Abstract:
A rear corner vehicle roof structure includes a rear structural pillar and a small cap-like reinforcement member. The rear pillar includes a vertically elongated base portion which transitions into a bifurcated upper end portion forming a longitudinally extending stub arm which is affixed to an associated side roof rail and a laterally extending stub arm which is affixed to an associated rear roof header. The reinforcement member includes a central bridge portion trifurcated to form extensions conforming to the pillar upper portion, the longitudinally extending stub arm and the laterally extending stub arm. The reinforcement member further includes peripherally flanged web segments disposed between circumferentially adjacent pairs of the pillar base portion, longitudinal and lateral stub arms. The flanged web segments are affixed to opposed continuous flange portions of the upper end portion and configured to support the central bridge portion in a spaced relation from the upper end portion.

Description:
TECHNICAL FIELD 
     The present disclosure relates to a roof structure of a vehicle body in general and an apparatus for reinforcing a roof structure of a vehicle body in particular. 
     BACKGROUND 
     Vehicle safety standards have evolved in an effort to provide safer passenger cars. A vehicle safety standard for roof crush resistance is FMVSS No. 216. The loading requirements of FMVSS No. 216 have been increased with the objective of providing greater protection for passengers in vehicle rollover events. The FMVSS standard will require that all vehicles meet a roof strength requirement of 3.0 times the vehicle weight. This requirement increase poses a significant challenge to all vehicle manufacturers. Increased roof strength requirements must be met while also achieving increased fuel economy that may demand lighter weight structures in the overall vehicle. 
     Large passenger vehicles often have three or more sets of vertical pillars supporting the roof structure. Pillars are typically referred to from front to rear as A, B, and C-pillars. Some vehicles also employ a fourth, D-pillar. In contrast, some small vehicles with only one row of doors have only two pillars. Vehicles with front and rear side doors generally have a middle B-pillar. The B-pillar defines the separation between separate front and rear door openings. Existing roof structures rely substantially on a mid-vehicle vertical B-pillar to sustain vertical roof crash loads. The size of the B-pillar required to meet roof crush requirements may obstruct access to the vehicle by occupants. It generally restricts the space available for door openings, and therefore the ease of entry and exit by the occupants of the vehicle. The B-pillar also limits the size of objects that are capable of being loaded through the door openings. The B-pillar may also obstruct the driver&#39;s field of view. The B-pillar also presents vehicle styling limitations, since its placement is often dictated by functional requirements. Although the B-pillar has been eliminated in certain vehicle types, such as light trucks, offering several styling and space advantages, meeting increasing roof strength requirements remains problematic. 
     One known vehicle roof system enabling elimination of the B-pillar transfers vertical roof loads onto an enhanced rear structure of the vehicle. An aspect of this system is the addition of upper cap reinforcement directly to assume roof crush loads applied at the front of the vehicle roof during testing. A specific load transfer mechanism is incorporated wherein vertical roof crush force applied near the front of the vehicle is transferred into both a torsional load upon a rear header of the vehicle and a bending moment upon the C-pillar of the vehicle. Although this system enabled elimination of the B-pillar, it does so by increasing the mass and complexity of the upper rear structure of the vehicle roof. For example, it requires several discrete elongated structural elements to form the C-pillar and the adjacent side and rear frames. 
     Conventional body frames are typically fabricated as multiple stamped sheet metal parts that are generally spot welded together. It is possible to improve the strength of conventional body frames by forming the sheet metal parts from high grade material such as dual phase and boron steels. Body frames may also be made stronger by using thicker gauge sheet metal components. However, the use of high strength alloys and thicker sheet metal may increase the weight of the vehicle and also increase the cost to manufacture the body frame. Even with the use of thicker alloy components, the roof portions of conventional design body frames may not always meet stringent test requirements for roof crush performance. 
     Although stamped members have been used in vehicle body structures for years, hydroformed components or members may be used in vehicles. Hydroforming is a cost effective way of shaping malleable metals into lightweight, structurally stiff and strong elements. One of the largest applications for hydroforming is the automotive industry, which makes use of complex shapes possible by hydroforming to produce stronger, lighter and more rigid unibody structures for vehicles. 
     Hydroforming allows complex shapes to be formed, which would be difficult to manufacture with standard solid die stamping. Furthermore, hydroformed parts can often be made with a higher stiffness to weight ratio and at a lower per unit cost than traditional stamped or stamped and welded parts. 
     Another known vehicle roof system configuration employs a roof rail integral with an A-pillar and a support pillar. The structure further includes a cross member. The A-pillar includes an inner surface, an outer surface, and a wall there between. The roof rail extends downwardly at a front end of the roof rail and extends downwardly at a rear end of the roof rail. The roof rail is integral to a one piece hollow A-pillar at the front end of the roof rail. The support pillar also includes an inner surface, an outer surface, and a wall there between. The support pillar also includes a tubular lower section that extends upwardly from the rocker. The upper section of the support pillar is integral to the rear end of the roof rail. Although providing certain advantages, this system can prove difficult to fabricate. 
     SUMMARY 
     A vehicle body structure having improved roof support is provided according to the embodiment disclosed herein. The upper end of a corner pillar is bifurcated into a longitudinally directed stub arm for supporting a side roof rail and a laterally directed stub arm for supporting a roof header. Peripheral segments of a reinforcement member are affixed to the corner pillar. 
     According to an embodiment of the description, a corner vehicle roof structure includes a corner pillar including base portion transitioning into a longitudinally extending stub arm affixed to an associated side roof rail and a laterally extending stub arm affixed to an associated roof header. A reinforcement member including peripherally flanged web segments is affixed to the corner pillar at discrete locations intermediate circumferentially adjacent pairs of the pillar base portion and stub arms, wherein the flanged web segments are affixed to the upper end portion and configured to support the central bridge portion in a spaced relation from the upper end portion. 
     According to another embodiment of the disclosure, a rear corner vehicle roof structure includes a rear pillar including a vertically elongated base portion transitioning into a bifurcated upper end portion forming a longitudinally extending stub arm affixed to an associated side roof rail and a laterally extending stub arm affixed to an associated rear roof header. A reinforcement member includes a central bridge portion which is trifurcated to form extensions aligning and registering with the pillar upper end portion, the longitudinally extending stub arm and the laterally extending stub arm. The reinforcement member further includes peripherally flanged web segments disposed intermediate circumferentially adjacent pairs of the pillar base portion and stub arms. The flanged web segments are affixed to the upper end portion and configured to support the central bridge portion in a spaced, generally parallel relation from the upper end portion. 
     According to yet another embodiment of the disclosure, a vehicle roof structure includes a left rear pillar and a right rear pillar, wherein each rear pillar is longitudinally spaced from a respective left front pillar and a right front pillar, and wherein said front and rear pillars provide vertical support of the roof structure. A left side roof rail extends longitudinally between the left front and left rear pillars and a right side roof rail extends longitudinally between the right front and right rear pillars. A front edge roof header extends laterally between the left and right front pillars, and a rear edge roof header extends laterally between the left and right rear pillars. The left and right rear pillars each comprise a vertically elongated base portion transitioning into a bifurcated upper end portion forming a longitudinally extending stub arm affixed to an end of an associated roof rail and a laterally extending stub arm affixed to an end of said rear roof header. Lastly, the left and right rear pillars each further comprise a reinforcement member including a central bridge portion trifurcated to form extensions aligned and registering with an associated pillar base portion, an associated longitudinally extending stub arm and an associated laterally extending stub arm. Each said reinforcement member also includes peripherally flanged web segments disposed intermediate circumferentially adjacent pairs of the associated pillar base portion and stub arms. The flanged web segments are affixed to the associated upper end portion and configured to support the central bridge portion in a spaced relation from the associated upper end portion. 
     These and other features and advantages of the disclosure will become apparent upon reading the following specification, which, along with the drawings, describes an embodiment of the disclosure in detail. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present apparatus will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a left (e.g., driver&#39;s) side elevation view of an exterior of a vehicle; 
         FIG. 2  is a left-rear side isometric view of the cabin structure similar to that of the vehicle of  FIG. 1 , including the rear wall panel and rear glass panels; 
         FIG. 3  is broken perspective view of a reinforcement member (e.g., section shear member) structurally incorporated with a rear upper side panel (e.g., C-pillar) of the cabin structure of  FIG. 2  from an exterior perspective; 
         FIG. 4  is a left side elevation view of the exterior of the vehicle of  FIG. 1  disposed within a standard roof strength test fixture; 
         FIG. 5  is a front elevation view of the exterior of the vehicle of  FIG. 1  disposed within a standard roof strength test fixture; 
         FIG. 6  is model of the upper portion of the rear side panel combined with the reinforcement member of  FIG. 3  subjected to a simulated roof crush test with the test fixture of  FIGS. 4 and 5  illustrating force loading imposed by such a test from an exterior perspective; 
         FIG. 7  is model of the upper portion of the rear side panel of  FIG. 3  without the reinforcement member subjected to a simulated roof crush test with the fixture of  FIGS. 4 and 5  illustrating force loading imposed by such a test at 70 mm displacement from an interior perspective; 
         FIG. 8  is a model of the upper portion of the rear side panel of  FIG. 3  without the reinforcement member subjected to a simulated roof crush test with the fixture of  FIGS. 4 and 5  illustrating force loading imposed by such a test at 100 mm displacement from an interior perspective; 
         FIG. 9  is an example of a graph of results from simulated roof crush tests (i.e., with and without the structural member) illustrating strength performance advantages of the disclosed embodiment; 
         FIG. 10  is an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on roof rail force versus time along the X axis; 
         FIG. 11  is an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on roof rail force versus time along the Y axis; 
         FIG. 12  is an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on roof rail force versus time along the Z axis; 
         FIG. 13  is an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on C-pillar force versus time along the X axis; 
         FIG. 14  is an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on roof rail force versus time along the Z axis; and 
         FIG. 15  is a cross-sectional view taken along lines  15 - 15  of  FIG. 3  illustrating the juxtaposition and interconnection of the rear upper side panel and the reinforcement member. 
     
    
    
     Although the drawings represent embodiments of the present apparatus and method, the drawings are not necessarily to scale and certain features may be exaggerated in order to illustrate and explain the present disclosure. The exemplification set forth herein illustrates an embodiment of the apparatus and method, in one form, and such exemplifications are not to be construed as limiting the scope of the present apparatus and method in any manner. 
     DETAILED DESCRIPTION 
     The present disclosure describes a reinforcement member, a.k.a. a “section shear member”, which overlays the “Y” shaped upper end of a vehicle body frame C-pillar joining the rear roof header and a side roof support member. The reinforcement member provides a mass-efficient reinforcement of the C-pillar, absorbing roof crush forces by resisting rotation of the C-pillar and buckling of the rear header. The reinforcement member includes a peripheral flange providing welding surfaces and a plurality of ribs increasing tensile strength, directing roof crush forces through the “Y” shaped upper end of a vehicle body frame C-pillar and resisting the onset of rear glass breakage. 
     The vehicle body frame includes a roof frame having a front header, a rear header and side supports extending between the front and rear headers. The rear header extends between the sides of the vehicle and defines a top structure for the rear window. The C-pillars define the side structures of the rear window. Each C-pillar has an upper end which is generally split so as to define a “Y” shape. Each end of the C-pillar is attached to an end of a respective rear header and side support. Typically, the frame is assembled by welding the parts together. The “Y” shape is subjected to complex loading (e.g., rotation+bending+twist) which, in turn, may cause the rear header to buckle, resulting in rear, sliding glass breakage. 
     The reinforcement member provides a structural support for the “Y” which counters the complex force (i.e., rotation+bending) so as to prevent or delay the rear header from buckling. This delays rear glass breakage, improving peak load for roof strength tests. 
     A frame assembly having a reinforcement member (e.g., section shear member) is provided. The frame assembly includes a C-pillar, a rear header and a side support, all of which defines a rear side portion of the vehicle frame. The C-pillar includes an end portion having a “Y” shape, wherein the ends of the “Y” (e.g., the prongs or stub arms) are welded to the ends of the respective rear header and side support. The reinforcement member is mounted to a medial surface of the C-pillar. Specifically, the reinforcement member is generally centered on the “Y”. The reinforcement member includes a peripheral flange having a welding surface for attachment to the outer edges of the “Y” shape of the C-pillar. The body of the reinforcement member may include a plurality of shaped ribs configured to increase the tensile strength of the reinforcement member and absorb complex loading (i.e., twisting+bending+rotation) of the C-pillar. 
     The reinforcement member provides structural reinforcement to the “Y” portion of the C-pillar, where because of the attachments to the rear header and the side support, a complex force is applied during an impact. The reinforcement member provides a mass-efficient reinforcement of the C-pillar of the vehicle which delays rear glass breakage which would otherwise cause peak load to drop. 
     In the following Detailed Description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific embodiments in which the disclosure may be practiced. In this regard, directional terminology, such as “top”, “bottom”, “front”, “back”, “leading”, “trailing”, etc. is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Furthermore, the axes (e.g., ±X, ±Y, and ±Z axes) are referenced on the drawings to provide a relative directional sense only. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. 
     For purposes of providing non-limiting definition and to enable clear understanding of the present disclosure, “longitudinal” means parallel to the direction of the Y axis, “lateral” means parallel to the direction of the X axis, and “vertical” means parallel to the direction of the Z axis. 
     Referring to  FIG. 1 , a vehicle (e.g., a pick-up truck)  10  has a roof  12  vertically supported by left and right side A-pillars  14  located at the forward end of the vehicle cabin, left and right side B-pillars  16  located at a longitudinally intermediate location of the vehicle cabin between front and rear sets of passenger doors  18  and  20 , respectively, and left and right side C-pillars  22  located at the rearward end of the vehicle cabin. A principle application of the present disclosure is in a region  24  adjacent the upper portion of the left and right side C-pillars  22 . 
     Referring to  FIG. 2 , an isometric view of a vehicle cabin reinforcement sub-structure is indicated generally at  26 . Panels forming the outer surfaces of the cabin are deleted for purposes of illustrating roof vertical support elements in the present disclosure which include only left and right A-pillars  28  and  30 , respectively, and left and right C-pillars  32  and  34 , respectively. No B-pillars are illustrated for purposes of clarity in the present disclosure. The vehicle cabin reinforcement substructure  26  forms a roof frame including a front edge roof header  35  extending laterally between the upper terminus of the left and right A-pillars  28  and  30 , respectively, a rear edge roof header  36  extending laterally between the upper terminus of left and right C-pillars  32  and  34 , respectively, a left side roof support rail  38  extending longitudinally between the upper terminus of the left A-pillar  28  and the upper terminus of the left C-pillar  32 , and a right side roof support rail  40  extending longitudinally between the upper terminus of the right A-pillar  30  and the upper terminus of the right C-pillar  34 . A rear closure panel  42  extends laterally between the lower portions of the left C-pillar  32  and the right C-pillar  34 . The rear edge roof header  36  defines a top structure for a rear window  44 . The left and right C-pillars  32  and  34 , respectively, define the side structures of the rear window  44 . 
     The most rigorous loads encountered by vehicle roof  12  previously described tend to occur during a vehicle rollover event. Federal Motor Vehicle Safety Standard (FMVSS) No. 216 is intended to simulate loads that occur when a vehicle roof  12  strikes the ground during a rollover event. The Standard requires minimum roof strength as a ratio of vehicle weight. Additionally, the Insurance Institute of Highway Safety (IIHS) publishes its own stringent roof strength requirement. While not mandatory, the latter rating is highly influential in customer decisions, and beneficial for manufacturers to have a high rating. Both tests are performed with essentially the same procedure, but demand different performance levels. 
     Referring to  FIG. 5 , an example roof strength test fixture  50  is illustrated. A large steel plate  52  of the test fixture  50  having prescribed dimensions and orientation is placed in contact with one side of the roof  12  of the vehicle  10 . During a roof strength test, the steel plate  52  is displaced downwardly along a prescribed angle and applies a steadily increasing force indicated by arrow  54 , as the steel plate  52  travels. This simulates contact of the roof  12  with the ground during a vehicle rollover event. For top scores the test standard may require that a force as much as 4.0 times the unloaded weight of the vehicle must be achieved before the steel plate  52  travels 5 inches (127 millimeters) from the point of initial contact. For light duty trucks with a 6000 pound maximum weight, 107,018 newtons may be required. 
     Referring to  FIG. 4 , a side view of the standard roof strength test fixture  50  is illustrated. The location of the rearmost edge  56  of the steel plate  52  in relation to the full vehicle  10  may be estimated based on test setup protocol. The resultant position of the rearmost edge  56  of the steel plate  52  is an intermediate position between the B-pillar  16  and the C-pillar  22  for longer vehicles. 
     The rear portion of the body structure may be employed to provide stiffness resistant to roof crush loads. Loads applied at the forward part of the roof  12  near the windshield generally do not receive resistance from the rear portion of the vehicle  10 . The center structure commonly assumes a large portion of the strength requirement through column loading on vehicles with a B-pillar  16 . It is desirable in some cases to eliminate the B-pillar  16  from the vehicle  10 . However, a load management strategy is required to meet structural demands. 
     Referring to  FIGS. 2 ,  3  and  15 , the components collectively comprising the vehicle cabin reinforcement substructure  26  are preferably separately formed of stamped steel or other suitable malleable material, and interconnected by weldments  46  or other suitable fastening methodology. The corresponding left and right side components (e.g., left C-pillar  32  and right C-pillar  34 ) are formed as virtual mirror images of one another. Accordingly, for the sake of brevity, only specific left side elements will be described in detail, it being understood that the description applies equally to both sides of the vehicle cabin reinforcement substructure  26 . 
     The left (e.g., driver side) C-pillar  32  comprises a vertically elongated base member  48  which is bifurcated at its upper terminus or upper end portion  49  in a “Y” configuration to define a first longitudinally directed stub arm  58  and a second laterally directed stub arm  60 . The base member  48  is sectionally shaped to define a central bridge portion  62  bi-directionally transitioning into opposed continuous mounting flanges  64  through integral interconnecting offset legs  66 . 
     The end of the left side roof rail  38  disposed adjacent the first longitudinally directed stub arm  58  of said left C-pillar  32  is sectionally shaped to define a central bridge portion  68  bi-directionally transitioning into opposed continuous mounting flanges  70  through integral interconnecting offset legs  72  and to matingly conform with complimentary features of said first longitudinally directed stub arm  58  for attachment thereto via said weldments  46 . 
     Similarly, the end of the rear edge roof header  36  disposed adjacent the second laterally directed stub arm  60  of said left C-pillar  32  is sectionally shaped to define a central bridge portion  74  bi-directionally transitioning into opposed continuous mounting flanges  76  through integral interconnecting offset legs  78  and to matingly conform with complimentary features of said second laterally directed stub arm  60  for attachment thereto via said weldments  46 . 
     A reinforcement member (e.g., section shear member)  80 , which is preferably formed of stamped steel or other suitable malleable material, is interconnected to the “Y” configured upper terminus of the elongated base member  48  by weldments  47  or other suitable fastening methodology. The gauge of the material employed to fabricate the reinforcement member  80  is preferably the same employed in the elongated base member  48 . The reinforcement member  80  includes a central bridge portion  82  which is trifurcated to define a first outward extension  84  aligned with the vertically elongated base member  48 , a second outward extension  86  aligned with the first longitudinally directed stub arm  58  and a third outward extension  88  aligned with the second longitudinally directed stub arm  60 . 
     The central bridge portion  82  of the reinforcement member  80  forms a first outer web segment  90  circumferentially interconnecting the first and second outward extensions  84  and  86 , respectively, of the elongated base member  48 . The first outer web segment  90  is sectionally shaped to form one or more flanges  92  through an interconnecting offset leg  94 . 
     The central bridge portion  82  of the reinforcement member  80  forms a second outer web segment  96  circumferentially interconnecting the second and third outward extensions  86  and  88 , respectively, of the elongated base member  48 . The second outer web segment  96  is sectionally shaped to form one or more flanges  98  through an interconnecting offset leg  100 . 
     The central bridge portion  82  of the reinforcement member  80  forms a third outer web segment  102  circumferentially interconnecting the third and first outward extensions  88  and  84 , respectively, of the elongated base member  48 . The third outer web segment  102  is sectionally shaped to form one or more flanges  104  through an interconnecting offset leg  106 . 
     The interconnecting weldments  47  join the flanges  92 ,  98  and  104  of the first, second and third web segments  90 ,  96  and  102 , respectively, to the flanges  64  of the elongated base member  48  to exclusively support the reinforcement member  80  on the “Y” shaped upper end portion  49  of the elongated base member  48 . The legs  94 ,  100  and  106  of the reinforcement member  80  are dimensioned and configured to space the central bridge portion  82  of the reinforcement member  80  from the adjoining central bridge portion  62  of the elongated base member  48 , as identified by reference numeral  116 . The central bridge portion  82  of the reinforcement member  80  has shaped upsets  108  and  110  formed therein which can direct roof crush loads received through the left side roof rail  38  into the elongated base member  48  and the rear roof header  36 , delaying onset of rear window  44  failure. Furthermore, the generally circumferential arrangement of the weldments  47  further tend to direct localized roof crush loads radially inwardly toward a node indicated by a star  112 , depicted by double headed arrows  114 , further delaying onset of rear glass  44  failure. In effect, the reinforcement member  80  acts as a focused truss system or shear plate by locally rigidifying the upper terminus of the elongated base member (e.g., C-pillar)  48  and thereby preventing or delaying “twisting” when subjected to roof crush loads without adding significant additional structure. 
     Referring to  FIG. 6 , a model of the upper portion of the rear side panel combined with the reinforcement member  80  subjected to a simulated roof crush test with the test fixture of  FIGS. 4 and 5  illustrating force loading imposed by such a test from an exterior perspective. The resultant loading gradations are depicted in the included table. 
     Referring to  FIG. 7 , a model of the upper portion of the rear side panel of  FIG. 3  without the reinforcement member  80  subjected to a simulated roof crush test with the fixture of  FIGS. 4 and 5  illustrating force loading imposed by such a test at 70 mm displacement from an interior perspective. The resultant loading gradations are depicted. 
     Referring to  FIG. 8 , a model of the upper portion of the rear side panel of  FIG. 3  without the reinforcement member  80  subjected to a simulated roof crush test with the fixture of  FIGS. 4 and 5  illustrating force loading imposed by such a test at 100 mm displacement from an interior perspective. The resultant loading gradations are depicted. 
     Referring to  FIG. 9 , an example of a force-displacement graph of results from simulated roof crush tests (i.e., with and without the reinforcement member  80 ) illustrates strength performance advantages of the disclosed embodiment wherein general stiffness is increased, peak force in increased, and additional strength is imparted after the rear glass breaks. 
     Referring to  FIG. 10 , an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on roof rail force versus time along the X axis. 
     Referring to  FIG. 11 , an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on roof rail force versus time along the Y axis. 
     Referring to  FIG. 12 , an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on roof rail force versus time along the Z axis. 
     Referring to  FIG. 13 , an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on C-pillar force versus time along the X axis. 
     Referring to  FIG. 14 , an example of a graph of results from the simulated roof crush tests (i.e., with and without the structural member) of  FIG. 9  focusing on roof rail force versus time along the Z axis. 
     It is to be understood that the present apparatus and method has been described with reference to specific embodiments and variations to provide the features and advantages previously described and that the embodiments are susceptible of modification as will be apparent to those skilled in the art. 
     Furthermore, it is contemplated that many alternative, common inexpensive materials can be employed to construct the basis constituent components. Accordingly, the forgoing is not to be construed in a limiting sense. 
     The present apparatus and method has been described in an illustrative manner, and it is to be understood that the terminology, which has been used is intended to be in the nature of words of description rather than of limitation. 
     Obviously, many modifications and variations of the present disclosure are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for illustrative purposes and convenience and are not in any way limiting, the present apparatus and method, which is defined by the following claims as interpreted according to the principles of patent law, including the Doctrine of Equivalents, may be practiced otherwise than is specifically described.