Security vestibule entry for controlled access to banks and the like

Claim 1

A security vestibule comprising a base, a top, a first wall extending from said base to said top along an arc of a circle having a first diameter, a second wall extending from said base to said top along an arc of a circle having a second diameter larger than said first diameter, opposed first circular tracks associated with said base and said top for engaging said first wall for displacement along said first tracks, opposed second circular tracks associated with said base and said top for engaging said second wall for displacement along said second tracks, said second tracks being concentric with and of larger diameter than said first tracks, said first and second walls forming doors of said vestibule and having a combined angular breadth equal to or greater than by a small amount 360°, said base and said top closing said vestibule at opposed ends thereof and said walls in selected positions thereof defining an entrance into and an exit from said vestibule across at least a portion of said base, said base being suitable for supporting at least one person thereon for passage through said vestibule between said entrance and said exit, and four vertically extending supports for supporting said top, said supports being at corners of a square having sides adjacent one of said first and said second tracks.