Patent Abstract:
Apparatus directed to the art of disengaging an input from an output at predetermined torque values. A torque limiting clutch capable of use as a solid drive unit and a torque limited unit for which the torque disengagement value is selectable. The torque limiting clutch has an overload assembly and a torque drive mechanism which may comprise a plurality of drive pins. Additionally, the torque limiting clutch may comprise seals to discourage contaminants from entering the clutch.

Full Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 61/732,671, filed 3 Dec. 2012, and entitled “Torque Limiting Clutch.” 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to releasable torque transmitting couplings and it is concerned more particularly with a self-releasing clutch which will disengage when a predetermined amount of torque is experienced. 
         [0003]    While the principal purpose of torque limiting clutches is to protect various types of power driven equipment against overload, such clutches have heretofore also been perfected to take care of several specific requirements. For instance, in many installations it is desirable that once the clutch has become disengaged due to an overload it should stay disengaged as long as the overload condition persists, and that the clutch can be reengaged by torque reversal at will when the overload condition has abated to the point where operation of the driven equipment can be resumed. When the clutch idles, that is, while its driving member continues to rotate and its driven member is at a standstill, friction losses between the driving and driven members and wear of the relatively engageable and disengageable clutch elements should be kept to a minimum. 
         [0004]    Further, the torque load at which the clutch becomes disengaged should be precisely fixed, that is, disengagement should take place at the exact moment when the torque reaches a given limit. In its engaged driving condition the clutch should provide a positive driving connection between the driving and driven shafts, that is, there should be no gradual yielding between the driving and driven clutch parts. The driving connection should be disrupted instantaneously when the given torque limit has been reached. In some installations it is also desirable that the driving and driven clutch parts can be reengaged in only one rotatively adjusted position relative to each other. This requirement usually has the purpose of maintaining a time relationship between several operating units that are driven from a single power source. Provisions should also be made to vary the torque limit at which the clutch will automatically disengage under an overload, and such variation to increase or decrease the torque limit should be possible conveniently without dismantling the clutch. Another provision which is frequently desired is that the clutch should be unidirectional, that is, it should provide torque control in one direction and solid drive in the opposite direction. Incorporated herein by reference is U.S. Pat. No. 3,893,553. 
         [0005]    Additionally, fluid or other contaminates entering a mechanism like the present invention may cause premature wear or failure. For example, fluid or other contaminants may enter during a parts cleaning procedure. Therefore, where exposure to fluid or dirt is possible, a clutch capable of limiting the exposure of internal parts to fluids or contaminates would be desirable. 
         [0006]    Furthermore, clutch characteristics may change upon clutch break-in. Therefore, a clutch that is manufactured to take into account break-in patterns would be desirable. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention disclosed herein relates generally to a torque limiting clutch, and more particularly to a more versatile and higher strength torque limiting clutch which may comprise additional drive pins to share torque loads, sealed components to prevent contaminants from entering the clutch, and machined components which replicate break-in wear patterns to maintain consistent clutch performance characteristics. 
         [0008]    One aspect of the invention provides a torque-limited clutch having a positive drive direction and a torque-limited drive direction with an outer clutch assembly and an inner clutch member separated radially by a rotor, the outer clutch assembly comprising a first housing coupled to a second housing, the first housing comprising at least one milled pocket having a first stop end and a second stop end, the first housing and the second housing each comprising a plurality of ball pockets each having a ball egress, the rotor comprising a first planar surface and a second planar surface wherein a plurality of overload assembly through-holes extend from the first planar surface through the second planar surface and at least one drive pin extends outward from the first planar surface, and a plurality of overload assemblies positioned substantially within the rotor overload assembly through-holes, the plurality of overload assemblies each comprising at least one ball and a biasing mechanism, whereby when the torque-limited clutch is used in the positive drive direction the at least one drive pin is positioned against the first stop end of the at least one milled pocket and when the torque-limiting clutch is used in the torque-limited drive direction the at least one ball is biased in one of the plurality of ball pockets and wherein the at least one ball exits the ball pocket along the ball egress upon the clutch experiencing a torque level exceeding a predetermined torque limit. 
         [0009]    The ball egress may be a circumferential chamfer about the ball pocket. 
         [0010]    The ball egress may also be a circumferential rounded path about the ball pocket. 
         [0011]    The ball egress may also be a contoured path following the path of the ball during a torque overload. 
         [0012]    The milled pocket first stop end and the milled pocket second stop end may be of substantially similar curvature of the drive pin. 
         [0013]    Another aspect of the invention provides a sealed torque-limited clutch having a positive drive direction and a torque-limited drive direction with an outer clutch assembly and an inner clutch member separated radially by a rotor, the outer clutch assembly comprising a first housing coupled to a second housing with a gasket placed therebetween, wherein the first housing is coupled to the second housing with self-sealing type screws, the first housing comprising a first housing protrusion with a first housing o-ring groove, a first housing o-ring positioned in the first-housing o-ring groove, and at least one milled pocket having a first stop end and a second stop end the second housing comprising a second housing protrusion with a second housing o-ring groove and a second housing o-ring positioned in the second housing o-ring groove, the first housing and the second housing each comprising a plurality of ball pockets each having a ball egress, the inner clutch having an inner clutch first sealing surface and an inner clutch second sealing surface, wherein the inner clutch first sealing surface is in contact with the first housing o-ring and the inner clutch second sealing surface is in contact with the second housing o-ring the rotor comprising a first planar surface and a second planar surface, a plurality of overload assembly through-holes extend from the first planar surface through the second planar surface and at least one drive pin extends outward from the first planar surface, and a plurality of overload assemblies positioned substantially within the rotor overload assembly through-holes, the plurality of overload assemblies each comprising at least one ball and a biasing mechanism, whereby when the torque-limited clutch is used in the positive drive direction the at least one drive pin is positioned against the first stop end of the at least one milled pocket, and when the torque-limiting clutch is used in the torque-limited drive direction, the at least one ball is biased in one of the plurality of ball pockets, and wherein the at least one ball exits the ball pocket along the ball egress upon the clutch experiencing a torque level exceeding a predetermined torque limit. 
         [0014]    The ball egress may be a circumferential chamfer about the ball pocket. 
         [0015]    The ball egress may also be a circumferential rounded path about the ball pocket. 
         [0016]    The ball egress may also be a contoured path following the path of the ball during a torque overload. 
         [0017]    The milled pocket first stop end and the milled pocket second stop end may be of substantially similar curvature of the drive pin. 
         [0018]    The first housing ball pockets may each have a first housing threaded channel extending through the exterior of the first housing wherein torque-adjustment screws may be inserted from the exterior of the first housing and through the first housing threaded channel to disengage the at least one ball from the first housing ball pockets. 
         [0019]    The torque-adjustment screws may be self-sealing type screws. 
         [0020]    The second housing ball pockets may each have a second housing threaded channel extending through the exterior of the second housing wherein torque-adjustment screws may be inserted from the exterior of the second housing and through the second housing threaded channel to disengage the at least one ball from the second housing ball pockets. 
         [0021]    The torque-adjustment screws may be self-sealing type screws. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a perspective view of a torque limiting clutch according to the present invention. 
           [0023]      FIG. 2  is a perspective, exploded view of the torque limiting clutch of  FIG. 1  utilizing a proposed embodiment according to the present invention. 
           [0024]      FIG. 3  is a perspective view of an embodiment of the inner hub shown in  FIG. 2 . 
           [0025]      FIG. 4  is a perspective view of an embodiment of the rotor shown in  FIG. 2 . 
           [0026]      FIG. 5  is a side view of the torque limiting clutch shown in  FIG. 1 . 
           [0027]      FIG. 6  is a cross-sectional view of the torque limiting clutch along line  6 - 6  of  FIG. 1 . 
           [0028]      FIG. 7A  is a cross-sectional view of the torque limiting clutch along line  7 A- 7 A of  FIG. 1  in a drive position. 
           [0029]      FIG. 7B  is a cross-sectional view of the torque limiting clutch along line  7 B- 7 B of  FIG. 7A  engaged in a solid drive rotation. 
           [0030]      FIG. 7C  is a cross-sectional view of the torque limiting clutch along line  7 C- 7 C of  FIG. 7A  engaged in a solid drive rotation. 
           [0031]      FIG. 8A  is a cross-sectional view of the torque limiting clutch along line  8 A- 8 A of  FIG. 1  in a disengaged position. 
           [0032]      FIG. 8B  is a cross-sectional view of the torque limiting clutch along line  8 B- 8 B of  FIG. 8A  in a disengaged position. 
           [0033]      FIG. 8C  is a cross-sectional view of the torque limiting clutch along line  8 C- 8 C of  FIG. 8A  in a disengaged position. 
           [0034]      FIG. 9A  is a cross-sectional view of the torque limiting clutch along line  9 A- 9 A of  FIG. 8A  during the process of clutch re-engagement. 
           [0035]      FIG. 9B  is a cross-sectional view of the torque limiting clutch along line  9 B- 9 B of  FIG. 8A  during the process of clutch re-engagement. 
           [0036]      FIG. 9C  is a cross-sectional view of the torque limiting clutch along line  9 C- 9 C of  FIG. 7A  re-engaged. 
           [0037]      FIG. 9D  is a cross-sectional view of the torque limiting clutch along line  9 D- 9 D of  FIG. 7A  re-engaged. 
           [0038]      FIG. 10A  is an exploded view of a second embodiment of the torque limiting clutch according to the present invention with a switch plate. 
           [0039]      FIG. 10B  is an exploded view of the torque limiting clutch of  FIG. 10A  without the switch plate. 
           [0040]      FIGS. 11A and 11B  illustrate the first housing with a second embodiment milled pocket according to the present invention. 
           [0041]      FIGS. 12A and 12B  illustrate the first housing with a second embodiment ball pocket according to the present invention. 
           [0042]      FIGS. 13A and 13B  illustrate the second housing with a third embodiment ball pocket according to the present invention. 
           [0043]      FIGS. 14A and 14B  illustrate the first housing with the third embodiment ball pocket shown in  FIGS. 13A and 13B  without a threaded channel according to the present invention. 
           [0044]      FIGS. 15A and 15B  illustrate the first housing with a fourth embodiment ball pocket according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0045]    Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
         [0046]    As shown in  FIG. 1 , an assembled view of an embodiment of the torque limiting clutch  10  according to the present invention is depicted. A first housing  110  and a second housing  150  are married together to create an outer clutch assembly  100  in which a rotor  400  (see  FIG. 2 ) and an inner hub body  350  (see  FIG. 2 ) reside. Each housing  110  and  150  has through-holes  114  and  154  (see  FIG. 2 ) that align with threaded holes  156  and  116  (see  FIG. 2 ), respectively, of the other housing to allow for a secured assembly with assembly screws  170  (see  FIG. 10A ). 
         [0047]    Continuing with  FIG. 2 , an exploded view of the torque limiting clutch  10  embodying the invention is shown. It comprises the outer clutch assembly  100  comprising the first housing  110  and the second housing  150 ; a drive key  200 ; the inner hub  300 ; at least one overload assembly  500  comprising torque adjustment screws  510 , balls  520 , and coil springs  540 ; and the rotor  400  which radially surrounds the inner hub  300  and is itself enclosed within the outer clutch assembly  100 . 
         [0048]    The first housing  110  comprises a substantially hollow cylindrical shape comprising a first planar surface  118  recessed within the first housing  110  and perpendicular to the central axis, a second planar surface  120  defining an interface, and an exterior planar surface  124  opposite the second planar surface  120 . Extending along the first housing  110  between the first planar surface  118  and the second planar surface  120  is an inner surface  122  and extending along the first housing  110  between the first planar surface  118  and the exterior planar surface  124  is a bearing surface  126  (best seen in  FIG. 11A ) in which a sleeve bearing  102  is placed. 
         [0049]    Additionally, an arcuate seating recess  112  is shown positioned in the inner surface  122  and at least one drive pin pocket  494  is located in the first planar surface  118 . 
         [0050]    Furthermore, the first planar surface  118  of the first housing  110  has ball pockets  530  in which the balls  520  of the overload assemblies  500  sit when the torque limited clutch  10  is in the drive position, discussed infra. For a more detailed look at the ball pockets  530  of the first housing  110  see  FIG. 11B . The ball pockets  530  are shown having a non-tapered sidewall  528  with a diameter D that is slightly less than the diameter of the balls  520 , thereby permitting each engaged ball  520  to sit in the respective ball pocket  530  wherein a minority of the ball  520  resides in the ball pocket  530 , thus promoting departure of the ball  520  from the ball pocket  530  upon a torque overload, discussed further below. 
         [0051]    A second embodiment ball pocket  550  is shown in  FIGS. 12A and 12B , wherein a chamfered path  552  extends about the periphery of the ball pocket  550 . 
         [0052]    Additionally, a third embodiment ball pocket  532  is depicted in  FIGS. 13A and 13B . Here, the ball pocket  532  has a contoured path  534 . The contoured path  534  provides a smoother egress for the residing ball  520  and reduces the break-in time as the path of egress is pre-formed, not formed over time by continuous wear. It is contemplated further that a second contoured path (not shown) may be formed opposite the first contoured path  534 . 
         [0053]    A method for producing the contoured path  534  may comprise providing tooling (not shown) for drilling the ball pocket  532 , drilling the ball pocket  532 , forming the contoured path  534  with the tooling as the tooling exits the ball pocket  532 . 
         [0054]    Moreover, a fourth embodiment 536 of the ball pockets is shown in  FIGS. 15A and 15B . Here the ball pocket  536  has a circumferential rounded path  538  for much the same reason as the contoured path  534  shown in  FIGS. 13A and 13B . 
         [0055]    Generally the radius of the contoured path  534  and the rounded path  538  will allow the ball to have a rolling contact with the rounded path  538  rather than a point contact as may occur with a non-contoured path like that of the ball pocket  530 . 
         [0056]    Sleeve bearings  102  may be placed in contact with the bearing surface  126 . A sleeve bearing  102  promotes smooth rotation of the inner hub  300  relative to the outer clutch assembly  100 . Although roller-type bearings are depicted here, other types of bearings or bushings are also contemplated by the present invention. 
         [0057]    The second housing  150  is nearly a mirror image of the first housing  110  whereby it has a first planar surface  158  having ball pockets  530 , a second planar surface  160 , an exterior planar surface  164 , an inner surface  162  having an arcuate seating recess  152 , and a bearing surface  166  for placement of a sleeve bearing  102 . 
         [0058]    Looking now to the inner hub  300  but still referring to  FIG. 2  and additionally to  FIG. 3 , the inner hub  300  has an exterior surface  310 , which has a slightly smaller diameter than the inner diameter of the rotor  400 . This slight variance allows for rotational movement of the inner hub  300  relative to the rotor  400 , while minimizing movement in a radial direction. Additionally, the inner hub  300  has two ends  340  which are positioned within the bearings  102  of the first housing  110  and the second housing  150 . Furthermore, a tangential pocket  610  is located on the exterior surface  310 . The pocket  610  interfaces with a detent assembly  600  comprising a plunger  630  and a coil spring  640 . Additionally, there is an arcuate seating recess  320  located in the exterior surface  310   
         [0059]      FIG. 4  illustrates the rotor  400 . The rotor  400  has a series of coil spring through-holes  470  that extend through the first planar surface  410  and the second planar surface  420  (hidden). Additionally, there is at least one drive pin opening  450  on the first planar surface  410 . Furthermore, the rotor  400  has a key slot  460  extending from the second planar surface  420  towards, but not to, the first planar surface  410 , and extends through the outer surface  440  and the inner surface  430 . The size of the key slot  460  corresponds to the diameter of the drive key  200  (see  FIG. 2 ). 
         [0060]    The rotor  400  also has a plunger through-hole  480  extending through the outer surface  440  and the inner surface  430 . It is in the plunger through-hole  480  in which the plunger  630  of the detent assembly  600  resides. The plunger through-hole  480  is positioned so as not to interfere with any of the coil spring through-holes  470  and so that at least a portion of the plunger through-hole  480  is at a position along the rotor&#39;s outer surface  440  so that the plunger  630  will not plunge into the arcuate seating recess  320  of the inner hub  300  when there is an overload and the inner hub  300  rotates freely relative to the rotor  400 . 
         [0061]    The drive key  200  resides in inner clutch arcuate seating recess  320  and the rotor key slot  460  when the clutch  10  is in the drive position. However, the drive key  200  resides in the rotor key slot  460  and the first and second housing arcuate seating recesses  112  and  152  when the clutch  10  is in a disengaged state, discussed further below. 
         [0062]    Additionally, the torque limiting clutch  10  has a torque drive means  490  comprising at least one drive pin  492  having a first end  494  and a second end  496 . The drive pin first end  494  is pressed into the drive pin opening  450  in the first planar surface  410  of the rotor, and the drive pin second end  496  resides in a milled pocket  498  located in the first planar surface  118  of the first housing  110  (as shown in  FIG. 6 ). The milled pocket  498  in the embodiment shown is larger than the drive pin  492 . This allows the drive pin  492 , and the rotor  400  it is pressed into, to rotate to some degree in order to allow the overload assemblies  500  to disengage (shown in  FIG. 8C ). 
         [0063]    Alternatively,  FIG. 11A  illustrates an alternative milled pocket  894 . The milled pocket  894  comprises a slot extending from a first stop end  896  to a second stop end  898 . The first stop end  896  and the second stop end  898  are arcuate to substantially match the curvature of the drive pin  492 . Additionally, the milled pocket  894  is milled into the first housing first planar surface  118  to follow the same path as the drive pin  492 . As the milled pocket  894  is more adaptive to the shape and travel path of the drive pin  492 , less material is removed from the first housing  110  which provides more rigidity (especially if more than one drive pin  492  are utilized) and promotes a more consistent and solid bushing/bearing  102  fit. 
         [0064]    Continuing to look at  FIG. 4 , along with  FIGS. 11A and 5 , a plurality of drive pins  492  and a plurality of milled pockets  894  are shown. Additional drive pins  492  located in additional milled pockets  894  will disperse the load more evenly across the outer clutch assembly  100  and will also increase the amount of force that may be transferred from an input shaft  20  to an output shaft  30  when the clutch is being used in a non-torque limiting direction (discussed further below) because the force will be more evenly divided among the drive pins  492 . It should be understood that reference to the input shaft and the output shaft is for reference only and therefore should not limit the torque limiting clutch to only this operational orientation. 
         [0065]      FIG. 7A  is a cross-sectional view of the torque limiting clutch  10 , further illustrating the internal elements. Here, it can be seen that each overload assembly  500  comprises torque adjustment screws  510 , balls  520  residing in their respective ball pockets  530  located in the first and second housings  110  and  150 , and coil springs  540  located in their respective coil spring through-holes  470 . Additionally, nitrogen cylinders or Belleville springs or another type of biasing mechanism known to one having ordinary skill in the art may be used in place of, or in conjunction with, the coil springs  540 . 
         [0066]    Furthermore, the torque required to disengage the torque limiting clutch  10  is determined by how many of the overload assemblies  500  are active. The overload torque setting may be adjusted by adding or removing short or long torque adjustment screws  510 . For example, if less overload torque is desired, long torque adjustment screws  510  are installed. The additional length of the long screw pushes the ball  520  out of its pocket  530  and into the through-bore  470 , thereby removing it from contact with the respective housing  110  or  150 . Installing long torque adjustment screws  510  in each end of an overload assembly  500  effectively disengages that overload assembly  500  making disengagement of the torque limiting clutch  10  achievable under less overload torque. Conversely, if more overload torque is desired, more of the overload assemblies  500  should be activated. This is accomplished by replacing long screws with short screws until the desired overload torque is achieved. 
         [0067]    Additionally, a sealed torque limiting clutch  700  more impervious to fluid or other contaminants is also contemplated by the present invention and is depicted in  FIGS. 10A and 10B .  FIG. 10A  depicts a sealed torque limiting clutch  700  with switch plate  40 . The sealed torque limiting clutch  700  comprises a first sealed housing  710  and a second sealed housing  750 , an extended inner clutch member  770 , and a gasket. As the sealing elements of the first sealed housing  710  are hidden from view in this figure, explanatory focus will be placed on the similar sealing elements of the second sealed housing  750 . As shown, the second sealed housing  750  comprises an o-ring protrusion  752  and an o-ring groove  754 . Similarly, the first sealed housing  710  comprises an o-ring protrusion  712  and an o-ring groove  714 , both hidden here but visible in  FIG. 14A . 
         [0068]    Furthermore, the extended inner clutch member  770  comprises a first sealing surface  772  and a second sealing surface  774 . 
         [0069]    Additionally, the gasket  780  provides a sealed junction between the first sealed housing  710  and the second sealed housing  750 . Moreover, housing o-rings  790  placed in the o-ring grooves  714  and  754  may comprise dynamic o-rings (for example, those made by Parker-Hannifin Corp.) as they will be used in a location subject to rotary movement of the extended inner clutch member first sealing surface  772  and the extended inner clutch member second sealing surface  774  when the clutch  700  is in a disengaged state. 
         [0070]    Furthermore, the switch plate  40  comprises studs  42  having rounded tips  44  that are inserted through switch plate holes  716  in at least one of the first sealed housing  710  and the second sealed housing  750  and which reside in depressions  482  in the rotor  400 . When the clutch  700  experiences a disengaging torque, the rotor  400  rotates while the switch plate studs  42  remain relatively stationary causing them to be forced out of the depressions  482  and against the planar surface  410 ,  420  of the rotor  400 . The lateral movement of the studs  42  relative to the clutch  700  is transferred to the switch plate  40  and moves the switch plate  40  to make a signaling connection, whether electrical or mechanical, to signal the torque overload. O-rings  46  located on the studs  42  reduce the likelihood of fluid or other contaminates entering the clutch  700  through the switch plate holes  716 . 
         [0071]      FIG. 10B  shows the sealed torque limiting clutch  700  of  FIG. 10A  but without the switch plate  40 . As the switch plate  40  is absent, the switch plate holes  716  may be filled with plugs  50  incorporating o-rings  46  to decrease the potential of fluid or other contaminates from entering the clutch  700 . 
         [0072]    Moreover, as shown in  FIGS. 14B and 15B , ball pockets  532  and  536  do not have a threaded channel  526  like those illustrated in  FIGS. 11B ,  12 B, and  13 B. This design feature may be provided to further reduce the likelihood of fluid or other contaminates from entering the clutch  700 . However, it is also contemplated that this design feature may be preferable on only one of the two housings  710 , 750  because adjustability of the amount of force required to disengage the clutch  700  may still be desired. 
         [0073]    Furthermore, it is contemplated that certain pieces of the clutch  700  may comprise stainless steel and the screws (i.e., the assembly screws  170  and the torque adjustment screws  510 ) in the clutch  700  may comprise self-sealing stainless steel screws to further limit damage due to exposure to fluid or other contaminants. As a non-limiting example, ZAGO® seal screws may be used. 
         [0074]    It is contemplated that the sealing measures herein disclosed reduce the likelihood of contaminants from entering the clutch  700  under pressure. The sealing measures would preferably maintain a seal up to approximately 14 psi, but maintaining a seal at greater pressures is also contemplated. 
         [0075]    Additionally, it should be known that the switch plate  40  may be used with the non-sealed torque limiting clutch  10  as well; however, the o-rings  46  may be optional. 
       Drive Position 
       [0076]      FIG. 7A  illustrates the clutch  10  according to the present invention in the drive position. In the drive position, the clutch  10  may be used in the torque limiting direction, as described below, or in a non-torque limiting direction as a solid drive unit (as depicted in  FIGS. 7B and 7C ). In  FIG. 7A , the overload assemblies  500  are engaged with the balls  520  located in their respective ball pockets  530 .  FIG. 7B  shows detent assembly  600 , wherein the plunger  630  is abutting a wall  620  of the tangential pocket  610 . Furthermore, the drive key  200  is located partially in the arcuate seating recess  320  of the inner hub  300  and the key slot  460  of the rotor  400 , thereby operably joining the rotor  400  and the inner hub  300  together.  FIG. 7C  illustrates the at least one drive pin  492  abutting the wall of the milled pocket  494  at point A, thereby operably joining the outer clutch assembly  100  to the rotor  400 . When used as a solid drive unit, the clutch  10  transfers input force from the input shaft  20  to the output shaft  30  through the at least one drive pin  492  in the direction of the arrows. All in all, the outer clutch assembly  100 , the rotor  400 , and the inner hub  300  are all operably joined together and move as one when in the drive position. 
       Torque Overload State 
       [0077]      FIGS. 8A-C  show the torque limiting clutch  10  when disengaged due to a torque overload. When the clutch  10  is used in the torque-limiting direction (the reverse of the solid drive direction), the input force is transferred from the input shaft  20  to the output shaft  30  through the overload assemblies  500 . Therefore, when a force is experienced by the clutch  10  that exceeds the predetermined torque limit, the clutch  10  will disengage. 
         [0078]    On a global level, in the event of a torque overload the inner hub  300  disengages from operable engagement with the rotor  400 , thereby disengaging the outer clutch assembly  100  and allowing the inner hub  300  to rotate independently. On a more local level, when the clutch  10  is in the drive position as depicted in  FIGS. 7A-C , the inner hub  300  and the rotor  400  are separably fixed together by the drive key  200 . When a load above the torque limit of the overload assemblies  500  is experienced, the excessive load causes the balls  520  of the overload assemblies  500  to overcome the spring force of the coil springs  540  and roll out of their respective ball pockets  530 . The inner hub  300  and the rotor  400  then continue to rotate, but independent of the outer clutch assembly  100 . 
         [0079]    Looking at  FIGS. 8B and 8C , as the inner hub  300  and the rotor  400  rotate together, the rotor  400  is stopped when the at least one drive pin  492  makes contact with the wall of the milled pocket  494  at point B. At this position the arcuate seating recesses  112  and  152  (not shown) of the outer clutch assembly  100  are in line with the drive key  200  and the arcuate seating recess  320  of the inner hub  300 . As the rotor  400  is now prohibited from further rotation, the continuing input force will further rotate the inner hub  300  relative to both the rotor  400  and the outer clutch assembly  100 . As the inner hub continues to rotate, the arcuate seating recess  320  of the inner hub  300  acts against the drive key  200  and forces the drive key  200  into the arcuate seating recesses  112  and  152  (see  FIG. 13A ) of the outer clutch assembly  100 , thereby operably linking the rotor  400  and the outer clutch assembly  100  and allowing the inner clutch member  300  to rotate independently of the rotor  400  and the outer clutch assembly  100 . Adjustment to the amount of overload force needed to disengage the clutch is achieved through the number of active torque adjustment screws  510  (shown in  FIG. 7A ) as discussed supra. 
       Re-Engagement of the Clutch 
       [0080]    After an overload disengages the clutch  10 , and the cause for the overload has been remedied, the clutch  10  may be reset to the drive position. This is accomplished by either rotating the inner hub  300 , the outer clutch assembly  100 , or both, in a direction opposite one another. As illustrated in  FIG. 9A , the inner hub  300  is rotated in the solid drive direction. Looking to  FIG. 9B , as the inner hub  300  is rotated, the plunger  630 , which is biased against the inner hub  300  by the spring  640  acting against the inner surface  122  of the outer clutch assembly  100 , abuts the wall  620  of the tangential pocket  610  located within the exterior surface  310  of the inner hub  300 . This operably links the inner hub  300  and the rotor  400 . The two continue to rotate together in the solid drive direction and the key slot  460  acts against the drive key  200 , and the drive key  200  moves from the arcuate seating recesses  112  and  152  (see  FIG. 13A ) of the outer clutch assembly  100  to the arcuate seating recess  320  of the inner hub  300 . 
         [0081]    Further rotation permits the balls  520  of the overload assemblies  500  to reseat in their respective ball pockets  530  (see  FIG. 9C ). Moreover, the at least one drive pin  492  is once again engaged with the wall of its respective milled pocket  494  at point A (as shown in  FIG. 9D ) and thereby re-engaging the clutch  10  in the drive position. 
         [0082]    The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.

Technology Classification (CPC): 5