This invention relates to an anti-tamper device, and particularly, but not exclusively, to an anti-tamper device for increasing the security of a cylinder mortice lock.

A cylinder mortice lock comprises a mortice lock which is mounted within, for example, a door or other fixture, for example, a window. The mortice lock is activated by means of a key which is fittable within a keyhole in a cylinder lock. Turning the key within the cylinder lock activates a cam which in turn activates a bolt thrower which results in the mortice lock either locking or unlocking as appropriate. The bolt thrower is typically positioned within the body of the door some distance from the cylinder lock.

The term "cylinder lock" or "cylinder mortice lock" is used to describe not only locks having a substantially circular cross section but also locks having other cross sections, for example, those having a substantially. oval cross section or so called "Euro-profile" cylinder mortice locks having a substantially "keyhole" cross section.

It is well known that it is relatively easy to tamper with a cylinder lock. Typically, a cylinder lock is positionable within a cylinder lock receiving aperture in a locking mechanism accessed via an aperture in a door. The cylinder lock has a portion of its outer surface threaded. The cylinder lock receiving aperture in the locking mechanism will also have a correspondingly threaded portion. The cylinder lock is thus held in place by threading the cylinder lock into the lock mechanism through the aperture in the door. Once the cylinder lock is in place, it is held in position by means of a grub screw passing through the lock mechanism which prevents further rotation of the cylinder lock within the lock mechanism.

Due to the physical dimensions of the door and of the lock, the cylinder lock is held in position in the door by means of only

a few threads and a grub screw.

Once the cylinder lock is in position a portion of the cylinder lock known as the head extends beyond a mounting surface of the door. It is relatively easy with the aid of, for example, a pipe wrench or vicegrips to rotate the cylinder thereby disengaging the grub screw from its retained position and allowing the cylinder lock to be removed. This results in the exposure of the bolt thrower in the lock mechanism.

The lock mechanism can then, for example, with the aid of a screwdriver, be moved into the unlocked position thus allowing access to a restricted area. Typically this may take 20 to 30 seconds.

Another potential weakness with a known cylinder mortice lock is that the surface of the door may be drilled to expose the bolt thrower. The bolt thrower may then be activated to move the lock mechanism to the unlocked position.

Alternatively, the cylinder lock mechanism may be drilled out allowing the cylinder lock to rotate in a conventional manner as if operated with a correct key. Alternatively, the face of the cylinder lock may be deformed to obtain purchase for an extracting tool.

According to the invention there is provided an anti-tamper device for securing a lock mounted in a fixture, the lock comprising a mortice lock mounted within the fixture, and a cylinder lock mounted in the fixture and having a head portion protruding from a mounting surface of the fixture, the anti- tamper device comprising a cylinder lock receiving portion shaped to receive the head of the cylinder lock and thus to substantially completely surround the protruding portion of the cylinder lock, and a keyhole access aperture allowing operation of the lock by means of a key.

The anti-tamper device according to the present invention therefore conceals the vulnerable outer surface of the head of the cylinder lock thus preventing a would be thief from gripping the surface of the head with, for example, a pipe wrench to rotate the cylinder off the grub screw.

Advantageously, the device comprises a collar having an inside diameter which is substantially equal to or slightly greater than the outside diameter of the cylinder head.

The collar may be positioned by removing the cylinder lock from the door in which it is mounted. The cylinder head may then be placed in the head receiving portion of the collar such that a first surface of the head is close to or abuts an inner surface of the collar.

Preferably the collar further comprises a head retaining means. The head retaining means may comprise, for example, a ring or a washer. Once the cylinder head has been placed in the head receiving portion of the collar, the head retaining means may be positioned on an opposite surface of the cylinder head to the first surface. The cylinder lock may then be replaced within the door.

This arrangement has the advantage that the collar is self fixing. The collar is arranged to be rotatable relative to the cylinder lock head if a force is applied to the surface of the collar. This means that if the collar is gripped by, for example, a pipe wrench, the force applied to the collar will result in the collar rotating.

Advantageously, the collar is held in position by means of one or more spring loaded pins which prevent rotation in normal use. However, the pins are weak, and application of force to the collar will result in the pins breaking allowing rotation of the collar.

The collar according to the present invention may be easily fitted to existing cylinder locks.

Advantageously, the collar further comprises a cover fittable within the key access aperture. The cover comprises a slit which allows a key to be inserted into a keyhole. The cover is rotatable within the key access aperture allowing a key to be turned in the keyhole, and therefore making both drilling of the cylinder lock mechanism and deformation of the face of the cylinder lock very difficult if not impossible.

The presence of the cover substantially conceals the vulnerable face of the head of the cylinder lock thus preventing a would- be-thief from drilling out the cylinder lock mechanism or deforming the face of the cylinder to obtain purchase for an extracting tool.

Alternatively, the anti-tamper device comprises an elongate bar comprising a cylinder lock receiving portion shaped to receive the protruding head portion of the cylinder, and a key access aperture allowing the lock to be operated by means of a key, and an elongate portion extending along a mounting surface of the door in which the lock is positioned.

The elongate bar allows a greater surface of the door to be covered, and is dimensioned and positioned such that the part of the door which would have to be drilled to allow access to the bolt thrower is covered by the elongate bar. This further adds to the security of the system.

The bar could be used in conjunction with the collar, in that the bar could be used on an external side of the door, and the collar could be used on an internal side of the door.

Embodiments of the invention will now be further described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a schematic representation of a first embodiment of the invention comprising a collar;

Figures 2, 3 and 4 are schematic representations of components of the collar of Figure 1;

Figure 5 is a schematic representation of a second embodiment of the invention comprising an elongate bar, and showing details of the security device fitted to a fixture.

Figure 6 is a schematic representation of the device of Figure 5 showing how the device may be fixed to a door;

Figures 7 and 8 are a schematic representations showing details of the device of Figure 5;

Figures 9 and 10 are schematic representations showing details of the device of Figure 5;

Figures 11a to llf are schematic representations showing details of a fixing of a device of Figure 5 to a door.

Figure 12 is a schematic representation of a conventional cylinder lock showing in more detail the grub screw locator V- groove and the final position of the cam in both locked and unlocked positions;

Figure 13 is a schematic representation of a further embodiment of the present invention showing the cam on a conventional cylinder lock repositioned by approximately 180° to the normal position shown in Figure 12.

Figures 14 and 15 are schematic representations of alternatively shaped cylinder mortice locks.

Referring to Figure 1, a first embodiment of an anti-tamper device according to the present invention is designated

generally by the reference numeral 10. The anti-tamper device is adapted to increase the security of a cylinder mortice lock. The cylinder mortice lock comprises a cylinder lock 11 positioned within a door 12 by. means of a threaded portion 13 which engages with a corresponding threaded portion in a cylinder receiving aperture in the lock mechanism. When the cylinder is in position, a portion of the cylinder known as the head 14 protrudes from the door.

The anti-tamper device 10 comprises a collar 15 comprising a cylinder head receiving portion 16. The head receiving portion 16 is dimensioned to allow the head 14 to fit within the aperture of the receiving portion 16. The cylinder is positioned within the collar 15 by initially removing the cylinder from the door 12. When the head 14 has been positioned within the head receiving aperture 16, a head retaining means 17 in the form of, for example, a ring is positioned on an opposite side of the head 14 to that in contact with the collar 15. The assembly is then re-positioned in the door 12 by screwing the cylinder lock 13 into the lock mechanism. Once in position, the device 10 is self fixing in that no other fixing is necessary to hold it in position.

A would be thief attempting to break the lock in order to enter a secured area to which access is prevented by means of the door 12 and the lock, will now find it much more difficult to break the lock. This is because if he attempts to grip the collar 15 by using, for example, a pipe wrench, the collar will merely rotate separately from the lock 13.

In order to allow authorised locking and unlocking of the lock 11, the collar 15 comprises a key access aperture 18 which allows an authorised person to insert a key into a keyhole in the cylinder lock.

Security is further increased by the presence of a disc 19 fittable within the key access aperture 18. The disc 19

comprises a slit (not shown) through which a key may be inserted. The disc 19 is rotatable within the aperture 18 to allow a key to be turned thus unlocking the lock 13.

Referring now to Figures 2 to 4, the device 10 is shown in more detail.

For convenience, rotation of the device 10 is prevented in normal use by the presence of two pins 40, 41 which protrude from the collar 15, and into the door 12. This facilitates authorised use of the lock. However, the pins 40, 41 are made from a very weak material, and if a force is applied to the collar, the pins will immediately snap allowing the collar to rotate.

The ring 17 serves to retain collar 15 to cylinder lock 11.

The key access aperture 18 in the collar 15 is offset to the same degree as the keyhole on the locking cylinder is offset in order to allow a key to be inserted into the keyhole with minimum clearance.

The device 10 may be positioned on either side of a door. It is equally important to prevent an unauthorised person from exiting a building from the inside. This is because a would-be thief may sometimes gain access to a building through, for example, a small window. If the would be thief wishes to make off with goods from the building which he has illegally entered, he must find another means of exit rather than, for example, a small window through which he entered. The device 10 may result in the thief being trapped within the building which thief may have to make a hasty exit via the small window through which he entered without taking any goods with him.

Referring now to Figure 5, a second embodiment of the invention is designated generally by the reference numeral 50. The device 50 comprises a cylinder head receiving portion 51, a key

access aperture 52, a disc 53, and an elongate bar 54. The cylinder 11 may be inserted into the device 50 in a similar manner to that described with reference to the device of Figure 1 but without the need for a retaining device 17. The device 50 is secured to a mounting surface of a door 12 by means of a concealed fixing 55 (shown in more detail in Figure 11) . An advantage of the elongate bar 54 is that the surface of the door 12 in the vicinity of the bolt thrower (not shown) is now covered by the elongate bar. This makes it very difficult, if not impossible for a would be thief to drill through the elongate bar in order to gain access to the bolt thrower.

Referring to Figure 11, the concealed fixings 55 are shown in more detail.

Referring to Figures 7 and 8 dimensions of the device 50 are shown in more detail.

Figures 9 and 10 show the key access aperture 52 and disc 53 in more detail.

Figures 11a to llf show the concealed fixing in more detail. The concealed fixing 55 comprises a central body 100, a bolt 101 and a screw 102. The concealed fixing 55 may be used in doors of various thicknesses by means of the screw 102 which may be screwed or unscrewed to provide an appropriate distance between the bolt head 103 and the screw head 104. Once the concealed fixing is in position, the device may be secured by means of a grub screw 105 which may be tightened by use of an alan key, or screwdriver.

Although the concealed fixing shown in these Figures has a variable length, an equally concealed fixing of a non-variable length may be used.

Referring to Figure 12, a conventional cylinder lock 120 is shown. The cylinder lock is screwed into position into a

cylinder receiving aperture in a lock mechanism contained in, for example, a door. A grub screw is inserted into position such that it is located in a V-groove 121 extending along the cylinder lock. Use of a key activates the cam 122 having an elongate end 123. Rotation of a key within a keyhole results in rotation of the cam 122 which in turn causes rotation of the elongate portion 123. The elongate portion 123 will come into contact with a bolt thrower which will activate the lock.

Turning now to Figure 13, a further embodiment of the invention is shown in which the cam 130 which is equivalent to the cam 122 of Figure 12, has been rotated by approximately 180° such that the elongate portion 131 now extends above the lock cylinder 132 as shown. This means that in the normal position, ie the position in which the key can be inserted or extracted with the lock either locked or unlocked, the elongate portion 131 will come into contact with the bolt thrower thus further adding to the security of the lock.

The anti-tamper device according to the present invention has been described in terms of a lock fitted into a door. However it is to be understood that the lock could be positioned in any similar fixture, for example, a window or a wall, and it is to be understood that the scope of the invention is not limited to an anti-tamper device for use with a lock in a door. In addition the device according to the invention could be used to protect any cylinder type lock.

The term cylinder lock, or cylinder mortice lock as used hereinabove includes locks having a substantially cylindrical cross section, as well as locks having other shaped cross sections such as substantially oval, or having a so called "Euro-profile". An oval cylindrical mortice lock is illustrated in Figure 14 and designated by the reference numeral 140.

A "Euro-profile" cylinder mortice lock is illustrated in Figure 15 and designated by the reference numeral 150.

Figure 14 is a schematic representation of a Euro-profile cylinder mortice lock showing the cross sectional shape of such a lock, and Figure 15 is a schematic representation of an alternatively shaped cylinder mortice lock.