Patent Publication Number: US-2019178007-A1

Title: Hook bolt for door lock

Description:
RELATED APPLICATIONS 
     This Application claims the benefit of U.S. Provisional Application No. 62/597,088, filed Dec. 11, 2017, entitled “HOOK BOLT FOR DOOR LOCK”. The entire contents of this application are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     Disclosed embodiments are related to an automatic hook engagement feature for a door lock. 
     BACKGROUND 
     Traditional locking hardware for swinging doors like a deadbolt are incompatible with sliding doors. Conventionally, a lock for a door is engaged or disengaged by a user or operator turning a knob (when operating the door from the “inside”) or using a key or other credential (when operating the door from the “outside”). A conventional deadbolt only lock prevents lateral movement of a swinging door (i.e., in the swinging direction) when the lock is engaged. Conventional deadbolt locks are incompatible with and thus fail to provide security in applications for use with sliding doors that move in a longitudinal (i.e., sliding) direction. 
     SUMMARY 
     A hook bolt for a latch assembly includes a deadbolt and at least one hook located at least partially within the deadbolt. The deadbolt is constructed and arranged to move between a retracted deadbolt position and an extended deadbolt position. The at least one hook is constructed and arranged to move between a disengaged position and an engaged position. The at least one hook is constructed and arranged to move from the disengaged position to the engaged position as the deadbolt moves from the retracted deadbolt position to the extended deadbolt position. 
     A latch assembly for a door includes a chassis, a deadbolt supported by the chassis, and at least one hook located at least partially within the deadbolt. The deadbolt automatically moves relative to the chassis between a retracted deadbolt position and an extended deadbolt position. The deadbolt is held in the retracted deadbolt position. The at least one hook is constructed and arranged to automatically move between a disengaged position and an engaged position. The deadbolt is held in the retracted hook position. A trigger cooperates with the deadbolt and is constructed and arranged to permit the deadbolt to move to the extended deadbolt position. The at least one hook is automatically moved from the disengaged position to the engaged position when the deadbolt is automatically moved from the retracted deadbolt position to the extended deadbolt position. 
     A door system in combination with a latch assembly of exemplary embodiments includes a door, the latch assembly coupled to said door, and a first handle coupled to said latch assembly and operable to open said door. 
     It should be appreciated that the foregoing concepts, and additional concepts discussed below, may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Further, other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings: 
         FIG. 1  illustrates a side view of a hook bolt disposed in a latch assembly according to one embodiment with the hook bolt in a retracted hook bolt position. 
         FIG. 2  illustrates a side view of the hook bolt of  FIG. 1  with the hook bolt in an extended hook bolt position; 
         FIG. 3  illustrates a side view of a hook bolt disposed in a latch assembly according to another embodiment with the hook bolt in an extended hook bolt position; 
         FIG. 4  illustrates a side view of the hook bolt of  FIG. 3  with the hook bolt in a retracted hook bolt position; 
         FIG. 5  illustrates a side view of a hook bolt disposed in a latch assembly according to yet another embodiment with the hook bolt in an extended hook bolt position; 
         FIG. 6  illustrates a side view of the hook bolt of  FIG. 5  with the hook bolt in a retracted hook bolt position; 
         FIG. 7  illustrates a side perspective view of a latch assembly including a hook bolt according to yet another embodiment; 
         FIGS. 8A-8C  illustrate detailed views of the hook bolt within the latch assembly of  FIG. 7 ; 
         FIGS. 9A-9D  illustrate detailed views of a latch bolt within the latch assembly of  FIG. 7 ; 
         FIGS. 10A-10B  illustrate detailed views of an auxiliary bolt within the latch assembly of  FIG. 7 ; 
         FIGS. 11A-11B  illustrate detailed views of a lock switch within the latch assembly of  FIG. 7 ; 
         FIG. 12  illustrates a side view of a latch assembly according to yet another embodiment with a hook bolt in an extended position; 
         FIG. 13  illustrates a side view of the latch assembly of  FIG. 12  with the hook bolt in a retracted position; 
         FIGS. 14A-14B  illustrate detailed views of the hook bolt within the latch assembly of  FIGS. 12-13 ; 
         FIGS. 15A-15B  illustrate detailed views of a latch bolt and an auxiliary bolt within the latch assembly of  FIGS. 12-13 ; 
         FIG. 16  illustrates a side view of a latch assembly according to yet another embodiment with a hook bolt in an extended position; 
         FIG. 17  illustrates a side view of the latch assembly of  FIG. 16  with the hook bolt in a retracted position; 
         FIGS. 18A-18C  illustrate views of embodiments of front, rear, and side plates respectively of a latch assembly; and 
         FIGS. 19A-19B  illustrate views of a door including a latch assembly. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to a hook bolt that includes one or more hooks for engaging a door jamb strike plate. The hook bolt may be used to secure either a sliding door or a swinging door. Accordingly the embodiments herein may be specifically described either with respect to a sliding door or a swinging door or both; however, it should be appreciated that the described embodiment may be utilized in any door style, as the disclosure is not limited in this respect. In one embodiment, the one or more hooks secures a sliding door by contacting an interior side of an associated door jamb strike plate, thereby preventing the sliding door from being retracted (i.e., slid open). Additionally, the hook bolt may afford increased security of a traditional swinging door by increasing the size of one or more lateral contact surface regions in the door jamb. The hook bolt may be employed in any conventional latch assemblies that include a deadbolt, which may provide an added benefit of reducing the cost and expense of developing various locking systems to fit different types of doors. Accordingly, a conventional deadbolt latch assembly including a hook bolt may be employed on a sliding door such that a sliding door can be locked using a latch assembly in a traditional form factor. Additionally, the hook bolt may cooperate with or otherwise include a deadbolt from which the one or more hooks automatically deploy when the deadbolt is extended. 
     The present disclosure also relates to an automatic latch assembly that deploys the hook bolt upon closing a door. The automatic latch assembly may be used to increase the security of a door by automatically releasing a biased hook bolt to secure the door. In this way, a door may be more consistently secured from unauthorized persons or inclement weather. 
     In one embodiment, the hook bolt includes a deadbolt and one or more hooks (also referenced to more generally herein as engagement members) positioned at least partially inside of the deadbolt. The hook bolt may be installed in a latch assembly, mortise lock, lock cylinder, or other locking system suitable for use with a swinging or a sliding door. The one or more hooks may be constructed and arranged to move from an disengaged position when the deadbolt is in a retracted deadbolt position to an engaged position when the deadbolt is moved toward the extended deadbolt position. Accordingly, the hook bolt may also include a hook actuator configured to move the one or more hooks as the deadbolt is moved from the retracted to the extended position, thereby causing the one or more hooks to engage an associated door jamb strike plate by projecting out of one or more sides of the deadbolt. That is, the one or more engagement members of the hook bolt extend out of the deadbolt perpendicular (i.e., laterally) to the longitudinal movement direction of the deadbolt. The hook actuator may also contact the one or more hooks as the deadbolt is retracted, thereby causing the hooks to move to a disengaged position substantially inside of the deadbolt (i.e., inside of the perimeter of the deadbolt). Thus, the hooks may be substantially contained within the deadbolt when the deadbolt is retracted, and may be moved to an engaged position as the deadbolt is extended. Such an arrangement may allow a hook bolt to be used on either a sliding door or a swinging door without a significant change in locking hardware, thereby reducing cost and improving simplicity of installation. 
     In some embodiments, the one or more hooks of the hook bolt may include one or more pivots by which the hooks rotate between the engaged and disengaged positions. According to this embodiment, the hook actuator may contact the one or more hooks to cause the one or more hooks to rotate about the pivot between the disengaged and engaged positions. Additionally, the hook actuator may be passive, such that the contact with the one or more hooks occurs automatically as the deadbolt is extended or retracted to move the one or more hooks between the disengaged and engaged positions. Thus, in the disengaged position the one or more hooks may be rotated by the hook actuator such that the hooks are substantially within the deadbolt and in an engaged position the one or more hooks may be rotated by the hook actuator such that the hooks deploy laterally outside of the deadbolt. In some embodiments, the hook may include a hook bend, a hook shank, and a lower hook leg. In such an arrangement, the hook bend may rotate through an opening in an associated door in a direction perpendicular to a longitudinal movement direction of the deadbolt. That is, the hook may rotate through the opening such that the hook shank is substantially parallel with the longitudinal movement direction of the deadbolt. In this position, the hook bend may be positioned outside of the opening, and the lower hook leg may be positioned inside of the opening. Thus, the hook may span the opening, such that the door can be secured to an associated door jamb strike plate located between the hook bend and the lower hook leg. 
     According to yet another embodiment, a linkage constructed and arranged to link together the motion of two or more hooks may be employed, such that one hook actuator may cause the two or more hooks to move to the disengaged or engaged positions concurrently. Such a linkage may be a link, a gear, or any other suitable structure for linking the two or more hooks and causing them to move together toward the disengaged or engaged position. According to this embodiment, two or more hooks may be deployed to the engaged position by a single hook actuator, such that number of actuators in the hook bolt is reduced. Additionally, such an arrangement may allow the two or more hooks to engage an associated door jamb at multiple locations, such that the failure of any one hook may not compromise the security of a locked door. Accordingly, such an arrangement may provide additional security than a lock employing a single hook. 
     In yet another embodiment, a latch assembly including a hook bolt may be installed on a door to automatically engage the hook bolt with a door jamb strike plate when the door is closed. The hook bolt may automatically move to an extended position when a door is closed, thereby causing one or more hooks to deploy. The hook bolt may include a deadbolt biasing member (e.g., a spring) that urges the hook bolt to the extended (i.e., locked) position. The hook bolt may further include a catch configured to hold the hook bolt in place when the door is not closed by resisting force from the deadbolt biasing member. The hook bolt may also include a slide mechanism arranged to allow a turning motion of a deadbolt handle to extend or retract the hook bolt. The slide mechanism may also be configured to prevent the retraction of the hook bolt without a corresponding turn of the deadbolt handle, thereby increasing the security of the door. 
     In yet another embodiment, the latch assembly may include an auxiliary bolt that cooperates with the hook bolt to automatically trigger the hook bolt to move into the extended position. The auxiliary bolt may be connected to an auxiliary biasing member that urges the auxiliary bolt to an extended auxiliary position. The auxiliary bolt may further include an auxiliary bolt head with an inclined face configured to retract the auxiliary bolt when the auxiliary bolt head strikes a door frame. The auxiliary bolt may include one or more tabs located on an auxiliary arm arranged to contact a guard lever. In some embodiments, the guard lever is moveable by the auxiliary bolt and includes a sear constructed and arranged to contact a catch on the hook bolt. The guard lever may be moved between a secure position and a free position by the one or more tabs or auxiliary arm on the auxiliary bolt as the auxiliary bolt is correspondingly retracted or extended. In the free position, the sear may contact and engage the catch on the hook bolt to resist urging force from the deadbolt biasing member and thereby prevent the hook bolt from being extended. In the secure position, the guard lever may be moved to a position where the sear is released from the catch, thereby releasing the hook bolt and allowing the hook bolt to automatically extend from the urging force received from the deadbolt biasing member. According to the present embodiment, the auxiliary bolt may prevent the hook bolt from moving to the extended position when the auxiliary bolt is in an extended position. When the auxiliary bolt is retracted the one or more tabs may force the guard lever to the secure position to release the sear from the catch which allows the hook bolt to extend. Such an arrangement may prevent an extension of the hook bolt that may otherwise cause jams or prevent damage to a door frame by releasing the hook bolt only when auxiliary bolt strikes a door frame and is sufficiently retracted. 
     In yet another embodiment, the latch assembly may include a lock switch configured to lock the operation of an attached door handle. For example, the latch assembly may include a lock switch constructed and arranged to selectively move a lock switch arm into a locked switch position or an unlocked switch position. In the locked switch position, the lock switch arm may engage a notch or other suitable structure on a door lever hub arranged to receive and mount a door handle, thereby preventing the rotation of the door handle and lever hub. In the unlocked switch position, the lock switch arm may move away from the notch or other suitable structure to allow free rotation of the door handle and lever hub. In some embodiments, the lock switch may prevent rotation of the lever hub and door handle only from one side (e.g., exterior side of the door). Such an arrangement may be beneficial to increase the security of the door by preventing manipulation of the door handle from outside of the secured space. In some cases, it may be beneficial to bypass the lock switch if a user has the appropriate credentials (e.g., a key). Accordingly, the lock switch may be moved to the unlocked switch position or otherwise move from engaging the lever hub to permit the rotation thereof by the hook bolt. Such an arrangement may allow a user with appropriate credentials (e.g., a key) to move the lock switch to the unlocked switch position from the exterior side of the door, thereby allowing the user to turn the door handle from said exterior side to open the door. 
     Now turning to the figures,  FIG. 1  depicts a hook bolt  120  which in this example is installed in a latch assembly  100  embodied here as a mortise lock for a door. The latch assembly  100  includes a chassis or housing  102  having front plate  104 , rear plate  106 , top plate  108 , bottom plate  110 , and side plates  112  (one side plate is omitted from  FIG. 1  to expose internal components of the latch assembly  100 ). The hook bolt  120  includes a deadbolt  150  and a hook  300 . The hook  300  includes a lower hook leg  301 , a hook bend  311 , and a hook shank  312 . As shown in  FIG. 1 , the deadbolt  150  is in a retracted deadbolt position and the hook  300  is in a disengaged position. In this position, the hook is located partially within the deadbolt. That is, the hook bend  311  and hook shank  312  are positioned within the deadbolt  150 , while lower hook leg  301  is located partially within the deadbolt, projecting out of the bottom of the deadbolt. As would be appreciated by one of skill in the art, the phrase “within the deadbolt” means within the external projected perimeter of the deadbolt. In this position, the hook is substantially contained within the deadbolt, such that the hook takes up little additional space inside the latch assembly not already occupied by the deadbolt. Thus, the hook bolt may be employed in a wide variety of doors and latch assemblies with deadbolt of a standard size, without requiring significant redesign or reconstruction. Of course, any suitable arrangement of the hook may be employed such that the hook is positioned at least partially within the deadbolt. 
     In the embodiment shown in  FIG. 1 , the hook  300  includes a pivot  306 , a lower hook leg  301  and a hook bend  311 . The pivot  306  is constructed and arranged to allow the hook to rotate (i.e., pivot) about the axis of the pivot. In some embodiments, the pivot may be a pin attached to the deadbolt  150  through a hole in the hook. However, any suitable structure may be employed, such that the pivot  306  allows the hook  300  to rotate about the axis of the pivot  306 . The hook bolt  120  also includes a hook actuator  302 , constructed and arranged as a passive hook actuator block with a contact area  304  constructed and arranged as a recess. Of course, the hook bolt actuator may be any suitable actuator that moves the hook between an engaged and disengaged position, including but not limited to an active actuator like a servo, motor, magnet, hydraulic actuator, or any other suitable actuator. In the depicted embodiment, contact area  304  contacts the lower hook leg  301  as it falls into the contact area when the deadbolt is moved between a retracted and extended deadbolt position. Of course, any suitable contact area may be employed such that the contact area contacts the hook as the hook bolt is moved from a retracted position to an extended position as the present disclosure is not so limited. When deadbolt  150  is moved to an extended position, the lower hook leg  301  moves into the contact area  304 , which provides a reaction force against the lower hook leg such that a torque is generated to rotate the hook  300  around pivot  306 . In the present embodiment, the lower hook leg  301  also falls into the contact area  304 , such that gravity provides a rotational force to pivot the hook  300  about pivot  306  to the engaged position. Of course, any suitable arrangement may be employed to rotate the hook toward the engaged position as the present disclosure is not so limited. As the hook is rotated around pivot  306 , hook bend  311  is lowered out of the bottom of the deadbolt to the engaged position (for example, see  FIG. 2 ). 
     According to the present embodiment, a door jamb strike  400  of an associated door includes an opening sized to receive the deadbolt  150  and the hook  300 . As discussed above, the hook  300  includes pivot  306 , hook bend  311 , hook shank  312 , and a lower hook leg  301 . In the engaged position, the hook shank  312  spans the opening of the door jamb strike plate, with the hook bend  311  preventing sliding or swinging movement of the door by contacting an interior side of the door jamb strike plate. Thus, the hook will prevent a sliding door from being opened, or afford additional security for a swinging door by increasing the size of one or more contact regions. In some embodiments, when the hook bolt is in the extended hook bolt position, the hook  300  is prevented from rotating about the pivot  306  by lower hook leg  301  and contact area  304  without a corresponding retraction of the deadbolt. In this embodiment, the lower hook leg  301  contacts the contact area  304  which provides a reaction force opposing any externally applied forces that may rotate the hook to a disengaged position, and thus the hook is prevented from rotating toward the disengaged position while the hook bolt is in the extended hook bolt position. When deadbolt  150  is retracted, lower hook leg  301  contacts contact area  304  which provides a reaction force to rotate the hook  300  up about pivot  306  to move the hook to the disengaged position wherein the hook is substantially contained within the deadbolt  150 . In certain embodiments, the hook  300  and hook actuator  302  may be arranged near the top of the deadbolt, such that the hook projects substantially outside of a top side of the deadbolt  150 , as the present disclosure is not so limited. 
     AS noted above, the latch assembly  100  depicted in  FIG. 1  includes a chassis  102  or housing having a front plate  104 , rear plate  106 , top plate  108 , and side plates  112  (one of which is omitted from  FIG. 1  to expose the internals of the latch assembly). Front plate  104  may have holes  114  through which screws or bolts may be used for securing or fastening the latch assembly  100  to a door. For example, there may be two holes, one at a top of front plate  104  and another at a bottom of front plate  104 , or there may be more or fewer holes. Other suitable devices for securing or fastening the latch assembly  100  to a door may also be used as the disclosure is not limited in this respect. Front plate  104  further includes openings for one or more of hook bolt  120 , latch bolt  122 , auxiliary bolt  124 , and lock switch  126 . Chassis  102  may be secured together by screws  116  passing through side plates  112 . For example, four screws, one at each corner of side plates  112 , may be used, or more or fewer screws or other fastening devices or methods in other suitable arrangements. Chassis  102  may be formed out of one or more pieces. For example, in some embodiments, rear plate  106 , top plate  108 , bottom plate  110 , and one of side plates  112  may be formed as a single integral piece of material (e.g., metal, plastic, or some other material or combination of materials) that is secured or fastened to front plate  104  or the opposing one of side plates  112  or both by, e.g., screws, bolts, rivets, snap or press fit, welding, or some other fastening device or method or combination of fastening devices or methods. In some embodiments, chassis  102  may include one or more slots in either or both of side plates  112  to facilitate moving or sliding pieces inside of the latch assembly. Chassis  102  may also include a hole or space  118  to receive a lock mechanism, such as a key-operated cylinder lock, an electromechanical lock, etc. 
     As shown in  FIG. 1 , hook bolt  120  also includes a deadbolt arm  156  and a deadbolt backstop  157 . Deadbolt  150  protrudes from chassis  102  and front plate  104  when the deadbolt is in an extended position and is within or substantially within a profile of the chassis  102  when the deadbolt is in a retracted position. In the depicted embodiment, deadbolt  150  is hollow, although the deadbolt may be solid with a recess formed therein to accommodate the hook. Of course, any other suitable arrangement for the deadbolt may be employed such that one or more hooks are accommodated by the deadbolt as the present disclosure is not so limited. Hook bolt  120  also includes a slide mechanism  152  extending from the deadbolt  150  and including one or more slots. Slide mechanism  152  includes one or more slots and lower deadbolt leg  154 . Deadbolt arm  156  is rotatably mounted in the chassis and has a protrusion that extends (into the page) into the cam slot of slide mechanism  152 . The deadbolt arm also includes a thumb turn  158  having a slot  163  about which the deadbolt arm  156  rotates. When thumb turn  158  is turned, for example by a user operating a knob or key engaging the thumb turn slot, the protrusion of deadbolt arm  156  contacts an edge cam slot in the slide mechanism  152  in a camming fashion and causes the hook bolt  120  to move relative to the chassis  102  between a retracted position and an extended position (see  FIG. 2 ). In one embodiment, the cam slot in the slide mechanism  152  is angled at a lower slot  203  thereof such that, when the hook bolt  120  is in the extended position (as shown in  FIG. 2 ), the hook bolt  120  is prevented from moving relative to the chassis  102  as the deadbolt arm  156  is aligned with the deadbolt  150  and a retracting force on the deadbolt will simply cause the lower slot  203  of the slot  201  to bear against the protrusion of the deadbolt arm  156  without rotating the deadbolt arm. The deadbolt backstop  157  includes a lower deadbolt lever arm  153  and is rotatably mounted in the chassis and connected to the deadbolt arm by a pin  155 , such that rotation of the deadbolt backstop and the deadbolt arm are linked. That is, rotation of the deadbolt backstop will rotate the deadbolt arm, and rotation of the deadbolt arm will rotated the deadbolt backstop. 
     The latch assembly  100  of  FIG. 1  also includes a lever hub  130  arranged to couple to a door handle via hole  194 . The lever hub includes a lever hub arm  132  and a lever spring  134  arranged to bias the lever hub to an upright position, as shown in  FIG. 1 . The lever hub arm  132  contacts an end  196  of an optional latch bolt (not shown in the figure). The end  196  is arranged to contact the lower deadbolt lever arm  153  of deadbolt backstop  157  when the lever hub is actuated by the associated door handle, thereby causing the hook bolt  120  to move toward the retracted position. Accordingly, the associated door handle may be able to actuate the hook bolt  120  and any optional latch bolt (not shown in the figure) to open a door with a single motion, thereby affording additional simplicity to the use of the latch assembly  100 . The lever hub  130  may also include a notch  198  arranged to receive a lock switch arm  192  which is connected to a lock switch rocker  190 . The lock switch arm  192  may be moved between a locked switch position and an unlocked switch position by the lock switch rocker  190 , such that in the locked switch position the lock switch arm  192  contacts notch  198  to prevent rotation or actuation of lever hub  130 . Accordingly, the lock switch rocker  190  may be used to prevent an associated door handle from being actuated on at least one side of a door. For example, the lock rocker switch  190  may be used to prevent the door handle from being actuated from an exterior (i.e., unsecured) side of a door, thereby improving security while still allowing a user on the interior (i.e., secured) side of a door to actuate the handle to unlock and open the door. As shown in the depicted embodiment, the lock switch includes an auxiliary actuator  191  arranged here as an electronic motor. The auxiliary actuator may cooperate with an authentication system, door management system, or other access control system to selectively move the lock switch arm  192  between the locked and unlocked positions. While an electronic motor is employed in the depicted embodiment, any suitable actuator may be used, such as a servo, linear actuator, electromagnet, hydraulic piston, etc. as the present disclosure is not so limited. 
       FIG. 2  depicts the hook bolt in the latch assembly of  FIG. 1  with the deadbolt  150  in an extended deadbolt position and the hook  300  in an engaged position. As shown in the figure, the deadbolt  150  is fully extended with deadbolt arm  156  in a lower cam slot of sliding mechanism  152 . Lower hook leg  301  is contacting hook actuator  302  at the contact area  304 , such that the hook  300  is rotated down about pivot  306  and is projecting substantially outside of the deadbolt  150 . As discussed above, door jamb strike  400  of an associated door includes an opening sized to receive the deadbolt  150  and the hook  300  as the hook rotates around and through the opening to the engaged position such that the hook shank  312  spans the opening. Thus, in the engaged position, the hook  300  prevents an associated sliding door from retracting (i.e., sliding open) by contacting an interior side of the door jamb strike plate  400 . In the depicted embodiment, the hook  300  is prevented from rotating about the pivot  306  by lower hook leg  301  and contact area  304  without a corresponding retraction of the deadbolt. The lower hook leg  301  contacts contact area  304  which provides a reaction force opposite to any externally applied forces that may rotate the hook to a disengaged position, and thus the hook is prevented from rotating back to the retracted position while the hook bolt is in the extended hook bolt position. Accordingly, the hook bolt can only be retracted by a corresponding rotation of the deadbolt arm  156 . Without wishing to be bound by theory, in the engaged position, the hook  300  also may afford additional security to a swinging door by increasing the size of one or more lateral contact regions which prevents the door from opening in a lateral (i.e., swinging) direction. 
     As shown in the depicted embodiment, when the hook bolt is in the extended position, the deadbolt backstop  157  contacts end  196  of an optional latch bolt. The lever hub  130  contacts end  196  via lever hub arm  132 , such that when a door handle attached through hole  194  is actuated the lever hub  130  rotates and causes deadbolt backstop to rotate deadbolt arm  156  through pin  155 . Accordingly, the deadbolt arm  156  moves up cam slot  200  to retract the deadbolt  150 . As the deadbolt  150  is retracted, lower hook leg  301  contacts contact area  304  which provides a reaction force (i.e. pushing or camming force) to rotate the hook  300  up about pivot  306  into the deadbolt. As shown in the figure, the contact area  304  is constructed and arranged as a recess with a ramp. The ramp allows the lower hook leg  301  to smoothly transition between the engaged and disengaged positions. Thus, the hook bolt  120  moves back to the retracted hook bolt position as shown in  FIG. 1 . Of course, any suitable contact area may be employed such that a reaction force provided by the contact area may reliably move the hook between the engaged and disengaged positions. 
       FIG. 3  shows another embodiment of a hook bolt  120  disposed within a latch assembly  100  embodied here as a mortise lock. In this embodiment, the hook bolt includes two hooks  300   a,    300   b  located at least partially within deadbolt  150 , with lowermost hook  300   a  including a lower hook leg  301 . The hook bolt  120  includes a linkage  308  joined to a linkage pin  307  located in a linkage slot  309 . The linkage  308  may rotate about linkage pin  307 . The linkage  308  links the motion of the hooks  300   a,    300   b,  such that the hooks  300   a,    300   b  are moved to the disengaged position or engaged position concurrently. Specifically, in the engaged position as shown in the figure, hook actuator  302  contacts lower hook leg  301  at contact area  304 . The contact area  304  provides a reaction force that creates a torque on a lowermost hook  300   a  to rotate about pivot  306  toward the engaged position. As lowermost hook  300   a  is rotated about pivot  306 , the linkage  308  attached to linkage pin  307  is forced to move in the direction of hook bolt extension along the linkage slot  309 , thereby causing uppermost hook  300   b  to rotate up into an engaged position along with lowermost hook  300   a.  Such a hook arrangement provides multiple regions of contact for the hook bolt  120 , thereby increasing security of the hook bolt mechanism. For example, if one hook was damaged (e.g., by an attempted break in), the other hook would still be able to secure the door. As shown in the depicted embodiment, the hooks  300   a,    300   b  engage an interior side of an associated door jamb strike  400 , which prevents a corresponding sliding door from retracting (i.e., being slid open), or otherwise increases security of a corresponding swinging door. 
     Similarly to the embodiment depicted in  FIGS. 1-2 , the hook bolt  120  depicted in  FIG. 3  is moved between an extended and retracted position by the deadbolt arm  156 . Deadbolt arm  156  contacts sliding mechanism  152  at a cam slot, which allows the rotation of deadbolt arm  156  to move the hook bolt  120  between an extended and retracted position. When the deadbolt arm  156  is in a lower position as shown in the figure, a lower portion of the cam slot of sliding mechanism  152  prevents the hook bolt from moving toward the retracted position. Thus, the hook bolt may be retracted by thumb turn  158  which is coupled to lock cylinder  117  to allow a user to move the deadbolt arm  156  by using a key or other credential. Such an arrangement may prevent the deadbolt from being retracted from an external force on an end of the deadbolt in an attempt to defeat the hook bolt, thereby increasing security of the hook bolt. While in the depicted embodiment a lock cylinder is used, any suitable structure may be employed, including but not limited to a deadbolt handle, electromechanical lock, etc. as the present disclosure is not so limited. 
       FIG. 4  shows the hook bolt  120  of  FIG. 3  in the retracted hook bolt position. As shown in the figure and explained above, the hooks  300   a,    300   b  include a lower hook leg  301  and linkage  308  with a pin  307  in a linkage slot  309 . The linkage  308  links the motion of the lowermost hook  300   a  and uppermost hook  300   b.  As the hook bolt is retracted the hooks  300   a,    300   b  contact front plate  104 , such that the front plate provides a reaction force that causes the hooks to rotate toward a disengaged position. As the hooks rotate toward the disengaged position, the linkage  308  moves relative to the deadbolt  150  in the direction of retraction, such that the hooks can move (i.e., rotate) to be substantially contained by the deadbolt. As shown in the figure, the hook bolt includes a hook actuator  302  including a contact area  304 . In the disengaged position, the lower hook leg  301  protrudes from the deadbolt  150 , such that when the hook bolt is moved toward the extended position the lower hook leg contacts the contact area  304  to move the hooks to the engaged position as described above. As the lower hook leg contacts the contact area and rotates lowermost hook  300   a,  the linkage transmits that motion to uppermost hook  300   b  though pin  307  as the linkage is moved along linkage slot  309  relative to the deadbolt in the extending direction. Thus, the contact of lower hook leg  301  is sufficient to deploy both hooks concurrently with an extending motion of the hook bolt. 
       FIG. 5  shows yet another embodiment of a hook bolt  120  disposed in a latch assembly  100  embodied as a mortise lock. In this embodiment, the hook bolt includes two hooks in an opposing vertical arrangement similar to that of  FIG. 3  as well as a hook actuator  302  with a contact area  304 . Lowermost hook  300   a  and uppermost hook  300   b  each have a pivot  306 , about which each hook  300   a,    300   b  pivots between an engaged and disengaged position. Additionally, lowermost hook  300   a  includes a lower hook leg  301 . In this embodiment, the lowermost hook  300   a  and uppermost hook  300   b  are formed with gear teeth  310  linking the two hooks together. The gear teeth may be formed into the hook, such that the hooks with gears may be created as a single piece, or the gear teeth may be added to the hook separately. Accordingly, the rotational movement of the hooks  300   a,    300   b  is linked, such that the lowermost hook  300   a  and uppermost hook  300   b  move concurrently between the engaged and disengaged positions. As shown in the figure, lower hook leg  301  contacts hook actuator  302  at contact area  304 , thereby forcing lowermost hook  300   a  to rotate around pivot  306  and down to project substantially outside of a bottom side of the deadbolt  150 . The gears  310  transfer the rotation of the lowermost hook  300   a  to rotation of the uppermost hook  300   b,  thereby causing the uppermost hook to rotate around pivot  306  and up to project substantially outside a top side of the deadbolt  150 . Thus, the hooks are moved to project laterally from the deadbolt. Such an arrangement may provide more consistent transfer of motion with reduced complexity by reducing the number of separate components in the hook bolt. The gear teeth  310  may be any suitable gear teeth arrangement to transfer the rotational motion of one hook to the other, including but not limited to cycloid or involute gear teeth. 
       FIG. 6  shows the hook bolt of  FIG. 5  in the retracted hook position. As shown in the figure and explained above, the hooks  300   a,    300   b  include a lower hook leg  301  and gear teeth  310 . The gear teeth  310  link the motion of the lowermost hook  300   a  and uppermost hook  300   b.  As the hook bolt is retracted the hooks  300   a,    300   b  contact front plate  104 , such that the front plate provides a reaction force that causes the hooks to rotate toward a disengaged position. As the hooks rotate toward the disengaged position, the gear teeth  310  mesh to link the motion of the hooks as they rotate to be substantially contained by the deadbolt. As shown in the figure, the hook bolt includes a hook actuator  302  including a contact area  304 . In the disengaged position, the lower hook leg  301  protrudes from the deadbolt  150 , such that when the hook bolt is moved toward the extended position the lower hook leg contacts the contact area  304  to move the hooks to the engaged position as described above. The gear teeth  310  link the motion of the hooks  300   a,    300   b,  such that the contact of lower hook leg  301  is sufficient to deploy both hooks simultaneously with an extending motion of the hook bolt. 
       FIG. 7  depicts latch assembly  100  having automatic deployment of the hook bolt. Hook bolt  120  includes hooks  300   a,    300   b,  deadbolt  150 , a deadbolt arm  156 , and a deadbolt backstop  157 . Hooks  300   a  and  300   b  are not completely shown in  FIG. 7  because they are at least partially contained within the deadbolt. Deadbolt  150  protrudes from chassis  102  and front plate  104  when hook bolt  120  is in the extended hook bolt position and is within or substantially within a profile of the chassis  102  when hook bolt  120  is in the retracted hook bolt position. When the hook bolt is in the extended hook bolt position, the hooks  300   a,    300   b  are in an engaged position, projecting out of the deadbolt. Hook bolt  120  also includes a slide mechanism  152  extending from the deadbolt  150  and including one or more slots. Slide mechanism  152  includes one or more slots (e.g., cam slot  201  shown in  FIGS. 8A-8C ) and lower deadbolt leg  154 . Hook bolt  120  also includes deadbolt arm  156  rotatably mounted within the chassis  102 . Deadbolt arm  156  has a protrusion that extends (into the page) into the cam slot  201  of slide mechanism  152  and a thumb turn  158  having a slot  163  about which the deadbolt arm  156  rotates. When thumb turn  158  is turned, for example by a user operating a knob or key engaging the thumb turn slot, the protrusion of deadbolt arm  156  contacts an edge cam slot  201  in the slide mechanism  152  in a camming fashion and causes the hook bolt  120  to move relative to the chassis  102  between a retracted hook bolt position and an extended hook bolt position (see  FIGS. 8A-8C ). In one embodiment, the cam slot  201  in the slide mechanism  152  is angled at a lower slot  203  thereof such that, when the hook bolt  120  is in the extended position (as shown in  FIG. 8A ), the hook bolt  120  is prevented from moving relative to the chassis  102  as the deadbolt arm  156  is aligned with the deadbolt  150  and a retracting force on the deadbolt will simply cause the lower slot  203  of the slot  201  to bear against the protrusion of the deadbolt arm  156  without rotating the deadbolt arm. 
     According to the present embodiment, the deadbolt  150  partially contains a lowermost hook  300   a  and an uppermost hook  300   b  which move from a disengaged position to an engaged position as the deadbolt  150  is extended. In this embodiment, the hooks  300   a,    300   b  are linked together, such that they move concurrently between the disengaged and engaged positions. Of course, any suitable arrangement of the hooks may be employed such that the hooks are automatically deployed as the hook bolt moves from a retract hook bolt position to an extended hook bolt position. In the depicted embodiment, the lowermost hook  300   a  includes a lower hook leg (see  FIGS. 8B-8C ) constructed and arrange to rotate the hooks  300   a,    300   b  between the engaged and disengaged positions, as discussed above. In this embodiment, as the hook bolt is moved toward the extended position, the lower hook leg contacts front plate  104  which provides a reaction force that causes the hooks  300   a,    300   b  to rotate and project out of the deadbolt. Similarly, as the hook bolt is moved toward the retracted position, the hooks  300   a,    300   b  contact the front plate  104  which provides a reaction force that causes the hooks  300   a,    300   b  to rotate toward the disengaged position, where the hooks are substantially contained by the deadbolt  150 . In some other embodiments, as explained above, the depicted hook bolt  120  may include a hook actuator with a contact area arranged to contact a lower hook leg to move one or more hooks between the disengaged and engaged positions. As shown in the figure, the hooks  300   a,    300   b  project substantially out of the deadbolt  150  when in the engaged position, and are positioned substantially inside of the deadbolt  150  when the hooks are in the disengaged position. 
     Lower deadbolt leg  154  may include one or more catches  160  (e.g. serrations, ratchets, teeth, cutouts) formed on a lower edge thereof. In some embodiments, the one or more catches  160  may be arranged to engage a portion of a sear or other suitable projection on an engagement side of the catch, thereby preventing the deadbolt  150  from extending. In some embodiments, the sear may be constructed and arranged to flex out of the way of the lower deadbolt leg  154  when the hook bolt  120  moves toward the retracted hook bolt position. In other embodiments, the sear is constructed rigidly so that the sear remains stationary relative to the guard lever as the hook bolt  120  moves toward the retracted hook bolt position, as the present disclosure is not so limited. The one or more catches  160  may be arranged to allow the sear or other suitable projection to slide past when the deadbolt  150  is retracted. In one such arrangement, the one or more catches  160  may be configured to allow the deadbolt  150  to retract unimpeded regardless of the position of the sear or other suitable projection, but may prevent the deadbolt  150  from extending without a corresponding action to move and release the sear. 
     Deadbolt arm  156  is coupled to a deadbolt backstop  157  by a peg  155  on deadbolt arm  156  which is inserted through an opening or hole in backstop  157 . Backstop  157  is configured to pivot about the screw  116  in the upper, right-hand side of the chassis  102 . A deadbolt biasing member  159  is coupled to deadbolt backstop  157  (e.g., by being connected to the peg  155 ). The deadbolt biasing member  159  is configured as an extension spring biased such that it tends to pull backstop  157 , which results in arm  156  engaging the slide mechanism  152  and ultimately causes hook bolt  120  to move the deadbolt  150  relative to the chassis  102  between a retracted hook bolt position and an extended hook bolt position. While in the present embodiment an extension spring is depicted, any suitable biasing member may be employed, including but not limited to a compression spring or torsion spring. In the arrangement shown, the deadbolt biasing member  159  is prevented from causing the hook bolt toward an extended hook bolt position by a sear  181  engaged in a catch  160  on lower deadbolt leg  154 , which prevents the deadbolt  150  from moving relative to the chassis between a retracted hook bolt position and an extended hook bolt position. This is described further below. 
     As shown in the present embodiment, the latch assembly  100  may further include a latch bolt  122  constructed and arranged to be operable by a door handle. In some embodiments, the hook bolt may be configured to be actuated by the door handle coupled to the latch bolt, such that the door can be operated traditionally by a single handle. According to this embodiment, the automatic hook bolt would increase door security while avoiding any additional steps for operation. Latch bolt  122  includes latch bolt head  162  and latch bolt cylinder  164 . Latch bolt head  162  includes an inclined surface configured to impact a door jamb, thereby forcing the latch bolt to move toward a retracted latch bolt position. The latch bolt head also protrudes from chassis  102  and front plate  104  when latch bolt  122  is in an extended latch bolt position and is within or substantially within a profile of the chassis  102  when latch bolt  122  is in the retracted latch bolt position. A latch biasing member  166  is surrounds a rod extending from the cylinder  164  and urges the latch bolt  122  to remain in the extended latch position. 
     A guard lever  180  includes a guard lever lower leg  182  and a guard lever arm  184 . In some embodiments, guard lever  180  is supported in chassis  102  by an end of lever arm  184  being attached to rear plate  106 . Guard lever  180  pivots relative to chassis  102  about the end of the guard lever supported in the rear plate  106 , between an upper or free position (see  FIG. 10A ) and a lower or secure position (see  FIG. 10B ). In some embodiments, the pivoting movement is controlled and limited by an extension of the guard lever near stopping end  186  extending laterally into a slot  188  formed in one or both of side plates  112 . When guard lever  180  is in its secure position, stopping end  186  of guard lever arm  184  acts to prevent latch bolt  122  from moving to its retracted position by contacting the latch bolt cylinder  164  and thereby blocking further retraction of the latch bolt  122  (see  FIG. 10B ). 
     In some embodiments, the guard lever arm  184  may include a guard biasing member (not shown in the figure) that urges the guard lever arm  184  toward either the secure or the free position. In one such arrangement, the guard lever arm  184  may include a spring that biases the guard member toward the secure position. In this embodiment, the first tab may prevent the downward movement of the guard lever arm  184  (i.e., toward the secure position) by engaging the guard lever  180  and forcing the guard lever arm  184  up (i.e., toward the free position). Accordingly, when the auxiliary bolt  124  retracts and the first tab  176  disengages with the guard lever arm  180 , the guard lever arm  184  may be urged by the guard biasing member to the secure position, thereby releasing the sear  181  and allowing hook bolt  120  to extend. In another embodiment, the guard lever arm  184  may be urged upwards by the guard biasing member toward the free position, and the auxiliary arm  172  may be constructed and arranged to engage the guard lever lower leg  182  and move the guard leg down (i.e., toward the secure position) when the auxiliary bolt is retracted. While some embodiments of the latch assembly  100  include a guard biasing member, it can be appreciated that any suitable arrangement whereby the guard lever may be moved between a free and a secure position may be employed. 
     As shown in  FIG. 7 , the sear  181  projects upwardly from the guard lever  180  and is configured to engage one of the catches  160  on lower deadbolt leg  154  when guard lever  180  is in its free position to prevent the deadbolt  150  from moving to the extended deadbolt position. Because of the angle of the catches  160 , the sear  181  does not prevent the hook bolt  120  from moving from the extended hook bolt position to the retracted hook bolt position. As shown in  FIG. 7 , the sear may be flexible, such that it can flex over the catches to allow easier retraction of the deadbolt  150  while still preventing the extension of the deadbolt  150  when the guard lever is in the free position. In some other embodiments, the sear may be constructed and arranged as a rigid tab extending from the guard lever arm  184 . When guard lever  180  moves to its secure position (see  FIG. 10B ), sear  181  becomes disengaged from the catch  160 , which allows hook bolt  120  to move to its extended hook bolt position. That is, the disengagement of sear  181  from the catches  160  on lower deadbolt leg  154 , allows deadbolt biasing member  159  to move deadbolt backstop  157  and deadbolt arm  156 , causing the protrusion on deadbolt arm  156  engaged with the slide mechanism  152  to move deadbolt  150  to its extended position. 
     Auxiliary bolt  124  includes tongue  170  and auxiliary arm  172 . Auxiliary bolt tongue  170  protrudes from chassis  102  and front plate  104  when auxiliary bolt  124  is in the extended auxiliary position and is within or substantially within a profile of the chassis  102  when auxiliary bolt  124  is in the retracted auxiliary position. Auxiliary bolt spring  174  is coupled with arm  172  and urges the auxiliary bolt  124  to remain in the extended auxiliary position. Auxiliary bolt arm  172  includes a first tab  176  and a second tab  178 . As shown in  FIGS. 7 and 10A , when auxiliary bolt  124  is in the extended position, the first tab  176  acts to prop up guard lever  180  by engaging its lower leg  182  to maintain guard lever  180  in its free position (allowing latch bolt  122  to move freely between its extended and retracted positions). As shown in  FIG. 10B , when auxiliary bolt  124  is retracted, the first tab  176  is disengaged from lower leg  182  and the auxiliary arm  172  and/or second tab  178  engage lower leg  182 , thereby moving the guard lever  180  to its secure position blocking latch bolt  122  from moving to its retracted position. In some embodiments, when latch bolt  122  is moved to its retracted position, latch bolt cylinder  164  makes contact with the second tab  178  of auxiliary bolt arm  172 , causing auxiliary bolt  124  to also move to its retracted position. 
     As shown in  FIG. 7 , the latch assembly  100  may include a lever hub  130  with two aligned latch arms  132  coupled to the latch bolt  122 , a lever spring  134 , and two aligned holes  194 . For example, a square shaft of a door handle may be inserted into each of the holes  194 , such as an inside door handle and an outside door handle in each respective hole  194 . The latch arms  132  are configured to move independently as the lever hub  130  rotates about an axis defined by the center of holes  194  between an open and a closed position, with lever spring  134  biasing them to their closed position as shown in  FIG. 7 . When the door handle inserted into the hold  194  rotates it will cause the corresponding latch arm  132  to move to its open position, engaging a contact at an end  196  of the rod extending from the latch bolt cylinder  164 , thereby causing latch bolt  122  to move to its retracted position. 
     In some embodiments, the hook bolt  120  is coupled to the latch bolt  122  and the lever hub  130  so that if hook bolt  120  is in its extended hook bolt position, moving a latch arm  132  to its open position will additionally cause hook bolt  120  to move to its retracted position. In particular, a lower extending leg  153  of the deadbolt backstop  157  contacts the latch bolt end  196  located at the end of the rod extending from the latch bolt cylinder  164  when the hook bolt  120  is in the extended position (see  FIG. 9A ). When a latch arm  132  is rotated (e.g., via a door handle coupled to the opening  194 ), the contact  196  is moved, which contacts the lower leg  153  and pivots the deadbolt backstop  157 , which rotates the deadbolt arm  156  so as to retract the deadbolt  150 . 
     As shown in  FIG. 7 , the latch assembly  100  may include a lock switch mechanism  126  which further includes a switch (e.g., a rocker switch)  190  and a lock switch arm  192 . Lock switch  126  has a locked switch position and an unlocked switch position. In some embodiments, lever hub  130  includes a notch  198  that is engaged by lock switch arm  192  when lock switch  126  is in its locked position, as shown in  FIGS. 7 and 11B . In these embodiments, at least one of the one or more levers  132  will be prevented from moving. For example, none of the door handles attached to hole  194  will be able to open the door, or in some embodiments, only the exterior door handle will be prevented from opening the door while the interior door handle remains unaffected. According to these embodiments, when lock switch  126  moves to its unlocked switch position, lock switch arm  192  disengages from notch  198  (see  FIGS. 9B-9D ), thereby allowing the latch arms  132  to move. In some embodiments, the latch bolt mechanism  120  is coupled to the lock switch mechanism  126  so that when deadbolt  156  is moved to its extended position, lock switch  126  and lock switch rocker  190  are placed in their respective locked positions. 
       FIGS. 8A-8C  further illustrate operation of the hook bolt  120  to move the deadbolt  150  relative to the chassis between an extended and a retracted deadbolt position and to move the hooks  300   a,    300   b  between disengaged and engaged positions. In  FIG. 8A , the deadbolt  150  is fully extended and deadbolt arm  156  is rotated to an aligned orientation with respect to the deadbolt  150  and engaged with the lower slot  203  of the sliding mechanism  152 . As shown in the figure, the hooks  300   a,    300   b  are in the engaged position, projecting laterally out of the deadbolt. In  FIG. 8B , the deadbolt  150  is in a midway position between fully extended and fully retracted positions as the deadbolt arm is rotated to engage the obliquely-angled portion of the cam slot  201 . In this position, the hooks have contacted front plate  104  and have rotated to the disengaged position, with lower hook leg  301  projecting out of deadbolt  150 . In  FIG. 8C , the deadbolt is fully retracted as the deadbolt arm has been fully rotated to engage the top end of the obliquely-angled portion of the cam slot  201 . The interaction between the slide mechanism  152  and the deadbolt arm  156  is also shown. For example, as the deadbolt moves from a retracted to an extended position, the arm  156  moves along the angled portion of the cam slot  201  in the slide mechanism  152 . As shown in  FIG. 8A , when in the deadbolt  150  is in extended position, the protrusion of arm  156  is at a position in the lower slot  203  of the cam slot  201  such that an inward force applied to deadbolt  150  will not result in the protrusion of arm  156  moving along slot  201 , thereby preventing such force from causing the deadbolt  150  to move to a retracted position 
       FIGS. 9A-9D  depict the various positions of lock switch  192  and lever hub  130  of the embodiment shown in  FIG. 7 . In  FIG. 9A , latch bolt  122  is fully extended and latch arms  132  (including inside latch arm  132   a  and outside latch arm  132   b ) are each in their respective closed positions. In  FIG. 9B , the latch bolt  122  is moved independently of the latch arms  132  against the bias of spring  166  (for example as the door is being closed and the latch bolt head  162  contacts the strike of the door frame) and is shown in a midway position between fully extended and fully retracted. Note that contact  196  and lower leg  153  remain stationary in contact with the latch arms  132 , as a head  167  at the end of the rod extending from the latch bolt cylinder  164  extends through the contact  196  as the latch bolt  122  retracts. The latch bolt cylinder  164  has made initial contact with second tab  178  of the auxiliary bolt arm  172 . In  FIG. 9C , the latch bolt  122  is fully retracted as is the auxiliary bolt  124 , again, independently of any movement of the latch arms  132 .  FIG. 9D  shows the latch bolt  122  fully retracted, as actuated by the outside lever  132   b  which is rotated to its open position (while inside lever  132   a  remains in its closed position) and contacting the end  196  of the rod extending from the latch bolt cylinder  164 , thereby causing latch bolt  122  to move to its retracted position. 
       FIGS. 10A-10B  further illustrate movement of the auxiliary bolt  124  relative to the chassis between an extended and a retracted position. In  FIG. 10A , the latch bolt  122  and the auxiliary bolt  124  are fully extended. Guard lever  180  is in its free position as first tab  176  contacts lower leg  182 . With the guard lever  180  in its free (i.e., raised) position, sear  181  engages a catch  160  on lower deadbolt leg  154 , thereby preventing extension of the deadbolt  150 . In  FIG. 10B , the auxiliary bolt  124  is fully retracted while the latch bolt  122  is still fully extended. This is the condition when the door is fully closed, the latch head  162  of the latch bolt  122  extends under the force of spring  166  into a latch pocket in the door frame but no pocket is provided in the door frame for the tongue  170  of the auxiliary bolt  124 , and thus the auxiliary bolt  124  does not extend. With latch bolt  122  extended and the auxiliary bolt  124  not extended, the guard lever  180  is in its secure position, with sear  181  disengaged from catch  160  on lower deadbolt leg  154 . With the sear  181  disengaged from the catch  160 , the deadbolt  150  is able to automatically extend by action of the deadbolt spring  159  acting on the deadbolt backstop  157 , which, in turn, due to the coupling of the deadbolt backstop  157  to the deadbolt arm  156  by the peg  155 , causes the deadbolt arm  156  to rotate and thereby extend the deadbolt  150 . Thus, when the door is closed, the deadbolt automatically extends into the locked position. 
       FIGS. 11A-11B  further illustrate movement of the lock switch mechanism  126  between its locked switch position and its unlocked switch position. In  FIG. 11A , the lock switch is in its open position, and lock switch arm  192  is disengaged from notch  198 . In  FIG. 11B , the lock switch is in its locked switch position, and lock switch arm  192  is engaged with notch  198 . As noted previously, the lock switch mechanism  126  may be coupled to the hook bolt  120  so that the switch is moved to its locked position when the deadbolt is extended. 
       FIG. 12  illustrates another embodiment of a latch assembly  100 . As shown in  FIG. 12 , the hook bolt  120  is in the extended position and the guard lever  180  is in the secure position. The relative positions of the hook bolt  120 , latch bolt  122 , and auxiliary bolt  124  as shown in  FIG. 12  may occur when a door including the latch assembly is secure, for example, when the door is closed. In this arrangement, the hook bolt  120  is in the extended position, with hooks  300   a,    300   b  in the engaged position projecting laterally outside of deadbolt  150 . Additionally, deadbolt arm  156  fully rotated such that the apex of the arm is in the lower slot  203  of slide mechanism  152  to prevent movement of the deadbolt toward the retracted position. Guard lever  180  is in a secure position caused by auxiliary bolt  124  being in a retracted position and therefore causing auxiliary bolt arm  172  to contact lower guard lever leg  182  and force the guard lever  180  down (i.e., toward the secure position). In the secure position, sear  181  (constructed and configured here as a rigid sear on a guard lever arm  184 ) is in a position away from lower deadbolt leg  154 , such that the sear  181  does not contact catch  160 . Thus, the hook bolt  120  is free to move toward an extended hook bolt position, and is urged toward the extended position by the urging member  159  through the deadbolt arm  156  and slide mechanism  152 . Latch bolt  122  is in the extended latch position, and urged toward the extended latch position by a latch biasing member  166 . 
     In the present embodiment, the guard lever lower leg  182  is configured as a hook positioned around first tab  176 . In this embodiment, the hook  182  acts to reliably move the guard lever arm  184  between the upper free position (see  FIG. 15A ) and the lower secure position (see  FIG. 15B ). As the auxiliary bolt  124  extends, the guard lever arm  184  is moved toward the free position by the hook  182  as it engages with first tab  176  of the auxiliary arm  172  to force the guard lever  180  up from the secure position to the free position. In the free position, the sear  181  engages the catch  160  to prevent the hook bolt  120  from extending. As the auxiliary bolt  124  retracts, the guard lever arm  184  is moved to the secure position by the hook  182  as it engages with first tab  176  and auxiliary arm  172  to force the guard lever  180  down from the free position to the secure position. In the secure position, the sear  181  is released from the catch  160 , thereby allowing the hook bolt  120  to extend. According to the present arrangement, the hook  182  may allow the guard lever arm  184  to be moved between the secure and free positions more reliably and consistently than an arrangement with no hook. For example, the guard lever  180  may be moved by hook  182  contacting both the first tab  176 , and auxiliary arm  172 , thereby improving reliability of the movement between the free and secure positions. Similarly, the hook  182  may cause first tab  176  to move the guard lever  180  toward the secure position as the auxiliary bolt extends, thereby preventing contact between the sear  181  and deadbolt lower leg  154  as the deadbolt is retracted and reducing the chance of a jam. While in the present embodiment the guard lever  180  is constructed and configured as a hook, and suitable shape may be employed that allows the guard lever  180  to be reliably moved between the free and secure positions by the auxiliary arm  172  and/or one or more tabs. 
     As described previously and in the present embodiment, the lower slot  203  in combination with the deadbolt arm  156  prevents the deadbolt  150  from being moved toward the retracted position without actuation from a handle or locking device that would rotate the deadbolt arm  156  out of lower slot  203 . In some embodiments, a handle may be installed in hole  136  that actuates latch bolt  122  and specifically latch bolt end  196 . Latch bolt end  196  contacts deadbolt backstop  157  when the hook bolt  120  is in the extended position. When the handle or locking device is actuated, the latch bolt end  196  may be moved to rotated deadbolt backstop  157  via lower leg  153 , thereby rotating deadbolt arm  156  via pin  155  to retract hook bolt  120 . According to this embodiment, the handle or locking device may retract the latch bolt  122  and hook bolt  120  simultaneously. Such an arrangement may be beneficial in order to simply operation of the latch assembly  100  from an interior side of a door, while still providing the enhanced security from the automatic deadbolt extension and deadlocking when the door is closed. 
     In the embodiment shown in  FIG. 12 , the hook bolt  120  includes a deadbolt biasing member  159  configured as a torsion spring located on a deadbolt arm  156 . Such an arrangement may be beneficial to reduce the occupied space of a chassis  102  of the latch assembly  100 , thereby freeing space for other possible components. According to the present embodiment, the latch assembly  100  includes a lock adjustment device  119 . The lock cylinder adjustment device  119  is constructed and configured to secure a lock mechanism, such as a key-operated cylinder lock, an electromechanical lock, or other suitable locking device in space  118 . In some embodiments, the lock adjustment device is accessible from front plate  104  of the chassis  102 . In such an arrangement, the lock adjustment device cannot be manipulated when the door is closed. 
     In the embodiment depicted in  FIG. 12 , the latch assembly  100  includes an auxiliary bolt guide  175 . Auxiliary bolt guide  175  transmits force from the auxiliary biasing member (not shown in the figure) to urge auxiliary bolt  124  toward the extended position. In some embodiments, auxiliary biasing member is configured as a compression spring located around the auxiliary guide  175 . The auxiliary biasing member is constructed and arranged to contact the auxiliary bolt guide  175  and auxiliary bolt arm  172 . Thus, a compressive force is created between the auxiliary bolt guide  175  and the auxiliary arm  172  which urges the auxiliary bolt  124  toward an extended auxiliary position. The auxiliary bolt guide  175  may also guide the auxiliary bolt between its extended and retracted positions by sufficiently contacting the auxiliary bolt arm  172  to prevent movement not toward its extended or retracted positions (e.g., lateral movement). According to the present embodiment, the auxiliary bolt guide  175  may be fixed to the chassis  102 , such that the auxiliary biasing member can urge the auxiliary bolt toward the extended position by contacting the auxiliary bolt guide  175  and auxiliary bolt leg  172 . 
     As depicted in  FIG. 12 , the deadbolt  150  may also include a deadlocking tab  151 . The deadlocking tab  151  is configured to engage a latch bolt head  162  to prevent the deadbolt from extending when the latch bolt is in a retracted latch position. Similarly, the deadlocking tab  151  prevents the latch bolt from retracting when the deadbolt  150  is in an extended position. Accordingly, the deadbolt is first retracted by deadbolt arm  156  in order for the latch bolt head  162  to retract. Without wishing to be bound by theory, such an arrangement may increase security of an adjoined door by increasing the number of locking points along the door frame, thereby increasing locking strength of the latch assembly  100 . In the present embodiment, the latch bolt head  162  is first extended in order for the hook bolt  120  to extend. Such an arrangement may prevent the deadbolt from extending prior to the complete closure of the door when the latch bolt head  162  is able to extend into a door frame pocket. By preventing the hook bolt  120  from extending prior to the latch bolt head  162  entering the door frame pocket, the deadbolt  150  may be sufficiently aligned with the door frame pocket such that the deadbolt avoids impacting the door frame which may cause a jam or other undesirable effects (e.g., damage to the door frame). 
       FIG. 13  illustrates the embodiment of the latch assembly  100  of  FIG. 12  with the hook bolt  120  in the retracted position and the guard lever in the free position. The relative positions of the hook bolt  120 , latch bolt  122 , and auxiliary bolt  124  as shown in  FIG. 13  may occur when an associated door is unsecure, for example, when the door is open. In this arrangement, the hook bolt  120  is in the retracted position, with the hooks accordingly in the disengaged position. In the disengaged position, the hooks are contained by the deadbolt  150  except for the lower hook leg  301  projecting out of the bottom of the deadbolt  150 . Also in this position, deadbolt arm  156  is rotated into angled cam slot  201  of slide mechanism  152  and the deadbolt  150  sufficiently contained within the chassis  102 . Guard lever  180  is in a free position caused by auxiliary bolt  124  being in an extended position and therefore causing first tab  176  to contact lower guard lever leg  182  and force the guard lever  180  up (i.e. toward the free position). In the free position, sear  181  on a guard lever arm  184  is close proximity with lower deadbolt leg  154 , such that the sear  181  contacts catch  160 . Thus, the hook bolt  120  is prevented from moving toward the extended position, and the sear  181  resists urging force from the deadbolt biasing member  159 . 
       FIGS. 14A-14B  further illustrate operation of the hook bolt  120  of  FIGS. 12-13  to move the deadbolt  150  relative to the chassis between an extended hook bolt position and a retracted hook bolt position. In  FIG. 14A , the deadbolt  150  is fully extended and deadbolt arm  156  is rotated to an aligned orientation with respect to the deadbolt  150  and engaged with the lower slot  203  of the slide mechanism  152 . Accordingly, hooks  300   a,    300   b  are in an engaged position, protruding laterally out of the deadbolt. In  FIG. 14B , the deadbolt is fully retracted as the deadbolt arm has been fully rotated to engage cam slot  201  of an obliquely-angled portion of the slide mechanism  152 . In this position, the hooks have been substantially rotated up into the deadbolt by contact with front plate  104 , with lower hook leg  301  projecting from the bottom side of the deadbolt. The interaction between the slide mechanism  152  and the deadbolt arm  156  is also shown. For example, as the hook bolt moves from a retracted to an extended position, the arm  156  moves along the angled portion of the slide mechanism  152 . As shown in  FIG. 14A , when in the deadbolt  150  is in extended position, the protrusion of arm  156  is at a position in the lower slot  203  of the slide mechanism  152  such that an inward force applied to deadbolt  150  will not result in the protrusion of arm  156  moving along lower slot  203 , thereby preventing such force from causing the hook bolt  120  to move to a retracted position. 
       FIGS. 15A-15B  further illustrate movement of the auxiliary bolt  124  of  FIGS. 12-13  relative to the chassis between an extended and a retracted auxiliary position. In  FIG. 15A , the latch bolt  122  and the auxiliary bolt  124  are fully extended. Guard lever  180  is in its free position as first tab  176  contacts and lifts lower leg  182  (i.e., moves lower leg  182  toward the free position). With the guard lever  180  in its free (i.e., upper) position, sear  181  engages a catch  160  on lower deadbolt leg  154 , thereby preventing extension of the deadbolt  150 . In  FIG. 15B , the auxiliary bolt  124  is fully retracted while the latch bolt  122  is still fully extended. This is the condition when the door is closed, the latch head  162  of the latch bolt  122  extends under the force of latch biasing member  166  into a pocket in the door frame but no pocket is provided in the door frame for the tongue  170  of the auxiliary bolt  124 , and thus the auxiliary bolt  124  does not extend. With latch bolt  122  extended and the auxiliary bolt  124  not extended, the guard lever  180  is in its secure position, with sear  181  disengaged from catch  160  on lower deadbolt leg  154 . With the sear  181  disengaged from the catch  160 , the deadbolt  150  is able to automatically extended by action of the deadbolt biasing member  159  acting on the deadbolt backstop  157 , which, in turn, due to the coupling of the deadbolt backstop  157  to the deadbolt arm  156  by the peg  155 , causes the deadbolt arm  156  to rotate and thereby extend the deadbolt  150 . Thus, when the door is closed, the deadbolt automatically extends into the locked (i.e., extended) position. 
       FIG. 16  illustrates yet another embodiment of a latch assembly  100  with the deadbolt  150  in the extended position and the guard lever  180  in the secure position. The relative positions of the hook bolt  120 , latch bolt  122 , and auxiliary bolt  124  as shown in  FIG. 16  may occur when an associated door is secure, for example, when the door is closed. In this position, the hook bolt  120  is in the extended position, with hooks  300   a,    300   b  in the engaged position projecting laterally outside of deadbolt  150 . Additionally, deadbolt arm  156  is fully rotated into lower slot  203  of slide mechanism  152 . In this embodiment, deadbolt arm  156  is urged into lower slot  203  by deadbolt biasing member  159  constructed and arranged as a torsion spring. Hook bolt  120  is able to extend as guard lever  180  is in the lower (i.e. secure) position. When the guard lever  180  is in the lower position, the sear  181  (constructed and arranged here as flexible projection attached to guard lever  180 ), is removed from contacting catch  160 , which would prevent deadbolt  150  from moving toward the extended position. Guard lever  180  is moved to the secure position by auxiliary bolt  124  when the auxiliary bolt is in a retracted position. Auxiliary bolt  124  includes tongue  170 , which is constructed and arranged with at least one inclined side to cause the auxiliary bolt to retract when tongue  170  strikes a door frame. The auxiliary bolt  124  also includes auxiliary bolt arm  172 , which further includes first tab  176 . As the auxiliary bolt is retracted by tongue  170 , auxiliary bolt arm  172  contacts lower guard leg  182 , thereby forcing the guard lever  180  down (i.e., toward the secure position). Auxiliary bolt  124  also includes auxiliary bolt guide  175  and auxiliary biasing member (not shown in the figure) located on the auxiliary bolt guide  175 . Auxiliary bolt guide  175  is connected to the auxiliary biasing member in order to urge the auxiliary bolt toward the extended position. In the present embodiment, the auxiliary biasing member is located on the auxiliary bolt guide, and the auxiliary bolt guide is rigidly mounted in chassis  102 , such that the urging member can urge auxiliary bolt  124  toward the extended position. 
     As shown in  FIG. 16 , guard lever arm  184  includes a stopping end  186  constructed and configured to prevent the retraction of latch bolt head  162  when the guard lever  180  is in the secure position. In certain embodiments, the pivoting movement of the guard lever arm  184  is controlled and limited by an extension of the guard lever near the stopping end extending laterally into a slot  188  formed in one or both of side plates  112 . When the guard lever  180  is in its secure position, the stopping end  186  of the guard lever arm acts to prevent the latch bolt  122  from moving to its retracted position by contacting the latch bolt cylinder  164  and thereby blocking further retraction of the latch bolt  122 . In some cases, it may be beneficial for the guard lever  180  to be moved to the free position when the handle is actuated, such that the stopping end  186  is moved away from the latch bolt cylinder  164  such that the latch bolt  122  can be retracted. Accordingly, the guard lever arm  184  includes a guard inclined section  185  constructed and arranged to abut the end  196  of the latch bolt  122 . When the end  196  is moved by a door handle, it abuts the guard inclined section  185  and moves the guard lever  180  toward the free position. As the guard lever  180  is moved toward the free position the stopping end  186  is lifted (i.e. moved toward the free position), such that the latch bolt  122  can retract without contacting the stopping end  186 . In such an arrangement, the guard lever  180  can be moved toward the free position and the latch bolt  122  can be retracted with a single actuation of the handle. 
     In some cases, it may be beneficial to prevent the hook bolt  120  from extended without using a deadlocking tab as described previously. Accordingly, the stopping end  186  may also prevent the hook bolt  120  from extending. In the case where guard lever  180  is in the free position, stopping end  186  is elevated above latch bolt cylinder  164  (see  FIG. 17 ). If the latch bolt  122  is in the retracted position, latch bolt cylinder  164  is moved to a retracted position, below stopping end  186  near slot  188 . In this position, the guard lever  180  is prevented from moving to the secure position as stopping end  186  contacts an upper portion of latch bolt cylinder  164 . Thus, the guard lever  180  remains in the free position even if auxiliary bolt  124  is retracted. According to the present embodiment, auxiliary bolt arm  172  is sufficiently below guard lever  180 , such that when the stopping end  186  abuts on the latch bolt cylinder  164  and prevents the guard lever  180  from moving to the secure position the auxiliary arm  172  is unable to contact and force guard lever  180  down (i.e. toward the secure position). Such an arrangement may prevent damage to latch assembly  100  in the case the latch bolt  122  is in the retracted position and force is applied to tongue  170  which may cause the auxiliary bolt  124  to retract. 
     In some embodiments, the latch assembly includes a hole  136  configured and arranged to attach a lever hub and/or a handle. The handle may be configured to actuate an end  196  of the latch bolt  122 . End  196  may also contact deadbolt backstop  157  via lower leg  153 . When the handle is actuated, the latch bolt  122  and latch bolt end  196  may move toward the retracted latch position. Accordingly, the deadbolt backstop  157  may be pivoted by the latch bolt end  196 , which may cause deadbolt arm  156  to be rotated by pin  155  which links the deadbolt backstop  157  and deadbolt arm  157 . As deadbolt arm  156  is rotated by deadbolt backstop  157 , hook bolt  120  is moved toward the retracted position by sliding mechanism  152 . Thus, when an attached handle is actuated, the latch bolt  122  and hook bolt  120  may be moved toward their respective retracted positions simultaneously. 
       FIG. 17  illustrates the embodiment of the latch assembly  100  of  FIG. 16  with the deadbolt  150  in the retracted position and the guard lever  180  in the free position. The relative positions of the hook bolt  120 , latch bolt  122 , and auxiliary bolt  124  as shown in  FIG. 17  may occur when an associated door is unsecure, for example, when the door is open. In this arrangement, the hook bolt  120  is in the retracted position, with the hooks accordingly in the disengaged position. In the disengaged position, the hooks are contained by the deadbolt  150  except for the lower hook leg  301  projecting out of the bottom of the deadbolt  150 . Also in this position, deadbolt arm  156  is rotated into an angled slot  201  of slide mechanism  152 . Hook bolt  120  is unable to extend as guard lever  180  is in the upper (i.e. free) position. When the guard lever  180  is in the free position, the sear  181  (constructed and arranged here as a flexible projection attached to guard lever  180 ) contacts catch  160  which prevents deadbolt  150  from moving toward the extended position and resists urging force from the deadbolt biasing member  159 . Guard lever  180  is moved to the free position by auxiliary bolt  124  when the auxiliary bolt is in an extended auxiliary position. Auxiliary bolt  124  also includes auxiliary bolt guide  175  and auxiliary biasing member (not shown in the figure). Auxiliary bolt guide  175  is connected to the auxiliary biasing member in order to urge the auxiliary bolt toward the extended position. In the present embodiment, the auxiliary biasing member is located on the auxiliary bolt guide  175 , and the auxiliary bolt guide  175  is rigidly mounted in chassis  102 , such that the urging member can urge auxiliary bolt  124  toward the extended position. The auxiliary bolt  124  also includes auxiliary bolt arm  172 , which further includes first tab  176 . As the auxiliary bolt is extended by auxiliary biasing member, first tab  176  contacts lower guard leg  182 , thereby forcing the guard lever  180  up (i.e., toward the free position). 
       FIGS. 18A-18C  further illustrate one embodiment of the chassis of the latch assembly  100 .  FIG. 18A  shows a front view of front plate  104 . Front plate  104  includes one or more screw holes  114  for mounting latch assembly  100  to a door. The front plate  104  further include cutouts to accommodate the hook bolt  120 , latch bolt  122 , auxiliary bolt  124  and allow their movement between extended and retracted positions.  FIG. 18B  shows a front view of rear plate  106 . Rear plate  106  includes one or more screw holes  114  for mounting latch assembly  100  to a door.  FIG. 18C  shows a side view of the bottom one of the side plates  112  with latch bolt  122  and auxiliary bolt  124  in their respective extended positions. The side plates  112  include one or more cutouts for mounting the components in the previously described embodiments, in addition to traditional door hardware components like handles, locking devices, etc. 
       FIGS. 19A-19B  illustrate one embodiment of a door system including a latch assembly  100 . As shown, a door system  700  includes a door  710  having a latch assembly such as latch assembly  100  installed thereon. As fully installed, the door system may further include an outside door handle  702  and an inside door handle  704 , each operable to open the door when unlocked. In some embodiments, inside door handle  704  may also be operable to open the door when it is locked. In some embodiments, a key  706  may be used to engage a key and core assembly which can lock or unlock the door system  700 . Of course, any suitable credential may be employed, such that an authorized user can operate the door system. In some embodiments, latch assembly  100  may be installed on a door by an end user. A thumb knob  708  is configured to operate the hook bolt  120  to selectively extend or retract the deadbolt  150 . In one embodiment, the knob  708  is coupled to slot of a thumb turn as shown previously. The latch assembly  100  is configured to automatically extend the hook bolt when the door  710  is closed as described above. In some embodiments, an associated door jamb strike plate for use with the door system may have an opening with an additional recess inside of the door jamb located in at least one direction perpendicular to the direction of movement of a hook bolt. Accordingly, the recess may be constructed and arranged to accommodate (i.e., receive) one or more hooks of the hook bolt that may deploy from a deadbolt that protrudes into the opening. Such an arrangement may prevent the one or more hooks from jamming in a door frame, or otherwise permit the hook bolt to reach the engaged position such that the door is secured. 
     While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art. Accordingly, the foregoing description and drawings are by way of example only.