Seat base frameworks for vehicle seats

A method for manufacturing a seat base framework for a vehicle seat which has a seat base and a backrest, this framework including a frame made of section pieces which includes two lateral longitudinal members each one extending between a rear end and a front end, the respective rear ends of the two lateral longitudinal members being intended for the mounting of the backrest of the seat and the respective front ends of these longitudinal members being joined together by a front crossmember, in which the frame of the framework includes two rigid section pieces of similar dimensions which each have an overall U shape, with a base arranged toward the front and two lateral branches which extend backward from the base as far as rear ends, the respective bases of the two section pieces being arranged substantially parallel to one another to form the front cross member of the frame, lateral longitudinal member being formed by two lateral branches belonging respectively to the two section pieces, associated with a vertical rigid fastening plate, the rear ends of these two lateral branches being separated from one another vertically and being fastened to said fastening plate, and the two section pieces being fastened rigidly to one another at two front fastening points situated respectively close to each lateral longitudinal member and toward the front of the frame, and in which the two rigid section pieces are fastened together by welding at the two front fastening points, the rear ends of the two section pieces also being fastened by welding to the two fastening plates, each lateral longitudinal member including a horizontal pivot which joins together the two lateral branches associated therewith, this pivot being arranged between the front fastening point situated close to said lateral longitudinal member and the rear ends of said two lateral branches, and the two pivots corresponding to the two lateral longitudinal members being aligned on a common axis, this method including the following steps:

• a) placing the two section pieces in a position close to the position which they are to occupy in the seat base framework,
• b) fastening the lateral branches of these section pieces together in pairs by means of the pivots,
• c) welding the two section pieces together at the two front fastening points,
• d) and welding the rear ends of the two section pieces to the fastening plates.

A method for manufacturing the seat base framework for a vehicle seat which has a seat base and a backrest, this framework including a frame made of section pieces which includes two lateral longitudinal members each one extending between a rear end and a front end, the respective rear ends of the two lateral longitudinal members being intended for the mounting of the backrest of the seat and the respective front ends of these longitudinal members being joined together by a front crossmember, in which the frame of the framework includes two rigid section pieces of similar dimensions which each have an overall U shape, with a base arranged toward the front and two lateral branches which extend backward from the base as far as rear ends, the respective bases of the two section pieces being arranged substantially parallel to one another to form the front cross member of the frame, each lateral longitudinal member being formed by two lateral branches belonging respectively to the two section pieces, associated with a vertical rigid fastening plate, the rear ends of these two lateral branches being separated from one another vertically and being fastened to said fastening plate, and the two section pieces being fastened rigidly to one another at two front fastening points situated respectively close to each lateral longitudinal member and toward the front of the frame, in which the two rigid section pieces are fastened together by welding at the two front fastening points, the rear ends of the two section pieces also being fastened by welding to the two fastening plates, each lateral longitudinal member including a horizontal pivot which joins together the two lateral branches associated therewith, this pivot being arranged between the front fastening point situated close to said lateral longitudinal member and the rear ends of said two lateral branches, and the two pivots corresponding to the two lateral longitudinal members being aligned on a common axis, and in which each pivot which joins together each lateral branch of the section pieces is also joined to a support leg which supports the seat base framework and is mounted in the manner of a fork joint between said lateral branches of the two section pieces, this method including the following steps:

• a) placing the two section pieces and two support legs in a position close to the position which they are to occupy in the seat base framework,
• b) fastening the lateral branches of the section pieces together in pairs by means of the pivots, mounting the two support legs in the manner of a fork joint between lateral branches of the two section pieces,
• c) welding the two section pieces together at the two front fastening points,
• d) and welding the rear ends of the two section pieces to the fastening plates.