Method for texturing the surface of non-woven fabric films

A non-woven fabric or film of thermoplastic material has a pattern impressed on its surface so that it has a more pleasing appearance. The film is pressed between the patterned surfaces of two mold bands and is passed through an electromagnetic field which heats a susceptor material in the film to soften the fabric or film so that the pattern will be impressed in it.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to methods and apparatus for fabricating 
non-woven fabrics and films and in particular for a method and apparatus 
for texturing the otherwise featureless smooth surface of such fabrics or 
films. 
2. Description of the Prior Art 
As far as is known, there is no prior art apparatus using an 
electromagnetic field to soften a thermoplastic strip so that it may be 
textured or patterned so as to have a more esthetically pleasing surface. 
SUMMARY OF THE INVENTION 
The present invention is summarized in that field apparatus for texturing 
the surface of a non-woven thermoplastic fabric or film sheet having a 
susceptor material therein includes a pair of endless mold bands at least 
one of which has a patterned surface formed thereon, drive means to drive 
the mold bands and to press the mold bands together for a portion of their 
length, the thermoplastic sheet being received between the mold bands 
where they are so pressed together, and electromagnetic energy generating 
means positioned so as to subject the thermoplastic sheet to an 
electromagnetic ffield to heat the susceptor material therein so that the 
thermoplastic sheet is impressed with the pattern on the patterned 
surface. 
It is an object of the present invention to provide non-woven thermoplastic 
mounting tapes for slide fasteners that have textured or patterned 
surfaces so that they are esthetically pleasing in appearance. 
It is another object of the present invention to form such textured or 
patterned surfaces rapidly and economically using as little energy as 
possible so as not to disrupt the structural integrity of the non-woven 
fabric or film. 
It is yet another object of the present invention to provide an apparatus 
for forming the textured or patterned surface that is readily adaptable to 
many types of textures and patterns and to various types of non-woven 
fabric and films of various types and sizes. 
Other objects, advantages and features of the present invention will become 
apparent from the following specification when taken in conjunction with 
the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Shown in FIG. 1 is a slide fastener, generally indicated at 10, constructed 
utilizing therein a pair of non-woven tapes which have been textured or 
patterned according to the present invention. The slide fastener 10 
includes a pair of mounting tapes 12 and 14, both of which are formed as 
non-woven strips of thermoplastic material and both of which have had 
their surfaces textured or patterned to resemble woven or knitted fabric 
by the method and apparatus of the present invention. These non-woven 
strips may be either simple extruded or cast films or may be non-woven 
fabric-like constructions in which grids of thermoplastic fibres are 
joined at intersections through the use of heat, adhesives, mechanical 
interlocks or the like. The mounting tapes 12 and 14 lie adjacent each 
other and each has a respective one of a pair of continuous trains of 
coupling elements 16 and 18 secured to its edge adjacent the other 
mounting tape. A slider 20 is entrained on the two trains of coupling 
elements 16 and 18 to move up and down them to successively engage and 
disengage the coupling elements from each other. The slider 20 is normally 
the last element added to the slide fastener 10, and the slide fastener 10 
without the slider 20, that is with just the two mounting tapes 12 and 14 
and the two trains of coupling elements 16 and 18 all interengaged with 
each other, is known as a slide fastener chain. In the manufacture of 
slide fasteners such as the slide fastener 10, a continuous slide fastener 
chain is cut into appropriate lengths and sliders 20 are mounted thereon 
to complete the slide fasteners. 
Shown in FIG. 2 is an apparatus, indicated generally at 30, for texturing 
the surface of an indefinite length work sheet 32 of suitable non-woven 
fabric material having initially a smooth surface. The work sheet may be 
either of the mounting tapes 12 or 14 with or without the trains of 
coupling elements 16 and 18 thereon, or may be any other suitable 
non-woven fabric strip, but is preferably a slide fastener stringer 
including, as described above, both the mounting tapes 12 and 14 with the 
trains of coupling elements 16 and 18 secured thereon and with the 
coupling elements of the trains 16 and 18 all interengaged with the 
coupling elements on the other train. Before entering the apparatus 30, 
the tapes 12 and 14 of the work sheet 32 are smooth and featureless films 
or fabrics of thermoplastic sheet material having smooth surfaces with a 
susceptor material either applied as a coating on both sides thereof or 
intermixed into the thermoplastic films themselves. Suitable susceptor 
materials include vinyl applied as a coating for use in a dielectric 
energy field or iron filings used in an electromagnetic induction field, 
as will be explained below. 
The apparatus 30 includes a first spaced pair of press wheels 34 and 36 
which have entrained around them a first endless mold band 38. A second 
spaced pair of press wheels 40 and 42 have entrained about them a second 
endless mold band 44, the pairs of press wheels 34 and 36 and 40 and 42 
and the mold bands 38 and 44 respectively being largely identical. The 
press wheels 34 and 40 are arranged adjacent each other as are the press 
wheels 36 and 42 so that the mold bands 38 and 44 are stretched tightly 
therebetween and firmly together for a portion of their length. An 
electromagnetic field (EMF) energy generator 46 is positioned around the 
mold band 44 and adjacent the portion of the mold bands 38 and 44 where 
they are pressed against each other. The EMF energy generator may be a 
source of either a radio frequency energy field or an electromagnetic 
induction field depending on the susceptor material in the work sheet 32. 
A pair of electrodes 48 and 50 of the EMF energy generator 46 are 
positioned on opposite sides of the pressed together mold bands 38 and 44. 
First and second sets of guide wheels 52 and 54 are provided at opposite 
ends of the apparatus 30 and receive the work sheet 32 therebetween. A 
supply reservoir 56 is provided to hold the work sheet 32 before the 
texturing operation and a receiving reservoir 58 is provided to receive 
the treated work sheet 32. 
A cross section of the mold band 38 is shown in FIG. 3. The mold band 38 
includes a support belt 60 formed of a material having a high resistance 
to elongation such as woven glass. Formed onto the support belt 60 is a 
shaping layer 62 of silicone or other suitable resilient material molded 
onto the support belt 60. The materials of both the support belt 60 and 
the shaping layer 62 are selected so as to be nonsusceptible in that they 
are relatively unaffected by the imposition of electromagnetic energy 
fields. The shaping layer 62 has a patterned surface 64 formed all along 
its exterior face and has a longitudinally extending channel 66 formed in 
it opening into the center of the patterned surface 64. A plurality of 
vent holes 68 are provided in the mold band 38 extending through both the 
shaping layer 62 and the support belt 60. The mold band 44 is largely 
identical to the mold band 38 although the pattern of the patterned 
surface 62 may be varied if so desired. 
In the operation of the apparatus 30 of FIG. 2, the press wheels 34 and 36 
are driven to rotate in a clockwise direction while the press wheels 40 
and 42 are driven in a counterclockwise direction to move the 
pressed-together portions of the mold bands 38 and 44 in a left-to-right 
direction as viewed in FIG. 2. The work sheet 32 is withdrawn by the 
moving mold bands from the supply reservoir and through the guide wheels 
52 and 54. Once in between the mold bands 38 and 44 the work strip 32 is 
held in place between the two shaping layers 62 with the patterned 
surfaces 64 contacting the work sheet 32. When the work sheet 32 is the 
slide fastener stringer the two tapes 12 and 14 are held between the 
patterned surfaces 64 while the interengaged trains of coupling elements 
16 and 18 are received in the channel 66 so that they will not be 
deformed. The mold bands 38 and 44 carry the work sheet 32 between the 
electrodes 48 and 50 so that the work sheet is subjected to an 
electromagnetic energy field created by the EMF energy generator 46. The 
susceptor material in the work sheet 32 is heated by the electromagnetic 
field, the heat being transferred to the surface of the thermoplastic 
material of the work sheet 32 to soften it. In its softened condition, the 
work sheet 32 is then impressed with the patterns of the patterned 
surfaces 64. The work sheet 32 then leaves the mold bands 38 and 44 and 
hardens with the patterns impressed on the surfaces of the mounting tapes 
12 and 14. The work sheet 32 is guided by guide wheels 54 into the 
receiving reservoir. 
As stated above, the EMF energy generator may be either a radio frequency 
energy generator or an electromagnetic induction field generator. For a 
work strip having a dielectric susceptor material, such as a vinyl coating 
on the outside of the sheet, a radio frequency device is used and the 
susceptor material is heated due to dielectric losses in the susceptor 
material. If an electromagnetic induction field generator is used, the 
susceptor material should be ferromagnetic, such as iron filings imbedded 
in the work sheet 32 itself, and these susceptor materials would heat the 
work strip because of the hysteresis losses which would be created in the 
ferromagnetic material by the alternating induction field. 
The pattern created on the mounting tapes 12 and 14 can be any desired 
pattern, but the invention is particularly useful for creating a 
simulation of either a knitted or woven appearance. This pattern on the 
mounting tapes 12 and 14 would obviate one of the major objections to the 
use of thermoplastic films, the shiny or slick appearance of the untreated 
film. Thus by using the present invention it is possible to obtain the 
desirable cost advantages of thermoplastic films while still overcoming 
one of the more objectionable characteristics of such films, their shiny 
appearance. 
Furthermore, in the fabrication of these non-woven fabrics or films, 
oriented fabric or films are often used to strengthen the material in 
particular directions. The present invention is particularly adapted for 
use with such oriented fabrics or films since the heating effect of the 
EMF field can be concentrated in specific areas of the sheet material, 
such as just on its outer surfaces, and thus would have minimal effect on 
the oriented material which would be greatly disturbed by a more thorough 
heating process. 
If desired any additional decorative steps may be added to the work sheet 
produced by the present invention. For instance, the raised portions of 
the pattern produced may be selectively colored by contact coating or may 
be coated with adhesive to accept flocking material for a further 
decorative effect. 
Inasmuch as the present invention is subject to many modifications, 
variations, and changes in detail, it is intended that all the subject 
matter contained in the aforegoing specification or in the accompanying 
drawings be interpreted as illustrative, and not in a limiting sense.