Tufted carpeting having stitches thermally bonded to backing

The back-loops of the stitches of pile yarn of a tufted carpet are fastened to the backing by thermal bonding, obviating the need for applying an adhesive coating to the underside of the backing. By preference, the thermal bonding is accomplished by using as the pile yarn a yarn made of or incorporating a synthetic thermoplastic material which becomes tacky at a temperature below that at which the backing is adversely affected. For instance, yarn made of or containing polyethylene may be thermally bonded to a backing made of nylon. The backing acts as a sufficient thermal barrier or heat sink as to prevent damage to the face pile during application of heat to the underside of the backing while conducting the thermal bonding step. Where other backings and coatings are omitted, a tufted carpet of superior porosity may be made, e.g. for use as a sand-filled artificial turf.

BACKGROUND OF THE INVENTION 
Typically, tufted carpeting is produced by stitching a plurality of rows of 
yarn loops through a previously-manufactured mesh-like backing so that the 
yarn protrudes above one face of the backing as a pile, and is drawn 
relatively closely against the opposite face of the backing. The pile, 
formed as yarn loops may be permitted to remain as loops, or it may be 
sheared or otherwise cut to create a cut pile rather than a looped pile. 
It is necessary to perform a further operation on the as-tufted product in 
order to lock the pile in place. Otherwise, even slight pulling on any of 
the loops or tufts of pile yarn will separate the yarn from the backing. 
In instances in which the pile is cut pile, pulling can separate 
individual tufts leaving naked spots, and in instances in which the pile 
is uncut pile, pulling on one loop can create a snag leaving a whole row 
or a segment of row as a naked strip on the carpet face. By far the 
heretofore most popular way of locking the tufted yarn to the backing has 
been to apply an adhesive to the back of the backing, after tufting, in 
such a manner as to adhere the back loops of the yarn to the backing, 
mechanically entrap the back loops of the yarn in a common matrix with the 
backing, and in order to obscure access to the back loops. 
As may be imagined, there are many variations in the constituency of tufted 
carpets, and in the processes and apparatus used for making tufted 
carpeting. For instance, some tufted carpeting is made by stitching yarn 
through two or more layers of backing, e.g. having two or more different 
gauges (number of picks per inch); see the Avery U.S. Pat. No. 4,426,415, 
issued Jan. 17, 1981. Multiple backings, when used, can strengthen the 
product, stiffen it, provide additional holding power against pulling-out 
of stitches, help to hold the face pile upright and help prevent 
back-coating composition from flowing excessively into the face pile as it 
is applied to the back. 
In some instances the or a layer of the backing is made of flexible plastic 
film or non-woven fabric, rather than a fabric mesh. In some instances the 
coating which is applied to the underside of the backing doubles in 
function as a non-slip surface-providing means; in other instances, the 
stitch-locking coating is itself backed with one or more layers of woven 
fabric, plastic film, non-woven fabric and/or a non-slip feature-providing 
coating. Backings are made from a variety of materials, including, without 
limitation, natural materials typified by jute, and synthetic polymeric 
materials typified by polypropylene. Backings are made of varous weights, 
gauges and weaves. 
For some applications, it is desirable that the combination of the backing 
layer or layers, the back-loops of the tufted yarn, the stitch-locking 
layer and additional layers provide a substantially continuous barrier 
separating the face of the carpet from the base on which the carpet is 
laid. For other applications the exact opposite--porosity through the 
carpeting from face to underside--is desirable or, indeed, essential. 
A particularly popular use of tufted carpeting is as artificial turf, both 
for playing surfaces for the conduct of sports activities such as 
football, baseball, soccer and the like, and for landscaping or decorating 
various indoor and outdoor sites. 
A recent practice in the use of artificial turf has involved the spreading 
of sand, soil, or some other filler material onto the surface of the turf. 
The purpose of the filler material is to provide a playing surface which 
is more closely similar to natural (grass/soil) playing surfaces. 
Artificial turf, as presently produced, does not allow sufficient 
quantities of filler material to be worked into the turf, does not allow 
for proper drainage of water from the surface, and erodes (wears out) too 
quickly when used with most filler materials. 
SUMMARY OF THE INVENTION 
The back-loops of the stitches of pile yarn of a tufted carpet are fastened 
to the backing by thermal bonding, obviating the need for applying an 
adhesive coating to the underside of the backing. By preference, the 
thermal bonding is accomplished by using as the pile yarn a yarn made of 
or incorporating a synthetic thermoplastic material which becomes tacky at 
a temperature below that at which the backing is adversely affected. For 
instance, yarn made of or containing polyethylene may be thermally bonded 
to a backing made of nylon. The backing acts as a sufficient thermal 
barrier or heat sink as to prevent damage to the face pile during 
application of heat to the underside of the backing while conducting the 
thermal bonding step. Where other backings and coatings are omitted, a 
tufted carpet of superior porosity may be made, e.g. for use as a 
sand-filled artificial turf. 
The principles of the invention will be further discussed with reference to 
the drawing wherein a preferred embodiment is shown. The specifics 
illustrated in the drawing are intended to exemplify, rather than limit, 
aspects of the invention as defined in the claims.

DETAILED DESCRIPTION 
(In this document, terms of orientation such as "face" and "underside" 
refer to the tufted carpeting in its usual orientation of use, i.e. the 
orientation depicted in FIG. 1. Of course, while the product is being 
manufactured, it or its precursor or components may be rightside-up, 
upside down, vertically oriented or rolled and, unless the contrary is 
evident from the context, terms of orientation as used herein should not 
be interpreted as referring to the product, its precurser or components 
while in such temporary states. For example, when the term "underside" is 
used, what is meant is the side which is the underside when the carpet is 
in normal use, regardless of whether that side is on the bottom, on the 
top or on the side while the product is being manufactured.) 
A section of tufted carpeting 10 is shown in FIG. 1 at a stage after the 
rows of stitches of yarn 12 have been stitched into the backing 14 by 
utterly conventional carpet tufting machinery. Both the yarn 12 and the 
backing 14 may be utterly conventional. In this particular drawing figure, 
because it is a longitudinal sectional view, only one row of stitches is 
visible. Other rows substantially like the one shown should be understood 
to be present in planes parallel to but successively further in front of 
and behind the plane of this drawing figure. 
In the instance depicted, the backing 14 is present in a plurality of (e.g. 
three) layers 16, 18, 20. However, any number of layers from one to 
several may be used, and if two or more are present they may be alike, or 
they may differ from one another, e.g. in weight, number of picks per 
inch, composition, kind and the like. Where three layers of backing are 
present, the upper layer I6 may be thought of as being the surface 
backing, the middle layer 18 may be thought of as being the intermediate 
backing, and the lower layer 20 may be thought of as being the bottom 
backing. 
Also in the instance depicted, the face loops of the pile yarn have been 
conventionally cut so as to form sheared pile, i.e. of individual tufts 22 
characterised by ends 24. In other instances, the pile loops may be left 
uncut, as is conventionally an alternative to cut pile. However, in either 
case, the backloops 26 of the pile yarn are, as a result of the 
conventional tufting yarn stitching and looping process, drawn 
comparatively tight against the underside 28 of the backing 14. 
In a conventional tufted carpet, the back-loops 26 would be fastened to the 
backing 14 by applying a coating of flexible adhesive material, e.g. foam 
rubber to the underside 28 of the backing. Although it would not 
necessarily depart from the principles of the present invention to provide 
some sort of coating on the underside of the backing after the backing had 
been tufted, e.g. to provide a non-slip surface, a pesticide or the like, 
it is believed to be an important departure of the present invention from 
the prior art to principally lock the pile yarn stitching to the backing 
by temporarily partially melting the back-loops 26 in order to cause them 
to become thermally bonded to the backing, e.g. to the bottom backing 20. 
Particularly in instances in which the backing is used in multiple layers, 
the layers above the bottom layer have an important function of preventing 
the face pile of the carpeting from being damaged by the heat as the 
back-loops 26 are being thermally bonded to the backing. 
In practice, the heating for effecting the thermal bonding may be applied 
in any of a variety of ways which may be found to be suitable. A way is 
simply running the underside of the as-tufted backing over a 
sufficiently-heated platen 30 at a sufficient rate to permit the necessary 
heat transfer to take place. Jets of heated gas likewise could be directed 
in a band against the underside of the as-tufted backing. If one of the 
backing lyers, e.g. the bottom backing were to incorporate an 
electrically-conductive material, e.g. a ferro-metal foil or fine 
ferro-metal particles, radio-frequency energy could be applied to the 
backing from either side in order to temporarily produce sufficient 
heating of the pile yarn where it penetrates or is disposed adjacent that 
layer in order to provide the desired thermal bonding. 
As shown in FIG. 2, when the resulting tufted carpeting 10 is laid on a 
base 34, e.g. topped by particulate material 36 such as sand, the 
carpeting 10 may have its voids (i.e. its interstitial spaces 38) 
partially filled with a particulate filler 40 such as sand, which, due to 
the preferable porosity of the carpeting 10 is in communication with the 
particulate material 36 of the base. 
The principles of the present invention are equally applicable to products 
which may be referred to as either carpet or artificial turf, and to 
products which incorporate either single or multiple layered backings, 
which may be either of woven construction or of solid, film-type 
construction. 
The invention applies to carpeting which is produced by stitching (tufting) 
loops through a backing material. The method of locking the stitches to 
the backing by thermal bonding, and the mechanism which allows for the 
locking of the stitches to the backing, are unique and significant 
features of this invention. 
By preference, dissimilar materials are used for the stitches and the 
backing, i.e. so that the back-loops of the tufted yarn can be thermally 
bonded to the backing at a lower temperature than one which would degrade 
the backing. Further, the backing mterial is selected such that it will 
readily accept the fusing of the stitches onto it. 
Another feature of the preferred embodiment of the present invention is the 
use of multiple layers of backings, for the dual purpose of structural 
integrity of the final product and thermal absorption of heat energy 
during the production process. The use of the multiple layers, as set 
forth, involves materials which will form a thermal barrier between the 
heat (supplied to the backing to fuse the stitches to the backing) source 
and the face pile. The absorption of heat in the multiple layers of 
backing keeps the temperature on the face pile below that which would 
result in degradation of the face pile. 
As a practical example, the carpet of the present invention may incorporate 
a polyethylene material for the tufted stitches and a nylon backing 
material. These materials may be of various weights and weaves, depending 
upon the product application. The fusion point of the polyethylene is 
approximately 300.degree. F. whereas the fusion point of the nylon is 
approximately 600.degree. F. Upon application of heat to the back side of 
the product, the polyethylene stitches fuse to the nylon backing forming a 
permanent bond of the stitches to the backing. The intermediate and upper 
layers of nylon backing, when used, form a heat sink: or thermal barrier 
because of the thermal properties of the backing material preventing 
unwanted heat transfer to the face pile. This process may be accomplished 
without the use of any separate (e.g. adhesive) bonding agent. 
When the principles of the present invention are practiced according to the 
preferred embodiment for producing a porous, particle-filled artificial 
turf such as is depicted in FIG. 2, the following features and functions 
may be obtained: 
(a) More upright stitches (tufts) in the final product, as opposed to 
stitches which have considerable lean (deviation from the vertical); 
(b) More receptivity to a filler material (soil, sand, etc.) because of the 
stitches being upright; 
(c) More uniform distribution of the filler material onto and into the 
artifical turf; 
(d) More and heavier stitches (and therefore more wearability) per unit 
surface area of product; 
(e) More uniform drainage capability of the product due to uniformly 
distributed porosity of product and numerous non-blocked drainage outlets 
through the backing; 
(f) Elimination of surface contamination of the product due to there being 
no bonding agent leaking through to the face of the turf; 
(g) Reduction of the cost of materials for the product due to the 
elimination of a separate bonding agent. 
Of course, in other practices of the invention, one or more of the above 
characteristics may be foregone, without departing in the main from the 
fundamental principles of the present invention. 
It should now be apparent that the tufted carpeting having stitches 
thermally bonded to backing as described hereinabove, possesses each of 
the attributes set forth in the specification under the heading "Summary 
of the Invention" hereinbefore. Because it can be modified to some extent 
without departing from the principles thereof as they have been outlined 
and explained in this specification, the present invention should be 
understood as encompassing all such modifications as are within the spirit 
and scope of the following claims.