The present invention relates to a lock cylinder for a locking mechanism for doors and other similar closures. Such lock cylinders are commonly called euro-lock cylinders or euro-cylinders.

A euro-lock cylinder is designed to operate a rotatable cam with a projecting cam lever that bears against a dead bolt or similar portion of a locking mechanism to move it to an open (retracted) or to a closed (extended) position when the cam is rotated. Rotation of the cam is usually accomplished either via a pin tumbler lock mechanism that requires a key to operate or via a thumb-turn mechanism. Locking mechanisms that comprise such a lock cylinder may incorporate a lock cylinder with two pin tumbler lock mechanisms on opposite sides of the cam so that keys are required to open a door from both sides. Alternatively, the lock cylinder may incorporate a tumbler lock mechanism on one side of the cam and a thumb-turn mechanism on the opposite side of the cam, the former typically being used on an exterior side of a door and the latter on an interior side. In both cases, the cam is usually selectively connected to one or other of these mechanisms by a biased clutch arrangement that is axially slidable between two positions wherein it is engaged by one of these arrangements to rotate the cam as the key or thumb-turn is rotated but is not engaged by the other of the arrangements in order that it can rotate freely relative thereto.

A problem with known locking mechanisms of this type is that they can be broken into with relative ease to gain access to the dead bolt of the locking mechanism. The application of force via a tool from the exterior side of the lock mechanism can break off part of the lock cylinder on one side of the cam, exposing the cam and allowing the cam to be rotated or removed to leave the locking mechanism exposed for further tampering.

The object of the present invention is to provide an improved lock cylinder that obstructs access to the locking mechanism and therefore any dead bolt operating arrangement forming a part of it if the lock cylinder is attacked and broken into. Hereafter and in the claims the word“normal’ describes a standard condition of the lock cylinder as it would leave the factory and under conditions of ordinary use after fitment, in other words when it has not been tampered with or broken into. The term“snapped condition” describes the condition of that part of a lock cylinder that remains in position in a locking mechanism after it has been broken into and part of it removed. The word“neutral” is used to describe the lock when in a normal condition when neither an interior or exterior side of the lock is engaged by a user by insertion of a key or by pressure on a thumb-turn.

According to the present invention there is provided a lock cylinder for a locking mechanism, the lock cylinder comprising

a casing defining a longitudinal axis;

a rotatably mounted cam comprising a radially projecting lever that is adapted to actuate the locking mechanism on rotation of the cam;

first and second cores rotatably mounted within the casing on either side of the cam respectively;

a clutch arrangement located between the first and second cores and comprising first and second clutch members for placing either the first or the second core into engagement with the cam by movement along a longitudinal axis of the lock cylinder against the force of a biasing means; and

first and second spring-loaded engagement mechanisms that are acted on respectively by the first and second clutch members and that are adapted to releasably connect either the first or the second clutch member and thereby the first or the second core to the cam dependent on which of said first and second cores is engaged by a user, connection of one of the first and second engagement mechanisms to the cam releasing the other of the first and second engagement mechanisms from such connection; and wherein

the second clutch member is adapted to move the second engagement mechanism into a position wherein it locks into engagement with the cam if the casing is broken and the first core removed. It will be appreciated that in this lock cylinder the engagement mechanism used to connect the second clutch member clutch to the cam is the same mechanism that is used to lock the second core to the cam when the casing is broken and the first core removed from the lock cylinder. This is different from the prior art, where a separate locking mechanism is required for this purpose. Also, after locking of the second core to the cam, the second clutch member remains movable along the longitudinal axis of the lock cylinder. This means that it can retract into the cam if an attempt is made to grasp it using pliers or similar. In addition, it will be appreciated that after locking of the second engagement mechanism to the cam, the second core is usable to rotate cam and therefore the lever to open the locking mechanism. As the second core is usually that on an interior side of a door, the lock cylinder will still permit occupants to open the door even after an attack on the lock. This is usually now a legal requirement of such lock cylinders for reasons of safety.

Other preferred but non-essential features of the present invention are described in the dependent claims appended hereto.

The present invention will now be described by way of example with reference to the accompanying drawings, in which:-

Fig. 1 is a side view of a first embodiment of lock cylinder in accordance with the present invention when in a normal condition;

Fig. 2 is an end view of the lock cylinder shown in Fig. 1 ;

Figs. 3 and 4 are sectional views along the lines III-III and IVI-IV in Figs. 1 and 2 respectively and show the lock cylinder in a neutral condition;

Fig. 5 is a perspective exploded view of the lock cylinder shown in Figs. 1 to 4;

Fig. 6 is a view similar to Fig. 3 but showing the lock cylinder when an external core thereof is connected to the cam; Fig. 7 is a view similar to Fig. 3 but showing a remaining part of the lock cylinder when in a snapped condition and to a slightly enlarged scale;

Fig. 8 is a perspective exploded view of a second embodiment of lock cylinder in accordance with the present invention;

Fig. 9 is a side view of the lock cylinder shown in Fig. 8 when in a normal condition;

Fig. 10 is an end view of the lock cylinder shown in Fig. 9;

Figs. 11 and 12 are sectional views along the lines XI -XI and XII-XII in Figs. 9 and 10 respectively and show the lock cylinder in a neutral condition;

Fig. 13 is a view similar to Fig. 11 but showing the lock cylinder when an external core thereof is connected to the cam;

Fig. 14 is a view similar to Fig. 11 but showing a remaining part of the lock cylinder when in a snapped condition along with a scrap view A of part thereof to an enlarged scale; and

Fig. 15 is a view to an enlarged scale of a locking spring forming part of the second embodiment of lock cylinder and showing four positions thereof superimposed on one another.

In the drawings and following description, details of lock mechanisms and other elements forming part of the described embodiments of lock cylinder that are not relevant to the present invention have been omitted for clarity. Also, respective components of the described embodiments of the invention that are identical with one another have been given the same reference numbers.

Both the first and the second embodiments of lock cylinder described by way of example herein comprise a casing 1 with first and second cylindrical portions 2 and 3 between which is a gap in which a cam 4 is located centrally of the casing 1. The cam 4 comprises a hollow cylindrical portion and a radially projecting lever 5 that is adapted to actuate a locking mechanism (not shown) on rotation of the cam 4, The locking mechanism will be housed in a lock case (not shown) fitted to a door and the lock cylinder adapted for location through the lock case so that the cylindrical portions 2 and 3 protrude from exterior and interior sides of the door in use. The cylindrical portions 2 and 3 define a longitudinal axis along which are respectively located first and second lock cores 6, 7 on opposite sides of the cam 4. The cores 6, 7 are retained in position by circlips 8 that locate in annular grooves 9 provided in the cylindrical portions 2, 3 and cores 6, 7 on either side of the cam 4. The circlips 8 permit rotation of the cores 6, 7 about their longitudinal axis but prevent their lateral movement along this axis. The cores 6 and 7 may comprise conventional pin tumbler lock mechanisms comprising a keyway 10 and bores 11 housing key pins (not shown) that are movable when a key is inserted into the keyway 10 to act on biased driver pins (not shown) located within corresponding bores (not shown) formed in a radially projecting part 12 of the casing 1. In other embodiments other lock mechanisms may be employed, for example wafer lock mechanisms. As is conventional, the radially projecting part 12 of the casing defines a cut-out portion 13 that accommodates and permits rotation of the lever 5 therethrough. Therefore, in order to strengthen the casing 1 at this position, a strengthening bar 14 is inserted into a channel in the casing 1 and screwed to the radially projecting part 12 on the interior and exterior sides of the casing 1. However, if the lock cylinder is attacked, it is important that the casing 1 snaps in a predetermined way. To this end the casing 1 is provided with one or more weakened areas in order that it breaks at a predetermined position conducive to operation of a locking mechanism, as is described below. In the illustrated embodiments the external side of the casing 1 is provided with a weakened area in the form of a sacrificial cut 15 that is located close to the cut-out portion 13. This ensures that most or the whole of the exterior cylindrical portion 2 can be broken away so that the first core 6 and other internal components of the lock cylinder, as described below, also fall away from remaining components of the lock cylinder.

It should also be appreciated that while the illustrated first and second embodiments of lock cylinder have first and second cores 6, 7 on opposite sides of the cam 4 that comprise pin tumbler lock mechanisms, other embodiments of lock cylinder in accordance with the invention may comprise a core 6 of a first pin tumbler lock mechanism on one side of the cam 4 and a core 7 of a thumb-turn mechanism on the other side of the cam 4. Such an arrangement will be familiar to those skilled in the art. In use, the core 6 of the lock cylinder is intended to be located on an exterior side of the door or closure and the core 7 is located on an interior side. It is therefore the core 6 on the exterior side of the cylinder that will be attacked with a view to its removal should a break-in be attempted and the core 7 that will remain in a snapped condition of the lock cylinder. In all the embodiments of the present invention the pin tumbler lock and thumb-turn mechanisms operate in a conventional way but the manner in which they interact with the cam 4 and a clutch arrangement provided to be selectively connected to one or other of these mechanisms is the subject of the present invention.

In both of the illustrated embodiments of the invention rotation of the cam 4 is effected by means of a clutch arrangement that is located between the first and second cores 6 and 7 and that comprises first and second clutch members 16 and 17 for placing respectively either the first or the second core 6, 7 into engagement with the cam 4 against the force of a biasing means. To this end the clutch members 16, 17 are each in the form of a substantially cylindrical bar that is movable along the longitudinal axis against the force of compression springs 18, 19 respectively that form the biasing means. The clutch members 16, 17 each locate within a cylindrical cavities formed at the inner ends of their respective cores 6, 7 and the compression springs 18, 19 are respectively located between the outer ends of the clutch members 16, 17 and end, internal faces of these cavities in the 6, 7. These internal faces of the cores 6, 7 are provided with a recess in which a reduced diameter end portion 20 of the clutch members 16, 17 locates and which is surrounded by the respective spring 18, 19. The other ends of the clutch members 16 and 17 define noses 21 that abut one within the cam 4. In the illustrated embodiments, when the lock cylinder is in a neutral position, as shown in Figs. 1 to 4 and in Figs. 9 to 12, and neither of the cores 6, 7 is engaged by a user the noses 21 abut one another centrally of the cam 4. However, should a key be inserted into one of the cores 6, 7, then the inner end of the key acts on the end 20 of the relevant clutch member 16, 17 and moves it inwardly of the cam 4. In turn, this moves the other of the clutch members 17, 16 outwardly of the cam 4. Figs. 6 and 13 show the situation where the exterior core 6 has been engaged by insertion of a key so that the clutch member 16 has been moved inwardly and pushed the clutch member 17 along the longitudinal axis against the force of its spring 19, which is thereby compressed. It can be seen that the noses 21 of the clutch members 16, 17 now abut on the internal side of the cam 4 rather than centrally.

Engagement of one of the cores 6, 7 occasioning movement of the clutch members 16, 17 also acts to place this core 6, 7 into engagement with the cam 4 by means of respective, spring-loaded engagement mechanisms as will now be described.

Turning now specifically to the illustrated first embodiment of the invention as shown in Figs. 1 to 7, each of the clutch members 16, 17 defines a cavity 22 therethrough in which part of its engagement mechanism is located. In this embodiment, this engagement mechanism comprises a pair of engagement members for the cam 4 in the form of spring bars 23, which are connected by a tension spring 24, and a respective pair of drive members 25. The spring bars 23 are similar to the spring bars used to connect a watch strap to a watch and comprise a hollow cylinder with short, spring-loaded bars extending from each end. They are arranged with their longitudinal axes parallel to the longitudinal axis of the lock cylinder and with the tension spring 24 connecting them radially through the cavity 22 on opposite sides of the clutch member 16, 17. When the tension spring 24 is not extended in a neutral condition of the lock cylinder as shown in Figs. 3 and 4, the spring bars 23 locate in respective apertures 26 in the cores 6, 7 that align with adjacent apertures 27 formed in the cam 4. The spring bars 23 lie mainly within their respective apertures 26 but protrude slightly into the apertures 27. During normal operation of the lock cylinder, the spring bars 23 of each clutch member 16, 17 are moved radially outwards by their respective drive members 25 so that they locate more fully into the apertures 27 in the cam 4 when the clutch member 16, 17 with which they are associated is engaged. When in this engaged position, as shown in Fig. 6, each spring bar 23 of the engaged side of the lock cylinder lies with its longitudinal axis aligned with the inner surface of the cam 4 and thereby connects its clutch member 16, 17 to the cam 4. Flence, when the core 6 or 7 associated with this clutch member 16 or 17 is rotated, the engaged clutch member 16 or 17 rotates and also rotates the cam 4. The pairs of spring bars 23 are moved into and out of the apertures 27 by their respective pair of drive member 25. The apertures 27 are therefore oval in outline and of a size commensurate with the length of the spring bars 23. The way in which the spring bars 23 are moved will now be described.

Each pair of drive members 25 comprises a pair of inserts that are located within the cavity 22 of the appropriate clutch member 6, 7 and that face one another along a surface that lies along the longitudinal axis of the lock cylinder. The drive members 25 are also pierced radially by a bore 28 through which the tension spring 24 connected the respective spring bars 23 passes. As the drive members 25 are located in the apertures 26 in their respective cores 6, 7 they are unable to move along the longitudinal axis of the lock cylinder. However, they are able to move radially. Radial movement is accomplished by virtue of each drive member 25 defining an angled face 29 that abuts a complementary angled face 30 defined by an end wall of the clutch member 16, 17 defining the hollow portion 22. The angled faces 30 of each clutch member 16, 17 each define an acute angle with respect to the longitudinal axis of the lock cylinder such that the end wall of the cavity 22 has an arrow-shaped surface in cross-section that points to the centre of the cam 4, the angled faces 30 of each clutch member 16, 17 defining positive and negative angles with respect to the longitudinal axis. Hence, the angled faces 30 of the two clutch members 16, 17 are mirror images of one another.

When the lock cylinder is in its neutral position, the abutting angled faces 29, 30 maintain a gap between the two drive members 25. However, when the clutch member 16, 17 is moved forward towards the cam 4 by engagement of its respective core 6, 7, the angled faces 30 act on the angled faces 29 of the drive members 25 that are thereby moved further apart and radially outwards against the force of the tension spring 24. This movement of the drive members 25 moves the spring bars 23 into an engaged position, as described above, wherein they are more fully located into the adjacent aperture 27 in the cam 4. However, at the same time, the other clutch member 17, 16 is moved against the force of its spring 19, 18 so that its angled faces 30 are retracted from the angled faces 29 of the drive members 25. This causes the drive members 25 to move closer together under the force of the tension spring 24 and therefore also moves the spring bars 23 completely out of the apertures 27 and fully into the apertures 26 in the clutch member 16, 17. This permits one of the clutch member 16, 17 to rotate in order to rotate the cam 4 while the other clutch member 17, 16 remains stationary likewise, when the clutch member 16, 17 is disengaged it moves back to its neutral position by virtue of the loading of the spring 19, 18 on the other clutch member 17, 1. The angled faces 29 also move in the opposite direction so that the drive bars 25 and the spring bars 23 move back to their neutral position. In this position, because the spring bars 23 are partially located in the apertures 27, the cam 4 is locked against rotation.

In order to thwart an attempt to gain access to a dead bolt operating arrangement actuated by the cam 4 if the lock cylinder is attacked and broken into, the engagement mechanism has been designed so that a remaining clutch member 17, which is typically that on the interior side of the lock cylinder, is adapted to move the remaining engagement mechanism into a position wherein it locks into engagement with the cam 4 if the casing 1 is broken and the exterior core 6 removed.

As described above, if the lock cylinder is attacked, the casing 1 is designed to snap along the line of the sacrificial cut 15 so that the exterior cylindrical portion 2 can be removed. This causes the clutch member 16 and its associated engagement mechanism comprising the spring bars 23, tension spring 24 and drive members 25 to fall away. This then permits the clutch member 17 on the interior side of the lock cylinder to move further into the cam 4 under the influence of the spring 19. Under normal circumstances, this movement of the clutch member 17 would be restrained by the presence of the other clutch member 16. However, once the lock cylinder has been snapped the clutch member 17 is free to move a greater distance along the longitudinal axis of the lock cylinder 1. This moves the drive members 25 further apart than in normal operation of the lock cylinder and thereby moves the spring bars 23 further outwards until they are fully located within the apertures 27 in the cam 4 and no longer straddle the core 7. The inner edge of each of the apertures 27 is provided with a projecting lip 31 and once the respective spring bar 23 has been pushed fully into the aperture 27 beyond the lip, the spring-loaded bars in its ends locate behind the lip 31 preventing the spring bar 23 from being retracted back into the clutch member 17 by the tension spring 24. This restrains further movement of the clutch member 17 into the cam 4 but also locks the cam 4 to the clutch member 17 and the core 7 as the drive members 25 now enter the apertures 27 and straddle the interface between the clutch member 17 and the cam 4. This means that it is still possible to rotate the remaining core 7 to unlock the lock cylinder 1 from the interior of the door to which it is fitted. However, the clutch member 17 itself is not restrained from movement along the longitudinal axis of the lock cylinder and tends to retract back into the core 7 if an attempt is made to grip its projecting nose 21 by pliers or similar in an attempt to wrench it from the remaining lock cylinder.

The engagement mechanism of the second embodiment of the invention will now be described with reference to Figs. 8 to 15.

In this embodiment, each engagement mechanism comprises a pair of specially shaped locking springs 32, as shown in Fig. 15. Each of these springs 32 is a flexure spring that has the shape of an eroteme or question mark with a coiling portion 33 and an anchoring portion that in this example comprises a leg 34 with an angled foot 35. The coiling portions 33 of each pair of springs 32 forms an engagement member for the cam 4 and are located in the cavity 22 of one or other of the clutch members 16, 17, each of which therefore accommodates two springs 32. The coiling portions 33 abut the angled faces 30 of the clutch member 16, 17 and locate within the apertures 26 formed in the cores 6, 7. They also project slightly into the adjacent apertures 27 in the cam 4 so that the free ends of the coiling portions 33 lie just inwardly of the internal rim of its respective aperture 27 on the outer side of the aperture 27, that is on the side closer to the respective end of the lock cylinder. This locks the cam 4 against any rotation when the lock cylinder is in a neutral condition. The leg 34 and the foot 35 of the spring 32 anchor the spring 32 in position. The leg 34 is located between the end of the adjacent core 6, 7 and the inner wall of the cam 4 adjacent the aperture 27. The foot 35 locates behind and bears against the outer side of the adjacent circlip 8.

The apertures 27 in the cam 4 in the second embodiment are substantially rectangular in shape and those on the interior side of the cam 4 are each provided with a projecting flange or lip 36 on the interior side of the aperture 27, as shown in Fig. 14. The reason for this and the mode of operation of the locking springs 32 will now be described.

In this embodiment when one of the clutch members 16, 17 is moved forward towards the cam 4 by engagement of its respective core 6, 7, the angled faces 30 of this clutch member 16, 17 act on the adjacent coiling portion 33 of the locking spring 32 and push this coiling portion 33 further into the adjacent aperture 27. This connects the clutch member 16, 17 and therefore its adjacent core 6, 7 with the cam 4 so that rotation of the core 6, 7 rotates the clutch member 16, 17 and also the cam 4. However, engagement of the clutch member 16, 17 forces the other clutch member 17, 16 to move so that its angled faces 30 are moved away from the coiling portions 33 of its locking springs 32. This allows the coiling portions 33 of these locking springs 32 to spring out of their adjacent apertures 27 so that they lie fully within the apertures 26. This allows the cam 4 to be rotated by rotation of the clutch member 16, 17 while the other clutch member 17, 16 remains stationary. The same happens in reverse if the other clutch member 17, 16 is engaged. However, when the clutch members 16, 17 are disengaged so that they move back to the neutral position by virtue of the loading of the springs 18. 19, then the angled faces 30 of the clutch members 16, 17 also move back to enable the coiled portions 33 of the locking springs 32 to return to their initial, neutral position.

As in the first embodiment, the locking springs 32 on the interior side of the lock cylinder are also capable of locking into engagement with the cam 4 if the casing 1 is broken and the exterior core 6 removed. In this circumstance the casing 1 snaps as described above so that the exterior cylindrical portion 2 can be removed along with the clutch member 16 and its associated locking springs 32. As before, this permits the clutch member 17 on the interior side of the lock cylinder to move into the cam 4 under the influence of the spring 19 by a greater distance than under normal circumstances. This increased movement enables the coiled portions 33 of the locking springs 32 in the clutch member 17 to spring further into the apertures 27 until the free ends of the coiled portions 33 locate behind the flanges 36, as shown in Fig. 14. This locks the locking spring 32 into this position, restrains further movement of the clutch member 17 into the cam 4 and also locks the cam 4 to the core 7. Hence, as in the first embodiment it is still possible to rotate the remaining core 7 and thereby the cam 4 to unlock the lock cylinder 1 from the interior of the door to which it is fitted but the clutch member 17 itself is not restrained against longitudinal movement along the longitudinal axis of the lock cylinder that it can retract back into the core 7 if an attempt is made to grip it.

It will be appreciate from the foregoing that the coiled portions 33 of the locking springs 32 are designed, in use, to move between four positions, three of which are shown superimposed on one another in Fig. 15 along with the original shape of the locking spring 32 as formed. A first position 37 of the coiled portion shows the locking spring 32 as formed when it is not under any external force. The position 38 shows the coiled portion 33 when the clutch member 16, 17 in which it is located is disengaged from the adjacent cam 4, the other clutch member 17, 18 being engaged. Position 39 shows the coiled portion 33 when the clutch member 16, 17 is in a neutral position. The final position 40 shows the coiled portion 33 after lock snapping when the locking spring 32 is locked to the cam 4. The position of the coiled portion 33 when the clutch member 16, 17 is engaged is between positions 39 and 40.

It will be appreciated that in the present invention the engagement mechanism used to connect the clutch members 16, 17 to the cam 4 is the same mechanism that is used to lock the core 7 to the cam 4 after lock snapping. This means that a separate locking mechanism is not required.

In a first modification to the described embodiments, it will be appreciated that the clutch members 16, 17 need only to define a single angled face and that the engagement mechanisms do not need to mirror one another on opposite sides of the clutch member 16, 17. Equally, in some other embodiments it may be appropriate for the clutch members 16, 17 to each define more than two angled faces and for the engagement mechanisms to be adapted accordingly. Also, the spring bars 23 and drive members 25 could be replaced by other components that act in the same way but are differently constructed. In another modification, the interior core 7 can be set up to be preferentially connected to the cam 4 in what may be called the neutral position. In such a case only one compression spring 19 is required on the interior side of the lock cylinder to return the clutch member 16, 17 back to this neutral position after engagement of the exterior core 6. The exterior clutch member 16 may then bear directly against the inner end of the core 6 without the imposition of a spring therebetween. However, the structure of the clutch members 16, 17 and of the respective engagement mechanisms may be identical to those described above. In a further modification to the second embodiment with a view to making the locking mechanism more compact, the single compression springs 18, 19 may each be replaced by pairs of springs located respectively on either side of the clutch members 16, 17.