Self-adjustable backrest device

Abstract

The self-adjustable backrest device supplements a seat surface such that said seat surface is a previously existing one and what is covered by the object of this invention adds a backrest or improves the existing one, for which purpose it comprises a mobile plate on which the user rests, wherein said plate swivels on a horizontal shaft that passes through a first set of hubs connected to the plate, that shaft being associated with a second set of hubs connected to a support that may be the backrest itself of the chair or easy chair on which the self-adjustable backrest is going to be used, in which case it will be referred to as pre-existing backrest, or it may be a fixed backrest which forms part of the device, in which case it will be referred to as backrest of the device. The device may include fixing elements to prevent its movement, such as legs, pegs, or a flap.

1 . *Self-adjustable backrest device of the type which supplement a seat surface characterized in that it comprises a mobile plate ( 1 ), a first set of hubs ( 2 ) connected to the mobile plate, a horizontal shaft ( 3 ) on which the plate swivels and a second set of hubs ( 4 ) associated on the one hand with the horizontal shaft and on the other hand connected to a support on which the self-adjustable backrest is disposed and configured as a pre-existing backrest or a fixed backrest which is a part of the device, wherein the shaft is disposed at a distance from the seat surface ( 10 ) of between 12 and 33 cm. 
     
     
         2 . *Self-adjustable backrest device of  claim 1  wherein it further comprises a rotation spring that associates the plate and the horizontal shaft forcing their relative position, preferably cushioned, in the resting position of which the plate is in an approximately vertical position.    
     
     
         3 . *Self-adjustable backrest device of  claim 1  wherein the shaft run is limited by a stop. 
     
     
         4 . Self-adjustable backrest device of  claim 1  wherein the assembly consisting of the mobile plate, first and second set of hubs and the support is included in a semi-rigid casing. 
     
     
         5 . Self-adjustable backrest device of  claim 1  wherein the lower part of the plate has an elastic element that closes the space between the plate and the seat surface. 
     
     
         6 . Self-adjustable backrest device of  claim 1  wherein the support is a backrest of the device ( 6 ) and is fixed. 
     
     
         7 . Self-adjustable backrest device of  claim 1  wherein the backrest of the device ( 6 ) has pegs ( 7 ). 
     
     
         8 . Self-adjustable backrest device of  claim 1  wherein the backrest of the device ( 6 ) has a flap ( 9 ).    
     
     
         9 . *Self-adjustable backrest device of  claim 1  wherein the connection of the first set of hubs and the plate comprises movement guides, the position of this first set of hubs being adjustable relative to the plate. 
     
     
         10 . *Self-adjustable backrest device of  claim 1  wherein the connection of the second set of hubs and the support comprises movement guides, the position of this second set of hubs being adjustable relative to the plate. 
     
     
         11 . Self-adjustable backrest device of  claim 1  wherein it has more than one plate. 
     
     
         12 . Self-adjustable backrest device of  claim 1  wherein the shaft is disposed at a distance from the seat surface ( 10 ) of between 18 and 27 cm.