Patent Document

FIELD OF THE INVENTION 
   The present invention relates generally to a pneumatic tool, and more particularly to a pneumatic cutting tool adapted for two handed operation. 
   BACKGROUND OF THE INVENTION 
   A conventional pneumatic cutting tool is shown in  FIG. 3 , and generally includes a body  60  housing a motor (not illustrated) which drives a shaft  61 . A protecting cover  65  is provided at an operating end  80  of the body  60 . A connecting tube  67  is further provided with one end connected to the shaft  61 . A relatively larger positioning collar  68  is defined on the connecting tube  67 . The positioning collar  68  has a protrusion part  69 , with inner thread  70 , where a bolt  72  attaches a circular cutter  71  to the connecting tube  67 . In operation, the motor drives the shaft  61 , connecting tube  67  and the cutter  71 , to rotate the cutter and perform the operation of cutting. 
   The conventional cutting tool provides convenient one-handed operation, but does not permit operation using two hands. However, one-handed operation is problematic as it easily affects the quality of work performed by the tool. Specifically, it is difficult to control vibrations of the tool, and consequently the precise shape of the article being cut. Moreover, single-handed operation is strenuous, which leads to operator fatigue. In addition to affecting the quality of work, there is a risk that the pneumatic cutting tool will slip out of the operator&#39;s single hand, which could have undesired consequences. 
   Accordingly, one object of the present invention is to provide an improved pneumatic cutting tool that can be gripped with both of the operator&#39;s hands to provide greater stability, and to eliminate the above-mentioned disadvantages. 
   Another object of the present invention is to provide an adjustable handle for a cutting tool, enabling convenient gripping of the tool in a plurality of positions. 
   SUMMARY OF THE INVENTION 
   The above-listed objects are met or exceeded by the present invention, in which a cutting tool has an extended length facilitating two-handed gripping of the tool. This results in greater stability during the operation of the tool, and facilitates the cutting operation. 
   A first objective of the present invention is to provide a cutting tool having an extended length. The length of the cutting tool is suitably configured to conveniently allow two handed support of the cutting tool during operation, providing better stability and control in cutting. 
   Another objective of the present invention is to provide a pneumatic cutting tool having an adjustable handle for accommodating the preferred positions of various operators using the tool. 
   More specifically, the present invention provides a pneumatic cutting tool having an extended length, including a body which has an opening defined therein, and a shaft rotatably mounted to and extended out of the opening of the body. A first connecting tube is connected to the shaft at one end and an extension rod is connected to the other end of the first connecting tube. One end of a cylinder is connected to the opening of the body at the opening, and a protecting cover is fitted on the other end of the cylinder. The extension rod is rotatably fitted inside the cylinder. A second connecting tube is connected to the other end of the extension rod, and to a positioning collar. A circular cutter is fitted onto the positioning collar. 
   According to one embodiment, the pneumatic cutting tool has a handle assembly which includes a rotatable tube having a handle attached that is slidably mounted onto the periphery of the cylinder. The position of the handle can be adjusted by loosening a threaded rod and moving the rotatable tube along the cylinder. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more clearly understood from the description as set forth below with reference to the accompanying drawings, wherein: 
       FIG. 1  is an exploded perspective view of a pneumatic cutting tool in accordance with the present invention; 
       FIG. 2  is a partial side view of the pneumatic cutting tool of  FIG. 1 , shown in partial cross-section; and 
       FIG. 3  is an exploded perspective view of a conventional pneumatic cutting tool. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in  FIGS. 1 and 2 , a pneumatic cutting tool includes a body  10  having a trigger  11  extending from it, and an opening  10   a  defined therein. The inner wall of the opening  10   a  has an inner thread  13 . A shaft  12  extends out of the body  10  through the opening  10   a , and is connected to a connecting tube  20 . The body  10  also houses a motor, which rotates the shaft  12 . 
   According to a preferred embodiment, the connecting tube  20  is screwed onto a threaded portion of the axle  12 . An extension rod  21  is then connected to the connecting tube  20 . Ends  21   a  and  21   b  of the extension rod  21  are each provided with a bearing  22 . 
   A cylinder  30  which is long enough to grasp in a hand, has a body end  38  and an operating end  39 . The body end  38  is connected to the body  10 . According to a preferred embodiment, the body end  38  engages the inner thread  13  of the body  10 . 
   The cylinder  30  has a through hole  31  ( FIG. 2 ) which receives the connecting tube  20  and the extension rod  21 . The through hole  31  can have two parts  31   a  and  31   b  which respectively receive the connecting tube  20  and the extension rod  21 . The through hole  31  also has parts  31   c  which allow the two bearings  22  to support the extension rod  21  in the through hole  31  of the cylinder  30 . According to a preferred embodiment, through hole part  31   a  has a greater diameter than through hole part  31   b.    
   In addition, the outer periphery of the cylinder  30  at its body end  38  has many facets  32  formed thereon and a tapered part  33  surrounding the facets  32 , such that the cylinder  30  can be easily attached to or detached from the body  10  using a wrench or the like. 
   The outer periphery of the cylinder  30  has an outer thread  34  defined on the operating end  39 . A circular radial surface  35  is formed at the operating end  39  proximate the outer thread  34 . Two facets  36  are formed in the outer thread  34  in a facing relationship to one another. 
   According to a further aspect of the preferred embodiment, a handle assembly including a rotatable tube  40  and a handle  43  is slidably mounted on the cylinder  30 . Preferably, the rotatable tube  40  has a threaded hole  41  configured to receive a threaded rod  42 . The handle  43  is connected to the threaded rod  42 . Thus, the threaded rod  42  secures the handle  43  to the rotatable tube  40 . The threaded rod  42  extends through the threaded hole  41  when the handle is tightened, to fix the rotatable tube  40  in a given position. 
   A cutting mechanism  5  includes a protecting cover  50  which slips over the outer thread  34  to abut the radial surface  35  of the cylinder  30 . A nut  51  fixedly locks the protecting cover  50  onto the cylinder  30 . A connecting tube  52  is provided with a positioning collar  53  on one end and two facets  54  on the other end. An inner thread  55  is defined inside the connecting tube  52  near the facets  54 , and is configured to engage end  21   b  of the extension rod  21 . 
   A protrusion part  56  of the connecting tube  52  is provided with an inner thread hole  57  located in the central part thereof. A circular cutter  58  has a central opening to allow itself to fit around the periphery of the protrusion part  56 . A bolt  59  is provided to pass through a washer  59   a  and screw into the central thread part  57  of the protrusion part  56 , such that the washer  59   a  is allowed to lock the circular cutter  58  onto the connecting tube  52 . 
   Referring once again to  FIGS. 1 and 2 , according to the preferred working position of an operator, the handle  43  can be moved to a suitable location along the outer periphery of the cylinder  30 . Loosening the handle  43  disengages the threaded rod  42  from the outer periphery of the cylinder  30 , permitting the rotatable tube  40  to be freely moved to a desired axial and radial position on the cylinder  30 . Then, tightening the handle  43  engages the threaded rod  42  with the outer periphery of the cylinder  30 , which fixes the handle  43  in the desired position. 
   In operation, the trigger  11  commences the motor to drive the shaft  12  together with the extension rod  21 , such that the extension rod  21  can simultaneously drive the connecting tube  52  to drive the circular cutter  58  to rotate and perform the cutting operation. Only one hand is required to actuate the trigger  11 , while the other hand grips the handle  43 . By using two hands for the cutting operation of the pneumatic cutting tool in accordance with the present invention, the cutting forces and vibrations are effectively diminished, resulting in higher efficiency and stability of the cutting operation. 
   In another embodiment, the present invention can be an extension assembly for an existing pneumatic cutting tool. The extension assembly includes a connecting tube  20  ( FIG. 1 ) having first and second ends, which the first end of the connecting tube  20  connected to the shaft  61  (FIG.  3 ). An extension rod  21  ( FIG. 1 ) has ends  21   a  and  21   b , where end  21   a  of the extension rod  21  is connected to the second end of the connecting tube  20 . The cylinder  30  has a body end  38  and an operating end  39 , where the body end  38  is appropriately threaded for connection to the opening of the body  60  (FIG.  3 ), and the extension rod  21  is rotatably fitted into the cylinder  30  (FIG.  1 ). The connecting tube  67  ( FIG. 3 ) with the positioning collar  68  is attached to end  21   b  ( FIG. 1 ) of the extension rod, and the protective cover is attached to the operating end  39  of the cylinder  30 . Finally, the bolt  72  ( FIG. 3 ) is used to attach the circular cutter  71  to the connecting tube  67 . The extension assembly can further include the adjustable handle assembly previously described. 
   While a particular embodiment of the pneumatic cutting tool adopted for two handed operation in accordance with the present invention has been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.

Technology Category: 7