Abstract:
A mortice lock for recessed installation into the edge of a door or door frame includes a deadlatching member that is mounted on a bolt assembly for pivoting movement. A drive shaft and hub can be rotated in either a clockwise or counterclockwise direction to cause bolt retraction. The drive shaft and hub can be locked against rotation, or not, by a lock that is mechanically connected to a cylinder cam rotated by a key. The drive shaft and hub can be locked against rotation, or not, by a lock that is mechanically connected to an assembly including the bolt assembly interacting with a separately activated kick off member such that on retraction of the bolt, depending on the position of the kick off member, the hub is locked against rotation. The bolt can be retracted by each of the key cylinder cam and the hub, in isolation.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation of International Application No. PCT/AU02/00849, filed Jun. 28, 2002, which claims priority from Australian Patent Application No. PR6046, filed Jun. 29, 2001. The disclosures of both applications are incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to a lock and more particularly to a mortice lock which is adapted for recessed installation into the edge of a door or door frame. 
   The invention has been primarily developed for installation in the aluminium frame of a glass sliding door and will be described with reference to this application. However, it would be appreciated that the invention is not limited to this particular application and is equally suited for installation in other types of doors. 
   BACKGROUND OF THE INVENTION 
   Numerous types of mortice locks are known. A problem common to most known mortice locks is their inability to be easily re-configured to suit different door backset distances. This requires different models of each lock for each backset distance, which adds to development and inventory cost. 
   Another problem is a lack of space efficiency of the internal components. Compactness is vital, especially for short backset distances. 
   Further, many known mortice locks can only operate in one handle turning direction, which causes operational problems with knobs, as they tend to be used in both directions. 
   Some mortice locks have the locking cylinder above the handle. This results in keys scratching the handle. Also, the large opening in the housing where the cylinder is fitted, allows sawdust and other debris to fall in to the lock mechanism and cause mechanical failure. 
   OBJECT OF THE INVENTION 
   It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages and, in general, to provide a mortice lock with fewer components than known mortice locks 
   SUMMARY OF THE INVENTION 
   Accordingly, in a first aspect, the present invention provides a mortice lock comprising: 
   a lock housing; 
   a bolt assembly adapted to move relative to the housing along a working direction between extended position and retracted positions; 
   a deadlatching member adapted to pivot between a deadlatching position preventing the bolt assembly from moving from the extended position to the retracted position and an closing position allowing the bolt assembly to move from the extended position to the retracted position; 
   wherein the deadlatching member is pivotally mounted on the bolt assembly for movement with the bolt assembly and adapted to pivot between said deadlatching and closing positions in a direction normal to the working direction. 
   The deadlatching member is preferably spring biased to the deadlatching position. 
   The bolt assembly is preferably spring biased to the extended position. 
   The lock housing preferably has a protuberance and, when in the closing position, the deadlatching member is adapted to travel with the bolt assembly past the protuberance and, when in the deadlatching position, the deadlatching member is adapted to travel with the bolt assembly into abutment with the protuberance. 
   The bolt assembly preferably includes a primary bolt and an auxiliary bolt and the deadlatching member is driven between the closing and deadlatching positions by relative movement between the primary bolt and the auxiliary bolt. 
   In an embodiment, the bolt assembly preferably also includes a bolt carrier to which: the primary bolt is rotationally mounted, the deadlatching member is pivotally mounted; and the auxiliary bolt is slidably mounted. The deadlatching member preferably includes a first protuberance adapted to abut the auxiliary bolt, whereby slidable movement of the auxiliary bolt relative to the primary bolt causes pivotal movement of the deadlatching member. 
   In another embodiment, the bolt assembly also includes a bolt carrier assembly to which: the primary bolt is rotationally mounted; the deadlatching member is pivotally mounted; and an auxiliary bolt assembly is slidably mounted. The deadlatching member preferably includes a protuberance adapted to abut the auxiliary bolt assembly, whereby slidable movement of the auxiliary bolt assembly relative to the primary bolt carrier causes pivotal movement of the deadlatching member. The auxiliary bolt assembly preferably includes the auxiliary bolt and an auxiliary bolt carrier. 
   The lock preferably also includes a drive shaft adapted to be driven about an axis by a handle or knob and a member adapted to pivot in response to rotation of said drive shaft, whereby initial pivotal movement of the member causes pivotal movement of the deadlatching member to the closing position and further pivotal movement of the arm causes sliding movement of the bolt assembly to the retracted position. 
   In a second aspect, the present invention provides a mortice lock comprising: 
   a lock housing; 
   a drive shaft adapted to be rotationally driven about an axis by a handle or knob; 
   a hub mounted on the shaft for rotation therewith from a first position towards either a second clockwise position and a third anti-clockwise position, the hub having a pair of spaced apart protuberances; and 
   a drive means adapted for movement relative to the housing, the drive means having a pair of formations and an engaging surface adapted, upon moving, to cause movement in a bolt retraction assembly, 
   wherein clockwise movement of the hub to the second position causes one of the protuberances to abut one of the formations and cause the drive member to move in a first direction and anti-clockwise movement of the hub to the third position causes the other of the protuberances to abut the other of the formations and also cause the drive member to move in the first direction. 
   In one form, the drive means is mounted for slidable movement relative to the housing. 
   In another form, the drive means is mounted for pivotal movement relative to the housing and incorporates the bolt retraction assembly therein. 
   The bolt retraction assembly is preferably moved to retract the bolt regardless of which direction (clockwise or anti-clockwise) the handle or knob is rotated. 
   The drive means is desirably spring biased in a second direction opposite the first direction and also biases the hub to the first position. 
   The lock desirably includes a pair of the drive shafts and a pair of the hubs, each mounted on one of the drive shafts, and the drive means contains two pairs of formations, wherein each one of the pairs of formations is adapted to engage each one of the pairs of protuberances when the hubs are in the first position. 
   In an embodiment, the bolt retraction assembly includes a pivotable latch arm and the drive member engaging surface is a gear rack adapted to engage with a gear portion provided on the latch arm. 
   In another embodiment, the bolt retraction assembly is an arm pivotally mounted to the lock housing. 
   In a third aspect, the present invention provides a mortice lock comprising: 
   a lock housing; 
   a drive shaft adapted to be rotationally driven about an axis by a handle or knob; 
   a hub mounted on the shaft for rotation therewith, the hub having a protuberance; and 
   a hub rotation locking means having a recess and adapted for slidable movement relative to the housing between a first position in which the protuberance is received within the recess and the hub is thus prevented from rotating and a second position in which the protuberance is remote the recess and the hub is thus able to rotate; 
   a locking device adapted for slidable movement relative to the housing in response to rotation of a cylinder cam; 
   an engagement means settable in a engaged position in which the hub rotation locking means and the locking device are joined for slidable movement together relative to the housing and an disengaged position in which the hub rotation locking means and the locking device are free from slidable movement together relative to the housing, 
   wherein, when the hub locking means is in the second position and said engagement means is set in said engaged position, rotation of the cylinder cam in a first direction slides the locking device and the hub rotation locking means together such that the protuberance is received in the recess and the hub is not able to rotate and, 
   when the hub locking means is in the second position and said engagement means is set in the disengaged position, rotation of the cylinder cam in said first direction slides the locking device only such that the protuberance remains remote from the recess and the hub is able to rotate. 
   Preferably, when the hub locking means is in the first position and the engagement means is set in the engaged position, rotation of the cylinder cam in a second direction opposite to the first direction slides the locking device and the hub rotation locking means together such that the protuberance is remote from the recess and the hub is able to rotate. 
   Preferably also, the engagement means travels between the engaged and disengaged positions in a direction normal to the direction of travel of the locking device. 
   The engagement means preferably includes an end that is received with an opening in the locking device in the engaged position and that is remote the opening in the disengaged position. 
   In one form, the engagement means is biased to remain in one of the engaged or disengaged positions by a detent. 
   In another form, the engagement means is biased to remain in one of the engaged or disengaged positions by spring legs. 
   The lock desirably includes a pair of the drive shafts and a pair of the hubs, each mounted on one of the drive shafts, and a pair of the engagement means, wherein each of the engagement means are independently settable with respect to the locking device. 
   In a fourth aspect, the present invention provides a mortice lock comprising: 
   a lock housing; 
   a bolt assembly adapted to move relative to the housing between extended and retracted positions, the bolt assembly having a first driving protuberance; 
   a kick off actuation member mounted for pivotal movement between an active position and an inactive position, the kick off member having a second driving protuberance; 
   a hub mounted on a drive shaft for rotation therewith; and 
   a locking device adapted for slidable movement relative to the housing between a locking position preventing rotation of the hub and an unlocking position allowing rotation of the hub; 
   wherein when the kick off member is in the inactive position and the bolt assembly is driven from the extended position towards the retracted position, the first driving protuberance passes the second driving protuberance without contact therebetween and causes no movement of the kick off member from the inactive position, and 
   wherein when the kick off member is in the active position and the bolt assembly is driven from the extended position towards the retracted position, the first driving protuberance contacts the second driving protuberance and causes initial pivotal movement of the kick off member to the active position and further pivotal movement of the kick off member in the same direction causing the locking device to be driven to the locking position. 
   The kick off member is preferably biased to remain in one of the active or inactive positions by a detent. 
   In one form, the kick off member is pivotally mounted to the casing. 
   In another form, the kick off member is pivotally mounted to the bolt assembly. 
   The lock housing preferably includes an aperture through which a tool end may pass into engagement with the kick off member to allow movement of the kick off member between the active or inactive positions. 
   In a fifth aspect, the present invention provides a mortice lock comprising: 
   a lock housing; 
   a bolt assembly adapted to move relative to the housing between extended and retracted positions; 
   a key cylinder cam adapted to be driven by a key or tab; 
   a drive shaft adapted to be driven by a handle or knob; 
   a hub mounted on the shaft for movement therewith; and 
   a bolt retraction assembly adapted to withdraw the bolt from the extended position to the retracted position in response to movement of each of the key cylinder cam and the hub, in isolation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the invention will now be described, by way of an example only, with reference to the accompanying drawings in which: 
       FIG. 1  is a rear partial perspective view of an assembled mortice lock according to a is first embodiment of the invention; 
       FIG. 2  is an exploded view of the lock shown in  FIG. 1  in the orientation of  FIG. 1 ; 
       FIG. 3  is a front partial perspective view of the lock shown in  FIG. 1 ; 
       FIG. 4  is an exploded perspective view of the lock shown in  FIG. 1  in the orientation of  FIG. 3 ; 
       FIG. 5  is an exploded perspective view of a bolt assembly from the lock of  FIG. 1 ; 
       FIGS. 6 and 7  are assembled rear perspective views of the bolt assembly shown in  FIG. 5  before and after door closure; 
       FIGS. 8 and 9  are partial side and top views respectively of the bolt assembly shown in  FIG. 6 ; 
       FIGS. 10 and 11  are partial side and top views of the bolt assembly shown in  FIG. 7 ; 
       FIG. 12  is a partial perspective view of the lock shown in  FIG. 1  and the bolt assembly shown in  FIG. 5  after door closure; 
       FIG. 13  is an enlarged detailed view of the components shown in  FIG. 12 ; 
       FIG. 14  is a partial perspective view of the lock shown in  FIG. 1  and the bolt assembly shown in  FIG. 5  before door closure; 
       FIG. 15  is an enlarged detail view of the components shown in  FIG. 14 ; 
       FIG. 16  is a side view of the bolt assembly shown in  FIG. 1  with a 23 millimetre backset; 
       FIG. 17  is a modified form of the bolt assembly shown in  FIG. 16  with a 60 millimetre backset; 
       FIGS. 18 ,  19  and  20  are side views of the lock shown in  FIG. 1  with the hub in first, second and third positions respectively; 
       FIGS. 21 and 22  are perspective views and side views respectively of the lock shown in  FIG. 1  with the bolt extended; 
       FIGS. 23 and 24  are perspective views and side views respectively of the lock shown in  FIG. 1  with the bolt retracted; 
       FIGS. 25 and 26  are partial perspective and side views of the bolt assembly and a bolt retraction arm showing the bolt in an extended position; 
       FIGS. 27 and 28  are partial perspective and side views respectively of a bolt assembly and a bolt retraction arm showing the bolt at the start of retraction; 
       FIGS. 29 to 32  are partial side views of the bolt assembly and a kick off member in various stages of operation; 
       FIGS. 33 to 36  are partial perspective views of the bolt assembly kick off member and locking device in various stages of operation; 
       FIG. 37  is a side view of the lock shown in  FIG. 1  with the kick off member set in an inactive position; 
       FIG. 38  is an enlarged detailed view of  FIG. 37 ; 
       FIG. 39  is a side view of the lock shown in  FIG. 1  with the kick off member set in an active position; 
       FIG. 40  is an enlarged detailed view of  FIG. 37 ; 
       FIG. 41  is an exploded perspective view of the hub locking means of the lock shown in  FIG. 1 ; 
       FIG. 42  is a partially assembled exploded view of the components shown in  FIG. 41 ; 
       FIG. 43  is a partial side view of the lock shown in  FIG. 1  with the engagement means in an engaged position; 
       FIG. 44  is an enlarged detailed view of  FIG. 43 ; 
       FIG. 45  is a partial side view of the lock shown in  FIG. 1  with the engagement means in a disengaged position; 
       FIG. 46  is an enlarged detailed view of  FIG. 45 ; 
       FIG. 47  is a side view of the lock shown in  FIG. 43 ; 
       FIG. 48  is a side view of the lock shown in  FIG. 45 ; 
       FIG. 49  is a rear partial perspective view of an assembled mortice lock according to a second embodiment of the invention; 
       FIG. 50  is an exploded view of the lock shown in  FIG. 49  in the orientation of  FIG. 49 ; 
       FIG. 51  is a front partial perspective view of the lock shown in  FIG. 49 ; 
       FIG. 52  is an exploded perspective view of the lock shown in  FIG. 51  in the orientation of  FIG. 51 ; 
       FIG. 53  is an exploded perspective view of a bolt assembly from the lock of  FIG. 49 ; 
       FIGS. 54 and 55  are assembled rear perspective views of the bolt assembly shown in  FIG. 53  before and after door closure respectively; 
       FIGS. 56 and 57  are side views of the bolt assembly shown in  FIGS. 54 and 55  respectively; 
       FIG. 58  is a partial perspective view of the lock shown in  FIG. 49  and the bolt assembly shown in  FIG. 53  after door closure; 
       FIG. 59  is an enlarged detailed view of the components shown in  FIG. 58 ; 
       FIG. 60  is a partial perspective view of the lock shown in  FIG. 49  and the bolt assembly shown in  FIG. 53  before door closure; 
       FIG. 61  is an enlarged detailed view of the components shown in  FIG. 60 ; 
       FIG. 62  is side a view of the lock shown in  FIG. 49  with a 23 mm backset; 
       FIG. 63  is a modified form of the lock assembly shown in  FIG. 62  with a 60 mm backset; 
       FIGS. 64 ,  65  and  66  are side views of the lock shown in  FIG. 49  showing hub operation; 
       FIGS. 67 and 68  are partial perspective and side views respectively of the bolt assembly and a bolt retraction arm showing the bolt in an extended position; 
       FIGS. 69 and 70  are partial perspective and side views respectively of a bolt assembly and a bolt retraction arm showing the bolt at the start of bolt retraction; 
       FIGS. 71 ,  72 , and  73  are side views of the lock shown in  FIG. 49  showing bolt retraction with a short cam; 
       FIGS. 74 ,  75 ,  76  and  77  are side views of the lock shown in  FIG. 49  showing bolt retraction and locking bar operation with a medium cam; 
       FIGS. 78 ,  79  and  80  are side views of the, lock shown in  FIG. 49  showing locking bar operation with a long cam; 
       FIGS. 81 and 82  are partial and complete side views respectively of the lock shown in  FIG. 49  configured with an inactive kick-off; 
       FIGS. 83 and 84  are partial and complete side views of the lock shown in  FIG. 49  configured with an active kick-off; 
       FIGS. 85 and 86  are partial side views of the lock shown in  FIG. 49  showing pre and post kick-off operation respectively; 
       FIGS. 87 and 88  are exploded and assembled perspective views of the hub locking means from the lock of  FIG. 49 ; 
       FIG. 89  is a partial side view of the lock shown in  FIG. 49  showing the locking bar engager engaged to the locking bar and disengaged from the lock housing; 
       FIG. 90  is an enlarged detail view of  FIG. 89 ; 
       FIG. 91  is a partial side view of the lock shown in  FIG. 49  showing the locking bar engager disengaged from the locking bar and engaged to the lock housing; and 
       FIG. 92  is an enlarged detail view of  FIG. 91 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to 48  show a first embodiment of a mortice lock  2   a  which includes examples of the five aspects of the invention. Turning firstly to  FIGS. 1 to 4 , the lock  2   a  includes first and second key cylinders  4  and  6  that each have associated cams  8  and  10 . The first key cylinder  4  is mounted to a lock housing  12  and the second key cylinder  6  is mounted to a lock housing cover  14 . A fore-end plate  16  is also mounted to the lock housing  12 . 
   The lock  2   a  includes a bolt assembly  17  comprised of a latch bolt  18 , a bolt carrier  20  with an associated bolt spring  22 , a bolt carrier retaining insert  24  and an auxiliary bolt  26  with an associated auxiliary bolt spring  28 . A deadlatching member, in the form of deadlatching rocker arm  30 , is pivotally mounted to the bolt assembly  17 , more particularly between the bolt carrier  20  and the bolt carrier retaining insert  24  as will be described in more detail below. The rocker arm  30  has an associated torsion spring  31 . 
   The lock  2   a  also includes external handles, such as knobs or levers (not shown), which are connected to a pair of conventional square cross section drive shafts (not shown) which are in turn connected to first and second hubs  32  and  34 . More particularly, each of the hubs  32 ,  34  has a corresponding square cross section aperture  36  for non rotationally engaging one of each of the drive shafts to transmit rotational movement from one of the handles to an associated one of the hubs  32 ,  34 . 
   The lock  2   c  also includes a drive means, in the form of a drive rack  40  and associated drive rack spring  42 , and a bolt retraction assembly, that includes a latch bolt retraction arm  44 , as will also be described in more detail below. 
   The lock  2   a  also includes a pair of hub rotation locking means, in the form of first and second hub locking sliders  46  and  48 , that each have an associated engagement means, in the form of first and second locking bar engagers  49  and  50 . The locking bar engagers  49 ,  50  can each be set in one of two positions in which an associated hub locking slider  46  and  48  respectively does, or does not, travel with movement of a locking bar  52 , as will also be described in more detail below. 
   The lock  2   a  also includes a kick off actuation member, in the form of kick off lever  54 , and a cylinder cam bolt retraction bar  56 , the operation of which will also be described in more detail below. 
   The features and operation of the deadlatching assembly will now be described in more detail with reference to  FIGS. 5 to 17 . As best seen in  FIG. 5 , the bolt carrier  20  and the bolt carrier retaining insert  24  are assembled by snap-engaging prongs  58  with corresponding recesses  60 . Each of the carrier  20  and the insert  24  include a partial tapered cylindrical recess  62  and  64  which correspond to, and receive therein, a similarly tapered shaft  66  extending from the latch bolt  18 . This allows the latch bolt  18  to be rotated about its longitudinal axis, as indicated by the doubled headed arrow  68 , for easy re-handing of the lock  2   a . The carrier  20  and the insert  24  also have other partial cylindrical recesses  70  and  72  which correspond to cylindrical portions  74  on the deadlatching rocker arm  30 . This allows the rocker arm  30  to pivot between a deadlatching position (see  FIGS. 7 ,  10 ,  11 ,  12  and  13 ) and an opening position (see  FIGS. 6 ,  8 ,  9 ,  14  and  15 ). The rocker arm  30  is biased to the deadlatching position by the torsion spring  31 . The rocker arm  30  also has first and second eccentric end protuberances  76  and  78  respectively. The protuberance  78  operatively engages with a protuberance  80  on the auxiliary bolt  26 . 
     FIGS. 12 and 13  show the latch bolt  18  in an extended position, as would occur after closure of a door. During a slam door closing action (ie. door closure without prior bolt retraction), the bolt  18  initially retracts as it travels over a strikeplate (not shown) and then extends under the influence of the spring  22  into the latch bolt opening present in a conventional strikeplate. As the stikeplate does not have an opening that corresponds to the auxiliary bolt  26 , the auxiliary bolt  26  is not able to extend as far as the latch bolt  18  when the door is closed. This results in the protuberance  80  not abutting, and thus not causing pivotable movement of, the second end protuberance  78  of the rocker arm  30 , as described above. The rocker arm  30  therefore pivots under the influence of the spring  31  until its other end protuberance  76  has pivotted to the position shown in  FIGS. 12 and 13 . As best shown in  FIG. 13 , when the rocker arm  30  is in this position, the first end protuberance  76  will abut a boss  82  on the cover plate  14  when the bolt  18  is attempted to be forced back into the housing  12 , in the direction of arrow  84 . Such movement of the bolt  18  is as would be experienced if an illegal opening of the lock  2   a  was attempted. This abutment  82  stops the latch bolt  18  from being retracted and thus stops the door from being opened. 
     FIGS. 14 and 15  show the lock  2   a  before door closure. As the auxiliary bolt  26  is able to extend to the same extent as the latch bolt  18 , the protuberance  80  abuts, and causes pivotable movement of, the second end protuberance  78  of the rocker arm  30  against the influence of the spring  31 . This pivotable movement of the rocker arm  30  causes its other end protuberance  76  to pivot to the position shown in  FIGS. 14 and 15 . As best shown in  FIG. 15 , when the rocker arm  30  is in this position the first end protuberance  76  clears the boss  82  on the cover plate  14  as the bolt  18  is forced back into the housing  12 , in the direction of arrow  84 , as would be experienced during a slam door closure. 
   The primary advantage of the deadlatching rocker arm  30  being pivotally mounted to the bolt assembly  17  is best described with reference to  FIGS. 16 and 17 .  FIG. 16  shows the lock  2   a  configured for a (standard) 23 millimetre backset (backset being the distance between the outside of the cover plate and the centre line of the hubs/actuation shafts). A 23 millimetre backset is suitable for an aluminium framed door.  FIG. 17  shows an almost identical lock  2   b  configured for use with a (standard) 60 millimetre backset, which is suitable for a standard timber door. Importantly, such a change can be simply achieved by the addition of two very simple extension pieces  86  and  88  to the bolt  18  and the auxiliary bolt  26  respectively, and the addition of a spacer block (not shown) to the housing  12 . Alternatively, longer versions (not shown) of the bolt  18  and auxiliary bolt  26  can be substituted. Also, larger versions (not shown) of the housing  12  and the cover  14  can be used to obviate the need for the spacer block. All other components of the lock  2   b  remain unmodified. Accordingly, the lock  2   a  can be easily configured for many different backsets with only very minimal componentry changes, thereby obviating the need for specific lock designs for specific applications and reducing development and inventory costs. 
   Also advantageous is that the bolt  18  in the lock  2   a  is able to be retracted, for door opening, by rotation of either exterior handle in either direction, as will now be described with reference to  FIGS. 18 to 28 . As best seen in  FIGS. 18 to 20 , the hub  34  has a pair of protuberances, in the form of angularly spaced apart shoulders  90  and  92 , and the drive rack  40  has a pair of formations, in the form of corresponding ledges  94  and  96 . The drive rack  40  also has an engaging surface, in the form of gear rack  98  (see  FIG. 2 ). The rack  98  engages with pinion gears  100  on the latch bolt retraction arm  44  (see also  FIG. 2 ). The drive rack  40  is biased in the direction of arrow  102  by the spring  42 , which in turn biases the hub  34  into the (first) position shown in  FIG. 18 . 
   If the exterior handle (not shown) is turned to rotate the hub anti-clockwise, as shown in  FIG. 19  the first shoulder  90  engages the first ledge  94  and drives the drive rack  40  in the direction of arrow  104  against the action of the spring  42 . As the retraction arm  44  is mounted for pivotable movement only, the (downward) movement of the gear rack  98  on the drive rack  40  causes the latch bolt retraction arm  44  to pivot in an anti-clockwise direction If the exterior handle (not shown) is turned to rotate the hub  34  in a clockwise direction, as shown in  FIG. 20  the second shoulder  92  engages the second ledge  96  which also drives the drive rack  40  in the direction of arrow  104  and causes counter-clockwise pivotable movement of the retraction arm  44 , as previously described. 
   The retraction of the latch bolt  18  by the latch bolt retraction arm  44  will now be described with reference to  FIGS. 21 to 24 , which correspond to the partial views shown in  FIGS. 25 to 28  respectively.  FIGS. 21 and 22  (see also  FIGS. 25 and 26 ) show the latch bolt  18  in an extended position and deadlatched. As has been previously described, the initial pivotable movement of the rocker arm  44  causes its distal end  106  to abut the first end protuberance  76  of the deadlatching rocker arm  30  and drive it from the deadlatching position to the opening position (see  FIGS. 23 ,  24 ,  27  and  28 ). As the rocker arm  30  is moved to the opening position, the distal end of the retraction arm  44  also abuts a boss  108  provided on the bolt carrier  20  and further anti-clockwise pivotable movement of the retraction arm  44  retracts the latch bolt  18  into the bolt casing  12  (see  FIG. 23 and 24 ). 
   It is advantageous for bolt retraction to be achievable with handle rotation in either direction, especially when the actuation handles are knobs. Further, when this handle operation is coupled with the re-handing ability of the latch bolt described above then a single lock is provided that is suitable for use in all installations regardless of inside/outside/left hand opening/right hand opening. 
   The operation of the cylinder cam bolt retraction bar  56  will also be described with reference to  FIGS. 21 to 24 . The bar  56  has a first end tab  110  which is received in a slot  112  in the drive rack  40 . The other end of the bar  56  has a second end tab  114 . The cam  8  of the first key, cylinder  4  abuts the second end tab  114  when initially rotated in an anti-clockwise direction. Further rotation of the cam  8  in the anti-clockwise direction drives the bar  56 , and thus the drive rack  40 , in the direction of arrow  104 . The movement of the drive rack  40  is identical to that caused by rotation of the hub  34 , as previously described, and causes the latch bolt retraction arm  44  to similarly retract the bolt  18  for door opening, as also previously described. 
   The advantages of this arrangement are two-fold. Firstly, when the cams  8  and  10  are used (see  FIGS. 2 and 4 ), regardless if the lock is locked or unlocked a closed door can be operated single handedly (ie. if unlocked—turn only key or turn only handle, if locked—turn only key). However, the cams  8  and  10  can also be shortened so they cause movement of only the locking bar  52  when unlocking or locking the lock  2 , thereby is requiring independent movement of the cylinder cam bolt retraction bar  56  to open an unlocked or closed door. Secondly, as the key cylinder cams  8  and  10  act with common componentry to that of the handle, the overall number of components in the lock  2   a  is reduced thereby simplifying manufacture and assembly. 
   The operation of the kick off lever  54  will now be described in more detail with reference to  FIGS. 29 to 40 . The kick off lever  54  has small and large stub shafts  116  and  118  respectively on its distal end. The shafts  116 ,  118  are pivotally received in corresponding recesses  120  (see  FIG. 2) and 122  (see  FIG. 4 ) provided in the lock housing  12  and lock housing cover  14  respectively. The lever  54  thus pivots about the shafts  116 ,  118  with respect to the lock housing  12  and the cover  14 . The bolt carrier retaining insert  24  has a drive boss  124  adjacent the lever  54  which itself has a drive boss  126 . The lever  54  also has a detent  128 , which travels within a slot  130  (see  FIG. 4 ) in the lock housing cover  14 , that is biased to either end of the slot  130 . The middle of the lever  54  has a raised portion with a slot  132  therein. When assembled, the slot  132  is accessible through an opening  134  (see  FIG. 2 ) in the lock housing cover  14 . A screw driver or like tool can be inserted through the opening  134  into the slot  132  and used to position the kick off lever  54  in a (inactive) position in which the detent  128  is held in the top of the slot  130  or a (active) position in which the detent  54  is held lower in the slot  130  (see  FIGS. 37 to 40 ). The distal end of the lever  54  also includes a shoulder  136  which protrudes into a recess  138  in the locking bar  52 . The recess  138  has a lower tab  139 . The locking bar  52  can be linked for movement with the first and second hub locking sliders  46  and  50  for locking and unlocking the lock  2 , as will be described in more detail below. For present purposes it is sufficient to say that driving the locking bar  52  in the direction of arrow  140  can unlock the lock  2 . 
     FIGS. 29 ,  30 ,  33  and  34  show the kick off lever  54  in the inactive position. During closure of a door, the bolt  18  rides over the strikeplate and is moved from an extended position ( FIGS. 29 and 33 ) to a retracted position (see  FIGS. 30 and 34 ). During this movement the drive boss  124  on the bolt carrier retaining insert  24  slides beneath the drive boss  126  on the lever  54  without any driving contact being made therebetween. Accordingly, this movement does not affect the position of the kick off lever  54  or the locking bar  52  and, when the kick off lever  54  is in the inactive position, closure of the door will not unlock the door. When the kick off lever  54  is in the active position ( FIGS. 31 ,  32 ,  35  and  36 ) then closing of the door as previously described causes the drive boss  124  to abut the lever drive boss  126  and pivot the lever  54  such that the shoulder  136  pivots in the direction of the arrow  140 . This causes the shoulder  136  to engage the recess tab  139  and drive the locking bar  52  in the direction of arrow  140 , thereby altering the lock  2   a  from locked to unlocked. 
   Placing the kick off lever  54  in the active position therefore provides a safe guard against inadvertent locking of the door upon closure. An advantage provided by the kick off lever  54  is that it operates in conjunction with a component of the lock used for other purposes (ie. the locking bar) thereby reducing the number of components and the production and assembly cost of the lock overall. 
   A more detailed explanation of the operation of the locking bar  52  will now be given with reference to  FIGS. 41 to 48 . As best seen in  FIGS. 41 and 42 , the locking bar  52  has a pair of upper recesses  142 . Each of the first and second hub locking sliders  46 ,  48  have a slotted recess  143  which receives one of the locking bar engagers  49 ,  50  therein. The engagers  49 ,  50  have a slot  144  which is accessible through an opening  146  in the lock housing  12  and cover  14  respectively. A screw driver or like tool can be inserted into the openings  146  to set the engagers  49 ,  50  in an engaged position in which an end of the engagers  49 ,  50  is received within one of the slots  142  (see  FIGS. 43 and 44 ) or a disengaged position in which the engagers  49 ,  50  do not enter the recess  142  (see  FIGS. 45 and 46 ). The engager&#39;s  49 ,  50  are held in either of the engaged or disengaged positions by their other end engaging one of two detent slots  148  (see  FIGS. 44 and 46 ) in the hub locking sliders  46 ,  48 . The other end of the locking bar  52  has an angled tab  1148 . 
   The engagers  49 , 50  each also have a protuberance  49   a , 50   a  respectively, which are each received in a L-shaped recess  149  in each of the locking housing  12  and lock housing cover  14 , as will be explained in more detail below. 
   When the (short version) cylinder cam  8  is driven in the counter-clockwise direction past the position shown in  FIG. 23 , it initially abuts the angled tab  1148 . Further anti-clockwise movement forces the locking bar  52  in the direction of arrow  150 . If either of the locking bar engagers  49  and  50  are set in the engaged position (see  FIGS. 43 ,  44  and  47 ) then such movement of the locking bar  52  will cause corresponding movement in the associated hub locking sliders  46 ,  48 . During this movement, the engager&#39;s protuberances  49   a ,  50   a  travel within the longer arm of one of the L-shaped recesses  149 . Each of the sliders  46 ,  48  also have a recess  152  which corresponds to the protuberance  154  on each of the hubs  32 ,  34  (see  FIGS. 2 and 4 ). Accordingly, driving the locking bar  52  and any engaged hub locking sliders  46 ,  48  also drives the associated recess  152  over the protuberance  154  which prevents rotation of the hub  32 ,  34  and locking of the door. It is important to note that the engagers  49 ,  50  are independently settable so as to allow the lock operator to set from which side or both the door may be locked. It is also important to note that the hubs  32 , 34  operate in both turning directions and that the engagement of the recesses  152  and the protuberances  154  also locks the hubs  32 , 34  against rotation in both directions. 
   When either of the engagers  49 ,  50  is set to the disengaged position (see  FIGS. 45 ,  46  and  48 ) then the key movement previously described will cause movement of the locking bar  52  in the direction  150  relative to the stationary hub locking slider  46  or  48 . Accordingly, the recess  152  shall remain free of the protuberance  154  and allow movement of the associated hub  32 ,  34  and unlocking of the door from that side. In this position, the engager&#39;s protuberances  49   a , 50   a  each remain in the shorter arm of one of the L-shaped recesses  149 . 
   The main advantage of this engager arrangement is that the engagers travel only as much as the locking bar and thus, in either position, do not add to the overall length of the locking bar and its associated components, as with known mortice locks. This reduces the space needed for the lock componentry and allows production of a smaller lock. Further, when the engagers  49 , 50  are set in the disengaged position, no movement is caused in the sliders  46 , 48  thereby reducing the number of moving parts in the lock  2   a  and associated friction. 
     FIGS. 49 to 92  show a second embodiment of a mortice lock  2   c  which includes examples of the five aspects of the invention. The lock  2   c  functions similar to the lock  2   a  and like reference numerals to those used in describing the lock  2   a  shall be used to indicate like or similar features with respect to the lock  2   c.    
   Tuning firstly to  FIGS. 49 to 53  the lock  2   c  includes first and second key cylinders  4  and  6  that each have associated cams  8  and  10 . The first key cylinder  4  is mounted to a lock housing  12  by a pin  13  and a second key cylinder  6  is mounted to a lock housing cover  14  by a pin  15 . A fore-end plate  16  is also mounted to the lock housing  12 . 
   The lock  2   c  includes a bolt assembly  17  (see  FIGS. 53 to 55 ) comprised of a latch bolt  18 , a bolt carrier  20  with an associated bolt spring  22 . The lock  2   c  also includes an auxiliary bolt assembly  226 , with an auxiliary bolt  26  and an auxiliary bolt carrier  27 , the latter being associated with an auxiliary bolt spring  28 . A deadlocking member, in the form of deadlatching pivot arm  30 , is pivotally mounted to the bolt assembly  17 , more particularly to the bolt carrier  20  as will be described in more detail below. The pivot arm  30  has an associated torsion spring  31 . 
   The lock  2   c  also includes external handles such as knobs or levers (not shown) which are connected to a pair of conventional square cross-section drive shafts (not shown) which are in turn connected to first and second hubs  32  and  34 . More particularly, each of the hubs  32 ,  34  has a corresponding square cross-section aperture  36  for non-rotationally engaging each one of the drive shafts to transmit rotational movement from one of the handles to an associated one of the hubs  32 ,  34 . 
   The lock  2   c  also includes a drive means and a bolt retraction assembly, that are incorporated into a latch bolt retraction member  244  as will also be described in more detail below. 
   The lock  2   c  also includes a pair of hub rotation locking means, in the form of first and second hub locking sliders  46  and  48 , that each have an associated engagement means, in the form of first and second locking bar engagers  49  and  50 . The locking bar engagers  49 ,  50  can each be set in one of two positions in which an associated hub locking slider  46  and  48  respectively does, or does not, travel with movement of a locking bar  52 , as will also be described in more detail below. 
   The lock  2   c  also includes a kick-off actuation member, in the form of kick-off block  54 , a cam pivot link  254  and a cylinder cam bolt retraction bar  56 , the operation of which will also be described in more detail below. 
   The features and operation of the deadlatching assembly will now be described in more detail with reference to  FIGS. 53 to 63 . As best seen in  FIG. 53 , the bolt carrier  20  includes a cylindrical recess  62  which corresponds to, and receives therein, a similar shaft  66  extending from the latch bolt  18 . The latch bolt  18  is retained adjacent the carrier  20  by a circlip  266 . The auxiliary latch bolt  26  is retained adjacent the auxiliary bolt carrier  27  by a circlip  366 . This allows the latch bolt  18  and the auxiliary latch bolt  26  to be rotated about their longitudinal axes, as indicated by the double headed arrow  68 , for easy re-handing of the lock  2   c . The carrier  20  has another cylindrical recess  72  which corresponds to cylindrical portion  74  (see  FIG. 52 ) on the dead latching pivot arm  30 . This allows the pivot arm  30  to pivot between a deadlatching position (see  FIG. 54 ,  55 ,  57 ,  58  and  59 ) and an opening position (see  FIGS. 54 ,  60  and  61 ). The pivot arm  30  is biased to the deadlatching position by the torsion spring  31 . The pivot arm  30  also has first, second and third protuberances  76 ,  78  and  79  respectively. The protuberance  78  operatively engages with a protuberance  80  on the auxiliary bolt carrier  27 . 
     FIGS. 58 and 59  show the latch bolt  18  in an extended position, as would occur after closure of a door. During a slam door closing action, the bolt  18  initially retracts as it travels over a strikeplate (not shown) and then it extends under the influence of the spring  22  into the latch bolt opening present in a conventional strikeplate. As the strikeplate does not have an opening that corresponds to the auxiliary bolt  26 , the auxiliary bolt  26  is not able to extend as far as a latch bolt  18  when the door is closed. This results in the protuberance  80  abutting, and causing pivotal movement of, the second protuberance  78  of the pivot arm  30 , as described above. This pivotal movement of the pivot arm  30  causes the first protuberance  76  to pivot to the position shown in  FIG. 58 and 59 . As best shown in  FIG. 59 , when the pivot arm  30  is in this position the first protuberance  76  abuts a boss  82  on the cover plate  14  when the bolt is attempted to be forced back into the housing  12 , in the direction of arrow  84 . Such movement of the bolt  18  is as would be experienced if an illegal opening of the lock  2   c  was attempted. The boss  82  stops the latch bolt  18  from being retracted and thus stops the door from being opened. 
     FIGS. 60 and 61  show the lock  2   c  before door closure. As the auxiliary bolt  26  is able to extend to the same extent as the latch bolt  18 , the protuberance  80  abuts, and causes pivotable movement of, the second protuberance  78  of the rocker arm  30  against the influence of the spring  31 . This pivotable movement of the rocker arm  30  causes the first protuberance  76  to pivot to the position shown in  FIGS. 60 and 61 . As best shown in  FIG. 61 , when the rocker arm  30  is in this position the first end protuberance  76  clears the boss  82  on the cover plate  14  as the bolt  18  is forced back into the housing  12 , in the direction of arrow  84 . Such movement of the bolt  18  is as would be experienced during a slam door closure. 
   The primary advantage of the deadlatching pivot arm  30  being pivotally mounted to the bolt assembly  17  is best described with reference to  FIGS. 62 and 63 .  FIG. 62  shows the lock  2   c  configured for a (standard) 23 mm backset. A 23 mm backset is suitable for an aluminium frame door.  FIG. 63  shows an almost identical lock  2   d  configured for use with a (standard) 60 mm backset which is suitable for a standard timber door. Importantly, such a change can be simply achieved by the addition of two very simple extension pieces  86  and  88  to the bolt  18  and the auxiliary bolt  26  respectively, and the use of an extended housing  12   a  Alternatively, longer versions (not shown) of the bolt  18  and auxiliary bolt  26  can be substituted. All other components of the lock  2   c  remain unmodified. Accordingly, the lock  2   c  can be easily configured for many different backsets with only very minimal componentry changes, thereby obviating the need for specific lock designs for specific applications and reducing development and inventory costs. 
   Also advantageous is that the bolt  18  in the lock  2   c  is able to be retracted, for door opening, by rotation of either exterior handle in either direction, as will now be described with reference to  FIGS. 64 to 70 . As best seen in  FIGS. 64 to 66 , the hub  34  has a pair of angularly spaced apart protuberances  90  and  92  and the latch bolt retraction member  244  has a pair of corresponding formations  94  and  96 . The latch bolt retraction member  244  is biased in the direction of arrow  202  by the spring  42 , which in turn biases the hub  34  into the (first position) shown in  FIG. 64 . 
   If the exterior handle (not shown) is turned to rotate the hub anticlockwise, as shown in  FIG. 66 , the first protuberance  90  engages the first formation  94  and pivots the latch bolt retraction member  244  in the opposite direction of arrow  202  and against the action of the spring  42  as the retraction arm  244 . If the exterior handle (not shown) is turned to rotate the hub  34  in a clockwise direction, as shown in  FIG. 65 , the second protuberance  92  engages the second formation  96  which also causes counter clockwise pivotal movement of the retraction arm  244 , as previously described. 
   The retraction of latch bolt  18  by the latch bolt retraction arm  44  will now be described with reference to  FIGS. 67 to 70 .  FIGS. 67 and 68  show the latch bolt  18  in an extended and deadlatched position. As has been previously described, the initial pivotal movement of the rocker arm  244  causes its distal end  106  to abut the third protuberance  79  of the deadlatching pivot arm  30  and drive the pivot arm  30  from the deadlatching position to an opening position. As the pivot arm  30  is moved to the opening position, the distal end of the retraction arm  244  also abuts a boss  108  provided on the bolt carrier  20  and further anticlockwise pivotal movement (see  FIGS. 69 and 70 ) of the retraction arm  244  retracts the latch bolt  18  into the bolt casing  12 . 
   It is advantageous for bolt retraction to be achievable with handle rotation in either direction, especially when the actuation handles are knobs. Further, when this handle operation is coupled with the re-handing ability of the latch bolt described above then a single lock is provided that is suitable for use in all installations regardless of inside/outside/left hand opening/right hand opening. 
   The operation of the retraction bar  56  will now be described with reference to  FIGS. 71 to 73 , which show the lock  2   c  with a “short” version of the cam  8  that has external gears  208 . The bar  56  has a first end tab  110  which engages a camming member  210  which is pivotally mounted to the lock cover  14 . The other end of the bar  56  has an opening  212  which engages with a spigot  214  provided on the retraction member  44 . When a key is inserted to the cylinder  4  and rotated, corresponding rotation is caused in the cam  8  which causes it to initially engage the cam member  210  (see  FIG. 72 ). Continued rotation of the cam  8  causes the cam member  210  to rotate to the position shown in  FIG. 73  which causes corresponding downward movement in the retraction bar  56 . This movement of the retraction bar  56  causes the retraction member  244  to pivot in an anticlockwise direction such that the distal end  106  of the retraction arm  244  abuts the boss  108  provided on the bolt carrier  20  and retracts the latch bolt  18  into the bolt casing  12 , in the manner previously described. The movement of the cam  8  does not influence the position of the cam pivot link  254 . Accordingly, the short cam is only able to retract the latch bolt. It cannot lock or unlock the locking bar. 
   The advantages of the short cam arrangement is the key cylinder cams  8  and  10  have a common component to that of the handle the overall number of components in the lock  2   c  is reduced thereby simplifying manufacture and assembly. 
   The operation of the locking bar  52  and the retraction bar  56  will now be described with reference to  FIGS. 74 to 77 , which show the lock  2   c  with a “medium” version of the cam  8  that has external gears  208  and a medium length finger  308 .  FIG. 74  shows the finger  308  rotated to a position that pivots the cam pivot link  254  anti-clockwise. This causes upward movement in the locking bar  52  that results in the lock  2   c  being locked, as will be described below.  FIG. 75  shows the finger  308  rotated to a position that pivots the cam pivot link  254  clockwise. This causes downward movement in the locking bar  52  that results in the lock  2   c  being unlocked, as will be described below.  FIG. 76  shows the finger  308  further rotated to a position that pivots the cam  8  such that the gears  208  initially engage the cam member  210 . Continued rotation of the cam  8  causes the cam member  210  to rotate to the position shown in  FIG. 77  which causes corresponding downward movement in the retraction bar  56 . This movement of the retraction bar  56  causes the retraction member  244  to pivot in an anticlockwise direction such that the distal end  106  of the retraction arm  244  abuts the boss  108  provided on the bolt carrier  20  and retracts the latch bolt  18  into the bolt casing  12 , in the manner previously described. 
   The advantages of the medium cam arrangement are two-fold. Firstly, regardless if the lock is locked or unlocked a closed door can be operated single handedly (ie. if unlocked—turn only key or turn only handle, if locked—turn only key). Secondly, as the key cylinder cams  8  and  10  have a common component to that of the handle the overall number of components in the lock  2   c  is reduced thereby simplifying manufacture and assembly. 
   The operation of the locking bar  52  will now be described with reference to  FIGS. 78 to 80 , which show the lock  2   c  with a “long” version of the cam  8  that has long length finger  408 .  FIG. 78  shows the finger  408  in a neutral position where it does not engage the cam pivot link  254 .  FIG. 79  shows the finger  408  rotated to a position that pivots the cam pivot link  254  clockwise. This causes downward movement in the locking bar  52  that results in the lock  2   c  being unlocked, as will be described below.  FIG. 80  shows the finger  408  rotated to a position that pivots the cam pivot link  254  anti-clockwise. This causes upward movement in the locking bar  52  that results in the lock  2   c  being locked, as will be described below. Accordingly, the long cam  8  is only able to lock or unlock the locking bar. It cannot retract the latch bolt. 
   The advantages of the long cam arrangement is, as the key cylinder cams  8  and  10  have a common component to that of the handle, the overall number of components in the lock  2   c  is reduced thereby simplifying manufacture and assembly. 
   By configuring each side of the lock  2   c  with appropriate short, medium or long cams, the lock  2   c  can be customised for different applications and access requirements. 
   The operation of the kick-off block  54  will now be described in more detail with reference to  FIGS. 81 to 84 . The block  54  pivots about shaft  74 , which is received within a corresponding recess in the bolt carrier  20 . The block  54  has a detent  228  which engages one of two corresponding detents  230  in the bolt carrier  20 . The block also includes a slot  232  which, after assembly, is accessible through an opening  234  (see  FIGS. 82 and 84 ) in the lock cover housing  14 . A screwdriver or like took can be inserted through the opening  234  into the slot  232  and used to position the kick-off block  54  in an inactive position (as shown in  FIGS. 81 and 82 ) or an active position (as shown in  FIGS. 83 and 84 ). The cam pivot link  254  has three portions  254   a ,  254   b  and  254   c . The portion  254   c  is positioned towards the kick-off block  54  and is also engaged with the locking bar  52 . The locking bar  52  can be linked for movement with the first and second hub-locking sliders  46  and  50  for locking and unlocking the lock  2   c , as will be described in more detail below. For present purposes is sufficient to say that driving the locking bar  52  in the direction of arrow  140  can unlock the lock  2   c.    
     FIGS. 81 and 82  show the kick-off block  54  in the inactive position. During closure of the door, the bolt  18  rides over the strikeplate and is moved from an extended position to a retracted position. During this movement the kick-off block  54  slides over the cam pivot link portion  254   c  without any driving contact being made therebetween. Accordingly, this movement does not affect the position of the kick-off block  54  or the cam pivot link  254  or the locking bar  52 . Therefore, when the kick-off lever  54  is in the inactive position, closure of the door will not unlock the lock  2   c.    
   When the kick-off block  54  is in the active position (see  FIGS. 83 to 84 ) then closing of the door as previously described causes the drive block to contact the cam pivot link portion  254   c . Further retraction of the bolt  18  results in the cam pivot link  254  being pivoted in an anticlockwise direction to position shown in  FIG. 86 . This causes the locking bar  52  to be driven in the direction of arrow  140 , thereby altering the lock  2   c  from locked to unlocked. 
   Placing the kick off block  54  in the active position therefore provides a safe guard against inadvertent locking of the door upon closure. An advantage provided by the kick off block  54  is that it operates in conjunction with components of the lock used for other purposes (ie. the locking bar and the cam pivot link) thereby reducing the number of components and the production and assembly cost of the lock overall. 
   A more detailed explanation of the operation of the locking bar  52  will now be given with reference to  FIGS. 87 to 92 . As best seen in  FIGS. 87 and 88 , the locking bar  52  has a pair of upper recesses  142 . Each of the first and second hub locking sliders  46 ,  48  have a slotted recess  143  which receives one of the locking bar engagers  49 ,  50  therein. The engagers  49 ,  50  have a tab  144  which is accessible through an opening  146  in the lock housing  12  and cover  14  respectively. A screw driver or like tool can be inserted into the openings  146  and push the tab  144  to set the engagers  49 ,  50  in an engaged position in which an end of the engagers  49 ,  50  is received within one of the slots  142  (see  FIGS. 89 and 90 ) or a disengaged position in which the engagers  49 ,  50  do not enter the recess  142  (see  FIGS. 91 and 92 ). The engagers  49 ,  50  are held in either of the engaged or disengaged positions by legs  49   b  and  50   b  engaging one of two detent slots  148  (see  FIGS. 90 and 92 ) in the hub locking sliders  46 ,  48 . The other end of the locking bar  52  has an angled tab  1148 , which engages a complimentary slot in the cam pivot link  254 . 
   The engagers  49 , 50  each also have a protuberance  49   a , 50   a  respectively, which are each received in a L-shaped recess  149  in each of the locking housing  12  and lock housing cover  14 , as will be explained in more detail below. 
   When the pivot cam link  254  is driven anti-clockwise, as described above, the locking bar  52  (which is connected thereto) is forced in the direction of arrow  150 . If either of the locking bar engagers  49  and  50  are set in the engaged position (see  FIGS. 89 and 90 ) then such movement of the locking bar  52  will cause corresponding movement in the associated hub locking sliders  46 , 48 . During this movement, the engager&#39;s protuberances  49   a ,  50   a  travel within the longer arm of one of the L-shaped recesses  149 . Each of the sliders  46 ,  48  also have a recess  152  which corresponds to the protuberance  154  on each of the hubs  32 ,  34  (see  FIGS. 50 and 52 ). Accordingly, driving the locking bar  52  and any engaged hub locking sliders  46 ,  48  also drives the associated recess  152  over the protuberance  154  which prevents rotation of the hub  32 ,  34  and locking of the door. It is important to note that the engagers  49 ,  50  are independently settable so as to allow the lock operator to set from which side or both the door may be locked. It is also important to note that the hubs  32 , 34  operate in both turning directions and that the engagement of the recesses  152  and the protuberances  154  also locks the hubs  32 , 34  against rotation in both directions. 
   When either of the engagers  49 ,  50  is set to the disengaged position (see  FIGS. 91 and 92 ) then the movements previously described will cause movement of the locking bar  52  in the direction  150  relative to the stationary hub locking slider  46 , 48 . Accordingly, the recess  152  shall remain free of the protuberance  154  and allow movement of the associated hub  32 ,  34  and unlocking of the door from that side. In this position, the engager&#39;s protuberances  49   a , 50   a  each remain in the shorter arm of one of the L-shaped recesses  149 . 
   The main advantage of this engager arrangement is that the engagers travel only as much as the locking bar and thus, in either position, do not add to the overall length of the locking bar and its associated components, as with known mortice locks. This reduces the space needed for the lock componentry and allows production of a smaller lock. Further, when the engagers  49 , 50  are set in the disengaged position, no movement is caused in the sliders  46 , 48  thereby reducing the number of moving parts in the lock  2   c  and associated friction. 
   The embodiments of the locks described above possess many specific advantages arising from the numerous inventive aspects of particular componentry. However, the locks are also generally advantageous over those of the prior art due to their reduced componentry and simplicity. 
   Although the invention has been described with reference to a specific examples, it will be appreciated with those skilled in the art that the invention may be embodied in many other forms. Further, many components have only been described with reference to one side of the locks and the skilled person will also appreciate that the same components on the other side of the locks operate in a similar manner.