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BACKGROUND 
       [0001]    The present invention relates to a device and method for selecting between spring rates in a single lock set assembly that supports multiple lockset trim types. 
         [0002]    A conventional door knob has a center of mass centered with the axis of the lock spindle. A conventional door lever, in contrast, has a center of mass offset some distance from the spindle axis. The gravitational force on this center of mass produces a torque about the spindle axis. To provide a counter torque to maintain the neutral position of the lever in a horizontal plane and to also resist increased operator torque due to the inherent mechanical advantage afforded a lever, a stiffer spring or additional springs are typically included in lock assemblies on which a lever will be installed. This is usually accomplished by manufacturing two separate lock assembly configurations: one with lighter springs for knobs, and a second one with heavier springs for levers. 
       SUMMARY 
       [0003]    In one embodiment of a latch assembly configured to attach to a door, the latch assembly includes one of a knob and a lever. The latch assembly further includes a latch extending from the door. A spindle is rotatable from a first position to a second position to move the latch from an extended position to a retracted position. A first biasing member is selectively operable to bias the spindle toward the first position. A second biasing member is selectively operable to bias the spindle toward the first position. An actuator is movable between a knob position in which only one of the first biasing member and the second biasing member biases the spindle toward the first position and a lever position in which both the first biasing member and the second biasing member cooperate to bias the spindle toward the first position. 
         [0004]    In one embodiment of a latch assembly configured to attach to a door, the latch assembly includes a latch extending from the door. A housing is coupled to the door and has an aperture defining a central axis therethrough. A spindle is received and configured to rotate within the aperture and to extend and retract the latch. First and second biasing springs are contained within the housing. An actuator is selectively movable to an operable position in which rotation of the spindle deflects the first and second biasing spring, and an inoperable position in which rotation of the spindle deflects only the first biasing spring. 
         [0005]    In one embodiment of a latch assembly configured to attach to a door, the latch assembly includes a spindle rotatable about a central axis to move a latch from an extended position to a retracted position in the door. An annular plate is fixed with respect to the door and includes a slot, a first face, and a projection extending from the first face. A retainer member includes a first face, a first protrusion extending from the first face, and a second protrusion extending from the first face. The retainer member is coupled to the spindle and rotatable about the central axis. A first spring is disposed between the first face of the annular plate and the first face of the retainer member. A second spring is disposed between the first face of the annular plate and the first face of the retainer member. The first and second springs are movable with the projection, the first protrusion, and the second protrusion. An actuator is selectively movable between a retracted position and an extended position through the slot to place the first and second springs into a mechanically parallel relationship. 
         [0006]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of a lock assembly having a lever handle. 
           [0008]      FIG. 2   a  is a perspective view of a selectable lock assembly with a knob handle. 
           [0009]      FIG. 2   b  is a perspective view of the selectable lock assembly of  FIG. 2   a  with a lever handle. 
           [0010]      FIG. 3   a  is an exploded view of the selectable lock assembly of  FIGS. 2   a  and  2   b.    
           [0011]      FIG. 3   b  is an exploded view of the selectable lock assembly of  FIGS. 2   a  and  2   b.    
           [0012]      FIG. 3   c  is another perspective view of the selectable lock assembly of  FIGS. 2   a  and  2   b.    
           [0013]      FIG. 4  is an end view of the selectable lock assembly of  FIGS. 2   a  and  2   b  in a neutral position. 
           [0014]      FIG. 5   a  is a perspective view of the selector of the selectable lock assembly of  FIGS. 2   a  and  2   b.    
           [0015]      FIG. 5   b  is a perspective view of the positioning member of the selector of  FIG. 5   a.    
           [0016]      FIG. 6   a  is a section view taken along line  6   a - 6   a  of  FIG. 2   a.    
           [0017]      FIG. 6   b  is an end view of the lock assembly of  FIG. 6   a  with clockwise rotation of the spindle. 
           [0018]      FIG. 6   c  is an end view of the lock assembly of  FIG. 6   a  with counterclockwise rotation of the spindle. 
           [0019]      FIG. 7   a  is a section view taken along line  7   a - 7   a  of  FIG. 2   b.    
           [0020]      FIG. 7   b  is an end view of the lock assembly of  FIG. 7   a  with clockwise rotation of the spindle. 
           [0021]      FIG. 7   c  is an end view of the lock assembly of  FIG. 7   a  with counterclockwise rotation of the spindle. 
           [0022]      FIG. 8   a  is an exploded view of another selectable lock assembly. 
           [0023]      FIG. 8   b  is a perspective view of the selectable lock assembly of  FIG. 8   a  as assembled. 
           [0024]      FIG. 9   a  is a top view of the selectable lock assembly of  FIG. 8   b  with the actuator disengaged. 
           [0025]      FIG. 9   b  is a perspective view of the actuator of the selectable lock assembly of  FIG. 9   a.    
           [0026]      FIG. 10   a  is a top view of the selectable lock assembly of  FIG. 8   b  with the actuator engaged. 
           [0027]      FIG. 10   b  is a perspective view of the actuator of the selectable lock assembly of  FIG. 10   a.    
           [0028]      FIG. 11   a  is a perspective view of an alternative actuator with the selectable lock assembly of  FIG. 8   a  and in the disengaged position. 
           [0029]      FIG. 11   b  is a partial perspective view of the actuator of  FIG. 11   a.    
           [0030]      FIG. 12   a  is a perspective view of the actuator of  FIG. 11   a  in the engaged position. 
           [0031]      FIG. 12   b  is a partial perspective view of the actuator of  FIG. 12   a.    
           [0032]      FIG. 13   a  is an exploded view of another selectable lock assembly. 
           [0033]      FIG. 13   b  is a perspective view of the selectable lock assembly of  FIG. 13   a  as assembled. 
           [0034]      FIG. 14  is an end view of the lock assembly of  FIG. 13   b.    
           [0035]      FIG. 15   a  is a perspective view of the selectable lock assembly of  FIG. 13   b  with the engagement rod disengaged. 
           [0036]      FIG. 15   b  is a section view taken along line  15   b - 15   b  of  FIG. 15   a.    
           [0037]      FIG. 16   a  is a perspective view of the selectable lock assembly of  FIG. 13   b  with the engagement rod engaged. 
           [0038]      FIG. 16   b  is a section view taken along line  16   b - 16   b  of  FIG. 16   a.    
       
    
    
     DETAILED DESCRIPTION 
       [0039]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. And as used herein and in the appended claims, the terms “upper”, “lower”, “top”, “bottom”, “front”, “back”, and other directional terms are not intended to require any particular orientation, but are instead used for purposes of description only. 
         [0040]      FIG. 1  illustrates the external portions of a lock assembly  10  mounted within a door  20 . As illustrated, the lock assembly  10  includes a lever  24  housing a key cylinder  28  with a cover  32  to conceal the interface of internal components of the lock assembly  10  with the door  20 . A latch  36  extends through a faceplate  40  mounted in the swing side end of the door  20  adjacent an opposing door frame (not shown). 
         [0041]    Referring to  FIGS. 2   a  and  2   b , an externally accessible selector  100  for adjusting the internal spring torque of a selectable lockset assembly  104  is disposed within a housing  110 . The housing  110  includes a position identifier  114  integrally formed as part of a front face  118  to enable a user to identify whether the lockset is configured for use with a knob (i.e., a knob icon  122 ) or a lever (i.e., a lever icon  126 ). A directional arrow  130  indicates the direction in which to rotate the selector  100  to achieve the desired state.  FIG. 2   a  shows the selector  100  configured for a knob  134 , while  FIG. 2   b  shows the selector  100  configured for a lever  138 . 
         [0042]      FIGS. 3   a  and  3   b  illustrate the selectable lock assembly  104  referenced with respect to a proximal end  151  and a distal end  153 .  FIG. 3   c  illustrates the lock assembly  104  as assembled. Referring to  FIGS. 3   a - 3   c , the lock housing  110  defines an aperture  154  having a central axis  158 . The aperture  154  receives a spindle  162  therethrough, which rotates in response to actuation of the handle  134  or the lever  138  (see, e.g.,  FIGS. 2   a  and  2   b ) to move a latch (not shown) from an extended position to a refracted position. The spindle  162  is externally secured through a retainer  166  and a retainer ring  170  that seat against the housing  110 . The spindle  162  receives a lock cylinder (not shown) into a proximal end  174  thereof in a manner known to those of skill in the art. Two elongated members  180 ,  182 , connected by arcuate sections  186 ,  188 , extend from a distal face  190  of the housing  110  and are together shaped to contain the remaining components of the selectable lock assembly  104  and further provide fixed reference points. 
         [0043]    With continued reference to  FIGS. 3   a - 3   c , an annular back plate  194  concentric with the axis  158  receives the distal end  198  of the spindle  162 . The back plate  194  includes a housing catch  204  projecting from a proximal face  208  that secures the back plate  194  within the housing  110  to inhibit relative rotation during operation. A slot  212  through the back plate  194  is diametrically spaced from the housing catch  204  and receives an actuator  220  that is operationally engaged by an adjustment member  224  of the selector  100 , as will be subsequently detailed. The slot  212  may be wholly bounded by the back plate  194  or may be disposed circumferentially at the edge of the plate  194 , i.e., as a notch. A projection or stop  230  extending from the distal face  234  of the back plate  194  opposite the housing catch  204  passively interacts with two substantially coplanar biasing members or springs—an upper spring  240  and a lower spring  244 —functionally positioned between the back plate  194  and a retainer member  250 . The biasing springs  240 ,  244  as illustrated are linear compression springs, each with a respective first end  260 ,  262  and a second end  264 ,  266 . The spring constants of the biasing springs  240 ,  244  will normally be substantially similar. A pair of opposing protrusions  270 ,  272  extending from the proximal face  276  of the retainer member  250  actively interact with the two biasing springs  240 ,  244 , as will be further described below. The retainer member  250  includes two generally curvilinear openings  280 ,  282  therethrough that mate with conforming slotted extensions  290 ,  292  formed at the distal end  198  of the spindle  162  such that the retainer member  250  rotates with the spindle  162 . The spindle  162 , annular back plate  194 , retainer member  250 , members  180 ,  182 , and sections  186 ,  188 , assembled together, form an arcuate channel within which the biasing springs  240 ,  244  can translate and deflect during operation. 
         [0044]    Referring to  FIG. 4 , a distal end view of the lock assembly  104  is illustrated in a neutral position, in which the handle, either the knob  134  or the lever  138  (not shown), is inactive and therefore does not generate a torque to rotate the spindle  162 . This is further reflected by the substantially horizontally positioned protrusions  270 ,  272  of the retainer member  250 . The biasing springs  240 ,  244  are consequently both in a relaxed state between the protrusions  270 ,  272  and on either side of the stop  230 . 
         [0045]    Referring to  FIGS. 5   a  and  5   b , the adjustment member  224  of the selector  100  is formed from a generally cylindrical shaft  300 , which defines a single thread root  304 . The shaft  300  is operable to rotate adjacent a complementary surface  310  formed in a proximal portion  314  of the actuator  220 . A partial thread crest  320  protrudes from the surface  310  to engage the thread root  304  and transform rotational motion of the adjustment member  224  to linear motion of the actuator  220  in the direction of the central axis  158 . A positioning member  324  of the actuator  220  includes first and second contact surfaces  328 ,  332  to interact with the biasing springs  240 ,  244  when the selector  100  is actuated, as will be further detailed below. An engagement interface  336  of the adjustment member  224  is operable with a screwdriver or similar tool, though additional configurations for manually rotating the adjustment member  224  are within the knowledge and skill of those in the art. An indicator  340  cooperates with the position identifier  114  of  FIGS. 2   a  and  2   b  and identifies whether the selector  100  is currently configured for a knob or a lever. 
         [0046]      FIGS. 6   a - 6   c  show a knob configuration. Referring to  FIG. 6   a , the locking assembly  104  is shown in a neutral position with no torque applied to the knob  134 . The stop  230  extending from the distal face  234  of the back plate  194  is shown in its fixed position adjacent the first end  262  of the lower biasing spring  244  (and equally adjacent to the second end  264  of the upper biasing spring  240 , not shown). As illustrated, in the knob configuration, the actuator  220  is retracted, i.e., proximally positioned, and does not extend through the slot  212  in the annular back plate  194 . 
         [0047]    Referring to  FIG. 6   b , in operation, during a clockwise rotation of the spindle  162  (see arrow  350 ) due to rotation of the knob  134  (not shown), the protrusion  272  of the retainer member  250  contacts the first end  260  of the upper biasing spring  240  and compresses the upper biasing spring  240  against the back plate stop  230 . This provides a counter torque to the applied torque of the knob. The lower biasing spring  244 , contacted at end  262  by the protrusion  270 , slides within the housing  110  in a circumferential path defined between the back plate  194  and the retainer member  250  and moves with and between the opposing protrusions  270 ,  272 . The lower biasing spring  244  is therefore not compressed and provides no counter torque to the applied torque of the knob. Referring to  FIG. 6   c , during a counterclockwise rotation of the spindle  162  (see arrow  354 ), the protrusion  272  contacts the second end  266  of the lower biasing spring  244  and compresses the lower biasing spring  244  against the back plate stop  230 . Due to the relatively equal spring constants between the upper and lower biasing springs  240 ,  244 , this motion provides an equal counter torque to the knob as is applied during clockwise rotation of the spindle  162 . The upper biasing spring  240 , contacted at end  264  by the protrusion  270 , slides within the circumferential path described above and moves with and between the opposing protrusions  270 ,  272 . The upper biasing spring  240  is therefore not compressed and provides no counter torque to the applied torque of the knob. In  FIGS. 6   b - 6   c , neither one of the first or second contact surfaces  328 ,  332  of the positioning member  324  interferes with the motion of the biasing springs  240 ,  244 . 
         [0048]      FIGS. 7   a - 7   c  show a lever configuration. Referring to  FIG. 7   a , the locking assembly  104  is shown in a neutral position with no torque applied to the lever  138 . In this configuration, the positioning member  324  of the actuator  220  extends through the slot  212  of the back plate  194 . The stop  230  is again fixed in place. 
         [0049]    Referring to  FIG. 7   b , in operation, during a clockwise rotation of the spindle  162  (see arrow  362 ) due to rotation of the lever  138  (not shown), the protrusion  272  contacts the first end  260  of the spring  240  and compresses the spring  240  against the back plate stop  230 , as in  FIG. 6   b , to provide a counter torque to the applied torque of the lever. Since the positioning member  324  is now fixed in place with the second contact surface  332  adjacent the second end  266  of the lower spring  244 , the protrusion  270  contacts the first end  262  of the lower spring  244  and compresses the lower spring  244  against the second contact surface  332 . Thus, both the upper biasing spring  240  and the lower biasing spring  244  are concurrently compressed, effectively adding their spring constants together in a mechanically parallel spring relationship to counter the torque applied at the lever. Referring to  FIG. 7   c , during a counterclockwise rotation of the spindle  162  (see arrow  366 ), the protrusion  272  contacts the second end  266  of the lower spring  244  and compresses it against the stop  230 , as in  FIG. 6   c . With the first contact surface  328  adjacent the first end  260  of the upper spring  240 , the protrusion  270  contacts the second end  264  of the upper spring  240  and compresses the upper spring  240  against the first contact surface  328 . The springs  240 ,  244  are again concurrently compressed in a mechanically parallel spring relationship to counter the torque applied by the lever. Thus, the lever arrangement receives about twice the restoring force as the knob arrangement. 
         [0050]      FIG. 8   a  illustrates another selectable lock assembly  400 , unassembled and referenced with respect to a proximal end  401  and a distal end  403 .  FIG. 8   b  illustrates the lock assembly  400  as assembled. Referring to  FIGS. 8   a - 8   b , the selectable lock assembly  400  includes a lock housing  410  defining an aperture  414  with a central axis  418  through which a spindle  422  rotates in response to actuation of a handle or a lever (not shown) to move a latch (not shown) from an extended position to a refracted position. The spindle  422  receives a lock cylinder (not shown) and is externally secured through a retainer  424  and a retainer ring  428  that seat against the housing  410 . 
         [0051]    With continued reference to  FIGS. 8   a  and  8   b , a spring holder  432  fixedly disposed within the housing  410  provides an arcuate track  436  for a first biasing spring  440 . In the present construction, the first biasing member or spring  440  is a linear compression spring with first and second ends  460 ,  462 . Lips  444 ,  448  at each end of the spring holder  432  constrain the motion of the first biasing spring  440  to deflection within the track  436 . A second biasing member or spring  450  is functionally disposed adjacent a retainer member, or spring cage  454 . The second biasing spring  450  is a torsion spring with first and second ends or legs  466 ,  468  positioned to engage an actuator  470  secured to the housing  410  with a clip  472 . The spring cage  454  includes two generally curvilinear openings  474 ,  476  therethrough that mate with conforming slotted extensions  480 ,  482  formed at the distal end of the spindle  422 . The spring cage  454  therefore rotates with rotation of the spindle  422 . Extending proximally from the spring cage  454  are first and second protrusions  490 ,  492  that interact with the first biasing spring  440 . Specifically, the first and second protrusions  490 ,  492  include lateral edges  494 ,  496  shaped to abut the first and second ends  460 ,  462 , respectively, of the first biasing spring  440 . An arm  500  also extending in the proximal direction from the spring cage  454  includes opposing grooves  502 ,  504  configured to catch the first and second ends  466 ,  468  of the second biasing spring  450 . The linear spring constant of the first biasing spring  440  and the torsion spring constant of the second biasing spring  450  may or may not be functionally equivalent, i.e., the combined spring rate for a lever installation can vary depending on the desired ratio between knob and lever installations. 
         [0052]    The actuator  470  is generally cylindrical in form and includes an engagement interface  520  operable with a screwdriver or similar tool. An identifier  524  describes the current state of the actuator (knob or lever) in the same manner as described for  FIGS. 2   a  and  2   b . A semicircular shaft  514  extends eccentrically from the distal face  510  of the actuator  470 . 
         [0053]    Referring to  FIGS. 9   a  and  9   b , the locking assembly  400  is shown in a neutral position with no torque applied to the spindle  422 . With the actuator  470  positioned for a knob handle, the first and second ends  466 ,  468  of the second biasing spring  450  are clear of the shaft  514 , i.e., the shaft  514  is not in engagement with either of the first or second ends  466 ,  468  of the torsion spring  450 . In operation, during clockwise rotation of the spindle  422 , which rotates the spring cage  454 , the first biasing spring  440  is deflected against the lip  448  (not shown) of the spring holder  432  by the interaction of the first lateral edge  494  of the protrusion  490  of the spring cage  454  against the end  460  of the first biasing spring  440 . The torsion spring  450  is free to rotate with the spring cage  422  via arm  500  unhindered by the shaft  514  of the actuator  470 . During counterclockwise rotation of the spindle  422 , which also rotates the spring cage  454 , the first biasing spring  440  is deflected against the lip  444  of the spring holder  432  by the interaction of the second lateral edge  496  of the protrusion  492  (not shown) of the spring cage  454  against the end  462  of the first biasing spring  440 . The only counter torque applied to the spindle  422  in either case is therefore by virtue of deflection of the first biasing spring  440 . 
         [0054]      FIGS. 10   a  and  10   b  also show the locking assembly  400  in a neutral position. Turning the actuator  470  to ‘lever’ from ‘knob’ rotates and repositions the shaft  514  between the first and second ends  466 ,  468  of the second biasing spring  450 . In operation, during clockwise or counterclockwise rotation of the spindle  422 , the first biasing spring  440  is deflected by the spring cage  454  as previously described, but the second biasing spring  450  is no longer free to rotate with the spring cage  454 . During clockwise rotation, the end  468  of the second biasing spring  450  is operably fixed against the shaft  514  while force is applied to the end  466  by the groove  502  of the arm  500 . During counterclockwise rotation of the spindle  422 , the end  466  of the second biasing spring  450  is operably fixed against the shaft  514  while force is applied to the end  468  by the groove  504 . Separation of the ends  466 ,  468  through rotation, which deflects the spring  450 , applies torque to the spindle  422  in excess of that supplied by the first biasing spring  440  alone. 
         [0055]    Referring to  FIGS. 11   a  and  11   b , an alternative actuator  540  is shown disposed within the housing  410 . The actuator  540  includes an accessible slide switch  544  with two positions. In  FIG. 11   a , the slide switch  544  is selected for a knob handle. As shown in  FIG. 11   b , the first and second ends  466 ,  468  of the second biasing spring  450  are clear of the blocking bar  550  of the actuator  540  and the second biasing spring  450  is free to rotate with the spindle  422  in the same manner previously described. In  FIG. 12   a , the slide switch  544  is selected for a lever handle and as shown in  FIG. 12   b , the blocking bar  550 , through radially inward movement, is functionally disposed between the first and second ends  466 ,  468  of the second biasing spring  450 , activating the second biasing spring  450  as previously described. 
         [0056]      FIG. 13   a  illustrates another selectable lock assembly  600 , unassembled and referenced with respect to a proximal end  601  and a distal end  603 .  FIG. 13   b  illustrates the lock assembly  600  as assembled. Referring to  FIGS. 13   a  and  13   b , a housing  610  includes an aperture  614  defining a central axis  618  that receives a spindle  622 . The spindle  622  rotates with the actuation of a handle or a lever (not shown) to move a latch (not shown) from an extended position to a retracted position. A spring plate  630  is rotatably fixed to the spindle  622  and includes a distally extending slotted wall  634  with upper and lower slots  638 ,  642 . A lever biasing member or spring  650  with a right-hand winding has an upper leg  654  and a lower leg  656  and is situated such that the upper leg  654  extends upward through the upper slot  638  of the spring plate  630  and the lower leg  656  extends downward distally of the slotted wall  634 . A knob biasing member or spring  670  with a left-hand winding and larger mean diameter than the lever spring  650  is concentrically nested over the lever spring  650  and has an upper leg  674  and a lower leg  676 . The upper leg  674  extends upward distally of the slotted wall  634  and abuts the edge  680  of a groove  682  formed in the wall  634 , best seen in  FIGS. 15   a  and  16   a . The lower leg  676  extends downward through the lower slot  642  of the spring plate  634  and abuts an edge  684  formed in the spring plate  630 . As illustrated, the lever spring  650  and the knob spring  670  are torsion springs. Alternative nested designs of the lever spring  650  and the knob spring  670  can be achieved by varying the coil winding direction, mean spring diameter, and spring leg orientation of each spring. 
         [0057]    With continued reference to  FIGS. 13   a  and  13   b , a lever spring plate  690  sits within the knob spring plate  630  enclosed by the slotted wall  634  and includes a pair of opposed distally extending arcuate arms  694 ,  696  positioned radially between the slotted wall  634  and the lever spring  670 . The lever spring plate  690  is selectively engaged and activated to rotate with the spindle  622  by actuation of an engagement rod or actuator  700  through a plate orifice  704 , as further described below. 
         [0058]    Referring to  FIG. 14 , an end view of the lock assembly  600  shows that the upper and lower legs  674 ,  676  of the knob spring  670  and the upper and lower legs  654 ,  656  of the lever spring  650  are held against rotation in one direction by diametrically opposed bosses  710  integrally formed as part of the lock housing  610 . As illustrated, the upper legs  674 ,  654  are blocked from counterclockwise rotation and the lower legs  656 ,  676  are blocked from clockwise rotation. 
         [0059]    Referring to  FIGS. 15   a  and  15   b , the locking assembly  600  is shown in a neutral position with no external torque applied. In the knob configuration, the actuator  700  is retracted and does not extend through the orifice  704  in the lever spring plate  690 . In operation, upon clockwise or counterclockwise rotation of the spindle  622 , the knob spring  670  is deflected by interaction with the edges  680 ,  684  in the knob spring plate  690 . Specifically, with clockwise rotation of the spindle  622  (viewed from the end), the edge  680  contacts and rotates the upper end  674  of the knob spring  670  against the operably fixed lower end  676 , and the upper slot  638  passes over and does not interact with the upper leg  654  of the lever spring  650 . With counterclockwise rotation of the spindle  622 , the edge  684  formed in the slotted wall  634  contacts and rotates the lower leg  676  of the knob spring  670  against the operably fixed upper leg  674 . Thus, counter torque to the actuation of the knob is provided by the knob spring  670  only. The lever spring plate  690  does not rotate with the spindle  622  until it is selectively engaged by the actuator  700 . 
         [0060]    Referring to  FIGS. 16   a  and  16   b , in the neutral position of the lever configuration, the actuator  700  is pushed into the lever spring plate orifice  704  to engage the lever spring plate  690 . In operation, this causes the lever spring plate  690  to rotate with the spindle  622  and the knob spring plate  630 . The interaction of the knob spring plate  630  and the knob spring  670  remains as previously described. With clockwise rotation of the spindle  622 , the upper arcuate arm  694  of the lever spring plate  690  contacts and rotates the upper leg  654  of the lever spring  650  to deflect it against the operably fixed lower leg  656  of the lever spring  650 . With counterclockwise rotation of the spindle  622 , the lower arcuate arm  696  contacts and rotates the lower leg  656  of the lever spring  650  against the operably fixed upper leg  654 . Due to the geometry of the lever spring plate  690 , the upper and lower arcuate arms  694 ,  696  also contact and rotate the upper and lower legs  674 ,  676  of the knob spring  670  in conjunction with the knob spring plate  630  as described in  FIGS. 15   a - 15   b . The counter torque to the actuation of the lever is thus provided by the combination of the knob spring  670  and the lever spring  650 . 
         [0061]    To switch from a knob trim to a lever trim, the user first removes the existing trim, manually alternates the selector  100  or actuator  470  (with, for example, a screwdriver) or slides the actuator  540  or  700  to the proper trim mode, and installs a new trim. Disassembly of the lock assembly  104 ,  400 ,  600  is not required. 
         [0062]    The single lock assembly  104 ,  400 ,  600  as described provides more than one spring rate to accommodate different trim configurations. This benefits manufacturers by reducing the number of parts necessary to be manufactured, stored and tracked, and benefits consumers by offering an easy opportunity to upgrade from knobs to levers without the need to purchase a new lock chassis assembly. 
         [0063]    Various features and advantages of the invention are set forth in the following claims.

Summary:
A latch assembly configured to attach to a door includes one of a knob and a lever. The latch assembly further includes a latch extending from the door. A spindle is rotatable from a first position to a second position to move the latch from an extended position to a retracted position. A first biasing member is selectively operable to bias the spindle toward the first position. A second biasing member is selectively operable to bias the spindle toward the first position. An actuator is movable between a knob position in which only one of the first biasing member and the second biasing member biases the spindle toward the first position and a lever position in which both the first biasing member and the second biasing member cooperate to bias the spindle toward the first position.