JP2002038859A - Boom type operating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boom type operating machine allowing supervisory control to be exerted, according to objectivity rather than an operator's subjectivity, over the magnitude of the force acting in the push-up direction of a boom, which is generated by the reaction force applied to the end section of the boom due to a drilling operation, and enabling the handling for averting various dangers in case of a dangerous condition during the drilling operation. SOLUTION: The boom type operating machine provided with an over-loading prevent device enables the calculation of the magnitude of the force acting in the push-up direction of the boom, which is generated by the reaction force applied to the end of the boom due to the drilling operation and permits the supervisory control to be exerted over the above force acting in the push-up direction by means of the over-loading prevent device for the purpose of allowing the operating machine to undergo the handling for averting the various dangers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boom type working machine, and more particularly to a boom type working machine, in which a drilling means such as a ground auger is attached to a tip of a boom such as a crane to perform drilling work. The present invention relates to a boom-type working machine capable of calculating an acting force and performing various danger avoidance processes.

[0002]

2. Description of the Related Art In recent years, in foundation works and the like, there has been a construction method in which a boring operation such as an earth drill, an earth auger or the like is attached to a tip portion of a crane boom to perform a boring operation. This construction method was developed to carry out pile driving work in which it is often difficult to carry a large foundation machine in terms of construction, such as a narrow work site in an urban area or a site where a three-point pile driver is not allowed. The drilling means has its own drive source such as a hydraulic or electric motor, and uses a pressurized oil or electric power supplied from the outside to drill the drill holes or buckets connected to the drive source. The drilling attachment inside the means is configured to rotate.

[0003] In the above method, the drilling means attached to the tip of the multi-stage telescopic boom is suspended downward while being held vertically to the ground. Further, while rotating the drilling attachment, the boom is pushed down in accordance with the drilling speed of the drilling means, thereby drilling a vertical hole for burying a pile.

[0004]

However, as described above, when the above drilling operation is performed using a crane equipped with a multi-stage telescopic boom, the drilling means is held vertically to the ground. In order to push down the boom in accordance with the drilling speed of the drilling means, it is necessary to simultaneously perform the operation of pushing down the boom and the operation of shortening the boom. Further, the condition of the ground varies depending on the stratum, and is not constant due to rocks, concrete pieces and the like, so that the drilling speed is not constant. Also, when the earth auger and earth drill are pulled out by drilling in the reverse direction after drilling, the force to push up the boom tip is always applied, so the boom push-up operation and boom extension operation are performed so that excessive force is not applied to the boom tip. And need to do.

[0005] If the reaction force due to the drilling and pulling operation received by the extremity of the telescopic boom through the drilling means becomes large, the reaction force generated in the push-up direction exceeds the proof strength of the boom, In some cases, the stability limit of the backward stability of the crane may be exceeded. Therefore, in the method of performing the drilling operation using the drilling means with a conventional boom type working machine, the operator must pay sufficient attention to safety measures such as breakage of the boom or overturning of the crane body. No. Therefore, there is a problem that an operator who performs the drilling operation with the working machine requires special skills.

[0006] Further, the conventional crane has no equipment for monitoring the magnitude of the acting force in the pushing direction received by the tip of the telescopic boom, and no safety device is provided. Therefore, there is no other way to sense the magnitude of the acting force in the pushing direction and the danger of the drilling operation than relying on the skill of the crane operator. However, there is a difference between operators depending on the operator.Therefore, when an operator who does not have the above-mentioned method performs drilling work with the above-mentioned method, or when an operator who has the above-mentioned method has a hole with the above-mentioned method, the operator has no skill. Even in the case of performing the pulling-out operation, carelessness may cause an accident such as breakage of the boom, the earth auger, or the earth drill, or the overturn of the crane body. Therefore, the purpose of the present invention is to measure the magnitude of the acting force in the push-up direction generated by the reaction force due to the drilling operation that the tip of the boom receives objectively without relying on the subjectivity of the operator. An object of the present invention is to provide a boom type work machine configured to perform a danger avoidance process of issuing a danger signal to an operator when a danger occurs.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a boom which is variable in length and can be freely raised and lowered, and which can be provided with a drilling means at a tip end thereof. In a boom type working machine, comprising: an angle detecting means for detecting an angle; a boom length detecting means for detecting a length of the boom; and a load detecting means for detecting a load applied to the boom. At the time of work, based on signals obtained from the angle detecting means, the boom length detecting means, and the load detecting means, an action in a pushing direction of the boom generated by a reaction force caused by the drilling work received by a tip portion of the boom. It is configured as a boom type working machine, comprising an overload prevention device configured to calculate a force. Therefore, various danger avoidance processes can be performed.

According to a second aspect of the present invention, there is provided a boom type working machine provided with the overload prevention device according to the first aspect, wherein the acting force in the pushing direction is a safety reference value of the boom type working machine. Further, it is provided with an alarm means for issuing a predetermined danger signal when a safety-side preliminary reference value is exceeded. Therefore, the danger avoidance process can be performed without stopping the machine by issuing the danger signal.

According to a third aspect of the present invention, in the boom type working machine according to the second aspect, the danger signal is changed according to the acting force. Therefore, in this case, it is possible to take measures such as changing the signal according to the degree of danger.

According to a fourth aspect of the present invention, in a boom type working machine according to the first, second, or third aspect,
When the acting force in the pushing direction exceeds the reference value, the operation of pushing down the boom is automatically stopped. Therefore, in the drilling operation, it is possible to prevent a major accident from occurring.

According to a fifth aspect of the present invention, in the boom type working machine according to the first, second, third or fourth aspect, the acting force in the pushing direction does not exceed the reference value. The boom is controlled as described above. Therefore, by controlling the boom, danger can be avoided without stopping the drilling operation.

According to a sixth aspect of the present invention, in the boom type working machine according to the first, second, third, fourth, or fifth aspect, the acting force in the push-up direction is controlled by a lifting load. And a display means for displaying the load in the opposite direction to the actual load. Therefore, when the acting force acting on the tip of the boom is in the direction of pushing up the boom, it is displayed as a load opposite to the actual load of the suspended load. Can be intuitively identified.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Embodiments embodying the present invention will be described for the understanding of the present invention. It should be noted that the following embodiments are merely examples embodying the present invention, and do not limit the technical scope of the present invention. Here, FIG. 1 is an information transmission block diagram of the overload prevention device according to the embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing a state of drilling work by a wheel type crane as an example of a boom type working machine according to the embodiment of the present invention, and FIG. 3 is a diagram showing a relationship between pressures in a boom hoist cylinder according to the embodiment of the present invention. FIG. 4 is a hydraulic circuit diagram according to the embodiment of the present invention, and FIG. 5 is a diagram illustrating a process of comparing the acting force in the pushing direction with a safety reference value or a preliminary reference value in the overload prevention device of the present invention. It is a flowchart as an example.

First, a basic configuration of a wheel type crane 20 (hereinafter, referred to as a crane) having a multi-stage telescopic boom will be described as an example of a boom type working machine with reference to FIGS. FIG. 2 shows an operation state in which a long tubular pile 50 is buried in the ground while performing a drilling operation. The crane 20 has an upper revolving unit 22 pivotably mounted thereon via a revolving bearing disposed in the center of a lower traveling unit 21.
3 and a pair of front and rear outriggers 24 for extending in the vehicle width direction at the time of work to lift the work machine and ensure stability.
Are provided. On the other hand, the upper revolving unit 22 includes:
A boom support frame 26 pivotally connected by a slewing bearing, a cab 27 for both traveling and work, a winch (not shown) around which a wire rope 28 for hanging load is wound, and a counterweight 29; A telescopic boom 30 is provided. In addition, boom 30
Is mounted on a rear upper portion of the boom support frame 26 by a boom foot pin 31 so as to be able to be raised and lowered. Further, as a driving means for raising and lowering the boom 30,
A boom hoist cylinder 7 is provided, one end of which is attached to the lower surface of the boom 30 and the other end of which is attached to the center of the boom support frame 26. On the other hand, an earth auger 40 as a drilling means is attached to the distal end portion 32 of the boom 30. Further, an earth auger 40 is attached to the tip portion 32 of the boom 30 as an example of a drilling means. Here, the earth auger 40 has a drilling drill 42 connected to a drive shaft of a driving unit 41 that generates a rotary drilling force. Further, the earth auger 40 is connected to the drive unit 4.
1 is provided at the lower end with a discharging device 4 for discharging the drilled soil.
3 and a pile holding device 44 that fits and holds the upper end of the pile so that the pile 50 does not rotate is connected with the drill 42 inserted. Here, the drilling work in the present invention is
It includes drilling and a drawing operation after drilling.
Further, an overload prevention device 5 shown in FIG. 1 is provided in the operator's cab as a means for preventing the work machine from hanging an excessively heavy load or for calculating the acting force in the push-up direction in the present invention. The overload prevention device 5 monitors and controls the state of the boom 30 by acquiring and calculating data from the following detectors or sensors. here,
The above-described detector or sensor is a cord-reel type boom length detector 1 that is an example of a boom length detection unit that detects the length of the boom, and an example of an angle detection unit that detects the angle of the boom. An angle detector 2, a head pressure sensor 3 and a rod pressure sensor 4 for detecting the oil pressure of a boom hoist cylinder 7 as an example of a load detector of the work machine.
And Further, a command output upon control by the overload prevention device 5 will be described later.

Next, a normal operation example of the boom of the boom type working machine will be briefly described with reference to FIGS. FIG.
It is necessary to move the rod of the boom hoist cylinder 7 upward to push up and raise the boom 30 shown in FIG. Therefore, by selecting the position of the boom control valve 8 which is the 6-port 3-position switching valve in FIG.
Pressure oil from the boom drive pump 9 is supplied to the head side of the boom hoist cylinder 7 to increase the pressure, and moves the rod of the boom hoist cylinder 7 upward to push up the boom. Further, in order to push down the boom, it is necessary to move the rod of the boom hoist cylinder 7 downward. Therefore, by selecting the position of the boom control valve 8, the pressure oil from the boom drive pump 9 is supplied to the rod side of the boom up / down cylinder 7 to increase the pressure, and the boom up / down cylinder 7 Move the rod down and depress the boom. When the position of the control valve 8 is selected, oil is not supplied to the head side and the rod side of the boom up / down cylinder 7, and the boom up / down operation is stopped.

The external force (hereinafter referred to as the acting force) applied to the boom tip of the boom type working machine that operates as described above is calculated by the actual load calculating device 6 of the overload prevention device 5 shown in FIG. And the operator is notified by the actual load display unit 15. Head pressure Ph obtained from the head pressure sensor 3 and the rod pressure sensor 4 attached to the head side and the rod side of the boom hoist cylinder 7
Then, based on the rod pressure Pr, the pressure P1 applied to the boom hoist cylinder 7 while supporting the boom 30 is calculated as follows. When the magnitude of the force that the boom hoist cylinder 7 supports the boom 30 is N, the boom hoist cylinder head side area Sh (see FIG. 3), and the boom hoist cylinder rod side area Sr (see FIG. 3), = Ph x Sh-Pr x Sr. Here, dividing both sides by Sh gives N / Sh = Ph- (Sr / Sh) × Pr. That is, N / Sh is the pressure when the boom hoist cylinder 7 is supporting the boom 30. This is,
This is P1 to be obtained.

The magnitude N of the force by which the boom hoist cylinder 7 supports the boom 30 depends on the boom 3
It is a force that includes its own weight of zero and the above-mentioned acting force. Accordingly, the pressure P1 at which the boom hoist cylinder 7 supports the boom 30 is made up of the following two pressure components. The pressure component supporting the weight of the boom 30 is P
j, if the pressure component supporting the weight of the suspended load is P2, then P1 = Pj + P2. Further, since the above-mentioned P2 may be known in order to calculate the above-mentioned acting force, P2 = P1-Pj.

Next, the acting force W is calculated from P2 as follows. W = P2 × k1 / R Here, k1 is a coefficient calculated based on the output value of the boom angle detector 2. R is the horizontal distance from the boom foot 20 in FIG. 2 to the suspended load position, and is determined from the boom length and the boom hoisting angle. Therefore, the output value of each of the boom length detector 1, the boom angle detector 2, the head pressure sensor 3, and the rod pressure sensor 4 is calculated by the above-described operation, and the action of the suspended load is performed. The force W will be calculated.

Next, the value of P2 will be described with reference to FIG. Normally, when the crane 20 suspends a load, the load suspended via the wire rope 28 acts on the boom tip portion 32 as an external force for pushing the boom down. Therefore, the boom hoist cylinder 7 has
Since a reaction force is generated to push up the rod 7a, P
1 becomes larger than Pj, and P2 becomes a positive value.

On the other hand, when a force is applied to the boom tip 32 in an upward direction (reverse to crane operation), the force acts in a direction in which the boom hoist cylinder 7 is extended (cylinder extension direction). Therefore, a reaction force is generated in the undulating cylinder 7 in the cylinder contracting direction (cylinder contracting direction) to push down the rod 7a, and P1 becomes smaller than Pj and P2 becomes a negative value.

When the boom type working machine is not hanging a suspended load, P2 is substantially zero. That is, when P2 takes a positive value, the actual load calculating device 6 in the overload prevention device 5 of FIG. 1 calculates the acting force W of a positive value, and conversely, when P2 takes a negative value. Is calculated as a negative acting force W. In the crane 20 according to the embodiment of the present invention, the boom hoisting cylinder 7 arranged on the lower surface of the boom is used.
However, it is needless to say that the value of P2 is opposite to that described above in a boom type working machine configured to pull up on the boom upper surface side. The specific working state of the boom-type working machine in which such calculations are performed is as follows. When the work machine is mounted with the earth auger, which is a drilling means, a downward force acts on the boom tip portion 32 due to the weight of the earth auger as in the case where a suspended load is suspended during crane operation. ing. Further, the working force W when the working machine is performing the drilling work with the earth auger mounted thereon.
Is as follows. When the drilling speed by drilling the earth auger 40 is faster than the pressing down speed of the boom 30, the earth auger 40 further pulls the tip 32 of the boom downward, and the acting force W increases. On the other hand, when the drilling speed is lower than the boom pushing-down speed, an upward force, that is, a force in the direction of pushing up the boom acts on the tip 32 of the boom, and the acting force W is reduced by the weight of the earth auger. Decrease. In other words, when the drilling speed of the earth auger 40 matches the depressing speed of the boom during the drilling operation, only the own weight of the earth auger 40 is displayed as the acting force W on the actual load display unit 15, The drilling or withdrawal resistance is added to or subtracted from the acting force W and displayed on the actual load display section 15. Therefore, Earth Auger 40
When the drilling speed of the earth auger 40 and the pressing speed of the boom coincide with each other during the drilling operation, the acting force W is calculated by the actual load calculating device 6. May be displayed on the actual load display unit 15 as substantially zero. Then, in the above-mentioned drilling operation, the state where no external force is applied to the tip end portion 32 of the boom, that is, by setting the target value when performing the operation of pushing down the boom to 0, the drilling operation can be performed safely. Becomes In addition, the actual load display section 15 displays ± each acting force W as a drilling resistance. The overload prevention device 5 is configured to display the acting force W on the conventional actual load display unit 15. However, only the acting force in the direction of pushing the boom is separately provided and displayed by providing a dedicated display unit. Is also possible. For example, a CRT which is an existing display means provided in a cab
Alternatively, the above contents may be displayed on a liquid crystal monitor device.
Also, the actual load display unit 15 or the CRT in the driver's cab
In order to enable the operator to easily recognize that an upward force is being applied to the tip 32 of the boom in the liquid crystal monitor device, for example, the acting force W is represented by an upward arrow or the like, The display may be sequentially changed in accordance with the value of the acting force, for example, by extending the arrow or changing the size of the arrow as the value of the force increases.

As described above, since the tip of the boom receives the reaction force due to the drilling operation, the reaction force in the direction of pushing up the boom moves from the tip of the boom to the boom up-and-down cylinder 7 as described above. Is transmitted to In such a case, the overload prevention device 5 performs the following control based on the calculated P2 as the acting force in the push-up direction received by the boom tip 32 increases.

In the following description, the preliminary reference value is defined as the maximum strength load for the acting force in the direction of lifting the boom and the critical load for falling down the crane rearward, which are obtained in the design stage of the work machine. , By adding a predetermined amount of value to the boom until the boom is damaged or the crane falls backward. That is, the preliminary reference value, when the acting force in the pushing direction exceeds the preliminary reference value,
This is a criterion for issuing a danger signal to the operator and determining that the drilling operation can be continued, and is a preliminary reference value on the safer side than the reference value described later. In addition, the reference value is higher in safety risk than the preliminary reference value, and when the reference value is exceeded, it is determined that continuation of the drilling operation is impossible, and This is a criterion for making a determination to automatically stop the drilling operation. The process of comparing the acting force in the push-up direction with the reference value and the preliminary reference value as described above will be described later with reference to the flowchart of FIG. Therefore, the overload prevention device 5 not only calculates the acting force in the pushing direction, but also compares the acting force in the pushing direction with the reference value or the preliminary reference value, thereby obtaining the acting force in the pushing direction. If the force exceeds the preliminary reference value, a function to notify the operator of the work machine of the degree of danger, or if the acting force in the pushing direction exceeds the reference value,
It also has a function to automatically stop the drilling operation.

Next, an example of comparing the acting force in the pushing direction with a safety reference value or a preliminary reference value will be described with reference to FIG. Here, S1, S2,... Are control procedure numbers. In the overload prevention device 5 of FIG.
Is calculated based on the value of (1) (S1). Next, it is determined whether the acting force in the pushing direction has exceeded the preliminary reference value (S2). If not, the force in the pushing direction is subsequently compared with the preliminary reference value. Also, when the acting force in the pushing direction exceeds the preliminary reference value, 1 in FIG.
A danger signal is issued to the operator by alarm means such as a lamp, a buzzer, and an audio alarm shown in FIG. 6 (S3). Further, it is determined whether the acting force in the pushing direction exceeds the reference value (S4). If not, the acting force in the pushing direction is continuously compared with the reference value. If the acting force in the pushing direction exceeds the reference value, the drilling operation is stopped (S5). Further, in issuing a danger signal to the operator by the alarm means, for example, by combining a plurality of alarm means emitting a sound or light such as a lamp, a buzzer, an audio alarm,
By changing the combination of alarm means according to the type and degree of danger, it is possible to more clearly convey the danger of the drilling operation to the operator.

The operation of the hydraulic system when the above-described drilling operation is automatically stopped will be described below with reference to the hydraulic circuit diagram of FIG. First, when it is determined that the drilling operation is to be stopped by the overload prevention device 5 (S5 in FIG. 5), the overload prevention device 5 activates the electromagnetic switching valve 12 for stopping the boom press-down operation, which is an electromagnetic switching valve. To a non-excited state. When the electromagnetic switching valve 12 for stopping the boom press-down operation is changed from the excited state to the non-excited state, the boom control valve 8 is moved to the position (stop) from the position (press-down operation). Therefore, the boom stops the pushing operation, and the drilling operation stops. A signal for automatically stopping such a boom raising / lowering operation is also input to a control unit of an earth auger (not shown), and the stop signal is output from the overload prevention device 5 and at the same time, the rotation of the drill is stopped. You may comprise so that it may be.

Further, the above-mentioned reference value or the preliminary reference value is set so that the acting force in the push-up direction generated by the reaction force due to the drilling work received by the tip portion of the boom does not exceed. It is also possible to control automatically. In FIG. 4, when the overload protection device 5 determines that the acting force in the pushing direction has a value close to the reference value or the preliminary reference value, the overload protection device 5 starts the electromagnetic proportional valve. The pressure in the boom push-down pipe is alleviated by operating 13 to lower the relief pressure of the boom lower relief valve 14. Therefore, the boom hoist cylinder 7 moves in the cylinder extension direction, and the reaction force generated in the boom hoist cylinder 7 against the acting force in the boom push-up direction at the tip of the boom is suppressed. This suppresses an increase in the bending moment generated between the tip of the boom and the pivot of the boom hoisting cylinder 7, so that damage to the boom can be prevented. In this way, control is exercised so that the acting force does not become too large.

In the operation of the boom type working machine as described above, the operator who operates the working machine is displayed with the actual load at the time of the crane work for hanging the suspended load during the drilling work as in the case of displaying the actual load. Also, the magnitude of the acting force in the direction of pushing up the boom can be displayed to the operator. In other words, in the actual load display section of the overload prevention device,
As in the case of the crane operation, the direction in which the tip of the boom is pulled downward is indicated by a positive sign (+), and the acting force in the boom pushing direction generated during the drilling work is indicated by a negative sign (-). The operator can always know the operation status during the drilling operation and the load status of the boom type working machine equipped with the drilling means. Also, by setting the weight of the drilling means in the overload prevention device in advance, when the boom is mounted with the drilling means and the drilling work is not performed, the display of the actual load display section is set to 0. . When the drilling speed of the drilling means is lower than the boom depressing speed, a negative value is displayed on the actual load display section to make it easier for the operator to grasp the state of the drilling work. And, by operating the work machine so as to ensure the safety of the drilling work by the operator's own judgment so as not to exceed the reference value already described above, the drilling work is automatically performed by the overload prevention device. Work can be performed efficiently without stopping. Also, it is possible to automatically control the boom so that the magnitude of the acting force in the boom push-up direction is always 0, or to calculate the ratio of the magnitude of the load to the boom strength reference obtained at the time of design, It is also possible to display the intensity load factor on the load factor display section.

[0028]

According to the present invention, there is provided a method for performing a drilling operation by attaching a drilling means to a distal end portion of a boom type working machine. With respect to the magnitude of the acting force in the push-up direction, the drilling operation is performed by the skill of the operator of the boom type working machine without monitoring using a device or the like and without providing a safety device. As described above, using the overload prevention device, which conventionally measures the actual load of a suspended load, measures the acting force in the lifting direction and operates the boom type work machine. It is possible to notify the operator of the magnitude of the acting force in the pushing direction and the risk of the drilling operation. Therefore, conventionally,
The drilling operation, which relied on the skill of the operator of the boom-type working machine, can be objectively monitored by an overload prevention device. Danger can be avoided. Further, the overload prevention device in the present invention,
It is only necessary to modify the software in the existing device, and the detector that provides various data to the overload prevention device is also conventional, so that the present invention can be implemented without increasing the cost. Becomes

The danger signal for notifying the operator of the boom type working machine of the danger of the drilling operation is generated by changing the danger signal in accordance with the acting force in the pushing direction. It is possible to take measures such as changing the signal.

Further, by providing a safety reference value for the acting force in the pushing direction, if the acting force in the pushing direction exceeds the reference value, the drilling operation by the above method is automatically stopped. It is also possible. Therefore, it is avoided that the above operation leads to a major accident.

Further, by controlling the acting force in the pushing direction so as not to exceed the reference value or the preliminary reference value, danger can be avoided without stopping the drilling operation.

Further, the acting force in the pushing direction of the boom, which is generated by the reaction force due to the drilling operation received at the tip end portion of the boom, is displayed on the actual load display section as a load opposite to the actual load of the suspended load. Therefore, since the operator can always intuitively identify the magnitude of the acting force acting on the tip of the boom, the operator himself can grasp the danger of the drilling work of the working machine and avoid the danger. Become.

[Brief description of the drawings]

FIG. 1 is an information transmission block diagram of an overload prevention device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a drilling operation by a wheel crane as an example of a boom type working machine according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between pressures in a boom hoist cylinder according to the embodiment of the present invention.

FIG. 4 is a hydraulic circuit diagram according to the embodiment of the present invention.

FIG. 5 is a flowchart as an example of comparing the acting force in the pushing-up direction with a safety reference value or a preliminary reference value in the overload prevention device according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Boom length detector 2 ... Angle detector 3 ... Head pressure sensor 4 ... Rod pressure sensor 5 ... Overload prevention device 7 ... Boom raising / lowering cylinder 7a ... Rod 8 ... Boom control valve 9 ... Boom drive pump 12 ... Boom depressing Electromagnetic switching valve for stopping operation 13 ... Electromagnetic proportional valve 14 ... Relief valve 15 ... Actual load display unit 20 ... Wheel type crane 16 ... Ramp, buzzer, sound alarm etc. 20 ... Wheel type crane 21 ... Lower traveling body 22 ... Upper revolving unit Reference Signs List 23 tire 24 outrigger 26 boom support frame 27 driver's cab 28 wire rope 29 counter weight 30 boom 31 boom foot pin 32 boom tip 40 40 earth auger 41 driving unit 42 drilling drill 43: earth removal device 44: pile holding device 50: pile

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B66C 23/90 B66C 23/90 H

Claims (6)

[Claims] 1. A boom which is variable in length and can be raised and lowered to allow a drilling means to be attached to a tip end thereof, an angle detecting means for detecting an angle of the boom, and a length of the boom. In a boom type working machine comprising a boom length detecting means for detecting and a load detecting means for detecting a load applied to the boom, when drilling by the drilling means, the angle detecting means, the boom length detecting means, An overload prevention device configured to calculate an acting force in a pushing direction of the boom generated by a reaction force due to the drilling operation received by the tip portion of the boom, based on a signal obtained from the load detecting means. A boom type working machine characterized by the above-mentioned. 2. An alarm means for issuing a predetermined danger signal when the acting force in the pushing direction exceeds a safety-related preliminary reference value further than a safety reference value of the boom type work machine. The boom type working machine according to claim 1, wherein: 3. The boom type working machine according to claim 2, wherein the danger signal changes in accordance with the acting force. 4. The system according to claim 1, wherein the operation of pushing down the boom is automatically stopped when the acting force in the pushing direction exceeds the reference value.
The boom type working machine according to claim 2 or 3. 5. The apparatus according to claim 1, wherein the boom is controlled so that the acting force in the pushing direction does not exceed the reference value. 4. The boom type working machine according to 4. 6. The display device according to claim 1, further comprising display means configured to identifiably display the acting force in the pushing direction as a load in a direction opposite to the actual load of the suspended load. The boom type working machine according to claim 2, 3, 4, or 5.