Abstract:
A latch mechanism has an input member and an output member. The mechanism has a first coupled condition at which the input and output members are coupled such that movement of the input member from its first position to its second position causes movement of the output member from its first position to its second position. The mechanism has a decoupled condition at which the input member is not coupled to the output member. The mechanism further includes a block member, which, with the mechanism in the decoupled condition, further prevents at least one of the input and output member from moving to its respective second position.

Description:
This application is a divisional patent application claiming priority to U.S. Nonprovitional patent application Ser. No. 10/080,365, filed on Feb. 21, 2002, now abandoned, which claims priority to United Kingdom (GB) Patent Application Number 0105120.0 filed on 2, Mar. 2001. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to mechanism, for a vehicle door latch. 
   Known vehicle door latches are lockable using a “free wheeling” principle. Thus, with the door unlocked, lifting of an outside door handle causes the door latch to open. Conversely, with the door locked, lifting of the outside door handle is still possible but a transmission path between the outside door handle and components of the door latch that retains the door in the closed position is broken. Essentially, a break is created in the transmission path. The components on the door handle side of the break are caused to move with the door handle while the components on the other side of the break do not move. A problem with this type of locking is that a space has to be provided for the components on the handle side of the break to move when the handle is lifted. 
   SUMMARY OF THE INVENTION 
   An inventive latch mechanism has an input member and an output member. The latch mechanism has a first condition at which the input and output member are coupled such that movement of the input member from its first position to its second position causes movement of the output member from its first position to its second position. The latch mechanism also has a second condition at which the input member is not coupled to the output member. The latch mechanism further has a blocking member, which, with the mechanism in its second condition, further prevents one of the input or output members from moving to its respective second position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
       FIGS. 1A to 1D  show a first embodiment of the present invention in various positions; 
       FIGS. 2A to 2D  show a second embodiment of the present invention in various positions; 
       FIG. 3  shows an isometric exploded view of  FIG. 2A ; and 
       FIGS. 4A to 4D  and  5 A and  5 D show isometric views of  FIGS. 2A to 2D , respectively. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIGS. 1A to 1D , there is shown a latch mechanism  10  mounted on a chassis  12  (only shown in  FIG. 1A ). A latch mechanism  10  includes an input member in the form of an input lever  20 , an output member in the form of a pin  30 , a clutch in the form of a link  40  and a blocking member  50 . 
   The input lever  20  is pivotally mounted at an input pivot  21  to the chassis  12 . The link  40  is pivotally mounted at pivot  41  to an end  20 B of the input lever  20 . The blocking member  50  is fixed in a stationary position on the chassis  12 . 
   The pin  30  is movable between the positions as shown in  FIG. 1A  and  FIG. 1C . The latch mechanism  10  typically forms part of a vehicle door latch arrangement. An inside door handle  300  and an outside door handle  302  are connected by a transmission path to an end  20 A of the input lever  20 . The pin  30  is connected to a pawl, which is capable of retaining a latch bolt (e.g., a rotating claw) in a closed position. The claw in turn can releasably retain a latch striker in order to retain an associated door in a closed position. Movement of the pin  30  from the position shown in  FIG. 1A  to the position shown in  FIG. 1C  causes the pawl to disengage the claw and allow the door to open. Thus, with the latch mechanism  10  in the position as shown in  FIG. 1A , the door is in an unlocked condition. Operation of the inside door handle  300  or the outside door handle  302  will cause the end  20 A of the input lever  20  to lift (i.e., the input lever  20  will rotate in counter-clockwise direction), causing the end  20 B to lower. This movement of the end  20 B results in an abutment  42  contacting and then moving the pin  30  to the position shown in  FIG. 1C . It should be noted that in  FIGS. 1A and 1C , the pivot  41 , the abutment  42  and the pin  30  are all aligned. 
   The latch mechanism  10  can be put into a locked condition as shown in  FIG. 1B  by rotating the link  40  so that it aligns with the blocking member  50  and no longer aligns with the pin  30 . Thus, when an attempt is made to lift the outside door handle  300 , the abutment  42  moves into contact with the blocking member  50 , and the outside door handle  300  cannot be fully lifted. The door therefore remains fully closed. 
   Thieves tend to apply excessive force to outside door handles  300  in the expectation of causing components of the door latch to fail in an attempt to gain entry to the vehicle. However, the present invention mitigates this problem. In the event that the blocking member  50  fails (e.g., it breaks off the chassis  12 ), the abutment  42  will bypass the pin  30 . Thus, the door still remains closed. 
   Under normal circumstances, the abutment  42  does not enter the space occupied by the blocking member  50 . Consequently, this space is available for other components of the latch, enabling a more compact latch design. Preferably, the blocking member  50  is not solely dedicated to acting just as a blocking member, but fulfills another function within the latch to further save space. 
   With reference to  FIGS. 2A to 5C , there is shown a further embodiment of the invention. The latch mechanism  110  has components that fulfill substantially the same function as those in the latch mechanism  10 . 
   The input lever  120  includes a hole  122 , which mounts on an input pivot pin  121 , which in turn is mounted on a chassis  112 . The input lever  120  includes an L shaped hole  123  and a further hole  124  for connection to an inside door handle  200  or an outside door handle  202 . 
   In this case, the output member is in the form of an output lever  130  having a pivot hole  131 , which is mounted on the input pivot pin  121 . Thus, it can be seen that the input lever  120  and the output lever  130  lie adjacent to one another and pivot about the same axis. The output lever  130  includes a slot  132 , which in the position shown in  FIG. 2A , substantially aligns with arm  123 A of an L shaped hole  123 . The output level  130  further includes an abutment  133  and an arm  134 . 
   A blocking member  150  is in the form of a link being pivotally mounted on the chassis  112  at a pivot  152  and having a abutment  153 . Adjacent the abutment  153 , there is a hole  154  in which is mounted a pin  161  of a link  160 . The link  160  includes a clutch at an end  160 A in the form of a pin  140 . The pin  140  engages in L shaped hole  123  of the input lever  120  and also in the slot  132  of the output lever  130 . 
   A pawl arm  170  is connected at an end  170 A to a pawl (not shown), which releasably retains a latch bolt (e.g., a rotating claw) to secure the door. Movement of the pawl arm  170  from the position shown in  FIG. 4A  to the position shown in  FIG. 4C  causes the pawl to rotate and allow the door to open. 
   Operation of the mechanism is as follows. With the mechanism in the position as shown in  FIGS. 2A ,  3  and  4 A, the pin  140  is located at the end  132 A of the slot  132  and hence at an end  125  of an L shaped hole  123 . As such, the input lever  120  and the output lever  130  are coupled together for rotation. Further, as seen from  FIG. 2A , the abutment  133  of the output lever  130  is not aligned with the abutment  153  of the blocking member  150  (i.e., the abutment  133 , the abutment  153  and the pivot  152  are not aligned). Thus, operation of the inside door handle  200  or the outside door handle  202  causes a hole  124  to move in the direction of arrow A of  FIG. 2A  to the position as shown in  FIG. 2C , which results in the arm  134  rotating the pawl arm  170  and thus opening the door. It should be noted that the abutment  133  has bypassed the abutment  153 , as shown in  FIG. 2C . 
   With the input lever  120  and the output lever  130  in the position shown in  FIG. 2A , the block member  150  can be rotated to the position as shown in  FIG. 2B . This has two effects, namely a) the abutment  153  aligns with the abutment  133  (i.e., the abutments  153  and  133  and the pivot  152  are aligned) to prevent movement of output lever  130  and b) the pin  140  is moved (by the link  160 ) to the end  132 B of the slot  132  and hence to the confluence of arms  123 A and  123 B of the L shape hole  123 , i.e., to position  126  (see  FIG. 3 ). 
   In the event that the inside door handle  200  or the outside door handle  202  is operated, movement of the input lever  120  causes the arcuate arm  123 B of the L shaped hole  123  to move past the pin  140 , which remains stationary. Compare  FIGS. 2B and 2D ). Accordingly, if the input lever  120  and the outside lever  130  corrode or otherwise stick together, then the door is still prevented from opening by engagement between the abutments  133  and  153 . Under these circumstances, it is not possible to move the associated door handle and this acts as an indicator that the mechanism is malfunctioning. Such an indicator is useful since a malfunction can be determined simply by attempting to operate the door handles. No internal examination of the door is required. 
   The mechanism can be used in the transmission path between an outside door handle and a latch bolt (i.e., it can be used to lock the door). Alternatively, the mechanism can be used between both the inside and outside door handles and the latch bolt, i.e., it can be used to superlock (or deadlock) the door. Alternatively, it can be used between an inside door and a latch bolt, especially on a rear door of a vehicle, i.e. 4  to provide a child safety function of the door latch.