An adjustable chair has a seat and a splat. The seat has a lower base, an upper base, a tilt adjusting device, a lower rotating shaft, and an upper rotating shaft. The lower base has an assembling space. The upper base is movably deposited on the lower base. The tilt adjusting device is deposited in the assembling space. The lower rotating shaft is rotatably deposited in the lower base and connected to the tilt adjusting device. The upper rotating shaft is deposited in the upper base. The splat is tiltably connected to the seat and has a backrest unit and two connecting legs. The backrest unit is deposited at a rear side of the seat. The connecting legs are connected to the backrest unit, are connected to the lower rotating shaft, and are pivotally connected to the upper rotating shaft.

A back adjusting and positioning structure of a chair is characterized in that: a backward tilt adjustment unit is disposed at the junction of a cushion frame and a back frame of the chair so that the backward tilt adjustment unit drives a screw segment with one end thereof extending inward to retract and/or protrude a blocking element coupled to a rear segment thereof in response to a knob's rotating in a predetermined direction, so as to control compression and/or expansion of a predetermined stop distance acquired by a spring fitted in the backward tilt adjustment unit, and in consequence the back in operation attains the required tightening and/or loosening state.

Embodiments provide a seat connecting device with an adjustable backrest, belonging to the technical field of swivel chairs. In the embodiments, the seat connecting device includes a seat back tightness control assembly including a control handle, a universal joint, a transmission rod, a first bevel gear, a second bevel gear, a lifting part, a mounting seat of the lifting part, and a tightness adjust rod. The present disclosure uses the universal joint to replace the original rope for transmission, improving the response timeliness of the force transmission of the product when adjusting the seat back elasticity; and improving the accuracy and controllability of the seat back elasticity adjustment. At the same time, relative to the use of rope adjustment method, the size of the force arm can be also effectively improved, the size of the force transmission of the product during regulation and the demand for the size of the force transmission are improved, the force requirements for the user is reduced, and the possibility of damage to the adjustment mechanism due to excessive input force when the product is adjusted is effectively reduced, thereby increasing the service life of the product.

This disclosure relates to a seat device (1) comprising an underframe (2) and a seat (3) connected to the underframe (2) in such a way as to pivot about a pivot seat axis (A1), there being provided means for elastically biasing the seat (3) in anti-clockwise rotation. The seat device (1) further comprises a lumbar part (42); rotationally secured to the seat (3), and a saddle (5) for supporting the top of the thighs of the user, the saddle (5) being connected to the front region of the seat (3).

A rebounding device includes a front member, a rear member, and a spring mechanism including a first biasing element and force adjustment assembly. The force adjustment assembly includes a spring element including a front planar surface and a rear planar surface connected at a rounded portion, wherein the front planar surface contacts an inner surface of the front member; a screw housing secured to an inner surface of the rear member, wherein the screw housing includes a longitudinal channel and a bore on an upper surface; a drive screw positioned through the bore and along the longitudinal channel of the screw housing; a threaded block positioned within the longitudinal channel of the screw housing, wherein the threaded block is configured to move vertically along the longitudinal channel, and wherein the rear planar surface of the spring element is secured to the threaded block.

Disclosed herein is a chair that includes a backrest portion, a seat portion coupled with the backrest portion, a column portion coupled with the seat portion, a linkage coupled with the backrest portion, a leaf spring in direct contact with the linkage, an arc-shaped toothed structure fixed translationally relative to the column portion, and a different toothed structure in contact with the arc-shaped toothed structure. The chair is also configured such that when a weight is applied to the seat portion, a fulcrum point of the leaf spring moves as the different toothed structure moves along the arc-shaped toothed structure to thereby shorten a working length of the leaf spring and provide an increased resistance to tilting of the backrest portion relative to the column portion. A process for assembling the chair and a weight-based tilt-resistance assembly for use with the chair are also described herein.

A chair that provides movement side-to-side about a first pivot axis positioned above the seat plane allows the user a wide range of dynamic movement, but does not require constant or excessive action on the part of the user to maintain a desired position. In addition and concurrently thereto, the structure may include a second pivot that is also positioned above the seat plane and that provides forward-and-back movement of the seat. The first and second pivot axes can be engaged synchronously or independently by the user as desired delivering infinite degrees of angles of movement. Said pivot axes are more closely adjacent to the human body pivot joints and axes. The seat and seat back may be joined together to a central spine frame that moves about the second pivot, thereby maintaining the seatback position and seat position relative to each other during forward-and-back movement of the spine along the second pivot. One or more biasing structures may be provided to urge the seat into forward-and-back and side-to-side neutral positions. If desired, the location of this forward-and-back neutral position can be statically adjusted by a user, and at least one of the biasing structures can hold this forward-and-back neutral position at a desired tension level thereby allowing a user to select the amount of force required to move the seat out of this defined forward-and-back neutral position. Moreover, an adjustment structure may be provided that allows for static adjustment of the seatback's position on the spine.

A chair is provided including a subframe, a seat element, a back element, a spring mechanism and an adjustment device. The spring mechanism includes a leaf spring, which is clamped on one side in the subframe, and a support, which is movable on a track between the leaf spring and the subframe. The adjustment device includes an adjustment member and a transmission mechanism. A movement of the adjustment member is translated into a movement of the support at a transmission ratio in a range of 1:0.5 and 1:4.

Disclosed herein is a reconfigurable apparatus that includes a backrest, a seat coupled with a column, a linkage statically attached to the backrest, a leaf spring in direct contact with the linkage, a first structure fixed to the column, and a second structure. The first and second structures each have one or more teeth. The chair is also configured such that when a weight is applied to the seat, the one or more teeth of the second structure move along the one or more teeth of the first structure to thereby shorten a working length of the leaf spring and provide an increased resistance to tilting of the backrest relative to the column. A process for assembling the reconfigurable apparatus is also described herein.

Embodiments provide a seat connecting device with an adjustable backrest, belonging to the technical field of swivel chairs. In the embodiments, the seat connecting device includes a seat back tightness control assembly including a control handle, a universal joint, a transmission rod, a first bevel gear, a second bevel gear, a lifting part, a mounting seat of the lifting part, and a tightness adjust rod.