Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED CYLINDER LOCK SYSTEM
Background of the Invention
(i) Field of the Invention
The present invention relates to increasing the security afforded by
mechanical locks and, particularly, to minimizing the possibility of the
availability of key blanks which may be cut to form unauthorized keys for such
locks. More specifically, this invention is directed to an improved cylinder
lock
and a novel key which, in cooperation, de>:rne a lock system which provides
highly secure access control. Accordingly, the general objects of the present
invention are to provide novel and improved methods and apparatus of said
character.
(2) Description of the Prior Art
Mechanical locks which employ one or more pin tumbler arrays are well
known in the art. In such prior locks, the pin tumblers are arranged in
"stacks"
which are radially displaceable with respect to the axis of rotation of a plug
or
core, such displacement occurring in response to insertion of a key in a
keyway
defined by the core. The pin tumbler stacks comprise at least an upper or
driver pin and an abutting, axially aligned driven or bottom pin, the pins
being
disposed in pin chambers provided in both the core and the surrounding shell
of the lock. The pin tumbler stacks are resiliently biased in the direction of
the
axis of core rotation and, when there is no key in the keyway, one pin of each
stack bridges the gap between the core and shell thus preventing relative
rotation therebetween. As a result of communication between the keyway and
the pin chambers in the core which receive the bottom pins, insertion of a
properly batted key in the keyway will result in pin tumbler stack
displacement
which typically places the interface between the driver and bottom pins at a
shear line defined by the core outer circumference. Thus, a properly batted
key
will permit the core, with the bottom pins, to rotate within the shell while
the
driver pins remain stationary. Core rotation will, through the action of a cam
or tailpiece mechanically coupled thereto, activate a locking mechanism or
latch.
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Locks of the type described briefly above are known in the art as
"cylinder" locks. The most common manner of defeating a cylinder lock
consists of "manufacture" of an unauthorized key. It is not possible to ensure
against the defeat of a cylinder lock by providing such a lock with a keyway
having a complex, i.e., very intricate, profile and/or through the use of
various
arrangements of pin tumbler stacks. The foregoing inability is, in part, a
function of the fact that various manufacturers will provide key blanks having
blades which, either as manufactured or as shaped using conventional
key-cutting machines, have a pro>:fle which will enable their use, after being
"cut", with locks which are sold in volume. Thus, there has been a long
standing desire for a lock system which affords increased security through
minimizing the possibility of unauthorized manufacture of replacement key
blanks and, particularly, for a lock system which affords the lock
manufacturer
the ability to exercise key control by means of being the sole source of the
key
portion of the system. In addition, a high level of security also dictates
that a
lock "trap" unauthorized keys and, especially, partly formed keys which are
being "patterned" in an attempt to defeat the lock.
Summary of the Invention
The present invention overcomes the above-briefly discussed and other
deficiencies and disadvantages of the prior art and, in so doing, provides a
novel cock system characterized by a key which, in part, has a unique profile.
A lock system in accordance with the present invention also encompasses a
novel and improved cylinder lock having elements which cooperate with the
aforementioned unique key profile to enable the relative rotation of the core
and, under certain circumstances, to also mechanically capture unauthorized
keys in the keyway.
A lock system in accordance with the invention includes a cylinder lock
with a core which, at the longitudinal position of at least one pin tumbler
stack,
is provided with a cut-out generally in the shape of a circular segment. With
the lock in the locked state, i.e., prior to rotation of the core relative to
the
shell, this cut-out will be out of alignment with the pin tumbler stack. The
cut-out is in communication with the keyway via an opening provided in a first
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side thereof. A plate member or segment is located in the cut-out, the plate
member being sized and shaped so as to be capable of limited movement
within the cut-out relative to the core, such movement being guided by
the internal diameter of the shell. Movement of the plate member may be
produced by a suitably shaped and located caroming projection, provided on
a first side of an authorized key, which extends through the opening in the
keyway first side. This caroming projection extends outwardly beyond the
plane of the side of the blank from which the key was formed and into the
segment-shaped cut-out. The plate member, when caused to move along a
path defined by the shell Internal diameter in response to contact with a
caroming projection on an authorized key, will function as an extension of the
core and will present an edge which generally corresponds to the shear line.
Thus, with an authorized key in the keyway, the core will appear to be
uninterrupted to the driver pin of a pin tumbler stack at the location of the
cut-out and the core rnay thus rotate past the point of registration of the
driver
pin and plate member without driver pin radial motion. However, in the case
of an unauthorized key, i.e., a key which lacks the caroming projection, core
rotation will cause the outer periphery of the plate 'member to be displaced
below the shear line and, in part, to define an opening into which the driver
pin
will move once the core has been rotated relative to the shell sufficiently to
fully
register the pin tumbler chamber in the shell with the cut-out in the core.
The
driver pin will, accordingly, move radially toward the axis of core rotation
so as
to bridge the shear line and prevent further core rotation in either the
clockwise
or counterclockwise direction. The lock will thus be rendered inoperable and
the unauthorized key will be trapped in the keyway.
A lock system in accordance with the invention also includes a suitably
shaped and located indentation in the opposite side of the key blade with
respect to the caroming projection. This indentation is in alignment with and
formed simultaneously with the oppositely disposed caroming projection. The
indentation is in registration with a chamber in the core which receives an
auxiliary locking pin. This chamber is, most expediently, oriented such that
its
axis is transverse to a plane defined by the side of a blank from which the
key
was formed. The auxiliary locking pin is resiliently biased outwardly whereby
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a first end thereof engages a cooperating recess in the inner diameter of the
shell, i.e., the auxiliary locking pin bridges the shear line with the lock in
the
locked state. The outwardly disposed end of the auxiliary locking pin and the
side wall of the cooperating recess in the shell are shaped such that relative
rotation between the core and the shell will, if movement of the auxiliary
locking pin against its spring bias is possible, cam the auxiliary locking pin
out
of the recess in the shell, the outer end of the locking pin sliding on the
internal
diameter of the shell during further core rotation. However, this ramming
action can occur only when a key blade having an indentation sized, shaped
and located to receive the second end of the auxiliary locking pin is present
in
the keyway. Thus, an authorized key for a lock system in accordance with the
invention must have both a uniquely shaped and positioned ramming
projection on a first side thereof and a properly positioned and shaped
locking
pin receiving indentation on the opposite second side thereof.
i5 Brief Description of the Drawing
The present invention may be better understood, and its numerous
objects and advantages will become apparent to those skilled in the art, by
reference to the accompanying drawing wherein like reference numerals refer
to Ilke elements in the several Figures and in which:
Figure 1 is a partial side elevation view, partly broken away to show
detail, of a cylinder lock in accordance with a preferred embodiment of the
present invention;
Figures 2 and 3 are perspective views, taken from opposite sides, of a
key of a lock system in accordance with the invention;
Figures 4A and 4B are cross-sectional, side-elevation views of a lock
system in accordance with the present invention at different stages of
operation, Figures 4A and 4B being views taken transversely with respect to
Figure 1 and depicting the lock of Figure 1 in combination with the key of
Figures 2 and 3;
Figures 5A - 5C are partial views of the blade of the key of Figures 2
and 3;
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Figure 6 is a view similar to Figure 4 which represents an attempt to
defeat a lock in accordance with the present invention employing a key having
only one of the blade features of the invention; and
Figures 7A and 7B are views similar to Figure 6 which represent the
result of attempting to defeat a lock in accordance with the present Invention
through the use of a key having only the other of the key blade features of
the
invention.
Description of the Disclosed Er~nbodiment
With reference to the drawings, a cylinder lock in accordance with the
present invention is indicated generally at i0. Lock i0, as is conventional,
comprises a core 12 which may be rotated, about an axis of rotation, relative
to a shell 14. In the disclosed embodiment, shell i4 includes an extension or
bible 16. A single linear array of pin chambers, such as chamber 18, are
provided in bible 16. The pin chambers 18, with the lock in the locked state,
are in axial registration with pin chambers 20 in core 12. Pin tumbler stacks,
which in the disclosed embodiment comprise an upper or driver pin 22 and a
driven or bottom pin 24, are provided in the registered pin chambers. The pin
tumbler stacks are resiliently biased radially in the direction of the axis of
rotation of core 12. In the disclosed embodiment the biasing is accomplished
by means of compression springs, such as the spring indicated schematically
at 26, which contact the outwardly disposed ends of the driver pins. A
tailpiece
or cam, not shown, will be connected to the end of core 12 disposed oppositely
to the end which defines the entrance to the keyway. The tailpiece will be
coupled to a latch mechanism or the like so that the lock may be employed to
selectively prevent and permit access to a space on one side of a door in
which
the lock Is installed.
The lock as described above is of conventional construction. It will thus
be understood by those skilled in the art that the configuration and location
of
the pin chambers and pin tumbler stacks may be varied without departing from
the invention. For example, there may be multiple arrays of pin chambers,
angularly offset from one another, and the pin tumbler stacks may include any
number of pins.
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Also in accordance with conventional construction, and as may be seen
from Figures 4, 6 and 7, a keyway 28 is provided in core 12. The keyway is in
~mmunication with the inwardly disposed ends of the pin chambers 20 in the
core and has a profile, i.e., a cross-sectional area, chosen by the lock
manufacturer. A conventional keyway includes a plurality of wards which, in
part, define the keyway cross-section. A correct key, i.e., a key which may be
inserted in the keyway, must have a blade with side surfaces milled so as to
be
complementary with these wards. Thus, starting from a key blank with parallel
sides, longitudinal cuts may be made so that the blade cross-section matches
i0 the keyway cross-section. Additionally, in order to operate the lock, the
key
blade must be further "cut", i.e., batted, to have surface irregularities
which
match the combination of the lock as determined by the location of the pin
tumbler stacks and the relative lengths of the individual pins forming the
stacks. In the least complicated arrangement, as shown in the drawings, the
key will be batted by removing material from the upper edge of the blade to
produce the customary serrated edge. The "combination" of a conventional
prior art cylinder lock is thus defined by the key blade profile and batting.
Insertion of a properly batted key into the keyway will establish contact
between the irregular upper edge of the key blade and the bottom pins and,
as depicted in Figures 4, 6 and 7, will result in movement of the pin tumbler
stacks against the bias of springs 26 so as to place the interface between the
driver and bottom pin of each pin tumbler stack at the shear line between the
core 12 and shell 14. When all of the pin tumbler stacks have been
repositioned from the locked state, i.e., the state where one pin of each
stack
bridges the shear line and thus is partly located in a pin tumbler chamber of
both the core and shell, rotation of the core relative to the shell is
permitted.
To summarize, in a conventional cylinder lock, in order to permit relative
rotation between the core and shell, the key blank must be provided with
longitudinal cuts on the sides to define a profile which matches the keyway
cross-section and must be cut to provide surface irregularities commensurate
with the lock combination defined by the pin tumbler stacks.
In accordance with the present invention, at the location of at least one
of the pin tumbler stacks, a circular segment is cut from core 12. This
segment
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is defined by a wall 30 which, with the exceptions to be discussed below, is
straight and continuous between two points of intersection with the shear
line.
In the disclosed embodiment, the spacing between keyway 28 and wall 30
increases from a first end of the wall, located adjacent the bottom of the
keyway, to an opposite end of wall 30 which is adjacent to the outer end of a
pin chamber 20. Thus, wall 30 defines a ramp. An opening 32 in wall 30
provides communication between the keyway and the space formed by the
circular segment cut-out. In the disclosed embodiment, opening 32 is located
at the base of a slot which defines a portion of the keyway profile. As
disclosed, and it will be understood that other arrangements are possible,
opening 32 is defined by a groove having a maximum depth which exceeds the
thickness of the wall separating the circular segment cut-out from the keyway.
A movable plate member 34 having a shape which is similar to, but
different from, the circular segment cut-out defined by wall 30 is inserted in
the
cut-out. Plate 34 has a first, straight side 36 which faces wall 30. In the
disclosed embodiment, side 36 is provided with a projection 38 which extends
into opening 32. Plate 34 also has a first arcuate side 40 which extends from
a first end of side 36, the radius of side 40 being substantially the same as
the
radius of core 12. Arcuate side 40 terminates at, i.e., merges with, a second
side surface 42 which may also be arcuate, as shown, or straight. Side surface
42 extends to the second end of straight side 36, i.e., the end of side 36
which
is disposed above the plane of the top of the keyway. The width of plate 34
is,
as may best be seen from Figure i, less than the diameter of the pin chamber
18 in bible 16.
Core 12 is provided with a blind hole 44 which, in part, extends into the
segment cut-out which, in part, is defined by wall 30. Hole 44 has a size and
shape complementary to the lower end of a driver pin 22. The axis of hole 44
intersects the circular segment cut-out. Consequently, plate 34 extends into,
and may effectively bridge, blind hole 44. Depending upon the position of
plate
34, access of pin 22 to hole 44 will either be permitted or blocked. The
position
of plate 34 is controlled in the manner to be described below.
A cylinder lock in accordance with the invention also comprises at least
a first auxiliary locking pin 50. Pin 50 has an axis and is disposed, for
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reciprocal movement, in a pin chamber 52 provided in core i2. Chamber 52
communicates, at a first end, with keyway 28 and, at its opposite end, with
the
circumference of core 12. Chamber 52 has an axis which, in the disclosed
embodiment, is oriented transversely with respect to a plane A-A defined by
the axes of the pin tumbler stacks, plane A-A thus also being a plane defined
by the keyway. Chamber 52 has two portions of different internal diameter
and thus defines a shoulder against which the first end of a biasing spring 54
is seated. The opposite end of biasing spring 54 contacts a shoulder on pin
50,
defined by the junction of two different diameter portions of the auxiliary
locking pin, and thus urges pin 50 in the direction of shell 14. Shell 14 is
provided with a recess 56 which receives the end of auxiliary locking pin 50
disposed outwardly with respect to the keyway. With the cylinder lock in the
locked state, the outwardly disposed end of auxiliary locking pin 50 will be
disposed in recess 56 as, for example, shown in Figure 6, i.e., auxiliary
locking
i5 pin 50 will extend across the shear line. Accordingly, auxiliary locking
pin 50
will cooperate with the pin tumbler stacks to prevent rotation of core 12 when
an authorized and properly bitted key is not present in keyway 28. The
opposite, inwardly disposed end of auxiliary locking pin 50 w111 normally,
i.e.,
when the lock is in the locked state, be substantially flush with the side of
keyway 28.
In the disclosed embodiment of a lock in accordance with the invention,
the outwardly disposed end of auxiliary locking pin 50 and a portion of the
wall
which def;nes recess 56, i.e., the wall portion 58 which extends from the
maximum depth of the recess in the direction of core rotation to the inner
diameter of shell 14, cooperate respectively in the manner of cam follower and
cam surface. Thus, when rotation of core 12 relative to shell 14 is enabled in
the manner to be described below, rotational force imparted to core 12 will
cause the cam follower outer end of auxiliary locking pin 50 to ride over the
cooperating cam surface 58 of recess 56 and the resulting camming action will
drive the auxiliary locking pin 50 axially inwardly toward the keyway. Such
axially inward motion, obviously, can occur only if a space having a size,
shape
and location adapted to accept the inner end of pin 50 is present.
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A key blank in accordance with the invention is indicated generally at
60 in Figures 2 and 3. Key blank 60 includes a bow portion 62 and a blade
portion 64, part of the blade portion being shown on an enlarged scale in
Figure 5. As is conventional, key blank 60 has a pair of oppositely disposed
planar sides 66, 68, a top edge 70 and an oppositely disposed bottom edge.
In the embodiment of the invention being described, wherein a single array of
pin tumbler stacks defines the conventional portion of the combination for
operating the lock, top edge 70 of blade 64 will be cut to an irregular shape
to
define the hitting. As key blank 60 is shown, the key profile commensurate
i0 with the keyway cross-section has, also in the conventional manner, been
produced by milling the sides 66 and 68, i.e., by removing material from the
planar side surfaces of the blank. Such milling will customarily be performed
by the lock manufacturer or, in the case of suppliers of "replacement" keys,
by
the key blank manufacturer. t~cksmiths also often have machinery for cutting
planar sided key blanks to achieve the requisite profile.
Key blank 60 is differentiated from the prior art by the provision, on a
first side thereof, of a caroming projection 72. Also, on the second opposite
side, a key blank in accordance with the present invention is provided with an
indentation 74. The preferred method of production of the caroming projection
and indentation is a stamping operation performed from the side of the key
blade which has indentation 74.
Figures 4A and 4B depict the operation of a lock in accordance with the
present invention with a correct, i.e., an authorized, key formed from the key
blank 60 of Figures 2 and 3. The insertion of such a correct key in keyway 28
will result in the establishment of contact between caroming projection 72 on
the key blade and projection 38 on plate member 34. Referring to Figure 5B,
it may be seen that the leading edge of projection 72 ramps upwardly to the
top of the projection. Contact between projections 72 and 38 will impart
clockwise movement relative to core 12 of plate member 34. This movement
will be guided by the inner diameter of shell 14 and thus plate member 34 will
be driven upwardly such that the junction of side 36 and surface 42 is in an
abutting relationship with the upper end of wall 30. This abutting
relationship
causes side surface 42 of the plate member to bridge blind hole 44.
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Accordingly, core i2 may be rotated within shell i2 and, during such rotation,
side 42 of plate 34 will initially prevent driver pin 22 from entering blind
hole
44, as depicted in Figure 4B. As rotation of the core continues, the arcuate
side 40 of plate 34 will contact the bottom of driver pin 44 and urge the
driver
pin against the bias of spring 26 so that rotation of the core to the unlocked
position may be accomplished.
Simultaneously with the operation described immediately above,
cooperation between cam surface 58 and the cam follower end of auxiliary
locking pin 50 will, as also depicted in Figure 4B result in the auxiliary
locking
pin being driven inwardly, such motion being permitted by the presence of the
indentation 74 of the key blade in registration with pin chamber 52. During
rotation of the core to the unlocked position of the lock, the cam follower
end
of auxiliary locking pin 50 will slide on the inner diameter of shell i4.
Referring to Figure 6, an attempt to operate the lock of the present
invention with a properly batted key having ramming projection 72 but lacking
indentation 74 will be unsuccessful because, as is readily apparent from the
drawing, the auxiliary locking pin SO cannot be disengaged from recess 56.
Referring to Figures 7A and 7B, insertion in keyway 28 of a key which
satisfies the lock combination except for the ramming projection 72 wail
permit
rotation of core i2 within shell 14. As the core is rotated in the clockwise
direction, it will carry the plate member 34. After a relatively small degree
of
rotation, as depicted in Figure 7B, the plate member will "flop" over so that
the
side 36 thereof abuts the wall 30, this "flopping" action will result from
either
or both of interaction between spring biased driver pin 22 and plate 34 or the
influence of gravity. When core rotation continues to the point where blind
hole
44 is in registration with pin chamber 18, the driver pin 22 will, under the
influence of spring 26, be driven into blind hole 44 until it bottoms on the
top,
i.e., the side 42, of plate member 34. At this point, because driver pin 22
will
bridge the shear line, further rotation of the core in either a clockwise or
counterclockwise direction will be prevented. Additionally, because of the
interaction between the immobilized bottom pins and top edge of the key
blade, the incorrect key will be trapped in the keyway, i.e., will not be
removable. If the above-described trapping action is desired for both the
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dockwise and counterclockwise directions of rotation of core 12, a second
plate
member will be provided and a second projection will be formed on the side of
the key blade which is oppositely disposed with respect to projection 72.
A lock in accordance with the invention may indude a plurality of plates
34 and oppositely disposed auxiliary locking pins 50. The location of the
plates
and auxiliary locking pins may be reversed with respect to that shown and both
relationships may be present in a single lock. Accordingly, as may be seen
from Figure 6, the shell 14 may expediently be provided with a pair of
oppositeiy disposed longitudinal grooves which define recesses 56 and 56'.
As may be seen from Figure 5B, where the lock is provided with plural
plates 34 on the same side of the keyway, projections 72 will be formed with
ramp surfaces on the leading surfaces on the leading and trailing edges.
Likewise, as necessary (but not shown), indentations 74 will have ramps on
both ends.
While a preferred embodiment has been shown and described, various
modifications and substitutions may be made thereto without departing from
the spirit and scope of the invention. Accordingly, it is to be understood
that
the present invention has been described by way of illustration and not
limitation.
