Abstract:
A rotary tool, such as an impact wrench, includes a housing having a forward end and supporting a motor. The motor has a motor shaft extending axially through the housing and defining an axis. The rotary tool further includes a frame coupled to the motor shaft and rotatable relative to the housing about the axis in response to rotation of the motor shaft. The frame defines an interior space. The rotary tool also includes a piston supported by the frame and moveable axially in the interior space and an output shaft supported in the forward end of the housing and rotatable about the axis. The output shaft has a plurality of cams. The piston is engageable with the plurality of cams to intermittently hammer the output shaft.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to rotary tools and, more particularly, to a drive system for a rotary tool.  
         BACKGROUND OF THE INVENTION  
         [0002]    A rotary tool, such as an impact wrench, generally includes a housing supporting a motor, a drive mechanism driven by the motor, an output shaft having a first end adapted to engage a fastener and a second end adapted to engage the drive mechanism. In impact wrenches, the drive mechanism generally includes a hammer member, which periodically impacts the output shaft, rotating the output shaft about a central axis to hammer or drive fasteners into or remove fasteners from a work piece.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention provides a rotary tool, such as an impact wrench. In one construction, the rotary tool includes a housing having a forward end and supporting a motor. The motor has a motor shaft extending axially through the housing and defining an axis. A frame is coupled to the motor shaft and is rotatable relative to the housing about the axis in response to rotation of the motor shaft. The frame defines an interior space. A piston is supported by the frame and is moveable axially in the interior space. An output shaft is supported in the forward end of the housing and is rotatable about the axis. The output shaft has a plurality of cams. The piston is engageable with the plurality of cams to intermittently deliver torque impulses to the output shaft.  
           [0004]    In another construction, the output shaft includes a rearward surface and the plurality of cams extend axially from the rearward surface. The piston includes an axially extending portion and the output shaft defines an aperture. The axially extending portion is receiveable in the aperture.  
           [0005]    In yet another construction, the frame defines an axially extending groove and the piston includes a plurality of radially extending arms. The plurality of radially extending arms are engageable in the axially extending groove to transfer rotational motion from the frame to the piston.  
           [0006]    In still another construction, the rotary tool includes a housing having a forward end and supporting a motor. The motor has a motor shaft extending axially through the housing and defining an axis. A frame is coupled to the motor shaft and is rotatable relative to the housing about the axis in response to rotation of the motor shaft. The frame has a first end and a second end and defines an interior space between the first end and the second end. A piston is supported in the frame and is moveable axially in the interior space between a retracted position, in which the piston is adjacent the second end, and an extended position, in which the piston is spaced a distance from the second end. An output shaft is supported in the forward end of the housing and is rotatable about the axis. The piston is engageable with the output shaft to deliver torque impulses to the output shaft about the axis when the piston is in the extended position.  
           [0007]    In another construction, the rotary tool includes a housing having a forward end and supporting a motor. The motor has a motor shaft extending axially through the housing and defining an axis. A frame is coupled to the motor shaft and is rotatable relative to the housing about the axis in response to rotation of the motor shaft. The frame defines an internal space. A piston is supported in the internal space for rotation with the frame about the axis. An output shaft is supported in the forward end of the housing and is rotatable about the axis. One of the output shaft and the piston has a protrusion. Another of the output shaft and the piston has a contoured recess. The protrusion is engageable in the recess to rotatably couple the output shaft and the piston. The protrusion cammingly engages the contoured recess to reciprocate the piston along the axis.  
           [0008]    The present invention also provides a method of operating the rotary tool.  
           [0009]    Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The present invention is further described with reference to the accompanying drawings, which show constructions of the present invention. However, it should be noted that the invention as disclosed in the accompanying drawings is illustrated by way of example only. The various elements and combinations of elements described below and illustrated in the drawings can be arranged and organized differently to result in constructions which are still within the spirit and scope of the present invention.  
         [0011]    In the drawings, wherein like reference numerals indicate like parts:  
         [0012]    [0012]FIG. 1 is a side view, partially in section, of a rotary tool embodying the present invention.  
         [0013]    [0013]FIGS. 2A and 2B are side views, partially in section, of a portion of a rotary drive system of the rotary tool shown in FIG. 1.  
         [0014]    [0014]FIG. 3 is an exploded view, partially in section, of the portion of the rotary drive system shown in FIGS. 2A and 2B.  
         [0015]    [0015]FIG. 4 is a side view, partially in section, of a housing of the rotary drive system shown in FIGS. 2A and 2B.  
         [0016]    [0016]FIG. 5 is a side view, partially in section, of a frame of the rotary drive system shown in FIGS. 2A and 2B.  
         [0017]    [0017]FIGS. 6A-6D illustrate a piston of the rotary drive system shown in FIGS. 2A and 2B.  
         [0018]    [0018]FIGS. 7A-7D illustrate an output shaft of the rotary drive system shown in FIGS. 2A and 2B.  
         [0019]    [0019]FIGS. 8A-8D are side views of the portion of the rotary drive system shown in FIGS. 2A and 2B operating in a forward mode.  
         [0020]    [0020]FIGS. 9A-9D are sectional views of the portion of the rotary drive system shown in FIGS. 2A and 2B operating in a forward mode. 
     
    
     DETAILED DESCRIPTION  
       [0021]    As used herein and in the appended claims, the terms “upper”, “lower”, “first”, “second”, “third”, “forward”, and “rearward” are used herein for description only and are not intended to imply any particular orientation, order, or importance.  
         [0022]    [0022]FIG. 1 illustrates a rotary tool  10 , such as, for example, an impact wrench embodying aspects of the present invention. The rotary tool  10  includes a housing  12  having a forward portion  16  and a rearward portion  18 , an operator&#39;s grip or handle  20 , a motor  22  (e.g., an air motor) having a motor shaft  24 , a trigger  26  operably coupled to the motor  22  to control motor speed, and a rotary drive system  28 . The motor shaft  24  defines a central axis A, which extends axially through the rotary tool  10 .  
         [0023]    The handle  20  includes an air channel  32  having an inlet  34 . In some constructions (not shown), the air channel  32  includes seals (e.g., O-rings, washers, etc.), filters (e.g., air strainers), and valves (e.g., spring-operated valves) for controlling air quality into and airflow through the rotary tool  10 . Additionally, in some constructions (not shown), the air channel  32  includes a throttle valve (not shown) that is operably connected to the trigger  26  for controlling the flow of air through the air channel  32 , the operating speed of the rotary tool  10 , and/or the torque generated by the rotary tool  10 . Also, in rotary tools  10  having forward and reverse modes, a reverse valve (not shown) may be positioned along the air channel  32  to direct air flow through the motor  22  in either of two directions (i.e., forward and reverse).  
         [0024]    The rearward portion  18  of the housing  12  defines a cavity  36  surrounding the motor  22 . The motor shaft  24  extends through the cavity  36  along the central axis A and is supported by bearings  38 ,  40  for rotation relative to the housing  12 . Pressurized air from the air channel  32  enters the rearward end of the cavity  36  and travels across the motor  22 , causing the motor  22  to rotate about the central axis A in a conventional manner. In some constructions, the cavity  36  is sealed (e.g., the cavity includes O-rings, washers, valves, etc.) to prevent unintended air exchange with the atmosphere. One having ordinary skill in the art will appreciate that while one type of air motor has been described herein and is shown in the figures, other types of air motors (not shown) could also or alternately be used. In other constructions (not shown), electric motors (not shown) could also or alternately be used.  
         [0025]    Fasteners (not shown) extend through the forward portion  16  of the housing  12  and into bores  42  located in the rearward portion  18  of the housing  12 , coupling the forward and rearward portions  16 ,  18  of the housing  12 . A seal (e.g., an O-ring, a washer, etc.)  46  is arranged between the forward and rearward portions  16 ,  18  to prevent airflow into or out of the housing  12  between the forward and rearward portions  16 ,  18 .  
         [0026]    With reference to FIGS. 1, 2A,  2 B,  3 ,  5 , and  8 A- 8 D, the rotary drive system  28  includes a flywheel or frame  44  supported in the forward portion  16  of the housing  12  for rotation about the central axis A. The frame  44  is a substantially cylindrical member having a forward surface  48 , a rearward surface  50  substantially parallel to the forward surface  48 , and a circumferential wall  52  extending therebetween. Together, the circumferential wall  52  and the interior surface of the forward portion  16  of the housing define a space  54 , which accommodates rotational movement of the frame  44  relative to the forward portion  16  of the housing  12 .  
         [0027]    With reference to FIG. 1, the rearward face  50  defines a recess  56  having a number of splines  60  extending radially into the recess  56 . A forward end of the motor shaft  24  includes splines  64 , which matingly engage corresponding splines  60 , operably coupling the frame  44  and the motor shaft  24  for concurrent rotation about the central axis A in either a forward (e.g., clockwise) or rearward (e.g., counterclockwise direction).  
         [0028]    As shown in FIGS. 1, 2A,  2 B,  3 ,  5 , and  8 A- 8 D, the forward and rearward surfaces  48 ,  50  of the frame  44  define an internal space  67  housing a quantity of lubricant (not shown). The interior surface  66  of the circumferential wall  52  includes first and second shoulders  68 ,  69  that extend radially into the internal space  67 . As shown in FIG. 5, the area of the internal space  67  rearward the second shoulder  69  has a first diameter D 1 , the area between the first and second shoulders  68 ,  69  has a second diameter D 2 , and the area forward the second shoulder  69  has a third diameter D 3 . As shown in FIGS. 2A, 3, and  5 , axial grooves  70  extend into the circumferntial surface  52  between the first and second shoulders  68 ,  69 . In some constructions, the frame  44  includes two axial grooves  70  spaced approximately 180 degrees apart. In other constructions (not shown), the frame  44  may include one, three, or more axial grooves  70  and the axial grooves  70  can be arranged in any of a number of configurations and orientations.  
         [0029]    The forward surface  48  defines a forward opening  71  communicating with the interior space  67 . A cover  72  is coupled to (e.g., threaded into, clamped onto, or otherwise fastened to) the forward surface  48  to seal the internal space  67 . In the illustrated construction, the cover  72  is threaded into forward surface  48  and a seal  74  (e.g., an O-ring, a washer, etc.) is clamped between the second shoulder  69  and the cover  72  to prevent fluid exchange between the internal space  67  and the space  54 . The cover  72  also defines an internal opening  76  opening along the central axis A and including a seal  78 .  
         [0030]    A bleed line  80  extends through the frame  44  for conveying lubricant from one portion of the internal space  67  to another portion of the internal space  67  (as described below). In the illustrated construction (see FIGS. 2A, 3, and  5 ), the bleed line  80  includes an axial channel  82  extending axially through the frame  44 , and a radial channel  84  that extends radially through the frame  44  and intersects the axial channel  82 . As shown in FIG. 2B, plugs  86  (e.g., a ball bearing, a threaded plug, etc.) seal two ends of the axial channel  82 . A first opening  88  of the axial channel  82  communicates with the internal space  67  and a second opening  90  of the axial channel  82  intersects an end of the radial channel  84 . An opening  83  of the radial channel  84  communicates with the internal space  67 . A valve (e.g., a needle valve)  96  is positioned in the radial channel  84  and is operable to selectively restrict and/or prevent fluid flow through the bleed line  80  (as explained in greater detail below). An operator and/or the manufacturer can increase or decrease fluid flow through the bleed line  80  by inserting a tool (e.g., a screwdriver, a wrench, etc.) through an opening  98  (shown in FIGS. 1, 2B,  3 , and  4 ) in the forward portion  16  of the housing  12  to adjust the position of the valve  96 .  
         [0031]    As shown in FIGS. 1, 2A,  2 B, and  8 A- 8 D, an output shaft or anvil  100  extends through the cover  72  and is supported in the forward portion  16  of the housing  12  by bushing  102  for rotation about the central axis A. However, in other constructions (not shown), other support structure, such, as for example, bearings can also or alternately support the output shaft  100 . Additionally, in other constructions (not shown) the output shaft  100  can be arranged to rotate about a second axis that is substantially parallel, or alternatively, at an angle relative to the central axis A.  
         [0032]    With reference to FIGS. 1, 2A,  2 B,  3 ,  7 A,  7 B,  7 D, and  8 A- 8 D, the output shaft  100  is substantially cylindrical and includes a forward or tool engaging end  104  that is adapted to support a fastener (e.g., a bolt, a screw, a nut, etc.) and/or a fastener engaging element (e.g., a socket). A base portion  106  of the output shaft  100  extends into the internal space  67  and includes two rearwardly extending cams  108 . In other constructions (not shown), the base portion  106  can include one, three, or more cams  108 . As shown in FIGS. 1 and 2B, the base portion  106  rests against the second shoulder  69 . Additionally, in some constructions, the diameter of the base portion  106  is substantially similar to the second diameter D 2  and the base portion  106  closely engages the circumferential wall  52  to prevent lubricant from leaking between the second shoulder  69  and the base portion  106 . The base portion  106  also defines an aperture  110  that extends axially into the output shaft  100  along the central axis A.  
         [0033]    As shown in FIGS. 1, 2A,  2 B, and  3 , in some constructions, seals  112  (washers, O-rings, etc.) are positioned between the cover  72 , the base portion  106  and/or the circumferntial surface  52  to prevent lubricant from exiting the internal space  67  via the forward opening  71 . Additionally, in some constructions, friction-reducing members  113  (e.g., bearings, low-friction washers, etc.) are positioned between the cover  72  and the base portion  106 .  
         [0034]    A piston (shown in FIGS. 1, 2A,  2 B,  3 ,  6 A- 6 D, and  8 A- 8 D)  114  includes a first end  116  and a second end  118  and is supported in the internal space  67  for rotational movement with the frame  44  about the central axis A and for reciprocating movement relative to the frame  44  along the central axis A. The first end  116  of the piston  114  is substantially cylindrical and is rotatably received in the aperture  110  at the base  106  of the output shaft  100 . A notch  120  extends circumferentially around the first end  116 . As shown in FIGS. 3, 6A, and  6 B, a forward end  122  of the notch  120  is contoured and includes a protrusion  147 . A fastener (e.g., a set screw, a key, a snap ring, etc.) and/or a radially extending protrusion  126  extends through an opening  128  (shown in FIG. 3) in the output shaft  100  and engages the notch  120  on the first end  116  of the piston  114  to slidably and rotatably couple the output shaft  100  and the piston  114 . Together, the notch  120  and the fastener  126  limit axial movement of the piston  114  along the output shaft  100 . More particularly, the piston  114  is moveable along the central axis A between a fully retracted position (shown in FIGS. 8A and 9A) and a fully extended position (shown in FIGS. 8B and 9B) and the distance between the fully retracted and fully extend positions is approximately equal to the axial length of the notch  120 . Additionally, the mating engagement of the fastener  126  and the notch  120  facilitate relative rotational motion between the piston  114  and the output shaft  100 .  
         [0035]    The second end  118  of the piston  114  is substantially cylindrical and has a diameter D 4  (see FIGS. 6A, 6C, and  6 D), which is substantially similar to the first diameter D 1 . More specifically, the second end  118  closely engages the circumferential wall  52 , preventing or reducing the flow of lubricant between the circumferential wall  52  and the second end  118  of the piston  114 .  
         [0036]    As shown in FIGS. 2A, 3,  6 A,  6 D,  8 A- 8 D and  9 A- 9 D, arms  132  (two arms  132  are shown) extend radially from the piston  114  between the first and second ends  116 ,  118 . In other constructions (not shown), the piston  114  can include one, three, or more arms  132 . The arms  132  engage axial grooves  70 , facilitating the transfer of rotational motion from the frame  44  to the piston  114 . Additionally, as described below, the arms  132  are moveable along the axial grooves  70  to facilitate axial movement of the piston  114  relative to the frame  44 . The mating engagement between the arms  132  and the axial groves  70  also prevents the piston  114  from pivoting about the central axis A relative to the frame  44 .  
         [0037]    As shown in FIGS. 1 and 8A- 8 D, the second end  118  of the piston  114  divides the internal space  67  into a first or forward chamber  134  and a second or rearward chamber  136 . Lubricant is moveable between the first and second chambers  134 ,  136  along the bleed line  80 , or alternatively, along a channel  138  (see FIG. 6D). As shown in FIGS. 3 and 6D, channel  138  extends axially through the second end  118  of the piston  114  and radially outwardly through a central portion of the piston  114  between the arms  132 , fluidly connecting the first and second chambers  134 ,  136 .  
         [0038]    As shown in FIGS. 1, 2B, and  3 , valve  96  is positioned along the bleed line  80  to control the flow of lubricant between the first and second chambers  134 ,  136 . As shown in FIGS. 1, 2A,  2 B,  3 ,  6 A- 6 D, and  8 A- 8 D, feet  140  extend axially from the second end  118  of the piston  114  and support valve  142 . As explained in greater detail below, valve  142  is operable to control the flow of lubricant along channel  138 . In the illustrated construction, valve  142  is a ball valve. However, in other constructions (not shown), other known valves can also or alternatively be used to control the flow of lubricant through channel  138 .  
         [0039]    During operation of the rotary tool  10 , the tool engaging end  104  (or a fastener engaging element coupled to the tool engaging end  104 ) is positioned to matingly engage a fastener (e.g., a nut, a bolt, a screw, etc.). To tighten the fastener or thread the fastener into a work piece (not shown), the rotary tool  10  is operated in a forward mode and to loosen the fastener or unthread the fastener from the work piece, the rotary tool  10  is operated in a reverse mode. FIGS. 8A-8D and  9 A- 9 D and the following description refer to operation of the rotary tool  10  in the forward mode. However, one having ordinary skill in the art will appreciate that the rotary tool  10  of the present invention can also or alternately be operated in a reverse mode and that operation of the rotary tool  10  in the reverse mode is substantially similar to operation of the rotary tool  10  in the forward mode.  
         [0040]    To initiate operation of the rotary tool  10 , an operator depresses the trigger  26 , causing power in the form of compressed air or electricity to energize the motor  22  and to rotate the motor shaft  24  in a forward direction (represented by arrow  146  in FIGS. 8A-8D and  9 A- 9 D) about the central axis A. The motor shaft  24  transfers rotational motion to the rotary drive system  28  via the mating engagement of splines  60 ,  64 .  
         [0041]    With reference first to FIGS. 8A and 9A, the piston  114  is in a fully retracted position (i.e., the piston  114  is in a rearward-most position in the internal space  67 ), and the fastener  126  engages a rearward-most position in the notch  120 . Additionally, the valve  142  is in a closed position, preventing lubricant from moving through the channel  138  between the forward and rearward chambers  134 ,  136 . Also, when the piston  114  is in the fully retracted position, the pressure of the lubricant in the forward and rearward chambers  134 ,  136  is approximately equal.  
         [0042]    With reference to FIGS. 8B and 9B, as the motor  22  begins to rotate the frame  44  about the central axis A, the frame  44  transfers rotational motion to the piston  114  via the mating engagement between the arms  132  and the grooves  70 . The notch  120  on the first end  116  of the piston  114  travels along the fastener  126  as the piston  114  rotates about the central axis A. As the contoured end  122  of the notch  120  travels across the fastener  126 , the fastener  126  pulls the piston  114  forward along the central axis A toward the base portion  106  of the output shaft  100 . In this manner, the piston  114  simultaneously rotates about the central axis A in the forward direction  146  and moves forward along the central axis A toward the output shaft  100 . As the piston  114  is pulled forward by the engagement between the fastener  126  and the contoured end  122  of the notch  120 , valve  142  moves from a first or closed position to a second or open position. In particular, as the piston  114  is pulled forward, the pressure in the forward chamber  134  increases. The increased pressure in the forward chamber  134  forces the ball portion of valve  142  rearwardly with respect to the second end  118  of the piston  114 , allowing lubricant to move through the channel  138  from the forward chamber  134  to the rearward chamber  136 .  
         [0043]    As the piston  114  continues to rotate about the central axis A, the fastener  126  rides along the contoured end  122 , moving the piston  114  forward along the central axis A to a forward-most position (shown in FIGS. 8B and 9B). When the piston  114  is in the forward-most position, forward portions of the arms  132  contact the base  106  of the output shaft  100 . In the illustrated construction, the contoured end  122  of the notch  120  includes protrusion  147 . In this construction, each time the piston  114  rotates about the central axis A, the fastener  126  engages the protrusion  147  once. More particularly, each time that the piston  114  rotates about the central axis A, the engagement between the protrusion  147  and the fastener  126  causes the arms  132  to contact the cams  108 . In other constructions (not shown), the notch  120  can have two, three, or more protrusions  147  for causing the arms  132  to contact the cams  108  two or more times each time the piston  114  rotates about the central axis A.  
         [0044]    With reference to FIGS. 8C and 9C, as the piston  114  moves forward along and rotates about the central axis A, the arms  132  are rotated into engagement with the cams  108  on the base  106  of the output shaft  100 . The impact between the arms  132  and the cams  108  transfers an impulse or force from the piston  114  to the output shaft  100 , causing the output shaft  100  to rotate about the central axis A in the forward direction  146 . The impact between the arms  132  and the cams  108  also causes the piston  114  to rebound a relatively short distance rearwardly along the central axis A and to rotate a relatively short distance about the central axis A in the reverse direction  148 . The rearward motion of the piston  114  causes an increase in pressure in the rearward chamber  136 . More particularly, in some constructions, the pressure in the rearward chamber  136  reaches between 1000 psi and 4000 psi (e.g., 3000 psi). After the initial impact, the forward rotation of the frame  44  about the central axis A, and in some cases, the increase in pressure in the rearward chamber  136 , causes the arms  132  to remain in contact with the cams  108  to transfer rotational energy to the output shaft  100 .  
         [0045]    Additionally, after the impact between the cams  108  and the arms  132 , the piston  114  begins to move rearwardly, disengaging the arms  132  from the cams  108 . More particularly, as shown in FIGS. 8D and 9D, as the piston  114  moves rearwardly along the central axis A, the arms  132  are moved rearwardly away from the cams  108  so that the arms  132  pass the second side of the cams  108  without contacting the cams  108 .  
         [0046]    As the piston  114  continues to rotate about the central axis A, the pressure difference between the forward and rearward chambers  134 ,  136  forces lubricant from the rearward chamber  136 , through bleed line  80 , past valve  96 , and into the forward chamber  134 . In this manner, the pressure in the rearward chamber  136  is reduced, allowing the piston  114  to move axially to the rearward-most position. Lubricant continues to move along the bleed line  80  from the rearward chamber  136  to the forward chamber  134  until the pressure of the forward and rearward chambers  134 ,  136  is approximately equal. In the illustrated construction, the pressure in the forward and rearward chambers  134 ,  136  is approximately equal when the arms  132  pass across the cams  108 .  
         [0047]    Once the piston  114  returns to the rearward-most position, the piston  114  continues to rotate with the frame  44  about the central axis A until the engagement between the notch  120  and the fastener  126  causes the piston  114  to move forwardly along the central axis A. In the illustrated construction, the piston  114  rotates approximately 200 degrees about the central axis A before the fastener  126  engages the protrusion  147  to re-initiate forward motion of the piston  114 . However, as explained above, in other constructions (not shown), the notch  120  can include two, three, or more protrusions  147 . In these constructions, the piston  114  can rotate less than 200 degrees before the mating engagement between the fastener  126  and one of the protrusions  147  causes the piston  114  to move forwardly along the central axis A.  
         [0048]    The constructions described above and illustrated in the drawings are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art, that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims.  
         [0049]    For example, one having ordinary skill in the art will appreciate that the size and relative dimensions of the individual parts of the rotary tool can be changed significantly without departing from the spirit and scope of the present invention.  
         [0050]    As such, the functions of the various elements and assemblies of the present invention can be changed to a significant degree without departing from the spirit and scope of the present invention.