with reference to fig1 of the drawings , it shows a plan view of a midsole in the form of a separate and distinct drop - in insert shown generally as web 10 which is provided with a large number of upstanding plugs 11 , these plugs are disposed in this embodiment along the entire midsole 10 , which extends from the toe portion 12 through the ball portion 13 to the heel portion 14 . in this embodiment each plug 11 is upstanding with respect to the web 10 , and is affixed to the web at its proximal end . each plug 11 in this embodiment displays a central aperture 16 . the entire midsole 10 is preferably manufactured by injection molding , in which case the web 10 of the midsole as well as the plugs 11 are of the same material , and in which case the web 10 is highly flexible but not air - permeable . such midsole then would be suitable for inclusion in an article of footwear , where the web 10 is in contact with the top of the outsole and the plugs 11 project upwardly . the most suitable material found for such midsole is that known as &# 34 ; supersoft &# 34 ; thermoplastic resin available from gls plastics of woodstock , ill . 60098 , u . s . a . ( sold by them under item # g3294 ). the material is made from a thermoplastic compound known as &# 34 ; kraton &# 34 ; ( tm ) supplied by the shell chemical company . the preferred kraton compounds ( because they are softest having shore a hardnesses [ d - 2240 ] of 27 and 34 ) are kraton d - 2104 and kraton d - 3226 . the resulting supersoft thermoplastic yields a midsole material having durometer readings below 30 , and preferably in the vicinity of 20 . inspite of the softness of the resultant midsole , it still exhibits excellent elasticity and long life . of course , there are other materials besides kraton , such as estane , polyvinyl chloride or rubber . the requisite characteristics of the material is that they yield plugs 11 that are easily compressible and significantly deformable ( generally having durometer readings below appr . 30 ) but that have long life and good elasticity in order to spring back to their original shape once compressive forces have been removed . the shape of the plugs 11 is not critical , and whether they are hollow or solid does not generally affect their deformability . in the embodiment of fig1 they are made hollow in order to save thermoplastic resin . turning now to fig2 and 3 , these show portions of the midsole shown in fig1 in perspective view and side elevation respectively . in fig3 it can be seen that this embodiment is provided with lower projections 20 , which provide a small amount of ventilation below the midsole . in fig4 the plugs are shown as items 20 and 21 . it will be seen that in the embodiments shown in fig4 the plugs are of varying thickness ( i . e . height ). such thickness or height is of course discretionary , but values below 10 mm would appear reasonable . the plugs may have a height between 3 mm and 10 mm . in fig5 it will be seen that the plugs 22 are held in place in the midsole by a web 10 which is centrally located with respect to the plugs 22 . this , of course , adds to cushionability of shocks . in fig3 and 5 , the central apertures 16 are shown in plugs 11 , 20 , 21 , and 22 as dotted lines . fig6 shows an embodiment in which a portion of midsole as shown in fig3 is provided with a top web 25 , which suitably can be prepared of porous material , or it can be a perforated material , thereby providing for some movement of air . in this figure , the plugs 11 are shown compressively deformed and bulging . fig7 shows a cut - away view of a shoe embodying one form of the present invention , in which the midsole shown in fig1 is in place on top of outsole 31 in a shoe . a flexible , air - permeable top - sole 30 is in place over the midsole . fig8 shows a variation wherein the outsole 31 in the embodiment shown in fig7 is replaced by outsole 32 , which is provided with a multiplicity of pockets 33 adapted to receive and retain plugs 11 of the type discussed above , thus eliminating the need for the web 10 to retain these plugs in place . plugs 11 may be retained permanently in holes 33 by adhesion means , or any other suitable means . fig9 shows an embodiment wherein an outsole 42 is provided during manufacture with cut - away portions 43 and 44 so that suitably sized and shaped sections 40 and 41 of web such as shown in fig2 , etc . fit directly into the spaces , thereby taking up less vertical room in the interior of the footwear . the web sections 40 and 41 comprising the &# 34 ; midsole &# 34 ; are also thus held effectively in place against lateral movement . it is , of course , possible to provide only one of the sections 40 and 41 . fig1 illustrates an embodiment of the invention in which a section of the web 10 such as shown in fig2 is provided with plugs 50 , which are solid plugs instead of the hollow plugs 11 shown in fig2 . it may be necessary to use even softer material for the plugs 50 , in order to maintain the desired high degree of compressibility , yielding a suitable extent to compression under the step of a wearer , while allowing the plug to bulge , and recover . fig1 shows still another embodiment of the present invention in which a portion of the web 10 similar to that in fig2 is provided with upstanding plugs 51 which are hollow , but essentially square in cross section . these various design parameters may be varied in order to achieve a maximum performance . such variables as the resiliency of the plastic material , the height and shape of the plugs , the distribution and number of the plugs per unit of area , variations in the heights of various plugs , or rows of plugs , hollow versus solid plugs , and the thickness of the walls in such hollow plugs , can all be varied for the purpose of achieving the objectives of the present invention . satisfactory results have been obtained using plugs having a cross - sectional area of appr . 0 . 5 cm 2 with a wall thickness of 1 to 3 mm if hollow . fig1 shows a further variation of the invention , in which the plugs are not all of the same length , wherein an insert 41 similar to the one shown in fig9 for the toe portion of a shoe or sandal . as may be seen from fig1 , the plugs 11 grow progressively shorter through plugs 52 to 53 as they approach the toe . the lengths of the plugs may be varied in any suitable manner to accommodate the geometry of the inside of the item of footwear . fig1 shows a further embodiment of a portion of a web in accordance with the present invention , wherein the plugs in the upper and lower webs are facing each other for added cushioning . again , the upper web should be flexible and preferably also air - permeable . in fig1 , the inner part of a heel section 60 of an outsole or midsole is shown which has a square recess 61 in it . the recess 61 has inserted therein a single large diameter cylindrical plug 62 which is shown in its fully compressively deformed position for explanatory purposes . as may be seen , the compressive deformation is causing the plug 62 to bulge but , of course , only to partially fill in the space between its circumference and the corners of the recess 61 , thus pumping air upwards every time the plug 62 bulges . in fig1 , a heel section 70 of a women &# 39 ; s shoe or sandal is shown , which has shown in it , for purposes of explanation , cylindrical recesses 71 and rectangular recess 72 . of course , any other polygonal recess may be used . plugs 73 and 74 , when installed in the recesses stick out as desired due to the recesses being shallower than the thickness or length of the plugs .
a midsole , partial midsole , or the like , for inclusion in an article of footwear having a flexible , air - permeable top sole , characterized by at least one plug in the heel region having a thickness sufficient to permit significant compression deformation along its thickness dimension accompanied by simultaneous significant bulging deformation in its circumscribing surface perpendicular to the thickness dimension ; the deformations occurring solely due to normal walking activity by any wearer of the footwear ; and the deformations thereby providing simultaneously for shock - absorption and ventilation during said normal walking activity .