Abstract:
The invention relates to an improved miter box for guiding a handheld portable circular saw. The miter box facilitates several conventional workpiece trim cuts using a handheld portable circular saw, including 45 degree and 90 degree straightcuts, as well as 45 and 90 degree straightcuts with a 45 degree undercut. The invention includes an I-beam that is formed from a rigid base plate having opposing first and second base plate edges disposed along its elongated length. A first and second flange can be respectively attached to the opposing first and second base plate edges. Each of the flanges can include a pair of opposing support faces. One or more transverse guide members can extend either 45, 135, or 90 degrees from one support face of the first flange to another support face of the second flange. The transverse guide member(s) and the support faces provide a friction reduced medium by which the bottom of a handheld portable circular saw&#39;s shoe can glide with greater ease and stability.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a Continuation-in-part of U.S. application Ser. No. 10/397,091 filed on Jun. 16, 2003 now abandoned. 

   BACKGROUND OF THE INVENTION 
   1. Statement of the Technical Field 
   The inventive arrangements relate to miter boxes for trim carpentry work. In particular, the invention relates to an improved miter box for guiding a handheld circular saw. 
   2. Description of the Related Art 
   In the field of trim carpentry work, it is desirable to use a saw guide or miter box to ensure a straight, smooth and accurate cut. Such cuts include 45 degree straightcuts to unite the corners of a door frame molding. Another example includes 90 degree straightcuts with a 45 degree undercut to unite baseboards at a corner of a room. Absent a saw guide or miter box, a user must typically mark a straight line in pencil with the help of a straightedge and protractor and attempt to manually guide the saw along the marked line. Moreover, making accurate and smooth straightcuts and undercuts in a workpiece using a handheld portable circular saw has been a long standing problem in the field. Handheld power saws, by their very nature, have no precise cutting path. Compounding the problem, the operational vibration caused by a handheld power saw makes it even more difficult to maintain a steady cutting path. Also, it is sometimes difficult to make certain cuts using circular saws that are designed for right handed individuals 
   Miter saws have been the common type of equipment used in the field of trim carpentry. However, there are several disadvantages in using a miter saw. First of all, miter saws are very expensive and are prone to be stolen or damaged at a construction site. Second, they are difficult to transport given their bulky size and relatively heavy weight. Moreover, given that the great majority of cuts used in trim carpentry work involve simple 45 and 90 degree angles, a miter saw&#39;s wide range of adjustable angle cuts would appear to be unnecessary for most types of trim work. 
   In the past, several kinds of portable miter boxes have tried to address some, but not all of the problems discussed earlier. Another unresolved problem using miter boxes is that they are usually adapted for right-handed saw operation only. Therefore, what is needed is a miter box that can be used universally with circular saws that are adapted for either right or left handed individuals. Additionally, the improved miter box should be designed so that it can assist in creating a 45 degree undercut along a 90 degree angled cut. In addition, the miter box should be designed such that the shoe of the handheld portable circular saw is afforded more stability and easier alignment with the saw guide of a miter box. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a miter box for guiding a circular saw. The miter box can include an I-beam formed from a rigid base plate. The rigid base plate can have opposing first and second base plate edges disposed along the elongated length of the rigid base plate. A first flange and a second flange can be respectively attached to the opposing first and second base plate edges along the elongated length of the rigid base plate. The first and second flanges can be disposed generally transverse to the rigid base plate so as to define one or more channels between the first and second flanges. 
   The first and second flanges can each have a pair of opposing support faces. The opposing support faces on each of the first and second flanges can be disposed along opposing edge portions of each of the first and second flanges distal from the rigid base plate. A distance between the first and second flange can be chosen so that it is less than a length of a shoe of a circular saw with which the miter box is designed to be used. Consequently, the table can always be supported on at least two transverse surfaces when performing a cut. 
   A first transverse guide member can extend from a first support face on the first flange to a second support face on the second flange. The first transverse guide member can include a first guide surface and a second guide surface. The first guide surface can extend transversely to the first and the second support faces disposed on the first and second flanges, respectively. The second guide surface can be aligned with at least a portion of the first and second support faces. The first guide surface can be positioned a predetermined distance from an end portion of the I-beam. For example, the predetermined distance can be less than a distance between a saw blade and a shoe edge of a circular saw. The first guide surface, the second guide surface, a portion of the first support face and/or a portion of the second support face can be formed of a friction reducing material. 
   The miter box can further include opposing third and fourth base plate edges. The opposing third and fourth base plate edges can respectively extend between opposing ends of the first and second base plate edges. Notably, the opposing first and second base plate edges can be of unequal length. Consequently, one or more of the third and fourth base plate edge portions can form an angle of either about 45 degrees or 135 degrees with one or more of the first and second base plate edges. Moreover, the first guide surface can form an angle of about 45 degrees or 135 degrees with one or more of the first and second base plate edges. 
   In addition to a first transverse guide member, the miter box can include a second transverse guide member. The second transverse guide member can also extend from the first support face on the first flange to the second support face on the second flange. The second transverse guide member can include a third guide surface and a fourth guide surface. The third guide surface can extend transversely to the first and the second support faces disposed on the first and second flanges, respectively. The fourth guide surface can be aligned with at least a portion of the first and second support faces. The third guide surface can be positioned a predetermined distance from an end portion of the I-beam. The predetermined distance can be less than a distance between a saw blade and a shoe edge of a circular saw. The third guide surface, fourth guide surface, a portion of the first support face, and a portion of the second support face can be formed of a friction reducing material. 
   The first and second flanges can each have a first and second flange end face. The first and second flange end faces can extend between the pair of opposing support faces on the first flange (first and third support faces) and on the second flange (second and fourth support faces). One or more of the first and second flange ends can each form a 45 degree angle with one or more of the pair of opposing support faces. Alternatively, both of the first and second flange end faces can form a 45 degree angle with one or more of the pair of opposing support faces. 
   In addition to the first and second transverse guide members, the miter box can include a third transverse guide member. The third transverse guide member can extend from the third support face on the first flange to the fourth support face on the second flange. The third transverse guide member can include a fifth guide surface and a sixth guide surface. The fifth guide surface can extend transversely to the third and the fourth support faces disposed on the first and second flanges, respectively. The sixth guide surface can be aligned with at least a portion of the third and fourth support faces. The fifth guide surface can be positioned a predetermined distance from an end portion of the I-beam. For example, the predetermined distance can be less than a distance between a saw blade and a shoe edge of a circular saw. The fifth and/or sixth guide surfaces and/or a portion of the third and/or fourth support faces can be formed of a friction reducing material. Furthermore, the third transverse guide member can be aligned with the first transverse guide member. 
   Another embodiment of the invention can include two or more spacer elements that can be attached to the support faces in order to provide greater stability to the miter box. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the miter box that is useful for understanding the invention. 
       FIG. 2  is a top view of the miter box that is useful for understanding the invention. 
       FIG. 3  is a bottom view of the miter box that is useful for understanding the invention. 
       FIG. 4  is a front elevational view of the miter box that is useful for understanding the invention. 
       FIG. 5  is a rear elevational view of the miter box that is useful for understanding the invention. 
       FIG. 6  is a right side elevational view of the miter box that is useful for understanding the invention. 
       FIG. 7  is a left side elevational view of the miter box that is useful for understanding the invention. 
       FIG. 8  is perspective view of another embodiment of the miter box that is useful for understanding the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring particularly to  FIG. 1 , there is shown an improved miter box  100 . The miter box  100  can include an I-beam comprised of a rigid base plate  101 . The rigid base plate  101  can include opposing first and second base plate edges,  102  and  103  respectively. The first and second base plate edges  102 ,  103  can be disposed along an elongated length of the rigid base plate  101 . The rigid base plate  101  and the miter box  100 , in general, can be formed of molded plastic, wood, or metal. However, the invention is not limited in this regard and other materials may be used so long as the miter box  100  can provide a strong and durable surface to support the weight of a workpiece  206  to be cut, a circular saw&#39;s weight and vibration, and the pressure applied by the user to the miter box when operating the saw. 
   A first flange  104  and a second flange  105  can be respectively attached to the opposing first and second base plate edges  102 ,  103  along the elongated length of the rigid base plate  101 . The first and second flanges  104 ,  105  can be disposed generally transverse to the rigid base plate  101  so as to define one or more channels  106  between the first and second flanges  104 ,  105 . For example, the flanges can form an angle of about 90 degrees with the base plate. The channels  106  can be formed to support the weight of a workpiece to be cut. The workpiece can be disposed through these channels and rest atop of the rigid base plate  101 . Moreover, the work piece can be held in place such that it is supported and aligned by the rigid base plate  101  and portions of interior faces of the first and second flanges  130 ,  131 . 
   The first and second flanges  104 ,  105  can each have a pair of opposing support faces  107 – 110 . The opposing support faces on the first flange  104  can include a first and a third support face,  107  and  109  respectively. The opposing support faces on the second flange can include a second and a fourth support face,  108  and  110  respectively. The opposing support faces  107 – 110  on each of the first and second flanges  104 ,  105  can be disposed along opposing edge portions  111 – 114  of each of the first and second flanges  104 ,  105  distal from the rigid base plate  101 . The combination of the first and second support faces  107 ,  108  can support a circular saw, where portions of a saw&#39;s shoe (referred to as  207  and shown using phantom lines in  FIGS. 2 ,  3 , and  5 ) rests on the support faces. Alternatively, if the miter box is turned upside-down, the combination of the third and fourth support faces  109 ,  110  can also be used to support a circular saw, where portions of the saw&#39;s shoe  207  rests on the support faces  109 ,  110 . 
   A first transverse guide member  115  can extend from the first support face  107  on the first flange  104  to the second support face  108  on the second flange  105 . The first transverse guide member  115  can include a first guide surface  116  and a second guide surface  117 . The first guide surface  116  can extend transversely to the first and the second support faces  107 ,  108  disposed on the first and second flanges  104 ,  105 , respectively. The second guide surface  117  can be aligned with at least a portion of the first and second support faces  107 ,  108 . A saw&#39;s shoe  207  can rest on the smooth surface formed from the combination of the first and second support faces  107 ,  108  and the second guide surface  117 . The side edge  205  of the shoe  207  can be aligned and guided by the first guide surface  116 . In order to facilitate the operation of the circular saw, the first and second support faces  107 ,  108  and the first and second guide surfaces  116 ,  117  can be formed or coated with a friction reducing material. Examples of friction reducing coatings include, but are not limited to polytetrafluoroethylene (PTFE), fluorinated ethylenepropylene (FEP), polyvinylidene fluoride (PVDF), perfluoroalkoxy (PFA), ethylene chlorotrifluoroethylene (ECTFE), molybdenum disulfide (MoS 2 ), and other polymer blends. The friction reducing material would allow the saw&#39;s shoe  207  to glide easier over the surfaces  107 ,  108 ,  116 ,  117  while the saw is in operation. 
   Referring now to  FIGS. 2 and 5 , the first guide surface  116  can be positioned a predetermined distance  202  from an end portion of the I-beam. The predetermined distance  202  can be less than a distance between a saw blade  204  (shown using phantom lines) and a shoe edge  205  of a circular saw  501  (both shown using phantom lines). The predetermined distance can be designed such that the end portions of the I-beam do not interfere with the cutting motion of the saw blade  204  when cutting a workpiece  206  (shown using phantom lines). 
   Referring back to  FIGS. 1 and 2 , the miter box  100  can further include opposing third and fourth base plate edges,  118  and  119  respectively. The opposing third and fourth base plate edges  118 ,  119  can respectively extend between opposing ends of the first and second base plate edges  102 ,  103 . The opposing first and second base plate edges  102 ,  103  can be of unequal length to provide an angled end(s) to the miter box. For example,  FIG. 1  shows how the third base plate edge portion  118  can form an angle β of 45 degrees with one or more of the first and second base plate edges  102 ,  103 . Similarly shown in  FIGS. 1 and 2 , the first guide surface  116  can form an angle α of about 45 degrees with one or more of the first and second base plate edges  102 ,  103 . Moreover, referring to  FIG. 3 , the fourth base plate edge portion  119  can form an angle δ of 90 degrees with one or more of the first and second base plate edges  102 ,  103 . Finally, the third guide surface  122  can form an angle E of about 90 degrees with one or more opposing edge portions  111 ,  112 . 
   In addition to a first transverse guide member  115 , the miter box  100  can include a second transverse guide member  120 , shown in  FIGS. 1 and 2 . The second transverse guide member  120  can extend from the first support face  107  on the first flange  104  to the second support face  108  on the second flange  105 . The second transverse guide member  120  can include a third guide surface  121  and a fourth guide surface  122 . The third guide surface  121  can extend transversely to the first and the second support faces  107 ,  108  disposed on the first and second flanges  104 ,  105 , respectively. The fourth guide surface  122  can be aligned with at least a portion of the first and second support faces  107 ,  108 . One or more cap frame(s)  130  can be disposed on portions of the support faces  107 – 110 . The cap frame(s)  130  can include a portion of one or more of the transverse guide members  115 ,  120 , and  127 . 
   A saw&#39;s shoe  207  can rest on the smooth surface formed from the combination of the first and second support faces  107 ,  108  and the fourth guide surface  122 . The side edge  205  of the shoe  207  can be aligned and guided by the third guide surface  121 . In order to facilitate the operation of the circular saw, the first and second support faces  107 ,  108  and the third and fourth guide surfaces  121 ,  122  can be formed or coated with a friction reducing material such as the ones discussed earlier. The friction reducing material would allow the saw&#39;s shoe  207  to glide more easily over the surfaces  107 ,  108 ,  121 ,  122  while the saw is in operation. 
   The third guide surface  121  can be positioned a predetermined distance  203  from an end portion of the I-beam. The predetermined distance  203  can be less than a distance between a saw blade and a shoe edge of a circular saw  205 . As mentioned earlier, the predetermined distance can be designed such that the end portions of the I-beam do not interfere with the cutting motion of the saw blade. 
   The first and second flanges  104 ,  105  can each have a first and second flange end faces  123 – 126 .  FIGS. 1 ,  6 , and  7  illustrate the placement of these end faces  123 – 126 . The first and second flange end faces of the first flange  123 ,  124  can extend between the pair of opposing support faces on the first flange (first and third support faces  107 ,  109 ). The first and second flange end faces of the second flange  125 ,  126  can extend between the pair of opposing support faces on the second flange (second and fourth support faces  108 ,  110 ). 
   Referring now to  FIGS. 1 ,  4 , and  5 , one or more of the first and second flange end faces  124 ,  126  can each form a 45 degree angle γ with one or more of the respective support faces  107 ,  108 . According to another embodiment of the invention, both of the first and second flange end faces  123 – 126  can form the 45 degree angle γ with one or more of the pair of opposing support faces  107 – 110 . Given that conventional circular saws have a mechanism whereby the saw blade can be tilted 45 degrees relative to a level shoe  207 , the 45 degree angle γ can be formed so that a circular saw ( 501 , shown using phantom outline) may be adjusted to perform 45 degree undercuts, as shown in  FIG. 5 . 
   In addition to the first and second transverse guide members  115 ,  120 , the miter box  100  can include a third transverse guide member  127 , shown in  FIGS. 1 and 3 . The third transverse guide member  127  can extend from the third support face  109  on the first flange  104  to the fourth support face  110  on the second flange  105 . The third transverse guide member  127  can include a fifth guide surface  128  and a sixth guide surface  129 . 
   The fifth guide surface  128  can extend transversely to the third and the fourth support faces  109 ,  110  disposed on the first and second flanges  104 ,  105 , respectively. The sixth guide surface  129  can be aligned with at least a portion of the third and fourth support faces  109 ,  110 . The saw&#39;s shoe  207  can rest on the smooth surface formed from the combination of the third and fourth support faces  109 ,  110  and the sixth guide surface  129 . The shoe edge  205  of the saw&#39;s shoe  207  can be aligned and guided by the fifth guide surface  129 . In order to facilitate the operation of the circular saw, the third and fourth support faces  109 ,  110  and the fifth and sixth guide surfaces  128 ,  129  can be formed or coated with a friction reducing material such as the ones discussed earlier. The friction reducing material would allow the shoe  207  to glide more easily over the surfaces  109 ,  110 ,  128 ,  129  while the saw is in operation. 
   The fifth guide surface  128  can be positioned a predetermined distance  202  from an end portion of the I-beam. The predetermined distance  202  can be less than a distance between a saw blade and a shoe edge  205  of a circular saw. As mentioned earlier, the predetermined distance can be designed such that the end portions of the I-beam do not interfere with the cutting motion of the saw blade. Furthermore, the third transverse guide member  127  can be aligned with the first transverse guide member  115 . This alignment of the first and third transverse guide members  115  and  127  can expand the functionality of the miter box by adapting the miter box for right or left handed saw users. 
   According to another embodiment of the invention shown in  FIG. 8 , one or more spacer elements  801  can be removably coupled to one or more support faces  107 – 110  in order to provide additional stability to the miter box  100 . When operating the saw with the miter box, the spacer element(s)  801  can be coupled to those support faces that are not in use. The spacer element  801  can include one or more tabs  802  that can frictionally engage with one or more notches  803  formed on the support faces  107 – 110 . In one alternative, the spacer element  801  and tabs  802  can be formed of a resilient and shock absorbent material to dampen the operational vibration of the circular saw  501 . Such resilent and shock absorbent material can include, but is not limited to, rubber/elastomer types such as polyurethane rubber, buna rubber, Viton® rubber, neoprene™, EPDM rubber, silicone RTV, fluorosilicone rubber, and other polymer materials. 
   While specific embodiments of the invention have been disclosed, it will be appreciated by those skilled in the art that various modifications and alterations to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.