Braking mechanism

Claim 1

IN A SLIDING DOOR CONSTRUCTION HAVING A DOOR, A RAIL, AND WHEELS ROTATABLY MOUNTED ON THE DOOR AND SUPPORTING THE SAME ON THE RAIL, A BRAKING MECHANISM COMPRISING A MEMBER FIXED TO THE DOOR AND HAVING A LOWER FRICTION SURFACE SLANTED AT A PREDETERMINED ANGLE WITH RESPECT TO THE RAIL, A MOVABLE WEDGE MEMBER HAVING A WEDGE ANGLE THE SAME AS THE SAID PREDETERMINED ANGLE, THE SAID MOVABLE WEDGE MEMBER HAVING AN UPPER SURFACE FOR SLIDABLY ENGAGING THE SAID FRICTION SURFACE AND A FLANGED BOTTOM FOR FITTING OVER THE RAIL, MEANS MOVABLY SUPPORTING THE WEDGE MEMBER ON THE DOOR FOR MOVEMENT BETWEEN AN INACTIVE POSITION WHERE IT IS SPACED FROM THE RAIL AND A BRAKING POSITION WHERE IT ENGAGES BOTH THE RAIL AND THE SAID FRICTION SURFACE, AND COMPRISING VERTICAL SIDE PLATES FIXED TO THE DOOR AT EACH SIDE OF THE FRICTION SURFACE, AND SAID PLATES AND MOVABLE WEDGE ELEMENT HAVING COOPERATING RIB AND GROOVE ELEMENTS EXTENDING PARALLEL TO SAID FRICTION SURFACE FOR GUIDING THE MOVABLE WEDGE MEMBER FROM SAID INACTIVE POSITION TO SAID BRAKING POSITION AND BEYOND THE SAID BRAKING POSITION, THEREBY PERMITTING MOVEMENT OF THE DOOR AND INCLINED SURFACE UPWARDLY ON THE WEDGE, AND OPERATING MEANS FOR MOVING THE WEDGE MEMBER FROM INACTIVE TO ACTIVE POSITION, THE SAID MEANS HAVING AN OPERATING STROKE BRINGING THE WEDGE INTO CONTACT WITH THE LOWER SURFACE OF SAID MEMBER AND WITH THE RAIL AND ALSO HAVING OVERTRAVEL PERMITTING FURTHER MOVEMENT OF THE DOOR WITH RESPECT TO THE WEDGE TO THE SAID POINT WHERE IT STOPS, THE COEFFICIENT OF FRICTION BETWEEN THE WEDGE AND SLANT SURFACE BEING LESS THAN THE TANGENT OF THE WEDGE ANGLE, WHEREBY THE DOOR RIDES UP THE WEDGE IN BRAKING POSITION TO A POINT WHERE IT STOPS, LIFTING A SAID WHEEL OFF THE RAIL, AND THEN SLIDES BACK DOWN TO BRING THE WHEEL BACK ON TO THE RAIL, THE COEFFICIENT OF FRICTION BETWEEN THE WEDGE AND RAIL BEING GREATER THAN THE FIRST MENTIONED COEFFICIENT OF FRICTION, WHEREBY THE WEDGE IN BRAKING POSITION REMAINS STATIONARY WITH RESPECT TO THE RAIL, AND THE DISSIPATION OF INITIAL KINETIC ENERGY IN FRICTION BETWEEN THE UPPER SURFACE OF THE SAID WEDGE MEMBER AND THE SAID FRICTION SURFACE REDUCES THE KINETIC ENERGY OF THE DOOR UPON RETURN OF THE WHEEL TO THE RAIL TO A VALUE SUCH THAT IT MAY BE STOPPED SUBSTANTIALLY DEAD.