Note: Descriptions are shown in the official language in which they were submitted.
~' -1-
BACKGROUND OF THE INVENTION
The invention relates to an axially contractable
actuator particularly suited for robotics applications.
Robotics technology is f re~uently presented with
the problem of mimicking the function of human hands and
arms. Mechanical analogies to hands and arms clearly must
include some replacement for the many human muscles used
to f lex and move the human f ingers, hands and arms. When
fluid power, either hydraulic or pneumatic, is used in
robotics, a f luid cylinder appears to be a likely
substitute for human muscles. However, high pressure
f luid requirements due to limited fluid cylinder size and
space and positicr.ing problems complicate the use of fluid
cylinders or make their use impossible for some
applications such as in self-propelling walking robots.
Fluid c~linders are also not entirely suitable as
actuators in the food and drug industries. Restrainers
must be used to contain dripping caused by leaking seals
and misaligned cylinder rods.
SUMMARY OF THE INVENTION
According to the invention, an actuator has first
connection means and second connection means at opposite
first and second ends of the actuator respectively and is
contractable along an axis extending between the
connection means. The actuator comprises rneans actuated
by the actuator being connectable to the connection
rneans. The actuator comprises at least one hollow,
flexible enclosure having an opening for adrnitting a
pressurized fluid. A constraining rneans extends about the
at least one enclosure for converting expansion of the
actuator transversely to the axis into contraction along
the axis when pressurized fluid is admitted into the at
G ~P
~ -la-
least one enclosure. The constraining means comprises a
plurality of non-stretchable, flexible tension links
intersecting to form a tubular network with meshes having
four or more sides. The links are connected together at
intersections of the network and are arranged so the links
approach alignment with the axis when the enclosure is
extended and so the meshes open up when pressurized fluid
is admitted to thc? enclosure.
According to another aspect of the invention, a
fluid operated actuator has expansible enclosure means
having a longitudinal axis, and an axially elongated state
and an axially contracted state. This fluid operated
actuator also includes means for admitting pressurized
fluid into the enclosure means for shifting the enclosure
means between the states. The fluid operated actuator
further includes constraining means disposed about the
enclosure means and comprises a plurality of tension links
connected together at a plurality of nodes which provides
a network having a plurality of open mesh areas. Each of
the mesh areas has at least four sides provided by the
associated tension links and the tension links of each
mesh area are substantially aligned generally in parallel
with the axis when in the elongated state. The tensio
links of each mesh area are disposed at a substantial
angle to each other when in the contracted state and the
enclosure means bulges outwardly through the mesh areas
when in the contracted state.
A further aspect of the invention provides a
fluid operated actuator assembly comprising an expansible
enclosure means having a longitudinal axis, an axially
elongated state and an axially contracted state. Tt-e
assembly includes means for admitting pressurized ~ id
into the enclos~lre means for shifting the enclosure means
between the states. The assermbly ~urther incl~c~es
constraining means disposed about the enclosure mealls and
comprises a plurllity of tension links connected tog~ther
~l ~'2~ 9~
-lb-
at a plurality of nodes, providing a networ~ having a
plurality of open mesh areas. Each of the mesh areas has
at least four sides defined by the associated tension
links. The tension links of each mesh area are in general
alignment when in the elongated state and the tension
links of each mesh area are disposed at a substantial
angle to each other when in the contracted state so that
the open area of the mesh areas is larger in the
contracted state than in the elongated state. The
enclosure means bulges outwardly through the mesh areas
when in the contracted state.
A still further aspect of the invention provides
a fluid operated actuator comprising an expansible
enclosure means having a longitudinal axis and an axially
elongated state and an axially contracted state and
includes means for admitting pressurized fluid into the
enclosure means for shifting the enclosure means between
the states. This actuator further comprises constraining
means disposed about the enclosure means and comprising a
plurality of tension links connected together at a
plurality of nodes to provide a plurality of open mesh
areas. Each of the mesh areas have at least four sides,
the sides of each mesh area being substantially aligned in
parallel with the axis of said enclosure means when in the
elongated state. The sides of each mesh area are disposed
at a substantial angle to each other when in the
contracted state. The enclosure means may be
non-elastomeric a,nd bulge outwardly through the mesh areas.
BRIEF DESCRIPTIOM OF THE DRAWINGS
Figure l is a side view of an actuator, according to
an embodiment of the invention, in a
pre-installation state;
Figure 2 is a side view of the actuator of Fiyure l
in an axially uncontracted state after
installation on a hinged arm;
g6
Figure 3 is a fragmentary view of an alternative
embodiment having a network with six-sided
meshes;
Figure 4 is a side view of the actuator of Figures 1
ancl 2 in an axially contracted position
aft:er installation;
Figure 5 is a diagrammatic side view illustrating in
sirnplified form the function of the network
of the actuator of Figures 1 - 4;
Figure 6 are diagrammatic perspective views
to 8 illustrating in simplified form the function
of the actuator of Figures 1 - 9;
Figure 9 is a perspective view, partly broken away,
of an
~G
b947/198
s~
actuator according to anothf?r r?mbooiment of the
IIIV~ tiOII;
f lgur(~ 10 l9 ~ll r?xplodf?d pf?rl3pf~c~vl? ~ w of tht? t~tu~tor of
Flgure 9;
Flgure-~ 11 is a pl~r~p~r:tivr? V~l?W of tht? fr~ction r~duclng layl?r of
the actuator r f F~gurl~9 9 all(l 1(I;
figur~? 12 i~ a pf?rspf~ctivr? YleW of tht~ ela~tolnt?ric t?nclo8ure of
thr? actuator of FigurH~ 9 to 11;
Fi9Ur~? 13 i9 a SHCtlO(I~I ViHW alollg linf? 13-13 of Flgurt? 11;
15 Flgure 14 i3 a sldB vicw of ~l~ actuator accordlllg to a further
embodimclIt of th~? inVt?lltlOn in all axially urlcontracted
9tatt?;
FigurH 15 i9 ~ Sidt? view of tht? ~ctuator of E19Urt? 13 Ill a~ ally
co~ltràcted stat~?;
f l9urt? 16 is a 8t?Ctioll~l ViHW alollg llrlt? 16-16 o f F l9urf? 15; ~lld
Fl9urH 17 ls a 9Hctional vlr?w alorlg lillt? 17-17 of ~ Igure 14.
C)ESCRIPTION OF THE PRE~ ERRED EMBODIMENTS
Fl9urr? I illu8trat~s an actuator I accordlng to ao
~?mbodimsnt of thr? illVCIItiOII. Tht? actuator has a hollow t?nclosurt? 2, in thls
30 C~i9B of an etastorlle?ric material. In othsr embodirnellts a plurallt~ of
cllclosures could bB us~?d togf?ther ill p~rallF?I. The ~?rlclosurr? may br? madt? of
rubb~?r, syrlthr?tlrc rubbBr or a suitable t?laatomBric plastic matt?rlal. Thf?
r?nclo8urr? i~ ClOSf?d at a flrSt f?lld 3 Wht?rr? lt l'S bolldt-d abollt a thrt-ad~l st-ld
or bolt 4. Tht~ ~3tud 4 provld~?s conllectloll me ll~8 for conllf~ctlll9 th~
s~
-- 4 --
actuator to a mounting bracket 8 as ser n in Figur~ 2. The stud 4 IS
conrlected to thH bracket by 8 pln 10. The mounting bracket i9 conllected tD
an articulated arm 39 by a bolt and nut comblnatiorl 14.
Ihe ~nclo~ur~ has a ~ecolld end 16 whlch 1~ opell in th~t
it 18 bonded about 8n Operl ended nipple IB. The nlppl~ h~ a thr~3adf!d outer
erld 22 adapted to enlgage a fitting 24 of a hose 26 a~ shown lo F~gure 4. In
this manrlr~r prssr~uri~0d fluid, such as hydrHulic fluid or pressurized air, can
b~ admitted into the open snd of the enclo3ure. The nipple is conllect0d to ~
10 bracket 23 by a nut 25 and thereby comprises a secolld conrlection means of
the actuator. Brucket 23 is mounted on th0 arm 39 by a nut and bolt
combination 27. The bracket and arm servH as an exHmple only of msans
actuated by the actuator.
The actuator has a network 28 of no~ trr~tchable,
flexiblH tension link~ 30 extel)d~ng about the enclo~ure. The links may be,
for example, flexibl~l braided w~rH covered with plastic. A plurallty of ~uch
wires are connected together at node~ 32 to form the es~entially tubular
nHtwork. Alternatively the llnks may be of other materialA s-Jch as ~ylon
20 twine. The network has u first end ~4. Similarly, the network has a secolld
erld 36. At Hnd 36 the wires comprising the network pas~ through ~ plurallty
of apertures 35 extelnding through a ring 20 and extendirlg circumfererltially
about the ring. The ring fits over nipple 18 snd butts ag~dinst end 16 of th~
enclosure. Knots ~7 s~re formed on the ends of ~he wires to retairl the ellds
of the wires on the ring. In a similar manller, end 34 of the network 28 Is
colmeoted to ring 6 fitted over stud 4.
In referrillg to the actuator, axi~l dimerlsiorls and
directions extend alorlg longitudirlal axis 38 of F~gurH 1 extendirlg betwE~e
30 the erlds of the erlclosure. Transverse dimerlsiorls and directions are
perperldicular to thbs axis.
Figure I illu~tratss the actuator in its prH-installation or
off-the-shelf collditloo. 1'ht! ellclosure 2 IS uustretched a~d the l~etwork 28
fits 1008ely r?boUt thf` (-`I~ OSUrf' IrI .I bag-llke ,na~ er. As may be oL?sr rved,
tht~rl1 I? C0119lderi;~bl(1 9paCI` betwt~ell the llntwork aoc1 the f~uclos-lrt exct l)t at
the ellds 54 alld -S6. It mr,y ulso br~ ot)served from F~lgurfls I alld 4 th~ the
rletwork has rneshes whlt h ar(? Iarger ul-?<?r the cellter of the lletwork to flt
the shapf? ofr th~- r xpc,oded f~rlclosure. Thr? mitshes are progresslvt?l~ smaller
towards the two nuds of the ellclosur(:.
Flgure 2 IllusLriites the a3ctuator Irl call extr odt~(l, Inlt.l.?l
collditlol~. Io this case, the el~closure hr~is bet-~l axlrilly strf tchr-d ul~tll the
lletwork fits closely abouL the 0rlclosure~ Thls e3 the axlally ullcolltracted
statf- oF the aettiator after lostallatiorl orl the arm 35' wlth a hl~lged or
artlculated jolrlt 41. The Inltial tells~orl rt3quired ~o mail~ttilo th~s
ullcolltracted at~ite is provlded by ,--, we~ght 43 conllf?cted to a bolt 45 oi~ thr-
el~d of thf? arm.
lu order to corltrrict the uctu~itor e.ixliilly~ pressurl~ d3
fluid Is adrnitted illto the erlclosure by hose 26 as Illustrated ~u Flc~urf 4.
Thf? pressurizHd fluid radmitted irIto the r~r.closurt-3 Cf~U9tlS r~idec?l eXpriII9I011 ~?S
showll ~r~ Figurt? 4 where tht~ r llclosurft bulges most prorn~nelltly ~?t the m~d-
2i9i poillt betw0ell its two el~ds. The lletwork acts as eollstrr~ g mearls wh~ch
Is, at the sam0 time, rad~ally expsl~r'iable, but eixlally cootractablP. Thc
wlrt-s or otht?r tt?llsiOIl lirlks cornprislllg thts? Ilt?twork i~rt? r sstllltl~311y Uoll-
strt-~cihahle. Coosequel~tly thc radisl expailsloll of the rle~twork, rausr-~t-. hy
the radir~l exp~illsloll of the ellclosuri?, must be taccompanlf3d t-~ ax!ril
cootrt,ctioll of thi? a-ictuator r~-is may i.?~? observr?d by comparll)g f Igures 2 ao
4. Irl ~I)e extelldcd cooditioll o~ 1 Igule 2,tl)f~ lk; lf t~lt3 ~erwolk apl)r~.le~
lifJII n~llt wit~) tl)i lorl(3itL~cl~ ;Ixi~ 3f`3 ~3f tl~t3 ll~tuilt(?r iiiusL~It( (I i~ t lJI~? 1.
A~; t~t~ ;I(`t~JI~t~)I` (llLl~)r~ t?s tl)f3 cxp~ ed C(~llriltjoll t?f 1- ItI~lr~ 4~ f? f~(lr si~
Int:Sllt'S t?~3t~rl Up riIlL~ .?iL)r()llCll il I ect~ t31Ir Siltl~3t~. l )LI31?r ~-?I~ J(Il "ll Sllilpl?'i f ()I
the meslIl)s mil~ IISI'd SUCIl a"~ the :;ix-sided l?t-twolk 2ba of 1- iqurt? ~. Io e Ir h
C<lSt~ tllB li(lkS Ill)~)ri)tlC~ i9r~mt?I~t Witll tllt? Inll(~itll~iiIltll i?XiS ill tlle t~xti?rlfit~l
COIlCIitir)l~ d t.llf' f(l!lr Sldf`d mr?SIleS llr ~?f~ly90rlS Operl Ul.? .lS the eoclf)cillre !~X-
r? i l O f ~ y ~
3( X~
SilICe tlIe entire SUI`fclCe arS~I l)f thc a(`tUat;-l` iS
empk)~ed ir-l a ful~ctior~ a~090US to cl pi3tl)1~ ilI a fluid cyiirlder, the resultarlt
axial pullir19 Forc~? is ~r-~ver.lI tirnes lal`yel` thal- thE~ tntil, folce exerted b~ the
prcs3urized fluid clCtill9 l)U a piStOrl inside a fluid cylinder of the S.lme
diamet~r as the actliatol.
1ll the Ibf~e embodirncllt therc is a telld~l1c~ for th~
etwork to colltr lct aXb~ ' f Ister th IO thc erlclosure, resultillg ir- bucklirlg l)F
the snclosure rlear its two euds as p~essurized fluid is intrL)duced. for this
10 reasorl, the netwurk has the loose pre-inst1llatioll stai~e showrl ill 1 igure 1.
Providir1(J the iuitial stretcr1 to the enclosure upoo installatiurl, .lS illustrated
ill Figure 2, prevellts tllis buckiirlg.
The theory of opr~ratiorl of the actuator 1 Ig explallled
wlth ri~ferHIlc~ to Figur~s 5 to 8. The ll~twork Is r~presi~llted by a 1~ ? 4~ sf
lerlgth L irl Flgure 5. At ollr el~ the l~lle is attach~d to 8 fixed moullt 42.
At the opposlte r-~lld, the Illle is attaohed to a load 44 slldably restll~g o
surfacH 46.
11l figure 5, a small force FL has be~n applied
perpendicular to the lir~r 40. The smalt forc~ FL produces a tt?oslon forc~
FT which is rnally tlmes larger thal~ the force FL for a small a~lgle a. At th~
same tlm~, the lo~d is mo~d a dlstallc~q D. Thc r~lat~ooships ar~? defloed by
the following ~quations:
¦fT1¦ = ¦FT2¦-)FLI2 1
¦FT¦ = ,FT1¦ +¦FT2¦ =¦FL¦
9i~
alld 1:) = L - L co~ a
f igur(- 6 shows all elastom~rlc tube or ellclo~ure 3 of
35 length L. Tht~ tubr-~ is seal(~d at both ellds, but has a port 5 for admlttll1g
J'~ ?si6
prr?ssuri~r?d fluid. Thr tube is surrourlded by eight i~oll-stretchs~blr?, flrtxiblr?
te~lsiol~ liuks 7, ol~ly thrr?f? of whicn carl be ss?r?ll from the ~llustrated sidrt. At
their first ellds ~, the lillks are collllr3ctr3d to mour~t 42. At eheir st?r oud euds
11, t~lt? Iir~ks are r~ol~ ?ct~?d to load 44 slidably rt?stillg oll a surfacr? 46.
Whell prt3ssurizt?d fluld IS ~rltroduct3d through port 51 a
pulling force F jB Cl eated due to radlal expar~siou o~ly of the ellclosure
surrour~ded by the links. Refr?rrirlg to Flgure 7, the loed 44 has tra~rtlled Sldistallcr3 D1 due to the rs~dial expallsioll. Dlsts~llce D1 is gre~ter thao thr-10 dlstallce D ùf Figure 5. Thls Is becs~use the links3 are I~OW deforms.3d il~tO the
arc ahaprt of Flgure 7 rather thal~ the stharp brtud of Flgure 5.
F = f PdS
5 8il~ a
where P = prt?srturr3 in8ide t3l~r.~10surt
S = surfacr? ares of erlclosurt?
tt = aoglr~3 bHtweell ct-l~trr~
axis 3H s~lld tarlglqllt 41 to 8 pOlllt 011 ellclo5urtt
sur f ace
If thr-3 links slre iuterculll~ected It regulslr iutr?r~ill^. t
form sl ontwurk 1 S, sls seel~ in f igure 8, ilnd the er-closurt3 is irlflslted, sl two-
25 fold .ll~plic~ttioo of the cstse of Figure 5 uccurs. r~irstly, tlle ,~ressuri~ed fiuldinsidr? the el~closure ~rovides Sl fùrce f~lOn9 the tube's Ineridiilos Sl9 Sl?ell io
Figure 7. Secolldly, tellsiurl forces Tl- rtlor~9 equ~ltors of the tube product?pullil~y forces Ps- sllorlg the links uf the nr3twurk. At the ss~me tirne i~ greiltel
cootrrlctiorl uf the slctuSItur uccurs~ Firstly, thr3 ellclosures Inericliilrri belld
30 iotO iul s~rc wllicb cilus~3s iictuiltor colltr ICtiOI~ rls slluwrl io Fi9Ul'e 7. Sec~ di~
due tu the reguls~r iutercollrll3ctiQrls of the l~etwork lioks, Ineridi.lo leoytlls
der`reslae ila tlle r3rlcl~1surr? t3xp<lrlds r-ldi~ y, ful t~le~ lcrr3ilsirlr~ t~le dr3~ 3r3 r3f
cootr Ictiorl D2 S13 'illOWrl ill Figure 8.
` 9~i,
An uxlally colltrartable actuatQr accordlug to the
illventiol~ of fers slgruficaot adval~tages ovt?r hydraulic or pnf-umatlc
cylindr rs. Thr-~ actuator i~ ea:i;c?r to manufactur~ aud could br3 cousiderablyless expf?lls~ve thao a cylirlder. No sealirlg or leakacJe problema are llkel~ to
5 occur becausf no slidillg seals are required as In the case of cyllndr rs. Thu~
it would be very attractive for installatloll where fluid leakage Is of grr at
concern. The actuator is unf3~fr~cted by 3ide forces ullllke fluld cyllllders
which c~nrlot tolerate sldf forccs. At the same tlme, the actu0tor cao be
ir~stalled more tlghtly thau hydraul~c cyllndt?rs, ullowlllg more sophlstlcatPd
10 robotlc srms ar~d hands to be dr?slgl~f d.
Flgures 9 to 12 Illustrate an alternat~ve actustor 1.1
which is gr?llerally slrnllur to actuator 1. Correspondlrlg parts are ournbr?rr-?d
the same w~th the addltional deslgl~r~tt~ol~ ".1".
Actuutor 1.1 has all ftoclosurr~t 2.1 whlch Is ~pu~dle-
ahapHd Irl the pre~ stallatior~ state of Figure 12. Thls utlows ~vel~ wall
thlcklles~ after oxpanslou of the el~clorurt~.
Actuator 1.1 alrio has a nf?twork 28.1 of llon-stretchuble,
flr-?xibls tellsloo links 30.1 which are ombedded In a layer 50 of fl~x~blP
material extelldlng about tho èrlclosure. The laycr may bf3 of a ~ul~able
flexible plastic, for oxsrnple. The layèr of material 19 loose aod bulges
outwardly at n~eshf s 52 lo thf? prc-l(lstallatiorl statrt. Thls perrnlt~? the layer
25 S0 to readlly r~tretch to the ullcos)tructftd ~tate evlqll though ~hn rnatt~ru~l
erJdll't b~t elu~tolnf?rlr. Thls also pro~ Idt~s u Inllamul rt ~llttu~lcrt by tht- IL~ r
50 U(~UI119t tr~ sYr?r9rt rtxpr~oslorl to tht? axl~lly colltr~ct.r)cl 8t~tFl. At t~lld 3t,. 1
wlres cornprl~ g the nr-?twork arc placed aud borlded Ir~slde ~emlclrculur
chullllel~? 35.1 e~telldlllg alollg a cyllrldt r 20.1. ~he chal~ll01s ure arrallged
~0 clrcum'erelltlully about thè cylinder. Thf! cyllllder flts over a olpple 18. !
alld IS bondtd to It. Wlre 37.1 19 woulld about cyllodt3r 20.l alld bollded to
retalo wirt3s of thr~ nr3twork on tho cyllllder. 11l a slrnllar mal~ller, e ld 34.1 of
the l~vtwork ~8.1 18 collnt?cted to c~llndttr 6.1 flttr?d over stud 4.1.
Actuator 1.1 also has a perforated frlctlon reduc~l-g
luyer 54 in the naturt of a thln rr silir nt sheet-llkr- tube betwl3rtll the layer 50
and the enclosure 2.1. I ayr?r 54 reduces reslstcirlce to expansioll cau~ed by
frlctlon betwer-3ll ~he nt-twork 28.1 and the enclosure 2.1 in colljuCtlOIl wlth5 layer 50. The perforatlolls 80 elimillate the vacuum that may be creclted
betweell layers. A sultclble~ lubricarlt 3uch as all oil, grerlse or petroleum
jelly is applled be~weell layer 54 url(i the erlclosure 2.1 to furthl3r redure
frlct~orl. The lubrlc~llt muy ul~o be appllrtd betw~tt~ll layf3r6 50 und 54. Layftr
54 has a first e~ld 5~ alld aecoud end 59. At first end 58 It 19 fltted over and10 bonded to a flrst erld 3.1 of rtlastomrtric enclo$ure 2.1. Slmllarly,at 9ecDrld
end 59 it i5 fittr d over and bonded to secolld end 16.1 of the elastomerlc
enclo~iure.
Actu~tor 1.1 may hUVr3 a longrtr expectrtd Il~H thun
15 actuator 1 due to thr~ rt1duc~3d frlct~oll and rollseguent reducHd we~r on thu
.snclorlure.
F~gures 14 - 17 ahow arl actuator 1.2 accordlng to a
further embodimerlt of the inventiorl. This embodiment f3mploys a combined
2û encloaurrt and network 60. The walls 62 are of arl elsstomerlc materlal, suchas rubber and sf3rvr3 as the enclosure. A network 63 of non-str~tchuble,
flexible links 64, such as braided wire, are embedded in walla 62. A aecoild
n0twork 66 of similar or llghter wire, for example, extellds across flach of
the meshes 68 of the lletwork 63. This second nHtwork stops undue outward
25 bulgulg of ellclosure 62 botweell the wires oF IlHtwork 63.
The actuator 1.2 i8 similar to previous embodimellts,
haVirl9 8 port 70 for conllecti~lg a hosf3 for supplylng a pre3surizctd fluld.
Riogs 74 and 76 provide conntctiol~ mealls at opposite ends of the actuator.
30 Wirr3s or l~nks 64 extend about the rings for udded strength as may he Ref'll !n
Figure 17. Rings 74 und 76 and links 64 are encapsuluted In suitable rlgld
plastic bodies 75 alld 77 at each end of the actus~or.
~'~'2~
-- ~o
Although ~u ~tlastomel IC matttr~al ~s pretr~rred for thl
nllclosure, other sheet-llke, flexlble, noll-perme?able mater~als of plastlc, for
examplrt, carl be used. Refr-?rrlllg to Flgure 9, the elltire actuator ma~
comprise the? network 28.1 ernbedded IU the noll-elastornerlc layer 50 wh~ch
5 af?rvr?s as thr? er~closurrt. The col~uectlr~g meal~s cQuld bt? of elthrtr the forrn
shown ~1l Figure 9 or thr form show~l IU Flgure 14. The maLel u~l ls
ovr?ra~zr?d al~d telld~ to bulge outwsr(lly betwet?ll the hilkri of the ur?twork.
Thla accommodate?s the llect?ss3ary expallsloi~ ar~d dlstortlorl of the ~?llcloaurt
without tht? Ilr?r?d of r~lastomr?l8c qualities.
