GB2586317A - Door lock - Google Patents

Abstract

A door lock comprising a lock unit 12, first and second handles (20, 22, fig 4) rotatably fast with first and second spindles (24, fig 6) respectively, a biased latch bolt 16, and a single rotatable latch cam 48 connected to the latch bolt so as to retract the latch bolt when rotated in a latch release direction. The latch cam is operatively connected with the first spindle such that movement of the first handle in an opening direction causes the latch cam to rotate and retract the latch bolt. Further provided is a cylinder lock 28 with cylinder cam 30 connectable with the latch cam and operative to rotate the latch cam in a latch release direction when the cylinder lock is actuated. Preferably the latch cam is directly driven by the first spindle and not operatively connected to the second spindle so that the latch is only operated by the first handle. There may be a deadbolt 18 connected to a rotatable follower cam 46. The latch cam may incorporate lost motion when rotated in a locking direction by providing abutments 69.

Description

Door Lock

Technical Field of the Invention

The present invention relates to locks for doors and other similar wings. The invention relates in particular to door locks having a sprung latch bolt which can be retracted using a handle on one side but which can only be retracted from the other side using a key.

Background to the Invention

It is known to provide a door lock having a sprung latch bolt which can be retracted to open the door using a handle on one side but which can only be retracted from the other side using a key. A door lock of this type will be referred to herein as a "door lock of the type defined".

Door locks of the type defined often have a deadbolt in addition to the latch bolt and are configured so that both the latch bolt and the deadbolt can be retracted using a handle on one side of the lock, whilst only the deadbolt can be retracted using a handle on the other side. Such door locks are typically fitted to an exterior door of a property so that the latch bolt can be retracted using a handle on the interior side to exit the property but only retracted from the exterior of the property using a key. This provides additional security as entry to the property can only be gained through the closed door using the key, even if the door is held on the latch bolt without the deadbolt engaged.

Whilst the known door locks of the type defined work well, the mechanisms they employ tend to be rather complex.

There is a need then for a door lock of the type defined which overcomes, or at least mitigates, some or all of the disadvantages of known door locks of the type defined There is also a need for a door lock of the type defined having an alternative latch mechanism which has fewer components than those in known door locks of the type defined.

There is a further need for a door lock of the type defined having an alternative latch mechanism than those in known door locks of the type defined.

Summary of the Invention

According to a first aspect of the invention there is provided a lock comprising a lock unit mountable in a recess in a door or other wing and first and second handles, a first spindle rotatably fast with the first handle and operably engageable with the lock unit, a second spindle rotatably fast with the second handle and operably engageable with the lock unit; the lock unit having a casing, a latch bolt movable between a retracted position and an extended position and which is resiliently biased to the extended position, and a single, rotatable latch cam operatively connected with the latch bolt so as to retract the latch bolt when rotated in a latch release direction, the latch cam being operatively connected with the first spindle when the first spindle is engaged with the lock unit such that, in use, movement of the first handle from a rest position in an opening direction causes the latch cam to be rotated in the latch release direction to retract the latch bolt, the lock including a cylinder lock operably engageable in the lock unit, the cylinder lock having a cylinder cam operably connectable with said latch cam when the cylinder lock is engaged in the lock unit, the cylinder cam being operative to rotate said latch cam in said latch release direction to retract the latch bolt when the cylinder lock is actuated to move the cylinder cam in an opening direction.

In a door lock according to the invention, a single latch lever is used to enable the latch bolt to be retracted from one side using a handle and from the other side using the cylinder lock on the other side of the lock. This simplifies the lock mechanism, reducing the overall number of components.

In an embodiment, the latch cam is directly driven by the first spindle to rotate in the latch release direction on movement of the first handle from a rest position in an opening direction. The direct engagement may comprise lost motion so the first handle can be moved in the locking direction from its rest position whilst the latch is in its extended position. In an embodiment, the second spindle is not operatively connected with the latch cam such that movement of the second handle in an opening direction from a rest position does not cause the latch cam to be rotated in the latch release direction to retract the latch bolt.

In an embodiment, the lock unit comprises a deadbolt movable between extended and retracted positions and a rotatable follower cam operably connected with said deadbolt to move the deadbolt to the retracted position when rotated in a first direction and to move the deadbolt to the extended position when rotated in a second direction opposite to the first, the follower cam being mounted for rotation about a common axis with the latch cam, each of the first and second spindles being operatively connected with the follower cam when engaged with the lock unit so as to rotate the follower cam in said first direction to retract the deadbolt when its respective handle is moved in an opening direction from a rest position and to rotate the follower cam in said second direction to extend the deadbolt when said respective handle is moved in a locking direction opposite to the opening direction from the rest position.

The operative connection between the first spindle and the latch cam may incorporate lost motion to enable the first handle to move from its rest position in the locking direction when the latch bolt is in its extend position. In an embodiment, the latch cam defines an aperture into which the first spindle extends when engaged in the lock unit, the latch cam defining a plurality of abutments spaced apart about a periphery of the aperture, the abutments configured to be engaged by the first spindle when the first spindle is rotated in response to movement of the first handle in said opening direction from its rest position resulting in rotational movement of the latch cam to retract the latch bolt, the abutments being spaced apart such that they are not engaged by the first spindle as it rotates in response to movement of the first handle from its rest position in a locking direction opposite to said opening direction.

In an embodiment, the lock unit comprises a first follower and a second follower, each of the first and second followers being mounted for rotation about said common axis, the first spindle engaging rotationally fast with the first follower when engaged with the lock unit and the second spindle engaging rotationally fast with the second follower when engaged with the lock unit, each of the first and second followers having driving formations for engagement with corresponding driven formations on the follower cam such that rotation of either one of the followers in response to movement of a respective one of the first and second handles from its rest position in an opening direction causes the follower cam to rotate in said first direction to retract the deadbolt and that rotation of either one of the followers in response to movement of a respective one of the first and second handles from its rest position in a locking direction causes the follower cam to rotate in said second direction to extend the deadbolt. Part of the latch cam may be located between said second follower and the follower cam, in which case, at least one of the corresponding driven formations on the follower cam or the drive formations on the second follower may extend through an aperture in the latch cam. The arrangement may be such that rotation of the second follower in response to movement of the second handle and second spindle does not cause the latch cam to retract the latch bolt.

The lock unit may comprise a resilient biasing arrangement for biasing each of the first and second handles to its rest position. In an embodiment, each of the followers comprises a circumferential array of teeth engaged with a corresponding array of teeth on a respective rack slidably mounted within the lock unit, each rack being biased by a resilient member to a neutral position, the arrangement being such that rotation of a follower in response to movement of its associated handle from its rest position in either of the opening or locking directions displaces the respective rack from its neutral position against the bias force of the resilient member. In an alternative embodiment, the lock unit has an upper return spring mechanism and a lower return spring mechanism, each of the followers having an upper return spring cam surface and a lower return spring cam surface for engagement with the upper and lower return spring mechanisms respectively. The arrangement may be configured such that on movement of either handle from its rest position in a locking direction, the upper spring cam surface on the respective follower actuates the upper return spring mechanism generating a bias force tending to move the handle back towards the rest position, such that when the handle is subsequently released, it is moved by the upper return spring mechanism to the rest position. The arrangement may be configured such that on movement of either handle from its rest position in an opening direction, the lower spring cam surface on the respective follower actuates the lower return spring mechanism generating a bias force tending to move the handle back towards the rest position, such that when the handle is subsequently released, it is moved by the upper return spring mechanism to the rest position. The lower return spring mechanism may have first and second lower return springs independently actuatable on movement by the first and second handles respectively, such that movement of the first handle in the opening direction is operative to actuate the first lower return spring and movement of the second handle in the opening direction is operative to actuate the second lower return spring. In this embodiment, the handles are held in the rest position by the lower return spring mechanism when not in use and the provision of independently actuatable lower return springs for each handle enables each of the handles to be held in the rest position whilst the other is moved in the locking direction The follower cam may be operatively connected with the deadbolt through a drive bar mounted for linear movement within the lock unit, wherein the follower cam is arranged to move the drive bar in a first linear direction when rotated in said first direction and to move the drive bar in a second linear direction opposite to the first when rotated in said second direction, the drive bar being operatively connected with the deadbolt such that movement of the drive bar in said first linear direction causes the deadbolt to move to its retracted position and that movement of the drive bar in said second linear direction causes the deadbolt to move to its extended position.

In an embodiment, the deadbolt is a hook bolt mounted for pivotal movement between its retracted and extended positions In which case, one of the hook bolt and the drive bar may have a drive formation which engages in a cam slot in the other of the hook bolt and the drive bar, the arrangement being configured such that liner movement of the drive bar is converted into pivotal movement of the hook bolt.

Alternatively, the deadbolt may be a sliding bolt mounted to the casing for linear movement between its retracted and extended positions. In which case, the direction of movement of the sliding bolt may be perpendicular to the direction of movement of the drive bar, and one of the sliding bolt and the drive bar may have a drive formation which engages in a cam slot in the other of the sliding bolt and the drive bar, the arrangement being configured such that liner movement of the drive bar is converted into linear movement of the sliding bolt in a direction perpendicular to the movement of the drive bar.

The lock unit may include a locking member which, at least when the deadbolt is extended, is movable between a locked position in which it inhibits movement of the drive bar to prevent the drive bar from moving to retract the deadbolt and an un-locked position in which it does not inhibit movement of the drive bar, wherein, when the cylinder lock is engaged in the lock unit, the cylinder cam is operative to move the locking member from its un-locked position to its locking position when the cylinder lock is actuated to move the cylinder cam in a locking direction and to move the locking member from its locking position to its un-locked position when the cylinder lock is actuated to move the cylinder cam in the opening direction.

The cylinder cam may be operatively connected to the latch cam by means of a latch arm, the latch arm being connected to the latch cam and having an abutment for engagement with the cylinder cam. In an embodiment in which the lock unit as a locking member as recited above, the latch arm may be movably mounted to the locking member such that the latch arm abutment is positioned for engagement with the cylinder cam when the locking member is in its un-locked position but is positioned so that it is not engageable by the cylinder cam when the locking member is in its locking position In accordance with a second aspect of the invention, there is provided a lock unit for use in the door lock according to the first aspect of the invention The lock unit may have any features of the lock unit in the door lock according to the first aspect of the invention as set out above In accordance with a third aspect of the invention, there is provided a door lock comprising a lock unit mountable in a recess in a door and first and second handles, a first spindle rotatably fast with the first handle and operably engageable with the lock unit, a second spindle rotatably fast with the second handle and operably engageable with the lock unit, the lock unit having a casing, a deadbolt movable between extended and retracted positions in response to movement of either of the first and second handles; a latch bolt movable between a retracted position and an extended position and which is resiliently biased to the extended position, and a rotatable latch cam operatively connected with the latch bolt so as to retract the latch bolt when rotated in a latch release direction, the latch cam being operatively connected with the first spindle when the first spindle is engaged with the lock unit such that, in use, movement of the first handle from a rest position in an opening direction causes the latch cam to be rotated in the latch release direction to retract the latch bolt, the lock including a cylinder lock operably engageable in the lock unit, the cylinder lock having a cylinder cam operably connectable with said latch cam when the cylinder lock is engaged in the lock unit, the cylinder cam being operative to rotate said latch cam in said latch release direction to retract the latch bolt when the cylinder lock is actuated to move the cylinder cam in an opening direction.

Detailed Description of the Invention

In order that the invention may be more clearly understood embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is an exploded view of a lock unit forming part of a door lock in accordance with a first embodiment of the invention; Figure 2 is a perspective exploded view of part of the lock unit of figure 1; Figure 3 Figures 5 to 9 is a view from one side of lock unit in figure 2 but with part of the casing ghosted and showing components of the lock unit in an assembled condition, is a perspective view through part of a door lock incorporating the lock unit of figure 1 but showing components of the lock in an assembled condition; are a series of somewhat schematic views from one side of the lock of figures 1 to 4 in an assembled condition with part of the casing ghosted to show internal details and illustrating operation of the lock from a first side using a first handle.

are a series views similar to those of figures 5 to 9 but taken from the other side of the lock and illustrating operation of the lock from a second side using a second handle; Figure 4 Figures 10 to 15 Figure 16 is an exploded view of a lock unit forming part of a door lock in accordance with a second embodiment of the invention, Figure 17 is an exploded view similar to that of figure 1 of a lock unit forming part of a door lock in accordance with a third embodiment of the invention; Figures 18 to 20 are a series of views of the lock unit of figure 17 illustrating operation of a handle return spring arrangement, the views being taken from one side of the lock unit, with the components of the lock unit in an assembled condition and the outer casing on that side omitted.

A first embodiment of a door lock 10 in accordance with the invention comprises a lock unit 12 with a casing 14. In use, the lock unit 12 is mounted in a recess along an edge of a door in a manner well known in the art.

It is expected that a door lock 10 in accordance with the invention will usually be mounted with the lock unit assembled into a vertical edge of a door arid this is the orientation in which the door lock 10 is shown in the accompanying drawings and described below. It should be understood that relative directional terms such as "vertical", "horizontal", "upper", "lower", "upward" and "downward" and the like as used herein, including in the claims, refer to the lock and its components when the lock is used in this orientation However, it will be appreciated that door locks in accordance with the invention could be used in other orientations.

The lock unit 12 includes a sprung latch bolt 16 and a deadbolt 18. The door lock unit 12 is operated via a first handle 20 on one side (referred to as the first side) and a second handle 22 on the other side (referred to as the second side). The first handle 20 is rotatably fast with a first spindle 24, whilst the second handle 22 is rotatably fast with a second spindle 26. The first and second spindles are each square section rods which engage with the lock unit from opposite sides along a common axis. The first and second spindles are rotatable about said common axis independently of one another when their respective handles are turned. The spindles 24, 26 may be integrally formed with their respective handles or they may be initially separate components which are attached to their respective handles. In the embodiment as illustrated, each handle 20, 22 is a lever type handle. However, it should be understood that the term "handle" as used herein, including in the claims, is intended to encompass any suitable actuator member that can be grasped by a user to rotate the respective spindle and operate the door lock unit, including without limitation a door knob or T-shaped handle for example.

The door lock 10 also includes a cylinder lock 28 which is operably engageable in the lock unit 12. The cylinder lock 28 includes a cylinder cam 30 which is rotated in response to actuation of a cylinder in the cylinder lock using a key. In the present embodiment, the cylinder lock is a Euro cylinder lock but other types of cylinder lock can be used. The cylinder lock will typically be actuatable by means of a key from either side. However, in certain embodiments the cylinder lock could be actuatable by means of a key from the second side only. The key may be a mechanical key and the cylinder lock may be a pin tumbler type lock. However, the cylinder lock may alternatively be electronically actuatable, say by means of an electronic key.

The door lock 10 is a lock of the type defined in which the sprung latch bolt 16 can be retracted using the first handle 20 but cannot be retracted using the second handle 22. In order to retract the latch bolt 14 from second side of the lock, the cylinder cam 30 is operably connected with the latch bolt 16 to enable the latch bolt 16 to be retracted using the key operated cylinder lock 28. Typically, the door lock 10 will be mounted so that the second side is on the exterior of the door such that entry through the closed door can only be obtained using an appropriate key to retract the latch bolt 16. This provides additional security as it requires use of the key to open the door from the outside even when the deadbolt 18 is not engaged and locked. However, it will be appreciated that locks in accordance with the invention could be used in any circumstance where it is desirable that a key must always be used to open a closed door from one side.

The casing 14 includes two component parts 14a, 14b which are assembled together to enclose the majority of the lock mechanism and to which various components of the lock mechanism are mounted. The parts 14a, 14b can be made of any suitable materials such as metallic materials. The casing 14 also includes a face plate 32 which closes an outer end of the lock unit casing when the lock unit is mounted in a door. The face plate includes a latch bolt aperture 34 through which the latch bolt 16 projects, at least when it is in its extended position, and a deadbolt aperture 36 through which the deadbolt 18 projects when it is extended.

The latch bolt 16 is slidably mounted in the casing 14 for movement between an extended or latching position and a retracted or non-latching position and is biased by a latch bolt spring 38 to the extended position. As is well known in the art, the latch bolt 16 is arranged to engage with a strike plate mounted to a door jam to hold the door closed and must be retracted against the bias force of the spring to open and close the door. The latch bolt 16 has an angled face 16a on one side which engages the strike plate when the door is pushed or pulled shut so that the latch bolt 16 is automatically retracted but has a flat face on the opposite side so that the latch bolt must be retracted using the lock mechanism to open the door when the door is closed and the latch bolt engaged. The latch bolt 16 is in two parts, a main part or latch lath 40 which is slidably mounted in the casing and a latch head 42 removably mounted to the latch lath and which engages with the strike plate. The latch head 42 is easily replaceable in the event it becomes damaged in use.

The deadbolt 18 is also mounted to the casing for movement between an extended position and a retracted position. In this embodiment, the deadbolt 18 is a hook bolt and is mounted within the lock unit 12 for pivotal movement between its extended and retract positions. In use, when the deadbolt 18 is retracted it is located wholly within the lock unit internally of the face plate 32. When extended, the deadbolt projects through the deadbolt aperture 36 in the face plate to engage with a strike plate or other feature on the door jam to hold the door closed. The deadbolt 18 is not biased to ether of its extended or retracted positions but must be positively moved between them using the first and second handles. The deadbolt 18 can be locked in its extended position when the door is closed using the cylinder lock 28 such that once the door is closed with the deadbolt engaged and locked, a key must be used to unlock the deadbolt to open the door.

As seen from right to left in figures 1, 2 and 4, the lock mechanism includes a first follower 44, a follower cam 46, a latch cam 48, and a second follower 50. The first follower 44, the follower cam 46, the latch cam 48, and the second follower 50 are all mounted for rotation about a common axis X, which is also the axis of rotation of the first and second spindles 24, 26 within the lock unit. The first follower 44 has a square aperture 52 which corresponds in size and shape to the first spindle and the second follower has a square aperture 54 which corresponds in size and shape to the second spindle. As can be seen best in figure 4, when the door lock 10 is assembled the first spindle 24 passes through the aperture 52 in the first follower and with clearance through an aperture 56 in the follower cam, with an end region of the first spindle 44 locating within an aperture 58 in the latch cam. The second spindle 26 engages in the aperture 54 in the second follower 50 but does not extend as far as the latch cam 48.

The first follower 44 is rotationally fast with the first spindle 24 and the second follower is rotationally fast with the second spindle 26.

The first and second handles 20, 22 and their respective spindles 24, 26 are typically provided as a handle set with each handle attached to a respective face plate (not shown) in a manner known in the art. After the lock unit 12 is mounted in the door and the cylinder lock 28 inserted, the first and second handles 20,22 and their respective spindles 24, 26 are mounted from either side, with the respective face plates fitted to the internal and external faces of the door sash. The face plates are secured together by means of countersunk screws which pass through the face plate of the first, internal handle and engage in tapped holes on the inner side of the face plate of the second, external handle 22. This prevents the handles and their spindles from being pulled out of the lock unit and the face plates can only be removed from the interior side of the door. Circlips may be mounted to the spindles 24, 26 to ensure that they engage in the lock unit 12 to the correct depth.

The lock 10 is arranged so that the first and second handles 20, 22 adopt rest positions when not being used. When either handle is in its rest position, their respective spindle 24, 26 and follower 44, 50, which are both rotationally fast with the handle, also adopt a rest position. In the present embodiment, the levers of the handles extend generally horizontally away from the outer edge of the door in which the lock is fitted when the handles are in their rest positions. The lock unit 12 includes biasing mechanisms for basing each of the first and second handles and their respective spindles and followers to the rest position. Each of the handles can be rotated by moving the lever downwardly or upwardly from the rest position. In the present embodiment, rotating the handles, spindles, and followers by moving the handle levers downwardly from their rest position is defined as movement in an opening direction whilst rotating them in the opposite direction by moving the levers upwardly from the rest position is defined as movement in a locking direction.

The biasing mechanisms for each of the handles are similar and so only a first biasing mechanism for the first handle 20 will be described in detail. The biasing mechanism for the first handle 20 includes the first follower 44, which is rotationally fast with the first spindle 24, and a first rack 60a slidably mounted to a return spring cassette 61 for linear movement of the first rack in a vertical direction relative to the return spring cassette and the casing to which the cassette 61 is mounted. The first rack 60a is resiliently biased to a neutral position by means of a first handle return spring 62a operative between the cassette 61 and the first rack 60a. The first handle return spring 62a is mounted under compression between an upper rack spring abutment 63a and a lower rack spring abutment 63b on the first rack. The first handle return spring 62a is also located between an upper cassette spring abutment 63c and a lower cassette spring abutment 63d on the cassette. The first rack 60a defines a linear array of teeth 64a which are engaged by a corresponding circumferential array of teeth 66a about an outer circumferential region of the first follower. The arrangement is configured such that when the first rack 60a is in the neutral position, the first handle 20, the first spindle 24, and the first follower 44 are held in their rest positions with the handle lever projecting generally horizontally. If the first handle lever is depressed downwardly from its rest position to move the handle in an opening direction, this will result in the first spindle 24 and first follower 44 also rotating in the opening direction (clockwise as seen when looking at the lock from the first side) driving the first rack 60a downwardly relative to the casing and compressing the first handle return spring 62a between the upper rack spring abutment 63a and the lower cassette spring abutment 63d. When the first handle is subsequently released, the first handle return spring 62a biases the first rack 60a back to its neutral position, rotating the first follower, first spindle and the first handle back to their rest positions. Movement of the first handle lever upwardly from its rest position to move the handle in the locking direction will rotate the first spindle and first follow 44 in the locking direction (anti-clockwise as seen when looking at the lock from the first side) driving the first rack 60a upwardly relative to the casing away from its neutral position so that the first handle return spring 62a is compressed between the lower rack spring abutment 63b and the upper cassette spring abutment 63c. When the first handle is subsequently released, the first handle return spring 62a biases the first rack 60a back to its neutral position, rotating the first follower 44, first spindle, and the first handle 20 back to their rest positions.

The second biasing mechanism for the second handle 22 is similar to the first, comprising a second rack 60b which is also slidably mounted to the return spring cassette 61 alongside the first rack 60a. A second handle return spring 62b is operatively engaged between the second rack 60b and the return spring cassette 61 in a manner similar to the first handle return spring and the first rack as described above. The second rack 60b has an array of teeth 64b which are engaged by a corresponding circumferential array of teeth 66b about an outer circumferential region of the second follower 28. The second biasing mechanism works in the same manner as the first, with rotation of the second handle 22 from its rest position resulting in the second follower 50 driving the second rack away from its neutral position against the bias force of the second handle return spring 62b, such that when the second handle is subsequently released, the second handle return spring 62b biases the second rack back to its neutral position to return the second handle, second spindle, and second follower 50 back to their rest positions. The first and second handle return springs 62a, 62b are shown in Figure 1 but omitted from the other drawings for clarity.

The above biasing mechanisms are exemplary only and alternative arrangements for biasing the first and second handles and their respective spindles and followers to a rest position can be used. One example of an alternative biasing mechanism is described below in relation the embodiment shown in figure 17.

The latch cam 48 has a main body portion 48a which is located between the follower cam 46 and the second follower 50. The main body portion 48a defines the aperture 58 in which an end region of the first spindle 24 engages. The latch cam also has a first actuating arm portion 48b which is arranged to engage with a corresponding drive abutment 68 on the latch lath 40 when the latch bolt is extended and the latch cam rotated in a first, latch release direction, which corresponds with the direction of rotation of the first handle and the first spindle 44 in an opening direction (that is to say in a clockwise direction when viewed from the first side of the lock). A driving connection with lost motion is provided between the latch cam 48 and the first spindle 24 by means of four abutments 69 spaced apart about a periphery of the aperture 58 into which the first spindle projects. The abutments 69 are arranged so that when the latch bolt 16 is in its extended position and the first handle 20 moved in an opening direction from its rest position, they are engaged by the corners of the first spindle 24 as it rotates so that the latch cam 48 is rotated together with the first spindle to bring the first actuating arm portion 48b into engagement with the drive abutment 68 on the latch lath 40 and move the latch bolt 16 towards its retracted position against the bias force of the latch bolt spring 38. When the first handle 20 is subsequently released after retracting the latch bolt, the latch spring 38 returns the latch bolt 16 to its extended position and the first handle biasing mechanism returns the first handle 20 to its rest position. The latch cam 48 will also be rotated back to a corresponding rest position. However, the spacing between the abutments 69 is arranged so that the first handle 20 can be moved from its rest position in a locking direction whilst the latch bolt 16 is extended without the first spindle 24 engaging the abutments 69 and/or rotating the latch cam 48 in way which limits the full range of movement of the first handle in the locking direction. In this regard, the latch cam 48 may be able to float to an extent when the latch bolt 16 is extended so that the first spindle 24 may engage the abutments 69 to rotate the latch cam to a small extent when the first handle moved in the locking direction to extend the deadbolt as described below.

The deadbolt 18 is moved between its extended and retracted positions by operation of either of the first and second handles 20, 22 acting through the follower cam 46 and a drive bar 70. The drive bar 70 is mounted within the casing for linear movement between a first position and a second position. When the lock unit is mounted in a vertical edge of the door, movement of the drive bar 70 is generally vertical between a lower, first position and an upper, second position. Upward movement of the drive bar 70 from the first to the second position will be referred to as movement of the drive bar in a first direction whilst downward movement of the drive bar from the second position to the first will be referred to as movement of the drive bar in a second direction. In the present embodiment where the deadbolt is a pivotal hook bolt, the drive bar 70 is operatively connected to the deadbolt in a manner which converts the linear movement of the drive bar 70 into rotary movement of the deadbolt 18. As illustrated, this may comprise a projection 72 on the drive bar 70 which engages in a cam slot (not shown) in the deadbolt 18. The cam slot and projection 72 are arranged such that when the drive bar is in its first, lower position the deadbolt is extended and when the drive bar is in its second, upper position the deadbolt is extended. The cam slot is shaped such that interaction between the projection 72 and the cam slot 74 causes the deadbolt to pivot between extended and retracted positions as the drive bar 70 is moved between its lower and upper positions. It will be appreciated that other arrangements for converting linear movement of the drive bar into rotary movement of the deadbolt 18 can be adopted. For example, a projection could be provided on the deadbolt and a corresponding cam slot formed in the drive bar, Movement of the drive bar 70 between its first and second positions is effected by the follower cam 46 in response to actuation of either of the first and second handles The follower cam has an actuator arm portion 76 with an abutment 78 which engages in an aperture 80 in the drive bar so as to move the drive bar in said first direction to retract the deadbolt when rotated in a first direction, which corresponds with rotary movement of either one of the handles in an opening direction, and to move the drive bar in said second direction to extend the deadbolt 1_8 when rotated in a second direction, corresponding to rotary movement of either one of the handles in a locking direction.

The first and second spindles 24, 26 do not directly engage the follower cam 46 but are each driving connected with the follower cam 46 through their respective follower 44, 55. Each of the first and second followers 44, 50 has a set of circumferentially spaced drive formations 84, 86 which project laterally toward the follower cam 46. The follower cam has corresponding sets of circumferentially spaced driven formations 88, 90 on either side which project laterally towards the respective follower, so that the driving and driven formations are intermeshed. The corresponding drive and driven formations are spaced apart circumferentially to provide a degree of lost motion in the driving connection between each follower 44, 50 and the follower cam 46. The driving connection between each of the followers 44, 50 and the follower cam 46 can be considered as being in the manner of a dog clutch with lost motion.

The driving connection between each of the followers 44, 50 and the follower cam 46 is arranged so that with the deadbolt 18 extended and the handles 20, 22 and followers 44, 50 in their rest positions, initial movement of either handle in its opening direction will rotate the respective follower 44, 50 to bring the corresponding drive and driven formations into engagement. Continued movement of the handle in its opening direction results in the follower cam 46 being rotated in its first direction such that the follower cam moves the drive bar 70 upwardly from its first position to its second position, retracting the deadbolt 18. When the handle is released after fully retracting the deadbolt, the handle is returned to its rest position by the respective biasing mechanism. However, the spacing between the corresponding drive and driven formations provides lost motion enabling the handle and follower to return to their rest positions without rotating the follower cam 46 so that the deadbolt 18 remains in its retracted position.

The driving connection between each of the followers 44, 50 and the follower cam 46 is also arranged so that with the deadbolt 18 retracted and the handles 20, 22 in their rest positions, initial movement of either handle in its locking direction will rotate the respective follower 44, 50 to bring the corresponding drive and driven formations into engagement. Continued movement of the handle in its locking direction results in the follower cam 46 being rotated in its second direction (anti-clockwise as seen when looking at the lock from the first side) to move the drive bar 70 downwardly from its second position to its first position extending the deadbolt 18. When the handle is released after fully extending the deadbolt, it is returned to its rest position by the respective biasing mechanism, with the lost motion provided by the spacing between the drive and driven formations enabling the handle and follower to return to the rest position without rotating the follower cam 46 so that the deadbolt 18 remains extended.

Since the latch cam 48 is located between the follower cam 46 and the second follower 50, one of the corresponding driven formations on the follower cam 46 projects towards the second follower 50 through an elongate aperture 92 in the latch cam whilst the other projects about an exterior edge of the latch cam so that rotation of the second follower and/or the follower cam 46 does not cause rotation of the latch cam 48.

Movement of the first handle 20 from its rest position in a locking direction is not inhibited by the latch cam 48 due to the lost motion in the driving connection between the first spindle 24 and the latch cam 48 as previously described.

The lock unit 12 includes a locking member or lockout block 94 which is slidably mounted within the casing for movement between unlocked and locked positions. When the deadbolt 18 is extended and the drive bar 70 in its first, lower position, the locking member 94 can be moved to its locked position where it engages with the drive bar 70 and prevents the drive bar from being moved to retract the deadbolt 18. The locking member 94 is moved between its unlocked and locked positions by the cylinder lock cam 30 in response to actuation of the cylinder lock 28 using a key. With the deadbolt 18 extended and the locking member 94 in its unlocked position, actuation of the cylinder lock 28 to rotate the cylinder cam 30 in a locking direction causes the cylinder cam 30 to engage with an abutment on the locking member 94 and move it to the locked position where it engages with the drive bar 70. In this configuration, the deadbolt 18 cannot be retracted using either of the handles as the locking member 94 prevents the drive bar 70 from moving and the deadbolt is locked. To unlock the deadbolt, the cylinder lock 28 is actuated using a key to rotate the cylinder and cylinder cam 30 in an unlocking direction such that the cylinder cam 30 engages a second abutment on the locking member to move it to the un-locked position.

The locking member 94 is slidably mounted within a locking member housing 96 which is mounted inside the casing. The locking member housing 96 is an additional security feature intended to resist tampering of the locking member 94, for example by drilling into the lock from either side. The locking member housing 96 encloses the locking member on either side and about an inner end and is made of a suitable material to resist drilling. The housing 96 may be made of a suitable metallic material such as steel, for example. However, the use of a locking member housing 96 is not essential and the locking member 94 could be slidably mounted directly to the casing 14. The feature of the locking member being slidably mounted in a housing within the casing may be claimed independently of other aspects of the lock 10.

Retraction of the latch bolt 16 from the second side of the lock is effected by means of the cylinder lock 28, whose cylinder cam 30 is operatively connected to the latch cam 48 by means of latch lever 98. The latch lever has a first end 98a and a second end 98b and is connected at the first end to a second actuating arm portion 48c of the latch cam. The latch leaver 98 is movably mounted to the locking member 94 close to its second end 98b by means of an elongate slot 100 in the latch lever which receives a projection 102 on a side of the locking member. This mounting arrangement enables the latch lever 98 to both pivot and slide relative to the locking member 94 whilst the connection of the first end 98a of the latch lever to the latch cam enables the latch lever to pivot relative to the latch cam. The latch lever 98 has an abutment 104 at its second end for engagement with the cylinder cam 30. The arrangement is configured such that when the latch bolt is extended and the locking member 94 is in its unlocked position, the cylinder cam 30 is able to engage with the abutment 104 on the latch lever when rotated from a rest position in an opening direction in response to actuation of the cylinder lock using a key. Engagement between the cylinder cam 30 and the latch lever abutment as the cylinder cam 30 is rotated in the opening direction causes the latch lever 98 to be moved upwardly, rotating the latch cam 48 in the latch release direction to retract the latch bolt. The latch bolt 16 can be held retracted using the key to hold the cylinder cam in engagement with the abutment 104 on the latch lever. When the key is released, the latch bolt spring 38 will bias the latch bolt back to its extended position, forcing the latch cam 48, the latch lever 98 and the cylinder cam 30 to return to their rest positions. With reference to figure 14, when the locking member 94 is moved to its locked position, the second end 98b of the latch leaver 98 is moved away from the cylinder cam 30 so that the abutment 104 on the latch leaver is no longer engageable by the cylinder cam 30. Accordingly, the latch bolt 16 cannot be released without first using the cylinder lock 28 to return the locking member 94 to its unlocked position.

Furthermore, when the locking member 94 is in its locked position, the geometry between the latch lever 98 and the latch cam 48 is such that upward movement of the latch lever 98 does not rotate the latch cam 48 in the latch release direction. This provides additional security to prevent attempts to release the latch bolt 16 by manipulating the latch lever 98 when the lock 10 is in a fully locked condition.

Operation of the door lock 10 from the first side using the first handle 20 will now be described with reference to Figures 5 to 9.

Figure 5 shows the lock 10 with both the latch bolt 16 and the deadbolt 18 extended, the first handle 20 in its rest position and the locking member 94 in its unlocked position. This would be the typical configuration of the lock when a door to which the lock is mounted is closed but not locked.

To open the door, the first handle 20 is rotated in its opening direction from the rest position as illustrated in Figure 6. This causes the first spindle 24 to engage the abutments 69 on the latch cam 48 and rotate the latch cam in the latch release direction to retract the latch bolt 16. At the same time, the first follower 44 is operative to rotate the follower cam 46 to lift the drive bar 70 and retract the deadbolt 18 so that the door can be opened After the door has been opened, the first handle 20 is released and is biased back to the rest position as shown in figure 7. The latch bolt 16 is moved to its extended position by the latch bolt spring 38, with the latch cam 48 also returning to its rest position. However, the deadbolt 18 remains retracted due to the lost motion in the drive connection between the first follower 44 and the follower cam 46, which allows the first follower to return to its rest position without rotating the follower cam 46 so that the drive bar 70 remains in its upper position. The door can now be closed by pushing or pulling it shut with the latch bolt 16 being automatically retracted against the bias of the latch bolt spring 38 as it engages an abutment of the strike plate on the associated door jam to enable to door to close, the latch bolt springing back out once it passes the abutment so that the door is held on the latch. In order to re-engage the deadbolt 18, the first handle 20 is moved from its rest position in a locking direction as illustrated in figure 8. The driving engagement between the first follower 44 and the follower cam 46 causes the follower cam to rotate in its second direction, moving the drive bar 70 downwardly to extend the deadbolt 18. Movement of the first handle in the locking direction is not impeded by engagement of the first spindle 24 with the latch cam 48 due to the spacing between the abutments 69 which provide adequate lost motion in the driving connection between the first spindle 24 and the latch cam 48. Once the deadbolt 18 is extended, the first handle 20 is released and returned to the rest position by the first handle biasing mechanism as shown in figure 9. Lost motion between the drive formations on the first follower 44 and the corresponding driven formations on the follower cam 46 enable the first handle and the first follower to return to their rest positions without rotating the follower cam so that the deadbolt 18 remains extended The door could now be locked by actuating the cylinder lock 28 using a key to move the locking member 94 to its locked position Operation of the door lock 10 from the second side using the second handle 22 will now be described with reference to Figures 10 to 16.

Starting with the lock 10 in its closed but unlocked configuration in which both the latch bolt 16 and the deadbolt 18 are extended and the locking member 94 in its unlocked position, the deadbolt 18 is retracted by rotating the second handle 22 in the opening direction from its rest position as illustrated in figure 10. During this movement, the second follower 50 is operative to rotate the follower cam 46 to move the drive bar 70 and retract the deadbolt 18. However, as the second spindle 26 is not operatively connected with the latch cam 48, the latch bolt 16 is not retracted. If the second handle 22 is released, it is biased back to its rest position by the second handle biasing mechanism as illustrated in figure I I The deadbolt 18 remains retracted due to the lost motion in the drive connection between the second follower 50 and the follower cam 46. In order to open the door from the second side, the latch bolt 16 is released using the key to actuate cylinder lock 28, rotating the cylinder and cylinder cam 30 in an opening direction so that the cylinder cam 30 engages the abutment 104 on the latch lever 98 as illustrated in figure 12. This moves the latch leaver 98 upwardly causing the latch cam 48 to rotate in the latch release direction and retract the latch bolt. The door can now be opened and the key is released so that the latch bolt 16 is moved back to its extended position by the latch bolt spring 38, with the latch cam 48 and latch lever 98 also returning to their rest positions. This is illustrated in figure 13. It will be appreciated that the key could be used to retract the latch bolt 16 at the same time as the second handle 22 is used to retract the deadbolt 18 rather than carrying out these operations sequentially.

With the deadbolt 18 retracted, the door can be closed by simply pushing or pulling it shut so that the latch bolt 16 automatically engages with the strike plate to hold the door shut. As illustrated in figure 14, to re-engage the deadbolt 18, the second handle 22 is raised moving it from its rest position in the locking direction so that the second follower 50 drives the follower cam 46 and the drive bar 70 to rotate the deadbolt 18 to its extended position. Figure 14 also illustrates actuation of the cylinder lock 28 to lock the deadbolt by rotating the cylinder and cylinder cam in a locking direction to move the locking member 94 to its locked position where it engages with the drive bar 70 to prevent the drive bar being raised to retract the deadbolt.

Subsequently releasing the second handle 22 allows it to return to its rest position, whilst the deadbolt 18 remains extended due to the lost motion in the drive connection between the second follower SO and the follower cam 46. The door is now fully locked as shown in figure 15. To unlock the door, the cylinder lock is actuated to move the locking member back to its unlocked position and the door can then be opened from either side as described above.

The door lock 10 in accordance with the invention provides a simple and effective mechanism in which enables the latch bolt 16 to be retracted from the first side using the first handle 20 but only retracted from the second side using the key actuated cylinder lock 28 In the embodiment described above, the deadbolt 18 is in the form of a pivotal hook bolt. Figure 16 illustrates an alternative embodiment of a door lock 10' in accordance with the invention in which the deadbolt 18' is in the form of a sliding bolt which moves linearly between extended and retracted position. In this embodiment, the drive bar 70' has a cam slot 106 and the deadbolt 18' has a projection 108 which engages in the cam slot. The cam slot 106 is profiled so that upward movement of the drive bar 70' from its lower, first position to its second, upper position causes the deadbolt to slide inwardly to its retracted position and that movement of the drive bar 70' from its upper, second position to its lower, first position causes the deadbolt 18 to slide outwardly to its extended position. The lock 10' is otherwise substantially identical to the first embodiment with movement of the drive bar 70' being effected via the follower cam 46 on movement of either of the first and second handles. The reader should refer to the detailed description of the first embodiment for further details.

A further embodiment of a door lock unit 12" forming part of a door lock 10" in accordance with the invention is illustrated in figures 17 to 20. The lock unit 12" is similar in construction and operation to the lock unit 12 according to the first embodiment described above and to which description the reader should refer for details. Accordingly, only aspects of the door lock unit 12" which differ significantly from that of the first embodiment will be described.

The most significant difference between the door lock unit 12" according to this third embodiment and that of the first embodiment, is the resilient biasing arrangement for returning the handles to their position. The resilient biasing arrangement in the door lock unit 12" does not use a rack and pinion system but has upper and lower return spring mechanisms 110", 112" which are engaged by corresponding upper and lower cam surfaces 114-, 116-on the first and second followers 44", SO-respectively. The upper cam surfaces 114" on each of the followers 44", 50" includes a flat upper cam surface region 114a" which transitions into a curved upper cam surface region 114b" at the rear end of the follower. The lower cam surfaces 116" are generally a mirror image of the upper cam surfaces, comprising a lower flat cam surface region 116a-which transitions into a curved lower cam surface region 116b" at the rear end of the follower. The upper and lower flat cam surface regions 114a", 116a" are aligned generally parallel to one another.

The upper return spring mechanism 110" includes an upper return spring cassette or housing 61a" mounted to the casing 14". An upper return spring 62a" is located in a vertically aligned blind bore in the cassette 61a". The blind bore is closed at its upper end and a lower end of the upper return spring projects beyond the cassette.

An upper return spring actuator 118a" is mounted in the upper return spring cassette 61a" for sliding movement in a vertical direction. The range of movement of the actuator 118a-relative to the upper spring cassette is limited. The actuator has a lower end plate 120" which in use extends below the exposed lower end of the upper return spring 62a" and is engaged by the upper cam surfaces 114" of the first and second followers in use. The latch bolt 16-is slidably mounted to the upper spring cassette 61a" in this embodiment.

The lower return spring mechanism 112" includes a lower return spring cassette or housing 61b" mounted to the casing 14-. First and second lower return springs 62b", 62c" are located side-by-side in a vertically aligned blind bore in the cassette 6 lb". The blind bore is closed at its lower end and the upper ends lower return springs project beyond the cassette. A corresponding lower return spring actuator 1186", 118c" is provided for each of the lower return springs. The actuators are each slidably mounted to the lower return spring cassette for independent movement in a vertical direction over a limited range. A first lower return spring actuator 118b has an upper end plate 122" which extends above the exposed upper end of the first lower return spring 62b" and in use is engaged by the lower cam surface 116" of the first follower 44". Similarly, the second lower return spring actuator 118c" has an upper end plate 124-which extends above the exposed upper end of the second lower return spring 62c" and in use is engaged by the lower cam surface 116" of the second follower 50".

Operation of the return spring arrangement will now be described with reference to figures 18 to 20.

In use, the first and second handles 20, 22 are normally held in their rest positions by the lower return spring mechanism, with the lower flat cam surface regions 116a" of the first and second followers 44", 50" engaging with the respective first and second return spring actuators I I 8b", I I Sc'' as illustrated in figure IX If either handle is moved from its rest position in a locking direction, that is to say the handle lever is raised, its respective follower 44", 50" is rotated to bring the respective curved upper cam surface region 114b" into engagement with the end plate 120" of the upper return spring actuator 118a-, with continued movement of the handle and follower acting to move the actuator upwardly, compressing the upper return spring 62a". This is illustrated in figure 19 which shows the position of the second follower 50 when the second handle is fully raised in the locking direction. The curved upper cam 114a-surface acting on the upper return spring actuator 118a" has compressed the upper return spring 62a". When the handle is subsequently released, the upper return spring 62a" expands back to its neutral position, biasing the follower 50" arid handle back to their rest positions. Movement of the first handle in the locking direction results in the upper cam surface 114" of the first follower acting on the end plate 120" of the upper return spring actuator 118a" to compress the upper return spring in a similar manner. When a handle is moved in the locking direction, the lower cam surface 116" of the respective follower is raised off the respective lower spring actuator. However, movement of the lower spring actuator is limited such that that the lower return spring only expands by a relatively small amount and does not interfere with operation of the lock unit.

If either handle is moved from its rest position in an opening direction, that is to say the handle lever is lowered, the respective follower is rotated so that the curved lower cam surface 116b" acts on the respective lower return spring actuator 118b", 118c" to move the actuator downwardly and compress the respective lower return spring 62b", 62c". This is illustrated in figure 20, which shows the position of the second cam follower 50" after the second handle has been moved to the fully open position. The second follower 50" has been rotated to move the curved low cam surface region 116b" into engagement with the end plate 124-of the second lower return spring actuator 118c", moving the actuator downwardly and compressing second lower return spring 62c". Since the first and second lower return springs 62b", 62c" are independently actuatable, the first handle is retained in its rest position by the first lower return spring and actuator. When the second handle is subsequently released, the second lower return spring 62c" expands back to its initial configuration rotating the second follower 50" and second handle back to their rest positions. It will be appreciated that movement of the first handle in the opening direction actuates the first lower return spring 62b" in a similar manner, with rotation of the first follower 44" resulting the curved lower cam surface region 116b" depressing the first lower return spring actuator 118b"to compress the first lower return spring 62b" whilst the second handle is held in the rest position by the second lower return spring and actuator.

In this embodiment, a separate and independently actuatable lower return spring 62b-, 62c-is provided for each handle so that each handle is held in the rest position when the other handle is moved in the opening direction. Furthermore, in the present embodiment where the handles are lever handles, the weight of the handle helps to return it to the rest position after the lever handle is raised in the locking direction so that a smaller spring force is required to return the handle to the rest position than when the handle is moved in the opening direction. Thus, only a single upper return spring 62a" is required. However, separate upper return springs could be used.

The lock is arranged so that there is a small clearance, in the region of 0.3mm between the followers and the upper and lower return spring actuators when the upper and lower flat cam regions 114a", 116a" are parallel to the end plates 120", 122", 124" of the return spring actuators. When the lock is not in use, the handles will fall to bring the flat lower cam surface regions 116a-into engagement with the respective end plates 122-, 124-of the lower return spring actuators 118b 118c", taking up this clearance. In order that the levers of the handles extend horizontally when the handles are in the rest position, the square apertures 52-, 54-in the first and second followers are suitably offset relative to the flat cam surface regions 114a", 116a". The return springs 62a", 62b-, 62c" are compression springs and are held under an initial pre-compression by their respective return spring actuator when the actuator is not engaged by a respective follower cam surface.

In other respects, the lock unit 12" is functionally the same as the lock unit 12 of the first embodiment, though the shapes of some of the components are charged. In part this is due to the lock unit 12" having a different backset from that of the first embodiment 12. Backset is the distance from the front of the face plate 32, 32-to the centre of the spindles. For example, whereas in the first embodiment 12, the drive bar has an aperture 80 in which the abutment 78 on the follower cam actuator arm 78 engages, in the third embodiment the drive bar 70-has slot 80" in which the follower cam abutment 78 engages. Whilst the lock unit 12" has a pivotal hook type deadbolt 18", the lock unit could be modified to use a sliding bolt type deadbolt as illustrated in figure 16.

Door locks 10, 10', 10" in accordance with the invention may form part of a multi-point locking system in which a number of further locking members are actuated when the deadbolt 18, 18', 18" is extended and retracted so that door can be secured to a door jam in several places. In this case, the drive bar 70, 70', 70" can be connected with upper and lower drive rails 130, 132; 130', 132'; 130", 132" which are moved together with the drive bar 70, 70', 70-in response to movement of the handles and which are operative to engage or disengage the further locking members The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims

Claims (2)

1. CLAIMSA door lock comprising a lock unit mountable in a recess in a door and first and second handles, a first spindle rotatably fast with the first handle and operably engageable with the lock unit, a second spindle rotatably fast with the second handle and operably engageable with the lock unit; the lock unit having a casing, a latch bolt movable between a retracted position and an extended position and which is resiliently biased to the extended position, and a single, rotatable latch cam operatively connected with the latch bolt so as to retract the latch bolt when rotated in a latch release direction, the latch cam being operatively connected with the first spindle when the first spindle is engaged with the lock unit such that, in use, movement of the first handle from a rest position in an opening direction causes the latch cam to be rotated in the latch release direction to retract the latch bolt, the lock including a cylinder lock operably engageable in the lock unit, the cylinder lock having a cylinder cam operably connectable with said latch cam when the cylinder lock is engaged in the lock unit, the cylinder cam being operative to rotate said latch cam in said latch release direction to retract the latch bolt when the cylinder lock is actuated to move the cylinder cam in an opening direction.
2. 2. A door lock as claimed in claim 1, wherein the latch cam is directly driven by the first spindle to rotate in the latch release direction on movement of the first handle from a rest position in an opening direction 3. A door lock as claimed in claim 1 or claim 2, wherein the second spindle is not operatively connected with the latch cam when engaged in the lock unit such that movement of the second handle in an opening direction from a rest position does not cause the latch cam to be rotated in the latch release direction to retract the latch bolt.4. A door lock as claimed in any one of claims 1 to 3, wherein the lock unit comprises a deadbolt movable between extended and retracted positions and a rotatable follower cam operably connected with said deadbolt to move the deadbolt to the retracted position when rotated in a first direction and to move the deadbolt to the extended position when rotated in a second direction opposite to the first, the follower cam being mounted for rotation about a common axis with the latch cam, each of the first and second spindles being operatively connected with the follower cam when engaged with the lock unit so as to rotate the follower cam in said first direction to retract the deadbolt when its respective handle is moved in an opening direction from a rest position and to rotate the follower cam in said second direction to extend the deadbolt when said respective handle is moved in a locking direction opposite to the opening direction from the rest position.A door lock as claimed in claim 4, wherein the operative connection between the first spindle and the latch cam incorporates lost motion to enable the first handle to move from its rest position in the locking direction when the latch bolt is in its extend position.6. A door lock as claimed in any one of claims Ito 5, wherein the latch cam defines an aperture into which the first spindle extends when engaged in the lock unit, the latch cam defining a plurality of abutments spaced apart about a periphery of the aperture, the abutments configured to be engaged by the first spindle when the first spindle is rotated in response to movement of the first handle in said opening direction from its rest position resulting in rotational movement of the latch cam to retract the latch bolt, the abutments being spaced apart such that they are not engaged by the first spindle as it rotates in response to movement of the first handle from its rest position in a locking direction opposite to said opening direction.7. A door lock as claimed in any one of claims 4 to 6, wherein the lock unit comprises a first follower and a second follower, each of the first and second followers being mounted for rotation about said common axis, the first spindle engaging rotationally fast with the first follower when engaged with the lock unit and the second spindle engaging rotationally fast with the second follower when engaged with the lock unit, each of the first and second followers having driving formations for engagement with corresponding driven formations on the follower cam such that rotation of either one of the followers in response to movement of a respective one of the first and second handles from its rest position in an opening direction causes the follower cam to rotate in said first direction to retract the deadbolt and that rotation of either one of the followers in response to movement of a respective one of the first and second handles from its rest position in a locking direction causes the follower cam to rotate in said second direction to extend the deadbolt. 9, 11. 12. 13.A door lock as claimed in claim 7, wherein part of the latch cam is located between said second follower and the follower cam, at least one of the corresponding driven formations on the follower cam or the drive formations on the second follower extending through an aperture in the latch cam.A door lock as claimed in claim 7 or claim 8, wherein the arrangement is such that rotation of the second follower in response to movement of the second handle and second spindle does not cause the latch cam to retract the latch bolt.A door lock as claimed in any one of claims 7 to 9, wherein the lock unit comprises a resilient biasing arrangement for biasing the first and second handles to their rest positions A door lock as claimed in claim 10, wherein each of the followers comprises a circumferential array of teeth engaged with a corresponding array of teeth on a respective rack slidably mounted within the lock unit, each rack being biased by a resilient member to a neutral position, the arrangement being such that rotation of a follower in response to movement of its associated handle from its rest position in either of the opening or locking directions displaces the respective rack from its neutral position against the bias force of the resilient member.A door lock as claimed in claim 10, the lock unit having an upper return spring mechanism and a lower return spring mechanism, each of the followers having an upper return spring cam surface and a lower return spring cam surface for engagement with the upper and lower return spring mechanisms respectively.A door lock as claimed in claim 12, wherein the arrangement is configured such that on movement of either handle from its rest position in an locking direction, the upper spring cam surface on the respective follower actuates the upper return spring mechanism generating a bias force tending to move the handle back towards the rest position, such that when the handle is subsequently released, it is moved by the upper return spring mechanism to the rest position.14. A door lock as claimed in claim 12 or claim 13, wherein the arrangement is configured such that on movement of either handle from its rest position in an opening direction, the lower spring cam surface on the respective follower actuates the lower return spring mechanism generating a bias force tending to move the handle back towards the rest position, such that when the handle is subsequently released, it is moved by the upper return spring mechanism to the rest position 15. A door lock as claimed in claim 14, wherein the lower return spring mechanism comprises first and second lower return springs independently actuatable by the first and second handles respectively, such that movement of the first handle in the opening direction is operative to actuate the first lower return spring and movement of the second handle in the opening direction is operative to actuate the second lower return spring.16. A door lock as claimed in any one of claims 4 to 15, wherein the follower cam is operatively connected with the deadbolt through a drive bar mounted for linear movement within the lock unit, wherein the follower cam is arranged to move the drive bar in a first linear direction when rotated in said first direction and to move the drive bar in a second linear direction opposite to the first when rotated in said second direction, the drive bar being operatively connected with the deadbolt such that movement of the drive bar in said first linear direction causes the deadbolt to move to its retracted position and that movement of the drive bar in said second linear direction causes the deadbolt to move to its extended position 17. A door lock as claimed in claim any one of the preceding claims, wherein the deadbolt is a hook bolt mounted for pivotal movement between its retracted and extended positions.18. A door lock as claimed in claim 17 when dependent on claim 16, wherein one of the hook bolt and the drive bar has a drive formation which engages in a cam slot in the other of the hook bolt and the drive bar, the arrangement being configured such that liner movement of the drive bar is converted into pivotal movement of the hook bolt 19. A door lock as claimed in claim any one of the preceding claims, wherein the deadbolt is a sliding bolt mounted to the casing for linear movement between its retracted and extended positions.20. A door lock as claimed in claim 19 when dependent on claim 16, wherein the direction of movement of the sliding bolt is perpendicular to the direction of movement of the drive bar, one of the sliding bolt and the drive bar having a drive formation which engages in a cam slot in the other of the sliding bolt and the drive bar, the arrangement being configured such that liner movement of the drive bar is converted into linear movement of the sliding bolt in a direction perpendicular to the movement of the drive bar.21. A door lock as claimed in any one of claims 16 to 20, wherein the lock unit comprises a locking member which, at least when the deadbolt is extended, is movable between a locked position in which it inhibits movement of the drive bar to prevent the drive bar from moving to retract the deadbolt and an un-locked position in which it does not inhibit movement of the drive bar, wherein, when the cylinder lock is engaged in the lock unit, the cylinder cam is operative to move the locking member from its un-locked position to its locking position when the cylinder lock is actuated to move the cylinder cam in a locking direction and to move the locking member from its locking position to its un-locked position when the cylinder lock is actuated to move the cylinder cam in the opening direction 22. A door lock as claimed in any one of the preceding claims, wherein the cylinder cam is operatively connected to the latch cam by means of a latch arm, the latch arm being connected to the latch cam and having an abutment for engagement with the cylinder cam.23. A door lock as claimed in claim 22 when dependent on claim 21, wherein the latch arm is movably mounted to the locking member, the latch arm abutment being positioned for engagement with the cylinder cam when the locking member is in its un-locked position, the abutment being positioned so that it is not engageable by the cylinder cam when the locking member is in its locking position.