Chair structure

Claim 1

A SWIVEL SEAT CAPABLE OF RETURNING ITSELF TO A FORWARDLY FACING POSITION, COMPRISING: A FLOOR-ENGAGING SUPPORT INCLUDING A HOLLOW TUBE AT THE UPPER END THEREOF, A SWIVEL SEAT MOUNTING MEMBER CARRIED BY SAID TUBE IN ITS UPPER END HAVING AN UPPER FLANGE IN PART RESTING ON AND IN PART FITTED WITHIN THE UPPER END OF SAID TUBE, A SLEEVE PORTION BELOW SAID FLANGE EXTENDING DOWWARDLY WITHIN THE TUBE AND HAVING AN EXTERNALLY THREADED REDUCED PORTION AT ITS LOWER END, SAID MEMBER HAVING A BORE EXTENDING VERTICALLY THERETHROUG, AND A SUBSTANTIALLY VERTICAL HOLE OFFSET FROM SAID BORE AND OPENING UPWARDLY THROUGH THE FLANGE; AN EXPANDABLE GRIPPING ELEMENT MOUNTED OVER SAID THREADED PORTION AND AGAINST A SHOULDER THEREABOVE AND HAVING A PLURALITY OF RADIALLY EXTENDING PROJECTIONS TILTED SLIGHTLY DOWNWARDLY FROM THE HORIZONTAL AND ENGAGING THE INNER WALL OF THE TUBE; A WASHER CARRIED BY SAID THREADED PORTION BELOW SAID ELEMENT AND IN CONTACT WITH SAID PROJECTIONS; AND A NUT ON SAID THREADED PORTION BELOW SAID WASHER TO HOLD SAID PROJECTIONS IN THEIR EXTENDED POSITIONS IN LOCKED ENGAGEMENT WITH THE TUBE, THEREBY SECURING SAID MEMBER TO THE TUBE; A SEAT ASSEMBLY HAVING BEARING MEANS ROTATABLY CARRIED ON SAID MOUNTING MEMBER FLANGE AND HAVING A DEPENDING SHAFT EXTENDING THROUGH SAID BORE, SAID SHAFT HAVING A LOWER THREADED PORTION EXTENDING BELOW SAID MEMBER, A NUT ON THE LOWER THREADED PORTIONS OF SAID SHAFT FOR PREVENTING REMOVAL OF SAID SEAT ASSEMBLY FROM SAID MOUNTING MEMBER; SAID SEAT ASSEMBLY ALSO HAVING A GENERALLY DOWNWARDLY FACING AND ARCUATELY CURVED CAM SURFACE INCLINED IN A PLANE MAKING AN ACUTE ANGLE WITH THE HORIZONTAL; AND A COMPRESSION SPRING CARRIED IN SAID HOLE WITH A GENERALLY VERTICALLY BIASED FOLLOWER MEMBER THEREABOVE FOR EXERTING A FORCE AGAINST SAID CAM SURFACE AND BIASING SAID SEAT ASSEMBLY TOWARDS ITS FORWARDLY FACING POSITION.