Patent ID: 12208564

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although only preferred embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. As described hereinafter, the present invention is capable of other embodiments and of being practiced or carried out in various ways.

Also, for the purposes of this specification, including the appended claims, certain terminology will be resorted to for the sake of clarity in describing the preferred embodiments. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art, and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. As used herein, the terms “oriented”, “orientation”, and “highly oriented” as applied to the strands of the outer hexagon and the strands or ribs and tri-nodes of the inner hexagon, as well as the term “partially oriented” or “partial orientation” as applied to the junctions of the outer hexagon shall have the meanings well known to those skilled in the art in connection with the geogrids over the past many years. For example, the term “partially oriented” as applied to the junctions of the outer hexagon is readily apparent when compared to the strands of the outer hexagon and the strands or ribs and tri-nodes of the inner hexagon in that the junctions are considerably larger and thicker, as illustrated in the drawings herein.

As such, the level of orientation in the geogrid is that which can be observed by examining the geogrid to determine the extent to which the thickness of the geogrid has been narrowed or thinned from the corresponding thickness of the starting sheet caused by the stretching or orientating process, as well as by the striations which can be observed in the geogrid by visual (naked eye) examination or scanning electron microscope. Such terms are not intended to require determination of striation on a molecular level, such as for example, by microscopic examination of orientation of the polymer molecules.

And, for the purposes of this specification, including the appended claims, the term “about” when modifying numbers expressing a number of sizes, dimensions, portions, shapes, formulations, parameters, percentages, quantities, characteristics and other numerical values used in the specification and claims, the term is meant to encompass the stated value plus or minus 10%.

In addition, for the purposes of this specification, including the appended claims, the terms “aperture” and “opening” are used interchangeably herein, and the terms are meant to describe any of the plurality of open spaces located within the strands or ribs of the multi-axial integral geogrid.

The present invention is directed to a multi-axial integral geogrid structure produced from a polymer sheet as the starting material. According to a preferred embodiment of the invention, the polymer sheet starting material is substantially flat, and preferably uniplanar or substantially uniplanar.

The invention is based on the fact that the polymer sheet, when converted to a multi-axial integral geogrid via a starting sheet having a selected pattern of holes or depressions and oven stretching process, produces a finished product that has unique characteristics relative to prior uniaxial, biaxial, and triaxial geogrids for purposes of soil and other aggregate reinforcement and stabilization, and other geotechnical applications.

FIG.1is a plan view of an integral geogrid according to the prior art, i.e., a triaxial integral geogrid according to the Walsh '112 patent. As shown inFIG.1, the triaxial integral geogrid200has a repeating triangle210geometry. The triaxial integral geogrid200includes a plurality of oriented strands205interconnected by partially oriented junctions235wherein the six triangular openings210surrounding each junction235create a repeating hexagon geometry.

FIG.2is a plan view of a monolayer multi-axial integral geogrid100according to a preferred embodiment of the present invention. The multi-axial integral geogrid100includes a plurality of interconnected, oriented strands having an array of openings therein, a repeating floating hexagon within a hexagon pattern of the interconnected, oriented strands and the openings, and including linear strands that extend continuously throughout an entirety of the multi-axial integral geogrid. More specifically, multi-axial integral geogrid100includes a repeating pattern of floating inner hexagons130within each outer hexagon110. The outer hexagon110includes a plurality of outer oriented strands or ribs120interconnected by partially oriented junctions115. The inner hexagon130includes a plurality of oriented connecting strands145and150interconnected by tri-nodes135, and encompasses a hexagon-shaped center opening170. The outer hexagon110is connected to the smaller inner hexagon130by a plurality of supporting strands or ribs140and160, which define a plurality of trapezoid-shaped openings180. At the center of each pattern of three adjacent outer hexagons110is a triangular shaped opening190. As shown, junctions115are much larger than tri-nodes135.

As is evident fromFIG.2, another feature of the multi-axial integral geogrid of the present invention is the linearly continuous nature of the outer strands120of the repeating outer hexagon pattern. That is, the oriented strands120are linearly continuous, via partially oriented junctions115, as they extend continuously throughout the entirety of the multi-axial integral geogrid in three different directions separated from each other by approximately 120°, and indicated by arrows120A,120B, and120C inFIGS.4and5. Those skilled in the art will appreciate that different orientations of the same basic geometry are possible after stretching, if an appropriate corresponding rotation of the punched starting sheet geometry is made. The linearly continuous nature of the strands120provides the necessary enhanced strength and in-plane stiffness to the multi-axial integral geogrid of the present invention.

FIG.3is a perspective view of a starting monolayer material sheet300having holes or depressions formed therein for forming the multi-axial integral geogrid shown inFIG.2. The monolayer starting sheet300used as the starting material for a multi-axial integral geogrid according to the present invention is preferably through-punched, although it may be possible to use depressions formed therein instead. According to the embodiment of the starting material in which depressions are formed in the sheet, the depressions are provided on each side of the sheet, i.e., on both the top and the bottom of the sheet.

The monolayer starting sheet300includes a repeating pattern310of holes320and spacing330that when oriented provide the floating hexagon within a hexagon pattern of the multi-axial integral geogrid shown inFIG.2. According to one possible embodiment of the present invention, the diameter of holes320is 3.68 mm, and the spacing of the holes330in millimeters is as shown inFIG.3A.

Preferably, the overall thickness of the monolayer material sheet300is from about 3 mm to about 10 mm and, more preferably, the overall thickness of the monolayer material sheet300is from about 5 mm to about 8 mm.

And, in general, the monolayer material sheet300is polymeric in nature. For example, the material of construction may include high molecular weight polyolefins, and broad specification polymers. Further, the polymeric materials may be virgin stock, or may be recycled materials, such as, for example, post-industrial or post-consumer recycled polymeric materials. According to the preferred embodiment of the invention, the high molecular weight polyolefin is a polypropylene.

FIG.4is a perspective view of the multi-axial integral geogrid100shown inFIG.2, andFIG.5is an enlarged perspective view of the multi-axial integral geogrid100shown inFIG.4. As is evident fromFIGS.4and5, the strands120,140,145,150, and160have what is known to one skilled in the art as a high aspect ratio, i.e., a ratio of the thickness or height of the strand cross section to the width of the strand cross section that is greater than 1.0 in accordance with the aforesaid Walsh HAR patents, U.S. Pat. Nos. 9,556,580, 10,024,002, and 10,501,896. While not absolutely necessary for the present invention, a high aspect ratio for the strands or ribs is preferred. Thus, the multi-axial integral geogrid of the present invention provides enhanced compatibility between geogrid and aggregate, which results in improved interlock, lateral restraint, and confinement of the aggregate.

FIG.5Ais an enlarged side schematic drawing illustrating a partial section of Rib A and adjoining junctions of an outer hexagon (SeeFIG.13) which form or define a part of one of three linear strong axis strands that extend continuously throughout the geogrids of the present invention. These strong axis strands provide the necessary strength and in-plane stability of the geogrids when engaging with, confining and stabilizing aggregate in civil engineering applications.FIG.5Bis a similar enlarged side schematic drawing illustrating a partial section of Ribs B and D and adjacent tri-nodes of an inner hexagon. Typical thicknesses for each of these components in accordance with the present invention are set forth inFIGS.5A and5B.

FIG.6is a partial plan view that illustrates certain structural limitations of the prior art triaxial integral geogrid shown inFIG.1. The repeating geometric element of the conventional triaxial integral geogrid200has one basic opening shape—a triangle—one limiting strand dimension, and a high ratio of junctions to connecting strands, one to three. As such, the conventional triaxial integral geogrid200provides no variation in either opening shape or size and a single confinement angle of 60°.

FIG.7is another plan view that illustrates structural attributes of the multi-axial integral geogrid100as shown inFIG.2. Again, while the prior triangular integral geogrid200shown inFIG.1has only one basic shape and one limiting strand dimension, the multi-axial integral geogrid100leverages three different basic opening shapes—a hexagon110, a trapezoid180, and a triangle190—varying strand sizes, and two different internal confinement angles—60° and 120°. Further, the multi-axial integral geogrid100includes only one junction per six connecting strands, and has three strands associated with each tri-node. As such, the multi-axial integral geogrid100can better accommodate varying angles and orientation of aggregate as it is distributed across the geogrid.

FIG.8is a graph that illustrates the range of distribution of individual aperture area in a prior art triangular integral geogrid200of the type shown inFIG.1. More specifically,FIG.8shows the distribution of individual aperture area associated with a triaxial integral geogrid commercially available from Tensar as a TriAx® TX160® geogrid. As is evident fromFIG.8, the individual aperture area associated with a conventional triaxial integral geogrid is relatively limited, providing a range of distribution of individual aperture area only from about 775 mm2to about 850 mm2, or a range of only about 75 mm2.

FIG.9is a graph that illustrates the range of distribution of individual aperture area in another prior art triangular integral geogrid200of the type shown inFIG.1. More specifically,FIG.9shows the distribution of individual aperture area associated with a triaxial integral geogrid commercially available from Tensar as a TriAx® TX130S® geogrid. As is evident fromFIG.9, the individual aperture area associated with this conventional triaxial integral geogrid is also relatively limited, providing a range of distribution of individual aperture area only from about 475 mm2to about 550 mm2, or a range of only about 75 mm2.

In contrast,FIG.10is a graph that illustrates the enhanced range of distribution of individual aperture area that may be attainable with the multi-axial integral geogrid100of the present invention shown inFIG.2. As is evident fromFIG.10, the range of distribution of individual aperture area associated with the multi-axial integral geogrid100is substantially greater than that provided by the triaxial integral geogrid, with the wider distribution of individual aperture area from about 475 mm2to about 800 mm2providing more optimal interaction with granular materials of varying particle size, and especially pronounced between from about 500 mm2to about 700 mm2, or a range of at least 200 mm2.

FIG.11is a plan view that illustrates the in-plane rotational stiffness of the prior art triaxial integral geogrid200shown inFIG.1. As is evident fromFIG.11, the prior art integral geogrid200has a partially oriented junction235that connects oriented strands205, with each of the strands205having approximately the same length.

In contrast,FIG.12is a partial plan view that illustrates the enhanced in-plane rotational stiffness that may be attainable with the multi-axial integral geogrid100of the present invention shown inFIG.2. Again, the multi-axial integral geogrid100includes the preferred repeating floating hexagon within a hexagon pattern having an outer hexagon110and a smaller inner hexagon130. The outer hexagon110includes a plurality of oriented strands120interconnected by partially oriented junctions115. The inner hexagon130includes a plurality of oriented strands145and150interconnected by tri-nodes135. The outer hexagon110is connected to the inner hexagon130by a plurality of oriented supporting or connecting strands140and160. By virtue of the shorter length of oriented strands140,145,150, and160relative to the length of strands205, the multi-axial integral geogrid100has increased in-plane rotational stiffness.

FIG.13is a partial plan view that illustrates the various strands of the multi-axial integral geogrid shown inFIG.2. The multi-axial integral geogrid100includes a repeating floating hexagon within a hexagon pattern having an outer hexagon110and a smaller inner hexagon130. The outer hexagon110includes a plurality of oriented strands120(also designated by “A” inFIG.13) interconnected by partially oriented junctions115. The inner hexagon130includes a plurality of oriented strands145(“B”) and150(“D”) interconnected by oriented tri-nodes135. The outer hexagon110is connected to the inner hexagon130by a plurality of oriented supporting strands140(“C”) and160(“E”). (The designations A, B, C, D, and E for the various strands are employed in the data of Tables A, B and E, presented hereinafter.)

According to one embodiment of the invention, the four strands150(D) and the two strands160(E) are the widest (thickest side-to-side) and the four strands140(C) are the tallest, all of which provides for strength and stiffness. The two strands145(B) are the thinnest, which provides for out-of-plane flexibility. The strands120(A) are representative of TX160® strands, and these strands are neither the tallest nor the widest, neither the strongest nor the most flexible, and as such they are middle ground and inadaptable without the presence of strands B, C, D, and E. Thus,FIG.13illustrates the impact of multiple strand dimensions on strength and stiffness. Other embodiments and dimensional relationships will readily occur to those skilled in the art.

Table A presents the height, width, and aspect ratio of each of the various strands for one example of the multi-axial geogrid100of the present invention as illustrated inFIG.13. While the values presented in Table A are representative of the height, width, and aspect ratio that may be associated with the multi-axial geogrid100of the present invention, they are presented for purposes of illustration, without intending to be limiting of the scope of the invention.

TABLE AStrandHeight (mm)Width (mm)Aspect RatioA2.861.122.55B2.051.101.86C3.161.112.84D3.131.322.37E2.631.292.03

Table B presents a comparison of aspect ratios associated with the various strands of the multi-axial integral geogrid100of the present invention with the aspect ratio of various commercial triaxial integral geogrids commercialized by Tensar.

TABLE BStrandInventionTX160 ®TX180 ™TX130S ®A2.551.471.621.85B1.86———C2.84———D2.37———E2.03———Average2.331.471.621.85ribaspectratio

As is evident from Table B, the multi-axial integral geogrid100has a higher aspect ratio on all strands compared to each of the conventional triaxial integral geogrids. Combined with the other features of the present invention's geometry, this higher aspect ratio provides better performance than the triaxial geogrids of the Walsh HAR patents.

Broad ranges and preferred parameters for the multi-axial geogrid according to the present invention as shown inFIGS.13and15are as follows.

Rib A has a height within a broad range of from 1 mm to 4 mm, a preferred range of from 2 mm to 3 mm, and a preferred dimension of 2.86 mm. The Rib A width has a broad range of from 0.75 mm to 3 mm, a preferred range of from 1 mm to 2 mm, and a preferred dimension of 1.6 mm. The Rib A length has a broad range of from 30 mm to 45 mm, a preferred range of from 35 mm to 40 mm, and a preferred dimension of 37 mm. The Rib A aspect ratio has a broad range of from 1:1 to 3:1, a preferred range of from 1.5:1 to 1.8:1, and a preferred value of 1.7:1.

The Rib B height has a broad range of from 1 mm to 3 mm, a preferred range of from 1.5 mm to 2.5 mm, and a preferred dimension of 1.6 mm. The Rib B width has a broad range of from 0.75 mm to 3.5 mm, a preferred range of from 1 mm to 3 mm, and a preferred dimension of 1.8 mm. The Rib B length has a broad range of from 15 mm to 25 mm, a preferred range of from 18 mm to 22 mm, and a preferred dimension of 21 mm. The Rib B aspect ratio has a broad range of from 0.75:1 to 2:1, a preferred range of from 1.2:1 to 1.4:1, and a preferred value of 1.3:1.

The Rib C height has a broad range of from 1 mm to 4 mm, a preferred range of from 2 mm to 3 mm, and a preferred dimension of 2.7 mm. The Rib C width has a broad range of from 0.75 mm to 3.5 mm, a preferred range of from 1 mm to 2.5 mm, and a preferred dimension of 1.6 mm. The Rib C length has a broad range of from 15 mm to 30 mm, a preferred range of from 20 mm to 25 mm, and a preferred dimension of 23 mm. The Rib C aspect ratio has a broad range of from 1:1 to 3:1, a preferred range of from 1.5:1 to 2.5:1, and a preferred value of 1.7:1.

The Rib D height has a broad range of from 1.5 mm to 4 mm, a preferred range of from 2 mm to 3.5 mm, and a preferred dimension of 2.3 mm. The Rib D width has a broad range of from 1 mm to 4 mm, a preferred range of from 1.5 mm to 2.5 mm, and a preferred dimension of 1.5 mm. The Rib D length has a broad range of from 10 mm to 30 mm, a preferred range of from 15 mm to 25 mm, and a preferred dimension of 18 mm. The Rib D aspect ratio has a broad range of from 1:1 to 3:1, a preferred range of from 1.4:1 to 1.7:1, and a preferred value of 1.6:1.

The Rib E height has a broad range of from 1 mm to 4 mm, a preferred range of from 1.5 mm to 3.0 mm, and a preferred dimension of 1.9 mm. The Rib E width has a broad range of from 0.75 mm to 3.5 mm, a preferred range of from 1 mm to 3 mm, and a preferred dimension of 1.7 mm. The Rib E length has a broad range of from 15 mm to 30 mm, a preferred range of from 20 mm to 25 mm, and a preferred dimension of 22 mm. The Rib E aspect ratio has a broad range of from 0.75:1 to 2:1, a preferred range of from 1:1 to 1.5:1, and a preferred value of 1.3:1.

And, as shown inFIG.5A, the outer hexagon110of the multi-axial integral geogrid100has a partially oriented junction115thickness (dimension “TO2”) having a broad range of from 3 mm to 9 mm, a preferred range of from 4.5 mm to 7.5 mm, and a preferred dimension of about 5.6 mm, and a strand or rib120thickness (dimension “TO1”) having a broad range of from 1 mm to 5 mm, a preferred range of from 1.5 mm to 3.5 mm, and a preferred dimension of about 2.8 mm.

In addition, as shown inFIG.5B, the inner hexagon130of the integral geogrid100has a tri-node135thickness (dimension “TI1” such as, for example, 2.1 mm) and a strand or rib145thickness (also dimension “TI1” such as, for example, 2.0 mm) and a strand or rib150thickness (also dimension “TI1” such as, for example, 3.1 mm) having a broad range of from 1 mm to 5 mm, and a preferred range of from 1.5 mm to 3.5 mm.

According to one preferred embodiment of the multi-axial integral geogrid shown inFIG.13, the “across the flats” dimension103(seeFIG.27B), i.e., the distance from one junction115of the outer hexagon (seeFIG.15) to the opposite junction115of the outer hexagon, is about 80 mm. And, for the same embodiment, the across the flats dimension, i.e., the distance from one tri-node135of the inner hexagon (seeFIG.15) to the opposite tri-node135of the inner hexagon, is about 33 mm.

The punch size/diameter has a broad range of from 2 mm to 7 mm, a preferred range of from 3 mm to 5 mm, and a preferred dimension of 3.68 mm. The major pitch in the first stretch direction has a broad range of from 5 mm to 9 mm, a preferred range of from 6 mm to 8 mm, and preferred dimension of 6.7088 mm. The minor pitch in the first stretch direction has a broad range of from 1 mm to 4 mm, a preferred range of from 2 mm to 3 mm, and a preferred dimension of 2.58 mm. The second major/minor pitch in the first stretch direction has a broad range of from 4 mm to 8 mm, a preferred range of from 5 mm to 7 mm, and a preferred dimension of 5.934 mm. The major pitch in the second stretch direction has a broad range of from 4 mm to 8 mm, a preferred range of from 5 mm to 7 mm, and a preferred dimension of 6.192 mm.

FIG.14is a partial plan view that illustrates the sole internal angle of confinement of the prior art triangular integral geogrid200shown inFIG.1. As is evident, the integral geogrid200having an across the flats dimension203(seeFIG.27A) has a single internal angle of confinement, i.e., an angle of about 60°. That is, about each junction235, the integral geogrid200has a total of six 60° angles of confinement. And, the integral geogrid200has a total of eighteen 60° confinement angles within the boundaries of a single hexagon. (The designation A shown inFIG.28Ais for the strand/rib of the prior art TriAx® geogrids employed in the data of Table E, presented hereinafter.)

FIG.15is a partial plan view that illustrates the two different internal angles of confinement of the multi-axial integral geogrid100of the present invention shown inFIG.2. Advantageously, by virtue of the geometry having inner hexagon130supported within outer hexagon110, and the five different strand types A, B, C, D, and E, the multi-axial integral geogrid100has a combination of 60° and 120° internal angles. That is, about junction115there are six 60° angles of confinement, and about tri-nodes135there are three 120° angles of confinement. And, the multi-axial integral geogrid100has a total of thirty confinement angles within the boundaries of a single outer hexagon110. Thus, across its range of apertures, the multi-axial integral geogrid100provides two angles of confinement, leading to enhanced aggregate confinement.

Table C below presents a comparison of node orientation, tensile element orientation, open area, and average aperture open area that may be attainable with the multi-axial integral geogrid100of the present invention with those features of various prior art triaxial integral geogrids.

TABLE CInventionTX160 ®TX130S ®Partially oriented384480720junctions per m2(measured andextrapolated)Oriented tensile222414242336elements per m2(measured andextrapolated)Angles of571330155096confinement perm2Open Area85%85%87%

As evident from Table C, when compared to TX160®, the multi-axial integral geogrid100of the present invention has 20% less partially oriented junctions115and 56% more oriented tensile elements120,140,145,150,160per square meter, thus providing both a significantly higher number of physical elements for aggregate particles to bear against, be confined by and interact with per unit area, and providing a significantly lower number of physical elements per unit area, i.e., partially oriented junctions, that contribute less to the geogrid's ability to engage, confine and stabilize the aggregate. Further, when compared to TX130S®, the multi-axial integral geogrid100of the present invention has 47% less partially oriented junctions115per square meter, and nearly the same amount of oriented tensile elements120,140,145,150,160per square meter, but a higher number of angles of confinement. These features thus provide a high number of physical elements for aggregate particles to bear against, be combined by and interact with per unit area, but with a significantly lower number of physical elements per unit area that contribute less to the geogrid's ability to engage and stabilize the aggregate.

FIG.16is a partial plan view that illustrates the six confinement elements in a specific distance of the prior art triangular integral geogrid200shown inFIG.1. PerFIG.16, the prior art integral geogrid200has six bearing elements, i.e., the six strands205that surround junction235.

FIG.17is a partial plan view that illustrates the twelve confinement elements in the same specific distance of the multi-axial integral geogrid100of the present invention shown inFIG.2. As is evident fromFIG.17, the multi-axial integral geogrid100has twelve bearing (confining) elements, i.e., the six strands120that form outer hexagon110, and the six strands that form inner hexagon130, i.e., the two strands145and the four strands150. That is, in a like-for-like hexagon size with similar across the flats distance103(seeFIG.27B), the multi-axial integral geogrid100provides twice as many confinement elements to bear against radial loading motion during compaction and trafficking. Thus, the multi-axial integral geogrid100provides twice as many elements that provide concentric-like resistance to aggregate movement.

FIG.18is a partial plan view that illustrates the eighteen angular nooks, all of the same angle, of the prior art integral geogrid200shown inFIG.1. As noted above, the integral geogrid200having the across the flats dimension203(seeFIG.27A) has a single internal angle of confinement, i.e., an angle of about 60°. That is, about each junction235, the integral geogrid200has a total of six 60° angles of confinement, or nooks. And, the integral geogrid200has a total of eighteen 60° confinement angles or nooks within the boundaries of a single hexagon.

FIG.19is a partial plan view that illustrates the thirty angular nooks, of varied angles, of the multi-axial integral geogrid100of the present invention shown inFIG.2. As noted above, by virtue of the geometry having inner hexagon130supported within outer hexagon110, and the five different strand types A, B, C, D, and E, the multi-axial integral geogrid100has a combination of 60° and 120° internal angles. That is, about each junction115there are six 60° angles of confinement or nooks, and about each tri-node135there are three 120° angles of confinement or nooks. And, the multi-axial integral geogrid100has a total of thirty confinement angles or nooks within the boundaries of a single outer hexagon110. Thus, across its range of apertures, the multi-axial integral geogrid100provides thirty independent (or unique) confinement angles or nooks, with two different internal angles of confinement, this combination of features leading to enhanced aggregate confinement.

FIG.20is a partial perspective view that illustrates the preferred floating nature of the inner hexagon130of the multi-axial integral geogrid of the present invention shown inFIG.2. The invention incorporates a resilient (or suspended) and adaptable inner hexagon130, which better accommodates aggregate during compaction by varying “out of plane” stiffness. The floating inner hexagon is relatively movable in the vertical Z-axis dimension and as such allows a meaningful degree of compliance or deflection during compaction.

In a preferred embodiment of the invention, this vertical compliance or deflection of the inner hexagon130can be as much as about 33% of the greatest thickness of the surrounding outer hexagon110. In other words, if the thickness116of the partially oriented junctions (which is the thickest component of the outer hexagon) is 6 mm, the out of plane compliance, or deflection “D,” of the floating inner hexagon130can be as much as about 2 mm. This resilient (or suspended) compliance extends over the entire area bounded by each outer hexagon110, the outer hexagon having a lesser degree of vertical compliance. It has been surprisingly discovered that this enhanced resilient (or suspended) compliance or deflection “D” of the inner hexagon enhances the ability of the geogrid100of the present invention to interlock with the aggregate.

As shown inFIG.29A, the inner hexagon130of integral geogrid100is capable of flexing (i.e., floating or deforming) upwardly, i.e., outwardly away from the plane of the outer hexagon110, to an extent that a distance “D” is equal to about 33% of the overall thickness of the surrounding outer hexagon110(with the overall thickness of outer hexagon110being essentially the thickness of junctions115). Correspondingly, as shown inFIG.29B, the inner hexagon130of integral geogrid100is capable of flexing (i.e., floating or deforming) downwardly, i.e., outwardly away from the plane of the outer hexagon110, to an extent that a distance “D” is equal to about 33% of the overall thickness of the surrounding outer hexagon110.

Moreover, the tendency for this resilient (or suspended) and adaptable inner hexagon130to sit above the subgrade and even to deflect further vertically upward if the subgrade is uneven provides the opportunity for improved lateral restraint and impedes aggregate from rolling over the strands140,145,150,160when subjected to repeated loading, with the outer hexagon110creating a second ring of confinement for aggregate to have to pass over. A conventional prior art multi-axial geogrid, like geogrid200, lacks this level of resilient (or suspended) compliance, and as such provides only one level of confinement.

FIG.21is a partial plan view that illustrates the localized zones of lower compliance201associated with individual strands or ribs205of the prior art integral geogrid200shown inFIG.1. That is, because the individual strands or ribs205connect the partially oriented junctions235, the prior art integral geogrid200has numerous localized zones of lower compliance201, and thus minimal resiliency.

FIG.22is a partial plan view that illustrates the localized zones of lower compliance101associated with individual strands or ribs120of the outer hexagon110, and the repeating zones of high resilient compliance102of the inner hexagon130, of the multi-axial integral geogrid100of the present invention shown inFIG.2. By virtue of the ability of the floating inner hexagon130to deflect vertically within outer hexagon110, the multi-axial geogrid100has a repeating zone of high resilient compliance102within each of the corresponding outer hexagons110.

To repeat, as illustrated inFIG.21, a conventional prior art tri-axial geogrid lacks the level of compliance over such a large area that characterizes the multi-axial integral geogrid of the present invention. As such, any compliance associated with the prior art triaxial geogrid is restricted to individual ribs which are constrained by the junctions located at either end. In contrast, per unit area, the geogrid of the present invention has an area of significant vertical resilient (or suspended) compliance in the order of about 50% to about 75% as shown inFIG.22. This contrasts with a conventional prior art multi-axial geogrid, as shown inFIG.21, which has no such zones of significant vertical compliance.

In one aspect of the present invention, the geogrid100represents a horizontal mechanically stabilizing geogrid. The repeating pattern of outer hexagons110including a plurality of outer oriented strands or ribs120interconnected by partially oriented junctions115comprise strong axis strands which extend continuously in a linear path throughout the geogrid as indicated by lines120A,120B, and120C inFIG.4. As will be noted fromFIG.4, the strong axis strands formed by outer oriented strand or ribs120interconnected by partially oriented junctions115, as indicated by lines120A,120B and120C in theFIG.4, extend continuously throughout the entirety of the geogrid without intersecting inside an outer hexagon. This feature provides the necessary strength and stability for the geogrids of the present invention. In another aspect, the ribs140,160which extend inwardly from the partially oriented junctions115and connect with the tri-nodes135of the floating inner hexagon145, or other geometric configuration described hereinafter, which is supported by such ribs comprise “engineered discontinuities” or “floating engineered discontinuities”.

The invention also relates to a method of making the above-described multi-axial integral geogrid100. The method includes providing a polymer sheet300; providing a patterned plurality of holes or depressions310in the polymer sheet300; and orienting the polymer sheet300having the patterned plurality of holes or depressions310therein to provide a plurality of interconnected, oriented strands120,140,145,150, and160having an array of openings170,180, and190therein, a repeating floating hexagon130within an outer hexagon110pattern of the interconnected, oriented strands and the openings, including three linear strands that extend continuously throughout the entirety of the multi-axial integral geogrid100.

In general, once the polymer sheet300has been prepared with holes or depressions, the multi-axial integral geogrid100can be produced from the sheet300according to the methods described in the above-identified prior art patents and known to those skilled in the art.

As indicated above, the hexagonal geometric shape of the outer hexagon110and smaller inner hexagon130are a preferred embodiment for providing the floating geometric configuration of the present invention. However, other geometric shapes are possible within the scope of the present invention. For example, the geometric shapes could be rectangular or square with four supporting or connecting strands connecting each inner corner of the outer rectangle or square to the corresponding outer corner of the smaller inner rectangle or square. Or, the geometric shapes could be triangular with only three supporting or connecting strands between adjacent inner corners of the outer triangle and outer corners of the smaller inner triangle. Other polygon shapes are also contemplated within the scope of the present invention.

In the rectangular or square embodiment of the present invention, described in the preceding paragraph, there would preferably be two linear strands defined by interconnected oriented strands and partially oriented junctions that extend continuously throughout the entirety of the geogrid for each outer rectangle or square, such continuous strands extending at an angle of approximately 90° from each other. In the triangular embodiment, there would preferably be three such linear strands for each outer triangle which extend from each other by approximately 120°, similar to linear strands120of the preferred hexagon embodiment described in detail herein.

Also, different geometric shapes could be possible without departing from the present invention. For example, the inner geometric shape could be a circular ring supported within the preferred outer hexagon shape with six supporting strands similar to the preferred embodiment disclosed herein. Thus, it is intended that the geometric shapes of the outer repeating structure and the inner or interior floating structure not be limited to identical geometric forms.

As described above and illustrated in the accompanying drawings, the geogrid embodiments disclosed herein comprise a monolayer structure; therefore, the composition of the starting sheet300illustrated in and described in the connection withFIG.3is comprised of a single polymer or copolymer.

While the preferred embodiment of the integral geogrid100has been described above with the outer hexagons110surrounding and supporting smaller floating inner hexagons130, the present invention also contemplates that the outer hexagons110can surround and support smaller inner hexagons130which do not float or flex (deform), but rather remain in the plane of the geogrid. Therefore, in accordance with the present invention, the integral geogrids100shown inFIGS.2,4and5, and made with the starting sheet material shown inFIG.3, can be made to have smaller inner hexagons which do not float or flex. Thus, the repeating hexagon within a hexagon pattern of the present invention is the same whether the inner hexagon130is able to float or not.

Lastly, it is clearly preferred that each of the outer hexagons110of the multi-axial integral geogrid100include the floating hexagon130within its interior thereof as disclosed in this application. On the other hand, it is possible by changing some individual punch patterns, or otherwise, to produce a multi-axial integral geogrid in which the hexagons130are surrounded and supported in only a portion of the outer hexagons110, and the other outer hexagons support a different interior structure, such as included in the prior art, without departing from the scope and intent of the present invention. So long as such modified integral geogrid includes one or more outer hexagons110which surround and support a floating or non-floating smaller inner hexagon130, and define the requisite arrays of substantially parallel linear strands that extend continuously throughout the entirety of the geogrid, i.e., strong axis strands in accordance with the disclosure contained herein, it is presently believed that such modified integral geogrid falls within the scope of the present invention.

As indicated in the “Related Art” section above, prior art geogrids utilize the concept of having apertures that are large enough to cause most of the aggregate particles to physically “fall into” the open space of the apertures. The geogrid then provides benefit by laterally constraining these particles as/when load is applied from above. As load is applied from above, the aggregate particles try to move down and out (laterally), and the geogrid prevents both from happening. As such, the fundamental premise of the prior art geogrids is that the aggregate particles need to “strike through” or “penetrate” the apertures. This strike through concept of the prior art is confirmed by the Walsh HAR patents whereby the high aspect ratio concept of tall/thin ribs to promote “confinement” provides even better resistance to the lateral spreading of the aggregate.

In contrast, the present invention has converted every other junction along the non-continuous strands into an open hexagon or other open geometric configuration. This unique configuration generates at least two meaningful changes. First, the present invention has created an aperture structure where a junction was present thereby introducing a “confining element” where there was a “non-confining element”. In the preferred embodiment, the aperture formed by the inner hexagon includes the creation of six ribs that form the hexagon, and these ribs are now available to interact with and support the aggregate, whereas the replaced junction is only a “point of connection” for the geogrid itself. Second, the present invention has reduced the aperture size for the six (6) trapezoidal apertures shown inFIGS.2and17, as compared to the triangular apertures of the triaxial geogrids shown inFIGS.1and16, to better retain and confine a wider range of aggregate sizes and quality.

As such, it has been surprisingly discovered that the “goal” of an improved geogrid in accordance with the present invention is not to have most the aggregate particles fall into the apertures, as previously embodied in the prior art. Rather, as demonstrated by the test results reported hereinafter, the geogrid configurations of the present invention create more functional elements in the geogrid per unit area than with the prior art structures (see Table C above), and it is a goal of the present invention not to have particles fall through the apertures but rather to have more of the aggregate particles partially penetrate into more apertures. This surprisingly new interaction between the geogrid100,200and the aggregate particles195,295, respectively, to be confined therein for the present invention versus the prior art is illustrated by the comparative drawings ofFIGS.25A and25B.

The foregoing surprising discoveries are demonstrated by the following tests and results therefrom.

TEST METHODS FOR EXAMPLES

Test 1—Retention

The performance of a multi-axial geogrid for improving interaction with a granular material was evaluated using a small scale test to simulate granular material being “cascaded” onto the geogrid following the installation methods outlined in published guidance (e.g., “Tensar Installation Guideline IG/TriAx,” Oct. 19, 2020). This small scale test comprises an open box on which a specimen of geogrid approximately 350 mm×350 mm is clamped above the open box. Then 2 kg of granular material graded to between 20 mm and 40 mm particle size is cascaded across the geogrid by a “brushing” action. A 20 mm to 40 mm particle grading is experimentally representative of a grading commonly used in constructing civil engineering structures, while removing excess variability associated with smaller or larger particle sizes. For each test, measurement is taken of the amount of granular material “captured” by the geogrid and the amount of granular material falling through the geogrid into the box below. A comparison is made of the two results. A geogrid better designed to “capture” the granular material will retain more granular material on the geogrid and allow much less material to fall into the open box beneath the geogrid specimen. Typical comparison is made on the basis of 10 repeated tests for each geogrid type, using the same 2 kg batch of granular material.

Test 2—Rutting

The performance of a multi-axial geogrid for resisting rutting due to vehicle traffic was evaluated using a small scale test to simulate well-established field tests such as the one described in Webster, S. L.; “Geogrid Reinforced Base Course for Flexible Pavements for Light Aircraft: Test Section Construction, Behavior Under Traffic, Laboratory Tests, and Design Criterial,”Report DOT/FAA/RD-92, December 1992. The small scale test was designed to reproduce the results of well-established field tests for traffic performance of multi-axial geogrids and comprises a test section consisting of an underlying clay subgrade, a single layer of geogrid, and a compacted granular sub base. The test section is subjected to the load of a single weighted wheel. The wheel traverses the test section along a single horizontal path, constantly reversing direction from one end of the test section to the other. A control test with no geogrid present will fail rapidly under such testing. For example, after 1000 passes or less of the wheel on an unreinforced test section, a deep rut will be formed. By using properly designed multi-axial geogrids as reinforcement, decreased amounts of rutting depth will occur for a given number of wheel passes compared to the unreinforced test section. This decreased rut depth has an impact on the lifetime of the civil engineering structure and can extend this lifetime by factors of up to 50 times that of an unreinforced structure. Hence, a roadway or other civil engineering structure reinforced in accordance with the present invention will have increased longevity and decreased maintenance requirements.

The aforesaid small scale test used in connection with the present invention is the same small scale test as described in the Walsh HAR patents (See U.S. Pat. No. 10,501,896, at col. 10, lines 43-67) and which generated the data reported therein.

Example—Test 1 (Retention)

The performance of a multi-axial geogrid for improving interaction with a granular material was evaluated using a small scale test to simulate granular material being “cascaded” onto the geogrid following the installation methods outlined in published guidance.

A sample of a commercially available prior art TriAx® geogrid200(seeFIG.23A) had a 2000 g batch of granular material295, graded between 20 mm and 40 mm particle size, cascaded across its surface. The material falling through the geogrid200into the box296below was weighed, as was the material retained upon the geogrid. This test was repeated 10 times for the same specimen and the same 2000 g batch of granular material was used in each repetition.

This experiment was then repeated for a specimen of the multi-axial integral geogrid100of the present invention, identified as Lab 79 (seeFIG.23B). Lab 79 was made from the same sheet material recipe as the prior art TriAx® geogrid200already tested. The same 2000 g batch of granular material195was used for assessing Lab 79 that was used to assess the prior art TriAx® geogrid.

The results are shown in Table D below:

TABLE DMass of Granular MaterialMass of GranularPassing ThroughMaterial Retained onGeogrid, gramsGeogrid, gramsPrior ArtInventionPrior ArtInventionTriAx ®Lab 79TriAx ®Lab 7917324726819531659136341186416986830219321702982981902181442186195817581032421897169053310194716827931819211712762881924177073230192786% passed4% passedRetainedRetainedthroughthrough on14% on96% onon averageaverageaverageaverage

The results shown in Table D above indicate that the combined effect of all the geometrical elements of the multiaxial geogrid100of the present invention greatly improve its ability to interact with the same granular material when compared to the prior art multi-axial geogrid. While the prior art geogrid only retained or captured 14% of the material cascaded across its surface with the remaining 86% falling through the geogrid, the geogrid of the present invention captures 96% of the granular material, with only 4% falling through into box296. This very large improvement in the ability of the geogrids according to the present invention to interact with granular material is beneficial in improving resistance to rutting in trafficking testing.

The test results reported in Table D are also shown in the Box Plots shown inFIGS.26A and26B. As can be seen inFIG.26A, a very large proportion of the 2000 g batch of granular material, as indicated by the test plots at501, passed through the TriAx® geogrid, and only a small proportion, as indicated by the plot test at502, was retained on the geogrid. In dramatic contrast, as shown inFIG.26B, only a small proportion of the same 2000 g batch of granular material passed through the geogrid of the present invention, as indicated by the test plots at503, whereas almost all of the aggregate was retained, as indicated by the test plot at504.

In accordance with the present invention, it has been surprisingly discovered that the ability of the geogrid “to retain” the aggregate in a standard retention test is a better predictor than the “strike through/penetration” concept employed by the prior art. More specifically, it is believed at the present time that for any particular aggregate a retention by the geogrid of at least 50% in the aforedescribed retention test should predict an effective geogrid in a composite structure comprising that tested geogrid and tested aggregate. More preferably, the retention test should show greater than 75% retention, and more preferably at least 90% or more.

Example—Test 2 (Rutting)

The performance of a multi-axial geogrid for resisting rutting due to vehicle traffic was evaluated using a small scale test to simulate well-established field tests.

Trafficking tests were carried out for the specimens shown in Table E below. This table shows data for eight (8) tests of the preferred floating hexagon within a hexagon geometry that is the subject of the present invention, and eighteen (18) tests for the prior art Walsh HAR patents geometry. The specimens were made from these same polymer material (polypropylene), the same punch pattern (except an additional punch was utilized for the specimens of the present invention in order to form the inner hexagon, and a range of similar starting sheet thickness, that produced geogrid samples having nominally the same hexagon across the flats (A/F) dimension203,103as illustrated inFIGS.27A and27B, respectively, which are duplicates of the prior Walsh HAR patents geogrid shown inFIG.6(prior art) and the geogrid of the present invention shown inFIG.7.FIGS.6(prior art) and7are reproduced again inFIGS.28A and28B, respectively, to set forth the dimensions of the apertures within the respective outer hexagons. In theFIG.6(prior art) samples, Dimensions A, B, and C=33 mm+/−3 mm, and in the invention samples: Dimension A=35 mm+/−3 mm; Dimension B=24 mm+/−3 mm; and Dimension C=30 mm+/−3 mm. The prior art specimens have rib aspect ratios that exceed well beyond those of the specimens that are made in accordance with the present invention. In Table E, Rib A shown inFIGS.13and14is used for comparison.

TABLE EAv.FinalsurfaceApertureStartingActualActualdefm. ForFinalsizeSheetRibRibRiblast 500pattern(mmthicknesswidthheightaspectpassesdescriptionAF)(mm)(mm)(mm)ratio(mm)Invention804.61.231.771.4529.9Invention804.61.231.771.4538.6Invention804.61.231.771.4539.5Invention815.451.141.751.5730.5Invention766.31.072.822.6322.1Invention766.31.072.822.6328.3Invention776.31.142.82.4722.1Invention807.51.492.942.1226.9Prior Art7732.540.720.2848.3Multi-axialPrior Art8031.080.870.8151.9Multi-axialPrior Art804.551.061.561.4741.0Multi-axialPrior Art804.551.061.561.4743.2Multi-axialPrior Art804.550.731.742.3846.4Multi-axialPrior Art804.550.661.972.9841.7Multi-axialPrior Art814.551.061.561.4742.9Multi-axialPrior Art814.551.061.561.4746.1Multi-axialPrior Art814.551.621.390.8643.7Multi-axialPrior Art796.30.692.824.0949.9Multi-axialPrior Art806.30.722.683.7237.2Multi-axialPrior Art806.451.32.11.6237.7Multi-axialPrior Art797.50.783.444.4139.2Multi-axialPrior Art808.51.513.522.3341.7Multi-axialPrior Art808.51.072.942.7539.5Multi-axialPrior Art808.51.193.512.9539.0Multi-axialPrior Art808.50.664.136.2639.2Multi-axialPrior Art828.51.133.913.4640.2Multi-axial

The data in Table E can be used to plot Rib Aspect Ratio against Surface Deformation after 10,000 passes, as an indicator of performance in terms of resistance to rutting. The foregoing plot is presented in theFIG.24of the drawings, where specimens of the present invention are identified as “InterAx”.

As evident fromFIG.24, the prior art multiaxial geogrids exhibited similar behavior to that shown in the FIG. 5 of the prior art Walsh HAR patents. There is tendency for the improvement in performance of the prior art geogrid to level off as the rib aspect ratio increases. While a rib aspect ratio of 1 limits surface deformation to around 45 mm surface deformation, an increase in aspect ratio to 2 reduces deformation to 42 mm. It takes an increase of aspect ratio to 5 to limit deformation to 40 mm.

For the geogrid specimens made according to the preferred geometry that is the subject of the present invention, an aspect ratio of 1.4 limits deformation to between 40 mm and 30 mm, while an increase in aspect ratio to 2.6 limits deformation to between 28 mm and 22 mm. This test data demonstrate the substantial improvement of the present invention over the geogrid of the prior art Walsh HAR patents in the suitability of the present invention to stabilize and strengthen aggregate in civil engineering applications.

As evident from the foregoing, the geogrids of the present invention offer significant improvement over prior art geogrids by reason of the unique structure and operation of the floating hexagon within a hexagon configuration to engage with, confine and strengthen aggregate in geotechnical applications.

More specifically, existing commercial prior art geogrids, irrespective of the manufacturing method, have utilized one basic repeating shape and size of aperture opening formed between the oriented ribs/strands and their junctions and nodes. Shapes such as rectangles, square, and triangles have been utilized. The use of one basic repeating shape of aperture also means that the angle formed between two adjacent ribs at an intersecting junction or node has always been the same throughout the geogrid.

Further, existing prior art geogrids, irrespective of the manufacturing method, have repeating continuous ribs in the primary directions. In a product with square or rectangular apertures, such as in the aforementioned Mercer patents, these ribs would be orthogonal and would typically run at 0° and 90° to the machine direction. In a product with triangular apertures, such as in the Walsh '112 patent, these ribs would be dependent on the form of the triangle. In a typical equilateral triangle these ribs would run at 30°, 90° and 150° to the machine direction.

Still further, existing commercial prior art geogrids, also irrespective of the manufacturing method, typically have ribs of roughly the same cross sectional area and aspect ratio, irrespective of the direction in which they run.

These similarities in features of prior art geogrids mean that the properties of the products which allow the geogrid to improve the performance of the geogrid as part of the composite matrix comprising geogrid and granular material are broadly similar throughout the body of the geogrid. These properties referred to in prior art would include (but not exclusively) aperture stability modulus, in-plane and out-of-plane stiffness of the geogrid, rib flexural stiffness in and out of plane, aperture open area, aperture shape, and rib aspect ratio.

Therefore, in accordance with the present invention, it was discovered that the performance of a geogrid in a composite matrix could be improved if the geogrid were more variable in both its repeating geometry as well as its individual features to better integrate with the granular materials that comprise the other component of the composite matrix. The majority of granular material employed as a component of the composite matrix are not uniform in shape or size, but are “graded” with ranges of size, e.g., 20 to 40 mm, 10 to 63 mm, 20 to 70 mm, etc. Typical grading curves for traditional commonly used granular materials are shown in the “Typical Aggregate Grading Curves” graph presented inFIG.31.

As traditional granular materials become more scarce and more expensive, a wider range of variability in the granular materials being utilized in construction is becoming more prevalent. This prevalence is driven to a large extent by the need to minimize the environmental impacts associated with quarrying of traditional high quality natural aggregates, for example energy and environmental impact of quarrying natural aggregates, pressure to close quarrying activities, impact of transporting quarried materials to site, greater desire to utilize locally available granular materials or recycled materials.

As such, it has been surprisingly discovered that the multi-axial geogrids of the present invention perform better in conjunction with the aforementioned poorer quality and more varied granular materials, and they also perform better with traditional well graded granular material, than prior art commercial geogrids. The geogrid configuration of the present invention out performs existing prior art geogrids and is no longer subject to the same “diminishing returns” rule that exist with the high aspect ratio prior art geogrid of Walsh HAR patents. While the size of the aperture in relation to the intended aggregate in a particular application has to be optimized in prior commercial geogrids, the aperture shape, size and internal angle have all been the same within the macro and micro level of each differently configured geogrid, with a tendency for geogrids based upon a repeating equilateral triangle pattern performing better than those based on rectangular or square openings. In contrast, according to the present invention, the multi-axial geogrid has a repeating geometry comprised of different shapes and sizes of apertures, plural angles of confinement, and formed from ribs of different lengths, heights and widths, in which the ribs preferably have an aspect ratio greater than 1.0; and with some of the ribs, i.e., strong axis strands, extending continuously in a linear fashion transversely and diagonally across the grid while other strands are interrupted to provide zones of local compliance, i.e. engineered discontinuities.

More specifically, with the new geometry and aperture/opening sizes and shapes, it has been surprisingly discovered that the present invention accomplishes two improvements in the containment and stabilization of a greater variety of aggregate. First, by having apertures/openings of different sizes and shapes, the geogrids of the present invention are better able to match with “natural” mineral aggregates that are sourced from quarries or mining methods of various sizes and shapes due to how they are sourced and processed. Second, the geogrids of the present invention better accommodate and stabilize “non-natural” aggregate alternatives, such as recycled concrete and glass which tend to have different physical properties from natural aggregates. While prior art geogrids have been configured for natural aggregates, the geometry of the present invention is able to successfully engage with, confine and stabilize both natural and non-natural aggregates.

Further to the foregoing, it has also been discovered in addition to the performance improvement obtained by the geogrids made in accordance with the present invention, that there should be projected savings in construction material costs, saving in time for construction of the geotechnical matrix embodying the geogrids of the present invention, as well as savings in the carbon dioxide equivalent (CO2e), (see https://www.sustainablebusinesstoolkit.com/difference-between-co2-and-co2e/) over the costs encountered with prior art commercial geogrids such as those made in accordance with the Mercer patents and the Walsh HAR patents. According to present estimates, and comparing geogrids of similar physical properties other than the Walsh HAR examples having high-aspect ratio ribs, and the examples of the present invention having the preferred geometry described in accordance with the present invention set forth herein, the cost savings achieved by geogrids made in accordance with the present invention can be as much as 10% up to 40% or more over the cost of using geogrids made in accordance with aforesaid prior art patents, as shown in Table F below.

TABLE FConventionalWalshConstruction,MercerHARPresentNo GeogridPatentPatentsInventionAggregate600 mm450 mm375 mm325 mmLayerThicknessCost/£55,356£46,392£41,160£38,172lane kmTime/4.3 days3.3 days2.8 days2.4 dayslane kmCarbon/232 Tonnes176 Tonnes147 Tonnes128 Tonneslane kmCO2eCO2eCO2eCO2e
As indicated above, Table F compares conventional “no geogrid” construction, Tensar's commercialized biaxial geogrid construction according to the original Mercer U.S. Pat. No. 4,374,798, Tensar's commercialized triaxial geogrid construction that falls under the Walsh HAR patents, and a projection for utilization of the present invention. The standard thicknesses of the aggregate layer for each of the comparative geogrids is set forth for the relative comparison. The calculations are based on “lane km”, which is a standard construction industry measure, at least in the United Kingdom and Europe. The “reference to “Tonne,” refers to metric ton (equal to 2,200 lbs).

The foregoing descriptions and drawings should be considered as illustrative of the principles of the invention. The invention may be configured in a variety of sizes and is not limited to the exact shape of the preferred hexagon within a hexagon embodiment. Further, since numerous modifications and changes may readily occur to those skilled in the art, it is not desired to limit the invention to the exact configurations and operation described and shown. Rather, all suitable modifications and equivalents may be resorted to, falling within this scope of the invention.