Patent Abstract:
A grinder with easily installable/detachable grinding disc, including: a main body in which a driving unit is disposed for driving a rotary shaft, an annular toothed section being formed on the circumference of the rotary shaft; a bracket rotatably disposed under the bottom face of the main body; a support tray disposed under the bracket, several rail channels being radially formed on the support tray; and a predetermined number of detent members respectively slidably disposed in the rail channels. When turning the bracket, the detent members are driven to move along the rail channels. When the detent members are contracted, the arched toothed sections of the inner ends of the detent members engage with the annular toothed section of the rotary shaft, whereby the rotary shaft cannot rotate for replacing grinding disc. After replacing the grinding disc, the detent members are moved outward along the rail channels to disengage from the rotary shaft.

Full Description:
This is a continuation-in-part of application Ser. No. 10/408,311, filed Apr. 8, 2003 now U.S. Pat. No. 6,752,704, the entirety of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention is related to a grinder, and more particularly to a grinder in which the rotary shaft can be fixed without using any tool for replacing the grinding disc. 
   A conventional pneumatic or electric grinder has a grinding disc mounted at bottom end for grinding or buffering a work piece. When grinding different work pieces, it is necessary to frequently replace the grinding disc. 
   In the conventional grinding structure, an eccentric rotary shaft is disposed at bottom end of the rotor (pneumatic grinder) or the motor (electric grinder). A hexagonal nut is fixed at bottom end of the rotary shaft. A worm is disposed at the center of the top face of the grinding disc. The worm is screwed in the nut, whereby the grinding disc is drivable by the rotary shaft. In addition, a protective sheath is disposed at bottom end of the grinder for covering the grinding disc and providing a protective effect. 
   The conventional grinder is equipped with a flat wrench. When replacing the grinding disc, the wrench is extended through the gap between the protective sheath and the grinding disc to fit onto the nut and prevent the rotary shaft from rotating. Under such circumstance, the grinding disc can be untightened or tightened. Such procedure is quite inconvenient, for the protective sheath obstructs the operator from seeing the nut. Therefore, it is hard for the operator to fit the wrench onto the nut. Moreover, the rotary shaft is eccentrically arranged and has unfixed position so that the operator often needs to try many times for wrenching the nut. 
   Furthermore, in case there is no tool available, it will be impossible to replace the grinding disc. 
   SUMMARY OF THE INVENTION 
   It is therefore a primary object of the present invention to provide a grinder in which a structure is provided for fixing the rotary shaft, whereby the grinding disc can be replaced without using any tool. 
   The present invention can be best understood through the following description and accompanying drawings wherein: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective assembled view of a preferred embodiment of the present invention; 
       FIG. 2  is a perspective exploded view according to  FIG. 1 ; 
       FIG. 3  is a longitudinal sectional view according to  FIG. 1 ; 
       FIG. 4  is a bottom view according to  FIG. 1 ; 
       FIG. 5  is a partially sectional view according to  FIG. 1 ; 
       FIG. 6  is a perspective assembled view of the support tray,. bracket and detent members of the present invention; 
       FIG. 7  is a top view according to  FIG. 6 , showing that the detent members are opened; 
       FIG. 8  shows that the rotary disc of the present invention is turned to another position; 
       FIG. 9  is a top view according to  FIG. 8 , showing that the detent members are closed; and 
       FIG. 10  is a bottom view of the present invention in the state of  FIG. 9 . 
       FIG. 11  is a perspective exploded view,of a part of another embodiment of the present invention; 
       FIG. 12  is a perspective exploded view of still another embodiment of the present invention; 
       FIG. 13  is a perspective assembled view of the embodiment of  FIG. 12 , showing that the detent members are opened; 
       FIG. 14  is a top view according to  FIG. 13 ; 
       FIG. 15  is a bottom view of the embodiment; 
       FIG. 16  is a view according to  FIG. 14 , showing that the detent members are closed; 
       FIG. 17  is a bottom view according to  FIG. 16 ; and 
       FIG. 18  is a bottom view of still another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Please refer to  FIGS. 1 and 2 . According to a preferred embodiment, the grinder  10  of the present invention includes a main body  20 , a rotary shaft  40 , a rotary disc  50 , a bracket  60 , a support tray  70  and detent members  80 . 
   The main body  20  has a barrel section  22 . At least the bottom end of the barrel section is circular. The main body also has a circular loop section  24  having a diameter larger than that of the barrel section  22  and positioned at bottom end of the barrel section. The inner circumference of the loop section has three connecting sections  26  arranged at equal intervals and connected between the barrel section  22  and the loop section  24 . The three connecting sections define three hollow sections  28  at equal intervals. In addition, two figure marks  30 ,  32  are disposed on top face of one of the connecting sections. Referring to  FIG. 3 , a space  34  is formed in the barrel section  22  in which a driving unit  35  is accommodated. In this embodiment, the grinder is a pneumatic grinder, the driving unit  35  is a pneumatic cylinder  36  in which a rotor  37  is disposed. 
   The rotary shaft  40  is eccentrically pivotally connected with bottom end of the driving unit  35  and is driven by the driving shaft  38  of the driving unit. The rotary shaft is eccentrically arranged so as to provide a vibration effect. The bottom end of the rotary shaft  40  is formed with an axial thread hole  42 . In addition, an annular toothed section  45  is formed along the circumference of the bottom end of the rotary shaft as shown in  FIG. 4 . 
   The rotary disc  50 , referring to  FIGS. 1 and 2 , in this embodiment, is composed of three arched bodies  52  having equal arch length (120 degrees). The three arched bodies  52  are annularly arranged around the loop section  24  to shield the top face of the connecting sections  26 . 
   The bracket  60  has a disc-like body section  62  and three legs  64  arranged on the circumference of the body section at equal intervals. In addition, the body section  62  is formed with a central through hole  65  and three oblique guide slots  66  at equal intervals. Each guide slot has an inner end  661  and an outer end  662 . In radial direction, the inner end  661  is closer to the center of the body section  62 , while the outer end  662  is farther from the center of the body section. The bracket  60  is mounted in the loop section  24  with the three legs  64  respectively extending through the three hollow&#39;sections  28 . Each leg is fixed at a pivot hole  521  of the arched body  52  by a screw.  69  as shown in  FIG. 5 . The three arched bodies  52  are respectively fixed with the three legs so that the arched bodies keep having a circular configuration without departing from each other. When rotating the rotary disc  50  on the loop section  24 , the bracket  60  is driven and moved. The legs  64  and the guide slots  66  are concentric with the body section  62  and the body section is concentric with the driving shaft  38  of the driving unit  35 . 
   The support tray  70  is formed with a central circular hole  72 . Three rail channels  74  are-radially formed on the top face of the support tray  70  at equal angular intervals. 
   Three plate-like detent members  80  respectively disposed in the three rail channels  74  and slidable along the rail channels. An inner end of each detent member  80  is formed with an arched toothed section  82  having several teeth. The three arched toothed sections  82  form a circular configuration. The pitch between the teeth of the toothed section  82  is equal to the pitch between the teeth of the annular toothed section  45  of the rotary shaft  40 . Three guide posts  84  are respectively fixed with the three detent members  80 . 
   After the detent members  80  are mounted into the support tray  70 , the support tray is fixedly connected with small projections  241  formed on inner circumference of the loop section  24  by three screws  86  as shown in  FIGS. 2 and 3 . Accordingly, the support tray is fixed in the loop section. The support tray and the detent members right attach to the bottom face of the body section  62  of the bracket  60 . Referring to  FIG. 6 , the three guide posts  84  are fitted in the guide slots  66 . The support tray  60  is concentric with the bracket  70 . 
   After the components  60 ,  70 ,  80  are mounted in the loop section  24 , as shown in  FIG. 3 , the annular toothed section  45  of the bottom end of the rotary shaft  40  extends into the bracket and the circular hole  72  of the support tray. 
   A hollow protective sheath  90  made of hard plastic or rubber material is fitted around the loop section  24  to provide a protective effect. 
     FIG. 1  is a perspective assembled view of the present invention, in which the rotary disc  50  has at least one window  55  (which is inward recessed in this embodiment). The window  55  corresponds to the connecting section  26  having the two marks  30 ,  32 . In  FIG. 1 , the window  55  is right positioned at the mark  30  which is a figure of a wrench. Under such circumstance, the rotary disc  50  is positioned in an opened position. In this position, as shown in  FIG. 7 , the guide posts  84  are positioned at outer ends  662  of the guide slots  66  and the three detent members  80  are expanded outward. In this state, referring to  FIG. 4 , the rotary shaft  40  is not restricted and can freely rotate. After activating the grinder, the rotary shaft can drive the grinding disc (not shown) to grind a work piece. 
   When replacing the grinding disc, the operator clockwise turns the rotary disc  50  to a closed position as shown in  FIG. 8 , in which the other mark  32  is exposed through the window  55 . The mark  32  is a figure showing that a wrench is fitted onto a nut to indicate the operator of the restriction of the rotary shaft. 
   Referring to  FIG. 8 , when the rotary disc  50  is clockwise angularly displaced, the bracket  60  is synchronously rotated. At this time, the angular positions of the three guide slots  66  are changed and the guide posts  84  are moved from the outer ends  662  of the guide slots to the inner ends  661  thereof as shown in  FIG. 9 . When the guide posts  84  are displaced, the detent members  80  are driven by the guide posts to inward slide along the rail channels  74  to a closed position, the three detent members contract and the arched toothed sections  82  thereof are closed into a complete circle. 
   Under such circumstance, referring to  FIG. 10 , the arched toothed sections  82  of the detent members are engaged with the annular toothed section  45  of the rotary shaft  40  to fix and prevent the rotary shaft from rotating. An operator can screw the worm of the grinding disc into the thread hole  42  of the rotary shaft or unscrew the worm out of the thread hole so as to replace the grinding disc. 
   It should be noted that when the three detent members  80  are closed, the three arched toothed sections  82  form a circle having a circumferential length equal to the circumferential length of the circle defined by the eccentric rotation of the rotary shaft  40 . Therefore, after the grinder stops operating, no matter in what angular position the rotary shaft stops, the rotary shaft is clamped and fixed by the detent members. 
   When activating the grinder, the rotary disc  50  is counterclockwise turned back to the opened position as shown in FIG.  1  to move the guide posts  84  to the outer ends of the guide slots. At this time, the detent members are restored to the expanded state as shown in  FIG. 7  and disengaged from the rotary shaft. 
   In addition, three locating sections  76  can be disposed on the support tray at equal intervals as shown in  FIG. 9 . Three dents  68  are disposed on the body section  62  of the bracket at equal intervals. Two sides of the dent  68  abut against the locating section  76  to serve as the dead end of the movement of the rotary disc and the bracket. 
   By means of simple operation, the rotary shaft can be fixed or released for replacing the grinding disc without using any tool. This is convenient and facilitates the operation. 
   The marks  30 ,  32  enable an operator to judge whether the rotary shaft is freely rotatable or fixed. 
     FIG. 11  shows the bracket  92  and detent members  95  of another embodiment of the grinder of the present invention. In this embodiment, three guide slots  96  are respectively formed on the three detent members  95 , while the three guide posts  94  are disposed on the bracket  92  and inserted in the guide slots  96 . Accordingly, when rotating the bracket  92 , the detent members  95  are driven to displace along the rail channels. 
     FIG. 12  shows still another embodiment of the grinder  100  of the present invention, in which the main body  110 , rotary disc  112 , bracket  114 , support tray  116  and detent members  120  are identical to those of the first embodiment. 
   This embodiment is mainly different from the first embodiment in that an inner end of one detent member  120   a  of the three detent members is formed with an arched toothed section  125 , while the inner ends  126  of the other two detent members  120   b ,  120   c  are free from any toothed section. The inner ends  126  can be plane faces, arched faces or inward recessed as shown in  FIG. 12 . 
   Similarly, referring to  FIGS. 14 and 15 , when the three detent members  120  are positioned in the expanded position, the rotary shaft  118  is not restricted so that the grinding disc is driven to freely rotate. 
   When replacing the grinding disc, the bracket  114  is turned to the closed position as shown in  FIG. 16  At this time, the three detent members  120  are driven to inward move along the rail channels  117  to the closed position as shown in  FIG. 17 . Under such circumstance, the toothed section  125  of the detent member  120   a  engages with the toothed section  119  of the rotary shaft  118  so that the rotary shaft cannot rotate. At this time, the grinding disc can be replaced. 
   When the three detent members are closed, in the case that the position of the rotary shaft  118  is not adjacent to the detent member  120   a , but one of the other two detent members  120   b  or  120   c , for example, adjacent to the detent member  120   b  as shown by phantom line of  FIG. 16 , during closing procedure of the detent member  120   b , the inner end  126  of the detent member  120   b  will push the rotary shaft to move. At this time, the center c of the rotary shaft will angularly displace along the arched line d to the position as shown by solid line of  FIG. 16 . Under such circumstance, the rotary shaft is engaged with the toothed section  125  of the detent member  120   a . In other words, when the detent members are closed, no matter where the rotary shaft is positioned the rotary shaft will be engaged with the detent member  120   a  and fixed. Also, after the three detent members are closed, the inner ends  126  of the detent members  120   b ,  120   c  define a narrow space within which the rotary shaft is restricted. Therefore, the rotary shaft cannot be disengaged from the detent member  120   a.    
     FIG. 18  is a bottom view of still another embodiment of the present invention, in which the inner ends of two detent members  130   a  of the three detent members  130  are formed with arched toothed sections  135 , while the inner end of the other detent member  130   b  is free from any arched toothed section. The inner end of the other detent member can be a plane face, arched face or inward recessed. 
   Similarly, when the detent members are closed, the rotary shaft cannot be disengaged from the detent members  130   a.    
   It should be noted that the bracket be directly exposed to outer side of the main body, whereby an operator can directly turn the bracket.

Technology Classification (CPC): 1