Variable-gauge knitted flexible inflatable wing and preparation method thereof

Abstract

The invention relates to a variable-gauge knitted flexible inflatable wing and a preparation method thereof, and relates to the technical field of aircrafts. The variable-gauge knitted flexible inflatable wing comprises a variable-gauge knitted base body, an airtight film covering layer, a shaping film covering layer and an air nozzle, the upper surface layer and the lower surface layer of the variable-gauge knitted base body are connected through spacing wires, and the spacing wires are knitted through an empty needle to form a telescopic structure; the airtight film covering layer covers the outer surface of the variable-gauge knitted base body to form a closed air cavity; the shaping film coating layer covers the outer surface of the airtight film coating layer and is at least used for restraining deformation of the airtight film coating layer, and the thickness of the shaping film coating layer is larger than that of the airtight film coating layer; the air nozzle is communicated with the air cavity. Through the telescopic spacing wires, the wings are tightly folded after being deflated, and the transportation and storage convenience is improved; during inflation, the spacing wires accurately control the distance between the upper layer and the lower layer, and high-precision control over the aerodynamic configuration is achieved in combination with constraint of the sizing film coating layer.

Description

Technical Field

[0001] The present application relates to the field of aircraft technology, and in particular to a variable-gauge knitted flexible inflatable wing and a preparation method thereof. Background Art

[0002] With the rapid development of aerospace and unmanned systems, small and medium-sized UAVs and deployable aircraft are increasingly being used in environmental monitoring, emergency rescue, geological surveying and mapping, and other fields, placing stringent demands on the lightweight, portability and rapid deployment capabilities of the equipment. Although traditional rigid wings can ensure the accuracy of aerodynamic shape, they have inherent defects such as heavy weight, limited transportation and storage volume, and slow deployment response, making it difficult to adapt to the maneuvering needs in complex scenarios. In this context, flexible inflatable wings, with their closed hollow cavity structure made of high-strength film and fabric, can form a rigid wing surface with load-bearing capacity through continuous internal inflation, showing significant advantages such as light weight, small volume after folding, fast deployment speed, and low manufacturing cost, especially in the field of small and medium-sized aircraft, showing great application potential.

[0003] To achieve high-precision aerodynamic shape control of inflated flexible wings, two typical technical paths have been formed in the industry. The first is to achieve shape control through external constraints. A rigid skeleton such as carbon fiber rods and aluminum alloy frames is added to the outer surface of the flexible wing, or a segmented rigid shell is covered. The mechanical limit of the rigid structure is used to constrain deformation during inflation and ensure that the wing surface meets the design parameters. This technology is more common in the design of simple inflatable wings for early low-speed aircraft. The other is to achieve shape control through internal multi-chamber support. The inner cavity of the wing is divided into dozens of independent sub-cavities along the wingspan direction. Each cavity is filled with nylon inflatable cylinders of a specific diameter. The tangent support of adjacent cylinders is used to form a continuous surface. In some designs, the curvature of the surface is fine-tuned by the pressure difference between the chambers. This has been used in the airfoil control of near-space airships. However, existing technical solutions all have some problems. While the solution of adding an external rigid skeleton can achieve high-precision conformal protection, the additional rigid structure increases the weight of the wing, and the volume after folding will also increase, which weakens the advantage of the inflatable structure being "lightweight and foldable", making it difficult to apply in some weight-sensitive scenarios. The internal multi-chamber support solution requires the design of an equal number of inflation and deflation valves and pipelines to match multiple independent chambers, resulting in increased complexity of the wing system and increased manufacturing costs. In addition, the fixed-diameter inflatable cylinder cannot adapt to the thickness gradient from the wing root to the wingtip. A larger diameter cylinder is required at the wing root to ensure structural strength, while a smaller diameter cylinder is required at the wingtip to achieve a thin design. In addition, the variable spacing range of the inflatable wing in the existing technical solution during the inflation process is generally a maximum of 30mm, which is a relatively small variable spacing range. Summary of the Invention

[0004] The purpose of this application is to provide a variable-gauge knitted flexible inflatable wing and a preparation method thereof to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above objectives, the technical solutions adopted in this application are: In one aspect, the present application provides a variable-gauge knitted flexible inflatable wing, comprising: A variable-gauge knitted base comprises an upper surface layer, a lower surface layer, and spacer yarns connecting the upper and lower surface layers, wherein the spacer yarns are knitted with open needles to form a retractable structure during the knitting process; An airtight coating layer is coated on the outer surface of the variable-gauge knitted base body and is enclosed together with the upper surface layer and the lower surface layer to form a closed air cavity; a shaping film layer covering the outer surface of the airtight film layer and at least used to constrain the deformation of the airtight film layer to maintain the preset aerodynamic curvature of the wing, wherein the shaping film layer is thicker than the airtight film layer; An air nozzle, which penetrates the shaping film layer and the airtight film layer and communicates with the air cavity; The spacer wire is stretched in an inflated state to form a preset spatial curved surface between the upper surface layer and the lower surface layer.

[0006] Furthermore, the range of the variable distance of the continuous gradient between the upper surface layer and the lower surface layer is 0-200 mm.

[0007] Furthermore, the upper surface layer and the lower surface layer are both woven from high-strength yarns, and the linear density of the high-strength yarns is 200-1000D.

[0008] Furthermore, the high-strength yarn includes one or more of aramid, ultra-high molecular weight polyethylene, carbon fiber and high-strength polyester.

[0009] Furthermore, the spacer filaments include one or both of aramid and ultra-high molecular weight polyethylene.

[0010] Furthermore, the diameter of the spacer wire is 0.2-0.6 mm.

[0011] Furthermore, the airtight coating layer includes a TPU film, and the thickness of the airtight coating layer is 0.01-0.1 mm.

[0012] Furthermore, the shaping coating layer includes a TPU film, and the thickness of the shaping coating layer is 0.1-0.5 mm.

[0013] On the other hand, the present application also provides a method for preparing a variable-gauge knitted flexible inflatable wing based on any of the above items, comprising the following steps: S1. Preparation of variable-gauge knitted substrate: A four-needle-bed computerized flat knitting machine is used, so that the front lower needle bed and the rear lower needle bed can knit the upper surface layer and the lower surface layer respectively, and spacer yarns can be inserted synchronously. The front upper needle bed and the rear upper needle bed of the four-needle-bed computerized flat knitting machine perform empty needle knitting, so that the spacer yarn forms a retractable structure; The spacer yarns, the upper surface layer and the lower surface layer are integrally woven to form a variable-gauge knitted base; S2. Preparation of primary airtight skin: Evenly apply a reactive adhesive layer on the upper surface layer and the lower surface layer; After laminating the airtight coating layer on the reactive adhesive layer, the layers are bonded by a hot pressing process, and an inflation area is reserved during the lamination process. The airtight coating layer is sealed by a high-frequency welding process, and the air nozzle is installed in the inflation area; Forming a primary airtight skin by constant pressure curing; S3, Inflatable Shaped Wings: The wings are formed by using a shaping mold, and a shaping film layer is attached to the inner wall of the shaping mold; Placing the primary airtight skin in a shaping mold, injecting a first constant-pressure gas through a gas nozzle, and maintaining the pressure for a first time for pre-lamination, then injecting a second constant-pressure gas, and maintaining the pressure for a second time for precise shaping to form the wing, wherein the pressure of the second constant-pressure gas is greater than the pressure of the first constant-pressure gas; Separate the wing from the mold.

[0014] Furthermore, in S1: the upper surface layer and the lower surface layer are both woven from high-strength yarns, and the linear density of the high-strength yarns is 200-1000D.

[0015] Furthermore, in S1: the high-strength yarn includes one or more of aramid, ultra-high molecular weight polyethylene, carbon fiber and high-strength polyester.

[0016] Furthermore, in S1: the spacer yarn includes one or both of aramid and ultra-high molecular weight polyethylene.

[0017] Furthermore, in S1: the diameter of the spacer wire is 0.2-0.6 mm.

[0018] Furthermore, in S2: the reactive adhesive layer includes one or more of moisture-reactive PUR melt adhesive, polycarbonate TPU adhesive and composite PC adhesive powder.

[0019] Furthermore, in S2: the temperature of the hot pressing process is 50-60°C.

[0020] Furthermore, in S2: the alternating electric field oscillation frequency of the high-frequency welding process is 20 MHz.

[0021] Furthermore, in S2: the constant pressure curing time is 24-48 hours.

[0022] Furthermore, in S3: the pressure of the first constant-pressure gas is 15-40 kPa, the first time is 2-3 minutes, the pressure of the second constant-pressure gas is 60-100 kPa, and the second time is 10-15 minutes.

[0023] Furthermore, in S3: after the wing is separated from the shaping mold, it is subjected to static pressure leak detection for at least 30 minutes.

[0024] The beneficial effects of the technical solution provided by this application include at least: (1) The present application connects a spacer wire with a retractable structure between the upper surface layer and the lower surface, so that the wing can be tightly folded after being deflated, which significantly improves the convenience of transportation and storage. At the same time, the spacer wire can accurately control the distance change between the upper and lower surface layers during the inflation process. Combined with the restraining effect of the shaping coating layer, high-precision control of the aerodynamic shape of the wing can be achieved.

[0025] (2) The variable-gauge knitted base of the present application is made of lightweight knitted material, combined with a thin airtight coating layer and a relatively lightweight shaping coating layer. The overall weight is greatly reduced compared to the traditional flexible inflatable wing with a hard frame.

[0026] It can be seen that how to achieve continuously variable spacing through the integrated design of the internal structure without introducing external rigid constraints, while taking into account the lightweight, foldable characteristics and high-precision conformal capability, is still a key technical issue that needs to be broken through in flexible inflatable wing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings: Figure 1 1 is a schematic diagram of a partial cross-sectional structure of the flexible inflatable wing in one embodiment of the present invention; Figure 2 1 is a front view of a shaping die in one embodiment of the present invention; Figure 3 This is a schematic structural diagram of a shaping die in one embodiment of the present invention; Figure 4 This is a flow chart for preparing the flexible inflatable wing in one embodiment of the present invention; Figure 5 Schematic diagram of different knitting needle numbers of loops on the front upper and rear upper needle beds in one embodiment of the present invention; Figure 6Schematic diagram of different knitting spans of loops knitted with empty needles on the front upper needle bed and the rear upper needle bed in one embodiment of the present invention; Figure 7 It is a schematic diagram of different knitting needle numbers and knitting spans of loops performed on the front upper and rear upper needle beds in an embodiment of the present invention.

[0028] Description of main reference numerals: 100, upper surface layer; 200, lower surface layer; 300, spacer wire; 400, airtight coating layer; 500, shaping coating layer; 600, shaping mold. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0030] Among them, the same parts are represented by the same figure marks. It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings of the present application specification, and the words "bottom" and "top", "inside" and "outside" refer to directions toward or away from specific parts, respectively. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application specification, the meaning of "multiple" is two or more.

[0031] Example 1 See also Figure 1A variable-gauge knitted flexible inflatable wing comprises a variable-gauge knitted base, an airtight coating layer 400, a shaping coating layer 500 and an air nozzle. The variable-gauge knitted base comprises an upper surface layer 100, a lower surface layer 200 and spacer yarns 300 connecting the upper surface layer 100 and the lower surface layer 200. The spacer yarns 300 are knitted with open needles to form a retractable structure during the knitting process. The airtight coating layer 400 is coated on the outer surface of the variable-gauge knitted base and is bonded to the upper surface layer 100 and the lower surface layer 200. 0 together enclose a closed air cavity; the shaping film layer 500 is coated on the outer surface of the airtight film layer 400, and is at least used to constrain the deformation of the airtight film layer 400 to maintain the preset aerodynamic curved surface of the wing. The thickness of the shaping film layer 500 is greater than that of the airtight film layer 400; the air nozzle passes through the shaping film layer 500 and the airtight film layer 400 and is connected to the air cavity; wherein, the spacer wire 300 is stretched in the inflated state to form a preset spatial curved surface between the upper surface layer 100 and the lower surface layer 200.

[0032] In this embodiment, if Figure 1 As shown, the upper surface layer 100 and the lower surface layer 200 are spaced apart, with spacer threads 300 disposed between them. These threads connect the upper surface layer 100 and the lower surface layer 200, providing both connection and support. The spacing of the spacer threads 300 woven between the upper surface layer 100 and the lower surface layer 200 varies depending on the shape of the wing and the desired aerodynamic curvature. This results in different lengths of the spacer threads 300 at different locations after inflation, creating a desired spatial curvature between the upper surface layer 100 and the lower surface layer 200. Specifically, during the knitting process, the spacer threads 300 are knitted using a specific empty needle knitting motion to form tucked loops, thereby forming a retractable structure. This allows the wing to flexibly adjust the spacing between the upper and lower surface layers 200 based on changes in internal air pressure when inflated. The airtight coating layer 400 is tightly wrapped around the outer surface of the variable-gauge knitted base, and together with the upper and lower surface layers 200, forms a closed air cavity, thereby effectively preventing gas leakage, ensuring stable air pressure in the air cavity, and providing continuous rigid support for the wing. The shaping coating layer 500 is arranged on the outer surface of the airtight coating layer 400, and its main function is to constrain the deformation of the airtight coating layer 400 and maintain the preset aerodynamic surface of the wing. The shaping coating layer 500 is selected to have a relatively large thickness, which provides the necessary shape retention ability while ensuring the overall lightness of the wing. In addition, the air nozzle passes through the shaping coating layer 500 and the airtight coating layer 400, and is connected to the air cavity for realizing the inflation and deflation operations of the air cavity. Its structural design takes into account both airtightness and ease of operation, and is usually equipped with a one-way valve to prevent gas backflow after inflation. During the specific working process, when in the folded storage state: when not inflated, the variable-gauge knitted flexible inflatable wing is in a folded state. At this time, the spacer wire 300 of the variable-gauge knitted base is in a relaxed state, and the upper and lower surface layers 200 are tightly fitted. The entire wing occupies a small space and is compact, making it easy to store and transport. When in the inflated and expanded state: gas is filled into the air cavity through the air nozzle. As the air pressure gradually increases, the air cavity expands, generating outward pressure on the variable-gauge knitted matrix. The spacer wire 300 is stretched under the action of pressure, driving the upper and lower surface layers 200 to gradually separate and expand into the shape of a preset spatial curved surface. At the same time, the airtight coating layer 400 ensures that the gas does not leak out and maintains stable air pressure. The shaping coating layer 500 constrains the overall shape from the outside to ensure that the wing is formed according to the preset high-precision aerodynamic shape. When in the deflated storage state: After the flight mission is completed, open the air nozzle to deflate. As the gas in the air cavity is discharged, the air pressure decreases, the spacer wire 300 gradually returns to a relaxed state, the upper and lower surface layers 200 fit together again, and the wing returns to a foldable state, which is convenient for subsequent storage and transportation. In the above structure, a retractable spacer wire 300 is connected between the upper surface layer 100 and the lower surface, allowing the wing to fold tightly after deflation, significantly improving the convenience of transportation and storage. At the same time, the spacer wire 300 can precisely control the distance change between the upper and lower surface layers 200 during inflation. Combined with the constraining effect of the shaping coating layer 500, high-precision control of the wing's aerodynamic shape can be achieved. Compared with internal multi-chamber support solutions, this wing can better adapt to the design requirements of thickness gradient changes with thick root and thin wingtip, ensuring the continuity of the wing surface curvature, allowing the wing to maintain good aerodynamic performance at different flight speeds and attitudes, effectively improving the flight efficiency and stability of the aircraft. In addition, the variable-gauge knitted base is made of lightweight knitted material, combined with the thin airtight coating layer 400 and the relatively lightweight shaping coating layer 500, the overall weight is significantly reduced compared to traditional flexible inflatable wings with a rigid frame. Moreover, this simple structural design greatly reduces the difficulty of wing maintenance, reduces maintenance costs, and improves the economy and reliability of the product.

[0033] Specifically, the range of the continuously gradient variable distance between the upper surface layer 100 and the lower surface layer 200 is 0-200 mm.

[0034] In this embodiment, during the knitting process, the tuck density formed by the empty needle knitting action of the spacer yarn 300 exhibits a precise gradient from the wing root to the wing tip. At the wing root, the spacer yarn 300 has a small tuck pitch and a large number of turns, resulting in a small initial spacing in the uninflated state. After inflation, the spacing can be stretched to a maximum distance of 180-200mm, meeting the thickness design requirements at the wing root. As the tuck pitch gradually increases and the number of turns decreases toward the wing tip, the corresponding maximum stretch distance after inflation decreases, reaching a minimum spacing of 0-30mm at the wing tip. A high-density knitting structure is used at the wing root to enhance load-bearing capacity, while a low-density texture is used at the wing tip to reduce weight. This ensures that the upper and lower surface layers 200 can deform synchronously with the spacer yarn 300 at different spacing states, forming a continuous and smooth spatial curved surface.

[0035] The natural transition from thick wing root to thin wing tip makes the wing's aerodynamic shape more in line with aerodynamic principles. The airflow on the wing surface flows more smoothly, effectively reducing the airflow separation phenomenon and improving the wing's lift characteristics and flight stability.

[0036] In the specific structure of the upper surface layer 100 and the lower surface layer 200, both the upper surface layer 100 and the lower surface layer 200 are woven from high-strength yarns with a linear density of 200-1000 D. The high-strength yarns include one or more of aramid, ultra-high molecular weight polyethylene, carbon fiber, and high-strength polyester.

[0037] In this embodiment, the high-strength yarn possesses excellent tensile strength and tear resistance. The linear density range of 200-1000D allows for flexible selection based on the load requirements of different wing parts. Higher-density yarn is selected for high-stress areas such as the wing root. This provides stable structural support for the wing during inflation, effectively resisting the tension generated by internal air pressure and preventing damage due to excessive force. This ensures the structural integrity of the wing in all inflation states and further enhances its load-bearing capacity. Materials such as aramid and ultra-high molecular weight polyethylene offer excellent weather and chemical resistance. They maintain stable performance in complex weather conditions such as high and low temperatures and humidity, and are less susceptible to aging and degradation. This significantly improves the wing's environmental adaptability, extends its service life, and enables reliable operation in a variety of operational scenarios. Furthermore, materials like carbon fiber and ultra-high molecular weight polyethylene inherently have low densities. Combined with a reasonable linear density, this ensures structural strength while effectively controlling the weight of the upper and lower surface layers 100 and 200. The yarn also possesses a certain degree of flexibility, adapting well to the expansion and contraction of the spacer filaments 300. During wing inflation and folding, it deforms synchronously with the upper and lower surface layers 200, preventing excessive rigidity from restricting the wing's morphological transformations. Alternatively, other high-performance yarns can be used as the high-strength yarn, as long as the linear density and fineness meet the aforementioned requirements. In a specific structure of the spacer wire 300, the spacer wire 300 includes one or both of aramid and ultra-high molecular weight polyethylene. The diameter of the spacer wire 300 is 0.2-0.6 mm.

[0038] Aramid and ultra-high molecular weight polyethylene (UHMWPE) are both high-strength fibers with tensile strengths 3-5 times that of ordinary polyester. They can withstand the tremendous tension during wing inflation, even at a diameter of 0.2-0.6mm. When the wing inflates, the spacer filaments 300 must stretch synchronously to support the upper and lower surface layers 200 in their desired curved form. Their thin diameter provides enhanced flexibility, allowing them to smoothly expand and contract with the changing curvature of the surface, avoiding localized stress concentrations caused by excessive rigidity. The spacer filaments 300 must maintain a stable stretched length during long-term wing inflation to maintain the precise aerodynamic shape of the wing. The creep resistance of aramid and UHMWPE effectively prevents surface collapse or deformation caused by material relaxation. Furthermore, the softness of the thin fibers allows the spacer filaments 300 to tightly contract after deflation, folding in line with the upper and lower surface layers 200 and effectively reducing their folded bulk. Other high-performance yarns can also be used for the spacer filaments, as long as their fineness meets the aforementioned requirements. Specifically, the airtight coating layer 400 includes a TPU film, and the thickness of the airtight coating layer 400 is 0.01-0.1 mm. The shaping coating layer 500 includes a TPU film, and the thickness of the shaping coating layer 500 is 0.1-0.5 mm.

[0039] In this embodiment, both the airtight coating layer 400 and the shaping coating layer 500 are made of TPU film, with thicknesses of 0.01-0.1mm and 0.1-0.5mm, respectively. TPU film inherently possesses excellent airtightness and a dense molecular structure. The 0.01-0.1mm thickness of the airtight coating layer 400 ensures excellent airtightness without excessively increasing the weight of the wing. This TPU film adheres closely to the surface of the variable-gauge knitted substrate, forming a continuous, non-porous sealing layer that effectively prevents gas leakage within the air cavity, maintaining a stable air pressure even when the wing is inflated for extended periods. This provides continuous, reliable rigid support and ensures the stability of the wing's aerodynamic shape. The shaping film layer 500 utilizes a TPU film that is slightly thicker than the airtight film layer 400. Leveraging TPU's unique combination of rigidity and flexibility, it effectively constrains the wing's shape while adapting to changes in shape during inflation, deployment, and deflation. A thickness of 0.1-0.5mm provides the shaping film layer 500 with sufficient structural strength to withstand airflow impact and the outward tension generated by the wing's internal air pressure, maintaining the wing's pre-set high-precision aerodynamic curve and preventing deformation from excessive aerodynamic loads during flight. Furthermore, the TPU film's flexibility allows it to deform synchronously with the expansion and contraction of the variable-gauge knitted base. This prevents cracking or breakage during folding due to excessive rigidity, ensuring the wing's foldable performance. Furthermore, the TPU film exhibits excellent weather and aging resistance, adapting to varying environmental conditions and resistant to cracking, hardening, or degradation. This ensures that the airtight film layer 400 and the shaping film layer 500 maintain their optimal performance over time, extending the wing's service life. Example 2 See also Figure 2-4 A method for preparing a variable-gauge knitted flexible inflatable wing comprises the following steps: S1. Preparation of variable-gauge knitted substrate: A four-needle-bed computerized flat knitting machine is used, wherein the front lower needle bed and the rear lower needle bed respectively knit the upper surface layer 100 and the lower surface layer 200, and simultaneously insert the spacer yarn 300; The front upper needle bed and the rear upper needle bed of the four-needle-bed computerized flat knitting machine perform an empty needle knitting action, so that the spacer yarn 300 forms a retractable structure; The spacer yarns 300, the upper surface layer 100 and the lower surface layer 200 are integrally woven to form a variable-gauge knitted base.

[0040] More specifically, in S1: Both the upper surface layer 100 and the lower surface layer 200 are woven from high-strength yarns with a linear density of 200-1000D. The high-strength yarns are selected from one or more of aramid, ultra-high molecular weight polyethylene, carbon fiber, and polyester. The spacer yarns 300 are selected from one or both of aramid and ultra-high molecular weight polyethylene. The diameter of the spacer yarns 300 is 0.2-0.6 mm. The reactive adhesive layer comprises one or more of moisture-reactive PUR melt adhesive, polycarbonate TPU adhesive, and composite PC adhesive powder.

[0041] S2. Preparation of primary airtight skin: A reactive adhesive layer is evenly coated on the upper surface layer 100 and the lower surface layer 200; After laminating the airtight coating layer 400 on the reactive adhesive layer, the airtight coating layer 400 is bonded by a hot pressing process. During the laminating process, an inflation area is reserved. The airtight coating layer 400 is sealed by a high-frequency welding process, and the air nozzle is installed in the inflation area. The primary airtight skin is formed by constant pressure curing.

[0042] In S2, the temperature of the hot pressing process is 50-60° C. The alternating electric field oscillation frequency of the high-frequency welding process is 20 MHz. The constant pressure curing time is 24-48 hours.

[0043] S3, Inflatable Shaped Wings: The wings are formed using a shaping mold 600, and a shaping coating layer 500 is attached to the inner wall of the shaping mold 600; The primary airtight skin is placed in a shaping mold 600, and a first constant-pressure gas is injected through a gas nozzle and maintained at this pressure for a first time for pre-lamination. A second constant-pressure gas is then injected and maintained at this pressure for a second time for precise shaping to form the wing. The pressure of the second constant-pressure gas is greater than that of the first constant-pressure gas. The wing is separated from the shaping mold 600 .

[0044] Specifically, in S3: the first constant pressure gas has a pressure of 15-40 kPa and a first time of 2-3 minutes, and the second constant pressure gas has a pressure of 60-100 kPa and a second time of 10-15 minutes. After the wing is separated from the shaping mold 600, a static pressure leak test is performed for at least 30 minutes.

[0045] In this embodiment, if Figure 4As shown in the figure, in the process of preparing the variable-gauge knitted matrix, a four-needle-bed computerized flat knitting machine (optional models include SHIMA SEIKI MACH2XS 153-12, MACH2XS 153-15, and MACH2X 153-18) is used. The front lower needle bed and the rear lower needle bed are made of high-strength yarns (aramid, ultra-high molecular weight polyethylene, carbon fiber, etc.) with good weather resistance and a linear density of 200D-1000D to weave the upper surface layer 100 and the lower surface layer 200. The spacer yarns 300 are made of high-performance fibers such as aramid and ultra-high molecular weight polyethylene with a diameter range of 0.2-0.6 mm to ensure the high load-bearing capacity and high weather resistance of the wing. The variable gauge effect is achieved through empty-needle knitting and back-looping: the front lower needle bed and the rear lower needle bed knit the upper surface layer 100 and the lower surface layer 200, respectively, and simultaneously insert the short-gauge spacer yarn 300. The variable gauge effect is achieved by forming tucks after the yarn is knitted with empty needles on the front upper and rear upper needle beds, making the spacer yarn a retractable structure. By varying the knitting span and the number of knitting needles, a continuous gradient gauge range of 0–200 mm is achieved. At the same time, all spacer yarns 300 are still woven integrally with the upper surface layer 100 and the lower surface layer 200, ensuring continuous force and airfoil accuracy. In addition, the tuck length of a single needle loop depends on the flat knitting machine gauge, differences in yarn raw materials, knitting density, and other factors, and can be flexibly adjusted according to demand.

[0046] In the process of preparing the primary airtight skin, the upper surface layer 100 and the lower surface layer 200 of the variable-gauge knitted substrate prepared in S1 are evenly rolled with a reactive adhesive layer of a set thickness by a gluing machine, and then an airtight coating layer 400 with a thickness of 0.01-0.1 mm is coated and hot-pressed at 60°C. This temperature range can not only soften the TPU film moderately during the hot pressing process, thereby enhancing the intermolecular bonding force with the reactive adhesive layer, but also avoid material degradation or deformation caused by high temperature, so that the airtight coating layer 400 is firmly bonded to the surface of the variable-gauge knitted substrate, and an inflation area is reserved during the laminating process. Subsequently, 20MHz high-frequency welding is used around the flange to achieve rapid edge sealing and preliminary airtight closure. At the same time, an air nozzle is welded in the inflation area. After lamination, the composite fabric is placed in a constant pressure leveling device for static curing for 24-48 hours. After cohesive cross-linking, a primary airtight skin with basic airtightness and shape retention is formed. The reactive adhesive layer usually takes a long time to complete the cross-linking and curing reaction. Hours of constant pressure curing ensure that the adhesive molecules form a complete three-dimensional network structure. Under constant pressure conditions, the internal stress between the variable-gauge knitted base and the airtight coating layer 400 is gradually released during the curing process, avoiding local debonding or deformation caused by stress concentration.

[0047] During the process of inflating and shaping the wing, a shaping mold 600 of the flexible inflatable wing can be prepared by 3D printing, such as Figure 2 、 Figure 3As shown, the shaping mold 600 is a cavity mold with upper and lower detachable cavities. First, easy-to-peel glue is scraped on the inner walls of the upper and lower cavities and a second layer of shaping film 500 with a thickness of 0.1-0.5 mm is applied. The pre-laminated fabric is placed in the mold, the positioning pins on the mold are locked, and pre-lamination is performed through the air nozzle at a low pressure of 15-40 kPa and maintained for 2-3 minutes. The first constant pressure gas of 15-40 kPa is used for pre-lamination, which can make the primary airtight skin gradually adapt to the mold surface in a lower stress state, avoiding local excessive stretching of the skin due to instantaneous high pressure, resulting in wrinkles or ruptures. During the 2-3 minute pre-lamination stage, the lower air pressure prompts the reactive adhesive layer to further flow and fill the gaps in the knitted substrate, thereby enhancing the interfacial bonding between the adhesive layer and the TPU film. The pressure is then increased to 60-100 kPa and maintained for 10-15 minutes to complete precise shaping. The second constant pressure gas of 60-100 kPa provides sufficient pressure to make the skin fully fit the inner wall of the mold, forming a high-precision aerodynamic shape. The higher air pressure can effectively eliminate the tiny gap between the skin and the mold, ensuring that the curvature deviation of the wing surface is within the qualified range. Finally, the locating pins on the shaping mold 600 are loosened, the flexible inflatable wing and the mold are separated, and the excess shaping film layer 500 is torn off. After passing the 30-minute static pressure leak test, it can be deflated and folded for storage. The static pressure leak test time of more than 30 minutes can capture extremely small leaks. Long-term pressure monitoring uses the principle of gas diffusion to make the pressure changes at potential leak points more obvious, improve the detection sensitivity, and ensure that the airtightness of the wing meets strict standards.

[0048] The following is the process of preparing the flexible inflatable wing according to the above preparation method: Example 3 Changing the number of knitting needles to achieve gradient spacing: Preparation of variable gauge knitted substrate: Use Shima Seiki MACH2XS 153-15 computer flat knitting machine, such as Figure 5 The yarns of the upper surface layer 100 and the lower surface layer 200 shown are 600 D high-strength polyester multifilament yarns, and the spacer yarns 300 are aramid monofilament yarns with a diameter of 0.40 mm. The yarns are knitted by empty needles to form tuck loops to realize a spacer fabric with variable gauge. The number of empty needle knitting needles n of the spacer yarns 300 can be set as needed in the range of 0–10 needles (for example, n = 0, 2, 4, 6, 8, 10). Figure 4 In the example, the number of empty needles of the spacer yarn 300 (a) is 10, and the number of empty needles of the spacer yarn 300 (b) is 4, which reflects the implementation method of gradient spacing in the same fabric.

[0049] Preparation of primary airtight skin: The prepared variable-gauge knitted substrate was placed on a double-roller gluing machine, and a moisture-reactive PUR melt adhesive with a thickness of 60 μm was evenly coated on the upper surface layer 100 and the lower surface layer 200. After the adhesive layer was coated, a 0.10 mm TPU film was immediately laminated as the airtight coating layer 400. The film was pressed in a flat-plate hot press at 60 °C and 0.25 MPa for 80 s to firmly bond the variable-gauge knitted substrate and the airtight coating layer 400. During the laminating process, the opening for the inflation nozzle was reserved and positioned, and then a 20 MHz high-frequency welding device was used to continuously weld and seal the entire circumference of the flange. At the same time, a reinforcing film of the same material was applied around the nozzle and welded in one go. After lamination, the semi-finished product was clamped in a constant pressure leveling device and placed in an environment of 23 °C and 55% RH for 48 hours. h, allowing the PUR adhesive to cool and set first and then react with ambient moisture to cross-link, ultimately obtaining a primary airtight skin with basic airtightness that can support the next step of in-mold inflation and shaping.

[0050] Inflatable wing: A shaping mold 600 with upper and lower detachable cavities is made of 3D-printed composite carbon fiber material. First, a 0.20 mm thick TPU liner film is applied to the inner surfaces of the two halves of the cavity with easy-to-tear, low-viscosity double-sided tape to prevent adhesion. The TPU liner film serves as the shaping film layer 500. After the variable-gauge composite fabric, which has been pre-sealed by the film, is accurately placed in the lower cavity, the mold is closed and the locating pins are locked. Subsequently, a low pressure of 40 kPa is slowly inflated into the interior of the wing through a welded air nozzle. This pressure is maintained for 3 minutes to ensure that the primary airtight skin and the shaping film layer 500 are fully bonded. After confirming that there are no wrinkles anywhere, the pressure is further increased to 60 kPa and maintained at this pressure for 12 minutes to complete precise shaping and solidify the adhesive layer using the mold cavity constraints. After shaping is completed, the locating pins are released, the upper and lower molds are separated, and the edges are trimmed.

[0051] Among them, under the condition that the span of the spacer wire is fixed at 10 needles at 300 mm, a continuously variable spacing height of about 0–100 mm can be obtained.

[0052] Example 4 Changing the knitting span to achieve gradient spacing: Preparation of variable gauge knitted substrate: On a Shima Seiki MACH2X 153-18 four-needle bed computerized flat knitting machine, Figure 6 As shown, the front lower needle bed and the rear lower needle bed are respectively made of 400 D aramid multifilament to knit the upper surface layer 100 and the lower surface layer 200, and the spacer yarn 300 is made of UHMWPE monofilament with a diameter of 0.30 mm. The number of empty needles knitted in different span sections is kept constant at 2, and the number of empty needles span of the spacer yarn 300 n can be set as needed within the range of 2-10 needles (for example, n = 2, 4, 6, 8, 10). Figure 6 In the example, the empty needle span of the spacer yarn 300 (a) is 8 needles, and the empty needle span of the spacer yarn 300 (b) is 2 needles, which reflects the implementation method of gradient spacing in the same fabric.

[0053] Preparation of the primary airtight skin: The prepared variable-gauge knitted substrate was placed on a double-roller gluing machine, and 30 µm thick polycarbonate TPU adhesive was applied to each surface. A 0.1 mm thick TPU film was then applied as the airtight coating layer 400. The coating was then pressed in a flatbed hot press at 50°C and 0.1 MPa for 75 seconds to securely bond the airtight coating layer 400 to the variable-gauge knitted substrate. Release paper was used to create a space for the inflation nozzle. A 20 MHz high-frequency welding device was then used to continuously seal the flanges. Reinforcement film was applied around the nozzle area and welded to the nozzle. After lamination, the substrate was clamped in a constant-pressure flattening device and cured at 25°C and 55% relative humidity for 24 hours to obtain the primary airtight skin.

[0054] Inflatable Wing: A 3D-printed aluminum alloy split cavity mold serves as the finalizing mold (600). The inner wall of the cavity is first coated with an easy-to-peel release agent and then covered with a 0.25 mm TPU mesh fabric as the finalizing film (500). The pre-laminated fabric is placed in the lower mold, and after the mold is closed, the locating pins are locked. A low-pressure pre-charge of 40 kPa is applied through an air nozzle and held for 2 minutes to form the inflatable wing. The pressure is then increased to 100 kPa and held for 10 minutes. The mold is then constrained to achieve precise shaping and final curing of the adhesive layer. The locating pins are released to separate the mold, and the excess finalizing film (500) outside the wing edge is trimmed.

[0055] Under the condition that the number of empty needles knitted with spacer yarn 300 is constant at 2, a continuously variable spacing height of about 30–120 mm can be obtained.

[0056] Example 5 Knitting span and knitting needle number are adjusted to achieve gradient spacing Preparation of variable gauge knitted substrate: Use Shima Seiki four-needle bed computerized flat knitting machine MACH2XS 153-12 to prepare variable gauge knitted substrate, such as Figure 7 As shown in FIG, the front lower needle bed and the rear lower needle bed are respectively made of 800 D aramid multifilament to weave the upper surface layer 100 and the lower surface layer 200, and the high-strength polyester multifilament with a diameter of 0.6 mm is used as the spacer yarns 30010 and 12. The empty needle knitting action is used to form a tuck loop to realize a spacer fabric with variable gauge. The number of empty needle knitting needles of the spacer yarn 300 (a) is 4 needles and the number of empty needle span needles is 11 needles. The number of empty needle knitting needles and the number of empty needle span needles of the spacer yarn 300 (b) are both 6 needles, which reflects the realization method of gradient gauge in the same fabric.

[0057] Preparation of primary airtight skin: Use a vibrating powder spreader to evenly spread 0.1mm composite PC rubber powder (melting point 110 ℃, particle size D) on the upper surface layer 100 and the lower surface layer 200 of the variable gauge knitted substrate. 50≈100 µm), laminated with 0.05 mm TPU film as an airtight coating layer 400, and then placed in a flat hot press, preheated at 60 ° C for 30 seconds to soften the rubber powder, then raised to 110 ° C and pressed at 0.28 MPa for 90 seconds to make the PC adhesive layer melt and penetrate into the fabric and firmly bond with the TPU film. During lamination, a nozzle position was reserved, and then a 20 MHz high-frequency welding device was used to continuously weld and seal along the flange, and a nozzle was welded at the nozzle reserved position. After lamination, the coated part was clamped into a constant pressure leveling device and left to stand at 23 ° C and 55% RH for 48 hours until the composite PC adhesive cooled, solidified and completely crystallized to form a primary airtight skin with basic airtightness.

[0058] Inflatable wing: A CNC-machined aluminum cavity mold is used as the shaping mold 600, and its inner wall is covered with a 0.30 mm TPU peelable liner film as the shaping film layer 500. The primary airtight skin is flatly laid into the lower mold and locked with a locating pin. A low pressure of 40 kPa is first inflated through an air nozzle for 2 minutes to fully fit the skin and the liner film. After there are no wrinkles, the pressure is increased to 80 kPa and maintained for 15 minutes. The mold cavity constraint helps the adhesive layer and the TPU film to thermally bond again, while accurately replicating the airfoil shape. After cooling, the locating pins are released, the mold pieces are removed in sequence, and the excess shaping film layer 500 outside the wing edge is trimmed.

[0059] It changes the number of empty needle knitting needles and the empty needle knitting span simultaneously according to the required length, and can achieve a continuously variable interval height of 0-200 mm.

[0060] In the embodiments disclosed herein, terms such as "installed," "connected," "connected," and "fixed" should be interpreted broadly. For example, "connected" may refer to a fixed connection, a detachable connection, or an integral connection; and "connected" may refer to a direct connection or an indirect connection via an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the embodiments disclosed herein based on specific circumstances.

[0061] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A variable gauge knitted flexible inflatable wing, characterized in that: include: A variable-gauge knitted base comprises an upper surface layer, a lower surface layer, and spacer yarns connecting the upper surface layer and the lower surface layer, wherein the spacer yarns are knitted with open needles to form a retractable structure during the knitting process; An airtight coating layer, which is coated on the outer surface of the variable-gauge knitted base body and encloses the upper surface layer and the lower surface layer together to form a closed air cavity; a shaping film layer covering the outer surface of the airtight film layer and at least used to constrain the deformation of the airtight film layer to maintain the preset aerodynamic curvature of the wing, wherein the shaping film layer is thicker than the airtight film layer; an air nozzle, which penetrates the shaping film layer and the airtight film layer and communicates with the air cavity; The spacer wire is stretched in an inflated state so as to form a preset spatial curved surface between the upper surface layer and the lower surface layer.

2. The variable gauge knitted flexible inflatable wing according to claim 1, characterized in that: The range of the variable distance of the continuous gradient between the upper surface layer and the lower surface layer is 0-200 mm.

3. The variable gauge knitted flexible inflatable wing according to claim 1, characterized in that: The upper surface layer and the lower surface layer are both woven from high-strength yarns, and the linear density of the high-strength yarns is 200-1000D; And / or, the high-strength yarn includes one or more of aramid, ultra-high molecular weight polyethylene, carbon fiber and high-strength polyester.

4. The variable gauge knitted flexible inflatable wing according to claim 1, characterized in that: The spacer yarns include one or both of aramid and ultra-high molecular weight polyethylene; And / or, the diameter of the spacer wire is 0.2-0.6 mm.

5. The variable gauge knitted flexible inflatable wing according to claim 1, characterized in that: The airtight coating layer includes a TPU film, and the thickness of the airtight coating layer is 0.01-0.1 mm.

6. The variable gauge knitted flexible inflatable wing according to claim 4, characterized in that: The shaping coating layer includes a TPU film, and the thickness of the shaping coating layer is 0.1-0.5 mm.

7. A method for preparing a variable-gauge knitted flexible inflatable wing according to any one of claims 1 to 6, characterized in that: The steps include: S1. preparing the variable-gauge knitted substrate: A four-needle-bed computerized flat knitting machine is used, wherein the front lower needle bed and the rear lower needle bed respectively knit the upper surface layer and the lower surface layer, and simultaneously insert the spacer yarn; The front upper needle bed and the rear upper needle bed of the four-needle-bed computerized flat knitting machine perform an empty needle knitting action, so that the spacer yarn forms a retractable structure; The spacer yarns, the upper surface layer and the lower surface layer are integrally woven to form the variable-gauge knitted base; S2. Preparation of primary airtight skin: Uniformly coating the upper surface layer and the lower surface layer with a reactive adhesive layer; After laminating the airtight coating layer on the reactive adhesive layer, the airtight coating layer is bonded by a hot pressing process, and an inflation area is reserved during the lamination process. The airtight coating layer is sealed by a high-frequency welding process, and the air nozzle is installed in the inflation area; Forming a primary airtight skin by constant pressure curing; S3, Inflatable Shaped Wings: The wing is formed by using a shaping mold, and the shaping coating layer is attached to the inner wall of the shaping mold; Placing the primary airtight skin in the shaping mold, filling it with a first constant-pressure gas through a gas nozzle, and maintaining the pressure for a first time for pre-lamination, then filling it with a second constant-pressure gas, and maintaining the pressure for a second time for precise shaping to form the wing, wherein the pressure of the second constant-pressure gas is greater than the pressure of the first constant-pressure gas; The wing is separated from the shaping mold.

8. The preparation method according to claim 7, characterized in that In said S1: The upper surface layer and the lower surface layer are both woven from high-strength yarns, and the linear density of the high-strength yarns is 200-1000D; And / or, the high-strength yarn comprises one or more of aramid, ultra-high molecular weight polyethylene, carbon fiber and high-strength polyester; and / or, the spacer filaments include one or both of aramid and ultra-high molecular weight polyethylene; And / or, the diameter of the spacer wire is 0.2-0.6 mm.

9. The preparation method according to claim 7, characterized in that In said S2: The reactive adhesive layer includes one or more of moisture-reactive PUR melt adhesive, polycarbonate TPU adhesive and composite PC adhesive powder; and / or, the temperature of the hot pressing process is 50-60° C.; And / or, the alternating electric field oscillation frequency of the high-frequency welding process is 20 MHz; And / or, the constant pressure curing time is 24-48 hours.

10. The preparation method according to claim 7, characterized in that In said S3: The pressure of the first constant-pressure gas is 15-40 kPa, the first time is 2-3 minutes, the pressure of the second constant-pressure gas is 60-100 kPa, and the second time is 10-15 minutes; And / or, after the wing is separated from the shaping mold, it is subjected to static pressure leak detection for at least 30 minutes.

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