Abstract:
A driver tool configured to engage and drive the head of a threaded fastener includes a shank defining a longitudinal axis. The shank has a mating end and a driver end. A driver head is coupled to the shank adjacent the driver end. The driver head includes a first driving portion having a substantially square cross section normal to the axis and a geometric center along the axis. The first driving portion includes four walls and a corner at an intersection of adjacent walls such that the first driving portion includes a first corner, a second corner, a third corner opposite the first corner, and a fourth corner opposite the second corner. The driver head further includes a second driving portion including a first flange extending radially outward from the first driving portion and a second flange extending radially outward from the first driving portion. The second flange is opposite the first flange, and each of the flanges includes an end wall having a midpoint. A plane passing through the first corner and the third corner of the first driving portion passes through the midpoints of the end walls of the second driving portion.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/150,153, filed Feb. 5, 2009, the entire contents of which is incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a hand tool, and in particular a drive device for combination head fasteners. 
         [0003]    Combination or “combo” head fasteners were developed to be driven by either a conventional flat-head type driver or a Phillips-head type driver. Some combination fastener head designs can also receive a Robertson type square driver. All three types of drivers have disadvantages when used with a combination head fastener. Flat-head drivers require a user to manually hold the driver bit substantially centered in the fastener head slot and aligned with the axis of the fastener shank, and care must be taken to maintain alignment between the fastener and driver. Phillips-head drivers are self-centering within the fastener head, but have a tendency to “cam-out” of the fastener head in high torque applications. Robertson drivers have a tendency to strip combination type fastener heads at relatively low torques. 
       SUMMARY OF THE INVENTION 
       [0004]    In one embodiment, the invention provides a driver tool configured to engage and drive the head of a threaded fastener. The driver tool includes a shank defining a longitudinal axis. The shank has a mating end and a driver end. A driver head is coupled to the shank adjacent the driver end. The driver head includes a first driving portion having a substantially square cross section normal to the axis and a geometric center along the axis. The first driving portion includes four walls and a corner at an intersection of adjacent walls such that the first driving portion includes a first corner, a second corner, a third corner opposite the first corner, and a fourth corner opposite the second corner. The driver head further includes a second driving portion including a first flange extending radially outward from the first driving portion and a second flange extending radially outward from the first driving portion. The second flange is opposite the first flange, and each of the flanges includes an end wall having a midpoint. A plane passing through the first corner and the third corner of the first driving portion passes through the midpoints of the end walls of the second driving portion. 
         [0005]    In another embodiment, the invention provides a bit for driving threaded fasteners. The bit includes a shank having a first end, a second end, a longitudinal axis and a first cross-sectional profile. A mating portion is coupled to the first end of the shank for mating the bit with a driving apparatus. A driving portion is coupled to the second end of the shank. The driving portion includes a recess driving portion and a slot driving portion. The recess driving portion has four walls and four corners forming a substantially square cross section normal to the longitudinal axis. The slot driving portion has a pair of flanges extending radially from opposing corners of the recess driving portion. 
         [0006]    In yet another embodiment, the invention provides a screwdriver configured to rotatably drive a threaded fastener head. The screwdriver includes a shaft having a central axis, a first end, and second end. A handle is coupled to the first end of the shaft and a driving head is coupled to the second end of the shaft. The driving head comprises a first driving portion including four walls and four corners defining a square cross section relative to the central axis. The first driving portion is configured to engage a central recess of the fastener head. The driving head further includes a second driving portion including a pair of flanges extending radially outward from opposing corners of the first driving portion. Each flange has a pair of opposing walls and an end wall extending therebetween. The second driving portion is configured to engage an elongated slot of the fastener head. The second driving portion extends radially outward from opposing corners of the first driving portion. 
         [0007]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a screwdriver according to one embodiment of the invention. 
           [0009]      FIG. 2  is a partial front perspective view of a driving head of the screwdriver of  FIG. 1 . 
           [0010]      FIG. 3  is a front view of the screwdriver of  FIG. 1 . 
           [0011]      FIG. 4  is a top view of a combination-type screw head. 
           [0012]      FIG. 5  is a perspective view of a screwdriver according to another embodiment of the invention. 
           [0013]      FIG. 6  is a partial front perspective view of a driving head of the screwdriver of  FIG. 5 . 
           [0014]      FIG. 7  is a partial front perspective view of a screwdriver according to another embodiment of the invention. 
           [0015]      FIG. 8  is a front perspective view of a combination bit according to one embodiment of the invention. 
           [0016]      FIG. 9  is a rear perspective view of the combination bit of  FIG. 8 . 
           [0017]      FIG. 10  is a front view of the combination bit of  FIG. 8 . 
           [0018]      FIG. 11  is a perspective view of a combination bit according to another embodiment of the invention. 
       
    
    
       [0019]    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 are for the purpose of description and should not be regarded as limiting. 
       DETAILED DESCRIPTION 
       [0020]      FIGS. 1-3  illustrate a screwdriver  10  according to one embodiment of the invention. The screwdriver  10  includes a handle  14  having a first end  18  and a second end  22 . A rounded pommel  26  is formed at the first end  18  of the handle  14 , and screwdriver shaft  30  projects outwardly from the second end  22  of the handle  14 . The handle  14  also includes gripping surfaces  34  for a user such that the user may grip the handle  14  for the tightening and loosening of a fastener, such as a screw head  38  ( FIG. 4 ). The handle  14  is coupled to the shaft  30 , and the user transmits torque from the handle  14  to the screw head  38  via the shaft  30 . In the illustrated embodiment, the handle  14  is fixedly coupled to the shaft  30 . In further embodiments, the handle  14  may be molded over a shaft extension, unitarily formed with the shaft, or otherwise fixedly or detachably coupled to the shaft. 
         [0021]    The shaft  30  extends from the handle  14  along a central axis  42  and includes a driver end  46 . A shaft length L, defined as a distance between the second end  22  of the handle  14  and the driver end  46 , may be of various lengths, depending on the particular application of the screwdriver. In the illustrated embodiment, the shaft length L is between approximately 90 mm and approximately 110 mm. Referring to  FIG. 1 , the shaft  30  has a rounded cross-sectional profile  50 , although in other embodiments, the shaft may have a hexagonal ( FIG. 5 ), square, triangular, or other cross-sectional profile. 
         [0022]    Referring to  FIGS. 1-3 , the driver end  46  of the shaft  13  includes a driving head  54 , which in the illustrated embodiment is integrally formed with the shaft  30  as a single piece. The driving head  54  may be integrally cast, forged or machined into the shaft  30 . Alternatively, the driving head  54  may be welded to the shaft  30 , or a female portion of the driving head  54  may be pressed or adhesively bonded over a male portion of the shaft  30 . Further, the driving head  54  may undergo various heat treatment, surface hardening, plating or coating processes to optimize the hardness, toughness, wear resistance, or corrosion resistance of the tool. 
         [0023]    The driving head  54  has a shape and configuration for mating with a combination or combo screw head  38 , an example of which is illustrated in  FIG. 4 . The combination screw head  38  can be driven by a conventional flat head, cross-head (i.e., Phillips), or square (i.e., Robertson) screwdriver. The head  38  has an outer diameter  58  and a cruciform-shaped drive socket  62 . The drive socket  62  is defined by a full-diameter slot  66  and a partial diameter elongated recess  70 . The recess  70  is substantially perpendicular to the slot  66 . The slot  66  is configured to receive a traditional flat-head type driver. The recess  70 , in combination with a central portion  74  of the slot  66 , is configured to receive a tapered, cruciform cross section of a Phillips-type driver. A square, central recess  78 , at the intersection of the slot  66  and the recess  70 , is surrounded by four diagonal walls  82 . The central recess  78  is configured to receive a Robertson-type driver. In most screws, the central recess  78  has a greater depth, measured from a top surface of the screw head, than the slot  66 . 
         [0024]    Referring to  FIGS. 2 and 3 , the driver head  54  includes a first driving portion  86  and a second driving portion  90 . The first driving portion  86  has a substantially square-shaped cross section, which is sized and shaped to mate with the central recess  78  of the combination screw head  38  ( FIG. 4 ). The first driving portion  86  includes four driving faces  94  and a corner  98  at the intersection of adjacent driving faces  94 . The first driving portion  86  is configured to engage with and drive the walls  82  of the screw head central recess  78 . 
         [0025]    The second driving portion  90  has a substantially rectangular-shaped cross section, which is sized and shaped to mate with the slot  66  of the combination screw head  38 . The second driving portion  90  is formed by flanges  102  that extend from opposite corners  98  of the first driving portion  86 . Each of the flanges  102  is formed by a pair of walls  106  extending outwardly from the first driving portion  86 . In the illustrated embodiment, the walls  106  are substantially parallel to each other. An end portion of each flange  102  includes an end wall  110 . In the illustrated embodiment, the first driving portion  86  and the second driving portion  90  share a common geometric center  114  along the central axis  42  of the shaft  30 . 
         [0026]    An angular orientation ⊖ between the first driving portion  86  and second driving portion  90  is defined by an angle between a first plane  116 , extending between the center  114  and a midpoint  118  of one of the driving faces  94  of the first driving portion  86 , and a second plane  120 , extending between the center  114  and a midpoint  122  of the nearest end wall  110  of the second driving portion  90 . In the illustrated embodiment, the angular orientation ⊖ of the first driving portion  86  is approximately 45 degrees. In further embodiments, the angular orientation ⊖ may require a 45 degree shift, depending on screw head and the orientation of the screw slot  66  relative to the central recess  78 , such that the midpoint  118  of the driving face  94  is aligned with the midpoint  122  of the nearest end wall  110 . 
         [0027]    The first driving portion  86  includes a distal end face  126  and the second driving portion  90  includes a distal end face  130 . The end face  130  of the second driving portion  90  has an axial offset  134  from the end face  126  of the first driving portion  86 . In the illustrated embodiment, the offset  134  corresponds to the difference in depth between the screw head slot  66  and the central recess  78 . The axial offset  134  allows for a greater depth of engagement between the first driving portion  86  and the central recess  78 , thereby allowing for higher torque transmission prior to stripping either the screw head or driver. 
         [0028]    Comparing the driving head  54  of  FIGS. 2-3  with the recess configuration of the exemplary screw head  38  of  FIG. 4 , the driving head  54  does not directly engage the recess  70  of the head  38 . The driving faces  94  of the first driving portion  86  engage the walls  82  of the central recess  78 , which allows the driving head  54  to provide a tighter fit with combination head screws than a conventional slotted screwdriver or Phillips screwdriver. Unlike Phillips or other cross-head type drivers, the driving head  54  has a reduced tendency to cam-out of the screw head when under high-torque. 
         [0029]    A transition region  138  extends between the shaft  30  and the driving head  54 , and the transition region  138  includes fillets  142 . In the illustrated embodiment, four fillets  142  are provided, each of the fillets  142  corresponding to one of the driving faces  94  of the first driving portion  86 . The fillets  142  increase the strength of the tool by minimizing torsional and/or bending stress concentrations in the transition region  138 . The transition region  138  is axially offset from the end faces  126 ,  130  of the driving head  54 ; therefore, the fillets  142  of the transition region  138  do not affect tool-to-fastener engagement. In further embodiments, other configurations and profiles are possible for the fillets  142 . 
         [0030]      FIGS. 5 and 6  illustrate a screwdriver  210  according to another embodiment of the invention. The screwdriver  210  is similar to the screwdriver  10  illustrated in  FIGS. 1-3 . Accordingly, features of the screwdriver  210  that are similar to the features of screwdriver  10  have been given similar reference numbers, plus 200. Also, only differences between the screwdriver  10  of  FIGS. 1-3  and the screwdriver  210  of  FIGS. 5-6  will be discussed in detail below and it should be understood that the features and alternative constructions of the screwdriver  10  discussed above could also be applied to the screwdriver  210 . 
         [0031]    Referring to  FIG. 5 , a shaft  230  of the screwdriver  210  has a hexagonal cross-sectional profile  250 . Referring to  FIG. 6 , a driving head  254  of the screwdriver  210  is sized and shaped to engage a #1 size combination screw head (not shown). The driving head  254  includes a first driving portion  286  and a second driving portion  290 . A distal end face  326  of the first driving portion  286  and a distal end face  330  of the second driving portion  290  are substantially flush, which allows for better tool-to-slot engagement on fasteners with a shallow central recess. The end face  326  of the first driving portion  286  has a conical profile  346  centered about a central axis  242 . An angle Φ is defined between the axis  242  and a line  348  tangent to the conical end face  326 . In the illustrated embodiment, the conical angle Φ is approximately 70 degrees. In other embodiments, the conical angle may be greater or less than 70 degrees. The conical profile  346  allows a user to more easily align the driver head  40  with a screw head. 
         [0032]      FIG. 7  partially illustrates a screwdriver  410  according to another embodiment of the invention. The screwdriver  410  is similar to the screwdriver  210  illustrated in  FIGS. 5-6 . Accordingly, features of the screwdriver  410  that are similar to the features of screwdriver  210  have been given similar reference numbers, plus 400. Also, only differences between the screwdriver  210  of  FIGS. 5-6  and the screwdriver  410  of  FIG. 7  will be discussed in detail below and it should be understood that the features and alternative constructions of the screwdriver  210  discussed above could also be applied to the screwdriver  410 . 
         [0033]    The screwdriver  410  includes a driving head  454  having a first driving portion  486  and a second driving portion  490 . In the illustrated embodiment, a distal end face  526  of the first driving portion  486  and a distal end face  530  of the second driving portion  490  are substantially flush. The driving head  454  is sized and shaped to engage a #2 size combination screw head (not shown). 
         [0034]      FIGS. 8-10  illustrate a combination bit  612  according to one embodiment of the invention. The combination bit  612  is for use with a screwdriver (not shown) having a handle and a shaft, whereby the bit  612  is removably coupled to the shaft of the screwdriver such that various bits may be interchangeably used with the screwdriver. The bit  612  includes a driving head portion  654  and a shank portion  630  that terminates at a mating end  616 . A transition region  738  between the shank portion  630  and the driving head portion  654  is defined by a plurality of fillets  742 . 
         [0035]    The driving head portion  654  of the combination bit  612  illustrated in  FIGS. 8-10  is similar to the driving head  54  of the screwdriver  10  illustrated in  FIGS. 1-3 . Accordingly, features of the driving head portion  654  that are similar to the features of the driving head  54  have been given similar reference numbers, plus 600. Also, only differences between the driving head  54  of  FIGS. 1-3  and the driving head portion  654  of  FIGS. 8-10  are discussed in detail above and it should be understood that the features and alternative constructions of the driving head  54  discussed above could also be applied to the driving head portion  654 . 
         [0036]    The shank portion  630  and mating end  616  have a hexagonal profile sized for use with an interchangeable-bit screwdriver body (not shown). The illustrated combination bit  612  is sized and shaped to mate with a standard 5/16″ driver body. The shank portion  630  may also be used with three-jaw chucks, such as those used in drills and powered screwdriver tools. In the illustrated embodiment, the bit  612  is formed from a magnetic ferrous-alloy so that it may be magnetically retained in a driver body using magnetic retention. In further embodiments, the bit may utilize a spring and ball detent to retain the bit within a driver body, such as is described below with respect to  FIG. 11 . 
         [0037]      FIG. 11  illustrates a double ended combination bit  812  according to one embodiment of the invention. The combination bit  812  is for use with a screwdriver (not shown) having a handle and a shaft, whereby the bit  812  is removably coupled to the shaft of the screwdriver such that various bits may be interchangeably used with the screwdriver. The bit  812  includes a first driving head portion  854 A, a second driving head portion  854 B, and a shank portion  830  that connects the two driving head portions  854 A and  854 B. In the illustrated embodiment, the driving head portions  854 A,  854 B are integrally formed at opposite ends of the detachable bit  812 . 
         [0038]    The driving head portion  854 A of the combination bit  812  illustrated in  FIG. 11  is similar to the driving head  254  of the screwdriver  210  illustrated in  FIGS. 5-6 . The driving head portion  854 A is sized and shaped to engage a #1 combination head screw. The driving head portion  854 B of the combination bit  812  illustrated in  FIG. 11  is similar to the driving head  454  of the screwdriver  410  illustrated in  FIG. 7 . The driving head portion  854 B is sized and shaped to engage a #2 combination head screw. Accordingly, features of the driving head portions  854 A,  854 B that are similar to the features of the driving heads  254 ,  454  have been given similar reference numbers, plus 800. 
         [0039]    The first driving head  854 A and the second driving head  854 B share a common longitudinal axis  842 . The illustrated combination bit  812  is sized and configured to mate with a standard 5/16″ driver body, though other embodiments may be appropriately sized for other uses. The shank may be of various lengths depending on the end-use. A spring and ball detent arrangement  956  is located at or near a midpoint of the shank portion  830 . The detent arrangement  956  is configured to engage a corresponding recess of a tool receptacle. 
         [0040]    Thus, the invention provides, among other things, a tool for driving combination-head threaded fasteners. Various features and advantages of the invention are set forth in the following claims.