Abstract:
This application relates generally to a reversible force or torque transfer device. This device may be used in many different applications. The example used for the illustrative purposes of this patent is a wrench. The present invention devises a reverse mechanism that can resist any amount (up to the shear strength of the material) of randomly generated forces that may cause this effect.

Description:
FIELD OF THE INVENTION 
       [0001]    This application relates generally to a reversible force or torque transfer device. This device may be used in many different applications. The example used for the illustrative purposes of this patent is a wrench. 
       BACKGROUND 
       [0002]    Extensive prior art exists in the field of indexing wrenches that are used to tighten or loosen fasteners. For the class of wrenches that employ roller clutches to transfer torque from the wrench to the fastener, it is possible that the geometric configuration of the wrench may result in forces that cause the reversing mechanism to be back-driven. If these forces are large enough, the reverse mechanism may enter a neutral position or cause the wrench to change direction. 
         [0003]    The present invention devises a reverse mechanism that can resist any amount (up to the shear strength of the material) of randomly generated forces that may cause this effect. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a perspective view of a wrench that includes the reverse mechanism device sub-assembly in accordance with the teachings of this disclosure. 
           [0005]      FIG. 2  is an exploded view of the reverse mechanism in accordance with the teachings of this disclosure. 
           [0006]      FIG. 3  is a close-up perspective view of the major parts that comprise the reverse mechanism device. 
           [0007]      FIG. 4  is a close up view of two of the reverse mechanism&#39;s major parts illustrating several important geometric features. 
           [0008]      FIG. 5  is a close up view of one of the reverse mechanism&#39;s major parts illustrating important geometric features. 
           [0009]      FIG. 6  is a close-up sectional view of the reaction forces present in reverse mechanism in accordance with the teachings of this disclosure. 
           [0010]      FIGS. 7   a ,  7   b , and  7   c  is a series of sectional views of the reverse as it moves from a forward (clockwise) to a reverse setting and then back to the forward setting, in accordance with the teachings of this disclosure. 
           [0011]      FIG. 8  presents a series of sectional views of the reverse as it moves from a forward (clockwise) to a reverse setting, in accordance with the teachings of this disclosure. 
           [0012]      FIGS. 9   a  and  9   b  present a series of views of the reverse mechanism detent hammer as it moves from a forward (clockwise) to a reverse setting, in accordance with the teachings of this disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring to  FIG. 1 , three perspective views of a wrench  200  that contains the reverse mechanism device  100  are shown. The moment arrows  101  and  102  illustrate the forces that must be applied to the thumb lever  112  and spindle tang  141  when operating the reverse mechanism  100 . In this case, applying the moment arrows  101  and  102  place the reverse mechanism  100  in the forward setting. The forward setting results in the wrench transferring torque in the clockwise direction (the wrench  200  is able to tighten a right-hand threaded fastener) when viewed from the back of the wrench (thumb lever  112  faces the user when held in this orientation). 
         [0014]    The reverse mechanism  100  is shown in an exploded state in  FIG. 2 . This figure provides additional perspective on how the parts of reversing mechanism  100  may assemble. For the purpose of this disclosure,  FIG. 2  allows the listing of parts with surfaces that develop reactionary forces when reverse mechanism  100  is operated. These are: rigid spindle  140 , rigid rollers  150 , rigid housing  160 , rigid detent slider  130 , rigid cage  120 , rigid detent hammer  190 , and rigid thumb lever  110 . 
         [0015]    Sub-assembly  300  in  FIG. 3  shows several parts of reverse mechanism  100  assembled in a perspective view. Sub-assembly  400  is a sectional view of the same parts. The sectional cut was applied so that the critical part surfaces that develop reactionary forces are visible. In sub-assembly  400  thumb lever  110  has been assembled to the cage  120  and held in place with the retaining clip  123  (clip  123  is hidden behind sliding detent  130 ). Rigid detent hammer  190  and flexible spring  195  are assembled in detent guide channel  111  and are also hidden by cage  120 . Rigid detent slider  130  is inserted into the cage channel  121  such that detent slider hole  131  fits over the rigid triangular boss  114  of rigid thumb lever  110 . Spindle  140  slides onto cage  120 , with detent grooves  141  or  142  mating with either sliding hammer tooth  135  or  136 . The geometry of this preferred embodiment does not require the spindle detent grooves to be mated with a particular detent tooth. This is by design. The detent grooves  141  and  142  are 180 degrees apart. The detent hammer teeth  135  and  136  are symmetrically offset from 180 degrees by the tooth angle  132  ( FIG. 4 ). In a less desirable embodiment, this relationship could be reversed and the detent teeth  135  and  136  could be 180 degrees apart and the detent grooves  141  and  142  could be symmetrically less than 180 degrees apart. 
         [0016]    The geometry of the parts comprising device  100  are designed to achieve near tangency of the rollers  150  with three enclosing contact surfaces: pillar surface  126 , rigid housing surface  162 , and spindle ramp surface  143   b  ( FIG. 4 ). When the reverse mechanism  100  moves from forward to reverse or the opposite, pillar width  124  and sliding detent tooth angle  132  must be carefully designed to create the near tangent conditions shown in  FIG. 4 . If pillar width  124  is increased, then tooth angle  132  must decrease. If the pillar width  124  decreases, then tooth angle  132  must increase. If tooth angle  132  increases too much, detent hammer teeth  135  and  136  are difficult to design without interference with the spindle surface  144  and the mechanism fails to work. Also, if pillar width  124  becomes too large, it is possible that it may interfere with roller  150  when large torque is transferred through device  100  and the roller  150  travels high up the ramp  143   b.    
         [0017]    By design, triangular boss  114  fits smoothly with sliding hammer surface  137  (see, for example, FIGS.  3 , 4 , 5 , 6 , and  7   a - c ). The shape of surface  137  is determined by the equation of line  134 . Equation of line  134  in Cartesian coordinates, is: 
         [0000]        x=r *sin(gamma), 
         [0000]        y=−r *cos(gamma)+[Total detent slide movement]/(2*sin((180−beta)/2))*sin((180−beta)/2−gamma),  Equation 1000
 
         [0000]    where:
       position x=0, y=0 is at the center of the part  130  (intersection of axis  138   a  and  138   b ,  FIG. 4 ),   r=radius  118 −radius  113  ( FIG. 5 ),   Total detent slide movement=2*distance  139   a  ( FIG. 4 ),   Beta=angle  119  ( FIG. 5 ),   gamma=from 0 degrees through (angle  125  (FIG.  3 )−2*(angle  133 )( FIG. 4 )).       
 
         [0023]    Surface  137  is symmetric about axis  138   a  and is the preferred shape for hole  131 . It provides for smooth motion of the sliding hammer  130  when thumb lever  110  is rotated. The shape of surface  137  also maintains a near tangency with both radiuses  116  and  117  (radii  116  and  117  are equal) with surface  137  simultaneously. The triangular boss angle  119  ( FIG. 5 ) affects the shape of hole  131  by way of equation 1000. The triangular boss corner radius  113  affects the shape of hole  131 . Distance  139   b  ( FIG. 4 ) is equal to radius  113 . The distance that sliding detent hammer must slide forward in order to engage a detent groove  141  or  142  (distance  139   a ,  FIG. 4 ) is also a variable in the equation of line  134 . Axis  139   c  is the location of thumb lever  110  center of rotation relative to sliding detent  130  when detent  135  is fully seated. 
         [0024]    Seat angle  133  ( FIG. 4 ) and triangular boss angle  119  ( FIG. 5 ) determine angular distance  128  ( FIG. 3 ), the angular distance between the centers of detent cups  121  and  122 . Angle  128  is: 
         [0000]      Angle 128=angle 119+2*(seat angle 133).  Equation 2000
 
         [0000]    Seat angle  133  affects the shape of hole  131  so that any reactionary forces cannot back-drive the triangular boss  114 . 
         [0025]      FIG. 5 , with several perspective views of thumb lever  110 , also illustrates in detail the preferred arrangement of the detent hammer  190  and thumb lever  110 . The detent hammer channel  111  is aligned with the thumb lever protrusion  112 . This allows the thickness  113  of the thumb lever to be relatively small compared to the depth of the detent channel  111 . The depth of detent channel  111  is configured so that a portion of the detent hammer  190  will protrude from the channel  111 . The height of this protrusion is slightly smaller than the depth of detent guide profile  123 . The portion of detent hammer  190  that protrudes from the surface of thumb lever  110  is inserted into the pocket that is formed by detent guide profile  123  ( FIG. 3 ) when the thumb lever  110  is assembled to the cage  120 . 
         [0026]    Referring to  FIG. 6 , arrow  200  represent a randomly applied moment to spindle  140  relative to the cage part  120 . Moments such as moment  200  can develop due to friction between parts and from moments applied perpendicular to the axis of rotation of device  100 . If sliding detent  130  and roller bearings  150  were temporarily removed from device  100 , spindle  140  could rotate freely about the cage part  120  at surface  230 . But, with the sliding detent  130  installed in reverse mechanism  100  and held in place by thumb lever triangular boss  114 , spindle  140  cannot rotate freely and any moments that develop result in reactionary forces  205  or  210  depending on the direction of the moment. If triangular boss  114  was temporarily removed from the device  100 , reactionary forces  205  or  210  would cause sliding detent  130  to slide in channel  121  such that detent tooth  135  or  136  is pushed away from detent groove  141  or  142 . The reactionary forces  215  and  220  keep sliding detent  130  in channel  121 . 
         [0027]    With the thumb lever triangular boss installed in device  100 , and positioned as shown in  FIG. 6 , sliding detent  130  is not free to push away from the detent grooves  141  or  142  in spindle  140 . Reactionary forces  225  develop that prevent such movement of sliding detent  130  due to a moment  200 . Furthermore, seat angle  133  positions the reactionary forces  225  such that the net resulting force passes to the left of thumb lever center of rotation  235 . This geometry creates a moment  245  and a resulting reactionary force  240 . This preferred arrangement results in a mechanism that cannot be back-driven by a moment  200  without shearing triangular boss  114 . Seat angle  133  could be zero or negative. If seat angle  133  were a negative value, device  100  would then begin to rely on detent hammer  190  to prevent triangular boss  114  from being back-driven. This is a less desirable configuration. In the preferred arrangement, the detent hammer  190  seated in detent pocket  121  or  122 , must only hold thumb lever  110  (and its triangular boss  114 ) in place until an operator applies moments  101  and  102 . 
         [0028]      FIGS. 7   a,b , and  c  are a series of cross-sectional views that illustrate the operation of reverse mechanism  100  when moments  101  and  102  are applied. The figures show device  100  going from a forward configuration (able to tighten a standard right-hand threaded fastener) to a reverse configuration (able to loosen a standard right-hand threaded fastener) at alpha=110 and then back to a forward configuration (alpha=110 through alpha=0′). 
         [0029]    In the  FIGS. 7   a - c  series, thumb lever  110  is rotated relative to cage  120 . The position of cage  120  and handle  160  is held fixed. Spindle  140  is free to move as necessary. Cage  120  and handle  160  are held fixed in the figures for the purpose of clearly illustrating the operation of device  100 . When operating device  100  with moments  101  and  102 , however, cage  120  and handle  160  need not have fixed positions. They also may move in response to applied moments  101  and  102 . The handle  160  may also have gravitational forces or other external forces applied. 
         [0030]    In  FIG. 7   a , alpha=0, thumb lever  110  is shown at its initial position. Thumb lever  110  has been rotated counter-clockwise relative to the plane of the printed page to its fullest extent possible and detent hammer  190  is fully seated in detent pocket  121 . Sliding detent tooth  135  is fully seated in detent groove  141  (device  100  could be assembled so that tooth  135  is seated in groove  142  and due to symmetry the figure would look identical, but assume it is groove  141  for the this description). With detent  135  fully seated, device  100  operates as a roller clutch (cite patent here?) that transmits torque to spindle  140  when handle part  160  rotates in the counter-clockwise direction relative to the printed page. High amounts of torque can be transferred through the wedging rollers  150 , up to the shear strength of spindle tang  141 . When handle  160  rotates clockwise relative to the printed page, rollers  150  in device  100  do not wedge. Device  100  now functions much like a roller bearing, transmitting a small amount of torque to spindle  140 . The small amount of torque transmitted is due to a combination of the lubricant viscosity and the friction that occurs between the freely sliding rollers  150  and handle surface  162 . Additional friction emanates from the surfaces of assembled parts  120 ,  160 ,  140  and  170  as these parts rotate relative to one another. 
         [0031]    In  FIGS. 7   a  and  7   b , device  100  is shown with alpha (thumb lever  110  rotation angle is measured from cup pocket  121 ,  FIG. 3 ) progressing in increments from alpha=0 degrees through alpha=110 degrees. At alpha=5 and alpha=10 degrees, the thumb lever  110  moves through the seat angle  133  but does not perform any work to retract detent tooth  135  from detent groove  141 . Through the first ten degrees of rotation thumb lever  110  is moving out of the seat angle whose geometry provides advantageous reactionary forces  225 . 
         [0032]    Sometime shortly after alpha exceeds 10 degrees, thumb lever triangular boss radius  116  ( FIG. 5 ) comes into contact with sliding detent hole inner surface  137  and begins performing work, retracting detent tooth  135 .  FIG. 7   a , alpha=20 degrees through alpha=50 degrees, shows detent  135  retracting from detent groove  141 . As detent tooth  135  retracts, applied moments  101  and  102  cause spindle  140  to rotate relative to both cage  120  and sliding detent  130  that is constrained in cage channel  121 . Spindle  140  rotates counter-clockwise relative to the printed page and is only limited in its initial rotation by the reactionary forces that develop between the detent tooth  135  and detent groove  141 . 
         [0033]      FIG. 6   a , alpha=60 is the approximate angle at which the rotation of thumb lever  110  retracts detent tooth  135  just clear of detent groove  141 . Spindle  140  is now free to rotate unconstrained by detent tooth  135 . At this point in the operation of device  100 , applied moments  101  and  102  causes spindle  140  to continue counter-clockwise rotation relative to the printed page. As spindle  140  rotates, spindle ramps  143   a  ( FIG. 4 ) come into contact with rollers  150 . Once in contact, ramps  143   a  sweep the rollers  150  counter-clockwise. As rollers  150  are relocated in a counter-clockwise direction, they also may come into contact with and slide along handle surface  162 . Spindle  140  and rollers  150  continue to rotate from applied moments  101  and  102  until rollers  150  approach pillar surfaces  127  (only one surface  127  is called out in  FIG. 4 . There are a total of eight surfaces  127  in device  100 ). At this point rollers  150  can begin to wedge and the rotation of spindle  140  due to applied moments  101  and  102  ends. Spindle  140  may stop rotating due to wedging of rollers  150  or do to contact of detent tooth  136  with detent groove  142  or both simultaneously. The magnitude of applied moments  101  and  102  and frictional forces determine which contact occurs first and stops the rotation of spindle  140 . In  FIG. 7   b , approximately at or between alpha=80 and alpha=90 the rollers  150  wedge or tooth  136  contacts the surface of detent groove  142 , stopping rotation of spindle  140 . 
         [0034]    At alpha=100,  FIG. 7   b , thumb lever  110  has pushed sliding detent  130  far enough down so that detent  136  is fully seated in detent groove  142 . The geometry of detent teeth  135 ,  136  and detent grooves  141 , 142  are self-seating. The large mechanical advantage generated by thumb lever  110  drives the detents into the matching detent grooves regardless of applied moment  102 , once the detent has engaged the detent groove that it mates with. When thumb lever  110  completes its 110 degree rotation (alpha=110,  FIG. 7   b ), device  100  is now reversed. It will now transmit torque from handle  160  to spindle  140  when the handle is rotated clockwise relative to the printed page. This corresponds to loosening a standard right-hand threaded fastener. 
         [0035]      FIGS. 7   b  and  7   c , alpha=110 through alpha=0′, illustrate reverse mechanism  100  as it operates to return to a ‘forward’ setting. To return to a ‘forward’ setting, moments  101  and  102  must be applied in the opposite direction from their representation in  FIG. 1 . At the end of this sequence where alpha=0′,  FIG. 7   c , device  100  is now back to its original configuration of alpha=0,  FIG. 7   a . When device  100  moves from alpha=110 to alpha=0′, movement of the parts is the nearly the same as that described for the movement from alpha=0 to alpha=110. The obvious differences are the reversal of the rotation direction and the different but symmetric reaction surfaces. The symmetry of operation should be obvious by inspection. 
         [0036]    There is a second technique by which device  100  can operate to affect the directional setting of the wrench. It is possible to grasp device  200  with a single hand such that the hand holds the handle  160  and spindle tang  141  simultaneously. Depending on the operational setting, a user may wish to or simply as habit prefer to employ this method. In this case, effectively the tang  141  becomes positionally fixed to the handle  160 .  FIG. 8  illustrates device  100  when it operates in this scenario, placing device  100  into a counter clockwise setting. Several thumb lever angles (alpha=63, 65, 70, 75, 80, 90, 100, and 110) are illustrated in sectional views of device  100 . The beginning thumb lever  110  angles have been omitted.  FIG. 8  begins with the thumb lever  110  angle alpha=63. At this point in the operation of device  100 , thumb lever  110  has rotated from alpha=0 to alpha=63. All parts have remained in their beginning positions except thumb lever  110  and sliding detent hammer  130  which has been retracted from detent groove  141 . At approximately alpha=63, detent  136  has just come into contact with detent groove  142 . Once in contact, the reactionary forces that develop between the detent  136  and detent groove  142  cause the spindle  140  to rotate. The rotation is illustrated in  FIG. 8 , alpha=65 through alpha=100 where the spindle rotates counter clockwise relative to the printed page. Because of the large mechanical advantage developed by thumb lever triangle  114  and sliding detent hammer shape  137 , detent  136  is powerfully driven into detent groove  142  and the rotation takes place even if the operator holds the handle  160  and tang  141  simultaneously. Indeed, the human hand is not strong enough to prevent the rotation because the mechanical advantage employed by the thumb lever  110  is so large. In  FIG. 8 , from alpha=100 to alpha=110, the thumb lever  110  moves through the seating angle  133  and the operation of device  100  is complete. 
         [0037]    Cage  120  has two detent pockets  121  and  122  that are connected by detent curve  123  ( FIG. 3 ).  FIGS. 9   a  and  9   b  illustrate how detent hammer  190  moves along detent curve  123  as device  100  is moved back and forth between its forward and reverse settings. As thumb lever  110  is rotated from alpha=0 through alpha=55, optional detent curve  123  forces detent hammer  190  to move towards the center of thumb lever  110 &#39;s axis of rotation. This movement causes spring  195  to compress and store energy. As thumb lever  110 &#39;s rotation passes alpha=55 degrees, spring  195  begins to release its stored energy. The reactionary forces  505  between detent  190  and detent curve  123  cause thumb lever  110  to rotate through the remaining angles (alpha=60 through alpha=110,  FIGS. 9   a  and  9   b ) under its own power. 
         [0038]    The preferred shape of optional detent curve  123  is such that the contact angle between detent hammer  190  and detent curve  123  is always at a 45-degree angle relative to the detent hammer longitudinal axis  191  (view  500 ,  FIG. 9   b —not drawn yet) of the detent hammer  190 . The equation for this line is: 
         [0000]        r dr/d theta= z,   Equation 3000
       where r and theta are variables describing a cylindrical coordinate system and z=1. Values other than z=1 will result in reactionary forces that required the user to exert more or less torque on thumb lever  110  in order to compress spring  195 .       
 
         [0040]    It will be appreciated by those of ordinary skill in the art that the invention can be embodied in other specific forms without departing from the spirit or essential character thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalents thereof are intended to be embraced therein.