JP3258471B2 - Crane or tower crane overload protection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload prevention device for a crane or a tower crane, and more particularly to a crane or a tower crane in which problems during maintenance and inspection work due to an overload prevention function and problems due to means for releasing the overload prevention function are improved. The present invention relates to an overload prevention device for a tower crane.

[0002]

2. Description of the Related Art In a conventional mobile crane, a telescopic boom is mounted on a vehicle body so as to be able to turn and raise and lower, and is turned in a predetermined direction by a turning motor and is raised up to a state where it is almost upright by a raising and lowering cylinder. I have. A trussed jib is attached to the end of the telescopic boom, and a heavy object is lifted and moved via a hanging hook that is lifted and lowered from the jib end. Recently, a mobile crane has been proposed in which a telescopic boom is attached in place of a jib to have a function as a tower crane. In such a crane truck, a first upright standing upright state by an up / down cylinder on a turning base of the vehicle body is provided.
The boom is extended to a desired height, and the second boom attached to the end of the first boom is extended while also being set to a substantially horizontal state by a dedicated up / down cylinder.
Work is performed by lowering the hanging hook hanging from the boom tip to the ground side.

[0003] In a mobile crane having the function of a tower crane, the second boom is extended in a horizontal direction at a high position, so that from the viewpoint of work safety, the lifting load and the falling moment due to this load are reduced. It is important to perform detection to prevent overload. Conventionally, in order to prevent this kind of overload, a load curve determined by the hanging load and the boom working radius is set in advance, and work in the safe work area defined by the load curve is performed while sensing the load and the working radius. The operation is stopped, and the operation exceeding the load curve is automatically stopped. When the automatic stop function is activated, each operating device is in a deadlock state. Therefore, an automatic stop release switch is provided, so that the stop function is released, so that operation can be performed only on the safe side.

[0004]

However, in the conventional overload prevention device, the operation range is determined by a hyperbolic characteristic determined by the relationship between the boom working radius and the load. Unless you can do it. For this reason, it is necessary to extend the undulating cylinder beyond the specified value during inspection and maintenance work that does not perform work, that is, expands and contracts the boom without load, so the limit load characteristic of the conventional overload prevention system However, there is a problem that the work cannot be performed due to the restriction by the judgment system.

In a tower crane operation in which the second boom is leveled or raised and lowered while the first boom is substantially upright, each of the first and second boom raising and lowering cylinders is extended to the stroke end, and the maximum is reached. In the raised state, the internal pressure of the cylinder becomes the relief pressure, and the overload prevention device receives the signal as an overload signal, and the automatic stop function operates, so that the operation in the direction of increasing the working radius of the crane, that is, the first and second operations. The operation of the boom in the prone direction becomes impossible, and the operation of the hoisting boom cannot be performed, which is a so-called deadlock state. Therefore, it was necessary to operate the cylinder by a release switch for releasing the overload prevention device.
In other words, even if the overload state is not reached, when the up-and-down cylinders of the first and second booms extend to the stroke end, a deadlock state occurs each time, and the cylinder must be operated by a release switch. Was very troublesome. Also, when the cylinder is operated again by the release switch, the overload prevention device is not working, so even if it is not overload at the stroke end position, it may be overloaded depending on the operating position of the cylinder, and danger cannot be avoided. was there.

The present invention focuses on the above-mentioned conventional problems, and provides a maintenance and inspection mode separately from the characteristics determined by the limit load curve in the overload prevention device, so that the cylinder can be extended beyond a specified stroke even without load. In order to make the inspection possible, the release switch is abolished to provide a safe system, and to avoid the danger associated with the abolition of the release switch, just before reaching the end of the cylinder stroke (before the pressure increases). It is an object of the present invention to provide a crane overload prevention device that ensures safety by adjusting the cylinder to stop.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, an overload protection device for a crane or a tower crane according to the present invention is first mounted on a base so as to be able to undulate via an undulating cylinder. In a crane or tower crane overload prevention device that stops operation when an overload is applied to a crane with a boom or a tower crane, determined from the hanging load and the maximum allowable working radius corresponding to this hanging load Work mode to determine the load curve to be set, and maintenance inspection mode to determine the load curve determined by the maximum allowable working radius corresponding to the empty load, set the load mode and switchable the mode, each load curve and sensing the suspended load and A configuration is provided with a controller that outputs a work stop by comparing work radii.

[0008]

In the overload protection device for a crane or a tower crane according to the second configuration , an overload acts on a crane or a tower crane provided with a boom that can be raised and lowered on a base via a lifting cylinder. In a crane or tower crane overload prevention device that stops operation in the event of a load, a work mode that determines a load curve determined from the hanging load and the maximum allowable working radius corresponding to this hanging load, and corresponding to an empty load A maintenance inspection mode that determines a load curve determined by the maximum allowable work radius to be set is set, and the mode is switchable so that a work stop output is made by comparing each load curve with a sensed hanging load and a work radius. Enter the stroke of the up-and-down cylinder even within the working area of the mode, and reach the stroke end. That it was configured to include a controller which enables cylinder deactivation previously.

[0010]

According to the above configuration, in addition to the normal operation mode determined by the allowable operation radius and the limit load, a maintenance inspection mode for defining an expanded allowable operation radius when the load is empty can be set and switched. In the load curve area in the maintenance and inspection mode, the boom extension operation can be made larger than in the normal operation mode. Therefore, even in the case where the automatic stop works beyond the limit in the normal operation mode, the extension of the boom is not hindered in the mode, so that the grease application operation can be performed smoothly, for example.

When the operation is performed beyond the limit value defined by the load curve, the overload prevention function is activated and the cylinder is automatically stopped. The cylinder can be deactivated before reaching. For this reason, the boom operation can be performed within the allowable range while the operation is stopped without using the automatic stop release switch mechanism, and the occurrence of a deadlock state of the boom can be prevented.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a crane or tower crane according to the present invention.

FIG. 4 is a side view of the mobile crane 10 provided with the overload prevention device according to the embodiment. Mobile crane 1
Numeral 0 has a vehicle body 12 that can run on wheels, and an outrigger 14 that can extend right and left before and after the vehicle body 12 is provided so that the vehicle body 12 can float and be stably held during crane work. A turning table 16 is provided at the center of the body 12.
The cab 18 and the boom base 20 are attached via
The crane boom means is attached to the boom base 20. The crane boom means includes a first boom 24 mounted on the base 20 so as to be able to be raised and lowered by a lifting cylinder 22, and a first boom 24 mounted on a distal end portion of the first boom 24 so as to be extendable in the horizontal direction. And a second boom 28 which can be raised and lowered by a raising and lowering cylinder 26 provided therebetween. Each of these booms 2
Each of the booms 4 and 28 is a multistage boom having a telescopic structure and can be expanded and contracted by a built-in telescopic cylinder. The first boom 24 functions as a vertical boom that extends to a desired height, and the second boom 28 is substantially horizontal. Acts as a horizontal boom that extends in the direction. Second boom 2
When the number 8 is set to the minimum value, it can be used as a normal crane, and can be used as a tower crane by extending the second boom 28. A main hook 30 is disposed at the distal end of the base boom portion of the second boom 28 for crane function, and an auxiliary hook 32 is disposed at a distal boom portion of the second boom 28 for tower crane function. These are lifted and lowered by a wire 36 drawn out from a winch means 34 mounted on the base side of the first boom 24.

The mobile crane 10 having such a configuration is provided with a controller 38 for stopping the operation for safety when an overload is detected. Due to the arithmetic processing by the controller 38, the up-and-down cylinder (hereinafter referred to as the first cylinder) 2 on the first boom 24 side.
2 is provided with an axle load sensor 40 for detecting the axle load, a boom angle detection sensor 42, and a length sensor 44 for detecting the length of the first boom 24. On the boom 28 side, a second axle load sensor 46 for detecting the axial load of the undulating cylinder (hereinafter, referred to as a second cylinder) 26, a second boom angle detection sensor 48, and a second boom 28 for detecting the length of the second boom 28. Two length sensors 50 are provided. Further, the first and second cylinders 2
Each of the cylinders 2 and 26 is provided with stroke sensors 52 and 54 for detecting the position immediately before the stroke end of the cylinder. The controller 38 inputs detection signals from these sensors, and calculates the suspension load, working radius,
The position before the second cylinders 22 and 26 reach the stroke end is input, and the suspension load is calculated mainly based on the detection signals from the sensors 46, 48 and 50 attached to the second boom 28, and the second load is used as a backup. The suspension load is calculated mainly based on the detection signals from the sensors 40, 42, and 44 attached to one boom 24.

The controller 38 first calculates the hanging load and the working radius. As shown in FIG. 1, the controller 38 inputs a signal from the sensor and sends it to the shaft load / posture / boom length calculator 56. It shall be taken. This calculation unit calculates the shaft load applied to the first boom 24 and the second boom 28, the boom tilt angle, and the working radius determined by each boom length, and is calculated by the first and second shaft load sensors 40 and 46. The axial load, the inclination angle by the first and second boom angle detection sensors 42 and 48, the length sensor 4
The boom length is calculated according to 4, 50.
As the axle load sensors 40 and 46, the undulating cylinders 22 and 26
Or a load cell set at a load point such as a cylinder swing fulcrum or the like, or a structure that detects the hydraulic pressure applied to the cylinder and converts it into a voltage signal can be used. The boom angle detection sensors 42 and 48 may have a structure composed of a combination of a pendulum and a potentiometer, and may have a structure that outputs a boom undulation angle with respect to the horizontal as an electric signal. Further, the boom length sensors 44, 5
Reference numeral 0 denotes a structure in which a drum attached to a predetermined position of the boom and a wire fed from the drum are connected to the tip of the boom, and a structure that detects the rotation amount of the drum that rotates according to the boom expansion and contraction by a potentiometer or the like may be used. The value calculated by the shaft load / posture / boom length calculation unit 56 is output to the correction processing unit 58, where the correction considering the frictional force of the first and second cylinders 22 and 26 and the deflection of the boom are considered. The correction is performed, the working radius and the hanging load calculating unit 62 calculate the working radius and the hanging load based on a predetermined calculation formula, and the result is output.

In the overload prevention device, if the detected load is equal to or larger than the limit load within the work radius based on the work radius and the suspension load as the calculation result, the overload is regarded as overload. Judge and stop the work. For this reason, the load characteristics that define the safe work operation area of the crane truck are determined in advance, compared with the limit load corresponding to the calculation work radius, and a warning is issued according to the proximity to the limit load, and when the load exceeds the limit load. If it does, an automatic stop signal is output. For example, for the stored total rated load calculation formula, boom length, outrigger state,
When the optimum constant is selected and input from the constant table corresponding to the direction of the upper revolving superstructure to the controller 38, and the working radius is input to obtain the rated total load characteristic, a characteristic line as shown in FIG. 5 is obtained. This indicates a so-called hyperbolic characteristic. By determining the rated total load (limit load) Wr from the actual working radius and comparing it with the actual hanging load Wa, it is possible to determine whether or not the work is in a dangerous state. When the suspension load Wa becomes equal to or greater than the limit load Wr, the operation is automatically stopped.

However, since the overload determination processing in such a work mode functions even when there is no suspended load,
In fact, even if you can extend the boom more,
There is a possibility that the boom can not be extended due to the regulation by the characteristic line. Therefore, in this embodiment, a load characteristic for maintenance and inspection is determined in advance in addition to the above-described function based on the characteristic of the hyperbola, and one of the modes is selected as necessary, and the switching is determined according to the use situation. Like that. For this reason, as shown in FIG. 1, the controller 38 includes a work mode setting device 64 that determines load characteristics used during normal work, and a maintenance mode setting device 66 that determines load characteristics during maintenance and inspection. And the operation panel 6 of the cab
The mode to be used is switched by a mode switching switch 70 attached to the switch 8 (see FIG. 4). The comparator 72 determines whether the mode is the work mode or the maintenance / inspection mode by the changeover switch 70, activates one of the setters 64 and 66 on the set mode side, and clears the contents of the existing mode from the memory. The load characteristics of the selected mode are read into the memory. The load characteristics determined by the maintenance / inspection mode setting device 66 are, as in the case of the work mode, the boom length, the outrigger state, An optimum constant is selected and input from the constant table corresponding to the direction to the controller 38, and a work radius is input to obtain a load characteristic, which is usually represented by a linear expression.

The outputs from the selected mode setting units 64 and 66 are input to a limit load calculating unit 74, where the limit load Wr is determined based on the value of the actual working radius input from the working radius calculating unit 60. We are trying to calculate. In both the work mode and the maintenance check mode, a load corresponding to the load characteristic line is calculated from the work radius. Then, the calculated limit load Wr is input to the load comparator 75 together with the output load Wa from the hanging load calculator 62, where the two are compared. The load comparator 75 activates the automatic stop signal generator 76 when the detected load Wa is equal to or greater than the limit load Wr, and activates the automatic stop signal generator 76 to operate the undulating cylinders 22 and 26 and the telescopic cylinder. Is output.

As described above, the controller 38 is provided with the cylinder stroke sensors 52 and 54 so as to detect a portion immediately before the cylinder stroke reaches the stroke end. These sensors 52, 5
4 may be constituted by a limit switch or the like, but a detection sensor based on a linear scale or an electric or magnetic signal can also be used. The detection signals from the stroke sensors 52 and 54 are determined by the comparator 78, and the stop signal generator 99 can be activated even when the position reaches the position immediately before the stroke end. As a result, even if the stop release switch for releasing the inoperable state when the automatic stop is performed is abolished, it is possible to escape from the deadlock state.

Next, the operation when an automatic stop signal is output from the controller 38 will be described with reference to FIGS. The mobile crane 10 has a first boom 24 and a second
A first cylinder 22 and a second cylinder 26 for raising and lowering the boom 28 are provided, and a first boom telescopic cylinder 80 and a second boom telescopic cylinder 82 for expanding and contracting each of the booms 24 and 28 are provided. These include pump 83
, And drives the first and second up-and-down cylinders 22 and 26 via a boom-up / down operation valve 84, and the first boom-extendable cylinder 80 and
The second boom telescopic cylinder 82 is driven. An on-off valve 88 is provided in the oil passage of each of the cylinders 22, 26, 80, and 82 to switch the operation target. Here, by switching the operation valves 84 and 86, each boom is operated in one of a rising direction, a prone direction, an extension direction, and a contraction direction. The pilot operation valves 90 and 92 for regulating the operation directions are respectively provided. Is provided. When the automatic stop signal is output from the controller 38, the operation is performed through an operation path in a danger operation direction (boom down direction and boom extension direction) that increases the working radius of the pilot operation valves 90 and 92. The loaded unload valves 94 and 96 are driven.

Further, another unload valve 100 is provided on the opposite side of the unload valve 94 in the pilot circuit of the boom raising / lowering operation valve 84, and the first and second boom raising / lowering cylinders reach positions immediately before the stroke ends. At this time, when a stop signal is output from the controller 38, the unload valve 100 is driven to return the boom up / down operation valve 84 to the neutral position, thereby stopping the operation of the up / down cylinders of the first and second booms.

Specifically, as shown in FIG. 3, the automatic stop signal from the controller 38 cuts off the electric signal to the solenoids of the unload valves 94 and 96, thereby switching from A to B. The pilot pressure on the A side 92 is drained. Since the unload valves 94 and 96 are operating paths in the boom lowering direction and the boom extension direction, the hydraulic pressure that increases the boom working radius is shut off by the automatic stop signal. When the up / down cylinders of the first and second booms reach the positions immediately before the stroke end and the up / down cylinders are stopped by the stop signal from the controller 38, if the load curve is within the limit, the controller 38 sends the unload valve 94 to the unload valve 94. Is not output, the unload valve 94 remains at the position A, and the boom can be operated on the downside.

According to such a configuration, when overload is prevented, the controller 38 is provided with a maintenance / inspection mode in addition to the operation mode. Operation becomes possible. In any mode, it is possible to secure work in a safe area while effectively preventing an overload that may cause the crane to overturn. Therefore, the grease application operation or the like that must be performed in an unloaded state can proceed without being hindered by the stop of the boom. In this embodiment, the boom is automatically stopped by mechanical, electric, or magnetic sensing before reaching the cylinder stroke end. Therefore, each cylinder is automatically stopped by the overload prevention device before the hydraulic pressure reaches the relief pressure. As a result, even if the overload automatic stop release switch is abolished, it is possible to escape from a state where the boom hoisting operation cannot be performed, and operation within the range of safety control is permitted.

[0024]

As described above, the overload prevention device for a crane or tower crane according to the present invention is applicable to a crane or tower crane provided with a boom that can be raised and lowered on a base via a lifting cylinder. In a crane or tower crane overload protection device that stops operation when a load is applied, a work mode that determines a load curve determined from a hanging load and a maximum allowable working radius corresponding to the hanging load, A maintenance and inspection mode that determines a load curve determined by the maximum allowable working radius corresponding to an empty load is set, and the mode is switchable so that a work stop output is made by comparing each load curve with a sensed hanging load and a working radius. In addition, the stroke of the up-and-down cylinder is input even within the working area of each mode, The cylinder operation can be stopped before the end of the low-end operation.This allows the operation beyond the range regulated by the normal operation mode to be performed within the safety control range when performing maintenance and inspection. And the operation within the safety control can be performed even if the automatic stop state is achieved.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of an overload prevention device according to an embodiment.

FIG. 2 is a main part hydraulic circuit controlled by an overload prevention device.

FIG. 3 is a diagram illustrating the gist of the hydraulic circuit.

FIG. 4 is a side view of a mobile crane equipped with the overload prevention device according to the embodiment.

FIG. 5 is a load characteristic diagram in a work mode.

[Explanation of symbols]

10 mobile crane, 12 body, 14.
・ Outrigger, 16 ・ ・ ・ Turntable, 18 ・ ・ ・ Driver cab,
20 ... boom base, 22 ... first cylinder, 24
... 1st boom, 26 ... 2nd cylinder, 28 ...
2nd boom, 30 main hook, 32 auxiliary hook, 34 winch means, 36 wire, 3
8 ... controller, 40 ... first axle load sensor, 4
2 1st boom angle detection sensor, 44 ... 1st length sensor, 46 ... 2nd axle load sensor, 48 ... 2nd boom angle detection sensor, 50 ... 2nd length Sensor, 52,
54: Stroke sensor 56: Shaft load / posture / boom length calculation unit 58: Correction processing unit 60:
Working radius calculation unit, 62 ... hanging load calculation unit, 64 ...
・ Work mode setting device, 66 ・ ・ ・ Maintenance / inspection mode setting device, 68 ・ ・ ・ Operation panel, 70 ・ ・ ・ Mode changeover switch, 72 ・ ・ ・ Comparator, 74 ・ ・ ・ Limit load calculation section, 75 ・ ・・ Load comparator, 76 ・ ・ ・ Automatic stop signal generator, 78 ・ ・ ・ Stroke comparator, 80 ・ ・ ・ First boom telescopic cylinder, 82 ・ ・ ・ Second boom telescopic cylinder, 83 ・ ・ ・ Pump, 84 ... Boom-relief operating valves,
86: boom expansion / contraction operation valve, 88: open / close valve, 9
0, 92: pilot operated valve, 94, 96: unload valve, 99: stop signal generator, 100:
Unload valve

Claims (2)

(57) [Claims] 1. An overload prevention device for a crane or a tower crane, wherein an operation is stopped when an overload is applied to a crane having a boom that is mounted on a base via an up / down cylinder via an up / down cylinder. A work mode that determines a load curve determined from a lifting load and a maximum allowable working radius corresponding to the lifting load, and a maintenance inspection mode that determines a load curve determined by a maximum allowable working radius corresponding to an empty load are set. An overload prevention device for a crane or a tower crane, comprising a controller capable of switching the mode and outputting a work stop by comparing each load curve with a sensed hanging load and a work radius. 2. An overload prevention device for a crane or a tower crane, which is configured to stop operation when an overload is applied to a crane having a boom that is mounted on a base so as to be able to be raised and lowered via a lifting cylinder. A work mode that determines a load curve determined from a lifting load and a maximum allowable working radius corresponding to the lifting load, and a maintenance inspection mode that determines a load curve determined by a maximum allowable working radius corresponding to an empty load are set. The mode can be switched, and a work stop output is made by comparing each load curve with the sensed hanging load and working radius, and the stroke of the undulating cylinder is input even within the working area of each mode, and a stroke end is input. Crane, characterized in that it is equipped with a controller capable of stopping cylinder operation before reaching Is a tower crane overload prevention device.