Patent Description:
It would be desirable to implement below a superstructure that receives percussive impacts an underlayment system that will reduce impact forces and therefore reduce the potential risk of injury associated with fall-related impacts on the surface. Potential benefits include reducing injury risk due to falls on the flooring surface, minimizing system cost, maintaining system durability, facilitating installation, abating noise while offering surface quality and comfort for both patients and caregivers.

While such underlayment layers provide some added benefit, they also increase system cost, installation complexity, and often reduce the durability of the top flooring material. To date, no commercially cost effective and durable underlayment system has been developed that provides a substantial injury risk reduction due to falls on the variety of flooring products. Several attempts have been made, but such approaches often fail to meet certain performance and cost effectiveness objectives.

One important aspect when considering deploying an underlayment system for impact protection is the consistency in performance over the entire surface. The impact performance of previous approaches varies substantially when comparing the center of the energy absorbing material and the seams or joints between adjacent energy absorbing materials. The seams between foams, rolls or panels, for example, lack cross linking or bonds between adjacent energy absorbers. These areas are weaker than the center of the energy absorber and deform at a lower applied load compared to the areas away from the seam. This results in areas where not only is the impact performance inconsistent across the surface, but also promotes loss of balance since locations are not visible. Finally, these areas can also promote inconsistent wear patterns in the floor covering that may result in visual and structural defects over time due the stress induced on the floor covering by the seams in the underlayment. While some technologies, like foam, may be weaker at the seams one can appreciate that other products like injection molded tiles maybe stronger at the seams and weaker in the center, again creating inconsistencies in impact, instability, and wear patterns across a flooring surface.

Another important aspect when considering deploying an underlayment system for impact protection is comfort and vibration damping under foot. The ideal underlayment product would provide both enhanced comfort under foot while providing enhanced impact protection. Conventional approaches historically accomplished this by adding layers to the construction which adds both cost and system complexity. For example, two layers of foam that differ in density and or chemistry may be layered beneath the flooring surface where a softer layer enhances comfort under foot and a second more firm layer enhances the impact absorbing properties. Injection molded tiles will often be assembled between a layer of compliant foam and the finished flooring product. Adding layers to flooring system result in added costs, complexity, and failure modes that are undesirable.

Against this background, it would be desirable to develop a progressive stage load distribution and absorption system that would underlay a superstructure material such as flooring system to mitigate injuries and soften footfalls, while reducing noise and vibration where possible.

Ideally, such a system would be of relatively low cost and present a low profile to minimize tripping, yet be durable. In several embodiments, an underlayment infrastructure would be compatible with a superstructure material such as sheet vinyl and carpet.

According to the invention, one or more of these objectives is achieved by a progressive stage load distributing and absorbing system as defined in claim <NUM>, preferable features thereof being defined in the dependent claims.

This disclosure includes a progressive or multi-stage load distributing and absorbing system that lies below a superstructure material which is exposed to percussive forces. The progressive stage load distributing and absorbing system is interposed between the superstructure material and a foundation below. In examples of the disclosure, such progressive systems offer a first and one or more subsequent levels of reaction to an impacting load, the reaction varying from a initially relatively compliant stage and then transforming to a gradually stiffer response to further load absorption. This behavior tends to offer a padded response to for example a heavy footfall or a tumbling patient. As a result, serious injury may be lessened or avoided.

Examples of the disclosure contemplate one or more progressive stage load distributing and absorbing tiles that are positioned side-by side. At least some of the tiles have a barrier layer that lies below the superstructure material - primarily to distribute, rather than absorb an impacting force, such as a heavy footfall. To cushion the blow, a load absorbing underlayment infrastructure is positioned below the barrier layer.

The underlayment infrastructure in a typical tile has one or more progressive stage "hat-shaped" (defined below) absorbing members. In an example, each of those members has a relatively stiff initial load transmission subsystem that preferably lies below and next to the barrier layer. This subsystem at first transmits forces from the hit to a relatively compliant stage absorbing subsystem. In this disclosure "relatively" broadly refers to the relative stiffness of the stiff and compliant absorbing subsystems in response to a hit. The compliant subsystem may be lowermost (preferably), or in some examples be uppermost. After the compliant subsystem deflects and perhaps bottoms out, the primary role of the stiff stage absorbing subsystem reverts to load absorption, rather than load transmission.

Consider one relatively stiff force transmission subsystem that primarily transmits, rather than absorbs energy. As noted earlier, it lies below the barrier layer. In that subsystem is a basal portion that preferably is positioned adjacent to the barrier layer. The basal portion originates as a sheet material that is preferably thermoformed to produce the stiff and compliant progressive stage absorbing members that constitute the disclosed infrastructure. Alternative methods include compression molding, casting, vacuum forming and injection molding.

In at least some of the stiff stage progressive absorbing members, a curvilinear wall extends from the basal portion toward the foundation. Preferably, such a wall has a draft angle (Θ, <FIG>) that lies between about <NUM> and <NUM> degrees. This wall has a top region extending from the basal portion and a bottom region at the opposite end portion of the wall. In examples, a shoulder portion extends inwardly from the bottom region. In other embodiments, the shoulder portion may not exist. In those cases, there is a somewhat continuous transition between the stiff and compliant stage subsystems.

Following impact upon the superstructure, ignoring optional adhesives, a load is transmitted across the barrier layer initially to the stiff stage subsystem of the progressive stage absorbing members of the underlayment infrastructure. Such load travels through the wall of the stiff stage absorbing subsystem, it reaches across a shoulder (if a shoulder exists) and then to the compliant stage absorbing subsystem before impinging on the foundation. If there is a rebound or recoil, such loads are delivered back to the stiff stage, which then assumes a more compliant role rather than its former load-transmission role. In such walls, load absorption is achieved by the wall bending inwardly or outwardly to or toward an un-deflected position.

One result of these subsystems cooperating in the described manner is that the compliant stage absorbing subsystem deflects before one or more of the stiffer transmission stage absorbing subsystems in response to the load. The relatively stiff subsystem is available to absorb what remains of the impacting load after the compliant stage has deflected or bottomed out. Consequently, footfalls are softened, vibration is lessened, noise is reduced and injury after a fall is mitigated.

Accordingly, examples of this disclosure include a progressive stage load distributing and progressive stage energy absorbing system that lies below a superstructure material which is exposed to continual or intermittent percussive loads. Often, such forces may cause a high localized pressure, such as when forces from a wheelchair are exerted through narrow wheels.

In the underlayment infrastructure, load absorption is mainly provided by groups of progressive stage absorbing members that are provided in tiles thereof (described below). Tiles are united by inter-engagement of overlapping barrier layers that overhang the ceilings of adjacent tiles.

<FIG> shows all features of claim <NUM> and represents an embodiment of the invention, the further figures representing examples provided for supporting the understanding of the invention.

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms without departing from the invention as defined by the claims. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ alternative examples of this disclosure.

This disclosure includes a progressive stage load distributing and absorbing system <NUM> (<FIG>) that lies below a superstructure material <NUM> which is exposed to steady or intermittent percussive forces. The progressive stage load distributing and absorbing system <NUM> is interposed between a superstructure material (such as tile or carpeting, for example) <NUM> and a foundation <NUM> below.

Examples have one or more progressive stage load distributing and absorbing tiles <NUM> (<FIG>). At least some of the tiles <NUM> have a barrier layer <NUM> that lies below the superstructure material <NUM> primarily to distribute, rather than absorb an impacting load, such as a heavy footfall or a rolling wheelchair. To cushion the blow, mute noise and deaden vibration, an underlayment infrastructure (described later) <NUM> is positioned below the barrier layer <NUM>.

The tiles <NUM> that house the underlayment infrastructure <NUM> have one or more progressive stage hat-shaped (defined below) absorbing members <NUM> (<FIG>). One or more of those members <NUM> have a relatively stiff load transmission subsystem <NUM> that delivers force to a compliant stage absorbing subsystem <NUM> that is the first subsystem to deflect. Preferably, the compliant stage <NUM> absorbing subsystem lies adjacent to the foundation <NUM>.

Included in the stiff force transmission (and later, residual force-absorbing) subsystem <NUM> is a basal portion <NUM> that in examples is positioned adjacent to the barrier layer <NUM> (<FIG>). The basal portion <NUM> originates as a sheet material that is preferably thermoformed to produce the progressive stage absorbing members <NUM> that constitute the disclosed infrastructure <NUM>.

A curvilinear wall <NUM> extends from the basal portion <NUM> toward the foundation <NUM>. In this context, "curvilinear" means curved when viewed from above or below and substantially linear before impact when viewed from the side. This wall <NUM> has a top region <NUM> extending from the basal portion <NUM> and a bottom region <NUM> at the opposite end portion of the wall <NUM>. In examples, a shoulder portion <NUM> extends inwardly from the bottom region.

After impact, loads are transmitted across the barrier layer <NUM> to the stiff force transmission subsystem <NUM>, and then to the compliant stage absorbing subsystem <NUM> that extends from the stiff stage subsystem <NUM>, in examples towards the foundation <NUM>.

To set the stage (returning to <FIG>), in exemplary embodiments of a progressive stage energy absorbing underlayment system <NUM>, there are four tiles <NUM> secured to one another. This arrangement of adjacent tiles produces four-tile seams and two-tile seams. Four areas are magnified in <FIG> to show three unique seam conditions compared to the tile central area. The tile central area (far left) has no seams and constitutes above <NUM>% of the system surface area. The other <NUM>% includes seams of various configurations that need to perform in a similar manner to the tile central area. This is in contrast with the four-tile seam (lower left) where four barrier layers intersect. The straight two-panel seam (lower right) and straight two-panel male/female registration seam (upper right) are also depicted in <FIG>.

In <FIG>, there is a staggered configuration that forms a progressive stage load distribution and energy absorbing system. This arrangement of adjacent tiles produces three-panel (<FIG>) and two-panel seams. Three areas have been magnified in <FIG> to show the remaining three unique seam conditions that contrast with the four shown in <FIG>. The two-tile sinusoidal edge seam (lower left) is where the trim edge of the adjacent underlayment infrastructure is sinusoidal. The three-tile seam (bottom middle) is where three barrier layers intersect. Finally, we see one example of the two-tile male/female registration sinusoidal edge seam (lower right).

<FIG> is a bottom view of one example of a thermoformed underlayment infrastructure <NUM> showing an array of energy absorbing members <NUM> in a hexagonal configuration. The basal portion <NUM> between adjacent members <NUM> may be planar or ribbed, depending on the desired layout. Generally, the hexagonal array is preferred due the dense arrangement of adjacent structures.

As described herein, there are three alternative examples of a representative compliant stage subsystem - a lobe feature, a star-shaped feature, and a configuration in which adjacent groups of members have different heights.

<FIG> is an isometric bottom view of a lobe example <NUM> of a compliant stage <NUM> in typical load absorbing members <NUM>. Here, there is an array of hat-shaped progressive stage absorbing members <NUM> that possess a male lobe <NUM> whose base <NUM> is recessed within the shoulder <NUM> of the member <NUM>. The lobe <NUM> is surrounded by a moat-like depression which is recessed into the shoulder. The top of the lobe extends beyond the plane of the shoulder, much like a tower that lies inside and above the moat. This moat draws material into itself during the thermoforming process and preferentially lobe walls.

<FIG> is an isometric view of a star-shaped feature <NUM> that crowns the compliant stage <NUM>. The star may have <NUM>-<NUM> arms <NUM>. A nucleus portion <NUM> of a star-shaped feature <NUM> has a geometry that may be selected from any number of polygonal shapes to create a feature that is both recessed within and protrudes from the shoulder portion <NUM> of the member <NUM>. This depth-up draw occurs largely because a small footprint creates a weakening and a lower resistance to an applied load for the "drawn feature" (e.g., compliant stage <NUM>) compared to a "host feature" (e.g., stiff stage <NUM>). Portions of the star may be relatively flat or be recessed.

<FIG> is sectional view through a third alternate ("sky scraper") example <NUM> of a progressive stage underlayment infrastructure <NUM> in which adjacent load absorbing members <NUM> or groups of load absorbing members are of different heights. Separating each of such members is a basal portion <NUM>, i.e., the substantially unchanged portion of the sheet that enters the thermoforming process. A curvilinear wall <NUM> extends there from and a floor <NUM> lies across the lower portion <NUM> of the curvilinear wall. Such a structure could be installed so that the basal portion <NUM> is positioned adjacent to the barrier layer <NUM>. In an inverted configuration (see, e.g., <FIG>), the basal portion <NUM> is positioned adjacent to the foundation <NUM>. Note that the plane (or ceiling or floor portion) of each member <NUM> is flat (i.e., it lacks a drawn feature) and lies parallel to the foundation <NUM>. The first section (I) shows that the system, at a minimum, bears the weight of the superstructure <NUM> itself. Under an applied load in excess of the taller member yield force, the taller weaker members begin compressing and absorbing a portion of the total load exerted (see, (II)). This continues until the floor of the shorter members contacts the foundation (see, (III)). At that stage, the force required to compress the system further is greater than that required to compress the taller members.

The compression characteristics of the taller and shorter members <NUM> can be tuned by selecting material type, material thickness, draw depth and the like to develop characteristics that enhance comfort under foot, dampen vibrations, or absorb sound. The third section (III) in <FIG> shows the response of the system to an even higher applied load. Under this load level, which is likely at a level tuned to reduce the risk of fall injury, both the taller and shorter members collapse in a controlled manner to absorb the impact load.

In each example of the compliant stage (see, e.g. <FIG>), there is a progressive collapse of members from the weakest to the strongest. However, there is an additional level of crush resistance. The first section (I) shows the compression of the drawn feature (e.g., a lobe) that extends from the member's floor in a direction opposite to that in which the stiff stage compliant subsystem lies. Once the drawn feature collapses (II), the load is transferred to the taller member (relatively stiff subsystem) which begins bearing its share of the load. Once the applied force exceeds the yield force of the taller members, they begin to collapse until they compress to the point where the smaller members contact the foundation (III). Finally, once an applied load exceeds the force required to yield the entire load distributing and absorbing system, the taller and shorter apertures collapse simultaneously IV).

<FIG> shows that the star-shaped embodiment of the compliant stage collapses in a somewhat different manner from the lobes in <FIG>.

Alternative examples include absorbing member shapes beyond those depicted (e.g., those having a wall that is not curvilinear, but having a drawn feature in the associated member floor). Such a wall may be curved for instance, when viewed from the side in an undeflected condition. If desired, ribs may be provided for added stiffness between load absorbing members. Further, arrays of members may be arranged in a configuration (in contrast to <FIG>) that is other than hexagonal. In some applications and environments, materials may be selected that are other than thermoplastic polyurethane and polycarbonate.

In one example of a progressive stage load distributing and absorbing underlayment system <NUM> (e.g., <FIG>), there are has four quadrilateral, preferably rectangular, tiles <NUM>. A representative tile appears in <FIG>. Such tiles are positioned relative to one another by interengaging mating registration features <NUM>, <NUM>, including male <NUM> and female <NUM> features provided along the edges of a barrier layer <NUM>. Each tile <NUM>, <NUM>, <NUM>, <NUM> has an infrastructure <NUM> with a plurality of absorbing members <NUM> for load absorption and a barrier layer <NUM> for load distribution.

In <FIG>, the barrier layer <NUM> (in this case) is quadrilateral with edges B1, B2, B3 and B4. A sub-assembly of underlying absorbing members <NUM> includes individual members <NUM> that are conjoined by basal portions <NUM> which, before for example thermoforming take the form of a planar basal sheet. The absorbing members <NUM> coordinate to form a periphery of the sub-assembly that in many cases is quadrilateral and has edges A1, A2, A3 and A4. Each barrier layer <NUM> preferably is securely affixed to one or more of the ceilings <NUM> in a tile. In some cases, the barrier layer <NUM> is affixed to one or more of the ceilings <NUM> by means for securing <NUM> such as an adhesive or by mechanical means including screws, rivets, pins and the like.

To promote inter engagement between tiles in an assembly, edge B1 of the barrier layer <NUM> overhangs edge A1 of the sub-assembly of absorbing members <NUM> and edge B2 overhangs edge A2. Thus, edges A3 and A4 of the sub-assembly of absorbing members <NUM> extend beyond overlying edges B3 and B4 of the barrier layer <NUM>. This arrangement creates an overhanging L-shaped platform <NUM> of the barrier layer <NUM> and an open L-shaped overhanging portion formed by the ceilings <NUM> of the absorbing members <NUM> in the sub-assembly. In adjacent tiles, the L-shaped overhanging portion <NUM> associated with a given tile <NUM> supports the L-shaped platform of the barrier layer <NUM> of an adjacent tile. One consequence of this arrangement is that adjacent tiles engage each other in such a way as to inhibit relative lateral movement therebetween.

As shown in <FIG>, interlocking engagement of adjacent tiles in a group is provided by mating registration features <NUM>, <NUM>. In a preferred example, these mating registration features <NUM>, <NUM> are trapezoidal in shape. For example, a male trapezoid <NUM> abuts a female trapezoid <NUM> along the edges of adjacent tiles <NUM>, <NUM>, <NUM>, <NUM>. It will be appreciated that there are alternative shapes of mating registration features, such as keyholes, sawtooth, semicircles, jigsaw-like pieces, etc..

As used herein the term "hat-shaped" includes frusto-conical, which may or may not be inverted, as described later. Such hat-shaped members <NUM> may have a top wall portion <NUM> that has a footprint which is circular, oval, elliptical, a cloverleaf, a race track, or some other rounded shape with a curved perimeter. Similarly, for a bottom wall portion <NUM> of an absorbing member <NUM>. As used herein the term "hat-shaped" includes shapes that resemble those embodied in at least these hat styles: a boater/skimmer hat, a bowler/Derby hat, a bucket hat, a cloche hat, a fedora, a fez, a gambler hat, a homburg hat, a kettle brim or up-brim hat, an outback or Aussie hat, a panama hat, a pith helmet, a porkpie hat, a top hat, a steam punk hat, a safari hat or a trilby hat. See, e.g., https://www. hatsunlimited. com/hat-styles-guide.

As used herein the terms "hat-shaped" and "frusto-conical" exclude structures that include a ridge line or crease in a continuous curvilinear wall <NUM> associated with an absorbing member <NUM>, because such features tend to promote stress concentration and lead to probable failure over time when exposed to percussive blows. They tend to concentrate, rather than distribute or absorb incident forces.

Connecting the basal portion <NUM> between absorbing members and the floor <NUM> of an absorbing member <NUM> in most examples is a curvilinear wall <NUM>. When viewed laterally, a curvilinear wall <NUM> appears substantially linear or straight before being subjected to an impact that may reign through the superstructure <NUM> on a barrier layer <NUM>. When viewed from above or below, the footprint of the bottom portion <NUM> or top portion <NUM> may appear circular, elliptical, oval, a clover leaf, a race-track or some other rounded shape with a curved perimeter.

The floor <NUM> of an absorbing member <NUM> may be flat or crenelated. As noted earlier, the floor <NUM> or in some cases the basal portion <NUM> may have a drawn lobe feature <NUM> or a star-shaped feature <NUM> extending therefrom.

The absorbing members <NUM> may be manufactured from a resilient thermoplastic and be formed into frusto-conical or hat-shaped members that protrude from a basal sheet <NUM> which before exposure to a forming process is substantially flat.

In one preferred example, the barrier layer <NUM> is made from a strong thin layer of a polycarbonate (PC), a composite or a metal or other suitable rigid material, the absorbing member <NUM> is made from a resilient thermoplastic polyurethane (TPU), and the means for securing <NUM> is provided by a pressure sensitive adhesive (PSA) which bonds well to both the PC and TPU.

Thus, an underlayment infrastructure <NUM> is created by the juxtaposition of a barrier layer <NUM> and an underlying infrastructure of progressive stage absorbing members <NUM>.

An assembly of absorbing members <NUM> and overlying barrier layer <NUM> forms a tile <NUM>. Adjacent tiles are inter-engaged by overlapping and underlapping edges of the barrier layer <NUM> in the manner described above. Preferably, a small, but acceptable, gap exists between barrier layers <NUM> associated with adjacent tiles.

If desired, a means for securing, such as an adhesive <NUM> can be applied to one or both surfaces prior to the application of pressure which then adhesively attaches a barrier layer <NUM> to a tile <NUM>. An underlayment infrastructure <NUM> is thus assembled when the edges of adjacent tiles are brought into registration through the inter-engagement of mating registration features <NUM>, <NUM> of adjacent edges of associated barrier layers <NUM>.

While a pressure sensitive adhesive is a preferred example of means for securing <NUM> a barrier layer <NUM> to the basal portion or ceiling <NUM> of a tile, alternatives for attaching overlapped tiles together through their associated barrier layers <NUM> include mechanical means for attaching such as Velcro®, tape, rivets, etc..

The overlap of the barrier layers <NUM> and proximity of the absorbing members <NUM> on adjacent tiles distributes a load applied to the barrier layer <NUM> over a broad area. Loads are evenly distributed when applied either on a seam between adjacent tiles or within a tile. Loads are at least partially absorbed by flexure and possible rebound of the compliant and stiff stages in the absorbing members.

In more detail, selected features of the disclosed progressive load distributing and absorbing system include:.

Traditional flooring systems, which are installed over rigid surfaces such as concrete, tend to have little energy absorbing capabilities, thereby posing a risk for fall related injuries. Due the rigid nature of their construction, they do however provide a consistent surface in terms of firmness and stability under foot. A rigid surface such as a foundation supports the flooring product over its entire area. This is essential for products like ceramic tile, glass tile, wood flooring, and the like.

One challenge in developing, installing, and maintaining an attractive, yet compliant flooring system that reduces the risk of injury lies in engineering the system to maintain a consistent firmness and stability over the entire flooring surface throughout its normal life cycle, while being compliant. The system must balance compliance needs, yet accommodate other activities like walking, running, rolling in a wheelchair, and supporting other items such as furniture, equipment, and other objects. An ideal load distributing and absorbing system needs to be firm and stable under foot under such normal activities and at the same time be engineered to deflect or stroke to the greatest degree possible during a potentially injurious fall or impact event.

Additionally, the layers of the load distributing and absorbing system need to work in concert in order to maintain an attractive appearance after years of repeated wear and abuse. Ideally, the system needs to remain unblemished before, during, and after impact events and everyday activities.

The disclosed system is engineered for performance consistency at any and all points. Seven unique conditions were identified to confirm performance consistency via the scientific method and statistical probability analysis. These conditions will be described below. This will be followed by a description of the test devices and their intended purpose. Finally, a statistical analysis will be reported below that analyzes the consistency in performance across the entire surface.

Thermoforming begins with a basal sheet of material of constant thickness. The thermoplastic raw material is heated to the softening point and then stretched over a form tool via vacuum, pressure, and mechanical means. The thickness of the thermoformed part is a function of the base raw material thickness, raw material type, form temperature, and tool geometry which includes depth of draft, draft angle, and the upper assist design and clearance. Generally, areas where the depth of draw is greatest, the material is stretched in multiple directions. This results in thinner wall profiles than areas that experience less stretching.

Load absorbing members typically have a thicker ceiling and floor, while there is substantial thinning in the curvilinear wall. These members produce a generally "square wave" force versus displacement response to an applied load. There is an initial ramp up in force until the wall buckles and then maintains a relatively constant reaction force to the applied load throughout the available stroke. In members formed from the same base thickness, ceteris paribus, taller structures will yield at a lower load level than shorter structures.

Representative applications and advantages include:.

Testing has demonstrated that use of various examples of the disclosed system may lead to a:.

Test data also indicate that the proposed progressive stage load distributing and absorbing systems have the potential to substantially reduce the risk of injury and improve the quality of life for both older adults and caregivers.

Claim 1:
A progressive stage load distributing and absorbing system (<NUM>) that is adapted to lie below a superstructure material (<NUM>) which is exposed to percussive forces, the progressive stage load distributing and absorbing system (<NUM>) being adapted to be interposed between the superstructure material (<NUM>) and a foundation (<NUM>), the progressive stage load distributing and absorbing system (<NUM>) comprising:
one or more load distributing and absorbing tiles (<NUM>), at least some of the tiles (<NUM>) having:
a barrier layer (<NUM>) that is adapted to lie below the superstructure material (<NUM>);
an underlayment infrastructure (<NUM>) positioned below the barrier layer (<NUM>), the underlayment infrastructure (<NUM>) including
one or more progressive stage hat-shaped absorbing members (<NUM>), at least some of the progressive stage hat-shaped absorbing members having:
a stiff stage absorbing subsystem with members having
a basal portion that is positioned adjacent to the barrier layer (<NUM>);
a curvilinear wall (<NUM>) extending from the basal portion, the curvilinear wall having a top region extending from the basal portion and a bottom region, and
a shoulder portion (<NUM>) extending from the bottom region; and
a compliant stage load absorbing subsystem that is adapted to extend from the shoulder portion towards the foundation (<NUM>), wherein
the compliant stage load absorbing subsystem (<NUM>) deflects before the stiff stage absorbing subsystem in response to the load,
characterized in that
the compliant stage load absorbing subsystem includes a star-shaped feature (<NUM>) and an assembly of hat-shaped absorbing members (<NUM>) that have different heights, wherein the star-shaped feature (<NUM>) has a polygonal configuration which includes a male feature that is recessed within and protrudes from the shoulder portion (<NUM>) of an associated absorbing member.