Abstract:
A novel cover for a safety restraint device is disclosed. The cover is well-adapted for use in vehicles with modular airbag components. The novel cover configuration of the present invention effectively hides any evidence of the seam through which the airbag deploys, thereby improving the appearance and tamper-resistance of the airbag. The cover includes a seam with a nonlinear portion that impedes folding or bending of the outer layer in conformance with the seam. The nonlinear portion of the seam may include bends and linear segments in a variety of shapes and sizes, in homogeneous or heterogeneous arrangements, as dictated by the design parameters of the airbag and the manufacturing processes used to make the cover. The cover module of the present invention may be used with an outer layer of material designed to conceal the seam. With such a configuration, the nonlinear portion of the seam may keep the outer layer from form fitting to the seam so that no visible indentation over the seam will be shown. Alternatively, the module may be made with a single-shot material, exclusive of any outer layer. An exposed surface of the airbag module may then be configured as a cosmetic surface, with the seam formed on the opposite side of the cosmetic surface. The nonlinear seam then reduces material deformation and obscures translucency to ensure that the cosmetic surface appears even and relatively flat, even without the use of a styling line.

Description:
BACKGROUND OF THE INVENTION 
   1. The Field of the Invention 
   The present invention relates to safety restraint devices for vehicles. More specifically, the present invention relates to hidden seams designed to permit airbag deployment without any evidence of the seam visible to a user. 
   2. The Relevant Technology 
   The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the ignition of an explosive charge. Expanding gases from the charge fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield. 
   During normal operation, the airbags are stowed behind covers to protect them from tampering and provide a more attractive interior facade for the vehicle. Seams, or deliberately weakened portions of the cover material, are included in the covers to ensure that the airbags deploy properly. Seams are necessary because, if the entire cover is made uniformly strong, random factors, such as manufacturing defects, in the cover will determine where the airbag emerges. It is necessary to ensure that deployment occurs at the proper location and time. Otherwise, a driver or passenger may not receive protection from the airbags, or may even be injured by improperly inflating airbags. 
   A seam may be a gap in the cover, held shut by threads, adhesives, etc. In the alternative, a seam may be constitute a line across the cover in which the material of the cover is formed thinner. In any case, the seam creates an inwardly-sloping region on the airbag cover. The seam may be on the inside of the cover, facing the airbag, or on the outside. Some covers include an outer layer of attractive material, such as leather, vinyl, or another plastic, that matches the remainder of the vehicle&#39;s interior. This layer also serves to cover the seam and hide it from view. 
   Other covers are made through “single-shot” construction, i.e., a manufacturing process in which only one single material is used. No cover layer is then used; rather, the surface facing the vehicle interior is made into a cosmetic surface through shaping and texturing. Styling lines are then typically molded into the cosmetic surface to obscure the underlying seam. 
   However, prior art seams typically have at least one long, straight section. Because of manufacturing methods currently used to attach the outer layer, the outer layer, if used, typically form-fits to the seam, creating an indentation in the outer layer over the seam. If no outer layer is used, a similar problem results because the styling line does not effectively fool anyone, and the styling line itself may be unsightly. If the styling line is omitted, a user may then “read through” the cosmetic surface and perceive the seam. Read through occurs because deformation of the material around the seam creates a visible indentation on the cosmetic surface. In many cases, the material of the seam is so thin that it is translucent to a user, who may then look through the cosmetic surface to perceive the seam or even the airbag inside the cover. 
   Consequently, nearly every vehicle with an airbag has a straight indentation or styling line in the interior finish. Since most airbags are placed at a location where they can protect a user from frontal impact, this indentation is nearly always directly in front of a person, in plain view. For this reason, the steering wheel and the passenger side dashboard of many vehicles prominently display a straight indentation or styling line covering the airbag. 
   The visible seam is problematic for a number of reasons. It may upset the design scheme of the interior material of the vehicle. Many modern vehicles utilize a smooth interior design that may be disrupted by the appearance of a seam in the middle of a panel. An automobile manufacturer may wish to employ curvilinear patterns on the interior finish of the vehicle. When combined with the straight indentations formed by prior art seams, however, such curvilinear patterns may appear incongruous and distracting. 
   Furthermore, a visible seam invites tampering by curious children and others. The seam is designed to yield to opening force, so it may be fairly easily broken to expose the airbag. If the airbag is tampered with, the owner may have to replace it, or may even be injured if it fails to deploy in the event of an accident. Even if no break is formed in the seam, the surface of the outer layer may be ruined by constant picking, poking, and scratching. 
   Moreover, another danger is present in vehicles in which interior airbag seams are visible. Some people form a habit of resting their hands in a certain fixed position on a surface, particularly over an irregularity such as a ridge, bump, or seam. For example, a driver may, while driving, subconsciously rub his or her fingers along the seam. Besides damage to the interior finish of the vehicle, this may ultimately cause injury to the driver when the airbag deploys. The rapid timing required to inflate an airbag before a person has struck a surface in the vehicle (such as the windshield) requires that the airbags open with explosive force. This will not typically injure a user situated normally in the vehicle, but body parts resting too close to the airbag, such as arms and hands, will be subject to the explosive force of the airbag&#39;s deployment. A user could then suffer serious injuries when the airbag deploys. 
   Even when known seams is not visible, they may be easily discovered by a user by simply pressing on the outer layer or cosmetic surface. In either case, if a linear seam is used behind the outer layer or cosmetic surface, the pressure causes the cover to fold inward along the seam, so that the seam is readily perceptible. Repeated application of pressure may even break the seam. Even if a seam is not otherwise visible, it is preferable, for many reasons, to ensure that it is entirely hidden from a user until the airbag deploys. 
   Accordingly, a need exists for a safety restraint device cover with a seam that will not be visible to a vehicle occupant, even when no styling line is used. The indentation produced by the seam is difficult to eradicate without the use of additional manufacturing processes to join disparate materials or alter the shape of the seam. Consequently, a need exists for a novel seam design that will not show through the outer layer, if a separate material is applied, or the cosmetic surface, if a single-shot, or single material process is used to form the cover. A need further exists for such a cover that is manufacturable through inexpensive processes such as stamping or molding. 
   BRIEF SUMMARY OF THE INVENTION 
   The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available airbag covers. Consequently, the present invention provides an easily manufactured airbag cover with a seam that remains hidden from view. 
   In accordance with the invention as embodied and broadly described herein in the preferred embodiment, a cover, including a novel seam design, is provided. The cover comprises a module insertable into a corresponding opening in the vehicle. An outer layer may also be applied to the module to hide the module from view. A seam may be formed in an outward-facing surface of the module to permit airbag deployment. The seam comprises a nonlinear portion, which includes a plurality of bends that discourage form-fitting of an outer layer over the seam. The bends may exist in a variety of configurations suitable for keeping the outer layer from folding into the seam. This permits the use of simple manufacturing processes, such as stamping and molding, to create the seam, without leaving an unsightly and potentially dangerous crease in the outer layer. 
   In the alternative, instead of the outer layer, a cosmetic surface may be formed on a portion of the module facing the vehicle interior. The nonlinear seam may then be formed in an inward-facing surface of the module. Such a nonlinear seam minimizes read through because the material does not deform uniformly to produce a translucent line. Even if the nonlinear seam does create translucent regions in the cosmetic surface, the translucent regions will be nonlinear, such that there is no viewpoint from which a user may see through any significant portion of the cover. There is no linear, regular feature to draw a viewer&#39;s attention. 
   Additionally, whether an outer layer or cosmetic surface is used, if a user presses against the cover, the cover does not deflect in such a way that the seam is easily discovered. The seam extends along multiple axes so that bending does not occur only along one axis, as with a linear seam. Rather, bending occurs along multiple axes, as would be expected for a surface with no weakened portions. In effect, since the seam, which forms a weakened region, is irregular, it will not be perceived by a user. 
   The nonlinear portion may be embodied in several different ways. For example, the seam may have a few larger bends of substantially equal size, with few or no straight sections between them. A larger number of smaller bends may also be used to decrease the width of the nonlinear portion, while retaining the novel benefits of the bends. In the alternative, the bends may have a very tight radius and simply connect linear segments in a zig-zag pattern. Linear segments may also be connected by bends arranged in pairs, to create a seam with a crankshaft-like appearance. Large-radius bends could even be used in combination with linear segments, perhaps by arranging the bends between symmetrical linear segments. 
   The bends and linear segments, if used, need not be uniform in arrangement or configuration. Any combination of the embodiments described above may be used according to the invention. Any seam in which no linear portion of any linear segment of any substantial length can be found is contemplated by the invention. Substantially linear or nonlinear side portions of the seam may also be provided to enlarge the size of the opening through which the airbag will deploy. Additionally, the seam need not follow a generally linear course, but may be generally circular, semicircular, polygonal, or otherwise in its overall shape. 
   In operation, expanding gases fill the airbag, and the airbag bursts through the seam. Openings may form at one end of the seam and propagate rapidly from there to the other end, or all parts of the seam may burst open simultaneously. If an outer layer is used, it may break open in similar fashion. In any case, despite the irregular shape of the seam, it will still open reliably as long as the seam is properly constructed, because the force tending to pull the seam apart will remain substantially the same as with a straight seam. The fact that the airbag deploys through a nonlinear opening will not substantially hinder its operation. 
   The seam of the present invention has application not only to driver and passenger side airbags, but also to other vehicle airbags. For example, side mounted airbags designed to protect occupants of a vehicle from lateral impact may utilize nonlinear tear seams to ensure that the lateral surfaces of the vehicle, such as doors, armrests, and side ceiling portions, do not show a seam or styling line where the airbag deploys. Similarly, airbags used to protect a vehicle occupant&#39;s legs may have a nonlinear tear seam hidden from view. 
   Thus, the current invention provides a novel, nonlinear seam for an airbag cover. If an outer layer is used, the nonlinear seam resists form-fitting of the outer layer over the seam by providing a number of bends into which the outer layer cannot easily fit. As a result, the outer layer maintains a much more attractive appearance and does not create a temptation for a person to tamper with the seam, or to maintain any body part in dangerously close proximity to the seam during operation of the vehicle. 
   Where a cosmetic surface is formed instead of the outer layer, the nonlinear seam prevents read through of the thinner material of the seam, and thus obviates any styling line used to hide the seam from view. The danger that a user will discover the seam and possibly even break open the cover by pressing on the outer layer or the cosmetic surface is further reduced. Hence, the seam of the present invention makes a vehicle safer, more attractive, and more wear-resistant than previously known seams. 
   These and other features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that the manner in which the above-recited and other advantages and objects of the invention are obtained will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
       FIG. 1  is an exploded view of a safety restraint device cover, including a module with a seam having a nonlinear portion, according to the invention; 
       FIG. 2  is a plan view of an alternative embodiment of a seam having a higher number of bends; 
       FIG. 3  is a plan view of another alternative embodiment of a seam having pointed bends; 
       FIG. 4  is a plan view of another alternative embodiment of a seam having a pairs of bends, the pairs oriented in consecutively opposite directions and separated by linear segments; 
       FIG. 5  is a plan view of another alternative embodiment of the seam having linear segments disposed on either side of the bends; 
       FIG. 6  is a plan view of another alternative embodiment of the seam having a mix of bends of different sizes and shapes intermingled with linear segments; and 
       FIG. 7  is a perspective view of the safety restraint device cover of  FIG. 1  with an outer layer attached, concealing the seam. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The presently preferred embodiments of the present invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the apparatus, system, and method of the present invention, as represented in  FIGS. 1 through 6 , is not intended to limit the scope of the invention, as claimed, but is merely representative of presently preferred embodiments of the invention. 
   As alluded to previously, airbags have become a great lifesaving tool for the automotive industry. For cosmetic and safety purposes, the airbags must be concealed underneath some type of solid, opaque cover after installation in a vehicle. Seams in the cover are necessary to ensure that the airbag inflates uniformly and through the correct part of the cover. 
   An outer layer may be applied to the cover to match the interior of the vehicle. However, known outer layers bend and fold to form-fit to the seam, thereby creating an unsightly, distracting, and even potentially dangerous indentation over the airbag. The outer layer may also be omitted in favor of single-shot construction, in which the cover is made from a single piece of material. With a single-shot cover, the seam is typically formed inside the cover. However, the seam may still be “read through” the cover, due to deflection the regions surrounding the seam and the translucent nature of many thinly-constructed plastics. 
   The present invention makes novel use of principles of material deformation to avoid the problems of the prior art. More specifically, a flat object bends far more readily than a bent or creased object. This is because bending is easiest along thin cross sections, and a bent or folded object has no thin cross section along which bending can easily occur. For example, houses with peaked roofs can bear far heavier loads than houses with flat roofs. Similarly, steel beams with an “I” shape are commonly used in construction because they withstand bending far more effectively than flat beams, without the expense and weight of a solid mass. In effect, an object that has already been bent or folded is somewhat thick along any cross section, and therefore is much more difficult to bend in a second direction. 
   The same principle applies to objects that have not yet been bent or folded. When an object is under multiple bending forces, each force limits the degree to which the other force can bend the object because bending in one direction increases the thickness of the object against bending in the other direction. As a result, the object may bend only slightly in all directions. 
   The current invention applies this principle to a seam for an airbag cover. Straight seams, like those of the prior art, will support the outer layer against bending in all directions except for one, so the outer layer will bend in the unsupported direction to fold into the seam. The present invention provides a meandering seam, so that the outer layer is supported against bending in all directions. Some bending may occur in all directions, but that bending is so minor as to be invisible to the naked eye. Additionally, small-scale, multi-directional bending precludes further bending in all directions. The operation of this principle is further illustrated in the following figures and their accompanying descriptions. 
   Referring to  FIG. 1 , one possible embodiment of a cover  10  according to the invention is shown. A module  12  is designed to be installed in an interior compartment (not shown) of a vehicle. The module  12  has a peripheral surface  14 , shaped to properly fit against a mating surface in the vehicle, and a face portion  15  with an exterior side  16  facing the seat of a vehicle occupant. A skirt  17  is attached to the face portion  15  or the peripheral surface  14 , and carries a series of locking tabs  18  designed to deform into locking engagement with corresponding structures in the interior compartment of the vehicle. 
   The module  12  may be integrally formed from any suitable material, including polymers, metals, ceramics, and composites. Alternatively, the various components of the module  12 , including the peripheral surface  14 , the face portion  15 , the and the skirt  17 , may be made from different materials assembled through means known in the art. The face portion  15  and skirt  17  are preferably made of an elastomeric, deformable material such as plastic. An airbag (not shown) may be attached to and installed with the module  12 , or may be installed within the interior compartment before installation of the cover  10 . 
   A seam  20  is formed in the face portion  15  to permit deployment of the airbag through the face portion  15 . The seam  20  may take many forms, including an incision clear through the face portion  15  held shut by sewn fibers, adhesives, welds, deformable locking members, or other retention mechanisms known in the art. Alternatively, the seam  20  may be simply a region in which the face portion  15  is made thinner than in the surrounding regions, so that the seam  20  is the first portion to separate under stress. In such a configuration, the material of the face portion  15  may slope inward from the exterior side  16  to create a seam  20  in the form of a trough. The seam  20  is not limited to the forms disclosed herein, but includes any thin structure made to create an opening in a surface under stress. 
   The seam  20  includes a nonlinear portion  21 , which is preferably centrally located on the face portion  15 . For the purposes of this application, “nonlinear” refers to any narrow structure extending along a path from one end of the structure to the other, wherein the path is not a straight line. Conversely, “linear” refers to narrow structures extending along a straight line from one end of the structure to the other. Accordingly, a nonlinear object may include linear segments if the overall path followed by the nonlinear object is not a straight line. The nonlinear portion  21  satisfies this nonlinearity requirement because the path followed by the nonlinear portion  21  between first and second ends  22  and  23  of the nonlinear portion  21  is not a straight line. 
   The seam  20  preferably also includes a first side portion  24  attached to the first end  22  of the nonlinear portion  21 , and a second side portion  25  attached to the second end  23  of the nonlinear portion  21 . The first and second side portions  24  and  25  are oriented generally perpendicular to the general orientation of the nonlinear portion  21  (a straight path between the first and second ends  22  and  23 ). The side portions  24 ,  25  enlarge the size of the opening formed when the airbag deploys, to permit more rapid and reliable deployment. 
   The nonlinear portion  21  includes a number of bends  26  that create a meandering path between the first and second ends  22  and  23 . According to this embodiment, the bends  26  are rounded. However, “bend” within this application is any feature in the nonlinear portion  21  that changes the path along the nonlinear portion  21  between the first and second ends  22 ,  23  in a clockwise or counterclockwise direction. Consequently, sharp turns as well as curves of any radius constitute “bends.” 
   An outer layer  30  may be attached to the exterior side  16  of the face portion  15  by a means known in the art, including but not limited to chemical and adhesive bonding, heat welding, RF welding, interference fitting, deformable locking members, and heat shrinking. The outer layer  30  may be made from any suitable material, including polymers, metals, ceramics, and composites. However, it is desirable that the outer layer  30  be attractive, inexpensive, and weak enough to tear or detach from the exterior side  16  of the face portion  15  to permit deployment of the airbag. The outer layer  30  should also match the interior trim of the vehicle. Consequently, plastics or other materials used in the vehicle interior are preferred. 
   The ability of the outer layer  30  to form fit to the seam  20  is dependent upon the stiffness of the material forming the outer layer  30 , the thickness of the outer layer  30 , and the geometry of the seam  20 . A thinner, more flexible outer layer  30  will more easily conform to the shape of the seam  20 . In order to permit deployment of the airbag, the outer layer  30  must be substantially thin and flexible. Thus, the geometry of the seam  20  is the critical factor in determining whether the seam  20  shows through the outer layer  30 . 
   Linear deformation, in the form of a straight crease or bend in the outer layer  30 , readily occurs because deformation develops only along a thin cross-sectional area. When the outer layer  30  is deformed in one direction, an intersecting deformation is much more difficult to form because the first deformation effectively increases the thickness, and thereby the sectional modulus, of the outer layer  30  along the line of the first deformation. Consequently, existing deformations in the outer layer  30  make the outer layer  30  effectively stiffer and more resistant to further deformation. 
   The bends  26  in the nonlinear portion  21  are critical for that reason. By constantly changing the direction in which the outer layer  30  would have to deform to conform with the seam  21 , the bends  26  do not enable the outer layer  30  to significantly deform in any direction. As a result, the outer layer  30  remains substantially flat, with a cavity between the seam  20  and the outer layer  30 , and the seam  20  is not visible to a passenger looking at the outer layer  30 . This effect will occur with any configuration of the seam  20  in which no linear or near-linear trough lies underneath the outer layer  30 . The curved bends  26  of this embodiment are especially effective because there is no straight line of any length in the nonlinear portion to which the outer layer  30  can conform itself. Depending on aesthetic and material considerations, the first side portion  24  and the second side portion  25  may be linear. The side portions  24 ,  25  may also be made nonlinear with a shape similar to that of the nonlinear portion  21 . 
   If desired, the outer layer  30  may also be omitted entirely, and the module  12  may be constructed of a “single-shot” material. Single-shot processing is simply a fabrication process, such as injection molding, that utilizes only a single material, and preferably one single process. The exterior side  16  of the module  12  may be specially formed, through texturing, aesthetic shaping, and the like, to create a cosmetic surface  16 . 
   If no outer layer  30  is used, the seam  20  is preferably formed on the inside of the module  12 , i.e., on the interior side of the face portion  15  (not visible in  FIG. 1 ). The seam  20  may otherwise be configured as described above, with a nonlinear portion  21 . The nonlinear portion  21  then prevents read through because there is no viewpoint from which a user may see through any substantial part of the seam  20 . A user perceives no significant unnatural variation in the cosmetic surface  16 . Thus, no styling line need be formed in the exterior side  16 . 
   Additionally, whether the outer layer  30  is used, or the exterior side  16  is rather made into a cosmetic surface  16 , pressure applied against the face portion  15  of the cover  10  by a user does not bend the face portion  15  along any single axis. The seam  20  presents a large variety of weakened bending axes, so that the face portion  15  bends inward in several directions when pressure is applied. The seam  20  thus remains imperceptible to a user, and a user has no reason to repeatedly exert any considerable pressure against the face portion  15 . 
   Referring to  FIG. 2 , an alternative embodiment of the seam  20  is presented. In this embodiment, the nonlinear portion  21  has a multiplicity of smaller bends  36  to decrease the width of the nonlinear portion. Smaller bends  36  may provide additional support for especially flexible, thin materials that may be used in the outer layer  30 . As with the embodiment of  FIG. 1 , there are no linear segments in the nonlinear portion  21 , and the side portions  24  and  25  may be as shown, or may be made nonlinear as well. 
   Referring to  FIG. 3 , another alternative embodiment of the invention is shown. In this configuration, the nonlinear portion  21  is composed of bends  40 , in the form of substantially sharp corners  40 , connected by linear segments  42 . The linear segments  42  are short enough to inhibit folding of the outer layer  30  into the seam  20 . Although possibly less effective at masking the seam  20  than the previous embodiments with rounded bends  26 ,  36 , the substantially sharp corners  40  may provide design and manufacturing advantages while still keeping the outer layer  30  out of the seam  20 . 
   Referring to  FIG. 4 , yet another alternative embodiment of the invention is depicted. Traveling from the first end  22  to the second end  23  of the nonlinear portion  21 , a counterclockwise bend  46  is followed by two adjacent clockwise bends  48 , which are followed by two counterclockwise bends  46 , etc. The counterclockwise and clockwise bends  46 ,  48  are separated by linear segments  50  like those of the previous embodiments. As with the previous embodiment, the linear segments  50  are short enough to prevent unidirectional deformation of the outer layer  30 . 
   Referring to  FIG. 5 , another alternative embodiment is shown. As depicted in  FIG. 5 , the nonlinear portion  21  need not be a homogeneous pattern of linear or nonlinear segments. First and second linear segments  56  and  57 , positioned at the first and second ends  22  and  23  of the nonlinear portion  21 , respectively, may be connected by a nonlinear segment  58 . The nonlinear portion  21  is still nonlinear because the path along the nonlinear portion  21  between the first and second ends  22  and  23  is only partially straight. 
   Referring to  FIG. 6 , yet another alternative embodiment is depicted. The nonlinear portion  21  of the seam  20  may include a mixture of bends  60  and linear segments  62  of various shapes and sizes. The seam  20  need not be precisely formed, and will not show through the outer layer  30  as long as the requisite nonlinear features are found. The bends  60  may also be distributed asymmetrically along the seam  20 . 
   Referring to  FIG. 7 , the cover  10  of the present invention is shown with the seam  20  hidden. If an outer layer  30  is used, it has been attached to the exterior side  16  of the cover  10 , as depicted in  FIG. 7 . The outer layer  30  may be installed by any known method, including but not limited to adhesive bonding, chemical bonding, heat bonding, vacuum forming, RF welding, mechanical fastening, swaging, and sewing. The outer layer  30  shows little or no sign of the seam  20  because the outer layer  30  is not form-fitted to the seam  20 . 
   However, if no outer layer  30  has been used, the exterior side  16  is simply formed as a cosmetic surface  16 . In such a case, the cover  10  appears as shown in  FIG. 7 , except that no outer layer  30  is present. The seam  20  is substantially invisible, even though there is no styling line on the cosmetic surface  16 , because the seam  20  is nonlinear and therefore prevents read through. Similarly, any deformation that occurs in the cosmetic surface due to the seam  20  is also relatively unobservable. 
   Thus, the cover  10  is ready for installation in a vehicle. The locking tabs  18  may be aligned with suitable receptacles in the vehicle so that the cover  10  is held firmly within the vehicle. The outer layer  30 , if present, appears simply as a panel; any designs be formed on the panel before or after installation in the vehicle without the interference of the seam  20 . 
   Accordingly, the principles of material deformation are effectively applied by the present invention. The meandering nature of the seam  20  ensures that there is no single axis along which the outer layer  30  can visibly bend. As a result, the seam  20  is effectively hidden, and will not interfere with design schemes for the vehicle interior. Furthermore, occupants of the vehicle are not drawn to damage the outer layer  30  over the seam or keep their arms and hands in dangerous proximity to the airbag. Thus, the novel seam  20  of the present invention keeps the outer layer  30  flat, thereby making the entire cover  10  for an airbag more attractive, hassle-free, and safe. 
   The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.