Patent ID: 7770986

Claim:
A pivot assembly comprising: a. a front pivot arm pivotally connected to a top bar and a bottom bar, and a rear pivot arm connected to the top bar and the bottom bar; b. said pivotally connections between said pivot arms and said bars forming an outer parallelogram; c. said pivot arms pivotally connected to a rigid element, said pivot arms rotating around said connection with said rigid element from an up position, through a middle position, and to a down position, the bars spaced apart in the middle position and touching in the up position and the down position; d. said connections between said pivot arms and said rigid element and said connections between said pivot arms and said bottom bar forming an inner parallelogram; e. said inner parallelogram forming a substantially rectangular shape in said up position and said down position, said inner parallelogram becoming undefined in said middle position; f. said outer parallelogram forming a substantially rectangular shape in said middle position, said outer parallelogram preventing warping when said pivot arms pass through said middle position, said outer parallelogram forming a non-rectangular shape in said up position and said down position.