The present invention relates to chairs and more particularly, to a chair adjustment structure.

For regular high-back chairs, the angle between the seat back and the seat pad cannot be automatically changed when the user rests his (her) back one the seat back. Thus, the user tends to feel uncomfortable after sitting on it for a long time. To eliminate this drawback, ergonomic chairs were created, allowing adjustment of the angle of inclination of the seat back to meet the user's need for sitting comfort.

However, when the user sits on the seat pad of a high-back chair, the user must move the hip backwards so that the user's back can be rested on the seat back of the chair. When the angle of inclination of the seat back is changed subject to the pressure from the user's back, the user's legs may become suspended in the air above the floor. The user will feel uncomfortable after sitting for a long time with this sitting posture. Further, when the user is going to leave from the chair, the chair does not provide any auxiliary push force for the user to help the user leave from the chair. Therefore, the user must apply a great force to the floor with the feet to leave from the seat of the chair.

WO 2007/124609 pertains to a gear mechanism for a chair with a pneumatic spring arranged vertically in the substructure and has a telescopically extensible piston rod for adjusting the height of a seat. The mechanism contains front and rear connecting means and pairs of spring units which are supported, in a bearing of the base and beneath bearing strips, in bearing blocks, the bearing strips being joined to the base from both sides.

EP 1 911 371 discloses a seating furniture item, comprising a seat support; a backrest support; a base support; a seat fastened on said seat support; a backrest fastened to said backrest support, said back rest support being articulately arranged on said base support, and said backrest support and said seat support being articulately connected with each other via two levers, one of said levers being positively guided directly on said base support.

WO 2005/120291 refers to a chair with a synchronizing mechanism. The mechanism comprises a fixed, horizontally running main rotary spindle; a horizontally running secondary rotary spindle which is pivoted about the main rotary spindle; a fixed base; a seat carrier pivotally arranged above the base, through which the secondary rotary spindle extends and on which a seat can be fastened; first connecting means articulated on the two rotary spindles; second connecting means arranged opposite the secondary rotary spindle as connection between the base and the seat carrier; a backrest fastened on the synchronizing mechanism. The backrest has extensions which are fitted in a self-supporting manner on the first connecting means.

WO 2008/124071 pertains to an adjustment device for chairs. The device comprises a back support capable of rotating around a shaft fastened to a support base, said support for the backrest being provided with a blocking plate provided with a plurality of openings, an insert being movable to engage and disengage said openings, and being provided with means to limit the travel of the insert capable of sliding in a defined track in the support base, and actuator being provided, operated by a rod connected to a handle that can be operated by the user, said actuator being movable by a release position to a lock position and vice-versa, in which said insert is selectively engaged in one of said openings, said actuator being connected to said insert.

The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a chair adjustment structure, which enables the chair to provide sitting comfort for the user.

It is another object of the present invention to provide a chair adjustment structure, which allows the user to leave from the chair with less effort.

To achieve the foregoing objects of the present invention, a chair adjustment structure according to the features of claim 1 is provided.

The chair adjustment structure further comprises a seat frame assembly pivotally connected to the top cover for mounting a seat pad, to provide a return force to the mounted seat pad.

The chair adjustment structure further comprises an angle adjustment device set. The angle adjustment device set comprises a locating plate movably forwards and backwards mounted to the base member and selectively engageable into one of a plurality of locating grooves at the top cover to adjust the angle of inclination of the seat frame assembly.

The chair adjustment structure further comprises a spring adjustment device set. The spring force adjustment device set comprises a knob rotatably mounted in the base member and having a screw rod extending from one side thereof and inserted through the spring member, and a screw nut threaded onto the screw rod of the knob and stopped against the bottom end of the spring member and rotatable to adjust the spring force of the spring member to the top cover.

When the back bracket is biased by an external force, the back bracket forces the top cover to incline upwardly through a small angle subject to the linking arrangement between the top cover and the back bracket. Therefore, the user will not suspend the feet in the air above the ground after having sat in position, and the chair installed with the chair adjustment structure can provide sitting comfort for the user.

• FIG. 1 is an elevational view of a chair adjustment structure in accordance with the present invention.
• FIG. 2 is an exploded view of the chair adjustment structure in accordance with the present invention.
• FIG. 3 is a sectional view, in an enlarged scale, of the chair adjustment structure in accordance with the present invention.
• FIG. 4 is an oblique bottom view of the top cover of the chair adjustment structure in accordance with the present invention.
• FIG. 5 is a side view of the present invention, showing the chair adjustment structure applied to a chair.
• FIG. 6 is similar to FIG. 5, showing the seat frame assembly biased upon a downward force at the seat pad.
• FIG. 7 is similar to FIG. 6, showing the angle of inclination of the back bracket and the top cover changed upon a force applied to the seat back.
• FIG. 8 is a top view of the present invention without the top cover and the seat frame assembly, showing that the locating plate is inserted into one locating groove of the positioning member.
• FIG. 9 is similar to FIG. 8, showing that the locating plate disengages from the positioning member.
• FIG. 10 is similar to FIG. 3, showing that the position of the screw nut of the spring force adjustment device set is adjusted and the spring member is compressed.

Referring to FIGS. 1-3 and FIG. 8, a chair adjustment structure 20 in accordance with the present invention is composed of a base member 30, a top cover 40, a spring member 50, a back bracket 60, a seat frame assembly 70, a spring force adjustment device set 80, and an angle adjustment device set 90.

The base member 30 has a pneumatic lifter mounting hole 32 for a pneumatic cylinder 16 of a chair 10 to pass through, as shown in FIG. 3 and FIG. 5. An actuating member 34 is pivotally connected to the base member 30, having one end thereof projecting into a top end of the pneumatic lifter mounting hole 32 and the other end thereof connected to a cord member 36, as shown in FIG. 3. Thus, the actuating member 34 can be biased by the cord member 36 to pivot and press the pneumatic lifter 16, thereby adjusting the elevation of the chair 10.

The top cover 40 has its middle part pivotally connected to the base member 30 and is located on the top side of the base member 30, having two bottom barrels 42 and a bottom positioning member 44, as shown in FIG. 4. Each barrel 42 has a notch 422 located at each of the two distal ends thereof. The positioning member 44 has two locating grooves 442.

The spring member 50 is mounted in the base member 30 and stopped with its top end against the top cover 40 to provide a return force for the top cover 40 while the top cover 40 is pressed, as shown in FIG. 3.

The back bracket 60 is adapted to hold the seat back 12 of the chair 10, as shown in FIG. 5, having two sidewalls 62. Each sidewall 62 has a first extension portion 64 disposed at one lateral side of the base member 30, a second extension portion 66 obliquely upwardly extending from the first extension portion 64, a first pivot portion 642 located on one end of the first extension portion 64 and pivotally connected to the base member 30, and a second pivot portion 644 located on the first extension portion 64 adjacent to the second extension portion 66 and pivotally connected to the top cover 40.

The seat frame assembly 70 comprises two axles 72, four links 74, four torsion springs 76, and a seat frame 78. The axles 72 are respectively pivotally inserted through the barrels 42 of the top cover 40, each having a pin 722 radially extending from one of the two distal ends thereof and respectively inserted through the notch 422 to the outside for stopping against the wall of the associating notch 422 to limit the angle of rotation of the axles 72 relative to the barrels 42. A bottom end of each of the links 74 is pivotally connected with one end of one of the axle 72. The torsion springs 76 are respectively mounted to the two distal ends of each of the two axles 72 with the opposite ends thereof respectively stopped against the top cover 40 and the links 74 to provide a torsional force for the links 74 for returning the links 74 to their former position while the links 74 are biased. The seat frame 78 is pivotally connected to top ends of the links 74 for holding a seat pad 14 of the chair 10.

The spring force adjustment device set 80 comprises a knob 82 and a screw nut 84. As shown in FIG. 3, the knob 82 is rotatably mounted to the base member 30, having a screw rod 822 inserted through the spring member 50. The screw nut 84 is threaded onto the screw rod 822 of the knob 82 and stopped against a bottom end of the spring member 50. When the knob 82 is rotated, the screw nut 84 can be driven by the screw rod 822 to compress the spring member 50, thus changing the spring force applied to the top cover 40 from the spring member 50.

The angle adjustment device set 90 comprises a control bar 92, a locating plate 94, and a linking member 96, as shown in FIG. 2 and FIG. 8. The control bar 92 comprises a linking segment 922 and a control segment 924. The linking segment 922 is pivotally connected to the base member 30, having an elongated slot 926. The control segment 924 extends outward from the linking segment 922 through the base member 30 for the user's operation. The locating plate 94 has an elongated slot 942 for a pin 38 of the base member 30 to pass through for enabling the locating plate 94 to move back and forth relative to the base member 30 and then to be selectively inserted into one of the locating grooves 442 of the positioning member 44 of the top cover 40, as shown in FIGS. 2, 4, and 8. In this embodiment, the linking member 96 is a torsion spring, having its one end inserted into the elongated slot 926 of the linking segment 922 of the control bar 92 and its other end connected to the locating plate 94 in such a way that the control bar 92 is operable to move the locating plate 94 forwards or backwards.

After the detailed recitation of the chair adjustment structure 20, the operation and features of the present invention are described hereinafter.

Referring to FIG. 6, when the user sits on the seat pad 14, the seat frame assembly 70 is forced to pivot. During pivoting movement of the seat frame assembly 70, the top cover 40 is moved with the seat frame assembly 70 relative to the base member 30, and meanwhile, the user is biased with the seat pad 14 to rest his (her) back on the seat back 12 of the chair 10. Thus, when sitting on the seat pad 14, the user can touch the seat back 12 without moving the body. When the seat back 12 bears the user's weight, as shown in FIG. 7, the back bracket 60 will pivot on the first pivot portion 642 relative to the base member 30 to change its angle of inclination. At this time, due to the effect that the second pivot portion 644 is pivotally connected to the top cover 40, the top cover 40 is inclined slightly upwards without movement along with the back bracket 60 to the same angle of inclination. Therefore, the user will not suspend the feet in the air above the ground after having sat in position, i.e. the chair 10 can provide sitting comfort to the user. When the user is going to leave from the chair 10 and then applies a force to the ground through the feet, the seat frame 78 gives an upward force to the user's hips subject to the return force of the spring member 76 to help the user leave from the chair 10 with less effort.

In addition, when it is intended to adjust the angle of the top cover 40, as shown in FIGS. 2 and 4, the user can push the control bar 92 forwards to pivot the linking segment 922 of the control bar 92 toward the locating plate 94. At this time, the linking member 96 will be forced to move the locating plate 94 forwardly away from the locating grooves 442 of the positioning member 44 of the top cover 40, allowing the user to adjust the angle of inclination of the top cover 40 subject to his or her requirement and the spring force applied by the spring member 50 to the top cover 40. After adjustment of the angle of inclination of the top cover 40, the user can pull the control bar 92 backward, as shown in FIGS. 2, 4 and 8. At this time, the linking segment 922 of the control bar 92 will force the linking member 96 to move the locating plate 94 backwards to be inserted into one of the locating grooves 442 of the positioning member 44 of the top cover 40, thus locking the top cover 40 in the adjusted position.

Further, when it is intended to change the spring force of the spring member 50 to the top cover 40, as shown in FIG. 10, the user can rotate the knob 82 to move the screw nut 84 upwardly along the screw rod 822 against the spring member 50, thus changing the return force of the spring member 50 to the top cover 40.

Furthermore, when it is intended to adjust the elevation of the chair 10, as shown in FIGS. 3 and 5, the user can pull the cord member 36 to pivot the actuating member 34 against the pneumatic lifter 16, thereby adjusting the elevation of the chair 10.

Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.