Patent ID: 9609953
Date: 2017-04-04
CPC Classifications: A47C,Y10T

Claim:
1. A spring back hinge mounted on sitting structure comprising: 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 a tension used in a flex of the back frame, thereby allowing a softer or firmer ride depending on the user's preference; 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 said 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 seat back mounting plate flange to provide resistance to rocking; said 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 backrest is mounted to said hinge plate.