FIELD The invention relates to a deadlock mechanism. BACKGROUND

Many existing locking mechanisms make use of a geared design. Typically, such locks comprise a cylinder, an actuator and a bolt. The cylinder is operated by the user of the lock and comprises one or more paddles, which extend radially from the centre of the cylinder and rotate about a central axis of the cylinder when the cylinder is turned. The actuator is pivotally attached to the casing of the lock and engages the cylinder paddle and the bolt, thereby coupling rotation of a key within the cylinder to motion of the bolt. Thus, when the key is turned in a first direction, the cylinder paddle engages with one or more teeth on the actuator, which rotates in the opposite direction. A second set of one or more teeth on the actuator mesh with a portion of the bolt and the rotation of the actuator causes the bolt to deploy, for example in a rotary manner or in a linear, rack-and-pinion-like manner. Thus, the components operate rather like gears. When the key is turned in a second direction, this action is reversed and the bolt retracts.

Such locks may also comprise a ratchet-and-pawl type deadlocking mechanism. The pawl is pivotally coupled to the casing and the bolt has a ratchet portion, which the pawl is biased to engage. A portion of the pawl cooperates with the cylinder to disengage the pawl from the bolt before the cylinder paddle engages the actuator.

The cylinders used in devices such as those described above are generally manufactured separately and have paddles which are provided in various standard sizes. The predefined size of the cylinder paddles fixes the distances and gear ratios between the cylinder, actuator, pawl and bolt to within a tolerance close to that achievable during the manufacture process. Small errors during manufacture can result in the device being inoperable. Accordingly, precise and therefore expensive manufacturing processes are required to ensure that each device operates correctly and provides a smooth locking action. An additional drawback with existing rotatable bolt mechanisms is that the aperture in the front plate through which the bolt passes must be sufficiently large to allow the length of the bolt to pass through when moving between a locked and an unlocked position. When the bolt is in a locked position, a large unfilled slot is left in the casing. As there is no supporting structure spanning this slot, the casing is likely to distort or collapse under the application of a compressive force to the sides of the casing. Accordingly, existing rotatable bolt designs are weak in comparison to their linear counterparts under a side load on the casing.

Accordingly, there is a need for an alternative solution.

SUMMARY

According to a first aspect of this invention, there is provided a deadlock mechanism comprising:

a bolt having a deployed configuration and a retracted configuration;

a deadlock member coupled to the bolt, the deadlock member moveable relative to the bolt to engage surrounding structure and thereby resist movement of the bolt from the deployed configuration; and

actuator means moveable between a first position in which the deadlock member is free to engage the surrounding structure and a second position in which the actuator means engages and retracts the deadlock member from the surrounding structure, thereby allowing the bolt to be moved to the retracted position.

By having a deadlock member moveable to engage surrounding structure and actuator means moveable to retract the deadlock member from the surrounding structure, a simple deadlock mechanism is provided, which requires no moving parts in the surrounding structure to deadlock the bolt when the bolt is in the deployed configuration. Accordingly, the deadlock mechanism can be easily installed into existing structures without requiring intricate modifications to the structure.

The deadlock member may be arranged to move linearly, for example by sliding, relative to the bolt. The bolt may comprise a first channel in which the deadlock member is slideably housed. The deadlock member may be slideably housed in the bolt. The bolt may comprise a guide pin and the deadlock member may comprise a guide track, such that movement of the deadlock member relative to the bolt is limited. In an alternative, the deadlock member may comprise a guide pin and the bolt may comprise a guide track. In a further alternative, the bolt may comprise at least one guide pin which cooperates with an edge of the deadlock member to define the movement of the deadlock member relative to the bolt. The at least one guide pin may comprise a roller. The bolt may be arranged to move relative to the surrounding structure between the deployed and retracted configurations. The movement of the bolt between the deployed and retracted configurations may be linear; it may be rotary. In the deployed configuration of the bolt, the deadlock member may be biased to engage surrounding structure.

The deadlock member may comprise a first edge having a substantially ramped portion such that the substantially ramped portion is arranged to abut surrounding structure during movement of the bolt from the deployed configuration towards the retracted configuration, so as to cause the deadlock member to retract, thereby allowing further movement of the bolt towards the retracted .configuration. The deadlock member may comprise a second edge arranged to abut the or other surrounding structure so as to resist movement of the bolt from the deployed configuration towards the retracted configuration. The second edge may be arranged such that the deadlock member can engage the surrounding structure to resist movement towards the retracted configuration, even if movement of the bolt into a fully deployed configuration is prevented. The second edge may also be ramped in order to achieve one or more of these functions. The actuator means may be coupled to the bolt. The actuator means may be pivotally coupled to the bolt and may also be coupled to allow translational movement of the actuator means relative to the bolt. The coupling may comprise a pivot. The coupling means may comprise one or more guide tracks and guide pins. The bolt may comprise a recess into which the actuator means protrudes. The channel may communicate with the recess.

The actuator means may be constrained to move along a particular path relative to the surrounding structure. The actuator means may comprise guide means, such as, a guide track or a shaped edge which interacts with the or other surrounding structure to constrain the movement of the actuator means along the path. The actuator means may be arranged to be engaged by a cylinder paddle. The actuator means may comprise a cylinder paddle-receiving portion. The cylinder paddle-receiving portion may be shaped to be engaged by a cylinder paddle. The actuator guide track or shaped edge may be configured to maximise contact between the cylinder paddle- receiving portion and the cylinder paddle during rotation of the cylinder paddle and subsequent movement of the actuator means relative to the surrounding structure. The guide track or shaped edge may be curved such that one or more ends thereof force the actuator towards the cylinder. The curve may be concave. The arrangement may be such that the cylinder-receiving portion, for at least part of the movement of the actuator means, follows a substantially arcuate path. The centre of substantially arcuate path may be about the centre of rotation of the cylinder paddle. A centre of rotation of the substantially arcuate path may substantially coincide with the centre of rotation of the cylinder paddle.

The actuator means may comprise a drive arm and a release member moveable relative to each other. The release member and the drive arm may be slideable relative to each other between a first relative configuration and a second relative configuration. One of the release member and the drive arm may comprise a guide track and the respective other may comprise a guide pin, such that movement of the release member relative to the drive arm is constrained thereby. The drive arm may comprise the drive means.

A first end of the drive arm may comprise the cylinder paddle-receiving portion. A first end of the release member may extend into the cylinder paddle-receiving portion in the first relative configuration such that, when rotating in a first direction, the cylinder paddle abuts the first end of the release member before engaging the cylinder paddle-receiving portion of the drive arm. The surrounding structure may comprise means on which the deadlock mechanism can be mounted. The surrounding structure may comprise a casing for the deadlock mechanism. The surrounding structure may comprise a locking pin against which the deadlock member can abut. The deadlock mechanism may further comprise an anti-tamper device. The anti- tamper device may resist access to the deadlock member. The anti-tamper device may resist an object retracting the deadlock member from the surrounding structure. The anti-tamper device may be coupled to the bolt. The anti-tamper device may be pivotally coupled to the bolt. A first end of the anti-tamper device may be pivoted to the bolt. A second end of the anti-tamper device may abut a surrounding structure.

The anti-tamper device may be a strengthening member. The strengthening member may be arranged substantially to fill an aperture, occupied by the bolt in the retracted configuration, when the bolt is in a deployed configuration. The width of the strengthening member may substantially correspond to the width of the bolt.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific embodiments in which the invention is embodied are described below by way of example only and with reference to the accompanying drawings, in which: Figure 1 shows a first embodiment of a deadlock mechanism and surrounding structure in a fully locked configuration;

Figure 2a shows the first embodiment of the deadlock mechanism and surrounding structure in a fully locked configuration with a side wall of the surrounding structure removed for clarity, with the bolt in a deployed configuration and the release member in a first position;

Figure 2b shows the first embodiment of the deadlock mechanism with the bolt between the deployed and retracted configurations and the release member in a second position;

Figure 2c shows the first embodiment of the deadlock mechanism with the bolt in the retracted configuration and the release member in the second position;

Figure 2d shows the first embodiment of the deadlock mechanism in a fully unlocked configuration, with the bolt in the retracted configuration and the release member in the first position; Figure 3a shows a second embodiment of the deadlock mechanism and surrounding structure with the bolt in the deployed configuration and the release member in the first position;

Figure 3b shows the second embodiment of the deadlock mechanism and surrounding structure with the bolt in the deployed configuration and the release member in the second position;

Figure 3 c shows the second embodiment of the deadlock mechanism and surrounding structure with the bolt in the retracted configuration and the release member in the first position; Figure 4a shows a third embodiment of the deadlock mechanism and surrounding structure having an anti-tamper device and with the bolt in the deployed

configuration; and Figure 4b shows the third embodiment of the deadlock mechanism and surrounding structure having an anti-tamper device and with the bolt in the retracted configuration.

SPECIFIC DESCRIPTION OF EXAMPLE EMBODIMENTS Figure 1 shows a deadlock mechanism 10 and a conventional cylinder lock 20. The deadlock mechanism 10 and cylinder 20 are mounted within a casing 30. The deadlock mechanism 10 comprises a bolt 40, a deadlock member in the form of a deadlock plate 60, actuator means in the form of a drive arm 50 and a release plate 70, and an anti-tamper device in the form of a strengthening arm 80. The cylinder 20 comprises a cylinder paddle 21. The casing 30 can be fitted to a door, with the cylinder 20 interacting with the deadlock mechanism 20 to lock and unlock the door by deploying and retracting the bolt 40, respectively.

The material of the casing 30, bolt 40, and strengthening arm 80 is mild steel. The material of the drive arm 50, deadlock plate 60 and release plate 70 is a mild steel alloy.

Each of these parts, together with its components, will now be described. The casing 30 has, when mounted for use, a back wall 31 , a front wall (not shown) and a side wall 32. Several cylindrical structures are mounted in the casing to extend between the front and back 31 walls. As best seen in Figure 2a, these include a pivot 33, a locking pin 34, a retaining pin 35 and a guide roller 36. The location and function of each of these structures will become apparent from the description hereinbelow of their function and interaction with other components. The front wall has an aperture for a key to be inserted into the cylinder 20. The side wall 32 has an aperture through which the bolt 40 projects, as shown in Figure 1. With continued reference to Figure 2a, the bolt 40 will now be described. A first end

47 of the bolt 40 is rounded and forms a segment of a circle. The bolt 40 is pivoted to the casing 30 by the pivot 33 at the centre point of the circle defined by the rounded first end 47 of the bolt 40, such that the second end of the bolt 40 can move between a deployed position in which the second end projects though the aperture in the side wall 32 (as shown in Figures 1 and 2a) and a retracted position in which the second end is retracted within the casing 30 (as shown in Figures 2c and 2d). As shown in Figure 2a, the bolt 40 has a solid section 41 and a cutaway section 42. The bolt 40 includes a cover (not shown) that encloses the cutaway section 42 and, together with adjacent structure of the bolt 40, defines a first aperture 44 at the rounded first end 47 of the bolt 40 and a second aperture 45 that extends along part of an edge of the bolt 40 and an adjacent part of the rounded first end 47.

The deadlock plate 60 is housed in the cutaway section 42 and can slide such that a first end of the deadlock plate 60 can project out of or retract into the first aperture 44 in the bolt 40. The bolt 40 includes first and second guide rollers 43 to guide the deadlock plate 60 as it projects out of and retracts into the first aperture 44. The first end of deadlock plate 60 is biased to protrude out of the first aperture 44 by a spring

48 acting under compression between structure of the bolt 40 at the end of cutaway section 42 and the second end of the deadlock plate 60.

The first end of the deadlock plate 60 comprises a first ramped portion 62 and a second ramped portion 63, meeting at a tip of the first end. The first ramped portion 62 is convex. The second ramped portion 63 is flat. The edge of the deadlock plate 60 that extends from the second ramped portion 63 comprises a third ramped portion 64 towards the second end of the deadlock plate 60, which slopes outwardly towards the second end of the deadlock plate 60 and is concave.

The drive arm 50 extends between the cylinder 20 and bolt 40 and has a flat front and back faces. The drive arm 50 is pivotally coupled to the bolt 40 by a pin 46 at a first end of the drive arm 50. The pin 46 is located on the bolt 40 between the pivot 33 and the second end of the bolt 40. The first end of the drive arm 50 extends through the second aperture 45 into the cutaway section 42 of the bolt 40. The drive arm 50 comprises a concave curved edge 54 along approximately half the length of the drive arm 50, adjacent the second end, which cooperates with the guide roller 36 of the casing 30 to constrain movement of the drive arm 50 along a predetermined path. The drive arm 50 also has a guide pin 52 near its centre and a cut-out portion 53 towards its second end shaped to receive the cylinder paddle 21. The release plate 70 extends face-to-face and along the flat front face of the drive arm 50. The release plate 70 is slideably mounted to the drive arm 50 at its first end via guide track 72 and pin 46, and at its second end via guide track 71 and guide pin 52. The first end of the release plate 70 extends through the second aperture 45 into the cutaway section 42 of the bolt 40. The second end of the release plate 70 protrudes into the cut-out portion 53 of the drive arm 50 in the first position of the release plate 70 as shown in figures 1 and 2a.

The strengthening arm 80 is pivotally coupled to the bolt 40 at its first end by pin 49. The casing also has additional cylindrical structures in the form of control pins 37 which confine the second end of the strengthening arm 80. The strengthening arm 80 is a steel bar that fills the width between the front and back 31 walls of the casing 30. In the deployed configuration of the bolt 40, the strengthening arm 80 is positioned in the aperture of the casing 30 left by the bolt 40. Thus, the strengthening arm 80 reinforces the casing, providing improved strength of the casing under a side load without the need for additional material to be added to the side wall 32 of the casing 30. As the strengthening arm 80 is positioned between the aperture in the side wall 32 and the deadlocking plate 60, it also acts as an anti-tamper device that prevents foreign objects inserted through the aperture in the side wall 32 from retracting the deadlocking plate 60 and thereby allowing the bolt 40 to rotate towards its retracted position. In operation, the deadlock mechanism 10 moves from a deadlocked configuration, as shown in Figure 2a, through to an unlocked configuration, as shown in Figure 2d, under the application of a torque to the cylinder 20 by a user inserting and turning a key. The operating mechanism will now be described with reference to Figures 2a to 2d.

With reference to Figure 2a, in the deadlocked configuration of the deadlock mechanism 10, the deadlocking plate 60, biased by the spring 48, protrudes out of the bolt 40 through the first aperture 44. With the bolt 40 in the fully deployed position, as shown in Figure 2a, the second ramped portion 63 of the deadlocking plate 60 abuts the locking pin 34. As the deadlocking plate 60 is constrained to slide only into or out of the bolt, rotation of the bolt 40 about the pivot 33 towards the retracted position (in a clockwise direction as shown in the Figures) is prevented. To unlock the deadlock mechanism 10 and rotate the bolt 40 into the retracted position shown in Figure 2d, the user rotates the cylinder paddle 21 in a first (clockwise) direction using a key. The cylinder paddle 21 thus rotates about the cylinder 20 towards the cut-out portion 53 of the drive arm 50. As the cylinder paddle 21 enters the cut-out portion 53, the cylinder paddle 21 abuts the second end of the release plate 70. Further rotation of the cylinder paddle 21 causes the release plate 70 to slide along the flat face of the drive arm 50 along the path defined by the guide tracks 71 and 72 and the pins 52 and 46.

As the release plate 70 slides along the drive arm 50, the first end of the release plate 70 abuts the third ramped portion 64 of the deadlocking plate 60. As the release plate 70 continues to slide along the drive arm 50, the first end of the release plate 70 slides along the third ramped portion 64 of the deadlocking plate 60 and causes the deadlocking plate 60 to retract into the bolt 40, against the biasing action of the spring 48.

The release plate 70 is fully extended relative to the drive arm 50 when the cylinder paddle abuts the edge of the drive arm 50 defining the cut-out portion 53. The first, fully extended position of the release plate 70 is shown in Figure 2b. When the release plate 70 is in its first, fully extended position, the deadlocking plate 60 is fully retracted into the bolt 40 and the second ramped portion 63 of the deadlocking plate 60 is clear of the locking pin 34.

Further rotation of the cylinder paddle 21 pushes the drive arm 50 along the path defined by the concave curved edge 54 of the drive arm 50 and guide roller 36. The shape of the curved edge 54 is such that the cylinder paddle 21 remains in contact with the edge of the drive arm 50 defining the cut-out portion 53 for an optimum extent of the rotation of the cylinder paddle 21. More specifically, the arrangement is such that, in being driven by the paddle 21 , the drive arm 50 moves at least partly about the axes of rotation of the paddle 21, thereby maintaining contact between the drive arm 50 and the paddle 21 for a greater part of the rotation of the paddle 21 that would otherwise be the case. As the deadlocking plate 60 has been retracted and its second ramped portion 63 is clear of the locking pin 34, the bolt 40 is free to rotate and movement of the drive arm 50 over the guide roller 36 causes the bolt 40 to rotate towards the retracted position via the pivot 46, as shown in Figures 2b and 2c.

When, after further rotation, the cylinder paddle 21 is no longer in contact with the drive arm 53, the bolt 40 is in its fully retracted position. As the cylinder paddle 21 moves out of the cut-out portion 53, the release plate 70 returns to its original position with respect to the drive arm 50 and disengages the third ramped portion 64 of the deadlocking plate 60. The spring 48 then causes the deadlocking plate 60 to extend out of the aperture 44 of the bolt 40 and the first ramped portion 62 abuts the retaining pin 35, thereby resisting, at least to some degree, rotation of the bolt 40 towards the deployed position. The deadlock mechanism 10 is now in the unlocked configuration, as shown in Figure 2d.

During the unlocking operation, the strengthening arm 80 rotates about the pivot 49 with respect to the bolt 40 until it comes to rest against the control pins 37 of the casing, as shown in Figure 2d. To return the deadlock mechanism 10 from the unlocked configuration shown in Figure 2d to the deadlocked configuration shown in Figure 2a. A user rotates the cylinder paddle 21 in a second (anticlockwise) direction using the key. Thus, the cylinder paddle 21 enters the cut-out portion 53 and abuts the drive arm 50, causing the drive arm to move in a direction away from the bolt 40. The motion of the drive arm 50 translates into rotation of the bolt 40 towards the deployed position because of the pivotal coupling at the pivot 46.

Due to the large degree of slope of the first ramped portion 62, as the bolt 40 rotates towards its deployed position, the first ramped portion 62 of the deadlocking plate 60 slides over the retaining pin 35, causing the deadlocking plate 60 to retract into the bolt 40. After continued rotation of the bolt 40, the first ramped portion 62 clears the retaining pin 35 and the deadlocking plate 60 returns to its fully extended position due to the biasing action of the spring 48. Similarly, after yet further rotation of the bolt 40, the first ramped portion 62 abuts and slides over the locking pin 34, again causing the deadlocking plate to retract into the bolt 40. When the bolt 40 has reached its fully deployed position, the first ramped portion 62 of the deadlocking plate 60 has cleared the locking pin 34 and the deadlocking plate 60 returns to its fully extended position due to the biasing action of the spring. The deadlock mechanism 10 is now in the deadlocked configuration shown in Figure 2a. In this position, attempts to rotate the bolt 40 towards the retracted position by applying a torque to its second end will result in the second ramped portion 63 of the deadlocking plate 60 abutting the locking pin 34, thereby preventing rotation of the bolt. As the second ramped portion 63 is slightly sloped, the deadlock mechanism can reach the deadlocked configuration of Fig. 2a even if the bolt 40 does not achieve its fully deployed position, for example if the door drops in its frame over time.

Figures 3a to 3c show a second embodiment of the locking mechanism. The device is similar to that of the first embodiment shown in Figures 1 to 2d. However, in place of the guide roller pins 43, the deadlocking plate 60 has a guide track 61 and the bolt 40 has a guide pin 43 a. The guide track 61 and guide pin 43 a cooperate to restrict the deadlocking plate 60 to linear motion with respect to the bolt 40 such that when the second ramped edge 63 abuts the locking pin 34, rotation of the bolt 40 from the deployed configuration to the retracted configuration is resisted.

Additionally, in place of the curved surface 54 of the drive arm 50 and the guide roller pin 36 of the first embodiment, the drive arm 50 has a guide track 51 and the casing 30 has a guide pin 36a. The guide track 51 and the guide pin 36a cooperate to constrain the movement of the drive arm 50 along a predetermined path, chosen to maximise the distance over which the drive arm 50 remains in contact with the cylinder paddle 21 during rotation of the cylinder 20.

Figures 4a and 4b show a third embodiment of the locking mechanism. The device is similar to that of the second embodiment described above, but in addition comprises an anti-tamper device 90. The anti-tamper device 90 is pivoted at its first end to the bolt 40 and is constrained at its second end by a control pin 37a comprised in the casing 30. The anti-tamper device 90 comprises a sprung steel strip that spans the width of the casing 30 between the top and bottom walls of the casing 30, thereby preventing objects inserted through the bolt aperture in the casing 30 from manipulating the release plate 60 when the bolt is in the deployed configuration, as shown in Figure 4a.

Whilst the above embodiments have been described as having a conventional cylinder lock and paddle, it should be readily appreciated that the invention may be carried out using any other actuation means, for example a thumbturn lever or a handle.