Device for adjusting the back rest of a seat

Claim 1

A SEAT ESPECIALLY FOR A MOTOR VEHICLE HAVING AN ADJUSTABLE BACK REST COMPRISING A RIGID SEAT FRAME, A SEAT PORTION SUPPORTED BY SAID SEAT FRAME, A BACK REST HAVING A RIGID BACK FRAME, SAID BACK FRAME COMPRISING TWO LEVERS, PIVOT MEANS FOR PIVOTALLY CONNECTING SAID LEVERS TO SAID SEAT FRAME, ONE OF SAID LEVERS HAVING TWO ARMS, A DRAW ROD PIVOTALLY CONNECTED TO THE FREE END OF ONE OF THE ARMS OF SAID TWO-ARMED LEVER, A PAIR OF INTERENGAGING THREADED ELEMENTS HAVING SELF-LOCKING SCREW THREADS, ONE OF SAID ELEMENTS FORMING A TUBULAR SPINDLE SURROUNDING THE FREE PART OF SAID DRAW ROD AND HAVING SCREW THREADS ON ITS SURFACE AND BEING ROTATABLE ABOUT THE AXIS OF SAID DRAW ROD BUT IMMVOABLE AXIALLY RELATIVE THERETO, AND OTHER ELEMENT BEING A SHELL-LIKE MEMBER PROVIDED WITH SCREW THREADS ON ITS INNER SURFACE THUS FORMING A NUT SEGMENT AND BEING MOUNTED ON SAID SEAT FRAME, SAID TWO THREADED ELEMENTS BEING ADAPTED TO BE ENGAGED WITH AND DISENGAGED FROM EACH OTHER SO THAT, WHEN SAID ELEMENTS ARE DISENGAGED SAID DRAW ROD MAY BE MOVED SUBSTANTIALLY IN ITS AXIAL DIRECTION FREE FROM SAID NUT SEGMENT FOR COARSELY ADJUSTING THE INCLINATION OF SAID BACK REST RELATIVE TO SAID SEAT, AND WHEN SAID ELEMENTS ARE ENGAGED, SAID SPINDLE MAY BE TURNED ABOUT ITS AXIS IN SAID NUT SEGMENT IN ONE OR THE OPPOSITE DIRECTION FOR FINELY ADJUSTING THE INCLINATION OF SAID BACK REST AND FOR LOCKING SAID BACK REST IN THE ADJUSTED POSITION BY MEANS OF SAID SELF-LOCKING SCREW THREADS.