Self-supporting staircase with center post consisting of individual structural elements

Claim 1

In a self-supporting staircase having a center post consisting of a plurality of individual interconnected structural elements, each structural element having a tread, an interior and means for tightly securing said structural elements relative to one another, the improvement comprising, in combination: said structural elements being provided, at one end, with an integrally formed projected portion that extends away from said one end of said structural element, has a externally threaded segment thereon and defines an upper horizontal annular surface, and, at the other end, with an integrally formed opening that defines a lower horizontal annular surface; said securing means including an internally thereaded member and being characterized in that, when a first structural elelment is assembled in conjunction with an adjacent structural element, said integrally formed projecting portion of the first structural element is positioned such that said externally threaded segment thereon extends through the opening of the adjacent structural element and the upper horizontal annular surface of the first structural element abuts the lower horizontal annular surface of the adjacent structural element defining an interface therebetween, said internally threaded member screwing onto said externally threaded segment and thereby securing the individual structural elements and their respective upper and lower horizontal annular surfaces relative to one another, and directing substantially all stress forces between adjacent structural members to be transmitted through the interface defined by said upper and said lower horizontal annular surfaces.