Locking mechanism with emergency opening feature useful for a safe or vault

A locking mechanism of the key lock type or code lock type for installation in a door of a vault or safe, includes at least one locking bolt for movement between a locking position in which a door is locked and an unlocking position in which the door is released for opening, an electromechanical actuator connected to the locking bolt for moving the locking bolt between the locking position and the unlocking position, a time delay circuit so interacting with the actuator as to delay operation of the actuator for a specified time period, with the time delay circuit being so positioned as to be inaccessible upon closed door and including an activation input for cooperation with a switch accessible from outside such that the time delay circuit is activated.

BACKGROUND OF THE INVENTION 
The present invention generally refers to a locking mechanism useful for 
the door of a safe or a vault, and in particular to a locking mechanism of 
a type having at least one key-type lock or combination-type lock which in 
unlocked position releases at least one locking bolt. 
Common to all type of locking mechanisms, hereinafter called "lock" for 
short, of any type and construction, is the problem associated with loss 
or forgetting the key to open a locked door. Regardless as to whether a 
mechanical key or an electronic key or a type of lock that operates on the 
basis of a numerical combination or code are involved, assistance of a 
third party is normally needed for opening the lock, either with the help 
of a master key or with a spare key or, in a worst case scenario, by force 
that leads to damage or destruction of the structure. The use of force to 
open the lock becomes especially unavoidable in those situations in which 
for security reasons the production of a master key or spare key is not 
permitted, or in which for reasons of time constraint a master key or 
spare key can not be made available in due time. 
SUMMARY OF THE INVENTION 
It is thus an object of the present invention to provide an improved 
locking mechanism, obviating the afore-stated drawbacks. 
In particular, it is an object of the present invention to provide an 
improved locking mechanism which can be unlocked undamaged even in 
situations when a spare key or a master key is lost, without requiring the 
use of force. 
These objects, and others which will become apparent hereinafter, are 
attained in accordance with the present invention by providing a time 
delay circuit which so interacts with an electromechanical actuator for 
moving the locking bolt assembly between the locking position and the 
unlocking position, as to delay operation of the actuator for a 
predetermined time period, with the time delay circuit being so positioned 
as to be inaccessible when the door is closed and including an activation 
input for cooperation with a switch accessible from outside such that the 
time delay circuit is activated for delaying operation of the actuator for 
the selected time period. 
The present invention is based on the teaching to provide a locking 
mechanism equipped with an emergency opening function that can easily be 
triggered at any time but delays the release of the locked position after 
a predetermined waiting period as selected by the authorized user to best 
suit to respective conditions. A choice of the appropriate time delay 
ensures that an unauthorized person, even when having knowledge about the 
emergency opening function, is prevented from accessing the safe or vault 
because the unauthorized person has no knowledge about the duration of the 
waiting period. In that respect, the locking mechanism according to the 
present invention differs from so-called time locks used in high security 
containers such as e.g. vaults of banks. The function of such time locks 
is based on allowing a release of the locking bolt or other locking 
mechanism at a preset time, e.g. within normal business hours of a bank, 
even when using the proper key, either by an authorized person or 
unauthorized person who has acquired the key. 
When incorporating a locking mechanism according to the present invention 
within any of the known mechanical locks, the mechanical actuators for the 
locking bolt interact with a coupling device which interrupts the 
kinematic chain of action between the mechanical actuators and the locking 
bolt either when the electromechanical actuator responds or, optionally, 
when the time delay circuit is activated. In the event the locking 
mechanism according to the present invention is used for an 
electromechanical lock, the already existing electromechanical actuator is 
used for actuating the locking bolt so that it is only necessary to modify 
the actuator in a way as to be responsive to the time delay circuit. 
Preferably, the switch located outside of the secured space and provided to 
trigger the emergency opening function through activation of the time 
delay circuit is a push button operated switch which may be located in an 
area where the key to the lock is inserted or where an opening code is 
inputted on a key pad. Suitably, the switch is placed in an area that is 
not immediately visible from outside so as to increase the safety aspect. 
In particular, the switch may be recessed so as to be actuatable only via 
a small and inconspicuous aperture, optionally by insertion of a pin or 
special tool. Persons skilled in the art will understand that the switch 
communicating with the activation input of the time delay circuit may 
certainly also be placed separate from the locking mechanism e.g. in a 
central monitoring room. This would be practicable e.g. in connection with 
lockers or safe deposit boxes, whereby the line connecting the time delay 
circuit to the switch may then be guided and masked invisibly from 
outside. 
Suitably, the time delay of the time delay circuit may be set by adjusting 
elements that are inaccessible when the door is closed. Alternatively, or 
in addition, the time delay may fluctuate within optionally adjustable 
limits in accordance with a random process. An unauthorized person, 
triggering the emergency opening lock, is thus not in a position to 
predict when the locking mechanism will be activated for release of the 
locking bolt. 
According to another feature of the present invention, the time delay 
circuit is so designed as to receive a reset impulse when the lock is 
released, e.g. by a key or inputted code, to open the door. This is 
advantageous in situations when a relatively long time delay is selected 
and set because there is no necessity to wait for the end of the time 
delay period, in the event the physical key is found or the user remembers 
the key code. 
Suitably, at least the actuator and the time delay circuit can be 
battery-powered. This is especially advantageous for safe deposit boxes in 
hotel rooms which for the most part already run on batteries for saving 
wire installations. However, it is certainly within the scope of the 
present invention to provide an external power supply for at least the 
electromechanical actuator and the time delay circuit, as alternative or 
in addition to the battery-operated power supply. Thus, when the entire 
locking mechanism runs on batteries, the emergency opening function is 
maintained even though the batteries, that are typically inaccessible from 
outside, become exhausted. 
According to another feature of the present invention, the switch is 
operatively connected to an acoustic or visual signaling device which is 
triggered upon activation of the switch. In this manner, the safety aspect 
against unauthorized use is enhanced. The signaling device can be designed 
in a tamper-proof manner, especially when used directly with the locking 
mechanism. In a simple case, the signal may be constituted by a light 
emitting diode integrated in the door. If the switch is already located in 
the door and thus directly associated to the locking mechanism, the light 
emitting diode may be incorporated in the switch. In some applications, 
such as spaces with numerous lockers or safe deposit boxes, it may be 
suitable to install the signaling device or, optionally, a second 
signaling device connected in parallel, in a central surveillance room 
from where it can then be determined whether or not the emergency opening 
function is triggered by an authorized person. 
As a consequence of its relatively simple structure, the emergency opening 
mechanism according to the present invention can easily be integrated 
subsequently in a conventional locking mechanism for vaults or safes. 
Then, at least the switch and the time delay circuit are designed as 
retrofit kit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Throughout all the Figures, same or corresponding elements are generally 
indicated by same reference numerals. 
Turning now to the drawing, and in particular to FIG. 1, there is shown by 
way of example a safe deposit box typically used in a hotel room, equipped 
with a locking mechanism according to the present invention. The safe 
deposit box has a door 1 which has incorporated therein a conventional 
electromechanical lock that includes two locking bolts 2a, 2b in 
superimposed spaced-apart parallel disposition. The locking bolts 2a, 2b 
are actuated in unison in a conventional manner by an electromechanical 
actuator 20 (see FIG. 4) e.g. in the form of an electromotor followed by a 
suitable gearing. The electromotor is controlled by a control circuit 21 
and is encased by a housing 3 secured to the inside of the door 1. 
Electric energy is supplied to the electromotor and associated control 
circuit 21 by four batteries retained in a battery bay 4, as shown in FIG. 
1 by broken lines. 
The control circuit 21 is operatively connected to a control panel located 
on the outside of the door 1. As shown in FIGS. 2 and 3, the control panel 
includes a casing 5 made of suitable plastic material and secured to the 
door 1. On the outside of the casing 5 is a key pad 6 for inputting 
numbers 0 to 9. Through inputting the proper combination of numbers 
forming the key code and actuation of a confirmation or enter key 7, a 
user may unlock and access the safe deposit box. The control panel further 
includes a light emitting diode (LED) 8, e.g. green, for indicating the 
position "locked" and a light emitting diode (LED) 9, e.g. red, for 
indicating the position "unlocked". 
Incorporated inside the door 1 in addition to the control circuit 21 is an 
emergency opening device in the form of a time delay circuit 22 which, as 
shown in FIG. 4, has an output operatively connected via the control 
circuit 21 to the electromotor which operates the locking bolts 2a, 2b. A 
time delay preset knob 10 is located at the inside of the door 1 and 
permits selection of a time delay period e.g. from several minutes to 
several hours through adjustment of e.g. a potentiometer forming part of 
the time delay circuit 22. Activation of the time delay circuit 22 is 
effected via a push button operated switch 13 which is located hidden from 
view on the underside of the casing 5 (FIG. 3) and triggered through 
insertion of a key or pin or the like tool. 
When the switch 13 is actuated, a steady or blinking light of a signaling 
mechanism, e.g. in the form of a third light emitting diode (LED) 14 gives 
indication of the actuation. After elapse of the set time delay period, 
the time delay circuit 22 outputs a signal to the control circuit 21 which 
in turn activates the electromotor for retracting the locking bolts 2a, 2b 
from their locked position into an unlocked position to permit opening of 
the door 1. In order to insure a withdrawal of the locking bolts 2a, 2b 
even when the batteries are exhausted, the locking mechanism has an 
auxiliary jack 15 next to the switch 13 for connection of an external 
power supply. 
If after activation of the emergency opening device via the push button 
switch 13, the correct code, i.e. number code selected for this particular 
lock, is inputted via the key pad 6, the time delay circuit 22 will be 
reset by a signal inputted by the control circuit 21. At the same time, 
the control circuit 21 triggers in its normal functioning mode a 
withdrawal of the locking bolts 2a, 2b. 
It is noted that the foregoing description generally refers to a time delay 
circuit without illustrating a particular example because such time delay 
circuits are generally known to persons skilled in the art. Also, the 
artisan has a wide variety of commercially available integrated circuits 
like e.g. NE 555 from e.g. Texas Instruments or SGS Thomson at his or her 
disposal to form time delay circuits that best suit the situation at hand 
so that a detailed description of such a time delay circuit has been 
omitted for sake of simplicity. 
However, typically, electromechanical locks contain frequently a 
microcontroller or microprocessor which is programmable to perform a 
variety of functions, including the function of the time delay circuit and 
other control functions. Additional functions can also be programmed. For 
example, the control logic can be so dimensioned as to maintain activation 
of the LED 14 for signaling use of the emergency opening function until a 
particular clear signal is inputted. Alternatively or in addition, the 
locking mechanism may be so programmed as to permit use of the particular 
key for the switch 13 and number code for only one time but would bar any 
further use. Also, the use of the third LED 14 for indicating triggering 
of the emergency opening function may be substituted by other signaling 
mechanism, e.g. by simultaneous blinking of LED 8 and LED 9. 
Persons skilled in the art will also understand that the application of a 
time delay circuit according to the present invention may also be provided 
in other type of locks, differing from the non-limiting example as shown 
in FIGS. 2 and 3. For example, locks are known which use an electronic 
key, e.g. in form of a plastics card which contains a so-called 
transponder. An electronic lock of this type is provided with a 
transponder reading unit that is housed within the casing 5 and is able to 
output a coded radio signal of slight range. The transponder of the 
electronic key receives this signal to convert it into a coded response 
signal which is then received by the reading unit and decoded. Certainly, 
an electronic lock of this type may also be modified to include a time 
delay circuit to enable opening of the safe deposit box or other container 
when the electronic key is lost in a manner described above. 
While the invention has been illustrated and described as embodied in a 
locking mechanism with emergency opening feature for use with a safe or 
vault it is not intended to be limited to only those safety locks but can 
be used in any other situation where a safety locking function may be 
desired and various modifications and structural changes may be made 
without departing in any way from the spirit of the present invention. 
What is claimed as new and desired to be protected by Letters Patent is set 
forth in the appended claims: