Method for producing a rigid structure based on curved metal tubes for forming a rear cantilever seat

Abstract

The invention relates to a method for producing a rigid structure ( 5 ) based on curved metal tubes for forming a seat ( 1 ) of the rear cantilever type such as a chair or an armchair, characterized in that it comprises at least the steps involving forming two elongated one-piece lateral elements ( 10 ) by bending, each element at least being formed by a first base tubular portion ( 11 ) extending forwards, at a first bottom front bending zone ( 12 ), by a first front tube ( 13 ) erected upright and extending rearwards, at a first top front bending zone ( 14 ), by a lateral seating tube ( 15 ), said tubes used during bending by said method being made of a high carbon content, preferably between approximately 0.85 and 2.1%, steel alloy and the bending operations being performed cold before any type of subsequent heat treatment for hardening the steel that is used.

1 . Method of producing a rigid structure based on metal tubes bent to form a seat of the rear cantilever type, such as a chair or an armchair, comprising the steps of:
 forming two one-piece elongated lateral members by bending said metal tubes, each of the two one-piece elongated lateral members made of a primary tubular foot portion extending forwardly and, at a level of a first lower frontal bending zone, extending as a front primary tube erected upwardly and, at a level of a first upper frontal bending zone, extending rearwardly as a lateral seat tube, said metal tubes used during the bending by said method being made of steel, and   carrying out a subsequent heat treatment for hardening the steel after bending said metal tubes.   
     
     
         2 . The method according to  claim 1 , wherein bending the metal tubes comprises bending the metal tubes which are made of steel having a carbon content between about 0.85 and about 2.1%. 
     
     
         3 . The method according to  claim 1 , wherein bending the metal tubes comprises bending solid tubes having a diameter between about 10 and about 25 mm. 
     
     
         4 . The method according to  claim 1 , wherein bending the metal tubes comprises bending the metal tubes forward and down and forward and up at approximately 90°, with a median bending radius of approximately 1.5 to 3 times the diameter of the metal tubes used. 
     
     
         5 . The method according to  claim 1 , wherein the step of forming the two one-piece elongated lateral members by bending comprises forming a single continuous arc of approximately 180° between the primary tubular foot portion and the lateral seat tube. 
     
     
         6 . The method according to  claim 1 , further comprising connecting the two one-piece elongated lateral members at the primary tubular foot portion of each of the two one-piece elongated lateral members to a third structural element which is formed of a hollow tube. 
     
     
         7 . The method according to  claim 6 , further comprising producing the third independent structural element in the form of two secondary tubular foot portions connected respectively and in a parallel manner to the primary tubular foot portion of each of the two one-piece elongated lateral members and each extending in a second lower front bending zone into a front secondary tube erected upwards parallel to the front primary tube, each front secondary tube extending in a second upper front bending zone, into a single front transverse tube delimiting a seat structure with the two lateral seat tubes. 
     
     
         8 . The method according to  claim 7 , further comprising providing the free ends of the solid tubes of the two one-piece elongated lateral members with undercut nipples having an external diameter identical to an internal diameter of the hollow tubes of the third independent structural element, then inserting said undercut nipples of the two one-piece lateral members into the hollow tubes of the third element over a length of 1 to 2 cm before soldering or welding the assembly to form the structure. 
     
     
         9 . The method according to  claim 8 , further comprising forming, by bending, an arc of 180° at a free end of the primary tubular foot portion to connect the free end of the primary tubular portion with a free end of the secondary tubular portions. 
     
     
         10 . The method according to  claim 6 , further comprising securing the front primary tube and the front secondary tube to each other with a reinforcing crossbar. 
     
     
         11 . The method according to  claim 10 , further comprising arranging said reinforcing crossbar at mid-height of the front primary tube and the secondary tube. 
     
     
         12 . The method according to  claim 6 , further comprising connecting, in extension of the lateral seat tubes, secondary lateral seat tubes, with rear tubes extending therefrom at a first high dorsal bending zone also belonging to the seat structure. 
     
     
         13 . The method according to  claim 12 , further comprising bending the two rear tubes upwardly at a second dorsal bending zone to form a backrest. 
     
     
         14 . The method according to  claim 12 , further comprising a subsequent step of attaching a rigid openwork plate or mesh or frame made of metal, between the front transverse tube, the lateral seat tubes, the secondary lateral seat tubes, and the rear seat tubes. 
     
     
         15 . The method according to  claim 14 , further comprising a subsequent step of inserting a two-part seat pad, a top part and a bottom part, sandwiching and thereby hiding from outside said plate, mesh, or frame. 
     
     
         16 . The method according to  claim 2 , wherein bending the metal tubes comprises bending the metal tubes which are made of steel having a carbon content between about 1.15% and about 2.0%. 
     
     
         17 . The method according to  claim 3 , wherein the bending the metal tubes comprises bending solid tubes having a diameter between about 15 mm and about 20 mm.