTION: A crane comprises: a support body; a boom 6; a sheave 11a arranged closer to a rear part S2 side than to a base end part E1 of the boom 6 on the support body; a sheave arranged closer to a front part S1 side than to the base end part E1 of the boom 6 on the support body; and a tension rope 7 which is arranged to extend from the vicinity of a tip end part E2 of the boom 6 to the rear part S2 side of the support body, and with which an end part 12a side is connected to the vicinity of the tip end part E2 of the boom 6 and an end part 12b side is stretched to the sheave 11a and supports the tip end part E2 of the boom 6. The end part 12b side of the tension rope 7 is stretched to the sheave 11a, is guided to the sheave, and faces upward on the sheave, and is connected to an intermediate part E3 of the boom 6.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a crane, and more particularly to a crane in which a tip end portion of a boom is supported rearward by a tension rope.

  Generally, a crane has a boom that can be expanded and contracted in multiple stages, and unloading work to a high place is performed by extending the boom greatly upward. At this time, since a large load is applied downward to the tip of the boom, there is a problem that the boom bends in the vertical direction. In recent years, there is a possibility that the bending will increase as the boom length increases, and a technique for suppressing the bending of the boom is required.

  Thus, for example, Patent Document 1 proposes a mobile crane that can achieve a large lifting capacity by suppressing boom deflection. In this mobile crane, a left winch and a right winch are mounted on a swivel. The left and right winches wind up the left and right ropes that are fixed to the tip of the boom to increase the tension. Deflection can be suppressed.

Japanese Patent No. 5629160

  However, the mobile crane of Patent Document 1 must always control the entire length of the rope by using the right and left winches, which has caused a heavy burden on the control.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a crane that easily suppresses the bending of the boom.

  A crane according to the present invention has a support, a boom that is supported by the support so as to be raised and lowered, and extends from the base end toward the front end of the support toward the front side of the support. A first sheave disposed rearward of the base end of the boom, a second sheave disposed forward of the base end of the boom in the support, and a rear portion of the support from the vicinity of the tip of the boom A tension rope that is arranged to extend to the side, connects one end side to the vicinity of the tip of the boom and has the other end side laid around the first sheave to support the tip of the boom, The other end side of the tension rope is routed around the first sheave and guided to the second sheave and is routed around the second sheave so as to face upward, and is connected to the middle portion of the boom. Is.

  Here, the tension rope has a support length that extends from the vicinity of the tip of the boom to the first sheave and an adjustment length that extends from the second sheave to the middle portion of the boom in accordance with the undulation of the boom. The sheave, the second sheave, one end side of the tension rope and the other end side of the tension rope have a change amount of the adjustment length of the tension rope support length according to the boom undulation. It is preferable that they are arranged so as to cancel all of them.

  Further, the support body and the boom may be connected to each other, and a hoisting cylinder for hoisting the boom by expansion and contraction may be further provided, and the tension rope may be arranged along the hoisting cylinder from the second sheave toward the middle portion of the boom. preferable.

  According to the present invention, the other end portion side of the tension rope is routed around the first sheave and guided to the second sheave, and is routed around the second sheave so as to face upward to the middle portion of the boom. Since it is connected, it is possible to provide a crane that easily suppresses bending of the boom.

It is a figure which shows the structure of the crane vehicle provided with the crane which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of a crane. It is a figure which shows a mode that a boom is knocked down so that the undulation angle may become small. It is a figure which shows the structure of the crane which concerns on Embodiment 2. FIG. FIG. 10 is a diagram illustrating a configuration of a crane according to a third embodiment. It is a figure which shows the structure of the crane which concerns on Embodiment 4. FIG. It is explanatory drawing which shows the calculation location of a crane.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1
In FIG. 1, the structure of the crane vehicle provided with the crane which concerns on Embodiment 1 of this invention is shown. This crane vehicle has a traveling vehicle 1 and a crane 2. In FIG. 1, a crane cab, a lifting work winch, a lifting work wire, a hook, and the like are omitted.

The traveling vehicle 1 is for traveling on a road or the like, and has wheels 3 and outriggers 4.
The outrigger 4 supports the posture of the crane vehicle during the crane operation, and extends from the traveling vehicle 1 to the side and supports the crane vehicle by grounding its tip.

The crane 2 has a swivel base 5 provided on the upper side of the traveling vehicle 1 so as to be capable of swiveling in a horizontal plane, and a base end E1 of the boom 6 is supported on the swivel base 5 so as to be raised and lowered. The boom 6 is attached so as to extend from the base end portion E1 toward the front end portion E2 toward the front portion S1 of the swivel base 5. And the tension rope 7 is arrange | positioned so that it may extend toward the rear part S2 side of the turntable 5 from the front-end | tip part E2 vicinity of the boom 6. FIG.
In addition, the turntable 5 has shown the support body in this invention. Here, the front part S1 and the rear part S2 of the swivel base 5 are determined according to the direction in which the boom 6 extends, and the side where the distal end E2 is located with respect to the base end E1 of the boom 6 is the front part S1. And the opposite side is the rear part S2.

FIG. 2 shows the configuration of the crane 2 in detail.
At the base end E1 of the boom 6, a root pin 8 for fixing the boom 6 to the swivel 5 so as to be raised and lowered is disposed. The boom 6 includes a basic boom having a box shape and a plurality of stage booms, and is extended and contracted by sliding the plurality of stage booms with respect to the basic boom.
A hoisting cylinder 9 extending from the swivel base 5 is attached to an intermediate portion E3 of the boom 6, specifically, in the vicinity of the tip of the basic boom. It is undulated in the center.

  A fixing portion 10a is provided in the vicinity of the distal end portion E2 of the boom 6, and a fixing portion 10b is provided in the middle portion E3 of the boom 6, specifically, in the vicinity of the distal end portion of the basic boom. Further, on the swivel 5, sheaves 11 a and 11 b are disposed on the rear S 2 side from the base end E 1 of the boom 6, and a sheave 11 c is disposed on the front S 1 side from the base end E 1 of the boom 6.

The fixing portion 10a is disposed on the rear surface portion of the boom 6, and the end portion 12a of the tension rope 7 is fixed.
The fixing portion 10b is disposed on the front surface portion of the boom 6, and the end portion 12b of the tension rope 7 is fixed.

The sheave 11 a is disposed in the vicinity of the rear portion S <b> 2 of the swivel base 5, and is configured to be rotatable around a rotation axis that extends in the width direction of the swivel base 5.
The sheave 11 b is disposed below the sheave 11 a in the rear portion S <b> 2 of the swivel base 5, and is configured to be rotatable around a rotation axis that extends in the width direction of the swivel base 5.
The sheave 11c is disposed in the swivel base 5 on the front part S1 side from the base end part E1 of the boom 6, specifically, on the front part S1 side from the base end part of the undulating cylinder 9. It is configured to be rotatable around a rotation axis extending in the width direction.

  The tension rope 7 extends from the end portion 12a fixed to the fixing portion 10a to the rear portion S2 side of the swivel base 5, and is then wound around the sheaves 11a and 11b and guided to the sheave 11c. That is, the tension rope 7 is arranged so as to extend around the sheave 11a and extend into the swivel base 5, and then around the sheave 11b so as to extend forward inside the swivel base 5 to the sheave 11c. Then, the tension rope 7 is laid around so as to face upward by the sheave 11c, and the end 12b of the tension rope 7 is fixed to the fixing portion 10b. Thereby, the tension rope 7 is installed so as to have a predetermined tension between the fixed portion 10a and the sheave 11a, and the tip E2 of the boom 6 is supported rearward.

  Here, the tension rope 7 is disposed so as to connect the sheave 11 c and the middle portion E 3 of the boom 6 in front of the base end E 1 of the boom 6. For this reason, the tension rope 7 changes the amount of change according to the undulation of the boom 6 having the support length L1 extending from the fixed portion 10a to the sheave 11a into the undulation of the boom 6 having the adjustment length L2 extending from the fixed portion 10b to the sheave 11c. The corresponding change is moved to cancel out. That is, the support length L1 and the adjustment length L2 of the tension rope 7 show opposite amounts of change according to the undulation of the boom 6.

Next, the operation of the first embodiment will be described.
First, as shown in FIG. 1, in a state where the outrigger 4 is extended to support the crane vehicle, the boom 6 is raised from the swivel 5 and extended to a predetermined length. And a load etc. are suspended from the front-end | tip part E2 of the boom 6 by the hook which is not shown in figure, and a crane operation | work is performed.
At this time, the tension rope 7 is stretched so as to have a predetermined tension between the fixed portion 10a and the sheave 11a. For this reason, the front-end | tip part E2 of the boom 6 can be supported back, and it can suppress that the boom 6 bends downward by loads, such as a load suspended from the front-end | tip part E2 of the boom 6. FIG.

Furthermore, in the crane work, the undulation angle of the boom 6 is changed sequentially. Conventionally, the tension rope 7 is stretched only between the vicinity of the tip E2 of the boom 6 and the rear S2 side of the swivel base 5, and in order to keep the tension of the tension rope 7 constant, the undulation angle of the boom 6 is set. Control was performed to change the total length of the tension rope 7 each time it was changed.
In the present invention, as shown in FIG. 2, the end portion 12b of the tension rope 7 is guided upward by the sheave 11c and fixed to the fixing portion 10b in front of the base end portion E1 of the boom 6. For this reason, the tension rope 7 can be automatically moved so as to cancel the change amount of the support length L1 that changes according to the undulation of the boom 6 with the change amount of the adjustment length L2.

For example, as shown in FIG. 3, when the boom 6 is tilted to reduce the undulation angle, the support length L1 of the tension rope 7 is increased while the adjustment length L2 is decreased. For this reason, the length of change in the support length L1 is compensated by the amount of change in the adjustment length L2 that is shortened, and the amount of change in the support length L1 can be canceled out by the amount of change in the adjustment length L2.
Here, the sheave 11a, the sheave 11c, the fixed portion 10a, and the fixed portion 10b cancel almost all of the change amount of the adjustment length L2 with respect to the change amount of the support length L1 of the tension rope 7 that changes according to the undulation of the boom 6. Are arranged as follows. For example, the sheave 11c and the fixing portion 10b can be arranged so that the tension rope 7 extends along the undulation cylinder 9 between the fixing portion 10b and the sheave 11c. The expansion / contraction amount of the hoisting cylinder 9 tends to substantially coincide with a value obtained by inverting the change amount of the support length L1 of the tension rope 7 that changes according to the hoisting of the boom 6, and the tension rope 7 along the hoisting cylinder 9. By disposing, the change amount of the support length L1 can be almost completely canceled by the change amount of the adjustment length L2.

In this way, the tension rope 7 is automatically moved according to the undulation of the boom 6 so that the tension is kept constant, and it is not necessary to change the entire length of the tension rope 7 every time the boom undulation angle is changed. The bending of the boom can be easily suppressed.
In addition, the tension of the tension rope 7 tends to increase as the hoisting angle of the boom 6 increases, that is, the amount of change in the adjustment length L2 tends to decrease with respect to the amount of change in the support length L1 of the tension rope 7. In some cases, it is preferable that the total length of the tension rope 7 when the undulation angle of the boom 6 is small is set longer in advance.

  According to this embodiment, since the change amount of the support length L1 of the tension rope 7 according to the undulation of the boom 6 is almost completely canceled by the change amount of the adjustment length L2, the tension of the tension rope 7 is automatically adjusted. It can be kept constant, and the downward bending of the boom can be easily suppressed. Further, since the tip end E2 of the boom 6 is supported only by the tension rope 7, it is not necessary to newly install a supporting mast on the tip end E2 of the boom 6, and a configuration for suppressing the bending of the boom 6 is provided. It can be simplified.

Embodiment 2
In the first embodiment, the tension rope 7 is arranged so that the tension is kept constant when the boom 6 is raised and lowered. It is preferable to change the total length of the tension rope 7 in accordance with the expansion and contraction of 6.
For example, as shown in FIG. 4, the tip winch 21 can be disposed in the vicinity of the tip end portion E <b> 2 of the boom 6 instead of the fixing portion 10 a of the first embodiment. The tip winch 21 is wound around the end 12 a of the tension rope 7, and winds or feeds the tension rope 7 according to the expansion and contraction of the boom 6.

  In the crane operation, when the boom 6 is raised and lowered, the adjustment length L2 of the tension rope 7 automatically changes so as to cancel almost all the change in the support length L1 as in the first embodiment. . On the other hand, when the boom 6 is expanded and contracted, the tension rope 7 is wound and unwound by the tip winch 21 in accordance with the expansion and contraction of the boom 6, and the tension rope 7 is adjusted to have a predetermined tension by adjusting the total length of the tension rope 7. Adapted to.

According to this embodiment, since the tension of the tension rope 7 is adjusted according to the undulation and expansion / contraction of the boom 6, the tension of the tension rope 7 can be maintained with high accuracy in a series of crane operations.
Note that an intermediate winch can be arranged in the intermediate portion E3 of the boom 6 in place of the fixed portion 10b of the first embodiment. The intermediate winch is wound around the end 12 b of the tension rope 7, and winds or unwinds the tension rope 7 according to the expansion and contraction of the boom 6. Thereby, the tension | tensile_strength of the tension rope 7 can be adjusted with high precision according to the undulation and expansion / contraction of the boom 6 similarly to the above.

Embodiment 3
In the first and second embodiments, the downward bending of the boom 6 is suppressed by the tension rope 7 extending from the tip E2 of the boom 6 to the rear S2 side of the swivel 5; By extending the tension rope 7 to two locations spaced apart in the width direction 5, it is possible to suppress lateral bending as well as downward bending of the boom 6.

  For example, as shown in FIG. 5, in the second embodiment, the sheave 11a is disposed on the right side S3 side in the vicinity of the rear portion S2 of the swivel base 5, and is newly placed on the left side S4 side in the vicinity of the rear portion S2 of the swivel base 5. A rear winch 31 can be arranged. Further, the sheave 11 c is arranged on the right side S 3 side in the front part S 1 of the swivel base 5, and the fixing part 32 is newly arranged on the left side part S 4 side in the front part S 1 of the swivel base 5. Further, a sheave 33 is disposed in place of the tip winch 21, and a sheave 34 is disposed in place of the fixing portion 10b.

The sheave 33 is connected so that the end 12a side of the tension rope 7 extending from the sheave 11a to the tip E2 of the boom 6 is connected to the tip E2 of the boom 6 and guided to the rear winch 31.
The sheave 34 connects the end portion 12b side of the tension rope 7 extending from the sheave 11c to the intermediate portion E3 of the boom 6 so as to be connected to the intermediate portion E3 of the boom 6 and led to the fixing portion 32.

The rear winch 31 winds and fixes the end 12 a side of the tension rope 7 extending from the sheave 33, and winds or feeds the tension rope 7 according to the expansion and contraction of the boom 6.
The fixing portion 32 fixes the end portion 12 b of the tension rope 7 extending from the sheave 34.

  That is, the tension rope 7 has two ends 12 a on the rear winch 31 and the sheave 11 a via the sheave 33 and two ends 12 b on the fixing portion 32 and the sheave 11 c via the sheave 34. Yes.

  In the crane work, a load or the like is suspended from the tip E2 of the boom 6. At this time, since the tip end portion E2 of the boom 6 is supported rearward by the tension rope 7, the downward bending of the boom 6 can be suppressed. Furthermore, since two tension ropes 7 are hung on the tip E2 of the boom 6, the boom 6 is supported from the left and right, and so-called lateral bending, in which the boom 6 is bent in the left-right direction, can be suppressed.

  Subsequently, when the boom 6 is raised and lowered, the support length L1 and the adjustment length L2 of the tension rope 7 are automatically changed so that the tension of the tension rope 7 is kept constant. Here, two tension ropes 7 are hung on the end portion 12a side corresponding to the support length L1 and the end portion 12b side corresponding to the adjustment length L2, so the support length L1 and the adjustment length are set. L2 is changed at an equivalent rate according to the undulations of the boom 6. For this reason, the tension rope 7 can change the adjustment length L2 so as to cancel out almost all the change amount of the support length L1 that changes according to the undulation of the boom 6, as in the second embodiment.

  Further, when the boom 6 is expanded and contracted, the tension rope 7 is wound and unwound by the rear winch 31 so that the tension of the tension rope 7 is kept constant, and the total length of the tension rope 7 is adjusted. In this way, by changing the total length of the tension rope 7 with the rear winch 31 according to the expansion and contraction of the boom 6, the tension of the tension rope 7 according to the undulation of the boom 6 can be automatically adjusted as it is.

According to the present embodiment, the boom 6 can be supported from the left and right by hanging the two tension ropes 7 through the sheave 33 disposed at the tip E2 of the boom 6, and the lateral deflection of the boom 6 can be reduced. Can be suppressed.
Note that it is sufficient that at least two ends 12a of the tension rope 7 can be hung. For example, in Embodiment 2, the sheave 11a is disposed on the right side S3 side in the vicinity of the rear portion S2 of the swivel base 5 and the rear portion of the swivel base 5 In the vicinity of S2, a rear winch or a fixing part may be newly disposed on the left side S4 side, and a sheave 33 may be disposed instead of the front end winch 21. By fixing the end 12a side of the tension rope 7 extending from the sheave 33 to the rear winch or the fixing portion, two ends 12a of the tension rope 7 can be hung between the sheave 11a.

Embodiment 4
In the first to third embodiments, the adjustment length L2 is changed so as to cancel almost all the change amount of the support length L1 of the tension rope 7 according to the undulation of the boom 6, but the change amount of the support length L1 is changed. It suffices that the amount of change in the adjustment length L2 can be canceled to some extent, and is not limited to the one that cancels all.

For example, as shown in FIG. 6, in the first embodiment, the tip winch 41 can be disposed instead of the fixing portion 10 a, and the tension detecting unit 42 and the tension adjusting unit 43 can be newly disposed.
The tip winch 41 is wound around the end 12a side of the tension rope 7, and winds or unwinds the tension rope 7.
The tension detector 42 is connected to the sheave 11a and detects the tension of the tension rope 7 extending from the sheave 11a to the tip E2 of the boom 6.
The tension adjusting unit 43 is connected to the tension detecting unit 42 and the tip winch 41, and drives the tip winch 41 based on the tension of the tension rope 7 detected by the tension detecting unit 42. The tension of the tension rope 7 is within a predetermined range. The length of the tension rope 7 is adjusted so as to be inside.

In the crane work, when almost all the change amount of the support length L1 of the tension rope 7 that changes in accordance with the undulations of the boom 6 is canceled by the change amount of the adjustment length L2, as in the first embodiment, The tension of the tension rope 7 can be kept constant. However, when the amount of change in the adjustment length L2 greatly fluctuates with respect to the amount of change in the support length L1 of the tension rope 7, it becomes difficult to cancel out all the amount of change in the support length L1.
At this time, the tension adjustment unit 43 determines whether the tension of the tension rope 7 is within a predetermined range based on the tension of the tension rope 7 detected by the tension detection unit 42. When the tension adjusting unit 43 determines that the tension of the tension rope 7 is outside the predetermined range, the tension adjusting unit 43 drives the tip winch 41 so that the tension rope 7 is wound or wound so that the tension is within the predetermined range. Feed out and change the total length of the tension rope 7.
Thus, when the tension of the tension rope 7 falls within a predetermined range, the tip winch 41 is stopped, and the tension rope 7 again adjusts the amount of change in the support length L1 according to the undulation of the boom 6 to the adjustment length L2. It is automatically moved so as to cancel with the amount of change.

  According to the present embodiment, when the change amount of the support length L1 of the tension rope 7 according to the undulation of the crane greatly varies with respect to the change amount of the adjustment length L2, the tip winch 41 is driven. Since the total length of the tension rope 7 is adjusted, the tension rope 7 can be kept at a predetermined tension with high accuracy.

  In the first to fourth embodiments described above, the end 12b side of the tension rope 7 is connected to the vicinity of the tip of the basic boom via the fixed portion 10b or the like. However, it is only necessary to be connected between the proximal end E1 and the distal end E2, and the present invention is not limited to this.

For example, in the first embodiment, a sheave is disposed near the center of the basic boom instead of the fixed portion 10b, and the sheave 11c is disposed on the right side near the front S1 of the swivel 5 and tension is applied on the left side. A front winch on which the end 12b side of the rope 7 is wound can be disposed. As a result, two tension ropes 7 are hung on the front winch and the sheave 11c via the sheave disposed on the basic boom on the end 12b side, and the change in the adjustment length L2 with respect to the change in the support length L1. The amount is about ½. For this reason, the adjustment length L2 shortened by connecting the end 12b side of the tension rope 7 to the vicinity of the center portion of the basic boom can be compensated by reducing the amount of change, and according to the undulation of the boom 6 Further, the change amount of the support length L1 and the change amount of the adjustment length L2 can be kept substantially equal.
In this way, by connecting the end 12b side of the tension rope 7 to the vicinity of the center of the basic boom, it is possible to reduce the load that the tip of the basic boom receives downward.

  The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these.

  As shown in FIG. 7, the end 12a of the tension rope 7 is fixed near the tip E2 of the boom 6 and the end 12b of the tension rope 7 is connected near the tip of the basic boom. It was set as the same structure. Here, the undulation angle of the boom 6 with respect to the horizontal line is θ, the length from the root pin 8 of the boom 6 to the fixed portion 10a at the tip is L3, and the length of the straight line T1 extending from the sheave 11a to the root pin 8 of the boom 6 is L4. The angle of the boom 6 with respect to the straight line T1 is α, the length of the straight line T2 extending from the sheave 11c to the root pin 8 of the boom 6 is L5, and the length of the straight line T3 extending from the root pin 8 of the boom 6 to the fixed portion 10b is L6. To do.

  As shown in Table 1 below, the length L3 of the boom 6 is set to 60 m, the length L4 of the straight line T1 is set to 2.5 m, the length L5 of the straight line T2 is set to 2.5 m, and the length L6 of the straight line T3 is set to 10 m. Then, the support length L1 and the adjustment length L2 of the tension rope 7 when the hoisting angle θ of the boom 6 was changed from 85 degrees to 5 degrees were calculated. Subsequently, a change amount R1 of the support length L1 of the tension rope 7 and a change amount R2 of the adjustment length L2 when the undulation angle θ is changed with reference to the time when the undulation angle θ of the boom 6 is 85 degrees. Calculated.

  As shown in Table 1, when the change amount R2 of the adjustment length L2 was added to the change amount R1 of the support length L1 of the tension rope 7, a value falling within a range of ± 0.020 m was shown. From this, it was found that the change amount R1 of the support length L1 of the tension rope 7 is almost completely canceled out by the change amount R2 of the adjustment length L2.

  Subsequently, the length L3 of the boom 6 is changed to 60 m, 50 m, 40 m, 30 m, and 20 m, and the total length of the tension rope 7 is changed corresponding to the length L3 of the boom 6 so that the hoisting angle θ of the boom 6 is changed. The support length L1 of the tension rope 7 when changing from 85 degrees to 5 degrees was calculated. Then, similarly to the above, the amount of change R1 of the support length L1 of the tension rope 7 when the undulation angle θ is changed is calculated with the undulation angle θ of the boom 6 being 85 degrees.

When the change amount R1 of the support length L1 calculated for the length L3 of each boom 6 was compared, it was found that the same distribution was shown with respect to the change in the undulation angle θ. That is, even if the boom 6 has a length L3 of 60 m, 50 m, 40 m, 30 m, and 20 m and the undulation angle θ is changed, the change amount R1 of the support length L1 of the tension rope 7 has changed at substantially the same value.
Thus, as in the second embodiment, by adjusting the entire length of the tension rope 7 according to the expansion and contraction of the boom 6, similarly, the support length L1 of the tension rope 7 according to the undulation of the boom 6 is set. It was found that the change amount R1 can be canceled by the change amount R2 of the adjustment length L2.

  1 traveling vehicle, 2 crane, 3 wheels, 4 outrigger, 5 swivel base, 6 boom, 7 tension rope, 8 root pin, 9 hoisting cylinder, 10a, 10b, 32 fixed part, 11a, 11b, 11c, 33, 34 sheave 12a, 12b Tension rope end, 21, 41 tip winch, 31 rear winch, 42 tension detector, 43 tension adjuster, E1 boom base end, E2 boom tip, E3 boom middle, S1 Swivel front, S2 Swivel rear, S3 Swivel right side, S4 Swivel left side, L1 support length, L2 adjustment length, L3 boom length, L4, L5, L6 Straight line length , Θ Boom undulation angle, α Boom angle.

Claims (3)

A support;
A boom having a base end supported by the support so as to be raised and lowered, and extending from the base end toward the front end of the support toward the front side;
A first sheave disposed on the rear side of the base of the boom in the support;
A second sheave arranged on the front side of the base of the boom in the support;
It is arranged so as to extend from the vicinity of the tip of the boom to the rear side of the support, and one end side is connected to the vicinity of the tip of the boom and the other end side is stretched around the first sheave. And a tension rope that supports the tip of the boom,
The other end side of the tension rope is routed around the first sheave and guided to the second sheave and is routed around the second sheave so as to face upward. Crane connected to the part. The tension rope has a support length that extends from the vicinity of the tip of the boom to the first sheave and an adjustment length that extends from the second sheave to the middle portion of the boom according to the undulation of the boom,
The first sheave, the second sheave, one end side of the tension rope, and the other end side of the tension rope change in the support length of the tension rope according to the undulation of the boom The crane according to claim 1, wherein the crane is arranged so that the amount of change in the adjustment length almost cancels out the amount. And further comprising a hoisting cylinder for connecting the support and the boom and hoisting the boom by expansion and contraction,
The crane according to claim 1 or 2, wherein the tension rope is disposed along the hoisting cylinder from the second sheave toward an intermediate portion of the boom.

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