Patent Publication Number: US-8528980-B1

Title: Seat back unit

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The invention relates to a seat back unit, and more particularly to a seat back unit having a herringbone-shaped structure formed by a vertical arch section of a backrest member and several transversal curved sections, and the herringbone-shaped structure conforms to the profile variation of the human body and provides different supporting forces according to the weights of different parts of the body. 
     (2) Description of the Prior Art 
     The people are seated at most of time in the daily life and the working period. Therefore, whether the chair is safe and comfortable has become the primary requirement of the people. 
     Although the existing chair has the seat back, the seat back has the stiff line profile, cannot satisfy the requirement of the body profile and cannot provide the independent supports for various parts of the body. In addition, the supporting force also cannot be adjusted. When a person is seated for a long time, the body tends to get tired. Because the supporting forces cannot be adjusted, the supporting forces applied to different parts of the body are different. After a long time, some parts of the body may feel uncomfortable, lack of energy, have aches and encounter the chronic back problem. 
     SUMMARY OF THE INVENTION 
     The invention is provided to solve the problem encountered in actually using a conventional seat back. 
     The invention provides a seat back unit, which is to be connected to a seat of a chair and comprises a main frame, a supporting member and a backrest member. The main frame is a L-shaped member having a vertical section and a horizontal section, a top end of the vertical section has a first hinge portion, a resting seat having an embedded concave portion is fixed to a middle segment of the vertical section, and connection projections are disposed on a junction between the vertical section and the horizontal section. The supporting member is a plate member having one end formed with a second hinge portion, and the other end formed with a crossing portion, which is embedded into the embedded concave portion of the resting seat. The backrest member is composed of a vertical arch section and transversal curved sections. The vertical arch section has a third hinge portion and a fourth hinge portion corresponding to the first hinge portion of the main frame and the second hinge portion of the supporting member, respectively. 
     The vertical arch section and the transversal curved sections of the backrest member are shaped into a herringbone-shaped structure. 
     The vertical arch section of the backrest member has the resilient force for automatically recovering to the original shape after the deformation caused by the supported weight. 
     Each transversal curved section of the backrest member is covered with a seat backrest pad made of a foam material. The pivotal connection portion between the first hinge portion of the main frame and the third hinge portion of the backrest member is covered by a headrest pad body in the form of an inverse-U shape. The headrest pad body is made of a foam material. 
     The seat back unit of the invention has the following advantages. 
     1. The vertical arch section and the transversal curved sections of the backrest member of the invention are shaped into the herringbone-shaped structure, which conforms to the profile variation of the human body and correspondingly provides different supporting forces according to the weights of different parts of the body. Thus, the loading pressures of various parts of the body have the average distribution, so that the fatigue of the cervical vertebra or vertebra of the seated person is eased, and the requirement of supporting the back of the seated person can be provided. 
     2. The vertical arch section of the backrest member of the invention has the resilient force for automatically recovering to the original shape after the deformation caused by the supported weight. The supporting member connected between the main frame and the backrest member can provide a stable supporting force when the backrest member is pressed and deformed, so that the backrest member supports the back of the seated person and has the comfortable flexibility and the stable security. 
     3. The supporting member is slantingly disposed between the backrest member and the main frame of the seat back unit of the invention. On end of the supporting member rests against and is fixed to the resting seat of the main frame and can be rotated relatively to the main frame. The other end of the supporting member is pivotally connected to the backrest member and can be rotated relatively to the backrest member. The supporting member prevents the supporting force of the backrest member from being concentrated at the same place, thereby enhancing the use security and the structural strength of the seat back unit. 
     Further aspects, objects, and desirable features of the invention will be better understood from the detailed description and drawings that follow in which various embodiments of the disclosed invention are illustrated by way of examples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view showing the invention connected to a chair seat. 
         FIG. 2  is an exploded view showing members of the invention. 
         FIG. 3  is a pictorial front view showing the invention. 
         FIG. 4  shows the details of the portion A of the invention. 
         FIG. 5  shows the details of the portion B of the invention. 
         FIG. 6  shows the details of the portion C of the invention. 
         FIG. 7  is a pictorial rear view showing the invention connected to the chair seat. 
         FIG. 8  is a pictorial front view showing the invention connected to the chair seat. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 to 3 , a seat back unit  1  of the invention is connected to a seat  21  of a chair  2  (see  FIGS. 7 and 8 ) and comprises a main frame  11 , a supporting member  12  and a backrest member  13 . 
     The main frame  11  is a L-shaped member having a vertical section  111  and a horizontal section  112 , as shown in  FIG. 2 . The top end of the vertical section  111  has a first hinge portion  113 , a resting seat  115  having an embedded concave portion  114  is fixed to the middle segment of the vertical section  111 , and several connection projections  116  are disposed on the junction between the vertical section  111  and the horizontal section  112 . 
     The supporting member  12  is a plate member having one end formed with a second hinge portion  121 , and the other end formed with a crossing portion  122 , as shown in  FIG. 2 . The crossing portion  122  is embedded into the embedded concave portion  114  of the resting seat  115 , as shown in  FIG. 5 . 
     The backrest member  13  is composed of a vertical arch section  131  and several transversal curved sections  132  with different widths. The vertical arch section  131  and the transversal curved sections  132  are shaped into a herringbone-shaped structure, as shown in  FIGS. 2 and 3 . A third hinge portion  133  and a fourth hinge portion  134  are disposed on the top end and the middle segment of the vertical arch section  131  and disposed corresponding to the first hinge portion  113  of the main frame  11  and the second hinge portion  121  of the supporting member  12 , respectively, as shown in  FIGS. 2 and 4 . In addition, a projection scarf joint  135  is disposed on the bottom end of the vertical arch section  131  corresponding to the connection projection  116  of the main frame  11 , as shown in  FIGS. 2 and 6 . Each transversal curved section  132  of the backrest member  13  is covered with a seat backrest pad  136 , as shown in  FIGS. 1 ,  7  and  8 . The seat backrest pad  136  is made of a foam material. The pivotal connection portion between the first hinge portion  113  of the main frame  11  and the third hinge portion  133  of the backrest member  13  is covered with a headrest pad body  137  in the form of an inverse-U shape. The headrest pad body  137  is made of a foam material. The vertical arch section  131  of the backrest member  13  has a resilient force for automatically recovering to the original shape after the deformation caused by the supported weight. 
     The practical assembling processes will be described in the following. First, the first hinge portion  113  of the main frame  11  is pivotally connected to the third hinge portion  133  of the backrest member  13 , as shown in  FIG. 4 . Next, the second hinge portion  121  of the supporting member  12  is pivotally connected to the fourth hinge portion  134  of the backrest member  13 , and the crossing portion  122  of the supporting member  12  is embedded into the embedded concave portion  114  of the resting seat  115 , as shown in  FIG. 5 . Then, the projection scarf joint  135  of the bottom end of the vertical arch section  131  of the backrest member  13  is fitted with the connection projection  116  of the main frame  11 , so that the backrest member  13  is firmly connected to the main frame  11 , as shown in  FIG. 6 , and the supporting member  12  is disposed between and crosses over the backrest member  13  and the main frame  11 . Finally, each seat backrest pad  136  is covered with the corresponding transversal curved section  132 , and the headrest pad body  137  covers the pivotal connection portion between the first hinge portion  113  of the main frame  11  and the third hinge portion  133  of the backrest member  13 , as shown in  FIGS. 1 ,  7  and  8 , and the seat back unit  1  of the invention is completed. 
     In practice, a rotatable supporting member  12  is slantingly disposed between the backrest member  13  and the main frame  11  of the invention seat back unit  1 . The supporting member  12  has one end, which rests against and is connected to the resting seat  115  of the main frame  11  and is rotated relatively to the main frame  11 . The supporting member  12  also has the other end, which is pivotally connected to the backrest member  13  and is rotatable relatively to the backrest member  13 . Since the supporting member  12  prevents the supporting force of the backrest member  13  from concentrating at the same place, the backrest member  13  supports the back of the seated person to provide the comfortable flexibility and the stable security. 
     In summary, the seat back unit of the invention as filed has the novelty, inventive steps and industry utility. 
     New characteristics and advantages of the invention covered by this document have been set forth in the foregoing description. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention. Changes in methods, shapes, structures or devices may be made in details without exceeding the scope of the invention by those who are skilled in the art. The scope of the invention is, of course, defined in the language in which the appended claims are expressed.