Leather vamp processing technology and tooling

Abstract

The present application relates to a kind of leather vamp processing technology and tooling, process includes the following steps: S1 skin treatment, skin is pretreated, and cut into multiple pieces according to vamp design drawing;S2 multiple pieces are positioned respectively in the corresponding position in cavity, the shape of cavity and the layout of piece are all corresponding with design drawing, glue channel is set in cavity along the edge of piece;S3 closed cavity, polyurethane is injected into cavity, polyurethane shunt fills glue channel;S4 setting, keep the closure of cavity, until the polyurethane in cavity is cured, remove the integrated vamp formed by piece bonding.This process uses low-temperature polyurethane as adhesive, and several pieces of leather are spliced into integrated complete vamp, and the joint is flat and beautiful, without layering and protruding ridge, and the process can be adapted to continuous processing production in assembly line, greatly reduce the labor intensity of technical workers, can improve processing efficiency, reduce labor cost.

Description

Technical Field

[0001] This application relates to the field of shoe upper processing, specifically to an improvement in shoe upper splicing processing technology, and more specifically to a leather shoe upper processing technology. Background Technology

[0002] Genuine leather shoes are favored by the public because they are comfortable, breathable, durable, stylish, and have a high-end feel; they even tend to fit better over time. However, the cost of genuine leather shoes remains high, and the styles are relatively limited, mainly because the properties of genuine leather restrict the processing techniques.

[0003] In existing technologies, genuine leather shoe uppers are joined together using a stitching technique. This requires thinning, punching holes, and stitching the edges of the cut leather pieces. The stitching process is then manual, with each piece individually processed by hand in a sewing machine. The finished uppers are then fitted into a shoe last, followed by low-temperature hot pressing for shaping and then cold pressing for final setting. This method inevitably results in overlapping leather layers at the stitching points, and uneven, protruding edges that can feel uncomfortable underfoot, reducing shoe comfort. Furthermore, the reliance on manual labor hinders production efficiency and increases costs. Additionally, the limited processing methods result in a lack of variety and design appeal in genuine leather shoes.

[0004] The following publicly available patent documents were found through a search: A seamless bonding method for leather products, public notice number CN 100443594C, is characterized by: using a peeling knife to bevel the edges of the flesh side of the two pieces of leather to be bonded together, with a width of 10mm, until the thickness is zero; sanding with a pneumatic grinding wheel to remove the delaminated surface of the pressed leather; bonding using high-frequency seamless bonding technology, followed by heating in a vacuum vulcanizing machine for 6 minutes at a temperature controlled at 60 degrees Celsius; reinforcement by applying a layer of hot-melt reinforcing material to the flesh side of the joint between the two leather pieces. This method overcomes the problem of protrusions at the joint affecting the aesthetics of the pressed leather bonding method, and is suitable for bonding various leathers and products (excluding embossed or raised leathers).

[0005] Analysis revealed that while this technology overcomes the limitations of stitching and avoids jagged edges, it requires a high-frequency machine and specialized molds, as well as a vulcanizing machine for heating. Compared to sewing, this process is more expensive and cannot be matched with rapid production lines, making it difficult to promote in the footwear industry and market. Summary of the Invention

[0006] The purpose of this application is to overcome the problems existing in the prior art and provide a leather shoe upper processing technology.

[0007] The purpose of this application is achieved as follows: A leather shoe upper processing technology includes the following steps: S1 leather surface treatment involves pre-treating the leather surface and cutting it into multiple leather pieces according to the shoe upper design drawing; S2 positions multiple leather pieces in corresponding locations within the cavity. The shape of the cavity and the layout of the leather pieces correspond to the design drawing. An injection channel is provided along the edge of the leather pieces within the cavity. S3 Closed cavity, polyurethane is injected into the cavity, and the polyurethane is diverted to fill the injection channel; S4 Keep the cavity closed until the polyurethane inside the cavity has cured completely, then remove the one-piece shoe upper formed by bonding the leather pieces.

[0008] Furthermore, the pretreatment of the leather surface in S1 includes a napping process on the edges of the leather piece.

[0009] Moreover, in S2, the specific method for positioning the leather pieces is as follows: multiple leather pieces are pre-fixed on a lining fabric that matches the shape of the cavity, and then the lining fabric and leather pieces are placed together inside the cavity.

[0010] Furthermore, the lining fabric leaves a gap at the seam between the leather pieces, and the lining fabric at the gap maintains a rough textured surface.

[0011] Furthermore, the width of the glue injection channel between the glue injection channel pieces is between 1 and 2 mm.

[0012] Moreover, the polyurethane used is specifically low-temperature polyurethane, with a curing temperature of 45-55℃ and a curing time of 5 minutes.

[0013] A genuine leather shoe upper processing fixture, used to implement any of the above-described leather shoe upper processing techniques, includes a mold, an injection device, a pressure holding assembly, and a heating device. The mold has a cavity, which includes a leather positioning groove corresponding to the design drawing and a glue injection channel; the mold has a glue injection hole that can connect the injection device and the cavity. The injection unit contains a sealed cavity that can hold liquid polyurethane. The injection unit is connected to the injection hole of the mold and can inject polyurethane into the cavity. The injection unit can maintain the pressure inside the sealed cavity. The pressure-holding component is located outside the mold to keep the mold closed and prevent it from being pushed up during the polyurethane reaction, thus changing the shape of the cavity. The heating device is located outside the mold and can continuously heat the mold to a temperature of 45-55℃.

[0014] Furthermore, it also includes a venting structure, specifically, a venting hole is opened on the mold at the end of the injection channel away from the injection hole, and the venting hole is connected to the outside of the mold.

[0015] The advantages and positive effects of this application are: 1. This process uses low-temperature polyurethane as an adhesive to splice several pieces of genuine leather into a complete shoe upper. The seams are flat and beautiful, without overlapping or protrusions, so as not to hurt the feet and improve the comfort of the leather surface.

[0016] 3. This process can be adapted to fully automated production, eliminating the need for manual sewing operations, which can significantly improve processing efficiency and reduce costs.

[0017] 3. This process can improve the utilization rate of small pieces of genuine leather, further save raw materials, and reduce the cost of high-grade leather.

[0018] 4. This process connects genuine leather shoe uppers at a low processing temperature. The curing temperature of low-temperature polyurethane is within the safe processing temperature range for genuine leather shoe uppers. The one-piece molded shoe upper made using this process relies on the chemical bonding and physical penetration of PU during its own reaction to bond the leather pieces together. The adhesion is reliable, and tests have shown that the strength of the bonded seams can reach the same strength as the leather surface, making it sturdy, durable, and not easy to break. Attached Figure Description

[0019] Figure 1 This is a flowchart of the processing technology in this embodiment; Figure 2 This is a schematic diagram of the mold in the closed state of Example 1 of the machining tooling.

[0020] Figure 3 This is a schematic diagram of the mold opening state of embodiment 1 of the machining tooling.

[0021] Figure 4 This is a schematic diagram of the in-mold injection channel in Example 2. Detailed Implementation

[0022] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present application.

[0023] See appendix Figure 1 As shown, a leather shoe upper processing technology includes the following steps: S1 leather surface treatment involves pre-treating the leather surface and cutting it into multiple leather pieces according to the shoe upper design drawing; Pre-treatment, in addition to the routine treatment before leather shoemaking, also includes napping the edges of the leather pieces. Nailing is to increase the effective connection between the leather pieces and polyurethane at the seams. In this process, the connection between the leather pieces is made by direct injection molding, which ensures reliable adhesion. S2 positions multiple leather pieces in their respective locations within the cavity, with the shape of the cavity and the layout of the leather pieces corresponding to the design drawing; The specific method is as follows: Pre-fix multiple leather pieces onto a complete lining fabric, then place the lining fabric and leather pieces together in the mold cavity, leaving gaps between the seams of the lining fabric corresponding to the leather pieces, with the fabric texture of the lining fabric exposed at the gaps. S3 Closed cavity, polyurethane is injected into the cavity. There are glue injection channels along the edge of the skin in the cavity. All glue injection channels are connected to glue injection holes. After the polyurethane passes through the glue injection holes, it flows into the glue injection channels. The width of the glue injection channel between the glue injection channels is 1 to 2 mm. In this embodiment, the width of the glue injection channel used in the experiment is 1.5 mm, which achieves good flow effect.

[0024] S4 Pressure Holding and Shaping: After the polyurethane in the mold cavity has cured completely, the one-piece shoe upper formed by bonding leather pieces is removed. Detailed analysis reveals that the connection methods in this process include: Chemical bonding: During the curing process, polyurethane forms covalent bonds with the polar groups (-OH / -NH) on the surface of the shoe upper.

[0025] Physical penetration: Liquid polyurethane penetrates into the leather fibers formed by napping and the fabric texture of the lining itself, "anchoring" the material after curing.

[0026] This process utilizes the chemical bonding and physical penetration of polyurethane during its own reaction to organically connect the leather pieces together, eliminating weak areas in the adhesive layer. The interface of the seam is a fusion of materials, rather than simply sandwiching the adhesive layer between the leather pieces.

[0027] The polyurethane used in the process is specifically low-temperature polyurethane, with a curing temperature of 45-55℃. The temperature does not damage the genuine leather and fully preserves the inherent advantages of the leather.

[0028] During the curing process, maintain a pressure of 0.3–0.5 MPa and a holding time of 1–3 minutes to ensure precise mold fit during the foaming and degassing process, ensuring proper alignment and avoiding misalignment and cavitation.

[0029] In this process, the core raw materials are cured at low temperature, and the peel strength at the joint is stable at 2.0 to 4.0 N / mm, eliminating the risk of the joints coming apart.

[0030] According to HG / T 3084-2023 "Injection Molded Shoes" (PU Sole), the upper-to-sole bonding strength is ≥ 1.4 N / mm to be considered qualified. The seam bonding strength made using this process can reach 2.0~4.0 N / mm, far exceeding the national standard, and the shoe upper has high reliability.

[0031] The polyurethane used in this application's process is a commonly used, industrially mature raw material, and polyurethane is also an environmentally friendly material. (It can be purchased directly), for example: (1) Adipic acid-diethylene glycol polyester (polyester polyol for shoe soles) Cured at 50℃, suitable for all shoe soles.

[0032] (2) PCL (polycaprolactone polyol): excellent low-temperature flexibility, the first choice for cold-resistant shoe soles.

[0033] Special copolyester for shoes: resistant to bending and cracking of shoe soles.

[0034] (3) Modified MDI prepolymer (for shoe PU): mild reaction, suitable for low temperature molding at 50℃.

[0035] Environmentally friendly low-temperature catalyst: organic bismuth and organic zinc, free of heavy metals, and meets national standards for footwear materials.

[0036] Foaming agent / smoothing agent: When used with a microporous insole, the foam cells remain stable and do not collapse at 50°C.

[0037] (4) Soft segment polyols: such as adipic acid-based polyester polyols (PBA, PDA), polycaprolactone PCL Advantages: wear-resistant, hydrolysis-resistant, resistant to repeated bending, good grip, and the sole does not turn white.

[0038] (5) Isocyanate: Modified liquefied MDI / low-activity TDI prepolymer.

[0039] Low-temperature catalytic system: organic bismuth + weak amine composite catalyst curing conditions: in-mold curing at 45-55℃, demolding at 30-60min, and full cross-linking at 50℃.

[0040] (6) Polyether-type cold-resistant PU (for use in extremely cold regions and snow sports shoes) Suitable for: snow boots, winter sports shoes in northern regions, and cold-resistant casual shoes.

[0041] (7) Polyols: PTMEG / High-elasticity polyether polyols.

[0042] Features: Does not harden or crack at -40℃, and does not crack at low temperatures.

[0043] Curing: Also paired with a bismuth-based low-temperature catalyst, it cures stably at 50℃ without bursting or becoming brittle.

[0044] A tooling for processing genuine leather shoe uppers, used to carry out leather shoe upper processing technology, includes a mold, an injection device, a pressure holding component, and a heating device. The mold has a cavity, which includes a leather piece positioning groove corresponding to the design drawing and a glue injection channel. The positioning groove accurately positions and places the leather piece to prevent the leather surface from moving and deforming. The mold has a glue injection hole, and the glue injection channel connects to the glue injection hole, which can also connect the injection device to the cavity. The injection device contains a sealed cavity that can hold polyurethane. The injection device can inject polyurethane into the cavity and maintain the pressure inside the sealed cavity. The pressure-holding component is used to keep the mold closed, maintain pressure inside the cavity, and prevent the polyurethane foam from expanding and lifting the mold, thus changing the shape of the cavity. The heating device continuously heats the mold to a temperature of 45-55℃. For example: thermal activation oven / baking line: temperature: 45~55℃, activation time: 3~5 minutes, judgment criteria: the adhesive surface is not sticky to the touch, has a slight tackiness, and exhibits weak stringing. Low-temperature curing environment / drying room: constant temperature of 50℃, complete cross-linking in 2~4 hours, achieving the highest peel strength; this process does not require pressure.

[0045] It also includes a venting structure, specifically, a venting hole is opened on the mold at the end of the injection channel away from the injection hole, and the venting hole is connected to the outside of the mold.

[0046] The positioning structure ensures accurate matching between the upper and lower molds, thereby ensuring accurate alignment of the glue injection channels of the upper and lower molds with the leather piece to be processed inside the cavity.

[0047] Example 1 A tooling for processing genuine leather shoe uppers, see attached document. Figure 2 , Figure 3 As shown, it includes an upper mold 1 and a lower mold 5. The upper mold 1 and the lower mold 5 are assembled by an opening and closing snap-fit. After the upper mold 1 and the lower mold 5 are closed, the injection channel of the upper mold 1 and the positioning groove of the lower mold 5 are interconnected and enclosed to form a closed injection cavity. By injecting low-temperature polyurethane molten liquid into the injection cavity, the integral bonding and composite between adjacent skin pieces 9 is achieved by utilizing the curing and molding characteristics of polyurethane.

[0048] To ensure the positional fit accuracy between the upper mold 1 and the lower mold 5, a limiting protrusion 4 is provided at each of the four corners of the edge of the upper mold 1, and a corresponding limiting groove is provided at each of the four corners of the edge of the lower mold 5. The limiting groove and the limiting protrusion 4 correspond one-to-one and are sized to fit together and limit each other.

[0049] In this embodiment, the upper mold 1 and the lower mold 5 are provided with a hinge pin 6 on one side. The upper mold 1 can be flipped open or closed to facilitate the insertion of the leather piece 9 or the removal of the finished product. The hinged installation method makes it easy to align the upper mold 1 and the lower mold 5. The lower mold 5 can also adopt a separate structure without connection.

[0050] A locking device 3 is provided between the outer edges of the upper mold 1 and the lower mold 5. In this embodiment, the locking device 3 includes a locking hook 34, a locking ring 33, a positioning block 32, and a handle 31. The locking hook 34 is fixedly connected to the middle of one side of the lower mold 5; the positioning block 32 is fixedly connected to the middle of one side of the upper mold 1. One end of the handle 31 is hinged to the positioning block 32, and a locking ring 33 is hinged to the middle of the handle 31 through a pin. The other end of the handle 31 is a free end. Lifting the free end of the handle 31 can drive the locking ring 33 to move, thereby hooking it onto the lock. Then, the free end of the handle 31 is brought close to the upper mold 1, so that the locking ring 33 is fixedly locked to the locking hook 34. In the snap-fit ​​assembly state, the upper mold 1 and the lower mold 5 are kept in close contact to prevent the upper mold 1 from being pushed up during the internal polyurethane foaming process.

[0051] Depending on the specific connection structure of the upper mold 1 and the lower mold 5, multiple locking devices 3 or other locking structures such as an external pressure machine can be selected.

[0052] The specific structures of the upper mold 1 and the lower mold 5 are as follows: The upper end face of the lower mold 5 is provided with a recessed positioning groove in the middle. The leather piece 9 to be bonded can be correspondingly positioned and placed inside the positioning groove. A gap for glue injection is left at the joint 8 position between the leather pieces 9 to be bonded. The upper mold 1 has a glue injection channel, the position of which corresponds to the position of the seam 8 between the leather pieces 9. The depth of the glue injection channel is 0.5-1mm, and the width of the glue injection channel is 1 to 2mm.

[0053] An injection through hole 2 is provided in the middle of the upper mold 1, which is connected to the injection channel 7. The injection through hole 2 is a flared conical hole. In this embodiment, the cone angle of the conical hole is 6°, which facilitates the connection of an external injection connector to inject polyurethane into the interior.

[0054] Because polyurethane reacts during processing to produce CO2 / air, venting holes (not shown in the diagram) are required on the mold to avoid problems such as bubbles, material shortages, and poor adhesion caused by insufficient venting. Multiple venting grooves, 0.5-1mm deep, are connected to the end of the arc-shaped flow channel away from the injection hole, leading to the outside of the mold. Multiple venting holes are spaced at intervals in the confluence flow channels with larger glue surfaces within the injection channel, with a spacing of 50-80mm, also leading to the outside of the mold.

[0055] Example 2 A tooling for processing genuine leather shoe uppers, see attached document. Figure 4 As shown, the difference lies in the design of the glue injection channel, which is different from that in Example 1.

[0056] The shape of the injection channel is designed to match the gap position of the leather patch, and is not limited to the channel shape shown in the attached figure.

[0057] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of other embodiments of this disclosure upon considering the specification and the disclosure of practical truth. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described in this disclosure. The specification and embodiments are considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

Claims

1. A leather shoe upper processing technology, characterized in that, Includes the following steps: S1 leather surface treatment involves pre-treating the leather surface and cutting it into multiple leather pieces according to the shoe upper design drawing; S2 positions multiple leather pieces in corresponding locations within the cavity. The shape of the cavity and the layout of the leather pieces correspond to the design drawing. An injection channel is provided along the edge of the leather pieces within the cavity. S3 Closed cavity, polyurethane is injected into the cavity, and the polyurethane is diverted to fill the injection channel; S4 Keep the cavity closed until the polyurethane inside the cavity has cured completely, then remove the one-piece shoe upper formed by bonding the leather pieces.

2. The leather shoe upper processing technology according to claim 1, characterized in that, The pretreatment of the leather surface in S1 includes fuzzing the edges of the leather piece.

3. The leather shoe upper processing technology according to claim 1, characterized in that, In S2, the specific method for positioning the leather pieces is as follows: multiple leather pieces are pre-fixed on a lining fabric that matches the shape of the cavity, and then the lining fabric and leather pieces are placed together in the cavity.

4. The leather shoe upper processing technology according to claim 3, characterized in that, The lining fabric has a gap at the seam between the leather pieces, and the lining fabric at the gap has a rough texture.

5. The leather shoe upper processing technology according to claim 1, characterized in that, The width of the glue injection channel between the leather pieces is 1 to 2 mm.

6. The leather shoe upper processing technology according to claim 1, characterized in that, The polyurethane used is specifically low-temperature polyurethane, with a curing temperature of 45-55℃ and a curing time of 5 minutes.

7. A tooling for processing genuine leather shoe uppers, characterized in that, The tool for implementing the leather shoe upper processing technology according to any one of claims 1 to 6 includes a mold, an injection device, a pressure holding assembly, and a heating device. The mold has a cavity, which includes a leather positioning groove corresponding to the design drawing and a glue injection channel; the mold has a glue injection hole that can connect the injection device and the cavity. The injection unit contains a sealed cavity that can hold liquid polyurethane. The injection unit is connected to the injection hole of the mold and can inject polyurethane into the cavity. The injection unit can maintain the pressure inside the sealed cavity. The pressure-holding component is located outside the mold to keep the mold closed and prevent it from being pushed up during the polyurethane reaction, thus changing the shape of the cavity. The heating device is located outside the mold and can continuously heat the mold to a temperature of 45-55℃.

8. The tooling for processing genuine leather shoe uppers according to claim 7, characterized in that, It also includes a venting structure, specifically, a venting hole is opened on the mold at the end of the injection channel away from the injection hole, and the venting hole is connected to the outside of the mold.

Images