Integrally molded fan component and manufacturing method thereof

Abstract

A method for manufacturing a fan blade or fan component of composite material, the method comprising using a permanent core having a plurality of interconnected surface channels on a surface thereof to promote resin flow; forming a reinforcing fabric envelope over the permanent core; a mold is closed over a permanent core of the reinforcing fabric encapsulant to form a mold cavity between a surface of the permanent core and an inner surface of the closed mold, and resin is injected into an opening of the closed mold to allow the resin to fill the entire mold cavity via surface channels of the permanent core to allow the resin to cure, and releasing the fan blade or fan component from the mold; wherein the injection of resin is accomplished with or without a positive pressure system, and wherein the permanent core is not removed from the fan blade or fan component prior to use.

Description

Technical Field

[0001] The present invention relates to large lightweight molded fan blades, fan stacks and other fan components and methods of making the same. Background Art

[0002] Composite materials are widely used across many industries due to their many advantages, such as design flexibility, light weight, chemical resistance, and reduced part count. Many industries, including automotive and transportation, construction, infrastructure and architecture, aerospace, energy, marine, and sports, have incorporated composite materials into their products to capitalize on these advantages. In the case of large commercial or industrial composite parts, such as fan blades, fan stacks, and other fan components used in large-scale industrial cooling towers, manufacturing is often completed in stages. For example, the process of manufacturing large fan blades from composite materials is typically completed in stages, with the primary structure being made from two separate parts: the suction side of the blade and the pressure side of the blade. Each blade piece is manufactured separately in separate molds using vacuum resin infusion, where liquid resin is injected into and reinforced by the fiber-reinforced structure. To maintain the lightness of the parts, the fiber content is kept high relative to the resin component of the composite material. This is important because the structural properties of composite materials primarily derive from the fiber reinforcement. The high fiber content improves structural properties, increasing tensile strength and stiffness while minimizing weight. After independently manufacturing two different solid integral composite parts, the two pieces are bonded together, resulting in a seam line and a number of bond areas, typically at the leading and trailing edges of the blade, and often along the centerline of the component (see Figure 1 ). Most very large lightweight composite fan blades are manufactured using this process. These large and lightweight composite fan blades are typically used in industrial applications such as cooling towers, heat exchangers, condensers, evaporators, underground ventilation, cooling and air ventilation.

[0003] Another method that has been successfully applied to the manufacture of large lightweight composite parts (such as wind turbine blades) is the so-called single-shot injection molding process. The result is a blade without seam lines, but the single-shot process requires the use of large vacuum bags and flexible inserts that are placed inside the part being manufactured (see Figure 2 ) and is then removed when molding is complete.

[0004] Other composite molding technologies include resin transfer molding ("RTM") and vacuum-assisted RTM ("VRTM" or "lightweight RTM"). In RTM, resin is injected into a two-part rigid mold to impregnate the fiber reinforcement. The process involves placing a dry fiber layup on the mold surface, closing the mold over the fiber layup and injecting a thermosetting resin into the mold under high pressure to impregnate the fiber layup. To avoid resin leakage, the mold is sealed by compressing a flange gasket on the outer surface of the mold. More often, the reinforcing fibers of the layup are non-oriented and are characterized by high permeability to allow easy flow of the resin; these material properties are necessary for RTM to allow the resin to flow adequately to fill the mold and impregnate all of the layups. Generally, the RTM process cannot be used to produce parts with a fiber reinforcement content greater than 50%. Attempts to increase the fiber content above 50% in the RTM molding process have reduced the permeability of the fiber reinforcement, resulting in the need to increase the injection pressure, which in turn requires an increase in the mold structural rigidity to avoid mold deformation or failure. Therefore, RTM is not suitable for molding very large, lightweight products, products with widely varying composite material thicknesses, products with complex geometries, or high-performance materials requiring oriented fiber fabric reinforcements. Furthermore, RTM requires very high mold strength and rigidity to prevent the mold from deforming or opening under high injection pressures. This requirement for heavy, reinforced molds leads to size limitations in the use of RTM, as mold cost and weight make it impractical for molding large structures.

[0005] VR™ (Lightweight RTM) is a variation of RTM that uses vacuum to pull the resin through a lightweight mold, resulting in substantially lower costs. However, VR™ suffers from the same inability as RTM to mold lightweight products, products with variable composite thickness, or products with complex geometries. Summary of the Invention

[0006] The bonding process of two (or more) part molded fan blades and components is a critical manufacturing step that, even when done correctly, can create weak points in the structure that can compromise the integrity of the part and its mechanical strength.

[0007] While RTM and VRTM molding processes do not require a bonding step to create seams, the geometry of the reinforcement layups and parts is limited due to process limitations. Therefore, RTM and VRTM are not optimal when structural requirements are high, such as in the case of large, lightweight fan blades.

[0008] The use of vacuum bags / flexible inserts for single-shot processes requires large amounts of consumable (non-reusable) material and presents limitations when the part geometry exhibits small details or narrow cavities where the vacuum bag cannot fit. Another disadvantage of single-shot processes is that the opening in the part must be large enough to remove the insert and inject the consumable material (see Figure 3 This requirement limits the types of multiple part / single part geometries that can be made using a single shot process. Furthermore, single shot molding processes are highly labor intensive due to the setup and removal of consumables.

[0009] Therefore, there is a need for a lower cost, less labor-intensive method to manufacture large lightweight and seamless molded composite parts with variable composite thickness and complex geometries.

[0010] The present invention overcomes the shortcomings of these prior art molding processes. According to one advantage of the present invention, there are no seams in the final product, which significantly improves the structural strength and reduces the time required for finishing. Manufacturing time is also significantly reduced in both the molding step and the removal of the bonding and finishing steps. Another important advantage is that consumable materials are no longer required. The process according to the present invention can be applied to the manufacture of any large lightweight composite fan blades and fan components (e.g., fan blades, hubs, stacks, ducts, chimneys, equipment housings, and panels) that would benefit from these advantages.

[0011] According to the present invention, a monolithic part is created through a single-step injection molding process in a closed mold, resulting in a seamless structure. The interior of the part contains a core material, which can be selected based on the structural, strength, and weight requirements of the finished part. Different materials can be used for the core, such as polymer foam or natural materials (such as balsa wood), among other possibilities. The core includes a series of channels on its surface that improve the infusion process, allowing resin to be injected into the part without the need for additional consumable materials, and using a vacuum that is only sufficient to create a low pressure within the mold, allowing atmospheric pressure to push the resin into the mold cavity. A positive pressure system, such as used in RTM methods, is not required to force the resin into the cavity, although low positive pressure can optionally be used. The channels are designed with a distribution pattern, depth, and spacing configured to ensure that the entire mold cavity is completely filled, even in parts with complex geometries (e.g., closed contours with internal details and / or double curvature (including changes in direction in two or more planes)), and that the reinforcement fabric is fully wetted by the resin, thus avoiding dry fabric spots that can compromise part quality. High performance reinforcements (such as glass, carbon or aramid oriented fiber fabrics) can be used, wherein the percentage of oriented fiber fabric can be from about 30% to about 100% of the reinforcement, preferably from about 60% to about 100%, and most preferably about 100%, to further increase the strength and stiffness of the composite material. The resulting improved manufacturing process reduces costs and improves the quality of the parts, eliminates finishing adjustment operations and eliminates the need to perform additional lamination to strengthen the parts. The resin infusion process of the present invention can produce parts containing about 55% to 70%, preferably about 70% fiber reinforcement. The amount of fiber reinforcement in the resin-fiber composite provides high mechanical properties and at the same time provides low structural weight. According to the method of the present invention, the size of the core relative to the finished product is selected to result in the same fiber content as the same part manufactured using vacuum resin infusion, so that the same level of mechanical properties is achieved at lower material and labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The foregoing summary, as well as the following detailed description of a preferred embodiment of the present invention, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, the accompanying drawings depict presently preferred embodiments. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. Specifically, while reference is made herein to the manufacture of large, lightweight fan blades for the exemplary purposes of describing the invention, the invention may also be used to manufacture small fan blades and other fan components, including hubs, housings, and stacks. In the accompanying drawings:

[0013] Figure 1 is a cross-sectional illustration of a prior art fan blade manufactured from top and bottom parts glued together.

[0014] Figure 2 is a cross-sectional illustration of a prior art fan blade manufactured using a single shot vacuum bag and infusion consumables.

[0015] Figure 3 is an illustration of a finished fan blade produced according to the single-shot process, showing the large opening through which the vacuum bag and infusion consumables are removed.

[0016] Figure 4 is a cross-sectional illustration of a fan blade core according to an embodiment of the present invention.

[0017] Figure 5 is a cross-sectional illustration of a finished fan blade showing the permanent core in the inner portion and the molded resin / reinforced fabric outer shell in accordance with an embodiment of the present invention.

[0018] Figure 6 Examples of channel patterns / networks embossed on, carved into, or integrally molded onto the surface of a core are shown according to various embodiments of the present invention. DETAILED DESCRIPTION

[0019] The invention begins by making a core that is generally in the shape of the final article, but reduced in size to a size sufficient to produce the molded covering layers of reinforcement fabric and resin of the final article.The core is preferably a single, unitary element. Figure 4 A cross section of a core 2 for a fan blade is shown, including surface channels 4, according to an embodiment of the invention. Figure 5 A cross section of a final manufactured fan blade according to an embodiment of the present invention is shown, wherein the reinforcing fabric and resin matrix 8 are shown cross-hatched on the core 2. According to the present invention, the core is not removed from the finished article and remains part of the finished article. The core has a network of channels 4 on its surface that is configured to disperse the resin on the surface of the core during molding of the final article. Figure 6An example of a channel network pattern is shown in FIG, although any pattern that provides uniform distribution of resin across the core and through the reinforcement fabric is suitable. The core can be made of any lightweight material that will retain its shape during the molding process of the final article. Examples of core materials include various foams (such as polyurethane foam) and balsa wood. The core can be manufactured using any known method suitable for the material, including molding, carving, machining, and the like. In the case of a molded core, for example, the core can be molded using a closed mold. According to one embodiment, a first mold section is mated with a second mold section to form a closed mold, and the closed mold is filled with polyurethane foam to produce a foam core comprising an integrally molded channel matrix. After the core is manufactured, again using any known method, a closed mold for the final article is prepared by laying the reinforcement fabric across the mold pieces, preferably in multiple layers. High-performance reinforcement materials such as glass, carbon, or aramid oriented fiber fabrics can be used, with the oriented fiber fabric comprising from about 30% to about 100% of the reinforcement material, preferably from about 60% to about 100%, and most preferably about 100%, further increasing the strength and stiffness of the composite material. The core is then placed in the final product mold part, and the remaining sections of the reinforcing fabric are laid across the exposed surface of the core. The mold is then closed and sealed. Resin is guided into one or more openings in the mold, which are communicated with one or more channels formed in the core, and resin is sucked through the mold via a vacuum / negative pressure source, which is communicated with the inside of the mold by one or more openings. The channels formed in the core allow resin to fill the entire mold cavity, saturate the reinforcing fabric, and fill all gaps, including the region of thickness variation within the same product, and products with complex geometric shapes (for example, closed profiles with internal details and / or double curvature (including changes in direction in two or more planes)). Once the resin is solidified according to known methods, the mold is opened to expose the fully molded product. Then, before transportation and / or assembly, final deburring and finishing can be carried out. Except for a single core, reinforcing fabric and resin, the finished product does not need other elements, parts or materials (except paint and / or other surface coatings). A vacuum is applied to fill the entire mold cavity with resin, but only enough to keep the air pressure inside the mold below ambient pressure, preferably 500 to 1000 mbar negative; if necessary, positive pressure can be applied to force the resin into the cavity. No additional reinforcement is used, and there is no need to seal or glue the top and bottom parts.

[0020] The present invention produces a final article having the same or improved structure, strength, weight, and surface characteristics as prior art fan blades, with substantially less material and labor costs.

[0021] Those skilled in the art will appreciate that changes may be made to the preferred embodiments described above without departing from the inventive concept thereof. It should be understood, therefore, that the present invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit and scope of the invention as outlined in this disclosure and as defined by the broadest reasonable reading of the appended claims when read in light of this specification.

Claims

1. A method for manufacturing a fan blade or fan component of a composite material, the fan blade or fan component comprising: A permanent core and a fiber-reinforced resin material, the method comprising: placing a plurality of layers of reinforcing fiber fabric in the shape of said fan blade or fan component on the bottom part of the closed mold, placing a permanent core on the plurality of reinforcing fiber fabric layers in the bottom portion of the closed mold, the permanent core having a shape approximating the shape of the fan blade or fan component; wherein the permanent core comprises a plurality of interconnected surface channels on its surface to facilitate resin flow, folding remaining portions of the plurality of reinforced dryness fabric sheets over exposed portions of the permanent core to form a reinforced fiber fabric encapsulated permanent core; closing the closing mold on the permanent core encapsulated by the reinforcing fiber fabric to form a mold cavity between a surface of the permanent core and an inner surface of the closing mold; injecting resin into the opening of the closed mold and allowing the resin to fill the entire mold cavity through the surface channels of the permanent core; allowing the resin to cure, and releasing the fan blade or fan component including the permanent core from the closed mold; and Wherein, the permanent core is not removed from the fan blade or fan component prior to use.

2. The method of claim 1 wherein the surface channels of the permanent core are integrally molded.

3. The method of claim 1, wherein the surface channels of the permanent core are formed after the permanent core has been molded.

4. The method of claim 1 , wherein a vacuum source is applied to the interior of the closed mold, the vacuum source being only sufficient to reduce the air pressure inside the closed mold to less than ambient air pressure.

5. The method of claim 1, wherein the fan blade or fan component has no seams or seam lines. The method of claim 1 , wherein the permanent core is a molded permanent core.

7. The method of claim 1, wherein the plurality of interconnected surface channels covers the entire surface of the permanent core.

8. The method of claim 1 wherein the permanent core is a single, unitary component.

9. The method of claim 1, wherein the reinforcing fiber fabric comprises a fiber fabric having greater than 60% orientation.

10. The method of claim 1, wherein the reinforcing fiber fabric comprises 60%-70% of the fiber-reinforced resin material.

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