Patent Publication Number: US-2011048202-A1

Title: Saw with digital measurement device

Description:
FIELD 
     This application relates to the field of power tools and more particularly to power saws, such as power miter saws. 
     BACKGROUND 
     Power saws, such as miter saws are typically used for cutting a work piece, for example, construction lumber. A miter saw typically include a base or platform on which a turntable is positioned. The turntable is used to support the work piece to be cut. A cutting assembly is connected to the turntable and is operable to perform a cutting operation on the work piece. The cutting assembly is configured to move upward and away from the turntable and downward toward the turntable in order to produce a cut. The cutting assembly is also configured to pivot in relation to the turntable in order to produce angled cuts. 
     A rip fence typically extends above the surface of the turntable. The rip fence includes a scale that allows the user to determine how far the work piece extends past the location of the cut. However, very long work pieces may extend past the end of the rip fence, making it difficult for the user to determine how far the end of the work piece is from the location of the cut. 
     In view of the foregoing, it would be desirable to provide a saw with an improved measurement device. It would also be desirable if such measurement device could be easily incorporated into a miter saw or a table saw. While it would be desirable to provide a saw that provides one or more of these or other features, the teachings disclosed herein extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned advantages or include one or more of the above-mentioned features. 
     SUMMARY 
     A saw comprises a blade configured to perform a cut on a work piece at a cutting position. The saw includes a measurement device configured to determine a distance. The measurement device includes a laser generator configured to emit a laser beam. A laser interference member is provided on the work piece with a portion of the laser interference member in the path of the laser beam. The laser interference member comprises a reflective surface configured to reflect the laser beam and an adhesive surface configured to adhere to the work piece. The measurement device further comprises a digital display configured to provide an indication of the determined distance. 
     In at least one embodiment, the saw is a miter saw. The miter saw comprises a table providing a surface for supporting the work piece. The cutting position is defined by a slot in the table, and the blade is configured to engage the slot. The blade is supported by a pivotable cutting arm. The pivotable cutting arm is configured to move the blade into the slot when the blade performs the cut. The miter saw further comprises a rip fence positioned above the table. The laser generator may be positioned on the rip fence. 
     In another embodiment, the measurement device is provided as a sensor wheel associated with the engagement surface. The sensor wheel is configured to rotate when the work piece is moved along the engagement surface. The measurement device is configured to determine a distance the work piece has moved along the engagement surface based upon rotation of the sensor wheel. The digital display provides an indication of the determined distance. The engagement surface may be a table of the saw, a rip fence, or any other work support engaging surface. 
     The above described features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings. While it would be desirable to provide a saw that provides one or more of these or other advantageous features, the teachings disclosed herein extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned advantages or include one or more of the above-mentioned features. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a front perspective view of one embodiment of a saw with a digital measurement device with a cutting assembly of the saw in a down position; 
         FIG. 2  shows a front view of a laser interference device for use with the digital measurement device of  FIG. 1 ; 
         FIG. 3  shows the saw of  FIG. 1  with the cutting assembly in an up position; 
         FIG. 4  shows the saw of  FIG. 3  with a work piece supported by the saw and a reflector positioned on an end of the work piece; 
         FIG. 5  shows an alternative embodiment of the saw of  FIG. 1  with the digital measurement device positioned above the rip fence; 
         FIG. 6  shows an alternative embodiment of the saw of  FIG. 1  with the digital measurement device provided as a roller provided on a table surface of the saw; 
         FIG. 7  shows the saw of  FIG. 5  with the cutting assembly in an up position; and 
         FIG. 8  shows an alternative embodiment of the saw of  FIG. 6  with the digital measurement device provided as an optical measurement device provided on the table surface of the saw. 
     
    
    
     DESCRIPTION 
     Referring now to  FIGS. 1-4 , there is shown a miter saw assembly  100 . The miter saw assembly  100  includes a digital measurement device  200  positioned thereon. The miter saw  100  comprises a base  102  and a turntable  104  that is rotatable on the base  102 . The miter saw assembly  100  further includes a cutting head  106  mounted on a cutting head support assembly  114 . The cutting head  106  (which may also be referred to herein as a “cutting assembly”) includes a motor  108  that is operable to rotate a circular saw blade  110 . The cutting head support assembly  114  is attached to the turntable  104  and configured to support the cutting head  106  such that the cutting head may move over the turntable  104  and perform cutting operations. 
     The cutting head support assembly  114  includes a bevel arm  116  pivotably connected to a cutting arm  118 . The bevel arm  116  (also referred to herein as a “bevel post”) provides a bevel support structure for the miter saw assembly. The bevel arm  116  is pivotally attached to the turntable  104 . The bevel arm is configured to pivot from a vertical position (as shown in  FIG. 3 ) to an angle of 45° (not shown) prior to a cutting operation. This pivoting allows the blade  110  of the cutting assembly  106  to approach the table  104  from a bevel angle and perform angled cuts, as is well known in the art. 
     The cutting arm  118  of the support assembly  114  provides a support for the cutting assembly  106 . The cutting arm  118  is configured to pivot upward and downward in relation to the turntable  104  and the base  102  during a cutting operation, as is well known in the art.  FIG. 1  shows the cutting arm  118  in a downward position and  FIG. 3  shows the cutting arm  118  in the upward position. 
     The cutting assembly  106  includes a handle  128  connected to the cutting arm  118  to facilitate movement of the cutting assembly  106  in relation to the turntable  104 . The handle  128  is designed and dimensioned to be grasped by a human hand when performing a cutting operation. This allows the user to easily pivot the cutting assembly  106  upward and downward. A switch  112  is provided on the handle  128  to allow the user to easily energize and de-energize the electric motor  108  during a cutting operation. A blade guard  136  covers the top portion of the circular saw blade  110 . 
     The circular saw blade  110  includes a generally circular plate having a central opening defined therein. A plurality of cutting teeth are attached to periphery of the plate, as is well known in the art. A dust chute  132  is positioned behind the blade  110  when the blade is in a downward cutting position. In this manner, the dust chute  132  receives sawdust and other debris created by the blade  110  when performing a cutting operation. 
     The circular saw blade  110  is used to cut a work piece  150  (see  FIG. 4 ) positioned on the table  104 . The table  104  provides a work surface that supports the work piece  150 . A slot  124  is formed in the table at a cutting location. The blade is configured to engage the slot during a cutting operation. In the embodiment of  FIGS. 1-4 , the slot  124  provides a void for the blade when the blade  110  completes a cut through the work piece  150 , thus preventing the blade from coming into contact with the table  104 . 
     A stationary table leaf  120  is provided adjacent to the turntable  104 . Another leaf is also provided on the opposite side of the turntable. The leaves  120  do not rotate with the turntable, and remain to the lateral sides of the saw  100 . The leaves  120  provide an additional support surface that may be used to support the work piece during a cutting operation. 
     Moveable work surface extensions  130  (which may also be referred to herein as “support extensions”) are provided to the outward side of the leaves  120 . The support extensions  130  are moveable from a retracted position (as shown in  FIG. 1 ) where the support extensions  130  are in close proximity to the leaves  120  to an extended position (as shown in  FIG. 2 ) where the support extensions  130  are removed from the leaves  120 . When in the extended position, the support extensions  130  provide an additional support surface for elongated work pieces (as shown in  FIG. 3 ). 
     A rip fence  134  is secured to the base  102  and positioned over the turntable  104 . The rip fence  134  provides a surface for aligning a work piece thereon, as shown in  FIG. 4 . The rip fence  134  also includes a scale  138 . The scale  138  provides an indication of the distance a work piece  150  extends from the cutting position (i.e., the slot  124 ). The scale  138  may also be used during a cutting operation to move a work piece a given distance in preparation for an additional cut. 
     The miter saw  100  includes a digital measurement device  200  positioned thereon. In the embodiment of  FIGS. 1-4 , the digital measurement device  200  includes a laser rangefinder  210 , a laser interference device  220 , and a digital display  230 . 
     The laser rangefinder  210  may be configured similar to any of various laser rangefinders known in the art. Such laser rangefinders typically include a laser generator, optics, a light detector, and associated electronics. The laser rangefinder  210  makes use of the generated laser beam to determine the distance to a reflective target. In particular, the laser rangefinder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the reflective target and measuring the time taken by the pulse to be reflected off the target and returned to the rangefinder. In order to ensure that only light from the laser generator is detected by the rangefinder, the laser is typically pulsed with a predetermined code. 
     In the embodiment of  FIG. 1 , the laser rangefinder  210  is provided on the rip fence  134 . The laser generator and associated electronics are contained within a protective housing provided by an end portion of the rip fence  132 . Two optical lenses  212 ,  214  are shown on the rip fence. One of the lenses  212  is used to emit a laser beam  216  (shown by the dotted line in  FIG. 1 ) in a direction extending generally away from the blade  110 . In particular, the laser generator and optical lens  212  emit the laser beam  216  in a direction that is substantially perpendicular to the flat side surface of the blade  110 . The other optical lens  214  is used to receive reflected laser light and direct such light to the light detector within the protective housing of the laser generator  210 . Even though the laser  216  is represented in  FIG. 1  as a dotted line, it will be recognized that the laser may be configured to cover a wider area, such as a thin cone-shaped laser. 
     A typical work piece being cut on a miter saw is a long thin material with constant cross-section, such as the work piece  150  shown in  FIG. 4 . With such work pieces, there is no natural surface for the laser  216  to reflect from. Thus, the digital measurement device  200  includes a separate reflective component from the laser rangefinder  210 . In the embodiment of  FIGS. 1-4 , this separate reflective component is the laser interference device  220  which is configured for attachment to the end of the work piece  150 . The laser interference device  220  includes a reflective surface that extends away from the work piece and is designed to reflect laser light back toward the light detector of the laser rangefinder  210 . 
     In the embodiment of  FIGS. 1-4 , the laser interference device  220  is provided in the form of a “T” shaped part. The part is generally comprised of a relatively lightweight plastic material, but may also be formed from any of various other materials, including wood or metals. 
     As best shown in  FIGS. 1 and 2 , the “T” shaped part  220  includes three wings,  222 ,  224  and  226 . One wing  222  includes a reflective surface  223 . The reflective surface  223  may be any surface capable of reflecting light from the laser beam  216  back to the laser rangefinder  210 . In at least one embodiment, the reflective surface  223  is a mirrored surface. 
     A second wing  224  includes an attachment surface  225  capable of securing the laser interference device  220  to the work piece  150 . In one embodiment, the attachment surface  225  is an adhesive surface including a low-tack, reusable pressure sensitive adhesive, such as the adhesive commonly used on office sticky notes. This adhesive allows the attachment surface  225  to be easily attached to the work piece  150  and easily removed from the work piece. In the event the adhesive surface  225  wears away over time, the user may use two-sided tape on the second wing  224  in order to provide continued adhesive properties. 
     The third wing  226  of the “T” shaped part  220  extends perpendicular to the first wing  222  and the second wing  224 . The third wing  226  may be smooth and clean on both opposing surface or may include at least one an adhesive surface similar to surface  225 . Such an additional surface may be used to provide additional adhesive properties to the part  220  and/or allows the part to be attached to the work piece  150  in additional orientations. In at least one embodiment, the third wing also includes an additional reflective surface. Such an additional reflective surface allows the “T” shaped part to easily reflect the laser  216  in different orientations. 
       FIG. 4  shows the “T” shaped part  220  attached to an exemplary work piece  150  with the adhesive surface  225  attached to the distal end  151  of the work piece  150  and the wing  222  with the reflective surface  223  extending outward from the work piece in the path of the laser  216 . The laser rangefinder  210  emits the laser  216  from lens  212 , in a direction away from the blade  110  and toward the laser interference device  220 . The laser  216  may be emitted as a narrow cone or similar shape such that it spreads slightly as it moves away from the laser generator. Thus, user is not required to make a precise directional shot at the reflective device, and some deviation from a straight target line will still allow some laser light to strike the reflective surface  223 . 
     When the detector of the laser rangefinder  210  detects reflected laser light through the lens  214 , the electronic circuitry provides a calculation of the distance the reflected light has travelled based on well known time of flight principles. This distance is then added to a known distance between the blade  110  and the laser generator to arrive at a total distance between the blade and the laser interference device at the end of the workpiece  150 . The measurement device  200  may be calibrated from the outside edge of the blade to show the actual distance from the blade  110  and associated cutting slot  124  on the table  104 . In addition, calibration may be adjusted by the user depending on which part of the cutting kerf the user wants to use. 
     After the distance from the blade  110  to the edge of the work piece is calculated by the laser rangefinder  210 , the distance is displayed on the digital display  230 . The digital display  230  may be an LCD screen, LED display, or any other display known to those of skill in the art. The display  230  may include a number of buttons that allow the user to calibrate the display, adjusted options, select modes, or otherwise program the display. 
     In addition to providing the user with the distance from the blade to the edge of the work piece, the measurement device  200  may also be configured such that the display  230  continuously shows the change in distance as the user adjusts the material on the table  104 . For example, consider a situation where a user cuts a 5 foot piece of material from a work piece and wants to remove and additional 1.5 feet from the work piece. The user may accomplish this by aligning the end of the work piece to the edge of the blade and then moving the work piece 1.5 feet as using the display shows the change in distance. In an associated algorithm, the user may select a current position as a “zero” position, and the display is programmed to show movements of the work piece from the “zero” position. Additional algorithms may also be incorporated in the measurement device  200  to calculate various lengths that may be useful to the user such as the lengths of a certain number of divisions. Each additional mode of operation may be selected by the user by selecting the appropriate buttons on the digital display  230 . 
     While the laser rangefinder  210  is shown in  FIGS. 1 ,  3  and  4  as contained within an end portion of the rip fence  134 , it will be recognized that the laser rangefinder  210  may also be positioned on other locations of the saw. Another possible location for the laser rangefinder is the back of the rip fence  134 , as shown in the embodiment of  FIG. 5 . In this embodiment, the laser rangefinder  210  includes a housing  118  that extends above the rip fence  134 . As can be seen in  FIG. 5 , the laser beam  216  may be directed at a significant angle relative to the work surface  150 . Accordingly, the actual distance of travel of the laser beam  216  may not be a true measure of the horizontal distance from the cutting sot  124  and the reflective device  220 . Thus, the laser rangefinder  210  may be equipped with a slope feature that allows the measurement device  200  to calculate the horizontal distance along the work piece based on the distance of laser travel and the incline of the laser generator. In at least one embodiment, the laser rangefinder  210  may be tilted on the work piece, allowing the user to orient the laser in the general direction of the reflective device. In this embodiment, the laser rangefinder is capable of determining the angle of laser incline relative to the table  104  and calculating the distance of the work piece  150  based on this incline and the distance of laser travel. 
     With reference now to  FIGS. 6 and 7 , in an alternative embodiment, the measurement device  200  comprises a linear measurement device  250  including a measurement wheel  260  positioned on one leaf  120  of the support surface and associated electronics. The device  250  is configured to transform rotational movement of the measurement wheel  260  into a linear measurement that is displayed on the digital display  230 . 
     In the embodiment of  FIGS. 6 and 7 , the rotatable measurement wheel  260  is rotatably mounted on the table leaf  120  such that a portion of the wheel  260  extends above the support surface provided by the leaf  120 . The remainder of the wheel  260  is provided below the support surface. It will be recognized that although the wheel  260  is provided in association with the support surface in the embodiments of  FIGS. 6 and 7 , the wheel  260  may be positioned differently on the saw in other embodiments. For example, the wheel  260  may be associated with any surface of the saw which the work piece is intended to engage, such as placement of the wheel  260  on the fence  134  or provided as an attachment at the end of the support surface. 
     The measurement wheel  260  generally includes a high friction outer surface comprised of a rubber, elastomer or similar material configured to grip the surface of various work pieces. The measurement wheel  260  is rotatably mounted on the saw and is connected to electronic measurement circuitry (not shown). The electronic measurement circuitry calculates a linear distance of travel based on rotation of the measurement wheel  260 . Similar to the embodiments of  FIGS. 1-5 , discussed above, the electronic measurement circuitry communicates with the digital display  230  to show the calculated linear distance. 
     In operation, a user slides a work piece along the support surface and over the measurement wheel  260  in the direction of arrow  270  of  FIG. 6 . Rotation of the wheel  260  is displayed as the change in linear position of the work piece. In at least one embodiment the measurement device  250  displays the movement of the work piece in 1/16 inch increments. 
     The display includes various modes of operation. In one mode, the display  230  may show a distance of movement of the work piece from a first position to a second position. In another mode, a user may use the measurement wheel  260  to measure the total distance between an edge of a work piece and the cutting slot  124 . In this mode, the user places the edge of the work piece on the wheel and slides the work piece in the direction of arrow  270 . As the work piece is moved in direction  270 , the wheel rotates, and the accumulated distance is shown on the digital display, plus the distance between the cutting slot  124  and the wheel. 
       FIG. 8  shows yet another alternative embodiment of the measurement device  200  where the rotatable wheel  260  is replaced with an optical measurement device  290 . The optical measurement device  290  may include a light emitting diode or a laser diode, a photo detector, and other electronic devices positioned behind a window  292  on the support surface or other surface associated with the work piece. In  FIG. 8 , the window  292  is positioned on the leaf  120  and the electronic devices are housed under the leaf  120 . Of course, the window may also be provided on another surface associated with an area of the saw where the work piece may move. The optical measurement device is configured to measure the distance of travel of the work piece relative to a point on the window  292 . The optical measurement device is configured to operate in a manner similar to an optical mouse. Accordingly, the LED or laser diode illuminates the surface of the work pieces as it moves relative to the window  292 . Images of the work piece are captured periodically by the photo detector and changes between one frame and the next are processed by an image processor and translated into movement and distance of travel using an optical flow estimation algorithm. 
     Although a saw with a digital measurement device has been described with respect to certain preferred embodiments, it will be appreciated by those of skill in the art that other implementations and adaptations are possible. For example, as discussed above, the measurement devices including the laser generator or roller may be differently positioned on the saw. As another example, the measurement display could also be positioned at a different location on the saw. Moreover, there are advantages to individual advancements described herein that may be obtained without incorporating other aspects described above. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.