Abstract: An adjustable seal assembly for maintaining a fluid tight seal in a vacuum vessel is provided. The disclosed adjustable seal assembly is particularly suited for sealing a vessel that includes two concentrically disposed sections having a small gap therebetween such that the vessel accommodates relative axial motion between the chamber section and the closure section. The disclosed adjustable seal assembly is comprised of a thin, fiber reinforced polymeric membrane having a first edge attached to a surface of one section of the vessel along the entire perimeter thereof and a second edge attached to a surface of the other section of the vessel thereby sealing the gap between the sections of the vessel. The body of the thin membrane is further disposed such that it generally forms an axially adjustable loop configuration within the small gap allowing the two sections of the vessel to move without breaking the seal.

Abstract: A lightweight foldable wheelchair is provided which comprises a seat having a base and a back hingedly attached to the base, the back being foldable to overlie the seat base; a pair of large wheels each demountably attached to the end of an axle at the bottom rear of the seat base and rearward of the center of gravity of the chair; a first strut having its rearward end hingedly mounted to the underside forward portion of the seat base of the seat; and a second strut having its rearward end hingedly mounted to the underside of the seat base of the seat rearwardly of the first strut and forward of the wheel axle, the forward ends of both struts abutting below and forward of the seat and securing a demountable caster wheel and hingedly mounted footrest, and the struts being foldable to underlie the seat. The wheelchair can therefore be folded into a compact configuration when the wheels are demounted.