Abstract:
A wrench with electronic torque display unit includes a torque adjustment mechanism which includes a sleeve, two gears, a rod and a movable tube, and a locking mechanism which includes a positioning cap, wherein the value of the torque to be output can be set by operating the adjustment mechanism by rotating the positioning cap. The pre-set value is displayed on the display screen so as to provide a wrench with convenient operation and precise feature.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a wrench with an electronic torque display unit which adjusts variable resistors by the revolutions of a small gear and a circuit board to detect the resistance so display in the electronic torque display unit. 
       BACKGROUND OF THE INVENTION 
       [0002]    A conventional wrench with an electronic torque display unit is disclosed in U.S. Pat. No. 5,537,877 and shown in  FIGS. 7 and 8 , wherein the wrench with a case A, a driving unit B, a knocking member C, a push unit D which is located in the case A and in contact with the knocking member C in axial direction such that the knocking member C does not knock the case A before the pre-set torque is reached. An adjustment unit can adjust the initial force of the push unit D to set the value of the pre-set torque. 
         [0003]    The push unit D includes a push member D 2  which is movable axially in the case A, a spring D 1  located between the push member D 2  and the knocking member C, a tubular handle F and a rod unit E. The handle F has a connection end rotatably connected with a second end of the case A and the rod unit has a first end inserted into the handle F and a second end of the rod unit E is inserted into the casa A and is connected with the push member D 2 . The first and second ends of the rod unit E are operated by the handle F and the case A. The push member D 2  is moved axially by rotating the handle F. 
         [0004]    The torque unit further includes a torque detection unit G which includes bodies G 1 , G 2 , a detection member G 3 , a transferring circuit G 4  electrically connected with the detection member G 3 , and a display unit G 5 . The bodies G 1 , G 2  are connected to the case A and the detection unit G is connected with the bodies G 1 , G 2 . The detection unit G generates a signal which is a signal regarding to the push member D 2 . The transferring circuit G 4  transfers the electronic signals into digital signals which are shown in the display unit G 5 . 
         [0005]    The present invention intends to provide a wrench with an electronic torque display unit which improves shortcomings such as inconvenience of use and less precise of the conventional torque display unit for wrenches. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention relates to a wrench comprising: 
         [0007]    a shank having a driving head connected to a first end of the shank and a ratchet member received in a recess defined in the driving head, two pawls pivotally engaged with the ratchet member and a switch lever connected with the pawls, a cover disposed on the driving head and closing the recess; 
         [0008]    a case fixedly connected to the shank and having a first end into which the shank is inserted and a second end which includes a first slot defined axially through a wall thereof; 
         [0009]    an electronic display unit connected to the case and including a first part and a second part, the first part having a circuit board and a display screen; 
         [0010]    a sleeve being a hollow member and having a first end thereof fixed to the second end of the case, a second end of the sleeve pivotally connected to a handle, the handle including a stepped hole defined in an open end thereof and a plurality of notches defined in the second end of the sleeve, variable resistors provided in the second end of the sleeve; 
         [0011]    a torque unit received in the case and the sleeve, the torque unit including a knocking member, a spring, a movable tube, a rod, a first gear, a second gear which has less number of teeth than that of the first gear, and a disk, the movable tube having first inner threads defined therein and a guide pin extending through the first slot in the case and guiding movement of the movable tube, the rod having a first end and a second end, the first end of the rod including first outer threads which are threadedly engaged with the first inner threads in the movable tube, the first gear fixed to the rod and the second gear engaged with the first gear and engaged with the variable resistors, the disk including engaging pins corresponding in position to the notches in the sleeve, and 
         [0012]    a pin extending through the handle and the rod. 
         [0013]    The first gear drives the second gear which is connected with the variable resistors, and the variable resistors are electrically connected with the electronic display unit. 
         [0014]    The wrench further comprises a positioning arrangement which includes second outer threads formed on the second end of the rod, a push member, the first gear and a collar fitted onto the rod and a positioning cap threadedly connected to the second outer threads with second inner threads defined in the positioning cap, the push member including dimples and a plurality of positioning pins connected to the first gear, the positioning pins being removably engaged with the dimples, the collar including a second slot. 
         [0015]    The primary object of the present invention is to provide an electronic torque display unit which shows the pre-set value of torque on the screen and generates sound when the wrench reaches the pre-set torque. The wrench is easily operated and the value of torque is easily to read from the display screen. 
         [0016]    The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is an exploded view to show the electronic torque display unit for wrenches of the present invention; 
           [0018]      FIG. 2  is a perspective view to show the wrench with the electronic torque display unit of the present invention; 
           [0019]      FIG. 3  is a cross sectional view to show the electronic torque display unit of the present invention, wherein the positioning cap is located at a position where the movable tube is not yet pushed by the rod; 
           [0020]      FIG. 4  is a cross sectional view to show the electronic torque display unit of the present invention, wherein the handle is rotated and the movable tube moves toward the spring; 
           [0021]      FIG. 5  is a cross sectional view to show the electronic torque display unit, when the circuit board detects the torque reaches the pre-set value, the positioning cap is rotated to engage the positioning pins with the dimples and the handle is locked and cannot be rotated; 
           [0022]      FIG. 6  is a diagram to show the circuit used in the electronic torque display unit of the present invention; 
           [0023]      FIG. 7  shows a cross sectional view of a conventional electronic torque display unit, and 
           [0024]      FIG. 8  shows the body of the conventional torque detection unit. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    Referring to  FIGS. 1 to 3 , a preferred embodiment of the present invention comprises a shank  1 , a hollow and elongate case  2 , an electronic display unit  3 , sleeve  4 , a handle  5 , a torque unit  6 , and a long pin  7 . 
         [0026]    The shank  1  has a first end and an opposite second end. A driving head  11  is disposed at the first end of the shank  1 , and a ratchet member  112  is received in a recess  111  defined in the driving head  11 . Two pawls  113  are pivotally engaged with the ratchet member  112  and a switch lever  114  is connected with the pawls  113  so as to change effective direction that the ratchet head  11  is allowed to rotate. A cover  115  is disposed on the driving head  11  and closes the recess  111 . 
         [0027]    The case  2  is fixedly connected to the shank  1 , and has a first end and a second end. The second end of the case  2  includes a first slot  21  defined axially through a wall thereof. 
         [0028]    The electronic display unit  3  is connected to the case  2  and includes a first part  31  and a second part  32 . The first part  31  has a circuit board  311  and a display screen  312 . The circuit board  311  detects the value that the pre-set torque is set and the display screen  312  shows the value of the torque. 
         [0029]    The sleeve  4  is a hollow member, and has a first end fixed to the second end of the case  2  and a second end connected to the handle  5 . A plurality of notches  41  are defined in the second end of the sleeve  4 . Variable resistors  42  are provided in the second end of the sleeve  4 . 
         [0030]    The handle  5  includes a stepped hole  51  defined in an open end thereof. 
         [0031]    The torque unit  6  is received in the case  2  and the sleeve  4 , and includes a knocking member  61 , a spring  62 , a movable tube  63 , a rod  64 , a push member  65 , a first gear  66 , a second gear  66 A which has less number of teeth than that of the first gear  66 , a disk  67 , a collar  68  and a positioning cap  69 . The knocking member  61  has a pin  611  which connects the knocking member  61  to the second end of the shank  1 . The movable tube  63  has first inner threads  631  defined therein, and a guide pin  632  extends through the first slot  21  in the case  2  and guides movement of the movable tube  63 . The rod  64  has a first end and a second end. The first end of the rod  64  includes first outer threads  641  and the second end of the rod  64  includes second outer threads  642 . The first outer threads  641  are engaged with the first inner threads  631  in the movable tube  63 . The push member  65  includes two side pins  651  connected thereto such that the push member  65  is fixed to the second end of the case  2 . The push member  65  includes multiple dimples  652 . The first gear  66  is fixed to the rod  64 , and multiple positioning pins  661  extend through the first gear  66 . The positioning pins  661  are located corresponding in position to the dimples  652 . The second gear  66 A is engaged with the first gear  66  and pivotally connected with the variable resistors  42  of the sleeve  4 . The disk  67  includes engaging pins  67  corresponding in position to the notches  41  in the sleeve  4 . One side of the disk  67  engages with the first gear  66 , and the other side of the disk  67  engages with the stepped hole  51  in the handle  5 . The collar  68  fits onto the second end of the rod  64  and has a second slot  681  defined therethrough in axial direction. The positioning cap  69  includes second inner threads  691  to engage with the second outer threads  642  of the rod  64 . 
         [0032]    The long pin  7  extends through the handle  5 , the collar  68  and the rod  64 . 
         [0033]    The first gear  66  drives the second gear  66 A which is connected with the variable resistors  42 . The variable resistors  42  are electrically connected with the electronic display unit  3 . 
         [0034]    The wrench comprises a positioning arrangement which includes the second outer threads  642  provided on the second end of the rod  64 , the push member  65 , the first gear  66  and the collar  68  fitted onto the rod  64  and the positioning cap  69  threadedly connected to the second outer threads  642  with the second inner threads  691  in the positioning cap  69 . The positioning pins  661  are removably engaged with the dimples  652 . When the circuit board  311  detects the output torque of the wrench reaches the pre-set value of the torque, the positioning arrangement locks the handle  5 . 
         [0035]    As shown in  FIG. 3 , when using the wrench, the positioning cap  69  is located at a rear position and away from the collar  68 , a gap is defined between the positioning cap  69  and the collar  68  so that the collar  68  does not push the two positioning pins  661  which do not engage with the dimples  652  and push against the push member  65 . By this arrangement, the handle  5  can drives the first gear  66  to set new torque. 
         [0036]    As shown in  FIG. 4 , when rotating the handle  5 , the rod  64  spins and rotates the movable tube  63 . The guide pin  632  is movably engaged with the first slot  21  so that the movable tube  63  moves axially and linearly. The spring  62  is then compressed by the movable tube  63 . 
         [0037]    As shown in  FIG. 5 , when the circuit board  311  detects that the torque output reaches the pre-set value of the torque, the positioning cap  69  is then rotated toward the collar  68  which urges the two positioning pins  661  of the first gear  66  to engage with the dimples  652  and secure the first gear  66 . By this arrangement, the handle  5  cannot be rotated so as to set the value. When the driving head  11  reaches the pre-set value of the torque, the knocking member  61  is disengaged from the shank  1  and generates a sound to acknowledge the user that the pre-set torque is reached. 
         [0038]    When the wrench is not in use, the handle  5  should be rotated to a position where the spring  62  is not compressed such that the spring  62  can be used for a longer period. 
         [0039]    As shown in  FIG. 6  which shows that the electronic torque display unit is operated by a direct current source  8 , wherein the first gear  66  drives the second gear  66 A by rotating the handle  5 . The second gear  66 A is engaged with the variable resistors  42  of the sleeve  4 . The variable resistors  42  are controlled by the number of the revolutions of the second gear  66 A. The circuit board  311  detects the value of the resistance and is electrically connected with the electronic display unit  3  so that the value of the torque is displayed on the display screen  312 . 
         [0040]    The variable resistors  42  output analog signals which are converted into digital signals via the circuit board  311  and the digital signals are displayed in the display screen  312 . 
         [0041]    While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.