Abstract:
A table saw having various embodiments of a measurement and display system. Several embodiments have at least one fence rail on which a removable fence is movably supported and comprise an elongated sensor strip that is located adjacent the fence rail and a sensing unit that is supported and positioned adjacent to the sensor strip and is capable of providing an electrical signal to a display unit that is indicative of the position of the sensor unit relative to the elongated sensor strip. A processing unit is operatively connected to the sensing unit and display unit to provide a digital readout of the position of the sensing unit. A switch is connected to the processing unit and is adapted to provide a zero or reference setting position.

Description:
[0001]     This is a divisional of application Ser. No. 10/823, 270, filed Apr. 13, 2004. 
     
    
       [0002]     BACKGROUND OF THE INVENTION  
         [0003]     Table saws of the type which have a circular cutting blade are well known and have been used by tradesmen and woodworkers for decades. Because they have a generally flat surface, large and small boards as well as plywood sheets can be cut to the appropriate size by typically setting a fence at the appropriate position to perform a cut along a desired line which is done by pushing the board or sheet across the tabletop and through the blade. Typically, the fence is adjustable by sliding along an elongated rail anchored at opposite ends of the table saw top, with the fence having a clamping mechanism to lock the fence once it has been placed in the desired position. Most users, when they know the width of the desired board will use a tape measure or other measure to position the fence to obtain the desired width by measuring between the edge of the blade to the fence. After the fence is in position, it is locked in place and users typically remeasure the distance to make sure that they have the fence in the correct position.  
         [0004]     While the manual measurement and setting of the position of the fence is the manner in which the fence has been positioned by most users over the years, in some instances it is highly desirable to have very accurate measurements which may be difficult depending upon the type of measuring device is being used. Most tape measures, for example, do not have accurate measurements beyond a 1/32 of an inch or less. Also, if the fence is moved during other types of cuts, it is not possible to reset the fence at exactly the same position that was used for a prior cut without going through the complete exercise again. If the user does not remember the prior cut distance, then additional measurements of a work-piece may be necessary in order to obtain the distance which must then be used to correctly position the fence. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1  is a front view of a first preferred embodiment of a table saw having a measurement and display system;  
         [0006]      FIG. 2  is a front view of a second preferred embodiment of a table saw similar to the table saw shown in  FIG. 1 , but having a tabletop extension shown in an extended position;  
         [0007]      FIG. 3  is a cross-section taken generally along the line  3 - 3  of  FIG. 2 ;  
         [0008]      FIG. 4  is a front view of a portion of the table saw shown in FIGS.  1  and 2 ;  
         [0009]      FIG. 5  is a section taken generally along the line  5 - 5  of  FIG. 4 ; and  
         [0010]      FIG. 6  is a front view of a third preferred embodiment illustrating a display unit having additional functionality relative to the display unit shown in  FIG.4 .  
         [0011]      FIG. 7  is a perspective view of an idealized illustration of a third preferred embodiment of a table saw having a measurement and display system;  
         [0012]      FIG. 8  is an end view of the embodiment shown in  FIG. 7  and illustrating a mounting bracket in phantom;  
         [0013]      FIG. 9  is an enlarged perspective of a portion of the embodiment shown in  FIG. 7 ;  
         [0014]      FIG. 10  is a perspective view of an idealized illustration of a fourth preferred embodiment of a table saw having a measurement and display system;  
         [0015]      FIG. 11  is a perspective view of an idealized illustration of a fifth preferred embodiment of a table saw having a measurement and display system;  
         [0016]      FIG. 12  is a perspective view of an idealized illustration of a sixth preferred embodiment of a table saw having a measurement and display system; and  
         [0017]      FIG. 13  is a perspective view of an idealized illustration of a seventh preferred embodiment of a table saw having a measurement and display system. 
     
    
     SUMMARY OF THE INVENTION  
       [0018]     A table saw having a measurement and display system has at least one fence rail on which a removable fence is movably supported. Several embodiments have an elongated sensor strip located adjacent the fence rail and a sensing unit that is supported and positioned adjacent to the sensor strip and is capable of providing an electrical signal to a display unit that is indicative of the position of the sensor unit relative to the elongated sensor strip. A processing unit is operatively connected to the sensing unit and display unit to provide a digital readout of the position of the sensing unit. A switch is connected to the processing unit and is adapted to provide a zero or reference setting position and this embodiment may include a second switch for changing between English and metric units.  
         [0019]     A second preferred embodiment includes a table extension which can be moved to increase the effective size of the table saw top so that larger work pieces can be supported during cutting. In this embodiment, the fence rail is connected to an extension rail so that the fence rail moves with the extension to thereby increase the range of the sensor strip and sensing unit for providing larger measurements.  
         [0020]     A third preferred embodiment includes a more sophisticated display and processor functionality, which, among other things, can display English units in decimal or fractions as well as store and recall important distance measurement positions.  
         [0021]     A fourth preferred embodiment includes a mounting mechanism that enables a relatively short and inexpensive sensor strip to be selectively positioned to increase the range of measurement of a fence along the width of the table saw and to adjust the measurement as a result of the position of the sensor strip.  
         [0022]     A fifth preferred embodiment operates with a sensing rail that is located on the front of the table saw, but has all other operative elements mounted on the fence.  
         [0023]     Sixth and seventh preferred embodiments operate with a string or tape position transducer device that interconnects a stationary location on the table saw and the movable fence.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     A first embodiment of a table saw of the present invention is shown in  FIGS. 1, 2  and  3  and illustrates a table saw, indicated generally at  10 , of the type which is configured to be supported by a table  12  or other support structure or frame having legs. It should be understood that the table saw  10  could be of the type which has its own support stand and may be more permanent rather than the one illustrated which is often referred to as a portable saw. The saw  10  has a base  14  in which the saw motor (not shown) is located with the motor driving a blade  16 , the height of which can be adjusted by conventional adjustment means (not shown) and which can also be angularly adjustable by an assembly that includes a wheel  18 .  
         [0025]     The saw  10  has a main tabletop  20 , a tabletop extension  22  and an adjustable fence, indicated generally at  24 , that has a handle  26  that can be raised and lowered to lock the fence in a desired lateral position relative to the blade. The fence has a base portion  28  that is slidably adjustable along a fence rail  30  that extends substantially the full width of the saw. While not illustrated, the fence preferably has its opposite end configured to ride on another fence rail which facilitate its sliding lateral movement, i.e., left and right as shown in  FIG. 1 .  
         [0026]     The table saw  10  illustrated in  FIG. 1  is shown with the extension  22  in an unextended position whereas in  FIG. 2 , the extension  22  is extended outwardly to the right. This is achieved by a locking knob  32  being loosened so that the fence rail  30 , which is supported by an extension rail  34  can be moved along the extension rail  34 . It should be understood that the fence  24  in  FIG. 2  has been moved relative to its position in  FIG. 1  to more clearly illustrate the manner in which the extension  22  moves relative to the extension rail  34 . The configuration which particularly illustrates the interoperability of the fence rail  30  and the extension rail  34  is shown in  FIG. 3 , with the extension rail  34  having a base portion  36  that is connected to the main top  20  by bolts  38 , screws, weldments or the like, with short transverse segment  40  extending away from the base  36  and then outwardly to form flanges  42  and transverse end segments  44 . The configuration provides a narrow space  46  between the top  20  and the extension rail  34  so that the fence rail  30  can easily slide relative to the extension rail  34  but be held captive so that any appreciable vertical and horizontal movement between the two components is prevented. An end cap  48  made of plastic or plastic-like material is preferably provided at opposite ends of the fence rail  30  and is preferably a resilient material that can be snap-fit into the interior of therail 30 .  
         [0027]     As best shown in  FIGS. 1, 2  and  3 , a display rail  50  is positioned below the fence rail  30  and is attached thereto by two brackets  52  which are located at opposite ends of the fence rail  30 . The brackets  52  have a front upper flange  54  upon which a spacer  56  is positioned with the flange  54  and spacer being connected to the fence rail  30  by a bolt  58  and nut  60 , screws, weldment or other equivalent attachment means. The opposite ends of the display rail  50  are attached to the bracket  52  by suitable screws, adhesive, bolts or the like (not shown). The display rail has a base portion  62  as well as transverse end portions  64  and return flanges  66  which define a recess in which a display unit, indicated generally at  70 , can be inserted and be held captive so that vertical and horizontal movement is prevented but which will permit sliding lateral movement, i.e., left or right as shown in  FIGS. 1 and 2 .  
         [0028]     On the backside of the bracket  52  a sensor strip  72  is attached by screws, bolts, adhesive or the like. A sensor strip  74  is attached to the sensor strip  72 , preferably using an adhesive material. While the cross section of the sensor strip  74  is shown in  FIG. 3  and is therefore illustrated to be located at the left end of the sensor strip  72 . In actuality, the length of the sensor strip  74  is preferably within the range of about 15 to about 25 inches and preferably about 20 inches with the left end of the sensor strip being approximately coextensive with the blade and extending to the right end thereof as shown in  FIG. 1 . In this regard, the drawing is technically in error, but does generally show the relative size and configuration of the strip relative to the sensor strip. It should also be understood that when the extension  22  is moved to the right as shown in  FIG. 2 , the left end of the sensor strip  74  will move to the right of the blade  16 .  
         [0029]     It should be understood that another preferred embodiment of the table saw may not include the extension  22  and therefore would not need to have the extension rail  34 , in which case the fence rail  30  would be attached directly to the table top  20  or other structure associated with the frame because the fence rail  30  would not move laterally.  
         [0030]     As shown in  FIG. 4 , the display unit  70  has an electronic display  76  that is mounted to a display block  78  that is preferably a unitary piece of aluminum or other metal that has an angled front face  80  with a suitable recess (not shown) in which the display  76  can be inserted, with the ends extending further outwardly so as to provide some protection against damage during use. The right end of the block  78  has a vertically oriented slot  82  that has a width that is closely matched to the outside diameter of a pin  84  that is attached to the fence base  28 . The pin  84  therefore causes the display unit  70  to move with the fence as it is laterally adjusted during use. Since the pin  84  merely rides in the slot  82  of the block  78 , the fence  24  can be lifted without difficulty from the table saw. However, when it is lowered into place so that the fence base  28  rides on the fence rail  30 , the pin  84  is closely fits in the slot  82 . The display  76  has a ribbon connector  86  that extends to a sensor  88  that is secured to the display block  78  by a bolt  90 , although adhesive or other attachment means may be used. The sensor  88  is configured relative to the sensor strip  72  so that the necessary tolerances between the two are maintained as the sensor  88  is moved along the sensor strip.  
         [0031]     A sensor  88  is secured to the display block  78  by bolts  90  and the sensor strip  72  has copper pads along its length that are positioned to provide a changing capacitance that is sensed by the sensor element  58  and which can thereby provide accurate measurement of incremental positions along the length of the rail. In this regard, it is preferred that the sensor strip  72  and sensor  88  be similar to those that are presently used in commercially available digital calipers. Other linear sensor technologies based on inductance, magnetostrictive effects or resistive elements can also be used.  
         [0032]     The display  76  has a front panel with a pushbutton switch  96  which is a zero set switch and a switch  98  which toggles between English and metric systems in the display window  100 . The display window is preferably a LCD display which has four integers  102  and a decimal  106  as well as a field  108  indicating inches or millimeters.  
         [0033]     During operation, when the fence  24  is positioned abutting the blade  16 , for example, an operator can depress the zero set pushbutton  96  which will result in the display window readout indicating a zero position. That having been done, if the user wants to position the fence so that a six inch wide cut of a work piece is desired, the fence  24  can be moved to the right until the display indicates that the fence has been moved 6.00 inches (or the appropriate millimeter conversion) at which time the user can lock the fence  24  in position by moving the lock handle  26  downwardly in the illustrated embodiment.  
         [0034]     If during the locking of the fence, the fence moves either left or right as shown in  FIG. 4 , the display  76  will so indicate, which enables the user to unlock the fence and correctly position it until the exact distance of six inches is locked into position. If the sensing strip/sensor has a 1/100 inch or 1/10 millimeter degree of accuracy, the fence can be positioned to that degree of accuracy.  
         [0035]     Turning to another preferred embodiment of the present invention and referring to  FIG. 6 , a display  110  is shown which has additional functionality. More particularly, the display has a pushbutton  112  which toggles between English and metric units and has a six integer display with two decimal points and a slash indicator which enables English units to be displayed in hundredths or in fractions and metric units to be displayed in thousandths or ten thousandths of an inch. Additionally, the display includes a zero pushbutton  114  as well as a store pushbutton  116  and a recall pushbutton  118  as well as an offset pushbutton  120 . The display is also operable to set and utilize a DADO blade offset as well as a fence offset in either 1/16 or 1/32 increments which enables a user to appropriately set the position.  
         [0036]     Another embodiment of the present invention is shown in  FIGS. 7-9  which comprises a table saw having a table top  20  that has an opening through which a saw blade  16  is positioned. A fence indicated generally at  24 ′ has a base  28 ′ that has a recess which cooperatively engages a fence rail  130  and is configured to slide along the fence rail  130  and be clamped to it. While the diagrammatic illustration of the fence  24  shown in  FIGS. 7, 8  and  9  is greatly simplified, it should be understood that a clamping or locking mechanism is preferably provided as is known to those of ordinary skill in the art.  
         [0037]     The fence rail  130  is attached to the table  20  by suitable bolts or the like that are located inside a pair of standoffs  131  which appropriately space the fence rail from the front edge of the tabletop  20 . A display  70 ′ is mounted on a block extrusion  132  that is coupled to the base  28 ′ of the fence  24 ′. The block extrusion  132  has an angled front portion  134  to which the display  70 ′ is attached and the top of the front portion  134  has a forwardly directed flange  136  that is substantially parallel to the base  28 ′ of the fence. A pin  138  mounted to the base  28 ′ extends into a slot in the flange  136  with the width of the slot being substantially equal to the outside diameter of the pin  138  so that movement of the fence along the sensing rail  130  will also move the block extrusion  132 .  
         [0038]     The block extrusion  132  also has a middle portion  140  that extends in the rearward direction and carries a T-shaped cross section  142  as well as a rearward extension  144  that is vertically oriented and provides a surface to which a sensing unit  146  is mounted. A flexible ribbon cable similar to the ribbon connector  86  shown in  FIG. 5  interconnects the sensing unit  146  to the display module  70 ′.  
         [0039]     The sensing unit has an opening  148  through which a sensing rail  150  is positioned, the sensing rail being mounted at opposite ends to an extension rail  152 . The extension rail  152  has a pair of rearward extensions  154  which have transverse extensions  156  that are directed toward each other and encompass the T-shape portion  142  of the block extrusion. The block extrusion  132  is supported by and can move relative to the extension rail  152  enabling the sensing unit  146  to provide a measurement of the position along the sensing rail  150  and provide a digital output of the position. Importantly, the length of the extension rail  152  is slightly greater than the length of the sensing rail  150  and a pair of brackets at each end attach the extension rail  152  to the sensing rail  150 . The extension rail is itself supported and held captive in the fence rail  130  which has an inclined inside front portion  160  that has a lower angled flange  162  and an upper flange  164  which surround the extension rail  152 . The extension rail  152  is movable relative to the fence rail  130  by a distance that is approximately equal to the length of the slot  166 .  
         [0040]     As is best shown in  FIG. 7 , the fence rail  130  has an elongated slot  166  through which a threaded bolt  168  is located, with the bolt having a knob  170  that can be rotated to tighten or loosen the bolt  168  which is threaded into an opening in the extension rail  152 . When it is loosened, the extension rail may be moved so that the knob will be moved along the length of the slot  166  which is approximately 12 inches in the illustrated embodiment. This means that the length of the sensing rail  150  is approximately the same length, with the width of the tabletop  20  being approximately two feet in total. However, it should be understood that a shorter or longer slot may be provided.  
         [0041]     When the knob  170  is loosened, the extension rail  152  can be moved along the slot  166  from the position that is shown to the far left end as shown in  FIG. 7 . Indicia such as a green dot  176  near the left end and a red dot  178  on the right end are provided together with green and red switches  176  and  178 , respectively, which the operator can press depending upon which end the knob  170  is positioned. By so doing, the processing means in the display module  70 ′ can automatically compensate for the changed position relative to the blade  16 . In this way, a 12 inch long sensing rail can be used to effectively measure across the entire width of the table. This is advantageous because the cost of sensing systems and particularly sensing rails dramatically increases with increased lengths.  
         [0042]     A fifth preferred embodiment is shown in a simplified diagrammatic fashion in  FIGS. 10 and 11 , and has a removable fence  24 ″ with a base  28 ″ that is configured to be supported on a fence rail  190  that is preferably an extrusion with a flat top and a front recess  192  which is configured to receive a sensing rail  194  that is attached to the rail by suitable means such as an adhesive, mechanical clips, screws, or the like. The fence rail  190  is attached to the saw table top  20  by two or more bolts  196  which extend from the fence rail  190  to the top  20  through standoffs  198  as shown in  FIG. 11 .  
         [0043]     As is shown in  FIG. 10 , the sensing rail  194  extends substantially across the entire front of the table saw. The fence  24 ″ has a mounting bracket  200  attached thereto for providing a support for a display module  70 ″ that may have structure and functionality that is similar to the structure of the display module  70  or  76 . A sensor unit  202  is mounted to the bottom  28 ″ of the fence  24 ″ and is positioned adjacent the sensor strip  194 . An advantage of this embodiment is that all components except the sensor strip  194  are mounted to the fence  24 ″, and no wires between the sensor unit  202  and the display module  70 ″ need to be exposed and therefore susceptible to damage during use. The fence can be easily removed from the table saw without the necessity of disengaging any parts, unplugging cables or other inconveniences.  
         [0044]     A sixth preferred embodiment is shown in  FIG. 12  and has a rotational position transducer unit  210  that is mounted to the table saw  212  and has a flexible tape  214  extending from the unit that extends to and is connected to a bracket  216  to which a display module  218  is attached. While a tape  214  is shown, it should be appreciated that a cable or string type of unit is commercially available and may be used. Regardless, the tape  214  is held under tension by a spring mechanism in the position transducer unit  210  and the unit generates an electrical signal that is indicative of the amount of tape or string that is pulled out of the unit  210 . The bracket  216  is supported by and slides along a bottom portion  220  of an extrusion  222  that extends along the front of the saw  212 . The extrusion has a recess  224  in which a fence  226  can slide with fence having a base portion  228  that has a downwardly extending pin  230  that can fit within a hole in the bracket  216 . This enables the fence  226  to be removably coupled to the bracket  216 . While not shown, the fence preferably has a locking mechanism to hold the fence in the desired position when that is determined. Power for operating the unit  210  can be provided by an AC source through cords  232 ,  234  and transformer  236 . Alternatively, a battery may be used if desired.  
         [0045]     The tape  214  can be attached to either the bracket  216  or the display unit  218  as desired. As the fence and bracket  216  are moved along the front of the table saw  212 , the tape  214  is wound and unwound from the unit and an electrical signal is generated and is communicated to the display unit  218 . In this embodiment, the communication is preferably accomplished by an infrared transmitter in the unit  210  and an infrared receiver in or adjacent to the display unit  218 . Other types of communication can be used as desired. Also in this embodiment, a zero button is used to calibrate the position of the fence at a zero position relative to the blade as has been previously described with regard to other embodiments, enabling the distance from the fence  226  to the blade of the saw to be displayed as the fence  226  is moved away from the blade the desired distance. An advantage of this embodiment is that the incremental cost for increased distances is significantly lower than for many other types of sensing strips or rails.  
         [0046]     A seventh embodiment is shown in  FIG. 13  and is similar to the embodiment of  FIG. 12 , except that a rotational position transducer unit is located within a display unit module  240  has a fence  242  mounted to it. While not shown, the fence  242  is preferably removable from the module  240  and a locking mechanism is either associated with the fence  242  or the module  240 . A tape  244  extends from the module  240  and is attached to a bracket  246  or the like that is attached to the table saw. This embodiment has an extrusion  248  that is similar to the extrusion  222  of  FIG. 12  in that it has a lower portion  250  on which a bracket  252  is slidably attached. The bracket  252  is attached to and carries the display module  240 . The operation of this embodiment is substantially similar to the embodiment shown in  FIG. 12 , but has the advantage that the position transducer unit is directly connected to the display unit and no independent communication capability is required.  
         [0047]     With regard to all of the embodiments described above, the sensing unit and sensor strip may have copper pads along its length that are positioned to provide a changing capacitance that is sensed by the sensor unit and which can thereby provide accurate measurement of incremental positions along the length of the rail. In this regard, it is preferred that the sensor strip and sensor element be similar to those that are presently used in commercially available digital calipers. However, other linear sensor technologies based on inductance, magnetostrictive effects, resistive elements or optical encoded techniques can also be used without departing from the spirit and scope of the invention.  
         [0048]     While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims.  
         [0049]     Various features of the invention are set forth in the following claims.