JPH10194679A - Tower crane safety equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damage of a crane structure due to overwinding of a rope by properly setting rope tension in compliance with an attitude of a tower boom or a jib in a safety device for a tower crane. SOLUTION: An angle of a tower boom 2 and an angle of a jib 3 are detected by means of a tower angle detector 21 and a jib angle detector 22, and on the basis of the detection results, a set tension serving as reference for derricking ropes 7, 12 is set. The detection results by means of derricking rope tension detectors 23, 24 are compared with the set tension, and then, an alarm is given or an engine is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device for a tower crane having a tower boom and a jib.

[0002]

2. Description of the Related Art In order to avoid damage to a structure caused by excessive winding of a tower hoisting winch, a jib hoisting winch or a hoisting winch, for example, Japanese Patent Application Laid-Open No. 7-215679.
In the official gazette, the rope tension is detected as a safety device of the tower crane, and the rope tension is compared with a preset turbulence generation limit tension or breakage limit tension, and when the rope tension reaches the limit tension, There is disclosed an apparatus that stops a winch to prevent the occurrence of rope turbulence and damage to a tower attachment.

[0003]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 7-215 is disclosed.
In the safety device for a tower crane described in Japanese Patent Application Laid-Open No. 679, the operation of hoisting and unwinding the rope is stopped by comparing a uniquely determined tension limit value with a rope tension detected by a rope tension detector. Is what you do. However, the work with the crane includes a preparation work at a preparation stage before the work and a cargo handling work for hanging the load, and the working posture of the crane greatly differs depending on the work content. And
Because the crane damage target area and the damage limit tension vary depending on the working posture, the safety device for a tower crane described in the above-mentioned Japanese Patent Application Laid-Open No. 7-215679 is not applicable to working postures other than a specific posture. Difficult,
It is necessary to take measures such as releasing the safety device according to the working posture.

SUMMARY OF THE INVENTION It is an object of the present invention to detect various postures of a tower boom, a jib or the like at the time of elevating operation, set a proper rope tension in accordance with the posture, and carry out a work. It is an object of the present invention to provide a safety device for a tower crane that can automatically prevent damage to a structure due to excessive winding.

[0005]

FIG. 1 shows an embodiment of the present invention.
Explaining in association with (1) to (2), the invention according to claim 1 is:
Tower fronts 2 and 3 each including a main body 1, a tower boom 2 movably mounted on the main body 1, and a jib 3 movably mounted on the tip of the tower boom 2.
And posture detecting means 21 and 22 for detecting the posture of the tower fronts 2 and 3, which are applied to a safety device of a tower crane having winch devices 4 and 13 for raising and lowering the tower fronts 2 and 3. Calculating means 60 for calculating the set rope tension required for the ropes 7 and 12 in the winch devices 4 and 13 based on the attitude of the tower fronts 2 and 3 detected by the towers 21 and 22, and detecting the tension of the ropes 7 and 12 The above object is further provided by further comprising rope tension detecting means 23 and 24 for obtaining a detected rope tension by performing a comparison and a comparison output means 60 for comparing the set rope tension with the detected rope tension and outputting a comparison signal based on the comparison result. To achieve.

According to a second aspect of the present invention, the comparison output means 60 comprises:
When the detected rope tension is larger than the set rope tension, a comparison signal is output. The third aspect of the present invention provides the comparison output means 6
Further, a stop means 60 for stopping the operation of the winch devices 4 and 13 based on the comparison result by 0 is further provided. Claim 4
The invention further comprises an alarming means 62 for issuing an alarm based on the comparison result by the comparison output means 60. In the invention according to claim 5, the set rope tension is a value which is smaller than the damage limit value of the tower front and capable of crane work.

In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments of the present invention are used to make the present invention easy to understand. However, the present invention is not limited to this.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a configuration of a tower crane provided with a safety device according to an embodiment of the present invention. As shown in FIG. 1, the tower crane includes a crane main body 1, a tower boom 2 rotatably supported by the crane main body 1, and a jib 3 rotatably supported by the tip of the tower boom 2. Consists of In the present embodiment, the tower boom 2 and the jib 3 together form a tower front. The crane body 1 is equipped with a tower boom hoisting winch drum 4 and a tower boom 2
A first pendant rope 5 is connected to the end of the first pendant rope 5, and the other end of the first pendant rope 5 is attached to the first bridle device 6. The tower hoisting rope 7 is wound around the tower boom hoisting winch drum 4, and the tower hoisting rope 7 is wound around the first bridle device 6 and the A-frame hanger device 6A a plurality of times. The tower boom 2 is raised and lowered by driving the tower boom hoisting winch drum 4.

A swing lever 8 is rotatably supported at the tip of the tower boom 2. One apex angle of the swing lever 8 is connected to the tip of the jib 3 via a second pendant rope 9, and one end of a third pendant rope 10 is attached to the other apex angle. The other end of the third pendant rope 10 is connected to the second bridle device 11. The jib hoisting rope 12 is wound around a jib hoisting winch drum 13 mounted on the crane body 1,
It is looped a plurality of times between the second bridle device 11 and the hanger device 11A. The swing lever 8 is rotated clockwise and counterclockwise by the jib hoisting winch drum 13 to move the jib 3 up and down.

A guide roller 2a protrudes from the rear side of the distal end of the tower boom 2. The swing lever 8 is shown in FIG.
The third pendant rope 10 approaches the tower boom 2 by rotating more than a certain angle in the clockwise direction from the state of FIG.
Pendant rope 10 contacts the guide roller 2a. When the third pendant rope 10 is extended and retracted in this state, the guide roller 2a rotates to support the third pendant rope 10.

A hook 14 is hung from the end of the jib 3, and the hook 14 moves up and down due to the extension and retraction of the rope 14a at a main winch (not shown) mounted on the main body. A back stop 15 protrudes from the rear surface of the jib 3. The back stop 15 projects from a backing plate (not shown) at the tip of the tower boom 2 so that the jib 3 does not move backward beyond a predetermined angle. Limit elevation. A backstop 17 is interposed between the rear surface of the tower boom 2 and the crane main body 1 to prevent the tower boom 2 from moving backward beyond a predetermined angle. The tower boom 2 has a jib 3 which is turned (downward) clockwise in FIG.
Is attached to the tower boom 2.

The tower boom 2 is provided with a tower angle detector 21 for detecting the angle of the tower boom 2, and the jib 3 is provided with a jib angle detector 22 for detecting the angle of the jib 3. The tower angle detector 21 and the jib angle detector 22 generally include an elevation angle of the tower boom 2 with respect to a reference angle when the tower boom 2 is horizontal (0 degree) (tower angle: θt). And the elevation angle of the jib 3 (jib angle: θj) are detected. In the present embodiment, for the sake of explanation, the tower angle θt is determined by setting the horizontal to the reference angle (0
Degrees), and the jib angle θj is a relative angle with respect to the tower boom 2.

In the vicinity of the tower boom hoisting winch drum 4, a tower hoisting rope tension detector 23 for detecting the tension (Tt) of the tower hoisting rope 7 is provided. In the vicinity of the jib hoisting winch drum 13, a jib hoisting rope 12 is provided. Tension (T
A jib hoisting rope tension detector 24 for detecting j) is attached.

FIG. 2 is a hydraulic circuit diagram of the tower crane safety device according to the present embodiment. As shown in FIG. 2, the hydraulic motor 31 and the hydraulic pump 32 are connected by a pipe via a direction control valve 33, a counter balance valve 35, and a crossover load relief valve 36, and the hydraulic pump 3
The oil discharged from tank 2 rotates hydraulic motor 31
It is discharged to 7. The hydraulic motor 40 and the hydraulic pump 3
2 are connected by a pipe via a direction control valve 41, a counter balance valve 43, and an overload relief valve 44, and oil discharged from the hydraulic pump 32 is supplied to the hydraulic motor 40.
Is discharged to the tank 44.

The tower boom hoisting winch drum 4 is connected to a drive shaft of a hydraulic motor 31.
With the rotation of, the raising and lowering of the tower hoisting rope 7 is performed. In addition, the above-mentioned jib hoisting winch drum 1
Reference numeral 3 is connected to the drive shaft of the hydraulic motor 40, and the jib hoisting rope 12 is extended and retracted with the rotation of the hydraulic motor 40.

The directional control valve 33 includes an operating pilot valve 5.
1 and the hydraulic pump 50 via the solenoid valves 52 and 53, and the directional control valve 33 is operated by operating the operation pilot valve 51. The direction control valve 41 is connected to the hydraulic pump 50 via an operation pilot valve 54 and solenoid valves 55 and 56, and the direction control valve 41 is operated by operating the operation pilot valve 54. Here, the solenoid valves 52, 5
3, 55 and 56 are normally switched to the position b shown in FIG. 2, and are switched to the position a when excited.

FIG. 3 is a control circuit diagram of the crane safety device according to the present embodiment. As shown in FIG. 3, a tower angle detector 21, a jib angle detector 22, a tower hoisting rope tension detector 23, and a jib hoisting rope tension detector 24 are connected to a control device 60. The above-described solenoid valves 52, 53, 55, and 56 are also connected to the control device 60. Further, the control device 60 includes an engine stop relay 61 for stopping the crane engine, an alarm device 6.
2. A hook winding up / down stop solenoid valve 63 for stopping the hoisting and lowering of the hook 14 and an indicator 64 for lighting an abnormal tension described later are connected.

FIG. 4 is a block diagram showing a detailed configuration of the control device shown in FIG. As shown in FIG.
Reference numeral 0 denotes an A / D converter 70, a CPU 71, a memory 72, and a D / A converter 73, and the above-described tower angle detector 21, jib angle detector 22, tower up / down rope tension detector 23, and jib up / down rope tension. The signal from the detector 24 is input to the CPU 71 via the A / D converter 70. Further, the CPU 70 receiving the signal makes the D / A converter 73
The control signal is selectively input to the above-described solenoid valves 52, 53, 55, 56, the engine stop relay 61, the alarm device 62, the hook winding up / down stop solenoid valve 63, and the indicator 64. Control these operations.

The memory 72 stores the values of the tower angle θt and the jib angle θj, that is, the tension of the tower hoisting rope 7 and the jib hoisting rope 1 corresponding to the attitude of the tower front.
2, the tower boom length Lt and the jib length Lj input before the work (for example, input from the boom length of the moment limiter and the jib length setting button), and the tower angle θt.
And control signal data under each condition of the jib angle θj.

The CPU 71 gives the tower angle θt and the jib angle θ
When j, the tower hoisting rope tension Tt and the jib hoisting rope tension Tj are input via the A / D converter 70, the set tension corresponding to the tower angle θt and the jib angle θj is read from the memory 72. In the CPU 71, the read set tension is compared with the tower hoisting rope tension Tt and the jib hoisting rope tension Tj, and control signal data corresponding to the comparison result is read from the memory 72.
Then, based on the control signal data, the D / A converter 7
3 to output a control signal.

Here, the control signal data includes the detected tower hoisting rope tension Tt and the jib hoisting rope tension T
When j is larger than the set tension, it is data for determining which winch automatically stops and what kind of alarm is issued according to the condition at that time.
Is stored as a table as shown in FIG.
In FIG. 5, the current status of the tower front and the status of the control performed according to the result of the comparison of the tension are indicated by a circle.

Next, examples of set tension based on the tower angle θt and the jib angle θj detected by the tower angle detector 21 and the jib angle detector 22 are shown in FIGS.
This will be described with reference to FIG. The posture shown in FIG.
8 shows a state in which the tower boom 2 is fixed to the tower boom 2 and lands on the ground, for example, a posture before work. In this posture, the tower angle detector 21 and the jib angle detector 22 respectively have the tower angle θt = 0 degree and the jib angle θj =
0 degrees is detected. That is, when the tower angle θt and the jib angle θj are both 0 degrees, the jib 3 is held by the tower boom 2 and connected by the connecting device 18 to land the tower boom 2 on the ground.

When the jib hoisting rope 12 is wound by the jib hoisting winch drum 13 in this position, a compressive force is generated on the guide roller 2a by the tension of the pendant rope 10, so that when the jib hoisting rope 12 is wound up too much, the guide roller 2a It may be damaged. Therefore, the set tension of the jib hoist rope 12 in this posture is set to a value that does not damage the guide roller 2a.

In the attitude shown in FIG. 7, the tower angle detector 21 and the jib angle detector 22 each have a tower angle θt = 3.
0 degrees and jib angle θj = 0 degrees are detected. This state is a state in which the jib 3 is connected to the tower boom 2 by the connecting device 18 and the tower boom 2 is raised. FIG.
, The tower angle detector 21 and the jib angle detector 22 respectively have the tower angle θt = 60 degrees and the jib angle θ
j = 0 degrees is detected. In this state, the jib 3 is connected to the tower boom 2 by the connecting device 18 and the tower boom 2
Is further caused from the state of FIG.

In the posture shown in FIGS. 7 and 8, when raising the tower boom 2, in order to prevent the slack of the jib hoisting rope 12 accompanying the hoisting of the tower boom 2, the jib hoisting of the tower hoisting rope 7 is performed simultaneously. It is necessary to wind the undulating rope 12. At this time, since the guide roller 2a may be damaged if the jib hoisting rope 12 is excessively wound as described above, the set tension of the jib hoisting rope 12 may cause the guide roller 2a to break even in the posture shown in FIGS. Value that does not occur.

In the attitude shown in FIG. 9, the tower angle detector 21 and the jib angle detector 22 respectively have a tower angle θt = 9.
0 degrees and jib angle θj = 0 degrees are detected. This state is a state in which the jib 3 is connected to the tower boom 2 by the connecting device 18 and the tower boom 2 stands upright. Note that, in the present embodiment, the tower angle θt is set to 90 degrees for the sake of explanation. However, the angle is actually slightly smaller than that in consideration of safety.

When the jib hoisting rope 12 is wound up to the working posture in which the jib 3 is raised from the state shown in FIG. 9, if the connection device 18 is forgotten to be removed, the tension of the jib hoisting rope 12 increases, and as described above. The guide roller 2a may be damaged. For this reason, the set tension of the jib hoisting rope 12 in the case shown in FIG. 9 is set to a value that does not damage the guide roller 2a. In this case, if the tower hoisting rope 7 is excessively wound, the tower boom 2
There is a possibility that the pack stop 17 or the mounting portion for preventing the rearward tilting may be damaged. In this case, the set tension of the tower hoisting rope 7 is set to a value that does not damage the backstop 17 and its mounting portion.

In the posture of FIG. 10, the tower angle detector 21
And the jib angle detector 22 respectively have a tower angle θt =
90 degrees and jib angle θj = 45 degrees, the tower angle θt = 90 degrees and jib angle 110 degrees in the posture of FIG. 11, and the tower angle θt = 90 degrees and jib angle θj in the posture of FIG.
= 150 degrees. These states are:
The posture until the connecting device 18 is released and the tower front is brought into a predetermined working state is shown. In this state,
If the jib hoisting rope 12 is excessively wound up beyond the posture of FIG. 12, the back stop 15 abuts against a backing plate (not shown) at the tip of the tower boom 2 to prevent the jib 3 from rising. Further, the jeep hoisting rope 12 is wound up, and the jib 3
When the force for tilting the back stop acts, the backstop 15 may be damaged. For this reason, FIGS.
In the posture of 2, the set tension of the jib hoisting rope 12 is set to a value at which the jib hoisting operation is possible and the back stop 15 is not damaged.

Similarly, in the case of carrying out the lifting work including the raising and lowering of the tower boom 2 like luffing, the set tension of the tower raising and lowering rope 7 and the jib raising and lowering rope 12 is a tension that allows the tower boom raising and lowering work. The value is set so that the backstop 17 is not damaged.

Here, the tension that allows the jib to be undulated and luffable and prevents breakage of the backstops 15 and 17 is a known rated load based on the load of the suspended load and the working radius provided in advance on the crane. This is a tension when the values in the table are satisfied and a value that can prevent breakage of the backstop. That is, as shown in FIGS. 13 and 14, the tension at which the tower front is broken is constant,
The rope tension required for the operation varies depending on the tower angle θt and the jib angle θj. Therefore, it is necessary to set the tension of the tower hoisting rope 7 and the jib hoisting rope 12 to a value larger than the tension required for the work and smaller than the tension at which the tower front is damaged.

FIG. 13 shows that the tower hoisting rope tension does not depend on the jib angle, and decreases as the tower angle increases and increases as the tower angle decreases. FIG.
Indicates that the jib hoisting rope tension is smaller as the jib angle is larger and larger as the jib angle is smaller, and is smaller as the tower angle is smaller and smaller as the tower angle is larger. These data of FIGS. 13 and 14 are stored in the memory 72 in advance. Note that these set tensions described above are applied to the guide roller 2a, the pack stop 15,
This value is determined by design in consideration of the strength of No. 17 and the like.

Next, the operation of this embodiment will be described. FIG. 15 is a flowchart showing the operation of the present embodiment. First, in step S1, the tower angle detector 2
1 and the output signal of the jib angle detector 22 (tower angle θ
t, jib angle θj) and tower undulation rope tension detector 2
3 and the output signals of the jib hoisting rope tension detector 24 (tower hoisting rope tension Tt, jib hoisting rope tension Tj) are read into the CPU 71. In the next step S2, the length Lt of the tower boom and the length Lj of the jib previously stored in the memory 72 are read into the CPU 71 before the work. Then, in step S3, based on the information obtained in steps S1 and S2, the set tension of the tower hoisting rope 7 and the jib hoisting rope 12 set as shown in FIGS. Read.

In the next step S4, step S
The setting tension read in step 3 is compared with the tower hoisting rope tension Tt and the jib hoisting rope tension Tj read in step S1. Then, when the tower hoisting rope tension Tt and the jib hoisting rope tension Tj are smaller than the set tensions, the process ends. If the tower hoisting rope tension Tt or the jib hoisting rope tension Tj is larger than the set tension, the process proceeds to step S5, and step S5 is performed.
In step 5, based on the comparison result in step S4, the control signal data is read from the memory 72 with reference to the table shown in FIG. Then, in step S6, the memory 7
The control signal is output using the control signal data read from the control signal 2. Then, in step S7, it is determined whether or not the work has been completed. If step S7 is negative, the process returns to step S1 and repeats the processing of steps S1 to S7. On the other hand, if step S7 is affirmed, the process ends.

As described above, since the processing of steps S1 to S7 is repeated until the work is completed, the processing is performed following the change in the attitude of the tower front based on the tower angle θt and the jib angle θj.

Then, the control signal output in step S6 corresponds to the above-described solenoid valves 52, 53, 55, 56,
The signals are selectively input to an engine stop relay 61, an alarm device 62, a hook winding up / down stop electromagnetic valve 63, and an indicator 64 to control the operation thereof.

For example, according to the table shown in FIG. 5, when the tower hoisting rope tension Tt is larger than the set tension during the operation, a control signal is output from the CPU 71 to the solenoid valve 52, and the solenoid valve 52 is moved to the position b. To the a position. Thereby, the supply of the pressure oil from the pump 50 to the pilot port of the direction control valve 33 is shut off, and the direction control valve 33 is switched to the neutral position. As a result, the supply of pressure oil from the pump 32 to the hydraulic motor 31 is shut off, the hydraulic motor 31 stops, and the tower boom hoist winch drum 4 stops. Therefore, the raising operation of the tower boom 2 stops. In addition, the CPU 71
, A control signal is input to the engine stop relay 61, the indicator 64, and the alarm device 62, the engine is stopped, the indicator 64 flashes, and an alarm is issued.

When the jib hoisting rope tension Tj is larger than the set tension during the raising of the tower,
A control signal is input from the CPU 71 to the solenoid valves 53 and 55, and the solenoid valves 53 and 55 are switched from the position b to the position a, whereby the operations of the hydraulic motor 31 and the hydraulic motor 40 are stopped. Accordingly, the tower boom hoisting winch drum 4 and the jib hoisting winch drum 13 stop, and the lowering operation of the tower boom 2 and the raising operation of the jib stop. At the same time, a control signal is input from the CPU 71 to the alarm device 62, the hook winding up / down stopping electromagnetic valve 63, and the indicator 64 to issue an alarm, the indicator 64 flashes, and the hook winding operation is stopped. In addition, in raising the tower, the tower hoisting rope may be loosened, and if the tower is tilted down while the jib hoisting rope is left as it is, undesired tension is generated in the jib hoisting rope, so the above-described control is performed. .

As described above, in the present embodiment, the tensions of the tower hoisting rope 7 and the jib hoisting rope 12 are set according to the attitude of the tower front, and the set tension and the actual rope tensions Tt, Tj are determined. In order to stop the movement of the rope or to perform operations such as stopping the engine or issuing an alarm, the limit value for stopping the hoisting and lowering of the rope is set on the tower front. It can be determined appropriately according to the posture. Therefore, it is possible to prevent damage to the structure due to excessive winding of the rope while maintaining the necessary tension according to the attitude of the tower front.

In this embodiment, existing devices such as the tower angle detector 21, the jib angle detector 22, the tower hoisting rope tension detector 23, and the jib hoisting rope tension detector 24 are used. Therefore, no special device is required, the configuration of the device can be simplified, and the reliability against failure can be increased.

In the above embodiment, a table as shown in FIG. 5 is stored in the memory 72, and the control signal data is set based on this table. Remember only data such as
The tower angle θt and the jib angle θj may be sequentially detected, and the set tension may be sequentially calculated based on the data stored in the memory 72. In the above embodiment,
As shown in FIG. 2, the solenoid valves 52 to 56 are switched from the position b to the position a by a signal from the CPU 71. However, a signal is always output to the solenoid valves 52 to 56, and the rope tension is larger than the set tension. CPU 71 is configured to shut off the signal when the
Is supplied to the pilot ports of the directional control valves 33 and 41 in the excited state, and is supplied from the pump 50 to the pilot ports of the directional control valves 33 and 41 in the non-excited state. You may comprise so that supply of oil may be interrupted.

[0041]

As described above in detail, according to the present invention, the set rope tension required for the rope of the winch device is calculated in accordance with the attitude of the tower front, and this set rope tension and the actually detected rope tension are detected. Compare the detected rope tension, based on the comparison result, stop the hoisting winch device,
Alternatively, since an operation such as stopping the engine or issuing an alarm is performed, the limit value for stopping the hoisting and lowering of the rope can be appropriately determined according to the attitude of the tower front. Therefore, it is possible to prevent damage to the structure due to excessive winding of the rope while maintaining the necessary rope tension according to the attitude of the tower front.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration of a tower crane provided with a tower crane safety device according to the present invention.

FIG. 2 is a hydraulic circuit diagram of the tower crane safety device according to the present embodiment.

FIG. 3 is a control circuit diagram of the tower crane safety device according to the present embodiment.

FIG. 4 is a block diagram showing a configuration of a control device.

FIG. 5 is a diagram showing a table of control signal data;

FIG. 6 is a state explanatory view illustrating the attitude of the tower front of the tower crane safety device according to the present embodiment.

FIG. 7 is an explanatory diagram illustrating a posture of a tower front of the tower crane safety device according to the present embodiment.

FIG. 8 is a state explanatory view illustrating the attitude of the tower front of the tower crane safety device according to the present embodiment.

FIG. 9 is a state explanatory view illustrating the attitude of the tower front of the tower crane safety device according to the present embodiment.

FIG. 10 is an explanatory diagram illustrating a posture of a tower front of the tower crane safety device according to the present embodiment.

FIG. 11 is a state explanatory view illustrating the attitude of the tower front of the tower crane safety device according to the present embodiment.

FIG. 12 is a state explanatory view illustrating the attitude of the tower front of the tower crane safety device according to the present embodiment.

FIG. 13 is a graph showing the relationship between tower angle and tower hoisting rope tension.

FIG. 14 is a graph showing the relationship between the jib angle and the jib hoisting rope tension.

FIG. 15 is a flowchart illustrating processing performed in the present embodiment;

[Explanation of symbols]

 2 Tower boom 3 Jib 21 Tower angle detector 22 Jib angle detector 23 Tower hoisting rope tension detector 24 Jib hoisting rope tension detector 60 Control device 61 Engine stop relay 62 Alarm device 63 Solenoid valve for hook winding up / down stop 64 Indicator

Claims (5)

[Claims] A winch device for raising and lowering the tower front by a rope; a tower front including a main body, a tower boom mounted on the main body so as to be able to move up and down, and a jib mounted to be movable up and down at the tip of the tower boom. A safety device for a tower crane, comprising: a posture detecting means for detecting a posture of the tower front; and a setting required for a rope in the winch device based on the posture of the tower front detected by the posture detecting means. Setting means for setting the rope tension; rope tension detecting means for detecting the rope tension to obtain a detected rope tension; comparing the set rope tension with the detected rope tension;
A safety device for a tower crane, further comprising a comparison output means for outputting a comparison signal based on the comparison result. 2. The tower crane safety device according to claim 1, wherein said comparison output means outputs said comparison signal when said detected rope tension is larger than said set rope tension. 3. The tower crane safety device according to claim 1, further comprising stopping means for stopping the operation of the winch device based on a comparison result by the comparison output means. 4. The tower crane safety device according to claim 1, further comprising an alarm unit for issuing an alarm based on a comparison result by the comparison output unit. 5. The safety device for a tower crane according to claim 1, wherein the set rope tension is a value that allows the crane to operate and is smaller than a damage limit value of a tower front.