Hydraulic bulging device and method for overflow type diaphragm valve body

Abstract

The invention relates to the technical field of metal pipe precise plastic forming, and discloses a hydraulic bulging device and method for an overflow type diaphragm valve body. The device comprises an upper die, a lower die, a first axial punch, a second axial punch, a radial V-shaped punch and a hydraulic driving system. The axial punch integrates the functions of sealing, liquid injection, pressure applying and material supplementing, liquid in a pipe blank is directly extruded through mechanical feeding to generate high pressure, an original independent ultrahigh pressure source is replaced, meanwhile, axial material supplementing is achieved, and a complex material supplementing mechanism is not needed. And the radial V-shaped punch is used for locally forming the overflow weir. The forming method comprises the steps of sealing and liquid injection of the axial punch, mechanical feeding of the bulging body and local forming of the overflow weir through the radial punch. The method has the advantages of equipment simplification, low cost, high forming precision, high material utilization rate and the like, and is suitable for efficient and precise manufacturing of overflow diaphragm valve bodies made of stainless steel and other materials.

Description

Technical Field

[0001] This invention relates to the field of precision plastic forming technology for metal pipes, specifically a progressive step-by-step hydraulic bulging precision forming method and apparatus for overflow diaphragm valve bodies. Background Technology

[0002] Overflow diaphragm valves are key actuators in fluid control systems. Their valve bodies typically have complex internal flow channels and external structures, especially with an overflow weir of a specific geometry. Traditional valve body manufacturing mainly employs casting or forging followed by machining, which suffers from low material utilization, long production cycles, high costs, and the potential for casting defects to affect sealing performance.

[0003] Hydraulic tubing forming technology has shown promise in valve body manufacturing due to its advantages such as one-piece forming of complex hollow components, high material utilization, and good product performance. However, traditional hydraulic tubing forming processes face significant challenges when forming parts with localized asymmetric protrusions: to obtain sufficient bulge volume and avoid breakage, an independent ultra-high-pressure liquid supply system is typically required to provide the forming internal pressure, while a precise axial feeding mechanism is also needed to push the material towards the thinning zone in real time during the later stages of bulging. This dual dependence on the high-pressure source and feeding mechanism results in an exceptionally complex, expensive, and difficult-to-control equipment system, greatly limiting the application of this technology in the mass production of medium- to low-cost valve bodies.

[0004] In the prior art, CN104785604B discloses a method and apparatus for impact hydraulic bulging of thin-walled double-layer metal tubes. This method utilizes the impact force during mold closing to generate high pressure in the liquid within the mold, and axial feeding is achieved through a horizontal guide post driven by a lead screw. While this method does not require an independent ultra-high pressure source, the controllability of the pressure generated by the "impact" is poor, making it difficult to meet the precise control requirements of high-precision valve bodies for the bulging pressure curve. Furthermore, its apparatus structure is complex, involving components such as dovetail grooves and positive and negative lead screws, resulting in high processing and assembly costs.

[0005] CN107520311B describes an impact hydraulic bulging device and method for thin-walled metal composite tubes. This method improves upon the former by using a screw jack as the feeding unit and integrating a liquid injector. However, it still falls under the category of "impact hydraulic bulging," where pressure generation depends on the impact compression of the descending upper die. The stability and precision control of the forming process remain limited.

[0006] CN121017358A discloses an electromagnetic-hydraulic composite bulging method and apparatus, which reduces the material's deformation resistance through electromagnetic pre-activation, and then combines it with hydraulics for precision bulging and shaping. This technology is mainly used for tube sheet-like parts, but it introduces a complex electromagnetic heating and magnetic field generation system, resulting in high equipment costs and complex process control. It is not suitable for low-cost, high-efficiency, and precision forming of parts such as overflow diaphragm valve bodies, which use stainless steel tubes as blanks and have specific local protrusion features.

[0007] Therefore, there is an urgent need to develop a new hydraulic bulging device and forming method that simplifies the equipment structure, controls the cost, and can integrally form the overflow diaphragm valve body with high quality. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a hydraulic bulging precision forming method and apparatus for overflow diaphragm valve bodies. This technical solution, through structural innovation and process optimization, abandons the traditional independent ultra-high pressure source and complex feeding mechanism. It utilizes the mechanical feed of an axial punch to directly generate controllable high pressure and simultaneously achieve axial feeding. Combined with a dedicated radial punch for local forming of the overflow weir, it achieves near-net-shape forming of the valve body at high efficiency, precision, and low cost.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a hydraulic bulging device for an overflow diaphragm valve body, comprising an upper die, a lower die, a first axial punch, a second axial punch, a radial V-shaped punch, and a hydraulic drive and PLC control system.

[0010] The upper and lower molds, when closed, form a main cavity for accommodating the tube blank, and a radial window is provided at the position corresponding to the overflow weir of the valve body. Both the upper and lower molds adopt a split structure, including a mold base and replaceable inserts. The advantages of this design are: firstly, friction between the tube and the mold during high-pressure forming can easily lead to wear on the working surface of the cavity; the split structure allows for the replacement of only the lower-cost inserts, rather than the expensive integral mold, significantly extending the overall service life of the mold and reducing maintenance costs; secondly, by replacing inserts with different cavities, the same mold body can adapt to the production of overflow diaphragm valve bodies of different sizes and shapes, greatly improving mold versatility and reducing mold investment for new product development.

[0011] The first axial punch and the second axial punch are disposed opposite to each other and are slidably and sealingly installed at the two end openings of the main cavity.

[0012] The radial V-shaped punch is located on the side of the main cavity, corresponding to the forming position of the overflow weir of the valve body, and can slide radially. Its working surface is a V-shaped structure adapted to the shape of the overflow weir.

[0013] The first axial punch has an axially oriented liquid passage, which is connected to the liquid passage in the base of the first axial punch in a zigzag pattern. The base of the first axial punch has an interface for communicating with an external liquid supply system, which is used to inject liquid into the sealed inner cavity of the tube blank. The connection between the base of the first axial punch and the external liquid supply system is equipped with a controllable stop valve, which is used to prevent backflow after the liquid is full.

[0014] The second axial punch and its corresponding punch base are solid structures with no liquid passage holes inside.

[0015] The ends of the first axial punch and the second axial punch are provided with tapered sealing heads and stepped shaft structures.

[0016] The first and second axial punches are not only sealing and liquid injection units, but more importantly, their axial feed motion is directly used to squeeze the liquid inside the tube blank to establish the internal pressure required for expansion, and at the same time realize the synchronous replenishment (feeding) of axial material.

[0017] In a second aspect, the present invention provides a hydraulic bulging method for an overflow-type diaphragm valve body using the above-mentioned device, comprising the following steps: S1. Mold assembly: Place the tube blank into the main cavity of the lower mold, and close the upper mold and the lower mold; S2, Sealing and Liquid Injection: Drive the first axial punch and the second axial punch to move towards each other, enter both ends of the tube blank and achieve sealing; inject liquid medium into the tube blank through the liquid passage of the first axial punch, and close the stop valve after it is full; S3, Main body expansion: Drive the first axial punch and the second axial punch to keep in sync and continue to feed towards each other. Through their mechanical displacement, they directly squeeze the liquid in the tube blank, causing the liquid pressure to rise sharply, so that the tube blank will undergo plastic expansion under the action of liquid pressure. The bulging process is completed step by step through multiple progressive subaxial feed operations. Between two feed operations, there is a forming interruption period to adjust forming conditions such as pressure, material state or liquid medium. Through multiple cycles, the material can be progressively and controllably fitted into the mold cavity. S4, Local Forming Overflow Weir: Drive the V-shaped radial punch to press into the predetermined position of the side wall of the expanded tube blank in the radial direction; during this process, according to the feedback of material flow and forming force, the first and second axial punches can perform coordinated feeding motion (feeding) or pressure maintenance, forming a dynamic coupling effect with the radial punch, so that under the constraint of the mold and the support of the internal liquid, the overflow weir structure is locally and accurately formed and tearing or wrinkling defects are prevented. S5. Unloading and Removing Parts: After forming is completed, the radial V-shaped punch retracts first; then, the first and second axial punches retract, the water stop valve opens to release the internal pressure; finally, the mold is opened, and the fully formed overflow diaphragm valve body is removed.

[0018] The core innovation of this invention lies in the fact that the first and second axial punches not only seal both ends of the tube blank, but their synchronous, opposing mechanical feed motions are also directly used to squeeze the liquid inside the tube blank, thereby establishing the internal high pressure required for expansion. Simultaneously, this axial feed motion naturally pushes the material at both ends of the tube blank towards the central expansion zone, achieving axial material replenishment. Thus, the axial punches integrate four major functions: sealing, liquid injection, pressure application (generating high pressure), and material replenishment.

[0019] The beneficial effects of the apparatus and method of the present invention are as follows: 1. Significantly simplified equipment and reduced costs: High pressure is directly generated and material is replenished synchronously by using the mechanical feed of the axial punch, completely eliminating the need for expensive independent ultra-high pressure pump stations and complex independent material replenishment control systems. The equipment structure is simplified and the manufacturing cost is significantly reduced. 2. High forming quality and precision: Employing a multi-step, progressive process of "first forming the overall body, then forming local features," the forming difficulty of complex shapes is reduced, effectively decreasing the risk of cracking and wrinkling. Mechanical material feeding results in more uniform wall thickness distribution, denser part structure, high dimensional accuracy, and good surface quality. 3. Strong process controllability: The bulging pressure is precisely controlled by the displacement of the axial punch, the pressure curve is stable and controllable, it is easy to realize closed-loop control, the process repeatability is high, and it is suitable for mass production; 4. Good mold economy: The split mold design concentrates the easily worn cavity surfaces in replaceable inserts, reducing maintenance costs and enabling quick mold changeover by replacing inserts, adapting to the needs of multi-variety production; 5. Optimized Liquid Injection System Design: The liquid inlet is located on the axial punch base rather than the punch itself, and connected by a zigzag water channel. This effectively isolates the impact of extremely high internal pressure during the forming process on the liquid supply system, improving system safety and service life. Furthermore, the liquid inlet structure is only installed on the side requiring injection, while the other side uses a solid structure. This reduces processing costs and avoids the sealing risks that may arise from complex liquid inlet paths. 6. Enhanced adaptability to forming processes: By employing a multi-pass progressive forming method, and decomposing the overall deformation into multiple "axial feed operations" with "forming interruption periods" in between, this invention forms a flexibly configurable forming process framework. This method does not limit the specific operations of the interruption periods, thus encompassing various process variations such as pressure holding, pressure release, and fluid change, exhibiting strong material adaptability and a wide process window. 7. More precise and intelligent forming process control: In the local feature forming stage, the axial punch and radial punch do not move independently, but rather coordinate and couple their movements according to process requirements. This dynamic control strategy can respond to the material state in real time, effectively solving the problems of insufficient material (easy to crack) or excess material (easy to wrinkle) in local forming, and significantly improving the success rate and quality consistency of forming complex structural parts; 8. Clearly defined scope of application: It is particularly suitable for the integrated precision forming of overflow diaphragm valve bodies made of stainless steel and other materials, providing an efficient and low-cost manufacturing solution for high-end fluid control components. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the hydraulic bulging device of the present invention; Figure 2 for Figure 1 Schematic diagram of the middle and lower die section and the axial and radial punches; Figure 3 for Figure 1 Schematic diagram of the upper and middle mold section; Figure 4 This is a cross-sectional schematic diagram of the tube blank sealing and liquid filling stages; Figure 5 A cross-sectional schematic diagram of the main bulging stage for the axial punch mechanical feed; Figure 6 This is a cross-sectional schematic diagram of the local forming overflow weir stage of the radial punch; In the figure: 1. First axial punch pressure plate; 2. First axial punch base; 3. First axial punch slide plate; 4. First axial punch; 5. Tube blank; 6. Lower die insert; 7. Lower die base; 8. First lower pad; 9. Second lower pad; 10. Upper pad; 11. Upper die base; 12. V-shaped radial punch; 13. Radial punch pressure plate; 14. Radial punch base; 15. Radial punch slide plate; 16. Second axial punch pressure plate; 17. Second axial punch base; 18. Second axial punch slide plate; 19. Second axial punch; 20. Upper die insert. Detailed Implementation

[0021] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only for explaining the present invention and do not constitute a limitation on the scope of protection of the present invention. Example 1

[0022] A hydraulic expansion device for an overflow diaphragm valve body, as described in the reference. Figures 1 to 3 ,include: The upper mold consists of an upper mold base 11, an upper pad 10, and an upper mold insert 20. And the lower mold composed of the lower mold base 7, the first lower pad 8, the second lower pad 9 and the lower mold insert 6; The upper mold insert 20 and the lower mold insert 6 form the main cavity of the valve body, and a radial window is provided at the overflow weir position.

[0023] The upper and lower molds adopt a split structure. The lower mold insert 6 is fixed to the lower mold base 7 with screws, and its inner surface is precisely machined with the main contour cavity of the lower half of the valve body. The first lower pad 8 and the second lower pad 9 are used to adjust the mold closing height and bear the forming force. The upper and lower molds are precisely guided by two guide pillars (not labeled in the figure) to ensure the mold closing accuracy.

[0024] The upper and lower molds adopt a split structure, which has dual significance: First, during the high-pressure bulging process, there is significant friction between the tube blank 5 and the cavity surface of the lower mold insert 6, which can easily lead to wear on the working surface. With the split structure, when the lower mold insert 6 is worn or damaged, only the relatively low-cost insert part needs to be replaced, without replacing the entire lower mold base 7 and other large components such as the backing plate. This greatly reduces maintenance costs and extends the service life of the mold body.

[0025] Secondly, the overflow diaphragm valve body comes in various specifications and sizes. By replacing the lower mold insert 6 with different cavity designs, the same set of lower mold body can adapt to the production needs of different products, which significantly improves the versatility and economy of the mold and reduces the mold investment for multi-variety production.

[0026] Similarly, the split design of the upper mold has the same advantages: the inner insert 20 of the upper mold serves as the direct forming surface, withstands high pressure and friction, and can be replaced individually; by replacing different inner inserts, valve bodies of various specifications can be produced. This modular design concept makes the mold more flexible and economical in dealing with wear and product changes.

[0027] After mold closing, the semi-open space formed by the upper mold insert 20 and the lower mold insert 6 becomes the main cavity. Crucially, at the position corresponding to the overflow weir of the valve body, the lower mold insert 6, lower mold base 7, upper mold base 11, and upper mold insert 20 are provided with through-hole radial windows. These windows, after mold closing, collectively form an open channel, providing space for the radial V-shaped punch 12 to enter. Therefore, the mold cavity formed after mold closing is closed in the main body of the valve body, but radially open at the predetermined overflow weir forming position. This is a key structural feature for achieving the multi-step process of "first overall bulging, then local extrusion."

[0028] The device also includes an axial punch unit: The first axial punch 4 and the second axial punch 19 are structurally symmetrical and are the core functional components of this invention. They are respectively mounted via the first axial punch slide 3 and the second axial punch slide 18, and driven by independent servo hydraulic cylinders, enabling high-precision synchronous opposite movement.

[0029] The punch front end is designed with a tapered sealing head and a stepped shaft feature to ensure a reliable liquid seal when inserted into both ends of the tube blank 5.

[0030] Both the first axial punch 4 and the first axial punch base 2 have fluid passage holes (Φ5mm in diameter) machined inside, and their fluid passages are interconnected in a zigzag pattern. Due to the significant pressure generated by the squeezed liquid during the expansion process, to protect the external pressure source and the first axial punch 4, the first axial punch base 2 is connected to the external liquid supply system (including a water pump, water tank, and low-pressure pipeline). An additional manual stop valve (or solenoid valve) can be added at the connection point to close the system after the liquid is full, preventing backflow. However, the second axial punch 19 and the second axial punch base 17 do not have fluid passage holes machined inside. This reduces processing costs and avoids potential sealing problems caused by complex fluid passage paths, ensuring a good seal at this end.

[0031] The first axial punch plate 1, the first axial punch base 2, the second axial punch plate 16, and the second axial punch base 17 are used to firmly fix the punch on its drive slide plate and transmit axial force.

[0032] The device also includes a radial punch unit: The V-shaped radial punch 12 is supported by the radial punch base 14 and connected to a radially arranged hydraulic cylinder via the radial punch slide 15, and is driven by the hydraulic cylinder. Its working surface is a precisely machined 120° V-shaped groove that perfectly matches the design shape of the valve body overflow weir.

[0033] The radial punch plate 13 is used to fix the V-shaped radial punch 12. This unit is independent of the axial punch system and can perform radial feed and retraction in a specific timing sequence under program control.

[0034] The device also includes a hydraulic and control system: the device is driven by an integrated hydraulic station that powers two axial servo hydraulic cylinders and one radial hydraulic cylinder.

[0035] The control system employs a PLC (Programmable Logic Controller) or CNC system, pre-programmed with multi-step forming procedures, and can execute progressive impact forming processes. The system can precisely control the synchronous displacement, speed, and dwell time of the axial punch, as well as the intervention timing and stroke of the radial punch. Equipped with high-precision pressure and displacement sensors, the system monitors the internal hydraulic pressure of the billet and the punch position in real time, achieving pressure-displacement adaptive closed-loop control. In progressive impact mode, the system can automatically adjust the feed rate, holding time, and depressurization degree of each impact based on a pre-set process curve or real-time feedback. Example 2

[0036] A hydraulic bulging method for an overflow diaphragm valve body, referring to... Figures 4 to 6Taking the forming of a certain type of 304 stainless steel overflow diaphragm valve body as an example, the multi-step hydraulic bulging method of the present invention is described in detail, including the following steps: S1. Billet preparation and mold loading: In this embodiment, a 304 stainless steel seamless tube with an outer diameter of Φ36mm, a wall thickness of 2.5mm, and a length of 150mm is selected as tube blank 5, and its inner and outer surfaces are cleaned. Install the lower mold part on the press worktable, and accurately place the tube blank 5 into the cavity positioning groove of the lower mold insert 6; Drive the press slide to move the upper mold downwards and close it with the lower mold; guide pillars and guide bushings ensure that the misalignment between the upper and lower cavities is less than 0.05mm after mold closing.

[0037] S2, Axial sealing and liquid filling, refer to Figure 4 : The PLC control system issues a command to drive the first axial punch 4 and the second axial punch 19 to move synchronously towards each other along the axial direction. The sealing heads at the front ends of the two punches are inserted into both ends of the tube blank 5. The stepped extrusion of the tube causes slight deformation, thereby achieving end sealing of the inner cavity of the tube blank. When the external water pump is started, the liquid medium (usually a water-based emulsion) is injected into the sealed inner cavity of the tube blank through the central liquid passage of the first axial punch 4. The injection pressure is about 2-5 MPa until the tube blank is completely filled with liquid and the air is discharged from the tiny gap between the tube blank and the punch. After the pressure sensor detects that the pressure inside the tube blank 5 has stabilized, the PLC controls the stop valve to close, sealing the liquid inside the tube blank 5. At this time, the liquid inside the tube blank 5 is completely sealed, preparing for the next step of mechanical pressurization.

[0038] S3, Mechanical feed type body bulging, refer to Figure 5 : After sealing and liquid injection are completed, the main body bulging stage begins. This embodiment adopts a step-by-step molding strategy, and the specific operation is executed by the control system program: First, under program control, the first axial punch 4 and the second axial punch 19 synchronously feed towards each other at a speed (e.g., 0.5 mm / s) for a distance (e.g., 1 / 5 of the total target feed of 30 mm, i.e., 6 mm). This first feed operation squeezes the liquid inside the tube, causing the pressure to rise from the initial filling pressure to (e.g., 80 MPa), and the tube blank 5 begins to undergo plastic deformation and partially conforms to the mold cavity; Subsequently, the first forming interruption period begins, during which the axial punch stops feeding and remains in its current position for 1 second (e.g., 2 seconds). During this period, the tube blank material undergoes stress relaxation under constant pressure, and the internal stress distribution is adjusted. Next, a second feed operation is performed, and the axial punch is fed synchronously at the same speed (or adjusted) for a distance (e.g., 5 mm), and the pressure inside the tube increases accordingly (e.g., 120 MPa), causing the tube blank to expand further; Then, the second forming interruption period begins. During this period, according to the preset program, after the axial punch stops feeding, it is controlled to retract synchronously by a small amount (e.g., 1 mm). This retraction action slightly increases the liquid volume, causing the pressure inside the tube to actively decrease to (e.g., 100 MPa), thus achieving the "unloading" adjustment of the material deformation process and helping to alleviate work hardening.

[0039] Following similar logic, the control system continues to execute the subsequent Nth feed operation and forming interruption period. The specific actions during the interruption period can be programmed according to process requirements, for example: Pressure holding: The punch remains stationary to maintain pressure; Partial pressure relief: The punch retracts slightly, actively reducing pressure; Complete reset and fluid replacement: During a certain interruption period, the programmable plunger can be completely withdrawn from the tube blank. After the liquid is discharged naturally, new liquid is refilled, then sealed and the next cycle begins.

[0040] This embodiment decomposes the total deformation (30mm) into multiple controllable steps through the above-described "feed-interruption (adjustment)-refeed" multiple cycles. Each adjustment during the interruption period provides the material with an opportunity for stress relaxation or state refresh. Finally, when the axial punch completes the total feed and the pressure sensor indicates that the pressure has stabilized at the target value (e.g., 150MPa), it indicates that the billet 5 has completely conformed to the valve body main contour cavity formed by the upper die insert 20 and the lower die insert 6, and the main body bulging stage is completed.

[0041] S4. Precision forming of localized V-shaped overflow weir, refer to... Figure 6 : After the main body bulging stage is completed, the overflow weir precision forming stage begins. The PLC control system drives the radial hydraulic cylinder, causing the V-shaped radial punch 12 to begin radially pressing into the side wall of the tube blank at a set speed (e.g., 0.3-0.8 mm / s).

[0042] During this process, the control system does not simply maintain the position of the axial punch, but dynamically controls the movement of the first axial punch 4 and the second axial punch 19 according to the preset program or real-time sensor feedback (such as internal pressure and displacement sensors).

[0043] Its collaborative control strategy includes: feeding mode: for materials with poor plasticity and easy tearing, when the radial punch extrudes the material to form a V-shaped protrusion, the control system instructs the axial punch to continue to feed synchronously in opposite directions at a lower speed (e.g., 0.1-0.3 mm / s), pushing more material to the overflow weir forming area to compensate for the thinning of the material at that point and prevent cracking.

[0044] Pressure maintenance / regulation mode: For materials with good plasticity but prone to wrinkling, the axial punch may make slight retraction or pressure release adjustments to balance the local pressure surge caused by radial extrusion and avoid instability and wrinkling.

[0045] Dynamic coupling: Typically, the movements of the axial and radial punches are coupled. The radial punch feed consumes material and may change the internal pressure, while the responsive movements of the axial punch (feed or fine-tuning) replenish material and stabilize pressure, thus creating a dynamically balanced forming environment.

[0046] Under the constraints of the mold cavity, the support of the internal high-pressure liquid, and the synergistic effect of axial feeding, the local material of the tube blank 5 is precisely squeezed and filled into the cavity of the V-shaped radial punch 12, forming an overflow weir structure with accurate dimensions, clear edges, and uniform wall thickness.

[0047] Due to the long-stroke feed of the radial punch and the coordinated feeding of the axial punch, the pressure inside the tube is controlled more smoothly, and the material can be driven to completely fill all the details of the mold cavity, ultimately forming a high-quality overflow diaphragm valve body.

[0048] S5. Unloading, mold opening, and part removal: After the overflow weir is formed, the V-shaped radial punch 12 first retracts to its original position; Next, the first axial punch 4 and the second axial punch 19 retract synchronously and detach from the formed valve body; Finally, the press slide rises, the upper die opens, and the operator removes the complete overflow diaphragm valve body from the lower die.

[0049] The valve body formed using this invention has continuous streamlines, uniform wall thickness, and precise overflow weir dimensions, fully meeting the usage requirements.

Claims

1. A hydraulic bulging device for an overflow-type diaphragm valve body, characterized in that, include: The upper and lower molds, when closed, form a main cavity for accommodating the tube blank, and a radial window is provided at the position corresponding to the overflow weir of the valve body; The first axial punch and the second axial punch are arranged opposite to each other and are slidably and sealingly installed at the two end openings of the main cavity; A radial V-shaped punch is located on the side of the main cavity, corresponding to the valve body overflow weir forming position, and can slide radially. Its working surface is a V-shaped structure adapted to the shape of the overflow weir. The first axial punch has an axially oriented liquid passage, which is connected to the liquid passage in the base of the first axial punch. Neither the second axial punch nor the corresponding base has any liquid passage holes inside; The axial feed motion of the first and second axial punches is directly used to squeeze the liquid inside the tube blank to establish expansion internal pressure, and at the same time realize axial material replenishment.

2. The apparatus according to claim 1, characterized in that, The upper and lower molds adopt a split structure, including a mold base and replaceable inserts.

3. The apparatus according to claim 1, characterized in that, The radial V-shaped punch is driven by a hydraulic cylinder, and its movement direction is perpendicular to the tube blank axis.

4. The apparatus according to claim 1, characterized in that, The first axial punch base is provided with an interface for communication with an external liquid supply system and is equipped with a controllable stop valve.

5. The apparatus according to claim 1, characterized in that, The ends of the first axial punch and the second axial punch are provided with tapered sealing heads and stepped shaft structures.

6. The apparatus according to claim 1, characterized in that, It also includes a hydraulic drive system and a PLC control system for controlling the synchronous movement of the first axial punch and the second axial punch, as well as the timing of the intervention of the radial V-shaped punch.

7. A hydraulic bulging method for an overflow-type diaphragm valve body, characterized in that, The apparatus according to any one of claims 1-6 comprises the following steps: S1. Mold assembly: Place the tube blank into the main cavity of the lower mold, and close the upper mold and the lower mold; S2, Sealing and Liquid Injection: Drive the first axial punch and the second axial punch to move towards each other and enter both ends of the tube blank to achieve sealing; fill the sealed tube blank cavity with liquid medium and close the stop valve; S3, Main body expansion: Drive the first axial punch and the second axial punch to continue to feed synchronously towards each other, and squeeze the liquid in the tube blank through their mechanical displacement, so that the liquid pressure increases and the tube blank undergoes plastic expansion until it fits the main contour cavity of the valve body formed by the upper and lower dies. S4. Localized overflow weir: While driving the V-shaped radial punch to press into the predetermined position of the side wall of the expanded tube blank in the radial direction, the first axial punch and the second axial punch are controlled to perform coordinated feeding, pressure holding or micro-adjustment movements according to the forming requirements, so that the material can be locally and precisely formed into an overflow weir structure under the coupling effect of internal liquid support and axial feeding. S5. Unloading and removing parts: The radial V-shaped punch, the first axial punch, and the second axial punch are retracted in sequence to release the internal pressure and open the mold to remove the formed valve body.

8. The method according to claim 7, characterized in that, The main body bulging process in step S3 is completed in steps through multiple progressive axial feed operations, with a forming interruption period between two feed operations; The progressive axial feed operation has three cases: The first method involves replenishing fluid, feeding and extruding with the axial punch, keeping the axial punch stationary to maintain pressure, and then feeding the axial punch again to apply pressure. The second method is: replenishing fluid - axial punch feeding and extrusion - axial punch retraction but not completely withdrawn from the pipe to relieve pressure - axial punch feeding and pressurization again. The second method is: replenishing fluid - axial punch feeding and extrusion - axial punch completely retracting and depressurizing - replenishing fluid again - axial punch feeding and pressurizing again. During the forming interruption period, at least one of the following operations is performed: Maintain the axial punch position and the pressure inside the tube; Control the axial punch to retract but not completely withdraw in order to reduce the pressure inside the tube; This allows the axial punch to completely exit the tube blank, completely depressurize the tube, and allow for the replacement of the fluid inside the tube. The progressive axial feed operation is performed alternately with the forming interruption period to form one or more forming cycles.

9. The method according to claim 7 or 8, characterized in that, In step S3, the feed rate and pressure of the axial punch are controlled in a closed loop based on the material properties and the amount of bulging.

10. The method according to claim 7, characterized in that, In step S4, the insertion depth and speed of the radial V-shaped punch are adjustable.

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