Preparation method of thermoplastic composite torsional spring and application of thermoplastic composite torsional spring in exoskeleton power assisting device

Abstract

The invention discloses a preparation method of a thermoplastic composite torsional spring and application of the thermoplastic composite torsional spring in an exoskeleton power assisting device.The preparation method comprises the following steps that firstly, polyamide resin is selected as a base material, nano-silicon dioxide powder is selected, and the base material and the nano-silicon dioxide powder are fully mixed through a high-speed mixer according to the mass ratio of 9: 1; forming a uniform prefabricated body; 2, aramid fibers are selected as a reinforcing material, and the preform and the reinforcing material in the step 1 are dried to ensure that the moisture content is lower than 0.5%; mass production of composite material torsion springs is achieved, and the full-automatic production process from material mixing to final products is achieved through efficient screw extrusion and metalloid torsion spring forming cutter forming processes. According to the process, the production efficiency is improved, the consistency and the stability of the product quality are ensured, and the production cost is remarkably reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermoplastic composite torsion springs, and specifically relates to a high-rigidity, lightweight thermoplastic composite torsion spring prepared by an extrusion molding process, and the application of the torsion spring in a lower limb exoskeleton power-assisting device. Background Art

[0002] With the increasing trend of population aging and the development of medical technology, lower limb exoskeleton assist devices are increasingly used in rehabilitation medicine, assisted walking, and enhancing human motor ability. These devices can help the elderly, the disabled, and those who need rehabilitation training to better carry out daily activities and improve their quality of life. However, although traditional metal springs have good mechanical properties, they have the following problems:

[0003] Heavy weight: Traditional metal torsion springs (such as steel springs) have a high density, which results in a heavy weight for the entire exoskeleton device. This not only increases the burden on the wearer, but may also affect their use experience and comfort.

[0004] Easy to corrode: Metal torsion springs are prone to rust in humid or corrosive environments, affecting their service life and reliability. Especially in outdoor or humid environments, the durability of metal springs is poor.

[0005] Poor fatigue resistance: When metal torsion springs are subjected to multiple alternating loads, they will deform and cannot fully return to their original position.

[0006] Composite materials are known for their light weight, high modulus and excellent specific strength, and their excellent corrosion resistance far exceeds that of traditional metals. Even in harsh environments such as high temperature, high humidity or salt spray, these materials can maintain their performance, thereby enhancing product reliability and reducing maintenance costs. In recent years, researchers are looking for alternative materials that are lighter, stronger, more corrosion-resistant and more cost-effective. Among them, thermoplastic composites have been widely used in many industries due to their excellent mechanical properties, lightweight effects and recyclability. Despite this, how to effectively apply these thermoplastic composites to the manufacture of torsion springs and ensure their efficient operation in lower limb exoskeleton assistive devices remains a key issue that needs to be addressed. Summary of the invention

[0007] During the research process, the inventors found that how to apply thermoplastic composite materials to the manufacture of torsion springs faces the following challenges:

[0008] Interface bonding: The interface bonding between the thermoplastic matrix and the reinforcing fibers is a key factor affecting the performance of composite materials. Poor interface bonding will lead to a decrease in the mechanical properties of the material, especially under high stress and fatigue conditions.

[0009] Molding process: Extrusion molding is a common method for molding thermoplastic composites, but it requires precise control of parameters such as temperature, pressure and speed to ensure that the materials are evenly mixed and formed into the desired shape.

[0010] The present invention aims to establish a complete production process for thermoplastic composite torsion springs by utilizing the lightweight and high-strength characteristics of composite materials and using recyclable thermoplastic materials for processing and production. At the same time, based on the production process of traditional metal torsion springs, a complete production process suitable for thermoplastic composite torsion springs is established. In addition, the thermoplastic composite torsion springs produced by the present invention can be used in human exoskeleton knee joint assist devices, which can not only effectively reduce the weight of the assist device, but also significantly improve its fatigue life, and have a wide range of application scenarios.

[0011] In order to achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: a method for preparing a thermoplastic composite torsion spring, characterized in that: the preparation method steps are as follows:

[0012] Step 1: Select polyamide resin as the matrix material, select nano-silicon dioxide powder, and fully mix the matrix material and the nano-silicon dioxide powder in a mass ratio of 9:1 through a high-speed mixer to form a uniform preform;

[0013] Step 2: Select aramid fiber as the reinforcing material, and dry the preform and the reinforcing material in step 1 to ensure that the moisture content is less than 0.5%;

[0014] Step 3: melt-mixing and extruding the reinforcing material and the preform in step 2 through an extruder to form a uniform elongated cylinder;

[0015] Step 4: The slender cylinder in step 3 is molded by a torsion spring forming device to form a thermoplastic composite torsion spring.

[0016] Furthermore, in step 1, the polyamide resin is preferably nylon 66; and the average particle size of the nano-silicon dioxide powder is 20-50 nanometers.

[0017] Furthermore, in step 2, the aramid fiber is preferably Kevlar fiber.

[0018] Further, in step 3, the extruder includes a heating device located at the front end of the screw, and the temperature provided by the heating device is 270-290 degrees;

[0019] The extruder includes a cooling device located at the front end of the heating device, and the temperature provided by the cooling device is 10-20 degrees;

[0020] The extrusion speed of the extruder is 10-30 mm / s.

[0021] Furthermore, in step three, the screw of the extruder is hollow along its axis, one end of the aramid fiber enters the extruder along the hollow portion of the screw, and sequentially passes through a heating device and a cooling device and is pre-installed at the discharge port of the extruder through an end cover.

[0022] Furthermore, in step four, the torsion spring forming device includes a driving part, a metal-like torsion spring forming knife fixing part, and a metal-like torsion spring forming knife moving part; the metal-like torsion spring forming knife fixing part and the metal-like torsion spring forming knife moving part are both provided with mutually matching forming grooves, and the forming grooves are adapted to the shape of the thermoplastic composite torsion spring.

[0023] The thermoplastic composite torsion spring is applied to an exoskeleton power-assisting device.

[0024] Furthermore, the exoskeleton assisting device includes a thigh fixing mechanism, a calf fixing mechanism, a thigh connecting frame, a calf connecting frame, and an adjustable preload mechanism arranged between the thigh connecting frame and the calf connecting frame; the thermoplastic composite torsion spring is arranged in the adjustable preload mechanism.

[0025] Furthermore, an adjustment cavity is provided between the thigh connecting frame and the calf connecting frame along the longitudinal direction thereof, and the adjustable preload mechanism comprises:

[0026] A positioning pin, wherein the positioning pin is installed on the thigh connecting frame, one end of the positioning pin extends into the adjustment cavity of the calf connecting frame and can move along the adjustment cavity;

[0027] An adjustment block, the adjustment block is mounted on the thigh connecting frame, the adjustment block is mounted in an adjustment cavity of the thigh connecting frame, and can move along the adjustment cavity;

[0028] An adjusting bolt, the adjusting bolt being mounted on the adjusting block and being movable in an adjusting cavity of the thigh connecting frame;

[0029] A fastening nut, wherein the fastening bolt is screwed onto the adjusting bolt;

[0030] A thermoplastic composite torsion spring is sleeved on the positioning pin, with one end abutting against the calf connecting frame and the other end abutting against the adjusting block.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) Achieve mass production of composite torsion springs. By adopting efficient screw extrusion and metal-like torsion spring forming knife forming processes, a fully automated production process from material mixing to final product is achieved. This process not only improves production efficiency and ensures the consistency and stability of product quality, but also significantly reduces production costs. Compared with traditional metal torsion spring manufacturing, the production process of thermoplastic composite torsion springs simplifies the steps, reduces the frequency of mold replacement, and has high material utilization and less waste. In addition, the production line can quickly adjust production to meet the needs of different customers, especially for large-scale production and customized orders. It has strong adaptability. Each batch of products undergoes rigorous mechanical property tests and environmental adaptability tests to ensure that all products leaving the factory meet high quality standards.

[0033] (2) The innovative extrusion molding technology combines a high-speed mixer and a screw mixer to ensure that the thermoplastic resin and nano-silica are fully and evenly mixed to form a uniform composite material, avoiding local defects and enhancing overall performance. The special metal-like torsion spring forming knife design, combined with a preheated metal mandrel as an intermediate support, enables the molten material to be evenly extruded and formed into the desired torsion spring shape. During the rapid cooling and shaping process, the temperature is controlled by a water cooling tank device to ensure the stability of the product size and avoid stress concentration and deformation.

[0034] (3) The application of thermoplastic composite torsion springs in exoskeleton power-assist devices has significantly improved the performance and user experience of the device. Compared with traditional metal torsion springs, this new material is lighter, which reduces the overall burden of the exoskeleton, improves the comfort and flexibility of the wearer, and is particularly suitable for long-term wear or high-intensity use scenarios. Composite materials have higher elasticity and fatigue resistance, which prolongs the service life and maintains stable performance even in complex working environments. In addition, its excellent wear resistance and corrosion resistance enable the device to be used for a long time in harsh environments without being easily damaged. Through the adjustable preload device, users can easily adjust the initial torque and working range according to their needs, better adapt to different movement modes and load changes, thereby enhancing the flexibility and personalized experience of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the structure of the extruder in this application document;

[0036] Figure 2 It is a schematic diagram of the extrusion molding structure in this application document (having a thermoplastic composite torsion spring);

[0037] Figure 3 It is a schematic diagram of the extrusion molding structure in this application document;

[0038] Figure 4 It is a schematic diagram of the structure of the exoskeleton power assist device in this application document;

[0039] Figure 5 It is a structural schematic diagram of the adjustable preload mechanism in this application document.

[0040] In the figure: feed inlet 1, extruder 2, Kevlar fiber 3, heating device 4, cooling device 5, end cover 6, metal-like torsion spring forming knife moving part 7, metal-like torsion spring forming knife fixing part 8, annular thrust device 9, positioning body 10, thermoplastic composite torsion spring 11, thigh connecting frame 12, thigh fixing mechanism 13, adjustment block 14, fastening nut 15, calf connecting frame 16, calf fixing mechanism 17. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] like Figure 1-Figure 5 As shown, the technical solution adopted by the present invention is as follows: This embodiment provides a method for preparing a thermoplastic composite torsion spring, and the steps of the preparation method are as follows:

[0043] Step 1: Select polyamide resin as the matrix material, select nano-silicon dioxide powder, and fully mix the matrix material and the nano-silicon dioxide powder in a mass ratio of 9:1 through a high-speed mixer to form a uniform preform;

[0044] Step 2: Select aramid fiber as the reinforcing material, and dry the preform and the reinforcing material in step 1 to ensure that the moisture content is less than 0.5%;

[0045] Step 3: melt-mix the reinforcing material and the preform in step 2 and extrude them through an extruder 2 to form a uniform elongated cylinder;

[0046] Step 4: The slender cylinder in step 3 is molded by a torsion spring molding device to form a thermoplastic composite torsion spring 11.

[0047] In step 1, it is necessary to select a suitable thermoplastic matrix material. In the selection of thermoplastic matrix materials, the performance of the matrix, the molding conditions and the price of the material should be taken into consideration, and the material with the best cost performance should be selected. Common thermoplastic materials include polyethylene, polyetheretherketone, polyimide and polyamide. Polyethylene is a lightweight, chemical-resistant, impact-resistant and insulating thermoplastic plastic, and is relatively expensive; polyetheretherketone is a high-performance thermoplastic polymer with excellent mechanical properties, heat resistance and chemical resistance. It exhibits good fatigue performance under cyclic loads and is suitable for parts that bear repeated loads for a long time, but because of its very expensive price, it is usually used in high-strength and high-durability occasions; polyphenylene sulfide has excellent heat resistance and chemical resistance, and its fatigue performance is also very good, especially in high temperature environments, but it usually has a large viscosity, and the surface is prone to irregularity during extrusion molding; polyamide has high tensile strength and impact toughness, especially relative to its density. Under repeated stress, polyamide exhibits good fatigue life and is relatively cheap. Therefore, polyamide is selected as the matrix material. Nylon 66 (PA66) is a material in the thermoplastic resin polyamide, which has high strength and high modulus, can provide excellent mechanical properties, and is suitable for applications with high loads. It also exhibits excellent wear resistance and fatigue resistance, and can maintain stable performance even in long-term use, and is particularly suitable for high wear and high stress environments. PA66 has good chemical resistance to most chemicals (such as oils, solvents, acids and alkalis), and has excellent processing properties, including good melt fluidity and suitability for a variety of manufacturing processes such as injection molding and extrusion molding, which facilitates the production of parts with complex shapes. In addition, it has a high melting point (about 260°C) and good thermal stability, which is suitable for applications in high temperature environments. At the same time, its lower density helps to achieve lightweight design and reduce overall weight.

[0048] In step 1, polyamide (PA) resin is used as the matrix material. This is because it not only has good fluidity and strong heat resistance, but also can maintain stable physical properties under high temperature environment. The selected resin particles are uniform and free of impurities to ensure good mixing effect and guarantee the quality of the final product. For the selection of nano-silica, high-purity powder with an average particle size in the range of 20-50 nanometers is selected. This powder can effectively enhance the mechanical properties, wear resistance and fatigue resistance of the composite material.

[0049] In step two, it is necessary to select a suitable material as a reinforcement material. Aramid fiber (such as Kevlar) is selected as a reinforcement material. Kevlar fiber 3 is known for its extremely high tensile strength (about 3.5GPa) and high elastic modulus (100-150GPa), providing excellent stiffness and mechanical properties. It has excellent wear resistance and fatigue resistance, can maintain performance for a long time in a high wear environment, and performs well under repeated loading conditions, and is suitable for applications that are subjected to high stress for a long time. Kevlar fiber 3 has good chemical resistance to most acids and alkalis and is suitable for a variety of chemical environments. Kevlar fiber 3 has good chemical compatibility with nylon 66 because they are both members of the polyamide family. This allows Kevlar fiber 3 to combine well with the nylon 66 matrix, so that it is evenly dispersed in the composite material.

[0050] In step 2, for the selection of nano-silicon dioxide, high-purity powder with an average particle size of 20-50 nanometers was selected, which can effectively enhance the mechanical properties, wear resistance and fatigue resistance of the composite material. In addition, in order to improve the dispersibility of nano-silicon dioxide in the resin matrix and the bonding strength with the interface, a silane coupling agent was used to perform a special surface treatment.

[0051] Pretreatment: Dry the base material and aramid fiber to ensure that the moisture content is less than 0.5%.

[0052] In step three, the matrix material and aramid fiber need to be extruded and melt-formed. The dried matrix material and nano-silicon dioxide are evenly mixed in a predetermined ratio (mass ratio of 9:1). The mixing process ensures that the nano-silicon dioxide can be evenly distributed in the matrix to enhance the performance of the material. To ensure uniform mixing, high-speed stirring or ball milling techniques are used to fully disperse the nano-silicon dioxide into the matrix material to avoid agglomeration. After mixing, it is sent to the extruder 2.

[0053] In the extruder 2 in step 3, a single screw extruder 2 is selected. The single screw extruder 2 comprises a heating device 4 located at the front end of the screw, and a cooling device 5 located at the front end of the heating device 4. The screw of the single screw extruder 2 is hollow along its axis.

[0054] The extruder 2 is equipped with a screw rod, which generates shear force by rotating to help further mix and homogenize the mixture. In order to ensure that the material reaches the best molten state during the extrusion process, a heating device 4 is provided at the outer end of the screw rod of the extruder 2, and the temperature can be adjusted according to the material characteristics to ensure that the mixed material is transformed from a solid state to a uniform molten state during the rotation of the screw rod. This process ensures that the molten mixture has sufficient fluidity to facilitate extrusion molding through the die.

[0055] The molten mixture is then uniformly extruded through a carefully designed die, the design of which ensures that the mixture forms an elongated cylinder with a predetermined diameter. The size and shape of the die and its coordination with the single screw extruder 2 are crucial to the quality of the final product. In order to provide additional support during the extrusion process, the center of the screw is connected to the end of the Kevlar fiber 3 through an open hole design. The Kevlar fiber 3 is connected to the center of the single screw die through a specific device to ensure that the fiber remains on the central axis of the cylindrical resin during the extrusion process, which plays a role in enhancing the mechanical properties of the material and providing intermediate support.

[0056] After the molten mixture is extruded through the screw die, the material quickly enters the cooling device 5. The cooling medium (such as water or air) in the cooling device 5 can quickly cool and shape the material to ensure that it maintains a cylindrical shape and solidifies the molecular structure of the material. After cooling, the shape of the elongated cylinder is stabilized to ensure that subsequent molding operations are not affected.

[0057] In this embodiment, a single screw extruder 2 is used for extrusion molding, and the temperature of the heating device 4 is set at about 280°C to ensure that the material can be fully melted and maintain good fluidity. Before feeding, the mixed material is thoroughly dried to remove moisture and prevent bubbles and holes from being generated during the extrusion process. The dried material is fed into the extruder feed port 1 through an automatic feeding system. The rotation of the screw not only ensures the constant feed rate, but also promotes the uniform mixing of the two materials. The rotation speed and thrust of the screw are optimized according to the material properties to ensure uniform mixing and uniform distribution.

[0058] During the extrusion process, the single-screw mixer is responsible for stirring and pushing the preform in step one forward, and then entering the heating zone for melting. The molten preform continues to be pushed forward by the screw mechanism. At the central axis position of the screw mixer, the disc-packed Kevlar fiber filament 3 is introduced into the center of the mixer through the opening of the central axis. The end of the Kevlar fiber filament is tied and connected to the center of the end cap 6. The end cap 6 provides a pre-tightening force to keep the fiber filament tight on the central axis. At the same time, the material at the cooling device 5 is pushed out after reaching a certain pressure. When the molten resin mixture enters the cooling device 5, it will infiltrate the Kevlar fiber filament to form a central axis reinforcement of the resin, thereby significantly improving the fatigue resistance and durability of the torsion spring, and playing a key role in improving the mechanical properties of the torsion spring.

[0059] During the extrusion process, the extrusion speed and pressure are strictly controlled to ensure that the molten material is extruded evenly and forms a consistent cross-sectional shape. The extrusion speed is 10-30mm / s. The temperature of the water cooling tank is controlled at 10-20℃, cold water is injected through the lower water inlet, and the water circulation system is used to keep the water temperature in the tank stable.

[0060] In step four, the slender cylinder in step three needs to be shaped into a torsion spring state by a torsion spring forming device. The torsion spring forming device includes a driving part, a metal-like torsion spring forming knife fixing part 8, and a metal-like torsion spring forming knife moving part 7; the metal-like torsion spring forming knife fixing part 8 and the metal-like torsion spring forming knife moving part 7 are both provided with mutually matching forming grooves, and the forming grooves are adapted to the shape of the thermoplastic composite torsion spring 11. The torsion spring forming device needs to have precise dimensional control and a smooth surface to reduce friction and improve the forming accuracy. After passing through the cooling device 5, the extruded slender cylindrical material will be shaped into a torsion spring by the torsion spring forming device. The specific steps are as follows:

[0061] First, the extruded elongated cylinder is pulled out a certain distance, and then the cylinder forming groove of the metal-like torsion spring forming knife moving part 7 is controlled to move to the lower end of the cylinder.

[0062] Furthermore, the metal-like torsion spring forming knife moving part 7 is pressed upward from the bottom under the action of the driving part, and the horizontal elongated cylindrical material is pressed into a ring structure.

[0063] Furthermore, while the metal-like torsion spring forming knife moving part 7 presses the slender cylinder upward, the control system moves forward and backward at a certain speed, so that the slender cylindrical material is smoothly fixed in the forming groove of the metal-like torsion spring forming knife moving part 7 and the metal-like torsion spring forming knife fixed part 8. This process requires precise control. When the forming groove of the metal-like torsion spring forming knife moving part 7 and the forming groove of the metal-like torsion spring forming knife fixed part 8 are closed, the movement is stopped. At this time, the slender cylinder will move along the forming groove formed by the metal-like torsion spring forming knife moving part 7 and the metal-like torsion spring forming knife fixed part 8, thereby gradually forming it into a ring-shaped body.

[0064] Further, the single screw extruder 2 continues to extrude the slender cylinder, and the outer cylindrical part of the positioning body 10 winds the annular body molded by the torsion spring forming device into a thermoplastic composite torsion spring 11, and fixes it. When the required number of turns is reached, the slender cylindrical material at the end of the extruder 2 is cut with a cutter. The metal-like torsion spring forming knife moving part 7 is moved away, and the cylindrical surface of the positioning body 10 carries the formed thermoplastic composite torsion spring 11.

[0065] When the first positioning body 10 completes the winding of a thermoplastic composite torsion spring 11, the control system will move it away for air cooling. At the same time, the second positioning body 10 begins to repeat the process of the first positioning body 10, continuing to wind the annular body formed by the torsion spring forming device to form a new thermoplastic composite torsion spring 11. This process is repeated, and a total of six positioning bodies 10 are involved to ensure the continuous operation of the production line.

[0066] When the sixth positioning body 10 is working, the thermoplastic composite torsion spring 11 on the first positioning body 10 has been basically cooled and formed. At this time, the annular thrust device 9 on the positioning body 10 is used to push out the thermoplastic composite torsion spring 11 that has been wound and formed. This cyclic production method realizes the automated production line manufacturing of thermoplastic composite torsion springs 11, and provides an effective solution for mechanisms that require a large number of such springs. In addition, this process is not only suitable for the production of composite torsion springs, but can also be used to produce similar types of components, greatly improving the production efficiency of composite materials. Compared with the traditional production method of composite torsion springs using mold molding, this method is more convenient and conducive to continuous production.

[0067] In another embodiment, an exoskeleton power-assist device is designed for middle-aged and elderly people with difficulty walking. The device is bound to the user's calves and thighs through a lightweight engineering plastic structure, and a composite torsion spring is used at the knee joint to assist walking. In the past, exoskeleton power-assist devices were often made of metal carbon steel. The shear modulus of carbon steel is about 77GPa, while the shear modulus of nylon 66 is about 4GPa, and the shear modulus of Kevlar fiber 3 is about 19GPa. The mechanical properties of the composite material can be improved by adding nano-silicon dioxide. Under the same specifications, the torque of the metal material torsion spring is about three times that of the composite material torsion spring. It can be equal to the composite material by simply expanding the wire diameter of the composite material to 1.5 times the wire diameter of the metal torsion spring. At the same time, the density ratio of the metal torsion spring to the composite material torsion spring is 7:1, so the weight of the torsion spring can be greatly reduced. In terms of price, although the price of carbon steel is slightly lower than that of the composite material, the raw material prices of both are very low, and the production process of carbon steel for torsion springs is also complicated. At the same time, thermoplastic polyamide has the advantage of being recyclable. Therefore, in general, the use of composite material torsion springs is more advantageous than metal springs.

[0068] In another embodiment, the exoskeleton assisting device includes a thigh fixing mechanism 13, a calf fixing mechanism 17, a thigh connecting frame 12, a calf connecting frame 16, and an adjustable preload mechanism arranged between the thigh connecting frame 12 and the calf connecting frame 16; the thermoplastic composite torsion spring 11 is arranged in the adjustable preload mechanism.

[0069] An adjustment cavity is provided between the thigh connecting frame 12 and the calf connecting frame 16 along the longitudinal direction thereof, and the adjustable preload mechanism comprises:

[0070] A positioning pin, the positioning pin is installed on the thigh connecting frame 12, one end of the positioning pin extends into the adjustment cavity of the calf connecting frame 16 and can move along the adjustment cavity;

[0071] An adjustment block 14, the adjustment block 14 is mounted on the thigh connecting frame 12, the adjustment block 14 is installed in an adjustment cavity of the thigh connecting frame 12, and can move along the adjustment cavity;

[0072] An adjusting bolt, which is mounted on the adjusting block 14 and is movable in the adjusting cavity of the thigh connecting frame 12;

[0073] A fastening nut 15, wherein the fastening bolt is screwed onto the adjusting bolt;

[0074] The thermoplastic composite torsion spring 11 is sleeved on the positioning pin, and one end of the thermoplastic composite torsion spring 11 abuts against the calf connecting frame 16 , and the other end abuts against the adjusting block 14 .

[0075] In order to be more suitable for different types of people, the exoskeleton device is equipped with an adjustable preload mechanism. By adjusting the position of the adjustment block 14 in the adjustment cavity of the thigh connecting frame 12, the rotation of the end of the thermoplastic composite torsion spring 11 is controlled to achieve different preloads.

[0076] The thigh fixing mechanism 13 and the calf fixing mechanism 17 are designed according to the average height of adults to ensure that they can meet the needs of most users. The rigid fixing device is placed on the back of the thigh and calf. The purpose is that when the user bends the knee joint of the leg, the force is mainly applied to the back of the thigh and calf. Through the connection of the rigid components, the force transmission effect is faster and more accurate. The front strap is connected to the strap hole on the fixing device, and the user can adjust the comfort of the binding by himself. At the same time, the thigh and calf are equipped with two straps, which makes the user more stable when wearing the device, simplifies the user's wearing and adjustment, and provides the user with a more comfortable experience while meeting the power assistance requirements.

[0077] This device not only uses a lightweight high-performance composite torsion spring for assistance, but also greatly improves the applicability of the group through an adjustable preload device. At the same time, the better force is ergonomic, which brings great comfort to the user group. The calf connecting frame 16 is placed on the inside, and the thigh connecting frame 12 is placed on the outside, which is more in line with the structure of the human leg.

[0078] In the lower limb exoskeleton assist device, qualified torsion springs are carefully installed in key parts, such as the knee and ankle joints, in order to provide the necessary power support. This design aims to reduce the user's physical burden, thereby improving walking efficiency and comfort.

[0079] The principle of the exoskeleton power assist device is that when the user is walking, running or squatting, the knee joint of the exoskeleton begins to move. As the movement progresses, the elastic element (torsion spring) of the exoskeleton begins to deform. For example, when the user bends his knee during walking, the spring is compressed, and the deformation of the elastic element causes its internal stress to increase, thereby storing energy. This energy exists in the form of elastic potential energy, and its magnitude is proportional to the deformation of the elastic element. Energy release is the reverse process of energy storage. When the user completes the preparatory action and starts the reverse movement (such as from bending the knee to straightening the knee), the elastic element begins to return to its original shape. During the recovery process, the elastic element converts the stored elastic potential energy into kinetic energy, which drives the joint movement of the exoskeleton, thereby providing power for the user's movements. During the energy release process, the power assist effect of the exoskeleton is most obvious, which can reduce the muscle strength required by the user to extend the joint.

[0080] In terms of fixing devices, the main frame is made of high-strength engineering plastics (such as polycarbonate), which maintains lightness while having good strength and toughness. Both the thigh and calf straps are made of highly elastic fabric straps (such as nylon or elastic fiber), combined with quick-release buckles to improve the comfort and convenience of wearing. The thigh strap surrounds the middle of the thigh and is equipped with a multi-point fixing system and soft cushioning pads to reduce pressure on the skin, and can be precisely adjusted through a fine-tuning knob. The surface of the strap is equipped with ventilation holes to enhance air circulation and prevent skin discomfort caused by long-term wear. The calf strap also uses a multi-point fixing system, which works in conjunction with the thigh strap to provide all-round support and is equipped with a fine-tuning knob to adapt to different calf sizes.

[0081] In terms of joint protection, a flexible protective layer is designed near the knee joint to allow natural bending while providing additional support and reducing impact during exercise. The hinge device simulates the natural range of motion of the knee joint, allowing bending and extension. Symmetrical hinge mechanisms are set inside and outside to provide additional support and stability. One end of the connecting rod is connected to the thigh or calf fixture, and the other end is connected through a hinge mechanism. A torsion spring is placed at the hinge to provide power assistance. The overall design aims to provide users with a comfortable and reliable lower limb exoskeleton power assistance experience through the synergy of the adjustable preload device and the fixture.

[0082] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a thermoplastic composite torsion spring, characterized in that: The preparation steps are as follows: Step 1: Select polyamide resin as the matrix material, select nano-silicon dioxide powder, and fully mix the matrix material and the nano-silicon dioxide powder in a mass ratio of 9:1 through a high-speed mixer to form a uniform preform; Step 2: Select aramid fiber as the reinforcing material, and dry the preform and the reinforcing material in step 1 to ensure that the moisture content is less than 0.5%; Step 3: melt-mix the reinforcing material and the preform in step 2 and extrude them into a uniform elongated cylinder through an extruder (2); Step 4: The slender cylinder in step 3 is shaped by a torsion spring forming device to form a thermoplastic composite torsion spring (11).

2. The method for preparing a thermoplastic composite torsion spring according to claim 1, characterized in that: In step 1, the polyamide resin is preferably nylon 66; and the average particle size of the nano-silicon dioxide powder is 20-50 nanometers.

3. The method for preparing a thermoplastic composite torsion spring according to claim 1, characterized in that: In step 2, the aramid fiber is preferably Kevlar fiber (3).

4. The method for preparing a thermoplastic composite torsion spring according to claim 1, characterized in that: In step 3, the extruder (2) comprises a heating device (4) located at the front end of the screw, and the temperature provided by the heating device (4) is 270-290 degrees; The extruder (2) comprises a cooling device (5) located at the front end of the heating device (4), and the temperature provided by the cooling device (5) is 10-20 degrees; The extrusion speed of the extruder (2) is 10-30 mm / s.

5. The method for preparing a thermoplastic composite torsion spring according to claim 4, characterized in that: In step three, the screw of the extruder (2) is hollow along its axis, one end of the aramid fiber enters the extruder (2) along the hollow part of the screw, and passes through the heating device (4), the cooling device (5) in sequence, and is pre-installed at the discharge port of the extruder (2) through the end cover (6).

6. The method for preparing a thermoplastic composite torsion spring according to claim 1, characterized in that: In step 4, the torsion spring forming device comprises a driving part, a metal-like torsion spring forming knife fixing part (8), and a metal-like torsion spring forming knife moving part (7); the metal-like torsion spring forming knife fixing part (8) and the metal-like torsion spring forming knife moving part (7) are both provided with mutually matching forming grooves, and the forming grooves are adapted to the shape of the thermoplastic composite torsion spring (11).

7. The thermoplastic composite torsion spring in the method for preparing the thermoplastic composite torsion spring according to any one of claims 1 to 6 is applied to an exoskeleton power-assisting device.

8. The use of the exoskeleton power-assist device according to claim 7, characterized in that: The exoskeleton assisting device comprises a thigh fixing mechanism (13), a calf fixing mechanism (17), a thigh connecting frame (12), a calf connecting frame (16), and an adjustable preload mechanism arranged between the thigh connecting frame (12) and the calf connecting frame (16); the thermoplastic composite torsion spring (11) is arranged in the adjustable preload mechanism.

9. The use of the exoskeleton power-assist device according to claim 8, characterized in that: An adjustment cavity is provided between the thigh connecting frame (12) and the calf connecting frame (16) along the longitudinal direction thereof, and the adjustable preload mechanism comprises: A positioning pin, the positioning pin being mounted on the thigh connecting frame (12), one end of the positioning pin extending into an adjustment cavity of the calf connecting frame (16) and being able to move along the adjustment cavity; An adjustment block (14), the adjustment block (14) being mounted on the thigh connecting frame (12), the adjustment block (14) being mounted in an adjustment cavity of the thigh connecting frame (12) and being movable along the adjustment cavity; An adjusting bolt, the adjusting bolt being mounted on the adjusting block (14) and being movable in an adjusting cavity located in the thigh connecting frame (12); A fastening nut (15), wherein the fastening bolt is screwed onto the adjusting bolt; A thermoplastic composite torsion spring (11) is sleeved on a positioning pin, one end of the thermoplastic composite torsion spring abuts against a calf connecting frame (16), and the other end of the thermoplastic composite torsion spring abuts against an adjustment block (14).

Images