Patent Publication Number: US-2005127687-A1

Title: Electronic latch apparatus and method

Description:
FIELD OF THE INVENTION  
      The present invention relates to latches and latching methods, and more particularly to devices and methods for electronically controlling and switching a latch between latched and unlatched states.  
     BACKGROUND OF THE INVENTION  
      Conventional latches are used to restrain the movement of one member or element with respect to another. For example, conventional door latches restrain the movement of a door with respect to a surrounding door frame. The function of such latches is to hold the door secure within the frame until the latch is released and the door is free to open. Existing latches typically have mechanical connections linking the latch to actuation elements such as handles which can be actuated by a user to release the latch. Movement of the actuation elements is transferred through the mechanical connections and will cause the latch to release. The mechanical connections can be one or more rods, cables, or other suitable elements or devices. Although the following discussion is with reference to door latches (e.g., especially for vehicle doors), the background information provided applies equally to a wide variety of latches used in other applications.  
      Most current vehicle door latches contain a restraint mechanism for preventing the release of the latch without proper authorization. When in a locked state, the restraint mechanism blocks or impedes the mechanical connection between the handle and a latch release mechanism, thereby locking the door. Many conventional door latches also have two or more lock states, such as unlocked, locked, child locked, and dead locked states. Inputs to the latch for controlling the lock states of the latch can be mechanical, electrical, or parallel mechanical and electrical inputs. For example, by the turn of a user&#39;s key, a cylinder lock can mechanically move the restraint mechanism, thereby unlocking the latch. As another example, cable or rod elements connecting a door handle to the latch release mechanism can be controlled by one or more electrical power actuators. These actuators, sometimes called “power locks” can use electrical motors or solenoids as the force generator to change between locked and unlocked states.  
      A number of problems exist, however, in the conventional door latches described above. For example, conventional restraint mechanisms in such latches are typically quite complex, with numerous parts often having relatively complicated movements. Such latches are thus more expensive to manufacture, maintain, and repair. This problem is compounded in latches having multiple lock states as mentioned above. These latches often require separate sets of elements corresponding to and controlling each lock state of the latch. Related to this problem are the problems of latch weight and size. The inclusion of more elements and more complex mechanisms within the latch generally undesirably increases the size and weight of the latch. In virtually all vehicle applications, weight and size of any component is a concern. Additionally, increased weight and size of elements and assemblies within the latch necessarily requires more power and greater force to operate the latch. Because power is also at a premium in many applications (especially in vehicular applications), numerous elements and complex assemblies within conventional door latches are an inefficiency that is often wrongly ignored. Not only are larger and more complex latches a power drain, but such latches are typically unnecessarily slow.  
      Another problem with conventional door latches relates to their operation. Particularly where a latch has multiple lock states, the ability of a user to easily and fully control the latch in its various lock states is quite limited. For example, many latches having a child locked state (i.e., the inside door handle is disabled but the outside door handle is not) require a user to manually set the child locked state by manipulating a lever or other device on the latch. Other latches do not permit the door to enter a dead locked state (i.e., both the inside and outside door handles being disabled). Also, conventional door latches generally do not permit a user to place the door latch in all lock states remotely, such as by a button or buttons on a key fob. These examples are only some of the shortcomings in existing door latch operability.  
      Still another problem of conventional door latches is related to power locks. The design of existing power lock systems has until now significantly limited the safety of the latch. Latch design limitations exist in conventional latches to ensure, for example, that dead locked latches operated by powered devices or systems will reliably unlock in the event of power interruption or failure. Such limitations have resulted in latch designs which permit less than optimal user operability. Therefore, a reliable design having a failure mode for an electrically powered latch which is electrically actuatable in all locked states remains an elusive goal.  
      In conventional door latches, yet another problem is caused by the fact that an unauthorized user can often manipulate the restraint mechanism within the latch and/or the connections of the latch to the door locks to unlock the latch. Because existing conventional door latches have at least some type of mechanical linkage from the user-actuated elements (e.g., lock cylinders) to the restraint mechanism in the latch, the ability of an unauthorized user to unlock the latch as just described has been a persistent problem.  
      In light of the problems and limitations of the prior art described above, a need exists for a latch assembly which has the fewest elements and assemblies possible, is smaller, faster, and lighter than existing latches, consumes less power in operation, is less expensive to manufacture, maintain, and repair, provides a high degree of flexibility in user operation to control the lock states of the latch, has a reliable design in the event of power interruption or failure, and offers improved security against unlocking by an unauthorized user. Each preferred embodiment of the present invention achieves one or more of these results.  
     SUMMARY OF THE INVENTION  
      In the most highly preferred embodiments of the latch assembly of the present invention, unlocked and locked states of the latch assembly are established by at least two different types of movement of a control element. The control element moves in a first manner through a first path when the latch assembly is in an unlocked state and in a second manner through a second path when the latch assembly is in a locked state. When the control element moves in the first manner, the control element imparts motion either directly or indirectly to a latch element or mechanism (e.g., a ratchet). Such motion moves the latch element or mechanism to move to its unlatched position to unlatch the door. In contrast, when the control element moves in a second manner, the control element does not impart motion (or sufficient motion) to the latch element or mechanism for unlatching the door. Therefore, whether movement or actuation of the control element by a user will unlatch the latch depends upon whether the control element moves in the first or the second manner. The latch assembly of the present invention operates to quickly change the manner of control element motion by preferably extending or retracting one or more elements that guide or limit the motion of the control element. Preferably, these elements are pins which are quickly extended and retracted by one or more actuators.  
      A highly preferred embodiment of the present invention has two control elements, pins, and actuators. In each control element, pin, and actuator set, the actuator can be extended to extend the pin into a hole in the control element and can also be retracted to retract the pin from the hole. When the actuator and pin are extended and thereby engage the control element, the control element preferably pivots through a first path about a first pivot point. However, when the actuator and pin are retracted and are thereby disengaged from the control element, the control element preferably pivots through a second path about a second pivot point. Movement of the control element through the first path preferably brings the control element into contact with a pawl that is coupled to the latch element or mechanism. This contact causes the latch element or mechanism to release, thereby unlatching the door. In contrast, movement of the control element through the second path preferably does not bring the control element into such contact, or at least into contact sufficient to release the latch element or mechanism. The control element in the second path therefore is in a locked state.  
      In the most highly preferred embodiments of the present invention, the actuators are electromechanical solenoids that perform quick retraction and extension operations to engage and disengage the control elements in their different lock states. The control elements preferably pivot about a hole in each control element that is engaged by the pin in the extended position and about a post, peg, or other element extending from each control element when the pin is not engaged therewith.  
      In referring herein to “retraction” and “extension” operations of solenoids and to “retracted” and “extended” positions of the solenoids, it should be understood that this is with reference to well known operation of conventional solenoids. Specifically, solenoids typically have one or more elements (such as an armature) which are controllable to extend and retract from the remainder of the solenoid in a well known manner. Terms such as retraction, retracted, extension and extended used herein in connection with a solenoid refers to such conventional solenoid operations.  
      When the latch assembly of the present invention is used on a vehicle door, a first control element is coupled via a linking member to an inside door handle and a second control element is preferably coupled to an outside door handle. When the pin corresponding to each control element is extended to engage the first and second control elements, respectively, actuation of the control elements by either handle causes the actuated control element to directly or indirectly move a ratchet to unlatch the door. This is the unlocked state of the latch assembly. When the pin corresponding to each control element is retracted to disengage the first and second control elements, actuation of the control elements by either handle does not move the ratchet or does so insufficiently to unlatch the door. This is the dead locked state of the latch assembly. When the pin corresponding to the first control element is extended to engage the first control element and when the pin corresponding to the second control element is retracted to disengage the second control element, actuation of the inside door handle will directly or indirectly move a ratchet to unlatch the door, but actuation of the outside door handle will not do so. This is the locked state of the latch assembly. When the pin corresponding to the first control element is retracted to disengage the first control element and the pin corresponding to the second control element is extended to engage the second control element, actuation of the outside door handle will move the pawl and unlatch the door, but actuation of the inside door handle will not do so. This is the child locked state of the latch assembly. Of course, in other embodiments of the present invention, one, three, or even more control element, pin, and actuator sets can be used as desired.  
      Latch assembly operations for placing the control elements in their locked and unlocked states are therefore quickly performed via actuators, and most preferably, by electro-magnetic solenoids. Also, the relatively small number of elements (e.g., an actuator, pin, control element, and, if desired, a pawl as described in more detail below) employed to place the latch assembly in its various lock states is a significant advantage over prior art latches. The latch assembly of the present invention is therefore lighter, smaller, can be operated using less power, and can be manufactured, maintained, and repaired at less expense.  
      In addition, the use of electrical actuators such as electromagnetic solenoids to place the control elements in their various states permits greater flexibility for users in controlling the various latch assembly lock states.  
      The latch assembly of the present invention also preferably has a control circuit for controlling the actuators. Most preferably, the control circuit is electrical and uses a sensing device to detect changes in the primary power supply (e.g., power loss, power interruption, etc.) supplying power to the latch assembly and to the actuators. At least as a safety feature, certain changes detected in the power supply preferably cause the actuators to automatically engage the pins with the control elements and to thereby unlock the latch assembly.  
      Because the mechanism for placing the latch assembly in its various lock states is preferably actuated electronically rather than by conventional mechanical means, the latch assembly is also more secure against unauthorized operation. More information and a better understanding of the present invention can be achieved by reference to the following drawings and detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention is further described with reference to the accompanying drawings, which show preferred embodiments 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 numerals indicate like parts:  
       FIG. 1  is a front perspective view, looking down, of a latch mechanism according to a preferred embodiment of the present invention;  
       FIG. 2  is a front perspective view, looking up, of the latch mechanism shown in  FIG. 1 ;  
       FIG. 3  is a rear perspective view, looking down, of the latch mechanism shown in  FIGS. 1 and 2 ;  
       FIG. 4  is an exploded view of the latch mechanism shown in  FIGS. 1-3 , viewed from the front;  
       FIG. 5  is an exploded view of the latch mechanism shown in  FIGS. 1-4 , viewed from the rear;  
       FIG. 6  is a front perspective view of the latch mechanism shown in  FIGS. 1-5 , with the front cover removed;  
       FIG. 7  is a front perspective view of the latch mechanism shown in  FIGS. 1-6 , with the front cover and the cover plate removed, and showing the control levers and the pawl of the latch mechanism;  
       FIG. 8  is a front elevational view of the latch mechanism shown in  FIG. 7 , with both the right and left control elements in their unactuated positions;  
       FIG. 9  is a front elevational view of the latch mechanism shown in  FIG. 7 , with the latch mechanism unlocked and with the right control element actuated;  
       FIG. 10  is a front elevational view of the latch mechanism shown in  FIG. 7 , with the latch mechanism unlocked and with the left control element actuated;  
       FIG. 11  is a front elevational view of the latch mechanism shown in  FIG. 7 , with the latch mechanism locked and with the right control element actuated;  
       FIG. 12  is a front elevational view of the latch mechanism shown in  FIG. 7 , with the latch mechanism locked and with the left control element actuated;  
       FIG. 13  is a rear elevational view of the latch mechanism shown in  FIGS. 1-12 , with the rear mounting plate removed and with the pawl engaged with the ratchet;  
       FIG. 14  is a rear elevational view of the latch mechanism shown in  FIGS. 1-13 , with the rear mounting plate removed and with the pawl disengaged from the ratchet;  
       FIG. 15  is a schematic diagram of a control circuit for the latch assembly of the present invention according to a preferred embodiment of the present invention; and  
       FIG. 16  is a exploded perspective view of a portion of the latch assembly with a manual override according to a preferred embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      While the latch assembly  10  of the present invention is useful in a variety of applications, it is particularly useful in vehicle applications such as for automotive and truck doors. In such applications, the latch assembly  10  preferably has a front cover  12 , a rear mounting plate  14  and a housing  16  which collectively enclose the internal elements and mechanisms of the latch assembly  10 . A highly preferred embodiment of the latch assembly  10  is shown in  FIGS. 1-3 . It should be noted that although the following description is with reference to the latch assembly  10  used in vehicle door applications (where application of the latch assembly  10  can be employed with excellent results), the latch assembly  10  can instead be used in many other applications. In fact, the present invention can be used in any application in which it is desirable to releasably secure one body to another. Such applications can be non-automotive and even in applications not involving doors.  
      The terms of orientation and direction are used herein for ease of description only and do not indicate or imply any required limitation of the present invention. For example, terms such as front, rear, left, right, clockwise, counterclockwise, upper, lower, first, and- second as used herein do not indicate or imply that the elements or operations thus described must be oriented or directed in a particular way in the practice of the present invention. One having ordinary skill in the art will recognize that opposite or different orientations and directions are generally possible without departing from the spirit and scope of the present invention. Also, it should be noted that throughout the specification and claims herein, when one element is said to be “coupled” to another, this does not necessarily mean that one element is fastened, secured, or otherwise attached to another element. Instead, the term “coupled” means that one element is either connected directly or indirectly to another element or is in mechanical communication with another element. Examples include directly securing one element to another (e.g., via welding, bolting, gluing, mating, etc.), elements which can act upon one another (e.g., via camming, pushing, or other interaction) and one element imparting motion directly or through one or more other elements to another element.  
      Where the latch assembly  10  secures a vehicle door to a door frame or vehicle body, the latch assembly  10  is preferably mounted in a conventional manner to the vehicle door. For example, the rear mounting plate  14  can be provided with fastener holes  18  through which threaded or other conventional fasteners (not shown) are passed and secured to the door. The latch assembly  10  can be secured to the door or to the vehicle body in a number of manners, such as by welding, screwing, bolting, riveting, and the like, all of which are well known to those skilled in the art. Further discussion of securement methods and elements is therefore not provided herein.  
      Similar to conventional latch assemblies, the latch assembly  10  is designed to releasably capture a striker  20  (see  FIG. 3 ) mounted on the vehicle body (or on the door if the latch assembly  10  is instead mounted on the vehicle body). For this purpose, the latch assembly  10  preferably has a ratchet or fork bolt  22  (see  FIGS. 4, 5 ,  13 , and  14 ) rotatably mounted therein for releasably capturing the striker  20 . The ratchet  22 , the rear mounting plate  14 , and the housing  16  each have a groove  24 ,  26 ,  27 , respectively, for receiving and capturing the striker  20  to latch the door shut. Specifically, the ratchet  22  is rotatable between a fully open position in which the grooves  24 ,  26 ,  27  align with one another to receive the striker  20 , and a range of closed positions in which the ratchet  22  is rotated to reposition the groove  24  of the ratchet  22  out of alignment with the grooves  26 ,  27  of the rear mounting plate  14  and the housing  16  (thereby capturing the striker  20  within the grooves  24 ,  26 ,  27 ). It should be noted that a number of different striker and ratchet designs exist which operate in well known manners to releasably secure a striker (or like element) to a ratchet (or like element). The preferred embodiments of the present invention are useful with these other conventional striker and ratchet designs as well. Such other striker and ratchet designs fall within the spirit and scope of the present invention.  
      With particular reference to  FIGS. 4 and 5 , the operation of the ratchet  22  in capturing and securing the striker  20  within the latch assembly  10  will now be further described. As indicated above, the use of a ratchet in a latch mechanism is well-known to those skilled in the art. In the latch assembly  10  of the present invention, the ratchet  22  is preferably provided with an aperture  28  for mounting the ratchet  22  to the rear mounting plate  14 . The aperture  28  is sized and shaped to rotatably receive a lower pivot post  30  extending from the rear mounting plate  14 . The lower pivot post  30  is preferably fastened to the rear mounting plate  14  in a conventional manner, such as by a riveting, screwing, bolting, or other conventional fastening techniques. The lower pivot post  30  can instead be made integral with the rear mounting plate  14 . Sufficient clearance is provided between the lower pivot post  30  and the aperture  28  of the ratchet  22  so that the ratchet  22  can rotate substantially freely about the lower pivot post  30 .  
      In order to control the movement of the ratchet  22  within the latch assembly  10 , rotation of the ratchet  22  is preferably limited at two locations as follows. First, the ratchet  22  is prevented from rotation beyond the point where the grooves  24 ,  26 ,  27  of the ratchet  22 , the rear mounting plate  14 , and the housing  16  are aligned for receiving the striker  20  as described above. This limitation exists due primarily to the manner in which the striker  20  moves through the grooves  24 ,  26 ,  27  as it enters the latch assembly  10 . When the striker  20  has rotated the ratchet  22  to the position shown in  FIGS. 4 and 5 , the striker  20  is preferably stopped by an elastomeric element  44  (described in more detail below) located between the rear mounting plate  14  and the housing  16 . Because the striker  20  is trapped between the grooves  24 ,  26 ,  27  of the ratchet  22 , the rear mounting plate  14 , and the housing  16  in this position, the ratchet  22  cannot rotate further in the counterclockwise direction as viewed in  FIG. 4 . In addition, the ratchet  22  is preferably provided with a stop pin  36  which fits into a stop pin groove  38  in the housing  16  (see  FIG. 5 ). As best viewed in  FIG. 5 , a ratchet spring  40  is also preferably fitted within the stop pin groove  38  and exerts a reactive force against the stop pin  36  when compressed by rotation of the ratchet  22  in the counterclockwise direction as viewed in  FIG. 4 . Therefore, when the ratchet  22  is rotated in the counterclockwise direction as viewed in  FIG. 4 , the ratchet spring  40  and the termination of the stop pin groove  38  in the housing  16  prevents further rotation of the ratchet  22  in the same direction.  
      To limit movement of the ratchet  22  in the clockwise direction as viewed in  FIG. 4 , the stop pin groove  38  has a terminal section  39  (see  FIG. 5 ) within which the stop pin  36  is stopped when the ratchet  22  is rotated under force of the ratchet spring  40  in the clockwise direction as viewed in  FIG. 4 . As such, the ratchet  22  is effectively limited in movement in one direction by the stop pin  36  against the ratchet spring  40  and by the striker  20  stopped by the elastomeric element  44  and trapped within the grooves  24 ,  26 ,  27 , and limited in movement in the opposite direction by the stop pin  36  within the terminal section  39  of the stop pin groove  38 .  
      It should be noted that the ratchet  22  is preferably biased into its unlatched position (clockwise as viewed in  FIG. 4 ) by the ratchet spring  40 . The latch assembly  10  therefore returns to an unlatched state unless movement of the ratchet  22  is interfered with as will be discussed in more detail below. When the striker  20  is inserted into the grooves  24 ,  26 ,  27  of the ratchet  22 , the rear mounting plate  14 , and the housing  16  in this unlatched position, the striker  20  presses against the lower wall  42  of the groove  24  in the ratchet  22  (see  FIG. 14 ) and thereby causes the ratchet  22  to rotate about the lower pivot post  30  against the compressive force of the ratchet spring  40  in the stop pin groove  38 . Further insertion of the striker  20  rotates the ratchet  22  until the striker  20  contacts and is stopped by the elastomeric element  44  (described below) and/or until the reactive force of the ratchet spring  40  stops the ratchet  22 .  
      Due to the high impact forces commonly experienced by the latch assembly  10  as the striker  20  enters and is stopped by the latch assembly  10 , it is desirable to cushion the impact of the striker  20  upon the latch assembly  10  as the striker  20  is stopped. To this end, one well-known element preferably used in the present invention is an elastomeric element  44  located behind the termination of the groove  26  in the rear mounting plate  14 . The elastomeric element  44 , secured in a conventional manner to the rear mounting plate  14  and/or to the housing  16 , is an impact absorbing article preferably made of an elastomeric material such as rubber, urethane, plastic, or other resilient material having a low deformation memory.  
      The elastomeric element  44  not only performs the function of absorbing potentially damaging forces experienced by the latch assembly  10  during striker capture, but also acts to reduce the operational noise emitted by the latch assembly  10 . One having ordinary skill in the art will appreciate that a number of other conventional damper and impact absorbing elements and devices can be used in the latch assembly  10  of the present invention to protect the latch assembly  10  from high impact forces and to reduce latch noise. These other damper and impact absorbing elements fall within the spirit and scope of the present invention.  
      The ratchet  22 , the rear mounting plate  14 , the elastomeric element  44 , and their operational relationship with respect to the striker  20  as described above is generally conventional and well known to those skilled in the art. In operation, prior art latch mechanisms employ one or more elements which interact or interfere with the ratchet  22  at particular positions in its rotation to prevent rotation of the ratchet  22  to its unlatched position once the striker  20  is inserted sufficiently within the latch assembly  10 . For example, such elements can be brought into contact with a stop surface  32  of the ratchet  22  when the ratchet  22  is in its latched position (i.e., rotated to a counterclockwise position as viewed in  FIG. 4 ). When it is desired to release the striker  20  in an unlatching procedure, the elements are removed from interference with the ratchet  22  and the ratchet  22  is returned to its unlatched position (e.g., by the ratchet spring  40 ). As described above in the Background of the Invention, the prior art mechanisms and elements used to selectively insert and remove such elements from the ratchet  22  are virtually always complex, expensive to manufacture, inefficient, and relatively slow.  
      In one preferred embodiment of the present invention, the latch assembly  10  has a pawl  54  as best seen in  FIGS. 4-12 . The pawl  54  is rotatably mounted upon an upper pivot post  34  extending from the rear mounting plate  14 . The upper pivot post  34 , like the lower pivot post  30 , is preferably attached to the rear mounting plate  14  by fastening, riveting, screwing, bolting, or other conventional fastening methods. The upper pivot post  34  can instead be made integral with the rear mounting plate  14 , if desired.  
      The pawl  54  preferably includes a cam  56  (see  FIGS. 5, 13 , and  14 ). The body of the pawl  54  is preferably located on a side of the housing  16  opposite the ratchet  22 . However, the cam  56  of the pawl  54  preferably extends through an aperture  58  within the housing  16  to place the cam  56  in selective engagement with the ratchet  22 . Specifically, the pawl&#39;s fit within the aperture  58  of the housing  16  is loose enough to permit an amount of movement of the cam  56  relative to the ratchet  22 . It should be noted that although the housing shape illustrated in the figures is preferred in the present invention, other housing shapes can be used (e.g., having a different aperture type for accepting different pawls  54 , cams  56 , and different pawl and cam motions, different housing interior shapes and sizes for accepting different control elements and control element motions, etc.). As best shown in  FIGS. 13 and 14 , the pawl  54  and the cam  56  can preferably be placed in one position ( FIG. 13 ) in which the cam  56  engages with the stop surface  32  of the ratchet  22  when the ratchet  22  is in its latched position and in another position ( FIG. 14 ) in which the cam  56  is retracted from and does not interfere with rotation of the ratchet  22 . In the retracted pawl position, the ratchet spring  40  causes the ratchet  22  to automatically rotate to its unlatched position shown in  FIG. 14  as described above.  
      The pawl  54  is preferably biased into its ratchet interfering position by a pawl spring  59 . Referring to  FIGS. 7-12 , it can be seen that the pawl spring  59  is preferably a compression spring contained between walls of the pawl  54  and the housing  16 . The pawl spring  59  biases the pawl  54  in a counterclockwise direction as viewed in  FIGS. 7-12 , thereby pressing the cam  56  toward the ratchet  22  on the opposite side of the housing  16 . It will be appreciated that although the pawl spring  59  is shown secured between walls of the pawl  54  and the housing  16 , such an arrangement and position is not required to perform the function of biasing the pawl  54  in the counterclockwise direction as viewed in  FIGS. 7-12 . Indeed, the pawl spring  59  can instead be rigidly attached at one end to a part of the pawl  54 , can be rigidly attached to an inside wall of the housing  16 , can be contained within walls solely in the pawl  54  or solely in the housing  16  (still permitting, of course, an end of the pawl spring  59  to exert force against the pawl  54  and another end to exert force against the housing  16 ), and the like. Any such configuration in which the pawl spring  59  is positioned to exert a force against the pawl  54  in a counterclockwise direction as viewed in  FIGS. 7-12  can instead be used in the present invention. Such alternative configurations are well known to those skilled in the art and are therefore encompassed within the spirit and scope of the present invention.  
      The preferred embodiment of the present invention just described also has at least one control element  52 . By moving the pawl  54  (e.g., rotating the pawl  54  in the preferred embodiment), the latch assembly  10  can be placed in its unlatched state or can be secured in its latched state by virtue of the pawl&#39;s relationship with the ratchet  22 . With proper positioning and control of the control element  52 , movement of the control element  52  to press and/or ride against the pawl  54  therefore moves the pawl  54  to release the ratchet  22  and thereby to release the striker  20 . With different positioning and control of the control element  52 , movement of the control element  52  does not impart movement to the pawl  54  and therefore does not release the ratchet  22  to release the striker  20 . As will now be described, the control element  52  of the present invention can be positioned and controlled in either manner to define an unlatched state of the latch assembly  10  and a latched state of the latch assembly  10 .  
      Turning to  FIGS. 7-12 , a highly preferred embodiment of the present invention has a right and a left control element  52 ,  53 , respectively. Once again, the terms “right” and “left” are used only for ease of description, and do not imply that these elements necessarily be in a right and left position with respect to each other or to other elements in the latch assembly  10 . Other orientations are possible and fall within the scope of the present invention. The control elements  52 ,  53  preferably act as levers in the latch assembly  10 , and are externally actuatable by a user. However, and as described below in greater detail, the control elements  52 ,  53  need not necessarily pivot (an inherent part of a lever&#39;s operation), but can instead translate and/or translate and rotate in alternate embodiments of the present invention. Therefore, the term “lever” as used herein does not necessarily require that the control elements  52 ,  53  pivot or exclusively pivot.  
      Referring to  FIGS. 4 and 7 - 12 , it can be seen that the right control element  52  preferably has a first pivot point A (see  FIGS. 8-12 ), an abutment post  60 , a linkage end  62 , and a lever end  64  opposite the linkage end  62 . The abutment post  60  is preferably in abutting relationship with a ledge  72  of the pawl  54  at a bearing surface  55  of the pawl  54 . Therefore, as shown in  FIG. 11 , when an actuating force is exerted (downwardly) against the linkage end  62  of the right control element  52 , the, right control element  52  rotates in a clockwise direction about the abutment post  60  which acts as a fulcrum for the right control element  52  and as a bearing surface against the bearing surface  55  of the pawl  54 . However, if the right control element  52  is also engaged for rotation about pivot point A, the same actuation force against the linkage end  62  of the right control element  52  rotates the right control element  52  and the pawl  54  together about pivot point A (rather than rotating the right control element  52  about the abutment post  60 ). In this latter case, the abutment post  60  acts as a bearing surface against the bearing surface  55  of the pawl  54  as the pawl bearing surface  55  is pushed downward. It can thus be seen that by engaging and disengaging the right control element  52  for pivotal movement about pivot point A, actuation of the right control element  52  will either rotate the pawl  54  or not rotate the pawl  54 , respectively.  FIG. 9  thus defines an unlocked state of the latch assembly  10  (with the right control element  52  engaged for rotation about pivot point A) because rotation of the pawl  54  will cause release of the ratchet  22  and the striker  20  (see  FIG. 14 ). Also,  FIG. 11  thus defines a locked state of the latch assembly  10  (with the right control element  52  disengaged from rotation about pivot point A) because the pawl  54  does not rotate with the right control element  52  to release the ratchet  22  and the striker  20  (see  FIG. 13 ). To better control the movement of the right control element  52  either in its locked state or in its unlocked state, highly preferred embodiments of the present invention have a groove  57  in the housing  16  within which the abutment post  60  of the right control element  52  is received (see  FIGS. 4 and 5 ). When the right control element  52  pivots about the abutment post  60 , the abutment post  60  rotates in place at the top of the groove  57 , held there by the bearing surface  55  of the pawl  54 . When the right control element  52  is instead engaged for pivotal movement about pivot point A, the abutment post  60  travels down the groove  57  while it pushes the pawl  54  in a clockwise direction.  
      With the above relationship between the right control element  52  and the pawl  54  in mind, switching between the locked and unlocked states of the right control element  52  is therefore ultimately dependent upon disengagement and engagement operations, respectively, of the right control element  52  for rotation about pivot point A. Such operations can be performed in a number of ways. The most highly preferred method in the present invention is via a pin  66  (see  FIG. 5 ) selectively retracted and extended by a high-speed actuator  68 . When the actuator  68  is placed in its extended position, the pin  66  is preferably inserted into an aperture  70  (see  FIGS. 7-12 ) in the right control element  52  at pivot point A, thereby controlling the right control element  52  to rotate about pivot point A when actuated by a user. When the actuator  68  is placed in its retracted position, the pin  66  is preferably retracted from the aperture  70 , thereby permitting the right control element  52  to pivot about the abutment post  60 . The arrangement just described therefore reduces the time for placing the control element  52  in its locked and unlocked positions to the time required for disengaging and engaging the right control element  52  with the pin  66 . This time can be quite short depending upon the type of actuator  68  used. In contrast to prior art devices which require engagement elements which operate parallel to the plane of motion of the control elements, the engagement elements of the present invention operate perpendicular to the plane of motion of the control elements. This arrangement also reduces the forces required to move the engagement elements. Accordingly, an actuator with a relatively short stroke can be used to place the control elements  52 ,  53  in their locked and unlocked states, which generally results in a faster motion. In fact, in highly preferred embodiments of the present invention, actuator extension and retraction operations can be completed in under 10 milliseconds. Prior art devices require significantly more time to perform comparable latch assembly operations. Of course, one or more manual actuators can instead be used in the present invention to manually insert the pin  66  or move any other engagement element into engagement with the control elements  52 ,  53 . The actuators described herein and the other major components of the latch assembly  10  are preferably constructed as modules, enabling ready replacement or substitution.  
      Following along very similar structural and operational principles as the right control element  52 , the left control element  53  also has a first pivot point B, a linkage end  74 , a lever end  76  opposite the linkage end  74 , and a rotation peg  75  defining a second pivot point C. Although the left control element  53  is also preferably a lever, in the preferred embodiment of the present invention shown in the figures, the left control element  53  is L-shaped and preferably has a cam surface  78  located adjacent the pawl  54 . Therefore, and as shown in  FIG. 12 , when an actuating force is exerted (downwardly) against the linkage end  74  of the left control element  53 , the left control element  53  preferably rotates in a counterclockwise direction about the rotation peg  75 . Accordingly, the left control element  53  does not act upon the pawl  54  during rotation of the left control element  53  about the rotation peg  75  as shown in  FIG. 12 . To prevent unwanted translational movement of the rotation peg  75  during the counterclockwise rotation of the left control element  53 , the rotation peg  75  preferably rests in a groove  80  of the cover plate  82  (see  FIGS. 4 and 5 ). Of course, other well known elements can be used to prevent this translation, such as a ledge or rib extending from the rear surface of the cover plate  82 .  
      However, if the left control element  53  is engaged for rotation about pivot point B, the same actuation force against the linkage end  74  of the left control element  53  rotates the left control element  53  to press the cam surface  78  of the left control element  53  into a cam surface  84  of the pawl  54 , thereby rotating the pawl  54  about the upper pivot post  34 . It can thus be seen that by engaging and disengaging the left control element  53  for pivotal movement about pivot point B, actuation of the left control element  53  will either rotate the pawl  54  or not rotate the pawl  54 , respectively.  FIG. 10  thus defines an unlocked state of the latch assembly  10  (with the left control element  53  engaged for rotation about pivot point B), because rotation of the pawl  54  will cause release of the ratchet  22  and the striker  20 . Also,  FIG. 12  thus defines a locked state of the latch assembly  10  (with the left control element  53  disengaged from rotation about pivot point B) because the pawl  54  does not rotate under camming force exerted by the left control element  53  to release the ratchet  22  and the striker  20 .  
      As with the right control element  52 , switching between the locked and unlocked states of the left control element  53  is therefore ultimately dependent upon disengagement and engagement operations, respectively, of the left control element  53  for rotation about pivot point B. Also as with the right control element  52 , the preferred method of performing such operations in the present invention is via a pin  86  (see  FIG. 5 ) selectively retracted and extended by a high-speed actuator  88 . When the actuator  88  is placed in its extended position, the pin  86  is preferably inserted into an aperture  90  (see  FIGS. 7-12 ) in the left control element  53  at pivot point B, thereby controlling the left control element  53  to rotate about pivot point B when actuated by a user. When the actuator  88  is placed in its retracted position, the pin  86  is retracted from the aperture  90 , thereby controlling the left control element  53  to pivot about its rotation peg  75  when actuated by a user. The arrangement just described therefore reduces the time for placing the left control element  53  in its locked and unlocked positions to the time required for disengaging and engaging the left control element  53  with the pin  86 . This time can be quite short depending upon the type of actuator  88  used).  
      For proper positioning of the right and left control elements  52 ,  53  within the latch assembly  10 , the latch assembly  10  preferably has at least one control element spring  92  (see  FIGS. 7-12 ). In the most preferred embodiment of the present invention, one control element spring  92  is connected in a conventional manner between the ends  64 ,  74  of the right and left control elements  52 ,  53 , respectively. Preferably, the control element spring  92  is connected to each end  64 ,  74  by being hooked onto posts formed near the ends  64 ,  74 . However, the control element spring  92  can be fastened to the ends  64 ,  74  in a number of other well known manners (e.g., via a fastener securing the ends of the spring  92  in place upon the ends  64 ,  74 , via welding, glue, epoxy, etc.). The control element spring  92  acts to bias the control elements  52 ,  53  toward one another and into their unactuated positions shown in  FIG. 8 .  
      One having ordinary skill in the art will recognize that the particular control element spring  92  and its location within the latch assembly  10  shown in the figures is only one of a number of different control element spring types and locations serving this biasing function. For example, two or more control element springs can instead be used to bias the control elements  52 ,  53  into their unactuated positions. In such a case, the control element springs can be attached between the ends  64 ,  74  and the housing  16 . Alternatively, the control element springs can be of a different form than the extension spring shown in the figures. For example, the control element springs can be coil, torsion, or leaf springs arranged in the latch assembly  10  to bias the control elements  52 ,  53  as described above. Such alternate biasing elements and arrangements fall within the sprint and scope of the present invention. Prior to describing the actuators  68 ,  88  and their operation in more detail, the mechanical actuation of the control elements  52 ,  53  will now be described. Each control element  52 ,  53  is provided with a linkage end  62 ,  74  upon which external forces are preferably exerted to actuate the control elements  52 ,  53 . In the case of the right control element  52 , the linkage end  62  is preferably an arm of the right control element  52  having an aperture  94  therethrough at its terminal portion. In the case of the left control element  53 , the linkage end  74  is preferably a post having an aperture  96  therethrough. When the latch assembly  10  is installed, an external linking element (not shown) is connected via the aperture  94  to the right control element  52  and an external linking element (also not shown) is connected via the aperture  96  to the left control element  53 . Because the left control element  53  is preferably located fully within the latch assembly  10 , the linking element is passed through a port  98  within the housing  16  and the cover  12  of the latch assembly  10 . Of course, the port  98  can take any number of shapes and locations within the housing  16  and/or the cover  12  to permit the external linking element to be connected inside the latch assembly  10  to the left control element  53 .  
      In the highly preferred embodiment of the present invention shown in the figures, the linking element connected in a conventional fashion to the right control element  52  is preferably a bar or member connected and directly actuated by, e.g., a door handle, while the linking element connected to the left control element  53  is preferably a cable which is secured in a conventional fashion to the linkage end  74 . The linking element connected to the left control element  53  is preferably passed out of the latch assembly  10  through the port  98 . It should be noted that although cables are preferred, other types of linking elements can be used, such as rods, bars, chains, string, rope, etc. In fact, the linking elements can even be made integral to or extensions of the control elements  52 ,  53  themselves. The particular type of linking element used is dependent at least in part upon the shape, size, and position of opening(s) in the cover  12  and/or the housing  16  to permit the control elements  52 ,  53  to be connected to the external linking elements. The particular type of linking element used can also depend upon whether attachment of the control elements  52 ,  53  to the linking elements is accomplished externally of the cover  12  and/or the housing  16  (such as in the case of the right control element  52  shown in the figures) or internally (such as in the case of the left control element).  
      The latch assembly  10  described above and illustrated in the figures finds particular application for doors having two handles, such as an internal handle and an external handle. In this application, one handle is connected to the right control element  52  and the other handle is connected to the left control element  53  via the linking elements described above. Therefore, actuation of one handle actuates one control element while actuation of the another handle actuates the other control element. The manner of connection of the linking elements to the handles is well known to those skilled in the art and is therefore not described further herein. It should also be noted that the linking elements need not necessarily be attached to door handles. Especially where the latch assembly  10  is used in applications not involving vehicle doors (or indeed, any type of door), the control elements  52 ,  53  can be actuated either indirectly via linking elements or directly to operate the latch assembly  10 . Any number of conventional elements and mechanisms can be linked to the control elements  52 ,  53  to effect their actuation as desired. As described above, the type of movement of the control elements  52 ,  53  (when actuated) is dependent upon whether the pins  66 ,  86  are extended or retracted to engage with the control elements  52 ,  53 . When the pins  66 ,  86  are extended by the actuators  68 ,  88  to engage the control elements  52 ,  53 , the control elements  52 ,  53  preferably pivot about pivot points A and B, respectively, which permits the control elements  52 ,  53  to exert motive force to the pawl  54 . When the pins  66 ,  86  are retracted by the actuators  68 ,  88  to disengage from the control elements  52 ,  53 , the control elements  52 ,  53  preferably pivot instead about abutment post  60  and rotation peg  75 , respectively, which prevents the control elements  52 ,  53  from exerting force upon the pawl  54  sufficient to move (rotate) the pawl  54 . Because the speed in which the control elements  52 ,  53  are placed in their locked and unlocked states is thus dependent upon the speed of the actuators  68 ,  88  to move the pins  66 ,  86 , it is desirable to use the fastest actuator type economically reasonable for the actuators  68 ,  88 . In the most preferred embodiment of the present invention, the actuators  68 ,  88  are each a two-position residual magnetic latching electromagnetic solenoid such as those commercially available from and sold by TLX Technologies of Waukesha, Wis. However, other conventional actuator types are possible, including other types of solenoids, conventional hydraulic or vacuum actuators, small motors, and even elements or assemblies which are manually operated to push and retract the pins  66 ,  86  to place the control elements  52 ,  53  into their locked and unlocked positions. Though not as preferred as two-position electromagnetic solenoids, these alternative actuators fall within the spirit and scope of the present invention.  
      The actuators  68 ,  88  are preferably connected to an electronic control circuit which is controllable by a user for placing the actuators  68 ,  88  in their engaged and disengaged states, thereby placing the latch assembly  10  in its unlocked and locked states, respectively. Upon command by the user, the electronic control circuit preferably generates electronic pulses to the actuators  68 ,  88  for controlling their movement. To secure against accidental or unauthorized actuation, a coded signal can be sent to the electronic control circuit. Coding of electronic signals is well known to those skilled in the art and is not therefore discussed further herein. The electronic control circuit can be powered in a conventional manner, such as by a battery, an alternator, a generator, a capacitor, a vehicle electrical system or other conventional power source.  
      With reference to the preferred embodiment of the present invention, the actuators  68 ,  88  are electromagnetic solenoids which can retain residual magnetism to hold the actuators  68 ,  88  in their retracted positions once they are moved thereto. When the actuators  68 ,  88  are moved to their extended positions, conventional springs (not shown) are preferably used to maintain their positions in the extended states. Therefore, when the actuators  68 ,  88  are in their retracted positions and held therein via the residual magnetism, a power pulse from the electronic control circuit is used to break the residual magnetism and to thereby extend the actuators  68 ,  88  via the springs into their extended positions. Conversely, when the actuators  68 ,  88  are in their extended positions and held therein by the springs, a power pulse from the electronic control circuit is used to force the actuators  68 ,  88  into their retracted positions against the force of the springs, and residual magnetism is used to keep the actuators  68 ,  88  in these positions.  
      In a highly preferred embodiment of the present invention, the electronic control circuit just described contains at least two power sources for the actuators  68 ,  88  in the latch assembly  10 . These power sources can comprise any conventional power sources including, without limitation, capacitors, batteries, alternators, generators and vehicle electrical systems.  
      For illustrative purposes only, a first power source is described herein as a battery and a second power source is described as a capacitor. During normal operation when the latch assembly  10  is powered continuously by the battery  120 , each capacitor  124  is continuously charged. Each capacitor  124  stores sufficient energy to break the residual magnetism of the electromagnetic solenoids  68 ,  88 . In the event of total power failure, the control circuit can automatically discharge the capacitors  124  to cause the actuators  68 ,  88  to unlock the latch assembly  10 . The latch assembly  10  can be completely unlocked or partially unlocked upon power failure. When the latch assembly  10  is used on a vehicle door, only the portion of the latch assembly  10  actuated by an inside door handle will be unlocked. This configuration enables the vehicle occupant to exit the vehicle while maintaining security against unauthorized entry. Alternatively, the user can unlock the latch assembly  10  manually (e.g., using a switch) using energy stored by the capacitors. Further, it may instead be desirable to have one capacitor for each actuator  68 ,  88  with enough charge to place the solenoids  68 ,  88  in their retracted positions. Therefore, even with power disconnected from the latch assembly  10 , there exists sufficient charge in the control circuit to lock the latch assembly  10  (either under command of the user or automatically by the control circuit). With multiple capacitors for each actuator  68 ,  88 , a preferred embodiment of the present invention has one capacitor for each actuator  68 ,  88  with sufficient energy to place the actuator  68 ,  88  in its locked position and another capacitor for each actuator  68 ,  88  with sufficient energy to place the actuator  68 ,  88  in its unlocked position.  
      The electronic control circuit is preferably also provided with a conventional electrical characteristic sensing circuit for detecting the power supplied to the electronic control circuit. Such sensing circuits (e.g., voltage or current sensing circuits) are well known to those skilled in the art and are therefore not described further herein except for the generalized example shown in  FIG. 15 . When the sensing circuit detects a change in an electrical characteristics beyond a predetermined level such as low voltage or current level, or loss of power such as due to a disconnected or failed power source, the control circuit preferably generates a signal to the actuators to place them in their unlocked positions to unlock the latch assembly  10 . Alternately, (though not preferred) when the sensing circuit detects the change, the control circuit can instead enable a control or button that can be actuated by the user to unlock the latch.  
      An exemplary automatic unlocking circuit  110  for unlocking the latch assembly  10  is shown in  FIG. 15 . It will be apparent to one of ordinary skill in the art that a wide variety of circuits and components different than that illustrated in  FIG. 15  and described below can be used equivalently. T 1  and T 2  are two PNP-type transistors connected in parallel. During typical operation, a delatching pulse applied at node  112  activates transistor T 1  and preferably comprises a conventional controlled voltage pulse sufficient to delatch the solenoid  68 ,  88 .  
      Transistor T 2 &#39;s base  114  is preferably connected to a resistor  116  connected to ground  118 , and is also preferably connected to a 12 volt battery or other voltage source  120  such as in a conventional vehicle electrical system.  
      When 12 volts D.C. from the battery  120  is present, T 2  is non-conducting and T 1  is non-conducting unless pulsed to ground  118 . The diode  122  keeps the capacitor  124  from discharging back to the rest of the system.  
      Accordingly, the capacitor  124  only discharges when one of the battery&#39;s electrical characteristics such as voltage level falls below a predetermined level. When this occurs, the base of T 2  approaches ground  118 . Therefore, T 2  turns on fully and the capacitor  124  can discharge through T 2  and send a release pulse through the solenoid  68 ,  88  thereby delatching the solenoid  68 ,  88  and unlocking the latch assembly  10 .  
      In addition to all of the preferred embodiments previously described, it will be appreciated by one having ordinary skill in the art that the particular arrangement and operation of the actuators  68 ,  88  described above for the most preferred embodiment of the present invention can take a number of other forms within the spirit and scope of the present invention. For example, the residual magnetism exerted upon the actuators  68 ,  88  to keep them in their retracted positions can instead be exerted upon the actuators  68 ,  88  to keep them in their extended positions, and the springs keeping the actuators  68 ,  88  in their extended positions can instead be used to keep the actuators  68 ,  88  in their retracted positions (i.e., the opposite solenoid arrangement as that described above). In such an arrangement, the latch assembly can operate in a similar manner as described above, with a dual power source (e.g., battery and capacitor), with a sensing circuit, and/or with similar electronic circuitry. Such an arrangement can be particularly useful in applications where it is desirable to place or keep the latch assembly  10  in its locked state in the event of power loss. When power is lost, interrupted, or otherwise changed in a predetermined manner, the sensing circuit preferably triggers the actuators to retract using the dual power source arrangement described above, thereby placing the latch assembly in its locked state.  
      Other embodiments of the present invention employ conventional solenoids using permanent magnets. These magnets retain the solenoid&#39;s armatures in both extended and retracted positions as is well known in the art. Other well known systems and elements can be used to achieve the function of the capacitors described above, and well known mechanical and electrical systems and elements can be used as alternatives to the springs and residual magnetism employed to control the positions of the actuators  68 ,  88 .  
      As indicated above, many alternatives to the use of electromagnetic solenoids for the actuators  68 ,  88  exist and are well-known to those skilled in the art. For example, the actuators can each be a rack and pinion assembly. As another example, the actuators can each be a motor turning a worm gear that meshes with an element (e.g., a threaded pin) to push and pull the element toward and away from the control elements  52 ,  53 . The element can instead be a wheel having teeth meshing with the worm gear. In such an arrangement, rotation of the worm gear causes rotation of the wheel. A pin or rod attached to the circumference of the wheel can then be moved toward or away from the control elements  52 ,  53  via rotation of the wheel. All other well known mechanisms for quickly extending and retracting a pin or other engagement element are useful with and fall within the spirit and scope of the present invention.  
      The actuators  68 ,  88  in the preferred embodiment of the present invention are preferably contained and substantially enclosed in the cover  12  and are preferably encapsulated therein by the cover plate  82  as best shown in  FIGS. 4-6 . The cover plate  82  is preferably provided with apertures  100 ,  102  for receiving the pins  66 ,  86 , respectively, which extend beyond the cover plate  82  when in their extended positions to interact with the control elements  52 ,  53 . The cover plate  82  also helps to protect the actuators  68 ,  88  from debris, dirt, etc., managing to enter the latch assembly  10  between the cover plate  82  and the housing  16 , and helps to control movement of the pins  66 ,  86 .  
      The pins  66 ,  86  are preferably mounted to or integral with the armatures of the actuators  68 ,  88 . It will be apparent to one of ordinary skill in the art that the pins  66 ,  86  need not necessarily be mounted to or be part of the armatures. Instead, the pins can be mounted to pin plates  104 ,  106  as shown in the figures. Further, depending largely upon the type of actuator used, the pins  66 ,  86  can extend within the actuators  68 ,  88  which directly control the movement of the pins  66 ,  86  into and out of the apertures  100 ,  102  in the cover plate  82 . Other pin arrangements will be recognized by those skilled in the art and are encompassed by the present invention.  
      In operation, the user of the preferred embodiment of the present invention described above has the ability to select from four locking modes of the latch assembly  10 : unlocked, locked, child locked, and dead locked. In the unlocked mode, the electronic control circuit described above preferably sends a signal or signals to both actuators  68 ,  88  to place them in their extended positions in which the pins  66 ,  86  are also in their extended positions. The pins  66 ,  86  thus interact with the control elements  52 ,  53  to control the control elements  52 ,  53  to pivot about pivot points A and B. By pivoting about pivot points A and B, the control elements  52 ,  53  are able to move the pawl  54  and release the ratchet  22  to unlatch the latch assembly  10  when the control levers  52 ,  53  are actuated by a user. In this unlocked state, actuation of either control lever  52 ,  53  (e.g., via the inside door handle or the outside door handle of a vehicle door) will therefore unlatch the latch assembly  10 .  
      In the locked mode, the electronic control circuit preferably sends a signal or signals to one of the two actuators  68 ,  88  to place it in its retracted position and a signal or signals to the other actuator  88 ,  68  to place it in its extended position. In the case of the latch assembly  10  illustrated in the figures, the upper actuator  68  controls the position of the upper pin  66  which is either engaged or disengaged with the right control element  52 , while the lower actuator  88  controls the position of the lower pin  86  which is either engaged or disengaged with the left control element  53 . While the control elements  52 ,  53  can be connected directly to door handles, the right control element  52  is preferably coupled by a linking element to the outside door handle while the left control element  53  is preferably coupled by a linking element to the inside door handle. The linking elements can comprise conventional linkages, rods, cables, linear actuators, rotary actuators and the like for transmitting torque, tensile forces and/or compressive forces. Thus, for the arrangement just described, the upper actuator  68  controls the locked and unlocked states of the outside door handle, and the lower actuator  88  controls the locked and unlocked states of the inside door handle.  
      Prior to describing the child locked mode of the latch assembly  10 , it should be noted that the term “child locked” is used herein for mode identification purposes only. The term itself is not intended to explicitly or implicitly define the arrangement and operation of the latch assembly  10 . In general use of the term, “child locked” typically means that the inside door handle of a vehicle door is not operable to unlatch the door, and does not provide any information about the operability of the outside door handle. However, for mode identification purposes herein, the term “child locked” means that the inside door handle is inoperable and the outside door handle is operable.  
      In the child locked mode for the particular arrangement of the latch assembly  10  described above, the upper actuator  68  is preferably in an extended position (controlled by the electronic control circuit) and the upper pin  66  is engaged with the right control element  52 . The right control element  52  is therefore in its unlocked state. The lower actuator  88  is preferably in a retracted position (also controlled by the electronic control circuit) and the lower pin  86  is disengaged from the left control element  53 . The left control element  53  is therefore in its locked state. Actuation of the inside door handle then causes the left control element  53  to move, but not in a manner imparting motive force to the pawl  54  to unlatch the latch assembly  10 . Actuation of the outside door handle causes the right control element  52  to pivot about pivot point A (engaged via the upper pin  66 ), thereby moving the pawl  54  to unlatch the latch assembly  10 . Therefore, in the child locked mode, the latch assembly  10  can be unlatched by the outside door handle but not by the inside door handle. It should be noted, however, that the outside door handle can be put into a locked state independent of the child locked mode.  
      In the dead locked mode, the electronic control circuit preferably sends a signal or signals to both actuators  68 ,  88  to place them in their retracted positions in which the pins  66 ,  86  are also in their retracted positions. The pins  66 ,  86  thus do not interact with the control elements  52 ,  53 , leaving the control elements  52 ,  53  to pivot about the abutment post  60  and the rotation peg  75 , respectively. By pivoting about the abutment post  60  and the rotation peg  75 , the control elements  52 ,  53  are unable to move the pawl  54  and release the ratchet  22  to unlatch the latch assembly  10  when the control levers  52 ,  53  are actuated by a user. In this dead locked state, actuation of either control lever  52 ,  53  (e.g., via the inside door handle or the outside door handle of a vehicle door) will therefore not unlatch the latch assembly  10 .  
      It will be appreciated by one having ordinary skill in the art that the principles of the present invention can be practiced with latch assemblies which are arranged in a significantly different manner than the preferred embodiment of the latch assembly  10  described above and illustrated in the drawings. Specifically, the connection of the upper actuator  68 , upper pin  66 , and right control element  52  to an outside door handle and the connection of the lower actuator  88 , lower pin  86 , and left control element  53  to an inside door handle can be reversed (i.e., the upper actuator  68  controlling the locked and unlocked states for the inside door handle and the lower actuator  88  controlling the locked and unlocked states for the outside door handle). In fact, the use of two actuators  68 ,  88 , two pins  66 ,  86 , and two control elements  52 ,  53  is only a preferred embodiment. More or fewer actuator, pin, and control element sets can be used depending upon the number of handles (or other user-actuated elements) desired to control the various locking modes of the latch assembly  10 . For example, one set can be used if the door only has one handle for latching and unlatching the latch assembly  10 . Also, multiple handles (or other user-actuated elements) can be coupled to the same control lever, if desired. In such a case, an inside and an outside handle can operate always in the same mode: locked or unlocked.  
      The cover  12 , housing  16 , and cover plate  82  of the latch assembly  10  are preferably made of plastic. However, the cover  12 , the housing  16 , and the cover plate  82  can be made from any number of other materials, such as steel, aluminum, iron, or other metals, urethane, fiberglass or other synthetic materials, composites, refractory materials such as glass, ceramic, etc., and even relatively unusual materials such as wood or stone. Depending upon the type of material used, the cover  12  can be made in a number of manners, such as via a heat and/or pressure sintering process, casting, injection or other molding, curing, extruding, stamping, pressing, firing, welding, etc. The materials and methods just described are well known to those skilled in the art and are encompassed by the present invention.  
      The rear mounting plate  14 , ratchet  22 , and pawl  54  are preferably made of steel, and the right and left control levers  52 ,  53  are preferably made of a castable or moldable material such as zinc or plastic. However, these elements can also be made from a variety of other materials including those noted by way of example in the preceding paragraph. Preferably, the ratchet spring  40 , the pawl spring  59 , the control element spring  92 , and the actuator springs (not shown) are each helical springs made of spring steel. However, one having ordinary skill in the art will recognize that any type of bias member capable of exerting motive force against the relevant elements can instead be used. Such other bias members include, without limitation, an elastomeric material such as rubber, urethane, etc. capable of storing and releasing an amount of force under pressure, magnets, fluid or gas-actuated diaphragms pressing against or pulling the device to be moved, vacuum or suction devices acting upon the element desired to be moved, electromagnets, electrical circuits or elements capable of generating a biasing force, etc. Of course, other spring types (such as conventional coil, torsion, or leaf springs) made from different spring materials can be used in lieu of the helical springs to accomplish the same functions. Although the manners in which the other types of bias members are fastened within the latch assembly can be quite different to create the same or similar biasing force described above, such other types of bias members fall within the spirit and scope of the present invention. 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 as set forth in the appended claims. For example, although the present invention can be employed with excellent results in vehicle doors, the present invention can be used in any application where one body is releasably latched to another body via a movable element (e.g., a ratchet) having a latched state and an unlatched state controlled by interference caused directly or indirectly by one or more control elements  52 ,  53 . Such applications can be in non-vehicle environments and can be virtually any size (e.g., from large canal door latches to miniature device latches). The moveable element need not necessarily be a ratchet or even rotate about a pivot point, but at least is selectively held in latched and unlatched states by either a pawl or like device or directly by a control element  52 ,  53 .  
      In light of the above, it should be noted that the particular device used to capture the striker  20  or other element captured by the latch assembly  10  can be significantly different than that described above and illustrated in the drawings. Though important to operation of the latch assembly  10 , other elements and mechanisms beside a pivotable ratchet and spring arrangement can be used to interact either with the pawl  54  or directly with the control lever(s)  52 ,  53  if a pawl  54  is not used. One skilled in the art will recognize that it is possible to eliminate the pawl  54  in alternative embodiments of the present invention and to design the control lever(s) to ride upon and limit the rotation of the ratchet  22  in much the same way as the pawl  54 . In such alternative embodiments, the inventive principles herein are still employed: moving a control element in one manner when engaged by an engagement element (e.g., a pin_controlled by a solenoid) and in another manner when disengaged. In one manner, the control element moves to directly or indirectly release the ratchet  22  and in another manner, movement of the control element does not directly or indirectly release the ratchet  22 . Where a pawl  54  is employed, sole rotational movement of the pawl  54  is not a requirement. For example, the pawl  54  can be shifted or translated against spring force in one direction when the control levers act upon the pawl  54  in their unlocked states and be unaffected when the control levers are in their locked states. Even a combined translation and rotation of the pawl  54  is possible when actuated by the control levers. Also, it should be noted that multiple pawls can be used, if desired, to interact with different stop surfaces of the ratchet  22  in more complex latch assemblies.  
      In addition to the variations and alternatives just discussed, the control elements  52 ,  53  can also be significantly different than described above and illustrated in the figures. The right and left control elements  52 ,  53  are disclosed herein as being generally straight and generally L-shaped, respectively. However, it is possible that both elements can be made identical (and placed on top of one another with their linkage ends  62 ,  74  adjacent to one another, placed in a similar orientation to that shown in the figures, etc.). Also, the control elements  52 ,  53  can be virtually any shape, as long as the control elements  52 ,  53  move in a first manner to directly or indirectly release the ratchet  22  as described above and to not do so when moving in a second manner, the manners of movement being controlled by engagement with the pins  66 ,  86 .  
      As described above and illustrated in the figures, the control elements  52 ,  53  are preferably selectively engaged for rotation about pivot points A and B, respectively, by pins  66 ,  86 . The pins  66 ,  86  are controlled by the actuators  68 ,  88  to be inserted into and retracted from the apertures  70 ,  90  in the control elements  52 ,  53 . This relationship is only one of a number of different engagement relationships possible in the present invention. Specifically, the pins  66 ,  86  are only one type of engagement element performing the function of controlling the movement of the control elements  52 ,  53  in a particular manner when engaged (e.g., by allowing only rotation of the control elements  52 ,  53  about pivot points A and B). The present invention resides not in the particular type or shape of engagement element, but in the control of the control elements  52 ,  53  when the pins  66 ,  86  are in their engaged states. Therefore, one having ordinary skill in the art will recognize that the location of the pins  66 ,  86  and the apertures  70 ,  90  can be reversed, with pins in the control elements  52 ,  53  fitting into apertures in the plates  104 ,  106  or actuators  68 ,  88 .  
      Engagement of the control elements  52 ,  53  by the actuators  68 ,  88  can also be performed for example, by bumps in the control elements  52 ,  53  fitting into dimples in the pin plates  104 ,  106  or actuators  68 ,  88  (or vice versa), by one or more teeth in the control elements  52 ,  53  and in the pin plates  104 ,  106  or actuators  68 ,  88  meshing together when engaged, by a magnetic or electromagnetic connection established between the pin plates  104 ,  106  or actuators  68 ,  88  and the control elements  52 ,  53 , etc. All such alternatives to the pin and aperture arrangement in the preferred embodiment of the present invention share the inventive principle of using an actuator to engage the control elements  52 ,  53  for controlling their movement as described above. It should be noted that the particular location of the pins, teeth, bumps, or other engagement elements need not necessarily be between the actuators  68 ,  88  and the control elements  52 ,  53 . Instead, the engagement elements can be located between the control elements  52 ,  53  and the housing  16 , if desired. For example, the pins, teeth, bumps, or magnets can be located on the housing  16  normally disengaged from the control elements  52 ,  53  when the actuators  68 ,  88  are in their retracted positions. When the actuators  68 ,  88  are extended, they can push the control elements  52 ,  53  into engagement with the pins, teeth, bumps, or magnets on the housing  16  to thereby engage the control elements  52 ,  53  for a particular motion (as the pins  66 ,  86  in the preferred embodiment described above do).  
      The latch assembly  10  of the present invention as disclosed herein employs an engagement element or elements such as pins  66 ,  86 , teeth, bumps, or magnets engaging with an element or elements such as apertures  70 ,  90 , teeth, dimples or magnets in the control elements  52 ,  53  (or vice versa). However, one having ordinary skill in the art will recognize that the engagement elements need not interact by inserting one engagement element into another (such as a pin  66 ,  86  into an aperture  70 ,  90  in the control elements  52 ,  53 ). Instead, the engagement elements can simply be actuated to provide guidance surfaces to control the movement of the control elements  52 ,  53  when actuated. For example, in the case of the pin and aperture arrangement of the preferred embodiment, the pins  66 ,  86  need not be inserted into apertures in the control elements  52 ,  53 . Instead, the pins  66 ,  86  can be inserted alongside the control elements  52 ,  53  so that when the control elements  52 ,  53  are actuated by a user, the pins  66 ,  86  guide the control elements  52 ,  53  along a particular path that is different than that taken by the control elements  52 ,  53  when the pins  66 ,  86  are retracted. The control elements  52 ,  53  need not therefore be limited for solely rotational movement (such as in the preferred embodiment of the present invention) in either state. In fact, movement of the control elements  52 ,  53  in the extended and retracted states of the pins  66 ,  86  can be purely translational or be a combination of rotation and translation. A broad aspect of the present invention resides not necessarily in the specific rotation, translation, or combined rotation and translation of the control elements  52 ,  53  in either their locked or unlocked states, but rather in a path of control element motion imparting movement to the pawl  54  (if used) in one actuator state and a path of control element motion not imparting such movement in a second actuator state. Because the two paths of motion are determined by the placement of the pins  66 ,  86  and the shape of the control elements  52 ,  53 , the path imparting motion and the path not imparting motion need not correspond to the extended and retracted positions of the pins  66 ,  86 . The path imparting motion and the path not imparting motion can correspond instead to the retracted and extended positions of the pins  66 ,  86 , as desired.  
      The latch assembly  10  can also include a manual override device coupled to at least one of the control element  52 ,  53 , the pawl  54  and the actuator  68 ,  88 . The manual override operates to change the states or modes of the latch assembly  10  in a supplemental manner to the manners previously described. The manual override can comprise a wide variety of manually actuated mechanical or electronic devices, but preferably comprises a lock. It will be apparent to one of ordinary skill in the art that the coupling of the manual override to the latch assembly  10  will vary depending upon the particular manual override selected. For example, where the manual override comprises a cylinder lock, any of the previously described linking elements can be used satisfactorily to couple the manual override to the latch assembly  10 . In one highly preferred embodiment, the cylinder lock includes a projection for driving a mechanical linkage that is connected directly to the engagement elements of the latch assembly  10 , such as to the linkage end  62  of the right control lever  52 . Alternatively, an electronic manual override such as an electronic lock can be electronically coupled to an electronic actuator, or can be used to actuate a mechanical element or linkage.  
      Two manual override assemblies are illustrated by way of example in  FIG. 16 . On the left in  FIG. 16  is a conventional user-activated lock pin  120  accessible from within the vehicle and used to manually override the latch assembly  10 . The lock pin  120  can be connected to a wedge shaped element  122  inserted within the latch assembly  10  as shown by the dashed lines. Specifically, a rod  124  or other conventional linking member can extend from the lock pin  120 , into an aperture  126  in the cover  12 , and to the wedge shaped element  122 . As such, lifting the lock pin  120  will move the wedge shaped element  122  in an upward direction as viewed in  FIG. 16 , thereby causing the wedge shaped element  122  to act upon the pin  66  to push it into its unlocked state (note that the rear end of the pin  66  preferably extends through and past the actuator  68  when in its fully retracted position). Depressing the lock pin  120  will permit the pin  66  to retract, when actuated, to place the pin  66  in its locked state again.  
      Another type of manual override is also shown by way of example in  FIG. 16 . Where, as preferred, the manual override is operated by a cylinder lock  120   a , the cylinder lock  120   a  can be connected to a wedge shaped element  122   a  inserted in the latch assembly  10 . Like the manual override  120 ,  122 ,  124  described above, a rod  124   a  or other conventional linking member can extend from the cylinder lock  120   a  into the aperture  126  in the cover  12 , and to the wedge shaped element  122   a . When the cylinder lock  120   a  is turned by an authorized user, the rod  124   a  and the wedge shaped element  122   a  act in a similar manner as described above to place the pin  66  in its locked and unlocked states. The manual overrides illustrated in  FIG. 16  are shown only by way of example. One skilled in the art will recognize that many other manual override devices and systems can instead be used to achieve the same result. Also, a manual override can be coupled to both pins  66 ,  86  or just to the lower pin  86 . Multiple manual override devices can also be used, if desired, to operate the same pin. It will be apparent to one of ordinary skill in the art that still other manual overrides can be used without departing from the present invention.