Back rest having an adjustable shaped element

Claim 1

A BACK SUPPORT ATTACHMENT FOR VEHICLE SEAT BACKS COMPRISING A PLATE HAVING A VERTICAL GUIDEWAY THEREIN, AN EXTERNALLY THREADED BUSHING IN SAID GUIDEWAY, A FLANGE ON SAID BUSHING ON ONE SIDE OF SAID PLATE, AN INTERNALLY THREADED CLAMPING RING ON THE OTHER SIDE OF SAID PLATE THREADEDLY ENGAGING SAID BUSHING, PINS ON THE FACE OF SAID CLAMPING RING, AN INTERNALLY THREADED BUSHING EXTENDING SLIDABLY THROUGH SAID FIRST MENTIONED BUSHING, A HAND WHEEL FIXED TO THE END OF SAID INTERNALLY THREADED BUSHING, SPRING MEANS BETWEEN SAID FIRST MENTIONED BUSHING SAID SAID WHEEL BIASING SAID WHEEL OUTWARDLY FROM SAID RING, RECESSES ON THE INNER FACE OF SAID WHEEL ENGAGEABLE WITH SAID PINS WHEREBY INWARD PRESSURE ON SAID WHEEL ENGAGES SAID PINS AND RECESES FOR ROTATING SAID RING RELATIVE TO SAID EXTERNALLY THREADED BUSHING TO RELEASE THE CLAMPING ACTION OF SAID RING AND SAID FLANGE TO PERMIT LINEAR VERTICAL MOVEMENT OF SAID BUSHING IN SAID GUIDEWAY, A THREADED PIN ENGAGING THE INTERNAL THREADS OF SAID INTERNALLY THREADED BUSHING, A SPRING ARM FIXED TO THE INNER END OF SAID PIN, MEANS SECURING ONE END OF SAID ARM IN SAID GUIDEWAY TO PRECLUDE ROTATION OF SAID PIN WHEREBY ROTATION OF SAID HAND WHEEL AND HENCE SAID INTERNALLY THREADED BUSHING MOVES SAID SPRING ARM INWARDLY OR OUTWARDLY RELATIVE TO SAID SEAT BACK, AND A BACK REST ELEMENT SECURED TO THE OTHER END OF SAID SPRING ARM.