since an inventive concept of the present invention depends upon a control of elastic properties of a component of an article of footwear , in particular , an outersole , through intelligent design of the component &# 39 ; s shape , it will not be inappropriate to give a brief , qualitative , overview of aspects of solid elasticity or strength of materials which are especially relevant to this invention . a modulus of elasticity , or stiffness , may be understood generically in an engineering sense as a stress , or force per unit area , divided by a strain , or displacement per unit length . this means qualitatively , that for a test piece of given dimensions and a given mode of deformation ( such as bending ), a stiffer material , i . e . one with a higher modulus , will require a greater amount of force to achieve a given deformation or bending , or , conversely , will bend or deform less for a given application of force than a less stiff material . even given a simple elastomeric material , such as injection molded - rubber , it is still possible , and indeed , inevitable , to acquire non - directionally uniform elastic properties , or stiffnesses , in a finished article or component , based on a shape of the component . it will become clear through a consideration of the remaining specification and drawings that a novel design of an outersole of a shoe confers upon the outersole an advantageous set of elastic behaviors or moduli in response to forces encountered in use . in fig1 a a cross section of a block 50 of generic elastic material is shown , subject to a moment , represented by curved arrows 52 , 54 , tending to bend the block around an axis ( not shown ) perpendicular to a plane of the paper and lying above an upper surface 51 . in this context , it should be noted that “ elastic ” calls our attention to the idea that we are regarding the block as a uniform piece of material with respect to the laws of elasticity , rather than as a member of any particular class of materials , such as the elastomers . in the present invention , however , an elastomeric , or rubber - like , compound will be used for fabrication of an outersole 120 ( fig3 ); in particular , a composition of thermo plastic rubber ( tpr ) or ( natural ) rubber . as is well known , in a block subject to such a bending , a compressive stress , indicated by double - tailed arrow 56 and a tensile stress , indicated by double - headed arrow 58 , are set up in regions approximately bisected by a central plane 60 , as further shown in fig1 a . any modification to block 50 tending to reduce stresses represented by arrows 56 , 58 will result in a larger deflection ( not shown ) of the block in response to a given bending moment , and hence in a lower stiffness or enhanced flexibility . a modification to an elastic block as adumbrated above is shown in fig1 b . a series of stress - relief notches or grooves 64 , 64 ′ et alia are cut into a surface 66 of block 62 ; a remaining surface of block 62 is thereby partitioned into a plurality of lands ( not separately designated ) or treads . it can be appreciated for purposes of application of block 62 as an outersole of a shoe ( not shown ), whereby surface 66 serves as a bottom or exterior surface of an outersole , that an ability of block 62 to absorb and redistribute stresses resulting from contact with irregularities , such as pebbles , 68 , 70 protruding from a ground surface g , is either not substantially reduced or in fact increased by introduction of grooves 64 , 64 ′ et alia . irregularity 68 for example lying under a land or tread surface ( not designated ) meets an unimpaired thickness d of , in the present context , an elastomeric material , which thickness is indeed better able to deform into surrounding grooves than an equivalent volume in a monolithic material . irregularity 70 on the other hand lying within a groove ( not designated ) is seen to cause no deformation of block 62 . generally , only an obstacle or irregularity intersecting a wall 72 or floor ( ceiling ) 74 ( fig1 b ) of a groove may cause a larger deformation of an upper surface 76 of a grooved block 62 than would be caused in solid block 50 by an equivalent irregularity . grooves 64 , 64 ′ et alia do on the other hand clearly relieve tensile stresses of a nature indicated by double - headed arrow 58 , and increase flexibility in response to bending moments of a nature represented by arrows 52 , 54 in fig1 a , as illustrated in fig1 d . the following points will be seen to plausibly arise from an elementary consideration of elasticity , or the strength of materials , in connection with structures similar to those of the present invention ( reference may be made to fig2 ): a ) given a first sequence of parallel grooves 102 , 102 ′, 102 ″ cut into an elastic slab 100 , a stiffness in bending about an adjacent parallel axis 104 will increase as axis 104 is displaced towards increasing spacing of the first sequence of grooves ( i . e ., in a direction x ); similarly b ) given a second sequence of parallel grooves 106 , 106 ′, 106 ″ cut into elastic slab 100 , perpendicular to first sequence , a stiffness in bending about an adjacent parallel axis 108 will increase as axis 108 is displaced towards increasing spacing of the second sequence of grooves ; and c ) for small displacements , a bending about an oblique axis 110 , lying in a plane spanned by axes 104 and 108 , may be approximately decomposed into bendings about axes parallel to axis 104 and axis 108 , and a material response be predicted from a local stiffness as a function of an adjacent spacing of grooves parallel to axis 104 and grooves parallel axis 108 . in other words , it is asserted , a local stiffness or modulus resisting bending about an axis parallel to a surface of an elastic , or more particularly , an elastomeric slab , may approximately controlled in two independent directions by a spacing or linear density of locally perpendicular stress - relief grooves . reference will now be made to fig3 in comprehending application of these principles to the present invention . a shoe outersole 120 composed of an elastormeric , or rubber - like , material . sets of grooves 122 , 123 , 124 , 125 and 126 , 127 , 128 , 129 start at opposite lateral edges e , f respectively of outersole 120 . it may be observed that sets 122 - 125 and 126 - 129 maintain substantially parallel , and slightly converging , orientations , terminating on a rear or heelmost element of an opposing set of indentations , so that grooves 122 et alia terminate on groove 129 , while grooves 126 et alia terminate on groove 125 ; generally the grooves are curvilinear or arcuate in form , and particular families of curves of smoothly varying curvature , such as paraboli or hyperboli , for ease in achieving a simple and aesthetic product design . heel - most grooves 125 , 129 together form a substantially v - shaped groove or indentation , having an apex , as may be understood from consultation of fig3 . this apical rearmost groove demarks a boundary of a foresole region a of outersole 120 , simultaneously comprising a forward boundary of a bridge or metatarsal support 134 , which support includes a v - shaped cutout , receiving the apex . the bridge element or support , in one embodiment , also extends into a heel 142 of outersole 120 , which arrangement increases strength of the outersole , by eliminating a joint which might otherwise open up at a forward boundary 143 of the heel , relieving stress by simultaneously moving a frontal surface 145 of a heel - support joint ( not separately designated ) to a less flexible , central , portion of the heel , and extending the joint with lateral faces 147 , 149 . outersole lands ( not separately designated ) formed in interstices of grooves 122 , 126 et alia are decorated or finished with surface patterns or micro - treads 130 , 132 et alia ( not shown ) in order to improve sole traction , and give the product a finished and aesthetically pleasing appearance . foresole a further comprises a forward , or toe region , aa , and a rearward grooved or grid region ab , while the metatarsal support spans an arch region b of the outersole . a final rearward or heel region c completes a gross geography of the outersole . it will be appreciated in light of discussion accompanying fig2 that a curvilinear diamond or grid pattern 140 formed by grooves sets 122 - 125 and 126 - 129 in the foresole region , together with extensions of either groove set to lateral edges e , f , results in significant variations in stiffness with varying position in the forsole , these variations having substantially independent components about two major axes of bending . it is believed that the particular two - component / two - dimensional variation achieved confers a novel utility on the present invention . in particular , extensions of grooves 122 et alia and 126 et alia to the lateral edges confer a first added flexibility about a frontal axis 136 in proximity to the edges . however , it will be apparent from the above discussion that in a region of the diamond pattern 140 an added flexibility about axis 136 is taken up equally by grooves at approximately a 45 degree angle to the axis , so that the first added flexibility in maintained essentially constant from edge to edge in a region of the diamond pattern and a lateral extension ( not separately designated ) thereof . however , it will likewise be apparent that a second added flexibility about a longitudinal or sagittal axis 138 is created in the same region of the diamond pattern , and that this second flexibility is confined largely to a centroid ( not separately designated ) of the foresole . it may thus be appreciated that an advantageous flexibility is maintained corresponding to a phalangeal movement , or upward flexure of the toes , and to pronating and supinating movements , or rolling of a sole of the foot inwardly and outwardly about longitudinal axis 138 respectively , but , that this flexibility is confined to a centroid of the foresole , avoiding an edge rolling or bending flexure parallel to and in a vicinity of the lateral edges of the outersole . by these considerations a normal and necessary degree of pronation and supination is facilitated , while an excessive and generally deleterious degree of these motions is restrained . a relative depth of grooves 122 , 126 et alia and outersole 120 is also a substantive feature of the present invention . as shown schematically in fig1 b , an outersole has a total thickness d , and a groove depth g & lt ; d . in one embodiment of the present invention , in a ball region , or vicinity of axis 136 , the outersole has a thickness d = 7 mm and a groove depth g = 5 mm . thus a remaining , uncut , thickness of outersole amount to only 2 mm . thus , in light of discussion surrounding fig1 a - 1d , it may be appreciated that a flexibility or stiffness of the outersole to bending about axis 126 is governed by a dimensions of 2 mm , while a cushioning and distribution of stress from irregularities in a ground surface is governed by a material dimension of d = 7 mm . it may be readily apprehended that a degree of flexibility about frontal axis 136 and parallel translations thereof in a ( drawing ) plane of fig3 decreases in a heelward direction as bridge 134 , also known as a shank support , is encountered , and further as heel 142 is met , as will be appreciated from an inspection of fig5 a . in prior art , a steel shank support ( not shown ) will be utilized internal to a composite sole construction , rather than external elastomeric support or bridge 134 . the internal steel shank support will result in a sharper fall of flexibility in a shank or metatarsal region of the shoe , as shown by a dashed curve 147 in fig5 a . external support 134 thus provides more gradual variation and better design control of elastic properties of an outersole over a length of longitudinal axis 138 , then is allowed by prior art . fig5 a shows a schematic graph of flexibility or degree of deformation for a fixed system of applied forces ( not illustrated ) about a frontal axis 136 as varying along a longitudinal axis 138 for outersole 142 . flexibility , or inverse stiffness , is a measure of degree of deformation of a structure in response to a given system of forces , in this case , a system tending to bend outersole 120 around frontal axis 136 and parallel displacements thereof ; flexibility is shown increasing along a vertical graph axis 144 in fig5 a . it will be appreciated that a moderate degree of flexibility in a toe region aa , or foremost section of foresole a , reaches a maximum at a point p , corresponding roughly to a position of axis 136 , in a rearward or grid region ab of the foresole , as shown along a horizontal graph axis 145 . in arch region b an increasing thickness of metatarsal support 134 , in particular in taper region 144 , results in a decrease in flexibility , passing through a point q corresponding towards a low plateau value in heel region c . flexibility about longitudinal axis 138 in a vicinity of frontal axes 136 and 136 ′ is graphed in fig5 b and 5c respectively . as shown in fig5 b , longitudinal flexibility , measured along frontal axis 136 and shown increasing along a vertical graph axis 146 , is at a relative minimum at lateral edges e and f , passes through a maximum at a point r , corresponding roughly to a center line or longitudinal axis 138 . in contrast , longitudinal flexibility as varying across frontal axis 136 , passing through bridge or metatarsal support 134 , is at a relative maximum at points corresponding to lateral edges e and f , and passes through a minimum at a point s , approximately corresponding to a location of center line or longitudinal axis 138 . fig4 shows a schematic perspective view of the outersole of fig3 showing a conformation of grooves 122 , 126 et alia , and a taper or wedge region 144 of bridge 134 , and permitting a general comprehension of features of the outersole . it may also be added that a principal embodiment of the invention utilizes tpr giving a hardness of 50 - 55 degrees in a forepart , or regions a and b , of the outersole , softer than a typical standard of greater than 55 degrees hardness in the industry , as will be understood by those schooled in the art . fig6 a illustrates a flat blank 150 , which is cut from a sheet of thermo plastic rubber ( tpr ), for use in making an upper portion of a shoe . blank 150 has a first or outer edge 152 , a second or inner edge 154 , and rear - seam edges 156 , 158 , as well as an outer surface 155 and an inner surface 165 . in a first forming operation ( not illustrated ) blank 150 is manufactured into a first - stage preform 162 by means of a special use sewing machine , known in the art as a cap beat crease machine ( not shown ). the crease machine , in the control of a skilled operator , creates a series of small creases or crimps 160 , 160 ′, 160 ″ et alia , tending to contract or draw together outer edge 152 of blank 150 . blank 150 is thereby distorted into partially convex preform 162 , as illustrated in fig6 b . in order to complete formation of an upper , a second special use sewing machine ( not illustrated ), known in the art as a disc feed overseaming machine ( not shown ), is employed to join a non - woven fabric midsole or insole to the first - stage preform by stitching , in order to form a second - stage preform 170 , an item shown in fig6 c . contemporaneously with this stage of processing a rear seam 168 is sewn , joining rear - seam edges , and the preform is mounted on a rigid thermoplastic form 172 , or last . the last is shown in isolation in fig7 illustrating that a similarity in form to a human foot , and an inclusion of a post or mounting hole 174 , to facilitate handling of the second - stage preform . preform 170 is now essentially a fully formed upper , but must be subjected to further processing to relieve stresses and imbue the upper with a permanent shape of a finished shoe . in a first step of a thermal processing stage , the preform is subjected to a 100 to 110 degree centigrade vulcanizing treatment , which removes residual stresses , or a “ shape - memory ” of a prior flat form of blank 150 . subsequently to the vulcanizing treatment material of the preform or new upper is subjected to a controlled chilling in a second step of thermal processing . the controlled chilling sets the material in a new shape or conformation of a shoe upper . following the second step of thermal processing , preform , now upper , 170 , is ready for final affixement to outersole 120 in a bonding operation . a substantially uniform layer of adhesive is interposed between upper 170 and outersole 120 , the upper and outersole subsequently joined and held together until a curing of the adhesive . a layer of open weave or net fabric ( not shown ) may be interposed between upper 170 and outersole 120 to improve adhesion and reinforce cured adhesive via a fiber reinforcing principle . the bonding operation substantially completes structural assembly of the shoe , leaving only non - structural items such as an innersole , or insert , and ornamentation such as buckles or straps , which do not significantly alter structural characteristics of the footwear .
a shoe comprises a flexible outersole , an insole and an upper , the upper being formed from a flat thermo plastic rubber blank , a toe cap first being fabricated in the blank by means of a teacup crease special - use sewing machine , the blank or preform subsequently affixed to a last and joined by a second special purpose sewing machine , or disc feed overseaming machine , to a non - woven fabric midsole or insole , substantially completing the upper . thermal processing on the resulting preform completes processing of the upper without use of an insole board . a third element of the shoe , the outersole , is unitary in construction , and equipped with a unique pattern of intersecting grooves , as well as an external bridge or instep support in lieu of an inner steel shank . following bonding of the upper and the outersole , a shoe of unique flexibility is produced , while still providing adequate protection to an active user &# 39 ; s foot .