Patent Publication Number: US-2011067540-A1

Title: Table saw with movable table and stationary rip fence

Description:
BACKGROUND OF THE INVENTION 
     The present invention is generally related to table saws, and more particularly to portable table saws. 
     Conventional table saws generally include a movable rip fence used to guide a piece of material, such as wood, as it is pushed towards a blade for cutting. The movable rip fence is generally designed to span between the front and rear edges of the cutting surface. The rip fence can be secured in position a given distance from the blade and is arranged to be generally parallel to the blade. In this way, a user can guide the material to be cut along the rip fence, cutting the material to a given width. 
     While the rip fence must be parallel to the blade for the table saw to operate properly and make accurate cuts, many rip fence designs are prone to some amount of misalignment from parallelism of the rip fence and blade. A misaligned rip fence can cause inaccurate cuts and can bind the blade as well as cause a buildup of excess heat in both the saw and the work piece. Excess heat in the material can cause scorch marks on the work piece. Additionally, misalignment of the fence relative to the saw blade results in increased drag on the saw blade causing the saw blade to slow down and resulting in a non-uniform, uneven cut. Further, misalignment can cause the work piece to bind in the saw blade, which may result in undesirable and dangerous “kickback,” where the work piece is thrown violently by the saw blade back toward the operator. Accordingly, it is important to maintain parallel alignment between the rip fence and the saw blade, since misalignment causes unsatisfactory results when using the saw, increased maintenance and blade replacement costs, and potential safety hazards. 
     SUMMARY OF THE INVENTION 
     An embodiment of the invention is directed to a power table saw having a frame structure configured to support a movable saw assembly. The table saw also includes a rip fence attached to the frame structure in a fixed position for contacting a work piece during a cutting operation by said table saw. Further, a table assembly is provided, having a top surface for supporting a work piece, a blade extendable through an opening in the top surface for cutting a work piece, and a motor mounted beneath the top surface for driving the blade. The table assembly is movably mounted on the frame structure so that the table assembly is adjustable, allowing a user to adjust the distance between the blade and the rip fence. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a power table saw according to an embodiment of the present invention; 
         FIG. 2  is a front-left isometric perspective view of the power table saw of  FIG. 1 ; 
         FIG. 3  is a front-right isometric perspective view of the power table saw of  FIG. 1 ; 
         FIG. 4  is a front view of the power table saw of  FIG. 1 , shown with the frame in an extended position and the blade near the rip fence; 
         FIG. 5  is a front-right isometric perspective view of the power table saw of  FIG. 1 , shown with the frame in an extended position and the blade near the rip fence; 
         FIG. 6  is a front view of the power table saw of  FIG. 1 , shown with the frame in an extended position and the blade distant from the rip fence; 
         FIG. 7  is a front-left isometric perspective view of the power table saw of  FIG. 1 , shown with the frame in an extended position and the blade distant from the rip fence; 
         FIG. 8  is a front view of the power table saw of  FIG. 1 , shown with the frame in an extended position and the blade in an oblique position; 
         FIG. 9  is a front-right isometric perspective view of the power table saw of  FIG. 1 , shown with the frame in an extended position and the blade in an oblique position; and 
         FIG. 10  is a front isometric perspective view of a powered table saw according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Various embodiments of the present invention are shown and described herein which provide relatively compact portable powered table saw having a stationary rip fence. In each of the embodiments, the rip fence is fixed relative to a frame of the saw, and a table assembly is movable, so that a cutting width of the table saw can be adjusted by a user. The rip fence is permanently or semi-permanently attached to the frame in a fixed position, and the table assembly is mounted on the frame so that it is movable relative to the rip fence. 
     In addition to providing a guide for the movable table assembly, the frame also helps to prevent damage to internal components of the saw assembly. Moreover, at least a portion of the frame in each of the various embodiments is extendable. When extended, the frame allows the table assembly to have a relatively large range of motion, while holding the saw assembly relatively stable Conversely, when the frame is not extended, the table is generally held in place by the frame, and the table saw assembly is relatively compact, allowing for easier transportation of the saw. 
     Turning to  FIGS. 1-9 , a first embodiment of the present invention is shown and comprises a powered table saw assembly that is generally designated at  10 . The table saw assembly  10  includes an extendable frame  12 , a fixed rip fence  14 , and a movable table assembly  16 . 
     The frame  12  is relatively open, allowing a user to easily grip the saw assembly by the frame when moving the saw. Alternatively, it is contemplated that in addition to the open frame design, the frame  12  includes handles for the user to grasp when moving the saw assembly  10 . The frame includes a pair of upper rails  18  and a pair of lower rails  20 , each preferably formed from hollow tubing. While the rails  18 ,  20  shown in  FIGS. 1-9  are formed from square tubes, the tubing may have any of a variety of cross-sectional shapes. Additionally, the tubing for the upper rails  18  and lower rails  20  is preferably made from metal such as steel, but may be made from any durable, rigid material. Also, the cross-sectional shape of the upper and lower rails  18 ,  20  may be any conventionally known shape and the material from which the rails are constructed may be any material known to those of skill in the art, provided that the resulting rails are capable of supporting at least the weight of the rip fence  14 , table assembly  16  and a work piece. 
     The upper rails  18  of the frame are separated from one another by a distance sufficient to allow the moving table assembly to be mounted between the upper rails. Additionally, the lower rails  20  are preferably separated from one another by a distance that is approximately equal to the distance between the upper rails  18 . 
     A pair of table-side extension portions  22  and a pair of fence-side extension portions  24  are generally C-shaped, and made of tubing similar to that used in forming the upper and lower rails  18 ,  20 . Specifically, the tubing used to form the extension portions  22 ,  24  is preferably made from the same material as that of the upper and lower rails  18 ,  20 , and has a similar cross-sectional shape as the rails, but is sized so that horizontal portions of the extension portions fit within the rails, forming a slidable telescoping extension to the rails. Preferably, the rails  18 ,  20  and extension portions  22 ,  24  are formed such that a user can easily extend the frame  12  fully when the saw assembly  10  is to be used, while preventing the user from over-extending the frame, which could result in a separation of one or more of the extension portions and one or more of the upper and lower rails. The frame  12  may optionally include a travel limiting mechanism when the extension portions  22 ,  24  are in a fully extended position. Further, the frame may include limit switches positioned near the extension portions  22 ,  24  that prevent operation of the saw assembly unless the extension portions are in the fully extended position. 
     As is shown in  FIGS. 4 ,  5 ,  8 , and  9 , a length of the horizontal portions of the fence-side extension portions  24  is preferably selected so that a portion of the table assembly  16  may pass below the rip fence  14 . A length of the horizontal portion of the table-side extension portions is selected to determine a travelling distance for the movable table assembly  16 . The extension portions  22 ,  24  also separate the upper rails  18  from the lower rails  20  by a distance sufficient to fully accommodate the table assembly  16   
     The frame  12  further includes one or more horizontal cross-pieces  26  mounted between the table side table-side extension portions  22  and also between the fence-side extension portions  24 . The horizontal cross-pieces  26  provide additional stability and rigidity to the frame  12 . Additionally, the cross-pieces  26  may serve to limit the movement of the table assembly  16 . 
     The frame  12  also optionally includes feet  28  attached to the bottom of the frame. The feet  28  are used to stabilize the frame and to provide a non-skid surface to help hold the saw assembly  10  stationary. The feet  28  may be attached to the frame  12  via screws or bolts, adhesives, welds, or any other method known in the art. 
     The rip fence  14  is mounted on the frame  12  and is fixedly attached to the frame&#39;s upper rails  18 , such that the rip fence is stationary with respect to the upper rails. The fence  14  therefore maintains a constant position and orientation relative to the upper rails  18 . The rip fence  14  may be attached to the upper rails using permanent or semi-permanent fasteners such as screws, bolts, rivets, adhesives, or the like, or may be integrally formed with the upper rails  18 . Moreover, the rip fence is preferably elevated slightly relative to the upper rails  18 , allowing the movable table assembly  16  to pass at least partially beneath it. 
     The rip fence  14  is generally planar, and is used for guiding a work piece across the saw assembly  10 . The rip fence  14  is preferably constructed from aluminum or steel, but may be made of any durable material with a relatively low coefficient of friction, allowing the work piece to slide easily along the fence. 
     The movable table assembly  16  is also mounted on the frame  12  and travels along the rails, allowing a user to adjust a cutting width for the saw assembly  10 . The table assembly  16  is movably attached to the upper rails  18  of the frame  12  using, for example, casters, ball bearings, drawer slides, or the like, so that the table assembly  16  can move freely along a single axis perpendicular to the rip fence  14 . Additionally, it is contemplated that the table assembly  16  be attached to the lower rails  20  using a similar mounting mechanism to provide additional support and stability. 
     The movable table assembly  16  may also include a locking mechanism used to hold the table assembly in place during a cutting operation. Further, the table assembly  16  includes a generally planar top surface  30  positioned higher than the upper rails  18  to allow a miter gauge to be inserted in miter slots on the table assembly. The top surface  30  made from a durable material, such as aluminum or steel, and is designed to help support and guide a work piece during operation of the saw assembly  10 . Further, the top surface  30  defines an opening  32 , allowing at least a portion of a saw blade  34  to pass through the opening and extend vertically above the top surface. 
     The saw blade  34  is any conventionally known blade for use in table saws. The blade&#39;s position may be altered by raising or lowering the blade  34  relative to the top surface  30 , or by tilting the blade to alter an angle θ between the blade and the top surface (i.e., a bevel angle). The bevel angle θ is adjusted using, for example, a crank and gear system  36  as shown in  FIGS. 1-9 . The bevel angle can be adjusted within a range of about 45° to about 90°. As an example,  FIGS. 1 ,  4 , and  6  show that the angle θ between the blade  36  and the top surface  30  is approximately 90°, while  FIG. 8  shows the angle θ between the blade and the top surface is acute. 
     Additionally, it should be noted that the generally planar surface of the rip fence  14  is configured to contact a work piece in a plane that is generally parallel to a plane defined by the blade  34  when the bevel angle is set to 90°. This helps to produce a clean cut from the saw blade and reduce the potential for work piece kickback. 
     A motor (not shown) mounted within the table assembly  16  drives the blade  34 , and may also be used to drive optional added components such as a vacuum for collecting sawdust or the like. The motor may be any conventionally known electrical or internal combustion motor capable of driving the saw blade at sufficient speed and power to cut through a variety of work pieces. Moreover, the motor may drive the blade  34  either directly or indirectly through, for example, a belt system. A switch controlling operation of the motor is preferably mounted on the table assembly, so that the switch moves with the table assembly. Alternatively, the switch may be mounted on the frame so that the switch remains in a stationary position even if the table assembly is moved. 
     As shown in  FIG. 7 , an additional support table  40  is preferably attached to the rip fence  14  for supporting a work piece during operation of the saw assembly  10 . The additional support table  40  is preferably removable or retractable so that it can be withdrawn so that it does not interfere with movement of the movable table assembly  16  or work piece when the table assembly is disposed in the vicinity of the rip fence  14 , and can be positioned to support the work piece when the table assembly is relatively distant from the rip fence. The additional support table  40  is disposed so that a top surface  42  of the additional support table is relatively coplanar with the table assembly top surface  30 . 
     Turning now to  FIG. 10 , a second embodiment of the present invention is shown and comprises a table saw assembly generally designated at  50 . The saw assembly  50  shares many components with the saw assembly  10  as shown in  FIGS. 1-9 , and like components have been designated using like reference numerals. 
     As shown in  FIG. 10 , the table saw assembly  50  includes a rip fence  14  and a movable table assembly  16 , both mounted on a frame  52 . The frame  52  includes a pair of upper rails  54  and a pair of lower rails  56 , separated by vertical supports  58 . Further, a lower extendable portion  60  is slidably attached to the lower rails  56 , so that it can be extended, providing increased stability to the assembly  50 . As in the first embodiment, one or more travel limiting mechanisms may be used with the extendable portion. 
     The rip fence  14  is fixedly mounted to the upper rails  54 , and is slightly raised relative to the upper rails, so that a portion of the movable table assembly  16  may pass beneath the fence. This configuration allows for making relatively narrow-width cuts in a work piece, since the blade can be positioned very close to the rip fence, without regard to the top surface  30  of the table assembly  16 . 
     As shown in  FIG. 10 , the table assembly  16  is slidably mounted to the upper rails  54  using drawer slides  62 . Alternatively, the table assembly  16  could be mounted to the upper rails  54  using casters, bearings, or the like, as described in the first embodiment. If the table assembly is mounted using drawer slides  62  as shown, the table assembly  16  can travel beyond the upper rails  54 , eliminating the need to extend the upper rails while retaining a relatively large range of motion. This results in a more compact footprint for the saw assembly  50 , increasing the ease of portability. 
     Also included is a safety guard  64  that at least partially surrounds a blade  34  on the movable table assembly  16 . The safety guard  64  is pivotably mounted in on the movable table  16  so that a work piece may pass beneath the cover to contact the blade  34 . However, the guard  64  helps to retain sawdust and debris created by the blade  34 , and additionally helps to prevent extraneous material from entering the blade&#39;s cutting path. Thus, the safety guard  64  helps to reduce accidental injury to a user&#39;s hands by reducing the possibility that the user&#39;s hand can contact the blade  34 . 
     While specific 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. 
     Various features of the invention are set forth in the appended claims.