JP2020117370A - Overload prevention device and crane - Google Patents

Abstract

A tension overload prevention device and a crane capable of effectively preventing excessive tension with a simple structure are provided. A first member (16) and a second member (17) are arranged opposite to each other with respect to a rope (14) and the rope (14) is stretched between them, and an elastic body (20) biases the second member (17) toward the rope (14). and displacement detection mechanisms 21 and 22 for detecting displacement of the second member 17 in the anti-biasing direction. The displacement detection mechanisms 21 and 22 are configured to detect the displacement of the second member 17 by the contact portion 21 and the contact switch 22 that are displaced with respect to the displacement of the second member 17 . [Selection drawing] Fig. 5

Description

TECHNICAL FIELD The present invention relates to a device for preventing excessive tension on a rope, and a crane to which the device is applied.

In a crane that uses a rope to carry a suspended load, the rope and the lifting gear may be moored to a boom when the cargo is not loaded. For example, in the case of a mobile crane equipped with a telescopic boom, a suspension rope unwound from a winch drum or a suspension device suspended from the suspension rope may hinder traveling. Therefore, while traveling, the boom is contracted and laid down, and while the suspension rope is wound around the winch drum to an appropriate length, the tip of the suspension rope or the suspension equipment is moored, and the suspension rope or suspension equipment is used for the crane boom. It is restrained so as not to move freely with respect to the body.

Here, when mooring a hanging rope or a hanger, it is necessary that the rope (mooring rope) used for mooring and the hanging rope maintain appropriate tension. If the tension is too low, the suspension ropes and hoists will not be properly restrained, and if they are too heavy, the mooring ropes and suspension ropes may be cut or damaged.

The tension of the mooring rope or the suspension rope can be adjusted by the amount of the suspension rope paid out from the winch drum which pays out the hanging rope. In other words, with the tip of the suspending rope or the suspending tool moored to the boom, rotate the winch drum to wind up the suspending rope, and stop the rotation of the winch drum when the tension reaches an appropriate range. Good.

Here, in order to determine an appropriate timing for stopping the winding, for example, a method of attaching a device as described in Patent Document 1 below to a hanging rope or a mooring rope and detecting the tension can be considered. ..

JP-A-58-115334

However, tension generally occurs when the rope is stretched in a straight line and does not occur when the rope is slack. Therefore, when considering the case where the winch drum is rotated at a constant speed to wind up the suspension rope, the tension is almost not detected until just before the suspension rope is in tension, and the suspension rope is not detected. It behaves as if it rises sharply from the moment it is stretched. Therefore, if a method of winding the hanging rope while monitoring the value of the tension is adopted, the tension may already be excessive at the time when the tension is detected. In order to avoid such a situation, it is conceivable to wind the hanging rope with a winch drum at an extremely low speed, but in that case, there is a problem that the mooring work takes time.

In view of the above situation, the present invention is to provide a tension overload prevention device and a crane that can effectively prevent overload of tension with a simple structure.

The present invention provides a first member and a second member which are arranged on opposite sides with respect to a rope and on which the rope is stretched between them, an elastic body which urges the second member toward the rope, and the first member and the second member. According to another aspect of the present invention, there is provided a tension overload prevention device, comprising: a displacement detection mechanism that detects a displacement of two members in the opposite biasing direction.

In the tension overload prevention device of the present invention, the displacement detection mechanism can be configured to detect the displacement of the second member by a contact portion and a contact switch that are displaced with each other as the second member is displaced.

In the tension overload prevention device of the present invention, the first member includes a support portion that supports one end of the elastic body, the second member is rotatably supported on one side by the first member, The other end of the elastic body may be attached to the other side.

In the tension overload prevention device of the present invention, the first member includes a first sheave on which the rope is wound, the second member includes a second sheave on which the rope is wound, and One side of the second member may be attached to one side, and the other side of the first member may be attached to a mooring portion to which the rope is moored.

In the tension overload prevention device of the present invention, the first member includes a first sheave on which the rope is wound, the second member includes a second sheave on which the rope is wound, and One side of the second member may be attached to one side, and a third sheave around which the rope is wound may be provided on the other side of the first member.

Further, the present invention is applied with the above-mentioned tension overload prevention device, and includes a hanging rope for hanging a suspended load, and a hanging drum for feeding the hanging rope, and the displacement detecting mechanism is used for displacement of the second member. The crane is characterized in that the rotation of the suspension drum is stopped by a contact signal input together.

According to the tension overload prevention device and the crane of the present invention, it is possible to obtain an excellent effect that the overload of tension can be effectively prevented with a simple structure.

It is a schematic diagram showing an example of the composition of the crane to which the tension overload prevention device of the present invention is applied. It is a front view which shows an example of the form of the tension overload prevention apparatus of this invention. It is the perspective view which looked at the tension overload prevention device of Drawing 2 from the slanting lower part. It is a front view which shows a part of crane which attached the excessive tension prevention apparatus. It is a front view which shows the tension overload prevention apparatus attached to the crane, and is an enlarged view which shows the principal part of FIG. It is a front view which shows the operating state of a tension overload prevention apparatus. It is a front view which shows another example of the form of the tension overload prevention apparatus of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an example of the form of a mobile crane. The crane 1 includes a boom 3 extending upward from a main body 2 and a crawler 4 as a traveling device mounted below the main body 2, A hook 5 serving as a suspending tool that is suspended from the tip of the boom 3 is adapted to carry a suspended load (not shown).

The main body 2 is rotatably supported by the crawler 4 via a rotary base 6. The boom 3 has a telescopic structure and is configured to be extendable/contractible, and the base portion is attached to the main body 2 so as to be capable of undulating via the undulating pins 3a.

A hoisting cylinder 12 having a hydraulic expansion/contraction mechanism is installed at a position in front of the base of the boom 3 in the main body 2. The hoisting cylinder 12 is installed so that the base part can hoist on the main body 2 side, and the tip end is rotatably connected to the boom 3 via a connecting pin 12a. The boom 3 is raised and lowered by expanding and contracting.

Further, the main body 2 is provided with a winch drum (suspension drum) 8 for suspending a suspended load, and a rope (suspension rope) 10 is extended from the winch drum 8.

The suspension rope 10 fed from the suspension drum 8 is wound around a guide sheave 7 provided above the rear portion of the main body 2, then extends forward, and is wound around a sheave 3b provided at the tip of the boom 3. .. Further, the suspension rope 10 extends downward from the sheave 3b, is wound around the hook 5, suspends the hook 5, and suspends a suspended load through the hook 5. The hook 5 can be operated up and down by unwinding or winding the hanging rope 10 from the hanging drum 8.

A mooring portion 3c for mooring the hook 5 is provided at a portion of the lower surface of the boom 3 closer to the base portion than the middle portion. The mooring portion 3c is, for example, a flange that protrudes from the lower surface of the boom 3 and has a hole. As shown in FIG. 4, a mooring rope (mooring rope) 14 is stretched between the hook 5 and the mooring portion 3c. Thus, the hook 5 can be moored to the boom 3.

Various operations such as expansion and contraction of the boom 3, traveling and direction change by the crawler 4, rotation of the rotating pedestal 6, rotation of the hanging drum 8, expansion and contraction of the hoisting cylinder 12 are controlled by the control device 13 provided in the main body 2. The control device 13 is a device that controls the operation of each part of the crane 1 via an operation signal (not shown) according to an operation input from the driver's seat. Further, a contact signal (not shown) is input to the control device 13 from the contact switch 22 of the tension overload preventing device 15 as described later.

From the mooring portion 3c to the mooring rope 14 moored to the mooring portion 3c, a tension overload preventing device 15 as shown in FIGS. 2 and 3 is attached as shown in FIGS. As shown in FIGS. 2 and 3, the tension overload prevention device 15 includes a first member 16 and a second member 17 rotatably supported with respect to the first member 16. A first sheave 18 and a second sheave 19 are attached to the first member 16 and the second member, respectively.

The first member 16 is configured to include a pair of brackets 16a extending in parallel with each other, and the brackets 16a are connected to each other by a connecting member 16b so as to have a constant gap therebetween. Both ends of the shaft 18a of the first sheave 18 are supported by the pair of brackets 16a at one end of the first member 16. The other end of the first member 16 is rotatably attached to the mooring portion 3c of the boom 3.

The pair of brackets 16a forming the first member 16 are provided at their intermediate portions with support portions 16c protruding in a direction orthogonal to the longitudinal direction of the brackets 16a. The support portions 16c project in parallel from the intermediate portions of the pair of brackets 16a in the same direction, and the elastic body 20 such as a helical spring is attached to the tip ends of the pair of support portions 16c. The elastic body 20 is disposed between the pair of support portions 16c, and one end of the elastic body 20 is rotatably attached to the support portions 16c so as to be sandwiched between the tip portions of the pair of support portions 16c. .. The other end of the elastic body 20 is located near the base of the support 16c and is connected to the second member 17.

The second member 17 is configured to include a pair of brackets 17a extending in parallel with each other, and the brackets 17a are connected to each other by a connecting member 17b so as to have a constant gap therebetween. The bracket 17a of the second member 17 is set to have a shorter dimension in the longitudinal direction than the bracket 16a of the first member 16, and the pair of brackets 17a is sandwiched by the pair of brackets 16a and has a pair of longitudinal brackets. 16a is arranged substantially along the longitudinal direction.

The one end of the pair of brackets 17a is rotatably attached to the shaft 18a of the first sheave 18 supported by the one end of the bracket 16a, and the other end of the bracket 17a is attached to the other end. Is rotatably attached to the other end of the elastic body 20. Thus, the elastic body 20 is attached between the tip of the support portion 16c of the bracket 16a that forms the first member 16 and the other end of the bracket 17a that forms the second member 17, and The second member 17 is biased in the direction from the tip end side to the base end side.

A second sheave 19 is attached to an intermediate portion of the second member 17 such that both ends of the shaft 19a are supported by the pair of brackets 17a. Further, both ends of the shaft 19a project to the outside of the bracket 17a and enter into holes 16d provided in the pair of brackets 16a located on both outsides of the bracket 17a. The hole 16d is a long hole provided along an arc centered on the shaft 19a and orthogonal to the longitudinal direction of the bracket 16a. By disposing the shaft 19a of the second sheave 19 in the hole 16d, While permitting rotation of the member 17 with respect to the first member 16, the range in which the second member 17 moves with respect to the first member 16 is limited.

Thus, the tension overload prevention device 15 of the present embodiment is configured as a compact device in which the first member 16 and the second member 17 that is displaced while being biased with respect to the first member 16 are connected to each other. Has been done.

The rotation axis of the first member 16 with respect to the mooring portion 3c, the rotation axis of the elastic body 20 with respect to the support portion 16c, the rotation axis of the second member 17 with respect to the first member 16 and the elastic body 20, the first sheave 18 and the second sheave 19. The axes 18a and 19a are parallel to each other. The longitudinal direction of the first member 16 and the second member 17, the extending direction of the support portion 16c, and the expanding and contracting direction of the elastic body 20 are orthogonal to the respective rotation axes.

The mooring rope 14, which is a rope, is arranged so as to pass between the first sheave 18 and the second sheave 19, as shown in FIG. The mooring rope 14 has its tip moored to the mooring portion 3c of the boom 3, while the midway portion near the tip passes along the side closer to the elastic body 20 with respect to the first sheave 18 and with respect to the second sheave 19. It is wound around the first sheave 18 and the second sheave 19 so as to pass through the side far from the elastic body 20.

In other words, with respect to the mooring rope 14 moored at its end to the mooring portion 3c, the first sheave 18 attached to the first member 16 and the second sheave 19 attached to the second member 17 are located on opposite sides to each other. The second sheave 19 is located between the mooring portion 3c and the first sheave 18 in the extending direction of the mooring rope 14. The mooring rope 14 is stretched between the first sheave 18 and the second sheave 19, and the second sheave 19 is urged toward the mooring rope 14 by the elastic force of the elastic body 20 (hereinafter, referred to as the The direction in which the two members 17 and the second sheave 19 are biased by the elastic body 20 against the mooring rope 14 is referred to as "biasing direction", and the direction opposite to the biasing direction is referred to as "anti-biasing direction". ..

Further, the tension overload prevention device 15 is provided with a displacement detection mechanism including a contact portion 21 and a contact switch 22 so as to detect the displacement of the second member 17 in the anti-biasing direction.

The contact portion 21 and the contact switch 22 come into contact with each other as the second member 17 is displaced in the anti-biasing direction, and the contact switch 22 detects the contact of the contact portion 21. The contact portion 21 is a plate-like member provided at a connecting portion between the other end of the second member 17 and the other end of the elastic body 20, and protrudes outward when viewed in the axial direction of the elastic body 20. The elastic body 20 has a surface orthogonal to the expansion/contraction direction. As the elastic body 20 expands and contracts, it moves along the axial direction of the elastic body 20.

The contact switch 22 is attached to one of the pair of support portions 16c, and is arranged so that the tip 22a faces the contact portion 21. When the contact portion 21 is displaced toward the tip of the support portion 16c due to the contraction of the elastic body 20, the contact portion 21 comes into contact with the tip portion 22a of the contact switch 22. In this way, the displacement detection mechanism can detect the displacement of the second member 17 associated with the contraction of the elastic body 20 with a simple configuration including the contact portion 21 and the contact switch 22. When the contact portion 21 contacts the tip 22a, the contact switch 22 inputs a contact signal (not shown) to the control device 13 (see FIG. 1).

Here, the case where the contact portion 21 is attached to the first member 16 and the contact switch 22 is arranged so as to move in accordance with the displacement of the second member 17 with respect to the first member 16 is illustrated. The arrangement of 22 is not limited to this, and the configuration of the displacement detection mechanism can be appropriately changed as long as the displacement of the second member 17 with respect to the first member 16 can be detected. For example, it is possible to attach the contact switch to the second member 17 and install the contact portion on the first member 16 side. Alternatively, the tip 22a of the contact switch 22 and the contact portion 21 may be arranged so as to come into contact with each other when the elastic body 20 expands and separate from each other when the elastic body 20 contracts. (This case will be described again later with reference to the drawings).

Next, the operation of the above-described embodiment will be described.

For example, when the crane 1 is running, as shown in FIG. 4, the suspension drum 8 is rotated and the suspension rope 10 is wound while the boom 3 is contracted/fallen down. At this time, as shown in FIGS. 4 and 5, the hook 5 attached to the hanging rope 10 is moored by the mooring rope 14 to the mooring portion 3c of the boom 3 to which the tension overload preventing device 15 is attached. Then, the suspension drum 8 is further rotated, and the suspension rope 10 is slowly wound up to an appropriate payout length.

As long as the unwinding length of the hanging rope 10 is such that the hanging rope 10 or the mooring rope 14 is loose, no large tension is generated in the hanging rope 10 or the mooring rope 14. In this state, as shown in FIG. 5, the second member 17 is pressed against the first member 16 by the elastic body 20 in the biasing direction, and is positioned on the upper side in the drawing. When the hanging rope 10 is further wound from this state and the winding amount exceeds the threshold value, the hanging rope 10 and the mooring rope 14 are in a tensioned state, and tension is generated in the mooring rope 14.

As described above, the portion of the mooring rope 14 wound around the second sheave 19 receives the urging force from the elastic body 20 via the second sheave 19. Seen from the second sheave 19, the second sheave 19 receives a reaction force from the mooring rope 14 in the anti-biasing direction, and the first sheave 18 receives the force from the mooring rope 14 in the urging direction. Has become. Here, when the tension generated on the mooring rope 14 by winding the suspension drum 8 (see FIG. 1) becomes large enough to resist the elastic force of the elastic body 20, the mooring rope between the tip and the first sheave 18 is pulled. 14 starts pushing back the second sheave 19 in the anti-biasing direction. As a result, as shown in FIG. 6, the second member 17 to which the second sheave 19 is attached is displaced in the anti-biasing direction, and the contact portion 21 contacts the tip portion 22 a of the contact switch 22. The contact switch 22 inputs a contact signal (not shown) to the control device 13 (see FIG. 1) of the crane 1. The controller 13 receives the contact signal and stops the rotation of the hanging drum 8.

By doing so, the rotation of the suspension drum 8 is automatically stopped at the stage when the tension generated in the mooring rope 14 becomes a level against the elastic force of the elastic body 20. Therefore, if the elastic body 20 having an appropriate elastic force is attached to the tension overload prevention device 15 in advance, the tension of the mooring rope 14 or the suspension rope 10 will be appropriate when the tension of the suspension rope 10 is shown. The winding is stopped, and the hanging rope 10 and the hook 5 are moored to the boom 3 with an appropriate tension. For example, when compared with a method in which a tension meter or the like is attached to the suspension rope 10 or the mooring rope 14 and the timing of stopping the suspension drum 8 is measured while monitoring the tension value, it can be quickly determined that the tension has exceeded a certain threshold value. And it can be detected automatically. Further, since the operation from the tension becomes a value equal to or higher than the threshold value until the suspending drum 8 is stopped can be performed quickly and automatically, excessive tension of the suspending rope 10 is caused by excessive winding. Hateful. The time and effort required for mooring the hanging rope 10 and the hooks 5 can be saved because there is no need for the trouble of rotating the hanging drum 8 very slowly in order to avoid excessive tension.

In addition, although the case where the lifting tool (hook) 5 attached to the hanging rope 10 is moored to the boom 3 via the mooring rope 14 is illustrated here, it is not necessary to use the lifting tool 5 and to attach it to the rope end of the hanging rope 10. When the suspended load is directly connected to perform the cargo handling, the suspension rope 10 is moored to the mooring portion 3c of the boom 3 and the tension overload prevention device 15 is used for the suspension rope 10 instead of the mooring rope 14. You can also Further, although the boom 3 is illustrated here as a position for mooring the hanging rope 10 and the hanger 5, it may be appropriately set other than the boom 3. For example, a mooring portion may be provided at an appropriate portion of the main body 2.

Further, in the above, the other end of the first member 16 is attached to the mooring portion 3c of the boom 3, and the tip of the mooring rope 14 is moored to the mooring portion 3c, and the tip of the mooring rope 14 and the first sheave 18 are attached. Although the case where the second sheave 19 is arranged between the wound portion and the wound portion is illustrated, the other end of the first member 16 is attached to the boom 3 or the like as shown as another embodiment in FIG. 7, for example. Instead of (or in addition to), the tension overload prevention device 15 in which the third sheave 23 is further provided at the other end of the first member 16 may be used. In such a case, the first sheave 18 and the third sheave 23 are located on the opposite side of the elastic body 20 with respect to the mooring rope 14, and the second sheave 19 is located on the elastic body 20 side. Will be wrapped around. According to the tension overload prevention device 15 as described above, the rope can be used at any position of the rope as long as the tension is generated. That is, it can be used not only in the vicinity of the tip of the mooring rope 14 moored to the mooring portion 3c (see FIG. 5) but also in the hanging rope 10 (see FIG. 1) between the tip of the boom 3 and the hook 5, for example. it can. However, in addition to the work of passing the rope for detecting the tension between the first sheave 18 and the second sheave 19, it is necessary to pass the rope between the second sheave 19 and the third sheave 23. Is slightly increased. With the tension overload prevention device 15 as shown in FIGS. 2 and 3, when mooring the hanging rope 10 or the hook 5, the mooring rope 14 or the tip of the hanging rope 10 is fixed to the first sheave 18 and the second sheave 19. It is easy to handle because it can be used by passing it through the space between the mooring and the mooring part 3c.

Further, in the case of the tension overload prevention device 15 shown in FIG. 7, the positional relationship between the elastic body 20 and the support portion 16c and the second sheave 19 is different from the examples shown in FIGS. The mounting position of the second member 17 on the first member 16 is also set to a position different from the shaft 18a of the first sheave 18. That is, in the tension overload prevention device 15, a rope (a mooring rope 14, a hanging rope 10 or the like) as a tension detection target is stretched between the first member 16 and the second member 17, and the first member is also stretched. It is important that 16 and the second member 17 are arranged on opposite sides of the rope, and that the second member 17 is biased toward the rope 14. As described above, can be appropriately changed according to various conditions and the like at the time of implementation.

In addition, in the tension overload prevention device 15 shown in FIG. 7, the positional relationship between the contact portion 21 and the contact switch 22 is different from the examples shown in FIGS. It is attached not to the support portion 16c on the same side as the elastic body 20 but to a part of the bracket 16a of the first member 16 on the side opposite to the elastic body 20 as viewed from the contact portion 21. In such an arrangement, the tip 22a of the contact switch 22 and the contact portion 21 come into contact when the elastic body 20 extends and separate from each other when the elastic body 20 contracts. That is, in the state where the second member 17 is biased toward the rope, the contact portion 21 contacts the tip 22a of the contact switch 22, and the second member 17 resists the biasing force of the elastic body 20 and counter biases it. The contact portion 21 separates from the tip 22a of the contact switch 22 when displaced in the direction. In this case, the control device 13 permits the suspension drum 8 (see FIG. 1) to rotate while the contact signal is being input, and detects the displacement of the second member 17 in the anti-biasing direction when the contact signal is not input. Under this condition, the suspension drum 8 stops rotating. Even in this case, similarly to the example shown in FIGS. 2 and 3, the displacement of the second member 17 with respect to the first member 16 can be detected, and the suspension drum 8 can be automatically stopped accordingly. It can be executed appropriately.

As described above, the tension overload prevention device 15 of the present embodiment is arranged on the opposite sides of the rope (mooring rope) 14, and the rope 14 is stretched between the first member 16 and the second member 17. The elastic member 20 that biases the second member 17 toward the rope 14 and the displacement detection mechanisms 21 and 22 that detect the displacement of the second member 17 in the opposite biasing direction. With this configuration, it is possible to quickly and automatically detect that the tension has exceeded the threshold value.

In the tension overload prevention device 15 of the present embodiment, the displacement detection mechanisms 21 and 22 detect the displacement of the second member 17 by the contact portion 21 and the contact switch 22 which are displaced with each other as the second member 17 is displaced. It is configured. With this configuration, the displacement of the second member 17 with respect to the first member 16 can be detected with a simple mechanism.

In the tension overload prevention device 15 of the present invention, the first member 16 includes a support portion 16c that supports one end of the elastic body 20, and the second member 17 is rotatably supported by the first member 16 on one side. At the same time, the other end of the elastic body 20 is attached to the other side. By doing so, the tension overload prevention device 15 can be configured as a compact device in which the first member 16 and the second member 17 that is displaced while being biased with respect to the first member 16 are connected to each other. ..

In the tension overload prevention device of the present invention, the first member 16 includes a first sheave 18 around which the rope 14 is wound, and the second member 17 includes a second sheave 19 around which the rope 14 is wound around. One side of the second member 17 may be attached to one side of the first member 16, and the other side of the first member 16 may be attached to the mooring portion 3c to which the rope 14 is moored.

In the tension overload prevention device of the present invention, the first member 16 includes a first sheave 18 around which the rope 14 is wound, and the second member 17 includes a second sheave 19 around which the rope 14 is wound around. One side of the second member 17 may be attached to one side of the first member 16, and the third sheave 23 around which the rope 14 is wound may be provided on the other side of the first member 16.

Further, the crane 1 of the present embodiment is provided with the above-described tension overload prevention device 15, is provided with a hanging rope 10 for hanging a hanging load, and a hanging drum 8 for feeding the hanging rope 10, and a displacement detection mechanism 21. , 22 to stop the rotation of the suspension drum 8 in response to a contact signal input with the displacement of the second member 17. In this way, since the operation from the tension becomes a value equal to or more than the threshold value until the suspending drum 8 is stopped can be automatically performed, the excessive tension of the suspending rope 10 caused by the excessive winding of the suspending rope 10 can be prevented. It can be made difficult to occur.

Therefore, according to the present embodiment, it is possible to effectively prevent the tension from being overloaded with a simple structure.

It should be noted that the tension overload preventing device and the crane of the present invention are not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

1 Crane 3c Mooring part 8 Winch drum (hanging drum)
10 ropes (hanging ropes)
14 ropes (mooring ropes)
15 Tension Overload Prevention Device 16 First Member 16c Supporting Part 17 Second Member 18 First Sheave 19 Second Sheave 20 Elastic Body 21 Displacement Detection Mechanism (Contact Part)
22 Displacement detection mechanism (contact switch)
23 Third Sheave

Claims (6)

A first member and a second member that are arranged on opposite sides of the rope and on which the rope is stretched between each other;
An elastic body that urges the second member toward the rope,
A tension overload prevention device, comprising: a displacement detection mechanism that detects a displacement of the second member in the opposite biasing direction. The displacement detection mechanism,
With the contact portion and the contact switch that are displaced with each other with the displacement of the second member,
The tension overload prevention device according to claim 1, wherein the device is configured to detect a displacement of the second member. The first member includes a support portion that supports one end of the elastic body,
The tension overload prevention according to claim 1 or 2, wherein one side of the second member is rotatably supported by the first member, and the other end of the elastic member is attached to the other side. apparatus. The first member includes a first sheave on which the rope is wound,
The second member includes a second sheave around which the rope is wound,
While one side of the second member is attached to one side of the first member,
The excessive tension preventing device according to claim 3, wherein the other side of the first member is attached to a mooring portion to which the rope is moored. The first member includes a first sheave on which the rope is wound,
The second member includes a second sheave around which the rope is wound,
While one side of the second member is attached to one side of the first member,
The excessive tension preventing device according to claim 3, further comprising a third sheave around which the rope is wound, which is provided on the other side of the first member. The tension overload prevention device according to any one of claims 1 to 5 is applied,
A suspending rope for suspending a suspended load, and a suspending drum for paying out the suspending rope,
A crane configured to stop the rotation of the suspension drum by a contact signal input from the displacement detection mechanism along with the displacement of the second member.

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