Patent Publication Number: US-2011062758-A1

Title: Item of Seating Furniture with Seat Depth Adjustment

Description:
BACKGROUND 
     This disclosure relates generally to an item of seating furniture, in particular a chair, with a seat depth adjustment. 
     Items of seating furniture of this type, in which the seat is mounted displaceably for the purpose of adaptation to the leg length of the seated person, are generally known. In this case, however, there is the problem that, in at least one extreme position of the seat, a horizontal gap with respect to frame parts of the item of seating furniture is produced, which horizontal gap may impair the seating comfort or in which objects may become jammed. 
     Although it would be possible to design the seat itself to be in two parts and to be displaceable per se, this interferes in the overall appearance and likewise impairs the seating comfort. 
     DE 201 08 172 U1 discloses a chair with an adjustable backrest for adjusting the seat depth. In said known chair, the backrest is mounted on a pivotable carrier. However, this solution is relatively complicated and is almost impossible to use with “synchronous mechanisms”. As used herein, the phrase “synchronous mechanism” relates to a mechanism of a chair where, when leaning back, the inclination of the backrest also results in an inclination of the seat via a mechanism coupling the backrest to the seat. 
     By contrast, an item of seating furniture of the type mentioned at the beginning, in which the seating comfort is not impaired, is distinguished by a simple construction and also is being suitable for use with synchronous mechanisms. 
     SUMMARY 
     Briefly stated, it is proposed to mount a pivotable lower backrest frame on the backrest frame, the lower backrest frame being connected to the rear part of the seat. The displaceable seat thereby remains connected to the backrest, and a horizontal gap does not arise between the backrest and seat, which horizontal gap could impair the seating comfort and interfere in the overall appearance of the item of seating furniture. 
     The item of seating furniture is preferably provided with a lumbar support, wherein the lumbar support is fastened on a lumbar support carrier which is mounted at one end on the backrest frame and at the other end on the lower backrest frame. The lumbar support can thereby follow a pivoting of the lower backrest frame and can thus be kept in an optimum position in relation to the seat even when the seat depth is adjusted. 
     In order to permit simple adjustment of the lumbar support, the lumbar support carrier is provided with a transverse carrier and a longitudinal carrier which is connected to the transverse carrier and to the lower backrest frame, wherein the longitudinal carrier preferably has a telescopic structure, and the lumbar support is mounted displaceably on the longitudinal carrier. 
     For optimum adaptation to the body build of the seated person, the lumbar support is preferably provided with adjustment means for adjusting the supporting depth. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment is explained with reference to the attached drawings, in which: 
         FIG. 1  shows a central section of an office swivel chair; 
         FIG. 2  shows a side illustration of the office swivel chair without a seat cushion; 
         FIG. 3  shows a perspective illustration of the frame construction of the office swivel chair; and 
         FIG. 4  shows a top view of the frame construction. 
     
    
    
     DETAILED DESCRIPTION 
     For this purpose, it should be noted that, in the above text and in the text below, the definitions of “at the front”, “at the rear”, “at the top”, etc. arise from the normal position of a chair. 
     According to  FIG. 1 , an office chair comprises a seat with a seat cushion carrier  5  and a seat cushion  3 , and a backrest frame  7 . The seat  1  is mounted displaceably forward and rearward on a seat carrier  9 , wherein the seat carrier  9  and the backrest frame  7  are connected to a main carrier  11  which is fastened to a chair pillar  13 . Furthermore,  FIG. 1  shows a seat mechanism  19  which permits a coordinated adjustment of the backrest frame  7  and seat, but does not relate to the adjustment of the seat depth and therefore is not explained further. 
     A lower backrest frame  17  which is connected at the lower end thereof to the rear edge of the seat  1  is mounted pivotably on the backrest frame  7 . Furthermore, a lumbar support  15  is provided, said lumbar support being mounted on a lumbar support carrier comprising a transverse carrier  21  and a longitudinal carrier  23 . 
     The arrangement of the last-mentioned elements is apparent in particular from the perspective illustration of  FIG. 3 , which shows the frame construction of the chair without a seat cushion. It is apparent from the illustration that the transverse carrier  21  extends between two struts of the backrest frame  7 . The longitudinal carrier  23 , which extends with respect to a transversely running strut of the lower backrest frame  17 , is fastened in the center of the transverse carrier  21 . Furthermore, the longitudinal carrier  23  has a telescopic connection  25 . 
     The backrest frame  17 , for its part, is connected to the backrest frame  7  via an articulated connection  29  comprising lamellas. 
       FIG. 3  furthermore shows that the seat cushion carrier  5  is designed as a plate which is manufactured from flexible material and, in the center, has a web  31  extending from the front rearward. The web  31  rests on the seat carrier  9  ( FIG. 1 ) and can be connected to the seat mechanism  19 . The resting action and the flexibility permit dynamic seating as the right/left loading changes. 
     In the region of the ischial tuberosities, the seat cushion carrier is provided with slots  35  which extend parallel to the side edges of the seat cushion carrier, and with slots  37  which extend parallel to the rear edge of said seat cushion carrier, in order to further increase the flexibility. 
     In the region of the side edges, the seat cushion carrier  5  is provided with slots  39  which extend from the side edge toward the web  31 . The length of said slots  39  increases the closer said slots are arranged to the rear edge of the seat cushion carrier  5 . 
     The precise arrangement of the slots is apparent in particular from the top view in  FIG. 4 . This figure furthermore shows adjustment means  41  for adjusting the supporting depth of the lumbar support  15 , i.e. for adjustment in the seat depth direction. The adjustment means  41  are designed in such a manner that they permit a depth adjustment of the lumbar support  15  separately, on the right and left, such as, for example, via eccentrics. 
     As illustrated by the double arrow in  FIG. 2 , which shows the chair without a seat cushion, the seat cushion carrier  5  is mounted displaceably in the depth direction in chair guides. In this case, the lower backrest frame  17  follows a movement of the seat cushion carrier  5  such that a horizontal gap cannot be produced.  FIG. 2  shows the seat cushion carrier  5  in a central position. 
     In this regard, it should also be noted that, in the use state of the chair, the backrest carrier is provided with a fabric covering, upholstery or the like. 
     The seat  1  can be secured in any of the intermediate positions thereof between the position located furthest to the rear and the position located furthest to the front. For this purpose, a rack (not illustrated) is preferably provided on the seat cushion carrier  5 , which rack can be brought into engagement with suitable tooth elements and can be actuated via a button  43 . 
     The foregoing description has been explained with reference to an office swivel chair, but the seat depth adjustment may also be used in other items of seating furniture, such as four-legged chairs, armchairs, sofas, etc.