Abstract:
A lock is disclosed having a set of pin tumblers in the lock cylinder in addition to the lever tumblers to prevent rotation of the cylinder without a key to release the driver pins that engage the cylinder and prevent rotation. The key has pin tumbler cuts on the edge of the key. Because the pin tumblers and the related pin tumbler cuts on the edge of key can be spaced randomly along the length of the key and because the lengths of the pin tumblers and the depths of the pin tumbler cuts in the key can be random, the ability to create a duplicate key rendered substantially more difficult then a key with only lever tumbler cuts.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a deadbolt lock, and more particularly to a prison cell deadbolt lock that incorporates both pin tumblers and lever tumblers to increase the difficulty of fabricating a duplicate key for the lock. 
       BACKGROUND OF THE INVENTION 
       [0002]    A prison cell lock conventionally is a deadbolt lock that incorporates lever tumblers for the lock. A key for such a conventional deadbolt lock with lever tumblers has key cuts that are rectangular and have depths that are multiples of usually the same increment. In the environment of a prison cell lock, prison inmates may be able to “read” the key cuts and thereby fashion a duplicate key. Moreover, a soft material may be used to acquire impressions of the key grooves and the key cut positions within the cylinder of the lock. 
       SUMMARY OF THE INVENTION 
       [0003]    In order to solve the problems associated with the possible fashioning of a duplicate key by “reading” the key cuts from observing the key and/or by taking an impression of the keyway of the lock cylinder, the lock of the present invention incorporates a set of pin tumblers in the cylinder in addition to the lever tumblers. The pin tumblers engage pin tumbler cuts on the edge of the key. Because the pin tumblers and the related pin tumbler cuts on the edge of key can be spaced randomly along the length of the key and because the lengths of the pin tumblers and the depths of the pin tumbler cuts on the edge of the key can be random, the ability to create a duplicate key by “reading” the pin tumbler cuts on the edge of the key including reading the spacing and depth of the pin tumbler cuts on the edge of the key is greatly reduced. Moreover, taking an impression of the keyway to ascertain the configuration of the pin tumbler cuts on the edge of the key is rendered substantially more difficult. 
         [0004]    Further objects, features and advantages will become apparent upon consideration of the following detailed description of the invention when taken in conjunction with the drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a perspective view of a lock and key in accordance with the present invention. 
           [0006]      FIG. 2A-2E  is a series of front elevation views of the lock, with the lock cover removed, showing the progression of positions of the lock from a locked position ( FIG. 2A ) to an unlocked position ( FIG. 2E ) in accordance with the present invention. 
           [0007]      FIGS. 3A-3C  is a series of section views of the lock showing the progression of positions of the lock from a locked position ( FIG. 3A ) to an unlocked position ( FIG. 3C ) in accordance with the present invention as seen along line  3 A- 3 A of  FIG. 2A , along line  3 B- 3 B of  FIG. 2C , and along line  3 C- 3 C of  FIG. 2E . 
           [0008]      FIG. 4  is a detail side elevation view of the cylinder of the lock in accordance with the present invention. 
           [0009]      FIG. 5  is a detail bottom plan view of the cylinder of the lock in accordance with the present invention. 
           [0010]      FIG. 6  is a detail front elevation view of the cylinder of the lock in accordance with the present invention. 
           [0011]      FIG. 7  is a detail side elevation view of the driver pin housing of the lock in accordance with the present invention. 
           [0012]      FIG. 8  is a section elevation view of the driver pin housing of the lock in accordance with the present invention as seen along line  8 - 8  of  FIG. 7 . 
           [0013]      FIG. 9  is a detail elevation view of the driver pin housing and the cylinder, partially in section, of the lock in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    Turning to  FIG. 1 , a lock  10  is shown comprising a housing  12  with a cover  14 . The cover  14  is held onto the housing  12  by means of a mounting screw  16 . The housing  12  and the cover  14  may be mounted to a prison cell door by means of bolts (not shown) inserted through mounting holes  18 . The bolts not only serve to hold the lock  10  on the prison cell door, but the bolts also serve to hold the housing  12  and the cover  14  together. 
         [0015]    A lock bolt  20  with a connected lock plate  22  is slidably mounted within the housing  12 . The lock bolt  20  has bearing surfaces  26  that engage the edges of the cover  14  to maintain alignment of the lock bolt within the housing  12 . The lock bolt plate  22  also has a slot  24  that engages a pivot post  40  to provide a bearing surface to align the lock plate  22  and the lock bolt  20  within the housing  12 . In addition, the lock bolt plate  22  has a lug  28  and a profiled follower surface  30 . The functions of the lug  28  and the profiled follower surface  30  will be described in greater detail below. 
         [0016]    A cylinder  32  with a keyway  36  is mounted for rotation within the housing  12 . The cylinder  32  includes a driving cam  34  that engages the profiled follower surface  30  of the lock bolt plate  22  in order to drive the lock plate  22  and the lock bolt  20  between an unlocked position ( FIGS. 2E and 3C ) and a locked position ( FIGS. 2A and 3A ) as the cylinder  32  is rotated by means of a key  66  inserted in the keyway  36 . The key  66  has a flat blade  74  with edges  71  and  72 . The edge  71  has a series of conventional lever tumbler cuts  68  that are rectangular and have depths that are multiples of usually the same increment. In accordance with the present invention, the opposite edge  72  of the flat blade  74  has a series of pin tumbler cuts  70  in the form of cylindrical bores. The spacing of the pin tumbler cuts  70  along the length of the key  66  may vary, and the depths of the pin tumbler cuts  70  may also vary. In addition, a number of dummy pin tumbler cuts  70  may be provided to disguise the number of pin tumblers that are actually incorporated into the cylinder  32  as will be described in greater detail below. 
         [0017]    As best shown in  FIGS. 4 and 9 , the cylinder  32  has a set of pin tumblers  52 . For purposes of illustration, three individual pin tumblers  52  are shown, but more or less pin tumblers may be used. The pin tumblers  52  are slideably mounted within radially extending pin tumbler chambers  54 . With reference to  FIGS. 2A-2E ,  8 , and  9 , a driver pin housing  58  is mounted in the housing  12  adjacent the cylinder  32 . The driver pin housing  58  has three driver pins  56  slideably mounted in driver pin chambers  57  ( FIG. 8 ). While three driver pins  56  are illustrated, more or less driver pins  56  may be used to match the number of pin tumblers  52  within the cylinder  32 . The driver pins  56  are biased to extend outward from the driver pin housing  58  by means of driver pin springs  60  that are mounted in the driver pin chambers  57  by means of setscrews  62 . A shear line  64  is defined where the driver pins  56  engage the pin tumbler chambers  54  of the cylinder  32 . 
         [0018]    With reference to  FIGS. 2A-2E  and  3 A- 3 C, a set of lever tumblers  38  are pivotally mounted on lever tumbler pivot post  40  within the housing  12 . Lever tumbler springs  42  bias the lever tumblers  38  in a clockwise direction and into engagement with the cylinder  32 . For the purposes of explanation, six lever tumblers  38  are illustrated. Consequently, the key  66  has six lever tumbler cuts  68  to match the six lever tumblers  38 . Each lever tumbler  38  has a lever tumbler engaging surface  46  that engages the lever tumbler cuts  68  of the key  66 . Each lever tumbler  38  also has a lever tumbler stop surface  48  that engages the lug  28  on the slide plate  22  in order to keep the lock bolt  20  from retracting into the housing  12  from the locked position ( FIGS. 2A and 3A ) to the unlock position ( FIGS. 2E and 3C ). Each lever tumbler  38  also has a lever tumbler notch  44  that engages the lug  28  on the slide plate  22  in order to keep the lock bolt  20  from moving from the unlock position to the locked position. Further, each lever tumbler  38  has a lever tumbler gap  50  communicating with the lever tumbler notch  44  to allow the lug  28  to move from the locked position ( FIGS. 2A and 3A ) to the unlock position ( FIGS. 2E and 3C ) when the lever tumblers  38  are aligned by means of the lever tumbler cuts  68  on the key  66 . 
         [0019]    The operation of the lock  10  is best understood by reference to  FIGS. 2A-2E  and  3 A- 3 C.  FIGS. 2A and 3A  illustrate the lock  10  in its locked position. In  FIG. 2A , the key  66  is not inserted in the keyway  36 , but in  FIG. 3A , the key  66  is inserted in the keyway  36  so that the relationship between the lever tumbler cuts  68  on the key  66  and the lever tumbler key engaging surfaces  46  can be shown. As shown in  FIGS. 2A and 3A , the cylinder  32  is in its initial locked position with the driver pins  56  extending outwardly from the driver pin housing  58  and into the pin tumbler chambers  54  ( FIG. 9 ) thereby preventing rotation of the cylinder  32 . As further shown in  FIG. 9 , once the key  66  is inserted into the keyway  36 , the pin tumblers  52  are forced by the action of the pin tumbler cuts  70  into engagement with the driver pins  56 . The engagement of the pin tumblers  52  with the driver pins  56  aligns the ends of the driver pins  56  with the shear line  64  so that the cylinder  32  is released for rotation, in this case in a counterclockwise direction. 
         [0020]    As the cylinder  32  rotates counterclockwise to the position shown in  FIG. 2B , the lever tumbler cuts  68  of the key  66  begin to engage the lever tumbler key engaging surfaces  46  of the lever tumblers  38 . The driving cam  34  of the cylinder  32  also engages the profiled follower surface  30  of the lock bolt plate  22  and thereby begins pulling the lock bolt  20  into the housing  12 . 
         [0021]    Further rotation of the cylinder  32  to the position shown in  FIGS. 2C and 3B , causes the lever tumbler cuts  68  of the key  66  to move the lever tumblers  38  into a position in which the lever tumbler gaps  50  of each of the lever tumblers  38  align so that the lug  28  of the lock bolt plate  22  can be pulled through the gaps  50  into the lever tumbler notches  44  by the camming action of the driving cam  34  of the cylinder  32  engaging the profiled follower surface  30  of the lock bolt plate  22 . 
         [0022]    As the cylinder  32  rotates to the position shown in  FIG. 2D , the lock bolt  20  is completely retracted into the housing  12 , and the lug  28  has passed through the lever tumbler gaps  50  and is within the lever tumbler notches  44 . 
         [0023]    When the cylinder  32  rotates to the fully unlocked position shown in  FIGS. 2E and 3C , the lever tumbler cuts  68  in the key  66  have allowed the lever tumblers  38  to return to their initial position thereby capturing the lug  28  within the lever tumbler notches  44  of each of the lever tumblers  38 . Consequently, the lock bolt  20  cannot be moved from the unlocked position to the locked position without the use of the key  66  to release the lug  28  from the lever tumbler notches  44 . 
         [0024]    While this invention has been described with reference to preferred embodiments thereof, it is to be understood that variations and modifications can be affected within the spirit and scope of the invention as described herein and as described in the appended claims.