Patent Publication Number: US-2009230703-A1

Title: Latch mechanism

Description:
REFERENCE TO RELATED APPLICATION 
     This application claims priority to United Kingdom Patent Application No. 0804973.6 filed Mar. 17, 2008. 
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to latch mechanisms, in particular to latch mechanisms which are lockable. 
     Lockable latch mechanisms are known in which, in an unlocked condition, operation of a handle causes a pawl to disengage from a latch bolt, thereby releasing the latch. When in a locked condition, the handle is operably disconnected from the pawl so that the handle “free wheels” when operated, i.e., operation of the handle does not disengage the pawl from the latch bolt. 
     Two such arrangements are shown in GB2342383 and U.S. Pat. No. 6,286,878. In these cases, the transmission paths between the handles and the pawls includes a gap. In the unlocked position, a wedge fills the gap, and in the locked position, the wedge is removed from the gap. When the door handle is actuated when the mechanism is in its locked position, if the mechanism is unlocked while the handle is still actuated, then a motor drives the wedge between the gap, thereby releasing the latch. The arrangement allows the handle to be pulled once the system is in the locked position, and by continuing to hold the handle, the door can be opened. It is not necessary to pull the handle, release the handle, and then pull the handle for a second time to open the latch. 
     However, the problem with this invention is that the power required to drive the wedge between the gap is significant, and hence a relatively powerful motor is required. Relatively powerful motors are expensive, bulky, heavy and require relatively large amounts of energy to operate. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved latch mechanism. The latch mechanism includes a latch chassis, a latch bolt having a closed position and an open position, a pawl having an engaged position at which the pawl holds the latch bolt in the closed position and a disengaged position at which the pawl allows the latch bolt to move to the open position, and a first release handle operably connected to the pawl via a transmission path to selectively move the pawl from the engaged position to the disengaged position. The transmission path includes a toggle linkage having a first link pivotable about a first axis and a second link pivotable about a second axis. The first link and the second link are pivotable relative to each other about a common axis. The latch mechanism includes a stop to limit rotation of the second link in a first direction relative to the first link. The toggle linkage has a first toggle linkage position where the common axis is positioned on a first side of a line joining the first axis and the second axis, and the stop is engaged to operably couple the first release handle with the pawl. The toggle linkage has a second toggle linkage position where the common axis is positioned on a second side of the line joining the first axis and the second axis to operably decouple the first release handle from the pawl. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  shows part of a latch mechanism in an unlocked rest position; 
         FIG. 2  shows the latch mechanism of  FIG. 1  in a locked rest position; 
         FIG. 3  shows the latch mechanism of  FIG. 1  in a locked position with an inside door handle in an actuated position; 
         FIG. 4  shows the latch mechanism of  FIG. 1  in a release position with the inside handle in the actuated position; 
         FIG. 5  shows the latch mechanism of  FIG. 1  in a locked position with an outside door handle in an actuated position; and 
         FIG. 6  shows the latch mechanism of  FIG. 1  in a release position with the outside handle in the actuated position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The figures show a latch mechanism  10  including a latch  11  having a latch chassis  12  (only part of which is shown). The latch  11  includes a latch bolt  14  (shown schematically in  FIG. 1 ) rotatable about an axis A between a closed position and an open position. A pawl  16  is rotatable about a pawl axis B between an engaged position, at which the pawl  16  holds the latch bolt  14  in a closed position, and a disengaged position, at which the pawl  16  allows the latch bolt  14  to move to the open position. 
     The latch  11  will typically be provided on a rear edge of a door, such as a vehicle door, for example a car. The latch mechanism  10  includes an inside handle IH (shown schematically in  FIG. 1 ) and an outside handle OH (shown schematically in  FIG. 1 ). A transmission path  18  selectively couples the inside handle IH and the outside handle OH to the pawl  16 . A toggle linkage  20  includes a first link  22  and a second link  24 . 
     The latch mechanism  10  also includes a linkage carrier  26 . The linkage carrier  26  is generally elongate and is guided to move laterally (when viewing the Figures) from the position shown in  FIGS. 1 and 2  to the position shown in  FIGS. 3 to 6 . There is a pin  28  at the right hand end (when viewing  FIG. 1 ) of the linkage carrier  26  which projects into the paper when viewing  FIG. 1 . The pin  28  is guided in a slot  30  of the latch chassis  12 . An edge of the slot  30  is sandwiched between an oval end  29  of the pin  28  and the region of the right hand end of the linkage carrier  26  obscured by the oval end  29 . 
     There is a pin  32  at the left hand end (when viewing  FIG. 1 ) of the linkage carrier  26  which is guided in a slot  34  of the latch chassis  12 . A chassis abutment  36  is provided above the left hand end (when viewing  FIG. 3 ) of the linkage carrier  26  to prevent the left hand end of the linkage carrier  26  moving upwardly during operation. An abutment  38  of the transmission path  18  is provided to ensure that the left hand end of the linkage carrier  26  does not move downwardly during operation. As such, the linkage carrier  26  is constrained to move laterally in the direction of an arrow C during operation. 
     The linkage carrier  26  includes a pin  40  towards its right hand end when viewing  FIG. 2 , which defines a first axis  42  of the first link  22 . The linkage carrier  26  also includes an elongate slot  44  and an abutment  46 . 
     The first link  22  has an arcuate end  48  which snap fits around the pin  40 . As such, the first link  22  is pivotable about the first axis  42 . The first link  22  also includes an arcuate portion  50  which snap fits around a pin (not shown, but which defines a common axis  52 ) of the second link  24 . The first link  22  and the second link  24  are therefore pivotable relative to each other about the common axis  52 . The first link  22  also includes an elongate slot  54  and an abutment portion  56 . The second link  24  is generally elongate and includes a pin (not shown, but which defines a second axis  58 ) which sits in the slot  44 . The second link  24  includes an abutment portion  60 . 
     A lever  62  (shown schematically) is pivotable about an axis D and includes an abutment  64  which is selectively engageable with the abutment  46  of the linkage carrier  26 . A lever  66  (shown schematically) is pivotable about an axis E and includes an abutment  68 . A lever  70  (shown schematically) is pivotable about a lever axis F and includes a pin  72  which sits in the elongate slot  54  of the first link  22 . A lock motor LM is operably coupled to the lever  70 . The second link  24  includes an abutment  74  which is selectively engageable with an abutment  76  of the transmission path  18 . 
     The transmission path  18  includes several transmission path portions:  18 A which couples the inside handle IH to the lever  62 ,  18 B which includes the lever  62 ,  18 C which includes the linkage carrier  26 ,  18 D which includes the first link  22 ,  18 E which includes the second link  24 ,  18 F which couples the abutment  74  of the second link  24  with the pawl  16 ,  18 G which couples the outside handle OH to the lever  66 , and  18 H which includes the lever  66 . 
     Operation of the latch mechanism is as follows. In summary, the first link  22  and the second link  24  can either act as a strut in compression to transmit a load from the pin  40  to the abutment  76 , or the strut formed by the first link  22  and the second link  24  can “buckle,” as shown in  FIG. 2 . Under these circumstances, a load applied at the pin  40  is not transmitted to the abutment  76  (see  FIG. 3 ). However, when the “buckled strut” formed by the first link  22  and the second link  24  is straightened by the lock motor LM, it moves to the position shown in  FIG. 4 , thereby transferring the force from the pin  40  to the abutment  76 . 
     In more detail, as shown in  FIG. 1 , the common axis  52  is positioned to one side (in this case below) of a line L drawn between the first axis  42  and the second axis  58 . In these circumstances, the abutment portion  56  of the first link  22  is engaged with the abutment portion  60  of the second link  24 , thereby forming a stop  78 . The stop  78  prevents the second link  24  rotating further clockwise about the common axis  52  relative to the first link  22 . As such, the first link  22  and the second link  24 , together with the appropriately positioned stop  78 , form a stable strut  80 . When the inside door handle IH is actuated, the movement of the inside door handle IH is transmitted via the transmission path portion  18 A to the lever  62 , which is caused to rotate clockwise (when viewing  FIG. 1 ) about the axis D, thereby causing the abutment  64  of the lever  62  to drive the linkage carrier  26  to the left when viewing  FIG. 1 . This causes the pin  40  to move to the left, and hence the strut  80  to move to the left, which results in the abutment  74  of the second link  24  engaging the abutment  76  and causing the transmission path portion  18 F to rotate about the pawl axis B, thereby moving the pawl  16  from its engaged position to its disengaged position, and hence allowing the latch bolt  14  to release the latch  11 . Operation of the inside handle IH with the latch mechanism  10  unlocked therefore moves the components from the  FIG. 1  position to the  FIG. 4  position. 
     With regard to the outside handle OH, starting at the  FIG. 1  position, operation of the outside handle OH causes the transmission path portion  18 G to rotate the lever  66  about the axis E, which causes the abutment  68  to engage and move the pin  32  of the linkage carrier  26  to the left when viewing  FIG. 1 . This causes the latch  11  to be released as the strut  80  engages the abutment  76  and rotates the transmission path portion  18 F about the pawl axis B to rotate the pawl  16  to disengage from the latch bolt  14 . Thus, when the outside handle OH is operated with an unlocked latch, the components move from the  FIG. 1  position to the  FIG. 6  position. 
     Note that in the  FIG. 6  position, the abutment  68  is engaged with the pin  32 , but the abutment  64  is spaced from the abutment  46 . This can be contrasted with  FIG. 4 , where the abutment  68  is spaced from the pin  32 , and the abutment  64  is in engagement with the abutment  46 . 
     Note that in  FIGS. 1 ,  4  and  6 , the lever  70 , and in particular the pin  72 , is in the same position. Because in  FIGS. 4 and 6  the first link  22  has moved leftwardly when compared with  FIG. 1 , the pin  72  is closer to the right hand end (when viewing  FIGS. 4 and 6 ) of the elongate slot  54  when compared with  FIG. 1 . 
       FIG. 2  shows the latch mechanism  10  in a locked position. In this case, the lever  70  has been caused to rotate counter-clockwise (by operation of the lock motor LM) about the lever axis F, thereby generally raising the pin  72 , which in turn causes the first link  22  to rotate clockwise about the first axis  42  to the  FIG. 2  position. This has caused the second link  24  to rotate about the second axis  58 . The left hand end of the second link  24  has also been caused to translate along the slot  44  i.e., the second axis  58  has been caused to translate along the slot  44 . Significantly, the common axis  52  lies on an opposite side (in this case above) of the line L drawn between the first axis  42  and the second axis  58 . As shown in  FIG. 2 , the strut  80  has “buckled.” When either the inside handle IH or the outside handle OH is actuated, the linkage carrier  26  will move to the left, and once the abutment  74  has engaged the abutment  76  continued movement of the linkage carrier  26  to the left will simply cause the strut  80  to buckle further (as shown in  FIG. 3 ). As such, the latch  11  will not release. It is the initial buckling of the strut  80  as shown in  FIG. 2  and continued buckling of the strut  80  as shown in  FIG. 3  that ensures the door is locked and will not open upon actuation of either the inside handle IH or the outside handle OH. Releasing either the inside handle IH or the outside handle OH will return the latch mechanism  10  from the  FIG. 3  position to the  FIG. 2  position. 
     In order to unlock the latch  11 , the lock motor LM is actuated to cause the lever  70  and the pin  72  to rotate in a clockwise direction about the lever axis F, thereby moving the components from the  FIG. 2  position to the  FIG. 1  position. 
     However, it is also possible for the components, starting at the  FIG. 2  position, to be moved to the  FIG. 3  position by actuation of the inside handle IH, and then be moved to the  FIG. 4  position (while the inside handle IH is still actuated) by actuation of the lock motor LM. 
     Thus, starting at the  FIG. 2  position, actuation of the inside handle IH will move the components to the  FIG. 3  position as described above. While the inside handle IH continues to be actuated, the lock motor LM can be operated to cause the lever  70  to rotate clockwise about the lever axis F. Because the pin  40  is being held in the  FIG. 3  position by the actuated inside handle IH, then as the lever  70  is rotated in a clockwise direction, the pin  72  drives the first link  22  in a counter-clockwise rotational direction about the first axis  42 . This causes the strut  80  to straighten out, resulting in the abutment  74  engaging and pushing on the abutment  76  to cause the pawl  16  to rotate. Note that throughout the process of moving the components from the  FIG. 2  position through the  FIG. 3  position to the  FIG. 4  position, the inside handle IH has not been released (i.e., it has not been returned to its rest position). Once the  FIG. 4  position has been achieved, then the inside handle IH can be released. 
     A similar mode of operation can be achieved by operating the outside handle OH. Thus, starting at the  FIG. 2  position, the outside handle OH can be actuated, thereby moving the components to the  FIG. 5  position. Whilst the outside handle OH continues to be actuated, the lock motor LM can be actuated, driving the lever  70  in a clockwise direction about the lever axis F, thereby moving the components to the  FIG. 6  position. Once the  FIG. 6  position is achieved the outside handle OH can be released. 
     As mentioned above, the line L shown in  FIGS. 1 and 2  passes through the first axis  42  and the second axis  58 . In both cases, the line L also passes through that part of the abutment  74  of the second link  24  that engages the abutment  76 . The point on the abutment  74  which is engaged by the abutment  76  is the point at which a resistive load (i.e., a load application point) is applied to the second link  24  during opening of the latch  11 . Thus, as shown in  FIG. 1 , the common axis  52  is positioned on one side (the lower side) of a line joining the first axis  42  to the load application point on the abutment  74 . On  FIG. 2 , the common axis  52  is positioned on another side (i.e., above) the line joining the first axis  42  with the load application point on the abutment  74 . 
     In further embodiments, the line L joining the first axis  42  and the second axis  58  need not be coincident with the line joining the first axis  42  and the load application point. 
     As mentioned above, the stop  78  is provided by the engagement between the abutment portion  56  of the first link  22  and the abutment portion  60  of the second link  24 . In further embodiments, the stop  78  could be provided by a portion of the first link  22  engaging a stop portion on the latch chassis  12 . Alternatively, the stop  78  could be provided by a portion of the second link  24  engaging a stop on the latch chassis  12 . 
     The last part of the transmission path portion, i.e., the transmission path portion  18 F, is relatively simple in as much as rotation of the abutment  76  directly rotates the pawl  16 . In further embodiments, the transmission path portion that couples the abutment  74  of the second link  24  with the pawl  16  could be more complicated. Thus, the present invention is applicable to latches as shown in WO2006087578. For example, the toggle linkage  20  of the present invention could act to move the release plate 70 of WO2006087578 out of disengagement with the release abutment  65  of the release lever  52 , thereby releasing the latch  10 . 
     The foregoing description is only exemplary of the principles of the invention. Many modifications and variations are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than using the example embodiments which have been specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.