JPH0754568A - Control device for hydraulic motor to drive kelly-bar - Google Patents

Abstract

PURPOSE:To eliminate the need for keeping the direction selector valve of a hydraulic motor for driving a telescopic kelly-bar at a neutral position for approximately two seconds to invalidate the torsional elasticity of the bar at the time of reversing and lifting the rotary drilling bucket of an earth drill biting a bottom hole, and realize a mud shakedown operation for suddenly reversing a bucket rotating direction. CONSTITUTION:A throttled passage 34 to a tank 3 is provided in such a way as capable of resetting a selector valve to a neutral position at the time of closing a normally open valve 23 laid at the intermediate position of a hydraulic circuit 7B for remotely operating the reverse rotation selecting pressure receiving section 4B of a direction selector valve. A relief valve 18 having set pressure equal to or lower than hydraulic motor drive pressure at a normal drilling process but higher than hydraulic motor drive pressure at a mud shaking down process, or a pressure switch is connected to a high pressure hydraulic circuit 2A for drilling. The normally open valve 23 is thereby closed, when the pressure of the circuit 2A exceeds a preset value. Also, when the pressure drops below the preset value, the normally open valve 23 opens, delayed by a time required for the torsional elasticity of a telescopic kelly-bar to disappear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth drill for punching the ground by pushing down an expandable kerry bar having a rotary excavation bucket for storing excavating debris at its lower end while driving it with a hydraulic motor.

[0002]

2. Description of the Related Art In a conventional earth drill, the distance between the directional control valve for controlling the Kelly bar driving hydraulic motor and the operating portion such as the operating pedal and the difference in the mounting position are large, so that the hydraulic motor is controlled. As shown in FIG. 1, the device includes a supply / discharge oil passage 2A for the Kelly bar drive hydraulic motor 1,
The directional control valve 4 which is always urged to return to the neutral position of the semi-open type in which both 2B communicate with the tank 3 is placed in the forward rotation position (left position in the drawing) and the reverse rotation position (right position in the drawing) for drilling. It is configured to be controlled by a remote control device 6 including a pair of left and right pressure reducing valves 5A and 5B that selectively perform pilot operation.

Therefore, normally, the pilot oil passage 7A between the forward rotation switching pressure receiving portion 4A of the direction switching valve 4 and the corresponding pressure reducing valve 5A, and the reverse pressure switching pressure receiving portion 4B of the direction switching valve corresponding to the pressure reducing portion 4B. The remote control device 6 in which the pilot oil passage 7B between the valve 5B and the valve 5B is connected to the tank 3 through the pressure reducing valve, respectively, is depressed by depressing the left end of the operation pedal 8 thereof. Reduces the pressure oil discharged from the pilot pump 9 from the oil passage 7A to the pressure receiving portion 4A on the left side of the directional control valve, the oil in the right pressure receiving portion 4B flows from the oil passage 7B to the pressure reducing valve 5B.
While being discharged to the tank via the directional control valve 4, the direction switching valve 4 switches to the left forward rotation position to supply the discharge pressure oil of the hydraulic pump 10 from the oil passage 2A to the hydraulic motor 1 and the return oil at that time to the oil passage 2B. And is discharged to the tank via the directional control valve 4 in sequence.

Therefore, for example, as shown in FIG. 2, the telescopic kelly bars 11 and 12 and the rotary excavation bucket 16 of the telescopic-shaped telescopic kerry bar consisting of at least the outer kelly bar 11 and the inner kerry bar 12, and the rotary excavation bucket 16 are located on the rotary 13. Since it is normally driven by the hydraulic motor 1, the rotary ring gear is pushed down by the pushing cylinder 15 along the vertical guide rail 14 supported by an appropriate means on the base of the earth drill. The ground G is drilled and drilled by the bucket 16 by applying a drilling thrust to the rotary drilling bucket 16 through frictional force generated between the outer end kelly bar 11 and the outer end kelly bar 11 and between the outer end kelly bar 11 and the inner end kelly bar 12, respectively. However, it is unavoidable that the torsion elastic deformation of the kelly bar increases as the depth of perforation increases.

Therefore, in order to discharge the cutting waste loaded in the bucket 16 by drilling, the upper end of the inner end kelly bar 12 is lifted by the crane suspension line 17 and the telescopic kerry bar is contracted, whereby the bucket is opened. To lift it to the ground, the operation pedal 8 of the remote control device is returned to the normal position in FIG. 1, and the directional control valve spring-returned to the neutral position (hydraulic motor drive stop position) shown in FIG. In this state, the frictional force is eliminated by rotating the hydraulic motor 1 in the reverse direction until the torsional elasticity of the kelly bar disappears. Next, the bite of the bucket 16 on the hole bottom of the excavating blade is released, and In order to reduce the lifting resistance, the directional control valve 4 had to be switched to the reverse position to lift the bucket.

This is because when the direction switching valve 4 is suddenly switched to the reverse position while the torsion elastic deformation of the kelly bar remains, the reverse rotation speed of the hydraulic motor 1 is 4000 to 5000 per minute due to the torsion elastic force of the kerry bar. This is because the hydraulic motor will be rapidly raised to the extent of rotation and cavitation will occur, which will damage the hydraulic motor in a short period of time. Although this phenomenon depends on the torsional rigidity of the kelly bar and the size of the outer diameter of the bucket, it usually starts from a kelly bar length of about 10 rice and is remarkable when the kerry bar length becomes 17 to 18 rice or more.

In order to avoid this, even if a throttle or accumulator is inserted in the middle of the pilot oil passage 7B between the reverse pressure switching pressure receiving portion 4B of the direction switching valve and the corresponding pressure reducing valve 5B,
If the directional control valve 4 is slightly switched to the reverse rotation position while the hydraulic motor is reversely rotated by the torsional elasticity of the kelly bar, the hydraulic motor is reversely rotated at an excessive speed. Not only there is a risk of shortening the service life, but when discharging the excavated debris in the bucket 16 that has been lifted above the ground, the rotation direction of the bucket is quickly switched between forward and reverse to remove the mud adhered by inertia. Switching operation becomes difficult.

Further, when the bucket 16 is lifted on the ground, the relative frictional force in the vertical direction of each part of the expansion and contraction kelly bar must be eliminated as described above, so that the supply / discharge between the direction switching valve 4 and the hydraulic motor 1 is performed. It is also not possible to insert a counterbalance valve in the oil passage.

[0009]

SUMMARY OF THE INVENTION According to the present invention, when the rotary excavation bucket is lifted after the completion of the boring stroke, even if the directional control valve is immediately switched to the reverse position without being held in the neutral position for a predetermined time or longer, the hydraulic pressure is changed. As well as reducing the driver's effort by not shortening the life of the motor, enabling the improvement of drilling efficiency, and the rotary cutback operation for mud removal of the rotary excavation bucket when discharging excavation debris as before. The purpose is to enable.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a normally open valve is inserted in the middle of a pilot oil passage between a reverse pressure switching pressure receiving portion of a directional control valve and a corresponding pressure reducing valve, and the normally open valve is closed. In order to sometimes return the directional control valve to the neutral position, the reverse rotation switching pressure receiving section and the tank are connected by a throttle passage,
And a low pressure relief valve with a small flow rate is connected to the high pressure side oil passage between the directional control valve and the hydraulic motor during perforation, and the set pressure of the low pressure relief valve is equal to or lower than the hydraulic motor drive pressure during perforation, Set the pressure higher than the hydraulic motor drive pressure during normal / reverse cutback operation in the rotating excavation bucket rotation direction when discharging cutting waste, and eliminate the torsional elasticity of the telescopic kerry bar that drives the hydraulic motor in reverse when the hydraulic motor drilling drive is stopped. A pressure accumulating means capable of holding the normally open valve in the closed position for a time necessary for the operation and a pilot operating part of the normally open valve are connected to the upstream side of the throttle inserted in the discharge oil passage of the low pressure relief valve. In place of the low pressure relief valve, a pressure switch having the same set pressure as that of the low pressure relief valve is connected to the high pressure side oil passage between the directional control valve and the hydraulic motor at the time of drilling to A pressure switch circuit is provided that closes the electromagnetically-operated normally open valve when the pressure switch contact is closed due to the increase in pressure in the passage, and the normally open valve is opened when the pressure switch contact is opened by stopping the drilling drive of the hydraulic motor. A timer may be incorporated in the pressure switch circuit to delay the return to the open position for a fixed time required for the elastic elasticity of the telescopic kelly bar to disappear.

[0011]

FIG. 1 shows an embodiment of the present invention, in which 18 is connected to a high pressure side oil passage 2A between a directional control valve 4 and a hydraulic motor 1 at the time of drilling through a small flow passage 19 of oil. In the low-pressure relief valve, the set pressure of the low-pressure relief valve 18 is higher than the hydraulic motor drive pressure at the time of the turning operation for rapidly switching the rotation direction of the rotary excavation bucket 16 for discharging the cutting waste, It is equal to or lower than the hydraulic motor drive pressure when drilling the ground.

Reference numeral 20 is a high pressure relief valve that relieves when the drilling blade of the rotary drilling bucket during drilling is engaged with rocks or the like to stop rotation, and 21 is an oil passage 22 from the low pressure relief valve 18 to the tank. The reference numeral 23 designates a normally inserted valve for pilot operation inserted in the middle of the pilot oil passage 7B between the reverse rotation switching pilot operating portion 4B of the direction switching valve 4 and the corresponding pressure reducing valve 5B. The open valve 23 is constantly urged to return to the open position shown by its own return spring, and the pilot oil passage 23a for closing the normally open valve is connected to the low pressure relief valve 1.
8 is connected to the discharge oil passage 22 between the throttle 21 and the normally open valve 23 is closed by the pilot hydraulic pressure of extremely low pressure (about 4 to 5 kilograms per square meter).

Reference numeral 24 denotes a pressure receiving portion 4 for reverse rotation switching of the direction switching valve 4.
A throttle passage communicating B with the tank 3 is shown.
The flow passage area of No. 4 is small so that the directional switching valve can be switched to the reverse position by operating the reverse switching pressure reducing valve 5B, but when the normally open valve 23 is closed, the directional switching valve is closed. It is possible to return spring 4 from the forward rotation position to the neutral position shown in the drawing.

Reference numeral 25 denotes a pressure accumulator connected to the discharge oil passage 22 between the relief valve 18 and the throttle 21. The pressure accumulator 25 rapidly changes the direction switching valve 4 from the forward rotation position to the reverse rotation position. It has a capacity necessary for closing the normally open valve 23 until the torsional elastic force of the telescopic kelly bars 11, 12 does not act on the hydraulic motor 1.

The set pressure of the low-pressure relief valve 18 is approximately one half of the set pressure of the high-pressure relief valve 20, and is made of at least one of sand, silt, clay, etc., and the N value of the standard penetration test is 50.
When drilling ground with general soil of less than, that is, below the hydraulic motor drive pressure at the time of normal drilling, when excavating waste, it is necessary to switch the rotation direction of the bucket quickly and reversely. Since the low-pressure relief valve is always opened at the beginning of perforation, if the throttle 21 is provided in the discharge oil passage 22 having a larger flow passage area than the normal oil passage 19, the low-pressure relief valve 18 immediately opens normally when the low-pressure relief valve 18 is relieved. The valve 23 is closed and the pressure accumulator 25 is instantaneously charged with a fixed amount of hydraulic energy. Since the flow rate of the low pressure relief valve during relief is smaller than the flow rate of the high pressure relief valve 20 during relief, energy loss during operation of the low pressure relief valve is small.

Accordingly, when the drilling stroke is interrupted or one drilling stroke is completed and the drilling waste is discharged, when the bucket 16 is lifted while the kelly bar is contracted, the drilling blade of the bucket 16 bites into the ground. When the remote control device 6 is operated so as to suddenly switch the directional switching valve 4 in the forward rotation position to the reverse rotation position in order to reduce the lifting resistance of the telescopic kelly bar as well as when the directional switching valve is removed, the directional switching valve first receives the reverse rotation switching pressure receiving portion. 4B is returned to the neutral position by the spring while sucking the oil in the tank from the throttle passage 24, the driving of the hydraulic motor 1 is stopped and the low pressure relief valve 18 is closed.
While the hydraulic energy of 5 is discharged to the tank 3 from the throttle 21, the normally open valve 23 is closed for the time required for the twisting elasticity of the telescopic kelly bar to disappear.

Next, when the hydraulic energy of the pressure accumulator 25 is discharged to the tank, the normally open valve 23 spring-returns to the open position, so that the pilot hydraulic pressure is supplied from the pressure reducing valve 5B to the reverse rotation switching pilot operating portion 4B. Then, the directional control valve 4 is switched from the neutral position to the reverse position, and the hydraulic motor 1 reversely rotates the kelly bar or the bucket 16 to release the bite of the bucket excavating blade with respect to the ground so that the telescopic kerry bar can be lifted. And That is, since the hydraulic motor is driven by the pressure oil discharged from the hydraulic pump after the twisting reaction force of the kelly bar has disappeared, there is no possibility that the hydraulic motor will rotate excessively as in the conventional case.

Further, in order to discharge the excavated debris in the bucket 16 hoisted on the ground, when the bucket is swiftly switched between the forward and reverse directions to remove the mud by the inertia, the driving oil pressure of the hydraulic motor is changed. Since the pressure is lower than the set pressure of the low pressure relief valve 18, the normally open valve 23 remains open.

The case where the pressure accumulator 25 is used as the pressure accumulating means for holding the normally open valve 23 in the closed position for a substantially constant time has been described above. However, the discharge oil passage 22 between the relief valve 18 and the throttle 21 is made of a rubber tube. It is also possible to use such an elastic tube and use the discharge oil passage itself as a pressure accumulating means.

The low pressure relief valve 18 of the embodiment shown in FIG.
In place of the above, as shown in FIG. 3, a pressure switch 26 having a set pressure equivalent to that of the low pressure relief valve is connected to the high pressure side oil passage 2A between the directional control valve 4 and the hydraulic motor 1 at the time of drilling by the oil passage 19. Then, the pressure switch circuit 28 for closing the electromagnetically-operated normally open valve 23 'is activated by the signal when the contact C of the pressure switch 26 is closed when the pressure in the high pressure side oil passage 2A exceeds the set pressure. The pressure switch 26 is provided so as to reduce the pressure in the high pressure side oil passage 2A when the driving of the hydraulic motor 1 is stopped.
When the contact C of the C is opened, the return of the normally open valve 23 'to the open position (normal position) is delayed by the constant time required for the torsional elasticity of the telescopic kelly bar to disappear for a fixed time. Obviously, it may be incorporated in the circuit 28 or the like. It should be noted that, in FIG. 3, the parts given the same reference numerals as the parts shown in FIG. 1 are corresponding parts.

[0021]

According to the present invention, when suspending a telescopic kerry bar with a rotary drilling bucket biting at the bottom of a hole by a crane at the time of interrupting the boring of general soil and at the end of one boring stroke, a hydraulic motor Even if the remote control device is suddenly switched from the normal rotation position to the reverse rotation position, the hydraulic motor reverses hydraulically with a delay of a substantially constant time required for the torsional elasticity of the telescopic kerry bar that drives the drilling hydraulic motor to reverse rotation to disappear. Since it is configured to be driven, it is not necessary to stop the remote control device in the neutral position for a certain time or more when the rotary excavation bucket is hoisted by the crane as in the past, and it is not only possible to improve the drilling efficiency but also the driver's effort. In addition, the mud removal work to quickly switch the direction of rotation of the rotary excavation bucket on the surface of which the cutting debris has adhered can be performed in the same manner as in the past. An effect that can.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention.

FIG. 2 is a vertical sectional front view showing a schematic configuration of an earth drill.

FIG. 3 is a hydraulic and electric circuit diagram of another embodiment of the present invention.

[Explanation of symbols]

 1 Kelly bar drive hydraulic motor 2A Supply / exhaust oil passage 2B Supply / exhaust oil passage 4 Direction switching valve 4A Forward rotation switching pressure receiving portion 4B Reverse rotation switching pressure receiving portion 5A Pressure reducing valve 5B Pressure reducing valve 6 Remote control device 18 Low pressure relief valve 21 Throttle 22 Release Oil passage 23 Pilot operated normally open valve 23 'Electromagnetically operated normally open valve 24 Throttle passage 25 Pressure accumulator 26 Pressure switch 27 Timer 28 Pressure switch circuit

Claims (2)

[Claims] 1. A telescopic kelly bar having an inner end kerry bar having a rotary excavation bucket for storing cutting waste attached to a lower end thereof to be lifted and lowered by a crane sling, a rotary hydraulic motor for driving and rotating the outer end kelly bar, and a perforating telescopic kerry bar. A device for applying thrust and a direction switching valve, which is always urged to return to a neutral position in which both the oil supply and discharge oil passages for the hydraulic motor communicate with the tank, are pilot operated to a forward rotation position and a reverse rotation position for drilling, respectively. In the earth drill equipped with the remote control device including the pressure reducing valve, the normally open valve is inserted in the middle of the pilot oil passage between the reverse pressure switching pressure receiving portion of the direction switching valve and the corresponding pressure reducing valve, and The reversing switching pressure receiving portion and the tank are connected by a throttle passage so that the directional switching valve can be returned to the neutral position when the valve is closed, and the directional switching valve at the time of drilling. A low pressure relief valve with a small flow rate is connected to the high pressure side oil passage between the hydraulic motor and the hydraulic motor, and the set pressure of the low pressure relief valve is equal to or lower than the hydraulic motor drive pressure at the time of drilling and the rotary excavation at the time of discharging the cutting waste. The pressure is set to a pressure higher than the hydraulic motor drive pressure at the time of the forward / reverse cutback operation in the bucket rotation direction, and when the drilling drive of the hydraulic motor is stopped, the elastic force of the telescopic kelly bar that drives the hydraulic motor in the reverse direction is eliminated for the time necessary to disappear. A Kelly bar driving hydraulic pressure characterized in that a pressure accumulating means capable of holding the normally open valve in the closed position and a pilot operating portion of the normally open valve are connected to an upstream side of a throttle inserted in the discharge oil passage of the low pressure relief valve. Motor control device. 2. The invention according to claim 1, wherein, instead of the low pressure relief valve, a pressure switch having the same set pressure is connected to a high pressure side oil passage between the directional control valve and the hydraulic motor at the time of drilling. A pressure switch circuit for closing the electromagnetically-operated normally open valve when the contact point of the pressure switch is closed due to the pressure increase in the high-pressure side oil passage, and when the contact point of the pressure switch is opened by stopping the driving of the hydraulic motor for punching. Control of a Kelly bar driving hydraulic motor characterized by incorporating a timer in the pressure switch circuit for delaying the return of the normally open valve to the open position for a fixed time necessary for the torsional elasticity of the telescopic Kelly bar to disappear. apparatus.