Abstract:
An actuator-controlled strike comprising a housing disposable within a doorframe and including a chamber for receiving a spring latch and a dead latch of a mortise-type lockset. A keeper is pivotably mounted within the chamber to restrain the spring latch. A pivotable spring latch lifter is positively driven by the keeper, and a pivotable dead latch release platform is supported by the keeper when the spring latch is locked within the strike. The keeper is released by the actuator and then may be rotated which causes rotation of the dead latch release platform, allowing the dead latch to enter the chamber. The keeper positively drives the spring latch lifter to lift the spring latch onto the external ramp of the strike. In an alternate embodiment, an internal ramp feature may be used instead of the spring latch lifter to positively lift the spring latch out of the chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/423,657, filed on Dec. 16, 2010, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to strike mechanisms for electrically locking or unlocking a door in a frame; more particularly, to such strike mechanisms wherein a mortise-type lockset having a spring latch and dead latch is electrically retained or released by the strike; and most particularly, to an electrically-controlled strike having a pivotable spring latch keeper, a spring latch lifter feature, and a pivotable dead latch release platform that cooperate in synchronized motion to lift and release a spring latch from the strike. In one aspect of the invention, the spring latch lifter feature pivots and is directly driven by rotation of the spring latch keeper to lift the spring latch out of the latch entry chamber. In another aspect of the invention, the spring latch lifter feature is an internal ramp, whose surface aligns with a nose of the keeper, and an external ramp to form a continuous incline and to lift the spring latch out of the latch entry chamber when the door is moved in an opening direction. 
       BACKGROUND OF THE INVENTION 
       [0003]    As is known in the art of door latching, typically an electrically-controlled strike is mounted in a frame portion of a door and engages a mortise-type lockset disposed on or in an edge portion of the door. Typically, the mortise-type lockset includes a spring latch and a dead latch that is linearly spaced-apart from the spring latch along the edge portion of the door. The spring latch is reciprocally moveable between an engaged position so that it can engage an entry chamber in the strike, thereby to secure the door in a fastened state, and a released position, wherein the door is released from the fastened state and is free to open. The dead latch is reciprocally moveable between an enabled position (extended) that permits movement of the spring latch from its engaged position to the released position and a disabled position (depressed) that prohibits movement of the spring latch from its engaged position to its release position. The spring latch is resiliently biased into an engaged position and the dead latch is resiliently biased into the enabled position. (When the dead latch is in the enabled, extended position, the spring latch is able to be depressed from its engaged position). 
         [0004]    U.S. Pat. No. 6,581,991 B2, the relevant disclosure of which is incorporated herein by reference, discloses an electrically-controlled strike comprising a housing adapted to be mounted in a frame portion of a door and having a cavity with a forwardly disposed opening that is sized and adapted to receive a spring latch and a dead latch when the door is in the closed state. The invention provides a single electrically actuated door latch structure that can be customized to a variety of spring latch and dead latch arrangements. 
         [0005]    U.S. patent application Ser. No. 12/851,848, filed Aug. 6, 2010 and assigned to Hanchett Entry Systems, Inc. discloses an improved door strike having a spring latch kicker and a dead latch release platform which can be adjusted to various positions in conjunction with the specific mortise lockset used. A rectangular housing is disposable within the frame of a door pivotably mounted in the frame. The housing includes an elongate opening defining an entry chamber for a spring latch and a dead latch of a mortise lockset in the door. An entrance ramp for the spring latch and dead latch extends from an edge of the housing. A keeper is pivotably mounted within the chamber to selectively engage and retain the spring latch. A kicker is also pivotably mounted within the chamber and is interlocked with the keeper and engageable by the spring latch. A dead latch release platform is also pivotably mounted within the chamber and is supported at an opposite end by the keeper when the spring latch is secured within the strike. When a release command is received, the keeper is allowed by means of an actuator, such as a solenoid, to rotate and then rotates, from a door-opening force, against the force of its return spring into a position from which the spring latch may be ramped out of the strike opening. The keeper rotation allows the dead latch release platform to pivot into the cavity against the force of a release platform return spring, thereby releasing the dead latch to be extended into the cavity which allows the spring latch to be ramped out as it is depressed into the door. The pivot action of the keeper and a leg of the keeper acting directly on the kicker causes the kicker to engage the nose of the spring latch and to boost the spring latch onto a ramp surface formed on a face of the keeper. The spring latch then leaves the kicker, climbs the ramp surface and exits the strike as the door opens in the frame. After the spring latch has cleared the strike, the keeper rotates to its lock position under the force of its return spring, the dead latch release platform returns to a position supported by the keeper under the force of its return spring so that the dead latch is held in its depressed position by the supported dead latch release platform upon closing the door. 
         [0006]    The dead latch release platform can be installed in any of a plurality of different vertical (along the long dimension of the housing) locations in the housing opening to accommodate any of a plurality of different lockset arrangements. 
         [0007]    What is needed in the art is an electrically-controlled strike wherein the dead latch release platform is positively driven by the keeper to its return position in preparation for relatching of a door. 
         [0008]    What is further needed is a strike wherein a spring latch lifter feature includes (1) a pivotable member that is driven by the keeper to positively and continuously push the spring latch onto the exit ramp during unlatching of the door, or (2) an internal ramp to form a continuous incline whose surface aligns with a ramped nose of the keeper and an external ramp to lift the spring latch out of the entry chamber when the keeper releases the spring latch and the door is moved in an opening direction. 
         [0009]    It is a principal object of the present invention to reduce the cost and complexity of an electrically-controlled strike for a door with a mortise lockset and to improve reliability of operation. 
       SUMMARY OF THE INVENTION 
       [0010]    Briefly described, an electrically-controlled strike in accordance with the present invention comprises a rectangular housing disposable within the frame of a door wherein said door is pivotably mounted in the frame. The housing includes an elongate entry chamber for a spring latch and a dead latch of a lockset in the door. (For purpose of explanation, the entry chamber should be considered as having a bottom, sides, outer corners adjacent the opening of the entry chamber, and inner corners at the juncture of the sides and bottom of the entry chamber.) An external ramp for the spring latch, and with some mortise locksets also for the dead latch, extends from an edge of the entry chamber. A curved keeper is pivotably mounted at an intermediate point within the chamber to selectively engage and retain the spring latch in the chamber. A dead latch release platform is pivotable on a platform bracket mounted within the chamber at an inner corner thereof and, by rotation of the spring latch keeper, is allowed to rotate in a first direction to permit extension of the dead latch. Rotation of the spring latch keeper in a second return direction positively drives the dead latch release platform to its initial position to depress the dead latch into the door. A spring latch lifter feature is also present in accordance with the invention. In one aspect of the spring latch lifter feature design, a spring latch lifter is pivotable on a spring latch lifter bracket mounted within the chamber near an outer corner thereof and is interlocked with the keeper for engaging the spring latch. The motion of the spring latch lifter in a first direction is positively controlled by the motion of the keeper. The spring latch lifter returns to its initial position by a return spring. In another aspect of the invention, the spring latch lifter feature is an internal ramp that aligns with a ramp surface on the spring latch keeper and an external ramp surface to form a continuous incline and to lift the spring latch out of the entry chamber when the door is moved in an opening direction. 
         [0011]    When a release command is received, the keeper is released by means of an actuator, such as a solenoid, and may be rotated by an opening force on the door into a position from which the spring latch may be ramped out of the strike opening. The keeper rotation allows the dead latch release platform to pivot into the entry chamber, which further allows the dead latch to extend into the entry chamber, which still further allows the spring latch to be ramped outwards of the entry chamber into the door. In one aspect of the design, the pivot action of the keeper also causes the spring latch lifter to engage the nose of the spring latch and then to continuously push the spring latch out of the entry chamber of the housing and onto the external ramp of the strike. The spring latch then exits the strike over the entrance ramp as the door opens in the frame. The spring latch lifter can be installed in multiple locations within the housing to accommodate differing lockset arrangements. 
         [0012]    In another aspect of the design, instead of the spring latch lifter positively pushing the spring latch out of the entry chamber, a three-part ramp contact surface is formed with the inclusion of the internal ramp thereby providing a continuous incline surface for the tip of the spring latch to first contact. The incline causes the spring latch to ride up its ramp surface and ascend out of the entry chamber as the door opens in the frame. Means are also provided so that the position of the internal ramp may accommodate differing lockset arrangements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0014]      FIG. 1  is a front elevational view of a door in a secure condition at a first door position (door closed) within a door frame and having a portion of the door frame broken away to show an electrically-controlled strike operable with a mortise-type lock assembly in the door; 
           [0015]      FIG. 2  is an isometric view of a prior art mortise lockset for use with an electrically-controlled strike in accordance with the present invention; 
           [0016]      FIG. 3  is a perspective view of a strike plate according to the prior art for use with a mortise-type dead latch assembly such as that shown in  FIG. 2  which would be replaced by an electrically-controlled strike in accordance with the present invention; 
           [0017]      FIG. 4  is a cross-sectional view showing a door having a mortise lockset latched in a frame having a prior art electrically-controlled strike, the strike being in secured mode; 
           [0018]      FIG. 5  is a cross-sectional view sequential to the view shown in  FIG. 4 , showing the prior art strike in an early stage of unlocking the spring latch and dead latch of the mortise lockset; 
           [0019]      FIG. 6  is a cross-sectional view sequential to the view shown in  FIG. 5 , showing the prior art strike in a later stage of unlocking the spring latch and dead latch of the mortise lockset; 
           [0020]      FIG. 7  is a cross-sectional view sequential to the view shown in  FIG. 6 , showing the prior art strike in a late stage of unlocking the spring latch and dead latch of the mortise lockset; 
           [0021]      FIG. 8  is an exploded isometric view of an electric door strike in accordance with the present invention; 
           [0022]      FIG. 9  is an isometric view from above of the electric door strike shown in  FIG. 8  with the faceplate omitted for clarity; 
           [0023]      FIG. 10  is a first isometric view from below of the electric door strike shown in  FIG. 9  with the housing made transparent for clarity, showing the strike in the locked position; 
           [0024]      FIG. 11  is a second isometric view like that shown in  FIG. 10 , showing the strike in the unlocked position; 
           [0025]      FIG. 12  is a first end view of the strike as shown in  FIG. 10 , showing the strike in a locked position; 
           [0026]      FIGS. 13A and 13B  are second end views similar to that shown in  FIG. 12 , showing the strike at a midpoint during release of the spring latch (the dead latch release platform is removed from  FIG. 13B , for clarity); 
           [0027]      FIG. 14  is a third end view similar to those shown in  FIGS. 12 and 13 , showing the strike as the spring latch reaches the external ramp 
           [0028]      FIG. 15  is an isometric view of an alternate keeper bench, in accordance with the invention; and 
           [0029]      FIG. 16  is an end view of the strike, with the alternate keeper bench of  FIG. 15 , in accordance with the invention, with the door moved in an opening direction and the spring latch in contact with the external ramp. 
       
    
    
       [0030]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate currently preferred embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    The present invention is broadly directed to an automated door latch release system that is adapted to be installed in a door jamb or frame so that it can operate with a mortise-type lock with a separate dead latch assembly such as those found in typical commercial and industrial applications. The present invention also encompasses a method for automated door release. The present invention is particularly adapted for use with security doors in industrial and commercial applications wherein the security system can be electronically activated to release the door so that it may be moved from a secured, or locked, first door position wherein it is secured within the door jamb to an open, or unlocked, second door position. The automated door lock release, also referred to herein as an “electrically-controlled strike,” is primarily adapted for use with a mortise-type lock assembly mounted in the door. A typical mortise-type dead latch assembly includes a spring latch and a dead latch that are spaced-apart from one another along the edge of the door. The present invention is specifically adapted to be mounted in the dimensions of a typical door jamb to interface with a variety of different styles of mortise-type dead locks. 
         [0032]    An automated door lock release or strike in accordance with the present invention is an improvement over the prior art automated door latch releases described hereinabove and is intended to function as a direct replacement thereof. 
         [0033]    Referring to  FIGS. 1 through 3 , for purposes of comparison an electric door strike assembly disclosed in U.S. Pat. No. 6,581,991 B2 comprises an automated door latch release  10  that is received in a cavity  12  in a typical door frame  14 . Actuator  10  includes an outer housing  16  that mounts its electrical and mechanical components. The electrical components in turn are electrically energized by means of wiring  20 . Actuator  10 , for example, may be electrically in communication with a source  17  of electrical power such as for example, a 12 or 24 volt circuit, and with a trigger device  22 . Activation of the trigger device causes the door latch actuator to activate. The trigger device  22  typically is a switch whose contacts selectively actuate the door latch actuator. The trigger device  22  may be incorporated into a control entry device such as a card reader or digital entry keypad wherein an authorized card is presented or an authorized code is entered into trigger device  22 . 
         [0034]    A typical door  24  is shown in  FIG. 1  in a first or closed position and is pivotably mounted to move in frame  14  between a closed position and an open position. 
         [0035]    Door latch release  10  is constructed to interface with a mortise-type lockset assembly  30  according to the prior art, exemplarily shown in  FIG. 2 . A prior art mortise-type lockset assembly  30  includes a spring latch  32  and a dead latch  34 . Spring latch  32  and dead latch  34 , when mounted in a door, are linearly spaced-apart from one another along the edge portion of the door. Both spring latch  32  and dead latch  34  are spring-biased to extend outwardly from lockset assembly  30 . Thus, as one of ordinary skill in the art can appreciate, spring latch  32  is slideably moveable between an advanced or “engaged position”, wherein the spring latch  32  is fully extended from the edge portion of the door such that it can engage the latch bolt receiving cavity  46  ( FIG. 3 ), and a retracted or “release position” wherein spring latch  32  is retracted into the door and becomes disengaged from the latch bolt receiving cavity  46 , allowing the door to open. 
         [0036]    Dead latch  34  similarly is reciprocally moveable between an extended or “enabling position” (enables depression of spring latch) and a depressed or “disabling position”. As is known in the prior art, when the dead latch is held in its disabling position, the spring latch bolt is prevented from moving from the engaged position to the release position. However, when the dead latch is allowed to extend into its enabling position within cavity  46 , the spring latch may reciprocate between the engaged position and the release position. In  FIG. 2 , dead latch  34  is shown in the extended or enabling position and spring latch  32  is shown in the engaged position. In this position of dead latch  34 , spring latch  32  is free to be urged into lockset assembly  30  in response to an opening force on door  24  as by a user rotating the door handle  29 . 
         [0037]    With reference now to  FIG. 3 , a prior art strike plate  36  for use with mortise-type locksets of the prior art, such as lockset assembly  30 , includes a rectangular central body portion  38  having oppositely projecting mounting tabs  40  provided with holes  42  adapted to receive screws for mounting on door frame  14 . A lateral flange  44  projects away from central body portion  38  in a slightly curved configuration so as to interact as a ramp with the curved edges of spring latch  32  and dead latch  34  when the door swings shut, driving both spring latch  32  and dead latch  34  into door  24 . Latch bolt receiving cavity  46 , in the form of an opening, is provided in central body portion  38  of strike plate  36  so that, when the door fully closes, spring latch  32  extends into receiving cavity  46  to hold the door in the closed position. Dead latch  34 , on the other hand, continues to bear against the surface of strike plate  36  in the region designated  48  and is held in the depressed or disabling position thereby to lock the door. However, and with reference to  FIG. 2 , mortise-type lockset assembly  30  typically includes a key lock  35  that includes a mechanism to selectively retain spring latch  32  in the engaged position or to release spring latch  32  so that it may move between the engaged position and the release position without extension of the dead latch. This arrangement is well known to those skilled in the art and is not part of the present invention. 
         [0038]    Referring now to  FIGS. 4 through 7 , for comparison purposes, electrically-controlled strike  110  in accordance with the device disclosed in parent application Ser. No. 12/851,848 comprises a housing  116  defining an entry chamber  118  therein. Strike plate  136  having a central cutout portion  150  is adapted to fit over housing  116 . Housing  116  is provided along an edge with a lateral flange  144  preferably running substantially the full longitudinal length of housing  116 , that serves as an entry ramp for a spring latch and dead latch arrangement as described below. 
         [0039]    A dead latch release subassembly  152  comprises a dead latch release platform  154  pivotably disposed in mount  156  mounted to housing  116  at an outer corner of entry chamber  118 . A compression spring  158  is disposed between platform  154  and mount  156  to resiliently urge subassembly  152  into the configuration shown in  FIGS. 4 and 7 . 
         [0040]    A spring latch keeper  166  is pivotably mounted longitudinally of housing  116  at the bottom of entry chamber  118  and, in the locked position ( FIG. 4 ), engages nose tang  164  to support dead latch release platform  154 . Thus, when door lockset assembly is in the locked mode, dead latch  34  is held in a depressed position within the door lockset assembly by dead latch release platform  154 . Surface  169  of keeper  166  further engages lockset spring latch  32  along surface  168 . The door opening force is applied in direction  178  substantially perpendicular to surface  169 , thus preventing door  24  from being opened. A return spring  167  disposed between keeper  166  and housing  116  urges keeper  166  toward the locked position shown in  FIG. 4 . 
         [0041]    A kicker  170  is also pivotably mounted longitudinally of housing  116  and rests against a leg  172  of keeper  166 . A return spring  173  is mounted on kicker  170  and constrained by housing  116 . A solenoid (not visible) is linearly operative against keeper  166  to selectively permit rotation of the keeper when an unlocked mode ( FIGS. 6 and 7 ) for mechanism  110  is desired. 
         [0042]    Referring now to  FIGS. 8 and 9 , an electric door strike  210  in accordance with the present invention comprises a housing  216  having first and second mounting flanges  217  for receiving a strike plate  236  and a shield  238 . Housing  216  defines an entry chamber  218  having inner corners  219  and outer corners  221 . A saddle  223  receives a plunger  225  of a linear solenoid  227  mounted in entry chamber  218  and connected electrically to leads  209 . A blocker  229  is associated with plunger  225 . A dead latch release subassembly  252  comprises a dead latch release platform  254  pivotably disposed in base  256  mounted to housing  216  at an inner corner  219 . A keeper bench  261  is mounted to housing  216  and comprises first and second journals  231  for receiving first and second keeper pivot pins  233 . Keeper  266  is pivotably mounted to keeper bench  261  on pins  233  at an intermediate position off-spaced from bottom  213  of housing. Keeper  266  includes at least one lifter actuation arm  235 . Bias spring  263  is also mounted on one of pins  233  for returning keeper  266  to the starting position after the unlocked spring latch has cleared the strike. External ramp  244  also comprises a closing wall  245  of housing  216 . First and second shims  247  may be included to position strike  210  correctly in a door frame cavity of a specific installation. A lifter subassembly assembly  270  comprises a lifter pivot bracket  272  mounted to a wall of housing  216  at an outer corner  221  thereof and a lifter  274  pivotably mounted in lifter pivot bracket  272 . 
         [0043]    Referring now to  FIGS. 10 and 11 , a strike locking and unlocking mechanism is shown in accordance with the present invention. 
         [0044]    In locked position, as shown in  FIG. 10 , solenoid plunger  225  is extended from solenoid  227 , placing blocker  229  in the rotational path of keeper tang  280 . In this locked position of keeper  266 , as described further below, a spring latch (not shown) captured within strike  210  is prevented from being able to leave entry chamber  218  of strike  210 . 
         [0045]    In unlocked position, shown in  FIG. 11 , solenoid plunger  225  is retracted by solenoid  227 , displacing blocker  229  from the rotational path of keeper tang  280 . In this unlocked position of keeper  266 , as described further below, a spring latch (not shown) captured within chamber  218  of strike  210  is able to cause keeper  266  to be rotated to the position shown and the spring latch is thus able to leave chamber  218  of the strike in response to door-opening force in direction  178 . 
         [0046]    Referring now to  FIGS. 12 through 14 , the sequence of actions of the various components is shown in proceeding from a fully locked position ( FIG. 12 ) to a fully unlocked position ( FIG. 14 ). 
         [0047]    In  FIG. 12 , keeper  266  is in the spring latch locked position, which is fully rotated in a clockwise direction as shown in the figure. The plane of keeper face  282  is orthogonal to the initial opening direction  178  of door  24 , which thereby serves to engage and lock spring latch  32  within entry chamber  218  of strike  210 . Further, a supportive nose  284  on keeper  266  engages dead latch release platform  254  and maintains the platform in a position that keeps dead latch  34  in its depressed, disabling position, and retracted into door  24 , thus preventing spring latch  32  from being unlocked. Keeper tang (not shown) is engaged by blocker  229 , preventing keeper  266  from rotating counter clockwise about pins  233  in response to any opening force exerted in direction  178  on door  24 . 
         [0048]    Referring now to  FIGS. 13A and 13B , blocker  229  has been retracted by solenoid plunger  225 , thereby allowing keeper  266  to rotate counterclockwise about pins  233  in response to an opening force exerted by spring latch  32  on face  282  in direction  178 . (In  FIG. 13B , dead latch release platform  254  has been removed for clarity). Lifter actuation arm  235 , which extends from keeper  266 , urges lifter  274  to begin clockwise rotation about lifter pivot axis  273  which is above the midpoint of housing  216  and preferably near an outer corner  221 . Because lifter  274  is initially in contact with spring latch  32  and is thus urged by lifter actuation arm  235 , lifter  274  remains in continuous contact with spring latch  32  and thus positively pushes spring latch  32  outward and onto external ramp  244 . Concurrently, as keeper nose  284  ( FIG. 13A ) begins to rotate counterclockwise with keeper  266 , dead latch platform  254  begins to rotate clockwise about axis  255 . As a corner  287  of dead latch platform  254  clears the nose of dead latch  34 , the spring associated with dead latch  34  urges dead latch  34  against face  289  of dead latch platform  254 , forcing the dead latch platform still further out of the way so that the dead latch may rapidly enter entry chamber  218 , which action completely releases spring latch  32 . 
         [0049]    Referring now to  FIG. 14 , the dead latch platform has again been removed for clarity. It is seen from  FIG. 14  that further counterclockwise rotation of keeper  266  about pin  233  causes face  282  to become an extension of external ramp  244 . Lifter  274  continues to rotate clockwise in continuous contact with spring latch  32  and thereby urges spring latch  32  onto external ramp  244 . Further force applied to door  24  in direction  178  causes spring latch  32  to climb external ramp  244  and thereby become free of strike  210 . Keeper spring  263  ( FIG. 8 ) biases keeper  266  in the clockwise direction. After unlocking is complete, spring  263  serves to return keeper  266  clockwise and the associated components to their respective locking starting positions as shown in  FIG. 12 . The cycle is completed by re-extension of plunger  225  from solenoid  227  to place blocker  229  again in rotational interference with keeper tang  280 , as shown in  FIG. 10 . 
         [0050]    Referring again to  FIG. 12 , in locking of door  24  by spring latch  32  within door strike  210 , door  24  is urged in a closing direction opposite to direction  178 . Spring latch  32  and dead latch  34  climb external ramp  244  from the outside, and also climb over the nose  290  of keeper  266 . As the nose of spring latch  32  clears keeper nose  290 , the spring latch immediately extends from door  24  into entry chamber  218  and is trapped behind keeper face  282  as described above. Because the dead latch is prevented by dead latch platform  254  from entering chamber  218 , spring latch  32  is effectively locked in strike  210 . 
         [0051]    In another aspect of the invention, where it may not be necessary to directly lift the spring latch out of the entry chamber when the keeper is released, lifter subassembly  270  may be replaced by a stationary ramp internal to the entry chamber. The stationary ramp provides an inclined surface for the tip of the spring latch to first contact as the door is moved in an opening direction after the keeper is released. The internal ramp initiates the assent of the spring latch out of the entry chamber as the spring latch transitions from first making contact with the internal ramp, then with the keeper nose and finally with the external ramp. Referring first to  FIG. 15 , modified keeper bench  361  is shown. Keeper bench  361  is identical to keeper bench  261  but for the addition of internal ramp feature  362  including ramp surface  364 . Keeper bench  361  is mounted to housing  216  similar to the mounting of keeper bench  261  to housing  216  and includes first and second journals  231  for receiving first and second keeper pivot pins  233  ( FIG. 8 ). Keeper  266  is pivotably mounted to keeper bench  361  on pins  233  ( FIG. 8 ). 
         [0052]      FIG. 16  shows electric door strike  310  in accordance with this aspect of the invention after door  24  has moved in an opening direction and the tip  369  of extended spring latch  32  is about to first make contact with external ramp  244  and at a point where the spring latch  32  has partially ascended out of entry chamber  218  after tip  369  has left contact with keeper face  282 . Note that, in  FIG. 16 , keeper  366  is in its unlatched, full counter-clockwise position and internal ramp surface  364 , keeper face  282  and external ramp  244  are aligned to form a continuous ramp contact surface  367 . 
         [0053]    As shown in  FIG. 16 , to aid in the transition of spring latch  32  out of entry chamber  218 , internal ramp surface  364  is disposed at a lesser angle than keeper face  282  and external ramp  244 , with the angles measured in reference to the opening direction of the door. However, it is understood that internal ramp surface  364  may be aligned at the same angle as face  282  and ramp  244  to form ramp contact surface  367 , or surface  364 , face  282  and ramp  244  may each be at different angles to form contact surface  367 . Also, as shown in  FIG. 15 , keeper bench  261  may include a pair of ramp features and ramp surfaces  362 , 364  to accommodate installed mortise-type locksets wherein the dead latch is above the spring latch or below the spring latch. Of course, since this aspect of the invention does not include lifter subassembly  270 , lifter actuator arm  235  ( FIG. 8 ) may be eliminated from keeper  366 . 
         [0054]    In the embodiments described above, dead latch release subassembly  252  is shown having a particularly shaped dead latch release platform designed to cooperate with the particular dead latch shown. However, it is understood that, within the scope of the invention, the dead latch release platform can take on other shapes necessary to cooperate with the design and location of its associated dead latch. 
         [0055]    While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.