Abstract:
A saw includes a housing, a motor, a saw blade, a base plate, and an alignment guide. The motor is at least partially provided in the housing. The saw blade is driven by the motor and defines a cutting plane. The base plate supports the housing. The alignment guide is attached to the base plate and has a laser, a scale, and an indicator. The laser is selectively rotatable and projects a laser beam in a laser plane about a first axis. The scale is positioned about the first axis and has a plurality of first graduations. The indicator is aligned with the scale and indicates a horizontal offset distance between the cutting plane and the laser plane along the base plate.

Description:
[0001]     The present invention relates to a guide for a power tool, for example, an alignment guide for a saw, such as a circular saw.  
         [0002]     A typical circular saw has a housing mounted to a base plate. A motor disposed in the housing powers a saw blade. The base plate typically has a notch to indicate the cutting plane as defined by the saw blade. In order to accurately make a cut, an operator typically scribes a line on a workpiece and aligns the notch with the line while cutting. In addition to the extra step of scribing a line, this method requires an operator to focus his eyes on the notch while cutting, leading to operator fatigue and potential errors as long lengths are cut.  
         [0003]     Circular saws with laser alignment guides for more precise movement during cutting have been developed to address this problem. These guides, however, are typically fixed to an upper blade guard and project a laser line along the cutting plane. For operators who wish to make cuts at a given offset distance from a reference line, the operator is first required to scribe a line parallel to the reference line, and then make the cut.  
         [0004]     U.S. Pat. No. 5,461,790 to Olstowski discloses a laser guide for a circular saw having a rotatable disk that allows an operator to vary the angular orientation of the laser guide with respect to the cutting plane. Because the rotatable disk may slide along an adjustable groove in the upper blade guard, the use of such a rotatable disk, however, requires an operator to measure the distance between the projected laser line and the blade every time an offset distance is adjusted or the disk slides along the groove. In addition, because the laser guide is mounted on the upper blade guard, it is difficult to retrofit existing circular saws with such laser guides. Further, the position of the laser guide on the circular saw may interfere with the workpiece or other parts as cuts are made.  
       SUMMARY  
       [0005]     Accordingly, embodiments of the present invention provide an alignment guide for a power tool. The alignment guide may be secured to the base plate or housing of a saw either integrally or attached as an accessory. Because the vertical distance between the axis of rotation of the alignment guide and the base plate is fixed, graduations that directly correspond to the horizontal offset distance may be placed on a scale or dial, allowing for quick adjustment and eliminating the need for an operator to determine the correlation between an angular adjustment and a given offset distance.  
         [0006]     According to one aspect of the invention, a saw comprises a housing, a motor, a saw blade, a base plate, and an alignment guide. The motor is at least partially provided in the housing. The saw blade is driven by the motor and defines a cutting plane. The base plate supports the housing. The alignment guide is attached to the base plate and has a laser, a scale, and an indicator. The laser is selectively rotatable and projects a laser beam in a laser plane about a first axis. The scale is positioned about the first axis and has a plurality of first graduations. The indicator is aligned with the scale and indicates a horizontal offset distance between the cutting plane and the laser plane along the base plate.  
         [0007]     According to another aspect of the invention, the vertical distance between the first axis and the base plate is fixed, and the first axis is substantially parallel to the cutting plane.  
         [0008]     Yet another aspect of the invention provides a base plate that supports the housing such that the housing is rotatable about a first axis. The laser is selectively rotatable and projects a laser beam in a laser plane about a second axis. The vertical distance between the second axis and the base plate is fixed, and the second axis is substantially parallel to the cutting plane. The scale is positioned about the second axis and has a plurality of first graduations. The indicator is aligned with the scale and indicates a horizontal offset distance between the cutting plane and the laser plane along the base plate.  
         [0009]     According to another aspect of the invention, the alignment guide is attached to the housing. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  shows a perspective view of the alignment guide of the present invention, shown mounted to a circular saw.  
         [0011]      FIG. 1A  is a detail view of the alignment guide of the present invention of  FIG. 1 .  
         [0012]      FIG. 2  is a front view of the alignment guide of the present invention, shown mounted to a circular saw.  
         [0013]      FIG. 3  is a side view of the alignment guide of the present invention, shown mounted to a circular saw.  
         [0014]      FIG. 4  is a top view of the alignment guide of the present invention, shown mounted to a circular saw.  
         [0015]      FIG. 5  is a perspective view of another embodiment of the alignment guide of the present invention, shown mounted to a circular saw.  
         [0016]      FIG. 6  is a front view of the alignment guide of the present invention illustrated in  FIG. 5 , shown mounted to a circular saw.  
         [0017]      FIG. 7  is a front view of the alignment guide of the present invention illustrated in  FIG. 5 , shown mounted to a circular saw at a bevel angle of forty-five degrees.  
         [0018]      FIG. 8  is a detail view of the alignment guide of the present invention illustrated in  FIG. 5 .  
         [0019]      FIG. 9  is a perspective view of another embodiment of the alignment guide of the present invention mounted to a jig saw.  
         [0020]      FIG. 9A  is a detail view of the alignment guide shown in  FIG. 9 .  
         [0021]      FIG. 10  is a side view of the alignment guide shown in  FIG. 9 .  
         [0022]      FIG. 11  is a front view of the alignment guide shown in  FIG. 9 . 
     
    
     DETAILED DESCRIPTION  
       [0023]     Referring now to  FIGS. 1-4 , an alignment guide  30  according to the present invention is shown mounted to a circular saw  10 . The circular saw  10  includes a housing  12  mounted to a base plate  20 . The housing  12  has a handle  13  and a trigger  14 . The trigger  14  activates a motor  16  disposed within housing  12 . The motor  16  rotates a saw blade  17  in the cutting plane  18  to cut the workpiece  100 . As seen in  FIG. 1 , the circular saw  10  may also feature a bevel adjustment  22  that allows the housing  12  and the saw blade  17  to rotate with respect to the base plate  20 , typically from 0 to 51.5 degrees. The base plate  20  has a blade guide notch  22  that is coplanar with the cutting plane  18  when the bevel angle is set to 0 degrees. Examples of such circular saws include the Ryobi® Model CSB131 7¼ inch 12 Amp Circular Saw or the Ryobi® Model R10631K 18 Volt Cordless Circular Saw available from One World Technologies, Inc. of Anderson, S.C., United States of America, and the Craftsman® Model 11426 5½ inch 19.2 Volt Cordless Trim Saw or the Craftsman® Model 11516 5½ inch 19.2 Volt Cordless Trim Saw with Laser available from Sears, Roebuck, and Co. of Hoffman Estates, Ill., United States of America.  
         [0024]     Referring to  FIGS. 1-4 , the alignment guide  30  includes a support body  32 , a laser housing  34 , a laser generator  36 , a dial  44 , and an indicator  48 . The support body  32  may be secured to the base plate  20  by screw or bolts (not shown), although other means of joining the two parts may be used, such as an adhesive, a snap or interference fit, etc. Alternately, the support body  32  may be integrally formed with the base plate  20 . As seen in  FIGS. 1A and 3 , the laser housing  34  is rotatably attached to the support body  32  and adjustably rotates about an axis of rotation  42 . The support body  32 , laser housing  34 , and dial  44  may be injection molded from a suitable plastic such as polycarbonate, acetal, or ABS (acrylonitrile-butadiene-styrene), although other materials may be used.  
         [0025]     The laser generator  36  is disposed within the laser housing  34 . The laser generator  36  may be a commercially available laser generator that produces a planar, fan shaped beam of light  38  that projects a laser line  40  onto the workpiece  100 . Alternately, the laser generator  36  may be assembled separately from a commercially available laser diode (not shown), a collimating lens (not shown), and an optical element (not shown) such as a cylindrical lens, an opaque slit, or a holographic optical element. The laser generator  36  is secured to the laser housing  34  such that planar beam  38  is coplanar with the axis of rotation  42 . The laser generator  36  may be adjustably secured to the laser housing  34  with set screws (not shown). Alternately, other known securing apparatus can be used to more easily facilitate the securing of the laser generator  36 . For example, a rotatable handle or a cam having a lever or other apparatus suitable for securing the laser generator  40  can be used. In addition, the laser generator  36  may be permanently secured to the laser housing  34  through an adhesive, a snap or interference fit, etc.  
         [0026]     The laser generator  36  may be powered through internal batteries (not shown) or an external power supply as desired. Alternately, the laser generator  36  may be powered directly from AC line current or through electrical cables connected to the electrical system of the circular saw  10 . An AC to DC converter and voltage reducers may be required if AC line current is used, as is known. A power switch (not shown) allows power from a battery or other power source to actuate the laser generator  36 . This switch may be integrally formed within the trigger  14 , activating power to the laser generator  36  as the trigger  14  is partially depressed. Alternately, a separate switch may be used to independently control power to the laser generator  36 .  
         [0027]     The dial  44  is rotatably coupled with the laser generator  36 , rotating about the axis of rotation  42 . The dial  44  has a scale  46  that may include a series of numbered graduations  47  that run axially along the outer circumference of the dial  44 . An indicator  48  is positioned on the support body  32  to indicate the degree of rotation of the dial  44  and the laser housing  34 . The indicator  48  may be printed, stenciled, marked, scribed, drilled, cut, etched, stamped, molded, etc. into the support body  32 . Alternately, the indicator  48  may be a separate piece, such as a label, mounted to the support body  32 . As seen in  FIG. 2 , “H” is defined as the vertical distance between the axis of rotation  42  and the top surface of the workpiece  100  as the base plate  20  is resting on it. The angle “θ” is defined as the angle formed by the laser plane  38  and a vertical line extending from the axis of rotation  42 . The horizontal distance between the cutting plane  18  and the axis of rotation  42  along base plate  20  is defined as “x”. The horizontal offset distance measured from projected laser line  40  to the cutting plane  18  is designated as “d”. Because the support body  32  fixes the axis of rotation  42  with respect to the base plate  20 , the distance “H” is fixed. This fixed, known distance allows for graduations  47  to directly correspond to the horizontal offset distance “d,” as seen in  FIG. 1A . These graduations  47  may be directly expressed as a horizontal offset distance “d”, rather than as an angle. At a zero reference point on the dial  44  that corresponds to an offset distance of zero, the projected laser line  40  is coplanar with the saw blade  17  and the cutting plane  18 . Further offset distances may be calculated from the following formula:  
         tan   ⁢           ⁢   θ     =       d   +   x     H         
 
 These offset distances may be expressed in inches, centimeters, or any other unit of linear measure. 
 
         [0028]      FIGS. 5-8  illustrate another embodiment of an alignment guide  60  mounted to the circular saw  10 . In the embodiment shown in  FIGS. 5-8 , the support body  62  is integrally formed with the bevel adjustment  24 . The laser housing  64  is rotatably attached to the support body  62  and rotates about an axis of rotation  72 . A laser generator (not shown), disposed within the laser housing  64 , produces a planar, fan shaped beam of light  68  which projects a laser line  70  onto the workpiece  100 . Other aspects of the alignment guide  60  are similar to the alignment guide  30  shown in  FIGS. 1-4  and described above.  
         [0029]     A first scale  74  is formed on the support body  62 . The first scale  74  may be printed, stenciled, marked, scribed, drilled, cut, etched, stamped, molded, etc. into the support body  62 , or formed as a separate piece such as a label. An indicator  78  is formed as a projection that extends from the laser housing  64 , sweeping along the first scale  74  as the laser housing  64  rotates about the axis of rotation  72 . The radial graduations  75  on the first scale  74  that correspond to the offset distance may be calculated as described above for the alignment guide  30  shown in  FIGS. 1-4 .  
         [0030]     The first scale  74  and the indicator  78  accurately reflect offset distances for circular saws having a bevel angle of zero degrees. In addition, if a circular saw has an axis of bevel rotation  80  that coincides with the intersection of the cutting plane  18  and the workpiece  100 , the first scale  74  will remain accurate. However, as seen in  FIGS. 6-7 , if a circular saw has an axis of bevel rotation  80  that is offset from the intersection of the cutting plane  18  and the workpiece  100 , the cutting plane  18  will shift with respect to the alignment guide  60  and the axis of rotation  72 . This offset requires an angular correction. As seen in  FIGS. 5-8 , a second scale  76  is provided concentrically with the first scale  74  on the support body  62 , with radial graduations  77  having an angular offset “θ1” that corresponds to the offset distance “s.” This angular offset “θ1” may be calculated from the following formula:  
         θ   ⁢           ⁢   1     =       tan     -   1       ⁢     s   H           
 
 The second scale  76  corresponds with a bevel angle of  45  degrees, although other bevel angles or additional scales corresponding to other bevel angles may be used by recalculating the angular offset due to the shift of the axis of bevel rotation  80 . 
 
         [0031]      FIGS. 9-11  illustrate another embodiment of an alignment guide  130  shown mounted to a jig saw  110 . Similar to the circular saw  10  described above, the jig saw  110  includes a housing  112  mounted to a base plate  120 . The housing  112  has a handle  113  and a trigger  114 . The trigger  114  activates a motor (not shown) disposed within housing  112 . The motor oscillates a saw blade  117  (shown in  FIGS. 10-11 ) in the cutting plane  118  to cut the workpiece  100 . The jig saw  110  may also feature a bevel adjustment that allows the housing  112  and the saw blade  117  to rotate with respect to the base plate  120 , typically from 0 to 45 degrees. Examples of such a jig saw include the Ryobi® Model OJ1802 18.0 Volt Cordless Orbital Jig Saw available from One World Technologies, Inc. of Anderson, S.C., United States of America, and the Craftsman® Model 11428 19.2 Volt Cordless Jig Saw available from Sears, Roebuck, and Co. of Hoffman Estates, Ill., United States of America.  
         [0032]     As seen in  FIGS. 9-11 , the alignment guide  130  is mounted to the jig saw housing  112 , although it may alternately be mounted to the base plate  120 . The alignment guide  130  includes a support body (not shown), a laser housing  134 , a laser generator (not shown), a dial  144 , and an indicator  148 . The support body may be integrally formed with the housing  112 . The laser housing  134  and dial  144  are rotatably attached to the housing  112  and adjustably rotate about an axis of rotation  142 . The dial  144  has a scale  146  that may include of a series of numbered graduations  147  that run axially along the outer circumference of the dial  144 . The indicator  148  is positioned on the housing  112  to indicate the degree of rotation of the dial  144  and the laser housing  134 . The laser generator produces a planar, fan shaped beam of light  138  that projects a laser line  140  onto the workpiece  100 . Other aspects of the alignment guide  130  are similar to the alignment guide  30  shown in  FIGS. 1-4  and described above.  
         [0033]     As seen in  FIG. 11 , “H2” is defined as the vertical distance between the axis of rotation  142  and the top surface of the workpiece  100  as the base plate  120  is resting on it. The angle “θ2” is defined as the angle formed by the laser plane  138  and a vertical line extending from the axis of rotation  142 . The horizontal offset distance measured from projected laser line  140  to the cutting plane  118  is designated as “d2”. Because the support body fixes the axis of rotation  142  with respect to the base plate  120 , the distance “H2” is fixed. This fixed, known distance allows for graduations  147  to directly correspond to the horizontal offset distance “d2.” These graduations  147  may be directly expressed as a horizontal offset distance “d2”, rather than as an angle. At a zero reference point on the dial  144  that corresponds to an offset distance of zero, the projected laser line  140  is coplanar with the saw blade  117  and the cutting plane  118 . Further offset distances may be calculated from the following formula:  
         tan   ⁢           ⁢   2     =       d   ⁢           ⁢   2       H   ⁢           ⁢   2           
 
 These offset distances may be expressed in inches, centimeters, or any other unit of linear measure. 
 
         [0034]     In operation, a switch (not shown) actuates the laser generator  40 . A fan-shaped planar laser beam  38 ,  68 ,  138  is projected from the laser generator  40 , and forms a projected laser line  40 ,  70 ,  140  on a workpiece  100 . By rotating the dial  44 ,  144  or the indicator  78  to correspond with a desired offset distance as indicated by graduations  47 ,  75 ,  77 ,  147  an operator can shift the laser line  40 ,  70 ,  140  to a desired offset distance left or right from saw blade  17 ,  117 . This allows an operator to accurately and quickly make cuts at a desired offset distance.  
         [0035]     The present invention is applicable to power tools having a cutting plane of operation such as circular saws, jig saws, table saws, miter saws, reciprocating saws, band saws, routers, laminate trimmers, and scroll saws. While the invention has been described with reference to details of the illustrated embodiments, these details are not intended to limit the scope of the invention as defined in the appended claims. For example, while the alignment guide has been illustrated as using a laser generator, other light sources may be used, such as lamps, light emitting diodes, etc. In addition, a vernier-type device may be used to allow for finer graduations. Alternately, a transmission may be coupled with the dial or scale and laser housing to allow for a mechanical disadvantage, which increases the rotational sensitivity and permits finer graduations and adjustment. Further, other units of measure may be used on the graduations, such as rotational units such as degrees or linear units such as millimeters, etc. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.