Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of the filing date of U.S. provisional application No. 60/543,835, filed Feb. 11, 2004. 

   BACKGROUND 
   This application relates to driving tools of the type used for driving fasteners or the like and, in particular, relates to rotational tools of the torque-limiting type. 
   Various types of driving tools, such as screwdrivers, nut drivers, wrenches and the like are known, as are torque-limiting tools, such as torque wrenches and torque-limiting screwdrivers. The latter types of tools are typically rather complex and expensive and are designed to be long-lasting and/or heavy-duty, particularly tools designed for use in commercial and industrial applications. Furthermore, driving tools, such as screwdrivers, nut drivers and the like, are commonly designed to have removable or replaceable bits for driving different sizes of fasteners, and this replaceability feature may complicate the design of the tool and add to the expense thereof. 
   However, there are various applications wherein tools need not survive heavy-duty, long-lasting use. For example, tools may be designed for specific uses, such as for sporting goods, furniture assembly, field assembly of products and certain military applications wherein the tool may be either relatively infrequently used or need only be used once or twice and, accordingly, may need only a single bit or workpiece-engaging member. For such applications it is desirable to have a tool which is low-cost and may be suitable for mass production and, if need be, could even be disposable, without sacrificing ergonomic features. 
   SUMMARY 
   This application discloses a driving tool which avoids disadvantages of prior drivers while having additional structural and operational advantages. 
   There is disclosed a driver which is of relatively simple and economical construction. 
   In particular, there is disclosed a low-cost, torque-limiting driving tool which is ergonomically designed. 
   In an embodiment, there is provided a torque-limiting driver includes a housing, a shaft carried by the housing for rotation relative thereto and having a workpiece-engaging tip projecting from the housing, a torque-limiting mechanism coupled between the housing and the shaft and responsive to rotation of the housing in a predetermined direction to rotate the shaft at torques below a predetermined torque and accommodating rotation of the housing relative to the shaft at said predetermined torque and above, a torque-determining structure disposed in the housing and movable relative to the torque-limiting mechanism for adjusting the predetermined torque, and the housing including a stop portion engageable with the torque-determining structure for preventing torque-adjusting movement thereof. 
   There may also be provided, in an embodiment, a method for indicating that a predetermined torque has been reached, including providing a torque-limiting mechanism responsive to rotation of a housing in a predetermined direction to rotate a shaft at torques below a predetermined torque and accommodating rotation of the housing relative to the shaft at said predetermined torque and above, moving a torque-determining structure for selectively adjusting the predetermined torque, and locking the torque-determining structure against movement to prevent unintentional change of the predetermined torque. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated. 
       FIG. 1  is a front elevational view of a torque-limiting driver; 
       FIG. 2  is a right-hand side elevational view of the driver of  FIG. 1 ; 
       FIG. 3  is a top plan view of the driver of  FIG. 1 ; 
       FIG. 4  is a bottom plan view of the driver of  FIG. 1 ; 
       FIG. 5  is a sectional view taken generally along the line  5 - 5  in  FIG. 2 ; 
       FIG. 6  is an enlarged, fragmentary sectional view of a portion of  FIG. 5 ; 
       FIG. 7  is a sectional view taken generally along the line  7 - 7  in  FIG. 1 ; 
       FIG. 8  is a reduced, exploded view of the driver of  FIG. 1 ; 
       FIG. 9  is a reduced, bottom plan view of the sleeve of the driver of  FIG. 5 ; 
       FIG. 10  is a sectional view taken generally along the line  10 - 10  in  FIG. 9 ; 
       FIG. 11  is an enlarged, perspective view of the lower cam of the driver of  FIG. 5 ; 
       FIG. 12  is a top plan view of the cam of  FIG. 11 ; 
       FIG. 13  is a sectional view taken generally along the line  13 - 13  in  FIG. 12 ; 
       FIG. 14  is an enlarged, inverted, perspective view of the upper cam of the driver of  FIG. 5 ; 
       FIG. 15  is a top plan view of the upper cam of  FIG. 14 ; 
       FIG. 16  is a sectional view taken generally along the line  16 - 16  in  FIG. 15 ; 
       FIG. 17  is an enlarged top plan view of the adjustment plug of the driver of  FIG. 5 ; 
       FIG. 18  is a sectional view taken generally along the line  18 - 18  in  FIG. 17 ; and 
       FIG. 19  is an enlarged, side elevational view of the cap of the driver of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1-8 , there is illustrated a torque-limiting driver, generally designated by the numeral  20  having a generally T-shaped housing  21 , which includes a generally T-shaped base member  22  having a hollow, generally cylindrical stem portion  23  with a tapered end  24  closed by a circular end wall  25  having a circular bore  26  formed axially therethrough. The upper end of the stem portion  23  is integral with a pair of laterally outwardly projecting and diametrically opposed arms  27 , each being provided with one or more cylindrical upstanding sockets  28  and with open-top receptacle slots  28   a . The inner surface of the tapered end  24  of the stem portion  23  is provided with a plurality of equiangularly spaced-apart and longitudinally extending keyways  29  (see  FIG. 5 ), which may be six in number. Referring also to  FIG. 19 , the upper end of the base member  22  is closed by an elongated, generally oval-shaped cap  30  having a top wall  31  integral around its periphery with a depending skirt  32  sized and shaped to mateably engage the upper peripheral edge of the base member  22  around the periphery of the arms  27  and the upper end of the stem portion  23 . Depending from the top wall  31  centrally thereof is a cylindrical, hollow neck  33 . Also depending from the top wall  31  are stakes  34  adapted to be mateably received in the sockets  28 . Plural blades  35  may extend radially outwardly from the neck  33  and may be six in number. The outer surface of the cap  30  may be provided with an overmolded grip  36  which may be formed of a suitable elastomeric material. 
   Referring in particular to FIGS.  5  and  7 - 10 , the driver  20  includes a sleeve  40  having an elongated, hollow, generally cylindrical body  41 , integral at one end with a pair of diametrically opposed and radially outwardly extending flanges  42 . Formed along the inner surface of the cylindrical body  41  at circumferentially spaced-apart locations are a plurality of longitudinally extending keyways  43  (see  FIGS. 5 and 10 ), which may be six in number. The cylindrical body  41  has a tapered end  44  closed by a circular end wall  45  having an axial bore  46  formed therethrough. The cylindrical body  41  is provided adjacent to the open end thereof with internal threads  47  ( FIG. 7 ). Formed on the outer surface of the tapered end  44  are longitudinally extending and radially outwardly projecting keys  49  ( FIGS. 8 and 9 ), which may be six in number. In assembly, the sleeve  40  is coaxially received in the stem portion  23  of the driver base member  22  to the position illustrated in  FIGS. 5 and 7 , with the end wall  45  seated on the end wall  25 , the keys  49  being respectively received in the keyways  29  and the flanges  42  respectively received in the receptacle slots  28   a  for retaining the sleeve  40  against rotation relative to the driver base member  22 . 
   Referring in particular to  FIGS. 5 ,  7  and  8 , the driver  20  includes an elongated shaft  50 , which may be hexagonal in transverse cross sectional shape and is provided at one end with a working tip  51 , adapted for mateable engagement with an associated workpiece, such as a fastener or the like. The shaft  50  is provided intermediate its ends with a circumferential groove  52 , in which is received a retaining ring  53  ( FIG. 6 ). The shaft is provided at the end opposite the working tip  51  with a bearing end face  54 . In assembly, the shaft  50  is received through the aligned bores  26  and  46  in the driver base member  22  and sleeve  40 , with the retaining ring  53  seated on the inner surface of the sleeve end wall  45 . A thrust washer  55  is also seated on the sleeve end wall  45  in surrounding relationship with the retaining ring  53 . The end face  54  of the shaft  50  is adapted for engagement with a ball bearing  56  in a manner to be described more fully below. 
   Referring also to  FIGS. 11-13 , the driver  20  includes a lower cam  60 , which has an elongated, cylindrical shank  61  integral at one end with a radially outwardly extending annular flange  62 , which is provided at its upper surface with a plurality of circumferentially spaced teeth  62 . Each tooth  62  has an axial face  64  and a sloping face  65 . A hexagonal bore  66  is formed axially through the lower cam  60  and is sized and dimensioned for mateably receiving the hexagonal shaft  50 . The annular flange  62  has an end face  67  opposite the teeth  63 , which has counterbores  68  and  69  formed therein coaxially with the bore  66  (see  FIG. 13 ). In assembly, the lower cam  60  is fitted down over the shaft  50  with the end face  67  seated on the sleeve end wall  45  and with the thrust washer  55  received in the counterbore  69  and the retaining ring  53  received in the counterbore  68 . The hexagonal bore  66  cooperates with the hexagonal shaft  50  to prevent rotation of the lower cam  60  relative to the shaft  50 , the counterbore  68  having a depth sufficient to accommodate slight axial movement of the shaft  50  relative to the lower cam  60 . 
   Referring now also to  FIGS. 14-16 , the driver  20  includes an upper cam  70 , having an annular body  71  with a cylindrical bore  72  formed axially therethrough. Formed in the lower face of the annular body  71  is a plurality of circumferentially spaced teeth  73 , each having an axial face  74  and a sloping face  75 . Projecting radially outwardly from the outer surface of the annular body  71  at equiangularly spaced-apart locations are a plurality of axially extending keys  76 , which may be six in number. The annular body  71  has an upper end face  77 . In assembly, the upper cam  70  is fitted down coaxially over the upper end of the shaft  50 , with the cylindrical shank  61  of the lower cam  60  received in the bore  72 , with the teeth  73  mateably engaging the teeth  63  of the lower cam  60 , and with the keys  76  respectively received in the keyways  43  of the sleeve  40 , as can best be seen in  FIGS. 5 and 7 . 
   Thus, the keys  76  lock the upper cam  70  against rotation relative to the sleeve  40 . The axial faces  74  of the teeth  73  respectively engage the axial faces  64  of the teeth  63  to prevent relative rotation of the upper and lower cams  70  and  60  in one direction, while the sloping teeth faces  75  and  65  engage to accommodate relative rotation of the upper and lower cams in the opposite direction. A helical compression spring  79  is fitted coaxially over the upper end of the shaft  50  within the sleeve  40  and is seated on the end face  77  of the upper cam  70 . 
   Referring now also to  FIGS. 17 and 18 , the driver  20  includes an annular adjustment plug  80  having an annular body  81  which is externally threaded, as at  82 , adjacent to one end thereof, and is provided with a cylindrical axial bore  83  therethrough between a lower end face  84  and an upper end face  85 . Formed in the upper end face  85  are a plurality of equiangularly spaced-apart radial slots  86 , which may be six in number. In assembly, the adjustment plug  80  is fitted coaxially over the upper end of the shaft  50  and threadedly engaged in the upper end of the sleeve  40 , for bearing against the upper end of the compression spring  79 . In this regard, the slots  86  may accommodate a screwdriver or the like. The extent to which the plug  80  is threaded into the sleeve  40  controls the amount of compression or preload on the spring  79  which, in turn, controls the force with which the upper cam  70  is driven into engagement with the lower cam  60  and, thereby, the limiting torque required to effect relative rotation of the lower and upper cam  60  and  70 , in a known manner. 
   To complete the assembly of the driver  20 , the ball bearing  56  is seated in the cylindrical neck  33  of the cap  30 , and the cap  30  is then fitted over the upper end of the base member  22 , to a mounted position illustrated in  FIGS. 5 and 7 . In this position, the cylindrical neck  33  is fitted down within the bore  83  of the adjustment plug  80  in surrounding relationship with the upper end of the shaft  50 , holding the ball bearing  56  against the end face  54  of the shaft  50 , and the stakes  34  are respectively received in the sockets  28 . The blades  35  on the cap  30  are respectively received in the radial slots  86  of the adjustment plug  80  for preventing it from loosening. The cap  30  may be snap-fitted to the base member  22 , or may be fixed thereto as by sonic welding, solvent welding or the like. It will be appreciated that, in the latter case, the driver  20  is permanently assembled, with the shaft  50  non-removably mounted in place. Thus, the driver  20  will be usable with only a single type (shape and size) of mating fastener or the like. The parts may be economically constructed and the driver  20  may even be disposable, being designed for only limited use. 
   It will be appreciated that, in use, the arms  27  of the driver may be rested in the palm of the user&#39;s hand, with the fingers wrapped beneath the arms and straddling the stem portion  23 . When the driver  20  is rotated in one direction, the shaft  50  will rotate with the housing  21  until a predetermined torque level is reached, at which point the biasing force exerted by the spring  79  is overcome to allow the sloping faces  75  of the upper cam  70  to slide up the sloping faces  65  of the lower cam  60  for the angular distance of one tooth, at which point the upper cam  70  will snap into engagement behind the next tooth of the lower cam  60 , providing a tactile and/or audible indication to the user that the predetermined torque has been reached. When the driver  20  is rotated in the opposite direction, it will operate as a standard driver with no torque-limiting feature, since the engaging axial faces  64  and  74  of the cam teeth will prevent relative rotation of the lower and upper cams  60  and  70 . 
   In a constructional model of the invention, the shaft  50 , the retaining ring  53 , the ball bearing  56  and the spring  79  may be formed of suitable metals, while the remaining parts may be formed of suitable plastics, which may be molded. From the foregoing, it can be seen that there has been provided an improved torque-limiting driver of simple and economical construction, which may be made disposable or for limited use and is provided with an ergonomical design. 
   The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants&#39; contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.

Technology Category: b