Carbon fiber spring, preparation method and shoe

Abstract

The invention discloses a carbon fiber spring, a preparation method and a shoe, and the method comprises the following steps: winding a carbon fiber prepreg on a prepared threaded five-axis cylindrical pin, putting the five-axis cylindrical pin into a mold, then putting the mold into an oven for baking, and repeating the winding and baking of the carbon fiber prepreg for many times to obtain the carbon fiber spring. The preparation method comprises the following steps: completing the multi-layer structure design of the carbon fiber spring, then carrying out cold press molding and hot press molding, and finally carrying out trimming, sand blasting and cleaning treatment to obtain the prepared carbon fiber spring. The mold is convenient to take, the demolding difficulty and the defective rate are reduced, smooth continuous production is guaranteed, the obtained product has high resilience force, meanwhile, the inherent light characteristic of a carbon fiber material is kept, and the method can be applied to a shoe resilience material.

Description

TECHNICAL FIELD

[0001] The present application relates to a spring, in particular a carbon fiber spring, a preparation method and a shoe. BACKGROUND

[0002] Running is a widely participated sport around the world, and its core biomechanical process involves repeated impact of the foot with the ground, energy storage and release. As the most important sports equipment, the core function of running shoes is to provide cushioning, stability and energy feedback to improve sports performance and reduce the risk of injury.

[0003] In the field of running shoe technology, the existing technology mainly relies on passive cushioning materials such as foaming materials and air cushions. These materials absorb the impact energy when the foot lands by deforming themselves, and their main role is "cushioning" rather than "boosting".

[0004] To further improve the efficiency of energy feedback, the industry has begun to explore the introduction of elastic energy storage elements in the sole, especially in the heel part. For example, some solutions propose to set up metal springs, plastic elastic arms or wave-shaped elastic sheets in the sole. These designs aim to store energy when the foot lands and release energy during the extension phase to provide additional propulsion.

[0005] Although the existing technology provides a variety of cushioning and energy feedback solutions, they still have many inherent defects, especially in achieving efficient, sensitive and lasting heel energy feedback:

[0006] (1) Defects of passive cushioning system based on foaming materials:

[0007] Low energy feedback rate: The deformation recovery speed of foaming materials is slow, and there is obvious energy dissipation (manifested as large hysteresis loss). Most of the impact energy is dissipated as heat energy, rather than converted into effective elastic potential energy to be fed back to the wearer, resulting in insufficient propulsion.

[0008] Material fatigue and performance degradation: Foaming materials will undergo irreversible plastic deformation after long-term repeated compression, causing the midsole to be "compacted", and the cushioning and rebound performance to decrease significantly, affecting the service life and performance consistency of the shoe.

[0009] (2) Defects of traditional elastic element (such as metal spring, plastic elastic sheet) solutions:

[0010] Conflict between weight and sensitivity: Metal springs can provide strong rebound force, but their density is large, which will significantly increase the weight of the shoe, not meeting the core demand of lightweight running shoes. At the same time, the activation of metal springs requires a certain initial load, and the response is not "sensitive" enough, making it difficult to achieve efficient energy storage-release cycle in the rapid touch-down process of running.

[0011] Fatigue fracture risk: Plastic or amorphous metal spring is prone to crack and eventually break due to material fatigue after experiencing high frequency of repeated bending for more than one million times, which is not reliable.

[0012] Mechanical orientation: Most of the existing elastic elements are simple in design, and their deformation and rebound direction is mainly concentrated in the vertical direction, which is difficult to adapt and optimize for the complex inversion biomechanics process of the heel when landing on the ground, and cannot improve the dynamic stability of the foot while providing vertical rebound.

[0013] (3) Limitations based on the pre-carbon plate technology: Limitations of the action stage and the population: the pre-carbon plate mainly optimizes the forefoot push-off stage, which is suitable for elite runners who land on the forefoot or full foot.

[0014] The effect is significant. However, for the vast majority of runners, who land on the rear foot, the boost effect of the carbon plate in the toe part is difficult to be effectively perceived and utilized, and the technical dividend cannot benefit a wider range of users.

[0015] Insufficient dynamic intervention of the heel: The carbon plate structure placed in parallel in the midsole cannot effectively intervene in the impact and subsequent foot inversion process at the moment of heel landing.

[0016] In addition, in the existing technology, carbon fiber products with continuous spiral curved surfaces and large winding angles are often difficult to demold from the integral mold. SUMMARY

[0017] To solve the above technical problems, the present application provides a carbon fiber spring, a preparation method and a shoe.

[0018] To solve the above technical problems, the present application adopts the following technical solutions:

[0019] A preparation method of a carbon fiber spring, the method comprising the following steps:

[0020] Preparation, carbon fiber material is soaked in resin to form carbon fiber prepreg, and the carbon fiber prepreg is cut according to the set length;

[0021] Prepare the mold, the mold is provided with five-axis cylindrical pins, and the five-axis cylindrical pins are in a threaded shape;

[0022] At least two carbon fiber prepregs are wound in front and back order along the bottom to top direction of the five-axis cylindrical pins, the second carbon fiber prepreg is wound on the periphery of the first carbon fiber prepreg and overlaps each other, and the both ends of the five-axis cylindrical pins are reserved with a predetermined length of carbon fiber prepreg;

[0023] After each winding of the carbon fiber prepreg, softening and extrusion are carried out once, the oven temperature is 60-70 DEG C, and baking is 1-2 min; or baking is carried out once between at least two windings, or preheating is carried out at 60-80 DEG C after at least two windings are completed;

[0024] The five-axis cylindrical pin is pressed, and the upper die and the lower die are closed;

[0025] Cold pressing forming, the mold is pressed at room temperature, and the excess material is trimmed;

[0026] Hot pressing forming, the mold is pressed at 130-160 DEG C;

[0027] The mold is opened, the five-axis cylindrical pin is taken out, the formed carbon fiber spring is taken off from the five-axis cylindrical pin, and trimming, sand blasting and cleaning treatment are carried out, so that the preparation of the carbon fiber spring is completed.

[0028] When cold pressing, 20-30 kg pressure is adopted, and pressure is maintained for 2-4 minutes.

[0029] When hot pressing, 100-150 kg pressure is adopted, and pressure is maintained for 20-30 minutes.

[0030] The mold comprises an upper die and a lower die, the lower die is fixed with a bearing plate, and the left sliding block and the right sliding block are movably arranged, the five-axis cylindrical pin is arranged on the bearing plate, and the left sliding block and the right sliding block extrude the five-axis cylindrical pin from both sides of the five-axis cylindrical pin.

[0031] The pin needle is movably arranged in the five-axis cylindrical pin.

[0032] The lower pressing plate is arranged in the upper die, the extrusion groove is arranged on the lower pressing plate, and the extrusion groove corresponds to the five-axis cylindrical pin.

[0033] The carbon fiber prepreg is composed of two 0 DEG carbon fiber materials superimposed, and the thickness parameter of the carbon fiber material is FAW100g-FAW200g.

[0034] The five-axis cylindrical pin comprises a plurality of independent and hollow rings, each ring is cut off along the axis direction, the bottom of the mandrel is provided with a bottom ring, the top is provided with a top ring, and a plurality of rings are located between the bottom ring and the top ring, and the plurality of rings form a spiral structure.

[0035] A shoe, wherein a carbon fiber spring is installed on the sole.

[0036] The present application has the following beneficial technical effects:

[0037] 1. Through the thread-like five-axis cylindrical pin, the problem that the carbon fiber product with continuous spiral curved surface and large winding angle cannot be demolded from the integral mold is solved, so that the large-scale and stable production of such high-performance carbon fiber spring becomes possible.

[0038] 2. The carbon fiber spring prepared has high interlayer bonding strength and structural toughness, and does not delaminate and break under pressure test, can withstand one-fold length stretching without plastic deformation under tension test, has high durability and reliability.

[0039] 3. Multiple winding forms a multi-layer structure, improves the anti-delamination ability and overall strength of the product.

[0040] 4. Each carbon fiber spring produced has highly consistent geometric dimensions and mechanical properties, such as stable stiffness coefficient, high product yield, and meets the strict requirements of industrial applications for standardization.

[0041] 5. The inner and outer surfaces of the finished spring are smooth and free of burrs, avoiding stress concentration points, and the sandblasted surface provides excellent adhesion for subsequent bonding with the sole material.

[0042] 6. The unification of light weight and high performance is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a three-dimensional structure diagram of the mold of the present application;

[0044] Figure 2 is an exploded structure diagram of the mold of the present application;

[0045] Figure 3 is a structure diagram of the five-axis cylindrical pin in the present application. DETAILED DESCRIPTION

[0046] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0047] In the description of the present application, it needs to be understood that, if there are terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features referred to. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0048] In the description of the present application, it needs to be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection. It can be mechanical connection, or electrical connection. It can be directly connected, or indirectly connected through intermediate medium, or it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0049] As shown in Figure 1 and 2 A method for preparing a carbon fiber spring, comprising the following steps:

[0050] Preparation, soaking carbon fiber material in resin to form carbon fiber prepreg, cutting the carbon fiber prepreg according to the set length. Two 0 degree carbon fiber prepregs can be used to form a stack; or 90 degrees; or one 0 degree and the other 90 degrees; or plus or minus 45 degrees, to adjust the stiffness and toughness of the spring in different directions. The thickness parameter of the carbon fiber material is FAW100g-FAW200g.

[0051] Prepare a mold containing a five-axis cylindrical pin 3, which is threaded. The mold includes an upper mold 1 and a lower mold 2. A support plate 4 is fixed on the lower mold 2. The support plate 4 has an arc-shaped groove for assembling the five-axis cylindrical pin 3. A left sliding block 5 and a right sliding block 6 are movably mounted on the lower mold 2. The five-axis cylindrical pin 3 is mounted on the support plate 4. The left sliding block 5 and the right sliding block 6 press the five-axis cylindrical pin 3 from both sides. The five-axis cylindrical pin 3 is internally fitted with a pin 7, which moves through either the left sliding block 5 or the right sliding block 6. A guide rail is provided on the lower mold 2, and the left and right sliding blocks 5 and 6 are correspondingly and movably mounted on the guide rail. The upper mold 1 contains a lower pressure plate 8, which has extrusion grooves that correspond one-to-one with the five-axis cylindrical pins. After mold closing, the lower pressure plate aligns with the support plate to extrude the five-axis cylindrical pins vertically, while the left and right sliding blocks extrude from both sides of the five-axis cylindrical pins. Multiple five-axis cylindrical pins can be simultaneously mounted on the support plate, allowing for the one-time molding of multiple carbon fiber springs.

[0052] like Figure 3 As shown, the five-axis cylindrical pin 3 includes several independent, hollow rings. Each ring is cut along the axial direction. The mandrel has a bottom ring and a top ring at its bottom and top, respectively. Several rings are located between the bottom and top rings, forming a spiral structure. Carbon fiber prepreg is wound around the rings sequentially, and the pin passes through the bottom ring, the rings, and the top ring to secure it. Using this five-axis cylindrical pin structure reduces the difficulty of removing the finished carbon fiber spring from the mold.

[0053] Three strips of carbon fiber prepreg material, each 50cm long, 6mm wide, and 0.2mm thick, were cut using a cutting machine. A total of three such prepreg strips were prepared. The specific operation is as follows:

[0054] First winding: Insert the pin into the five-axis cylindrical pin. The first carbon fiber prepreg strip is wound around the five-axis cylindrical pin of the mold, starting from the bottom, leaving a 5cm length at the end before winding. Wrap upwards along the surface of the five-axis cylindrical pin, continuing forward after reaching the top, allowing the carbon fiber prepreg strip to form a circle on the mold surface. Then cut along the edge. After the first winding is complete, use a jig or clamp to compress the five-axis cylindrical pin portion of the mold, including the newly wound prepreg strip, and then mount it on the mold's support plate. Place the mold in an oven at 60℃-70℃ for 1 minute. Baking softens the material, making it easier to form a flat strip during extrusion. After extruding into a flat strip, open the mold and remove the five-axis cylindrical pin wrapped with carbon fiber prepreg.

[0055] Second winding: winding the second carbon fiber prepreg strip around the periphery of the first strip, the second winding overlaps the first winding, forming higher structural strength and not breaking under pressure. The second winding is the same as the first winding, leaving a length at both ends to form a complete base on both sides. After winding, trim the ends with scissors along the edge, press again with a jig or clamp, then put it into the mold again, bake in the oven for 1 min and take it out.

[0056] Third winding: winding the third carbon fiber prepreg strip around the periphery of the second strip, while the third winding overlaps the second winding, the winding method is the same as the second winding, leaving a length at both ends to form a complete base on both sides. After winding, trim the ends with scissors along the edge, press again with a jig or clamp, then put it in the B plate, bake in the oven for 1 min and take it out.

[0057] After winding all five-axis cylindrical pins with carbon fiber prepreg, push the left and right sliding blocks to press the pin and material, then lower the upper mold to complete the mold closing and the mold entering process.

[0058] Cold pressing, using 20-30 kg pressure, holding for 2-4 minutes, pressing the mold at room temperature to achieve preforming and trimming excess material.

[0059] Hot pressing, pressing the mold at 130-160°C, using 100-150 kg pressure, holding for 20-30 minutes to cure the resin inside. To better cure, use a stepwise temperature rise, for example, first raise the temperature to 100°C at a rate of 80°C / h, then raise the temperature to 140°C at a rate of 120°C / h, and then raise the temperature to 150°C at a rate of 150°C / h, to better control the flow and reaction of the resin and reduce internal stress.

[0060] Unmolding, taking out the five-axis cylindrical pin, removing the formed carbon fiber spring from the five-axis cylindrical pin, and then performing post-processing to complete the preparation of the carbon fiber spring.

[0061] Post-processing specifically includes:

[0062] Deburring: grinding the outer periphery with a grinder at low speed to prevent the product from breaking down, using a small file to start from the middle hole, and grinding the burrs on the inner surface. The sign of grinding completion is that both sides are smooth and not rough.

[0063] Sandblasting: use a manual sandblaster to roughen the surface, both front and back surfaces need to be operated.

[0064] Cleaning: use a high-pressure air gun to clean the product for about 5-10 seconds, and the surface is clean after cleaning to complete the production of the product.

[0065] In addition, in this application, during the winding of carbon fiber prepreg, one baking and pressing is carried out between multiple windings; or preheating is carried out at a temperature of 60-80℃ after all winding is completed. Different methods have different effects:

[0066] 1. After each winding, baking is carried out to soften the resin in the prepreg by heating, so that it is more easily deformed under pressure and conforms to the mold, thereby being preformed into an accurate flat strip shape, laying the foundation for subsequent overall hot pressing, avoiding material wrinkles, breakage or uneven resin distribution caused by direct cold pressing.

[0067] 2. Only one baking is carried out during winding or preheating is carried out after all winding is completed, which can save process, but will affect the preforming between layers.

[0068] For the material of the five-axis cylindrical pin, stainless steel material can be selected. If aluminum material is used, surface spraying of Teflon can be considered to reduce the difficulty of demolding. If the material is steel, the surface needs to be mirror polished, otherwise it is difficult to take out the mold.

[0069] A "dissolvable or meltable mandrel material" can also be used, such as a low-melting-point metal alloy, a water-soluble polymer material, or a high-density gypsum to make the five-axis cylindrical pin. After the product is cured, the mandrel is melted / dissolved by heating or water bath to take it out, thereby achieving non-destructive demolding. This scheme is particularly suitable for molds with more complex internal structures that cannot be disassembled mechanically.

[0070] For the soaking liquid of carbon fiber, different systems of prepreg such as epoxy resin, bismaleimide resin, or thermoplastic resin (such as PEEK, PA) can be used to adapt to different curing temperatures and final performance requirements.

[0071] Molding process: In addition to the molding of this application, "winding-vacuum bag hot pressing tank" or "winding-pultrusion" composite material molding process can also be used, as long as it can realize the directional winding and curing of fibers.

[0072] Test

[0073] The prepared carbon fiber spring is subjected to pressure test, tensile test, and stiffness coefficient test.

[0074] Pressure test

[0075] The carbon fiber spring is fixed on the test equipment, and the lower assembly is used to press the carbon fiber spring. The pressing strength is 93N, which can reach the full compression length without breaking or delamination.

[0076] Tensile test

[0077] The original length of the carbon fiber spring is 3.5 cm, and the maximum stretching length can reach 34 mm, which is one time of the original length, and the stretching force reaches 4.6 kgf. After unloading, the carbon fiber spring can restore the original length, proving that one time of the original length is within the plastic deformation range.

[0078] Stubborn coefficient test

[0079] When the spring is fully compressed to the bottom, the pressure is 93 N, the compression amount is 7 mm, the original length is 35 mm, and the length after compression is 28 mm. According to Hooke's law:

[0080] F = kx

[0081] k = F / x

[0082] k = F / x

[0083] k = F / x

[0084] K = 9.1 N / 0.007 m = 1300 N / m

[0085] The stubborn coefficient of the spring is 1300 N / m.

[0086] The carbon fiber spring prepared in the application is applied to shoes, which can be installed in the heel part of the shoes, from passive buffering to active energy management.

[0087] Specific action: initial contact with the ground (buffering period): the spring is compressed, not simply absorbing the impact, but efficiently converting the vertical downward impact energy into its own elastic potential energy storage. According to the test data (stubborn coefficient k = 1300 N / m), this buffering process is linear and controllable, avoiding sharp impact force peaks, thereby significantly reducing the impact load from the heel to the knee and hip joints. Mid-support period (transition and extension period): when the foot transitions from eversion to inversion and prepares to lift off the ground, the stored elastic potential energy is quickly released. This released energy produces a slight upward and forward rebound force, assisting the heel to lift off the ground and smoothly transitioning to the forefoot extension stage. It provides runners with a more efficient and protective heel landing experience

[0088] Mechanical mechanism:

[0089] Through its high rebound characteristics, it undertakes part of the eccentric work that would otherwise be done by the calf muscles, Achilles tendon and plantar fascia. This means that the load on the human body's own muscle-tendon system is reduced. During the extension stage, the energy released by the spring assists the muscles in concentric contraction, providing additional propulsion. This "energy storage and release" mechanism simulates and enhances the natural spring effect of the Achilles tendon, making each step more energy-efficient.

[0090] Controllable stiffness: The stiffness of the spring 1300 N / m provides a stable foundation. For runners with excessive pronation, this stable heel structure can provide better lateral support during the initial ground contact, resist excessive arch collapse, and guide the foot into the mid-stance phase with a more neutral, stable posture. Fast energy release: The fast springback response of the spring helps the foot quickly correct from a pronated state, reducing the time the foot spends in a non-neutral position and thus reducing the risk of overuse injuries such as knee pain and shin splints caused by abnormal force lines. Enhance the stability of the heel when landing, help control abnormal foot movement and reduce the risk of injury.

[0091] In addition, for runners who are heavier or seek more stability, springs with higher k values can be manufactured; for elite runners who seek light and fast springback, the k value and deformation curve can be adjusted to provide more explosive feedback. This ability to customize the mechanical response, which traditional homogeneous foam materials cannot achieve, allows the product to precisely match different human mechanics needs from rehabilitation training to competitive sports.

[0092] It should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some of the technical features, but any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of manufacturing a carbon fiber spring, characterized by, The method comprises the following steps: Preparation, carbon fiber material is soaked in resin to form carbon fiber prepreg, and the carbon fiber prepreg is cut into a set length; Preparation of the mold, the mold is provided with a five-axis cylindrical pin, and the five-axis cylindrical pin is in a threaded shape; At least two carbon fiber prepregs are wound along the bottom to top direction of the five-axis cylindrical pin in a front-to-back order, and the carbon fiber prepreg of the previous time is wound on the periphery of the carbon fiber prepreg of the previous time and overlaps with each other, and the two ends of the five-axis cylindrical pin are reserved with a preset length of carbon fiber prepreg; After each winding of the carbon fiber prepreg, softening and extrusion are performed once, the oven temperature is 60-70 DEG C, and the baking time is 1-2 min; or between at least two windings, baking is performed once, or after multiple windings, preheating is performed at a temperature of 60-80 DEG C; The mold is opened, and the five-axis cylindrical pin is taken out; The five-axis cylindrical pin is pressed tightly, and the upper die and the lower die are closed; Cold pressing forming, the mold is pressed at room temperature, and the excess material is trimmed; Hot pressing forming, the mold is pressed at 130-160 DEG C; The mold is opened, the five-axis cylindrical pin is taken out, the formed carbon fiber spring is taken off from the five-axis cylindrical pin, and trimming, sand blasting and cleaning treatment are performed to complete the preparation of the carbon fiber spring.

2. The method of claim 1, wherein the carbon fiber spring is prepared by the steps of: In the cold pressing forming, a pressure of 20-30 kg is used, and the pressure is maintained for 2-4 minutes.

3. The method for preparing a carbon fiber spring according to claim 1, characterized in that, In the hot pressing forming, a pressure of 100-150 kg is used, the pressure is maintained for 20-30 minutes, and a step temperature is used, at least two heating rates from low to high are used.

4. The method of claim 1, wherein the carbon fiber spring is prepared by the steps of: The mold comprises an upper die and a lower die, the lower die is fixed with a bearing plate, and the left and right sliding blocks are movably arranged, the five-axis cylindrical pin is arranged on the bearing plate, and the left and right sliding blocks extrude the five-axis cylindrical pin from both sides of the five-axis cylindrical pin. ​ 5. The method for preparing a carbon fiber spring according to claim 4, characterized in that, The pin needle is movably arranged in the five-axis cylindrical pin.

6. The method for preparing a carbon fiber spring according to claim 1, characterized in that, The lower plate is arranged in the upper die, the extrusion groove is arranged on the lower plate, and the extrusion groove corresponds to the five-axis cylindrical pin.

7. The method for preparing a carbon fiber spring according to claim 1, characterized in that, The carbon fiber prepreg is composed of at least two carbon fiber materials with the same angle or different angles, and the thickness of the carbon fiber material is FAW100g-FAW200g.

8. The method for preparing a carbon fiber spring according to claim 1, characterized in that, The five-axis cylindrical pin comprises a plurality of independent and hollow rings, each ring is cut off along the axial direction, the bottom and the top of the mandrel are respectively provided with a bottom ring and a top ring, and the plurality of rings are arranged between the bottom ring and the top ring, and the plurality of rings form a spiral structure.

9. A carbon fiber spring, characterized by, Prepared by the method of any one of claims 1-8.

10. A shoe characterized by The carbon fiber spring of claim 9 is mounted on the sole.

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