Patent ID: 9060610
Filing Date: 2015-06-23
Classification: A47C,Y10T

Abstract:
1. A spring back hinge mounted on sitting structure comprising: said sitting structure having a side and floor supporting member; said sitting structure having a seat frame and a backrest; said sitting structure having a left side and a right side; said spring back hinge being mounted to one of said left side or said right side, or mounted to both said left and right sides structure; said spring back hinge being mounted so as to allow a user to rock said backrest fore and aft independently of moving said seat frame; said spring back hinge being adapted to allow for mechanical adjustment of the tension used in the flex of the back frame, thereby allowing a softer or firmer ride depending on the user's preference; said spring back hinge including a spring-lock spring mechanism adapted to fix the back position by engaging a lever, whereby the seat back hinge can operatively connect standard seat frame units with interchangeable back frames; said sitting structure includes a chair base frame; said spring back hinge is attached to said chair base frame; said chair base frame has arm and leg portions and includes a plate or web that interconnects said arm and leg portions into a structural unit; said spring back hinge being formed with a hinge plate and a base plate; said hinge plate has a seat back mounting plate flange; said hinge plate is pivotally attached to said base plate; said hinge plate is movably connected to base plate with a fastener and spring whereby the fastener is fixed to said base plate and passes through the seat back mounting plate flange while the spring bears on said flange to provide resistance to rocking; a spring surrounds said fastener and is compressible by adjustment of a tension member, which tension member can then be adjusted to increase or decrease the tension on the hinge plate; said seating unit is provided with a lock assembly; said lock assembly has a lock plate formed to define a lever handle, a locking cam and a locking arm with a pin receiving area between said cam and said arm; said plate being rotatably mounted on a lock rod; said lock rod is rotatably and slidably mounted in said base plate; a locking pin being fixed in said supporting member; a spring strap holding said lock assembly in a selected position; said lock plate is rotatable against said spring strap between an unlocked position in which said pin is unengaged and a locked position in which said pin receiving area engages said pin; said backrest is attached to said spring back hinge with mounting bolts; said mounting bolts additionally mounting said spring straps; said spring straps are ‘L’ shaped with the long arm of the “L” being mounted and the shorter arm of the “L” capturing said lock rod to maintain a locked or unlocked position of the locking plate; said seating structure is made up of a chair base frame acting to support a seat frame and a backrest frame; two spring hinge assemblies are attached via said base plates to said seat frame; said backrest frame is mounted to said hinge plates said spring back hinge is mounted to said chair base frame.