CA2072997A1 - Device and method for absorbing impact energy - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An energy absorption device comprising; an elongate body (103) arranged along a longitudinal axis to receive an axial impact force at a first end thereof; apparatus arranged adjacent a second end of the body for deformation thereof;
die apparatus (104) for producing deformation of the body and ring fixed to the die apparatus (104) and surrounding the body. Also disclosed is a repeatable energy absorption device including crushing apparatus having threaded apparatus on its outside surface. Upon receipt of the axial impact, the first end of the body moves outside surface. Upon receipt of the axial impact, the first end of the body moves from a first position away from the crushing apparatus to a second position closer to the crushing apparatus. The device additionally includes threaded sleeve apparatus (106) having a first end for supporting the crushing apparatus and for moving the crushing apparatus toward the first end after the axial impact to return the first end of the body to the first position.

Description

~ - )91/06786 PCT/~IS90/06421 72~7 DEVICE AND METHOD FOR ABSORBING IMPACT ENERGY

The pres~nt invention relates to a device for absorbing impact ener~y.
In many dynamic systems, there is sometimes created a destructive deceleration which develops within : 5 a relatively short distanoe. While in certain circumstances, a compart~ent subject to distortion may provide an adequate survival space, nevertheless, the human body cannot wi~hstand deceleration forces, above a certain limit.
~hs ef~iciency of an energy absorbing device is given by the ratis:
SE~ (specific energy absorbed) = energy absorbed/device weight.
A com~on unit of specific ~nergy is J/g. (Joules/gram~.
~he desirabl~ ~eature~ of an energy absorbing device are as follow:
it should provid~ a pr~dictable FORCE vs.
DEFORMATION trace;
th8 rapid lo~dins~ rate ~xpec~ed in crashes should not chang~ the FORCE v~O DEFORMATION bahaviour:
it should operate under both tension ~nd co~pression;
the dQvice should be aea light and as small as po~sibl~:
2S th~ specific en~rgy ab~orp~ion (SEA) should be high:
it ~hould 3~Q gcono~it:z~l to manufacture;
it should b~ r~liable and maintenance-free for a lons p~riod of time:

91/06786 - 2 - PC~/US~ 9 9 ~ -it should not be adversely af~ected by dirt, corrosion or other environmental factors;
the person involved should be decelerated in the most efficient manner possible, while maintaining the loading enviro~ment within the limits of human and/or payload tolerance:
its stroke should be relatively long as compared to its total length (i.e~ a high troke ef~iciency), T~ere are many EA devices for impact applications, the most oo~on on~s utilize deformation of ~etals and rictio~ to dissipate en~rgy. Some examples are as follows:
Device SEA~J/g.) 1 5 ~
axial compression of a steel tube 25 axial compression o~ an Al tube 16 steel strap/wire over die or roller 4 steel inver~ion tube 4 20 basic elong~tion o~ s~eel 14 crushing a rigid foa~ 20 stQQl rod pulled throu~h a tu~e 2 tube ~laring 3 controlled crushing of a ~e~al tube 45 controll~d ~rushing of struc~ural honeyco~b 40 controll~d Axial cru~hing o~ a co~posite tube w~h Xevlar~R~ rein~orcing ~iber 20 with glass r~in~orcing fl~r60 with carbon r~inforcing ~iber ~ 100.
~
It should b~ noted that in the las~ thr~ ca~es ~controll~d axial cxu~hing o~ a cc~posite tube) ~he reported SEA v~lu~s r~r to ~he ab~orbing mat~rial and not to ~h~ entire device. ~oreover, carbon ~ibers are relativ~ly exp~n3i~e. In addition to ~he above ~xa~ples, therQ exi~t ~EA devices ~sed on an elastic ele~ent such as springs, co~pre~sed ga. and fluids.

SUE~STITUTE SHEET

091/06786 PCT/U~9~

However, their stroke is short, the force incre~ses and they become almost rigid. Their strong recovery and bounce bacX are undesirable. In some cases (pneumatic/hydraulic shock absorbers) a valve forces fluid out at a predesigned pressure; such devices have SEA in the range 5 to 25 J/g.
In U.S. Patent No. 4,523,730 (Martin), th~re is disclosed an energy absorbing seat arrangement, particularly for a helicopter, in which a seat pan is carried by a frame slidably mounted on parallel upwardly extending pillars secured to the helicopter. Normally, downward sliding o~ the frame on the pillars is prevented ~ither by metal rods extending through drawing dies, or by a de~ormable ~etal tube and a mandrel extending through the tube. In the event of a crash, the rod~ are drawn through the dies or the ~andr~l through the deformable tube. However, this ~etal/metal arrangement, like other similar arrange~ents, su~fers from a relatively low SEA, the ract that it is very restricted as to its pot~ntial ~or cross-sectional area reduction (~aximum elongation of a ductile stainless steel is only 45-50%), dependence on ~etal/metal friction to ~aintain a uniform load ~s unpredictable, while oxidation may alter tho properties of the ~et~l/metal interace. As will be 8~sn~ the present inv~ntion do2~ not utiliz~ a metal/~tal arrangement and thus avoids such pro~lem~.
~ .S. Patent 3,865,418 d~scribes an ener~y ab ~rbing de~ice ~or a v~h~cle includ~ng a oylinder having a ~tepped inn~r dia~Qt~r ~nd in which an annular plastic ~lug i~ ~x~rud~d bo~we~n the ~ylinder and a stepped ra~ The Qtroke ef~ic~ncy i~ s than one hal~ of the length o~ th~ d~vice.
U.S~ Patent 2,997,3~5 to Pe~er~on described a kinetic energy ab$orber in whi~h piston foroes an extrudabl~ body ~hrough a nozzle~ UOS. Patent 3,380,557 describ~s ~ variabl~ kins~lc energy a~sor~er in which a SIJBSTITUTE SHlEET

~91/06786 P~/US~0/0~21 - 4 - 2~2~7 piston serially forces a plurality of extrudable bodies, each having an increased resistance to extrusion, through a nozzle. Both of these patent.c employ a cylinder formed of heavy metal in order to withstand the high pressure produced during extrusion. The pro~osed structure is relatively heavy and thereSore the absorber has a reactively low SEA. The piston stroke is limit~d to the le~gth of the cylind~r and thus the stroke 2fficiency of the absor~er i~ limited to less than one half of the overall ~bsorber length. Furthermore, during stroking, the friction force between the extrudable plastic material and the cylinder wall decreases producing a consequent reduction in the s~opping force of the ab~orber, as the stroke progress~s.
U.S. Patent 3,S32,380 de~cribes an energy absorbing devic2 for a r~traint belt. GB Patent Application 1,506,157 describes an energy absorbing device employinq a piston and extrudable material which is similar to that described in U.S. Patent 3,865,418 but employs a smooth cylinder. U.K. Published Patent Application 2,048,430 de~cribes a devic~ absorbing energy by extrusion.
It is ~n object of the pr~sent invention to provid~ an n~rgy ~b~orption ~vic~ having th9 desirabl~
properti~ list~d abov~. Anoth~r ob~ect o~ the present in~ntion i~ to pro~id~ ~uch a devicc h~ving ~pecific ~n~rgy ab~orption gen~rnlly higher than the SE~'s of prior ~rt E~ deYice~.
Th~ prQs~n~ i~vQn~ion e~ploys th~ realization that a ~olid body o~ ductil~ ~a~r~al i~ capable of tr~n~mittin~ ~xial force~ therethrough, g~nerally without di88ipation 0~ thQ fo~ce in non-axial direction~.
Further object~ of the in~ntion will be appar~nt ~rom the d~scrip~ion which fsllows.
~ha pr~nt inv~ntion accordingly provides an SUE~5TITUTE SHElEiT

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e~ergy absorption device which comprises an elongate body of a ductile material arranged alo~g a longitudinal axis arranged to receive an axial impact force at a first end thereof along the longitudinal axis, apparatus adjacent a second end of the body of ductile material for extrusion thereo~, the body of ductile material being operative to transmit the axial impact force axially therethrough ~rom the first end ~o the second end.
In accordance with the prssent invention the pistons and cooper~ting ~ylinders required by the prior art, which add significan~ weight and grea~ly limit the stroke efficiency may b2 eliminated. A high SEA is provided.
In accordance with one prsferred embodiment of the invention a relatively thin walled sleeve may be provided to prevent bucXling of the elongate body.
Preferably, the sleeve i8 ~rangible during extrusion at the second ~nd, so ~s to enable the available stroke length to be nearly equ2l to the overall length of the energy absorbing dQvice.
Preferably, th~ body o~ ductile material comprisQs at le~st one discrQte ductile solid element which undergoes reduc~ion of its eross-sectional area 25 ~nd ~ n p~rticular ~nd~rgoQs co~bin~d dQ~or~ation of sh~ar compression and elongatlon~ The solid element is prof~rably ~ormed of a poly~er, such a~ Nylon 6, Nylon 5-6, Nylon 6,12, Polypropyl~ne, Polycarbonate, Poly~ul~on~, Polyethar~th~rk~to~e, or Stilan, ~anu~actur~d by R~yche~ Corpora~ion o Caltfornia, o~
~5A. Tho ~ork of d~or~tion, plU5 fr1ction between the ductil~ ~olid and ~h~ ~olid surface of ~hatev~r is used to e~ect r~duction o~ th~ cro~-sectional area, absorb th~ kln~ti~ energy of a dec~l~rating objec~, In accordancQ w~th th~ inv~ntion, th~ cross-sectional area a~ aforesa~d i3 reduc~d ~y at least 25%, preferably at lea~t 40% and most pre~erably at least 50%.

91/06786 P(~r/~lS90/06421 - 6 - ~ ~7 In a particular embodiment, the invention provides a device for absorbing impact energy, which comprises in operative co~bination: at lPast one discrete ductile elongate solid body which receives an impact force and retains its coherence when undergoing reduction of its cross-sectional area by not less than 25~; a rigid element defining a r~stricted space having a smaller cross-s~ctional area than the at least one discrete ductile solid shape, whereby when the shape is subjected to a foroe which induces it to pas~ through the restricted space, the ~aller ~ross-sectional area is such that the shape by passage through the re~tricted space experi~nces a reduction in cro~s-~ectional area of not less than 25~: and a transmission, which may include a piston, for trans~itting i~pact Qnergy incident on the device to the ~t least one di~crete ductile solid shape, whereby the latter is subjected to a force which induces it to at least in part pass through the restricted space.
In another embodi~ent, the invention provides a method for absorbing i~p2ct energy, which compri~es the step oP applying ~n imp~ct ~orc~ along a longitudinal axi~ to a ~irs~ ond of ~n elongate body of a du~tila ~at~rial arrangod along the longitudinal axis, theraby cau8~ng it to bo ~xtruded by ~pparatus arranged ad~ ace~t a s~cond end o~ the body of ductile material, wh~r~in th~ ~longate body o~ du~til~ ~a~erial is ope~ating to tran~ th~ ~xial impact ~orce axially ~h~r~through ~rom ~h~ fir~t ~nd to the s~cond end.
In accord~nce wit~h ~ pr~rlr~d eD~bodimant of the invention, t~h~ bcxdy of ductile ~a~erial i~ su~bjec~ed to a ~orc~, tr~nsmi~ting ~ 18~ t pal~: of the i~pac~
energnr ~o ~t loas~ one di~cr~te d~ctile solid shape, wher~by t~he latter i~ æu~bject~d ~o A forc~, w~ich ~ay includ~ e.g. comp~Q~siv~ and/or tensional forces~ which reduces its crosso~ectional arsa ~y not less than 25~, while t~he ductil~ ~oli~ ~int~in~ it3 coherence. The SU B ~a`T7Ta~ T E~ S H ~ Elr ~9l/06786 PCT/US90/0~21 - 7 - ~72~7 force is preferably one which induces the discrete ductile solid shape ~o at least in part pas~ through a restrict2d space, and the latter may be defined by a rigid part and would have a smaller cross-~ectional area than the di~crete ductile solid shape, whereby when the shape is subjected to a force which induces it to pass at least in part through the re~tricted space, the smaller cross-~ectional area is such that the shape by passage through the re tricted space experiences a reduction in cross-s~ctional area o~ not less than 25%.
In accordance with an al~ernative embodiment of the present invention, there is provided a device for absorbing ener~y during an axial initial impact and during an elastic rebound i~ a direction opposite that of the axial initial impact, comprising an elongate body arranged along a longitudinal axis which comprises elongate flbers along its axis and which is operative to receive the ~xi~l initial i~pact force at a first end thereof along the longitudinal axis. The device also comprises appar~tu~ arranged ad;acent a second end of the body for defor~ation ~hereof~ The apparatus includes die apparatus for producing deformation of the body and ring2d app~ratu~ fixed tc the die apparatus and spac~d ~hereSro~ ~or surrounding the body adjacent the die app~ratu~ and for breaking the elongate fibers into elongate stringlike elements which ~aintain high tensile ~tr~ng~n ~urlng th~ tic rebound.
Ther~ is ~urther provid~d, in accordance wi~h th~ pre~ont inv~ntion, a r~p~atabl~ energy absorption device co~pri~ing, a d~for~able and cru~ha~l~ body arrang~d alo~g a longitudinal ~xis op~ra~ to receive an axial i~pact for~ at a ~irst ~nd ~hereof along the lcngitudinal ~Xi8, de~or~ing and cru~hing apparatus arrang~d adjacent a second ~nd of th~ body for deformation thereor and ~or crush~ng of the crushable sleeve where~n ~he deforminy and cru~hiny apparatus includ~ ~hre~d~d apparatus on ~n outside surface thereof ~WS~8TITUTE SHEET

` 91/067Xfi PCT/US~0/0~21 2~7~9~

and wherein upon receipt of the axial impact, the first end of the body moves f rom a f irst positio.n away from the deforming and crushing appara~us to a second position closer to the deforming and crushing apparatus and threaded sleeve apparatus having a first end for suppsrting the deforming and crushing apparatus and for moving the deforming and crushing apparatus toward the first end after the axial impact thereby to return the ~irst end of the body to the first position.
Additionally, there is provided, a vehicle with an energy absorption device co~prisiny a chassis, a bumper for receiving axial impact forces and an energy absorption device disposed between the chassis and the bumper for absorbing impact energy comprising a deformable and crushahle body arranged along a longitudinal axis operative to receive the axial impact forces at a first end thereo~ along the longitudinal axis, deforming and crushing apparatus arranged adjacent a sQcond end of the body for ~e~or~ation and crushing ther~of, the body b~ing operative to transmit the axial impact force axially th~rQthrough ~rom the first end to the second end and to moYe ~rom a first posi~ion to a second posit~on in con~qu~nc~ of the axial impact force and re3toring apparatu~ for re~toring the energy absorption d~vic~ from ~hQ ~econd position to ~he firs~
po61tlon.
Th~r~ i~ provid~d, in accordance with ~n em~odim~nt o~ ~h~ present invention, an energy ab~orption d~v~ce ~or ~b80r~ing i~pact energy co~prising a d~or~abl~ and cru~h~ble body arrang~d along a longitudin~l ~xis oper~tiv~ ~o receiYe the axial impac~
foxce~ ~t ~ fir~t and th~reo~ along ~he longitudinal axis, d~or~ing and cru~h~ng apparatu~ arr~nged adjacent a second end o~ the body ~or de~o~mation and crushing ther~of, th~ body ~ein~ oper~t~v~ to trans~i~ the axial i~pact rorce axially th~r~through fro~ the first end to the s~cond end and to ~o~e ~ro~ a ~irst posi~ion to a ~ U 8 8TIT U TE ~ H EEFr - ~9l/06786 PCT/US90/~21 9 ~ 7 second po~ition in consequence of the axial impact force and restoring apparatus for restoring the energy absorption device from the second position to the first position.
Ther~ is further provided, in accordance with the present invention, an Qnergy absorption device including a cruchable sl~eve operative to receive said axial impact force at a ~irst end thereof, crushing apparatus arranged adj~c~nt a second end of said body for crushing o~ the crushable sleeve, said crushing apparatu~ including a die having an outer conical sur~ace and a cage apparatus for ~nclosing the die and for producing crushing of the crushable sleeve, wh~rein th~ cage app ratu~ have a plurality o~ slots and an inner surface and wherein the erushing occurs between the conical surface and th~ inner surfacs in the area of each of ~he plurali~y of ~lots.
Finælly, in accordance with the present invention, the energy absorption device also includes apparatus ~or adjusting the location of thç die with re~pect to the cage appar~tus thereby to control th~
amount of ~nergy absorb~d.
Figure 1 illustrates in section an embodiment of the pre~nt invention:
Figure 2 illu~trate~ in section, a falling w~ight ~xp~riment on th~ ~m~odi~ent of Fig. l;
Flgur~ 3 ~llustrat~ in 3~ction a further o~bodim~nt o~ th~ pr~s~nt invention;
Figur~ 4 illu~tr~s a preferred e~bodi~nt of 30 the present in~ention, in p~rtially ~u~ away sec~ional illustration;
F~gure~ 5A - 5C illustrate in section a second pre~rr~d ~mbodi~nt of ~h~ pra~ent inYen~ion use~ul for ab~orbing high i~p~ct ~n~rgy;
F$gur~ 6A and 6~ illw trat~ in sac~ion ~le~ntq o~ the embodi~en~ o~ ~igure 5A;
Figures 7A ~ 7C ~llustr~e a car bumper system SUE~ TITUTE SHEET

9l/06786 PCT/US90/0~21 - lo 2~7~
utilizing the e~bodi~ent of Figure 5A:
Figures 8A and 8B illustrate an alternati~e embodiment of elem~nts of the embodiment of Figure 5A;
Fiqures 9 and 10 illus~rate further embodiments of the pre ent invention; and Figure 11 illuætrates an embodiment of the present invention incorpor~ted into a collapsible seat.
According to a particular embodiment of the invention, ~he discrete ductile sol~d ~hape is in the form of a billet which has a conically -chaped head, the axis of sy~metry of thi~ head being directed towards the hole of a die, 80 that wAen impact occurs, the billet begins to be extruded therethrough. The SEA of the shape i~ preferably at least 40, more preferably at least 50, yet more pre~erably at least 70 and most preferably at l~ast 80 J/g. While for purposes of illustration reference will ~Q ~ade herein ~o bille~s, it will~e appreciated by persons sXilled in the art that other suitable shapes may be made to undergo the required reduction in cro~-sectional area, normal to the stroke direction.
It has been ~ound in accordance with the invention, that the h~gher th~ cros~-sectional ratio between the die's inl~t and it~ outlet (i.e. the draw r~tio ~ DR), that a matQrial ~an tolerate witho~t br~aking, tho highsr i~ th~ pres~ure required ~o pass it through thQ d~, snd the higher i8 ~he wor~ don~ on the ~xtruded ~at~ri~l. Each ~2terial has a different ~xi~u~ u ~ul DR (although in g~neral this will usually b~ han ~), and the pre~ure required ~o ~orce it through a die ~ay also vary. How~r, the material of th~ billet should not br~ak in ~he di~, it should ~aintain its continui~y until e~erging ther~rom.
Otharwise, rupturQ of the ~a~erial in the die ~ay cause sh~rp changes in ~he ~gnitud~ and direction o~ ~he force and the dec~leration, ~nd tho en~rgy ab~or~ing proce~s i~ destabilized. Material~ which ~ay not be ~ ~ ~ STIT ~ T~ S H EE~

' ~91/06~86 PCT/~IS90/0~21 2~29~7 used ~or the device of the invention may be illustrated by two extre~es, namely, low viscosity fluids in which the pressure required to pas~ them through a given die and the worX done are low, and materials which are so hard that it i~ practically impossible to pass them through a die.
The work don2 i8 the sum of two components:
the friction between the billet and the die, and the work requir~d to reshape the billet. The friction component should be li~i~ed in m~gnitude, in those cases where it is difficult to control the ~o~al force causing the friction and/or in those ca~es where heat evolved at the die-billet interface cannot be dissipated efficiently. The work done to reshape the billet is desirable, since it is three-dimensional work, the heat generated being absorbed throughout the bill~t's vol~me.
The SE~ o~ the billet is directly proportional ~o the extrusion pre~sur2 and inver~ely proportional to the billet's dQnsity, a~ ~ay be seen from the equation:
(1) SEA ~ O.O9alp/d where d is the density of the billet ~aterial expressed in g./om3 units and p i~ ~he extrusion pressure expressed in kg . /cm2 unit~ .
It w~ ~urpri~ingly di~covered in accordance with the prssQnt in~ention ~h~t i~ the billet is made of a po~.y~ar~c ~terial, th~n it SE~ i~ u~ually higher, co~par~d W~th other ~at~rial~ ~uch a~ ~chanic lly ~trong~r ~etzls. ~oreover, poly~Qric materl~ls can u~ually be ~xtruded through al conventiorl~l die, witXout 30 ext~rnal h~tinq, ~nd th~y g~n~r~lly develop s:onsider~ble s~re3~ hout breAking in th~ die, a~ high strsk~ ~p~d~, with high cro~s s~ctional reductions rate~. In fac'c, 1:heir g~nerally lower density compared with metals ~agnifi~d th~ir ~ adv~ntage. Part:icularly 35 u3e~ul in accordanc~ wi~ ha inv~n~ion are billets made fro~n ductile polyamid~s and polyolefins. Exemplary polyol~fins ar~ poly6~yl~n~ and polypropyl~ne, S~JB~3TITOJTE Sl-lEFr ~9l/067~6 PCT/US90/0~21 - 12 - ~r~ 9~7 preferably of high ~olecular wei~ht; among polyethylen~s, most preferred is that of ultra high molecular weight. In general for a given DR, the higher the molecular weight of the polyethylene, the higher the SEA. Presently preferr~d is polyethylen~ having a molecular weight of about 3.3 x 106. However, it was surprising to find that aboYe this molecular weight, the SE~ fell, at least for DR' 5 above 4, at testing velocities o~ 0.025~eter~/sec. and above, due to either extrudate cracking, or breakage in the die.
In connection with th~ present i~vention, it has been observed that on room temp~rature extrusion of 50m~ polymer~ through a die, even at a high feed rate (such as e.g. 11 ~ters/s~c.), t~e extrudate elongation exceeded the reported values of the ultimate elongation at room temperature of a slow speed tensile test.
Examples are given in the ~ollowing Table:
Polymer Report~d Elo~ga~ion Elongation Found _________ _____________________r_______________________ Nylon 6 and 6/6 300% 400%
Polyacetal 100% 400%
Polycaxbonate 110% 186%
Rigid PVC 80% 186%
___________;______________ ___O________________________ Th~se ob~rvations are Yurpri3ing, ~ince polymers are rat~ iti~s and would b~ exp~c~2d to Pail due to brittl~ness at ~ higher ra~a ~n il~ t~st. Since the ~n~rgy abso~ed ~y a matQrial i8 ~ product of d~for~t~on ~orce and str~in displ~c~ent, thi~
dQ~onstr~t~d ~xtra du~ y i~ v~xy u~ful in providing an incr~sed ~ount of en~rgy that ~ poly~er can absorb 2nd thua th~ for~going poly~eric ~ri~ ay be ad~antag~ou~ly e~ployQd in ~ccord nce with ~he present i~vention.
Th~ S~A values tha~ wer~ calculated fro~
experimental data, ~or som~ polymeric systems, w~re found to ba excep~ionally high, when compared with 8 ~ ~ STIT W T E 8 H EE~r - ~91/06786 PCT/US90/06421 13 - 2~2~
values know in the art, as have been set out above.
Examples are given in the following Table. It will be appreciated that th~ higher the D~ that a material can b~ extruded through without breaking, the higher is its SEA.
Polymer DR SEA(J/g-3 Polyethylene~ 6.l 244 Polypropyl~ne 6.l 352 lO Nylon 6 6.l 367 Nylon 6/6 5 346 Nylon 6/6 6.l 440 The overall SEA of an energy absorbing device is egual to or lower than that o~ the material per se.
Thus, the upper limit on the efficiency o~ an E~ device is determined by the intrinsic energy absorption capability o~ the particular material. The concept of the pre~ent invention enables the design and conætruction of ~icient and lightweight energy absorption devices.
It has al80 been discovered in accordance with the pre~nt invention that an additive such as carbon black, when incorporated into ~he polymeric material ~5 increa~Q~ it~ SEA. HowevQr, at higher concentrations, it low2rs tb8 potential ~aximum DR due to embrit~lement o~ the ~xtrud~te. C3rbon black has th2 a~vantage~ of prov~dinq ultraviolet pro~ction, and dissipating static ~l~ctricity, by making ~h~ polymer el~ctrically conducti~Q. Th~ el~c~rical conduc~ivity may also be u~ful for ~lectrical heating of th~ billet to control it3 EA per~or~ance.
The prQ~en~ i~Y~n~ion may be applied to load limiting d~vices in general aviation ea~s, as part of landing g~ar in helicopt~r~ and other craf~, bumper syste~s for ground tran~por~ation vehicl2s, safety fe~ces on highways, ~t th~ botto~ of an elevator pier to SU~STIT~TE SHEET

' 91/067~6 PCT/US90/0~21 - 14 - ~72~7 counteract the effects of free falling crashes, for payload parachuting, and for any other system~ where it is desirable to control the effects of deceleration.
Thus, the transmission means referred to above ~ay be at least part of a structural component of any of these items.
Generally, the at least one discrete ductile solid shape may comprise at least one member selected from polymer~ and non~poly~eri waxes, e.g. hydrocarbon waxes. Suitable polymers are, for example, polyol~fins (e.g. polypropylene or ultra high molecular weight polye~hylene), polyamides, polyacetal, poly(haloal~enes), polyetherether ketones and polycarbonates. Other ingredients which may be present are e.g. carbon ~lack, ~etals, me~al salts, other metal compounds, silica, antioxidants, tabilizers, plasticizers, lubricants, crosslinking agents, powder ~iller~, fibers, flake~, microbeads and microballoons.
The at l~ast one discrete duc~ile ~olld shape is typic~lly placed in a 31~eve which supports the solid shape ag~inst buckling. A piston i~ used to force the ductile 801id towards th~ die and the sleeve is operative to guide the pi to~'s motio~. ThQ sleeve is typically elongat~ and i8 strong enough to maintain mechanical in~egrity under i~pact (i.e. the elongate ~l~ev~ do~s not buckl~ or crack). To ~hi~ end, i~ is typically ~nuf~ctur~d ~rom ~trong ~ut lightwe~qht ~a~rial~.
Alt~rnativ~ly, the ~ ve can be a crusha~le sl~Qv~ whiCh ~ov2~ with ~he ~uc~ solid as it is being ~ pushed toward~ a cru~hing location on a die~ The por~ion o~ th~ cru~habl~ sl~eYe w~ch i above the die support~ tha por~ion o~ th~ duc~ilQ solid which is above the die: how~ver, a& ~A~ ~u~tila ~olid-crusha~le sleeve co~bination reaches the die, th~ due~ile solid is extruded t~rough the ~ol~ of the di~ and ~he crushable sle~ve fra~ffl~nts and open~ flower;like around ~he base ~3U~3~TITUTE SHEET

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of the die. Thus, ~he cru~hable sleeve supports the ductile solid and additionally ab~orbs some impact energy.
Fuxth~r, the die can be placed in an enclosing structure, such as a cage, which comprises slots through whioh the crushable sleeve frag~ents oan flow. The invention will now be illustrated by th2 following non-limitative Exa~ple~.
A billet 80 ~. in length, diameter 10.26 mm., 10 and havinq a 20- conical tip, was machined from co~mercially available polypropylene rod (d = O.92 g./cm,3, ~elting range - 165 ~o 170-C.). The billet (2, Fig. 1) was placed in a steel elongate sleeve (43 of inner diameter ll mm. A conical die (6) having a 20-cone a~gle, 11 mm. inlet diameter and a 4.45 m~.
diameter, 10 ~. long outlet, was pressure fitted to ~he end of the elongate ~leeve. A ~atching ste~l piston (8) was insert~d into the other end of the elongate sleeve, so that the billet was between the piston and the die.
All parts wer~ lubricated with ~ hydraulic oil. Theassembly was placed in ~ hydraulic press (not illu~trat~d 2xcept for ~he special bore (10) in the base (14) of the pre~5, whi~h allows free extrusion. When activ~ted, tha hydraulic r~ pushed th~ pis~on in the 25 d~rectiorl o~ arrow tl2) inl:o the a~onga~e sleeve, at a r~ta o~ 0.025 met~r/~c., ~x~rudin~ the polypropylene k through thQ die. T~e ~xtrusion foroe, recorded at a ~t~ady s~a~e, was 30.8 ~2.4 kN. ~rior to tha exp~rl~nt, the tempera~ur~ of th~ roo~ and the billet w~ 13-C. ~hQ SEA of thi~ ~lllet wa~ de~erminQd to be 352 J/g. m a extrudate had a fibrillated, rough ~urfac~, ~o~e 45- off axi~ ~cars, but it was n~varthale~ cont~nuou~ and ~trong.
A~ h Exa~pl~ he apparatus illus~rated in Fig. 1 wa~ u~ed. A billet 80 ~m. in l~ngth, diameter 8.2 m~., and having a 20 conical ~ip, wa~ machinad from co~rcially ~vail~ble polyethylene ~olded rod SUBSTITUTE Sl-IEET

~9ltO6786 PCT/US90tO~21 - 16 - 2~7~7 (American-Hoechst HostalQn GUR-412, estimated average MW

3.3 x 1o6). The billet was placed in a steel elongate sleeve o inner diameter 9 mm. A conical die having a 20 cone angle, 9 mm. inlet diameter and a 4.45 mm.
diameter, 10 mm. long outlet, was pressure fitted to the end of the elongate ~leeve. A ~atching steel piston was inserted into the other end of the elongate sleeve, so that the billet was between the piston and the die. All parts were lubricated with ~ hydraulic oil. The ass~bly was placed in a hydraulic press having a special bore to allow fre~ extrusion. When activated, the hydraulic ram pushed the piston in~o the elongate sleeve, at a rate of 0.025 meter/sec., extruding the polyethylene billet through the die. The extrusion pressure, recorded at a steady state, was 1585 +0 bars.
Prior to the experiment, the temperature of ~he room and the billet was 10C. The 5EA of thi~ billet was determined to be 166 J~g. Ex~rusion proceeded evenly;
the extrudate surfac~ wa~ smoo~h, without any cracks or pinhol~s. The DR was about 4.1.
A~ w~th Example I, the apparatus illustrated in Fig. 1 waG us~d. A billet 80 ~m. in length, diameter 8.2 ~m., and haY~ng a 20- conical ~ip, was machined from commercially avail~ble polyQthyl~ne ~olded rod (American-HoQch~t Ho~talen GUR-415, e~timat~d average MW
5 x 106). Tha billet w~s pl~ced in a elongate steel ~leov~ o~ innQr di~met~r 9 ~0 A conical die havin7 a 20- cone ~ngle, 9 ~. lnl~ diameter ~nd a 4.45 mm.
dia~et~r, 10 ~. long outl~, w~ pr~sure ~ltted ~o the end of th~ elongate sleev~. A ~atch~ng ~eel pi~ton wa~
insert~d into the other end o~ the elongat~ sleeve t 50 that th~ bille~ was ~atw~n ~he pi~ton and ~he di~
parts wer~ lubricat~ with a hydraulic oil. The asse~bly was placed in a hydraulic pre~ having a speci~l bor~ to ~llow fr~ ~xtru~ion. When a¢tivated, the hydraulic ram push~ th~ pi~ton into ~he elongate sle~ve, a~ ~ r ~ o~ 0,025 ~eter/~ec., ~xtruding the - `~91/06~86 PCT/US90/0~21 - 17 ~ 9~
polyethylene billet through the die. Th~ extrusion pressure, recorded at a steady state, was 1640 +200 bars. Prior to the experi~ent, the temperature of the room and the billet was lO-C. The SEA o~ this billet was determined to be 173 J/g. Although the extrudate didn't break, deep ductile cracks turning to a continuous helical crack, covered its surface.
Extrusion pressure varied about 25~. The DR was 4.l.
It will be appr~ciated that ~riction forces between the billet and the elongate sleeve vary as the billet moves toward and through the die.
A billet (22, Fig. 2) l50 mm. in length, diam~ter lO ~m., and having a 20- ~oni~al tip, was ~achined from co~mercially available polyethylene molded rod tA~erican-Hoechst Hostalen GUR 412, estimated average MW 3.3 x lo6~, and placed in a steel elongate sleeve (24) of inner diameter ll m~. A conical die (26) having a 20- cone angle, ll ~m. inlet diameter and a 6.5 mm~ diamet~r, lO m~. long outlet, was pressure fitted to the end o~ the elongate sieeve. A matching steel piston (28) was inserted into the other end o~ the elongate sleeve, 80 that ~h~ billet wa~ between the piston and the die. All part~ ~ere lubricat~d with a hydraulic oil. Th~ asse~bly w~s plaoed vertically (piston pointing ~pward), via fitand (32), with central space ~42) to allow a rre~ exi~ ~or th~ extrudate, on a 4 cm.
thic~ ~t~al basQ pl~t~ (30)~ which w~ levelled on concr~te ~oundatlon (34). ~ 34 c~. long, 12.2 cm.
dia~tor ~tQ~l rod t3~), waighing 31 kg. was li~ted to a h~igh~ o~ 1.75 ~t~r~ ~y ~ean~ o~ a nylon rope attached at ring (44) and ~ light pull~y ~not ~hown~; friction ~or~Q in ~rsQ f211i~g wa. 1 k~. The weight huns within a ~ertic~l plastic pip~ (38) (14~2 cm. inside diameter), ~he w~ight ~a~ing 8 longitudinal plastic fins (40) to center it in the pip~, with ~n ~verage clearance between the finned weiqht and the pipe~s inner surface of 2 ~m.
While f~lling, th~ weigh~ did no~ ~ak~ contact with the Sl3E~STlTl.lTE ~SHIEE~T

`~9l/06786 PCT/~IS-90/0~21 - 18 - ~
inner surface of the pipe. The rope wa~ re~eased, and the weight fell, impacting the piston, pushing it 8.2 cm. into the elongate sleeve, until it came to rest at the top of the piston, supported by the inner wall of the pipe. The weight came to rest quietly and the ~xtrudate surface was smooth and uncracked. The kinetic energy o~ the impacting weight was 515 J. Since the piston's ~troke was 8.2 cm., ~he average force was 515/0.082 - 6280 N or 640 kg~. The SEA was 85 J/g., for a DR of 2.86.
A~ with Example IV, the ~pparatus iliustrated in Fig. 2 wAs used. A billet 130 mm. in length, diameter 10 Dm., ~nd having a 20- conical tip, was machined from com~ercially available nylon-6 rod (Akzo Chemie "AXulon"), and placed in a steel elongate slesve of inner diameter 11 mm. A coni~al die having a 20-cone angle, 11 mm. inlet diameter and a 4.9 ~m.
diamet~r, 1~ mm. long outlet, was pressure fitted to the end of the elongat~ sleeve. A matching steel piston was inserted into the other end of the elongate sleeve, so that the billet was batween the pis~on and the die. All parts were lubricated wi~h a hydraulic oil. The assQmbly was placed v~rtically (piston pointing up~ard) on a base that had a cQnter bore to allow a free exit .
for the ~xtrudate. The die a~s~bly wa~ placed on a o~ thlck ~tQel plate that was l~vell~d on a concrete found~tion. A 34 cm. lonq, 12.2 cm~ diame~er steel rod, w~ighing 31 kg. was lift~d ~o a h~ight of 7 meters by m~an3 0~ a nylon rope ~nd ~ light pull~y (rriction force 30 in ~r~ falling: 1 kg.). Th~ waight hung within a vertical pla~tic pipe (14.2 cm. inside ~iameter), the w@ight having 8 longi~udinal pla~tic fins to center it in the plp~, with an aYe~ge clear~nc~ betw~en the finn~d w~ight and th~ pip~3 inner ~urface of 2 mm~
Whil~ ~alling, ~ha w~ight did no~ ~ak~ co~tact with thP
inner 3ur~AoQ of the pipe. ~h~ rope was released, and th~ weight fell, imp~.ti~g ~he pas~on, pushing it into ~31JB~3T~TUTIE SltEET

- ~91/06786 PCT/US90/0~21 - 19 -- 2~7~99 ~
the elongate sleeve, until it came to rest at the top of the piston, supported by the inner wall o~ the pipe.
The weight came to rest quietly after pushing the piston 6.8 cm., and the extrudate ~urface was smooth and uncracked. The velocity at first con~act was estimated at 11.7 meters/sec. The kinetic energy of the impacting weight was about 2060 J. 5ince the ~ull stroke wasn't utilizQd, the weight was lifted again to a 3 meter height and dropped on th~ ~A device. At this time the stroke was 2.55 cm. long, when the weight stopped.
Since the first impact defor~ed the hillet to attain the elongate sleeve's inner diameter (1.1 cm.), the SEA of the billet during the second stroke could be calcula~ed, neglscting air resis~ance and EA by the steel/concrete base. Estimated value of SEA was 319 J/g, while the DR
was S. The decelerating average force was about 36 kN.
The surface of the extrudate was smooth, with no cracks or pinholQs.
A~ with Exampl~ V, the apparatus illustrated in Fig. 1 was used. H~w~ver, the thickness o~ elongate sleeve 4 wa3 reduced to 0.8 mm. ~ billet 150 mm. in length diameter 10 ~ nd h~ving a 20- conical ~ip, was machined ~ro~ commer~i~lly available nylon-6 rod (Akzo Chemie ~kulon~), and placed in the thinned steel ~longat~ ~leove o~ ~nn~r dia~ter o~ 11 ~m. A conical die h~ving a 20- cone angl~, 11 m~. inle~ diæmeter and a 6 ~m. d~am~ter, lO mm. long outlet; wa~ pressure fitted to th~ end o~ tha elong~ ev~. ~ matching steel piston W~5 in~ed l~ato the o~her ~nd o~ ~he slee~re, so 30 that the billet wa~ lo~:ated be~ween th~ piston and the die. The ~xp4riment ~as s:onduc:ted a~; with Example V.
~ow~ver, the w~ight was dropp~d from a height o~ 5 ~un.
Th~ welght c~ to reE~ a~t~r pushing the piston 8~ ikm.
The ~xtnadat~ surf~c~ w~ ooth 2md ~ncracked. The 35 velo¢ity at ~$rst contact Wa8 e~ti~ated at 9 m./sec.
The steel ~longat~ ev~ dt d not brQak or de~orm, 'chough th~ deceler~ting ~or~::e was 17 . 5 kN, or 1. 79 ~IJB5TITUTE SHEE~T

91/06786 PCT/US90/0~21 - 20 - 2~2~
metric tons. Estimat~d value of SEA for the billet material was 195 J/g, while the extrusion draw ratio was 3.36.
The ultimate tensile strength o~ the elongate sleeve's steel is about 60,000 psi, or 4218 kgf (cm*cm).
If the extrusion pres~ure (equal in all directions), then th~ wall thickness required to sustain the related hoop stress i~ 3.08 ~. ThQ actual wall thickness was 0.8 mm., or 26% of the ~ini~al desisn thickness.
It will be appreciated that the elongate : sleeve ~unctions, i~ thi~ e~ample, to support the billet and to guide the piston as ~he two elements moved toward the die. For this example, the elongate sleeve was manufactured of steel, although it could alternatively have been manufactured from m~terials such as other metals, ceramics, carbon or poly~ers. The ~longate sleeve should be ~trong but lightweight and able to maintain mechanical integrity in the fac~ of an impact.
A bille~ S2 (Fig. 3) lO0 ~m. in length, diameter l9~6 ~m. and having a 20' conical tip, was machined ~rom comm~rcially availabl2 nylon-6 rod (Akzo Chemie "Akulonn), and placed vertically in a steel die 53 tFig. 3), 80 that an 80 ~. long ~ection of the billet protruded above the entrance o~ the die. The 2S conical dia having a 20 d~grees cone angle, 20 ~m. inlet dia~ter ~nd a 16 ~m. diam~t~r, 8 ~m. long outlet, was pl~c~d vertic~lly on ~ ba~e th~t had ~ c~nter bore to allow ~ ~r~e exit for th~ ~xtruda~. The die as~embly was plac~d on a 40 ~m. ~hick st~al pl~t~, a~ illustrated in Fig. 2 with two chang~s: neither ~ s~eeve nor a piston w~r~ pr~santO Th~ proc~dur~ oP Example V wa~
applied, gh~.-w~igh~ ~as dropp~d fro~ a ~ m. height, i~pacting ~h~ upper part of ~h~ billet, pushing it in~o th~ di~ 53 mm. un~il it c~me to r~s~0 ~he b~llet did not bu~kl~, Extrudata ~aintained ~ts continuity, with not crack~ or pinhol~s. Extrugion force was 2~ kN or 2.2 m~tric ton Th~ SE~ wa~ 64 J/g., ~or a die draw V91/06786 PCT/US90/~21 - 21 - 2~7~9~7 ratio of 1.56.
A billet 70 (Fig. 4~ 170 mm. in length, diameter l9 ~m. and having a 20 degrees conical tip, was machined from commercially available nylon-6 rod (Alzo Chemie "Akulon"). The billet was coated with an oil film, and in~erted into a iberglass reinforced polyester crushable sleev~ 72, having an inner diameter of 20 m~. and 150 mm. in length.
The composite crushable ~leeve was produc~d by the pultrueion process. The crushable sleeve's front end, and t~e billet in it were inserted into a die 74 having at its center a conical bore 76 which accommodates the tip 78 of the billet 70. The inlet diameter o~ the die was 20 ~., the outlet's diameter was 14 ~. and the cone angl~ was 20 degrees.
The inner surface of the co~posite crushable sleeve was located at a sl2eve-crushing zone 80 of the die. A m~tallic bushing 82 supported the co~posite crushable ~leeve's outer ~urfac2. The upper ends of the billet and the composlt~ crushable sleeve, were at the same heigh~. The die as~embly was arranged ~o allow unimpedQd ~xit o~ th~ extrudate.
A ~ree ~alling w~ight was dropped on ~he billet's/composite'~ upper ends, from a height of 7 m., according to thQ procedure tha~ is described in Example IV. The w~ight came to r~st after ~troking 35 ~m. The extrudat~ w~ un¢rack~d and h~ a s~ooth surfa~e. 35 . o~ tho co~posite cru~h~bl~ sl~ve w~ crushed and op~n~d flow~rlik~ around the ~as~ o~ die 74. Above ~he ~etalllc bushing, ~ha co~po~it~ crushab~e sleeve did not ~reak. ~h~ d~c~l~rating ~or~ was about 59 kN, or 6 m~tric tons~ Th0 d~vi~ S~ (wh~n w~ights of ~oth bill~t and cru~h~ble sleQvQ w~r2 ~onsid~red), was 83 J/g. Tha ~pparatu~ o~ Fig. 4 i~ a pi~tonles~ deYice wher~ mo~t o~ the ~topping ~orca is trans~itted through the bill~t. Th~ co~posi~ ~rushable sleeY~ supports the bill~t ~gainst buckling and ab~orb~ al~o so~e ener~y SUBSTITUTI; SHEET

~91/067X6 PCT/~'S~/06421 - 22 - ~ ~2~
while being crushed.
In accordance with a preferred e~ odiment of the invention, the composite crushable sleeve is fixed to the billet and moves together therewith~ According S to one embodiment of the invention, the billet does not completely fill the sleeve. According to a~ alternative embodiment of the invention, the sleeve may be provided without the billet. In ~11 embodi~ents, the ~rushable sleeve is preferably for~d oP fiber rein~orced plastic.
It will be appreciated that the crushable sleeve performs as a~ elongated sleeve above the metallic bushing 82 with tha exception that the crushable sleeve moves with the billet 70 toward the crushing zone 80 of the die 74. Additionally, in this ex~ple, there is no piston which pushes the billet toward~ the die.
It will further be ~ppreciated that the crushable sleeve must be ~ade of a material ~hat will brea~ in an organized and predictable manner such that its frag~ents do not jam in the die 74. Suitable ~aterials for the crushable sleeve include ceramics, metals, carbon and poly~ers with the abovementioned restrictlon that th~y break in a controllable manner.
Both the crushable sleeve ~he elongate sleeve may preferably b~ compris~ of a reinforcing-mater~al/m~trix co~po~ite. Th~ reinforcing ~aterial can b~ in ~ny ~ap~ and ~orm, ~U~h a~ con~inuous rovings, chopped strands, mats, fabric8~ ~apes~ and whiskers and flak~s, ~nd is typically ~anu~ac~ured from glass, 30 carbon, c~r~ics, k~oron, k~vl~r, ul~ra high ~aolecular weight poly~thylenQ, or oth~r poly~eric or me~allic fib~rg~. T~ trix ~t~ri~ typically a ~ler~1105etting or ~heropla~ic polymer such a~ epoxy, polyest~r, polyvinyle~ter, polyphenylenesul f ide, 35 polyimide, or polya~ideiD~id~.
Th~ Gompo~ite-sl~eve is typically manufactur~d via ~ila~nt ~nd prepr~g windis~g, pultru~:ion, casting or 8UBSTITILJTE~ SHEET

- )9l/067X6 PCT/US90/0~21 ~ ~ 7 ~
molding, or any other method which will produce a composite sleeve.
It will further be appreciated that the device of the present invention ~aintains its mechanical integrity during an ela~tic rebound which typically occurs after a crash. In the embodiment of Fig~ 4, during impact, the ductilq ~olid i~ extruded through the hole in the die, after which it 3well , and the crushabls l~ve i~ brok~n into elongate stringlike elements. During an elastic rebound, the ductile solid and the cxu~hable leeve would ideally move in~an upward directions. Howe~er, moving them in the upward direction requires worX to be expended since the swollen extruded ductile solid and the ~lowerlike crushed co~posite sleeve are not easily returned to their previous shapes. Thus, 1t will be appreciated that the abovementionQd embodiment of the pre~ent invention absorbs energy dur~ng th~ elastic rebound and reduces its affect.
A billet 100 (Fig~. 5A - 5C) 210 mm. in length, 23 mo. in diameter ~nd having a tip 101, was machined from commercially available nylon-6 rod (Akzo Chemie ~Akulon~). ThQ bill~t 100 was inserted into a pultruded polyester/~ib~rgl~s~ crusha~le sleeve 102 ha~ing an inner diametQr o~ 24 m~., an outer diameter of 29.5 ~m. and a length of 200 ~m. The bill~t 100 and sl~va 102 ~orm an ~long~t~d body 103 which is typically co~ered ~t a ~irs~ end by an i~pact ~ur~aGe 99, typically o~ m~tal. I~ will b~ appr~ciated that the cru~hable sleQ~ 102 did not touch ~h~ billet 100 at the location o~ tha tip 101.
~ s~cond end o~ ~h~ ~longat~ body 103 wa~
in3~rted into de~or~ing ~nd crushing apparatus 104 located inside a thread~d ~le~ve 106~
Appara~us 104 typically co~prlses a die 110 having a conical bore 112 for deor~ing billet 100 upon it~ receipt of ~n axi~l force along a longitudinal axis T~ tET

~9l/06786 PCT/US~0/0~21 - 24 - 2~72~7 108. Die 110 additionallY compris~s a conical outer surface 116 located between two cylindrical portions 118 and 120 of differing diameter, wherein portion 118 has a smaller diameter than 120.
Apparatus 104 additionally typically comprises a cage 114 for enclosing die 110. Cage 114 typically comprise~ a base 122, upon which sits die 110, which includes a hole 124 through which a deformed billet can pass. ~ase 122 is shown in ~ig. 6B. Integrally attached to the base 122 is a cylindrical frame comprising ~n upper portion 126, typically threàded on its outside surface thereby to engage with the threaded sleeve 106, and a lower portion 128 comprising a multiplicity o~ slots 130, typically 3 - 16, shown in Fig. 6A. The inner dia~eter o~ the cylindrical frame is typically slightly larger than the outer diameter of portion 120 of the di~ 110.
. Sleeve 106 typically comprises a cylinder 130 which is threaded on an innQr surface 131 ~hereby to engage wi~h the threaded upper portion 126~ and a flange 132 typically for attaching the device of the present inYention to a fix0d sur~e.
Elongate body ~03 was ins~rted into apparatus 104 as ~ollows: billet 100 was inser~ed into die 110 so 25 that its tip lOl fit into and through conical bore 112 and cru~h~bl~ ev~ 102 was in~r~Qd between the die 110 and th~ upper portion 1~6 ~nd ra~d on conical out-r surfac6 116. A gap ~17 i8 ~ypically formed be~w~on thQ outer sur~ce of ~h~ crushæbl~ sleeve 102 and ~hQ inn~r surface o~ upp~r port~on 126. The first end of th~ elongate body 103 pro~ectad an extension length dl o~lO0 ~m. ~bov~ the flange 132 and the entire a~bly o~ body 103, app~r~tus 104 and sle~ve 106 was supported at the rlang~ 132 by a heavy walled steel sle~v~ ~not ~hown).
a free ~alling 30 kg. st~el weight having a cylindrical shape was drspp~d onto ~he impact surface 99 ~31J13STITUTE SHEI~

~91/06786 PCT/US90/0~21 - 25 - 2~2~7 fro~ a height of 7.5 m, according to the procedure described in Example IV. ~he wei~ht came to rest tArough forcing the elongate body 103 into the apparatus 104, as shown in Fig. 5B.
A portio~ 140 of billet 100 was extruded through the die 110 and out through hole 124. A portion of crushable ~leeve 102 wa crushed against the conical surface 116 and was forc~d out of the cage 114 and into an inner space 138 oP the ~leeve 106 through the multiplicity of slots 130, ther~by breaking the portion o~ the crushable sleeve 102 into a ~ultiplicity of crushed strips 142. ~nergy was expended through the extrusion o~ the billet 100, throuqh the crushing of the sleeve 102 ~nd through the frictional move~ent of the cr~shed strips 142 through the lots 130 and against the inner surface 131 of sleeve 106. It will be appreciated that, in order for the crushable sleeve 102 to break into the strips 142, the cross-sectional area between the conical surf~ce 116 and an inner surface of the lower portion 128 of cage 114 at the point of crushing of the crushable sle~v~ 102 ~hould b~ greater than or equal to the cross-s~ctional arRa o~ the crushable sleave 102 before crushing.
The stroke o~ the free falling weight was 28 .
~., reducing th~ 2xten~ion l~ngth to a length of 72 mm.
above the ~lange 132, marked d2, and thQ ~opping force wa~ c~lcul~ted a~ 7~ kN. Th~ por~ion o~ the ~longa~e body 103 ~bov~ th~ dis 110 did not crush or cr~ck.
As ~hown in Fig. 5C, thQ ~xtension leny~h dl i~ recov~r~d to enable th~ devic~ o~ the pre~ent invent~on to bQ reu~d. To r~co~er ~h~ extension length dl~ ~ppara~ua 104; wi~h ~h~ b~dy 103 inside o~ it, is turned wlth re~pect ~o thread~d ~leave 106 towards flange 132.
Accordingly, furthor impact-~ can be performed.
A second and ~hird i~pact per~or~ed with the abovedescribed elong~t~ body 103 yielded similar resul~s ~ ~ B ~T U T~ S ~ ~E~r ~91/06786 PCT/US40/06421 - 26 - 2~2~7 to the fir~t impact.
The device described herein can be used for an automotive bumper sy~tem 150 attached to a car chassis 154 as shown in Figs. 7A 7C. The bumper system 150 comprises a bumper 152 attached to prior art energy absorbing devices, such a~ an ~lastic element 156 and a hydraulic shock ab~orbe~ lS8, which, in turn, are attached to the device of the present invention, marked 158, typically through i~pact surface 99. Sleeve 106 is typically attached to chassis 154 via flange 132.
Alternativ~ly, the device 158 oP the present invention can ~e att~ched to the prior art device~ via sleeve 106 and the impact surface 99 ~an be attached to the chassis 154. The state of th~ dQvice 158 of the present invention as shown in Fig. 7~ is shown in de~ail in Fig. 5A.
In the pres~nce of an i~pac~ force on the bumper 152, ~uch as might occur during a traffic accident, the bump~r 152 tr~n~mits force to the impact surface 99, causing the elo~at~ body 103 to be forced into the apparatu~ 104 thQreby causing energy to be di~sipated. The bumper ~yst~ 150 is then in the state illuskrated in Fig. 7B wher~in the extension length is d2. This is shown in detail in Fig. 5B.
The bu~per sy~tem 150 is rastored ~o a useful ~tat~, as ~hown in Fig. 7C and ln ~etail in Fiy. 5C, by turning the apparatu~ 10~ w~h ra~pect ~o sleeve 106 towards flange 132.
According to an alternativ~ embodiment of ~he pr~ent inYention, ~llu~rated in Figs. 8A and 8B, ~he deforming ~nd crushing app21ra~us, ~n~rked lS9, is compri~d of a di~3, markQd 160, an~ a cage~ marked 166, who~e locat~ on~ ~rith resp~c~ éo ~ach o~her ~re changeable. Die 160 i~ forD~ed wi~h threads 16~ on the outside of a bottom portion 164. The c2~ge 16~ is formed with ~atc:hing threads 168 for~ed on l:he surface of hsle 124 . In thi8 ~nner, ~ h~1 ght o~ dle 160 within cage SUBSTI~IJTE SHEE~T

. ~91/06786 PCT/~S~0/0~21 - 27 - 2~2997 166 can be changed so as to change the location of the conical surface 116 with respect to the incoming crusha~le sleeve 102 thereby to change the angle, m~rked ~1 on Pig. 8A and 2 on Fig. 8B, at which the crushed strips 142 of the crushabl~ sleeve 102 leave through the slots 130. Fig. 8B shows the die 160 in a position to produce 2 which is a s~aller angl~ than ~1 of Fig. 8A.
The smaller the angle of l~aving, tAe more energy is dissipated by the c~u~hable sleeve 102.
The embodiment o~ Figs. 8A and 8B can be utilized with a body 103 comprising a billet 100 and crushable sleeve 102, or, alternatively, the body 103 can be co~prised only of the crush~ble sleeve 102.
~n energy absorption device utilizing appar~tus 159 can be implemented in safety systems, such as seats, ~or loads of varying weight. For example, in ~ crash landing of an aircraft, the deceleration of a heavy seated person and a light seated person will differ significantly when an identical load limiting device is applied to thQm. ~owever, they ideally should be decelerat~d at an id~ntical, safe rate, until their crash velocity is raduc~d to clo~e to zero. This requires that the en~rgy absorbing device for a heavy person apply more force for th~ same stro~e, thereby absorbing more ~nergy, than i8 ne~ded for a light per~on~ I~ the person's woigh~ i~ known a priori, an ~nergy ~bsorption devic~ utilizinq th~ apparatus 159 of Figs. 8~ and 8~ can accordingly chànge the location of die 160 with r~spect to ~ag~ 166.
A ~at do~ignQd to ab~or~ energy in a crash is shown in Fig. 11. The ~Qat, ~arked 201, is typically a collapsibl~ ~ner~y absorbinq ~a~ with legs 203 hinged to bo~h ~h~ ~loor 204 and a ba~e 202 of the ~eat 2Ql.
The base 202, floor 20~ ~nd lags 203 comprise a parallelogr~m 205 along who~e ~hort di~gonal is placed the device of the pr~ ~nt in~ention, marked 206. The de~ice 206 c~n b~ the ~evice of any o~ the embodiments SUBSTITUTE SHEEl-~91/0678~ PCT/~ g 7 shown hereinabove and particularly in the embodiment of Figs. 8A and 8B.
In a crash situation, the seat 201 will collapse forward toward the floor 204 and will place a compressive axial impact force on the device 206.
A further altern~tive embodiment of the present invention, utilizing a tensile force rather than a compressive impact force, is shown in Fig. 9. In this embodiment, the elongate body, marked 170, comprising a lo billet 171 and a crushable sleeve 173, is formed with a hollow bore 17~ within which is a ~trong wire 1i4, such as of steel.
The strong wire 174 is attached at a first end ~o a plug 176 via an anchoring device 178, such as a lock nut, and at a second end to a source of tensile force. The compre~sion plug 176 is firmly attached to a first end o~ the elongate b~dy 170.
The elongate body 170 iY deformed and crushed via d~forming and cru~hing appar~tus 180, loca~ed at a second end of the elonga~e body 170. Apparatus 180 compris~s a ~leeve ~upporting ring or cage 182 for supporting the cru habl~ sleeve 173, a crushing and oxtrudinq di~ 184 ~or crushing the crushable sleeve 173 and for extruding the billet 171. The cage 182 ha~ a ~5 multiplicity of ~lots~183 ~hrough which ~low psrtions 185 o~ crushod ~ v~. Apparatus 180 ~dditionally ~ompri~e~ mQ~ns 186 for ~ttaching the die 184 ~o the c~ge 182, ~u~h a8 2atching threads on die 1~4 and on cage 182 (a~ ~hown in Fig. 9) for ~d~ustably adjusting the location of th~ die 184 r~lative to the c2ge 182, or glu~ for pQrmanen~ly ~et~ing the loca~ion of the die 184 nd th~ cage 182.
The Qlongate ~ody 170 $8 d~ormQd and crush~d, in a ~ann~r similar to that de~cribed hereinabove in 3S con~unction wi~h previou~ odiments, in ~he presence of a ~nsile force on ~trong wire 174. The wire 174 is pulled tow~rds apparatu , cau~in~ the compression plug ~9~/06786 PCTt S9n/0~2l ~2~7 to push the elongate body 170 into apparatus 180. It will be appreciated that apparatus 180 is supported by a support (not shown) which has a hole in it to allow for the flow o~ the defor~ed billet 171.
Reference i~ now made to Fig. 10 whi~h illustrates a further alternatiYe embodiment illustrating the use of a ten~ile forc~ rather than a compr~ssive impact force. In this embodiment, the extrusion o~ he billet 171 and the crushing of the crushable sleev~ 173 do not occur at th~ same location and therefore, there is relative motion between the billet 181 and the crushable sleeve 173.
The extrusion occurs at a conical extrusion die 190, located at a first end of the elo~gate body 170 and supported by a support (not shown) with a hole in i~
to allow for the flow of the deformed billet 171.
Extrusion die l90 addi~ionally comprises a sleeve support portion 191 for supporting the crushable sleeve in the area o~ the ~xtrusion.
The crushing occurs at a crusher 192 located at a second end of the elongate body 170. The crusher 192 compr~ 8~S a cxusher cup 200 and a support caga 194 with a multiplicity o~ ~lot~ 196 through which flow crushed sleeva portions 198. The height of the crusher 25 cup 200 w~th r~spect to th~ location~ of the slots 196 i8 ~d~ustabl~ via ~eans 202 for attaching the crusher cup ~00 to ~h~ cage 192. ~Q ns 202 ~ight be comprised of matching threads on crusher cup 200 and on cage 194 (as shown in Fig. 10) ~or adjus~ably a~justing the loc~tion o~ the crusher cNp 200 r~l tive to the cage 194, or it ~ight b~ co~pris~d of glue for permanently setting the location3 o~ ~h~ cru~her cup 200 and the cage 194.
~he ad~ust~ent of cage 194 wi~h respect to 35 cru~her cup 200 reduce~ the free length of the slots 196 thereby decrea~ing ~he crushing angle of ~he crushable sleeve 1~3. As has been described h2r~inabove, the S~JBSTITUTE SHEET

1 ~91/06786 PCT/~IS90/0~421 o ~72~

smaller th~ crushing angle for the crushable sleeve 173, the more force is required to push crushed sleeve portions 198 out of slots 196.
While the present invention has been particularly described, it will be appreciated by persons skilled in the art that many modifications and variations ~ay be made without departing from the concept of the invention. 8y way of illustration only, the cone-shaped end of the billet of ductile material may be pointed, or the point may be sheared off laterally to form a cone frustu~, or the overall-billet may have the shape of two coaxial longitudinally opposed cone-frustum-ended billets (of the same or different diameters, and having ~he sa~e or different cone anyles), in which the frustums may be joined by a coaxial "waist"; or instead of a billet there by be used a sheet which is extrud~d through rollers or through a slot. Thus it will be evident that such (and other) modi~ications and variations may be made without departing ~rom the spirit or scope of the invention as set forth in the appended claims.

Claims (19)

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

1. An energy absorption device comprising:
an generally unsupported continuous, single elongate body of a ductile material arranged along a longitudinal axis to receive an axial impact force at a first end thereof along the longitudinal axis, and means arranged adjacent a second end of the body of ductile material for extrusion of said second end, most of the body of ductile material being operative to transmit, in a self-supporting manner, the axial impact force axially therethrough from the first end to the second end.

2. An energy absorption device according to claim 1, and comprising a relatively thin walled sleeve disposed, initially in a non-contacting manner, about said elongate body for preventing buckling thereof.

3. A device for absorbing energy during an axial initial impact and during an elastic rebound in a direction opposite that of said axial initial impact, comprising:
an elongate body arranged along a longitudinal axis and comprising a body of ductile material surrounded by a crushable sleeve, the elongate body being operative to receive said axial initial impact force at a first end thereof along said longitudinal axis;
means arranged adjacent a second end of said body for deformation thereof said means including die means for producing deformation of said body and ring means fixed to said die means and spaced therefrom for surrounding said body adjacent said die means, said die means and said ring means cooperative to locally break said crushable sleeve into elongate stringlike elements which maintain high tensile strength during said elastic rebound.

4. An energy absorption device comprising:
a continuous, single elongate body of a ductile material surrounded by a crushable sleeve which is fixed to said body, arranged along a longitudinal axis to receive an axial impact force at a first end thereof along the longitudinal axis, and means arranged adjacent a second end of the body of ductile material and the crushable sleeve for extrusion and crushing thereof, the body of ductile material and the crushable sleeve being operative to transmit the axial impact force axially therethrough from the first end to the second end and the crushable sleeve being crushed at the same time that said body is extruded.

5. a method for absorbing impact energy, which comprises the step of:
applying an impact force along a longitudinal axis to a first end of a generally unsupported continuous, single elongate body arranged along said longitudinal axis, thereby causing said elongate body to be deformed at a second end of said elongate body by apparatus arranged adjacent said second end, wherein said elongate body is operative to transmit, in a self-supporting manner, the axial impact force axially therethrough from the first end to the second end.

6. A method for absorbing impact energy, which comprises the steps of:
applying an impact force along a longitudinal axis to a first end of a single, continuous elongate body arranged along said longitudinal axis, thereby causing said elongate body to be deformed by apparatus arranged adjacent a second end of said elongate body, wherein said elongate body is operative to transmit generally the entirety of the axial impact force axially therethrough from the first end to the second end and to move from said first end from a first position to a second position in consequence of said axial impact force; and restoring said first end to said first position from said second position.

7. An energy absorption device according to claim 1, and wherein said axial impact force is a tensile force.

8. An energy absorption device comprising:
a continuous, single elongate body of a ductile material enclosed in a crushable sleeve and arranged along a longitudinal axis to receive a tensile axial impact force at a first end thereof along the longitudinal axis, and means arranged adjacent a second end of the body of ductile material for extrusion thereof the body of ductile material and the crushable sleeve being operative to transmit generally the entirety of the tensile axial impact force axially therethrough from the first end to the second end; and crushing means for crushing said crushable sleeve located at said first end.

9 An energy absorption device comprising:
an elongate body of a ductile material arranged along a longitudinal axis operative to receive an axial impact force at a first end thereof along said longitudinal axis;
a crushable sleeve disposed about said elongate body operative to receive said axial impact force at a first end thereof;
deforming and crushing means arranged adjacent a second end of said body for deformation thereof and for crushing of said crushable sleeve, said deforming and crushing means including:
die means for producing deformation of said elongate body, wherein said die means have an outer conical surface; and cage means for enclosing said die means and for producing crushing of said crushable sleeve, wherein said cage means have a plurality of slots and an inner surface and wherein said crushing occurs between said conical surface and said inner surface in the area of each of said plurality of slots.

10. An energy absorption device according to claim 9, and also comprising a threaded sleeve and wherein said cage means include threaded means for moving said deforming and crushing means inside of said threaded sleeve.

11. An energy absorption device according to claim 9, and also including means for adjusting said die means with respect to said cage means thereby to control the amount of energy absorbed.

12. A repeatable energy absorption device comprising:
a deformable and crushable body arranged along a longitudinal axis operative to receive an axial impact force at a first end thereof along said longitudinal axis, deforming and crushing means arranged adjacent a second end of said body for deformation and crushing thereof wherein said deforming and crushing means include threaded means on an outside surface thereof and wherein upon receipt of said axial impact, said first end of said body moves from a first position away from said deforming and crushing means to a second position closer to said deforming and crushing means; and threaded sleeve means having a first end for supporting said deforming and crushing means and for moving said deforming and crushing means toward said first end after said axial impact thereby to return said first end of said body to said first position.

13. A vehicle with an energy absorption device comprising:
a chassis;
a bumper for receiving axial impact forces; and an energy absorption device disposed between said chassis and said bumper for absorbing impact energy comprising;
a deformable and crushable body arranged along a longitudinal axis operative to receive said axial impact forces at a first end thereof along said longitudinal axis;
deforming and rushing means arranged adjacent a second end of said body for deformation and crushing thereof, the body being operative to transmit said axial impact force axially therethrough from said first end to said second end and to move from a first position to a second position in consequence of said axial impact force;
and restoring means for restoring said energy absorption device from said second position to said first position.

14. A vehicle with an energy absorption device comprising:
a chassis;
a bumper for receiving axial impact forces; and an energy absorption device disposed between said chassis and said bumper for absorbing impact energy comprising;
a deformable and crushable body arranged along a longitudinal axis operative to receive said axial impact forces at a first end thereof along said longitudinal axis;
deforming and rushing means arranged adjacent a second end of said body for deformation and crushing thereof wherein said deforming and crushing means include threaded means on an outside surface thereof and wherein upon receipt of said impact forces, said first end of said body moves with said bumper from a first position away from said deforming and crushing means to a second position closer to said deforming and crushing means; and threaded sleeve means having a first sleeve end attached to said chassis for supporting said deforming and crushing means for for moving said deforming and crushing means toward said first sleeve end after said impact forces have been received thereby to return said first end of said body to said first position.

15. AN energy absorption device for absorbing impact energy comprising;
a deformable and crushable body arranged along a longitudinal axis operative to receive an axial impact force at a first end thereof along said longitudinal axis;
deforming and crushing means arranged adjacent a second end of said body for deformation and crushing there-of, the body being operative to transmit said axial impact force axially therethrough from said first end to said second end and to move from a first position to a second position in consequence of said axial impact force; and restoring means for restoring said energy absorption device from said second position to said first position.

16. A seat with an energy absorbing device comprising:
a collapsible seat frame having at least two legs hingeably attached between said seat frame and a floor, wherein said at least two legs form two sides of a parallelogram and said seat frame and said floor form the other two sides of said parallelogram; and an energy absorbing device attached along a short diagonal of said parallelogram, said device comprising:
an elongate body of a ductile material arranged along a longitudinal axis operative to receive an axial impact force at a first end thereof along said longitudinal axis;
a crushable sleeve disposed about said elongate body operative to receive said axial impact force at a first end thereof;
deforming and crushing means arranged adjacent a second end of said body for deformation thereof and for crushing of said crushable sleeve, said deforming and crushing means including:
die means for producing deformation of said elongate body, wherein said die means have an outer conical surface; and cage means for enclosing said die means and for producing crushing of said crushable sleeve, wherein said cage means have a plurality of slots and an inner surface and wherein said crushing occurs between said conical surface and said inner surface in the area of each of said plurality of slots.

17. An energy absorption device comprising:
a crushable sleeve operative to receive an axial impact force at a first end thereof;
crushing means arranged adjacent a second end of said body for crushing of said crushable sleeve, said crushing means including:
die means having an outer conical surface; and cage means for enclosing said die means and for producing crushing of said crushable sleeve, wherein said cage means have a plurality of slots and an inner surface and wherein said crushing occurs between said conical surface and said inner surface in the area of each of said plurality of slots.

18. An energy absorption device according to claim 17 and also including means for adjusting said die means with respect to said cage means thereby to control the amount of energy absorbed.

19. A seat with an energy absorbing device comprising:
a collapsible seat frame having at least two legs hingeably attached between said seat frame and a floor, wherein said at least two legs form two sides of a parallelogram and said seat frame and said floor form the other two sides of said parallelogram; and and energy absorbing device attached along a short diagonal of said parallelogram, said device comprising:
a crushable sleeve operative to receive an axial impact force at a first end thereof;
crushing means arranged adjacent a second end of said body for crushing of said crushable sleeve, said crushing means including:
die means having an outer conical surface; and cage means for enclosing said die means and for producing crushing of said crushable sleeve, wherein said cage means have a plurality of slots and an inner surface and wherein said crushing occurs between said conical surface and said inner surface in the area of each of said plurality of slots.