Process for manufacturing the frame of a back rest of a vehicle

Details Process for manufacturing the frame of a back rest of a vehicle Process for manufacturing the frame of a back rest of a vehicle

1997-08-04

2000-02-01

Ryan, Patrick

Metal fusion bonding

Process

With shaping

29745218, 297391, 297410, B60N 244

Patent

active

060192739

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Technical Field
The invention relates to a process for producing the frame of the backrest of a motor vehicle seat.
2. Description of Related Art
Backrest frames of motor vehicle seats normally consist of metal and have the shape of an inverted U. The legs of the U are furthermore called the longitudinal bar, the base piece the transverse bar.
The backrest frame is the most strongly loaded in frontal collisions (from back or from front) of the motor vehicle when the individual occupying the seat is accelerated with the torso and head against the backrest and headrest. In this process, the longitudinal bar is flexurally loaded around an axis which lies horizontally and transversely to the direction of travel. The transverse bar is flexurally loaded around an axis which forms the intersection line between the backrest frame and a vertical frame parallel to the direction of travel. The transverse bar is torsionally loaded at the location of the headrest attachment.
The greatest bending moment occurs on the ends of the longitudinal bar on the seat surface side. With increasing distance from these ends the bending stress becomes less in the longitudinal bars.
For the purposes of lightweight construction, the metal part which forms the backrest frame at all locations should have a cross-sectional area which is matched as accurately as possible to the maximum load to be withstood. Backrest frames which are made from a round pipe or extruded section which have a constant cross sectional area over their length are therefore disadvantageous, since the minimum cross-sectional area caused by the locations of greatest possible stress is also maintained at those locations at which major stress need never be expected.
The disadvantage of the constant profile cross section is bypassed in frames which are produced as castings or from folded and bent sheet metal. However these frames cause high tool costs and a larger number of expensive production steps and quality assurance measures. Castings moreover have lower ductility, i.e. they break at low deformation.


SUMMARY OF THE INVENTION

The object of the invention is to make available a backrest frame with a cross-sectional area which is matched to the maximum stress to be expected at the respective locations, and which is comprised of a metallic alloy which can be better formed than cast alloys and which can be produced with fewer processing steps as compared to a sheet metal structure.
To achieve this object, as the base piece a straight metallic, rolled or extruded profile part with an I-shaped cross-sectional area which is constant over the profile length is used, with a length which corresponds to the stretched length of the backrest frame. In the longitudinal middle part of the profile part, material is removed from its web, for example, by punching in the direction perpendicular to the web so that an opening is formed with a greatest dimension which is at least parallel to the profile direction. This opening is closed again in another step by pressing on the two profile chords by means of a pressing device in the longitudinal area in which the opening was formed parallel to the plane of the web and perpendicularly to the profile direction so that the two chords move toward one another, and thus, the web of the profile becomes narrower until the two edges of the opening which lie opposite one another in the web plane perpendicular to the profile direction abut. Then these abutting edges are joined to one another by welding. Finally, the profile part is bent into a U-shape around axes which lie at least roughly perpendicularly to the profile direction and parallel to the surface formed by the web.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated using drawings:
FIG. 1 shows a backrest frame in a frontal view,
FIG. 2 shows the original cross-sectional area of the profile part used as the initial material for the backrest frame (enlarged).
FIG. 3 shows the unformed profile part used as the initial material for the backres

REFERENCES:
patent: 1684062 (1928-09-01), Leach et al.
patent: 2720914 (1955-10-01), Doty et al.
patent: 5412860 (1995-05-01), Miyauchi et al.
patent: 5499863 (1996-03-01), Nakane et al.
patent: 5769499 (1998-06-01), Dudash et al.

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