BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a movable chair backrest which is mainly composed of an upper board and a lower board connected by a resilient sheet, wherein the upper board is pivotally attached to a front of a backrest frame and the lower board is attached to the backrest frame with a bouncing board so that the chair backrest operationally deforms according to user's back curve to provide buffer efficiency.

2. Description of Related Art

In structure of chair, backrest is important in design to support body back. Moreover, to improve comfortable level, the design for human body engineering is indispensable.

In the conventional art of chair design, an adjuster is particularly secured inside the backrest to adjust. Although the backrest can be changed, by operating the adjuster, to make the chair fit to different users' backs having different sizes, a user has to sit in a certain gesture to obtain the benefit of body engineering. When the user changes the gesture, the backrest after adjusting cannot provide comfortable support because the backrest is fixed and has no corresponding adjustment immediately. Therefore, the adjuster is important to users and is operated frequently to keep the chair comfortable always. Not only the operation of the adjuster is frequent and troublesome but also the adjuster will be malfunctioned often correspondingly. If not to control the adjuster, the user easily gets tired after sitting on the chair for a long duration. Such many drawbacks are attributable to that the user has to adjust the conventional chair again often.

SUMMARY OF THE INVENTION

A main objective of the present invention is to provide a movable chair backrest that automatically changes shapes to correspond to user's gestures.

To achieve the foregoing objective, the movable chair backrest comprises an upper board and a lower board connected to the upper board; the upper board pivotally attached to a backrest frame; the lower board secured to the backrest frame by a bouncing board, wherein:

the upper board and the lower board are connected by a resilient sheet;

and

the bouncing board pushes the lower board apart from the backrest frame to make a buffering distance between the backrest frame and the backrest.

Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a movable chair backrest in accordance with the present invention;

FIG. 2 is a perspective view of the movable chair backrest in accordance with the present invention;

FIG. 3 is a cross-sectional side view of the movable chair backrest;

FIG. 4 is an operationally cross-sectional side view of the movable chair backrest;

FIG. 5 is an operationally perspective view of movable chair backrest, wherein the lower board swings; and

FIG. 6 is an operationally perspective view of an embodiment of the movable chair backrest in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A movable chair backrest in accordance with the present invention is substantially composed of an upper board pivotally attached to a front of a to backrest frame. A lower end of the upper board is connected to a lower board it by a resilient sheet. A bouncing board connects between the lower board and the backrest frame. Therefore, the lower board operationally swings forward, backward, rightward, leftward relative to the upper board to correspond to different sitting and leaning gestures of a user.

A movable chair backrest in the present invention is illustrated in a first embodiment in which the backrest 1 is composed of an upper board 11 and a lower board 12 (as shown in FIG. 1). An upper end of the upper board 11 is pivotally attached to a backrest frame 2 in front thereof. Moreover, a bottom end of the lower board 12 is secured to the backrest frame 2 by a bouncing board 3 (as shown in FIG. 2), wherein:

- The backrest 1: The backrest 1 has an upper board 11 and a lower board 12. A bottom end of the upper board 11 is connected to a top end of the lower board 12 by a resilient sheet 13 to combine (the resilient sheet 13 is made of resilient, soft and endurable material, for example: rubber).
- Backrest frame 2: the backrest frame 2 is a Y-shaped frame and its bottom end is combined to a seat to serve as a supporting frame (as shown in FIG. 3). Multiple buffering blocks 21 are mounted on the backrest frame 2 corresponding to edge of the bottom end of the upper board 11.

By having above construction, the upper end of the upper board 11 has two ears 111 extending backward to correspondingly align with the pivotal holes 22 on the backrest frame 2 for pivotal connection. Additionally, to two ends of the bouncing board 3 are respectively secured to the bottom end of the lower board 12 and the backrest frame 2 so that the lower board 12 can be pushed forward by the supporting of the bouncing board 3 to make the whole backrest 1 raised from the backrest frame 2 (the bottom end of upper board 11 is also raised by the forward supporting of the lower board 12 to perform a gap (a buffering distance) between the upper board 11 and the backrest frame 2). Thus, the movable chair backrest is completed.

When a user sits and leans on the backrest 1, the upper board 11 can correspondingly buffer and support the back of the user (the upper board 11 has buffer efficiency by the forward or backward movement because of connecting to the bouncing board 3 mounted on the lower board 12; when the leaning force is strong, the multiple buffering blocks 21 on the backrest frame 2 is directly abutted by the upper board 11 and deforms to provide buffer efficiency to the pressure of the upper board 11.) The user's waist leans on the lower board 12 so that the lower board 12 is directly influenced by the waist to move forward or backward by resilient deformation of the bouncing board 3 (as shown in FIG. 4). Therefore, the backrest 1 automatically responses to fit user's back and thus has adjustment efficiency to make users feel comfortable for compliance of body engineering. Moreover, when the user's sitting gesture changes to slightly turn aside to lean on the backrest 1, the lower board 12 operationally rotates correspondingly to the twist of the waist (As shown in FIG. 5 within a certain range. The lower board 12 rotates rightward or leftward relatively to the upper board 11 by the resilient sheet 13, wherein the bouncing board 3 is correspondingly twisted by the rotating force.), so that the lower board 12 embraces the user's waist all the time and rotates correspondingly to provide support. Therefore, the user has no stiff or tired feeling even sitting on the chair for a long duration. Moreover, the backrest 1 sufficiently provides buffering and supporting efficiency to keep user's spine at right position and comfortable.

To make the resilient sheet 13 has better combination to the upper board 11 and the lower board 12, the resilient sheet 13 has multiple stubs 131 to wedge into multiple recesses 101 correspondingly defined on the upper board 11 and the lower board 12.

Another embodiment of the movable chair backrest in accordance with the present invention further has a headrest 4 with a supporting rod 41 to mount on the backrest frame 2 (as shown in FIG. 6). The headrest 4 cooperates with the backrest 1 to support user's head and back.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present invention of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts any be resorted to without departing from the spirit and scope of the invention.