JPH0971391A - Safety device of tower crane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grasp stop timing of a tower jib by overwinding regardless of a position of a tower boom. SOLUTION: A tower boom angle detector 21 to detect a ground angle θb of a tower boom, a tower jib angle detector 22 to detect a ground angle θj of a tower jib, a relative angle computing element part 211 to compute a relative angle θr in accordance with the angles θb, θj detected by both of the detectors 21, 22 and a comparison operating part 213 to compare the computed relative angle θr and an alarm working angle θw output from a memory 212 with each other are provided. The alarm working angle θw is set larger than the relative angle at the time when the tower jib is automatically stopped by overwinding. A specified alarm signal is output from the comparison operating part 213 to an alarm 25 at the time when the relative angle θr is smaller than the alarm working angle θw, and an alarm is generated.

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 for preventing a tower jib from being raised too much.

[0002]

2. Description of the Related Art A type of safety device for tower cranes is called a jib overwinding prevention device. This device prevents the tower jib from being overraised due to overwinding of the tower jib up and down winch.The limit switch attached to the tower boom detects that the tower jib has been raised to a predetermined limit position, and responds to this. The solenoid valve provided in the hydraulic circuit of the crane is switched to the neutral position to cut off the supply of pressure oil to the drive motor of the winch for raising and lowering the jib. In the case where such a device is provided, if the overwinding prevention device operates while the tower jib is operating at a normal working speed, the tower jib suddenly stops and the shock causes the shake of the load. Therefore, the crane operator checks beforehand the ground angle of the tower jib (the angle of the tower jib with respect to the horizontal plane) when the jib overwinding prevention device operates, and the ground angle of the tower jib displayed on the driver's seat indicator is overwound. The tower jib was operated so that the hoisting speed of the winch would be reduced and a stop shock would not occur when the angle of the protective device approached was approached.

[0003]

In recent years, as a mode of use of a tower crane, an example in which a tower boom is undulated during work is increasing for the purpose of improving operability and expanding a work range. In the above-described jib overwinding prevention device, the limit switch attached to the tower boom detects the limit position of the tower jib in the upright direction, so that the jib overwinding prevention device is activated when the attitude of the tower boom changes. The ground angle of the tower jib at that time also changes. For this reason,
If the posture of the tower boom is changed during work, it is not possible to determine at what stage the jib over-winding prevention device will operate only by the angle of the tower jib displayed on the display, and the tower jib will be unnecessarily slowed down. Operation to deteriorate work efficiency,
Sometimes the jib overwinding prevention device was activated earlier than expected, causing a shake.

An object of the present invention is to provide a safety device for automatically stopping a tower jib when it is raised too much.
The objective is to be able to accurately know the stop timing of the tower jib regardless of the posture of the tower boom.

[0005]

1 to 3 showing an embodiment of the present invention, the invention of claim 1 relates to a relative angle θr of a tower jib 5 to a tower boom 2.
Reaches the limit value θs in the standing direction of the tower jib 5,
It is applied to a safety device for a tower crane that outputs a stop signal for the standing motion of the tower jib 5. Then, relative angle detecting means 21, 22, 211 for detecting the relative angle θr,
The difference (θr−θs) between the relative angle θr detected by the relative angle detecting means 21, 22, 211 and the limit value θs is a predetermined threshold value (θ).
The alarm signal output means 213 which outputs an alarm signal when it decreases within w−θs) achieves the above-mentioned object. 2 to 4, the invention of claim 2 is applied to the safety device for a tower crane according to claim 1, and the angular velocity detecting means 2 for detecting the angular velocity ωj of the tower jib 5 is used.
2, 215 and the threshold value (θw−θs) based on the detection results of the angular velocity detecting means 22, 215 so that the threshold value (θw−θs) becomes larger when the angular velocity ωj of the tower jib 5 is larger than when the angular velocity ωj is small. ) Changing threshold value changing means 216. Referring to FIG. 2, FIG. 3 and FIG. 6, the invention of claim 3 is the tower boom 2
It is applied to a safety device of a tower crane that outputs a stop signal for the standing operation of the tower jib 5 when the relative angle θr of the tower jib 5 to the limit value θs in the standing direction of the tower jib 5 reaches. Then, the relative angle detecting means 21, 22, 211 for detecting the relative angle θr, and the relative angle detecting means 21,
The display means 26 for displaying the relative angle θr detected at 22 and 211 is provided to achieve the above-mentioned object. Figure 1
Referring to FIG. 3 and FIG. 6, the invention of claim 4 is applied to the safety device of the tower crane of claim 1 or 3, and detects the angle θb of the tower boom 2 with respect to a specific reference plane HP. Based on the boom angle detection means 21, the jib angle detection means 22 for detecting the angle θj of the tower jib 5 with respect to the specific reference plane HP, and the detection results of the boom angle detection means 21 and the jib angle detection means 22, the relative angle θr is calculated. The relative angle detecting means includes a calculating means 211 for calculating. The invention according to claim 5 is applied to the safety device for a tower crane according to claim 4, wherein the boom angle detecting means 21 and the jib angle detecting means 22 are the overload preventing devices 21, 22 for the tower crane,
It is also used as an information input means in 200. Explaining with reference to FIG. 2, FIG. 3 and FIG. 9, the invention of claim 6 is such that when the relative angle θr of the tower jib 5 to the tower boom 2 reaches a limit value θs in the standing direction of the tower jib 5, It is applied to a safety device of a tower crane that outputs a stop signal for standing motion. The boom angle detecting means 21 for detecting the angle θb of the tower boom 2 with respect to the specific reference plane HP, the jib angle detecting means 22 for detecting the angle θj of the tower jib 5 with respect to the specific reference plane HP, and the relative angle θr are limited. Jib angle detection means 2 when the value is θs
The angle θjs to be detected at 2 is the boom angle detecting means 21.
And a jib angle display means 27 for displaying the angle θjs specified by the specifying means 218 and the angle θj detected by the jib angle detecting means 22, respectively. To achieve the above-mentioned object.

According to the first aspect of the invention, the difference (θr-θs) between the relative angle θr and the limit value θs accompanying the standing motion of the tower jib 5
When is decreased to within a threshold value (θw−θs), the alarm signal output means 213 outputs an alarm signal. If this alarm signal is given to the alarm device 25 to generate an alarm by sound or the like, the operator can be surely aware that the limit value θs approaches, in other words, the timing at which the tower jib 5 automatically stops approaches. You can In the invention of claim 2, the higher the angular velocity ωj when the deceleration operation of the tower jib 5 is started in response to the alarm from the alarm device 25 or the like, the greater the movement amount of the tower jib 5 until the actual speed is sufficiently reduced. On the other hand, when the angular velocity ωj of the tower jib 5 is large, the warning signal is issued earlier than when it is small. Therefore,
There is no danger that the alarm will be delayed during high-speed work (when the angular velocity ωj is large) that requires an early deceleration operation, and automatic stop will not work before the tower jib 5 slows down sufficiently. It does not happen that the deceleration operation of the tower jib 5 is unnecessarily prolonged after the start of. In the third aspect of the invention, the relative angle θr detected by the relative angle detection means 21, 22, 211 is displayed on the display means 26. Since the limit value θs of the relative angle is constant regardless of the posture of the tower boom 2,
If this value is known to the operator beforehand, the limit value θs
The stop timing of the tower jib 5 can be accurately grasped from the comparison between the relative angle θr displayed on the display means 26. In the invention of claim 4, the angle θb detected by the boom angle detection means 21 and the angle θj detected by the jib angle detection means 22.
From, the relative angle θr is calculated. In the invention of claim 5, the angles θb and θj detected by the boom angle detection means 21 and the jib angle detection means 22 are also used as input information of the overload prevention device, and the overload is detected from these detected angles θb and θj. A physical quantity required for the determination, for example, the working radius of the tower crane is calculated. In the invention of claim 6, the stop timing of the tower jib 5 can be accurately grasped by comparing the two angles θj and θjs displayed by the jib angle display means 27.

Incidentally, in the section of means and action for solving the above-mentioned problems for explaining the constitution of the present invention, the drawings of the embodiments of the present invention are used for making the present invention easy to understand. Is not limited to the embodiment.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to FIGS. 1 to 11, parts common to each other are designated by the same reference numerals.

-Embodiment of First Invention- An embodiment of the first invention will be described with reference to FIGS. FIG. 2 shows a schematic structure of a tower crane according to an embodiment of the invention. 1 is a crane main body having a lower traveling structure and an upper revolving structure, and 2 is a tower connected to the crane main body 1 so as to be able to move up and down. The boom 3 is a boom hoisting rope attached to the upper end of the tower boom 2, 4 is a boom hoisting winch that winds and unwinds the boom hoisting rope 3 to elevate the tower boom 2, and 5 is the upper end of the tower boom 2. A tower jib movably connected, 6 is a jib hoisting rope for hoisting the tower jib 5, and 7 is a swing lever. The swing lever 7 is roughly configured by combining three members in a triangular shape. One of the three vertices is rotatably connected to the upper end of the tower boom 2, and the other two vertices are the jib undulating rope 6 and the jib pendant. Rope 8
Are connected to each. The upper end of the jib pendant rope 8 is connected to the upper end of the tower jib 5. 9 is a jib hoisting winch that winds and unwinds the jib hoisting rope 6 to hoist the tower jib 5, 10 is a hook for hanging, 11 is a hoisting rope for the hook 10, and 12 is hoisting and unwinding for the hoisting rope 11. It is a winding winch that goes up and down to raise and lower the hook 10.

Reference numeral 20A is a control device for performing data processing required for overload prevention and the like. In the embodiment of the present invention, a tower boom angle detector 21, a tower jib angle detector 22, a load detector 23, and a jib overwinding detection switch 24 are provided as means for inputting information to the control device 20A. The values detected by these information input means will be described with reference to FIG. 3. The tower boom angle detector 21 detects an angle (hereinafter, referred to as a boom angle) θb of the tower boom 2 with respect to the horizontal plane HP to detect a tower jib angle. Bowl 22
Detects the angle (hereinafter referred to as the jib angle) θj of the tower jib 5 with respect to the horizontal plane HP. The jib overwinding detection switch 24 uses a limit switch that is turned on / off according to the displacement of a movable part such as a plunger, and is attached to the upper end of the tower boom 2. Relative angle between tower boom 2 and tower jib 5 (extended line L of tower jib 2
The angle between 2 and the tower jib 5) θr is a predetermined limit angle θs
Then, the movable part (not shown) of the jib overwinding detection switch 24 is pushed by the tower jib 5, and a predetermined ON signal is output from the jib overwinding detection switch 24. The positions of the tower jib 5 at the limit angle θs and the alarm operating angle θw described later are indicated by imaginary lines Ps and Pw in the figure, respectively. The load detector 23 detects the tension of the jib pendant rope 8 as a physical quantity related to the actual load of the suspended load of the hook 10.

Next, the control device 20A will be described with reference to FIG. The control device 20A has an overload prevention unit 200 and a jib overwinding prevention unit 210A. The overload prevention unit 200 prevents lifting of a load heavier than the limit load (maximum load that can be lifted by the hook 10). The boom angle θb detected by the two angle detectors 21 and 22 and the jib Based on the working angle calculator 201 that calculates the working radius of the crane from the angle θj and the known length of the tower boom 2 and the known length of the tower jib 5, and a table in which the working radius and the limit load created in advance are associated with each other. And the limit load calculation unit 202 that calculates the limit load corresponding to the current working radius
And an actual load calculator 20 that calculates the actual load acting on the hook 10 based on the rope tension detected by the load detector 23.
3 is compared with the limit load and the actual load calculated by both the calculation units 202 and 203, and a comparison calculation unit 20 that outputs a predetermined automatic stop signal when the actual load exceeds the limit load
And 4. When the automatic stop signal is output from the comparison calculation unit 204, the supply of pressure oil to various actuators that perform the lifting operation of the crane is blocked, and the lifting operation becomes impossible. For example, winches 4, 9, and 1 in FIG.
The control valve provided in the drive circuit of the hydraulic motor (not shown) that is the drive source of No. 2 is constrained to the neutral position by the automatic stop signal so that the hydraulic oil is confined in each hydraulic motor, thereby lifting the overload. Be blocked. There are various methods for determining whether or not there is an overload, but the present invention can be applied as long as the boom angle θb and the jib angle θj are used as input information.

On the other hand, the jib overwinding preventing portion 210A is for preventing the tower jib 5 from being raised too much due to overwinding of the jib undulating winch 9, and from the boom angle θb and the jib angle θj detected by the angle detectors 21 and 22, Relative angle of both θr
(= Θb−θj, see FIG. 3) Relative angle calculator 21
1, a memory 212 for storing the alarm operating angle θw, a relative angle θr calculated by the relative angle calculation unit 211, and a memory 2
Comparison calculation unit 21 for comparing the alarm operating angle θw from 12
And 3. As shown in FIG. 3, the alarm operating angle θw is set to be larger than the limit angle θs, that is, the relative angle θr when the limit switch 24 is turned on. For example, when the limit angle θs is 15 °, the alarm operating angle θw is set to about 17 ° to 20 °. The comparison calculation unit 213 outputs a predetermined alarm signal to the alarm device 25 when the relative angle θr calculated by the relative angle calculation unit 211 is equal to or smaller than the alarm operating angle θw,
In response to this, the alarm device 25 issues a predetermined alarm to the crane operator. The alarm device 25 is provided near the driver's seat of the crane. As the alarm device 25, an alarm device that emits an alarm sound or lights or blinks an alarm light, or a device that appeals to hearing and sight may be appropriately selected. An input means for writing an arbitrary alarm operating angle θw in the memory 212 may be provided.

Further, the jib overwinding prevention section 210A is provided with a stop signal output section 214 for outputting a tower jib automatic stop signal in response to the output of the ON signal from the jib overwinding detection switch 24. . By the output of the tower jib automatic stop signal, the operation of the jib up and down winch 9 in the winding direction is automatically stopped. In order to stop the winch 9, for example, a control valve that controls the supply of pressure oil to a drive motor (not shown) of the winch 9 is restrained in a neutral position, and the supply of pressure oil to the drive motor is blocked and driven. Trap return oil in the return line from the motor.

According to the tower crane constructed as described above, the relative angle θr and the alarm operating angle θw are compared to switch the output and stop of the output of the alarm signal and the alarm operating angle θw.
Is set to be slightly larger than the limit angle θs, the alarm 25 is provided immediately before the jib overwinding detection switch 24 is turned on and the tower jib 5 is automatically stopped regardless of the posture of the tower boom 2. Gives an alarm. Therefore, the operator can accurately grasp the timing at which the tower jib 5 automatically stops, and the speed of the tower jib 5 can be reduced within the required minimum range immediately before the automatic stop works to prevent the shake of the load due to the stop shock.

-Embodiment of Second Invention- An embodiment of the second invention will be described with reference to FIGS. 4 and 5. The overall structure of the tower crane is as shown in FIG. As shown in FIG. 4, in the embodiment of the present invention, the control device 20A of the embodiment of the first invention described above is used as the control device 2.
It is changed to 0B. The jib overwinding prevention unit 210B of the control device 20B includes the jib overwinding prevention unit 210 of FIG.
Instead of the memory 212 of A, an angular velocity calculation unit 215 and a memory 216 are provided. Angular velocity calculation unit 215
Calculates the angular velocity ωj of the tower jib 5 by differentiating the jib angle θj detected by the tower jib angle detector 22. The memory 216 stores in advance a table in which the angular velocity ωj and the alarm operating angle θw are associated with each other according to the diagram of FIG.

From the angular velocity calculation unit 215, the current angular velocity ωj
Is output, the memory 216 outputs the alarm operating angle θw corresponding to the angular velocity ωj. Here, FIG. 5 is an example when the above-mentioned limit angle θs (see FIG. 3) is 15 °, and the alarm operating angle θw increases in the range of 17 ° to 20 ° as the angular velocity ωj increases. With this setting,
When the angular velocity ωj of the tower jib 5 is high, the alarm timing is early, and when the angular velocity ωj is low, the alarm timing is late.

-Embodiment of the Third Invention- An embodiment of the third invention will be described with reference to FIG. The overall structure of the tower crane is as shown in FIG. As shown in FIG. 6, in the embodiment of the present invention, the control device 20A of the embodiment of the first invention described above is changed to a control device 20C. The jib overwinding prevention unit 210C of the control device 20C corresponds to the jib overwinding prevention unit 210A of FIG. 1 from which the memory 212 and the comparison calculation unit 213 are omitted. Then, the relative angle θr calculated by the relative angle calculation unit 211 is directly displayed on the display device 26 by the operator.
The display 26 can be appropriately selected from an analog pointer type and a digital display type. In the crane of FIG. 2, the relative angle θr when the jib overwinding detection switch 24 is turned on (the limit angle θs of FIG. 3)
Is constant regardless of the posture of the tower boom 2, so if the operator is informed of the limit value θs by displaying it in the vicinity of the display unit 26, the operator can see the limit value θs and the relative value displayed on the display unit 26. By comparing the angle θr, the timing of the automatic stop of the tower jib 5 can be grasped, and immediately before that, the deceleration operation similar to the conventional one can be performed to avoid the stop shock of the tower jib 5.

-Embodiment of Fourth Invention- An embodiment of the fourth invention will be described with reference to FIGS. 7 and 8. The overall structure of the tower crane is as shown in FIG. As shown in FIG. 7, in the embodiment of the present invention, the control device 20B shown in FIG. 4 described above is changed to a control device 20D composed of a microcomputer and its peripheral devices. The memory 217 of the control device 20D includes the overload prevention unit 200 and the jib overwinding prevention unit 2 of FIG.
Information necessary for various calculations in 10B is stored. FIG. 8 shows a routine relating to control of the alarm device 25 by the control device 20D. In this process, the boom angle θb and the jib angle θj detected by the angle detectors 21 and 22 are read in step S1, and the relative angle θr (= θb is read in step S2.
−θj) is calculated. In a succeeding step S3, the tower jib 5 is differentiated by differentiating the jib angle θj read in the step S1.
The present angular velocity ωj is calculated, and the alarm operating angle θw corresponding to the calculated angular velocity ωj is specified in step S4. In order to specify the alarm operating angle θw, a table similar to that stored in the memory 216 of FIG. 4 may be written in the memory 217 in advance.

After the alarm operating angle θw is specified, the process proceeds to step S5, and it is determined whether the relative angle θr calculated in step S2 is larger than the alarm operating angle θw. When the relative angle θr is larger than the alarm operating angle θw, the output of the alarm signal to the alarm device 25 is stopped in step S6, and the relative angle θr is changed to the alarm operating angle θw.
In the following cases, the process proceeds to step S7 and an alarm signal is output to the alarm device 25. After that, the process returns to step S1. When the jib overwinding detection switch 24 is turned on during the process of FIG. 8, the standing operation of the tower jib 5 is stopped as an interrupt process. The control related to the overload prevention may be alternately performed with the process shown in FIG. 8 at an appropriate cycle.

-Embodiment of the Fifth Invention- An embodiment of the fifth invention will be described with reference to FIGS. The overall structure of the tower crane is as shown in FIG. As shown in FIG. 9, in the embodiment of the present invention, the controller 20A of the embodiment of the first invention described above is replaced by the controller 20.
It is changed to E. The jib overwinding prevention unit 210 of the control device 20E includes a relative angle computing unit 211, a memory 212 and a comparison computing unit 2 of the jib overwinding prevention unit 210A of FIG.
A memory 218 is provided instead of 13. Memory 2
18, the boom angle θb and the jib overwinding detection switch 2
Jib angle when 4 is turned on (angle θjs in Fig. 3, below,
It is called the limit ground angle. ) Is stored according to the diagram of FIG. Note that FIG. 10 shows an example in which the limit angle θs (see FIG. 3) is 15 °.

From the tower boom angle detector 21 to the memory 2
When the boom angle θb is input to 18, the limit ground angle θjs corresponding to the boom angle θb is output from the memory 218, and the value is input to the display 27. Display 27
The current jib angle θj detected by the tower jib angle detector 22 is also input to, and both angles θj and θjs are simultaneously displayed on the display 27. The display 27 is configured as shown in FIG. 11, for example. This indicator 27 is a scale 27 for displaying an angle.
0 and the jib angle θj detected by the jib angle detector 22.
And a second pointer 272 for displaying the limit ground angle θjs output from the memory 218. According to the above configuration, the operator can calculate the difference between the current jib angle θj displayed on the display 27 and the limit ground angle θjs,
That is, the timing of automatic stop of the tower jib 5 can be grasped from the difference between the first pointer 271 and the second pointer 272, and the stop shock of the tower jib 5 can be prevented by the deceleration operation similar to the conventional one. The display 27 may be a digital display type.

In the embodiment of the invention described above, the tower boom angle detector 21 is boom angle detecting means, the tower jib angle detector 22 is jib angle detecting means, and the relative angle computing section 2 is used.
11 is a calculating means, both angle detectors 21 and 22 and a relative angle calculating section 211 are relative angle detecting means, and a comparison calculating section 213.
Is an alarm signal output means, and the tower boom angle detector 21 and the angular velocity calculation unit 215 are angular velocity detection means.
16 is a threshold value changing means, display 26 is a display means, angle detectors 21 and 22 and an overload prevention unit 200 are an overload prevention device, memory 218 is a specifying means, and display 27 is a jib angle display means. Configure each. The boom angle θb
The relative angle θr may be directly detected by providing an angle detector between the tower boom 2 and the tower jib 5 without being limited to the example of calculating the relative angle θr from the jib angle θj. Overload prevention unit 20
0 may be omitted. The angular velocity of the tower jib 5 is not limited to the example obtained by differentiating the jib angle θj, but may be obtained from a physical quantity related to the angular velocity, for example, the rotational speed of the jib undulating winch 9 or the flow rate of pressure oil to its drive motor. It is also possible to set a plurality of threshold values for outputting an alarm signal and change the alarm to a more urgent one as the threshold value is approached. The boom angle θb and the jib angle θj are not limited to the angles from the horizontal plane HP, and may be angles from the vertical plane or other reference planes. The relative angle may be the opening angle between the tower boom 2 and the tower jib 5 (complementary angle of θr in FIG. 3).

[0023]

As described above, according to the first aspect of the invention, regardless of the posture of the tower boom, the warning signal is output before the tower jib is automatically stopped due to its overraising, so the tower jib is automatically stopped. The operator can always grasp the timing accurately. Therefore, the work can be efficiently performed at the required work speed until just before the automatic stop works, and the speed of the tower jib can be sufficiently reduced immediately before the automatic stop works to reliably avoid the shake of the load due to the stop shock. According to the invention of claim 2, the output timing of the alarm signal can be optimized according to the angular velocity of the tower jib. In the invention of claim 3, the relative angle displayed on the display means can be used to grasp the timing at which the tower jib is automatically stopped, and the work can be performed efficiently at the required work speed until just before the automatic stop works, and immediately before the automatic stop works. The speed of the tower jib can be sufficiently reduced to reliably avoid the shake of the load due to a stop shock. In the invention of claim 4, the relative angle can be obtained from the tower boom angle and the tower jib angle which are commonly used as information input means such as an overload prevention device. Claim 5
According to the invention of claim 1, the safety device according to the invention of claim 1 or 3 can be constructed by utilizing the detection information of the tower boom angle detecting means and the tower jib angle detecting means necessary for specifying the working radius in the overload preventing device of the tower crane. Therefore, the cost can be reduced by reducing the number of constituent parts, and the safety device can be easily added to the existing tower crane. Claim 6
In the invention, since the timing at which the tower jib is automatically stopped can be grasped by comparing the two angles displayed by the jib angle display means, work can be performed efficiently at the required work speed until just before the automatic stop works, and Just before the stop works, the speed of the tower jib can be reduced sufficiently to reliably avoid the shake of the load due to the stop shock.

[Brief description of drawings]

FIG. 1 is a block diagram of a control system in a tower crane according to an embodiment of the first aspect of the present invention.

FIG. 2 is a diagram showing an overall configuration of a tower crane according to an embodiment of the invention.

FIG. 3 is a diagram schematically showing the tower crane of FIG.

FIG. 4 is a block diagram of a control system in the tower crane according to the second embodiment of the present invention.

5 is a diagram showing a correspondence relationship between a jib angle stored in a memory of FIG. 4 and an alarm operating angle.

FIG. 6 is a block diagram of a control system in the tower crane according to the third embodiment of the present invention.

FIG. 7 is a block diagram of a control system in the tower crane according to the fourth embodiment of the present invention.

8 is a flowchart showing a control procedure of an alarm device executed by the control device of FIG.

FIG. 9 is a block diagram of a control system in the tower crane according to the fifth embodiment of the present invention.

10 is a diagram showing a correspondence relationship between a boom angle stored in the memory of FIG. 9 and a limit ground angle of a tower jib.

11 is a diagram showing an example of the display unit of FIG.

[Explanation of symbols]

2 tower boom 5 tower jib 20A, 20B, 20C, 20D, 20E control device 21 tower boom angle detector 22 tower jib angle detector 23 load detector 24 jib overwinding detection switch 200 overwinding prevention part 210A, 210B, 210C, 210E jib Overwinding prevention part θb Boom angle θj Jib angle θr Relative angle between tower boom and tower jib θs Limit of relative angle θw Alarm operating angle

Claims (6)

[Claims] 1. When the relative angle of the tower jib with respect to the tower boom reaches a limit value in the standing direction of the tower jib,
In a safety device for a tower crane that outputs a stop signal for the standing motion of the tower jib, a relative angle detection unit that detects the relative angle, a difference between the relative angle detected by the relative angle detection unit and the limit value is A safety device for a tower crane, comprising: an alarm signal output unit that outputs an alarm signal when the amount of decrease is within a predetermined threshold value. 2. An angular velocity detecting means for detecting an angular velocity of the tower jib, and based on a detection result of the angular velocity detecting means so that the threshold value becomes larger when the angular velocity of the tower jib is larger than when the angular velocity is small. The safety device for a tower crane according to claim 1, further comprising threshold changing means for changing the threshold. 3. A safety device for a tower crane that outputs a stop signal for the standing motion of the tower jib when the relative angle of the tower jib with respect to the tower boom reaches a limit value in the standing direction of the tower jib. A safety device for a tower crane, comprising: angle detection means; and display means for displaying the relative angle detected by the relative angle detection means. 4. Boom angle detecting means for detecting an angle of the tower boom with respect to a specific reference surface, jib angle detecting means for detecting an angle of the tower jib with respect to a specific reference surface, the boom angle detecting means and the jib. 2. The relative angle detecting means includes a calculating means for calculating the relative angle based on a detection result of the angle detecting means.
Or the safety device for a tower crane according to item 3. 5. The tower crane safety device according to claim 4, wherein the boom angle detection means and the jib angle detection means are also used as information input means in the overload prevention device of the tower crane. . 6. When the relative angle of the tower jib with respect to the tower boom reaches a limit value in the standing direction of the tower jib,
In a safety device for a tower crane that outputs a stop signal for standing movement of the tower jib, boom angle detection means for detecting an angle of the tower boom with respect to a specific reference plane, and a jib for detecting an angle of the tower jib with respect to the specific reference plane. An angle detecting means, an specifying means for specifying an angle to be detected by the jib angle detecting means when the relative angle is the limit value, in accordance with a detection result of the boom angle detecting means, and the specifying means. And a jib angle display means for displaying the angle specified by the jib angle detection means and the angle detected by the jib angle detection means, respectively.