Abstract:
A tumbler pin lock includes an auxiliary locking mechanism including an auxiliary locking pin to provide enhance locking in addition to the locking provided by the tumbler pins so that the lock remains locked even if the tumblers are picked or bumped into their unlocked positions.

Description:
[0001]    This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application Ser. No. 61/039,864, filed Mar. 27, 2008, the disclosure of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to cylinder locks and particularly to pin tumbler cylinder locks with axial sliding detainers that provide a secondary locking mechanism in the cylinders. 
         [0004]    2. Discussion of the Background 
         [0005]    An ongoing problem for people using locks is other people trying to pick these locks. Pin tumbler locks, a traditional type of lock, are so common that one can buy tools specifically designed to pick a pin tumbler lock. At the same time, pin tumbler technology is well known, and consumers are comfortable with pin tumbler keys. As described below, many have looked to develop an improved lock that is less susceptible to lock picking. 
         [0006]    A. Sohm in U.S. Pat. No. 1,141,215 discloses a cylinder where the plug contains moveable wards, or sliders, that are pushed axially by the insertion of the key. The sliders have a key contact surface and a projecting blade that extends into the shell. The shell contains annular grooves that will accept the projecting blade when the sliders are correctly positioned by the key. When the blades are positioned within the annular grooves, the plug is free to turn. 
         [0007]    The moveable wards or sliders of this invention are primary locking elements in the cylinder. They also directly block the rotation of the plug within the shell. 
         [0008]    B. Perkut in German Pat. No. DE 2 828 343 teaches two locking concepts. The first one (see  FIG. 5 ) is of a moveable ward or slider that is very similar to the Sohm patent, but is used as a secondary locking mechanism in a pin tumbler cylinder. The slider  12 ′ has a blade  34  that extends into the shell and must be pushed by the key to an unlocked position, whereupon the blade is located in an annular ring  38  in the shell. This slider directly blocks the rotation of the plug within the shell. 
         [0009]    The second locking concept (see  FIGS. 1-4 ) also uses the slider as an auxiliary locking mechanism. The slider  12 , interfaces with a ball  20  that extends from the plug into the shell and blocks the rotation of the plug. The slider has a cavity  18  that will accept the ball when the slider is pushed to a correct axial position. When both the primary tumbler pins  106   a  and  106   b  and the slider are correctly aligned, the rotation of the plug forces the ball out of the shell into the plug and into the cavity  18  in the slider. Thus the plug can rotate freely. This slider provides an intermediary member, the ball, to block the rotation of the plug within the shell. However the curved shape of a ball will allow the plug to turn even if the slider is not precisely positioned. 
         [0010]    G. Brandt in U.S. Pat. No. 5,615,566 also discloses a cylinder where the plug contains an auxiliary locking element, or slider, in addition to the regular pin tumblers. The Brandt slider  16  has a projecting blade  54  that extends out the back side of the plug and fits into a notch  24  in the shell. When the slider is pushed to the rear-most position by the insertion of the key, the slider is pushed out of the notch in the shell, and if the tumbler pins are also correctly aligned, the plug is free to rotate. The slider directly blocks the plug from rotating within the shell. 
         [0011]    P. Field et al. in U.S. Pat. No. 6,477,875 discloses a cylinder where the plug contains sliders  24  or  24 ′ that move axially and provide tertiary locking mechanisms in the cylinder. The rotating pins must be correctly elevated for the shear line and also be rotationally aligned for the sidebar mechanism  16  or  16 ′ before the cylinder will unlock. Additionally, the sliders in the Field invention have projecting blades  32  or  32 ′ that are used to block the sidebar mechanism. The slider must be positioned at the correct axial location before the sidebar can contact the rotating pins. This slider blocks the motion of the sidebar in the plug. 
         [0012]    Additional detailed specifications of a sidebar cylinder with a P. Field et al. slider and the key interface is provided in U.S. Pat. No. 6,945,082. 
         [0013]    B. Field et al. in U.S. Pat. Application Publication 2007/0137272 teaches a cylinder that contains a sidebar  18  that is axially positioned by the side of a key. When moved to the correct position, the ends of the sidebar are at a location to allow the sidebar to cam into the plug and contact the side of the keyblade. If the key blade is configured with a shape corresponding to the edge of the sidebar  36 , the sidebar can move and allow the plug to rotate. The sliding sidebar directly blocks rotation of the plug in the shell. 
         [0014]    The inventor has found that these lock designs have room for improvement. In particular, these additional mechanisms require valuable space within a traditional pin and tumbler design, and thus require that locks incorporating these features must be large or, alternatively, if a large lock is not possible, these features must be foregone. 
       SUMMARY OF THE INVENTION 
       [0015]    It is an object of this invention to provide a secondary locking mechanism within a cylinder whereby the primary tumbler pins are left unchanged and the secondary mechanism will provide for additional master keying levels without changing the key hole in the cylinder. 
         [0016]    It is desirable to reduce the size and configuration of the components in a cylinder with an auxiliary slider mechanism, so that the mechanism can be used to key together, in the same key system, cylinders of various sizes and shapes. 
         [0017]    It is desirable to provide a new smaller secondary locking mechanism in a cylinder, so that the key that will operate a slider and sidebar cylinder will also operate in a cylinder without space to accommodate a sidebar mechanism, thus providing expanded keying systems. 
         [0018]    Aspects of the invention are embodied in a lock comprising a cylindrical plug having an axially-extending keyway adapted to receive a conforming key, a plurality of tumbler pins, an auxiliary locking pin, and a slider. The tumbler pins are disposed within radially-oriented tumbler pin holes formed in the cylindrical plug and adapted to control rotation of the cylindrical plug and are constructed and arranged to be engaged by a properly configured key inserted into the keyway and to be positioned by the key within their respective tumbler pin holes so as to permit the cylindrical plug to rotate. The auxiliary locking pin is disposed within the cylindrical plug and is moveable between a first position in which a portion of the auxiliary locking pin extends out of a hole formed in an outer wall of the cylindrical plug and a second position in which the auxiliary locking pin is retracted into the hole. The slider is disposed within the cylindrical plug and is moveable in an axial direction between a first position and a second position. The slider is constructed and arranged to be engaged by a cooperating key inserted into the keyway to move the slider from the first position to the second position, and the slider is operatively inter-engaged with the auxiliary locking pin such that the auxiliary locking pin is in its first position when the slider is in its first position and the auxiliary locking pin moves from its first position to its second position when the slider is moved from its first position to its second position. 
         [0019]    Further aspects of the invention are embodied in a lock comprising a cylindrical plug having an axially-extending keyway adapted to receive a conforming key, a plurality of tumbler pins, and an auxiliary locking pin. The tumbler pins are disposed within radially-oriented tumbler pin holes formed in the cylindrical plug and adapted to control rotation of the cylindrical plug and are constructed and arranged to be engaged by a properly configured key inserted into the keyway and to be positioned by the key within their respective tumbler pin holes so as to permit the cylindrical plug to rotate. The auxiliary locking pin is disposed within the cylindrical plug and is moveable between a first position in which a portion of the auxiliary locking pin extends out of a hole formed in an outer wall of the cylindrical plug and a second position in which the auxiliary locking pin is retracted into the hole. The auxiliary locking pin includes a key contact projection extending into the keyway and constructed and arranged to be engaged by a conforming key to move the auxiliary locking pin from its first position to its second position as the conforming key is inserted into the keyway. 
         [0020]    These and other features, aspects, and advantages of the present invention will become apparent to those skilled in the art after considering the following detailed description, appended claims and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is an exploded perspective view of a cylinder lock with an auxiliary locking mechanism according to one embodiment. 
           [0022]      FIG. 2  is a cross-sectional perspective view of the cylinder lock without a key inserted and with a slider and an auxiliary locking pin both in respective first positions. 
           [0023]      FIG. 3  is an end view of the cylinder lock without a key inserted. 
           [0024]      FIG. 4  is a side cross-sectional view of the cylinder lock along the line  4 - 4  in  FIG. 3  with the slider and the auxiliary locking pin both in respective first positions. 
           [0025]      FIG. 5  is a side view of the cylinder lock without a key inserted. 
           [0026]      FIG. 6  is an end cross-sectional view of the cylinder lock along the line  6 - 6  in  FIG. 5  with the slider and the auxiliary locking pin both in respective first positions. 
           [0027]      FIG. 7  is a cross-sectional perspective view of the cylinder lock with a key inserted into the lock and with the slider and the auxiliary locking pin both in respective second positions. 
           [0028]      FIG. 8  is an end view of the cylinder lock with a key inserted into the lock with the slider and the auxiliary locking pin both in respective second positions. 
           [0029]      FIG. 9  is a side cross-sectional view of the cylinder lock along the line  9 - 9  in  FIG. 8  with the slider and the auxiliary locking pin both in respective second positions. 
           [0030]      FIG. 10  is a side view of the cylinder lock with a key inserted. 
           [0031]      FIG. 11  is an end cross-sectional view of the cylinder lock along the line  11 - 11  in  FIG. 10  with the slider and the auxiliary locking pin both in respective second positions. 
           [0032]      FIG. 12  is a perspective view of a key for use in the cylinder lock of the present invention. 
           [0033]      FIG. 13  is a rear perspective view of a slider for use in an auxiliary locking mechanism according to the present invention. 
           [0034]      FIG. 14  is a front perspective view of the slider. 
           [0035]      FIG. 15  is a bottom rear perspective view of the slider. 
           [0036]      FIG. 16  is a top plan view of a cylinder plug of an alternative embodiment cylinder lock. 
           [0037]      FIG. 17  is a bottom plan view of the cylinder plug shown in  FIG. 16 . 
           [0038]      FIG. 18  is a side view of a cylinder lock. 
           [0039]      FIG. 19  is an end cross-sectional view of the cylinder lock along the line  19 - 19  in  FIG. 18  showing an alternative embodiment without a key inserted and with an auxiliary locking pin in a first position. 
           [0040]      FIG. 20  is a side view of a cylinder lock with a key inserted 
           [0041]      FIG. 21  is an end cross-sectional view of the cylinder lock along the line  21 - 21  in  FIG. 20  showing the alternative embodiment with the auxiliary locking pin in a second position. 
           [0042]      FIG. 22  is an end cross-sectional view of the cylinder lock along the line  19 - 19  in  FIG. 18  showing the alternative embodiment with the auxiliary locking pin in a third position. 
           [0043]      FIG. 23  is a side view of a key for use in the alternative embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0044]      FIG. 1  illustrates an exploded view of a cylinder lock  10  according to one embodiment of the invention. Cylinder lock  10  includes a cylindrical plug  70 , a control sleeve  20 , a shell  40 , a faceplate  100 , and an auxiliary locking mechanism  120  The cylinder lock  10  shown in  FIG. 1  is of the type known as a small format interchangeable core cylinder. This is for the sole purpose of illustrating an embodiment of the inventive lock incorporating an auxiliary locking mechanism and is not intended to be limiting, as the auxiliary locking mechanism could be incorporated into other locks as well. 
         [0045]    The shell  40  includes an upper section  42  and a lower section  52 . Lower section  52  has a hollow, generally cylindrical configuration. The upper section  42  has a solid, generally cylindrical configuration and includes tumbler pin holes  44  which receive conventional tumbler pins  90  (i.e., pin stacks). Upper section  42  includes a recess  46  extending along the axial length of the shell  40  along the bottom of the upper section  42 . The shell  40  further includes a flanged protrusion  50 , configured to interlock with recessed portion  104  (e.g., a dovetail slot) formed in the faceplate  100 . The lower section  52  of the shell  40  is hollow to receive the control sleeve  20  and the plug  70 . Service holes  54  formed in the bottom of the lower section  52  of the shell  40  allow a locksmith to remove tumblers from the tumbler holes  44  to re-key the lock  10 . A cutaway section  56  is formed in the rear of the lower section  52  of the shell  40 . 
         [0046]    The control sleeve  20  is housed inside the shell  40 . Control sleeve  20  has a hollow, cylindrical configuration with a raised portion  22 . Tumbler holes  24  formed in the raised portion  22  of the control sleeve  20  align with tumbler holes  44  formed in the shell  40  when the control sleeve  20  is inserted into the shell  40 , such that tumblers  90  inside may move up and down to control rotation of the plug  70  in a conventional manner. Service holes  30  formed in the bottom of the control sleeve  20  align with service holes  54  formed in the shell  40 . The control sleeve  20  includes a control lug  26  along part of one side of the raised portion  22 . Raised portion  22  of the control sleeve  20  is received within the recess  46  formed in the upper section  42  of the shell  40 , and control lug  26  interlocks with the bottom of the upper section  42  of the shell  40  to lock the control sleeve  20  within the shell  40 . The control sleeve  20  further includes an auxiliary locking pin hole  32 . 
         [0047]    The faceplate  100  includes a guard  102  with a recess  104  (e.g., a dovetail slot) which mates with the flanged protrusion  50  of the shell  40  and a ring  106  which rests against the opening of the lower section  52  of the shell  40 . 
         [0048]    The plug  70  is mounted for axial rotation within the control sleeve  20 , which is disposed within the lower section  52  of the shell  40 . Tumbler holes  72  are formed in the plug  70  and communicate with a keyway  80  formed axially into the plug  70 . Plug  70  further includes an auxiliary locking pin hole  78 . Tumblers  90  disposed within the tumbler holes  72  operate along with a key in a conventional manner to control rotation of the plug  70 . This rotating action is generally used to release a latching mechanism (not shown). A retainer groove  74  formed in the rear end of the plug  70  receives a retainer clip  76  for securing the plug  70  within the sleeve  20  and shell  40 . 
         [0049]    Pin stacks  90  of various bottom pins  92 , master wafers, top pins  96 , and springs  94  are positioned in the tumbler holes  72 ,  24 , and  44 . Arrangements of spring loaded pins provide master keying capability and are well known in the lock art. 
         [0050]    The head  86  of the plug  70  has a stepped perimeter which mates with the ring  106  on the faceplate  100 . The head  86  of the plug  70  provides the entry to a keyway  80 . The entry has formed keyway guides  82  which extend across the face of the entry. These guides, formed by the depressions, may be useful in guiding a key (shown later) into the keyway  80  by redirecting the force of the oncoming key along the face of the depression such that the key is aligned with the keyway  80 . 
         [0051]    The cylinder plug  70  of the small format interchangeable core cylinder shown includes two longitudinally extending blind bores  88  (see  FIGS. 2 ,  4  and  9 ) bored parallel to the keyway  80  from the rear portion of the barrel of the cylinder plug  70 . One bore  88  is formed on each side of the keyway  80 , and the two bores  88  engage with corresponding prongs of a tailpiece (not shown), all of which are rotatably disposed in the cylinder shell  40 , to operate the lock mechanism as the key turns. 
         [0052]    The auxiliary locking mechanism  120  includes an auxiliary locking pin  122 , a pin spring  134 , a pin-actuating slider  136 , and a slider spring  152 . Further details of the auxiliary locking mechanism  120  are shown in  FIGS. 2 ,  4 ,  6 ,  7 ,  9  and  11 . 
         [0053]    The auxiliary locking mechanism  120  is housed inside the plug  70 . More specifically, the slider  136  and slider spring  152  are disposed within an axially arranged slider cavity  160 , and the locking pin  122  and the pin spring  134  are disposed with a pin cavity  170  formed generally a right angle to the slider cavity  160  (See  FIGS. 4 and 9 ). The slider  136  is biased by spring  152  disposed between a back end of the slider  136  and a back end of the cavity  160  opposite the forward end of the slider cavity  160  (i.e., toward the head  86  of the plug  70 ). 
         [0054]    The auxiliary locking pin  122  includes an upper shaft  124 , which is surrounded by the pin spring  134 , and a lower point, or tip,  128  that is in contact with the slider  136 . The auxiliary locking mechanism  120  effects auxiliary locking by the top  126  of the upper shaft  124  extending through auxiliary locking hole  78  and  32  (formed in the plug  70  and the control sleeve  20 , respectively) into gap  48  defined within recess  46  adjacent the raised portion  22  (see  FIGS. 4 and 6 ). The locking pin  122  then resists rotation of the plug  70  by contacting the sides of hole  32 . The auxiliary locking pin  122  must provide enough strength to resist a rotational force upon the plug  70 . In particular, if a lock  10  were compromised by aligning the tumblers with the shear line (e.g., by bumping the lock), the auxiliary locking pin  122  ought to be able to resist rotation of the plug  70 . A preferred material for the auxiliary locking pin  122  is stainless steel. 
         [0055]    The top  126  of the auxiliary locking pin  122  is sloped to conform with the peripheral curvature of cylindrical plug  70 . 
         [0056]    The auxiliary locking pin  122  includes a radial shoulder  130  to provide a stop for the pin spring  134 . A shoulder projection  132  protrudes from the shoulder  130  toward the face of the locking cylinder  10 . The auxiliary locking pin spring  134  is disposed around the upper shaft  124  and extends from the shoulder  130  into a counterbore formed coaxially with pin hole  78  to provide a downward biasing force upon the auxiliary locking pin  122 . The shoulder projection  132  is rectangular in cross-section and is sized to conform to the sides of the auxiliary pin cavity  170 , as shown in  FIGS. 6 and 11 , to ensure that the auxiliary locking pin  122  does not rotate around its longitudinal axis. Because the tip  126  of the locking pin  122  is sloped to conform to the plug  70 , it is important that the pin  122  maintain a consistent orientation and not rotate about its longitudinal axis. If the auxiliary locking pin  122  were to rotate about its longitudinal axis, the top  126  of the auxiliary locking pin  122  would slope in a direction not conforming with the curvature of the plug  70 . 
         [0057]    The bottom tip  128  of the auxiliary locking pin  122  sits atop the slider  136 . 
         [0058]    As shown in  FIGS. 13-15 , slider  136  includes an angled notch  142  which defines angled side walls  144 , a rear body portion  138 , a spring hole  140  formed in the rear body portion  138  in an axial orientation with respect to the plug  70 , and a curved bottom portion  146  having a curvature generally conforming to the peripheral curvature of the plug  70 . Slider  136  further includes a side projection  148  defining a contact surface  150 . When the slider  136  is installed in the slider cavity  160 , the side projection  148  and the contact surface  150  extend into the keyway  80 , and the bottom portion  146  conforms to the curvature of the plug  70 , so the slider  136  is retained within the slider cavity  160  by the control sleeve  120 . 
         [0059]    As shown in  FIGS. 2 and 4 , the slider spring  152 , having one end inserted into spring hole  140 , urges the slider  136  toward a first position at the forward end of the slider cavity  160 . As shown in  FIGS. 2 ,  4 , and  6 , with the slider  136  in this forward position, the pin  122  contacts the top of the rear main body  138  of the slider, thereby holding the pin in a first position with the upper shaft  124  extending through the auxiliary pin locking hole  122  into the gap  48  to prevent rotation of the plug  70  and preventing the pin  122 , which is biased downwardly by the pin spring  134 , from moving from this first position. When engaged by a key (as described in more detail below), the slider  136  is moved, against the bias of the slider spring  152 , to a second position toward the back of the slider cavity  160 . Meanwhile, the tip  128  of the auxiliary locking pin  122  slides along the top of the slider and into the notch  142 , sliding along the angled wall  144  to the bottom of the notch  142 , as shown in  FIGS. 7 ,  9 , and  11 . With the pin  122  moved into this second position, the upper shaft  124  withdraws from the gap  48 , through the auxiliary pin hole  32  formed in the control sleeve  20 , so that the plug  70  may rotate within the control sleeve  20 . 
         [0060]    When a key is removed, the slider  136  is allowed to move under the force of spring  152  from the second position to the first position toward the front of the slider cavity  160 . The tip  128  of the auxiliary locking pin  122  slides up along the angled wall  144  to the top of the rear main body  138  of the slider  136 . The upper shaft  124  again protrudes through auxiliary locking pin hole  32  into gap  48 , and the plug  70  is again locked against rotation. 
         [0061]    Preferably, the angled side walls  144  of the notch  142  form an angle of about 90°. If the angles of the side walls  144  are too steep, then it will be difficult for the tip  128  of the auxiliary locking pin  122  to slide up the side wall  144  and out of the angled groove  142  as the slider  136  moves from the back, second position to the forward, first position. On the other hand, if the angles of the side walls  144  are too shallow, the linear distance required for the angled notch  142  to reach the necessary depth to permit the upper shaft  124  of the locking pin  122  to fully withdraw from the gap  48  will be too great, which will require an unnecessarily long slider. 
         [0062]    A key  200  configured for use in the cylinder lock  10  is shown in  FIG. 12 . Key  200  includes a bow  202 , which may include a key ring hole  204 , a shoulder, or key stop,  206 , and a key blade  208 . Key blade  208  includes a biting edge  210  having teeth  212 . A slider catch  218  is formed in a lower, forward edge of the key blade  208 . The slider catch  218  comprises a slider cut  220 , which is intended to move past the slider (not shown), and a slider contact surface  222 , which is intended to engage the slider contact surface  150 . The distal end of the key blade has a tip stop  224 . Blade profile features, such as longitudinal shelf  214 , may be provided to control access to the keyway by forming a keyblade and keyway to have conforming profiles permit the only the correctly-profiled key to be inserted into a keyway. 
         [0063]    When key  200  is inserted into the keyway  80 , the teeth  214  of the biting  210  engage pin stacks  90  to elevate the tumblers to correct positions to unlock the plug  70 . The depth to which the key  200  can be inserted into the keyway  80  will be determined by the shoulder  206  or the tip stop  224 . Also, the slider contact surface  222  will engage the contact surface  150  of the slider  136  to move the slider from the first, locking position shown in  FIGS. 2 ,  4 , and  6  to the second, unlocked position shown in  FIGS. 7 ,  9  and  11 . 
         [0064]      FIGS. 16-23  illustrate components of a cylinder lock according to an alternative embodiment of the invention. The cylinder lock according to this alternative embodiment, like cylinder lock  10  described above, includes an auxiliary locking mechanism which includes an auxiliary locking pin, but does not include a slider which actuates the pin.  FIG. 18  shows a side view of a cylinder lock  310 , and  FIG. 19  shows a cross-section of the cylinder lock  310  of  FIG. 18 . Cylinder lock  310  includes a cylindrical plug  370 , a control sleeve  320 , a shell  40 , a faceplate  100 , and an auxiliary locking pin  422  As with cylinder lock  10  described above, cylinder lock  310  shown in  FIGS. 18-22  is of the type known as a small format interchangeable core cylinder. This is merely for the purpose of illustrating this alternative embodiment of the inventive lock incorporating an auxiliary locking mechanism and is not intended to be limiting, as the auxiliary locking mechanism could be incorporated into other locks as well. 
         [0065]    The shell  40  of the alternative embodiment shown in the figures is identical to shell  40  described above, and thus the description will not be repeated. 
         [0066]    The control sleeve  320  is housed inside the shell  40 . Control sleeve  320  has a hollow, cylindrical configuration with a raised portion  322 . Tumbler holes  324  formed in the raised portion  322  of the control sleeve  320  align with tumbler holes  44  formed in the shell  40  when the control sleeve  320  is inserted into the shell  40 , such that tumblers (described above) inside may move up and down to control rotation of the plug  370  in a conventional manner. Service holes  330  formed in the bottom of the control sleeve  320  align with service holes  54  formed in the shell  40 . The control sleeve  320  includes a control lug  326  along part of one side of the raised portion  322 . Raised portion  322  of the control sleeve  320  is received within the recess  46  formed in the upper section  42  of the shell  40 , and control lug  326  interlocks with the bottom of the upper section  42  of the shell  40  to lock the control sleeve  320  within the shell  40 . The control sleeve  320  further includes an upper auxiliary locking pin hole  332  and a lower auxiliary locking pin hole  334 . 
         [0067]    The faceplate  100  of the alternative embodiment and its engagement with shell  40  is identical to faceplate  100  described above, and thus the description will not be repeated. 
         [0068]    The plug  370  is mounted for axial rotation within the control sleeve  320 , which is disposed within the lower section  52  of the shell  40 . Tumbler holes  372  are formed in the plug  370  and communicate with a keyway  380  formed axially into the plug  370 . Tumblers (described above) disposed within the tumbler holes  372  operate along with a key in a conventional manner to control rotation of the plug  370 . 
         [0069]    Plug  370  further includes an auxiliary locking pin hole  378 , which includes an upper pin cavity  472  and a lower pin cavity  470  having a smaller diameter than the upper spring cavity  472 . As shown in FIGS.  16  and  17 —which show top and bottom plan views, respectively, of the cylinder  370 —an area, designated by reference number  382 , between the hole  378  and keyway  380  and one of the tumbler holes  372  is broached. The purpose of this broached area will be described below. 
         [0070]    The auxiliary locking pin  422  is disposed within auxiliary pin locking hole  378 . The auxiliary locking pin  422  includes a shaft  424 , an upper tip  426 , a spring shoulder  430 , a key contact projection  432 , and a lower point, or tip,  428 . A pin spring  434  surrounds the upper shaft  424 . The auxiliary locking pin  422  effects auxiliary locking by the upper tip  426  of the auxiliary locking pin  422  extending from the auxiliary locking pin hole  378  through auxiliary pin hole  332  formed in the control sleeve  320  and into gap  48  defined within recess  46  adjacent the raised portion  322  (see  FIG. 19 ). The locking pin  422  resists rotation of the plug  370  by contacting the sides of hole  332 . A preferred material for the auxiliary locking pin  422  is stainless steel. 
         [0071]    The tip  426  of the auxiliary locking pin  422  may be sloped to conform with the peripheral curvature of cylindrical plug  370 . 
         [0072]    The spring shoulder  430  of the auxiliary locking pin  422  provides a stop for the pin spring  434 . More specifically, spring shoulder  430  has a transverse dimension (e.g., diameter) that is greater than that of the upper shaft  424  and the upper tip  426 . The bottom of the spring shoulder  430  forms a radial flange that is substantially perpendicular to the longitudinal axis of the auxiliary locking pin  422 . In the illustrated embodiment, the top  426  has a smaller transverse dimension (e.g., diameter) than the spring shoulder  430  so as to fit within the gap  48 . Also, as seen in  FIGS. 19 ,  21 , and  22 , the lower pin cavity  470  has a smaller transverse dimension (e.g., diameter) than the upper pin cavity  472 . The change in dimension between the lower pin cavity  470  and the upper pin cavity  472  defines a radial ledge. 
         [0073]    Pin spring  434  surrounds a portion of the upper shaft  424  and resides within the upper pin cavity  472  where it is retained between the radial flange defined at the bottom of the spring shoulder  430  and the radial ledge defined at the transition of the lower pin cavity  470  and the upper pin cavity  472 . 
         [0074]    Pin spring  434  biases the auxiliary locking pin  422  upwardly. Thus, when the locking pin  422  is unengaged by a key, as shown in  FIG. 19 , it is in a first position, extending, under the bias force provided by the pin spring  434 , through the upper auxiliary locking pin hole  332  of the control sleeve  320  to prevent the cylindrical plug  370  from rotating. 
         [0075]    The auxiliary locking pin  422  also includes a key contact extension  432 , which extends laterally through the broached area  382  adjacent the lower pin cavity  470  into the keyway  380 .  FIG. 20  shows a side view of the cylinder lock  310  with a key  500  inserted into the keyhole thereof.  FIG. 21  is a transverse cross section of the cylinder lock  310  and key  500  taken through the auxiliary locking pin  422 . As shown in  FIGS. 20 and 21 , when a properly configured key  500  (described in more detail below) is inserted into the keyway  380 , it engages the extension  432  and pulls the auxiliary locking pin  422  down into a second position in which the upper tip  426  of the pin  422  is retracted into the plug  370  to thereby permit the plug  370  to rotate with respect to the control sleeve  320 . 
         [0076]    As shown in  FIG. 22 , if the auxiliary locking pin  422  is moved down too far within the auxiliary locking pin hole  378  into a third position (for example, if engaged by the wrong key or if the pin is moved down too far in an attempt to pick the lock), the lower tip  428  of the pin  422  will extend through the lower auxiliary locking pin hole  334  of the control sleeve  320  to again prevent rotation of the plug  370 . 
         [0077]    When the key is removed, the auxiliary locking pin  422  is allowed to move under the force of pin spring  434  from the second position shown in  FIG. 21  back to the first position shown in  FIG. 19  so that the upper tip  426  again protrudes through upper auxiliary locking pin hole  332  into gap  48 , and the plug  370  is again locked against rotation. 
         [0078]    A key  500  configured for use in the cylinder lock  310  is shown in  FIG. 23 . Key  500  includes a bow  502 , which may include a key ring hole  504 , a shoulder  506 , and a key blade  508 . Key blade  508  includes a biting edge  510  having teeth  512 . The key  500  also includes a key stop  516 . 
         [0079]    A pin groove  514  is formed along the key blade  508 . The pin groove  514  comprises a groove, or channel, having a first portion  518  which receives the key contact projection  432  when the key  500  is first inserted into the keyway  380  and the auxiliary locking pin  422  is in its first position. Progressing along the key blade  508 , the pin groove  514  includes a transition  520 , which, in the illustrated embodiment, moves closer to the bottom edge of the blade  508 , to a terminal portion  522  of the groove  514 . As the projection  432  moves along the groove  514 , while the key  500  is inserted into the keyway  480 , it moves from the initial portion  518 , through the transition  520 , and down to the terminal portion  522 . The pin  422  is thus pulled down into the second position, retracted into the plug  370 , thereby allowing the cylinder to rotate, assuming the tumblers are also properly aligned. 
         [0080]    The auxiliary locking pin  422  is installed into the plug  370  by dropping it down into the auxiliary pin locking hole  378 . The broached area  382  allows the pin  422 , with the extending projection  432 , to be inserted into the hole  378 . 
         [0081]    In a further embodiment, a cylinder lock may include an auxiliary locking mechanism comprising more than one auxiliary locking pin of the type shown in  FIG. 19 . That is, multiple auxiliary locking pins  422  can be provided along the length of the keyway  380 , each locking pin having a key contact projection  432  at a different height, so that the pins are lowered by different amounts to permit rotation of the cylinder plug. The pin groove provided in a proper key would be shaped to accurately position each locking pin  422  into its respective second position. If the wrong key is used, and one or more pins is(are) moved too little or too much, the upper tip  426  or the lower tip  428  of the locking pin  422  will be engaged in the upper pin hole  332  or the lower pin hole  334  of the control sleeve  320  to prevent the cylinder plug from rotating. Such an arrangement may not, however, be possible if the cylinder includes longitudinal bores (such as longitudinal bores  88  shown in  FIGS. 2 and 4 ). 
         [0082]    Thus, a preferred embodiment has been fully described above with reference to the drawing figures. Although the invention has been described based upon this preferred embodiment, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions could be made to the described embodiments within the spirit and scope of the invention.