Self-balancing locking mechanism for doors

1. A self-balancing locking mechanism for actuating a locking pin-bar assembly of a door, comprising:

a drive shaft mounted to the door and having an axis of rotation;

a cam mounted to the drive shaft;

at least one actuator plate having a proximal end with a radial slot formed therein and installed about the drive shaft, and a distal end coupled to the locking pin-bar assembly that is slidably supported adjacent a perimeter of the door; and

at least one linkage bar having a proximal end pivotably coupled to the cam at a radial distance from the axis of rotation, and a distal end pivotably coupled to a mid-span of the actuator plate,

wherein rotation of the cam causes the linkage bar to drive the actuator plate along a radial axis and engage the locking pin-bar assembly with a side edge of a door frame, and the radial slot to bear on the drive shaft and balance off-axis loads applied by the linkage bar to the actuator plate.

2. The locking mechanism of claim 1 , wherein the radial axis is a horizontal radial axis intersecting the axis of rotation of the drive shaft and the locking pin-bar assembly engages a vertical side edge of the door frame.

3. The locking mechanism of claim 2 , wherein the distal end of the linkage bar is coupled to the mid-span of the actuator plate at a distance vertically-offset from the horizontal radial axis.

4. The locking mechanism of claim 2 , further comprising first and second actuator plates being driven in opposite directions along the horizontal radial axis by first and second linkage bars to engage first and second locking pin-bar assemblies with opposite vertical side edges of the door frame.

5. The locking mechanism of claim 2 , further comprising at least one vertically-oriented actuation bar having a proximal end pivotably coupled to the cam and a distal end coupled to an additional locking pin-bar assembly that engages a horizontal side edge of the door frame.

6. The locking mechanism of claim 1 , wherein the proximal end of the linkage bar is over-rotated beyond a radial reference line extending from the axis of rotation to the distal end of the linkage bar, and the locking pin-bar assembly is withdrawn a pre-determined over-center retract distance from a fully-extended position.

7. The locking mechanism of claim 6 , further comprising a stationary pin installed within an arc-segment slot formed into the cam and limiting the over-rotation of the cam.

8. The locking mechanism of claim 7 , wherein the arc-segment slot has an arc length ranging from about forty-five degrees to about ninety degrees.

9. The locking mechanism of claim 1 , wherein the door and door frame further comprise a door and a door frame of a safe.

10. An internally-balanced locking mechanism for securing a door of a safe, comprising:

a drive shaft mounted through the door of the safe and having an axis of rotation;

a cam mounted to the drive shaft;

at least two actuator plates, each having a proximal end with a lateral slot formed therein and installed about the drive shaft, and a distal end coupled to opposing locking pin-bar assemblies that are slidably supported adjacent a perimeter of the door of the safe, respectively; and

at least two linkage bars, each having a proximal end pivotably coupled to the cam at a radial distance from the axis of rotation, and a distal end pivotably coupled to a mid-span of one of the actuator plates,

wherein rotation of the cam causes the linkage bars to drive the actuator plates in opposite directions along a horizontal radial axis and engage the locking pin-bar assemblies with opposite vertical side edges of a door frame of the safe, and the at least two lateral slots bear on the drive shaft and balance off-axis loads applied by the linkage bars to the actuator plates.

11. The locking mechanism of claim 10 , wherein the distal end of the linkage bar is coupled to the mid-span of the actuator plate at a vertically-offset distance from the horizontal radial axis.

12. The locking mechanism of claim 10 , further comprising at least one vertically-oriented actuation bar having a proximal end pivotably coupled to the cam and a distal end coupled to an additional locking pin-bar assembly that engages a horizontal side edge of the door frame.

13. The locking mechanism of claim 10 , wherein the proximal ends of the at least two linkage bars are over-rotated beyond a radial reference line extending from axis of rotation to the distal ends of the linkage bars, and the opposing locking pin-bar assemblies are withdrawn a pre-determined over-center retract distance from a fully-extended position.

14. The locking mechanism of claim 13 , further comprising a stationary pin installed within an arc-segment slot formed into the cam and limiting the over-rotation of the cam.

15. The locking mechanism of claim 14 , wherein the arc-segment slot has an arc length ranging from about forty-five degrees to about ninety degrees.

16. A method of actuating a locking pin-bar assembly of a door to engage with a door frame, comprising:

rotating a drive shaft mounted to the door in a first direction, the drive shaft having an axis of rotation and a rotatable cam coupled thereto;

causing a linkage bar to drive an actuator plate along a radial axis and engage the locking pin-bar assembly with a side edge of the door frame,

wherein the linkage bar has a proximal end pivotably coupled to the cam at a radial distance from the axis of rotation and a distal end pivotably coupled to a mid-span of the actuator plate, and

wherein the actuator plate has a distal end coupled to the locking pin-bar assembly that is slidably supported adjacent a perimeter of the door; and

causing a radial slot formed into a proximal end of the actuator plate to bear on the drive shaft and balance off-axis loads applied by the linkage bar to the actuator plate.

17. The method of claim 16 , further comprising over-rotating the proximal end of the linkage bar beyond a radial reference line extending from the axis of rotation to the distal end of the linkage bar, and withdrawing the locking pin-bar assembly a pre-determined over-center retract distance from a fully-extended position.

18. The method of claim 17 , further comprising limiting the over-rotation of the proximal end of the linkage bar with a stationary cam stop.

19. The method of claim 18 , wherein the cam stop further comprises a stationary pin having a base fixed to the door and a pin body end positioned within an arc-segment slot formed into the cam.

20. The method of claim 16 , further comprising:

rotating the drive shaft mounted to the door in an opposite direction;

causing the linkage bar to pull the actuator plate along the radial axis and disengage the locking pin-bar assembly with the side edge of the door frame, and

causing the radial slot to bear on the drive shaft and balance off-axis loads applied by the linkage bar to the actuator plate.