The present invention relates generally to an improved system for anchoring carpeting to the floor, and more particularly to an improved carpet tack strip whose base or substrate is formed from a synthetic resinous formulation capable of being penetrated by tack elements and pre-nail elements, with those elements being tightly lodged and retained in the strip.

Carpet securing elements, commonly called "tack strip" has long been used to retain the edge portions of floor carpeting in place. In accordance with the prior art, this tack strip comprises a plywood base, typically four feet in length and one inch wide, which is passed through a nailing machine used to insert a large plurality of nails or tacks through the thickness dimension of the strip so that they project from the upper surface thereof at a predetermined angle. The strip may also be provided with pre-nails which are nail elements also inserted through the plywood base but intended to be hammered down so as to fasten the tack strip to a wooden or concrete floor surface. Typically, the substrates used to retain the tacks and pre-nails in place are produced from large plywood sheets which are cut into strips. This process tends to be quite wasteful with approximately four percent of a plywood sheet being converted to sawdust and scrap as the saw blades pass through to create the strips of a desired width. Moreover, when subjected to the nailing process, the plywood strips

will frequently splinter, resulting in further rejects and waste. When splintering occurs as the strips are being fed through the tack inserting machinery, it becomes necessary to shut down the production while the jam is cleared. This, too, increases the manufacturing cost beyond that which it should be.

The prior art tack strips with plywood base creates still further problems during the carpet installation process. First of all, the plywood substrates are rigid and cannot be formed around corners. This requires frequent cutting of the strips as the work progresses around the perimeter of the room. Because of the inconsistencies and irregularities in the plywood material, the retaining force afforded to the tacks is inconsistent and when the carpet is stretched and forced onto the tacks, they sometimes are loosened to the point where they can swivel and no longer serve to provide an adequate anchoring force. Plywood tack strips can only be used once and cannot be removed and reused because the removal process destroys the substrate.

Still another problem associated with the prior art plywood substrate tack strip comes into play when such tack strip is adhesively bonded rather than nailed to, say, a concrete floor prior to carpeting. It can happen due to manufacturing irregularities in the fabrication of the plywood from which the strips are cut that discontinuities exist between lamination. When the pulling force of the stretched carpet is applied, the wood layers delaminate requiring removal and replacement.

SUMMARY OF THE INVENTION In accordance with the present invention an improved synthetic resinous formulation is provided from which the substrate means of the carpet securing 5 elements may be fabricated in a pour molding or extrusion molding process. In this connection, the formulation for the synthetic resinous material is that of a filled polyurethane substance having a density of between about 30 pounds per cubic foot and

10 65 pounds per cubic foot. Such a density is achieved when pulverized inert ingredients are employed as the filler in ah amount ranging from a minimum of about 10% to a maximum of 36%. The material is in the form of a dispersion or liquid, and consists essentially of

15. polyurethane comprising the reaction product of a polyisocyanate and a polyol consisting of a linear polyether with plural hydroxyl groups thereon. This material is reacted, in the presence of a catalyst, with methylene di-isocyanate. While formulations

20 similar to the above have been known in the past, the present invention relates to the application of this material as a substrate means for retention of carpet securing tack and pre-nail elements in strip form.

As indicated hereinabove, plywood strips have

25 traditionally and typically been employed as the substrate material. The present polyurethane substrate material provides significant advantages over plywood. For example, the resistant nature of polyurethanes to either rot or mildew is advantageous

30 in marine applications, and furthermore the polyurethane is not subject to attack or deterioration by termites. When the strips are formed in a pour molding operation, shipping and handling costs are

much lower than when plywood is employed. The chemicals can be shipped in bulk to the place of manufacture and then mixed at the time of manufacture. Thus, the volume of the shipped material is much less than the volume of plywood for producing an equivalent number of strips of equal length.

Polyurethane strips made in accordance with the present invention can readily be cut with a snip-tool, a feature not possible with plywood as employed in the past inasmuch as the plywood product is difficult to cut and/or sever without creating splintering along the body of the substrate. The urethane product may be readily bent to conform to an irregular floor surface, and furthermore may be notched in order to allow it to be bent to confirm readily to an inside or outside corner. Such notching is an advantage possessed by the material in addition to the ease by which it may be cut.

Also, as has been indicated, the polyurethane strip, due to its excellent plastic memory, tends to hold the individual tacks at their desired angle reactive to the substrate.surface, even when subjected to substantial forces caused by lateral tension in the stretched and retained carpet. OBJECTS

Therefore, it is a primary object of the present invention to provide an improved substrate material for use as a retainer of carpet retaining tacks and pre-nail elements. It is a further object of the present invention to provide an improved substrate for retention of carpet securing tack and pre-nail elements in strip form, and wherein the substrate is fabricated from a

synthetic resinous formulation consisting essentially of an inert ingredient of particle filled polyurethane dispersion.

Still another object of the invention is to provide a synthetic material to be used as a tack strip substrate which can be removed and reused without destroying the strip material.

Yet another object of the invention is to provide a tack strip having a synthetic resinous formulation consisting essentially of inert ingredient particle- filled polyurethane dispersion as its substrate and which can be produced in continuous lengths and which can be passed through a tacking machine on a continuous basis rather than as individual pieces of precut length.

Other and further objects of the present invention will become apparent to those skilled in the art upon a study of the following specification, appended claims, and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a length of carpet retaining strip fabricated in accordance with the present invention; and

Figure 2 is a vertical sectional view taken along the line and in the direction of the arrows 2-2 of Figure 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with the present . invention, the carpet retaining strip generally designated 10 includes a substrated body or means 11 into which there has been inserted a plurality of carpet securing tack elements 12-12 along with pre-nail elements IS¬ IS. As indicated, the substrate means 11 is arranged

in elongated strip form, and possesses a cross- sectional profile of the form as indicated in Figure 2. The strip 11 is preferably approximately 5/16ths inch thick and 3/4ths - l inch in width. The pins 12 are driven through the thickness dimension of the substrate 11 and project outwardly from the top surface 14 thereof at an angle of approximately 22°. The pins are spaced along first and second rows in a staggered relationship approximately 1-1/2 inches apart, the rows being approximately l/4th inch from one another. While in Figure 1, only two rows of pins are indicated, conventional tack strip may also be constructed using three rows of pins. The prenails 13 are conveniently spaced at 6 inch intervals along the length dimension of the tack strip and approximately halfway across the width dimension thereof.

With attention being directed to Figure 2, it will be seen that the cross-sectional profile includes a recessed area or zone defined by the angle The angle preferably is in the range of between about 15° and 25°, and is designed to permit tucking of the carpet edge under the edge of the strip. Again, such angular cross-section profiles have been known and utilized in connection with carpet securing strips in the past. With plywood substrates of the prior art, however, the angle tended to be quite small so as to eliminate undue waste during the cutting operation. With the material of the present invention being molded or extruded, there is no waste and the angle can be set to afford proper holding of the carpet.

As indicated hereinabove, the substrate 11 consists of a formulation consisting essentially of a frothed or chemically blown polyurethane. In order to

better comprehend the nature of this formulation, the following example is given for its preparation.

EXAMPLE A Component Percent by Weight Polyol, a linear polyether 35% - 40% with plural hydroxyl groups

Cross-linking agent consisting essentially of methylene di-isocyanate 15% - 20% Reinforcing filler, or inert ingredients with an average particle size of between 0.5 microns and 35.0 microns 10% - 36% Catalyst

(typically amines, tin soaps, organic tin compounds) 10% - 15%

Chemical blowing agents or frothing agents (mechanical) 3% - 5%

The above formulation is normally prepared as a prepolymer, and when formed, is blended with a second component consisting essentially of methylene di- isocyanate. The prepolymer and methylene di¬ isocyanate are mixed on a basis of 80 percent to 20 percent, respectively.

For flexibility, flexible polyurethanes are normally based on polyoxypropylene-diols with a molecular weight of about two thousand, and triols with molecular weights up to about four thousand. Such polyurethanes are, of course, known and commercially available.

In forming the blend of materials, the constituents making up the prepolymer are initially

placed within a large vat and, using a pump blending system, these components, together with the added methylene di-isocyanate, are thoroughly blended until homogenous, and thereafter, immediately introduced into an extruder, a pour mold, a rotary mold or a vacuum mold. In the manufacture, the cross-linking temperature is maintained between about 260o and 300°F, it being noted that the urethane compound being produced and described above undergoes cross-linking at about 280°F. A conventional blowing agent or frothing agent is employed which, under these environmental conditions, becomes volatile and fugitive, and forms the appropriate cellular product with the density indicated. Blowing agents and frothing agents compatible with polyurethanes and capable of activation at the temperatures indicated are, of course, commercially available.

By way of a specific formulation, the prepolymer (component A) is formulated as follows: EXAMPLE B

Component A Percent by Weight

Cross-linking agent . 15-20 consisting essentially of methylene di-isocyanate Component B

Polyol, a linear polyether 35-40 with plural hydroxyl groups Reinforcing filler, inert 10-36 ingredients an average particle size of between 0.5 microns and 35 microns

Catalyst (typically amines, 10-15 tin soaps, organic tin compounds)

Chemical blowing or frothing 3-5 agents (mechanical)

It can be seen, then, that in accordance with the present invention there is provided a tack strip substrate material which can readily be cut into appropriate size pieces during the carpet installation process without decreasing the overall strength or structure. Unlike wood, the substrate is impervious to moisture and thus can be used for marine applications in both fresh and salt water. Moreover, being moldable or extrudable, the tack strip substrate can be produced without any significant waste and with a minimum of manual labor involved. This greatly reduces the overall manufacturing cost of the product as compared to the prior art.

This invention has been described herein in considerable detail in order to comply with the Patent Statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment details and operating procedures, can be accomplished without departing from the scope of the invention itself. What is claimed is: