Patent Publication Number: US-2005127127-A1

Title: Safety switch of screwdriver

Description:
FIELD OF THE INVENTION  
      The present invention relates to screwdrivers, and particular to a safety switch of a screwdriver which has a sample and easily assembled structure.  
     BACKGROUND OF THE INVENTION  
      Screwdrivers are general tools for the carpenters and currently they become more useful for DIY (do-it-yourself) workers. In the prior art, the main concern in designing screwdrivers is the speed and convenience of the screwdriver, but recently, the safety use of screwdrivers becomes more and more important in design of the screwdrivers.  
      In one prior art, a slide seat is used to control the movement of a turning unit so as to control the triggering operation of the trigger by a first flange on the turning unit, thereby, a predetermined effect can be acquired. In another prior art, a sliding seat resists against and rotates an elastomer  44  so that a buckling portion will shift a stop to rotate through a predetermined angle and thus the body of the screwdriver will triggering the trigger to have a predetermined effect.  
      In above said prior arts, there are so many components to make the structure complicate. Thereby, the cost is high and the assembly work is tedious. As a result the yield ratio is low.  
     SUMMARY OF THE INVENTION  
      Accordingly, the primary object of the present invention is to provide a safety switch of a screwdriver having a driver body. The safety switch of a screw comprises a push unit; a trigger pivotally installed on the driver body; a receiving space being installed within the trigger for receiving the push unit; a safety rod; one end of the safety rod being installed at a front end of the driver body; and another end of the safety rod being installed at a front end of the trigger; the safety rod being movable into or out of the trigger for pushing the push unit.  
      The push unit comprises an torsion spring enclosing a pivotal post; a buckle; one end of the torsion spring resisting against the buckle for returning the trigger; an ejecting unit resisting against the buckle; an end of the ejecting unit being formed with a bevel for pushing a valve rod of the driver body so as to trigger a screwdriver; and an elastomer; one end of the elastomer being hooked to the ejecting unit; and another end of the elastomer being hooked to the trigger.  
      When the safety rod is pressed; the buckle moves to resist against an upper side ejecting unit; and then when the trigger is pressed, the protrusion of the ejecting unit will move forwards to be buckled into the buckling hole; and the push unit moves to push the valve rod so as to trigger the screwdriver.  
      The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a structural exploded view about the safety switch of a screwdriver of the present invention.  
       FIG. 2  is a partial perspective view of the safety switch of a screwdriver of the present invention.  
      FIGS.  3  to  5  shows the operation of the safety switch of a screwdriver of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      In order that those skilled in the art can further understand the present invention, a description will be described in the following in details. However, these descriptions and the appended drawings are only used to cause those skilled in the art to understand the objects, features, and characteristics of the present invention, but not to be used to confine the scope and spirit of the present invention defined in the appended claims.  
      With reference to  FIGS. 1 and 3 , the safety switch of a screwdriver of the present invention is illustrated. The safety switch includes a driver body  10 , a trigger  20 , a safety rod  30 , and a push unit  40 .  
      The trigger  20  is pivotally installed on the driver body  10 . A receiving space  21  is formed within the trigger  20  for receiving the push unit  40 . A front end of each of two sides of the trigger  20  has a first pivotal hole  22 . A pivotal post  50  passes through a first positioning hole  11  and the first pivotal hole  22  so as to fix the trigger  20  to the driver body  10 . A lower predetermined position of the first pivotal hole  22  is formed with two longitudinal slits  23 . Furthermore, a slot  24  is formed aside the two slits  23 . A through hole  25  is formed aside the slot  24  far away from the slits  23  for positioning a second pin  52 .  
      The safety rod  30  contains a touch end  31  and a push end  32 . The touch end  31  is installed at a front end of the driver body  10 . The push end  32  is installed in front of the trigger  20 . The push end  32  is movable into and out of the trigger  20  for pushing the push unit  40 .  
      The push unit  40  is installed by a torsion spring  41 , a buckle  42 , an ejecting unit  43 , and an elastomer  44 . The torsion spring  41  encloses the pivotal post  50 . One end of the torsion spring  41  resists against the driver body  10  and another end thereof resists against the buckle  42 . By the elastic potential of the torsion spring  41 , the torsion spring  41  will push the buckle  42  to return the trigger  20 .  
      Each of the two sides of the buckle  42  is protruded with two blocks  42   a  for inserting into the slits  23  of the trigger  20 . When being pushed by the push end  32  of the safety rod  30 , the blocks  42   a  insert into the slits  23 . Moreover, a lateral side of the buckle  42  is formed with a buckling hole  42   b  for buckling the ejecting unit  43 .  
      The ejecting unit  43  has a trench  43   a  at a middle portion thereof. A first pin  51  is pivotally installed in the slots  24  of the trigger  20 . One end of the ejecting unit  43  is a protrusion  43   b  for resisting against the buckling hole  42   b  of the buckle  42 . A hook hole  43   c  is formed at a rear and lower end of the ejecting unit  43  for hooking the ejecting unit  43 . Besides, a lateral surface of the ejecting unit  43  is a bevel  43   d  which resists against a valve rod  12  of the driver body  10  for triggering a nail.  
      A front end of the ejecting unit  43  has a front hook  44   a  and a rear end thereof has a rear hook  44   b . The front hook  44   a  hooks hook hole  43   c  of the ejecting unit  43  and the rear hook  44   b  hooks the second pin  52 .  
      The structural feature of the present invention is the bevel  43   d  formed on the ejecting unit  43 . When the trigger  20  applies a force to the ejecting unit  43 , the bevel  43   d  of the ejecting unit  43  will generate a horizontal and a vertical force component. When one component is cancelled by the buckle  42 , the ejecting unit  43  moves so as to push the valve rod  12  so trigger the screwdriver.  
      Referring to FIGS.  3  to  5 , in operation, generally, the push end  32  of the safety rod  30  is pressed. Then the push end  32  will push the buckle  42  to move to the side of ejecting unit  43 . When the trigger  20  is pressed, the protrusion  43   b  of the ejecting unit  43  will move forwards to be buckled into the buckling hole  42   b  so that the push unit  40  pushes the valve rod  12  to trigger the screwdriver.  
      With reference to  FIG. 5 , if the trigger  20  is pressed firstly, the ejecting unit  43  will move to be at a front side of the valve rod  12  so as not to push the valve rod  12 . When the safety rod  30  is pressed again, although the buckle  42  is pushed to move, the valve rod  12  cannot be triggered so as to have a safety effect.  
      As above mentioned, in the present invention, by the bevel  43   d  of the ejecting unit  43 , and by the simple structure of the ejecting unit  43  and the buckle  42 , the present invention can be assembled easily and rapidly. As a result, the cost is reduced and the yield ratio is improved. In the present invention, by the principle of dynamics and elastic potential of the elastomer, the object of safety operation is achieved.  
      The present invention is thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.