Abstract:
A secure container comprises an external wall including a door ( 56 ) and a lock ( 36 ) for securing the door ( 56 ). The lock ( 36 ) comprises a lock mechanism ( 47 ) located internally of the wall ( 56 ) and a plate ( 40 ) mounted between the wall ( 56 ) and the lock mechanism ( 47 ). The plate ( 40 ) is tiltable in response to applied pressure.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method and apparatus for the protection of locks against forcible entry. The invention has particular application in the protection of security locks as found on, for example, safes against attack by drilling. 
     It is obviously important that locks and in particular lock mechanisms be protected against unauthorized access; such access attempts are often made by force. One field where locks must be secure against such attacks is in the area of self-service terminals (SSTs) used to deposit or dispense valuable media, particularly financial services centers (FSCs) and automated teller machines (ATMs); FSCs and ATMs are nearly always accessible to the public, and are known to contain large amounts of cash. 
     A conventional ATM contains a safe in which the banknotes to be dispensed by the ATM are stored. Access to the safe is gained through a door provided with a conventional safe lock, typically a combination lock. The lock mechanism is mounted on the inner face of the safe door and controls the release of a locking bar or bolt which secures the door. 
     At present, the lock is protected by the provision of what is known as a hard plate; that is, a plate of fully hardened steel mounted in an enclosure between the safe door and the lock mechanism. To open the safe door forcibly without damaging the valuable media within the safe it is necessary to drill through the safe door and the hard plate, typically at a number of locations, to gain access to the lock mechanism, which is then forced to release the locking bar or bolt. A conventional hard plate and a lock fitted with such a hard plate are shown in FIGS. 1 and 2 of the accompanying drawings. 
     Existing hard plates are capable of withstanding a drilling attack from carbide tipped drills for at least 10 minutes. However, drilling technology is constantly improving and recently developed solid carbide drills, although very brittle, are able to penetrate existing hard plates in a relatively short period. 
     A further problem with existing hard plates that has been identified by the applicants is that, once a hard plate is freed from its support on the lock spindle, which may be achieved by hammering the spindle into the safe, the hard plate may be pushed to the rear of the hard plate enclosure by the pressure of a drill. The plate comes to rest adjacent the internal lock mechanism, which provides a secure substrate for the drilling operation, and thus facilitates breach of the lock. 
     Provision of ever-harder and more drill-resistant hard plates is technically feasible. However, the cost of such materials would add disproportionally to the manufacturing costs of an ATM, the safe already being one of the most expensive single elements of a typical ATM. 
     SUMMARY OF THE INVENTION 
     It is among the objects of embodiments of the present invention to alleviate or obviate these and other problems of existing lock security features. 
     According to the present invention there is provided a secure container comprising: 
     an external wall including a door; and 
     a lock for securing the door, the lock comprising a lock mechanism located internally of the wall and a plate mounted between the wall and the lock mechanism, the plate being tiltable in response to applied pressure. 
     The invention also relates to a lock for fitting to such a secure container, and further to a hard plate for fitting to such a lock. 
     In use, the plate will tilt or move in response to applied pressure, away from the point of application. Thus, the plate will move to evade the point of a drill on the application of drilling pressure, such that the cutting point of the drill will have difficulty gaining or be unable to gain adequate purchase to begin cutting through the plate. The tilting of the plate will also result in the drill being subject to lateral forces; the hardest drills, such as solid carbide drills, are very brittle and are likely to break if an attempt is made to drill into a hard surface that is at an angle other than perpendicular to the drill axis. 
     Preferably, the material from which the plate is made is itself resistive to cutting by a drill, to provide additional security. Materials known in the art may be used, such as fully toughened steel. Alternatively, or additionally, the plate may be coated with a cutting resistant material. 
     Preferably, the plate is mounted on a pivot, conveniently at or adjacent the center of the plate. The pivot is conveniently provided by a tapered bush mounted on or around a lock spindle, which spindle extends from the internal locking mechanism to the exterior of the lock. 
     Preferably, the plate has a convex outer surface. Such a surface will tend to deflect a drill point and increase the likelihood of brittle drills snapping. 
     Preferably also, the plate is tiltable such that at least a part of the plate outer surface is at an angle of at least 31° from the plane of the adjacent container wall. Standard metal drills have a point angle of at least 118° (for drilling relatively hard metals the point angle tends to be higher), such that a drill extending through a hole drilled perpendicular to the container wall will cause the plate to tilt to an angle at which the drill point will be unable to achieve a point contact with the plate and thus will be unable to initiate the drilling of a hole in the plate. 
     Preferably, the plate is rotatable, most preferably through 360°. This is most conveniently achieved by mounting a circular hard plate in a corresponding circular lock housing. This construction provides an additional degree of freedom of movement for the plate, increasing the difficulty in stabilizing the plate to facilitate drilling and prevent breakage of brittle drills. 
     Preferably, the container is a safe, which may be incorporated in an automated teller machine (ATM). 
     According to a further aspect of the present invention, there is provided a method of protecting a lock mechanism provided in a secure container, the method comprising providing a tiltable plate between the lock mechanism and an external wall of the container. 
     According to another aspect of the present invention there is provided a secure container comprising: 
     an external wall including a door; 
     a lock for securing the door, the lock comprising a lock mechanism located internally of the wall and a plate mounted between the wall and the lock mechanism, the plate having an external surface which is inclined relative to the wall. 
     The plate surface may be inclined, conical, frusto-conical, concave or convex, or otherwise configured such that a drill located in a drilled hole in the container wall which is perpendicular to the wall will contact the plate surface at an angle other than 90°, and preferably at an angle such that the drill point will not contact with the plate surface, such that the drill point is unable to initiate drilling of a hole in the plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other aspects of the present invention-will now be described by way of example only and with reference to the accompanying drawings in which: 
     FIG. 1 shows a typical prior art hard plate; 
     FIG. 2 is a schematic cross-section of a lock fitted with the hard plate of FIG. 1; 
     FIG. 3 is a schematic cross-section of a lock fitted with a hard plate according to an embodiment of the present invention; and 
     FIG. 4 shows a sketch of a drill bit contacting the hard plate of FIG.  3 . 
    
    
     DETAILED DESCRIPTION 
     Referring first to FIG. 1, this shows a typical prior art hard plate  10  for a safe door lock. The hard plate  10  comprises a generally rectangular flat plate of hardened steel. The plate  10  has a notch  12 , which rests upon a bolt of the lock (not shown) in order to support the plate  10 , and an aperture  14 , through which passes the spindle of the lock. 
     The plate  10  is located between an outer wall of the safe, typically the safe door, and the internal locking mechanism of the lock, as illustrated in FIG.  2 . The assembled lock  20  includes an exterior lock dial  22 , mounted on a lock spindle  24  which passes through the safe door  26  and through the hole  14  in the hard plate  10 . The spindle  24  passes into a lock casing  28  and is connected to the internal lock mechanism (not shown) contained therein. A mounting bracket  30  for the lock casing  28  provides an enclosure in which the plate  10  is mounted. 
     In one recognized method of attempting to gain unauthorized access to the safe, the lock dial  22  is knocked off the spindle  24 , which is then hammered into the lock casing  28  such that the spindle  24  is driven into, and dislodges, the lock casing cover  29 . A drilling attack then commences on the safe door  26  and the plate  10  until access has been gained to the interior of the lock casing  28 . A number of holes will normally have to be drilled to gain sufficient access to the lock mechanism, and the limited space will normally require that the holes are drilled one at a time; typically, a first operator equipped with a power drill will crouch in front of the safe door, while a second operator pushes the first operator towards the door to provide a load on the drill. Once the necessary holes have been drilled, further hammer attacks on the lock mechanism inside the casing  28  may then serve to disengage the lock and allow the door  26  to be opened. 
     Reference is now made to FIG. 3 of the drawings, which shows a lock  36  fitted with a hard plate  40  according to the present invention. The parts of the lock  36  in this Figure are generally similar to those shown in FIG.  2 . However, in this instance the hard plate  40  has a convex outer surface  41 . Further, the plate  40 , the lock casing  46  containing the lock mechanism  47 , and the lock mounting bracket  48  are circular, such that the plate  40  may rotate within the enclosure defined by the bracket  48 . The plate  40  is freely mounted on the lock spindle  50 , and is supported by a tapered bush  42  which surrounds the lock spindle  50 . Provision of the bush  42  enables the plate  40  to pivot about the spindle  50 ; thus, when force is applied to a point on the plate  40 , the plate will tend to pivot in the direction shown by arrows A, the bush  42  and the bracket  48  being dimensioned to permit the plate  40  to pivot to a predetermined minimum inclination, as described below. Accordingly, if a drill point comes into contact with the outer surface of the plate  40 , the plate  40  will move away from the drill, which is therefore unable to gain purchase to begin cutting. 
     The contact between the plate  40  and a drill  52  is shown in schematic detail in FIG. 4, where the hard plate  40  is shown tilted due to the drill bit  52  pressing against the plate  50  in the course of an attempted drill attack. Due to the ability of the plate  40  to pivot to a minimum predetermined inclination on contact with a drill  52 , the point  54  of the drill  52  does not contact the plate  40 , as described below. 
     A standard metal drill has a point angle “P” of 118°, and tilting of the plate  40  such that the plate surface is at an obtuse angle of greater than 121° to the drill axis, which will generally be perpendicular to the safe door  56  (the drill will typically pass through a hole drilled in the door  56  perpendicular to the door surface), will prevent the point  52  from contacting the plate  40 . Thus, the drill cannot begin cutting through the plate  40 . Furthermore, solid carbide drills are very brittle, and the lateral forces induced in such a drill being pushed into the plate  40  will tend to cause the drill to snap. 
     Thus, it can be seen that provision of a curved, pivotable and rotatable hard plate in conjunction with a safe lock will serve to reduce the likelihood of a drill attack successfully penetrating the lock, and so increase the security of the lock. 
     It is to be understood that the foregoing is for illustrative purposes only, and that various modifications may be made to the apparatus described herein without departing from the scope of the invention. For example, the hard plate may be fixed, but provided with an inclined outer surface, that is the hard plate may be conical or the like.