Patent Publication Number: US-6711924-B2

Title: Freewheeling lock apparatus and method

Description:
BACKGROUND OF THE INVENTION 
     A wide variety of keyed locks or locking mechanisms exist for preventing unauthorized or unwanted entry and/or use of various items and devices including without limitation vehicles, houses, drawers, doors, and the like. While conventional keyed locks and locking mechanisms are generally effective in preventing such unwanted entry and/or use, certain tools and methods have been devised to defeat or overcome the effectiveness of keyed locks in order to forcefully gain entry to and/or use of the locked item. 
     One well-known manner of overcoming a lock is to pick the lock. Picking a lock requires a great deal of knowledge about the internal workings of the particular lock being picked, and is often relatively time consuming. In addition, locks are continually being improved to make the process of picking certain types of locks extremely difficult, if not altogether impossible. Due to the inherent challenges of picking a lock, certain groups having primarily malicious intentions (most notably car thieves) have devised other commonly used methods for overcoming a lock. By inserting a rigid item (such as a screwdriver) into the lock instead of the appropriate key, and subsequently applying a sufficient torque to that item, many locks can be overcome by force. Such locks typically fail in one of two manners when forced as just described. In a first failure mode, the internal components of the lock (e.g. the lock tumblers, the lock cylinder, and the like) are broken such that the lock cylinder can be rotated with respect to the lock housing. Generally, rotation of the lock cylinder is all that is required to defeat many locks. In a second failure mode, the internal lock components remain intact while the lock housing itself breaks free of the structural item to which it is secured (e.g. a vehicle steering column or vehicle door). Oftentimes, dislodging the lock housing in this manner and rotating the entire lock assembly has the same effect as rotating the lock cylinder with respect to the housing, resulting in the lock being defeated. 
     In order to prevent the defeat of a lock by forcefully rotating the lock as just described, some lock designs employ strengthened lock components and strengthened connections between the lock and the object to which the lock is secured. However, these design changes have been largely unsuccessful because the resulting locks are still subject to damage by attempts to overpower the lock, can often be overcome with even greater force, and are often excessively robust and expensive to manufacture and install. Furthermore, strengthening of the lock components can require a subsequent strengthening of the lock connection, which can then require additional strengthening of other lock components, resulting in a costly and on-going cycle of lock re-design. 
     Other attempts to protect keyed locks and locking mechanisms from being overpowered include the development of freewheeling locks. Freewheeling locks are constructed such that rotation of the lock cylinder with substantially any item other than the correct key inserted causes the lock cylinder to disengage from those lock components needed to unlock the lock (e.g., a lock drive mechanism). In this way, forced rotation of the lock cylinder does not result in unlocking or overcoming the lock. 
     SUMMARY OF THE INVENTION 
     In an effort to improve upon known locks, some embodiments of the present invention provide a locking mechanism including a housing defining a cavity and a central axis and having a receiving end, a retaining end, and a first cam surface that is adjacent to the receiving end, and a sleeve received at least partially within the cavity and having a second cam surface engageable with the first cam surface of the housing, and a clutch surface. In such embodiments, a lock cylinder is received at least partially within the sleeve and has a locked configuration and an unlocked configuration. The lock cylinder and the sleeve are coupled for rotation together when the lock cylinder is in the locked configuration. 
     Some embodiments of the present invention have a clutch member that is received at least partially within a housing cavity and is movable therein. The clutch member can be engaged with the lock cylinder for joint rotation when the lock cylinder is rotated in the unlocked configuration. When the lock cylinder is rotated in the locked configuration, the clutch member moves within the cavity and disengages the lock cylinder. An actuator is coupled to the clutch member such that the actuator rotates with the clutch member, and the actuator and the clutch member are axially movable with respect to each other. 
     In addition, some embodiments of the present invention provide a lock assembly having a housing that at least partially defines a cavity and has a central axis, an actuator rotatably coupled to the housing and substantially axially fixed with respect to the housing, and a lock cylinder received at least partially within the cavity, having a locked configuration and an unlocked configuration, and rotatable with respect to the housing in both the locked and unlocked configurations. A clutch selectively couples the lock cylinder and the actuator for rotation together depending upon the configuration of the lock cylinder when the lock cylinder is rotated. 
    
    
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description and drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is further described with reference to the accompanying drawings, which show preferred embodiments of the present invention. However, it should be noted that the invention as disclosed in the accompanying drawings is illustrated by way of example only. The various elements and combinations of elements described below and illustrated in the drawings can be arranged and organized differently to result in embodiments which are still within the spirit and scope of the present invention. 
     FIG. 1 is a perspective view of a freewheeling lock mechanism according to an embodiment of the present invention; 
     FIG. 2 is a front exploded perspective view of the freewheeling lock mechanism of FIG. 1; 
     FIG. 3 is a rear exploded perspective view of the freewheeling lock mechanism of FIG. 1; 
     FIG. 4 is a cross-sectional view of the freewheeling lock mechanism of FIG. 1, taken along line  4 — 4  of FIG. 1; 
     FIG. 5 is a cross-sectional view of the freewheeling lock mechanism of FIG. 1, taken along line  5 — 5  of FIG. 7; 
     FIG. 6 is a perspective view of the freewheeling lock mechanism of FIG. 1, showing a portion of the freewheeling lock mechanism removed; 
     FIG. 7 is a perspective view of the freewheeling lock mechanism of FIG. 6, shown rotated in a locked condition; 
     FIG. 8 is a perspective view of the freewheeling lock mechanism of FIG. 6, shown partially rotated in an unlocked condition; and 
     FIG. 9 is a perspective view of the freewheeling lock mechanism of FIG. 6, shown fully rotated in an unlocked condition. 
     Before the various embodiments of the invention are described in detail, it is to be understood that the present invention is not limited in its application to the details of construction and the arrangements 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 understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1-9 illustrate a locking mechanism  10  according to an embodiment of the invention. With reference to FIGS. 1-3, the locking mechanism  10  includes an outer housing  14 , a lock cylinder  18  received within the housing  10 , and a sleeve  22  also received with the housing  10  and surrounding at least a portion of the lock cylinder  18 . The embodiment illustrated in FIGS. 1-9 also includes an intermediate engagement member in the form of a clutch disk  26 , and an actuator element  30 . 
     The housing  14  provides a generally cylindrical, open-ended cavity  32  and defines a central axis  34 . In this regard, the housing  14  can take any shape within which the lock cylinder  18  can be received, and in some embodiments (such as that shown in the figures) is generally round. The housing  14  can enclose any amount of the lock cylinder  18  desired, such as by surrounding the length of the lock cylinder as shown in the figures. 
     The housing  14  can include outwardly extending mounting protrusions  36  that are securable to, among other things, a vehicle door or vehicle steering column that is to be lockably secured by the locking mechanism  10 . The mounting protrusions  36  can take a variety of different forms and are generally determined by the device or mechanism (e.g. a vehicle part or assembly) to which the locking mechanism  10  is to be secured. 
     A cylinder-receiving end  38  of the housing  14  includes an internal lip  42  in the housing  14  for limiting travel of the sleeve  22  toward the cylinder-receiving end  38  of the housing  14 . In other embodiments, sleeve travel in this direction can be limited in any other manner desired, such as by one or more bosses, pins, neck portions, and other features of the housing  14  (as well as element attached to the housing  14 ), each of which falls within the spirit and scope of the present invention. 
     For purposes that will be described in greater detail below, the housing  14  also includes a cam surface  46  extending radially into the cavity  32  and facing axially away from the receiving end  38 . The cam surface  46  defines one or more axially extending cam projections  50  within the cavity  32 . In some embodiments of the invention, the cylinder-receiving end  38  further includes an outer groove  51  that is configured to engage an end cap  52  of the locking mechanism  10 . The end cap  52  can be shaped to generally overlie and surround the cylinder-receiving end  38  of the housing  14  when engaged with the outer groove  51 . Alternatively, the end cap  52  (where used) can be directly or indirectly attached to the housing  14  in any other conventional manner. 
     Opposite the cylinder-receiving end  38  of the housing  14  is a retaining end  54 . The retaining end  54  of the housing  14  can be the same size as the cylinder-receiving  38  end or can have any other size desired, and in some embodiments (such as that illustrated in the figures) is somewhat diametrically enlarged with respect to the receiving end  38  of the housing  14 . 
     For purposes that will be described below, the retaining end  54  of the housing  14  illustrated in the figures includes a radially outwardly extending boss  58  that surrounds a through hole  62  communicating with the cavity  32 . The through hole  62  receives a pin  64  that extends radially into the cavity  32 . Although the boss  58  is not required, the boss  58  provides strength for the housing  14  adjacent to the pin  64 . The retaining end  54  can also include one or more axially and circumferentially extending notches or cutouts  66  that define a return-spring reaction tab  68  on the housing  14 . 
     The lock cylinder  18  is received within the cavity  32  and can take any conventional lock cylinder form. By way of example, the lock cylinder  18  in the illustrated embodiment includes a barrel portion  78  that houses a plurality of lock tumblers  82 . Other types of tumbler or pin-type lock cylinders can be employed in conjunction with the present invention as desired. Although the lock cylinder  18  can have any shape, the lock cylinder  18  illustrated in the figures includes an end flange  86  that seats against the internal lip  42  in the housing  14  when the lock cylinder  18  is inserted into the cavity  32 . The internal lip  42  assists in properly positioning the lock cylinder  18  with respect to the housing  14 , and can be replaced with any number of other elements and structure capable of performing the same function (including those described above with reference to the internal lip  42 ). 
     At one end of the lock cylinder  18  is a key slot  90  that receives a key (not shown). When an appropriate key is inserted into the lock cylinder  18 , the lock tumblers  82  engage the key and move within the barrel portion  78  to predetermined positions such that the lock cylinder  18  is placed in an unlocked state. If no key or an incorrect key is inserted into the lock cylinder  18 , one or more of the lock tumblers  82  will be improperly positioned, and the lock cylinder  18  will remain in a locked state. 
     In some embodiments of the present invention, the lock cylinder  18  also includes a sidebar  94  that radially extends from the barrel portion  78  when the lock cylinder  18  is in the locked state. In such embodiments, the sidebar  94  can be operatively coupled to the lock tumblers  82  such that when the appropriate key is inserted and the lock tumblers  82  move to their predetermined positions, the sidebar  94  moves radially inwardly with respect to the barrel portion  78  to a retracted position corresponding to the unlocked state of the lock cylinder  18 . In alternate embodiments of the present invention, such a sidebar is not employed. Instead, when the lock cylinder  18  is in the locked state, one or more of the tumblers  82  extend radially outwardly from the lock cylinder  18  to engage a housing or other adjacent element and to thereby prevent rotation of the lock cylinder  18 . When an appropriate key is inserted into the lock cylinder  18 , all of the tumblers are retracted into the barrel portion  78  to permit rotation of the lock cylinder  18 . The specific operation of and interaction between the key and the lock tumblers  82  (as well as between the lock tumblers  82  and the sidebar  94 , where employed) are well known in the art and are therefore not discussed further herein. While one specific type of lock cylinder  18  is illustrated in the drawings, substantially any type of rotatable lock cylinder is suitable for use with the present invention. 
     The lock cylinder  18  in the illustrated embodiment also has an axially extending boss  98  (substantially aligned with the central axis  34  when the lock cylinder  18  is received within the cavity  32 ) that helps to maintain the position of the lock cylinder  18  in the locking mechanism  10 . The boss  98  can have any shape desired, such as the generally cylindrical shape shown in the figures. With continued reference to the illustrated embodiment, one or more dogs  102  extend axially away from the barrel portion  78  and radially outwardly from the boss  98 . As illustrated, two dogs  102   a ,  102   b  are provided at substantially diametrically opposed positions, one of which ( 102   a ) is substantially radially aligned with the sidebar  94 . The dog  102   a  is configured to extend radially beyond the barrel portion  78  such that the dog  102   a  and the sidebar  94  extend from the barrel portion (substantially the same distance in the illustrated embodiment) when the lock cylinder  18  is in the locked condition and the sidebar  94  is extended. In some embodiments, the boss  98  includes a circumferential groove  100  extending around its distal end for receiving a clip  170  that retains the elements of the locking mechanism  10  in their proper relative positions. 
     The sleeve  22  in the illustrated embodiment is generally tubular and is received within the annular space formed between the housing  14  and the lock cylinder  18  when the lock cylinder  18  is inserted into the cavity  32 . An outer surface  110  of the sleeve  22  faces the housing  14 , and an inner surface  114  of the sleeve  22  faces the barrel portion  78  of the lock cylinder  18 . The sleeve  22  has at least one aperture or recess  118  within which tumblers  82  of the lock cylinder  18  can be received. The sleeve  22  can have a single aperture or recess  118  in those embodiments of the present invention having one set of tumblers  82  located in one circumferential position in the lock cylinder  18 . Alternatively, the sleeve  22  can have multiple apertures or recesses  118 , such as where multiple sets of tumblers  82  are located in different circumferential locations in the lock cylinder  18 . For example, the sleeve  22  in the illustrated embodiment has two diametrically opposed elongated slots  118  corresponding to two sets of tumblers  82 . 
     The apertures or recesses  118  in the sleeve  22  can have substantially any shape and can be positioned substantially anywhere along the sleeve  22 . In some embodiments of the invention, the apertures or recesses  118  may be excluded altogether. The shape and positioning of the apertures or recesses  118  is largely dependent upon the configuration of the lock cylinder  18 . By way of example only, the sleeve  22  in the illustrated embodiment has two axially elongated slots  118  for receiving the lock tumblers  82  that extend beyond the barrel portion  78  when the lock cylinder  18  is in the locked state. When the tumblers  82  are extended into the elongated slots  118 , the tumblers  82  prevent rotation of the lock cylinder  18  with respect to the sleeve  22 . The axially elongated slots  118  can also perform drainage functions for the locking mechanism  10 . 
     One end of the sleeve  22  includes a generally annular cam surface  122  that engages the cam surface  46  of the housing  14 . The cam surface  122  provides one or more axial cam recesses  126  that are configured to receive one or more cam projections  50  of the housing  14 . The other end of the sleeve  22  includes a generally annular clutch-engaging surface  128  that slidingly engages the clutch disk  26 , depending upon the state (e.g. locked or unlocked) of the lock cylinder  18 . As will be described further below, the “clutch” portion of the lock mechanism is provided by the sleeve  22  and the disk  26 , which selectively drivingly or slidingly engage one another. 
     For those embodiments of the preset invention employing a sidebar  94  as described above, the sleeve  22  can also include an aperture or recess  130  for receiving the sidebar  94 . As with the apertures or recesses  118  of the sleeve  22 , the aperture or recess  130  for the sidebar  94  can have any shape and location suitable for receiving the sidebar  94 . In the illustrated embodiment for example, the aperture or recess  130  is an axially extending groove  130  recessed with respect to the inner surface  114  for receiving the sidebar  94  when the sidebar  94  is extended. In some preferred embodiments of the invention, the engagement between the sidebar  94  and the aperture or recess  130  alleviates the need for engagement between the tumblers  82  and the apertures or recesses  118 . In this respect, some embodiments of the invention can include tumblers  82  that do not extend from the lock cylinder  18  regardless of the condition (e.g. locked or unlocked) of the lock cylinder  18 . 
     With continued reference to the illustrated embodiment of the present invention, the overall length of the sleeve  22  is selected such that when the end flange  86  of the lock cylinder  18  is engaged with the internal lip  42  of the housing  14 , the cam projections  50  are aligned with and received by the cam recesses  126 , and the dogs  102   a ,  102   b  of the lock cylinder  18  extend axially beyond the clutch-engaging surface  128  toward the retaining end  54  of the housing  14  (see FIG.  4 ). 
     The engagement member or clutch disk  26  can have any shape desired, dependent at least partially upon the shape and position of the boss  98  and the sleeve  22 . With reference to FIGS. 2 and 3 for example, the engagement member or clutch disk  26  is generally round, is received by the retaining end  54  of the housing  14  and includes a central aperture  134  that receives the boss  98  of the lock cylinder  18 . The clutch disk  26  can include two or more (e.g. four as illustrated) radially extending protrusions  138  that define substantially equally angularly spaced apart cutouts or notches  142  therebetween. In some embodiments, one side of the clutch disk  26  includes a substantially annular protrusion  146  that surrounds the central aperture  134 , while the other side of the clutch disk  26  includes one or more axial recesses  150  that extend radially outwardly from the central aperture  134 . In the illustrated embodiment for example, the clutch disk  26  includes two recesses  150  that are substantially diametrically opposed to each other (although other numbers and arrangements of such recesses  150  are possible depending at least in part upon the number and arrangement of the dogs  102   a ,  102   b  on the lock cylinder  18 ). The recesses  150  are adapted and configured to receive the dogs  102   a ,  102   b  of the lock cylinder  18 , such that rotational movement of the lock cylinder  18  is transmitted to the clutch disk  26  due to driving engagement between the dogs  102   a ,  102   b , and the recesses  150 . 
     The actuator element  30  can perform a single function or can perform two or more functions. For example, the actuator element  30  can be employed to retain elements of the locking mechanism  10  in place, can be employed to connect the locking mechanism  10  to the device controlled thereby, and/or can be employed to assist in properly positioning the lock cylinder  18  within the locking mechanism  10 . In the illustrated embodiment, the actuator element  30  has at least some portion that is received by the retaining end  54  of the housing  14  and includes a central aperture  154  that receives the boss  98  of the lock cylinder  18 . The actuator element  30  can include an end wall  158  that defines the end of the locking mechanism  10 . 
     The actuator element  30  can also include one or more (e.g. three as illustrated) angularly spaced-apart dogs or projections  162  that extend axially inwardly with respect to the cavity  32 , as well as a protrusion  164  (e.g., an annular projection as shown in the figures) that also extends axially inwardly with respect to the cavity  32 . The axial dogs or projections  162  can take any shape desired, including rod-shaped or bar-shaped elements extending from the actuator element  30 . However, in some embodiment such as that shown in the figures, the axial dogs or projections  162  are shaped to match features of the clutch disk  26  with which they mate. 
     If employed, the protrusion  164  can surround any part or all of the aperture  154 . Also if employed, the projections  162  can be shaped and arranged to extend into the notches  142  formed in the clutch disk  26  such that rotational movement of the clutch disk  26  (e.g. in response to rotational movement of the lock cylinder  18  and driving engagement of the dogs  102   a ,  102   b  and the recesses  150 ) imparts rotational movement to the actuator element  30  due to driving engagement between the projections  162  and the clutch protrusions  138 . For reasons that will become apparent below, at least one of the notches  142  in the clutch disk  26  is not engaged or otherwise occupied by the projections  162 . 
     The lock mechanism  10  can be connected to a latch or other mechanism to be locked by a number of different elements and structure on the lock mechanism  10 . By way of example only, the lock mechanism  10  in the illustrated embodiment has a lock output tab  166 , extending from the actuator element  30 . More specifically, the actuator element  30  in this embodiment includes a lock output tab  166  extending axially and radially away from the end wall  158 . The lock output tab  166  can be connected to, among other things, a latching device or an ignition switch for a vehicle such that rotational movement of the actuator element  30  moves the lock output tab  166  and locks/unlocks a connected device. As an alternative to a lock output tab  166 , the actuator element  30  can have an actuator shaft extending axially from the actuator element  30 , substantially aligned with the central axis  34  of the locking mechanism  10  and coupled to a vehicle ignition, door latch, or other mechanism for locking and unlocking the mechanism by rotation of the actuator shaft. In still other embodiments, the actuator element  30  can have one or more apertures, bosses, flanges, fingers, or other connecting points to which one or more cables, rods, levers, or other elements can be connected for transmitting motion from the locking mechanism to a device connected thereto. 
     The above-described lock output tab  166 , axially extending shaft, and alternative connecting points of the actuator element  30  are only a small number of examples of lock output mechanisms. Many elements and mechanisms for transmitting rotational movement of the lock mechanism to rotational, translational, and other types of movement for actuation of various devices (e.g. door latches and vehicle ignitions) are well known to those skilled in the art. Each of these actuating elements and devices can be used in combination with the teachings of the present invention and fall within the spirit and scope of the present invention. The use of the locking mechanism  10  in a vehicle and/or for locking and unlocking a door latch is merely exemplary. Many other uses and applications for the locking mechanism  10  according to the present invention would be contemplated by those of skill in the art. 
     As mentioned above, the end of the boss  98  extending away from the barrel portion  78  of the lock cylinder  18  has a circumferential groove  100  for receiving a clip  170 . In this regard, when the locking mechanism illustrated in the figures is assembled (see FIGS.  4  and  5 ), a portion of the lock cylinder boss  98  extends beyond the end wall  158  of the actuator element  30  such that the circumferential groove  100  in the end of the boss  98  is exposed. The retaining element  170  (e.g., a C or E-clip, a retaining ring, and the like) is positioned in the circumferential groove  100  to secure the components of the locking mechanism  10  within the housing  14 . In other embodiments of the present invention, the boss  98  (or at least the end thereof) can be threaded so that a nut or other conventional fastener can used in place of or in addition to the retaining element  170 . In still other embodiments, the actuator element  30  is retained in place with respect to the housing  14  and the other elements of the locking mechanism  10  by one or more inter-engaging lips and grooves (e.g., a circumferential groove in the housing  14  within which a flange, lip, rib, or other circumferential protrusion of the actuator element  30  extends, and the like). Still other manners of connection between the actuator element  30  and the lock cylinder  18  are possible, each permitting relative rotation between the actuator element  30  and the housing  14  and each falling within the spirit and scope of the present invention. 
     In some embodiments of the present invention such as that shown in the figures, it is desirable to bias the clutch disk  26  toward the sleeve  22 . A number of different spring elements in a number of different locations can be employed for this purpose. In the illustrated embodiment for example, the locking mechanism  10  includes a biasing element in the form of a helical compression spring  174  located between the clutch disk  26  and the actuator element  30 . In other embodiments, other types of spring elements can be employed, such as leaf springs, resilient bushings, Belleville washers, and the like. The spring  174  in the illustrated embodiment surrounds and receives the annular protrusions  146 ,  164 , although such protrusions are not required to bias the clutch disk  26  as described above. The spring  174  is compressed between the clutch disk  26  and the actuator element  30  such that a biasing force is applied to the clutch disk  26 , thereby biasing the clutch disk recesses  150  into engagement with the lock cylinder dogs  102   a ,  102   b . In addition to biasing the clutch disk  26  into engagement with the lock cylinder  18 , the spring  174  can also provide a biasing force between the lock cylinder  18  and the actuator element  30 , thereby reducing the amount of rattling that occurs between various lock components of the locking mechanism  10 . 
     In addition to the compression spring  174 , another biasing element can also be provided to bias the lock cylinder  18  and/or the actuator element  30  toward a predetermined angular orientation with respect to the housing  14 . For example, a torsion spring  178  can be connected to the housing  14  and to the actuator element  30  or clutch disk  26  to bias the actuator element  30 , clutch disk  26 , and lock cylinder  18  toward an unactuated position. In the illustrated embodiment, the torsion spring  178  engages the reaction tab  68  on the housing  14  and at least one of the projections  162  of the actuator element  30  in such a way that rotation of the actuator element  30  with respect to the housing  14  creates an angular biasing force in the torsional spring  178 . The biasing force acts against rotation of the actuator element  30  and urges the actuator element  30  back toward its original angular position. One having ordinary skill in the art will appreciate that other types of springs and spring elements can be employed to urge the actuator element  30  and/or lock cylinder  18  to an unactuated position with respect to the housing  14 , and that such springs and spring elements can be connected to provide this biasing force in a number of different manners, each one of which falls within the spirit and scope of the present invention. For example, some embodiments of the invention can include a single spring that functions as the compression spring  174  and the torsion spring  178 . 
     In some embodiments, it is desirable to limit movement of the actuator element  30  in the unlocked state of the locking mechanism  10  and/or to limit movement of the clutch disk  26  in the locked state after the dogs  102   a ,  102   b  of the lock cylinder  18  are disengaged from the clutch disk  26 . In the embodiment shown in FIGS. 1-9, the pin  64  of the locking mechanism  10  provides this limit. The through hole  62  (see FIGS. 4 and 5) in the housing, and therefore the pin  64 , is positioned such that when the lock cylinder  18  has not been rotated, the pin  64  is substantially angularly aligned with one of the notches  142  in the clutch disk  26  (see FIG.  6 ). Specifically, the pin  64  is radially aligned with the notch  142  that is not engaged or occupied by the axial projections  162  of the actuator element  30 . In addition, the pin  64  is axially offset from the clutch disk  26  toward the retaining end  54  of the housing  14 . 
     If the lock cylinder  18  is rotated with the proper key inserted, the actuator element  30  will rotate until one of the actuator element projections  162  engages the pin  64 , thereby preventing further rotation of the actuator element  30  and lock cylinder  18  (see FIG.  9 ). The pin  64  and projection  162  are configured to allow sufficient rotation of the actuator element  30  (e.g. through the angle Omega) such that the device to which the actuator element  30  is coupled (e.g. a door latch, a vehicle ignition switch, and the like) can be effectively actuated. As will be described in greater detail below, if the lock cylinder  18  is rotated without the proper key inserted, the clutch disk  26  is axially moved until the pin  64  is received within a notch  142  of the clutch disk to prevent frictional engagement of the sleeve  22  and clutch disk  26  from turning the clutch disk  26  (or at least to limit the rotation of the clutch disk  26 ). 
     Given the arrangement and configuration of the various components described above, the locking mechanism  10  provides free rotation of the lock cylinder  18  within the housing  14  when an attempt to rotate the lock cylinder  18  is made using substantially any item other than the appropriate key (e.g. the wrong key, a screwdriver, or the like). As used herein, “free rotation” of the lock cylinder  18  is means that rotation of the lock cylinder  18  does not impart significant rotational movement to the actuator element  30  or otherwise imparts insufficient rotational movement to the actuator element  30  to fully actuate the device connected to the locking mechanism  10 . By restricting the amount of rotational movement transmitted from the lock cylinder  18  to the actuator element  30  to a relatively small angle (e.g. the angle alpha of FIG. 7, which is significantly smaller than the angle Omega of FIG.  9 ), operation of the device or mechanism to which the actuator element  30  is coupled is precluded. Of course, if the appropriate key is inserted into the lock cylinder  18 , rotation of the lock cylinder  18  results in less restricted rotation (and in some embodiments, unrestricted rotation) of the actuator element until such time as the actuator element projection  162  engages the pin  64 . Accordingly, by using the appropriate key, the locking mechanism  10  is fully operational to lock/unlock or activate/deactivate the associated device or mechanism to which the actuator element  30  is coupled. 
     With continued reference to the embodiment of the present invention illustrated in FIGS. 1-8, when substantially any item other than the appropriate key is used to rotate the lock cylinder  18 , the lock cylinder  18  remains in the locked condition such that the sidebar  94  remains extended and projects into the groove  130  in the sleeve  22  (see FIGS.  4  and  5 ). As such, the lock cylinder  18  and the sleeve  22  are substantially rotatably fixed to each other. In alternative embodiments, the tumblers  82  may also or alternatively extend from the lock cylinder  18  and project into the slots  118  to rotatably fix the lock cylinder  18  to the sleeve  22 . In response to coupled rotation of the lock cylinder  18  and the sleeve  22  together, the cam projections  50  in the housing  14  and the cam recesses  126  in the sleeve  22  engage each other and urge the sleeve  22  axially toward the retaining end  54  of the housing  14 . 
     As the sleeve  22  moves axially along the housing  14 , the clutch-engaging surface  128  of the sleeve  22  engages the clutch disk  26  such that the clutch disk  26  is urged against the biasing force of the compression spring  174  axially toward the retaining end  54  of the housing  14 . As the clutch disk  26  moves axially in this manner, the clutch recesses  150  become disengaged from the dogs  102   a ,  102   b . At this time, the lock cylinder  18  and the clutch disk  26  are no longer drivingly coupled for rotation together. In addition, movement of the sleeve  22  as described above brings the sleeve groove  130  over the radially extending drive dog  102   a , thereby bringing the sleeve groove  130  and drive dog  102   a  into driving relationship. Substantially simultaneously, and also due to axial movement of the clutch disk  26 , the clutch disk notch  142  that is not occupied by one of the actuating element projections  162  receives the pin  64 . 
     The angle of rotation of the clutch disk  26  (and therefore, of the actuator element  30  in its locked state) can vary widely depending at least in part upon the size of the notch  142  and the radial clutch protrusions  138 . Similarly, the angle of rotation of the actuator element  30  in its unlocked state can vary widely depending at least in part upon the distance between the pin  64  and the axial projection  162  that limits movement of the actuator element  30 . In some embodiments, the angle of rotation of the clutch disk  26  in the locked state of the locking mechanism  10  is less than about 30 degrees. In other embodiments, this angle is about 15 degrees or less. 
     Once the clutch protrusion  138  engages the pin  64  in the locked state of the locking mechanism  10 , further rotation of the clutch disk  26  is prevented. During axial movement of the clutch disk  26  in some embodiments, the clutch notches  142  and the axial projections  162  of the actuator element  30  slide axially with respect to each other such that there is substantially no axial movement of the actuator element  30  with respect to the housing  14 . The locking mechanism  10  and the device to which the mechanism  10  is attached are configured such that the small amount of actuator element rotation that occurs as the clutch disk  26  is disengaged from the lock cylinder  18  does not fully operate, actuate, or otherwise influence the state (e.g., locked or unlocked) of the device. 
     With continued reference to the embodiment illustrated in FIGS. 1-9, as the lock cylinder  18  and the sleeve  22  continue to rotate together, the cam recesses  126  disengage the cam projections  50 , and the clutch recesses  150  disengage the dogs  102   a ,  102   b  (see FIG.  5 ). Also, the clutch disk  26  and the actuator element  30  remain substantially stationary (both axially and rotationally) with respect to the housing  14  due to engagement between the clutch disk  26  and the pin  64  while the clutch-engaging surface  128  slidingly engages the clutch disk  26 . In the illustrated embodiment having two cam recesses  126  and two cam projections  50 , once the lock cylinder  18  and the sleeve  22  have been rotated approximately  180  degrees, the cam recesses  126  and cam projections  50  are once again aligned (albeit with an opposite cam recess  126  and cam projection  50 ) and the biasing force of the compression spring  174  urges the clutch disk  26  and the sleeve  22  axially toward the cylinder-receiving end  38  of the housing  14 , thereby re-engaging the cam recesses  126  with the cam projections  50 , and the clutch recesses  150  with the lock cylinder dogs  102   a ,  102   b . Still further rotation of the lock cylinder  18  in a forceful manner repeats the disengagement/re-engagement cycle. Accordingly, the lock cylinder  18  can by continuously rotated by an improper key or other object without imparting significant rotational force to the actuator element  30 , tumblers  82 , or sidebar  94 , thereby preventing alteration of or damage to the locking mechanism  10  and preventing the device connected thereto from becoming unlocked. Regardless of whether the lock cylinder  18  is rotated in the locked or unlocked condition, the lock cylinder  18  remains substantially axially fixed with respect to the housing. 
     In other embodiments of the present invention in which fewer or more apertures or recesses  118 ,  130  are provided in the sleeve  22 , the lock cylinder  18  can be rotated different amounts before being re-engaged with the housing  14  in a manner similar to that described above. For example, in embodiments having a single set of tumblers  82  and a single elongated aperture  118  in the sleeve  22 , the lock cylinder  18  can be rotated approximately 360 degrees to become re-engaged with the sleeve  22 . 
     In some embodiments, if the lock cylinder  18  is forcibly rotated when in the locked condition through a sufficient angle to result in axial translation of the sleeve  22 , but not so far as to allow the lock cylinder dogs  102   a ,  102   b  to re-engage with the clutch recesses  150 , engagement between the radially extending cylinder dog  102   a  and the sidebar groove  130  of the sleeve  26  facilitates returning the lock to an operative mode using the appropriate key. Specifically, when the appropriate key is inserted into a partially rotated lock cylinder  18 , the sidebar  94  and/or the tumblers  82  (depending upon the configuration of the lock cylinder  18 ) are retracted from the groove  130  and/or the elongated apertures  118 , respectively, so that the sidebar  94  and/or the tumblers  82  no longer couple the sleeve  22  and the lock cylinder  18  for rotation together. With this in mind, the radially extending dog  102   a  and the groove  130  are configured to couple the lock cylinder  18  and the sleeve  22  for rotation together when the sidebar  94  and/or the tumblers  82  are retracted. Thus, the lock cylinder  18  can be restored to a normal operating condition by rotating the lock cylinder  18  with the appropriate key filly inserted until such time as the cam projections  50  and the cam recesses  126  are again aligned, the sleeve  22  snaps axially toward the receiving end  38  of the housing  14  (under influence of the spring  174 ), and the clutch disk  26  snaps axially toward the receiving end  38  of the housing as the dogs  102   a ,  102   b  are one again received within the clutch recesses  150 . 
     During normal operation of the embodiment illustrated in FIGS. 1-9, when the appropriate key is inserted into the lock cylinder  18 , the sidebar  94  (and/or the tumblers  82  if so configured) retracts into the barrel portion  78  of the lock cylinder  18  such that the lock cylinder  18  and the sleeve  22  are no longer coupled for rotation together. It will be appreciated that for locks that do not include a sidebar (e.g. “tumbler locks”), the tumblers fully retract within the barrel portion  78  of the lock cylinder  18  to decouple the lock cylinder  18  from the sleeve  22 . 
     When the lock cylinder  18  is subsequently rotated, the sleeve  22  remains substantially stationary with respect to the housing  14 . As such, there is substantially no axial movement of the sleeve  22  or the clutch disk  26 , and the clutch recesses  150  remain engaged with the lock cylinder dogs  102   a ,  102   b . In addition, because the radial clutch disk protrusions  138  do not engage the pin  64 , the clutch disk  26  is free to rotate with respect to the housing  14 . Thus, as the lock cylinder  18  is rotated, the clutch disk  26  and the actuator element  30  are also rotated due to the engagement between the dogs  102   a ,  102   b  and the recesses  150  as well as the engagement between the clutch disk notches  142  and the actuator element projections  162 . Rotation of the actuator element  30  through a sufficient angle results in operation of the device to which the actuator element is coupled (e.g., actuation of the device to a locked or unlocked state). Once the lock cylinder  18  has been sufficiently rotated, the torsional spring  178  (if employed) returns the lock cylinder  18  to its original angular orientation with respect to the housing  14 . Regardless of whether the lock cylinder  18  is rotated with the appropriate key inserted or not, the lock cylinder  18  can remain substantially axially fixed with respect to the housing  14 . 
     In addition to preventing forceful turning of the lock cylinder  18  by inserting an object into the key slot  90 , the locking mechanism  10  also prevents substantial rotation of the actuator element  30  by grasping, pulling, or otherwise directly manipulating the actuator element  30 . For example, if the locking mechanism  10  is installed in a vehicle door, attempts to overcome the lock may be made by inserting a thin piece of metal including a small hook (often referred to as a “slim-jim”) between the outer door housing and the door glass. The hook is then engaged with the lock output tab  166  in an effort to move the lock output tab  166  sufficiently to unlock the vehicle door. If such an attempt to overcome the locking mechanism  10  is made, the lock output tab  166  will only be movable through the relatively small angle alpha such that unlocking of the door is substantially prevented. Specifically, as the actuator element  30  is rotated, the driving engagement between the projections  162  and the clutch protrusions  138  causes the clutch disk  26  to rotate with respect to the housing  14 . Also, the driving engagement between the clutch recesses  150  and the dogs  102   a ,  102   b  impart rotation to the lock cylinder  18  which in turn imparts rotation to the sleeve  22  due to the engagement between the sidebar  94  (which remains extended) and the groove  130 . As discussed above, rotation of the sleeve  22  with respect to the housing  14  causes the sleeve  22  and the clutch disk  26  to move axially toward the retaining end  54 . Such axial movement of the clutch disk  26  causes one of the radial clutch disk protrusions  138  to engage the pin  64 , thereby preventing further rotation of the clutch disk  26 . Because the clutch disk  26  and the actuator element  30  are substantially always coupled for rotation together, preventing further rotation of the clutch disk  26  prevents further rotation of the actuator element  30 . As such, once the actuator element  30  is rotated through the relatively small angle alpha, further rotation of the actuator element  30  (which would result in unlocking of the door) is substantially prevented. 
     The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims. For example, a number of alternatives exist to the use of a pin  64  and housing through-hole  62  for limiting rotation of the clutch disk  26  and/or the actuator element  30 . In some embodiments, the housing  14  can be provided with one or more internal projections, fingers, bosses, or other features that are integral with the housing  14  or are otherwise secured to the housing  14  and that perform the same or similar functions as the pin  64 . 
     Furthermore, the housing  14  can be constructed of two or more elements or portions, such as a receiving end  38  and a retaining end  54  connected together in any conventional manner. Such a two-piece housing  14  can be configured to receive a pin as described above, can include integrally formed radially inwardly extending projections on one or both of the ends  38 ,  54 , can include other types of projections (e.g. axial projections formed on the retaining end  54 ) that engage the clutch disk  26  and/or the actuator element  30  upon axial movement of the clutch disk  26  to prevent rotation thereof, and the like. 
     The dogs  102   a ,  102   b  in the illustrated embodiment are located at an end of the barrel portion  78  of the lock cylinder  18 , and are spaced on opposite sides of the boss  98  extending from the barrel portion  78 . It should be noted, however, that other elements and features of the lock cylinder  18  could be employed to selectively drivably engage the clutch disk  26  as described above. The bar-shaped dogs  102   a ,  102   b  illustrated in FIGS. 3 and 4 can be replaced by one or more elements having any shape that mates with one or more recesses in the clutch plate  26 . By way of example only, the bar-shaped dogs  102   a ,  102   b  can be replaced by one or pins axially extending from the barrel portion  78  of the lock cylinder  18  into apertures in the clutch disk  26 , one or more flanges or ribs that extend radially from the clutch disk  26  and that can be received within axially-extending recesses, grooves, or other apertures in the end of the barrel portion  78  of the lock cylinder  18 , and the like. Any other engaging or mating elements on the lock cylinder  18  and clutch disk  26  can be employed for enabling the lock cylinder  18  to be releasably engaged with the clutch disk  26  for selectively transmitting rotational force from the lock cylinder  18  to the clutch disk  26 . 
     Although the elements of the lock cylinder  18  can have the same shape as recesses in the clutch disk  26 , such correspondence is not required to practice the present invention. In still other embodiments, the lock cylinder  18  and clutch disk  26  have sufficient frictional engagement between one another that additional features or elements intended for transmitting rotational force to the clutch disk  26  are not necessary. It should also be noted that element(s) on the lock cylinder  18  for transmitting rotary force to the clutch disk  26  need not necessarily be located at the end of the barrel portion  78  of the lock cylinder  18 , but can instead extend from or otherwise be located on the boss  98  of the lock cylinder  18 . 
     It will be appreciated by one having ordinary skill in the art that a number of elements in the present invention can have significantly different shapes and structure while still performing the same or similar functions as those described above. Such elements fall within the spirit and scope of the present invention. For example, the sleeve  22  of the locking mechanism  10  need not necessarily surround the lock cylinder  18  as described above and illustrated in the figures. Instead, the lock cylinder  18  can be any body or frame that can transmit axial force to the clutch disk  26  as described above, that has a cam surface as also described above, and that can transmit rotational force from the tumblers  82  and sidebar  94  to the cam recesses  126  for generating disengagement from the housing  14 . As used herein and in the appended claims, the term “sleeve” refers to all such elements capable of functioning in this manner. 
     The cam recesses  126  of the sleeve  22  and the cam projections  50  of the housing  14  provide camming action that generates disengagement of the sleeve  22  from the housing  14  when sufficient torque is exerted upon the sleeve  22 . In this regard, any cam surface on the sleeve  22  and any cooperating cam surface on the housing  14  can be selected to cause axial separation of these elements in reaction to such torque. Specifically, cam recesses and cam projections can be located on the housing  14  and sleeve  22 , respectively. In addition, the cam surfaces can be stepped, curved, ramped, or can take any shape capable of producing the axial displacement just described. If desired, multiple cam surfaces (e.g., multiple recesses, projections, steps, ramps, and the like) can be employed about the sleeve  22  and the inside of the housing  14  for the same purpose.