Abstract:
A key for operating a security fastener having a lock pattern includes a retractable key pattern. The key pattern has an operational extension position in which the key pattern is enabled for substantial engagement with a security fastener having a matching lock pattern, thereby allowing operation of the matching security fastener. The key pattern is also capable of retreating a non-operational retraction position in which the key pattern is not capable of substantial engagement with a security fastener having a non-matching lock pattern, thereby preventing operation of the non-matching security fastener.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not Applicable  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0003]      1 . Field of the Invention  
         [0004]     The present invention relates to keys for security (anti-theft) fasteners such as locking wheel nuts and wheel bolts used to secure vehicular wheels.  
         [0005]     2. Description of the Prior Art  
         [0006]     By way of background, locking wheel nuts and wheel bolts are commonly used to attach wheels to axle hub assemblies of automobiles and other vehicles. These security fasteners are designed with security features that are intended to thwart theft by rendering the fasteners difficult to remove with conventional tools. In particular, the fasteners do not have the usual hexagonal head pattern found on conventional nuts and bolts, and instead have smooth cylindrical side walls that cannot be gripped by standard wrenches. Fastener removal requires the use of a special security key having a key head formed with a unique key pattern that matches a corresponding lock pattern formed on the fastener end face. It is to improvements in security keys of the foregoing type and the prevention of unauthorized security fastener removal that the present invention is directed.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     The foregoing goals are achieved and an advance in the art is provided by an improved key for operating a security fastener having a lock pattern. The key features a retractable key pattern that is normally in an operational extension position in which it is enabled for substantial engagement with a security fastener having a matching lock pattern, thereby allowing operation of the matching security fastener. However, in the event that an outside tampering force in excess of a normal operational force is applied to the key pattern (such as the force that would be imparted if an attempt was made to slam the key pattern into a security fastener having a non-matching lock pattern), the key pattern will retract into a non-operational retraction position in which it is prevented from substantially engaging a security fastener having the non-matching lock pattern, thereby preventing operation of the non-matching security fastener.  
         [0008]     In exemplary embodiments of the invention, the key includes a retraction control member that can be alternatively implemented using a biasing element, a breakable element, a crushable element or any other suitable expedient that will resist retraction of the key pattern until the tampering force is applied. The retraction control member is located to engage a key head that carries the key pattern at one end thereof. The key head is disposed in a key well that accommodates movement of the key head as the key pattern retracts. The key well is part of a key housing that includes a base end adapted for imparting torque to the key, such as by way of a handle or a gripping tool, and a fastener-receiving end that may include an open-ended shroud for guiding the key onto the end of a security fastener. A stop surface is provided on the key for contacting an area of the security fastener as the key pattern retracts to a retraction position under application of the tampering force. The stop surface prevents the security fastener&#39;s lock pattern from following the key pattern into the key well to its retraction limit. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0009]     The foregoing and other features and advantages of the present invention will be apparent from the following more particular description of the preferred embodiments of the invention, as illustrated in the accompanying Drawings, in which:  
         [0010]      FIG. 1  is an exploded perspective view of a first key exemplary construction in accordance with the invention;  
         [0011]      FIG. 2A  is a cross-sectional centerline view of the key of  FIG. 1 ;  
         [0012]      FIG. 2B  is a cross-sectional centerline view of an alternative version of the key of  FIG. 1 ;  
         [0013]      FIG. 3  is a composite perspective view showing the manipulation of the key of  FIG. 1  into engagement with a security fastener having a matching lock pattern;  
         [0014]      FIG. 4A  is a cross-sectional centerline view of the key of  FIG. 1  with its key pattern in an operational extension position in operational engagement with a security fastener having a matching lock pattern;  
         [0015]      FIG. 4B  is a cross-sectional centerline view of the key of  FIG. 1  with its key pattern in a non-operational retraction position due to a tampering force applied by a security fastener having a non-matching lock pattern;  
         [0016]      FIG. 5  an exploded perspective view of a second exemplary key construction in accordance with the invention;  
         [0017]      FIG. 6A  is a cross-sectional centerline view of the key of  FIG. 5  with its key pattern in an operational extension position;  
         [0018]      FIG. 6B  is a cross-sectional centerline view of the key of  FIG. 5  with its key pattern in a non-operational retraction position;  
         [0019]      FIG. 7  is an exploded perspective view of a third exemplary key construction in accordance with the invention;  
         [0020]      FIG. 8A  is a cross-sectional centerline view of the key of  FIG. 7  with its key pattern in an operational extension position;  
         [0021]      FIG. 8B  is a cross-sectional centerline view of the key of  FIG. 7  with its key pattern in a non-operational retraction position;  
         [0022]      FIG. 9  is an exploded perspective view of a fourth exemplary key construction in accordance with the invention;  
         [0023]      FIG. 10A  is a cross-sectional centerline view of the key of  FIG. 9  with its key pattern in an operational extension position;  
         [0024]      FIG. 10B  is a cross-sectional centerline view of the key of  FIG. 9  with its key pattern in a non-operational retraction position;  
         [0025]      FIG. 11  is an exploded perspective view of a fifth exemplary key construction in accordance with the invention;  
         [0026]      FIG. 12A  is a cross-sectional centerline view of view of the key of  FIG. 11  with its key pattern in an operational extension position; and  
         [0027]      FIG. 12B  is a cross-sectional centerline view of the key of  FIG. 11  with its key pattern in a non-operational retraction position. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     With reference now to the above-identified Drawings, wherein like reference numbers designate like elements in all of the several views, embodiments of the invention will now be presented by way of five exemplary key constructions representing alternative implementations of the inventive subject matter. The five exemplary constructions are respectively shown in  FIGS. 1-4B ,  5 - 6 B,  7 - 8 B,  9 - 10 B and  11 - 12 B. Except as otherwise indicated below when discussing alternative retraction control member constructions, it will be understood that all components used in the disclosed key constructions are fabricated from either steel, titanium, high-strength aluminum or other durable suitable materials for automotive and vehicular use.  
         [0000]     I. FIRST EXEMPLARY KEY CONSTRUCTION  
         [0029]     Turning now to  FIG. 1 , a key  2  according to a first exemplary key construction includes a key housing  4  having a base end  6  and a fastener-receiving end  8 . By way of example only, the base end  6  can be formed as a male drive element of hexagonal shape that is either integrally formed with the main cylindrical portion of the housing  4  or attached thereto as a separate element. This configuration allows the base end  6  to receive a handle (not shown) or a tool (not shown), such as a wrench, that is capable of imparting operational torque to the housing  4 . Other suitable male (or female) configurations providing a torque transfer capability may likewise be used for the design of the base end  6 , including but not limited to external or internal shapes that are hexagonal, square, star, slotted, pinned, to name but a few. For example, in a female drive configuration, the base end  6  could be formed with a square internal opening in the housing  4  so that the key  2  can be mounted in the manner of a conventional socket to a conventional socket wrench. Note that the base end  6  could also be configured itself as a handle or a tool that is integrally formed as part of the housing  4 .  
         [0030]     The fastener-receiving end  8  of the housing  4  can be configured as a generally tubular shroud  10  that is either integrally formed with the main cylindrical portion of the housing  4  or attached thereto as a separate element. The shroud  10  extends from a recessed ledge portion  12  of the housing  4  and can be of any suitable length consistent with its function of helping guide the key  2  onto the end of a security fastener. If desired, however, the shroud  10  could be eliminated, in which case the fastener-receiving end  8  of the housing  4  will be defined by the ledge  12 , which would no longer be recessed. The ledge  12  itself is formed as a generally annular surface that is transversely oriented relative to the housing&#39;s longitudinal axis. It terminates inwardly at the edge of a key well  14  formed in the housing&#39;s main cylindrical portion. As shown in  FIG. 1 , and as described in more detail below, the key well  14  is configured to carry a biasing element in the form of a coil spring  16  and a key head  18  therein.  
         [0031]     With additional reference now to  FIG. 2A , the key well  14  is shown to include a bore  20  and a main guide way  22 . The bore  20  is adapted to carry the spring  16  and to slideably receive a stem  24  of the key head  18 . Note that the bore  20  and the stem  24  are optional insofar as the spring  16  could be located in the main guide way  22  and engage a key head configured without a stem. However, the design shown in  FIG. 2A  ensures proper guidance of the key head  18  by slideably supporting the stem  24  as it interacts with the spring  16 . Although the bore  20  and the stem  24  are both shown to be cylindrical in cross-sectional shape, it will be appreciated that other shapes could also be used.  
         [0032]     One end of the bore  20  can be closed by a back wall  26  of the key well  14  in order to support the base of the spring  16 . Alternatively, in lieu of the closed back wall  26 , an annular ledge (not shown) could be formed to support the spring  16 . Thus, although the key well  14  is shown to closed-ended, it need not be so and could open to the base end of the housing  4  if desired. The other end of the bore  20  opens to the main guide way  22 . The main guide way  22  extends to a key head-receiving opening  28  where the key well  14  meets the ledge  12 . An enlarged intermediate guide flange portion  30  of the key head  18  slideably engages the sides of the key well&#39;s main guide way  22 . It will be seen that the guide flange  30  and the guide way  22  are both hexagonal in cross-sectional shape. This allows torque to be transferred from the housing  4  to the key head  18 , which can then transfer torque to a security fastener through a key pattern to be described below. It will be appreciated that many other configurations could be used to provide the required housing-key head torque transfer, including but not limited to other non-circular cross-sectional configurations, spline configurations, pin configurations, set-screw configurations, to name but a few. Indeed, any configuration that enables the key head  18  to slide within the key well  14  with little or no rotation can be used.  
         [0033]     The end face of the key head&#39;s stem  24  contacts an end of the spring  16  that is opposite the key well&#39;s back wall  26 . The other end of the key head  18 , which faces the housing&#39;s fastener receiving end  8 , is provided with a key pattern  32  (best shown in  FIG. 1 ). The key pattern  32  is shown by way of example only to be formed as a continuous raised curvilinear projection. However, it should be understood that the key pattern  32  could be implemented using any suitable male (or female) drive configuration that allows the key  2  to impart torque to a security fastener. For example, a continuous recessed curvilinear channel could be used for the key pattern  32 . Non-continuous drive patterns could also be used, including but not limited to male (or female) pin configurations, slot configurations, star configurations, hexagonal configurations, square configurations, to name but a few.  
         [0034]     The key head  18  can be retained within the key well  14  in several ways.  FIG. 2A  shows one exemplary alternative in which the ledge  12  is staked around the key head-receiving opening  28  in order to trap the key head by engaging its guide flange  30 .  FIG. 2B  shows another construction in which the guide flange  30  is trapped by a retaining ring  34  seated in an annular groove  36  located adjacent to the key head-receiving opening  28 .  
         [0035]     Turning now to  FIGS. 3 and 4 A- 4 B, the improved security features of the key  2  will now be described. Initially, the key head  18  is in an operational extension position in which the key pattern  32  is extended toward the housing&#39;s fastener-receiving end  8  by virtue of the spring  16 . As shown in  FIG. 3 , the key  2  is maneuvered into alignment with the head of a security fastener  36  and advanced onto the fastener using the shroud  10  as a guide. As shown by the double-headed arrow in  FIG. 3 , slight rotation of the key  2  may be required to bring the key into proper operational alignment with the security fastener  36 . The security fastener  36  can be of any desired type, including but not limited to a vehicular lug nut or lug bolt, a vehicular spare tire winch drive, etc. The security fastener  36  could also be a non-vehicular fastener.  
         [0036]     Among the security features of the security fastener  36  of  FIGS. 3 and 4 A- 4 B is a tubular shroud  38  that freely spins relative to the remainder of the security fastener if an attempt is made to engage the shroud with a gripping tool. The security fastener  36  further includes a lock pattern  40  formed as a continuous curvilinear key receiving groove in the security fastener&#39;s generally planar end face  42 . A raised curvilinear projection could also be used if the key pattern  32  is formed as a recessed curvilinear channel. Other lock pattern configurations will be required if other key pattern configurations are used. Note that in  FIGS. 3 and 4 A, the lock pattern  40  is assumed to match the key pattern  32 .  FIG. 4B  shows the key  2  being used with a security fastener  36 A having a non-matching lock pattern  40 A.  
         [0037]     As shown in  FIG. 4A , because the lock pattern  40  is configured to mate with the key pattern  32 , the key pattern in an operational extension position will substantially engage the lock pattern when the key  2  is advanced onto the security fastener  36 , thereby allowing the security fastener to be operated by way rotation thereof under torque applied by the key. For example, if the security fastener  36  is a vehicular lug nut or lug bolt, the key  2  can be used to turn the security fastener into and out of locking engagement in a vehicle wheel installation in which a vehicle wheel (not shown) is secured to a hub or other mounting structure (not shown).  
         [0038]     In  FIG. 4B , it is assumed that an attempt has been made to use the key  2  on a security fastener  36 A whose lock pattern  40 A is not configured to mate with the key pattern  32 . In that case, the key pattern  32  in an operational extension position will not engage the lock pattern  40 A and the non-matching security fastener  36 A cannot be operated by the key  2 . If an attempt is made to jam the key  2  onto the non-matching security fastener  36 A by applying an excessive tampering force (e.g., due to a hammer blow delivered to the base  6  of the key  2 ), the tampering force will be reacted by the immovable end face  42 A of the security fastener against the key pattern  32 . This tampering force will tend to urge the key head  18  toward the back wall  26  of the key well  14  against the biasing force of the spring  16 . This means that the key pattern  32  cannot be forced into engagement with the non-matching security fastener  36 A. Instead of being able to gain a purchase on the security fastener  36 A as a result of the tampering force, the key pattern  32  will simply retract toward the key well  14  into a non-operational retraction position. As this occurs, the spring  16  will act as a retraction control member that controls retraction of the key pattern  32  according to the amount of tampering force that is applied. Note that the spring  16  will return the key pattern  32  to an operational extension position once the tampering force is removed. Thus, the non-operational retraction position is only temporary in the first exemplary key construction represented by the key  2 .  
         [0039]     It will be appreciated that the spring  16  should be designed so that forces associated with normal use of the key  2  to operate an authorized matching security fastener will not appreciably deflect the spring. However, the spring  16  should yield under the higher tampering force. Implementing the spring  16  as a helical coil made from steel stock of suitable gauge thickness will allow the key  2  to operate in the manner described above. It should further be understood that other spring designs may likewise be used to provide the biasing force needed for the key head retraction control function, including but not limited to Belleville spring washers as well as other biasing elements made from deformable resilient materials such as compressible rubber or the like. Resilient cushions, such as gas-filled bladders, could also be used.  
         [0040]     As an additional security measure, a stop surface can be associated with the key housing  4  to contact an area of the non-matching security fastener  36 A as the key pattern  32  retracts. This will prevent the security fastener&#39;s non-matching lock pattern  40 A from following the key pattern  32  to its retraction limit wherein the key head  18  bottoms out in the key well  14 . The stop surface may reside at various locations on the key  2  depending on the geometry of the key and the size and shape of the non-matching security fastener  36 A. For example, as shown in  FIG. 4B , a stop surface may be provided by the housing&#39;s fastener receiving end  8  if the shroud  10  is present and is of sufficient length to engage a corresponding surface of the non-matching security fastener  36 A during retraction of the key pattern  32 . In  FIG. 4B , this corresponding surface is located on the front face of a tapered seat member of the non-matching security fastener  36 A. If the shroud  10  is not present, or is of reduced length, or if the security fastener  36 A has no surface to contact the shroud, the ledge  12  of the housing  4  can act as a stop surface that engages (for example) the forward end face of the non-matching security fastener&#39;s tubular shroud  38 A as the key pattern  32  retracts. In some cases, the fastener receiving end  8  and the ledge  12  of the key  2  could both act as stop surfaces in different situations depending on the type of non-matching security fastener being contacted by the key. As such, some key constructions may provide plural application-specific stop surfaces. Alternatively, it may be the case that neither the fastener receiving end  8  nor the ledge  12  engages any portion of a security fastener, in which case some other surface (such as a prong or a tang on the shroud  10 ) may be provided to perform this function.  
         [0000]     II. SECOND EXEMPLARY KEY CONSTRUCTION  
         [0041]     Turning now to  FIGS. 5, 6A  and  6 B, a key  102  according to a second exemplary key construction of the invention is similar in many respects to the key  2  of the first exemplary key construction, as indicated by the use of corresponding reference numbers incremented by a value of 100. The primary difference between the key  202  and the key  2  is that the former does not use the spring  16  as a retraction control member. Instead, the spring  16  is replaced with a breakable element  116  made from plastic (e.g., ST801 type 6/6 polyamide nylon or the like) or other readily breakable material, such as soft metal, etc. In addition, the housing  104  is modified such that the key well  114  comprises only a primary guide way  122  of hexagonal cross-sectional shape. It does not include a separate bore such as the bore  20  in the key housing  4  described above. The key head  118  is also modified insofar as it lacks a stem.  
         [0042]     As shown in  FIG. 6A , the breakable element  116  is formed with a disk-shaped base flange  116 A that rests against the back wall  126  of the key well  114 . Extending from the base flange  116 A is a central post  116 B that is sized to mate with a central longitudinal bore  118 A formed in the key head  118 . A thin, disk-shaped key pattern support flange  116 C is mounted on the post  116 B in spaced relation to the base flange  116 A. The support flange  116 C engages a base end of the key head to limit the distance that the post  116 B penetrates into the bore  118 A. The breakable element  116  thus acts as a retraction control member that maintains the key pattern  132  in an operational extension position until a tampering force is applied. More particularly, the thickness of the support flange  116 C is controlled to shear, rip, rupture or tear from the post  116 B, and/or to bend or fold, when a desired breakaway force is applied. It will be appreciated that a higher breakaway force can be obtained by increasing the thickness of the support flange  116 C, and visa versa.  
         [0043]     In  FIG. 6B , it is assumed that a tampering force has been applied to the key pattern  132 , and that the support flange  116 C has sheared at its point of connection to the post  116 B. This allows the post  116 B to advance into the bore  118 A, enabling the key head  118  to slide toward the back of the key well  114 . The key pattern  132  will thereby retract to a non-operational retraction position. Note that because the breakable element  116  is used in lieu of a biasing element, the key pattern  132  will tend to remain in a retraction position after the tampering force is removed, rendering the key  102  inoperable even for authorized use with a matching security fastener.  
         [0000]     III. THIRD EXEMPLARY KEY CONSTRUCTION  
         [0044]     Turning now to  FIGS. 7, 8A  and  8 B, a key  202  according to a third exemplary key construction of the invention is similar in many respects to the key  102  of the second exemplary key construction, as indicated by the use of corresponding reference numbers incremented by a value of 100. The primary difference between the key  202  and the key  102  is in the design of the retraction control member. In particular, a modified breakable element  216 , made from plastic (e.g., ST801 type 6/6 polyamide nylon or the like) or other readily breakable material, such as soft metal, etc., is used in lieu of the breakable element  116  described above. The housing  204  is the same design used for the housing  4  of the first exemplary key construction. The key well  214  of the housing  204  thus includes both a bore  220  and a main guide way  222 . The key head  218  is similar to the key head  18  of the first exemplary key construction, except that it includes a post  218 A extending from the stem  224 .  
         [0045]     As shown in  FIG. 8A , the breakable element  216  is formed with a main bushing  216 A that is sized to slideably engage the sides of the key well bore  220 . A thin, disk-shaped key pattern support flange  216 B is mounted on the end of the main bushing  216 A that faces the key well&#39;s main guide way  222 . The support flange  216 B engages the back of the key well&#39;s main guide way  222 . A central bore  216 C in the breakable element  216  extends through the main bushing  216 A (or at least a portion thereof). The central bore  216 C is sized to receive the key head&#39;s post  218 A. The breakable element  216  thus acts as a retraction control member that maintains the key pattern  232  in an operational extension position until a tampering force is applied. More particularly, the thickness of the support flange  216 B is controlled to shear, rip, rupture or tear from the main bushing  216 A, and/or to bend or fold, when a desired breakaway force is applied. It will be appreciated that a higher breakaway force can be obtained by increasing the thickness of the support flange  216 B, and visa versa.  
         [0046]     In  FIG. 8B , it is assumed that a tampering force has been applied to the key pattern  232 , and that the support flange  216 B has sheared at its point of connection to the main bushing  216 A. This will allow the main bushing  216 A to retreat deeper into key well&#39;s bore  220 , enabling the key head  218  to slide toward the back of the key well  214 . The key pattern  232  will thereby retract to a non-operational retraction position. Note that because the breakable element  216  is used in lieu of a biasing element, the key pattern  232  will tend to remain in a retraction position after the tampering force is removed, rendering the key  202  inoperable even for authorized use with a matching security fastener.  
         [0000]     IV. FOURTH EXEMPLARY KEY CONSTRUCTION  
         [0047]     Turning now to  FIGS. 9, 10A  and  10 B, a key  302  according to a fourth exemplary key construction of the invention is similar in many respects to the key  202  of the third exemplary key construction, as indicated by the use of corresponding reference numbers incremented by a value of 100. The primary difference between the key  302  and the key  202  is in the design of the retraction control member. In particular, a modified breakable element  316  in the form of a pin, made from plastic (e.g., ST801 type 6/6 polyamide nylon or the like) or other readily breakable material, such as soft metal, etc., is used in lieu of the breakable element  216  described above. The housing  304  is the same design used for the housing  104  of the second exemplary key construction, except that there are a pair of opposing pin-receiving holes  304 A formed in the sides of the key well  314 . The key head  318  is similar to the key head  118  of the second exemplary key construction, except that there is no longitudinal bore. Instead, a transverse bore  318 A can be provided to extend laterally through the key head&#39;s guide flange  330 .  
         [0048]     As shown in  FIG. 10A , the breakable element  316  is formed as a pin that extends through the holes  304 A in the key housing  304  and which may also extend through the key head bore  318 A, if present. Alternatively, the breakable element  316  could be located behind the key head&#39;s guide flange  330 , in which case the key head bore  318 A is not required. The breakable element  316  acts as a retraction control member that maintains the key pattern  332  in an operational extension position until a tampering force is applied. More particularly, the thickness of the breakable element  316  is controlled to shear, rip, rupture or tear, and/or to bend or fold, in two places on opposite sides of the key head  318  (i.e., at the location of the holes  304 A) when a desired breakaway force is applied. It will be appreciated that a higher breakaway force can be obtained by increasing the thickness of the breakable element  316 , and visa versa.  
         [0049]     In  FIG. 10B , it is assumed that a tampering force has been applied to the key pattern  332 , and that the breakable element  316  has sheared in the manner described above. This will allow the key head  318  to slide toward the back of the key well  314 . The key pattern  332  will thereby retract to a non-operational retraction position. Note that because the breakable element  316  is used in lieu of a biasing element, the key pattern  332  will tend to remain in a retraction position after the tampering force is removed, rendering the key  302  inoperable even for authorized use with a matching security fastener.  
         [0000]     V. FIFTH EXEMPLARY KEY CONSTRUCTION  
         [0050]     Turning now to  FIGS. 11, 12A  and  12 B, a key  402  according to a fifth exemplary key construction of the invention is similar in many respects to the key  302  of the second exemplary key construction, as indicated by the use of corresponding reference numbers incremented by a value of 100. The primary difference between the key  402  and the key  302  is in the design of the retraction control member. In particular, a crushable element  416 , made from a relatively rigid yet collapsible foam, or other readily crushable material, is used in lieu of a breakable element. The housing  404  is the same design used for the housing  4  of the first exemplary key construction. The key well  414  of the housing  404  thus includes both a bore  420  and a main guide way  422 . The key head  418  is the same design used for the key head  18  of the first exemplary key construction, and thus includes a stem  424 .  
         [0051]     As shown in  FIG. 12A , the crushable element  416  is shaped as a cylinder and resides within the key well&#39;s bore  420 . One end of the crushable element  416  is seated against the key well&#39;s back wall  426 . The other end of the crushable element  416  bears against the end face of the key head&#39;s stem  424  and supports the key head  418  against slideable movement toward the back of the key well  414 . The crushable element  416  thus acts as a retraction control member that maintains the key pattern  432  in an operational extension position until a tampering force is applied.  
         [0052]     As shown in  FIG. 12B , when a tampering force is applied to the key pattern  432 , the crushable element  416  will collapse within the bore  420 . This will allow the key head  418  to slide toward the back of the key well  414 . The key pattern  432  will thereby retract to a non-operational retraction position. Note that because the crushable element  416  is used in lieu of a biasing element, the key pattern  432  will tend to remain in a retraction position after the tampering force is removed, rendering the key  402  inoperable even for authorized use with a matching security fastener.  
         [0053]     Accordingly, a key with a retractable key pattern has been shown and described according to several exemplary constructions. While various embodiments have been disclosed, many other variations would also be possible within the scope of the invention. For example, although various designs for implementing a retraction control function have been set forth, it should be apparent to persons skilled in the art in light of the teachings herein that there are innumerable design alternatives that could also be used. Examples include but are not limited to the use of retention elements that operate along the sides of the key well, such as ball detent mechanisms, deformable or breakable retaining rings or bushings, and flanges that are either separately attached or integrally formed on the key head or the key well, etc. Another design approach would be to establish an interference fit between the key head and the sides of the key well. Obtaining a proper interference fit with the required breakaway force could be aided by providing knurling on the key head or the key well, providing a deformable bushing between the key head and the key well, or by forming the stem of the key head as a slotted tube that is compressed by the key well side walls (or by an insert in the key well). Tapering the key well side walls or forming a chamfer therein (or providing a tapered or chamfered insert in the key well) could be used to apply a compressive force on the key head that increases as the key pattern retracts.  
         [0054]     In view of these and many other potential alternative design possibilities, it should be understood that the invention is not to be in any way limited except in accordance with the spirit of the appended claims and their equivalents.