A pneumatic control device with a series-parallel structure consisting of four solenoid valves

Abstract

The present invention relates to a pneumatic control device of a series-parallel structure composed of four solenoid valves, including: solenoid valve A, solenoid valve B, solenoid valve C, solenoid valve D, four air locks, a pressure transmitter, a connecting joint and a connecting pipeline; a filter pressure reducing valve is arranged behind an air source, and the air passage behind the filter pressure reducing valve is divided into two ways, respectively connected to one end of two air lock valves, and the other ends of the two air lock valves are respectively connected to the air inlet of solenoid valve A and the air inlet of solenoid valve C. The beneficial effects of the present invention are as follows: the pneumatic control device provided by the present invention can be used for the series-parallel redundant control of four solenoid valves, and the four-way solenoid valves can be independently configured with air sources and power supplies, which are more reliable; the problem of low reliability of existing single solenoid valves is overcome; the malfunction of a single solenoid valve causing a shutdown event of a certain device or system is avoided; the probability of solenoid valve refusal to operate can be reduced; the pneumatic control device is convenient to combine, the process is simple, and the circuit is reliable.

Description

Technical Field

[0001] The invention belongs to the technical field of automatic control devices, and in particular relates to a pneumatic control device with a series-parallel structure composed of four solenoid valves. Background Art

[0002] Pneumatic actuators are widely used in the field of modern industrial control. Many pneumatic actuators are designed with very complex functions such as power failure, air loss, and signal loss retention. However, when a main solenoid valve in the circuit fails, the pneumatic actuator will open or close abnormally and lose the retention function. This control method is mainly limited to single-control solenoid valves such as two-position three-way valves, which do not have abnormal retention functions such as power failure. In some important industrial control fields, especially in the power, oil, natural gas and other industries, the malfunction of the solenoid valve will cause a certain device or even the entire system to stop. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a pneumatic control device with a series-parallel structure consisting of four solenoid valves.

[0004] The pneumatic control device of the series-parallel structure composed of four solenoid valves includes: solenoid valve A, solenoid valve B, solenoid valve C, solenoid valve D, four air locks, pressure transmitter, connecting joints and connecting pipelines; a filter pressure reducing valve is arranged after the air source one, and the air passage after the filter pressure reducing valve is divided into two ways, respectively connected to one end of the two air lock valves, and the other ends of the two air lock valves are respectively connected to the air inlet of the solenoid valve A and the air inlet of the solenoid valve C (the solenoid valve A and the solenoid valve C share one air source); the air outlet of the solenoid valve A is connected to the exhaust port of the solenoid valve C; a filter pressure reducing valve is arranged after the air source two, and the filter pressure reducing valve is arranged after the filter pressure reducing valve. The air passage behind the valve is divided into two routes and respectively connected to one end of the remaining two air lock valves, and the other ends of the remaining two air lock valves are respectively connected to the air inlet of solenoid valve B and the air inlet of solenoid valve D; the air outlet of solenoid valve B is connected to the exhaust port of solenoid valve D; the air outlet of solenoid valve C and the air outlet of solenoid valve D are connected together as the air outlet of the entire pneumatic control device; an air passage is led out from the connecting air passage between the air outlet of solenoid valve A and the exhaust port of solenoid valve C, and the air passage is connected to the connecting air passage between the air outlet of solenoid valve B and the exhaust port of solenoid valve D, and the pneumatic control device realizes series-parallel redundant control of four solenoid valves.

[0005] As a preferred embodiment, solenoid valve A and solenoid valve B share one power supply, and solenoid valve C and solenoid valve D share one power supply (obviously, the four power supplies can be independently configured with gas sources and are more reliable).

[0006] Preferably, a manual stop valve is provided on the connecting airway between the air outlet of solenoid valve A and the air outlet of solenoid valve B, a manual stop valve is provided on the airway behind the air outlet of solenoid valve C, and a manual stop valve is also provided on the airway behind the air outlet of solenoid valve D.

[0007] Preferably, a pressure gauge is provided on the airway before the exhaust port of solenoid valve C; a pressure gauge is provided on the airway before the exhaust port of solenoid valve D; a pressure gauge is provided on the airway after the outlet port of solenoid valve C, and a pressure gauge is also provided on the airway after the outlet port of solenoid valve D.

[0008] The working method of the pneumatic control device with a series-parallel structure composed of four solenoid valves specifically comprises the following steps:

[0009] Step 1: When the pneumatic control device is in normal use and the air source 1, air source 2 and power supply are normal, perform steps 1.1 to 1.2;

[0010] Step 1.1, when the pneumatic control device outputs air intake to the actuator: solenoid valve A, solenoid valve B, solenoid valve C and solenoid valve D are energized at the same time; the air inlet of solenoid valve A is connected to the air outlet of solenoid valve A, the air inlet of solenoid valve B is connected to the air outlet of solenoid valve B, the air inlet of solenoid valve C is connected to the air outlet of solenoid valve C, and the air inlet of solenoid valve D is connected to the air outlet of solenoid valve D; air source 1 passes through the air inlet of solenoid valve C to the air outlet of solenoid valve C to supply air to the actuator, and air source 2 passes through the air inlet of solenoid valve D to the air outlet of solenoid valve D to supply air to the actuator; at this time, the exhaust port of solenoid valve C is not connected to the air outlet of solenoid valve C, the exhaust port of solenoid valve D is not connected to the air outlet of solenoid valve D, and solenoid valve A and solenoid valve B are both in standby state;

[0011] Step 1.2, when the control device controls the actuator to exhaust air outward: solenoid valve A, solenoid valve B, solenoid valve C and solenoid valve D lose power at the same time; the air outlet of solenoid valve A is connected to the exhaust port of solenoid valve A, the air outlet of solenoid valve B is connected to the exhaust port of solenoid valve B, the air outlet of solenoid valve C is connected to the exhaust port of solenoid valve C, and the air outlet of solenoid valve D is connected to the exhaust port of solenoid valve D; the instrument air in the actuator passes through the air outlet of solenoid valve C to the exhaust port of solenoid valve C, and then passes through the air outlet of solenoid valve A to the exhaust port of solenoid valve A for discharge, and the instrument air in the actuator also passes through the air outlet of solenoid valve D to the exhaust port of solenoid valve D, and then passes through the air outlet of solenoid valve B to the exhaust port of solenoid valve B for discharge;

[0012] Step 2: When a single solenoid valve fails or loses power, execute steps 2.1 to 2.2, and the pneumatic control device still outputs the air source normally;

[0013] Step 2.1, if one of solenoid valve A and solenoid valve B fails during normal operation of the output gas source: Assuming that solenoid valve A fails, the gas outlet of solenoid valve A is connected to the exhaust port of solenoid valve A. Since the gas outlet of solenoid valve A is also connected to the gas outlet of solenoid valve B, the gas source 2 passes through the gas inlet of solenoid valve B to the gas outlet of solenoid valve B, and then passes through the gas outlet of solenoid valve A to the exhaust port of solenoid valve A and is connected to the atmosphere. The air pressure is reduced, resulting in the isolation of the air lock valve in front of solenoid valve D; while the gas source 1 still supplies gas to the actuator through the solenoid valve C to maintain normal output gas source;

[0014] Step 2.2, if one of the solenoid valves C and D fails during normal operation of the gas source output: Assuming that the solenoid valve C fails, the outlet of the solenoid valve C is connected to the exhaust port of the solenoid valve C, and the exhaust port of the solenoid valve C is connected to the outlet of the solenoid valve A and then to the inlet of the solenoid valve A; the solenoid valves A and B are normally energized, the gas source 1 passes through the solenoid valve A and then is output through the solenoid valve C, and the gas source 2 passes through the solenoid valve B and then is output through the solenoid valve C;

[0015] Step 3: When a single power supply fails, executing steps 3.1 to 3.2 will not cause abnormal operation of the actuator, and the pneumatic control device will still control the actuator normally;

[0016] Step 3.1, when the power supply shared by solenoid valves A and B is de-energized, the power supply shared by solenoid valves C and D is still energized, and air source 1 enters the actuator through the air inlet of solenoid valve C to the air outlet of solenoid valve C; air source 2 enters the actuator through the air inlet of solenoid valve D to the air outlet of solenoid valve D;

[0017] Step 3.2, when the power supply shared by solenoid valves C and D is powered off, the power supply shared by solenoid valves A and B is still powered, and gas source 1 passes through the air inlet of solenoid valve A to the air outlet of solenoid valve A, and then passes through the exhaust port of solenoid valve C to the air outlet of solenoid valve C to enter the actuator; gas source 2 passes through the air inlet of solenoid valve B to the air outlet of solenoid valve B, and then passes through the exhaust port of solenoid valve D to the air outlet of solenoid valve D to enter the actuator.

[0018] The beneficial effects of the present invention are as follows: the purpose of the present invention is to overcome the low reliability of the existing single solenoid valve, which can not only avoid the occurrence of a device or system shutdown event caused by the malfunction of a single solenoid valve, but also reduce the probability of the solenoid valve refusing to operate. The present invention provides a control device with a series-parallel redundant design of solenoid valves, which has the advantages of convenient combination, simple process, reliable circuit, and the ability to implement monitoring and online testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of a series-parallel pneumatic control device;

[0020] Figure 2 It is a schematic diagram of a series-parallel pneumatic control device with a test part;

[0021] Explanation of the accompanying drawings: solenoid valve A1, solenoid valve B2, solenoid valve C3, solenoid valve D4, filter pressure reducing valve 5, air lock valve 7, solenoid valve A air inlet 8, solenoid valve A air outlet 9, solenoid valve A exhaust 10, solenoid valve C air inlet 11, solenoid valve C air outlet 12, solenoid valve C exhaust 13, solenoid valve B air inlet 14, solenoid valve B exhaust 15, solenoid valve B air outlet 16, solenoid valve D air inlet 17, solenoid valve D exhaust 18, solenoid valve D air outlet 19, manual stop valve 20, pressure gauge 21, actuator 22. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for ordinary persons in the art, without departing from the principle of the present invention, the present invention can also be modified in some ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0023] The present invention proposes a more reliable pneumatic control device composed of four electromagnetic valves in a series-parallel structure, thereby improving the reliability of equipment operation.

[0024] like Figure 1 As shown, the pneumatic control device of the series-parallel structure composed of four solenoid valves is a symmetrical structure, including: solenoid valve A1, solenoid valve B2, solenoid valve C3, solenoid valve D4, four air locks 7, a pressure transmitter, a connecting joint and a connecting pipeline; a filter pressure reducing valve 5 is arranged behind the air source 1, and the air passage behind the filter pressure reducing valve 5 is divided into two paths, respectively connected to one end of the two air lock valves 7, and the other ends of the two air lock valves 7 are respectively connected to the air inlet 8 of the solenoid valve A and the air inlet 11 of the solenoid valve C (the solenoid valve A1 and the solenoid valve C3 share one air source); the air outlet 9 of the solenoid valve A is connected to the exhaust port 13 of the solenoid valve C; the air source 2 A filter pressure reducing valve 5 is arranged at the back, and the air passage after the filter pressure reducing valve 5 is divided into two routes and respectively connected to one end of the remaining two air lock valves 7, and the other ends of the remaining two air lock valves 7 are respectively connected to the air inlet 14 of the solenoid valve B and the air inlet 17 of the solenoid valve D; the air outlet 16 of the solenoid valve B is connected to the air outlet 18 of the solenoid valve D; the air outlet 12 of the solenoid valve C and the air outlet 19 of the solenoid valve D are connected together as the air outlet of the entire pneumatic control device; an air passage is led out from the connecting air passage of the air outlet 9 of the solenoid valve A and the exhaust port 13 of the solenoid valve C, and the air passage is connected to the connecting air passage of the air outlet 16 of the solenoid valve B and the exhaust port 18 of the solenoid valve D.

[0025] The working method of the pneumatic control device composed of four solenoid valves in series-parallel structure is as follows:

[0026] 1) When the pneumatic control device is in normal use, and the air source 1, air source 2 and power supply are normal:

[0027] When the pneumatic control device outputs air intake to the actuator 22: solenoid valve A1, solenoid valve B2, solenoid valve C3 and solenoid valve D4 are energized at the same time; the air inlet 8 of solenoid valve A is connected to the air outlet 9 of solenoid valve A, the air inlet 14 of solenoid valve B is connected to the air outlet 16 of solenoid valve B, the air inlet 11 of solenoid valve C is connected to the air outlet 12 of solenoid valve C, and the air inlet 17 of solenoid valve D is connected to the air outlet 19 of solenoid valve D; air source 1 supplies air to the actuator 22 through the air inlet 11 of solenoid valve C to the air outlet 12 of solenoid valve C, and air source 2 supplies air to the actuator 22 through the air inlet 17 of solenoid valve D to the air outlet 19 of solenoid valve D; at this time, the exhaust port 13 of solenoid valve C is not connected to the air outlet 12 of solenoid valve C, the exhaust port 18 of solenoid valve D is not connected to the air outlet 19 of solenoid valve D, and the solenoid valve A1 and the solenoid valve B2 are both in standby state;

[0028] When the control device controls the actuator 22 to exhaust air outwards: the solenoid valve A1, the solenoid valve B2, the solenoid valve C3 and the solenoid valve D4 lose power at the same time; the solenoid valve A outlet 9 is connected to the solenoid valve A exhaust port 10, the solenoid valve B outlet 16 is connected to the solenoid valve B exhaust port 15, the solenoid valve C outlet 12 is connected to the solenoid valve C exhaust port 13, and the solenoid valve D outlet 19 is connected to the solenoid valve D exhaust port 18; the instrument gas in the actuator 22 passes through the solenoid valve C outlet 12 to the solenoid valve C exhaust port 13, and then passes through the solenoid valve A outlet 9 to the solenoid valve A exhaust port 10 for discharge, and the instrument gas in the actuator 22 also passes through the solenoid valve D outlet 19 to the solenoid valve D exhaust port 18, and then passes through the solenoid valve B outlet 16 to the solenoid valve B exhaust port 15 for discharge;

[0029] 2) When a single solenoid valve fails or loses power:

[0030] If during the normal operation of outputting the gas source, one of the solenoid valves A1 and B2 fails: Assuming that the solenoid valve A1 fails, the gas outlet 9 of the solenoid valve A is connected to the exhaust port 10 of the solenoid valve A. Since the gas outlet 9 of the solenoid valve A is also connected to the gas outlet 16 of the solenoid valve B, the gas source 2 is connected to the atmosphere through the gas inlet 14 of the solenoid valve B to the gas outlet 16 of the solenoid valve B and then through the gas outlet 9 of the solenoid valve A to the exhaust port 10 of the solenoid valve A. The air pressure is reduced, resulting in the actuation and isolation of the gas lock valve 7 in front of the solenoid valve D4; while the gas source 1 still supplies gas to the actuator 22 through the solenoid valve C3 to maintain the normal output gas source;

[0031] If during the normal operation of the gas source output, one of the solenoid valves C3 and D4 fails: Assuming that the solenoid valve C3 fails, the gas outlet 12 of the solenoid valve C is connected to the exhaust port 13 of the solenoid valve C, and the exhaust port 13 of the solenoid valve C is connected to the gas outlet 9 of the solenoid valve A and then to the gas inlet 8 of the solenoid valve A; the solenoid valves A1 and B2 are normally in the energized state, the gas source 1 passes through the solenoid valve A1 and then is output through the solenoid valve C3, and the gas source 2 passes through the solenoid valve B2 and then is output through the solenoid valve C3; the pneumatic control device still outputs the gas source normally;

[0032] 3) When a single power supply fails, it will not cause abnormal operation of the actuator, and the pneumatic control device can still control the actuator 22 normally;

[0033] When the power supply shared by solenoid valves A1 and B2 is de-energized, the power supply shared by solenoid valves C3 and D4 is still energized, and the gas source 1 enters the actuator 22 through the gas inlet 11 of the solenoid valve C to the gas outlet 12 of the solenoid valve C; the gas source 2 enters the actuator 22 through the gas inlet 17 of the solenoid valve D to the gas outlet 19 of the solenoid valve D;

[0034] When the power supply shared by solenoid valves C3 and D4 loses power, the power supply shared by solenoid valves A1 and B2 is still energized, and gas source one passes through the air inlet 8 of solenoid valve A to the air outlet 9 of solenoid valve A, and then passes through the exhaust port 13 of solenoid valve C to the air outlet 12 of solenoid valve C to enter the actuator 22; gas source two passes through the air inlet 14 of solenoid valve B to the air outlet 16 of solenoid valve B, and then passes through the exhaust port 18 of solenoid valve D to the air outlet 19 of solenoid valve D to enter the actuator 22.

[0035] like Figure 2 As shown, a manual stop valve 20 is installed on the connecting airway between the air outlet 9 of solenoid valve A and the air outlet 16 of solenoid valve B, a manual stop valve 20 is installed on the airway after the air outlet 12 of solenoid valve C, and a manual stop valve 20 is also installed on the airway after the air outlet 19 of solenoid valve D. A pressure gauge 21 is installed on the airway before the exhaust port 13 of solenoid valve C; a pressure gauge 21 is installed on the airway before the exhaust port 18 of solenoid valve D; a pressure gauge 21 is installed on the airway after the air outlet 12 of solenoid valve C, and a pressure gauge 21 is also installed on the airway after the air outlet 19 of solenoid valve D. Implement online solenoid valve testing to check the operation of related solenoid valves.

[0036] If you need to conduct an online test on solenoid valve A1 and solenoid valve C3, you can close the manual stop valve V1 and manual stop valve V2, keep the manual stop valve V3 in the open state, first conduct an online test on solenoid valve A1, observe the changes in the pressure gauge P1, and then conduct an online test on solenoid valve C3 while keeping the solenoid valve A1 in the de-energized state, and observe the changes in the pressure gauge P2. According to the same test method, close the manual stop valve V1 and manual stop valve V3, keep the manual stop valve V2 in the open state, and conduct an online test on solenoid valve B2 and solenoid valve D4.

Claims

1. A pneumatic control device with a series-parallel structure consisting of four solenoid valves, characterized in that: include: Solenoid valve A (1), solenoid valve B (2), solenoid valve C (3), solenoid valve D (4), four air locks (7), a pressure transmitter, a connecting joint and a connecting pipeline; a filter pressure reducing valve (5) is arranged behind the air source one, the air passage behind the filter pressure reducing valve (5) is divided into two paths and connected to one end of the two air lock valves (7) respectively, the other ends of the two air lock valves (7) are respectively connected to the air inlet (8) of the solenoid valve A and the air inlet (11) of the solenoid valve C; the air outlet (9) of the solenoid valve A is connected to the exhaust port (13) of the solenoid valve C; a filter pressure reducing valve (5) is arranged behind the air source two, the air passage behind the filter pressure reducing valve (5) is divided into two paths and connected to one end of the remaining two air lock valves (7) respectively, the other ends of the remaining two air lock valves (7) are respectively connected to the air inlet (14) of the solenoid valve B and the air inlet (17) of the solenoid valve D; the air outlet (16) of the solenoid valve B is connected to the exhaust port (13) of the solenoid valve C; The invention relates to a pneumatic control device for controlling a pneumatic device and a pneumatic control device for controlling a pneumatic device. The pneumatic control device comprises ...

2. The pneumatic control device of the series-parallel structure composed of four solenoid valves according to claim 1, characterized in that: A pressure gauge (21) is provided on the air passage before the exhaust port (13) of the electromagnetic valve C; a pressure gauge (21) is provided on the air passage before the exhaust port (18) of the electromagnetic valve D; a pressure gauge (21) is provided on the air passage after the air outlet (12) of the electromagnetic valve C, and a pressure gauge (21) is also provided on the air passage after the air outlet (19) of the electromagnetic valve D.

3. A method for operating a pneumatic control device having a series-parallel structure of four solenoid valves as claimed in claim 1, characterized in that: The specific steps include: Step 1: When the pneumatic control device is in normal use and the air source 1, air source 2 and power supply are normal, perform steps 1.1 to 1.2; Step 1.1, when the pneumatic control device outputs air to the actuator (22): solenoid valve A (1), solenoid valve B (2), solenoid valve C (3) and solenoid valve D (4) are energized at the same time; the air inlet (8) of solenoid valve A is connected to the air outlet (9) of solenoid valve A, the air inlet (14) of solenoid valve B is connected to the air outlet (16) of solenoid valve B, the air inlet (11) of solenoid valve C is connected to the air outlet (12) of solenoid valve C, and the air inlet (17) of solenoid valve D is connected to the air outlet (1 9); air source 1 passes through the air inlet (11) of solenoid valve C to the air outlet (12) of solenoid valve C to supply air to the actuator (22); air source 2 passes through the air inlet (17) of solenoid valve D to the air outlet (19) of solenoid valve D to supply air to the actuator (22); at this time, the exhaust port (13) of solenoid valve C is not connected to the air outlet (12) of solenoid valve C, the exhaust port (18) of solenoid valve D is not connected to the air outlet (19) of solenoid valve D, and both solenoid valve A (1) and solenoid valve B (2) are in standby state; Step 1.2, when the control device controls the actuator (22) to exhaust gas outwards: the solenoid valve A (1), the solenoid valve B (2), the solenoid valve C (3) and the solenoid valve D (4) are de-energized at the same time; the solenoid valve A outlet (9) is connected to the solenoid valve A exhaust port (10), the solenoid valve B outlet (16) is connected to the solenoid valve B exhaust port (15), the solenoid valve C outlet (12) is connected to the solenoid valve C exhaust port (13), and the solenoid valve D outlet (19) is connected to the solenoid valve D exhaust port (18); the gas in the actuator (22) passes through the solenoid valve C outlet (12) to the solenoid valve C exhaust port (13), and then passes through the solenoid valve A outlet (9) to the solenoid valve A exhaust port (10) to be discharged, and the gas in the actuator (22) also passes through the solenoid valve D outlet (19) to the solenoid valve D exhaust port (18), and then passes through the solenoid valve B outlet (16) to the solenoid valve B exhaust port (15) to be discharged; Step 2: When a single solenoid valve fails or loses power, execute steps 2.1 to 2.2, and the pneumatic control device still outputs the air source normally; Step 2.1, if one of the solenoid valves A (1) and B (2) fails during normal operation of the gas source output: Assuming that the solenoid valve A (1) fails, the gas outlet (9) of the solenoid valve A is connected to the exhaust port (10) of the solenoid valve A. Since the gas outlet (9) of the solenoid valve A is also connected to the gas outlet (16) of the solenoid valve B, the gas source 2 is connected to the atmosphere through the gas inlet (14) of the solenoid valve B to the gas outlet (16) of the solenoid valve B and then through the gas outlet (9) of the solenoid valve A to the exhaust port (10) of the solenoid valve A. The air pressure is reduced, causing the air lock valve (7) in front of the solenoid valve D (4) to be actuated and isolated; while the gas source 1 still supplies gas to the actuator (22) through the solenoid valve C (3); Step 2.2, if during the normal operation of the gas source output, one of the solenoid valves C (3) and the solenoid valve D (4) fails: Assuming that the solenoid valve C (3) fails, the solenoid valve C outlet (12) is connected to the solenoid valve C exhaust (13), and the solenoid valve C exhaust (13) is connected to the solenoid valve A outlet (9) and then to the solenoid valve A inlet (8); the solenoid valves A (1) and B (2) are normally in a powered state, and the gas source 1 passes through the solenoid valve A (1) and then through the solenoid valve C (3) for output, and the gas source 2 passes through the solenoid valve B (2) and then through the solenoid valve C (3) for output; Step 3, when a single power supply fails, execute steps 3.1 to 3.2, and the pneumatic control device still controls the actuator (22) normally; Step 3.1, when the power supply shared by the solenoid valve A (1) and the solenoid valve B (2) is powered off, the power supply shared by the solenoid valve C (3) and the solenoid valve D (4) is still powered, and the gas source 1 enters the actuator (22) through the gas inlet (11) of the solenoid valve C to the gas outlet (12) of the solenoid valve C; the gas source 2 enters the actuator (22) through the gas inlet (17) of the solenoid valve D to the gas outlet (19) of the solenoid valve D; Step 3.2, when the power supply shared by solenoid valves C (3) and D (4) is powered off, the power supply shared by solenoid valves A (1) and B (2) is still powered, and gas source 1 passes through the gas inlet (8) of solenoid valve A to the gas outlet (9) of solenoid valve A, and then passes through the gas outlet (13) of solenoid valve C to the gas outlet (12) of solenoid valve C to enter the actuator (22); gas source 2 passes through the gas inlet (14) of solenoid valve B to the gas outlet (16) of solenoid valve B, and then passes through the gas outlet (18) of solenoid valve D to the gas outlet (19) of solenoid valve D to enter the actuator (22).

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