HOOK TAPE FOR JOINING

Abstract: A substrate (10, 30) is joinable to at least two sheets along at least one edge of each sheet to join the sheets together along the edge to create a seam. A first substantially central longitudinal axis (16) divides the substrate into a first portion (18) between a first longitudinal edge (12) and the first longitudinal axis (16) and a second portion (20) between a second longitudinal edge (14) and a longitudinal location located along a line that is between the second longitudinal edge and up to the first longitudinal axis. The substrate includes a plurality of hooks (26) formed in the first and second portions such that substantially all of the hooks in the first portion and in the second portion face the first longitudinal axis.

Description: HOOK TAPE FOR JOINING TECHNICAL FIELD The present invention relates to hook tape for use with mechanical fasteners. More particularly, the present invention relates to hook tape for mechanical fasteners used for holding substrates. BACKGROUND OF THE INVENTION Conventional carpet includes one or more pieces cut to cover a selected area. In many residential applications, the perimeter of the carpet is generally fixed in position by tack strips, strips of wood nailed or glued to the floor and having upstanding spikes, which can be oriented, to penetrate the lower surface of the carpet and hold it in position. In many commercial applications, the entire carpet is generally glued to the concrete subfloor. U.S. Patent No. 4,822,658 discloses a carpet fastening system in which the carpet is fastened to the floor using hook and loop fasteners. The looped half of the fastening system is located on the carpet backing and the hooked half is located on the floor. The hooked half can be in the form of a tape that is nailed, stapled, or adhered to the floor around the perimeter of the floor. For larger areas, more than one piece of carpet is joined together to make a sheet sufficiently large to cover the area. Seams of these carpet sheets are conventionally joined by stitching the edges together or by taping the edges together such as by adhesive tape like hot melt tape. In the conventional carpet laying procedures, in seaming the edges of the two pieces of carpet which are to abut each other, one must take great care to make sure the seam is not impaired by extraneous matter. This extraneous matter can be loose threads, carpet fragments, or other detritus. It is difficult to avoid small amounts of pile being turned downwardly to be caught in the seam and damaging the continuous surface of pile on the upper side of the carpet and impairing the perfection of the joint between the carpet edges. The '658 patent, as well as U.S. 5,191,692, also discusses using hook and loop fasteners along the seams of the carpet when more than one piece of carpet is used to cover an area. A temporary cover for the hook tape is used to prevent the carpet or unwanted surfaces from contacting the hooks before the carpet is to be finally attached to the floor. U.S. 5,479,755 discloses a method of installing carpet using hook and loop fasteners by applying water to the carpet to expand the carpet, attaching the carpet to the hooks while wet, and allowing the contraction of the carpet as it dries to enhance the attachment of the looped back carpet to the hooks. Conventional hook and loop fasteners are also used at the carpet seams. Many other disclosures of hook and loop fasteners are known. For example, U.S. 5,300,058 discloses various embodiments of fasteners having hooks oriented in particular and plural directions. U.S. 5,505,747 discloses hooks having various diverse shapes. None of these references or technologies suggests anything about using oriented hook tape to secure carpet seams. There is a need for a hook tape that creates a tight seam and prevents relative movement in the sections of carpet without raising the carpet at the seam. There is a need for such a hook tape in which the seam and the tape are hidden under the carpet, and in which the carpet can be adjusted and repositioned without the tape requiring using any covering material for the hook material. SUMMARY OF THE INVENTION The invention is a substrate which is joinable to at least two sheets along at least one edge of each sheet to join the sheets together along the at least one edge to create a seam or joint. The invention is also a method of joining. The substrate has first and second longitudinal edges and a first substantially central longitudinal axis. This axis divides the substrate into a first portion between the first longitudinal edge and the first longitudinal axis and a second portion between the second longitudinal edge and a longitudinal location located along a line that is between the second longitudinal edge and up to the first longitudinal axis. The substrate includes a plurality of hooks formed in both the first and second portions such that substantially all of the hooks in the first portion and in the second portion are oriented to face the first longitudinal axis at an angle with the first longitudinal axis. The substrate can optionally have a second substantially central longitudinal axis located between the first longitudinal axis and the second longitudinal edge. The second portion is located between the second longitudinal edge and the second longitudinal axis, and the substrate has a third portion located between the first and second longitudinal axes. The substrate can optionally include additional hooks in the third portion. The hooks can be one of: uni-directional hooks facing the first longitudinal axis, uni- directional hooks facing the second longitudinal axis, bi-directional hooks, and both uni-directional and bidirectional hooks. Also, the substrate can have additional regions beyond the first and second portions with additional hooks there. Again, these hooks can be one of: uni-directional hooks facing the first longitudinal axis, uni-directional hooks facing the second longitudinal axis, bi-directional hooks, and both uni-directional and bi-directional hooks. The sheets can be one of floor coverings, wall coverings, billboard coverings, drum coverings, column coverings, fabrics, surgical drapes, belts, and roofing materials. The sheets can be flexible or inflexible, and formed of the same or of different materials. In one embodiment, the sheets are sections of carpet and the substrate is a tape. Also, the substrate can have a hook density of 31-310 hooks/cm 2 . Also, the substrate can create shear force ratios greater than 6. The substrate can be joinable to at least one section of a sheet along at least one edge of the section to affix the sheet to an object along the at least one edge, without joining two sections. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a top view of a hook tape according to the present invention. Figure 2 is a side sectional view taken along line 2-2 of Figure 1. Figure 3 is a top view of a hook tape according to another embodiment of the present invention. Figure 4 is a side sectional view taken along line 4-4 of Figure 3. Figures 5 and 6 are side views illustrating further hook shear strength test steps. Figures 7a-7r are cross-sectional views of various hook shapes. Figures 8a-8d are cross-sectional views of other hook-shaped die cavities. Figure 9 is a schematic view of an apparatus for making hook tape according to the present invention. Figure 10 is a schematic view of another apparatus for making hook tape according to the present invention. Figure 11 is a top view of a sample of hook tape used for an experiment. Figure 12 is a cross-sectional view of the sample of Figure 11. Figure 13 is a cross-sectional view of another sample of hook tape used for another experiment. DETAILED DESCRIPTION The invention is an article, such as a substrate, which uses uni-directional engaging members, such as hooks, to seam work pieces, such as carpet, together and to hold them over a holding surface, such as a floor, wall, or ceiling. The substrate is joinable to at least two sheets along at least one edge of each sheet to join the sheets together along the edge to create a seam or joint. A bi-directional hook array is an array of hooks that have a shear ratio close to 1. A uni-directional hook array is an array of hooks that have a shear ratio greater than 1. The shear ratio is determined by the test procedure explained below. In the illustrated embodiments the substrate is a hook tape and is used, as shown, to fasten planar sheets like floor coverings such as carpet to a floor. As shown in Figures 1 and 2, the hook tape 10 has a first longitudinal edge 12, a second longitudinal edge 14, and a first substantially central longitudinal axis 16. This longitudinal axis (which can be but need not be at the center of the hook tape 10) divides the hook tape into a first portion 18 between the first longitudinal edge 12 and the first longitudinal axis 16 and a second portion 20 between the second longitudinal edge 14 and a longitudinal location located along a line that is between the second longitudinal edge and up to the first longitudinal axis. For example, the first longitudinal axis 16 can be centrally located and the first and second portions 18, 20 can each extend for half of the hook tape 10. As shown, the second portion is defined at one side by a second longitudinal axis 22 which is spaced from the first longitudinal axis 16. The area between the first and second longitudinal axes 16, 22 defines a third portion 24. The hook tape 10 includes a plurality of hooks 26, which can optionally be formed in a two-dimensional array, such that substantially all of the hooks 26 in the first portion 18 and in the second portion 20 are oriented to both face the first longitudinal axis 16, as best shown in Figure 2. The hooks 26 can face the first longitudinal axis 16 at a right angle with the first longitudinal axis or at any other angle. For example, angles from 30°-90° (up to 60° from orthogonal) with the first longitudinal axis can be used. The hook orientations can vary. There is no restriction on whether the hooks twist, tip, droop, or are otherwise skewed. Also, the orientation of the hooks need not be identical. As shown in Figures 3 and 4, the hook tape 30 can have a set of hooks in the third portion 24 between the first and second longitudinal axes 16, 22. This hook tape 30 includes a plurality of bi-directional hooks 27 located in the third portion 24. Some hooks 27 in the third portion 24 are oriented to face the first longitudinal axis 16 and other hooks 27 are oriented to face the second longitudinal axis 22 such that hooks 27 in the third portion 24 face each other. As is evident from the embodiments of Figures 1-4, the common feature of this invention in all embodiments is at least one portion of uni-directional hooks. When seaming or joining two sheets, it is desirable to have opposing sets of uni-directional hooks. Given this, there are many different additional supplementary hook configurations. The opposing uni-directional hooks can abut each other or there can be a central space between them. In this central space can be no hooks, unidirectional hooks facing in either direction, bi- directional hooks, or both uni-directional and bidirectional hooks. Similarly, in each of the two regions beyond the uni-directional hooks on the side of the hooks opposite the seam, there can be no hooks, uni-directional hooks facing in either direction, bi- directional hooks, or both uni-directional and bidirectional hooks. Any combination of additional hooks or additional regions can be used. The hook tape can be used to seam, or simply to affix, floor coverings, wall coverings, drum coverings, column coverings, fabrics, surgical drapes, belts, such as conveyor belts and abrasive belts, and roofing materials to itself, to another covering or sheet, or to a support surface. In other words, sheets, such as carpeting can be secured to a surface at edges of the sheets that do not connect to other sheets, using the hook tape of this invention. The hook tape is not limited to seaming applications. The hook tape can be used with rigid or flexible sheets, and two sheets of dissimilar materials or construction can be used. The hook tape can have a hook density of 31-310 hooks/cm 2 (200-2000 hooks/in 2 ) , although higher and lower densities also can be used. The hook tape can have a hook having an overall length of from approximately 0.13 mm to 2.60 mm. Other size hooks can be used depending on the application. The hooks can be formed of an organic material such as a thermoplastic material or a thermosetting material. The thermoplastic material can include polyethylenes, polypropylenes, polyurethanes, polyamides, polyolefins, polyesters, and combinations of these materials. The hook material can also include additives such as fillers, fibers, antistatic agents, lubricants, wetting agents, surfactants, pigments, dyes, coupling agents, plasticizers, flame retardants, and suspending agents. The shape of the hooks is not critical as long as the hooks can be arranged uni-directionally. The shape can be any shape such as those shown and described in U.S. Patent No. 5,505,747. Some of these shapes are shown in Figures 7i, 7o, 7p, 7q, and 7r. (The remainder of the shapes shown in Figure 7 can be used in the third portion of the hook tape.) Additional hook-shaped die profiles for making uni-directional hooks are shown in Figures 8a-8d. In one embodiment, the hooks can have at least one head provided on a stem, as shown in the side views illustrated in Figures 7a-7n. The head can also, or instead, be provided at other locations along the stem, as shown in Figures 7k and 71, for example. A head means any structure that extends radially beyond the periphery of the stem in at least one direction. The head can have any suitable three-dimensional shape, such as, for example, a hemisphere, a sphere, a cube, a mushroom cap, a cylinder, a cone, a pyramid, a disc, or a barb. It is preferred, although not required, that the head have at least one undercut portion that extends away from the stem at approximately a 90° angle, such as the heads shown in Figures 7a, 7b, 7e, 7f, 7g, 7i, 7j, and 7k, to engage the engaging structure of an opposed mating surface. It is also possible to provide a head having portions that extend toward the base of the stem, creating an "underhang" portion of the head. In other embodiments, each stem is provided with two or more heads, the shape of which may be selected as desired. In the embodiment of Figures 7o-7r, the hooks have an included distal end angle of less than approximately 90°. The included distal end angle α, is defined as the included angle between a straight line perpendicular to the second major surface at the proximal end of the hook (line LI) and a straight line extending through and concentric with the distal end of the hook (line L2) . When angle α is less than approximately 90°, the distal end of each hook is adapted to engage an engaging structure of an opposed surface, and yet may be released from that structure by an appropriate tensile force. The hooks can be made of various materials. The hooks can be cast, molded, extruded or coextruded, printed, or woven from plastic. The hook tape components can be the same or different materials. The hook tape of Figures 1-4 can be made integrally as one piece. Alternatively, these hook tapes can be made of multiple pieces, such as separate first, second, and third portions. These multiple pieces can be fastened together in any known manner. For example, they can be attached or joined such as by sewing, stapling, bonding, or welding to each other; or they can be attached or joined to a surface on which the sheets are to be seamed together. Both one piece and multiple piece hook tape constructions fall within the definition of the claimed substrate. One feature of this invention is using hooks that are uni-directional; hooks that, in a given portion of the hook tape, face the same crossweb direction. Although all of the hooks in a given portion need not face this direction, it is better if most or all do. Another feature of this invention is the ability to slide the sheet across the hooks of the tape in one direction, toward the seam, which allows the user to apply pressure to the sheets at the seam. This then fully extends the loops of the sheet to eliminate the movement or play that is inherent in hook and loop attachment systems. With a conventional system that uses only bi-directional hooks, such as 4,822,658, this is not possible without damaging the hooks or loops. The best way to eliminate the hook and loop play is install the sheet, such as carpet, so that the loops are extended to their full length. This can best be done by peaking the carpet at the seam before engagement of the fastening members. With only bidirectional hooks a separation device must be used, such as a piece of cover tape that would prevent engagement, as described by U.S. 5,191,692. This is a cumbersome process because after the cover tape is removed engagement is achieved. Realignment is not possible without fully removing the carpet from contact with the hooks, which can result in hook or loop damage. There is also a potential for seam gapping caused by the carpet shifting before the cover tape is removed. With uni-directional hooks the engagement may be ratcheted as tightly as the installer desires. A gapped seam may be corrected by "bumping" the carpet with a tool similar to a "Deluxe Knee Kicker" model 10-412 or by using a "Mini-Stretcher with Seam Repair Kit" model 10-117 both of which are available from Roberts Consolidated Industries Inc., City of Industry California. This type of operation can be done easily with uni-directional hooks. There needs to be enough extra carpet at the seam so that when the carpet is brought down onto the hooks, each edge of the carpet will be pushed away from the seam. As the carpet is pushed away from the seam it will engage to a very high level with the uni-directional hooks. The movement or play between the engaged hook and loop fastening members is caused by the ability of the loops to move back and forth after engagement without having much shear force placed upon the seam. If the loops are first tensioned at the seam by extending them to the end of their natural play, this hook and loop play is eliminated because the fastening members stay under tension. Another advantage of this uni-directional hook tape is that the carpet can be repositioned to correct gaps that may occur after the initial carpet installation. Gapped seams can readily form from slight movement of the carpet due to changes in the humidity. This causes the carpet to swell or shrink. Previously designed hook tapes cannot easily correct seam gapping because after engagement of the fastening members they cannot be laterally moved without damaging the engaging members. The conventional way to repair a gapped seam is to cover the hooks before reinstallation. This is a laborious exercise and does not insure that the seam will remain correctly butted. This uni-directional hook tape where the hooks of the first and second sections face the same direction is also useful around the perimeter or edge of a sheet for affixing the sheet to another sheet or to a support surface. Examples of this include transitions among carpet, vinyl, and tile, or the edges of carpet. This hook tape can be used to adjustably secure any covering on any object, and can be used on non-planar objects, such as, for example, upholstery on furniture where the covering is wrapped around the object. Example 1 A hook tape of the invention was made as follows, with hooks being fabricated generally in accordance with the teachings of U.S. Patent No. 4,894,060 (Nestegard) , using an apparatus and process such as that shown in Figure 9 (which is described in detail in U.S. Patent No. 5,505,747 and shown in its Figure 6, whose specification is incorporated by reference) . An extrusion die included a die opening adapted to form elongate rail fastener members having a base sheet and a plurality of rails projecting from the base sheet as shown in Figure 2. A random polypropylene copolymer available from Union Carbide under the designation U7C06 was heated to a temperature of approximately 248°C (478°F) and extruded using a 63.5 mm single screw extruder available from Killion. The extruder was operated at 95.2 rpm to produce an output speed of approximately 7.7 m/min (25.1 ft/min) through the die opening to form the rail fastener members. The cross-sectional profile of the rail members generally resembled the design shown in Figure 8a. The rail fastener was quenched in water at 8.3°C (47°F) and allowed to cool for approximately 20 seconds to promote solidification of the rails and the base sheet. Referring to Figure 8a, the rails measured 0.97 mm (0.038 in) wide from the tip of hook profile to back of the hook base (dimension a) , and were spaced at approximately 1.524 mm (0.060 in) as measured from the center of the base of the hooks (dimension b) . The thickness of the base sheet was approximately 0.18 mm (0.007 in) (dimension c) . The rails were cut transversely using a high speed rotary blade to approximately 0.318 mm (0.0125 in) (dimension d) , drawn over a roll heated to a temperature of approximately 160°C (320°F) , and stretched in the machine direction to a ratio of approximately 2.6 to 1 to form a multitude of discrete hooks. After stretching, the resultant hooks were 0.58 mm (0.023 in) high (including the thickness of the base sheet (dimension e) , were spaced at approximately 0.94 mm (0.037 in) from the center of the base (dimension b) , and the thickness of the base sheet (dimension c) was approximately 0.084 mm (0.0033 in). An adhesive transfer tape (Scotch brand VHB™ 950 5 mil transfer tape, commercially available from Minnesota Mining and Manufacturing Company St. Paul, MN) was hand laminated using a rubber roller to the non hook side of the base sheet to form a hook tape of the invention. Example 2 A second hook tape of the invention was prepared using the materials and the procedure of Example 1 except that the extrusion die included a die opening adapted to form a rail fastener member having a base sheet and a plurality of rails projecting from the base sheet as shown in Figure 8b. The rails measured 0.84 mm (0.033 in) wide from tip of hook profile to back of hook base (dimension a) , and were spaced at approximately 1.524 mm (0.060 in) from center to center of the hook base (dimension b) . The thickness of the base sheet was approximately 0.25 mm (0.010 in) (dimension c) . The rail members were cut and stretched as in Example 1 to form a multitude of discrete hook members. After stretching, the resultant hook were 0.74 mm (0.029 in) high (includes the thickness of the base sheet) (dimension e) , were spaced at approximately 0.94 mm (0.037 in) (dimension b) , and the thickness of the base sheet was approximately 0.1 mm (0.004 in) (dimension c) . The adhesive transfer tape of Example 1 was hand laminated using a rubber roller to the non hook side of the base sheet to form a hook tape of the invention. Example 3 A third hook tape of the invention was prepared using the materials and the procedure of Example 1 except that the extrusion die included a die opening adapted to form a rail fastener member having a base sheet and a plurality of rails projecting from the base sheet as shown in Figure 8c. The rails measured 0.84 mm (0.033 in) wide from tip of hook to back of the hook base (dimension a) , and were spaced at approximately 1.524 mm (0.060 in) from the center to center of the hook base (dimension b) . The cross- sectional profile of the rail members generally resembled the design shown in Figure 8c and are arranged as in Figure 2. The thickness of the base sheet was approximately 0.23 mm (0.009 in) (dimension c) . The rail members were cut and stretched as in Example 1 to form a multitude of discrete hooks. After stretching, the resultant hooks were 0.69 mm (0.027 in) high (includes the thickness of the base sheet (dimension e) , were spaced at approximately 0.94 mm (0.037 in) (dimension b) , and the thickness of the base sheet was approximately 0.1 mm (0.004 in) (dimension c) . The adhesive transfer tape of Example 1 was hand laminated using a rubber roller to the non hook side of the base sheet to form a hook tape of the invention. Example 4 Preparation of a hook tape with only one portion of the tape having uni-directional hooks with the hook profile of Figure 8d was made as follows. The hooks were fabricated generally in accordance with the teachings of U.S. Patent No. 5,058,247 (Thomas et al . ) , the contents of which is incorporated herein by reference, using an apparatus and process such as that shown in Figure 10 (which is described in detail in U.S. Patent No. 5,505,747 and shown in its Figure 7, whose specification is incorporated by reference) . The mold used to form the hooks was a gravure roll. The surface of the gravure roll included a plurality of frustoconical cavities, with a diameter at the roll periphery of 1.0 mm (0.04 in) and a depth of about 0.5 mm (0.02 in). The grid density was about 50 cavities/cm 2 (325 cavities/in 2 ) . A polyester hot-melt adhesive available from Bostik Company of Middleton, Mass. under the designation 7199 was extruded onto the gravure roll at a melt temperature of approximately 220°C (428°F) . The gravure roll was maintained at a temperature of approximately 180°C (356°F) during coating. A 0.02 mm (0.0009 in) thick polyester web made internally by the Minnesota Mining and Manufacturing Company, similar to that sold by Imperial Chemical Industries Americas, Inc. of Wilmington, Delaware under the designation Type S, was conveyed adjacent the gravure roll, such that the gravure roll printed the hot-melt adhesive onto the polyester web. The surface speed of the gravure roll at the printing interface was approximately 6 to 8 m/min (20 to 26 ft/min) . As the polyester web separated from the gravure roll, the molten polyester adhesive was suspended between each of the cavities and the web, and was severed by a heated wire made of an alloy of nickel, iron, and chromium. The position of the heated wire should allow for the formation of the desired hook shape. The exact location of the heated wire depends on the operating process parameters and environmental conditions. Typically, the hot wire was disposed approximately 39 to 47 mm (1.56 to 1.88 in) from the nip point in the machine direction, and approximately 4.8 to 7.9 mm (0.19 to 0.31 in) radially outward of the backing roll, and approximately 1.5 to 4.8 mm (0.06 to 0.19 in) radially outwardly from the print roll. This produced hooks having a cross-sectional profile as shown in Figure 8d. The adhesive transfer tape of Example 1 was hand laminated using a rubber roller to the non hook side of the base sheet. Experiment 1 An initial experiment was done to prove the concept of the uni-directional hook in reducing seam gapping. Simulated seams were prepared using a hook tape test sample 40 (see Figure 11) composed of various hook tapes outlined in Table 1 below and 2.54 cm (1 in) wide by 17.8 cm (7 in) long pieces of loop backed carpet 42 (Lee's Commercial Carpet "Faculty IV" style number DK167, commercially available from Lee's, a division of Burlington Industries, Inc., Greensboro, NC) cut with the 17.8 cm (7 in) dimension in the machine direction. Each hook tape test sample was 25.8 cm 2 in area and was adhered to a 5.1 cm wide x 12.7 cm long x 0.95 cm thick (2 in x 5 in x 3/8 in) low density polyethylene (LDPE) panel . The hook tapes were arranged on a panel 44 as shown in Figure 11 to form a hook tape test sample 40. A seam 46 was then made by overlaying two pieces of carpet 42 onto the hook tape sample 40 as shown in Figure 12. A 1 kg weight 48 was then suspended from one of the free ends of the carpet strip 42. After 30 minutes the amount of seam 46 gap between the two carpet strips 42 was measured. In the samples, there were two equal (6.45 cm 2 ) portions of hook tape, A and B, on each side of the seam location, as shown in Figure 11. Comparative Sample 1 is an example of a known bi-directional hook tape seaming system. Sample 2 is an example of the second embodiment of the invention shown in Figures 3 and 4. Sample 3 is an example of the invention with the uni-directional hooks extending to the center of the hook tape. Table 1 shows the materials used for the portions A and B and reports the resulting seam gap. Table 1 * SJ3510 is SJ3510 High Tack Single Liner 3M Hook Tape, commercially available from Minnesota Mining and Manufacturing Company, St. Paul MN. The hooks on this tape are bi-directional; they face both toward the seam and away from the seam. The tape has a liner which covers the hooks and which is removed before engaging the loops. The data show that when a uni-directional hook tape was used (Sample 2 and Sample 3) there was less seam gap than for the bi-directional hook tape (Comparative Sample 1) . Experiment 2 A second experiment was performed to determine the effect of uni-directional hook tape on seam gapping. The carpet used was Mohawk "Basic El ements" carpet with the Scott and Fyfe Loop style number 336.17.02 (Scotscraig Works, Tayport, Fife, Scotland) on the back, manufactured by Mohawk, Dublin, GA. The carpet was cut 7.6 cm (3 in) wide in the cross direction. Four hook tape test samples were constructed as follows. In the samples, there were two portions of hook tape, A and B, on each side of the seam location, as shown in Figure 13. Samples 1 and 2 are similar except for the length of the portion A. They represent a known bidirectional hook tape seaming system. Sample 3 is similar to the second embodiment of the invention shown in Figures 3 and 4. Sample 4 is similar to the first embodiment of the invention shown in Figures 1 and 2. The specific sample compositions (with the lengths of the hook portions in cm) are shown in Table 2. Table 2 * SJ3508 is SJ3508 Low Tack Single Liner 3M Hook Tape, available from Minnesota Mining and Manufacturing Company, St. Paul, MN. The hooks on this tape are bi- directional; they face both toward the seam and away from the seam. The tape has a liner which covers the hooks and which is removed before engaging the loops. The hook tape test samples 40 were attached to a subfloor 52 as shown in Figure 13. Each strip of carpet 42 was fastened on one end to the subfloor 52 using 10.2 cm (4 in) of SJ3508 tape as perimeter tape 50 as shown in Figure 13. The carpet measured 125 cm (49 in) from the inside edge of the perimeter tape 50 to the center of the seam 46 or hook tape test sample. Before using, the carpet strips were hydrostabilized according to the hydrostabilization procedure described in U.S. Patent No. 5,479,755. Approximately 1 gallon of tap water was used to wet all eight carpet strips. This amount of water kept the carpet wet to the touch for 90 minutes. After 90 minutes, a first carpet strip 42 was engaged with one half of a hook tape test sample. A second carpet strip 42 was engaged with the remaining half of the hook tape test sample 40, abutting the first carpet strip. Then both perimeter tapes 50 were engaged. After 24 hours and after 4 days, the seam gap of the two carpet strips was measured. The results are reported in Table 3 below. Table 3 These data show that the seam with all uni- directional hooks (Sample 4) gave the least amount of seam separation after 4 days and therefore has the most shear force of the hook tape test samples. It was observed that the carpet was still damp to the touch after 24 hours. Experiment 3 The shear strength of the hooks of a hook tape of the invention was measured for a shearing force applied in the direction of the hooks (as in Figure 6) and for a shearing force applied in the direction opposite the hooks (as in Figure 5) . Modified test method ASTM D5169, entitled "Test method for shear strength (dynamic method) of hook and loop touch fasteners", (November 1991, volume 07.02 of the annual book of ASTM standards) was used to provide the shear strength and to calculate the shear force ratio. A 5.1 cm (2 in) wide x 2.54 cm (1 in) long piece of the hook tape to be tested was applied to a 5.1 cm (2 in) x 7.6 cm (3 in) aluminum panel. Several 10.4 cm (4 in) wide tapes of Examples 1, 2, and 3 were cut in half to provide the 5.1 cm (2 in) wide x 2.54 cm (1 in) pieces. A 2.54 cm (1 in) wide x 10.2 cm (4 in) long strip of loop-backed carpet (Lee's Commercial Carpet "Faculty IV" style number DK167, commercially available from Lee's, a division of Burlington Industries, Inc., Greensboro, NC) cut with the 10.2 cm (4 in) dimension in the cross direction was overlapped and engaged with the hook tape in two different orientations to form the test samples. The shear Force F c was measured on a sample in which the hook direction was counter to the direction of separation, as shown in Figure 5. The shear Force F a was measured on a sample wherein the hook direction was aligned with the direction of separation, as shown in Figure 6. Each test sample was tested using an Instron Tensile Tester at a crosshead speed of 30.5 cm/min (12 in/min) and the peak shear force required to break the bond between the hooks and loops was recorded in lb/in 2 and converted to kg/cm 2 . The shear force ratio was calculated as the ratio of F c to F a . The data is reported in Table 4 below. (Three replicates were run to generate each data point.) Table 4 (1) ULTRA-MATE HTH #811 Hook 9914, bi-directional hook tape available from VELCRO USA, INC. Manchester New Hampshire . (2) ULTRA-MATE HTH #805 Hook 9999, bi-directional hook tape available from VELCRO USA, INC. Manchester New Hampshire, with an adhesive transfer tape, available from Minnesota Mining and Manufacturing Company St. Paul, MN, under the designation Scotch brand VHB™ 950 5 mil transfer tape hand laminated to the non hook side of the tape. It is clear from the data that the uni-directional hook tape has significantly higher shear force ratios than bi-directional hook tapes. This allows sliding in one direction to apply pressure toward the seam which will extend the loops of the sheet and eliminate the movement or play prevalent in hook and loop attachment systems. The uni-directional tapes have very low resistance to sliding when the loop substrate is in an aligned direction with the hooks, and a very high resistance to sliding when the shear direction is counter to the hooks. The bi-directional tapes have relatively high shear strength in both shear directions. Experiment 4 Installation of wall paper using hook tape was simulated on a wall made of 5 mm (0.375 in) thick plywood sheets screwed to a wood frame. The area to be covered was 1.83 m (6 ft) high and 1.56 m (61.5 in) wide. Various hook tapes were applied to the plywood wall and a loop tape was applied to the wall paper. Vertical centering lines were drawn on the plywood wall at a distance of 52.1 cm (20.5 in), 104.2 cm (41 in), and 156.3 cm (61.5 in) as measured from the right edge of the plywood wall. The plywood surface was primed by brushing on one coat of "Polycrylic Protective Finish" available from Miniwax® Company, Inc., Montvale, NJ in the areas where the hook tapes were to be applied. The finish was allowed to dry completely before attaching the hook tapes . A 5 cm (2 in) wide tape that was one-half of the 10.1 cm (4 in) hook tape of Example 1 was applied to the primed plywood across the total length of the top edge and down the total length of the right edge of the wall with the hooks pointing toward the edge and away from the center of wall. The hook tape was covered with a cover strip of 5.1 cm (2 in) wide Guilford Loop style 32275 to prevent premature engagement of the hook and loop. A 10.2 cm (4 in) wide hook tape of Example 1 was centered on the 52.1 cm (20.5 in) line, with 5.1 cm (2 in) on each side of the line, the liner was removed, and the tape was applied with a rubber roller. The hook tape was covered with a cover strip of 10.2 cm (4 in) wide Guilford Loop style 32275 to prevent premature engagement of the hook and loop. A 10.2 cm (4 in) wide piece of SJ3510 3M Hook Tape was centered on the 104.2 cm (41 in) line, applied with a rubber roller. A 5.1 cm (2 in) wide piece of SJ3510 3M Hook Tape was aligned on the inside of the 156.3 cm (61.5 in) line, applied with a rubber roller. A loop tape was prepared using Loop style number 32275 manufactured by Guilford Mills, Inc., Greensboro, NC and adhesive transfer tape, available from Minnesota Mining and Manufacturing Company, St. Paul, MN, under the designation Scotch brand VHB™ 950 5 mil transfer tape hand laminated using a rubber roller to the back side of the loops, cut into strips approximately 5 cm (2 in) wide. The loop strips were hand laminated to the perimeter edges of the back of the wall paper sheets (Luxury Textured Vinyl, 52.1 cm (20.5 in) wide manufactured by Graham and Brown, Harwood Street, Blackburn BB1 3DB England, under the tradename "Super Fresco" Pattern 12718 lot #020) that were cut to approximately 213 cm (7 ft) lengths. The wall paper with loop tape attached was rolled up to form a roll. Three sheets of wall paper were then attached to the wall using the following general procedure: a wall paper roll was centered between two longitudinal pieces of hook tape. The loop tape on the top edge of the wall paper was engaged to the hook tape on the top edge of the wall by hand rubbing and the roll was allowed to unwind. The cover strip was removed from the first longitudinal piece of hook tape and the wall paper was engaged by hand rubbing to the hooks. The cover strip (if present) was removed from the second longitudinal piece of hook tape and the wall paper was engaged by hand rubbing to the hooks . A first sheet of wall paper was attached to the wall between the right edge of the plywood and the 52.1 cm ( 20.5 in) line using the above procedure. A second sheet of wall paper was attached to the wall between the 52.1 cm (20.5 in) line and the 104.2 cm (41 in) line using the above procedure except that the cover strip was removed and the hooks engaged approximately 30.5 cm (1 ft) at a time. A tight seam between the first and second wall paper sheets was made by pushing the two abutting wall paper sheets together. A third sheet of wall paper was attached to the wall between the 104.2 cm (41 in) line and the 156.3 cm (61.5 in) line using the same procedure as used for the second sheet. A seam between the second and third wall paper sheets was made by pushing the two abutting wall paper sheets together. The seam gap was greater where SJ3510 3M Hook Tape used than for the seam made with the hook tape of Example 1 because the sheets could not be easily slid together. It was concluded that the uni-directional hook tape has the advantage of being able to align the wall paper sheets to correct a gapped seam without fully disengaging from the hooks of the hook tape.

Claims: CLAIMS 1. A substrate 10, 30, which is joinable to at least one section of a sheet along at least one edge of the section to affix the sheet to an object along the at least one edge, wherein the substrate comprises a plurality of hooks 26 such that substantially all of the hooks face in the direction toward the edge of the sheet . 2. The substrate 10, 30, of claim 1 wherein the object is another sheet and the substrate is joinable to at least two sheets along at least one edge of each sheet to join the sheets together along the at least one edge to create a seam, wherein the substrate has first and second longitudinal edges 12, 14, and a first substantially central longitudinal axis 16 dividing the substrate into a first portion 18 between the first longitudinal edge and the first longitudinal axis and a second portion 20 between the second longitudinal edge and a longitudinal location located along a line that is between the second longitudinal edge and up to the first longitudinal axis, wherein the substrate comprises a plurality of hooks 26 formed in both the first and second portions 18, 20 such the shear force ratio is at least 6. 3. The substrate 10, 30 of claim 1 wherein the object is another sheet and the substrate is joinable along at least one edge of each sheet to join the sheets together along the at least one edge to create a seam, wherein the substrate 10, 30 has first and second longitudinal edges 12, 14 and a first substantially central longitudinal axis 16 dividing the substrate into a first portion 18 between the first longitudinal edge and the first longitudinal axis and a second portion 20 between the second longitudinal edge and a longitudinal location located along a line that is between the second longitudinal edge and up to the first longitudinal axis, wherein the substrate comprises a plurality of hooks 26 formed in both the first and second portions such that substantially all of the hooks in the first portion 18 and in the second portion 20 are oriented to face the first longitudinal axis 16. 4. The substrate of 10, 30 claim 3 wherein the sheets are sections of carpet, wherein the substrate creates a tight seam and prevents relative movement in the sections of carpet without raising the carpet at the seam, wherein the seam and the substrate are hidden under the carpet, and wherein the substrate does not require using any covering material for the hook material during installation of the carpet. 5. The substrate 10, 30 of claim 3 wherein the substrate has a second substantially central longitudinal axis 22 located between the first longitudinal axis 16 and the second longitudinal edge 14, wherein the second portion 20 is located between the second longitudinal edge and the second longitudinal axis, wherein the substrate has a third portion 24 located between the first and second longitudinal axes, wherein the substrate further comprises additional hooks 26 in the third portion 24 which are one of: uni-directional hooks facing the first longitudinal axis, uni-directional hooks facing the second longitudinal axis, bi-directional hooks, and both uni-directional and bi-directional hooks. 6. The substrate 10, 30 of claim 3 wherein in each of two regions beyond the first and second portions 18, 20 on the side of the hooks 26 opposite the seam, there are additional hooks which are one of: uni-directional hooks facing the first longitudinal axis, uni-directional hooks facing the second longitudinal axis, bi-directional hooks, and both unidirectional and bi-directional hooks. 7. A method of joining at least first and second sections of carpet on a floor along at least one edge of each section to abut and join the sections together along the at least one edge to create a seam, the method comprising: placing a substrate 10, 30 on the floor at the desired location of the seam, wherein the substrate has first and second longitudinal edges 12, 14 and a first substantially central longitudinal axis 16 dividing the substrate into a first portion 18 between the first longitudinal edge and the first longitudinal axis and a second portion 20 between the second longitudinal edge and a longitudinal location located along a line that is between the second longitudinal edge and up to the first longitudinal axis, wherein the substrate comprises a plurality of hooks 26 formed in both the first and second portions 18, 20 such that substantially all of the hooks in the first portion and in the second portion are both oriented to face the first longitudinal axis, wherein the substrate creates a tight seam and prevents relative movement in the sections of carpet without raising the carpet at the seam, wherein the seam and the substrate are hidden under the carpet, and wherein the substrate does not require using any covering material for the hook material during installation of the carpet; placing the first section of carpet on the substrate; placing the second section of carpet on the substrate such that the at least one edge creates a seam; pressing the first and sections of carpet onto the substrate; and adjusting at least one of the sections of carpet on the substrate without removing the carpet from the substrate.

Inventors: BURLEIGH MALCOLM B, ECKHARDT CAREY J, FALLENSTEIN GARNETT T JR, MONTGOMERY RALPH L, NARUM TIMOTHY N, SCHRAEDER BETH A, BURLEIGH, MALCOLM, B., ECKHARDT, CAREY, J., FALLENSTEIN, GARNETT, T., JR., MONTGOMERY, RALPH, L., NARUM, TIMOTHY, N., SCHRAEDER, BETH, A.
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1998
Main classification: A47G27
IPC codes: A44B18, A47G27