GB2202577A

GB2202577A - Combination locks

Info

Publication number: GB2202577A
Application number: GB08806676A
Authority: GB
Inventors: Cyril Hilsum
Original assignee: General Electric Co PLC
Current assignee: General Electric Co PLC
Priority date: 1987-03-20
Filing date: 1988-03-21
Publication date: 1988-09-28
Anticipated expiration: 2008-03-21
Also published as: GB2202577B; GB8706679D0; GB8806676D0

Abstract

A combination lock comprises an electronic circuit arrangement for comparing a keyed-in number or sequence of numbers with a preset number or sequence, the keyed-in numbers being displayed on a digital display, such as an LCD display. The circuit arrangement may allow only a small number of attempts at the required combination, before either giving an audible alarm or preventing further access for a period of several minutes, in order to prevent an unauthorised user from quickly running through all possible combinations. <IMAGE>

Description

Cbi nation Locks This invention relates to combination locks.

Such locks are fitted, for example on security cabinets, and have hitherto generally been mechanical devices comprising, say, one or more rotatable dials on the periphery of which are inscribed a series of different numbers, it being necessary for an operator to rotate the dial or dials so as to line up a predetermined sequence of these numbers, i.e. the combination number, with a given mark, a mechanical linkage then causing release of the lock so as to enable the door of the cabinet to be opened.

In such locks the rotation of the dials is necessarily slow, and they must be manipulated so that the required numbers are accurately aligned with the mark, which can be irksome for a user in a hurry. Mechanical wear of the dials is also a problem, this in some cases giving an indication of the combination number enabling release of the lock.

It is an object of the present invention to provide an alternative form of combination lock wherein the above problems are avoided.

According to the present invention in a combination lock comprising memory means for storing a predetermined sequence of digits, an electrically addressable digital display, manually operable means for enabling digits which are to be displayed on said display to be set by an operator, and electric circuit means effective to initiate release of the lock when the digits displayed on the display have a predetermined relationship to said predetermined sequence of digits, said memory means is arranged to store information in respect of operation of said manually operable means.

Said information may relate to the number of occasions on which the release of said lock has been attempted or effected and/or the times at which said release has been attempted or effected over a given period.

The combination lock may for example be fitted within a padlock or may be mounted in the door of a security cabinet.

A combination lock which is mounted in the door of a security cabinet may be energised from a battery accessible from outside the cabinet, the lock being arranged to remain in or fail-safe to the locked condition if the battery voltage falls below a predetermined level.

The digital display is suitably a liquid crystal display.

Such a display has the advantage of extremely low power consumption.

Preferably the circuit means includes means to suspend operation of the lock if an operator sets more than a predetermined number of times a series of digits on the display which do not have said predetermined relationship to said sequence of digits. Such a lock will have the advantage that an unauthorised user will not be able to run quickly through all combinations of digits.

A combination lock in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawing, which is a schematic diagram of the lock.

Referring to the drawing, the lock to be described is fitted on a security cabinet 1 and comprises electronic circuitry 3 mounted on the door 4 of the cabinet, the circuitry 3 being energised from a battery 5. The circuitry includes a memory 7 capable of storing an eight digit number, this number being settable by means of a set button or buttons 9 provided on the inside of the door 4. Mounted on the outside of the door are an eight digit liquid crystal display 13 and a display button 15 which is effective to cause the display 13 to show any number which may be set by a user, using controls 17 also carried on the outside of the door.The lock also includes a spring loaded metal spigot 19 carried by the edge of the door, the spigot 19 being arranged to project into a notch 21 in the door frame of the cabinet such that the combination of spigot and notch effectively locks the door 4 of the cabinet. The spigot 19 is arranged to be withdrawn from the notch 21 to unlock the door 4 by the action of an electromagnet 11, under the control of the circuitry 3. The door 4 also carries a release handle 23 of conventional form for a security cabinet.

In use of the display the user uses the set button 9 to program the memory 7 with a desired combination of four two-digit numbers, zero counting as a valid digit, use of the set button 9 causing the display 13 to display the set numbers. Releasing the set key will cause the numbers no longer to be visible on the display 13.

In order to open the door subsequently it is necessary for the user to press the display button 15, the display 13 initially displaying a series of zeros. Using the controller 17, the user must now change the displayed digits in turn, either individually or as groups of two or more to match the combination of numbers previously set in the memory 7. When the display number matches this combination of numbers, the electronic circuitry 3 activates the electromagnet 11 so that it pulls the spigot 19 from the notch 21 against the action of the spring, the door then being openable by the action of the release handle 23, a plate 25 on which encloses the retracted spigot 19. After a few seconds the electromagnet 11 will release the spigot, which will then attempt to return to its previous position under the action of the spring, but will be prevented from doing so by the action of the plate.As the release handle is turned back releasing the spigot when the door is shut, the spigot will fall back into the notch 21 thus again locking the door.

The spigot 19 may alternatively be arranged to lock the release handle 23 against rotation, with a locking tongue or tongues (not shown) either being released or positively withdrawn when the handle is rotated after operation of the electromagnet 11.

It will be appreciated that whilst the form of the electronic circuitry 3 is not described, it may be readily devised. It will be seen that the circuitry may be analogous to that used in a liquid crystal display alarm clock. Thus coincidence of the combination number set in the memory 7 and the number set on the display 13 will instead of operating a buzzer as in an alarm clock cause activation of the electromagnet 11. An oscillator may be incorporated in the circuit to charge a capacitor which is in turn used to activate the electromagnet, so that an electromagnet requiring a higher voltage than that supplied by the battery 5 may be used.

In order to prevent an unauthorised user from using the controller 17 to run quickly through all the combinations of numbers on the display 13, the circuitry 3 may be arranged to impose electronic delays which allow only a small number of combinations to be tried, so as to allow a small number of setting errors by an authorised user, before stopping access to the display for a period of time, typically several minutes. Alternatively or additionally the display 13 can be arranged such that the displayed numbers vanish after, for example, three tries, and do not reappear for several minutes. It may be advantageous In some circumstances to incorporate an audible alarm within the lock which operates after, for example three tries. This alarm could be arranged to run the battery down, automatically preventing further tries as well as deterring an unauthorised user.The display 13 may be arranged to incorporate an indication that the alarm has operated.

It will be appreciated that it is a particular advantage of a combination lock in accordance with the invention that no matter how frequently the lock is used, there will be no physical or mechanical wear and thus no indication of the combination of digits stored in the memory. It will also be appreciated that the number of digits programmed within the memory and subsequently displayed will depend on the level of security required. The lock may be made more secure by arranging for the display 13 to display less than the complete combination of digits set in the memory 7, so that a predetermined sequence is required to release the lock rather than a set of numbers of a length indicated by the capacity of the display 13.

A louvred film may be positioned in front of the display 13 so as to provide a further level of security in that an observer will then not be able to watch an authorised user setting the correct combination of digits on the display.

Whilst it is particularly advantageous to use a liquid crystal display in view of its low power consumption, a combination lock in accordance with the invention may, in principle, use any other form of digital display, for example light emitting diodes. Where a liquid crystal display is used however, the display and circuitry will use such low power that they may be driven from small dry batteries.

The lock will be fail safe in that the door will be locked in the event that the battery is low. The battery will, of course, have to be replaceable from the outside of the cabinet.

The electronic circuitry 3 may include a counter to record the number of times the lock has been opened, and the count recorded may be displayed automatically or on call. A digital clock circuit (not shown) may also be included, so that the time or times at which the lock has been released or release has been attempted over a given period may be stored and subsequently displayed.

Claims

1. A combination lock comprising memory means for storing a predetermined sequence of digits, an electrically addressable digital display, manually operable means for enabling digits which are to be displayed on said display to be set by an operator, and electric circuit means effective to initiate release of the lock when the digits set by said operator have a predetermined relationship to said predetermined sequence of digits wherein said memory means is arranged also to store information in respect of operation of said manually operable means.

2. A combination lock in accordance with Claim 1 wherein said information relates to the number of occasions on which the release of said lock has been attempted or effected and/or the times at which said release has been attempted or effected over a given period.

3. A combination lock in accordance with Claim 1 or Claim 2 which is fitted within a padlock.

4. A combination lock in accordance with Claim 1 or Claim 2 which is mounted in the door of a security cabinet and which is arranged to be energised from a battery accessible from outside the cabinet, the lock being arranged to remain in or fail-safe to the locked condition if the battery voltage falls below a predetermined level.

5. A combination lock in accordance with any preceding claim in which the digital display is a liquid crystal display.

6. A combination lock in accordance with any preceding claim in which the circuit means includes means to suspend operation of the lock if an operator sets more than a predetermined number of times a series of digits on the display which do not have said predetermined relationship to said sequence of digits.

7. A combination lock according to any preceding claim in which the circuit means is operable to activate an electromagnet which moves a metal spigot so as to release the lock.

8. A combination lock substantially as hereinbefore described with reference to the accompanying drawing.