Note: Descriptions are shown in the official language in which they were submitted.
~36~75
The present inventlon relates to a method o$ and apparatus for
seaming sheets comprising thermoplastic polymers.
By the ~erm "sheets comprising thermoplastic polymers" is meant
films produced from thermoplastic polymers, and fabrics, such as, for example,
knitted, woven, or non-woven fabrics, comprising fibres formed from thermo-
plastic polymers. Preferably the fabrics comprlse at least 5% by weight o$
thermoplastic fibres, desirably at least 20% by weight of such fibres, and
even more desirably are comprised entirely of such fibres The term "fibres"
is meant to include both continuous filaments and staple fibres.
It is known to use a heat fusion process to seam sheets comprising
thermoplas~ic polymers such as, for example, fabrics comprised of filaments
or fibres spun from thermoplastic polymers. In such a process the fusion
conditions must be very accurately controlled otherwise blobs of molten poly-
mer are produced which may give rise to seams having a poor transverse
strength. Fur~hermore, in a weld so produced in a fabric, the polymer is
melted throughout the thickness of the fabrics and the surface texture is
destroyed along the seam.
According to the present invention there is provided an improved
process for seaming together two fabrics comprising fibers formed from
thermoplastic polymers comprising heating the fabrics and combining the
fabrics by passing them through a nip and exposing a line of contact
between the fabrics to a heat source, wherein the improvement comprises
directing at said line of contact a pulsed or chopped focused beam of
energ~ from a laser traversable along said line of contact of said fabricsJ
said energy of said beam being sufficient ~o melt at least part of said
contacting surfaces of said fabrics, but being insufficient to penetrate
through said fabrics.
In particular, according to the present invention, a process for
seaming together two sheets comprising thermoplastic polymers comprises
bringing together part of one sheet wit~ part o$ the other sheet and direct
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364qs
ing at their line of contact at least one focused beam of energy from a laser.
The sheets are pressed together along or in the vicinit~ of the line
of contact to enable the surfaces of the sheets to make intimate contact.
This ensures that those parts of the surfaces of the sheets softened by the
effect of the laser beam are brought together whilst still in the softened
condition to form a strong seam. The laser beam is pulsed or chopped, the
energy of the pulse b0ing sufficient to melt at least part of the opposing
surfaces of the sheets, but insufficient to penetrate completely through the
sheet, thus preserving the surface texture of the fabric in the area of the
seam.
During the seaming process the two sheets may be held stationary
relative to each other and to the laser beam, or there may be a stepwise or
continuous relative movement between the laser beam and the sheets. The
two sheets may be brought together by any suitable method provided that the
line of contac* of the sheets is sufficiently exposed to allow the laser
beam to reach the line of contact. Thus, for example, th0 sheets may be
brought together by passing them between two plates, around two bars, or
between two moving belts. Preferably the shee~s are passed through a pair
of adjustable nip rolls, at least one of the sheets being passed around
part of its associated roll before entering ~he nip to adequately expose
the line of contact of the sheets. The laser beam is then directed into
the nip of the rolls.
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~036~q5
Acoording to a further aBpeot of the pre~ent invention
there is provided a process for seaming together tHo ~heot~ through
a pair of nip rolls whereby at leAst one of th~ sheetu pa~ses around
part of its as~ooiated roll before entering the nip~ and dire¢tinK
at least one laser beam at the line of oontaat of the two ~heetsO
Depending upon the complexity of the shape of the ueamo
required~ one or more laser beam~ may be uued~ the beam~ beine
sither static or capable of being traver~ed along the lin~ of
contact of the ~h2ets. When a moveable laser beam is used~ the
speed of the nip rolls and the position of the laser beam relative
to the sheets may be controlled by a programmer~ such as~ for e~ample~ '
a punched tape~ or a magnetic tape~ to produce comple~ed shaped seam3~ ;
for e~ample~ cur~ed ~eams.
The laser beam~ particularly when it iB pulsed or ohopped~
may be osoillated over a narrow width to produce a seam compri~ing
two or more rows of weld points~
Where it is required to out the fabric after a seaming
operation~ the seamed fabric after leaving the nip of the roll~ may
pa~s into a cutting device. A las2r cutting device is particularly
suitable~ in which case the laser beam or beams may be ccntrolled by
the same programmer which controls the seaming laser beam or beams and
nip roll speed.
The process of the present in~sntion iB suitable for the
~eaming of woven9 knitted~ or non-woven fabrics during the manufacture
25 ` of artioles of apparal~ such as~ for example~ dresses~ smockst jackst3
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1~364q5
and trousers, the seaming replacing the conventional ~ewing stage.
The prooess iB particularly ~uitable for the m~s production of
garments controlled by a oomputerO
According to a further aspeot of the present i~vention~ there
i~ provided an apparatus for seaming together two sheet~ oompri~ing
ther~oplastio polymers~ the apparatu3 having mean~ for bringlng
together part of one sheet with part of the other shest to form a line
of oontact~ and a laser for directing a focused beam of energy towards
a line correspondi~g to the line of contact of the sheets.
Seams produced by the process of the present invention may
be very narrow~ oomprising a single weld or a single row of weld
points~ or it may oomprise a number of adjacent rows of weld~ or
weld points. Since only the opposing surfaoes of the sheats are
exposed to the laser beam~ no blobs produced by the polymer melting
are visible on the outer surfaoes of the seamed sheets. Seams
produoed in fabrio by the present prooess have partioular advantages
over seams produoed by oonventional welding/fu~ion method~. Thus~
because the fabrio on the outer surfaoes of the fabric is not fused~
it helps to distribute over a wide area any ~tresses which may be
applied to a seam~ thereby increasing the strength of the seam.
Where open ended seams 9 for example in a patch pocket~ are
produced by the process of the present invention~ it is desirable
to close-off the end~ of the seams by~ for example~ spot weldLng
or stitohing.
10369~75
The invention will now be further de~cribed by way of
e2ample with reference to the accompanying drawing which diagrammati-
cally illustrates an apparatus for performing the process of the
invention.
The apparatus shown is suitable for seaming together two
fabrics oomprising thermoplastic filaments or fibres in such a
manner that the ~eamed fabric~ may be subsequently cut to provide
partially formed artiolee of apparel. It compri~es fabric supply
rolls 1 and 2 and roll~ 3 and 4 which form a nip through which the
fabrio pas~e~ to be taken up by a means not shownO Pointing into
the nip of the roll~ are two pulsed laser bean~J 5 a~d 6~ The nip
rolls 3 and 4 are driven by an electric motor not shown and th~
la~er beam~ 5 and 6 are traversed along the nip 7 by means not
shown~ the speed of the nip rolls and the position of the laser
beam being controlled by a computer means not shown.
The fabric is pa~sed through the nip rolls 3 and 4 at a
controlled spe0d and the positon of the laser beam~ 5 and 6 and
their timing of activation iB controlled SO that the fabric is
sèamed as at 8 which~ when subsequently cut~ provides a partially
formed dress~ the seaming at 10 forming the shoulders and at 9
forming the sides of the dress.
Apparatus of the type shown in the drawing~ except that
it had a single fixed laser beamt was u3ed to seam together various
type~ of fabricO A "chopped~ beam from a C02 laser of appro~imately
~ 25 50 watt~ power was used and the fabric was fed through the nip roll~
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at a rate to produoe 5 to 6 point bonds per inch. The ~sam strength~
measured u~in~ an Instron Tensile Testing Machine (~egistered Trade
~ark)~ for the ~abricu are given in the table.
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/ype of Fabrio Seam utrsngth
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40 gauge Ra~chel knit 167 dtex f 30 CRIMPLENE 1300
and 15 tex x 2 worsted-~pun 10 ~ wool
(5.1 oz per ~q.yd.)
Warp knit r~lon (3.4 oz per sq.yd.) 2173
Warp knit 167 dte~ f 30 CRIMPLkNE 99o
(6~6 oz per sq.yd.)
Warp knit CRIMPL ~ nylon Jaspe'¦CHIMPLENE 623
(2-5 oz per sq.yd~)
Nylon (4 oz per sq~yd.) 2272
TERYLENE/CRI~PLENE woven fabric
(4.2 bz per ~q.yd) 2542
lO~o TE~YLENE warp knit (4.4 oz per sq.yd~) 1642
CRIMPLENE~nylon Jaspe'~ CRIMPLENE~ TERYLENE and
nylon warp knit fabric (3.2 oz per sq.yd.) 1200
(CRIMPLENE and TERYLENE are Registered Trade Marks)
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