FORMATION OF FLUID TANKS

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is related to and claims priority benefits from U.S. Provisional

Application Serial No. 62/926,150, filed on October 25, 2019, entitled “Solid Puzzle Mandrel for Vehicle Tanks,” the entire contents of each of which are hereby incorporated by this reference.

FIELD OF THE DISCLOSURE

[0002] The field of this disclosure relates to a removable mandrel for use in manufacturing a composite tank or pressure tank. The removable mandrel is formed using puzzle-like technology such that it can be assembled and disassembled in pieces. The mandrel forms a support during formation of the tank, and then the components can then be removed in individual pieces from the interior of the tank once formation is complete.

BACKGROUND

[0003] Commonly, such fluid tanks or pressure tanks are manufactured via filament winding. Filament winding is a fabrication technique that can be used for manufacturing open structures, such as cylinders, or closed end structures, such as pressure vessels or tanks. The process involves winding filaments under tension over a rotating mandrel. The mandrel rotates around a spindle or shaft that has an axis. A delivery eye on a carriage traverses horizontally (usually in line with the axis of the rotating mandrel), and lays down fibers onto the mandrel in a desired pattern or angle. Common filaments used are glass or carbon, impregnated in a bath with resin as they are wound onto the mandrel. Once the mandrel has been wound and is completely covered to the desired thickness, the resin is allowed to cure. Depending upon the resin system that is used and its cure characteristics, the rotating mandrel may be covered with a vacuum bag and placed in an oven or under radiant heaters until the wound material is cured (autoclave or out-of-autoclave cure). The disclosed puzzle mandrel technique is not limited to filament winding but may also be designed to be used for hand lay up applications to build different shapes of composite parts. Once the resin has cured, the mandrel may be removed or extracted, leaving the hollow final product. Removal of the mandrel can create certain challenges. For example, during manufacturing of aircraft water and waste composite tanks, the industry’s current trapped tooling design uses a solid mandrel that requires a complete washout procedure to remove the mandrel from the cured composite tank. This means that the mandrel is not re-usable. Improvements to mandrels that allow the mandrel to be removable and reused are desirable. The disclosed solid mandrel design allows for a removal technique for multiple reuses of the mandrel.

SUMMARY

[0004] Accordingly, the present inventors have designed a puzzle-like mandrel that may be used in manufacturing vehicle water and waste composite tanks. The puzzle mandrel is provided in a configuration that allows it to be assembled, used for tank formation, then disassembled via individual components. The individual components of the mandrel can be removed from the tank opening once the tank has been formed and completed.

[0005] The terms “invention,” “the invention,” “this invention” “the present invention,” “disclosure,” “the disclosure,” and “the present disclosure,” used in this patent are intended to refer broadly to all of the subject matter of this patent and the patent claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below. Embodiments of the invention covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this patent, any or all drawings and each claim.

[0006] According to certain embodiments of this disclosure, there may be provided a puzzle mandrel for use in formation of a fluid tank, comprising a central core positioned around a shaft; a plurality of removable components configured to be assembled together in a shape that defines an interior surface of the fluid tank, wherein each component in the plurality of removable components is removable through a tank opening after formation of the fluid tank. In the preceding or any subsequent examples, at least some of the plurality of removable components may be secured to one another via magnets. In any of the preceding or any subsequent examples, at least some of the plurality of removable components may be secured to one another via a spring plunger system. In any of the preceding or any subsequent examples, the spring plunger system may include a first component comprising a plunger with a plunger shaft, a shaft tip, and a ring, with a corresponding component comprising a receiving opening for receiving the shaft tip. In any of the preceding or any subsequent examples, at least some of the plurality of removable components may be secured to one another via a pin. In any of the preceding or any subsequent examples, the plurality of removable components may have flat surfaces, curved surfaces, or a combination of both. In any of the preceding or any subsequent examples, the plurality of components may comprise a polyurethane foam or high density polyethylene.

[0007] There is also provided a method of using a puzzle mandrel to form a fluid tank, comprising: providing a puzzle mandrel comprised of a plurality of components that are configured to fit together to form a shape defining an interior of the fluid tank; assembling the plurality of components together; winding a fluid tank using the mandrel, wherein the fluid tank has an opening; and removing the plurality of components through the opening of the fluid tank. In any of the preceding or any subsequent examples, the puzzle mandrel may be used in filament winding or a hand lay-up application.

BRIEF DESCRIPTION OF THE DRAWINGS [0008] Figure 1 is an exploded perspective view of one embodiment of a puzzle mandrel.

[0009] Figure 2 is a side perspective view of a puzzle mandrel core and shaft.

[0010] Figure 3 is an exploded perspective view of a plurality of components that forms the puzzle mandrel.

[0011] Figure 4 is an exploded perspective view of initial formation of the puzzle mandrel of Figure 3.

[0012] Figure 5 is a front perspective view of the formed and assembled mandrel of

Figure 3.

[0013] Figure 6 is a front plan view of a tank formed around a puzzle mandrel, showing the tank opening. [0014] Figure 7 is a front plan view of a mandrel grid, showing the front plan view of individual components and corresponding shapes that allow the mandrel to fit together.

[0015] Figure 8 is a side perspective view of a formed tank around the mandrel.

[0016] Figure 9 is a side perspective view of the core being removed from the opening of the tank. [0017] Figure 10 is a side perspective view of the plurality of components being removed from the opening of the tank. [0018] Figure 11 is a side perspective view of the formed tank (now hollow) and the reassembled mandrel that was used to form the tank.

[0019] Figure 12 is a side perspective transparent view illustrating various securement systems that may be used in order to secure mandrel components to one another.

[0020] Figure 13 is a front perspective view of a tank formed around mandrel, with the core removed.

[0021] Figure 14 is a front perspective view illustrating various fasteners that may be secure the core in place.

[0022] Figure 15 is a top perspective view of an individual mandrel component, illustrating various securement systems.

[0023] Figure 16 is a side transparent view illustrating various securement systems.

[0024] Figure 17 is a side transparent view illustrating an alternate view of various securement systems.

[0025] Figure 18 is a front transparent view of the securement systems of Figures 15-

17.

[0026] Figure 19 is a schematic view illustrating a process for filament winding.

[0027] Figures 20A shows a rear perspective view of a tank end.

[0028] Figure 20B shows a side plan view of a tank end.

DETAILED DESCRIPTION

[0029] Embodiments of the present disclosure provide a puzzle mandrel 10 that is designed to be assembled and disassembled in a plurality of individual pieces. Once assembled, the puzzle mandrel 10 is used as a form for manufacture of a composite pressure tank that is formed via filament winding. Figure 19 shows an exemplary process of filament winding. In this process, a mandrel rotates around a spindle or shaft as fibers or filaments are laid down in a pattern onto the rotating mandrel. The resulting tank that is formed is cured, and once finished, useable as a pressure tank. In many instances, the mandrel itself forms an interior surface of the tank. However, there are instances when the mandrel should be removed from the tank once it has been formed, and this can present challenges.

[0030] As shown by Figure 1, the present disclosure thus provides a puzzle mandrel

10. This mandrel 10 is divided into a plurality of components 12. Once assembled together, the components 12 all form the solid mandrel 10. Figure 1 shows a side perspective exploded view of the components 12 and a central core 14. The core 14 provides a central support for the components 12. In a specific example, the core 14 may be provided with a small cut 15 or place of material removed from each corner of the face of the components that forms the core 14, which can help prevent adjacent components from sliding. Figure 1 also illustrates that some components 12 may have one or more curved surfaces 16 in order to form an outer curvature of the tank. Other components may be provided with one or more flat surfaces 18 such that they abut one another in direct side-to-side contact. In addition to supporting the components 12, the core 14 also supports a shaft 20 that may function as a spindle that is used to rotate the mandrel in order to lay down filaments or fibers. The core 14 and shaft 20 are illustrated by Figure 2. These components may be bonded to one another in any appropriate manner, such as welded, use of adhesive, mechanically fastened, or any other appropriate attachment.

[0031] Reference will now be made to assembly of the mandrel 10. As illustrated by

Figure 3, the components 12 are shown in a disassembled configuration. This embodiment illustrates a mandrel 10 comprised of about 16-20 individual components, but it should be understood that fewer or more components may be used, depending upon the size of the desired tank to be formed. As an initial step, the components 12a that will be mounted closest to the core 14 are generally secured first. One or more fasteners 22 may be used to help secure the inner-most components 12a to the core 14. These fasteners 22 may generally be screws but it should be understood that other types of fasteners are possible for use. Fastening components 12a to the core 14 is generally referred to herein as a “first level securement.”

[0032] Next, additional components 12b forming a next layer of the solid “puzzle” may then be secured to the inner-most components 12a. This secondary fastening is generally referred to herein as “secondary securement.” Figure 4 illustrates two such components 12b being secured to components 12a. This securement is generally done via a securement system that uses securing features that are capable of being released internally. As background, an operator would have a difficult time releasing internal screws to disassemble the components 12 from one another. Accordingly, the present inventors have developed various ways to secure the components to one another that allow for ease of release from within the formed tank. Exemplary secondary securement members may be spring plungers, pins, magnets, or a combination thereof. These features will be described further below with respect to disassembly of the solid puzzle mandrel 10. Figure 5 illustrates an assembled solid puzzle mandrel 10. [0033] This solid puzzle mandrel 10 design allows a removal of the individual components 12 for multiple reuses of the mandrel 10. As is shown by the formed mandrel 10 of Figure 5, the general goal is to provide a plurality of components 12 that collectively can be secured to one another in order to form the desired shape of the inner surface of the tank to be formed. Additionally, the components 12 should be sized and shaped such that they can be disassembled from one another and removed from the formed tank via the resulting tank opening 24, shown by Figure 6. In other words, after the final tank T is formed by a filament winding around the external surface of the mandrel 10, the components 12 are designed to be removed through the opening 24, preferably without damaging the inner surface of the tank. In a specific example, if the opening 24 has a 9” diameter, each component 12 should be provided with a size/shape that allows it to be removed through the 9” diameter. In a specific example, the components 12 may all have sides (either flat surfaces 18 or curved surfaces 16) that are no larger than 6” in width.

[0034] As shown by Figure 7, the concept is to generate a dividable grid (with the term

“grid” being used to refer to some components being square and some components having alternate dimensions and/or curved surfaces) that includes a plurality of components 12 that all fit into one another and form the inner surface of the tank (also referred to as tank T). All components are sized and shaped so that they can fit through the resulting opening 24. For example, if the diameter is 9”, the components will generally have a 6” square shape or smaller so all the components can fit through the opening 24. (Again, it should be understood that the 9”/6” example is used for illustration only, and other dimensions are possible and considered within the scope of this disclosure.)

[0035] Figure 8 illustrates a completed tank T manufactured using a solid puzzle mandrel 10. Figures 9-11 illustrate removal of the solid puzzle mandrel 10 from the tank T. As shown in Figure 9, the central core 14 and shaft 20 is removed through the opening 24. Then, as shown in Figure 10, the individual components 12 are released from one another and also removed through the opening 24. Figure 11 illustrates the completed (and now hollow) tank T, with the solid puzzle mandrel 10 reassembled outside the tank T. Figures 12-18 illustrate one way that the individual components 12 may be secured to one another. These figures are provided for illustration and exemplary purposes only, and it should be understood that other securement features are possible and considered within the scope of this disclosure. [0036] Figure 12 illustrates a solid puzzle mandrel 10 in a transparent perspective, showing various securement features used to secure the individual components 12 to one another. This embodiment uses a combination of fasteners, pins, spring plungers, and magnets. [0037] As is shown by Figure 13, the core (not shown in this Figure) is generally removed from the center of the mandrel first. The central core 14 is removed together with the shaft 20 so that the side components can be released from one another and also fit through the tank opening 24. The core 14 can be secured to its adjacent components (all referenced as components 12a in Figures 13 and 14) via traditional fasteners 22, such as screws, nut and bolt fasteners, or any other option. Once the fasteners 22 are released, the core 14/shaft 20 combination can easily slide out of the mandrel 10.

[0038] Removal of the components 12 from the tank T can be more challenging because the size of the opening 24 generally prevents a user’s hand from easily reaching into the tank T in order to release the components 12 from their securement to one another. Accordingly, it is generally desirable to put the contact surfaces 16, 18 of the components 12 together, but not secure them permanently. In one embodiment, magnets 26 may be used to help secure the contact surfaces 16, 18 of the components 12 to one another. Additionally or alternatively, a spring plunger system 28 may be used to position and help secure the contact surfaces 16, 18 of the components 12 to one another.

[0039] Referring now to Figure 15, there is a shown one of the components 12a that is secured adjacent the core 14 when the mandrel 10 is assembled. This component has both a plurality of magnets 26, as well as a spring plunger system 28. Magnets 26 are used to maintain the shape of the mandrel. They pull and hold the components together when the mandrel is formed. Spring plunger system 28 is used for alignment of the components. They secure the components to one another and prevent them from rotating or sliding out of the place from the mandrel shape/form. Although it has been found beneficial to use both magnets 26 and a spring plunger system 28 with the mandrel in order to build the tank shown in the figures, it should be understood that only a single connection may be needed for other shapes or designs. As described below, some components may use solely magnets 26 and fasteners 22 in order to maintain a desired connection to adjacent components.

[0040] Referring first to the magnets 26, one or more components 12 may be provided with one or more magnets 26. The magnets 26 are generally positioned on a side of a component 12 so that a magnet 26a with first pole will be positioned adjacent a magnet 26b with an opposite pole, so that the magnets will be attracted to one another and help hold the components to one another. This is illustrated by Figure 16. For example, in reference back to Figure 12, for component surfaces that should be held to one another, a magnet 26 on a first surface of a first component will have an opposite pole to a magnet on a second surface of a second component. Although it has been found that magnets are particularly useful, it should be understood that other types of temporary securement systems may be used. Non-limiting examples include double-sided tape, hook and loop fasteners, dovetail sliding, as well as other securement systems.

[0041] This disclosure will now refer to the spring plunger system 28, as shown by

Figure 15 and the cross-sectional view of Figure 16. The spring plunger system 28 allows a plunger 30 positioned on one component to be received by a receiving opening 32 on a second, adjacent component. In order to allow ease of access to each plunger 30, the plunger(s) 30 may be provided with a ring 34. For further ease of access, each component may have a cavity 36 in which the spring plunger system 28 is housed. As shown by Figure 15, the cavity 36 shown is provided as an indented portion on the flat surface 18. The particular cavity 36 shown in this example is sized and shaped such that it can accommodate two plungers 30. Cavities 36 also define holes for receiving tooling in order to render the components easier to handle and dismantle from one another.

[0042] As shown by Figure 16, the plunger shafts 38 may have a spring 50 encircling the shaft 38. Providing a spring 50 allows retraction of the plunger 30 into the cavity 36 when the user (or a user-controlled instrument) connects with and pulls ring 34 inwardly into cavity 36. This releases connection between the shaft tip 40 and a corresponding receiving opening 32 on another component, such that the component 12 supporting the plunger 30 is released from the adjacent component with the receiving opening 32. When the released component is pulled by force, the force will generally overcome any magnetic force that may also be holding the components together. (For assembly, when the ring 34 is retracted and then released, the spring 50 provides a quick rebound for positioning of the shaft tip 40 into a corresponding receiving opening 32 on another component.) The adjacent components illustrated by Figure 16 also have magnets 26 (shown as 26a and 26b) as secondary securing systems.

[0043] Figure 17 illustrates another example of a component 12 that has two spring plunger systems 28. A first spring plunger system 28c connects the component 12 with a first adjacent component 12c, and a second spring plunger system 28d connects the component 12 with a second adjacent component 12d.

[0044] Figures 12 and 16-18 also illustrate optional pins 42 that may be used for alignment of the individual component 12 so that they do not slide with respect to one another during the filament winding process. Figures 17 and 18 show removal openings 44. Removal openings 44 are provided within some of the components for removal and release of the components 12. A tool may be inserted into the tank opening 24, received by one of the removal openings 44, and pressure on the tool can help remove the component 12 from the tank.

[0045] Although various exemplary positions of the magnets 26, spring plunger system

20 and pins 42 are shown and described, it should be understood that any appropriate combination of these securement features may be used in order to maintain the desired positioning and securement of the individual components 12 with respect to one another. [0046] The tank is formed via filament winding, which necessarily applies a compression to the mandrel 10. For perspective, Figure 19 shows one example of a filament winding machine. One grid design that has been found beneficial is to generate the components from a square grid, as much as possible, in order to provide as many flat surfaces 18 in contact with one another as possible. An exemplary grid geometry is illustrated by Figure 7. This geometry can also make it easier to machine the mandrel 10, reducing the number of complex surfaces to be machined, which can lead to reduced lead time and cost savings. What defines the size and shape of the puzzle mandrel 10 is ultimately the diameter and shape of the pressure tank to be formed. The removability of the mandrel also means that the mandrel will be reusable. If a part/component were to get damaged, it could be replaced instead of requiring a whole mandrel.

[0047] Because of the curved nature of the tank to be formed, it is generally necessary, however, to have a plurality of outer components with curved surfaces 16. As shown by the figures, some of the external components around the perimeter of the mandrel 10 are thinner than the more internal components near the core 14. Additionally, the external components typically do not have a plunger 30 but instead may have only a plunger receiving opening 32. All components are optionally provided with magnets 26.

[0048] The material used to form the mandrel 10 should generally be hard enough to support the compression process without deformation. It is also generally desirable that the material be light enough so that handling and winding is not hindered by the weight of the mandrel. In one example, the material used may be a high temperature polyurethane foam that can withstand high temperatures and high compressions. One specific exemplary material may be Last-a-Foam® FR-4718 or other densities that are compatible with pressure and temperature cure cycle of the resin used, manufactured and sold by General Plastics Manufacturing Company. Possible options are FR4730 and FR-4740. Another exemplary material may be high density polyethylene (HDPE). It should be understood that other materials are possible and considered within the scope of this disclosure. The selected material(s) should generally be able to withstand the high pressure of filament winding, and the heat and pressure of autoclaving that is used to cure the carbon fiber-resin laminates.

[0049] In one example, each of the components may be coated with polytetrafluoroethylene (e.g., Teflon™) or other type of nonstick coating for protection and/or to allow the components to slide with respect to each other. This may be done via a spray, a tape or cover, a painted-on or doctor blade process, or any other appropriate coating method. It is also possible to coat the entirety of the external surface of the mandrel with a similar material. This can help prevent the resin used in filament winding from penetrating inside the contact surfaces of the solid puzzle mandrel 10. Foam sealer may be added to reduce or prevent dimensional change, generate a smooth surface, and provide wear protection. In a specific example, Sealer P-78 was added to fill foam pores and generate a smooth surface finish as well structural strength to foam.

[0050] In the specific version shown in the figures, there are twenty total components

12. Two components are attached to the shaft 20 and form the core 14, with one upper component 60 and one lower component 62, sandwiching the shaft 20. The upper component 60 and lower component 62 are illustrated by Figure 7. A smaller rear component 64 supports the shaft and prevents its damage. This smaller rear component 64 is illustrated by Figures 20A and 20B. Smaller rear component 64 is the bossend portion that is at the polar opposite end of the tank from the tank opening 24. Smaller rear component 64 helps to position and support the union between the shaft 20 and the upper and lower components 60, 62. This component may be made of metal in order to help support pressure during winding. It may be permanently bonded to the shaft 20 and component 60, 62. Including components 60 and 62, there are 19 nineteen individual components 12 provided to fill out the mandrel 10 and define the inner tank surface/tank volume. [0051] The subject matter of certain embodiments of this disclosure is described with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described.

[0052] It should be understood that different arrangements of the components depicted in the drawings or described above, as well as components and steps not shown or described are possible. Similarly, some features and sub-combinations are useful and may be employed without reference to other features and sub-combinations. Embodiments of the invention have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Accordingly, the present invention is not limited to the embodiments described above or depicted in the drawings, and various embodiments and modifications may be made without departing from the scope of the claims below.