Abstract:
An electronic torque wrench has a lever arm pivotally coupled to a head member which is adapted for coupling to an associated fastener for rotation therewith about the rotational axis thereof, a torque sensing device being disposed on the head member for movement therewith relative to the lever arm. Different embodiments are provided for different degrees of relative angular movement between the head member and the lever arm.

Description:
BACKGROUND  
         [0001]    This application relates to torque applying and measuring apparatus and, in particular, to electronic torque wrenches. The application relates specifically to indexable torque wrenches.  
           [0002]    Typically, torque wrenches, such as electronic torque wrenches, provide an elongated lever arm with a coupling mechanism, such as a drive lug, on a coupling head fixed at an end of the lever arm and disposed for coupling to an associated socket tool, fastener or other device to be torqued. In a typical arrangement, the coupling device includes a drive lug projecting from the lever arm substantially perpendicular thereto. U.S. Pat. No. 4,643,030 discloses such an arrangement, wherein the torque sensing means comprises a strain gauge assembly disposed on the coupling head and connected by suitable electrical connections to display apparatus carried by the lever arm. In many cases, in using such a fixed-head wrench, a universal joint or the like is required between the head and the fastener in order to reach the fastener. This decreases the accuracy of the measurement.  
           [0003]    It is also known to provide indexable torque wrenches, wherein the coupling head is indexable or pivotally movable relative to the lever arm to facilitate access to fasteners in certain applications, such a wrench being disclosed, for example, in U.S. Pat. No. 4,958,541. In such wrenches the torque sensing means, such as a strain gauge assembly, is located on the lever arm.  
         SUMMARY  
         [0004]    This application discloses improved torque wrenching techniques which avoid disadvantages of prior techniques while affording additional structural and operating advantages.  
           [0005]    An aspect of the disclosed technique is the provision of an indexable-head torque wrench which affords accurate torque measurement.  
           [0006]    In connection with the foregoing aspect another aspect is provision of an indexable-head torque wrench wherein the accuracy of the torque measurement is enhanced. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    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.  
         [0008]    [0008]FIG. 1 is a top plan view of a first embodiment of torque wrench;  
         [0009]    [0009]FIG. 2 is a side elevational view of the torque wrench of FIG. 1;  
         [0010]    [0010]FIG. 3 is an enlarged, fragmentary, perspective view of the torque wrench of FIG. 1 with a protective boot added;  
         [0011]    [0011]FIG. 4 is a fragmentary, perspective view of the underside of the working end of the torque wrench of FIG. 2, with a protective sleeve removed;  
         [0012]    [0012]FIG. 5 is a view similar to FIG. 3 of an alternative torque wrench embodiment, with the protective boot removed;  
         [0013]    [0013]FIG. 6 is a perspective view of the yoke of the torque wrench of FIG. 5; and  
         [0014]    [0014]FIG. 7 is a reduced, fragmentary, side elevational view of the torque wrench of FIG. 5, illustrating different positions of the head. 
     
    
     DETAILED DESCRIPTION  
       [0015]    Referring to FIGS.  1 - 4 , there is illustrated an electronic torque wrench, generally designated by the numeral  10 , having an elongated lever arm  11  with a working end  12  and a handle end  13 . The lever arm  11  includes an elongated, substantially tubular shaft  14  and a housing  15  mounted on the shaft  14  and enclosing approximately the rear two-thirds thereof. The housing  15  may be of generally two-part construction and may be provided with a handle grip  16 . Mounted in the housing  15  may be a user interface  17 , including a suitable display  18 , which may be a digital electronic display, and a control keypad  19 . The lever arm  11 , the housing  15  and the circuitry and structure disposed within the housing  15  may be substantially the same as that disclosed in the copending U.S. application Ser. No. 10/293,006, filed Nov. 13, 2002, and entitled “Electronic Torque Wrench,” the disclosure of which is incorporated herein by reference.  
         [0016]    Mounted to the working end  12  of the shaft  14  is a yoke, generally designated by the numeral  20 , which has an elongated, substantially cylindrical body  21  (FIG. 3) telescopically received within the working end of the tubular shaft  14 , and fixedly secured in place therein, as by screws  22  (FIG. 2). The body  21  may be provided with a circumferential flange against which is seated an O-ring  21   a  for sealing against the end of the shaft  14 . Formed diametrically through the body  21  forwardly of the O-ring  21   a  is a slot  23 , which is generally rectangular in transverse cross-section and has an axis substantially perpendicular to the plane of the display  18 . Formed diametrically through the body  21  along an axis substantially perpendicular to that of the slot  23  and intersecting the slot  23  is a bore  24  (FIG. 3).  
         [0017]    Mounted on the body  21  is an elongated head  25 , which has a substantially cylindrical shank  26  provided at one end thereof with a reduced coupling end  27 , which has flattened opposite sides so that it fits upwardly through the slot  23  with a predetermined clearance at the forward and rearward ends thereof Shank  26  is provided at the opposite end thereof with a drive square  28 , which may be provided with a suitable spring-loaded detent ball in a known manner. The coupling end  27  is pivotally coupled in the slot  23  by a pivot pin  29  extending through the bore  24  and through a complementary bore (not shown) in the coupling end  27 . The end clearance between the coupling end  27  and the slot  23  permits a slight pivotal movement of the head  25  about the axis of the pivot pin  29 , the total pivotal travel of the head  25  being less than forty-five degrees, the head  25  being illustrated in the drawings substantially at the midpoint of its pivotal range.  
         [0018]    Referring in particular to FIG. 4, there is mounted on the rear side of the head shank  26  a strain gauge assembly  30 , which may be of the type disclosed in the aforementioned copending application Ser. No. 10/293,006. The assembly  30  includes four gauges arranged in a bridge network, including two deflection sensing gauges  31  and  32  and Poisson correction and temperature compensation gauges  33  and  34 . The terminal strips of the gauge assembly are connected via ribbon wires  35  to electronics in housing  15 , the wires  35  extending upwardly into the lower end of the slot  23  and then rearwardly, longitudinally of the body  21 , along a suitable channel (not shown). A cylindrical sheath or sleeve  36  may be provided in surrounding relationship with the shank  26 , covering the strain gauge assembly  30  and protecting it in use, the sheath  36  being formed of any suitable material, such as a suitable elastomeric material. A flexible and resilient boot  38  may be provided for enclosing the working end  12  of the shaft  14 , the O-ring  21   a  and the portion of the body  21  projecting from the shaft  14 , as well as the head  25  down to the drive square  28 . The boot  38  (FIG. 3) may be of unitary, one-piece construction and may be formed of a suitable rubber or elastomeric material and will protect the yoke  20 , and particularly the pivot assembly thereof, from dust, dirt and the like, as well as protecting the yoke from potentially damaging contact with surrounding surfaces in use.  
         [0019]    As was indicated above, the slot  23  is dimensioned to accommodate a slight pivoting forward and rearward movement of the head  25  to facilitate access to fasteners in certain applications. However, because the strain gauge assembly  30  is mounted on the head  25 , it is always aligned in use with the rotational axis of the fastener being torqued, so that the relative angular position of the head  25  relative to the lever arm  11  has no effect on the value of the torque sensed by the strain gauge assembly  30 .  
         [0020]    Referring to FIGS.  5 - 7 , there is illustrated another embodiment of electronic torque wrench, generally designated  10 A, which is substantially the same as the torque wrench  10 , described above, except that, in place of the yoke  20 , there is provided a yoke  40 , having an elongated cylindrical body  41  telescopically received in the working end of the shaft  14  and secured in place by any suitable means. The yoke  40  differs from the yoke  20 , described above, fundamentally in that its forward portion is in the form of a clevis  22 , having legs  42 A which cooperate to define therebetween a slot  43 . Diametrically aligned bores  44  extend through the arms  42   a . The yoke  40  is provided with a head  45  having a shank  46 , integral at one end thereof with a coupling end  47  with flattened sides which extends into the slot  43  of the clevis  42 . The shank  46  is integral at its opposite end with a drive square  48 . A pivot pin  49  extends through the bores  44  and through a complementary bore (not shown) in the coupling end  47  for pivotally connecting the head  45  to the clevis  42 . Because of the clevis nature of this coupling, it will be appreciated that the head  45  is capable of a pivotal movement through at least 180 degrees, as illustrated in FIG. 7.  
         [0021]    The strain gauge assembly  30  may be mounted on the shank  46  of the head  45 , preferably being mounted on a side thereof. The strain gauge assembly and the shank  46  may be enclosed within a suitable sheath  50 , having a sleeve portion  51  which encompasses the adjacent end of a suitable cable  52  providing electrical connection to the strain gauge assembly  30  and extending through a suitable hole  53  in the yoke  40  for connecting to the electronics in the housing  15 , in a known manner. The side mounting of the strain gauge assembly  30  on the head  45  accommodates the full range of pivotal movement of the head  45  without having to provide an unduly large slack portion of the cable  52 . It will be appreciated that, if desired, a suitable boot, like the boot  28  described above, could be provided for protecting the yoke  40 . Again, it will be appreciated that, because the strain gauge assembly is mounted on the head  45 , it remains in alignment with the rotational axis of the fastener being torqued, the sensed value of torque being substantially unaffected by the pivotal orientation of the head  45 .  
         [0022]    From the foregoing, it can be seen that there has been provided an improved electronic torque wrench with an indexable head, which provides sensed torque values which are unaffected by the orientation of the head relative to the lever arm of the wrench.  
         [0023]    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.