Patent Publication Number: US-2010117421-A1

Title: Backrest for a chair, and chair comprising the same

Description:
The invention relates to a chair backrest and to a chair with such a chair backrest. 
     The prior art discloses swivel chairs with a two-part backrest surface divided into a lordosis-supporting region and an upper backrest region. 
     Such swivel chairs cannot be adjusted satisfactorily to the person sitting in them and allow only a small number of different sitting positions. 
     The object of the present invention is therefore to provide a chair backrest which can be better adjusted to the person sitting in the chair, and also a chair with such a chair backrest. 
     This object is achieved by the subject matter of the independent patent claims. Advantageous developments can be gathered from the dependent claims. 
     A chair backrest according to the invention comprises an outer backrest frame with two backrest-frame legs, and an inner, in particular H-shaped, tensioning frame with two lateral tensioning-frame legs, between which are arranged a flexible covering and an extensible and compressible transverse tensioning-frame connection, which may be of in particular rearwardly convex shaping and allows the tensioning-frame legs to be compressed and extended resiliently in the lateral direction. The chair backrest further comprises at least one handwheel which is, preferably two handwheels which are, arranged on the outside of a backrest-frame leg and has/have a threaded rod which runs through the backrest-frame leg. The handwheel can be used to draw the respectively adjacent tensioning-frame leg closer, in which case the transverse tensioning-frame connection is extended and the flexible covering is tensioned, and the handwheel can likewise be used to move the adjacent tensioning-frame leg away, in which case the transverse tensioning-frame connection is compressed and the flexible covering is loosened. 
     According to a basic idea of the invention, the tensioning level of the flexible covering of the inner tensioning frame, which is suitable in particular for the lordosis region, can be adjusted flexibly, in which case the tensioning frame, with the flexible covering, adapts optimally to the person sitting in the chair, in particular to the person&#39;s back. Such a chair backrest with a flexibly adjustable covering provides a high level of sitting comfort, in addition is straightforward to produce and very reliable. 
     According to a first embodiment of the invention, the threaded rod of the at least one handwheel engages in a mating nut, in particular in a round threaded element with mating nut, arranged on or in a lateral tensioning-frame leg, and it thus causes, in a straightforward but simultaneously effective manner, the tensioning of the flexible covering to be varied. It is advantageous here if the mating nut is fixed in relation to the tensioning-frame leg, which can be straightforwardly achieved if the mating nut has a transverse tensioning bolt which is located in a depression provided on the inside of the tensioning-frame leg. 
     A further embodiment of the invention provides a tilting mount for the inner tensioning frame, the inner tensioning frame being mounted in a pivotable manner in relation to the outer backrest frame. It is advantageous here if the at least one handwheel is located axially on the tilting mount of the inner tensioning frame, outside the backrest. It is particularly advantageous if two handwheels are provided, these being located axially on the tilting mount of the tensioning frame, to the right and left outside the backrest. 
     According to a further basic idea of the invention, the provision of such a tilting mount for the inner tensioning frame can further increase the sitting comfort in that the flexible covering of the tensioning frame additionally adapts to the chair user&#39;s back in respect of the inclination locations. It is thus possible for the flexible covering of the tensioning frame to adapt optimally to the chair user&#39;s back, on the one hand, in respect of deformation as a result of the flexible covering and, on the other hand, in respect of inclination thereof as a result of the tiltable mounting, and to provide enhanced ergonomics and further-improved sitting comfort. 
     According to a further advantageous embodiment of the invention, the tilting mount is achieved in that at least one radial longitudinal aperture is, preferably two radial longitudinal apertures are, formed in the backrest-frame legs and accommodates/accommodate at least one guide pin or guide screw, preferably two guide pins or guide screws, which are connected to the adjacent tensioning-frame leg. These radial longitudinal apertures make it possible for the tensioning frame to pivot. Furthermore, the ends of the radial longitudinal apertures form stops for the at least one guide pin or guide screw, preferably for the two guide pins or guide screws, and thus advantageously make it possible for the tensioning frame to pivot, and also limit this pivoting movement. 
     According to an advantageous development of the invention, the inside of the tensioning-frame legs has arranged on it in each case one terminating disk, in which the at least one guide screw engages or to which the at least one guide pin is connected. This achieves a particularly compact design of the chair backrest and, if a mating nut or round threaded element is arranged on or in the tensioning-frame leg, it is fixed by the terminating disk and secured against possibly falling out. 
     It is particularly advantageous if, in order to damp the pivoting movement and/or the lateral movement of the inner tensioning frame in relation to the outer backrest frame, a respective damping element, in particular a rubber element, is arranged between the backrest-frame legs and the respectively adjacent tensioning-frame legs, the threaded rod and the at least one guide pin or the at least one guide screw running through this damping element. The rubber element here is of preferably elastic design. Providing the damping element advantageously damps the stopping action of the guide pins or guide screws in both directions of rotation. 
     In order to reduce the friction between the threaded rod and aperture in the backrest-frame leg, and thus to ensure straightforward rotatability of the at least one handwheel, a mount, in particular a needle-groove mount for the threaded rod, can be arranged between the threaded rod and the aperture in the backrest-frame leg. 
     Furthermore, it is advantageous if an unscrewing-prevention means is provided for the threaded rod. 
     If the outer backrest frame also has a flexible covering in an upper backrest region, the level of sitting comfort can be increased yet further. 
     According to a further embodiment of the invention, it is possible for the outer backrest frame to be arranged on a backrest carrier and to be telescopically height-adjustable thereon, as a result of which the chair backrest can be adapted particularly advantageously to the height of the person sitting in the chair and the level of sitting comfort can be increased yet further. 
     If handwheels are provided on both sides of the outer backrest frame and have threads running counter to one another, that is to say one handwheel has a right-handed thread and the other has a left-handed thread, the two handwheels can be rotated, as far as the person sitting in the chair is concerned, in the same direction in order to tension the flexible covering and to reduce the tensioning of the covering. 
     The invention also relates to a chair backrest with an outer backrest frame with two backrest-frame legs and with an inner tensioning frame which is arranged within the outer backrest frame and has two lateral tensioning-frame legs, a flexible covering being arranged in each case between the two backrest-frame legs and between the two tensioning-frame legs. Providing such flexible coverings both for the back and for the lordosis region ensures a high level of sitting comfort. 
     The invention further relates to a chair, in particular to a swivel chair with a chair backrest of the type described above. The advantages of such a chair or swivel chair correspond to the advantages described above with reference to the chair backrest. In order to avoid repetition, these advantages will not be cited again. 
    
    
     
       The invention will be explained in more detail hereinbelow by way of an exemplary embodiment and with reference to the accompanying figures, in which: 
         FIG. 1  shows a perspective view of a chair backrest as seen obliquely from the rear, 
         FIG. 2  shows an exploded drawing of a sub-region of the chair backrest from  FIG. 1  as seen from the front, and 
         FIG. 3  shows an overall view of a chair with a chair backrest as described in  FIGS. 1 and 2 . 
     
    
    
       FIG. 1  shows a perspective view of a chair backrest  100  as seen obliquely from the rear. 
     The chair backrest  100  comprises an outer backrest frame  1  with two laterally arranged backrest-frame legs  11  and  12  which are connected to one another, in an upper region, by a curved, convex, upper transverse connection  13  and, in a central to lower region, by a curved, convex, lower transverse connection  14 . At that location at which the lower transverse connection  14  meets the backrest-frame legs  11  and  12 , the latter each have a slight bend and, at this location, rotatable handwheels  6   a  and  6   b  are arranged axially on the tilting mount of the H-shaped tensioning frame  4 , in each case on the right-hand and left-hand outer side of the backrest-frame legs  11  and  12 . 
     The chair backrest  100  further comprises a U-shaped backrest carrier  2 , of which the legs run within the lower portions of the backrest-frame legs  11  and  12 , and on which the outer backrest frame  1  can be displaced upward and downward and is thus telescopic and height-adjustable. Furthermore, in an upper region, between the backrest-frame legs  11  and  12 , the outer backrest frame  1  has a flexible web-like first sheet-like covering  15 , which forms the upper backrest region. 
     A somewhat narrower, H-shaped tensioning frame  4  is fastened such that it is mounted in a tiltable manner in the lower third of the outer backrest frame  1 . This H-shaped tensioning frame  4  comprises two tensioning-frame legs  41  and  42 , each running parallel to the backrest-frame legs  11  and  12 , and a transverse tensioning-frame connection  43 , which connects the tensioning-frame legs, is curved in the rearward direction and runs convexly. A second sheet-like covering  44  is mounted between the tensioning-frame legs  41  and  42 , and this covering forms the lordosis region. 
     The handwheels  6   a  and  6   b  provide for mounted fastening of the tensioning-frame legs  41  and  42  of the H-shaped tensioning frame in such a way that, by virtue of the two handwheels  6   a  and  6   b  being rotated, the tensioning-frame legs  41  and  42  can be forced apart from one another and pushed together slightly, in which case the second sheet-like covering  44  can be tensioned and loosened and thus adjusted individually to the user&#39;s requirements. 
     By virtue of the handwheels  6   a  and  6   b  being rotated, the tensioning-frame legs  41  and  42  can be drawn apart from one another and pushed together, with resilient movement of the transverse tensioning-frame connection  43 , such that it is possible to vary the distance between the tensioning-frame legs  41  and  42 . The chair backrest  100  according to the exemplary embodiment is designed such that each of the two tensioning-frame legs  41  and  42  can be displaced over a distance of 0.8 cm, in which case, when use is made of both handwheels  6   a  and  6   b,  it is possible to achieve a total difference in width of 1.6 cm between the two tensioning-frame legs  41  and  42 . The rubber elements  8  here can serve as damping means for the tensioning-frame legs  41  and  42 . 
     In the exemplary embodiment, the two handwheels  6   a  and  6   b  each have a thread, and these threads run counter to one another, that is to say one has a left-handed thread and the other has a right-handed thread, in which case the two handwheels  6   a  and  6   b,  as far as the person sitting in the chair is concerned, are rotated in the same direction in order to tension the second sheet-like covering  44  and to reduce the tensioning. 
     At the same time, the H-shaped tensioning frame  4  can be pivoted or tilted about the pivot axis defined by the center points of the handwheels  6   a  and  6   b,  in order for the alignment of the tensioning frame  4  to be adapted optimally to the user&#39;s requirements. 
       FIG. 2  shows an exploded drawing of a sub-region of the chair backrest  100  as seen from the front. 
       FIG. 2  shows the handwheel  6   a  with a threaded rod  61 . Located at the bend of the backrest-frame leg  11  is an axial bore  1   c  with a needle-groove mount  1   d,  through which the threaded rod  61  runs when the handwheel  6   a  is in the inserted state. The needle-groove mount  1   d  reduces the friction of the threaded rod  61  and thus ensures easy rotatability of the handwheel  6   a.    
     Also formed at the bend of the backrest-frame leg  11  are two radial longitudinal apertures  1   a  and  1   b  for guide screws  10   a  and  10   b  and two bores  1   e  and  1   f  for rubber-element fastening screws  8   a  and  8   b.    
     The tensioning-frame leg  41  contains an axial bore  4   e  for accommodating a round threaded element  7 . This round threaded element  7  has, on its rear side, a transverse tensioning bolt  7   a  which engages in a corresponding depression provided on the inside of the tensioning-frame leg  41  and which thus secures the round threaded element  7  against rotation. The tensioning-frame leg  41  further comprises bores  4   a  and  4   b  for terminating-disk fastening screws  9   a  and  9   b,  by means of which a terminating disk  9  arranged on the inside of the tensioning-frame leg  41  is fixed to the tensioning-frame leg  41 . Furthermore, the tensioning-frame leg  41  comprises tensioning-frame-leg bores  4   c  and  4   d  for accommodating the guide screws  10   a  and  10   b.    
     An annular rubber element  8  with four through-passages is provided between the inside of the backrest-frame leg  11  and the outside of the tensioning-frame leg  41 . This rubber element  8  serves for damping the pivoting movement and the lateral movement of the H-shaped tensioning frame  4  in relation to the outer backrest frame  1 . The rubber element  8  is screwed firmly to the inside of the backrest-frame leg  11  by means of rubber-element fastening screws  8   a  and  8   b,  which engage in the bores  1   e  and  1   f  of the backrest-frame leg  11 . 
     The guide screws  10   a  and  10   b  run into the radial longitudinal apertures  1   a  and  1   b  of the backrest-frame leg  11 , through the apertures in the rubber element  8 , and through the tensioning-frame-leg bores  4   c  and  4   d,  and engage in the corresponding threaded bores in the terminating disk  9 . The rubber element  8  is elastic and allows the guide screws  10   a  and  10   b  to rotate between the stops of the radial longitudinal apertures  1   a  and  1   b.    
     In practice, the H-shaped tensioning frame  4  can be automatically tilted or pivoted, and thus individually adjusted, by the chair user leaning against it with his back or pelvic region. The pivoting movement of the H-shaped tensioning frame  4  in relation to the outer backrest frame  1  is limited by the guide screws  10   a  and  10   b  striking against the stops of the radial longitudinal apertures  1   a  and  1   b.    
     When the H-shaped tensioning frame  4  is pivoted, the guide screws  10   a  and  10   b  move in the radial longitudinal apertures  1   a  and  1   b  and the rubber element  8 , which does not have such apertures, is deformed, as a result of which the pivoting path is simultaneously made possible and limited and as a result of which, in addition, the H-shaped tensioning frame  4  is easily returned to the starting position. 
     Irrespective of the pivoting movement of the H-shaped tensioning frame  4 , it is possible to vary the tensioning of the second sheet-like covering  44 , to be precise by virtue of the handwheels  6   a  and  6   b  being rotated. 
     In order to increase the tensioning of the second sheet-like covering  44 , at least one of the two handwheels  6   a  and  6   b  is rotated in one direction, as a result of which the threaded rod  61  draws the round threaded element  7 , and thus the respective tensioning-frame leg  41  or  42 , closer to the adjacent backrest-frame leg  11  or  12 , respectively. 
     When the tensioning-frame legs  41  and  42  are drawn apart, correspondingly, the second sheet-like covering is tensioned, in which case the person sitting in the chair feels a greater level of resistance. If the handwheels  6   a  and  6   b  are rotated in the opposite direction, then the second sheet-like covering  44  can be loosened, in which case the person sitting in the chair feels a lower level of resistance in the lordosis region. The transverse tensioning-frame connection  43  here, which is of pronounced convex formation, is resiliently compressed or extended in each case. 
     According to the invention, the first sheet-like covering  15  of the upper backrest region and the second sheet-like covering  44  of the lordosis region are configured as flexible coverings. 
       FIG. 3  shows an overall view of a chair with the chair backrest  100  described above. 
     LIST OF DESIGNATIONS 
     
         
           100  Chair backrest 
           1  Outer backrest frame 
           1   a,    1   b  Radial longitudinal apertures 
           1   c  Axial bore 
           1   d  Needle-groove mount 
           1   e,    1   f  Bores 
           11 ,  12  Backrest-frame legs 
           13  Upper transverse connection 
           14  Lower transverse connection 
           15  First sheet-like covering 
           2  Backrest carrier 
           4  H-shaped tensioning frame 
           41 ,  42  Tensioning-frame legs 
           43  Transverse tensioning-frame connection 
           44  Second sheet-like covering 
           4   a - d  Tensioning-frame leg bores 
           6   a,    6   b  Handwheels 
           61  Threaded rod 
           7  Round threaded element 
           7   a  Transverse tensioning bolt 
           8  Rubber element 
           8   a,    8   b  Rubber-element fastening screws 
           9  Terminating disk 
           9   a,    9   b  Terminating-disk fastening screws 
           10   a,    10   b  Guide screws