Folding linkage

A mechanism according to either previous claim wherein path is provided by a curved slot in the fourth bar in which a pin attached to the first bar slidably engages.

A mechanism according to any previous claim wherein a fifth bar is pivotally attached to the first bar.

A mechanism according to any previous claim wherein the second bar and the third bar are constrained such that they pass through a precisely collinear relationship when the mechanism is transformed from the folded state to the open state and are held in a braced state in the open position when subjected to compressive forces.

A mechanism according to any previous claim wherein the linkage forms part of a chair, the second and third bar being part of one leg of the chair, and the fourth bar forming part of another leg of the chair.

A linkage mechanism including four pivoting bars, having an open position in which the first bar forms one side of a substantially triangular shape, the second and third bars are generally collinear to form the second side of the triangular shape, and the fourth bar forms the third side of the triangular shape, and a closed position in which the first bar, second bar, third bar and fourth bar are substantially aligned, the first bar being pivotally joined to the second bar, the second bar being pivotally joined to the third bar, the third bar being pivotally joined to the fourth bar, and the fourth bar being pivotally joined to the first bar, the second bar and the third bar being constrained such that they pass through a precisely collinear relationship when the mechanism is transformed from the folded state to the open state and are held in a braced state in the open position when subjected to compressive forces, and there being provided a release member attached to the second and/or the third bar capable of displacement causing the second bar and third bar to pass through the precisely collinear relationship in order to remove the braced state so that the structure can be folded.

A folding chair, including seat bar pivotally joined to a upper first leg bar, the upper first leg bar being pivotally joined to a lower first leg bar, the lower first leg bar being pivotally joined to a second leg bar, the second leg bar being pivotally joined to the seat bar, having an open position in which the seat bar forms one side of a substantially triangular shape, the upper first leg bar and lower first leg bar are generally collinear to form the second side of the triangular shape, the second leg bar forming the third side of the triangular shape, and a closed position in which the seat bar, upper first leg bar, lower first leg bar and second leg bar are substantially aligned.

A linkage mechanism substantially as herein described and illustrated.