A two-stage stroke self-controlled precision metering valve

Abstract

This invention relates to a two-stage stroke self-controlled precision metering valve, comprising a metering valve cylinder body, a metering valve body, and a metering valve nozzle. An inner flow channel cavity is provided within the metering valve body. The metering valve cylinder body is mounted on the upper end of the metering valve body, and the metering valve nozzle is mounted on the lower end of the metering valve body. A docking valve seat is also mounted on the metering valve body, forming an inlet pipe and an outlet circulation pipe. The inlet pipe and the outlet circulation pipe communicate with the inner flow channel cavity through a connecting hole on the metering valve body. The invention is characterized by further including an actuation component with an opening and closing valve stem assembly. The actuation component includes a half-open actuation component and a fully open actuation component, both of which are located within the inner flow channel cavity of the metering valve body. This solution achieves precise regulation of fluid flow, meeting the accurate flow requirements under different operating conditions and ensuring good sealing performance and elasticity even under high pressure conditions.

Description

Technical Field

[0001] This invention relates to the field of metering valves, and in particular to a two-stage stroke self-controlled precision metering valve. Background Technology

[0002] In precision fluid control applications such as chemical engineering and printing, materials sensitive to shear forces, such as UV inks and high-solids-content liquids, are prone to solidification due to frictional heat generated by moving valve components, leading to valve jamming and sealing failure. Traditional valves (such as single-stage piston valves) have significant drawbacks:

[0003] Single-stage opening and closing modes are difficult to achieve gradual flow regulation, and pulse discharge or sudden flow changes are prone to occur during micro-distribution. Existing two-stage valves (such as bellows-sealed valves) rely on double-stroke cylinders and composite valve stems to achieve graded control, but bellows are prone to fatigue damage, and cylinder response delay affects accuracy (for example, CN217784289U requires mechanical linkage between the large valve stem 14 and the small valve stem 4 to achieve two-stage regulation).

[0004] To address these issues, recent technical solutions (such as new precision metering valves) have attempted to employ dual actuation components (half-open / fully-open) and a flexible buffer structure. However, the mechanical linkage between the valve stem and valve seat in the half-open state (such as the slide rod-slide structure) still carries the risk of wear. Furthermore, the two-stage reset accuracy is affected by the liquid viscosity, leading to flow fluctuations when switching between the half-open and fully-open states. Summary of the Invention

[0005] This invention proposes a valve structure that combines anti-curing sealing, millisecond-level response, and stepless flow regulation. It is a two-stage stroke self-controlled precision metering valve that achieves high-precision dynamic distribution while avoiding mechanical friction, thus solving the aforementioned problems existing in the use of the prior art.

[0006] The technical solution of this invention is implemented as follows:

[0007] A two-stage stroke self-controlled precision metering valve includes a metering valve cylinder body, a metering valve body, and a metering valve nozzle. The metering valve body has an inner flow channel cavity. The metering valve cylinder body is mounted on the upper end of the metering valve body, and the metering valve nozzle is mounted on the lower end of the metering valve body. A detachable docking valve seat is also mounted on the metering valve body, forming an inlet pipe and an outlet circulation pipe. The inlet pipe and outlet circulation pipe communicate with the inner flow channel cavity through a connecting hole on the metering valve body. The valve is characterized by further including an actuation component with an opening and closing valve stem assembly, which includes a half-open actuation component and a fully open actuation component. Both the half-open and fully-open actuators are located within the inner flow channel cavity of the metering valve body. The half-open actuator includes an upper valve stem, a lower piston, and an inner elastic element. The fully-open actuator includes a lower valve seat, an outer elastic element, and an upper piston. The metering valve cylinder body has an upper inner cavity and a lower inner cavity. The upper end of the upper valve stem is located in the upper inner cavity and connected to the upper piston. The lower piston is mounted on the upper valve stem and is located in the lower inner cavity. The metering valve cylinder body has an air inlet that pushes the upper and lower pistons. A metering valve cover is installed on the metering valve body.

[0008] The lower section of the upper valve stem of the metering valve extends into the valve body of the metering valve. The lower valve seat of the metering valve is located below the upper valve stem of the metering valve. The end of the lower valve seat is located on the nozzle of the metering valve and controls the opening and closing of the nozzle. The lower valve seat of the metering valve has a valve passage. The upper opening of the valve passage communicates with the inner flow channel cavity, and the lower opening of the valve passage communicates with the nozzle of the metering valve. The lower section of the upper valve stem of the metering valve extends into the lower opening of the valve passage to open and close the lower opening of the valve passage. The upper ends of the outer elastic element and the inner elastic element both abut against the upper wall of the metering valve cover. The lower end of the inner elastic element is installed on the upper valve stem of the metering valve, and the lower end of the outer elastic element is installed on the end face of the lower valve seat of the metering valve.

[0009] Preferably, the lower valve seat of the metering valve has elongated slides on both sides. The length of the slides serves as the distance for the upper valve stem of the metering valve to move. The slides on both sides are connected to the valve passage. The upper valve stem of the metering valve, located in the valve passage of the lower valve seat, is equipped with a slide rod. The slide rod extends on both sides of the slide rod. When the upper valve stem of the metering valve moves to the upper end of the slide and touches it, it drives the lower valve seat of the metering valve to move upward.

[0010] Preferably, the valve stem of the metering valve is provided with a pin, and the lower end of the aforementioned internal elastic element is disposed on the pin.

[0011] Preferably, the valve cover of the metering valve is machined with an inner countersunk hole and a semi-open air inlet. A packing skeleton and a sealing element are installed on the inner countersunk hole. The sealing element and the skeleton are installed sequentially on the inner countersunk hole. An active space is formed between the valve body of the metering valve and the lower piston. The semi-open air inlet is connected to the active space, so that the lower piston is pushed upward by pressurizing through the semi-open air inlet, thereby driving the upper valve stem of the metering valve to open and achieve the semi-open state.

[0012] Preferably, the seal has an upper annular portion and a lower annular portion, the lower annular portion having an inner groove, and the lower annular portion having an inner sealing end face facing the upper valve stem end face of the metering valve.

[0013] Preferably, the lower opening of the valve passage is tapered, and the upper valve stem of the corresponding metering valve is also machined into a tapered structure, and a metering valve upper valve stem sealing ring is installed on the upper valve stem of the metering valve.

[0014] Preferably, the lower valve seat of the metering valve is machined into a conical ring end face, and the corresponding metering valve nozzle is machined into an inner conical surface. The conical ring end face of the lower valve seat and the inner conical surface of the metering valve nozzle are in surface contact. A metering valve lower valve seat sealing ring is installed on the lower valve seat, and the sealing ring is located between the conical ring end face of the lower valve seat and the inner conical surface of the metering valve nozzle.

[0015] Preferably, the upper section of the metering valve cover is installed on the metering valve cylinder body, and the lower section of the metering valve body is installed on the metering valve body, with a first sealing ring and a second sealing ring installed between each pair.

[0016] Preferably, a V-shaped groove is formed on the lower end face of the lower annular portion.

[0017] Preferably, the V-groove has circumferentially distributed mounting holes, and a spring is installed in each mounting hole.

[0018] In summary, the beneficial effects of the present invention are as follows:

[0019] This invention discloses a two-stage stroke self-controlled precision metering valve:

[0020] This precision metering valve, through its valve stem assembly, including a half-open and a fully open actuator, can precisely control the opening degree of the valve passage. In the half-open state, the lower section of the upper valve stem extends to the lower opening of the valve passage. By adjusting the position of the upper valve stem, the opening size of the lower opening of the valve passage can be changed, thereby achieving fine regulation of the fluid flow rate and meeting the precise flow requirements under different operating conditions.

[0021] Its structural design ensures that the fluid flow rate remains stable during transportation, unaffected by upstream pressure fluctuations. The internal and external elastic components provide stable restoring force to the valve stem and seat, ensuring a smooth transition during valve opening and closing, avoiding sudden flow changes caused by pressure variations, and thus achieving stable fluid transportation.

[0022] This metering valve incorporates seals and sealing rings in several key areas, such as the upper valve stem sealing ring, the lower valve seat sealing ring, and the upper and lower annular portions of the seals. These seals form a tight seal at the connections between the valve stem and valve seat, and between the valve body and valve cover, effectively preventing fluid leakage from gaps under high pressure or high viscosity conditions, and ensuring that the fluid flows along a predetermined path within the valve body.

[0023] The lower end of the valve passage features a tapered design, which is compatible with the tapered valve stem of the metering valve. The tight fit of the tapered sealing surface further enhances the sealing effect. When the valve stem closes the valve passage, the tapered sealing surface provides a larger sealing area and more uniform sealing pressure, thereby better preventing fluid leakage.

[0024] Because it employs a pneumatic drive system, compressed air enters through the inlet of the metering valve cylinder body, pushing the upper and lower pistons to move rapidly, thus achieving rapid opening and closing of the valve stem. Compared to manual or electric drives, pneumatic drives offer faster response times and greater driving force, enabling valve opening and closing actions to be completed in a short time, thereby improving fluid transport efficiency in the production process.

[0025] This metering valve can be integrated with an automated control system to precisely control the valve's opening degree and opening / closing time by controlling the compressed air pressure and flow rate at the inlet. On automated production lines, valve opening and closing programs can be preset according to production process needs, enabling unattended automated operation, further improving production efficiency and reducing labor costs.

[0026] The structural features of this metering valve enable it to handle high-viscosity fluids, reducing resistance during flow. Simultaneously, the powerful pneumatic drive provides sufficient force to overcome the flow resistance of high-viscosity fluids, ensuring proper opening and closing even under such conditions and enabling metered delivery. Furthermore, the seals and elastic components are made of high-pressure resistant materials, ensuring excellent sealing performance and elasticity even under high-pressure conditions.

[0027] The various components of this precision metering valve, such as the metering valve cylinder body, valve body, nozzle, and valve stem assembly, all adopt a modular design. This design allows each component to be disassembled and replaced independently, facilitating routine maintenance and repair. When a component malfunctions, it is not necessary to replace the entire valve; only the damaged part needs to be replaced, significantly reducing maintenance costs and time.

[0028] The metering valve cover is detachably connected to the metering valve cylinder body and valve body using methods such as bolt connections, facilitating disassembly and assembly. Additionally, mounting holes and locating pins are provided on the valve body and cover for quick and accurate positioning during installation, improving disassembly and assembly efficiency. Furthermore, easily damaged parts such as the packing skeleton and seals are easily replaceable, further reducing maintenance difficulty. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of a two-stage stroke self-controlled precision metering valve according to this embodiment.

[0031] Figure 2 This is a planar schematic diagram of a two-stage stroke self-controlled precision metering valve.

[0032] Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure in the middle BB direction.

[0033] Figure 4 for Figure 3 A magnified view of a section at point I.

[0034] Figure 5 for Figure 3 A magnified view of section II in the middle.

[0035] Figure 6 for Figure 3 A magnified view of a section at point III.

[0036] Figure 7 This is a three-dimensional schematic diagram of the lower valve seat of a metering valve.

[0037] Figure 8 This is a plan view of the lower valve seat of a metering valve.

[0038] Figure 9 for Figure 8Schematic diagram of the cross-sectional plane of AA.

[0039] Figure 10 This is a schematic diagram of the structure of the metering valve cover.

[0040] Figure 11 This is a schematic diagram of the sealing element.

[0041] Figure 12 This is a planar schematic diagram of the seal.

[0042] Figure 13 for Figure 12 A schematic cross-sectional view of the CC section.

[0043] Figure 14 A schematic diagram of a structure for adding a spring to a seal.

[0044] Figure 15 This is a schematic diagram of the closed state of a two-stage stroke self-controlled precision metering valve.

[0045] Figure 16 This is a schematic diagram of the structure of a two-stage stroke self-controlled precision metering valve in its half-open state.

[0046] Figure 17 This is a schematic diagram of the fully open state of a two-stage stroke self-controlled precision metering valve.

[0047] 1. Metering valve cylinder body; 1-1. Upper inner cavity of metering valve cylinder; 1-2. Lower inner cavity of metering valve cylinder; 2. Metering valve body; 3. Inner flow channel cavity; 4. Metering valve nozzle; 4-1. Inner conical surface; 5. Connecting valve seat; 5. Discharge circulation pipe; 5-2. Feed pipe; 6. Metering valve cover; 6. Half-open air inlet; 6-2. Inner countersunk hole; 7-1. Second sealing ring; 7-2. First sealing ring; 8. Packing skeleton; 9. Sealing element; 9-1. Inner sealing end face; 9-2. Spring; 9-3. V-groove; 10. Upper valve stem of metering valve; 13-1. Inner elastic element; 13-2. Outer elastic element; 14. Pin; 15. Lower valve seat of metering valve; 15-1. Conical ring end face; 16. Valve passage; 16-1. Lower opening of valve passage; 16-2. Upper opening of valve passage; 17. Sealing ring; 18. Slide rail; 19. Upper valve stem sealing ring of metering valve; 20. Slide rod; 111. Upper piston. Detailed Implementation

[0048] The following will refer to the appendices in the embodiments of the present invention. Figure 1-17 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0049] Example

[0050] like Figures 1 to 17 As shown, this embodiment discloses a two-stage stroke self-controlled precision metering valve, which includes the following structural components:

[0051] Main structure: Metering valve cylinder body 1: mounted on the upper end of the metering valve body 2. Internally, it has two independent inner cavities: the upper inner cavity 1-1 and the lower inner cavity 1-2. A magnetic induction switch is installed at the upper end of the metering valve cylinder body 1, providing a new type of on / off feedback.

[0052] The valve body 2 of the metering valve has an inner flow channel cavity 3 in the center. The cylinder body 1 is installed at the upper end of the valve body, the metering valve nozzle 4 is installed at the lower end, and the valve seat 5 is installed on the side wall of the valve body.

[0053] Metering valve nozzle 4: Installed at the lower end of the metering valve body 2, serving as the final outlet for the material.

[0054] The docking valve seat 5 is a detachable structure mounted on the metering valve body 2, forming the inlet pipe 5-2 and the outlet circulation pipe 5-1. The inlet pipe 5-2 and the outlet circulation pipe 5-1 communicate with the inner flow channel cavity 3 through a connecting hole on the valve body 2. This port allows for easy disassembly and cleaning of the internal dye, preventing dye contamination; it also serves a rinsing function.

[0055] The metering valve cover 6 is mounted on the metering valve body 2. The upper section of the metering valve cover 6 is connected to the metering valve cylinder body 1. The metering valve body 2 is equipped with a first sealing ring 7-2 and a second sealing ring 7-1 to ensure a seal. The metering valve cover 6 has an inner countersunk hole 6-2 and a semi-open air inlet 6-1. A packing skeleton 8 and a sealing element 9 are sequentially installed inside the inner countersunk hole 6-2. The sealing element 9 has an upper annular portion 91 and a lower annular portion 92. The lower annular portion has an inner countersunk groove, and its end face forms an inner sealing end face 9-1 facing the upper valve stem of the metering valve. A V-groove 9-3 is also formed on the lower end face of the lower annular portion. Circumferentially distributed mounting holes are formed on this V-groove 9-3, and springs 9-2 are installed in these mounting holes to enhance the seal.

[0056] Actuation components: Located within the inner flow passage cavity 3 of the metering valve body 2, including a half-open actuation component and a fully open actuation component, wherein:

[0057] Half-open execution components:

[0058] The upper valve stem 10 of the metering valve extends into the inner cavity 1-1 of the metering valve cylinder and is connected and fixed to the upper piston 111.

[0059] Lower piston 11-1: Installed on the upper valve stem 10 of the metering valve and located in the lower inner cavity 1-2 of the metering valve cylinder. A movable space is formed between the metering valve body 2 and the lower piston 11-1. The semi-open air inlet 6-1 of the metering valve cover 6 communicates with this movable space.

[0060] Internal elastic element 13-1: For example, a helical spring. Its upper end abuts against the lower wall of the metering valve cover 6, and its lower end is mounted on the pin 14 on the upper valve stem 10 of the metering valve.

[0061] Full execution components:

[0062] The lower valve seat 15 of the metering valve is located below the upper valve stem 10 of the metering valve. Its end (preferably machined into a conical ring end face 15-1) is positioned on the corresponding inner conical surface 4-1 of the metering valve nozzle 4, used to control the opening and closing of the nozzle 4. A valve passage 16 is machined inside the lower valve seat 15. The upper opening of the valve passage 16 communicates with the inner flow channel cavity 3, and the lower opening 16-1 (preferably conical) communicates with the metering valve nozzle 4 through a slide rail 18. A lower valve seat sealing ring 17 is installed on the lower valve seat 15. This sealing ring 17 is located between its conical ring end face 15-1 and the inner conical surface 4-1 of the nozzle, ensuring a seal. The lower valve seat 15 has elongated slide rails 18 on both sides. The length of the slide rails 18 limits the movement distance of the upper valve stem 10 of the metering valve, and the two slide rails 18 communicate with the valve passage 16.

[0063] External elastic element 13-2: For example, a helical spring. Its upper end abuts against the lower wall of the metering valve cover 6, and its lower end is mounted on the end face of the lower valve seat 15 of the metering valve.

[0064] Upper piston 111: As mentioned above, it is connected to the upper valve stem 10 of the metering valve and is located in the upper inner cavity 1-1 of the cylinder.

[0065] 3. Connection and actuation mechanisms:

[0066] The lower section of the upper valve stem 10 of the metering valve passes through the upper opening 16-2 of the valve passage, and its end (preferably machined into a tapered structure 10-1 adapted to the lower opening of the valve passage) is used to open and close the lower opening 16-1 of the valve passage. A metering valve upper valve stem sealing ring 19 is installed on this tapered structure.

[0067] A slide rod 20 is installed on the upper valve stem 10 of the metering valve, which is located in the valve passage 16 of the lower valve seat 15. The two ends 20-1 of the slide rod 20 extend into the slide passages 18 on both sides of the lower valve seat 15. When the upper valve stem 10 of the metering valve moves upward until the slide rod 20 abuts the upper end of the slide passage 18, it can drive the lower valve seat 15 of the metering valve to move upward together.

[0068] The working principle of this invention is as follows:

[0069] 1. Initial / Closed State:

[0070] refer to Figure 15When there is no compressed air input, the elastic force of the inner elastic element 13-1 acts downward on the upper valve stem 10 of the metering valve, causing the conical sealing surface at its lower end to press against the lower valve seat 15 of the metering valve at the lower valve port 16-1 (conical port), thus closing the material downward flow channel (i.e., closing the nozzle).

[0071] At the same time, the elastic force of the external elastic element 13-2 acts downward on the lower valve seat 15 of the metering valve, so that its conical ring end face 15-1 is pressed and sealed on the inner conical surface 4-1 of the metering valve nozzle 4 by the sealing ring 17 of the lower valve seat of the metering valve, thus ensuring double closure.

[0072] The material can enter the inner flow channel cavity 3 through the feed pipe 5-2 and circulate through the discharge circulation pipe 5-1.

[0073] 2. Half-open state (precise measurement):

[0074] refer to Figure 16 Compressed air is introduced into the active space through the semi-open air inlet 6-1, as shown at point D in the figure.

[0075] Air pressure acts on the lower end face of the lower piston 11-1, pushing the lower piston 11-1 to move upward against the elastic force of the inner elastic element 13-1.

[0076] The lower piston 11-1 drives the upper valve stem 10 of the metering valve to move upward.

[0077] When the upper valve stem 10 of the metering valve moves upward, the conical sealing surface at its lower end moves away from the lower valve port 16-1 by a certain distance (the stroke is controlled by the stroke of the lower piston), opening a smaller flow section. At this time, the slide rod 20 moves within the slide rail 18, but does not contact the upper end of the slide rail. Therefore, the lower valve seat 15 of the metering valve remains in the state of pressing the nozzle 4 under the action of the external elastic element 13-2.

[0078] Since the lower valve seat 15 of the metering valve still seals the nozzle 4, the material accumulates in this chamber and is in a state of waiting for precise discharge (or precise discharge of a small flow rate can be achieved by controlling the opening time).

[0079] 3. Fully open (rapid emission):

[0080] refer to Figure 17 Compressed air is input into the upper inner cavity 1-1 of the metering valve cylinder through the air inlet of the metering valve cylinder body 1 (usually located at the control upper piston). This is shown at point E in the figure.

[0081] Air pressure acts on the upper end face of the upper piston 111, pushing the upper piston 111 to move downward against the combined elastic force of the inner elastic element 13-1 and the outer elastic element 13-2.

[0082] The upper piston 111 drives the upper valve stem 10 of the metering valve to continue moving upward (at this time, the lower piston 11-1 may follow).

[0083] The upper valve stem 10 of the metering valve moves upward until the slide rod 20 on it abuts against the upper end of the slide rail 18 of the lower valve seat 15 of the metering valve.

[0084] After the slide rod 20 contacts the upper end of the slide rail 18, the upward force is transmitted through the slide rod 20 to the lower valve seat 15 of the metering valve, causing the entire lower valve seat 15 of the metering valve to move upward against the elastic force of the external elastic element 13-2.

[0085] The lower valve seat 15 of the metering valve moves upward, and its conical ring end face 15-1 is separated from the inner conical surface 4-1 of the metering valve nozzle 4. At the same time, the conical end of the upper valve stem 10 of the metering valve is also away from the lower opening of the valve passage 16, and the material flow channel is fully opened (both the valve passage and the nozzle outlet are open), so as to realize the rapid and large flow rate of material discharge.

[0086] 4. Reset to the off state:

[0087] Cut off the compressed air in the upper inner cavity 1-1 of the cylinder and release the pressure in the active space 12.

[0088] Under the elastic force of the internal elastic element 13-1, the upper valve stem 10 of the metering valve drives the upper piston 111 and the lower piston 11-1 to move downward.

[0089] When the valve stem 10 of the metering valve moves down, its conical end first re-seals the lower opening of the valve passage 16 (closing the valve passage).

[0090] At the same time, under the elastic force of the external elastic element 13-2, the lower valve seat 15 of the metering valve also moves downward, and its conical ring end face 15-1 is pressed and sealed again on the inner conical surface 4-1 of the metering valve nozzle 4 by the sealing ring 17 (closing the nozzle), restoring the initial closed state.

[0091] This embodiment achieves two operating modes—precise low-flow metering (half-open) and rapid high-flow discharge (fully open)—through independent half-open and fully-open actuators, meeting different process requirements. In the half-open state, only the valve stem sealing port is open, providing good flow controllability. Combined with time control, high-precision metering can be achieved. A multi-seal design—conical seal + sealing rings (upper valve stem sealing ring, lower valve seat sealing ring) and valve cover (packing, sealing element, V-groove spring)—ensures no leakage in the closed state. The ingenious design of the slide rod and slideway allows a single drive source (upper cylinder chamber) to sequentially control the valve stem opening and lower valve seat lifting, achieving the fully open function. Internal and external elastic elements provide actuation buffering and ensure reliable reset and closure after air pressure release. Modular design: components such as the cylinder body, valve body, valve cover, and valve seat are connected by sealing rings, facilitating maintenance.

[0092] The present invention provides a half-open actuator and a full-open actuator, which can respectively achieve two different opening degrees; through the cooperation of the upper and lower inner cavities of the cylinder and the elastic element, the full stroke control of half-open-full-open-close is automatically completed.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A two-stage stroke self-controlled precision metering valve, comprising a metering valve cylinder body, a metering valve body, and a metering valve nozzle, wherein an inner flow channel cavity is provided within the metering valve body, the metering valve cylinder body is mounted on the upper end of the metering valve body, the metering valve nozzle is mounted on the lower end of the metering valve body, and a detachable docking valve seat is also mounted on the metering valve body, the docking valve seat forming an inlet pipe and an outlet circulation pipe, the inlet pipe and the outlet circulation pipe communicating with the inner flow channel cavity through a connecting hole opened on the metering valve body, characterized in that: It also includes an actuator assembly with an opening and closing valve stem assembly. The actuator assembly includes a half-open actuator assembly and a fully open actuator assembly, both of which are located within the inner flow channel cavity of the metering valve body. The half-open actuator assembly includes an upper valve stem, a lower piston, and an inner elastic element. The fully open actuator assembly includes a lower valve seat, an outer elastic element, and an upper piston. The metering valve cylinder body has an upper inner cavity and a lower inner cavity. The upper end of the upper valve stem is located in the upper inner cavity and connected to the upper piston. The lower piston is mounted on the upper valve stem and located in the lower inner cavity. The metering valve cylinder body has an air inlet for moving the upper and lower pistons. A metering valve cover is installed on the metering valve body. The lower section of the upper valve stem of the metering valve extends into the valve body. The lower valve seat of the metering valve is located below the upper valve stem. The end of the lower valve seat is mounted on the metering valve nozzle and controls the opening and closing of the nozzle. The lower valve seat has a valve passage, the upper opening of which communicates with the inner flow channel cavity, and the lower opening of which communicates with the metering valve nozzle. The lower section of the upper valve stem extends into the lower opening of the valve passage to open and close it. The upper ends of both the outer and inner elastic elements abut against the upper wall of the metering valve cover. The lower end of the inner elastic element is installed on the upper valve stem of the metering valve, and the lower end of the outer elastic element is installed on the end face of the lower valve seat of the metering valve. The lower valve seat of the metering valve has elongated slides on both sides. The length of the slides serves as the distance for the upper valve stem of the metering valve to move. The two slides are connected to the valve passage. The upper valve stem of the metering valve, which is located in the valve passage of the lower valve seat of the metering valve, is equipped with a slide rod. The slide rod extends on both sides of the slide rod. When the upper valve stem of the metering valve moves to the upper end of the slide and touches it, it drives the lower valve seat of the metering valve to move upward.

2. The two-stage stroke self-controlled precision metering valve according to claim 1, characterized in that: The valve stem of the metering valve is provided with a pin, and the lower end of the aforementioned internal elastic element is set on the pin.

3. A two-stage stroke self-controlled precision metering valve according to claim 1 or 2, characterized in that: The metering valve cover is machined with an inner countersunk hole and a semi-open air inlet. A packing skeleton and a sealing element are installed on the inner countersunk hole. The sealing element and the skeleton are installed sequentially on the inner countersunk hole. An active space is formed between the metering valve body and the lower piston. The semi-open air inlet is connected to the active space, so that the lower piston is pushed upward by pressurizing the semi-open air inlet, thereby driving the upper valve stem of the metering valve to open and achieve the semi-open state.

4. The two-stage stroke self-controlled precision metering valve according to claim 2, characterized in that: The seal has an upper annular portion and a lower annular portion. The lower annular portion has an inner groove and an inner sealing end face facing the valve stem end face of the metering valve.

5. The two-stage stroke self-controlled precision metering valve according to claim 1, characterized in that: The lower opening of the valve passage is tapered, and the upper valve stem of the corresponding metering valve is also machined into a tapered structure. A metering valve upper valve stem sealing ring is installed on the upper valve stem of the metering valve.

6. The two-stage stroke self-controlled precision metering valve according to claim 1, characterized in that: The lower valve seat of the metering valve is machined into a conical ring end face, and the corresponding metering valve nozzle is machined into an inner conical surface. The conical ring end face of the lower valve seat and the inner conical surface of the metering valve nozzle are in surface contact. A metering valve lower valve seat sealing ring is installed on the lower valve seat, and the sealing ring is located between the conical ring end face of the lower valve seat and the inner conical surface of the metering valve nozzle.

7. The two-stage stroke self-controlled precision metering valve according to claim 1, characterized in that: The upper section of the metering valve cover is connected to the metering valve cylinder body, and the lower section of the metering valve body is installed on the metering valve body, with a first sealing ring and a second sealing ring installed between each pair.

8. The two-stage stroke self-controlled precision metering valve according to claim 4, characterized in that: A V-shaped groove is cut on the lower end face of the lower annular part.

9. The two-stage stroke self-controlled precision metering valve according to claim 8, characterized in that: The V-groove has circumferentially distributed mounting holes, and springs are installed in the mounting holes.

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