Note: Descriptions are shown in the official language in which they were submitted.
CA 02249802 1998-10-06
FINGERPRINT ACTIVATED LOCK
FIELD OF THE INVENTION
The present invention relates to electronic physical access control devices,
and more
particularly to fingerprint-activated locks.
BACKGROUND OF THE INVENTION
Fingerprint-based physical access control benefits users, who do not need to
carry
physical credentials (such as keys or cards) or to memorize a secret code. For
the facility owner, it
also provides a higher level of security in that access permissions are
granted and tracked on a
strictly personal basis, and the capability to obtain such permissions cannot
be duplicated, lost or
stolen. A number of commercial fingerprint-based access control products
recently appeared on
the market. Examples include the VeriprintTM 2000 unit by Biometric
Identification Inc.
(www.biometricid.com), FingerscanTM (also called TouchLockTM) product family
by Identix
International (www.fingerscan.com.aul, and Friend-TouchTM by Yamatake
(www.yamatake.co.ipl. All available systems physically separate the
fingerprint processing
module from the electric lock module and require an external power source to
operate.
Generally, a fingerprint-based access control system has a registration mode
and a
collation mode. During registration mode, enabled by a "master user", one or
more of a person's
fingerprints are processed and their key features, usually a set of
fingerprint minutiae (endings or
bifurcations of ridges), are stored in a database of authorized users. In the
collation mode, a
person requesting access submits a fingerprint image to the system. The system
extracts the
fingerprint's key features from the image, then evaluates the degree to which
the features in the
submitted fingerprint match the ones of a record in its database. If, and only
if, a strong match is
found, the person is allowed access.
Due to computational and algorithmic limitation, commercially available
fingerprint-
based physical access systems currently require the assignment of a user
identification code to be
entered by the user as part of the entry request process. The code is used by
the system to
eliminate the need for a lengthy search through the complete set of fingers
registered with the
system before deciding whether to grant access permission. Recent improvements
in fingerprint
matching algorithms and increases in the computational power of embedded
processors have now
CA 02249802 1998-10-06
made it possible to conduct searches through hundreds of fingerprints in under
one second.
Identicator Technology (www.identicator.com), amongst others, now offers
hardware and
software capable of achieving this. While Identicator uses a compact optical
sensor, sensors on a
single silicon chip, offering an even more compact design, are also available
from a number of
other companies, such as Veridicom (www.veridicom.com), or Hams Authentec
(www.semi.harris.com).
While the removal of the user's need to enter an identification code is a
straightforward
improvement to existing fingerprint access control systems, there remain other
deficiencies:
1. Installation requires a significant time and effort of professional
installers, since it involves
the connection of the fingerprint processing device to the electric locking
system and to an
external power source, preferably with a back-up battery to ensure operation
when power is
disconnected. Even if the fingerprint processing electronics are converted to
operate on
batteries, known electrical locks require a substantial amount of energy to
activate their
mechanical assemblies. To operate the door locking mechanism, such assemblies
energize an
electric motor or a solenoid for a substantial period of time (a second or
more), greatly
shortening the usable life of consumer batteries. Known battery-operated door
locking
mechanisms also frequently place additional restrictions on users, such as
requiring the user
to turn a knob or open the door within a limited time period or to actively re-
lock the door
after entry.
2. Users are often falsely barred entry due to inconsistencies in their
placement of a finger
against the sensor's surface. Typical errors, especially in the early period
of usage, include
submitting a finger not previously registered, exposing a portion of a finger
diffei~ent from the
one used during registration, and variations in the pressure applied on the
finger during
fingerprint image acquisition.
3. To obtain passage, users need to execute a sequence of separate motions,
first to submit their
fingerprints for collation and then to unlatch and open the door. This
sequence prolongs the
entry or exit through the door. A compromise then needs to be made to either
sacrifice
convenience by keeping the door locked, or to sacrifice security by keeping
the door
unlocked for extended periods of time.
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CA 02249802 1998-10-06
By way of background, current access control mechanisms are described in
United States
patent 5493621 to Matsumura, USP 5701770 to Cook and Mutray, USP 5775142 to
Kim, USP
5475996 to Chen, USP 5339662 to Goldman and USP 5678868 to Williams and Kirby.
An
overview of lock technology, both mechanical and electrical, appears in "The
Complete Book of
Locks and Locksmithing" by Bill Philips (ISBN 0-07-049866).
SUMMARY OF THE INVENTION
This invention seeks to provide a compact fingerprint-activated lock
mechanism, which
minimizes the time and motions required of authorized users attempting to gain
passage;
minimizes the likelihood of inconsistent positioning and pressure applied to
the user's finger
during the acquisition of fingerprint image for collation; minimizes
electrical energy
consumption; and is economical to manufacture, install and maintain.
In accordance with this invention, there is provided an electric lock
comprising a locking
member releasably movable between a locked and an unlocked position; a movable
member,
operatively coupled to said locking member and manually operable for applying
a load on said
1 S locking member in a direction of said unlocked position; a fingerprint
sensing means, including a
fingerprint sensor associated with said movable member for producing a control
signal in
response to an eligible fingerprint; and release means responsive to said
control signal for
releasing said locking member in said locked position to allow said locking
member to move
under said load to said unlocked position, whereby said load is obtained by
manual manipulation
of said movable member.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described by way of example only
with
reference to the accompanying drawings, in which
Figure 1 shows an external perspective view of the unsecured (outside) and
front sides of
the lock fitted into a door,
Figure 2 shows an external view of the secured side of the lock,
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CA 02249802 1998-10-06
Figure 3 shows a side view of the locking mechanism in a locked state,
Figure 4 shows a front view of the locking mechanism in a locked state,
Figure 5 shows a top view of the locking mechanism in a locked state,
Figure 6 shows a perspective view of the locking mechanism in a locked state,
Figure 7 shows a side view of the locking mechanism after it was electrically
unlocked,
Figure 8 shows a side view of the locking mechanism when it is being manually
unlocked,
Figure 9 shows a side view of the locking mechanism after the door was opened,
Figure 10 shows a perspective view of an alternative embodiment using a ribbon
spring,
and
Figure 11 shows a diagram of the electrical control system.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to Figure l, a door 1 contains a locking mechanism to allow
discriminating
access to a space, such as a building, an office, a safe or a cabinet. When
the door is in a locked
state, a deadbolt 5 is placed in a corresponding opening in strike plate 8
mounted on a door frame
(not shown). A user wishing to open the door from the outside grabs handle 2
and presses their
thumb against pushbutton 3. A fingerprint sensor 4 is mounted to the surface
of pushbutton 3,
allowing the lock to acquire an image of the user's fingerprint as the spring-
loaded pushbutton 3
starts travelling inward. The vertical orientation of the fingerprint sensing
surface reduces the
likelihood of dust and dirt residing on the surface and, therefore, provides
for a better fingerprint
image quality.
As will be further explained below, if the user is authorized to unlock the
door, the lock
retracts deadbolt S at about the same time the user completes depressing
pushbutton 3. This then
allows the user to push or pull the door open. If the user is not authorized
to unlock the door, the
deadbolt remains extended. A standard pin-tumbler cylinder 9 is provided as
well, to allow
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unlocking the door in the rare cases where the lock electronics fail to
operate properly, for
example due to battery failure. Users will typically hide the mechanical key
away for
emergencies and will not use it during the normal operation of the lock.
An unlocking knob 21 on the other side (inside) of the door allow free exit
passage for
any user. A spring-loaded tongue 6 may protrude out of the lock's front plate
7 below deadbolt 5.
Since strike plate 8 does nor contain an opening opposite tongue 6, the tongue
is retracted when
the door is closed and is free to protrude only when the door is open. It thus
serves as a door
open/close sensor.
Figure 2 shows an external view of the lock from the door's inside. A user
wishing to
unlock the door for exit only needs to turn knob 21. A set of control
pushbuttons 23 and a display
24 allow users to operate various functions of the lock, as commonly provided
in electrical access
control systems. These include adding and removing users, registering
additional fingers, setting
time-dependent access permissions, reviewing the entry/exit log, etc. The
display 24 is normally
turned off to preserve energy, but is fumed on once the user touches any of
the control
pushbuttons 23. When battery charge becomes too low, a warning message is
flashed periodically
on the display 24. The user then lifts cover 25 to replace the battery.
Figures 3, 4, 5 and 6 provide various views on the internal lock mechanism
when it is in a
locked position. Lock frame 19 is secured to the door. Tail 16 of deadbolt 5
is linked to the back
end of frame 19 through links 18 and 39, having a common joint 40. Spring 41
operates between
frame 19 and link 39 to provide a down bias to joint 40. Push solenoid 26 is
mounted on frame 19
under joint 40 such that its pin 27 blocks the down movement of joint 40.
Deadbolt 15 is,
therefore, blocked from retracting into the lock even under a forcible entry
attempt. -
Pushbutton 3 is connected via wire spring 12 to the tail 16 of deadbolt 5.
Spring 12 pivots
around pin 29 which is secured to the lock's housing, and is therefore
stationary with respect to
frame 19. The deadbolt end of spring 12 is placed in a hole 17 in tail 16.
Under normal operation,
a person wishing entry places their thumb on the finger sensing surface 4 of
pushbutton 3 and
then applies pressure on the pushbutton. As the pressure reaches a fixed
threshold to overcomes
the resistance of spring 12, the pushbutton starts moving inward. This action
causes switch 28 to
close, in turn energizing the electronic circuitry using power provided by
battery 31. A fingerprint
image is then acquired by sensor 4 and is communicated to the processor
circuitry mounted on
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CA 02249802 1998-10-06
PCB 30. As pushbutton 3 continues to travel inward, it energizes spring 12,
which then exerts a
growing retraction force on tail 16 of deadbolt 5. If the processor determines
that the user is
unauthorized to open the lock, it shuts itself down and nothing filrther
happens, maintaining the
door in a deadlocked state.
If, however, the processor detemnines that the user should be allowed to open
the door, it
energizes solenoid 26 for a brief moment. This causes solenoid pin 27 to be
pushed towards joint
40, in turn causing it to bend upward. The bending path away from the solenoid
is unhindered
allowing the deadbolt to retract under the force of spring 12, in the process
transferring energy
from spring 12 to spring 48 mounted between the back side of deadbolt 5 and
frame 19. This
allows the user to push the door open unhindered. Following the brief
energizing of the solenoid,
the processor may shut all power off, since the door will remain unlocked for
as long as the user
is depressing pushbutton 3.
As the angle of joint 40 when locked can be made close to 180 degrees, only a
very small
fraction of the force spring 12 applied to link 18 is transmitted by the joint
to resist the pushing of
solenoid pin 27. The total amount of time the solenoid needs to be activated
to guarantee
unlocking is, therefore, typically less than 50 milliseconds and, in virtually
all cases, less than 100
milliseconds.
Figure 7 shows the state of the lock mechanism once it has been unlocked by
the brief
energizing of solenoid 26, but before the user has opened the door.
The lock may also be unlocked mechanically by rotating either inside knob 21
or outside
pin-tumbler cylinder 9 using a matching key. Lever 11 is secured on one side
to bar 10, and has
an L-shaped configuration at the other end, with bar 45 extending under tail
16 (see Figure 8).
Counterclockwise rotation of knob 21 or cylinder 9 causes bar 10 to turn and
to push bar 45
against dog-leg protrusion 42 of link 18. As figure 8 shows, this causes joint
40 to move away
from solenoid pin 27, freeing the deadbolt to retract. Bar 45 then pushes
against protrusion 43 of
deadbolt tail 16, pulling the deadbolt into the retracted position and
unlocking the door.
Referring to Figure 4, bar 10 is connected to tail 46 of cylinder 9 such that
fuming handle
21 counterclockwise does not require cylinder 9 to turn. Switch 47 is
positioned such that it is
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CA 02249802 1998-10-06
normally open, but closes when cylinder 9 is turned. Switch 47 is used to
signal the processor that
a manual unlocking event has occurred, allowing such events to be logged for
fixture auditing.
Referring now to Figure 7, when the door is in a closed position, whether
locked or not, a
tongue 6 is held at a retracted position by strike plate 8. Tongue 6 is biased
to extend out of the
S lock's front by a leaf spring 13 secured at one end to the front plate 7 by
bolt 14. The other end of
leaf 13 reaches just under deadbolt 5. As shown in Figure 5, tongue 6 is
narrower than deadbolt S.
When the door opens tongue 6 is thus released prior to deadbolt 5. The release
causes the upper
end of leaf spring 13 to enter a notch 1 S in deadbolt S, holding it in a
retracted position even
while the user releases pushbutton 3. The new state of the locking mechanism
is shown in Figure
9. The lock will remain in this state for as long as the door is held open,
allowing it to close again
without the interference of deadbolt 5.
Closing the door causes strike plate 8 to push in tongue 6, and, therefore,
bends back
spring leaf 13. This causes the upper end of leaf 13 to retract out of notch
15, thereby releasing
deadbolt 5 to be extended into the corresponding opening in the strike plate
by the force of spring
48. The lock is thus restored to its fully deadlocked position shown in
Figures 3, 4, 5 and 6.
In an alternarive embodiment, the jointed links 18 and 39 with their
associated joints, the
biasing spring 41 and deadbolt sprint 48, may all be replaced by a single
ribbon of spring steel 44
as shown in Figure 10. The ribbon is biased to bend towards pin 27 of solenoid
26 by
appropriately slanting the mounts of ribbon 44 to fi-ame 19 and tail 16.
Mechanical unlocking
may be provided by bar 45 lifting ribbon 44 away from pin 27. This ribbon-
based mechanism
will not withstand attempts at a forced entry as well as the jointed links
mechanism described
above, but this alternative is simpler and cheaper to produce.
Figure 11 shows the electronic circuitry mounted on PCB 30. Thicker lines
represent
power connections, while thinner ones represent low-power signals. The closing
of switch 28 by
the movement of pushbutton 3 (not shown), causes the output of OR gate 38 to
move to a high
state, in turn causing MOSFET power transistor 35 to provide a ground
connection to processor
32. The power from battery 31 then energizes processor 32 with its associated
memory. Processor
32 immediately raises one of the other inputs to OR gate 38, ensuring that it
will continue to
receive power regardless of the state of switch 28. It then proceeds to
energize sensor 4 through
power transistor 34. Sensor 4 acquires the submitted fingerprint image and
transmits it to
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processor 32. To save energy, processor 32 then shuts off power to sensor 4.
Using a program
stored in its ROM, the processor performs feature extraction from the
fingerprint image and
compares the submitted features with the features of fingerprints of
authorized users stored in its
non-volatile (Flash) RAM memory.
S If the collation succeeds, it energizes solenoid 26 using power transistor
36 for a brief
moment. This causes the door to unlock as described above. The processor thin
registers the
unlocking event in the log it keeps in its non-volatile memory, using the date
and time provided
to it by real-time clock 33. Clock 33 has its own small battery to enable it
to operate even when
battery 31 is being replaced. Finally, the processor enables shutting off
power to itself by
removing the signal from the gate of transistor 3S.
If the door is unlocked manually, using a key to tum cylinder 9 (see Fig. 4),
switch 47
closes, causing the processor 32 to be energized, similarly to the operation
of switch 28. Upon
starting up, the processor reads the state of switch 47 and realizes that it
is closed, indicating a
manual unlocking event. The processor registers the event in the event log,
then shuts the power
1S off.
The connection of power to processor 32 may also be triggered when pressing
any one of
control pushbuttons 23 (see Figure 2). The processor then energizes LCD
display 24 and interacts
with the user as necessary. When no more user requests are received for a pre-
determined amount
of time, eg, 30 seconds, the processor shuts power off to display 24 and to
itself, preserving
energy.
As described herein, retracting the deadbolt in the current invention involved
only
enabling a short electrical pulse to a solenoid, consuming less energy than
prior art designs. This
allows the lock to be battery-operated, with batteries lasting years before
requiring replacement.
In turn, this greatly reduces the effort and expense involved in installing
and maintaining such
2S locks, and eliminates lockout during power grid interruptions. In addition,
unlike prior-art locks,
no shear or friction forces are applied to the solenoid pin regardless of user
actions. The solenoid
therefore need not be powerful and can be of a compact and economical design.
This design also
eliminates wear and tear associated with prior art designs, thereby increasing
the lock's reliability
and longevity.
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Another reason for the reducrion in installation effort is that the
fingerprint sensor is
integrated with the door lock itself, eliminating the need to mechanically
mount two separate
assemblies and to electrically connect them to power sources and to each
other.
The use of a thumb-pushbutton above a vertically oriented fixed handle
provides a
number of advantages over other arrangements. The thumb contains the most
feature-rich
fingerprint, hence its use reduces the likelihood of errors in fingerprint
collation. Either hand may
be equally employed to open the door. In case one of the thumbs' fingerprint
is damaged, or is
hidden by a bandage or a glove, the other hand may be conveniently used
instead. Users will
naturally submit the same fingers (thumbs) during registration and during
collation, reducing the
likelihood of false authorization rejections due to the submission of a non-
registered finger.
Finally, this arrangement is convenient to operate whether the door opens by
pushing or by
pulling.
Users wishing to unlock and open the door are required by the current
invention to
merely apply pressure to a thumb pushbutton. With a sufficiently fast
processor, the door will be
unlocked for authorized users by the time the pushbutton is fully depressed,
creating the illusion
that the door is always unlocked for them. This provides a substantial
improvement over prior art,
where unlocking a fingerprint-based access control mechanism involves a
sequence of separate
motions and an associated delay.
By using a handgrip and a thumb-pushbutton and by triggering the acquisition
of a
fingerprint image only once a predetermined level of pressure has been applied
to the pushbutton,
the current invention is more likely than prior art to obtain consistent
images of fingerprints even
without any user training. -
The embodiment involves a small number of parts and is quite tolerant of
production
inaccuracies. It is also compact and will operate independent of gravity,
allowing its parts to be
easily rearranged to fit into limited spaces of various shapes.
The embodiment described a fully self contained unit which uses fingerprint
collation to
control entry but allows for free exit. Straightforward modifications, well
known in the art of
electronic access control system design, should allow for access to the lock's
database contents by
an external computer and for the addition of exit control. When a physical
wire connection is
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CA 02249802 1998-10-06
made between the lock and an external computer, it makes sense to also provide
an external
power supply to replace or augment the battery-powered lock described here.
Although the invention has been described with reference to certain specific
embodiments, various modifications thereof will be apparent to those skilled
in the art without
departing from the spirit and scope of the invention as outlined in the claims
appended hereto.
