A painting tool and a painting method

Abstract

The present application relates to the technical field of coating, in particular to a coating tool and a coating method. The coating tool comprises a base assembly, a positioning assembly comprising a positioning tube, a sealing unit and an elastic unit, one end of the positioning tube is fixed to the base assembly, the other end of the positioning tube extends away from the base assembly, the fixed end of the positioning tube and the base assembly is lower than the other end of the positioning tube in the vertical direction, the sealing unit is fixed to the end of the positioning tube close to the base assembly and is sleeved on the outer peripheral wall of the positioning tube, one end of the elastic unit is fixed to the outer peripheral wall of the positioning tube and the other end extends away from the positioning tube in the radial direction of the positioning tube, and the first state of the coating tool comprises that the elastic unit is deformed and abuts against the inner peripheral wall of the cylinder assembly, so that the elastic unit is electrically connected with the cylinder assembly. Thus, the problem of unstable electrical connection of the electrophoretic coating tool is solved.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and more specifically, to a coating fixture and a coating method. Background Technology

[0002] In metal surface treatment technology, coating processes are mainly divided into two categories: one is spray coating, which uses spraying equipment to atomize paint and apply it to the surface of the workpiece; the other is electrophoretic coating, which uses an electric field to achieve film formation. The latter, with its excellent coverage and uniform film thickness, is widely used for the protection and decoration of various metal parts. Electrophoretic coating involves the directional migration of charged paint particles dispersed in the coating solution under the drive of an external electric field, ultimately depositing them on the workpiece surface, which serves as one of the electrodes, thus forming a continuous and dense coating. This process requires the workpiece to remain energized throughout the coating process; therefore, a specialized conductive structure is necessary to stably introduce the power current into the workpiece. For workpieces with internal holes, an assembly that combines positioning and conductivity is often used in engineering—inserted into the workpiece's internal hole, both restricting the workpiece's spatial position in the bath and simultaneously acting as a bridge for current conduction.

[0003] However, in actual use, because the positioning component and the inner hole of the workpiece are usually designed with a clearance fit, and the workpiece is subjected to a continuous upward buoyancy in the coating liquid, the relative position between the workpiece and the positioning component is prone to slight shifting. Once displacement occurs, the conductive surfaces in contact may partially separate or the contact pressure may be insufficient, leading to intermittent electrical connection and fluctuating contact resistance. This unstable contact directly interferes with the stable current delivery, ultimately affecting the uniformity of the electrophoretic deposition process and potentially causing quality problems such as uneven coating thickness and density. Summary of the Invention

[0004] To address the problem of unstable electrical connections in electrophoretic coating fixtures, this invention provides a coating fixture and a coating method.

[0005] Firstly, this application provides a painting fixture, comprising:

[0006] Base assembly;

[0007] The positioning assembly includes a positioning tube, a sealing unit, and an elastic unit; one end of the positioning tube is fixed to the base assembly, and the other end of the positioning tube extends away from the base assembly; the fixed end of the positioning tube to the base assembly is lower than the other end of the positioning tube in the vertical direction; the sealing unit is fixed to the end of the positioning tube near the base assembly and is sleeved on the outer peripheral wall of the positioning tube; one end of the elastic unit is fixed to the outer peripheral wall of the positioning tube, and the other end extends away from the positioning tube in the radial direction.

[0008] The first state of the painting fixture includes deformation of the elastic unit and contact with the inner peripheral wall of the cylinder assembly, so that the elastic unit is electrically connected to the cylinder assembly.

[0009] Optionally, the elastic unit includes a first elastic part; one end of the first elastic part is fixed to the outer peripheral wall of the positioning tube, and the other end extends away from the positioning tube along the radial direction of the positioning tube.

[0010] The first state of the painting fixture includes deforming through the first elastic part and abutting against the inner peripheral wall of the cylinder assembly, at least applying a downward force to the cylinder assembly.

[0011] Optionally, the elastic unit includes a second elastic part; one end of the second elastic part is fixed to the outer peripheral wall of the positioning tube, and the other end extends away from the positioning tube along the radial direction of the positioning tube.

[0012] The first state of the painting fixture includes deformation through the second elastic part and contact with the inner peripheral wall of the cylinder assembly, at least applying an upward force to the cylinder assembly.

[0013] Optionally, there are two second elastic parts, and the two second elastic parts and the first elastic part are arranged along the circumference of the positioning tube; the first elastic part is arranged vertically below the two second elastic parts.

[0014] Optionally, the sealing unit includes a support module and a sealing module; the support module includes a support plate and a support ring; the support plate is fixed to one end of the positioning tube near the base assembly and is sleeved on the positioning tube; one end of the support ring is connected to the outer peripheral wall of the support plate, and the other end extends in a direction away from the base assembly; the sealing module includes a sealing plate and a sealing ring; the sealing plate is fixed between the support plate, the support ring and the positioning tube; one end of the sealing ring is connected to the sealing plate, and the other end extends in a direction away from the base assembly.

[0015] Optionally, the sealing ring extends further away from the base assembly than the support ring extends further; the inner peripheral wall of the end of the sealing ring away from the base assembly is provided with a guide slope.

[0016] Optionally, the positioning unit includes a balance hole and a positioning tube; the balance hole is located on the base assembly or the positioning tube; the balance hole connects the cavity between the positioning tube and the cylinder assembly to the outside; V2 / V1 is less than a safety setting value; wherein, V2 is the volume of the gas in the first cavity after compression, V1 is the volume of the gas in the first cavity before compression, and the first cavity is the connecting area between the balance hole and the positioning tube and the cylinder assembly.

[0017] Secondly, this application provides a coating method, applicable to any of the coating fixtures described in the first aspect; the coating method includes:

[0018] Triggered by a painting command, the cylinder assembly is fitted onto the positioning tube, reaching a first state; wherein, the first state includes the elastic unit deforming and abutting against the inner peripheral wall of the cylinder assembly;

[0019] Based on reaching the first state, the painting fixture and cylinder assembly are placed in the painting tank to reach the second state; wherein, the second state includes the cylinder assembly floating and compressing the elastic unit.

[0020] Based on the time from reaching the second state to the first set time, the painting fixture and cylinder assembly are removed from the painting tank.

[0021] Optionally, F1 < F2; where F1 is the downward force exerted by the elastic element on the cylinder assembly in the first state, and F2 is the downward force exerted by the elastic element on the cylinder assembly in the second state.

[0022] Optionally, the positioning unit includes a balancing hole;

[0023] Painting methods also include:

[0024] After the painting fixtures and cylinder assemblies are removed from the painting tank, they are placed in the drying chamber and dried for a second set time.

[0025] To solve the problem of unstable electrical connections in electrophoretic coating tooling, this invention has the following advantages:

[0026] Through the sealing unit, after the cylinder assembly is installed in place, the sealing unit and the open end of the cylinder assembly form a compression seal, preventing the coating liquid from seeping into the inner wall of the cylinder assembly through the gap between the positioning tube and the inner wall of the cylinder assembly, thus preventing the coating from depositing in non-coating areas. The force generated by the elastic deformation of the elastic unit automatically compensates for the fluctuations of the cylinder assembly caused by buoyancy, ensuring that the elastic unit and the cylinder assembly always maintain a tight contact, ensuring stable electrical connection throughout the electrophoretic coating process, thereby ensuring the uniformity and density of the electrophoretic deposition layer, and significantly improving the coating quality and production yield of the cylinder assembly. Attached Figure Description

[0027] Figure 1 A side view schematic diagram of a painting fixture according to one embodiment is shown;

[0028] Figure 2 A schematic diagram of the structure of a painting fixture according to one embodiment is shown;

[0029] Figure 3 A schematic diagram of the positioning component structure of a painting fixture according to one embodiment is shown;

[0030] Figure 4 A front view schematic diagram of the positioning component of a painting fixture according to one embodiment is shown;

[0031] Figure 5 A schematic diagram of the positioning unit structure of a painting fixture according to one embodiment is shown;

[0032] Figure 6 A schematic diagram of the sealing module structure of a painting fixture according to one embodiment is shown;

[0033] Figure 7 A schematic diagram of the cylinder assembly structure of a painting fixture according to one embodiment is shown.

[0034] Reference numerals: 10 Base assembly; 11 Base body; 12 Stand body; 20 Positioning assembly; 21 Positioning unit; 211 Positioning tube; 212 Balance hole; 22 Sealing unit; 221 Support module; 2211 Support plate; 2212 Support ring; 222 Sealing module; 2221 Sealing plate; 2222 Sealing ring; 23 Elastic unit; 231 First elastic part; 232 Second elastic part; 30 Cylinder assembly; 31 Cylinder ring; 32 Cylinder bottom. Detailed Implementation

[0035] The present disclosure will now be discussed with reference to several exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and thus implement the present disclosure, and are not intended to imply any limitation on the scope of the disclosure.

[0036] As used herein, the term "comprising" and its variations are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment". The term "another embodiment" is to be interpreted as "at least one other embodiment". The terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments and are not intended to limit the indicated devices, elements, or components to having a specific orientation or being constructed and operated in a specific orientation. Furthermore, some of the above terms may be used to indicate other meanings besides orientations or positional relationships; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application according to the specific circumstances. In addition, the terms "installed", "set up", "equipped with", "connected", and "linked" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, elements, or components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. Furthermore, the terms "first," "second," etc., are mainly used to distinguish different devices, elements, or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0037] Electrophoretic coating is a widely used process in the field of metal surface treatment. It utilizes an external electric field to cause paint particles suspended in a coating solution to migrate directionally and deposit onto the surface of a workpiece, which serves as an electrode, thereby forming a uniform coating on the workpiece's outer surface. During electrophoretic coating, the workpiece needs to remain charged; therefore, a conductive structure is required to reliably conduct the power current to the workpiece. For the cylinder assembly 30 of this application, one end is open and the other end is closed; as... Figure 7As shown, the assembly includes a cylinder bottom 32 and a cylinder ring 31. The cylinder bottom 32 is a closed end, and the cylinder ring 31 is connected to the cylinder bottom 32. A common practice is to insert a positioning component 20 into the cylinder ring 31, which both positions the cylinder assembly 30 in the coating bath and provides electrical conductivity. When a clearance fit is used between the positioning component 20 and the cylinder ring 31, the workpiece is subject to buoyancy in the coating liquid, which can easily cause the relative position between the workpiece and the positioning component 20 to shift. This can lead to separation or poor contact of the conductive contact surfaces, resulting in unstable electrical connections. This instability can affect the continuous and reliable conduction of current, potentially negatively impacting the quality and uniformity of the electrophoretic coating.

[0038] Example 1:

[0039] In this embodiment, as Figure 1 As shown, in order to solve the above-mentioned technical problems, this application provides a painting fixture for painting a cylinder assembly 30 with one end open, including: a base assembly 10 and a positioning assembly 20; the base assembly 10 provides a stable installation foundation and positioning reference for the entire fixture, ensuring that the fixture as a whole maintains a definite posture in the painting tank.

[0040] like Figure 3 As shown, the positioning assembly 20 includes a positioning tube 211, a sealing unit 22, and an elastic unit 23. One end of the positioning tube 211 is fixed to the base assembly 10, and the other end of the positioning tube 211 extends away from the base assembly 10. The positioning tube 211 provides stable guidance and radial limitation for the cylinder assembly 30 to be fitted into the positioning tube 211. The fixed end of the positioning tube 211 to the base assembly 10 is lower than the other end of the positioning tube 211 in the vertical direction, that is, the positioning tube 211 is inclined upward, which allows the cylinder assembly 30 to smoothly slide down the positioning tube 211 to the preset working position under its own weight. The sealing unit 22 is fixed to the end of the positioning tube 211 near the base assembly 10. It is fitted onto the outer peripheral wall of the positioning tube 211. In actual use, the inner wall of the cylinder assembly 30 needs to be assembled with other parts, so the inner wall of the cylinder assembly 30 is not allowed to be painted. Only the outer peripheral surface of the cylinder assembly 30 needs to be painted. Through the sealing unit 22, when the cylinder assembly 30 is fitted into place, the sealing unit 22 and the open end of the cylinder assembly 30 form a compression seal, which blocks the paint liquid from seeping into the inner wall of the cylinder assembly 30 along the gap between the positioning tube 211 and the inner wall of the cylinder assembly 30, and prevents the paint from depositing in the non-painted area. One end of the elastic unit 23 is fixed to the outer peripheral wall of the positioning tube 211, and the other end extends away from the positioning tube 211 along the radial direction of the positioning tube 211.

[0041] The first state of the coating fixture involves the deformation of the elastic unit 23, which then abuts against the inner peripheral wall of the cylinder assembly 30, thus electrically connecting the elastic unit 23 to the cylinder assembly 30. The force generated by the elastic deformation of the elastic unit 23 automatically compensates for the fluctuations in the cylinder assembly 30 caused by buoyancy, ensuring that the elastic unit 23 and the cylinder assembly 30 maintain a tight contact at all times. This allows the current to be smoothly conducted sequentially from the base assembly 10, the positioning tube 211, and the elastic unit 23 to the cylinder assembly 30, ensuring stable electrical connection throughout the electrophoretic coating process. This, in turn, ensures the uniformity and density of the electrophoretic deposition layer, significantly improving the coating quality and production yield of the cylinder assembly 30. Specifically, the base assembly 10, the positioning tube 211, and the elastic unit 23 are all made of conductive materials.

[0042] Furthermore, such as Figure 2 As shown, the base assembly 10 includes a base body 11 and a stand body 12; the stand body 12 is fixed vertically to the base body 11; multiple positioning components 20 can be fixed on the stand body 12, enabling the same tooling to simultaneously support multiple cylinder assemblies 30, achieving parallel operation of multiple cylinder assemblies 30, and improving the efficiency of batch processing multiple workpieces within a single electrophoretic coating cycle. Preferably, the multiple positioning components 20 are evenly spaced, resulting in a more uniform overall force distribution and improved aesthetics.

[0043] Furthermore, such as Figure 4 and Figure 5 As shown, the elastic unit 23 includes a first elastic part 231; one end of the first elastic part 231 is fixed to the outer peripheral wall of the positioning tube 211, and the other end extends away from the positioning tube 211 along the radial direction of the positioning tube 211; preferably, the first elastic part 231 is a spring sheet, and the gap between the first elastic part 231 and the outer peripheral wall of the positioning tube 211 gradually increases along the fitting direction of the cylinder assembly 30.

[0044] The first state of the painting fixture includes deformation of the first elastic part 231 and contact with the inner peripheral wall of the cylinder assembly 30, applying at least a downward force to the cylinder assembly 30. This force can be inclined downward or vertically downward, originating from the elastic restoring force generated by the first elastic part 231 when the cylinder assembly 30 is fitted onto the positioning tube 211, and increasing with the increase of the buoyancy experienced by the cylinder assembly 30 in the painting tank. As a result, the contact between the positioning tube 211 and the cylinder assembly 30 becomes increasingly tight, ensuring that current can be stably conducted from the positioning tube 211 through the first elastic part 231 to the cylinder assembly 30, achieving a reliable electrical connection.

[0045] Furthermore, such as Figure 4 and Figure 5As shown, the elastic unit 23 includes a second elastic part 232; one end of the second elastic part 232 is fixed to the outer peripheral wall of the positioning tube 211, and the other end extends away from the positioning tube 211 along the radial direction of the positioning tube 211; preferably, the second elastic part 232 is a spring sheet, and the gap between the second elastic part 232 and the outer peripheral wall of the positioning tube 211 gradually increases along the fitting direction of the cylinder assembly 30.

[0046] The first state of the painting fixture includes deformation of the second elastic part 232 and abutment against the inner peripheral wall of the cylinder assembly 30, applying at least an upward force to the cylinder assembly 30. This force can be inclined upward or vertically upward, originating from the compression of the second elastic part 232 when the cylinder assembly 30 is fitted onto the positioning tube 211, i.e., provided by elastic restoring force. Since the cylinder assembly 30 compresses the second elastic part 232 due to gravity during fitting, this second elastic part 232 is added to balance its positioning and ensure consistent gaps between the inner wall of the cylinder assembly 30 and the outer wall of the positioning tube 211, thereby improving coating uniformity. Based on the downward force provided by the first elastic part 231, the second elastic part 232 applies an upward force. The two work together to subject the cylinder assembly 30 to bidirectional elastic constraint, thus making its radial position on the positioning tube 211 more stable and reliable.

[0047] Furthermore, such as Figure 4 and Figure 5As shown, two second elastic parts 232 are provided. After the painting fixture enters the painting tank, the cylinder assembly 30 is affected by buoyancy in addition to gravity, and the gravity is greater than the buoyancy. In order to ensure the positioning balance of the cylinder assembly 30, two second elastic parts 232 are specially provided to jointly balance the gravity. The two second elastic parts 232 and the first elastic part 231 are arranged along the circumference of the positioning tube 211, thereby forming three elastic contact points located at different positions in the circumference of the positioning tube 211, realizing multi-point and multi-directional conductive contact, which significantly improves the contact reliability. The first elastic part 231 is arranged vertically below the two second elastic parts 232. Preferably, the first elastic part 231 and the two second elastic parts 232 are evenly spaced in the circumference and are located in the same cross section, that is, they are evenly distributed at an angle of 120° to each other in the cross section. Thus, the three contact points apply radial elastic restoring forces to the inner wall of the cylinder from three different directions, and the directions of each force are 120° to each other. The combined action of these three radial forces ensures that any tendency of the cylinder assembly 30 to become eccentric in the horizontal direction is limited and corrected by the elastic restoring force in the opposite direction. This guarantees that the cylinder assembly 30 maintains good coaxiality with the positioning tube 211 throughout the entire electrophoretic coating process, effectively avoiding problems such as poor local contact, inadequate sealing, or uneven coating thickness caused by eccentricity, and significantly improving the positioning accuracy and coating quality of electrophoretic coating. The first elastic part 231 is located directly below the axis of the positioning tube 211, and two second elastic parts 232 are symmetrically located on both sides of the first elastic part 231. The first elastic part 231 located directly below directly generates a downward pressing force opposite to the buoyancy, effectively counteracting the upward tendency of the workpiece and ensuring reliable pressing of the sealing unit 22. The horizontal component forces of the symmetrical second elastic parts 232 on both sides cancel each other out, preventing lateral displacement of the workpiece and providing balanced auxiliary support from above. Together, the three components form an inverted triangular force structure centered on the axis, which forces the workpiece to be coaxially aligned with the positioning tube 211 and ensures the stability of the cylinder assembly 30's posture, ultimately ensuring uniform coating and stable current conduction.

[0048] Furthermore, such as Figure 6As shown, the sealing unit 22 includes a support module 221 and a sealing module 222; the support module 221 includes a support plate 2211 and a support ring 2212; the support plate 2211 is fixed to one end of the positioning tube 211 near the base assembly 10 and is sleeved on the positioning tube 211, providing a stable installation foundation and axial positioning reference for the entire sealing unit 22, ensuring that the position of each subsequent sealing component relative to the positioning tube 211 is accurate and reliable; one end of the support ring 2212 is connected to the outer peripheral wall of the support plate 2211, and the other end faces away from the outer peripheral wall. Extending from the base assembly 10, it provides initial guidance and restraint to the outer wall end of the cylinder assembly 30 in the radial direction, guiding the cylinder assembly 30 smoothly into the positioning tube 211 and limiting its excessive radial displacement. It also creates an annular accommodating space between the support plate 2211 and the inner wall of the workpiece, providing a reliable support frame for the sealing module 222. The sealing module 222 includes a sealing plate 2221 and a sealing ring 2222. The sealing plate 2221 is fixed to the support plate 2211, the support ring 2212, and the positioning tube 211. During the process, after painting, the cylinder assembly 30 and painting fixture need to be placed in a drying chamber for drying. Since the sealing module 222 is made of rubber, repeated drying can cause the rubber to age and crack, potentially detaching from the positioning tube 211. Therefore, a support module 221 is provided to limit excessive expansion of the sealing module 222. Simultaneously, the sealing plate 2221 is securely clamped within the annular accommodating space. This is achieved through the support plate 2211 and support ring 2212 forming a radial limit, preventing the sealing plate 2221 from deteriorating during long-term use. The sealing plate 2221 is not displaced or dislodged, ensuring that it maintains the correct shape and position during operation. One end of the sealing ring 2222 is connected to the sealing plate 2221, and the other end extends away from the base assembly 10. When the cylinder assembly 30 is installed, the extended end of the sealing ring 2222 forms a squeezing contact with the outer wall end of the cylinder assembly 30. The sealing pressure is generated by the elastic deformation of the sealing ring 2222 itself, thereby effectively preventing the coating liquid from seeping into the depth of the inner hole of the workpiece along the gap between the positioning tube 211 and the inner wall of the workpiece.

[0049] Furthermore, such as Figure 6As shown, the extension length of the sealing ring 2222 in the direction away from the base assembly 10 is greater than the extension length of the support ring 2212. When the cylinder assembly 30 is fitted from top to bottom along the positioning tube 211, the end of the sealing ring 2222 away from the base assembly 10 contacts the end of the cylinder assembly 30 before the support ring 2212, and this contact part is not restricted by the support ring 2212, so that the cylinder assembly 30 can be fitted onto the positioning tube 211 more smoothly without applying excessive external force. The inner peripheral wall of the end of the sealing ring 2222 away from the base assembly 10 is provided with a guide slope. The guide slope gradually shrinks inward from the end of the sealing ring 2222, which can smoothly guide the cylinder assembly 30 into the annular gap between the sealing ring 2222 and the positioning tube 211. At the same time, as the cylinder assembly 30 is fitted deeper, the guide slope gradually squeezes the sealing ring 2222, so that its elastic deformation gradually increases, and the contact pressure with the outer wall of the cylinder assembly 30 is steadily established, thereby ensuring the uniformity and reliability of the seal.

[0050] Furthermore, such as Figure 4 and Figure 5As shown, the positioning unit 21 includes a balancing hole 212 and a positioning tube 211. The balancing hole 212 is located on the base assembly 10 or the positioning tube 211. The balancing hole 212 connects the cavity between the positioning tube 211 and the cylinder assembly 30 to the outside. Since the cylinder assembly 30 only needs to be coated on its outer peripheral wall, its inner peripheral wall area should avoid contact with the coating liquid. Therefore, during the coating process, it is necessary to ensure that the cavity between the positioning tube 211 and the cylinder assembly 30 is completely sealed to prevent the coating liquid from seeping into the inner wall area. Conventionally, the positioning tube 211 is set as a completely sealed tube. However, after the electrophoretic coating is completed, the coating fixture and the cylinder assembly 30 together need to be sent into the drying chamber for curing. If the cavity remains completely sealed during the drying stage, as the temperature inside the chamber rises, the gas inside the cavity will expand due to heat, generating high-pressure gas. If the pushing force exerted by the high-pressure gas on the cylinder assembly 30 exceeds the constraint force of the elastic unit 23, it may cause the cylinder assembly 30 to bounce off or even detach from the positioning tube 211, which could not only damage the workpiece but also cause a safety accident. To avoid this risk, this embodiment provides a balance hole 212 on the positioning tube 211 or the base assembly 10, connecting the cavity to the external environment and providing a pressure relief channel for the heated and expanding gas, preventing the cylinder assembly 30 from being bounced off due to internal pressure accumulation. However, the introduction of the balance hole 212 also brings new problems: the coating liquid may seep into the inner wall of the cylinder assembly 30 through this hole. In actual use, after the coating liquid enters the positioning tube 211, the gas space in the cavity is compressed and tends to be sealed again. At this time, the pressure of the gas sealed in the cavity will increase, forming an inhibitory effect on the continued seepage of the coating liquid. To ensure that the gas pressure is always sufficient to resist the penetration force of the coating liquid, the volume change ratio of the cavity needs to be limited, so V2 / V1 is less than the safety setting value. Here, V2 is the volume of the gas in the first cavity after compression, and V1 is the volume of the gas in the first cavity before compression. The first cavity is the communication area between the balance hole 212 and the positioning tube 211 and the cylinder assembly 30. That is, the ratio of the volume of the gas in the first cavity after compression to the volume before compression is less than the safety setting value. This ensures that after the coating liquid enters, the pressure increment generated by the compression of the gas in the cavity is sufficient to balance or exceed the penetration driving force of the coating liquid, thereby effectively preventing the coating liquid from further contacting the inner wall of the cylinder assembly 30.

[0051] Example 2:

[0052] This application also provides a coating method, which is applied to any of the coating fixtures in Embodiment 1; the coating method sequentially executes steps S10, S20 and S30.

[0053] Step S10: Based on the coating command trigger, the cylinder assembly 30 is fitted onto the positioning tube 211 to reach the first state; wherein, the first state includes the deformation of the elastic unit 23 and its contact with the inner peripheral wall of the cylinder assembly 30; before the cylinder assembly 30 enters the coating tank, the initial conductive contact and positioning between the elastic unit 23 and the workpiece are established, thereby providing a reliable electrical connection basis and constraint for the subsequent electrophoresis process.

[0054] Step S20: Based on reaching the first state, the coating fixture and cylinder assembly 30 are placed in the coating tank to reach the second state. The second state includes the cylinder assembly 30 floating and compressing the elastic unit 23. The cylinder assembly 30 floats relative to the positioning tube 211 due to buoyancy in the coating liquid. This floating displacement further compresses the elastic unit 23, which is already in a deformed state. The elastic restoring force of the elastic unit 23 increases synchronously with the increase of compression, thereby automatically increasing the contact pressure between the elastic unit 23 and the inner peripheral wall of the cylinder assembly 30. This ensures that the conductive contact surface is tighter and more reliable even under the condition of maximum buoyancy. The elastic unit 23 makes full use of buoyancy, which originally caused poor contact, and transforms it into a positive effect of increasing the conductive contact pressure. This completely overcomes the problem of poor contact caused by the movement of the cylinder assembly 30 in the coating liquid due to buoyancy in the traditional process, ensuring that the electrophoretic coating has uniform thickness and good density. At the same time, it simplifies the operation process and improves coating efficiency and product yield.

[0055] In step S30, based on the time from reaching the second state to the first set time, the coating fixture and cylinder assembly 30 are removed from the coating tank. After reaching the second state, the first set time is maintained, so that the cylinder assembly 30 maintains a stable immersion posture and conductive state in the coating liquid under the combined action of the clamping force continuously applied by the elastic unit 23 and the sealing unit 22, thereby ensuring continuous and stable current transmission throughout the electrophoretic deposition process.

[0056] Furthermore, F1 < F2; where F1 is the downward force exerted by the elastic unit 23 on the cylinder assembly 30 in the first state, and F2 is the downward force exerted by the elastic unit 23 on the cylinder assembly 30 in the second state. In the second state, the elastic unit 23 applies a greater downward clamping force to the cylinder assembly 30. This increased downward force is dynamically balanced with the upward buoyancy force on the cylinder assembly 30. As the buoyancy force increases, the compression of the elastic unit 23 increases, and the downward force increases synchronously. Thus, the buoyancy force itself drives the elastic unit 23 to adaptively increase the clamping force, transforming the buoyancy force that originally caused poor contact into a positive factor that enhances conductive contact.

[0057] Furthermore, such as Figure 4 and Figure 5As shown, a balance hole 212 is provided on the positioning tube 211; the coating method executes steps S10, S20, S30 and S40 in sequence.

[0058] In step S40, based on the removal of the painting fixture and cylinder assembly 30 from the painting tank, the painting fixture and cylinder assembly 30 are placed in the drying chamber and dried for a second set time. By setting a balance hole 212, and after the painting fixture and cylinder assembly 30 are removed from the painting tank, they are placed together in the drying chamber and dried for the second set time. When the painting fixture and cylinder assembly 30 rise from the painting tank and leave the liquid surface, the balance hole 212 connects the inside of the positioning tube 211 with the outside atmosphere, providing a pressure relief channel for the gas that expands due to heat between the positioning tube 211 and the cylinder assembly 30, preventing the cylinder assembly 30 from being bounced off due to internal pressure accumulation.

[0059] Those skilled in the art will understand that the above embodiments are specific examples of implementing this disclosure, and in practical applications, various changes can be made in form and detail without departing from the scope of this disclosure.

Claims

1. A painting fixture, characterized in that, The painting fixture is used for painting cylinder assemblies with one open end; the painting fixture includes: Base assembly; A positioning assembly includes a positioning tube, a sealing unit, and an elastic unit. One end of the positioning tube is fixed to the base assembly, and the other end of the positioning tube extends away from the base assembly. The fixed end of the positioning tube to the base assembly is lower than the other end of the positioning tube in the vertical direction. The sealing unit is fixed to the end of the positioning tube near the base assembly and is sleeved on the outer peripheral wall of the positioning tube. One end of the elastic unit is fixed to the outer peripheral wall of the positioning tube, and the other end extends away from the positioning tube in the radial direction. The first state of the painting fixture includes deforming through the elastic unit and abutting against the inner peripheral wall of the cylinder assembly, thereby electrically connecting the elastic unit to the cylinder assembly.

2. The painting fixture according to claim 1, characterized in that, The elastic unit includes a first elastic part; one end of the first elastic part is fixed to the outer peripheral wall of the positioning tube, and the other end extends away from the positioning tube along the radial direction of the positioning tube. The first state of the painting fixture includes deforming through the first elastic part and abutting against the inner peripheral wall of the cylinder assembly, thereby applying at least a downward force to the cylinder assembly.

3. A painting fixture according to claim 2, characterized in that, The elastic unit includes a second elastic part; one end of the second elastic part is fixed to the outer peripheral wall of the positioning tube, and the other end extends away from the positioning tube along the radial direction of the positioning tube. The first state of the painting fixture includes deforming through the second elastic part and abutting against the inner peripheral wall of the cylinder assembly, thereby applying at least an upward force to the cylinder assembly.

4. A painting fixture according to claim 3, characterized in that, Two second elastic parts are provided, and the two second elastic parts and the first elastic part are arranged along the circumference of the positioning tube; the first elastic part is arranged vertically below the two second elastic parts.

5. A painting fixture according to claim 1, characterized in that, The sealing unit includes a support module and a sealing module; the support module includes a support plate and a support ring; the support plate is fixed to one end of the positioning tube near the base assembly and is sleeved on the positioning tube; one end of the support ring is connected to the outer peripheral wall of the support plate, and the other end extends away from the base assembly; the sealing module includes a sealing plate and a sealing ring; the sealing plate is fixed between the support plate, the support ring and the positioning tube; one end of the sealing ring is connected to the sealing plate, and the other end extends away from the base assembly.

6. A painting fixture according to claim 5, characterized in that, The sealing ring extends further away from the base assembly than the support ring; the inner peripheral wall of the end of the sealing ring away from the base assembly is provided with a guide slope.

7. A painting fixture according to claim 1, characterized in that, The positioning unit includes a balance hole and the positioning tube; the balance hole is located on the base assembly or the positioning tube; the balance hole connects the cavity between the positioning tube and the cylinder assembly to the outside; V2 / V1 is less than a safety setting value; wherein, V2 is the volume of the gas in the first cavity after compression, V1 is the volume of the gas in the first cavity before compression, and the first cavity is the communication area between the balance hole and the positioning tube and the cylinder assembly.

8. A coating method, characterized in that, The coating method is applied to a coating fixture as described in any one of claims 1-7; the coating method includes: Triggered by a painting command, the cylinder assembly is fitted onto the positioning tube, reaching a first state; wherein, the first state includes the elastic unit deforming and abutting against the inner peripheral wall of the cylinder assembly; Based on achieving the first state, the painting fixture and the cylinder assembly are placed in the painting tank to achieve the second state; wherein, the second state includes the cylinder assembly floating and compressing the elastic unit; Based on the time from reaching the second state to the first set time, the painting fixture and the cylinder assembly are removed from the painting tank.

9. A coating method according to claim 8, characterized in that, F1 < F2; where F1 is the downward force exerted by the elastic unit on the cylinder assembly in the first state, and F2 is the downward force exerted by the elastic unit on the cylinder assembly in the second state.

10. A coating method according to claim 8, characterized in that, The positioning unit includes balance holes; The coating method further includes: The painting fixture and the cylinder assembly are removed from the painting tank and placed in a drying chamber to dry for a second set time.

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