Patent Publication Number: US-2006006669-A1

Title: Vehicle latch apparatus and method

Description:
BACKGROUND OF THE INVENTION  
      Conventional vehicle latches prevent separation between latched elements, such as a vehicle door and door frame, a vehicle hood, trunk lid, or tonneau cover and adjacent vehicle portions, and the like. Some conventional vehicle latches also perform one or more additional functions. For example, some vehicle latches provide clearance between a hood, trunk lid, tonneau cover, or other closure panel and adjacent vehicle portions when the latch is in an unlatched state, such as in cases where user access for opening the closure panel is desired. In some applications, these latches provide resistance to the weight of a closure panel hinged about a horizontal axis.  
      Conventional vehicle latches are often used with or include a variety of elements and assemblies to separate a closure panel from adjacent vehicle portions when the latch is unlatched. For example, some conventional latches rely upon the force from one or more springs or other biasing elements at a hinge of the closure panel to separate the closure panel from adjacent vehicle portions when the latch is unlatched. However, due to their locations, such biasing elements typically provide relatively little mechanical advantage in separating the closure panel from adjacent vehicle portions. In cases where one or more biasing elements at the hinge are also used to assist in opening the closure panel to a fully-opened position, such biasing elements can require substantial force to close the closure panel, and can increase the force required to unlatch the latch due to increased friction between latch components. Also in such cases, the force exerted by the biasing elements typically increases as the closure panel is closed, and is greatest when the closure panel is in its closed position—a condition that is not always desirable. Although lower-strength springs or other biasing elements can instead be used, such biasing elements are often not strong enough to open the closure panel, or do so to an insufficient degree.  
      Other conventional vehicle latches rely upon the force from one or more springs or other biasing elements that are part of the latch or are otherwise located nearer to a free end of the closure panel. However, these latch and biasing element configurations typically have the same shortcomings as the latch and biasing element configurations described above, including higher closing forces and increased unlatching forces.  
     SUMMARY OF THE INVENTION  
      Some embodiments of the present invention provide a vehicle latch for releasably securing a striker with respect to the latch, wherein the vehicle latch comprises a ratchet pivotable about an axis between a latched position in which the ratchet retains the striker and an unlatched position in which the striker can be removed from the ratchet; and a lever engagable with the striker and pivotable about the axis to at least assist in moving the striker from a first position with respect to the axis to a second position with respect to the axis, wherein the second position is located a greater distance from the axis than the first position.  
      In some embodiments of the present invention, a vehicle latch for releasably securing a striker with respect to the latch is provided and comprises a ratchet having a latched position in which separation of the striker from the ratchet is restricted and an unlatched position in which the striker can be separated from the ratchet; and a lever pivotable with respect to the ratchet, the lever biased in a pivoting direction and positioned to exert an unlatching force on the striker, the unlatching force having a first magnitude when the ratchet is in the latched position and a second magnitude when the ratchet is in the unlatched position, the second magnitude greater than the first magnitude.  
      Some embodiments of the present invention provide a vehicle latch for releasably securing a striker with respect to the latch, wherein the vehicle latch comprises a ratchet having a latched position in which movement of the striker is restricted by the ratchet and an unlatched position in which the striker is removable from the ratchet; a lever pivotable with respect to the ratchet, the lever engagable with the striker and pivotable to bias the striker toward a disengaged position with respect to the ratchet in the unlatched position of the ratchet, the lever having a first position when the latch is in a latched state and a second position when the latch is in an unlatched state; and a spring coupled to the lever and positioned to exert a varying torque on the lever at different positions of the lever, the torque having a first magnitude when the lever is in the first position and a second magnitude with the lever in the second position, wherein the first magnitude is smaller than the second magnitude.  
      In some embodiments of the present invention, a method of unlatching a vehicle latch from a striker is provided, and comprises applying a first force to a pivotable lever when the latch is in a latched state, the first force having a radial component and a tangential component with respect to an axis about which the lever is pivotable; disengaging a pawl from a ratchet; moving the ratchet from a latched position in which the ratchet restricts removal of the striker from the vehicle latch toward an unlatched state in which the striker is removable from vehicle latch; pivoting the lever; moving the striker with respect to the ratchet by pivoting the lever; and applying a second force to the lever when the latch is in an unlatched state, the second force having a radial component and a tangential component with respect to the axis, wherein the tangential component of the second force is greater than the tangential component of the first force.  
      Some embodiments of the present invention provide a method of unlatching a vehicle latch from a striker to release a portion of a closure panel of a vehicle from the vehicle, wherein the method comprises applying a torque to a lever while the latch is in a latched state; disengaging a pawl from a ratchet; pivoting the ratchet about a pivot from a latched position in which the ratchet restricts removal of the striker from the vehicle latch toward an unlatched position in which the striker is removable from the ratchet; pivoting the lever in a first direction after disengaging the pawl from the ratchet; increasing the torque on the lever as the lever pivots in the first direction; and moving the striker with the lever from a first distance with respect to the pivot to a second distance greater than the first distance with respect to the pivot.  
      In some embodiments of the present invention, a method of releasably securing a striker with respect to a vehicle latch to releasably secure a closure panel of the vehicle to the vehicle is provided, wherein the vehicle latch has an unlatched state in which the striker is insertable into the vehicle latch and a latched state in which a ratchet restricts removal of the striker from the vehicle latch, and wherein the method comprises exerting a force upon a lever by the striker while the vehicle latch is in the unlatched state; moving the striker towards a latched position of the striker; moving the lever towards a latched position of the lever by moving the striker; pivoting the ratchet from an unlatched position of the ratchet to a latched position of the ratchet; and decreasing a resistance force exerted upon the striker by the lever as the striker is moved toward the latched position of the striker.  
      Further aspects of the present invention, together with the organization and operation thereof, will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention is further described with reference to the accompanying drawings, which show an embodiment of the present invention. However, it should be noted that the invention as disclosed in the accompanying drawings is illustrated by way of example only. The various elements and combinations of elements described below and illustrated in the drawings can be arranged and organized differently to result in embodiments which are still within the spirit and scope of the present invention.  
      In the drawings, wherein like reference numeral indicate like parts:  
       FIG. 1  is a perspective view of a latch assembly according to an embodiment of the present invention, shown in a latched state engaged with a striker;  
       FIG. 2  is a perspective view of the latch assembly illustrated in  FIG. 1 , shown in an unlatched state disengaged from the striker;  
       FIG. 3  is an exploded perspective view of the latch assembly illustrated in  FIGS. 1 and 2 ;  
       FIG. 4  is an elevational view of the latch assembly and striker illustrated in  FIGS. 1-3 , shown with the latch assembly in the latched state engaged with the striker;  
       FIG. 5  is another elevational view of the latch assembly and striker illustrated in  FIGS. 1-3 , shown with the latch assembly in an unlatched state;  
       FIG. 6  is another elevational view of the latch assembly and striker illustrated in  FIGS. 1-3 , shown with the latch assembly in an unlatched state and the striker moved away from the ratchet;  
       FIG. 7  is a planar view of a latch assembly according to another embodiment of the present invention, shown in a latched state;  
       FIG. 8  is a planar view of the latch assembly illustrated in  FIG. 7 , shown in an unlatched state;  
       FIG. 9  is a perspective detail view of the latch assembly illustrated in  FIGS. 7 and 8 , shown with the latch assembly in the latched state;  
       FIG. 10  is another perspective detail view of the latch assembly illustrated in  FIGS. 7 and 8 , shown with the latch assembly in an unlatched state; and  
       FIG. 11  is another perspective detail view of the latch assembly illustrated in  FIGS. 7 and 8 , shown with the latch assembly in an unlatched state and the striker moved away from the ratchet. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT  
      An embodiment of a latch assembly according to the present invention is illustrated in  FIGS. 1-6 . With reference first to  FIG. 1 , a latch assembly  10  is illustrated in a latched state in which a striker  12  is retained by the latch assembly  10 . As shown in  FIG. 2 , the latch assembly  10  also has an unlatched state in which the striker  12  is released from the latch assembly  10 .  
      The latch assembly  10  releasably engages the striker  12  to control the release of a movable closure panel  18  of a vehicle (see  FIGS. 4-6 ). The movable closure panel  18  can be any openable panel of a vehicle, including without limitation a hood, door, trunk, liftgate, tonneau cover, window, and the like. The term “closure panel” does not indicate or imply that such elements must be planar or substantially planar in shape. Such elements can have any shape suitable for covering and uncovering an opening of a vehicle, such as a doorway, an engine compartment, a trunk, truck bed, or other storage area, and the like.  
      In some embodiments, the striker  12  is coupled to a closure panel  18  and the latch assembly  10  is coupled to the vehicle adjacent the closure panel  18  (e.g., to a frame, a body panel, or other vehicle portion). Therefore, when the striker  12  is released from the latch assembly  10 , the striker  12  and closure panel  18  can be moved away from the latch assembly  10  and adjacent vehicle portion, thereby moving the closure panel  18  to an opened position. In other embodiments, the latch assembly  10  can instead be coupled to the closure panel  18 , and the striker  12  can instead be coupled to another portion of the vehicle. Therefore, the following description refers to the striker  12  coupled to the closure panel  18  and the latch assembly  10  coupled to an adjacent vehicle portion by way of example only.  
      The latch assembly  10  and striker  12  can be mounted directly to the vehicle portion and closure panel  18 , respectively. Alternatively, the latch assembly  10  and/or striker  12  both can be directly or indirectly coupled to their respective vehicle portions (e.g., upon a mounting block, fixture, bracket, or other element or assembly coupled to the vehicle portion and closure panel  18 ), if desired. As used herein and in the appended claims, the term “coupled” does not necessarily mean that one element is directly fastened to another element. Instead, the term “coupled” means that one element is directly or indirectly connected to another element or is in mechanical communication with another element. Examples of elements “coupled” together include elements directly connected to one another (e.g., via welding, bolting, gluing, frictionally engaging, mating, etc.), elements connected to one another by one or more other elements, elements acting upon one another (e.g., via camming, pushing, or other interaction), and an element imparting motion directly or through one or more other elements to another element.  
      As illustrated in  FIGS. 1-6 , some embodiments of the latch assembly  10  according to the present invention can include a frame  14 . The frame  14  can provide one or more mounting locations for coupling the latch assembly  10  to the vehicle or closure panel  18 , and can provide one or more mounting locations for various other components of the latch assembly  10 . The frame  14  can have any shape desired, such as a substantially planar shape, a body having portions extending in different directions and/or at different angles, and the like. Also, the frame  14  can include one or more elements, such as bars, panels, rods, and the like. Elements of the frame  14  can be coupled in any manner, such as by welding, brazing, fasteners, adhesive or cohesive bonding material, inter-engaging elements, and the like. In some embodiments, part or all of the frame  14  is manufactured by stamping, bending, casting, molding, machining, or other forming operations. Accordingly, the term “frame” encompasses structures defined by one or more elements manufactured in any manner.  
      In some embodiments of the present invention, a ratchet  20  is coupled to the frame  14  and is movable between a latched position in which the ratchet  20  captures and retains the striker  12  and an unlatched position in which the striker  12  is free to be removed from the ratchet  20 . For example, the ratchet  20  in the illustrated embodiment of  FIGS. 1-6  is coupled to a pivot  38  that is coupled to the frame  14 , and is rotatable about an axis  37  at the pivot  38 . In some embodiments, the pivot  38  can be integral with or otherwise non-rotatable with respect to the ratchet  20  or the frame  14 . In other embodiments, the pivot  38  is rotatable with respect to the ratchet  20  and the frame  14 . In the illustrated embodiment of  FIGS. 1-6 , the pivot  38  is a separate element fixed with respect to the frame  14  and about which the ratchet  20  can pivot.  
      In some embodiments, the rotational range of the ratchet  20  is limited in one or more manners and by one or more elements. For example, the range of rotation of the ratchet  20  toward a latched position can be limited by one or more stops, such as one or more walls, bosses, lips, ribs, bumps, pins, or other elements of the latch assembly  10 . Such stops can be in any location in the latch assembly  10  in which the stops can perform this function, including without limitation on the frame  14  or pawl  26  of the latch assembly  10 , on the lift lever  36  of the latch assembly  10  (described below), and the like. In the illustrated embodiment of  FIGS. 1-6 , the frame  14  has a projection  16  positioned to limit rotation of the ratchet  20  past the unlatched position shown in  FIGS. 2, 5 , and  6 . In other embodiments, one or more other stops can limit rotation of the ratchet  20  past a latched position, if desired.  
      The ratchet  20  can have an opening  22  (see  FIGS. 3-6 ) positioned to receive the striker  12  when the ratchet  20  is in the unlatched position and retaining the striker  12  when the ratchet  20  is in the latched position. In some embodiments, the ratchet  20  is biased toward the unlatched position to allow the striker  12  to enter and exit the opening  22 . The ratchet  20  can be biased by one or more springs of any type, such as one or more extension, compression, leaf, or torsion springs, magnet sets, elastic members, and the like. In some embodiments, such springs can be directly coupled to the ratchet  20 . Such springs can also or instead be coupled to the pivot  38  for rotatably biasing the pivot  38  (e.g., in those embodiments in which the pivot  38  is integral with the ratchet  20  or is otherwise fixed against rotation with respect to the ratchet  20 ). The springs can also be coupled to the frame  14  or other structure adjacent the latch assembly  10  when installed on the vehicle. In the illustrated embodiment of  FIGS. 1-6 , a torsion spring  23  (see  FIG. 3 ) is mounted upon the pivot  38 , and has one end coupled to the frame  14  and another end coupled to the ratchet  20  for biasing the ratchet  20  toward its unlatched position.  
      Some embodiments of the present invention include a pawl  26  coupled to the frame  14  and movable with respect to the ratchet  20  in order to releasably retain the ratchet  20  in one or more latched positions. For example, the pawl  26  in the illustrated embodiment of  FIGS. 1-6  is coupled to a pivot  32  that is coupled to the frame  14 , and is rotatable about an axis  33  at the pivot  32 . In some embodiments, the pivot  32  can be integral with or otherwise non-rotatable with respect to the pawl  26  or the frame  14 . In other embodiments, the pivot  32  is rotatable with respect to the ratchet  20  and the frame  14 . In the illustrated embodiment of  FIGS. 1-6 , the pivot  38  is a separate element fixed with respect to the frame  14  and about which the ratchet  20  can pivot.  
      The pawl  26  can be biased into engagement with the ratchet  20  in order to limit rotation of the ratchet  20  in at least one rotational position of the ratchet  20 . The pawl  26  can be biased by one or more springs of any type, including those mentioned above with reference to the ratchet spring. Also, the spring for the pawl  26  can be coupled to bias the pawl  26  in any of the manners described above with reference to the ratchet spring. By way of example only, the pawl  26  in the illustrated embodiment of  FIGS. 1-6  is biased toward engagement with the ratchet  20  by a spring  27  on the pivot  32 . The spring  27  is a torsion spring, and has one end coupled to the frame  14  and another end coupled to the pawl  26 . The spring  27  is stopped by a tab  29  on the pawl  26  in the embodiment of  FIGS. 1-6 , although the spring  27  can be coupled to the pawl  26  in any other manner in order to exert spring force upon the pawl  26 ).  
      As mentioned above, the pawl  26  is movable with respect to the ratchet  20  to releasably retain the ratchet  20  in one or more latched positions, such as one or more rotational positions of the ratchet  20  illustrated in  FIGS. 1-6 . The ratchet  20  can have one or more abutment surfaces  24  (see  FIG. 3 ) that abut the pawl  26  in such positions. The abutment surface(s)  24  can be any surface of the ratchet  20 , such as a surface of a step, recess, notch, protrusion, or other portion of the periphery of the ratchet  20 . When the pawl  26  is moved into engagement with the ratchet  20 , engagement of the pawl  26  with one or more abutment surfaces  24  of the ratchet  20  can prevent the ratchet  20  from rotating to its unlatched position. However, when the pawl  26  is moved out of engagement with the ratchet  20  (in some cases, against the biasing force of the pawl spring  27 ), the ratchet  20  is free to rotate to its unlatched position. As described above, in some embodiments the ratchet  20  rotates under the biasing force of a ratchet spring  23 .  
      In some embodiments, the pawl  26  is coupled to a release mechanism (not shown). The release mechanism can be located anywhere relative to the latch assembly  10 , such as at a location adjacent the latch assembly  10  or in a location remote from the latch assembly  10 . The release mechanism can be a handle, key cylinder, electrical actuator, lever, button, or any other manual or powered user control. When actuated, the remote release mechanism can move the pawl  26  out of engagement with the ratchet  20 . By way of example only, in some embodiments the release mechanism includes a cable (not shown) coupled to the pawl  26  in any manner, such as through an aperture  28  in the pawl  26  as shown in the illustrated embodiment of  FIGS. 1-6 . In some embodiments, the cable can also be coupled to the frame  14  at one or more locations in order to further secure the cable (e.g., to secure the sheathing of a Bowden cable) and/or to route the cable. For example, the frame  14  in the illustrated embodiment of  FIGS. 1-6  has a mount  30  to which the cable can be connected. The mount  30  can take any form and shape desired, and in some embodiments is an apertured portion of the frame  14  through which the cable passes. When the cable is actuated by a release mechanism coupled to the cable, the cable moves the pawl  26  out of engagement with the ratchet  20 , thereby permitting the ratchet  20  to rotate to its unlatched position. In other embodiments, the pawl  26  can be coupled to a cable in any other manner, such as by conventional fasteners, crimping, and the like. Also, in some embodiments the pawl  26  can be coupled to a remote release mechanism by one or more other elements (other than or in addition to a cable), such as one or more rods, levers, and the like.  
      Some embodiments of the latch assembly  10  also include a lift lever  36  movable to push the striker  12  in a direction away from the latch assembly  10  when the latch assembly  10  moves toward and/or is in an unlatched state. The lift lever  36  can be coupled to the frame  14 , the ratchet  20 , or another component of the latch assembly  10  while still performing this function. For example, in the embodiment illustrated in  FIGS. 1-6 , the lift lever  36  is coupled to or is integral with the pivot  38  (described above), and is rotatable about the same axis  37  as the ratchet  20 . An advantage in such embodiments is the use of fewer parts and/or a more compact design of the latch assembly  10 . In other embodiments, the lift lever  36  is coupled to or is integral with another pivot (not shown), and is rotatable about an axis at the pivot. This lift lever pivot can extend from the ratchet  20 , from the frame  14 , or from another component of the latch assembly  10 . In such embodiments, the axis of rotation of the lift lever  36  can be parallel to the axis of rotation  37  of the ratchet  20 , and in some embodiments can be axially aligned with the axis of rotation  37  of the ratchet  20 . However, in other embodiments, these axes need not necessarily be aligned or parallel.  
      With continued reference to the illustrated embodiment of  FIGS. 1-6 , in some embodiments the lift lever  36  can be pivotable with respect to the ratchet  20 . In such embodiments, the rotational range of the lift lever  36  can be limited in one or more manners and by one or more elements, including any of those described above with reference to limiting rotation of the ratchet  20 . In the illustrated embodiment of  FIGS. 1-6 , the lift lever  36  is limited by a projection  39  (see  FIG. 1 ) of the lift lever  36  stopped by a surface of the ratchet  20 . Therefore, the lift lever  36  in the illustrated embodiment of  FIGS. 1-6  can pivot with respect to the ratchet  20 , but has a rotational range limited by the ratchet  20 .  
      In some embodiments, the lift lever  36  is pivotable through a range of positions as the latch assembly  10  moves between latched and unlatched states. In the unlatched state, the lift lever  36  is biased toward an unlatched position by a spring (e.g., an extension spring  40  in the illustrated embodiment of  FIGS. 1-6 ), and exerts force upon the striker  12  in a direction away from the latch assembly  10 . The lift lever  36  need not necessarily contact or engage the striker  12  for this purpose. For example, in some cases an element is located between the lift lever  36  and the striker  12 , and transmits force from the lift lever  36  to the striker  12 . In other embodiments (such as the illustrated embodiment of  FIGS. 1-6 ), the lift lever  36  engages and biases the striker  12  in a direction away from the latch assembly  10 .  
      The biasing force upon the striker  12  by the lift lever  36  can be exerted through a range of positions of the ratchet  20 , such as from a latched position of the ratchet  20  (see  FIGS. 1 and 4 ) through an unlatched position of the ratchet  20  (see  FIGS. 2, 5 , and  6 ), or in any portion of this range. In the illustrated embodiment of  FIGS. 1-6 , the lift lever  36  exerts a biasing force upon the striker  12  to a position in which the striker  12  is substantially out of the opening  22  of the ratchet  20  in the unlatched position of the ratchet  20 .  
      As described above, the lift lever  36  is biased toward an unlatched position by a spring. This lift lever spring can take any form, including any of those described above with reference to the springs of the ratchet  20  and pawl  26 . In the illustrated embodiment for example, the lift lever spring is an extension spring  40  coupled to the lift lever  36  and to the frame  14 . In other embodiments, the spring can be a compression spring coupled to and between the lift lever  36  and the frame  14 . Still other types of springs can be used, and fall within the spirit and scope of the present invention.  
      The spring  40  in the illustrated embodiment of  FIGS. 1-6  is coupled to the lift lever  36  at a location a distance from the axis of rotation  37  of the lift lever  36 . Therefore, the spring  40  exerts a force along a vector  50  that does not pass through the axis of rotation  37  of the lift lever  36  (see  FIGS. 4-6 ). The position and orientation of the force vector  50  is determined at least in part by the connection locations of the spring  40  on the frame  14  and lift lever  36 . The resulting torque upon the lift lever  36  biases the lift lever  36  in a rotational direction in which the lift lever  36  exerts force upon the striker  12  as described above.  
      When sufficient force is applied to the lift lever  36  by the striker  12  (e.g., as the closure panel  18  is moved toward a closed position), the lift lever  36  in the illustrated embodiment of  FIGS. 1-6  pivots about the axis of rotation  37  of the lift lever  36  against the bias force of the ratchet spring  23  and the spring  40  coupled to the lift lever  36 . As such, the striker  12  is able to enter the opening  22  in the ratchet  20  and move the ratchet  20  to its latched position. The lift lever  36  can remain biased against the striker  12  in the latched state of the latch assembly  10  due to stored energy in the spring  40  coupled to the lift lever  36 . In some embodiments, however, a pawl or other element or mechanism can be used to selectively prevent the lift lever  36  from exerting a biasing force against the striker  12  when the latch assembly  10  is in a latched state. Upon release of the pawl  26  from the ratchet  20 , the lift lever  36  can move the striker  12  in a direction away from the latch assembly  10  and to a position in which the striker  12  can be or is removed from the opening  22  in the ratchet  20 .  
      In some embodiments of the present invention, the lift lever  36  is biased to exert a first amount of force upon the striker  12  when the lift lever  36  is in a latched position, and a greater amount of force upon the striker  12  when the lift lever  36  is in an unlatched position. As described in greater detail below, such an arrangement can result in lower forces required to close the closure panel  18  and/or lower forces required to unlatch the latch assembly  10 . The lift lever  36  can be biased as just described by using a spring (e.g., an extension spring  40  in the illustrated embodiment of  FIGS. 1-6 ) exerting different amounts of force in different rotational positions of the lift lever  36 . This varying force can be generated by changing the state of the spring and/or by changing the position of the spring with respect to the axis of rotation  37  of the lift lever  36 . With reference to the illustrated embodiment of  FIGS. 1-6 , for example, different rotational forces are exerted upon the lift lever  36  by flexing the spring  40  to different lengths and by changing the position of the spring  40  with respect to the axis of rotation  37  of the lift lever  36 . By changing the length of the spring  40 , the magnitude of force exerted by the spring  40  changes. Also, by changing the position of the spring  40  with respect to the axis of rotation  37  of the lift lever  36 , the moment arm of the lift lever  36  changes, thereby changing the rotational force upon the lift lever  36 . Either or both manners of changing the rotational force upon the lift lever  36  can be used in different embodiments of the present invention.  
      With continued reference to the embodiment of  FIGS. 1-6 , the length and position of the spring  40  changes as the lift lever  36  rotates, thereby resulting in different forces exerted upon the striker  20  at different rotational positions of the lift lever  36  (i.e., a striker force profile). By changing the spring  40  with another spring having different characteristics and/or by changing the position of the spring  40  with respect to the axis of rotation  37  of the lift lever  36 , different striker force profiles can be generated for the latch assembly  10 . Such striker force profiles can include forces of the lift lever  36  upon the striker  20  that increase, decrease, or remain substantially constant as the lift lever  36  is pivoted toward an unlatched position, forces of the lift lever  36  upon the striker  20  that increase and then decrease, decrease and then increase, increase or decrease and then remain substantially constant for an amount of lift lever rotation (or vice versa), and the like.  
      With reference again to the illustrated embodiment of  FIGS. 1-6 , the position of the spring  40  in the latch assembly  10  is selected to produce a moment on the lift lever  36  in the latched position of the lift lever  36  and a greater moment on the lift lever  36  in the unlatched position of the lift lever  36 . In this manner, a relatively low force is exerted by the lift lever  36  upon the striker  12  when the striker  12  is in a latched position, and a higher force is exerted by the lift lever  36  upon the striker  12  when the striker  12  is in an unlatched position.  
       FIGS. 1 and 4  show the latch assembly  10  in a latched state. In this state, the spring  40  is in an extended state producing a rotational force upon the lift lever  36 . Although the spring  40  exerts a relatively large amount of force upon the lift lever  36  in this state (compared to the less extended state of the spring  40  illustrated in  FIGS. 2, 5 , and  6 ), the spring  40  also produces a relatively low amount of torque upon the lift lever  36  in this state. When the latch assembly  10  is in a latched state as shown in  FIGS. 1 and 4 , the force vector  50  of the spring  40  is relatively close to the axis of rotation  37  of the lift lever  36 . Therefore, although the spring  40  is stressed and produces a relatively large force upon the lift lever  36 , the torque on the lift lever  36  and the force exerted by the lift lever  36  upon the striker  12  is relatively low.  
      With reference to  FIG. 4 , when the force exerted by the spring  40  upon the lift lever  36  is broken into a radial component  50   r  and a tangential component  50   t , the tangential component  50   t  is relatively small compared to the radial component  50   r . Since the radial component  50   r  of the force passes through the axis of rotation  37  of the lift lever  36 , the radial component  50   r  of the force produces no torque on the lift lever  36 . However, the tangential component  50   t  of the force produces a torque equal to the tangential component  50   t  multiplied by the distance the tangential component  50   t  is applied from the axis of rotation  37  of the lift lever  36  (i.e., the moment arm of the lift lever  36 ). Since the tangential component  50   t  is relatively small, the torque on the lift lever  36  is also relatively small.  
       FIGS. 2, 5 , and  6  show the latch assembly  10  in an unlatched state. In this state, the spring  40  is less extended than the spring state illustrated in  FIGS. 1 and 4 . Therefore, the spring  40  exerts a lower amount of force upon the lift lever  36  compared to the latched state of the spring  40  illustrated in  FIGS. 1 and 4 . However, the spring  40  also produces a larger amount of torque upon the lift lever  36  in the state illustrated in  FIGS. 2, 5 , and  6 . As best shown in  FIGS. 5 and 6 , the force vector  50  of the spring  40  is farther away from the axis of rotation  37  of the lift lever  36  than when the latch assembly  10  is in the latched state. Therefore, although the spring  40  is less stressed and produces a lower amount of force upon the lift lever  36 , the torque on the lift lever  36  and the force exerted by the lift lever  36  upon the striker  12  is higher than when the latch assembly  10  is in the latched state.  
      With reference to  FIGS. 5 and 6 , when the force exerted by the spring  40  upon the lift lever  36  is broken into a radial component  50   r  and a tangential component  50   t , the tangential component  50   t  is larger than when the latch assembly  10  is in the latched state. Since the radial component  50   r  of the force passes through the axis of rotation  37  of the lift lever  36 , the radial component  50   r  produces no torque on the lift lever  36 . However, the tangential component  50   t  of the force produces a torque equal to the tangential component  50   t  multiplied by the distance the tangential force  50   t  is applied from the axis of rotation  37  of the lift lever  36  (i.e., the moment arm of the lift lever  36 ). Since the tangential component  50   t  is larger than when the latch assembly  10  is in the latched state, the torque on the lift lever  36  is greater.  
      In the illustrated embodiment of  FIGS. 1-6 , the torque upon the lift lever  36  increases as the lift lever  36  is pivoted to its unlatched position as described above. This relationship is achieved in part by coupling the spring  40  such that the force vector  50  of the spring  40  moves away from the axis of rotation  37  of the lift lever  36  as the lift lever  36  moves to its unlatched position, thereby increasing the moment arm of the lift lever  36  as the lift lever  36  moves to its unlatched position. The force vector  50  need not necessarily pass through or in close proximity to the axis of rotation  37  of the lift lever  36  in the latched position of the lift lever  36 . Instead, similar latch characteristics can be produced for any spring force vector  50  located a larger distance from the axis of rotation  37  in an unlatched position than in a latched position.  
      As mentioned above, the position of the spring  40  relative to the lift lever  36  and the characteristics of the spring  40  at least partially define the profile of torques upon the lift lever  36  at different rotational positions of the lift lever  36 . This torque profile can be changed by changing the position of the spring  40  relative to the lift lever  36  (e.g., changing the location and/or orientation of the spring  40  in the latched and unlatched states of the lift lever  36 , changing the locations at which the spring  40  is coupled to the lift lever  36  and/or to the frame  14 , and the like), arid/or by changing the type of spring  40  used (e.g., using a spring  40  having a different spring constant or spring force curve). For example, the spring  40  in the embodiment of  FIGS. 1-6  can be replaced with another spring having a different force curve, such as a spring  40  exerting greater force when extended and/or less force when relaxed, relative to corresponding forces exerted by the spring  40  in the illustrated embodiment of  FIGS. 1-6 . In such embodiments, the lift lever  36  can have increased torque when the lift lever  36  is in the latched position and/or reduced torque when the lift lever  36  is in the unlatched position (compared to the embodiment of  FIGS. 1-6  described above). Alternatively, the spring  40  in the embodiment of  FIGS. 1-6  can be replaced with another spring exerting reduced force when extended and/or greater force when relaxed, relative to corresponding forces exerted by the spring  40  in the illustrated embodiment of  FIGS. 1-6 . In such embodiments, the lift lever  36  can have increased torque when the lift lever  36  is in the unlatched position and/or reduced torque when the lift lever  36  is in the latched position (compared to the embodiment of  FIGS. 1-6  described above).  
      As another example, the spring  40  and the lift lever  36  can be positioned relative to one another so that the force vector  50  of the spring  40  is located a greater distance from the axis of rotation  37  of the lift lever  36  when the lift lever  36  is in a latched position than when the lift lever  36  is in an unlatched position. In such an embodiment, when the lift lever  36  is rotated to an unlatched position as described herein, the force vector  50  of the spring  40  moves nearer to the axis of rotation  37  of the lift lever  36  as the spring  40  relaxes. Accordingly, the spring  40  and lift lever  36  can exert more biasing force against the striker  20  in the latched state than in the unlatched state.  
      As yet another example, the spring  40  can be selected to have a force curve in which the mechanical advantage provided by an increasing or decreasing moment arm (from pivoting the lift lever  36  as described above) is substantially offset by increasing or decreasing forces exerted by the spring  40  as the spring  40  is flexed. In such a manner, the resulting force exerted by the lift lever  36  upon the striker  12  can be constant or substantially constant throughout any portion or all of the range of movement of the lift lever  36 .  
      The position of the spring  40  relative to the lift lever  36  and the characteristics of the spring  40  can be selected in any combination resulting in an increase or decrease in torque upon the lift lever  36  as the lift lever  36  is pivoted between latched and unlatched positions. By way of example only, a spring  40  generating reduced spring forces can be positioned at greater distances from the axis of rotation  37  of the lift lever  36  to result in an increase or decrease in torque upon the lift lever  36  as the lift lever  36  is pivoted to an unlatched position. As another example, a spring  40  generating greater spring forces can be positioned at smaller distances from the axis of rotation  37  of the lift lever  36  to result in an increase or decrease in torque upon the lift lever  36  as the lift lever  36  is pivoted to an unlatched position. The resulting increase or decrease in torque upon the lift lever  36  can be dependent at least in part upon the size of the spring forces and the distances between the force vector  50  of the spring  40  and the axis of rotation  37  of the lift lever  36  as the lift lever  36  is pivoted.  
      The spring characteristics (e.g., the spring force curve of the spring  40 , the length of the spring  40 , and the like) and relative positions of the lift lever  36  and spring  40  can be selected so that any torque profile can be generated upon the lift lever  36  through the range of motion of the lift lever  36 . The torque upon the lift lever  36  can increase, decrease, stay substantially constant, or have combinations of such characteristics in any sequence as the lift lever  36  is pivoted. In the illustrated embodiment of  FIGS. 1-6 , however, the torque upon the lift lever  36  decreases as the lift lever  36  is pivoted to its latched position, thereby providing the latch characteristics described above. Accordingly, in the illustrated embodiment of  FIGS. 1-6 , the forces exerted upon the striker  12  by the latch assembly  10  when the striker  12  is in a latched position are relatively low compared to forces exerted upon the striker  12  by the latch assembly  10  when the striker  12  is in other positions (e.g., in movement of the striker  12  toward an unlatched position). Latches having such a feature can be used in applications where forces urging the striker  12  to an unlatched position should be reduced or minimized when the latch assembly  10  is in a latched state.  
      With continued reference to the illustrated embodiment of  FIGS. 1-6 , when the latch assembly  10  is released from the latched state, both the lift lever  36  and the ratchet  12  can be biased into respective open and unlatched positions as shown in  FIGS. 2, 5 , and  6 . In the unlatched or released state of the latch assembly  10 , the striker  12  can rest upon the lift lever  36 . Depending at least in part upon the shape of the ratchet  12 , the shape of the lift lever  36 , the ranges of rotation of the ratchet  12  and lift lever  36 , the torque upon the lift lever  36  generated by the spring  40 , and the amount of force upon the striker  12  in a direction toward the latch assembly  10 , the lift lever  36  can move the striker  12  out of the opening  22  in the ratchet  12 , or can instead move the striker  12  to a position still within the ratchet opening  22 . As shown in  FIGS. 2, 5 , and  6 , the torque on the lift lever  36  in the unlatched position is sufficient to move the striker  12  out of the opening  22  in the ratchet  20 . In some embodiments, the striker  12  is moved sufficiently to create a clearance between the closure panel  18  and an adjacent portion of the vehicle (not shown) for a person to insert a finger or hand, such as to grasp and/or move the closure panel  18 , to actuate one or more elements behind the closure panel  18 , and the like.  
      Forces exerted upon the striker  12  when the illustrated latch assembly  10  is in a latched state can be transmitted to one or more surfaces of the ratchet  20  (e.g., upon one or more edges of the ratchet opening  22  in some embodiments), and therefore to the ratchet  20 . In conventional latch assemblies, forces upon a ratchet in its latched state are often responsible for generating higher frictional engagement with a pawl and/or other elements of the latch assembly, thereby increasing the force needed to release the pawl from the ratchet and/or other elements of the latch assembly. By reducing the amount of force exerted upon the striker  12 , some embodiments of the present invention reduce the amount of force exerted upon the ratchet  20  and pawl  26 . In this manner, the amount of force needed to release the pawl  26  from the ratchet  20  can be reduced. In some embodiments, this force can be reduced even though the spring  40  exerts a relatively high force when in the latched state of the latch assembly  10  as described above.  
      As also described above, in some embodiments the lift lever  36  exerts a decreasing force upon the striker  12  as the striker  12  is moved to a latched position. For example, as the striker  12  in the illustrated embodiment of  FIGS. 1-6  moves from the unlatched position shown in  FIGS. 2, 5 , and  6  to the latched position shown in  FIGS. 1 and 4 , the lift lever  36  exerts a decreasing force upon the striker  12  in a direction away from the latch assembly  10 . Accordingly, the closure panel  18  can become increasingly easier for a user to close as the closure panel  18  is moved to a closed and latched position.  
      In operation of the illustrated embodiment of  FIGS. 1-6 , when a closing force is applied to a closure panel  18  in the position of  FIG. 6 , a force is applied to the striker  12  to move the lift lever  36  in a counter-clockwise direction (as viewed in the figures). This force is exerted against the torque on the lift lever  36  exerted by the spring  40 . However, as the lift lever  36  in  FIG. 6  moves toward the latched position shown in  FIGS. 1 and 4 , the torque caused by the spring  40  decreases. As the lift lever  36  moves, the striker  12  enters the opening  22  in the ratchet  20 , and engages a portion of the ratchet  20  to rotate the ratchet  20  in a counter-clockwise direction. In some embodiments, the striker  12  moves with respect to the axis of rotation of the ratchet  20  as the striker  12  moves the lift lever  36  to its latched position. Upon rotation of the ratchet  20  toward the latched state shown in  FIGS. 1 and 4 , a portion of the ratchet  20  at least partially surrounds a portion of the striker  12  and blocks the path of the striker  12  out of the latch assembly  10 . Furthermore, as the ratchet  20  rotates toward the latched position, the pawl  26  engages the abutments  28  on the ratchet  20  to prevent rotation of the ratchet  20  toward an unlatched position. In the latched position shown in  FIGS. 1 and 4 , the ratchet  20  is prevented from rotating toward an unlatched position, and the striker  12  is prevented from escaping the latch assembly  10 . The striker  12  can also be biased against the ratchet  20  by energy stored in the spring  40  coupled to the lift lever  36 .  
      To unlatch the latch assembly  10  illustrated in  FIGS. 1-6 , the pawl  26  is disengaged from the ratchet  20  by pulling upon a cable (not shown) coupled to the pawl  26  at the aperture  28  in the pawl  26 . Energy stored in the latch assembly  10  during the latching process is thereby released. This allows the ratchet  20  and the lift lever  36  to rotate toward their unlatched positions due to the torques on the ratchet  20  and lift lever  36 . As the lift lever  36  moves toward the unlatched position shown in  FIGS. 2, 5 , and  6 , the torque on the lift lever  36  increases, exerting an increasing force upon the striker  12  as the striker  12  is moved toward an unlatched position. Also, in some embodiments, the lift lever  36  moves the striker  12  away from the axis of rotation  37  of the ratchet  20  during at least part of the motion of the lift lever  36 . For example, the lift lever  36  in the embodiment of  FIGS. 1-6  moves the striker  12  away from the axis of rotation  37  of the ratchet  20  in a range of movement of the lift lever  36 , including when the ratchet  20  has stopped pivoting and the lift lever  36  continues to move the striker  12  out of the ratchet opening  22 . When the ratchet  20  reaches the unlatched position shown in  FIGS. 2 and 5  (stopped by the projection  16  from the frame  14 ), the lift lever  36  continues to rotate to lift the striker  12  from the opening  22  in the ratchet  12  and to provide greater clearance between the closure panel  18  and an adjacent portion of the vehicle. Upon reaching the position shown in  FIG. 6 , further rotation of the lift lever  36  is stopped by the projection  39  of the lift lever  36  upon the ratchet  20 .  
       FIGS. 7-11  illustrate another embodiment of a latch assembly according to the present invention. This embodiment uses similar elements and has many of the same operational features as the embodiments described above with reference to  FIGS. 1-6 . Accordingly, the following description focuses primarily upon those elements and features that are different from the embodiments described above. Reference should be made to the above description for additional information regarding the elements, features, and possible alternatives to the elements and features of the latch assembly  110  illustrated in  FIGS. 7-11  and described below. Elements and features of the embodiment shown in  FIGS. 7-11  that correspond to elements and features of the embodiments described with reference to  FIGS. 1-6  above are designated hereinafter in the 100 series of reference numbers.  
      Like the embodiment of the present invention illustrated in  FIGS. 1-6 , the embodiment illustrated in  FIGS. 7-11  has a frame  114 , a pawl  126  releasably engagable with a ratchet  120 , and a lift lever  136 . The ratchet  120  and lift lever  136  are both coupled to the frame  114  by a pivot  138 , and are rotatable about an axis  137  at the pivot  138 . The pawl  126  is also coupled to the frame  114  by a pivot  132  for movement with respect to the ratchet  120 . The pawl  126  in the embodiment of  FIGS. 7-11  is rotatable about an axis  133  that is substantially parallel to the axis of rotation  137  of the ratchet  120  and lift lever  136 . In other embodiments, the pawl  126  can be rotatable about an axis having any other orientation with respect to the axis of rotation  137  of the ratchet  120  and/or lift lever  136  while still being movable into and out of engagement with the ratchet  120  to selectively prevent movement of the ratchet  120  to an unlatched position. As described above, the pawl  126  can also be movable in other manners for this purpose.  
      The pawl  126  can be actuated in any of the manners described above with reference to the embodiment of  FIGS. 1-6 , and can be actuated by any number of different release mechanisms. In the embodiment of  FIGS. 7-11 , the pawl  126  can be coupled to a lock cylinder, a handle, or other user-manipulatable device coupled to the pawl  126  at an aperture  128  in the pawl  126 . This connection can instead be made at another feature of the pawl  126 , such as at a boss, flange, lip, mount or other feature of the pawl  126 . The pawl  126  illustrated in  FIGS. 7-11  is also coupled to an electric motor  131  by a gear assembly  134  (see  FIGS. 7 and 8 ), and can be moved by actuation of the electric motor  131  and gear assembly  134 . Accordingly, the latch assembly  110  illustrated in  FIGS. 7-11  can be released by manual or powered devices. In other embodiments, two or more manual devices and/or two or more powered devices can be coupled to the latch assembly  110  for this purpose.  
      In some embodiments of the present invention, a wear portion of the ratchet  120  comprises a material that is different than a remainder of the ratchet  120 . The wear portion can have lower friction properties and/or can be more resistant to wear than the materials of the remainder of the ratchet  120 , and can be coupled thereto in a number of different manners. In the illustrated embodiment of  FIGS. 7-11 , for example, a wear portion  121  of the ratchet  120  is overmolded upon the remainder  125  of the ratchet  120 , which can comprise metal, plastic, composite material, or other sufficiently strong material. An overmolded wear portion  121  can provide a secure connection between the wear portion  121  and the remainder  125  of the ratchet  120 , and in some embodiments can be manufactured at relatively low cost. In other embodiments, the wear portion  121  is coupled to the remainder  125  of the ratchet  120  in any other manner, such as by adhesive or cohesive bonding material, by inter-engaging elements, by pins, screws, rivets, and other fasteners, and the like.  
      The wear portion  121  of the ratchet  120  can comprise plastic, UHMW, urethane, nylon, and the like, although any other material can be used. The wear portion  121  is positioned to contact the pawl  126 , and can provide reduced friction between the ratchet  120  and the pawl  126  and/or improved resistance to ratchet wear. In some embodiments, the pawl  126  only contacts the ratchet  120  at the wear portion  121 . However, in other embodiments, the pawl  126  can contact the remainder  125  of the ratchet  120  in one or more locations or ranges of locations on the ratchet  120 . Also, in some embodiments, one or more abutment surfaces  124  of the ratchet  120  can be located on the wear portion  121 . For example, the ratchet  120  illustrated in  FIGS. 7-11  has an abutment surface  124  on the wear portion  121  of the ratchet  120 .  
      The ratchet  120  in the embodiment of  FIGS. 7-11  is rotatable between latched and unlatched positions in order to capture a striker  112  as described in greater detail above. As best shown in  FIGS. 7, 10 , and  11 , the ratchet  120  can rotate to an unlatched position in which the striker  112  is or can be removed from the ratchet  120 . The ratchet  120  can be stopped in this position in any of the manners described above. In the embodiment of  FIGS. 7-11 , the ratchet  120  is stopped by a wall  151  of the frame  114 .  
      The ratchet  120  illustrated in  FIGS. 7-11  is also biased by a spring  123  coupled to the ratchet  120 . The spring  123  can be coupled to the ratchet  120  at a flange or other projection  152  of the ratchet  120  as shown in  FIGS. 7-11 , or can instead be coupled to bias the ratchet  120  in any of the other manners described above. Also, the spring  123  can be coupled to a location of the pawl  126  as illustrated, or can be coupled to the frame  114  or other part of the latch assembly  110 .  
      With continued reference to the embodiment illustrated in  FIGS. 7-11 , the lift lever  136  is rotatable between latched and unlatched positions, and is biased toward an unlatched position by a torsion spring  154  coupled to the lift lever  136 . The torsion spring  154  can be coupled to the lift lever  136  in any manner, such as to a projection  156  as illustrated in  FIGS. 7-11 , to an aperture or other feature of the lift lever  136 , and the like. The torsion spring  154  can also have a portion positioned to contact the frame  114  or other part of the latch assembly  110 .  
      When the latch assembly  110  illustrated in  FIGS. 7-11  is in a latched state, the striker  112  is received within an opening  122  of the ratchet  120 , and the lift lever  136  is rotated to a latched position as shown in  FIGS. 7 and 9 . When the latch assembly  110  is released by actuating the pawl  126  as described above, the ratchet  120  and lift lever  136  each rotate toward their respective unlatched positions shown in  FIGS. 8, 10 , and  11  under biasing force from their respective springs  123 ,  154 . However, the ratchet  120  illustrated in  FIGS. 7-11  is stopped by the wall  151  of the frame  114 , while the lift lever  110  can continue to rotate to the position shown in  FIGS. 8 and 11 . The lift lever  110  can therefore continue to move the striker  112  in a direction away from the latch assembly  110 . In some embodiments, the lift lever  136  moves the striker  112  at least partially out of the opening  122  in the ratchet  120 .  
      In some embodiments, the rotational range of the lift lever  136  can be limited in one or more manners and by one or more elements, including any of those described above with reference to limiting rotation of the ratchet  20  in the embodiment of  FIGS. 1-6 . In the illustrated embodiment of  FIGS. 7-11 , the lift lever  136  is limited by the projection  156  of the lift lever  136  stopped by a surface of the ratchet  120 . Any surface of the ratchet  120  can be used for this purpose. In the embodiment of  FIGS. 7-11 , for example, the projection  156  of the lift lever  136  is stopped by the projection  152  of the ratchet  120 . Therefore, the lift lever  136  in the illustrated embodiment of  FIGS. 7-11  can pivot with respect to the ratchet  120 , but has a rotational range limited by the ratchet  120 . In other embodiments, rotation of the lift lever  136  can be limited by direct or indirect contact between any other portion of the lift lever  136  and any other portion of the ratchet  120 .  
      The embodiments described above and illustrated in the figures are presented by way of example only, and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention. For example, in the illustrated embodiments of  FIGS. 1-11 , a lift lever  36 ,  136  is used to move the striker  12 ,  112  from the ratchet  20 ,  120 , and is separate from and movable with respect to the ratchet  20 ,  120 . However, in other embodiments, the latch assembly  10 ,  110  can have a ratchet  20 ,  120  that is integral with the lift lever  36 ,  136  or that is coupled to the lift lever  36 ,  136  so that the lift lever  36 ,  136  is not rotatable with respect to the ratchet  20 ,  120 . Thus, some embodiments of the present invention can use the other features of the present invention to bias the lift lever  36 ,  136  and/or ratchet  20 ,  120  in a manner similar to the manner in which the lift lever  36 ,  136  is biased in the illustrated embodiments of  FIGS. 1-11 .  
      As another example, various elements of the latch assembly  10 ,  110  are described as being pivotable or rotatable. It will be appreciated that in alternative embodiments, such elements can be coupled to permit other types of movement while still performing the functions of such elements as described herein. By way of example only, the pawl  26 ,  126  in the illustrated embodiments of  FIGS. 1-11  is rotatable about a pawl pivot  32 ,  132  in order to releasably engage the ratchet  20 ,  120 . In alternative embodiments, the pawl  26 ,  126  can move in other manners, such as by translating (e.g., wherein the pawl  26 ,  126  is slidably coupled to the frame  14 ,  114 , such as by one or more grooves or other elongated apertures in the frame  14 ,  114 ) or by a combination of translation and rotation. In such cases, the pawl  26 ,  126  can be coupled to the frame  14 ,  114  in any suitable manner to enable such motion.  
      As yet another example, in some embodiments of the present invention, a lift lever spring  40 ,  154  can be coupled to the lift lever  36 ,  136  and/or to the frame  14 ,  114  in two or more locations, each providing different moments on the lift lever  36 ,  136  in the latched and/or unlatched positions of the lift lever  36 ,  136 . The spring  40 ,  154  can therefore be installed in different manners to change the manner in which the latch assembly  10 ,  110  operates, such as to increase or decrease the required closing and latching force of the latch assembly  10 ,  110 , to change the force needed to unlatch the latch assembly  10 ,  110 , and the like.