Abstract:
A table saw having a stationary blade and a parallel moveable blade for straightening uneven dimensional lumber of the type used in cabinetry and other relatively fine woodworking. The table saw has a workpiece support frame with a lateral blade opening allowing the moveable blade to be shifted laterally and adjust the spacing between the blades. Powered feed rollers located above the table are used to clamp and feed a workpiece through the table while preventing kickback. A sacrificial fence including a blade guard recess is associated with the stationary blade, and includes a shutoff switch automatically activated to disable the stationary blade for solo use of the moveable blade.

Description:
RELATED APPLICATIONS/PRIORITY BENEFIT CLAIM 
     Not applicable. 
     FIELD 
     The subject matter of the present application is in the field of table saws with circular saw blades. 
     BACKGROUND 
     Circular blade sawmills using multiple circular saw blades are known, sometimes referred to as “edgers” or “edger mills”. Edgers are generally used to take the bark off the edges of fresh-sawn boards, or to straighten crooked boards. “Gang” edgers usually have a pair of spaced circular blades driven on a common shaft with a fixed spacing. “Shifting” edgers also have pairs of spaced blades, but at least one of the blades in the pair can be moved left and right to adjust the blade spacing and thus the width of the board. A chain and gripping mechanism is often used to pull the lumber through the blades. 
     A good example of a prior art shifting edger is the Corley Junior Edger, manufactured as early as the 1940&#39;s by the Corley Manufacturing Company of Chattanooga, Tenn. The Corley Junior Edger had a stationary blade and a movable blade driven on a common shaft. 
     Two-bladed edger mills are usually mounted on long steel roller frames, and are useful for processing lumber on a commercial scale. Edger mills are not as useful for home hobbyists or small commercial carpenters, who generally use smaller single-bladed table saws. 
     BRIEF SUMMARY 
     I have invented a table saw that is useful as both a table saw and an edger for relatively fine work on dimensional lumber, especially for straightening boards used in cabinetry. My table saw has a table with a stationary circular saw blade mounted at one side of the table, and a parallel, independently-driven, moveable circular saw blade at a home position on an opposite side of the table. The home position is the maximum spacing of the moveable blade from the stationary blade, for example about 12.5″ inches. The table has a fixed front support edge, a fixed rear support edge, a stationary side support edge associated with the stationary blade, and a moveable side support edge associated with the moveable blade. The support edges define a planar saw table frame with a lateral blade pathway between them, the pathway having a width corresponding to the diameter of the moveable blade. The moveable blade and the moveable side support edge can be moved laterally as a unit in the pathway toward the stationary blade, adjusting the spacing of the blades to trim uneven boards of varying width. 
     The table saw further includes a pair of height adjustable, powered (“live”) feed rollers spaced above the table at the front and rear support edges. The rollers are adjustable downwardly to clamp the board against the saw table frame, and to feed the board longitudinally to the blades from the front to the rear, without kickback. 
     The stationary side of the table includes a sacrificial fence having a home position spaced outwardly from and parallel to the stationary blade, at a distance equal to the minimum spacing of the moveable and stationary blades. The fence functions as a lumber guide for making fine trimming cuts with the stationary blade, i.e. cuts less than the minimum spacing between the blades. The fence is moveable inwardly toward the stationary blade, and includes a blade recess in the sacrificial material equal to or greater than the blade thickness. The recess receives the blade in a blade-guard position when the fence is moved into contact with the blade. A switch is associated with the fence in the blade-guard position, the switch disabling the stationary blade so that the moveable blade can be used alone in various positions. 
     These and other features and advantages of the invention will become apparent from the detailed description below, in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of an exemplary table saw according to the invention, showing the moveable blade and the fence in different positions using phantom lines. 
         FIG. 2  is a front elevation view of the table saw of  FIG. 1 , showing the moveable blade, the fence, and the feed rollers in different positions using phantom lines. 
         FIG. 3  is a cutaway side view of the table saw of  FIG. 1 , in particular showing the stationary blade and fence. 
         FIG. 4  is a top plan view of the table saw similar to  FIG. 1 , but showing the the fence moved into a blade guard position disabling the stationary blade. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 through 3 , a table saw  10  is shown in exemplary form in order to teach how to make and use the claimed invention. Table saw  10  has a table  11  forming a housing H enclosing two saw blades  30 ,  40  below an upper work support frame including a front support edge  12 , a rear support edge  14 , an at least partially moveable side support edge  16 , and a stationary side support edge  18 . The support edges together define a substantially flat, planar saw table frame or work support surface  19  for supporting dimensional lumber W ( FIG. 3 ) fed through the table from front to rear. The saw table frame  19  in turn defines a lateral blade pathway  119  between the support edges, the pathway defining an open area of travel for a moveable saw blade between sides  16  and  18 . 
     The term “table” should be understood broadly to include not only freestanding tables with their own legs or frames, but also built-in workpiece supporting surfaces, for example built into a cabinet or some other structure in a workshop enclosing or housing the two saw blades. The term “edges” should be understood broadly, generally as the sides of the workpiece supporting frame around the blades and defining the lateral blade pathway, and not limited only to the outermost edge portions of the table&#39;s workpiece supporting frame  19 . Support edges  12 ,  14 ,  16  and  18  may be fairly wide with substantial flat surface area to provide good support for a board being fed through the table saw. 
     Table  11  may be self-supported on a stand or legs  20 , and preferably has a protective hood  22  spaced at least several inches above the table surface. Table  20  may be made from various materials known for such uses, including but not limited to wood and metal. Hood  22  may be transparent, for example made from a plastic such as polycarbonate, and may be height adjustable relative to work surface  19  on its own frame or legs  23 . Hood  22  is preferably detachably mounted to the table, for example on hinges, so that it can be swung up and out of the way for access to the blades, when needed. 
     Table saw  10  also includes a pair of independently driven circular saw blades  30  and  40  of known type, each for example powered by an associated electric motor M and drive shaft of known type, mounted parallel to one another and preferably aligned coaxially. Moveable blade  30  is moveably mounted on the table frame at moveable side support edge  16 , while stationary blade  40  is mounted in a fixed position associated with stationary side edge  18 . Blades  30  and  40  are parallel to one another in order to make parallel side-straightening cuts on lumber when used in tandem. Both blades extend upwardly through the associated portions of the saw table frame  19 , i.e. their respective side support edges, through elongated slots  31 ,  41 , with approximately half or less of the diameter of each blade extending above the work surface  19 . Illustrated blades  30  and  40  may be substantially identical in size, as shown. 
     Moveable blade  30  can be translated laterally across pathway  119  from its home position to a point close to stationary blade  40 . For example, the farthest spacing of moveable blade  30  from stationary blade  40  might be approximately 12.5″ inches, while the closest spacing might be approximately 1.5″ inches. Blade  30  has a diameter less than the front-to-rear width of pathway  19  so that it moves without interference with the front and rear edges of the saw table frame. Moveable side support edge  16  includes an inner portion  16   a  that moves with blade  30 , as in the illustrated example, leaving a stationary portion  16   b  to better maintain the rigidity of the saw table frame. Optionally, the entire side support edge  16  could move with blade  30 . As the moveable portion of side edge  16  moves with blade  30 , the effective working width of the saw table frame decreases to accommodate the width of the workpiece W being trimmed. 
     Various mechanisms can be used to translate blade  30  across the table. In the illustrated example, the moveable portion of moveable side edge  16  (e.g., inner portion  16   a ) is slidingly mounted at its front and rear ends to lateral slots  12   a  and  14   a  in the inner (pathway-facing) edges of front and rear side support edges  12  and  14 . Alternately, moveable side edge  16  and blade  30  could be mounted on a carriage slidingly mounted to the undersides of front and rear support edges  12  and  14 , or to an extendable drive shaft, or some other known type of mechanism for translating the support edge  16  and blade  30  back and forth across the width of the table. Motor M driving blade  30  may be mounted to move with blade  30 , or could be located in a fixed position with an elongated or extendable drive shaft accommodating the movement of the blade relative to the motor. 
     Various mechanisms can also be used to lock moveable blade  30  and its moveable portion of side edge  16  in a desired adjusted position. For example, where side edge  16  is passive, i.e. moved by the operator manually, a mechanical securing device  17  such as common slide locks (thumbscrew, cam handle, etc.) used in conventional adjustable table saw fences can be used to lock blade  30  and side edge  16  to the front and/or rear support edges  12 ,  14  at the desired spacing from stationary blade  40 . 
     A sacrificial guide fence  50  is associated with stationary blade  40 , located outwardly of the blade at stationary side support edge  18 . Fence  50  is “sacrificial” in the sense that it preferably includes an outer guide  51  and an inner layer or surface  52  made from a sacrificial material softer than the blade  40 , preventing blade damage in the event of contact, and capable of being replaced at intervals as it wears down. For example, sacrificial inner layer  52  may be made from a flat piece of wood, screwed or clamped to an outer metal guide portion  51  of fence  50 . Alternately, the fence  50  could be a solid material whose is protected from damaging contact with the saw blade by positive stops  151  on the outside edge or underside of the table. 
     Fence  50  is laterally moveable from its home position spaced farthest from blade  40  ( FIGS. 1-3 ) to a blade-guard position in which the width of blade  40  is fully contained or shrouded within recess  52   a , whether or not the fence is in contact with blade  40  ( FIG. 4 ). For this purpose the inner sacrificial layer  52  of fence  50  includes a recess  52   a  sized to receive blade  40 , i.e. having a length equal to or greater than the diameter of the portion of the blade exposed above the table, and having a depth equal to or greater than the maximum thickness of blade  40  (usually defined by its “kerf”). Recess  52   a  extends only partway along fence  50 , leaving flat workpiece-guiding faces  53  to the front and rear of the recess. 
     Fence  50  may have a height greater than the height of blade  50  above saw table frame  19 , in order to fully shroud the blade, if desired. 
     The maximum spacing of fence  50  from blade  40  in the fence home position is equal to the minimum spacing between blades  30  and  40 , for example 1.5″ as mentioned above. The adjustable fence spacing allows a user to make trimming cuts having a width less than the minimum spacing of the moveable and stationary blades  30  and  40 , using only the stationary blade and with the advantage of the fence guiding the wood. Fence  50  may be locked into its various adjusted positions by a known mechanism commonly used for table saw fences, such as a clamp  17 . 
     A kill switch  60  is associated with fence  50  in the blade-guard position to disable the stationary blade  40 , for example mounted on the saw table frame  19  near the rear end of fence  50 . Switch  60  may be a mechanical contact type switch engaged by an end of fence  50 , or a photocell switch, or any other known type of switch capable of sensing the presence of a fence  50  in the blade guard position. Switch  60  may be electrically connected to motor M associated with stationary blade  40 , or to the motor&#39;s power supply, either directly or through an external controller or other circuitry, to interrupt power to the motor M driving blade  40  when the switch is activated. Switch  60  could also be connected to a clutch controller mechanism that disconnects motor M from blade  40 , or to any other blade-stopping mechanism or system that disables blade  40  when fence  50  is in the blade-guard position. 
     When switch  60  is activated to turn off stationary blade  40 , as best shown in  FIG. 4 , moveable blade  40  may still run independently, allowing the saw table  10  to be used like a conventional single-bladed table saw, but with the added benefit of a laterally adjustable saw blade. It may be desirable for some circumstances to provide a manually operated kill switch  60 ′ at the front of the saw table, as shown in  FIGS. 2 and 3 , in order to shut off the stationary blade  40  independently of fence  50 . 
     Saw table  10  also includes one or more powered or “live” feed rollers  70 , for example located above the front and rear support edges  12  and  14  as shown and powered to rotate in a feed-through direction by one or more motors M 2  schematically shown in  FIGS. 2 and 3 , connected in a known manner to rotate the rollers, for example with a shaft drive or belt drive. Rollers  70  positively feed lumber L from the front to the rear of the saw table, through one or both blades  40 ,  50  depending on the cutting mode (single- or double-bladed). Rollers  70  are preferably height adjustable, for example slidably mounted in tandem on vertical supports  72  above the saw table frame  19 , and may be covered with a grip-enhancing and/or cushioning material to promote contact with the lumber and/or to protect the lumber&#39;s surface finish. The height of rollers  70  can be adjusted to firmly engage and clamp the lumber to the saw table frame  19  and to grip and feed the lumber through the saw blades without “kickback” toward the front of the saw table. Various mechanisms for adjusting and securing the rollers  70  to the desired height and clamping/feeding pressure against the lumber are possible. For example, rollers  70  or their supports  72  may be secured to a vertically-driven carriage, for example one or more hydraulic cylinders or a screw gear carriage schematically illustrated at  74  that allows the rollers  70  to be moved up and down with a crank handle, similar to the crank-driven tubular screw gear height adjustment mechanism on a common wood planer. As shown in  FIGS. 1, 2 and 4 , the rollers  70  have a length at least equal to the maximum spacing of the moveable blade  30  from the stationary blade  40  such that the rollers are coextensive with the open lateral blade pathway  119  when the moveable blade  30  is in the home position. 
     Description of Operation 
     In operation, to straighten or trim a typical piece of elongated dimensional lumber workpiece W, for example a 1×6″ inch rectangular board with irregular or non-parallel edges, the spacing of moveable blade  30  from stationary blade  40  would be adjusted to less than 6″ inches apart, by moving blade  30  from its home position toward blade  40 . Once blade  30  and its moveable side edge/support  16   a  are secured in position using clamp  17 , the blades  30  and  40  and the rollers  70  would be turned on. Workpiece W would then be fed into the front roller  70  associated with front support edge  12 , the roller grabbing the board, holding it firmly against the saw table frame  19  (initially, front support edge  12 ), and feeding it to and through the rotating blades so that each blade removes a desired portion of one of the board&#39;s side edges. The rear roller  70  would grab the trimmed board L (including the trimmed portions) at the rear of the table to continue feeding it smoothly through the table and to increase the roller force working to prevent kickback of the board. The power of the rear roller  70  also allows the operator to remove his hand from the end of the board as it approaches the front roller  70  to finish the cuts. 
     It will be understood that the disclosed embodiments represent presently preferred examples of how to make and use the invention, but are intended to enable rather than limit the invention. Variations and modifications of the illustrated examples in the foregoing written specification and drawings may be possible without departing from the scope of the invention. It should further be understood that to the extent the term “invention” is used in the written specification, it is not to be construed as a limiting term as to number of claimed or disclosed inventions or discoveries or the scope of any such invention or discovery, but as a term which has long been conveniently and widely used to describe new and useful improvements in science and the useful arts. The scope of the invention should accordingly be construed by what the above disclosure teaches and suggests to those skilled in the art, and by any claims that the above disclosure supports in this application or in any other application claiming priority to this application.