Patent Abstract:
An impact driver includes a sleeve, a striking unit and a chuck. The sleeve includes a bore with an open end and a polygonal section near the open end. The striking unit can strike a bit partially inserted in the sleeve through the open end. The chuck includes a ring, a tube, a spring and a ball. The tube includes a polygonal section movably inserted in the polygonal section of the bore of the sleeve, a circular section extended through the ring, an annular rib formed thereon, a polygonal bore for receiving the bit, and at least one aperture in communication with the polygonal bore. The spring is compressed between the annular rib and the sleeve. The ball includes a portion placed in the aperture and another portion movable into the polygonal bore.

Full Description:
BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to a driver and, more particularly, to an impact driver. 
     2. Related Prior Art 
     An impact driver is a tool that delivers a strong, sudden rotational and downward force. In conjunction with a toughened screwdriver bit or a socket, an impact driver is often used to loosen a large threaded bolt or nut that is corrosively “frozen” or over-torqued. The direction can be reversed for situations where screws have to be tightened with torque greater than a screwdriver can reasonably provide. 
     A manual impact driver includes a sleeve provided around a core. The sleeve is much heavier than the core. The sleeve includes a spline formed on an internal face. The core includes a curved groove defined in the periphery. The spline is inserted in the curved groove. Thus, a user can hold the sleeve with one hand and use a hammer to strike the sleeve with the other hand to exert a turning force on the core and any bit attached to the core. The tool translates the movement of the sleeve to the rotation of the core to generate large values of torque. At the same time, the striking blow from the hammer forces the impact driver and the bit down into the screw. 
     Another type of impact driver uses a motor to automatically deliver rotational forces. These have the advantage of greatly increased speed. They are most often used in construction and manufacturing to replace screwdrivers where speed and operator fatigue are an issue. In some situations however, this type falls short since current designs cannot deliver the downward blow of a manual unit. This can be especially true on very stubborn fasteners. It is a common misconception that motorized impact drivers deliver a downward force when in fact they deliver no downward force at all. 
     The prior art is focused on provide adequate torque for driving a screw. There is however an important and unaddressed issue to drive a screw into a piece of material precisely in a desired position and direction. 
     The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art. 
     SUMMARY OF INVENTION 
     It is the primary objective of the present invention to provide an impact driver for driving a screw into a piece of material precisely in a desired position and direction. 
     To achieve the foregoing objectives, the impact driver includes a sleeve, a striking unit and a chuck. The sleeve includes a bore with an open end and a polygonal section near the open end. The striking unit can strike a bit partially inserted in the sleeve through the open end. The chuck includes a ring, a tube, a spring and a ball. The ring is connected to the sleeve. The tube includes a polygonal section movably inserted in the polygonal section of the bore of the sleeve, a circular section extended through the ring, an annular rib formed thereon, a polygonal bore for receiving the bit, and at least one aperture in communication with the polygonal bore. The spring is compressed between the annular rib and the sleeve. The ball includes a portion placed in the aperture and another portion movable into the polygonal bore. 
     Other objectives, advantages and features of the present invention will be apparent from the following description referring to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention will be described via detailed illustration of two embodiments referring to the drawings wherein: 
         FIG. 1  is an exploded view of an impact driver according to the first embodiment of the present invention; 
         FIG. 2  is a cross-sectional view of the impact driver shown in  FIG. 1 ; 
         FIG. 3  is a side view of a bit attached to the impact driver shown in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the impact driver in another position than shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of the impact driver in another position than shown in  FIG. 4 ; 
         FIG. 6  is a cross-sectional view of an impact driver according to the second embodiment of the present invention; and 
         FIG. 7  is a side view of an automatic tool for actuating the impact driver shown in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Referring to  FIGS. 1 through 5 , there is shown an impact driver according to a first embodiment of the present invention. The impact driver includes a sleeve  10 , a striking unit  20  and a chuck  50 . The striking unit  20  includes a guiding element  21 , a hammer  30  and a pusher  40 . The chuck  50  includes a ring  51 , a tube  60  and two balls  70 . 
     The sleeve  10  includes a bore  15  axially defined therein. The bore  15  includes a first polygonal section  12 , a first circular section  13 , a second circular section  11  and a second polygonal section  18 . The first polygonal section  12  is preferably a hexagonal section. The diagonal line of the first polygonal section  12  is shorter than the diameter of the first circular section  13  that is longer than the diameter of the second circular section  11 . The second polygonal section  18  is preferably a hexagonal section. The distance between any two opposite facets of the second polygonal section  18  is longer than the diameter of the second circular section  11 . There is a thread  19  extending on the periphery of the sleeve  10  near the open end  17 . 
     A polygonal rod  14  is fit in the first polygonal section  12  so that the bore  15  includes a closed end  16  near the first polygonal section  12  blocked by the polygonal rod  14 . The bore  15  further includes an open end  17  near the second polygonal section  18 . 
     The guiding element  21  is an annular element with two a bore  23  axially defined therein. The bore  23  includes two sections. The diameter of the first section of the bore  23  is shorter than that of the second section of the bore  23 . The guiding element  21  further includes a first conical concave face  22  at an end near the first section of the bore  23  and a second conical concave face  22  between the first and second sections of the bore  23 . 
     The hammer  30  includes a first section  33  and a second section  32 . The diameter of the first section  33  is longer than that of the second section  32 . The length of the first section  33  is shorter than that of the second section  32 . A bore  34  is defined in the hammer  30  axially. The bore  34  includes an open end in the first section  33  and a closed end in the second section  32 . 
     The pusher  40  includes a first section  43 , a second section  42  and a third section  44 . The diameter of the first section  43  is shorter than that of the second section  42 . The diameter of the second section  42  is shorter than that of the third section  44 . The length of the first section  43  of the pusher  40  is longer than the depth of the bore  34  of the hammer  30  for reasons to be given. 
     The ring  51  includes a bore  53  axially defined therein. The bore  53  includes two sections. The diameter of the first section of the bore  53  is longer than that of the second section of the bore  53 . A shoulder  54  is formed between the first and second sections of the bore  53 . The ring  51  further includes a thread  52  extending on a portion of the wall of the first section of the bore  53 . 
     The tube  60  is a tubular element. On the outside, the tube  60  includes an annular rib  61  formed between a circular section  62  and a polygonal section  63 . On the inside, the tube  60  includes a polygonal bore  65  axially defined therein, a circular bore  66  axially defined therein, and two apertures  67  defined therein in a radial manner. The polygonal bore  65  extends throughout the circular section  62  of the tube  60  and extends in a portion of the polygonal section  63  of the tube  60 . The circular bore  66  is axially defined in the other portion of the polygonal section  63  of the tube  60 . 
     Referring to  FIG. 2 , a spring  31  and the hammer  30  are placed in the first circular section  13  of the sleeve  10 . The spring  31  is compressed between the closed end  16  of the chamber of the sleeve  10  and the second section  32  of the hammer  30 . The guiding element  21  is fit in second circular section  11 , near the first circular section  13 . Thus, the spring  31  and the hammer  30  are kept in the first circular section  13  of the sleeve  10 . 
     The sections  43  and  42  of the pusher  40  are inserted in a spring  41 . An end of the spring  41  and the first section  43  of the pusher  40  are sequentially placed in the second section of the bore  23  of the guiding element  21 . The spring  41  is compressed between the second conical face  22  and the third section  44  of the pusher  40 . It should be noted that the pusher  40  is not coaxial with the guiding element  21  and the hammer  30 . 
     The polygonal section  63  of the tube  60  is inserted in the second polygonal section  18  of the sleeve  10  through a spring  64 . The spring  64  is compressed between the open end  17  of the sleeve  10  and the annular rib  61  of the tube  60 . The sections  42  and  44  of the pusher  44  are placed in the circular bore  66  of the tube  60 . Each of the balls  70  and a spring  71  are sequentially placed in a respective one of the apertures  67 . 
     The ring  51  is placed around the tube  60  and the sleeve  10 . The thread  52  of the ring  51  is engaged with the thread  19  of the sleeve  10 . Thus, the pusher  40 , the holder  60 , the balls  70  and the springs  41 ,  64  and  71  are kept in position. 
     Referring to  FIG. 3 , a root of a bit  80  is inserted in the polygonal bore  65  of the tube  60  while a tip  82  of the bit  80  is placed outside the tube  60 . The root of the bit  80  is biased against the third section  44  of the pusher  40 . A reduced portion  81  of the bit  80  is pinched by the balls  70  biased by the springs  71 . Although not shown, the tip  82  of the bit  80  is placed against a head of a screw while a tip of the screw is placed against a piece of wood or metal such as aluminum. Although not shown, the polygonal rod  14  is connected to an automatic tool such as a pneumatic or electric tool. 
     In operation, the automatic tool is pushed toward the piece of wood or metal. The screw is abutted against the piece of wood or metal by the bit  80 . The bit  80  is kept in position by the screw. The tube  60  is moved further into the sleeve  10  by the bit  80  because the tube  60  sticks to the balls  70  that are trapped by the reduced portion  81  of the bit  80 . Thus, the spring  64  is further loaded. Eventually, the spring  64  is adequately loaded to overcome the springs  71  to push the balls  70  out of the reduced portion  81  of the bit  80  and move the tube  60  away from the sleeve  10  as shown in  FIG. 4 . Again, the bit  80  is held firmly in position by the tube  60 . 
     The pusher  40  is moved by the bit  80 . The spring  41  is further loaded by the pusher  40 . The hammer  30  is moved by the pusher  40  since they are not coaxial with each other. The spring  31  is further loaded by the hammer  30 . 
     Referring to  FIG. 5 , the second conical face  22  of the guiding element  21  guides the second section  42  of the pusher  40  so that the pusher  40  is coaxial with the hammer  30  to allow insertion of the first section  43  of the pusher  40  into the bore  34  of the hammer  30 , i.e., to allow the spring  31  to move the hammer  30  toward the pusher  40  fast. Eventually, the hammer  30  strikes the pusher  40 . The pusher  40  strikes the bit  80 . The bit  80  strikes the screw. The screw makes a dent in the piece of wood or metal precisely in a desired position. The automatic tool is actuated to drive the screw into the piece of wood or metal via the impact driver. 
     With the previous production of the dent, the screw is driven in the piece of wood or metal precisely in the desired position. Moreover, with the previous with the previous production of the dent, the screw is driven in the piece of wood or metal precisely in the desired direction, i.e., the axis of the screw is perpendicular to the surface of the piece of wood or metal. 
     Referring to  FIG. 6 , there is shown an impact driver according to a second embodiment of the present invention. The second embodiment is like the first embodiment except including a sleeve  90  instead of the sleeve  10 . The sleeve  90  is like the sleeve  10  except that the bore  15  includes a polygonal section  91  instead of the polygonal section  12 . The polygonal section  91  is a square bore. There is a recess  93  defined in one of four facets  92  of the polygonal section  91 . 
     Referring to  FIG. 7 , there is shown an extensive element formed with a hexagonal section  94 , a square section  95  and a spring-biased ball attached to the square section  95 . The square section  94  of the extensive element can be inserted in the square section  91  while the spring-biased ball can be placed in the recess  93 . 
     There is shown an automatic tool  96  that includes a square axle  97  and a spring-biased ball attached to the square axle  97 . Alternatively, the square axle  97  can be inserted in the square section  91  while the spring-biased ball can be placed in the recess  93 . 
     The present invention has been described via the detailed illustration of the embodiments. Those skilled in the art can derive variations from the embodiments without departing from the scope of the present invention. Therefore, the embodiments shall not limit the scope of the present invention defined in the claims.

Technology Classification (CPC): 1