Patent Document

BACKGROUND OF THE INVENTION  
       [0001]     The present invention generally relates to power hand tools and more particularly to circular saws.  
         [0002]     Power hand tools such as circular saws have been commonly known for decades and generally have a foot plate that slides on a work piece that is being cut, a circular saw blade that may have a diameter as small as a few inches or as large as seven or more inches, with the saw blade extending through an opening generally perpendicular to the plane of the foot. The saw is typically driven by an electric motor that is powered by either an AC or DC power source, the DC power source often being a battery pack or the like.  
         [0003]     Circular saws are commonly used on construction sites to saw boards that are used in framing a building or for cutting large plywood or other material sheets into smaller pieces, all of which are known to those skilled in the power hand tool art. Such circular saws have been the subject of much research and development and significant improvements have been made in their design and construction over the many decades that they have been used.  
         [0004]     Significant developments have included improved blade guards, both above and below the blade for protecting a user from injury, with the lower blade guards being designed to be moved out of the way when a board or the like is to be cut. Ergonomic developments have been made so that user handles, including main handles or auxiliary handles, facilitate the easy cutting of a sheet or board along a desired path. The early circular saws were designed to only make perpendicular cuts relative to the work piece, but later developments included an adjustable bevel angle capability.  
         [0005]     Even with the many improvements that have been made in the design of circular saws, a common problem that continues to exist is the accumulation of sawdust and/or other debris on the line of cut which hinders the user from following the desired cut line to produce a straight and accurate cut. Improvements in motors that are used in circular saws and other hand tools have resulted in the motors being smaller in size relative to the power that they develop. Because cutting of some materials, particularly those which are relatively thick, put a significant load on the motor, it is necessary to have an adequate flow of air near the motor to dissipate heat during operation. Because of this requirement, many motors have an internal fan blade driven by the motor to expel air from the motor enclosure or housing for the purpose of cooling the motor. The air has been expelled through openings that have been positioned at many different locations in circular saws of the prior art.  
         [0006]     While the circular saw designs are sufficient to expel the air and dissipate heat during operation, little regard has heretofore been made in directing the air in any particular direction or for any apparent purpose other than to expel the air from inside the motor housing.  
       SUMMARY OF THE INVENTION  
       [0007]     The preferred embodiment of the present invention comprises one or more louvers in the housing of a hand tool such as a circular saw, which direct the air toward a specific location that includes the work piece, together with providing openings in other components of the tool located between the louvers and the portion of the work piece that the saw is approaching so that sawdust and other debris that is produced during operation of the tool will be blown out of the way and will not interfere with the line of sight of the user.  
         [0008]     The preferred embodiment is a circular saw having a gearbox located adjacent the output of the motor between the motor and the saw blade, with the gearbox having directional louvers that direct air produced by an internal fan blade used to cool the motor toward the portion of the work piece that is to be cut. The preferred embodiment also comprises a bevel quadrant structure located on the front of the foot of the circular saw, with the quadrant having one or more airflow vents within it so that the air expelled through the directional louvers can also flow through the foot quadrant toward the portion of the work piece that the saw blade is approaching and thereby remove the sawdust and/or other debris from the line of cut. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a generally front perspective of a circular saw illustrating the preferred embodiment of the present invention, and particularly illustrating the directional louvers in a gearbox of the saw as well as a bevel quadrant having a plurality of airflow vents through which air generated by the internal fan of the circular saw can pass to clear the line of cut of the saw of sawdust and other debris;  
         [0010]      FIG. 2  is another front perspective view similar to  FIG. 1 , but taken from a higher elevation;  
         [0011]      FIG. 3  is a plan view of the inside of a portion of the gearbox end casting illustrating the configuration of the louvers therein and the direction of flow produced by the internal fan blade of the circular saw illustrated in  FIG. 1 ; and  
         [0012]      FIG. 4  is a perspective view illustrating a portion of the saw motor and the internal fan blade which creates the airflow that is expelled through the louvers of the gearbox. 
     
    
     DETAILED DESCRIPTION  
       [0013]     The preferred embodiment of the present invention is shown in  FIGS. 1-4  and is directed to a circular saw of the type which has a motor housing  10  in which a motor  11  is located, a saw blade  12  that is protected by a blade housing  14 , the blade housing  14  being attached to a gearbox end casting  16  that is in turn connected to the housing  10  and which has a number of vent openings  18  through which air from a fan  20  is expelled during operation of the circular saw. The circular saw also has a forward auxiliary handle  22  as well as a main handle (not shown) that is typical with such circular saws.  
         [0014]     The circular saw also has a generally flat foot assembly  24  which preferably has an integrally formed quadrant structure  26  that is part of a bevel adjusting mechanism that is configured to enable the saw to cut a work piece at an adjustable bevel angle. Preferably, the bevel angle can be adjusted from perpendicular to approximately 55° from perpendicular by pivoting the motor housing  10  as well as the blade  12  and  14  around a pivot axis defined by a bolt  28 .  
         [0015]     In the embodiment illustrated in  FIG. 1 , the blade housing  14  has a raised center portion  30  that is generally aligned with the plane of the blade  12 . A notch  32  in the front edge of the foot  24  is also provided to indicate a more accurate line of the cut when set at a zero degree bevel that results from cutting by the blade  12 . As shown in  FIG. 3 , the air that is generated by the fan blade  20  flows in a generally counterclockwise direction in the housing  10  as shown by the arrows  34  and exits out of vent openings  18  defined by louvers  36 . There are four louvers  36  which have slightly different lengths and angular orientations, but all are oriented to direct the air flow produced by the fan blade  20  forwardly of the circular saw toward the portion of the work piece that is to be cut generally along the line  38 .  
         [0016]     The quadrant  26  is preferably integrally formed with the foot  24  in the embodiment illustrated in the drawings, but it should be understood that the quadrant can also be separately made and attached to the foot  24 . As illustrated in the drawings, the foot  24  is configured to provide an adjustable bevel angle when it is rotated relative to the saw housing  10 , blade  12  and blade housing  14  about the axis of the bolt  28  and a separate bolt (not shown) located at the rear of the foot  24 .  
         [0017]     A clamping lever  40  attached to the motor housing  10  is slidable in an arcuate slot  42  having a radius that is constant around the bolt  28 . When the lever  40  is rotated in the counterclockwise direction as shown in  FIG. 1 , it loosens the mechanism so that the foot can be rotated relative to the motor housing  10  to cause the blade  12  to be moved to a different bevel angle. When the angle is at the desired location, the lever  40  can be rotated in the clockwise direction to tighten the same and hold the saw at the desired bevel angle. A lower blade guard lift lever  44  is shown to the left of the blade housing  14  and this lever enables the user to manually move the lower guard as is sometimes necessary during operation of a circular saw.  
         [0018]     While the air that is expelled from the motor housing  10  through the openings  18  is directed forwardly, the quadrant  26  has openings  46  as well as the slot  42  which function as vents and permit the air to pass relatively unimpeded through the quadrant  26  onto the work piece along the line of cut. This enables the flow to blow away sawdust that would likely otherwise accumulate were it not for the quadrant permitting passing of the air flow through it.  
         [0019]     As a result of this airflow, the user seldom experiences the deposit of sawdust or debris produced by the cutting of whatever material is being cut on the line of cut which often necessitates interruption of the cutting operation.  
         [0020]     While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.  
         [0021]     Various features of the invention are set forth in the following claims.

Technology Category: 7