Abstract:
A viewing window for covering an aperture in a hand-held circular saw includes an optically transmissive member adapted to be coupled with the guard. The member is movable between a closed position, wherein the member substantially covers the aperture, and the open position, wherein the member at least partially uncovers the aperture, to allow the cleaning of the member. A structure is provided for biasing the member to the closed position.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 08/655,803 now U.S. Pat. No. 5,822,964, filed with the U.S. Patent and Trademark Office on May 31, 1996. 
    
    
     STATEMENT REGARDING FEDERALLY-SPONSERED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     This invention relates to the field of hand-held power saws and, more particularly, to a viewing window in a circular saw blade guard. 
     Hand-held power circular saws have been popular woodworking tools for many years. In a typical sawing operation, the user begins by marking or otherwise identifying a desired line along which to saw the material to be cut. The user then guides the saw during cutting, manually aligning the blade with the desired line of cut. Maintaining this alignment manually can be difficult because the typical circular saw has a blade guard that obscures the user&#39;s view of the blade at the point of cutting and thus impedes the user&#39;s ability to accurately align the blade with the desired cutting line. 
     To overcome this difficulty, one alternative has been to provide the circular saw with a guide slot. Typically located on the base of the saw, the guide slot is so aligned ahead of the blade in the forward cutting direction to provide a visual indication of the anticipated blade path through the workpiece. During operation, the user typically positions the saw so that the guide slot, and thus the blade, are aligned with the line of cut. This approach can provide a satisfactory cut, unless the saw blade is improperly aligned with the guide slot. A blade is typically oriented at a predesignated location on an arbor driven by the saw motor. Deviations from this orientation can occur causing misalignment between the blade and the guide slot. The guide slot will then incorrectly indicate the blade path, and the user relying on the guide slot will less likely cut the material as desired. Furthermore, since the blade is covered by the saw guard, the user cannot directly monitor the blade travel and, therefore, may not detect the misalignment until substantial cutting has occurred. As a result, the workpiece may be ruined. 
     To overcome these limitations, another alternative has been to supply the saw guard with a transparent viewing window covering an aperture in the saw guard. Such a window enables direct observation of the saw blade as it enters the workpiece, which in turn enables the user to better maintain a desired cutting path. For example, U.S. Pat. No. 1,830,579 to Wappat provides an observation opening in the side wall of a hand-held circular saw guard. However, the use of a side wall viewing port did not permit the user to saw from a comfortable position behind the saw and at the same time monitor the progress of the blade. Furthermore, to the extent the air currents directed towards the inside surface of the viewing pane were not sufficient to clear the pane of dust, manual clearing of the pane would be required which could more directly expose the saw blade. 
     A viewing window covering an aperture on the outside circumference of a circular saw blade guard is disclosed in U.S. Pat. No. 4,450,627 to Morimoto. This viewing window is coupled with the saw guard in a variety of ways, including by means of a press fit, a sliding fit or a side hinge. When the viewing window requires cleaning, however, it must either be removed or substantially opened, thereby exposing the saw blade area. After cleaning, if the user neglects to install or close the viewing window, sawing operation without the viewing window in place could occur. The user may not notice the missing viewing window until sawing operations have begun, and cut material could be ejected through the uncovered aperture. The side hinge structure disclosed in this patent allows complete exposure of the aperture in the saw guard. 
     To overcome these and other limitations in the prior art, an improved viewing window is desirable for a circular saw guard that is easily cleanable without requiring full exposure of the saw guard aperture. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a clear viewing window in a circular saw guard to cover an aperture in the guard so as to minimize exposure of the aperture during cleaning. A related object is to provide such a window that is easy to operate and inexpensive to manufacture and assemble. 
     It is a further object of the present invention to provide a clear viewing window for a circular saw guard so biased as to better ensure that the window returns to the closed position after cleaning. 
     It is a further object of this invention to provide a means for biasing a viewing window in a circular saw guard to the closed position on the outside of the saw guard and in a manner less likely to be affected by material generated during saw operation. 
     It is a further object of this invention to allow easy cleaning of a viewing window for a circular saw guard while greatly reducing any necessary exposure of the aperture. A related object is to provide a viewing window that is not easily removed from the saw guard and thus less likely to be misplaced. 
     According to the present invention, the foregoing and other objects are obtained by supplying a circular saw guard with a transparent viewing window whose movement is constrained so as to greatly reduce or eliminate exposure of the aperture during cleaning. In one embodiment, the viewing window is hingedly coupled with the guard to rotate outwardly from the periphery of the guard about an axis parallel to the rotational axis of the blade. In this embodiment, the window is supplied with a means for biasing it to a closed position during use. The window may also be carried in a frame and supplied with a means for limiting its travel to minimize exposure of the aperture during cleaning. In another embodiment of the invention, the viewing window may be larger than the aperture in the saw guard. Tabs forming slots may be provided in the saw guard proximal the aperture to receive a rectangular, planar window that can slide laterally between the use position and the cleaning position. Alternatively, the oversize window may be triangular in shape and pivot about a single point in the periphery of the saw guard. In another embodiment, the window may be approximately the same size as the aperture and be adapted to rotate along its longitudinal axis within the aperture between a use position and a cleaning position. In a further embodiment, the window may be fixedly mounted to the saw guard proximate a second aperture oriented to permit convenient cleaning of the inside surface of the window with a cleaning tool or compressed air introduced through the second aperture. During sawing operations, the second aperture may be covered with a removable plug retained in the second aperture by a press fit. 
     Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon an examination of the following, or may be learned by practice of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings which form a part of this specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views: 
     FIG. 1 is a front perspective view showing a viewing window of the present invention in the closed position. 
     FIG. 2 is a partial side elevation view taken along line  2 — 2  of FIG. 1 showing the viewing window in the closed position. 
     FIG. 3 is a partial side elevation similar to FIG. 2 except showing the viewing window in the open position. 
     FIG. 4 is a partial top plan view taken along line  4 — 4  of FIG. 2 with part of the viewing window being broken away to show particular details of construction. 
     FIG. 5 is a partial side elevation view taken along line  5 — 5  of FIG. 2 with part of the viewing window assembly being broken away to show particular details of construction. 
     FIG. 6 is a partial side elevation view taken along line  6 — 6  of FIG. 1 showing the viewing window in the closed position and the saw assembly broken away to show particular details of construction. 
     FIG. 7 is a front perspective view of a second embodiment of the present invention showing the viewing window in the closed position and, in phantom lines, in an open position. 
     FIG. 8 is a front perspective view of a third embodiment of the present invention showing a viewing window slidably coupled with the circular saw guard. 
     FIG. 9 is a front perspective view showing a fourth embodiment of the present invention wherein the viewing window pivots about a single point as shown by the indicating directional arrow. 
     FIG. 10 is a front perspective view of a fifth embodiment of the present invention showing a viewing window coupled with the circular saw guard and a plug removable from a second aperture to access the window for cleaning purposes. 
     FIG. 11 is a front perspective view of a sixth embodiment of the present invention wherein the viewing window rotates about its longitudinal axis lying on the periphery of the circular saw guard. 
     FIG. 12 is a partial side elevation view taken along line  12 — 12  of FIG. 11 showing the viewing window in the closed position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in greater detail, a power circular saw is shown designated generally by  20 . Saw  20  has a motor  22  operably attached to a circular saw blade  21 . A power cord  24  supplies electrical power to motor  22 . The upper portion of blade  21  is surrounded by a saw guard  26  secured to motor  22 . Saw  20  further has a base  28  with a guide notch  30 . Provided in saw guard  26  is an aperture  46  for viewing blade  21  as it travels through a workpiece  102 . 
     A window assembly  31  for covering aperture  46  and embodying the principles of the present invention is shown in FIG.  1 . Window assembly  31  is comprised of a frame  34  and an optically transmissive window  32  coupled therewith. Although window  32  is depicted as a generally planar rectangular structure in the drawings, window  32  can be of any suitable shape and curvature. Window assembly  31  is coupled with saw guard  26  by a fastener  36 , such as a pin or rivet, that passes through an aperture in frame  34  and through a corresponding aperture in saw guard  26 . In this configuration, window assembly  31  is rotatable outwardly from saw guard  26  about an axis parallel to the rotational axis of saw blade  21 . A second fastener  48  may be provided that passes through an aperture on the opposite side, and along the rotational axis, of frame  34 . Fastener  36  is often sufficient to pivotally support frame  34  and it may not be necessary to have fastener  48 . Frame  34  has a flange  39  extending generally downwardly from one side. Flange  39  extends from the side of frame  34  that is opposite fastener  36 . Flange  39  is generally perpendicular to window  32  and has an elongated arcuate slot  40  through which a stop pin  38  passes and frictionally couples with an aperture in saw guard  26 . Disposed longitudinally between stop pin  38  and the opposite end of slot  40  is a compression spring  42 . Slot  40  serves to contain spring  42  and to limit the travel of window assembly  31 . As will be understood by those skilled in the art, additional means for retaining spring  42  may be provided, such as a retaining pin  41  protruding from frame  34  into slot  40  and into one end of spring  42 . Saw guard  26  is preferably provided with a recessed area  44  about the edge of aperture  46  adapted to complementally receive window assembly  31  when in the closed position. 
     In operation, the viewing window of the present invention is movable between a closed position, as shown in FIG. 2, and an open position, as shown in FIG.  3 . In the closed position, spring  42  is slightly compressed, biasing window assembly  31  to the closed position sufficiently to generally maintain that position. Window assembly  31  can be moved to the open position by applying an external force outwardly from saw guard  26 . The window assembly  31  then rotates about its axis to partially expose aperture  46 . Opening window assembly  31  causes spring  42  to compress and thereby to exert an increased bias on window assembly  31  to the closed position. Further opening of window assembly  31  is prevented when pin  41  contacts stop pin  38 . If pin  41  deflects downwardly due to increased pressure, fully compressed spring  42  will also prevent further opening of the window. In the open position, the inside portion of window  32  may be cleared of dust by a brush or other cleaning instrument. After cleaning operations are complete, window assembly  31  is released and thereupon returns to the closed position through the force exerted by spring  42 . Alternatively, window assembly  50 , comprised of a frame  52  and a window  54 , may be biased to the closed portion using a torsion spring  56  as shown in FIG.  7 . As is apparent, window assembly  31  provides easily manufactured and efficient structure to allow easy cleaning of a viewing window. 
     FIG. 8 shows another window assembly embodying the principles of the present invention. In this embodiment, saw guard  26  is provided with an aperture  59 . Located in saw guard  26  proximate the aperture are the tabs  60 ,  62 ,  64  and  66  forming a lateral slot. A window  58  is slidably coupled with saw guard  26  by insertion into the slot formed by tabs  60 ,  62 ,  64  and  66 . Window  58  is sufficiently larger than the aperture to enable the window to slide a sufficient distance for cleaning. 
     In operation, window  58  slides laterally in the direction of the arrow shown in FIG. 8 to substantially expose the portion of the window  58  that had previously covered aperture  59  as shown in broken lines. This portion of the window may be cleaned with a brush or other appropriate material. 
     FIG. 9 shows another window assembly embodying the principles of the present invention. In this embodiment, saw guard  26  is provided with an aperture  72  covered by a window  68 . A pivot pin  70  or other suitable fastener passes through window  68  and through an aperture in the periphery of saw guard  26 . For reasons of mechanical geometry arising from placement of pivot pin  70 , both window  68  and aperture  72  are preferably triangular shaped. Window  68  is furthermore larger than aperture  72  and is able to move from side to side. In operation, an external force is applied to window  68  causing it to pivot a desired distance in the direction of the force. Because window  68  is larger in size than aperture  72 , the portion of window  68  previously covering the aperture can be exposed for cleaning as shown by the broken lines in FIG.  9 . 
     FIG. 10 shows another window assembly embodying the principles of the present invention. In this embodiment, a first aperture  76  in saw guard  26  is covered by a window  74 . Saw guard  26  is further provided with a second aperture  78  proximate and generally perpendicular to aperture  76 . Aperture  78  can be covered by a removable plug  80 . In operation, plug  80  is removed to enable a cleaning tool or compressed air to be introduced through aperture  78  to dislodge dust from the underside of window  74 . 
     FIG. 11 shows another window assembly embodying the principles of the present invention. In this embodiment, saw guard  26  is provided with an aperture  82 . A window assembly  83  is adapted to be coupled with saw guard  26 . Window assembly  83  is comprised of a transparent elongated, planar element  84  having planar ribs  86 ,  88 ,  90  and  92  disposed longitudinally on, and perpendicular to, planar element  84 . Pivot pins  94  and  96  are located on opposite ends of element  84  along its longitudinal center axis. Pin guides  98  and  100  are provided in saw guard  26  to complementally receive pins  94  and  96 . A pin retainer  102  is placed over pivot pin  94  to retain its position in pin guide  98 . Pin retainer  102  is held in place by fasteners  104  and  106 . Similarly, a pin retainer  108  is placed over pivot pin  96  to retain its position in pin guide  100 . Pin retainer  108  is held in place by fasteners  110  and  112 . In operation, window assembly  83  is shown in a closed position in FIG. 12, whereby element  84  covers aperture  82 . Window assembly  83  can be rotated about its longitudinal axis defined by pins  94  and  96  to permit cleaning. During rotation, planar ribs  86 ,  88 ,  90  and  92  serve to minimize exposure of aperture  82 . 
     From the foregoing, it will be seen that this invention is one well-adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.