An all-aluminum badminton racket glue tee structure and tee bonding process

Abstract

The application relates to the badminton racket processing field and particularly discloses a full-aluminum badminton racket gluing T-shaped structure and a T-shaped structure gluing process, which comprises an aluminum alloy T-shaped body formed through die casting, the T-shaped body comprises two groups of transversely arranged insertion sleeves for being connected with frame tubes, one group of vertically arranged insertion sleeves for being connected with middle rods, the three groups of sleeves are internally hollow insertion cavities; the inner walls of the three groups of insertion sleeves are provided with segmented stepped gap structures, two-stage annular glue storage exhaust grooves and flow guide channels, the three groups of sleeve ports are integrally formed with sealing glue blocking convex rings; one end of the three groups of sleeves away from the ports is formed with a vacuumizing hole; the segmented stepped gap structure is sequentially divided into a port sealing section, a middle gluing section and a bottom limiting section from outside to inside, the insertion gap of the port sealing section is 0.1 mm, the insertion gap of the middle gluing section is 0.25-0.3 mm, the bottom limiting section comprises a limiting step for limiting the insertion depth of an aluminum tube, and the vacuumizing hole is located near the limiting step.

Description

Technical Field

[0001] This application relates to the field of badminton racket tee connector assembly and processing, and in particular to an all-aluminum badminton racket adhesive tee structure and tee bonding process. Background Technology

[0002] All-aluminum alloy badminton rackets generally adopt a glue-insertion three-way connection structure, eliminating the traditional argon arc welding process. They rely on two-component room temperature epoxy resin to fill the gap between the three-way connector and the frame and shaft to achieve fixation.

[0003] The existing adhesive tee structure has obvious technical defects, with the core problems concentrated in the epoxy resin filling and sealing process: 1. Incomplete filling and numerous internal air bubbles: The existing tees use a uniform gap insertion structure with equal diameter. When applying glue manually or by ordinary glue-pouring methods, the air inside the sleeve cannot be completely expelled, and it is very easy to leave closed air bubbles. At the same time, the fluidity of the glue is uncontrollable, and there are often gaps and voids deep in the sleeve. The glue layer is discontinuous, and stress is concentrated when under force, which leads to the failure of the sleeve to come off or crack after hitting the ball and after hot and cold cycles.

[0004] 2. Severe glue leakage during insertion and compression: The existing T-joint has no buffered glue storage structure. During the rapid insertion of aluminum tubes, the glue in the gap is squeezed by instantaneous high pressure, and a large amount of glue overflows from the tube opening. This not only contaminates the appearance of the racket frame and shaft, but also causes the loss of effective adhesive layer, insufficient thickness, and a significant decrease in bonding strength. Furthermore, the subsequent grinding process is cumbersome and increases production costs.

[0005] 3. Poor adhesive layer fit and weak adhesion: Ordinary smooth inner wall tees rely solely on adhesive bonding without mechanical interlocking structure; at the same time, traditional self-leveling epoxy adhesives are prone to flow and have a large curing shrinkage rate. After curing, the adhesive layer is prone to delamination from the aluminum wall, resulting in poor torsional and impact resistance, limiting the string tension of rackets and leading to a high after-sales failure rate.

[0006] 4. High internal stress and poor consistency during curing: Conventional constant temperature curing mode has no stress release structure, resulting in uneven shrinkage of the adhesive during curing, which aggravates the problems of voids and cracks in the adhesive layer, and leads to large differences in the quality of batch products.

[0007] In summary, the existing glue-insertion three-way structure lacks targeted venting, glue storage, glue blocking, and fitting structure design, making it impossible to achieve full and gapless epoxy resin filling. The glue leakage defect is difficult to eradicate, which seriously restricts the quality and service life of all-aluminum glued badminton rackets. Therefore, structural improvement is urgently needed. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a leak-proof, gap-free all-aluminum badminton racket adhesive tee structure. This solves the problems of existing tee epoxy resin filling with gaps, air bubbles, and insufficient glue, resulting in easy glue leakage at the joint, low adhesive layer bonding strength, and poor product consistency. It achieves full and zero-gap filling of the adhesive gap with epoxy resin, while eliminating glue overflow and leakage, thus improving the overall structural strength and service life of the racket.

[0009] The technical solution for the all-aluminum badminton racket adhesive T-joint structure provided in this application is as follows: A T-joint structure for an all-aluminum badminton racket includes a die-cast aluminum alloy T-shaped T-joint body. The T-joint body comprises two sets of horizontally arranged insert sleeves for connecting to the frame tube, and one set of vertically arranged insert sleeves for connecting to the shaft. All three sets of sleeves have hollow insert cavities for inserting the aluminum frame tube and aluminum shaft, which are then filled with epoxy resin for bonding and fixing. The key feature is that the inner walls of all three sets of insert sleeves are provided with a segmented stepped gap structure, two-stage annular glue storage and venting grooves, and a flow guiding channel. All three sets of sleeve ports are integrally formed with sealing and glue-blocking protrusions. A vacuum hole is formed at the end of each sleeve furthest from the port. The segmented stepped gap structure is divided into a port sealing section, a middle bonding section, and a bottom limiting section from the outside to the inside. The insertion gap of the port sealing section is 0.1 mm, the insertion gap of the middle bonding section is 0.25–0.3 mm, and the bottom limiting section includes a limiting step for restricting the insertion depth of the aluminum tube. The vacuum hole is located near the limiting step.

[0010] Optionally, the two-stage annular glue storage and venting channel includes a primary glue storage channel and a secondary venting glue storage channel. The primary glue storage channel is located at the junction of the port sealing section and the middle bonding section, and is used to collect excess glue. The secondary venting glue storage channel is located in the middle bonding section of the sleeve.

[0011] Optionally, the flow channel is located on the inner wall of the middle bonding section, extending axially along the insertion sleeve and communicating with the secondary exhaust storage tank, while the flow channel is separated from the primary storage tank.

[0012] Optionally, the inner wall of the middle bonding section is also formed with a spiral anti-slip and flow-guiding pattern, which is separated from the primary glue storage tank.

[0013] Optionally, the sleeve base wall thickness is 2.5mm, and the remaining effective wall thickness after grooving is ≥1.8mm; the thickness of the port sealing ring is 3.0mm; the wall thickness of the central intersection area of ​​the tee body is 3.5~4.0mm, and the corner adopts R-arc transition.

[0014] Optionally, an annular gas collecting groove is formed on the end face of the limiting step near the middle bonding section. The outer diameter of the annular gas collecting groove is smaller than the outer diameter of the aluminum tube, and one end of the vacuum hole is connected to the annular gas collecting groove.

[0015] Optionally, a bonding process for an all-aluminum badminton racket tee, employing an all-aluminum badminton racket adhesive tee structure, is characterized by including the following steps: S1. Pretreatment of bonding surfaces: The aluminum frame tube, aluminum middle rod and the inner wall of the tee insertion cavity are roughened by CNC sandblasting, cleaned by plasma to remove impurities, and then sprayed with silane coupling agent to dry and activate the bonding surfaces. S2. Adhesive pretreatment: Thixotropic two-component room temperature epoxy resin is used. After mixing, vacuum degassing is performed to eliminate air bubbles inside the adhesive. S3. Posture adjustment: The workpiece is tilted at a 30° to 35° angle, and all three sets of plug sleeves are at a 30° to 35° angle to the horizontal plane. S4. Negative pressure vacuum exhaust: All air in the cavity can be drawn out in an orderly manner through the top ventilation gap, inclined tube, secondary exhaust storage tank and micro-guide channel to the bottom negative pressure area, completely eliminating micro air bubbles and air-stuck cavities. S5. Vacuum quantitative glue injection: Under continuous vacuum in S4, the glue is injected synchronously and quantitatively from three sets of casing ports through a triaxial synchronous glue injection device. The glue injection volume is precisely controlled to be 70%-80% of the total volume of the casing cavity. Combined with the high thixotropic properties of epoxy resin, the glue adheres stably to the middle and front bonding area of ​​the lower half of the casing wall. A continuous and open ventilation gap is maintained at the top of the casing wall, which is open to the atmosphere throughout the process to avoid the cavity being sealed and trapped. S6. Servo Precision Insertion and Positioning: The aluminum tube is inserted into place using a uniform low-speed servo propulsion method. The bottom step of the insertion sleeve is used for limiting the position. Excess glue is stored in a two-stage annular glue storage and venting groove. The end glue-blocking protrusion ring is used to achieve a seal and prevent leakage. S7. Ultrasonic-assisted dense filling: After the insertion is completed, low-frequency ultrasonic vibration is performed to promote the epoxy resin to penetrate into the micro gaps of the texture and eliminate the micro gaps in the adhesive layer. S8. Segmented micro-vibration curing: Multi-segment stepped temperature control combined with full-process micro-vibration mode is used to complete the pre-curing, main curing and post-curing treatment of epoxy resin, to compensate for curing shrinkage and eliminate internal stress of the adhesive layer.

[0016] Optionally, the following steps may also be included. S9. Non-destructive testing and sorting: Ultrasonic scanning is used to inspect the adhesive layer of the T-joint to screen out defective products with insufficient adhesive, air bubbles, or delamination, while good products flow into subsequent processes.

[0017] Optionally, the stepped temperature control parameters in S8 include 40℃ pre-curing for 30 minutes, 65℃ main curing for 60 minutes, and 80℃ post-curing for 20 minutes, with low-frequency micro-vibration maintained throughout the curing process.

[0018] Optionally, the thixotropic two-component room-temperature epoxy resin consists of component A and component B. Component A includes 75 parts of E51 epoxy resin, 12 parts of butyl glycidyl ether, 9 parts of hydrophobic fumed silica, 1.5 parts of silicone defoamer, and 2.5 parts of wetting and dispersing agent; component B includes 22 parts of 650 polyamide curing agent, 3 parts of DMP-30 accelerator, 2 parts of hydrophobic fumed silica, and 1 part of leveling and defoaming agent.

[0019] In summary, this application includes at least one of the following beneficial technical effects: (1) Completely achieves full and void-free epoxy resin filling: Through the combination structure of two-stage glue storage and venting groove + spiral flow channel + vacuum potting + ultrasonic penetration filling, the air inside the insertion cavity can be completely discharged, eliminating macroscopic bubbles, glue-deficient voids and microscopic layered voids. After curing, the glue layer is continuous and dense, with a 100% filling qualification rate, which completely solves the core defects of traditional adhesive tees such as internal loose bonding and void bonding. (2) Eliminate glue leakage and overflow throughout the process: Relying on the physical sealing structure of the segmented stepped gap and the port glue-blocking protrusion ring, and with the built-in glue storage tank to buffer excess glue, the glue overflow during the insertion and curing process is eliminated from both structural and process dimensions. There is no need for a lot of grinding and glue repair in the later stage, which simplifies the production process and reduces production costs. (3) Significantly improved bonding strength and stability: The spiral pattern forms a mechanical interlocking structure between the glue and aluminum material. Combined with multi-segment micro-vibration curing, it eliminates the internal stress of the glue layer. The glue layer is free from delamination and shrinkage cracks. The anti-torsion and anti-impact performance of the three-way connector is significantly improved, effectively solving the problems of detachment, cracking and deformation during racket use. It can be adapted to higher string tensions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of an embodiment of this application; Figure 2 It is along Figure 1 A schematic diagram of the longitudinal sectional structure; Figure 3 This is a schematic diagram of the internal structure of the insertion sleeve.

[0021] Reference numerals: 1. Insert sleeve; 2. Sealing and sealing protrusion ring; 3. Vacuum hole; 4. Port sealing section; 5. Middle bonding section; 6. Limiting step; 7. Primary adhesive storage tank; 8. Secondary exhaust adhesive storage tank; 9. Guide channel; 10. Spiral anti-slip guide texture; 11. T-junction center; 12. Annular gas collecting groove; 13. Converging hole. Detailed Implementation

[0022] The following is in conjunction with the appendix Figure 1 —3 provides further detailed description of this application.

[0023] This embodiment provides a mass-producible, leak-proof, gapless filling aluminum tee structure. The tee body is made of die-cast aluminum alloy and has an overall T-shaped structure. It includes two sets of horizontally arranged plug sleeves for connecting with the frame tube and one set of vertically arranged plug sleeves for connecting with the center rod. The three sets of sleeves are integrally formed.

[0024] All three sets of insertion sleeves 1 have hollow insertion cavities inside, used for inserting aluminum frame tubes and aluminum center rods, and filling them with epoxy resin for bonding and fixing. The inner walls of all three sets of insertion sleeves 1 are provided with a segmented stepped gap structure, two-stage annular resin storage and venting grooves, and a flow guiding channel 9.

[0025] All three sets of sleeve ports are integrally formed with sealing and adhesive-blocking protrusions 2. The sealing and adhesive-blocking protrusions 2 flexibly fit against the outer wall of the aluminum tube, forming a physical sealing barrier, preventing adhesive leakage during insertion and completely solving the problem of adhesive leakage at the pipe opening.

[0026] A vacuum hole 3 is formed at the end of the three sets of sleeves furthest from the port. The segmented stepped gap structure is divided into a port sealing section 4, a middle bonding section 5, and a bottom limiting section from the outside to the inside. The insertion gap of the port sealing section 4 is 0.1 mm, the insertion gap of the middle bonding section 5 is 0.25-0.3 mm, and the bottom limiting section is provided with a limiting step 6 to limit the insertion depth of the aluminum tube. The vacuum hole 3 is located near the limiting step 6. The insertion gap here refers to the gap between the side wall of the aluminum tube and the insertion sleeve 1 after the aluminum tube is inserted in the center. That is, the difference between the outer diameter of the aluminum tube and the inner diameter of the insertion sleeve 1 is 0.2 mm. The intersection of the three insertion sleeves 1 is a tee center 11. The vacuum holes 3 of the three insertion sleeves 1 are all connected to the tee center 11. A converging hole 12 is opened on the tee center, and the converging hole 12 is connected to an external vacuuming device.

[0027] Each set of sleeves has two levels of annular grooves on its inner wall, forming two levels of annular glue storage and venting channels, including a primary glue storage channel 7 and a secondary venting glue storage channel 8. The primary glue storage channel 7 is located at the junction of the port sealing section 4 and the middle bonding section 5, and is specifically used to receive excess glue that overflows during insertion and compression, preventing glue from overflowing. The secondary venting glue storage channel 8 is located in the bonding section area in the middle of the sleeve, and can conduct and release the sealed air in the cavity in real time during glue pouring and insertion, completely eliminating air bubbles and voids, while storing excess glue to compensate for the shrinkage of epoxy curing and prevent gaps due to insufficient glue after curing.

[0028] The inner wall of the bonding section 5 in the middle of the sleeve is provided with a composite flow guiding and interlocking structure, including an axially extending flow guiding channel 9 and a spiral anti-slip flow guiding pattern 10. The axial flow guiding channel 9 extends along the axial direction of the insertion sleeve 1 and is only connected to the secondary exhaust storage tank 8, not to the primary storage tank 7 on the port side. It can accurately guide the air in the cavity to the secondary exhaust storage tank 8 and the bottom vacuum hole 3 to be discharged, enhance the exhaust effect of dead corners of the pipe wall, and at the same time avoid air leakage and pressure loss from the port side during the negative pressure pumping process. The bonding section 5 in the middle is also provided with a spiral anti-slip flow guiding pattern 10, which can guide the epoxy glue to flow evenly and fill layer by layer during glue pouring, avoid glue accumulation and gaps. After curing, the glue is embedded in the inside of the pattern to form a mechanical interlocking structure, which greatly improves the bonding adhesion and anti-torsion performance, and further eliminates the delamination gap between the glue layer and the pipe wall.

[0029] Structural dimensional parameters: Standard inner diameter of the sleeve is 7.0mm, effective total length of the insertion cavity is 18mm; basic wall thickness of the sleeve is 2.5mm, thickness of the port sealing ring is 3.0mm, wall thickness of the intersection area of ​​the tee center 11 is 3.8mm, and the corner has a 1.5mm rounded transition; Sleeve segment parameters: axial length of the port sealing section 4 is 4mm, clearance is 0.1mm, axial length of the middle bonding section 5 is 12mm, clearance is 0.25~0.3mm, axial length of the bottom limiting section is 2mm, and the vacuum hole 3 is located near the limiting step 6. Specifically, it is an annular limiting step 6 with an inner diameter of 3mm. An annular gas collecting groove 12 is formed on the end face of the limiting step 6 near the middle bonding section 5. The vacuum hole 3 penetrates the limiting step 6 and is connected to the annular gas collecting groove 12 at one end. There are 8 vacuum holes 3 evenly distributed along the circumference. The primary adhesive storage tank 7 has a depth of 0.4 mm and a width of 1.2 mm, while the secondary venting adhesive storage tank 8 has a depth of 0.5 mm and a width of 1.5 mm. The inner wall of the middle bonding section 5 is provided with a spiral anti-slip guide pattern 10 with a pitch of 2 mm and a depth of 0.3 mm, forming a composite venting structure with the axial guide channel 9. The axial guide channel 9 extends from its junction with the limiting step 6 through the secondary venting adhesive storage tank 8 to a distance of 72 mm from the primary adhesive storage tank. The axial guide channel 9 has a depth of 0.25 mm and a width of 0.8 mm, with 8 grooves arranged circumferentially. The spiral anti-slip guide pattern 10 extends from its junction with the limiting step 6 through the secondary venting adhesive storage tank 8 to a distance of 72 mm from the primary adhesive storage tank. This means that a 2 mm smooth surface is always maintained between the middle bonding section 5 and the primary adhesive storage tank 7, serving as a negative pressure isolation barrier.

[0030] The casing base wall thickness is uniformly 2.5mm, and the remaining effective wall thickness after the inner wall is grooved is ≥1.8mm, which meets the minimum safe wall thickness requirements of the die-casting process and eliminates the risk of deformation and cracking; the wall thickness of the intersection area of ​​the tee center 11 is 3.5~4.0mm, and the corner adopts R round arc transition to eliminate stress concentration and adapt to high-pressure wire pulling and high-frequency ball impact; the thickness of the end sealing ring is 3.0mm, which flexibly fits with the outer wall of the aluminum tube to form a reliable physical sealing barrier.

[0031] Example 2: A bonding process for a three-way connector on an all-aluminum badminton racket, using the three-way connector structure of Example 1, includes the following steps: S1. Pretreatment of pipe fittings and tees: The formed aluminum frame pipe, aluminum middle pipe and die-cast tee are successively subjected to CNC sandblasting roughening to ensure that the surface roughness R of the guide texture is 1.6~3.2μm. Then, the surface oxide film and oil are removed by low temperature plasma cleaning for 10s. After spraying silane coupling agent, the surface is dried with hot air at 60℃ to improve the adhesion of epoxy adhesive. S2. Adhesive Preparation and Vacuum Degassing: A special thixotropic two-component room-temperature epoxy resin is selected and prepared strictly according to the precise formula ratio. This thixotropic two-component room-temperature epoxy resin consists of component A and component B: component A consists of 75 parts E51 epoxy resin, 12 parts butyl glycidyl ether, 9 parts hydrophobic fumed silica, 1.5 parts silicone defoamer, and 2.5 parts wetting and dispersing agent; component B consists of 22 parts 650 polyamide curing agent, 3 parts DMP-30 accelerator, 2 parts hydrophobic fumed silica, and 1 part leveling and defoaming agent. After uniformly mixing and stirring according to the standard ratio, the mixture is placed in a 0-0.08MPa vacuum environment for 30 seconds to completely eliminate the air bubbles inside the adhesive, ensuring the purity and filling density of the adhesive.

[0032] Properties of thixotropic two-component room-temperature epoxy resin: 1. The static yield strength after mixing is ≥180Pa. Under normal pressure, negative pressure and inclined working conditions, it does not flow, fall or slip under its own weight. The adhesive adheres stably to the lower half of the sleeve and will not slip and block the bottom vacuum nozzle. 2. Shear-free static viscosity ≥120000mPa・s, solid paste, with permanent top-through venting gap; 3. Under the shearing action of servo insertion, the viscosity drops to 2000-5000 mPa·s. The low viscosity and high fluidity allow it to perfectly penetrate and fill tiny bonding gaps of 0.25-0.3 mm.

[0033] 4. Curing shrinkage rate ≤0.6%, with a micro-reservoir shrinkage compensation design, eliminating curing shrinkage gaps and loose adhesion.

[0034] 5. Shear bond strength to aluminum alloy substrate ≥22MPa, dense bonding, peel resistance, and impact resistance, suitable for high-tension stringing and high-frequency ball hitting conditions.

[0035] S3. Attitude adjustment: First, adjust the workpiece as a whole to a 30° to 35° tilt position, so that the three sets of plug sleeves 1 are all at an angle of 30° to 35° with the horizontal plane, forming a staggered air passage structure. S4. Negative Pressure Vacuum Exhaust: Open the vacuum port 3 at the bottom step for negative pressure exhaust. All air in the cavity can be drawn out in an orderly manner along the complete air path consisting of the top ventilation gap, the inclined pipe, the secondary exhaust storage tank 8, and the axial guide channel 9, converging at the bottom negative pressure area. This completely eliminates defects such as microscopic gaps and air bubbles in the pipe wall and air-trapped cavities at the bottom of the pipe, achieving exhaust without dead zones in the cavity. After the negative pressure exhaust is completed, turn off the vacuum equipment and appropriately replenish the cavity with atmospheric pressure air. The replenished air is concentrated in the top through-flow air path, forming a controllable transition air path with no dead zones or residual air.

[0036] S5. Vacuum Quantitative Glue Injection: Under continuous vacuum conditions as described in S4, a triaxial synchronous glue injection device is used to synchronously and quantitatively inject glue from three sets of sleeve ports. The glue injection volume is precisely controlled to be 70%-80% of the total volume of the sleeve cavity. Combined with the high thixotropic properties of epoxy resin, the glue adheres stably to the lower half of the sleeve wall and is bonded to the middle and front section bonding area. It will not flow towards the lowest point of the intersection at the center of the tee 11, nor will it block the vacuum hole 3 at the step. At the same time, a continuous and unobstructed ventilation gap is maintained at the top of the sleeve wall, allowing it to be fully connected to the atmosphere and completely avoiding air stagnation in the cavity. The 30°-35° lateral tilt of the workpiece completely breaks the dead angle of air accumulation at the top of the horizontal sleeve, providing a conductive basis for subsequent negative pressure venting.

[0037] S6. Servo Precision Insertion Positioning: Servo insertion at a uniform low speed of 5mm / s, with the aluminum tube precisely positioned against the bottom limit step 6. During insertion, the adhesive layer is stably compressed, and excess adhesive automatically flows into the two-stage adhesive storage tank for storage and compensation. The adhesive-blocking protrusion at the end fits tightly against the outer wall of the aluminum tube to achieve physical sealing, completely preventing adhesive overflow and leakage. At the same time, the top transition air is squeezed out from the sleeve end as the insertion progresses, leaving no air residue.

[0038] S7. Ultrasonic-assisted dense filling: After the insertion and positioning are completed, 40kHz low-frequency ultrasonic vibration is used for 60s. The cavitation effect is used to make the glue fully penetrate into the axial guide channel 9, the spiral pattern and the micro grooves of the aluminum material, completely eliminating micro gaps and achieving full adhesion and full dense filling of the glue layer.

[0039] S8. Segmented micro-vibration curing: The semi-finished product is sent into a three-segment temperature-controlled tunnel oven, accompanied by low-frequency micro-vibration throughout the process; 40℃ for 30 minutes for pre-curing to remove small molecules, 65℃ for 60 minutes for main curing and shaping, and 80℃ for 20 minutes for post-curing and reinforcement, releasing the internal stress of the adhesive layer, compensating for curing shrinkage, eliminating shrinkage gaps and adhesive layer cracking, and ensuring the consistency of filling multiple tubes.

[0040] S9. Non-destructive testing and sorting: After curing, the T-joint adhesive layer is scanned around by an ultrasonic probe to automatically identify defective products with insufficient adhesive, bubbles, or delamination. Good products enter the subsequent grinding and coating processes.

[0041] The traditional equal-diameter gap smooth inner wall tee, manual glue injection, and room temperature natural curing process are adopted, with all other materials and fitting parameters being completely consistent with Example 1. Testing showed that the traditional process resulted in an adhesive layer porosity ≥25%, a 100% glue overflow rate, 30% lower bond shear strength, and a batch yield of only 75%. In contrast, the combined structure and process of this example achieves a zero adhesive layer porosity, completely eliminates glue overflow defects, significantly improves bond strength, and achieves a batch yield ≥99%.

[0042] Compared to conventional horizontal placement adhesive application processes, this patented tilted orientation offers a significant advantage in air venting: While a vacuum at the bottom can remove most of the air from the cavity in a horizontal placement, a continuous, sealed thin-layer air gap easily forms between the upper wall of the horizontal sleeve and the adhesive. This microscopic blind spot cannot be completely eliminated by negative pressure, a common problem in the industry characterized by microscopic bubbles, fine voids, and localized loose adhesion. This patent, through an overall 30°–35° tilted layout, completely eliminates the dead zone of air accumulation at the top of the horizontal sleeve, ensuring complete airflow throughout all areas of the inner wall of both high and low sleeves. The minute amount of air trapped in the gaps along the upper edge of the sleeve can then converge along the tilted sleeve and guide channels to the lowest negative pressure area in the center and be completely extracted, thus completely eliminating microscopic air accumulation defects from a structural perspective. After the negative pressure evacuation is completed, outside air will enter the cavity through the top gap. However, at this time, the air is no longer scattered and stagnant in the microscopic dead corner, but is concentrated in the through-type orderly air passage at the top of the sleeve, forming a unique controllable exhaust channel. When the aluminum tube is subsequently inserted and pushed inward, the adhesive layer moves forward as a whole, squeezing the cavity, and the air flows to the vacuum hole 3 at the bottom and is discharged.

[0043] In this overall tilted position, the horizontal sleeves on both sides of the tee form a staggered layout with one high and one low (tilted upwards and tilted downwards), while the vertical insertion sleeve 1 tilts upwards. Combined with the patented internal flow-guiding and adhesive-storing structure and the properties of the thixotropic epoxy adhesive, simultaneous, bubble-free, leak-free, and adhesive-free filling of the two horizontal sleeves at both the high and low positions is achieved. This completely solves the industry pain points of air pockets, bubble accumulation, adhesive shortages at the bottom, and adhesive leakage in the sinking horizontal sleeve under the tilted condition of a rigid tee. The specific principle of the dual-tube filling is as follows: 1. High-position upturned horizontal pipe filling and venting principle: The high-positioned horizontal pipe has an open, upward-facing end. This process uses a metered glue-filling method at the end, combined with the properties of a highly thixotropic adhesive. The adhesive spreads completely and adheres to the lower half of the pipe wall, creating a continuous, unobstructed venting gap at the top of the pipe wall, rather than sealing the entire pipe. This top-through gap forms a continuous atmospheric pressure channel, ensuring the pipe cavity remains open to the atmosphere and completely avoiding the problem of air trapped by negative pressure in a sealed environment. The adhesive remains stably in the bonding area of ​​the front section of the pipe and does not flow towards the lowest point of the tee center 11. During negative pressure evacuation, the gap at the top of the pipe wall, the secondary exhaust storage tank 8, and the guide channel 9 form a complete air path. The residual air inside the insertion sleeve 1 and the air in the micro gaps of the pipe wall can converge towards the central low-level vacuum hole under the dominance of the bottom negative pressure and be completely drawn away. The excess glue generated by the insertion and extrusion can be stably stored in the primary storage tank 7, and the glue-blocking structure at the port simultaneously blocks the overflow of glue, ensuring extremely high filling density.

[0044] 2. Low-position sinking horizontal tube filling and venting principle: The low-position horizontal tube tilts downward with the side inclination of the rigid body and the port faces downward at an angle. Conventional self-leveling adhesive is very prone to problems such as glue leakage, air trapping in the dead corner at the bottom of the tube, and insufficient glue accumulation at the bottom. This patent completely solves this defect through a dual adaptation of structure and adhesive: First, it uses high thixotropic epoxy resin, which has high viscosity and anti-flow properties in a static state, and can stably adhere to and fill the lower half of the sleeve wall, preventing leakage due to the downward orientation of the pipe opening, while maintaining a continuous ventilation gap at the top of the pipe wall; Second, the overall inclined layout of the sleeve completely opens up the sealed dead corner of the traditional horizontal pipe bottom. Relying on the top through-hole and the flow guide channel 9, the air trapped at the bottom of the pipe can be gathered upward along the inclined pipe body, and then gathered towards the lowest vacuum area in the center, and finally uniformly removed by the bottom vacuum nozzle, completely eliminating the defect of air trapped and accumulating at the bottom of the pipe; Third, the port sealing section 4 and the sealing adhesive blocking protrusion ring 2 form a physical seal, combined with the 70%-80% quantitative glue filling process at the pipe opening, precisely controlling the glue layer filling range, maintaining the top ventilation channel, and preventing glue overflow and glue shortage problems at the bottom of the pipe opening.

[0045] The entire process only involves adjusting the overall tilt of the workpiece. The 90° inherent angle of the integrated tee fitting remains constant, with no structural deformation or bending damage. It perfectly matches the rigid body linkage physical characteristics of the rigid T-shaped tee and simultaneously meets the high standard of glue-filling process requirements of simultaneous vacuum filling with double horizontal pipes and a central pipe with zero bubbles and zero glue leakage.

[0046] (3) Vacuum negative pressure potting: The method of quantitative potting at both ends of the pipe and constant pressure suction at the bottom is adopted to accurately control the amount of potting to 70% to 80% of the total volume of the inner cavity of the casing. Combined with the characteristics of high thixotropic epoxy resin, which has high viscosity, does not flow or collapse, the adhesive only adheres to the lower half of the pipe wall of the casing and is stably retained in the middle and front bonding area. It will not fill the entire cavity or fall down to block the central vacuum hole. Combined with the 30°–35° lateral tilt of the tee, a continuous, long, open venting gap is naturally formed at the top of the sleeve wall, allowing full ventilation to the atmosphere and completely solving the industry-wide problem of full glue sealing of the port and air stagnation in the cavity. The staggered sleeve posture completely eliminates the dead zones of air trapped at the top and bottom of the sleeve that are traditionally filled with horizontal glue. Air in the sleeve and the micro-crevices in the sleeve wall can be uniformly drawn out along the top venting gap, the tilted tube and the guide structure to the negative pressure area at the bottom, and then orderly extracted. It adapts to the differentiated venting paths of high and low sleeves, and eliminates the problems of air bubbles in high and low sleeves and insufficient glue at the bottom.

[0047] Summary of Effects: 1. Unique Structural Innovation: Existing traditional adhesive tees only disclose the basic framework of "T-shaped sleeve insertion + adhesive bonding," which can only achieve a simple fixing effect without any targeted leak prevention, venting, or shrinkage compensation structures. This application features a unique four-in-one structure: segmented stepped sealing gap, two-stage adhesive storage and venting double grooves, port sealing adhesive-blocking convex ring, and spiral flow guiding interlocking texture. This not only solves the problem of adhesive overflow during insertion but also actively vents air from the cavity, compensates for adhesive curing shrinkage, and forms mechanical interlocking strength. It is a composite functional structure that existing single smooth sleeve structures completely lack, and no prior art documents disclose related technical features.

[0048] 2. Disruptive Innovation in Core Process Logic: Existing patents and mass production processes uniformly adopt a processing logic of first inserting a tube to seal the cavity, followed by glue filling. This structural mode inherently suffers from air trapping defects in the cavity, inevitably producing air bubbles, voids, and weak adhesion problems that the industry has long been unable to eradicate. This application breaks through the industry's inherent technical bias and innovatively proposes a reverse process logic of first vacuum quantitative pre-filling of glue, followed by servo low-speed insertion and extrusion to achieve compaction. This fundamentally avoids the problem of residual air sealing. This core process combination is not recorded in the existing patent database.

[0049] 3. A dedicated system for gapless filling: Traditional technologies rely solely on the natural filling of adhesive without any auxiliary compaction methods. This application features a complete compaction system consisting of vacuum degassing of adhesive, dynamic negative pressure injection into the cavity, ultrasonic micro-penetration, and segmented micro-vibration curing. Double vacuum eliminates internal and external air bubbles, ultrasonic filling of micro-gaps, and stepped curing eliminates shrinkage voids, achieving 100% gapless bonding from multiple dimensions, far exceeding the filling effect and product stability of traditional technologies.

[0050] 4. Unique Adaptive Design for Leak-Proof Adhesive Technology: Traditional structures lack adhesive storage and sealing mechanisms, making it prone to adhesive overflow during the entire process of dispensing, joining, and curing, requiring manual post-workout sanding and repair. This application achieves controllable adhesive overflow, zero external leakage, and eliminates the need for extensive sanding through a combination of volume-matched quantitative dispensing, stepped port sealing, and a built-in adhesive storage tank to buffer excess adhesive. The structure is highly compatible with the process, solving the long-standing adhesive leakage problem in the industry.

[0051] In the description of this invention, it should be understood that the terms "upper," "lower," "left," and "right," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or a specific orientational structure and operation. Therefore, they should not be construed as limitations on the invention. Furthermore, "first" and "second" are only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "multiple" means two or more.

[0052] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0053] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A T-joint structure for an all-aluminum badminton racket, comprising a die-cast aluminum alloy T-joint body, wherein the T-joint body includes two sets of horizontally arranged insert sleeves for connecting to the frame tube, and one set of vertically arranged insert sleeves for connecting to the shaft, all three sets of insert sleeves having hollow insert cavities for inserting the aluminum racket frame tube and aluminum shaft and filling them with epoxy resin for bonding and fixing; characterized in that: All three sets of insert sleeves have a segmented stepped gap structure, a two-stage annular glue storage and venting groove, and a flow guiding channel on their inner walls. All three sets of sleeve ports have an integrally formed sealing and glue-blocking protrusion ring. A vacuum hole is formed at the end of each of the three sets of sleeves away from the port. The segmented stepped gap structure is divided into a port sealing section, a middle bonding section, and a bottom limiting section from the outside to the inside. The insertion gap of the port sealing section is 0.1 mm, the insertion gap of the middle bonding section is 0.25 to 0.3 mm, and the bottom limiting section includes a limiting step for limiting the insertion depth of the aluminum tube. The vacuum hole is located near the limiting step.

2. The all-aluminum badminton racket adhesive T-junction structure according to claim 1, characterized in that: The two-stage annular glue storage and venting channel includes a primary glue storage channel and a secondary venting glue storage channel. The primary glue storage channel is located at the junction of the port sealing section and the middle bonding section, and is used to collect excess glue. The secondary venting glue storage channel is located in the middle bonding section of the sleeve.

3. The all-aluminum badminton racket adhesive T-junction structure according to claim 2, characterized in that: The flow channel is located on the inner wall of the middle bonding section, extending axially along the insertion sleeve and communicating with the secondary exhaust storage tank. The flow channel is separated from the primary storage tank.

4. The all-aluminum badminton racket adhesive T-joint structure according to claim 2, characterized in that: The inner wall of the middle bonding section is also formed with a spiral anti-slip and flow-guiding pattern, which is separated from the primary glue storage tank.

5. The all-aluminum badminton racket adhesive T-junction structure according to claim 1, characterized in that: The sleeve base wall thickness is 2.5mm, and the remaining effective wall thickness after grooving is ≥1.8mm; the thickness of the port sealing ring is 3.0mm; the wall thickness of the central intersection area of ​​the tee body is 3.5~4.0mm, and the corner adopts R-arc transition.

6. The all-aluminum badminton racket adhesive T-junction structure according to claim 1, characterized in that: An annular gas collecting groove is formed on the end face of the limiting step near the middle bonding section. The outer diameter of the annular gas collecting groove is smaller than the outer diameter of the aluminum tube. One end of the vacuum hole is connected to the annular gas collecting groove.

7. A bonding process for an all-aluminum badminton racket tee, employing the all-aluminum badminton racket adhesive tee structure as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Pretreatment of bonding surfaces: The aluminum frame tube, aluminum middle rod and the inner wall of the tee insertion cavity are roughened by CNC sandblasting, cleaned by plasma to remove impurities, and then sprayed with silane coupling agent to dry and activate the bonding surfaces. S2. Adhesive pretreatment: Thixotropic two-component room temperature epoxy resin is used. After mixing, vacuum degassing is performed to eliminate air bubbles inside the adhesive. S3. Posture adjustment: The workpiece is tilted at a 30° to 35° angle, and all three sets of plug sleeves are at a 30° to 35° angle to the horizontal plane. S4. Negative pressure vacuum exhaust: All air in the cavity can be drawn out in an orderly manner through the top ventilation gap, inclined tube, secondary exhaust storage tank and micro-guide channel to the bottom negative pressure area, completely eliminating micro air bubbles and air-stuck cavities. S5. Vacuum quantitative glue injection: Under continuous vacuum in S4, the glue is injected synchronously and quantitatively from three sets of casing ports through a triaxial synchronous glue injection device. The glue injection volume is precisely controlled to be 70%-80% of the total volume of the casing cavity. Combined with the high thixotropic properties of epoxy resin, the glue adheres stably to the middle and front bonding area of ​​the lower half of the casing wall. A continuous and open ventilation gap is maintained at the top of the casing wall, which is open to the atmosphere throughout the process to avoid the cavity being sealed and trapped. S6. Servo Precision Insertion and Positioning: The aluminum tube is inserted into place using a uniform low-speed servo propulsion method. The bottom step of the insertion sleeve is used for limiting the position. Excess glue is stored in a two-stage annular glue storage and venting groove. The end glue-blocking protrusion ring is used to achieve a seal and prevent leakage. S7. Ultrasonic-assisted dense filling: After the insertion is completed, low-frequency ultrasonic vibration is performed to promote the epoxy resin to penetrate into the micro gaps of the texture and eliminate the micro gaps in the adhesive layer. S8. Segmented micro-vibration curing: Multi-segment stepped temperature control combined with full-process micro-vibration mode is used to complete the pre-curing, main curing and post-curing treatment of epoxy resin, to compensate for curing shrinkage and eliminate internal stress of the adhesive layer.

8. The bonding process for an all-aluminum badminton racket tee as described in claim 7, characterized in that, It also includes the following steps S9. Non-destructive testing and sorting: Ultrasonic scanning is used to inspect the adhesive layer of the T-joint to screen out defective products with insufficient adhesive, air bubbles, or delamination, while good products flow into subsequent processes.

9. The bonding process for an all-aluminum badminton racket tee as described in claim 7, characterized in that: The S8 step temperature control parameters include 40℃ pre-curing for 30 minutes, 65℃ main curing for 60 minutes, and 80℃ post-curing for 20 minutes, with low-frequency micro-vibration maintained throughout the curing process.

10. The bonding process for an all-aluminum badminton racket tee as described in claim 7, characterized in that: The thixotropic two-component room-temperature epoxy resin consists of component A and component B. Component A includes 75 parts of E51 epoxy resin, 12 parts of butyl glycidyl ether, 9 parts of hydrophobic fumed silica, 1.5 parts of silicone defoamer, and 2.5 parts of wetting and dispersing agent. Component B includes 22 parts of 650 polyamide curing agent, 3 parts of DMP-30 accelerator, 2 parts of hydrophobic fumed silica, and 1 part of leveling and defoaming agent.

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