JP2000296992A - Safety device of tower crane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of excessive tension in a jib hoisting rope by simple structure. SOLUTION: A load detector is provided in a connection device connecting a boom 2 and a jib 3 to detect the connection force (tensile force S) between the boom 2 and jib 3. Since this tensile force S has a specified correlation with the tension T of a jib hoisting rope 13, when rope tension T increases, tensile force S also increases. Then, when tensile force S reaches a specified predetermined value S0 (corresponding to the allowable limit value T0 of rope tension T), a control signal 1 is output to the solenoid of a solenoid valve to stop the hoisting drive of a jib hoisting winch 12 and the lowering drive of a boom hoisting winch 4. Through these operations, the generation of excessive force in the jib hoisting rope 13 is prevented.

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 A tower crane is provided with a jib that can be folded at the tip of a tower boom. When the tower is turned over after the crane operation is completed, a boom hoist rope is first wound up by a boom hoist winch. With the boom upright, lower the jib hoisting rope with the jib hoisting winch, fold the jib forward and fold it to the front of the boom, and secure the folded jib to the boom with the coupling device. After that, the boom hoisting rope is wound down by the boom hoisting winch, and the boom integrated with the jib is turned over to the front of the aircraft. At this time, since the jib hoisting rope is tensioned with the lowering of the boom hoisting rope, the jib hoisting rope is wound down by the jib hoisting winch simultaneously with the lowering of the boom hoisting rope. When the tower is turned upside down, the boom hoisting rope is wound up by the boom hoisting winch to bring the tower boom integrated with the jib into the upright state.
At this time, the jib hoisting rope is in a relaxed state as the boom hoisting rope is hoisted, so that the jib hoisting rope is hoisted by the jib hoisting winch simultaneously with the hoisting of the boom hoisting rope.

In the above-mentioned operation, if the lowering speed of the jib hoisting winch is lower than the lowering speed of the boom hoisting winch when the tower is turned down, or the hoisting speed of the jib hoisting winch is increased when the tower erects. If the speed is higher than the speed, the tension of the jib hoisting rope becomes excessive, and there is a possibility that the support member (for example, a guide roller) of the rope and the coupling device may be damaged. A tower crane provided with a safety device for avoiding such a problem is disclosed, for example, in Japanese Utility Model Laid-Open No. 6-35288. In the safety device described in this publication, when the tension of the jib hoisting rope detected by the tension detector reaches a preset limit tension, the hoisting and lowering of the winch is stopped, and thereby, the jib hoisting rope This prevents excessive tension.

[0004]

By the way, the tension of the jib hoisting rope in the ordinary crane work is considerably larger than the tension of the jib hoisting rope in the tower hoisting work (setup work) (for example, about 10 times). Therefore, when detecting the tension of the jib hoisting rope as in the apparatus described in the above-mentioned publication, a large-capacity (large-load) tension detector is required in accordance with ordinary crane work. However, if the tension detector has a large capacity, it is difficult not only to accurately detect the rope tension at the time of raising and lowering the tower, but also the device becomes large and difficult to handle, and the cost increases.

It is an object of the present invention to provide a safety device for a tower crane which can prevent the generation of excessive tension of a jib hoisting rope with a simple configuration without detecting the tension of the jib hoisting rope. .

[0006]

Means for Solving the Problems (1) Referring to FIGS. 1 to 7 showing one embodiment, the invention according to claim 1 is characterized in that a tower boom 2 which rises and falls by raising and lowering a boom raising and lowering rope 5 is provided. , A jib 3 that rises and falls when the jib hoisting rope 13 is raised and lowered. The load detecting means 24, 25, 41, 44 has a correlation with the tension of the jib hoisting rope 13 and detects an abnormal load which is a load that damages the structures 9, 20.
And stopping means 39, 40 for stopping at least the hoisting operation of the jib hoisting rope 13 and the lowering operation of the boom hoisting rope 5 when an abnormal load is detected by the load detecting means 24, 25, 41, 44. Thereby, the above-mentioned object is achieved. (2) As shown in FIGS. 1, 8 to 10, the tower boom 2 which rises and lowers by raising and lowering the boom hoisting rope 5 and the jib hoisting rope 13 raises and lowers the tip of the tower boom 2 as shown in FIGS. The present invention is applied to a safety device for a tower crane having a jib 3 that rises and falls in response to the movement of a swinging swing lever 7 that rotates. Then, the connection detecting means 26 for detecting the connection between the tower boom 2 and the jib 3 and an abnormality which has a correlation with the tension of the jib hoisting rope 13 and is a rotation amount of the swing lever 7 which damages the structures 9 and 20. The connection between the tower boom 2 and the jib 3 is detected by the rotation amount detection means 47 for detecting the rotation amount and the connection detection means 7, and
When the abnormal rotation amount of the swing lever 9 is detected by the rotation amount detecting means 47, at least the hoisting of the jib hoisting rope 13 and the stopping means 39, 40 for stopping the falling of the boom hoisting rope 5 are provided. The objectives achieved are achieved.

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. First Embodiment FIGS. 1 and 2 are side views showing a configuration of a tower crane provided with a safety device according to an embodiment of the present invention. FIG. FIG. 2 shows a crane operation state after the tower stands. As shown in FIGS. 1 and 2, the tower crane includes a crane body 1, a tower boom 2 that is rotatably supported by the crane body 1, and a rotatable shaft that is rotatably supported by the tip of the tower boom 2. Jib 3 In FIG. 1, the jib 3 is fixed to the front side of the tower boom 2 by a connecting device 20, and both are integrally raised and lowered in the A or B direction.

The crane body 1 is equipped with a boom hoisting winch drum 4.
The first boom connected to the tip of the tower boom 2 by winding or unwinding the boom hoisting rope 5 wound around
The tower boom 2 is raised and lowered via the pendant rope 6. A swing lever 7 is rotatably supported at the tip 2 a of the tower boom 2. This swing lever 7
Of the jib 3 through the second pendant rope 8
At the other apex via a guide roller 9 provided on the back side of the tower boom tip 2a.
One end of the pendant rope 10 is attached.
The other end of the third pendant rope 10 is the bridle device 1
It is attached to 1. The crane main body 1 is equipped with a jib hoisting winch 12.
The jib hoisting rope 13 wound around the bridle device 11
The swing lever 7 is rotated via the third pendant rope 10 by winding or paying out the jib hoisting rope 13, and the jib 3 is raised and lowered. As shown in FIG. 2, a hoisting winch 14 is further mounted on the crane main body 1. The hoisting rope 15 wound around the hoisting winch 14 is taken up or extended to suspend it from the end of the jib 3. The hook 16 is moved up and down.

When the tower boom 2 and the jib 3 fixed by the connecting device 20 as shown in FIG. 1 are to be erected in the direction A, the boom hoisting rope 5 and the jib hoisting rope 13 are simultaneously wound. In this case, if the winding speed of the jib hoisting rope 13 is too high compared to the winding speed of the boom hoisting rope 5, the swing lever 7 rotates in the direction A about the tip 2a as a fulcrum. 2. Excessive tension acts on the third pendant ropes 8,10. On the other hand, when the tower boom 2 and the jib 3 are turned in the B direction, the boom hoisting rope 5 is fed out and the jib hoisting rope 13 is also fed out. In this case, the jib hoisting rope 1
3 is too slow as compared with the feeding speed of the boom hoisting rope 5, the swing lever 7 rotates in the direction A around the tip 2a as described above, so that the jib hoisting rope 13 and the second, Third pendant rope 8,1
Excessive tension acts on zero. When an excessive tension Tmax acts on the jib hoisting rope 11 and the second and third pendant ropes 8 and 10 as described above, an excessive load (abnormal load) is applied to parts such as the guide roller 2a and the connecting device 20 which are rope supporting parts. ) Acts, and a part (the weakest part) of those parts may be damaged. In order to avoid the damage, in the present embodiment, the jib hoisting rope 13 is
Is kept within a predetermined value T0 (for example, Tmax × 0.9, which is called an allowable limit tension).

Hereinafter, the features of the first embodiment will be described. FIG. 3 is an enlarged view of a part a of FIG. 1 showing a connection state between the tower boom 2 and the jib 3. As shown in FIG. 3, the connecting device 20 includes a hook 22 rotatably connected to the boom 2 via a pin 21 and a holder 23 fixed to the jib 3 at a position corresponding to the hook 22. Holder 2
3 is a base portion 23a protruding toward the boom 2,
A pipe portion 23b abutting on the base portion 23a in the width direction of the jib 3 (perpendicular to the paper surface), and the boom 2 and the jib 3 are connected by hooking the hook 22 to the pipe portion 23b as shown in the figure. Is done. A load detector 24 such as a load cell is stored in the base portion 23a, and a tensile force S from the hook 22 acting on the base portion 23a by the load detector 24.
Is detected. This tensile force S has a predetermined correlation with the tension T of the jib hoisting rope 13. The tensile force S also increases as the rope tension T increases, and when the rope tension T reaches the allowable limit tension T0, the tensile force S is increased. Becomes S0.

FIG. 4 is a hydraulic circuit diagram for a winch of a tower crane equipped with the safety device according to the first embodiment. As shown in FIG. 4, the winch hydraulic circuit includes a main pump 31, a hydraulic motor 32 for driving a boom hoisting winch and a hydraulic motor 33 for driving a jib hoisting winch, each of which rotates by pressurized oil supplied from the main pump 31. Control valves 34 and 35 for controlling the flow of pressure oil from the main pump 31 to the hydraulic motors 32 and 33, respectively;
Operation levers 36 and 37 operated to drive these control valves 34 and 35, respectively, and operation levers 36 and 37
The pilot chamber 34 of the control valves 34, 35 according to the operation amount of
Pilot valves 36a, 36b, 37a, 37b for controlling pilot pressure supplied to a, 34b, 35a, 35b
A hydraulic pump 38 for supplying pressure oil to the pilot valves 36a, 36b, 37a, 37b, and an electromagnetic valve provided between the pilot valve 36a corresponding to the lowering operation of the boom 2 and the pilot chamber 34a of the control valve 34 And a solenoid valve 40 provided between the pilot valve 37b corresponding to the hoisting operation of the jib 3 and the pilot chamber 35b of the control valve 35. The solenoid valves 39 and 40 are switched by an electric signal I from the control device 25.

The controller 25 receives the detected value S from the load detector 24, and the controller 25 detects the detected value S.
And a tensile force S0 corresponding to a preset allowable limit tension T0 are determined. If it is determined that S> S0, the controller 25 outputs an electric signal I to the solenoids 39s and 40s of the solenoid valves 39 and 40, and the solenoids 39s and 40s are excited. by this,
The solenoid valves 39 and 40 are respectively switched to the position (a), and the supply of pressure oil from the hydraulic pump 38 to the pilot chambers 34a and 35b of the control valves 34 and 35 is prohibited. on the other hand,
When it is determined that S ≦ S0, the output of the electric signal I to the solenoids 39s and 40s of the solenoid valves 39 and 40 is stopped, and the solenoids 39s and 40s are demagnetized. As a result, the solenoid valves 39 and 40 are switched to the positions (b), respectively, and the supply of pressure oil from the hydraulic pump 38 to the pilot chambers 34a and 35b of the control valves 34 and 35 is permitted.

Next, the operation of the safety device according to the first embodiment will be specifically described. When erecting the tower crane in the inverted state, first, the tower boom 2 and the jib 3
Are connected integrally by the connecting device 20. Next, the boom raising / lowering operation lever 36 and the jib raising / lowering operation lever 37
At the same time, the pilot valves 36b and 37b are driven in accordance with the operation amount, and the pilot pressure oil from the hydraulic pump 38 is supplied to the pilot chamber 34 of the control valves 34 and 35.
b, 35b. As a result, the control valves 34 and 35 are switched to the position (b), respectively, and the pressurized oil from the main pump 31 is supplied to the hoisting motors 32 and 33 via the control valves 34 and 35, respectively. And jib 3 are operating levers 36 and 37, respectively.
It is erected at a speed corresponding to the operation amount of.

Here, when the operation amount of the jib hoisting operation lever 37 becomes larger than the operation amount of the boom hoisting operation lever 36, and the winding speed of the jib hoisting rope 13 becomes faster than the winding speed of the boom hoisting rope 5, The jib hoisting rope 13 is tensioned, and a tensile force S acts on the connecting device 20. When the tensile force S exceeds a predetermined value S0 (corresponding to the allowable limit tension To), an electric signal I is output to the solenoids 39s and 40s of the respective solenoid valves 39 and 40 as described above, and the solenoid valves 39 and 40 Each is switched to the position (a). As a result, the supply of the pilot pressure to the pilot chamber 35b of the control valve 35 is stopped, the control valve 35 is switched to the neutral position, the rising operation of the jib 3 is stopped, and the control valve 35 is supplied to the pilot chamber 34a. The supply of the pilot pressure is blocked, and the inversion operation of the boom 2 is prohibited. That is, in this state, only the raising operation of the boom 2 and the inversion operation of the jib 3, which are operations for reducing the tension T of the jib hoisting rope 13, can be performed. At this time, when the boom raising / lowering operation lever 36 is hoisted, the tension T of the jib raising / lowering rope 13 decreases with the rising operation of the boom 2,
The tensile force S acting on the connecting device 20 gradually decreases. When the pulling force S becomes equal to or less than the predetermined value S0, the output of the electric signal I to the solenoids 39s and 40s of the respective solenoid valves 39 and 40 is stopped as described above, and the solenoid valves 39 and 40 are respectively positioned (b). Is switched to. Thereby, the supply of the pilot pressure to the pilot chamber 35b of the control valve 35 is permitted, the control valve 35 is switched to the position (b) side, and the jib 3 is raised again.

As described above, the tower boom 2 and the jib 3 are integrally erected, and when the angle of the boom 2 (the angle between the boom 2 and the ground) reaches a predetermined angle (for example, 88 °), the operating lever for raising and lowering the boom. 36 and the operating lever 37 for raising and lowering the jib are returned to the neutral position, and the control valves 34 and 35 are switched to the neutral position to switch the boom raising winch 4 and the jib raising winch 1.
2 are stopped. In this state, the connecting device 2
0, and then the hoisting operation of the jib hoisting operation lever 37 causes the control valve 35 to move to the position (b) according to the operation amount.
Side, and the jib hoisting winch 12 is driven to hoist. As a result, as shown in FIG. 2, the jib 3 is raised upward while being separated from the tower boom 2, and the setup work is completed.

On the other hand, when the tower boom 2 in the upright state is turned over, first, the jib 3 is turned forward by the lowering operation of the jib raising / lowering operation lever 37, and thereafter the boom 2 and the jib 3 are connected. The connection is made by the device 20. Next, when the operation lever 36 for raising and lowering the boom and the operation lever 37 for raising and lowering the jib are simultaneously lowered, the pilot valves 36a and 37a are driven in accordance with the operation amounts, and the pilot pressure oil from the hydraulic pump 38 is supplied to the control valves 34 and 37. 35 pilot rooms 34
a, 35a. Thereby, the control valves 34 and 35 are switched to the position (a) side, and the pressurized oil from the main pump 31 is supplied to the hoisting motors 32 and 33 via the control valves 34 and 35, respectively. The jib 3 inverts at a speed corresponding to the operation amounts of the operation levers 36 and 37, respectively.

Here, when the operation amount of the operation lever 36 for raising and lowering the boom becomes larger than the operation amount 37 of the operation lever for raising and lowering the jib, and the feeding speed of the boom raising and lowering rope 5 becomes faster than the feeding speed of the jib raising and lowering rope 13, the jib raising and lowering is performed. The rope 13 is tensioned, and a tensile force S acts on the connecting device 20. When the tensile force S exceeds a predetermined value S0 (corresponding to the allowable limit tension T0), the solenoid valves 39 and 40 are operated in the same manner as described above.
Are switched to the position (a). As a result, the supply of the pilot pressure to the pilot chamber 34a of the control valve 34 is stopped, the control valve 34 is switched to the neutral position, the inversion operation of the boom 2 is stopped, and the control valve 35 is moved to the pilot chamber 35b of the control valve 35. Supply of the pilot pressure is inhibited, and the jib standing-up operation is prohibited. That is, in this state, only the falling operation of the jib 3 and the rising operation of the boom 2, which are operations for reducing the tension of the jib hoisting rope 13, can be performed. At this time, if the jib hoisting operation lever 37 is turned over, the jib hoisting rope 1
3, the tensile force S acting on the coupling device 20 gradually decreases. When the pulling force S becomes equal to or less than the predetermined value S0, the solenoid valves 39 and 40 are respectively switched to the positions (a) and supply of the pilot pressure to the pilot chamber 34a of the control valve 34 is permitted, as described above. Thereby, the control valve 34 is switched to the position (a), and the boom 2 is turned over again. When the tower boom 2 is completely turned down, the operation levers 36, 37 are returned to the neutral position to stop the driving of the winches 4, 12, and the setup operation is completed.

As described above, according to the first embodiment, the load detector 24 is provided in the connecting device 20 for connecting the tower boom 2 and the jib 3, and the detected value S exceeds the preset set value S0. In this case, the tension T of the jib hoisting rope 13 is determined to be excessive, and the hoisting drive of the jib hoisting winch 12 and the lowering drive of the boom hoisting winch 4 are stopped, so that it is not necessary to detect the rope tension. With a simple configuration, the tension T of the jib hoisting rope 13 can be suppressed to the allowable limit value T0 or less, and the guide roller 20 and the connecting device 2
Damage to components such as 0 can be prevented. In this case, since the load detector 24 is dedicated to the setup work, it may be of a small capacity, and the accuracy in determining that the tension T of the jib hoisting rope has exceeded the allowable limit value T0 is improved.

-Second Embodiment- Next, a second embodiment of the present invention will be described. In the second embodiment, the tension T of the jib hoisting rope 13 is set to an allowable limit value T0 based on the load acting on the guide roller 9.
Try to keep it below. 5 is an enlarged view of a portion b in FIG. 1, and FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5, showing the configuration of the base end of the guide roller 9. 5 and 6, the same portions as those in FIG. 1 are denoted by the same reference numerals, and the differences will be mainly described below. As shown in FIGS. 5 and 6, a mounting seat 9 a is fixed to the base end of the guide roller 9 supported from the back side of the tower boom 2, and a retractable plate is provided between the mounting seat 9 a and the boom 2. A plurality of (12) springs 41 are stacked and stored. The guide roller 9 and the boom 2 are fastened via bolts 42 and nuts 43 with the disc spring 41 extended, and a gap cl is provided between the base end surface of the guide roller 9 and the boom 2. The disc spring 41 can be contracted within the range of the gap cl. Also, the mounting seat 9
The limit switch 44 is mounted on the side surface of the b.
Are protruding. The limit switch 44 is off (non-contact) in the initial state, and is turned on when it comes into contact with the projection member 45 due to the contraction of the disc spring 41.

The contraction amount L of the disc spring 41 and the jib undulation rope 1
3 has a predetermined correlation with the tension T of the jib hoisting rope 13. When the tension T of the jib hoisting rope 13 increases, the compressive force acting on the guide roller 9a increases and the contraction amount L of the disc spring 41 increases. When the rope tension T reaches the allowable limit tension T0, the contraction amount L becomes L0. Therefore, in the initial state (the state of the rope tension T = 0), the limit switch 44 is installed at a predetermined distance L0 from the protrusion 45, and the rope tension T = T0.
Turns on the limit switch 44. by this,
It is possible to determine whether the tension T of the jib hoist rope 13 is within the allowable limit value T0 by turning on / off the limit switch 44. The number and shape of the disc springs 44 to be stacked are appropriately changed according to a desired contraction amount L0 of the disc springs 44.

FIG. 7 is a hydraulic circuit diagram of a tower crane equipped with a safety device according to the second embodiment. The same parts as those in FIG. 4 are denoted by the same reference numerals, and the differences will be mainly described below. As shown in FIG. 7, in the second embodiment, the solenoids 39s,
40s is connected to a power supply 46 via a limit switch 44. As described above, the limit switch 44 is turned on when the tension T of the jib hoisting rope 13 reaches the allowable limit tension T0, whereby the solenoids 39s, 40s of the solenoid valves 39, 40 are excited, and the solenoid valves 39, 40 The position is switched to (a). When the solenoid valves 39 and 40 are switched to the position (a), the supply of the pressure oil to the pilot chambers 34a and 35b of the control valves 34 and 35 is prohibited, and the inversion operation of the boom 2 and the standing operation of the jib 3 are stopped. Is done.
Further, from this state, the boom 2 is raised or the jib 3 is turned over, and the tension T of the jib hoisting rope 13 is reduced to the allowable limit value T0.
When it becomes below, the limit switch 44 is turned off, and the solenoids 39s and 40s of the solenoid valves 39 and 40 are demagnetized.
As a result, the solenoid valves 39 and 40 are switched to the position (b), and the inversion operation of the boom 2 and the erect operation of the jib 3 are enabled again.

As described above, in the second embodiment, the disc spring 41 and the limit switch 44 are provided at the base end of the guide roller 9.
When the compressive force S0 corresponding to the allowable limit tension T0 of the jib hoisting rope 13 acts on the disc spring 41, the limit switch 44 is turned on to excite the solenoids 39s and 40s of the solenoid valves 39 and 40, and the jib hoisting Winch drum 4
Is stopped, and the lowering drive of the boom hoisting winch drum 12 is stopped. Therefore, the control device 25 and the like are unnecessary, and the configuration is further simplified. Further, the guide roller 9 is separated from the jib hoisting rope 13 during the crane operation (see FIG. 2), so that excessive tension does not act on the guide roller 13, so it is not necessary to increase the compressive strength of the disc spring 41. Absent.

Third Embodiment Next, a third embodiment of the present invention will be described. In the third embodiment, the jib hoisting rope 13 is determined based on the connection state of the connection device 20 and the amount of rotation of the swing lever 7.
Is kept below the allowable limit value T0. FIG. 8 is an enlarged view of a part a of FIG. 1 and FIG. 9 is an enlarged view of a b part of FIG. 8 and 9, the same portions as those in FIGS. 1 and 3 are denoted by the same reference numerals, and the differences will be mainly described below. As shown in FIG. 8, a limit switch 26 is provided on the base 23 a of the holder 23 of the connecting device 20, and a projection 22 a is provided on the tip of the hook 21 corresponding to the limit switch 26.
When the hook 21 is locked to the pipe portion 23b of the holder 23 (in a connected state) and the projection 22a contacts the limit switch 26, the limit switch 26 is turned on, and the hook 2
1 is disconnected from the pipe portion 23b (unconnected state), and when the protrusion 22a is separated from the limit switch 26, the limit switch 26 is turned off.

As shown in FIG. 9, a limit switch 47 is fixed to a bracket 2a at the end of the boom 2 which rotatably supports the swing lever 7. The tip of the limit switch 47 is set at a predetermined distance from the swing lever 7 in the initial state (solid line), and the limit switch 47 is turned off in this state. The rotation amount θ of the swing lever 7 and the tension T of the jib hoisting rope 13 have a predetermined correlation. When the tension T of the jib hoisting rope 13 increases, the counterclockwise direction of the swing lever 7 (arrow direction) ) Also increases. For example, when the tension T of the jib hoisting rope 13 reaches the allowable limit tension T0, the rotation amount becomes θ0, and when the tension T of the jib hoisting rope 13 further increases (Tmax described above), the rotation amount θ of the swing lever 7 becomes excessive (abnormal). (Rotation amount) Parts such as the guide roller 2a and the coupling device 20 may be damaged. Therefore, in the present embodiment, the limit switch 47 is installed at a position corresponding to the rotation amount θ0 of the swing lever 7, and the limit switch 47 is turned on when the rope tension T = T0. The tip 47a of the limit switch 47 is formed of a bendable spring, and when the swing lever 7 is rotated during a crane operation, for example, as shown by a dotted line, the tip 47a is also bent.

FIG. 10 is a hydraulic circuit diagram of a tower crane equipped with a safety device according to the third embodiment. The same parts as those in FIG. 4 are denoted by the same reference numerals, and the differences will be mainly described below. As shown in FIG.
In the embodiment, the solenoids 39 of the solenoid valves 39 and 40 are used.
s and 40 s are power supplies 4 via limit switches 26 and 47.
6 is connected. When the hook 22 is locked by the pipe portion 23b of the holder 23 and the swing lever 7 rotates by an amount corresponding to the allowable limit tension T0 of the jib hoisting rope 13, both the limit switches 26 and 47 are turned on, thereby the electromagnetic valves 39 and The 40 solenoids 39s, 40s are excited, and the solenoid valves 39, 40 are switched to the position (a). When the solenoid valves 39, 40 are switched to the position (a), the supply of the pressure oil to the pilot chambers 34a, 35a of the control valves 34, 35 is prohibited, and the inversion operation of the boom 2 and the standing operation of the jib 3 are stopped. Is done. In this state, the boom 2 is raised or the jib 3 is turned over, and when the tension T of the jib hoisting rope 13 falls below the allowable limit value T0, the limit switch 47 is turned off and the solenoids 39s of the solenoid valves 39 and 40 are turned off.
40 s is demagnetized. Also, when the hook 22 is removed from the pipe portion 23b of the holder 23 by a normal crane operation or the like, the limit switch 26 is turned off and the solenoid valve 3 is turned off.
The 9, 40 solenoids 39s, 40s are demagnetized. As a result, the solenoid valves 39 and 40 are switched to the position (B), and the boom 2 can be turned over and the jib 3 can be raised.

As described above, in the third embodiment, the limit switch 2 is connected to the connecting device 20 and the end of the boom 2 respectively.
The limit switches 26 and 47 are turned on when the boom 2 and the jib 3 are connected, and the swing lever 7 is rotated by the allowable limit tension T0 of the jib hoisting rope 13 (θ0). Thus, the solenoids 39s and 40s of the solenoid valves 39 and 40 are excited to stop the hoisting drive of the jib hoisting winch 12 and the lowering drive of the boom hoisting winch 4. As a result, the change in the angle of the swing lever 7 during the setup operation becomes less than the predetermined value θ0, and the boom 2
The tower can be raised and lowered in a stable state without increasing the change in the attitude of the jib 3 with respect to.

In the above embodiment, the connecting device 20
And the load acting on the guide roller 9 or the amount of rotation of the swing lever 7 is the allowable limit tension T of the jib hoisting rope 13.
The hoisting of the jib hoisting winch 12 and the lowering drive of the boom hoisting winch 4 are stopped when it reaches 0, but it acts on other places having a correlation with the tension T of the jib hoisting rope 13. Load and displacement (angle change, etc.)
The lifting drive of the jib hoisting winch 12 and the lowering drive of the boom hoisting winch 4 may be stopped based on the above. In addition, not only the hoisting of the jib hoisting winch 12 and the lowering of the boom hoisting winch 4 but also the driving of the winches 4 and 12 may be stopped. In this case, the drive stop of the winches 4 and 12 may be released by operating a release switch or the like.

In the correspondence between the above-described embodiment and the claims, the load detector 24, the control device 25, the disc spring 41 and the limit switch 44 serve as load detecting means, the limit switch 26 serves as connection detecting means, and the limit switch 47 serves as a limit detecting means. Constitute the rotation amount detecting means, and the solenoid valves 39 and 40 constitute the stopping means.

[0030]

As described above in detail, according to the first aspect of the present invention, when an abnormal load which has a correlation with the tension of the jib hoisting rope and damages the structure is detected, According to the second aspect of the present invention, when the tower boom and the jib are connected to each other, the tower boom and the jib have a correlation with the tension of the jib hoisting rope and detect an abnormal rotation amount that is a rotation amount of the swing lever that damages the structure. At least, the jib hoisting rope hoisting operation and the boom hoisting rope hoisting operation are stopped.Therefore, without detecting the jib hoisting rope tension, the excessive tension of the jib hoisting rope can be achieved with a simple configuration. Can be prevented from occurring.

[Brief description of the drawings]

FIG. 1 is a side view showing a setup operation state of a tower crane equipped with a safety device according to an embodiment of the present invention.

FIG. 2 is a side view showing a crane working state of the tower crane equipped with the safety device according to the embodiment of the present invention.

FIG. 3 is an enlarged view (a part enlarged view of FIG. 1) of the connecting device constituting the safety device according to the first embodiment of the present invention.

FIG. 4 is a hydraulic circuit diagram of the tower crane safety device according to the first embodiment of the present invention.

FIG. 5 is an enlarged view of a base end portion of a guide roller constituting a safety device according to a second embodiment of the present invention (an enlarged view of a portion b in FIG. 1).

FIG. 6 is a sectional view taken along line VI-VI of FIG. 5;

FIG. 7 is a hydraulic circuit diagram of a tower crane safety device according to a second embodiment of the present invention.

FIG. 8 is an enlarged view (an enlarged view of a part of FIG. 1) of a connecting device constituting a safety device according to a third embodiment of the present invention.

FIG. 9 is an enlarged view (b part enlarged view of FIG. 1) of a boom tip constituting a safety device according to a third embodiment of the present invention.

FIG. 10 is a hydraulic circuit diagram of a tower crane safety device according to a third embodiment of the present invention.

[Explanation of symbols]

 2 Tower boom 3 Jib 5 Boom hoisting rope 7 Guide roller 9 Swing lever 13 Jib hoisting rope 20 Connecting device 24 Load detector 25 Control device 39,40 Solenoid valve 41 Disc spring 26,44,47 Limit switch

Continued on the front page (72) Inventor Yuki Ijiri 650, Kandachi-cho, Tsuchiura-shi, Ibaraki F-term in Tsuchiura Plant of Hitachi Construction Machinery Co., Ltd. (Reference) 3F204 AA04 BA02 CA05 FB04 FB14 FB18 FC08 FD02 FD09 3F205 AA07 BA01 CA02 CA04 DA01 HA06 HC01

Claims (2)

[Claims] 1. A safety device for a tower crane having a tower boom raised and lowered by hoisting and lowering a boom hoisting rope and a jib raised and lowered by hoisting and lowering a jib hoisting rope, wherein the safety device has a correlation with the tension of the jib hoisting rope. A load detection unit that detects an abnormal load that is a load that damages a structure, and when the abnormal load is detected by the load detection unit,
A safety device for a tower crane, comprising: stopping means for stopping at least the hoisting operation of the jib hoisting rope and the lowering operation of the boom hoisting rope. 2. A tower crane having a tower boom raised and lowered by raising and lowering a boom raising and lowering rope, and a jib raising and lowering in response to a movement of a swing lever pivoted at a tip end of the tower boom by raising and lowering a jib raising and lowering rope. In the safety device, a connection detecting unit that detects a connection between the tower boom and the jib, and an abnormal rotation amount that has a correlation with a tension of the jib hoisting rope and is a rotation amount of the swing lever that damages a structure. Rotation amount detection means for detecting the connection of the tower boom and the jib by the connection detection means, and at least the abnormal rotation amount of the swing lever is detected by the rotation amount detection means, Stopping means for stopping the winding of the jib hoisting rope and the inversion of the boom hoisting rope, Safety device that tower crane.