Patent Publication Number: US-6904689-B2

Title: Guide device

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to novel guide device for cutting lap joints with a router or laminate trimmer, and more particularly to a lap joint jig by which lap joints can be easily cut with exceptional accuracy in a very short time. The jig enables hobbyists to produce professional looking lap joints without the need for various templates, fences, or complicated procedures. The present jig also allows a number of lap joints to be produced continuously so that a number of framing projects, etc. can be accomplished on a scale approaching mass production. 
   2. Description of the Related Art 
   Miter joints, as represented in  FIG. 8 , are one method of making rectangular frames, etc., but they are difficult to make accurately, even more difficult to make visually attractive and tend to be relatively weak. As an alternative, lap joints are a professional method of producing frames for pictures, doors, etc., by which the end grain of the wood along the sides of the frame can be hidden, while achieving an incredibly strong frame joint. The work of forming lap joints for picture frames, etc., has been performed in several ways, all of them requiring a number of steps and adjustments that introduce inaccuracies into the work. These processes make forming a frame that is square, strong and elegant a daunting task for all but the most experienced wood workers, both hobbyist and professional alike. For example, as shown in  FIGS. 9 and 10  one conventional method requires three templates, a 90 degree and 45 degree right and left hand templates  21 ,  22  &amp;  23  respectively. First, one of the templates is placed on a workpiece  24  and a cut  25  is formed by a rotary bit of a router  28  which is rested on the template, as seen in FIG.  11 . The bit of the router must be run along the edge of the template while the router is held firmly on top of the template. This is not very easy to do as the router is only partially supported on the template, as shown in the figure, easily ending up in uneven cuts as a result of a tilted router. Another conventional method of making lap joints is with the use of dado blades  29  as shown in FIG.  12 . However, one of the disadvantages of this method is the need to make an accurate cut at the starting point, a technique that requires a good eye and steady feed of the workpiece into the dado blades. As a result, inaccurate corner points or variances in the mitered cut mar the resultant frame with poor fit and reduced strength. Further, other methods using guides or fences have been proposed, but all suffer from being very complicated and inaccurate. 
   To overcome these problems, the present inventor developed, a novel guide device or jig for cutting lap joints by which extremely accurate lap joints can be easily formed without the need for templates, measurements or a variety of special fences. 
   SUMMARY OF THE INVENTION 
   The present invention has been made with a view to solve the problems stated above and its object is to provide a guide device for cutting lap joints and more particularly to a lap joint jig by which lap joints can be accurately and easily formed. 
   According to this invention, a guide device or jig for cutting a lap joint is provided which includes a rectilinear guide member or offset blade held within a frame. The frame is in a generally Y-shaped configuration and comprises a yoke portion at the top of the Y for holding the rectilinear guide member or offset blade in the first stage of preparing a lap joint, and a guide portion in the stem or leg of the Y for guiding a movable member or stopper, the movable stopper being lockable along the guide portion. The guide portion extends to be co-linear with one side of the yoke portion with the movable stopper extending perpendicular to thereto, forming a first adjustable guide surface. The other side of the guide portion forms an angle of 45 degrees with the other side of the yoke. A fixed stopper is formed near the junction of the yoke and this other side of the guide portion, the fixed stopper describing a 90 degree angle with this side of the yoke, with the apex of the angle set to be along the plane of the bottom of the offset blade when inserted. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a principal portion of the present device, the view also showing the offset blade as inserted in the yoke; 
       FIG. 2  is a side view of the present device shown in  FIG. 1 ; 
       FIG. 3  is a perspective view for explaining a method of cutting a lap joint using the present invention; 
       FIG. 4  is a perspective view for further explaining a method of cutting a lap joint using the present invention; 
       FIG. 5  is a view of two types of lap joints that can be made using the present invention; 
       FIG. 6  is a plan view of the present device showing the use of the movable stopper; 
       FIG. 7  is a perspective view of another embodiment of the invention; 
       FIG. 8  is a view of two types of conventional miter joints; 
       FIG. 9  is an explanatory view of templates used in a prior method of cutting a lap joint; 
       FIG. 10  is an explanatory view describing a prior method of cutting a lap joint using templates; 
       FIG. 11  is an explanatory view further describing the prior method of cutting a lap joint; 
       FIG. 12  is an explanatory view describing another prior method of cutting a lap joint. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of a guide device for lap joints according to this invention will be described hereunder with reference to the drawings. 
   In  FIG. 1 , one embodiment of the jig is shown in which  1  denotes a frame, the frame  1  consisting of a top portion  1   a  and a bottom portion  1   b ,  2  denotes a yoke portion of the frame (better viewed in FIG.  2 ),  2   a  being a removable portion of the frame,  3  is a guide portion of the frame with  3   a  being a guide way for a movable stopper  4 . A locking member  4   a  is provided in the movable stopper  4  so that the movable stopper may be locked in any position along the guide way  3   a . On the opposite side of the guide portion a fixed stopper  5  is formed. An offset blade  6  is comprised of a suitably trimmable material such as plastic with a pair of guide holes  6   a ,  6   a  (as shown in  FIG. 7 ) for fixing the guide member in the yoke. A pair of guide pins  8 ,  8  appropriately spaced from each other are provided in a pair of guide holes  9 ,  9  opened in the yoke portion of the frame  1  by suitable methods such as by press fitting. Guide pins  8  may also be screws removably threaded into the yoke  2 . Screws  10  are provided to hold the top and bottom portions  1   a ,  1   b  of the frame  1  together. In this way, the top portion  1   a  of the frame may be removed for insertion or removal of the offset blade  6 . 
   As can be seen from the drawings, the jig forms a sort of modified Y, with one arm of the Y extending at 45 degrees in relation to the foot of the Y and the other arm extending in a co-linear relationship with the leg or stem of the Y, to form a straight surface with the guide portion  3 . 
   The operation of this embodiment will be described below. As shown in  FIGS. 1 &amp; 3 , the offset blade  6  is inserted into the yoke portion  2  by first removing top portion  1   a . The top portion is then reattached to fix the offset blade  6  on the guide pins or screws  8 . Here it must be explained that the offset blade  6  can either be of a trimmable material or made to be an exact width for use with a particular make of laminate trimmer as will be explained in more detail later. Next, a work piece  11  or picture frame side in this example, is inserted along the 45 degree side of the Y to rest against the fixed stopper  5 . Then, a fence  12  is inserted into the yoke to ride along the top side of the offset blade  6 , as seen in FIG.  4  and clamped onto the work piece  11  by a c-clamp, for example. As can be understood from the drawings, the inside corner of the work piece  11  lays along the edge of the offset blade so that the fence  12  is spaced the width of the offset blade from the end corner of the work piece  11 , to form a 45 degree angle therewith. The clamped fence  12  and work piece  11  are then removed from the frame  1  maintaining their 45 degree relationship. 
   As seen in  FIG. 5 , two types of lap joints are particularly facilitated by using the jig of the present invention. Both types of lap joints are not only inherently strong, but useful for making picture frames, door frames and the like. With the fence clamped to the work piece  11  as described above, a mitered half-lap joint can be easily produced in the rail by cutting with a laminate trimmer along the work piece  11  while guiding the edge of the trimmer along the fence clamped to the work piece at precisely 45 degrees. Since the offset blade is either trimmed or initially made to be the same width as the distance from the edge of the trimmer to the closest edge of the cutting blade, guiding the trimmer along the fence will give an exact cut at 45 degrees along a line that runs accurately through the apex of the corner of the work piece  11 . This accurate cut performed on all four frame sides will provide a frame with the first cuts for making close fitting half lap joints having very accurate mitered points. The depth of cut is adjusted on the trimmer according to normal practice in order to give a flat surface to the finished frame, usually to cut down to half the thickness of the workpiece. 
   However, to finish the mitered half-lap joints, a square cut is also needed on the two work pieces  11  that are to become stiles  11   a  for a picture frame in this embodiment, the remaining two sides being rails  11   b . The square cuts are performed by using the movable stopper  4  with the offset blade  6  installed as before. First, as shown in  FIG. 6 , the end of a work piece  11  is placed against the straight surface formed along the guide portion  3 , with the long side of the work piece  11  riding along the offset blade  6 . The movable stopper  4  is then moved snugly against the other long side of the work piece  11  and locked in place by the locking member  4   a , and then the work piece  11  is removed. Therefore, it can be seen that this sets the distance from the offset blade  6  to the inside edge of the stopper  4  to be the same as the width of any of the work pieces  11 . Next, the stile to be cut is set lengthwise along the straight surface of the frame  1  with the end thereof resting against the locked movable stopper  4 , the distance between the edge of the offset blade and the end of the stile  11   a  being equal to the width of any work piece  11 . The stile is then clamped to the offset blade with a c-clamp or the like to maintain this distance, and the fence  12  is then inserted into the yoke to ride along the top of the offset blade  6  as before. The fence is then firmly clamped to the stile  11   a  and the clamp holding the blade  6  to the workpiece is released to allow the frame  1  to be removed from the clamped stile and fence. Again, using the trimmer adjusted to the correct depth, a square cut is performed guided by the fence allowing a straight accurate cut on both stiles to complete mitered half-lap joints. 
   Further, it goes without saying that end-lap joints can be cut by just performing the above procedure using the straight surface for square cuts on all work pieces. Also, it can be seen that only one fence setting is required using the device if the other work pieces are aligned and clamped alongside the work piece. 
   In  FIG. 7 , another embodiment of the jig is shown in which  13   a  is a removable portion of the yoke  13 . Here the guide pins  8  are preferably screws removably threaded into the yoke  13 . In this way, only the removable portion  13   a  of the yoke need be removed for insertion or removal of the offset blade  6 . 
   The operation of this embodiment will be described. As shown in  FIG. 7 , the offset blade  6  is inserted into the yoke portion  13  by first removing removable portion  13   a . The removable portion is then reattached to fix the offset blade  6  on the guide pins or screws  8 . This makes the fixing of the offset blade more convenient without the need to remove all of the top portion  1   a  of the frame. 
   As can be seen from the above, the present guide device for lap joints greatly facilitates the process of cutting both mitered half lap joints and end lap joints without the use of the templates, multiple fences, t-squares, etc. that are conventionally used. This allows reductions in both time spent making frames and in the number of inaccuracies that are inherently introduced with conventional methods. It provides even hobbyist woodworkers with a tool that allows the cutting of joints that are crisp, accurate and flush, resulting in frames with surprisingly professional appearance. The device is also compact, size being regulated only by the width of frames to be produced, so that storage is much less of a problem than encountered by using conventional methods. Further, due to the provision of both the movable stopper and fixed stopper, only one device is needed for a variety of frame projects, a versatility that can be appreciated by hobbyist with limited resources and/or space. Also, when the removable portion is provided, offset blade changes can be carried out rapidly making it easier to use different blades for a variety of trimmers or projects.