This invention relates to pin tumbler cylinder assemblies for use in locks, and keys for insertion into such cylinder assemblies. The invention also relates to key blanks from which keys embodying the invention can be cut and to methods of operating pin tumbler cylinder assemblies .

Pin tumbler cylinder assemblies are well known. In a common design, a pin tumbler cylinder assembly comprises a cylinder housing, a plug rotatably mounted in the cylinder housing, a keyway extending along the longitudinal axis of the plug and open at a front end of the plug to allow insertion of a key, a plurality of tumbler pin passageways extending inwardly from the circumference of the plug to the keyway, and a plurality of driver pin passageways extending outwardly from the interior of the cylinder housing, the tumbler pin passageways being aligned with the driver pin passageways in one rotational position of the plug, a plurality of tumbler pins slidably mounted in respective tumbler pin passageways, a plurality of driver pins slidably mounted in respective driver pin passageways and a plurality of compression springs resiliently biasing respective driver pins inwardly. The driver pins bear against the tumbler pins biasing them into the keyway and, without a key inserted in the keyway, the driver pins extend across the split line of the plug and prevent the plug rotating in the cylinder housing. When the correct key is inserted, however, the top of the blade of the key engages the tumbler pins pressing them outwardly by respective distances determined by the shape of the key. With the correct key fully inserted, the radially outer end of each tumbler pin is located at the split line between the plug and the cylinder housing so that each tumbler pin is contained wholly within the plug but each driver pin is contained wholly within the cylinder housing. The key for use in such a cylinder assembly commonly comprises a bow and a profiled blade, the profiled blade having a particular cross-section matched to the cross- section of the keyway to allow insertion of the blade into the keyway as a sliding fit and including a plurality of notched regions along its top, each for engaging a respective tumbler pin. As the key is inserted, the radially inner ends of the tumbler pins ride up and down the notched top of the key blade in the manner of cam followers, with the key blade acting as the cam. Thus the angle of inclination of the notches to the longitudinal axis of the key blade is not very steep, typically not more than about 45 degrees. Of course the notches are of different depths so that the radially inner ends of the tumbler pins, which are of different lengths, rest at different levels in the notches when the key is inserted. It is also common for key blanks to be provided, for example, to locksmiths to allow them to cut a key of a particular notched pattern for a customer. The key blank is supplied with the blade already cut to the cross- sectional shape that is desired, but the locksmith then forms a particular required pattern of notches along the top of the blade. Such notches can be formed readily by a simple milling tool which can produce the same profile across the whole width of the lock. That makes the equipment required by the locksmith simpler.

It is an object of the invention to provide a pin tumbler cylinder assembly of an improved design.

It is also an object of the invention to provide a key for use in a pin tumbler cylinder assembly, which key enables certain improvements to be made.

It is further an object of the invention to provide a key blank suitable for forming an improved key for a pin tumbler cylinder assembly. It is yet further an object of the invention to provide a method of operating a pin tumbler cylinder assembly, which method enables certain improvements to be obtained.

According to a first aspect of the invention there is provided a pin tumbler cylinder assembly comprising a cylinder housing, a plug rotatably mounted in the cylinder housing, a keyway extending along the longitudinal axis of the plug and open at a front end of the plug to allow insertion of a key, a plurality of tumbler pin passageways extending inwardly from the circumference of the plug to the keyway, and a plurality of driver pin passageways extending outwardly from the interior of the cylinder housing, the tumbler pin passageways being aligned with the driver pin passageways in one rotational position of the plug, a plurality of tumbler pins slidably mounted in respective tumbler pin passageways, a plurality of driver pins slidably mounted in respective driver pin passageways and a plurality of resilient biasing means for resiliently biasing respective driver pins inwardly, wherein the tumbler pins include a telescopic tumbler pin assembly including an outer pin and an inner pin slidably mounted in the outer pin, the inner pin being arranged to be resiliently biased inwardly by the associated driver pin and the outer pin being arranged to be biased inwardly by resilient means acting between the radially inner and outer pins, wherein the plug is prevented from rotating relative to the cylinder housing by the telescopic tumbler pin assembly except when the radially inner end of the outer pin of the telescopic pin assembly projects inwardly into the keyway further by a predetermined amount than the radially inner end of the inner pin of the telescopic pin assembly.

By providing a telescopic tumbler pin assembly with an inner pin that is resiliently biased inwardly by the driver pin, for example by contact of the radially inner end of the driver pin against the radially outer end of the inner pin, whilst requiring the outer pin to project radially inwardly into the keyway further by a predetermined amount than the inner pin to allow the plug to rotate, a cylinder of improved security is obtained. The improved security arises from the increased difficulty of picking the lock and the special nature of the key required to operate the lock. The key is required to drive the inner pin radially outwardly further than the outer pin by a predetermined amount .

The driver pin passageways and the tumbler pin passageways may conveniently extend precisely radially from the axis of rotation of the plug, but that is not essential. Where reference is made in this specification to radially inner and radially outer ends of the pins, that should be understood as indicating merely which end of a pin is being referred to, rather than that the pin necessarily extends in a precisely radial direction.

As will be understood, where reference is made to the cylinder assembly including a plurality of tumbler pins, one or more of those "pins" may be conventional single pins and one or more of those "pins" is a telescopic pin assembly. It is within the scope of the invention for only one of the tumbler pins to provide a telescopic tumbler pin assembly, but it may be preferred that the tumbler pins include a plurality of telescopic tumbler pin assemblies, each including an outer pin and an inner pin slidably mounted in the outer pin, the inner pin being arranged to be resiliently biased inwardly by driving of the driver pin and the outer pin being arranged to be biased inwardly by resilient means acting between the inner and outer pins, wherein the plug is prevented from rotating relative to the cylinder housing by the telescopic tumbler pin assembly except when the radially inner end of the outer pin of the telescopic pin assembly projects inwardly into the keyway further by a predetermined amount than the radially inner end of the inner pin of the telescopic pin assembly. It is indeed possible for all the tumbler pins to be provided by telescopic tumbler pin assemblies, but generally it will be preferred that a mixture of conventional tumbler pins and telescopic tumbler pin assemblies are provided, preferably with more pins of the conventional kind.

The driver pins are preferably resiliently biased inwardly by respective compression springs disposed in the driver pin passageways outside the driver pins.

The driver pin passageways and the tumbler pin passageways are preferably disposed in a common plane. Preferably there is only one such common plane, but it is within the scope of the invention for there to be two or even three or more such planes. Where there is more than one common plane, those planes are preferably equiangularly spaced about the axis of rotation of the plug.

The resilient means acting between the inner and outer pins in the or each telescopic tumbler pin assembly preferably comprises a compression spring. It may be compressed between opposing shoulders on the exterior of the inner pin and the interior of the outer pin.

The driver pin in the driver pin passageway that is aligned with the tumbler pin passageway of the or each telescopic tumbler pin assembly is preferably of reduced cross-section at its radially inner end, whereby it is able to drivingly engage the inner pin of the or each telescopic tumbler pin assembly without engaging the outer pin.

Preferably the radially inner end of the inner pin of the or each telescopic tumbler pin assembly is chamfered. That facilitates the riding of the pin over the key blade as it is inserted into the keyway. Similarly the radially inner end of the outer pin of the or each telescopic tumbler pin assembly is preferably chamfered. In the arrangement described above the inner pin of the telescopic pin assembly is biased towards the keyway by an associated driver pin which preferably directly engages the inner pin. The cylinder assembly may also incorporate a further telescopic pin assembly in which the inner pin of the further assembly is biased away from the keyway. More particularly, the tumbler pins may include a further telescopic tumbler pin assembly including a further outer pin and a further- inner pin slidably mounted in the further outer pin, the further outer pin being arranged to be resiliently biased inwardly by the associated driver pin and the further inner pin being arranged to be biased outwardly by resilient means acting between the further inner and outer pins, wherein the plug is prevented from rotating relative to the cylinder housing by the further telescopic tumbler pin assembly except when the radially inner end of the further inner pin of the further telescopic pin assembly projects inwardly into the keyway further by a predetermined amount than the radially inner end of the further outer pin of the further telescopic pin assembly.

By providing a telescopic tumbler pin assembly with an inner pin that is resiliently biased outwardly, whilst requiring the inner pin to project radially inwardly into the keyway further by a predetermined amount than the outer pin to allow the plug to rotate, a cylinder of improved security is obtained. The improved security arises from the increased difficulty of picking the lock and the special nature of the key required to operate the lock. The key is required to accommodate the inner pin when it is driven radially inwardly further than the outer pin by a ^" predetermined amount against the resilient bias between the outer and inner pins.

The driving of the inner pin into the key can be effected by a camming action of the radially inner end of the driver pin on the radially outer end of the inner pin as the plug begins to be rotated in the cylinder housing. It is within the scope of the invention for only one of the tumbler pins to be a further telescopic tumbler pin assembly, but the tumbler pins may include a plurality of further telescopic tumbler pin assemblies, each including a further outer pin and a further inner pin slidably mounted in the further outer pin, the further outer pin being arranged to be resiliently biased inwardly by the associated driver pin and the further inner pin being arranged to be biased outwardly by resilient means acting between the further inner and outer pins, wherein the plug is prevented from rotating relative to the cylinder housing by the further telescopic tumbler pin assembly except when the radially inner end of the further inner pin of the further telescopic pin assembly projects inwardly into the keyway further by a predetermined amount than the radially inner end of the further outer pin of the further telescopic pin assembly. The resilient means acting between the further inner and outer pins in the or each further telescopic tumbler pin assembly preferably comprises a compression spring. It may be compressed between opposing shoulders on the exterior of the inner pin and the interior of the outer pin.

The driver pin in the driver pin passageway that is aligned with the tumbler pin passageway of the or each further telescopic tumbler pin assembly is preferably recessed at its radially inner end, whereby it is able to drivingly engage the further outer pin of the or each further telescopic tumbler pin assembly without engaging the further inner pin. The. further inner pin is preferably able to be accommodated in the recess when it is biased into that position by the resilient means acting between the further inner and outer pins.

The recess at the radially inner end of the driver pin preferably has sloping sides. The sides may for example slope at an angle of 45 degrees or less to the axis of rotation of the plug. Preferably the sides slope at an angle of 25 to 45 degrees, and, in a particular example, at an angle of about 35 degrees to the axis of rotation of the plug. The radially outer end of the further inner pin is preferably chamfered, so it too has sloping sides. The sloping sides of the inner pin may for example slope at an angle of 45 degrees or less to the axis of rotation of the plug. Preferably the sides of the inner pin slope at an angle of 25 to 45 degrees, and, in a particular example, at an angle of about 35 degrees to the axis of rotation of the plug. Preferably the inclinations of the sloping sides of the radially inner end of the driver pin and of the radially outer end of the further inner pin are the same; that facilitates the driving inwardly of the inner pin into a recess in a key as the plug begins to be rotated in the cylinder housing.

The radially inner end region of the further inner pin of the or each further telescopic tumbler pin assembly is preferably of substantially constant exterior cross- section. This is a special feature which is unconventional in a tumbler cylinder lock where the radially inner end region of the pin would normally be tapered to facilitate riding of the pin over notched regions of a key blade as a key is inserted. If the further inner pin is moved into the recess in the key only after the key is fully inserted, then riding of the pin over the key blade is not required and a square end to the pin becomes acceptable and has the advantage of providing a more positive engagement between the key and the cylinder. Furthermore, as described more fully below, it becomes possible to use a key with a recess for accommodating the inner pin that has sides extending substantially perpendicular to the axis of the blade of the key. The radially inner end of the further outer pin of the or each further telescopic tumbler pin assembly is preferably chamfered. That facilitates the riding of the outer pin over the key blade as it is inserted into the ^; keyway . Whilst it is within the scope of the invention for the inner and outer pins not to be held together in any way, in a preferred form of telescopic tumbler pin assembly, the inner pin is restrained from separating from the outer pin. This may be convenient at the manufacturing stage when handling the assemblies and also subsequently. For example it may be desirable to provide a locksmith with one or more telescopic pin assemblies to replace conventional pins in a pin tumbler cylinder assembly and it is then advantageous if the telescopic pin assembly can be handled as a single part. The inner pin may be a push fit in the outer pin and may also be able to be removed from the outer pin by sufficient force, rather than being permanently retained within the outer pin. The inner pin may have a waisted intermediate portion mounted in a surrounding portion of the outer pin.

Whilst it is possible for the tumbler pin passageways, and the associated tumbler pins, to have any of a wide variety of cross-sections, it is preferred that they are of circular cross-section. Similarly it is preferred that the driver pin passageways, and the associated driver pins are of circular cross-section. The cylinder assembly may further include a key inserted in the keyway.

The key preferably comprises a bow and a blade, the blade including a plurality of notched regions along its top, each engaging a respective tumbler pin, wherein one of the notched regions is provided at the base of the notch with an upwardly projecting portion engaging the inner pin of the telescopic tumbler pin assembly.

The key preferably has a single blade extending from the bow of the key. The blade preferably has relatively narrow edges along its top and bottom and relatively broad sides .

Providing an upwardly projecting portion on the key within a notched region of the key represents a special feature of the key that renders the key of an exceptional design that is necessary to operate the cylinder assembly of ^■ the first aspect of the invention. That enables security to be increased. At the same time, it is a simple matter for the key also to be able to be used in a conventional tumbler pin cylinder lock that is without any telescopic pin assemblies. Thus the key may be "backwards compatible" . Where reference is made to the "top" or the "top edge" of the blade of the key, it will be understood 'that this is the part of the key that engages the tumbler pins and that in most conventional locks is located at the top of the key when the key is correctly inserted into a conventionally installed lock. Of course, it is within the scope of the invention for the lock to be installed in a different orientation so that the "top" or the "top edge" of the key blade is then located elsewhere, for example along the bottom of the blade.

The notched regions of the key are conventionally provided at equispaced intervals along the blade of the key and that is the preferred arrangement in the present invention, but is not essential: for example the spacing of adjacent driver and tumbler pin passageways may vary along the length of the cylinder assembly and it would then be preferred that the spacing of the notched regions similarly varied.

The upwardly projecting portion is preferably generally in the shape of a dome and more preferably of approximately frusto-conical shape. It is within the scope of the invention in a broad aspect for the upwardly projecting portion to be of constant cross-section in the direction across the blade of the key; that has the advantage that it can be formed by a simple milling procedure at the same time and with the same simple machine as is used to form the notched regions both in the key for use in the invention and in a conventional key for a pin tumbler cylinder assembly. We have found, however, that it is preferable for the upwardly projecting portion to be of varying cross-section across the blade of the key. That is the case for example when the upwardly projecting portion is generally dome shaped. Such an arrangement has the apparent disadvantage that the required shape of projection cannot be formed by the same simple machine as is used to form the notched regions, but a special machine is required. For example, a dome of circular cross-section may be formed by a milling tool that rotates about the axis of the dome and that is moved down onto the top of the blade in a direction perpendicular to the blade. A further disadvantage of such a formation might be seen as the requirement for key-cutters to have machinery capable of forming the upwardly projecting portions in the keys when converting a key blank into a key; it is possible, however, for a manufacturer to form the, say, one or two upwardly projecting portions in notches in each key blank and supply the key blanks in that form with the rest of the blade free of notches. Of course that leads to there being a variety of different key blanks, with each form of key blank being able to be cut subsequently in a conventional way by a key-cutter to produce the final keys with a full set of notched regions (typically 6) of the required depths. Thus, it is preferred that a majority of the notched regions are not provided with a projecting portion suitable for engaging a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin.

The blade of the key is preferably formed with a constant cross-sectional shape defining longitudinal ribs and/or grooves along the blade. Such shapes of key are well known per se. The cross-sectional shape is preferably formed by the manufacturer and is preferably present in a key blank for the key.

As explained above, it is within the scope of the first aspect of the invention to provide a further telescopic pin assembly in which the inner pin of the further assembly is biased away from the keyway. In such a case, it is preferred that at least one of the notched regions of the key is provided at the base of the notch with a recessed portion suitable for engagement by a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin in which the inner pin is slidably mounted. In the case just described, it is preferred that walls defining the recessed portion at each of its opposite ends are inclined at an angle of more than 60 degrees to the longitudinal axis of the blade. Preferably, the walls are substantially perpendicular to the longitudinal axis of the blade. This is a special feature which is unconventional in a key for a tumbler cylinder lock where such recesses would generally have sloping edges to facilitate riding of a pin over the recessed portion of the key blade as a key is inserted. If the pin is moved into the recessed portion in the key only after the key is fully inserted, then riding of the pin over the key blade is not required and a perpendicular wall to the recessed portion becomes acceptable and has the advantage of providing a more positive engagement between the key and the cylinder.

Also as explained above, while it is within the scope of the invention in a broad aspect for the recessed portion to be of constant cross-section in the direction across the blade of the key and that has the advantage that it can be formed by a simple milling procedure at the same time and with the same simple machine as is used to form the notched regions both in the key of the invention and in a conventional key for a pin tumbler cylinder assembly, it is preferred that the recessed portion is of varying cross- section across the blade of the key. More particularly, the recessed portion may comprise a cavity, which is preferably of substantially circular cross-section, but may also be of non-circular cross-section (for example of oval or square cross-section) . Preferably the cross-section of the inner pin of the telescopic tumbler pin assembly that is able to be received in the cavity is matched to the cross-section of the cavity.

For the reasons already explained above, a majority of the notched regions are preferably not provided with a recessed portion suitable for engagement by a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin. According to a second aspect of the invention there is provided a pin tumbler cylinder assembly comprising a cylinder housing, a plug rotatably mounted in the cylinder housing, a keyway extending along the longitudinal axis of the plug and open at a front end of the plug to allow insertion of a key, a plurality of tumbler pin passageways extending inwardly from the circumference of the plug to the keyway, and a plurality of driver pin passageways extending outwardly from the interior of the cylinder housing, the tumbler pin passageways being aligned with the driver pin passageways in one rotational position of the plug, a plurality of tumbler pins slidably mounted in respective tumbler pin passageways, a plurality of driver pins slidably mounted in respective driver pin passageways and a plurality of resilient biasing .means for resiliently biasing respective driver pins inwardly, wherein the tumbler pins include a telescopic tumbler pin assembly including an outer pin and an inner pin slidably mounted in the outer pin, the outer pin being arranged to be resiliently biased inwardly by the associated driver pin and the inner pin being arranged to be biased outwardly by resilient means acting between the inner and outer pins, wherein the plug is prevented from rotating relative /to the cylinder housing by the telescopic tumbler pin assembly except when the radially inner end of the inner pin of the telescopic pin assembly projects inwardly into the keyway further by a predetermined amount than the radially inner end of the outer pin of the telescopic pin assembly.

By providing a telescopic tumbler pin assembly with an inner pin that is resiliently biased outwardly, whilst requiring the inner pin to project radially inwardly into the keyway further by a predetermined amount than the outer pin to allow the plug to rotate, a cylinder of improved security is obtained. The improved security arises from the increased difficulty of picking the lock and the special nature of the key required to operate the lock. The key is required to accommodate the inner pin when it is driven radially inwardly further than the outer pin by a predetermined amount against the resilient bias between the outer and inner pins.

The driving of the inner pin into the key can be effected by a camming action of the radially inner end of the driver pin on the radially outer end of the inner pin as the plug begins to be rotated in the cylinder housing.

The driver pin passageways and the tumbler pin passageways may conveniently extend precisely radially from the axis of rotation of the plug, but that is not essential. Where reference is made in this specification to radially inner and radially outer ends of the pins, that should be understood as indicating merely which end of a pin is being referred to, rather than that the pin necessarily extends in a precisely radial direction.

As will be understood, where reference is made to the cylinder assembly including a plurality of tumbler pins, one or more of those "pins" may be conventional single pins and one or more of those "pins" is a telescopic pin assembly. It is within the scope of the invention for only one of the tumbler pins to provide a telescopic tumbler pin assembly, but it may be preferred that the tumbler pins include a plurality of telescopic tumbler pin assemblies, each including an outer pin and an inner pin slidably mounted in the outer pin, the outer pin being arranged to be resiliently biased inwardly by the associated driver pin and the inner pin being arranged to be biased outwardly by resilient means acting between the inner and outer pins, wherein the plug is prevented from rotating relative to the cylinder housing by the telescopic tumbler pin assembly except when the radially inner end of the inner pin of the telescopic pin assembly projects inwardly into the keyway further by a predetermined amount than the radially inner end of the outer pin of the telescopic pin assembly. It is indeed possible for all the tumbler pins to be provided by telescopic tumbler pin assemblies, but generally it will be preferred that a mixture of conventional tumbler pins and telescopic tumbler pin assemblies are provided, preferably with more pins of the conventional kind.

The driver pins are preferably resiliently biased inwardly by respective compression springs disposed in the driver pin passageways outside the driver pins.

The driver pin passageways and the tumbler pin passageways are preferably disposed in a common plane. Preferably there is only one such common plane, but it is within the scope of the invention for there to be two or even three or more such planes. Where there is more than one common plane, those planes are preferably equiangularly spaced about the axis of rotation of the plug.

The resilient means acting between the inner and outer pins in the or each telescopic tumbler pin assembly preferably comprises a compression spring. It may be compressed between opposing shoulders on the exterior of the inner pin and the interior of the outer pin.

The driver pin in the driver pin passageway that is aligned with the tumbler pin passageway of the or each telescopic tumbler pin assembly is preferably recessed at its radially inner end, whereby it is able to drivingly engage the outer pin of the or each telescopic tumbler pin assembly without engaging the inner pin. The inner pin is preferably able to be accommodated in the recess when it is biased into that position by the resilient means acting between the inner and outer pins .

The recess at the radially inner end of the driver pin preferably has sloping sides. The sides may for example slope at an angle of 45 degrees or less to the axis of rotation of the plug. Preferably the sides slope at an angle of 25 to 45 degrees, and, in a particular example, at an angle of about 35 degrees to the axis of rotation of the plug. The radially outer end of the further inner pin is preferably chamfered, so it too has sloping sides. The sloping sides of the inner pin may for example slope at an angle of 45 degrees or less to the axis of rotation of the plug. Preferably the sides of the inner pin slope at an angle of 25 to 45 degrees, and, in a particular example, at an angle of about 35 degrees to the axis of rotation of the plug. Preferably the inclinations of the sloping sides of the radially inner end of the driver pin and of the radially outer end of the inner pin are the same; that facilitates the driving inwardly of the inner pin into a recess in a key as the plug begins to be rotated in the cylinder housing.

The radially inner end region, of the inner pin of the or each telescopic tumbler pin assembly is preferably of substantially constant exterior cross-section. This is a special feature which is unconventional in a tumbler cylinder lock where the radially inner end region of the pin would normally be tapered to facilitate riding of the pin over notched regions of a key blade as a key is inserted. If the inner pin is moved into the recess in the key only after the key is fully inserted, then riding of the pin over the key blade is not required and a square end to the pin becomes acceptable and has the advantage of providing a more positive engagement between the key and the cylinder. Furthermore, as described more fully below, it becomes possible to use a key with a recess for accommodating the inner pin that has sides extending substantially perpendicular to the axis of the blade of the key.

The radially inner end of the outer pin of the or each telescopic tumbler pin assembly is preferably chamfered. That facilitates the riding of the outer pin over the key blade as it is inserted into the keyway. . In the arrangement according to the second aspect of the invention described above, the inner pin of the telescopic pin assembly is biased away from the keyway. The cylinder assembly according to the second aspect of the invention may also incorporate a further telescopic pin assembly in which the inner pin of the further assembly is biased towards the keyway. More particularly, the tumbler pins may include a further telescopic tumbler pin assembly including a further outer pin and a further inner pin slidably mounted in the further outer pin, the further inner pin being arranged to be resiliently biased inwardly by the associated driver pin and the further outer pin being arranged to be biased inwardly by resilient means acting between the further inner and outer pins, wherein the plug is prevented from rotating relative to the cylinder housing by the further telescopic tumbler pin assembly except when the radially inner end of the further outer pin of the further telescopic pin assembly projects inwardly into the keyway further by a predetermined amount than the radially inner end of the further inner pin of the further telescopic pin assembly.

By providing a telescopic tumbler pin assembly with an inner pin that is resiliently biased inwardly by the driver pin, for example by contact of the radially inner end of the driver pin against the radially outer end of the inner pin, whilst requiring the outer pin to project radially inwardly into the keyway further by a predetermined amount than the inner pin to allow the plug to rotate, a cylinder of improved security is obtained. The improved security arises from the increased difficulty of picking the lock and the special nature of the key required to operate the lock. The key is required to drive the inner pin radially outwardly further than the outer pin by a predetermined amount .

It is within the scope of the invention for only one of the tumbler pins to provide a further telescopic tumbler pin assembly, but the tumbler pins may include a plurality of further telescopic tumbler pin assemblies, each including a further outer pin and a further inner pin slidably mounted in the further outer pin, the further inner pin being arranged to be resiliently biased inwardly by the associated driver pin and the further outer pin being arranged to be biased inwardly by resilient means acting between the further inner and outer pins, wherein the plug is prevented from rotating relative to the cylinder housing by the further telescopic tumbler pin assembly except when the radially inner end of the further outer pin of the further telescopic pin assembly projects inwardly into the keyway further by a predetermined amount than the radially inner end of the further inner pin of the second telescopic pin assembly.

The resilient means acting between the further inner and outer pins in the or each further telescopic tumbler pin assembly preferably comprises a compression spring. It may be compressed between opposing shoulders on the exterior of the inner pin and the interior of the outer pin .

The driver pin in the driver pin passageway that is aligned with the tumbler pin passageway of the or each telescopic tumbler pin assembly is preferably of reduced cross-section at its radially inner end, whereby it is able to .drivingly engage the further inner pin of the or each further telescopic tumbler pin assembly without engaging the further outer pin. Preferably the radially inner end of the further inner pin of the or each further telescopic tumbler pin assembly is chamfered. That facilitates the riding of the pin over the key blade as it is inserted into the keyway. Similarly the radially inner end of the further outer pin of the or each further telescopic tumbler pin assembly is preferably chamfered.

Whilst it is within the scope of the invention for the inner and outer pins not to be held together in any way, in a preferred form of telescopic tumbler pin assembly, the inner pin is restrained from separating from the outer pin.

This may be convenient at the manufacturing stage when handling the assemblies and also subsequently. For example it may be desirable to provide a locksmith with one or more telescopic pin assemblies to replace conventional pins in a pin tumbler cylinder assembly and it is then advantageous if the telescopic pin assembly can be handled as a single part. The inner pin may be a push fit in the outer pin and may also be able to be removed from the outer pin by sufficient force, rather than being permanently retained within the outer pin. The inner pin may have a waisted intermediate portion mounted in a surrounding portion of the outer pin.

Whilst it is possible for the tumbler pin passageways, and the associated tumbler pins, to have any of a wide variety of cross-sections, it is preferred that they are of circular cross-section. Similarly it is preferred that the driver pin passageways, and the associated driver pins are of circular cross-section.

The cylinder assembly may further include a key inserted in the keyway.

The key preferably comprises a bow and a blade, the blade including a plurality of notched regions along its top, each engaging a respective tumbler pin, wherein one of the notched regions is provided at the base of the notch with a recessed portion suitable for engaging the inner pin of the telescopic tumbler pin assembly. The key preferably has a single blade extending from the bow of the key. The blade preferably has relatively narrow edges along its top and bottom and relatively broad sides .

Providing a recessed portion on the key within a notched region of the key represents a special feature of the key that renders the key of an exceptional design that is necessary to operate the cylinder assembly of the second aspect of the invention. That enables security to be increased. At the same time, it is a simple matter for the key also to be able to be used in a conventional tumbler pin cylinder lock that is without any telescopic pin assemblies. Thus the key may be "backwards compatible".

Where reference is made to the "top" or the "top edge" of the blade of the key, it will be understood that- this is the part of the key that engages the tumbler pins and that in most conventional locks is located at the top of the key when the key is correctly inserted into a conventionally installed lock. Of course, it is within the scope of the invention for the lock to be installed in a different orientation so that the "top" or the "top edge" of the key blade is then located elsewhere, for example along the bottom of the blade.

The notched regions of the key are conventionally provided at equispaced intervals along the blade of the key and that is the preferred arrangement in the present invention, but is not essential: for example the spacing of adjacent driver and tumbler pin passageways may vary along the length of the cylinder assembly and it would then be preferred that the spacing of the notched regions similarly varied.

When a key is inserted into the keyway and the tumbler pin passageways and the driver pin passageways are aligned, then it is preferred that the inner pin is resiliently biased out of engagement with the recessed portion and projects at its radially outer end into the driver pin passageway of the cylinder housing. It will be appreciated that this feature of the inner pin of the telescopic tumbler pin assembly being out of contact with the key is a special feature of the invention. When the plug is rotated so that the tumbler pin passageways and the driver pin passageways are not aligned, then it is preferred that the recessed portion receives the inner pin of the telescopic tumbler pin assembly.

It is preferred that walls defining the recessed portion at each of its opposite ends are inclined at an angle of more than 60 degrees to the longitudinal axis of the blade. Preferably, the walls are substantially perpendicular to the longitudinal axis of the blade. This is a special feature which is unconventional in a key for a tumbler cylinder lock where such recesses would generally have sloping edges to facilitate riding-of a pin-over the recessed portion of the key blade as a key is inserted. If the pin is moved into the recessed portion in the key only after the key is fully inserted, then riding of the pin over the key blade is not required and a perpendicular wall to the recessed portion becomes acceptable and has the advantage of providing a more positive engagement between the key and the cylinder. It is within the scope of the second aspect of the invention in a broad aspect for the recessed portion to be of constant cross-section in the direction across the blade of the key and that has the advantage that it can be formed by a simple milling procedure at the same time and with the same simple machine as is used to form the notched regions both in the key of the invention and in a conventional key for a pin tumbler cylinder assembly. We have found, however, that it is preferable for the recessed portion to be of varying cross-section across the blade of the key. More particularly, the recessed portion may comprise a cavity, which is preferably of substantially circular cross-section, but may also be of non-circular cross- section (for example of oval or square cross-section) . Preferably the cross-section of the inner pin of the telescopic tumbler pin assembly that is able to be received in the cavity is matched to the cross-section of the cavity. Such an arrangement has the apparent disadvantage that the required shape of projection cannot be formed by the same simple machine as is used to form the notched regions, but a special machine is required. For example, a cavity of circular cross-section may be formed by a milling tool that rotates about the axis of the cavity and that is moved down onto the top of the blade in a direction perpendicular to the blade. A further disadvantage of such a formation might be seen as the requirement for key- cutters to have machinery capable of forming the recessed portions in the keys when converting a key blank into a key; it is possible, however, for a manufacturer to form the, say, one or two recessed portions in notches ^' in each key blank and supply the key blanks in that form with the rest of the blade free of notches. Of course that leads to there being a variety of different key blanks, with each ,form of key blank being able to be cut subsequently in a conventional way by a key-cutter to produce the final keys with a full set of notched regions (typically 6) of the required depths. Thus, it is preferred that a majority of the notched regions are not provided with a projecting portion suitable for engaging a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin.

The blade of the key is preferably formed with a constant cross-sectional shape defining longitudinal ribs and/or grooves along the blade. Such shapes of key are well known per se. .The cross-sectional shape is preferably formed by the manufacturer and is preferably present in a key blank for the key. As explained above, it is within the scope of the second aspect of the invention to provide a further telescopic pin assembly in which the inner pin of the further assembly is biased inwardly towards the keyway. In such a case, it is preferred that at least one of the notched regions of the key- is provided at the base of the notch with an upwardly projecting portion suitable for engaging a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin in which the inner pin is slidably mounted. ■ In the case just described, it is preferred that the upwardly projecting portion is generally in the shape of a dome and more preferably of approximately frusto-conical shape .

Also as explained above, while it is within the scope of the invention in a broad aspect for the upwardly projecting portion to be of constant cross-section in the direction across the blade of the key and that has the advantage that it can be formed by a simple milling procedure at the same time and with the same simple machine as is used to form the notched regions both in the key of the invention and in a conventional key for a pin tumbler cylinder assembly, it is preferred that the upwardly projecting portion is of varying cross-section across the blade of the key, as is the case with the dome shape referred to above.

For the reasons already explained above, a majority of the notched regions are preferably not provided with an upwardly projecting portion suitable for engagement by a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin.

In the description above reference has been made in the context of the first aspect of the invention to a key and it has already been made clear that the key is of special design.

Accordingly, in a first aspect of the invention, there is provided a key for use in an inline pin tumbler cylinder assembly comprising a bow and a single blade extending from the bow, the top edge of the blade including a plurality of notched regions, each for engaging a respective tumbler pin, wherein at least one of the notched regions is provided at the base of the notch with an upwardly projecting portion suitable for engaging a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin in which the inner pin is slidably mounted.

Providing an upwardly projecting portion on the key within a notched region of the key represents a special feature of the key that renders the key of an exceptional design suitable for use in a cylinder assembly of a kind described elsewhere in the specification. That enables security to be increased. At the same time, it is a simple matter for the key also to be able to be used in a conventional tumbler pin cylinder lock that is without any telescopic pin assemblies. Thus the key may be "backwards compatible" . Where reference is made to the "top" or the "top edge" of the blade of the key, it will be understood that this is the part of the key that engages the tumbler pins and that in most conventional locks is located at the top of the key when the key is correctly inserted into a conventionally installed lock. Of course, it is within the scope of the invention for the lock to be installed in a different orientation so that the "top" or "top edge" of the key blade is then located elsewhere, for example along the bottom of the blade.

The notched regions of the key are conventionally provided at equispaced intervals along the blade of the key and that is the preferred arrangement in the present invention, but is not essential: for example the spacing of adjacent driver and tumbler pin passageways may vary along the length of the cylinder assembly and it would then be preferred that the spacing of the notched regions similarly varied. The upwardly projecting portion is preferably generally in the shape of a dome and more preferably of approximately frusto-conical shape. It is within the scope of the invention in a broad aspect for the upwardly projecting portion to be of constant cross-section in the direction across the blade of the key; that has the advantage that it can be formed by a simple milling procedure at the same time and with the same simple machine as is used to form the notched regions both in the key of the invention and in a conventional key for a pin tumbler cylinder assembly. We have found, however, that it is preferable for the upwardly projecting portion to be of varying cross-section across the blade of the key. That is the case for example when the upwardly projecting portion is generally dome shaped. Such an arrangement has the apparent disadvantage that the required shape of projection cannot be formed by the same simple machine as is used to form the notched regions, but a special machine is required. For example, a dome of circular cross-section may be formed by a milling tool that rotates about the axis of the dome and that is moved down onto the top edge of the blade -in a direction perpendicular to the blade. A further disadvantage of such a formation might be seen as the requirement for key-cutters to have machinery capable of forming the upwardly projecting portions in the keys when converting a key blank into a key; it is possible, however, for a manufacturer to form the, say, one or two upwardly projecting portions in notches in each key blank and supply the key blanks in that form with the rest of the blade free of notches. Of course that leads to there being a variety of different key blanks, with each form of key blank being able to be cut subsequently in a conventional way by a key- cutter to produce the final keys with a full set of notched regions (typically 6) of the required depths. Thus, it is preferred that a majority of the notched regions are not provided with a projecting portion suitable for engaging a respective inner pin of a telescopic tumbler pin assembly comprising an inner pin and an outer pin.

The blade of the key is preferably formed with a constant cross-sectional shape defining longitudinal ribs and/or grooves along the blade. Such shapes of key are well known per se. The cross-sectional shape is preferably formed by the manufacturer and is preferably present in a key blank for the key.

As explained elsewhere in the specification, it is possible to provide a cylinder assembly with a further telescopic pin assembly in which an inner pin of the further assembly is biased away from the keyway. In such a case, it is preferred that at least one of the notched regions of the key is provided at the base of the notch with a recessed portion suitable for engagement by a respective inner pin of a telescopic tumbler pin assembly comprising an inner pin and an outer pin in which the inner pin is slidably mounted.

In the case just described, it is preferred that walls defining the recessed portion at each of its opposite ends are inclined at an angle of more than 60 degrees to the - longitudinal axis of the blade. Preferably, the walls are substantially perpendicular to the longitudinal axis of the blade. This is a special feature which is unconventional in a key for a tumbler cylinder lock where such recesses would generally have sloping edges to facilitate riding of a pin over the recessed portion of the key blade as a key is inserted. If the pin is moved into the recessed portion in the key only after the key is fully inserted, then riding of the pin over the key blade is not required and a perpendicular wall to the recessed portion becomes acceptable and has the advantage of providing a more positive engagement between the key and the cylinder. Also as explained above, while it is within the scope of the invention in a broad aspect for the recessed portion to be of constant cross-section in the direction across the blade of the key and that has the advantage that it can be formed by a simple milling procedure at the same time and with the same simple machine as is used to form the notched regions both in the key of the invention and in a conventional key for a pin tumbler cylinder assembly, it is preferred that the recessed portion is of varying cross- section across the blade of the key. More particularly, the recessed portion may comprise a cavity, which is preferably of substantially circular cross-section, but may also be of non-circular cross-section (for example of oval or square cross-section) . Preferably the cross-section of the inner pin of the telescopic tumbler pin assembly that is able to be received in the cavity is matched to the cross-section of the cavity.

For the reasons already explained above, a majority of the notched regions are preferably not provided with a recessed portion suitable for engagement by a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin.

The notched regions of the key are conventionally provided at equispaced intervals along the blade of the key and that is the preferred arrangement in the ^" present ^' invention, but is not essential: for example the spacing of adjacent driver and tumbler pin passageways may vary along the length of the cylinder assembly and it would then be preferred that the spacing of the notched regions similarly varied.

When a key is inserted into the keyway of a cylinder assembly specially designed to suit the key with tumbler pin passageways and driver pin passageways of the cylinder assembly aligned, then it is preferred that an inner pin of a telescopic tumbler pin is resiliently biased out of engagement with the recessed portion and projects at its radially outer end into the driver pin passageway of the cylinder housing. When the plug is rotated so that the tumbler pin passageways and the driver pin passageways are not aligned, then it is preferred that the recessed portion receives the inner pin of the telescopic tumbler pin assembly. In the description above reference has been made in the context of the key of the first aspect of the invention to a key blank of special design, which may be used to form the key according to the invention.

Accordingly, the present invention also provides a key blank suitable for forming a key for use in an inline pin tumbler cylinder assembly, the key blank comprising a bow and a single blade extending from the bow, the top edge of the blade being provided with an upwardly projecting portion suitable for engaging a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin in which the inner pin is slidably mounted.

The upwardly projecting portion is preferably generally in the shape of a dome and more preferably of approximately frusto-conical shape.

The top edge of the blade may be further provided with a recessed portion suitable for engagement by a respective inner pin of a further telescopic tumbler pin assembly comprising the inner pin and an ^" ^buter pin in which the inner pin is slidably mounted.

Walls defining the recessed portion at each of its opposite ends are preferably inclined at an angle of more than 60 degrees to the longitudinal axis of the blade and more preferably are substantially perpendicular to the longitudinal axis of the blade.

The recessed portion preferably comprises a cavity which is preferably of substantially circular cross- section, but may also be of non-circular cross-section (for example of oval or square cross-section) . Preferably the cross-section of the inner pin of the telescopic tumbler pin assembly that is able to be received in the cavity is matched to the cross-section of the cavity.

In the description above reference has been made in the context of the second aspect of the invention to a key and it has already been made clear that the key is of special design. Accordingly, in a second aspect of the invention, there is provided a key for use in an inline pin tumbler cylinder assembly comprising a bow and a single blade extending from the bow, the top edge of the blade including a plurality of notched regions each for engaging a respective tumbler pin, wherein at least one of the notched regions is provided at the base of the notch with a recessed portion suitable for engagement by a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin in which the inner pin is slidably mounted.

Providing a recessed portion on the key within a notched region of the key represents a special feature of the key that renders the key of an exceptional design suitable for use in a cylinder assembly of a kind described elsewhere in the specification. That enables security to be increased. At the same time, it is a simple matter for the key also to be able to be used in a conventional tumbler pin cylinder lock that is without any telescopic pin assemblies. Thus the key may be "backwards compatible". Where reference is made to the "top" or the "top edge" of the blade of the key, it will be understood that this is the part of the key that engages the tumbler pins and that in most conventional locks is located at the top of the key when the key is correctly inserted into a conventionally installed lock. Of course, it is within the scope of the invention for the lock- to be installed in a different orientation so that the "top" or the "top edge" of the key blade is then located elsewhere, for example along the bottom of the blade.

The notched regions of the key are conventionally provided at equispaced intervals along the blade of the key and that is the preferred arrangement in the present invention, but is not essential: for example the spacing of adjacent driver and tumbler pin passageways may vary along the length of the cylinder assembly and it would .then be preferred that the spacing of the 'notched regions similarly varied.

When a key is inserted into the keyway of a cylinder assembly specially designed to suit the key with tumbler pin passageways and driver pin passageways of the cylinder assembly aligned, then it is preferred that an inner pin of a telescopic tumbler pin is resiliently biased out of engagement with the recessed portion and projects at its radially outer end into the driver pin passageway of the cylinder housing. When the plug is rotated so that the tumbler pin passageways and the driver pin passageways are not aligned, then it is preferred that the recessed portion receives the inner pin of the telescopic tumbler pin assembly.

It is preferred that walls defining the recessed portion at each of its opposite ends are inclined at an angle of more than 60 degrees to the longitudinal axis of the blade. Preferably, the walls are substantially perpendicular to the longitudinal axis of the blade. This is a special feature which is unconventional in a key for a tumbler cylinder lock where such recesses would generally have sloping edges to facilitate riding of a pin over the recessed portion of the key blade as a key is inserted. If the pin is moved into the recessed portion in the key only after the key is fully inserted, then riding of the pin over the key blade is not required and a perpendicular wall to the recessed portion becomes acceptable and has the advantage of providing a more positive engagement between the key and the cylinder.

It is within the scope of the second aspect of the invention in a broad aspect for the recessed portion to be of constant cross-section in the direction across the blade of the key and that has the advantage that it can be formed by a simple milling procedure at the same time and with the same simple machine as is used to form the notched regions both in the key of the invention and in a conventional key for a pin tumbler cylinder assembly. We have found, however, that it is preferable for the recessed portion to be of varying cross-section across the blade of the key. More particularly, the recessed portion may comprise a cavity, which is preferably of substantially circular cross-section, but may also be of non-circular cross- section (for example of oval or square cross-section) . Preferably the cross-section of the inner pin of the telescopic tumbler pin assembly that is able to be received in the cavity is matched to the cross-section of the cavity. Such an arrangement has the apparent disadvantage that the required shape of cavity cannot be formed by the same simple machine as is used to form the notched regions, but a special machine is required. For example, a cavity of circular cross-section may be formed by a milling tool that rotates about the axis of the cavity and that is moved down onto the top of the blade in a direction perpendicular to the blade. A further disadvantage of such a formation might be seen as the requirement for key-cutters to have machinery capable of forming the recessed portions in the keys when converting a key blank into a key; it is possible, however, for a manufacturer to form the, say, one or two recessed portions in notches in each key blank and supply the key blanks in that form with the rest of the blade free of notches. Of course that leads to there being a variety of different key blanks, with each form of key blank being able to be cut subsequently in a conventional way by a key-cutter to produce the final keys with a full set of notched regions (typically 6) of the required depths. Thus, it is preferred that a majority of the notched regions are not provided with a projecting portion suitable for engaging a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin. The blade of the key is preferably formed with a constant cross-sectional shape defining longitudinal ribs and/or grooves along the blade. Such shapes of key are well known per se. The cross-sectional shape is preferably formed by the manufacturer and is preferably present in a key blank for the key.

As explained elsewhere in the specification, it is possible to provide a cylinder assembly with a further telescopic pin assembly in which an inner pin of the further assembly is biased inwardly towards the keyway. In such a case, it is preferred that at least one of the notched regions of the key is provided at the base of the notch with an upwardly projecting portion suitable for engaging a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin in which the inner pin is slidably mounted.

In the case just described, it is preferred that the upwardly projecting portion is generally in the shape of a dome and more preferably of approximately frusto-conical shape . Also as explained above, while it is within the scope of the invention in a broad aspect for the upwardly projecting portion to be of constant cross-section in the direction across the blade of the key and that has the advantage that it can be formed by a simple milling procedure at the same time and with the same simple machine as is used to form the notched regions both in the key of the invention and in a conventional key for a pin tumbler cylinder assembly, it is preferred that the upwardly projecting portion is of varying cross-section across the blade of the key.

For the reasons already explained above, a majority of the notched regions are preferably not provided with an upwardly projecting portion suitable for engagement by a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin.

In the description above reference has been made in the context of the second aspect of the invention to a key blank of special design, which may be used to form the key according to the second aspect of the invention.

Accordingly, in a second aspect the present invention also provides a key blank suitable for forming a key for use in an inline pin tumbler cylinder assembly, the key blank comprising a bow and a single blade extending from the bow, the top edge of the blade being provided with a recessed portion suitable for engagement by a respective inner pin of a telescopic tumbler pin assembly comprising the inner pin and an outer pin in which the inner pin is slidably mounted.

Walls defining the recessed portion at each of its opposite ends are preferably inclined at an angle of more than 60 degrees to the longitudinal axis of the blade and more preferably are substantially perpendicular to the longitudinal axis of the blade.

The recessed portion preferably comprises a cavity which is preferably of substantially circular cross- section, but may also be of non-circular cross-section (for example of oval or square cross-section) . Preferably the cross-section of the inner pin of the telescopic tumbler pin assembly that is able to be received in the cavity is matched to the cross-section of the cavity.

— The top- edge of the blade is preferably further provided with an upwardly projecting portion suitable for engaging a respective inner pin of a further telescopic tumbler pin assembly comprising the inner pin and an outer pin in which the inner pin is slidably mounted.

The upwardly projecting portion is preferably generally in the shape of a dome and more preferably of approximately frusto-conical shape.

As already described above, a special feature of the operation of certain cylinder assemblies according to the invention is the way in which an inner pin of a telescopic tumbler pin assembly is caused to enter into a key as the plug begins to be rotated in the cylinder. Accordingly the invention still further provides a method of operating a pin tumbler cylinder assembly, comprising the steps of inserting a key into a keyway to displace tumbler pins in the lock, including a tumbler pin comprising a telescopic tumbler pin assembly including an inner pin and an outer pin in which the inner pin is slidably mounted, one of the pins of the telescopic tumbler pin assembly extending across the split line between the cylinder housing and the plug, and subsequently turning the key in the lock to cause said one of the pins to be cammed radially inwardly into a recess in the key and move to a position where the radially outer end of said one of the pins no longer projects into the cylinder housing to obstruct rotation of the plug in the housing.

In the method described above, the pin tumbler cylinder assembly may incorporate any of the features described above. Preferably the cylinder assembly is an assembly according to the second aspect of the invention. Throughout this specification reference is made to a "cylinder housing" in which a plug is rotationably mounted.

The term "cylinder housing" is one commonly used for the component of the assembly in which the plug is rotatably mounted, but is should not be taken to imply any particular shape. Commonly the cylinder housing is of non-circular cross-section having a radially extending portion in which the driver pin passageways may be provided. Also, although the cross-sectional shape of the cylinder housing will often be approximately constant along its length, this is not a requirement of the present invention.

Whilst various aspects of the invention have been described above in the context of cylinder assemblies, keys and key blades and a method of operating a cylinder assembly, it should be understood that feature described in one context may also be provided in another context, even when that is not explicitly stated. For example, a key blank according to the invention may have any of the features described in respect of a key according to the invention where those features can be reflected in the key blank. Similarly, a key according to the invention may have any of the features described in respect of a cylinder assembly where 'those features can be reflected in the key.

By way of example certain embodiments of the invention will now be described with reference to the accompanying schematic drawings, of which:

Fig. IA is a side view of a key with driver and tumbler pins of a cylinder assembly shown, but without the plug or the cylinder housing of the cylinder assembly being shown; Fig. IB is a sectional side view from the opposite side to Fig. IA of the key, driver pins and tumbler pins shown in Fig. IA;

Fig. 1C is a sectional side view similar to Fig. IB but to a larger scale and showing only approximately the region included in Fig. IB and labelled with the letter C; Fig. 2A is an isometric view of the key shown in

Figs. IA to 1C;

Fig. 2B is a side view of the key shown in Fig. IA; Fig. 2C is a cross-sectional view through the blade of the key along the lines C-C in Fig. 2B showing the cross-sectional shape of the key to a larger scale; Fig. 3A is a side view of a key with driver and tumbler pins of a cylinder assembly shown, but without the plug or the cylinder housing of the cylinder assembly being shown; Fig. 3B is a sectional side view from the opposite side to Fig. 3A of the key, driver pins and tumbler pins shown in Fig. 3A; Fig. 3C is a sectional side view similar to Fig. 3B but to a larger scale and showing only approximately the region included in Fig. 3B and labelled with the letter C; Fig. 4A is an isometric view of the key shown in

Figs. 3A to 3C;

Fig. 4B is a side view of the key shown in Fig. 3A; Fig. 4C is a cross-sectional view through the blade of the key along the lines C-C in Fig. 4B showing the cross-sectional shape of the key to a larger scale;

Fig. 5A is a front end view of a complete cylinder assembly; and

Fig. 5B is a sectional view along the lines B-B of

Fig. 5A.

It should be understood that the cylinder assembly and key shown in Figs. 3A to 3C and 4A to 4C is not itself an embodiment of the first aspect of the invention but ^' illustrates features of a cylinder assembly and key that may be incorporated in an embodiment of the first aspect of the invention, as described with reference to Figs. 5A and 5B. Similarly, it should be understood that the cylinder assembly and key shown in Figs. IA to 1C and 2A to 2C is not itself an embodiment of the second aspect of the invention but illustrates features of a cylinder assembly and key that may be incorporated in an embodiment of the second aspect of the invention, as described with reference to Figs. 5A and 5B. Referring first to Figs. IA to 1C, there is shown a key suitable in the particular example shown, for insertion into a cylinder assembly having six sets of tumbler pins and driver pins. The key comprises a bow 1 and has a single blade 2 extending from the bow 1. Six tumbler pins 3A to 3F are shown resting on the top edge of the blade 2 of the key with respective driver pins 4A to 4F resting on top of the tumbler pins. The drawings show the position with the correct key inserted into the cylinder, with the result that the tops of the tumbler pins 3A to 3F, which are of varying lengths, all end at a common split line 5 which coincides with the interface between the plug and the cylinder housing, so that the plug is free to rotate in the cylinder housing with the key inserted. Such an arrangement, as described in general terms above will be very familiar to those skilled in the art and is the conventional arrangement for a cylinder assembly in this kind of lock, first designed by Linus Yale in the 19- ^th century. For the sake of clarity, in Figs. IA to 4C, the plug and cylinder housing of the assembly are not shown but they are of an entirely conventional design very well known to those skilled in the art. The plug is of circular cross-section having a keyway extending along its longitudinal axis and open at a front end of the plug to allow insertion of a key. The plug is rotatably mounted in a cylinder housing. A plurality of tumbler pin passageways extend radially inwardly from the exterior of the plug to the keyway and a plurality of driver pin passageways extend radially inwardly from the exterior of the top of the cylinder housing to its interior surface. When the plug is in one particular rotational position, the tumbler pin passageways are each aligned with respective driver pin- passageways. The driver pin passageways are closed off at their outer ends. A tumbler pϊrf, driver ^" pin and compression spring are provided in each aligned pair of tumbler pin and driver pin passageways with the tumbler pin at the radially innermost position and the compression spring at the radially outermost position. The compression spring resiliently biases the driver pin inwardly and the driver pin in turn resiliently biases the tumbler pin inwardly. The tumbler pin passageways and driver pin passageways are equispaced along the length of the plug and cylinder housing. The tumbler pins are of varying length. In the example shown in Figs. IA to 1C each' of the six tumbler pins is of a different length. In order for the plug to become free to rotate in the cylinder housing the tumbler pins must all be lifted to the position shown in

Figs. IA to 1C where the radially outer ends of the tumbler pins coincide with the split line 5.

The design of cylinder assembly as so far described is very well known. A special feature of the design of assembly is the construction of the tumbler pins 3A to 3F and the construction of the radially inner ends of the driver pins 4A to 4F as will now be described.

Each of the tumbler pins 3A to 3F comprises a telescopic tumbler pin assembly consisting of an inner pin 31, an outer pin 32 and a compression spring 33. The inner pin 31 is slidably mounted in the outer pin 32 and has a waisted portion 34 around which the compression spring 33 is provided. The compression spring 33 is compressed between a shoulder 35 on the inner pin and a shoulder 36 on the outer pin 32.

The outer pin 32 has a passageway 37 at its radially inner end region within which the radially inner end 39 of the inner pin 31 is slidably received and the passageway 37 is narrowed at the radially outer end of the inner end region, at the location referenced 38 in Fig. 1C. The radially inner end 39 of the inner pin 31 does not pass freely through the narrowed location 38 but can be pushed through that region when the inner pin 31 with the spring 33 placed around its waisted portion 34 is first assembled in the outer pin 32. Thereafter, unless or until a similar force is applied to the inner pin 31, the pin 31 and the spring 33 are retained slidably mounted in the outer pin 32 and can thus be handled as a single unit.

Each of the driver pins 4A to 4F is of reduced cross- section at its radially inner end, to form an end portion 41 which bears against the inner pin 31 of a respective telescopic tumbler pin assembly. Since each driver pin is resiliently biased inwardly by the compression spring provided in the driver pin passageway outside the driver pin, the inner pin 31 is in turn biased inwardly. The outer pin 32 is not directly driven by the driver pin, but is resiliently biased inwardly by the compression spring 33 acting between the inner pin 31 and ^' the outer pin 32. The spring 33 exerts a smaller force than the spring acting on the radially outer end of the driver pin.

Referring now also to Figs. 2A to 2C, the key blade 2 is in most respects the same as a conventional key. For example, as shown especially in Fig. 2C, it is of a constant cross-sectional shape defining longitudinal ribs 21 and grooves 22. Those ribs and grooves 21, 22 are shaped to correspond to the profile of the keyway in the plug, into which the key is intended to be inserted. In addition the key 2 is formed with a series of notched regions, in this particular example six notched regions 2A to 2F spaced at equal distances along the key corresponding to the spacing of the tumbler pins 3A to 3F.

The special feature of the blade 2 is the provision of a frustoconical dome 23 at the centre of each notched region. Each dome 23 is of the same size and shape having sloping sides 24, sloping at an angle of about 45 degrees to the longitudinal axis of the blade 2 and a flat top 25 parallel to the longitudinal axis of the blade.2. Figs. IB and 1C show the way in which the telescopic tumbler pin assemblies cooperate with the blade of the key. As shown, the dome 23 of each notched region is received within the outer pin 32. The inner pin 31 is therefore biased radially inwardly by the driver pin into contact with the top 25 of the dome 23 and the outer pin 32 is biased radially inwardly by the spring 33 into contact with the part of the notched region immediately surrounding the dome. Thus the radially inner end of the outer pin 32 projects inwardly further than the radially inner end of the inner pin 31. The lengths of the inner and outer pins are- chosen such that in this position, the radially outer ends of the inner and outer pins 31, 32 are coincident with the split line 5. The operation of the assembly shown in Figs. IA to 2C will now be described, starting from a position (not shown in the drawings) where a key has not yet been inserted into the assembly. At that stage, as in a conventional cylinder assembly, the inner and outer pins of each telescopic pin assembly are biased inwardly into the keyway. As the blade 2 of the key is inserted a sloping face 26, sloping at an angle of about 45 degrees to the longitudinal axis of the blade 2, at the leading end of the key comes into engagement first with the outer pin 32 of the telescopic tumbler pin assembly 3F. The radially inner end of the outer pin 32 is chamfered to provide surfaces sloping at about 45 degrees to the longitudinal axis of the keyway and as the key is inserted the outer pin 32 rides up the sloping face 26. The inner pin 31 then also comes into contact with the sloping face 26 and, similarly, rides up the sloping face 26, the radially inner end of the inner pin 31 also being chamfered (with a slight rounding) to facilitate the riding of the pin up the face 26. As will now be understood, the inner and outer pins 31, 32 of the assembly 3F continue to ride up and down over the top edge of the blade 2 as the key is inserted into the lock and the inner and outer pins 31, 32 of the assemblies 3A to 3E act in a similar way as the key is inserted.

-Once the key is fully inserted the inner and outer pins of each telescopic tumbler pin assembly are in the positions shown in Figs. IA to 1C. As can be seen, in each case the outer pin 32 of the telescopic tumbler pin assembly projects further into the keyway by a certain distance than the inner pin and that distance is the same for all the assemblies 3A to 3F. As already explained, in those positions of the inner and outer pins, the outer ends of all those pins are coincident with the split line 5 and the key can therefore be rotated, rotating the plug in the cylinder housing.

Once the key returns to its original orientation, with the key blade vertical and the notched regions on the top in this particular example, the key can be removed from the plug with the inner and outer pins 31, 32 riding over the key blade in a reverse of the sequence when the key is inserted.

Referring now to Figs. 3A to 4C, there is shown a key, tumbler pin and driver pin arrangement which is in many respects very similar to the arrangement shown in Figs. IA to 2C. For ease of understanding identical or very similar parts are referenced by the same reference numerals as shown in Figs. IA to 2C. The description below is directed mainly to those features of the arrangement shown in

Figs. 3A to 4C that differ from those shown in Figs. IA to 2C.

Firstly, it should be noted that the driver pins 4A to 4F are all provided with conical recesses 401 at their radially inner ends and therefore are biased into direct engagement with the outer pins 32 of the telescopic tumbler pin assemblies. Secondly, it should be noted that the inner pin 31 of each tumbler pin assembly is provided at its radially outer end with a conical face 301 matched to the conical recess 401. In the example shown the angle of the cone is about 120 degrees.

In the arrangement shown in Figs. 3A to 4C the outer pin 32 is biased radially inwardly by direct engagement with the driver pin and the compression spring 33 acts to - bias the inner pin 31 radially outwardly. In the drawings the inner pins 31 are shown in their radially innermost positions but in practice it will be understood that, when the tumbler pin passageways and the driver pin passageways are aligned, the inner pins 3.1 are biased outwardly from the positions shown to a position in which the conical faces 301 of the inner pins are received in the conical recesses 401 of the driver pins and the inner pins 31 therefore extend across the split line 5.

Also in the arrangement shown in Figs. 3A to 4C, the radially inner ends of the inner pins 31 are provided with straight-sided ends (without chamfers) . The key blade 2 is similarly provided with cavities 201 in the centres of the notched regions, the cavities having a circular cross- section matched to the cross-section of the inner pins 31 so as to be able to receive them as a loose fit.

Before a key is inserted, the outer pins of each telescopic tumbler pin assembly are biased radially inwardly into the keyway and the inner pins 31 are biased upwardly (radially outwardly) so that the conical faces 301 of the inner pins are received in the conical recesses 401 of the driver pins and the radially inner ends of the inner pins 31 do not therefore project radially inwardly beyond the radially inner ends of the outer pins 32. As the key is inserted, therefore it is the radially inner ends of the outer pins 32 only that engage the key- blade 2 and ride over the notched regions of the blade 2. It will be noted that the outer pins 32 of the arrangement shown in Figs. 3A to 4C are chamfered in the same way as the outer pins of the arrangement shown in Figs. IA to 2C.

When the key is fully inserted the pins adopt the positions shown in Figs. 3A.to 4C except that as explained above, the conical faces 301 of the inner pins are received in the conical recesses 401 of the driver pins and the inner pins 31 therefore extend across the split line 5. In the conventional cylinder assembly, when a pin extends across the split line 5 the plug is prevented from rotating in the cylinder housing. In the arrangement shown, however, this is not the case. As a user tries to turn the key, the inner pins 31 are driven radially inwardly against the bias of the springs 33 by a camming action between the conical faces 301 and the conical recesses 401 and the radially inner ends of the inner pins 31 are accommodated in the cavities 201 in the key. This is the position of the inner pins 31 shown in the drawings (see Fig. 3C for example) . In this position the radially outer ends of the inner and outer pins are coincident with the split line 5 and the plug is therefore free to rotate in the cylinder housing. As the key returns to its original orientation, with the key blade vertical and the notched regions on the top in this particular example, the inner pins 31 again are biased outwardly by the springs 33 into the conical recesses 401, moving the radially inner ends of the inner pins 31 out of the cavities 201 and therefore allowing the key to be removed from the keyway.

In the two arrangements described above each tumbler pin comprises a special telescopic assembly. That is convenient for the purposes of illustration and showing six different lengths of telescopic tumbler pin assembly, <but in practice it will usually be preferred to have some conventional tumbler pins and perhaps one, two or three telescopic tumbler pin assemblies. If desired a cylinder assembly may include one telescopic tumbler pin assembly of the kind shown in Figs. IA to 1C and one telescopic tumbler pin assembly of the kind shown in Figs. 3A to 3C, together with other conventional tumbler pins and/or other telescopic tumbler pin assemblies of either kind. For convenience the exterior diameter of a telescopic tumbler pin assembly (the exterior diameter of the outer pin 32) is the same as the exterior diameter of a conventional tumbler pin on an existing cylinder assembly. It is thus possible to incorporate the telescopic tumbler pin assembly into an existing cylinder assembly, together ^" with the appropriate driver pin.

Of course, the key required will depend upon what combination of conventional tumbler pins, telescopic tumbler pins as shown in Figs. IA to 1C, and telescopic tumbler pins as shown in Figs. 3A to 3C are employed. Thus one key may have both one or more domes 23 and one or more cavities 201. Whilst the key is specially designed to operate with the special telescopic tumbler pin assemblies, the same key can be used to operate a cylinder assembly having only conventional tumbler pins, in this case any cavities 201 on the key simply have no effect on the function of the key and the domes 23 define the innermost positions of the radially inner ends of the conventional tumbler pins.

Figs . ^λ 5A and 5B show a cylinder assembly with both a cylinder housing 501 and a plug 502 shown. The drawings also show a key .having a bow 1 and a blade 2 inserted into the assembly but not yet turned to rotate the plug. In the particular example of Figs. 5A and 5B, the cylinder assembly has six sets of tumbler pins and driver pins. Four of the sets comprise tumbler pins 503 and driver pins 504 of conventional design, but the assembly also includes a tumbler pin 3D and driver pin 4D of the kind shown in Figs. IA to 1C and a tumbler pin 3B and driver pin 4B of the kind shown in Figs. 3A to 3C, those tumbler pins and driver pins and associated parts being referenced by the same reference numerals as are used in Figs. IA to 1C and 3A to 3C respectively, as are other parts that are shown in Figs. 5A and 5B and correspond to parts shown in other drawings. Compression springs that bias all of the driver pins inwardly are referenced by numerals 505A to 505F. The key includes ribs 21 and grooves 22 and notches of a conventional kind but, at the location of the tumbler pin of the kind shown in Figs. IA to 1C the key includes a dome 23 and at the location of the tumbler pin of the kind ^■ shown in Figs. 3A to 3C, the key -includes a cavity 201 of circular cross-section. The dome 23 and the cavity 201 are formed in the key by a milling operation carried out in a direction perpendicular to the axis of the blade (a vertically upwards direction as seen in Fig. 5B), but the notches may not be formed at this stage if the key is provided as a blank to a key cutter.

The keys shown in the drawings can be cut fully at a factory but they may also be supplied only partly cut as key blanks. For example the key shown in Figs. 5A and 5B may be supplied as a key blank in which the ribs 21 and the grooves 22 are already present and, in addition, the dome 23 and the cavity 201 are formed. The key cutter then cuts the notches in the key blank in the same way as for a conventional key using the same equipment. Since the dome and the cavity may each be provided, in the example shown, at any of six different locations, and the height of the dome or the bottom of the cavity may be any of six chosen heights, very many different key blanks are available.

Also shown in Figs. 5A and 5B is a cam actuator 506 which is rotatably coupled to the plug 502 so as to rotate with the plug, as is conventional. The cam actuator will typically drive a locking bolt between an extended, locking position and a retracted, released position.

It should be understood that Figs. 5A and 5B are provided simply to show by way of example one complete assembly, but it is within the scope of the invention for a wide variety of other assemblies to be employed and of course it is not necessary for both pins of the kind exemplified by Figs. IA to 1C and pins of the kind exemplified by Figs. 3A to 3C to be present. Also there may be a smaller proportion of conventional pins (including none at all) or indeed all the pins except one may be conventional or of some other special design.

It will also be noted that in Figs. 5A and 5B, the cylinder assembly is the opposite way up to the assemblies shown in the previous drawings, with the result that the "top edge" ^{" "} of the bl'ade of the key is at the bottom.