JP7614973B2 - Regulators for drilling hydraulic motors - Google Patents

Description

This disclosure relates to a regulator for a hydraulic motor for drilling.

Conventionally, excavators equipped with a drilling unit that excavates a vertical hole in the ground have been known. Excavators are also called earth drills. The drilling unit includes a drilling shaft that extends vertically and a drilling bucket attached to the lower end of the drilling shaft. For example, Patent Document 1 discloses a drilling unit that uses a hydraulic motor as a rotating machine that rotates the drilling shaft.

JP 2008-255765 A

The hydraulic motor used in the drilling unit, i.e., the drilling hydraulic motor, is desirably of a variable displacement type so that the torque can be changed according to the drilling load. When the hydraulic motor is of a variable displacement type, the capacity of the hydraulic motor is changed by a regulator.

For example, when the excavation load is low, the regulator minimizes the hydraulic motor capacity, causing the hydraulic motor to rotate at low torque and high speed, and when the excavation load is high, the regulator maximizes the hydraulic motor capacity, causing the hydraulic motor to rotate at high torque and low speed.

When drilling a deep vertical hole in the ground, the drilling shaft of the drilling unit has a telescopic structure. With such a long drilling shaft, the shaft is significantly twisted when the bucket hits hard rock and drilling becomes impossible. Therefore, when an operator reverses the rotation of the hydraulic motor, the twist in the drilling shaft is released, causing the hydraulic motor to over-rotate, which may place excessive stress on the components of the hydraulic motor.

The present disclosure therefore aims to provide a regulator for a hydraulic motor for drilling that can reduce over-rotation of the hydraulic motor caused by the release of torsion in the drilling shaft.

The present disclosure relates to a regulator for changing the capacity of a hydraulic motor for drilling, comprising a small diameter portion and a large diameter portion, a servo piston in which an annular surface of the large diameter portion on the side of the small diameter portion faces a first pressure receiving chamber, and an end face of the large diameter portion opposite the small diameter portion faces a second pressure receiving chamber, the inlet pressure of the hydraulic motor is introduced into the first pressure receiving chamber, and the servo piston moves in a direction in which the capacity of the hydraulic motor decreases as the pressure introduced into the second pressure receiving chamber increases, and a first switching valve connected to an input path and a tank path through which the inlet pressure of the hydraulic motor is supplied and connected to the second pressure receiving chamber by a pressure regulating path, the pressure regulating path A regulator for a hydraulic motor for drilling is provided, which comprises a first switching valve that connects the first flow path to either the input path or the tank path, and a second switching valve that is interposed between a first flow path on the first switching valve side of the pressure regulating path and a second flow path on the second pressure receiving chamber side, and to which a bypass path branching off from the input path is connected, and the second switching valve connects the first flow path to the second flow path when the inlet pressure of the hydraulic motor is smaller than a set value and connects the bypass path to the second flow path when the inlet pressure of the hydraulic motor is larger than the set value under a condition in which the capacity of the hydraulic motor is maintained at a maximum by the first switching valve.

This disclosure makes it possible to reduce over-rotation of the hydraulic motor caused by the release of torsion in the drilling shaft.

FIG. 2 is a schematic configuration diagram of a regulator of a hydraulic motor for excavation according to one embodiment. FIG. 2A is a side view of the excavator, and FIG. 2B is an enlarged view of the excavator unit. FIG. 13 is a schematic configuration diagram of a regulator according to a modified example. FIG. 13 is a schematic configuration diagram of a regulator according to another modified example.

Figure 1 shows a regulator 2 for a hydraulic motor 9 for drilling according to one embodiment. The hydraulic motor 9 is included in a drilling unit 15 as shown in Figure 2B, and the drilling unit 15 is mounted on the excavator 1 as shown in Figure 2A.

The excavator 1 includes a frame 11 that extends vertically, and a drilling unit 15 is attached to this frame 11. The drilling unit 15 includes a base 16 that is connected to the frame 11, a drilling shaft 17 that extends vertically through the base 16, and a bucket 18 that is provided at the lower end of the drilling shaft 17. The drilling shaft 17 is supported on the base 16 so as to be rotatable and slidable vertically.

A reducer 19 is attached to the base 16, and a hydraulic motor 9 is attached to the reducer 19. The hydraulic motor 9 rotates the drilling shaft 17 in the drilling direction or anti-drilling direction via the reducer 19.

The excavation shaft 17 has a telescopic structure that can expand and contract. The excavation shaft 17 is moved up and down via a wire 13 by the hoisting unit 12 of the excavator 1, and is extended or shortened. More specifically, the excavation shaft 17 includes multiple tubular bodies of different diameters, and the nth tubular body counting from the outside is at least partially fitted into the n-1th tubular body. In the illustrated example, the number of tubular bodies is three, but this is not particularly limited.

As shown in FIG. 1, the hydraulic motor 9 has a pair of ports 91 and 92 that switch between being an inlet port and an outlet port depending on the direction of rotation. The ports 91 and 92 are connected to the supply and exhaust paths 9a and 9b, respectively.

The hydraulic motor 9 is a variable displacement axial piston motor. The hydraulic motor 9 includes a rotating unit composed of a plurality of pistons and a cylinder block, and a casing that houses the rotating unit. In this embodiment, the hydraulic motor 9 is a swash plate motor having a swash plate 90.

The regulator 2 changes the capacity of the hydraulic motor 9. Specifically, the regulator 2 includes a servo piston 4 and a housing 20 that slidably holds the servo piston 4. Furthermore, the regulator 2 includes a first switching valve 5 and a second switching valve 7 incorporated in the housing 20.

The housing 20 may be divided into a part that holds the servo piston 4, a part that incorporates the first switching valve 5, and a part that incorporates the second switching valve 7. The housing 20 may also be integrated with the casing of the hydraulic motor 9.

The regulator 2 is supplied with the inlet pressure Pi of the hydraulic motor 9 through the input path 3. The input path 3 includes a pair of selection paths 31, 32 connected to the supply and discharge paths 9a, 9b, and a supply path 33 where these selection paths 31, 32 join. Check valves 35, 36 are provided in the selection paths 31, 32, respectively. In other words, the higher of the pressures in the supply and discharge paths 9a, 9b is the inlet pressure Pi, and this inlet pressure Pi is guided to the supply path 33 through the corresponding selection path 31 or 32.

The servo piston 4 includes a small diameter portion 41 and a large diameter portion 42. The annular surface of the large diameter portion 42 on the small diameter portion 41 side faces the first pressure receiving chamber 4a, and the end face of the large diameter portion 42 opposite the small diameter portion 41 faces the second pressure receiving chamber 4b.

As described above, in this embodiment, the hydraulic motor 9 has a swash plate 90, and the servo piston 4 is connected to the swash plate 90. When the servo piston 4 moves in the direction from the large diameter portion 42 to the small diameter portion 41, the capacity of the hydraulic motor 9 decreases, and when the servo piston 4 moves in the direction from the small diameter portion 41 to the large diameter portion 42, the capacity of the hydraulic motor 9 increases. Hereinafter, the direction from the large diameter portion 42 to the small diameter portion 41 is referred to as the "capacity decreasing direction," and the direction from the small diameter portion 41 to the large diameter portion 42 is referred to as the "capacity increasing direction."

The first pressure receiving chamber 4a is connected to the supply path 33 of the input path 3 described above. In other words, the inlet pressure Pi of the hydraulic motor 9 is introduced into the first pressure receiving chamber 4a. The second pressure receiving chamber 4b is connected to the first switching valve 5 by the pressure adjustment path 6. The second switching valve 7 is disposed on the pressure adjustment path 6.

The servo piston 4 moves in the flow rate reducing direction as the pressure introduced into the second pressure receiving chamber 4b increases. When the pressure introduced into the second pressure receiving chamber 4b becomes greater than a predetermined value corresponding to the area difference between the first pressure receiving chamber 4a and the second pressure receiving chamber 4b and the servo piston 4 moves in the flow rate reducing direction until it abuts against the minimum side stopper, the capacity of the hydraulic motor 9 becomes minimum. On the other hand, when the pressure introduced into the second pressure receiving chamber 4b becomes smaller than the predetermined value and the servo piston 4 moves in the capacity increasing direction until it abuts against the maximum side stopper, the capacity of the hydraulic motor 9 becomes maximum.

The input path 3 also includes a branch path 34 that branches off from the supply path 33. The branch path 34 is connected to the first switching valve 5. The first switching valve 5 is also connected to a tank path 5a. The tank path 5a communicates with the space inside the casing of the hydraulic motor 9 and with the tank via piping that connects the casing to the tank.

The first switching valve 5 connects the pressure regulation passage 6 to either the branch passage 34 or the tank passage 5a. In this embodiment, the first switching valve 5 is a two-position valve that can be switched between a first position, which is the left position in FIG. 1, and a second position, which is the right position in FIG. 1. In this embodiment, the first position is a neutral position. In the first position, the first switching valve 5 connects the pressure regulation passage 6 to the tank passage 5a, and in the second position, the branch passage 34 connects the pressure regulation passage 6. However, contrary to this embodiment, the second position may be a neutral position. In addition, the first switching valve 5 may be a three-position valve having a third position between the first and second positions that blocks all flow paths connected to the first switching valve 5.

More specifically, the first switching valve 5 includes a sleeve 52 slidably held in the housing 20, and a spool 51 slidably held in the sleeve 52. The spool 51 is connected to the servo piston 4 via a spring 46 and a feedback lever 45. In other words, the position of the servo piston 4 is fed back to the spool 51.

With this structure, when the first switching valve 5 is in the second position, the pressure Ps introduced into the second pressure receiving chamber 4b is adjusted so that the forces acting on both sides of the large diameter portion 42 of the servo piston 4 are balanced. In other words, when the first switching valve 5 is in the second position, the pressure Ps introduced into the second pressure receiving chamber 4b is adjusted by connecting the pressure regulating passage 6 with the branch passage 34. The adjusted pressure Ps is smaller than the inlet pressure Pi of the hydraulic motor 9.

In this embodiment, the first switching valve 5 is driven by an electrical signal. The first switching valve 5 is electrically connected to the control device 21, and is switched from the first position to the second position when a command current is sent from the control device 21. The control device 21 is also electrically connected to pressure sensors 22 and 23 provided in the supply and discharge paths 9a and 9b. The higher of the pressures in the supply and discharge paths 9a and 9b is detected by the pressure sensor 22 or 23 as the inlet pressure Pi.

With respect to the control device 21, the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general purpose processors, special purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and/or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. If the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and/or the processor.

In this embodiment, when the inlet pressure Pi of the hydraulic motor 9 detected by the pressure sensor 22 or 23 is lower than the first set value α and the load is low, the control device 21 supplies a command current to the first switching valve 5 to switch the first switching valve 5 to the second position. This adjusts the pressure Ps introduced into the second pressure receiving chamber 4b as described above. As a result, the hydraulic motor 9 rotates with a torque and rotation speed according to the inlet pressure Pi.

On the other hand, when the hydraulic motor 9 is under high load and the inlet pressure Pi detected by the pressure sensor 22 or 23 is greater than the first set value α, the control device 21 stops supplying a command current to the first switching valve 5. This causes the first switching valve 5 to return to the first position, and the pressure regulating path 6 communicates with the tank path 5a. As a result, the pressure in the second pressure receiving chamber 4b becomes nearly zero, and the capacity of the hydraulic motor 9 becomes maximum. Therefore, the hydraulic motor 9 rotates with high torque and low rotation speed.

However, the first switching valve 5 does not necessarily have to be switched based on the inlet pressure Pi of the hydraulic motor 9. For example, a capacity selection switch may be employed to allow the operator to select whether or not to fix the capacity at a large capacity, and the control device 21 may supply a command current to the first switching valve 5 to switch the first switching valve 5 to the second position unless the capacity selection switch selects to fix the capacity at a large capacity. The first switching valve 5 may also be driven by a pilot pressure. That is, the first switching valve 5 may have a pilot chamber for moving the spool 51, and the solenoid proportional valve connected to this pilot chamber may be controlled by the control device 21.

The second switching valve 7 is interposed between the first flow path 61 on the first switching valve 5 side of the pressure regulating path 6 and the second flow path 62 on the second pressure receiving chamber 4b side. A bypass path 75 branching off from the supply path 33 is connected to the second switching valve 7.

The second switching valve 7 functions as a safety valve under high load conditions, in other words, when the capacity of the hydraulic motor 9 is maintained at its maximum by the first switching valve 5. The second switching valve 7 is a two-position valve that can be switched between a first position, which is the left position in FIG. 1, and a second position, which is the right position in FIG. 1. In this embodiment, the first position is the neutral position. In the first position, the second switching valve 7 connects the first flow path 61 to the second flow path 62, and in the second position, the second switching valve 7 connects the bypass path 75 to the second flow path 62.

In this embodiment, the second switching valve 7 is driven by pilot pressure. The second switching valve 7 includes a spool 71 slidably held in the housing 20. The second switching valve 7 further includes a first pilot chamber 72 for moving the spool 71 in a direction for switching from the second position to the first position, and a second pilot chamber 73 for moving the spool 71 in a direction for switching from the first position to the second position.

The first pilot chamber 72 is connected to a first pilot flow path 81 that branches off from the first flow path 61 of the pressure regulating path 6. Therefore, when the first switching valve 5 is in the second position and the load is low, the pressure Ps adjusted by the first switching valve 5 is introduced into the first pilot chamber 72, and when the first switching valve 5 is in the first position and the load is high, the pressure in the first pilot chamber 72 becomes almost zero.

The second pilot chamber 73 is connected to a second pilot flow path 82 that branches off from the bypass path 75. The second pilot flow path 82 may branch off from the supply path 33 or the branch path 34 of the input path 3. Therefore, the inlet pressure Pi of the hydraulic motor 9 is introduced into the second pilot chamber 73. A throttle 83 is provided in the second pilot flow path 82.

The second switching valve 7 switches from the first position to the second position when the pressure in the second pilot chamber 73 becomes greater than the pressure in the first pilot chamber 72 plus the second set value β. The second set value β is a value greater than the first set value α used to determine whether the load is low or high as described above. The second set value β is also set to be greater than the maximum inlet pressure Pm of the hydraulic motor 9 expected during rotation of the bucket 18, i.e., during excavation.

The hydraulic circuit including the hydraulic motor 9 includes a relief valve. The first set value α is 70-90% of the relief pressure of the relief valve, and the second set value β is a value between the first set value α and the relief pressure. For example, the relief pressure of the relief valve is 34 MPa, the first set value is 30 MPa, and the second set value is 31-33 MPa.

When the load is low, i.e., when Pi<α, the pressure Ps introduced into the second pressure receiving chamber 4b is adjusted by the first switching valve 5 as described above, so that the pressure difference between the inlet pressure Pi of the hydraulic motor 9 introduced into the second pilot chamber 73 and the pressure Ps introduced into the first pilot chamber 72 does not become greater than the second set value β. Therefore, the second switching valve 7 is maintained in the first position.

On the other hand, when the load is high, i.e., when Pi>α, the pressure in the first pilot chamber 72 is almost zero, but as described above, the second set value β is set to be greater than the maximum inlet pressure Pm of the hydraulic motor 9 expected during excavation, so the second switching valve 7 is maintained in the first position while the bucket 18 is rotating.

When the bucket 18 hits hard rock and becomes unable to excavate, the inlet pressure Pi of the hydraulic motor 9 rises further and exceeds the second set value β. Then, the second switching valve 7 switches from the first position to the second position, and the bypass 75 communicates with the second flow path 62 of the pressure regulating path 6. This introduces the inlet pressure Pi of the hydraulic motor 9 into the second pressure receiving chamber 4b, minimizing the capacity of the hydraulic motor 9 and reducing the torque of the hydraulic motor 9. As a result, even if the drilling shaft 17 is significantly twisted before the inlet pressure Pi of the hydraulic motor 9 exceeds the second set value β, the torsion of the drilling shaft 17 is eliminated by the amount of the reduction in the torque of the hydraulic motor 9. Therefore, the rotation speed of the hydraulic motor 9 during reverse rotation can be reduced compared to when the drilling shaft 17 is significantly twisted.

In other words, even if the operator issues a command to the hydraulic motor 9 to rotate in reverse to resolve a state in which excavation is not possible, the hydraulic motor 9 rotates in reverse with the torsion of the drilling shaft 17 eliminated by the amount of torque reduction, so over-rotation of the hydraulic motor 9 caused by the release of the torsion of the drilling shaft 17 can be reduced.

Furthermore, in this embodiment, a restriction 83 is provided in the second pilot flow path 82, so that the second switching valve 7 can be prevented from switching due to the surge pressure of the hydraulic motor 9, i.e., a sudden change in the inlet pressure Pi.

(Modification)
The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

For example, the second switching valve 7 does not necessarily need to be driven by pilot pressure, but may be driven by an electrical signal. However, if configured as in the above embodiment, the second switching valve 7 can be automatically switched.

Also, as in the modified regulator 2A shown in FIG. 3, two throttles 63, 64 may be provided in the first flow path 61 of the pressure regulating path 6. In this case, a bypass 65 may be provided to bypass one of the throttles 63 or 64, and a check valve 66 may be provided in this bypass 65 to permit flow from the second switching valve 7 to the first switching valve 5 but prohibit flow in the opposite direction.

Various configurations can be adopted for the first switching valve 5. For example, as shown in FIG. 3, the second position may be a neutral position, and the first switching valve 5 may include a piston 53 that pushes the spool 51 in a direction to switch from the second position to the first position. In the example shown in FIG. 3, the first switching valve 5 includes two pilot chambers 54, 55 for operating the piston 53. One pilot chamber 54 is connected to the supply path 33 by a pilot flow path 5b, and a signal pressure is introduced to the other pilot chamber 55 through a pilot flow path 5c. For example, the signal pressure is normally set to zero, and is set to a high pressure when the operator wants to fix it at a large capacity.

In the example shown in FIG. 3, the feedback lever 45 is connected to the sleeve 52, and the position of the servo piston 4 is fed back to the sleeve 52.

Alternatively, as in the modified regulator 2B shown in FIG. 4, the position of the servo piston 4 does not have to be fed back to the first switching valve 5. In the example shown in FIG. 4, the first switching valve 5 includes a pilot chamber 56 for moving the spool 51 in a direction to switch from the second position to the first position, and this pilot chamber 56 is connected to the supply path 33 by a pilot flow path 5d.

(summary)
The present disclosure relates to a regulator for changing the capacity of a hydraulic motor for excavation, comprising a servo piston including a small diameter portion and a large diameter portion, an annular surface of the large diameter portion on the side of the small diameter portion facing a first pressure receiving chamber, and an end face of the large diameter portion opposite the small diameter portion facing a second pressure receiving chamber, wherein an inlet pressure of the hydraulic motor is introduced into the first pressure receiving chamber, and the servo piston moves in a direction in which the capacity of the hydraulic motor decreases as the pressure introduced into the second pressure receiving chamber increases, and a first switching valve connected to an input path and a tank path through which the inlet pressure of the hydraulic motor is supplied, and connected to the second pressure receiving chamber by a pressure regulating path, a first switching valve that connects a first passage on the first switching valve side of the pressure regulating passage to either the input passage or the tank passage; and a second switching valve that is interposed between a first passage on the first switching valve side of the pressure regulating passage and a second passage on the second pressure receiving chamber side, and to which a bypass passage branching off from the input passage is connected, the second switching valve being configured to connect the first passage with the second passage when an inlet pressure of the hydraulic motor is smaller than a set value and to connect the bypass passage with the second passage when the inlet pressure of the hydraulic motor is larger than the set value under a condition in which a maximum capacity of the hydraulic motor is maintained by the first switching valve.

According to the above configuration, when the hydraulic motor is under high load and the inlet pressure is greater than the first set value, the first switching valve connects the pressure regulation path to the tank path, so that the pressure in the second pressure receiving chamber becomes almost zero and the capacity of the hydraulic motor becomes maximum. Therefore, the hydraulic motor rotates at high torque and low rotation speed. In this state, if the bucket hits hard rock and becomes unable to excavate, and the inlet pressure of the hydraulic motor further increases and exceeds the second set value, the second switching valve connects the bypass path to the second flow path of the pressure regulation path. As a result, the inlet pressure of the hydraulic motor is introduced into the second pressure receiving chamber, the capacity of the hydraulic motor becomes minimum, and the torque of the hydraulic motor decreases. As a result, even if the drilling shaft is significantly twisted before the inlet pressure of the hydraulic motor exceeds the second set value, the twist of the drilling shaft is eliminated by the amount of the reduction in the torque of the hydraulic motor. Therefore, the over-rotation of the hydraulic motor caused by the release of the twist of the drilling shaft can be reduced.

The second switching valve is switched between a first position in which the first flow path is connected to the second flow path and a second position in which the bypass is connected to the second flow path, and the second switching valve includes a spool, a first pilot chamber for moving the spool in a direction to switch from the second position to the first position, and a second pilot chamber for moving the spool in a direction to switch from the first position to the second position, and a first pilot flow path branching from the first flow path of the pressure regulating path may be connected to the first pilot chamber, and a second pilot flow path branching from the bypass or the input path may be connected to the second pilot chamber. With this configuration, the second switching valve can be automatically switched.

A throttle may be provided in the second pilot flow passage. This configuration makes it possible to prevent the second switching valve from switching due to surge pressure of the hydraulic motor, i.e., a sudden change in the inlet pressure.

For example, the hydraulic motor may include a swash plate and the servo piston may be coupled to the swash plate.

REFERENCE SIGNS LIST 15 Excavation unit 17 Excavation shaft 2 Regulator 3 Input path 4 Servo piston 41 Small diameter portion 42 Large diameter portion 4a First pressure receiving chamber 4b Second pressure receiving chamber 5 First switching valve 5a Tank path 6 Pressure adjusting path 61 First flow path 62 Second flow path 7 Second switching valve 71 Spool 72 First pilot chamber 73 Second pilot chamber 75 Bypass path 81 First pilot flow path 82 Second pilot flow path 83 Throttle 9 Hydraulic motor 90 Swash plate

Claims (4)

A regulator for varying the displacement of a hydraulic motor for drilling, comprising:
a servo piston including a small diameter portion and a large diameter portion, an annular surface of the large diameter portion on the side of the small diameter portion facing a first pressure receiving chamber, and an end face of the large diameter portion opposite the small diameter portion facing a second pressure receiving chamber, wherein an inlet pressure of the hydraulic motor is introduced into the first pressure receiving chamber, and the servo piston moves in a direction in which the capacity of the hydraulic motor decreases as the pressure introduced into the second pressure receiving chamber increases;
a first switching valve to which an input passage to which an inlet pressure of the hydraulic motor is supplied and a tank passage are connected and which is connected to the second pressure receiving chamber by a pressure adjustment passage, the first switching valve communicating the pressure adjustment passage with either the input passage or the tank passage;
a second switching valve, which is interposed between a first flow path on the first switching valve side of the pressure regulating path and a second flow path on the second pressure receiving chamber side, and to which a bypass path branching off from the input path is connected, the second switching valve communicating the first flow path with the second flow path when an inlet pressure of the hydraulic motor is smaller than a set value and communicating the bypass path with the second flow path when the inlet pressure of the hydraulic motor is larger than the set value under a condition in which a maximum capacity of the hydraulic motor is maintained by the first switching valve;
A regulator for a hydraulic motor for drilling comprising: the second switching valve is switched between a first position in which the first flow path is connected to the second flow path and a second position in which the bypass path is connected to the second flow path,
the second switching valve includes a spool, a first pilot chamber for moving the spool in a direction for switching from the second position to the first position, and a second pilot chamber for moving the spool in a direction for switching from the first position to the second position,
2. The regulator of a hydraulic motor for excavation according to claim 1, wherein a first pilot flow passage branching from a first flow passage of the pressure regulating passage leads to the first pilot chamber, and a second pilot flow passage branching from the bypass passage or the input passage leads to the second pilot chamber. The regulator of a hydraulic motor for drilling according to claim 2, wherein the second pilot flow passage is provided with a restriction. the hydraulic motor includes a swash plate;
4. A regulator for a hydraulic motor for drilling as claimed in claim 1, wherein the servo piston is connected to the swash plate.

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