U.S. patent number 3,786,658 [Application Number 05/265,930] was granted by the patent office on 1974-01-22 for restrictive manipulation limited try mechanism for a combination lock.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to Frank H. Swaim.
United States Patent |
3,786,658 |
Swaim |
January 22, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
RESTRICTIVE MANIPULATION LIMITED TRY MECHANISM FOR A COMBINATION
LOCK
Abstract
A combination lock having a restrictive manipulation or
limited-try feature o prevent the opening of the lock by trial and
error manipulation. The mechanism recognizes and counts each
unsuccessful attempt at finding the proper code. After a
predetermined number of unsuccessful attempts to open the lock, the
mechanism renders the lock unopenable, without the knowledge of the
illicit manipulator but will continue to accept additional
manipulations. A registering device, associated with the mechanism,
will reset to permit the opening of the lock by the owner only when
the proper code is dialed before the predetermined number of
unsuccessful attempts has been reached.
Inventors: |
Swaim; Frank H. (Silver Spring,
MD) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
23012464 |
Appl.
No.: |
05/265,930 |
Filed: |
June 23, 1972 |
Current U.S.
Class: |
70/333R;
70/DIG.49 |
Current CPC
Class: |
E05B
37/08 (20130101); Y10T 70/7424 (20150401); Y10S
70/49 (20130101); E05B 37/0024 (20130101) |
Current International
Class: |
E05B
37/00 (20060101); E05B 37/08 (20060101); E05b
037/08 () |
Field of
Search: |
;70/1.5,1.7,333R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Craig, Jr.; Albert G.
Attorney, Agent or Firm: Sciascia; R. S. Cooke; J. A.
McGiehan; Donn
Claims
What is claimed as new and desired to be secured by Letters Patent
of the United States is:
1. An improvement in combination locks having tumblers with gates
and a fence-lever for improving the security thereof from
unauthorized manipulation comprising
a limited-try mechanism cooperating with said tumblers and said
fence-lever which prevents opening of the lock after a
predetermined plurality of attempts have been made using the
improper combination, the action of said mechanism undetectable by
a manipulation.
2. The improvement of claim 1 wherein
said limited-try mechanism includes blocking means preventing said
fence-lever from cooperating with said tumbler gates to preclude
the opening of the lock.
3. The improvement of claim 2 wherein
said limited-try mechanism further includes means for mechanically
registering cumulatively the number of unsuccessful attempts to
open the lock.
4. The improvement of claim 3 wherein
said limited-try mechanism further includes reset means to permit
opening the lock when the proper combination is used before the
predetermined plurality of attempts have been made.
5. The improvement of claim 4 wherein said limited-try mechanism
further includes means permitting resetting by a tool from the
outside of the lock after the predetermined plurality of attempts
have been made to open the lock.
6. The improvement of claim 5 wherein said limited-try mechanism
further includes means for monitoring the plurality of attempts to
open the combination lock on the face of the lock without notifying
an unauthorized manipulator that the predetermined number has been
reached.
7. The improvement of claim 2 wherein
the limited-try mechanism further includes means for actuating an
alarm when the predetermined plurality of attempts have been made
to open the lock.
8. An improvement in a combination lock having tumblers with gates,
a cam wheel, a fence-lever, and a dial on the face comprising:
a limited-try mechanism comprising:
a pusher pawl cooperating with the fence-lever when it does not
enter the gates;
a ratchet wheel rotatably advanced one step by said pusher pawl
each time the fence-lever comes in contact with said pusher
pawl;
a holding pawl coating with said ratchet wheel to hold it in the
advanced position;
a cam surface having a slot on the side of said ratchet wheel;
a lockout bar in slidable relationship with said cam and coacting
with and precluding the entry of the fence lever into the tumbler
gates when said lockout bar enters said slot in said cam
surface,
whereby said limited-try mechanism renders the lock unopenable
after the predetermined plurality of trys using the improper
combination has been made and whereby said limited-try mechanism is
reset by using the proper combination before the predetermined
plurality of trys has been made.
9. The improvement of claim 8 wherein said limited-try mechanism
further comprises:
a tell-tale dial outside the lock and coupled with said ratchet
wheel to indicate the plurality of attempts made to open the
lock.
10. The improvement of claim 9 further comprising:
an alarm coupled with said limited-try mechanism indicating when
the predetermined plurality of attempts have been made.
11. The improvement of claim 10 further comprising:
a keyway through the face of the lock connecting with said
limited-try mechanism; and
a key insertable in said keyway and coacting with said limited-try
mechanism to reset said ratchet wheel permitting the lock to be
opened by the use of the proper combination.
12. The improvement of claim 8 wherein:
said holding pawl is releasable from said ratchet wheel by contact
with the fence-lever when the proper combination is used and said
fence-lever enters the tumbler gates.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to locks for securing a depository
and, more particularly, to manipulation-proof combination locks.
Combination locks are thought to provide good security against
unauthorized entry because they require a certain succession of
numbers to be set on a dial to gain entrance. However, present
combination locks are vulnerable to manipulation by a knowledgable
expert using the sense of feel, sight and sound and given enough
time to make a number of trial combinations of numbers to finally
open the lock. A background study of the owner of the lock,
including his birthdate, his wife's birthdate, anniversary date,
children's birthdates, etc., will often provide the required
combination to the particular lock. However, even with this
knowledge and skill, an expert will have to make a number of
manipulations or trials before he finds the successful combination
of numbers. If the combination lock was provided with a mechanism
which would render the lock unopenable after a predetermined number
of unsuccessful tries, the security of the depository would be
greatly enhanced.
Locks have a long history of providing good security against
unauthorized entry to dwelling houses, vehicles, safes, cabinets,
and other such security depositories. Key locks having a keyway
and, therefore a hole, permit entry into the internal mechanism of
the lock and allow manipulation of the tumblers with a pick and
turning device. This procedure, called "picking," will readily open
any key lock. Combination locks are far superior to key locks
because there is no keyway or ready entrance into the internal
mechanism for a key or adding nitroglycerin. Combination locks
require a certain succession of numbers to be set on an outer dial
through a left and right pattern of rotations of said dial before
it may be opened. The most sophisticated combination lock has 100
possible settings for each directional turn of the dial, and some
require as many as seven directional turns. The most common type
combination lock has three directional turns, thus providing one
million possible combination settings. A five directional turn lock
will provide 10 billion possible combination settings. With these
number of possible combinations, the average person would consider
it an impossibility to open such a lock, but to a knowledgable
expert, they represent only a challenge. The vast number of
possible combinations is of little concern to the expert
manipulator who knows the characteristic of the lock and uses this
knowledge to find the proper code to gain entry. His technique is
to make a quantity of tries designed to minimize the amount of
manipulations of the dial and the amount of time spent opening the
depository.
Attempts in the past to increase the security afforded by
combination locks have generally been directed to elimination of
the possibility of attack by forceable means, such as drilling into
the lock so that the combination may be set mechanically, or by
adding heat and explosive shields to reduce the possibility of
attack by torch cutting or "blowing open" the closure to the
depository. Few, if any, attempts have been made to solve the
problem of surrepticious entry by manipulation of the combination
lock, because the general public is of the opinion that modern
sophisticated locks cannot be manipulated to opening. But, as
discussed above, these locks are susceptible to being manipulated
to opening by a knowledgable expert, a fact known to those
practicing in the security field.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to enhance the
security provided by a combination lock.
Another object of the invention is to provide additional
intelligence to a combination lock.
A further object of the invention is to provide a combination lock
having the ability to distinguish betweeen authorized manipulation
and unauthorized manipulation.
A still further object of the present invention is to provide a
combination lock with the ability to register the quantity of
attempts at manipulation.
Still another object of the present invention is to provide a
combination lock which is able to incapacitate the locking
mechanism to prevent opening without the knowledge of the
manipulator.
Still another object of the instant invention is to provide a
combination lock with provisions to automatically reset the
registering mechanism when authorized manipulation takes place
prior to reaching the predetermined number of unsuccessful attempts
at manipulation.
A still further object of the instant invention is to provide a
means in combination locks to re-establish the limited-try feature
for again accepting authorized attempts at manipulation after the
predetermined number of attempts has been reached.
Briefly, these and other objects of the present invention are
attained by the use of a restrictive manipulation or limited-try
mechanism which substantially prevents opening the combination lock
by trial and error manipulation. This feature recognizes and
registers each unsuccessful attempt at finding the proper code and,
after a predetermined number of tries, precludes the conventional
fence-lever from entering the gates in the tumblers, thus rendering
the lock unopenable. The register mechanism will continue to accept
additional manipulations without the knowledge of the illicit
manipulator that he is locked out. The register device, however,
will reset to permit the fence-lever to enter the gates upon
application of the proper code, if the predetermined number of
unsuccessful attempts has not been reached, and thus will permit
the opening of the lock by the owner.
The means by which the mechanism registers the number of
unsuccessful tries at opening the lock includes a pawl in contact
with the fence-lever and a spring loaded ratchet wheel against
which the pawl operates. If the proper code in not set in, and the
manipulator attempts to open the locking bar of the typical
combination lock, the fence-lever can not drop into the gates of
the tumblers, but rather comes to rest on the outer edge of the
tumbler wheels. The fence-lever then slightly rotates on the wheels
and also makes contact with the pawl, thus pushing th ratchet wheel
and registering one stroke. If desired, the ratchet wheel may be
coupled to an indicator on the face of the lock to indicate the
number of advances or strokes that the ratchet wheel has taken.
Further, if desired, a keyway and special key may be provided to
release and reset the ratchet wheel to the original position. Also,
an additional set of tumbler wheels engaged by the limited-try
mechanism can be used to re-set the mechanism for a fresh start by
the owner.
The invention involves a technique to restrict or limit the number
of tries and attempts to find a lost or unknown code of a
combination lock, as by an unauthorized person seeking entry to the
depository by manipulation or surrepticious entry. This feature
will recognize and distinguish between attempts at unauthorized and
authorized manipulation. The feature can be made to limit the
number of unauthorized tries or attempts in search of the proper
code, and a predetermined number may be designed into the
mechanism. Then, for the purpose of this discussion, the
predetermined number may be established as five. Therefore, the
manipulator in search of the unknown code is limited to five
attempts to open the lock. Upon reaching the fifth attempt, the
restrictive manipulation mechanism will perform its function,
causing the lock to become unopenable. In this state, the lock
mechanism retains the ability to receive additional attempted codes
and even the proper code, but will cease to recognize any. The lock
will now refuse to open and is permanently locked. Further, other
functions that the limited try feature performs at the end of the
fifth attempt may be to explosively blow up the lock, sound an
alarm or bell, or otherwise indicate that unauthorized manipulation
has been underway.
An additional important ability of this invention is to recognize
the proper code set into the combination lock before reaching the
improper fifth attempt. When the proper code has been set up on the
combination lock dial, the limited-try feature recognizes it and
automatically returns the registering ratchet wheel to its original
position. This feature is considered necessary because it takes
into account the possibility of human error of the owner when he
manipulates the lock with the knowledge of the proper code but
makes a mistake in dialing the correct numbers. He will exercise
extreme care not to reach the fifth attempt at opening the lock
wnen he knows he will be then permanently locked out.
This invention also automatically advises the master or owner of
the security depository that attempts at manipulation have taken
place. This information will warn him to take precautionary
measures to eliminate further illicit attempts at opening this
combination lock. The information may be provided by a window or
dial on the face of the lock so that the master can observe the
unauthorized manipulation attempts by the tell-tale register. A
visual indicator will also notify the observer that the full number
of unsuccessful tries has been made and that other means will now
have to be used to open the depository.
Under emergency conditions, the limited-try feature will permit the
owner to intentionally perform a lock-out condition, thereby
precluding anyone to open the lock. After the emergency, the owner
can reset the lock to its functioning condition.
BREIF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the invention and many of the
attendant advantages thereto will be readily appreciated as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings wherein:
FIG. 1 is a isometric view partially cut away showing the
limited-try mechanism in association with a standard combination
lock;
FIG. 2 is a plan view of the rear of a combination lock partially
cut away to show the detail of the limited-try mechanism; and
FIG. 3 is a side view of a combination lock partially cut away
showing the details of the limited-try mechanism.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now the drawings, wherein like reference numerals
designate corresponding parts in the several views, there is shown
in FIG. 1 generally a combination lock 10. The conventional lock
comprises a casing 12, and a base 14 which is the internal rear
surface of the face plate secured to a door (not shown) with
suitable fastener means.
The casing 12 contains a plurality of tumblers 16 mounted for
rotation with a shaft and a dial (both not shown). Each of the
tumblers 16 has a suitable notch or gatee 18, all of which must be
in proper alignment in order to eventually nestle a fence-lever 24.
Note FIGS. 2 and 3. As shown in FIG. 2, forward of the said
tumblers 16 is a drive wheel cam 20 having a radially indented cam
slot 22 therein. Coacting with the drive wheel cam 20 is a
fence-lever 24 having an integral, rearward extending bar 26 to
co-acting with the gates 18 in the tumblers 16, best shown in FIG.
1. This construction, just described in general, is conventional
with most combination locks and further details are considered
unnecessary.
The fence-lever 24, as shown in FIG. 2, is shown in two positions,
one solid and the other as dot-dash phantom to show its cooperation
with a limited-try mechanism 28 according to the invention.
The limited-try mechanism 28, according to the present invention,
comprises a pusher lever 30, also shown in one solid and the other
dot-dash phantom, mounted for rotation about a pivot screw 32.
Pusher lever 30 has a surface which is contacted by the fence-lever
24 when an attempt is made to open the lock, and will hereinafter
be further explained. At an eccentric pivot point 34 on push lever
30 is attached for articulation a feeder pawl 36. Feeder pawl 36 is
spring-biased into engagement with the teeth of a ratchet wheel 40
by a spring 38 having an arm hooked over the back of the feeder
pawl 36 and helically wound about the eccentric pivot point 34. The
ratchet wheel 40 is spring-biased for clockwise rotation by a
helically wound spring 42, shown in FIG. 3, under the ratchet wheel
40. The ratchet wheel 40 is mounted for rotation on an axis 44
extending above the top surface of the ratchet wheel. Further, on
the top surface of the ratchet wheel is a circular cam surface 46
interrupted by a notch 47. A lockout bar 48 is pivotally attached
to the extended portion of the axle 44 by a cross pin 50 and is in
contact with and normally in a raised position on the circular cam
surface 46. The ratchet wheel 40 is held from freely rotating
clockwise by a holding pawl 52 having a tooth engaging portion 51
and a lever portion 53 about a screw 54. The holding pawl 52 is
spring-biased into engagement with the ratchet teeth by a spring
56.
In operation, assuming the normal manipulating procedure to open a
combination lock with 5 sets of numbers and therefore 5 tumblers,
the dial is first turned to the left or counterclockwise a minimum
of six times. This action causes the lock spindle to pick up all
five tumblers. The dial is then stopped at the first number setting
of the code of the combination, thus aligning one of the gates in
the tumbler with the fence-lever. The dial is then turned to the
right passing the next number four times and stopping on it the
fifth time to align the second tumbler. The dial is then turned to
the left passing the third number of the code three times and
stopping the fourth, then turned to the right two times past the
fourth number and stopping the third time, then turned left once
past the fifth number and stopping the second time. This procedure
aligns the gates 18 of the five tumblers 16 with the fence-lever
24. The dial finally is turned to the right to zero thus aligning
the cam slot 22 of the drive wheel 20 with the fence-lever 24.
Then, depending on the type of lock, the dial is held on zero and
the locking bar located in the center of the dial is rotated, or
the dial is continued to be turned to the right. Turning the
locking bar disengages the cam wheel 20 and permits the
spring-loaded fence lever 24 to enter the aligned gates 18 of the
tumblers 16. By turning the dial further to the right, the bolt of
the lock is withdrawn and the depository is opened. This normal
manipulation procedure of the lock does not engage the limited-try
mechanism except at the end of the final opening turn when the
fence-lever 24 strikes the lever portion 53 of holding pawl 52 to
pivot the tooth engaging portion 51 out of engagement with the
ratchet wheel 40 permitting it to rotate counterclockwise to the
original reset position.
For unauthorized manipulation in search of the proper code to open
the lock, the following action takes place. The manipulator turns
the dial in the same sequence as oulined above with a selected set
of numbers, perhaps from a list as previously described. When the
dial is finally turned to zero and the locking bar located in the
center of the dial is turned or the dial is continued passed zero,
and presuming the improper code was inserted, the bar 26 of
fence-lever 24 contacts at least one of the edges of the tumblers
16 rather than entering the gates 18. When this attempt or try is
made to open the lock as by rotating the dial to the right beyond
zero, the fence-lever 24 now makes contact with the push lever 30
which pushes the feeder pawl 36 into one of the teeth and rotates
the ratchet wheel 40 one stroke or one tooth position. The holding
pawl 52 engages the tooth next advanced by the bias of spring 56
and holds the ratchet wheel 40 in the counterclockwise advanced
position.
The unauthorized manipulator, after finding that the lock will not
open, will no doubt insert a second combination of numbers and
repeat the opening operation. Again, if the proper combination has
not been set in, the bar 26 of fence-lever 24 will rest on the edge
of the tumblers 16 and when an attempt is made to open the lock,
the fence rotates and makes contact with the pusher lever 30 which
subsequently advances the ratchet wheel 40 another position
counterclockwise. The limited-try mechanism has now registered the
two attempts made to open the lock with the wrong set of numbers.
Without knowing this, the unauthorized manipulator continues
inserting combination codes searching for the proper code that will
open the lock. Upon reaching the fifth attempt, the ratchet wheel
40 has been advanced to the fifth tooth position. In this position,
the cam surface 46 on the top surface of the ratchet wheel reaches
a point where the lockout bar 48 will fall into the notch 47 by
virtue of the bias of spring 49 under the crosspin 50. In this
lockout position, any attempts, authorized or unauthorized, to open
the lock, will cause the fence-lever to advance and its inside
surface 25 will strike the distal end of the lockout bar 48 thereby
precluding the bar 26 from entering the gates 18 of the tumblers
16. As can be now understood, the limited-try mechanism has
rendered the lock unopenable and the manipulator is completely
locked out. The locking mechanism will continue to refuse to
recognize any code of numbers set in, and the manipulator is
unaware that this action has taken place.
The master or owner of the depository will be aware of this
condition when he is sure that he has set in the proper code,
because the lock refuses to recognize the proper code. If desired
in the construction of the lock, a hole may be provided to accept a
special tool or key that may be inserted to release the holding
pawl 52 from the ratchet wheel 40 allowing the ratchet wheel to
rotate clockwise by virtue of its spring bias to its original
position lifting the lockout bar 48 from behind the fence-lever
24.
This novel invention also recognizes that the owner of the
depository may inadvertantly set in the improper code when
attempting to open the combination lock. From the prior discussion,
it is obvious that he has at least four tries. However, as is
obvious from the prior discussion, the limited-try mechanism
operates only when the combination has been set in, the dial
returned to zero, the locking bar in the center of the dial has
been set, and an attempt is made to draw the bolt or open the lock.
If, when the owner is dialing in the combination and realizes he
has inadvertantly set in an improper number, he should begin from
the start by redialing the proper combination. As soon as the
proper combination of numbers has been used, prior to the lockout
feature operating at the fifth try, the limited-try mechanism will
be automatically reset.
Obviously, numerous modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that, within the scope of the appended
claims, the invention may be practised otherwise than as
specifically described herein.
* * * * *