AN ADJUSTABLE BACKREST FOR THE SEATS OF VEHICLES, PARTICULARLY CARS

Abstract: The front supporting surface of the backrest is defined by an array of flexible elements (7) located side by side and having a generally S-shaped configuration with a lower forwardly convex curve (4) for supporting the lumbar region of the back and an upper forwardly concave curve (5) for supporting the upper dorsal region. Adjustment means (10, 11) enable the curvature of the flexible elements (7) to be altered selectively so as to obtain the best adaption of the backrest (1) to the characteristics of the person occupying the seat.

Description: The present invention relates to backrests for vehicle seats. Such backrests are constituted essentially by a structure for supporting the back of the person occupying the seat, made so as to be resiliently yielding and covered, at least on the front part of the seat, with a mass of padding. In general, apart from its characteristics of flexibility and the ability to vary the inclination of the backrest selectively relative to the squab of the seat, the configuration of the support structure is fixed: in other words, there is no provision for the possibility of obtaining a precise adaptation to the anthropometric characteristics and to the driving and/or travelling tastes of the person occupying the seat. In numerous sectors, for example, that of home and office furnishings, seats or armchairs have already been suggested, in which the backrest has, so to speak, a vertebral structure which enables its vertical profile to be varied selectively. The use of solutions of this type in the automotive field, however, is difficult to envisage, above all for reasons of cost. More specifically, the present invention relates to a seat having the features set forth in the pre-characterising portion of Claim 1, which is known, e.g. from US-A-2843 195. The object of the present invention is to provide a backrest for vehicle seats in which the curvature of the nackrest can be varied selectively along its vertical axis, so as to adapt it to the different convexities and concavities of different individuals, while the backrest (and the seat as a whole) retains characteristics of structural simplicity which enable it to be produced on a large scale at economically acceptable costs. According to the present invention, this object is achieved by virtue of a backrest for vehicle seats having the further feature set forth in Claim 1. In the backrest according to the invention, it is thus possible to vary the vertical profile of the backrest to make it straighter or less straight, that is, more or less undulating in the vertical direction, thus enabling each person to select the preferred type of the back support. In that respect, also FR-A-1310 770 is of interest to the invention. Further developments in line with Claim 1 are referred to in the dependent claims. The invention will now be described, purely by way of non-limiting example, with reference to the appended drawings, in which: Figure 1 shows in detail a possible embodiment of the backrest of the invention, and Figure 2 is a section taken on the line VIII-VIII of Figure 1. In the drawings, the backrest of a car seat (not illustrated in its entirety), for example, the seat intended to be occupied by the driver of a car, is generally indicated 1. In the nackrest 1, whose outer profile is schematically indicated by broken lines in Figures 1 and 2, it is generally possible to distinguish a front face 2 against which the back of the person occupying the seat rests, a rear face 3, as well as, looking at the backrest 1 in a vertical direction, a lower portion 4 intended to support the lumbosacral region of the person occupying the seat and an upper portion 5 intended to support the upper dorsal region of the person. According to a known solution, the backrest 1 is constituted by a framework covered on both its faces, and particularly the front face 2, with a mass of padding, not explicitly shown in the drawings. The framework is usually constituted by an outer frame 6 having the general shape of an inverted U and by a resilient frame connected peripherally to the frame 6 so as to support the padding in a resiliently yielding manner. In the seat according to the invention, this frame is constituted by a plurality of flexible filiform elements 17 which extend between the upper and lower ends of the backrest 1. As can better be seen in the schematic views of Figures 1 and 2, which may be equated to vertical sections of the backrest 1, the elements 17 have a generally S-shaped profile. In each element 17 can be seen: a lower curve 8 intended to support the lumbosacral region of the back of the person occupying the seat, and an upper curve 9 intended to support the upper dorsal region of the trunk. The curvatures of the two curves 8 and 9 face in opposite directions. In particular, the lower curve 8 may be defined as "forwardly convex", in that its curvature faces towards the rear face 3 of the backrest 1. The upper curve 9, on the other hand, may be said to be "forwardly concave", in that its radius of curvature faces towards the front face 2 of the backrest 1. The backrest 1 according to the invention has provision for the possibility of selective alteration of the shape of the lower curve 8 and the upper curve 9 of the elements 17, through the whole range between the condition of greatest curvature (a very undulating vertical profile) and the condition of least curvature (backrest substantially straight). As a guide, it can be said that, as the height of the person occupying the seat increases, there is a tendency to change gradually towards the least undulating profile. In fact, very tall people do not usually find that a seat of standard dimensions conforms fully to the curvature of their backs: indeed, the profile of the seat is optimised for subjects considered to be of average size within the range of the motoring population. As far as the variation of the curvature of the upper region (the curve 9 of the elements 17) is concerned, the resilience of the elements 7 (which are prestressed so as to tend to return automatically towards the most undulating profile of Figure 1) may in itself be sufficient to ensure a correct operation of the seat. The dimensions and resilient characteristics of the elements 17 may, however, be selected so as to be differentiated, for example, with the use of more yielding elements 17 in correspondence with the central part of the backrest and stiffer elements 17 near the two edges. In this way, it appears possible to achieve more effective lateral restraint throughout the vertical extent of the backrest 1. In the embodiment illustrated in Figure 1, the flexible elements are constituted by string steel strips 17 having a thickness of 1-2mm and a width of 10-15mm. The strips 17 may be made, for example, by a mechanical cutting operation from a continuous strip of string steel, so as to form narrow upper and lower end parts, 17a and 17b respectively. The upper ends 17a may be inserted in corresponding elongate slots provided in an upper cross member 18 which connects the two sides of the frame 6 immediately below the top transverse part of the frame 6 itself. The slots, indicated 18a, are oriented transverse the seat so that the strips 17 are kept securely aligned with the front face 2 of the backrest 1 in the direction of their width. Approximately halfway up the backrest 1, the two vertical arms of the frame 6 are connected by another cross member 19, also provided with slots 19a through which the strips pass. The lower ends 17b of the strips are inserted into an attachment structure associated with the shaft 10 whose rotation, controlled by a biassing spring 20, enables the vertical profile of the seat to be varied selectively. In this case (see the side view of Figure 2) the connection of the lower ends 17b to the shaft 10 is effected so as not only to achieve a simple coupling, but also to produce a bending stress in the lower ends 17b of the strips 17. For this purpose (see the front view of Figure 1) a bow 21 which projects downwardly of the shaft 10 is fixed to the shaft, usually by welding. A flexible coupling structure 22 is fixed to the bow 21, also by welding, and projects from the bow 21 in a cantilevered manner, forwardly and downwardly relative to the seat. The structure 22 is provided with slots 22a, each of which accommodates within it the lower end 17b of one of the strips 17. As a result of the rotation of the shaft 10, therefore, the bow 21 and the framework 22 as a whole may be moved selectively throughout the range between the two end positions, respectively a lower-rear one shown by a continuous line in Figure 2 and an upper-front one shown by a broken line in Figure 2. As a result of the movement between these end positions, as well as longitudinally compressing or extending the strips 17, the frame 21 and the structure 22 also achieve a certain bending of the ends 17b. This fact may be understood if it is considered that the structure can be likened, as regards each strip 17, to a sort of spring bracket connected at one end to the frame 21 and acting at the opposite end on the end 17b. When the bow 21 and the structure 22 are raised towards the upper-front end position, the strips 17 are compressed longitudinally so that the bracket is bent downwardly to cause corresponding bending, with consequent downward rotation, of the free end in which the end 17b of the strip is inserted. As a result of this bending rotation, the lower end 17b of the strip rotates, tending to increase the curvature of the lower portion of the strip. It is thus possible to achieve a more precise shaping of the lower portion of the seat.

Claims: 1. A backrest for vehicle seats with a support structure (17) for the back of the person occupying the seat, comprising a support structure defined by an array of flexible element (17) extending generally vertically side by side, and having a lower forwardly convex curve (8) for supporting the lumbar of the back and adjustement means (10, 11, 20, 21, 22) which selectively alter the curvature of the lower curve (8) of the flexible element (17), the back rest including an outer frame (6) characterised in that: the flexible elements have a generally S-shaped configuration with an upper forwardly concave curve (9) for supporting the upper dorsal region, the outer frame (6) of the backrest having generally an inverted-U-shaped configuration with two side arms and a top part, and a shaft (10) which extends to connect the side arms at their lower ends and is selectively rotatable (11), said flexible elements (17) extending substantially between the top part of the outer frame (6) and the rotatable shaft (10); and the backrest includes, in a position intermediate the top part of the outer frame (6) and the shaft (10), a cross member (19) for guiding the flexible elements (17), the cross member being fixed to the sides of the outer frame (6) and is provided with profiled parts (19a) defining seats for guiding the flexible elements (17). 2. A backrest according to Claim 1, characterised in that the adjustment means comprise actuator elements (10) which cause longitudinal traction of the flexible elements (17). 3. A backrest according to Claim 1, characterised in that the adjustment means comprise actuator elements (10, 20, 21, 22) which cause longitudinal compression of the flexible elements (17). 4. A backrest according to Claim 2 or Claim 3, characterised in that the adjustment means (20, 21, 22) can exert a bending force on the flexible elements (17b). 5. A backrest according to anyone of Claims 1 to 4, characterised in that the adjustment means (10, 11; 20, 21, 22) act primarily on the lower ends of the flexible elements (17). 6. A backrest according to Claim 1, characterised in that the flexible elements are constituted by flexible strips (17). 7. A backrest according to Claim 1 and Claim 4, characterised in that the shaft (10) is associated with a reaction structure (21, 22) which projects downwardly from the shaft (10) in a generally bracket-like arrangement, the reaction structure being provided with attachment formations (22) for connection of the lower ends (17b) of the flexible elements (17). 8. A backrest according to Claim 7, characterised in that the attachment formations (22) are resiliently flexible as a result of the reaction force exerted by the flexible elements (17) when the flexible elements (17) are compressed due to rotation of the rotatable shaft (10), the bending of the attachment formations (22) causing corresponding bending of the flexible elements (17) in the direction corresponding to an increase in the curvature of the lower curve (8) of the flexible elements (17).

Inventors: DAL MONTE, ANTONIO
Applicants: FIAT AUTO S.P.A.
Application year: 1988
Main classification: B60N2
IPC codes: A47C7, B60N2