Abstract:
A safety guard assembly for use on a handheld power saw is disclosed. The assembly includes a safety guard, a locking mechanism, and a weight. The safety guard is swingably mounted on the hood of the saw. The locking mechanism allows the guard to be swung to an open position and locked in position. In a kick-back situation, the locking mechanism quickly releases. The weight forces the guard to swing rapidly down over the guard, thereby providing protection from the saw blade.

Description:
BACKGROUND INFORMATION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to power saws. More particularly, the invention relates to a safety guard for such saws. 
         [0003]    2. Discussion of the Prior Art 
         [0004]    Handheld circular power saws are commonly used tools. Saw operations with a circular saw are inherently dangerous operations that require some skill in operation of the saw and a great deal of care. One of the well-known hazards of operating this type of saw is that “kick-back” can sometimes occur. This can happen for any number of different reasons, such as when the work piece shifts or binds, or the cutting operation is done too high on the blade. The upper half of the saw blade rotates away from the direction of the saw operator and for purposes of discussion, this direction will hereinafter be referred to as the counterclockwise direction. When, for example, the work piece binds, the high acceleration of the saw forces the saw to move upward and back toward the operator, hence the term “kick-back.” It is possible for the operator to suffer severe, even lethal, cut injuries as a result of a kick-back. 
         [0005]    What is needed, therefore, is a saw guard for handheld power saws that will prevent kick-back injuries. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The invention is a blade guard for a hand-held power saw. The guard according to the invention is constructed such, that, upon kick-back, the guard immediately drops into place over the exposed portion of the saw blade, thereby preventing cut injuries to the operator, even if the saw should come into contact with the body of the operator. 
         [0007]    The blade guard according to the invention works under the principle of inertia. The guard comprises two side members that cover the blade when the saw is not in use. The guard is held in the closed position by a spring-biased locking pin or plunger that is affixed to the hood. Inertial weights are provided on the side members. 
         [0008]    The operator moves the locking pin from its locking position and raises the guard prior to use of the saw. The locking pin then snaps into a recess or detent on the guard to lightly secure the guard in the raised position. Should the saw kick back, inertia will cause the locking pin to pop out of the detent, allowing the guard to immediately swing closed and become locked in the closed position, thereby preventing the saw blade from injuring the operator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. The drawings are not drawn to scale. 
           [0010]      FIG. 1  illustrates a conventional handheld circular saw (prior art). 
           [0011]      FIG. 2  is a side plan view of a circular saw blade, with a safety guard according to the invention affixed to the hood and in the closed position. 
           [0012]      FIG. 3  is a side plan view of the circular saw blade of  FIG. 2 , with the safety guard according to the invention shown in the open position. 
           [0013]      FIG. 4  is a front plan view of the circular saw blade, illustrating the hood and the two side members of the safety guard according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    The present invention will now be described more fully in detail with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown. This invention should not, however, be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be complete and will fully convey the scope of the invention to those skilled in the art. 
         [0015]      FIG. 1  shows a conventional handheld circular saw  10 . The saw has a saw blade  2  that is partially covered with a hood  8 . The hood  8  encloses that portion of the saw blade  2  that is closest to the operator. A portion of the saw blade  2 A remains unhooded, i.e., exposed, this portion being the operative area of the saw blade in a normal sawing operation. The saw  10  is held at the handle  6  by the operator. The particular illustration of the handheld circular saw  10  is that of a Husqvarna 371K concrete saw. This is for illustration purposes only and in no way limits the use of the inventive device to this brand or style of a power saw. The safety guard according to the invention described below may be used on various types of handheld saws that have a hood over at least an upper portion of the saw blade. For purposes of discussion, the hood  8  will be defined as having a front edge  8 A that is on the upper portion of the hood and farthest away from and a rear edge  8 B that is closest to the handle  6 . 
         [0016]      FIGS. 2-4  illustrate a saw blade guard  100  according to the invention that is suitable for installation on a conventional handheld circular saw, such as the saw  10 .  FIG. 2  is a side plan view of the saw blade guard  100 , showing the guard  100  in a closed position, covering almost entirely the normally exposed or unhooded portion  2 A of the saw blade  2 . The guard  100  comprises a guard  110  that is pivotably affixed to the front edge  8 A of the hood  8  via a pivot means  112 . In the embodiment shown, the guard  110  includes two side members  110 A,  1108  that are coupled to each other by means of a bridge  114 , to ensure that the side members operate as a single unit. An example of a suitable pivot means  112  is a pivot pin or nub that is attached to or integrated into each side of the hood  8 , with the guard  110  having an aperture or snap connector for rotatably affixing each side of the guard  110  or the bridge  114  to the respective pivot means  112 . 
         [0017]    A spring-biased locking means  120  in the form of a locking pin or plunger  122  is affixed to the hood  8  by conventional means. In the embodiment shown, the locking means  120  includes a leaf spring  124  that urges the locking pin  122  in a direction away from the pivot means  112 , that is, toward the end of the saw  10  that is closest to the saw operator. The locking pin  122  is affixed to the lower end of the leaf spring  124 . At least one of the side members  110  has a first detent or recess  126  for receiving the locking pin  122  to lock the guard  110  in a closed position. It is also possible to provide a sleeve on the hood  8  that receives the pin  122 , so as to constrain movement of the pin to a back-and-forth direction. A weight  130  is affixed or incorporated into each side of the guard  110 . The weight  130  is shown in  FIGS. 2 and 3  with hatch lines, for purposes of accentuation only. It is understood that the shape, location, and/or weight of the weight  130  may all vary, depending on the actual embodiment of the saw with which the guard  100  is intended to be used, and that the depictions of the shape and location of the weight  130  shown in the illustrated embodiment are not intended as limitations. 
         [0018]      FIG. 3  is the same side plan view as that of  FIG. 2 , but shows the saw blade guard  100  in the raised position, with the unhooded portion  2 A of saw blade  2  exposed, ready for a sawing operation. The guard  110  has been pivoted about the pivot means  112 , thereby raising it and exposing the unhooded portion  2 A of the saw blade  2 . A second detent  128  is provided in the same guard  110  or side member that has the first detent  126 . To raise the guard  110 , the operator presses against the leaf spring  124  to release the locking pin  122  from the first detent  126 . The guard  110  can now be swung upward so that the second detent  128  is brought in a position to receive the locking pin  122 . This secures the guard  110  in the raised position. 
         [0019]      FIG. 4  is a front cross-sectional view of the saw with the saw guard  100  in the closed position, showing the weights  130  that are incorporated into the side members  110 A and  110 B. The weights  130  serve to force the guard  110  to the closed position during a kick-back. When, for example, the workpiece binds the saw  10 , the saw blade  2  forces the saw  10  to move in the upward direction very quickly and with a lot of force. The second detent  128  is constructed so as to provide a minimal holding force. The upward rotational force of the kick back will force the locking pin  122  out of the second detent and the guard  110  will swing very quickly to the closed position. 
         [0020]    A stop may be provided on the hood  2 , above the bridge  114 , to prevent the guard  110  from swinging past the exposed portion  2 A of the saw blade  2 . 
         [0021]    The safety guard  100  is illustrated on a circular saw, but it is understood, that the guard may easily be adapted for use with other types of handheld saws. 
         [0022]    It is understood that the embodiments described herein are merely illustrative of the present invention. Variations in the construction of the safety guard may be contemplated by one skilled in the art without limiting the intended scope of the invention herein disclosed and as defined by the following claims.