Abstract:
A door latch arrangement ( 10 ) includes a latch bolt ( 12 ) releasably retainable in a closed position by a pawl ( 14 ). The pawl is connected to an inside release member ( 26 ) by a first transmission path ( 28 ). The first transmission path is interruptible by operation of a first actuator ( 32 ). The pawl is further connected to an outside release member ( 16 ) by a second transmission path ( 18 ), the second transmission path being interruptible by operation of a second actuator ( 22 ). The door latch arrangement further includes a detection device for detecting when the inside release member is operated. The first and second actuators are controlled by a control device ( 36 ), operable in response to signals from the detection device to provide for override unlocking.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority to United Kingdom (GB) Patent Application Number 0121066.5 filed on 31 Aug. 2001. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to door latch arrangements, and in particular, door latch arrangements having a one pull or two pull override unlocking feature. 
   Door latch arrangements are known which have a motor operable to break or block an outside transmission path from an outside door handle to a pawl of the latch arrangement to lock a door latch. Such latch arrangements also have a motor operable to break or block an inside transmission path between an inside door handle and the pawl to provide for a child safety feature. Such latches further include a mechanical linkage between the inside transmission path and the outside transmission path, which operates when the inside door handle is pulled and the latch is in a locked condition to unlock and open the door latch such that when a driver or passenger exits the vehicle and slams the door he is not inadvertently locked out of his vehicle. This is known as a one pull override unlocking feature. 
   Other door latches are known which include three motors, the first two operating to provide a lock function and a child safety function, as described above and a third motor operable to provide a superlock function. 
   A problem with such known latches is that they are complicated and require many components. Furthermore, they are not interchangeable when a different operation is required. 
   SUMMARY OF THE INVENTION 
   Thus, according to the present invention, there is provided a door latch arrangement including a latch bolt releasably retainable in a closed position by a pawl. The pawl is connected to an inside release member by a first transmission path, which is breakable or blockable by operation of a first actuator. The pawl is further connected to an outside release member by a second transmission path, which is breakable or blockable by operation of a second actuator. The door latch arrangement further includes a detection device for detecting when the inside release member is operated. The first and second actuators are controlled by a control device, operable in response to signals from the detection device to provide for override unlocking. 
   Advantageously such a system provides for override unlocking through a simple detection device. In particular, it is not required to have a mechanical link between the inside and outside transmission paths for override unlocking. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example only, with reference to the drawings in which  FIG. 1  shows a schematic view of a door latch arrangement according to the present invention. 
       FIG. 1  shows a schematic view of a door latch arrangement according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   For the avoidance of doubt, following terms are now defined: 
   A latch is in an unlocked security condition when operation of an inside door handle or an outside door handle causes opening of the latch. 
   A latch is in a locked security condition when operation of an outside door handle does not unlatch the latch but operation of an inside door handle does unlatch the latch. 
   A latch is in a superlocked security condition where operation of an outside or an inside door handle does not unlatch the latch. In particular, it should be noted that multiple operations of the inside and outside door handles, in any sequence, does not unlatch the latch. 
   A latch is in a child safety “on” security condition when operation of an inside door handle does not unlatch the latch but operation of an outside door handle may or may not unlatch the latch depending on whether the latch is in an unlocked or locked condition. 
   Override unlocking is a function whereby operation of an inside door handle, with the latch in a locked condition, causes unlocking of the latch. 
   Note that override unlocking is applicable to a latch in a locked child safety “off” condition, and is also applicable to a latch in a locked child safety “on” condition. In particular, starting from a locked child safety on condition of a latch having override unlocking, an actuation of the inside handle will unlock the door, but this operation or any subsequent operation of the inside door handle will not unlatch the door since the child safety feature is “on.” Nevertheless, once the latch has been unlocked by actuation of the inside door handle, a subsequent operation of the outside door handle will unlatch the latch. In particular, it should be noted that this situation is different from a superlocked latch, since in the former case, a particular sequence of handle operations, i.e. operation of the inside handle followed by operation of the outside handle, will open the door. This is not the case for superlocking. 
   One pull override unlocking is a function whereby with the latch in a locked child safety “off” condition, a single pull of the inside door handle results in unlocking of the door and also unlatching of the door. 
   Two pull override unlocking is a function, whereby with the latch in a locked child safety “off” condition, a first pull of the inside door handle results in unlocking of the latch but does not result in unlatching of the latch. However, a further operation of the inside door handle will then cause the latch to unlatch. 
   With reference to  FIG. 1 , there is shown a latch arrangement  10  including a latch bolt in the form of a rotating claw  12 , which can be held in a closed position by pawl  14 . In further embodiments, claw  12  may have a first safety abutment for engagement by pawl  14  in order for an associated door to be held in a first safety position, where the door is not fully closed, but nevertheless is prevented from opening. 
   An outside door handle  16  is operably connected to the pawl  14  via a second transmission path  18 . A second break/block device  20  is provided in second transmission path  18 , thus dividing second transmission path  18  into path  18 A, which connects outside door handle  16  to the second break/block device  20  and path  18 B, which connects the second break/block  20  device to the pawl  14 . 
   The second break/block device  20  is illustrative here of two embodiments. First, there can be provided a break in the second transmission path  18 , such that operation of the outside door handle  16  is possible, thus moving path  18 A but in view of the break  20  path  18 B does not move. Alternatively, there can be provided a block  20  such that the outside door handle  16  and path  8 A cannot be moved. Either embodiment is applicable to the present invention. 
   Thus, with second break/block device  20  acting to connect path  18 A with path  18 B or in the further embodiment with second break/block device  20  acting so as not to block movement of path  18 A, operation of the outside door handle  16  causes path  18 A to move path  18 B and lift the pawl  14  such that the claw  12  can release an associated striker, thus enabling the door to open. Second break/block device  20  is operable via motor  22  to move between a break/block position and a position where path  18 A is connected to path  18 B or where path  18 A is unblocked. 
   The latch arrangement  10  further includes an inside door handle  26 , a first transmission path  28 , a first break/block device  30 , which divides the first transmission path  28  into path  28 A and path  28 B, and motor  32 . Operation of these components is similar to their corresponding components associated with the outside door handle  16 . In particular, the first break/block device  30  is similarly illustrative here of two embodiments. The position of the inside door handle  26  can be determined by a detection device, in this case in the form of a switch  34 . 
   A control device  36  is operable to control motors  22  and  32  and hence determine the security condition of the latch. Typically, the control device  36  would be a microprocessor or an integrated control unit (ICU). 
   In this case components  12 ,  14 ,  18 B,  20 ,  28 B,  30 ,  22 ,  32  and parts of path  18 A and path  28 A are provided on a latch  38  as indicated by the dotted line. When the invention is applied to a passenger or driver&#39;s door of a car (automobile), then typically the latch  38  will be provided on a rear shut face of the door. The outside door handle will be positioned mid-way up a rear outer face portion of the door, and the inside door handle will be provided mid-way up and towards the front on the inside of the door to provide for good ergonomics. The switch  34  can be provided at a suitable location either adjacent to the inside door handle  26  or part way along path  28 A or even within the latch  38 . 
   The control device  36  can also be located at any convenient location. Note, however, that the physical position of the components shown in  FIG. 1  is primarily defined by packaging requirements and is not critical to the working of the invention. 
   The control device  36  can receive various inputs  100  that dictate the security condition of the latch as required by the user. Typically, the user will be provided with door mounted, or dash board mounted switches in order for the user to be able to indicate the required security condition. Remote control devices or passive entry devices can also be used to indicate a required security condition. 
   Possible security conditions are:
         locked, child safety on;   locked, child safety off;   unlocked, child safety on;   unlocked, child safety off; and   superlocked.       

   Upon receipt of an appropriate input  100 , the control device  36  will ensure that motors  22  and  32  move their corresponding second break/block device  20  and first break/block device  30  to an appropriate position if necessary. 
   Thus, starting from a superlocked condition, an input  100  requiring a change in the security condition to locked will result in motor  32  moving the first break/block device  30  to a connected/unblocked position such that subsequent operation of the inside door handle  26  will unlatch the door. Under such circumstances, the second break/block device  20  will remain in an unchanged position ensuring that operation of the outside door handle  16  does not unlatch the latch. 
   In particular, it should be noted that in a superlocked condition both first break/block device  30  and second break/block device  20  are in a break/block position. An input  100  requiring a change of security condition to locked child safety “on” will not result in any change to the position of the first break/block device  30  and second break/block device  20 . 
   Control device  36  can also receive signals from switch  34  indicating the position of the inside door handle  26 . The control device  36  can be programmed to act in either a one pull override use locking mode or a two pull override locking mode. 
   Thus, with control device  36  programmed as a one pull override function, operation of the inside door handle  26  with the latch  38  in a locked condition will actuate switch  34  sending a signal  40  to control device  36 , which, in turn, actuates motor  22  to connect/unblock second break/block device  20  to unlock the latch  38  whilst simultaneously the inside door handle  26  will move path  28 A and  28 B (since the latch  38  is in a locked condition and hence the first break/block device  30  connects/unblocks first transmission path  28 ), resulting in the door opening. 
   However, with control device  36  programmed as a two pull override function, operation of the inside door handle  26 , with the latch  38  in a locked condition, will actuate switch  34 , sending a signal  40  to control device  36 , which, in turn, actuates motor  22  to connect/unblock second break/block device  20  to unlock the latch  38 . However, under these circumstances, the first break/block device  30  acts to break/block the first transmission path  28 , hence the door does not unlatch. 
   Once the inside door handle  26  has been returned to its rest position (which preferably can be determined by switch  34 ), only then does the control device  36  actuate motor  32  to connect/unblock first break/block device  30 . Thus, a subsequent operation of the inside door handle will then cause the latch  38  to open. 
   Thus, by providing a simple software change to the control device  36 , it is possible to provide for one pull override unlocking or two pull override unlocking with the same components. 
   Note that with the latch  38  in an unlocked or superlocked condition, whilst switch  34  is operated as the inside door handle  26  is operated, it is not necessary for the control device  36  to operate motors  32  or  22 . 
   The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.