JP7645543B2 - Hydraulic Control Device - Google Patents

Description

The present invention relates to a hydraulic control device for appropriately controlling the opening and closing of flap gates and other devices installed at the outlet of a sluice gate or a waterway to prevent backflow.

Conventionally, flap gates or the like are installed at the outlet of a general culvert or flow channel in order to prevent backflow from the downstream side.
However, conventional flap gates have problems such as poor drainage performance because the water passage is normally closed, and debris can easily get caught, resulting in incomplete closure. In addition, when the downstream water level fluctuates drastically due to waves or the like, the gate body repeatedly opens and closes vigorously in sync with the water level fluctuations, causing repeated violent collisions between the gate body and the door stopper for a long period of time, resulting in noise and damage.

The applicant has therefore developed a hydraulic control device for a forced-open gate, as described in Patent Document 1 (JP Patent Publication No. 2019-112860, see especially paragraphs 0020-0021 and Figures 4 and 5), in which the gate body is normally kept in an open state to achieve high drainage performance, and when the downstream water level reaches or exceeds a predetermined level, the float valve switches to a closed position, causing the gate body to close under its own weight, thereby reliably stopping the water.

JP 2019-112860 A

However, in the hydraulic control device for the forced-open type gate described in Patent Document 1, when the gate body is opened and closed automatically (the state in FIGS. 5 and 6), the speed at which the hydraulic oil moves is set by the flow control valve (11), and the opening and closing speed of the gate body is always below a predetermined speed. This causes a problem that the gate body does not open quickly, especially when it is opened only by the water pressure of the drainage flow from the upstream side (the state in FIG. 6).
Furthermore, when performing a forced opening operation of the flap gate, in order to change from the state shown in Figure 6 to the state shown in Figure 7, it is necessary to close the first stop valve (12) and open the second stop valve (13), and after completing the forced opening operation, it is necessary to carry out the reverse operations.
The first objective of the present invention is to solve these problems and provide a hydraulic control device which can smoothly open the gate body with minimal resistance when the gate body is opened due to the water pressure of the drainage flow from the upstream side, and which can suppress flapping of the gate body due to waves by slowing down the closing speed when the water level downstream reaches a predetermined level or above, causing the float valve to switch to the closed position and the gate body to close under its own weight.
A second object of the present invention is to provide a hydraulic control device that can forcibly open a gate by simply operating the hydraulic pump, without operating any valves or valves, and that does not require any operation of valves or valves even after the forced opening operation is completed.

The invention according to claim 1 is
A hydraulic control device for a gate that is closed by its own weight,
A double-rod hydraulic cylinder (3) having a rod (8) that moves in conjunction with the movement of hydraulic oil, a front oil port (3a) and a rear oil port (3b);
a door body (1) that moves in a closing direction when the rod (8) moves to the side where the front oil port (3a) is located, and moves in an opening direction when the rod (8) moves to the side where the rear oil port (3b) is located;
a first communication pipe (10) communicating between the front oil port (3a) and the rear oil port (3b);
a check valve (11) provided in the first communication pipe (10) and allowing hydraulic oil to flow only in a direction from the rear oil port (3b) to the front oil port (3a);
a second communication pipe (12) that communicates the front side and rear side of the check valve (11) in the first communication pipe (10);
The system is characterized by comprising a float valve (4b) provided in the second communicating pipe (12) which opens when the water level (19b) downstream of the gate reaches or exceeds a predetermined water level, and a flow control valve (13) which adjusts the flow rate of the hydraulic oil so that it does not exceed a predetermined flow rate.

The invention according to claim 2 provides the hydraulic control device according to claim 1,
A hydraulic tank (18) for storing hydraulic oil;
a hydraulic pump (17) that supplies hydraulic oil from the hydraulic tank (18) to the double rod type hydraulic cylinder (3);
a hydraulic oil supply pipe (14) connecting a hydraulic oil outlet of the hydraulic pump (17) to the front oil port (3 a) side of the check valve (11) of the first communicating pipe (10) or connecting the hydraulic oil outlet to the float valve (4 b) and the flow control valve (13) of the second communicating pipe (12) to the front oil port (3 a) side;
a supply check valve (15a) provided in the hydraulic oil supply pipe (14);
a hydraulic oil discharge pipe (16) connecting the hydraulic tank (18) and the rear oil port (3b) side of the check valve (11) of the first communicating pipe (10) or connecting the hydraulic tank (18) and the rear oil port (3b) side of the float valve (4b) and the flow control valve (13) of the second communicating pipe (12);
and a check valve (15b) with a discharge pilot provided in the hydraulic oil discharge pipe (16),
When hydraulic oil is supplied from the hydraulic tank (18) to the double-rod hydraulic cylinder (3) via the hydraulic pump (17), the hydraulic oil supply pipe (14), the supply check valve (15a), the first connecting pipe (10), and the front oil port (3a), hydraulic oil is discharged from the double-rod hydraulic cylinder (3) to the hydraulic tank (18) via the rear oil port (3b), the first connecting pipe (10), the hydraulic oil discharge pipe (16), and the discharge pilot-equipped check valve (15b).

The invention according to claim 3 is the hydraulic control device according to claim 2,
The hydraulic tank (18), the hydraulic pump (17), the hydraulic oil supply pipe (14), the supply check valve (15a), the hydraulic oil discharge pipe (16) and the discharge pilot-equipped check valve (15b) are capable of being detachably connected to the first communicating pipe (10) or the second communicating pipe (12).

According to the invention of claim 1, there are provided a first communicating pipe (10) communicating the front oil port (3a) and the rear oil port (3b) of the double-rod hydraulic cylinder (3), a check valve (11) provided in the first communicating pipe (10) and allowing the hydraulic oil to flow only in the direction from the rear oil port (3b) to the front oil port (3a), a second communicating pipe (12) communicating the front side and the rear side of the check valve (11), a float valve (4b) provided in the second communicating pipe (12) and opening when the water level (19b) downstream of the gate reaches or exceeds a predetermined water level, and a flow control valve (13) for adjusting the flow rate of the hydraulic oil so that it does not exceed a predetermined flow rate. Therefore, when the float valve (4b) is in a closed state, the hydraulic oil flows without resistance from the rear oil port (3b) to the front oil port (3a), and the gate body (1) is smoothly opened by the water pressure of the drainage flow from the upstream side, etc. Since the hydraulic oil does not flow from the front oil port (3a) to the rear oil port (3b), once the door body (1) is opened, it can be kept in that open state.
In addition, when the float valve (4b) is in the open state, hydraulic oil flows from the front oil port (3a) to the rear oil port (3b) via the flow control valve (13), so that the gate body (1) moves in the closing direction under its own weight. However, the action of the flow control valve (13) slows down the operating speed, thereby making it possible to suppress flapping of the gate body (1) due to waves, etc.

According to the invention of claim 2, in addition to the effects of the invention of claim 1, a hydraulic oil supply pipe (14), a supply check valve (15a), a hydraulic oil discharge pipe (16), a check valve with a discharge pilot (15b), a hydraulic pump (17) and a hydraulic tank (18) are provided to forcibly open the door body (1). When hydraulic oil is supplied from the hydraulic tank (18) to the double-rod hydraulic cylinder (3) via the hydraulic pump (17), the hydraulic oil supply pipe (14), the supply check valve (15a), the first connecting pipe (10) and the front oil port (3a), the hydraulic oil is discharged from the double-rod hydraulic cylinder (3) to the hydraulic tank (18) via the rear oil port (3b), the first connecting pipe (10), the hydraulic oil discharge pipe (16) and the check valve with a discharge pilot (15b), so that the hydraulic pump (17) It is possible to provide a hydraulic control device that can forcibly open the gate by simply activating the valve, and does not require the operation of valves, etc., even after the forced opening operation is completed.

According to the invention of claim 3, in addition to the effect of the invention of claim 2, the forced opening device for forcibly opening the door body (1), which is the hydraulic tank (18), hydraulic pump (17), hydraulic oil supply pipe (14), supply check valve (15a), hydraulic oil discharge pipe (16), and discharge pilot check valve (15b), can be detachably connected to the first communication pipe (10) or the second communication pipe (12), so there is no need to install the forced opening device permanently, and the forced opening device can be prevented from being destroyed by earthquakes, tsunamis, strong winds, vandalism, etc.

FIG. 2 is a perspective view of an upper hinge type flap gate according to the first embodiment. FIG. 4 is a diagram showing the state of the hydraulic operation device according to the first embodiment (during automatic opening operation). FIG. 4 is a diagram illustrating the flow of hydraulic oil in the first embodiment (during automatic opening operation). FIG. 4 is a diagram illustrating the flow of hydraulic oil in the first embodiment (during automatic closing operation). FIG. 4 is a diagram showing the state of the hydraulic operation device etc. according to the first embodiment (when closed). FIG. 13 is a diagram showing the state of the hydraulic operation device according to the second embodiment (during automatic opening operation). FIG. 11 is a diagram illustrating the flow of hydraulic oil in the second embodiment (at the time of forced opening). FIG. 13 is a diagram showing the state of the hydraulic operation device according to the third embodiment (when forcibly opened). FIG. 13 is a diagram showing a modified example of the hydraulic operation device etc. according to the second embodiment (during automatic opening operation).

The following describes the embodiment of the present invention using examples.

FIG. 1 is a perspective view of an upper hinge type flap gate according to a first embodiment.
As shown in Figure 1, in the upper hinge type flap gate of Example 1, a gate body 1 is suspended freely rotatably by a hinge hardware 6 at the boundary between the upstream waterway and the downstream waterway, and when no external force is applied, the gate body 1 closes the outlet of the upstream waterway by its own weight.
In addition, a door body drive arm 1a is provided on the upper part of the door body 1 and is hingedly connected to a tip metal fitting 9 provided at the tip of the rod 8 of the double-rod hydraulic cylinder 3, so that the opening and closing operation of the door body 1 and the extension and retraction operation of the rod of the double-rod hydraulic cylinder 3 are always synchronized.
The double rod hydraulic cylinder 3 is attached to a trunnion bearing 7 so that it can swing freely, and when the door body 1 opens, the rod 8 contracts, and when the door body 1 closes, the rod 8 extends. Conversely, when the rod 8 contracts, the door body 1 opens, and when the rod 8 extends, the door body 1 closes.
Furthermore, a float 4a and a float valve 4b, which will be described later, are stored inside the float device storage box 4c, and a door stopper 5 is provided around the outlet of the upstream waterway.

FIG. 2 is a diagram showing the state of the hydraulic operation device according to the first embodiment during an automatic opening operation, and FIG. 3 is a diagram for explaining the flow of hydraulic oil in that state.
The front oil port 3a and the rear oil port 3b of the double-rod hydraulic cylinder 3 are connected by a first connecting pipe 10, and the first connecting pipe 10 is provided with a check valve 11 that allows hydraulic oil to flow only in the direction from the rear oil port 3b to the front oil port 3a.
In addition, the front side (the side closer to the front oil port 3a) and the rear side (the side closer to the rear oil port 3b) of the check valve 11 in the first communicating pipe 10 are connected by a second communicating pipe 12, and the second communicating pipe 12 is provided with a float valve 4b that opens when the downstream water level 19b in the water passage 2b downstream of the gate reaches or exceeds a predetermined water level, and a flow control valve 13 that adjusts the flow rate of the hydraulic oil so that it does not exceed a predetermined flow rate.
Here, the double-rod hydraulic cylinder 3 has the characteristic that the amount of hydraulic oil inside the cylinder does not change even when the rod 8 is extended or retracted, so that the hydraulic oil can flow freely between the front oil port 3a and the rear oil port 3b, allowing the rod 8 to be freely extended or retracted by external force.
Therefore, in the state shown in Figure 2 where the downstream water level 19b is lower than the specified water level, the float 4a is lowered, and the float valve 4b is closed, the second communicating pipe 12 is closed and hydraulic oil can only flow from the rear oil port 3b to the front oil port 3a, resulting in a gate open holding state where only the rod 8 of the double-rod hydraulic cylinder 3 can be retracted.
In the gate open holding state, as shown in FIG. 3, the door body 1 tries to open in the drainage direction due to the water pressure of the upstream water level 19a, and the rod 8 tries to move in the direction of the black arrow.
Then, the hydraulic oil flows in the first communication pipe 10 from the rear oil port 3b to the front oil port 3a as shown by the white arrow, thereby performing the automatic opening operation.
Then, even if the upstream water level 19a drops and the water pressure decreases, the hydraulic oil cannot flow through the first communicating pipe 10 from the front oil port 3a to the rear oil port 3b, so the rod 8 of the double-rod hydraulic cylinder 3 cannot extend and the door body 1 is maintained in the open state.

FIG. 4 is a diagram for explaining the flow of hydraulic oil in the first embodiment during automatic closing operation, and FIG. 5 is a diagram showing the state of the hydraulic operating device and the like according to the first embodiment when the door body 1 is closed.
When the downstream water level 19b rises from the state shown in Figure 3, the float 4a rises and the float valve 4b opens, resulting in the state shown in Figure 4 in which the gate open holding state is released, and the rod 8 of the double-rod hydraulic cylinder 3 becomes able to both extend and retract.
In this state, the gate body 1 can perform automatic opening and closing operations in response to fluctuations in the upstream water level 19a and the downstream water level 19b.
In other words, when the upstream water level 19a is higher than the downstream water level 19b and the water pressure in the drainage direction of the upstream water level 19a is greater than the water pressure due to the downstream water level 19b and the pressure due to the weight of the gate body 1, the automatic opening operation is performed and water is drained from the upstream side of the gate in the downstream direction.
Conversely, when the upstream water level 19a is lower than or equal to the downstream water level 19b and the water pressure in the discharge direction of the upstream water level 19a is smaller than the water pressure due to the downstream water level 19b and the pressure due to the weight of the door body 1, as shown in Figure 4, the door body 1 will try to close toward the gate due to the water pressure due to the downstream water level 19b and the weight of the door body 1, and the rod 8 will try to move in the direction of the black arrow.
As a result, the hydraulic oil flows through the first communicating pipe 10 and the second communicating pipe 12 in the direction from the front oil port 3a to the rear oil port 3b, as indicated by the white arrows, so that the door body 1 moves in the closing direction and an automatic closing operation is performed, ultimately resulting in the state shown in Figure 5.
At this time, the flow rate of the hydraulic oil flowing through the second communication pipe 12 does not exceed a predetermined flow rate due to the action of the flow control valve 13, so the extension speed of the rod 8 is limited and the automatic closing speed of the door body 1 is slow. Therefore, it is possible to prevent the door body 1 from closing at high speed and causing a violent collision with the door stop 5, and it is possible to prevent noise and damage.

FIG. 6 is a diagram showing the state of the hydraulic operation device and the like according to the second embodiment during an automatic opening operation.
The upper hinged flap gate of Example 2 and the upper hinged flap gate of Example 1 have exactly the same structure, and the hydraulic operating device also has exactly the same configuration with respect to the first communicating pipe 10, the check valve 11, the second communicating pipe 12, the float 4a, the float valve 4b and the flow control valve 13.
The difference between the second embodiment and the first embodiment is that the second embodiment is provided with a hydraulic oil supply pipe 14, a supply check valve 15a, a hydraulic oil discharge pipe 16, a discharge pilot-equipped check valve 15b, a hydraulic pump 17, and a hydraulic tank 18. Therefore, the same members as those in the first embodiment are given the same numbers, and the following description will focus mainly on the differences from the first embodiment.

As shown in FIG. 6 , the hydraulic operating device of the second embodiment is obtained by adding to the hydraulic operating device of the first embodiment a hydraulic tank 18 for storing hydraulic oil, a hydraulic pump 17 for supplying hydraulic oil from the hydraulic tank 18 to the double-rod hydraulic cylinder 3, a hydraulic oil supply pipe 14 for connecting a hydraulic oil outlet of the hydraulic pump 17 to the front oil port 3 a side of the check valve 11 of the first communicating pipe 10, a supply check valve 15 a provided in the hydraulic oil supply pipe 14, a hydraulic oil discharge pipe 16 for connecting the hydraulic tank 18 to the rear oil port 3 b side of the check valve 11 of the first communicating pipe 10, and a check valve with a discharge pilot 15 b provided in the hydraulic oil discharge pipe 16.
Furthermore, unless the hydraulic pump 17 is operated, the supply check valve 15a and the discharge pilot-equipped check valve 15b will prevent hydraulic oil from flowing through the hydraulic oil supply pipe 14 and the hydraulic oil discharge pipe 16. Therefore, when the float valve 4b is closed, as in Figure 3 of the first embodiment, when the door body 1 is pushed in the drainage direction by the water pressure of the upstream water level, the hydraulic oil flows through the first communicating pipe 10 from the rear oil port 3b to the front oil port 3a, performing an automatic opening operation. Even if the water pressure of the upstream water level thereafter decreases, the hydraulic oil will not flow through the first communicating pipe 10 in the direction from the front oil port 3a to the rear oil port 3b, so the rod 8 of the double-rod hydraulic cylinder 3 cannot extend and the door body 1 is maintained in the open state.
Furthermore, when the float valve 4b is open, the rod 8 of the double-rod hydraulic cylinder 3 can be extended and retracted, as in the first embodiment, and the door body 1 automatically opens and closes in response to fluctuations in the upstream water level 19a and the downstream water level 19b.

FIG. 7 is a diagram for explaining the flow of hydraulic oil in the second embodiment at the time of forced opening.
When the valve is forcibly opened, the hydraulic pump 17 is operated to supply hydraulic oil from the hydraulic tank 18 .
The hydraulic oil supplied from the hydraulic tank 18 is supplied to the front oil chamber via the hydraulic oil outlet of the hydraulic pump 17, the hydraulic oil supply pipe 14, the supply check valve 15a, the hydraulic oil supply pipe 14, the first connecting pipe 10, and the front oil port 3a, as indicated by the white arrows.
When hydraulic oil is supplied to the front oil chamber, the rod 8 contracts, and the hydraulic oil in the rear oil chamber is discharged into the hydraulic tank 18 via the rear oil port 3b, the first connecting pipe 10, the hydraulic oil discharge pipe 16, the check valve with discharge pilot 15b, and the hydraulic oil discharge pipe 16, as shown by the white arrows.
Then, the tip metal member 9 moves toward the double rod hydraulic cylinder 3, forcing the door body 1 into the open state.
The check valve with discharge pilot 15b operates to prevent the flow of hydraulic oil from the rear oil port 3b to the hydraulic tank 18 except when hydraulic oil is supplied from the hydraulic tank 18 by the hydraulic pump 17.

FIG. 8 is a diagram showing the state of the hydraulic operation device according to the third embodiment when forced opening is performed.
The upper hinged flap gate of Example 3, like that of Example 2, has exactly the same structure as the upper hinged flap gate of Example 1, and the hydraulic operating device at the time of forced opening has the same configuration as that of Example 2, except that the hydraulic oil supply pipe 14 and the hydraulic oil discharge pipe 16 are connected to the supply connection port 14a and the discharge connection port 16a, respectively.
Therefore, the same components as those in the first and second embodiments are given the same numbers, and the following description will mainly focus on the differences from the second embodiment.

Under normal conditions (when automatic opening is activated, automatic closing is activated, and when closed), the hydraulic operating device of Example 3 is not connected to a forced opening device consisting of a hydraulic oil supply pipe 14, a supply check valve 15a, a hydraulic oil discharge pipe 16, a check valve with discharge pilot 15b, a hydraulic pump 17, and a hydraulic tank 18. In the event that the opening angle becomes small and the drainage capacity becomes low due to reasons such as low water pressure at the upstream water level, the hydraulic oil supply pipe 14 and the hydraulic oil discharge pipe 16 of the forced opening device are connected to the supply connection port 14a installed on the forward oil port 3a side of the check valve 11 of the first communicating pipe 10 and the discharge connection port 16a installed on the rear oil port 3b side of the check valve 11 of the first communicating pipe 10, respectively, and then the hydraulic pump 17 is operated.
Then, due to the same flow of hydraulic oil as shown in Figure 7 of the second embodiment, the hydraulic oil in the hydraulic tank 18 is supplied to the front oil chamber and the hydraulic oil in the rear oil chamber is discharged to the hydraulic tank 18, forcing the door body 1 into the open state, and when the door body 1 is fully open, the hydraulic pump 17 is stopped.
Furthermore, even if the hydraulic oil supply pipe 14 and hydraulic oil discharge pipe 16 of the forced opening device are disconnected from the supply connection port 14a and the discharge connection port 16a after the door body 1 is fully open, hydraulic oil will not flow through the first communicating pipe 10 in the direction from the front oil port 3a to the rear oil port 3b, so the rod 8 of the double-rod hydraulic cylinder 3 cannot extend and the door body 1 is maintained in the open state.
Furthermore, even if there is a very small amount of hydraulic oil leakage, the opening angle of an upper hinged flap gate will become smaller by about 1 to 2 degrees per month. However, if the opening angle is forced to 20 degrees, it will be possible to maintain a sufficient open state against discharge of water from upstream for approximately six months.

Modifications of the first to third embodiments are listed below.
(1) In the first to third embodiments, the flow control valve 13 is provided on the rear oil port 3b side of the float valve 4b of the second communicating pipe 12. However, the flow control valve 13 may be provided on the front oil port 3a side of the float valve 4b of the second communicating pipe 12.
(2) In Examples 1 to 3, an upper hinged flap gate was used, but in all of the examples, any gate, such as a miter gate, may be used as long as it is a gate that closes under its own weight and moves in the opening or closing direction depending on the water pressure of the upstream water level or the downstream water level.

(3) In the second and third embodiments, the hydraulic oil supply pipe 14 connects the hydraulic oil outlet of the hydraulic pump 17 to the forward oil port 3 a side of the check valve 11 of the first communicating pipe 10. However, as shown in FIG. 9 , the hydraulic oil outlet of the hydraulic pump 17 may connect the hydraulic oil outlet of the hydraulic pump 17 to the forward oil port 3 a side of the float valve 4 b and the flow control valve 13 of the second communicating pipe 12.
In addition, the hydraulic oil discharge pipe 16 connects the hydraulic tank 18 to the rear oil port 3b side of the check valve 11 of the first communicating pipe 10, but as shown in Figure 9, the hydraulic tank 18 may also connect the hydraulic tank 18 to the rear oil port 3b side of the float valve 4b and the flow control valve 13 of the second communicating pipe 12.
Furthermore, the hydraulic oil supply pipe 14 may be connected as shown in FIG. 6 and the hydraulic oil discharge pipe 16 may be connected as shown in FIG. 9, or conversely, the hydraulic oil supply pipe 14 may be connected as shown in FIG. 9 and the hydraulic oil discharge pipe 16 may be connected as shown in FIG. 6.

REFERENCE SIGNS LIST 1 gate body 1a gate body drive arm 2a upstream waterway 2b downstream waterway 3 double rod hydraulic cylinder 3a front oil port 3b rear oil port 4a float 4b float valve 4c float device storage box 5 door stop hardware 6 hinge hardware 7 trunnion bearing 8 rod 9 tip hardware 10 first communicating pipe 11 check valve 12 second communicating pipe 13 flow control valve 14 hydraulic oil supply pipe 14a supply connection port 15a supply check valve 15b check valve with discharge pilot 16 hydraulic oil discharge pipe 16a discharge connection port 17 hydraulic pump 18 hydraulic tank 19a upstream water level 19b downstream water level

Claims (3)

A hydraulic control device for a gate that is closed by its own weight,
A double-rod hydraulic cylinder having a rod that moves in conjunction with the movement of hydraulic oil, a front oil port, and a rear oil port;
a door body that moves in a closing direction when the rod moves to the side where the front oil port is located and moves in an opening direction when the rod moves to the side where the rear oil port is located;
a first communication pipe communicating between the front oil port and the rear oil port;
a check valve provided in the first communication pipe and configured to allow hydraulic oil to flow only in a direction from the rear oil port to the front oil port;
a second communication pipe that communicates the first communication pipe with a front side and a rear side of the check valve;
a float valve that is provided in the second communicating pipe and opens when the water level downstream of the gate reaches or exceeds a predetermined water level, and a flow control valve that adjusts the flow rate of hydraulic oil so that it does not exceed a predetermined flow rate. A hydraulic tank for storing hydraulic oil;
a hydraulic pump for supplying hydraulic oil from the hydraulic tank to the double rod type hydraulic cylinder;
a hydraulic oil supply pipe connecting a hydraulic oil outlet of the hydraulic pump to a front oil port side of the check valve of the first communicating pipe, or connecting the hydraulic oil outlet to a front oil port side of the float valve and the flow control valve of the second communicating pipe;
A supply check valve provided in the hydraulic oil supply pipe;
a hydraulic oil discharge pipe connecting the hydraulic tank and the rear oil port side of the check valve of the first communicating pipe or connecting the hydraulic tank and the rear oil port side of the float valve and the flow control valve of the second communicating pipe;
a check valve with a discharge pilot provided in the hydraulic oil discharge pipe,
2. The hydraulic control device according to claim 1, wherein when hydraulic oil is supplied to the double-rod hydraulic cylinder from the hydraulic tank via the hydraulic pump, the hydraulic oil supply pipe, the supply check valve, the first communicating pipe, and the front oil port, the hydraulic oil is discharged from the double-rod hydraulic cylinder to the hydraulic tank via the rear oil port, the first communicating pipe, the hydraulic oil discharge pipe, and the check valve with discharge pilot. 3. The hydraulic control device according to claim 2, wherein the hydraulic tank, the hydraulic pump, the hydraulic oil supply pipe, the supply check valve, the hydraulic oil discharge pipe, and the discharge pilot-equipped check valve are detachably connectable to the first communicating pipe or the second communicating pipe.