CA2206433A1

CA2206433A1 - Shoe and foot prosthesis with bending beam spring structures

Info

Publication number: CA2206433A1
Application number: CA002206433A
Authority: CA
Inventors: Rustem Igor Gamow; Hugh M. Herr
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-11-29
Filing date: 1995-11-29
Publication date: 1996-06-06
Also published as: US5701686A; AU4412496A; EP0794713A1; WO1996016565A1; US6029374A

Abstract

A midsole system for a running shoe or foot prosthesis have a sole spring, a heel spring and/or a forefoot spring; the system stores energy of foot impact and releases it during the running cycle. A preferred embodiment provides bending beam sole systems for shoes or foot prostheses comprising a bending beam heel spring, a bending beam forefoot spring, a two-coupled spring sole system, or a three-coupled spring sole system. The sole systems of this invention maximize stability, cushioning, and walking or running economy.

Description

CA 02206433 1997-0~-29 PCT~US95115S70 SHOE AND FOOT PROSTHESIS WITH BENDING BEAM SPRING STRUCTURES

Techl. ~a' Field The invention relates to sprin~ systems for use espe~ 'ly with a shoe or foot proall.es;a.
S The spring systems include a bendin~ beam heel sprin~, a bendinq beam forefoot sprin~, a two-coupled-sprin~ bendin~ beam confi~uration, and a three-coupled- spriny bendiny bedm confi~uration. Each sprin~ system is desi~--ed to behave o,u~ 'ly b ~-,lecl-an --'ly and structurally within a shoe sole or foot ,o(oall-esis.

~dcl~.r~und of the Invention Develo,~e,s of elastic shoe soles are co,,r-unled with the proLl~n. of storiny eneryy in the sole of the shoe and releasin~ the ener~y in a manner which improves walkiny and runnin~
econo",~ while at the same time ach ~/;,-~ adequate shoe stability and cush;on ~~.

Many e~d--~ s of runnin~ shoes exist; however, very few, if any, have been er"brdced by runners and foot spee- ' . Studies of the dynamics of the human foot reveal that the lonyitudinal arch of a human foot, with its numerous joints and lly;ll"t:nla, is capable of returniny 70% of the ener~y put into it and that it is far more ~rri~,;enl than the soles of the best existin~
runnin~ shoes. ~ge Discovery, October l 989 (pp. 77-83). If runners could run with bare feet, many would prefer to do so. However, impact forces are too ~reat and the foot needs proLeclion, espe-i~'ly on hard surfaces.

Proposed sprin~ desi~ns for shoe soles have not been entirely sdlisrd~;Lory. The sprin~
~ structures are not o~li",?~y li~ht and erri~ie.,l while still meetin~ biomechanical stiffness and stability req~- ~",e"Ls. These problems are overcome by the present invention. The inventors hereof have desi~ned an optimal heel sprin~ and ~orerooL spriny. In addition, the inventors hereof have discovered that for heel-toe runnin~, ener~y should be stored in the sole of the shoe at heel-strike and then, in turn, this stored ener~y should be released at a critical time and in a _ _ _ _ _ CA 02206433 1997-0~-29 W O96/16S65 PCTrUS95/15S70 particular manner to enhance toe-off propulsion. A two and three coupled spring system was des;~oed which achieves this heel to toe lldnsrer of ener~y.

While purportin~ to provide for maximum pe-rullllance~ the latest technolc~"~ in elastic shoe soles fails to achieve the ultimate desi~n which permits maximum stora~e and return of energy while still achiev;n~ shoe stability and cusl--~ n I~ in a variety of iocolllolion modes rangin~ from heel-toe walking and running, flat-footed runnin~ (long-di~ldnce) and toe runnin~
(sl~ril~Lil~

U.S. Patent No. 4,941,273 (Gross) d;scloses an athletic shoe havin~ a sole allan~elll~llL
which CGlli ~ IS an elastic band exLerl~ I~ throu~h a lon~itudinal p~csa~eway in the mid-sole.
The purpose of this device is to create an artificial tendon which stores and l~.leases ener~y during the runnin~q cycle. However, this heel sprin~ desi~n is inadequate for several reasons.
Most importantly, the sprinp sLirr,-ess does not incfease with increasin~ runnin~ speed, an essc.llial heel sprin~ peltull..ance reql~ b...e..l.

On the other hand U.S. Patent No. 4,492,046 (Kosova) desc.iL.es a sole of a runnin~
15 shoe having a ~,vire sprin~. The wire sprin~ serves to bias the anterior portion of the sole from the hecl (back of shoe) forward to the arch re~ion, sepa-aLin~ the anterior of the sole into upper and lower pGI Lions. The objective of this device is to enhance the runner's pel run''ance by reducin~ impact at heel-strike and launchinn the runner forward into a colllrol: ''e stride.
Unfortunately, this wire sprin~ confi~uration could not be oplill -"y li~ht while at the same time 20 adequately stifl' for both runnin~ and walkin~. Addiliondl material would have to be used within the wire frame to achieve adequate heel stiffnesses. This addiLional material would most likely reduce the overall heel spring ~:rri~;ency.

The latest commercially available elastic shoes fail to coll.~!eL~ly address the desired attributes of a properly desi~ned shoe with sprin~s. For example, air bladde(s have been used in 25 shoe soles in an attempt to increase walkin~ and runnin~ economy. Researchers have found that it is difficult to achieve shoe stability while simultaneously achievin~ measurable incr~ases in econollly usGn5~ air sprinçls. Other co.. er~ ~"y available shoes, althou~h claimin~ to rdc;l;ldLe propulsion at toe-off, are inc~pable of storin~ suLsld--lial amounts of ener~y at heel-strike, a'lov,~ kinetic and potential ener~ies to be lost to heat.

Similar challen~es have collrlonLed developer~ of lower-extremity prosthetic limbs.
While it has er~e.,lt:d suLslarllial improvements, prosthetic r~sedl.,-l- has so far focused almost exclusively on simulation or d~. l; lion of a natural foot in an attempt to provide the amputee CA 02206433 1997-0~-29 PCTrUS95/lS570 with a normal ~ait and a ~reater de~ree of co..-ru, L. See U.S. Patent No. 4,652,266 (Truesdell).
A recent improvement emer~in~ from (esearch is the Colle~e Park Foot desi~n d;sclosed in U.S.
~ Patent No. 4,892,554 (Re~ti ~son). This desi~n des.,.iLes a prosll~ c foot havin~ an ankle l"e,..ber, a heel ...e---ber and an ~long~,led ...~laLar:,al-toe l..e...b~. coupled to each other for 5 rslative pivotal movements. The toe ...t:...bt:. is partially bifurcated at its forward end to provide independe.,ll~ flexible toe sesliùn-s at the inner and outer sides of the foot. This desi~n thus l~pr~senl~ a three-point balance system a~ ;"~ a stable support matchin~ that of a natural foot.

One notable ex~c"lion is the device d;,closed in U.S. Patent No. 4,822,363 (Phillips).
10 This patent desc,ibes a cûlll~)G~;le prosthetic foot having a le~ portion, a foot portion and a heel portion all rigidly joined and all three provided with sul,sld.~lial elaslicil~J to allow return of ener~y abs~-L,ed and permit the amputee to en~a~e in sports such as runnin~ and playin~
tennis. Unde.:,landably, this desi~n has met with ~eneral approval from amputees who are sport enthusiasts, and at the same time enjoyed co..""ercial success.
The above .J;s~losed invention does not contain a mechanis... whereby ener~y absû,l,ed at heel-strike can be stored and later released at toe-off as does the two and three coupled sprin~ systems ~I;c~Qsed herein.

The present invention ~e:presenl:~ a si~--iri~.a,-l improvement over the priot art. The purpose of the present invention is to .. - .. i~e ener~y losses durin~ the impact phase and to use these ener~ ~s to improve the runner's overall economy. The desi~n can be incorporated into either a shoe for use with a natural foot or a foot prosll.esis specially fabricated for amputees wishing to pa. lic;"ale in athletic activities. Moreover, the present invention maximizes the runner's performance in all runnin~ modes includin~ heel-toe runnin~, sp(i..lin~ and runnin~

2 5 flat-footed.

~ummary of the Invention This invention co...p.ises o~.li-,.ally desig..ed heel and forefoot sprin~ structures for absorbin~ the ener~y of impact of the heel and fo.etoûl a~ainst a surface, r~spec;lively. Durin~
30 foot contact in walkin~ and runnin~, the stored ener~y in the heel and rort r-~ot sprin~s is released to enhance heel and forerool lift-off from said surface, respectively. In addition, this invention co""~rises coupled sprin~ sole systems for absorL,in~ the ener~y of impact of the heel of the foot a~ainst a surface and r-_lcO~ said ener~y after sufficient delay to allow said foot to CA 02206433 1997-0~-29 W O96/16565 PCTrUS95/lS570 .

roll forward, whereby said ~elaased ener~y provides a ho~icu~Lal and vertical co...ponenI of force to the front portion of said foot to anhance forward lift of said foot.

This invention dt---.on .l-dles how t-rr~ .,L sprin~s can be used in walkin~ and runnin~
5 shoe soles and pro~ elic feet to maximize shoe or prosthetic foot cush ~ a ~~, stability and erri.,;an.,~. The term "sprin~" as used in this document is defined as follows. When forces co...p.ess, bend, or stretch a body, the body is said to be a "sprin~" if it returns to its ori~inal shape after the forces are released. Tha body is conside.~d an "t~rricier,l sprin~ if 70% or more of the work done to deform the body can be pe. rur".ed by the body itself as it returns to its 10 original shape, i.e. the sprin~ provides 70% ener~y return. An ener~y return of 90% or hi~her is prerer~ed for the heel, ro,erooL, and coupled sprin~ structures desc,iLed in this document. To attain this, the present invention provides sprin~ structures made of suitable ener~y-absû-~material, e.~., a carbon fiber composite or other suitable ...a~e-ials known to the art havin~ non-plastic prope. Iies.
The coupled sprin~s may consist of a plurality ~two or more) of sprin~s positioned with respect to each other such that ener~y absorl,ed by a first sprin~ or sprin~s is l.dnsrel.ed to one or more additional sprin~s and ~eleased by said addiLional sprin~ or sprin~s. The first sprin~ or sprin~s are posiIioned beneath the foot so as to absorb ener~y from impact of the foot a~ainst a surface (referred to herein as ~heel-strike"), and release the absorbed ener~y in such a way as to allow at least a portion of eneray to be absorL,ed by second sprin~ or sprin~s. Said second sprin~ or sprinas release the eneray aaainst the u--de-:-ide of the front portion of the foot, i.e., at or near the ball of the foot to provide both an upward and a forward co,l.pone.,l of force to propel the fool: forward and upward (referred to herein as "toe-off"). In addition a ror~roul sprin~ be~ins 1:o store ener~y when the forefoot strikes the runnina surface and continues to con.press as the center of pressure moves into the forefoot re~ion. E~uansion of the forefoot sprin~ enhances toe-off propulsion.

By this arran~ement sufficient delay is provided between absor~,lion of ener~y from the 3 0 heel-strike and release of ener~y back to the front part of the foot to allow the foot to roll forward in a ncrmal walkin~ or runnin~ ~ait before the ener~y is relcased to enhance toe-off propulsion.

The first sprin~ or sprin~s may be directly attached to the second sprin~ or sprin~s, or there may be bntervenin~ sprin~s or ri~id members between them. Any ar-dn~er..enI of sprin~s 35 and other ~"ember~ may be used so lona as eneray is absorbed at heel-strike, delayed to allow rollin~ forward of the foot, and transferred to the front portion of the foot for release.

CA 02206433 1997-0~-29 One e...bo.'- nent of this invention cG~Iprises a sole spring coupled to a heel sprin~. The sole spring is a lur~ional sprin~ with a bendin~ axis located approximately 2/3 of the midsole length from the heel end. The sole sprin~ bends and stores ener~y when the foot flexes about the .,.~la~arsal-phaldl-~eal joints commonly referred to as the ball of the foot joint. The heel sprin~ is coupled to the sole spring at the bending axis or t~l-,rJea. the ben~'- ~9 axis and the heel end of the midsole. The sprin~s have to be erri~.;.",l and li~ht wei~ht. The heel spring(s) could be oyster sprin~s, saucer sprinss~ helical sprin~s, bendin~ beam sprin~s, or a co...~~ ndliûn thereof. The sole sprin~ could be a bending beam spring made out of metal or p.t5te.~bly carbon co...posil~ with a bnnding axis as defined above.

One embûdiment of this invention consisl~ of a sole system ro.. p.i:.i.,~q three coupled sprin~s, a heel sprin~, a sole sprin~, and a rûre~oo~ sprin~. The heel and sole sprin~S to~ether pr~re,ably form a lon~itudinal arch when in an equ "' .ium or relaxed state. The sole sprin~
bends and stores ener~y when the foot flexes about the ",~lald,:,al-phalan~eal joints commonly referred to as the ball of the foot joint. The heel sprin~ is coupled to the sole spring at the bendin~ axis or between the bendin~ axis and the heel end of the midsole. The rort rouL sprinçl is coupled to the sole spring at the bendin~ axis or b~l~r,er,n the bendin~ axis and the toe end of the midsole. The word "coupled" does not necessarily mean rigidly dllacl,ed. If two parts are coupled lu~t:ll,er, a force exerted on one will influence the other. This does not require the parts to be ri~idly dlldched. A~ain, the sprin~s have to be erric,cnl and li~htwei~ht. The heel 20 and forefoot sprin~s could be oyster sprin~s, saucer springs, helical springs, bending beam sprin~s, or a combination thereof. Once again, the sole spring could be a bending beam spring made out of metal or p.~rt.dbly carbon composite with a bending axis as defined above.

One embodiment of the sole system of this invention co..")li~es a heel sprin~ formed by upper and lower bendin~ beams. The bendin~ beams are coupled together near the fore end of 2 5 the heel sprin~. By definition, the fore end of a spring structure is closer to the front end or toe end of a shoe or foot prosthesis than its aft end whereas the aft end is closer to the heel end of a shoe or foot prosthesis than its fore end. The heel spring is positioned beneath the human foot between the heel and the ,.,aLdlal:.al-phala"~eal (M-P) joints, also called the ball-of-the-foot joint, approximately, in a shoe, and in an analo~ous position in a foot prosthesis. As will be appdre.,l, the aft end of the heel sprin~ must extend far enou~h toward the heel to be co""~ressed at heel strike, and the fore end must not extend so far forward as to i,)lelre~t with flexin~ of the ball-of-the-foot joint.

From the sprin~'s aft end, where the beams are not adjoined, the beams converge toward one another when passing toward the spring's fore end. A bendin~ beam axis is formed CA 02206433 1997-0~-29 where the bendin~ beams conver~e. A coupled re~ion is located between the ben ~" ~q beam sxis and the sprin~'s fore end. The bendin~ beams are not connecled by a ."echan-~' hin~e but rather are coupled lo~,ll,er such that when the sprin~ is co",p-essed by an outside a~ent, the ber, ' )~ beams bend toward one another and store energy. The curvature and lape,i"q of the various heel spring se-,lions is critical to the ~ ~ "ecl)an " ' and structural pe~ ru~ ance of the heel sprinq. These desi~n details will be fully des~.-il,ed in the next section.
Durin~ a heel-toe walkin~ or runnin~ sequence, the heel sprin~ be~ins to cGr,.u.ess and store energy when the heel strikes the ~round. As the foot rolls forward, the co--.~.ressed sprinq ~A~,ands, thrustin~ the heel upwards away from the ~round. Durin~ foot contact in runnin~ and walkinq, the heel sprin~ can reduce impact forces, I~, ~-iLe ankle pronalion for shoe sole a, _',c lions, and store ener~y if desiqned properly.

Another embodiment of the sole system of this invention co---prises a sole sprinq coupied to a heel sprinq. The sole sprinq is a bendin~ beam with a bendin~ axis located approximately 2/3 of the sole system len~th from its aft end. In a shoe sole, the sole sprin~
bends about tl-is axis and stores enerqy when the foot flexes about the metatarsal-phalan~eal joints r,o..,r"only referred to as the ball of the foot joint. In a prosthetic foot, the bendin~ of the sole sprin~ about this axis simulates natural ",eldlarsal-phalan~eal joint flexion. The heel sprin~, formed by upper and lower bendinq beams as desc-,il,ed earlier, is coupled to the sole sprinq such that the bendin~ beam axis is posilioned bel~,~,n the aft end of the sole system and the sole sprin~ axis. The word "coupled~ does not necessd.il./ mean ri~idly attached. If two parts are coupled to~ether, a force exerted on one will influence the other. This does not require the parts to be ri~idly attached.

Durin~ a heel-toe walkin~ or runnin~ sequence, the heel sprin~ co--,presses and stores ener~y as the heel of the shoe or prosthesis strikes the ~round. In a shoe sole, the co",p,~ssed heel sprinq then exerts a force unde"-eàll. the user's heel, thrustin~ the heel upward as the foot flexes about the ",elald,:,al-phalangeal joints. Durin~ this flexion period, the sole sprin~
cor"~r~sses about the sole sprin~ axis and stores ener~y. The sprin~ exerts a torque about the ",eldld,:,al-phalan~eal joints, enhancin~ toe-off propulsion. In a prosthetic foot, the expansion of the heel sprin~ enables the amputee to bend the sole sprin~ about its sole sprin~ axis. The sole sprin~ ener~y then ~ives the amputee toe-off propulsion. Thus, effectively the elasti enerqy stored at impact is l.ansre--~d to the sole sprin~. Elastic ener~qy is stored in the sole system early in the foot contact period and then released to the user late in the period to enhance or create toe-off propulsion. This method of deliverin~ the heel sprin~ ener~y to the walker or runner is believed to be optimal.

CA 02206433 1997-0~-29 W O 96/16565 PCTrUS95/lS570 A further e.,-bcd ~,e"l of the sole system of this invention consiaL:, of a r~.~rOO~ sprinç
formed by upper and lower bendin~ beams. The bendin~ beams are coupled log~ er near th fore end of the sprin~. The forefoot sprin~ is pG.;Lioned such that when the user puts wei~ht on the toes, the sprin~ co~ sses. The sprin~ is posilioned beneath the human lFoot between the user's toes (fore end of the human foot) and the M-P (ball-of-the-foot) joint, approximately, and in an ana'e~a:c location in a foot ,ulO~Ih3S S. From the sprin~'s aft end, where the beams are not adjoined, the beams converge toward one another when passing toward ths spring's fore end. A benl ,~ beam axis is formed where the tGnd- )g beams conver~e. A coupled region is located between the bendin~ beam axis and the sprin~'s fore end. The ben ' ~g beams are not connected by a mechanical hin~e but rather are coupled together such that when the spring is cG""~ressed by an outside a~ent, the bendin~ beams bend toward one another and store ener~y. The curvature and la~e~i"~ of the various sprin~ seclions is critical to the bi~ "echanical and structural pe~ror--lance of the forefoot sprin~. These desi~n details will be fully described in the next section.

During foot contact in walking and running, the forefoot spring begins to col,l~,tess and store ener~y when the forefoot of the shoe or prosll,esis strikes the s1round. In a shoe sole, as the ..,eldldrsal-phalan~eal joints be~in to extend during toe-off propulsion, the cG",p,t:ssed sprin~ expands, thrustin~ the roreroot upwards away from the ground. In a pru~ lic foot, the compressed forefool spring expands, thrusting the proslhelic foot away from the ground. The foreroot spring can reduce impact forces, l~ I "i~e ankle s~, lalion in shoes, and store ener~y if des;~"ed properly.

Another embodiment of the sole system of this invention consisls of a sole system CGIll,~daill~ three coupled sprin~s: a heel sprin~, a sole sprin~, and a forefoot sprin~. As described earlier, the sole spring is a bending beam with a bendin~ axis located approximately 2/3 of the sole system length from its aft end. In a shoe sole, the sole spring bends about thi axis and stores enerSIy when the foot flexes about the "leld~drsal-phalan~eal joints commonly referred to as the ball of the foot joint. In a plos~ Lic foot, the bending of the sole sprin~ about 3 0 this axis simulates natural melaldraal-phalan~eal joint flexion. The heel sprin~, formed by upper and lower bending beams as described earlier, is coupled to the sole sprin~ such that the bending beam axis is positioned between the aft end of the sole system and the sole spring axis.
The rorerool spring, formed by upper and lower bending beams as desc(ibed earlier, is coupled to the sole sprin~ such that the ben ' ~ beam axis is pos;Lioned between the fore end of the sole system and the sole spring axis. A~ain, the word "coupled" does not necessarily mean CA 02206433 1997-0~-29 W O 96116S65 PCTrUS9Stl5570 rigTdly attached, or even touchin~. If two parts are coupled to~ether, a force exerted on one will influence the other. This does not require the parts to be rigidly alldched.

When tl-e heel of a shoe or foot pro~lhesis strikes the ~round during a heel-toe walking or running sequence, the heel spring cGIl~ sses and stores ener~y. After heel impact, the k~ruùl of the shoe or foot prosthesis strikes the ~round and the rorerooL sprin~ be~ins to cGr"p,ess. The forerool sprin~ continues to cor-~ ss as the center of pressure moves into the ro(erool re~ion. The shiftin~ of wei~ht from the heel to the forefoot enables the heel sprin~ to release its ener~y, l~ro,Q~" ~9 the heel upward away from ths ground. The heel sprin~ energy helps to bend the sole sprin~ as disc~ssed earlier. After this bendin~ period, rurt,rool lift-off begins. The forefoot sprin~ be~ins to release its energy pushing on the bottom of the rorerool.
Durin~ the same period, the sole sprinn r~laases its energy credling or enhanc;n~ toe-off propulsion. Thus, durinn this final period, both the sole spring and the fort:fûol sprin~ release energy propelling the walker or runner upwards and forwards.
Each of the last four embo.- --enls desc-il,ed above have advanta~es and disad~,d--ld~es over the other l:hree with re~ard to b-omechanical pe, ror..,ance, structural pe, ru~--,ance, or manufacturin~ cost pe- rur--,ance. For example, the three coupled sprin~ sole system is IJ omecl-ani~ "y superior to the two coupled spring sole system, and the two coupled spring sole system is superior to the bending beam heel sprin~ sole system. However, the three coupled spring sole system is more costly to manufacture than the two coupled sprin~ sole system, and the two coupled sprin~ sole system is more costly than the bendin~ beam heel sprin~ sole system. Each bendin~ beam sole system desc(ibed herein has been designed to nneet a specific need in the shce or prosthetic foot market place.

All emb~ "eriL:, of spring sole systems could be either permanently glued into the sole of a shoe, or the sole systems could be part of modular shoes where the springs snap into or out of a shoe sole. In addition, the sprin~s could be attached to the bottom of a conventional shoe using straps or the like, or to the bottom of an orthotic brace shoe. Still further, the sprin~s could be used as part of a p(oslllt,lic foot with the springs placed inside a cosmetic foot 3 0 cover.

The exact nature of this invention as well as other objects and advantages thereof will be readily appar~ l from considerdlion of the following speciricdLion related to the drawings.

CA 02206433 1997-0~-29 W O96/1656S PCTnUS95/lS570 Brief Des~..;vlion of the Drawinus Fi~ure 1 shows a pe~ec;li~e view of a bendin~ beam heel sprin~.

Fi~ure 2 shows a se~lional view taken on the line 2-2 in Figure 1.

Fi~ure 3 shows a se.;lional view taken on the line 2-2 in Fi~ure 1 with the device tilted up at an angle from the ~round.
Figure 4 shows the same view as in Fi~ure 3 except the an~le between the heel sprin~
and the ~round is reduced.

Fi~ure 5 shows a sectional view taken on the line 5-5 in Figure 2.

Fi~ure 6 shows a sectional view taken on the line 6-6 in Fi~ure 2.

Figure 7 shows a sectional view taken on the line 7-7 in Figure 2.

Fi~ure 8 shows a secLional view taken on the line 2-2 in Fi~ure 1 with (8A~ a ~lirrt, ' ,~
wedge and a bumper or a stop i-.se. led between the bending beams and ~8B) a continuous coupled re~ion.

Figure 9 shows a se.,lional view taken on the line 9-9 in Figure 1.

Fi~ure 10 shows a secLional view taken on the line 9-9 in FiS~ure 1 with the lower bending beam twisted toward the medial spring side.

Fi~ure 11 A shows a seclional vi2w taken on the line 9-9 in Fi~ure 1 with the lower bending beam twisted toward the lateral spring side, and Figure 11 B shows a pe-:.pe~ e view 20 of a bendin~ beam heel sprin~ with a dia~onal bendin~ beam axis.

Fi~ure 12 is a perspective view of a coupled two sprin~ sole system.

Fi~ure 13 shows a sectional view taken on the line 13-13 in Fi~ure 12.

Fi~ure 14 shows a seclional view taken on the line 14-14 in FiS~ure 13.

Fi~ure 15 shows a se.,~ional view taken on the line 15-15 in Fi~ure 13.

CA 02206433 1997-0~-29 W O96/16S65 PCTrUS95/15570 Figure 16 shows the two coupled sprin~ sole system with the sole sprin~ co"-pressed at the sole spring axis.

Fi~ure 17 is a perspe~ Je view of a bendin~ beam tOItzrùOt spring.

Figure 1! 8 shows a se~lional view taken on the line 18-18 in Figure 17.

Figure 119 shows a se~lional view taken on the line 19-19 in Figure 18.

Figure 20 shows a se~;lional view taken on the line 20-20 in Figure 18.

Figure ;21 shows a sectional view taken on the line 21-21 in Fi~ure 18.

Figure 2Z shows a perspective view of a three coupled sprin~ sole system.

Fi~ure Z3 shows a midsole system of this invention using oyster leaf sprin~s as heel and 10 fo~ruol springs.

Figure 24 shows an oyster sprin~ in equilibrium position (24A) and cor"~.rt:ssed position ~24B).

Figure 25 shows multiple oyster springs used as heel sprin~s and forefoot sprin~s.

Fiqure 26 shows multiple helical sprin~s used as heel springs and forefoot springs.

Figure 27 shows a saucer spring.

Figure 28 shows a saucer spring with air sack.

Figure 29 shows multiple saucer sprin~s used as heel sprin~s and forefoot sprin~s.

Dçtailed DescrirJlion of the Preferred Embodiments The t."~w;nD prin- . Ies ~overn the improved sole system of this invention: -CA 02206433 1997-0~-29 W O 96/16565 PCTrUS95115570 1. The system should not inhibit the natural movements of the bio!o1 ' loco.,.oLur system, i.e., the foot and ankle must be able to bend freely. Thus, the sole sprin~ of this - invention should bend with the foot.

2. The system should store ener~y upon impact of the shoe with the running surface (durin~ the impact phase of the runnin~ cycle), ~ a.~11ess of what portion of the foot strikes the surface initially. The cou~ 'ed sprin~ sole systems of this invention satisfy this principle.

3. Stored energy should be released to ~nhance s~ hle,. )g of the foot at toe-off to ~--aAi".i~ runnin~ economy.

It is desil. '-'e that the sole system of this invention flex with the natural movements of the foot. Thus, the sole sprin~ should rotate about an axis co"espondin~ to the natural axis of rotation of the foot near the ball of the foot.

One aspect of this invention is a heel spring. During a heel-toe walkinS~ or runnin~
sequence, a heel spring begins to co",pr~ss and store energy as the heel of the shoe or foot proslhesis strikes the ~round. Durin~ this period, a heel spring can reduce impact forces, .", "i~e ankle prùhdlion in shoes, and store ener~y if desi~ned properly.

In Fiqure 1, a perspecli~e view of an opli",i~ed heel sprin~ is sketched. In Figure 2, the sagittal plane cross sectional view (line 2-2 in Figure 1 ) taken through the approximate heel spring center line is shown. The spring has a fore end 11 and an aft end 13. Relative to the foot of the shoe user, the spring's aft end 13 would be closer to the user's heel than the sprinSl's fore end 11, and the sprin~'s fore end 11 would be closer to the user's toes than the spring's aft end 13. Two bending beams, an upper beam 17 and a lower beam 1~, form the spring. When the heel sprin~ is cor"pressed by an outside agent, the bendin~ beams 15 and 17 bend towards each other and store energy. The transverse axis where the bending beams conver~e will be referred to as the bending beam axis 19. Bending beams 15 and 17 are coupled together at and near the fore end 11 of the heel sprin~. The re~ion between the bending beam axis 19 and the fore end of the sprin~ 11 will be referred to as coupled region 21.
-The geometries of the bending beam heel sprin~ are critical to the spring's pe, ro""ance structurally and ~i~ "echani~,'1y. The first feature of interest is the curvature of the bendin~
3 0 beams 15 and 17 in the fore and aft :'i eclions defined by axis 23 of Fi~ure 2. In Fi~ure 2, the heel sprin~ is sketched without the bending beams co,.,urtsssed or distorted by an outside agent in anyway; the spring is sketched in its natural eq~ ium state. The curvature of each bending CA 02206433 1997-0~-29 W O96/16565 PCTrUS95/15S70 beam chan~es concavity. Arrows 15 and 17 point to the localions where the lower and upper beam curvatures chan~e concavity, rusper-lively. Between these points of concavity chan~e and the bendin~ beam axis 19 each beam is concave downwards. These beam seclions will be referred to as 1he concave downwards re~ions; the top and bottom surfaces of these beam 5 5e. lions form eontinuous concave dow"~d(ds lines in the fore and aft d-~e~;lions 23 in Fi~ure 2.
~ut-rleal each beam's point of concavity chan~e and its aft end the curvature is concave upwards. Thess beam s~;lions will be referred to as the concave upwards re~ions; the top and bottom surfaces of these beam se~;lions form continuous concave upwards lines in the fore and aft ' ~e~;lions 23 in Figure 2. For the lower beam's lower surface 4, arrow 27 points to the beam section where the radius of curvature is s.. ~'le l in the concave upwards re~ion, and arrow 25 points to the beam section where the radius of curvature is smallest in the concave downwards re~ion. For each beam, the minimum radius of curvature in the concave upwards region is less than the minimum radius of curvature in the concave downwards re~ion.

The second feature of interest is the curvature of coupled region 21 in the fore and aft .' ~eclions defi~led by axis 23 in Fi~ure 2. Co~ 'ed re~ion 21 does not chanqe concavity and is concave upwards; the top and bottom surfaces of coupled region 21 form continuous concave upwards lines in the fore and aft direcLions in Figure 2.

Bendin~ beam and coupled re~ion curvature is critical to the performance of the heel spring for several reasons. The upper continuous surface of the heel spring formed by the upper surface 8 of upper beam 17 and the upper surface 10 of coupled re~ion 21 fits nicely to the underside of a shoe user's foot. The shoe user's heel fits into the concave upwards re~ion of the upper surface 8 of upper bendin~ beam 17, and the concave downwards re~ions of the upper bendin~ beam's upper surface 8 and coupled re~ion's upper surface 10 follow the natural curvature of the shoe user's arch. Thus, the curvature of the upper surface of upper beam 8 is more critical than that of the upper beam's lower surface 14, and the curvature of the upper surface of coupled re~ion 10 is more critical than that of the coupled re~ion's lower surface 12.
The curvature of the lower beam 15 is even more critical. As the sprin~ is co,-.pressed, the top 3 0 and bottom beams bend towards one another and store ener~y. The normal forces required to cG~press the bendin~ beams towards one another a unit dislance are less when theco.,.pressive forces act at lar~e bendin~ beam ",or.enl arms compared to smaller moment arms.
The bendin~ beam moment arm is defined as the di;,Ldnce from the bendin~ beam axis 19 to the point of force ap~ Lion ~dislance lu in Figure 2 is the lar~est possible upper bendin~ beam moment arm). The fact that the sprin~ is more difficult to cor"~ ss closer to the bending beam axis 19 and that the lower bending beam 15 has a concave upwards re~ion is i",po, L~nL for walking and runnin~. As a person chan~es speed from walkin~ to running, the peak vertical CA 02206433 1997-0~-29 W O 96116~65 PCTrUS95/lS570 ground rea~,lion force i..~ ases. (When the foot is in contact with the ~round in walkin~ or runnin~, the foot pushes on the ~round, and the ~round pushes a~ainst the foot. The latter is the ground (ed~;lion force. The cG...pone--l of this ~round ~ea.,lion force vector in the vertical ;lion is the "vertical ~round rea~.lion force.") In addition, as shown in Fi~ures 3 and 4, the 5 angle between the bottom of the foot and the runnin~ surface at the instant of first foot contact decreases as speed i..creases. Thus, as speed i..c(easas, the lower ben ' ~D beam ...o...enl arm at first foot contact dec.~,asas due to a rollin~ effect of the concave upwards re~ion on the ~round. The reduction in .~.or -enl arm increases the required force to cGr ."r~ss the bendin~
beams a unit distance, .lirre.. .~ the heel sprin~ at hi~her locG...olion speeds. In Fi~ure 3, the sa~ittal plane cross- seclional view of the heel spring is skelcl)ed with the an~le between the ground 28 and the heel sprin~ at ~3 and a lower bendin~ beam moment arm at 13. Point P3 is the contact point between the heel sprin~ and the ~round 28. Fi~ure 3 depicts the typical an~le of the heel sprin~ with the ~round at the instant of first foot contact durin~ walkin~. In Fi~ure 4, the same view is sketched except the an~le between the heel sprin~ and the ~round 28 is reduced as would be the case durin~ running. This reduction in an~le causes the point of contact P4 to move towards the fore end of the heel sprin~, causin~ the lower be--~in~ beam ...Gr..enl arm 14 to become smaller. The maDnitude of the minimum radius of curvature in the concave upwards re~ion of lower beam 15 can be altered to chan~e the rate at which the l--o~ nl arm chan~es with chan~es in the an~le between the heel sprin~ bottom and the ~round 28. When the heel sprin~ is inside a shoe sole, the outsole or tread will be a~ainst the bottom surface of the heel sprin~. Thus, the bottom surface of the shoe will take on the curvature of the bottom surface of the lower bendin~ beam.

The minimum radius of curvature in the concave downwards re~ions of both beams 15 and 17 should be maximized, and the beams should be sy----~ l-ic with each other such that the curvature of lower surface 14 of upper beam 17 matches the curvature of the upper surface 16 of lower bendin~ beam 15 to l--ir, ~-i~e the chances of br~ e during use. For a heel sprin~
that is opli..,i~ed b D",echan ~?'ly and structurally, the minimum radius of curvature in the concave upwards re~ion should be less than the minimum radius of curvature in the concave 3 0 downwards re~ion for the upper surface of upper bendin~ beam 8, and for the lower surface of lower bendin~ beam 4. However, it is more critical for the lower bending beam's lower surface 4 to have this specific curvature than for the upper beam's upper surface 8.

To s~"-"--d-i~e, in a preferred embodiment at least one heel sprin~ bendin~ beam should 3 5 have a curvature in the fore and aft directions having the rc,llov~ p-- pe. Iies:

1 ) a concave upwards re~ion near the aft end of the bendin~ beam;

CA 02206433 1997-0~-29 W O96/16565 PCTrUS9S/15570 2) a concave downwards re~ion near the fore end of the bending beam ~i.e. around bendin~ beam axis 19); and 3) a minimum radius of curvature in the concave downwards region which is ~reater than the minimum radius of curvature in the concave upwards region.

The curvature dimensionl~ss ratio is defined as the minimum radius of curvature in the concave downwards re~ion divided by the minimum radius of curvature in the concave upwards region, or z= RCd Rcu ~1 ) The ratio should be greater than one. A p-~r~ ed range is between 2 and 40. A most pr~:r~ d range is between 5 and 30.

AddiLiondl ~eometric features important to the pe.rur--,ance of the heel sprin~
structurally and b-~ ~-echanically are the Idperi.,g of bending beams 15 and 17 and coupled region 21 in height or thickness. The II, c ness of coupled region 21 is tapered largest at the bending beam axis 19 and s" -"~Sl at the fore end 11 of the heel spring as sketched in Figure 2.
Fi~ure 5 shows seclional view 5-5 of Figure 2 with a ll. k~,ess of h5, and Figure 6 shows sectional view 6-6 of Figure 2 with a thickness of h6. Since coupled region 21 is tapered largest at bending beam axis 19 and smallest at the fore end 11 of the heel spring, h6 > h5.
Bending beams 15 and 17 are also tapered. Fi~ure 7 shows sectional view 7-7 of Fi~ure 2 with a thickness of h7. Since upper beam 17 is tapered, hu > h7 where hu is the thickness of upper bending beam 17 at bending beam axis 19. It is to be understood that lower bending beam 15 is tapered similarly to upper beam 17 as skelched in Figure 2. The gradual tapers of bending beams 15 and 17 and coupled region 21 make the heel spring optimally li~ht but still structurally durable. Tapering as taught herein does not subsld"lially change beam stiffness.
To su"""a,i~e, an opLi,-.all~ ht bending beam heel spring has the following features:

1 ) bending beams with tapered Ll,irk ,esses largest at the bending beam axis and s-- ~ l at the aft end of each ~~:spe~ e bendin~ beam; and CA 02206433 1997-0~-29 W O96/16565 PCTrUS9511SS70 2) a coupled re~ion with a tapered lh'ch ~ess largest at the bending beam axis and sl~ 5~L at the fore end of the heel spring.

The length of a te~ 9 beam is defined as the dislance from the bending beam axis 19 5 in Fi~ure 2 to the ben ~ beam's aft Qnd. In Figure 2, disLance lu is the ben-'- .9 beam length for the upper beam 17, and di~Ld,.ce ll is the ber~ beam len~th for the lower beam 15. The maximum lh '<n~ss of a bend- )~ beam is located at bending beam axis 19 in Figure 2, or hu for upper beam 17 and hl for lower beam 15 ~see FiRure 6). The upper ben ' ~ beam's ~" "ension'ess ratio is defined as the length of the beam divided by its maximum bending beam 10 ll, 'c.,ess, or _ lu h hU (2) The lower bendin~ beam's ~ ,.ensionless ratio is defined as the len~th of the beam divided by its maximum bending beam ll,i 'c.,ess, or ll ~h = hl (3) Expeti",enl~ were pe, ru""ed in which the bending beam d;",ensionless ratios (both upper and lower beams) were varied in heel spring prototypes and tested for L' "echar-ee' pe,to""ance. The heel sprin~ prototypes were illsell~d into the soles of running shoes and 2 0 tested for shoe cushionin~, stability, and economy at running speeds around 4 meters/second.
Running shoe t ~n,echan'~e' pe,ru""ance was most s;~";ricd"~ i"creased in the prototype heel springs with bending beam d;.~,ension~ess ratios nu",er'~"y between 18 and 35. A preferred ran~e is between 20 and 33. For most runners, the most preferred bending beam dimension'ess ratio fell between 22 and 31.

Several heel sprinU ",aLe,ial systems includin~ carbon fiber composite and fiberglass were considered during this invesli~dlion. Although, as will be apprecialed by those skilled in the art, the ~" "ension'ess ratio varies with the type of material used, the above ran~es are suitable for the ",al~rials tested and are applic-'!e to dirr~ nl foot sizes.

Fi~ure 8A shows the heel sprin~ cross sectional view of Fi~ure 2 with a slirr~"' ,~ wed~e 3 0 27 and a bumper or a stop 25 between bending beams 15 and 17. StiffeninS~ wedge 27 is an inrldi ble air cha",ber or a sprin~y material or the like desi~ned to i"crease the heel spring ~Lirr"ess for dirr~(t:11L body wei~hts. Bumper or stop 25 is a hardenin~ material (its stiffness i"cr~ases with inc,eases in co",p~ession distance) designed to stop bending beams 15 and 17 CA 02206433 1997-0~-29 W O96/16565 PCTrUS95/15570 from co".press;n~ con,F!-Jtely lo~e:Llle~ to ",, IliLd the chance of bendin~ beam br~ e durin~
use. As will be apprecidLed by those skilled in the art, bendin~ beam 15 and stop 25 should be bonded lo~ ll,er as one piece, and the curvature of the bottom surface 14 of bending beam 17 should be adjusted to match the curvature of upper surface 32 of stop 25.
Fi~urn ~B shows the heel sprin~ cross s~.lional viaw of Fi~ure 2 except with a modified coupled re~ion. Cou. 'ed re~ion 26, located b~L~r~3en bendin~ beam axis 19 and the sprin~'s fore end, is formed by eklen ~ the material of the upper bendin~ beam 17 throu~h to the lower bending beam 15. This desi~n of coupled re~ion 26 is quite attractive from a structural pe.:.~,eclh/e and a manufacturin~ cost pe-~ecli~e. Other, less attractive, coupled reqion desiqns include gluin~ or cla",r ~ the upper and lower bendin~ beams to~e~l-er throughout the coupled re~ion.

Fiqure 9 shows the sectional view 9-9 of Fi~ure 1. This heel sprin~ is to be used with the left foot. Upper and lower bendin~ beams 17 and 15 are shown, respe~;Lively, alonq with bendinq beam axis 19 and the heel sprinq's medial and lateral sides.

Figure 10 shows the same view as in Fiqure 9 except with the lower bendin~ beam twisted toward the medial sprin~ side. A torque Tm d." actinq about an axis passin~ throuqh point 29 in Fi~ure 10 (the medial aft corner of the lower beam) and perpendicular to the flat paqe, twists the lower bendinq beam 15 towards the heel sprin~'s medial side. Point 29 in Figure 10 and coupled reqion 21 in Fi~ure 2 are both rigidly fixed in space so that the entire sprin~ does not L.dnslaLe when torque Tm d." is applied. The required torque needed to twist the lower bending beam up at an an~le ~m~ divided by that derle1Lion an~le Ç!1m~ will be referred to as the medial torsional stiffness Km~-l-Fi~ure 11A shows the same view as in Fi~ure 9 except this time with the lower bendin~
beam twisted loward the lateral sprin~ side. A torque Tl.e.,." actin~ about an axis passin~
throu~h point 31 in Fi~ure 11A (the lateral aft corner of the lower beam) and perpendicular to the flat pa~e, twists the lower bendin~ beam 15 towards the heel sprin~'s lateral side. Once a~ain, point 31 in Fi~ure 11A and coupled re~ion 21 in Fi~ure 2 are both ri~idly fixed in space so that the entire sprin~ does not L,dnslaLe when torque T,.~.,.,is applied. The required torque needed to twist the lower bendin~ beam up at an angle ~I, divided by that d~rlecLion an~le ~p,, will be referred to as the lateral Lo,:,;onal sLirr"ess K,.,.,~

The tOI :,;onal stiffness ratio is defined as the lateral torsional stiffness divided by the medial Lorsional .Lirr~ess, or CA 02206433 1997-0~-29 W O96/16S65 PCTrUS95/15570 r ~ t-r~l ~ 1 (4) .
E~nz~i~ne~ were pe,ru""ed in which the l~raional slirr~ess ratio was varied in heel spring prûtotypes and tested for b-o .,ecl.a" ' pe,rul.l.a"ce. The heel sprinS~ prototypes were 5 in~e. I~d into the soles of runnin~ shoes and tested for shoe cusl, Dn ,9 and stability at runnin~
speeds around 4 meters/second. Shoe ~ush Dn ~ was i~,c~eased and foot/ankle pf~,ndlion was decr,as~d most s;~-,ir;canll~ in the prototype heel sprin~ with a Ic":-ional .lirr~eSS ratio nu",~,; 'y ~reater than or equal to one. A pr~hll~d ran~e is between 1 and 10. For most runners, the most prere"~d tû~s;onal slirrlless ratio fell between 1.1 and 5.

There are several In~lllOdS that may be used to vary lorsional slirrness ratio. In a p(6r~ned er"bor' "en~ of this invention in which the heel sprin~ is formed from a composite ",ale,ial, the I~Jraional slirrl~ess ratio may be varied by varyin~ the de~ree of fiber rotation in the bending beams as is known to the art. The plerelldd method of varying the tor~;onal stiffness ratio is to vary bendins~ beam length from the medial to the lateral sprin~ sides. In FiS~ure 11 B, a pe,~pe~ /e view of a ben ,9 beam heel sprin~ is skelched sho~ the medial and lateral sprinn sides (left foot heel sprin~ end- ~ beam axis 19 runs dia~onally across the heel sprins~
i", reas;,)51 the bendinç~ beam len~th from the medial side to the lateral side. The beam length ~ "ension ?ss ratio is defined as the bending beam length on the lateral sprin~ side divided by the bending beam len~th on the sprin~'s medial side, or ~ Ll Lm The beam length dimension'ess ratio should be greater than or equal to one so that the tor:,;onal slirr"ess ratio is in the proper numerical range discussed earlier. A p~erer~ed range is between 1 and 2.5. For most runners, the most preferred length d "ension'ess ratio should be between 1 and 2.

The heel sprin~l can be pe""ane,~ lued into the sole of a shoe or the sprin~ could be a part of a modular shoe system where the heel spring snaps into and out of a shoe sole. Used as a midsole component, the heel sprin~ would be inserted between the outsole (tread) and the insole upon which the foot directly rests. In addition, the heel spring can be attached to the bottom of a conventional shoe using straps or the like, or to the bottom of an orthotic brace 3 0 shoe. Still further, the heel sprin~ could be used as part of a pro~ lic foot with the spring placed inside a COS~eliC foot cover.

CA 02206433 1997-0~-29 W O96/16S65 PCTrUS95115570 It should be unde,~L.od that the bendin~ beam heel sprin~ as specir "y desc~ ed herein could be altered without deviatin~ from its funda....:..ldl nature. For tt,-a...~le, the lower and/or upper bendin~ beams 15 and 17 respec~ ely, could be cut down the heel center line from the aft end 13 to the coupled re~ion 21 to form four bendin~ beams, two upper beams and 5 two lower beams. Still further, addilional ele...e..la may include a heel cup and an arch support built into the heel sprin~ itself. Still further, a material or air wed~e could be used h,l.r~en the upper and lower heel sprin~ bendin~ beams to ill~.fedst heel sprin~ sLirr~-ess for dirrer~riL body weights as shown in Fi~ure 8A.

Another emhc " ,.enL of this invention is a two coupled sprin~ sole system. In Fi~ure 12, a pei:.pecli.~e view of a coupled two sprin~ sole system is sketched. In Fi~ure 13, the sa~ittal plane cross seclional view (line 13-13 in Fi~ure 12~ taken throu~h the approximate sole system center line is shown. The sole system has a fore end 33 and an aft end 35. Relative to the foot of the shoe user, the sole system's aft end 35 would be closer to the user's heel than 15 the sole system's fore end 33, and the sole system's fore end 33 would be closer to the user's toes than the sole system's aft end 35. Two sprin~s form the sole system: a bendin~ beam heel sprin~ formed by upper beam 39 and lower beam 37; and a sole sprin~ 40 composed of a fore end extendin~ forward from the heel sprin~ and an aft end composed of the upper bendin~
beam 39 of the heel sprin~. As the heel sprin~ is cG..,pfessed, bendin~ beams 39 and 37 bend towards each other and store ener~y. Once a~ain, the transverse axis where the bendin~ beams conver~e will be referrad to as the bendin~ beam axis 41. The sole sprin~ 40, extendin~ from the fore end 33 of the sole system to its aft end 35, is coupled to the heel sprin~. In this dss~ ,lion, the upper bendin~ beam 39 is shared by the sole sprinW 40 and the heel sprin~.

The desi~n details of the bendin~ beam heel sprin~ are p(t r~-dbiy as described earlier in the heel sprin~ section of this document.

The sole spring 40 is a bendin~ beam with a transverse bendin~ axis located approximately 2t3 of the sole system length Lo from its aft end 35 (see Fi~ure 13). This bendin5~ axis will be referred to as the sole sprin~ axis. In Fi~ure 13, the sole sprin~ axis is 3 O located at the sectional line 14-14. When the shoe user's foot is attached to the sole system, the sole sprin~ 40 bends about this axis and stores ener~y when the foot flexes about the m~lald.~al-phalan~eal joints commonly referred to as the ball of the foot joint. In Fi~ure 16, the two coupled sprin~ sole system is sketched with the sole sprin~ compressed at the sole sprin~
axis 44. Forefoot forces F~o ~OOt press the front portion of the sole sprin~ a~ainst ri~id surface 42. When a force Fo acts near the aft end 35 of the sole system, the sole sprinS~ bends at the CA 02206433 1997-0~-29 sole sprin~ axis 44. The ben ' ~ beam axis 41 is located between the aft end 35 of the sole system and the sole sprinS~ axis 44.

Durin~ a heel-toe walkin~ or run~ins sequence, the heel sprin~ corl,~f~sses and stores enerSIy as the heel of the shoe or ~r~,slhesis strikes the ~round. In a shoe sole, the c~ r~ssed heel sprin~ then exerts a force u--de---ea~ the user's heel, thrustin~ the heel upward as the foot flexes about the I~ laldl~al-phaldn~eal joints. DurinD this flexion period, the sole sprinSI
colllpresses about the sole spring axis and stores ener~y. The sprin~ exerts a torque about the Illcldldlaal-phalanqeal joints, enhanc;n~ toe-off propulsion. In a prosthetic foot, the eA~,ansion of the heel spring enables the amputee 10 bend the sole sprin~ about its sole sprin~ axis. The sole spring energy then gives the amputee toe-off propulsion. Thus, effectively the elastic ener~y stored at impact is transferred to the sole sprin~. Elastic ener~y is stored in the sole system early in the foot contact period and then l~ileased to the user late in the period to enhance or create toe-off propulsion. This method of deliverin~ the heel sprin~ energy to the walker or runner is believed to be optim31.

For the heel sprin~ ener~y to be effectively lldnsrt~ d to the sole sprin~, the l~rldliOnship between the stiffnesses of the upper and lower bendin~ beams to the stiffness of the sole spring 40 at the sole sprin~ axis 44 is critical. Throu~h L c llechan cP' expelill'e''ldLion~
it has been found that the maximum bendin~ beam hei~ht or thickness at the bendin~ beam axis 41 divided by the hei~ht or lh ~k less of the sole sprin~ 40 at the sole sprin~ axis 44 has to be within a particular numerical ran~e for the heel sprin~ energy to be effectively l.an~rt~ d to the sole sprin~. This ~" llensionless number will be called the heel sprin~/sole sprin~ thickl.ess ratio.
For the upper bendin~ beam 39, this ratio is:
hu ~h hS (6) where hu is the maximal ll,-~k -ess of the upper bendin~ beam 39 (see Fi~ure 15) and hs is the thickness of the sole sprin~ 40 at the sole sprin~ axis 44. The lhickness hs is sketched in Figure 14, sectional view 14-14 of Figure 13. For the lower bendin~ beam 37, the ratio is:
_ hl h - hS (7) 3 0 where hl is the maximal thickness of the lower bendin~ beam 37 Isee Fi~ure 15).

Expeli,llelll~ were pelr~rll.ed in which the heel sprin~/sole sprin~ II, h less ratios (both upper and lower beams) were varied in sprin~ prototypes and tested for biomechan ~-' CA 02206433 1997-0~-29 W O96/16565 PCTAUS95/1~570 pt~rullllance. The heel sprin~ ener~y was most effectively Llanar~r,ed to the sole spring with heel sprin~/sobe sprin~ Ihi~k ~ess ratios nu-"eri--"y ~reater than one. A preferred ran~e is between 2 and 20. For most runners, the most pfer,a.,ed heel sprin~/sole sprin~ thickness ratios fell b~ .,en 3 and 10.

S The two coupled sprin~ sole system could be pe,,-,anu,.Ll~ ~lued into the sole of a shoe, or the sprin~ system could be a part of a rnodular shoe system where the sole system snaps into or out of a shoe sole. In addilion the sole system could be allached to the bottom of a conve"lional shoe usin~ straps or the like, or to the bottom of an orthotic brace shoe. Still further, the sole system could be used as part of a prusLl,eLic foot with the sprin~ placed inside a cos",~Lic foot cover.

It should be understood that the two coupled sprin~ sole system as specirically described herein could be altered without deviatin~ from its fundamental nature. For example, additional upper and lower bendin~ beams could be used in the heel sprin~, and a dirrt rt "L
coupled re~ion desipn could be employed as was desc,il,ed earlier. The sole sprin~ could be made separately from the heel sprin~ and positioned relative to the heel sprin~ by a clamp or by the shoe casing such that the sole sprin~ axis is beneath the ball of the foot, and that the bendin~ beam axis is between the sole sprin~ axis and the aft end of the sole system. Still further, a material or air wed~e could be used between the upper and tower heel sprin~ bendin~
beams to i"crease heel sprin~ ~lirr"ess for dirr~r~nl body wei~hts. Further, the heel sprin~ rnay comprise at le~ast one sprin~ type known to the art other than disrlosed herein, includin~ an oyster sprin~, a helical sprin~ or saucer sprin~ as described herein.

A further aspect of this invention is a forefoot sprin~. Durin~ a walkin~ or runnin~
sequence, a forefoot sprin~ be~ins to cor"press and store ener~y as the forefoot of the shoe or proslll~Lic foGt strikes the ~round. Durin~ this period, a forefoot sprin~ can reduce impact forces and store ener~y if des;~")ed properly.

In Fi~ure 17 a perspective view of an opLi",i~ed forefoot sprin~ is sketched. In Fi~ure 18, the sa~ittal plane cross sectional view ~line 18-18 in Fi~ure 17) taken throu~h the 3 0 approximate ~orefoot sprin~ center line is shown. The sprin~ has a fore end 43 and an aft end 45. Relative to the foot of the shoe user, the sprin~'s aft end 45 would be closer to the user's heel than the sprin~'s fore end 43, and the sprin~'s fore end 43 would be closer to the user's toes than the sprin~'s aft end 45. Two bendin~ beams, an upper beam 49 and a lower beam 47, form the sprin~. When the forefoot sprin~ is co""~ressed, the bendin~ beams 47 and 49 bend to r./ards each other and store ener~y. The transverse axis where the bendin~ beams CA 02206433 1997-0~-29 W O 96/16565 PCTrUS9S/15570 conver~e will be referred to as the bendin~ beam axis 51. The bendin~ beams 47 and 49 are coupled together at and near the fore end 43 of the rOr~rUOI sprin,ra. The re~ion between the ben ~ a beam axis 51 and the fore end of the rorerool sprinJ 43 will be referred to as coupled re~1ion 53.
The r"leG",~I,ies of the ber,l -9 beam for~root sprinç~ are critical to the spring's pffl rUnlldl-~e structurally and b ~ ~-echan'~ "y. The first feature of interest is the curvature of the b~n ~" ,r~,~ beams 47 and 49 and the ~. oupled re,lion 53 in the fore and aft " e-. lions defined by axis 48 in Fir,lure 18. In Fi5~ure 18, the bending beams 47 and 49 and the coupled re~ion 53 10 do not chan~e concavity and are concave-upwards. The top surface of coupled region 53 and upper beam 49 form a continuous conc3ve-upwards line in the fore and aft ~ clions, and the bottom surface of coupled region 53 and lower beam 47 form a continuous concave-upwards line in the fore and aft .li.ecliuns.

Bendin~ beam and coupled region curvature is critical to the pe. ~ur"~ance of the forefoot spring for several reasons. The shoe user's forefoot fits nicely onto the concave upwards curvature of the upper beam's and the coupled region's upper surfaces 52 and 46 respeclively.
The concave upwards curvature of the lower surface of coupled rer,~ion 50 and lower beam 56 is not as critical as the upper surface of upper beam 52 and coupled region 46. However, as 2 0 sketched in Fi~ure 18, the curvature of this lower surface in the fore and aft " ecLions 48 should be concave upwards Opli-- ~'1y. This lower surface curvature to the forefoot spring enables the spring to roll against the running surface during use. In addition, the upper and lower bending beams should be sy------eL-ic with each other, such that the curvature of the upper surface of the lower beam 58 ",aLches that of the lower surface of the upper beam 54, to ". ,' "i~e the chances of the sprin,r~ bn~ 'a durinr,~ use.

To su-..."d,i~e, in a preferred ernbor" "ent at least one rorerool spring bending beam should have a curvature in the fore and aft ~ r, lions havinr~l no chanrJe in concavity and be concave upwards.

3 0 Additional r,~eometric features imlportant to the performance of the heel sprin,r,~
structurally and t'o ..echanically are the tapering of bendinr~ beams 47 and 49 and coupled region 53 in height or ~ -ess. The ll, . k ,ess of coupled rer~aion 53 is tapered lar,r~est at the bendinr,l beam axis 51 and smallest at the fore end 43 of the forefoot sprin~ as sketched in Fi~ure 18. Fi~ure 19 shows sectional view 19-19 of Fi,raure 18 with a Ll,;~kr,ess of h19, and Fir~lure 20 shows sectional view 20-20 of Fir,aure 18 with a thickness of h20. Since coupled reSIion 53 is tapered larrJest at bending beam axis 51 and S~ L at the fore end 43 of the CA 02206433 1997-0~-29 W 096116S65 PCTrUS9~15/70 forefoot sprin~, h20 ~ h19. Bendin~ beams 47 and 49 are also tapered. Fi~ure 21 shows SG~;Iional view 21-21 of Figure 18 with a thickness of hZ1. Since upper beam 49 is tapered, hu ~ h21 where hu is the Lll e~lu-ess of upper bendin~ beam 49 at bendin~ beam axis 51 (see Finure 20). It fiS to be unde.~Lood that lower bending beam 47 is tapered similarly to upper beam 49 as sketched in Fi~ure 18. The ~radual tapers of bendin~ beams 47 and 49 and coupled re~ion 53 make the rO~t~ruOl sprin~ o~ y li~ht but still structurally durable.

To summarize, an optimally li~ht bendin~ beam rort root sprin~ has the rellD,v~,;
features:
1 ) bendin~ beams with tapered lh ~' nesses lar~est at the bendin~ beam axis and smallest at the aft end of each r~s~eclive bendin~ beam; and 2) a coupled re~ion with a tapered tl,;ck.,ess lar~est at the bendin~ beam axis and slll?~lest at the fore end of the forefoot sprin~.

The len~th of a bendin~ beam is defined as the distance from the bendin~ beam axis 51 in Fi~ure 18 to the bendin~ beam's aft end. In Fiçlure 18, disldl ce lu is the bendin~ beam len~th for the upper beam 49, and .lisLd, ce ll is the bendin~ beam len~th for the lower beam 47. The maximum heiS~ht or Ihi lu ,css of a bendin~ beam is located at the bendinS~ beam axis 51 in Fi~ure 18, or hu for upper beam 49 and hl for lower beam 47 (see Fi~ure 20). The upper bendin~ beam's s~ "ansionless ratio is defined as the len~th of the beam divided by its maximum bending beam Ll,;cl~"ess, or ~ _ lu f hu (8) The lower bending beam's dimensionless ratio is defined as the len~th of the beam divided by its maximum bendin~ beam thickness or ~y = 11 Experiments were performed in which the bendin~ beam di.llensionless ratios (both upper and lower beams) were varied in forefoot sprin~ prototypes and tested for biomechanical performance. The forefoot sprin~ prototypes were inserted into the soles of runnin~ shoes and tested for shoe cushionin~, stability, and econor"~/ at runnin~ speeds around 4 meters/second.
Runnin~ shoe biomechanical pe.r."",ance was most si~nificantly increased in the prototype forefoot sprin~s with bendin~ beam d- Ilension'ess ratios numerically between 18 and 35.

CA 02206433 1997-0~-29 W O 96/16S65 PCTrUS95/15570 F~rulably this ratio is between 20 and 33. For most runners, the most preferred belld ~ beâm dimens;on'ess ratios fell between 22 and 31.

The forefoot sprin~ could be pq~ an~ lued into the sole of a shoe, or the sprin~could be a part of a modular shoe system where the forerool sprin~ snaps into or out of a shoe sole. In addilion, the ro~erool sprin~ could be aLld~ ed to the bottom of a con~,enlional shoe usin~ straps or the like, or to the bott~m of an orthotic brace shoe. Still further, the rore~ool spring could be used as part of a ,c~ Lht~ foot with the rorerool spring placed inside a COS~ i., foot cover.

It should be I ~-deraluod that the forefoot sprin~ as speciricall~ desc.iL.ed herein could be altered without deviatin~ from its funddlllt:llldl nature. As with the heel sprin~, ad~liLiol al upper and lower ber, ' ,g beams could be used. For example, the lower andlor upper bendin~ beams 47 and ~9 r~: ,pec;lively, could be cut down the rorerool center line from the aft end 45 to the coupled region 53 to form four ben ' l~ beams, two upper beams and two lower bearns. In addilion, the coupled region of the foreroot sprin~ could be formed by extending the bendin~
beam material of an upper beam throu~h to a lower beam. Still further, a material or air wedge could be used between the upper and lower bending beams to increase forefoot spring stiffness for dirr~ body wei~hts.

Another e.,.bc. ..~.-L of this invention co--"~rises a three coupled spring sole system. An improvement in biomechan - ' pe, ror",ance can be achieved over the two coupled sprin~ sole system desc,ibed earlier by addin~ a rc~r~rool sprin~ to the system of springs. A perape~live view of the three coupled sprin~ sole system is sketched in Figure 22. The details of the bending beam heel, sole and forefoot sprin~ desi~ns are p,ere,dbly as described earlier in the heel and for~roul spring se.,lions of this document. The forefoot sprin~ is coupled to the sole spring such that the fo,~:rooL sprin~'s bending beam axis 55 is located between the sole spring axis 57 and the fore end 59 of the sole system. The aft end 61 of the for~root sprin~ is located approximately under the sole spring axis 57. The heel sprin~/sole sprin~ thickness ratio discussed earlier should not change when the forefoot spring is added to the two coupled spring sole system; the ,lirr~ess of the sole sprin~ for bendin~ about the sole sprin~ axis 57 should not 3 0 increased when the forefoot sprin~ is c:oupled to the sole spring. Several coupling means could be used ~o achieve this objective. For example, the forefoot sprin~ could be ~lued or clamped onto just the fore end 59 of the sole sVstem, or the forefoot sprin~ could be placed inside a shoe casin~, holdin~ the spring in the correct position without increasin~ the sole sprin~ bending :,lirr"ess. Thus, here aDain, the word 1coupled" does not necessarily mean ri~idly attached or CA 02206433 1997-0~-29 W O96116565 PCTrUS95/15570 even touchin~, but rather "placed in cooperative ~elalionsh with" so that force from the release of one sprin~ v~lill push on the coupled sprin~ ",e",ber.

When the heel of a shoe or foot pluslhesis strikes the ~round durin~ a heel-toe walkin~
or runnin~ sequence, the heel sprin~ cu""~r~sses and stores ener~y. After heel impact, the ~c,rerûol of the shoe or foot pro:,ll,esis strikes the ~round and the ru,~:rooL sprin~ be~ins to co",,ur~ss. The rO~rOO~ sprin~ continues to co""~ress as the center of pressure moves into the forefoot re~ion. The shiftin~ of wei~ht frorn the heel to the forefoot enables the heel sprin~ to release its energy, pre,~ the heel upward away from the ~round. The heel sprinç~ ener~y helps to bend the sole sprin~ as discussed earlier. After this bendin~ period, fc,reroot lift-off be~ins. The fGrefoot sprin~ be~ins to release its ener~y pushin~ on the bottom of the rO~ root.
Durin~ the same period, the sole sprin~ felaases its ener~y creatin~ or enhancin~ toe-off propulsion. Thus, durin~ this final period, both the sole sprin~ and the for.:root sprin~ release ener~y propellin~ the walker or runner upwards and forwards.
The coupled three sprin~ sole system could be permanently ~lued into the sole of a shoe, or the sole system could be part of a modular shoe where the sprin~s snap into or out of a shoe sole. In addition, the sprin~s could be dlldched to the bottom of a conventional shoe usin~
straps or the like, or to the bottom of an orthotic brace shoe. Still further, the sprin~s could be used as part of a prosthetic foot with the sprin~s placed inside a CoSIll~lic foot cover.

It should be understood that the three coupled sprin~ sole system as speciri--"ydescribed herein could be altered without deviatin~ from its fundalllenldl nature. For example, additional upper and lower bendin~ beams could be used in the heel and forefoot sprin~s, and dirrtrenl coupled re~ion desi~ns could be employed as was described earlier. Still further, a material or air wed~e could be used between the upper and lower heel and forefoot sprin~
bendin~ beams to increase heel and forefoot sprin~ stiffnesses for dirr~r~nl body wei~hts.
Further, the heel sprin~ or forefoot sprin~ may colllprise at least one sprin~ type known to the art other than ~licclosed herein, includin~ an oyster sprin~, a helical sprin~ or a saucer sprin~ as 3 0 described hereafter.

In Figure 23, oyster leaf springs are used as heel sprin~s 64 and forefoot sprin~s 62, attached to sole sprin~ 60 which is a bendin~ beam spring. The oyster sprinçl is formed by two or more opposing leaf sprin~s. This sprin~ type may work nicely in some shoe aFplic Lions because the sprin~ slirr,.ess does not ioc.t:ase appreciably with increasil)~ sprin~ deflection, an illlpol~dnl shoe sprin~ chala.;lerisLic.

CA 02206433 1997-0~-29 W O96116~65 PCTAUS9511S570 In Fi~ure 24, the oyster sprin~ is sketched in both the cGmpressed (24B~ and equilibrium (24A) conJi~ions.

To adjust the required force to C~ reas an oyster a unit disldnce, an air sack placed ~ within the oVster could be used. The air pressure within the sack could be ~~; Icted via an air hose, valv~, and pump system. The front and back surface of the air sack should be COh~ ' led SO that the sack does not bulse outward and bauk~rJald from the oyster when inflated. With this constraint, the air sack would press a~ainst the inside surfaces of the oyster sprin~, ill.,leasin~ the force to cG~Ilpress the oyster a unit di;.ldnce. Several oyster sprin~/air sack systems could be used as heel and rul~rOOl sprin~s. The user could adjust the air pressure within each oyster to find the optimal midsole slirrlless in each re~ion of the shoe sole.

In Figure 25, multiple oyster sprin~s are used as heel sprin~s 78 and 80 and r~rt:rool sprin~s 82, 84 and 86, attached to sole sprin~ 88. ~n~ axis 90 of sole sprin~ 88 is shown by a dotted line. Each oyster sprin~ could have a dirrerenl slirr--ess and each slirr.-ess could bs adjusted usin~ the air sack component.

Helical sprin~s may also be used as shown in Fi~ure 26. Similar to the sprin~s desc,il,ed earlier, the helical sprin~ stiffness does not inc~:ase with i.~c.t:asillo sprin~ derleclion. Similar to the oyster sprin~, the helical spring slirrl,ess could be adjusted by usinçl an air sack placed inside the helical sprin~ cone. In Fi~ure 26, multiple helical sprinçls are used as heel sprin~s 91, 92 and 94 and fol~rool sprin~s 96 and 98. A~ain, bendin~ axis 90 of sole sprin~ 88 is shown by a dotted line. Each helical sprin~ could have a dirrel~ ,lirrlless and each :.lirrlless could be adjusted using the air sack cGIllponenl.

In Fi~ure 27, a saucer sprin~ is chown. A saucer spring is formed by two or more leaf sprin~s opposin~ one another similar to an oyster sprin~. However, unlike an oyster sprin~, a saucer sprin~ has a circular holi~ulllal cross section with an elliptical vertical cross section.
Similar to all the sprin~s described earlier, the saucer sprin~ stiffness does not illwease appreciably with in~,reasil)~ sprin~ d~rleclion. Similar to the oyster and helical sprin~s, the saucer sprin~ stiffness could be adjustedl by usin~ an air sack placed inside the saucer.

In Fi~ure 28, a saucer sprin~ with air sack inside is shown, havin~ air hose 100 and hole for air hose 102.

CA 02206433 1997-0~-29 W O96/16565 PCTrUS95/15570 In Figure 29, multiple saucer sprin~s are used as heel sprin~s 104, 106 and 108 and two as rr,-~rool sprin~s 110 and 112. Each saucer sprin~ could have a dirrt:r~:"l ~lirr"ess and each ~lirr..ess couldl be adjusted usin~ an air sack component placed inside the saucers.

It should be u--de.:.lood that the invention as speciri P"y desc-iLed herein could be 5 altered without deviatin~ from its funda.-.erldl nature. For example, the forefoot and heel sprin~s would not have to be all one sprin~ type as desu-iL,ed herein. For example, the heel spring could be two bendin~ beams and the forerool sprin~ could be a saucer. Still further, the springs could be anaLc,..i,r"y shaped to i.-Lt:~race with the user's foot properly. The top surface of the one, two, and three sprin~ Dles could be shaped to meet the natural curvature of the lO user's foot bottom.

The stren~th or :,Lirr--ess of the sole sprin~ should be less than that of the heel sprin~ so as to permit effective L-dnsrer of energy from the heel sprin~ to the sole sprin~.

Additionally, the width, len~th and shape of the sprin~s can be altered so that the device inLe.rdces effectively with the ardLu-- --' curves of the human foot. The .., dsoles may also co--.~ ri~e composite arch supports and/or composite heel cups.

The term "coupled sprin~" herein includes the case where not only the release of a first spring co-..p--3sses an adjace--l or linked sprin~ when the device is in use, but also the case where the con-pr~ssion of the first sprin~ also co---presses a second adjacent or linked sprin~.
Thus in one e-..b- ' ..enL of this invention, the pressure of heel-strike a~ainst the heel sprin~ also causes absorl,Lion of ener~y by a forerooL sprin~ which is released at toe-off to enhance toe-off propulsion.

The sprin~ confi~uration can be either an inte~ral part of the sole or affixed to the bottom of a sole of a shoe or prosthesis. Additional eleri.er,L~, e.~., wed~es filled with air, may be employed to reS1ulate the sprin~ ~Lirr~ess to meet various requirements and conditions for the benefit of the person usin~ the device.

It is therefore to be understood that within the scope of the appended claims, the invention may be practiced in ways other than as specifically described herein.

Claims

CLAIMS:

1. A sole system for a shoe or foot prosthesis which comprises:

a heel spring made of a material such that said spring has an energy return of at least 70% formed by upper and lower bending beams;

wherein said bending beams converge to form a bending beam axis and a coupled region;

wherein said upper and lower bending beams are capable of bending toward each other;

wherein the curvature in the fore and aft directions of at least one upper or lower surface of at least one bending beam changes concavity;

wherein the aft end of said bending beam s surface has a concave upwards region and the fore end has a concave downwards region; and wherein the curvature dimensionless ratio in in the range Z > 1.

2. The sole system of claim 1 wherein the curvature dimensionless ratio is in the range 2 ~ Z
~ 40.

3. The sole system of claim 1 wherein the curvature dimensionless ratio is in the range 5 ~ Z
~ 30.

4. The sole system of claim 1 wherein an air bladder is positioned between said upper and lower bending beams.

5. The sole system of claim 1 wherein at least one bending beam has a tapered thickness largest at the bending beam axis and smallest at the aft end of said bending beam.

6. A sole system for a shoe or foot prosthesis which comprises:

a forefoot spring formed by upper and lower bending beams;

wherein said bending beams come together to form a bending beam axis and a coupled region;

wherein said upper and lower bending beams are capable of bending toward each other;

wherein the curvature of at least one bending beam's upper or lower surface in the fore and aft directions is concave upwards.

7. The sole system of claim 6 wherein at least one bending beam has a tapered thickness largest at the bending beam axis and smallest at the aft end of said bending beam.

8. A sole system for a shoe or foot prosthesis which comprises:

a spring made of a material such that said spring has an energy return of at least 70% formed by upper and lower bending beams;

wherein said bending beams converge to form a bending beam axis and a coupled region;

wherein said upper and lower bending beams are capable of bending towards each other; and wherein the bending beam dimensionless ratio for each beam is in the range 18 ~

~h ~ 35.

9. The sole system of claim 8 wherein the bending beam dimensionless ratio for each beam is in the range 20 ~ ~h ~ 33.

10. The sole system of claim 8 wherein the bending beam dimensionless ratio for each beam is in the range 22 ~ ~h ~ 31.

11. The sole system of claim 8 wherein at least one bending beam has a tapered thickness largest at the bending beam axis and smallest at the aft end of said bending beam.

12. The sole system of claim 8 wherein an air bladder is positioned between said upper and lower bending beams.

13. The sole system of claim 8 wherein said spring is a heel spring.

14. The sole system of claim 8 wherein said spring is a forefoot spring.

15. A sole system for a shoe or foot prosthesis which comprises:

a heel spring made of a material such that said spring has an energy return rate of at least 70% formed by upper and lower bending beams;

wherein said bending beams converge to form a bending beam axis and a coupled region;

wherein said upper and lower bending beams are capable of bending towards each other; and wherein at least one bending beam has a torsional stiffness ratio in the range .GAMMA. ~
1.

16. The sole system of claim 15 wherein at least one bending beam has a tapered thickness largest at the bending beam axis and smallest at the aft end of said bending beam.

17. The sole system of claim 15 wherein at least one bending beam has a torsional stiffness ratio in the range 1 < .GAMMA. ~ 10.

18. The sole system of claim 15 wherein at least one bending beam has a torsional stiffness ratio in the range 1.1 ~ .GAMMA. ~ 5.

19. The sole system of claim 15 wherein the beam length dimensionless ratio is in the range .pi.
~ 1.

20. The sole system of claim 15 wherein the beam length dimensionless ratio is in the range 1 < .pi. ~ 2.5.

21. The sole system of claim 15 wherein the beam length dimensionless ratio is in the range 1 < .pi. ~ 2.

22. The sole system of claim 15 wherein an air bladder is positioned between said upper and lower bending beams.

23. A sole system for a shoe or foot prosthesis which comprises:

a sole spring made of a material such that said spring has an energy return of at least 70% compressible about a transverse sole spring axis positioned at a pointapproximately 2/3 of the length of the sole spring from the aft end of the sole spring thereof;

a heel spring formed by upper and lower bending beams coupled to said sole spring;

wherein said bending beams converge to form a bending beam axis;

wherein said bending beam axis is between said sole spring axis and the aft end of the sole spring; and wherein the heel spring/sole spring thickness ratio for each heel spring bendingbeam is in the range ~ > 1.

24. The sole system of claim 23 wherein the heel spring/sole spring thickness ratio for each heel spring bending beam is in the range 2 ~ ~ ~ 20.

25. The sole system of claim 23 wherein the heel spring/sole spring thickness ratio for each heel spring bending beam is in the range 3 ~ ~ ~ 10.

26. The sole system of claim 23 wherein at least one bending beam has a tapered thickness largest at the bending beam axis and smallest at the aft end of said bending beam.

27. The sole system of claim 23 wherein an air bladder is positioned between said upper and lower bending beams.

28. A sole system for a shoe or foot prosthesis which comprises:

a sole spring compressible about a transverse sole spring axis positioned at a point approximately 2/3 of the length of the sole spring from the aft end of the sole spring thereof;

a heel spring formed by upper and lower bending beams coupled to said sole spring;

wherein said bending beams converge to form a heel spring bending beam axis;

wherein said heel spring bending beam axis is between said sole spring axis an the aft end of the sole spring; and a forefoot spring formed by upper and lower bending beams coupled to said sole spring;

wherein said forefoot spring bending beams converge to form a forefoot spring bending beam axis;

wherein said forefoot spring bending beam axis is between said sole spring axis and the fore end of the sole spring.

29. The sole system of claim 28 wherein an air bladder is positioned between said upper and lower bending beams.

30. The sole system of claim 28 wherein at least one bending beam has a tapered thickness largest at the bending beam axis and smallest at the aft end of said bending beam.

31. A sole system for a shoe or foot prosthesis which comprises:

a sole spring having a heel end and a toe end compressible about a transverse axis positioned at a point approximately 2/3 of the length of the sole spring from the heel end thereof; and a heel spring non-pivotally coupled to the sole spring between the transverse axis and the heel end;

wherein the thickness of the sole spring at the transverse axis is less than its thickness where the heel spring attaches to the sole spring.

32. The sole system of claim 31 wherein said heel spring is selected from the group consisting of double bending beam leaf springs, oyster springs, helical springs, and saucer springs.

33. The sole system of claim 31 wherein said heel spring is equipped with an air sack.

34. A sole system for a shoe or foot prosthesis which comprises:

a sole spring made of a material such that said spring has an energy return of at least 70% having a heel end and a toe end compressible about a transverse axis positioned at a point approximately 2/3 of the length of the sole spring from the heel end thereof;

a heel spring coupled to the sole spring between the transverse axis and the heel end; and a forefoot spring coupled to the sole spring between the transverse axis and the toe end;

wherein the thickness of the sole spring at the transverse axis is less than its thickness where the heel spring attaches to the sole spring.

35. The sole system of claim 34 wherein said forefoot spring is selected from the group consisting of double bending beam leaf springs, oyster springs, helical springs, and saucer springs.

36. The sole system of claim 34 wherein said forefoot spring is equipped with an air sack.

37. A midsole system for a shoe or foot prosthesis which comprises:

a sole spring having a heel end and a toe end compressible about a transverse axis positioned at a point approximately 2/3 of the length of the sole spring from the heel end thereof; and at least one heel spring, selected from the group consisting of double bending beam springs, oyster springs, helical springs, and saucer springs, non-pivotally coupled to the said sole spring wherein the stiffness of the sole spring is relatively less than that of the heel spring.