Abstract:
A guide for steadying the path of a cutting tool and enabling force to be applied to compress a workpiece on opposing sides of the path of the tool.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a guide for a tool and, more particularly, to a guide for steadying the path of a tool while enabling a compressive force to be applied to a workpiece on both sides of the path of the tool. 
     Many materials, such as, fiberglass thermal insulation, fiber batting, and foam materials, comprise sheets or batts of loosely amalgamated fibers or a matrix of relatively fragile cells. Typically, these materials are cut to size using a knife or other hand-held tool. However, the thickness of the sheet of material may be substantially greater than the length of the cutting element or blade of the tool. Further, the fragility of the sheet of material often makes it difficult to obtain a clean cut and avoid pulling material out of the sheet. The most effective method of cutting this type of material comprises compressing the material while repeatedly drawing a cutting tool across the workpiece. Compressing the material reduces the thickness of the workpiece and consolidates the fragile material reducing tear out to produce a cleaner cut. 
     Referring to FIG. 1, typically, a person desiring to cut sheet or workpiece of compressible material places a straightedge  20  on the upper surface  22  of the workpiece  24  at one side of the desired cutting path. Pressure applied to the straightedge with one hand compresses the material while the second hand draws the knife or other cutting tool  26  along the side of the straightedge to cut the material. Even when the material is compressed, several passes with the cutting tool  26  may be required to cut completely through the workpiece  24 . When the tool  26  severs the material of the workpiece  24 , the portion of the material on the side of the cut opposite the straightedge  20  is substantially free to expand toward its uncompressed state. If it is necessary to repeat drawing the tool  26  across the workpiece  24 , the expanded material adjacent to the cutting path can interfere with the user&#39;s hand and the cutting tool  26 . In addition to making it difficult to repeat the cutting action, the expanded material  28  can make it difficult to keep the cutting tool against the straightedge producing an uneven edge and often causing the fragile material to be torn from the workpiece. 
     What is desired, therefore, is a device to steady the path of the cutting tool and facilitate the application of force to compress the workpiece on both sides of the cut until the material is completely severed, even if several passes of the tool are required. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a prior art method of cutting a sheet of a compressible material. 
     FIG. 2 is a perspective view of an embodiment of the inventive cutting guide. 
     FIG. 3 is an end-view of the cutting guide of FIG. 2 illustrating compression of the workpiece on opposing sides of the cut during use. 
     FIG. 4 is a perspective view of the cutting guide of FIG. 2 illustrating compression of a workpiece. 
     FIG. 5 is a cross-section of a channel-shaped platen for a cutting guide. 
     FIG. 6 is a bottom view of a platen of a cutting guide having a space shape configuration. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Cutting thick batts or sheets of loosely amalgamated fibers or fragile cellular material, such as fiberglass insulation, fiber batting, and foam, can be problematic. Referring in detail to the drawings wherein similar parts of the invention are identified by like reference numerals, and more particularly to FIG. 1, to effectively cut materials of this type with a knife or other handheld cutting tool  26 , a person will typically place a straightedge  20  on the top surface  22  of the workpiece  24  along the proposed cutting path, apply force to the straightedge to compress the material and reduce its thickness, and then draw the cutting tool along the straightedge using the side to guide the motion of the tool. Several passes of the tool may be required to completely sever the material of the workpiece  24 . Once the tool begins cutting, the material is severed along the cut and the material  28  on the side of the cut opposite the straightedge is no longer restrained and can expand substantially toward its uncompressed state. This material often interferes with the cutting tool and the hand of the person wielding it. 
     The present inventor concluded that maintaining pressure on both sides of the cutting path during repeated passes of the cutting tool would promote ease and effectiveness in cutting compressible material and produce cleaner cuts. Referring to FIGS. 2,  3 , and  4 , the cutting guide  50  of the present invention comprises, generally, a platen  52  having a substantially planar first surface  54  to be placed in contact with the upper surface  22  of a workpiece  24  to be cut. The individual using the cutting tool  26  can place one hand on the spaced apart upper, second surface  60  of the platen  52  and exert a force substantially normal to the surface  22  of the workpiece  24  to compress the material and reduce its thickness. Portions of the platen  52  define the edge  62  of an elongated aperture  64  that is displaced from the peripheral sides  56  of the platen  52 . With the lower planar surface  54  of the guide  50  in contact with the upper surface  22  of the workpiece  24 , the blade  27  of the cutting tool  26  can be inserted through the aperture  64  into the workpiece  24 . The cutting tool  26  can be held against the edge  62  of the aperture  64  to steady the motion of the tool as it is drawn across the surface of the workpiece  24 . 
     While the platen  52  of the cutting guide  50  illustrated in FIG. 2 is an elongated rectangular prism with ruling  66  along one edge of the upper surface, the cutting guide may employ a platen of another shape or cross-section. For example, FIG. 5 illustrates a platen  80  having a channel shaped cross-section comprising a base  82  having a substantially planar lower base surface  84  and a plurality of ribs  86  projecting from the upper surface  88  of the base  82 . The channel shaped cross-section enhances the stiffness of a light weight platen. Likewise, the lower surface of the platen need not be rectangular. Referring to FIG. 6, the platen  102  of the cutting guide  100  can have a lower surface with the shape of any convenient space figure and may include one or more apertures  106 ,  108  with shapes to guide the cutting tool on any desired cutting path. 
     To use the cutting guide, the user places the guide  50  on the upper surface  22  of the workpiece  24  to be cut with the aperture  64  aligned with proposed cutting path. The user applies force to the upper surface  60  of the platen  52  with a first hand to compress the material under the guide to reduce the thickness of the workpiece  24  and consolidate the material to reduce tear out. With the second hand, the user inserts the cutter  27  of the tool  26  into the aperture  64  so that the cutter  27  projects below the lower surface  54  of the guide and into the material to be cut. While the aperture need only be sufficiently wide to permit the cutter  27  of the cutting tool  26  to be inserted, the present inventor determined that an aperture  64  approximately 0.5 inch wide or wider will permit inserting the end of a typical utility knife through the platen  54  increasing the depth of the cut that is possible with a cutting element of fixed length. With the cutter  27  of the tool  26  engaging the material of the workpiece  24 , the user can draw the tool across the workpiece using the edge  62  of the aperture  64  to steady the tool and guide its path of travel. Since the aperture  64  and, therefore, the cutting path of the tool  26  is displaced from the periphery of the platen  52 , the lower surface  54  of the guide  50  remains in contact with the surface  22  of the workpiece  24  on both sides of the cutting path of the tool. With continued exertion of force on the cutting guide, the user can continue compression of the material of the workpiece  24  and enjoy unobstructed access to the cutting path during repeated passes of the tool  26 . 
     The detailed description, above, sets forth numerous specific details to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, and components have not been described in detail to avoid obscuring the present invention. 
     All the references cited herein are incorporated by reference. 
     The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.