Patent Publication Number: US-7707864-B1

Title: Locking device

Description:
RELATED APPLICATIONS 
   This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 60/602,164, entitled “HIGH SECURITY LOCKING APPARATUS AND METHODS,” filed on Aug. 17, 2004, which is herein incorporated by reference in its entirety. 

   BACKGROUND OF INVENTION 
   1. Field of Invention 
   The invention relates generally to locking devices, and in particular, to the design and manufacture of locks. 
   2. Discussion of Related Art 
   A key-based lock is a mechanical fastening device which may be used on a door, vehicle, or container, for example, in order to prevent access to anyone without a correct key. Most modern locks employ a conventional “pin and tumbler” system to recognize when a correct key has been inserted into a lock. A conventional lock typically includes a plug (e.g., a cylinder)  20 , a housing  22  (into which the plug fits) and a plurality of movable elements. Pairs of key pins and movable elements  28  (e.g., drive pins) are associated with one another. The pairs are disposed vertically with the key pin  26  below the moveable element  28  which engages the top of the key pin  26  in a shaft  30  which is present in the plug  20  and the housing  22 . Springs in each shaft bias the associated moveable element  28  in the direction of the key pin  26 . The moveable elements  28  push on the associated key pin  26  to maintain the position of the key pin  26  and the moveable element  28 . Both the key pin  26  and the moveable element  28  may vary in length, however, in most conventional locks, the moveable elements  28  are typically all of the same length. 
   When no key is inserted in the conventional pin and tumbler lock, the key pin  26  is completely inside the plug  20 , while the moveable element  28  is partially in the plug  20  and partially in the housing  22 . The position of the moveable elements  28  keeps the plug  20  from turning (e.g., rotating). Thus, when no key (or the incorrect key) is inserted in the lock, the moveable elements  28  substantially fix the position of the plug  20  within the housing  22 . 
   When a key is inserted in a conventional lock, the series of notches in the key push the pairs of key pins  26  and moveable elements  28  upward by varying amounts. An incorrect key moves at least one pair of key pins  26  and moveable elements  28  an incorrect amount such that either: 1) the pair is not moved far enough (i.e., the moveable element  28  continues to extend into both the housing  22  and the plug  20 ); or 2) the pair is moved too far upward (i.e., the key pin  26  extends into both the housing  22  and the plug  20 ). 
   A correct key moves each pair of key pins  26  and moveable elements  28  upward just enough so that an abutment surface occurring where the key pin  26  contacts the moveable element  28  aligns with the space where the plug  20  and the housing  22  meet (this boundary between the plug  20  and the housing  22  may be referred to as a shear line  38 ). Accordingly, a correct key moves the pairs of key pins  26  and moveable elements  28  into a position where all of the moveable elements  28  are inserted completely in the housing  22 , while all of the key pins  26  rest completely in the plug  20 . Thus, with no key pins  26  or moveable elements  28  interfering with a rotation of the plug  20  in the housing  22 , the plug  20  rotates freely about an axis of rotation, and the bolt or locking device is able to move. Conventional locks are typically employed in a locking system where the plug  20  is mechanically connected to a cam, which in turn operates a spring to engage and disengage a latch. 
   Although locks are used for security purposes, the conventional lock may be opened without a key (e.g., the lock may be picked) thereby reducing or eliminating the effectiveness of the lock. Lock picking takes advantage of manufacturing tolerances and manufacturing defects present in virtually all conventional locks. These tolerances and defects allow the plug  20  to be rotated slightly in the housing  22  even when the lock is locked. Consequently, each moveable element  28  may rest on the shear line  38  when the abutment surface of a pair of key pins  26  and moveable elements  28  is aligned with the shear line  38  and the rotation of the plug  20  in the locked position is forced by an amount allowed by the manufacturing tolerance and/or defect. Lock pickers typically employ a tension wrench (i.e., a tensor) and a pick to pick a lock. In practice, the tension wrench is inserted into the keyhole and twisted slightly. The twisting of the wrench acts to rotate the plug  20  slightly, owing to the small spaces left in the shafts between the edges of the moveable elements  28  and the plug  20  (these are the manufacturing tolerances/defects referred to above). The rotation creates a ledge along the shear line  38  on which the moveable elements  28  can rest. The moveable element  28  rests on a ledge created by the portion of the outer surface of the plug  20  located at the radially inward end of the portion of the shaft  30  within the housing  22 . The lock picker has in effect offset the portion of the shaft  30  in the housing  22  and the portion of the shaft  30  in the plug  20 , i.e., the shaft in the housing  22  is no longer coaxially located with the shaft in the plug  20 . 
   The pick is applied to each pair of key pins  26  and moveable elements  28  so that each moveable element  28  resides entirely within the housing  22  while resting on the ledges provided by the plug  20  at the shear line  38 . The key pins  26  are then allowed to drop while a rotational force remains applied to the plug  20 . If the proper amount of torque is applied, the key pins  26  fall back into the plug  20 , while the Moveable elements  28  are caught on the ledge created by the slightly rotated plug  20 . If this is accomplished, there are no longer any pins binding the plug  20  to the cylinder housing  22  and the plug can freely rotate as though the correct key had been used, i.e., the lock is unlocked. 
   Some known locks have been created with additional security features in an attempt to improve the security offered by the conventional lock designs. One such lock design is described in U.S. Pat. Nos. 5,289,709 and 6,718,807. The lock design described therein includes a side bar and rotating pins. 
   An example is illustrated in  FIG. 1 . Here, the key pins have a valley  54  cut into the side, and the bottom edges  56  of the key pins (the part that contacts the key) are not horizontal (as in most locks), but are instead beveled to a range of angles. The proper key also has beveled teeth designed to match the beveled edge of the key pin in such a way as to rotate the pins to the proper orientation. This rotation aligns the valleys in the side of the key pins with extensions  58  extending from the side bar  44 . When the extensions do not lie in the valleys, the side bar is pushed out slightly, so that it lies between the plug and the cylinder housing. This prevents the plug from rotating, just as the pins do. When the pins are all rotated correctly, the protrusions from the side bar all lie in the valleys in the key pins, and the side bar moves out of the way, allowing the plug to rotate and the lock to open (assuming, of course, that the pins have been raised to the appropriate heights). 
   Although such designs may improve the security of the lock in view of some traditional lock-picking approaches, these designs may be successfully picked by employing other methods of lock picking. One such method, which has been reported, is the employment of a diamond rake bent at a 15 degree angle, which rakes both the pin heights and the pin rotations at the same time. Another reported method is the use of a bumping device which consists of a key with all its teeth cut to the maximum depth, whose beveling matches that of the correct key. The ‘bump key’ is then hit with some force to bump the key pins in the same manner as a lock gun, while holding the key pins at the correct rotational alignment. Thus, while these designs may increase the security of a lock, they may still be picked by an individual skilled in the craft of lock picking. 
   Another known variation in some conventional locks includes “mushroom” moveable elements, which, in one version, have a bottom that is shaped like an upside-down mushroom (other shapes are also possible for the “mushroom” moveable element, as shown at the top of  FIG. 2 ). All these configurations are sometimes referred to, generally as “mushroom drivers.” In conventional locks with “mushroom” moveable elements, as shown in  FIG. 2 , the mushroom-shaped portion  28 A of the moveable element  28  may get caught between the housing  22  and the plug  20  if too much torque is applied when picking. While these pins may make the picking process more difficult, they present only a marginal increase in difficulty, especially if one employs mechanical or electrical devices such as pick guns. 
   SUMMARY OF INVENTION 
   In one aspect, a lock includes a housing with a plug located in the housing. The plug is adapted to rotate in the housing about an axis. The lock also includes a moveable element comprising a first region with a first diameter, a second region with a second diameter that is less than the first diameter, and a third region with a third diameter that is less than the second diameter. The moveable element is located at least partly in the housing. The moveable element is adapted to move in an axis of motion substantially radial relative to the axis of the plug and to prevent rotation of the plug when the moveable element is in a first position along the axis of motion and to allow rotation of the plug when the moveable element is in a second position along the axis of motion. The second region is located closer to the axis of the plug than the first region, and at least a part of the third region is located closer to the axis of the plug than the second region. 
   In one embodiment, an insert provides a shaft located in the plug and the moveable element is adapted to move in the insert. According to a further embodiment, a second region is located closer to the axis of the plug than a first region, and a protrusion, with a third diameter that is greater than the second diameter and less than the first diameter, protrudes from the second region. In a version of this embodiment, a difference between one half of the first diameter and one half of the third diameter is greater than twice a difference between one half the diameter of the shaft and one half of the first diameter. 
   In another aspect, a lock includes a housing, a plug adapted to rotate in the housing about an axis, and a moveable element that travels in a first shaft located in the housing and in a second shaft located in the plug, the moveable element including a protrusion, where a method of manufacture includes acts of inserting into the second shaft an insert including at least one recess adapted to receive the protrusion, locating the moveable element in one of the first shaft or the second shaft, and locating the plug in the housing. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The accompanying drawings are not intended to be drawn to scale. For purposes of clarity, not every component may be labeled in every drawing. In the drawings: 
       FIGS. 1A-1B  are views of another prior art lock; 
       FIG. 2  is a view of yet another prior art lock; 
       FIG. 3  is a view of a moveable element in accordance with one embodiment of the invention; 
       FIG. 4  is a view of an embodiment of a moveable element installed in a lock in accordance with an embodiment of the invention; 
       FIG. 5  is a view of another embodiment of a moveable element installed in a lock in accordance with an embodiment of the invention; 
       FIG. 6  is a view of the lock shown in  FIG. 5  with the moveable element in a different position; 
       FIG. 7  is a view of yet another embodiment of a moveable element installed in a lock in accordance with an embodiment of the invention; 
       FIG. 8  is a view of the moveable element and lock according to the embodiment of  FIG. 7 ; 
       FIG. 9  is a view of the moveable element and lock according to the embodiment of  FIG. 4 ; 
       FIG. 10  is a view of a further embodiment of a moveable element and a lock according to an embodiment of the invention; 
       FIG. 11  is a view of the moveable element and a lock according to the embodiments of  FIG. 10 ; 
       FIG. 12  is a view of multiple embodiments of moveable elements according to embodiments of the invention; 
       FIG. 13  is a sectional view of a moveable element according to a still further embodiment of the invention; 
       FIG. 14  is a view of an embodiment of a moveable element according to an embodiment of the invention; 
       FIG. 15  is a view of another embodiment of a moveable element according to an embodiment of the invention; 
       FIG. 16  is a view of yet another embodiment of a moveable element according to an embodiment of the invention; 
       FIG. 17  is a view of a further embodiment of a moveable element according to an embodiment of the invention; 
       FIG. 18  is a view of another embodiment of a moveable element according to an embodiment of the invention; and 
       FIG. 19  is a view of yet another embodiment of a moveable element according to an embodiment of the invention. 
   

   DETAILED DESCRIPTION 
   This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing”, “involving”, and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
   In view of the foregoing, various embodiments of the present disclosure are directed to a lock designed to substantially impede known lock-picking techniques. 
   According to various embodiments of the present invention, a locking apparatus employs one or more moveable elements (e.g., driver pins) designed to improve the security of the locking apparatus. In one or more versions of these embodiments, the modified moveable elements are employed in a lock that uses a pin and tumbler design. In some embodiments, one or more modified shaft(s) also are employed, in a complimentary arrangement with the modified moveable element(s), to prevent the lock from being opened without the correct key, i.e., rendering the lock substantially “pick-proof.” 
   Methods of manufacturing a lock in accordance with one or more embodiments of the invention are also described. 
   In one embodiment, the moveable elements are modified so as to create a multi-tiered moveable element having at least one ledge between different regions of the moveable element. In a version of this embodiment, a two-tiered moveable element including two portions with respectively different diameters may be formed so as to create a ledge on the pin. A variety of structures, however, may be employed alone or in combination to provide a moveable element with one or more ledges. As is described in greater detail below, these ledges can be included to increase the security of a lock employing the moveable element, i.e., they make the lock more difficult to pick. 
   Referring to  FIG. 3 , a moveable element  300  in accordance with an embodiment of the invention is shown. The moveable element  300  includes a first region  280 , and a second region  280 A. The first region  280  has a first diameter D 1  and the second region  280 A has a second diameter D 2 . The moveable element  300  also includes protrusions  46 , a ledge  50 , and an alignment element  52 . 
   According to one embodiment, the moveable element travels in an axis of motion A 1 . For example, if the moveable element  300  of  FIG. 3  is employed in a lock using a pin and tumbler design, the axis of motion A 1  is linear. Further, where a lock having a plug is employed as described, the axis of motion A 1  of the moveable element may be radial or substantially radial relative to an axis of rotation A 2  of the plug  20 . In one embodiment, the axis of motion A 1  is located coaxially with a central longitudinal axis of the moveable element  300 . 
   The ledge  50  is formed where the first region  280  meets the second region  280 A because the two regions do not have the same diameter. The first region  280  may also be referred to as the head of the moveable element  300 . As shown in  FIG. 3 , the first region  280  is located a greater distance from the axis of rotation A 2  than is the second region  280 A. Thus, in one embodiment, a surface  282  formed at the radially outward end of the moveable element  300  (relative to the axis of rotation) engages a spring that applies a radially inward force on the moveable element  300 . Further, an abutment surface  284  is located at the opposite end of the moveable element  300 . That is, the abutment surface  284  is located at the radially inward end of the moveable element  300  relative to the axis of motion A 2 . In one embodiment, the abutment surface  284  engages a surface of a key pin that is associated with the moveable element  300 . 
   The moveable element  300  may include any number of regions (e.g.,  280 ,  280 A) of varying diameters. In one embodiment, the diameter (e.g., D 1 , D 2 ) of each successive region (e.g.,  280 ,  280 A) decreases as the moveable element  300  is traversed from the radially outward end (e.g., surface  282 ) to the radially inward end (e.g., surface  284 ). That is, any region located radially inward of the first region  280  has a smaller diameter than the diameter D 1  of first region  280 , and any region located inward of the second region  280 A has a smaller diameter than the diameter D 2  of the second region  280 A. As a result, multiple ledges (e.g., ledge  50 ) can be formed by the moveable element  300 . 
   In one embodiment, the protrusion  46  extends substantially radially outward from the second region  280 A relative to the axis of motion A 1 . In a version of this embodiment, the protrusion is a bar that extends through the moveable element  300 . In another version, the protrusion  46  includes two separate elements  46 A and  46 B. In yet another version, the protrusion  46  includes only one of the elements  46 A and  46 B. In one embodiment, the diameter of the protrusion  46  is less than at least one region (e.g., first region  280 ) located radially outward of the protrusion relative to the axis of rotation A 2 . In a version of this embodiment, the diameter of the protrusion  46  is greater than any region that is located at least partly radially inward of the protrusion (e.g., second region  280 A). A protrusion  46  may provide another region on the moveable element  300 . Thus, in one embodiment of the moveable element  300  of  FIG. 3 , the location of the protrusion  46  is a third region having a third diameter measured from the radially outward end of the element  46 A (relative to the axis of motion A 1 ) to the radially outward end of the element  46 B. 
   In one embodiment, the protrusion extends 360° annularly about the axis of motion. For example, in one embodiment, the protrusion projects in disc like fashion 360° around the moveable element  300 . In other embodiments, the protrusion  46  protrudes from the moveable element  300  continuously about the axis of motion A 1  for less than 360° annularly. That is, according to one embodiment, there is a single element (e.g., element  46 A or element  46 B) that extends in disc like fashion part of the way around the moveable element  300 . In yet another embodiment, the protrusion  46  protrudes from the moveable element  300  at discontinuous locations about the axis of motion, creating one or more elements that extend in fan like fashion part or all of the way around the moveable element  300 . 
   The alignment element  52  may take the form of a projection, a channel, a groove, a recess or any other structure that prevents or limit the movement (e.g., rotation about the A 1  axis) of the moveable element  300  within, for example, a shaft within which the moveable element  300  travels. That is, the alignment element  52  acts to maintain the proper orientation of the moveable element  300  within a lock. The alignment element  52  may by itself limit the movement of the moveable element  300 . In addition, in one embodiment, the alignment element  52  is combined with one or more additional elements to maintain the proper orientation of the moveable element  300  within a lock. (One such embodiment is illustrated from a top-down perspective in  FIG. 13 .) For example, the element  52  may be a projection that is retained within a channel located in the wall of a shaft within which the moveable element  300  travels. In one or more embodiments, alignment elements (e.g., elements  52 ,  52 A) are included in each of the moveable element  300  and the plug  20 . As shown in  FIG. 13 , the plug  20  includes a first alignment element  52  (e.g., a longitudinal projection), and the moveable element  300  includes a second alignment element  52 A (e.g., a longitudinal groove). 
   Although having a generally cylindrical shape as shown in  FIG. 3 , the moveable element  300  may be any shape that allows the moveable element  300  to prevent a lock from being opened when the moveable element  300  is at a first position on the axis of motion A 1  while allowing the lock to be opened when the moveable element  300  is at a second position on the axis of motion A 1 . For example, a cross section of the various regions (e.g.,  280 ,  280 A) of the moveable element  300  may be any geometric shape including circular, elliptical, or any polygon. Further, the various regions (e.g.,  280 ,  280 A) need not have the same shape, for example, region  280  may have a circular cross section while region  280 A may have a cross section that is triangular in shape. 
   The terms diameter and radius are not intended to imply that the dimension being referred to is a dimension of an object of any particular shape (e.g., cylindrical, circular). In other words, diameters can be measured for a moveable element  300  having a cross section of any shape including irregular, polygonal or circular. Thus, when referring to the dimensions at a protrusion (e.g., protrusion  46 ) the diameter is the width of the moveable element  300  at the protrusion. The term radius generally refers to a distance from an axis located at the center of the moveable element to the most radially outward point (relative to the axis of the moveable element) of the object being measured, e.g., the moveable element or a part thereof (a region, a protrusion, etc.). 
     FIG. 4  shows another embodiment of a moveable element  301  located in a lock  80 . A shaft  30  is provided in the housing of the lock  80 . In addition, a shaft  30 A is provided in the plug  82 . The shaft  30  and the shaft  30 A are coaxially located when the lock  80  is in the locked position.  FIG. 4  also illustrates a recess  48  located in a wall  84  of the shaft  30 A in the plug  82 . As is described in greater detail below, the recess  48  acts to capture the protrusion  46  when an attempt is made to pick the lock  80 . 
     FIG. 5  illustrates a cross-sectional view of a lock  80  according to one embodiment of the invention. In  FIG. 5 , a moveable element  302  is disposed in shaft  30  in the housing  22  and shaft  30 A in the plug  20  in a manner similar to that discussed above in connection with conventional locks. A key pin  26  also is disposed in the shaft  30 A below the moveable element  302 . 
   In the embodiment of  FIG. 5 , however, the moveable element  302  includes multiple regions (e.g., regions  280 ,  280 A) with different diameters. Thus, a two-tiered moveable element is provided with a ledge  50  located at a point where the two regions (e.g.,  280   280 A) meet. Such a multi-tiered moveable element effectively requires a lock to be picked twice, once to move all the moveable elements  302  such that a first ledge  50  is located at the shear line  38 , as shown in  FIG. 6 , then to further move each moveable element  302  in the lock  80  so that the radially inward surface  284  is positioned at the shear line  38  between the housing  22  and the plug  20 . The multi-tiered moveable elements  302  cannot be picked to the shear line immediately because the manufacturing tolerances/defects that allow a conventional lock to be picked (as discussed above) are not large enough to allow a rotation of the plug sufficient to rest the radially inward surface  284  of the multi-tiered moveable element  302  onto the edge of the shear line  38  created by the slightly rotated plug  20  until all the moveable elements  302  are positioned such that the first ledge  50  is located at the shear line  38 . Thus, a lock  80  employing a multi-tiered moveable element  302  including two or more regions having different diameters provides one approach for improving the pick-resistance of a locking system. 
   Referring to  FIG. 14 , an embodiment of a moveable element is shown which includes three regions, for example, the first region  280  with a first diameter, the second region  280 A with a second diameter, and a third region  280 B with a third diameter. As a result, two ledges are formed by the moveable element  308 , a first ledge  50 A and a second ledge  50 B. Also, the radially inward surface  284  is present on one side of the third region  280 B in the embodiment shown in  FIG. 14 . 
   Examples of an axis of motion A 1 , an axis of rotation A 2 , and a direction of plug rotation R according to one embodiment of the invention are included in  FIG. 6  for reference. 
   According to other embodiments, as illustrated in  FIGS. 3 ,  4  and  7 , one or more protrusions  46  may be included in a region  280 A of a multi-tiered moveable element. According to a further embodiment, the protrusion  46  extends around the entire perimeter of the region  280 A and forms a disc-like ring around the multi-tiered moveable element (e.g., moveable element  304 ). In another embodiment, the protrusion  46  does not extend around the entire perimeter of the region  280 A, but instead may include multiple discontinuous protrusions (e.g., elements  46 A,  46 B) oriented transversely to a center axis  68  of the moveable element  304 . In yet another embodiment, the protrusion  46  may be shaped as a bar, cylinder, or any other shape consistent with a function of the protrusion  46 , for example, generally to make a lock more difficult to open without the correct key. Each protrusion may extend substantially perpendicular from an axis  68  of the moveable element. In still another embodiment, the protrusion may be placed on only one side of the pin, forming a semicircle in the case of the disk-like embodiment or a single bar in the case of the bar-shaped protrusion embodiment. In a still further embodiment, for example, as shown in  FIG. 7 , a radial dimension  66  of the protrusion  46  (i.e., the distance from the central axis  68  of the moveable element  304  to the most radially outward end of the protrusion  46 ) is less than a radial dimension  70  of the region  280  of moveable element  304 . Regardless of the type of protrusion  46  that may be included with the moveable element (e.g., moveable element  304 ), the protrusion  46  may form a separate region with the radial dimension  66 , or it may be included in a region (e.g., region  280 A) where the region has a radial dimension  71  and the protrusion has radial dimension  66 . In addition, the region  280 A where a protrusion is located may be further defined by a first region radially outward of the protrusion  46  and a second region radially inward of the protrusion (relative to, for example, the axis of rotation). In one embodiment, a protrusion  46  is defined as an area with a diameter that is greater than the diameter of an area located radially inward of the protrusion and greater than the diameter of an area located radially outward of the protrusion. In view of the foregoing, again it should be appreciated that a number of different arrangements are possible for implementing one or more protrusions on one or more regions of a moveable element according to various embodiments of the present invention. 
   In the embodiments shown in  FIGS. 4 and 7 , a recess  48  is made in the wall  84  located in the shaft  30 A. The recess  48  is capable of receiving the protrusion  46 . The recess  48  may extend for any distance into the plug  82 . For example, the recess  48  may go through the plug  82 , and may also be made through the cylinder housing. In versions of these embodiments, the protrusion  46  is located on the moveable element (e.g.,  301 ,  304 ) so that the protrusion  46  is located adjacent to and is aligned with the corresponding recess  48  when the ledge  50  is aligned with the shear line  38 , as illustrated in  FIG. 7 . 
   As shown in  FIG. 8 , an attempt to rest the ledge  50  on a surface  88  of the plug  82  by further rotation of the plug  82  in the direction R (this being necessary to position a second moveable element (e.g., moveable element  301 ,  304 ) into the same configuration as illustrated in  FIG. 7 , or to continue picking the lock when all of the moveable elements (e.g.,  301 ,  304 ) are positioned as is illustrated in  FIG. 7 ) is likely to result in the protrusion  46  being captured within the recess  48 . As a result, an individual employing a traditional lock-picking approach is faced with a moveable element  304  secured in a position which prevents the plug  82  from being rotated to an unlocked position because the moveable element  304  is unable to move along the axis A 1  in the shaft ( 30 ,  30 A) and is positioned between the plug  82  and the housing  22 . The individual is now forced to rotate the plug  82  in a clockwise direction relative to the axis A 2  (i.e., remove the applied torque). Rotating the plug  82  backwards in order to unbind the protrusions  46  from the recesses  48  in the plug  82  is likely to result in one or more moveable elements  304  falling back into the shaft  30  in a fully unpicked position, e.g., radially inward. As a result, the individual may be forced to begin the lock-picking process again. More specifically, because the plug  82  cannot rotate far enough in the direction R to reach the radially inward surface of the protrusions  46 , the moveable elements  304  cannot be moved to the point where surface  284  rests on surface  88  without first resting all of the moveable elements  304  in the lock  80  to their respective ledges, e.g., ledge  50 . 
   According to one embodiment, the protrusions  46  have a shorter radial dimension  66  (relative to the axis  68 ) than a radial dimension  70  of the region  280  of the moveable element  304 , such that a difference between a radius of a first region  280  and a radius of a protrusion  46  (the difference being labeled  73  in  FIG. 7 ) is greater than twice a difference between a radius  75  of the shaft  30  and the radius  70  of the first region  280 . As a result, the protrusions  48  cannot rest on the surface  88  before the ledge  50  rests on the surface  88 . That is, because only a limited rotation of the plug is possible (an amount determined by the smallest manufacturing tolerance/defect) while the moveable elements  304  bind the plug  82  to the housing  22 , the widest section of the moveable element rests on the plug  82  at the shear line  38  first. Thus, the ledge  50  will rest on the surface  88  when the radial dimension  66  of a protrusion  46  is smaller than a radial dimension  70  of the region  280 , such that a difference between a radius of a first region  280  and a radius of a protrusion  46  is greater than twice a difference between a radius  75  of the shaft  30  and the radius  70  of the first region  280 . In one embodiment, the largest difference between the radius  75  of the shaft  30  and the radius  70  of the first region  280  is selected from among all the moveable elements and respective shafts combinations found in the lock. That is, the difference is determined for each moveable element relative to the shaft that it travels in. Then, the difference between the radius of the first region  280  and the radius of the protrusion  46  (i.e., dimension  73 ) on each moveable element is determined based on the largest difference. As mentioned above, the difference between the radial dimension  66  and the dimension of the first region  280  is identified with reference character  73 . 
     FIG. 9  shows a lock  80  in accordance with the embodiment shown in  FIG. 4  where a protrusion  46  is engaged in a recess (e.g., a recess  48 ) so that the moveable element  301  is prevented from moving further in the axis of motion A 1 . 
   In yet another embodiment, as shown in  FIG. 10 , multiple protrusions  46  are present on one or more moveable elements  306 . While  FIG. 10  shows two such protrusions  46 , it should be appreciated that the invention is not limited in this respect, as moveable elements  306  according to different embodiments may include three or more protrusions  46 . Further, according to one embodiment, a lock  80  employs multiple moveable elements  306  each with one or more protrusions  46 . Where each moveable element  306  includes multiple protrusions (e.g., protrusions  49 A and  49 B), the protrusions may be of equal length on each moveable element  306 . That is, a first protrusion  49 A located on a first moveable element  306  has a length equal to a first protrusion located on a second moveable element  306  in the lock  80 , and a second protrusion  49 B located on the first moveable element has a length equal to a second protrusion  49 B located on the second moveable element. In a version of this embodiment, the first protrusion on each moveable element  306  (e.g., protrusion  49 A) is located an equal distance from a reference point on the moveable element  306  (e.g., the ledge  50  or the surface  284 ), and a second protrusion on each moveable element  306  (e.g., protrusion  49 B) is located an equal distance from the reference point. 
   According to one embodiment, multiple protrusions  46  located on a moveable element  306  equidistant from the ledge  50  have the same radius  66  (e.g., a maximum radius). Thus, in one embodiment, protrusion  49 A is a first plurality of protrusions located further radially outward (relative to the axis of rotation A 2 ) than protrusion  49 B which in this embodiment is a second plurality of protrusions. In a version of this embodiment, the protrusions  49 A include a plurality of protrusions which each have a length (e.g., a radius) that is smaller than a length of region  280  and greater than the length of the plurality of protrusions  49 B. A similar approach (i.e., protrusions  46  with graduated lengths according to their respective distance from surface  284  or ledge  50 ) can also be employed with a series of single protrusions located at various locations along the moveable element  306 . In addition, a combination of single and multiple protrusions may be employed. 
   As also illustrated in  FIG. 10 , the shaft  30 A may include multiple recesses  48  (e.g., located in the plug  90 ) which can accept multiple protrusions (e.g., protrusions  49 A and  49 B). In one embodiment, two recesses  48  are located in the wall  84  of the shaft  30 A so that both protrusions  49 A and  49 B can be captured in separate recesses  48 A and  48 B at the same time according to, for example, the alignment shown in  FIG. 11 . In a version of this embodiment, the distance between the two protrusions is the same as the distance between the protrusion  49 A and the ledge  50 . As a result, the recess  48 A accepts the protrusion  49 B when the protrusion  49 A is at the shear line  38  and the plug  90  is rotated in the direction R. In addition, the recess  48 A accepts the protrusion  49 A when the ledge  50  is at the shear line  38 . 
   Where multiple protrusions at different radial distances along the axis A 1  from ledge  50  are located on a moveable element in a lock, an individual attempting to open the lock may be required to rest each successive protrusion (e.g., protrusions  49 A and  49 B) on a surface (e.g., surface  88 ) at the shear line  38  before the lock can be opened without the correct key. Thus, in one embodiment employing multiple moveable elements  306 , the longest protrusion on each moveable element must be moved to the shear line  38  before the next longest protrusion on each moveable element is moved to the shear line  38 . This process (e.g., the gradual movement of the moveable element  306  away from the axis of rotation A 2 ) is repeated in order to rest the surface  284  of each moveable element at the shear line  38 . In addition, where the length of protrusions vary from one moveable element to the next moveable element, attempts to open the lock require that each moveable element be moved in succession beginning with the moveable element with the longest protrusion, assuming a lock with no difference in defect from shaft to shaft. 
   If an individual attempts to circumvent the sequential approach described here (e.g., a shorter protrusion  49 B is moved to the shear line  38  first), a moveable element  306  with a longer protrusion will have that protrusion move into a recess  48  when torque is applied to the plug  90 . In theory, if the moveable element with the longest protrusion were picked first, then very careful rotation of the plug might allow an individual to rest the protrusion  46  on the shear line edge  38  without any of the protrusions on the other moveable elements  306  moving into a recess  48 . This procedure could possibly be repeated for the moveable element  306  with the next longest protrusion, and so on until all the moveable elements are moved to the level of the protrusions (e.g., protrusions  49 B). 
   It should be appreciated that if the manufacturing tolerances/defects in the lock  80  do not allow for movement of the moveable elements  306  in the order prescribed by the varying radial dimensions of the protrusions, the lock may prove impossible to pick. Such a result may be achieved because, as each moveable element  306  is moved to a position where it rests on the plug  90 , the plug  90  rotates farther from a rest position with applied torque. These small rotations, which are associated with the inherent tolerances/defects in the lock, may be sufficient to cause the protrusions of the moveable elements  306  resting on the shear line  38  to move into corresponding recesses. When this occurs it may become impossible to open the lock without the correct key because one or more protrusions may prevent the surface  284  of a moveable element  306  from being moved to the shear line  38 . 
   In the multi-protrusion embodiments illustrated in  FIGS. 10 and 11 , the lock inhibits operation without a key (i.e., lock-picking) in at least the following four ways. 
   First, the configuration of the region  280 A prevents the plug  90  from being rotated far enough to allow the surface  284  of the moveable elements  306  to rest on the surface  88  at the shear line  38 . Thus, each moveable element  306  is moved to a position where the ledge  50  aligns with the shear line  38  before the plug  90  can be rotated far enough to move the moveable element further such that a protrusion (e.g., one of protrusions  49 A and  49 B) can rest on the surface  88 . In such an embodiment, a moveable element  306  cannot be moved directly from a first position where the ledge  50  is on the surface  88  to a second position where the surface  284  is on the surface  88  because of the interruption provided by the protrusions (as is described in further detail below). 
   Second, when a moveable element is moved to a position where a ledge  50  is at the shear line  38 , the protrusions are adjacent to the recesses (e.g.,  48 A and  48 B). If any rotational torque is applied to the plug  90  at this point, the protrusions  49 A,  49 B are captured in the recesses to prevent further movement of the moveable elements along the axis A 1 . 
   Third, if one were to successfully move each of the moveable elements  306  to a position where the ledge  50  rests on the surface  88  without allowing the upper protrusions to engage a recess (this would take a great deal of precision and would have to be done by hand), the moveable element would then have to be moved to a position where the upper protrusion  49 A rests on the surface  88 . Where the lower protrusions  49 B vary in length from moveable element to moveable element, the moveable elements would then have to be moved in a specific order (i.e. an ordering scheme will be created), starting with the moveable element with the longest lower protrusion  49 B, assuming a lock with no difference in tolerance/defect from shaft to shaft. If the proper order is not selected, the moveable elements  306  that include the longer lower protrusions  49 B will have their lower protrusion engage a recess. As a result, those moveable elements will be bound to the plug  90  and prevent any further movement in the direction of axis A 1  of those moveable elements. 
   Fourth, if the above problems are overcome and the lower protrusions of each moveable element are located at the shear line  38 , the moveable elements must still be moved such that surfaces  284  rests on the surface  88 . 
   The above described embodiments may also prevent the successful use of both raking and pick guns. In particular, the torque required to use a pick gun or a rake is likely to cause the protrusions to move into the recesses at some point during the lock-picking process, thus thwarting the attempt at picking. Even if the pick gun or rake operation allowed movement of the moveable elements, rakes and pick guns act to “set” pins (that is, accomplish the task of getting the moveable elements to rest at the shear line  38 ) in an order determined by the tolerances/defects in the lock, which is not necessarily the order that the moveable elements must be moved because of the length-varying protrusions. Furthermore, it should be noted that width of the key pins will prevent rotation of the lock beyond the defect during the picking process, assuming the radius of the key pin is the same or larger than the radius of the widest portion of the moveable element, i.e., the first region  280 . If the radius of the key pin is greater than the widest portion of the moveable element, the tolerance/defect upon which the length of the various protrusions is determined may be based on the tolerance/defect associated with a key pin and its associated shaft. Thus, in the common arsenal of lock picking methods, this leaves only the individual picking of each moveable element individually as a viable alternative, and, as described above, even this method is presented with challenges that may prove impossible to overcome. 
   If all the moveable elements are locked into place by the protrusions, there may be a method by which the relative key pin heights could be measured and in order to reproduce a key using this information. However, this would only work if the ledges of the multi-tiered moveable elements were cut to the same height. 
   In yet other embodiments of a lock according to the invention, as illustrated in  FIGS. 12A , B, and C, the ledges  50 A,  50 B and  50 C of the multi-tiered moveable elements are cut at various heights (relative to surface  284 ) to prevent this method from working. In addition, according to one embodiment, the protrusions may sit at different distances from the surface of the moveable elements. 
   In yet another embodiment, a lock includes a plurality of multi-tiered moveable elements, where a distance L from a surface  284  to a ledge  50  of each moveable element varies, and first or second protrusions  49 A,  49 B are different lengths. A method of manufacture may include the manufacture of a variety of moveable elements whereby a quantity of the types of moveable elements exceeds the maximum number of moveable elements to be used in a given lock. For example, twenty types of moveable elements could be made, each type having a unique height of the ledge (as measured from the surface  284 ) and a unique length of the protrusion closest to the surface  284 , as the basis for a seven pin lock. Seven moveable elements can be drawn arbitrarily from this pool of twenty types for any given lock to make it difficult to predict in advance any features of a particular lock according to the present invention. In general, according to one version of any of the embodiments discussed herein, one or more sets of protrusions may be designed to vary in length. 
   In yet another embodiment, as shown in  FIG. 13  (which is a top cross-section of a moveable element  300 ), an alignment element (e.g., a guide)  52  also may be cut into a portion of the moveable element  300  and fitted into the shaft  30  in the housing  22  such that the moveable element cannot rotate, but instead moves only in the axis of motion A 1 . Such an approach may ensure that the protrusions  46  stay rotationally aligned with the recesses  48 . 
   As previously mentioned, manufacturing tolerances and/or manufacturing defects typically provide enough freedom of movement of a plug  82  locked in a housing  22  to allow conventional locks to be picked. More specifically (referring again to  FIG. 7 ), some excess space is available in the shaft  30  between the moveable element  304  and the walls  84  of the shaft  30  when the plug  82  is in an “at-rest” position with no torque applied to it. A plug  82  can be rotated to the extent that this excess space allows. That is, the moveable element  304  will be forced in a direction perpendicular to the axis  68  by the rotation of the plug  82  until the moveable element is “pinned” against the wall  84  of the shaft  30 . At this point, traditional approaches rely on the ability to move the moveable element  304  so that the surface  88  on the plug  82  is moved to engage the surface  284  on the moveable element at the shear line  38 . This can be prevented, however, with embodiments described herein by providing a moveable element where a difference between a radius of a first region  280  and a radius of a protrusion  46  is greater than twice a difference between a radius of the shaft  30  and the radius of the first region  280 . Provided that the axis  68  is coaxially located with the center of the shaft  30  (i.e., the moveable element  304  is centered in the shaft), such a result is achieved, for example, in the embodiment shown in  FIG. 14 , when the radial distance  70  less the radial distance  66  is greater than twice as large as the radial distance  75  less the radial distance  70 . 
   The embodiment described above results in the rotation of the plug  82  being stopped by the pinned moveable element  304  before the plug has traveled far enough to align the surface  88  with a radially inward surface of the second region. A similar relationship between the radial distance  66  and the radial distance  71  can also be employed in the manner described above. Further, where a moveable element  304  includes multiple regions of varying diameters that form multiple ledges  50  such a relationship can be employed at each region, i.e., each region can include a protrusion where the difference between the radius of a first region with a protrusion and the radius of a protrusion on a second region is greater than twice a difference between the radius of the shaft and the radius of the first region. 
   In a further embodiment where a lock with multiple moveable elements with multiple protrusions protruding from the same region is employed, the difference between a first protrusion and a second protrusion protruding from the region is larger than the largest difference between two differences between a radius of a shaft  30  and the maximum radius of the corresponding moveable element (where the relationship between the diameter of shaft  30  and the maximum radius of the corresponding moveable element is determined for each moveable element/shaft combination in the lock). 
   Referring to  FIG. 15 , an insert  340  may be employed to adapt the plug  92  to include one or more recesses  48 . An inside diameter of the insert  340  forms the shaft  30 A that the moveable element  310  is located in when at least part of the moveable element  310  is located in the plug  92  as shown in  FIG. 15 . Accordingly, the plug  92  is adapted to include openings to receive the inserts  340 . 
   A lock  100  employing the insert  340  may be manufactured efficiently because any recesses  48  need not be manufactured directly in the plug  92 . Instead, in one embodiment, an insert  340  is manufactured with one or more recesses  48  and inserted in the plug  92 . The moveable element is located in either the shaft  30  or the shaft  30 A and the plug is located in the housing. The shafts  30 ,  30 A are coaxially located when the lock  100  is in an at rest position; therefore, in one embodiment, the moveable element  310  is located in the housing  22  and plug  92 , after the plug  92  is installed in the housing  22  and the shafts  30 ,  30 A are aligned. The insert  340  need not be cylindrical in shape but may be any shape through which a moveable element can travel where the insert  340  includes one or more recesses  48  that can engage a protrusion protruding from the moveable element. Additionally, an insert  340  can be employed in any of the embodiments described herein. 
   The approaches described thus far can be employed in yet further embodiments as illustrated in  FIGS. 15-18 . For example, where three or more regions (e.g., regions  280 ,  280 A,  280 B) are employed, one or more protrusions (e.g., protrusions  46 A,  46 B) can protrude from one of the regions (e.g., region  280 B in  FIG. 15 ) or from a plurality of regions (e.g., regions  280 A and  280 B in  FIG. 16 ). Further, as shown in  FIGS. 17 and 18 , a plurality of protrusions (e.g., protrusions  46 A,  46 B,  46 C) may extend from one or more regions of a moveable element (e.g., moveable elements  314 ,  316 ). The protrusions  46 A,  46 B and  46 C may each be the same diameter as in  FIG. 17  or the protrusions  46 A,  46 B and  46 C may be of different diameters as in  FIG. 18 . 
   It should be clear from the foregoing description that moveable elements are designed to prevent rotation of the plug in the lock. In one more embodiment, however, a small amount of freedom of movement (including freedom of rotational movement) remains as a result of manufacturing tolerances/defects. 
   It should be appreciated that all combinations of the foregoing concepts are contemplated as being part of the inventive subject matter disclosed herein. Having thus described several illustrative embodiments, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of this disclosure. While some examples presented herein involve specific combinations of functions or structural elements, it should be understood that those functions and elements may be combined in other ways according to the present invention to accomplish the same or different objectives. In particular, acts, elements, and features discussed in connection with one embodiment are not intended to be excluded from similar or other roles in other embodiments. Accordingly, the foregoing description and attached drawings are by way of example only, and are not intended to be limiting. 
   Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.