JP2013050019A - Self-weight descent mechanism and self-weight descent method for gate using hydraulic piston motor as driving source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which enables a hydraulic fluid with pressure to be continuously supplied to a hydraulic piston motor for ascent/descent of a gate until the complete descent of the gate without use of an electric power source when the gate descends by self-weight.SOLUTION: A hydraulic motor for boost pressure and a hydraulic pump for boost pressure, which is driven by the hydraulic motor for boost pressure, are provided. When a gate 3 descends by self-weight, a hydraulic piston motor 7 runs by utilizing rotation of a wire drum 3 wound with a wire 2 connected to the gate. An outlet side in the case of the action of the hydraulic piston motor as a hydraulic brake and an inlet side of the hydraulic motor for boost pressure are connected together to make the hydraulic motor for boost pressure run by hydraulic pressure generated by the running of the hydraulic piston motor. An outlet side of the hydraulic pump for boost pressure and an inlet side in the case of the action of the hydraulic piston motor as the hydraulic brake are connected together to make a hydraulic fluid with pressure supplied to the hydraulic piston motor.

Description

  The present invention provides a self-weight drop mechanism for a gate that allows a self-weight drop without using a power source when the gate of a wire drum type sluice gate using a hydraulic piston motor requiring a boost pressure as a drive source is lowered. And a method for lowering the dead weight.

  Conventionally, the gate of a wire drum type sluice gate is generally raised by an electric motor or a hydraulic motor. In addition, the gate weight of the sluice gate is lowered by the gate weight while the hydraulic pump or hydraulic motor acts as a hydraulic brake and the amount of oil is adjusted to adjust the descent speed.

  For example, as shown in Patent Document 1, when an electric motor is used to raise the gate and a hydraulic pump is used to adjust the speed when descending, the lowering hydraulic pump is used for adjusting the descending speed. Therefore, a general gear pump can be used. In this case, the brake force is adjusted by adjusting the discharge amount from the gear pump, and the gate lowering speed is adjusted.

  On the other hand, when the gate is raised and lowered by a single hydraulic motor, a corresponding driving force is required to raise the gate, so use a piston motor that can easily secure the driving force. There is a need. A rotary hydraulic motor such as a gear pump with a lot of oil leakage and poor output efficiency is not suitable for a purpose of raising a heavy gate.

  Incidentally, when the hydraulic piston motor is rotated by a load, the suction side (inlet side) hydraulic oil needs to be supplied with a certain amount of boost pressure in order to prevent the occurrence of cavitation. For example, in the case of an axial piston motor, a boost pressure of 0.2 MPa or more is required. Therefore, when the hydraulic piston motor is operated as a hydraulic brake when the gate is lowered, the hydraulic oil supplied to the inlet side needs to have a necessary boost pressure.

  When operating the hydraulic piston motor as a hydraulic brake when the gate weight drops, the operation discharged from the hydraulic piston motor outlet side is one way to supply hydraulic oil with boost pressure to the suction side (inlet side) port. There is a method of circulating oil directly to the port on the inlet side. In this case, no electric power is required to circulate the hydraulic oil. However, since the heat generated during the gravity drop is received with a limited amount of oil in the piping, an oil cooler or a flushing circuit is required. Therefore, a power source for that purpose is required, and therefore it cannot be used when the power source is lost.

  On the other hand, in order to avoid the heat generation, it is conceivable to return the hydraulic oil discharged from the hydraulic piston motor outlet side to the tank and supply it from the tank to the hydraulic piston motor inlet side through a separate line. In this case, since it is only necessary to receive heat from the entire oil in the tank, it is not necessary to provide an oil cooler. In this case, when the power source is available, the hydraulic pump is driven by an electric motor, and hydraulic oil having the necessary boost pressure is supplied from the hydraulic pump to the suction side (inlet side) of the hydraulic piston motor. It can function as a hydraulic brake and adjust the speed of descending its own weight.

JP 2006-97822 A

  However, since the electric motor cannot be used in the case of power loss, it is necessary to drive the hydraulic pump by some method and supply hydraulic oil having the necessary boost pressure to the suction side of the hydraulic piston motor. For example, even when the power supply is lost during a disaster, it may be necessary to lower the gate at a safe speed and close it. It is an important issue to be able to supply the hydraulic piston motor continuously until the gate is fully lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to use a hydraulic piston motor that requires boost pressure as a drive source without lowering the weight of the gate without using a power source. Hydraulic oil with the necessary boost pressure is supplied to the suction side of the hydraulic piston motor so that the hydraulic piston motor can act as a hydraulic brake without causing cavitation. It is to provide a mechanism and a method for lowering its own weight.

  In order to achieve the above object, the gate weight drop method using a hydraulic piston motor as a driving source according to the present invention is a method in which the gate is suspended by a wire, the wire is wound around a wire drum, and the wire drum is boosted pressure. In a sluice gate that is rotated by a hydraulic piston motor that needs to be moved and the gate is raised and lowered by the hydraulic piston motor, the hydraulic piston motor acts as a hydraulic brake to reduce the speed of the gate's own weight lowering When the gate descends due to its own weight, the hydraulic piston motor is rotated using the rotation of the wire drum around which the wire connecting the gate is wound, and the hydraulic pump is operated as a hydraulic pump. The hydraulic pressure generated by this rotation The strike pressure hydraulic motor is rotated, the boost pressure hydraulic pump is driven by the rotation of the boost pressure hydraulic motor, and hydraulic oil having pressure is supplied from the oil tank to the hydraulic piston motor by the boost pressure hydraulic pump. It is characterized by that.

  Further, the self-weight lowering mechanism of the gate using the hydraulic piston motor according to the present invention as a drive source is a hydraulic piston in which the gate is suspended by a wire, the wire is wound around a wire drum, and the wire drum requires a boost pressure. In a sluice gate rotated by a motor and lifted and lowered by the hydraulic piston motor, the hydraulic piston motor acts as a hydraulic brake to adjust the speed of lowering the weight of the gate. A boost pressure hydraulic motor and a boost pressure hydraulic pump driven by the boost pressure hydraulic motor are provided, and when the gate is lowered due to its own weight, the rotation of the wire drum around which the wire connecting the gate is wound is used. Rotate the hydraulic piston motor to make a hydraulic brake The hydraulic pressure generated by the rotation of the hydraulic piston motor by connecting the outlet side when the hydraulic piston motor acts as a hydraulic brake when the gate is lowered and the inlet side of the boost pressure hydraulic motor. The hydraulic oil for boost pressure is rotated by the hydraulic pressure, and the outlet side of the hydraulic pump for boost pressure is connected to the inlet side when the hydraulic piston motor acts as a hydraulic brake when the gate is lowered, and the hydraulic oil has a boost pressure. Is supplied to the hydraulic piston motor.

  In the present invention, it is preferable that the hydraulic oil discharged from the boost pressure hydraulic motor is returned to the oil tank, and an inlet side of the boost pressure hydraulic pump is connected to the oil tank.

  In the present invention, the hydraulic oil discharged from the boost pressure hydraulic motor is bifurcated, a part is returned to the oil tank, and the rest is connected to the outlet side of the boost hydraulic pump. It is preferable that the hydraulic oil discharged from the hydraulic pump is supplied to the hydraulic piston motor, and the inlet side of the boost pressure hydraulic pump is connected to the oil tank.

  According to the present invention, when a gate using a hydraulic piston motor requiring a boost pressure as a driving source is lowered by its own weight, the boost pressure required on the suction side of the hydraulic piston motor is obtained by using the action of the gate being lowered by its own weight. Since the hydraulic piston motor can be operated as a hydraulic brake by supplying the hydraulic oil having it, the hydraulic piston motor can be operated as a hydraulic brake even when the power supply is lost, and the gate can be lowered by its own weight while adjusting the lowering speed. It becomes possible.

  Similarly, when a gear pump with relatively good suction performance is used instead of a piston motor as a hydraulic brake for lowering its own weight in a wire drum sluice gate, the tank and gear pump that are the supply source of hydraulic oil are remotely located and piping Even when the required suction cannot be ensured due to loss, the boost pressure hydraulic pump and boost pressure hydraulic motor configured as in the present invention are provided, the boost pressure hydraulic motor is rotated by the gear pump, and the boost pressure hydraulic motor is used for boost pressure. It is an effective means to drive the hydraulic pump and supply hydraulic oil having pressure to the suction side of the gear pump by the boost pressure hydraulic pump.

It is a schematic explanatory drawing which shows an example of the dead weight fall mechanism of the gate which used the hydraulic piston motor of this invention as a drive source. It is a hydraulic unit circuit diagram of the self-weight lowering mechanism of the gate which uses the hydraulic piston motor of this invention shown in Example 1 as a drive source. It is explanatory drawing for demonstrating the principal part of the dead weight fall mechanism of the gate which uses the hydraulic piston motor of this invention shown in Example 1 as a drive source. It is a hydraulic unit circuit diagram of the self-weight fall mechanism of the gate which used the hydraulic piston motor of this invention shown in Example 2 as a drive source.

Prior to the description of the embodiments, the hydraulic piston motor, boost pressure and boost pressure hydraulic motor used in the present invention will be described.
The hydraulic piston motor used in the present invention is also referred to as a hydraulic plunger motor. For example, an axial piston motor, a star piston motor, a multi-stroke piston motor, or the like can be used. Further, the hydraulic piston motor may have its drive shaft directly connected to the wire drum or may be attached via a reduction gear.

  When the hydraulic piston motor is rotated by a load, that is, when it functions as a pump, the hydraulic oil is viscous and therefore has a large suction resistance. Therefore, the hydraulic oil is not sufficiently sucked into the cylinder when the piston is lowered. The internal pressure may drop and cavitation may occur. Therefore, in order to prevent the occurrence of cavitation, it is necessary to always supply the hydraulic oil to the suction side (inlet side) with a pressure higher than a certain level, and the pressure exceeding the required level becomes the boost pressure.

  The required boost pressure varies depending on the type and rotation speed of the hydraulic piston motor, the viscosity of the hydraulic oil used, and the oil temperature. For example, in the case of an axial piston motor, it depends on the number of rotations used, but about 0.2 MPa or more. Boost pressure is required. Further, when the pipeline is long, the pipeline resistance is large, and the pressure loss is large, a boost pressure with a margin is required.

  On the other hand, the hydraulic oil having the required boost pressure is sent from the boost pressure hydraulic pump to the suction side of the hydraulic piston motor, and the boost pressure hydraulic pump is driven by the boost pressure hydraulic motor. The boost pressure hydraulic motor is driven by the hydraulic oil discharged by the hydraulic piston motor being rotated by its own weight drop and functioning as a pump. Therefore, in order to generate the necessary boost pressure, it is necessary to satisfy the formula Po × Q ≧ (Pi + α) × Q in FIG. 3 described later. Note that Po is the pressure of hydraulic oil discharged when the hydraulic piston motor is rotated due to its own weight drop, Pi is the boost pressure of hydraulic oil supplied to the hydraulic piston motor (as described above, for example, 0.2 MPa Α is the pressure loss, and Q is the flow rate of the hydraulic oil.

  Next, an embodiment of a self-weight drop mechanism and a self-weight drop method using the hydraulic piston motor of the present invention as a drive source will be described with reference to the drawings.

  As shown in FIG. 1, the sluice gate 1 includes a gate 3 of its own weight W suspended by a wire 2, a wire drum 4 around which the wire 2 is wound, a reduction gear 5 and a hydraulic push-up brake 6. 4 and a hydraulic unit 8 that controls the rotation of the hydraulic piston motor 7. These configurations are the same as those of a conventionally used wire drum type sluice gate except for a boost pressure motor and a boost pressure pump described later.

  As the hydraulic piston motor 7, for example, an axial piston motor that requires a boost pressure of 0.2 MPa or more is used, but other types of hydraulic piston motors described above may be used. In the present invention, the hydraulic piston motor 7 is provided with a mechanical brake 7a, but the mechanical brake is not necessarily provided. For example, when the brake is operating, the brake torque is generated by the force that presses the friction plate against the counterpart plate with a spring, and when a pressure higher than the spring force is applied to the brake release port, the brake plunger presses the spring, The friction plate is separated from the mating plate so that the brake is released. Further, the reduction gear 5 can be appropriately selected as necessary, and may not be necessary. In the illustrated example, an example in which two wire drums 4 are used is shown, but the number of wire drums is not limited.

The hydraulic unit 8 includes a pressure source 9 mainly composed of a hydraulic pump, an operation panel 10 composed of various valves and instruments, and an oil tank 11 for hydraulic oil. Hereinafter, details of the hydraulic unit 8 will be described together with the operation of raising and lowering the gate 3 with reference to the hydraulic unit circuit diagram shown in FIG.

First, the case where the gate 3 is raised will be described. In this case, it is wound up by a normal method.
A hydraulic pump 12 for driving a hydraulic piston motor 7 connected to the wire drum 4 is driven by an electric motor 13. The hydraulic oil in the oil tank 11 is sent from the port A of the hydraulic piston motor 7 through the solenoid valve 14, the stop valve 15, the counter balance valve 27, and the stop valve 16 to the motor casing by the hydraulic pump 12, and the motor is rotated. The hydraulic oil is discharged from the port B and is returned to the oil tank 11 through the stop valve 17, the stop valve 18, the electromagnetic valve 14, and the return filter 25. When the wire drum 4 is rotated to wind the wire 2 around the wire drum 4 to raise the gate 3, the hydraulic piston motor 7 is rotated by the hydraulic pump 12 in this manner to rotate the wire drum 4.

Next, the case where the gate 3 is lowered by its own weight when the power source is lost will be described.
First, the stop valve 20 is closed. Then, the manual pump lever 26 is operated to generate the brake release pressure, the mechanical brake 7a of the hydraulic piston motor 7 is released to make the hydraulic piston motor 7 free, the stop valve 19 is opened, and the opening degree of the flow control valve 21 is increased. Adjust as appropriate. Then, the lock of the hydraulic push-up brake 6 is released. Then, the gate 3 starts to fall due to its own weight by opening the hydraulic closing circuit. When the gate 3 is lowered, the wire 2 is unwound from the wire drum 4, and the wire drum 4 is rotated in the direction opposite to that during winding.

  The flow control valve 21 is preferably a pressure compensation type that can stably adjust the flow rate. Even if the mechanical brake 7a of the hydraulic piston motor 7 is not necessarily provided, since the counter balance valve 27 is provided between the stop valves 15 and 16, the hydraulic piston motor 7 can hold the stopped state.

  When the wire drum 4 rotates in the direction opposite to that at the time of winding, the hydraulic piston motor 7 also rotates in the reverse direction. Since the hydraulic piston motor 7 functions as a pump by being rotated by the rotation of the wire drum 4, the hydraulic oil is discharged from the port A and passes through the stop valve 16, the stop valve 19, and the flow control valve 21, and the boost pressure hydraulic motor 22. And is returned to the oil tank 11 through the return filter 25.

  On the other hand, when the boost pressure hydraulic motor 22 rotates, the boost pressure hydraulic pump 23 connected thereto is rotated. The hydraulic oil in the oil tank 11 is sent to the port B of the hydraulic piston motor 7 through the check valve 24 and the stop valve 17 by the rotation of the boost pressure hydraulic pump 23. In this way, while the gate 3 is dropping its own weight, the boost pressure hydraulic pump 23 is driven by rotating the boost pressure hydraulic motor 22 with the hydraulic oil discharged from the hydraulic piston motor 7, and the boost pressure is reduced. The hydraulic oil which has is supplied to the hydraulic piston motor 7.

  Next, the relationship between the hydraulic piston motor 7 and the boost pressure hydraulic pump 23 according to the present invention will be described in detail with reference to FIG. FIG. 3 is for explaining the relationship among the hydraulic piston motor 7, the boost pressure hydraulic motor 22, and the boost pressure hydraulic pump 23, which are essential parts of the present invention, and other elements are omitted. Moreover, the following shows numerical values as an example, and the present invention is not limited to these numerical values.

The hydraulic piston motor 7 is an axial piston motor with a rated pressure of 27.5 MPa, a required oil amount of 65 L / min, a capacity of 175 cm ³ per rotation, and a required minimum boost pressure of 0.2 MPa. The gate 3 has its own weight W of about 160 tons. If the total number of wire rope suspensions is 12 and the total sheave efficiency is 0.834, the wire rope tension at the time of winding is 110.567 kN. If the drum diameter of the wire drum 3 is 1.526 m and the drum efficiency is 0.95, the drum torque at the time of lowering is 160.288 kN · m. Here, when the total reduction ratio of the gear and the reduction gear is 892.222 and the operation efficiency of the gear and the reduction gear is 0.875, the reduction gear input shaft torque at the time of lowering is 0.157 kN · m. The hydraulic piston motor 7 has a capacity of 175 cm ³ per rotation at an oil flow rate of 65 L / min, and the input shaft torque at the time of lowering is 0.157 kN · m. The pressure is 5.637 MPa. Therefore, when the pressure loss is taken into consideration, the power generated when the weight of the gate drops is about 5 kW.

On the other hand, the boost pressure hydraulic motor 22 is a gear motor with a rated pressure of 15.7 MPa and a discharge amount of 51 cm ³ per one rotation of the pump shaft. The boost pressure hydraulic pump 23 is a working hydraulic feed pump with a discharge pressure of 2.0 MPa (0.5 MPa). With a relief valve), the discharge amount per rotation of the pump shaft is 65 cm ³ (97.5 L / min at 1500 rpm), and the hydraulic oil tank capacity is 630 L. In consideration of pressure loss and the like, it is desirable to select a boost pressure hydraulic pump 23 having a discharge amount of about 1.1 times or more the amount of oil discharged from the hydraulic piston motor 7.

  As described above, the power generated when the gate falls by its own weight is about 5 kW. On the other hand, the boost pressure hydraulic pump 23 has a discharge amount of about 90 L / min in the range of discharge pressure of 0.1 to 2.0 MPa at 1450 rpm, and the required power at that time is 1 kW to 4.8 kW. Therefore, even if all pressure losses are included, the boost pressure hydraulic pump 23 is sufficient to provide a flow rate of 65 L / min with a boost pressure of 0.2 MPa. Therefore, the equation Po × Q ≧ (Pi + α) × Q is satisfied. In addition, Po is the pressure of the hydraulic oil discharged when the hydraulic piston motor is rotated by its own weight drop, Pi is the boost pressure of the hydraulic oil supplied to the hydraulic piston motor, α is the pressure loss, and Q is the hydraulic oil Is the flow rate. As long as this range is satisfied, hydraulic oil having the required boost pressure can be supplied to the hydraulic piston motor. However, Pi (boost pressure) is required to be 0.2 MPa or more in this embodiment. The boost pressure can be adjusted by a relief valve attached to the boost pressure hydraulic pump 23.

  Further, the amount of hydraulic oil discharged from the port A of the hydraulic piston motor 7 can be adjusted by adjusting the flow control valve 21. By adjusting this, the speed of lowering the dead weight of the gate 3 can be adjusted. From the balance with the Po × Q ≧ (Pi + α) × Q formula, for example, the lowering speed at about 0.3 m / min to 0.45 m / min. It is appropriate to adjust the flow control valve 21 so that However, the speed can be freely changed as long as the above formula is satisfied by selecting the boost pressure hydraulic motor 22 and the boost pressure hydraulic pump 23.

  Next, another example of the self-weight lowering mechanism of the gate using the hydraulic piston motor of the present invention as a drive source will be described with reference to FIG. In this embodiment, the hydraulic oil discharged from the boost pressure hydraulic motor is bifurcated, a part is returned to the oil tank, and the rest is connected to the outlet side of the boost hydraulic pump and discharged from the boost hydraulic pump. The hydraulic oil is supplied to the hydraulic piston motor together with the hydraulic oil, and the inlet side of the boost pressure hydraulic pump is connected to an oil tank. In addition, description is abbreviate | omitted about the part similar to Example 1, and only a different part is demonstrated.

  As shown in FIG. 4, the discharge side of the boost hydraulic motor 22 is connected to the return filter 25 via a relief valve 28 and a check valve 29. Further, the branch is made before the relief valve 28, and this branched line is connected to the line on the outlet side of the boost hydraulic pump 23, and is connected between the stop valves 17 and 18 via the check valve 24. Here, for example, the set pressure of the relief valve 28 is set to 0.2 MPa, and the discharge pressure of the boost hydraulic pump 23 is set higher than this.

  With such a configuration, when the gate 3 descends by its own weight, part of the hydraulic oil discharged from the boost hydraulic motor 22 is returned to the oil tank 11 via the relief valve 28, the check valve 29, and the return filter 25. Further, as described in the first embodiment, since the discharge pressure of the hydraulic piston motor 7 is about 5.6 MPa, the hydraulic oil discharged by operating the boost hydraulic motor 22 has a pressure of 0.2 MPa or more. Therefore, the remaining hydraulic oil is sent to the port B of the hydraulic piston motor 7 through the check valve 24 together with the hydraulic oil discharged from the boost hydraulic pump 23.

  In the case of this embodiment, the capacity of the oil tank 11 is determined in a state other than the time when the dead weight is lowered due to heat generation. However, if the capacity of the oil tank 11 is determined only when the weight is lowered, the oil is discharged from the boost hydraulic motor 22. Unlike the case of the first embodiment, the total amount of the hydraulic oil is not returned to the oil tank 11 and is returned to the hydraulic piston motor 7 while maintaining a certain pressure (for example, 0.2 MPa). Since the amount of hydraulic oil supplied via the boost hydraulic pump 23 may be smaller than that in the first embodiment, the oil tank 11 can be downsized, and the discharge amount of the boost hydraulic pump 23 is also smaller than that in the first embodiment. Therefore, the size of the entire apparatus can be reduced as compared with the first embodiment.

DESCRIPTION OF SYMBOLS 1 Sluice gate 2 Wire 3 Gate 4 Wire drum 5 Reduction gear 6 Hydraulic push-up brake 7 Hydraulic piston motor 7a Mechanical brake 8 Hydraulic unit 9 Pressure source 10 Operation panel 11 Oil tank 12 Hydraulic pump 13 Electric motor 14 Electromagnetic valve 15, 16, 17 , 18, 19, 20 Stop valve 21 Flow control valve 22 Boost pressure hydraulic motor 23 Boost pressure hydraulic pump 24 Check valve 25 Return filter 26 Manual pump lever 27 Counter balance valve 28 Relief valve 29 Check valves A and B ports

Claims (4)

A gate is suspended by a wire, the wire is wound around a wire drum, the wire drum is rotated by a hydraulic piston motor that requires boost pressure, and the gate is raised and lowered by the hydraulic piston motor. At the sluice gate,
In order to operate the hydraulic piston motor as a hydraulic brake and adjust the speed of lowering the weight of the gate,
When the gate descends due to its own weight, the hydraulic piston motor is rotated by utilizing the rotation of the wire drum around which the wire connecting the gate is wound, and the hydraulic brake is operated and the hydraulic pump is functioned. The hydraulic pressure generated causes the boost pressure hydraulic motor to rotate,
The boost pressure hydraulic pump is driven by the rotation of the boost pressure hydraulic motor,
The gate weight drop method using a hydraulic piston motor as a drive source, wherein hydraulic oil having pressure is supplied from an oil tank to the hydraulic piston motor by the boost pressure hydraulic pump. A gate is suspended by a wire, the wire is wound around a wire drum, the wire drum is rotated by a hydraulic piston motor that requires boost pressure, and the gate is raised and lowered by the hydraulic piston motor. At the sluice gate,
In order to operate the hydraulic piston motor as a hydraulic brake and adjust the speed of lowering the weight of the gate,
A boost pressure hydraulic motor and a boost pressure hydraulic pump driven by the boost pressure hydraulic motor are provided,
When the gate descends due to its own weight, the hydraulic piston motor is rotated using the rotation of the wire drum around which the wire connecting the gate is wound, and it acts as a hydraulic brake and functions as a hydraulic pump,
An outlet side when the hydraulic piston motor acts as a hydraulic brake when the gate is lowered is connected to an inlet side of the boost pressure hydraulic motor so that the boost pressure hydraulic motor is rotated by the hydraulic pressure generated by the rotation of the hydraulic piston motor. As well as
When the gate is lowered, the outlet side of the boost pressure hydraulic pump is connected to the inlet side when the hydraulic piston motor acts as a hydraulic brake so that hydraulic oil having a boost pressure is supplied to the hydraulic piston motor. Self-weight drop mechanism using a hydraulic piston motor as a drive source.   3. The hydraulic piston motor according to claim 2, wherein hydraulic oil discharged from the boost pressure hydraulic motor is returned to an oil tank, and an inlet side of the boost pressure hydraulic pump is connected to the oil tank. The self-weight drop mechanism of the gate using as a driving source.   The hydraulic oil discharged from the boost pressure hydraulic motor is bifurcated, a part is returned to the oil tank, and the rest is connected to the outlet side of the boost hydraulic pump and discharged from the boost hydraulic pump. The gate of the gate using the hydraulic piston motor as a drive source according to claim 2, wherein the hydraulic piston motor is supplied to the hydraulic piston motor together with oil, and an inlet side of the boost pressure hydraulic pump is connected to the oil tank. Self-weight drop mechanism.

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