Abstract: A locking device for a rotatable chair or table includes a middle vertical tube, an annular closing member fixed on an upper end of the middle vertical tube, a protective outer tube fitting around the middle vertical tube, having an inner wall provided with the same shape of as the annular closing member and having a plurality of screw holes formed in an upper end portion, and screws screwing in the screw holes of the protective outer tube. The screws can be screwed inward tightly against an outer surface of a piston rod extending out of the air pressure bar contained in the middle vertical rod. When the piston rod is locked immovable by the screws, the chair or table is also locked immovable, being fixed tightly with an upper end of the piston rod.

Abstract: An adjustable armrest assembly has a fixed seat, a control seat disposed on the fixed seat, a pad seat disposed on the control seat, a main body disposed on the pad seat, and a cover plate covering the main body. The fixed seat has two through apertures. The control seat has two stepped holes, two threaded apertures, and two upper grooves. The main body has a lower recess receiving the pad seat and the control seat, an upper recess receiving an elastic plate, and a separation plate. Two slide seats are inserted in the stepped holes. Two hollow cylinders are inserted in the upper grooves.

Abstract: An armrest device has a main body, a cover plate, and an armrest support plate. The main body has a first chamber, a second chamber, a middle post, a groove, a first seat, and a second seat. The armrest support plate has a corrugated slot and a plurality of recess apertures.A hook device has a shaft rod, a notch, and a through aperture. A coiled spring is inserted in the groove and the notch. An elastic plate covers the first chamber and the second chamber. A guide plate is disposed on the elastic plate. A press plate is disposed on the second seat. A press panel is disposed on the first seat. The armrest support plate is confined between the press plate and the press panel.

Abstract: An adjustable armrest device has a fixed seat, a main body covering an upper portion of the fixed seat, and an insert block disposed between the main body and the fixed seat. The fixed seat has two through apertures. The insert block has two stepped holes, two threaded apertures, and two upper grooves. The main body has a lower recess receiving the insert block, two threaded holes, a circular recess hole, a circular blind hole, two round recess holes, and two round blind holes. Two slide seats are inserted in the stepped holes. Each slide seat has a through hole receiving a threaded fastener. Two hollow cylinders are inserted in the upper grooves. Two bolts pass through the through apertures and the threaded apertures to fasten the fixed seat and the insert block together.