Collapsible seat structures

A volume frame foldable in two dimensions mutually at right angles, comprising, when extended,

• a pair of opposite sides of corresponding form, each such side comprising elongate elements and a first plurality of pivot connection means, such elements of each such side including at least one element which is an upright front leg, an element which is an upright back leg, and two generally parallel spaced apart rigid elements which join the front leg to the back leg through said pivot connection means, said pivot connection means being a pair spaced along each said rigid element and disposed at two corners of the quadrilateral formed thereby of which said front leg and said back leg are opposite sides, each pivot connection means of said pair affording a horizontal axis associated with each rigid element and directed from side to side of the volume frame, thereby enabling folding of the frame in one of said dimensions by pivoting of each said front leg about one said horizontal axis and pivoting of each said back leg about another horizontal axis in the back to front sense of the frame with concurrent mutual approach of said front leg, said back leg and said rigid element in each said side frame, the frame further comprising:
• at least one collapsible X frame and a second plurality of pivot connection means each having two degrees of pivotal freedom including pivotal freedom about a horizontal axis directed from side to side of the volume frame, which X frame lies in a plane extending in the lateral sense of the volume frame and inclined to a front plane and a back plane which contain, respectively, each said front leg and each said back leg, said X frame having a pair of lower ends and a pair of upper ends, of which X frame one such lower end and one such upper end are each pivotally connected by a respective pivot connection means of said second plurality thereof to one of said opposite sides of the volume frame whereas the other such lower end and the other such upper end are each pivotally connected by a respective pivot connection means of said second plurality thereof to the other of said opposite sides of the volume frame, thereby enabling folding of the frame in the other of said dimensions by collapse of said X frame;
• and
• at least one tie means having two ends of limited separability by which ends said tie means are connected in the volume frame in triangulating relationship with said X frame for supporting the volume frame when extended.

A collapsible wheel chair frame foldable in two dimensions mutually at right angles, comprising, when extended,

• a pair of opposite sides of corresponding form, each such side comprising four elongate elements and a first plurality of pivot connection means, the elements of each such side including an upright front leg, an upright back leg, and an upper and a lower generally parallel spaced apart rigid elements which join the front leg to the back leg through said pivot connection means, said pivot connection means being a pair spaced along each said rigid element and disposed at the four corners of the quadrilateral formed thereby of which said front leg and said back leg are opposite sides, each pivot connection means of said pair affording a horizontal axis associated with each rigid element and directed from side to side of the chair frame, thereby enabling folding of the frame in one of said dimensions by pivoting of each said front leg about one said horizontal axis and pivoting of each said back leg about another horizontal axis in the back to front sense of the frame with concurrent mutual approach of said front leg, said back leg and said rigid element in each said side, the frame further comprising:
• a first collapsible X frame and a second plurality of pivot connection means each having two degrees of pivotal freedom including pivotal freedom about a horizontal axis directed from side to side of the chair frame, which X frame lies in a plane extending in the lateral sense of the chair frame and inclined downwardly from a front plane to a back plane which contain, respectively, each said front leg and each said back leg, said first X frame having a pair of lower ends and a pair of upper ends, of said first X frame one such lower end and one such upper end are pivotally connected by a respective pivot connection means of said second plurality thereof to one of said opposite sides of the chair frame whereas the other such lower end and the other such upper end are pivotally connected by a respective pivot connection means of said second plurality thereof to the other of said opposite sides of the chair frame, thereby enabling folding of the chair frame in the other of said dimensions by collapse of said X first frame;
• an upward extension of each said back leg forming a frame for a backrest;
• a rearward extension of each said lower rigid element;
• a second X frame extending between said upward extension and said rearward extension and connected for pivoting during folding of said chair frame and positioned to brace the upward extension when the chair frame is extended;
• and
• at least one tie means having two ends of limited separability by which ends said tie means are connected in the chair frame in triangulating relationship with one of said X frames for supporting the chair frame when extended.