Seat back hinge-latch

Claim 1

A COMBINATION SEAT BACK HINGE AND LATCH MECHANISM COMPRISING, A PAIR OF HINGE BLADES ADAPTED TO BE MOUNTED RESPECTIVELY ON A CHAIR SEAT FRAME AND A CHAIR BACK FRAME, HINGE MEANS PIVOTALLY INTERCONNECTING SAID HINGE BLADES FOR RELATIVE ROTATION ABOUT A FIRST AXIS, A LOCK ABUTMENT EXTENDING FROM ONE OF SAID BLADES IN SPACED RELATION TO SAID FIRST AXIS, A LATCH BAR PIVOTALLY MOUNTED UPON THE OTHER OF SAID HINGE BLADES ABOUT A SECOND AXIS SPACED FROM SAID FIRST AXIS SO THAT RELATIVE ROTATION BETWEEN SAID HINGE BLADES TO LOWER THE BACK FRAME MOVES SAID SECOND AXIS TOWARD SAID ABUTMENT, SAID LATCH BAR BEING FORMED WITH A LATERALLY EXTENDING MANUAL CONTROL ARM PORTION AND BEING FORMED WITH A PLURALITY OF RECESSES ADAPTED TO RECEIVE WITH SAID LOCK ABUTMENT THEREIN, SPRING MEANS BIASING SAID LATCH BAR TO MOVE INTO ENGAGEMENT WITH SAID LOCK ABUTMENT, THE PARTS BEING SO DIMENSIONED AND RELATIVELY ARRANGED THAT SAID LATCH BAR IS OPERABLE TO HOLD THE SEAT BACK IN A SELECTED ONE OF A SERIES OF PREDETERMINED VERTICALLY INCLINED ATTITUDES, AT LEAST ONE OF SAID RECESSES BEING SHAPED TO PRESENT A SHOULDER TO ENGAGE AGAINST AND PREVENT RELEASE FROM