Abstract:
The present invention relates to a table saw having a stationary worktable having a work surface, a base for supporting the worktable, a motor-driven cutting device mounted between the worktable and base and at least one auxiliary support device disposed beside the worktable. The auxiliary support device is pivotal relative to the stationary table and the auxiliary support device can be converted between a extended position and a folded position. The auxiliary support device pivots upwardly when it converts from the extended position to the folded position and provides adequate support for making accurate cuts and is convenient to store or transport.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a power tool such as a table saw having an auxiliary support device. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    A conventional table saw comprises a stationary table, a circular blade rotatably mounted on the stationary table and an auxiliary support device movable relative to the stationary table. The auxiliary support device serves to extend the size of the stationary table and permits a larger workpiece to be readily supported on the working surface of the stationary table such that the workpiece can be conveniently moved past the saw blade and such that it is adequately supported for making accurate cuts. 
         [0003]    U.S. Pat. No. 4,955,941 discloses an auxiliary support device of a table saw which is releasably fastened to a principal table. When the table saw is in an operative and supportative position, the auxiliary support device may be positioned in any fashion relative to the principal table. When the table saw is in its collapsed mode for storage or transportation, the auxiliary support device is detached from the table saw and stored independently elsewhere. 
         [0004]    US-A1-2005/0092155 discloses an auxiliary support device of a table saw which is movable between a first position where the auxiliary support device is extended into a work supporting position and a second position where the auxiliary support device is oriented into a stored position. The auxiliary support device is folded between the first and second position and supported in the first position via a brace. 
         [0005]    US-A1-2007/0006703 discloses a table saw comprising a stationary table and a movable table movable linearly relative to the stationary table. 
         [0006]    Prior worktable side extensions may be secured to a worktable by means of a plurality of fastener screws or bolts. The resulting structure is very complex and it is difficult to assemble the side extensions to the worktable or detach the side extensions from the worktable. In addition, the structure utilises a large space when not in use and is inconvenient to store or transport. 
         [0007]    Other prior worktable side extensions may be movable between the supporting position and stored position. For example, where the extensions are retractable, the apparatus becomes more compact and easier to move. For example, if the extensions are foldable towards the base of the table saw, the length of the extensions does not exceed the limits of the height of the table saw otherwise the extensions will take up more space or be inconvenient to store. 
       SUMMARY OF THE INVENTION 
       [0008]    The primary objective of the present invention is to provide a table saw which provides adequate support for making accurate cuts and is convenient to store or transport. 
         [0009]    Another objective of the present invention is to provide a table saw having a scale device that can facilitate a user reading the cutting length of a wooden workpiece directly and precisely. 
         [0010]    A further objective of the present invention is to provide a table saw, wherein when the auxiliary support device is pivoted to the extended position to support a wooden workpiece having a longer cutting length, the user can read the values of the gauge measure of the scale device so as to obtain the cutting length of the wooden workpiece directly. 
         [0011]    A still further objective of the present invention is to provide a table saw, wherein the values of the gauge measure of the scale device indicates the longer cutting length of the wooden workpiece precisely thereby enhancing the work efficiency of the table saw. 
         [0012]    Viewed from a first aspect the present invention provides a table saw comprising: 
         [0013]    a stationary worktable having a work surface; 
         [0014]    a base for supporting the worktable; 
         [0015]    a motor-driven cutting device mounted between the worktable and base so as to be operatively prominent from the work surface; and 
         [0016]    at least one auxiliary support device adjacently mounted pivotally relative to the worktable, wherein the auxiliary support device is convertible between an extended position and a folded position and is pivotal upwardly when converted from the extended position to the folded position. 
         [0017]    The configuration of the table saw according to the present invention is very simple and its manufacture is low cost. 
         [0018]    Preferably the auxiliary support device defines an upper support surface substantially parallel to the work surface in the extended position or the folded position. 
         [0019]    Preferably the auxiliary support device is a framework which comprises a first rod, a second rod and a third rod connected between the first rod and the second rod. 
         [0020]    Preferably the auxiliary support device has a support length L 2  which is larger than the height H between the work surface and bottom of the base. 
         [0021]    Preferably the worktable has a support length L 1  greater than the support length L 2  of the auxiliary support device. 
         [0022]    In a preferred embodiment, the table saw further comprises a pair of brackets disposed on opposite edges of the worktable, wherein each bracket has a support surface for supporting the auxiliary support device. 
         [0023]    Preferably the table saw further comprises a detachable support plate with a support surface which is disposed on the auxiliary support device, wherein the support surface of the support plate is substantially co-planar with the work surface of the worktable. 
         [0024]    Preferably the table saw further comprises a scale system. The scale system may be printed or sculpted on the upper surface of the first support and the first guide rod and the scale system also can be calibrated to any scale such as the English or metric system. 
         [0025]    Preferably the worktable has a stationary support equipped with a pair of guide rails and the auxiliary support device is equipped with a pair of guide rods, wherein the scale system has a dual scale disposed on one of the guide rails and series scale values disposed on one of the guide rods, wherein the dual scale is aligned with the series scale values. 
         [0026]    The scale system may comprise a scale tape with a first end fixed to the first guide rail and a second end which is movable with respect to the first guide rod. Alternatively the first end of the scale tape may be movable with respect to the first guide rail and the second end of the scale tape may be fixed with respect to the first guide rod. The scale system may further comprise an elastic member (eg spring) mounted either between the second end of the scale tape and the end of the first guide rod or between the first end of the scale tape and the first guide rail. 
         [0027]    The scale system may comprise a first scale ruler fixed to the first guide rail and a second scale ruler movable with respect to the first guide rod. Alternatively the first scale ruler is movable with respect to the first guide rail and the second scale ruler is fixed with respect to the first guide rod. The scale system may further comprise an elastic member (eg spring) mounted between the second scale ruler and the first guide rod. 
         [0028]    Preferably the table saw further comprises a movable rip fence selectively mounted on the stationary support or the auxiliary support and a scale indication pointer disposed on the rip fence. 
         [0029]    In a preferred embodiment the table saw further comprises a safety device mounted between the stationary support and the auxiliary support. 
         [0030]    Preferably the auxiliary support is equipped with a pair of guide rods and a third rod which define a first support surface and a second support surface respectively, wherein the first support surface and the second support surface can be converted to work in accordance with the extended position and folded position of the auxiliary support. 
         [0031]    Preferably the first support surface and the second surface are each provided with a scale system, wherein at least one scale system is provided with series scale values. 
         [0032]    Preferably the first support surface is the upper surface of the auxiliary support and the second support surface is the bottom surface of the auxiliary support, wherein when the auxiliary support is in the extended position, the first support surface is adjacent the work surface and when the auxiliary support is in the folded position, the second surface is adjacent to the work surface. 
         [0033]    Preferably the first support surface and the second support surface are lower than the work surface. 
         [0034]    In a preferred embodiment, the table saw further comprises at least one locking device mounted operatively between the guide rods and workable for locking the auxiliary support relative to the worktable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The present invention will now be described in a non-limitative sense with reference to the accompanying Figures in which common reference numerals represent corresponding parts throughout, wherein: 
           [0036]      FIG. 1  is a perspective side view of a table saw according to a first embodiment of the present invention; 
           [0037]      FIG. 2  is a plane view of the table saw shown in  FIG. 1 ; 
           [0038]      FIG. 3  is a partial enlarged view of the table saw shown in  FIG. 2  which shows two zero scales of a gauge; 
           [0039]      FIG. 4  is a partial enlarged view of the table saw shown in  FIG. 2  which shows the connection of the scales respectively disposed on a first support and a second support; 
           [0040]      FIG. 5  is a partial enlarged view of the table saw shown in  FIG. 2  which shows a pointer disposed on a fence; 
           [0041]      FIG. 6  is a front view of the first embodiment of the present invention which shows the first support in a work position; 
           [0042]      FIG. 7  is a perspective side view of the first embodiment of the present invention which shows the first support in a folded position; 
           [0043]      FIG. 8  is a partial enlarged view of the table saw shown in  FIG. 7 ; 
           [0044]      FIG. 9  is a perspective side view of the first embodiment of the present invention which shows the first support pivoted to the folded position from the work position; 
           [0045]      FIG. 10  is a perspective side view of a table saw according to a second embodiment of the present invention; 
           [0046]      FIG. 11  is a partial enlarged view of E indicated in  FIG. 10 ; 
           [0047]      FIG. 12  is a partial enlarged view of F indicated in  FIG. 10 ; 
           [0048]      FIG. 13  is an enlarged cross-sectional view take alone line G-G in  FIG. 10 ; 
           [0049]      FIG. 14  is a perspective side view of a table saw according to a third embodiment of the present invention; 
           [0050]      FIG. 15  is a partial enlarged view of H indicated in  FIG. 14 ; 
           [0051]      FIG. 16  is a partial enlarged view of I indicated in  FIG. 14 ; 
           [0052]      FIG. 17  is an enlarged cross-sectional view take alone line J-J in  FIG. 14 ; 
           [0053]      FIG. 18  is a perspective side view of a table saw according to a fourth embodiment of the present invention which shows an auxiliary support device pivotal with respect to the table saw; 
           [0054]      FIG. 19  is a perspective side view of the table saw shown in  FIG. 18  which shows the auxiliary support device in a first work position; 
           [0055]      FIG. 20  is an enlarged cross-sectional view take alone line K-K in  FIG. 19 ; 
           [0056]      FIG. 21  is a perspective side view of the table saw shown in  FIG. 19  which shows the auxiliary support device ready to pivot; 
           [0057]      FIG. 22  is an enlarged cross-sectional view take along line L-L in  FIG. 21 ; and 
           [0058]      FIG. 23  is a perspective side view of the table saw shown in  FIG. 18  which shows the auxiliary support device in a second work position. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0059]    Referring to  FIG. 1 , a table saw  1  according to a first embodiment of the invention comprises a base  2  having a receiving cavity  21 . A circular cutting blade  4  is mounted within the receiving cavity  21  and is driven by a motor (not shown). A storage cavity  22  is formed at an upper periphery of the base  2  and a substantially rectangular stationary worktable  3  is disposed on and supported by the base  2 . The worktable  3  has a planar upper work surface  31  for supporting a workpiece. The upper work surface  31  includes a transverse cutting slot  32  through which the cutting blade  4  partially extends for cutting. The cutting blade  4  is used to cut a material such as wood that is pushed laterally along the upper work surface  31 . 
         [0060]    A riving knife  5  is disposed behind the cutting blade  4  and operated as a splitter to prevent two cut workpiece parts from closing on one another. A blade guard  6  at least partially encloses the blade  4  and pivotally associates with the riving knife  5  to keep the cutting blade  4  non-exposed when the blade  4  is in a cutting position or a non-cutting position to ensure operator safety. A trigger device  7  under the work table  3  is mounted at one side of the base  2  and is switched straightforwardly by an operator. The table saw  1  further comprises a stationary support  8  which is equipped with a pair of spaced apart guide rails  14 ,  14 ′ at opposite edges of the worktable  3 . The first guide rail  14 ′ is located at the edge closest to the operator and the second guide rail  14  is at the opposite edge remote from the operator. The pair of guide rails  14 ,  14 ′ is fastened to the work table  3  by screws  81 . 
         [0061]    An auxiliary support  9  is connected pivotally to the worktable  3  via a pair of gemel devices  10  (only one shown) such that the auxiliary support  9  can be pivoted between an extended position and a folded position. Each gemel device  10  includes a first join unit  101  fixed on the auxiliary support  9 , a second join unit  102  fixed to the worktable  3  and an axis  103  disposed on the worktable  3 . Each guide rail  14 ,  14 ′ comprises an elongate body  82  with a square cross-section. The auxiliary support  9  is a framework which is substantially U-shaped and includes a first guide rod  91 , a second guide rod  93  parallel to the first guide rod  91  and a connecting rod  92  connected between the first guide rod  91  and the second guide rod  93 . Each of the first guide rod  91 , second guide rod  93  and connecting rod  92  has an upper surface which together define an upper support surface substantially parallel with the work surface  31  when the auxiliary support  9  is in the extended position or in the folded position. 
         [0062]    A rip fence  11  is movable relative to the worktable  3  and includes a fence body  11   a  slidably mounted on the worktable  3 . A first connecting seat  11   b  and a second connecting seat  11   c  are respectively formed on opposite ends of the fence body  11   a . The second connecting seat  11   c  includes a viewing window which is formed of transparent material and a scale indication pointer  111  disposed on the viewing window (as shown in  FIG. 5 ). A locking device  307  is pivotally mounted on the second connecting seat  11   c  for locking and unlocking the rip fence  11 . The pair of guide rails  14 ,  14 ′ can be used to guide the rip fence  11  as the rip fence  11  slides on the worktable  3  and this arrangement is suitable for short or wide cuts. When the rip fence  11  is unlocked, it can be selected to mount the auxiliary support  9 . The first guide rod  91  and the second guide rod  93  can be used to guide the rip fence  11  as the rip fence  11  slides on the auxiliary support  9  and this arrangement is suitable for long cuts. When cutting is over, the rip fence  11  is detached and held in the storage cavity  22  (shown with broken lines). 
         [0063]    The pair of guide rails  14 ′,  14  and the pair of guide rods  91 ,  93  are hollow-shaped such that the weight of the table saw is minimised. A detachable support plate  13  provided with an upper support surface is attached to the guide rods  91 ,  93  for supporting a longer workpiece. The support plate  13  is unnecessary when a short workpiece is to be cut so it can be detached from the guide rods  91 ,  93  and held in the storage cavity  22 . 
         [0064]    As shown in  FIGS. 2 to 5 , the table saw  1  further includes a scale system  20  for indicating the cutting length of the workpiece. The scale system  20  comprises a dual scale, namely a first measurement scale  201  and a second measurement scale  202 . The first guide rail  14 ′ of the stationary support  8  has a first end equipped with a first scale zone  2011  and a second end equipped with a second scale zone  2012 . Each of the first scale zone  2011  and the second scale zone  2012  has a plurality of markings whose values increase outwardly and include a first zero  2011 ′ of the first measurement scale  201  and a second zero  2012 ′ of the second measurement scale  202 . In direction B, the first measurement scale  201  includes a series scale 0.1.2.3.4.5. In direction C, the second measurement scale  202  includes a first series scale 0.1.2.3.4.5 . . . 10 formed on the first guide rail  14 ′ and a second series scale 11.12.13.14.15 . . . formed on the first guide rod  91 . Each scale value of the second measurement scale  202  respectively formed on the stationary support  8  and the first guide rod  91  is exclusive and non-repetitive. Thus the second measurement scale  202  is a sequential measurement device which is suitable for measuring a longer workpiece. 
         [0065]    Referring to  FIGS. 2 and 5 , when it is desired to cut a longer workpiece, the rip fence  11  slides on the guide rods  91 ,  93  of the auxiliary support  9  until the scale indication pointer  111  is aligned to a desired scale value of the second measurement scale  202 . The rip fence  11  is then secured in position. The desired scale value indicates the distance from the cutting blade  4  to one side of the fence body  11   a  close to the cutting blade  4 . The workpiece can be pushed against the side of the rip fence  11   a  and along the upper work surface  31  of worktable  3  while it is being cut by the cutting blade  4 . 
         [0066]    When it is desired to cut a shorter workpiece, the rip fence  11  is placed on either the right or left side of the cutting blade  4  and is secured a predetermined distance away from the cutting blade  4 . Viewed in direction A, when the rip fence  11  is mounted on the left side of the cutting blade  4 , the workpiece is against the right side of the fence body  11   a  along the upper work surface  31  whilst it is cut by the cutting blade  4 . Alternatively, when the rip fence  11  is mounted on the right side of the cutting blade  4 , the workpiece is against the left side of the fence body  11   a  along the upper work surface  31  whilst it is cut by the cutting blade  4 . The first zero  2011 ′ of the first measurement scale  201  and the second zero  2012 ′ of the second measurement scale  202  are respectively disposed on the upper surface of the first guide rail  14 ′ where the scale indication pointer  111  is positioned when the rip fence  11  is immediately adjacent the cutting blade  4 . Each zero  2011 ′,  2012 ′ is therefore aligned relative to the cutting blade  4  but not necessarily in the position on the scale aligned with the cutting blade  4 . The last scale value on each side of the cutting blade  4  is such that the scale indication pointer  111  on the rip fence  11  reads the maximum distance from the cutting blade  4  when the rip fence  11  is in its furthest position. 
         [0067]    Referring to  FIGS. 2 and 6 , the auxiliary support  9  is held in its extended position and fixed with respect to the worktable  3  during the cutting operation. The second measurement scale  202  of the guide rod  91  is fixed with respect to the auxiliary support  9 . The first measurement scale  201  of the guide rail  14  is aligned with the second measurement scale  202  of the guide rod  91 . The scale system  20  is linear and designed so that the operator can read the scale value directly according to the scale indication pointer  111 . 
         [0068]    As shown in  FIG. 6 , the length L 2  of the auxiliary support  9  in its extended position exceeds the height H from the work surface  31  to the bottom of the base  2 . When the auxiliary support  9  is pivoted to the folded position (see  FIG. 7 ), the length L 2  of the auxiliary support  9  is within the scope of the length L 1  of the worktable  3  such that the auxiliary support  9  will not take additional space in package or transport. However, when the auxiliary support  9  is pivoted to the extended position, the added support length of the auxiliary support  9  and scale system  20  helps the operator to make longer cuts accurately. The upper support surface of the auxiliary support  9  is lower than the work surface  31  and there is a distance D between them. The upper surface of the support plate  13  is coplanar with the work surface  31 . 
         [0069]    As shown in  FIGS. 7 and 8 , a safety device  12  is mounted between the stationary support  8  and the auxiliary support  9 . The safety device  12  comprises a first guard  121  connected to the first guide rail  14  via a screw  123  and a second guard  122  connected to the first guide rod  91  via a screw  124 . Each of the first guard  121  and second guard  122  comprises a plurality of metal plates which are spaced apart from each other and substantially semi-circular. The metal plates of the first guard  121  cross the metal plates of the second guard  122  whenever the auxiliary support  9  is in the extended or folded position such that the safety device  12  protects the fingers of the operator from injury. Referring to  FIG. 9 , when the auxiliary support  9  is pivoted upwardly around the axis  103  (direction R) from the extended position to the folded position, the second guard  122  is pivoted together with the auxiliary support  9  relative to the worktable  3 . 
         [0070]    As shown in  FIG. 9 , a pair of brackets  314  is respectively disposed on opposite sides of the table saw  1  (only one is shown). Each bracket  314  is provided with a support surface  314   a  for supporting the bottom of the first guide rod  91  and the second guide rod  93 . The auxiliary support  9  comprises a tool box  94  mounted between the two guide rods  91 ,  93  for retaining accessories such as a ruler or a screwdriver during cutting. The tool box  94  has a first side wall  942 , a second side wall  943  and a base  941  which are respectively welded between the two guide rods  91 ,  93 . Each upper surface of the first side wall  942  and the second side wall  943  is lower than the upper surface of the guide rods  91 ,  93  such that the upper surface of the guide rods  91 ,  93  can lie on the upper surface of the guide rails  14  when the auxiliary support  9  is in the folded position. 
         [0071]      FIGS. 10-13  illustrate a second embodiment of the present invention. The primary difference between the first embodiment and the second embodiment is the scale system. Wherever possible the numerals used in respect of the description of the first embodiment hereinbefore have been retained for like components in the description hereinafter. The scale system  20   a  comprises a scale tape  15   a  with a first end  152   a  fixed to the first guide rail of the stationary support  8   a  and a second end  151   a  which is movable with respect to the first guide rod of the auxiliary support  9   a . A smooth groove  911   a  is formed on the upper surface of the first guide rail and the first guide rod for receiving the scale tape  15   a . As illustrated in  FIG. 11 , a spring  16   a  is disposed between the second end  151   a  of the scale tape  15   a  and the end of the first guide rod. The spring  16   a  has a first end  161   a  hooked into a hole  1511   a  which is formed on the scale tape  15   a  and a second end  162   a  connected to the end of the first guide rod via a screw  19 . The scale value of the scale tape  15   a  is similar to the dual scale of the first embodiment and the second measurement scale of the scale tape  15   a  is sequential. When the first guide rod is in the extended position, the scale tape  15   a  is tensioned by the spring  16   a  such that an accurate measurement can be made according to the scale value of scale tape  15   a  whenever a clearance exists between the first guide rod and first guide rail. The scale tape  15   a  is made of soft material so as to be foldable together with the first guide rod when the auxiliary support  9   a  pivots to its folded position. 
         [0072]      FIGS. 14 to 17  show a third embodiment of the present invention. The primary difference between the first embodiment and the third embodiment is the scale system. Wherever possible the numerals used in respect of the description of the first embodiment hereinbefore have been retained for like components in the description hereinafter. The scale system  20   b  comprises a first scale ruler  17   b  fixed to the first guide rail of the stationary support  8   b  and a second scale ruler  18   b  movable with respect to the first guide rod of the auxiliary support  9   b . A smooth groove  911   b  is formed on the upper surface of the first guide rail and first guide rod for retaining the first scale ruler  17   b  and the second scale ruler  18   b . As illustrated in  FIG. 15 , a spring  16   b  is mounted between the second scale ruler  18   b  and the first guide rod. The spring  16   b  has a first end leaning against one end of the second scale ruler  18   b  and a second end leaning against the end wall of the groove  911   b  of the first guide rod. The scale value of the scale ruler  17   b ,  18   b  is similar to the dual scale of the first embodiment. The first measurement scale is disposed on the first scale ruler  17   b  whilst partial scale values of the second measurement scale are disposed on the first scale ruler  17   b  and others disposed on the second scale ruler  18   b . When the first guide rod is in the extended position, the second scale ruler  18   b  is pushed by the spring  16   b  to touch the first scale ruler  17   b  such that an accurate measurement can be made according to the scale value of scale system  20   b  whenever a clearance exists between the first guide rod and first guide rail. 
         [0073]      FIG. 18  shows a fourth embodiment of the present invention which is similar to the aforementioned embodiments. The worktable  3   c  has a planar upper work surface  31   c  for supporting a workpiece which includes a cutting slot  32  through which the cutting blade  4  partially extends for cutting the workpiece. The table saw  1   c  comprises an auxiliary support  300  which is a substantially U-shaped framework which includes a pair of parallel guide rods  301 ,  302  respectively located at opposite edges of the worktable  3   c  and a connecting rod  303  connected between the first guide rod  301  and the second guide rod  302 . Each of the first guide rod  301 , second guide rod  302  and the connecting rod  303  has an upper surface which together define a first support surface and has a bottom surface which together define a second support surface. The first support surface and the second support surface are respectively parallel to the work surface  31   c  when the auxiliary support  300  is in the extended position or in the folded position. Each of the first guide rod  301  and the second guide rod  302  has a first end and a second end. A longitudinal opening  308  (only one is shown) is disposed adjacent the second end remote from the connecting rod  303  and is provided with a left end and a right end. A spindle  309  is mounted in the longitudinal opening  308  such that the auxiliary support  300  can pivot relative to the spindle  309  in direction R 1  to the folded position or pivot relative to the spindle  309  in direction R 2  to the extended position. A pair of brackets  314 ,  314 ′ is respectively disposed on opposite edges of the worktable  3   c . Each bracket  314 ,  314 ′ is provided with a support surface  314   a ,  314   a ′ for selectively supporting the upper surface or the bottom surface of the first guide rod  301 . In addition, a locking device  315  is mounted between the second guide rod  302  and worktable  3   c  for locking the position of the auxiliary support  300 . 
         [0074]    As shown in  FIG. 19 , when the auxiliary support  300  is in the folded position, the base of the first guide rod  301  and the second guide rod  302  are supported on the brackets  314 ,  314 ′. The U-shaped framework is just outside the worktable  3   c  but the length of the auxiliary support  300  is still within the scope of the length of the base  2  such that the auxiliary support  300  will not take additional space in package or transport. The spindle  309  is in the longitudinal opening  308  against the left end and the locking device  315  secures the position of the auxiliary support  300  relative to the worktable  3   c . The first support surface defined by the first guide rod  301  and the second guide rod  302  and the connecting rod  303  is in a first work plane X 1  which is parallel to and lower than the work surface  31   c . The fence body  11   a  of the movable rip fence  11  rides on the work surface  31   c  and the two connecting seats  11   b ,  11   c  are respectively secured on the guide rods  301 ,  302 . The locking device  307  is pivotal to lock or unlock the rip fence  11 . A first scale system M 1  is disposed on the upper surface of the second guide rod  302 . The first scale system M 1  comprises a dual scale, namely a first measurement scale located at the left side of the cutting blade  4  and a second measurement scale approximately located at the right side of the cutting blade  4 . Each measurement scale has a plurality of markings whose values are gradually increased from a mediate portion of the second guide rod  302  to two ends of the second guide rod  302 . Thus the operator can make cuts at the left side of the blade  4  or at the right side of the blade  4  according to the position of the rip fence  11 . The scale indication pointer  111  of the transparent viewing window of the second connecting seat  11   c  indicates the cutting length of the workpiece from the blade  4  to one side of the fence body  11   a . The workpiece can be pushed against the side of the rip fence  11   a  and along the upper work surface  31   c  of worktable  3   c  while it is being cut by the cutting blade  4 . 
         [0075]    As shown in  FIGS. 18 to 20 , the locking device  315  comprises a locking pole  316 , a chamber  316   a  disposed in the locking pole  316 , a spring  317  and a steel ball  318  at least partially received in the chamber  316   a . The spring  317  is connected to the steel ball  318  flexibly. The locking pole  316  is fastened to the worktable  3   c  via screws  322  and is adjacent to the end of the second guide rod  302  away from the connecting rod  303 . The second guide rod  302  has two lockholes  321  (only one is shown in  FIG. 20 ) disposed on the inner side. The steel ball  318  of the locking pole  316  can be selected to engage the lockholes  321 . When the steel ball  318  engages the first lockhole  321  of the second guide rod  302 , the auxiliary support  300  is locked in the folded position. When the steel ball  318  engages the second lockhole  321  of the second guide rod  302 , the auxiliary support  300  is locked in the extended position (see  FIG. 23 ). Referring to  FIG. 19 , the auxiliary support  300  is located in the first work plane X 1  and the steel ball  318  of the locking pole  316  engages the first lockhole  321  of the second guide rod  302 . 
         [0076]    As shown in  FIGS. 21 and 22 , an outside force acts on the auxiliary support  300  firstly to pull the auxiliary support  300  away from the bracket  314  for a distance to avoid interference. The steel ball  318  disengages the first lockhole  321  and the spindle  309  is moved to depend on the right end of the longitudinal opening  308  such that the auxiliary support  300  can pivot around the spindle  309  in direction R 2  from the folded position to the extended position. 
         [0077]    As shown in  FIG. 23 , when the auxiliary support  300  is pivoted to the extended position, the steel ball  318  of the locking device  315  engages the second lockhole  321  of the second guide rod  302 . The auxiliary support  300  is locked in its extended position and the upper surfaces of the guide rods  301 ,  302  are supported on the brackets  314 . The second support surface defined by the guide rods  301 ,  302  lies in the second work plane X 2  which is parallel to and lower than the work surface  31   c . The first work plane X 1  and the second work plane X 2  are co-planar. The rip fence  11  is slidably mounted on the first guide rod  301  and the second guide rod  302 . A second scale system M 2  disposed on the upper surface of the second guide rod  302  comprises a serial measurement scale composed of a plurality of markings whose values are gradually increased from the second end adjacent the spindle  309  to the first end of the second guide rod  92 . The first scale value of the second end of the second guide rod  92  is not a zero scale. The first value is disposed according to the practical distance from the cutting blade  4  to the second end of the second guide rod  92  such that the operator can make longer cuts according to the serial measurement scale. If necessary, a support plate  323  is provided with a support surface parallel to the work surface  31   c  and can be disposed detachably between the first guide rod  301  and the second guide rod  302  for supporting a longer workpiece. 
         [0078]    When cutting is over, the operator detaches the rip fence  11  from the guide rods  301 ,  302  and pivots the auxiliary support  300  upwardly around the spindle  309  from the extended position to the stored position in direction R 1  in  FIG. 18 . The table saw  1   c  becomes more compact and easier to move from work site to site. 
         [0079]    Although the invention has been explained in relation to its preferred embodiments as mentioned above, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the resent invention. It is, therefore, contemplated that the appended claim or claims will cover such modifications and variations that fall within the true scope of the invention.