A multifunctional swivel chair tray includes a main body. The main body is connected with a warping plate through a second rotating shaft. An ascending and descending block penetrates through the second rotating shaft. The ascending and descending block is connected with an ascending and descending driving mechanism. A first adjusting rod penetrates through one side of the main body. The first adjusting rod is connected with a multi-spring grouping adjusting mechanism. A second adjusting rod is arranged on another side of the main body. The second adjusting rod is connected with a gear adjusting mechanism. The warping plate is connected with a base plate through a third rotating shaft. A slide plate is slidably connected onto the base plate. A slide plate locking mechanism is arranged between the base plate and the slide plate.

A chair includes a back member and arm brackets. The back member is tapered toward an end that is adjacent to a seat. The arm brackets are attached under a bottom portion of the seat. Each arm bracket is adjustable to provide a seat clearance area for the seat when one or more of the arm brackets are adjusted up to approximately 90 degrees from an original upright position.

A body support assembly includes a seat assembly and backrest assembly supported by a tilt control assembly. Methods of using and assembling the body support assembly are provided.

A lower chair for supporting an upper chair on which a user sits. The lower chair including a base, a swivel mechanism supported by the base and defining a vertical swivel axis, and a four-bar linkage mounted to the swivel mechanism for rotation about the swivel axis. The four-bar linkage includes a coupler link that moves about a coupler curve. The lower chair also includes a column having a lower end affixed to the coupler link for movement of the lower end along the coupler curve. The column defines a column axis and is adapted to support the upper chair.

An adjustment device for a chair, comprising an oscillating mechanism composed of a first plate, associated with a central gas-operated post for the height adjustment of a seat. A second plate is articulated to the first plate so that it can oscillate, by means of a pair of first pivots and is fixed to a backrest. A linkage is articulated to the first plate, by means of a second pivot, and is in turn articulated, by a third pivot, to a third plate, with which the seat can be associated. The third plate is articulated to the second plate. Elements are associated with the linkage for connection to at least one slat or leaf spring, which is arranged on a plane that is substantially parallel to the plane of the seat and is adapted to elastically contrast the inclination of the second plate with respect to the first plate.

An adjustment device for a chair, comprising an oscillating mechanism composed of a first plate, associated with a central gas-operated post for height adjustment of a seat, to which a second plate, fixed to a backrest, is articulated so that it can oscillate by a first pivot.

A third plate is articulated and interposed, respectively by a second pivot and a third pivot, between the first plate and the second plate, and can be associated with the seat.

The first plate has elements for connection to at least one slat or leaf spring which is adapted to elastically contrast the inclination of the second plate with respect to the first plate.

A seating arrangement includes a base member, and an integrally formed support member coupled to the base member and supporting a seat moveable from an upright position to a reclined position, wherein a portion of the support member is bendable as the seat moves from the upright position to the reclined position such that a first side of the support member is put in tension and a second side generally opposite the first side is put in compression, and wherein the first side includes a tensile substrate so that the first side has as higher modulus of elasticity than the second side.

A chair of an aspect of the present disclosure includes: a support base; and a chair body including a seat frame that extends in the forward-rearward direction and forms at least part of a seat, and a back frame that is provided in the rear end of the seat frame to be pivotable around an axis O1 extending in the left-right direction, extends upward from the seat frame, and forms at least part of a backrest. The support base includes a slider that supports, in front of the axis O1, the seat frame movably in the forward-rearward direction, and a backrest-supporting shaft that supports, below the axis O1, the back frame pivotably around an axis O2 extending in the left-right direction.

A seating arrangement includes a seat portion, a back portion, a support member caused to move between first and second positions, and a back recline lock arrangement that includes an actuator, a lock member caused to move between a locked position when the actuator is in an engaged position where the lock member prevents the support member from moving from the first position toward the second position, and an unlocked position when the actuator is in a disengaged position, and wherein the actuator is configured to move from the disengaged position to the engaged position when the chair back is in the reclined position, and the lock member is prevented from moving from the unlocked position to the locked position until the back assembly is moved from the reclined position to the upright position.

A chair includes a base, a receptacle coupled to an upper end of the base, and a seat shell forming a seat surface. The seat shell is supported by the receptacle. The chair also includes a back shell forming a back surface. The back shell is connected to the seat shell on both sides of the seat surface and on both sides of the back surface. The back shell includes an extension extending from the back surface to the receptacle under the seat shell. The extension is elastically deformable.