Patent Publication Number: US-2004051367-A1

Title: Upholstered seat element and a method for its manufacture

Description:
DESCRIPTION  
       [0001] The invention relates to an upholstered seat element, in particular for vehicle seats, comprising a layer of padding enclosed in a cover. The invention relates further to a method of manufacturing such an upholstered seat element, in which a layer of padding is provided with a cover.  
       [0002] Such upholsterd seat elements for vehicle seats are known in widely diverse constructions. In practice, as a rule, many processing steps are required for the manufacture of such seat elements. The first step is often to produce a molded object, made of rubberized hair, to serve as carrier for a layer of padding that usually consists of a molded foam material. Comfort is often assisted by adding a layer of soft material that can “breathe” and/or absorb moisture.  
       [0003] Finally, on top of this structure there is disposed a cover comprising a large number of sewn seams, in order to ensure that the cover will conform to the shape of the prepared seat element, so that it follows uniformly the contours of the padding below it, is stretched smooth everywhere and encloses the padding reliably as far as the back surface of a seat element.  
       [0004] In a more comfortable vehicle seat, such a seat element includes not only a broad middle part, sometimes termed a “mirror”, but also adjacent side parts that provide the user with lateral support. In such a case the covering is naturally still more complicated in structure, and prior to assembly is sewn together from several cover pieces, so as to fulfill the requirements mentioned above.  
       [0005] Even when templates are available for the manufacture of such covers, and markers are provided to assist coordination of the various cover pieces when they are sewn together, it seems obvious that this sewing process is very laborious and entails considerable cost. Furthermore, such sewing work of course involves tolerances, which in the most unfavorable cases can add up so that when the cover is being installed, appreciable correction may be needed. This, again, contributes to an undesirable increase in the manufacturing costs.  
       [0006] The object underlying the present invention is thus to disclose an upholsterd seat element, in particular for vehicles, as well as a method for its manufacture, with which such seat elements can be produced in a simpler manner in order to reduce the manufacturing costs.  
       [0007] The object is achieved in accordance with the invention in that an upholsterd seat element of the kind cited at the outset is constructed so that the cover encloses the layer of padding from one side, and tension is applied to pull it around the circumference of a cushion carrier, whereupon the edge of the cover is directly attached to the circumferential region of the cushion carrier on its side that faces away from the padding layer.  
       [0008] With such a seat element the object is satisfactorily achieved. Owing to the fact that the cover is attached directly to the cushion carrier, sewing work on the cover can be entirely eliminated. Because the cover is pulled into position and attached while under tension, the cover lies smoothly on the padding layer, so that the shape of the seat element can be specified by the cushion carrier.  
       [0009] In a further development of the seat element in accordance with the invention it is provided that the cover is so positioned that its edge is folded around the circumference of the cushion carrier, in particular is pulled around it in a U shape. Thus a particularly reliable fixation of the cover is ensured.  
       [0010] In a further development of the seat element in accordance with the invention it is provided that the cover is attached with a large number of individual attachment elements, so that the attachment sites are spaced apart from one another around the periphery of the cushion carrier. In this way the attachment elements can be positioned in a targeted manner, i.e. precisely where fixation of the cover is desired. It is obviously not necessary for this attachment to be continuous along the entire periphery of the cushion carrier, or the entire edge of the cover.  
       [0011] In particular the attachment elements can take the form of pins, cotter pins, rivets or clamps, as long as they hold the cover firmly to the cushion carrier and keep the cover under tension.  
       [0012] In one embodiment of the seat element the attachment elements are stuck through the peripheral part of the cushion carrier and the edge of the cover.  
       [0013] In another embodiment the attachment elements are pushed over the edge of the cover and the peripheral part of the cushion carrier so that they clamp the cover and carrier together.  
       [0014] It is especially advantageous for the attachment elements, after they have been put into position, to be secured against being pulled away from the cover and the cushion carrier, so as permanently to maintain the tension under which the cover has been placed. For this purpose, when they are in position the attachment elements can be bent over, riveted or hooked into attachment eyelets. Furthermore, the attachment elements can be equipped with barbs that facilitate their introduction but counteract forces tending to pull them out.  
       [0015] In a further development of the seat element in accordance with the invention it is provided that in each element two cushion units with separate covers, padding layers and cushion carriers are disposed side by side and, along the apposed edges of the covers, are fixed to one another with shared attachment elements that simultaneously fix the stretched covers in position.  
       [0016] This measure enables fewer attachment elements to suffice for the seat element. At the same time, it is ensured that the cushion units are suitably aligned with one another. This is interesting, for example, when an appropriate side part is to be disposed next to the middle part or “mirror” of a seat element. It will be obvious that such a side part can be disposed on each side of the mirror or middle part, by the same means.  
       [0017] It is especially advantageous for the cushion carriers in the seat element in accordance with the invention to have a degree of elasticity, at least in their peripheral region, so that two units connected together can be arranged at an angle to one another. This feature makes it unproblematic to produce a shell-like shape when the seat requires it.  
       [0018] In a further development of the seat element in accordance with the invention it is provided that a backing spring arrangement is inserted under the cushion carrier, which reinforces the layer of padding from the back or replaces it. In such a case the padding layer can be made thinner or the spring arrangement, if appropriately constructed, can even serve as a substitute for the padding layer to a great extent.  
       [0019] In a special embodiment it is provided that the backing spring arrangement comprises a plurality of strip-shaped spring elements spaced apart from one another and coupled or fixed to one another near their ends.  
       [0020] A backing spring arrangement of this kind can be profiled or preformed in a manner suitable to ensure the desired comfort during operation, or a support appropriate to the shape of an operator&#39;s body.  
       [0021] In a special embodiment of the backing spring arrangement it is provided that the spring elements have a zig-zag configuration in the longitudinal direction, so as to form a plurality of mushroom-shaped projections disposed next to one another. This measure achieves good stability as well as support appropriate to the body shape.  
       [0022] Such a backing spring arrangement can be used not only in a seat element but also in an element for a back rest, in which case the spring elements are advantageously oriented in a direction transverse to the seat element.  
       [0023] In a further development of the seat element in accordance with the invention it is provided that the cushion carrier consists of a flat, molded part made of plastic, metal or a plastic-metal composite and at its periphery comprises a circumferential ridge around which the edge of the cover is pulled.  
       [0024] By this means good shape-stability of the cushion carrier is ensured, while its configuration can be adapted to the prevailing circumstances. The cushion carrier can, for example, have the shape of a lath grid within which the individual webs are suitably profiled, in which case the cushion carrier extends over or supports both the region of the middle part or mirror, and also the region of the side parts.  
       [0025] For this purpose the cushion carrier advantageously has a three-dimensional configuration that determines the shape of the seat element, such that the cushion carrier serves the function of providing a spring support for a seat back or a shell to support a seat cushion.  
       [0026] In the seat element in accordance with the invention the cover is advantageously constructed in one piece and consists of a textile material, plastic, imitation leather or genuine leather. All materials are equally well suited for the seat element.  
       [0027] The padding layer can be made of plastic foam, a nonwoven woolen or polyester fabric, or rubberized hair as well as combinations of these materials. The basic construction of the seat element and the attachment of the cover do not change, regardless of which of these is used.  
       [0028] In a further development of the seat element in accordance with the invention it is provided that the cover and the padding layer are made of the same or similar plastic materials, and in the region of U-shaped channels with a decorative function the materials are permanently joined to one another by a thermoforming process.  
       [0029] Such channels in the form of decorative seams can be provided in both the horizontal and the vertical direction. They serve on one hand to fix the cover to the layer of padding, and on the other hand can also be superimposed on the cover design as decoration.  
       [0030] The method in accordance with the invention for manufacturing a seat upholstery element, in which a cover is disposed over a layer of padding, comprises the following process steps:  
       [0031] (a) a cover is laid into a forming tool with U-shaped cross section and is fixed therein,  
       [0032] (b) a layer of padding is set into the cover,  
       [0033] (c) a cushion carrier is placed onto the layer of padding and the edge of the cover is folded inwardly so that it passes around the circumference of the cushion carrier,  
       [0034] (d) pressure directed into the forming tool is applied to the cushion carrier by means of a plunger, so that the material of which the layer of padding is made is compressed to a specified thickness and at the same time the tension of the cover is adjusted, and  
       [0035] (e) while the tension created in step (d) is maintained, the edge of the cover is fastened directly to the periphery of the cushion carrier.  
       [0036] Such a method eliminates the need for sewing work; instead, the cover made of the selected material can be laid directly into an appropriate forming tool and retained in an initial position therein, for example by applying a subatmospheric pressure.  
       [0037] It is also not necessary to use a pre-shaped cushioning element as the layer of padding. By appropriate adjustment of the shape of the forming tool on one hand, and that of the cushion carrier on the other hand, it is possible to obtain the desired configuration of the seat upholstery element.  
       [0038] After the procedural steps cited above have been carried out, the seat upholstery element can be removed from the forming tool and installed in a suitable frame or bearing block of a vehicle seat.  
       [0039] In a further development of the method in accordance with the invention it is provided that the cover is attached to the cushion carrier by means of a plurality of attachment elements spaced apart from one another. The number of attachment elements that are required will depend on the configuration of the individual seat element, the criterion being that enough should be provided to ensure the necessary retention and smoothing of the cover.  
       [0040] It is especially advantageous for the attachment elements to be attached at substantially the same time. This can be achieved, for example, in that the attachment elements are inserted into a plunger component of the forming tool which, after the cover has been placed under the specified tension, presses them directly into the previously prepared attachment receptacles of the cover or the cushion carrier.  
       [0041] In the method in accordance with the invention the attachment elements, in one embodiment, can be attached in such a way that they clamp the edge of the cover to the periphery of the cushion element; in another embodiment the attachment elements can be stuck through both the edge of the cover and the periphery of the cushion element and thereafter fixed in position. In either case it is ensured that the cover, while kept under tension, is fixed in position over the layer of padding.  
       [0042] In this process it is advantageous to provide some means of ensuring that after the attachment elements have been fixed in position, they cannot be accidentally released. This can be achieved by riveting, inserting pins or cotter pins which are then bent or spread out, or similar means. The attachment elements can also be equipped with barbs, which likewise prevent their accidental release.  
       [0043] In a further development of the method in accordance with the invention it is provided that two cushion units as specified in the steps (a) to (d) are prepared side by side, and that subsequently a part of the forming tool that has served as a barrier between the units is removed, so that the adjacent sides of the two units can be brought into contact. Then in step (e) the two apposed units are attached to one another with shared attachment elements, which simultaneously fix the pre-stretched covers in position. By this means the seat upholstery elements can be assembled to form quite complicated structures.  
       [0044] In a further development of the method in accordance with the invention it is provided that a backing spring arrangement comprising a plurality of strip-shaped spring elements is inserted under the cushion carrier and is made integral with the seat element. This additionally simplifies the manufacturing procedure, even when complex structures of the seat element are required.  
       [0045] In a further development of the method in accordance with the invention it is provided that the same or similar plastic materials are used for the cover and the layer of padding, and that a thermoforming process is used to incorporate U-shaped channels into the cover and padding, which serve both as decoration and as regions in which the materials are permanently joined to one another. This can be accomplished, for example, by using a forming tool that is partially heated, so that it produces a local thermoplastic deformation of the cover as well as the underlying padding layer that is sufficient to connect the two structures together.  
       [0046] It is particularly advantageous when polyester is used for the cover and the padding layer, and these are fused or welded to one another in the region of the channels by the thermoforming process.  
       [0047] In the method in accordance with the invention, when a foam material with a constant thickness is used for the padding layer, in particular a material supplied in rolls, the manufacturing process can be additionally simplified. That is, no initial shaping process is required for the layer of padding. The pressure applied by the above-mentioned piston adjusts such a layer of padding to the desired thickness, and the material is shaped appropriately by the interaction of the forming tool and the cushion carrier. 
     
    
    
     [0048] In the following the invention is explained, also regarding additional characteristics and advantages, with reference to exemplary embodiments, the description of which is assisted by the attached drawings, wherein  
     [0049]FIG. 1 is a schematic sectional view to explain the method in accordance with the invention for the manufacture of a seat upholstery element;  
     [0050]FIG. 2 is a schematic sectional view to explain a modified embodiment of the method in accordance with the invention for the manufacture of a seat upholstery element;  
     [0051]FIG. 3 shows another phase in the method in accordance with the invention as shown in FIG. 2;  
     [0052]FIG. 4 is a schematic sectional view to explain a backing spring arrangement for a seat upholstery element in accordance with the invention;  
     [0053]FIG. 5 is a schematic plan view of a backing spring arrangement for such a seat element;  
     [0054]FIG. 6 is a schematic side view to explain the production of a U-shaped channel to serve as a decorative seam in a seat element in accordance with the invention; and  
     [0055]FIG. 7 is a perspective drawing to explain such a decorative seam, which was produced by the method according to FIG. 6. 
    
    
     [0056] In the following, reference will first be made to FIG. 1, which shows a method for manufacturing a seat upholstery element in accordance with the invention. Visible in the lower region is a forming tool  50  with a lower part  52  and a side part  54  as well as a plunger  58  on the upper side. The profiled lower part  52  and the side part  54  together form a mold cavity to accommodate a cover  10 , which is suitably arranged therein and held in position, for example by suction openings (not shown).  
     [0057] The cover  10  can consist of any suitable material, for example textile materials, plastics, imitation or genuine leather.  
     [0058] Onto the cover  10  is placed a layer of padding  20 , which can be made of a variety of suitable materials, such as plastic foam, a nonwoven wool or polyester fabric, rubberized hair or combinations of these materals.  
     [0059] This padding layer need not be a pre-formed molded object, but rather can also be a loose material or a piece of foam material with a uniform thickness, such as may be obtained in a roll. As explained in more detail below, the padding layer  20  will in any case be given the desired shape by the method described below.  
     [0060] Onto the padding layer  20  is placed a cushion carrier  30 . This can be a flat molded piece of plastic, metal or a plastic-metal composite material. The cushion carrier  30  advantageously has at its periphery  32  a circumferential ridge  34 , which makes the carrier sufficiently rigid.  
     [0061] The cushion carrier  30  has a three-dimensional configuration designed as desired in order to specify the shape that will be given to the seat element and ensure the necessary support for a user. In this regard the cushion carrier  30  can be made so as to function as a backing spring for a seat back or else as a shell to support a seat cushion.  
     [0062] In the region of its periphery  34  or the associated ridge  32 , the cushion carrier  30  can comprise apertures or through holes  36  that can serve to receive attachment elements  40 , as indicated schematically on the right side in FIG. 1.  
     [0063] In the arrangement according to FIG. 1 an attachment element  40  of this kind has been set into a receptacle  59  provided for this purpose. This indicates schematically that such attachment elements  40  are prepared for use in attaching the cover  10  to the cushion carrier  30 .  
     [0064]FIG. 1 also makes clear that the edge of the cover  10  has been folded around the ridge  32  and hence the periphery  34  of the cushion carrier  30 . The plunger  58  of the forming tool  50  is advanced from above in the direction of the arrow F and imposes the stamping pressure required to reduce the padding layer  20  to a specified thickness and simultaneously create tension in the cover  10 .  
     [0065] It should be evident that this adjustment of initial tension can be achieved reproducibly and does not depend on any sort of tolerances in the cover or the padding layer. In particular, the attachment of the cover can be brought about with no need for any kind of sewing work.  
     [0066] As attachment elements  40  pins, cotter pins, rivets or clamps can be used; these are either stuck transversely through corresponding apertures or through holes  36  and then fixed in position, for example by bending them over, spreading them apart or riveting. Alternatively, U-shaped clamps can employed by pushing them down over the U-shaped edge  12  of the cover  10  and the enclosed ridge at the periphery  32 , and then closing the clamp. When closed, such clamps can be hooked into the apertures or through holes  36  at the periphery  32  of the carrier  30 .  
     [0067] In the method in accordance with the invention, it is also possible for a larger part of the edge  12  of the cover  10  to be folded over, so that it extends into the region between the plunger  58  and the cushion carrier  30 . This measure enhances the tension applied to the cover  10 . Alternatively or in addition, the plunger  58  can comprise entrainment or suction devices that reliably pull the edge  12  of the cover  10  around the periphery  32  of the carrier  30  and thus apply tension. These measures are not represented individually in the drawing.  
     [0068] The edge  12  of the cover  10  does not itself need to be provided with apertures or through holes. The attachment elements  40 , which as a rule are made of metal or plastic, are sufficiently solid to penetrate the material of which the cover  10  is made, and thus to fix it to the cushion carrier  30 . The attachment elements  40  are advantageously equipped with barbs, which allow penetration through the cover  10  but counteract withdrawal of the attachment elements  40 .  
     [0069]FIG. 2 shows a modified embodiment of the method in accordance with the invention. Elements that are identical in the two figures of the drawings are identified by the same or corresponding numerals. In this case two cushion units are produced at the same time, being situated in corresponding forming tools  50  that are separated from one another by a partition or sliding barrier  56 . The shapes produced by the forming tools are different in the left and right regions.  
     [0070] Both cushion units are prepared in the same way, as explained above. In the present case only the plunger  58  on the right is provided with apertures  59  to receive corresponding attachment elements  40  (not shown). At the same height, in the middle region of the cushion carriers  30 , apertures or through holes  36  are provided.  
     [0071] This arrangement makes it possible, after removal of the partition or sliding barrier  56 , to bring the two units together and, in the region of the folded-over edges  12  of the covers  10  that are now apposed to one another, to connect and attach both covers with a shared attachment element  40 . On the right side of the right plunger  58  corresponding attachment elements  40  are provided and employed for fixation.  
     [0072] The cushion carriers  30  have a degree of elasticity, at least in their peripheral region, so that two cushion units thus connected together can be disposed at a certain angle to one another, as indicated schematically by the slanted configuration in the right region of FIG. 2 and FIG. 3. As a result, for example, it is possible to construct seat elements with side parts slightly tilted with respect to the middle part or “mirror” of a seat. The slant in the beveled region where the covers  10  are adjacent to one another is, of course, greatly exaggerated in the drawing.  
     [0073]FIG. 4 shows schematically a cross section through a so-called backing spring arrangement  60 ; in this example it consists of a plurality of strip-like spring elements or leaf springs  62 , as indicated schematically in FIG. 4. These strip-like spring elements  62  are advantageously spaced apart from one another as shown in FIG. 5. Near their ends such spring elements  62  are coupled by a connector  66 , as indicated schematically in FIG. 5 by the fixation points  68 .  
     [0074] A backing spring arrangement  60  with such a substantially flat construction can, for example, be disposed below the cushion carrier  30 , opposite the cover  10 , and thus reinforce the padding layer  20  or replace it, at least in part. This depends on the particular circumstances and the requirements with respect to comfort.  
     [0075] In a special embodiment according to FIG. 4 the spring elements  62  have a zig-zag configuration in the long direction, so as to produce a plurality of mushroom-shaped protrusions or elevations  64  disposed side by side. The dimensioning and profiling of the spring elements  62  are adjusted to suit the particular circumstances, with the aim of achieving the desired elasticity and firmness.  
     [0076] In FIG. 6 is shown schematically how U-shaped channels are incorporated into such a seat element. This is possible in particular when the cover  10  on one hand and the padding layer  20  on the other hand are made of the same, similar or at least compatible plastic materials, which can be shaped permanently as desired by a thermoforming process. It is particularly advantageous when, for instance, polyester is used for both the cover  10  and the padding layer  20 .  
     [0077] For this purpose the seat element comprising cushion carrier  30 , padding layer  20  and cover  10  is disposed between a base plate  74  and a tool  70  with a projection  72 , which produces a channel  14  having a decorative appearance. The projection  72  of the tool  70  can be heated, at least in part, so as to carry out a thermoplastic shaping process. In this process the materials of which the cover  10  and the padding layer  20  are composed become fused with or welded to one another in the region of the channel  14  currently being formed. It is also possible to use a cover  10  that on its inner surface is laminated with a thermal adhesive, which is activated when the tool  70  is inserted so as to glue the cover to the padding layer  20 .  
     [0078] By this means a local fixation of the cover  10  to the padding layer  20  is achieved. This contributes to the general fixation of the cover  10  and also produces a decorative effect. Such channels  14  can be formed both in the long direction and also in the transverse direction of the seat element.  
     [0079] Finally, FIG. 7 shows schematically, in a perspective drawing, the appearance of the seat element after the channel  14  has been incorporated.  
                               List of reference numerals                                        10   Cover       12   Edge       14   Channel       20   Layer of padding       30   Cushion carrier       32   Periphery       34   Ridge       36   Aperture or through hole       40   Attachment element       50   Forming tool       52   Lower part       54   Side part       56   Partition       58   Plunger       59   Recess       60   Backing spring arrangement       62   Spring element       64   Elevation or projection       66   Connector       68   Fixation point       70   Tool       72   Projection       74   Base plate