Patent Publication Number: US-2012031156-A1

Title: Tool-less rekeyable lock cylinder

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None. 
     MICROFICHE APPENDIX 
     None. 
     GOVERNMENT RIGHTS IN PATENT 
     None. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lock cylinder, and, more particularly, to a tool-less rekeyable lock cylinder. 
     2. Description of the Related Art 
     When rekeying a cylinder using a traditional cylinder design, the user is required to remove the cylinder plug from the cylinder body and replace the appropriate pins so that a new key can be used to unlock the cylinder. This typically requires the user to remove the cylinder mechanism from the lockset and then disassemble the cylinder to some degree to remove the plug and replace the pins. This requires a working knowledge of the lockset and cylinder mechanism and is usually only performed by locksmiths or trained professionals. Additionally, the process usually employs special tools and requires the user to have access to pinning kits to interchange pins and replace components that can get lost or damaged in the rekeying process. Finally, professionals using appropriate tools can easily pick traditional cylinders. 
     In U.S. Pat. No. 6,860,131, there is disclosed a rekeyable lock cylinder that includes a cylinder body with a plug body and carrier sub-assembly disposed therein. The plug body includes a plurality of spring-loaded pins and the carrier assembly includes a plurality of racks for engaging the pins to operate the lock cylinder. A tool is inserted into a tool-receiving aperture on the plug body face to move the carrier in a longitudinal direction from an operating position to a rekeying position. In the rekeying position, the racks are disengaged from the pins and a second valid key can replace the first valid key. The second valid key is inserted into the keyway of the plug body, and then the tool is released to reengage the racks with the pins to complete the rekeying process. 
     SUMMARY OF THE INVENTION 
     The present invention provides a tool-less rekeyable lock cylinder, which facilitates the rekeying of a lock cylinder without the need for lock disassembly or tools. 
     The invention, in one form thereof, is directed to a rekeyable lock cylinder having a longitudinal axis. The rekeyable lock cylinder includes a plug assembly and a lock cylinder. The plug assembly includes a plug body, a plurality of key followers, a plurality of racks, and a rack carrier. The plug body has a keyway configured to receive a key. The plurality of key followers is moveably disposed in the plug body. The plurality of racks is movably disposed in the rack carrier. The plug body has a proximal end and a distal end. The rack carrier is longitudinally moveable relative to the plug body between the proximal end and the distal end. The rack carrier has a cam follower that extends outwardly from the rack carrier. The lock cylinder body includes a cylinder wall having an interior surface defining an interior void in which the plug assembly is rotatably disposed, and has a cam track configured on the cylinder wall at the interior surface to guide the cam follower of the plug assembly. The cam track has a ramp portion configured to longitudinally displace the cam follower and the rack carrier as the plug assembly is rotated about the longitudinal axis relative to the lock cylinder body to facilitate selective disengagement of the plurality of racks from the plurality of key followers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a rekeyable lock cylinder configured in accordance with an embodiment of the present invention; 
         FIG. 2  is an exploded view of the lock cylinder of  FIG. 1 ; 
         FIG. 3  is a perspective view of a plug assembly of the lock cylinder of  FIG. 1 , illustrating a carrier sub-assembly with a locking bar disposed in a locking position and a cam follower extending outwardly from the curved surface of the rack carrier; 
         FIG. 4  is a top plan view of the plug assembly of  FIG. 3  showing the rack carrier in the proximal position, and having a key inserted in the keyway; 
         FIG. 5  is a top plan view of the plug assembly of  FIG. 3  showing the rack carrier in the distal position to facilitate rekeying of lock cylinder of  FIG. 1 , and having a key inserted in the keyway; 
         FIGS. 6A and 6B  are opposite perspective views of the plug body of the plug assembly of  FIGS. 3-5 ; 
         FIG. 7  is a plan view of the rack carrier of the plug assembly of  FIGS. 3-5 , with the a cam follower inserted into a recessed opening in the rack carrier; 
         FIG. 8A  is a top view of the cam follower and arc-shaped base of  FIG. 7 . 
         FIG. 8B  is a side view of the cam follower and arc-shaped base of  FIG. 7 , and showing an embodiment of a spring that is interposed between the rack carrier and the cam follower to bias the cam follower outwardly away from the rack carrier; 
         FIG. 9  is a section view taken along line  9 - 9  of  FIG. 7 , and illustrating the cam follower and integral arc-shaped base, and biasing spring; 
         FIG. 10  is an end view of the lock cylinder body taken from the front end, with the plug assembly removed; and 
         FIG. 11  is a planar representation of the annular interior surface of the lock cylinder body of  FIG. 10 , showing the cam track and illustrating a normal path. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. For convenience, and ease of discussion, both an individual element and a plurality of like individual elements may be referenced by the same element number. The exemplifications set out herein illustrate one embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and particularly to  FIGS. 1 and 2 , there is shown a lock cylinder  10  configured in according to an embodiment of the present invention. Lock cylinder  10  includes a lock cylinder body  12 , a plug assembly  14  and a retainer  16 . Lock cylinder  10  has a longitudinal axis  18  that extends through the central elongate portion of lock cylinder  10 . 
     Referring also to  FIG. 10 , lock cylinder body  12  is formed as a generally cylindrical body having an interior void  20 , a front end  22 , a back end  24 , and a cylinder wall  26  having an interior surface  28 . Interior surface  28  defines the interior void  20 . Plug assembly  14  is rotatably disposed in the interior void  20  of lock cylinder body  12 . Retainer  16  retains plug assembly  14  in lock cylinder body  12 , and may be in the form of a snap ring. 
     Longitudinal axis  18  extends through the interior void  20  from front end  22  to back end  24 , and defines a corresponding rotational axis  18  for plug assembly  14 . Cylinder wall  26  includes an interior, locking bar groove  30 . In the present embodiment, a generally V-notch locking bar groove  30  extends longitudinally along a portion of lock cylinder body  12  from the front end  22  toward the back end  24  in a direction parallel to longitudinal axis  18 . 
     Referring also to  FIGS. 3-5 , in conjunction with  FIG. 2 , plug assembly  14  includes plug body  32 , a plurality of key followers  34 , a plurality of biasing springs  36 , and a carrier sub-assembly  38 . Carrier sub-assembly  38  includes a rack carrier  40 , a plurality of racks  42 , biasing member  44 , a locking bar  46 , and locking bar return springs  48 . 
     Plug body  32  includes a plug face  50 , an intermediate portion  52  and a drive portion  54 . Plug body  32  has a proximal end  32 - 1  and a distal end  32 - 2 . A keyway  56  extends from plug face  50  into intermediate portion  52 , with keyway  56  being configured to receive a key  58  for operating lock cylinder  10 . A pair of channels  60  extends radially outwardly for receiving anti-drilling ball bearings  62  ( FIGS. 2 ,  6 A and  6 B). Drive portion  54  includes an annular wall  64  with a pair of opposed projections  66  extending radially inwardly to drive a spindle or torque blade (neither shown). Drive portion  54  further includes a pair of slots  68  formed in its perimeter for receiving retainer  16  to retain plug body  32  in lock cylinder body  12 . 
     Intermediate portion  52  includes a main portion  70  formed as a cylinder section, a first planar surface  72  and a second planar surface  74  ( FIGS. 2 ,  6 A and  6 B). The first planar surface  72  further includes a plurality of bullet-shaped, rack-engaging features  78 . Each of the first planar surface  72  and the second planar surface  74  extends generally parallel to longitudinal axis  18 , with the second planar surface  74  being offset 90 degrees from, e.g., perpendicular to, the first planar surface  72 . The second planar surface  74  defines a recess  80  for receiving a spring retaining cap  82  ( FIGS. 2-5 ). 
     Spring-retaining cap  82 , illustrated in  FIG. 2 , includes a curvilinear portion  84 . The thickness of the curvilinear portion  84  is set to allow the curvilinear portion  84  to fit in recess  80  with the upper surface  88  flush with intermediate portion  52  of plug body  32 , as illustrated in  FIGS. 3-5 . A plurality of spring alignment tips  92  extend from downwardly from curvilinear portion  84  to engage the plurality of biasing springs  36 . In addition, a pair of cap retaining tips (not shown) may extend from downwardly from curvilinear portion  84  to engage corresponding alignment openings (not shown) formed in plug body  32 . 
     Intermediate portion  52  further includes a plurality of guide channels  100  configured to receive and guide the respective plurality of key followers  34 . Guide channels  100  extend transversely to the longitudinal axis  18  of lock cylinder body  12  and plug body  32 , and parallel to first planar surface  72 , in direction D 1 . The plurality of key followers  34  are individually biased toward keyway  56  in direction D 1  by a corresponding number of the plurality of biasing springs  36 . Each key follower of the plurality of key followers  34  is located to extend across keyway  56 . 
     Referring also to  FIGS. 6A and 6B , the plurality of guide channels  100  are configured to conform to the shape of the plurality of key followers  34  to guide the bidirectional movement of the plurality of key followers  34  in guide channels  100  in the direction D 1 , e.g., parallel to first planar surface  72 , while restraining movement of the plurality of key followers  34  in guide channels  100  in a direction transverse to the direction D 1 , e.g., perpendicular to first planar surface  72 , such as in a direction D 2  transverse to keyway  56 . As will be understood by those skilled in the art with reference to the various figures, the term “restraining” refers to allowing standard engineering clearance tolerances in a respective pin/channel combination without permitting transverse motion of key followers  34  between two transverse spaced positions, e.g. in transverse direction D 2 , in the respective guide channels  100 . 
     Guide channels  100  extend from the second planar surface  74  partially through plug body  32 , with the sidewalls of guide channels  100  open to the first planar surface  72 . In other words, as shown in  FIGS. 2 ,  6 A and  6 B, each guide channel of the plurality of guide channels  100  has a sidewall opening  102 , with the sidewall openings  102  collectively defining retention supports  102 - 1 ,  102 - 2 ,  102 - 3 ,  102 - 4 ,  102 - 5 ,  102 - 6 . A respective pair of retention supports  102 - 1 ,  102 - 2 ;  102 - 2 ,  102 - 3 ;  102 - 3 ,  102 - 4 ;  102 - 4 ,  102 - 5 ; and  102 - 5 ,  102 - 6  cooperates with its respective guide channel  100  to restrain transverse movement of a respective key follower of the plurality of key followers  34  in a respective guide channel  100 , e.g., in direction D 2  transverse to keyway  56 . In the present embodiment, as illustrated in  FIGS. 2 ,  6 A and  6 B, each guide channel of the plurality of guide channels  100  is formed as a cylinder having sidewall opening  102  in the form of an axial sidewall slot. 
     Referring again to  FIG. 2 , in the present embodiment, each of the plurality of key followers  34  is in the form a cup-shaped pin. Each of the plurality of key followers  34  is generally cylindrical and has a central longitudinal depression  104  for receiving an end portion of a respective biasing spring of the plurality of biasing springs  36 . Each biasing spring of the plurality of the plurality of biasing springs  36  may have a non-constant diameter to aid in reception in the respective depression  104 . Each of the plurality of key followers  34  also has an engagement protrusion  106  in the form of a single gear tooth that is configured and positioned to extend into a respective sidewall opening  102  in plug body  32 . The single gear tooth forming engagement protrusion  106  may include beveled sides to facilitate smooth engagement with, and disengagement from, the respective rack of the plurality of racks  42  during the rekeying process. 
     Referring to  FIGS. 4 and 5 , rack carrier  40  of carrier sub-assembly  38  is longitudinally moveable relative to plug body  32  between the proximal end  32 - 1  of plug body  32  and the distal end  32 - 2  of plug body  32 , i.e., between a proximal position  40 - 1  and a distal position  40 - 2  of rack carrier  40 . Biasing member  44 , e.g., a coil return spring, is engaged with rack carrier  40  to bias rack carrier  40  toward the proximal end  32 - 1  of plug body  32 . Thus, biasing member  44  is engaged with rack carrier  40  to continually tend to bias rack carrier  40  toward the proximal end  32 - 1  of plug body  32  to the proximal position  40 - 1  for rack carrier  40 . 
     Referring to  FIGS. 2 ,  6 A and  9 , rack carrier  40  is positioned adjacent to first planar surface  72 , and is configured for sliding engagement along first planar surface  72  in a direction parallel to longitudinal axis  18 . The proximal position  40 - 1  is associated with the proximal end  32 - 1  of plug body  32  where each of the plurality of racks  42  is engaged with a respective key follower of the plurality of key followers  34 . The distal position  40 - 2  is associated with the distal end  32 - 2  of plug body  32  wherein the plurality of racks  42  is disengaged from the plurality of key followers  34 . 
     Rack carrier  40  includes a body  108  in the form of a cylinder section that is complementary to the main portion  70  of plug body  32 , such that rack carrier  40  and the main portion  70  combine to form a cylinder that fits inside lock cylinder body  12 . The body  108  of rack carrier  40  includes a curved surface  110  and a flat surface  112 . The curved surface  110  includes a locking bar recess  114 . Locking bar recess  114  further includes a pair of return spring-receiving bores  116  ( FIG. 2 ) for receiving locking bar return springs  48 . 
     The flat surface  112  of rack carrier  40  includes a plurality of parallel rack-receiving slots  118 . Each of the plurality of rack-receiving slots  118  is configured to respectively slidably receiving a corresponding rack of the plurality of racks  42 . Locking bar recess  114  extends inwardly from the curved surface  110  to intersect with each of the plurality of parallel rack-receiving slots  118 . Locking bar recess  114  is configured to slidably receive locking bar  46 , which is spring biased toward locking bar groove  30  of lock cylinder body  12 . When lock cylinder  10  is assembled, locking bar  46  is disposed within lock cylinder body  12 . 
     Each of the plurality of racks  42  is movably disposed in a respective guide slot of the plurality of rack-receiving slots  118 . Each rack of the plurality of racks  42  has at least one engagement groove  120  (see  FIG. 2 ), e.g., formed by a pair of teeth, to selectively receive the engagement protrusion  106 , e.g., in the form of gear tooth, of a respective key follower of the plurality of key followers  34 , with the engagement protrusion  106  extending into the sidewall opening  102  between a respective pair of retention supports. In some embodiments, the engagement protrusion  106  of a respective key follower of the plurality of key followers  34  may extend into and through the sidewall opening  102  to facilitate engagement with a respective engagement groove  120  of a respective rack  42 . Each of the plurality of racks  42  further includes a locking bar engaging groove  122 , and includes a semi-circular recess  124  for engaging the bullet-shaped, rack-engaging features  78  on first planar surface  72 , as illustrated in  FIG. 2 . 
     The spring-loaded locking bar  46  is sized and configured to slidably fit in locking bar recess  114  in rack carrier  40 . Locking bar  46  is formed as an elongate member having a tapered triangular side edge  126  that is configured to be received by locking bar groove  30  of cylinder wall  26 . Opposite the triangular side edge  126 , locking bar  46  includes a longitudinally extending gear tooth  128  configured to be selectively received in locking bar engaging grooves  122  of the plurality of racks  42  when locking bar engaging grooves  122  of the plurality of racks  42  are in longitudinal alignment relative to longitudinal axis  18 , as is the case when a proper key  58  is inserted into keyway  56 . 
     Lock cylinder body  12  is configured to prevent a rotation of plug assembly  14  relative to lock cylinder body  12  when no key, or an invalid key, is inserted into keyway  56 . For example, when no key, or an invalid key, is inserted into keyway  56 , locking bar engaging groove  122  of the plurality of racks  42  are not in longitudinal alignment relative to longitudinal axis  18 , and thus locking bar  46  is retained in locking bar groove  30  of lock cylinder body  12  by one or more of the plurality of racks  42 , and thus prevents rotation of plug assembly  14  relative to lock cylinder body  12 . Lock cylinder body  12  is configured to prevent a rotation of plug assembly  14  relative to lock cylinder body  12  when an invalid key is inserted into keyway  56 . 
     In accordance with an aspect of the present invention, rack carrier  40  further includes having a cam follower  130  that extends outwardly from the curved surface  110  of rack carrier  40 . More particularly, as shown in  FIGS. 7 ,  8 A and  8 B, cam follower  130  is in the form of a pin that extends outwardly from an arc-shaped base  132 . In the present embodiment, cam follower  130  is formed integral with arc-shaped base  132 . Rack carrier  40  has a recessed opening  134  extending inwardly into rack carrier  40  from the exterior curved surface  110 . Cam follower  130  and arc-shaped base  132  are inserted into the recessed opening  134 . A spring  136  is interposed between rack carrier  40  and cam follower  130  to engage the arc-shaped base  132  to bias cam follower  130  outwardly from the exterior curved surface  110  away from the longitudinal axis  18 . Spring  136  is formed in a shape to reduce the interior space needed to accommodate spring  136  when in spring  136  is in a compressed state. In the present embodiment, spring  136  is a coil spring having a pyramidal profile. As an alternative, spring  136  may be a leaf spring having a curved profile. 
     Referring to  FIGS. 10 and 11 , a cam track  138  is configured on the annular cylinder wall  26  of lock cylinder body  12  at the interior surface  28  to guide cam follower  130  of plug assembly  14 . As used in the previous sentence, the term “configured on” is intended to encompass a cam track machined into or built up from the cylinder wall  26 . Cam track  138  has at least one a ramp portion (diverging ramp portions  140  being shown in the present embodiment) configured to longitudinally displace cam follower  130  and rack carrier  40  (see  FIGS. 4 and 5 ), from the proximal end  32 - 1  toward the distal end  32 - 2 , as plug assembly  14  is rotated about the longitudinal axis  18  relative to lock cylinder body  12  to facilitate selective disengagement of the plurality of racks  42  from the plurality of key followers  34 . Stated differently, a respective ramp portion  140 - 1  or  140 - 2  of cam track  138  is configured to displace rack carrier  40  from proximal position  40 - 1  toward the distal position  40 - 2  as plug assembly  14  is rotated about the longitudinal axis  18  relative to lock cylinder body  12 . 
     More particularly, in the exemplary embodiment shown in  FIG. 11 , cam track  138  has an annular track portion  142 , a V-shaped portion  144 , an apex  146  of the V-shaped portion  144  corresponding to a home position HP, a first detent feature  148 - 1 , a second detent feature  148 - 2 , a first return path  150 - 1 , and a second return path  150 - 2 . The apex  146  of the V-shaped portion  144  corresponds to the home position HP for plug assembly  14  relative to lock cylinder body  12  of lock cylinder  10 . Also, each of the first detent feature  148 - 1  and the second detent feature  148 - 2  defines a respective rekeying position RP for lock cylinder  10 . In the present embodiment, not only does the home position HP correspond to the apex  146  of the V-shaped portion  144 , but in addition the home position HP defines the home orientation of plug assembly  14  relative to lock cylinder body  12 , wherein keyway  56  is substantially vertical with respect to lock cylinder body  12  in the orientation as shown in  FIGS. 1-3  and  6 A. 
     The V-shaped portion  144  defines the pair of diverging ramp portions  140 , individually identified as a first ramp portion  140 - 1  and a second ramp portion  140 - 2 . The V-shaped portion may extend through the cylinder wall  26  and form a triangle cutout, as shown for example in  FIGS. 1 ,  2  and  11 . The home position HP is located at the apex  146  of the V-shaped portion  144 , with the V-shaped portion  144  extending distally from the home position HP to the annular track portion  142 . Stated differently, the home position HP is located at a base of the respective ramp portions  140 - 1 ,  140 - 2 . Each of the first ramp portion  140 - 1  and the second ramp portion  140 - 2  of the pair of diverging ramp portions  140  of cam track  138  is configured to displace rack carrier  40  toward the distal position  40 - 2  as plug assembly  14  is rotated about the longitudinal axis  18  relative to lock cylinder body  12 . 
     Referring again also to  FIGS. 4 and 5 , biasing member  44  engaged with rack carrier  40  biases rack carrier  40  toward the proximal end  32 - 1  of plug body  32  to the proximal position  40 - 1 , i.e., biases cam follower  130  toward the home position HP and into the apex  146  of the V-shaped portion  144 . Thus, for example, beginning with cam follower  130  of plug assembly  14  being positioned at the apex  146  of the V-shaped portion  144 , rotating plug assembly  14  in a clockwise direction  154  will result in cam follower  130  engaging and traveling along the first ramp portion  140 - 1  against the biasing force exerted by biasing member  44 . Likewise, beginning with cam follower  130  of plug assembly  14  being positioned at the apex  146  of the V-shaped portion  144  (home position HP), rotating plug assembly  14  in a counterclockwise direction  152  will result in cam follower  130  engaging and traveling along the second ramp portion  140 - 2  against the biasing force exerted by biasing member  44 . However, in either case, a rotation of plug assembly  14  from the home position HP to a respective rekeying position RP (e.g., respective detent feature  148 - 1  or  148 - 2 ) causes cam follower  130  to move along one of the diverging ramp portions  140  to in turn move rack carrier  40  from the proximal position  40 - 1  toward the distal position  40 - 2  to disengage the plurality of racks  42  from the plurality of key followers  34  to facilitate the rekeying of the rekeyable lock cylinder  10 , wherein each of the respective rekeying positions RP is defined in the annular track portion  142  by a respective detent feature  148 - 1 ,  148 - 2 . 
     The annular track portion  142  defines a distal extent of movement of rack carrier  40  associated with the distal position  40 - 2 , and thus defines the distal position  40 - 2  of rack carrier  40 . In the present embodiment, cam track  138  is configured such that cam follower  130  of plug assembly  14  reaches the annular track portion  142  after a rotation of plug assembly  14  relative to the home position HP in a rotational range of 20 degrees to 70 degrees either in the counterclockwise direction  152  or the clockwise direction  154  relative to the home position HP. In the exemplary embodiment, and referring to  FIG. 11 , cam follower  130  of plug assembly  14  reaches the annular track portion  142  after a rotation of plug assembly  14  relative to the home position HP of about 20 to 30 degrees, either in the counterclockwise direction  152  or the clockwise direction  154  relative to the home position HP, at which time the plurality of racks  42  is disengaged from the plurality of key followers  34  (see also  FIG. 5 ). 
     The annular track portion  142  includes a first annular track segment  142 - 1  and a second annular track segment  142 - 2 . Each respective annular track segment  142 - 1 ,  142 - 2  terminates in a respective return path, i.e., first return path  150 - 1  or second return path  150 - 2 . The respective first return path  150 - 1  or second return path  150 - 2  is angularly offset from the respective one of the pair of diverging ramp portions  140 , and more particularly, in the present embodiment is angularly offset by 90 degrees from the home position HP at 0 degrees. For example, the first return path 150-1 may be located at the 90 degree position in the counterclockwise direction  152  from the home position HP, and the second return path  150 - 2  may be located at the 90 degree position in the clockwise direction  154  from the home position HP. Each respective return path  150 - 1 ,  150 - 2  facilitates a return of rack carrier  40  to the proximal position  40 - 1  (see  FIG. 4 ) to reengage the plurality of racks  42  with the plurality of key followers  34 , with the return being effected by biasing member  44  that is engaged with rack carrier  40  that continually tends to bias rack carrier  40  toward the proximal end  32 - 1  of plug body  32  to the proximal position  40 - 1 . After rack carrier  40  is returned to the proximal position  40 - 1 , plug assembly  14  is rotatable in either the counterclockwise direction  152  or the clockwise direction  154  with rack carrier  40  remaining in the proximal position  40 - 1  until cam follower  130  reengages one of the diverging ramps of the V-shaped portion  144 . 
     Return path  150 - 1  is configured with a respective beveled side wall portion  156 - 1 , and return path  150 - 2  is configured with a respective beveled side wall portion  156 - 2 , to engage and depress cam follower  130  upon further rotation of plug assembly  14  relative to lock cylinder body  12  such that cam follower  130  leaves cam track  138 , with rack carrier  40  in the proximal position  40 - 1 , to travel along a neutral path  158 , depicted by the horizontal dashed line in  FIG. 11 . The neutral path  158  corresponds to the state of plug assembly  14  with rack carrier  40  in the proximal position  40 - 1 . Cam follower  130 , traveling along the neutral path  158 , reengages cam track  138  when cam follower  130  reaches the apex  146  of the V-shaped portion  144  (home position HP) as plug assembly  14  is rotated relative to lock cylinder body  12 . 
     By utilizing a configuration having the V-shaped portion  144  having the first ramp portion  140 - 1  and the second ramp portion  140 - 2  diverging from the apex  146 , the present invention facilitates rekeying of lock cylinder  10  by a partial rotation of plug assembly  14  relative to lock cylinder body  12  in either of the counterclockwise direction  152  or clockwise direction  154 , relative to the home position HP. However, those skilled in the art will recognize that rekeying may be limited to a rotation of plug assembly  14  in the counterclockwise direction  152  by elimination of the second ramp portion  140 - 1 . Likewise, rekeying may be limited to a rotation of plug assembly  14  in the clockwise direction  154  by elimination of the first ramp portion  140 - 2 . 
     In general, referring to  FIG. 2 , without any key inserted in keyway  56 , the key followers  34  are biased to the bottom of guide channels  100  and, based on the cut of the valid key to be inserted into keyway  56 , racks  42  are disposed at various positions in rack-receiving slots  118  of rack carrier  40  with racks  42  engaged with the key followers  34 . In this configuration, locking bar  46  extends from rack carrier  40  to engage locking bar groove  30  in lock cylinder body  12  to prevent plug assembly  14  from rotating in lock cylinder body  12 . In addition, the bullet-shaped, rack-engaging features  78  are misaligned with the semi-circular recess  124  in racks  42  and therefore interfere with movement of racks  42  parallel to the longitudinal axis  18  of lock cylinder  10 , preventing lock cylinder  10  from being rekeyed. 
     When a valid key  58  is inserted therein at the home position HP, as illustrated in  FIG. 4 , the key followers  34  in guide channels  100 , and in turn racks  42  in rack-receiving slots  118 , are repositioned such that locking bar engaging groove  122  of each of the plurality of racks  42  are longitudinally aligned (see also  FIG. 2 ). As such, locking bar engaging grooves  122  are aligned with the extended gear teeth  128  on locking bar  46 , and thus locking bar  46  is free to cam out of locking bar groove  30  in lock cylinder body  12  with the rotation of plug assembly  14  relative to lock cylinder body  12 . At the same time, the bullet-shaped, rack-engaging features  78  are aligned with the semi-circular recess  124  in racks  42 , as illustrated in  FIG. 2 , allowing racks  42 , and rack carrier  40 , to move parallel to the longitudinal axis  18  of lock cylinder  10 . 
     To rekey lock cylinder  10 , the valid key  58  is inserted into keyway  56 , and plug assembly  14  is rotated approximately 20 to 60 degrees such that cam follower  130  travels along the respective ramp portion  140 - 1 ,  140 - 2  to the annular track portion  142 , and may be retained by a respective detent feature  148 - 1 ,  148 - 2  in the annular track portion  142 . Referring to  FIGS. 4 and 5 , during the rotation of plug assembly  14 , rack carrier  40  is moved from the proximal position  40 - 1  to the distal position  40 - 2 , thereby disengage racks  42  from the key followers  34 . At this stage of the rekeying process, the semi-circular recesses  124  of the plurality of racks  42  are respectively engaged with the bullet-shaped, rack-engaging features  78  of plug body  32 , which retains the longitudinal alignment of locking bar engaging grooves  122  of the plurality of racks  42  relative to locking bar  46  (see also  FIGS. 2 and 6A ). Also, at this stage of the rekeying process, the valid key  58  is removed and replaced with a new key to which lock cylinder  10  is to be rekeyed. Upon insertion of the new key (similar to key  58  but having a different key follower lift profile) into keyway  56 , each of the plurality of key followers  34  is thus vertically positioned relative to the lift profile of the new key. The new key is rotated such that cam follower  130  returns to the neutral path  158 , thereby returning rack carrier  40  to the proximal position  40 - 1 , and in turn reengaging each of the plurality of key followers  34  with a respective rack of the plurality of racks  42 . 
     At this point, lock cylinder  10  is keyed to the new key and the previous valid key is no longer able to operate lock cylinder  10 . 
     While this invention has been described with respect to embodiments of the invention, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.