Patent Application
20130309438
Self-reinforced thermoplastic composites have found utility in a variety of fields. Much of the previous innovation has focused on performance attributes, including the ability to shape, reshape and join the composite pieces. Some attention has been given to the material in terms of its potential for recycling and closed-loop “cradle-to-cradle” product cycles or systems.
The assignee hereof is in the business of implementing environmentally friendly solutions as its members successfully demonstrated on the Plastiki project. The Plastiki boat was built using a composite frame securing 12,000 two-liter bottles for buoyancy. The frame elements, together with the boat cabin, furniture, rudder and other structural features we built from srPET (self-reinforced polyester) material. Thus, if ever stripped of its rigging, the Plastiki can be fully recycled. It can be inserted into the PET recycling stream and fully utilized in any number of newly-minted consumer goods.
The building of the Plastiki and its voyage across the Pacific Ocean are well publicized. The vessel embodies a vision of recycled/recyclable product use. Through this vision, the public learned key messages of conservation.
Unexpected, however, was the public's keen interest in the underlying srPET technology upon which the craft was built. Government representatives, academic leaders, corporate chiefs and others voiced immediate interest in high-value structural goods produced with this recycled “high-tech” material. That interest represents a need which has not been met by others working in the thermoplastic composites field.
To be sure, many of the components produced according the to the present inventions can be (and have been) made otherwise. For example, a boat rudder or surf board fin can be contour-machined from a simple block of pre-consolidated layers of thermoplastic composite material. But the cost of a machining approach (in terms of time, wear-and-tear on equipment, material waste, etc.) is extraordinary in comparison to structures made according to the teachings herein. Also, parts produced according to the present inventions compare favorably to injection molded pieces in terms of cost and finish. However, they offer marked performance advantages.
The present inventions provide a cost effective solution for producing contoured thermoplastic composite goods—especially long fiber reinforced goods. So-produced, these goods offer tremendous market potential and the ability to source production without extreme sensitivity to labor cost. Unlike many existing composite industry production approaches, the subject approach is highly amenable to automation. Yet, the subject approach is still perfectly suitable for production in rural or under-developed locale.
The contours of the shaped goods made according to the present inventions are produced employing a topo-slice stacking approach. As with terrain features illustrated in a topographical map, the contours in the goods produced according to the inventions can vary in two dimensions across the height/depth of the article. Stated otherwise, the structures may be curved or contoured in two directions across the surface of the part perpendicular to a third direction (i.e., varying in shape in both in X and Y directions when progressing along a Z-axis as contrasted to an I-beam or structural C-shapes which have a consistent cross-section taken along the Z-axis).
In one aspect, cutout layers of fiber reinforced composite material including a thermoplastic polymer matrix are stacked upon one another. These layers may be fully flexible fabric layers. Or they may be stiffer partially or fully heat-bonded and consolidated (i.e., compressed under heat to remove air pockets/content) layers. As described below, certain advantageous mixed layering approaches are contemplated. Likewise, advantages are noted in connection with employing bonded/consolidated (at least in part) members alone.
The subject goods are advantageously produced using srPET composite material to facilitate recycling. High melt (a high tenacity/reinforcement fiber component) and lower melt (a matrix material component) portions of the srPET material are advantageously comingled with one another in tows of material woven into fabric. When heated to an appropriate temperature, the low-melt material flows to impregnate the solid-phase high-melt material. Upon cooling (in the case of srPET) a monomeric (and thus easily recyclable) composite material results. However, it is to be understood that the teachings herein are not limited to use of srPET, but generally applicable to other thermoplastic composite materials such as produced by Comfil, Inc. and others. Several examples of suitable thermoplastic composite materials offered by the noted vendor are presented in the table below:
Other suitable materials to form layers of composite material utilized in the present inventions are described in any of U.S. Pat. Nos. 3,765,998; 4,414,266; 4,238,266; 4,240,857; 5,401,154; 6,828,016; 6,866,738 and US Publication Nos. 2001/0030017 and 2011/10076441 and others.
Regardless of material choice, according to one aspect of the present inventions, a stack of composite layer cutouts is set in a mold and heated to bond the layers together. With starting material that is fully bonded/consolidated, molding cycle times are reduced. It may be further reduced by using even lower melt temperature film adhesives on or between the pre-consolidated layers. Still, the layers may comprise un(heat) modified fabric incorporating matrix material or layers of fabric or matt together with some number (i.e., more or less in number) of flowable thermoplastic layers to provide the composite material matrix in the final composite layer(s).
Indeed, using pre-consolidate layers offers the additional advantage of eliminating distortion of fiber direction during molding. In essence, the “fixed” composite cloth does not deform/stretch, bunch, fold or kink the fibers. Also, the process effectively eliminates shrinkage issues commonly incurred when comingled or dry fiber tape thermoplastic hybrid fabrics are heated to thermoforming temperatures.
However configured, the stack can be setup in a mold such that material expansion upon heating provides the requisite internal pressure to produce a fully consolidated final part (i.e., a piece without significant air bubbles). Such a setup may simply involve clamping opposing mold pieces in a heated press, it may involve individually spring-loaded mold pieces set in an oven, or any other appropriate approach as commonly employed in bonding and consolidating thermoplastic composites (e.g., the so-called “trapped-rubber” approach in which a releasable silicone rubber layer provides pressured upon heating).
Additional optional aspects of the inventions concern the manner in which steps between the topo layer stack are smoothed to produce finished goods with a suitable surface finish. By “suitable” what is meant depends on the context. Namely, aerodynamic/fluid-flow and/or consumer grade finishes may require an extremely uniform and smooth finish.
Complex three-dimensional shapes are optionally produced in accordance with the present inventions. They are “complex” in two domains. One domain involves stacking pieces to define topographically varying layered structures. The other domain involves provision to smooth-out the topography. Namely, smooth surface net-shape pieces (or near net-shape pieces requiring minor/cosmetic surface finishing/machining) are formed in connection with a molding approach in which tuned mold gaps (and—optionally—relief ports) permit flow of the thermoplastic composite matrix material to fill or span transitions between the fabric layers and/or adhere edges. In other words, the relation between layered “slices” of material and the wall of a mold cavity are provided to enable matrix material flow to fill-in the steps of the stack as webbing. Likewise, the manner in which the slices (typically cutout sections of a larger composite material sheet) are stacked can have an impact on such material flow as illustrated below.
For the purpose of using the matrix material integrated in a comingled tow to produce the desired flow-fill and/or surface finish, a higher percentage (e.g., 50-60% or upwards) of matrix-to-structural fiber mix in the fabric employed may be desired in the composite material. Proportionally “doping” a comingled composite fabric in this manner provides for a desirable amount of matrix material to flow and fill and smooth the final shape. An entire part may be produced using such fabric. Alternatively, doped fabric (or comingled thermoplastic mat) may be set exclusively over stepped layers (where practical) as a functional veil or cap layer. Another capping approach involves using a matt or film of flowable matrix-type/like material only over stepped surfaces.
To conform to dramatic topographical variation, either the film, matt or fabric can be strategically cut, scored or relieved at sections to permit draping. For such purposes, the material is advantageously unbonded/unconsolidated so that it can conform to the underlying structure as best as possible. However, parts with limited or low convexity/concavity may employ stiffer capping members and rely on a complimentary mold surface to push the part into shape. Incorporating provision for vacuum in a mold element may alternatively, or additionally, be used in connection with such a matter or otherwise.
Yet, it will often be the case that the topographic layers are not overlaid by other material so that the steps formed between the layers directly face the mold surface. In some instances, the topography may simply not allow for material overlay without wrinkles or buckling in the material. In other instances, interference to polymer flow within a part by virtue of a topping layer or with reshaping perimeter fibers of the composite layer(s) will not be acceptable.
With specific reference to this last consideration of perimeter fiber manipulation, it may be desirable that the perimeter fibers in composite material are free to face, front or form the surface of the part. Particularly where a sharp, durable edge is desired in the final piece (or an intermediate product thereto) running reinforcement fiber all of the way to the edge of the structure where they can be splayed or flattened out against the surface of a mold cavity when heated to force matrix material flow (instead of being covered) can be desirable. Skateboards so-produced offer an example detailed below.
Interior features to the product may be incorporated as well—or in the alternative to the optional complexities described above. Specifically, product body coring and through-hole locating techniques are contemplated. As a variation of a location feature, screws or bolts may be used to make or pass through multiple aligned layers. Flow of matrix material around the fastener threads during heating then define female threading in the part. If/when the fastener is removed, the resulting threaded socket can serve as a convenient and durable attachment interface for supplemental hardware (such as skateboard trucks, hinges, other composite parts, etc.).
In another approach, threaded metal inserts are incorporated in the piece. These may be exposed at the surface or encased such that the surface of the part is drilled-out to open the socket. Alternatively, the member(s) encased in the finished part may only serve the purpose of leave-behind locating dowels/pins (such elements produced in foam, solid plastic or otherwise).
Layer separation techniques may also be employed. In one example, a stack of cutouts is laid-up with a non-bonding layer between opposing surfaces. PTFE may be used for this purpose. A living hinge between finished (or substantially finished) sub-section pieces can be constructed this way. Alternatively, an open pocket can be formed by air pressure expansion of an otherwise consolidated and bonded-together stack of material. Such an approach may be useful in the production of hot water solar panels. Likewise, channels may be incorporated (e.g., using straw elements or by preserving separated/separating sections to be opened by a secondary shaping procedure as per above) to fluidly couple various chambers together. Parallel and series arrangements are contemplated as are more complex possibilities.
As referenced above, in preparation for producing parts according to the present inventions, all of the desired shapes/sizes can be cut from pre-bonded/consolidated material. Using a CNC drag knife or other means to shape the pieces (such as stamping, water-jet cutting, etc.), kits of parts can be produced with minimal waste generated between parts arranged in complimentary or “nested” fashion. Utilizing material that is at least partially bonded is useful for handling. Utilizing fully bonded/consolidated material offers advantages in terms of heat transfer and minimizing cycle time.
In a sense, the complimentary cutout approach resemble a puzzle-piece pattern. More literally, it is contemplated that the cutout pieces may be configured assembly into larger layer sections utilizing a jigsaw fit technique—especially with fully or partially consolidated parent material.
In this regard, unique interfitting/interlocking shapes may be employed to ensure only one possible assembly configuration. The interlocking sections/portions of pieces may be capped or sandwiched between facing sections/portions. The interlocking members be interleafed with non-interlocking facing/capping layers. In any case, such features may assist in terms of design for assembly and/or in creating larger surfaces than the parent material from which the shapes are cut. The approach may also provide assistance in conforming to curved surfaces (e.g., in assembling a ball or globe) or another structure. In any case, the interfitting elements (optimally referred to as tongue & grove elements, lock & key elements or otherwise) are heated with the rest of the material (in a mold, press or vacuum bagged to a surface, etc.) to cause matrix polymer to flow and permanently lock the final shape of the product upon cooling.
Instead of arranging the cutout pattern in complimentary fashion during cutout and/or assembly, the pieces may instead be organized for side-by-side molding and connected by bridges of material for handling purposes, then stacked with other sequential slices in the mold. The bridges may be received by mold section gaps to allow for gang-molding multiple cavities at the same time. Such an approach maximizes production efficiency.
Even with such an approach (i.e., the bridge-connected cutout approach) waste can be eliminated in another manner. Specifically, the so-called “waste” from cutting out patterns to produce topographical part elements can itself be “engineered”. Uniform size chips or biscuits can be cut, punched or stamped from between the sections of the main-body material. These “engineered” leftovers are advantageously strong given their incorporation of long fiber reinforcement. They may be collected in a hopper and fed into a re-shaping process in which a three-dimensional body (such as by folding, bending or stamping) is produced. In one example, chip fill so-engineered is poured into a cavity within a part produced with topographical slices. When the part is heated to bond the layers together, the fill is sintered into an intermediate-weight coring material. A roofing shingle is advantageously so-produced. Alternatively, the material may be used as feed stock for extrusion or injection molding. In which case, the pieces may be sized in order to provide an ideal length to the long fiber reinforcement incorporated in the material. As such, it may serve as feed stock according to methods of producing Low Weight Reinforced Thermoplastic Composite (LWRT) as taught in co-pending provisional patent application entitled, “Low Weight Reinforced Thermoplastic Composite Goods” to the assignee hereof as filed on even date herewith and incorporated herein by reference in its entirety.
In all, it is to be understood that the innovations presented herein include a number of thermoplastic construction “tools” suitable for producing high-value self-reinforced composite structural goods (recreational and otherwise). These may be paired/utilized in connection with known techniques for handling such material. The present inventions also include the subject products, kits (for production, distribution, sale or otherwise) in which they are included and methods of manufacture and use. More detailed discussion is presented in connection with the figures below.
The figures provided herein may be diagrammatic and are not necessarily drawn to scale, with some components and features exaggerated for clarity. Variations of the inventions from the examples pictured are contemplated. Depiction of aspects and elements of the inventions in the figures are not intended to limit the scope of the inventions. However, the content of the figures may serve as the basis for claim limitations—as originally presented or as introduced by amendment.
As per above, the present inventions include constructional techniques as well as finished goods produced thereby. The techniques can be regarded as new “tools” that can be applied broadly across the composites fields, especially within the self-reinforced composite field. As such, various exemplary embodiments are described below. Reference is made to these examples in a non-limiting sense. They are provided to illustrate more broadly applicable aspects of the present inventions. Various changes may be made to the inventions described and equivalents may be substituted without departing from the true spirit and scope of the inventions. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s), spirit or scope of the present inventions. All such modifications are intended to be within the scope of the claims made herein.
Turning to
In any case, the provision of cutouts and the layering of them is performed to yield final parts (i.e., products) different than the simple radius-filler and beam-type elements known in the art such as those in U.S. Pat. No. 6,709,538 and US Publication No. 2007/016559. These known shapes and associated approaches are consistent in shape along an axis during after molding. The method of products according to the present inventions are thus distinguished in each of their curvilinear cutout and final shapes, curved surfaces and such other feature as described herein.
However configured; the layers may be stacked on an assembly platen, table or platform and subsequently be vacuum bagged, run through a press, or assembled within a mold that is closed or set within a press, etc. At 150, the assembly is heated (typically under pressure, or with pressure caused by thermal expansion) to cause a matrix material in the thermoplastic composite material to flow and fill in the steps. As such, a webbing of a matrix material from the (optionally comingled) thermoplastic composite material forms a substantially uniform exterior surface between the layer perimeters.
Next, at 160 the assembly is cooled, allowing the matrix material to solidify and set a final shape. Such cooling may be actively accomplished, under ambient conditions or otherwise. A final product may receive further finishing at 170 such as trimming-off of solidified flow through mold gates, parting-off ganged pieces, etc.
Through the layering, the steps between the layers define a curved surface of the structure. The curvature may be defined in two different directions. Further, the opposite sides of the structure may both be curved, with opposite convexity. Optionally, no layer in the assembly to be heated or the final consolidated structure has a periphery substantially overhanging another relative to a facing surface of a mold cavity in which it is set and heated, and the flow filled steps produce a uniform surface exposed as an exterior surface of the final structure upon mold cavity removal. Alternatively, the flow filled steps may define a substantially planar surface in the finished part. In any case, the finally shaped part may be bonded to a similar or identical part (as in two sub-assembly halves of a structure) at 180 to produce a final part at 190.
During manufacture, coring material (e.g., structural foam, honeycomb, LWRT, etc.), locator pins, mold bosses, etc. may be received by the layers (e.g., during layering 110) per variations described below, or otherwise. Other variations to the methods as may subsequently be claimed will also be apparent given the structure of the exemplary embodiments described in detail below.
In a first product example,
When the cut-out interior slices are independently stacked upon one another (as opposed to being included in a pre-laminated structure), the core pieces offer assistance for alignment thereof. For this purpose, the members may be sized to offer a close-fit or light press-fit relationship. The strategic use of cavities left open for the insertion of core elements are also potentially useful for weight reduction, tuning flexural characteristics and for vibration absorption.
Pre-punched or milled holes 230 where through-hole bolt patterns may be desired in the final part to enable rapid and simplified alignment of the various layers with pins through the mold. Further assisting assembly, the use of multiple thin layers of composite material enables bowing and/or slippage between the elements as they are stacked into a contoured mold cavity.
As further illustrated in
In certain cases, additional (i.e., more than strictly necessary) optional layer(s) of composite are used and stacked into a mold to develop higher pressures as the matrix is squeezed out of the pre-consolidated panels at thermoplastic flow temperatures. Alternatively, a “trapped rubber” element (e.g., a silicone rubber pad—shaped to fit within the mold cavity and defining a wall thereof) can be employed to expand as it heats and provide the pressure. Such an element may advantageously include a texture features to integrally mold “grip tape” (or other) features into the surface of the part such as functional and/or cosmetic texturing to a shingle so-produced.
Except for such areas to be trimmed off in a finishing step, the molded part is otherwise net shaped upon exit from the mold. This result can advantageously be accomplished with the need to profile cut the sheets of composite material. Rather, steps 256 between layers (as shown in either of
In another variation, the specialty layer may be a slice in the stack that serves as a release ply (e.g., comprising PTFE). It may go to the edge of the fiber reinforced layers or terminate inboard of them. In the former case, matrix material filling an adjacent mold cavity section 252 can leave a bead along the finished part to serve as a living hinge. In the latter case, the release ply may facilitate separation of the layers along to ply for a reforming step to expand the part and form a bladder. In yet another variation, the specialty layer is a dissolvable member to provide for (ultimate) layer separation. Various water soluble or chemical-solvent dissolvable foams or substrates may alternatively be employed. Still further, the specialty layer may be a layer of silicone rubber to facilitate producing molding pressure.
Another option aspect concerns part alignment utilizing insert pins or dowels internal to the part as illustrated in
More generally,
Reference to
In any case, it can be observed that the smaller layers 314 are set in what will be the interior of the part. They are, thus, hidden in a sense “underneath” relatively larger outer layers 316. Regardless, their different varying extent produces the curved exterior shape in each subcomponent 312/312′.
Essentially, a comparison of the approaches shown in each of
In the case of the embodiments pictured in any of
Notably, at least the uppermost slice in the stack “U” (see final pieces illustrated in
In any case, cutouts 400 are shown fully overlapped within mold 500, set within multiple mold cavities 502. As shown, the proximal extent display topographical contours. The extent of these can be varied to incorporate any more of the shingle intended to be shown on a completed roof. As such, capping shingles may be surrounded by visually appealing features.
In any case, mold 500 includes connector gates 504 to permit outflow of excess matrix material. A top or cover 506 to the mold may be bolted-on, or alignment pins may be provided in guide holes 508. Optional connector section 510 between the mold cavities accommodate bridges 410. A textured and/or contoured silicone pad 520 may also be secured within the mold (or press) elements. Such a pad may be to provide pressure upon heat expansion, a pattern for surface texturing or both.
The proximal extent 610 of the coordinated set 620 of shingles is pictured as a series of complex curves by topographical lines depicting a natural or “enhanced” shape. The sculptural graphics (i.e., complex curvature) between each separate/separable unit is coordinated with the other to be visually attractive and avoid jumps or discontinuities that interfere with the visual and physical operation of the system. Namely, squared/sharp/discontinuous edges are avoided, thus reducing pockets for water stagnation and fungus growth, catching clothing, etc. when treading on the roof, etc. The shingles may be individual/separable, or variously bonded together in a lot as shown.
As for such association of shingles or other elements with one another for manufacture or for final assembly,
In
Unique interfitting/interlocking shapes and/or orientations may be employed to ensure only one possible assembly configuration as shown. The interfitting/interlocking elements 702/702′ may be overlaid (or trapped between two) facing member(s) 720 to secure the puzzle lock for ease of handling upon selective application of heat to flow and bond matrix material (e.g., through ultrasonic welding, etc.). Similar layers may be stacked in a mold to complete a final part or series of parts to subsequently be separated. The interlocking members be interleafed with non-interlocking facing/capping layers or similarly-constructed puzzle-piece members where the interfitting elements are staggered/unaligned.
In any case, the features may assist in terms of design for assembly and/or in creating larger surfaces than the parent material from which the shapes are formed/cut. The approach may also provide assistance in conforming to curved surfaces (e.g., in assembling a ball or globe) or another structure. In any case, with panels 700 constructed as shown in
In
It is contemplated that any optional feature of the inventive variations described may be set forth and claimed independently, or in combination with any one or more of the features described herein. Reference to a singular item, includes the possibility that there is a plurality of the same items present. More specifically, as used herein and in the appended claims, the singular forms “a,” “an,” “said,” and the include plural referents unless specifically stated otherwise. In other words, use of the articles allow for at least one of the subject item in the description above as well as the claims below. Likewise, a matter described as “substantially” having some quality includes the possibility that it fully or completely possesses that quality. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only,” “alone” and the like in connection with the recitation of claim elements, or use of any type of “negative” claim limitation.
Without the use of such exclusive terminology, the term “comprising” in the claims shall allow for the inclusion of any additional element irrespective of whether a given number of elements are enumerated in the claim, or the addition of a feature could be regarded as transforming the nature of an element set forth in the claims. Except as specifically defined herein, all technical and scientific terms used herein are to be given as broad a commonly understood meaning as possible while maintaining claim validity.
The breadth of the present inventions are not to be limited to the examples provided and/or the subject specification, but rather only by the scope of the claim language. Use of the term “invention” herein is not intended to limit the scope of the claims in any manner. Rather it should be recognized that the “invention” includes the many variations explicitly and implicitly described herein, including those variations that would be obvious to one of ordinary skill in the art upon reading the present specification. Further, it is not intended that any section or subsection of this specification (i.e., the Summary, Detailed Description, Abstract, Field of the Invention, etc.) be accorded special significance in describing the inventions relative to another or the claims. Any of the teachings presented in one section, may be applied to and/or incorporated in another. The same holds true for the teaching of any of the related applications with respect to any section of the present disclosure. The related applications are:
This application is a continuation of International Application No. PCT/US2012/023031, filed Jan. 27, 2012, which claims priority to U.S. Provisional Application Ser. No. 61/437,492, filed Jan. 28, 2011, both of which are incorporated by reference herein in their entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 61437492 | Jan 2011 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2012/023031 | Jan 2012 | US |
| Child | 13950899 | US |
