CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application 61/681,546 filed Aug. 9, 2012, the contents of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to locks, and more particularly, but not exclusively, relates to disc tumbler locks. 
     BACKGROUND 
     Conventional disc-style cylinders suffer from a variety of disadvantages and problems including misalignment of the lock discs and susceptibility to lock-picking. For example, the discs can easily become misaligned, in which case the user must rotate the key back and forth to re-align the discs. Furthermore, there is no indication to the user that the key is fully inserted, and the key and contacted discs will turn through the first portion of their travel (usually 90 degrees) even when the key is only partially inserted. Because the key turns, the user might incorrectly assume that that key has been inserted correctly, but the lock will not open due to the partial insertion of the key. This can lead to user frustration and confusion, and often results in the user applying too much force which may cause the key to break. Additionally, in conventional disc-style cylinders, it is possible for a skilled lock-picker to feel the change in tension as one or more discs rotate. A release of tension typically indicates the correct position for a disc, thereby increasing susceptibility of the lock to be picked. 
     There is therefore a need for unique and inventive apparatuses, systems and methods to address various disadvantages and problems associated with conventional disc-style cylinders. 
     SUMMARY 
     Unique locking cylinders are disclosed. In an exemplary embodiment, a locking cylinder includes a locking disc, a driver disc and a catch. The catch selectively prevents rotation of the locking disc. The driver disc is operable to move the catch between a first position in which the catch prevents rotation of the locking disc, and a second position in which the catch does not prevent rotation of the locking disc. In the second position, the catch may apply pressure to the locking disc. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is an elevational illustration of a lock assembly according to an embodiment of the present invention in a first state or operational configuration. 
         FIG. 2  is an elevational illustration of the lock assembly of  FIG. 1  in a second state or operational configuration. 
         FIG. 3  is a perspective illustration of a subassembly of the lock assembly of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is hereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
     With reference to  FIGS. 1-3 , an illustrative locking system  100  according to one form of the invention generally includes a tumbler system having a locking bar  102  that interacts with disc stack  104  including a plurality of locking discs  110  and at least one driving disc  120 , a plug housing  130  at least partially surrounding the disc stack  104 , a movable catch  140 , and a biasing mechanism  142  that exerts a biasing force against the movable catch  140  to engage the movable catch  140  against the disc stack  104 . Although a particular type of a tumbler system is illustrate in  FIGS. 1-3 , it should be understood that other types and configurations of tumbler systems are also contemplated for use in association with the locking system  100  including, for example, a pin tumbler system. Furthermore, while the movable catch  140  is illustrated as a pivoting member that is pivotally movable between one or more operational positions, it should be understood that the movable catch  140  may be movable in additional or alternative directions. 
     In the illustrated embodiment, the locking discs  110  and the driving disc  120  are coaxially aligned along an axial centerline or axis C, and together form at least a portion of the disc stack  104 . While five locking discs  110  are shown in the illustrated embodiment, it should be appreciated that the disc stack  104  may include more or fewer locking discs  110 . Each locking disc  110  is generally cylindrical in shape, and may include a circumferential outer surface  111 , a groove or indentation  112  formed in the circumferential outer surface  111 , a keyway  114  positioned generally along the axial centerline C, a radial protrusion  116  projecting radially beyond the circumferential outer surface  111 , and a hooked-shaped recess  118  extending between the circumferential outer surface  111  and the radial protrusion  116 . In the illustrated embodiment, the radial protrusion  116  has a first width w 1  at its radially distal extent (i.e., farthest from the axial centerline C) and a smaller second width w 2  at its radially proximal extent (i.e., closest to the axial centerline C). As should be appreciated, the hooked-shaped recess  118  provides the radial protrusion  116  with an undercut region. 
     The groove/indentation  112  is sized and configured to receive the locking bar  102  ( FIG. 2 ), and the keyway  114  is sized and configured to receive a corresponding mechanical key (not shown). In an aligned operational configuration/position of the locking discs  110 , the grooves/indentations  112  are axially aligned with one another and/or are axially aligned with the axial channel  132  in the plug housing  130 . In a misaligned operational configuration/position of the locking discs  110 , the grooves/indentations  112  are not aligned with one another and/or are not aligned with the axial channel  132  in the plug housing  130 . In the illustrated embodiment, the radial protrusion  116  generally includes an arcuate outer surface  115  extending generally in a circumferential direction, and an interference surface  117  extending inwardly from the arcuate outer surface toward the circumferential outer surface  111 . 
     In the illustrated embodiment, the driving disc  120  is configured substantially similar to the locking discs  110 , having a generally cylindrical shape and including a circumferential outer surface  121 , a groove or indentation  122  formed in the circumferential outer surface  121  and sized and configured to receive the locking bar  102 , and a keyway  124  positioned generally along the axial centerline C and configured to receive the corresponding mechanical key (not shown). In an aligned operational configuration/position of the driving disc  120 , the groove/indentation  122  is axially aligned with the axial channel  132  in the plug housing  130 . In a misaligned operational configuration/position of the driving disc  120 , the groove/indentation  122  is not axially aligned with the axial channel  132  in the plug housing  130 . The driving disc  120  also includes a radial protrusion  126  projecting radially beyond the circumferential outer surface  121 . The radial protrusion  126  generally includes an arcuate outer surface  125  extending generally in a circumferential direction, and a contact or bearing surface  127  extending inwardly from the arcuate outer surface  125  toward the circumferential outer surface  121 . 
     In the illustrated embodiment, each radial protrusion  116  of the locking discs  110  and the radial protrusion  126  of the driving disc  120  defines a generally uniform outer radius. In other words, the distance between the axial centerline C of disc stack  104  and the outermost portion of each radial protrusion  116 ,  126  is substantially equal. However, it is also contemplated that one or more of the radial protrusions  116 ,  126  may have a greater or lesser outer radius relative to one or more of the other radial protrusions. For example, the outer radius of radial protrusion  126  may be greater than the outer radius of the radial protrusions  116 . Furthermore, while the arcuate outer surfaces  115 ,  125  of the radial protrusions  116 ,  126  each define a substantially uniform arc radius (corresponding to the outer radius of protrusions  116 ,  126 ), in other embodiments, the arcuate outer surfaces  115 ,  125  may not necessarily define of a uniform arc radius. 
     As described in further detail below, the radial protrusions  116  of the locking discs  110  interact with the movable catch/pivoting member  140  to prevent rotation of the locking discs  110  about the axial centerline C when the pivoting member  140  is in a closed position or operational configuration ( FIG. 1 ), and the radial protrusion  126  of the driving disc  120  is configured to interact with the pivoting member  140  and pivot the pivoting member  140  away from and out of the closed position or operational configuration ( FIGS. 2 and 3 ). In the illustrated embodiment, the driver disc  120  including the groove/indentation  122  provides a more compact system because the component that disengages the alignment mechanism is also one of the discs which interacts with the tumbler system, and no additional cylinder length is necessary to implement the system. However, in other embodiments, the driving disc  120  need not necessarily include the groove/indentation  122 . In such embodiments, the tumbler system may be configured to engage only the locking discs  110 , and not the driving disc  120 . 
     In the disc stack  104 , the drive disc  120  may be positioned behind the locking discs  110 . That is to say, when a mechanical key is inserted into the keyway of the locking system  100 , the shank of the key will pass through the keyway  114  of each of the locking discs  110  before entering the keyway  124  of the driving disc  120 . This configuration, combined with the fact that the locking discs  110  cannot rotate unless the driving disc  120  has pivotally displaced the pivoting member  140  away from and out of the closed position, prevents the locking discs  110  from rotating in the absence of full insertion of a properly configured key into the keyway of the locking system  100 . However, in other embodiments, some or all of the locking discs  110  or other locking elements may be positioned behind the driving disc  120 . 
     In the illustrated embodiment, the plug housing  130  has a generally cylindrical configuration and is sized and shaped to retain the disc stack  104  within the interior region of the plug housing  130 . Additionally, the plug housing  130  includes an outer surface  131  and an axial channel  132  configured to receive the locking bar  102 . When the plug housing  130  is installed into a corresponding lock shell (not illustrated), the axial channel  132  is aligned with a channel formed in the shell, thereby forming a chamber in which the locking bar  102  is positioned. In embodiments which utilize pin tumblers, the axial channel  132  may be replaced by individual tumbler shafts. 
     When at least one of the grooves or indentations  112 ,  122  of the discs  110 ,  120  is not properly aligned with the axial channel  132  of the plug body  130 , the locking bar  102  will contact the corresponding circumferential outer surface  111 ,  121  and will be blocked from radial displacement into the grooves/indentations  112 ,  122 . This configuration defines a locked state of the locking system  100  ( FIG. 1 ) in which the locking bar  102  is positioned partially in axial channel  132 , and also protrudes beyond the circumferential outer surface  131 . In the locked state, the locking bar  102  provides an interference between the plug body  130  and the lock shell, thereby preventing the plug body  130  from rotating with respect to the lock shell. Regardless of the type of tumbler system used, if any of the grooves/indentations  112 ,  122  are not aligned with the axial channel  132 , a portion of the tumbler system will protrude radially beyond the circumferential outer surface  131 , thereby maintaining the locking system  100  in the locked state. 
     When each of the grooves/indentations  112 ,  122  are aligned with the axial channel  132  of the plug body  130 , the locking bar  102  is free to travel radially inward into each of the aligned grooves/indentations  112 ,  122 . This configuration defines an unlocked state of the locking system  100  ( FIG. 2 ) in which the locking bar  102  is positioned partially in the axial channel  132 , and partially in the aligned grooves/indentations  112 ,  122 . In the unlocked state, the locking bar  102  does not provide an interference between the plug body  130  and the lock shell, and the plug body  130  is therefore free to rotate with respect to the lock shell. In embodiments which utilize additional or alternative tumbler systems, the unlocked state will allow the plug body to rotate with respect to the lock shell. For example, if the tumbler system includes pin tumblers, the driven pins will not protrude beyond outer circumferential surface  131 . 
     In the illustrated embodiment, the pivoting member  140  rotates about a pivot point or axis  141  that may be arranged generally parallel with the axial centerline C, and is biased toward a closed position ( FIG. 1 ) via the biasing mechanism  142 . The pivot point/axis  141  may be maintained in a stationary position with respect to the plug housing  130 , and may be coupled to the lock shell. In the illustrated embodiment, the biasing mechanism  142  includes a biasing member  143  which exerts a biasing force onto the pivoting member  140  through a connection or bearing member  144 . The bearing member  144  may be integral with, attached to, or positioned in contact with the pivoting member  140 . In some embodiments, the biasing member  143  may directly engage the pivoting member  140 , thereby eliminating the bearing member  144 . In the illustrate embodiment, the pivoting member  140  is constrained to pivotal movement. However, in other embodiments, the pivoting member  140  may additionally or alternatively be movable in another direction. 
     The pivoting member  140  may extend generally in an axial direction along disc stack  104  (i.e., along the axial centerline C), and includes an arcuate inner bearing surface  145 , an interference contact surface  147  that terminates at a tip portion  148 , and an extended distal portion  149 . The inner bearing surface  145  is configured to be displaced along the outer surfaces  115 ,  125  of the radial protrusions  116 ,  126  once the pivoting member  140  has been moved away from and out of the closed position. In the illustrated embodiment, the inner bearing surface  145  is of a constant arc radius that generally corresponds to the outer arc radius of the outer surfaces  115 ,  125  of the radial protrusions  116 ,  126 . It is also contemplated that the inner bearing surface  145  may have a varying arc radius, for example, if the outer surfaces  115 ,  125  of the radial protrusions  116 ,  126  do not define a substantially uniform outer arc radius. 
     As should be appreciated, the interference surface  147  of the pivoting member  140  is configured to prevent rotation of the locking discs  110  about the axial centerline C when the pivoting member  140  is in the closed position ( FIG. 1 ). In the closed position, the interference surface  147  of the pivoting member  140  is generally radially aligned with the interference surfaces  117  of the locking discs  110 , thereby blocking the rotational travel path of the radial protrusions  116  and preventing rotation of the locking discs  110 . Because the locking discs  110  cannot rotate, they will remain in an aligned position. If a user attempts to rotate one or more of the locking discs  110 , the interference surface  147  will engage the interference surface  117 , thereby preventing rotation of the locking disc. By maintaining the locking discs  110  in the aligned position until a proper key is fully inserted into the keyway of the locking system  100 , the locking system  100  not only alerts the user when the key is not fully inserted, but also obviates the need for a user to turn the key back and forth in order to realign the discs. 
     To reduce internal stresses resulting from a user applying excessive force to the key when the pivoting member  140  is in the closed position, it is desirable to increase the area of contact between the interference surfaces  117  and  147 . To this end, the radial protrusions  116  and the pivoting member  140  may be configured such that interference surfaces  117 ,  147  are substantially parallel to one another when they are positioned in contact with one another. Additionally, in the illustrated embodiment, each locking disc  110  is configured such that when the pivoting member  140  is in the closed position, the tip portion  148  is positioned at least partially within the hooked recesses  118  of the locking discs  110 , thereby increasing the area of contact between interference surfaces  117 ,  147 . It is also contemplated that the hooked recess  118  may be absent in one or more of locking discs  110 , in which case the tip portion  148  may contact the circumferential surface  111 . 
     The extension  149  of the pivoting member  140  is generally aligned in the axial direction with the driver disc  120 , and is configured to interact with the radial protrusion  126  of the driver disc  120 . While the extension  149  extends beyond the interference surface  147  substantially only along the curved arc defined by the pivoting member  140 , it is also contemplated that an extension may extend in a direction toward the radial protrusion  126 . When the driver disc  120  is rotated, the contact bearing surface  127  urges the extension  149  away from the axial centerline C, thereby pivotally displacing the pivoting member  140  away from and out of the closed position. 
     When the outer surface  115  of the locking discs  110  contacts the inner surface  145  of the pivoting member  140 , the pivoting member  140  will be positioned in an open position ( FIG. 2 ) wherein the interference surface  147  is no longer radially aligned with the interference surfaces  117  of the locking discs  110 , and the locking discs  110  are thereby free to rotate about the axial centerline C. When the pivoting member  140  is positioned in the open position, the biasing mechanism  142  continues to exert a biasing force onto the pivoting member  140 . This biasing force causes the inner bearing surface  145  to exert a radially inward force onto the outer surfaces  115 ,  125  of the radial protrusions  116 ,  126 , thereby resulting in a corresponding frictional force which resists rotation of the discs  110 ,  120  about the axial centerline C. This frictional force continues to resist rotation of the discs  110 ,  120 , even when the disc&#39;s groove/indentation  112 ,  122  is aligned with the axial channel  132  of the plug body  130 . The added frictional force increases the difficulty of sensing a change in resistive force, making it much more difficult for a person attempting to pick the lock to determine when the discs are in the proper position for unlocking of the lock system  100 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described, and that all changes and modifications that come within the spirit of the inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred, or more preferred used in the description indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.
A lock apparatus including a plurality of locking discs rotatable about a rotational axis between locked and unlocked states and each having a locking engagement surface, at least one driver disc rotatable about the rotational axis and having a driving engagement surface, a movable catch having a catch surface that abuts the locking engagement surface of the locking discs when the movable catch is in a locked position such that rotation of the locking discs is inhibited. The catch surface does not abut the locking engagement surface of the locking discs when the movable catch is in an unlocked position such that rotation of the locking discs is enabled. The driving engagement surface of the driver disc engages a portion of the movable catch upon rotation of the driver disc to thereby displace the movable catch from the locked position to the unlocked position.