Cylinder lock with thumb turn

Abstract

A cylinder lock comprising an inner thumb-turn barrel 16 rotationally coupled to cam (20, fig.3), an external lock barrel selectively coupled to the thumb-turn barrel via a clutch upon insertion of a key such that rotation of external barrel rotates the cam via the thumb-turn barrel. The clutch includes a sleeve 36 axially movable from a first normal position to a second axial position, e.g. during lock snapping of cylinder housing in which the clutch is unable to engage the thumb-turn. Preferably the clutch includes an axially movable clutch plate 32 with a spindle 34; the clutch plate rotationally coupled to the outer cylinder, the spindle includes radial lugs 38 selectively coupling in slots 30 of thumb-turn barrel upon insertion of external key, spring 40 biasing clutch to disengage from thumbturn. Preferably a spring biased tamper pin 48 engages within a groove 60 in clutch sleeve when sleeve is moved to second position during snapping attack preventing axial movement of clutch sleeve back to the first position. Spindle 34 may be two part sprung telescopic spindle to accommodate misalignment of thumbturn slots 30 with lugs 38 during insertion of the external key until rotated into alignment.

Description

Field of the Invention The present invention concerns a lock cylinder. More particularly, but not exclusively, this invention concerns a lock cylinder resistant to snap attacks. Background of the Invention Lock cylinders may be subject to various types of attack. For example, lock cylinders may be damaged in an attempt to gain access to the internal workings of a lock, which may allow an attacker to unlock the lock and gain unauthorised entry through the door or window the lock was securing. Some lock attacks include snapping the external part of the lock cylinder away from the internal part of the lock cylinder, and manipulating a clutch in the lock cylinder in such a way as to unlock the lock, or alternatively looking to directly manipulate the mechanism of a lock once exposed by a snapping attack. In order to prevent this, some lock cylinders are provided with sacrificial sections to control the snapping of the external part of the lock cylinder, and spring-loaded clutches which move into a secure position once the external part of the lock cylinder has been removed. However, spring-loaded clutches may jam or otherwise be prevented from moving the clutch into a secure position, potentially leaving the clutch open to external interference. For example, some attacks may comprise the attacker squirting liquid into the lock or lock cylinder, and then freezing the liquid with a compressed air-spray. The frozen liquid may hold a spring-loaded clutch in a vulnerable position following a snapping attack. The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved lock cylinder. Summary of the Invention The present invention provides, according to a first aspect, a lock cylinder comprising a cylinder housing, a thumb-turn barrel and an external lock barrel located within the cylinder housing, a rotatable cam rotatably coupled with the thumb-turn barrel, such that rotation of the thumb-turn barrel causes rotation of the rotatable cam, and a clutch comprising a clutch sleeve with a first position with respect to the cam which allows selective engagement of the clutch with the thumb-turn barrel when a suitable key is inserted into the external lock barrel, such that rotation of the external lock barrel causes rotation of the thumb-turn barrel, and disengagement of the clutch and the thumb-turn barrel when no key is inserted in the external lock barrel, and second position with respect to the cam in which the clutch sleeve has moved laterally with respect to the first position, and in the second position the clutch is unable to engage with the thumb-turn barrel. As would be understood by the skilled person, a lock cylinder conventionally has an internal side and an external side. The internal side is accessible on the secure side of the door or window the lock cylinder is attached to, and the external side is accessible on the unsecure side of the door or window the lock cylinder is attached to. The thumb turn will typically be located on the secure side of the door or window the lock cylinder is attached to. The skilled person will also appreciate that a lock cylinder has a longitudinal axis extending from the internal side to the external side of the lock cylinder, and movement of components along this longitudinal axis is movement in a lateral direction. The skilled person will also be familiar with the conventional lock barrel pin tumbler arrangement where a series of spring-loaded pins require alignment via a suitably shaped key in order to allow rotation of the lock barrel. If no key is present, or an unsuitable key is inserted into the lock barrel, the spring-loaded pins prevent the rotation of the lock barrel. This provides the conventional locking and unlocking process as follows. When approaching the lock from the external side, the processes comprises inserting a suitable key into the external lock barrel, thereby resulting in rotational engagement of the external lock barrel with the thumb-turn barrel via the clutch, and rotating the key such that the lock barrel also rotates within the cylinder housing, which consequently also causes the thumb-turn barrel and cam of the lock cylinder to rotate. When the key is removed, the clutch disengages from the thumb-turn barrel, which is no longer rotationally coupled to the external lock barrel, and is free to rotate by manipulation of a thumb turn attached to the thumb turn barrel. When approaching the lock from the internal side, the thumb turn is rotated, thereby causing the cam to rotate. The cam may move into a position in which the cam engages with an aperture in a door frame, for example, or may drive an additional locking element to extend from a door or window into a corresponding aperture in a door or window frame. When the clutch sleeve is in the second position, the clutch may no longer engage with the thumb-turn barrel, meaning manipulation of the cam can only be achieved by movement of the thumb turn. Therefore, the lock cylinder may only be unlocked from the secure side of the lock. Preferably, the clutch sleeve is moved into the second position when the lock cylinder experiences a snapping attack, wherein the cylinder housing is snapped and the external lock barrel and surrounding cylinder housing is moved away from the remainder of the lock cylinder. Advantageously, the action of snapping the cylinder housing and removing it from the remainder of the lock cylinder physically moves the clutch sleeve into the second position. The clutch may comprise a clutch plate. The clutch plate may be laterally moveable relative to the clutch sleeve. The lateral movement of the clutch plate relative to the clutch sleeve may be limited. The clutch plate may be rotationally connected to the external lock barrel, such that rotation of the external lock barrel results in rotation of the clutch plate. The clutch plate may comprise one or more lugs or wings that extend into corresponding slots in the external lock barrel. A retaining clip may be positioned to laterally connect the external lock barrel and the clutch plate. In such an arrangement, lateral movement of the external lock barrel will result in lateral movement of the clutch plate. The clutch may comprise a clutch plate and a spindle attached to the clutch plate. The spindle may be rotationally connected to the clutch plate, such that rotation of the clutch plate results in rotation of the spindle. The thumb-tum barrel may comprise one or more slots. The slots may be located at the end of the thumb-turn barrel closest to the cam. The spindle may comprise one or more lugs sized to be slidable into the one or more slots in the thumb-turn barrel, such that the spindle and thumb-turn barrel then become rotationally connected, where rotation of the spindle results in rotation of the thumb turn barrel. When a suitable key is inserted into the external lock barrel, the clutch plate may be pushed laterally towards the thumb-turn barrel, causing the spindle to move towards the thumb-turn barrel, and the one or more lugs sliding into the corresponding one or more slots in the thumb-turn barrel. The clutch is now rotationally connected to the thumb-turn barrel. The clutch may comprise a spring, which biases the clutch away from the thumb-turn barrel, such that when a key is not inserted into the external lock barrel, the one or more lugs do not extend into the corresponding one or more slots, and the clutch and the thumb-turn barrel are not rotationally connected to one another. The spindle may be a two-part spindle. The two-part spindle may comprise a fixed spindle and a spindle sleeve. The one or more lugs may extend from the spindle sleeve. The spindle sleeve may be rotationally connected to the fixed spindle, such that rotation of the fixed spindle results in rotation of the spindle sleeve. The spindle sleeve may be laterally moveable with respect to the fixed spindle. Such an arrangement may allow for the misalignment of the one or more slots in the thumbturn barrel and one or more corresponding lugs extending from the spindle sleeve. Once inserted, a key may be rotated, causing the external lock barrel to rotate, and consequently the spindle sleeve will also rotate, and at some point, the one or more lugs will align with the one or more corresponding slots in the thumb-turn barrel. The spindle sleeve may be biased against the thumb-turn barrel such that when the one or more lugs align with the corresponding one or more slots, the spindle sleeve moves laterally, such that the one or more lugs and one or more slots engage, thereby rotationally coupling the clutch to the thumb-turn barrel. The skilled person will appreciate that the opposite arrangement could be provided, with one or more lugs extending from the thumb turn barrel and one or more corresponding slots being located in the spindle. The lock housing may comprise a break line. The break line may be located between the external lock barrel and the cam. The break line may be a section of material removed from the lock housing, and / or may be a weakened part of the lock housing. In the event of a snapping attack, the lock housing may snap at the break line, and the lock housing and the external lock barrel may be pulled away from the remainder of the lock cylinder. As the external lock barrel is pulled away from the remainder of the lock cylinder, the clutch may also be pulled laterally away, for example via a retaining clip laterally connecting the external lock barrel with the clutch plate. The lateral movement of the clutch as a result of a snapping attack may move the clutch into the second position. The lock housing may comprise a biased pin, for example a pin biased by a spring. The clutch sleeve may abut the biased pin when the clutch sleeve is in the first position, such that free rotational movement of the clutch sleeve is possible. The clutch sleeve may comprise a groove. When the clutch sleeve is moved to the second position, the lateral movement of the clutch sleeve may align the groove with the biased pin, such that the bias pin moves into the groove. Once the biased pin has moved into the groove, the biased pin may prevent any further lateral movement of the clutch sleeve. For example, if the lock cylinder is snapped, and the attacker attempts to push the clutch back into engagement with the thumb-turn barrel, the biased pin holds the clutch sleeve in position and prevents this. The skilled person will appreciate that the arrangement may be reversed, such that a biased pin is contained within the clutch sleeve which extends into a corresponding groove in the lock housing when the clutch sleeve moves laterally into the second position. As in the alternative arrangement, the biased pin will engage with the groove to prevent further lateral movement of the clutch sleeve. It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa. Description of the Drawings Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: Figures 1 and 2 show side views of a lock cylinder according to a first embodiment of the invention; Figures 3 and 4 show cross-sectional views of the lock cylinder; Figure 5 shows an exploded view of the lock cylinder; Figure 6 shows the lock cylinder after a snapping attack; Figure 7 shows the clutch of the lock cylinder; Figures 8 and 9 shows a cross-sectional views of the clutch shown in figure 7, and Figure 10 shows an exploded view of the thumb-turn barrel and cam of the lock cylinder. Detailed Description Figure 1 shows a lock cylinder 10 comprising a lock housing 12. Within the lock housing 12 there is an external lock barrel 14 and a thumb-turn barrel 16. The thumb-turn barrel 16 comprises a protrusion 18 which extends beyond lock housing 12, to which a thumb turn (not shown) may be connected to allow a user to rotate the thumb-turn barrel 16 within the lock housing 12. A cam 20 is provided between the external lock barrel 14 and the thumb-turn housing 16. The lock cylinder 10 is configured to be inserted through a door leaf (not shown) with a suitably sized and shaped lock aperture, and the lock cylinder 10 is conventionally secured within the lock aperture via a bolt being screwed into the cylinder housing 12. The lock cylinder 10 has a longitudinal axis X-X, and where movement is described as being lateral, the movement is parallel to the longitudinal axis X-X. Where movement is described as being rotational, it is rotational around the longitudinal axis X-X. The cam 20 may be rotated between a position in which the cam 20 is housed within the external boundaries of the cylinder housing 12, and a position in which the cam 20 extends away from the external boundaries of the cylinder housing 12. This may allow the cam to extend into an appropriate aperture within the frame of the door leaf or may drive a lock mechanism associated with the lock cylinder 10 to engage with a corresponding aperture. As can be seen in the cross-sectional view shown in Figure 3, the lock cylinder 10 is of the type commonly referred to in the art as a pin tumbler / thumb-turn lock. The lock cylinder 10 may be operated from one side using a key, and the opposite side by the rotation of a thumb turn. The external lock barrel 14 includes a series of pins which may be engaged by a suitably shaped key in order to allow rotation of the external lock barrel 14 within the cylinder housing 12. The internal pin arrangements of the external lock barrel 14 are conventional and well understood by a skilled person, so no further description will be provided. Figure 10 is an exploded view of the cam 20 and thumb-turn barrel 16. A lug 22 extends from an end of the thumb-turn barrel 16 into a lug receiving slot 24 in the cam 20, thereby rotationally coupling the thumb-turn barrel 16 and the cam 20, such that if the thumb-turn barrel 16 is rotated around the axis X-X, the cam 20 is also rotated around the axis X-X and vice versa. A retaining clip 26, as show in figure 5, engages with a corresponding groove 28 in the thumb-turn barrel 16, permanently coupling the cam 20 and the thumb-turn barrel 16 together. The skilled person will appreciate that permanent coupling, in this sense, means that in all normal operation and when the lock cylinder 10 subject to a snap attack, the cam 20 and the thumb-turn barrel 16 remain connected. The thumb-turn barrel 16 also comprises a pair of slots 30 which allow selective engagement with the external lock barrel 14 as will be explained in more detail below. A clutch plate 32 is fixed to a two-part spindle 34, the two-part spindle 34 extending through a clutch sleeve 36. The clutch sleeve 36 is housed within a cavity in the cam 20 and in a first position, as shown in figures 3 and 4, has one end face that abuts the thumb-turn barrel 16 and one end face that abuts the external lock barrel 14. The two-part spindle 34 comprises a distal end away from the clutch plate 32, with a pair of lugs 38 located at the distal end, the pair of lugs 38 configured to be slidable into the corresponding pair of slots 30 in the thumb-turn barrel 16. When the pair of lugs 38 are slid into to engagement with the pair of slots 30, rotational movement of the external lock barrel 14 is transferred to the clutch plate 32, via the two-part spindle 34, and causes the thumb-turn barrel 16 to rotate. The rotation of the thumb-turn barrel 16 results in the consequent rotation of the cam 20. The two-part spindle 34 is laterally movable through the clutch sleeve 36. When no key is inserted in the external lock barrel 14, a spring 40 biases clutch plate 32 and two-part spindle 34 such that the pair of lugs 38 do not extend into the slots 30, thereby allowing free rotation between the thumb-turn barrel 16 and the external lock barrel 14. When no key is inserted in the external lock barrel 14, the cam may only be rotated by rotation of the thumb turn attached to the thumb-turn barrel 16. When a suitable key is inserted into the external lock barrel 14, the external lock barrel becomes rotationally coupled to the thumb-turn barrel 16, therefore enabling rotation of the key to cause rotation of the cam 20. The two-part spindle 34 comprises a fixed spindle 42 and a spindle sleeve 44. The fixed spindle 42 is fixed to the clutch plate 34 via a through pin such that rotational movement and lateral movement of the clutch plate 34 is directly transferred to the first part 42. The spindle sleeve 44 is located away from the clutch plate 34, and is secured to the fixed spindle 42 such that rotational movement of the fixed spindle 42 is directly transferred to the spindle sleeve but a small amount of lateral movement, corresponding to the length of the lugs 38, is allowed. Such a connection is provided by a through pin being secured in a fixed position relative to the spindle sleeve, with a through slot in the fixed spindle allowing the lateral movement. Such an arrangement compensates for the position of the slots 30 in the thumb-turn barrel 16 being variable, depending on how far the thumb-turn has been rotated by a user. If the slots 30 and lugs 32 exactly align when a key is inserted into the external lock barrel 14, the external lock barrel 14 will immediately be rotationally coupled to the thumb-turn barrel 16. If the slots 30 and lugs 32 are not exactly aligned, rotation of the external lock barrel will result in rotation of the spindle sleeve 44. Whilst the fixed spindle 42 will have moved laterally towards the thumb-turn barrel on insertion of the key, the spindle sleeve 44 with remain in the same lateral position until rotation of the spindle sleeve 44 causes the slots 30 and lugs 32 to align. At this point, a spring 46 biasing the spindle sleeve 44 relative to the fixed spindle 42 will push the spindle sleeve 44 such that the lugs 32 engage with the slots 30, and the external lock barrel 14 is rotationally coupled to the thumb-turn barrel 16. As can be seen in figures 3, 4, and 6, the lock housing 12 comprises a pin 48 and biasing spring 50. In normal operation, the clutch sleeve 36 is in a first position abutting the pin 48, pushing against the biasing spring 50, with the pin 48 being fully contained within the housing 12 and providing no obstruction to the movement, lateral or rotational, of the clutch sleeve 36. The lock housing 12 comprises a break line 52 located between the outer lock barrel and the cam 20. If the lock cylinder 10 is subjected to a snapping attack, the lock housing 12 will break at the break line 52, as shown in figure 6. Removal of the broken part of the lock housing 12 will also result in the removal of the external lock barrel 12. A spring clip 54, located to the cam side of the clutch plate 32, is received within a corresponding groove 56 in the external lock barrel 12. When the lock housing 12 is snapped, and the external lock barrel 12 removed, the spring clip 54 will pull the clutch plate 32, and consequently clutch sleeve 36 and two-part spindle 34, away from the cam 20. The clutch sleeve 36 includes a groove 60 of reduced diameter, into which the pin 48 will then extend under the bias of the spring 50. Rotational movement of the clutch sleeve 36 is still possible, but lateral movement is prevented by the pin 48 engaging with the groove 60. The lateral movement of the clutch sleeve 36 and two-part spindle 34 is such that it is no longer possible for the lugs 38 to engage with the slots 30. Therefore, the thumb-turn barrel 16, and consequently the cam 20, can no longer be rotated from the external side of the lock cylinder 10. However, the cylinder lock is still operable by rotation of the thumb turn. Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described. In the embodiments described above, various lugs and slots, and pins and grooves have been described. The skilled person will appreciate that these may be switched for one another in alternative embodiments of the invention. For example, the lugs extending from the spindle sleeve could extend from the thumb-turn barrel, and the slots in the thumb-turn barrel could be situated in the spindle sleeve. The biased pin located in the lock housing could be positioned within the clutch sleeve, and the groove in the clutch sleeve could be part of the lock housing. Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

1. A lock cylinder comprising:a cylinder housing,a thumb-turn barrel, andan external lock barrel located within the cylinder housing,a rotatable cam rotatably coupled with the thumb-turn barrel, such that rotation of the thumb-turn barrel causes rotation of the rotatable cam, anda clutch comprising a clutch sleeve with a first position with respect to the cam which allows selective engagement of the clutch with the thumb-turn barrel when a suitable key is inserted into the external lock barrel, such that rotation of the external lock barrel causes rotation of the thumb-turn barrel, and disengagement of the clutch and the thumb-tum barrel when no key is inserted in the external lock barrel, and second position with respect to the cam in which the clutch sleeve has moved laterally with respect to the first position, and in the second position the clutch is unable to engage with the thumb-turn barrel.

2. A lock cylinder as claimed in claim 1, wherein the lock housing contains a biased pin, and the clutch sleeve comprises a groove into which the biased pin extends when the clutch sleeve moves into the second position, such that further lateral movement of the clutch sleeve is prevented.

3. A lock cylinder as claimed in claim 1 or claim 2, wherein the clutch comprises a clutch plate, the clutch plate laterally moveable relative to the clutch sleeve and rotationally connected to the external lock barrel, such that rotation of the external lock barrel results in rotation of the clutch plate.

4. A lock cylinder as claimed in claim 3, further comprising a retaining clip positioned to laterally connect the external lock barrel and the clutch plate.

5. A lock cylinder as claimed in any preceding claim, wherein the clutch comprises a clutch plate and a spindle attached to the clutch plate, the spindle beingrotationally connected to the clutch plate, such that rotation of the clutch plate results in rotation of the spindle.

6. A lock cylinder as claimed in claim 5, wherein the thumb-turn barrel comprises one or more slots located at the end of the thumb-turn barrel closest to the cam, and the spindle comprises one or more lugs sized to be slidable into the one or more slots in the thumb-turn barrel, such that the spindle and thumb-turn barrel then become rotationally connected, where rotation of the spindle results in rotation of the thumb turn barrel.

7. A lock cylinder as claimed in claim 6, wherein the spindle is a two-part spindle comprising a fixed spindle and a spindle sleeve, the one or more lugs extending from the spindle sleeve.

8. A lock cylinder as claimed in claim 7, wherein the spindle sleeve is rotationally connected to the fixed spindle, such that rotation of the fixed spindle results in rotation of the spindle sleeve, and the spindle sleeve is laterally moveable with respect to the fixed spindle.

9. A lock cylinder as claimed in any preceding claim, wherein the lock housing comprises a break line located between the external lock barrel and the cam.

10. A lock cylinder as claimed in claim 9, the lock cylinder configured such that if the external lock barrel is pulled away from the remainder of the lock cylinder during a snapping attack, the clutch is also pulled laterally away, such that the clutch is moved into the second position.

11. A lock cylinder as claimed in claim 9 or claim 10, when dependent on claim 4, wherein the retaining clip is positioned such that if the external lock barrel is pulled away from the remainder of the lock cylinder during a snapping attach, the clutch is also pulled laterally away, such that the clutch is moved into the second position.

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