CA1114155A - Athletic shoe - Google Patents

Abstract

Abstract of the Disclosure A shoe and its method of manufacture in which an upper and preformed rubber outsole are joined by a foamed polyurethane, injection-molded midsole. The rubber outsole and polyurethane foam midsole combine to provide a lightweight and flexible shoe compressively conformable to the flexing foot and having strong traction and long wear.

Description

Field of -the Invention This invention relates to athletic shoes.

sackc~round of the Invention Athletic shoes, particularly those used in court games such as tennls and squash, should ideally combine several characteristics: lightweight; flexibility, so as to conform to foot bending; good court grip; long-wear; and resilient cushion-ing for foot comfort; Shoe manufacturers have attempted for sorne time to achieve these properties in an ine~pensive yet high quality shoe. But up to now, their shoes have had serious draw-backs. Three general types of court shoe structures are kno~n:
rubber sole vulcanized to an upper; an intermediate rubber biscuit vulcanized between a preformed rubber sole and an upper;
and injection-molded soles bonded to an upper. Injection molded soles have been prepared by high-pressure in3ection of PVC resin or by lo~-pressure injection of a charge of foamable material, e.g., polyurethane, Eollowed by foaming of the charge. With -; injection molding, multi-step molding processes have been ~sed, wherein a midsole is molded against an upper and then an outsole - 20 is ir~ediately molded ac~ainst thc midsole. The all-rubber shocs, .~ . .
whilc e:~hihiting good grip and wear and also havin~ fair re-silient cushionincJ, are heavy and sornewhat infle~ible, thus tend-; ing to tire the user, and e~pensive to manu~acture. Shoes in-jcction molded from rvC are inc.~pellsive and lonc3 wearincl, but o~fcr poor gri2 and littlc resilient cushioning for comfort. .

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Shoes injection mol~ed from polyurethane foam are lightweight, flexible, and resilient, b~lt provide poor grip and wear resistance. Poor grip results because a tread design must be used that will not trap air bubbles during low pressure molding, thus ruling out a good gripping tread. The softness of the material contributes to its poor wear.
Summary of the Invention All of the sought-after court shoe characteristics can be achieved according to the present invention by providing a flexible athletic shoe comprising: an upper including a lower edge adapted for bonding to polyurethane,a flexible rubber outsole conformable to the flexing foot and having an outer surface, a foamed polyurethane, injection molded midsole m situ bonded by said polyurethane to both said outsole and to said upper, whereby said rubber outsole and polyurethane foam midsole combine to provide a relatively inexpensive, lightweight and flexible athletic shoe compressible conformable to the flexing foot with a flexible sole having strong court traction and long wear.
According to the method of the invention the flexible light-weight athletic shoe is manufactured by ta) treating the upper surface of a preformed, rubber outsole to prepare it for bonding to polyurethane, (b) inserting said outsole, treated side up, in the bottom of a mold, (c) mounting an upper on a last, said upper having a lower edge adapted for ; bonding to polyurethane, ; (d) lowering the last and upper into the mold so as to be spaced above ~he ~ ~
rubber outsole, ~ -(e) injecting a charge of foamable polyurethane between the outsole and the last, ~f) allowing the polyurethane to foam to form the midsole and to bond in situ ~

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The siloe is preferably manufactured by treating the inner surface of a preformed rubber outsole to prepare it for bonding to polyurethane, inserting the treated sole into the bottom of a mold, mounting the preformed upper on a last, lowering the last and closing the mold rings, with the last spaced above the rubber outsole, injecting a charge of foamable polyurethane between the outsole and the last, and allowing the polyurethane to foam under self-generated pressure to form the midsole and to bond m situ simultaneously with the outsole and upper.
Preferred embodiments of the method feature: the step of raising the -outsole upward in t~e mold after injection of the charge of polyurethane until the inner surface of the outsole engages a fin element extending into the mold ~-around the periphery of the shoe, whereby the fin element prevents the poly-urethane, while it foams, from spilling over the sides of the rubber outsole;
preparing the inner surface of the rubber outsole for bonding to the poly-urethane by:
ta) roughening the inner surface;
(b~ chlorinating the inner surface;
~c) applying a cement that bonds to both rubber and polyurethane, and (d) drying the cement;
the step of heat-activating the cement prior to insertion of the outsole in ~-. the mold; and of employing cement of urethane type.

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The invention also provides a flexible athletic shoe formed by the method as above, comprising a flexible upper havin~ a lower edge in situ bonded to a foamed 1exible polyurethane sole, characterized by a flexible rubber outsole conformable to the flexing foot and having an outer surface providing playing court traction, and said foamed polyurethane sole is a midsole in situ bonded by said polyurethane to both said outsole and to said upper, providing a lightweight and fle~ible athletic shoe compressively conformable to the flex-ing foot with a flexible sole having strong court tractionand long wear.
Preferred embodiments of the fle~ible athletic shoe feature a tread pattern on the lower surface of the flexible rubber outsole tllat includes flexible rubber projections with sharp corners for enhanced grip; the rubber sole has a molded tread including pillars with sharp lower edges, to give good ::
grip for sudden stops; the upper that is in situ bonded by ;~ ::
the polyurethane to the flexible outsole is of string-lasted ; form with its lower edge comprising stitching and string e~-~ectively in situ bonded to the rubber outsole; the midsole : has a density of between 0.4Q and 0.75; the rubber includes natural rubber; the midsole has a structure providing open spaces to increase compliance and reduce weight; an insole is laid over the top of the midsole after molding; the poly-urethane is of the polyester type. -- , " . ~, - . , : i "

Preferred Embodiment The structure and manufacturinq process of a preferred embodiment of the invention will now be described, after first briefly describing the drawings.
Fig. 1 is a perspective view, partially cross sectioned, o the preferred shoe embodiment.
Fig. 2 is a plan view of the tread design of the out-~ sole.
; Fig. 3 is an elevation view of the shoe in use.
Fiq. 4 is an enlarged, somewhat diagrammatic view of a portion of the outsole not under load.
Fig. 5 is an enlarged, somewhat diagrammatic view of ` a portion of the outsole under a load typical of the situation when the wearer seeks to suddenly stop his forward motion.
Figs. 6a throuqh 6f are cliagrammatic vie~s of the various manuf~cturing steps used to prepare the rubber outsole for bondinq.
- Fig. 7 is a diagrammatic, perspective view showin~ th~e rubbcr outsole inscrted in a mold and thc upper mounted on a 20 last read~ for inscrtion into the mold. ;;~

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Fig. 8 is a diagrammat;c, perspective view showing the upper and last in the mold.
Figs. 9 and 9a are cross-sectional views through the mold and shoe, showing the two vertical positions of the outsole during the molding process.
Fig. 10 is a diagrammatic, perspective view, partially broken away, of the shoe and mold at the completion of molding.
Turning to Fig. 1, there is shown athletic shoe 10. It has a preformed rubber outsole 12, (com~ination of natural rubber and synthetic, marketed by American Biltrite under the designation SBR*) a polyurethane foam midsole 14 (BayFlex* 250B, a polyester foamable urethane manufactured by Mobay Chemical Corporation, Pittsburg, Pennsylvania), a conventional full-extent insole 16J and a combination upper 18, composed of nylon body 20, leatheredging~i.e. foxing) 22J and vinyl heel trim 24. Rubber outsole 12 has a pattern of pillars 26 separated by regions of textured surface 28 (Figs. 2 and 4). As a result of use of a conventional high pressure mold for premolding the sole, the lower ends of the pillars have relatively sharp corners 30, and the pillars are relatively deep. Midsole 14 has a honeycomb-like structure of hollow regions 32 and ridges 34 in ~he region back of the metatarsal area, a geometry provided by suitable formations in the bottom of the metal last. The density of the foamed solid portions of the midsole is 0.5, and it is 3/16 inch thick at i~s thinnest point. The upper is string lasted, with string and stitching 36 originally exposed and thus bonded in the substance of the midsole. ~-* Trademark :, .

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The athletic shoe is espccially suited for indoor court g~mcs such as squash, racketball, or handball. In such sports, the wearer often needs to suddenly stop. The rubber outsole 12 provides needed resilient traction for stopping bv means of the desirable friction qualities of rubber, the rela-tively sharp e~posed edges 30 of the pillars and the resilient deflection maae possible by the considerable depth of the ~illars.
The relative hardness of rubber gives the outsole long wear.
During a sudden stop, as illustrated i.n Fig. 5, the foam pol~urethane midsole 14 compresses and absorbs shock in region A that would other~lise be felt by the foot, and allows the upper - and the outsole to shift their relative positions, with the up~er conforming to the natural bend of the foot while the sole grips the surface. This midsole compressive effect can be opti-mized by selection of the chemical makeup of the polyurethane and selection of an appropriate amount of blowinq agent as well as by forming the midsole as ~ compliant pattern of ridges and spaces.

Manufacture of the shoe beglns wlth a preformed ruhber outsole 12 and preforMed up~er. Re~erring to Figs. 6a to 6~, the inner surface of thc ou~sole is pre~ared for bondin~
to the midsole by first rougllenil-~ it with sand2aper or a rough-ing tool (Fig.6a), then washing with a chlorinating primer (~3184 Compo Industries,Inc.) ~Fig.6b), then drying the prinEr (Fi~.6c) th~lcoating the upper surfaces with cement (l~4624 ure~lane adhesive~ Compo Industries, . : . : ::

Inc.) (Li~.6d), ~en dryinc3 a second tin~ (Fic3.6c), and just before nolding, , heat-activating the c ~ nt (Fig.6f). The chlorination e~poses oxysen radicals in the rubber outsole ~or bonding with the cement.
To complete the shoe, the prepared outsole is placed on the vertically-movable sole plate 42, the preformed upper 18, string lasted around metal last 40 (Fig. 7), is lo~Jered to the mold (Figs. 8 and 9), and the vertically split mold rings 4a are closed together. Each ring is comprised of upper and lo~ler halves 46, 48 held together by bolts. A thin fin 50 (Fig. 9a) runs all around the mold interior, extending a short distance into the mold from between the two halves 46, 48. The fin prevents the polyurethane of the micsole from leaking down over the sides of the rubber outsole. It also assures a well de~ined -color boundary bet~een the dark-colored outsole and light-colored midsole. Mold sole plate ~2 is initially held in its lo;~ered posi-tion (Fig. 9), and a measured amount of polyurethane is introcluced through inlet port 50. This ~ol~urethane does not initiall~ fill the mold. It is metered into the mold by timing the interval durir.~ whicil gear pumps 52, 5~ are turned on.
The pumps delivcr thc two componcnts A, ~ (isocvarlate and polyol rcsin)~to mixer-injector 5G, whicll turns at about lS, ~no rpm.
~tcr the moasurcd amount o~ tlle mi:~ture is injcctod, sole plate ~2 nlo~cs up to cllcJaqc the uppcr, outsid~ cd-,c of out5010 1 .
h fi.n 50 (~ig. 9a) and to closc off inlct ~ort 5~. T1IC
pol~uro~ha:le c:~allds ~/itllin t]lO mokl as it foaln!;, allcl ~onds tc t!~o ru!~l~e ouLso~c nnc! ~G L!~c lon-!lor cùsin9 o' tho u!)ucr. Tc `: ~

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p~-remove the finished shoe, the mold rings 44 are separated (not shown).
Other embodiments are within the following claims.
For each sport or use the pattern of the sole bottom is appropriately selected, for instance a typical basketball or tennis bottom is employed for shoes designed for those sports.~ -Here again the edges of various gripping projections of the soles can be sharply defined to provide good traction and grip, and to present a pleasins stylized appearance as well. Comparable materials to those mentioned for the example from other suppliers and variations thereon can be used to good effect following the invention (for instance in certain instances polyurethane of the polyester type may be selected for the midsole).
The assembly steps can in some instances be varied, for instance the adhesive properties of the polyurethane may be ; employed to bond to the outsole, omitting the separate cement.
Similarly the specific dimensions can be varied in accordance with recosnized principles of athletic shoe designers.
What is claimed is:

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Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A flexible athletic shoe comprising:
an upper including a lower edge adapted for bonding to polyurethane, a flexible rubber outsole conformable to the flexing foot and having an outer surface, a foamed polyurethane, injection molded midsole in situ bonded by said polyurethane to both said outsole and to said upper, whereby said rubber outsole and polyurethane foam midsole combine to provide a relatively inexpensive, lightweight and flexible athletic shoe compressively conformable to the flexing foot with a flexible sole having strong court traction and long wear.

2. A method for manufacturing the athletic shoe of claim 1, comprising the steps of:
(a) treating the upper surface of a preformed, rubber outsole to prepare it for bonding to polyurethane, (b) inserting said outsole, treated side up, in the bottom of a mold, (c) mounting an upper on a last, said upper having a lower edge adapted for bonding to polyurethane, (d) lowering the last and upper into the mold so as to be spaced above the rubber outsole, (e) injecting a charge of foamable polyurethane between the outsole and the last, (f) allowing the polyurethane to foam to form the midsole and to bond in situ with the rubber outsole and the upper.

3. The method of claim 2 further comprising the step of raising the outsole upward in the mold after injection of the polyurethane until the upper surface of the outsole engages a fin element extending into the mold around the periphery of the shoe, whereby the fin element prevents the polyurethane from spilling over the sides of the rubber outsole.

4. The method of claim 2 further comprising the steps of preparing the inner surface of the rubber outsole for bonding to the polyurethane by:

(a) roughening the inner surface;
(b) chlorinating the inner surface;
(c) applying a cement that bonds to both rubber and polyurethane, and (d) drying the cement.

5. The method of claim 4 further comprising the step of heat-activating the cement prior to insertion of the outsole in the mold.

6. The method of claim 5 wherein said cement is a urethane type.

7. The shoe of claim 1 wherein said midsole has a density of between 0.40 and 0.75.

8. The shoe of claim 1 wherein said rubber includes natural rubber.

9. The shoe of claim 1 wherein said midsole has a honeycomb structure to increase compliance and reduce weight.

10. The shoe of claim 1 further comprising an insole laid over the top of said midsole after molding.

11. The shoe of claim 1 wherein said rubber sole has a tread pattern on its lower surface that includes flexible rubber projections with sharp corners for enhanced grip.

12. The shoe of claim 1 wherein said polyurethane is of the polyester type.

13. The shoe of claim 1 wherein said upper in situ bonded by said polyurethane to said flexible outsole comprises flexible sheet-form material bondable to polyurethane, said upper being of string-lasted form with said lower edge of said upper comprising stitching and string effectively in situ bonded to said rubber outsole.