Conforming Air Cell Design and Method of Manufacture

Abstract

A design and method of manufacture for a conforming air cell device to be used for seating, vibration and shock isolation, custom fitting and other applications. Interconnected air cells are formed from two thin sheets of highly resilient thermoformed plastic, so that once inflated, the air cells readily conform to the shape of the user while equalizing pressure from cell to cell. The manufacturing method simultaneously thermoforms both halves of the cell structure, followed immediately by joining these halves while still at the material's forming temperature. The result is a relatively complex matrix of air cells, interconnecting passages and one or more inflation features in a single manufacturing process, greatly simplifying the manufacturing process over previous methods. The design and method of manufacture result in an extremely lightweight, flexible and compactable system that quickly inflates and deflates, and can easily be taken and used anywhere it is needed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

It is to be understood that while certain forms of the present invention are illustrated, it is not to be limited to the specific forms described and shown. The illustrated application is for an air-filled seat cushion, though other applications would include products such as bedding, air-casts, air inserts for footwear, cushioning for sensitive electronics and the like. It will be apparent to those skilled in the art that various applications can be made from this technology without departing from the scope of the invention.

FIG. 1 is a perspective view of a seating application for the invention;

FIG. 2 is a top view of same seating application;

FIG. 3 is a partial top view showing air cell shape and interconnectivity;

FIG. 4 is a cross section showing air cell shape and interconnectivity;

FIG. 5 is a close-up view of the airflow channel design;

FIG. 6 is a perspective of mold sides A and B in preparation for thermoforming;

FIG. 7 is a flow-chart describing the twin-sheet thermoforming process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, a perspective view is shown of a preferred embodiment of the invention, in applying the concept for an improved seat cushion. Two thin sheets of highly resilient plastic (approximately 0.010″ thick to 0.040″ thick) are used to form a top half 10 and bottom half 12 in opposing protrusions which when joined, create a multiplicity of individual air cells 14. Plastic types that have the resilient properties desired for the present invention include thermoplastic polyurethanes, highly flexible polypropylenes, soft vinyls, flexible polyethylenes and the like. The intent of the plastic is to create soft, very pliable air cells while being adequately robust to support internal pressures and resist puncture. The plastic could be colored for improved aesthetics, to result in a translucent gray or opaque blue for example. This device could be inserted into a fabric cover to give it a softer feel, customize the look of the seating system, and protect it against damage. It could also be incorporated directly into a seating system such as an office chair or automotive seat. The overall dimensions of the preferred embodiment are approximately 1.5 inches thick, 20 inches wide and 16 inches deep.

In the manufacturing process of the present invention, a cylindrical port 16 is formed to mate with a shut-off valve that allows inflation of the air cell matrix, adjustment of pressure based on user preference, and deflation for easy transport from place to place. Additional ports can also be formed to provide further control of air flow. In one embodiment, ports 18 and 20 are created similar to port 16, to allow shutoff of flow between right and left sides of the air cell matrix. This could provide the added benefit of stabilizing the user from side to side, especially useful for maintaining proper sitting posture or preventing excessive body lean in activities where a stable upright position is desired, such as flying aircraft or racing automobiles

FIG. 2 shows a top view of the same seating application, with references to FIGS. 3 and 4 for further detail. In this preferred embodiment, the air cells on the left side of the air matrix are isolated from air cells on the right, so that air must flow through the dashed tubing shown from port 18 into port 20 and back. This flow can also be blocked with the addition of a simple clamping device or additional valve, which would completely stabilize the cushion from side to side. Allowing a restricted amount of flow through this tube would serve to partially stabilize the user, providing a delayed response as air takes more time to move out of the cells being pressed upon. This feature provided a surprise benefit of creating a “breathing” sound, making the cushion feel and sound alive and responsive to adjustments in user posture.

FIG. 3 shows a close-up of one corner of the seating application. When joined, material from both halves creates a thin web 22 between all air cells of approximately 0.020″ to 0.040″ thick. The air cells are interconnected by small passages 24 which serve to equalize pressure in all cells while allowing rapid inflation and deflation and maintaining flexibility between cells. Spacing of the air cells 26 is designed to allow flexibility of the system as well allowing air to flow freely between the exterior walls of the cells and away from the user. With proper spacing and air cell shape, the present invention leaves pathways of air between compressed air cells, down along the webbing, and out the sides of the air matrix. When a user shifts his or her weight on the device, air is pushed through these passages and recycled to help remove heat.

Referring now to FIGS. 4 and 5, a cross-section of the air cell matrix is shown to elaborate on further details. These views show the opposing protrusion design of the air cell's top half 10 and bottom half 12 more clearly. This opposing protrusion design makes the air cell matrix more stable and less susceptible to “shearing” over, compared to a design that had tall cells extending up from a flat base. Thin web 22 is shown here and which holds the entire air matrix together. At specific locations of this webbing, small air passages 24 are formed to allow air to flow from one air cell to another. These passages have a special cross section as shown more clearly in FIG. 5. This narrow eye shape allows more flexibility than other shapes such as cylindrical or U-shaped passages, by allowing the material to flex more closed or open, depending on stresses applied. In addition, this shape helps to avoid “hard spots” that would be created by a other designs, and is significantly easier for the plastic to form into, maintaining a more even plastic distribution.

In the preferred embodiment of the invention, some air passages are larger in size to allow for more rapid inflation and deflation to occur. These passages are strategically placed along the air flow route from the inflation valve, through air passages to ports 18 and 20 and into the left side of the air matrix. The larger passages effectively “spread” the flow of air, exposing more of the small air passages 24 to maximum flow during inflation and deflation. Flow in and out of an inlet valve attached to port 16 is therefore more closely matched to the sum of what the internal passages can accommodate. The result is a faster inflation and deflation of the entire matrix, making this process much more convenient, which is especially useful for travel purposes.

It should be noted that the parting line 28 between the upper and lower air cell halves can be altered to further tailor the design. In other words, the air cell halves do not need to be equal in thickness. For example, a shallow bottom half with taller top half could be used to create thicker plastic on the bottom and thinner plastic on the top, providing more robustness on the bottom with more comfort on the top half. The depth of cells can therefore be used to control the amount of thinning that occurs when the plastic forms into the cells for a specific function. At its extreme, the air cells could have a fully formed top half mated to a flat bottom. This however would create a tendency for the cells to shear over as discussed previously and would cause other detrimental effects.

In another embodiment of the invention, holes or slots could be added in the webbing area between air cells, so that air could flow from the top half of the air matrix through to the bottom and visa versa. This increased in air flow could be used to keep the user cooler than without holes.

In yet another embodiment, ports in the air cell matrix could be configured so as to link multiple parts together, creating a larger supporting surface as needed. This could be used, for example, to create a bedding surface from multiple smaller parts. This would have the advantage of being able to further tailor the system based on need, while also avoiding the cost of building a much larger mold for production (a significant cost).

For any of these embodiments, a control system could be added to control pressure automatically, by used of an electric air pump and electronic control box. This could be used, for example, to cycle the air pressure through separate quadrants, or to maintain pressure in multiple sections at different levels.

Method of Manufacture

The preferred method of manufacture of the present invention is twin-sheet thermoforming. This process has large advantages over prior approaches in the manufacture air-filled seating devices. The following section helps to summarize this process from beginning with plastic selection to ending with finished parts.

The twin-sheet thermoforming process begins with extrusion of the chosen plastic to a desired film thickness. Exact thickness of plastic should be determined before production by forming parts from various plastic thicknesses first (for example, targeting 0.020″ thick film). This is because some amount of sagging occurs when the plastic is heated and before it is vacuum formed against the molds. This sagging thins the material slightly, so that the resulting thickness for finished parts is lessened to some degree. Since extrusion companies have minimum orders, and larger runs reduce overall cost per pound of film, it is important to take the time to determine what the right thickness is based on the actual forming process. This will avoid purchasing plastic that is either too thin or too thick.

Plastic is then extruded based on the width necessary to envelope the mold and be clamped into “clamp frames” outside the edges of the mold. Typically, about one half inch in extra width is needed on each side of the mold to permit this. As discussed previously, a number of plastic types could be used for the present invention, including but not limited to urethanes, vinyls, polypropylenes, polyethylenes and special formulations that combine some of these together (for example vinyl with urethane to minimize cost).

The extruded plastic is then delivered to a company capable of twin-sheet thermoforming thin plastic film. As mentioned earlier, this process involves simultaneous thermoforming of top and bottom halves of a plastic part, then quickly joining these halves together while at the plastic's forming temperature. In the case of the present invention this would result in a complex matrix of air cells, interconnecting passages and one or more inflation features in a single manufacturing process, greatly reducing manufacturing costs over previous methods. Also as mentioned earlier, one major benefit of this method over prior approaches is in the elimination of RF welding. By forming both sides at the same time and mating both halves together in the same operation, many subsequent problems with RF welding can be eliminated. Weld lines can be much more tightly controlled, handling damage from RF welding can be avoided, and final trimming can be accomplished before the thermoformed parts are ejected from the vacuum molds. The production rate with twin-sheet thermoforming can be accomplished much faster than single sheeting and RF welding, minimizing machine time and therefore cost.

Twin-sheet thermoforming offers a number of other benefits which may not be apparent to those skilled in the art of thermoforming. First, twin-sheet thermoforming allows much more elaborate designs to be manufactured as detailed above, enabling the creation of the present invention and variations within its scope. Second, twin-sheet thermoforming allows creation of interfacing ports for the attachment of air valves and the like, as opposed to previous methods which require additional processes for this.

Third, twin-sheet thermoforming allows interconnecting air channels of multiple designs to easily be designed in and formed, as well as features to avoid excess thinning of plastic for the present invention. Fourth, twin-sheet thermoforming is very repeatable, ensuring high-quality parts can be consistently made, unlike other manufacturing methods. Fifth, when parts are joined in this process, heated material pushes inwards at the weld seam, forming a “bead” of material along all welds for extra strength. This is especially important when starting with a thin film of plastic as with the present invention. RF welding, in contrast, relies on the width of the weld, or “weld margin” for sealing strength. Sixth, the twin-sheet thermoforming process results in slightly thicker plastic closer to the parting line 28, because it cools when it first touches this area, then stretches into the depth of the forming cavities. This material distribution allows the vertical air cell walls to maintain a tube-like shape while under the load of the user, allowing air to flow more freely in a horizontal direction and out the perimeter of the air cell device. Finally, twin-sheet thermoforming allows parts to be trimmed as part of the forming process, by designing the molds to cut through the forming material as they are pressed together, removing the “flash” (waste material) used to hold the plastic in clamp frames described earlier.

Twin-sheet thermoforming has some additional benefits as well. It allows the function and/or look of the product to be changed by simply using a different thickness, type, or color of plastic. The same tooling can support manufacturing with all of these options, greatly reducing manufacturing cost to make these changes. If a change in design needs to be made, a new set of forming plates can be machined and attached to the mold bases (which interface with the manufacturer's vacuum and cooling systems) used with the initial forming plates. The cost of a new set of forming plates for the size of the present invention is very reasonable (less than $3,000 depending on complexity).

FIG. 6 shows the thermoforming molds A (number 30) and B (number 32) in perspectives for clarity, to help illustrate the twin-sheet thermoforming process. The forming plates are the exact shape for each half of the air cell matrix of the present invention, and include many small vacuum holes that allow the heated plastic film to be vacuum formed against this shape. The vacuum holes are sized so that they avoid pulling plastic into them in the forming process, so for example using 0.020″ thick film as a rule of thumb would require no larger than 0.020″ dia holes (very small). These forming plates are each mounted to a mold base 34 that interfaces with the manufacturer's twin-sheet machine, and includes mounting provisions, plumbing for vacuum and cooling tubes to control the temperature of the forming plates during manufacture. This temperature is very important, as it effects how the plastic thins out when it is vacuum formed against the forming plates. The mold base/forming plate assemblies (collectively called molds) are then mounted into the twin-sheet thermoforming machine, where they are aligned so as to mate together properly and provide a desired gap, or end thickness of material, where the forming plates come together. This gap is controlled by stops which are set to ensure that the forming plates come together the same distance every time. Once this is accomplished, clamp frames are installed to hold “blanks” of plastic film (one for the top and one for the bottom). The forming process can then begin.

For the forming process, two “blanks” (pre-cut sheets) of plastic 36 are loaded into their respective clamp frames, and then moved into a large oven that provides even heating of the blanks. This oven is usually computer controlled, and has an infrared eye that records temperature across the blanks when they exit the oven to ensure proper temperature control. The heated blanks are moved between molds A (30) and B (32), where one blank is vacuum formed against the mold A and one is vacuum formed against the mold B. Immediately following this, both molds are brought together so that the top half of the part is fused to the bottom half at the parting line. It is crucial that the forming and joining process happens very quickly, as heat is quickly lost from thin plastic. If timing from the oven to joining of halves is excessive, proper fusing of the materials will not occur.

The formed part is then ejected from the mold, die-cut on the perimeter (if not already trimmed in the mold), and ready for installation of pneumatic fittings to complete the system. Because of the weld bead, it may be necessary to smooth out the inner bore of the interfacing ports so that they properly seal tightly against their respective pneumatic fittings. FIG. 7 shows a flow-chart of the twin-sheeting process for further clarification.

Utilizing the twin-sheet thermoforming process to create the present invention has valuable benefits over methods to create prior air-filled devices. The benefits of this manufacturing approach make the present invention feasible in terms of design and cost, allowing its unique function and performance to be manufactured as efficiently as possible.

It is to be understood that while certain forms of the present invention have been illustrated, it is not to be limited to the specific forms described herein. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention or its potential applications.

Claims

1. A conforming and supportive air cell cushioning device comprising: a) upper and lower sheets of plastic that are each formed into a plurality of air cell halves;b) said formed sheets joined at a common parting line to form a plurality of air-tight cells;c) said air cells being interconnected with air flow passages to equalize pressure from cell to cell and;d) overall pressure of interconnected cells controlled by means of one or more inflation valves.

2. The cushion of claim 1 manufactured through the process of twin-sheet thermoforming, wherein said upper and lower sheets of plastic are simultaneously heated in an oven, then are vacuum formed against specialized molds to form upper and lower air cell surfaces, and sealed together at the common parting line by bringing said molds together while at the plastic's forming temperature.

3. The cushion of claim 2 where the forming process includes creating one or more features for attachment of inflation valves.

4. The cushion of claim 2 wherein flash material is trimmed off when upper and lower molds are pressed together.

5. The cushion of claim 2 wherein multiple parts are made with each forming cycle.

6. The cushion of claim 1 such that the common parting line of the air cells serves to stabilize each air cell from side to side, to minimize the likelihood of shearing over when under load.

7. The cushion of claim 1 where the parting line can be either in the middle or off to one half of the air cells to create a specific cushioning effect.

8. The cushion of claim 1 such that individual air cells are generally hexagonal in shape extending from the parting line, with rounded outer edges and angled side walls as necessary so that when compressed under load there remains a flow path of air along the outer cushion surface to the surface of the user, in order to prevent heat buildup.

9. The cushion of claim 1 such that individual air cells are generally rounded in shape extending from the parting line, with rounded outer edges and angled side walls as necessary so that when compressed under load there remains a flow path of air along the outer cushion surface to the surface of the user, in order to prevent heat buildup.

10. The cushion of claim 1 wherein holes or slots are added between air cells to allow for the vertical flow of air down and away from the user.

11. The cushion of claim 1 such that interconnected air passages are of a narrowed eye shape, to allow for flexibility between air cells and easier vacuum forming.

12. The cushion of claim 1 such that interconnected air passages are slightly larger where needed to facilitate faster inflation and deflation.

13. The cushion of claim 1 where interconnected passages are grouped from side to side or from front to back in order to enhance stability of the user, such that quadrants of air cells can remain separated with separate inflation features, or remain connected through orificed passages.

14. The connected orificed passages of claim 13 where said orificing produces a “breathing” sound when the user shifts their supported weight.

15. The cushion of claim 1 where additional ports are used to mate multiple cushions together, creating a larger supporting surface as needed.

16. The cushion of claim 1 where cooling or heating air is made to pressurize the device and flow it at the same time, by orificing pressurant air through an overboard bleed valve.

17. The cushion of claim 1 wherein said sheet of plastic are comprised of “soft-handed”, highly compliant materials such as polyurethane, vinyl, polyurethane/vinyl blends, or polypropylene.

18. The cushion of claim 1 wherein said sheets of plastic are between 0.010″ and 0.040″ thick.