Patent Publication Number: US-2007101776-A1

Title: Mortice lock

Description:
This invention concerns mortice locks of the type including a deadbolt which is retained within a lock case and movable between an unlocking position wherein the deadbolt is disposed within the lock case, and a locking position in which it extends outwardly from a fore-end thereof.  
      The invention is particularly concerned with providing a mortice lock of this kind wherein the “throw” of the deadbolt from the front or fore-end of the casing is as much as 20 mm within a standard lock case of 63.5 mm (nominal).  
      Conventionally, it has not been possible to construct a lock of this size with a 20 mm bolt throw using a mechanism which both extends and retracts the deadbolt in a positive manner and prevents the bolt from being pushed back manually from its outermost locking position.  
      In locks of this kind there is usually provided a rotary driving mechanism which may be a key, a key cam or a cylinder cam which makes contact with the deadbolt to extend and retract it during rotation of the driving mechanism. In order to ensure the maximum throw of the bolt head the driving mechanism should maintain contact with the deadbolt throughout its movement, yet allow the bolt to pass over the axis of rotation of the driving mechanism when the bolt is retracted.  
      According to the present invention there is provided a mortice lock including a deadbolt retained within a lock case and movable between an unlocking position wherein the deadbolt is disposed within the lock case, and a locking position in which it extends outwardly from a fore-end thereof, and a driving mechanism rotatable about an axis transverse to the direction of movement of the deadbolt and having a cam which connects with and moves the deadbolt between said positions; characterised by at least one contact member mounted on and movable with respect to the deadbolt between a first position in which the contact member maintains contact with the driving member to effect a full throw of the deadbolt in one direction, and a second position to enable a full throw of the deadbolt in an opposite direction.  
      The driving member may be a key.  
      The driving member may be cylinder cam.  
      The driving member may be a key cam associated with multiple levers.  
      Two contact members may be mounted on the deadbolt one of which maintains contact with the driving member throughout movement of the deadbolt into the locking position, the other maintaining contact with the driving member throughout movement of the deadbolt into the unlocking position.  
      Each contact member may be movable into a position in which it prevents movement of the deadbolt.  
      The or each contact member may have a cam follower residing in a track in the lock case, the track being formed to effect movement of the contact member between its first and second positions.  
      The deadbolt may, in its locking position, extend from the fore-end of the lock case by 20 mm. 
    
    
      Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:— 
       FIG. 1  is an exploded view of a mortice lock made in accordance with a first embodiment of the invention; and  
      FIGS.  2  to  12  illustrate the lock of  FIG. 1  assembled and showing progressive movement of the lock mechanism between an unlocking and a locking position of a deadbolt being part of the lock. 
    
    
      Referring now to  FIG. 1 , the mortice lock comprises a lock case  10 ,  11  having a for-end plate  12  with apertures  13  and  14  through which extend a latch  15  and a deadbolt  16  respectively.  
      Within the lock case  10 ,  11 , in this example, is a cylinder lock  17  having a driving member in the form of a rotatable cam  18  which rotates about the axis of a barrel  19  which is turned by a key inserted into a slot  20 .  
      A pair of contact members  21 ,  22  are slidably mounted on the deadbolt  16  having pins  23  and  24  respectively, which permit limited vertical movement within slots  25  and  26  respectively in the deadbolt  16 . A dummy lever  27  moves horizontally within the lock case along with deadbolt  16  and has a pin (not shown) which rides in a horizontal track  28  in the lock case  10 . The pins  23  and  24  are also constrained to ride in a curved track  31  as will be described.  
      The latch  15  mounted on a latch pin  29  together with appropriate springs, is normally retained in a position extending outwardly from apertures  13  but is retracted within the casing during closure of a door in which the lock is inserted. The latch mechanism itself forms no part of the present invention, being of a standard design.  
      A spring  30  urges the sliding contact members  21  and  22  in a downwards direction in relation to deadbolt  16  during operation of the lock.  
      Referring now to  FIG. 2 , it will be seen that the dead lock  16  is in its unlocking position wholly contained within the lock casing  10 ,  11  but with its forward end substantially flush with the front of the fore-end plate  12 . In this position the cam  18  is in a fully unlocking position and is in contact with a lower region of the sliding contact member  22  which itself is in a lowermost position with respect to the deadbolt  16 .  
      In this position, the other sliding contact member  21  is in its uppermost position with respect to the deadbolt  16  and is thus located overhead of the body of the cylinder cam  17 .  
      Referring now to  FIG. 3 , as the cam  18  is rotated in an anti-clockwise direction in the drawing, it leaves contact with sliding contact member  22  then making contact with the lower region of the sliding contact member  21 .  
      Referring now to  FIG. 4  with continued rotational movement of the cam  18  it pushes the sliding contact member  21  towards the left hand side of  FIG. 3  thus starting to advance the deadbolt  16  from the casing. Thus, the pin  24  of sliding contact member  22  commences its travel upwardly in the track  31  whereby the member  22  starts to rise.  
       FIG. 5  shows the sliding contact member  22  in a further elevated position while cam  18  continues to push against sliding contact member  21  to advance the deadbolt  16  further from the casing.  
      Referring now to  FIG. 6  it will be seen that the sliding contact member  22  has reached its maximum height with the pin  24  at the highest point of the track  31 , and in this position the sliding contact member  21  is starting to descend constrained by the track  31  while the bolt  16  continues to advance from the casing.  
       FIG. 7  shows the position of maximum extension of the deadbolt  16 . This extension is 20 mm in the present example as required by the design of this mortice lock in a standard 63.5 mm casing. The extended throw to 20 mm is provided by continuous contact between the cam  18  and the then lowered sliding contact member  21 . It will be seen also that in this position the sliding contact member  22  is at its maximum height and has therefore been permitted to ride over the top of the cylinder cam  17 .  
      Contact of the cam  18  with the bottom of the sliding contact member  21  prevents the deadbolt  16  from being pushed back into the casing so that the 20 mm throw is maintained.  
      Referring now to  FIG. 8 , it will be seen that if the cam  18  is allowed to rotate even further in an anti-clockwise direction thus to move out of contact with the sliding contact member  21 , nevertheless, the bolt cannot be pushed back very far because the sliding contact member  21  would then come into contact with the top of the body of the cylinder cam  17 .  
      Referring now to  FIG. 9 , it will be seen that as the cam  18  is rotated in the clockwise direction it comes into contact with the lower end of the sliding contact member  22  to commence retracting of the deadbolt  16 .  
       FIG. 10  shows a continuation of this movement whereupon the sliding contact member  21  rises to a point where, in  FIG. 11 , it may pass over the top of the body of the cylinder cam  17 . Also in that position, the sliding contact member  22  is beginning to descend towards its lowermost position, and in  FIG. 12  it is shown in that position such that the cam  18  will continue to push back the bolt  16  into its fully retracted position once again as shown in  FIG. 12 . Thus the parts are returned to their respective positions as illustrated in  FIG. 2 .  
      The spring  30  which locates over a pin  32  in the casing  10  bears against the upper edge of dummy lever  27  to urge the sliding contact members  21  and  22  into their lowermost positions. However, the sliding members are permitted to rise by pushing against the spring  30  when constrained by the track  31 .  
      It will be appreciated that a mortice lock made in accordance with the invention ensures a maximum bolt throw by maintaining a connection between the driving mechanism and the bolt for a maximum extent of rotation of the driving mechanism, while allowing the bolt, or parts connected thereto, to rise and thus pass over the body of the driving mechanism. The arrangement further provides that the bolt cannot be pushed back when in any of its positions of extension from the lock case.  
      The cylinder cam  17  may be replaced by a multiple lever assembly as required for three, five or seven lever locks which provide additional security. In such an arrangement, the cam  18  is replaced by a key cam which receives the forward end of the key and is rotated by it.  
      In a simplified embodiment a key itself may advance and retract the deadbolt by direct contact with the sliding contact members  21  and  22 .  
      The contact members may be rotatably or otherwise movable with respect to the bolt  16  thus to extend the range of contact between the cam  18  and the bolt  16 , to provide the extended bolt throw in accordance with the invention.  
      The contoured track  31  in the casing may be replaced by wedges or other abutment means mounted in the casing and contacted by the contact members.