Backrest for a chair, and chair comprising the same

Abstract

The invention relates to a backrest for a chair, comprising: an external backrest frame ( 1 ) that has two backrest frame legs ( 11, 12 ); an internal (H-shaped) stretching frame ( 4 ) that has two lateral stretching frame legs ( 41, 42 ) between which a flexible covering ( 44 ) and an extensible and compressible (convex) stretching frame transversal connection ( 43 ) are arranged; and at least one hand wheel ( 6 a, 6 b ) that is disposed externally on a backrest frame leg ( 11, 12 ) and is fitted with a threaded bar ( 61 ) which extends through the backrest frame leg ( 11, 12 ). The threaded bar ( 61 ) allows the adjacent stretching frame leg ( 41, 42 ) to be pulled closer such that the stretching frame transversal connection ( 43 ) is extended and the flexible covering ( 44 ) is stretched while allowing the adjacent stretching frame leg ( 41, 42 ) to be moved away such that the stretching frame transversal connection ( 43 ) is compressed and the flexible covering ( 44 ) is slackened.

1 . A chair backrest comprising:
 an outer backrest frame ( 1 ) with two backrest-frame legs ( 11 ,  12 ); an inner (H-shaped) tensioning frame ( 4 ) with two lateral tensioning-frame legs ( 41 ,  42 ), between which are arranged a flexible covering ( 44 ) and an extensible and compressible (convex) transverse tensioning-frame connection ( 43 ); and   at least one handwheel ( 6   a,    6   b ) which is arranged on the outside of a backrest-frame leg ( 11 ,  12 ) and has a threaded rod ( 61 ) which runs through the backrest-frame leg ( 11 ,  12 ) and by means of which the adjacent tensioning-frame leg ( 41 ,  42 ) can be drawn closer, in which case the transverse tensioning-frame connection ( 43 ) is extended and the flexible covering ( 44 ) is tensioned, and by means of which the adjacent tensioning-frame leg ( 41 ,  42 ) can be moved away, in which case the transverse tensioning-frame connection ( 43 ) is compressed and the flexible covering ( 44 ) is loosened.   
   
   
       2 . The chair backrest as claimed in  claim 1 , in which the threaded rod ( 61 ) engages in a mating nut ( 7 ), in particular a round threaded element ( 7 ), arranged on or in a lateral tensioning-frame leg ( 41 ,  42 ). 
   
   
       3 . The chair backrest as claimed in  claim 2 , in which the mating nut ( 7 ) is fixed in relation to the tensioning-frame leg ( 41 ,  42 ). 
   
   
       4 . The chair backrest as claimed in  claim 3 , in which the mating nut ( 7 ) has a transverse tensioning bolt ( 7   a ) which is located in a depression on the inside of the tensioning-frame leg ( 41 ,  42 ). 
   
   
       5 . The chair backrest as claimed in  claim 1 , in which the inner tensioning frame ( 4 ) is mounted in a pivotable manner in relation to the outer backrest frame ( 1 ). 
   
   
       6 . The chair backrest as claimed in  claim 5 , in which at least one radial longitudinal aperture is, preferably two radial longitudinal apertures ( 1   a,    1   b ) are, formed in the backrest-frame legs ( 11 ,  12 ) and accommodates/accommodate at least one guide pin or guide screw, preferably two guide pins or guide screws ( 10   a,    10   b ), which are connected to the adjacent tensioning-frame leg ( 41 ,  42 ) and form a stop for the at least one guide pin or guide screw, preferably for the two guide pins or guide screws ( 10   a,    10   b ). 
   
   
       7 . The chair backrest as claimed in  claim 6 , in which the inside of the tensioning-frame legs ( 41 ,  42 ) has arranged on it in each case one terminating disk ( 9 ), in which the at least one guide screw ( 10   a,    10   b ) engages or to which the at least one guide pin is connected. 
   
   
       8 . The chair backrest as claimed in  claim 5 , in which, in order to damp the pivoting movement and/or the lateral movement of the inner tensioning frame ( 4 ) in relation to the outer backrest frame ( 1 ), a respective damping element, in particular a rubber element ( 8 ), is arranged between the backrest-frame legs ( 11 ,  12 ) and the respectively adjacent tensioning-frame legs ( 41 ,  42 ), the threaded rod ( 61 ) and the at least one guide pin ( 10   a,    10   b ) running through this damping element. 
   
   
       9 . The chair backrest as claimed in  claim 1 , in which, in order to reduce the friction, a mount, in particular a needle-groove mount ( 1   d ) for the threaded rod ( 61 ), is provided between the threaded rod ( 61 ) and the aperture ( 1   c ) in the backrest-frame leg ( 11 ,  12 ). 
   
   
       10 . The chair backrest as claimed in  claim 1 , in which the outer backrest frame ( 1 ) has a flexible covering ( 15 ). 
   
   
       11 . The chair backrest as claimed in  claim 1 , in which the outer backrest frame ( 1 ) is arranged in a height-adjustable manner on a backrest carrier ( 2 ). 
   
   
       12 . The chair backrest as claimed in  claim 1 , in which two handwheels ( 6   a,    6   b ) are provided and have threads running counter to one another in order that the same direction of rotation, implemented from the chair, effects greater or lesser tensioning of the flexible covering in each case. 
   
   
       13 . A chair backrest comprising:
 an outer backrest frame ( 1 ) with two backrest-frame legs ( 11 ,  12 ); and   an inner tensioning frame ( 4 ) which is arranged within the outer backrest frame ( 1 ) and has two lateral tensioning-frame legs ( 41 ,  42 ),   a flexible covering ( 15 ,  44 ) being arranged in each case between the two backrest-frame legs ( 11 ,  12 ) and between the two tensioning-frame legs ( 41 ,  42 ).   
   
   
       14 . A chair, in particular a swivel chair with a chair backrest as claimed in  claim 1 .