Abstract:
An impact tool includes a housing, a motor supported in the housing and defining a first axis, an output shaft rotatably supported in the housing about a second axis oriented substantially normal to the first axis, and an impact mechanism coupled between the motor and the output shaft and operable to impart a striking rotational force to the output shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/414,296 filed on Nov. 16, 2010, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to tools, and more particularly to power tools. 
     BACKGROUND OF THE INVENTION 
     Impact tools or wrenches are typically utilized to provide a striking rotational force, or intermittent applications of torque, to a tool element and workpiece (e.g., a fastener) to either tighten or loosen the fastener. Conventional impact wrenches (i.e., either pneumatic or battery-powered) typically include a pistol grip-style housing having a handle portion grasped by the operator of the impact wrench and a motor portion extending from the handle portion. As a result of such a configuration, conventional impact wrenches are often difficult to maneuver within small work spaces. 
     SUMMARY OF THE INVENTION 
     The invention provides, in one aspect, an impact tool including a housing, a motor supported in the housing and defining a first axis, an output shaft rotatably supported in the housing about a second axis oriented substantially normal to the first axis, and an impact mechanism coupled between the motor and the output shaft and operable to impart a striking rotational force to the output shaft. 
     Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of an impact tool according to a construction of the invention. 
         FIG. 2  is a side view of the impact tool of  FIG. 1 . 
         FIG. 3  is an exploded perspective view of the impact tool of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of the impact tool of  FIG. 1  through line  4 - 4  in  FIG. 1 . 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
       FIGS. 1-4  illustrate an impact tool  10  including a drive end  14  having a non-cylindrical bore  18  ( FIG. 4 ) within which a fastener, a tool bit, or a driver bit  20  may be received. In the illustrated construction of the tool  10 , the non-cylindrical bore  18  includes a hexagonal cross-sectional shape. However, the non-cylindrical bore  18  may be shaped in any of a number of different ways to receive any of a number of different fasteners, tool bits, and/or driver bits  20 . The drive end  14  includes an output shaft  22  ( FIG. 3 ) having a detent (not shown) utilized to lock or axially secure the fastener, tool bit, and/or driver bit  20  to the drive end  14  of the tool  10 , a sleeve  30  positioned over the output shaft  22  for actuating the detent between a locked and an unlocked configuration, and a biasing member (e.g., a compression spring  26 ) for biasing the sleeve  30  toward a position in which the detent is in the locked configuration. Alternatively, the detent, the sleeve  30 , and the spring  26  may be omitted from the output shaft  22 , such that the fastener, tool bit, and/or driver bit  20  is not lockable to the drive end  14  of the tool  10 . 
     With reference to  FIG. 4 , the impact tool  10  includes a housing  34 , a motor  38  supported in the housing  34 , and a transmission  42  ( FIG. 3 ) operably coupled to the motor  38  to receive torque from the motor  38 . The output shaft  22  is rotatable about an axis  46  and operably coupled to the transmission  42  to receive torque from the transmission  42 . 
     In the illustrated construction of the tool  10 , the housing  34  includes a motor support portion  48  in which the motor  38  is contained, and a battery support portion  50  in which a battery pack  54  is removably received. The battery pack  54  is located directly below the motor  38  from the frame of reference of  FIG. 4 , such that the motor  38  and the battery pack  54  define respective parallel axes  55 ,  56 . As is discussed below, the motor support portion  48  is grasped by the user of the tool  10  during operation. Because of the positioning of the battery pack  54  relative to the motor  38  within the housing  34 , the motor  38  and the battery pack  54  substantially fit within the envelope of the user&#39;s wrist to facilitate maneuverability of the tool  10  in small work spaces. In other words, the impact tool  10  is sufficiently compact to permit the user to maneuver the tool  10  throughout the range of motion of the user&#39;s wrist without the housing  34  or the battery pack  54  interfering with the user&#39;s arm. 
     The battery pack  54  is electrically connected to the motor  38  via a variable-speed trigger switch  60  to provide power to the motor  38 . As shown in  FIG. 4 , the trigger switch  60  is located on a side wall  64  of the housing  34  between the respective axes  55 ,  56  of the motor  38  and battery pack  54  to provide ergonomic access to the trigger switch  60  while the user is grasping the motor support portion  48  of the housing  34 . The battery pack  54  is a 12-volt power tool battery pack  54  and includes three lithium-ion battery cells. Alternatively, the battery pack  54  may include fewer or more battery cells to yield any of a number of different output voltages (e.g., 14.4 volts, 18 volts, etc.). Additionally or alternatively, the battery cells may include chemistries other than lithium-ion such as, for example, nickel cadmium, nickel metal-hydride, or the like. Alternatively, the tool  10  may include an electrical cord for connecting the motor  38  to a remote electrical source (e.g., a wall outlet). 
     The tool  10  also includes a direction switch  68  ( FIGS. 1 and 2 ) that is toggled between a first position, in which the motor  38  is activated to rotate the output shaft  22  in a forward (i.e., clockwise) direction, and a second position, in which the motor  38  is activated to rotate the output shaft  22  in a reverse (i.e., counter-clockwise) direction. 
     The motor  38  is configured as a direct-current, can-style motor  38  having a motor output shaft  58  upon which a pinion  62  is fixed for rotation ( FIG. 3 ). In the illustrated construction of the tool  10 , the pinion  62  is interference or press-fit to the motor output shaft  58 . Alternatively, the pinion  62  may be coupled for co-rotation with the motor output shaft  58  in any of a number of different ways (e.g., using a spline fit, a key and keyway arrangement, by welding, brazing, using adhesives, etc.). As a further alternative, the pinion  62  may be integrally formed as a single piece with the motor output shaft  58 . 
     With reference to  FIGS. 3 and 4 , the transmission  42  includes a single stage planetary transmission  66  and a transmission output shaft  70  functioning as the rotational output of the transmission  42 . The transmission  42  also includes a gear case  74  within which the planetary transmission  66  is received. The gear case  74  is fixed to the motor  38  (e.g., using fasteners), and the combination of the gear case  74  and the motor  38  is clamped between the opposite halves of the housing  34  ( FIG. 3 ). 
     With continued reference to  FIG. 3 , the planetary transmission  66  includes an outer ring gear  94 , a carrier  98  rotatable about the motor axis, and planet gears  102  rotatably coupled to the carrier  98  about respective axes radially spaced from the motor axis  55 . The outer ring gear  94  includes radially inwardly-extending teeth  106  that are engageable by corresponding teeth  110  on the planet gears  102 . The outer ring gear  94  also includes radially outwardly-extending protrusions  114 , and the gear case  74  includes corresponding slots (not shown) within which the protrusions  114  are received to rotationally fix the outer ring gear  94  to the gear case  74 , and therefore the housing  34 . Alternatively, the outer ring gear  94  may be fixed to the gear case  74  in any of a number of different ways (e.g., using snap-fits, an interference or press-fit, fasteners, adhesives, by welding, etc.) As a further alternative, the outer ring gear  94  may be integrally formed as a single piece with the gear case  74 . 
     The carrier  98  includes an aperture  134  having a non-circular cross-sectional shape (e.g., a “double-D”) corresponding to that of a first end  118  of the transmission output shaft  70  ( FIG. 3 ). As such, the first end  118  of the transmission output shaft  70  is received within the aperture  134  and co-rotates with the carrier  98  at all times in response to activation of the motor  38 . Alternatively, the transmission output shaft  70  may be non-rotatably coupled to the carrier  98  in any of a number of different ways. 
     With continued reference to  FIG. 3 , the tool  10  includes an impact mechanism  138  including an impact mechanism housing  140  clamped between the opposed halves of the tool housing  34  and a drive shaft  142  supported for rotation within the housing  140 . In the illustrated construction of the tool  10 , the housing  140  includes an upper housing portion  126  and a lower housing portion  130  interconnected to the upper housing portion  126  (e.g., using fasteners, etc.). The upper housing portion  126  includes a support  143  in which a needle bearing  145  is received ( FIG. 4 ). A cylindrical first end  148  of the drive shaft  142  is supported by the needle bearing  145  for rotation relative to the housing  140 . An opposite, second end  152  of the drive shaft  142  is piloted or supported for rotation relative to the housing  140  by the output shaft  22 . 
     With reference to  FIGS. 3 and 4 , the impact tool  10  also includes a right-angle bevel gear arrangement  156  coupled between the motor  38  and the drive shaft  142 . Particularly, the bevel gear arrangement  156  includes a bevel ring gear  160  coupled for co-rotation with the drive shaft  142  and a bevel pinion gear  164  engaged with the bevel ring gear  160  and coupled for co-rotation with a second end  168  of the transmission output shaft  70  (e.g., using an interference fit, a key and keyway arrangement, etc.). As shown in  FIG. 4 , the bevel pinion gear  164  is coaxial with the motor axis  55 , and the bevel ring gear  160  is coaxial with the axis  46  of the output shaft  22 . As such, the respective axes  55 ,  46  of the motor  38  and the output shaft  22  are oriented substantially normal to each other (i.e., at a right or 90-degree angle). 
     With reference to  FIGS. 3 and 4 , the impact mechanism  138  further includes a hammer  146  supported on the drive shaft  142  for rotation with the shaft  142 , and an anvil  150  coupled for co-rotation with the output shaft  22 . In the illustrated construction of the tool  10 , the anvil  150  is integrally formed with the output shaft  22  as a single piece and includes opposed, radially outwardly extending lugs  172  ( FIG. 3 ). 
     The shaft  142  includes two V-shaped cam grooves  158  (only one of which is shown in  FIG. 3 ) equally spaced from each other about the outer periphery of the shaft  142 . Each of the cam grooves  158  includes two segments that are inclined relative to the axis  46  in opposite directions. The hammer  146  has opposed lugs  162  and two cam grooves  166  ( FIG. 4 ) equally spaced from each other about an inner periphery of the hammer  146 . Like the cam grooves  158  in the shaft  142 , each of the cam grooves  166  is inclined relative to the axis  46 . The respective pairs of cam grooves  158 ,  166  in the shaft  142  and the hammer  146  are in facing relationship such that a cam member (e.g., a ball  167 , see  FIG. 3 ) is received within each of the pairs of cam grooves  158 ,  166 . The balls  167  and the cam grooves  158 ,  166  effectively provide a cam arrangement between the shaft  142  and the hammer  146  for transferring torque between the shaft  142  and the hammer  146  between consecutive impacts of the lugs  162  upon the corresponding lugs  172  on the anvil  150 . The impact mechanism  138  also includes a compression spring  178  positioned between the hammer  146  and the bevel ring gear  160  to bias the hammer  146  toward the anvil  150 . A thrust bearing  182  is positioned between the hammer  146  and the spring  178  to permit relative rotation between the spring  178  and the hammer  146 . 
     As previously discussed, the second end  152  of the drive shaft  142  is piloted or supported for rotation by the combination of the anvil  150  and the output shaft  22  ( FIG. 4 ). The anvil  150 , in turn, is supported for rotation within the impact mechanism housing  140  by a bushing  186 . Alternatively, a roller bearing may be utilized in place of the bushing  186 . 
     In operation of the tool  10 , the motor support portion  48  is grasped by the user of the tool  10  during operation. Because of the positioning of the battery pack  54  relative to the motor  38  within the housing  34 , the motor  38  and the battery pack  54  substantially fit within the envelope of the user&#39;s wrist to facilitate maneuverability of the tool  10  in small work spaces. Furthermore, the tool  10  may access small work spaces that would otherwise be inaccessible to conventional impact tools or impact wrenches. 
     During operation, the motor  38  rotates the drive shaft  142 , through the transmission  42  and the bevel gear arrangement  156 , in response to actuation of the trigger switch  60 . The hammer  146  initially co-rotates with the drive shaft  142  and upon the first impact between the respective lugs  162 ,  172  of the hammer  146  and anvil  150 , the anvil  150  and the output shaft  22  are rotated at least an incremental amount provided the reaction torque on the output shaft  22  is less than a predetermined amount that would otherwise cause the output shaft  22  to seize. However, should the reaction torque on the output shaft  22  exceed the predetermined amount, the output shaft  22  and anvil  150  would seize, causing the hammer  146  to momentarily cease rotation relative to the housing  140  due to the inter-engagement of the respective lugs  162 ,  172  on the hammer  146  and anvil  150 . The shaft  142 , however, continues to be rotated by the motor  38 . Continued relative rotation between the hammer  146  and the shaft  142  causes the hammer  146  to displace axially away from the anvil  150  against the bias of the spring  178  in accordance with the geometry of the cam grooves  158 ,  166  within the respective drive shaft  142  and the hammer  146 . 
     As the hammer  146  is axially displaced relative to the shaft  142 , the hammer lugs  162  are also displaced relative to the anvil  150  until the hammer lugs  162  are clear of the anvil lugs  172 . At this moment, the compressed spring  178  rebounds, thereby axially displacing the hammer  146  toward the anvil  150  and rotationally accelerating the hammer  146  relative to the shaft  142  as the balls  167  move within the pairs of cam grooves  158 ,  166  back toward their pre-impact position. The hammer  146  reaches a peak rotational speed, then the next impact occurs between the hammer  146  and the anvil  150 . In this manner, the fastener, tool bit, and/or driver bit  20  received in the drive end  14  is rotated relative to a workpiece in incremental amounts until the fastener is sufficiently tight or loosened relative to the workpiece. 
     Various features of the invention are set forth in the following claims.