Patent Publication Number: US-9896051-B2

Title: Truck bumper shell and method of retrofit installation

Description:
This application is a divisional of U.S. patent application Ser. No. 14/336,319, filed on Jul. 21, 2014, entitled TRUCK BUMPER SHELL AND METHOD OF RETROFIT INSTALLATION, issued as U.S. Pat. No. 9,487,170, which claims the benefit of U.S. Provisional Application Ser. No. 61/856,882, filed Jul. 22, 2013, entitled TRUCK BUMPER SKIN SYSTEM AND METHOD OF REPAIR, the entire contents of which are incorporated herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to pre-formed thin-walled members, or bumper shells, used to cover vehicle bumpers (such as truck bumpers) having new or damaged show surfaces, and more particularly relates to a bumper covering system that adds value in terms of appearance, customizability, novelty and curb appeal; protects the bumper from minor damage, reduces repair expense, improves ease of repair; and that provides optional new lighting and visual effects. 
     Bumpers used on most body-on-chassis trucks have traditionally been stamped steel, either chromed or painted, serving both decorative/styling and impact protection functions. The manufacturing process of stamping steel and the fact the stamping needs to provide an impact function places many styling restraints on these types of bumpers. Additional molded plastic trim pieces that cover portions of the stamping are used to provide some styling differentiation or function, such as a step pad. These trim pieces are usually molded-in-color black and textured and attached to the bumper with integrated snap fits and clips (see  FIG. 1 ). 
     Improvements are desired for several reasons. For example, bumpers quickly become worn or damaged, yet it is excessively expensive or impossible to have them repaired, such that truck owners do not get them repaired. This happens despite the fact that many truck owners are very proud of their trucks and want the truck to be a show piece (even after heavy use). Still further, many truck owners want to be able to customize their trucks, both to make the truck unique and customized to their personality, but also often to “make a statement” with their truck. However, existing bumper covering systems are generally either too expensive to allow the truck owner to make the truck unique, and/or do not cover existing damage. For example, full fascia systems require expensive tooling, resulting in high cost of amortization and subsequent painting. Although chrome bumpers cannot be repaired to their original state, small dents/dings can be pounded out, ground down, and the bumper painted. However, this repair is very time consuming and costly and the paint is easily scratched off, with the underlying chrome showing through. Bumpers can also be vinyl wrapped. However, the thin vinyl conforms to the surface of the bumper, thus any existing damage would read through to the outer surface. The reader&#39;s attention is directed to the discussion of prior art bumpers illustrated in  FIGS. 1-4  below. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a method of repair comprises attaching a pre-formed polymeric shell to a formed vehicle bumper beam to cover a show surface of the vehicle bumper beam, the pre-formed polymeric shell having a non-planar three-dimensional internal surface that generally matches an original undamaged shape of the show surface and having sufficient rigidity to maintain a shape of the polymeric shell without full contact against the show surface of the formed vehicle bumper beam. 
     In another aspect of the present invention, a method of trimming a shell component comprises using a vacuum-forming tool to form a vacuum-molded component that includes a shell and a raised tool guide extending around a perimeter of the shell, the raised tool guide being at a specific distance from a desired trim edge of the shell; and cutting the shell from the component using a cutting tool that slideably engages the raised tool guide as the cutting tool is moved around the shell. 
     In another aspect of the present invention, a method of customizing a bumper on a vehicle comprises providing a vehicle bumper beam with a convex outer surface; vacuum-forming a molded component from a sheet of constant thickness material to form a shell having walls of similar thickness but with some stretched wall thicknesses and having a shaped inner surface matching a portion of the convex outer surface; aesthetically treating an outer surface of the shell to form an aesthetic outer surface; and attaching the molded component to the vehicle bumper beam with the aesthetic outer surface covering a juxtaposed mating portion of the convex outer surface of the vehicle bumper beam, to thus give the vehicle a new customized bumper appearance. 
     In another aspect of the present invention, a method of repair comprises forming a sheet of constant thickness into a three-dimensionally concavely-shaped shell with inner surface replicating a mating show surface of a vehicle component and with an outer surface aesthetically treated to provide a customized appearance different than the mating show surface of the vehicle component; and attaching the shell to the vehicle component to thus cover the mating show surface of the vehicle component. 
     These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-4  are perspective views illustrating various prior art bumper systems discussed below. 
         FIG. 5  is a perspective view of a shell for covering an end of a bumper beam, the shell embodying the present invention. 
         FIGS. 6A-6D  are two perspective views and two cross-sectional views showing installation of the shell in  FIG. 5  to a truck bumper beam in a bumper system,  FIGS. 6C and 6D  showing alternative integral attachment flange configurations. 
         FIG. 6E  is a perspective view of a complete bumper beam and bumper system, with the present shell including first and second end shells and a center shell, each including edge-located integral attachment flanges and inboard tab inter-fit with each other and with the existing bumper system for secure retrofit attachment. 
         FIG. 7  is a perspective view of a modified shell (also called a “shell component”) similar to  FIG. 6B  but modified to have a different outer surface profile. 
         FIGS. 8A-8B  are perspective views of an as-formed vacuum-molded component that includes the end shell of  FIG. 5  and that includes a raised ridge forming a guide for a cutting tool, such as a router shown in  FIG. 8B . 
         FIG. 8C  is a side view of the router in  FIG. 8B , and  FIGS. 8D and 8E  are top and side schematic views showing engagement of a router guide with the guiding ridge on the vacuum-molded component of  FIGS. 8A-8B  and also showing a relative position of the router&#39;s cutter. 
         FIGS. 9A-9D  are shell coverings like that shown in  FIG. 5 , but with different surface treatments, and  FIG. 9E  is a cross section through  FIG. 9A  showing different layers including a soft/tacky layer of polyurethane for energy absorption and adhesion to underlying metal bumper surface being covered. 
         FIG. 10  is a perspective view of an existing truck bumper system in prior art. 
         FIGS. 11, 12A-12E and 13  are views of modified innovative shell coverings installed over the end of the bumper system in  FIG. 10 , each having a different light-passing portion therein,  FIG. 11  showing a light-passing portion in the form of letters,  FIGS. 12A-12B  showing an unlit and lighted version of a light-passing portion with the window forming a duck head,  FIG. 12C  showing a vertical cross section through  FIG. 12B  including an electro luminescent (EL) film generating light for shining through the window,  FIG. 12D  showing a light-passing portion forming a trademarked brand or symbol,  FIG. 12E  showing a vertical cross section through  FIG. 12D  including showing a colored outer panel placed across the window on the shell, and  FIG. 13  showing a grille-like light-passing portion forming a rear bumper light (or back-up light). 
         FIGS. 14A-14B  are perspective views of a bumper beam in prior art bumper system, where the beam has a rusted out spot ( FIG. 14A ) and a damaged dented spot ( FIG. 14B ). 
         FIG. 15  is a perspective view of a shell of the present innovation installed on the beam of  FIGS. 14A-14B . 
     
    
    
     DESCRIPTION OF PRIOR ART 
       FIG. 1  illustrates a bumper system  25  in prior art where its stamped bumper beam (illustrated as beam  30 ) is limited to simple shapes. The exposed steel of the beam  30  is directly exposed to damage from impacts (minor and major), such as rock impingement, scratches, or low speed impacts/bumps/scuffs, as well as environmental damage such as corrosion. Because the mild steel used in stamping bumpers can be relatively easily formed in to a permanent shape, these minor impacts can lead to permanent dents and dings that cannot be easily repaired, thus requiring expensive full replacement. Attached to the illustrated beam  30  are “bumper-covering accessories” (also called “existing trim” herein), such as top end tread pieces  31  and  32  and center tread piece  33 , and other components such as license plate light  34 . Each of the illustrated trim  31 - 33  only cover a portion of the beam  30 , and in particular include a horizontal section covering an associated top surface of the beam  30 , and include downwardly-extending outer flanges  31 A- 33 A, respectively, covering an upper horizontal edge of a vertical portion of the beam  30 . The trim  31 - 33  (and other bumper covering components) are attached by many different means, such as mechanically and/or adheringly. As used herein, the term “trim” (and “tread pieces”) is not intended to be unnecessarily limiting, and instead are intended to be interpreted as including various bumper covering components attached to a bumper beam to cover selected areas of the beam for aesthetics and/or function. 
     The bumper system  25  is intended to illustrate a variety of existing prior art bumper systems, and it will be apparent to persons skilled in this art that the present innovation is not believed to be limited to only being used with the specifically illustrated bumper system nor the specifically illustrated bumper components shown. For example,  FIGS. 2-4  show various truck rear ends incorporating a bumper system ( 25 ) not unlike that shown in  FIG. 1 . The investigation shows that the edges  31 A- 33 A and also the edges  31 B- 33 B usually have (or often have) an unfastened edge or free/unattached outer edge portion. Sometimes, stickers or adheringly attached thin-sheet coverings  35  ( FIG. 4 ) are used on exposed portions of the beam  30 . Persons skilled in the art of vehicle bumper systems will understand that the bumper system  25  is sufficient to exemplify a large number of such existing bumper systems, and that the present concept is not limited to only being used with the specific illustrated bumper system  25 . 
     Because of the high cost of tooling the stamped bumpers, OEMs (original equipment manufacturers, such as automotive companies that assemble and sell vehicles) do “styling refreshments” as a truck model ages. Sometimes, the styling refreshments are done because consumers are giving the vehicles poor marks. However, the styling refreshments do not usually include the bumpers, because of high cost. In addition, the fact that the bumper shape/style is directly linked to the impact and structural integrity of the bumper system is also a deterrent to providing many options or model “freshening” due to the additional engineering and validation costs. Specifically, any structural change to a bumper system may require validation testing, which is expensive, time consuming, and a significant event that adds time delays and high cost to bringing new/refreshed models to market. 
     In contrast, it is noted that the bumpers used on most uni-body passenger vehicles are typically constructed of a very stiff and strong tubular reinforcement or impact bar made from UHSS or Aluminum. A plastic or foam isolator or energy absorber is typically used on the face of the impact bar to absorb low speed impacts and prevent permanent damage. These bumper systems are completely covered by a mostly decorative fascia or cover molded from a flexible/elastomeric material, such as TPO (thermoplastic olefin) or RRIM (reinforced reaction injection molded part) so as to be resilient to low speed impacts. These decorative fascias can be sculpted by designers independent of the impact bar shape to enhance the styling and aerodynamics of the vehicle and have negligible influence on impact performance. Therefore, when it comes time to refresh or differentiate the look of the vehicle, these fascias are usually one of the first things changed . . . because of the significant effect on the style of the vehicle, the relatively low cost of re-tooling, and the minimal re-engineering or validation (since the bumper beam under the fascia can remain the same). 
     Current options available to truck owners that would like to restyle/customize the look of their truck bumper and/or add protection are usually either by: 1) Replacing the entire bumper with an aftermarket bumper (see  FIG. 2 —showing a typical aftermarket rear truck bumper), or 2) Covering the entire bumper with a large molded plastic fascia that would typically require additional painting at a body shop (see  FIG. 3 —showing a typical aftermarket rear truck bumper cover), or 3) Through applying a decorative film (car wrap) directly on to the surface of the steel bumper (see  FIG. 4 —showing a truck bumper with directly applied decorative film). Each of these alternatives has certain limitations that the current invention is designed to overcome. For instance, replacing the current OEM bumper with an aftermarket bumper is expensive and may not meet the same functional performance of the OEM bumper. The aftermarket molded fascias are also expensive, especially with the addition of paint costs, are typically not very durable, and may not fit well. The decorative films cannot change the geometric styling of the bumper, do not add significant protection for the bumper or cover existing damage, and cannot be taken off and re-used. They are also difficult to install, thus typically requiring a professional installer at additional expense. Thus, known bumper covering systems do not satisfy several known limitations and/or problems associated with existing bumpers, nor worn/damaged bumpers as noted above. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     A bumper shell  50  (also sometimes called a “skin” or “shell covering” or “shell component” herein) is a molded plastic piece of semi-rigid resilient-but-stiff component designed to form fit over (or “glove onto”) the exposed outer steel surface of a truck bumper. The shells  50  at right and left ends of the bumper are mirror images of each other, such that a description of shells  50  in  FIGS. 5-6B, 7, 9A-9D, 11, 12A-12B, 12D, 13 and 15  are sufficient for an understanding by persons skilled in this art. The illustrated shell  50  is typically 1.5 to 3 mm thick (or more preferably about 2 mm thick), and molded from a transparent material such as PET-G, Acrylic, or Polycarbonate (see FIG.  5 ). It can be any shape or style needed to cover a bumper beam, in terms of height, length, L-shape, and concavity, and may have (as many) attachment tabs or edge flanges as needed. The shell  50  can be made from an opaque material if a light-passing section is not required and volumes are sufficient to support the use of different materials, as discussed below. 
     The illustrated shell  50  is a vacuum-formed thin-walled form-fit decorative component, referred to as a “shell” herein due to is self-supporting resilient-but-relatively-rigid shape. The shell  50  includes a front vertical wall portion  51 , a wrapped-end portion  52 , and a reversely-formed lower flange  53  extending under portions  51 - 52 . Its upper edge  54  and inboard edge  55  include outwardly-extending integrally-formed attachment flanges  56  and/or long attachment tabs  57  shaped to tuck under the free edges  31 A- 33 A,  31 B- 33 B discussed above ( FIG. 1 ). The flanges  56 /tabs  57  preferably are positioned on enough edges of the shell  50  to secure the shell  50  to a beam  30 . It is noted that the wrapped-end portion  52  and/or the lower flange  53  may be additionally attached via double sided tape or clips. 
     The shell  50  has a concavely-shaped inner surface  58  that mateably engages and generally matches a curved show surface of the associated existing bumper beam ( 30 ). It is noted that vacuum-forming processes and tooling are particularly adapted to manufacture shells  50  patterned after the existing bumper beam  30  at low cost, even with low volume production runs. The shell  50  further includes an aesthetically treated outer surface  59  that aesthetically covers the underlying curved show surface of the beam  30 . The attachments  56 - 57  are adapted to attach the shell  50  to the existing vehicle bumper beam  30  via the flanges  56 /tabs  57  tucking under the free edge of the existing trim accessories  31 - 33 . As noted above, additional attachments can be used if necessary to securely hold the shell(s)  50  on the beam ( 30 ), such as mechanical or adhesion based attachments. 
       FIG. 5  illustrates one such molded plastic transparent bumper shell. However, as noted above, other thicknesses and materials can be used. Nonetheless, it is noted that thin parts such as these bumper shells with large projected surface area are difficult to mold via injection molding, and further it is noted that injection molding requires expensive tooling. For that reason, vacuum forming is the preferred method for forming these thin shells (including the shell in  FIG. 5 ), especially when considering there may be multiple different models and some lower volume runs. Nevertheless, it is contemplated that a scope of the present innovation includes various molding technologies (including injection molding, transfer molding, and compression molding) as a forming option, particularly when volumes are high enough to justify the cost of capital. It is noted that non-clear materials can be used to manufacture shells when no backlighting is applied. 
     Rather than one large piece that covers the entire bumper like current aftermarket fascia products, which also would require very large tools and molding presses, the present bumper shell innovation includes combining multiple shells  50 ,  50 C to cover a bumper beam (see  FIG. 6E ) by preferably dividing the task into two or more pieces, and further they only cover the exposed metal portions of bumpers (and do not cover the existing plastic trim). Specifically,  FIG. 6E  illustrates a three-piece shell covering including beam-end-covering shells  50  and center shell  50 C. The center shell  50 C is not unlike shells  50  ( FIG. 5 ) but instead includes flanges and tabs shaped to engage the free edge of the center bumper step under the license plate area, and to engage adjacent edges of the end-covering shells  50 . By splitting the system into  3  shells  50  and  50 C, this helps keep tooling cost down, which is very important for aftermarket products. In addition, it helps maintain the functions of the existing plastic trim and some continuity of style with the rest of the truck. It also allows for more precise gap/fit adjustments to match the surrounding truck features than other one piece solutions (aftermarket bumpers and fascia). 
     Multi-piece shell coverings of the present invention provide additional advantages. By being separated into separate pieces, the material is also allowed to move during expansion and contraction due to temperature changes without distortion (which can be a problem on current full length fascia alternatives). Also, the multi-piece designs present a “natural aesthetic” for many truck bumper designs, because the OEM&#39;s (original equipment manufacturer&#39;s) style applies a plastic trim through the middle of the bumper, making a natural left and right half. Notably, some existing bumpers have a chromed or painted steel bumper beam that is continuous from left to right, so there is no natural break. (See  FIG. 2 .) However, in these cases, a left and right bumper shell can be formed with a third piece/shell bridging between the two. (See  FIG. 6E .) This third piece (i.e. the center shell) can either have the same look (texture/pattern/color) as the left and right shells, or it can be intentionally made different, such as a black intermediate shell/trim piece, depending on the desired style. This middle piece would normally be in the towing area, which is normally the most susceptible area for damage to the bumper, such as from hitching a trailer. Therefore, this third/middle piece can be constructed of a thicker and more elastomeric/impact resistant material, such as TPO, to minimize damage to the bumper. It may also be replaced independently, if damaged. The intersecting edges of the center piece and the side pieces are offset to reduce the visibility of the joint as shown below, with the center piece always on top to retain the side pieces against the bumper. The center piece is typically attached to the bumper with magnetic or double-sided tape. Since many truck bumpers are damaged in the center/hitch mount area from towing incidents. The center cover section may also be applied as a “stand alone” piece, i.e. without the side pieces, as an individual cover for the damaged center section of truck bumpers. 
     Intersection joint design between a bumper shell and existing trim: A unique feature of the present bumper shell  50  (and  50 C) is the offset perimeter flanges  56  and tabs  57 , (like those shown in  FIGS. 5 and 6A-6D ), which are formed in the bumper shell so they can be tucked under the existing plastic trim pieces of the bumper and thereby provide the main attachment function and to completely hide most edges, creating a very high quality look. Since the shell components have significant structural strength, the perimeter flanges and any attachment tabs extending therefrom are sufficient to securely retain the present bumper shell components in place. 
       FIG. 6  illustrates a bumper shell  50  installed with flanges/tabs  56 / 57  tucked under existing plastic trim. By keeping the shell thin (such as less than 3 mm), it is relatively easy to tuck the flanges between the bumper and the existing trim pieces with minimal distortion of the trim and minimal effect on the re-installation effort of the trim piece. Any remaining free edges (such as along a lower edge or outer vertical edge on the wrapped portion) can be attached with re-useable methods, such as magnetic tape or clips, if necessary. For more permanent installation, other means, such as double sided tape may also be used. Therefore, the bumper shell is not only easy to apply in a matter of minutes, but the individual pieces or complete cover can also be removed and replaced if desired for changing the look of the truck or if damaged. This is not possible with current alternatives. 
     In order to create a “solid feel” and “dampened sound” rather than a hollow “plasticky” sound and feel inherent with plastic covers, the back side of the present bumper shell&#39;s inner surface  58  is coated with a soft elastomer layer  62 , such as polyurethane (TPU) or Latex. The soft coating can be relatively smooth or “ribbed” (see  FIGS. 9E, 12C, 12E ), depending on the amount of gap to be filled. This coating creates a soft interface that dampens sound, overcomes minor surface differences, and provides a direct load path to create a solid/supported feel that the customer will consider higher quality. This soft elastomer is typically applied with a coarse paint brush or flexible applicator. 
     A preferred method is to form a ribbed pattern in the coating layer&#39;s ( 62 ) bumper-engaging interface by wiping it with a flexible squeegee that has a ribbed/toothed edge when the coating has just cured enough to begin to maintain some shape. When the completed bumper shell is applied to the bumper, the thin raised ribs bend over/compress where the shell first comes in contact with the bumper, thus more able to adjust for gap variation, which is particularly important if the bumper has been distorted/damaged. The special coating formulation is developed such that when dry, the coating surface remains slightly “tacky”, such that when the bumper shell is applied to the bumper, it will “cling” to it. The additional and novel “clinging” affect provided by the soft coating greatly aids in securing the bumper shell to the entire bumper surface. However, as contrasted by an adhesive that is more permanent, the soft coating allows the shell  50 , 50 C to be repositioned and/or removed. This elastomeric lining/interface also provides the electro-luminescent panel light source (described in next section) additional protection from moisture and abrasion. Raised/projected areas  60  ( FIG. 7 ) can also be formed in the bumper shell components and filled with the elastomeric material in order to create an in molded “bumperet”, providing additional low speed impact protection for the truck. (See  FIG. 7 , which shows a bumper shell with outwardly “projected” area for added styling effect and filled internally for increased impact resistance.) 
     In addition, when the manufacturing method is vacuum forming, a new technique has been developed to eliminate the need for additional trim fixtures, set up fees, and high charge rates for CNC trimming operations generally required for trimming out vacuum formed parts. Thus, this novel concept saves significant capital and piece cost expense. It comprises forming a raised area, or shoulder, into the tool around the perimeter of the part to be vacuum-formed. A blank flat sheet is heated to a desired softened temperature suitable for vacuum forming by drawing a vacuum under the blank, to draw it down onto the surface of the tool  70 . See  FIGS. 8A-8C , with  FIG. 8B  showing a vacuum-formed part  65  on a vacuum form tool  70 , the vacuum-formed part  65  having a raised perimeter  71  (also called “shoulder” or “integral raised guide”) around each of the two shells  50  formed. 
     By way of example, as shown in  FIGS. 8B, 8D-8E , the raised perimeter  71  acts as a tool guide for guiding around the part ( 50 ) a manually-operated cutting tool such as a router or die grinder  72  with a rotating cutter/bit  73  and router-attached ridge-engaging guide. In  FIG. 8D , a bottom of the router is illustrated by the large diameter, the router guide is illustrated by the intermediate circle, and the router cutter is illustrated by the smaller diameter. The material cutaway by the router cutter is illustrated by two parallel router-cut lines extending from the cutter downward in  FIG. 8D , with the left line illustrating an edge of the shell  50  cut out by this technique. In the example, the raised perimeter  71  was 0.4-0.5″ tall, the router cutter was a ⅛ inch bit, and the illustrated bit collar/guide was 0.665″ diameter. The resulting cut line along an edge of the part was 0.395″ inboard from the raised perimeter  71 . It is noted that the raised perimeters  71  can include undulations for forming the particular perimeter desired on the shell  50 , including for example protruding “bumps” to form the tab  57  or form clearance areas for fasteners on the existing bumper that the shell must fit around. Persons skilled in this art will thus understand the many significant advantages using the technique set forth above. 
     It is noted that a variety of different guides or ridge-followers can be used and still be within a scope of the present invention. The illustrated special guide is a cylindrical bushing or follower used on the rotating cutting tool or router. It is unusual since it is positioned to engage a raised ridge located above the cutter (as opposed to known routers where a guide is below the router cutter). The illustrated router guide is shaped to be maintained in contact with this raised perimeter shoulder  71  during the trimming operation. The illustrated guide bushing is fabricated with a specific diameter such that the cut for the bumper shell edge is always a specific/constant distance from the raised perimeter guide. The cutting bit is extended through a hole in the center of the guide, and the guide is attached securely to the rotating cutting tool/router. The trim operation should always occur in a clockwise direction around the part, so the direction of blade rotation helps keep the guide bushing against the shoulder, thus minimizing any tendency for the blade to wander away from its intended position. 
     With this method, the need for an additional vacuum fixture is eliminated as is the need for expensive CNC routing of the part, saving a substantial amount of money, especially for lower run quantities. The trim guide is trimmed off with the rest of the blank and sent to a recycler. For larger run quantities, CNC routing is advised for trimming out the part. For even higher volumes, when injection molding is used, the part does not require trimming. 
     It is contemplated that the outer surface  59  of the present innovative shells  50  may be decorated in many different ways with an outer surface covering  63  ( FIG. 9E ) and as illustrated by  FIGS. 9A-9E , and by using several different methods, such as: A) wrapped with a pre-printed adhesive backed vinyl  63  ( FIG. 9E ) such as used for decorative vehicle wraps after forming, B) formed using either a material with a pre-printed or laminated pattern/color, C) in-mold decorated by inserting a printed film or panel in an injection mold and injecting the shell material on the back surface of the film, D) using the hydrographic process of dipping the formed part into a vat of water where the graphic image to be transferred is floated on the surface. 
     A preferred and novel method for low volume applications where a backlit image/logo is desired on the bumper shell is the wrapped vinyl method on a shell  50  made using a clear bumper shell material. The window area where the backlighting is desired can either be pre-cut into the film before application to the shell and held in place with transfer tape until application, or cut out of the film after application and removed from the film in the region to be backlit when the design shapes are simple, such as circular or rectangular. 
     Images/logos for backlighting can be achieved using several methods. For example, they can be made by printing (or other indicia  66 , see  FIG. 11 ) on translucent colored vinyl and applied to the exposed surface of the bumper shell over the cut out region (i.e. in a “window” area  67 ). (See  FIG. 11 .) Typically, the image sticker is oversized such that there is approximately ⅛ inch of overlap with the cut out area to allow for placement variation and potential material shrinkage differences. Alternatively, the image may also be reverse printed and applied to the inside surface of the bumper shell, so as to expose the printed image through the transparent/clear bumper shell where the decorative film has been trimmed away. Some images are created by the cut out shape in the vinyl with a colored translucent film applied on the backside of the shell. Still other possibilities include a standard window shape cut from the vinyl and covered by a colored translucent vinyl  63 A ( FIG. 12E ) either on outside (with prescribed overlap, see  FIG. 12E ) or on the backside surface of the bumper shell so as to cover the cut out vinyl region. Available commercial or custom stickers (translucent or not, see for example the “bowtie” Chevy symbol in  FIG. 12D ) purchased separately from licensed vendors by the end user can then be placed over the window area by the customer, thus allowing complete freedom of image choice without the need for individual licensing. 
     The image area (i.e. window  67 ) can be then backlit via several available methods, including electro-luminescent (EL) panel/tape  68  ( FIGS. 12C or 12E ) or LED lighting, which have proven to be particularly effective while maintaining a minimal total cross-sectional thickness (e.g. &lt;0.125″). In particular, a preferred method for areas directly and closely covering the hard bumper surface is with ultra-thin EL panel technology. These panels are approximately the thickness of a credit card, so they can be sandwiched between the bumper shell and surface of the bumper behind the image to be backlit without the need to modify the bumper or distort the shape of the shell. They are typically held in place with tape, although other bonding measures can be used. Also, since they are flat, relatively flexible, and do not utilize a bulb, they can flex to the typical gentle curvatures of a bumper and withstand minor impacts without damage. However, they are susceptible to damage from moisture, so the elastomeric coating, which is applied to the back side of the bumper shell after the EL panel is installed, helps to seal out moisture and protect the panel from damage. 
     From the basic new concepts noted above, there are at least four major advancements from current available options for truck bumpers. These include 1) providing a form-fit decorative shell over a stamped/formed bumper (including retrofittable attachment), 2) providing a carrier/lens for adding lighted effects, 3) providing protection against rock impingement, small “dings”, and rust, (as well as a method of retrofittably covering same without large expense), and 4) providing a relatively inexpensive repair to an already damaged bumper. 
     More specifically in regard to the subject of providing a form-fit decorative shell over a stamped bumper, the truck bumper shells of the present invention will allow the truck owner to overcome the styling constraints on the stamped steel bumpers and limitations of alternative solutions by changing the surface appearance (texture, pattern, color, and shape) of the exposed steel portions through the application of decorative films, customized paint, molded-in colorants/patterns, printed patterns, or mold-behind graphics on to the thin (&lt;3 mm) plastic bumper shell. As explained, the bumper shells can be molded to exactly match the contours of the existing bumper. However, additional geometric styling freedom is possible through localized geometric changes to the molding while still being supported by the steel structure of the bumper and not degrading its impact performance as per the basic concept. A novel concept has been developed for attaching the shell to the bumper by tucking the flanges under the existing trim pieces and coating the backside of the bumper shell with a soft and tacky coating, such that it “clings” to the bumper surface and/or by adhesive foam tape. Through these means, no modification of the bumper is required. The bumper shells can be easily applied (and removed), if desired, without damaging the bumper cover or underlying bumper, thus maintaining a pristine bumper underneath. 
     Examples of the decorative opportunities for restyling the truck are shown in  FIGS. 9A-9D .  FIG. 9E  illustrates one laminar arrangement forming the shell  50 . In  FIG. 9E , the decorative layer is the left outer layer, while the intermediate middle layer is a transparent polymeric shell, and the innermost layer on the right side is a layer of soft/tacky material that adheringly clings to the metal bumper beam&#39;s surface. The tacky material both fills minor bumps and defects in the bumper beam&#39;s surface, and also absorbs small shocks and impacts directed against the shell  50  by road stones and the like. It is contemplated that the soft/tacky material can be applied with a trowel to form a plurality of parallel ridges that assist in filling in surface defects and in forming an impact-absorbing structure on the bumper beam. 
     In regard to providing a carrier/lens for adding lighted effects, the truck bumper shells can be molded from a transparent polymeric material, such as PET-G, Acrylic, or Polycarbonate using either the vacuum forming or injection molding process to give the shell its shape and thickness. See  FIGS. 12A-12B  and the related cross section  FIG. 12C , and also see  FIG. 12D  and the related cross section  FIG. 12E . Since the bumper shell is mainly designed to fit snuggly over the existing bumper, it is significant that a durable lighting technology has been identified that is thin enough to be “sandwiched” between the bumper shell and the rigid steel bumper surface without distorting the plastic shell or requiring modification of the steel bumper. Existing known bumper lighting technologies typically use either incandescent bulbs or LEDs (see  FIG. 10 ). Because of the depth requirement of each of these technologies (i.e.  FIG. 10 ), they each either require a raised/projected surface to be placed behind or for a depression or hole to be made on the bumper. 
     Contrastingly, the present invention applies a technology called electro-luminescence (see  FIGS. 12C and 12E ), which is essentially creating light by applying a charge (current) with electrodes to a film constructed of light emitting phosphor materials and laminated with a protective film. These electro-luminescent (EL) films come in the form of thin tapes or panels that are typically only 0.02 inch thick. The EL panels are flexible enough to form around gentle 3D contours, such as those found in typical stamped truck bumper surfaces (which cannot be accomplished without great effort with the alternative technologies). By selecting particular colors and lighting arrangements, words or phrases can be made to stand out, especially when viewed at dusk or night. See  FIG. 11  where the word “COOL” is luminated and made to stand out from the word “ECOOLOGICIAL”. Also, see  FIGS. 12A-12B , where a duck head profile is made to stand out when lit ( FIG. 12B ).  FIG. 12C  illustrates the arrangement of layers, with the outermost layer on the left providing background printed indicia, a first intermediate layer (next to the outermost layer) being a transparent shell material, a second intermediate layer (to the right of the other intermediate layer) being the EL tape/film, and the right innermost layer being the soft/tacky layer discussed above.  FIG. 12D  illustrates the opening defining a “bowtie” Chevy symbol (trademark of General Motors), with the outmost layer having a center area that lights up at a first brightness and a perimeter that is thinner and that lights up with an increased brightness over the center area. It is noted that there are an infinite number of variations that can be done, using a combination of window shapes, translucent films applied over the window, brightly-lit perimeters, and the like. It is conceived that custom stickers can be printed on and applied to the “flat” areas on the shell, such as the rectangular area illustrated in  FIGS. 12D-12E . 
     Notably, most state highway laws require that rearward facing lights on the vehicle be diffused and under a particular illumination (candle) power. Since the generated light of the EL panel is evenly diffused across the surface of the panel, it does not create “hot spots” of light behind the image to be backlit like a bulb or LED, so they meet this requirement without the addition of a diffusing lens. Still further, the light-passing window can form a pattern not unlike a rear light (see  FIG. 13 ). 
     The EL panel noted above is typically adhered to the backside of the bumper shell by taping (or other bonding means) around the perimeter in the area where the backlighting is desired, such as where a printed vinyl film or other semi-transparent image will be placed/created on the bumper shell. The size of the EL panel can be pre-specified from the manufacturer to fit the desired backlit area or trimmed (requiring re-sealing of the cut edges with protective tape) to the desired shape/size. 
     By using the present approach with EL panel, images of almost any kind, such as company logos, licensed logos from others, words/messages, etc. can be either printed on vinyl film and applied to the outside surface of the bumper shell or airbrushed directly on to the bumper shell, thus making a very impressive backlit mobile advertising space. In most cases the EL panel will have a white light emitted with the color of the image coming from what is used on the vinyl sticker to create the image. However, EL panels that emit colors other than white may also be used. In some states, the colors of light on the rear of the vehicle are limited to red, amber, or white. 
     The EL panel is charged through a connection to the tail lamp wiring of the vehicle. This can be done in many different ways, depending on the desire of the truck owner. For instance, it can be tied in to the running lamps, so they illuminate when the headlights or parking lights are turned on. They can also be tied in with the blinkers or stop lamps, illuminating when either of those conditions occurs. The wires can be connected by splicing in along the OEM wire harness to the tail lamps or connected to the trailer light receptacle. In each case, a small transformer is required to establish the correct voltage and amperage to the EL panel and to convert the current from DC to AC. 
     Once the image is applied to the transparent bumper shell, the rest of the bumper shell is either covered with a decorative film, with a cut-out for the image or painted after masking the image. If using decorative film, the cut-out for the back-lit image can either be a simple perimeter, such as a square, rectangle, circle, or oval around the image or the cut-out can be CNC printed/cut out of the decorative film to intermingle with the logo, such as the background between letters, etc. In this case, the film is positioned in the printer with specific datum points, the printed vinyl logo/image can be placed in correct position on the backside of the decorative film, and then the film plus logo is applied in correct position according to the datums on the bumper shell. Another method is to apply the logo/image to the shell first, over the backlit region, and then applying the decorative film by first carefully positioning the logo cut-out over the logo and smoothing out the film from the center of the logo to the perimeter of the bumper shell. Still another method is to cut out the wrapped film on the bumper shell in the desired shape/size of window, then carefully place the logo image “sticker” over the cut out area with approximately ⅛ inch overlap at the edges to account for placement variation and thermal growth effects.  FIG. 12A  shows an example of a backlit bumper shell not illuminated, and  FIG. 12B  shows it illuminated. 
     It is believed that this additional illumination of the rear of the truck can provide additional visible warning to vehicles coming up from behind for increased safety, especially at night or in bad weather conditions. 
     Although it is feasible to backlight a directly-applied decorative film to the bumper, this is not preferred since a thickness of the panel, and the wire route would visibly distort the film and would not be as well protected from damage. 
     In another situation, where raised/projected areas of the bumper shell are desired, there is room to add LED lights behind the projected area and backfilled/potted with elastomer (similar to the bumperet) for another lighted look. These lights can be tied in to light at the same or different time as the EL panel, such as for blinkers or additional stop lamps (see  FIG. 13 ). 
     The present innovation also provides protection against rock impingement, small “dings”, and rust. It does so much like protective covers are used on such things as mobile phones and other electronic devices to provide the expensive device additional protection from scratches, impacts, moisture, etc. The illustrated present bumper shells are designed to protect a new bumper to help maintain it in pristine condition. Truck bumpers are very expensive to replace, costing between $500-$1,200 for OEM replacement parts. Steel is especially susceptible to rust and bumpers are subjected to many harsh environments, such as snow, road salt, debris, etc. The chrome or paint covering of the bumper is meant to protect the steel from rusting, but these protective coatings are oftentimes compromised/breached by rock impingement, small impacts, or scratches. When these coatings are breached, rust forms very quickly, not only rapidly degrading the look of the truck, but over time, also compromising the integrity of the bumper itself (see  FIG. 14 ). 
     The bumper shells, including the soft elastomer interface and some systems including additional raised areas filled with elastomeric material can provide substantial protection against common damaging events such as rock impingement, scratches, and low speed impacts, prolonging the life span of the bumper in its pristine condition. Decorative films directly applied to the bumper provide some protection for very minor impacts, like light rock impingement, but is significantly lower protection than that provided by the bumper shell, due to its thicker substrate and elastomeric interface. In addition, directly applied wrap films cannot cover dents, punctures, or significant rust. Aftermarket bumper fascias provide greater protection than the films, but are often made of materials that are easily damaged themselves, such as fiber glass. 
     Since a new bumper is so expensive, in many cases, a damaged truck bumper is never replaced and the truck owner has had to accept the degradation of their trucks appearance. However, much like an old house with peeling paint or damaged exterior can look new again with the application of siding, the bumper shells provide a new decorative outside surface to a bumper that may have already sustained some minor dents, dings, scratches and/or the onset of rust. In addition, in many instances, unless severe structural damage and/or distortion of the bumper has already occurred, more substantial dents can be pounded back to near the original shape. A filler material such as used in the body repair industry can then be used to fill in the remaining depressions and filed/sanded to approximate the original surface. Now, a set of bumper shells can be applied to the damaged bumper in the same manner as explained previously for a new bumper. If the trim pieces have been damaged, they must be replaced. Although, the original surface will never look new again, when installation of the bumper shells is completed, the bumper will have a great new look as shown in  FIG. 15 . 
     Unlike directly applied decorative film, the bumper shell of the present innovation will cover any remaining imperfections in the repair job and will serve to help protect the repaired bumper from new damage. (See  FIGS. 14A and 14B  illustrating a damaged bumper beam, and  FIG. 15  is illustrating a shell covering the damaged beam.) With this new approach, truck owners will not only save some money and have a new customized look for their truck, but will also reduce the waste and energy associated with the disposal of the old bumper and creation of a new one, including the environmentally damaging chroming process. The application of bumper shells has a much lower environmental impact than full replacement. 
     Thus, it is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.