Abstract:
A vertical elevating device of a table saw includes an elevating base fixed on a rotating base, a main shaft mechanism, an elevating mechanism and a rotating mechanism. The elevating base includes a shaft for fixing with a round saw blade unit, an auxiliary elevating unit vertically set under the shaft and fixed on the rotating base, a guiding rod located at its two sides respectively in parallel with the auxiliary elevating unit, and a threaded guiding rod positioned at its one side and having its bottom fixed on the rotating base. The elevating mechanism is installed at one side of the rotating base, connected with the threaded guiding rod to move the elevating base up and down while whirling the elevating mechanism. With the auxiliary elevating unit focusing the support point on the gravitational center, the elevating base moves smoothly with a saved force.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to a table saw, particularly to one having a vertical elevating device. 
         [0003]    2. Description of the Prior Art 
         [0004]    As shown in  FIG. 1 , a conventional vertical elevating device of a table saw includes an elevating base  1 , a shaft  2  fixed at the center of the elevating base  1 , a round saw blade unit  3  pivotally installed at the shaft  2  and driven by a pulley having its belt (not shown in the Figure) mounted between the shaft  2  and a motor (not shown in the Figure), and a main guiding rod  4  and a sub-guiding rod  5  respectively installed axially at its two ends. The main guiding rod  4  is employed to support the elevating base  1 , having a larger outer diameter than that of the sub-guiding rod  5 , which is used for guiding the elevating base  1 . Obliquely positioned on the elevating base  1  to correspond to the main guiding rod  4  is an air cylinder  6  that is operated to provide an auxiliary pushing force while lifting the elevating base  1 , and a buffering force while lowering the elevating base  1 . And, a rotating base  7  is installed aside the round blade  3  for restricting the elevating base  1  positioned within the table saw. 
         [0005]    Next,  FIG. 2  is a side view of another conventional vertical elevating device of a table saw, showing a long lever arm distance (d) between the main guiding rod  4  and the sub-guiding rod  5 , so that it is far from the gravitational center of the central axis (a) of the elevating base  1 . And, as the main force of supporting the elevating base  1  comes from the main guiding rod  4  instead of the gravitational center of the central axis (a) of the elevating base  1 , the gravitational center of the elevating base  1  is so easily deviated that a copper washer  8  has to be installed at the upper portion and the lower portion of the main guiding rod  4  respectively, employed to adjust the gap between the main guiding rod  4  and the elevating base  1  to keep its support point located on the copper washers  8 . Moreover, an air cylinder  6  is obliquely installed to be positioned out of the central axis (a) of the elevating base  1 , apt to split its force to make the elevating base  1  unable to be effectively balanced. 
       SUMMARY OF THE INVENTION 
       [0006]    The objective of this invention is to offer a vertical elevating device of a table saw. 
         [0007]    The characteristics of the invention are a rotating base, an elevating base, a main shaft mechanism, an elevating mechanism and a rotating mechanism. The elevating base includes a shaft positioned at its central axis for pivotally fixing with a round saw blade unit, an auxiliary elevating unit vertically set under the shaft to coincide with the central axis of the elevating base and fixed on the rotating base, a guiding rod located at its two sides respectively in parallel with the elevating auxiliary unit, and a threaded guiding rod positioned at its one side and having its bottom fixed on the rotating base. An elevating mechanism is installed at one side of the rotating base, connected with the threaded guiding rod so as to enable the elevating base to move up and down while whirling the elevating mechanism. With help of the auxiliary elevating unit to keep its support point focused on the gravitational center, the elevating base can be kept well balanced to move smoothly with a saved force. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]    This invention is better understood by referring to the accompanying drawings, wherein: 
           [0009]      FIG. 1  is a side perspective view of a conventional vertical elevating device of a table saw; 
           [0010]      FIG. 2  is a simple illustration of the conventional vertical elevating device of a table saw, showing it being operated; 
           [0011]      FIG. 3  is a perspective view of a preferred embodiment of a vertical elevating device of a table saw in the present invention, showing it being installed in the main body of a table saw; 
           [0012]      FIG. 4  is a perspective view of the preferred embodiment of a vertical elevating device of a table saw in the present invention; 
           [0013]      FIG. 5  is an exploded perspective view of the preferred embodiment of a vertical elevating device of a table saw in the present invention; 
           [0014]      FIG. 6  is a side perspective view of the preferred embodiment of a vertical elevating device of a table saw in the present invention, showing it under operation; and 
           [0015]      FIG. 7  is a side view of the preferred embodiment of a vertical elevating device of a table saw in the present invention, showing it being operated. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]      FIG. 3  is a perspective view of a preferred embodiment of a vertical elevating device of a table saw in the present invention, showing it being pivotally installed in a table  101  of a main body  100  of a table saw. And, the vertical elevating device is to be assembled together with a blade guard  200  and a round saw blade unit  300  to enable them to extend above the table  101  to carry out sawing with a thickness properly adjusted. Meanwhile, a gap (c) is maintained between the blade guard  200  and the round saw blade unit  300  while being lifted up or lowered down. The vertical elevating device in the present invention includes a rotating base  10 , an elevating base  20 , a main shaft mechanism  30 , an elevating mechanism  40  and a rotating mechanism  50 . 
         [0017]    The rotating base  10 , with reference to  FIGS. 4 and 5 , is formed semi-circular, provided with a connecting groove  11  formed at the top of its two sides respectively for being mounted on a U-shaped sliding rail  121  of a U-shaped base  12 , by which the rotating base  10  is installed at two corresponding sides of the main body  100 . The rotating base  10  is also provided with an elevating groove  13  cut at its central upper portion with an opening facing upward, three screws  14  used to fix a sector gear  15  on the lower portion of its left side, and a rectangular slot  16  formed in the upper portion of its right side. The sector gear  15  has teeth  151  formed along its lower edge. And, a cover  17  shaped similar to the rotating base  10  is assembled aside and appropriately spaced apart the rotating base  10  for a dust-proof purpose. 
         [0018]    The elevating base  20  is installed at the inside of the rotating base  10 , provided with a shaft  21  positioned at its central axis (b) to transversely rest on the center of the opening of the elevating groove  13 . The shaft  21  has its intermediate portion mounted with a sleeve  211 , its rear end linked with a pulley  22 , and its front end extended out of the rotating base  10  for pivotally fixed with the round saw blade unit  300 , with a nut  302  engaged with the shaft  21  to keep a round blade  301  restrictively positioned between the outside of the rotating base  10  and the cover  17 . Vertically located along the central axis (b) of the elevating base  20  and below the shaft  21  is an auxiliary elevating unit  23 , which is an air cylinder filled with nitrogen to enable a reciprocating rod  24  axially fitted in the air cylinder to reciprocate for buffering. The reciprocating rod  24  has its bottom end fixed at the inside of the rotating base  10  to keep the auxiliary elevating unit  23  positioned at the gravitational center of the elevating base  20  and the rotating base  10 . In addition, the elevating base  20  is as well provided with two guiding holes  25   a  and  25   b  vertically bored at two sides of the central axis (b) in parallel with the elevating auxiliary unit  23 , two guiding rods  26   a  and  26   b  respectively inserted in the guiding holes  25   a  and  25   b  and having their top end and their bottom end fixed on the rotating base  10  to be positioned inside the round blade  301 , and a threaded guiding hole  26  vertically bored next to the guiding hole  25   a.    
         [0019]    And, as shown in  FIG. 6  that is a perspective side view of the vertical elevating device, a threaded guiding rod  27  is engaged with the threaded guiding hole  26 , provided with a positioning base  271  engaged around its bottom portion and having its one side fixed on the rotating base  10 , and a driven bevel gear  272  transversely fixed at the bottom of the positioning base  271  and formed with teeth  273  around the circumference. With reference to  FIGS. 4 and 5  again, a blade guard base  28  is installed at one side of the elevating base  20  near the guiding hole  25   b  to extend through the rectangular slot  16  of the rotating base  10  to stay between the rear side of the rotating base  10  and the cover  17 , used to fixedly position the collapsible blade guard  200 . The blade guard  200  is formed as an arc corresponding to the circumference of the round blade  301 , enabling itself to be spaced apart with the round blade  301  by a gap (c) while being adjusted and fixed by the blade guard base  28 . 
         [0020]    The main shaft mechanism  30 , as shown in  FIGS. 4 and 5 , is positioned outside the elevating base  20  to exactly coincide with the central axis (b), moving up and down along with the elevating base  20 . The main shaft mechanism  30  is provided with a motor  31  transversely located in parallel with the shaft  21 , and a pulley  33  fixed at the central shaft of the motor  31 . Mounted on the pulley  22  of the shaft  21  and the pulley  33  of the motor  30  is an endless driving belt  34  utilized to drive the round blade  301  to whirl. Referring to  FIG. 7 , a top view of the vertical elevating device, the motor  31  is fixed on the elevating base  20  by means of a first bar  32  located at two sides of the motor  31  respectively and a second bar  321  located at the central bottom of the motor  31 . 
         [0021]    The elevating mechanism  40 , as shown in  FIG. 6 , is installed under the threaded guiding rod  27 , provided with a first rotary wheel  41 , a first driving rod  42 , and a driving bevel gear  43  formed around the end of the first driving rod  42 . The first driving rod  42  is inserted through the sector gear  15  to reach the bottom of the threaded guiding hole  27 , fixed with the sector gear  15 . The driving bevel gear  43  is provided with teeth  431  for engaging with the teeth  273  of the driven bevel gear  272 . 
         [0022]    The rotating mechanism  50 , as shown in  FIGS. 5 and 7 , is assembled under the sector gear  15 , including a second rotary wheel  51 , a second driving rod  52 , and a worm  53  formed around the end portion of the second driving rod  52  for engaging with the teeth  151  of the sector gear  15 . 
         [0023]    In using, as shown in  FIG. 6 , when the round saw blade unit  300  is to be lifted up to a proper position for cutting a piece of wood, the elevating mechanism  40  has to be clockwise rotated to make the teeth  431  of the driving bevel gear  43  engaged with the teeth  273  of the driven bevel gear  271  of the threaded guiding rod  27 , so that the threaded guiding rod  27  can be driven to immovably whirled to enable the threaded guiding hole  26  moved up to simultaneously raise up the elevating base  20 . By the time, the gas compressed in the auxiliary elevating unit  23  is to be gradually decompressed to push the reciprocating rod  24  to gravitationally help the elevating base  20  moving up along the guiding rods  26   a  and  26   b  vertically, so as to simultaneously lift up the main shaft mechanism  30  to enable the round saw blade unit  300  to carry out sawing. As the guiding rods  26   a  and  26   b  are positioned close to the gravitational center of the elevating base  20  to have a lever arm distance (d) between them shorter than that of the conventional vertical elevating device shown in  FIG. 2 , torque is shrunk to make the pushing force intensified on the central axis (b) of the elevating base  20 , achieving a good structural rigidity to keep the elevating base  20  well balanced without biasing while lifted up, obtaining a purpose of saving force. 
         [0024]    On the contrary, in case the elevating base  20  is to be lowered down, the elevating mechanism  40  has to be counterclockwise rotated to likewise make the teeth  431  of the driving bevel gear  43  engaged with the teeth  273  of the driven bevel gear  271  of the threaded guiding rod  27 . By the time, the gas in the elevating auxiliary unit  23  is compressed to keep the elevating base  20  steadily lowered, and the main shaft mechanism  30  is synchronously moved down. In addition, as shown in  FIG. 7 , when the cutting angle is to be shifted, the rotating mechanism  50  has to be turned around to keep the worm  53  engaged with the teeth  151  of the sector gear  15  to enable the rotating base  10  to whirl for consecutively driving the elevating base  20  to bias, with a help of the elevating auxiliary unit  23 . 
         [0025]    The advantages of the invention are described below as can be seen from the foresaid description. With the auxiliary elevating unit  23  and the pivot positioned at the central axis (b) of the elevating base  20  to help the elevating base  20  vertically moving along the guiding rods  26   a  and  26   b  that are installed close to the inside of the central axis (b) of the elevating base  20  and parallel to the auxiliary elevating unit  23 , the lever arm distance (d) between the guiding rods  26   a  and  26   b  is thus shorter than that of the conventional vertical elevating device, resulting in a shrunk torque to relatively have an intense pushing force and a good structural rigidity, so as to keep the elevating base  20  well balanced without deviation while lifted up for achieving a smooth operation and a purpose of saving force. 
         [0026]    While the preferred embodiment of the invention has been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications that may fall within the spirit and scope of the invention.