Insurance companies require doors and windows to be securely locked to prevent unauthorised access. Final exit doors are typically locked/unlocked from both sides with the same key and there is a risk when the door is locked from the inside that the key may not be available to unlock the door in an emergency, for example to allow escape in a fire.

This is a particular problem in situations where the final exit door provides the only means of escape, for example in the case of multi- storey flats.

Accordingly, there is a need for a lock capable of providing security on both sides of a closure and of providing safety such that the closure can always be opened from the inside in an emergency such as a fire.

It is an object of the present invention to provide a lock and a locking system that combines security and safety in a simple, reliable manner.

According to a first aspect of the present invention there is provided apparatus for locking a closure, the apparatus being operable from one side of the closure by a first key to lock and unlock the closure, and from the other side of the closure by a second key to lock and unlock the closure, the second key being movable between first and second positions wherein, in the first position, the second key can be inserted in and withdrawn from the apparatus and, in the second position, the second key is held captive in the apparatus.

Preferably, the second key is movable from the first position to the second position to lock the closure and from the second position to the first position to unlock the closure. In this way, when the closure is locked with the second key, the second key is held captive until the closure is unlocked. As a result, after locking the closure with the second key, the second key is available to unlock the closure in an emergency.

Advantageously, the apparatus is arranged so that the closure is locked/unlocked from the outside by the first key and is locked/unlocked from the inside by the second key. In this way, when the closure is locked from the inside, the second key is retained in place so that the closure can be unlocked in an emergency, for example to allow the occupant (s) to escape a fire.

Preferably, the apparatus comprises a first cylinder operable by the first key and a second cylinder operable by the second cylinder wherein operation of either cylinder to lock the closure actuates a locking mechanism to fasten the closure in a closed position.

In one embodiment, the apparatus is arranged so that the first cylinder is operable to lock and unlock the closure if the second key is present in the second cylinder. In this way, the closure can be locked and unlocked from the outside by the first key if the second key is in place on the inside.

Preferably, the cylinders are linked so that, if the closure is locked from the outside with the second key in place on the inside, the second key is moved to the retained position. In this way, the second key cannot be removed from the inside without unlocking the closure.

In this way, the apparatus may be employed on a final exit door where the door can be locked/unlocked by the first key from the outside and by the

second key from the inside. As a result, the apparatus combines security on both sides with safety by ensuring the door can be opened from the inside in an emergency.

Advantageously, the cylinders are linked via a floating cam. For example, an inner end of a rotatable plug of each cylinder may be coupled to the cam for transmitting rotation of the plug to the cam when the associated key is inserted and uncoupled from the cam when the key is removed.

Preferably, the cam is arranged to permit rotation of the plug of the first cylinder to remove the first key when the closure has been locked from the outside without unlocking the closure and the cam is held in place on removal of the first key by a retainer. As a result, if the second key was present in the second cylinder, the second key cannot be removed until the closure is unlocked either from the inside or from the outside.

Advantageously, the cam is rotatable in response to rotation of the cylinder plugs to operate a locking mechanism for securing the closure in a closed position. For example, the locking mechanism may include a bolt movable between locked and unlocked positions by rotation of the cam in opposite directions. A plurality of bolts may be provided for operation simultaneously, for example the locking mechanism may comprise an espagnolette.

According to a second aspect of the invention there is provided a method of locking and unlocking a closure comprising providing a locking mechanism operable by a first key on one side of the closure and by a second key on the other side of the closure, and arranging the second key to be held captive when the closure is locked from the other side with the second key.

In this way, when the closure is locked with the second key, the second key cannot be removed without unlocking the closure thereby ensuring the second key is available to unlock the closure in an emergency. This is especially beneficial where the closure is a final exit door and the second key is arranged to lock/unlock the closure from the inside.

According to a third aspect of the invention there is provided a locking system for locking and unlocking a plurality of closures, the locking system comprising apparatus for locking and unlocking each closure, wherein each apparatus includes a key that is held captive when the closure is locked and is released when the closure is unlocked, the arrangement being such that the closures can be unlocked in sequence by using the key that is released when unlocking each closure to unlock the next closure in the sequence.

In this way, the final closure in the sequence cannot be unlocked until all the preceding closures have been unlocked and the closures are locked by reversing the sequence of key transfer between the closures. In this way, the last closure in the sequence is the first closure to be unlocked and this cannot be locked until all the preceding closures have been locked. As a result, the user can be sure that all of the closures have been unlocked or locked when operating the final closure.

According to a fourth aspect of the invention there is provided a method of locking/unlocking a plurality of closures in a predetermined sequence comprising the steps of locking/unlocking at least one closure in the sequence by a key released from a preceding closure in the sequence.

In this way, the closures can be locked/unlocked in sequence by key transfer between successive closures that ensures all the closures in the

sequence have been locked/unlocked on reaching the final closure in the sequence. As a result, the final closure in the sequence cannot be unlocked with any of the preceding closures locked and vice versa.

This is of particular benefit where some of the closures in the sequence are emergency exit doors. Thus, sequential locking/unlocking ensures the emergency exits are locked for security when leaving the building through the last door in the sequence and are unlocked for safety when the last door in the sequence is a main or public entrance to the building.

These and other features, benefits and advantages of the invention in each of its aspects will be apparent from the following description of exemplary embodiments of the invention with reference to the following drawings wherein:- Figure 1 is a diagrammatic view of a lock according to a first embodiment of the invention; Figure 2 shows a right hand cam of the lock shown in Figure 1 as viewed in the direction of arrow A in Figure 1; Figure 3 shows a cam stump of the lock shown in Figure 1; Figure 4 shows a left hand cam of the lock shown in Figure 1 as viewed in the direction of arrow A in Figure 1; Figure 5 shows a sectional view of a lock according to a second embodiment of the invention; Figure 6 shows a view of the lock shown in Figure 5 from the inside of a building;

Figure 7 shows a view of the lock shown in Figure 5 from the outside of a building; Figure 8 shows a side view of a thumb turn key of the invention for operating the lock from inside the building; Figure 9 shows an end view of the thumb turn key; Figure 10 shows a schematic of a building comprising a locking system according to the invention; Figure 11 shows a perspective view of a section of an entrance and exit door of the locking system shown in Figure 10; Figure 12 shows a sectional view of the entrance and exit door; Figure 13 shows a view from the inside of the building of the lock on an externally lockable door of the locking system of the invention, in a locked condition; Figure 14 shows the lock of Figure 13 in an unlocked condition; Figure 15 shows a view from the inside of the building of the lock on internally lockable door of the locking system of the invention, in a locked condition; and Figure 16 shows the lock of Figure 13 in an unlocked condition.

Referring first to Figures 1 to 4 of the accompanying drawings, there is shown in Figure 1 a lock 1 for a final exit door (not shown) comprising a

lock cylinder 2 operable by a key 4 on the inside of the door and a lock cylinder 3 operable by a key 5 on the outside of the door.

In this embodiment, the first and second locking cylinders 2 and 3 comprise respective cylinders of a double cylinder lock. The cylinders 2 and 3 can be of any type, including pin tumblers and wafer tumblers.

The door can be locked and unlocked from the outside by the key 5 and from the inside by the key 4. The keys 4 and 5 are different such that key 4 cannot operate locking cylinder 3 and key 5 cannot operate locking cylinder 2.

The key 5 can be removed from the cylinder 3 in both conditions. The key 4 can be removed from the cylinder 2 in the unlocked condition and is held captive in the locked condition.

The key 4 may comprise a thumb turn of the type described in more detail later with reference to the second embodiment of the invention. It will be understood, however, that other arrangements that allow the key 4 to be removed in the unlocked condition and retained in the locked condition may be employed in this invention. The key 5 may be of conventional type for use with cylinder locks.

In this way, when the door is locked on the inside, the key 4 is held in place and is available to unlock the door in an emergency to allow the occupants to escape, for example in a fire.

In one arrangement, the key 4 is arranged to prevent operation of the lock from the outside by the key 5 when the door is locked from the inside and the key 4 is retained in position.

In this way, the key 4 has to be removed to allow the door to be locked from the outside when leaving the building and a master key is provided to allow the door to be unlocked from the outside if the door has been locked from the inside.

More preferably, however, the door can be locked and unlocked from the outside by the key 5 if the key 4 is present in the lock. In this way, if the door is locked from the inside so the key 4 is held captive in the lock, the door can be unlocked with key 5 from the outside.

As a result, a key holder can gain access to the building if the door has been locked from the inside. Similarly, if the door is locked from the outside without removing key 4 on the inside, the key 4 is rotated to the position in which it is held captive in the lock and cannot be removed with the door in the locked condition.

To achieve the above operation, a floating cam 6 (Figure 2) is provided between the cylinders 2,3. Each cylinder 2,3 has a rotatable plug (not shown) with a keyway to receive the associated key 4,5.

The cam 6 has a through hole 7 in which the inner ends of the cylinder plugs are received. Each plug is coupled to the cam 6 for transmitting rotation of the plug to the cam 6 when the associated key 4,5 is inserted and is uncoupled from the cam 6 when the key 4,5 is removed.

The cam 6 has a radial follower 8 co-operable with a bolt carrier (not shown) in response to rotation of the cam 6 to move a bolt (not shown) of the lock 1 between the locked and unlocked conditions.

In the locked position, the bolt projects from the door to enter a keeper on the frame to prevent opening of the door. In the unlocked position, the bolt is withdrawn from the keeper to allow the door to be opened.

The cam 6 has a slot 9 that permits rotation of the plug of cylinder 3 to remove the key 5 when the door has been locked from the outside without unlocking the door.

The cam 6 is held in place on removal of the key 5 by a cam stump 10 (Figure 3) mounted in the lock case. The cam 6 is handed by virtue of the slot 9. Figure 2 shows a right hand cam and Figure 4 shows a left hand cam.

In use, when the door is unlocked, the keys 4 and 5 can be freely inserted in and removed from the plug of the associated cylinder 2,3. The door can be locked from either side by inserting and turning the appropriate key 4,5 to rotate the cam 6 and throw the bolt to the locked condition.

If the door is locked from the inside, the key 4 is held captive in the lock and can only be removed by turning the key 4 to rotate the cam 6 in the reverse direction and withdraw the bolt to unlock the door. In this way, the key 4 cannot be removed with the bolt in the locked condition when the door is locked from the inside.

If the door is locked from the outside, the key 5 can be removed with the bolt in the locked condition by rotating the key 5 to a release position without unlocking the door as permitted by the slot 9 in the cam 6.

If the door was locked from the outside with the key 4 in the plug of the cylinder 2 on the inside of the door, turning the key 5 to lock the door is transmitted via the cam 6 to the plug of the cylinder 2 which is rotated to

the position in which the key 4 is held captive in the lock and cannot be removed.

If the key 5 is then turned to allow the key 5 to be removed, the position of the cam 6 does not change and the key 4 remains in the captive position. As a result, the key 4 cannot be removed until the door is unlocked either by turning the key 4 from the inside or by inserting and turning the key 5 from the outside to rotate the cam 6 to withdraw the bolt.

In this way, the cam 6 links operation of the cylinders 2,3 to ensure the key 4 is held captive in the locked condition and released in the unlocked condition whether the door is locked/unlocked from the inside or the outside with the key 4 in place.

If the door was locked from the outside with the key 4 removed from the plug of the cylinder 2 on the inside of the door, the plug is uncoupled from the cam 6 and remains in the unlocked position when the cam 6 is rotated by rotation of the plug of the cylinder 3 when locking the door with the key 5 on the outside of the door.

As a result, the key 4 can be inserted in the plug of the cylinder 2 on the inside of the door if it desired to unlock the door from the inside after it has been locked from the outside.

As will be appreciated from the foregoing description, the lock 1 includes first and second lock cylinders 2,3 operable from opposite sides of the closure by first and second keys 4,5 respectively wherein the key 4 for operating the lock 1 on the inside of the closure is retained in the associated cylinder 2 in a locked condition of the lock 1.

As a result, the key 4 is present to allow the closure to be unlocked from the inside to allow the occupant (s) to open the closure in an emergency, for example to escape a fire. The presence of the key 4 does not interfere with the operation of the lock 1 from the outside thereby combining safety and security.

With reference now to Figures 5 to 9 of the accompanying drawings, a lock for a closure according to a second embodiment of the invention is shown in which like reference numerals are used to indicate corresponding parts.

As shown in Figures 6 and 7, a security escutcheon cover 11 and a sub- escutcheon cover 12 encase the cylinders 2 and 3 to provide protection for the lock against forced entry. In this embodiment, the escutcheon covers 11 and 12 are separate. However, it will be understood that the escutcheon covers 11 and 12 can be a one-piece integral cover.

The escutcheon cover 11 surrounding cylinder 2 has a circular opening 13 to allow access to a keyhole 14 of the locking cylinder 2 and a U-shaped recess 16.

As best shown in Figures 8 and 9, the key 4 has a thumb turn 4a provided with a projection 4b extending radially from the centre of the thumb turn 4a. In use, the key 4 is inserted into keyhole 14 such that the projection 4b is within the recess 16.

The cover 11 provides abutments 17a, 17b for the projection 4b such that rotational movement of the key 4 in the cylinder 2 is restricted to less than 360° in either direction from a central position.

In this embodiment, the key 4 is rotatable through 135° in both the clockwise and anti-clockwise directions from the central position shown in Figure 6 to either one of two end positions. The symmetry of the escutcheon cover 11 ensures the lock 1 is non-handed.

In use, rotation of the key 4 from the central position to either one of the end positions throws the bolt to the locked position and rotation of the key back to the central position withdraws the bolt to the unlocked position. The key 4 can be inserted and removed from the cylinder 2 in the central position and is retained in place in each of the end positions.

In this way, when the door is locked from the inside using key 4, the key 4 cannot be removed. As a result, in an emergency, for example in a fire, the key 4 will be in the lock 1 if the door has been locked from the inside enabling the door to be unlocked and opened.

In this embodiment, when key 4 is in place in the cylinder 2, the lock 1 cannot be operated from the outside by inserting key 5 into cylinder 3.

As a result, when leaving the building, key 4 is removed to allow the door to be locked from the outside by key 5.

In this way, key 4 cannot be left in place in the cylinder 2 when locking the door from the outside and the door cannot be opened from the inside without key 4.

In a modification (not shown), locking cylinder 3 may be operable by a master key from the outside to unlock the lock 1 in an emergency even when the key 4 is held captive within locking cylinder 2.

In this way, the door can be opened from the outside in an emergency after locking from the inside. For example, the master key could be in

the possession of a responsible neighbour, landlord or security guard for the building.

As will now be appreciated from the foregoing description of two embodiments, the lock 1 provides both safety and security for the user.

The lock 1 is suitable for use in a final exit door and has particular application in situations where the final exit door is the only means of escape in an emergency, for example in blocks of flats over 4.5 metres high (two storeys high) Referring now to Figures 10 to 16 of the accompanying drawings, there is shown in Figure 6 a building provided with a locking system according to the invention.

A door 105 provides the main entrance/exit to the building. The door 105 opens to a corridor 104 leading to separate rooms 102. Each room 102 has an emergency exit door 106-110 that provides an alternative exit route from the room 102 in an emergency such as a fire.

As described in more detail later herein, door 110 is the only door that can be unlocked and locked from outside the building. The first person to enter the building, unlocks door 110 and enters the building through this door.

On unlocking door 110, a key is released from the lock on the inside of door 110. The key that is released is then used to unlock the next door in the sequence, door 109 from the inside.

On unlocking door 109, another key is released that can be used to unlock door 108 and so on until the last door has been unlocked. The main entrance door 105 is the last door to be unlocked in the sequence.

In this way, the doors 105-109 are unlocked in sequence by a key released from unlocking the previous door in the sequence. The doors 105-110 are locked in the reverse sequence with door 110 being the last door to be locked from outside on leaving the building.

Apparatus for locking and unlocking emergency exit door 110 is shown in Figures 11 to 16 and includes a key operated lock 112 and a panic lock 111.

The panic lock 111 comprises a touch bar 114 operable from within the building and a spring loaded latch 115. The latch 115 extends from the door 110 into a keeper in the frame to hold the door 110 closed. When the door 110 is unlocked, it is held closed by the panic lock 111 and can be opened from the inside in an emergency, for example in a fire, by pushing the touch bar 114 to withdraw the latch 115 from the keeper.

The lock 112 comprises a locking mechanism 116 on the outside of the door 110 and control means 113 on the inside. The locking mechanism 116 is operable by a key (not shown) from outside the building and the control means 113 is operable by keys 119 and 120 from inside the building.

The locking mechanism 116 comprises a locking cylinder mechanically connected to a dead bolt 121. Rotation of the locking cylinder 116 throws the dead bolt 121 from a locked position to an unlocked position or vice-versa.

In the locked position the dead bolt 121 extends from the door 110 into a keeper (not shown) in the frame of the door 110 to prevent opening of the door 110 by actuation of the panic lock 111. In the unlocked position,

the dead bolt 121 is withdrawn from the keeper to allow the door 110 to be opened with the panic lock 111.

The control means 113 comprises a pair of dummy cylinders 117 and 118 operated by keys 119 and 120 from inside the building. Insertion of key 119 into dummy cylinder 117 prevents the locking mechanism 116 being used to lock the door 110 from the outside.

The dummy cylinders 117,118 are provided with cam plates 117a, 118a that rotate with the cylinders 117, 118 and are provided with cut-outs 117b, 118b co-operable with the cam plate 117a, 118a of the adjacent cylinder 117,118 to allow or prevent rotation of the cylinders 117,118.

Two conditions of the dummy cylinders 117 and 118 are shown in Figures 13 and 14. In the condition shown in Figure 13, the locking mechanism 116 can be operated to lock or unlock the door 110 from the outside and dummy cylinder 118 is prevented from being rotated by location of cam plate 117a in cut-out 118b. In this position of the dummy cylinder 118, key 120 is held captive within the dummy cylinder 118.

When door 110 is unlocked and key 119 inserted into dummy cylinder 117, the cylinder can be rotated through 180° to the position shown in Figure 14. The dummy cylinder 118 is then freed for rotation through 180° to the position shown in Figure 14. In this position, key 119 is held captive in dummy cylinder 117 and prevents the door 110 being locked from the outside.

Rotation of the dummy cylinder 118 to the position shown in Figure 14 allows the key 120 to be removed from the dummy cylinder 118 and prevents rotation of dummy cylinder 117 by location of cam plate 118b in cut-out 117a. Key 120 is used to lock/unlock door 109 as described later.

Accordingly, in the condition shown in Figure 13, the door 110 can be unlocked from the outside using the locking mechanism 116. In the condition shown in Figure 14, the door 110 cannot be locked using the locking mechanism 116 due to the presence of key 119 in dummy cylinder 117.

Key 119 cannot be removed from dummy cylinder 117 until key 120 is inserted back into dummy cylinder 118 and the control means 113 changed back to the condition shown in Figure 13. The door 110 can then be locked from the outside.

Emergency exit doors 106-109 are locked/unlocked from the inside of the building by a modified form of the above-described apparatus in which locking cylinder 116 is omitted and dummy cylinder 117 replaced by a key operated locking cylinder to move the deadbolt 121 between locked and unlocked positions.

The doors 106-109 are unlocked in sequence starting with door 109 that is unlocked by key 120 released when door 110 is unlocked and ending with door 106 that releases a key (not shown) to unlock the main entrance door 105. Each door 106-109 is held closed in the unlocked condition by a panic lock as described above that allows the door to be opened in an emergency by actuating the touch bar 114 to withdraw the latch 115.

Two conditions of the locking cylinder 117'and dummy cylinder 118'of door 109 are shown in Figures 15 and 16. In the condition shown in Figure 15, the door 109 is locked and dummy cylinder 118'is prevented from rotating by location of cam plate 117a'in cut-out 118b'.

Key 121 for locking/unlocking the next door in the sequence, door 108, is held captive in the dummy cylinder 118'. Door 109 is unlocked by inserting key 120 released from door 110 into locking cylinder 117'and rotating the cylinder 117'through 180° to the position shown in Figure 16.

Dummy cylinder 118'can now be rotated through 180° by the key 121 to the position shown in Figure 16 in which the key 121 can be removed from the dummy cylinder 118'. The key 120 is held captive in the locking cylinder 117'which is prevented from rotating by location of the cam plate 118a'in cut out 117b'.

The key 121 released when door 109 is unlocked is then used to unlock the next door, door 108, in the sequence. This releases another key (not shown) to unlock the next door, door 107, in the sequence, which in turn releases another key (not shown) to unlock the next door, door 106 in the sequence.

The arrangement of the locking cylinder 117'and dummy cylinder 118' on door 109 is repeated for each of doors 108,107, 106 and will be understood from the description of door 109. The key released when door 106 is unlocked is used to unlock the main entrance door 105.

Door 105 has a lock (not shown) operable by the key released from door 106 that is held captive in the lock when the door 105 is unlocked. In this way, the key cannot be returned to lock door 106 until door 105 is locked.

As will now be understood from the above description, the main entrance door 105 cannot be unlocked until all of the emergency exit doors 106- 110 have been unlocked.

In this way, the locking system 100 ensures that all the emergency exit doors 106-110 can be opened by the panic locks before the main entrance door 105 is opened. In this way, the fire safety requirements for the building are met.

To lock the doors 105-110, the above-described unlocking sequence is reversed in a locking sequence beginning with locking of door 105 and ending with locking of the final exit door 110.

As a result, on exiting the building and locking door 110 from the outside the building, all the other doors 105-109 have to be locked first. In this way, the building is properly secured when the last person leaves and locks the building.

Furthermore, none of the doors 105-110 can be unlocked from inside the building as the keys for operating each of the locking mechanisms 117 is held captive in a control means 113 of a lock of one of the other doors 106-110. In this way, improved security is provided.

All the locks 111 described comprise protective escutcheon covers as described with reference to the second embodiment of the invention. The locking cylinders 116,117'and dummy cylinders 117,118, 118'may be of wafer tumbler or pin tumbler type.

In an alternative embodiment, the control means does not comprise dummy cylinders 117,118, 118'but just comprises key holes. Insertion and removal of the keys into/from the holes blocks/allows operation of the locking mechanisms 116,117'as described above such that the doors 105-110 have to be locked/unlocked in a predetermined sequence.

In another modification, cylinder 118 of doors 106-109 is the locking mechanism and cylinder 117 the dummy cylinder of the control means.

The keys for operating the locking mechanism are held captive in the locking mechanism of the door 106-109 when the door 106-109 is locked.

The locking mechanism is blocked from operating in the locked condition of the door 106-109 by the position of dummy cylinder 117.

The sequential locking system may be provided on all the doors of a building or alternatively, provided only on doors of a particular enclosed area of a building, for example just one floor.

The invention includes modifications and alterations that would be envisaged by a person skilled in the art and are within the scope of the invention described herein. For example, the escutcheon cover may be omitted.

The locks may provide single point locking or be adapted to provide multi-point locking by operating a plurality of bolts simultaneously, for example an espagnolette.

The cam plates with cut-outs for selectively allowing/preventing rotation of the cylinders may be replaced by any other suitable means for controlling operation of the lock to release/retain a key in place, for example a gear mechanism.