Abstract:
A method for cutting sheet material including positioning the material on an upper surface of a guide table having slots. A blade of a saw is aligned with one of the slots and the saw is energized. The blade is advanced through the sheet material with the blade in the slot to cut the material along a line corresponding to the slot. Apparatus for cutting sheet material is also disclosed. The apparatus includes a saw and a guide table including an upper surface having a plurality of elongate slots therein for receiving the saw blade to guide the saw along the surface.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to a method and apparatus for cutting sheets of material such as uncured epoxy foam material.  
           [0002]    Often, composite components such as those used in gas turbine engines are made by stacking sheets of material in predetermined orientations. The individual stacked sheets or laminae are activated to bond them together to form the composite components. Frequently, the sheets of material are made of a foam or film epoxy material having paper backing covering each face prior to use.  
           [0003]    Conventionally, a knife and a straight edge are used to cut the sheet material to desired sizes and shapes prior to stacking them. However, as the sheets are cut, the technician simultaneously must hold the straight edge in place on the sheet material, hold the knife against the straight edge and press the knife against the sheet material with sufficient force to cut the material. If the knife becomes spaced from the straight edge or the straight edge moves, the cut will not be straight. Further, this procedure sometimes produces slivers of the material, slivers of the paper backing, and/or slivers of the straight edge. If the slivers are not found and removed, they can become embedded in the components. In addition, as the material becomes thicker, this conventional method becomes more difficult.  
           [0004]    Another conventional method and apparatus for cutting sheet material is a wire cutter including a table for receiving the material having a tensioned wire laying in a slot and a shuttle for guiding the wire upward through the material thereby cutting the material. However, the adhesive properties of the sheet material cause the material to adhere to the wire and the shuttle mechanism thereby reducing their effectiveness. Further, as the material thickness increases, there is an increased likelihood of the wire breaking, causing a need for maintenance.  
           [0005]    Sometimes when the sheets are stacked, they become misaligned. Thus, stacking the sheets before cutting them may be desirable. However, stacking the sheets makes the material thicker thereby making the material more difficult to cut.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention includes a method for cutting sheet material comprising positioning the sheet material on an upper surface of a guide table having a plurality of slots. A blade of a saw is aligned with a first slot in the guide table. The saw is energized to actuate the blade of the saw and the blade is advanced through the sheet material while maintaining the blade in the slot to cut the material along a line corresponding to the slot.  
           [0007]    In another aspect, the present invention includes a saw for cutting sheet material comprising a body and a motor mounted inside the body having an energized state and a de-energized state. Further, the saw includes a blade adapted for cutting the sheet material connected to the motor so that the blade moves with respect to the body when the motor is in the energized state and a base plate mounted on the body for slidably engaging the sheet material as the blade cuts the sheet material. The plate has a lower surface covered with polytetrafluoroethylene for reducing friction between the base plate and the sheet material as the plate slidably engages the sheet material.  
           [0008]    In yet another aspect, the present invention includes apparatus for cutting sheet material comprising a saw having a blade adapted for cutting the sheet material and a guide table including an upper surface for receiving the sheet material. The surface has a plurality of elongate slots therein for receiving the saw blade to guide the saw along the surface. Each of the slots has a uniform and equal width greater than a kerf of the saw blade, a length at least as great as a length of cut for the sheet material, and a height sufficient to accommodate at least a portion of the saw blade when the sheet material is received by the upper surface of the guide table and the saw engages the sheet material.  
           [0009]    Other features of the present invention will be in part apparent and in part pointed out hereinafter. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a rear elevation of a guide table and a saw of the present invention shown cutting sheet material positioned on top of the guide table;  
         [0011]    [0011]FIG. 2 is a top plan of the guide table having a sheet of material thereon;  
         [0012]    [0012]FIG. 3 is a side elevation of the guide table and the saw shown cutting a sheet of material; and  
         [0013]    [0013]FIG. 4 is a side elevation of a blade used in the saw of the present invention. 
     
    
       [0014]    Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    Referring now to the drawings and in particular to FIG. 1, apparatus of the present invention is designated in its entirety by the reference number  10 . The apparatus is intended for cutting sheet material, generally designated by  12 . The apparatus  10  comprises a guide table, generally designated by  14 , and a saw, generally designated by  16 .  
         [0016]    The guide table  14  comprises a base  20  and a series of C-channels  22  fastened to the base with screw fasteners  24  (e.g., ¼-20 flathead machine screws threaded into tapped holes in the base). The channels  22  are uniformly spaced by elongate slots  26  which extend parallel to each other and are equally spaced across an upper surface, generally designated by  28 , of the guide table  14 . Although the base  20  and channels  22  may be made of other materials without departing from the scope of the present invention, in one embodiment they are made of 6061-T6 aluminum. Further, although the base  20  may have other dimensions without departing from the scope of the present invention, in one embodiment the base has a length  30  (FIG. 2) of about 30 inches, a width  32  (FIG. 2) of about 19.93 inches and a thickness  34  of about 0.50 inch. Preferably, the length  30  of the base  20  matches that of the table  14  and is at least as great as a length  36  of cut for the sheet material  12  as shown in FIG. 2. As further illustrated in FIG. 1, although the channels  22  may have other dimensions without departing from the scope of the present invention, in one embodiment each channel has a height  40  of about 2.00 inches and a width  42  of about 1.18 inch. Each of the slots  26  has a width  44  greater than a kerf  46  of the saw  16 . In one embodiment, each of the slots  26  has a width  44  of about 0.07 inch. In an alternate embodiment (not shown), the channels  22  have progressively wider widths  42 . For example, each channel  22  may have a width  42  that is 0.125 inch wider than the adjacent channel so the slot  26  spacing progressively increases by 0.125 inch. This arrangement permits the guide table  14  to be used to cut sheet material  12  into pieces having different widths without moving the material between cuts.  
         [0017]    As illustrated in FIG. 1, each of the channels  22  includes a vertical web  50 , an upper flange  52  extending laterally from an upper end of the web, and a lower flange  54  extending laterally from a lower end of the web opposite the upper end. The screw fasteners  24  mounting the channels  22  to the base  20  extend through holes  56  in the lower flange. Each of the upper flanges  52  has a top surface  58 . Collectively, these top surfaces  58  form the upper surface  28  of the table  14 .  
         [0018]    As illustrated in FIG. 3, the saw  16  is a conventional reciprocating saw such as a 2.0 amp, 24 watt saw sold under the trade name Power Plus by Milwaukee Electric Tool Corporation of Brookfield Wis. The saw  16  includes a housing  60 , a handle  62  and a base plate  64 . A lower surface  66  of the plate  64  is treated to reduce friction between the surface  66  and the sheet material  12  being cut. In one embodiment, polytetrafluoroethylene impregnated tape (e.g., Teflon® tape) is applied to the lower surface  66  to prevent the plate  64  from sticking to the material. A conventional motor (not shown) mounted inside the housing  60  is attached to a chuck  68  adapted for releasably mounting a blade  70  to the saw  16  so the blade extends downward through the base plate  64 . The motor may be energized to reciprocate the blade  70  in a direction perpendicular to the lower surface  66  of the base plate  64 . Although other blades may be used without departing from the scope of the present invention, in one embodiment the blade  70  is a model number VA-6004 blade sold by Milwaukee Electric Tool Corporation. The blade  70  is modified by cutting it to length. In one embodiment, the blade  70  is modified as shown in FIG. 4 to have a working blade length  72  of between about 2.15 inches and about 2.25 inches. Further, a lower end  74  of the blade  70  is cut at an angle  76  of between about 40 degrees and about 60 degrees to provide a sharp point  78 . As will be appreciated by those skilled in the art, each slot  26  in the table  14  has a depth corresponding to the height  40  of the channels  22 . Preferably, each slot  26  has a depth sufficient to accommodate at least a portion of the saw blade  70  when the sheet material  12  is received by the upper surface  28  of the guide table  14  and the saw  16  engages the sheet material.  
         [0019]    In one embodiment, the sheet of material  12  comprises a plurality of sheets or laminae  80  stacked atop each other. Preferably, the stacked laminae  80  produce a sheet  12  having the desired uniform thickness  82 . Further, as will be appreciate by those skilled in the art, the cutting length  72  of the blade  70  preferably is greater than the thickness  82  of the sheet  12 . Prior to stacking the laminae, a paper backing (not shown) is removed from each of the sheets except on the top surface of the upper most sheet and the bottom surface of the lower most sheet. The laminated sheet material  12  is positioned on the table  14  so one of the slots  26  of the table is immediately below a place on the sheet material where a cut is desired. Once in position, the sheet material  12  is fastened in place on the table  14  with tape or the like (not shown) . The saw  16  is positioned above the table  14  so the base plate  64  rests on the top surface  82  of the material  12  and the blade  70  extends downward through the selected slot  26  where the cut is to be made. The saw  16  is energized to reciprocate the blade  70  and the operator advances the saw so the blade travels along the slot  26  and cuts the material  12  along a straight line corresponding to the slot. After each cut, resulting pieces of material may be removed before the saw  16  is indexed to the next slot  26  where a cut is desired and the process is repeated.  
         [0020]    The method and apparatus described above provide several advantages over previous methods for cutting sheet material. First, the method allows for cutting sheet material in uniform pieces of desired dimensions having even edges. In contrast, previous methods often resulted in pieces having uneven edges. The polytetrafluoroethylene base plate of the saw allows for the saw to advance smoothly over the material without becoming stuck. Furthermore, the slots in the guide table ensure that the cut made by the saw is in a straight line.  
         [0021]    In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.  
         [0022]    When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.  
         [0023]    As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.