Drive mechanism for overhead doors

Claim 1

A COUNTER-BALANCED DRIVE MECHANISM FOR AN ARTICULATED OVERHEAD SLIDING DOOR THAT IS MOVABLE IN GUIDEWAYS THAT EXTEND UPWARDLY ALONGSIDE AN OPENING FOR THE DOOR AND THEN REARWARDLY, SAID DOOR HAVING GUIDE MEANS CARRIED ON OPPOSITE SIDES OF THE DOOR AND ENGAGEABLE WITH SAID GUIDEWAYS FOR GUIDING MOVEMENT OF THE DOOR FROM A VERTICAL CLOSED POSITION ACROSS THE OPENING TO AN OVERHEAD SUBSTANTIALLY HORIZONTAL OPEN POSITION IMMEDIATELY ABOVE THE OPENING, SAID MECHANISM COMPRISING MEANS MOUNTING A SEPARATE WINDING DRUM ABOVE AND ADJACENT EACH SIDE OF THE OPENING TO ROTATE ABOUT A HORIZONTAL AXIS, A SEPARATE CABLE ENGAGED UPON EACH DRUM AND HAVING A LOWER END CONNECTED IN FIXED RELATION TO A CORRESPONDING LOWER SIDE OF THE DOOR, DRIVE MEANS CONNECTED TO ROTATE SAID DRUMS IN UNISON EITHER IN A DOOR OPENING DIRECTION OR IN A DOOR LOWERING DIRECTION, COUNTERBALANCING MEANS CONNECTED TO SAID DRUMS AND ACTING IN UNISON THEREON TO ASSIST ROTATION THEREOF IN A DOOR OPENING DIRECTION AND TO OPPOSE ROTATION THEREOF IN A DOOR CLOSING DIRECTION, FIRST CONTINUOUSLY ACTIVE SLACK TAKE-UP MEANS ON THE DOOR ADJACENT ONE LOWER SIDE THEREOF AND CONNECTED TO ENGAGE A PORTION OF THE CORRESPONDING CABLE ADJACENT BUT SPACED FROM THE LOWER END THEREOF TO RESILIENTLY PULL SUCH CABLE TO A TAUT CONDITION, AND SECOND CONTINUOUSLY ACTIVE SLACK TAKE-UP MEANS ON THE DOOR ADJACENT THE OTHER LOWER SIDE THEREOF AND CONNECTED TO ENGAGE A PORTION OF THE CORRESPONDING CABLE ADJACENT BUT SPACED FROM THE LOWER END THEREOF TO RESILIENTLY PULL SUCH CABLE TO A TAUT CONDITION, EACH SLACK TAKE-UP MEANS COMPRISING A DOOR MOUNTED THIMBLE HAVING SAID CABLE PORTION TRAINED REVERSELY THEREABOUT FOR FREE SLIDING MOVEMENT RELATIVE THERETO, A DOOR MOUNTED SPRING MOUNT, AND AN ELONGATED COIL SPRING LOCATED ON THE SPRING MOUNT AND HAVING ONE END ANCHORED AGAINST ROTATION AND AN OPPOSITE END PROVIDING A SWINGABLE ARM TERMINATING IN A HOOK ENGAGED ABOUT THE CABLE AT A POINT BETWEEN THE THIMBLE AND THE LOWER END OF THE CABLE.