The present invention relates to cylinder locks. More specifically, the present invention provides a cylinder lock having improved security features.

Existing cylinder locks have been found to be vulnerable to attack by applying a lateral force to the cylinder lock until it breaks into two pieces, whereby the broken piece on the attack side can then be removed allowing access to the locking cam. Such attacks can be successful because a cylinder lock is inherently weak across the portion that bridges the cam and connects each cylinder in a double cylinder lock, or across the portion that connects the cylinder to a back-plate in a single cylinder lock.

Attempts have been made to improve cylinder locks by inserting a length of material into the bridging portion to strengthen it. Other modifications include providing a line of weakness, such as a break slot, in the housing. This is intended to cause the cylinder lock to break at that weakened point in the housing, rather than across the bridging portion, if a lateral force is applied to the cylinder lock, thereby leaving part of the cylinder housing in the lock to inhibit access to the locking cam.

An aim of the present invention is therefore to provide a cylinder lock having improved security features.

According to the present invention there is provided a key-operated lock mechanism, comprising: a first housing defining a first bore; a first rotatable lock member mounted in the first bore and adapted to receive a key thereby to release the first lock member for rotation within the first bore; a second housing connected to the first housing in a spaced arrangement; and a locking cam co-axial with and connected to the first rotatable lock member for rotation therewith, the locking cam being disposed externally of and between the first and second housings, wherein a separate bridging member is adapted to receive a portion of each of the first and second housings and to be secured thereto to thereby interconnect the first housing and second housing, the bridging member being arranged to have substantially the same external cross-sectional shape and dimensions, in a radial plane relative to the axis of rotation of the lock member and locking cam, as has corresponding parts of each of the first and second housing.

An advantage of this invention is that, if the cylinder locking is attacked, the first housing will tend to break before the bridging member. This arrangement means that at least part of the first housing will remain in the lock aperture, even if the broken part of the first housing is removed, thereby inhibiting access to the locking cam. Existing cylinder housings can easily be adapted to incorporate the stronger bridging member.

Preferably, a tapped hole is provided through the bridging member in a direction transverse to the axis of rotation for securing the lock mechanism in an aperture in a door, such that the cylinder lock can be secured in a door via the bridging member. Hence, if the cylinder lock is attacked and the first housing is broken, the bridging member should remain fixed in the door in its aperture, together with the remaining portion of the first housing to which it is connected, and thereby inhibit access to the locking cam .

Preferably, the first housing has a line of weakness, such that the housing breaks at said line of weakness before failing anywhere else when a sufficient lateral force is applied to the cylinder lock.

Preferably, the line of weakness is a slot provided through part of the first housing. Preferably, the slot is provided through at least part of the first bore. Preferably, the slot contains filler material to inhibit any ingress of dirt into the first housing.

Preferably, the bridging member comprises a material that is harder than that of the first housing. Preferably, a tapped hole is provided on an external surface of the bridging member for receiving a member with a corresponding screw thread to provide a projection from the bridging member to inhibit a tool from being positioned over the bridging member.

Preferably, the locking cam is spaced from the first housing and the bridging member further comprises a first guard member arranged in the space between the first housing and the locking cam, the first guard member having substantially the same external cross-sectional shape and dimensions in a radial plane relative to the axis of rotation of the lock member and locking cam as has the corresponding portions of the first housing.

Preferably, the locking cam is spaced from the second housing and the bridging member further comprises a second guard member arranged in the space between the second housing and the locking cam, the second guard member having substantially the same external cross-sectional shape and dimensions in a radial plane relative to the axis of rotation of the lock member and locking cam as has the corresponding portion of the second housing.

Preferably, the guard member is at least in part hoop-shaped having a bore suitable to allow the rotatably locking member to engage with the locking cam.

Preferably, a plurality of corresponding holes are provided in the bridging member and the first and second housings such that pins can be inserted through said corresponding holes to secure the bridging member to the first and second housings.

Preferably, the shape and dimensions of the housings correspond to a Euro profile cylinder.

Preferably, the second housing defines a second bore having a second rotatable lock member mounted therein, which is adapted to receive an external input and thereby be rotated within the second bore, and wherein the axis of rotation of the second lock member is co-axial with the axis of rotation of the (first) lock member and the locking cam, which locking cam is also connected to the second lock member for rotation therewith.

Preferably, the locking cam is configured to rotate with either the first lock member or the second lock member. Preferably, the second rotatable lock member is adapted to receive a key thereby to release the second lock member for rotation within the second bore, wherein said external input is rotation of the key.

According to the present invention there is also provided a key- operated cylinder lock, comprising: a first housing defining a first bore; a first rotatable lock member mounted in the first bore and adapted to receive a key thereby to release the first lock member for rotation within the first bore; a locking cam co-axial with and connected to the first rotatable lock member for rotation therewith, the locking cam being disposed externally of and spaced from the first housing; and a guard member secured to the first housing and arranged in the space between the first housing and the locking cam, the guard member having substantially the same external cross-sectional shape and dimensions in a radial plane relative to the axis of rotation of the first lock member and locking cam as has the first housing. An advantage of this invention is that if the cylinder lock is attacked and part of the first housing is broken, the cam guard will inhibit access to the locking cam even if the broken first housing, or broken part thereof, is removed.

Preferably, a tapped hole is provided through the guard member in a direction transverse to the axis of rotation for securing the lock mechanism in an aperture in a door, such that the cylinder lock can be secured in a door via the guard member. Hence, if the cylinder lock is attacked and the first housing is broken, the guard member should remain fixed in the door in its aperture, thereby inhibiting access to the locking cam. Preferably, the first housing has a line of weakness, such that the first housing breaks at said line of weakness before failing anywhere else when a sufficient lateral force is applied thereto.

Preferably, the line of weakness is a slot provided through part of the first housing. Preferably, the slot is provided through at least part of the first bore. Preferably, the slot contains filler material to inhibit any ingress of dirt into the first housing. Preferably, the guard member comprises a material which is harder than that of the first housing.

Preferably, the guard member has a tapped hole on an external surface for receiving a member with a corresponding screw thread to provide a projection from the guard member to inhibit a tool from being positioned over the lock mechanism.

Preferably, a plurality of corresponding holes are provided in the guard member and the first housing such that pins can be inserted through said corresponding holes to secure the guard member to the first housing.

Preferably, the shape and dimensions of the first housing correspond with those of a Euro profile cylinder.

Preferably, the lock mechanism further comprises: a second housing defining a second bore; and a second rotatable lock member mounted in the second bore and adapted to receive an external input and thereby be rotated within the second bore, the second housing being secured to the guard member and thereby connected to the first housing in an opposed arrangement such that the axis of rotation of the second lock member is coaxial with the axis of rotation of the first lock member and the locking cam, the locking cam further being connected to the second lock member for rotation therewith.

Preferably, the locking cam is configured to rotate with either the first lock member or the second lock member.

Preferably, the second rotatable lock member is adapted to receive a key thereby to release the second lock member for rotation within the bore, wherein said external input is a rotation of the key.

Preferably, the locking cam is disposed externally of and spaced from the second housing and the guard member is further arranged in the space between the second housing and the locking cam. Preferably, the second housing has substantially the same external cross sectional shape and dimensions in a radial plane relative to the axis of rotation of the lock members and locking cam as has the first housing.

Preferably, the guard member is at least in part hoop-shaped having a bore suitable to allow the rotatably locking member to engage with the locking cam.

An example of the present invention will now be described with reference to the following figures, in which:

Figure 1 shows a standard double-sided cylinder lock;

Figure 2 shows a double-sided cylinder lock having a bridging member connecting the two housings of the cylinder lock, according to the present invention;

Figure 3 shows the bridging member of Figure 2 in more detail;

Figure 4 shows a double-sided cylinder lock having a bridging member which further comprises two guard members arranged to protect the cam; and Figure 5 shows a double-sided cylinder lock having only a single guard member.

Referring to Figure 1 initially, there is shown a standard double cylinder lock, generally indicated 10, as is well known in the art. The particular cylinder lock 10 shown in Figure 1 , and indeed throughout the accompanying figures, has a "Euro profile", although it will be appreciated that the present invention is not limited to a Euro profile double cylinder lock.

As is well known, the standard cylinder lock 10 comprises a first housing 1 1 connected to a second housing 12 in a spaced arrangement with a rotatable locking cam 13 disposed externally of and between the two housings 1 1 , 12. The housings 1 1 , 12 are integrally formed as a single component from the same material. A mounting hole 14 for securing the cylinder lock 10 within an aperture in a door (not shown) is provided adjacent the locking cam 13, at a point where the first and second housings 1 1 , 12 join together. The mounting hole 14 is provided in a transverse direction through the cylinder lock 10 and is preferably tapped to receive securing means, such as a bolt, having a corresponding screw thread.

The first housing 11 defines a bore 15, within which is mounted a rotatable locking member 16. The rotatable locking member 16 is arranged coaxially with the locking cam 13 and is rotatably connected to the locking cam 13, typically by a cluster (not shown) that is configured to enable the locking cam 13 to be rotated by the rotatable locking member 16.

The rotatable locking member 16 is key-operated, and may be a part of a tumbler lock, a wafer tumbler lock or disc tumbler lock, the components of which are all housed within the housing 11. These types of lock are well- known and hence will not be explained in detail here.

The second housing 12 also defines a bore (not shown), within which may be mounted a rotatable locking member 17. The rotatable locking member 17 in the second housing 12 may also be key-operated, similar to the rotatable locking member mounted in the first housing 11. Alternatively, it may be hand-operated, comprising a 'thumb-turn cylinder' (not shown), for example, as is well-known in the art. In the example shown, each housing 11 , 12 contains a first rotatable lockable member 16 and a second rotatable lockable member 17, respectively.

The second rotatable lockable member 17 is also rotatably connected with the locking cam 13, again typically by a cluster (not shown). Preferably, the clusters are configured to permit the locking cam 13 to be rotated independently by rotation of either the first or second rotatable locking member 16, 17.

Figure 2 shows a first embodiment of the present invention, wherein a cylinder lock 110 comprises a first housing 111 and a second housing 112 connected in a spaced arrangement by a separate bridging member 118 that spans the locking cam 113. The bridging member 118 has a mounting hole 114 for securing the cylinder lock 110 into a door (not shown). The bridging member 118 is, preferably, formed of a harder material than that of the housings 111 , 112, such as hardened steel. In terms of operation and purpose, the cylinder lock 110 is very similar to the standard cylinder lock 10, shown in Figure 1 and described above.

In addition to the bridging member 118, each of the housings 111 , 112 should, ideally, also incorporate a line of weakness, 119, 120, positioned between each end of the cylinder lock 110 and the bridging member 118, respectively. The line of weakness 119, 120 will preferably comprise a slot which passes through at least part of the bore portion 121 , 122 of each housing 111 , 112. The slot may contain a filler material to inhibit the ingress of dirt into the housing. If only one line of weakness 119 is provided then it should be provided in the housing 111 that will be exposed on the external side of a door to which it is to be fitted.

As can be seen from Figure 3, the bridging member 118 comprises two portions 123, 124 each adapted to receive a portion of the first and second housings 111 , 112, respectively, and to be secured thereto.

The bridging portion 118 is provided with a plurality of holes 125 on the two receiving portions 123, 124, which holes 125 are aligned with corresponding holes (not shown) provided on the first and second housings 111 , 112. Securing pins 126, or other suitable securing means, are inserted through the holes 125 to secure the bridging member 118 to the housings 111 , 112. The securing pins 126 are, ideally, finished to be flush with the surface of the bridging member 118.

A recessed section 127 of the bridging member 118, which is recessed to allow the locking cam 113 to rotate, comprises a solid section of material arranged to span the space between the first and second housings 111 , 112 in which the locking cam 113 is disposed. The recessed section 127 connects the two receiving portions 123, 124 together. The bridging member 118 is ideally formed from a single piece of material.

The housings 111 , 112 may be formed separate components, each with edges adapted to fit into the receiving portions 123, 124 of the bridging member 118. Alternatively, a standard cylinder lock 10 may be machined into two separate housings 1 1 1 , 1 12, removing the portion that connects the housings 1 1 1 , 1 12 together, and adapting the edges, as required.

As can be seen from Figure 3, the bridging member 1 18 is arranged to have substantially the same external cross-sectional shape and dimensions, in a radial plane relative to the axis of rotation of the rotatably lock member 1 16 and locking cam 1 1 3, as has corresponding parts of each of the first and second housing 1 1 1 , 1 12.

Figure 4 shows an embodiment of a double cylinder lock 210 similar to the arrangement described above for Figures 2 and 3, but wherein the bridging member now comprises first and second guard members 228, 229 for protecting either side of the locking cam 213. Accordingly, the locking cam 213 is spaced from each of the first and second housings 21 1 , 212, such that the first guard member 228 is arranged in the space between the first housing 21 1 and the locking cam 21 3, and the second guard member 229 is arranged in the space between the second housing 212 and the locking cam 213.

The first and second guard members 228, 229 each have substantially the same external cross-sectional shape and dimensions in a radial plane relative to the axis of rotation of the rotatable lock members 216, 217 and locking cam 213 as has the corresponding portions of the first and second housings 21 1 , 212, respectively.

Furthermore, in this embodiment the first guard member 228 can be said to be secured to the first housing 21 1 and the second guard member 229 can be said to be secured to the second housing 212.

A mounting hole 214 is provided for mounting the cylinder lock 210 within an aperture in a door (not shown) using suitable fixing means, and a line of weakness 219 is provided in at least the first housing 21 1 .

Additionally, a tapped hole 230 is provided on an external surface of the bridging member 218 for receiving a member with a corresponding screw thread, such as a grub screw (not shown), to provide a projection from the bridging member 218 to inhibit a tool from being positioned over the bridging member 218 in an attack.

Figure 5 shows an embodiment of a cylinder lock 310 similar to the cylinder lock 210 of Figure 4, with the difference that the bridging member 318 comprises a single guard member 328, which is arranged in a space provided between the first housing 311 and the locking cam 313.

The guard member 328 has substantially the same external cross- sectional shape and dimensions in a radial plane relative to the axis of rotation of the first rotatable lock member 316 and locking cam 313 as has corresponding portions of the first housing 311.

Furthermore, in this embodiment the guard member 328 can be said to be secured to the first housing 311. It will be recognised that the bridging member 318 shown in Figure 5 could easily be adapted for use with a single cylinder lock (not shown).

A mounting hole 314 is provided for mounting the cylinder lock 310 within an aperture in a door (not shown) using suitable fixing means, and a line of weakness 319 is provided in at least the first housing 311.

In both of the embodiments shown in Figures 4 and 5 and described above, the guard members 228, 229, 328 are preferably in the form of hoops, each having a bore corresponding to that defined in the respective housings to which the guard members are secured. This allows the rotatable lock members mounted in the housings to rotatably engage with the locking cam 213, 313 through the hoops, via clusters (not shown), or other suitable means.

Ideally, a line of weakness is provided in each of the first and second housings.

Although not shown, each of the bridging members 118, 218, 318 could be may also be provided with a tapped hole on an outer surface to receive a threaded member, such as a grub screw, to provide a projection, similar to the arrangement described for the cylinder lock 210 shown in Figure 4. It will be recognised that the present invention is not limited to the particular embodiments described herein.

An example of a Euro profile cylinder lock mechanism according to the present invention may comprise a bridging member, preferably made from case hardened steel, 'wrapped' around a pre-machined standard Euro profile double cylinder. The bridging member may have two substantially U-shaped cradle portions, each with a 10mm overall width and wall thickness of 2mm, connected by a solid region having an area of 10mm x 10mm.

Each cylinder housing may be pre-machined or otherwise adapted to fit into the substantially U-shaped cradle portions. The housings may be secured to the bridging member using, for example, six "M2" fixings threaded through corresponding 2.5m holes provided in the bridging member and housings, although pins driven into the holes are preferred as securing means. At least two of the fixings in each housing may be inserted in opposite directions for each of the housings, for added strength.

A line of weakness can be cut into at least one of the cylinder housings on or past the second line of pins (with respect to the locking cam) of a tumbler lock arrangement, or similar, mounted in that housing. The position of the line of weakness provided in a housing will, however, depend on the length of the bridging member.