Patent Publication Number: US-7219434-B2

Title: Metal cutting circular saw with integral sight window

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional of U.S. patent application Ser. No. 10/474,986, filed on Oct. 16, 2003, which is a US National Stage of International Application No. PCT/US02/10519, filed 3 Apr. 2002, which claims the benefit of U.S. application Ser. No. 09/827,817, filed 6 Apr. 2001, now U.S. Pat. No. 6,543,143. The disclosures of the above applications are incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to a circular saw and- more particularly to a metal cutting circular saw having a viewing window on the upper guard and which is specifically designed to protect the user from metal chips. 
   BACKGROUND AND SUMMARY OF THE INVENTION 
   One of the problems associated with the use of a handheld circular saw is properly aligning the saw so that the desired cut is achieved. Typically, a user will draw a line on the material to be cut. This line represents the location of the desired cut. The problem arises when the user of the handheld circular saw attempts to align the blade with the line on the material. The problem continues as the user attempts to keep the blade tracking on the desired cut line. 
   To assist in the alignment, circular saws are typically provided with a guide slot. The guide slot is usually located on the planar cutting base or shoe of the saw, and is positioned in front of, and in line with, the circular saw blade. The user positions the saw so that the line on the material appears in the guide slot. While the provision of such a guide slot does aid the user in proper saw alignment, problems still exist. Because the blade is covered by a saw guard, the user cannot see the blade as it exits the material and therefore cannot directly monitor the travel of the blade. Attempts have been made to allow the user of the saw to view the blade as it exits the material, thereby allowing the user to properly guide the blade along the desired cut line. Viewing windows have been provided to allow the user of the saw to properly align the saw to the work piece by allowing them to view the blade. While this viewing window solves the problems to some degree, its positioning remains a problem. 
   If the viewing window is not properly positioned, the user will be unable to see the blade exiting the material due to the reflection of light by the transparent section of the viewing window. To compensate, the user may attempt to reposition the light sources, such as a flashlight, or may reposition himself/herself relative to the saw. This repositioning can affect efficiency as well the quality of the work being performed. If the user repositions himself/herself relative to the saw, the resulting position may be an uncomfortable or unsafe one from which to operate the saw. Further, the trial and error necessary to find a proper position of saw, user and light source waste the user&#39;s time. 
   The position of the viewing window and the saw guard must also count for the chips that are generated as the saw cuts through the work piece. This problem is particularly relevant when the circular saw is used for cutting metal. Thus, there is also a need in the art for metal cutting circular saws to be equipped to protect the user from chips and debris while cutting metal materials. Accordingly, it is an object of the present invention to provide a window assembly in the upper guard of a circular saw in a position so as to minimize any light reflected into the eyes of the person using the saw. 
   It is another object of the present invention to provide a guard design which controls and minimizes the ejection of chips along with a saw shoe, and lower guard design which is optimized for the same purpose. It is a further object of the present invention to provide an upper guard which is made of strong material and which provides plenty of light to be passed therethrough to illuminate the cutting line and blade interface area. 
   These and other objects of the present invention are obtained by providing a circular saw including a motor and blade drivingly attached to the motor. An upper blade guard is provided in partial covering relationship over the blade and includes a perimeter outer surface disposed between first and second side surfaces. The upper blade guard includes a first sight window disposed in the first side surface and disposed in a plane angularly offset from a plane of the blade. The upper blade guard also includes a second sight window disposed in the second side surface of the upper blade guard. A light window is disposed in the front portion of the perimeter outer surface of the upper blade guard. The upper blade guard is made from metal and the first and second sight windows and light window are integrally formed as a one-piece member. The upper blade guard includes a first portion attached to the motor housing and a second portion attached to the first portion. The sight window unit is disposed between the first and second portions of the upper blade guard and is secured therein by a fastener. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
       FIG. 1  is a front perspective view showing a metal cutting circular saw having an upper guard with an integral sight window according to the principles of the present invention; 
       FIG. 2  is a side elevation view of the saw of  FIG. 1 ; 
       FIG. 3  is a front elevation of the saw of  FIG. 1  and illustrating the front light window in the upper guard; 
       FIG. 4  is a right side elevation view of the saw of  FIG. 1  and partially illustrating the right side sight window according to the principles of the present invention; 
       FIG. 5  is a top view of the saw of  FIG. 1 ; 
       FIG. 6  is an exploded perspective view of the upper guard, sight window, saw blade, and shoe according to the principles of the present invention; 
       FIG. 7  is a side elevation view of the cover portion of the upper guard assembly according to the principles of the present invention; 
       FIG. 8  is a rear plan view of the cover portion of the upper guard assembly; 
       FIG. 9  is a side elevation view of the inner side of the cover portion of the upper guard assembly; 
       FIG. 10  is a side elevation view of the main assembly portion of the upper guard assembly according to the principles of the present invention; 
       FIG. 11  is a side elevation view of the inner side of the main assembly portion of the upper guard assembly; 
       FIG. 12  is a rear elevation view of the main assembly portion of the upper guard assembly; 
       FIG. 13  is a cross-sectional view taken along line  13 - 13  of  FIG. 11 ; 
       FIG. 14  is a left perspective view of the sight window unit according to the principles of the present invention; 
       FIG. 15  is a right perspective view of the sight window unit shown in  FIG. 14 ; 
       FIG. 16  is a bottom view of the sight window unit shown in  FIG. 14 ; 
       FIG. 17  is a cross-sectional view taken along line  17 - 17  of  FIG. 16 ; 
       FIG. 18  is a right side view of the sight window unit shown in  FIG. 14 ; 
       FIG. 19  is a left side view of a sight window unit shown in  FIG. 14 ; 
       FIG. 20  is a cross-sectional view taken along line  20 - 20  of  FIG. 18 ; 
       FIG. 21  is a side elevation view of the inner surface of the lower guard; 
       FIG. 22  is a rear elevation view of the lower guard; 
       FIG. 23  is a side elevation view of the outer surface of the lower guard; 
       FIG. 24  is a top plan view of the saw shoe with the pivot bracket and pivot slot bracket mounted thereon; 
       FIG. 25  is a side view of the saw shoe and brackets shown in  FIG. 24 ; 
       FIG. 26  is an exploded perspective view of the upper guard, sight window, saw blade, and shoe according to a second embodiment of the present invention; 
       FIG. 27  is an exploded perspective view of the upper guard, sight window, saw blade, shoe, and lower guard; 
       FIG. 28  is a left perspective view of an encapsulated sight window unit according to the second embodiment of the present invention; 
       FIG. 29  is an exploded left perspective view of an ultrasonically welded sight window unit according to the second embodiment of the present invention; 
       FIG. 30  is a left perspective view showing a metal cutting circular saw having an upper guard with an integral sight window according to a third embodiment of the present invention; and 
       FIG. 31  is a side elevation view of the main assembly portion of the upper guard assembly according to the third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
   Referring to the drawings in greater detail, and initially to  FIG. 1 , a metal cutting power circular saw designated generally by numeral “10” is shown. Saw  10  has a motor  12  which is operably attached to a circular saw blade  14 . A battery pack  16  is mounted to a handle portion  18 . The battery pack  16  supplies electrical power to motor  12 . The upper portion of blade  14  is surrounded by an upper blade guard assembly  20 . Upper blade guard assembly  20  is fixedly secured to motor  12 . A lower portion of blade  14  is surrounded by a lower saw guard  22 . Saw  10  further has a saw shoe  24  defining a planar base with an elongated slot  26  for receiving the circular saw blade  14  therethrough. 
   Lower guard  22  exposes the lower portion of blade  14  in a manner that is well known in the art. More specifically, the front edge  22   a  of lower guard  22  engages the leading edge of a work piece (not shown). As the saw passes further into the work piece, the lower guard  22  is rotated generally rearwardly and upwardly to expose the lower portion of the blade  14 . Lower guard  22  is spring loaded so that when saw  10  is disengaged from the work piece, the lower guard  22  returns to its forward, lower blade covering position. 
   The saw shoe  24  is pivotally mounted to the motor  12  by a forward pivot bracket  28  which is mounted to the saw shoe  24  and includes upwardly extending ears  30  which receive an extension  32  of the motor housing therebetween for pivotally mounting the saw shoe  24  to the motor  12 . As shown in  FIGS. 24 and 25 , an arcuate bracket  34  is mounted to a rear portion of the saw shoe  24 . The arcuate bracket  34  includes an arcuate slot  36  which is adjustably engaged with the motor  12  to vary the angular orientation of the saw shoe  24  with respect to the motor  12  in a manner that is well known in the art. 
   As best shown in  FIG. 6 , the upper blade guard assembly  20  includes a cover half portion  40  disposed on an outboard side of the blade  14  and an assembly half portion  42  disposed on an inboard side of the blade  14 . The cover half portion  40  and assembly half portion  42  are each made of die-cast aluminum. The assembly half portion  42  includes mounting bosses  42   a  (best shown in  FIGS. 10 and 12 ) which are used to mount the upper blade guard assembly  20  to the motor  12 . The cover half portion  40  of the upper guard assembly has a unique angled exterior window frame portion  44  in which a sight window  46  is placed to provide an optimized viewing aperture for the user while using the saw  10 . The cover half portion  40  includes a plurality of mounting bosses  46  which align with corresponding mounting bosses  48  provided on the assembly half portion  42  for mounting the cover half portion  40  to the assembly half portion  42  of the upper guard assembly  20 . Each of the mounting bosses  46  include an aperture  50  extending therethrough for receiving a fastener  52  (best shown in  FIGS. 1 and 2 ) therethrough. The fasteners  52  are threadedly received within bosses  48  of the assembly half portion  42  of the upper blade guard assembly  20 . 
   The assembly half portion  42  includes a second window frame  54  disposed in the side surface of the assembly half portion  42 . The cover half portion  40  and assembly half portion  42  each are provided with a window frame recessed portion in the outer periphery surface thereof for, in combination, defining a third window frame. 
   A sight window unit  60  is provided including first sight window portion  46 , a second sight window portion  62 , and a front light window portion  64  integrally formed as a unitary piece. As best shown in  FIGS. 14–20 , the sight window unit  60  is formed as a unitary member and includes a mounting boss portion  66  which is received by the front boss portions  46 ,  48  of the cover half portion and assembly half portion  40 ,  42  of the upper blade guard assembly  20 . The mounting boss  66  maintains the proper orientation of the sight glass unit  60  within the upper guard assembly  20 . The molded screw boss  66  is trapped around the mounting bosses of the cover half portion and assembly half portion  40 ,  42  of the blade guard assembly  20 . 
   The upper guard halves  40 ,  42  are configured with the necessary recesses  68 ,  70  (see  FIGS. 9 and 11 , respectively) to receive the sight window unit  60 . The angled orientation of the first sight window  46  is designed to provide the optimum viewing aperture while using the saw. Although this angle may vary with regard different saw applications, the sight window  46  is disposed at an angle “a” of between 20 and 60 degrees relative to the side surface of the cover half portion  40  of the upper blade guard assembly  20  as best illustrated in  FIG. 8 . According to a preferred embodiment of the present invention, the first sight window is disposed between approximately 35 to 40 degrees relative to the side surface of the cover half portion  40  of the upper blade guard  20 . The window frame portion  44  projects outwardly from the side surface of the cover half portion  40  of the upper blade guard assembly  20 . 
   The second sight window  62  is provided in the right side of the blade guard assembly  20  and is substantially flush with the surface of the blade guard. The light window  64  which is provided along the front edge in the lower front periphery surface of the blade guard  20  permits light to enter into otherwise dark areas of the guard enclosure. The sight window unit  60  functions as an integral part of the guard system and thereby protects the end user from chip spray. The design of the sight window unit  60  and the position of the windows  46 ,  62 , and  64  allows for cutting line of sight to be visual from both sides of the upper guard assembly  20 . 
   The sight window unit  60  is a clear plastic material that is hard shell dip-coated in a silicone-based material to extend the clarity of the sight window for long periods of product use. The design is enhanced to provide maximum visibility of the cut line while virtually eliminating the glare or reflective characteristics associated with sight windows. The design accomplishes this by the angular positioning of the sight window  46  as well as the extended projecting window frame portion  44  which allows a clear view of the attack point of the blade. The three-part window design allows for adequate light penetration to the front, left, and right interior surfaces of the upper guard  20 . 
   The lower guard  22  is designed with closed in areas around the sides of the blade to minimize the openings for metal chips to escape, and impact an end user. The lower guard  22  is preferably made from die-cast aluminum. The lower guard  22  provides a safe guard function and allows for easy access for blade replacement and removal. The lower guard  22  is provided with a lift lever  74 , as shown in  FIG. 1  which is configured to operate smoothly around the angled exterior sight window feature  44 ,  46  of the upper guard assembly  20 . The lower guard  22  includes an inboard wall portion  80  and an outboard wall portion  82 , as best illustrated in  FIG. 23 . The inboard wall portion  80  includes an aperture  84  which is rotatably mounted about a hub for pivotal movement thereabout. The outboard wall portion  82  of the lower guard  22  extends approximately 75 percent of the distance from the outer peripheral edge  86  of the lower guard  22  to the pivot axis  88  of the lower guard  22 . In other words, as illustrated in  FIG. 23 , the distance X between the outer periphery  86  and the inner end  90  of the outboard wall portion  82  is greater than approximately 60 percent of the distance Y from the outer periphery surface  86  to the center of rotation  88  of the lower guard  22 , and preferably approximately 75 percent. This provides a lower guard that covers a much larger portion of the blade  14  than prior designs. In particular, the lower guard  22  of the present invention covers approximately 40 percent more of the saw blade  14  than standard guards on wood cutting circular saws. In a preferred embodiment, the distance X of the present invention is approximately 62 millimeters versus standard guards which have a distance of approximately 40 millimeters. The increased blade coverage of the present invention provides a significant enclosure of the blade  14  to prevent metal chips from escaping and impacting a user. 
   The saw shoe  24  is provided with a saw blade opening  26  that has a narrow opening portion  26   a  at the attack point of the blade while providing the proper field of vision of the cut line while the end user sights through the sight window apertures. The narrow portion  26   a  of the saw blade opening  26  is uniquely configured to minimize chip spray and prevent small cut off stock from entering the upper guard by minimizing the hazard of the guard ingesting materials that could damage the carbide blade. Likewise, this feature controls the chip spray away from impact points of the sight window thereby adding to the life performance of the sight windows. The shoe  24  is made of stainless steel to prevent the accumulation of metal chip build and provide a highly durable work surface. The kerf indicator  94  is designed to allow the user to easily align the work piece to the blade cutting location. The kerf indicator  94  has a geometry which allows direct alignment in tough-to-see locations, such as when it is dark. The shoe is equipped with a line indicator  96  marking the position of the blade. The combination of the kerf indicator  94  and blade marking line  96  provide a “gun sight” approach allowing the user ease of sighting the cut line to cut on the work piece. 
   With particular reference to  FIGS. 26–29 , a metal cutting power circular saw, designated generally by numeral “110” is shown according to a second embodiment of the present invention with portions removed for clarity. Saw  110  is similar to saw  10 ; therefore, like parts are designated with like reference numerals. 
   The upper portion of blade  14  is surrounded by an upper blade guard assembly  120 . As been shown in  FIGS. 26 and 27 , the upper blade guard assembly  120  includes a cover half portion  140  disposed on an outboard side of the blade  14  and an assembly half portion  142  disposed on an inboard side of the blade  14 . The assembly half portion  142  includes mounting bosses  142   a,  which are used to mount the upper blade guard assembly  120  to the motor  12 . The cover half portion  140  of the upper guard assembly  120  has a unique angled exterior window frame portion  144  in which a sight window  146  is placed to provide an optimized viewing aperture for the user while using the saw  110 . The cover half portion  140  includes a plurality of mounting bosses  147  which align with corresponding mounting bosses  148  provided on the assembly half portion  142  for mounting the cover half portion  142  the assembly half portion  142  of the upper guard assembly  120 . Each of the mounting bosses  147  includes an aperture  150  extending therethrough for receiving a fastener  52  therethrough. The fasteners  52  are threadedly received within bosses  148  of the assembly half portion  142  of the upper blade guard assembly  120 . 
   With particular reference to  FIGS. 26–28 , a sight window unit  160  is provided including the first sight window portion  146 . As been shown in  FIGS. 28 and 29 , the sight window unit  160  is formed as a unitary member and includes a mounting boss portion  166 , which is received by the front boss portions  147 , 148  of the cover half portion  140  and assembly half portion  142  of the upper blade guard assembly  120 . Additionally, the sight window unit  160  further includes a snap fit portion  167  generally having a protruding member  167   a  terminating at a head portion  167   b.  The mounting boss  166  and the snap fit portion  167  maintain the proper orientation of the sight window unit  160  with the upper guard assembly  120 . That is, the molded screw boss  166  is trapped around the mounting bosses of the cover half portion  140  and the assembly half portion  142  of the blade guard assembly  120 . Additionally, the snap fit portion  167  extends through and engages an opening  140   a.  More particularly, head portion  167   b  passes through opening  140   a  and engages an outboard surface of cover half portion  140  through a snap fit relationship. 
   A light window  164  is provided in the front periphery surface of the blade guard  120  so as to permit light to enter into otherwise dark areas of the guard enclosure. The sight window unit  160  functions as an integral part of the guard system and thereby protects the end user from chip spray. As best seen in  FIG. 26 , the cover half portion  140  and assembly half portion  142  each are provided with a window frame recessed portions  156  and  158 , respectively, in the outer periphery surface thereof for, in combination, defining a window retaining frame. As best seen in  FIG. 27 , light window  164  includes an increased thickness or wear surface  164   a  disposed along the backside thereof. Wear surface  164   a  is provided so as to prolong the life of light window  164 , since this portion of the light window may be exposed to excessive wear due to direct chip spray. Light window  164  further includes a pair of opposing tab members  164   b,  which are adapted to engage corresponding recesses (not shown) formed in the window frame recessed portions  156  and  158 . Preferably, light window  164  is a frosted polycarbonite window, which provides a generally uniform light. 
   The sight window unit  160  is a clear plastic material that is hard shell dip-coated in a silicone-based material to extend the clarity of the sight window for long periods of product use. The design is enhanced to provide maximum visibility of the cut line while virtually eliminating the glare or reflective characteristics associated with sight windows. The design accomplishes this by the angular positioning of the sight window  146  as well as the extended projecting window frame portion  144 , which allows a clear view of the attack point of the blade. This window design allows for adequate light penetration to the front and left interior surfaces of the upper guard  20 . 
   With particular reference to  FIGS. 28 and 29 , it is anticipated that sight window unit  160  may be formed by any one of a number of known manufacturing processes. By way of nonlimiting example, sight window unit  160  may be formed using an injection molding encapsulation process. According to this process, a chemically strengthened piece of low iron, white soda lime glass  160   a  is disposed within an injection mold cavity and molding material, such as ABS plastic material, is injected around the glass insert  160   a  to form a unitary member. In this regard, the glass  160   a  is encapsulated by the injection molding process. A scratch resistant adhesive film may be positioned over glass insert  160   a  as a protective shield to prevent injury to the user should the glass break due to impact or tool drop. However, it should be understood that this film may be laminated between a pair of glass sheets, which together would define glass  160   a.    
   Alternatively, as seen in  FIG. 29 , sight window unit  160  may be formed using an ultrasonic weld process. Specifically, a glass insert  160   a′  is received within an opening  160   b′  formed in a frame  160   c′.  The opening  160   b′  is appropriately sized so as to receive glass insert  160   a′  therein. A cover  160   d′  is then disposed on top of glass insert  160   a′  and adjacent opening  160   b′  of frame  160   c′.  The cover  160   d′  is then ultrasonically welded to the frame  160   c′  along opening  160   b′  to form a unitary member. As set forth above, a scratch resistant adhesive film may be positioned over glass insert  160   a′  as a protective shield to prevent injury to the user should the glass break due to impact or tool drop. 
   With particular reference to  FIGS. 26–29 , a metal cutting power circular saw, designated generally by numeral “210” is shown according to a third embodiment of the present invention. Saw  210  is similar to saws  10  and  110 ; therefore, like parts are designated with like reference numerals. 
   The upper portion of blade  14  is surrounded by an upper blade guard assembly  220 . As been seen in  FIG. 30 , the upper blade guard assembly  220  includes a cover half portion  240  disposed on an outboard side of the blade  14  and an assembly half portion  242  disposed on an inboard side of the blade  14 . The assembly half portion  242  includes a unique sight window  246 , which is placed to provide an optimized viewing aperture for the user while using the saw  210 . Sight window  246  is preferably positioned at a lower forward corner of assembly half portion  242  to provide line of the sight viewing of blade  14  from an inboard or motor position. As best seen in  FIG. 30 , this is particularly useful when the saw is oriented at a 45 degree angle relative to saw shoe  224 . In this configuration, viewing windows of conventional circular saws are oriented away from the user&#39;s line of sight, thereby inhibiting safe and accurate operation of the circular saw. 
   As best seen in  FIG. 31 , sight window  246  is generally comprised of a plurality of inclined parallel slots  246   a.  The plurality of inclined parallel slots  246   a  are each sized so as to be within European compliance requirements while, simultaneously, providing a sufficient viewing area. By providing a plurality of slots rather than a single opening, the size of the viewing area is maintained without compromising the safety of the user or by exposing the user to flying particles. 
   The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.