Patent Publication Number: US-2005115639-A1

Title: Multifunctional auxilliary base system for electric woodworking routers

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      60/520,388  
     FEDERALLY SPONSORED RESEARCH  
      Not Applicable  
     SEQUENCE LISTING OR PROGRAM  
      Not Applicable  
     BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      This invention relates to hand held woodworking routers, specifically an auxiliary base that allows users to switch tasks, guides and accessories quickly, even between different sizes and brands of routers.  
      2. Background of the Invention  
      Hand-held woodworking routers can perform a wide range of tasks and this utility can be greatly increased by attaching auxiliary bases, guides and other accessories. Offset bases for added control and stability, edge guides for rabbet and dado milling, circle cutting jigs, center cutting adapters, dust collectors, curved edge guides, and a host of other add-on bases expand the usefulness of the hand held routers.  
      Often, changing these bases and accessories requires tools and time that the woodworker can better employ in other ways. Further difficulties are encountered if a woodworker owns more than one brand or size of router, since each may have specific and distinctive mounting holes. This means that these jigs and fixtures are generally usable only on one brand or size of router.  
      An additional problem is encountered in the bit opening of the router base plate. For maximum safety and best results, the base plate opening should be sized properly for the bit being used, and template routing requires a special base plate that accepts some form of guide bushing. This is typically accomplished by switching between base plates with differing sized openings, or with changeable openings in a single base plate.  
      Lastly, specific and specialized tasks may require a purpose-built accessory, necessitating the user to create their own requiring yet another base plate change-over.  
      Inventors, tool suppliers and woodworking authors have acknowledged these issues, and solutions have been presented any number of times both in the marketplace and in print.  
      For example Eagle America Corp. offers in their catalog an auxiliary base plate called a “Router Tri-Jig” that incorporates an offset base with an edge guide and circle cutter. This same company also offers for sale a different base plate called a “4-in-1 Universal Router Base Plate” that addresses the bit opening issue, but these two are not designed to be used together or in conjunction with any other accessory.  
      ShopNotes Issue 61, Volume 11, contains plans and instructions for an auxiliary base system that can perform five separate functions without changing the base, but the system is limited to those five operations, and cannot use guide bushings.  
      U.S. Pat. No. 5,452,751 to Engler and McCann, and U.S. Pat. No. 6,070,626 to Tully show router bases that perform multiple functions. The Engler and McCann design performs up to eight functions, but two different router mounting locations are required to utilize all of the functions, and is relatively large for hand-held router operations. This unit also lacks the ability to adjust the bit opening size. Tully shows a three-function base, but it is limited to three specific functions and also lacks the ability to size the opening for the bit.  
      In conclusion, insofar as I am aware, no router base or accessory provides for more than a fixed number of specific functions, and none can be easily moved between different styles or brands of routers. All of these bases, while useful, do not constitute a modular, systematic approach to increasing the router&#39;s functionality and limiting changeover time between functions, and none allow for easy custom adaptation by the user.  
     BACKGROUND OF THE INVENTION—OBJECTS AND ADVANTAGES  
      The invention, an improved auxiliary router base plate for electric woodworking routers, contains a profile groove that accepts a mating profile beam. This profile beam is part of each accessory, allowing the user to switch accessories, and hence router functions, quickly and without tools, even switching accessories from one router to another. The profile of the groove and beam are such that the beam is self-centering on the groove maintaining a close tolerance relative to the base plate and the router. This groove and beam arrangement further allows the user to create custom accessories for specific tasks utilizing the auxiliary base plate, maintaining the ability to use these shop-built accessories between different routers.  
      The base plate also contains a means for clamping the beam, preventing movement once set. This clamping mechanism allows for positioning the accessories relative to the cutting edge of the tool and holding them in place during use.  
      The base plate further contains a means for switching between different throat plates to accommodate various diameters of bits and provide for the use of guide bushings.  
     SUMMARY  
      In accordance with the present invention an auxiliary router base plate is comprised of a body having a profiled slot milled along the major axis to accept multiple tools and accessories. This router base plate, along with it&#39;s attendant accessories and throat plates comprise a cohesive, modular system for expanding the capabilities of the router, simplifying operational changes, allowing use of accessories between different types and brands of routers, as well as enabling the user to more easily create shop-built accessories for specific tasks. 
    
    
     DRAWINGS—FIGURES  
       FIG. 1  shows the router base plate, a generic electric woodworking router, some, but not all, of the possible accessories mounted on the profile beam, and a number of the interchangeable throat plates.  
       FIG. 2  shows a left underside view of the router base plate including the profile groove, profile beam, locking tab access hole, grip block, grip knob and locking knob and one of the throat plates.  
       FIG. 3  shows the rear right of the base plate including the profile slot, locking tab access hole, router mounting holes, and grip block mounting holes.  
       FIG. 4  shows the underside of the router base plate in plan view with section view A-A showing the profile groove in cross section and B-B showing the throat plate groove in cross section.  
       FIG. 5  shows an exploded view of the grip block assembly showing the grip block, grip block base plate, locking tab, grip knob, locking knob, and the grip knob fastener.  
      FIGS.  6 A-C show three views of the base plate  11  with alternative embodiments of the profile groove  13 . 
    
    
     DRAWINGS—REFERENCE NUMERALS  
     
         
           11  base plate  
           13  profile groove  
           15  grip block  
           16  grip block base plate  
           17  grip knob  
           18  grip knob fastener  
           19  locking knob  
           21  profile beam  
           21 A edge guide  
           21 B trammel guide  
           23  throat plate groove  
           24  throat plate mounting holes  
           25  throat plate  
           25 A wide opening throat plate  
           25 B bushing adapter throat plate  
           27  electric woodworking router  
           29  router mounting hole  
           31  locking tab  
           32  locking tab access hole  
           33  grip block mounting hole  
           34  grip knob mounting hole  
           35  locking knob mounting hole  
           36  clearance hole  
           37  guide bushing  
           37 A guide bushing lock nut  
       
    
     DETAILED DESCRIPTION—FIGS.  1 - 5  PREFERRED EMBODIMENT  
      The preferred embodiment of the present invention is illustrated in  FIGS. 1 through 5 . In the preferred embodiment the base plate  11  is constructed of polycarbonate, however may be constructed of any material of similar stiffness and dimensional tolerance such as nylon, wood, metal or phenolic in accordance with the invention.  
      The base plate  11  of the invention has router mounting holes  29  on the primary, or wider, end for attaching an electric woodworking router  27 . Located concentrically between said router mounting holes  29  is an opening, known as a throat in the art, for the router bit to extend through the base plate  11  in order to reach the work piece. The lower edge of this throat contains a throat plate groove  23  and throat plate mounting holes  24  to locate and secure any one of several throat plates  25 ,  25 A,  25 B.  
      The base plate  11  also contains a profile groove  13  running longitudinally along the base plate  11  beginning at the throat and exiting the minor end of the base plate  11 . In the preferred embodiment of the invention, the cross section of the profile is shown in  FIG. 4  section A-A. A locking tab access hole  32  is provided through the top face of the base plate  11  extending into the centerline of the profile groove  13  providing access for the locking tab  31  to engage and secure the profile beam  21  when in use.  
      Grip block mounting holes  33  are provided on the minor end of the base plate  11  on each side of the profile groove  13  to secure the grip block plate  16  and grip block  15  to the base plate  11 .  
      The invention further possesses a profile beam  21  with a cross section profile that closely fits into the profile groove  13  of the base plate  11  while retaining the ability to freely move longitudinally within the profile groove  13 . In the preferred embodiment, this profile beam  21  is constructed of nylon or other material with similar stiffness and dimensional tolerance.  
      As shown in  FIG. 5 , the locking tab  31  is constructed as part of the grip block plate  16 , and in the preferred embodiment, is fabricated from polycarbonate. This plate also provides a clearance hole  36  for the grip knob fastener  18  protruding from the grip block  15 .  
      In the preferred embodiment the grip block  15  is constructed of wood. All perimeter edges and all top face edges are rounded. Two through holes are provided, a grip knob mounting hole  34  for the grip knob fastener  18  to pass through and a locking knob mounting hole  35  for the locking knob  19 . The grip block  15  is mounted to the grip block base plate  16  and base plate  11  in such a fashion as to allow the stud of the locking knob to engage the locking tab  31 . The locking knob  19  flexes the locking tab  31  through the locking tab access hole  32  in the base plate  11  thereby engaging the profile beam  21  preventing movement of the profile beam  21 .  
     FIGS.  6 A,  6 B,  6 C—ALTERNATIVE EMBODIMENTS  
      While the profile groove  13  in base plate  11  is central to the purpose and scope of the invention, the shape of the profile groove  13  can be any one of a number of suitable shapes as shown in FIGS.  6 A-C. The profile must be such that the profile beam  21  can only be moved longitudinally and not along any other axis. Provided this restriction, the actual shape of the profile groove  13  and the profile beam  21  is unimportant. Three possible alternative embodiments are shown.  FIG. 6A  shows a dovetail profile,  FIG. 6B  shows an oribund profile, and  FIG. 6C  shows a shouldered profile.  
      Operation  
      In operation the base plate  11  remains attached to the electric woodworking router  27  as the user performs the required milling operations. For using a bearing guided cutting tool for example, the flat profile beam  21  is inserted into the profile groove  13  to provide a smooth and flat base for the router. The additional area of the base plate  11  and the offset of the grip knob  17  from the cutting tool provides increased control of the entire system, particularly around the corners of the work piece where less that one quarter of a standard base plate would be in contact with the work piece. The rounded front portion of the base plate  11 , being concentric to the cutting tool, allows for use in conjunction with a typical straight edge guide when needed.  
      To change over to routing with the edge guide  21 A, the profile beam  21  is removed and replaced with the edge guide  21  A. The edge guide  21  A is set to the desired position relative to the cutting bit, and clamped in position using the locking knob  19 .  
      In a like manner, many other tasks can be performed by mounting the appropriate accessories to the base plate  11 . All such accessories include a profile beam  21  to allow for mounting to the base plate  11 . A list of the possible accessories includes but is not limited to: 
          Profile beam  21  for offset base operations or mounting custom shop-built accessories.     Edge guide  21 A for cutting dados and rabbets.     Variable radius edge guide for cutting rabbets and dados on curved parts.     Centering base for mortise and groove cutting.     Trammel guide  21  B for circle cutting.     Edge band trimmer.     Dust collection cup.     Router table insert plate.        

      In addition to utilizing the profile beam  21  and like accessories, the throat plate  25  can be changed to provide different throat opening sizes for different sizes of cutting tools. Providing a close fitting throat opening is widely recognized within the art as promoting operational safety and milling accuracy. An additional bushing adapter throat plate  25 B is provided to accept a guide bushing  37 , common to the art, for template routing.