Abstract:
A power door latch assembly consists of a ratchet ( 50 ) for engaging a door striker, a pawl ( 52 ), a rotary actuator ( 54 ) for rotating the ratchet ( 50 ) towards the closed position and for disengaging the pawl ( 52 ) and a drive actuator ( 96 ) for driving the rotary actuator ( 54 ). The drive actuator ( 96 ) includes a prime mover ( 98 ) an output member ( 104 ) in engagement with the rotary actuator ( 54 ), and releasable coupling ( 102 ) coupled between the prime mover ( 98 ) and the output member ( 104 ) for selectively transferring torque between the prime mover ( 98 ) and the rotary actuator ( 54 ). A drive controller ( 108 ) is coupled to the releasable coupling ( 102 ) and is configured for disengaging the prime mover ( 98 ) from the rotary actuator ( 54 ) when the ratchet ( 50 ) is disposed in either the open or closed positions.

Description:
This application is a 371 of PCT/CA00/00164 filed Feb. 18, 2000, which claims benefit to provisional application 60/120,585 filed Feb. 18, 1999. 

   FIELD OF THE INVENTION 
   This present invention relates to a latch assembly for and unlatching a member to and from a pillar in particular, the present invention relates to a powder door latch assembly for securing and unsecuring a vehicle door. 
   BACKGROUND OF THE INVENTION 
   A typical motor vehicle door is mounted in a door frame on the vehicle and is movable between open and closed positions. Usually the door is held in a closed position by the latching engagement between a spring-biased ratchet pivotally mounted inside the door latch and a U-shaped striker secured to the door frame. The ratchet is most often spring-biased toward the unlatched position to release the striker and is maintained in the latched position to hold the striker by a spring-biased pawl or other mechanical structure. The ratchet cannot pivot to release the striker until the pawl is moved. 
   The majority of these door latches are exclusively manually operated both to unlatch the door and to relatch the door. Typically, the manual release handles are provided on the inside and outside of the door to release the ratchet from the striker by moving the pawl so that the door can be opened. The door is closed and relatched by manually pivoting the door so that the ratchet impacts the striker with sufficient force to pivot the ratchet to the latched position against the spring force exerted by the ratchet spring. 
   It is often difficult, however, to completely close and latch manually latching vehicle doors on current model vehicles because the desire to reduce vehicle weight and to improve fuel economy has led engineers to design vehicles with relatively thin and lightweight doors. Often relatively hard door seals are used with these thin, lightweight doors to improve sealing around the door, particulary at high driving speeds. Because many vehicle doors are relatively lightweight and have relatively hard door seals, many vehicles doors often have insufficient internal energy when pushed closed to compress these hard door seals and fully pivot the ratchet to the latched position to latch the door. 
   Power assisted door latch assemblies have been developed to overcome the problems associated with latching doors with lightweight construction and hard door seals. Power assisted door latch assemblies allow low internal energy or soft closure of the lightweight doors without the need to slam the door even with the increased seal pressure that results from relatively hard door seals. Existing power associated door latch assemblies typically function to latch a vehicle door in one of two ways: 1) by forcing the ratchet to pivot in the closing direction after engagement with the striker or 2) by forcing the striker to move in a door-closing direction after the striker is fully engaged with the ratchet. 
   Use of either type of power associated door latch assembly decreases the noise associated with door closing and decreases the manual effort needed to completely close the door. Power assisted door latch assemblies are disclosed by Ishikawa (U.S. Pat. No. 4,986,579), Kobayahi (U.S. Pat. No. 5,273,324) and Dowling (U.S. Pat. No. 5,520,425). In Ishikawa, the door latch assembly includes an electric motor for rotating the spring-biased ratchet from the partially closed to the fully closed position, and an electric switch for activating and deactivating the electric motor. In Kobayashi, the door latch assembly includes a rotatable lever for rotating the ratchet plate into the fully closed position, an electric motor manipulating the lever, and a mechanical linkage extending between the lever and the ratchet plate for rotating the ratchet plate into the fully closed position. In Dowling, the door latch assembly includes a motor driven gear, and a flexible wire extending between the driven gear and the ratchet for rotating the ratchet from the partially closed to the fully closed position. However, Ishikawa requires a complex rotary actuator for operating the switch, whereas the mechanical link and the flexible wire used respectively in Kobayshia and Dowling inefficiently transfers mechanical torque between the electric motor and the ratchet plate. 
   Latch assemblies which provide both power assisted opening and power assisted closing are also in use. In these power assisted latch assemblies, the same source of power, typically an electric motor mounted within the vehicle door, is used both to open the latch and to close the latch. The mechanical locking mechanism and some door opening handles can be eliminated from the vehicle door when these latch assemblies are used. 
   Power assisted opening and closing latch assemblies are taught by Bernard (U.S. Pat. No. 4,664,430), Kleefeldt (U.S. Pat. No. 4,518,180) and Tamiya (U.S. Pat. No. 5,232,253). These types of latching assembly are often advantageously used with powered sliding vehicle doors in which the latch must be released before the power door opening mechanism can be actuated to open the door. Bernard uses a cylindrical ratchet plate and a disc rotatably mounted on a common shaft, a pawl pivotally mounted on the disc for engagement with the ratchet plate, and an electric screw drive for rotating the disc between an open latch position and a close latch position. Kleefeldt uses a motor-driven gear and a sliding toggle linkage mechanically coupled to the driven gear for opening and closing the ratchet Tamiya uses a rack-driven link for rotating the ratchet from the open position to the closed position, and a lever coupled to the link for releasing the pawl from the ratchet to allow the ratchet to be rotatably driven back to the open position. However, Bernard stresses the electric motor by using the motor as brake to retain the ratchet plate in the closed position, whereas the latching mechanisms taught by Kleefeldt and Tamiya may not be reliable in environments where the door is forcefully closed into the latch. Also, the sliding toggle linkage used by Kleefeldt limits the mechanical torque which is ultimately applied to the ratchet 
   Accordingly, there remains a need for a simple, cost-effective power-assisted door latch assembly which efficiently transfers torque from the electric motor to the ratchet Further, there remains a need for a power-assisted door latch assembly which limits the stress applied to the electric motor by the ratchet. 
   SUMMARY OF THE INVENTION 
   According to the present invention, there is provided a power door latch assembly which addresses some of the deficiencies of the prior art 
   The power door latch assembly, according to the present invention, comprises a ratchet for engaging a door striker, a pawl for engaging a detent surface provided on the ratchet for selectively resisting rotation of the ratchet towards the open position, a rotary actuator for rotating the ratchet towards the closed position and for disengaging the pawl from the detent surface, and a drive actuator for driving the rotary actuator. The drive actuator includes a prime mover, an output member in engagement with the rotary actuator, and a releasable coupling coupled between the prime mover and the output member for selectively transferring torque between the prime mover and the rotary actuator. The power door latch assembly also includes a drive controller for controlling operation of the drive actuator. The drive controller is coupled to the releasable coupling and is configured for disengaging the prime mover from the rotary actuator when the ratchet is disposed in either the open or closed positions. 
   According to the preferred embodiment of the invention, the door latch assembly provides for the power assisted opening and closing of a vehicle door with respect to a vehicle door frame between a closed position wherein the door is latched to a striker mounted on the door frame and an opened position in which the door is unlatched from the striker. The door latch assembly has a ratchet which cooperates with a mouth of a housing to releasably retain the striker. The door latch assembly also includes a pivotal pawl mounted in cooperating relation with the ratchet for biased movement into a holding position wherein the ratchet is held (1) in the secondary latched position against movement toward the unlatched position and (2) in the primary latched position against movement toward the secondary latched position. The pawl can be moved out of the holding position into a releasing position to allow the ratchet to move toward and into the unlatched position. The door latch assembly further includes a sector gear constructed and arranged to be moved from a null position in one direction through a closing stroke into a closing position and from the closing position through a return stroke to the null position and from the null position in an opposite direction through an opening stroke into an opening position and from the opening position through a return stroke into the null position. An actuator assembly includes a reversible electric motor and a clutch assembly for selectively driving the sector gear. The electric motor is operable (1) when energized to rotate in one direction to drive the sector gear through the closing stroke thereof and (2) when energized to rotate in an opposite direction to drive the sector gear through the opening stroke thereof. The sector gear has a closing arm constructed and arranged to cause a movement of the ratchet from the secondary latched position thereof to the primary latched position thereof. The sector gear has an opening arm constructed and arranged to cause a movement of the pawl from the holding position thereof to the releasing position thereof to release the ratchet. 
   Preferably, the sector gear has a spring for urging the sector gear to move through the return strokes thereof from opening and closing positions thereof when the actuator is de-energized. 
   Preferably the door latch assembly includes an energizing closing switch constructed and arranged to be actuated in response to the movement of the ratchet into the secondary latched position thereof to energize the electric motor to thereby move the sector gear through a closing stroke so that the closing arm causes the ratchet to move from the secondary latched position thereof into the primary latched position thereof and a closing de-energizing switch constructed and arranged to be actuated in response to the movement of the ratchet into the primary latched position thereof to de-energize the electric motor and allow the spring system to effect a return stroke of the sector gear. The power operated driving assembly further includes a manually operable opening energizing switch constructed and arranged to energize the electric motor in response to a manual actuation thereof to move the sector gear through an opening stroke so that the opening structure thereof causes the ratchet to move out of the primary position thereof to allow the door to be moved into an open position and a timer closing de-energizing switch constructed and arranged to be actuated in response to the movement of the pawl into the releasing position thereof to de-energize the electric motor after a predetermined time and allow the spring system to effect a return stroke of the sector gear. 
   Preferably, the ratchet and the sector gear am pivotally mounted about a common axis and the pawl is pivotally mounted about an axis that is parallel to the common axis. 
   Preferably, the door latch assembly includes a housing having a striker receiving opening therein constructed and arranged to be mounted in the vehicle door so that the opening receives the striker during a door closing movement. The ratchet is pivotally mounted on the housing with the striker engaging structure facing outwardly within the opening when the ratchet is in the unlatched position. The latching structure extends within the opening when the ratchet is in the latched positions. The housing carries the pawl, the sector gear and the power operated driving assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
       FIG. 1  is an elevational view of the left side of a conventional four-door vehicle; 
       FIG. 2  is an isolated fragmentary perspective view of the interior of a front door of the vehicle shown in  FIG. 1 ; 
       FIG. 3  is a perspective view at a first side of a power assisted door latch assembly embodying the principles of the present invention; 
       FIG. 4  is a perspective view of a second side of the power assisted door latch assembly shown in  FIG. 3 ; 
       FIG. 5  is a perspective view similar to  FIG. 3  of the door latch assembly with a first cover and a second cover removed; 
       FIG. 6  is a perspective view similar to  FIG. 4  of the door latch assembly with the second over removed; 
       FIG. 7  is a schematic view showing a power operated driving assembly, a power source, a voltage source and controller for the door latch assembly; 
       FIG. 8  is an elevational view showing a plurality of parts of the door latch assembly including a ratchet, a pawl, a sector gear, a first switch member and a second switch member in a primary latched configuration with a conventional striker shown in sectional view mounted on a door frame shown in fragmentary view, 
       FIG. 9  is a view similar to  FIG. 8  showing the pawl in a releasing position and the sector gear in an opening position; 
       FIG. 10  is a view similar to  FIG. 8  showing the door latch assembly in an unlatched position; 
       FIG. 11  is a view similar to  FIG. 8  showing the door latch assembly in a secondary latched position; 
       FIG. 12  is a view similar to  FIG. 11  showing the door latch assembly in a secondary latched position and showing the sector gear partially rotated in a closing direction; and 
       FIG. 13  is a view similar to  FIG. 12  showing the ratchet in a primary latched position and showing the sector gear fully rotated in a closing direction. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a left side elevational view of the exterior of a conventional motor vehicle that has a front door  12  and a back door  14 . Each door  12 ,  14  has an exterior handle  16  and a door latch opening button  18 . The front door  12  has a conventional key-operated lock cylinder to lock and unlock the door  12 . 
   A power operated door latch assembly  22  constructed according to the principles of the present invention is mounted on each door of the vehicle  10  for the power assisted latching and unlatching of each door. 
     FIG. 2  shows an isolated view of the inside of the front door  12 . Two hinges  24  are secured to a first inner edge  28  of the door  12  to pivotally mount the door  12  to a door frame on the vehicle  10  in a conventional manner so the door can be moved between open and closed positions. A power operated door latch assembly  22  is mounted on a second outer edge  30  of the door. The door  12  has an interior door release switch  32  to unlatch the door latch assembly  22  with power assistance and an interior manual door release handle  34  to manually unlatch the door  12  using a manual override. 
   A conventional U-shaped striker is rigidly secured to the door frame of the vehicle  10  in a conventional manner. When the door  12  is moved to the closed position, the door  12  pivots into the door frame and the door latch assembly  22  impacts the striker to latch the door  12 . 
   Referring to  FIGS. 3 and 4 , the door latch assembly  22  includes a housing  36  and a first cover  38  and second cover  40  secured to the first cover  38 . The covers  38 ,  40  are secured to the housing  36  by conventional staking pins  42 ,  44  or other suitable fasteners. The housing  36  engages threaded holes  46  to mount the door latch assembly  22  to a door  12  with conventional bolts or other suitable means. Housing  36  has a mouth structure  31 . Tab  93  on the second cover  40  extends through a slot  95  in the first cover  38  and two tabs  97 ,  99  on the first cover  38  clip over the edge of the second cover  40  at  101 ,  103  to close the door latch assembly  22 . 
   Referring to  FIG. 5 , the housing  36  has a conventional bushing  58  for rotatably mounting the ratchet  50  on pin  44  ( FIG. 6 ) between an unlatched or open position and a primary latched or closed position. Ratchet  50  has a conventional detent fork structure having a notch  110  presenting a primary detent surface  126 . The ratchet  50  has a secondary detent  128  spaced circumferentially from the primary detent  126 . The ratchet  50  has a contoured edge diametrically opposite the notch  110  presenting a cinch drive area  132  and a release clearance area  114 . Ratchet  50  cooperates with the mouth  31  to engage and cinch the striker  106  ( FIG. 8 ) to hold the door closed. 
   Housing  36  has a conventional bushing  56  for rotatably mounting the pawl  52  on pin  42  (FIG.  6 ). Arcuate slot  66  receives connecting arm  64  and allows travel of the pawl  52  between a latching position and a full release overtravel position. Pawl spring  68  extends between the housing  36  and the pawl  52  to bias the pawl  52  against the ratchet  50  to follow the contours of the circumference thereof. Housing  36  has a channel for retaining the pawl spring  68 . 
   Referring to  FIG. 6 , a sector gear  54  is commonly mounted on pin  44  on a side of the housing opposite the ratchet  50 . Sector gear  54  is mounted in such a manner that the sector gear  54  is able to rotate relative to or independently of the ratchet  50 . The sector gear  54  has an opening or releasing arm  70  which extends tangentially from a toothed portion  55 . The sector gear  54  also has a closing or cinching arm  72  which extends axially from the toothed portion  55 . Coil springs  74  are mounted around sector bearing cylinder  59  with a first end  77  engaging the housing  36  and a second end  79  engaging the sector gear  54 . Springs  74  bias sector gear  54  into a null position. 
   Housing  36  has an arcuate slot  57  through which closing arm  72  extends for engagement with cinch drive area  132  of ratchet  50 . As sector gear  54  rotates, it will rotate independently of the ratchet  50  until it engages the cinch drive area  132 . In the release direction, the travel of sector gear  54  is not obstructed by the ratchet  50  due to the release clearance area  114 . Thus, sector gear  54  has a “lost motion” relative to the ratchet  50 . 
   A release lever  62  is commonly mounted on housing bushing  56  on opposite sides of the housing  36  from the pawl. Housing  36  has an arcuate slot  66  through which connecting arm  64  ( FIG. 5 ) extends coupling the pawl  52  and the release lever  62  together for pivotal movement as a single unit. Release lever  62  has a hub from which arms  112 ,  117  (FIG.  8 ),  134 ,  136  and  137  radially extend. 
   Pin  42  provides pivotal support for the pawl  52  and release lever  62  and the pin  44  provides pivotal support for the ratchet  50  and the sector gear  54 . Therefore, the pin  44  defines a rit pivot axis for both the ratchet  50  and the sector gear  54  and the pin  42  defines a second pivot axis for the pawl  52  and release lever  62 . These two axes are essentially parallel. 
   A first electrical switch  76  ( FIG. 5 ) is mounted on the housing  36  and positioned to engage the outer cam surface of the release clearance area  114  as the ratchet  50  rotates. The pivotal movement of ite ratchet  50  will switch or toggle the switch  76  between an “on” state and an “off” slate. A second electrical switch  78  is mounted on housing  36  and positioned to engage arm  112  of the release lever  62 . The pivotal movement of the release lever  62  will switch or toggle the switch  78  between an “on” state and an “off” state. Each switch  76 ,  78  has two conventional electrical connectors  81  ( FIG. 3 ) to connect the switches to a controller  108  (FIG. 
   Wire  80  and bowden wire  82  engage arm  137  of release lever  62 . The outer sheath of the bowden wire  82  is mounted to the housing to effect actuation of the bowden wires. Each end of the wires  80 ,  82  has a cap  87 ,  89  which allows the wires  80 ,  82  to slide relative to the release lever  62 . Thus, wires  80  and  82  do not interfere with the movement of the pawl  52  between the holding and releasing positions during power assisted door opening and closing. 
   Referring to  FIG. 7 , actuator  96  is mounted on the face of the plate  40 . Actuator  96  includes a motor  98  and a clutch assembly to selectively drive the sector gear  54 . The second cover  40  has an opening  48  ( FIG. 4 ) through which a drive shaft  100  extends A drive gear  104  is mounted on the drive shaft  100  and engages the sector gear  54  to provide torque amplification for movement of the sector gear  54  and the pawl  52 . The motor  98  and clutch assembly  102  are energized by the vehicle&#39;s electrical system which is schematically represented as a voltage source  107 . The motor  98 , clutch assembly  102  and the drive shaft  100  are mounted within the door  12 . A portion of the drive shaft  100  is carried in the door latch assembly  22  to support the drive gear  104  in the housing  36  and engage the sector gear  54  with the drive gear  104 . 
   A controller  108  controls the motor  98  and clutch assembly  102  by energizing and de-energizing the same in response to switching signals from the switches  18  and  32  on the door  12 , a remote control  199  and the switch members  76 ,  78  in the door latch assembly  22 . 
   The covers  38 ,  40  are preferably made of steel or other appropriate material. The ratchet  50  and first pawl member  52  are preferably made of steel or other suitable metal, having a plastic cover  94 . The release lever  62  and the sector gear  54  can be made of any suitable plastic or metal. The conventional bushings  56 ,  58  are integral with the housing  36  and are preferably a composite material such as nylon. 
   The Primary Latched Position 
     FIG. 8  shows the neutral or equilibrium configuration of the door latch assembly  22  when the door is closed and latched. The ratchet  50  is in a primary latched position and the striker  106  is held in a notch  110  in the ratchet  50  to hold the door closed. The ratchet  50  is held in the primary latched position by the pawl  52 . 
   Arm  112  on the release lever  62  holds the switch  78  in a depressed position. Release clearance area  114  of the ratchet  50  maintains the first switch  76  in a depressed position. The sector gear  54  is in the null position. 
   There is a small gap or design clearance  116  between the opening arm  70  on the sector gear  54  and arm  117  when the latch assembly  22  is in the primary latched position and the sector gear  54  is in the null position. 
   In this position, the clutch assembly  102  is de-energized to prevent any torque from the ratchet  50  or the sector gear  50  from being applied to the motor  98 . 
   Unlatching and Opening the Door with Power Assistance 
   To unlatch the door latch assembly  22  with power assistance, any one of the switches  18  or  32  on the door  12  or a switch  119  on the remote control  199  is actuated. Each switch  18 ,  32 ,  119  functions as an energizing switch and is independently operable to energize the motor  99 . When the motor and clutch assembly  102  are energized, the motor  98  rotates the drive gear  104  in a first rotational direction to drive the sector gear  54  out of the null position in an opening direction through an opening stroke to an opening position. The opening direction of the sector fib gear  54  is the counterclockwise direction in  FIGS. 8-9 . 
   As the sector gear  54  pivots from the null position to its opening position, the releasing arm  70  contacts the arm  117  of release lever to pivot the pawl  52  from its latching position to its releasing position. Ratchet  50  pivots from the primary latched position to an unlatched position to release the striker  106  so the door can be opened. 
   Although the ratchet spring  118  provides enough force to pivot the ratchet  50  from the primary latched position to the unlatched position when the pawl  52  is moved to the releasing position, it can be understood that the seal pressure exerted by the door seal on the door also tends to move the door latch assembly  22  and the striker apart when the door is unlatched which tends to rotate the ratchet  50  to the unlatched position. However, it will also be appreciated that due to the torque amplification of the drive gear  104  acting upon the sector gear  54 , the potential energy stored in the ratchet spring  118  will be greater than prior art devices. Consequently, the ratchet  50  will be able to pivot to the unlatched position with greater force than prior art devices and without increasing the size of the motor  98 . 
   When the pawl  52  is in the releasing position, the arm  112  is moved away from the second switch  78  to toggle the second switch  78 . When the ratchet  50  pivots from the primary latched position to the unlatched position, the cam surface of the release clearance area  114  of the ratchet  50  moves out of contact with the first switch  76  to toggle the first switch  76 . In response to the toggling of the first switch  76 , the control circuitry  108  de-energizes the motor  98 . The actuator  96  holds the sector gear  54  in its opening position until the ratchet  50  has pivoted to the unlatched position. When the clutch assembly  102  is disengaged, the sector gear  54  pivots from the opening position through a return stroke back to its null position under the spring force provided by one of the sector springs  74 . Consequently, any torque from the ratchet  50  or the sector gear  50  is precluded from being applied to the motor  98 . 
   Closing and Relatching the Door with Power Assistance 
   Referring to  FIGS. 10  to  13 , the door latch assembly  22  engages striker  106  which enters the mouth  31  and engages the ratchet  50  which responsively pivots from the unlatched position toward the primary latched position. Because of the door seal pressure and the relatively lightweight of the vehicle door, the door may not have sufficient momentum to rotate the ratchet  50  all the way to the primary latched position. 
   Usually, the ratchet  50  is rotated to allow the pawl  52  to abut secondary stop  128 . The ratchet  50  is retained in the secondary latched position. When the door latch assembly  22  is in the secondary latched position, the striker  110  is captured in the notch  110  and the door is partially closed and cannot be reopened without moving the pawl  52  to its releasing position. 
   When the pawl  52  engages the secondary stop  128 , the arm  112  depresses the second switch  78 . In response, the controller  108  energizes the motor  98  and clutch assembly  102 . The motor  98  rotates the drive gear  104  in a second direction to cause the sector gear  54  to pivot in a closing direction through a closing stroke in a closing direction. The cinching arm  72  on the sector gear  54  contacts cinching stop  132  of the ratchet  50  so that continued movement of the sector gear  54  in the closing direction pivots or cinches the ratchet  50  from the secondary latched position to the primary latched position. The pawl  52  engages primary detent  126  to retain the ratchet  50  in the primary latched position. 
   When the ratchet  50  returns to the primary latched position, the releasing stop  114  of the ratchet  50  depresses and toggles the first switch  76 . Both switches  76 ,  78  are now depressed. The first switch  76  functions as the closing de-energizing switch which signals the controller  1108 , in responsive to the movement of the ratchet  50  moving into the primary latched position, to de-energize the motor  98  and disengage the clutch assembly  102 . When the clutch assembly  102  is de-energized, springs  74  return the sector gear  54  from the closing position through a return stroke to the null position. The drive gear  104  and the drive shaft  100  freely rotate with the sector gear  54  as it returns to the null position. When the sector gear  54  is back in the null position, the door latch assembly  22  is again in the neutral or equilibrium position with any torque from the ratchet  50  or the sector gear  50  being precluded from being applied to the motor  98 . 
   Unlatching and Opening the Door with Manual Override 
   The opening button  18  functions as an electrical switch when it is partially depressed through its actuation stroke and functions as a mechanical release means when it is fully depressed through its actuation stoke. Therefore, the opening button  18  is used to open the door with power assistance by partially depressing the button  18  through its actuation stroke and is used to open the door  12  manually with a mechanical override by fully depressing the button  18  through its full actuation stroke. The interior door release handle  34  on the inside of the door  12  is used to unlatch the door  12  manually with mechanical override. 
   The interior door release handle  34  is operatively connected through Bowden wire  80  to the pawl  52 . By actuating the interior door release handle  34 , the Bowden wire  80  is pulled to move the pawl  52  from its holding position to its releasing position to disengage the pawl  52  from the ratchet  50 . The ratchet  50  then moves to its unlatched position under the spring force of the ratchet spring  118  and the seal load on the door  12 . 
   The button  18  in the door  12  is mechanically linked in a conventional manner to the release wire  82 . If the button  18  is fully depressed, it pulls the wire  82  in a direction to move the pawl from its holding position to its rotating position to release the ratchet  50 . 
   It can be appreciated that the manual override provided by the button  18  and the interior handle  34  can release the ratchet  50  from either the primary latched position or secondary latched position to open the door  12 . Each manual release  18 ,  34  functions independently and each holds the pawl  52  in the releasing position as long as the manual release  18  or  34  is held in an actuated position by the person opening the door  12 . 
   It is contemplated to use many conventional manual release handles to unlatch the door latch assembly  22 . It is also contemplated to use the door latch assembly  22  can also be used with any conventional manual or power operated door locking and unlocking system. 
   It can be understood that to close the open door and relatch the same in the primary latched position without power assistance, for example, in the event of a power failure, the door  12  is simply closed with greater force than is ordinarily used when power assistance is available. The manual closing force is applied to the door  12  must be sufficient to rotate the ratchet  50  to the primary latched position so the pawl  52  can move back into its holding position and engage the first tooth portion  109  of the ratchet  50 . The door  12  must be closed hard enough to sufficiently compress the door seal on the door frame to allow relatching. 
   It is understood that the illustrated operation is exemplary only and not intended to be limiting. 
   The latch assembly  22  can be used in other applications. The door lath assembly can be used, for example, on a powered sliding door opening mechanism can start. It is contemplated to use the door latch assembly in a vehicle door which includes a power mechanism to move the door from the open position to the secondary latched position with power assistance. 
   The above-described embodiment of the invention is intended to be an example of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention, as defined in the appended claims.