US Patent 9957720 Retractable staircase and method

A retractable staircase is disclosed for ascending and descending between a lower elevation and an upper elevation. The retractable staircase comprises a main frame and staircase pivotally coupled to an upper surface. A drive causes a first lifting displacement defining an ascending compound displacement by simultaneously causing an ascending pivot displacement and an ascending slide displacement of the staircase. The drive causes a second lifting displacement defining only the ascending staircase pivot displacement and the ascending frame pivot displacement. The drive maintains the staircase in the upper elevation. The drive causes a first descending displacement defining only a descending staircase pivot displacement. The drive causes a second descending displacement defining a descending compound displacement by simultaneously causing the descending staircase pivot displacement and the descending slide displacement of the staircase. The drive causes an extended length in the tether for positioning the staircase in the lower elevation.