Abstract:
A latching system for live bolts as in a door retains the live bolts within the door until the door is closed. A latch holds a live bolt link against travel that would insert the live bolts into the door body jamb until a link lifter forces the link out if the latch against the bias of a hold-down spring. The link lifter can take the form of an inclined surface on a cam mounted on the hinge side of the door. The cam engages the door body jamb as the door closes and travels into the door until the link lifter engages and lifts the link out of the latch.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/055,755, filed on Aug. 14, 1997, which provisional application is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The invention relates to latching systems for live bolts. 
     BACKGROUND 
     Live bolt systems for doors can be damaged when an operator tries to close the door with the live bolts extended. In safes, this can occur after the safe door has been opened and the handle of the safe is accidentally bumped or turned, extending the live bolts. In some cases, damage is done to other components of the door or even to the safe itself. Repair or replacement of the damaged parts can be costly and may result in a period during which the safe cannot be used. Thus, there is a need for a live bolt system that will not extend the live bolts as a result of accidental bumping or unintentional turning of a safe door handle. 
     Latching systems exist in the prior art, but suffer from disadvantages that need to be overcome. Many systems, such as gravity-biased live bolt systems, involve a long series of cams, bars, and levers, creating a relatively high risk of failure as a result of the large number of parts involved. In addition, the large number of parts increases the cost of such systems. A need therefore exists for a lower cost latching system with fewer parts to reduce the risk of failure. 
     Other systems, such as some spring-biased systems, are simpler, but have other problems. While fewer parts are used, these systems still use more parts than necessary, resulting in higher system cost and complexity. Additionally, accidental latch release is likely as a result of actuator placement and design. If the actuator is changed to prevent accidental release, then the door becomes difficult to close. Therefore, a need exists for a simpler, lower cost latching system that is more secure against accidental release, but does not inhibit closing of the door. 
     SUMMARY OF THE INVENTION 
     Our live bolt latching system provides automatic retention and release of live bolts with fewer parts than prior art systems. Our system is also more secure against accidental release of the live bolts. A spring biases a live bolt link into a latch that prevents live bolt extension. A cam preferably mounted in the hinge side of the door actuates a link lifter that moves the link out of the latch when the door is closed, allowing the bolts to extend. In the preferred embodiment of our invention, springs bias the live bolts for automatic extension of the live bolts upon closure of the door. Because of the design and placement of the cam, accidental release of our latching system is much less likely than in prior art systems. Further, our latching system is less likely to fail because it uses fewer parts than prior art latching systems. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of the back of a safe door including a live bolt latching system according to the invention. 
     FIG. 2 is an elevation view of the back of the safe door shown in FIG.  1 . 
     FIG. 3 is a cross section of the door shown in FIG. 2 taken along line  3 — 3 . 
     FIG. 4 is a side view of the cam and link lifter of the invention. 
     FIG. 5 is a top view of the cam and link lifter shown in FIG.  4 . 
     FIG. 6 is a schematic side view of the latching system of the invention as it appears when the door is open. 
     FIG. 7 is a schematic side view of the system of FIG. 6 as it appears when the door is almost all the way closed, with the link lifted almost completely out of the latch. 
     FIG. 8 is a schematic side view of the system of FIGS. 6 and 7 as it appears when the door is closed after the latch has been removed from the latch and moved toward the door jamb. 
     FIG. 9 is a schematic side view of an alternative embodiment of the invention as it appears when the door is open. 
     FIG. 10 is a schematic side view of the alternative embodiment of the invention shown in FIG. 9 as it appears when the door is almost completely closed, with the link lifted almost completely out of engagement with the latch. 
     FIG. 11 is a schematic side view of the system of FIGS. 9 and 10 as it appears when the door is closed after the latch has been removed from the latch and moved toward the door jamb. 
     FIG. 12 is a schematic side view of another embodiment of the invention as it appears when the door is open. 
     FIG. 13 is a schematic side view of the alternative embodiment of the invention shown in FIG. 12 as it appears when the door is almost completely closed, with the link lifted almost completely out of engagement with the latch. 
     FIG. 14 is a schematic side view of the system of FIGS. 12 and 13 as it appears when the door is closed after the latch has been removed from the latch and moved toward the door jamb. 
    
    
     DESCRIPTION OF THE INVENTION 
     Our invention can be used in any door, gate, or related body, but is preferably used in the doors of insulated steel shell safes. Such a safe door  1  is shown in the Figures and comprises a front door plate  2  attached to a door jamb  3  with insulation  4  of some sort filling the space between the plate  2  and the door jamb  3 . The door jamb  3  is a part on the door  1  and the body jamb  13  of the door is a part mounted on a frame for the door or in the body of a safe or other structure. A combination lock knob  5  and a handle  6  are mounted on the exterior of the front plate  2  for operating a combination lock  10  and a live bolt system  20 , respectively. The knob  5  and the handle  6  are attached to spindles  7  running through the insulation  4  to components mounted on the back of the door jamb  3 . The spindles  7  pass through bushings  8  that extend from the back of the front door plate  2  to the door jamb  3 . The bushings  8  also have stubs  9  projecting rearwardly of the door jamb  3  on which components of the combination lock  10  and the live bolt system  20  are mounted. The stub  9  of the combination lock bushing  8  carries the driver  11  and tumblers  12  of the combination lock  10 . The stub  9  of the handle bushing  8  carries the driver  21  and components for the live bolt system of the door. 
     The live bolt system driver  21  drives links  22 - 25  connected to live bolts  26  mounted near the sides of the door  1 . When the handle  6  rotates, the handle spindle  7  transmits the rotation to the driver  21 . The driver  21  is preferably a pinion comprising teeth  30  that engage the teeth of racks  31  on the links. The engagement of the racks  31  with the pinion teeth  30  causes substantially linear translation of the links  22 - 25  in response to rotation of the handle  6 . Linear motion of the links  22 - 25  then causes linear motion of the live bolts  26  into and out of the body of the safe or body jamb  13  of the door  1  in accordance with operation of the handle  6 . 
     According to the preferred embodiment of our invention as shown schematically in FIGS. 6-11, the link  24  nearest the hinge side  50  of the door is acted upon by the latching system  40  we have invented. The link  24  passes over an actuator  41 , preferably a cam, mounted between a set of guide walls  42  attached to the back of the door jamb  3 . Each guide wall  42  has a step or recess  43  formed in it, the steps or recesses  43  being aligned with the link  24  such that they act as latches for the link  24 . While the preferred embodiment uses a step or recess  43  in each guide wall  42  to retain the link  24 , an alternative embodiment can use a projection  48  on the guide wall  42  that engages a step or recess  49  in the link  24  to retain the link  24  in a latched position as shown schematically in FIGS. 12-14. 
     The cam  41  is biased toward the hinge side  50  of the door  1  by a spring  47 . The link  24  is preferably biased into the latch  43  by a force that can be provided by gravity or a resilient body, such as a spring or a resilient link  24 . A hold-down spring  46 , preferably a leaf spring mounted on a post  45  on the side of the link  24  opposite the door hinge  51 , biases the link  24  into the latches  43 . The latches  43  in the guide walls  42  prevent motion of the link  24  toward the hinge  51 , thus preventing travel of the live bolts  26  carried by the link  24  into the body of the safe or the body jamb  13  of the door  1 . Because of the rack and pinion arrangement of the live bolt system, when this link  24  is held in place, all links  22 - 25  are held in place, and none of the live bolts  26  can enter the body of the safe or the body jamb  13  of the door  1 . 
     The cam  41  protrudes from the side of the door  50  such that it engages the body of the safe as the door  1  is closing. As the door  1  continues to close, the cam  41  travels toward the link  24  between the guide walls  42 . A link lifter  44 , preferably formed as part of the cam  41 , lifts the link  24  out of the latches  43  against the bias of the hold-down spring  46  as the cam  41  moves toward the link  24 . The link lifter  44  can be an inclined surface of the cam  41  leading from a thinner or recessed section of the cam  41  to a thicker section of the cam  41 . Thus, as the cam  41  travels toward the link  24 , the effective thickness of the cam  41  at the point of contact with the link  24  increases. 
     When the door  1  is fully closed, travel of the cam  41  causes the link  24  to move out of the latch. In the preferred embodiment, at least a small clearance is provided such that the link  24  clears the lip of the recesses  43 . Springs  27  attached to the door jamb  3  and to the links  22 - 25  bias the links  22 - 25  toward the body of the safe or body jamb  13  of the door  1 , forcing the live bolts  26  into the body of the safe or the body jamb  13  of the door  1 . Thus, the links  22 - 25  and live bolts  26  are locked in an open position until the door  1  is substantially fully closed, at which point the live bolts  26  are automatically inserted into the body of the safe or the body jamb  13  of the door  1 . Because the live bolts  26  are latched in place until the door  1  is closed, and because the latching occurs automatically when the door  1  is opened, damage due to attempted closures of the door  1  with the live bolts  26  extended is prevented. Further, because the latching system  40  and cam  41  are disposed on the hinge side  50  of the door, the risk of accidental release of the latching system  40  by bumping the cam  41  is minimized. 
     All parts of the live bolt and latching systems  20 ,  40  are preferably made from resinous material except for the links  22 - 25 , the live bolts  26 , and the springs  27 ,  46 ,  47 . The links  22 - 25  and the live bolts  26  are preferably made of die cast metal. The springs  27 ,  46 ,  47  are preferably formed of spring steel. The hold-down spring  46  can be of any suitable type, but is preferably a leaf spring. The springs  27  biasing the links  22 - 25  toward the sides of the door  1  and the spring  47  biasing the cam  41  are preferably coil springs. 
     PARTS LIST 
       1  Door 
       2  Front door plate 
       3  Door jamb 
       4  Insulation 
       5  Combination lock knob/dial 
       6  Handle 
       7  Spindles 
       8  Bushings 
       9  Stubs of bushings 
       10  Combination lock 
       11  Combination lock driver 
       12  Tumbler discs 
       13  Body jamb of the door 
       20  Live bolt system 
       21  Live bolt driver 
       22 - 25  Live bolt links 
       26  Live bolts 
       27  Link biasing spring 
       30  Pinion teeth on live bolt driver 
       31  Rack teeth on link 
       40  Latching system 
       41  Cam/Actuator 
       42  Guide wall 
       43  Recess/latch 
       44  Link lifter 
       45  Post 
       46  Link biasing spring 
       47  Cam biasing spring 
       48  Projection on guide wall 
       49  Step or recess in link 
       50  Hinge side of door 
       51  Hinge