Abstract:
A method and tool for repairing worn seams in sheet materials, such as linoleum or vinyl floor coverings, is disclosed. The tool is a specially constructed, double bladed utility knife. The tool has dual cutting blades that are rigidly secured to the tool for precision cutting. The blades are set at a slightly divergent angle relative to one another, and the distance between the blades is adjustable. The tool may be used to repair a damaged seam in a floor covering as follows. First, the blades are set to span the widest portion of the damaged portion of the seam. Cutting pressure is applied and the tool is drawn along the seam to remove the damaged portion. The blades are then adjusted to a slightly wider-apart position, and the tool is used in a similar manner to cut a repair piece from a matching piece of material. The repair piece is then adhered to the floor and will fit snugly between the adjoining pieces of material to accomplish a perfect repair of the seam.

Description:
This application is a division of application Ser. No. 09/503,974, filed Feb. 14, 2000, now U.S. Pat. No. 6,308,422. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     My invention relates to tools and methods for repairing seams in certain types of sheet materials. More particularly, my invention relates to repairing seams in pliable sheet materials that are used as functional and decorative surface coverings, such as linoleum or vinyl floor coverings. Such materials are adhered to the surface (usually a floor) that is to be covered. Butt seams are used to join separate pieces of such materials when the desired area cannot be covered by a single piece. Hereinafter, I use the term “sheet materials” to refer only to pliable sheets of materials that are relatively smooth on both major surfaces, such as sheets of vinyl and other polymeric materials, and laminates thereof. I use “floor coverings” to refer only to such sheet materials that are used to cover floors, excluding rigid flooring such as wooden laminates or ceramic tiles, and excluding textiles such as carpeting. 
     2. Description of the Related Art 
     When abutting pieces of floor covering are seamed together and glued in place, the seam will often degrade over time because of exposure to traffic, moisture, cleaning chemicals, and dirt. Contamination will eventually penetrate the seam and degrade the adhesive holding the floor covering to the floor at the seam. When the adhesive becomes degraded, the floor covering will lift from the floor at the seam, lending the seam an unsightly puckered appearance and making the seam more vulnerable to further damage. In order to repair the damaged portion of the seam, it is usually necessary to carefully cut out and replace it with a fresh patch of matching material. The patch must match the removed portion&#39;s pattern and shape perfectly, or the repair will be visible. 
     Currently, no tools like my invention are available for repairing seams in floor covering materials. A craftsperson must make do with conventional cutting tools, such as construction knives and straight edges to accomplish the precision repair job required. It is very difficult to exactly match the shape and decorative pattern of the patch to that of the removed portion. It is especially difficult to exactly match the edge surfaces of the patch to the edge of the removed portion so that the resulting butt seam will be as good as the original. To make a perfect seam, a craftsperson must cut the patch to exactly match the removed portion not only in the two-dimensional geometry of the floor, but also along the third dimension defined by the sheet thickness along its edge. A mismatch in any dimension will create a weakness or visible imperfection along the edges of the patch. Consequently, only the most skilled craftspeople are able to repair the seam so that the patch is both invisible and durable, and only by the exercise of great care. 
     Various double-bladed knifes, scalpels, and cutting tools exist for cutting various materials, and some of these double-bladed tools may be capable of cutting floor coverings. However, no existing tool is adapted for repairing damaged seams in floor coverings like my device, and no method like my method has been developed before. 
     Thus, a need exists for way to repair damaged seams in floor coverings that is easier to use than present methods, and consistently achieves a perfect repair that is invisible and durable. It is further desirable that any tool used for the repair be rugged, reliable, easy to operate, and relatively inexpensive so that it may be used by professional craftspeople and amateurs alike. 
     SUMMARY OF THE PRESENT INVENTION 
     Objects and Advantages 
     The chief object and advantage of my invention are to make it much easier and faster than present methods to perfectly repair a damaged seam in floor coverings. Craftspeople and amateur repair people of many different skill levels and abilities are able to competently repair a seam using my tool and method. My invention consists of a hand held precision cutting tool and a method for using the tool to repair a seam. I have designed the tool to be inexpensive to construct, rugged, reliable, and easy to operate. The method for using it consists of a limited number of steps that are easy to teach, easy to learn, and easy to do. My repair procedure can also be performed much more quickly than current methods. Thus, my invention will be of value to anyone who needs to repair seams in sheet materials, and especially floor coverings. 
     Theory of Operation 
     My repair tool is essentially a specially designed double-bladed precision knife with adjustable blades. The dual blades are nearly parallel but are inclined slightly to make a cut that is beveled slightly away from the centerline of the tool, to undercut the material being repaired. Each blade is a rigid precision blade and is securely fixed to the body of the tool near each blade&#39;s working edge. Thus the cutting blades are more stable than blades in conventional utility knives and are capable of making precision cuts. The distance between the blades is adjustable by means of a fine pitch adjustment screw attached to a thumbwheel. The adjustment screw is back loaded to remove adjustment slop and prevent unintentional movement of the screw. 
     To use my repair tool, an operator sets the distance between the blades to just slightly wider than the widest portion of the damaged seam to be removed. The operator then draws my tool along the seam with the blades straddling the seam, while applying downward cutting pressure. The operator then removes the material between the parallel cuts, and cleans out the resulting groove. Then, from a piece of scrap material that matches the pattern of the removed material, the operator cuts a strip of the same length and pattern as the removed material. This will serve as the repair strip. However, before cutting the repair strip, the operator adjusts the blades of the knife to be slightly wider apart than when cutting out the damaged portion of the seam. This ensures that the repair strip will fit snugly into the groove previously cut in the material to be repaired. The operator then applies a small amount of flooring adhesive along the bottom of the groove and, using a roller, presses the repair strip in place along the groove. The matching bevels of the repair strip and the groove help to lock the repair strip in place. Furthermore, the edges of the repair piece match the groove perfectly and are uniformly snug along the length of the patch. Thus, the repair strip is held firmly in place with its edges as good or better than the original seam. To complete the repair, the operator applies a conventional seam sealing adhesive to seal the patch and protect it from contamination. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is an isometric view of my repair tool shown cutting a piece of floor covering. 
     FIG. 1B in an isometric view at about ¾ scale of an alternative embodiment of my repair tool. 
     FIG. 2 is a plan view of the interior of a first body section of my repair tool. 
     FIG. 3 is a plan view of the interior of a second body section of my repair tool. 
     FIG. 4 is a cross section through section  4 — 4  shown on FIG.  2 . 
     FIG. 5 is a cross section through section  5 — 5  on FIG. 6, showing various details of construction and assembly of my repair tool. 
     FIG. 6 is a plan view of the exterior of my repair tool from the side of the first body section. 
     FIG. 7 is a plan view of the exterior of my repair tool from the side of the second body section. 
     FIG. 8 is a cross section through section  8 — 8  on FIG. 7, showing various details of construction and assembly of my repair tool. 
     FIG. 9 is a top view of my repair tool, showing the cutting blades spread apart in a wide position, with dashed lines indicating the position of selected hidden interior parts. 
     FIG. 10 is a top view of my repair tool, showing the cutting blades in their closest or narrowest position, with dashed lines indicating the position of selected hidden interior parts. 
     FIG. 11 is a partial breakaway plan view of my repair tool from the side of the second body section, showing the mounting position of the cutting blade and adjustment screw. 
     FIG. 12 is an isometric diagram illustrating the method for using my repair tool to repair a seam. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The preferred structure of my repair tool  20  is depicted in FIGS. 1A through 11. FIGS. 2 through 11 are drawn full scale. The basic form and strength of tool  20  is preferably provided by first body section  22  and second body section  24 , which together form a handle  21 . My repair tool  20  is preferably a hand tool operable by one or two hands of one person. Body sections  22  and  24  are preferably cast from a durable metal such as aluminum or similar lightweight and economical die casting alloys. For lighter weight and lower cost, at the expense of some durability, sections  22  and  24  may be molded from hard and durable plastics such as Nylon®. Sections  22  and  24  may also be milled from any hard and durable material, but molding or casting is preferable for volume production. 
     Sections  22  and  24  are preferable joined at their second end  25  by fastener  32  to form a handle  21 . Fastener  32  is positioned so that mating surfaces  33  and  35  of sections  22  and  24  will touch along the length of tool  20  when adjustment screw  38  is in the close position, as shown in FIG.  10 . Fastener  32  and the portion of sections  22  and  24  rearward of fastener  32  will then exert a gradually increasing back load on adjustment screw  32  as it is adjusted from a close position to a wider position, as shown in FIG.  9 . To provide an appropriate amount of adjustability and back load, the centers of adjustment screw  38  and fastener  32  are preferably spaced four to five inches apart. Fastener  32  is preferably a one-quarter inch steel machine screw, or similar fastener. Sections  22  and  24  may be disassembled by removal of fastener  32  to permit replacement of blades  28  and  30 . 
     In an alternative embodiment, an additional fastener  39  is provided at the second end  25  of tool  20  as shown in FIG.  1 B. The additional fastener provides additional lateral stability between body sections  22  and  24  that helps stabilize the tool through the operating range of adjustment screw  32 . However, I prefer to omit fastener  39  if possible and use a guide means, such as a mating pin and recess, at the first end  23  of the tool to provide lateral stability. Those skilled in the art will recognize that a variety of other means are possible for securing the body sections  22  and  24  while at the same time providing for adjustment of the distance between blades  28  and  30  at first end  23 . 
     Blades  28  and  30  are precision steel cutting blades. I obtained the blades as universal  3  hole mini utility knife blades from Industrial Blades Limited of Malvern, Pa., and modified them by scoring and breaking the blades between each of the three mounting holes. Blades  28  and  30  are preferably flat, trapezoidal, with one cutting edge, and a mounting hole located in the approximate center of each blade. Various other types and configurations of blades may be adapted for use with my invention. It is important, however, that any blade used with my invention have a sharp cutting edge, be relatively stiff and precision ground for repeatability of mounting and cutting, and be positively and firmly attached to its respective mounting surface  29  or  31  of body section  22  or  24  near the blade&#39;s cutting edge. In order to cut floor covering with the necessary precision, the blade must be able to bear heavy hand pressure without noticeable movement or deflection. 
     Blades  28  and  30  are mounted to sections  22  and  24 , respectively, as shown in FIGS. 9,  10 , and  11 . Each blade is oriented with one of its non-cutting edges against shoulder  54  or  55 , respectively, and its cutting edge oriented towards the bottom side  27  of tool  20 . Fasteners  44  and  45 , respectively, attach blades  28  and  30  to mounting surfaces  29  and  31  of sections  22  and  24 . Fasteners  44  and  45  are preferably 6-32 flat head screws or similar small fastener and are adapted to fit into threaded holes  46  and  47  shown in FIGS. 5 and 8. 
     For purposes of repairing seams in floor coverings, when sections  22  and  24  are in their closest position, shown in FIG. 10, blades  28  and  30  are preferably touching at their rearward portions and have their tips about 0.10 inch apart. When sections  22  and  24  are in their furthest apart position, shown in FIG. 9, the tips of blades  28  and  30  are about 0.35 inches apart. This range of adjustability is useful for most floor covering repairs. Of course, the range of adjustability of the repair tool suitable for use with my invention could vary from the preferred range without departing from the scope of my invention. 
     Mounting surfaces  29  and  31  are preferably inclined with respect to mating surfaces  33  and  35  of body sections  22  and  24 , at angles α and α′, respectively, shown in FIGS. 5 and 8. As a result, blades  28  and  30  diverge when mounted in tool  20  with an angle of divergence equal to α plus α′. The purpose of the divergence is to provide for a beveled undercut, visible in FIG. 12, when tool  20  is used to cut a groove or repair strip. I have found it preferable that α and α′ both be about 2°, making the total divergence angle of blades  28  and  30  equal to 4°. Other divergence angles or no divergence angle would provide some functionality. However, if the divergence angle is much greater than 4°, blades  28  and  30  are more likely to cut a ragged edge. In addition, the amount of undercut is greater than needed to repair the seam and will make it more difficult to position the repair strip correctly. Conversely, if the divergence angle is much less than 4°, the undercut is less effective for locking the repair strip in place. Those skilled in the art of tool design will recognize other means for inclining blades  28  and  30  to provide a suitable undercut, other than the method I have disclosed. Various means for providing an undercut may be used, without departing from the scope of my invention. 
     My repair tool is preferably provided with a means for adjusting the distance between blades  28  and  30 . My preferred means for adjustment is an adjustment screw  38  connected to thumbwheel  26 . As shown in FIGS. 9 and 10, section  24  at the bottom of recess  43  is maintained against bearing surface  36  of adjustment screw  38  by the compression supplied by fastener  32 . Turning thumbwheel  26  so adjustment screw  38  advances out of threaded hole  49  (shown in FIGS. 5 and 6) drives bearing surface  36  against section  24 , thereby increasing the distance between blades  28  and  30 . Turning thumbwheel  26  in the opposite direction has the opposite effect, bringing the blades closer together. The pressure supplied by fastener  38  against bearing surface  36  provides a continual backload on screw  38 , eliminating adjustment slop and creep. 
     Body sections  22  and  24  are preferably provided with openings  66  and  67 , shown in FIGS. 9 and 10. Thumbwheel  26  is preferably mounted on adjustment screw  38  so it protrudes through openings  66  and  67  in handle  21 . This mounting position makes tool  20  sleeker and more compact than mounting thumbwheel  38  on the exterior of the tool. It also tends to protect thumbwheel  26  from accidental movement and impact. To facilitate my preferred mounting, body section  22  is provided with boss  40 , shown in FIG.  5 . Boss  40  permits threaded hole  49  to be of sufficient length for operation of adjustment screw  38 . In an alternative embodiment, adjustment screw  38  passes through one of either body section  22  or  24 , and thumbwheel  26  is mounted on a side of the exterior of tool  20  as shown in FIG.  1 B. 
     Adjustment screw  38  is preferably about the same diameter as fastener  32  to avoid excessive stress on both screw  38  and fastener  32 . Screw  38  is preferably provided with a fine thread having a relatively small pitch. Various suitable threads sizes are known in the art for providing fine and precise adjustment capability. 
     Tool  20  is preferably provided with a roller  34  useful for my repair method. The roller  34  is preferably located on the second end  25  of tool  20  at the corner opposite to fastener  32 , as shown in various figures, including FIG.  6 . Roller  34  is preferably made from a suitable hard plastic material. Roller  34  is preferably mounted on retention pins  50  and  51  of sections  22  and  24 , respectively, when sections  22  and  24  are assembled. Pins  50  and  51  have the advantage of being integral with sections  22  and  24 , thereby eliminating the need for additional parts. When sections  22  and  24  are disassembled by removing fastener  32 , the preferred mounting permits roller  34  to be removed and replaced. Roller  34  is preferably configured, mounted, and positioned as shown in FIGS. 5 and 6, but other suitable sizes, mountings, and locations for roller  34  are possible, or roller  34  may be omitted entirely, without departing from the scope of my invention. 
     The interior of handle  21  is preferably provided with various recesses in body sections  22  and  24  to accommodate interior components, provide for storage of replacement and auxiliary components, and for lightening the tool body. Recesses  42  and  43  accommodate thumbwheel  26 . Recesses  57  and  58  are for storage of a container holding spare blades. Recesses  62  and  62  form an interior recess in handle  21  for holding a wrench for fasteners  44  and  45 . A cross section of recesses  57  and  61 , which are typical of recesses  58  and  62  also, is shown in FIG.  4 . Recesses  59  and  60  are for lightening the tool body and could also be used for storage of small components, if desired. 
     For convenience of the user, body sections  22  and  24  are preferably provided with recesses  61  and  62  (respectively) which together provide an interior recess in handle  21  for storage of a suitable Allen wrench for adjusting fasteners  44  and  45 . As an additional convenience, body sections  22  and  24  are preferably provided with threaded holes  64  and  65 , respectively, for holding spare fasteners to replace fasteners  44  or  45 , if needed. 
     My method for using my repair tool to repair a seam in floor coverings adhered to a floor is diagrammed in FIG.  12 . My method could be adapted for use with any tool having two cutting blades suitable for cutting floor coverings, so long as the blades are positioned to make parallel cuts the proper distance apart so as to remove only the damaged portion of the seam. It is preferable for the cutting blades of the tool to be inclined away from one another to undercut the floor covering material and to provide a matching bevel on the repair strip. Prior to development of my repair tool, no tools suitable for use with my method were available. Steps of my method are diagrammed in sequence from the top to bottom of FIG. 12, following the arrows and letter sequence. 
     A piece of floor covering  100  on a floor  102  with a damaged seam  108  is represented in step A at the top of FIG.  12 . The distance between the blades of tool  20  is adjusted to just slightly wider than the widest portion of the damaged seam to be removed. Tool  20  is placed at the first end of the damaged portion of the seam so that a first blade is on a first side of the seam, and a second blade is on a second side of the seam. Tool  20  is then drawn along the length of the damaged portion of the seam to the second end of the damaged portion with the blades straddling the damaged portion of the seam. While tool  20  is drawn along the seam, downward cutting pressure is applied to tool  20 , cutting through floor covering  100  to floor  102  and creating two parallel cuts straddling the damaged portion of the seam, as shown in FIG. 12 step B. The operator then removes the material between the parallel cuts and cleans out the resulting groove  112  in floor covering  102 . Then, the operator selects a piece of scrap floor covering material  101  selected to match the decorative pattern of the material removed from floor covering  100 . The operator cuts a strip of the same length and pattern as the removed material from the selected scrap piece  101  as shown in FIG. 12 step C. This becomes repair strip  104  shown in FIG. 12 step D. 
     However, before cutting repair strip  104 , the blades of tool  20  are preferably adjusted to be slightly wider apart than when cutting out the damaged portion of the seam. Increasing the distance between the blades at least one but no more than ten thousands of an inch is optimal for most materials and seams. With the preferred embodiment of my repair tool, turning adjustment screw  38  approximately one quarter turn will make a proper adjustment. A proper adjustment ensures that repair strip  104  will fit snugly into the groove  112 . 
     After cutting the repair strip, the operator trims its ends to fit into the groove  112  and match the surrounding floor covering  100 . The operator then applies a small amount of flooring adhesive  106  along the bottom of the groove  112 . The operator positions the repair strip  104  in groove  112  so that the pattern on strip  104  matches the adjoining floor covering  100 . Using a roller  110 , the operator presses the repair strip in place along the groove  112  as shown in FIG. 12 step E. My repair tool is equipped with roller  34  for this purpose, but almost any roller may be used. The matching bevels of repair strip  104  and the groove  112  help to lock the repair strip in place. Furthermore, the edges of repair piece  104  match the groove  112  perfectly and are uniformly snug along the length of the patch. Thus, repair strip  104  is held firmly in place with its edges matching the repaired piece as well or better than the original seam. To complete the repair, a conventional seam sealing adhesive is applied over the surface of the repaired area to weld the repair strip in place and seal it from contamination. 
     Thus I have provided a way to easily and quickly perform perfect repairs of damaged seams in abutting pieces of floor covering. Craftspeople and amateur repair people of many different skill levels and abilities are able to competently repair a seam using my tool and method. My repair tool is inexpensive to construct, rugged, reliable, and easy to operate. The method for using it is easy to teach, easy to learn, and easy to do. Thus, my invention will be of value to anyone who needs to repair seams in sheet materials, and especially floor coverings. 
     Various modifications and alterations of the embodiments of my invention will become apparent to those skilled in the art without departing from my invention&#39;s scope. The scope of my invention is limited only by the elements of the claims that follow, and is not limited by the particular embodiments that I have disclosed.