Patent Publication Number: US-7900491-B2

Title: Rekeyable lock assembly and method of operation

Description:
The present invention relates generally to lock cylinders and particularly to lock cylinders that can be rekeyed. More particularly, the invention relates to lock cylinders that can be rekeyed in situ and without using a master key. 
     BACKGROUND OF THE INVENTION 
     Rekeying a conventional lock cylinder is a task best left to a professional locksmith because it involves removing the lock cylinder from the lock installation and then disassembling it. The original pins are then replaced by different pins to accommodate the cut of the new key, and the lock is reassembled. This requires a working knowledge of the lockset and cylinder mechanism and requires access to replacement pins. 
     These considerations can intimidate an ordinary consumer, prompting the hire a professional locksmith or to buy a new lockset. Either way, the consumer must spend money. In addition, professionals using appropriate tools can easily pick traditional cylinders. 
     The present invention overcomes these and other disadvantages of conventional lock cylinders. The lock cylinder of the present invention operates in a transparent way that presents the familiar experience of inserting a key and rotating the key in the lock cylinder, as with current cylinders. However, in the present invention, that same familiar experience is used to rekey the lock cylinder. Thus, the user does not require any special knowledge, training, or tools to rekey the lock cylinder of the present invention. 
     SUMMARY OF THE INVENTION 
     A rekeyable lock cylinder includes a housing and a plug assembly. The plug assembly includes a plug body and a carrier, a plurality of pins disposed in the plug body, a plurality of racks disposed in the carrier for engaging the pins, and a locking bar disposed in the carrier for engaging the housing. When the plug body is rotated from a home position to a second position within the housing, the locking bar aligns with a reset groove formed in the housing. While the plug assembly is in the second position, the carrier is moved longitudinally relative to the plug body to a learn position, allowing the locking bar to enter the reset groove, thereby locking the carrier in the learn position. At the same time, the racks disengage from the pins. In the learn position, the original key is removed and a replacement key is inserted into the lock cylinder. Being disengaged from the racks, the pins are free to accommodate the bitting of a replacement key. With the replacement key in the lock cylinder, the plug assembly is rotated from the second position, causing the carrier to move out of the learn position and the racks to reengage the pins in response to movement of the carrier, whereupon the lock cylinder is keyed to the replacement key. 
     In operation, a user inserts a valid key in the lock and rotates the plug assembly to a reset position. The user then pushes against the carrier by inserting a tool in an aperture in the lock face, or depressing an internally mounted push button or the like. Pushing the carrier moves it longitudinally to a learn position, where the locking bar engages a reset groove in the cylinder housing side wall. Features on the locking bar cooperate with complementary features in the reset groove to retain the carrier in the learn position. 
     When the carrier is in the learn position, the user withdraws the valid key, inserts a replacement key with different bitting, and rotates the plug assembly from the reset position. The rotation of the plug assembly cams the locking bar out of the reset groove, allowing a biasing spring to move the carrier back to its original position. At this point, the lock cylinder is keyed to the replacement key and the original valid key no longer operates the lock. 
     Other features and advantages will become apparent from the following description when viewed in accordance with the accompanying drawings and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a lock cylinder according to the present invention. 
         FIG. 2  is a perspective view of a plug assembly. 
         FIG. 3  is a top plan view of the plug assembly of  FIG. 2 . 
         FIG. 4  is a perspective view of the lock cylinder housing of  FIG. 1 . 
         FIG. 5  is a section view taken along lines  5 - 5  in  FIG. 4 . 
         FIG. 6  is a section view taken along lines  6 - 6  of  FIG. 4 . 
         FIG. 7  is a section view through an assembled lock cylinder in a locked configuration. 
         FIG. 8  is a section view through an assembled lock cylinder with a valid key in the keyway. 
         FIG. 9  is a section view through an assembled lock cylinder with the plug assembly rotated 90° in the cylinder housing. 
         FIG. 10  is a section view taken along lines  10 - 10  of  FIG. 9 . 
         FIG. 11  is a section view through an assembled lock cylinder in the learn configuration. 
         FIG. 12  is a section view taken along lines  12 - 12  of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     As with conventional lock cylinders, the present cylinder  10  has a locked condition and an unlocked condition. However, the present lock cylinder  10  further includes a reset condition wherein the lock cylinder can be put into a “learn” mode. In the “learn” mode, the original key can be removed and replaced by another key and, when the new key is removed, the lock cylinder  10  is rekeyed to the new key. The original key no longer operates the rekeyed lock cylinder  10 . 
     The lock cylinder  10  according to the present invention is illustrated in  FIG. 1-2  and includes a cylinder housing  12  having a longitudinal axis  14 , a plug assembly  16 , and a retainer  17 . The plug assembly  16  includes a plug body  18  defining a plurality of pin chambers  20 , and a carrier  22  defining a plurality of slots  24 . The plug body  18  further includes a generally planar surface  46  that has a plurality of reset alignment features  48 . The retainer  17  engages grooves  44  cut in the plug body  18  to retain the plug assembly  16  in the cylinder housing  12 . 
     A plurality of pins  26  and springs  28  are disposed in the pin chambers  20 , and a plurality of racks  32  is disposed in the slots  24 . A locking bar  34  and biasing springs  36  are disposed in a locking bar-receiving chamber  38  formed in the carrier  22 . 
     As best seen in  FIG. 7 , each rack  32  includes a plurality of gear teeth and an alignment notch  56  on a pin-facing edge thereof and a locking bar-receiving notch  58  on the opposite edge. Preferred pins  26  are generally cup-shaped with a cylindrical sidewall  50  and a finger  52 , or gear tooth, extending from the sidewall to engage the gear teeth of the racks  32 . As in conventional locks, the pins  26  are disposed in the pin chambers  20  to move with the bitting of the key  78 . In the present lock cylinder, however, the engagement of the pins  26  with the racks  32  causes the racks  32  to move up and down in the slots  24 . When a valid key  78  is inserted into the lock cylinder  10 , as illustrated in  FIG. 7 , the alignment notches  56  line up with the reset alignment features  48 . 
     The locking bar  34  includes an engaging edge  40  and a locking edge  42 , with the locking edge further including a reset notch  42 A. When the valid key  78  is inserted into the lock cylinder  10 , the engaging edge  40  of the locking bar  34  is aligned with the locking bar-receiving notch  58 . 
       FIGS. 2 and 3  illustrate the lock cylinder  10  in the locked condition, but with the cylinder housing  12  removed for clarity. As illustrated, a carrier spring  60  normally biases the carrier  22  toward a forward position adjacent the plug face  62 . The locking bar  34  is disposed in the locking bar-receiving chamber  38  and is biased outwardly by the biasing springs  36 .  FIG. 3  shows the racks  32  engaged with the pins  26  and the locking bar  34  extending beyond the carrier  22 . 
     The cylinder housing  12 , as seen in  FIGS. 4-6 , includes a generally cylindrical sidewall, an access panel  66 , and a spring retainer  68 . The sidewall has an interior surface  64  that defines a pair of diametrically opposed reset grooves  70  and a locking groove  74 . The locking groove  74  receives the locking bar  34  when the lock cylinder  10  is in the locked condition (see  FIG. 7 ), while one of the reset grooves  70  receives the locking bar  34  when the lock cylinder is in a learn condition, to be discussed below with respect to  FIG. 11 . 
     The reset grooves  70  are segmented into front and back segments  70   a ,  70   b , respectively, separated by a bridge  72 . The bridge  72  is sized and configured to enter the locking bar&#39;s reset notch  42   a  to allow the locking bar  34  to enter the reset groove  70 . However, the locking bar  34  is normally biased by the carrier spring  60  to prevent alignment of the reset notch  42   a  and the bridge  72 . 
     The illustrated lock cylinder  10  uses two reset grooves  70  to provide two reset positions, but only one reset groove  70  is necessary for the operation of the rekeying function. One of the reset grooves  70  receives the locking bar  34  during a rekeying operation, depending upon which way the key is turned in the lock. 
       FIG. 7  illustrates the lock cylinder  10  in the locked condition. The locking bar  34  is retained in the locking groove  74  by the rack  32 , thereby preventing the plug assembly  16  from rotating in the cylinder housing  12 .  FIG. 8  illustrates the lock cylinder  10  with a valid key  78  inserted in the keyway. As illustrated, the pin  26  rides up on the key  78 , lifting the rack  32  with it and aligning the rack&#39;s locking bar-receiving notch  58  with the locking bar  34 . The locking bar-receiving notch  58  provides adequate clearance for the locking bar  34  to cam completely out of the locking groove  74 , allowing the plug assembly  16  to rotate in the cylinder housing  12  to the condition illustrated in  FIGS. 9-12 . 
       FIGS. 9 and 10  illustrate the lock cylinder  10  wherein the lock cylinder  10  is unlocked and in the reset condition. In this configuration, the locking bar  34  is aligned with one of the reset grooves  70 , but the carrier spring  60  is biasing the carrier  22  against the plug face  62 , causing a misalignment between the bridge  72  and the lock bar reset notch  42   a . By virtue of the misalignment, the bridge  72  prevents the locking bar  34  from entering the reset groove  70 . However, in this condition, the carrier  22  can be moved longitudinally to the learn position illustrated in  FIGS. 11 and 12 , wherein the racks  34  are disengaged from the pins  26  and the lock cylinder  10  can be rekeyed. 
       FIGS. 11 and 12  illustrate the carrier  22  to the learn position. A user inserts a reset tool  7  through an aperture  76  formed in the plug face  62  and pushes against the carrier  22 . As the carrier  22  moves, multiple actions occur near simultaneously. First, the racks  32  move out of engagement with the pins  26 . As the racks  32  disengage from the pins  26 , the racks&#39; alignment notches  56  receive the reset alignment features  48 , thereby maintaining the alignment between the locking bar  34  and the racks  32 . When the racks  32  and pins  26  are completely disengaged, the locking bar&#39;s reset notch  42   a  aligns with and receives the bridge  72 , allowing the locking bar  34  to enter the reset groove  70  under the biasing force of the springs  36 . By entering the reset notch  42   a , the bridge  72  retains the locking bar  34  and, thereby, the carrier  22  in the learn position. 
     It will be appreciated by the reset notch and bridge could be switched, such that the cylinder housing sidewall would include the notch and the locking bar would include the bridge. Moving the carrier to the learn position would still result in the engagement of the bridge and notch to retain the carrier in the learn position. 
     In the learn position, the pins  26  are free to move up and down, thereby allowing the key  78  to be withdrawn and replaced by a different key. As the replacement key is inserted, the pins  26  follow its bitting. When the replacement key is fully inserted, the user rotates the lock cylinder  10  out of the reset condition, thereby camming the locking bar  34  out of the reset groove  70 . As the locking bar  34  cams out of the reset groove  70 , it once again engages the locking bar-receiving notches of the racks  32 . Simultaneously, the bridge  72  exits the locking bar&#39;s reset notch  42   a , allowing the carrier  22  to move longitudinally toward the plug face  62  under the biasing force of the carrier spring  60 . As the carrier  22  moves toward the plug face  62 , the racks  32  reengage the pins  26 , but now the pins  26  and racks  32  are set to match the replacement key. 
     The above-described embodiments, of course, are not to be construed as limiting the breadth of the present invention. Modifications and other alternative constructions will be apparent that are within the spirit and scope of the invention as defined in the appended claims. For example, the segmented groove in the cylinder housing sidewall could have socket, rather than a bridge, separating the front and back segments. Accordingly, the locking bar would have a projection replacing the notch, and movement of the carrier to the learn position would cause the projection to enter the socket.