Abstract:
A miter saw design with a cutting arm pivot mechanism that allows the pivot point of the cutting arc to move in a predetermined path in the plane described by the rotating cutting surface. The “floating pivot” enables the tool to accommodate larger pieces of material than conventional miter saws with the same diameter cutting blade. This design also allows the saw to be more compact, lighter in weight, and less complex in comparison to the sliding miter saw. Thus, a miter saw can be provided that provides the cutting capacity of a larger saw with less weight, bulk, and cost than the current alternatives.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This Application is a continuation of application Ser. No. 11/786,070, filed with the U.S. Patent and Trademark Office on Apr. 10, 2007, and a continuation-in-part of application Ser. No. 10/796,666 entitled Miter Saw with Increased Cutting Capacity, filed with the U.S. Patent and Trademark Office on Mar.    8 ,  2004   , now U.S. Pat. No. 7,201,091. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to miter saws, specifically those miter saws used to cut wood, metals, and plastics. 
         [0004]    2. Background of the Invention 
         [0005]    Saws and other apparatuses designed for cutting or performing other working operations on a workpiece, particularly miter saws, typically include mechanisms for moving the saw blade or cutting tool in relationship to the workpiece. Examples of such equipment include miter saws that are adapted for allowing the user to selectively move the saw blade in a vertical plane for cutting. Miter saws are used to make a precise end cuts in these materials, and one of the primary defining characteristics of these types of saws is the maximum capacity in length and depth of cut. It is generally desirable to have a saw with enough capacity to cut the most commonly encountered materials for the job at hand. Two methods of increasing capacity are well understood by the industry. The first method is to increase the diameter of the cutting blade in order to increase the effective cross section of the cut. The primary drawbacks of this method is that the entire saw must be made larger to accommodate a larger saw blade, which adds weight, volume, and cost to the saw. 
         [0006]    The second method typically uses a rail and bearing assembly that allows the cutting head to traverse across the material to be cut, thereby increasing the effective cross section of the cut. This method also has significant drawbacks, due to increases in material costs, weight, and complexity. 
         [0007]    The intent of the discovery process was to determine if there was another method to increase the capacity of a miter saw that avoided or minimized the increase in weight, volume, cost, and complexity. Such a saw would be very beneficial to a user who is interested in a miter saw with the capacity of a larger saw without increased size and weight. Saws with large capacity tend to be heavy, bulky, and expensive. On the other hand, saws that are less heavy and more compact often do not have the capacity necessary to meet the user&#39;s requirements. From the foregoing, it is apparent that there is a need for a miter saw with increased saw capacity without adding significantly to the cost, weight, and size of the unit. 
         [0008]    U.S. Pat. No. 7,201,091, which was granted on Apr. 10, 2007, describes a miter saw design that uses a “floating pivot” mechanism to accommodate workpieces that are larger than conventional miter saws with the same diameter cutting blade. This design also allows for a lighter, more compact, and less complex unit than a sliding miter saw. U.S. Pat. No. 7,201,091 envisions a pivot assembly consisting of two bearing surfaces and a fixed track to constrain and guide the saw&#39;s motor assembly in the preferred cutting path. This mechanism is constructed in a way such that the pivot point of the cutting arc is not fixed at a single point. Instead, the pivot point is allowed to move in the same plane as the cutting surface, which has the effect of increasing the effective radius of the cutting edge. 
       SUMMARY 
       [0009]    It is, therefore, an object of the present invention to provide a miter saw with increased capacity that avoids the disadvantages of the prior art. 
         [0010]    Another object of the present invention is to provide a miter saw that can safely make a longer cut. A related object is to provide a miter saw having a floating pivot point. 
         [0011]    This improvement results in a miter saw with the capacity of a larger saw without increasing the diameter of the saw blade or the addition of a sliding rail assembly. The improved miter saw can be made smaller, lighter, and for less cost than a typical unit can. 
         [0012]    This invention improves some of the features described in U.S. Pat. No. 7,201,091, which uses smooth bearings as pivot surfaces and a smooth track to guide the bearings. One advantage of this arrangement is increased cutting capacity with a simple, lightweight, and compact design. However, such bearing arrangement also has the potential for sideways movement, which is due to the tendency for the low friction surfaces of the pivot bearings and track to slide in all directions, providing the potential for the cutting blade to move slightly from side to side. Unintended movement of the cutting blade can introduce inaccuracy into the cutting path of the saw blade, which is undesirable in a miter saw. 
         [0013]    The present invention introduces geared surfaces to the pivot bearing and pivot track assembly. It will be understood by those skilled in the mechanical arts that different gear tooth styles and configurations may be utilized in this assembly. One of the benefits of using geared surfaces is the tendency for the gear teeth to control the off-axis movement of the pivot mechanism as the saw blade traverses through its full range of cutting motion. 
         [0014]    Accordingly, the present invention contemplates the use of linear gears on one or both sides of the track. The pivot gears engage the linear gear on whichever side each respective pivot gear is biased towards. The movement of the pivot gears within the linear gear provides the cutting path of the saw blade. 
         [0015]    This invention enables a miter saw with increased cutting capacity, having a cutting surface that is mounted on a rigid arm with an improved pivot mechanism. The pivot mechanism is constructed in a way such that the pivot point of the cutting arc is not fixed at a single point. Instead, the pivot point is allowed to move in the same plane as the cutting surface, which has the effect of increasing the effective radius of the cutting edge. 
         [0016]    The various features of novelty that characterize the invention will be pointed out with particularity in the claims of this application. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above and other features, aspects, and advantages of the present invention are considered in more detail, in relation to the following description of embodiments thereof shown in the accompanying drawings, in which: 
           [0018]      FIG. 1  is a right-side perspective view of a prior art miter saw design, showing the cutting blade affixed to an arm that pivots about a fixed point. 
           [0019]      FIG. 2  is a right-side perspective of a prior art sliding-type miter saw design, showing the cutting blade affixed to an arm that pivots about a fixed point. 
           [0020]      FIG. 3  is a right-side perspective of a miter saw with a pivot mechanism that incorporates the present invention. 
           [0021]      FIG. 4  is an enlarged view of a portion of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    The invention summarized above and defined by the enumerated claims may be better understood by referring to the following description, which should be read in conjunction with the accompanying drawings in which like reference symbols are used for like parts. This description of an embodiment, set out below to enable one to build and use an implementation of the invention, is not intended to limit the enumerated claims, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent assemblies do not depart from the spirit and scope of the invention in its broadest form. 
         [0023]      FIG. 1  is a right-side perspective view of a typical prior art miter saw design that shows a circular saw blade  10  affixed to a rotating motor shaft at  13 . This assembly is mounted to an arm  15  that is pivotably attached to a stationary table  18  at a single pivot point  20 . Pivot point  20  becomes the origin of the XYZ axes where the cutting surface is defined by the X-Z plane. The cutting path, indicated generally at  22 , is described by an arc of radius R, which is the fixed distance between the pivot point  20  and the motor shaft  13  in the Y-Z plane. The depth and width of cut is defined by a chord of the saw blade as it passes into a slot on the stationary table  18  and the distance from the motor shaft  13  to the surface of the table  18 . 
         [0024]      FIG. 2  is a right-side perspective view of a typical prior art sliding miter saw design that shows the circular saw blade  10  affixed to rotating motor shaft  13 . This assembly is mounted to an arm  15  that is pivotably mounted to the front part of the sliding rail assembly  25  at a single pivot point  20 . Rail assembly  25  is constrained along the Z-axis by a stationary bearing assembly  28 . The lateral movement of rail assembly  25  produces an action that causes the pivot point  20  to move along the cutting plane for a distance L. This increases the width of cut by enabling the cutting path  22  with radius R to traverse across the work surface. 
         [0025]      FIG. 3  shows a right-side perspective of one example of an improved miter saw that employs a “floating pivot” as contemplated by the present invention. The saw, indicated generally as  30 , comprises blade  33  affixed to motor shaft  35  to form a blade and motor assembly  37 , which is affixed to a rigid arm  40 . The rigid arm  40  is movably attached to a stationary bracket  43  on the back of stationary table  46 . 
         [0026]    Referring to  FIG. 4 , arm  40  is attached to post  43  by a pivot assembly  51  comprising two bearing surfaces  53 ,  54 . Such bearing surfaces  53 ,  54  may be rolling bearings or other suitable bearings. In a preferred embodiment, the pivot assembly  51  further comprises a fixed track  58 , such that bearings  53 ,  54  are constrained in the fixed track  58  in the post  43 . Such track  58  is sized and configured to enable the bearings  53 ,  54  to move within the track  58 , causing the pivot point of arm  40  to shift. As shown in  FIG. 4 , the bearing surfaces  53 ,  54  may comprise toothed gears or pinions and the track  58  may also include a toothed rack that enables the toothed gears or pinions to engage therein. For purposes of illustration, the drawings show the use of straight cut pinions and a linear gear for the pivot track. Typically, the gear in the track  58  will only be included on one side of the track  58 . One skilled in the relevant art can readily determine whether the gear should be on the top or bottom side of the track  58 . In some embodiments, such gear may be on the top side for one portion of the track  58  and on the bottom side for another portion of the track  58 . As the blade and motor assembly  37  moves down towards a work surface, the bearings  53 ,  54  and track  58  in pivot assembly  51  cause the effective (or floating) pivot  60  to move in an eccentric arc. This in turn produces a cutting path  63  with radius R that is not semicircular. Instead, the cutting path  63  follows an eccentric path in the Y-Z plane that results in an increased width of cut at the work surface. 
         [0027]    The disclosed embodiment shows the pivot assembly comprising a pair of toothed gears and a toothed rack. In an alternate embodiment, the floating pivot can be achieved by a cam assembly, by a pulley system, or by a gear assembly. Other methods of achieving such floating pivot will become apparent to those skilled in the art by following the teaching of the present invention. In some embodiments, the track  58  will be contained in the post  43  and the bearings  53 ,  54  will be contained in the arm  40 . In other embodiments, the track  58  will be contained in the arm  40  and the bearings  53 ,  54  will be contained in the post  43 . 
         [0028]    In operation a user operates the improved miter saw  30  in a normal manner by placing the material to be cut on the stationary saw table  46  and moving the blade assembly  37  and arm  40  down toward the material using a typical handle assembly (not shown). As the user applies downward pressure on the blade assembly  37 , the pivot assembly  51  described by bearings  53 ,  54  and fixed track  58  enables the blade  33  to move along the cutting arc  63  without deviation. The user is able to make a wider cut because the blade  33  moves parallel to the surface of table  46  as the cutting path  63  changes from an eccentric curve to a straight path along the Z-axis. 
         [0029]    In an alternate embodiment, a biasing mechanism, such as a spring assembly, can be incorporated into the pivot assembly  51  to enable the cutting arm  40  to return to the upright position easily and safely. 
         [0030]    The invention has been described with references to a preferred embodiment. While specific values, relationships, materials and steps have been set forth for purposes of describing concepts of the invention, it will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the basic concepts and operating principles of the invention as broadly described. It should be recognized that, in the light of the above teachings, those skilled in the art could modify those specifics without departing from the invention taught herein. Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It is intended to include all such modifications, alternatives and other embodiments insofar as they come within the scope of the appended claims or equivalents thereof. It should be understood, therefore, that the invention might be practiced otherwise than as specifically set forth herein. Consequently, the present embodiments are to be considered in all respects as illustrative and not restrictive.