Abstract:
A latch bolt set has a latch bolt and a trigger bolt assembly comprising a trigger bolt. The latch bolt has a retracted position, a projected position, an intermediate position and is biased to the projected position. The trigger bolt has a retracted first position, a projected second position, and is biased to the second position. An operator retracts the latch bolt from the projected to the retracted position. The trigger bolt assembly engages with the operator to support the latch bolt in the intermediate position when the trigger bolt is in the second position. When the trigger bolt is moved to the first position, the trigger bolt assembly automatically allows the latch bolt to move to the projected position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is the national stage of International Application No. PCT/US97/06174 filed Apr. 16, 1997 which claims priority from U.S. Provisional Application No. 60/015,758 filed Apr. 16, 1996. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to dead bolt lock sets which are employed to secure doors. More particularly, the present invention relates generally to dead bolt lock sets wherein the dead bolt is projectable to an extended position in the strike of the door. 
     Conventional dead bolts are typically employed alone or in combination with self-latching latch bolts to secure a doorway. The self-latching latch bolt typically has a beveled latch bolt and a spring for biasing the latch bolt in the extended position. Self-latching latch bolts provide the advantage of automatically latching the door when it is closed, and with certain lock mechanisms, automatically locking the door under such circumstances. 
     Conventional spring biased latch bolts, however, are susceptible to tampering to allow unauthorized access. Tools or other slim items can be slipped between the door and the door frame to engage the beveled edge of the latch and force the latch bolt back into the latch set, thereby allowing the door to be opened. III-fitting doors, or doors that warp or change over time, can become more susceptible to this form of tampering. 
     Dead bolts have been employed to overcome some of these deficiencies. Dead bolts typically define a squared-off end that is less susceptible to tampering than the beveled end of a typical self-latching latch bolt set. Furthermore, dead bolts are typically not spring loaded, therefore maintaining the dead bolt in an extended position until the lock mechanism is employed to retract it. In addition, dead bolts typically have a longer throw or extension of the bolt for additional locking strength. A deficiency of dead bolts is that they must typically be manually engaged. Furthermore, a dead bolt is usually paired with a self-latching latch bolt, thereby requiring an additional opening in the strike for reception when the door is in the closed position. 
     SUMMARY OF THE INVENTION 
     Briefly stated, a latch bolt set in accordance with the invention has a self-latching bolt which is projectable to an enhanced extension or projection position relative to a lock case. The latch bolt set includes a latch bolt and a trigger bolt. The latch bolt has a projected position, a retracted position, and an intermediate position between the projected and retracted positions. The latch bolt is biased to the projected position. The latch bolt is preferably adapted for engagement into a conventional door strike defining a single strike opening. The trigger bolt also has a projected position and a retracted position into the lock case. The trigger bolt is also biased to the projected position. The trigger bolt is configured and positionable so that when the door is closed, the trigger bolt engages the flat surface of the door strike and does not project into an opening in the strike. 
     An operator assembly retracts the latch bolt from the projected to the retracted position. The operator assembly is typically operated by a door user employing a handle or knob, but can also be operated by other well-known electromechanical assemblies. The operator assembly is further lockable by well known mechanical or electromechanical systems. The trigger bolt assembly engages with the operator assembly to maintain the latch bolt in the intermediate position when the trigger bolt is in the projected position. In a self-latching mode with the door open, the trigger bolt is in the projected position and the latch bolt is in the intermediate position. 
     The latch bolt is preferably constructed so that a beveled distal portion of the latch bolt extends from the door when the latch bolt is in the intermediate position. The portion of the latch bolt disposed in the latch set in the intermediate position defines a latch plate having a substantially rectilinear exterior engagement surface. The trigger bolt also has a distal beveled portion which extends from the latch set in the projected position. The edge of the door strike engages the bevels of the trigger bolt and latch bolt and drives each bolt to the retracted position when the door swings to the closed position. The trigger bolt assembly disengages from the operator assembly as the trigger bolt is driven to the retracted position. The disengagement of the trigger bolt assembly from the operator assembly allows the latch bolt to extend to the projected position into the opening defined by the door strike when the door is fully closed. In this position, the beveled end of the latch bolt is maintained inside the strike where it is generally inaccessible and therefore is highly resistant to tampering by the use of screw drivers or other slim tools typically surreptitiously employed to retract the latch bolt and thereby unlock the door. 
     The operator assembly retracts the latch bolt from the projected position to the retracted position, to therefore allow the door to be opened. The trigger bolt returns to the projected position when the door is in the open position, resetting the trigger bolt assembly such that the trigger bolt assembly re-engages the operator assembly. The re-engagement of the trigger bolt assembly to the operator assembly maintains the latch bolt in the intermediate position. 
     In a further embodiment in accordance with the invention, the latch bolt is locked into the projected position whereby the latch bolt can practically be retracted only by the operator assembly. A lock bar engages the latch bolt to prevent the latch bolt from being moved to the intermediate or retracted positions. The lock bar prevents potential unauthorized entry by maintaining the latch bolt in the projected position despite the presence of a countering force on the latch bolt applied by a tool or other object. The operator assembly disengages the lock bar to retract the latch bolt. 
     An object of the invention is to provide a new and improved selflatching latch bolt assembly for efficiently securing a door to a door frame. 
     Another object of the invention is to provide a new and improved latch bolt set having a latch bolt which is positionable at an intermediate position for self-latching and a projected position for locking. 
     A further object of the invention is to provide a new and improved latch bolt set which implements a high level of security and is highly resistant to tampering. 
     These and other objects and advantages of the invention will become apparent from the following specification and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side sectional view, partly in phantom and partly broken away, of a latch bolt set and a strike for a configuration wherein the door is closed and the bolt is fully projected; 
     FIG. 2 is a side sectional view, partly in phantom and partly broken away, of the latch bolt set and strike of FIG. 1 for a configuration wherein the door is closed and the inside or outside lever is engaged and depressed; 
     FIG. 3 is a side sectional view, partly in phantom and partly broken away, of the latch bolt set of FIG. 1 for a configuration wherein the door is open and the inside or outside lever is depressed; 
     FIG. 4 is a side sectional view, partly in phantom and partly broken away, of the latch bolt set of FIG. 1 for a configuration wherein the door is open and the inside or outside levers are disengaged and in a neutral position and the latch bolt is in a self-latching position; 
     FIG. 5 is a top plan view, partly in phantom, of the latch bolt set of FIG. 4; 
     FIG. 6 is a side elevational view of the latch bolt set of FIG. 1 illustrating the bolt in a maximum projected position; 
     FIG. 7a is a fragmentary view, partly exploded and partly in schematic, illustrating a step in reversing the latch bolt; 
     FIG. 7b is a second fragmentary side view, partly exploded and partly in schematic, illustrating a second step in reversing the latch bolt; 
     FIG. 7c is a third fragmentary side view, partly exploded and partly in schematic, illustrating a third step in reversing the latch bolt; and 
     FIG. 7d is fourth fragmentary side view, partly exploded and partly in schematic, illustrating a fourth step in reversing the latch bolt. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings wherein like numerals represent like parts throughout the figures, a latch bolt set in accordance with the present invention is generally designated by the numeral 10. The latch bolt set is mounted in the mortise of a door 12 and is adapted to engage the strike 14 of a door frame 16. The strike 14 may be bi-handed, i.e., suitable for use for either a left- or right-handed door installation. A latch operator, such as a lever, door knob or other conventional operator (none illustrated), connects via a spindle 18 for operating the latch set. The latch bolt set may be employed with a conventional mechanical door operator or an electronic door operator having an automatic clutch mechanism, such as disclosed in co-pending U.S. Application Ser. No. 08/524,349 filed Sep. 6, 1995. 
     The latch set 10 is operable to throw the latch bolt to an extended projected position when the door is closed and also to provide a lock bar to prevent the latch bolt from being improperly retracted when the door is closed and properly latched. The latch set is also adapted to be bi-handed, i.e., easily convertible for use in connection with either a left- or right-handed door installation. 
     The latch set comprises a substantially rectangular case 20 which provides a mounting frame for the components as well as a protective housing and a support for mounting the latch set in the mortise of a door. The case 20 has a frontal faceplate 22. The faceplate 22 is disposed in opposing parallel relationship to the strike 14 when the door 12 is closed. 
     The latch bolt 30 is a generally trapezoidal member (as viewed from the top) having a beveled forward tip 32. The latch bolt has a central bore 31 which receives a forward end portion of a throw rod 34. The latch bolt may be threaded to the throw rod 34 or secured by a set screw 35 which is received in a recess 37 of the rod. A counter bore 36 at the rear end of the bolt 30 receives the forward end of a spring 38 which is secured at the opposing end by a stop 40 fixedly mounted to the case to provide a support for the slidably received throw rod 34. The spring functions to bias the latch bolt to the protected position into the strike. 
     A lever arm 50 having an angled distal engagement end 52 is mounted for rotation with the operator spindle 18. The engagement end 52 has two angled surfaces 53, 55 which engage against a shoulder 54 fixedly mounted to the throw rod 34 for retracting the latch bolt 30. As best illustrated by comparing FIG. 1 and FIG. 2, the surfaces 53, 55 engage the shoulder 54 in surface-to-surface relationship to define stable extreme projected and retracted positions of the latch bolt 30. A cam 56 and a guide pin 58 are mounted in fixed relationship with the lever arm for engagement with a lock bar 60. The lock bar is pivotally mounted to the case and includes a distal notch 62 which is engageable with the lower corner of the latch bolt to prevent the latch bolt from being improperly retracted into the latch bolt case when it is in the projected position as illustrated in FIG. 1. In the activated lock bar position illustrated in FIG. 1, the lock bar surface is supported in a generally horizontal orientation by the guide pin 58. When the lever arm 50 is rearwardly rotated by the operator, the guide pin 58 disengages from the lock bar 60 which pivots to engage and rest on the cam 56 as best illustrated in FIG. 2. 
     A trigger bolt assembly 70 comprises a trigger bolt 72 which is operatively mounted to a trigger rod 74. The trigger rod 74 slides in a bracket 76 along an axis parallel to the throw rod 34. The bracket 76 is fixed relative to the case. The outer portion of the trigger bolt has a bi-beveled tip 73 (FIG. 5). A cup-like retainer 78 is fixedly mounted to the trigger rod for retaining a spring 80 which biases between the fixed bracket and the retainer 78 to bias the trigger bolt to a full projected position as illustrated in FIG. 4. The inner (rear) end 82 of the trigger rod 70 is tapered to facilitate engagement with the underside of a lever 84. When the trigger bolt engages the strike, the spring 80 is compressed between the retainer and the bracket as illustrated in FIGS. 1 and 2, and the lever 84 rests on the end 82 of the trigger rod. 
     When the operator is released, the engagement arm 50 is biased to pivot counterclockwise as illustrated in the drawings and an angled surface 57 of the engagement end 52 engages the distal end of the lever 84 as illustrated in FIG. 4 so that the latch bolt 30 is in a stable self-latching (intermediate) position as best illustrated in FIG. 4. When the door is closed and the trigger bolt engages the strike, the trigger rod 74 is forced rearwardly to disengage (upwardly pivot) the lever 84 from the engagement with the lever arm 50, thereby forwardly forcing the throw rod 34 and the latch bolt 30 to the extreme projected position which is typically one inch from the faceplate 22 of the latch bolt case as best illustrated in FIG. 1. In the self-latching position, the latch bolt is typically projected approximately one half inch from the faceplate 22. 
     It will be appreciated that the latch bolt set has application in conjunction with the conventional mechanical door operators or sophisticated electronically controlled door operators. As illustrated in FIG. 1, when the door is closed, the latch bolt 30 is projected to the extreme projected position under the bias of the throw spring 38. The lock bar 60 is positioned to prevent tampering with the latch bolt 30 by withdrawing the latch bolt into the lock case. The trigger bolt 72 is in a retracted position due to the engagement against the face of the strike. 
     With reference to FIG. 2, when the door is closed and the operator lever is engaged and depressed, the engagement arm 50 rearwardly pivots to retract the latch bolt 30. The trigger bolt 72 remains in the compressed retracted position. When the door is open, the trigger bolt projects forwardly under the bias of the trigger spring 80 and the lever 82 pivots clockwise downwardly. The compression spring 38 forces the latch bolt 30 forwardly to the intermediate self-latching position which is defined by the engagement of the lever 84 with the engagement arm 50 as best illustrated in FIG. 4. In a self-latching position, the latch bolt is typically projected approximately a half inch, and the lock bar 60 pivots downwardly to permit the inward retraction of the latch bolt. 
     When the door is closed, then the trigger bolt 72 and rod 74 are forced rearwardly to disengage the lever 84 from arm 50 which allows the engagement arm 50 to pivot forwardly to the projected latch bolt position of FIG. 1. 
     With reference to FIGS. 6 and 7a-d, the latch bolt set is also adapted to be bi-handed. A central recess 90 is formed in the lock case to permit access to the set screw 35 when the latch bolt is in the projected position as illustrated in FIG. 6. With reference to FIG. 7a, the set screw 35 is removed from the latch bolt and the latch bolt 30 thus is permitted to be removed from its engagement with the throw rod 34 as illustrated in FIG. 7b. The bevel relationship on the latch bolt is then reversed in a manner equivalent to a 180° rotation about the axis of the throw rod 34, and the latch bolt is remounted to the throw rod. The set screw 35 is then re-engaged to secure the latch bolt to the throw rod with the latch bolt now being reversed for the opposite hand as opposed to the configuration of FIGS. 1-6. The latch bolt is therefore symmetric about a central plane through the latch bolt. It will be appreciated that the trigger bolt and the latch bolt are not required to be symmetrical about the plane through the latch case. The trigger bolt and latch bolt may be offset relative to the case center line. The width of the door and the position of the mortise of the door, in combination with the offset, determine the latch bolt and trigger bolt position. The position is determined so that the latch bolt aligns with the center line of the strike opening. 
     In addition, the associated strike 14 may be bi-handed. The strike opening is configured for symmetry about a transverse plane through the strike plate. Therefore, the same strike plate can be employed for left and right hand doors for reduced costs. 
     While a number of embodiments have been set forth for purposes of describing the invention, the foregoing descriptions are not a limitation of the invention. Accordingly, various modifications, adaptations and alternatives may also occur to one skilled in the art without departing from the spirit and the scope of the present invention.