Patent Publication Number: US-6984169-B2

Title: Bi-directional rotation pneumatic grinding tool

Description:
FIELD OF THE INVENTION 
   The present invention relates to a bi-directional rotation pneumatic grinding tool and particularly to a pneumatic tool capable of rotating in the positive direction or the reverse direction depending on different requirements to direct sparks, grinding debris or dusts generated in the grinding process in a desired direction. 
   BACKGROUND OF THE INVENTION 
   There are many types of grinding machines. They mostly rotate in a unidirectional manner at low speed and high torque to process rough surfaces. To suit different grinding surfaces, they can be classified in flat grinding and side grinding by the operation mode. As the grinding machines are designed in many different types, they are widely used in many industries such as iron work, machinery, wood working, molding, automobiles and motorcycles, repairs and maintenance, glass fibers, electronics, and the like. Different sizes of granule of the grinding piece may be selected to perform required operations such as polishing, rust removing, glue removing, grinding, wax polishing, edge trimming, drilling, or the like. 
   Refer to  FIG. 1  for a typical operation section of the conventional unidirectional rotation grinding machine that rotates at low speed and high torque. It includes a fastening mechanism. As shown in the drawing, the operation section has an output shaft  6  extending outwards. The output shaft  6  is coupled with a bearing  7  and screws a coupling head  1 . The coupling head  1  has a fastening hole  11  and is engaged with a fastener  2 . When in use, a grinding piece  4  is sandwiched and anchored between the coupling head  1  and the fastener  2 . The output shaft  6  is driven by a driving mechanism to rotate at high speed to drive the grinding piece  4  to rotate in one direction. When the unidirectional grinding machine performs grinding operation, sparks, grinding debris, powders or dusts are inevitably generated. The sparks may spew to the surrounding and cause fire when inflammable goods are around. Dusts produce environmental pollution. The grinding debris scatter around and may cause severe hazards to the health and safety of operators. 
   Moreover, due to the conventional grinding machines rotate in one direction, when grinding a narrower working piece or corners, the grasp section of the grinding machines is constrained due to design limitation and allows only surface machining to be performed on the working piece. Some corners cannot be machined smoothly by the conventional grinding machines, and operators have to adopt other operating gestures or approaches to do machining operation. Those abnormal operation methods often affect grinding quality and produce defects on the machining surface. 
   In addition, when the grinding piece  4  rotates at high speed, a greater torque occurs on the exposed section of the output shaft  6 . Because of the length of the output shaft  6  or uneven distribution of the torque, the output shaft tends to occur deformation or even damage. 
   SUMMARY OF THE INVENTION 
   The primary object of the invention is to resolve the aforesaid disadvantages and overcome the drawbacks of the prior art. The invention includes a connection member to enable the invention to rotate positively or reversely according to different requirements. Thus sparks, grinding debris or dusts generated in the grinding process may be directed in a desired direction to avoid polluting operation environment or hurting people and working pieces. 
   Another object of the invention is to have the connection member entirely encasing a fastener to achieve even distribution of torque on the fastener and prevent deformation or damage of the fastener caused by uneven distribution of the torque. 
   In order to achieve the foregoing objects, the bi-directional rotation pneumatic grinding tool of the invention includes a body which has an operation section and a grasp section. The operation section drives an output shaft to rotate in both directions. The output shaft has positive threads formed in the interior and reverse threads formed on the outside. The output shaft also couples with a fastening mechanism. The fastening mechanism includes a coupling head which has one end forming a fastening section with reverse threads formed therein, a connection member screwed on a front section of the output shaft, a latch section located on the other end of the connection member that has reverse threads, an anchor member fastening to the latch section, and a fastener which has positive threads running through the anchor member and engaging with the positive threads formed on the inner wall of the output shaft. By means of the fastening mechanism that has elements of positive and negative threads and may be fastened tightly with one another, the invention can rotate positively or reversely according to different requirements without loosening. And sparks, grinding debris or dusts generated in the grinding process may be directed in a desired direction without polluting the operation environment or hurting people and the working pieces. 
   The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of the fastening mechanism of a conventional pneumatic grinding machine. 
       FIG. 2  is an exploded view of the present invention. 
       FIG. 3  is a fragmentary sectional view of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Please refer to  FIGS. 2 and 3  for an exploded and a fragmentary sectional view of the present invention. The bi-directional rotation pneumatic grinding tool of the invention is designed for machining surfaces. It includes a body  8  which has an operation section  81  and a grasp section  82 . The operation section  81  has an actuator  13  to drive an output shaft  6  to rotate in both directions. The output shaft  6  further is coupled with a fastening mechanism. The fastening mechanism consists of a coupling head  1 , a connection member  5 , an anchor member  2  and a fastener  3 . The output shaft  6  has an inner wall which has positive threads  61  and an outer wall which has reverse threads  62 . 
   The output shaft  6  also is coupled with a bearing  7  to reduce friction between the output shaft  6  and the fastening mechanism. 
   The coupling head  1  has two ends communicating with each other. One end is formed in a stepwise manner and has a fastening section  11  with reverse threads  111  formed therein to engage with the reverse threads  62  of the output shaft  6  and to be in contact with the inner perimeter of the bearing  7 . The other end of the coupling head  1  forms a connecting section  12  with an anchor hole  121  formed thereon. 
   The connection member  5  has two ends communicating with each other and is made from a material of a great hardness. It is housed in the coupling head  1  and has one end forming a polygonal latch section  51  which has reverse threads  511  formed therein to couple with the reverse threads  62  on the outer wall of the output shaft  6 , and other end forming an engaging section  52  which has reverse threads  521  formed on the outer wall thereof. 
   The anchor member  2  has two ends communicating with each other. It has a coupling section  22  on one end with reverse threads  221  formed therein to engage with the reverse threads  521  on the outer wall of the engaging section  52  of the connection member  5 , and the other end forming a stop section  21  which has a latch trough  211 . 
   The fastener  3  has positive threads  32  and one end forming a bucking section  31 . The rear section of the positive threads  32  runs through the anchor member  2  and the front section of the positive threads  32  engage with the positive threads  61  in the output shaft  6 . It is entirely encased in the elements of the fastening mechanism. 
   Referring to  FIG. 3 , when in use, a grinding piece  4  is sandwiched between the anchor member  2  and the coupling head  1  and is fastened securely by the fastener  3 . The output shaft  6  and the grinding piece  4  are driven by the driving mechanism to rotate at high speed. As the latch section  51  of the connection member  5  may be coupled with the reverse threads  62  on the outer wall of the output shaft  6 , and the reverse threads  521  on the outer wall of the engaging section  52  of the connection member  5  may be coupled with the reverse threads  221  of the coupling section  22  of the anchor member  2 , and the positive threads  32  of the fastener  3  may run through various elements and engage with the positive threads  61  on the inner wall of the output shaft  6 , hence when the invention rotates clockwise (positive direction), the reverse threads  221  and  521  of the anchor member  2  and the engaging section  52  of the connection member  5  that have been engaged with each other may be turned loose due to the reverse rotation. But because the positive threads  32  and  61  of the fastener  3  and the output shaft  6  are engaged with each other and positive rotation occurs, they are coupled with each other tightly. On the contrary, when the invention rotates counterclockwise (reverse direction), the fastener  3  and the output shaft  6  rotate in the reverse direction and tend to become loose. However, the anchor member  2  and the engaging section  52  of the connection member  5  are coupled tighter because of the positive rotation. Therefore, by means of the mutual coupling relationship between the positive threads and the reverse threads  111 ,  221 ,  32 ,  511 ,  521 ,  61 , and  62  on various elements of the fastening mechanism, the invention may rotate positively or reversely without loosening. And sparks, grinding debris and dusts generated in the grinding process may be directed in a desired direction to avoid polluting the environment or hurting people and working pieces. 
   Moreover, the fastener  3  is encased entirely in the connection member  5 . Deformation or damage may be prevented resulting from uneven torque, and operation efficiency may be improved. 
   In addition, The positive threads and the reverse threads mentioned above may be interchanged according to different user requirements. Namely, the positive threads may be changed to reverse threads while the reverse threads may be changed to positive threads.