Note: Descriptions are shown in the official language in which they were submitted.
Background of the Invention
The present invention relates to the production of
; needled, non-woven tubings and is concerned, more particularly,
with the continuous production of such tubings with lowered weight
per unit wall area and, with the capability of producing such
tubings of minimal diameter and reduced weight per unit of wall
area of the tubing.
~ Brief Discussion of the Prior Art
1~:
A variety of attempts have been made in the production
~ 10 of tubular textiles having structural properties suitable for
'~; industrial and surgical services such as industrial filtering
or de-watering and as vascular prostheses.
Earlier attempts involved the use of woven or knitted
;~i media, either installed as a sleeve about heterogeneous structure
~,~ ` or as a tubular extension between terminal portions of ducts or
' ~ fittings. However, the permeability of the textile tube is an
i~ important, sometimes critical, factor in the success of the tubes
! in these services. Furthermore the uniformity of the desired
permeability, throughout the length and full surface area of the
~ ,~
~ 20 tube, is~especially important in many such services.
.
Where variations in permeability are encountered there
occurs a corresponding variation in fluid flow and a consequent
disruption of the uniformity of the operation.
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Where the structural properties of the tube are relied
upon during its service and such variations in permeability are
3 present, there occurs a corresponding structural weakness in the
areas of excess permeability. Such weakness subsequently may
cause distension or even rupture of the tube wall.
Prior attempts in improving the permeability of such
tubes and control of the uniformity of the tube during its
production have involved inclusions in the fabric, such as stray
i ~ fibers, velouxed webs, or flocking of the web and, tufting or
looping of the exterior portion or faces of the web.
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However, the more recent and more successful approaches
t have been predicated upon the use of non-woven, non-knitted webs
of material strands, usually reerred to as felted webs. These
"felted" material tubes have afforded many advantages over the
woven- or knitted-material sleeves.
s An especially effective and advantageous tubing of
i needled, non-woven fabric is disclosed in my U.S. Patent
3,530,557 issued September 29, 1970.
~ While these tubes of non-woven fabric are in demand and
u 20 of distinct advantage in industrial applications as filter media,
roller sleeves, and the like, the most exacting requirements to
be met thereby are in the field of surgery,
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in which human life is directly dependent upon the several
qualities of the tubing.
Therefore, it ;s appropriate to detail these re-
quirements and the reasons therefor~, it being apparent to
those skilled in the art that the tubings exhibiting successul ~ ¦
accomodation of these surgical requirements will provide - ~ '
comparable advantages in the other, industrial services ¦
-~ Tn service as~vascular prosthe~is, the precise
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pèrmeabilit~ and a uniformity thereof are an ~bffe~e necessity.
; The permeability requirements appear to be self- :
contradictory~in this service, since the ~unction o~ the
tubular prosthesis is that o replacing diseased or damaged
¦~vascuLar sections and3 accordingly, serving as a conduit for
blood between healthy or undamaged vascular sections. In
service~ there~ore, the tubing necessarily is to be substa~- ~ I
Lially impervious to blood and ies constituents. :. : ~;¦
Uowever, in order to achieve adequate healing at ¦ i
the suture~points an~ tissue:generation along the prosthe~is, ~ ~ ¦
it is necessary that the wall structure of the tubing be I ~ i
permeable to permit radial.migration o~ cellular matter to
enable tissue migration radially into the tubing to form a :
"li.~e" vascular member encasing, and structurally supported
by, the tubular prosthesis
The pre~erred solution to these apparently contra~
dictory requirements has been that of pro~iding permeable '
tubing which is made initially i~permeable, before installation~
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by a pre-clotting step which closes the interstices o the
'. tubular wall sufficiently to make the t.ubing impermeable when
: ` installed. Eventually, the clotted matter is to be replaced `
1; I by celluLar întrusion through the tube-wall interstices, and
absorption of the clotted material.
Howe~er, the presence of the pre-clotted matter
makes such prosthesis potentially hlghly-thrombogenic. Ac- : ',
cordingly, it is imperative that the structure of the tubing
; !:pro~lde for secure adhesion and.retention of all such clot.ted
matter, in order to avOid release and a consequent thrombus
I ~ downstream of the prosthesi5
This requirement of providing optimal surfaces for
. I ~adherence¦~f.clotted matter also serves to the advantage of
¦~the:subsequent progression:of. new tissue into and through the
~all~of~the tubing.~ Accordingly, the interstitial and sur- -
~face:characteristics are ~mportant~to the succesful service i
: :of the~tubing,~along with the close control o~ the permea~
: :- ~ bility. :~
¦ : The:de5ired permeability~ however, necessarily is
:: ~ I to be uniform both along the length of the tubing and about ~ I
-its circumference~ Significant variations from such uni-
¦~. ormity can prevent passage of desired constituents, if the
~, permeability is below the preselected level. ~here are~s
of excessi~e permeability are present,e~cessive rates of
constituent transfer may occur and the concomitant struc-
¦ tural differences or wealcness make the tube wall prone to
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distension, ballooning, aneurysmal dilation or even rupture at
that zone.
i The non-woven tubing of my U.S. Patent No. 3,530,557
i has proven to be quite advantageous over prior tubings, and
especially so in sèrvice as a vascular prosthesis, and meets the
several requirements set forth hereinbefore.
~' However, the production of the tubing required close
j~ synchronization of the layer-winding speed and the tube take-up
rate, especially since the tube take-up apparatus exerts a
~ 10 tension upon the tubing.
The problems encountered in the production of such
tubings become even more acute when it is desired to produce
relatively small tubes such as are often desired as vascular
prostheses.
Prior systems have included units for winding and
~ needling a non-woven web on a mandrel which is longitudinally
¦ grooved to~provide a trough for picks which continuously move the
formed tub mg parallel to the axis of the mandrel. These machines,
therefore, are limited to relatively large diameter mandrels, to
accomodate the withdrawing equipment, in the order-of about 40~n,
the actual size depending upon the size of the slide rollers and
the length of their pins.
A further limitation of such units involves the wall-
strength of the finished tube, the minimum strength of which has
required about 4r . This corresponds to a weight
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of from 350 to 400 grams per square meter of wall area
A reduc~ion of these dimensions and weights has
t been possible with the use of the prior discharge mecha-
nisms. Consequently, the prior means of withdrawal and dis-
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! charge of the tubing of such installations have been costly
; 1 and imposed problems i.n the operation and versatility of the
installa~ion. '
¦~ Therefore~ prior methods and installations for
i forming non-woven tubings have not been found to be entirely
1~ ¦ sa~is~actory i~ all respects.
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¦ Ob~ects of the Invention .1
¦ ~ It is an object of the present invention to provide
¦ an~improved system for producing needled tubing of non woven
~abric.
- ~ ~ It is another object of the present invention to
- l~provide an improved system for producing tubing of non~woven
I abric which is wound in overlapping layers and needled at
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multiple angles.
I It is a further object of the present invention to
provide tubing of non-woven fabric which is wound in over-
lapping layers on a mandrel, needled at multiple angles, and
pressed against ~he mandrel by an external pressing roll.
It is yet another object of the present inventlon to
~ provide needled, non-woven tubing formed on a mandrel, the
- ¦l tubing being rotated on the mandrel by external driving rolls.
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A further object of the present invention is the
provision of a needled, non-woven tubing -formed on a mandrel,
the tubing being discharged from the mandrel by a helical
sur~ace and relative rotation between the tubing and the helical
¦, surface - i
Another object of the present invention is the pro~
vision of a needled, non-woven tubing formed on a mandrel and
!i needled at multiple angles, while being pressed against the
mandrel and rotated by rotating pressure rolls, and discharged
rom the mandrel by its rotation agai~st a helical sur~ace
on the mandrel.
A further object o the present invention is the
i provision o a~needled, non-woven tubing which is formed on
; I A ~sndrel, radially compressed and then discharged from ~he
mandre~.
Summar~_of the Invention
- In~general, the preferred ~orm of the presen~ in
; ¦ vention comprises a tube-winding and needling station including~
. ¦~a tapered ma~drel having needle apertures in its region of
¦ larger diameter, a reciprocating bar having a plurality of
needles aligned with the needle apertures, and at leas~ one
dri~ing roll in pressing rel~tionship with the tubing being
) -Eormed. PreEerably, the mandrel includes a helical surface
i downstream of the needle apertures and within the zone of
pressure of the driving roll.
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The present invention is capable of continuously
producing high quality non-woven tubing in diameters down to
4 or 5 mm and with reduced weight per unit of wall area. This
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can be accomplished without the requirement of special pre-
paration equipment 9 such as carding installations, with only
a narrow band of thin, non~woven material being supplied directly
¦ to the winding unit. Therefore, the distortion and longitu-
dinal orientation of the fibers which are typical o. the prior
art can be avoided and the desired, multiple inter-engagement
I
j of the fibers can be obtained, while the cost of tube-withdrawing
equipment is avoided. ` '
¦ Brie D _ cription of the Drawin
¦ ~ ~ A better understanding of the~invention and its
l objects ~a~ be derived from the ollowing description and
accompanying drawings, in which:
Figure 1 is a partly-schematic side elevation of
a tube-forming installation embodying the~invention
¦ Figure 2 is a plan view of the i~stallation of
¦ Figure 1, and
¦ Figure 3 is a view of a portion of Figure 2, on an
i enlarged~scale, with portions r~moved for clarity and showing
details of the tube-forming unit.
Detailed Description of the Preferred Em~odiment
As shown in the drawings~ the preferred form of tube-
¦11 forming apparatus according to the invention comprises an
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installation including a conveyor l, a nip-roller 2, an
orienting and transfer station including first and second
. rolls 3 and 4, respectively, and a conveyor 5 for delivering
the pressed web to a needling and tube-forming machine 6.
i The web received on the conveyor 1 may be a com-
mercial web, as rece;ved, or may be subjected to a pre-carding~ i
step if desired. The web typically comprises ibers which
: I æ e felted with their lengths oriented generally longitudinally
! o~ the web and in generally parallel relationship.
¦ The material of the web may be a textile, metal or
: mineral fibers or ilaments, or a mixture thereof. The fibers S
;~ . or filaments are to be very thin. a~d flexible. ~ ¦
The tube-forming unit 6 includes a sta~ionary mandrel
~i ha~ing~a plurality o needle apertura 8 for receiving re- i
ciprocating needles 9 of a needling head 10. The mandrel 7
tapers toward a discharge.end remote from the needling zone ~ j
i and includes a helical section 11
: ~ :. : ~ The helical section preferably is formed with saw~
: ~ toothed flights 12 which indi~idually taper outwardly to an
apex 13 at their trailing or downstream edge The flights 1~ ¦
progre5sively~enlarge in diameter towaxd the center or an . ¦
¦~ intermediate ~one of the helix and again reduce in diameter
toward the discharge end. The axis of the helical section is
~ coaxial with the axis of the mandrel and the tubing
il Flanking the stationary mandrel, a pair of drive
I rolls 14 and 14' are mounted substantial:Ly diametrically l ¦
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opposite each other on hinged yokes 15, 15' which are adjustably
biased by means of compression springs 16, 16' and lever arms
to rock inwardly to press the rollers 14, 14' inwardly toward
the mandrel.
The rollers 14, 14' preferably are parallel to the
tapered mandrel surface and are covered with rubber or another
material suitable for providing a driving friction against a
tube in position on the mandrel. The amount of pressure with
' which the rollers bear against the tube may be adjusted by means
of threaded hand wheels 17, 17'. The rollers are driven by
suitable variable-speed drive means, not shown, via universal
joints 18 and 18'.
The needling head 10 is driven by conventional means
and has associated therewith a stripper or foot member 19 which
is curved to conform to the material contour in the needling
zone to prevent lifting of the needled material by retraction
,~ of the needles. The needles are barbed, with the wide portion
~i ~ of the barbs facing the penetrating point to catch fibers and
to draw the fibers inwardly through underlying layers of the
windlngs.
I The needling procedure is as disclosed in my afore-
¦ mentioned U.S. Patent No. 3,530,557 and the tube product is
therefore needled by a plurality of needles at differing angles
with respect to the radius of the tubing.
The several conveyors 1 and 5 and rolls 2, 3 and 4
~¦~ preferably are all driven by variable-speed drives to provide
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a precise rate o-f feed of the sliver or web to the tube forming
. uni~. In order to stabilize this critical supply factor and to
initiate a ~ee~eab~e transverse re-orientation of the fibers,
il it is preferable to draw the web thr~ugh the nip rolls 2 at ,
a linear speed slightly in ~cess of the speed of the belt ,.lZ
' conveyor 1 ; deposit the web in thinned form on the surface .
' of the roll 3 by rotating the roll at a peripheral speed
considerably higher than the linear speed through the nip
, rollsj~ and coliect thc web in a partially-jumbled condition~
with its fibers partiall~ transversely-reoriented, on Il
¦ the roll 4, which is rotated at a much lower peripheral speed I i
¦ than the roll 3. This initial :Eiber reorientation is en~
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hanced if the rolls 3 and 4 are provided with tractive surfaces,
such as metallic card cloth, and a stripping comb 2~: is
~ positioned adjacent the conveyor 5 to:strip the sliver or
~web~from the roll 4.
:~ The speed of the conveyor 5 is then matched~to : ~ ~
suppl~ the web to the~drive~roll 14 at the;desired rate.: - ,`
O eration of the Preferred Embodimen~ 1:
In operation, a suitably-prepared, extremely thin
¦¦ sliver or web o~ material is supplied to the roll 14 and passes
¦I t~erearound to wind on the ma~drel and subsequently is needled
Il at multiple angles to form the non-woven tubing. Each needle
penetration drives fibers from the outer layers angularly
into the subjacent layers, thereby firmly securing and in-
terlocking the windings into a continuous tubing
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i The continuous tubing thus produced is driven around
~he statîonary mandrel by the drive rolls 14 and 14' and, as
a result of the presence of the helix 11 against which it /S
i~ pressed, continuously ejects itself or literally screws itself
¦, off the stationary mandrel.
This self-ejecting efEert is actually enhanced by the
shrinkage tendency of the tubing, w~en it is so needled~ The
i shrinka~e, the taper of the mandrel and the enlargement o the
helix thus cooperate in the ejection of the tubing, instead
of the shrinkage being effective to oppose removal of the tubing,
thereby requiring tensioning stresses to be imposed ~or with-
drawal.
In dit~ect contrast to longitudinal-stretching or
hdrawal of~tubing, the tubing formed in accordance with the
¦~present invention is actually compressed radially on the helix
¦ and~is~, therefore, pressed off the mandrel without longitudinal
distortions.
~ The actual taper of the mandrel will depend upo~ ~he
type o~ iber and its shrinkage tendency upon needling, and
may be in the order of 1.5 to 2 taper.
Preferab~y, the helix is formed as a threadably- j
! interchangeable component of the mandrel, so that helices o
I ~ di~fering pitches may be employed. i
Variation of the ejection rate of the tubing may be !
; accomplished by the use of dif~erent helices and by adjustment
¦l, of the speed of the drive rollers, thereby modiEying the wall
~! thickness o the tubLng, ~or a given rate o~ web intake.
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It should be noted that the supply o:E the incoming
; web over the surface of the drive roller 14 is especially ad-
..vantageous. The resultant flattening or pressing o the web
between the drive roller 14 and the mandrel 7 thus orients '~
,and de-lofts the web prior to the needling step. This pre~
.ferably,is augmented by~positioning the final conveyor 5 in
almost tangent relationship to~the roller 14.
Therefore~ it is apparent that the present invention ',
,provides a unique method and apparatus for producing non-woven
tubings and a new fo~m of tubing which is subjected to radial
compression immediately after its formation.
. The radial compression of the tube wall not only
¦forms a relatively thin wall~ but also has a densifying effeci~ -
which~tends to~reduce the initial permeability of the.structure . `
i without permanently.altering the~permeability or weakening the
wall~structure, as may Dccur when such tubing is subjected ta
su~stan~ial longitudinal ~tensions.
The continuous, uniform~ejection of the tubing as it
:: is formed provides for a uniform o~erlapping and stitch-locking t,
of the~turns, which is of extreme importan~e i~ very thin-walled, I
: ,small~diameter tubing and oE great advantage in tubing o larger ~ ¦
: Idimenstons.
'~, Although dif~erent shapes or flight-profiles may be
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¦ ~ it has been found that the sawtooth profile disclosed ,
,provides a particularly accurate and uniform ejection of the
,tubing, I
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` Tubing produced .in accordance with the present
invention has been particularly effective in surgical service as
vascular prostheses, not only by reason of the advantages
attributable to non-woven tubing, but also as a' consequence of
the reliability which`is achieved in small-diameter tubings of
very small wall-thickness. Tubings have been produced in the
range of from 4 to 30 millimeters and with wall thicknesses as
low as 0~5mm. It is to be understood, however, that the advantages
deriveable from the present invention are also appropriate to
tubings of diameters larger than 30mm.
Furthermore, although the present invention has been
disclosed and discussed with particular regard to its exceptional
advantages in terms of vascular prostheses, it is to be under-
stood that the tubing of the present invention may be employed in
1,
~, several industrial services including tanneries, paper mills and
~ as filtering or dewatering surfaces.
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