STEPLADDER Russian patent published in 2012 - IPC E06C1/14 

FIELD: construction.

SUBSTANCE: stepladder comprises the main stand with two legs arranged at the angle a to each other and at least one step between them, and a flap stand with two arranged legs at the angle to each other, joined with the main one by means of hinged joints and their fastening elements. Fastening elements of both hinged joints are arranged on one axis, each of two hinged joints is made in the form of two hollow semi-hinged joints, installed on the main and flap stands, and on surfaces of the above semi-hinged joints facing each other and their opposite sides there are cylindrical ledges, end surfaces of contact of which with each other and with fastening elements are made at the angles α/2 to the appropriate surface of the semi-hinged joints, at the same time at least one of cylindrical ledges facing each other is made circular to form a circular groove inside it, having diameter, which is larger than the diameter of the other opposite cylindrical ledge, and the latter is placed in the above circular groove.

EFFECT: increased reliability and increased stiffness of the structure.

3 dwg