Automatic balancing system for pressure in pipeline

Abstract

The utility model relates to an automatic balancing system for pressure in a pipeline. The automatic balancing system comprises a balancing barrel, a piston, an air cylinder, a balancing pipe, a liquid inlet pipe and a container, the liquid inlet pipe is connected into the container, and a pipeline, exposed out of the container, of the liquid inlet pipe is connected with a balance pipe; the upper end of the balance pipe is communicated with the bottom of the balance cylinder; a piston is arranged in the balance cylinder; the piston is fixed to the lower end of a piston rod in an air cylinder arranged above the balance barrel. An upper cavity and a lower cavity of a cylinder piston for fixing a piston rod in the cylinder are respectively communicated with a pipeline provided with a pneumatic control electromagnetic valve; the pneumatic control electromagnetic valve is electrically connected with the change-over switch so as to control compressed air entering the air cylinder to push the piston rod to move up and down; the change-over switch is electrically connected with the electromagnetic stop valve to control opening and closing of a gas path of compressed gas entering the air cylinder. The utility model overcomes the potential safety hazard of larger pressure change in the pipeline caused by thermal expansion and cold contraction due to the change of factors such as environment temperature and the like, and has the characteristics of energy conservation and safety.

Description

Technical Field

[0001] The utility model relates to the technical field of internal pressure control of a pipeline for conveying liquid in a static state, in particular to an automatic pressure balancing system in a pipeline. Background Art

[0002] Many industries, especially food, medicine, biology, and dairy industries, require that the valves at both ends of a section of pipeline be closed when the pipeline is not transporting liquid due to their production process requirements. After a period of time, due to changes in factors such as ambient temperature, the pressure in the closed pipe section will increase or decrease, or form positive pressure or negative pressure. Especially for pipelines laid in the open air, in the summer under direct sunlight, in areas north of the Yellow River in China, the pressure in the pipeline will increase from normal pressure to more than 2.0MPa, and the pressure increase in areas south of the Yangtze River will be higher, resulting in a large positive pressure in the pipeline, and in colder areas, a large negative pressure will be formed in the pipeline, which brings hidden dangers to the safety of pipeline operation and even accidents. The main reason is that the liquid enclosed in the pipe section will expand and contract under the influence of ambient temperature, resulting in changes in pressure in the pipe, which will cause huge safety risks. Utility Model Content

[0003] In order to overcome the above-mentioned defects of the prior art, the purpose of the utility model is to provide an automatic pressure balancing system in a pipeline.

[0004] The utility model is realized by adopting the following technical solutions:

[0005] A system for automatically balancing the pressure in a pipeline comprises a balancing cylinder, a piston, a cylinder, a balancing pipe, a liquid inlet pipe and a container; the liquid inlet pipe is connected to the container, and a balancing pipe is connected to a pipeline of the liquid inlet pipe exposed outside the container; the upper end of the balancing pipe is communicated with the bottom of the balancing cylinder; a piston is arranged in the balancing cylinder; the piston is fixed to the lower end of a piston rod in a cylinder arranged above the balancing cylinder; the upper and lower cavities of the cylinder piston to which the piston rod is fixed in the cylinder are respectively communicated with a pipeline provided with an air-controlled solenoid valve; the air-controlled solenoid valve is electrically connected to a conversion switch to control the compressed gas entering the cylinder to push the piston rod to move up and down; the conversion switch is electrically connected to an electromagnetic stop valve to control the opening and closing of the air path of the compressed gas entering the cylinder.

[0006] Furthermore, the bottom of the balancing cylinder is lower than the highest liquid level in the container; the piston in the balancing cylinder divides the space in the balancing cylinder into two upper and lower cavities; the piston is sealed and connected to the inner wall of the balancing cylinder via a sealing ring.

[0007] Furthermore, an automatic exhaust valve is provided on the surface of the piston in the balancing cylinder; and there is air in the two cavities in the balancing cylinder.

[0008] Furthermore, a CIP cleaning port is provided on the side of the balancing cylinder, and a breathing port is provided on the upper end surface of the balancing cylinder.

[0009] Furthermore, a first magnetic switch and a second magnetic switch are respectively provided at the upper and lower ends of the cylinder; the first magnetic switch is used to detect whether the cylinder piston has reached the upper limit position of the cylinder. When the cylinder piston reaches the upper limit position of the cylinder, the first magnetic switch sends a signal to the electromagnetic stop valve, and the air path of the compressed gas entering the cylinder is closed through the electromagnetic stop valve; the second magnetic switch is used to detect whether the cylinder piston has reached the lower limit position of the cylinder. When reaching the lower limit position of the cylinder, the second magnetic switch sends a signal to the electromagnetic stop valve, and the air path of the compressed gas entering the cylinder is closed through the electromagnetic stop valve.

[0010] Furthermore, a first switch valve is provided at the liquid inlet end of the liquid inlet pipe, and a second switch valve is provided on the outer pipe connecting the liquid inlet pipe and the container; the lower end of the balance pipe is connected to the horizontal section of the liquid inlet pipe located between the first switch valve and the second switch valve.

[0011] Furthermore, a spring is installed above or below the piston in the balancing cylinder, so that the balancing tube is initially in a positive pressure or negative pressure state.

[0012] Furthermore, the control circuit of the pneumatically controlled solenoid valve, the conversion switch and the solenoid stop valve includes:

[0013] AC power supply: provides power;

[0014] The conversion switch includes a first contact of the conversion switch, which is used to control the rise of the fixed piston rod in the cylinder; a second contact of the conversion switch, which is used to control the fall of the fixed piston rod in the cylinder; and a third contact of the conversion switch, which is used to control the fixed piston rod in the cylinder to be in an intermediate balance position.

[0015] Air-controlled solenoid valve: The air-controlled solenoid valve is provided with an air-controlled solenoid valve right coil and an air-controlled solenoid valve left coil; control the entry position of the compressed air entering the cylinder;

[0016] Solenoid stop valve: controls the opening and closing of the pipeline for compressed air entering the cylinder.

[0017] Furthermore, the first contact of the conversion switch, the second contact of the conversion switch and the third contact of the conversion switch are connected to the AC power supply in parallel; the series circuit of the first contact of the conversion switch is connected in sequence with the cylinder rising signal light, the second magnetic switch contact and the right coil of the air-controlled solenoid valve; the series circuit of the second contact of the conversion switch is connected in sequence with the cylinder descending signal light, the first magnetic switch contact and the left coil of the air-controlled solenoid valve; the series circuit of the third contact of the conversion switch is connected with the conversion switch stop position signal light; the circuit connected between the cylinder rising signal light and the second magnetic switch contact is provided with the second magnetic switch contact, the cylinder lower limit signal light and the electromagnetic stop valve; the circuit connected between the cylinder descending signal light and the first magnetic switch contact is provided with the first magnetic switch contact, the cylinder upper limit signal light, and then connected to the electromagnetic stop valve; the lead wires of the right coil of the air-controlled solenoid valve, the left coil of the air-controlled solenoid valve and the electromagnetic stop valve are connected to the AC power supply.

[0018] In summary, the utility model has the following beneficial effects: the system automatically balances the pressure in the pipeline during normal operation of the pipeline, and does not require manual operation, and is green and energy-saving. Secondly, it overcomes the potential safety hazard of large pressure changes in the pipeline caused by thermal expansion and contraction due to changes in ambient temperature and other factors. The system can also be cleaned to keep the balance cylinder clean, improve the service life of the balance cylinder and the sealing performance of the system, thereby ensuring the adaptive balance of the pressure in the pipeline and avoiding safety risks caused by sudden changes in the pressure in the pipeline. In addition, the medium in the pipeline of this application is isolated from the atmosphere, meeting the process requirements of the food, dairy, biological, and pharmaceutical industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the utility model system;

[0020] Figure 2 and Figure 3 This is a schematic diagram of the structure of the balance pipe of the utility model system when it is under negative pressure or positive pressure;

[0021] Figure 4 This is a schematic diagram of the control principle of the conversion switch and the air-controlled solenoid valve of the utility model;

[0022] Among them: balance cylinder 1; piston 2; sealing ring 3; piston rod 4; cylinder 5; air-controlled solenoid valve 6; automatic exhaust valve 7; CIP cleaning port 8; breathing port 9; balance pipe 10; liquid inlet pipe 11; first switch valve 12; second switch valve 13; conversion switch 14; container 15; electromagnetic stop valve 16; first magnetic switch 17; second magnetic switch 18; spring 19; first contact K1 of conversion switch; second contact K2 of conversion switch; third contact K3 of conversion switch; first magnetic switch contact (K4-1, K4-2); second magnetic switch contact (K5-1, K5-2); cylinder rising signal lamp LB1; cylinder falling signal lamp LB2; conversion switch stop position signal lamp LB3; cylinder upper limit signal lamp LB4; cylinder lower limit signal lamp LB5; right coil DF1-1 of air-controlled solenoid valve; left coil DF1-2 of air-controlled solenoid valve; electromagnetic stop valve DF2. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0024] Example 1

[0025] like Figures 1 to 4As shown, a system for automatically balancing the pressure in a pipeline comprises a balancing cylinder 1, a piston 2, a cylinder 5, a balancing pipe 10, a liquid inlet pipe 11 and a container 15; the liquid inlet pipe 11 is connected to the container 15, and the balancing pipe 10 is connected to the pipeline of the liquid inlet pipe 11 exposed outside the container 15; the upper end of the balancing pipe 10 is communicated with the bottom of the balancing cylinder 1; a piston 2 is arranged in the balancing cylinder 1; the piston 2 is fixed to the lower end of the piston rod 4 in the cylinder 5 arranged above the balancing cylinder 1; the upper and lower cavities of the cylinder piston in the cylinder 5 to which the piston rod 4 is fixed are respectively communicated with the pipeline provided with the air-controlled electromagnetic valve 6; the air-controlled electromagnetic valve 6 is electrically connected to the conversion switch 14 to control the compressed gas entering the cylinder 5 to push the piston rod 4 to move up and down; the conversion switch 14 is electrically connected to the electromagnetic stop valve 16 to control the opening and closing of the air path of the compressed gas entering the cylinder 5. The container 15 is a tank or other container for storing fluid. In the utility model, when the liquid in the closed pipe section expands and contracts due to changes in ambient temperature, the piston 2 in the balance cylinder 1 will move up and down with the change in the volume of the cavity in the cylinder. When the temperature rises, the liquid expands and the piston 2 moves upward. When the temperature drops, the liquid shrinks and the piston 2 moves downward accordingly. Through this system, the problem of pressure changes in the closed pipe section can be automatically balanced and resolved to ensure that the pressure in the closed pipe section is within the designed safe range value, and solves the safety hazard of large pressure changes in the pipeline caused by thermal expansion and contraction of the pipe section closed at both ends due to changes in ambient temperature. In addition, in the present application, the medium in the pipeline is isolated from the atmosphere, meeting the process requirements of the food, dairy, biological, and pharmaceutical industries. Therefore, dangerous media such as alcohol in the pipeline can be isolated from the atmosphere to prevent danger.

[0026] As a preferred embodiment, the bottom of the balancing cylinder 1 is lower than the highest liquid level in the container 15; the piston 2 in the balancing cylinder 1 divides the space in the balancing cylinder 1 into two upper and lower cavities; the piston 2 is sealed and connected to the inner wall of the balancing cylinder 1 through a sealing ring 3. During installation, the lower plane of the balancing cylinder 1 is slightly lower than the highest liquid level in the container 15. The specific value of the lower plane is determined based on the local seasonal temperature variation range, the physical properties of the medium in the pipeline, and the volume of the closed pipeline section. When the pipeline enters a closed state after conveying liquid, the automatic balancing device also enters an automatic balancing working state.

[0027] As a preferred embodiment, the upper and lower ends of the cylinder 5 are respectively provided with a first magnetic switch 17 and a second magnetic switch 18; the first magnetic switch 17 is used to detect whether the cylinder piston has reached the upper limit position of the cylinder. When the cylinder piston reaches the upper limit position of the cylinder, the first magnetic switch 17 sends a signal to the electromagnetic stop valve 16, and the electromagnetic stop valve 16 closes the air path of the compressed gas entering the cylinder 5; the second magnetic switch 18 is used to detect whether the cylinder piston has reached the lower limit position of the cylinder. When reaching the lower limit position of the cylinder, the second magnetic switch 18 sends a signal to the electromagnetic stop valve 16, and the electromagnetic stop valve 16 closes the air path of the compressed gas entering the cylinder 5.

[0028] As a preferred embodiment, a first switch valve 12 is provided at the liquid inlet end of the liquid inlet pipe 11, and a second switch valve 13 is provided on the outer pipe connecting the liquid inlet pipe 11 and the container 15; the lower end of the balance pipe 10 is connected to the horizontal section of the liquid inlet pipe 11 located between the first switch valve 12 and the second switch valve 13.

[0029] Example 2

[0030] On the basis of Example 1, an automatic exhaust valve 7 is provided on the surface of the piston 2 in the balancing cylinder 1; there is air in the two cavities in the balancing cylinder 1, and the air enclosed in the balancing cylinder 1 below the piston 2 is discharged into the cavity above the piston 2 through the automatic exhaust valve 7 due to the squeezing of the liquid entering the balancing cylinder 1 from the balancing pipe 10, and then discharged out of the cylinder from the breathing port 9 on the cover plate provided above the balancing cylinder 1. After all the air is automatically discharged, the automatic exhaust valve 7 is closed. A CIP cleaning port 8 is provided on the side of the balancing cylinder 1, and a breathing port 9 is provided on the upper end surface of the balancing cylinder 1. When the pipeline is cleaned hygienically, the conversion switch 14 is provided with three buttons of rising, falling and stopping. The button of the conversion switch 14 is operated to make the piston rod 4 in the cylinder 5 rise or fall, and the compressed air entering the cylinder 5 through the pipeline pushes the cylinder piston, driving the piston 2 of the balancing cylinder 1 to rise or fall, so as to ensure that the inner surface of the balancing cylinder 1 is cleaned to the maximum extent and kept in a clean state, thereby improving the use effect and service life. Figure 2 and Figure 3As shown, a spring 19 is installed above or below the piston 2 in the balancing cylinder 1, so that the balancing pipe 10 is initially in a positive pressure or negative pressure state to meet the initial state usage requirements under specific process conditions. When preparing to transport liquid, the first switch valve 12 and the second switch valve 13 are both opened, and the liquid flows into the container 15 from the liquid inlet pipe 11. As the liquid level in the container 15 rises, the liquid level in the balancing pipe 10 also rises synchronously. After the liquid enters the balancing cylinder 1, the space below the piston 2 of the balancing cylinder 1 is pushed by the rising liquid level, and the air below the piston 2 is discharged from the automatic exhaust valve 7 until the liquid fills the cavity below the piston 2. After stopping the delivery of liquid into the container 15, according to the process requirements, the first switch valve 12 and the second switch valve 13 are closed to form a closed pipe section. When the liquid in the pipeline expands and contracts due to the influence of the ambient temperature, since the pipe section is connected to the balancing cylinder 1 through the balancing pipe 10, the liquid in the balancing cylinder 1 will drive the piston 2 to move up and down, thereby automatically balancing the pressure, so that the pressure in the pipeline is always at normal pressure, eliminating the safety hazard of overpressure or negative pressure in the closed pipe section.

[0031] Example 3

[0032] like Figure 4 As shown, the utility model discloses a control circuit of the pneumatically controlled solenoid valve 6, the conversion switch 14 and the solenoid stop valve 16, including:

[0033] AC power supply: provides power;

[0034] The conversion switch includes a first conversion switch contact K1, which is used to control the rise of the fixed piston rod 4 in the cylinder 5; a second conversion switch contact K2, which is used to control the fall of the fixed piston rod 4 in the cylinder 5; and a third conversion switch contact K3, which is used to control the fixed piston rod 4 in the cylinder 5 to be in an intermediate equilibrium position.

[0035] Air-controlled solenoid valve: The air-controlled solenoid valve is provided with an air-controlled solenoid valve right coil DF1-1 and an air-controlled solenoid valve left coil DF1-2; control the entry position of the compressed air entering the cylinder 5;

[0036] Solenoid stop valve DF2: controls the opening and closing of the pipeline for compressed air entering cylinder 5.

[0037] As a preferred embodiment, the first contact K1 of the conversion switch, the second contact K2 of the conversion switch and the third contact K3 of the conversion switch are connected in parallel to an AC power supply; the series circuit of the first contact K1 of the conversion switch is connected in sequence to the cylinder rise signal lamp LB1, the second magnetic switch contact K5-2 and the right coil DF1-1 of the air-controlled solenoid valve; the series circuit of the second contact K2 of the conversion switch is connected in sequence to the cylinder fall signal lamp LB2, the first magnetic switch contact K4-2 and the left coil DF1-2 of the air-controlled solenoid valve; the series circuit of the third contact K3 of the conversion switch is connected to the conversion switch stop signal lamp LB1, the second magnetic switch contact K5-2 and the right coil DF1-1 of the air-controlled solenoid valve; Stop signal light LB3; the line connected between the cylinder rising signal light LB1 and the second magnetic switch contact K5-2 is provided with the second magnetic switch contact K5-1, the cylinder lower limit signal light LB5 and the electromagnetic stop valve DF2; the line connected between the cylinder descending signal light LB2 and the first magnetic switch contact K4-2 is provided with the first magnetic switch contact K4-1, the cylinder upper limit signal light LB4, and then connected to the electromagnetic stop valve DF2; the lead wires of the air-controlled solenoid valve right coil DF1-1, the air-controlled solenoid valve left coil DF1-2 and the electromagnetic stop valve DF2 are connected to the AC power supply.

[0038] The specific working process is as follows: when the pipeline needs to be cleaned due to process requirements, the conversion switch 14 is turned from the stop position to the rising position, the first contact K1 of the conversion switch is closed, and the AC power is controlled through the first contact K1 of the conversion switch, the cylinder rising signal light LB1, and the second magnetic switch contact K5-2 (normally closed without electricity), and the right end coil DF1-1 of the air-controlled electromagnetic valve is turned on. The compressed air enters the cavity below the piston of the cylinder 5 through the electromagnetic stop valve DF2 (normally open without electricity) and the air-controlled electromagnetic valve, and the piston rises, driving the piston 2 of the balance cylinder 1 to move upward. The piston of the cylinder 5 rises to the upper end, and the second magnetic switch contact K5-1 is closed; the AC power is turned on the coil of the electromagnetic stop valve DF2 through the first contact K1 of the conversion switch, the cylinder rising signal light LB1, and the second magnetic switch contact K5-1 of the conversion switch, and the electromagnetic stop valve DF2 is actuated to close the air path of the compressed air entering the cylinder 5. At the same time, the second magnetic switch contact K5-2 opens, the right coil DF1-1 of the air-controlled solenoid valve loses power, and the air-controlled solenoid valve returns to the middle position, keeping the piston of cylinder 5 locked at the upper end, and also keeping the piston 2 of the balancing cylinder 1 stationary at the upper end. After the balancing cylinder 1 is cleaned, the conversion switch is turned to the lowering position. At this time, the coil of the electromagnetic stop valve DF2 loses power, and the electromagnetic stop valve DF2 is turned on. The AC power supply is connected through the second contact K2 of the conversion switch, the cylinder descent signal light LB2, and the first magnetic switch contact K4-2, and the left end coil DF1-2 of the air-controlled solenoid valve is turned on. The compressed air input from the external pipeline enters the upper cavity of the piston of cylinder 5 through the electromagnetic stop valve DF2 and the air-controlled solenoid valve, pushing the piston down, driving the piston 2 of the balancing cylinder 1 to move down, the piston of cylinder 5 drops to the lower end, and the first magnetic switch contact K4-1 is closed. The AC power is connected to the electromagnetic stop valve DF2 through the second contact K2 of the conversion switch, the cylinder descending signal lamp LB2, and the first magnetic switch contact K4-1, closing the compressed air path entering the cylinder 5. At the same time, the first magnetic switch contact K4-2 is opened, the coil DF1-2 at the left end of the air-controlled electromagnetic valve loses power, and the air-controlled electromagnetic valve returns to the middle position, keeping the piston of the cylinder 5 locked at the lower end, and also keeping the piston 2 of the balance cylinder 1 stationary at the lower end. Then turn the conversion switch back to the stop position, the electromagnetic stop valve DF2 loses power and is in a passage state, and the cleaning procedure is now completed.

[0039] Although the above describes and illustrates the specific implementation methods of the present invention in detail, it should be pointed out that: we can make various equivalent changes and modifications to the above implementation methods based on the concept of the present invention, and the functional effects produced by them still do not exceed the spirit covered by the specification, and they should all be within the protection scope of the present invention.

Claims

1. An automatic pressure balancing system in a pipeline, characterized in that: It includes a balancing cylinder, a piston, a cylinder, a balancing pipe, a liquid inlet pipe and a container; the liquid inlet pipe is connected to the container, and the balancing pipe is connected to the pipeline of the liquid inlet pipe exposed outside the container; the upper end of the balancing pipe is connected to the bottom of the balancing cylinder; a piston is arranged in the balancing cylinder; the piston is fixed to the lower end of the piston rod in the cylinder arranged above the balancing cylinder; the upper and lower cavities of the cylinder piston where the piston rod is fixed in the cylinder are respectively connected to the pipeline with an air-controlled solenoid valve; the air-controlled solenoid valve is electrically connected to the conversion switch to control the compressed gas entering the cylinder to push the piston rod to move up and down; the conversion switch is electrically connected to the electromagnetic stop valve to control the opening and closing of the air path of the compressed gas entering the cylinder.

2. The automatic pressure balancing system in a pipeline according to claim 1, characterized in that: The bottom of the balancing cylinder is lower than the highest liquid level in the container; the piston in the balancing cylinder divides the space in the balancing cylinder into two upper and lower cavities; the piston is sealed and connected to the inner wall of the balancing cylinder through a sealing ring.

3. The automatic pressure balancing system in a pipeline according to claim 2, characterized in that: An automatic exhaust valve is arranged on the piston surface in the balancing cylinder; and there is air in the two cavities in the balancing cylinder.

4. The automatic pressure balancing system in a pipeline according to claim 1, characterized in that: The side of the balancing cylinder is provided with a CIP cleaning port, and the upper end surface of the balancing cylinder is provided with a breathing port.

5. The automatic pressure balancing system in a pipeline according to claim 1, characterized in that: A first magnetic switch and a second magnetic switch are respectively provided at the upper and lower ends of the cylinder; the first magnetic switch is used to detect whether the cylinder piston has reached the upper limit position of the cylinder. When the cylinder piston reaches the upper limit position of the cylinder, the first magnetic switch sends a signal to the electromagnetic stop valve, and the air path of the compressed gas entering the cylinder is closed through the electromagnetic stop valve; the second magnetic switch is used to detect whether the cylinder piston has reached the lower limit position of the cylinder. When reaching the lower limit position of the cylinder, the second magnetic switch sends a signal to the electromagnetic stop valve, and the air path of the compressed gas entering the cylinder is closed through the electromagnetic stop valve.

6. The automatic pressure balancing system in a pipeline according to claim 1, characterized in that: A first switch valve is arranged at the liquid inlet end of the liquid inlet pipe, and a second switch valve is arranged on the outer pipe connecting the liquid inlet pipe and the container; the lower end of the balance pipe is connected to the horizontal section of the liquid inlet pipe between the first switch valve and the second switch valve.

7. The automatic pressure balancing system in a pipeline according to claim 1, characterized in that: A spring is installed above or below the piston in the balance cylinder, so that the balance pipe is initially in a positive pressure or negative pressure state.

8. An automatic pressure balancing system in a pipeline according to any one of claims 1 to 7, characterized in that: The control circuit of the pneumatically controlled solenoid valve, the conversion switch and the solenoid stop valve comprises: AC power supply: provides power; The conversion switch includes a first contact of the conversion switch, which is used to control the rise of the fixed piston rod in the cylinder; a second contact of the conversion switch, which is used to control the fall of the fixed piston rod in the cylinder; and a third contact of the conversion switch, which is used to control the fixed piston rod in the cylinder to be in an intermediate balance position. Air-controlled solenoid valve: The air-controlled solenoid valve is provided with an air-controlled solenoid valve right coil and an air-controlled solenoid valve left coil; control the entry position of the compressed air into the cylinder; Solenoid stop valve: controls the opening and closing of the pipeline for compressed air entering the cylinder.

9. The automatic pressure balancing system in a pipeline according to claim 8, characterized in that: The first contact of the conversion switch, the second contact of the conversion switch and the third contact of the conversion switch are connected to the AC power supply in parallel; the series circuit of the first contact of the conversion switch is connected in sequence with the cylinder rising signal light, the second magnetic switch contact and the right coil of the air-controlled solenoid valve; the series circuit of the second contact of the conversion switch is connected in sequence with the cylinder descending signal light, the first magnetic switch contact and the left coil of the air-controlled solenoid valve; the series circuit of the third contact of the conversion switch is connected with the conversion switch stop position signal light; the circuit connected between the cylinder rising signal light and the second magnetic switch contact is provided with the second magnetic switch contact, the cylinder lower limit signal light and the electromagnetic stop valve; the circuit connected between the cylinder descending signal light and the first magnetic switch contact is provided with the first magnetic switch contact, the cylinder upper limit signal light, and then connected to the electromagnetic stop valve; the lead wires of the right coil of the air-controlled solenoid valve, the left coil of the air-controlled solenoid valve and the electromagnetic stop valve are connected to the AC power supply.

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