Patent Publication Number: US-2020277813-A1

Title: Load prevention for door latches

Description:
FIELD 
     Disclosed embodiments are related to a load prevention device for door latches and related methods of use. 
     BACKGROUND 
     Exit devices are typically used to secure doors in high-occupancy structures where operability in crowded conditions is desirable. Multi-point latching devices are commonly used in environments where high security or sever weather resistance is required. For example, many multi-point latches are used in FEMA rated applications such as hurricane and tornado shelters. In some cases, these multi-point latching devices include an exit device, which is configured to actuate the multi-point latching device to allow a door to be opened. Multi-point latching devices may employ vertical rods or cables which are concealed inside of the door or attached to the outside of an interior surface of the door. 
     SUMMARY 
     In some embodiments, a latching device includes a first latch movable between a first latch engaged position and a first latch disengaged position, where in the first latch engaged position the first latch is configured to engage a pocket of an associated door frame, and a blocker configured to move between a blocker engaged position and a blocker disengaged position, where the blocker is configured to engage the pocket when the blocker is in the blocker engaged position. The blocker is configured to resist a force applied to an associated door in a direction of egress. 
     In some embodiments, a method for operating a latching device includes moving a latch toward an latch engaged position from a latch disengaged position, moving a blocker from a blocker disengaged position to a blocker engaged position, wherein in the blocker engaged position the blocker is partially disposed in a pocket of an associated door frame, moving the latch to the latch engaged position, wherein in the latch engaged position the latch is partially disposed in the pocket, resisting a force applied to an associated door in a direction of egress with the blocker, operating an actuator to move the latch toward the latch disengaged position, and moving the blocker to the blocker disengaged position. 
     In some embodiments, a latching device includes a hook latch configured to rotate been a latch engaged position and a latch disengaged position, where the hook latch includes an engagement surface configured to engaged an associated strike plate of a door frame, and where the engagement surface is configured to reduce a frictional force between the hook latch the associated strike plate when the hook latch is moved to the latch disengaged position. 
     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  is a perspective view of one embodiment of an exit device including a side latch; 
         FIG. 2  is a rear elevation view of the exit device of  FIG. 1 ; 
         FIG. 3  is a front elevation view of the exit device of  FIG. 1 ; 
         FIG. 4  is a perspective view of one embodiment of an actuator for the exit device of  FIG. 1 ; 
         FIG. 5  is a right side elevation view of the actuator of  FIG. 4 ; 
         FIG. 6  is a rear elevation view of the actuator of  FIG. 4 ; 
         FIG. 7A  is an enlarged right side view of section  7 A of  FIG. 4 ; 
         FIG. 7B  is an enlarged left side view of section  7 B of  FIG. 1 ; 
         FIG. 8  is a perspective view of one embodiment of a side latch for the exit device of  FIG. 1 ; 
         FIG. 9  is a perspective view of the side latch of  FIG. 8  with a cover removed; 
         FIG. 10  is another perspective view of the side latch of  FIG. 8  with a cover removed; 
         FIG. 11  is an enlarged elevation view of section  11  of  FIG. 10 ; 
         FIG. 12  is a perspective view of the side latch of  FIG. 9  and one embodiment of a rod guide; 
         FIG. 13  is a perspective view of one embodiment of a transom latch for the exit device of  FIG. 1 ; 
         FIG. 14  is another perspective view of the transom latch of  FIG. 13 ; 
         FIG. 15  is a front elevation view of one embodiment of a door including an exit device according to exemplary embodiments described herein; 
         FIG. 16  is a side elevation view of the door of  FIG. 16 ; 
         FIG. 17  is a front elevation view of another embodiment of a door and a door frame; 
         FIG. 18  is a top schematic of one embodiment of an exit device securing a door; 
         FIG. 19  is a front schematic of the exit device of  FIG. 18 ; 
         FIG. 20A  is a perspective view of one embodiment of a hook latch and a blocker; 
         FIG. 20B  is a perspective view of the hook latch and blocker of  FIG. 20B  in a blocker disengaged position; 
         FIG. 21  is a top schematic of the hook latch and blocker of  FIG. 20A  in a secure position; 
         FIG. 22  is a top schematic of the hook latch and blocker of  FIG. 20A  in an unsecure position; 
         FIG. 23  is a front schematic of the hook latch and blocker of  FIG. 20A  in a secure position; 
         FIG. 24  is a front schematic of the hook latch and blocker of  FIG. 20A  in an unsecure position; 
         FIG. 25  is a perspective view of another embodiment of a hook latch and a blocker; 
         FIG. 26  is a top schematic of the hook latch and blocker of  FIG. 25  in a secure position; 
         FIG. 27  is a top schematic of the hook latch and blocker of  FIG. 25  in an unsecure position; 
         FIG. 28  is a front schematic of the hook latch and blocker of  FIG. 25  in a secure position; 
         FIG. 29  is a front schematic of the hook latch and blocker of  FIG. 25  in an unsecure position; 
         FIG. 30  is a front schematic of another embodiment of a hook latch and a blocker in a secure position; 
         FIG. 31  is a front schematic of the hook latch and blocker of  FIG. 30  in an unsecure position; 
         FIG. 32  is a front schematic of another embodiment of a hook latch and a blocker in a secure position; 
         FIG. 33  is a front schematic of the hook latch and blocker of  FIG. 32  in an unsecure position; 
         FIG. 34  is a block diagram of one embodiment for a method of operating a latching device; 
         FIG. 35  is a top schematic of yet another embodiment of a latch securing a door; 
         FIG. 36  is a top schematic of yet another embodiment of a latch securing a door; 
         FIG. 37  is a top schematic of yet another embodiment of a latch securing a door; 
         FIG. 38  is a top schematic of yet another embodiment of a latch securing a door; and 
         FIG. 39  is a top schematic of yet another embodiment of a latch securing a door. 
     
    
    
     DETAILED DESCRIPTION 
     In some cases, exit devices employed on a door are tested to standards for operability when high loads are placed on the door in a direction of egress (i.e., in a direction which the door swings open). These types of loading conditions typically invoke high friction between various latches and bolts of the exit device which are in contact with a door frame as the load on the door is increased. These added frictional forces typically increase the force used to operate the exit device which may be undesirable when easy operation of the exit device is desired. In some cases, multi-point latching devices fitted with an exit device have multiple latching points which may induce friction and increase minimum force for operation of the exit device. 
     In view of the above, the inventors have recognized the benefits of a load blocker which reduces the load on various latches actuated by an exit device when a door is under a high force loading condition. Such an arrangement may reduce the force used to operate an exit device when, for example, multiple people are pressing against the door. The load blocker may reduce the mechanical advantage of the loading on a latch, remove loading on the latch entirely, or otherwise reduce the loading directly applied to the latch. The inventors have also recognized the benefits of a load blocker on hook latches which induce high friction under high loading conditions. Additionally, the inventors have recognized the benefits of employing a load blocker with one or more latches of a multi-point latching device to reduce the force used to operate the multi-point latching device. 
     In some embodiments, a load blocker for a latching device is configured to rotate between an engaged position in which the load blocker retains the door in a secured state under a high load condition, and a disengaged position in which the load blocker allows the door to open. The load blocker may cooperate with a latch of the latching device to move between the engaged position and disengaged position. For example, the movement of the latch from a latch retracted (i.e., disengaged) position to a latch extended (i.e., engaged) position may move the load blocker from the disengaged position to the engaged position. The load blocker may also be held in the engaged position by the latch, or by a separate mechanical element actuable by the latching device. In either case, the load blocker may direct force received from during a high load condition on the door away from the latch, may reduce the coefficient of friction one the latch, or otherwise reduce the effective resultant frictional force on the latch when the latching device is operated (e.g., via an exit device, handle, etc.). In some embodiments, the load blocker may be configured as a door having a plate hinged at a latch opening formed in the door or latching device (e.g., exit device, mortise lock, etc.). The blocker may pivot about the hinge as the latch is moved between the latch extended position and latch disengaged position so that the blocker stays between the latch and a door strike or jamb which resists motion of the door under high loading conditions (e.g., in a direction of egress). Thus, the load blocker may cooperate with the latch to secure a door under high loading conditions. In some embodiments, the load blocker may be configured to secure the door in a direction of egress (i.e., a direction in which the door swings open) and the latch may be configured to secure the door in a direction of ingress (i.e., a direction in which the door swings closed). Such an arrangement may be desirable in cases where wind based pressure or airborne debris resistance is desirable, as the latching device may retain high security towards external forces via the latch but may still have a low operation force when the door is under high loading conditions, as will be discussed further below. 
     Traditionally, multi-point latching exit devices are employed in doors to provide additional security or strength. These conventional exit devices employ vertical rods or tethers linked to a central actuator, by which a user can operate multiple latches with the same actuator. The vertical rods may be attached to the exterior of an interior door surface, or may be concealed inside of the door. Typically, these exit devices include a transom latch, a jamb latch, and a threshold latch providing three point fastening for the door which is suitable for environments with high wind and the associated risks of pressure and windborne objects impacting the secured door. Because conventional multi-point exit devices include a threshold latch, space must be made in the floor to accommodate the threshold latch. As many commercial floors are composed of a concrete slab, the installation of conventional threshold latches may be an expensive, time consuming, and laborious process. Additionally, because the threshold latch is formed in the floor, a threshold latch head and corresponding latch head receptacle may collect dirt or grime which may degrade the performance of the exit device over time or inhibit secure locking. In cases where the exit device is at least partially concealed inside of a door, maintenance or repairs of threshold latches with degraded performance may be expensive and time consuming. Additionally, installation or removal of threshold latches concealed in the door typically require removal of the door panel which is time consuming and labor intensive. 
     In view of the above, the inventors have recognized the benefits of a multi-point locking or latching device which includes a transom latch coupled to a first rod and a side latch coupled to a second rod which in combination secure a door. The side latch may include a hook latch head configured to positively grasp the door jamb when engaged. Such an arrangement may be beneficial to withstand high wind pressure loads and windborne objects in accordance with modern safety standards. The side latch may be easily installed or removed via a mortise opening in the door without removal of a door panel. The inventors have also recognized the benefits of an actuator including two cams which apply force to the first and second rods concurrently when a lever is rotated to promote reliable activation of the transom latch and side latch. In some embodiments, the side latch may be combined with a load blocker to improve resilience to wind or airborne debris while reducing the operational force of the latching device under high loading. 
     In some embodiments, an exit device includes an actuator, a transom latch, a side latch, and a load blocker. The actuator may be operatively coupled to the transom latch and the side latch so that the transom latch and side latch may be operated concurrently by a single actuation of the actuator. Additionally, the load blocker may cooperate with the side latch to be operated concurrently with the side latch. In some embodiments, the actuator may be connected to the transom latch by a first (i.e., upper) rod and the side latch connected to the side latch by a second (i.e., lower) rod, such that when the actuator is actuated by a user, the first rod and second rod may be moved linearly along their respective axes to operate the transom latch and side latch. When the side latch is in the engaged position (i.e., extended position), the load blocker may be disposed between the side latch and a portion of a door strike or door jamb which resists the opening of the door when the door is under high loading conditions. The load blocker may inhibit contact between the side latch and the portion of the door strike or door jamb which resists the opening of the door so that high loading on the side latch may be reduced or otherwise controlled to keep an the force of operation of the exit device low. 
     Turning to the figures, specific non-limiting embodiments are described in further detail. It should be understood that the various systems, components, features, and methods described relative to these embodiments may be used either individually and/or in any desired combination as the disclosure is not limited to only the specific embodiments described herein. 
       FIG. 1  is a perspective view of one embodiment of an exit device  100  (e.g., a latching device) including an actuator  150 , a side latch  200 , and a transom latch  250 . As shown in  FIG. 1 , a first rod  170  operatively couples the actuator to the transom latch  250  and a second rod  172  operatively couples the actuator to the side latch  200 . According to the depicted embodiment, the exit device is configured to be mounted inside of the door (not shown in  FIG. 1 ), so that a majority of the components are substantially concealed from view. Of course, the exit device may visible or partially concealed, as the present disclosure is not so limited. As shown in  FIG. 1 , the exit device is arranged with the first and second rods in a vertical orientation, with the transom latch configured to engage a door transom and the side latch configured to engage a door jamb. As the transom latch and side latch are both linked to the same centralized actuator, the transom latch and side latch may be actuated concurrently to selectively secure or release a door. 
     According to the embodiment shown in  FIG. 1 , the actuator  150  includes a chassis  152 , a lever  160 , a first cam  162 A coupled to a first rod holder  164 A, and a second cam  162 B coupled to a second rod holder  164 B. The lever is rotatably mounded to the chassis  152  and is configured to rotate about an axis which is parallel with a longitudinal axis of the first rod  170  and second rod  172 . The first cam and second cam are also rotatably mounted to the chassis and are held by first guide wall  154 A and second guide wall  154 B, respectively, such that both of the cams rotate about an axis substantially orthogonal to the rotational axis of the lever. The first rod holder  164 A is configured to secure the first rod  170  to the actuator, and is slidably mounted to the chassis so that the first rod may be moved along its longitudinal axis (i.e., a first axis). Likewise, the second rod holder  164 B is configured to secure the second rod  172  to the actuator and is slidably mounted to the chassis to allow the second rod to be moved along its longitudinal axis (i.e., a second axis). The first rod holder is coupled to an end of the first cam so that rotational motion of the first cam causes linear motion of the first rod holder along the first axis. The second rod holder is coupled to an end of the second cam so that rotational motion of the second cam causes linear motion of the second rod holder along the second axis. As will be discussed further with reference to  FIGS. 4-5 , when the lever is rotated (i.e., actuated), the lever engages at least one of the first cam and the second cam to rotate the first and second cams in opposite directions. As the first and second cams are coupled to the first and second rod holders, respectively, the first rod holder is moved in a first direction along the first axis and the second rod holder is moved in a second direction along the second axis as the cams are rotated. According to the embodiment shown in  FIG. 1 , the first direction and second direction may be opposite one another such that the first rod holder and second rod holder are moved closer to one another when the lever is actuated (e.g., rotated). 
     As shown in  FIG. 1 , the side latch  200  includes a chassis  202 , a face plate  204  and a hook latch head  206 . The chassis is configured to fit into a mortise opening formed in a door, and may be secured to the door by the face plate. The hook latch head is rotatably mounted to the chassis via hook latch head pin  208 . As shown in  FIG. 1 , the side latch is coupled to the second rod  172  by a rod coupler  220  which fits around the second rod. Spring clips  222 A,  22 B, releasably secure the second rod inside the rod coupler. As will be discussed further with reference to  FIGS. 10-11 , the rod coupler transmits longitudinal motion of the second rod into rotational motion of the hook latch head, so that movement of the second rod along the second axis may move the hook latch head between an engaged position and a disengaged position. In the state shown in  FIG. 1  the hook latch head is in an engaged position, projecting past the face plate  204  so that the hook latch head would engage an associated door jamb when adjacent a hook latch head receptacle. According to the embodiment of  FIG. 1 , the second rod  172  is disposed partially in a rod guide  174 . The second rod guide includes a rod guide slot  176  which receives a second rod pin  173  disposed on the second rod. The second rod guide substantially constrains the second rod to linear movement along the second axis (i.e., the longitudinal axis of the second rod). 
     According to the embodiment of  FIG. 1 , the side latch may be disposed below a centerline of a door such that the door may be secured at different portions of the door (e.g., top and bottom portions). Without wishing to be bound by theory, the distance of the side latch head from the top of the door may at least partially determine the amount of deflection of a door place under pressure or impact loads. Accordingly, in some embodiments, the hook latch head of a side latch may positioned below a top of a door by a distance greater than ½ of the door length, ⅝ of the door length, ⅔ of the door length, ¾ of the door length, or any other appropriate distance. Correspondingly, the hook latch head may be positioned below a top of a door by a distance of less than ⅝ of the door length, ⅔ of the door length, ¾ of the door length, the door length, of any other appropriate distance. Combinations of the above noted ranges are contemplated, as the present disclosure is not so limited. 
     As shown in  FIG. 1 , the transom latch  250  includes a chassis  252 , a face plate  254 , a latch head  260 , and a trigger  262 . The latch head  260  may be directly coupled to the first rod  170  so that movement of the first rod along the first axis (i.e., a longitudinal axis of the first rod) moves the latch head between an engaged and disengaged position. According to the depicted embodiment, the latch head  260  does not include a substantially inclined face, and will therefore not automatically retract when the latch head contacts a transom strike plate. In order to prevent interference or premature engagement of the latch head with a transom strike plate, the transom latch includes a lockout  266  which is controlled by the trigger  262 . According to the embodiment of  FIG. 1 , the lockout is configured to allow movement of the latch head toward a disengaged position (i.e., where the latch head is substantially retracted to clear a transom strike plate without interference). However, the lockout is configured to prevent movement of the latch head toward an engaged position (i.e., where the latch head is substantially extended to engage a transom strike plate). Accordingly, when the transom latch head is retracted the lockout will retain the transom latch head in the disengaged position so that the transom latch head does not interfere with door opening or closing. The trigger  262  is configured to move between an extended position and a retracted position and includes an inclined face which is suitable to automatically retract the trigger when the trigger contacts a transom strike plate. As shown in  FIG. 1 , the trigger is configured to engage the lockout when the trigger is moved to the retracted position with a lockout engagement portion  264  configured as a camming surface. When the trigger engages the lockout (e.g., along a camming surface) the lockout may release the transom latch head  260  so that the latch head may move to the engaged position to secure the door once the door is closed. Thus, the latch head and trigger arrangement shown in  FIG. 1  may allow for automatic latching of the transom latch head without inclusion of an inclined face on the transom latch head. According to the embodiment shown in  FIG. 1 , the chassis  252  is coupled to a transom rod guide  257  which includes a transom rod guide slot  258  with receives a first rod pin  171  disposed on the first rod to substantially constrain the movement of the first rod to linear movement along the first axis (i.e., the longitudinal axis of the first rod). 
       FIG. 2  is a rear elevation view of the exit device  100  of  FIG. 1 . As shown in  FIG. 2 , the rear panel of the side latch  200  has been removed to show the internal components of the side latch. As discussed previously, the side latch includes a hook latch head  206  rotatably coupled to a chassis by a hook latch head pin  208  and a rod coupler  220  operatively coupled to the second rod  172  so that linear movement of the second rod is converted into rotational motion of the hook latch head. As shown in  FIG. 2 , the hook latch head includes a plurality of gear teeth  207  disposed in an arc in a circumferential arrangement around the hook latch head pin  208 . Correspondingly, the rod coupler includes a slide body  221  which includes a plurality of gear teeth  216  configured to mesh with the teeth of the hook latch head. As shown in  FIG. 2 , the slide body  221  is disposed around guide rail  214  so that the slide body is constrained to move in a linear direction along the guide rail parallel to the longitudinal axis of the second rod. Accordingly, the rod coupler forms a rack and the hook latch head forms a pinion so that linear movement of the second rod is converted into rotational movement of the hook latch head which may be used to move the hook latch head between the hook engaged and hook disengaged positions. 
     As shown in  FIG. 2 , the actuator  150  also includes a rear actuator rod guide  177  which is configured to substantially constrain the first rod  170  and first rod holder  164 A as well as the second rod  172  and second rod holder  164 B to linear movement along the first axis of the first rod and second axis of the second rod, respectively. Accordingly, the actuator may use camming motions to precisely and reliably move the first and second rods along their longitudinal axis to actuate the transom latch and side latch. 
       FIG. 3  is a front elevation view of the exit device  100  of  FIG. 1 . As discussed previously, the actuator  150  includes a lever  160 , a first cam  162 A, a second cam  162 B which cooperate to move the first rod  170  and second rod  172  along the first axis and second axis, respectively. As shown in  FIG. 3 , the first cam is coupled to the first rod holder  164 A by a first linkage  166 A and the second cam is coupled to the second rod holder by a second linkage  166 B. The first and second cam linkages are rotatably linked (e.g., by a linkage pin) to both their respective cams and rod holders so that the rotational motion of the cams may be converted into linear motion of the rod holders. 
     As discussed previously, the transom latch includes a trigger  262  and a lockout  266  which cooperate to allow the latch head  260  to automatically extend into a transom strike plate without interference when the door is being opened or closed. As shown in  FIG. 3 , the lockout  266  interfaces with a plurality of ratchet teeth  256  so that the latch head  260  is progressively retained at it is moved to the disengaged (i.e., retracted) position. When the trigger  262  is moved from the extended position shown in  FIG. 3  to the retracted position, the lockout engagement portion  264  cams the lockout out of engagement with the ratchet teeth so that the latch head  260  may move to toward the engaged position. Of course, while ratchet teeth are employed in the depicted embodiment, any suitable progressive or non-progressive retaining element may be employed, as the present disclosure is not so limited. As shown in  FIG. 3 , the transom latch includes a biasing member configured as a compression spring which urges the latch head toward the engaged position. Accordingly, when released by the trigger, the latch head may automatically move to the engaged position under influence of the compression spring. Of course, while a compression spring is employed in the embodiment of  FIG. 3 , any suitable biasing member may be employed as the present disclosure is not so limited. 
     According to the embodiment shown in  FIG. 3 , the biasing member  268  may apply an urging force to the first rod  170  so that the first rod is urged to a position which corresponds to the transom latch head  260  being in an engaged position. As the urging force is transmitted through the first rod to the actuator and from the actuator to the side latch through the second rod, the hook latch head  206  may also be urged toward a hook engaged position. Thus, the linkage of the first rod and second rod through the actuator may allow a single biasing member to be employed in any one of the transom latch, actuator, and side latch. Such an arrangement may be beneficial to simplify installation and reduce parts and cost. 
       FIG. 4  is a perspective view of one embodiment of an actuator  150  for the exit device of  FIG. 1 . As discussed previously, the actuator is configured to allow a first rod  170  and a second rod  172  to move concurrently along a first axis (corresponding to a longitudinal axis of the first rod) and a second axis (corresponding to a longitudinal axis of the second rod), respectively. As best shown in  FIG. 4 , the lever  160  is rotatably mounted to the chassis by a hinge portion  161 . A cam engagement portion  167  of the lever engages both the first cam  162 A and the second cam  162 B. The first cam and second cam are rotatably mounted to a first guide wall  154 A and a second guide wall  154 B, respectively. Accordingly, when the lever is rotated about the hinge portion, the cam engagement portion  167  will engage both the first cam and second cam to rotate the cams in opposite directions about parallel axes. The first cam is coupled to a first rod holder  164 A by a first linkage  166 A which converts the rotational motion of the cam to linear motion of the first rod holder. The first rod holder and first linkage are at least partially disposed in a first linkage slot  155 A formed in the first guide wall  154 A which at least partially constrains to the first linkage and first rod holder to linear movement. Similarly, the second cam is coupled to a second rod holder  164 B by a second linkage  166 B which is disposed at least partially in second linkage slot  155 B formed in the second guide wall. According to the embodiment shown in  FIG. 4 , when the lever is rotated about the hinge portion  161 , the cams draw the first rod holder and second rod holder closer together, thereby applying tension through the rods to a transom latch and/or side latch. Of course, in other embodiments, the cams may rotated to move the first rod holder and second rod holder further apart to apply compression through the rods, as the present disclosure is not so limited. As shown in  FIG. 4 , the relative position of the first and second rods to the first and second rod holder may be adjusted by rotating a first adjustment nut  168 A or a second adjustment nut  168 B, respectively. 
     As shown in  FIG. 4 , the actuator also includes a slider  190  disposed in a slider slot  194  formed in the chassis  152  of the actuator. The slider includes a first inclined camming surface  192 A and a second inclined camming surface  192 B which are configured to selectively engage the lever  160  to rotate the lever. As will be discussed further with reference to  FIG. 6 , the slider  190  may be operatively coupled to an interior handle or other actuator so that the lever may be actuated from a side of the door from which the lever is not accessible. When the slider engages the lever, the lever may be cammed to correspondingly rotate the first and second cams  162 A,  162 B to actuate an associated lock with the first rod  170  and second rod  172 . According to the embodiment of  FIG. 4 , the lever may be operatively connected to a user interfacing element such as a paddle, push bar, or other suitable arrangement so that a user may easily actuate the lever. 
       FIG. 5  is a right side elevation view of the actuator  150  of  FIG. 4 . As best shown in  FIG. 5 , the first rod  170  and the second rod  172  are moveable along their longitudinal axes by movement of the first rod holder  164 A and second rod holder  164 B, respectively. The first rod holder is constrained at least partially to linear movement by first linkage pin  165 A which is disposed in the first linkage slot  155 A and couples the first rod holder to the first linkage (see  FIG. 4 ). Likewise, the second rod holder is constrained at least partially to linear movement by second linkage pin  165 B which is disposed in second linkage slot  155 B and couples the second rod holder to the second linkage (see  FIG. 4 ). According to the embodiment shown in  FIG. 5 , the first and second rods have coincident axes (i.e., the longitudinal axes of both rods are coincident). Accordingly, when the lever  160  is actuated the first and second rods are moved toward or apart from one another along the same coincident axis. As shown in  FIG. 5 , the first cam  162 A is rotatably coupled to the first guide wall  154 A by first cam pin  163 A and the second cam  162 B is rotatably coupled to the second guide wall  154 B by a second cam pin  163 B. In the depicted embodiment, the first cam and second cam are configured to rotate equally in opposite directions about their respective axes when engaged by the lever  160 . As shown by the dashed arrows, in this embodiment, the first cam rotates clockwise relative to the page to move the first rod holder in a first direction (see dot-dash arrow) while the second cam rotates in a counterclockwise direction relative to the page to move the second rod holder in a second direction (see long-dot-dash arrow, where the first direction and the second direction are opposite one another and move the first and second rod holders closer together). Correspondingly, when the cams rotate in opposite directions the first and second rods will move further apart along their coincident axes. According to the embodiment of  FIG. 5 , rotation of the lever by a user may move the first and second rods closer together along their coincident axes, applying tension through the rods to move any associated lock to a disengaged position. 
     According to the embodiment shown in  FIG. 5 , the actuator includes first and second deadlatching catches  153 A,  153 B formed as a part of the first linkage slot  155 A and second linkage slot  155 B. The deadlatching catches are configured to prevent movement of the first rod holder  164 A or second rod holder  164 B without direct actuation of the lever  160 . That is, force applied directly to the first or second rods may cause the first linkage pin  165 A and second linkage pin  165 B to engage and abut against first deadlatching catch  153 A and second deadlatching catch  153 B, respectively. Thus, force which is externally applied to the exit device (e.g., to a transom latch head or a hook latch head) may not move the rods to release the door. If the actuator is properly actuated, rotation of the first cam  162 A and the second cam  162 B may draw the first pin and second pin out of the deadlatching catches and into the first linkage slot  155 A and second linkage slot  155 B. The direction of rotation of the first cam and the second cam may be suitable to draw the pin out of the deadlatching catch to allow the first rod holder and second rod holder to move toward one another to release the door upon direct actuation of the lever  160 . 
       FIG. 6  is a rear elevation view of the actuator  150  of  FIG. 4 . As best shown in  FIG. 6 , the actuator includes a handle mount  199  including a wing  198  configured to engage one of two tabs  196  of a slider (see  FIG. 4 ). The tabs are disposed in slider slot  194 . When an attached handle is turned, the wing  198  may engage one of the tabs  196  to slide the slider in the slider slot  194 . As discussed previously, this movement may cause an inclined camming surface of the slider to engage the lever  160  to actuate the exit device (e.g., by moving the first rod holder and second rod holder toward one another). Of course, while a handle attachment and wing are shown in  FIG. 6 , any suitable arrangement may be employed to allow the exit device to be actuated from a side of the door where the lever is not accessible. 
       FIG. 7A  is an enlarged right side view of section  7 A of  FIG. 4  and  FIG. 7B  is an enlarged left side view of section  7 B of  FIG. 1  depicting first cam  162 A and second cam  162 B with the lever removed for clarity. As shown in  FIG. 7A , the first cam includes a first cam lobe  184 A, a first upper arm  183 A, and a first lower arm  182 A. Similarly, as shown in  FIG. 7B , the second cam includes a second cam lobe  184 B, a second upper arm  183 B, and a second lower arm  182 B. As shown in  FIG. 7A , the first upper arm engages the second lower arm. As shown in  FIG. 7B , the second upper arm engages the first lower arm. Accordingly, the first and second cams are intermeshed and will rotate together about the first cam pin  163 A and second cam pin  163 B, respectively. That is, even in the case of misalignment of the lever so that the lever only engages one of the cam lobes, the cams will rotate concurrently so that the coupled rod holders will also move concurrently. Additionally, forces transmitted from one rod holder another rod holder may be transmitted through the intermeshed cams without interference or input of the lever. Thus, the intermeshed cam may provide reliable concurrent actuation of the exit device. 
       FIG. 8  is a perspective view of one embodiment of a side latch  200  for the exit device of  FIG. 1 . As discussed previously, the side latch includes a hook latch head  206  which is configured to rotate between a hook engaged position and a hook disengaged position. The hook latch head is rotatably mounted to the chassis  202  via a hook latch head pin  208 . Additionally, as shown in  FIG. 8 , the chassis includes a hook latch head slot  203  which receives a hook latch head guide  209 . In addition to guiding the hook latch head through rotational motion, the hook latch head slot  203  may also be used to set predetermined limits on the range of rotation of the hook latch head. That is, the hook latch head slot may determine the range of motion of the hook latch head so that the hook latch head may be reliably moved between the hook engaged and hook disengaged position to secure a door. 
       FIG. 9  is a cutaway perspective view of the side latch  200  of  FIG. 8  with a portion of the chassis  202  removed to show the internal components of the side latch. As discussed previously, the side latch includes a rod coupler  220  and a hook latch head  206 . The rod coupler includes a slide body  221  which receives linear motion of second rod  172  and converts it into rotary motion of the hook latch head via gear teeth  216 . As best shown in  FIG. 9 , the slide body  221  is slidably coupled to the chassis  202  via a guide rail  214  disposed in a guide channel  211  formed in the slide body. The guide rail is secured in the guide channel  211  with a first clip  212 A and a second clip  212 B which secure the slide body to the guide rail but allow the slide body to move with second rod  172  to move the hook latch head between the hook engaged position and the hook disengaged position. 
       FIG. 10  is another cutaway perspective view of the side latch  200  of  FIG. 8  showing the interface between the rod coupler  220  and the second rod  172 . As shown in  FIG. 10 , the rod coupler includes a channel  223  which is formed to accommodate the second rod. The rod coupler also includes a first spring clip  222 A and a second spring clip  222 B which releasably secure the second rod  172  in the channel. The rod coupler also includes a plurality of grooves  224  which are formed in a transverse direction across the channel  223 . The grooves are each configured to receive a retaining ring  210  which is attached to the second rod. The retaining ring may be releasably secured to an annular groove in the second rod so that the retaining ring may be used to transmit longitudinal force from the second rod. When the retaining ring is disposed in one of the grooves, force may be transmitted from the second rod to the rod coupler and vice versa via the interface between the groove and retaining ring. The spring clips  222 A,  222 B keep the retaining ring secure in the groove. Without wishing to be bound by theory, providing a plurality of grooves may allow for simplified installation of the side latch into a door. As will be discussed further with reference to  FIG. 11 , rather than adjusting the position of the retaining ring or second rod which may be concealed in a door, the side latch may be pushed into a mortise opening and the retaining ring will align with and engage the nearest groove of the plurality of grooves  224 . Thus, minimal adjustment of the rod or the side latch may be necessary to install the side latch. 
       FIG. 11  is an enlarged elevation view of section  11  of  FIG. 10  showing the plurality of grooves  224  and retaining ring  210  in detail. As discussed previously, the second rod  172  is disposed in the rod coupler channel  223  and secured therein by spring clips  222 A,  222 B. Of course, while multiple spring clips are shown in  FIGS. 10-11 , any number of suitable retaining elements may be employed, as the present disclosure is not so limited. As best shown in  FIG. 11 , each of the plurality of grooves includes a first inclined lead-in  225 A, and second inclined lead-in  225 B, and a retaining groove  226 . The inclined lead-ins may be suitable to guide the retaining ring into the nearest groove when the side latch is inserted into a mortise opening. That is, the lead-ins allow the second rod and retaining ring  210  to self-align with the nearest groove based on the camming action of the inclined lead-ins. Once disposed in the retaining groove  226 , the retaining ring may transmit force between the rod coupler  220  and the second rod so that the hook latch head (see  FIGS. 8-9 ) may be moved between a hook engaged and a hook disengaged position. According to the embodiment shown in  FIGS. 10-11 , the rod coupler includes nine grooves which provide a suitable amount of self-adjustability between the side latch and the second rod. However, any suitable number of grooves may be employed to provide any suitable amount of adjustability, including, but not limited to, as few as two grooves and as many as 20 grooves. 
       FIG. 12  is a perspective view of the side latch  200  of  FIG. 9  and one embodiment of a rod guide  174 . As shown in  FIG. 12 , the rod guide includes a rod channel  175 , and rod guide slot  176 , and a base  180 . The base is configured to be mounted to the threshold portion of a door to secure the rod guide to the door. The rod channel  175  receives the second rod  172  and may be shaped and sized to limit the range of motions for the second rod. That is, the second rod may be closely fit or have a complementary shape with the rod channel so that the second rod is substantially constrained to linear motion along its longitudinal axis and alignment between the second rod and side latch is maintained. Additionally, the rod guide slot  176  is configured to receive a second rod pin  173  so that the motion of the second rod is further limited to motion along its longitudinal axis. Such an arrangement may promote reliable and consistent actuation of the side latch. Additionally, as shown in  FIG. 12 , the rod guide may extend from the bottom the door past to a position proximate the chassis  202  of the side latch. That is, the rod guide may be approximately equidistant from the bottom of a door relative to the bottom of the chassis of the side latch. Such an arrangement may provide substantial stability to the second rod without interference with the installation or operation of the side latch. Of course, the rod guide may have any suitable shape or extend any suitable distance from the bottom of the door to effectively guide the second rod, as the present disclosure is not so limited. 
       FIG. 13  is a perspective view of one embodiment of a transom latch  250  for use in the exit device of  FIG. 1 . As discussed previously, the transom latch is configured to secure an associated door to a door frame transom. The transom latch includes a chassis  252  which is secured in the top of the door by transom face plate  254 . The transom latch includes a latch head  260  and a trigger  262 . The trigger  262  has an inclined face and is configured to automatically retract when the trigger strikes a transom strike plate, whereas the latch head  260  is not configured to automatically retract. Accordingly, the trigger may be employed to time the release of the latch head  260  so that the latch head does not interfere with a transom strike plate when opening or closing the door, as will be discussed further with reference to  FIG. 14 . As shown in  FIG. 13 , the chassis  252  of the transom latch includes a transom rod guide  257  which is configured to receive the first rod  170 . The first rod guide includes a transom rod guide slot  258  configured to receive a first rod pin  171  which constrains the motion of the first rod to linear motion along its longitudinal axis and maintains alignment of the first rod with the transom latch. Accordingly, the first rod  170  may be used to reliably move the latch head  260  between engaged and disengaged positions with linear motion. 
       FIG. 14  is another perspective view of the transom latch  250  of  FIG. 14  showing the lockout  266  and trigger  262  in detail. As best shown in  FIG. 14 , the trigger  262  is configured to slide on trigger supports  259  disposed in trigger slot  265 . The trigger includes a lockout engagement portion  264  which is configured as a camming surface which moves the lockout when the trigger is moved from the extended position shown in  FIG. 14  to a retracted position. The lockout  266  is disposed on a rotatable lockout arm  267  and is configured to engage a plurality of ratchet teeth  256 . The lockout may be spring loaded so that the lockout positively engages the ratchet teeth in a resting position. The ratchet teeth are configured to allow the latch head  260  to move from the engaged position (e.g., extended position) shown in  FIG. 14  to a disengaged position (e.g., a retracted position) but does not allow the opposite motion. Accordingly, when the latch head is retracted by activation of an associated actuator and tension applied through a first rod, the lockout progressively engages the ratchet teeth to maintain the latch head in the disengaged position. When the associated actuator is released (e.g., when the door is fully open), the latch head is kept in the disengaged position by the lockout against the urging of a biasing member  268  which urges the latch head toward the engaged position. When the door closes and the trigger is retraced by a transom strike plate, the lockout engagement portion (i.e., a first camming surface) engages the rotatable lockout arm (i.e., a second camming surface) to move the lockout up and away from the ratchet teeth. When the lockout clears the ratchet teeth, the latch head may automatically return to the engaged position under influence from the biasing member  268 . The trigger  262  may be configured so that the lockout does not clear the ratchet teeth to release the latch head until the latch head is positioned over a transom latch head receptacle so that interference during extension is minimized or eliminated. 
     According to the embodiment shown in  FIG. 14  and as discussed previously, the biasing member  268  may be used to bias the entirety of the exit device mechanism toward a secure position (i.e., where all associated latches are in engaged positions). Accordingly, the lockout  266  may also be used to control the motion of the entirely of the exit device, and, in particular, an associated side latch having a hook latch head (see  FIGS. 8-9 ). That is, when the exit device is actuated and the latch head is moved to a disengaged position, a hook latch head of the side latch may also be moved to a hook disengaged position. When the lockout engages the ratchet teeth  256 , it may hold both the latch head  260  and the hook latch head in the disengaged positions so that there is no interference opening and closing the door. When the trigger causes the lockout to clear the ratchet teeth, the latch head and the hook latch head may be released so that they may be moved to the engaged and hook engaged positions, respectively. The trigger may be configured to release the latch head and hook latch head once each of the latch heads is positioned over a corresponding receptacle so that interference between the latch heads and the door frame is reduced or eliminated. 
       FIG. 15  is a front elevation view of one embodiment of a door  400  including and exit device  100  according to exemplary embodiments described herein. As shown in  FIG. 15 , the door includes an exit device  100  having a transom latch head  260 , a trigger  2662 , and a hook latch head  206  which projects from a side of the door. According to the state shown in  FIG. 15 , the exit device is in the secured position with the transom latch head  260  in an engaged position and the hook latch head  206  in a hook engaged position which would secure the door to an associated door frame transom and door jamb, respectively. As discussed previously, the trigger  262  may be configured to allow the transom latch head and the hook latch head to extend automatically when the door is closes without significant interference with the door frame. As shown in  FIG. 15 , the door also includes a handle  402  and a keyhole  404 . The handle may be coupled to a handle attachment of an actuator of the exit device, so that the handle may be turned to move the transom latch head and hook latch head toward a disengaged position and hook disengaged position, respectively. The keyhole may be operated with the use of a corresponding key which may be used to selectively allow use of the handle (i.e., lock or unlock the handle of the door). Of course, any suitable locking device and user interface for interacting with the exit device may be employed in a door, as the present disclosure is not so limited. 
       FIG. 16  is a side elevation view of the door  400  of  FIG. 15 . As shown in  FIG. 16 , the side of the door opposite that of the handle  402  includes a push bar  408  which may be used to actuate a lever of the exit device  100 . That is, a user may push on the push bar  408  to rotate the lever to move the hook latch head  206  and transom latch head  260  toward a disengaged position and hook disengaged position, respectively, to release the door. In some embodiments, the push bar may be positioned on an interior side of the door which swings outward for efficient egress of an interior space. Of course, while a push bar is shown in  FIG. 16 , any suitable user interface device which allows a user to actuate the exit device may be employed, as the present disclosure is not so limited. According to the embodiment shown in  FIG. 16  and discussed previously, a key  406  may be used to selectively allow actuation of the exit device with the handle  402 . Such an arrangement may be beneficial to lock an exterior side of the door on which the handle may be disposed. In some embodiments, the exit device may include an optional third latch head  410  disposed near the handle  402  and push bar  408  which is moved between an engaged position and disengaged position in conjunction with the transom latch head  260  and hook latch head  206 . Of course, any suitable number of latch heads or bolts may be employed in the exit device to secure the door to an associated door frame, as the present disclosure is not so limited. 
       FIG. 17  depicts one embodiment of a door including a first door panel  400 , a second door panel  500 , and a door frame  600  having a mullion  602 . The first door panel is mounted to the door frame at a first hinge interface  412  and the second door panel is mounted to the door frame at a second hinge interface  512 . As shown in  FIG. 18 , a first handle  402  is mounted to the first door panel and is configured to operate an exit device attached to the door. The exit device may include a transom latch and a side latch, similar to the embodiment shown in  FIGS. 15-16 . Additionally a keyhole  404  may be used to selectively secure the first handle  402 . According to the embodiment of  FIG. 17 , the exit device attached to the first door panel includes a side latch which engages the mullion  602 . The mullion may be secured to the door frame transom and an underlying floor so that the secured door may withstand impacts or other forces. According to the embodiment shown in  FIG. 17 , the second door panel also accommodates an attached exit device which is operable with a second handle  502 . Additionally, a second keyhole may be used in conjunction with a key to selectively secure the second handle. The exit device attached to the second door panel may be similar to that attached to the first door panel. In some embodiments, an exit device attached to the second door panel may not include a central actuator, and may instead include a transom bolt, mullion bolt, or bottom bolt which may be manually moved to secure the door. Of course, the second door panel may have any suitable exit device, latch head, bolt, or lock so that the door may be selectively secure to the door frame, mullion, or underlying floor, as the present disclosure is not so limited. 
       FIG. 18  is a top schematic of one embodiment of an exit device  600  securing a door  602  for use under high loading conditions. As shown in  FIG. 18 , the exit device includes a push bar  604  configured to be depressed to retract the latch  620 . The latch  602  of  FIG. 18  is configured as a hook latch (see  FIG. 19 ), although any suitable latch may be employed. According to the state shown in  FIG. 18 , the hook latch is in the engaged position and projects into a pocket  612  formed in a door frame  610  adjacent the door. The door is configured to swing open in the direction shown by the dashed arrow (i.e., up relative to the page). When the hook latch is in the engaged position shown in  FIG. 18 , the hook latch engages an egress loading side  613  of the door pocket  612  to resist the opening the of the door. The push bar  604  may be operable under these high loading conditions to retract the hook latch. Without wishing to be bound by theory, the force of operation to depress the push bar and retract the hook latch is dependent on the high loading on the hook latch at the egress loading side  613  of the door pocket. That is, the high loading force is transmitted to the egress loading side of the door pocket via the hook latch, and this contact force generates a resultant frictional force on the hook latch when the hook latch is moved toward the disengaged (i.e., retracted) position. Accordingly, this added friction increases the force to operate the push bar and retract the hook latch. As noted previously, this added force may increase the force of operation of the push bar which may be undesirable for emergency scenarios. 
       FIG. 19  is a front schematic of the exit device  600  of  FIG. 18  with the hook latch  620  shown isolated for clarity. According to the view shown in  FIG. 19 , the door  602  opens out relative to the page. As shown in  FIG. 19 , the hook latch is in the engaged (i.e., extended) position and projects into the pocket  612  of the door frame  610 . In particular, a hook end  622  of the hook latch projects through a strike plate  614  which forms an opening to the pocket. Accordingly, the hook latch prevents the door from opening. According to the embodiment shown in  FIG. 19 , the hook latch includes a tail end  624  which is mounted in the door  602 . The hook latch is configured to rotated about the tail end (e.g., about a pin) between the engaged and disengaged positions (for example, see  FIGS. 8-9 ). Accordingly, the hook latch is operable via the push bar (see  FIG. 18 ) to move between engaged and retracted positions. 
       FIG. 20A  is a perspective view of one embodiment of a hook latch  620  and a load blocker  630 . According to the embodiment of  FIG. 20A , the load blocker is configured to reduce a resultant frictional force during retraction of the hook latch when a door  602  is place under high loading conditions (e.g., in a direction of egress). In particular, the load blocker is configured to reduce a resultant torque on the hook latch as it is rotated between an engaged position shown in  FIG. 20A  and a disengaged position in which the hook latch is disposed in a latch opening  606  to reduce the operational force of an exit device when the door is loaded. As shown in  FIG. 20A , the load blocker  630  includes a plate  632 , an engagement beam  634 , and a hinge  636 . The plate  632  is sized and shaped to correspond to the size of the latch opening  606  formed in the door  602  so that the plate may be rotated about hinge  636  to be flush with the latch opening or project from the latch opening as shown in  FIG. 20A . According to the embodiment of  FIG. 20A , the hinge is arranged so that the plate  632  rotates about a longitudinal axis (i.e., vertical axis) of the door. Of course, the latch opening  606  may also be formed in a mortise lock or other suitable structure to allow the hook latch to extend from the door and retract into the door. 
     According to the embodiment of  FIG. 20A , the engagement beam  634  is configured to transfer force between the plate  632  and the hook latch  620 . That is, the engagement beam  634  is shaped and sized such that the engagement beam spans a gap between the hook latch and the plate so that force may be transferred therebetween. Accordingly, when a high load is applied to the door  602  (e.g., in a direction of egress or door opening shown by the dashed arrow), the plate  632  of the load blocker is configured to contact a door strike plate or pocket to resist the force. This force is resisted through the transmission of the force through the engagement beam to the hook latch, which prevents rotation of the plate about the hinge towards the latch opening  606 . As noted previously, the hook latch  620  may be configured to rotate between the engaged position and the disengaged position. Accordingly, by transmitting high loading force to the hook latch via the engagement beam, any frictional force generated is applied closer to the pivot point of the hook latch that would be the case if the hook latch directly engaged a door strike plate or pocket. Additionally, in some embodiments, the smaller contact patch between the hook latch and the engagement beam may reduce a coefficient of friction of the hook latch relative to a hook latch engaging the pocket or a strike plate. Accordingly, the resultant frictional torque from the engagement beam  634  resisting the rotation of the hook latch towards the disengaged position is less than a resultant frictional torque from the hook latch directly engaging the door strike plate or pocket. Thus, the operational force for retracting the hook latch under high loading conditions may be reduced, as will be discussed further with reference to  FIGS. 21-24 . 
     In some embodiments, the engagement beam  634  may be shaped or composed of a low friction material suitable to reduce the coefficient of friction between the engagement beam and the hook latch. For example, the engagement beam may be composed of polyoxymethylene, acetal, polyacetal, polyformaldehyde, or nylon material. Additionally, the engagement beam may be shaped to reduce irregularities or sharp edges in the contact patch between the engagement beam and the hook latch. For example, the beam may be formed as a cylinder. Of course, the engagement beam may have any suitable shape, as the present disclosure is not so limited. 
       FIG. 20B  depicts the hook latch and blocker  630  of  FIG. 20A  in a blocker disengaged position. As shown in  FIG. 20B , the plate  632  of the blocker has been rotated to be flush with the latch opening  606  formed in the door. The plate substantially covers the latch opening so that the hook latch and other components disposed therein are covered. Such an arrangement may inhibit vandalism such as stuffing the latch opening with various materials. Additionally, such an arrangement may inhibit general dirt and grime buildup inside the latch opening. Of course, the plate  632  and the latch opening  606  may have any desirable shape and arrangement, as the present disclosure is not so limited. 
       FIGS. 21-22  are top schematics of the hook latch  620  and blocker  630  of  FIG. 20A  in a secure position and an unsecure position, respectively. As shown in  FIG. 21 , the hook latch  620  in in an engaged position, projecting into a pocket  612  of the door frame  610 . Similarly, the plate  632  of the blocking member  632  also extends into the pocket, and is adjacent a portion  613  of the pocket which the plate contacts to resist an opening motion of the door in the direction shown by the dashed arrow (i.e., up relative to the page). As noted previously the plate includes a hinge  636  about which the plate rotates between a blocker engaged position shown in  FIG. 21  and a blocker disengaged position shown in  FIG. 22 . The blocker also includes an engagement beam  634  which spans a gap between the plate  632  and the hook latch  620  which prevents the rotation of the plate about the hinge towards the blocker disengaged position. That is, the engagement beam contacts the hook latch  620  when a high load is applied to the door in the direction of egress to prevent rotation of the plate and the opening of the door  602 . Accordingly, when a high load is applied to the door  602  the opening of the door is resisted by the hook latch indirectly through engagement beam  634  and plate  632 . In contrast, when an external load is place on the door (e.g., from wind pressure, airborne objects, or attempts at forcing the door) the hook latch engages the pocket  612  of the door frame direction to resist the force. In some embodiments, the door frame may also include stop molding which also resists force applied externally. 
       FIG. 22  shows the hook bolt in a disengaged position and the blocker in a blocker disengaged position so that the door  602  may be opened. From the state shown in  FIG. 21 , the plate  632  of the blocker has rotated about the hinge  636  towards the door (i.e., counterclockwise relative to the page) until the plate is flush with the door or otherwise clears the door frame  610 . According to the embodiment of  FIGS. 21-22 , the blocker may move automatically to the blocker disengaged positioned under a high load. That is, as the hook latch keeps the plate in the engaged (i.e., extended) position shown in  FIG. 21 , retraction of the hook latch may allow the contact force at the door pocket to rotate the plate  632  about the hinge towards the blocker disengaged position. In some embodiments, the load blocker  630  may include a biasing member (e.g., compression spring, extension spring, torsion spring which urges the blocker to the blocker disengaged position. In other embodiments, the blocker may include a retraction projection configured to contact the hook latch as the hook latch is moved to the disengaged (i.e., retracted) position. In this embodiment, the contact between the retraction projection and the hook latch may move the blocker to the blocker disengaged position. According to the embodiment of  FIGS. 21-22 , when the blocker is in the blocker disengaged position, the plate  632  may substantially cover a latch opening through which the hook latch extends and retracts. Accordingly, the blocker may be moved to the blocker engaged position by the hook latch when the latch is moved to the engaged position. That is, the hook latch may contact the plate  632  to push the plate open as the latch extends to engage the pocket  612  of the door frame. Thus, no actuator distinct from that used to extend or retract the hook latch is needed to move the blocker between the blocker engaged position and the blocker disengaged position. 
     As noted previously, according to the embodiment of  FIGS. 21-22 , when the blocker  630  is in the blocker disengaged position, the plate  632  may substantially cover a latch opening through which the hook latch extends and retracts (see  FIG. 20B ). Such an arrangement may be beneficial to inhibit vandalism of the latching device when the door  602  is open. That is, keeping the latch opening closed when the blocker is the blocker disengaged position may inhibit items being jammed or stuffed into the latching device, or from dirt or other material entering the latch opening. Such an arrangement may improve reliability of the latching device over period of long-term installation. 
       FIGS. 23-24  are front schematics of the hook latch  620  and blocker  630  of  FIG. 20A  in the secure position and the unsecure position, respectively. As shown in  FIG. 23 , the hook latch is disposed in the pocket  612  formed in the door frame  610  through a door strike plate  614  to secure the door  602  from being opened. Similarly, the plate  632  of the blocker is also disposed in the pocket  612  through the strike plate  614  and is configured to contact the pocket with a high load is applied to the door. The engagement beam  634  transfers the load on the plate to the hook latch and prevents the rotation of the plate to the blocker disengaged position shown in  FIG. 23 . As shown in  FIG. 24 , the blocker has rotated about hinge  636  to the blocker disengaged position where the plate  632  is not disposed in the pocket  612  of the door. In particular, the plate  632  is aligned and flushed with the door so that the blocker does not inference with movement of the door. Similarly, the hook latch is in a disengaged position and has been rotated approximately 90 degrees from the engaged position so that no portion of the hook latch projects from the door. Accordingly, the door may be opened under a high load in the state shown in  FIG. 24 . 
     According to the embodiment shown in  FIG. 23-24  and as discussed previously, the combination of the blocker  630  and the hook latch  620  may reduce the operational force used to move the hook latch from the engaged position to the disengaged position when the door  602  is under a high load. As shown in  FIG. 23 , the plate  632  and engagement beam  634  transfer the load between the hook latch and pocket to a portion of the hook latch which is nearer its axis of rotation. Accordingly, a resultant frictional torque induced by rotating the hook latch to the disengaged position may be reduced relative to a resultant frictional torque on a hook latch without a blocker as a result of the reduction in moment arm. That is, without the blocker  630 , the hook latch may contact the strike plate  614  or another portion of the pocket  612  which is a further distance from the axis of rotation of the hook latch than the contact patch between the engagement beam and the hook latch. Thus, the operational force for retracting the hook latch may be lowered by the blocker and engagement beam. 
       FIG. 25  is a perspective view of another embodiment of a hook latch  620  and a blocker  630  of a latching device which decouples high loading from the hook latch under normal operating conditions. Similarly to the embodiment of  FIGS. 20A-24 , the blocker and hook latch are disposed in a latch opening  606  formed in a door  602 . The blocker includes a plate  632 , and a hinge  636  about which the plate rotates between a blocker engaged position (shown in  FIG. 25 ) and a blocker disengaged position where the plate is flush with the latch opening  606 . In contrast to the embodiment of  FIGS. 20A-24 , the blocker also includes a wedge  638  and a bar  640  which are configured to receive a high load applied to the door, thereby preventing the high load from being transmitted to the hook latch. That is, the blocker transfers the high load applied to the door  602  to an associated door strike or pocket while the hook latch remains unloaded. According to the embodiment of  FIG. 25 , control of the hook latch may move the bar  640  to selectively secure the rotation of the blocker so that no additional actuators or linkages between a latching device and a latching location are employed. That is, the bar  640  includes a camming surface  646  configured to engage the hook latch when the hook latch is moved to the disengaged position, as will be discussed further below with reference to  FIGS. 26-29 . Of course, in other embodiments, the bar  640  may be controlled by an actuator of a latching device and any suitable linkage, as the present disclosure is not so limited. 
       FIGS. 26-27  are top schematics of the hook latch  620  and blocker  630  of  FIG. 25  in a secure position and an unsecure position, respectively. As shown in  FIG. 26 , the plate  632  of the blocker is disposed in a pocket  612  formed in a door frame  610 . The plate is adjacent a portion  613  of the pocket which contacts the plate to resist motion of the door under a high load (i.e., an egress load in the direction indicated by the dashed arrow). Additionally, the hook latch  620  is disposed in the pocket  612  and is configured to secure the door against external loads (e.g., wind pressure, airborne debris, etc.). As shown in  FIG. 26 , the wedge  638  is disposed between the plate  632  and the bar  640 . In the state shown, the bar  640  is configured to contact the wedge to prevent rotation of the blocker about the hinge  636  to the blocker disengaged position. When a high load is applied to the door, force is transmitted through the bar, wedge, and plate to the door frame, thereby bypassing force transmission though the hook latch. Accordingly, the hook latch  620  may not contact any portion of the door frame when the door is high loaded and therefore no resultant frictional force or torque will be generated. Correspondingly, the operational force of the hook latch may be kept low even during high load situations. 
     As shown in  FIG. 27 , the plate  632  and wedge  638  have rotated about the hinge  636  to the blocker disengaged position. That is, the plate  632  is flushed with the door  602  so that the blocker clears the door frame. Similarly, the hook latch  620  is disposed in the door  602  in a disengaged position. As shown in  FIG. 27 , the bar  640  has been cammed to a rotational position 90 degrees offset from the position shown in  FIG. 26 . That is, the bar has been rotated about an axis parallel to a transverse axis of the door (i.e., left and right of the page) through rotation of the hook latch  620  to the disengaged position. Accordingly, when a push bar  604  is depressed in the state shown in  FIG. 26 , the hook latch is rotated toward a retracted or disengaged position while the blocker maintains the door in a secured position, resisting any high load. As the hook latch approaches the disengaged position, the hook latch contacts and cams the bar  640  along a camming surface  646  to the second rotational position, in which the bar no longer contacts the wedge  638  to resist rotation of the blocker to the blocker disengaged position. That is, the hook latch contacts and pushes the bar out of the way of the wedge as the hook latch is moved toward the disengaged position. As a result, the force from the high load bearing on the plate and/or force from a biasing member moves the blocker to the blocker disengaged position shown in  FIG. 27 . Thus, this sequential retraction of the hook latch and blocker allows the door  602  to be opened once both are in their respective disengaged positions shown in  FIG. 27 . Any added force on the hook latch during a retraction from a high load is merely the force applied to cam the bar out of the way of the wedge  638 , which allows the operational force used to retract the hook latch to remain low even for large high loads. Of course, while a camming surface formed on the bar is shown in  FIGS. 25-29 , the camming surface may instead be formed on the hook latch, as the present disclosure is not so limited. 
       FIGS. 28-29  are front schematics of the hook latch  620  and blocker  630  of  FIG. 25  in the secure position and the unsecure position, respectively. As noted previously and as shown in  FIG. 28 , in the secure position the hook latch  620  and the blocker  630  extend into the pocket  612  of the door frame  610  to secure the door against high loads and/or external loads. In particular, the hook latch  620  and plate  632  extend through a door strike  614  which forms an opening to the pocket. The wedge  638  is positioned on the plate and is configured to transfer force between the plate  632  and the bar  640  when the blocker is in the blocker engaged position shown in  FIG. 28 . As shown in  FIGS. 28-29 , the bar  640  is supported by a bar holder  642  which is configured to rotate about bar axis  644 , but is constrained in other direction of rotation. Accordingly, the blocker engaged position, the bar receives force from the wedge in a direction approximately parallel to the bar axis which is resisted by the bar holder  644 . However, when the hook latch retracts to the disengaged position shown in  FIG. 29 , the hook latch may cam the bar along camming surface  646  to rotate the bar and bar holder about the bar axis  644  out of the path of the wedge  638 , as shown in  FIG. 29 . 
     In the state shown in  FIG. 29 , the hook latch  620  and the blocker  630  are each in their respective disengaged positions. That is the hook latch  620  is disposed entirely within the door  602  and the plate  632  is flushed with the door, and may substantially cover a latch opening formed in the door. Correspondingly, the wedge  638  has also been rotated into the door about hinge  636 . The bar  640  has been cammed about a bar axis so that the bar is no longer in the path of the wedge, which allowed the blocker to move to the blocker disengaged position relative to the state shown in  FIG. 28 . Accordingly, retraction of the hook latch may also allow the blocker to be moved to the blocker disengaged position under force of the high load or a biasing member which may be included to bias the blocker to the blocker disengaged position. This blocker biasing member may also keep the plate  632  flushed with the door when the door is moved when opened, and may further improve resiliency to vandalism as discussed previously. From the state shown in  FIG. 29 , extension of the hook latch may cause the hook latch to contact the wedge and/or plate  632  to force the block towards the blocker engaged position. That is, movement of the latch alone may be sufficient to move the blocker to the blocker engaged position. Similarly, movement of the hook latch may cam the bar rotate the bar back to a position in which the bar prevents rotation of the blocker toward the blocker disengaged position. Alternatively, in some embodiments the bar and/or bar body may include a bar biasing member configured to urge the bar to the state shown in  FIG. 28  where the bar resists motion of the blocker to the blocker disengaged position. In this embodiment, the hook latch may not contact the bar as the hook latch is extended, and the bar may move into position to secure the blocker once the wedge clears the space to be occupied by the bar. In other embodiments, the bar may be actuated by a separate linkage which may move the bar linearly or in any other suitable direction to selectively move the bar in and out of engagement with the wedge  638 . For example, a linkage may move the bar  640  into the bar body  642  when an actuator of a latching device is operated to allow the blocking member to retract, as will be discussed further with reference to  FIGS. 30-31 . 
       FIGS. 30-31  depict another embodiment of a hook latch  620  of a latching device  600  and a blocker with a bar  640  which maintains the blocker in the blocker engaged position. Similarly to the embodiment of  FIGS. 25-29 , the blocker includes a plate  632  and a wedge  638  which are configured to rotate about a hinge through a strike plate  614  and into a door pocket  612  when the blocker is in the blocker engaged position shown in  FIG. 30 . As shown in  FIG. 30 , in the blocker engaged position the blocker is retained in position by the bar  640  contacting the wedge  638  and preventing rotation of the blocker toward the blocker disengaged position shown in  FIG. 31  and thereby transferring a load on the door  602  away from the hook latch  620 . According to the depicted embodiment and in contrast to the embodiment of  FIGS. 25-29 , the bar is configured to retract and extend from a bar holder  642 . That is, the bar linearly reciprocates between a bar extended position shown in  FIG. 30 , and a bar retracted position shown in  FIG. 31 . As shown in  FIG. 31 , when the bar is retracted the bar no longer interferes with the wedge  638  and the blocker is able to be rotated to the blocker disengaged position under force of a load applied to the door in a direction of egress or under force of a biasing member. The bar may be coupled to an actuator of the latching device (e.g., a push bar, handle, etc.) and may be moved to the bar retracted position when the actuator is operated with an operational force. 
       FIGS. 32-33  depict another embodiment of a hook latch  620  of a latching device  600  and a blocker with a bar  640  which maintains the blocker in the blocker engaged position. Similarly to the embodiment of  FIGS. 25-29 , the blocker includes a plate  632  and a wedge  638  which are configured to rotate about a hinge through a strike plate  614  and into a door pocket  612  when the blocker is in the blocker engaged position shown in  FIG. 32 . As shown in  FIG. 32 , in the blocker engaged position, the blocker is retained in position by the bar  640  contacting the wedge  638  and preventing rotation of the blocker toward the blocker disengaged position shown in  FIG. 33 . In contrast to prior embodiments, the bar  640  of  FIGS. 32-33  is coupled to or formed with the hook latch  620  and rotates concurrently with the hook latch as the hook latch moves between an engaged position (see  FIG. 32 ) and a disengaged position (see  FIG. 33 ). Accordingly, when a load is applied to the door  602 , the blocker resists the force by the plate  632  contacting the door pocket  612  or strike plate  614  and the load is transferred to the bar via the wedge  638 . The load may be transferred to the hook latch in a direction towards a pin about which the hook latch rotates. The pin of the hook latch may resist the force as may various transmission elements which may couple the hook latch to an actuator of the latching device, such as a vertical rod. According to the embodiment of  FIGS. 32-33 , the force received by the bar by the blocker may urge the hook latch toward the disengaged position. A sear, trigger, or other arrangement of the latching device may then be used by an operator to retract the hook latch using a force applied to the door  602  in a direction of egress. Thus, the arrangement shown in  FIGS. 32-33  may decrease or otherwise reduce the operational force of a door when the door is under a high load in a direction of egress. 
       FIG. 34  is a block diagram for one embodiment of a method for operating a latching device having a blocker according to exemplary embodiments described herein. At block  700 , a latch begins moving toward an engaged position from a disengaged position. For example, a hook latch may be moved from a first rotational position toward a second rotational position to begin extending the hook latch from the door. As another example, a latch may be linearly moved from a first linear position to a second linear position. At block  702 , a blocker is opened with the latch as the latch moves toward the engaged position. For example, the blocker may include a plate which substantially covers a latch opening which may be contacted by the latch. Opening the blocker may include rotating the blocker about a hinge, or may include moving a blocker linearly (for example, see  FIG. 35 ). At block  704 , the latch is moved to the engaged position. In the engaged position, the latch may secure the associated door from external loads place on the door (e.g., wind pressure, airborne debris, etc.). At block  706 , the blocker resists force applied to an associated door in a direction of egress (i.e. a direction in which the door opens) with the blocker. For example, the blocker may transfer the load to the latch at a mechanically advantaged portion (e.g., by reducing a moment arm for resultant frictional forces on a latch) or may resist the force directly (e.g., with a bar). At block  708  an actuator is operated to move the latch to the disengaged position. For example, the actuator may be a push bar of an exit device, or may be a handle or lever. At block  710  the blocker may be closed. Closing the blocker may include moving the blocker into the associated door or flushed with the associated door. In some embodiments, the steps in blocks  708  and  710  may happen concurrently. 
       FIG. 35  is a top schematic of yet another embodiment of a latching device  600  having a latch  620  securing a door  602 . As shown in  FIG. 35 , the latching device does not include a blocker, but includes a curved high load face  616  configured as a convex surface arranged along a portion  613  of a pocket  612  which resists a high egress load applied to the door. Without wishing to be bound by theory, the curved high load face may reduce sharp contact patches, thereby reducing the coefficient of friction between the door frame and the latch. Additionally, the curved face may convert from of the high load contact forces into a normal force directing the latch toward a retracted or disengaged position. This normal force may assist an operator in using an actuator to open the door. Thus, the curved high load face may be employed to reduce the coefficient of friction and/or generate normal forces which reduce the retraction force of the latch under high loads. The embodiment of  FIG. 35  may be employed in combination with other embodiments described herein to further reduce the operational force for retracting the latch  620  under a high load. 
       FIG. 36  is a top schematic of yet another embodiment of latching device  600  having a latch  620  securing a door  602 . As shown in  FIG. 36 , the latching device does not include a blocker, but includes allow friction material  618  arranged along a portion  613  of a pocket  612  which resists a high load applied to the door. Without wishing to be bound by theory, the low friction material may reduce the coefficient of friction between the door frame and the latch. Additionally, as shown in  FIG. 36  the latch  620  includes a low friction latch material  626  configured to contact the low friction material  618  disposed in the pocket  613 . The low friction material and low friction latch material may be formed of polyoxymethylene (or another acetal, polyacetal, or polyformaldehyde), nylon, or any other suitable material, as the present disclosure is not so limited. Thus, the low friction materials may be employed to reduce the coefficient which reduces the retraction force of the latch under high loads. The embodiment of  FIG. 36  may be employed in combination with other embodiments described herein to further reduce the operational force for retracting the latch  620  under a high load. 
       FIG. 37  is a top schematic of yet another embodiment of a latching device  600  including a latch  620  securing a door  602 . As shown in  FIG. 37 , the latching device does not include a blocker, but instead the latch  620  is offset relative to a center of a pocket  612  of a door frame  610  and/or door  602 . More specifically, the latch  620  is spaced a first distance D 1  from a portion  613  of the pocket  612  which resists force when the door is placed under high loading as shown by the dashed arrow. According to the embodiment of  FIG. 37 , such a latch arrangement may be employed in combination with one or more other latches which are not spaces from their respective pockets. When the latch of  FIG. 37  is employed with other non-offset latches, before the latch  620  engages the pocket of the door frame, the door may move or deflect in the direction of opening. That is, the other non-offset latches may resist the load applied to the door, and the latch  620  may only contact the portion  613  of the pocket  612  when the door deflects or moves to eliminate the first distance D 1 . Accordingly, the gap may prevent or otherwise reduce contact between the latch  620  and the door pocket  612  when used in combination with one or more other non-offset latches, thereby reducing the resultant frictional forces when the latch  620  is moved to a disengaged position. Such an arrangement may be particular beneficial for hook latches which rotate between engaged positions and disengaged positions, as this rotation may generate significant frictional forces under a high load. The embodiment of  FIG. 36  may be employed in combination with other embodiments described herein to further reduce the operational force for retracting the latch  620  under a high load. 
       FIG. 38  is a top schematic of yet another embodiment of a latching device  600  having a latch  620  securing a door  600 . According to the embodiment of  FIG. 38 , the latching device also includes a second latch  628  which is adjacent to the latch  620  and extends into the same pocket  612 . The second latch  628  is disposed adjacent a first portion  613  of the pocket  612  which resists forces applied to door under high loading, while the latch  620  is positioned adjacent a second portion  615  which resists external forces applied to the door. Accordingly, when the door is undergoing high loading, the second latch  628  secures the door, while under external loading the latch  620  may secure the door. According to the embodiment of  FIG. 38 , the latch  620  may be a hook latch which rotates between engaged and disengaged positions, whereas the second latch  628  is configured as a latch bolt which moves linearly between the engaged and disengaged positions. The latch  620  and the second latch  628  may be coupled to one another to move between the engaged and disengaged positions concurrently. Without wishing to be bound by theory, the resultant frictional forces generated by a hook latch which increase an operational force of a latching device under load may be greater than those generated by a latch bolt under load because of the different in retraction motion (i.e., rotational motion versus linear motion). For example, the mechanical advantage of a frictional force working with a moment arm on a rotating latch may increase the operational force of a door more so than frictional force on a reciprocating latch. Accordingly, the arrangement of  FIG. 38  may reduce the operational force to retract the latch  620  and the second latch  628  when the door is under high loading. As shown in  FIG. 34 , the second latch  628  also includes an inclined face  629  which is configured to convert some of the contact forces between the second latch and the pocket into normal forces which assist the retraction of the second latch. That is, as the second latch begins retracting, the inclined face may contact the pocket and this contact may urge the second latch toward a disengaged position. Such an arrangement may further reduce the operational force to retract the latch  620  and the second latch  628 . The embodiment of  FIG. 38  may be employed in combination with other embodiments described herein to further reduce the operational force for retracting the latch  620  under a high load. 
       FIG. 39  is a top schematic of yet another embodiment of a latching device  600  having a latch  620  securing a door  600 . According to the embodiment of  FIG. 39 , the latch  620  is a hook latch which rotates between a latch engaged position and a latch disengaged position and is sized and shaped to reduce resultant friction when the latch is moved to the latch disengaged position and an associated door is loaded in a direction of egress. As shown in  FIG. 39 , the hook latch is curved or tapered to reduce the side of a contact patch between the hook latch and a strike or pocket  612  formed in a door frame  610 . That is, the hook latch has a convex surface configured to engage an associated door pocket  612  or door strike. Such an arrangement may reduce the coefficient of friction between the hook latch and the strike or door pocket. In some embodiments, the hook latch may rotate on a bearing about an axis of rotation of the hook latch. Such an arrangement may reduce the resultant friction generated when the hook latch is rotated to the latch disengaged position. The embodiment of  FIG. 39  may be employed in combination with other embodiments described herein to further reduce the operational force for retracting the latch  620  under a high load. 
     It should be understood that a latching device such as an exit device latch may include any suitable number and type of latches in any suitable location which may employ blockers to reduce operational force under high loading of a door. For example, in some embodiments, an exit device operable with a push bar may operate a single latch at a center portion of a door. In other embodiments, an exit device may be operate multiple latches which are coupled with one or more vertical rods, such as transom latches, bottom latches, or side latches disposed away from a central portion of a door. Additionally hook latches, deadbolts, or latch bolts may be employed in any of these latching locations. Accordingly, it is contemplated that exemplary embodiments of blockers described herein with reference to  FIGS. 20A-34  may be applied to any latching device having a latch, as the present disclosure is not so limited. 
     In some embodiments, door secured with latching devices according to exemplary embodiments described herein may be suitable for use with exit devices in high loading situations. For example a latching device may be cycle tested to at least 500,000 cycles, and, in some embodiments, at least 1,000,000 cycles. During this cycle testing, the watching device may be preloaded with a weight. In some embodiments, while the door is latched, a force of 20 to 22 lbf (˜80 to 98 N) is applied in the direction of the door swing, 3 inches from a latch edge and 40 inches from the floor. After the preload force is applied, the hardware is then actuated, the door opens, closes, and latches, completing the cycle. Of course, in other embodiments, greater preload may be applied to the door or any other suitable preload for cycle testing. In some embodiments, the door may be tested to a high load of at least 250 lbs (˜1100 N) in a direction of egress. Under this load, the latching device may be operable with a force of under 50 lbs (˜220 N) to retract one or more latches retaining the door against the 400 lbs high load. In a loaded or unloaded condition, latching devices of exemplary embodiments herein may be operable with a force of under 15 lbs (˜66 N), 5 lbs (˜22 N), and or any other suitable operational force. The high load testing may be performed before and after cycle testing as described above, except the latching device may be tested to at least 100,000 cycles before a second high load test. Of course, doors secured by the latching devices of embodiments described herein may meet any suitable standards for use in high occupancy areas, including, but not limited to UL 305, ANSI/BHMA A156.3, NFPA 101, IBC, and/or any other modern or updated testing standard, as the present disclosure is not so limited. 
     In some embodiments, doors secured with latching devices according to exemplary embodiments described herein may be suitable for use in high wind areas. For example, a door secured by the latching device of  FIG. 1  may withstand a first impact from a 6.8 kg 2×4 piece of lumber traveling at a speed between 80 mph and 100 mph near the transom latch. The same secured door may then subsequently withstand a subsequent second impact from a 6.8 kg 2×4 piece of lumber traveling at a speed between 80 mph and 100 mph near the actuator. Finally, the same secured door may subsequently withstand a subsequent third impact from 6.8 kg 2×4 piece of lumber traveling at a speed between 80 mph and 100 mph near a hinge interface of the door. In cases where a pair of doors is employed and at least one is secured with a latching device according to exemplary embodiments disclosed herein, the secured door may withstand a subsequent fourth impact from a 6.8 kg 2×4 piece of lumber traveling at a speed between 80 mph and 100 mph near a mullion interface between the two doors. Additionally, a door secured by an latching device of exemplary embodiments described herein may withstand positive or negative pressure as a result of wind speeds between 130 and 250 mph. Withstanding the above noted impacts or pressures may be determined at least partially by measuring perforation of a witness screen placed proximate the door. That is, a door withstands impact or pressure when a #70 unbleached kraft paper witness screen with its surface secured in place on a rigid frame installed within 5 inches of the interior surface of the door remains unperforated after the impact or pressure. Furthermore, a door may withstand impact or pressure when permanent deformation of the door measured from a straight edge held between two undeformed points on the door is less than or equal to 3 inches. Of course, doors secured by the latching devices of embodiments described herein may meet any suitable standards for use in high wind areas, storm shelters, etc., including, but not limited to ICC 500, FEMA P361, FEMA P320, or any other modern or updated testing standard, as the present disclosure is not so limited. 
     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.