Abstract:
A lock unit for a vehicle includes a rotatable catch biased in an opening direction about a catch rotation axis toward an open position of the lock unit in which a first recess of the catch is configured to receive a striker of the vehicle. Additionally, the catch includes a second recess disposed before the first recess in the opening direction. A pawl including a slot rotatable about a fixed pawl pivot axis is biased toward both the catch and the pawl pivot axis. The pawl includes a blocking arm which extends into the second recess of the catch when the lock unit is in a secondary latched position. A blocking lever of a ratchet abuts the blocking arm of the pawl against the catch in a primary latched position of the lock unit preventing rotation of the pawl away from the catch. When the lock unit is forced from the secondary latched position to the primary latched position, the pawl moves in a longitudinal direction of the slot avoiding the rotational blocking action of the ratchet.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to door latches, and more specifically to a lock unit for the door of a vehicle utilizing a pawl having a slot mounted on a fixed pawl pivot axis. 
     BACKGROUND OF THE INVENTION 
     Lock units customarily used for side-doors of motor vehicles utilize a latching mechanism, known as a catch, which receives a catch-bolt, or striker, disposed on a pillar of the vehicle doorframe. The catch is biased to an open position wherein a slot of the latch housing is aligned with a recess of the catch. As the door is shut, the striker enters the recess through the slot and rotates the catch to a closed position in which the striker is retained in the recess by a pawl which prevents the catch from rotating toward the open position. Typically the pawl is heavily biased towards the catch with the interface of the two comprised of a further negative biased angle to resist high acceleration forces. The latch housing is typically made of plastic and may be closed sealingly all-around by a cover outside the region of the slot. Such lock units typically include at least one release lever (e.g., an inside or outside door handle) and a displaceable locking mechanism (e.g., a lock cylinder at or in the outside door handle or a slide button disposed inside the window pane area of the door). In such a case, with the locking mechanism unlocked, the motion of the inside or outside door handle is interconnected through the mechanism and the motion separates the connection of the pawl and the catch by overcoming the pawl bias forces, thereby allowing the spring-loaded catch to move to the open position. 
     As required by law, lock units for doors, hatches and tailgates of motor vehicles must be provided with a secondary latched position in addition to the primary latched position. This secondary latched position falls between the primary latched position and the open position such that if the catch fails to reach the primary latched position, the door will be retained shut in the secondary latched position rather than moving all the way to the open position, which would obviously be dangerous to an occupant of a moving vehicle. In addition to preventing the vehicle door from opening during travel, the secondary latched position is also perceptible when a user does not close the vehicle door with sufficient force. By law, the secondary latched position leaves the door visibly ajar when the vehicle door is closed with too little force to be noticed that it is not securely latched. By applying additional force (e.g., leaning against the vehicle door), the latching mechanism can be forced into the primary latched position and the door completely shut. 
     When released from the primary latched position by actuating the release lever, the pawl abruptly breaks away from the corresponding locking surface of the catch and the spring-loaded catch moves at a high velocity to the open position. The abrupt movement of the locking surfaces against one another results in a significant opening clack followed immediately by a second significant clack caused by the catch making impact with a limit stop as it reaches the open position. Owing to the high forces biasing the locking surfaces of the pawl and catch against one another (and also biasing the catch toward the limit stop), the noises caused by opening the vehicle door are quite loud. Additionally, the high impacts on the pawl and catch can cause damage to the lock unit and severely limit its useful life, especially since most of the impact occurs along the locking surfaces. 
     German Patent Application No. DE 10 2007 003 948 A1 describes a multi-pawl latching mechanism which reduces both the latching noises during opening and the forces required to actuate the latching mechanism. The locking surfaces of the catch and a first pawl are correspondingly chamfered and canted to achieve a smooth and gradual sliding when the locking surfaces are released from one another. Because the locking surfaces were designed to reduce the resultant shear forces caused by the locking surfaces pressing against one another while the catch is released, the forces required to actuate the locking mechanism are also correspondingly reduced. Further, due to the reduction in forces acting on the latching mechanism, the noise produced during opening is significantly reduced. 
     However, because the locking surfaces are designed to slide relatively easily with respect to one another, the latching mechanism is not self-latching (i.e., the locking surfaces do not hold the catch in place on their own) and requires a pawl blocking lever to hold the first pawl against the catch in the primary latched position. Additionally, to achieve a secondary latched position, a second pawl is also required. To prevent the pawl blocking lever from engaging in the secondary latched position during closing, the second pawl is disposed in a separate plane from the catch, the first pawl and the blocking lever. The secondary latched position is achieved if the primary latched position fails to engage (e.g., first pawl slides off the catch) by a bolt extending from the catch to the plane of the second pawl which abuts a blocking arm of the second pawl in the opening path of the catch. Providing the second pawl on a different plane and the introduction of the bolt into the catch can be costly from a manufacturing standpoint, however. Thus, while the multi-pawl design effectively reduces opening noise and latch actuation forces, it requires multiple different components at multiple planes of the latching mechanism, thereby making the device relatively complex and expensive to manufacture. 
     SUMMARY OF THE INVENTION 
     In order to reduce size and manufacturing costs, the primary and secondary latched positions of a lock unit should reside on the same plane as the catch. Further, providing a single blocking arm of a single pawl to achieve the primary and secondary latched positions helps to further simplify the design and ensure consistent operation. However, the lock unit should still utilize a smooth release of locking surfaces to minimize noise and actuation forces. In addition, the design should take into account manufacturing tolerances such that minor dimensional variations will not adversely effect the performance of the lock unit. 
     In an embodiment, the present invention provides a lock unit having a pawl disposed intermediate a catch and a blocking lever. The catch is rotatable and biased in an opening direction about a catch rotation axis toward an open position of the lock unit in which a first recess of the catch is configured to receive a striker of the vehicle. Additionally, the catch includes a second recess disposed before the first recess in the opening direction. The pawl includes a slot rotatable about a fixed pawl pivot axis and is biased toward both the catch and the pawl pivot axis. Further, the pawl includes a blocking arm which extends into the second recess of the catch when the lock unit is in a secondary latched position. The blocking lever abuts the blocking arm of the pawl against the catch in a primary latched position of the lock unit. When the lock unit is forced from the secondary latched position to the primary latched position, opposite the opening direction of the catch, the pawl moves in a longitudinal direction of the slot and avoids displacement of the blocking lever. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present invention will be more readily apparent from the following detailed description and drawings of illustrative embodiments of the invention in which: 
         FIG. 1  is a front view of a lock unit in accordance with an embodiment of the present invention in the primary latched position; 
         FIG. 2  is a front view of a lock unit in accordance with an embodiment of the present invention with the catch released from the primary latched position; 
         FIG. 3  is a front view of a lock unit in accordance with an embodiment of the present invention in the open position; 
         FIG. 4  is a front view of a lock unit in accordance with an embodiment of the present invention in the catch over-travel position; 
         FIG. 5  is a front view of a lock unit in accordance with an embodiment of the present invention in the secondary latched position; 
         FIG. 6  is a front view of a lock unit in accordance with an embodiment of the present invention after linear travel of the pawl from the secondary latched position; and 
         FIG. 7  is a front view of a lock unit in accordance with an embodiment of the present invention during reset of the linear position of the pawl. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 and 3 , a lock unit  10  according to an embodiment of the present invention is shown in the primary latched position and the open position, respectively. The lock unit  10  includes a baseplate  12  for mounting the lock unit  10  to a door, hatch or tailgate of a vehicle with a slot  14  facing a striker  16  mounted to the vehicle body. Typically, the striker  16 , or catch bolt, is a pin or U-shaped bracket mounted to a partition at the rear side of the vehicle doorframe and extending into the plane of the door opening. The lock unit  10  is typically mounted opposite the vehicle door hinges with the leading edge  13  of the baseplate  12  facing the striker  16  and the components of the lock unit  10  being disposed in the vehicle door. With such a configuration, as the vehicle door is shut, the striker  16  extends into the slot  14  of the baseplate  12  and into a first recess  22  of a catch  20  to rotate the catch  20  from an open position ( FIG. 3 ) to a primary latched position ( FIG. 1 ). It is noted where the striker  16  is located on the vehicle door, the lock unit  10  is mounted to the vehicle body and, regardless of its placement, a housing or cover could also be provided in addition to or in lieu of the baseplate  12  to further protect the components of the lock unit  10 . 
     In one embodiment, the catch  20 , pawl  40  and ratchet  60  can be relatively flat parts made from metal or plastic. A pawl spring  50  may be connected to the pawl  40  in by securing one end of the spring behind peg  42 , which can be added to the pawl  40  by a subsequent operation, but may be integrally formed by a molding process. However, in other embodiments, the pawl spring  50  may be connected to the pawl  40  in other ways, e.g., by rotatably positioning one end of a torsion spring into a hole in the pawl  40 . In another, less efficient embodiment the pawl may be biased by individual springs towards the catch  20  and longitudinally towards the pawl axis  46 . The baseplate  10 , and any housing covering the lock unit  10 , can also be formed by plastic injection molding. In another embodiment, the lock unit  10  is constructed from metal or a combination of metal and plastic components. 
     In  FIG. 1 , the vehicle door is fully closed and the lock unit  10  is in the primary latched position. The catch  20 , which is mounted to a catch rotation axis  24  via catch mounting hole  26 , retains the striker  16  in a first recess  22 . The catch  20  is biased by a spring to rotate about the catch rotation axis  24  in the opening direction S 1 , but is retained in the primary latched position by a blocking arm  48  of a pawl  40  which, in turn, is held in place by a blocking lever  62  of a ratchet  60 . The ratchet  60  is mounted adjacent the pawl  40  to a ratchet rotation axis  68  via a ratchet mounting hole  69 . A primary stop  32 , which may be located at the bottom of the first recess  22  or on the periphery of the catch  20  between the first and second recesses  22 ,  30 , contacts the blocking arm  48  of the pawl  40 . Because the contact faces of the primary stop  32  and the blocking arm  48  are designed so as to slide smoothly apart (e.g., by incorporating positive angled, sloped surfaces of gradually-reduced incline), the blocking lever  62  is provided abutting a stop  54  of the pawl  40 . 
     Regardless of the relative placement of the blocking lever  62  and stop  54 , the ratchet  60  may be prevented from rotating by the normal force from the stop  54  running through the ratchet rotation axis  68 . However, it is preferable to limit the rotation of the ratchet  60  about the ratchet rotation axis  68  using a ratchet spring  70 , which may be a torsion spring having one end connected to the baseplate  12  and the other end connected to the ratchet  60  at a spring support  66 . Thus, even if the force from the stop  54  causes a moment to be applied to the ratchet  60  (i.e., normal force does not run through the ratchet rotation axis  68 ), the ratchet spring  70  will hinder rotation and maintain contact between the blocking lever  62  and the stop  54 , thereby maintaining the position of the pawl  40  and preventing the primary stop  32  from coming free from the blocking arm  48 . Limit stops (e.g., protrusions extending from the baseplate  12 ) could also be used to limit the rotation of the ratchet  60 , as well as the catch  20  and the pawl  40 , to a predetermined range of motion. According to an embodiment, the rotation of the ratchet  60  is at its limits in the clockwise direction when in the primary latched position and is biased to that position by ratchet spring  70 . 
     In order to open the vehicle door, the lock unit  10  is released from the primary latched position shown in  FIG. 1  by moving the blocking lever  62  away from the stop  54 . Preferably, the ratchet  60  is connected to an operating link  72  at spring support  66 , or at another point of the ratchet  60 , so as to enable a rotation of the blocking lever  62  counter-clockwise away from the stop  54  as shown in  FIG. 2 . The operating link  72  is connected outside the lock unit  10  to an inside and/or outside door handle (e.g., designed as a rod assembly or Bowden cable) which is actuated by a user opening the vehicle door. Alternatively, the rotation of the ratchet  60  could be controlled by a servo motor and operated by a switch or sensor. 
     Referring to  FIG. 2 , the lock unit  10  is shown immediately after release of the catch  20  from the primary latched position. It is noted that the release is rather quick since only one lever needs to be actuated to release the catch  20 . Once the blocking lever  62  clears the stop  54 , the spring force of the catch  20  causes it to rotate and the primary stop  32  slides smoothly along the blocking arm  48 , thereby causing the pawl  40  to rotate in a clockwise direction toward the ratchet  60 . At this point, the blocking lever  62  is accommodated in a recessed portion  52  of the pawl  40  adjacent the stop  54 . 
     Once the primary stop  32  clears the blocking arm  48  at the position shown in  FIG. 2 , the catch  20  is free to rotate in the opening direction S 1 . Due to the speed of rotation of the catch  20  and the transitional curved surfaces of the blocking arm  48  and the secondary stop  34 , the lock unit  10  skips over the secondary latched position shown in  FIG. 5  as the second recess  30  and secondary stop  34  of the catch  20  slide past the blocking arm  48 . The catch  20  continues to rotate until it is stopped by the baseplate  12  through slot  14 , full extension of the spring or by a different limit stop as shown in the open position of  FIG. 3 . While the catch  20  rotates, its spring force in the opening direction S 1  pushes the striker  16  through the slot  14  toward the leading edge  13  of the base plate  12 , thereby separating the vehicle door from the body. In this manner, the lock unit  10  is self-opening since it does not require external actuation forces after release. 
     Referring to  FIG. 3 , the ratchet  60  can continue to rotate in a counter-clockwise direction during and/or after the full-travel of the catch  20  by the continuing actuation of the operating link  72  such that a release edge  64  presses, against a release arm  56  of the pawl  40  to rotate it away, clear from the catch  20 . This position could be maintained by locking the ratchet  60  in position until the vehicle door is closed. However, preferably, the open position of the lock unit  10  is achieved once ratchet  60  is released to abut blocking lever  62  against the lever retaining wall  55  of the recessed portion  52  and the pawl spring  50  rotates the pawl  40  back toward the catch  20  such that the blocking, arm  48  abuts the sliding surface  36  of the catch  20 . 
     When a user closes the vehicle door, the striker  16  enters into the slot  14  and hits against a striking edge  38  of the first recess  22 . The force of the door as it closes causes the striker  16  to press against the striking edge  38  of the first recess  22 , thereby rotating the catch  20  against the spring force opposite the opening direction S 1 . During initial rotation, the blocking arm  48  of the pawl  40  slides along the sliding surface  36  of the catch  20 . Similarly to the release of the catch  20  when opening the door, the second recess  30  and the primary stop  32  will slide past the blocking arm  48  such that the secondary latched position shown in  FIG. 5  is bypassed as long as the door is shut with sufficient force. In such a case, the catch  20  may reach an over-travel position shown in  FIG. 4 . After the primary stop  32  of the catch  20  clears the blocking arm  48  of the pawl  40 , the pawl spring  50  rotates the pawl  40  sufficiently away from the ratchet  60  such that the blocking lever  62  travels with its tip along the lever retaining wall  55  until it exits the recessed portion  52 , at which point, the ratchet spring  70  rotates the blocking lever  62  back to its position below the stop  54 . In one embodiment, the blocking lever  62  has a rounded tip to facilitate a smooth sliding along the lever retaining wall  55 , which may also be canted and preferably extends from stop  54  towards the catch  20 . 
     However, in a case where the vehicle door is not shut with sufficient force (i.e., closed too slowly), the lock unit  10  enters into the secondary latched position shown in  FIG. 5 . The secondary latched position falls between the primary latched position and the open position such that if the primary latched position is not engaged, the lock unit  10  will not disengage to the open position which would release the vehicle door during travel and place the vehicle occupants at considerable risk. Latching mechanisms can release from the primary latched position due to the outward force applied by the vehicle door compression seals, vehicle vibrations and impacts to the vehicle and the like; when this occurs, the latching mechanism must have a secondary latched position to prevent the door from opening. 
     Referring to  FIG. 5 , the secondary latched position according to an embodiment of the present invention is shown. When a user shuts the vehicle door too slowly, the second recess  30  of the catch  20  does not slide past the blocking arm  48  of the pawl  40 ; rather, after sliding surface  36  slides past the blocking arm  48 , the blocking arm  48  is pressed into the second recess  30  of the catch  20 , thereby assuming the secondary latched position. In response to the continued closing of the vehicle door, or an additional external force which may be applied by the user or a servo motor, the catch  20  continues to rotate opposite the opening direction S 1 . When this happens, the exit edge  31  of the second recess  30  presses against the blocking arm  48  in the direction of the slot  44 . The pawl spring  50  abuts peg  42  disposed on the pawl  40 , or is otherwise connected to the pawl  40 , such that it biases the pawl  40  toward both the catch  20  and the pawl pivot axis  46 . The force translated to the pawl  40  by the exit edge  31  pressing against the blocking arm  48  is at least partially, and preferably substantially, in a longitudinal direction L of the slot  44 . 
     Referring to  FIG. 6 , the lock unit  10  is shown traveling from the secondary latched position toward the primary latched position after linear travel of the pawl  40  in the longitudinal direction L of the slot  44 . The pawl spring  50  biases the pawl  40  in the direction of spring force S 2  toward the catch  20  and the fixed pawl pivot axis  46 . For better understanding of the forces, spring force S 2  is shown as a resultant vector of two component forces, a first force component S 3  acting along the longitudinal direction L of the slot  44  and a second force component S 4  acting in the direction of the catch  20 . The force applied to the pawl  40  by the catch  20  as it rotates opposite the opening direction S 1  is generally in the longitudinal direction L of the slot  44  due to the relative locations of the contact faces of the exit edge  31  and the blocking arm  48 . The exit edge  31  is gradually curved to achieve a smooth sliding against the curved edge of the blocking arm  48 . Preferably, the contact face of the blocking arm  48  is shorter and has a steeper curve while the contact face of the exit edge  31  is longer and more linear to ensure a sufficient and consistent force in the longitudinal direction L of the slot  44  while exit edge  31  and blocking arm  48  slide against one. However, many different complementary surfaces can be used on the exit edge  31  and blocking arm  48 , such as flat and rounded, chamfered and canted, etc. 
     The pawl  40  is biased toward the pawl pivot axis  46  in the longitudinal direction L of the slot  44  by first force component S 3  and biased toward the catch  20  by the second force component S 4 , together spring force S 2 . The force applied to the pawl  40  as the exit edge  31  slides against the blocking arm  48  counter-acts the first force component S 3  to compress the pawl spring  50  and move the pawl  40  linearly along the longitudinal direction L of the slot  44  while the second force component S 4  holds the pawl  40  against the catch  20 . Once the pawl linear travel exceeds the stationary tip of the blocking lever  62 , the pawl is free to rotate clockwise away from catch  20 . At the point shown in  FIG. 6 , the pawl pivot axis  46  is located near the opposite end of the slot  44  and the stop  54  has essentially cleared the tip of the blocking lever  62  due to the linear travel of the pawl  40 . At this point, the downward rotation of the pawl  40  as the blocking arm  48  slides to the transition region between the exit edge  31  and primary stop  32  allows the blocking lever  67  to move into the recessed portion  52  along the lever retaining wall  55 . 
     Referring to  FIG. 7 , the lock unit  10  is moving back to the primary latched position as the catch  20  is released from the blocking arm  48  of the pawl  40 . Thus, while the catch  20  continues to rotate opposite the opening direction S 1 , the pawl  40  is moving in the opposite direction of the catch  20 . Since the pawl  40  is also moving toward the primary latched position, the speed of rotation of the catch  20  can be slow or even stopped depending on the range of movement of pawl  40  along the longitudinal direction L of the slot  44 . 
     As the primary stop  32  of catch  20  nears the primary latched position, the blocking arm  48  of pawl  40  slides smoothly up along primary stop  32 . The linear reset of pawl  20  relative to the pawl pivot axis may or may not take place with a rotation of the ratchet  60 . The positive slope between the blocking arm  48  and primary stop  32  are sufficient to allow pawl  40  to rotate into the catch  20  and clear blocking lever  62  with only slight over-travel rotation of catch  20 . If the first force component S 3  is sufficient to overcome ratchet spring  70  and the speed slow enough to overcome the stationary inertia of ratchet  60 , the linear reset of pawl  20  may take place through rotation of the ratchet  60  prior to the catch  20  reaching the primary latched position. After reaching the position of the lock unit  10  shown in  FIG. 7 , the primary stop  32  begins to slide smoothly down along the blocking arm  48  and the tip of the blocking lever  62  slides smoothly down along the lever retaining wall  55  until it is released to rest below the stop  54  to return the lock unit  10  to the primary latched position (cf.  FIGS. 7 and 1 ). 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.