Abstract:
A rug underlay comprising a centered layer of needle punched fiber batting, an upper outer corrugated layer of heat fused fibers, and a lower outer thin layer of a low friction spun woven polyester scrim. This article is used as a padding or an underlay for wall-to-wall carpeting.

Description:
BACKGROUND OF THE INVENTION 
     Wall-to-wall carpeting is usually installed with an underlay or padding to provide comfortable walking. It is somewhat difficult to install such carpeting over a normal underlay because of the need to stretch the carpeting toward the wall over an underlay that tends to cling to the carpeting. This causes uneveness in the underlay and the carpeting. Contrary to other carpet and underlay structures, in this instance it would be desirable for the face of the underlay which contacts the carpeting to be of low friction so the carpet can slide easily over the underlay during installation. Relative sliding after installation is not a problem since both the carpeting and the underlay are fixed around the entire perimeter. 
     The general structure of the overlay described in my U.S. Pat. Nos. 4,504,537 and 4,504,538 is admirably suited for the purposes of the present invention except for the central stiffening lattice and the upper layer which contacts the carpeting. That upper layer has been modified to provide the properties needed for purposes of this invention. 
     It is an object of this invention to provide a novel rug underlay having characteristics suitable for use with wall-to-wall carpeting. It is another object of this invention to provide a rug underlay of fibrous material having a uniform consistence, no unpleasant odor, and a clean appearance. It is still another object of this invention to provide a rug underlay having a carpet contacting surface that has low friction and will permit carpeting to slide over it easily. Still other objects will be apparent from a more detailed description of this invention which follows. 
     BRIEF DESCRIPTION OF THIS INVENTION 
     This invention provides a rug underlay comprising a central needle punched fiber batting, a lower outer corrugated surface of partially heat fused fibers produced by heat fusing and corrugating the lower surface of said central layer and an upper outer thin layer of a low friction spun woven polyester scrim. In preferred embodiments of this invention the fiber batting comprises a mixture of a majority of polypropylene fibers and a minority of nylon fibers, polyester fibers, and cotton fibers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which: 
     FIG. 1 is a schematic illustration in perspective indicating how a mass of fiber batting is needle punched into a compressed fibrous central layer; 
     FIG. 2 is a cross section through the rug underlay of this invention; and 
     FIG. 3 is a plan view of the top layer of the rug underlay with a portion thereof folded so as to show the lower outside layer of the underlay. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The central core 10 of the rug underlay of this invention comprises a mass of fibrous material compressed into a layer about 1/4 to 1/2 inch thick. This central core 10 can be made in any of several ways but it has been found most desirable to perform it by a needle punching operation which is depicted in FIG. 1. A mass of fiber batting 11 is subjected to a needle punching operation in a press in which a plurality of closely spaced, barbed needles 12 are punched through batting 11 enough times to compress the batting 11 to a very thin dense layer of intertwined fibers. It is preferable to subject a mass of fibers to a carding operation to produce fiber batting 11 with most of the fibers in the batting generally parallel with each other. Such a carded fiber batting produces a more desirable structure for this invention than a batting that has not been carded. Needle punching is a common operation employed in the fiber industry to intertwine fibers and filaments into a felt-like layer of material. In general a mass of fiber batting is needle punched to a thin layer which is then turned over and another mass of batting is applied to the opposite surface and needle punched again. These operations are repeated with new layers of batting applied to opposite sides of the needle punched layer until a central core 10 has been produced of the desired thickness, preferably about 5/16 inch. The fibers in the batting may be any type of natural or synthetic fibers, although snythetic are preferred such as polyprolefin, nylon, polyester, acrylic polymer, etc. Preferably, the fibers are polypropylene of mixtures of a majority of polypropylene, and a minority of nylon, polyester and cotton. 
     The central layer 10, as described above, is then treated to produce a lower layer 14 which will cling to any lower underlay or to the floor on which it is laid. Lower layer 14 is a surface of partially fused fibers having a stiff hard feeling as compared to the compressed fibers of the central core. Lower layer 14 also has some fiber ends projecting upwardly which can be sensed by rubbing this surface with one&#39;s fingers or by looking at the surface through a microscope. These fiber ends produce a good frictional contact with wooden or masonry flooring or with an underlay covering the floor. A preferred method of producing surface 14 is by applying sufficient heat to partially fuse the fibers at one of the outside surfaces of central layer 10 of needle punched fibers described previously. The corrugated appearance of lower layer 14 may be achieved by passing the underlay under a heated roller having a pattern of raised ridges. The roller is heated to a sufficiently high surface temperature to cause partial fusing of the fibers at the outer portion of layer 10 as they pass under the roller. This action produces a semistiff corrugated surface having a pattern of depression 15 that provides an excellent grip for flooring or another underlay. 
     It is not critical that corrugated depressions 15 be in any particular design to provide the proper contact between the underlay and the flooring below the underlay. The design may be parallel ridges and grooves, a geometric design such as squares, triangles, etc.; or any other design of ridges and valleys which will provide a good grip on the adjoining surface and, at the same time provide a good cushioning effect. A particularly preferred design is a simple pattern of parallel depressions 15 about 1/4-1/2 inch apart. Each depression 15 being about 1/16 inch wide and 1/16 inch deep. 
     Upper layer 16 is a thin layer of low friction fibrous material bonded to the upper surface of the central core 10 of needle punched fibers so as to provide a slightly slippery contact with the underside of a carpet lying on that surface. This layer may be made of any suitable type of fiber, preferably, a polyester in a spun woven pattern. Such a layer need not be more than about 0.001 inch thick. Layer 16 may be attached to central layer 10 by any of a variety of means. For example, layer 16 may be lightly needle punched onto the outside surface of central layer 10. An adhesive may be applied to the surface of central layer 10 and layer 16 pressed thereon. Still another procedure is to press layer 16 onto layer 10 and apply sufficient heat to cause a partial melting of the fibers at the interface, which upon cooling will be firmly intertwined with each other. 
     FIG. 3 shows the general appearance of the underlay with corrugated surface of parallel depressions or grooves 15 on lower layer 14 and with the spun woven fibrous upper layer 16. An appropriately prepared underlay of the construction described above may have a thickness of about 5/16 inch for a weight of approximately 30 ounces or a thicker structure of about 1/2 inch for a weight of about 48-52 ounces. Thicknesses and weights between these extremes are also readily prepared as may be understood by those skilled in the art. 
     While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.