JP2021139510A - Industrial furnace - Google Patents

Abstract

To provide an industrial furnace capable of applying prescribed pressure to an object to be treated.SOLUTION: An industrial furnace 10 comprises: a container-shaped furnace body 12; a punch 18 applying pressure to an object 14 to be treated; a press cylinder 20 moving the punch 18; a first supply line 44 connected from a first pump 42 to the press cylinder 20 with a low pressure line 58 in parallel with a high pressure line 60 in a mid-course thereof; a low pressure control valve 62 switching between passing and stopping of liquid in the low pressure line 58; a high pressure control valve 64 switching between passing and stopping of the liquid in the high pressure line 60; and a booster cylinder 66 provided in the high pressure line 60.SELECTED DRAWING: Figure 2

Description

The present invention relates to an industrial furnace.

Conventionally, an industrial furnace has been developed in which an object to be treated made of powder is sintered at high temperature and high pressure to produce a high-density and high-purity material. For example, Patent Document 1 below includes a punch that presses an object to be processed and a pusher that moves the punch up and down. The pusher is integrated with the piston rod of the press cylinder and is moved up and down by the press cylinder. The press cylinder is driven by a hydraulic device.

For example, the hydraulic pressure device 200 of FIG. 7 supplies and discharges a liquid (hydraulic oil) to the press cylinder. The hydraulic device 200 is a press cylinder 202 that moves the pusher up and down, a pump 204, a motor 206 that drives the pump 204, a switching valve 208 that controls the flow of liquid supplied to the press cylinder 202, and a pump 204 to the press cylinder 202. A supply line 210 for supplying the liquid, a low pressure control unit 212 for supplying the liquid to the press cylinder 202 at a low pressure, and a high pressure control unit 214 for supplying the liquid to the press cylinder 202 at a high pressure are provided.

The low-pressure control unit 212 includes a low-pressure line 216 connected to the supply line 210, a low-pressure control valve 218 for switching between passing and stopping of the liquid in the low-pressure line 216, and a proportional control valve 220 for controlling the flow rate of the liquid in the low-pressure line 216. .. The high-pressure control unit 214 includes a high-pressure line 222 connected to the supply line 210, a high-pressure control valve 224 for switching between passing and stopping of the liquid in the high-pressure line 222, and a proportional control valve 226 for controlling the flow rate of the liquid in the high-pressure line 222. ..

The hydraulic pressure device 200 includes a pressure sensor 228 that detects the pressure of the liquid discharged from the pump 204, a relief valve 230 for preventing the pressure of the liquid in the supply line 210 from exceeding a predetermined value, and a liquid in the tank 232 at once. A squeeze 234 for preventing the discharge is provided.

When the liquid is supplied from the pump 204 to the press cylinder 202 through the supply line 210, the low pressure control unit 212 or the high pressure control unit 214 is driven. First, it is assumed that the low pressure control valve 218 is opened and the high pressure control valve 224 is closed. The low-pressure control valve 218 and the proportional control valve 220 of the low-pressure control unit 212 are driven to gradually increase the pressure of the liquid supplied to the press cylinder 202. When the pressure of the liquid supplied to the press cylinder 202 reaches a predetermined value, the low pressure control valve 218 is closed and the high pressure control valve 224 is opened. By driving the high-pressure control valve 224 and the proportional control valve 226 of the high-pressure control unit 214, the pressure of the liquid supplied to the press cylinder 202 is gradually increased from a predetermined value. In this way, the pressure of the liquid supplied to the press cylinder 202 is gradually increased by switching to the high pressure control unit 214 after the low pressure control unit 212 (FIG. 8).

2000-073106

However, when switching from the low pressure control unit 212 to the high pressure control unit 214, a surge pressure 240 may occur due to a change in hydraulic pressure (FIG. 8). The surge pressure 240 applies a high voltage to the object to be processed at once. The object to be processed may be damaged by the surge pressure.

Therefore, an object of the present invention is to provide an industrial furnace capable of applying a predetermined pressure to an object to be processed without generating a surge pressure.

In order to solve the above problems, the heat treatment furnace according to the present invention has the following configuration.

The industrial inverter of the present invention includes a container-shaped furnace body, a punch that applies pressure to an object to be processed in the internal space of the furnace body, a press cylinder that moves the punch, a first motor, and the first motor. An inverter device to be driven, a tank for storing liquid, a first pump driven by the first motor to discharge the liquid stored in the tank, and a low-pressure line connected from the first pump to a press cylinder on the way. The first supply line in parallel with the high-pressure line, the low-pressure control valve that switches the passage and stop of the liquid in the low-pressure line, the high-pressure control valve that switches the passage and stop of the liquid in the high-pressure line, and the high-pressure line. It is provided with a pressure boosting cylinder provided.

According to the present invention, by controlling the discharge amount of the liquid of the first motor by using the pressure boosting cylinder in the high pressure line, it is possible to prevent the pressure surge generated when switching from the low pressure line to the high pressure line. Since an abnormally high pressure is not applied to the object to be processed, a predetermined process can be performed on the object to be processed until the end. It is possible to prevent damage to the object to be processed during processing.

It is a figure which shows the structure of the industrial furnace of this application. It is a figure which shows the structure of the hydraulic pressure apparatus which drives a press cylinder. It is a graph which shows the relationship between the pressure and time of the liquid supplied to a press cylinder when the hydraulic pressure apparatus of FIG. 2 is used. It is a figure which shows the structure of the industrial furnace using two punches. It is a figure which shows the structure of the hydraulic pressure apparatus which drives the press cylinder of the industrial furnace of FIG. It is a figure which shows the structure of the hydraulic pressure apparatus which drives a press cylinder by one pump. It is a figure which shows the structure of the hydraulic pressure apparatus which drives the press cylinder of the conventional industrial furnace. It is a graph which shows the relationship between the pressure and time of the liquid supplied to a press cylinder when the hydraulic pressure apparatus of FIG. 7 is used.

An embodiment of the present invention will be described with reference to the drawings. A plurality of embodiments may be described, and even in different embodiments, the same member may be designated by the same reference numeral and the description thereof may be omitted.

[Embodiment 1]
The industrial furnace 10 shown in FIG. 1 includes a container-shaped furnace body 12, a punch 18 for applying pressure to an object to be processed 14, a press cylinder 20 for moving the punch 18, and a hydraulic pressure device 22 for driving the press cylinder 20. To be equipped with.

[Furnace]
The furnace body 12 has a cylindrical shape, and both ends thereof can be opened and closed with lids. When the lid is closed, the internal space 24 of the furnace body 12 becomes a closed space. The internal space 24 of the furnace body 12 is pressurized or depressurized. The withstand voltage of the furnace body 12 is, for example, about 10 MPa, which is changed depending on various designs.

The heat insulating body 26 is arranged in the internal space 24 of the furnace body 12. The insulation 26 is made of a heat resistant material such as graphite felt or graphite foil. The heater 30 is arranged in the internal space 28 formed by the heat insulating body 26. Examples of the heater 30 include a graphite rod heater. The heat insulating body 26 prevents the heat of the heater 30 from being dissipated to the outside. For example, the object 14 to be processed is processed at a temperature of about 1300 to 2300 ° C. The heat insulating body 26 selects a material that can withstand such a temperature.

A gas source for introducing gas into the internal space 24 of the furnace body 12 and the internal space 28 of the heat insulating body 26 (not shown), and a pump for exhausting gas from the internal space 24 of the furnace body 12 and the internal space 28 of the heat insulating body 26. (Not shown). The object 14 to be treated is treated in a predetermined gas atmosphere. For example, the gas may be nitrogen, argon, hydrogen, carbon monoxide, helium, methane, etc. A plurality of gases may be introduced into the internal space 24 of the furnace body 12 and the internal space 28 of the heat insulating body 26 at the same time. A fan may be provided in the furnace body 12 so that the gas is uniformly mixed in the internal space 24 of the furnace body 12 and the internal space 28 of the heat insulating body 26.

[punch]
The punch 18 descends from the information of the spacer 34. The object to be processed 14 is arranged on the spacer 34, the object to be processed 14 is sandwiched between the punch 18 and the spacer 34, and the punch 18 further applies a predetermined pressure to the object to be processed 14. The pusher 38 is fixed to the punch 18, and the pusher 38 is moved up and down to move the punch 18 up and down.

[Press cylinder]
The press cylinder 20 is a hydraulic (hydraulic) cylinder. The press cylinder 20 supplies or discharges a liquid (hydraulic oil) to the cylinder, so that the piston in the cylinder moves linearly. A piston rod is attached to the piston. As the piston moves linearly in the cylinder, the pusher 38 integrated with the piston rod moves up and down.

[Hydraulic device]
The piston of the press cylinder 20 is driven by the hydraulic device 22 shown in FIG. The hydraulic device 22 adjusts the positions of the first motor 40, the first pump 42 for discharging the liquid, the first supply line 44 for supplying the liquid from the first pump 42 to the press cylinder 20, and the piston of the press cylinder 20. A back pressure control unit 46 is provided for this purpose.

[1st motor]
The first motor 40 drives the first pump 42. The first motor 40 is driven by a signal input from the inverter device 48. The value of the pressure sensor 52 that detects the pressure of the liquid in the first supply line 44 is input to the control device 50. A signal is sent from the control device 50 to the inverter device 48 according to the value of the pressure sensor 52. The first motor 40 is controlled so that the pressure of the discharged liquid becomes a predetermined value.

[1st pump]
The first pump 42 discharges the liquid stored in the tank 54 toward the press cylinder 20. A relief valve 56 may be provided between the first supply line 44 and the tank 54 so that the pressure of the discharged liquid does not exceed a certain value.

[First supply line]
The first supply line 44 is connected from the first pump 42 to the press cylinder 20, and is a pipe that sends the liquid discharged by the first pump 42 to the press cylinder 20. The low-voltage line 58 and the high-voltage line 60 are in parallel in the middle of the first supply line 44. The low pressure line 58 is used when the pressure of the liquid supplied to the press cylinder 20 is low, and the high pressure line 60 is used when the pressure of the liquid supplied to the press cylinder 20 is high. The low pressure and the high pressure are relative pressures, and for example, about 2000 kN is defined as the boundary between the low pressure and the high pressure. The low pressure line 58 and the high pressure line 60 are not used at the same time, and any of the lines 58 and 60 is used to supply the liquid to the press cylinder 20.

The low pressure line 58 is provided with a low pressure control valve 62. The low pressure control valve 62 switches between passing and stopping the liquid in the low pressure line 58. The low-voltage control valve 62 is in a state in which the check valve is selected unless the solenoid is excited, and the valve is opened by exciting the solenoid. By opening the low pressure control valve 62, the liquid can be supplied from the low pressure line 58 to the press cylinder 20.

The high pressure line 60 includes a high pressure control valve 64 and a pressure boosting cylinder 66. The high pressure control valve 64 switches between passing and stopping the liquid in the high pressure line 60. The high-pressure control valve 64 is in a state in which the check valve is selected unless the solenoid is excited, and the valve is opened by exciting the solenoid. By opening the high pressure control valve 64, the liquid can be supplied from the high pressure line 60 to the press cylinder 20 via the pressure increasing cylinder 66.

A pressure sensor 68 for detecting the pressure of the liquid supplied to the press cylinder 20 in the first supply line 44 is provided. The value of the pressure sensor 68 is input to the control device 50, and the control device 50 excites one of the solenoids of the low pressure control valve 62 and the high pressure control valve 64 according to the pressure value (not shown).

The pressure boosting cylinder 66 is provided between the high pressure control valve 64 and the press cylinder 20. The pressure boosting cylinder 66 is a cylinder for increasing the pressure of the liquid supplied to the press cylinder 20 according to the pressure boosting ratio. The pressure boosting cylinder 66 allows the pressure of the liquid in the high pressure line 60 to be higher than the pressure of the liquid in the low pressure line 58.

A relief line 70 is connected to the high voltage line 60. The relief line 70 is a line through which liquid flows from between the pressure increasing cylinder 66 and the press cylinder 20 to the tank 54. The relief line 70 is provided with a relief control valve 72 and a throttle 74. The relief control valve 72 switches between passing and stopping the liquid in the relief line 70. The relief control valve 70 is in a state in which the check valve is selected unless the solenoid is excited, and the valve is opened by exciting the solenoid. By opening the relief control valve 70, the liquid flows from the high pressure line 60 to the tank 54.

The pressure boosting cylinder 66 includes a sensor (not shown) that detects the position of the piston. For example, the sensor can use a sensor that uses a magnet to detect changes in magnetic flux that differ depending on the position of the piston. The output of the sensor is input to the control device 50, and the control device 50 controls the excitation of the solenoid of the relief control valve 72 according to the position of the piston (not shown). The reason why the control is necessary will be explained.

Since the object to be processed 14 is heated for processing as described above, the object to be processed 14 may expand due to heat. In addition, the punch 18 and the like may also undergo thermal expansion. This expansion pushes back the piston of the press cylinder 20. Further, the piston of the pressure boosting cylinder 66 is also pushed back, but when the piston of the pressure boosting cylinder 66 is pushed back to the first pump side, it is not pushed back any further. The pressure of the liquid between the press cylinder 20 and the pressure increasing cylinder 66 increases, and the desired pressure cannot be applied to the object 14 to be processed.

From the above, when the low pressure line 58 is switched to the high pressure line 60, the piston of the pressure boosting cylinder 66 is set to the intermediate position in the cylinder. Specifically, when the low pressure line 58 is switched to the high pressure line 60, the relief control valve 72 is opened so that the liquid flows from the relief line 70 to the tank 54, and the piston of the pressure boosting cylinder 66 is inside the cylinder. Move to an intermediate position. After that, the relief control valve 72 is closed so that the liquid is supplied from the pressure boosting cylinder 66 to the press cylinder 20. Even if the piston of the pressure increasing cylinder 66 is pushed back, the piston can move, so that the liquid can be supplied to the press cylinder 20 at an appropriate pressure.

[Back pressure control unit]
The back pressure control unit 46 pushes back the piston of the press cylinder 20 moved by the liquid supplied from the first supply line 44. The back pressure control unit 46 is provided in the second motor 76, the second pump 78 driven by the second motor 76, the second supply line 80 connected from the second pump 78 to the press cylinder 20, and the second supply line 82. A back pressure control valve 84 is provided.

The second motor 76 drives the second pump 78, and the second pump 78 discharges the liquid in the tank 54. The second motor 76 may be driven by an inverter device in the same manner as the first motor 42. A relief valve 86 may be provided between the second supply line 80 and the tank 54 so that the pressure of the liquid discharged from the second pump 78 does not exceed a certain value.

The first supply line 44 and the second supply line 80 are connected to the press cylinder 20, the first supply line 44 is connected to the piston on the opposite side of the piston rod, and the second supply line 80 is connected to the piston. It is connected to the piston rod side. When the liquid is supplied to the press cylinder 20 from the first supply line 44, the piston rod is pushed out from the cylinder, and when the liquid is supplied to the press cylinder 20 from the second supply line 80, the piston rod is housed in the cylinder. .. By supplying the liquid from both supply lines 44 and 80, the position of the piston can be finely adjusted.

The back pressure control valve 84 switches between passing and stopping the liquid in the second supply line 80. The back pressure control valve 84 is in a state in which the check valve is selected unless the solenoid is excited, and the valve is opened by exciting the solenoid. By opening the back pressure control valve 84, the liquid flows through the second supply line 80. The back pressure control valve 84 is controlled by the control device 50.

[others]
A path for discharging the liquid from the press cylinder 20 to the tank 54 may be provided. Alternatively, when the liquid is discharged from the press cylinder 20 to the tank 54, the relief pressure of the relief valves 56 and 86 is controlled, and the low pressure control valve 62 and the back pressure control valve 84 are sent to the tank 54 via the relief valves 56 and 86. Liquid may flow.

[Processing method]
A method for treating the object to be processed 14 using the industrial furnace 10 of the present application will be described. (1) The object to be processed 14 is placed on the spacer 34, and the object to be processed 14 is pressed by the punch 18.

(2) The lid of the furnace body 12 is closed, the temperature of the heater 30 is raised, and the temperature of the internal space 28 of the heat insulating body 26 is raised. At this time, if necessary, gas is introduced into the internal space 24 of the furnace body 12 and the internal space 28 of the heat insulating body 26, and gas is exhausted from the internal space 24 of the furnace body 12 and the internal space 28 of the heat insulating body 26.

(3) When the atmospheric temperature with respect to the object to be processed 14 reaches a predetermined state, the inverter device 48 drives the first motor 40. The first pump 42 discharges the liquid stored in the tank 54.

(4) The low pressure control valve 62 is opened, the high pressure control valve 64 is closed, and the relief control valve 70 is closed. The liquid is supplied to the press cylinder 20 through the low pressure line 58. The inverter device 48 controls the first motor 40 so that the pressure of the liquid gradually increases (period A in FIG. 3).

(5) When the pressure of the liquid reaches a predetermined pressure, the low pressure control valve 62 is closed, the high pressure control valve 66 is opened, and the relief control valve 72 is opened. The line through which the liquid flows is switched from the low pressure line 58 to the high pressure line 60. Further, since the relief control valve 72 is opened, the liquid is returned from the high pressure line 60 through the relief line 70 to the tank 54 (period B in FIG. 3). The piston of the pressure boosting cylinder 66 moves, but the piston of the press cylinder 20 does not move.

When the line through which the liquid flows is switched from the low pressure line 58 to the high pressure line 60 in this way, the liquid discharge pressure of the first pump 42 is reduced by the pressure increasing ratio of the pressure increasing cylinder 66. The inverter device 48 obtains the value of the pressure sensor 52 and controls the first motor 42 to control the discharge pressure of the liquid of the first pump 42. By reducing the liquid discharge pressure of the first pump 42, the low pressure line 58 can be smoothly switched to the high pressure line 60, and surge pressure can be prevented.

(6) When the piston of the pressure boosting cylinder 66 moves to the intermediate position of the cylinder, the relief control valve 72 is closed from the state of (5) above. The liquid is supplied to the press cylinder 20 through the high pressure line 60. The inverter device 48 controls the first motor 40 so that the pressure of the liquid gradually increases (period C in FIG. 3). The pressure of the liquid discharged by the first motor 40 is increased by the pressure increasing cylinder 66. Due to the pressure increase of the pressure increasing cylinder 66, the pressure of the liquid in the high pressure line 60 becomes higher than that in the low pressure line 58.

(7) When the liquid in the press cylinder 20 reaches a predetermined pressure, the pressure is maintained until the treatment on the object 14 to be processed is completed.

In the above (4) to (6), the second motor 76 is driven to discharge the liquid from the second pump 78. The back pressure control valve 84 is opened to supply the liquid to the press cylinder 20. Liquid is supplied to the press cylinder 20 from the first supply line 44 and the second supply line 80. When the piston of the press cylinder 20 is moved by the liquid supplied from the first supply line 44, the liquid is also supplied from the second supply line 80 to push the piston, so that the movement of the piston is slowed down and the piston The position can be fine-tuned. It is also possible to push back the position of the piston if it moves too much.

When the treatment for the object 14 to be processed is completed, the object 14 to be processed is cooled and the object 14 to be processed is taken out. When the object 14 to be processed is taken out, the liquid is supplied from the second supply line 80 to the press cylinder 20, the liquid is discharged from the first supply line 44, and the piston rod is housed in the press cylinder 20. The punch 18 is separated from the object to be processed 14, and the object to be processed 14 can be taken out.

As described above, in the present application, when the low pressure line 58 is switched to the high pressure line 60, the pressure surge is prevented by reducing the liquid discharge amount of the first pump 42 according to the pressure increasing ratio of the pressure increasing cylinder 66. Can be done. By supplying a high-pressure liquid to the press cylinder 20 from the state where the piston position of the pressure boosting cylinder 66 is set to the intermediate position of the cylinder, even if the object 14 to be processed expands due to heat and the piston rod of the press cylinder 20 is pushed back. The piston of the pressure increasing cylinder 66 does not return to the first pump side, and the liquid can be supplied to the press cylinder 20 at an appropriate pressure. By supplying the liquid from the second pump 78 to the press cylinder 20, the movement of the piston of the press cylinder 20 is slowed down, and the piston can be delicately aligned.

[Embodiment 2]
Punches 18 may be provided at the top and bottom as in the industrial furnace 90 of FIG. The object to be processed 14 is installed on the lower punch 18, and the two punches 18 sandwich and press the object to be processed 14. In this case, as in the hydraulic device 92 of FIG. 5, two press cylinders 20 are provided, and each press cylinder 20 moves the pusher 38 up and down. The first supply line 44, the second supply line 80, and the like for each press cylinder 20 are the same as those in the first embodiment, and the description thereof will be omitted.

[Embodiment 3]
The hydraulic pressure device 100 of FIG. 6 includes a switching valve 102. The switching valve 102 is a valve that switches the flow of liquid to the press cylinder 20. The switching valve 102 includes two solenoids so that the liquid does not flow when both solenoids are not excited. When one of the solenoids is excited, the valve is switched to supply the liquid from the first supply line 44 to the press cylinder 20, and the liquid is discharged from the press cylinder 20 to the second supply line 80. When the other solenoid is excited, the valve is switched to supply the liquid from the second supply line 80 to the press cylinder 20, and the liquid is discharged from the press cylinder 20 to the first supply line 44. The liquid discharged from the press cylinder 20 flows to the tank 54 through the line 104 discharged from the switching valve 102. A throttle 106 may be provided on the line 104 for discharging the liquid in the tank 54 so that the liquid is not discharged at once.

(Paragraph 1) The industrial inverter according to one aspect includes a container-shaped furnace body, a punch that applies pressure to an object to be processed in the internal space of the furnace body, a press cylinder that moves the punch, and a first motor. , The inverter device that drives the first motor, the tank that stores the liquid, the first pump that is driven by the first motor and discharges the liquid stored in the tank, and the connection from the first pump to the press cylinder. A first supply line in which a low-pressure line and a high-pressure line are arranged in parallel on the way, a low-pressure control valve that switches the passage and stop of a liquid in the low-pressure line, and a high-pressure control valve that switches the passage and stop of a liquid in the high-pressure line. And a pressure boosting cylinder provided in the high pressure line.

According to the industrial furnace described in the first item, the pressure generated when switching from the low pressure line to the high pressure line by controlling the discharge amount of the liquid of the first pump according to the pressure increasing ratio of the pressure increasing cylinder of the high pressure line. Surge can be prevented.

(Item 2) The industrial furnace switches between a relief line for flowing liquid from the pressure boosting cylinder to the tank and the passage and stop of the liquid in the relief line, and adjusts the amount of liquid in the cylinder of the pressure boosting cylinder. It is equipped with a relief control valve that adjusts the position of the piston in the cylinder.

According to the industrial furnace described in item 2, the liquid is returned from the relief line to the tank and the position of the piston of the pressure boosting cylinder is adjusted, so that the object to be processed expands and the piston of the pressure boosting cylinder is pushed back. Occasionally, it is possible to prevent the piston of the boosting cylinder from returning to the first pump side. Specifically, the liquid is returned from the relief line, and the position of the piston is adjusted to a position where it does not come into close contact with the end of the cylinder on the first pump side. More preferably, the position of the piston is adjusted to the center of the cylinder.

(Item 3) The industrial furnace is driven by a second motor, a second pump that is driven by the second motor and discharges the liquid stored in the tank, and a second supply that supplies the liquid from the second pump to the press cylinder. It includes a line and a back pressure control valve that switches between passing and stopping the liquid in the second supply line.

According to the industrial furnace according to the third item, the position of the piston of the press cylinder can be finely adjusted by supplying the liquid to the press cylinder from the first supply line and the second supply line.

In addition, the present invention can be carried out in a mode in which various improvements, modifications and changes are made based on the knowledge of those skilled in the art without departing from the gist thereof.

10, 90: Industrial reactor 12: Furnace 14: Object 18: Punch 20: Press cylinder 22, 92, 100: Hydraulic device 24: Internal space of furnace 26: Insulation 28: Internal space of insulation 30 : Heater 34: Spacer 36: Base 38: Pusher 40, 76: Motor 42, 78: Pump 44: First supply line 46: Back pressure control unit 48: Inverter device 50: Control device 52, 68: Pressure sensor 54: Tank 56, 86: Relief valve 58: Low pressure line 60: High pressure line 62: Low pressure control valve 64: High pressure control valve 66: Pressure boosting cylinder 70: Relief line 72: Relief control valve 74: Squeeze 80: Second supply line 84: Back Pressure control valve 102: Switching valve

Claims (3)

A container-shaped furnace body and
A punch that applies pressure to the object to be processed in the internal space of the furnace body,
A press cylinder that moves the punch,
With the first motor
The inverter device that drives the first motor and
A tank for storing liquid and
A first pump driven by the first motor and discharging the liquid stored in the tank,
The first supply line, which is connected from the first pump to the press cylinder and has a low-pressure line and a high-pressure line in parallel on the way,
A low-pressure control valve that switches between passing and stopping the liquid in the low-pressure line,
A high-pressure control valve that switches between passing and stopping the liquid in the high-pressure line,
The pressure boosting cylinder provided in the high pressure line and
Industrial furnace equipped with. A liquid escape line that allows liquid to flow from the pressure boosting cylinder to the tank,
A relief control valve that adjusts the position of the piston in the cylinder by switching the passage and stop of the liquid in the liquid relief line and adjusting the amount of liquid in the cylinder of the pressure boosting cylinder.
The industrial furnace according to claim 1. With the second motor
A second pump driven by the second motor and discharging the liquid stored in the tank,
A second supply line that supplies liquid from the second pump to the press cylinder,
A back pressure control valve that switches between passing and stopping the liquid in the second supply line,
The industrial furnace according to claim 1 or 2.

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