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 . A self-adjustable backrest device to supplement a seat surface, the backrest device comprising: a mobile plate ( 1 ), a first set of hubs ( 2 ) connected to the mobile plate, a second set of hubs ( 4 ) removably connected to a support ( 9 ), and a horizontal shaft ( 3 ) connected to the first set of hubs, supported by the second set of hubs and engaging a rotation spring ( 8 ) so that the mobile plate is pivotable with respect to the second set of hubs, wherein the horizontal shaft is disposed at a distance from the seat surface ( 10 ) of between 12 and 33 cm. 
     
     
         2 . The self-adjustable backrest device according to  claim 1 , wherein the rotation spring, preferably cushioned, is disposed in a resting position where the mobile plate ( 1 ) is disposed in an approximately vertical position. 
     
     
         3 . The self-adjustable backrest device according to  claim 1 , further comprising a stop ( 11 ) for limiting the movement of the mobile plate. 
     
     
         4 . The self-adjustable backrest device according to  claim 1 , wherein the second set of hubs is adjustable in height along the support. 
     
     
         5 . The self-adjustable backrest device according to  claim 1 , wherein the mobile plate includes more than one element. 
     
     
         6 . The self-adjustable backrest device according to  claim 1 , wherein the distance from the seat surface is between 18 and 27 cm.