U.S. patent application number 11/983004 was filed with the patent office on 2008-06-05 for disassemble covering.
Invention is credited to Alfredo Meneghin, Michel Therin.
Application Number | 20080127682 11/983004 |
Document ID | / |
Family ID | 37392884 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080127682 |
Kind Code |
A1 |
Meneghin; Alfredo ; et
al. |
June 5, 2008 |
Disassemble covering
Abstract
The present disclosure describes a knit comprising at least one
meshing sheet which includes at least one free chain yarn and at
least one non-meshing sheet which includes at least one yarn which
makes a 180 degree turn at the free chain yarn. Methods of
producing the knit are also described.
Inventors: |
Meneghin; Alfredo; (Lyon,
FR) ; Therin; Michel; (Lyon, FR) |
Correspondence
Address: |
CARTER, DELUCA, FARRELL & SCHMIDT, LLP
445 BROAD HOLLOW ROAD, SUITE 225
MELVILLE
NY
11747
US
|
Family ID: |
37392884 |
Appl. No.: |
11/983004 |
Filed: |
November 6, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11409026 |
Apr 24, 2006 |
7290410 |
|
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11983004 |
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60673768 |
Apr 22, 2005 |
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Current U.S.
Class: |
66/170 |
Current CPC
Class: |
D10B 2509/08 20130101;
D04B 21/12 20130101; D10B 2403/0311 20130101 |
Class at
Publication: |
66/170 |
International
Class: |
D04B 1/22 20060101
D04B001/22 |
Claims
1. A method of producing a knit comprising: forming at least one
meshing sheet and at least one non-meshing sheet, wherein the
meshing sheet includes at least one free chain yarn and the
non-meshing sheet includes at least one yarn which makes a
180.degree. turn at the free chain yarn.
2. The method of claim 1 wherein the knit comprises at least one
percent of free chain yarns.
3. The method of claim 1 wherein the meshing sheet is formed from
yarns that are knitted according to a chart 1-0/0-1/1, and the
non-meshing sheet is formed from yarns that are knitted according
to a chart 0-0/2-2//.
4. The method of claim 3 wherein a guide bar for the meshing sheet
is drawn continuously and full, and a guide bar for the non-meshing
sheet is drawn continuously and full.
5. The method of claim 1 wherein the knit is formed using a meshing
sheet and two non-meshing sheets.
6. The method of claim 5 wherein the meshing sheet is obtained from
one guide bar and each of the two non-meshing sheets is obtained
from one guide bar.
7. The method of claim 5 wherein two guide bars of the two
non-meshing sheets move symmetrically in relation to one another
and are offset from one another in the direction of production of
the knit.
8. The method of claim 5 wherein the yarns of the meshing sheet are
knitted according to a chart 1-0/0-1//, the yarns of the first
non-meshing sheet are knitted according to a chart
1-1/3-3/2-2/0-0//, and the yarns of the second non-meshing sheet
are knitted according to a chart 3-3/2-2/0-0/1//.
9. The method as claimed in claim 6, wherein the guide bar of the
meshing sheet is drawn continuously and full, the guide bar of the
first non-meshing sheet is drawn continuously and 1 full, 1 empty,
3 full, 1 empty, 1 full, 3 empty, and the guide bar of the second
non-meshing sheet is drawn continuously and 1 full, 1 empty.
10. The method of claim 1 further comprising the step of subjecting
the knit to a thermosetting operation.
11. A knit comprising at least one meshing sheet which includes at
least one free chain yarn and at least one non-meshing sheet which
includes at least one yarn which makes a 180.degree. turn at the
free chain yarn.
12. The knit of claim 11 wherein the free chain yarn is spaced
irregularly along the knit.
13. The knit of claim 11 wherein the free chain yarn is spaced
regularly along the knit.
14. The knit of claim 11 wherein the knit comprises at least one
percent of the free chain yarn.
15. The knit of claim 11 wherein the knit comprises at least ten
percent of free chain yarns.
16. The knit of claim 11 wherein the knit comprises a first
non-meshing sheet and a second non-meshing sheet.
17. The knit of claim 11 wherein the knit is made from yarns of at
least one biocompatible material.
18. The knit of claim 17 wherein the at least one biocompatible
material is selected from polypropylene, polyester, polyamide and
combinations thereof.
19. The knit of claim 11 wherein the knit is made from a mixture of
biocompatible yarns that are bioabsorbable and biocompatible yarns
that are not bioabsorbable.
20. The knit of claim 11 wherein the knit has a thickness ranging
from about 0.20 mm to about 0.40 mm.
21. The knit of claim 11 wherein the knit comprises holes having a
diameter ranging from about 0.3 to about 1.5 mm.
22. The knit of claim 11 wherein the knit is thermoset.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a prosthetic knit having
zones that can be unraveled and permit easy separation of knitted
bands or tapes in the direction of production of the knit. These
bands or tapes can be used as textile medical devices that may or
may not be implanted in the human body.
[0002] Textile devices that are not implantable include, for
example, compresses, textile support dressings, etc. Devices that
can be implanted in the human body include, for example, textile
prostheses in general, such as wall reinforcements in parietal
surgery for example, urethral support tapes in the treatment of
female stress urinary incontinence, and in the treatment of pelvic
floor disorders, which are generally found mainly in females and
are also referred to as prolapses.
[0003] These textile devices generally need to have a specific
strength suited to their application. This is particularly the case
of textile prostheses implanted in the human body. Thus, parietal
reinforcements are used to replace and/or strengthen and/or support
the abdominal wall, at least on a temporary basis. Likewise,
suburethral support tapes have to support the middle urethra,
preferably in a definitive and permanent manner. The same applies
to support implants used in the treatment of prolapses.
[0004] These textile prostheses therefore need to have a certain
dimensional stability. To achieve this, these textile prostheses
are generally subjected to a thermosetting step which increases
their dimensional stability. The prostheses are then easier to
manipulate.
[0005] However, the manipulation of tapes of small width,
particularly with a view to a thermosetting operation, is
particularly awkward and may lead to substantial numbers of tapes
being discarded when they become unusable because the thermosetting
has not been carried out properly. Moreover, thermosetting each
tape on an individual basis means that the thermosetting of the
tapes is not homogeneous and not reproducible.
DESCRIPTION OF THE PRIOR ART
[0006] It has been proposed to produce knits of large width that
have the properties of break strength, elasticity and porosity
desired for these implants, and then to cut the tapes or implants
from these knits.
[0007] However, these support implants must be able to be cut into
narrow tapes of the order of 1 cm in large lengths, for example of
the order of 50 cm, without unraveling or curling. By "curling" we
mean, in the context of the present application, the spontaneous
rolling-up of the tape about its longitudinal axis under tension
along its length. These implants have to retain sufficient
mechanical properties in this form, particularly of strength, while
at the same time limiting as far as possible the release of
particles, that is to say yarn ends, when they are stressed.
Preferably, these implants must also allow mechanically stable
tissue anchoring.
[0008] Therefore, a problem posed by the cutting method lies in the
fact that the edges of the implants are frayed. This results in
release of particles, particularly in cases of elongation, and thus
loss of yarns. Moreover, the macroporous elastic implants that are
cut out are difficult to use without a protective sheath. The
reason is that, because of their elasticity and non-smooth edges,
these implants attach themselves to the patient's tissues and risk
constituting a rasp in the event of a sharp bend, and they deform,
curl up and release particles. It is for this reason that they are
generally provided in a protective sheath, which complicates the
surgical intervention.
[0009] There is therefore a need for a knit, in particular a
macroporous prosthetic knit, which would make it possible to obtain
textile medical devices, in particular support implants, for
example in the form of tapes, that are easy to produce and to
manipulate and do not have frayed edges, and which would provide
tapes that have undergone homogeneous thermosetting.
SUMMARY OF THE INVENTION
[0010] The present invention aims to meet this need by making
available a knit having zones that can be unraveled and permit easy
separation, in the direction of production of the knit, of knitted
bands or tapes, in particular macroporous bands or tapes, and made
from a monofilament of biocompatible material, in particular by
removal of one or more specific chain yarns, the removal of said
yarn or yarns permitting separation of said knit into tapes with
smooth edges and without risk of fraying.
[0011] The present invention relates to a knit, preferably an
openworked prosthetic knit, made in one piece and based on an
arrangement formed by at least two sheets of yarns, preferably made
from a biocompatible polymer material, comprising at least one
first sheet that defines a first chain structure and at least one
or more non-meshing sheets, of partial weft, each of these
non-meshing sheets defining a structure, wherein said knit
comprises at least one free chain yarn, a free chain yarn being
defined as a chain yarn for which, along the entire longitudinal
dimension of the knit, all yarn of said non-meshing sheets
approaching said free chain yarn makes a 180 degree turn at this
free chain yarn.
[0012] The present invention also relates to the use of a knit as
defined above, for obtaining a textile medical device, in
particular a prosthetic product for surgical use, in particular for
obtaining a support implant for the treatment of stress urinary
incontinence and/or prolapses.
[0013] The invention further relates to a textile medical device
which is obtained by unraveling of at least two free and preferably
consecutive chain yarns of the knit as defined above, preferably
along the length of the longitudinal dimension of said knit.
[0014] The present invention also relates to a method of production
of a knit, preferably of an openworked prosthetic knit, made in one
piece, based on an arrangement formed by at least two sheets of
yarns, preferably of a biocompatible polymer material, which method
comprises the following step:
production of a knit on a knitting machine or Raschel machine, with
a first sheet and one or more non-meshing sheets, said first sheet
being drawn continuously or intermittently and being obtained from
one guide bar, the chart followed for knitting the yarns of said
first sheet leading to the formation of a chain, said non-meshing
sheets being drawn continuously or intermittently, each of said
non-meshing sheets being obtained from one guide bar, the chart
followed for knitting the yarns of each non-meshing sheet being
such that for at least one yarn of the chain structure, called a
free chain yarn, seen in the direction of production of the knit,
all yarn of said non-meshing sheets approaching said free chain
yarn makes a 180 degree turn at this free chain yarn.
[0015] The knit according to the invention permits production of a
large number of homogeneous tapes, in particular tapes that have
been thermoset homogeneously. The knit according to the invention,
preferably produced in large width, for example a width ranging
from 1.2 to 1.5 meters, is easy to manipulate and, therefore, to
thermoset. Moreover, the thermosetting performed on a section of
large width, for example a section that is from 1.2 to 1.5 m wide
in the case of a knit according to the invention, is particularly
homogeneous, and the textile medical devices, in particular the
implants, obtained from this knit, in the form of tapes separated
by unraveling of the free chain yarns, are also homogeneous and
reproducible.
[0016] The textile medical device, in particular the support
implant, according to the invention has excellent tensile strength
and may have minimal elasticity and is therefore eminently suitable
for production of a support implant for the treatment of stress
urinary incontinence and prolapses, without any need to use a
protective sheath.
[0017] Moreover, by virtue of its method of production, the textile
medical device according to the invention has smooth, non-traumatic
and stable edges, that is to say with no risk of fraying or of
release of particles. Finally, all the textile medical devices, in
particular all the tapes or implants, obtained from the same knit
according to the invention have undergone homogeneous thermosetting
and are easy to manipulate.
[0018] In the present application, "prosthetic knit" is understood
as meaning a knit intended to be implanted in the human or animal
body in the form of a prosthesis or any other component produced at
least in part with said knit.
[0019] In the present application, "openworked knit" is understood
as meaning a knit whose structure or structures determine holes or
gaps within the thickness of the knit, these holes or gaps being
able to constitute channels that open out on either side of the
knit. An openworked knit of this kind, also called macroporous,
permits better tissue integration.
[0020] The expression "meshing sheet" is understood, in the present
application, as a sheet of yarns for which the chart followed for
knitting the yarns leads to the formation of meshes. In a known
manner, a sheet with a chain structure is a meshing sheet, whereas
sheets of partial weft are non-meshing sheets.
[0021] In the present application, "free chain yarn" is understood
as a chain yarn that is not completely crossed by any weft yarn,
or, to put it another way, a chain yarn for which all weft yarn
approaching and interacting with this chain yarn, for example by
being linked with it, then makes a 180 degree turn at this chain
yarn, and this applies along the entire longitudinal dimension of
the knit.
[0022] In the present application [0023] the mass per unit area of
a knit is measured according to ISO 3801, [0024] the breaking
strength of a knit in the longitudinal direction and in the
transverse direction is measured according to ISO 13934-1, [0025]
the elongation under 2 daN in the longitudinal direction is
measured according to ISO 13934-1.
[0026] In a preferred embodiment of the invention, the knit
comprises at least one percent of free chain yarns spaced regularly
or irregularly along the transverse dimension of the knit.
[0027] More preferably, the knit comprises at least ten percent of
free chain yarns spaced regularly along the transverse dimension of
the knit.
[0028] Advantageously, the knit according to the invention
comprises a non-meshing sheet with the following chart:
0-0/2-2//.
[0029] In a preferred embodiment of the invention, the knit
according to the invention comprises at least two non-meshing
sheets. The reason for this is that the presence of two non-meshing
sheets, in particular of two intersecting non-meshing sheets, that
is to say sheets whose respective guide bars move symmetrically in
relation to one another, offset from one another in the direction
of production of the knit on the knitting machine, makes it
possible to obtain tapes and/or implants exhibiting very good
resistance to lateral compression. Thus, when the two opposite
longitudinal edges of a textile medical device, in particular of a
tape and/or implant, obtained from the knit according to the
invention, are compressed, for example between two fingers, this
textile medical device, in particular this tape and/or implant,
retains significantly the same width. Preferably, the loss of width
of a medical device, in particular of a tape and/or implant,
according to the invention, under the effect of its two opposite
longitudinal edges being compressed between two fingers, is less
than 10%. The medical devices, in particular the tapes and/or
implants, according to the invention are therefore particularly
stable with respect to their manipulation and to their passage
through possible auxiliary equipment (eyes of needles, cannulas,
etc.) and through the patient's tissue (limitation of cord
effect).
[0030] In a preferred embodiment of the invention, the knit
comprises a first non-meshing sheet and a second non-meshing sheet,
said first non-meshing sheet having the chart 1-1/3-3/2-2/0-0//,
said second non-meshing sheet having the chart
3-3/2-2/0-0/1-1//.
[0031] Preferably, the distance between said free chain yarns,
along the transverse dimension of the knit, ranges from 0.5 cm to 2
cm, preferably from 0.5 cm to 1.5 cm.
[0032] Preferably, the knit according to the invention is a
prosthetic knit. Thus, preferably, the knit is made from
monofilament or multifilament yarns of a biocompatible polymer
material chosen from polypropylene, polyester, polyamide and
mixtures thereof. Advantageously, said biocompatible polymer
material is polypropylene.
[0033] In another embodiment, the knit according to the invention
is made from monofilament or multifilament yarns of a biocompatible
and bioabsorbable polymer material.
[0034] In yet another embodiment, the knit according to the
invention is made from a mixture of biocompatible yarns that are
bioabsorbable and of biocompatible yarns that are not
bioabsorbable.
[0035] Preferably, the knit according to the invention is made from
monofilament yarns having a diameter ranging from 0.05 mm to 0.15
mm, preferably of approximately 0.10 mm.
[0036] Preferably, the knit according to the invention has a
thickness ranging from 0.20 mm to 0.40 mm, preferably of
approximately 0.30 mm.
[0037] Preferably, the knit according to the invention is an
openworked knit. Thus, in a preferred embodiment of the invention,
the knit according to the invention comprises holes having a
diameter ranging from 0.3 to 1.5 mm, preferably ranging from 0.3 to
0.9 mm. Such a knit permits production of a support implant that
has good tissue anchoring.
[0038] Preferably, the knit according to the invention is
thermoset.
[0039] Preferably, the textile medical device according to the
invention has a width ranging from 0.5 cm to 2 cm, preferably
ranging from 0.5 cm to 1.5 cm.
[0040] Advantageously, the textile medical device according to the
invention has a mass per unit area ranging from 40 to 100
g/m.sup.2, preferably from 50 to 75 g/m.sup.2, and more preferably
from 50 to 60 g/m.sup.2.
[0041] Preferably, the textile medical device according to the
invention has a thickness ranging from 0.20 mm to 0.40 mm,
preferably of approximately 0.30 mm.
[0042] Preferably, the textile medical device according to the
invention comprises holes having a diameter ranging from 0.3 to 1.5
mm, preferably ranging from 0.3 to 0.9 mm.
[0043] Preferably, the textile medical device according to the
invention has a breaking strength, in the longitudinal direction
and transverse direction, ranging from 20 to 90 N, preferably from
40 to 90 N, preferably from 55 to 75 N, more preferably from 60 to
70 N, measured according to ISO 13934-1.
[0044] Thus, the textile medical device according to the invention
has excellent mechanical strength, or breaking strength, and at the
same time quite a low mass per unit area. A textile medical device
of this kind is particularly advantageous as a support implant,
because it provides effective support of the organs to be treated
and at the same time reduces to a minimum the mass of the implanted
foreign body.
[0045] Preferably, the textile medical device according to the
invention has an elongation under 2 daN, in the longitudinal
direction, of less than or equal to 15%, more preferably of less
than or equal to 10%, measured according to ISO 13934-1. Such a
textile medical device is thus particularly stable
dimensionally.
[0046] Preferably, the textile medical device according to the
invention is an openworked prosthetic device and constitutes a
support implant for the treatment of stress urinary incontinence
and/or prolapses.
[0047] Moreover, since the textile medical device according to the
invention preferably corresponds to a zone of the knit according to
the invention that is situated between two consecutive free chain
yarns, it does not comprise free chain yarns. There is therefore no
risk of its unraveling.
[0048] Preferably, the knit according to the invention is produced
by a method comprising the following step:
production of a knit on a knitting machine or Raschel machine, with
a first sheet and one or more non-meshing sheets, said first sheet
being drawn continuously or intermittently and being obtained from
one guide bar, the chart followed for knitting the yarns of said
first sheet leading to the formation of a chain, said non-meshing
sheets being drawn continuously or intermittently, each of said
non-meshing sheets being obtained from one guide bar, the chart
followed for knitting the yarns of each non-meshing sheet being
such that for at least one yarn of the chain structure, called a
free chain yarn, seen in the direction of production of the knit,
all yarn of said non-meshing sheets approaching said free chain
yarn makes a 180 degree turn at this free chain yarn.
[0049] Preferably, the chart followed for knitting the yarns of
each non-meshing sheet is such that for at least one percent,
preferably for at least ten percent, of the yarns of the chain
structure, called free chain yarns, seen in the direction of
production of the knit, all yarn of said non-meshing sheets
approaching said free chain yarns makes a 180 degree turn at these
free chain yarns.
[0050] Therefore, according to the method of manufacture of the
knit according to the invention, all chain yarns, be they free or
not, are knitted with the same guide bar.
[0051] In one embodiment of the method according to the invention,
a single non-meshing sheet is used, the yarns of the first sheet
for the chain structure being knitted according to a chart
1-0/0-1//, the yarns of the non-meshing sheet being knitted
according to a chart 0-0/2-2//.
[0052] Preferably, the guide bar of the first sheet is drawn
continuously and full, and the guide bar of the non-meshing sheet
is drawn continuously and full.
[0053] In a preferred embodiment of the method according to the
invention, at least two non-meshing sheets are used. Preferably,
two non-meshing sheets are used, the guide bars of said two
non-meshing sheets moving symmetrically in relation to one another,
offset from one another in the direction of production of the
knit.
[0054] Advantageously, a first non-meshing sheet and a second
non-meshing sheet are used, the yarns of the first sheet for the
chain structure being knitted according to a chart 1-0/0-1//, the
yarns of the first non-meshing sheet being knitted according to a
chart 1-1/3-3/2-2/0-0//, the yarns of the second non-meshing sheet
being knitted according to a chart 3-3/2-2/0-0/1-1//.
[0055] Preferably, the guide bar of the first sheet for the chain
structure is drawn continuously and full, the guide bar of the
first non-meshing sheet is drawn continuously and 1 full, 1 empty,
3 full, 1 empty, 1 full, 3 empty, and the guide bar of the second
non-meshing sheet is drawn continuously and 1 full, 1 empty.
[0056] Advantageously, the two guide bars of the two non-meshing
sheets move in partial weft under three needles, symmetrically in
relation to one another, and offset from one another in the
direction of production of the knit. Such knitting, with the weft
bars moving symmetrically in relation to one another and thus
intersecting, makes it possible to obtain better holding of the
chains and thus better resistance to lateral compression of the
implants and/or tapes that are obtained from the knit according to
the invention.
[0057] The knit, on leaving the knitting machine, is preferably
subjected to a thermosetting operation. The knit is therefore easy
to manipulate, in particular for the unraveling step. Moreover, all
the tapes and implants obtained from the same thermoset knit
exhibit a homogenous thermosetting, making it possible to better
guarantee the homogeneity of the physico-mechanical properties from
one tape to another after unraveling.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] The invention will be better understood from the following
description in which reference is made to the attached drawings,
where:
[0059] FIG. 1 is a simplified schematic representation of a knit
comprising a first sheet of chain structure, and two non-meshing
sheets,
[0060] FIG. 2 represents a prosthetic knit according to the
invention in which two free chain yarns are partially
unraveled,
[0061] FIG. 3 is a drawing of a view taken with a Hitachi S 800
scanning electron microscope at a magnification of .times.20,
showing the unraveling of a free chain yarn in a knit according to
the invention,
[0062] FIG. 4 is a drawing of a view taken with a Hitachi scanning
electron microscope at a magnification of .times.20, showing the
core of an implant according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0063] In FIG. 1, for a knit according to the invention, E-E'
defines the transverse direction or dimension of the knit, F-F' the
longitudinal direction or dimension of the knit, and G-G' the
diagonal direction or dimension of the knit.
[0064] This figure shows the movements of the chain yarns and of
the weft yarns for a knit according to the invention having a chain
sheet and two non-meshing sheets. The yarns A and A1 of the chain
structure are indicated by thick solid lines. The yarn A1 is a free
chain yarn within the meaning of the present invention. Yarns A are
chain yarns which are not free within the meaning of the present
invention. The yarns of the first non-meshing sheet are indicated
by thin solid lines: these are the yarns B. The yarns of the second
non-meshing sheet are shown by a broken line: these are the yarns
C.
[0065] In this example, the first guide bar, corresponding to the
chain structure, is drawn continuously and full. The second guide
bar, corresponding to the first non-meshing sheet and to the yarns
B, is drawn continuously and 1 full, 1 empty, 3 full, 1 empty, 1
full, 3 empty. The third guide bar, corresponding to the second
non-meshing sheet and to the yarns C, is drawn continuously and 1
full, 1 empty.
[0066] The knitting charts for these three sheets are as follows:
[0067] the chain sheet (yarns A and A1): 1-0/0-1//, [0068] the
first non-meshing sheet (yarns B): 1-1/3-3/2-2/0-0//, [0069] the
second non-meshing sheet (yarns C): 3-3/2-2/0-0/1-1//.
[0070] Thus, the chain yarn A1, as it is shown in FIG. 1, is not
completely crossed by any weft yarn, or, to put it another way, all
weft yarn, that is to say all yarn B or C, approaching said chain
yarn A1, is optionally linked with said chain yarn A1, and then
makes a 180 degree turn at this chain yarn A1.
[0071] The free chain yarn A1 can thus be unraveled without
affecting the adjacent chain yarns A, which are not free within the
meaning of the present application, and, therefore, without
destructuring the knit on either side of this yarn A1. By pulling
the chain yarn A1, the part of the knit situated to the left of
this yarn A1 is separated from the part situated to the right of
this yarn A1 without unraveling these two parts.
[0072] Moreover, because all weft yarn approaching the yarn A1
makes a 180 degree turn at this yarn A1, the edges of the separated
parts have only one yarn B or C making an 180 degree turn and for
this reason are smooth. No fraying takes place.
[0073] This unraveling of a free chain yarn A1 in a knit according
to the invention can be seen in FIG. 3, which is the drawing of a
photograph, taken with the Hitachi S 800 scanning electron
microscope, at a magnification of .times.20, of a zone of
unraveling of a knit according to FIG. 1 and of Example 1 of the
present application. In the upper part of the figure, the yarn A1
is unraveled and the parts of the knit on either side of this yarn
A1 have not been destructured. Their edges are smooth: only one
yarn C makes a 180 degree turn. No yarn of the knit is cut or
frayed. As appears clearly from FIG. 3, thanks to the specific
threading of the yarns of the non-meshing sheets, the yarn C doing
a one hundred and eighty degree turn at the edge of a separated
part is integral with the core of said separated part. In this
figure, the yarn A1 is in the process of unraveling. Thus, at the
bottom of the figure, the yarn A1 is still meshed with the yarns C
approaching it.
[0074] At the end of the unraveling, that is to say when the yarn
A1 has been unraveled along the entire length of the knit, the yarn
A1 is removed from the knit according to the invention, and the two
parts of the knit situated on either side of this yarn A1 are
completely separated. By unraveling a second free chain yarn in the
same way, a tape is separated completely from the knit. The
distribution of the yarns A1 allows the width of each tape to be
determined with great precision.
[0075] FIG. 2 is a schematic representation of a knit 1 according
to the invention for which the free chain yarns A1 are spaced
regularly within the knit. Two of these yarns, the yarns A11 and
A12, are partially unraveled. Thus, by completely unraveling these
free chain yarns A11 and A12, a textile medical device 2 according
to the invention is obtained.
[0076] The core of a textile medical device according to the
invention is shown in FIG. 4, which is the drawing of a photograph
taken with the Hitachi S 800 scanning electron microscope at a
magnification of .times.20. The core of a textile medical device
according to the invention preferably corresponds to a zone of the
knit according to the invention situated between two consecutive
free chain yarns. Therefore, the textile medical device itself does
not comprise free chain yarns. There is therefore no risk of its
unraveling.
EXAMPLE
[0077] A knit according to the invention was produced from a
monofilament yarn of polypropylene, diameter 0.10 mm, on a Raschel
machine, with a chain sheet and two non-meshing sheets, the
following charts being used for the various sheets: [0078] the
chain sheet: 1-0/0-1//, [0079] the first non-meshing sheet:
1-1/3-3/2-2/0-0//, [0080] the second non-meshing sheet:
3-3/2-2/0-0/1-1//.
[0081] The first guide bar, corresponding to the chain structure,
was drawn continuously and full. The second guide bar,
corresponding to the first non-meshing sheet, of partial weft, was
drawn continuously and 1 full, 1 empty, 3 full, 1 empty, 1 full, 3
empty. The third guide bar, corresponding to the second non-meshing
sheet, of partial weft, was drawn continuously and 1 full, 1 empty.
The two partial wefts were drawn so as to move under nine chain
yarns, by which means it was possible to finally obtain tapes
separated by approximately 1 cm of width each. Therefore, in this
example, 1 chain yarn in 10, that is to say ten percent, was a free
chain yarn within the meaning of the invention.
[0082] The gauge used was 24 needles.
[0083] The guide bars of the two non-meshing sheets moved in
partial weft under three needles, symmetrically in relation to one
another, offset from one another in the direction of production of
the knit.
[0084] This knit corresponds to the structure represented in FIG. 1
of the present application.
[0085] On leaving the knitting machine, the knit was subjected to a
thermosetting operation.
[0086] The knit had the following characteristics: [0087]
thickness: approximately 0.3 mm, [0088] diameter of the meshes:
approximately 1 mm.
[0089] Tapes were obtained from this knit by unraveling at least
two consecutive free chain yarns. The tapes had the following
characteristics: [0090] thickness: approximately 0.3 mm, [0091]
diameter of the meshes: approximately 1 mm, [0092] width:
approximately 1 cm, [0093] mass per unit area: approximately 50
g/m.sup.2, [0094] breaking strength measured by the method
according to ISO 13934-1 on a tape with a width of 1 cm and a
length of 20 cm: 66 N.
[0095] The tape thus obtained by unraveling of at least two free,
and preferably consecutive, chain yarns of the knit according to
the invention has excellent tensile strength and is thus eminently
suitable for use as, or for production of, a support implant for
treating stress urinary incontinence and prolapses.
[0096] For example, an implant measuring 20 cm in length, or cm in
length, or even 40 cm in length, can be prepared from this
tape.
[0097] Moreover, by virtue of its method of production, this
implant has edges, in particular longitudinal edges, which are
smooth and do not cause trauma. Finally, all the tapes or implants
obtained from the same knit have undergone homogeneous
thermosetting and are easy to manipulate.
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