Locks – Operating mechanism – Key
Reexamination Certificate
2000-03-31
2003-02-25
Gall, Lloyd A. (Department: 3676)
Locks
Operating mechanism
Key
C070S492000
Reexamination Certificate
active
06523381
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates generally to sidebar locks, and more particularly, to a sidebar lock including a sidebar which includes a longitudinal interruption at or near the longitudinal midpoint of the sidebar which interrupts any inclined plane formed by the sidebar being canted when a key coded different from the correct code is inserted into the lock barrel.
Traditional sidebar locks include a lock barrel, a stationary sleeve extending around the lock barrel, and a spring biased sidebar on the lock barrel which projects into a slot in the sleeve to prevent rotation of the lock barrel unless a mating key is present in the lock barrel. The lock barrel is coupled to an output mechanism which, by way of example, can be a vehicle ignition switch, a latch for a vehicle door, deck, hatch, lift gate or tail gate, the bail on a padlock, levers on panel locks, residential and commercial door latches, etc. For example, the lock barrel can have a lever or drive shaft attached thereto. The lever can be linked to the latch by a rod or cable arrangement. The drive shaft can be coupled with a latch or with a cable drive to the latch.
One such sidebar lock is illustrated in
FIGS. 28 and 29
, which are labeled “Prior Art”. The sidebar lock is mechanically unlocked by a mating or “correct” key (not shown) inserted into the lock barrel
122
for aligning a plurality of tumblers
124
to withdraw a sidebar
126
from a sidebar groove
129
in a sleeve
130
. The sidebar
126
prevents rotation of the lock barrel in the absence of the “correct” key in the lock barrel. The sidebar lock illustrated in
FIGS. 28 and 29
has a key
120
with nearly the same code as the “correct” key, commonly called a cousin key, inserted into the lock barrel. As will be described, for such condition, the sidebar
126
can be retracted partially from the sidebar groove
129
in the sleeve at an inclined angle to the axis of the lock barrel as shown in FIG.
28
.
The tumblers
124
include notches
127
which are normally out of alignment with an edge
128
of the sidebar so that the tumblers
124
force the sidebar radially outward, against the force of sidebar bias springs
131
and
132
into the sidebar groove
129
in sleeve
130
. In such position, the sides
133
and
134
of the sidebar
126
cooperate with the sides of the sleeve groove to prevent the lock barrel from rotating relative to the sleeve. The “correct” key aligns tumblers
124
in the lock barrel
122
, allowing the edge
128
of the sidebar
126
to be received in the notches
127
, permitting the sidebar to be retracted into the lock barrel. With the sidebar retracted, the lock barrel can be rotated within the sleeve
130
to actuate the output mechanism.
Depending upon the number and location of the tumblers
124
supporting the sidebar
126
, the sidebar can be retracted partially from the sidebar groove
129
in the sleeve at an inclined angle to the axis of the lock barrel as shown in FIG.
28
. This is particularly true when a key, such as a cousin key
120
, with nearly the same code as the “correct” key, is used. For such condition, the surface of edge
138
of the sidebar forms an inclined plane which bridges the shear line
140
between the lock barrel and the sleeve. The inclined plane formed by edge
138
allows relative sliding movement between the sidebar and the sleeve, causing the sidebar to be driven into the lock barrel if the lock barrel is forcibly rotated. To reduce this occurrence, lock manufacturers generally limit the number of usable key codes so that very similar keys are not produced.
The prior art sidebar lock, shown in
FIG. 28
, includes a conventional sidebar, such as the sidebar
126
shown in
FIGS. 30-33
. The sidebar is biased into the barrel lock by bias springs
131
and
132
which are supported on mounting surfaces
141
and
142
of the sidebar defined by reduced height portions located at opposite ends of the sidebar. The springs
131
and
132
can be held in place by spring clips
136
. The edge
138
of the sidebar
126
can be forced out of the sidebar groove when the lock barrel is forcibly rotated when a cousin key is present in the keyslot, with the inclined edge
138
of the sidebar sliding along the surface of the sleeve
130
, whereby the sidebar is forced into the lock barrel.
Because of the reduced height end portions of the prior art sidebar
126
, the engagement of the sidebar
126
with the groove
129
in the sleeve
130
is limited by this design. This significantly decreases the effort required to forcibly rotate the lock barrel when a cousin key is present in the key slot, with the inclined edge
138
of the sidebar sliding along the surface of the sleeve
130
, thereby forcibly driving the sidebar into the lock barrel.
Forcibly driving the sidebar into the lock barrel can cause the sidebar to be plastically deformed at edge
128
of the sidebar
126
at the point of engagement with the tumblers and/or compress the tumbler springs
143
, thus defeating the locking function.
When a key having a code that is very similar to the correct code is used, the rotational force required to defeat the locking function is a small fraction of the rotational force the lock can normally withstand. Accordingly, manufacturers are limited in the number of key codes they can offer. The present invention significantly increases the number of robust key codes. The greater the number of robust codes available, the greater the security of the lock.
SUMMARY OF THE INVENTION
The disadvantages and limitations of the background art discussed above are overcome by the present invention. With this invention, there is provided a new and improved sidebar lock which comprises a sleeve including a sidebar groove extending longitudinally along a surface of the sleeve and a lock barrel supported within the sleeve for rotation relative to the sleeve. The lock barrel is adapted for connection to an output mechanism. The sidebar lock includes a sidebar which is movable radially relative to the lock barrel between an extended position in which an edge of the sidebar extends into the sidebar groove and cooperates with the sidebar groove to prevent relative rotation between the lock barrel and the sleeve, and a retracted position in which the sidebar is retracted into the lock barrel, permitting relative rotation between the lock barrel and the sleeve. In accordance with the invention, either the edge of the sidebar or a surface of the sleeve adjacent to the sidebar include an interruption. In one embodiment, the interruption is a gap in an edge surface of the sidebar. In another embodiment, the interruption is an indentation in an edge surface of the sidebar. In a further embodiment, the interruption is provided by widening the sidebar groove in the sleeve.
The surface interruption negates the effect of an inclined plane, formed as the result of the sidebar being partially withdrawn from a sidebar groove in the sleeve such that the sidebar extends at an angle relative to the axis of the lock barrel. Without such surface interruption, a key having a coding similar to the coding for the mated key for the lock, can cause the sidebar to be slid along the surface of the sleeve and be driven out of the sidebar groove.
The present invention significantly increases the number of robust key codes. The greater the number of robust key codes that are available, the greater the security of the sidebar lock.
REFERENCES:
patent: 2003086 (1935-05-01), Liss
patent: 2024441 (1935-12-01), FitzGerald
patent: 2036747 (1936-04-01), FitzGerald
patent: 2405911 (1946-08-01), Swanson
patent: 2660876 (1953-12-01), Spain
patent: 3002268 (1961-10-01), Spain
patent: 3080744 (1963-03-01), Spain
patent: 3287944 (1966-11-01), Crumb
patent: 3410123 (1968-11-01), Jacobi
patent: 3455130 (1969-07-01), Basseches
patent: 4561270 (1985-12-01), Spreng
patent: 5001914 (1991-03-01), Edwards
patent: 5454246 (1995-10-01), Mueller
patent: 5540071 (1996-07-01), Reikher
patent: 5611225 (1997-03-01), Resch et al.
p
Hall Kenneth R.
Ritz Alan J.
Gall Lloyd A.
Michael & Best & Friedrich LLP
Strattec Security Corporation
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