Abstract:
A jig apparatus that allows one to cut arches in a work piece quickly and efficiently. It is comprised of a bar that has sliding adjustable clamps that secure a cable which go around pulleys on a router or other cutting device that when the cable is pulled taut, creates a path for the router or other cutting device to follow while it cuts thus cutting an arch into the work piece. Prior to this apparatus one would have to cut this arch with a template which had been previously tooled. This jig apparatus creates a template and cut all in one step.

Description:
REFERENCE TO RELATED APPLICATIONS 
     Reference to PROVISIONAL PATENT—APPLICATION No. 60/124,012 FILLING DATE Mar. 12, 1999. 
    
    
     BACKGROUND OF INVENTION 
     Although there are many different jigs or devices made to make different size circles, there is no such item to make an arch. An arch differs from a circle in that it may vary in its proportions even as an elipse varies from a circle. This arch is not just an enlarged section of a circle, but may be a portion of an elipse. There are no other jigs available for purchase, that are made to cut arches with a router or other cutting tools. 
     In the production of decorative arches that are used at the top of a bookcase, for instance, the width of the bookcase determines the width of the arch. If there are varying size widths, one would need varying sized arches. If the difference in widths is large, for example 12″, a matching arch in a set of bookcases will be cut higher into one stock than on the other. If the center of the arch needs to maintain a reveal, such as 2″, the two arches will need to vary in their spread. This jig is able to adjust to that change quickly and readily. Consider the difference in the performance of a regular miter box and a compound miter box. Both will cut a single 45 degree angle, but the compound miter box can cut a compound miter required to solve specialized crown moulding installation problems. The latter would create a double angle cut. So it is with the arch cutting jig, in that it can cut an arch out of a compound-circle, rather than just a simple circle. For the cabinetmaker to make an arch with the use of present technology, he must use one of three methods. [1] He must freehand an arch on his work piece or pattern, [2] use a bent thin and narrow piece of wood to create the arch and trace it on his work piece or pattern, or [3] create a jig with a pair of nails and a string and using a pencil, trace the arch onto the work piece or pattern. Each of these present methods require him to draw, cut shape or sand to a finished product and possibly cut again if he is using a pattern, to finally get the desired result. At the end of a considerable amount of time he has one arch done. If the arches are to be all the same on the bookcase, this product can be used as a pattern as well as to cut the other arches from it. But if the arches vary, even by a few inches, one would have to go through this long process over and over again. It should be appreciated that there is a need for a quick, accurate, and easily adjustable arch cutting jig apparatus. 
     Method # 3 is a step above free-handing each arch for it allows you to create many accurately drawn arches. By taking two nails and tacking them into a piece of wood a specified distance apart you can then take a loop of string, whose diameter is larger than the distance of the two nails and circumvent the two nails, thus creating a jig. By putting a pencil against the upper edge of string, one can draw a perfect arch from nail to nail. The arch cutting jig apparatus uses this same principle to create a pathway for the cutting tool&#39;s bit to follow. By using a cutting tool, it creates a 90 degree cut which thereby creates a finished product quickly and efficiently. This arch cutting jig apparatus fills the need that exists in the making of multi-sized arches. 
     BRIEF SUMMARY OF INVENTION 
     There is a need today for a quick, efficient, and variable arch cutting jig. Rather than drawing and cutting arches by hand, this jig allows one to set up the desired arch and cut it quickly and cleanly with a router or other cutting device, creating a sharp detailed arch. Present methods allow one to only trace cut by hand, and refine with a sander to get to the desired product. This is tedious and time consuming, especially if there are multiple, varying—sized arches to make. 
    
    
     BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS 
     FIG. 1 is a plan or top view of a router showing various parts as per invention. 
     FIG. 2 is a perspective view of the Bar and Plate Assembly of FIG.  1 . 
     FIG. 3 is a perspective view of the Bar cross-section of FIG.  1 . 
     FIG. 4 is a perspective view of the Sliding Clamp or Holding Device of FIG.  3 . 
     FIG. 5 is a perspective view of the Pulleys mouted to the router base. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The following description of the preferred embodiment of the invention is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention. The following detailed description is a suitably contemplated mode of carrying out the present invention. The spirit of the concept of this jig apparatus may be expressed in ways not mentioned here. One must interpret by an overall assesment. 
     With reference now to the drawings and particularly to FIG. 1, the arch cutting jig apparatus is comprised of a bar  14  wooden or aluminum, having a slot  13  [See FIG.  3 ] which receives a sliding clamp  12 . There are two sliding clamps  12  one on either side of the length-wise center point  19  [FIG.  2 ] of the bar. This present bar is 72″ in length. The other dimensions of bar  14 , thickness and depth, should be strong enough for the pressure exerted by the cutting tool  16  pulling against the bar  14 . Wood should be at least 1″ by 2″, respectively, and made from maple or a similar dense hardwood. Aluminum should be at least 1½″ by 1½″. 
     The center point  19  [FIG.  2 ] of the bar  14  is marked as a fixed zero with reversing numerations  25  [FIG.  3 ] fixed above the slot  13  to indicate the position of the sliding clamps  12  to {fraction (1/16)}″ increments. In this instance, the numerations go from 0″ to 36″ in either direction from the center point  19 . With this setup, the clamps  12  are able to move to equal positions from the center point  19 , thus creating a symetrical cut in workpiece  17 . In this application, the clamps  12  represent the two nails of method # 3, mentioned in the background of invention section. Reiterating this concept, the nails are tacked at a specified distance apart into the workpiece. Circumvent the two nails with a loop of string, whose diameter is greater than the distance between those two nails. Then using a pencil to draw, run the pencil along on the upper inner edge of the string, thus drawing an arch on the work piece. On the arch cutting jig apparatus, the clamps  12  substitute for the nails, but because they are moveable and slide, they are adjustable to different sized arches. The clamps  12  clamp in two directions. One way is to clamp to the bar  14  to prevent it from sliding during operations. This is done with a {fraction (3/16)}″ carriage bolt  21  on either side of the clamp  12  with a wing nut  22  securing it to the bar  14  [See FIG.  4 .] The other direction that it clamps is through the upper center of the clamp  12  through a pair of toothed jaws [See FIG.  3 ] Through these jaws runs a wire cable  18  [at least ⅛″ thick] that runs from one clamp  12  to the other clamp  12 . This cable  18  is at least 120″ long to accommodate the different size arches that will be cut. The cable  18  represents the upper portion of the string mentioned in method #3. 
     The arch cutting jig is an apparatus in which one can use one&#39;s own router or cutting device  16 , although a plunge router is recommended. The router  16  is used in the jig but is purchased separately from the invention. Included with the invention are three pulleys  24  that are attached to the front upper edge of the router  16  [FIG.  5 ] in this application they are comprised of plastic with a hole down the center, attached with a 1¼″ screw that is tapped into the base of the router  16  the pulleys  24  are loose so that they may spin as necessary. These pulleys  24  will project perpendicularly up from the top of the router base  23 . The cable  18  will now pass through the left-hand clamp  12 , around the three pulleys  24  ,then through the right-hand clamp  12 . [See FIG.  5 ] 
     Now refering to FIG. 2 one other feature that the arch cutting jig apparatus has is an adjustable plate  15  that extends either side of the center point  19  and parallel to to the bar  14  on the upper side. The plate  15  allows you to adjust the height of the cut into your workpiece  17 . When combined with the width adjustment of the clamps  12 , one is able to create different eliptical paths for the router  16  to follow. This plate  15  made of aluminum here, is centered by length to the bar  14  through the use of two perpendicular adjustable rods  20  These rods  20  project through holes in the bar  14  and are secured by two thumb screws or wing nuts  22  from a perpendicular direction underneath the bar  14 , thus making them adjustable for different size needs. [See FIG.  2 ] An example would be an 18″ plate  15  extending 9″ either side from the center point  19 , secured with 10″ rods  20  adjusting through holes in the bar  14 . 
     The arch cutting jig apparatus is intended to be mounted to a flat surface such as a work bench which is large enough to accommodate the workpiece  17  and jig it can be attached with screws through pre-drilled holes at the end and the middle of the bar  14 . 
     To actually cut an arch on this jig, let us look at FIG. 1 place workpiece  17  above the plate  15  and center workpiece  17  lengthwise on the bar  14 . Make your chosen adjustments to the rods  20  and to the clamps  12 . Secure them and then secure your workpiece  17  and your jig apparatus. Refering to FIG. 5, set the router  16  with the cable  18  around the pulleys  24  and place the router base  16  firmly to the furthest most left-hand side of the workpiece face  17  while you keep the cable  18  tight, pulling away from the bar  14  and the right-hand clamp  12 . While keeping pressure on the router  16  against the cable  18 , you will create a triangle with the bar  14  as the bottom of the triangle and the cable  18  as the upper two sides. While maintaining pressure on the router  16  and keeping tension on the cable  18  plunge the bit into the surface of the workpiece face  17  and move to the right following the path created by the tensioned cable  18 . See FIG.  1 . The tension on the cable  18  is what establishes the path of your arch and maintaining the tension of the cable  18  is what secures the integrity of your finished product. Removing a ¼″ depth of cut into your workpiece  17  each time will allow you to maintain a manageable degree of accuracy. The perpendicular cut of the router  16  and the tension on the cable  18 , maintains the proper pattern and will enable you to make a quick and clean-cut arches that requires little or no finishing. Thus after you have initially set up your jig you may make repeated duplicates in a very short time. With slight adjustments to your jig set-up, you can easily make the various arches necessary for your cabinets, quickly and easily.