GB2541322A

GB2541322A - A cylinder lock having a clutch mechanism with an axially movable tab

Info

Publication number: GB2541322A
Application number: GB1619361.7A
Authority: GB
Inventors: Chang Edward; Gokhale Neil; Rogers John; Stewart Steve
Original assignee: Avocet Hardware UK Ltd
Current assignee: Avocet Hardware UK Ltd
Priority date: 2011-05-17
Filing date: 2011-05-17
Publication date: 2017-02-15
Anticipated expiration: 2031-05-17
Also published as: GB2541321B; GB201108178D0; GB2491099B; GB2491099A; GB2541321A; GB2541322B

Abstract

A cylinder lock with a first lock actuator 104, a second lock actuator (Figure 3, 108), a cam (Figure 5, 107) between the first and second lock actuators and arranged for rotation about an axis between a locked and unlocked position, and a clutch mechanism 110 arranged to selectively engage the first lock actuator with the cam for rotation therewith. A cylinder lock wherein the clutch mechanism 110 comprises an axially movable clutch body (126 figure 1a) having a tab 138 arranged to engage a recess 136 on the cam where the tab is axially movable relative to the body. The tab may be resiliently biased towards the cam and may be movable from an extended position to a retracted position in which it is partially contained within a recess in the clutch body.

Description

A cylinder lock having a clutch mechanism with an axially movable tab

The present invention is concerned with cylinder locks. More specifically, the present invention is concerned with Euro-profile cylinder locks utilising pin-tumbler type locking mechanisms.

Euro-profile cylinder locks are generally known in the art and one such lock is shown in the applicant's co-pending application published as W02009/156731. In the aforementioned application, an improved clutch is provided which has the ability to travel between a first position in which an exterior lock actuator is engaged to a lock cam, a second position in which an interior lock actuator is engaged with the lock cam and a third over-travel position in which the clutch is engaged with the interior lock actuator and cannot be moved. The third position is entered into upon the removal of a component of the lock mechanism, in particular the external lock actuator. This system inhibits manual manipulation of the lock components, and in particular prevents manual manipulation of the clutch upon removal of the exterior lock actuator by a potential intruder.

In the above application, upon removal of the external lock actuator, the clutch is biased by a spring to move in an axial direction towards the exterior actuator (thereby forming a load path between the interior actuator and cam) before it is engaged by a radially sprung pin in a detent to lock it into the third position. Such an arrangement requires more space than a two position clutch, so that movement between three discrete positions is possible.

Many known cylinder locks do not have the ability for keys to be simuhaneously inserted from both the interior and exterior sides and the lock actuator turned. Often the clutch is moved between interior and exterior engaging positions by the ends of the key inserted into the relevant actuator. As such, if the interior key has been left in the lock cylinder, it is not possible to insert the exterior key as the clutch will not be able to move into the space inhabited by the blade of the interior key.

This may be overcome by using a cam which can be compressed. For example two parts of the cam, being resiliently biased apart may be pushed together by insertion of both keys. Such a system encounters problems when the cam is out of position, as will be explained below.

In order to engage a cylinder lock cam, each side of the clutch has a radially projecting tab which engages a corresponding groove on the cam when the relevant key is inserted. The engagement of the tab in the groove transfers torque from the clutch to the cam when the key is turned. A problem arises if the key is left in the interior actuator in a misaligned position (i.e. partially or fully unlocked). When the user inserts a key into the exterior actuator, the clutch cannot be completely compressed because the tab on the exterior side clutch is misaligned with the corresponding recess on the cam. The key cannot, therefore, be fully inserted. A similar problem exists in cylinder locks which utilise thumb turn bolts on the interior side.

In the case of thumb turn bohs, this problem is overcome by spring loading the exterior side clutch to the exterior actuator. The exterior side clutch is provided with enough space within the cam to move to an intermediate position whereby the key is fully inserted but the tab is not engaged with the cam recess. When the key is turned, the interior side clutch turns until the tab and recess align, at which point the tab snaps into the recess and the load path between the exterior side actuator and cam is established. A problem with this solution is that more space within the cam is required in order to permit the clutch to have an "intermediate" position. As in all cylinder lock applications, there is only a limited amount of space in which these components can be located.

As mentioned above, the tip of the blade of a key actuates the clutch with a traditional cylinder lock. As well as performing this function, it should be noted that the key is required to be positioned correctly relative to a set of pins which are resiliently biased within the lock actuator. In pin tumbler locks, for example, a series of pairs of pins known as key pins and driver pins are assembled to span a shear line between a plug and a barrel of the lock actuator. When the correct key is inserted, the pins are urged radially outwardly until the interface between the key pin and driver pin coincides with a shear line. At this point the plug can be rotated within the barrel allowing unlocking to take place.

It will be understood that this type of key to lock actuator alignment is required in all cylinder locks, not just pin tumbler type locks.

It is therefore important that the key is correctly aligned relative to the plug. In traditional lock assemblies this has been achieved by the use of a key stop which is simply an abutment within the plug against which the end of the key sits. A problem with this solution is that the tolerance on the key stop has to be linked to the tolerances on each of the pins which increases the manufacturing cost of the actuator. Space for the key stop also needs to be made.

It is an aim of the present invention to overcome or at least mitigate one or more of the above referenced problems.

According to a first aspect of the invention there is provided a cylinder lock comprising: a first lock actuator, a second lock actuator, a cam disposed between the first and second lock actuators and arranged for rotation about a cam axis between a locked and unlocked position, a clutch mechanism arranged to selectively engage the first lock actuator with the cam for rotation therewith, wherein a first component of the clutch mechanism is axially moveable relative to, but captured by the first lock actuator in an axial direction such that removal of the first lock actuator causes removal of the component.

Advantageously, tying the clutch to the first lock actuator means that removal of the first lock actuator results in removal of the clutch, thereby ensuring that the clutch can no longer be easily manipulated.

Preferably the first component of the clutch mechanism comprises a male member engaging a female recess of the first lock actuator. Preferably the male member comprises an abutment captured by the first lock actuator. The abutment may be a circumferentially extending flange engageable with an endwall of the female recess.

This permits radial insertion of the first component. Preferably the flange extends from two opposite sides of the male member to provide a more stable abutment.

Preferably the first component of the clutch mechanism is movably mounted to a second component of the clutch mechanism, and resiliently biased towards the cam.

This permits dual-key functionality-allowing a key to be inserted to actuate the clutch regardless of the position of any recess on the cam which the first component may engage.

Alternatively, the first component of the clutch mechanism may comprise a recess engaged by a restraining member of the first lock actuator.

Preferably the restraining member is a wire component, for example the wire component is a wire ring wrapped around a part of the first lock actuator.

The restraining member may be a circlip.

Preferably the first component of the clutch mechanism comprises an axially extending tab engaged with the first lock actuator, and the recess is formed in the tab.

Preferably the tab is movably mounted to a second component of the clutch mechanism, and resiliently biased towards the cam. This facilities dual-key insertion.

According to a second aspect of the invention there is provided a cylinder lock comprising: a first lock actuator, a second lock actuator, a cam disposed between the first and second lock actuators and arranged for rotation about a cam axis between a locked and unlocked position, a clutch mechanism arranged to selectively engage the first and/or second lock actuator with the cam for rotation therewith, wherein the clutch mechanism comprises a clutch body being axially movable relative to the first lock actuator, and a tab arranged to engage a recess on the cam, in which the tab is axially movable relative to the body.

Preferably the tab is resiliently biased towards the cam. Advantageously, should the recess on the cam be out of position (by virtue of the fact that the second lock actuator is turned away from the locked position and the key left in), a key can be inserted from the first lock actuator side and the clutch rotated until the tab can "snap out" into the cam recess when the tab and recess become aligned.

By making the male part of the mating relationship between the clutch and the cam resiliently biased, additional space is not required in the lock mechanism. The key can simply be turned to the correct position, at which point the male formation will be urged to the extended position and engage with the cam for rotation.

Preferably the tab is movable from an extended position to a retracted position in which it is at least partially contained within a recess in the clutch body.

Preferably the tab is captured so as to have a limited range of motion relative to the first lock actuator, the clutch body being disposed between the tab and the first lock actuator. This means that should the first lock actuator be removed, the clutch body is also removed, which makes manual manipulation of the lock more difficult.

Preferably the clutch body comprises a lug projecting into the first actuator to rotatably constrain the clutch body and the actuator, in which the lug is received at least partially within the tab.

Preferably the clutch body comprises a lug projecting into the first actuator to rotatably constrain the clutch body and the actuator, in which the tab is received at least partially within the lug.

According to a third aspect of the invention there is provided cylinder lock comprising: a first lock actuator defining a key slot and having a locked condition, a second lock actuator, a cam disposed between the first and second lock actuators and arranged for rotation about a cam axis between a locked and unlocked position, a clutch mechanism arranged to selectively engage the first lock actuator with the cam for rotation therewith, the clutch mechanism having a first side on a first lock actuator side of the cam, wherein the first side of the clutch mechanism defines an opening aligned with the key slot in a direction parallel to the cam axis when the first lock actuator is in the locked condition.

Advantageously, the provision of an opening such as a notch, or groove, or bore, through the clutch allows the key tip to enter upon insertion. This permits the clutch and key to sit closer together, allowing the clutch a greater range of motion within the lock mechanism. It will be noted that the key will still urge the clutch into the cam (as required), but a much closer fit can be achieved.

Preferably the clutch comprises a second side on a second lock actuator side of the cam, the first side of the clutch comprises a first side clutch component abutting a component of the second side, and, the opening is defined in the first side clutch component.

Preferably the first side clutch component defines a central shaft passing through the cam to abut the second side of the clutch.

Preferably the opening extends from a periphery of the first side clutch component in a generally radial direction to the central shaft. It may be formed by a recess formed in the periphery of the first side clutch component, and is preferably tapered to widen towards the periphery.

Preferably the first side clutch component defines a circular periphery, such that the periphery of the first side clutch component can be surrounded by the first lock actuator such that it can rotate therein.

Alternatively the opening may be formed by an axially extending through-bore in the first side clutch component.

Preferably the first side of the clutch comprises more than one component, and each component defines an opening aligned with the key slot.

Preferably the opening defines a uninterrupted path from the first lock actuator to the cam. According to a fourth aspect of the invention there is provided a cylinder lock comprising: a key having a blade defining a key stop recess, a lock actuator having a barrel, a plug rotatably received therein such that the barrel and plug define a shear line therebetween, a pin tumbler arrangement spanning the barrel and plug to selectively prevent relative rotation thereof in which the plug comprises a key stop mechanism positioned on a plug side of the shear line, the key stop mechanism comprising a key stop member and a resilient element biasing the key stop member towards the key to engage the key stop recess to locate the key.

In this way the key can be located easily within the plug.

Preferably the blade of the key comprises a bow, the blade comprises plurality of tumbler pin recesses.

Preferably the tumbler pin recess are defined between the bow and the key stop recess.

Preferably the key stop recess is defined proximate a tip of the blade such that the pins do not "ride over" the recess.

Preferably the tumbler pin recesses are defined on a first surface of the blade, and the key stop recess is defined on a second, different, surface of the blade.

Preferably the second surface is 90 degrees from the first surface.

Preferably the key stop member is spherical.

Preferably the key stop member and the resilient element are inserted into the plug from an exterior side and are sealed with a key stop plug.

An example cylinder lock in accordance with the present invention will now be described with reference to the accompanying figures in which:- FIGURE 1 is a partially exploded perspective view of an exterior side of a first cylinder lock in accordance with the present invention; FIGURE la is a perspective view of a component of the cylinder lock of Figure 1; FIGURE lb is a perspective view of an alternative design of the component of Figure 1 a; FIGURE 2 is a perspective view of some of the components of the cylinder lock of Figure 1; FIGURE 3 is a perspective view of both the interior and the exterior lock actuators of the cylinder lock of Figure 1; FIGURE 4a is an unexploded view similar to that of Figure 1 with the cylinder lock in a first condition; FIGURE 4b is an unexploded view similar to that of Figure 1 with the cylinder lock in a second condition; FIGURE 5 is a perspective exploded view of the cylinder lock of Figure 1 from the reverse angle; FIGURE 6a is a perspective view of a component of a second cylinder lock in accordance with the present invention; FIGURE 6b is a perspective view of an alternative design of the component of Figure 6a; FIGURE 7a is a plan view of the second cylinder lock according to the present invention in a first condition; FIGURE 7b is a section view along the line VII-VII of figure 7a; FIGURE 8a is a plan view of the second cylinder lock of Figure 6a in a second condition; FIGURE 8b is a section view along the line VIII-VIII of figure 8a; FIGURE 9a is a plan view of the second cylinder lock of Figure 6a in a third condition; FIGURE 9b is a section view along the line IX-IX of figure 9a; FIGURE 10a is a plan view of a part of the lock actuator.

Referring to Figure 1, there is provided a part of a cylinder lock 100 having an associated key 102. An exterior (or "outside") lock actuator 104 is shown in Figure 1, in addition to a shackle 106. Tuning to Figure 3, an interior lock actuator 108 is also shown.

In addition to the exterior lock actuator 104 and the shackle 106, Figure 1 shows several components of an exterior side clutch 110.

The exterior lock actuator 104 comprises a barrel 112 which has a cylindrical portion 114 and a radially projecting portion 116 extending therefrom. A generally cylindrical plug 118 is disposed within the cylindrical portion 114 and is able to rotate relative thereto. The plug 118 defines a key slot 148 at its outer periphery (see Figure 2) to receive the key 102. The key slot 148 extends the whole axial length of the plug 118. At 90 degrees from the key slot 148, there is positioned a clutch slot 150. The clutch slot 150 extends only partially along the plug 118. At its interior end the plug 118 defines a circumferential groove 152 in its outer surface.

The plug 118 is also configured to receive the key 102 as shown in Figure 1. A pin tumbler mechanism 119 is installed between the plug 118 and the barrel 112 as is known in the art. Therefore, it will be appreciated that upon insertion of the correct key 102, the plug 118 may be rotated relative to the barrel 112 by the key 102. A similar arrangement exists on the lock interior side actuator 108 and is not described in detail here.

The shackle 106 comprises a central body 120 having a first shaft 122 and a second shaft 124 projecting in opposite directions therefrom. Each of the shafts 122,124 engages the exterior lock actuator 104 and the interior lock actuator 108 respectively in order to hold them in a relatively spaced position astride the central body 120, as shown in Figure 5.

When the cylinder lock 100 is fully assembled, a cam 107 comprising a rotatable cam shaft 123 and a cam lever 125 is disposed between the barrels of the lock actuators 104, 108 for rotation about a central axis X. The exterior side clutch assembly 110 comprises a clutch body 126, as shown in Figures 1 and la in particular. The clutch body 126 has a disc-like portion 128 with a central axially extending clutch pin 130 extending therefrom and away from the exterior lock actuator 104. A radially extending slot 132 is defined in the disc-like portion 128. A plug engagement lug 134 extends from the disc-like portion 128 in the opposite direction to the clutch pin 130. The lug 134 is positioned at a radially outer position of the disc-like portion 128, 90 degrees from the slot 132 and extends in a direction parallel to the clutch pin 130 (i.e. parallel to direction X).

The lug 134 defines a longitudinally extending "D" shaped bore 136, the function of which will be described below. The lug 134 fits within the clutch slot 150 to provide a smooth surface. This is advantageous because it prevents the driver pins of the tumbler arrangement 119 engaging the clutch slot 150 when the key is inserted and the plug rotated. Even when the plug 134 is in an extended position, the area of exposed clutch slot 150 is insufficient for the driver pins to enter, which would jam the lock.

Referring to Figure ib, in which all reference numerals are 1000 greater, a alternative clutch body 1126 is shown without a slot 132.

Moving back to the embodiment of figure la, a separate cam engaging tab 138 is provided being generally "D" shaped in cross section and having an axially extending shallow groove 140 formed in the outer surface thereof The groove 140 defines first and second end walls 142,144. The tab 138 is dimensioned to be slidably received within the bore 136 of the lug 134 and is outwardly biased therefrom by a compression spring 146.

Turning to Figure 2, the assembly of the exterior side clutch 112 with the external lock actuator 104 can be seen. The clutch body 126 is abutted against the plug 118 such that the lug 134 is fully engaged with the clutch slot 150. Therefore, the clutch body 126 is rotatably fixed to the plug 118. The tab 138 is inserted into the bore 136 in the lug 134 such that the groove 140 is generally aligned with the groove 152 in the plug 118. A wire clip 154 is then inserted into the groove 152 and sits in the groove 140 of the tab 138 such that ahhough the tab 138 is able to move back and forth, its motion limited by the abutment end walls 142,144 with the wire clip 154.

As shown in Figure 2, no key is present in the plug 118 and therefore, the clutch 126 is able to fully engage the plug 118 (it is biased in this position by a spring -not shown).

When the cylinder lock 100 is operated in a normal fashion, a key 102 can be inserted into the exterior side lock actuator 104. Upon doing so, the end of the key 102 pushes the clutch body 126 towards the interior lock actuator. As this occurs, the tab 138 which is urged out of the bore 136 by the spring 146, engages a corresponding recess on the cam 107 such that the barrel 112 and clutch 110 become rotationally engaged with the cam. At this point, providing the correct key is inserted and the key and driver pins have aligned across the shear line, rotation of the key 102 will unlock the lock.

It is conceivable that the interior side key may have been left in the interior lock actuator 108. The interior lock actuator 108 may have also been rotated (with the cam) to a position whereby the relevant recess on the cam interior is not aligned with the tab 138. Under normal circumstances, this would prevent advancement of the clutch body 126 towards the interior lock actuator 108.

Because in the present invention the tab 138 is biased by the spring 146, the clutch body 126 may advance without accompanying advancement of the tab 138, for example, as shown in Figure 4. The key 102 can then be rotated which in turn rotates the plug 118 until the tab 138 reaches the correct position at which point it resiles axially under the force of the spring 146 and "snaps" into the cam recess. The cam can then be rotated from the exterior side. A further advantage of the present invention is that the wire clip 154 holds the tab 138 in position. If the external lock actuator 104 is removed by an intrnder, then the clutch body 116 necessarily is pulled with it because the wire clip 154 will react against the end wall 144 of the tab 138.

It will also be noted that the tip of the blade of the key 102 inserted into the lock actuator engages the slot 132 (as shown in Figure 4). This allows the clutch body 126 a greater range of motion in use. The key can still engage and urge the clutch body 126 at its centre.

Turning to Figure 5, the cylinder lock 100 is shown with both the exterior lock actuator 104, the interior lock actuator 108, the shackle 106 and the cam 107 present.

The plug 118 of the exterior lock actuator 104 is shown in exploded form.

As can be seen in Figure 5, the plug 118 comprises a through bore 156 defined in a side wall thereof opposite the key slot 148. A catch ball 158 is inserted through the bore 156 followed by a compression spring and a seal plug 162, which is held in the side wall of the plug 118 such that the ball 158 is captured within the plug 118.

Turning to the key 102, it is provided with a bow 164 and a blade 166, extending therefrom. The blade 166 comprises a number of indentations 168 for receiving the various pins of the pin tumbler arrangement (not shown). On a side wall of the blade 166, there is provided a v-shaped indentation 170. When the blade 166 is inserted into the plug 118 of the lock actuator 104, and when the key 102 has reached the desired position, the ball 158 engages with the indentation 170 under the bias of the spring 160. This locates the key 102 in the correct position and in particular, at the position at which the indentations 168 are aligned with the pin tumbler mechanism in order to provide smooth opening of the lock.

Turning to Figures 6a to 10b, an alternative arrangement of the cylinder lock 100 is shown, in which similar components are numbered 100 greater.

Referring to Figures 7a to 9b, a cylinder lock 200 is provided having an associated key 202 (see Figure 8a). The key 202 has a bow 264 and a blade 266 extending therefrom.

As shown in Figure 7b, the cylinder lock 200 comprises an exterior lock actuator 204 and an interior lock actuator 208. A shackle 206 joins the interior and exterior lock actuators 208, 204 per cylinder 100. A cam 207 is mounted for rotation about an axis X', between the exterior and interior lock actuators 204, 208.

The exterior lock actuator 204 comprises a barrel 212 having a cylindrical portion 214 and a radially projecting portion 216 extending therefrom. A generally cylindrical plug 218 is disposed within the cylindrical portion 214 and is able to rotate relative thereto. A key slot 248 is provided in the periphery of the plug 218 and is substantially similar to the key slot 148 described above. The plug 218 defines a clutch slot 250 at 90 degrees to the key slot 248. Clutch slot 250 is straight and terminates in an obround recess 251 opening radially outwardly from the plug 218 at the end opposite the cam 207. What is important about the obround recess it that it defines a pair of circumferential abutment shoulders 219, 221 in the wall of the plug 218.

The cam 207 comprises a rotatable cam shaft 223 and a radially projecting cam lever 225 projecting therefrom. The cam lever 225 is configured to actuate a lock mechanism of a door (not shown). Therefore rotation of the cam 207 can actuate a door lock between a locked and unlocked condition. A clutch body 226 is shown in Figure 6a in detail. The clutch body 226 is similar to the clutch body 126; i.e. it has a disc-like portion 228 and clutch pin 230 extending axially therefrom and away from the exterior lock actuator 204. A radially extending slot 232 is defined in the disc-like portion 228. A plug engagement lug 234 extends from the disc-like portion 228 in the opposite direction to the clutch pin 230. The lug 234 is positioned at a radially outer position of the disc-like portion 228, substantially at 90 degrees from the slot 232 and extends parallel to the direction X'.

The lug 234 differs from the lug 134 in that it defines a cylindrically concave surface 302 which faces radially outwardly from the disc-like portion 228 and extending for the majority of the length of the lug 234. The concave surface 302 terminates in an abutment 304 projecting radially outwardly therefrom at and end opposite the disc-like portion 228. A first groove 306 and a second groove 308 are formed in the disc-like portion 228 either side of the lug 234. The grooves 306, 308 are generally straight and parallel.

As an aside it will be noted that the clutch body 226 could also be provided without the slot 232. As shown in Figure 6b a clutch body 1226 comprises a generally disc-like portion 1228 with a projecting pin 1230, the portion 1228 does not have a slot 232 defined therein. This particular embodiment would not have the benefits of the slot 232.

Turning back to Figure 7b, a cam engaging tab 238 is provided. The tab 238 is generally cuboid in shape and having one open side (such that it forms a five sided "box". A pair of abutment flanges 240, 241 are provided extending in opposite directions from one end of the tab 138 as will be described below. The end of the tab opposite the flanges 240, 241 comprises an engaging formation 243 shaped to engage a corresponding recess on the interior of the clutch.

The sub-assembly of the clutch body 226 and the exterior lock actuator 204 is as follows. The cam body 226 is assembled adjacent the plug 218 such that the plug engagement lug 234 sits slidably within the clutch slot 250. A compression spring 253 is positioned within the concave surface 302 of the lug 234. The tab 138 is then placed radially inwardly into the clutch slot 250 such that the flange 240 sits within the orifice 251. As shown in Figure 7b, the tab 238 is urged by the spring 253 such that the abutment 304 of the lug 234 is contacted by the end surface of the engaging tab 238. In other words the abutment 304 constrains the axial movement of the tab 238.

The long sidewalls of the tab 238 sit within the grooves 306, 308 and constrain the motion of the tab 238 such that it can only move in a direction parallel to axis X'.

In use, a key 202 is inserted into the cylinder lock 200 as shown in Figure 8a and 8b.

As shown in Figure 8b, the tip of the key blade 266 engages the clutch body 226 in order to advance it further into the cam 207.

Flow the assembly behaves depending on the rotational position of the cam 207 can be seen by contrasting Figures 8 (a and b) and 9 (a and b).

As can be seen from Figure 8b, the cam 207 is out of position (i.e., not in a locked position) as a result of previous use by the interior lock actuator 208. As such, there is no slot for the engaging formation 243 of the tab 238 to engage on the interior of the cam 207.

As this is the case, the compression spring 253 is compressed and the tab 238 remains in position whilst the lug 234 travels with the body 226.

Because the blade 266 can be fully inserted into the plug 218, the relevant tumbler pins can be aligned and the plug 218 rotated along with the clutch body 226 until the lug 238 locates within the appropriate slot within the cam 207.

This should be contrasted with the conditions shown in Figures 9a and 9b in which the cam 207 is correctly orientated such that the engaging formation 243 of the tab 238 can advance into a corresponding slot on the interior of the cam 207 to provide rotatable engagement between the plug 218 and the cam 207.

The contrasting positions of the tab 238 in Figures 8 (a and b) and 9 (a and b) can be seen in Figures IOa and IOb in which in Figure IOa, the tab 238 is not aligned with a corresponding recess on the cam 207 (per figures 8a and 8b), but in Figure IOb it is (per figures 9a and 9b).

Referring also to Figures IOa and IOb, it can be seen that the tab 238 can travel no further to the right (i.e., towards the cam 207) than as is shown in Figure IOb due to the presence of the flange 240 abutting with an inner surface of the orifice 251.

It will be understood that the tab 238 is also constrained by an abutment of the flanges 240, 241 with the shoulders 219, 221. Any attempt to remove the exterior lock actuator 204 will result in the tab 238 being pulled with it, and because of contact between the interior surface of the tab and the abutment 304 of the body 226, the clutch body 226 will also be removed. This provides a similar functionality to the wire clip of the cylinder lock 100 (i.e. tying the clutch body to the first lock actuator) but with the benefit of a lower part count.

Claims

1. A cylinder lock comprising: a first lock actuator, a second lock actuator, a cam disposed between the first and second lock actuators and arranged for rotation about a cam axis between a locked and unlocked position, a clutch mechanism arranged to selectively engage the first and/or second lock actuator with the cam for rotation therewith, wherein the clutch mechanism comprises a clutch body being axially movable relative to the first lock actuator, and a tab arranged to engage a recess on the cam, in which the tab is axially movable relative to the body.

2. A cylinder lock according to claim 1 in which the tab is resiliently biased towards the cam.

3. A cylinder lock according to claim 1 or 2 in which the tab is movable from an extended position to a retracted position in which it is at least partially contained within a recess in the clutch body.

4. A cylinder lock according to claim 3 in which the tab is captured so as to have a limited range of motion relative to the first lock actuator, the clutch body being disposed between the tab and the first lock actuator.

5. A cylinder lock according to any of claims 2 to 4 in which the clutch body comprises a lug engaging a recess in a rotatable plug of the first lock actuator.

6. A cylinder lock according to claim 5 in which the recess in the rotatable plug extends to a periphery of the plug, and in which one or both of the tab and the lug substantially fill the recess to provide a smooth outer surface of the plug.

7. A cylinder lock according to any of claims 1 to 6 in which the clutch body comprises a lug projecting into the first actuator to rotatably constrain the clutch body and the actuator, in which the lug is received at least partially within the tab.

8. A cylinder lock according to any of claims 1 to 6 in which the clutch body comprises a lug projecting into the first actuator to rotatably constrain the clutch body and the actuator, in which the tab is received at least partially within the lug.