Patent Publication Number: US-2021172200-A1

Title: Modular lock plug

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. patent application Ser. No. 14/194,546 filed on Feb. 28, 2014, the contents of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to locks, and more particularly but not exclusively relates to locks including modular plugs. 
     BACKGROUND 
     Lock cylinders occasionally include locking sidebars which selectively prevent rotation of a plug with respect to a shell. Certain conventional locks of this type suffer from a variety of limitations. Therefore, a need remains for further improvements in this technological field. 
     SUMMARY 
     In one form, a plug assembly includes a plug, a sidebar movably mounted on the plug, and a plurality of rack pins seated in the plug. The sidebar is biased to an outer position in which the sidebar extends beyond an outer surface of the plug. Each rack pin is a single-piece unitary structure including a key-following leg and a sidebar-engaging leg. The sidebar-engaging leg includes at least one true gate and a plurality of false gates. When a true gate of each rack pin is aligned with the sidebar, the sidebar is free to move radially inward to an inner position. Further embodiments, forms, features, and aspects of the present application shall become apparent from the description and figures provided herewith. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a perspective illustration of a lock cylinder according to an embodiment of the present invention. 
         FIG. 2  is an exploded view of the lock plug used in the lock cylinder of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the lock cylinder of  FIG. 1  in a locked state. 
         FIG. 4  is a cross-sectional view of the lock cylinder of  FIG. 1  in an unlocked state. 
         FIG. 5  is a perspective illustration of a plug body and cover plate according to an embodiment of the present invention. 
         FIG. 6  is a perspective illustration of a rack pin according to an embodiment of the invention. 
         FIG. 7  is an exploded assembly illustration of a lock cylinder according to another embodiment. 
         FIG. 8  is a top-down cross-sectional illustration of the lock cylinder depicted in  FIG. 7 . 
         FIG. 9  is a perspective illustration of a rack pin used in the lock cylinder depicted in  FIG. 7 . 
         FIG. 10  is an exploded assembly illustration of a lock cylinder according to another embodiment. 
         FIG. 11  is a top-down cross-sectional illustration of the lock cylinder depicted in  FIG. 10 . 
         FIG. 12  is a cross-sectional illustration of the lock cylinder depicted in  FIG. 10  taken along the cut line XII-XII depicted in  FIG. 11 . 
         FIG. 13  is a cross-sectional illustration of the lock cylinder depicted in  FIG. 10  taken along the cut line depicted in  FIG. 11 . 
         FIG. 14  illustrates a subassembly of the lock cylinder depicted in  FIG. 10  with a key. 
         FIG. 15  is an elevation&amp; illustration of the subassembly depicted in  FIG. 14   
         FIG. 16  illustrates cross-sectional views of a conventional lock cylinder and the lock cylinder depicted in  FIG. 10 . 
         FIG. 17  is a perspective illustration of a handle assembly according to one embodiment. 
         FIG. 18  is a cross-sectional illustration of the handle assembly depicted in  FIG. 17 . 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
     As used herein, the terms “longitudinal”, “lateral” and “transverse” are used to denote motion or spacing along or substantially along three mutually perpendicular axes. In the coordinate plane illustrated in  FIG. 7 , the X-axis defines the longitudinal directions (including a proximal direction and a distal direction), the Y-axis defines the lateral directions, and the Z-axis defines the transverse directions. These terms are used for ease of convenience and description, and are without regard to the particular orientation of the system with respect to the environment. For example, descriptions that reference a longitudinal direction may be equally applicable to a vertical direction, a horizontal direction, or an off-axis orientation with respect to the environment. Additionally, motion or spacing along one direction need not preclude motion or spacing along another of the directions. For example, elements which are described as being “laterally offset” from one another may also be offset in the longitudinal and/or transverse directions, or may be aligned in the longitudinal and/or transverse directions. The terms are therefore not to be construed as limiting the scope of the subject matter described herein. 
     With reference to  FIG. 1 , an illustrative lock cylinder  100  includes a shell  101  and a plug assembly  200 . The shell  101  includes a shell body  120 , and the shell  101  may further include a tower  103  configured to allow the cylinder  100  to be installed into an existing lock cylinder housing. In the illustrated embodiment, the tower  103  is configured such that the lock cylinder  100  can be installed into a small format Interchangeable core (SFIC) housing. However, it is also contemplated that the shell  101  may have another configuration such as, for example, full size, mortise, rim, or key-in-knob/lever, or the shell  101  may alternatively be towerless. 
     With additional reference to  FIGS. 2 and 3 , the plug assembly  200  is positioned partially within a generally cylindrical chamber  122  defined by the shell body  120 . The plug assembly  200  includes a plug  210 , a cover plate  220 , a sidebar  230 , and a plurality of rack pins  240 . The shell body  120  also includes a longitudinal groove  123  configured to receive a portion of the sidebar  230 . 
     The plug  210  includes a faceplate  211 , a recessed portion  212 , a longitudinal channel  213 , a plurality of cavities  214 , and a keyway  219  configured to receive a key. The recessed portion  212  is configured as an arcuate portion of the plug  210  and sized and shaped to receive the cover plate  220 . The recessed portion  212  has a recess radius R 212  which is less than the plug body radius R 210 . The channel  213  extends in the axial direction of the plug  210 , and is configured to the receive the sidebar  230  and the biasing members  203 . Each of the cavities  214  is configured to receive a rack pin  240  and a biasing member  204 , and is connected to the recessed portion  212 , the longitudinal channel  213 , and the keyway  219 . Upon insertion of a key into the keyway  219 , each rack pin  240  can engage both the sidebar  230  and the key. 
     The cover plate  220  is configured as an arcuate plate including terminal surfaces  221  and slots  225 . The inner radius of the cover plate  220  corresponds to the recess radius R 212 , and the outer radius corresponds to the plug body radius R 210 . The cover plate  220  is configured to be received in the recess  212  such that the cover plate  220  is rotatably coupled to the plug  210 , in the illustrated form, the cover plate  220  comprises an arc having a central angle greater than 180°, and the terminal surfaces  221  are separated by a distance less than the diameter across the recess  212 . While the exemplary cover plate  220  comprises an arc having a central angle of about 200°, other central angles are also contemplated. In certain embodiments, a cover plate may have a central angle between 185° and 315°, between 190° and 280°, or between 195° and 220°. In other embodiments, the arc may have a central angle less than 180°. An exemplary form of one such cover plate is described below with reference to  FIG. 5 . 
     The illustrated cover plate  220  is slightly flexible such that separating the terminal surfaces  221  by a distance corresponding to the diameter across the recess  212  does not cause permanent deformation of the cover plate  220 . This in turn allows the cover plate  220  to be installed into the recess  212  by pressing the cover plate  220  into the recess  212  via a snap-fit action. When installed in the recess  212 , the cover plate  220  is rotatably clamped to the plug  210 . As such, the cover plate  220  can rotate about the longitudinal axis of the plug  210  within the confines of the recess  212 , but movement in the radial or axial direction of the plug  210  is substantially prevented. The term “substantially”, as used herein, may be applied to modify a quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related. For example, with radial and axial movement of the cover plate  220  substantially prevented, the cover plate  220  may nonetheless be capable of slight radial and/or axial movement so long as the cavities  214  remain covered. 
     While the exemplary cover plate  220  is installed in the above-described snap-fit manner, it is also contemplated that the cover plate  220  may be installed by sliding the cover plate into the recess  212  such as, for example, prior to affixing the faceplate  211 . Alternatively, the recess  212  may extend to the end of the plug  210  opposite the faceplate  211 , and the cover plate  220  may be slid into the recess  212  and retained therein by a ridge or retainer. 
     The cover plate  220  is rotatable about the longitudinal axis of the plug,  210  between a closed position ( FIG. 3 ) and an open position, and is capable of rotating between the closed position and the open position without being decoupled from the plug  210 . In the closed position, the cavities  214  are covered by the cover plate  220 , and the rack pins  240  and the biasing members  204  are retained in the cavities  214 . When the plug assembly  200  is removed from the shell  101 , the closed cover plate prevents the cylinder  100  from “exploding” without requiring the use of a plug follower. In the open position of the cover plate  220 , the cavities  214  are exposed, and the rack pins  240  can be inserted into or removed from the cavities  214 . This allows the plug assembly  200  to be completely assembled prior to being installed in a shell appropriate for the lock type. The modular nature of the plug assembly  200  enables installation of the same plug in any of a variety of shells corresponding to different lock types. 
     Rotation of the cover plate  220  from the open position and/or the closed position is resisted by a ridge  215  formed on the plug  210 . When the cover plate  220  is in the closed position, the ridge  215  contacts one of the terminal surfaces  221 , When the cover plate  220  is in the open position, the ridge  215  is positioned in the slot  225 . The distance by which the ridge  215  protrudes from the surface of the recessed portion  212  is great enough to resist incidental rotation of the cover plate  220 , but small enough that intentional rotation is not prevented. In other words, the ridge  215  prevents rotation of the cover plate  220  in the absence of a threshold torque being applied to the cover plate  220 . In certain embodiments, the ridge  215  may be a bump having a small length in the longitudinal direction. In other forms, the ridge  215  may extend in the longitudinal direction of the plug  210 . Additionally, the cross-section of the ridge  215  may be curvilinear, rectilinear, or a combination thereof. In certain embodiments, the plug  210  may include a plurality of ridges, or the ridge  215  may be omitted from the plug body. For example, one or more ridges may be formed on the cover plate  220 , and correspondingly shaped grooves may be formed on the plug  210 . 
     The sidebar  230  is positioned in the longitudinal channel  213  and is biased radially outward by the biasing members  203 . The sidebar  230  includes a body portion  231 , a cam surface in the form of a tapered portion  232  on the radially outer side of body portion  231 , and an interference member in the form of a protrusion  233  located on the radially inner side of the body portion  231 . In the illustrated form, the interference member  233  includes a pair of recesses, and springs  203  are seated in the recesses and bias the sidebar  230  radially outward. Other than the recesses, the exemplary interference member is a single contiguous protrusion  233 . In other embodiments, the interference member may comprise a plurality of discrete protrusions, each configured to engage one of the rack pins  240 . 
     The height of the body portion  231  corresponds to the height of the channel  213  such that movement of the sidebar  230  is substantially confined to the radial direction of the plug  210 . In the illustrated form, the height of the protrusion  233  is less than the height of the body portion  231 , although it is also contemplated that the body portion  231  and the protrusion  233  may be the same height or substantially the same height. Furthermore, while the tapered portion  232  is depicted as having a substantially rectilinear cross-section, it is also contemplated that the tapered portion  232  may comprise a curvilinear profile. 
     The rack pins  240  are positioned in the cavities  214  along with the biasing members  204 . When the cover plate  220  is in the closed position, the biasing members  204  urge the rack pins  240  toward the keyway  219 . Each rack pin  240  includes a first leg  241  and a second leg  242 . In the illustrated embodiment, the first leg  241  is arranged perpendicular to the second leg  242 , although other configurations are also contemplated. For example, in certain embodiments, the legs  241 ,  242  may be arranged substantially perpendicular to one another, or may be offset relative to one another by an oblique angle. In the illustrated embodiment, the second leg  242  extends from the end of the first leg  241  in only a single direction, and the rack pin  240  can thus be considered to comprise an L-shaped rack pin. 
     The first leg  241  is positioned at least partially in the keyway  219  and is configured to travel along the top cut of a key. The first leg  241  may include a tapered bottom surface (i.e., angled or curved) to facilitate such travel. When the key is inserted into the keyway  219 , each of the rack pins  240  moves in a lateral direction substantially perpendicular to the longitudinal direction of key insertion as the first leg  241  travels along the top cut of the key. Due to the fact that the biasing members  204  urge the first legs  241  into contact with the key, the position of each of the rack pins  240  corresponds to the root depth of the key at the point of contact. If a rack pin  240  is blocked from moving in the necessary direction, interference between the blocked rack pin  240  and the teeth of the key prevents the key from being inserted or extracted. 
     The second leg  242  includes at least one notch  243  configured to receive a portion of the protrusion  233 . One or more of the rack pins  240  may include more than one notch  243  such that the plug assembly  200  can be master-keyed. When the notch  243  is aligned with the protrusion  233 , the protrusion  233  can enter the notch  243 . This defines an unlocking position of the rack pin  240  in which the rack pin  240  does not prevent the sidebar  230  from moving radially inward. When the notch  243  is misaligned with the protrusion  233 , the protrusion  233  engages a contact surface  244  of the second leg  242 . This defines a locking position of the rack pin  240  wherein the rack pin  240  prevents the sidebar  230  from moving radially inward. 
     The alignment or misalignment of the notch  243  and the protrusion  233  is determined by the vertical position of the rack pin  240 , which in turn depends upon the root depth of an inserted key at the corresponding bitting position. When a proper key is inserted, each rack pin  240  is located in the unlocking position with one of its notches  243  aligned with the protrusion  233 . This configuration defines an unlocked state of the plug assembly  200  wherein the sidebar  230  is free to move radially inward. When an improper key is inserted, at least one of the rack pins  240  will be positioned in the locking position wherein none of its notches  243  are aligned with the protrusion  233 . This configuration defines a locked state of the plug assembly  200  in which the sidebar  230  is prevented from moving radially inward. 
     With additional reference to  FIG. 4 , the operation of the cylinder  100  will now be described in further detail.  FIG. 3  illustrates the plug assembly  200  in a home position wherein the biasing members  203  urge the sidebar to an extended position in which at least part of the tapered portion  232  is positioned in the groove  123 . The plug assembly  200  is also in the locked state since the protrusion  233  is not aligned with the notch  243 , and the interaction of the protrusion  233  and the contact surface  244  prevents the sidebar  230  from moving radially inward. In other words, the rack pin  240  retains the sidebar  230  in the extended position. Due to the fact that the sidebar  230  cannot move radially inward, the surfaces of the groove  123  interfere with the tapered portion  232 , thereby preventing rotation of the plug assembly  200  with respect to the shell  101 . The sidebar  230  is the only element that crosses the shear line of the cylinder  100  as the rack pins  240  are contained within the plug  210  by the cover plate  220 . 
     As described above, when a proper key is inserted into the keyway, each rack pin  240  has a notch  243  aligned with the protrusion  233 , and the sidebar  230  is thereby free to move radially inward. In this unlocked state, rotation of the plug assembly  200  causes a surface of the groove  123  to interact with the tapered portion  232 , thereby urging the sidebar  230  radially inward. In other words, the surfaces of the groove  123  and the tapered portion  232  are cam surfaces configured to urge the sidebar  230  radially inward upon rotation of the plug assembly  200 . Once the plug assembly  200  has been sufficiently rotated, the sidebar  230  is positioned in a retracted position ( FIG. 4 ) wherein the protrusion  233  is received in a notch  243  of each rack pin  240 . In this rotated position of the plug assembly  200 , the tapered portion  232  is positioned in contact with an inner surface of the shell  101 , thereby retaining the protrusion  233  within the notches  243 . As noted above, in order for the key to be inserted into or extracted from the keyway  219 , the rack pins  240  must be free to travel. In the rotated position of the plug assembly  200 , however, such travel is blocked due to the protrusion  233  being retained within the notch  243 . As such, when the plug assembly  200  is in the rotated position, the key cannot be extracted. 
     As the plug assembly  200  is rotated back to the home position, the biasing members  203  urge the sidebar  230  radially outward into the groove  123 . The protrusion  233  is thus removed from the notch  243 , and the rack pins  240  again become free to travel, thereby permitting extraction of the key. Once the key is extracted, the biasing members  204  urge the rack pins  240  to their initial positions ( FIG. 3 ) wherein the protrusion  233  is misaligned with the notches  243 , and the plug assembly  200  is positioned in the locked state. 
     With continued reference to  FIGS. 1-4 , the exemplary lock cylinder  100  also includes a control member  130 . The control member  130  is rotatable with respect to the shell  101  and includes a control lug  132  configured to engage a corresponding notch in the cylinder housing. In a first angular position of the control member  130  ( FIG. 1 ), the control lug  132  radially protrudes from the shell  101  into the cylinder housing notch, thereby preventing the cylinder  100  from being removed from the cylinder housing. When the control member  130  is rotated to a second angular position, the control lug  132  is positioned within the tower  103 , and the cylinder  100  can be removed from the cylinder housing. 
     As illustrated in  FIG. 2 , the plug  210  may further include a control pin cavity  217 , and the cover plate  220  may further include an opening  227  The control pin cavity  217  and the opening  227  are positioned such that, when the cover plate  220  is in the closed position, the opening  227  is aligned with the control pin cavity  217 . When the plug assembly  200  is in the home position ( FIG. 3 ) and the cover plate  220  is in the closed position, the control pin cavity  217  and the opening  227  are aligned with a correspondingly-sized cavity formed in the control member  130  The control pin cavity  217  has disposed therein a control pin operable in a first position in which a portion of the control pin extends into the control member cavity, and a second position in which the control pin does not extend into the control member cavity. The control pin is configured to interact with and engage a feature of a control key wherein the control pin is in the first position when a proper control key is inserted in the keyway  219 , and is in the second position when a proper control key is not so inserted. 
     When a proper control key is inserted, the plug assembly  200  is positioned in the unlocked state and the control pin is in the first position. In this state, rotation of the plug  210  also causes rotation of the control member  130  due to the control pin extending into the control member cavity. Once the control member  130  is in the second angular position, the control lug  132  is positioned within the tower  103 , and the cylinder  100  can be removed from the cylinder housing in certain embodiments, the control pin may interact with sidemilling on the control key such that the position of the control pin is independent of the key top cut, thereby providing more security and control. 
     Once the cylinder  100  has been removed from the cylinder housing, the plug assembly  200  can be removed from the shell  101  for re-pinning. In order to re-pin the plug assembly  200 , a user rotates the cover plate  220  from the closed position to the open position, wherein the cover plate  220  may be retained by the ridge  215 . The user removes at least some of the springs  204  and the rack pins  240  from the cavities  214 . The user may simply rearrange some of the rack pins  240  (i.e., by placing at least some of the rack pins  240  in different cavities  214 ), may replace one or more of the rack pins  240  with new rack pins, or a combination thereof. The springs  204  are then placed back into the cavities  214 , and the cover plate  220  is rotated back to the closed position, where the cover plate  220  is retained by the ridge  215 . The user next inserts the plug assembly  200  into the shell  101  (or another shell of the same, similar, or different format), inserts the cylinder  100  into the cylinder housing, and rotates the plug assembly  200  and the control member  130  to a position in which the control lug  132  prevents removal of the cylinder  100  from the cylinder housing. Because the plug assembly  200  is self-contained, there is no need to position springs and driving pins in the shell  101  during assembly, thereby reducing the time and complexity of the pinning process. 
       FIG. 5  illustrates a second exemplary plug  310  and a cover  320 . The plug  310  is configured substantially similar to the plug  210  and includes a recessed portion  312  having a radius less than that of the remainder of the plug  310 , and a plurality of cavities  314  configured to receive rack pins such as the rack pins  240 . The recessed portion  312  constitutes an arcuate portion of the plug  310 . The central angle of the arc defined by the recessed portion is hereinafter referred to as the recess angle α. 
     The cover  320  includes a cover plate  322  positioned in the recessed portion  312 , and keepers  324  which rotatably couple the cover  320  to the plug  310 . The cover plate  322  is arcuate in geometry and has a central angle hereinafter referred to as the cover plate angle β. The cover plate  322  has an inner radius corresponding to the radius of the recessed portion  312 , and an outer radius corresponding to the outer radius of the plug  310 . The keepers  324  may be positioned in a circumferential groove on the plug  310 . In the illustrated embodiment, the arcuate keepers  324  have a central angle of greater than about 190° and less than about 300°, and are snap-fit into the circumferential groove in a manner similar to that described above with respect to the cover plate  220 . In other embodiments, the keepers  324  may have a greater central angle, which may be up to 360°. In other words, the keepers  324  may be complete circles circumferentially surrounding a portion of the plug  310 . In still further embodiments, the keepers  324  may have a lesser central angle, and may be positioned in grooves on the faceplate and/or the end of the plug  310  opposite the faceplate. 
     The cover plate  322  is rotatable about the longitudinal axis of the plug  310  along the recess  312 . In an open position of the cover plate  322 , the cavities  314  are exposed, and rack pins and biasing members can be inserted into or removed from the cavities  314 . With the cover  320  in a closed position, the cavities  314  are covered and the pins and springs are retained within the cavities  314 . In the illustrated embodiment, the plug  310  includes two ridges  315  which extend along the axial direction of the plug  310 , and are configured to resist rotation of the cover plate  322  from the closed position. The ridges  315  may be configured substantially similar to the ridge  215 , and the descriptions of the illustrated and alternative features of the ridge  215  are equally applicable to the ridges  315 . 
     In the illustrated embodiment, the recess angle α is slightly greater than twice the cover plate angle β, and the ridges  315  bisect the recessed portion  312  into first and second recessed sections, and with the angular span of each corresponding to the cover plate angle β. For example, if the cover plate angle β is 30°, the recess angle α may be between about 62° and about 70°. As such, the cover plate  322  can be stably positioned in either the open position or the closed position, and the ridges  315  will retain the cover plate  322  in the selected position until the user rotates the cover plate  322  to the new position. In this manner, the ridges  315  facilitate the pinning process and ensure that the cover plate  322  remains in the closed position when installed into a shell (such as the previously-described shell  101 ). 
     While the cover plate  322  comprises an arc having a central angle of about 30°, other central angles are contemplated. In certain embodiments, the cover plate  322  may comprise an arc having a central angle between 10° and 180°, between 15° and 90°, or between 20° and 45°. In certain embodiments, the recess angle α may be more than twice the cover plate angle β. In further embodiments, the recess angle α may be less than twice the cover plate angle β, in which case the cover plate  322  may include slots configured engage the ridges  315  when the cover plate  322  is in the open or closed position in a manner similar to that described with reference to the slots  225 . Furthermore, in certain embodiments, the ridges  315  need not bisect the recessed portion  312 . 
     A common form of picking locks includes applying torque to a lock plug and adjusting the position of a pin until the resistive force provided by the pin changes. This change in resistive force is interpreted by the picker as an indication that the pin or tumbler is aligned with the shear line, and will in turn no longer prevent rotation of the plug. The process is repeated until each of the pins is in the unlocking position, and the plug can then be rotated. To combat such picking, certain embodiments of the invention may include anti-tampering features. An exemplary form of such anti-tampering features will now be described with reference to  FIGS. 2 and 6 . 
       FIG. 6  depicts an alternative form of the rack pin  440  which may be utilized in certain embodiments of the invention. The rack pin  440  is substantially similar to the previously-described rack pins  240 , and similar reference characters are used to denote similar features. In the interest of conciseness, the following description focuses primarily on features which are different than those previously described with reference to the rack pins  240 . 
     In the present form of the rack pin  440 , the second leg  442  includes upper and lower portions extending from the first leg  441  in opposite directions, thereby defining the rack pin  440  as a T-shaped rack pin. The upper and lower portions may engage the walls of the rack pin cavities  214 , thereby substantially constraining motion of the rack pin  440  to a lateral axis parallel to the second leg  442  during key insertion. 
     The second leg  442  also includes a plurality of false gate notches  446  formed in the contact surface  444 . Each of the false gate notches  446  is defined by a pair of adjacent protrusions  447 . If an unauthorized person attempts to pick the lock using the above-described method, the torque provided by the picker urges the sidebar  230  radially inward, and the protrusion  233  in turn comes into contact with the contact surface  444 . When the picker adjusts the position of the rack pin  440  with a picking tool, the sidebar protrusion  233  engages one of the false gate notches  446  or the protrusions  447 , thereby changing the resistive force provided by the rack pin  440 . The picker will falsely interpret this change in resistive force as indication that the rack pin  440  is in an unlocking position. Because the rack pin  440  is actually in the locking position, however, the engagement of the sidebar protrusion  233  and the contact surface  444  prevents rotation of the plug assembly  200 , as described in detail above. 
     The first leg  441  also includes features which differ from the depictions of the first leg  241 . For example, the first leg  441  includes a tapered portion  445  configured to facilitate travel of the rack pin  440  along the top cut of the key during key insertion. The tapered portion  445  may have a shape corresponding to the bitting length and tooth angle which are standard for a particular form of key. In such cases, the tapered portion  445  may be positioned flush with adjacent teeth when the key is fully inserted such that the rack pin  440  substantially prevents movement of the key in either direction when the plug assembly  200  is in the rotated position. The first leg  441  may also include a hub  449  configured to be received in one end of a spring  204  to prevent the spring  204  from sliding out of engagement with the first leg  441  during operation. 
     While the figures depict only the L-shaped rack pin  240  and the T-shaped rack pin  440 , other forms of rack pin are also contemplated. In certain embodiments, one or more of the rack pins may include a third leg on the opposite side of the first leg from the second leg. In such embodiments, the second and third leg may each extend in only one direction (i.e., U-shaped configuration), may both extend in opposing directions (H-shaped configuration), or one of the vertical legs may extend in both directions and the other may extend in only one direction (h-shaped configuration). In such embodiments, the third leg may include sidebar-receiving notches, and the plug assembly  200  may include a second sidebar similar to the sidebar  230 , which in turn prevents rotation of the plug assembly  200  when the protrusion of the second sidebar is not aligned with the notches in the third leg. 
     With reference to  FIGS. 7 and 8 , a lock cylinder  500  according to another embodiment includes a shell  510 , a plug  520  rotatably mounted in the shell  510 , a sidebar  530  movably coupled to the plug  520 , and a plurality of rack pins  540  seated in the plug  520  and operable to selectively prevent movement of the sidebar  530 . The cylinder  500  is operable by a key  590 , and may further include a check pin  560  movably seated in the plug  520 . 
     In the illustrated form, the shell  510  is of the key-in-lever format and includes a shell body  511  and a narrow bible or tower  514  extending, from the shell body  511 . The shell body  511  defines a generally cylindrical chamber  512  and a longitudinal groove  513 . In embodiments in which the cylinder  500  includes the check pin  560 , the shell  510  may also include a recess  516  sized and configured to receive a portion of the check pin  560 . 
     The plug  520  is rotatably mounted in the chamber  512 , and a shear line  501  is formed between the outer surface of the plug  520  and the inner surface of the shell  510 . As will be appreciated, the shear line  501  is an annular boundary which circumferentially surrounds the plug  520 . The plug  520  includes a keyway  521 , a longitudinal channel  523  sized and configured to receive the sidebar  530 , and a plurality of rack pin cavities  524  in communication with the keyway  521  and the channel  523 . The keyway  521  extends along a longitudinal axis X and a lateral axis Y. The longitudinal and lateral axes X, Y define an imaginary boundary plane  580  which divides the plug  520  into a first plug section  581  and a second plug section  582 . The plug  520  may also include an annular channel  525 , and the cylinder  500  may further include a clip  505  to prevent the plug  520  from being removed from the shell  510 . As illustrated in  FIG. 8 , the clip  505  may be received in the annular channel  525  and abut a distal end of the shell  510 . As described in further detail below, the plug  520  may also include a longitudinal trough  522  and/or a check pin cavity  526 . 
     The sidebar  530  is seated in the longitudinal channel  523  and is biased in a radially outward direction such as, for example, via the springs  503 . The sidebar  530  includes a radially outer cam suffice or tapered portion  532  and a radially inner interference member  533 . When the plug  520  is in a home position, the sidebar  530  crosses the shear line  501  and the tapered portion  532  is received in the groove  513 . 
     The sidebar  530  has an outer position, an inner position, and an intermediate position. In the outer position, the sidebar  530  crosses the shear line  501 , and the tapered portion  532  is received in the groove  513 . When a torque is applied to the plug  520 , engagement between the tapered portion  532  and the surface of the groove  513  causes the sidebar  530  to cam radially inward by a small amount to the intermediate position. In the intermediate position, the sidebar  530  crosses the shear line  501 , and the tapered portion  532  is engaged with a tapered surface of the groove  513 . If the sidebar  530  is blocked from further radially inward movement by one or more of the rack pins  540 , the sidebar  530  prevents further rotation of the plug  520 . If the sidebar  530  is free to travel radially inward, rotation of the plug  520  causes the sidebar  530  to cam radially inward to the inner position as the tapered portion  532  travels along the tapered surface of the groove  513  and into contact with the inner surface of the shell  510 . In the inner position, the sidebar  530  is received within the longitudinal channel  523 , and does not cross the shear line  501 . As such, further rotation of the plug  520  is enabled. 
     With additional reference to  FIG. 9 , each rack pin  540  includes a first or key-engaging leg  541  and a second or sidebar-engaging leg  542 . As with the above-described rack pins  240 ,  440 , each rack pin  540  is configured as a single-piece, unitary structure, and the first and second legs  541 ,  542  are integrally formed with one another. The first leg  541  includes a key-following surface  545  configured to engage an edge-cut  594  on the key  590 . The first leg  541  also includes a cylindrical portion  548 , which in turn defines a cup  549  sized and configured to receive a portion of a spring  503 . The second leg  542  is arranged substantially perpendicular to the first leg  541 , and includes a contact surface  544  which faces the sidebar  530 . The contact surface  544  includes at least one receiving notch or true gate  543  and a plurality of shallow notches or false gates  546 . 
     As illustrated in  FIG. 8 , each rack pin cavity  524  includes a first runner  584  configured to receive the first leg  541 , and a second runner  585  configured to receive the second leg  542 . The first runner  584  includes a circular portion configured to receive the cylindrical portion  548  of the first leg  541 . The first runner opens to the keyway  521  and extends in a first lateral direction (illustrated as an upward direction) therefrom. As an edge-cut key  590  is inserted into the keyway  521 , the key-following surfaces  545  of the first legs  541  travel along the edge-cut bitting profile  594 . The second runner  585  extends in a second lateral direction (illustrated as a downward direction) front the first runner  584 . The second runner opens to the longitudinal channel  523  such that the true gates  543  become selectively aligned with the interference member  533  as the rack pins  540  travel in the lateral directions. While other forms are contemplated, in the illustrated embodiment, the circular portion of each first runner  584  is centered on the boundary plane  580 , and each of the second runners  585  is formed in the first plug section  581 . 
     Each of the false gates  546  is formed between a pair of adjacent protrusions  547  which define the lateral widths of the false gates  546 . The lateral widths of the true gate  543  and each of the false gates  546  is sufficient to receive a portion of the interference member  533 . As a result, when the interference member  533  is aligned with one of the true gates  543  or one of the false gates  546 , the interference member  533  will enter the aligned gate as the sidebar  530  cams radially inward to the intermediate position. Each false gate  546  also has a transverse depth which is less than the depth of the true gate  543 . When the interference member  533  is aligned with one of the false gates  546 , the rear surface of the false gate  546  prevents the sidebar  530  from camming radially inward to the inner or unlocking position. As such, the sidebar  530  is retained in the intermediate position, and further rotation of the plug  520  is prevented. Additionally, when the interference member  533  is received in one of the false gates  546 , engagement between the interference member  533  and the adjacent protrusions  547  prevents the rack pin  540  from moving to a position in which the true gate  543  is aligned with the interference member  533 . In other words, the rack pin  540  is retained in a locking position and is unable to move to an unlocking position. 
     In the illustrated form, each of the true gates  543  is defined, by an upper surface  586  and a lower surface  587 . Similarly, the interference member  533  is defined by an upper surface  588  and a lower surface  589 . Each of the surfaces  586 - 589  is arranged substantially perpendicular to the boundary plane  580  such that the interference member  533  and the true gates  543  are provided with correspondingly-shaped cross-sections which may be substantially rectangular. As described in further detail below, it is also contemplated that the interference member  533  and/or the true gates  543  need not be provided with a rectangular cross-section. 
     As noted above, the cylinder  500  may also include a check pin  560  seated in a check pin cavity  526  formed in the plug  520 . The check pin  560  includes an arm  562  extending into the keyway  521 , and a cylindrical body  564  positioned in the check pin cavity  526 . The body  564  also includes an extension  566  extending beyond the arm  562 . The check pin  560  is operable in a locking position and an unlocking position, and may be biased toward the locking position by a spring  506 . In the locking position, the body  564  is positioned in the plug  520  and the extension  566  is received in the recess  516  formed in the shell  510 . The check pin  560  thus crosses the shear line  501 , and thereby prevents rotation of the plug  520 . In the unlocking position, the check pin  560  does not cross the shear line  501 , and therefore does not prevent rotation of the plug  520 . The key  590  may include a ramp configured to urge the arm  562  radially inward, thereby moving the check pin  560  to the unlocking position when the key  590  is fully inserted. 
     In the illustrated embodiment, the plug  520  includes a longitudinal trough  522  connected with the circular portions of the first runners  584 , and the cylinder  500  further includes a cover plate  502  seated in the trough  522 . During assembly, the rack pins  540  may be inserted into the rack pin cavities  524 , and springs  504  may be inserted into the cups  549 . The cover plate  502  may be subsequently placed in the trough  522 , thereby retaining the springs  504  and rack pins  540  within the rack pin cavities  524 . In certain forms, the cover plate  502  may be securely coupled to the plug  520  such as, for example, by a swaging operation. In other embodiments, the cover plate  502  may be releasably coupled to the plug  520  such as, for example, by clips. In further embodiments, the cover plate  502  may simply be retained within the trough  522  by the inner surface of the shell  510 . It is also contemplated that the cover plate  502  may be omitted. For example, the rack pin cavities  524  may be in the form of blind bores which open at only one end. In such embodiments, the springs  504  and rack pins  540  may be inserted through the side of the plug  520  opposite the illustrated trough  522 . 
     With reference to  FIGS. 10-13 , a lock cylinder  600  according to another embodiment includes a shell  610 , a plug  620 , a first sidebar  630 , and a plurality of rack pins  640 , each of which is sized and shaped substantially similar to those described above with reference to the lock cylinder  500 . The cylinder  600  also includes a plurality of finger pins  660  and a second sidebar  670 . As described in further detail below, in certain embodiments, the cylinder  600  may be considered to include a shell  610  and a plug assembly  609 , which constitute the remaining elements of the cylinder  600 . 
     Each of the finger pins  660  is seated in a finger pin cavity  626  formed in the plug  620 . More specifically, each finger pin cavity  626  is formed in the second plug section  682 . Each finger pin  660  includes a finger  662  which extends into the keyway  621 . Each finger pin  660  also includes a cylindrical body  664  which includes a pair of recesses  663  defining a ridge  666 . 
     The second sidebar  670  is seated in a longitudinal channel  627  formed in the plug  620 . The longitudinal channel  627  is formed in the outer surface of the second plug section  682  and is connected with the finger pin cavities  626 . The second sidebar  670  is biased in a radially outward direction such as, for example, by one or more springs  607 . The second sidebar  670  includes a cam surface or tapered portion  672  formed on a radially outer side thereof. The second sidebar  670  also includes an interference member  673  formed on a radially inner side thereof. The interference member  673  has formed therein a plurality of gaps  676 . The interference member  673  and gaps  676  are sized and configured to matingly engage the recesses  663  and ridges  666  of the finger pins  660 . In other words, the recesses  663  are operable to receive the interference member  673 , and the gaps  676  are operable to receive the ridges  666 . 
     The second sidebar  670  has an outer position and an inner position. In the outer position, the second sidebar  670  crosses the shear line  601  and the tapered portion  672  is received in a correspondingly shaped groove  617  formed in the shell  610 . When the second sidebar  670  is blocked from radially inward movement, interference between the shell  610  and the sidebar  670  prevents rotation of the plug  620 . When the second sidebar  670  is free to move radially inward, engagement between the groove  617  and the tapered portion  672  causes the sidebar  670  to cam radially inward to the inner position in response to rotation of the plug  620 . 
     Each of the finger pins  660  has a locking position and an unlocking position. In the locking position, the recesses  663  are misaligned with the interference member  673  and/or the ridge  666  is misaligned with the gap  676 . When in the locking position, the finger pin  660  prevents the second sidebar  670  from camming radially inward. More specifically, when the second sidebar  670  moves radially inward, the interference member  673  comes into contact with the body  664  and/or the ridge  666 . 
     With additional reference to  FIGS. 14 and 15 , the cylinder  600  is operated by a key  690  including a first bitting profile  694  and a second bitting profile  696 . The first bitting profile  694  is formed in a narrow edge of the key  690  and is configured to index the rack pins  640  to the unlocking positions. The second bitting profile  696  is formed in a broad side surface of the key  690  and is configured to index the finger pins  660  to the unlocking positions. 
     As the key  690  is inserted into the keyway  621 , the fingers  662  of the finger pins  660  enter a groove  697  in which the second hitting profile  696  is formed. The second bitting profile  696  engages the fingers  662 , thereby causing the finger pins  660  to slide and rotate within the finger pin cavities  626 . When the key  690  is fully inserted, each of the rack pins  640  and finger pins  660  is in the unlocking position. More specifically, the first sidebar interference member  633  is aligned with a true gate  643  in each of the rack pins  640 , the second sidebar interference member  673  is aligned with each of the recesses  663 , and each of the ridges  666  is aligned with a corresponding one of the gaps  676 . As a result, each of the sidebars  630 ,  670  is free to cam radially inward, and the plug  620  can thereby be rotated. 
     As noted above, the rack pins  640  are movable in first and second lateral directions. In  FIGS. 12-15 , the lateral axis Y is depicted as a vertical axis, and the first and second lateral directions are illustrated as upward and downward directions. In the interest of clearly and concisely describing the disclosed subject matter, specific language will be used with reference to the orientation illustrated in the Figures. It is to be understood that terms such as “upper”, “lower”, “above”, and “below” are used for ease of convenience and description, and should be construed as limiting the disclosed subject matter. 
     With specific reference to  FIG. 15 , the first sidebar  630  and the rack pins  640  of the instant embodiment are configured slightly different from the previously-described sidebar  530  and rack pins  540 . In the illustrated form, the true gates  643  and the interference member  633  have a non-rectangular cross-section, and more specifically a wedge-shaped cross-section. The true gate  643  is defined in part by an upper surface  686  and a lower surface  687 . The interference member  633  is correspondingly-shaped and is defined, in part, by an upper surface  688  and a lower surface  689 . The upper surfaces  686 ,  688  extend substantially entirely along the transverse direction, or substantially perpendicular to the lateral directions in which the rack pin  640  slides. In other words, the upper surfaces  686 ,  688  extend substantially perpendicular to the boundary plane  680 . The lower surfaces  687 ,  689  are obliquely offset from the upper surfaces  686 ,  688 , and extend in both the transverse and lateral directions. In other words, the lower surfaces  687 ,  689  extend toward the upper surfaces  686 ,  688  and the boundary plane  680  at an oblique angle. 
     As noted above, the previously-described interference member  533  and the true gates  543  are provided with rectangular cross-sections. In such forms, the interference member  533  and the true gates  543  may need to be manufactured within relatively tight tolerances. If the alignment of the interference member  533  and the true gate  543  is off even slightly when the key is inserted, the interference member upper surface  588  may be positioned above the true gate upper surface  586 , or the interference member lower surface  589  may be positioned below the true gate lower surface  587 . In either case, the interference member  533  will engage the contact surface  544 , and the sidebar  530  will be blocked from moving radially inward beyond the intermediate position. In order to avoid this situation, each of the surfaces  586 - 589  are preferably formed with tight tolerances. 
     The wedge-shaped cross-sections of the instant embodiment may alleviate some of the above-described manufacturing difficulties. Specifically, in the instant embodiment, the sidebar  630  will be blocked from radially inward movement beyond the intermediate position if the interference member upper surface  688  is positioned above the true gate upper surface  686 . However, if the interference member lower surface  689  is slightly misaligned with the true gate lower surface  687 , the sidebar  630  may be able to move radially inward until the lower surfaces  687 ,  689  engage one another. When the lower surfaces  687 ,  689  engage one another, the rack pin  640  is urged into contact with the edge-cut bitting profile  694 , thereby preventing further lateral travel of the rack pin  640 . 
     If the misalignment between the lower surfaces  687 ,  689  is greater than a threshold amount, for example as a result of an unauthorized or improperly cut bitting profile  694 , the sidebar  630  is blocked from moving to the inner position. As a result, the sidebar  630  continues to cross the shear line  601 , and rotation of the plug  620  is prevented. If the misalignment between the lower surfaces  687 ,  689  is small, for example within manufacturing tolerances, the sidebar  630  may nonetheless be able to move to the inner position. Due to the fact that slight misalignment between the lower surfaces  687 ,  689  does not necessarily prevent the sidebar  630  from moving beyond the intermediate position, the lower surfaces  687 ,  689  may be formed with looser tolerances than the upper surfaces  686 ,  688  without adversely affecting the locking capabilities of the lock cylinder  600 . 
     With reference to  FIG. 16 , the lock cylinder  600  is illustrated along with a conventional lock cylinder  700 . The conventional cylinder  700  includes a shell  710 , a plug  720  rotatably seated in the shell  7110 , and -a pin tumbler system including a plurality of driving or top pins  730  and a plurality of driven or bottom pins  740 . The lock cylinder  700  is of a standard six-pin format, and includes six of the top pins  730  and six of the bottom pins  740 . The shell  710  is also of a standard six-pin format, and includes a tower  714  including six top pin chambers  713  which house the top pins  730 . Similarly, the plug  720  is of a standard six-pin format, and includes six bottom pin chambers  724  which house the bottom pins  740 . 
     Certain features and dimensions of the standard six-pin lock cylinder  700  are constrained by the various assemblies in which the lock cylinder  700  is used. For example, the tower  714  of a standard six-pin shell  710  is generally less than 1.25 inches in length, and may be in the range of one inch to 1.125 inches, between 0.75 inches and one inch, or between 0.875 inches and 1.125 inches. Additionally, the tower  714  of a standard format key-in-lever shell  710  commonly includes a tapered cutout  715  and/or a rectangular cutout  716 . The length constraint and the cutout sections  715 ,  716  limit the amount of space available for the top pin chambers  713 . As such, additional tumbler sets cannot be added to the standard six-pin cylinder  700  without decreasing the size of the pins  730 ,  740 , which can in turn lead to decreased strength and other deleterious or negative effects. 
     In the illustrated lock cylinder  600 , the exterior profile of the shell  610  is substantially similar to that of the standard shell  710 , and may be identical thereto. In other words, the shell  610  may be of a standard six-pin format such that the cylinder  600  may be installed in assemblies designed to accept the standard cylinder  700 . Due to the fact that the cylinder  600  does not require top pins in the tower  614 , the top pin chambers may be omitted from the shell  610  in certain embodiments. In such embodiments, the shell  610  may nonetheless be considered to be of a standard six-pin format due to the fact that the shell  610  has the same exterior profile as the standard shell  710 . 
     As noted above, the lock cylinder  600  does not require driving pins in the tower  614 . As such, the rack pin cavities  624  need not align with top pin chambers in the tower  614 . With the necessity for alignment obviated, a greater amount of longitudinal space within the plug  620  is available for the rack pin cavities  624 . For example, the proximal-most rack pin cavity  624  may be aligned with the tapered cutout  715 ′ of the tower  614 , and the distal-most rack pin cavity  624  may be aligned with the rectangular cutout  716 ′ in the tower  614 . In certain forms, this additional space may enable the inclusion of a seventh rack pin  640  within a lock cylinder format which would otherwise allow for only six tumbler sets. As will be appreciated, the number of unique bitting codes available for a lock cylinder increases exponentially as additional bitting positions are added, thereby increasing the overall security of the lock. 
     In the illustrated embodiment, the lock cylinder  600  includes the shell  610  and a modular plug assembly  609  which includes the remaining elements of the lock cylinder  600 . In certain embodiments, the shell  610  may be a dummy shell sized and configured for use in a standard lock cylinder format. Due to the fact that top pin chambers are not required in the shell  610 , the tower  614  of the dummy shell  610  may be substantially solid. In other words, the top pin chambers need not be formed in the dummy shell  610 , which may in turn reduce the cost of manufacturing. In other embodiments, the shell  610  may be omitted, and the plug assembly  609  may be manufactured and/or sold as a modular unit. In further embodiments, the plug assembly  609  may be manufactured and/or sold with a housing of another form. 
     With reference to  FIGS. 17 and 18 , a handle assembly  800  according to one embodiment includes a manual actuator in the form of a handle  802 . The handle  802  includes a shank  810  and a lever  804  extending therefrom. The shank  810  includes a cylindrical chamber  812 , a first longitudinal groove  813 , and a second longitudinal groove  817 , each of which are substantially similar to the corresponding elements described above with reference to the shell  610 . In other words, the shank  810  replaces the shell  610 , and acts as the housing for the plug assembly  609 . The plug assembly  609  may be axially retained within the shank  810  by the clip  605 . 
     Certain conventional handle assemblies have required that the shank  814  be provided with an extension  815  in order to accommodate the tower of the lock cylinder installed therein. However, due to the fact that the plug assembly  609  does not require a tower, the extension  815  may be omitted. In certain embodiments, the shank  810  may have a circular cross-section. Additionally, because the shank  810  need only accommodate the plug assembly  609 , the greatest width of the shank  810  may be 0.75 inches or less in certain embodiments. In other embodiments, the greatest width of the shank  810  may be in the range of 0.5 inches to one inch, or 0.75 inches to 1.25 inches. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.