Abstract:
An entry door lock system includes an energy storage device ( 27 ) to permit unlatching if unlatching movement of a door handle occurs before the latch has been unlocked. The device ( 27 ) is passive if unlocking occurs before unlatching movement of the door handle. The invention avoids the need for repeat movement of the door handle in cases where unlocking follows initial door handle movement.

Description:
[0001]    This application claims priority to U.S. patent application Ser. No. 09/654,234, filed Sep. 2, 2000, which claims priority to Great Britain Patent Application No. 9920869.6, filed on Sep. 4, 1999.  
         BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to a latch for doors and the like, and particularly to a door latch of a vehicle.  
           [0003]    Known passive entry type car door lock systems work by the driver having about his person a radio frequency card which, as he approaches his own vehicle, is recognized by the vehicle and the vehicle then unlocks itself. On certain passive entry systems the recognition process only starts when an outside door handle is initially moved by the driver. Under such circumstances the electrical power actuator which unlocks the door does so in a fraction of a second and before the door handle has been fully lifted, thus allowing the opening of the door.  
           [0004]    However, if the door handle is lifted quickly it can beat the unlocking actuator leaving the door locked with the handle in the up position. The driver must release the handle and then lift it again to open the door, and this can be frustrating to some drivers.  
           [0005]    One known solution to this problem is to provide an actuator which both unlocks and also unlatches a door latch. However, significantly more power is required to unlatch than to unlock thus requiring a bigger actuator.  
         SUMMARY OF THE INVENTION  
         [0006]    According to the invention there is provided a latch comprising a housing, a locking member of the housing movable between locked and unlocked conditions, a latch release member of the housing movable between closed and open conditions and a latching member of the housing movable between latched and unlatched conditions, movement of the latch release member to the open condition causing movement of the latching member to the unlatched condition when the locking member is in the unlocked condition, and movement of the latching member to the unlatched condition being prevented when the locking member is in the locked condition, wherein an energy storage device is provided between the latch release member and said latching member, and a blocking member of the housing is movable from a disengaged condition to an engaged condition in which movement of said latching member to the unlatched condition is prevented when the locking member is in the locked condition, movement of the latch release member to the open condition causing said energy storage means to bias said latching member to the watched condition when said blocking member is in the engaged condition, movement of said blocking device to the disengaged condition permitting movement of said latching member to the unlatched condition under the action of said bias.  
           [0007]    The present invention overcomes the prior art problems by storing energy in e.g. an unlatching spring. If the driver opens the door handle quickly, the spring energy is used to unlatch after the power actuators have unlocked the door. If the driver opens the door handle slowly then the spring is not required to store or release energy.  
           [0008]    Preferably the locking member, latching member, latch release member and blocking member are pivotally mounted on said housing. In the preferred embodiment, the blocking member is movable in the opposite sense to the locking member. The latching member and latch release member may be pivoted about the same axis. The energy storage device may be a tension spring.  
           [0009]    The locking member may include a force transmission element insertable between the latching member and the latch releasing member in order to transmit motion therebetween in the unlocked condition. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    Other features will be apparent from the following description of a preferred embodiment shown by way of example only in the accompanying drawings, in which:  
         [0011]    [0011]FIG. 1 shows in plan a vehicle door latch mechanism according to the present invention, and in the unlocked and latched condition;  
         [0012]    [0012]FIG. 2 shows the mechanism of FIG. 1 in the locked and latched condition;  
         [0013]    [0013]FIG. 3 shows the mechanism of FIG. 1 in the locked condition with unlatching attempted;  
         [0014]    [0014]FIG. 4 shows the mechanism of FIG. 3 in the unlocked condition and with unlatching completed;  
         [0015]    [0015]FIG. 5 is an enlarged perspective view of the latch components comprising the invention;  
         [0016]    [0016]FIG. 6 is an enlarged perspective view of the pawl lifter and release arm of the invention;  
         [0017]    [0017]FIG. 7 is a plan view of the components illustrated in FIG. 6;  
         [0018]    [0018]FIG. 8 is a schematic representation of a prior art mechanism; and  
         [0019]    [0019]FIG. 9 is a schematic representation of a mechanism according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    Numerous parts are illustrated in the drawings accompanying this specification, however only those parts necessary for understanding the present invention are explained in detail.  
         [0021]    The invention is illustrated schematically with reference to FIGS. 8 and 9.  
         [0022]    The known arrangement of FIG. 8 includes a pivotable release lever  14 , and a pivotable cam lifter  15 . A locking link  22  is insertable between the lever  14  and lifter  15 . When the link  22  is inserted, the lever  14  can transmit motion to the lifter  15  to release the door latch. When the link is withdrawn, the arcuate range of movement of the lever is insufficient to move the lifter; accordingly in this condition the latch cannot be released by the lever  14 .  
         [0023]    [0023]FIG. 9 illustrates the invention. A blocking device  17  is movable to prevent releasing movement of the lifter  15 . The lever  14  and lifter  15  are however linked by a spring  27 . In this configuration, the lever  14  is still unable to actuate the lifter when in the locked condition (link  22  withdrawn). However the lifter is placed under load via the spring  27  such that if the blocking device is withdrawn, the lifter will rotate to latch the door.  
         [0024]    Thus a repeat motion of the door release lever to permit insertion of the locking link  22  is not necessary.  
         [0025]    With reference to FIGS.  1 - 7 , a preferred embodiment of a door latch mechanism comprises a housing  10  having a locking member in the form of a locking lever  11  pivotable therein about an axis A extending perpendicularly to the plane of the drawing. The lever is pivotable, typically under the action of an electrical actuator, and has upright pegs  12 , 13  for attachment to other parts of the mechanism, to be described below.  
         [0026]    A latch release member in the form of a release lever  14  is pivotable about an axis B extending perpendicularly to the plane of the drawing. Also pivotable about axis B are a latching member in the form of a pawl lifter  15  and an outside handle lever  16 . The levers  14 , 16  and pawl lifter  15  are engageable in various ways for movement together, as will become apparent.  
         [0027]    A blocking member in the from of a pawl lifter blocking lever  17  is pivotable about a third axis C, parallel to axes A and B, and has two arms  18 , 19 . The first arm  18  is slotted and is engaged with peg  12  such that anti-clockwise movement of locking lever  11  results in clockwise movement of blocking lever  17 , and vice-versa. The second arm  19  constitutes a blocking member movable into and out of engagement with a blocking arm  21  of the pawl lifter  15 .  
         [0028]    A locking link  22  is slotted at one end  23  to engage the upright peg  13 , and has a depending leg  24  insertable between the release lever  14  and pawl lifter  15  in order to transmit movement therebetween.  
         [0029]    As illustrated in FIG. 5, the leg  24  passes through a slot  25  of the release lever, and is engageable with an upstanding abutment  26  of the pawl lifter  15  (FIG. 6).  
         [0030]    An energy storage device in the form of hairpin spring  27  located about axis B has free ends bearing on a release lever arm  28  and the pawl lifter abutment  26 , thereby to urge the release lever arm  28  and pawl lifter blocking arm  21  apart (FIG. 6).  
         [0031]    A release lever abutment  29  is engageable with the pawl lifter blocking arm  21  to restrict clockwise movement of the release lever relative to the pawl lifter.  
         [0032]    In order to return the release lever  14  to the unlatched condition of FIG. 1, a second hairpin spring (not shown) acts about axis B between the housing  10  and a return arm  33  of the release arm.  
         [0033]    In use arcuate movement of the pawl lifter  15  disengages the door latch in order to permit the vehicle door to be opened. The release lever arm  28  of the release lever is in use connected to an internal door handle, and an external release am  32  of the pawl lifter  15  is in use engageable with the external door handle lever  16 . Different release arms ensure independent movement, in a known manner.  
         [0034]    Operation of the latch mechanism is as follows:  
         [0035]    [0035]FIG. 1 shows the door latch in the unlocked condition. The blocking lever  17  is pivoted anti-clockwise out of possible engagement with the pawl lifter blocking arm  21 . The peg  13  is clockwise to the maximum extent and the locking link is urged downwards (as viewed), for example by a light spring (not shown). In this condition the leg  24  is between the release lever  14  and the pawl lifter abutment  26 ; accordingly anti-clockwise movement of the release lever  14  is transmitted directly to the pawl lifter  15 , which also moves anti-clockwise since the blocking arm  21  is unobstructed. Thus the door latch is released, and the components assume the configuration illustrated in FIG. 4.  
         [0036]    It will be noted that the bottom part of the release lever slot  25  (as viewed) is narrowed somewhat so that the leg  24  is a relatively tight fit; this reduces lost motion in the mechanism.  
         [0037]    [0037]FIG. 2 shows the latch mechanism in the locked condition. The locking lever  11  is pivoted anti-clockwise, thus pivoting the blocking lever  17  clockwise so as to obstruct anti-clockwise movement of the blocking arm  21 . The locking link  22  is lifted out of engagement with the abutment  26 , and accordingly direct mechanical actuation of the pawl lifter  15  by the release lever  14  is not possible.  
         [0038]    If in this condition the release lever  14  is pivoted, the hairpin spring  27  is stressed, and urges the pawl lifter  15  anti-clockwise; movement is however prevented by the blocking lever  17  and the door cannot be unlatched. This condition occurs in use when the door handle is moved to the open condition, but the lock actuator has not been energized, or has not been energized sufficiently in advance.  
         [0039]    If however the lock actuator is energized whilst the door handle is in the open condition, the locking lever pivots clockwise, thus releasing engagement of the blocking lever  17  and blocking arm  21 . As a consequence, the pawl lifter rotates anti-clockwise under the action of the hairpin spring  27 , and the door is unlatched.  
         [0040]    Downwards movement of the locking link  22  is prevented by the abutment  26  until pivoting of the pawl lifter  15  has occurred. However the slot in the upper end of the locking link  22  permits the necessary pivoting of the locking lever  11  and peg  13 , and eventually the link  22  is permitted to move down as the pawl lifter pivots to the latch released condition illustrated in FIG. 4.  
         [0041]    The invention thus provides an economical and uncomplicated means of overcoming the problem of rapid door handle movement. Furthermore the invention can readily be applied to existing mechanism if required. In the preferred embodiment, the additional components required are hairpin spring  27  and associated spring reaction members, and blocking lever  17 .