Cylinder lock

Abstract

A double cylinder lock comprising a body (110) and first and second key operated cylinders (120a,120b) each with a plunger 600a,600b engageable with a rotator / cam 700. When no key is inserted into fir

Description

This invention is a cylinder lock. Cylinder locks are a type of lock commonly used to secure doors and the like and comprise a cylinder rotatable within a lock body upon insertion of a correct key. The locking mechanism which prevents rotation of the cylinder relative to the lock body includes a series of pins and springs, which extend into the cylinder from the lock body until the correct key is inserted. Upon insertion of the correct key, the pins are aligned to permit rotation. The cylinder is engaged with a rotator and cam which is engaged with a bolt mechanism on a door. When the cylinder is rotated, the rotator and cam actuate the door mechanism to unlock the door from a door frame. Whilst a single cylinder may be provided for one-way access to a door, generally cylinder locks will incorporate two opposed locks, one either side of the door to enable locking and unlocking from either side. Such locks may be referred to in the art as full or double Euro cylinder locks. Alternatively, one side of the lock may include a thumb-turn lock in place of a keyed lock. Cylinder locks have the disadvantage that they can be picked by placing a series of levers into the keyhole thereof to depress the pins in the locking mechanism to the correct position to unlock the cylinder. Furthermore, the cam of the lock can be accessed by snapping the cylinder out of the lock using pliers or similar. Once accessed, the cam can be actuated with a lever such as a screwdriver to unlock the door's bolt mechanism. Attempts have been made to block access to the cam if the cylinder has been snapped off. In particular, the cylinder may include a break point so that the place where the cylinder is snapped can be controlled, and prevent access to the cam. However, the cam can sometimes still be accessed after the cylinder has been broken. The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge. The present invention addresses shortcomings with cylinder locks, and in particular provides a locking mechanism that is secure against attempts to pick the locking mechanism or snapping off a cylinder. According to the present invention there is provided a cylinder lock for actuating a door mechanism, the cylinder lock comprising: a body; opposed first and second cylinders comprising, respectively, first and second keyholes disposed in opposite ends thereof for receiving a key, the first and second cylinders being rotatable relative to the body when actuated by a correctly fitting key inserted into the first or second keyhole; a rotator and cam being rotatable relative to the body when actuated by the key inserted into the first or second keyhole, the cam being disposed to engage, in use, the door mechanism; a first plunger (drive member / actuator) disposed in the body between the rotator and first cylinder; and a second plunger (drive member / actuator) disposed in the body between the rotator and second cylinder. When no key is inserted into the first or second keyhole, the first and second plungers are biased to a first axial position whereby the first and second plungers are engaged with the rotator and at least one of the first and second plungers are engaged with the body to prevent rotation of the first and second cylinders. When a key is inserted into the first or second cylinder, the respective first or second plunger is pushed by the key to a second axial position whereby rotation of the cylinder containing the key, the rotator and the cam is permitted. The first and second plungers each comprise an engagement member that extends into one of a plurality of engagement apertures on the rotator when the first and second plungers are in the first axial position, to prevent rotation of the rotator relative to the first or second plunger. When the first plunger is in the second axial position, the second plunger is in a third axial position whereby the at least one engagement member is disengaged from the rotator, to permit rotation of the rotator relative to the second plunger, and wherein when the second plunger is in the second axial position, the first plunger is in a third axial position whereby the at least one engagement member is disengaged from the rotator, to permit rotation of the rotator relative to the first plunger. The plurality of engagement apertures comprises a first interference engagement aperture positioned to receive the engagement member, thereby enabling return of the respective plunger to the first axial position from the third axial position, when the rotator is rotated to a position that is redundant for actuation of the door mechanism. The positioning of the first interference engagement aperture to be redundant for actuation of the door mechanism is such that movement of a plunger caused by a correctly fitting key will not enable the engagement member being received by the first interference engagement aperture. However, in situations where movement of a plunger is caused by something other than a correctly fitting key, such as lock picking tools, the interference engagement aperture may interfere with the attempted tampering of the lock by receiving the engagement member to prevent an intended full actuation of the door mechanism. In addition to the plunger being engaged with the body of the lock when in the first axial position to prevent rotation of the cylinder, the cylinder may also include a standard pin and spring mechanism to further lock the cylinder. Advantageously, this would mean that only a specific key could unlock the lock. Furthermore, a lock picker, even if they are able to overcome the pin and spring mechanism, would not know to also slide the plunger, which would be hidden from view, to the second axial position. The plurality of engagement apertures may comprise a pair of actuation engagement apertures positioned to receive the engagement member when the rotator is rotated to first and second orientations wherein a rotation of the rotator between the first and second orientations corresponds to a full actuation of the door mechanism. The first interference engagement aperture may be positioned adjacent one of the actuation engagement apertures. The plurality of engagement apertures may further comprise a second interference engagement aperture positioned adjacent the same actuation engagement aperture as the first interference engagement aperture such that the first and second interference engagement apertures are arranged adjacently to either side of one of the actuation engagement apertures. The first and second cylinders and first and second plungers may be coaxial, and the first and second plungers may be slidable in a channel defined by the body along the axis between the first and second axial positions. The first and second plungers may each further comprise an axial pin that extends into an axial aperture extending the length of the rotator, wherein the axial pins remain in the axial aperture when the first and second plungers move between the first and second axial positions. The axial pins and axial aperture may extend centrally relative to the first and second plungers and rotator respectively. Such axial pins may be cylindrical to enable the plungers to rotate relative to the rotator. The axial pin could extend form the plunger or could be a shaft on which the plunger is slidably mounted, the shaft comprising an abutment to retain the shaft within the plunger. The engagement member may be shorter than the axial pin so that the axial pin may remain engaged with the rotator, but the engagement member may be engaged or disengaged with the rotator. The first and second plungers may each comprise more than one engagement member. For example, the first and second plungers may each comprise two engagement members, which may be provided either side of the axial pin, but other arrangements are envisaged. The (or each) engagement member may be shaped as a pin similarly to the axial pin. Alternatively, the (or each) engagement member may comprise a profile extending from the plunger which is wider than the axial pin and which engages with a corresponding recess in the axial aperture, so that the profile may disengage from the recess but the axial pin in retained in the axial aperture. A slidable drive member, such as a cylindrical rod, may be disposed in the axial aperture between respective ends of the axial pins of the first and second plungers, so when the first or second plunger is pushed by the key, the other plunger is pushed along the axial aperture by the slidable drive member. When the first or second plunger is pushed into the second axial position by the key, the slidable drive member between the respective ends of the axial pins of the plungers, if present, will push the other of the first or second plungers into the third axial position. When the plungers are in the respective second / third axial positions, the plunger in the second axial position is unlocked, permitting the cylinder containing the key to be rotated. Meanwhile, and the plunger in the third axial position is locked by engagement to the lock body, but the at least one engagement member of the locked plunger is disengaged from the rotator permitting the rotator to rotate relative to the locked plunger. The first and / or second plungers may comprise a generally circular cross section and further comprise opposed engagement ears on the circumference thereof to engage with corresponding slots on the body of the cylinder lock, whereby the engagement ears and slots permit coaxial movement of the first and second plungers between the first, second and third axial positions, and permit rotation of the plunger only when in the second axial position. The slots may be generally 'T' shaped permitting lateral movement of the plungers along the axis between the first, second and third axial positions, but preventing rotation when in the first or third axial positions and permitting rotational movement when in the second axial position. Alternative means of engaging the plunger to the lock may be envisaged. The first and second plungers may be biased to the first axial position by a biasing member. Therefore, the plungers and the cylinders revert to being locked when a key is removed and the engagement members on the plungers are engaged with the rotator to prevent rotation. The first and second plungers may be attached respectively to the first and second cylinders with the one or more biasing member, wherein the biasing member is a spring. Such springs may be arranged to bias the plungers to the first axial position, and also secure the plungers to their respective cylinder, so that when the cylinders are rotated by a key the plungers rotate as well. The plungers may also comprise a recess to engage with the key to aid rotation of the plunger. One or more spring permits the plungers to be pushed or pulled back to the first axial position from the second or third axial positions. Alternative biasing means may be provided. The rotator may comprise at least one abutment member located in an aperture extending from the axial aperture, wherein the at least one abutment member is covered by the axial pin of the first or second plunger, the abutment member arranged such that if the axial pin of the first or second plunger is removed from the rotator, the abutment member moves to block the axial aperture. The abutment member or members provide a security mechanism whereby if a cylinder is snapped off and the plunger is removed, the abutment member will block the axial aperture of the rotator to prevent access to the cam and / or the other plunger. Should one of the plungers be removed, the other plunger will remain in or revert to the first axial position and thus lock the rotator, to prevent the rotator from rotating and actuating the door mechanism. The abutment members may be a pin, ball bearing, shutter or similar. The first and second plungers may be attached to the body of the lock via a circlip which will still permit lateral and rotational movement, but when the cylinder is snapped off will ensure that the plunger is also removed and not left in the rotator. A break point, sometimes known in the art as a break slot, may be provided in the lock body and aligned with one or both of the first and second cylinder, so that if the cylinder is broken off it will break at a specified point so that the rotator and cam cannot be accessed. One way in which a door mechanism may be accessed after breaking a lock is by inserting a lever, such as a screwdriver, under the lock body and forcing it upwards. The cylinder lock may further comprise a pin extending from the underside of the lock body which engages with a door when the lock is installed, and which prevents access to the lever and movement of the lock within the door. Embodiments of the present invention will now be described in detail, but by way of example only, with reference to the following drawings in which: Figure 1A shows an end view of a cylinder lock according to the present disclosure; Figure IB shows a cross-sectional view of the cylinder lock shown in Figure 1A through line A-A; Figure IC shows a cross-sectional view of the cylinder lock shown in Figures 1A and IB through line B-B; Figure 2A shows a side view of a plunger as shown in Figures IB and IC; Figure 2B shows an underside view of the plunger of Figure 2A; Figure 2C shows an upper side view of the plunger shown in Figures 2A and 2B; Figure 2D shows a cross-sectional view of the plunger shown in Figure 2C through line A-A; Figure 3A shows a side view of a rotator as shown in Figure IB and IC; Figure 3B shows an end view of the rotator as shown in Figure 3A; Figure 3C shows a cross-sectional view of the rotator shown in Figure 3B through line A-A; Figure 3D shows a cross-sectional view of the rotator shown in Figure 3B through line B-B; Figure 4A shows an end view of a lock body as shown in Figures 1A-1C; Figure 4B shows a side view of the lock body as shown in Figure 4A; Figure 4C shows an underside view of the lock body as shown in Figures 4A and 4B; Figure 5 shows a cross-sectional view of a cylinder lock according to an embodiment of the present invention; Figure 6A shows a side view of a plunger as shown in Figure 5; Figure 6B shows an upper side view of the plunger shown in Figure 6A; and Figure 7 shows an end view of a rotator as shown in Figure 5. As best shown in Figures 1A-1C, there is shown a cylinder lock generally indicated 100 comprising a body generally indicated 110. The body 110 of this example is generally symmetrical along a vertical axis and comprises two locks, which in use may be provided on either side of a door. The cylinder lock 100 comprises two opposed cylinders generally indicated 120a,120b each having a keyhole 130a,130b, the walls of the cylinder 120a,120b and keyholes 130a,130b defining a channel 140a,140b extending the length of the cylinder 120a,120b for insertion of a key to operate the locks. The cylinders 120a,120b are housed within and are rotatable relative to the body 110 when unlocked. A lower section 380 of body 110 beneath the cylinders 120a,120b houses a series of pins and springs 150 which extend into respective apertures 160 at the base of the cylinders 120a,120b when locked. These pins and springs 150 prevent rotation of the cylinders 120a,120b relative to the body 110 when locked, and can be unlocked by insertion of a correct key which aligns the pins. The pins and springs 150 are a standard locking mechanism for a cylinder lock and will not be discussed in any further detail. Disposed in the body 110 between the cylinders 120a,120b is a rotator generally indicated 170 connected to a cam 180 which in use engages with a door mechanism such as a bolt to lock and unlock a door to a door frame. Plungers generally indicated 190a,190b are disposed in a cavity 200a,200b between the cylinders 120 and the rotator 170. The plungers 190a,190b are attached to an end of respective cylinders 120a,120b with springs 210. Figures 2A-2D show the plungers 190a,190b in more detail. Plungers 190a,190b comprise a body 220 having a generally circular cross section. The body 220 comprises a base 230 which comprises a recess 240 for receiving a key during use and two apertures 250 to which springs 210 are attached and retained. Extending from the base 230 are opposed circumferential engagement ears or wings 260 which in use engage with the body 110 of the cylinder lock in the cavities 200a,200b. An upper surface 270 of the plungers 190a,190b comprises a cylindrical axial pin 280 and two shorter engagement members 290, also shaped as pins in this example. As shown best in Figures 3A-3D, rotator 170 comprises a generally cylindrical body 300 with an axial aperture 310 extending the full length through the body 300. Two pairs of engagement apertures 320,330 extend partially into the body 300 of the rotator 170. As shown in Figure IB and IC, the axial aperture 310 receives the axial pins 280 of plungers 190a,190b and the pair of engagement apertures 320, 330 receive the engagement members 290 of plungers 190a,190b respectively. Turning back to Figure 3A, the outer surface of body 300 comprises two circumferential grooves 340 to locate the rotator 170 in the body 110 of the cylinder lock 100. As best shown in Figure 3D, abutment members are provided in the body 300 of the rotator 170 in an aperture. In this example, the abutment members are in the form of guard pins 350. The end of the guard pins 350 are flush with the axial aperture 310 extending through the centre of the rotator 170. The guard pin 350 are placed so that, as best shown in Figure IB, they are blocked by the axial pins 280 of plungers 190a,190b when the axial pins 280 are in the axial aperture 310. Further apertures 360 are provided in line with the guard pins 350 to receive the guard pins 350 as will be described later. Figures 4A-4C show the body 110 of the cylinder lock 100 in more detail. The body 110 comprises a cylindrical, substantially tubular upper section 370 and a lower section 380. The upper section 370 defines a central channel 390 for receiving the cylinders 120a,120b and an opening 400 for receiving the rotator 170 and cam 180. The lower section 380 comprises a screw hole 410 for affixing the cylinder lock 100 to a door and a series of openings 420 which receive the springs and pins 150. The body 110 comprises two break points 430 which are provided as a security mechanism. If the cylinder lock were broken with a pair of pliers to gain access to the rotator 170 and cam 180 to actuate the locking mechanism of the door, the body 110 will break at the break points 430 and, as will be described later, in so doing will actuate a security mechanism to prevent access to the rotator 170 and cam 180. A central part of the body between the break points may be constructed from steel or alternatively the entire body could be made of brass. An axis is defined from keyhole 130a to 130b along channels 140a and 140b of cylinders 120a and 120b and through the axial pins 280 of plungers 190a and 190b and through the axial aperture 310 of rotator 170. As shown in Figure IBand IC, a slidable drive member 440 is disposed in the axial aperture 310 of rotator 170 between the ends of the axial pins 280 of the plungers 190a,190b. As shown in Figures IB and IC, both locks of cylinder lock 100 are at rest in a locked state. The pins and springs 150, although not shown here, are engaged with apertures 160 in cylinders 120a,120b to prevent rotation of the cylinders 120a,120b relative to the body 110. Furthermore, plungers 190a,190b are partially engaged with the body 110 and the rotator 170. This position of partial engagement will be referred to as the "first axial position". The engagement ears 260 of plungers 190a,190b are engaged with T-shaped slots (not shown) in the inside walls of central channels 390 of the body 110 within cavity 200. These slots provide for slidable movement of the plungers 190a,190b along the axis, but when the plungers 190a,190b are in the first axial position as shown in Figure IB and IC, rotation of the plungers 190a,190b relative to the body 110 is not permitted. Furthermore, since the plungers 190a,190b are attached to the cylinders 120a,120b with springs 260, engagement of the plungers 190a,190b to the walls of the body 110 also prevent rotation of the cylinders 120a,120b even if the pins and springs 150 are disengaged. The engagement of the plungers 190a,190b when in the first position therefore makes it much more difficult to pick the lock 100 and increases the security of the lock. The axial pins 280 of plungers 190a,190b and engagement members 290 are engaged with axial aperture 310 and other apertures 320, 330 of the rotator 170. Since the plungers 190a,190b are engaged with the walls of the body 110 in the first position, the engagement members 290 prevent rotation of the rotator 170 relative to the body 110. When a correctly fitting key is inserted into keyhole 130a and into channel 140a it will actuate two mechanisms. Firstly, the key will correctly position the pins and springs 150 to unlock this part of the lock as per a traditional cylinder lock. Furthermore, the end of the key will engage with the recess 240 of the plunger 190a and push plunger 190a to a so-called "second axial position" whereby the engagement ears 260 slide in the slots of the wall of the body 110 to the second axial position where the engagement ears 260 and slots permit rotational movement of plunger 190a. As plunger 190a is pushed into the rotator 170, axial pin 280 of plunger 190a will push slidable drive member 440 along the axial aperture 310 of rotator 170 and push the axial pin 280 of plunger 190b. Plunger 190b will be pushed away from rotator 170 into a so-called "third axial position" whereby engagement members 290 are disengaged from the engagement apertures 330 in rotator 170. When plunger 190a is in the second axial position and plunger 190b is in the third axial position, cylinder 120a and plunger 190a, rotator 170 and cam 180 can be rotated freely relative to the body 110. When the key is released from cylinder 120a the springs 210 will bias both plungers 190a,190b back to the first axial position and lock both locks. The same mechanism would operate if the key were inserted into keyhole 130b. As best shown in Figures IB and 3D, the rotator 170 contains two guard pins 350 disposed in apertures within the body of the rotator 170. As shown in Figure IB, the guard pins 350 abut the axial pins 280 of the plungers 190a,190b. Plungers 190a,190b are attached to the body 110 of the lock 100 with a circlip 450, which permits translational and rotational movement of the plungers 190a,190b. If one of the cylinders 120a or 120b is snapped off at a respective break point 430, the whole cylinder 120a or 120b and plunger 190a or 190b will typically be removed. When axial pin 280 of the plunger 190a or 190b is taken out of the axial aperture 310, the guard pin 350 will extend into the respective further aperture 360 and block the axial aperture 310. This will prevent access to the other plunger to unlock it. As show in Figure IB, a pin 460 extends from the underside of the lock body 110. When the cylinder lock 100 is installed in a door, pin 460 prevents a lever being inserted between the lock and the door to raise the lock and access the door mechanism. As mentioned above, if a person (such as a burglar) is trying to unlock the door mechanism without a correctly fitting key, the person may snap one of the cylinders 120a,120b at a respective break point 430. From here on, it will be assumed that the person attempting to unlock the door mechanism is positioned on the left-hand side of the cylinder lock 100 shown in Figure IB and is therefore accessing the cylinder lock 100 via the 'near-side' cylinder 120a. The other cylinder will be referred to as the 'far-side' cylinder 120b and related components may be referred to similarly. However, it will be appreciated that the same principles apply, irrespective of which side of the cylinder lock 100 is considered the near side or the far side. The typical next step for a burglar would be to remove the whole near-side cylinder 120a and respective plunger 190a, resulting in the near-side abutment member (e.g. guard pin 350) blocking access to the slidable drive member 440 and preventing the door mechanism from being unlocked. However, if the person recognises that removal of the near-side plunger 190a will result in the guard pin 350 extending into the axial aperture 310 to block access to the slidable drive member 440, the person may learn additional or alternative measures to bypass the action of the abutment member. For example, freeze spray could be injected into the cylinder lock 100 to temporarily freeze the guard pin 350. This may provide enough time to remove the near-side plunger 190a and insert a tool, such as a screwdriver, into the axial aperture before the guard pin 350 moves to block the axial aperture. The tool could then be used to push the slideable drive member 440 and move the far-side plunger 190b to the third axial position, disengaged from the rotator 170. The rotator could then be freely rotated if the person has suitable tools to mimic the action of the near-side plunger 190a being actuated by a key. Alternatively, the burglar may find a way of further breaking the cylinder lock 100 to maintain the near-side plunger 190a in place while the respective cylinder 120a is removed. The near-side plunger may then be delicately manipulated in an attempt to actuate the door mechanism, for example with needle nose pliers. Accordingly, an additional security measure may be desired to further increase the difficulty of overcoming the cylinder lock, especially against unusually practised and / or knowledgeable individuals. Figure 5 shows a cylinder lock 500 according to an embodiment of the invention. The cylinder lock 500 is similar to the cylinder lock 100 shown in Figures 1A-1C, except the plungers 190a,190b and rotator 170 of cylinder lock 100 are replaced by a pair plungers 600a,600b (shown more clearly in Figures 6A and 6B) and a rotator 700 (shown more clearly in Figure 7) respectively. Referring to Figures 6A and 6B, the plungers 600a,600b are identical to the plungers 190a,190b except that the plungers 600a,600b comprise only a single engagement member 690. Referring now to Figure 7, the rotator 700 is similar to the rotator 170 except that the rotator 700 comprises four engagement apertures 720 rather than two. The four engagement apertures 720 include a pair of actuation engagement apertures 730a,730b (equivalent to the two engagement apertures 320 of rotator 170) and additionally comprises first and second interference engagement apertures 740a,740b. In the event that a person has bypassed the security measure of the abutment member (e.g. guard pin 350) as alluded to above, that person will first push the slideable drive member 440 to move the far-side plunger 600b to the third axial position where it is disengaged from the rotator 170, and then attempt to rotate the rotator 700 in order to actuate the door mechanism. It would then be necessary to turn the rotator a full 180° to actuate the door mechanism. Prior to the slideable drive member 440 being pushed, the engagement member 690 (Figures 6A and 6B) of the far side plunger 600b will be partially engaged with the first actuation engagement aperture 690. Accordingly, pushing the slideable drive member 440 will move the far side plunger 600b to the third axial position wherein the engagement member 690 is disengaged from the first actuation engagement aperture 690, but the far-side plunger 600b will be biased towards the first axial position (i.e. towards the rotator 700. The biasing of the plunger 600b towards the first axial position means that, as the rotator 700 is rotated, the engagement member 690 will be biased towards engaging with the first or second interference engagement apertures 740a,740b (depending on the direction that the rotator 700 is turned). Engagement of the engagement member 690 with the first or second interference engagement apertures would therefore prevent, at least temporarily, the complete 180° rotation of the rotator 700 required to actuate the door mechanism. Although the return of the far-side plunger 600b to the first axial position may not, in and of itself, be a terminal obstruction to the person attempting to overcome the cylinder lock, it adds an additional layer of interference and complexity that could crucially slow down actuation of the door mechanism. This may result in the lock tampering act taking long enough that it is noticed by a neighbour or passer-by, for example. It may also cause the person tampering with the lock sufficient confusion to withdraw whatever tool is blocking the guard pin 350, at which point the guard pin would move into place blocking the axial aperture 310 and preventing any further access. Accordingly, the security of the cylinder lock 500 shown in Figure 5 is increased relative to the cylinder lock 100 shown in preceding figures. In other embodiments of the invention, the rotator may comprise only one interference engagement aperture. This may be suitable if, for example, the rotator can only be turned in one direction to actuate the door mechanism. Alternatively, the rotator may comprise more than two interference engagement apertures, to add even further complexity to the cylinder lock. In further embodiments of the invention, the plungers 190a, 190b having two engagement members 290 may be used rather than the plungers 600a, 600b having a single engagement member 690. In such embodiments, a corresponding rotator may comprise an additional two interference engagement apertures positioned symmetrically to the first and second interference apertures 740a,740b relative to a central axis of the rotator so that the pair of engagement members 290 would have a 5 corresponding pair of interference engagement apertures with which to engage. Alternatively, the first and second interference apertures 740a,740b may be moved so that they are positioned opposite to one another relative to the central axis of the rotator (for example, each at 90° to both actuation engagement apertures 730a,730b), such that each of the two engagement members 290 could engage with a respective 10 one of the first and second interference actuation members simultaneously. Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features 15 and parameters of the invention.

Claims

1. A cylinder lock for actuating a door mechanism, the cylinder lock comprising:a body;opposed first and second cylinders comprising, respectively, first and second keyholes disposed in opposite ends thereof for receiving a key, the first and second cylinders being rotatable relative to the body when actuated by a correctly fitting key inserted into the first or second keyhole;a rotator and cam being rotatable relative to the body when actuated by the key inserted into the first or second keyhole, the cam being disposed to engage, in use, the door mechanism;a first plunger disposed in the body between the rotator and first cylinder; anda second plunger disposed in the body between the rotator and second cylinder; wherein:when no key is inserted into the first or second keyhole, the first and second plungers are biased to a first axial position whereby the first and second plungers are engaged with the rotator and at least one of the first and second plungers are engaged with the body to prevent rotation of the first and second cylinders;when a key is inserted into the first or second cylinder, the respective first or second plunger is pushed by the key to a second axial position whereby rotation of the cylinder containing the key, the rotator and the cam is permitted;the first and second plungers each comprise an engagement member that extends into one of a plurality of engagement apertures on the rotator when the first and second plungers are in the first axial position, to prevent rotation of the rotator relative to the first or second plunger;when the first plunger is in the second axial position, the second plunger is in a third axial position whereby the at least one engagement member is disengaged from the rotator, to permit rotation of the rotator relative to the second plunger, and wherein when the second plunger is in the second axial position, the first plunger is in a third axial position whereby the at least one engagement member is disengaged from the rotator, to permit rotation of the rotator relative to the first plunger; andthe plurality of engagement apertures comprises a first interference engagement aperture positioned to receive the engagement member, thereby enabling return of the respective plunger to the first axial position from the third axial position, when the rotator is rotated to a position that is redundant for actuation of the door mechanism.

2. A cylinder lock as claimed in claim 1, wherein the plurality of engagement apertures comprises a pair of actuation engagement apertures positioned to receive the engagement member when the rotator is rotated to positions associated with a full actuation of the door mechanism.

3. A cylinder lock as claimed in claim 2, wherein the first interference engagement aperture is positioned adjacent one of the actuation engagement apertures.

4. A cylinder lock as claimed in claim 3, wherein the plurality of engagement apertures further comprises a second interference engagement aperture positioned adjacent the same actuation engagement aperture as the first interference engagement aperture such that the first and second interference engagement apertures are arranged adjacently to either side of one of the actuation engagement apertures.

5. A cylinder lock as claimed in any preceding claim, wherein the first and second cylinders and first and second plungers are coaxial, and the first and second plungers are slidable in a channel defined by the body along the axis between the first and second axial positions.

6. A cylinder lock as claimed in any preceding claim, wherein the first and second plungers each further comprise an axial pin that extends into an axial aperture extending the length of the rotator and, wherein the axial pins remain in the axial aperture when the first and second plungers move between the first and second axial positions.

7. A cylinder lock as claimed in claim 6, wherein a slidable drive member is disposed in the axial aperture between respective ends of the axial pins of the first and second plungers, so when the first or second plunger is pushed by the key, the other plunger is pushed along the axial aperture by the slidable drive member.

8. A cylinder lock as claimed in claim 6 or claim 7, wherein the rotator comprises at least one abutment member located in an aperture extending from the axial aperture, wherein the at least one abutment member is covered by the axial pin of the first or second plunger, the abutment member arranged such that if the axial pin of the first or second plunger is removed from the rotator, the abutment member blocks the axial aperture.

9. A cylinder lock as claimed in any preceding claim, wherein the first and / or second plungers comprise a generally circular cross section and further comprise opposed engagement ears on the circumference thereof to engage with corresponding slots on the body of the cylinder lock, whereby the engagement ears and slots permit 5 coaxial movement of the first and second plungers between the first second and axial positions, and permit rotation of the plunger only when in the second axial position.

10. A cylinder lock as claimed in any preceding claim, wherein the first and second plungers are biased to the first axial position by a biasing member.1011. A cylinder lock as claimed in claim 10, wherein the first and second plungers are attached respectively to the first and second cylinders with one or more biasing member, wherein the biasing member is a spring.15 12. A cylinder lock as claimed in any claim, wherein the cylinder lock furthercomprises a pin extending from the underside of the lock body to engage with a door when the lock is installed.17

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