Abstract:
A shell and core interchangeable lock assembly for use in a shell housing. The core includes a rotatable pin plug and the shell includes a substantially cylindrical body with a pin chest therein. A mechanism which captures the shell and core within the shell housing includes an integral retainer ring and lug which is attached to the core. The mechanism allows rapid insertion and removal of the shell and core by the use of a correctly bitted control key. The mechanism additionally has a sub-mechanism for preventing its operation by accident or by tampering without the appropriate control key.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to mechanical locks, and more particularly, to shell and core lock assemblies that are removable from a shell lock housing mounted on a wall of an enclosure. 
     BACKGROUND OF THE INVENTION 
     A variety of mechanical locks are known, including locks to secure dwellings, buildings, vehicles, compartments, access hatches, gates, etc. Mechanical locks typically have a rotatable core plug containing a key slot. The insertion of a correctly-bitted key displaces tumbler pins within the lock, thereby allowing the core plug to rotate. The rotation of the core plug actuates an locking bolt or the like that locks or unlocks the structure or enclosure that the lock is a part of. If the key is not a correctly-bitted key, either the key will not be able to fully enter the slot, or the lock will not be allowed to rotate. 
     “Shell and core” lock assemblies are known in the art wherein the lock components include separate cylindrical shells and cores that can together be installed with a housing into a wall of an enclosure. Improvements upon such shell and core lock assemblies have made the core and shell removable from the shell housing by the use of a special control key so as to facilitate lock replacement or re-keying. In a removable core lock, the core and shell, including the key plug and tumbler pins, can be removed from the lock using the control key while leaving the remaining lock housing in place. A removable shell and core lock offers the advantage of being able to easily and cheaply change the keying of the lock without removing and replacing the entire lock apparatus by simply removing the shell and core, and then fitting the shell with a new core. Removable core locks may be commonly used in numerous applications where the frequent rekeying of locks is anticipated. The advantages include not only a lesser cost in hardware replacement, but also significant time and labor savings. 
     An exemplary prior art lock having a removable lock core is disclosed in U.S. Pat. No. 5,070,715 to Smallegan et al. The removable shell and core disclosed in Smallegan is locked inside the shell housing using a compound locking pin which is de-activated by the turning of a control key. During normal lock operation, this locking pin is spring biased into locked position such that it protrudes out of the lock core and into a slot in the shell housing such that the core and shell cannot be axially removed from the housing. 
     Unfortunately, the prior art removable-core locks commonly have a complicated structure whereby the cores and shells are retained in the shell housing by a series of spring-biased tumbler pins or other movable internal retaining devices comprised of multiple parts. When the core is removed from such locks, these retaining devices have an unfortunate propensity for falling out of the lock or becoming unseated from a desired position. Additionally, normal wear and tear, and contamination such as dirt, often makes removable cores and shells having such spring loaded locking mechanisms difficult to install and remove, or even completely non-functional. 
     Therefore, there remains a need in the art for a shell and core lock assembly that can be sold and delivered as a unit by a manufacturer for incorporation in enclosures, wherein the core can be easily and efficiently removed and replaced without problems of existing removable core devices and with increased strength and durability. 
     SUMMARY OF THE INVENTION 
     A shell and core interchangeable lock assembly for use in a shell housing is disclosed. The core comprises a rotatable pin plug and the shell comprises a substantially cylindrical body with a pin chest therein. A mechanism which captures the shell and core within the shell housing comprises an integral retainer ring and lug which is attached to the core. The mechanism allows rapid insertion and removal of the shell and core by the use of a correctly bitted control key. The integral ring and lug construction allows the capturing mechanism to advantageously be controled directly by the rotation of the control key and without multiple spring biasing mechanisms. The mechanism thereby prevents lock operation and core changing by accident or through tampering. 
     The above and other features, aspects, and advantages of the present invention will be further understood from the following description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a removable core lock according to embodiments of the present invention taken along the plane of the key blade. 
     FIG. 2 is a cross sectional view of a removable core lock according to embodiments of the present invention taken perpendicular to the plane of the key blade along line  2 — 2  from FIG. 1 in the state when a control key is not inserted. 
     FIG. 3 is a cross sectional view of a removable core lock according to embodiments of the present invention taken perpendicular to the plane of the key blade along line  2 — 2  from FIG. 1 in the state after a control key is first inserted. 
     FIG. 4 is a cross sectional view of a removable core lock according to embodiments of the present invention taken perpendicular to the plane of the key blade along line  2 — 2  from FIG. 1 in the state after a control key is inserted and then rotated. 
     FIG. 5 is a perspective view of a locking retainer ring used in preferred embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a cross section of an interchangeable lock core cylinder according to an embodiment of the present invention. The lock shell  22  has an upper portion in which the lock pins  15  and lock pin springs  16  are located, and an attached lower portion which has a cylindrical bore in which the core key plug  21  is co-axially installed. The function and operation of the upper portion of the lock shell  22 , namely the pins and tumblers, is well known in the art and will not be further discussed here. Instead, the discussion will focus on the rightmost portion of the FIG. 1 near cross-sectional line  2 — 2  where the mechanism for locking the shell  22  and core plug  21  within the lock housing  100  (depicted in FIG. 2) is located. 
     Core plug  21  is inserted into a cylindrical borehole formed in the core shell  22  as is known in the art such that the pins from the core shell  22  and the key plug  21  communicate. A lower control pin l is installed inside the key plug  21  at the far end of the keyway  24 . A locking retainer ring  200  is placed on the plug  21  with a retainer ring driving notch  218  on its inside diameter which is aligned with lower control pin  17 . Lower control pin  17  additionally is aligned such that it is connected to upper control pin  212  through intermediate control pin  214 . All three control pins  212 ,  214 , and  17  are biased downward by control pin spring  18  which is retained in place by spring cover  19 . A core plug cap  23  is installed on the end of core  21  after the retainer ring  200  to fix the core  21  within the core shell  22  borehole. 
     A control key  25  is shown inserted in keyway  24  of the core  21  in FIG. 1. A line  25   b  shown in phantom indicates the point at which a standard key (i.e, a key which merely unlocks the lock) would terminate. The small additional projection  25   a  provided on the distal end of the control key  25  to the right of line  25   b  is the only difference between standard key and control key  25 . 
     FIG. 2 depicts a cross-sectional view of the core locking mechanism according to one embodiment of the present invention fixed inside a shell housing  100  taken perpendicular to the keyway  24  along cross-sectional line  2 — 2 . In FIG. 2, keyway  24  is empty, meaning that control key  25  is not inserted into the core plug  21 . Without a control key  25  inserted fully into keyway  24 , lower control pin  17  is biased downward by control pin spring  18  through upper control pin  212  and intermediate control pin  214  such that control pin,  17  fits completely within core  21 . Thus, FIG. 2 depicts the situation where either no key is inserted into the keyway  24 , or where a standard key (a key having identical bittings to the control key  25 , but lacking appendage  25   a ) is being used to unlock the locking mechanism by rotating key plug  21  relative to the shell  22 . It will be readily understood by one skilled in the art that in order to allow the unhindered rotation of core  21  relative to locking retainer ring  200  by a standard key, lower control pin  17  and intermediate control pin  214  should meet at a surface which is substantially level with the outer circumference of core  21 . 
     Due to the downward force placed on both the intermediate control pin  214  and upper control pin  212  by spring  18 , keyway cover  219  is provided to prevent intermediate control pin  214  from entering keyway  24  during rotation of the core  21  relative to the shell  22  during normal lock operation. 
     Locking retainer ring  200  as depicted cross-sectionally by FIG.  2  and dimensionally by FIG. 5, has a retainer ring sleeve  201  and a retainer ring lug  211 . The retainer ring sleeve has a circular aperture  201   a  which is adapted to receive core plug  21  in substantially close contact while still allowing core plug  201  to be freely rotated within the aperture by a correctly standard key. 
     The retainer lug  211  is a protrusion connected to the retainer ring sleeve  201  which is adapted to fit into a slot  101  formed in the shell housing  100 . With lug  211  extending into slot  101  as shown in FIG. 2, both the shell  22  and core  21  are locked in place such that they cannot be withdrawn axially from the shell housing  100 . 
     As shown in the figures, intermediate control pin  214  preferably extends through the body of locking retainer ring  200  through a slot  214   a.  This allows for an integral construction of lug  211  and retainer ring  201  which provides structural strength, while still allowing the vertical displacement of lower control pin  17  to be communicated to upper control pin  212 . 
     Without the insertion of a control key  25 , upper control pin  212  is biased downward by spring  18  into retainer ring locking notch  217  (notch  217  being labeled in FIGS. 3-5) formed in the upper surface of lug  211 . This prevents the locking retainer ring from rotating due to shear caused by the rotation of core  21  with a standard key, and thus keeps the lug  211  inside slot  101 . Therefore, accidental removal of the shell  22  and core  21  without a control key  25  is prevented. 
     Comparing FIG. 2 collectively to FIGS. 1,  3  and  4 , it can be seen that insertion of control key  25  into the keyway  24  of core  21  displaces the lower control pin  17  upward due to the presence of projection  25   a.  This elevation of the control pin  17  forces intermediate control pin  214  and upper control pin  212  upward against the bias provided by spring  18 . As shown by FIG. 3, this upward displacement is large enough to move upper control pin  212  completely out of the locking notch  217 . 
     As shown in FIG. 3, the insertion of the control key  25  completely into keyway  24  not only unseats upper control pin  212  from locking notch  217 , but also simultaneously moves lower control pin  17  upward into retainer ring driving notch  218  formed on the inside circumference of retainer ring sleeve  201 . With lower control pin  17  thus engaging the retainer ring driving notch  218 , the core  21  can no longer be rotated without simultaneously rotating retainer sleeve  201  and thereby laterally moving lug  211 . 
     From the position depicted in FIG. 3, the control key can be rotated so as to disengage lug  211  from slot  101 , as depicted in FIG.  4 . It can be seen by comparison of FIGS. 3 and 4 that rotation of the control key by only a few degrees is necessary to move lug  211  from the secured position in FIG. 3 to the installation position in FIG.  4 . This small degree of rotation is controlled by the abutment of upper control pin  212  with the opposing lateral walls of locking notch  217  and rotation stop notch  216  formed on the upper surface of lug  211 . Once the control key  25  has been rotated to the installation position, the control key  25 , core  21 , and shell can be slid axially from the shell housing  100 . 
     It will be apparent to one skilled in the art that once shell and core have been removed, a new core can be installed into the lock housing such that different keys are required to open the lock. This can achieved either by installing a completely different shell and core pair, or by fitting a new core into the removed shell in place of the old core and then installing them into the housing. 
     After a new shell and core pair has been axially slid into the housing (status depicted by FIG.  4 ), the control key  25  is rotated from its installation position to its secured position (status depicted in FIG.  3 ). This rotation causes lug  211  to engage slot  101 , and allows control key  25  to be removed from keyway  24 . When control key  25  is withdrawn, lower control pin  17 , intermediate control pin  214 , and upper control pin  212  all move downward due to the biasing force of spring  18  (status depicted in FIG.  2 ). In this manner, upper control pin  212  returns to engagement with locking notch  217  such that locking retainer ring  200  is again prevented from rotating with core  21  due to shear forces. 
     Accordingly, with the present invention a shell, core, and shell housing assembly can be delivered to an installation location for an enclosure. The shell, core, and shell housing can be attached to the enclosure such that the shell and core are removably retained in the enclosure. The shell and core can be removed as described hereinabove so as to quickly and easily re-key the lock for the enclosure. The shell and core of the present invention also has an improved engagement mechanism with the housing such that it not only avoids the use of multiple movable parts, but also provides an improved and durable engagement member that can be easily manufactured and can be handled without substantial risk of damage, etc., that could potentially interfere with operation. 
     While the invention has been described in detail above, the invention is not intended to be limited to the specific embodiments as described. It is evident that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments described herein without departing from the inventive concepts.