A method and apparatus for precision hydroforming of bellows

Abstract

The present application relates to a kind of bellows precision hydraulic forming method and device, method includes: obtaining the bellows precision hydraulic forming device formed with forming cavity, tube blank is placed in forming cavity, wherein, bellows precision hydraulic forming device includes upper sealing assembly, several die sheets, backing plate and lower sealing assembly, upper sealing assembly, several die sheets and lower sealing assembly are coaxially arranged, and several die sheets are arranged between upper sealing assembly and lower sealing assembly;In the case where the bellows precision hydraulic forming device is second state, pressure control component controls the pressure in tube blank to be kept at second pressure value for at least 1 min, wherein, second pressure value is at least 5 times forming pressure value;After forming, each die sheet is adhered, and the shape and size of bellows are stabilized by the method of keeping pressure for a certain time, significantly reduce the elastic rebound of bellows, reduce the workload of subsequent bellows shaping process.

Description

Technical Field

[0001] This invention relates to the field of metal bellows manufacturing technology, and in particular to a method and apparatus for precision hydraulic forming of bellows. Background Technology

[0002] Bellows-type mechanical seals are widely used due to their excellent performance and high reliability, and can be applied in high-speed, high-pressure, high-temperature, and low-temperature conditions. Existing bellows forming dies and methods can, to some extent, solve problems such as mold marks after forming and improve the dimensional accuracy of the bellows. However, existing die designs and forming processes cannot achieve the dimensional accuracy required for sealing bellows, and no methods are provided for controlling the waveform shape accuracy and dimensional accuracy of the bellows' outer diameter. Therefore, it is necessary to optimize the design of existing forming dies and innovate the forming process to meet the stringent dimensional tolerance requirements of sealing bellows. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method and apparatus for precision hydraulic forming of bellows, which solves the problem that the existing mold design and forming process methods cannot achieve the required dimensional accuracy for sealing bellows, and do not provide a method for controlling the waveform shape accuracy and dimensional accuracy of the bellows outer diameter.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0007] In a first aspect, embodiments of the present invention provide a method for precision hydraulic forming of bellows.

[0008] This invention provides a method for precision hydroforming of bellows, comprising:

[0009] A precision hydraulic forming device for bellows with forming cavities is obtained. The tube blank is placed in the forming cavity. The precision hydraulic forming device for bellows includes an upper sealing assembly, several mold pieces, a pad, and a lower sealing assembly. The upper sealing assembly, several mold pieces, and the lower sealing assembly are coaxially arranged, and several mold pieces are arranged between the upper sealing assembly and the lower sealing assembly. A pad with a thickness equal to the height of the pad is arranged on both sides of the mold pieces so that the precision hydraulic forming device for bellows forms a first state.

[0010] The internal pressure of the tube blank is controlled by the pressure control component, so that the internal pressure of the tube blank reaches the forming pressure value, and the pad is removed when the internal pressure of the tube blank reaches the forming pressure value.

[0011] When the pad is removed from the bellows precision hydraulic forming device, axial pressure is applied to the bellows precision hydraulic forming device to make adjacent mold pieces move towards each other along their axis, and the internal pressure of the tube blank is controlled to maintain the forming pressure value until several mold pieces are put together, so that the bellows precision hydraulic forming device forms a second state.

[0012] When the bellows precision hydraulic forming device is in the second state, the pressure control component controls the pressure inside the tube blank to be maintained at a second pressure value for at least 1 minute, wherein the second pressure value is at least 5 times the forming pressure value.

[0013] Disassemble the precision hydraulic forming device for bellows to obtain bellows.

[0014] Optionally, the step of obtaining the pad height value includes:

[0015] The height of the pad is calculated based on the first real-time data and the pad height equation. The first real-time data includes the corrugated cavity peak radius, the corrugated cavity trough radius, the length of the transition zone, and the template thickness.

[0016] Alternatively, the equation for the height of the pad is:

[0017] ;

[0018] in, For the height value of the pad, For the corrugated cavity crest radius, For the radius of the corrugated cavity trough, For the length of the transition zone, This refers to the thickness of the template.

[0019] Optionally, the step of obtaining the forming pressure value includes:

[0020] The forming pressure value is calculated based on the second real-time data and the forming pressure equation. The second real-time data includes the corrugated pipe wall thickness, material tensile strength, and corrugated pipe inner diameter.

[0021] Optionally, the forming pressure equation is:

[0022] ;

[0023] in, For bellows forming pressure, For the corrugated pipe wall thickness, For the tensile strength of the material, This refers to the inner diameter of the bellows.

[0024] Secondly, embodiments of the present invention provide a precision hydraulic forming apparatus for bellows.

[0025] The present invention provides a bellows precision hydraulic forming apparatus for implementing the forming method of any one of the first aspects, comprising an upper sealing assembly, a plurality of mold pieces and a lower sealing assembly arranged coaxially, with a pad disposed between adjacent mold pieces;

[0026] The bellows precision hydraulic forming device has a forming cavity inside for supporting the tube blank during forming.

[0027] The pressure control component is connected to the forming cavity and is used to control the pressure inside the forming cavity.

[0028] Optionally, the upper sealing assembly also includes:

[0029] Upper sealing outer ring;

[0030] The upper sealing cap is detachably installed at the inner ring opening of the upper sealing outer ring.

[0031] Optionally, the lower sealing assembly includes:

[0032] Lower sealing outer ring;

[0033] The lower sealing cap is detachably installed at the inner ring opening of the lower sealing outer ring.

[0034] Optionally, the template includes:

[0035] Mold core, at least two mold cores form a full ring piece, and the inner ring opening of the full ring piece forms a corrugated mold cavity;

[0036] The retaining ring is detachably installed at the outer ring opening of the full ring piece to fix the mold cores in the same group to each other.

[0037] Optionally, the pressure control component includes:

[0038] A low-pressure pump, connected to the forming cavity;

[0039] A high-pressure pump is connected to the forming cavity and is connected in parallel with a low-pressure pump;

[0040] The first shut-off valve, connected in parallel with the low-pressure pump and the high-pressure pump, is used to control the connection between the forming cavity and the outside.

[0041] A direct-acting relief valve is connected to the forming cavity and is connected in parallel with the low-pressure pump, the high-pressure pump, and the first shut-off valve;

[0042] The second shut-off valve is located between the direct-acting relief valve and the high-pressure pump.

[0043] (III) Beneficial Effects

[0044] The beneficial effects of this invention are as follows: In the second state of the bellows precision hydraulic forming device, the pressure control component controls the pressure inside the tube blank to be held at a second pressure value for at least 1 minute, wherein the second pressure value is at least 5 times the forming pressure value. After forming, the various mold pieces are bonded together, and the shape and size of the bellows are stabilized by holding the pressure for a certain period of time. This significantly reduces the elastic rebound of the bellows and reduces the workload of subsequent bellows shaping processes. Because the shape of the bellows is confined within the mold cavity, the holding pressure can be greater than the forming pressure without causing the outer diameter of the bellows to continuously increase or the bellows to break. Therefore, a pressure greater than the forming pressure can be used to hold the bellows, improving the poor fit between the bellows and the mold caused by factors such as the type of bellows material and structural form, so that the waveform fits better with the mold cavity and the desired corrugated shape is obtained. Meanwhile, by appropriately adjusting the thickness of the mold plate during the mold forming cavity design and appropriately increasing the holding pressure and holding time during the holding pressure process, problems such as high yield strength ratio, excessive material springback after forming, and waveform dimension deviation caused by titanium alloys, high temperature alloys, and corrosion-resistant alloys can be solved. Attached Figure Description

[0045] Figure 1 This is a schematic flowchart of the bellows precision hydraulic forming method of the present invention;

[0046] Figure 2 This is a schematic diagram of the front cross-sectional structure of the bellows precision hydraulic forming apparatus of the present invention in its first state.

[0047] Figure 3 This is a schematic diagram of the front cross-sectional structure of the second state of the bellows precision hydraulic forming apparatus of the present invention.

[0048] Figure 4 This is a top view of the mold structure of an embodiment of the bellows precision hydroforming apparatus of the present invention;

[0049] Figure 5 This is a schematic diagram of the front cross-sectional structure of the mold piece in an embodiment of the bellows precision hydraulic forming apparatus of the present invention;

[0050] Figure 6 This is a schematic diagram of the main structure of the mold core in an embodiment of the bellows precision hydroforming apparatus of the present invention;

[0051] Figure 7 This is a schematic diagram of the front cross-sectional view of the fixing ring in an embodiment of the bellows precision hydraulic forming apparatus of the present invention;

[0052] Figure 8 This is a cross-sectional view of the tube blank according to an embodiment of the present invention;

[0053] Figure 9 for Figure 8 A magnified structural diagram of part A.

[0054] [Explanation of Labels in the Attached Images]

[0055] 200, Forming cavity; 300, Upper sealing assembly; 310, Upper sealing outer ring; 320, Upper sealing cover; 400, Mold piece; 401, Corrugated mold cavity; 410, Mold core; 420, Fixing ring; 500, Pad; 600, Lower sealing assembly; 610, Lower sealing outer ring; 620, Lower sealing cover; 700, Pressure control assembly; 710, Low-pressure pump; 720, High-pressure pump; 730, First shut-off valve; 740, Direct-acting relief valve; 750, Second shut-off valve; 800, Tube blank. Detailed Implementation

[0056] To better explain and facilitate understanding of the present invention, a detailed description of the invention is provided below with reference to the accompanying drawings and specific embodiments. In this document, directional terms such as "upper" and "lower" are used interchangeably with other directional terms. Figure 2 The orientation is used as a reference.

[0057] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0058] Firstly, please refer to Figure 1 The flowchart of a bellows precision hydraulic forming method provided in this application embodiment may specifically include: S110-S150.

[0059] S110, Obtain a bellows precision hydraulic forming device with a forming cavity 200, and place a tube blank 800 in the forming cavity 200. The bellows precision hydraulic forming device includes an upper sealing assembly 300, a plurality of mold pieces 400, a pad 500, and a lower sealing assembly 600. The upper sealing assembly 300, the plurality of mold pieces 400, and the lower sealing assembly 600 are coaxially arranged, and the plurality of mold pieces 400 are disposed between the upper sealing assembly 300 and the lower sealing assembly 600. A pad 500 with a thickness equal to the height of the pad is disposed on both sides of the mold pieces 400 so that the bellows precision hydraulic forming device forms a first state.

[0060] The steps for obtaining the height value of the pad 500 include: calculating the height value of the pad based on the first real-time data and the pad height equation. The first real-time data includes the corrugated cavity peak radius, the corrugated cavity trough radius, the length of the transition zone, and the template thickness.

[0061] The equation for the height of the pad is:

[0062] (1);

[0063] in, For the height value of the pad, For the corrugated cavity crest radius, For the radius of the corrugated cavity trough, For the length of the transition zone, This refers to the thickness of the template.

[0064] S120, the internal pressure of the tube blank 800 is controlled by the pressure control component 700 so that the internal pressure of the tube blank 800 reaches the forming pressure value, and the pad 500 is removed when the internal pressure of the tube blank 800 reaches the forming pressure value.

[0065] S130, when the pad 500 is removed from the bellows precision hydraulic forming device, axial pressure is applied to the bellows precision hydraulic forming device to make the adjacent mold pieces 400 move towards each other along their axis, and the internal pressure of the tube blank 800 is controlled to maintain the forming pressure value until the several mold pieces 400 are put into contact with each other, so that the bellows precision hydraulic forming device forms a second state.

[0066] The steps for obtaining the forming pressure value include: calculating the forming pressure value based on the second real-time data and the forming pressure equation. The second real-time data includes the corrugated pipe wall thickness, material tensile strength, and corrugated pipe inner diameter.

[0067] The forming pressure equation is as follows:

[0068] (2);

[0069] in, For bellows forming pressure, For the corrugated pipe wall thickness, For the tensile strength of the material, This refers to the inner diameter of the bellows.

[0070] S140, when the bellows precision hydraulic forming device is in the second state, the pressure control component 700 controls the pressure inside the tube blank 800 to be maintained at the second pressure value for at least 1 minute, wherein the second pressure value is at least 5 times the forming pressure value;

[0071] S150, remove the precision hydraulic forming device for bellows to obtain bellows.

[0072] As described above, the bellows precision hydraulic forming method first obtains a bellows precision hydraulic forming device with a forming cavity 200. This device includes an upper sealing assembly 300, several mold plates 400, and a lower sealing assembly 600 arranged coaxially. A pad 500 with a thickness equal to the pad height is placed on both sides of the mold plates 400 to form a first state for the bellows precision hydraulic forming device. The bellows precision hydraulic forming device in its first state has a forming cavity 200 formed inside. The forming cavity 200 is coaxially arranged with the upper sealing assembly 300, the mold plates 400, and the lower sealing assembly 600. The tube blank is placed inside the forming cavity 200. The upper sealing assembly 300 and the lower sealing assembly 600 are located at both ends of the forming cavity 200, sealing the interior of the tube blank 800. In the first state, a pad space for placing the pad 500 is formed between adjacent mold plates 400. Due to the upper sealing... Component 300 and lower sealing component 600 are disposed on both sides of several mold pieces 400. Therefore, the mold pieces 400, upper sealing component 300, and lower sealing component 600 also form a space for placing the pad 500. When the pad 500 is placed in the space, the pad 500 is in close contact with the mold piece 400, upper sealing component 300, and lower sealing component 600. The height of the pad 500 determines the outer diameter of the bellows and whether the bellows can completely fit with the forming cavity 200 after forming. Therefore, the height of each pad 500 is... The tolerances should be consistent, and the height of the pad is calculated according to formula (1). After the bellows precision hydraulic forming device forms the first state, the upper sealing component 300 is limited, the low-pressure pump 710 in the pressure control component 700 is started, and the tube blank 800 is quickly filled with liquid through the lower sealing component 600. The forming liquid is deionized water. After the tube blank 800 is filled with deionized water, the high-pressure pump 720 in the pressure control component 700 is started. The high-pressure pump 720 is started to make the pressure reach the forming pressure value. The forming pressure value is calculated according to formula (2).After the internal pressure of the tube blank 800 reaches the forming pressure value, the tube blank 800 expands and deforms, tightly fitting against the mold plate 400. In this state, the internal pressure of the tube blank 800 is unloaded through the pressure control component 700, and the pad 600 is removed. Because the tube blank 800 has expanded and deformed, the deformed tube blank 800 allows the mold plate 400 and the upper sealing component 300 to remain in their original positions. After removing the pad 600, the high-pressure pump 720 in the pressure control component 700 continues to pressurize the tube blank 800 to the forming pressure value. Simultaneously, axial pressure is applied to the bellows precision hydraulic forming device through external equipment. For example, the bellows precision hydraulic forming device is placed vertically on a horizontal surface, with the lower sealing component 600 abutting against the horizontal surface. Applying axial pressure to the bellows precision hydraulic forming device is equivalent to applying compressive force to the upper sealing component 300, causing the bellows tube blank 800 to expand outwards while being axially compressed. During the axial compression process, the volume of the tube blank 800 gradually decreases, causing the internal pressure of the tube blank 800 to increase. In order to stabilize the internal pressure of the tube blank 800 at the forming pressure value, the direct-acting relief valve 750 in the pressure control component 700 is activated. For example, the direct-acting relief valve 750 can achieve 10L / min overflow pressure regulation under a high pressure of 150MPa, keeping the internal pressure of the tube blank 800 fluctuating no more than 5% relative to the forming pressure value, until several mold pieces 400 are attached together. At the same time, the upper sealing component 300 and the lower sealing component 600 are also attached tightly to the mold pieces 400. At this time, the tube blank 800 expands outward to completely fit with the forming cavity 200, so that the bellows precision hydraulic forming device is in the second state. In this state, the pressure control component 700 controls the internal pressure of the tube blank 800 to be maintained at the second pressure value for at least 1 minute, wherein the second pressure value is at least 5 times the forming pressure value and the second pressure value is the holding pressure.

[0073] After the pressure holding is completed, the pressure holding pressure is released, the axial limit of the bellows precision hydraulic forming device is removed, and the upper sealing component 300, several mold pieces 400 and the lower sealing component 600 are removed in sequence to obtain the formed bellows. This method can achieve the one-time forming of multiple bellows. The ratio of the outer diameter to the inner diameter of the bellows can reach between 1.2 and 1.5. The dimensional deviation and shape of the formed bellows are better than those of bellows manufactured by traditional hydraulic forming process, and no subsequent shaping or correction is required.

[0074] By combining engineering experience and finite element simulation analysis, the pressure control component 700 controls the internal pressure of the tube blank 800 to maintain pressure at least 5 times the forming pressure value for at least 1 minute to address the changes in bellows size caused by the elastic rebound of the bellows material after the forming pressure is unloaded. This can solve problems such as high yield strength ratio, large material rebound after forming, forming difficulties, and waveform size deviation caused by titanium alloys, high temperature alloys, and corrosion-resistant alloys.

[0075] like Figures 2 to 9 As shown, according to a second aspect of the embodiments of this application, a bellows precision hydraulic forming apparatus is provided for implementing any of the bellows precision hydraulic forming apparatuses described above. The apparatus includes an upper sealing assembly 300, a plurality of mold plates 400, and a lower sealing assembly 600 arranged coaxially. A pad 500 is disposed between adjacent mold plates 400. The bellows precision hydraulic forming apparatus has a forming cavity 200 formed inside for supporting the formed tube blank 800. A pressure control assembly 700 communicates with the forming cavity 200 and is used to control the internal pressure of the forming cavity 200.

[0076] In this technical solution, the bellows precision hydroforming device includes an upper sealing assembly 300, several mold plates 400, and a lower sealing assembly 600 arranged coaxially. A pad 500 is disposed between adjacent mold plates 400, serving as support and spacing. In this device, a forming cavity 200 is formed inside the bellows precision hydroforming device to hold the formed tube blank 800. For example, the size and shape of the forming cavity 200 are set according to the required bellows specifications to ensure that the tube blank 800 can be accurately formed within it.

[0077] The pressure control component 700 is connected to the forming cavity 200. Its main function is to control the pressure inside the forming cavity 200. For example, the pressure control component 700 can be a combination of equipment such as a hydraulic pump, pressure sensor and control valve. By monitoring and adjusting the pressure in real time, it can ensure that the tube blank is subjected to appropriate pressure during the forming process.

[0078] In actual operation, the tube blank 800 is first placed in the forming cavity 200, and then the pressure in the forming cavity 200 is gradually increased by the pressure control component 700. The upper sealing component 300 and the lower sealing component 600 ensure the sealing of the forming cavity 200 and prevent pressure leakage. The die 400 presses the tube blank 800 under pressure, while the pad 500 ensures that the spacing between the die 400s is uniform, thereby making the forming of the corrugated pipe more precise.

[0079] For example, the upper sealing assembly 300 and the lower sealing assembly 600 may be made of high-strength sealing materials to ensure good sealing performance under high pressure; the mold plate 400 may be made of wear-resistant materials to extend its service life; for example, the pressure sensor in the pressure control assembly 700 should have high accuracy and high response speed to provide timely and accurate feedback of pressure information.

[0080] like Figure 2 and Figure 3As shown, in some examples, the upper sealing assembly 300 further includes: an upper sealing outer ring 310; and an upper sealing cap 320, which is detachably installed at the inner ring opening of the upper sealing outer ring 310.

[0081] In some examples, the lower sealing assembly 600 includes: a lower sealing outer ring 610; and a lower sealing cap 620, which is detachably installed at the inner ring opening of the lower sealing outer ring 610.

[0082] As described above, the upper sealing outer ring 310 and the upper sealing cap 320 form a seal on the inside of the bellows blank 800 at the upper part of the blank 800, and the lower sealing outer ring 610 and the lower sealing cap 620 form a seal on the inside of the bellows blank 800 at the lower part of the blank 800. Furthermore, exemplarily, the upper sealing outer ring 310 and the lower sealing outer ring 610 also function as forming molds. The lower part of the upper sealing outer ring 310 has a half-corrugated cavity 401, which, after being fitted with the adjacent mold piece 400, forms a complete corrugated cavity 401. The lower sealing outer ring 610... The upper part has a half corrugated cavity 401, which forms a complete corrugated cavity 401 after being attached to the adjacent mold piece 400. The upper and lower parts of the mold piece 400 each have a half corrugated cavity 401, which forms a complete corrugated cavity 401 after being attached to the adjacent mold piece 400, the upper sealing outer ring 310 or the upper sealing outer ring 610. A pad 500 is placed in the gap between the adjacent mold piece 400 or between the mold piece 400 and the upper sealing outer ring 310 or the lower sealing outer ring 610. The pad 500 is in close contact with the mold piece 400, the upper sealing outer ring 310 or the lower sealing outer ring 610.

[0083] like Figures 2 to 7 As shown, in some examples, the mold plate 400 includes: a mold core 410, at least two mold cores 410 forming a full ring plate, the inner ring opening of the full ring plate forming a corrugated mold cavity 401; and a fixing ring 420, detachably installed at the outer ring opening of the full ring plate, for fixing the mold cores 410 in the same group to each other.

[0084] In this technical solution, the mold plate 400 includes a mold core 410 and a fixing ring 420. The mold core 410 is the basic unit that makes up the full ring plate. Two mold cores 410 are tightly fitted along the sidewalls to form a complete circle. Two semi-corrugated cavities 401 are symmetrically distributed on both sides of the mold core 410. The inner diameter of the mold core 410 is machined into a rounded corner, and the radius of the rounded corner is consistent with the radius of the corrugated pipe trough. In actual operation, an appropriate number of mold cores 410 can be selected to form a full ring plate according to the requirements of different specifications of corrugated pipes, so as to meet the forming requirements of corrugated pipes of different sizes and shapes.

[0085] The retaining ring 420 is detachably installed at the outer ring opening of the full ring piece. The function of the retaining ring 420 is to fix the mold cores 410 in the same group to each other, ensuring that the mold cores 410 will not be relatively displaced during the hydroforming process, thereby ensuring the forming accuracy of the bellows. When it is necessary to replace the mold piece 400 of different specifications, the retaining ring 420 can be easily removed to replace the mold core 410 or the entire mold piece 400 assembly.

[0086] For example, the pad 500 has a rectangular or square cross-section. The length or height of the rectangle (the side length of the square) is the difference between the single wave unfolding length and the thickness of the template 400. The two planes with the length or height of the pad 500 and the difference are used as working planes. The corrugated pipe blank 800 is a seamless pipe or plate / strip welded together to form a welded pipe with longitudinal welds. It can be one or more layers nested together.

[0087] For example, the chamfer radius at the inner diameter of the upper sealing outer ring 310, the lower sealing outer ring 610, and the semi-corrugated cavity 401 of the mold plate 400 is consistent with the radius of the corrugated pipe trough; the thickness of the mold core 410 is consistent with the corrugated pipe pitch, and after being fitted with the upper and lower adjacent mold cores 410, a complete corrugated cavity 401 can be formed; the fixing ring 420 is fitted with the mold core 410 with a small clearance, and after the forming pressure is unloaded, the fixing ring 420 can be separated from the mold core 410.

[0088] like Figure 2 As shown, in some examples, the pressure control assembly 700 includes: a low-pressure pump 710 connected to the forming cavity 200; a high-pressure pump 720 connected to the forming cavity 200 and in parallel with the low-pressure pump 710; a first shut-off valve 730 connected in parallel with the low-pressure pump 710 and the high-pressure pump 720 for controlling the connection between the forming cavity 200 and the outside; a direct-acting relief valve 740 connected to the forming cavity 200 and in parallel with the low-pressure pump 710, the high-pressure pump 720 and the first shut-off valve 730; and a second shut-off valve 750 disposed between the direct-acting relief valve 740 and the high-pressure pump 720.

[0089] In this technical solution, the pressure control component 700 includes a low-pressure pump 710, a high-pressure pump 720, a first shut-off valve 730, a direct-acting relief valve 740, and a second shut-off valve 750.

[0090] The first shut-off valve 730 is connected in parallel with the low-pressure pump 710 and the high-pressure pump 720 to control the connection between the forming cavity 200 and the outside. By controlling the opening and closing of the first shut-off valve 730, the pressure in the forming cavity 200 can be maintained or released.

[0091] The direct-acting relief valve 740 is connected to the forming cavity 200 and is connected in parallel with the low-pressure pump 710, the high-pressure pump 720 and the first shut-off valve 730. The direct-acting relief valve 740 can automatically open when the pressure exceeds the set value, which plays a safety protection role and prevents the equipment from being damaged or the quality of the bellows from being damaged due to excessive pressure in the forming cavity 200.

[0092] The second shut-off valve 750 is located between the direct-acting relief valve 740 and the high-pressure pump 720, and is used to further control the connection between the high-pressure pump 720 and the direct-acting relief valve 740. Under certain circumstances, the output pressure of the high-pressure pump 720 or the direct-acting relief valve 740 can be adjusted or protected by operating the second shut-off valve 750.

[0093] The low-pressure pump 710 is connected to the forming cavity 200, and can quickly deliver liquid to the forming cavity 200 in the initial stage to meet the initial deformation requirements of the tube blank 800. The high-pressure pump 720 is also connected to the forming cavity 200 and is connected in parallel with the low-pressure pump 710. After the tube blank 800 is filled with liquid, the high-pressure pump 710 is started to make the pressure inside the tube blank 800 reach the corrugated tube forming pressure, causing the corrugated tube blank 800 to expand and deform and fit tightly against the mold plate 400. The position where the tube blank 800 expands and deforms can fix the mold plate 400. At this time, the internal pressure of the tube blank 800 is unloaded, the gasket 500 is removed, and the high-pressure pump 720 is started again to pressurize the inside of the corrugated tube blank 800. When the forming pressure is reached, the tube blank 800 expands radially. At the same time, axial force is applied to the upper sealing assembly 300 to make each mold piece 400 fit together. During this process, the tube blank 800 is limited by the forming cavity 800 of the mold during radial expansion and fits completely with the forming cavity 200 of the mold. The internal volume of the tube blank 800 first increases and then decreases. The increase in internal pressure of the tube blank 800 caused by this factor is caused by the direct-acting overflow valve 740 to overflow the excess forming fluid to maintain the stability of the forming pressure. After each mold piece fits together, the second shut-off valve 750 continues to pressurize the inside of the corrugated tube blank 800 before closing the direct-acting overflow valve 740, and controls the internal pressure of the tube blank 800 to be maintained at the second pressure value for at least 1 minute.

[0094] Example

[0095] like Figures 4 to 9 As shown, Figure 9 The metal bellows is made from tube blank 800 using the precision hydraulic device described in this technical solution. The inner diameter φ1 of the metal bellows is 65±0.2mm, the outer diameter φ2 is 80.3±0.3mm, the corrugation L1 is 5.08mm, the effective length L2 is 12.7±0.3mm, it adopts a double-layer structure, the single-layer wall thickness A1 is 0.12mm, the number of corrugations is 3, and the forming pressure of the metal bellows is 4.5MPa.

[0096] The design adopts, for example Figure 4 and Figure 5The template 400 shown is designed with a thickness of t=4.6mm, which is 90% of the wave pitch, based on previous engineering practice. The radius of the semi-corrugated cavity 401 is r1=R1.15, slightly smaller than the wave thickness fillet radius R1.39. The fillet radius at the inner diameter of the mold core is r2=R1.15, consistent with the wave trough radius. The inner diameter of the mold cavity is machined to φ3, which is 80. +0.1 The dimensional accuracy has been improved compared to the drawing requirement of φ80.3±0.3mm.

[0097] like Figures 4 to 7 The mold plate 400 consists of a retaining ring 420 and a mold core 410. The two mold cores 410 are tightly fitted along their side walls to form a complete circle. The retaining ring 420 is fitted with a small gap outside the mold core 410.

[0098] The forming method is as follows:

[0099] Step 1, according to Figure 2 The complete set of forming molds is assembled with the tube blank 800 to achieve sealing of the upper and lower ends of the tube blank 800;

[0100] Step 2: Place the lower sealing assembly 600 on the equipment base and connect it to the external hydraulic system. Use a press to axially limit the upper sealing assembly 300.

[0101] Step 3: Close the first shut-off valve 730 and the second shut-off valve 750, and start the low-pressure pump 710 to quickly fill the inside of the tube blank 800 with forming liquid through the lower sealing assembly 600;

[0102] Step 4: Open the second shut-off valve 750 and start the high-pressure pump 720 to make the pressure inside the tube blank 800 reach 4.5MPa, so that the corrugated tube blank 800 expands and deforms and fits tightly with the mold plate 400, which can fix the mold plate 400.

[0103] Step 5: Turn off the high-pressure pump 720, unload the internal pressure of the tube blank 800, and remove the gasket 500;

[0104] Step 6: Restart the high-pressure pump 720 to pressurize the inside of the corrugated tube blank 800. When the pressure reaches 4.5MPa, the tube blank 800 expands radially. At the same time, axial pressure is applied to the upper sealing assembly 300 to make each mold piece 400 fit together. During this process, the tube blank 800 is limited by the mold cavity 200 during radial expansion and fits completely with the mold cavity 200. The internal volume of the tube blank 800 first increases and then decreases. The increase in internal pressure of the tube blank 800 caused by this factor is caused by the direct-acting overflow valve 740 to overflow the excess forming liquid to maintain the stability of the forming pressure.

[0105] Step 7: After each mold piece 400 is bonded, close the second shut-off valve 750 and continue pressurizing the inside of the corrugated pipe blank 800 to a pressure of 30 MPa, hold the pressure for 5 minutes. The bonding and pressure holding status of the mold pieces 400 are as follows. Figure 2 As shown;

[0106] Step 8: Turn off the high-pressure pump 720, open the first shut-off valve 730 to unload the pressure, remove the mold, and obtain the metal bellows.

[0107] Using this implementation scheme, the outer diameter of the formed corrugated pipe is φ80. -0.1 mm, effective length 13 -0.3 The forming accuracy and product quality are 100% qualified, with the stiffness and effective area indicators meeting the standards.

[0108] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0109] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0110] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," or "on top" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," or "beneath" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0111] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0112] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for precision hydraulic forming of bellows, characterized in that, The method includes: A precision hydraulic forming device for bellows with a forming cavity is obtained. The tube blank is placed in the forming cavity. The precision hydraulic forming device for bellows includes an upper sealing assembly, several mold pieces, a pad, and a lower sealing assembly. The upper sealing assembly, several mold pieces, and the lower sealing assembly are coaxially arranged, and several mold pieces are disposed between the upper sealing assembly and the lower sealing assembly. A pad with a thickness equal to the height of the pad is disposed on both sides of the mold pieces so that the precision hydraulic forming device for bellows forms a first state. The steps for obtaining the height value of the pad include: calculating the height value of the pad based on the first real-time data and the pad height equation. The first real-time data includes the corrugated cavity peak radius, the corrugated cavity trough radius, the length of the transition zone, and the template thickness. The internal pressure of the tube blank is controlled by the pressure control component, so that the internal pressure of the tube blank reaches the forming pressure value, and the pad is removed when the internal pressure of the tube blank reaches the forming pressure value. When the pad is removed from the bellows precision hydraulic forming device, axial pressure is applied to the bellows precision hydraulic forming device to make the adjacent mold pieces move towards each other along their axis, and the internal pressure of the tube blank is controlled to maintain the forming pressure value until the several mold pieces are put into contact with each other, so that the bellows precision hydraulic forming device forms a second state. The mold pieces include mold cores, which are the basic units that make up the full ring pieces. Two mold cores are tightly attached along their side walls to form a complete circle as a mold cavity, and the tube blank is completely attached to the mold cavity. When the bellows precision hydraulic forming device is in the second state, the pressure control component controls the pressure inside the tube blank to be maintained at a second pressure value for at least 1 minute, wherein the second pressure value is at least 5 times the forming pressure value; the bellows precision hydraulic forming device is then removed to obtain the bellows. The pressure control assembly includes: a low-pressure pump connected to the forming cavity; a high-pressure pump connected to the forming cavity and in parallel with the low-pressure pump; a first shut-off valve connected in parallel with the low-pressure pump and the high-pressure pump, used to control the connection between the forming cavity and the outside; a direct-acting relief valve connected to the forming cavity and in parallel with the low-pressure pump, the high-pressure pump and the first shut-off valve; and a second shut-off valve disposed between the direct-acting relief valve and the high-pressure pump, which controls the initial deformation and expansion deformation of the tube blank through the low-pressure pump and the high-pressure pump, precisely controls the input and release of pressure through the first shut-off valve and the second shut-off valve, and maintains pressure stability through the direct-acting relief valve.

2. The bellows precision hydroforming method as described in claim 1, characterized in that, The equation for the height of the pad is: H=π(r1+r2)+2a-t; Where H is the height of the pad, r1 is the radius of the corrugated cavity peak, r2 is the radius of the corrugated cavity trough, a is the length of the transition zone, and t is the thickness of the template.

3. The bellows precision hydroforming method as described in claim 1, characterized in that, The steps for obtaining the forming pressure value include: calculating the forming pressure value based on the second real-time data and the forming pressure equation. The second real-time data includes the corrugated pipe wall thickness, material tensile strength, and corrugated pipe inner diameter.

4. The bellows precision hydroforming method as described in claim 3, characterized in that, The forming pressure equation is: ； Where p is the forming pressure of the bellows, h is the wall thickness of the bellows, σb is the tensile strength of the material, and d is the inner diameter of the bellows.

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