Patent Publication Number: US-2006016310-A1

Title: Miter saw

Description:
FIELD OF THE INVENTION  
      The present invention relates to a power tool (in particular to a miter saw) having one or more micro-adjusting and locking mechanisms.  
     BACKGROUND  
      A known miter saw comprises a base for positioning a workpiece, a turntable which is mounted on the base and is rotatable about the axis of the base and a supporting arm pivotally mounted in a vertical plane of the turntable or mounted in the turntable via sliding bars. The supporting arm is pivotable relative to the turntable in a plane perpendicular to the turntable. The saw unit includes a motor and a blade driven by the motor to cut the workpiece. In general, a scale is located in the base to indicate the pivot angle of the turntable. A positioning means includes a detent claw disposed in one of the turntable and the base, together with a detent recess disposed in a preset position in the other one of the turntable and the base. The preset position secured by a lever is disposed between the turntable and the base and indicates an angle of the turntable relative to the base such as 0, 15° or 22.5°.  
      The detent claw of the conventional positioning means slides easily into the recess when the detent claw is close to the detent recess. However positioning the positioning means leads to inaccuracies and it is difficult to make micro-adjustments at small angles. Clamping after positioning may cause the preset angle to offset. In addition, inaccurate cutting may occur because of non-clamping of the positioning means.  
      Alternatively, it is known to set the position of the supporting arm manually by turning the saw unit to an approximate angle indicated by the scale. The supporting arm is threadedly locked by the rotary shaft or a screw and retained accurately by frictional forces generated by a locking mechanism. However positioning in this manner is subject to inaccuracies and it is difficult to make micro-adjustments. The working position of the saw unit will be offset because the frictional force of the locking mechanism is insufficient to overcome its own weight thereby causing the saw unit to cut the workpiece inaccurately.  
     SUMMARY OF THE INVENTION  
      The present invention seeks to overcome the shortcomings of a conventional miter saw by exploiting micro-adjusting and locking means for accurate positioning and reliable locking of either or both of the supporting arm or turntable.  
      In one embodiment of the invention the miter saw includes a base, a turntable, a first rotary shaft joining the base with the turntable, a supporting arm and a saw unit. It further comprises a first micro-adjusting and locking mechanism itself comprising a first wormgear which is fixed to the base, a first worm, a first micro-adjusting handle which is connected to the first worm, a first eccentric sleeve, a first actuator (such as a first lock-release knob) which is connected to the first eccentric sleeve and a first elastic element (eg first torsion spring). The first wormgear is coaxially disposed on the first rotary shaft. The first worm is rotatably inserted into the first eccentric sleeve. An axis of the first worm is parallel to but not overlapping the axis of the first eccentric sleeve. The first elastic element is disposed between the turntable and the first lock-release knob. The first worm is engaged with the first wormgear when the first micro-adjusting and locking mechanism is in a first working state. The first worm is disengaged from the first wormgear when the first micro-adjusting and locking mechanism is in a second working state.  
      By releasing the turntable in the second working state the operator is able to manually adjust the position of the turntable relative to the base. In the desired position, the turntable may be locked again in the first working state. Micro-adjustment of the position of the turntable relative to the base in the first working state is possible by manipulating the first micro-adjusting handle.  
      The first worm is typically a first elongate worm. Preferably between the first working state and the second working state, the axis of the first worm diverges in a parallel manner from the axis of the first rotary shaft. Particularly preferably the axis of the first worm arcs away from the axis of the first rotary shaft. Preferably in the first working state the axis of the first worm and the axis of the first eccentric sleeve are in a common plane substantially parallel to the turntable. Preferably in the second working state the axis of the first worm and the axis of the first eccentric sleeve are in a common plane substantially perpendicular to the turntable.  
      Preferably the first eccentric sleeve is rotatably connected to the turntable.  
      Preferably the first elastic element is a torsion spring, one end of which is connected to the turntable and the other end of which is connected to the first eccentric sleeve or the first actuator.  
      Preferably the first actuator is fixed to the first eccentric sleeve.  
      In a preferred embodiment, the miter saw further comprises: 
          a shoulder formed on the first eccentric sleeve and     a recess formed in the first actuator for latching the shoulder.        

      In a preferred embodiment, the miter saw further comprises: 
          a sleeve disposed in the turntable, wherein the sleeve is slidably mounted on the first rotary shaft and the first wormgear is fixed to the sleeve.        

      Preferably the first actuator is mounted coaxially on the first eccentric sleeve.  
      Generally the supporting arm is pivotable relative to the turntable in a plane perpendicular to the turntable. The supporting arm may be connected to the base or turntable.  
      The first micro-adjusting handle may be connected coaxially to a distal end of the first worm.  
      The first elastic element may bias the first actuator from the position in which it actuates the first worm into the second working state to the position in which the first worm is in the first working state.  
      In one embodiment of the invention the miter saw includes a base, a turntable, a second rotary shaft, a supporting arm which is pivotally connected to the second rotary shaft and a saw unit. It further comprises a second micro-adjusting and locking mechanism itself comprising a second wormgear which is fixed to the second rotation shaft, a second worm, a second micro-adjusting handle which is disposed on the second worm, a second eccentric sleeve, a second actuator (such as a second lock-release knob) which is connected to the second eccentric sleeve and a second elastic element (eg a torsion spring) which is disposed between the supporting arm and the second actuator. The second wormgear is coaxially disposed on the second rotary shaft. The second worm is rotatably inserted into the second eccentric sleeve. The axis of the second worm is parallel to but not overlapping the axis of the second eccentric sleeve. The second worm is engaged with the second wormgear when the second micro-adjusting and locking mechanism is in a first operating state. The second worm is disengaged from the second wormgear when the second micro-adjusting and locking mechanism is in a second operating state.  
      By releasing the supporting arm in the second operating state the operator is able to manually adjust the position of the supporting arm relative to the turntable. In the desired position, the supporting arm may be locked again in the first operating state. Micro-adjustment of the position of the supporting arm relative to the turntable in the first operating state is possible by manipulating the second micro-adjusting handle.  
      The second worm is typically a second elongate worm. Preferably between the first operating state and the second operating state, the axis of the second worm diverges in a parallel manner from the axis of the second rotary shaft. Particularly preferably the axis of the second worm arcs away from the axis of the second rotary shaft. Preferably in the first operating state the axis of the second worm and the axis of the second eccentric sleeve are in a common plane substantially parallel to the supporting arm. Preferably in the second operating state the axis of the second worm and the axis of the second eccentric sleeve are in a common plane substantially perpendicular to the supporting arm.  
      Preferably the second eccentric sleeve is rotatably connected to the turntable.  
      Preferably the second elastic element is a torsion spring, one end of which is connected to the turntable and the other end of which is connected to the second eccentric sleeve or the second actuator.  
      Preferably the second actuator is fixed to the second eccentric sleeve.  
      Preferably the miter saw further comprises: 
          a shoulder formed on the second eccentric sleeve and     a recess formed in the second actuator for latching the shoulder.        

      Preferably the second actuator is mounted coaxially on the second eccentric sleeve.  
      Preferably a supporting sleeve is disposed on the second worm.  
      The second elastic element may bias the second actuator from the position in which it actuates the second worm into the second operating state to the position in which the second worm is in the first operating state.  
      The second micro-adjusting handle may be connected coaxially to a distal end of the second worm.  
      The present invention exploits the engagement of a wormgear with a worm to offer secure locking and precise positioning of the turntable and/or of the supporting arm. In the meantime, the micro-adjusting handle offers fine rotary adjustment of the turntable and/or the supporting arm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a side view of an embodiment of the miter saw according to the present invention;  
       FIG. 2  shows a top view of the embodiment of the miter saw according to the present invention without the saw unit and parts of the supporting arm;  
       FIG. 3  shows an enlarged sectional view of  FIG. 2  along the direction A-A;  
       FIG. 4  shows a sectional view of  FIG. 3  along the direction of axis X 1  when the micro-adjusting and locking mechanism is in a locked state;  
       FIG. 5  shows a sectional view of  FIG. 3  along the direction of axis X 1  when the micro-adjusting and locking mechanism is in an unlocked state;  
       FIG. 6  shows a sectional view of  FIG. 1  along the direction C-C;  
       FIG. 7  shows a sectional view of  FIG. 6  along the direction B-B;  
       FIG. 8  shows a sectional view of  FIG. 6  along the direction D-D, when the wormgear is in an engaged state; and  
       FIG. 9  shows a sectional view of  FIG. 6  along the direction D-D, when the wormgear is in a disengaged state. 
    
    
     DESCRIPTION OF THE INVENTION  
      Referring to  FIGS. 1, 2  and  3 , a miter saw includes a base  1  and a turntable  2  pivotally mounted on the base  1  about a first rotary shaft  3  joined to the base  1  and to the turntable  2 . A sleeve  15  is integrally formed in the turntable  2  and intimately encloses the rotary shaft  3 . A supporting arm  4  is connected to a saw unit  5  for cutting a workpiece. First and second micro-adjusting and locking mechanisms  6  and  6 ′ are disposed in the turntable  2  and the supporting arm  4  respectively.  
      The angle of the turntable  2  relative to the base  1  may be manually adjusted by the operator according to the demands of the workpiece and locked in position by the first micro-adjusting and locking mechanism  6 . The first micro-adjusting and locking mechanism  6  comprises a wormgear  10  fixed to the sleeve  15  and a worm  8  engageable with the wormgear  10 . The worm  8  is supported proximally by a supporting block  13 . A micro-adjusting handle  14  is connected coaxially to a distal end of the worm  8 . An eccentric sleeve  9  is disposed between the worm  8  and the turntable  2  and is fixedly mounted to a lock-release knob  7 . A torsion spring  11  is disposed between the turntable  2  and the lock-release knob  7 . The worm  8  has a plurality of engaging recesses  102  corresponding to a plurality of toothed engaging blocks  101  on the base  1 . The engaging recesses  102  engage the engaging blocks  101  to fix the wormgear  10  to the base  1 .  
      A supporting sleeve  12  is fixed to the eccentric sleeve  9 . Both the supporting sleeve  12  and the eccentric sleeve  9  play the role of eccentric sleeves. The eccentric sleeve  9  encloses the worm  8  and its axis X 2  is parallel to and spaced apart from the axis X 1  of the worm  8 . The eccentric sleeve  9  is rotatably and threadedly connected to the turntable  2 .  
      As shown in  FIGS. 4 and 5 , the eccentric sleeve  9  has a shoulder  21 . The lock-release knob  7  has a recess  22  to fit the shoulder  21  to form a unitary member. The torsion spring  11  is received in a retaining groove  23  formed in the turntable  2 . One end of the torsion spring  11  is received in the wall of the retaining groove  23 . The other end of the torsion spring  11  is received in the wall of a retaining groove  24  formed in the lock-release knob  7 .  
      Referring to  FIGS. 3 and 4 , the first micro-adjusting and locking mechanism  6  is in a locked state which means the turntable  2  is stable and is not manually rotatable about the first rotary shaft  3 . In this state, the wormgear  10  and the worm  8  are engaged. In a direction perpendicular to the horizontal surface, the axis X 2  of the eccentric sleeve  9  and the axis X 1  of the worm  8  are parallel and spaced apart from each other. When (in this position) the turntable  2  needs to be finely adjusted (angle change less than 1°), the micro-adjusting handle  14  is rotated to rotatably actuate the worm  8  so that the wormgear  10  engaged with the worm  8  fine adjusts the angle of the turntable  2 .  
      Referring to  FIG. 4 , in order to manually adjust the position of the turntable  2  relative to the base  1 , the lock-release knob  7  is rotated to rotate the eccentric sleeve  9  about its axis X 2  which rotatably drives the worm  8 . As shown in  FIG. 5 , when the eccentric sleeve  9  rotates to a position such that the distance between the axis X 2  of the eccentric sleeve  9  and the axis X 1  of the worm  8  in the direction perpendicular to the horizontal surface is zero, the worm  8  is disengaged from the wormgear  10  and the micro-adjusting and locking mechanism  6  is in an unlocked state. This means that the turntable  2  is manually rotatable about the first rotary shaft  3 . When the turntable  2  is rotated to a preset angle, the lock-release knob  7  is released to its resting position under the restoring force of the torsion spring  11  and the eccentric sleeve  9  and the worm  8  are driven to their locked state. Because the wormgear  10  and the worm  8  are interlockable, the micro-adjusting and locking mechanism  6  of the present invention can be safely and accurately locked.  
      Further referring to FIGS.  6  to  8 , the miter saw has a mounting block  103  for fixing one end of a guiding rail  104 . A second rotary shaft  25 ′ is fixedly connected to the mounting block  103 . The supporting arm  4  is pivotally connected to the second rotary shaft  25 ′. A second micro-adjusting and locking mechanism  6 ′ is connected to the supporting arm  4  and the second rotary shaft  25 ′. The second micro-adjusting and locking mechanism  6 ′ is similar to the first micro-adjusting and locking mechanism  6  in structure and function and the same numerals as used in FIGS.  1  to  5  are used in FIGS.  6  to  9  to denote equivalent structural parts. The angle of the supporting arm  4  relative to the turntable  2  is manually adjusted according to the demands of the workpiece and is locked in position by the second micro-adjusting and locking mechanism  6 ′. The second micro-adjusting and locking mechanism  6 ′ comprises a wormgear  10 ′ which is tightly mounted on the second rotary shaft  25 ′, a worm  8 ′ which is engageable with the wormgear  10 ′, a micro-adjusting handle  14 ′ disposed on one end of the worm  8 ′, a lock-release knob  7 ′, an eccentric sleeve  9 ′ disposed between the worm  8 ′ and the supporting arm  4  and a torsion spring  11 ′ disposed between the supporting arm  4  and the lock-release knob  7 . A supporting sleeve  12 ′ is disposed on the worm  8 ′.  
      As shown in  FIG. 6 , the eccentric sleeve  9 ′ has a shoulder  21 ′. The lock-release knob  7 ′ has a recess  22 ′ to fit the shoulder  21 ′ to form a unitary member. The torsion spring  11 ′ is received in a retaining groove  23 ′ formed in the supporting arm  4 . One end of the torsion spring  11 ′ is received in the wall of the retaining groove  23 ′. The other end of the torsion spring  11 ′ is received in the wall of a retaining groove  24 ′ formed in the lock-release knob  7 ′.  
      When the angle of the supporting arm  4  relative to the turntable  2  needs to be manually adjusted and the supporting arm  4  needs to be locked in a certain position, the second micro-adjusting and locking mechanism  6 ′ may be manipulated in the same way as the first micro-adjusting and locking mechanism  6  described above.