JP7253966B2 - Crane overload protection system - Google Patents

Description

The present invention relates to a crane overload protection system.

In general, a climbing crane is used for constructing a structure such as a high-rise building, and has a structure as shown in FIG.

In FIG. 9, reference numeral 1 denotes a climbing crane. The climbing crane 1 is provided with a mast 2 which is installed on a floor plate inside a structure and serves as a support section capable of successively adding mast blocks 2a upward. A revolving body 4 is rotatably arranged on the top of the mast 2 through an elevating unit 3 capable of elevating along the mast 2 . A jib 5 is attached to the revolving body 4 so that it can be raised and lowered, and a rearwardly extending counter frame 6 is integrally provided. Above the counter frame 6, a hoisting drum 9 for hoisting and lowering a hoisting wire rope 8 for suspending a hoisting tool 7 for lifting from the tip of the jib 5, and a hoisting wire rope 10 of the jib 5 are hoisted and lowered. A hoisting drum 11 is installed for doing so. The revolving body 4 is provided with a guy support 12. At the top of the guy support 12, a sheave 13 around which the hoisting wire rope 8 unwound from the hoisting drum 9 is wound, and the hoisting drum. A sheave 14 around which the hoisting wire rope 10 let out from 11 is wound is arranged. Further, at the tip of the jib 5, a sheave 15 around which the hoisting wire rope 8 is wound is arranged.

For example, Japanese Patent Laid-Open Publication No. 2002-300003 discloses a general technical level related to the climbing crane 1 as described above.

On the other hand, the climbing crane 1 includes a load detector 20, a jib angle detector 30, an overload prevention device 40, a controller 50, and a display 60, as shown in FIG. 10(a). It is equipped with an overload protection system.

The load detector 20 is composed of a load cell or the like for detecting the tension acting on the hoisting wire rope 8 and measures the actual load of the suspended load acting on the climbing crane 1 .

The jib angle detector 30 measures the inclination angle of the jib 5 .

The overload prevention device 40 has a rated load curve with respect to the working radius of the jib 5 set, obtains the working radius of the jib 5 based on the tilt angle measured by the jib angle detector 30, and determines the working radius of the jib 5 based on the working radius. A rated load is obtained from a rated load curve, and when it is determined that the actual load measured by the load detector 20 exceeds the rated load, a signal to stop the operation of the climbing crane 1 is output.

The controller 50 (PLC: Programmable Logic Controller) makes an emergency stop of the operation of the climbing crane 1 when the operation stop signal output from the overload prevention device 40 is input.

The indicator 60 displays the actual load, the working radius of the jib 5, etc., and also displays an alarm when the operation stop signal output from the overload prevention device 40 is input. .

As shown in FIG. 10(b), the rated load curve set in the overload prevention device 40 is horizontal until the working radius increases to a certain value due to the jib 5 falling from the upright state. The maximum rated load is maintained by displacement, and after the working radius exceeds a certain value, the load rating gradually decreases as the jib 5 falls down and the working radius increases. there is

For example, Patent Document 2 can be cited as a prior art document that discloses the overload prevention device as described above.

JP-A-2004-59321 JP 2017-178502 A

The load detector 20 disclosed in Patent Document 2 for detecting the tension acting on the hoisting wire rope 8 is, for example, in the case of a conventional drum balance type crane, a hoisting wire rope as shown in FIG. 8 is connected to a sheave 13b dedicated to load detection which is wound around. Although the load detector 20 such as a tension-type load cell is shown in FIG. 11, a load detector 20 such as a compression-type load cell may be used. In this case, a lever (not shown) having a fulcrum at its intermediate portion is interposed between the load detector 20 such as a compression type load cell and the sheave 13b.

Incidentally, in the example shown in FIG. 11, the hoisting wire rope 8 unwound from the hoisting drum 9 is wound around the sheave 13a at the top of the guy support 12, and then wound around the sheave 13b dedicated to load detection. Furthermore, the sheave 13c at the top of the guy support 12, the sheave 15a at the tip of the jib 5, the sheave 7b for suspending the sheave 7a of the sling 7, the sheave 15b at the tip of the jib 5, and the sheave 13d at the top of the guy support 12 are sequentially hung. , is wound on the luffing drum 11 .

However, the hoisting wire rope 8 unwound from the hoisting drum 9 has two systems, left and right, and the load detector 20 is not provided on the sheave 13b of the right system shown in FIG.

The hoisting wire ropes 10 fed out from the left and right hoisting drums 11 are respectively attached to the sheave 14a at the top of the guy support 12 and to the hoisting pendant sheave block 16 connected to the tip of the jib 5 via the hoisting pendant rope 10a. A sheave 14b attached to the top of the guy support 12, a sheave 14c at the top of the guy support 12, a sheave 14d attached to the pendant sheave block 16, and a sheave 14e attached to the swing sheave block 17 projecting from the top of the guy support 12. , which can be connected.

However, as described above, if the load detector 20 is connected to the load-detecting sheave 13b around which the hoisting wire rope 8 is wound, the number of sheaves increases and the installation of the climbing crane 1 becomes difficult. In some cases, the hoisting wire rope 8 needs to be hung around the sheave 13b dedicated to load detection, and the hoisting wire rope 8 must be lengthened accordingly, so an improvement has been desired.

The present invention has been made in view of the conventional problems described above, and avoids an increase in the number of sheaves. To provide a crane overload protection system that does not require lengthening.

The present invention includes a load detector that measures a load,
a jib angle detector for measuring the inclination angle of the jib;
A rated load curve for the working radius of the jib is set, the working radius of the jib is obtained based on the tilt angle measured by the jib angle detector, the rated load is obtained from the rated load curve based on the working radius, and the load is detected. An overload prevention device that determines the actual load of the suspended load acting on the crane based on the load measured by the instrument, and outputs a crane operation stop signal when the actual load is determined to exceed the rated load. A crane overload protection system comprising:
Said load detector relates to a crane overload protection system which is mounted on the top of a guy support and incorporated in the shaft of a sheave around which a hoisting wire rope is wound.

Further, the sheave at the top of the guy support can be arranged so that the hoisting wire rope has a fixed pay-out angle and retraction angle.

According to the overload protection system for a crane of the present invention, an increase in the number of sheaves can be avoided, and an extra operation on the sheave dedicated to load detection of the hoisting wire rope at the time of installation of the crane and lengthening of the hoisting wire rope can be avoided. An excellent effect can be obtained that it can be made unnecessary.

1 is a perspective view showing a first embodiment of a crane overload protection system of the present invention; FIG. FIG. 2 is a schematic diagram showing the relationship between the measured value and the tension of the hoisting wire rope in the first embodiment of the overload protection system for cranes of the present invention; 1 is a schematic diagram showing a state in which a hoisting wire rope is separated from a sheave in the first embodiment of the overload protection system for a crane of the present invention; FIG. FIG. 4 is a schematic diagram of a second embodiment of a crane overload protection system of the present invention that avoids the situation of FIG. 3; FIG. 4 is a schematic diagram showing the relationship between the measured value and the tension of the hoisting wire rope in the first reference example of the overload protection system for a crane of the present invention; FIG. 5 is a schematic diagram showing the relationship between the measured value and the jib axial force in the second reference example of the overload protection system for cranes of the present invention. FIG. 10A is a side view and a plan view showing a jib in a third embodiment of the overload protection system for a crane of the present invention; FIG. 5 is a diagram showing the bending moment, shearing force, and axial force acting on the connecting pin of the jib in the third embodiment of the overload protection system for cranes of the present invention; 1 is a schematic configuration diagram showing an example of a general climbing crane; FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of the conventional overload prevention apparatus, (a) is a control block diagram, (b) is a rated load curve figure. FIG. 11 is a perspective view showing an example of a location where a load detector of a conventional overload prevention device is arranged;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIGS. 1 and 2 show a first embodiment of the overload protection system for cranes of the present invention, and in the figures, the same reference numerals as in FIGS. 9 to 11 represent the same parts.

The crane overload protection system of the first embodiment comprises a load detector 20, a jib angle detector 30, an overload protection device 40, a controller 50, and an indicator 60. , is the same as the conventional example shown in FIG.

In the case of the first embodiment, the load detector 20 is incorporated in the shaft of the sheave around which the hoisting wire rope 8 is wound to measure the load P. As shown in FIG. Here, the sheave around which the hoisting wire rope 8 is wound can be a sheave 13 arranged on the top of the guy support 12, and a load cell is incorporated in the shaft of the sheave 13 as a load detector 20. It has become.

The jib angle detector 30 measures the inclination angle θ _J of the jib 5 .

The overload prevention device 40 is provided with a rated load curve for the working radius R of the jib 5, obtains the working radius R of the jib 5 based on the inclination angle θ _J measured by the jib angle detector 30, and determines the working radius R of the jib 5. The rated load is obtained from the rated load curve based on R, the actual load of the suspended load acting on the climbing crane 1 is obtained based on the load P measured by the load detector 20, and the actual load exceeds the rated load. When it is determined that the operation of the climbing crane 1 is stopped, a signal for stopping the operation of the climbing crane 1 is output.

Next, the operation of the first embodiment will be described.

When the climbing crane 1 is used to lift a load, the load detector 20 first measures the load P acting on the sheave 13 around which the hoisting wire rope 8 is wound.

At the same time, the inclination angle θ _J of the jib 5 is measured by the jib angle detector 30 .

Subsequently, based on the inclination angle θ _J of the jib 5 measured by the jib angle detector 30, the working radius R of the jib 5 is obtained by the overload prevention device 40. FIG.

Further, in the overload prevention device ₄₀ , the payout angle _θW1 of the hoisting wire rope 8 wound around the sheave 13 is obtained based on the inclination angle θJ of the jib 5 measured by the jib angle detector 30. At the same time, the pull-in angle _θW2 of the hoisting wire rope 8 wound around the sheave 13 is obtained.

Thereafter, based on the load P measured by the load detector 20 and the extension angle θW1 and retraction angle _θW2 obtained by the overload prevention device 40, the tension of the hoisting wire rope ₈ is adjusted to the climbing crane 1. is determined by the overload prevention device 40 as the actual load F due to the suspended load acting on.

Further, in the overload protection device 40, a rated load is obtained from a preset rated load curve based on the working radius R, and the actual load F is compared with the rated load.

When the overload prevention device 40 determines that the actual load F exceeds the rated load, the operation of the climbing crane 1 is stopped.

When the overload protection device 40 determines that the actual load F does not exceed the rated load, the operation of the climbing crane 1 is continued, and the same steps as described above are repeated.

A method of calculating the extension angle θ _W1 , the retraction angle θ _W2 , and the actual load F (tension F) will be described in detail below with reference to FIG.

In the example shown in FIG. 2, the sheave 13 around which the hoisting wire rope 8 is wound is disposed on the top of the guy support 12, and a load detector 20 such as a load cell is incorporated in the shaft of the sheave 13. The measured value of the load due to is P.

The height _HT from the upper surface of the rotating body 4 to the sheave 15 at the tip of the jib 5 is the height from the upper surface of the rotating body 4 to the hoisting center (foot pin 5a) of the jib 5, where _LJ is the length of the jib 5. is H _F , the inclination angle θ _J of the jib 5 is measured by the jib angle detector 30, so
H _T =L _J sin θ _J +H _F
is required as Incidentally, in FIG. 2, _WF is the horizontal length from the turning center to the hoisting center of the jib 5 (foot pin 5a).

Also, if the horizontal length from the turning center to the sheave 13 at the top of the guy support 12 is _WG , and the height from the upper surface of the rotating body 4 to the sheave 13 at the top of the guy support 12 is _HG , the working radius is: Since R is obtained based on the inclination angle _θJ of the jib 5,
(W _G +R) tan θ _W1 =H _T -H _G
A relationship is established.

That is, the delivery angle is
θ _W1 = tan ⁻¹ {(H _T −H _G )/(W _G +R)}
=tan ⁻¹ {(L _J sin θ _J +H _F −H _G )/(W _G +R)}
more sought after.

Furthermore, when the height from the upper surface of the revolving body 4 to the hoisting drum 9 is H _D and the horizontal length from the revolving center to the hoisting drum 9 is _WD ,
(H _G −H _D ) tan θ _W2 =W _D −W _G
A relationship is established.

That is, the pull-in angle is
θ _W2 = tan ⁻¹ {(W _D −W _G )/(H _G −H _D )}
more sought after.

The load P to be measured is the tension F acting on the hoisting wire rope 8 unwound from the sheave 13 to the tip side of the jib 5, and the hoisting wire rope 8 drawn from the sheave 13 to the hoisting drum 9 side. It is a resultant force with the acting tension F, and if the resolution angle of the load P with respect to the tension F is φ, from the vector synthesis relational expression,
F=P/2cosφ
φ=( _θW1 + _θW2 +90°)/2
A relationship is established.

That is, since the tension F becomes the actual load, the actual load is
F=P/[2 cos {(θ _W1 +θ _W2 +90°)/2}]
=P/[2 cos {tan ⁻¹ {(L _J sin θ _J +H _F −H _G )/(W _G +R)}
+tan ⁻¹ {(W _D −W _G )/(H _G −H _D )}+90°]/2}]
more sought after.

In the case of the first embodiment, it is not necessary to connect the load detector 20 to the sheave 13b (see FIG. 11) dedicated to load detection around which the hoisting wire rope 8 is wound, unlike the conventional case. In addition to eliminating the need to increase the number of the hoisting wire ropes 8, it is possible to omit the operation of winding the hoisting wire ropes 8 around the sheave 13b dedicated to load detection when installing the climbing crane 1, and the hoisting wire ropes 8 are not lengthened. done.

In this way, an increase in the number of sheaves can be avoided, and it is possible to eliminate the need for extra work to wind the sheave 13b dedicated to load detection of the hoisting wire rope 8 and lengthening the hoisting wire rope 8 when the climbing crane 1 is installed.

The sheave 13 disposed on the top of the guy support 12 is a sheave 13d around which the hoisting wire rope 8 wound on the hoisting drum 11 shown in FIG. It can also be incorporated as a vessel 20.

In this case, in the above formula, _WG is the horizontal length from the turning center to the sheave 13d at the top of the guy support 12, and _HG is the height from the upper surface of the rotating body 4 to the sheave 13d at the top of the guy support 12. By replacing _WD with the horizontal length from the turning center to the hoisting drum 11, and replacing H _D with the height from the upper surface of the rotating body 4 to the hoisting drum 11, the tension F is obtained as the actual load in the same manner as described above. be able to.

By the way, as shown in FIG. 3, when the jib 5 stands almost vertically, the hoisting wire rope 8 unwound from the hoisting drum 9 stops contacting the sheave 13, and no load is applied to the load detector 20. , the load P may become unmeasurable by the load detector 20 . Alternatively, even if the hoisting wire rope 8 contacts the sheave 13, the payout angle _θW1 and the retraction angle _θW2 increase, the measured value of the load P becomes extremely small, and the tension F calculated from the load P The error of the value may become large.

In order to solve such problems, for example, as in the second embodiment of the crane overload prevention system of the present invention shown in FIG. It is effective to dispose so that the angle θ _W1 and the pull-in angle θ _W2 are constant.

In the second embodiment shown in FIG. 4, at a position adjacent to the sheave 13 at the top of the guy support 12, regardless of the inclination angle _θJ of the jib 5, the payout angle θ _W1 and the retraction angle θ _W2 of the hoisting wire rope 8 are provided. is arranged, and a load detector 20 such as a load cell is incorporated in the shaft of the sheave 13'.

In the case of the second embodiment shown in FIG. 4, even if the jib 5 stands almost vertically, the hoisting wire rope 8 unwound from the hoisting drum 9 is always in contact with the sheave 13' and the load detector 20 is detected. It is possible to prevent the load P from becoming unmeasurable by the load detector 20 without losing the load. Moreover, since the delivery angle θ _W1 and the retraction angle θ _W2 of the hoisting wire rope 8 with respect to the sheave 13′ are constant, the measured value of the load P does not become extremely small, and the load P can be calculated from the load P. The error in the value of the tension F does not increase, and the measurement accuracy can be kept constant.

Incidentally, although it is necessary to add the sheave 13', unlike the conventional sheave 13b exclusively used for load detection, there is no need to perform extra work such as lengthening the hoisting wire rope 8 and winding it around.

FIG. 5 shows a first reference example of the overload protection system for a crane of the present invention. A load cell is incorporated as a load detector 20 on the shaft of the sheave 15. As shown in FIG.

In this case, the delivery angle is, as described above,
θ _W1 = tan ⁻¹ {(H _T −H _G )/(W _G +R)}
=tan ⁻¹ {(L _J sin θ _J +H _F −H _G )/(W _G +R)}
more sought after.

The load P to be measured is the tension F acting on the hoisting wire rope 8 unwound downward from the sheave 15, and the hoisting wire rope 8 drawn from the sheave 15 to the sheave 13 side of the top of the guy support 12. It is a resultant force with the acting tension F, and if the resolution angle of the load P with respect to the tension F is η, from the vector synthesis relational expression,
F = P/2 cos η
η=(90°−θ _W1 )/2
A relationship is established.

That is, since the tension F becomes the actual load, the actual load is
F=P/[2 cos {(90°−θ _W1 )/2}]
=P/[2 cos {90°-tan ^-1 {(L _J sin θ _J +H _F -H _G )
/(W _G +R)}/2}]
more sought after.

Thus, the sheave around which the hoisting wire rope 8 is wound is the sheave 15 disposed at the tip of the jib 5, and the load cell is loaded on the shaft of the sheave 15 as in the first reference example shown in FIG. Even if it is incorporated as the detector 20, an increase in the sheave is avoided, and the hoisting wire rope 8 at the time of installation of the climbing crane 1 is excessively hung around the sheave 13b dedicated to load detection and the hoisting wire rope 8 is lengthened. can be made unnecessary.

FIG. 6 shows a second embodiment of the crane overload protection system of the present invention, in which the load detector 20 is incorporated in the foot pin 5a of the jib 5. As shown in FIG.

The foot pins 5 a of the jib 5 are subjected to an axial force P 3 which is the sum of the axial force P ₁ due to the load of the suspended load and _the axial force P ₂ due to the self weight _FJ of the jib 5 .

When the load of the suspended load and the tension of the hoisting wire rope ₈ are F and their resultant force is P, the axial force P1 due to the load of the suspended load is the tension component _FK of the hoisting wire rope 10. It becomes the resultant force with P.

The axial force _P2 due to the weight _FJ of the jib 5 is the resultant force of the weight _FJ of the jib 5 and the vector _FV parallel to the hoisting wire rope 10 (hoisting wire rope 8). The dead weight _FJ of the jib 5 can be preset as a known value, and the vector _FV can be obtained based on the inclination angle _θJ of the jib 5 and the payout angle _θW1 of the hoisting wire rope 8. The axial force _P2 due to the self weight _FJ of the jib 5 can be calculated. Although the self weight _FJ of the jib 5 is actually a distributed _load acting on the entire jib 5, FIG. .

That is, _P2 is subtracted from the value of _P3 = _P1 + _P2 measured by the load detector 20, P is calculated backward from _P1 , and F can be obtained as the actual load.

Thus, even if the load detector 20 is incorporated into the foot pin 5a of the jib 5 as in the second reference example shown in FIG. It is possible to eliminate the need for extra winding work for the sheave 13b dedicated to detection and for lengthening the hoisting wire rope 8. - 特許庁

7 and 8 show a third embodiment of the crane overload protection system of the present invention, in which the load detector 20 is incorporated in the connecting pin 5b of the jib 5. As shown in FIG.

As explained in the second reference example _shown in FIG. Then, as shown in FIG. 8, a bending moment M and a shearing force τ due to the weight of the jib 5 act.

When the jib 5 is constructed by connecting one upper chord member 5c and two lower chord members 5d with braces 5e as shown in FIG. Let h _u be the height, h _d be the height from the lower chord 5d to the axis of the jib 5, and h be the height from the lower chord 5d to the upper chord 5c.

Furthermore, if the cross section of the jib 5 is made into a straight line extending in the vertical direction and modeled as a member supported at both ends at the upper and lower ends, a load of M/h acts on the upper chord member 5c and the lower chord member 5d. A load of M/2h acts on each string, and a shearing force of τ/3 acts on each string on the upper chord member 5c and the lower chord member 5d.

On the other hand, if P _u is the axial force acting on the upper chord member 5c, P _d is the axial force acting on the lower chord member 5d, and Z is the width from the axis of the jib 5 to the lower chord member 5d, then the axis of the jib 5 is The relational expression of the balance of the moment about the radial axis is
0= _Pd .(-Z)+ _Pd.Z
0=P _u ·h _u +2P _d ·(−h _d )
becomes,
P _d =P _u · _hu /2h _d
becomes.

Also, the relational expression of the balance of the axial force is
P ₃ =P _u +2P _d
becomes,
P ₃ =P _u +2(P _u · _hu /2h _d )
= P _u + (P _u · _hu /h _d )
= P _u (1+h _u /h _d )
= P _u (h _d +h _u )/h _d
= P _u h/h _d
∴ P _u = P ₃ ·h _d /h
becomes.

Also, from the relational expression of balance of the axial force, P ₃ =P _u +2P _d
= P ₃ ·h _d /h+2P _d
becomes,
2P _d =P ₃ (1−h _d /h)
= P ₃ (hh _d )/h
=P ₃ ·h _u /h
∴P _d =P ₃ ·h _u /2h
becomes.

The resultant force of the axial force acting on the position of the connection pin 5b in which the load detector 20 of the jib 5 is incorporated, the reaction force against the bending moment, and the reaction force against the shear force is the measured value of the load detector 20. The information necessary for obtaining the actual load is the reaction force generated by the bending moment M with respect to the upper chord member 5c or the lower chord member 5d. For this reason, the axial force _Pu or axial force _Pd obtained by the above calculation and the reaction force generated by the shear force τ on the upper chord member 5c or the lower chord member 5d are subtracted from the measured value of the load detector 20 for correction. Then, the reaction force generated by the bending moment M with respect to the upper chord member 5c or the lower chord member 5d is obtained.

As shown in FIG. 7, the connection pin 5b is provided at a connecting portion of the jib 5 which is divided into a plurality of parts. .

In the model shown in FIG. 8, the axial force vector exists on the axis of the jib 5. If the vector of the axial force deviates from the axis of the jib 5, The accompanying bending should be considered separately.

Furthermore, the horizontal force (wind load, etc.) acting on the jib 5 basically does not affect the measurement value of the load detector 20. , and averaging those measurements, it is also possible to compensate for the effects of said horizontal force and further increase accuracy.

Thus, even if the load detector 20 is incorporated into the connection pin 5b of the jib 5 as in the third reference example shown in FIGS. It is possible to eliminate the need for an extra operation of winding the sheave 13b dedicated to detecting the load of the rope 8 and lengthening the hoisting wire rope 8. - 特許庁

In the case of the first embodiment shown in FIGS. 1 and 2, the sheave around which the hoisting wire rope 8 is wound is the sheave 13 provided on the top of the guy support 12. As shown in FIG. With this configuration, the tension of the hoisting wire rope 8 is adjusted based on the load P measured by the load detector 20 and the extension angle _θW1 and retraction angle _θW2 obtained by the overload prevention device 40. It is stably obtained by the overload prevention device 40 as the actual load F due to the suspended load acting on the climbing crane 1 .

In the case of the second embodiment shown in FIG. 4, the sheave 13' at the top of the guy support 12 is arranged so that the hoisting wire rope 8 has a constant pay-out angle and a constant retraction angle. With this configuration, regardless of the upright state of the jib 5, the hoisting wire rope 8 unwound from the hoisting drum 9 is always in contact with the sheave 13', and the load P measured by the load detector 20 is extremely high. This is effective in avoiding a decrease, suppressing an error in the value of the tension F calculated from the load P, and maintaining constant measurement accuracy.

Further, in the case of the first reference example shown in FIG. 5, the sheave around which the hoisting wire rope 8 is wound is the sheave 15 arranged at the tip of the jib 5 . Even with this configuration, it is possible to avoid an increase in the number of sheaves, and it is possible to reduce the length of the hoisting wire rope 8 as well as the sheave 13b dedicated to detecting the load of the hoisting wire rope 8 when the climbing crane 1 is installed. may be unnecessary.

On the other hand, in the case of the second reference example shown in FIG. 6, the load detector 20 is incorporated in the foot pin 5a of the jib 5. Even with this configuration, it is possible to avoid an increase in the number of sheaves, and it is possible to reduce the length of the hoisting wire rope 8 as well as the sheave 13b dedicated to detecting the load of the hoisting wire rope 8 when the climbing crane 1 is installed. may be unnecessary.

7 and 8, the load detector 20 is incorporated in the connecting pin 5b of the jib 5. As shown in FIG . Even with this configuration, it is possible to avoid an increase in the number of sheaves, and it is possible to reduce the length of the hoisting wire rope 8 as well as the sheave 13b dedicated to detecting the load of the hoisting wire rope 8 when the climbing crane 1 is installed. may be unnecessary.

It should be noted that the overload protection system for cranes of the present invention is not limited to the above-described embodiments, and is applicable not only to climbing cranes but also to any crane having a jib. In addition, it goes without saying that various modifications can be made without departing from the gist of the present invention.

1 climbing crane (crane)
2 Mast 2a Mast Block 3 Lifting Unit 4 Revolving Body 5 Jib 5a Foot Pin 5b Connection Pin 5c Upper Chord 5d Lower Chord 5e Brace 6 Counter Frame 7 Hoist 7a Sheave 7b Sheave 8 Hoisting Wire Rope 9 Hoisting Drum 10 Luffing Wire Rope 10a Luffing pendant rope 11 luffing drum 12 guy support 13 sheave 13' sheave 13a sheave 13b sheave 13c sheave 13d sheave 14 sheave 14a sheave 14b sheave 14c sheave 14d sheave 14e sheave 15 sheave 15a sheave 15b sheave 16 luffing pendant sheave block 17 luffing swing sheave block 20 load detector 30 jib angle detector 40 overload prevention device 50 controller 60 indicator P load P ₁ axis force P ₂ axis force P ₃ axis force P _d axis force _Pu axis force F Actual load (tension)
F _J own weight F _K tension component F _V vector R Working radius θ _J tilt angle θ _W1 extension angle θ _W2 retraction angle HT Height from top surface of _T rotating body to sheave at tip of jib _HG Top surface of rotating body to guy support _WG Horizontal length from turning center to top sheave of guy support L _J Jib length _HF Height from upper surface of rotating body to jib undulation center _WD From turning center Horizontal length to the hoisting drum H _D Height from the upper surface of the rotating body to the hoisting drum _WF Horizontal length from the swing center to the jib undulation center M Bending moment τ Shear force h Length from the lower chord to the upper chord Height h _u Height from jib axis to upper chord h _d Height from lower chord to jib axis Z Width from jib axis to lower chord

Claims (2)

a load detector for measuring a load;
a jib angle detector for measuring the inclination angle of the jib;
A rated load curve for the working radius of the jib is set, the working radius of the jib is obtained based on the tilt angle measured by the jib angle detector, the rated load is obtained from the rated load curve based on the working radius, and the load is detected. An overload prevention device that determines the actual load of the suspended load acting on the crane based on the load measured by the instrument, and outputs a crane operation stop signal when the actual load is determined to exceed the rated load. A crane overload protection system comprising:
An overload protection system for a crane in which the load detector is mounted on the top of the guy support and built into the shaft of the sheave around which the hoisting wire rope is wound. 2. The overload protection system for a crane according to claim 1 , wherein the sheave at the top of said guy support is arranged such that the pay-out angle and retraction angle of said hoisting wire rope are constant.

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