GB2343408A

GB2343408A - Producing a seat body including a moulding step

Info

Publication number: GB2343408A
Application number: GB9926133A
Authority: GB
Inventors: Dieter Wolfrum
Original assignee: MAGNA SEATING SYSTEMS GmbH
Current assignee: MAGNA SEATING SYSTEMS GmbH
Priority date: 1998-11-06
Filing date: 1999-11-04
Publication date: 2000-05-10
Anticipated expiration: 2019-11-04
Also published as: GB2343408B; FR2785580A1; GB9926133D0; DE19851269A1; IT1314210B1; FR2785580B1; ITMI992316A1; ITMI992316A0

Abstract

A method for the production of a seat body, having a concave surface, is disclosed. The seat body consists of a moulding (2) having a concave surface (3) and of a seat section (4) covering this concave surface. A covering blank (5) is laid onto a convex perforated plate (10), the shape of which corresponds to that of the concave surface (3) of the moulding (2), and is moulded over the entire area onto the perforated plate (10) as a result of the action of a vacuum, whilst those zones of the covering blank (5) which bear on the convex perforated plate (10) are at a point lower than the geodetically highest point (20) (Figure 3 - not shown) of the latter are upset in the direction of their surface. An intermediate layer (6) is laid onto the covering blank (5) and adhesively bonded. A mould upper part (25) is then pressed onto the intermediate layer (6) under the action of heat, in order to cure the covering layer (5) together with the intermediate layer (6) to form a seat section (4). Finally, the seat section (4) thus produced is laid onto the concave surface (3) of the moulding (2) and fastened at its edge (7) to the edge of the concave surface (3) of the moulding.

Description

2343408 MET-HOD FOR THE PRODUCTION OF A SEAT BODY HAVING A CONCAVE USEFUL

SURFACE The invention is concerned with the method for the production of a seat body having a concave useful surface, the said seat body consisting of a moulding having a concave surface and of a seat section covering this concave surface and having a covering blank. The term "seat body" is intended to refer both to backrests and to actual seat parts. Such seat bodies are used for seat furniture, for passenger seating in public transport and for passenger seats in motor vehicles.

Particularly in vehicles, a body-matching shape and lateral hold when travelling around bends make it necessary to design concave surfaces both for the person's back and for the person's bottom. It is known from practice to produce, as a seat section, a covering blank laminated onto a foam and usually also pressed into shape and to bond this covering layer to the moulding. When the covering blank is being pressed into shape, however, either creases or tensile stresses, or both, occur. The former is unsightly, is uncomfortable for the seated person and is unacceptable to the customer. The second leaves inherent stresses which cause the adhesive bond to come loose during the service life. The seat section then loses its concave shape and rests loosely on the moulding, thus giving an untidy appearance and also being uncomfortable.

The adhesive bonding of the seat section and moulding is also a disadvantage, because it obstructs the usually optional accommodation of seat heating coils or seat sensors and, overall, also results in the seated person being uncomfortable.

2 The object of the invention, therefore, is to propose a method which avoids these disadvantages and which makes it possible to produce, at as low a manufacturing outlay as possible, seat bodies which are permanently 5 of attractive shape and comfortable. This is achieved by means of the following steps: a) a covering blank is laid onto a convex perforated plate, the shape of which corresponds to that of 10 the concave surface of the moulding, in such a way that the outside of the said covering blank faces the perforated plate; b) the covering blank is moulded over the entire area 15 onto the perforated plate as a result of the action of a vacuum on that side of the perforated plate which faces away from the covering blank, whilst those zones of the covering blank which bear on the convex perforated plate at a point 20 lower than the geodetically highest point of the latter are upset in the direction of their surface; C) an intermediate layer is laid onto the covering 25 blank, the contact faces of the covering blank and intermediate layer being adhesively bonded to one another; d) a mould upper part, the shape of which corresponds 30 to that of the concave surface of the moulding, is pressed onto the intermediate layer under the action of heat, in order to cure the covering layer together with the intermediate layer to form a seat section.; 35 e) the seat section thus produced is laid onto the concave surface of the moulding and fastened at 3 its edge to the edge of the concave surface of the moulding.

The vacuum therefore acts through the perforated plate, which constitutes a lower mould half, on the covering blank. Apart from the influence of gravity, the latter is initially plane and stress-free. The attractive action of the vacuum increases sharply with a decreasing distance between the perforated plate and covering blan k. As a result, the covering blank is attracted progressively downwards from the geodetically highest point of the perforated plate. By virtue of this progressive attraction, that zone of the covering blank which is sucked firmly onto the perforated plate can no longer be displaced. It nevertheless does not tend to form creases, since it is inherently pushed together somewhat in the direction of its surface. There are therefore no tensile stresses which would be left behind as inherent stresses in the seat section and, after some time, would cause the adhesive bond to become loose.

The bonded-on intermediate layer ensures, after curing, that the seat section remains dimensionally stable for its entire service life, and therefore does not need to be adhesively bonded to the moulding, as a result of the surface displacement of the intermediate layer when the latter is being laid onto the already shaped covering blank and because the foam cells on the contact face are broken open. However, this makes it easy to exchange the seat body and install and exchange seat heating coils or seat sensors, and, moreover, improves comfort for the seated person.

In a development of the method according to the invention, when the covering blank is being moulded onto the perforated plate (step b)), a sliding frame is laid onto the covering blank and, together with the

Claims

- 4 edge of the covering blank, descends onto the perforated plate (Claim 2). The sliding frame makes it considerably easier to mould onto the perforated plate in a crease-free manner in the case of a somewhat stiffer covering blank. Since the sliding frame is merely an aid, the main work of course being done by the vacuum, it does not need its own drive, but, instead, descends due to its own weight, the covering blank slipping through somewhat below it. The covering blank does not need to be gas-permeable in order to be moulded on, the vacuum exerting its action even under these circumstances. Close-packed textiles, synthetic leather or even real leather may also be used. If the covering blank consists of a conventional gas-permeable textile, in a development of the method the intermediate layer may also be moulded onto the already shaped covering blank with the aid of a vacuum (Claim 3). In a preferred embodiment, the covering blank is a textile laminated onto a 1 to 6 mm, preferably about 3 mm thick foam layer and forming the outside (Claim 4) and the intermediate layer consists of foam and is 3 to 20 mm, preferably 4 to 7 mm thick (Claim 5). These ratios have proved particularly favourable for crease-free moulding-on and for sitting comfort. In an advantageous development of the method, the mould upper part is likewise designed as a perforated plate and the action of heat for curing purposes is carried out by blowing through a hot air stream (Claim 6). Consequently, the curing time can be minimized and uniform curing achieved at a low outlay in terms of apparatus. Furthermore, it is within the scope of the method for the covering blank to have an edge strip which projects beyond the intermediate layer and, outside the concave surface, is connected to the moulding (Claim 7) or is stitched to further textile blanks (Claim 8). Consequently, without any additional outlay, the next machining step following the method according to the invention is immediately prepared and made easier. When the sliding frame is used for positioning the intermediate layer (Claim 9), the accuracy of fit of the seat section is also increased. Since, on account of the perforated plate, the method according to the invention does not need a high vacuum, the latter can be generated very economically by means of a simple fan (Claim 10). The invention is described and explained below by means of Figures of which: Figure I shows a cross section through a seat body 20 produced by the method according to the invention, Figure 2 shows diagrammatically the first step of the method according to the invention, Figure 3 shows diagrammatically the second method 25 step, Figure 4 shows diagrammatically the third method step, Figure 5 shows diagrammatically the fourth method step. Figure I shows a cross section through a seat body 1 which may be both a backrest and an actual seat part. In any event, it has a (cylindrically or spherically concave) contour. It consists of a moulding 2 with a concave surface 3 corresponding to the concave contour and of a seat section 4 which, according to the invention, in turn consists of a covering blank 5 and of an intermediate layer 6. The covering blank 5 has, on both sides, an edge strip 7 which, for example, is fastened in the moulding 2 by means of clips 8. The edge strips 7 may, however, also be stitched to adjoining cloth blanks (not illustrated). The moulding 2 consists, for example, of a polyurethane foam of sufficient crushing resistance. The covering blank 5 is, for example, a textile material which forms the visible side and, on its invisible side, is laminated onto a laminating foam with a bulk density of about 35 to 60 kg /M3 and a thickness of 3 mm. The intermediate layer consists for example, of laminating foam with a bulk density of 35 to 60 kg /M3 and is 5 mm thick. Figure 1 also indicates a seat sensor 9 which is arranged below the seat section 4. In order to produce such a seat body by the method according to the invention, use is made of an apparatus, illustrated diagrammatically by way of example in Figure 2, which possesses, as it were as a lower mould half, a perforated plate 10 which is stretch-mounted onto a work table 11 which forms an air-type box and is connected to a suction-draught fan 12 via flaps 13. The perforated plate 10 has a concave shape, which corresponds to the concave surface 3 of the moulding 2, and is scattered, on its entire surface coming into contact with the covering blank 5, with holes which have, for example, a diameter of 1.5 mm and are distant from one another by about the same amount. It can be seen that the still plane covering blank 5 has, 'as compared with the final dimension, an oversize 16 which forms the edge of the covering blank. The covering blank 5 is laid, with its outside 15 (the good side) downwards, onto the perforated plate 10, and a sliding frame 14, which may be guided in a lowerable manner, but without a special drive, is then laid onto the said covering blank. If, then, see Figure 3, the fan 12 is switched on or the flaps 13 are opened, with the result that a vacuum is. I ormed in the space 18, in each case zones of the covering blank 5 are attracted to the perforated plate downwards in contour lines, starting from the geodetically highest point 20 at which the covering blank f irst comes to rest, and the said zones are laid onto the perforated plate and are prevented by the vacuum from being displaced, which would lead to tensile stresses. They are assisted, at the same time, by the sliding frame 14 which accompanies them downwards under its own weight and past the underside of which the oversize 16 of the edge slides and is at the same time, as it were, smoothed out, thus counteracting the formation of creases. Then, see Figure 4, the contact faces 22 of the intermediate layer 6 and of the covering blank 5 are coated with a suitable adhesive (a polyurethane 2-component adhesive would, for example, be suitable), and the intermediate layer 6 is laid onto the covering blank 5. The sliding frame 14 assists in exact positioning. If the covering blank is impermeable to air, the laying-on operation may be carried out by hand, whilst, if the covering blank 5 is air-permeable, the moulding-on operation is carried out, as before, by means of the vacuum in the space 18. For the curing, see Figure 5, of the seat section 4 constructed in its way, a mould upper part 25 is pressed onto the intermediate layer 6, this being indicated by the arrow 26. The mould upper part 25 may otherwise be a perforated plate. Slipped over the latter is a hood 27 which is flowconnected to the fan 12 via a circulating-air duct 28 having a heating body 29, so that the air stream 30 generated by the said fan is returned to the hood 27 via the heating body 29. Since the seat section 4 is compressed between the perforated plates 10 and 25, the hot air stream 30 can 8 flow through it, and it is cured particularly quickly and uniformly. During curing, the structure and shape of the seat section 4 are stabilized, in that, due to the surface displacement of the covering blank 5 and intermediate layer 6 when they are being laid in place, the foam cells located near the contact face 22 partially burst and thus also stabilize the adhesive layer. The product obtained is therefore internally stress- free and will preserve its shape for a very long time. It therefore also no longer has to be bonded adhesively to the moulding 2. It is sufficient to fasten it to the moulding 2 by means of the non-laminated edge strip 7, this being carried out by means of clips 8 in the exemplary embodiment shown (Figure 1). The edge strip 7 may, however, be stitched to adjacent blanks which are not illustrated. 9 - PATENT CLAIMS:

1. Method for the production of a seat body having a concave useful surface, the said seat body consisting of a moulding (2) having a concave surface (3) and of a seat section (4) covering this concave surface, characterized by the following steps:

a) a covering blank (5) is laid onto a convex perforated plate (10), the shape of which corresponds to that of the concave surface (3) of the moulding (2), in such a way that the outside (15) of the said covering blank faces the perforated plate (10); b) the covering blank (5) is moulded over the entire area onto the perforated plate as a result of the action of a vacuum on that side of the perforated plate (10) which faces away from the covering blank (5), whilst those zones of the covering blank (5) which bear on the convex perforated plate (10) at a point lower than the geodetically highest point (20) of the latter are upset in the direction of their surface; c) an intermediate layer (6) is laid onto the covering blank (5), the contact faces (22) of the covering blank (5) and intermediate layer being adhesively bonded to one another; d) a mould upper part (25), the shape of which corresponds to that of the concave surface (3) of the moulding (2), is pressed onto the intermediate layer (6) under the action of heat, in order to cure the covering blank (5) together with the intermediate layer (6) to form a seat section (4); e) the seat section (4) thus produced is laid onto the concave surface (3) of the moulding (2) and f astened at its edge (7) to the edge of the concave surface (3) of the moulding.

2. Method according to Claim 1, characterized in that, when the covering blank (5) is being moulded onto the perforated plate (10) (step b)), a sliding frame (14) is laid onto the covering blank (5) and, together with the edge (16) of the covering blank (5), descends onto the perforated plate (10).

3. Method according to Claim 1, characterized in that the intermediate layer (6) is also moulded onto the covering blank (5) with the aid of a vacuum.

4. Method according to Claim 1, characterized in that the covering blank (5) is a textile laminated onto a 1 to 6 mm, preferably about 3 mm thick foam layer and forming the outside (15).

S. Method according to Claim 1, characterized in that the intermediate layer (6) consists of foam and is 3 to 20 mm, preferably 4 to 7 mm thick.

6. Method according to Claim 1, characterized in that the mould upper part (25) is likewise designed as a perforated plate and the action of heat for curing purposes is carried out by blowing through a hot air stream (30).

7. Method according to Claim 1, characterized in that the covering blank (5) has an edge strip (7) which projects beyond the intermediate layer (6) and, outside the concave surface (3), is connected to the moulding (2).

8. Method according to Claim 1, characterized in that 5 the covering blank (5) has an edge strip (7) which projects beyond the intermediate layer (6) and, outside the concave surface (3), is stitched to further textile blanks.

9. Method according to Claim 2, characterized in that the sliding frame (14) is used for positioning the intermediate layer (6).

10. Method according to Claim 1, characterized in that the vacuum is generated by a fan (12) arranged below the perforated plate.