Patent Publication Number: US-2012031248-A1

Title: Pull-rod locking device for a miter saw

Description:
RELATED APPLICATION DATA 
     This application claims the benefit of CN 201020280045.6, filed Aug. 3, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The subject disclosure generally relates to a pull-rod type miter saw. 
     The pull rod in a miter saw of the type having a slide cutting function generally needs to be locked during packaging, transmitting, and conveying. The pull rod is usually locked by means of screw thread, which is simple, economic, and widely used in the industry. This common locking device takes the form of a knob and screw in appearance. An operator may rotate the knob for locking until the head of the screw bears against the circular surface of the pull rod. The pull rod is thereby locked by means of the pressing force exerted on the pull rod by the screw, namely, by the large static friction force between the pull rod and the screw. 
     However, locking the pull rod with a common knob and screw has the following defects: 
     1. It seems to be cheap in appearance; 
     2. The operator needs to rotate the device several cycles to lock the pull rod, thus the operation of the device is not convenient; and 
     3. The locking force, which is dependent upon the working experience of the operator, will destroy the surface of the pull rod if the force is too large and locking of the pull rod can not be achieved if the force is too small. 
     SUMMARY 
     The following describes a pull-rod locking device for a miter saw which overcomes the disadvantages noted above. To this end, the pull-rod locking device comprises a locking element for locking the pull rod and an operation part or handle for manual operation thereof. The pull-rod locking device is movable between a locking position and a releasing position with respect to the pull rod. Switching between the locking position and the releasing position is achieved by adjusting the operation part in a certain manner. In the locking position, the locking element will be placed into contact with the pull rod and, in the releasing position, the locking element will be distanced from the pull rod by a predetermined distance. In certain embodiments, the pull-rod locking device will engage with at least one locating structure on the miter saw to maintain the pull-rod locking device in a locking state or a releasing state. The pull-rod locking device for the miter saw described hereinafter thus has a simple structure, can ensure efficient locking of the pull-rod with an even force, will not damage the face of the pull rod, and has a relatively more pleasing visual effect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject device will be described with reference to the following drawings wherein: 
         FIG. 1  is a side view of an exemplary pull-rod miter saw machine constructed according to the description that follows; 
         FIG. 2A  is a schematic view illustrating that the pull-rod locking handle of the miter saw of  FIG. 1  as placed into a locking state; 
         FIG. 2B  is a schematic view illustrating the pull-rod locking handle of the miter saw of  FIG. 1  as placed into a releasing state; 
         FIG. 3  is a sectional view of the pull-rod locking device of the miter saw of  FIG. 1 ; and 
         FIG. 4  is an exploded view of the pull-rod locking device of the miter saw of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The following describes a pull-rod locking device used in a pull rod type miter saw or other similar machines. The pull-rod locking device is mounted on one side of the pull rod, and comprises a locking element for locking the pull rod and an operation part for manual operation. By operating the operation part, the pull-rod locking device may be switched between a locking position and a releasing position. Specifically, in the locking position, the pull-rod locking device interferes with the pull rod directly or indirectly by acting on the pull rod or another trapping device, thereby preventing the pull rod from sliding with respect to the saw body of the miter saw. In the releasing position, the pull-rod locking device is not in interference with the pull rod, thus the pull rod can slide with respect to the saw body of the miter saw, thereby performing some functional operation such as a cutting. The pull-rod locking device may be switched between the releasing position and the locking position by an adjustment in a substantially constant range, and such an adjustment is visible and convenient. 
     Referring to  FIG. 1 , illustrated is a pull rod type miter saw  1  according to one preferred embodiment. As illustrated, the miter saw  1  includes a cutting head  11  and a slide brace assembly  17 . When the cutting head  11  is in a horizontal cutting position, it can slide back and forth along the pull rod  171  with the aid of the linear bearing  151  on the rocker arm assembly  15 , so that a cutting of the object (not shown) positioned on the platform  12  can be achieved. The pull-rod locking handle assembly  16  is installed on one side of the pull rod  171  for locking the slide brace assembly  17  in the case of packaging, transittings, and conveyance, so that damages to the miter saw  1  due to accidental relative sliding can be avoided. The pull-rod locking handle assembly  16 , being installed on one side of the pull rod  171 , need not be limited to any specific position such as left, right, top or bottom, but may be installed in any position that allows the pull-rod locking handle assembly  16  to release or lock the pull rod  171  simply. 
     Referring to  FIGS. 2A and 2B , the pull-rod locking handle assembly  16  has two functions: locking and releasing. In the state of locking, the pull-rod locking device is in a locking position where the pull rod is fixed and cannot move; the state of releasing is relative to the state of locking, and in this state, the pull-rod locking device is in a releasing position where the pull rod can move freely. In the present embodiment, the pull-rod locking device can be switched between the locking and releasing states by rotating the assembly  16  a fixed angular amount. In this way, a visible and convenient operation indication is provided for operators. 
     The rocker arm  151  of the miter saw  1  is formed with two recesses  153  and  154  thereon which correspond to the locking position and the releasing position respectively. A locating element is provided on the pull-rod locking handle assembly  16 , which can elastically engage with the recesses  153  and  154  for locating the pull rod  171  and for indicating the present state thereof when locking or releasing the pull rod  171 . Preferably, a guiding groove  155  is formed between the two recesses  153  and  154  to facilitate the sliding of the locating element between the two recesses. When the locating element is slid from the guiding groove  155  to the recess  153  or  154 , a loud noise may be produced so that the operator is reminded that the pull rod  171  has been released or locked. 
     Referring to  FIGS. 3 and 4 , the pull-rod locking handle assembly  16  includes a locking element and a handle assembly  16  mounted on the locking element and operated manually by the users of the miter saw. In the present embodiment, the locking element takes the form of a screw  166  mounted to one side of the pull rod  171  by passing through a threaded hole (not shown) in the linear bearing  152 . By screwing in and out of the threaded hole, the screw can move inwards to abut against the surface of the pull rod  171  for locking or move outwards to disengage from the pull rod  171  for releasing. In the present embodiment, it is configured such that the locking position and the releasing position can be switched between by rotating the screw  166  through 90 degrees. In this way, the guiding groove  155  is correspondingly formed in the shape of one quarter of a circle. Certainly, depending on the specific circumstances, other arc length ranges are also possible for achieving the switching of the positions. Once the initial position between the locking screw and the pull rod is adjusted, for the locking or releasing operation each time, as long as the screw  166  is rotated in a certain arc range about its centre line to move towards or away from the pull rod for a substantially constant distance, locking or releasing of the pull rod may be achieved, which is very convenient for the operator. In the locking position, the screw  166  closely contact the pull rod towards the surface of the locked pull rod; and in the released position, the screw  166  is distanced from the pull rod by a predetermined distance towards the surface of the locked pull rod. In other embodiments, the locking element may further have a soft surface arranged on the end of the screw  166  facing the locked pull rod so as to get a better close contact with the pull rod in the locking position and further protect the surface of the pull rod. In other embodiments, the locking element may be other elements in other forms and structures. 
     In the present embodiment, the locating element of the pull-rod locking handle assembly  16  may take the form of a positioning pin  162 . The positioning pin  162  is arranged in a mounting hole  167  on the handle assembly or lever  161 . A first spring  163  is arranged in the mounting hole  167 , which can elastically bears against the positioning pin  162  outwards so that the positioning pin  162  can slide smoothly between the two recesses and the guiding groove. The positioning pin  162  may be assembled in the mounting hole  167  by means of its enlarged head portion (not shown) or a fixing element so as to prevent it from disengaging from the mounting hole  167 . 
     It should be noted that, the locating recesses are provided for locating the positioning pin  162  in a stable state when it is in the releasing and locking positions, that is to say, the positioning pin  162  will not move away from the locking position automatically due to shaking to affect conveyance safety, or move away from the releasing position automatically and interfere with the pull rod to affect the normal cutting. This relative stable state may be achieved in other ways, for example, by providing a clamping groove, a magnet attracting components or an additional fixing element, which may have the same effect to some degree. 
     Certainly, if the applications of the miter saw is relative stable, that is to say, if it is not necessary to worry about in these applications that the pull-rod locking handle assembly  16  may automatically disengage from the locking or releasing position due to shake or collision, the locking element of the locking handle assembly  17  may be omitted to make the structure more compact. However, in this case, an indicating marker is preferably provided for indicating the locking or releasing position to the operator. The marker may be indication character or pattern marked in the surface of the miter saw, meanwhile, an indicating line (not shown) would be arranged in the pull-rod locking handle  16 , which aligns with the indicating marker for indicating the releasing state or the releasing state. The combination of the indicating line and the indicating maker can be applied in the practice with the recesses or the like simultaneously. 
     When the pull-rod locking handle assembly  16  is screwed into the threaded hole, it is possible that the locking handle  161  after screwing may be random in orientation, that is to say, in the locking and releasing positions, it is most likely that the positioning pin  162  is not accommodated in the locating recesses  153  and  154 , or the handle assembly  16  is not aligned with the indicating marker of the miter saw. To resolve this problem, a clutch structure is arranged between the pull-rod locking handle  161  and the screw  166 . 
     This clutch structure may be embodied by an inner toothed hole  1611  on the locking handle  161  and a polygonal head  1661  on the screw  166 . The inner toothed hole  1611  is formed in one end of the assembling portion  1610  of the pull-rod locking handle  161 , within which the polygonal head  1661  is accommodated. Due to the design of the polygonal and inner toothed hole, the polygonal head  1661  may be accommodated in the inner toothed hole  1661  again after the screw  166  and the handle  161  is rotated by a certain angular amount (for example, 30 degrees). This angle by which the screw  166  and the handle  161  is rotated to enable the polygonal head  1661  to be accommodated again in the inner toothed hole  1611  may be determined by the number of the sides of the polygonal head  1661  as well as the inner toothed hole  1611 . Once the polygonal head  1661  enters into the inner toothed hole  1611 , the two are engaged with each other and cannot move relatively, then a certain torque can be transmitted between the polygonal head  1661  and the locking handle  161 . 
     It can be known from the above that, if the locking position of the screw  166  is not aligned with the position of the positioning pin  162  in the recess  153 , the locking handle  161  may be disengaged from the screw  166 , and rotated by an angle, and then engaged again, as a result, the screw is switched from one accommodated state to another accommodated state with respect to the locking handle  161 , the locking position of the positioning pin  162  is then adjusted. 
     In order to facilitate the adjustment of the locking position, a stopping element is arranged in the locking handle  161 . As shown in  FIG. 4 , the stopping element is a stepped screw  164 , which includes a body portion  1641 , a stopping portion  1642  with a larger section at one end thereof, and a threaded portion  1643  with a smaller section at the other end thereof. A through hole  1612  is formed on the tip of the inner toothed hole  1611 , through which the stepped screw  164  extends into the inner toothed hole  1611  and engages with the screw  166  with its threaded portion  1643 . The body portion  1641  may slide axially in the through hole  1612  and the stopping portion  1642  cannot pass through the through hole  1612 . Preferably, the stepped screw  164  and the screw  166  are concentric with each other. When the locking position needs to be adjusted, the locking handle  161  may be disengaged from the screw  166 , by this time, in the presence of the stepped screw  164 , the locking handle  161  may not be disengaged from the screw  166  as a locking element, but moves back and forth along the centre line of the stepped screw  164  and the screw  166  and is restricted between the stopping portion  1642  and the screw  166 . In the locking or releasing operation, the locking handle  161  may be rotated about the centre line so as to facilitate the operation of the user. 
     Preferably, a spring element is provided in the locking handle  161 , which is a second spring  165  surrounding the body portion  1641 . With the spring force of the second spring  165 , the locking handle  161  can be provided with a spring restoring force so as to tend towards the locking element all the time. When no external force is exerted to the locking handle  161 , the locking handle is pressed onto the locking element, as a result, the comfort ability and convenience of the user operation may be further enhanced. As shown in  FIG. 4 , the locking handle  161  is also provided with a gripping portion  1613  for the user exerting a force by finger, which further facilitates the user operation. The gripping portion  1613  may be used for indicating the locking state and the releasing state in combination with an indicating maker provided upon the miter saw  1 . 
     In order to obtain a good locking effect, the screw  166  may have a larger screw thread or double-start thread to increase the pitch of the screw thread. 
     It should be noted that, in the present embodiment, the locking screw is selected as an device to directly contact the pull rod of the miter saw. However, other fittings, as long as they can obtain the same object, that is to say, as long as they can obtain the effect of approaching and locking and disengaging and releasing the pull rod by the switch between the two positions, may be used in other embodiments of the present invention. 
     In addition, as the embodiment of the pull-rod locking device of the present invention, the pull-rod locking handle assembly  16  takes the form of an “assembly” including a locking handle  161  and a screw  166  engaged with each other. It can be seen from the description that it is not necessary for the present invention to use a separated structure, and a one-piece structure may also be possible. 
     The above contents disclose preferred embodiments of the present invention which are not to be used to limit the scope of the present invention. Rather, any technical solutions obtained by equivalent replacements or changes will be regarded as part of the scope of this invention.