Abstract:
In a pneumatic grinder with an improved air intake control apparatus, a press board is designed on the bottom of a handle of the grinder and disposed at a position proximate to a grinding head, and a force applying end of the press board is turned by fingers by means of a first lever-and-fulcrum pivoting method, so that a pulling end of the press board pulls a pull rod of the air intake control apparatus to move downward and allows air to circulate. The operation by fingers is easier than the operation by pressing a palm onto the top of a handle at the press board. A second lever design allows a speed adjusting knob of the air intake control apparatus to be situated at a position nearer to the grinding head.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pneumatic grinder with an improved air intake control apparatus, and more particularly to a technology of controlling an air intake by turning a press board by fingers. 
     2. Description of the Related Art 
     Referring to  FIG. 6  for a conventional pneumatic grinder, and an air intake control apparatus  41  of this kind of pneumatic grinders is installed at a position of a handle  42  proximate to a grinding head  43 , such that when a user holds the handle  42  for a grinding job, the user presses onto a press board  411  of the intake control apparatus  41  by the center of a palm, and an end of the press board  411  is pivotally connected to a top surface of the handle  42  and at a position proximate to the grinding head  43 , and another end of the press board  411  is lifted towards a rear end of the handle  42 , wherein the bottom of a middle section of the press board  411  presses downward onto a rod  412 , so that when the user presses the press board  411  by a palm, the rod  412  is pressed downward by the press board  411  at the same time to drive a valve rod  413  of the air intake control apparatus  41  to circulate air, so as to drive a pneumatic motor  44  at the position of the grinding head  43 . 
     However, the conventional way of holding the grinder is very inconvenient and not favorable for a user&#39;s grip, because the user&#39;s wrist and lower arm are driven to move while the user&#39;s palm is pressing onto the press board  411 , and thus the prior art takes much efforts and causes the grinding head  43  to shake easily. As a result, errors may be produced in the grinding job. Pressing the press board  411  by a palm also causes an inconvenient grip, so that when the pneumatic motor is operated and vibrated, the grip may be loosened easily. 
     Therefore, the technique of designing the press board of the air intake control apparatus  41  at the top of the handle  42  as described above requires feasible solutions and improvements. 
     In other words, if users can operate the tool by fingers, then the requirement for the controlling the operation can be met, since fingers are the most skillful part of a human hand. 
     If the original design of using a palm to press onto the press board of the aforementioned conventional grinder is replaced by a design of using fingers for the operation of the grinder, the shortcomings of the conventional grinder can be overcome. To let the press board be pressed and operated directly by fingers when a user holds the handle by a hand, it is necessary to redesign and install the press board at the bottom of the handle, but such arrangement will change the positions of many related components of the air intake control apparatus. It is noteworthy to point out that the space at the bottom of the handle of the grinder and proximate to the grinding head is narrower than the space at the top of the handle and proximate to the grinding head, so that when the press board is redesigned and installed at the bottom of the handle and proximate to the grinding head, the press board will move much further to the rear side of the handle than its original position at the top of the handle. Since the air intake control apparatus comes with a speed adjusting knob, therefore it is necessary to redesign a rotating portion of the speed adjusting knob at the top of the handle when the press board is designed at the bottom of the handle. Furthermore, the original way of using an end of the press board for a pivotal connection and pressing makes the position of the speed adjusting knob closer to the middle section of the handle, such that when a user holds the handle by a hand, the user will feel a sudden obstacle, and find it uneasy or uncomfortable to hold the handle. 
     Although the press board of the conventional grinder can be redesigned at the bottom of the handle, such that users can press and operate the press board directly by fingers, yet the grinder with an adjusted position of the press board still has an existing problem that users find it uneasy to hold the handle due to the position of the speed adjusting knob. 
     SUMMARY OF THE INVENTION 
     Therefore, it is a primary objective of the present invention to overcome the foregoing shortcomings of the prior art by providing a pneumatic grinder with an improved air intake control apparatus, wherein a press board of the air intake control apparatus of the grinder is designed at the bottom of a handle of the grinder and disposed at a position proximate to the grinding head, such that when a user holds the handle, the user can turn and press onto a force applying end of the press board upward by fingers, and uses a first lever-and-fulcrum method to drive a pulling end of the press board to pull a pull rod of the air intake control apparatus, and the pull rod is pulled to drive the valve rod, so as to allow air to circulate and drive a pneumatic motor. 
     Another objective of the present invention is to design a press board of an air intake control apparatus by means of a lever pivotal method, so that the position of a speed adjusting knob of the air intake control apparatus at the top of the handle is closer to the grinding head, and when the speed adjusting knob is designed at the top of the handle and proximate to the holding position, the problem of an uneasy or uncomfortable grip can be solved. 
     To achieve the foregoing objectives, the air intake control apparatus of the present invention comprises: 
     a grinding head, having a casing, and the casing having a chamber, and the chamber installing a pneumatic motor therein, and the pneumatic motor being connected to a grinding disc at an external end of a motor axle of the pneumatic motor, and the grinding disc being situated at an opening position of a bottom of the chamber of the casing; 
     a handle, coupled to the grinding head, and extended transversally outward from a lateral side of the casing, and the handle having an air intake passage disposed transversally therein, and the air intake passage being composed of a large-diameter passage and a small-diameter passage, and an end of the small-diameter passage being interconnected to the chamber, and another end of the small-diameter passage being interconnected to an end of the large-diameter passage, and another end of the large-diameter passage being interconnected to the outside, and the handle having an exhaust passage disposed below the air intake passage, and an end of the exhaust passage being interconnected to the outside, and another end of the exhaust passage being interconnected to the chamber, and the handle having a through hole longitudinally penetrating the handle, and the through hole also penetrating the small-diameter passage of the air intake passage; and 
     an air intake control apparatus, including a speed adjusting knob, a pull rod, a press board, a washer, a valve, a valve rod, a spring and a hollow pipe. 
     The speed adjusting knob is comprised of a rod and a rotating portion, and the rod penetrates through the through hole and passes through the small-diameter passage and protrudes out from the bottom of the handle, and the rotating portion is disposed at the top of the rod for rotating the rod to adjust speed, and the rod has an accommodating space extended axially inward from the bottom of the rod and disposed at the position of the small-diameter passage, and an airflow guide hole corresponding to a distal opening of the large-diameter passage. 
     The pull rod is passed from the bottom of a rod of the speed adjusting knob rod and disposed in the accommodating space, and the pull rod has a transversal opening disposed proximate to the top of the pull rod and penetrates through both sides of the pull rod, and the bottom of the pull rod is protruded downward and out from the bottom of the rod. 
     The press board is disposed at the bottom of the handle, and forms a pulling end on the press board and proximate to an end of the grinding head, and the pulling end is connected to the bottom of the pull rod, and another end of the press board forms a force applying end and has a protrusion disposed on the top of the press board between the pulling end and the force applying end, and the protrusion is pivotally coupled to the bottom of the handle. 
     The washer is installed in the large-diameter passage, and a lateral side of the washer is pressed and connected to walls of a radial hole of the large-diameter passage and at a distal opening proximate to the small-diameter passage, and another lateral side of the washer is pressed and connected to a lateral side of the valve, and another lateral side of the valve is pressed by an end of the spring, and another end of the spring is pressed by an end of a hollow pipe in the large-diameter passage, and an end of the valve rod passes through the center of the valve, and the valve rod passes from the large-diameter passage through a penetrating hole at the center of the washer into the small-diameter passage, and another end of the valve rod is situated in an airflow guide hole of the rod and passed through a transversal through hole of the pull rod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a section view of a pneumatic grinder in accordance with the present invention; 
         FIG. 2  is an enlarged view of the air intake control apparatus as depicted in  FIG. 1 ; 
         FIG. 3  is a section view of a pneumatic grinder with a press board being turned and pressed in accordance with the present invention; 
         FIG. 4  is an enlarged view of the air intake control apparatus as depicted in  FIG. 3 , wherein a press board is turned and pressed, and the press board pulls a pull rod down to drive a valve rod to move downward, and the valve rod drives the valve to shift into a conduction state; 
         FIG. 5  is a schematic view of the handle held by a hand as depicted in  FIG. 3 , wherein the press board is turned and pressed upward by fingers; and 
         FIG. 6  is a schematic view of a prior art pneumatic grinder wherein a press board is disposed at the top of a handle, and the press board is pressed downward to a rod. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 to 5  for a structure of a pneumatic grinder of the present invention according to a preferred embodiment of the present invention, the preferred embodiment is provided for the purpose of illustrating the invention only, but not intended for limiting the invention. 
     In  FIGS. 1 and 2 , the pneumatic grinder of the invention comprises: 
     a grinding head  1 , having a casing  11 , and the casing  11  has a chamber  111 , and the chamber  111  installs a pneumatic motor  12  therein, and the pneumatic motor  12  is connected to a grinding disc  13  at an external end of a motor axle  121  of the pneumatic motor  12 , and the grinding disc  13  is situated at an opening position of a bottom of the chamber  111  of the casing  11 , wherein the casing  11  further includes a dust cover  14  disposed at the bottom of the casing  11  and situated around the top of the grinding disc  13 ; 
     a handle  2 , coupled to the grinding head  1 , and extended transversally outward from a lateral side of the casing  11 , and the handle  1  has an air intake passage  22  disposed transversally therein, and the air intake passage being  22  is composed of a large-diameter passage  221  and a small-diameter passage  222 , and an end of the small-diameter passage  222  is interconnected to the chamber  111 , and another end of the small-diameter passage  222  is interconnected to an end of the large-diameter passage  221 , and another end of the large-diameter passage  221  is interconnected to the outside, and the handle  2  has an exhaust passage  23  disposed below the air intake passage  23 , and an end of the exhaust passage  23  is interconnected to the outside, and another end of the exhaust passage  23  is interconnected to the chamber  111 , and the handle  2  contains a dust extracting passage  24  disposed below the exhaust passage  23 , and an end of the dust extracting passage  24  is interconnected to the outside, and another end of the dust extracting passage  24  is interconnected to the top of the grinding disc  13 , and the handle  2  has a through hole  25  longitudinally penetrating the handle  2 , and the through hole  25  also penetrates the small-diameter passage  222  of the air intake passage  22 ; and 
     an air intake control apparatus  3 , including a speed adjusting knob  31 , a pull rod  32 , a press board  33 , a washer  34 , a valve  35 , a spring  36 , a hollow pipe  37  and a valve rod  38 . 
     The speed adjusting knob  31  is comprised of a rod  311  and a rotating portion  312 , and the rod  311  penetrates the through hole  25 , and passes through the small-diameter passage  222  and protrudes out from the bottom of the handle  2 , and the rotating portion  312  is disposed at the top of the rod  311  for rotating the rod  311  to adjust a speed, and the rod  311  having an accommodating space  311 A extended axially inward from the bottom of the rod  311  and disposed at the position of the small-diameter passage, and an airflow guide hole  311 B corresponding to a distal opening of the large-diameter passage, and the rod  311  of the speed adjusting knob  31  is latched and fixed to the handle  2  by a latch  313 . 
     In this embodiment, a pressing surface  261  is formed around the periphery of a through hole  25  around the top of the handle  2 , and the bottom of the rotating portion  312  of the speed adjusting knob  31  is pressed and connected to the pressing surface  261  for positioning the rotating portion  312 . 
     The pull rod  32  is passed from the bottom of a rod  311  of the speed adjusting knob rod  31  and disposed in the accommodating space  311 A, and has a transversal opening  321  disposed proximate to the top of the pull rod  32  and penetrates through both sides of the pull rod  32 , and the bottom of the pull rod  32  is protruded downward and out from the bottom of the rod  311 . 
     The press board  33  is disposed at the bottom of the handle  2 , and forms a pulling end  331  on the press board  33  and proximate to an end of the grinding head  1 , and the pulling end  331  is connected to the bottom of the pull rod  32 , and another end of the press board  33  forms a force applying end  332 , and has a protrusion  333  disposed on the top of the press board  33  between the pulling end  331  and the force applying end  332 , and the protrusion  333  is pivotally coupled to the bottom of the handle  2 . 
     The vertical distance from the force applying end  332  to the bottom of the handle  2  is greater than a vertical distance from the pulling end  331  to the handle  2 , and the length from the protrusion  333  to the force applying end  332  is greater than the length from the protrusion  333  to the pulling end  331 , so that the press board  33  is tilted with respect to the bottom of the handle  2 , and users can apply a force onto the force applying end  332  easily. 
     In this embodiment, the bottom of the pull rod  32  further includes a protrusion  322 , and the pulling end  331  of the press board  33  has a pulling portion  334  latched to the protrusion  332  at the bottom of the pull rod  32  and provided for users to pull the pull rod  32  by the pulling end  331  of the press board  33 . 
     The washer  34  is installed in the large-diameter passage  221  of the air intake passage  22 , and a lateral side of the washer  34  is pressed and connected to walls  221 A of a radial hole of the large-diameter passage  221  and at a distal opening proximate to the small-diameter passage  222 , and another lateral side of the washer  34  is pressed and connected to a lateral side of the valve, and another lateral side of the valve  35  is pressed by an end of the spring  36 , and another end of the spring  36  is pressed by an end of a hollow pipe  37  in the large-diameter passage  221 , and the hollow pipe  37  has a hollow passage  371  penetrating both ends, and the hollow passage  371  is interconnected with the large-diameter passage  221  of the air intake passage  22 , and an end of the valve rod  38  is passed and fixed at the center of the valve  35 , and the valve rod  38  is passed from the large-diameter passage  221  through a penetrating hole  34  at the center of the washer  34  to the small-diameter passage  222 , and another end of the valve rod  38  is situated in the airflow guide hole  311  of the rod  311  and passed into a transversal through hole  321  of the pull rod  32 . 
     Therefore, the force applying end  332  of the press board  33  is turned upward, such that when the pulling end  331  of the press board  33  pulls the pull rod  32 , the pull rod  32  is shifted downward to drive the valve rod  38  into a slanting position, and a plurality of ventilation holes  351  on the valve  35  are interconnected with and the penetrating hole  341  of the washer  34 , so as to circulate air into the chamber  111  to drive the pneumatic motor  12 . 
     Referring to  FIGS. 3 to 5 , a user holds the handle  2  from the top towards the bottom by a hand, and turns and presses the press board  33  with respect to the bottom of the handle  2  by fingers. The force applying end  332  of the press board  33  is turned upward by fingers, so that the press board  33  is pivoted with respect to the handle  2  by the protrusion  333 . Now, the pulling end  331  of the press board  33  uses the protrusion  333  as a fulcrum for the pivotal turning by the lever principle to move downward. Therefore, the pulling end  331  pulls the pull rod  32  to move downward to drive the pneumatic motor  12  as described above. 
     In summation of the description above, the press board of the air intake control apparatus is installed at the bottom of the handle and proximate to the grinding head in accordance with the present invention, and a first lever-and-fulcrum principle is used, such that when a user holds the handle, the user can turn and press the force applying end of the press board by fingers flexibly and easily, and the position of the rotating portion of the speed adjusting knob of the air intake control apparatus at the top of handle can be closer to the grinding head, so as to avoid an uneasy and uncomfortable grip.