Abstract:
A vertical panic exit device is interchangeably mountable on either left-hand opening or right-hand opening doors and comprises a latch mechanism for engagement with a strike mounted to a doorjamb to alternately transition a door mounted to the jamb in a latched and unlatched configuration. A central portion includes a push bar; an action rod interlinked to said push bar such that a depression of the push bar causes the action rod to be translated in a direction orthogonal to the push bar, and a center case mechanism movable between a latched and an unlatched position. The center case mechanism comprises a housing, and a main link carriage horizontally slidably mounted within the housing. The main link carriage is linked to and is acted upon by the action rod for translation between the latched and unlatched position. An actuator link has a first end pivotally attached to the main link carriage. A pivoting member is pivotally mounted to the housing and has first and second pivotal attach points. A second end of the actuator link is selectively coupled to one of either the first or second attach points. When the second end of the actuator link is selectively coupled to the first attach point, it configures the center case mechanism for latching and unlatching a right handed opening door, and when selectively coupled to the second attach point, it configures the center case mechanism for latching and unlatching a left handed opening door. A slider is vertically slidably mounted within the housing and is in movable engagement with the pivoting member such that a pivoting motion of the pivoting member causes the slider to slide in a vertical direction. The slider includes at least one attach point for connection with the latch mechanism.

Description:
BACKGROUND OF TEE INVENTION. 
     1. Field of the Invention 
     The invention relates to door hardware, and more particularly to a panic exit device with a panic bar pad actuating mechanism that latches the door at the top and bottom rather than at the side. 
     2. Description of the Related Art 
     Panic exit devices are commonly used on doors in public settings. The push pad translates a user&#39;s push against a moveable bar into the unlatching of the doors latch mechanism, allowing the pedestrian entry or exit. For example, U.S. Pat. No. 3,614,145 entitled “Dogging Device for Panic Exit Latch and Actuator Assembly,” discloses a standard push pad assembly which translates a forward motion of the pad into a lateral motion that withdraws a latch bolt from a strike plate. U.S. patent application Ser. No. 09/056,261, filed Apr. 7, 1998, now U.S. Pat. No. 6,009,732, entitled “Panic Exit Device”, describes the related art, and discloses an improved panic exit device that can be used in either a horizontal installation, where the latch interconnects with a strike mounted in the vertical portion of the door frame, or that can be adapted to be used in a vertical installation, wherein the latch and locking rod interconnect with strikes mounted in the door header and in the floor. Improvements upon the standard push pad assembly that are disclosed in the Panic Exit Device patent include an improved latch deadlocking mechanism, an improved latch to pad mechanism, a pad lock down feature, a universal mounting plate and easily mounted strike, and a vertical rod-bottom deadlocking mechanism in the center case of the device. This application discloses further improvements upon the vertical panic exit device disclosed in the Panic Exit Device patent. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a panic exit device and fire exit device used on doors in schools, hospitals, public buildings and other commercial buildings. The device comprises a center case mechanism combined with a pad actuating mechanism and a top latch mechanism. The center case mechanism controls the top or bottom actuating rods. The top actuating rod controls the top latching mechanism mounted at the top of the door. The device incorporates several novel features including: (1) a simplified dual deadlocking design; (2) a simplified center case mechanism that is “non-handed,” meaning that it can be installed on either a right-hand opening door or a left-hand opening door; and (3) an improved and simplified deadlocking mechanism located at the upper latch rather than in the center case mechanism. 
     One aspect of the invention is a vertical panic exit device interchangeably mountable on either left-hand opening or right-hand opening doors. The device comprises a latch mechanism for engagement with a strike mounted to a doorjamb alternately transition a door mounted to the jamb in a latched and unlatched configuration. A central portion includes a push bar; an action rod interlinked to said push bar such that a depression of the push bar causes the action rod to be translated in a direction orthogonal to the push bar, and a center case mechanism movable between a latched and an unlatched position. The center case mechanism comprises a housing, and a main link carriage horizontally slidably mounted within the housing. The main link carriage is linked to and is acted upon by the action rod for translation between the latched and unlatched position. An actuator link has a first end pivotally attached to the main  2 ink carriage. A pivoting member is pivotally mounted to the housing and has first and second pivotal attach points. A second end of the actuator link is selectively coupled to one of either the first or second attach points. When the second end of the actuator link is selectively coupled to the first attach point, it configures the center case mechanism for latching and unlatching a right handed opening door, and when selectively coupled to the second attach point, it configures the center case mechanism for latching and unlatching a left handed opening door. A slider is vertically slidably mounted within the housing and is in movable engagement with the pivoting member such that a pivoting motion of the pivoting member causes the slider to slide in a vertical direction. The slider includes at least one attach point for connection with the latch mechanism. 
     Another aspect of the present invention is a center case mechanism for a vertical panic exit device that is operable between a latched and an unlatched position. The center case mechanism comprises a housing and a main link carriage horizontally slidably mounted within the housing. The main link carriage being translatable between the latched and the unlatched positions. An actuator link has a first end pivotally attached to the main link carriage. A pivoting member is pivotally mounted to the housing and has first and second pivotal attach points. A second end of the actuator link is selectively coupled to either one of the first or second attach points. When the second end of the actuator link is selectively coupled to the first attach point it configures the center case mechanism for latching and unlatching a right handed opening door, and when selectively coupled to the second attach point it configures the center case mechanism for latching and unlatching a left handed opening door. A slider is vertically slidably mounted within the housing and is in movable engagement with the pivoting member such that a pivoting motion of the pivoting member causes the slider to slide in a vertical direction. The slider includes at least one attach point for connection with a latch mechanism. 
     Yet another aspect of the present invention is an upper latching mechanism for a vertical panic exit device. The latching mechanism comprises a housing and a latch pivotally mounted to the housing. The latch is pivotable between an extended latched position for engagement with the doorjamb mounted strike, and a retracted position for opening the door. An actuator rod receptacle is slidably retained in the housing, and a linkage interconnects the latch and the receptacle. The linkage translates an upward movement of the actuator rod receptacle to a downward retracted pivoting of the latch. 
     These and other advantages of the invention will be further understood and appreciated by those skilled in the art by reference to the following written specification, claims, and appended drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a perspective view of a door having mounted thereon a panic exit device embodying the present invention. 
     FIG. 2 is a perspective view of the center portion of the vertical panic exit device including the push bar. 
     FIG. 3 is a perspective view of center case mechanism. 
     FIG. 4 is a perspective view of the pivoting member within the center case mechanism. 
     FIGS. 5 a ,  5   b , and  5   c  show front, side, and rear views of the slider within the center case mechanism. 
     FIG. 6 illustrates the center case to pad mechanism that translates the forward motion of the on of the main link carriage. 
     FIGS. 7 a  and  7   b  illustrate the center case mechanism from the rear and front respectively, showing the panic exit device in a closed and latched position. 
     FIGS. 8 a  and  8   b  illustrate the center case mechanism from the rear and front respectively showing partial movement of the center case mechanism when the push pad actuator is depressed. 
     FIGS. 9 a  and  9   b  illustrate the center case mechanism from the rear and front respectively showing the panic exit device in an open and unlatched position. 
     FIGS. 10 a  and  10   b  illustrate the center case mechanism from the rear and front respectively showing the engagement of the deadlock feature when the door is in a closed and latched position. 
     FIG. 11 shows a sectional view of the center case mechanism taken along line XI—XI of FIG. 3 showing the main link carriage and its interface with the housing and the deadlocking plate. 
     FIG. 12 is a side view showing the dogging mechanism, lock cylinder, bracket, action rod, and hook member. 
     FIGS. 13 a ,  13   b , and  13   c  illustrate the dogging mechanism, showing the interaction of the latching element within the dogging mechanism and the hook member. 
     FIG. 14 is a perspective view of the upper latch mechanism and upper latch. 
     FIG. 15 shows the two step vertical hold arm within the upper latch mechanism. 
     FIGS. 16 a ,  16   b , and  16   c  show the action of the two step vertical hold arm as the actuating rod receptacle moves up and the upper latch retracts. 
     FIGS. 17 a ,  17   b , and  17   c  show the operation of the deadlocking lever in the upper latch mechanism. 
     FIGS. 18 a , and  18   b  show the interface of the lower locking pin with the lower vertical actuating rod, and the lower cover profile. 
     FIG. 19 is a perspective view showing the mounting plate for the upper latch mechanism. 
     FIG. 20 is a cross-sectional view of the door and rod cover taken along the line XX—XX of FIG. 18 b.    
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     For purposes of description herein, the terms “upper”, “lower”, “right”, “left”, “rear”, “front”, “vertical”, “horizontal”, and derivatives thereof shall relate to the invention as oriented in FIGS. 1 and 3. However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     The vertical panic exit device of the present invention improves upon prior art devices in a several areas. First, it incorporates an improved latch deadlocking design. The center case and the upper latch mechanism both incorporate deadlock features as described below. The deadlock feature of the center case functions as the deadlock feature of the bottom bolt, and as a secondary redundant deadlock of the upper latch mechanism that incorporates its own deadlock feature. However, the top latch deadlock does not function to deadlock the lower bolt. Second, the device includes a simplified center case mechanism that is “non-handed,” meaning that it can be installed on either a right-hand opening or a left-hand opening door. Third, the present invention incorporates an improved and simplified fire locking mechanism located at the upper latch, rather than in the center case mechanism. Finally, the improved vertical panic exit device includes an improved lower cover at the bottom of the door. The lower cover provides a gentle transition between the surface of the door and the outer surface of the cover, making the design more compatible with the requirements of the Americans with Disabilities Act (ADA). 
     FIG. 1 shows the vertical panic exit device  100  of a preferred embodiment as it would appear in use, mounted on a door  50 . Although this style of panic exit is used primarily on double doors with a strike in the header and a strike in the floor, only a single door is shown in FIG. 1 for simplicity. A second adjacent door would typically employ a mirror image configuration. A push pad actuator or push bar  106  is shown mounted to the door  50  along with a dogging mechanism  112 , case filler  108 , and an end cap  10 . Dogging mechanism  112  is optional and is not required for operation of the preferred embodiment, and by building codes cannot be included in a fire exit device. A center case mechanism  200  (FIG. 3) under cover  212  is used to translate the motion of the push bar  106  to a pair of vertical actuating rods  202  and  204 , located under covers  201  and  203 , respectively. Vertical actuating rod  204  controls a latching mechanism  300  (FIG. 14) located under cover  209  and a latch  210 . As vertical actuating rod  204  moves upward, latching mechanism  300  operates to translate the upward motion into a retraction of latch  210 . Vertical actuating rod  202  controls the vertical translation of a bolt  206  for engagement and disengagement with a corresponding floor aperture (not shown). When push pad actuator  106  is depressed against door  50 , vertical actuating rods  202  and  204  and latching mechanism  300  operate cooperatively to retract both bolt  206  and latch  210  so that the door may open freely. 
     FIG. 2 shows a perspective view of the center portion of the vertical panic exit device  100 . The center portion includes a base plate  102  (FIG. 12) covered by a housing  104 . Push pad actuator  106  is captured by the base plate  102  so that it can move between a first, outward position and a second inward or depressed position. The push pad actuator  106  can extend the entire length of the base plate, but in a preferred embodiment, push pad actuator  106  only extends a portion of the length of the base plate  102 . A case filler  108  can be used to fill the unused length of the base plate  102 . An end cap  110  can be used to prevent any lateral movement of the push pad actuator  106  or case filler  108 . The end cap  110  also presents a smoother aesthetically pleasing surface. The case filler  108  can have an opening to accept dogging mechanism  112  which is coupled between the case filler  108  and the push bar  106 . As will be discussed in greater detail below, the dogging mechanism  112  is used to lock the push bar in its second, inward, and open position. Finally, center case mechanism  200  (FIG. 3) is housed under cover  212  and is operably engaged with push bar  106 . 
     FIG. 3 is a perspective view of center case mechanism  200 . Center case mechanism  200  includes housing  122  which is mounted to mounting bracket  121 . Bracket  121  is mounted flush to an inner surface  52  of door  50 . Housing  122  includes a main portion and two “arm” portions, designated  122   a  and  122   b  in FIG.  3 . Center case mechanism  200  also includes an internal cover  124  which couples to the housing  122  and extends outward from the housing  122 . The internal cover  124  couples to and encloses a main link carriage  128 , via pin  130  which slides along slots  126 . A deadlocking plate  140  (FIG. 7 a ) is captured between the main link carriage  128  and the housing  122 . Deadlocking plate  140  is connected to main link carriage  128  such that lateral movement of carriage  128  results in a like lateral movement of plate  140 . The main link carriage  128  and deadlocking plate  140  retract in response to the movement of the push pad actuator  106 . Details regarding the operation of the main link carriage  128  and the deadlocking plate  140  are provided below. 
     The main link carriage  128  is coupled to a first end of actuator linkage  120  with a pin and bushing combination  129  thereby permitting the pivotal movement of linkage  120  about pin and bushing  129 . The second end of actuator linkage  120  includes a slot  123  that couples actuator linkage  120  to pivoting member  116  at either post  116   a  (as shown in FIG. 3) or post  116   b  and is retained thereon by locking  118 . As will be discussed in further detail below, when actuator linkage  120  is coupled to post  116   a  of pivoting member  116 , the center case mechanism is set for installation on a right hand opening door. Alternatively, when actuator linkage  120  is coupled to post  116   b  of pivoting member  116 , the center case mechanism  200  is set for installation on a left hand opening door. Thus, the center case mechanism  200  is not “handed,” in the sense that a left hand design is different from a right hand design. Reconfiguring the “handedness” of center case mechanism  200  is accomplished by switching actuator linkage  120  between posts  116   a  and  116   b  and rotating center case mechanism  200  one-hundred-eighty degrees within its vertical plane. Actuator linkage  120 , when properly configured, is on the upper one of posts  116   a  and  116   b . The individual installing the panic exit device  100  on the door  50  can easily accomplish configuring center case mechanism  200  immediately prior to installation. 
     FIG. 4 shows a perspective view of pivoting member  116 . As shown in FIG. 4, pivoting member  116  includes posts  116   a  and  116   b , which couple to actuator linkage  120  as discussed above. Pivoting member  116  also includes pins  117  and  119 . 
     Referring again to FIG. 3, pivoting member  116  pivots about pin  117 . Pin  117  also couples pivoting member  116  to internal cover  124 . Pin  119  couples to slider  114  by engaging slot  114   e  (FIGS. 5 a  &amp;  5   b ). When main link carriage  128  and actuator linkage  120  move horizontally is response to depression of the push pad actuator  106 , pivoting member  116  pivots about pin  117  and pin  119  translates slider  114  in a vertical upward direction, thus translating horizontal motion to vertical motion. 
     Referring now to FIGS. 3 and 5 a - 5   c , slider  114  includes cavities  114   a  and  114   b , which are sized to accept and capture the heads of bolts  205  and  207 . Bolts  205  and  207  couple to internally threaded vertical actuating rods  202  and  204 , respectively. Bolts  205  and  207  are retained within cavities  114   a  and  114   b  by locking plates  136  and  138  respectively. The range of vertical motion of slider  114  is limited by shoulders  114   c  and  114   d , which contact stops  132  and  134 , respectively, at the outer ranges of allowable motion of slider  114 . An intermediate buffer material such as a soft plastic coating or insert can be included to reduce the noise of slider  114  contacting stops  132  and  134 . Stops  132  and  134  are retained in housing arms  122   a  and  122   b , respectively. A deadlocking stop  114   f  is positioned midway along the rear face of slider  114 . 
     FIG. 6 illustrates the mechanism interlining the push bar  106  with center case mechanism  200  that translates the depressive motion of the push bar  106  into the lateral motion of the main link carriage  128 . The push bar  106  is connected to an action rod  158  by a rocking mechanism  160 . When push bar  106  is depressed toward door  50  rocking mechanism is pivoted about a vertical axis thereby translating the depressive motion applied to the push bar  106  into a lateral movement of the action rod  158 . The action bar is coupled to the main link carriage  128  by a hook  162  that engages pin  130 . 
     FIG.11 shows a cutaway view of the center case mechanism  200  showing main link carriage  128  and its interface with the housing  122  and the deadlocking plate  140 . As shown in FIG. 11, housing  122  includes flange  122   c , and main link carriage  128  includes flange  128   a  and two pairs of tabs, designated as  128   b  (first pair) and  128   c  (second pair). Tabs  128   b  and  128   c  extend through slots in the deadlocking plate  140  and in the housing  122 , thus capturing the deadlocking plate  140  between the main link carriage  128  and the housing  122  and causing the main link carriage  128  and the deadlocking plate  140  to move together. Rod  139  couples to housing flange  122   c , and extends through a hole in flange  128   a  Compression spring  141  is telescoped over rod  139  and exerts a biasing force against flange  128   a  of main link carriage  128 , thus biasing main link carriage  128  and deadlocking plate  140  toward slide  114 . This position situates the center case mechanism  200  as shown in FIGS. 7 a/b , with deadlocking plate  140  extended fully and deadlocking stop  114   f  on slider  114  below the deadlocking plate  140 . Thus, when the center case mechanism  200  is in this position, the door is locked on the outside, i.e., the door cannot be opened from the outside and can only be opened from the inside by pushing on the push bar  106 . 
     FIGS. 7 a/b - 9   a/b  illustrate operation of the center case mechanism  200 , showing the movement of the center case mechanism  200  when the push pad actuator  106  is depressed. The “a” suffixed figures illustrate mechanism  200  from the rear showing the relationship of deadlocking plate  140  with respect to slide  114 , and the “b” suffixed figures illustrate mechanism  200  from the front showing the corresponding movement of link  128  and pivoting member  116 . In FIGS. 7 a/b , the center case mechanism is shown in its starting, locked position, as it would appear when the push pad actuator  106  has not been depressed. Shoulder  114   d  of slider  114  is resting against stop  134  and limits the downward travel of slider  114 . Deadlocking stop  114   f  on the rear side of slider  114  is below deadlocking tab  142  of the deadlocking plate  140 , insuring that slider  114  is prohibited from moving upward to disengage the upper latch  210  and lower peg  206  thereby maintaining door  50  in a closed and latched position. 
     Referring now to FIGS. 8 a/b , the push pad actuator  106  is partially depressed. Carriage link  128  and actuator linkage  120  are being translated to the right approximately 0.30 inch thereby causing pivoting member  116  to begin pivoting about pin  117 . (Note: dimensional references herein with respect to FIGS. 7 a/b - 10   a/b  are for illustrative purposes only and can vary according to the design of a specific embodiment.) As pivoting member  116  pivots about pin  117 , pin  119  is moved vertically upward and by reason of its engagement in slot  114   e  correspondingly translates slider  114  vertically upward. As carriage link  128  and deadlocking plate  140  are drawn away from slider  114 , deadlocking tab  142  is horizontally withdrawn from the vertical path of deadlock stop  114   f , thereby allowing slider  114  unobstructed vertical travel in an upwards direction causing the upward translation of vertical actuating rods  202  and  204 . 
     Referring now to FIGS. 9 a/b , the push pad actuator  106  has been completely depressed. Carriage link  128  and deadlock plate  140  have reached their maximum translation of 0.60 inch to the right limited by compression of spring  141  and the contact of shoulder  114   c  with stop  132 . Slider  114  has traveled upward its full distance of 0.767 inch. Pivoting member  116  has reached its maximum rotation about pin  117  and pin  119  has reach its maximum vertical upward travel. Actuating rods  202  and  204  have correspondingly been raised to effect unlatching of door  50  to permit door  50  to be swung open. The operation of the unlatching effected by actuating rods  202  and  204  are discussed in further detail below. Upon release of push pad actuator  106 , the weight of slider  114  and rods  202  and  204  in combination with the biasing force of spring  141  automatically return center case mechanism  200  to its latched configuration as shown by FIGS. 7 a/b.    
     FIGS. 10 a/b  show the interaction of deadlock stop  114   f  and deadlock tab  142  to maintain door  50  in its latched configuration when push pad actuator  106  is not depressed. In the event that an attempt is made to vertically translate slider  114  without depressing push pad actuator  106 , the door will remain latched in a “deadlock” condition. Without depressing push pad actuator  106 , carriage link  128  and deadlock plate  140  remain in their leftmost position. In this position, deadlock tab  142  extends within the reach of deadlock stop  114   f . As slider  114  is vertically raised, deadlock stop  114   f  contacts stationary deadlock tab  142 . The upward movement of slider  114 , wherein deadlock stop  114   f  contacts stationary deadlock tab  142 , is facilitated by slot  123  in the second end of actuator linkage  120  and the movement of pin  116   a  or  116   b  therein. Slot  123  in actuator linkage  120  is required in order to permit the upward movement of slider  114  without a corresponding lateral movement of deadlock plate  140 , thereby resulting in the contact of deadlock stop  114   f  with deadlock tab  142 . As long as deadlock plate  140  remains stationary (no depression of push pad actuator  106 ), deadlock tab  142  blocks deadlock stop  114   f  and prevents the upward translation of slider  114 , thus maintaining panic exit device  100  in a latched condition. 
     FIGS. 12 and 13 a - 13   c  illustrate the interaction of the dogging mechanism  112  with the action rod  158  and lock cylinder  112   a . The dogging mechanism  112  is mounted to a bracket  166  that is affixed to case filler  108 . The dogging mechanism  112  and bracket  166  are not coupled to the base plate  102 , thus allowing the assembly to be easily removed in the factory or during installation for an alternate function such as replacement of worn parts or upgrading to new assemblies. Shims  170  can be used for height adjustments needed for different lock cylinder links on commercially available lock cylinder styles. 
     The dogging mechanism  112  comprises a latching element  168  which can engage a second hook element  164  coupled to the action rod  158 . As shown in FIGS. 13 b  and  13   c , the latching element  168  has a cam surface  168   a  Latching element  168  includes along projecting tail to prevent it from blocking the movement of action rod  158 . When the latching element  168  is rotated, cam surface  168   a  engages the hook element  164  when the action rod  158  and main link carriage  128  are fully retracted, thus dogging the latch bolt into an open position. In order to rotate dogging mechanism  112 , a key is inserted into lock cylinder  112   a , shown in FIG. 12, which is coupled to tail piece  112   b  as shown in FIGS. 13 a - 13   c . Tail piece  112   b  slides in slot  112   c  in latching element  168 . As tail piece  112   b  reaches either side of slot  112   c , it causes latching element  168  to rotate and engage or disengage the action rod  158  via the hook element  164 . Slot  112   c  can be made variable widths to accommodate different rotational requirements of different commercially available lock cylinders as well as to allow the key to be rotated back to its home position for removal. 
     Detents  168   b  allow the dogging mechanism to be positively positioned in a variety of positions. For example, three detents are shown in FIGS. 13 a - 13   c . The detents can serve other purposes as well. For example, when the dogging mechanism is in the second detent, as shown in FIG. 10 b , then an electrical contact  168   c  could be made to initiate an electrical control signal, for instance, to control a security notification, solenoid or other apparatus. If a solenoid were actuated, it could possibly even retract the action bar. FIG. 10 c  illustrates the dogging mechanism seizing the hook element  164  and the action rod  158  in position. 
     FIG. 14 is a perspective view of the upper latch mechanism  300  and upper latch  210 . Upper latch mechanism  300  includes a mounting plate  301  (more fully described below), housing  302 , an actuator rod receptacle  304 , first linkage  306 , a pair of pivoting linkages  308  and  310 , and a pair of third linkages  312  and  314 . FIG. 14 also shows two-step vertical hold arm  316 , deadlocking lever  318 , upper latch  210  which further includes pin  372 , torsion spring  320 , fire lock spring  322 , fire lock bushing  324 , and meltable element  326 . 
     As shown in FIG. 14, actuator rod receptacle  304  couples to housing  302  via pin  328 , which engages slots  330  and  332  (not shown) in housing  302 . Actuator rod receptacle  304  receives upper vertical actuating rod  204 , which is held in place by setscrews  338 . 
     Actuator rod receptacle  302  includes slot  302   a . As shown in FIG. 14, first linkage  306  couples at a first end to actuator rod receptacle  302  and pin  328 . The second end of first linkage  306  couples to the first end of pivoting linkages  308  and  310 . Pivoting linkages  308  and  310  pivot about pin  344 , and couple at their second end to the first end of third linkages  312  and  314 . The second ends of third linkages  312  and  314  couple to latch  210  via pin  346  (FIGS. 16 a-b ). 
     Two step vertical hold arm  316  is coupled to housing  302  by pin  348  and lock rings  350 ,  352 , and  354 . Two step vertical hold arm  316  includes pin  356 , which extends through slot  358  in housing  302 . Deadlocking lever  318  couples to housing  302  with pin  344 . Deadlocking lever  318  further includes pin  366 , which extends through slot  368  in housing  302 . Torsion spring  320  biases the latch  210  in an outward, extended position, and biases two step vertical hold arm deadlocking lever  318  in an upward position by engaging pins  356  and  366 . Torsion spring  320  is held in place by pins  356 ,  366 , and  372 . Pin  372  also couples latch  210  to housing  302 . 
     FIG. 15 shows two step vertical hold arm  316  in further detail. As shown in FIG. 15, two step vertical hold arm  316  includes slide surface  316   a , curved step  316   b , curved step  316   c , and lever  316   d.    
     To operate the latch, when the push pad  106  is pushed, the center case mechanism  200  operates as described above to raise slider  114  and vertical actuating rod  204  approximately 0.75 inch. This raises the actuator rod receptacle  304  and first linkage  306 , which in turn causes pivoting linkages  308  and  310  to pivot about pin  344  and pull back linkages  312  and  314 . This action pulls back latch  210  into its fully retracted position. 
     FIGS. 16 a - 16   c  show the action of the two step vertical hold arm  316  during this process. As the actuator rod receptacle  304  moves upward and operates the linkages as described above pin  328  slides along slots  330  and  332  (FIG. 14) in housing  302 . Because two step vertical hold arm  316  is biased to bear against pin  328  by torsion spring  320  acting upon a bottom surface of pin  356 , pin  328  slides along slide surface  316   a  of two step vertical hold arm  316 . As pin  328  continues its travel along slot  330  and reaches the end of slide surface  316   a , torsion spring  320  causes pin  328  to engage with curved step  316   b . Similarly, as pin  328  continues upward, torsion spring  320  causes pin  328  to engage with curved step  316   c . Two curved steps  316   b  and  316   c  are provided for improved holdback. On sagging doors, it may be possible to retract the latch and slip the door out of engagement without hitting the second step (if there were only one step). In such an incidence, the bolt  206  would re-extend while the door  50  was opening and cause damage to the flooring. At this point, actuator rod receptacle  304  is at the top of its travel and held in place by pin  328 , which is: seated in curved step  316   c . Latch  210  is fully retracted and able to clear the strike  54  in the door header  56 . The door  50  can be opened and the latch  210  will be held in the retracted position until the door  50  returns to its closed position, at which time the strike  54  in the door header  56  contacts lever  316   d  and pushes it toward door  50 . This action overcomes the biasing force of the torsion spring  320  upon two step vertical hold arm  316 , and unseats pin  328  from curved step  316   c . Torsion spring  320  then pushes latch  210  to its extended position, pulling back linkages  312  and  314 , which in turn cause pivoting linkages  308  and  310  to pivot about pin  344  and push first linkage  306  downward, which pushes actuator rod receptacle  304  downward to its initial position. 
     FIGS. 17 a - 17   c  show the operation of the deadlocking lever  318 . When the door  50  is deadlocked, as described above, the deadlocking plate  140  in the center case mechanism  200  prevents the slider  114  from moving vertically upward. The center case mechanism  200  therefore prevents the actuator rod receptacle  304  from moving upward and thereby preventing the latch  210  from retracting. The deadlocking lever  318  operates as a fail safe mechanism, preventing the latch  210  from movement due to external forces, such as an attempt to override the deadlock by prying latch  210 . 
     As shown in FIG. 17 a , torsion spring  320  pushes against pin  366  to bias the deadlocking lever  318  in a counterclockwise position about pin  344 . In other words, torsion spring  320  causes the deadlocking lever  318  to nearly contact pin  372  at the upper end, and to bear upon pin  328  at the lower end. When the door is deadlocked, actuator rod receptacle  304  and deadlocking lever  318  remain in their initial position. Any movement of latch  210  beyond the lost motion  376  shown in FIG. 17 a  is arrested by pin  372  coming into contact with the deadlocking lever  318 , as shown in FIG. 17 b . In normal operation, as shown in FIG. 17 c , the actuator rod receptacle  304  rises, pushing pin  328  upwards along slot  332  (Opposite slot  330  as shown in FIG.  14 ). Pin  328  slides across sloped surface  318   a  of deadlocking lever  318 , which causes deadlocking lever  318  to rotate clockwise about pin  344 , allowing pin  372  to clear the deadlocking lever  318  as latch  210  retracts. 
     The deadlocking lever  318  also functions as a fire lock. Referring back to FIG. 14, fire lock spring  322 , fire lock bushing  324 , and meltable element  326  are coupled to housing  302  via pin  374 . The outer diameter of meltable element  326  is small enough that it does not interfere with the motion of the deadlocking lever  318  in normal operation. However, in the event of a fire, the elevated temperature will melt meltable element  326 . Fire lock spring  322  will then push fire lock bushing  324 , which has a larger outer diameter than meltable element  326 , against housing  302 , above actuator rod receptacle  304 . The larger outer diameter of fire lock bushing  324  prevents deadlocking lever  318  from rotating counterclockwise as described above. Pin  372  engages the deadlock lever  318  and prevents latch  210  from retracting. 
     Referring now to FIGS. 14 &amp; 19, mounting plate  301  is used to mount upper lathing mechanism  300  to door  50 . Mounting plate  301  is positioned in a desired location on door  50  by use of measurements or with a template (not shown). A template can align mounting plate  301  a predetermined distance from the edge of door  50  in both the horizontal and vertical directions. The template would provide accurate placement of upper latching mechanism  300  with respect to existing strike  254  (FIGS. 16 a - 16   c ) or to locate a combination of a new strike  254  and latch mechanism  300 . A typical template would have edges to bear against the horizontal and vertical edges of the upper portion of door  50  and further include a feature to locate plate  301  with respect. thereto. Mounting plate  301  can be affixed to door  50  by fasteners inserted through holes  380  in a base  382  of plate  301 . Mounting plate  301  has left and right flanges  384  and  385  respectively. Flanges  384  and  385  have upper tabs  386  and  387  extending upward from an upper end of flanges  384  and  385 . Base  382  includes at a lower end, tailpiece  388  extending downwardly therefrom. Tailpiece  388  has upturned sides  390  and  391  that further include tabs  392  and  393 . Tabs  392  and  393  in combination with base  382  defame horizontal slot  394 . 
     After mounting plate  301  is attached to door  50 , upper latching mechanism  300  is installed by placing mechanism  300  between flanges  384  and  385 , and inserting until housing  302  contacts base  382  of mounting plate  301 . Mechanism  300  is then allowed to slide down whereby the lower edge of housing  302  is captured by horizontal slot  394 , and housing tabs  303  (FIG. 14) are captured by upper tabs  386  and  387  of mounting plate  301 . Mechanism  300  can then be affixed to mounting plate  301  by fasteners inserted in holes  395  and  396  in flanges  384  and  385  respectively and engaging matching threaded holes in housing  302 . In this manner, once the mounting plate  301  has been properly aligned on door  50 , mechanism  300  can be replaced without requiring re-alignment with center case mechanism  200 . To effect replacement, the attaching fasteners are removed and the old mechanism  300  is lifted out of the retaining slots in mounting plate  301  and a new mechanism is inserted and attached with like fasteners. 
     As shown in FIG. 1, upper mechanism  300 , vertical actuating rods  204  and  202 , and bolt  206  and its interface with vertical actuating rod  202  are protected by covers  209 ,  203 ,  201 , and  208 , respectively. FIGS. 18 a - 18   b  show the bottom bolt  206 , its structure and interface with vertical actuating rod  202 , and its cover  208 . Bracket  400  mounts to the door and includes an aperture shaped to accept the lower edge of cover  201 . As shown in FIG. 18 a , vertical actuating rod  202  extends through bracket  400  and couples to bolt  206  via internal threads above bracket  401 . Bolt  206  is free to slide up and down through collars  402  and  403  coupled to bracket  401 . 
     FIG. 18 b  shows a closeup of the transition from cover  201  to cover  208 . As shown in FIG. 18 b , cover  208  is designed to effect a gentle transition from the surface of the door to the surface of the cover, making the improved vertical panic exit device  100  fully compliant with ADA requirements. Referring also to FIG. 20, rod cover  201  includes an internal bent flange  220  on both sides of cover  201  thereby forming an internal shoulder  222 . U-shaped bracket  224  having upturned flanges  225  is mounted to door  50  in vertical alignment with and behind rod  202 . Flanges  225  have an external lip  226  extending longitudinally along bracket  224 . Cover  201  attaches in a snap-on manner wherein the sides of cover  201  are resilient and displace around lips  226  until cover  201  is in its desired position. Shoulders  222  seat below lips  226  thereby retaining cover  201  on bracket  224 . Cover  201  is thereby readily removable and does not require the use of separate fasteners. Cover  203  is attached in like manner to cover  201 . 
     Although the best mode for carrying out the present invention has been described in the foregoing detailed description and illustrated in the accompanying drawings, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions of steps without departing from the spirit of the invention. Accordingly, the present invention is intended to encompass such rearrangements, modifications, and substitutions of steps as fill within the scope of the appended claims.