Anti-locking quick switching device and method for hydraulic system

Abstract

The invention relates to an anti-locking quick switching device of a hydraulic system, an oil inlet of the quick switching device is connected with an oil outlet of a quick balancing device, a working oil port of the quick switching device is connected with a plunger type cylinder through a corresponding high-pressure ball valve and a pipeline, and an oil return port of the quick switching device is communicated with an oil return pipeline. An oil inlet of the quick balancing device is communicated with the oil inlet pipeline, an oil discharge port of the quick balancing device is communicated with the unloading pipeline, and the unloading pipeline, the oil return pipeline and the oil inlet pipeline are respectively communicated with the oil tank through corresponding high-pressure ball valves; and the quick switching device is connected with the control unit through a port. The anti-locking quick switching device for the hydraulic system has the advantages that the corresponding high-pressure ball valves are mounted in front of and behind the anti-locking quick switching device for the hydraulic system, so that maintenance personnel can repair and replace conveniently; and a pressure relay is arranged on the balance pipeline, so that the pressure during a fault can be detected, a pressure signal can be transmitted to a PLC (Programmable Logic Controller) for feedback control and monitoring and adjusting the working state of the plunger type cylinder, and an operator can conveniently observe the working state at any time.

Description

Technical Field

[0001] The invention relates to rolling mill equipment, and in particular to a hydraulic system anti-locking fast switching device and method. Background Art

[0002] In hot rolling enterprises, hydraulic balancing systems are widely used. However, hydraulic locking often occurs during the production process. For example, the main shaft balancing system of the 1700 line R1 rolling mill has always had high pressure and jamming on the upper and lower mill main shafts during roll changing since the end of 2017. This causes the mill main shaft and the working roll to rise and fall out of sync, and the heights of the two ends of the working roll are inconsistent, resulting in the working roll being unable to be pulled out and being stuck in the mill frame, causing serious wear of the mill slide and damage to the main shaft flat head cover. The cost of repairing the mill main shaft is high, and the cost of spare parts is very high. The R1 rolling mill spindle balancing system was caused by reasons such as electrical control panel button failure, operator misoperation, and hydraulic system valve jamming, which resulted in the hydraulically controlled one-way valve closing during the descent of the mill spindle, and the closing pressure was greater than the system opening pressure, resulting in pressure lock. The mill spindle was also locked, causing a roller jam accident. In addition, during the rolling process of the R1 rolling mill, valve jamming sometimes occurred, making it impossible to ensure that the mill spindle was in a balanced position. High or low pressure would cause the balancing angle of the mill spindle to increase or decrease, thereby reducing the gap between the spindle and the bearing, resulting in major accidents such as grinding the bearing and replacing the spindle. Summary of the invention

[0003] The purpose of the present invention is to provide a hydraulic system anti-locking quick switching device and method, so as to achieve good control of the pressure during rolling or roll changing, reduce the equipment accident rate, reduce equipment costs, improve production efficiency, reduce the safety hazards caused by this part to the steel rolling equipment, and avoid accidents when grinding the bearings and replacing the main shaft.

[0004] To achieve the above object, the present invention is implemented through the following technical solutions:

[0005] A hydraulic system anti-lock quick switching device comprises a quick switching device and a quick balancing device, wherein the oil inlet of the quick switching device is connected to the oil outlet of the quick balancing device, the working oil port of the quick switching device is connected to the plunger cylinder through a pipeline via a corresponding high-pressure ball valve, the oil return port of the quick switching device is connected to the oil return pipeline, the oil inlet of the quick balancing device is connected to the oil inlet pipeline, the oil unloading port of the quick balancing device is connected to the unloading pipeline, the unloading pipeline, the oil return pipeline and the oil inlet pipeline are respectively connected to the oil tank via corresponding high-pressure ball valves; the quick switching device is connected to the control unit through a port.

[0006] It also includes a two-position four-way solenoid reversing valve, a three-way pressure reducing relief valve, a hydraulically controlled non-return valve, and a speed regulating valve. The oil outlet of the speed regulating valve is connected to the plunger cylinder through a pipeline, the oil inlet of the speed regulating valve is connected to the oil outlet of the hydraulically controlled non-return valve, the oil inlet of the hydraulically controlled non-return valve is connected to the working oil port of the two-position four-way solenoid reversing valve, the oil inlet of the two-position four-way solenoid reversing valve is connected to the oil outlet of the three-way pressure reducing relief valve, the oil inlet of the three-way pressure reducing relief valve is connected to the oil inlet pipeline, the oil return port of the two-position four-way solenoid reversing valve is connected to the oil return pipeline, and the two-position four-way solenoid reversing valve is connected to the control unit through a port.

[0007] It also includes a pressure relay. A pressure relay is installed on the working oil port of the two-position four-way solenoid reversing valve, the working oil port of the quick switching device and the pipeline of the plunger cylinder. The pressure relay is used to detect the balance pressure. The pressure relay is connected to the control unit through a port.

[0008] It also includes an overflow valve, the oil outlet of the overflow valve is connected to the plunger cylinder through a pipeline, and the oil inlet of the overflow valve is communicated with the oil return pipeline.

[0009] The fast switching device includes a three-position four-way electromagnetic reversing valve, the fast balancing device includes a three-way pressure reducing relief valve, and the three-position four-way electromagnetic reversing valve is connected to the control unit through a port.

[0010] The control unit is a PLC, the digital output terminals of the PLC are respectively connected to the three-position four-way solenoid directional valve and the two-position four-way solenoid directional valve, and the digital input terminals of the PLC are respectively connected to the normally open contacts of the pressure relay.

[0011] The quick balancing device and the corresponding high-pressure ball valve are arranged in the first control valve block; the quick switching device is arranged in the second control valve block.

[0012] A hydraulic system anti-lock fast switching method, comprising:

[0013] S1. During the rolling process, when the balance pressure reaches the lower limit setting value of the pressure relay, after the delay setting time, the PLC issues a command to make the three-position four-way electromagnetic reversing valve switch from the middle position to the ‖ position, and then the three-way pressure reducing relief valve delivers the regulated balance pressure oil to the plunger cylinder to keep the plunger cylinder in a balanced state;

[0014] S2. During the roller changing process, when the balance pressure reaches the upper limit setting value of the pressure relay, after the delay setting time, the PLC issues a command to switch the three-position four-way electromagnetic reversing valve from the middle position to the × position, so that the pressure oil in the plunger cylinder is quickly unloaded and an alarm is issued.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. Install the hydraulic system anti-locking quick switching device in parallel with the original balance system in the workshop. The oil outlet of the relief valve is connected to the plunger cylinder through a pipeline, and the oil inlet of the relief valve is connected to the return oil pipeline, so that the pressure during rolling or roll changing can be well controlled, the equipment accident rate can be reduced, the equipment cost can be reduced, the production efficiency can be improved, the safety hazards caused by this part to the steel rolling equipment can be reduced, and the accidents of grinding and replacing the main shaft can be avoided;

[0017] 2. The three-position four-way solenoid reversing valve and the two-position four-way solenoid reversing valve are respectively arranged in two groups of control valve blocks, one group is a quick switching device, and the other group is a quick balancing device. The space is small and the pipeline is saved. The two groups of valve blocks are installed in series. Due to the complex on-site working environment, the outer surface of the valve block is treated with anti-corrosion to increase corrosion resistance;

[0018] 3. The hydraulic system anti-lock quick switching device is equipped with corresponding high-pressure ball valves in front and behind, which is convenient for maintenance personnel to repair and replace. It has a simple structure and is easy to disassemble.

[0019] 4. A pressure relay is installed on the balance pipeline to detect the pressure in case of failure and transmit the pressure signal to the PLC for feedback control, monitor and adjust the working status of the plunger cylinder, and facilitate the operator to observe at any time;

[0020] 5. Consider the impact of hydraulic shock caused by pressure fluctuation during balancing on other hydraulic equipment, and use high-pressure hose installation to reduce hydraulic shock;

[0021] 6. The control valve block is installed independently, the inlet and outlet pressure oil of the valve block are connected by flanges, and the unloading and return oil are connected by unions, which is convenient for maintenance and disassembly;

[0022] 7. During production, pressure monitoring is used to keep the spindle pressure in a balanced state at all times, completely preventing major accidents caused by pressure loss during grinding and spindle replacement; pressure monitoring is used when changing rollers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the system control diagram of the anti-lock quick switching device of the hydraulic system;

[0024] Figure 2 This is the original spindle balancing system control diagram;

[0025] FIG3 is a schematic structural diagram of a fast balancing device of a hydraulic system anti-lock fast switching device;

[0026] FIG4 is a schematic diagram of the structure of a quick switching device of a hydraulic system anti-lock quick switching device;

[0027] In the figure: 1- plunger cylinder 2- speed control valve 3- overflow valve 4- hydraulically controlled one-way valve 5- two-position four-way electro-hydraulic reversing valve 6- three-way pressure reducing overflow valve 7- two-position four-way electromagnetic reversing valve 8- high-pressure ball valve 9- quick switching device 10- quick balancing device 11- pressure relay 12- control box 101- inlet pressure flange pipe 102- outlet pressure flange pipe 103- inlet pressure measuring point 104- outlet pressure measuring point 105- balancing main valve block 106- unloading pipeline 107- oil return pipeline 201- quick switching main valve block 203- inlet control flange pipe 204- outlet control flange pipe 205- oil return pipe. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0029] The original balance system of the workshop is shown in Figure 2 , including a two-position four-way solenoid reversing valve, a three-way pressure reducing relief valve, a hydraulically controlled one-way valve, a speed regulating valve, and a relief valve. The oil outlet of the speed regulating valve is connected to the plunger cylinder through a pipeline, the oil inlet of the speed regulating valve is connected to the oil outlet of the hydraulically controlled one-way valve, the oil inlet of the hydraulically controlled one-way valve is connected to the working oil port of the two-position four-way solenoid reversing valve, the oil inlet of the two-position four-way solenoid reversing valve is connected to the oil outlet of the three-way pressure reducing relief valve, the oil inlet of the three-way pressure reducing relief valve is connected to the oil inlet pipeline, and the oil return port of the two-position four-way solenoid reversing valve is connected to the oil return pipeline; after the transformation, the hydraulic system anti-locking quick switching device is installed in parallel with the original balancing system of the workshop, the oil outlet of the relief valve is connected to the plunger cylinder through a pipeline, and the oil inlet of the relief valve is connected to the oil return pipeline, see Figure 1 , a hydraulic system anti-lock quick switching device, comprising a quick switching device, a quick balancing device, and a pressure relay, the oil inlet of the quick switching device is connected to the oil outlet of the quick balancing device, the working oil port of the quick switching device is connected to the plunger cylinder through a pipeline through a corresponding high-pressure ball valve, the oil return port of the quick switching device is connected to the oil return pipeline, the oil inlet of the quick balancing device is connected to the oil inlet pipeline, the oil unloading port of the quick balancing device is connected to the unloading pipeline, the unloading pipeline, the oil return pipeline, and the oil inlet pipeline are respectively connected to the oil tank through the corresponding high-pressure ball valve; a pressure relay is provided on the working oil port of the two-position four-way solenoid reversing valve, the working oil port of the quick switching device, and the pipeline of the plunger cylinder, the pressure relay is used to detect the balancing pressure, the quick switching device comprises a three-position four-way solenoid reversing valve, the quick balancing device comprises a three-way pressure reducing overflow valve, the control unit is a PLC, the digital output end of the PLC is respectively connected to the three-position four-way solenoid reversing valve and the two-position four-way solenoid reversing valve, and the digital input end of the PLC is respectively connected to the normally open contact of the pressure relay. See Figure 3 and Figure 4. The quick balancing device and the corresponding high-pressure ball valve are arranged in the control valve block 1, and the quick switching device is arranged in the control valve block 2.

[0030] A hydraulic system anti-lock fast switching method, comprising:

[0031] S1. During normal rolling, when the balancing pressure reaches the lower limit setting value of the pressure relay, a delay of 1 second is issued through the PLC to switch the three-position four-way solenoid valve of the fast switching valve group from the middle position to the ‖ position, and then the three-way pressure reducing relief valve of the fast balancing valve group delivers the regulated balancing pressure oil to the plunger cylinder, so that the plunger cylinder continues to maintain a balanced state, and the fault is resolved in a very short time, thereby achieving normal rolling.

[0032] S2. During the roller changing process, when the balance pressure reaches the upper limit setting value of the pressure relay, a delay of 0.5 seconds is issued, and a command is issued through the PLC to switch the three-position four-way solenoid valve of the quick-switching valve group from the middle position to the × position, so that the pressure oil of the plunger cylinder is quickly unloaded to avoid roller jamming, and an alarm is issued to solve the fault. After the fault is solved, the next step of roller changing can be carried out.

[0033] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0034] [Example 1]

[0035] A system control diagram of a technical method for intelligent anti-lock fast switching of hydraulic system, see Figure 1, including a balancing cylinder 1, a speed regulating valve 2, a relief valve 3, a hydraulically controlled non-return valve 4, a three-way pressure reducing relief valve 6, a two-position four-way electromagnetic reversing valve 7, a high-pressure ball valve (8-1, 8-2, 8-3, 8-4), a quick switching device 9, a quick balancing device 10, a pressure relay 11, and a control box 12; the system pressure oil is reduced in pressure through the three-way pressure reducing relief valve 6 and then enters the two-position four-way electro-hydraulic reversing valve 5. When the two-position four-way electro-hydraulic reversing valve 5 is in the ‖ position, oil is supplied to the system, and when it is in the × position, the pressure of the balancing cylinder 1 is unloaded, and the balancing cylinder 1 begins to descend; the two-position four-way electro-hydraulic reversing valve 5 The outlet of the energized hydraulic reversing valve 5 is connected to the hydraulically controlled non-return valve 4. When the two-position four-way electromagnetic reversing valve 7 is in the ‖ position, the hydraulically controlled non-return valve 4 is controlled to open in reverse, and in the × position, the non-return valve 4 cannot be opened in reverse; the outlet of the hydraulically controlled non-return valve 4 is connected to the speed regulating valve 2, and the outlet of the speed regulating valve 2 is connected to the pipeline of the balancing cylinder 1 for speed control, and the overflow valve 3 is connected in parallel with the balancing cylinder 1 to play a safety protection role when the pressure is too high during rolling; the high-pressure ball valve 8-2 is connected to the quick balancing device 10, and the unloading pipeline of the quick balancing device 10 is connected to the high-pressure ball valve 8-3, and the high-pressure The ball valve 8-3 is connected to the system unloading pipeline, the return oil pipeline of the quick balancing device 10 is connected to the high-pressure ball valve 8-4, the high-pressure ball valve 8-4 is connected to the system return oil pipeline, and the quick balancing device 10 provides the required pressure for the system; the pressure pipeline balanced by the quick balancing device 10 is connected to the quick switching device 9, when the electromagnetic reversing valve of the quick switching device 9 is in the middle position, the pressure oil is stopped and remains locked, when the electromagnetic reversing valve of the quick switching device 9 is in the ‖ position, oil is supplied to the system, and when it is in the × position, the system quickly unloads to prevent locking. ; The outlet pipeline of the quick switching device 9 is connected to the high-pressure ball valve 8-1, and the outlet of the high-pressure ball valve 8-1 is connected to the outlet pipeline of the speed regulating valve 2 and is connected in parallel with the relief valve 3; the high-pressure ball valves (8-1, 8-2, 8-3, 8-4) are designed for easy maintenance; the pressure relay 11 is installed on the pipeline of the balance cylinder 1 to monitor the balance pipeline. The pressure relay 11 feeds back the pressure value to the control box 12 through monitoring. The control box 12 controls the electromagnetic reversing valve in the quick switching device 9 by setting the pressure value, so that the system obtains the required control state.

[0036] [Example 2]

[0037] In a hot-rolled strip steel plant, the main shaft balancing system of a rough rolling mill, during the rolling process, due to the abnormality of the three-way pressure relief valve 6, the three-way pressure relief valve 6 has poor anti-pollution ability and often produces valve jamming. The rise or fall of system pressure will make the balance state of the balance cylinder 1 invalid, and the bearing controlled by the balance cylinder 1 will begin to tilt, so that the working state of the bearing gradually changes from plane contact to line contact, and finally the bearing is burned. After using a technical method of intelligent anti-locking fast switching of hydraulic system, three pressure control points are set through pressure relay 11, respectively making SP1, SP2 , SP3, SP1 is the lower limit of the pressure of the balancing system, SP2 is the upper limit of the pressure of the balancing system, SP3 is the upper limit of the pressure of the balancing system; when the balancing pressure reaches the SP1 point set by the pressure relay 11, the pressure relay 11 will feed back the signal to the control box 12, and the control box 12 will control the electromagnetic reversing valve in the fast switching device 9 to switch to the ‖ position through the program, and the system pressure will be quickly adjusted to the normal pressure through the fast balancing device 10 to prevent major accidents such as grinding the bearings and replacing the main shaft, and the control box 12 will send out an alarm signal to notify the operator to handle it.

[0038] During the roller changing process, due to the failure of the button on the electrical control panel, the operator's misoperation, or the failure of the hydraulic system valve, the hydraulically controlled one-way valve 4 is closed during the descent of the main shaft, and the closing pressure is greater than the system opening pressure, and then it is locked by pressure, causing a roller jamming accident. After using a technical method for intelligent anti-locking and fast switching of the hydraulic system, through the monitoring of the pressure relay 11, when the balance pressure reaches the SP3 point set by the pressure relay 11, the pressure relay 11 feeds back the signal to the control box 12, and the control box 12 controls the electromagnetic reversing valve in the fast switching device 9 to switch to the × position through the program, and the system pressure is quickly unloaded to prevent locking and prevent roller jamming accidents. The control box 12 sends an alarm signal to notify the operator to handle it. When the processing is completed and manually reset, normal roller changing operations are carried out.

[0039] The original spindle balancing system, see Figure 2 When the above-mentioned rolling problem occurs, the only option is to passively replace the three-way pressure reducing relief valve 6 to make the system pressure reach a stable state. At this time, the main shaft and the bearing have been burned; when the above-mentioned roll replacement problem occurs, the only option is to adjust the relief valve 3 for unloading. The accident handling is very slow and there is no intelligent control, which seriously affects on-site production and brings immeasurable economic losses to Anshan Iron and Steel Group Corporation.

[0040] A technical method of intelligent anti-locking and fast switching of hydraulic system is adopted. Through intelligent independent control and ingenious design, the pressure of the balancing system is effectively controlled within the ideal fluctuation range, which can prevent the occurrence of roller jamming accidents and avoid major accidents such as grinding and replacing the main shaft. It can quickly solve on-site problems, improve the efficiency of roller replacement, and eliminate the time for replacing accident spare parts, thereby greatly improving the stability of the balancing system, making maintenance more convenient, and saving a lot of energy and costs. This application method of intelligent anti-locking and fast switching of rolling mill balancing system can also be applied to the balancing hydraulic control system of other industries to meet the requirements of on-site use.

[0041] The present invention installs the hydraulic system anti-lock quick switching device in parallel with the original balancing system of the workshop, the oil outlet of the overflow valve is connected to the plunger cylinder by a pipeline, and the oil inlet of the overflow valve is connected to the return oil pipeline, so that the pressure during rolling or roller changing is well controlled, the equipment accident rate is reduced, the equipment cost is reduced, the production efficiency is improved, the safety hazard caused by this part to the steel rolling equipment is reduced, and the accident of grinding and replacing the main shaft is avoided; the three-position four-way electromagnetic reversing valve and the two-position four-way electromagnetic reversing valve are respectively arranged in two groups of control valve blocks, one group is a quick switching device, and the other group is a quick balancing device, which has a small space and saves pipelines. The two groups of valve blocks are installed in series. Due to the complex on-site working environment, the outer surface of the valve block is treated with anti-corrosion to increase corrosion resistance; the front and rear of the hydraulic system anti-lock quick switching device are equipped with corresponding The high-pressure ball valve is convenient for maintenance personnel to repair and replace, with a simple structure and easy disassembly; a pressure relay is installed on the balancing pipeline to detect the pressure in case of a fault and transmit the pressure signal to the PLC for feedback control, monitor and adjust the working status of the plunger cylinder, and facilitate operators to observe at any time; considering the impact of the hydraulic shock caused by the pressure fluctuation during balancing on other hydraulic equipment, a high-pressure hose installation form is adopted to reduce the hydraulic shock; the control valve block is installed independently, the valve block inlet and outlet pressure oil are connected by flanges, and the unloading and return oil are connected by live joints, which are easy to repair and disassemble; during production, pressure monitoring is used to keep the spindle pressure in a balanced state at all times, completely solving the major accidents of grinding bearings and replacing spindles caused by pressure out of control; pressure monitoring is used when changing rollers.

Claims

1. A hydraulic system anti-lock fast switching device, characterized in that: It includes a quick switching device and a quick balancing device. The oil inlet of the quick switching device is connected with the oil outlet of the quick balancing device. The working oil port of the quick switching device is connected with the plunger cylinder through a pipeline via a corresponding high-pressure ball valve. The oil return port of the quick switching device is connected with the oil return pipeline. The oil inlet of the quick balancing device is connected with the oil inlet pipeline. The oil unloading port of the quick balancing device is connected with the unloading pipeline. The unloading pipeline, the oil return pipeline and the oil inlet pipeline are respectively connected with the oil tank through corresponding high-pressure ball valves. The quick switching device is connected with the control unit through a port.

2. The anti-lock fast switching device for a hydraulic system according to claim 1, characterized in that: It also includes a two-position four-way solenoid reversing valve, a three-way pressure reducing relief valve, a hydraulically controlled non-return valve, and a speed regulating valve. The oil outlet of the speed regulating valve is connected to the plunger cylinder through a pipeline, the oil inlet of the speed regulating valve is connected to the oil outlet of the hydraulically controlled non-return valve, the oil inlet of the hydraulically controlled non-return valve is connected to the working oil port of the two-position four-way solenoid reversing valve, the oil inlet of the two-position four-way solenoid reversing valve is connected to the oil outlet of the three-way pressure reducing relief valve, the oil inlet of the three-way pressure reducing relief valve is connected to the oil inlet pipeline, the oil return port of the two-position four-way solenoid reversing valve is connected to the oil return pipeline, and the two-position four-way solenoid reversing valve is connected to the control unit through a port.

3. The anti-lock fast switching device for a hydraulic system according to claim 1, characterized in that: It also includes a pressure relay. A pressure relay is installed on the working oil port of the two-position four-way solenoid reversing valve, the working oil port of the quick switching device and the pipeline of the plunger cylinder. The pressure relay is used to detect the balance pressure. The pressure relay is connected to the control unit through a port.

4. The anti-lock fast switching device for a hydraulic system according to claim 1, characterized in that: It also includes an overflow valve, the oil outlet of the overflow valve is connected to the plunger cylinder through a pipeline, and the oil inlet of the overflow valve is communicated with the oil return pipeline.

5. The anti-lock fast switching device for a hydraulic system according to claim 2, characterized in that: The fast switching device comprises a three-position four-way electromagnetic reversing valve, the fast balancing device comprises a three-way pressure reducing relief valve, and the three-position four-way electromagnetic reversing valve is connected to the control unit through a port.

6. The anti-lock fast switching device for a hydraulic system according to claim 2, characterized in that: The control unit is a PLC, the digital output end of the PLC is respectively connected to the three-position four-way electromagnetic reversing valve and the two-position four-way electromagnetic reversing valve, and the digital input end of the PLC is respectively connected to the normally open contact of the pressure relay.

7. The anti-lock fast switching device for a hydraulic system according to claim 1, characterized in that: The quick balancing device and the corresponding high-pressure ball valve are arranged in the first control valve block; the quick switching device is arranged in the second control valve block.

8. The device according to any one of claims 1 to 7 is used in a method for rapid switching of hydraulic system anti-lock, characterized in that: include: S1. During the rolling process, when the balance pressure reaches the lower limit setting value of the pressure relay, after the delay setting time, the PLC issues a command to make the three-position four-way electromagnetic reversing valve switch from the middle position to the ‖ position, and then the three-way pressure reducing relief valve delivers the regulated balance pressure oil to the plunger cylinder to keep the plunger cylinder in a balanced state; S2. During the roller changing process, when the balance pressure reaches the upper limit setting value of the pressure relay, after the delay setting time, the PLC issues a command to switch the three-position four-way electromagnetic reversing valve from the middle position to the × position, so that the pressure oil in the plunger cylinder is quickly unloaded and an alarm is issued.

Images