Abstract:
A re-keyable lock provides a cylinder that may be removed from the cylinder housing when the cylinder is in the unlocked state allowing the lock to be re-keyed with a standard key. A blocking element may be removed by a user having access to the keyhole and otherwise serves to retain the cylinder in the cylinder housing during the unlocked state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application 61/651,344 filed May 24, 2012 and hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to key activated locks and in particular to a lock that may be “re-keyed” by replacement of the lock cylinder without the removal of the lock from the door. 
       BACKGROUND OF THE INVENTION 
       [0003]    Key activated locks may have a rotatable plug held against rotation within a cylinder by a set of tumblers that extend across an interface between the rotatable plug and the cylinder when the key is removed. When a key is inserted, the tumblers are aligned with the interface and the plug may rotate to actuate a lock mechanism, such as a bolt, that may be retracted or allowed to retract after rotation of the lock cylinder. 
         [0004]    In many commercial environments, it is necessary to frequently change the keys associated with a lock, for example, upon changeover of personnel or the loss of a key. This “re-keying” may be done by replacing the tumblers of the plug of the lock or the entire cylinder. Disassembly of the lock to remove the cylinder requires access to the “inside” of the door and/or the bolt, this requirement preventing defeat of the lock by removal of the cylinder from the “outside” when the door is locked and closed. 
         [0005]    Re-keying operations are relatively time-consuming and may require the services of a skilled professional locksmith. Accordingly, it is also known to use “interchangeable core” locks whose cylinders may be readily replaced from the outside of the door and when the door is closed without disassembly of the lock. Removal of the cylinder in such circumstances is possible without compromising the security provided by the lock by permitting removal of the cylinder only by a user having a special “control key” different from the normal keys used with the lock. Rotation of the control key retracts tabs or other features on the cylinder that normally hold the cylinder in the cylinder housing, allowing the cylinder to be removed and replaced with a different cylinder. Turning the cylinder with a standard operator key does not affect these locking tabs or features. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides an interchangeable core lock that does not require a separate control key but that permits re-keying and cylinder replacement using only the standard operator keys used with the lock. The invention allows the cylinder to be removed only when the lock is in the unlocked state thus preventing individuals without keys from changing or defeating the lock. Inadvertent removal of the core is prevented by a low-security secondary locking feature that may be released from the “outside” of the door with common tools or by hand. The invention provides simple re-keying without the complexity or cost of a standard interchangeable core cylinder. 
         [0007]    Specifically, in one embodiment, the invention provides a replaceable cylinder lock having a cylinder housing with a chamber holding a cylinder, the cylinder providing a plug having a keyhole for receiving a key therein and tumbler pins activated by the key to allow rotation of the plug with respect to the cylinder between a lock and unlock position. A bolt communicating with the plug may move between a lock state for locking a door when the plug is in the lock position and an unlocked state for unlocking the door when the plug is in the unlock position. An interlock, communicating with the plug to move therewith, retains the plug and cylinder within the cylinder housing only when the plug is in the lock position and not when the plug is in the unlock position. 
         [0008]    It is thus a feature of at least one embodiment of the invention to allow “rekeying” of a lock by replacement of the lock cylinder without the need for a special key different from the normal keys used with the lock. 
         [0009]    The replaceable cylinder lock may include a blocking element positionable by a user having access to the keyhole in either of a first position blocking the cylinder within the chamber and a second position not blocking the cylinder within the chamber. 
         [0010]    It is thus a feature of at least one embodiment of the invention to prevent inadvertent dislodgment of the cylinder when in the unlocked state during normal use. 
         [0011]    The blocking element may be positionable by the user without use of the key. 
         [0012]    It is thus a feature of at least one embodiment of the invention to provide a relatively simple blocking element design recognizing that high-security is not required for this element. 
         [0013]    The blocking element may be an escutcheon positionable about the keyhole to retain the cylinder within the chamber by capturing a portion of the cylinder. 
         [0014]    It is thus a feature of at least one embodiment of the invention to implement the blocking function in the existing escutcheon element. 
         [0015]    The escutcheon maybe retained on the cylinder housing by a threaded set screw having a head receiving a tool excluding a standard slotted screw driver. 
         [0016]    It is thus a feature at least one embodiment of the invention to prevent casual removing of the blocking element while allowing it to be removed with readily available commodity tools. 
         [0017]    The interlock may be a tab extending rearward from the plug to engage and disengage a surface of the cylinder housing with rotation of the plug. 
         [0018]    It is thus a feature at least one embodiment of the invention to provide an extremely simple mechanism for retaining the cylinder within the cylinder housing that may make use of the security provided by the pre-existing tumbler pins. 
         [0019]    The surface of the cylinder housing engaged by the tab may be a plate having an opening permitting axial passage of the tab with the plug in a first rotated state and blocking axial passage of the tab of the plug in the second state. 
         [0020]    It is thus a feature of at least one embodiment of the invention to use a mechanically simple interlocking mechanism protected from access by the plug itself. 
         [0021]    The plate may be a steel plate fitting within a brass cylinder housing. 
         [0022]    It is thus a feature of at least one embodiment of the invention to permit manufacture of the cylinder housing from easily machined material while providing for high strength against forcible extraction of the plug, for example, by a slide hammer. 
         [0023]    The replaceable cylinder lock may include a detent retaining the bolt against locking when the cylinder is removed from the cylinder housing. 
         [0024]    It is thus a feature of at least one embodiment of the invention to prevent misalignment of internal elements of the lock during the cylinder replacement. 
         [0025]    The detent may provide for a positive locking of the bolt in the unlock position when the cylinder is removed. In one example, the detent may provide a spring-actuated pawl moved by insertion of the cylinder within the cavity housing away from interference with a rotating member rotated by the plug. 
         [0026]    It is thus a feature of at least one embodiment of the invention to positively unlock the lock during cylinder replacement by sensing the presence or absence of the cylinder. 
         [0027]    Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a fragmentary perspective view of a door lock assembly using the lock of the present invention; 
           [0029]      FIG. 2  is an exploded perspective view of one embodiment of the lock of the present invention showing the lock cylinder fitting within a cylinder housing as held by a primary and secondary locking feature; 
           [0030]      FIG. 3  is a fragmentary cross-section of the cylinder housing showing the primary locking feature that may retain the cylinder within the cylinder housing; 
           [0031]      FIG. 4   a  is a figure similar to  FIG. 3  showing a passage of a rearwardly extending T-tab on the lock cylinder through a corresponding retention slot in cylinder housing when the cylinder is in the unlocked state; 
           [0032]      FIG. 4   b  is a figure similar to  FIG. 4   a  showing movement of the T-tab to lock within the retention slot when the cylinder is in the lock state; 
           [0033]      FIG. 5  is an elevational cross-section taken along line  5 - 5  of  FIG. 1  (with the retention slot removed for clarity) showing engagement of the T-tab with a transition cam communicating with the locking mechanism with an anti-rotation pawl retracting with insertion of the lock cylinder into the cylinder housing and further showing an escutcheon providing the secondary locking feature for the lock cylinder; 
           [0034]      FIG. 6  is a front elevational view of the transition cam showing engagement of the anti-rotation pawl when the cylinder is removed; 
           [0035]      FIG. 7  is a fragmentary cross-section similar to that of  FIG. 5  showing the retention slot integrally formed with the cylinder housing; 
           [0036]      FIG. 8  is a figure similar to that of  FIG. 7  showing the retention slot as an insertion into the lock housing; and 
           [0037]      FIG. 9  is a flowchart describing the steps of replacing the cylinder of the present invention. 
       
    
    
       [0038]    Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0039]    Referring now to  FIG. 1 , a lock  10  may provide for an escutcheon  12  exposing a keyhole  16  of a cylinder  14  on an outside surface  18  of the door  20 . The keyhole  16  may allow for insertion of the blade  22  of a key  24  into the keyhole  16  along an insertion axis  25  generally perpendicular to the plane of the outside of the door  20 . As is understood in the art, the blade  22  includes a set of axially spaced ridges whose heights uniquely position tumblers within the lock  10  for rotation of an inner portion of the cylinder  14  termed the plug  15 . Rotation of the plug  15  of the cylinder  14  may then operate an internal locking mechanism to extend or retract (or permit extension or retraction) of a bolt  30  that may be received within an aperture of the strike plate (not shown) on the door jam. 
         [0040]    Referring to  FIGS. 1 and 2 , the cylinder  14  may provide a cylindrical outer portion having an upwardly extending tumbler tower  34  holding tumbler pins, drivers and springs as is generally understood in the art. The cylinder  14  may be received in a corresponding chamber  37  of a cylinder housing  38  having a circular bore for receiving the cylindrical outer portion of the cylinder  14  and a slot for receiving the tumbler tower  34 . The cylinder housing  38  is retained and fixed in the door  20 , for example, by means of a outer threaded surface  40  (for mortise lock cylinder) or by machine screws passing through the door (for a rim lock cylinder) according to methods well known in the art. 
         [0041]    When the cylinder  14  is fitted within the chamber  37  of the cylinder housing  38 , the cylinder  14  may be retained by a secondary retaining element formed by the escutcheon  12  fitting over the end of the cylinder housing  38 . Generally the escutcheon  12  has a frustoconical skirt  42  extending from a planar base  45 , the latter providing a circular opening  46  that provides access to keyhole  16  but prevents removal of the lock cylinder  14 , for example, by interference between the base  45  of the escutcheon  12  outside of the opening  46  and the tumbler tower  34 . The escutcheon  12  may be attached to the cylinder housing  38  at a corresponding frustoconical supporting surface  44  on the front of the cylinder housing  38 . Specifically, frustoconical skirt  42  of the escutcheon  12  may be locked to the supporting surface  44  on the front of the cylinder housing  38  using a set screw  26  that may pass through the skirt  42  to engage a corresponding dimple  48  in the supporting surface  44  of the cylinder housing  38 . As will be explained more fully below, the escutcheon  12  provides relatively low security retention of the cylinder  14  within the cylinder housing  38  that prevents the cylinder  14  from being inadvertently removed so long as the escutcheon  12  is in place. Nevertheless, the escutcheon  12  can be removed with simple tools (for example a hex wrench or Torx™ wrench) applied to the set screw  26  from the outside (e.g. the insecure side) of the door  20 . 
         [0042]    As is understood in the art, the cylinder  14  includes a plug  15  communicating with the keyhole  16  that may rotate with respect to the remainder of the cylinder  14  when a proper key  24  is inserted in the keyhole  16  and the tumblers appropriately aligned. This plug  15  communicates with a T-tab  50  projecting axially rearward from the cylinder  14  to rotate with rotation of the plug  15  of the cylinder  14 . The T-tab may be received by a transition cam  52  held in the rear of the cylinder housing  38  which may in turn communicate with a locking mechanism  54  operating the bolt  30 , as described above, based on the rotational position of the T-tab  50  according to techniques generally understood in the art. 
         [0043]    Referring now to  FIG. 3 , the cylinder housing  38  may support, at its rear, a stop wall  56  having a retention slot  58  through which the T-tab  50  may pass when the plug  15  of the cylinder  60  is in an unlocked state corresponding to its position when a proper key has been inserted and rotated to unlock the lock  10 . Referring to  FIG. 4   a , in this regard, the T-tab  50  provides a blade  62  having radially extending tabs lying within a horizontal plane when the lock  10  is unlocked and that may fit through corresponding horizontally extending portions of the retention slot  58  in this configuration. Referring to  FIG. 4   b , rotation of the plug  15  of the cylinder  14  by 90° (or other predetermined angle as indicated by arrow  64 ) to a locked state, moves the blade  62  to a vertical position perpendicular to the horizontal extension of the slot  58  preventing subsequent removal of the cylinder  14  along axis  25  while the cylinder  14  is in this locked state. The interengagement of the T-tab  50  and the retention slot  58  provides a primary locking mechanism holding the cylinder  14  in the cylinder housing  38 . Generally, it will be understood, therefore, that retention or release of the cylinder  14  is provided by the same key  24  that operates the bolt  30  eliminating the need for a separate control key or the complexity of an interchangeable core cylinder mechanism. The interengagement of the T-tab  50  and the retention slot  58  as operated by the operator key  24  provides the same security against cylinder removal as that required for the unlocking of the door  20 . Only when the cylinder  14  is in the unlocked state (implicitly at a time when there is no motivation to defeat the lock by removing its cylinder) can the lock cylinder  14  be removed. Accidental or casual removal of the lock cylinder  14  in this unlocked state is prevented by escutcheon  12  providing the secondary locking mechanism described above. 
         [0044]    The lock  10  thereby provides a high-security cylinder retention element in the form of the interengagement of the T-tab  50  and the retention slot  58  coupled with a low security retention feature in the form of the interference between the escutcheon  12  as retained by set screw  26  and the tumbler tower  34  or other projecting feature of the non-rotating portions of the cylinder  14 . Importantly, the low security retention feature does not require exclusive distribution of an unlocking feature such as a control key but can be operated with commonly available tools. 
         [0045]    Referring now to  FIGS. 5 and 6 , blade  62  of the T-tab  50 , after extending through the retention slot  58 , may engage a transition cam  52  with the blade  62  fitting in a corresponding slot  82  in a front surface of that transition cam  52  to link the two elements with respect to rotation about axis  25 . The transition cam  52  is supported within a bore of the cylinder housing  38  to rotate generally along insertion axis  25  with rotation of the plug  15  of the cylinder  14  (and the blade  62  of the T-tab  50 ) and communicate that rotation to a standard lock mechanism interface feature  70  communicating with standard lock mechanisms  54 . It will be understood that the interface feature  70  may be freely adjusted to be compatible with the requirements of different standard lock mechanisms  54 . 
         [0046]    Free rotation of the cam  52  when the cylinder  14  is removed is prevented by means of an anti-rotation pawl  72  that is normally pushed rearward by contact between the anti-rotation pawl and a rear edge of the tumbler tower  34  against a countervailing biasing of a spring  74 . When the cylinder  14  is in place within the cylinder housing  38 , the anti-rotation pawl  72  aligns with a groove  76  of the transition cam  52  allowing free rotation of the transition cam  52 . 
         [0047]    Referring specifically to  FIG. 6 , when the cylinder  14  is removed, however, the anti-rotation pawl moves forward to engage a flat  80  on an outer periphery of the transition cam  52  preventing rotation of the transition cam  52  from its unlocked orientation, the orientation where the slot  82  is generally in a horizontal orientation. 
         [0048]    Referring to  FIGS. 2 and 5 , the transition cam, anti-rotation pawl  72  and spring  74  are retained in the cylinder housing  38  by a cover plate  83  having an opening  84  allowing rearward exposure of the interface feature  70 . 
         [0049]    Referring now to  FIG. 7 , the retention stop wall  56  may be integrally machined into the cylinder housing  38  or, as shown in  FIG. 8 , may be an inserted disk pressed to fit against a ridge formed in the cylinder housing  38  preventing its forward or rotary motion. This latter configuration, for example, allows the stop wall  56  to be a high-strength steel material, for example, inserted into a readily machined brass cylinder housing  38 . 
         [0050]    Referring now to  FIG. 9 , replacement of the cylinder for re-keying may be accomplished by removing the escutcheon  12  as indicated by process block  100  and then unlocking the cylinder  14  with an operator key  24  as indicated by process block  102 . The old cylinder  14  may then be removed as indicated by process block  104  and a new cylinder  14  inserted in the place of the old cylinder  14  as indicated by process block  106 , the new cylinder  14  being in an unlocked state to match the orientation of the transition cam  52 . At process block  108 , the new cylinder may be locked, locking the new cylinder  14  into place as shown in  FIG. 4   b , and the key removed after which the escutcheon  12  may be replaced as indicated by process block  110 . 
         [0051]    Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, the terms such as “inside”, “outside”, “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “left”, “right”, “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence, or order unless clearly indicated by the context. 
         [0052]    When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
         [0053]    Various features of the invention are set forth in the following claims. It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention.