A device for controlling the opening and closing of a flow channel by using the air pressure of an air spring rubber air bag

Abstract

The application discloses a device for controlling the opening and closing of a flow channel by air pressure of an air spring rubber air bag, which comprises an air pressure control part and a valve part, the air pressure control part is provided with an air pressure space and a pressure transmission part, a communication channel is arranged between the air pressure space and the rubber air bag, the air pressure in the air pressure space is equal to the air pressure in the rubber air bag, the valve part is arranged on a liquid filling flow channel and is provided with a gate valve part for making the liquid filling flow channel in a closed or open state, one end of the pressure transmission part bears the air pressure in the air pressure space, and the other end acts on the gate valve part, and in application, the closing or opening of the gate valve part is controlled by the air pressure in the air pressure space through the pressure transmission part. The device has the advantages that the device is used to replace the conventional automatic control system for controlling the opening and closing of the flow channel, the setting is simplified, the cost is reduced, the reliability of application is enhanced, and the device has a small size and does not need to occupy a large installation space.

Description

Technical Field

[0001] This invention relates to an emergency response device for depressurization of the rubber airbag in the air spring of a train bogie, specifically a device that uses the air pressure of the rubber airbag in the air spring to control the opening and closing of the flow channel, belonging to the field of air spring safety protection technology. Background Technology

[0002] The train's air springs are installed between the bogies and the carriages, providing vertical and horizontal (mainly lateral and longitudinal) vibration damping while supporting the carriages.

[0003] The main components of an air spring are a rigid base at the bottom, an auxiliary spring in the middle, and a rubber air bladder at the top. The rubber air bladder is inflated to give it elasticity with a set stiffness, which is sufficient to support the car body and reduce vibration.

[0004] The rubber airbag has a top cover and a wear plate at the top of the auxiliary spring, with an inflation space between the top cover and the wear plate. When the rubber airbag suddenly deflates, the top cover sinks under the weight of the carriage and presses against the wear plate of the auxiliary spring. To prevent sudden deflation of the rubber airbag from causing significant carriage tilting and instability, the gap between the top cover and the wear plate is generally set between 15 and 35 mm. This limits the tilting of the carriage, avoiding damage to the car body and major accidents. In the event of a rubber airbag deflation, the train will slow down and proceed to the nearest station for handling. In such cases, if the destination station is far away, to ensure operational safety and minimize the impact on the track speed, the train cannot be forced to reach the destination station for handling.

[0005] From the above facts, it can be seen that when a rubber airbag suddenly leaks air and depressurizes:

[0006] 1. Trains must slow down, affecting the overall speed of the line and increasing the scheduling burden.

[0007] 2. The train can only stop at the nearest station and cannot choose a suitable station to stop at further ahead, making it even more difficult to reach the final destination. Passengers may have to transfer at small stations with insufficient transfer facilities. For example, the fourth station ahead is a major station, while the first three are small stations. Major stations have spare trains for transfers and basic maintenance capabilities. However, with existing air spring technology, it is impossible to choose a more distant major station; it can only stop at the nearest small station. Small stations do not have spare trains (or carriages), and transferring passengers can only be diverted by passing trains or wait for dispatched trains, which inevitably delays the passengers' journey. Summary of the Invention

[0008] To address the aforementioned issues, our company has conducted a series of studies. One such study involves installing a hydraulic support mechanism between the air spring's base and the auxiliary spring. This mechanism includes a cylinder-like structure for injecting liquid (12), with the liquid (12) piston-like component bearing the load above the air spring. When the rubber airbag suddenly ruptures and depressurizes, causing the air spring's support height to drop, liquid (12) is rapidly injected into the hydraulic support mechanism through the installed filling channel, raising the liquid level (12) in the hydraulic support mechanism and thus raising the auxiliary spring, providing timely height compensation for the air spring's support height. To achieve this effect, a device capable of controlling the opening and closing of the filling channel must be installed. This device requires that the channel be tightly closed under normal conditions, but must respond promptly and open the channel when the rubber airbag suddenly ruptures and depressurizes. Based on existing technology, we are considering using system control technology, namely, installing pressure or height sensors, a control system connected to the sensors, and an actuator controlled by the control system. However, such a control system is quite complex, and configuring each air spring increases investment costs. More importantly, the chance of the rubber airbag bursting is very low, and the equipment is used very infrequently, almost always remaining idle. This makes it prone to aging and failure, and it cannot be used when it is truly needed.

[0009] Therefore, the technical problem to be solved by the present invention is: how to set up a low-cost and reliable closing and opening device for controlling the closing and opening of the liquid filling channel.

[0010] To address the above problems, the technical solution proposed by this invention is as follows:

[0011] A device for controlling the opening and closing of a flow channel using an air spring rubber bladder includes an air pressure control unit and a valve unit. The air pressure control unit has an air pressure space and a pressure transmission component. There is a connecting air passage between the air pressure space and the rubber bladder. The air pressure in the air pressure space is equal to the air pressure inside the rubber bladder. The valve unit is located on the liquid flow channel and has a gate valve that allows the liquid flow channel to be in a closed or open state. One end of the pressure transmission component bears the air pressure of the air pressure space, and the other end acts on the gate valve. In application, the air pressure of the air pressure space controls the closing or opening of the gate valve through the pressure transmission component.

[0012] Furthermore, the pneumatic control unit includes a pneumatic cylinder, which has an open end and a closed end. The pressure transmission component consists of a pneumatic piston fitted inside the pneumatic cylinder cavity and a push rod with one end connected to the outer end of the pneumatic piston. The other end of the push rod extends out of the open end of the pneumatic cylinder cavity and acts on a gate valve. The pneumatic piston can slide within the pneumatic cylinder cavity. The pneumatic piston divides the pneumatic cylinder cavity into a pneumatic space located at the closed end and a normal pressure space located at the open end.

[0013] Furthermore, the valve part has a hydraulic cylinder, which has an open end and a closed end of the hydraulic cylinder cavity; the gate valve is a hydraulic piston fitted inside the hydraulic cylinder cavity, which divides the hydraulic cylinder cavity into a hydraulic space located at the closed end and an atmospheric pressure space located at the open end; the filling channel is disconnected into an input section and an output section, the input section is connected to the hydraulic space, and the output section is connected to the atmospheric pressure space, with its output port located in the atmospheric pressure space close to the hydraulic piston. When the hydraulic piston slides towards the open end of the hydraulic cylinder cavity, expanding the hydraulic space until the output port is located within the hydraulic space, the input section and the output section of the filling channel are connected through the hydraulic space.

[0014] Furthermore, the outer periphery of the hydraulic piston has a hydraulic seal ring to prevent liquid leakage from the hydraulic space.

[0015] Furthermore, a connecting plate is provided between the pneumatic cylinder and the hydraulic cylinder to fix them together as an integral device. The opening end of the pneumatic cylinder cavity and the opening end of the hydraulic cylinder cavity are coaxially fixed on both sides of the connecting plate. The connecting plate has a hole in the middle, one end of which is connected to the push rod of the pneumatic piston, and the other end is connected to the hydraulic piston through the hole.

[0016] Furthermore, the pneumatic cylinder has a pressure-sealing ring between the opening end of the pneumatic cylinder chamber and the central connecting plate. The inner edge of the pressure-sealing ring is a pressure-sealing inner conical surface that extends radially and centripetally into the atmospheric pressure space. The pressure-sealing ring is pressed and sealed with the edge of the pneumatic cylinder opening. The bottom end face and side face of the pneumatic piston have a pressure-sealing outer conical surface that matches the pressure-sealing inner conical surface.

[0017] Furthermore, there is a ventilation gap between the push rod and the inner wall of the hole, and the connecting plate is provided with an air hole that communicates with the outside world in a normal pressure space.

[0018] Furthermore, a separator capable of expanding and rupturing is provided between the hydraulic space and the atmospheric pressure space of the hydraulic cylinder, and the periphery of the separator is sealed and fixed to the inner wall of the cylinder cavity.

[0019] Furthermore, the thickness of the separator gradually decreases from the periphery to the center, making the central region a crack-prone area; when the outer conical surface of the pneumatic piston presses against the inner conical surface of the compression ring, the end face of the hydraulic piston abuts against the separator to prevent the crack-prone area from breaking.

[0020] Furthermore, the hydraulic pressure in the hydraulic space is greater than the air pressure in the pneumatic space, and the area of ​​the hydraulic piston subjected to liquid pressure is smaller than the area of ​​the pneumatic piston subjected to gas pressure, so that the pressure of the hydraulic piston subjected to liquid is less than the pressure of the pneumatic piston subjected to gas.

[0021] Beneficial effects:

[0022] 1. This device replaces the conventional automatic control system, simplifying setup and reducing costs. It eliminates the need for pressure sensors, sensor-connected control systems, and actuators controlled by the control system.

[0023] 2. Enhanced application reliability. Because it does not rely on various complex electrical components, it avoids the problem of electronic control equipment components aging and failing due to prolonged inactivity, thus failing to function properly when truly needed.

[0024] 3. The device is small in size and does not require a large installation space. Attached Figure Description

[0025] Figure 1 A cross-sectional schematic diagram of the air spring using this device;

[0026] Figure 2 This is a cross-sectional schematic diagram of the device, showing that the device is in the off state under normal conditions.

[0027] Figure 3 This is a cross-sectional view of the device in the open state after the rubber airbag bursts, the sealing membrane expands and cracks to form a rupture. Arrow A in the figure indicates the flow direction of gas in the air pressure space after the rubber airbag bursts, arrow B indicates the rupture formed after the liquid in the hydraulic space passes through the separator membrane, arrow C indicates the liquid in the input section enters the hydraulic space, and arrow D indicates the liquid in the expanded hydraulic space flows to the hydraulic support mechanism through the output section.

[0028] In the diagram: 1. Pneumatic cylinder; 101. Pneumatic space; 102. Atmospheric pressure space one; 2. Pneumatic piston; 201. Pressure-sealing outer conical surface; 202. Push rod; 3. Hydraulic cylinder; 301. Hydraulic space; 302. Atmospheric pressure space two; 4. Hydraulic piston; 401. Hydraulic sealing ring; 5. Central connecting plate; 501. Hole; 502. Air hole; 6. Pressure-sealing ring; 601. Pressure-sealing inner conical surface; 7. Separator membrane; 701. Crack-prone area; 702. Tear opening; 8. Rubber airbag; 9. Fluid filling channel; 901. Input section; 902. Output section; 9021. Output port; 10. Connecting air passage; 11. Gas; 12. Liquid; 13. Hydraulic support mechanism. Detailed Implementation

[0029] The present invention will now be further described with reference to the accompanying drawings:

[0030] like Figure 1 As shown, the filling channel 9 for injecting liquid 12 into the hydraulic support mechanism 13 is a high-pressure channel. Its high internal pressure is reflected in the fact that the liquid 12 in the cylinder cavity of the cylinder structure of the hydraulic support mechanism 13 can still fill the cylinder cavity with liquid 12 under the premise that it is sufficient to support the load above the air spring.

[0031] like Figure 1 As shown in Figure 3, a device for controlling the opening and closing of a flow channel using the air pressure of an air spring rubber bladder includes an air pressure control unit and a valve unit. The air pressure control unit has an air pressure space 101 and a pressure transmission component. There is a connecting air passage 10 between the air pressure space 101 and the rubber bladder 8, so that the air pressure in the air pressure space 101 is equal to that in the rubber bladder 8. The valve unit is provided on the liquid filling flow channel 9 and has a gate valve that puts the liquid filling flow channel 9 into a closed or open state. One end of the pressure transmission component bears the air pressure of the air pressure space 101, and the other end acts on the gate valve, so that the liquid filling flow channel 9 is in a closed state. When the rubber bladder 8 suddenly ruptures and leaks air, the air pressure space 101 and the rubber bladder 8 are depressurized simultaneously through the connecting air passage 10. The gate valve loses the air pressure transmitted from the air pressure space 101 by the pressure transmission component, so that the liquid filling flow channel 9 is quickly put into an open flow state. In this way, the filling channel 9 can be closed or opened using pneumatic control of hydraulic pressure via the aforementioned device, eliminating the need for pressure sensors, a control system connected to the sensors, and actuators controlled by the control system. Simultaneously, it avoids the problem of electronic control equipment aging and failing due to prolonged inactivity, resulting in malfunction when truly needed. Compared to existing technologies, the setup is greatly simplified, the device is small and low-cost, and it does not rely on electrical components, eliminating the risk of aging and failure, thus ensuring reliable operation.

[0032] The pneumatic control unit has a pneumatic cylinder 1, which has an open end and a closed end. The pressure transmission component consists of a pneumatic piston 2 fitted inside the cylinder cavity of the pneumatic cylinder 1 and a push rod 202 with one end connected to the outer end of the pneumatic piston 2. The other end of the push rod 202 extends out of the open end of the pneumatic cylinder cavity and acts on the gate valve. The pneumatic piston 2 can slide inside the cylinder cavity of the pneumatic cylinder 1. The pneumatic piston 2 divides the cylinder cavity of the pneumatic cylinder 1 into a pneumatic space 101 located at the closed end of the pneumatic cylinder cavity and an atmospheric pressure space 102 located at the open end of the pneumatic cylinder cavity.

[0033] The valve section includes a hydraulic cylinder 3, which has an open end and a closed end. The gate valve is a hydraulic piston 4 fitted inside the cylinder cavity of the hydraulic cylinder 3. The hydraulic piston 4 divides the cylinder cavity of the hydraulic cylinder 3 into a hydraulic space 301 located at the closed end and a normal pressure space 302 located at the open end. The filling channel 9 is divided into an input section 901 and an output section 902. The input section 901 communicates with the hydraulic space 301, and the output section 902 communicates with the normal pressure space 302. The hydraulic cylinder 4 is connected to the hydraulic cylinder 4. Its output port 9021 is located in the atmospheric pressure space 302 close to the hydraulic piston 4. When the hydraulic piston 4 slides towards the opening end of the hydraulic cylinder cavity, so that the hydraulic space 301 is expanded to the point where the output port 9021 is located in the hydraulic space 301, the input section 901 and the output section 902 of the filling channel 9 are connected through the hydraulic space 301. The high pressure liquid flow in the input section 901 can enter the output section 902 through the expanded hydraulic space 301, so as to realize the opening and flow of the filling channel 9.

[0034] The hydraulic piston 4 has a hydraulic seal ring 401 on its outer periphery for leakage of liquid 12 from the hydraulic space 301.

[0035] A central connecting plate 5 is provided between the pneumatic cylinder 1 and the hydraulic cylinder 3 to fix them as an integral device. The opening end of the pneumatic cylinder chamber of the pneumatic cylinder 1 and the opening end of the hydraulic cylinder chamber of the hydraulic cylinder 3 are coaxially fixed on both sides of the central connecting plate 5. The central connecting plate 5 has a hole 501 in the middle, one end of which is connected to the push rod 202 of the pneumatic piston 2, and the other end is connected to the hydraulic piston 4 through the hole 501.

[0036] To ensure that the air pressure in atmospheric pressure space 102 and atmospheric pressure space 302 is at atmospheric pressure, there is a ventilation gap between push rod 202 and the inner wall of hole 501, and an air hole 502 is provided on the central connecting plate 5 to connect atmospheric pressure space 102 with the outside.

[0037] To ensure that the liquid 12 in the filling channel 9 can fill the hydraulic support mechanism when the hydraulic seal ring 401 is depressurized, the hydraulic pressure of the hydraulic space 301 is preset to be greater than the air pressure of the air space 101. To ensure that the pneumatic piston 2 can press against the hydraulic piston 4 via the push rod 202, and simultaneously to ensure that the pneumatic piston 2 can press against the inner conical surface 601 of the pressure-sealing ring 6 as described below, the pressure-bearing area of ​​the hydraulic piston 4 under the pressure of the liquid 12 is designed to be smaller than the pressure-bearing area of ​​the pneumatic piston 2 under the pressure of the gas 11, thus making the pressure of the liquid 12 on the hydraulic piston 4 less than the pressure of the gas 11 on the pneumatic piston 2.

[0038] A pressure-sealing ring 6 is located between the opening end of the pneumatic cylinder chamber of pneumatic cylinder 1 and the central connecting plate 5. The inner edge of the pressure-sealing ring 6 is a pressure-sealing inner conical surface 601 extending radially towards the atmospheric pressure space 102. The pressure-sealing ring 6 is pressed tightly and sealed with the edge of the cylinder opening of pneumatic cylinder 1. The bottom end face and side face of pneumatic piston 2 have a pressure-sealing outer conical surface 201 that cooperates with the pressure-sealing inner conical surface 601. Under normal conditions, the pressure-sealing outer conical surface 201 of pneumatic piston 2 is pressed tightly against the pressure-sealing inner conical surface 601 of pressure-sealing ring 6. This arrangement can prevent the gas 11 in the pneumatic space 101 from leaking and can also limit the movement of pneumatic piston 2. When the pressure of liquid 12 on hydraulic piston 4 is less than the pressure of gas 11 on pneumatic piston 2, it can prevent pneumatic piston 2 from continuing to slide towards the opening end of pneumatic cylinder chamber.

[0039] A pressure-expandable rupture-resistant membrane 7 is provided between the hydraulic space 301 and the atmospheric pressure space 302 of the hydraulic cylinder 3. The periphery of the membrane 7 is sealed and fixed to the inner wall of the cylinder cavity. The thickness of the membrane 7 gradually decreases from the periphery to the center, forming a crack-prone area 701 in the center of the membrane 7. The membrane 7 has a certain degree of elasticity. When the outer conical surface 201 of the pneumatic piston 2 presses against the inner conical surface 601 of the pressure ring 6, the end face of the hydraulic piston 4 abuts against the membrane 7 to prevent the crack-prone area 701 from rupturing. In this way, under normal conditions, the hydraulic space 301 can be tightly sealed for a long time to prevent the leakage of the liquid 12 in the hydraulic space 301.

[0040] The basic working principle of the device of this invention is as follows:

[0041] Under normal conditions, the high pressure of the air pressure space 101 is used to make the hydraulic piston 4 press against the separator 7 through the air pressure piston 2 and the push rod, so that the separator 7 does not break. The output section 902 and the input section 901 of the filling channel are separated by the separator 7, so that the filling channel 9 is in a closed state.

[0042] When the rubber airbag 8 suddenly ruptures, the gas 11 in the air pressure space 101 is depressurized. The high-pressure liquid 12 in the hydraulic space 301 can push the hydraulic piston through the separator 7, causing the fragile area 701 of the separator 7 to rupture under high pressure, forming a rupture 702. The high-pressure liquid 12 continues to push the hydraulic piston 4 through the rupture 702, causing the hydraulic space 301 to expand until the output port 9021 is located in the hydraulic space 301. The high-pressure liquid 12 in the input section 901 of the filling channel 9 enters the output section 902 through the expanded hydraulic space 301, thereby opening the filling channel 9.

[0043] It should be noted that in the prior art, since the piston needs to move axially in the cylinder, it is difficult to achieve a long-term absolute seal between the piston and the inner wall of the cylinder under high pressure, even if piston rings are used. Therefore, in this invention, a pressure-sealing ring 6 and a separator 7 are designed to address the sealing problem between the pneumatic piston 2 and the hydraulic piston 4 and their respective inner walls of the cylinder, so as to ensure the absolute seal of the liquid 12 in the hydraulic space 301 and the gas 11 in the pneumatic space under long-term high pressure.

[0044] The above embodiments are only used to describe the present invention more clearly, and should not be regarded as limiting the scope of protection covered by the present invention. Any equivalent modifications should be regarded as falling within the scope of protection covered by the present invention.

Claims

1. A device for controlling the opening and closing of a flow channel using the air pressure of an air spring rubber bladder, characterized in that: The device includes a pressure control unit and a valve unit. The pressure control unit has a pressure space (101) and a pressure transmission component. There is a connecting air passage (10) between the pressure space (101) and the rubber air bladder (8). The pressure in the pressure space (101) is equal to the pressure in the rubber air bladder (8). The valve unit is located on the liquid filling channel (9) and has a gate valve that allows the liquid filling channel (9) to be in a closed or open state. One end of the pressure transmission component bears the pressure of the pressure space (101), and the other end acts on the gate valve. In application, the pressure space (101)... The air pressure is controlled by a pressure transmission component to close or open the gate valve; the air pressure control unit has an air cylinder (1), which has an open end and a closed end; the pressure transmission component is an air piston (2) fitted inside the cylinder cavity of the air cylinder (1) and a push rod (202) with one end connected to the outer end of the air piston (2). The other end of the push rod (202) extends out of the open end of the air cylinder cavity and acts on the gate valve. The air piston (2) can slide inside the cylinder cavity of the air cylinder (1); the air piston (2) divides the cylinder cavity of the air cylinder (1) into The pneumatic space (101) is located at one closed end of the pneumatic cylinder cavity, and the atmospheric pressure space (102) is located at one open end of the pneumatic cylinder cavity; the valve part has a hydraulic cylinder (3), which has an open end and a closed end of the hydraulic cylinder cavity; the gate valve is a hydraulic piston (4) fitted inside the cylinder cavity of the hydraulic cylinder (3), which divides the cylinder cavity of the hydraulic cylinder (3) into a hydraulic space (301) located at one closed end of the hydraulic cylinder cavity and an atmospheric pressure space (302) located at one open end of the hydraulic cylinder cavity; the filling channel (9) is disconnected into an input section. (901) and output section (902), the input section (901) is connected to the hydraulic space (301), the output section (902) is connected to the atmospheric pressure space (302), and its output port (9021) is located in the atmospheric pressure space (302) close to the hydraulic piston (4). When the hydraulic piston (4) slides to the opening end of the hydraulic cylinder cavity, so that the hydraulic space (301) expands to the point where the output port (9021) is located in the hydraulic space (301), the input section (901) and output section (902) of the filling channel (9) are connected through the hydraulic space (301).

2. The device for controlling the opening and closing of a flow channel using the air pressure of an air spring rubber bladder according to claim 1, characterized in that: The hydraulic piston (4) has a hydraulic seal (401) on its outer periphery to prevent the liquid (12) in the hydraulic space (301) from leaking out.

3. The device for controlling the opening and closing of a flow channel using the air pressure of an air spring rubber bladder according to claim 1, characterized in that: The pneumatic cylinder (1) and the hydraulic cylinder (3) are connected by a central connecting plate (5) that fixes them together as a whole device. The pneumatic cylinder cavity opening end of the pneumatic cylinder (1) and the hydraulic cylinder cavity opening end of the hydraulic cylinder (3) are fixed on opposite sides of the central connecting plate (5) on the same axis. The central connecting plate (5) has a hole (501) in the middle. One end is connected to the push rod (202) of the pneumatic piston (2), and the other end is connected to the hydraulic piston (4) through the hole (501).

4. The device for controlling the opening and closing of a flow channel using the air pressure of an air spring rubber bladder according to claim 1, characterized in that: The pneumatic cylinder (1) has a pressure ring (6) between the opening end of the pneumatic cylinder cavity and the central connecting plate (5). The inner edge of the pressure ring (6) is a pressure inner cone surface (601) extending radially and centripetally towards the atmospheric pressure space (102). The pressure ring (6) is pressed and sealed with the edge of the cylinder mouth of the pneumatic cylinder (1). The bottom end face and the side face of the pneumatic piston (2) have a pressure outer cone surface (201) that matches the pressure inner cone surface (601).

5. The device for controlling the opening and closing of a flow channel using the air pressure of an air spring rubber bladder according to claim 4, characterized in that: There is a ventilation gap between the push rod (202) and the inner wall of the hole (501), and the central connecting plate (5) is provided with an air hole (502) that connects the atmospheric pressure space (102) to the outside.

6. The device for controlling the opening and closing of a flow channel using the air pressure of an air spring rubber bladder according to claim 4, characterized in that: The hydraulic space (301) of the hydraulic cylinder (3) is provided with a separator (7) that can expand and rupture under pressure between the hydraulic space (301) and the normal pressure space (302). The periphery of the separator (7) is sealed and fixed to the inner wall of the cylinder cavity.

7. The device for controlling the opening and closing of a flow channel using the air pressure of an air spring rubber bladder according to claim 6, characterized in that: The thickness of the separator (7) gradually decreases from the periphery to the center, making the central area a crack-prone area (701). When the outer conical surface (201) of the pneumatic piston (2) presses against the inner conical surface (601) of the compression ring (6), the end face of the hydraulic piston (4) abuts against the separator (7) to prevent the crack-prone area (701) from breaking.

8. The device for controlling the opening and closing of a flow channel using the air pressure of an air spring rubber bladder according to any one of claims 1-7, characterized in that: The hydraulic pressure of the hydraulic space (301) is greater than the air pressure of the pneumatic space (101), and the pressure area of ​​the hydraulic piston (4) subjected to the liquid (12) pressure is smaller than the pressure area of ​​the pneumatic piston (2) subjected to the gas (11) pressure, so that the pressure of the hydraulic piston (4) subjected to the liquid (12) is less than the pressure of the pneumatic piston (2) subjected to the gas (11).

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