Abstract:
The composite model construction uses a semi-flexible expanded polypropylene foam plastic core with a thin, semi-rigid polycarbonate plastic shell adhesively attached to the core. The core includes various rigid structural members installed therein, as required, for sufficient structural stiffness for the model. The core and plastic shell components may be formed by injection molding, vacuum forming, or other processes. The model construction method provides a highly accurate outer surface for a model, with the outer shell being formed with scale details, such as panel seams, rivet lines, etc. during the molding or forming process. A motor or other prime mover may be added to the composite model body. The materials used in the composite model are resilient with a flexible yet tough outer shell to resist impact damage, and allow repairs to be made quickly and easily when required.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/536,906, filed Jan. 16, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to miniature model vehicle construction methods and materials. More specifically, the present invention comprises the use of reinforced non-rigid foam plastic material for the core of a model structure, with a thin, preformed, semi-rigid plastic sheet material used to cover the foam core with its reinforcements.  
         [0004]     2. Description of the Related Art  
         [0005]     Miniature models, particularly flyable aircraft models, have conventionally been constructed of relatively lightweight materials using much the same componentry as in full-scale aircraft. While weight is not so critical in model boats and cars, it is still of some concern in that better performance is achieved with lighter weight vehicles. However, such traditional construction methods are quite time consuming, with the average total flight or operating time of a model being considerably shorter than the required building time.  
         [0006]     As a result, different materials have been used by many model builders in more recent model construction. Expanded polystyrene plastic (e.g., Styrofoam®) has been used to form the core material of various model structures, such as the fuselage, wings, and empennage for model aircraft. While such material is light in weight, it has numerous disadvantages in model construction. Polystyrene foam plastic is relatively brittle, and is subject to serious impact damage when used in operating models. Moreover, the porous material does not accept a fine finish, and requires covering with other materials in order to provide a realistic and aerodynamic finished model.  
         [0007]     Thin, flexible Mylar® plastic covering material, sold under the trade name Monokote® or Ultracoat®, has been used to cover foam plastic core model structures, as well as more traditional built-up balsa model structures. Such thin, flexible plastic sheet material has certain advantages over traditional paint-like coating materials, e.g., butyrate dope, in that it requires only a single operation to coat the model with no drying or curing time required, and provides a very glossy, attractive, and aerodynamically clean finish. However, it can be somewhat tedious to apply, in that it can be difficult to work around compound curves and requires a heating iron to soften the adhesive backing and shrink the material during the process to provide a taut covering. Even then, the finish is unsuitable for scale models (i.e. those models that replicate, in miniature, full size vehicles), as no scale panel seams, rivet lines, rib stitching, etc. may be formed in such a covering or coating without extensive additional labor, and the glossy finish may not be suitable for many scale models. Also, while the material is relatively durable, it is not completely resistant to punctures and tears, does nothing to protect the underlying structure from damage in the event of a hard impact, and requires frequent maintenance.  
         [0008]     The present inventor is aware of a large number of different materials and techniques which have been used in the past to construct model vehicles. One such technique is described in German Patent Publication No. 3,234,935 published on Mar. 22, 1984, that shows a model aircraft structure (e.g., wings and fuselage with traditional structural members comprising wooden ribs and formers) covered with a series of laminated foam and plastic panels. These panels are formed of relatively thin, composite sheets built up from a thin layer of foam, a printed plastic layer, a protective plastic film, and a plastic reinforcement layer. Another German Patent Publication, No. 3,438,602 published on Apr. 24, 1986, describes a model component, in particular a wing, formed of a polystyrene plastic foam core, a polyurethane foam coating, and an outer skin. The skin and core are placed within a mold and the polyurethane foam is injected between the skin and core, forcing the skin to conform to the inner contours of the mold.  
         [0009]     None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus a composite model construction and method solving the aforementioned problems are desired.  
       SUMMARY OF THE INVENTION  
       [0010]     The composite model construction and method comprises the use of a semi-flexible foam plastic core material, e.g., expanded polypropylene (EPP) foam, with semi-rigid plastic shell panels formed, e.g., from polycarbonate, adhesively attached to the foam core. Other semi-flexible foams or plastic shell material having similar properties may be used in lieu of those noted above, if so desired. Additional structure, e.g., spars, hard points for attachment of components to one another, etc., is installed in the foam core components as required. The foam plastic material used in the present invention is similar to plastics used in forming flexible foam “noodles” used as pool toys, as well as in some types of life vests and the like, and provides a certain amount of resilience in the event of impact rather than breaking or becoming permanently compressed, as is commonly experienced with models that utilize polystyrene foam components.  
         [0011]     The thin, semi-rigid plastic shell components used in the present model construction also provide a limited degree of resilience in the event of impact, but are sufficiently rigid and sturdy to accept permanently-formed detail molding therein, e.g., simulated panel seams, rivet lines, etc. A modeler may quickly and easily construct a model having a high degree of scale fidelity using the present model construction system. Yet, the materials may be patched and repaired to some extent if damaged, or entire shell components may be replaced as required. This assemblage of resilient plastic foam and flexible plastic outer shell provides improved solutions in model construction and use, specifically increased durability, simplicity of scale replication, and ease of repair.  
         [0012]     These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is an exploded perspective view of a model aircraft fuselage structure according to the present invention, illustrating various details thereof.  
         [0014]      FIG. 2  is an exploded perspective view of a wing panel assembly for a model aircraft according to the present invention.  
         [0015]      FIG. 3  is a chordwise elevation view in section of a model aircraft wing constructed in accordance with the present system.  
         [0016]      FIG. 4  is a transverse elevation view in section of a model aircraft fuselage constructed in accordance with the present system.  
         [0017]      FIG. 5  is a perspective view of a completed model aircraft constructed in accordance with the present system.  
         [0018]      FIG. 6  is a perspective view of a completed model boat constructed in accordance with the present system.  
         [0019]      FIG. 7  is a perspective view of a completed model car constructed in accordance with the present system. 
     
    
       [0020]     Similar reference characters denote corresponding features consistently throughout the attached drawings.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     The present invention comprises various embodiments of a model or miniature vehicle, a kit for the assembly thereof, and a method of manufacturing such a kit. While the miniature vehicle may be a model aircraft, as shown in  FIGS. 1 through 5 , it will be seen that the present invention lends itself to application to miniature or model boats and cars as well.  
         [0022]      FIG. 1  of the drawings provides an exploded perspective view of the fuselage and vertical empennage structure  10  of a model airplane kit or assembly according to the present invention, with  FIG. 4  providing an elevation view in section of the completed fuselage structure  10  and  FIG. 5  providing a perspective view of an exemplary model or miniature aircraft constructed in accordance with the present invention. The composite model construction provides for the use of a resilient foam plastic material, e.g., expanded polypropylene (EPP) foam, for the core components, i.e., left and right fuselage halves  12  and  14 , the vertical fin core  16 , and rudder core  18 . Such foam core components may be formed in master molds by injection molding for mass production purposes, or may be cut by means of an electrically resistive hot wire, or carved or otherwise formed by hand where mass production is impracticable.  
         [0023]     These components may have cavities formed therein to save weight and/or provide room for various components, e.g., a fuel tank/battery compartment  20 , receiver/relay compartment  22 , lightening voids  24 , etc. (The purposes indicated by the names of the above compartments and cavities, may be altered as desired by the builder of the model.) The two fuselage core components  12  and  14  are essentially mirror images of one another, although the vertical fin  16  may be formed integrally with either of the fuselage halves  12  or  14  if so desired. Thus, the various cavities, compartments, and voids  20  through  24  shown in the right side fuselage component  14  will be understood to be present in the left side component  12  as well.  
         [0024]     The use of expanded polypropylene provides great flexibility and resilience for the foam core components  12  through  18 , allowing them to recover and return to their original shapes after all but very severe impacts. However, chemical mixtures of expanded polypropylene and polystyrene and/or other foam plastic(s) (e.g., expanded polyethylene) may be used as desired. The foam plastic core material should be relatively flexible and resilient in order to preclude damage due to relatively minor or moderate impacts.  
         [0025]     The composite model construction also provides for the use of relatively thin, single ply, semi-rigid plastic outer shell components, e.g., polycarbonate plastic sheet or similar plastic, formed by vacuum molding or the like, for the outer covering components, i.e., left, right, top, and bottom fuselage panels, respectively  26  through  32 ; left side, right side and leading edge panels and tip cap  34  through  40  for the vertical fin core  16 ; and left side and right side panels and tip cap  42  through  46  for the rudder core  18 . More or fewer such covers, panels, and/or caps  26  through  46  may be provided for the fuselage structure  10  of  FIG. 1 , as desired, with it being possible to combine some of the panels as a single unit in some cases.  
         [0026]     The use of a thin, single ply, semi-rigid polycarbonate material to cover the EPP foam core structure of models in accordance with the present invention provides the ideal ratio of strength to lightness and rigidity to flexibility for an outer covering for the relatively flexible core structure of models built in accordance with the present system.  
         [0027]     Moreover, such polycarbonate sheet material is easily molded or formed (e.g., vacuum forming) to conform closely to the underlying shape of the foam core structure when adhesively attached thereto. The relatively firm surface (as opposed to flaccid sheet covering materials, such as fabrics, iron-on films, and Mylar®) is capable of holding scale detail thereon when formed, such as the simulated structural panel seams and rivet lines  48  shown on the outer surfaces  50  of the left side and top fuselage panels  26  and  30  and left side vertical fin and rudder covers or panels  34  and  42 . Such polycarbonate sheet material is reasonably flexible to absorb relatively minor impacts, but yet has sufficient rigidity to hold its shape and provide accurate scale detail when formed to simulate full-scale vehicles.  
         [0028]     The relatively soft EPP foam plastic material, from which the core components are formed, precludes direct mechanical attachment of various components to one another. Accordingly, a series of structural reinforcements may be provided for the attachment of various components to the underlying foam plastic core structure. For example, a separate engine mount plate assembly  52  may be adhesively attached to the nose of the assembled fuselage core halves  12  and  14 , with a lower wing attachment plate  54  secured to the bottom of the core halves  12  and  14  and a tailwheel mounting plate  56  secured to the aft end of the fuselage core halves  12  and  14 . Obviously, these components are installed in accordance with the basic configuration of the aircraft model, e.g., a high wing pusher powered model would have the engine mount at the rear of the structure and the wing attach plate in the top of the fuselage. Additional reinforcement (not shown) could be provided for the fuselage core halves  12  and  14 , if desired.  
         [0029]     Additional mounting structure is provided for the hinge attachment of the rudder  18  to the vertical fin  16 , by means of a vertical fin rear spar  58  and rudder leading edge spar  60 . These spars  58  and  60 , as well as the various “hard point” mounting components  52  through  56 , may be formed of woods conventionally used in aircraft construction, e.g., balsa, spruce, or basswood, or perhaps harder woods such as ash, in either straight grain or laminated plywood form, as desired for the particular installation. Alternatively, metal or composite material may be used for these components, e.g., aluminum or perhaps carbon fiber material as desired.  
         [0030]      FIG. 2  of the drawings provides an exploded view of an exemplary left wing panel assembly  62  which may be used with the fuselage assembly  10  of  FIG. 1 , with  FIG. 3  illustrating a chordwise section view of the completed wing panel  62  assembly. It will be understood that the unshown right wing assembly is a mirror image of the left wing assembly  62  of  FIG. 2 , with horizontal tail surfaces being smaller but having a similar general configuration (excepting provision for landing gear attachment). A single expanded polypropylene foam plastic (or polypropylene and other foam plastic mix, or other resilient foam) wing panel  64  is provided, with the wing panel  64  being covered by a series of semi-rigid plastic panels comprising an upper wing panel  66 , lower wing panel  68 , leading edge panel  70 , and wing tip  72 . As in the case of the various covering panels shown in  FIG. 1 , the wing and control surface panels of  FIG. 2  may be provided with simulated structural scale detailing  48  upon their outer surfaces  50 , if so desired.  
         [0031]     A rear spar  74  providing for control surface attachment is secured to the trailing edge of the wing panel core  64 , in the manner of the vertical fin rear spar  58  shown in  FIG. 1 . A control surface core  76  (e.g., flap or aileron) is covered by an upper and lower thin polycarbonate or other semi-rigid plastic panel, respectively  78  and  80 . One or both of the control surface panels, e.g., the lower panel  80 , may include a leading edge flange  82 . A control surface spar  75  is provided for structural reinforcement and control surface attachment.  
         [0032]     The flexible nature of the polypropylene foam plastic material from which the cores are formed, in combination with the semi-rigid property of the covering panels, results in a composite structure which may be too flexible to withstand extreme aerodynamic or other loads when in operation. This is particularly true of larger models. Accordingly, additional rigid structural reinforcement may be provided in the form of a rigid wing spar  84  embedded in a spanwise wing spar channel or cavity  86  molded or otherwise formed within the foam plastic wing panel core  64  to closely fit the rigid structural member. Other rigid structural members may be provided, e.g., a landing gear and wing center section attachment plate  88 , which provides for removable attachment of the wing structure  62  to the wing attachment plate  54  permanently mounted in the fuselage structure  10  (shown in  FIG. 1 ). This facilitates transport of the model in a “knockdown” configuration, i.e., with the wing structure  62  removed from the fuselage structure  10 .  
         [0033]     The various polycarbonate or other plastic material covering panels may provide a very accurate fit over the underlying core components. For aerodynamic purposes and sometimes for accurate scale appearance, the various panels should fit closely with one another with no overlap. One means of carrying out the accuracy of fit desired while still providing a flush outer surface for the covering panels is through an inwardly formed (i.e., slightly into the core material) “joggle”  90 , or offset in one cover panel edge, with the joggle  90  having just sufficient offset depth to match the thickness of the panel to which it is joined. Such joggle lap joints are illustrated in  FIGS. 2 through 4 , and are somewhat exaggerated in  FIG. 2  in order to show the concept clearly. In this manner, the panels may be joined with their outer surfaces  50  flush with one another and completely sealing the underlying core material from fuels, cleaning solvents, etc. which may contact the surfaces from time to time.  
         [0034]     The panels are adhesively applied to the underlying cores, with those panels having joggled edges  90  being applied first, and adjacent panels having plain edges applied next to overlay the joggled edges  90 . The joggled edges  90  may be formed with their inner lips extending upwardly or to the rear, in order that any fuels, solvents, etc. which may collect within the joint will drain or flow from the joint when the model is positioned upright, rather than working into the adhesive in the joint and ultimately working into the underlying core. Other types of joints may be used for the covering panels of the present construction system if so desired, e.g., butt joints, externally uneven lap joints, etc., but such joints do not provide both the flush outer surface and the relatively wide adhesion area between panels, that the illustrated joggle or offset joints  90  provide.  
         [0035]      FIG. 5  provides a perspective view of a completed miniature aircraft  100  or model airframe which has been constructed in accordance with the present composite model construction and method. While no engine or cowling is installed on the model aircraft  100  of  FIG. 5 , the engine is not a component per se of the present model or miniature vehicle construction, and the model may generally be operated without a cowling. However, a cowling formed of polycarbonate plastic sheet material, other plastic material, or fiberglass may be installed to surround and cover most or all of the engine to provide a finished appearance and/or more accurate scale appearance for the model  100 . It should be noted that  FIG. 5  lacks shell details, e.g. panel lines, rivets, etc., for clarity.  
         [0036]     While  FIGS. 1 through 5  illustrate an exemplary structure for a model aircraft, it should be understood that the present model or miniature vehicle construction system and method extend well beyond the model aircraft field. Other types of model or miniature vehicles may be constructed in accordance with the materials and methods described herein. For example, many different types of model aircraft may be constructed using the present system, e.g., helicopters and gyroplanes, gliders, and innumerable variations of powered, fixed wing aircraft. Non-flying vehicle models may also be constructed in accordance with the present model construction system, with  FIGS. 6 and 7  illustrating additional variations.  FIG. 6  illustrates a model or miniature boat  200 , while  FIG. 7  provides an illustration of a model car  300  which may be constructed in accordance with the present model construction system. It will be appreciated that the model boat  200  of  FIG. 6  may represent virtually any of innumerable different watercraft, from miniature personal watercraft to smaller sail and powerboats, on up to models of larger boats and ocean going ships. In much the same manner, the model car  300  of  FIG. 7  may represent a number of different wheeled and tracked ground vehicles, ranging from go-karts and the like to cars, trucks, and industrial off-road vehicles to tractors and various tracked military vehicles, as desired.  
         [0037]     The present model or miniature vehicle construction system lends itself well to use in forming a model construction kit containing most or all of the components required for completion of a model vehicle. For example, all of the various plastic foam core components and all of the plastic shell covering panels could be included in a single kit box or package for a given model. Any structural reinforcement members (e.g., spars, bulkheads, stiffeners, etc.), engine and other component mounting components, brackets, etc., landing gear, and other hardware could also be included in the kit, depending upon the degree of completeness and cost level desired for the kit.  
         [0038]     If the present model or miniature vehicle structure is provided as a kit for consumer purchase, some means may be provided for the mass production of the various components of the kit. The materials described herein provide another advantage for mass production, in that the materials are readily adapted to volume manufacture. The foam plastic core material is easily injection molded, with molding of the components requiring only a few minutes or less once the molds have been formed. Vacuum forming of the plastic shell covering panels is accomplished just as easily, once the master forms have been developed. Other components, e.g., spars, bulkheads, stiffeners, etc., may be quickly produced using conventional CNC machinery and die cutting processes known in the art. The components comprising the completed kit may then be conventionally packaged (boxed, etc.) with appropriate assembly instructions, and delivered to retail outlets or directly to the consumer for use.  
         [0039]     In conclusion, the present model or miniature vehicle construction system provides a much improved means of constructing a model aircraft, boat, or car, whether operable or for static display. The present construction system is particularly well suited for operating models which are subject to impact from time to time. The resilient nature of the foam plastic core material, in combination with the thin, semi-rigid but somewhat flexible preformed plastic covering shell(s) or panel(s), allow both the core and the outer covering panel(s) to flex upon impact and return to their original shapes where the impact is insufficient to cause permanent deformation or damage. In the event that permanent damage is incurred, the present model structure is easily repaired by (1) removing the damaged exterior panel(s) by peeling it from the underlying core and/or working a suitable adhesive solvent between the panel(s) and core, (2) cutting away and filling the underlying damaged core with an appropriate material, e.g., construction foam or an undamaged section of identical material, and (3) replacing the removed, damaged cover or shell material with a new shell component (or patching the original outer covering shell component, if so desired). The result is a model which is “good as new,” with a minimal amount of time required for the repair. Using the present system, a modeler may return the model to operation perhaps in the same afternoon as the damage was incurred, while equivalent damage to a conventional structure would perhaps require a full day or more for repair.  
         [0040]     The provision of an adhesively attached, preformed covering system for the present model construction may also allow the model builder to remove one set of covering panels and install a different set on the same underlying core assembly, if so desired. This is particularly valuable for scale model construction, where various versions (e.g., civil and military) of the same aircraft or other vehicle have been developed and the model builder wishes to change the appearance of the model from one to the other. The model builder may provide an extremely accurate scale representation of a different actual vehicle than the original in merely a few hours of work, using the present model vehicle construction system. The differences between different variations of the same vehicle may extend only to different paint schemes, which the covering panels of the present system may be colored to represent, or may extend to relatively minor changes in window location, fender flares for ground vehicles, wingtip configuration for aircraft, etc., which the covering panels can easily be made to represent as desired. Where differences are sufficient to result in some difference between the underlying core and the overlying plastic shells or covering, the shells may be formed to have a somewhat different shape or greater thickness in those areas where they may not be supported by the underlying core, or where additional strength in the outer covering or shell may be desired.  
         [0041]     The present system also lends itself well to semi-scale or non-scale models. The surface finishing panels may be provided with less than totally accurate scale details, if so desired, or may be provided with a completely smooth and undetailed surface in order to provide maximum aerodynamic efficiency. The present system allows for plastic panels to be provided in various colors as well as offered in different finishes such as laminated colored, metal or metal-like films or with screen printed or computer printed graphics. Additionally, the model builder can elect to apply conventional paints or similar coatings, plasticized films, fabrics, paper, or similar materials as desired to provide the desired appearance, just as in the case of more conventional model construction. Thus, the present model or miniature vehicle construction provides the model builder with a much quicker and more efficient means of constructing a model, while also providing greater durability and ease of repair for such a model if damaged. The present model construction system will thus be greatly appreciated by all modelers who prefer model construction systems which require minimal effort and time to complete.  
         [0042]     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.