Abstract:
The invention concerns a method for producing a cover element for a lining of a motor vehicle seat element, comprising at least one thickness of foam ( 4 ) and a cap ( 3 ) made at least from a covering material, in which the forming of the cover element comprises the steps of placing said cap against a matrix ( 62 ) defining the apparent shape of the cover element, with the covering material on the matrix side; holding the cap ( 3 ) pressed against the matrix by suction; inserting, said layer of foam ( 4 ) against the back of said covering material; and applying a forming punch ( 64 ) defining a rear face of the cover element.

Description:
[0001]    The present patent application claims the priority benefit of French patent application FR13/57721 which is herein incorporated by reference. 
       BACKGROUND 
       [0002]    The present disclosure generally relates to motor vehicle seats and, more specifically, to the forming of upholstery for a seat element (seat bottom piece, backrest, headrest, armrests). 
       DISCUSSION OF THE RELATED ART 
       [0003]    It has already been provided, for example, in document WO-A-2010/010281, to form upholstery for a motor vehicle seat in the form of a foam support block adapted to a frame element of the seat having a cover element formed by cold forming of foam sprayed onto a polypropylene substrate and placed on the reverse side of a textile material, of skin or of a synthetic material, to define the visible shape of the seat element. 
       SUMMARY 
       [0004]    An embodiment aims at improving the forming of upholstery for motor vehicle seats. 
         [0005]    An embodiment aims at providing a method of forming upholstery for a motor vehicle seat element. 
         [0006]    An embodiment aims at providing a solution improving the aspect of the cover element. 
         [0007]    An embodiment aims at providing a solution particularly adapted to a skin covering, for example, of leather type. 
         [0008]    Thus, an embodiment provides a method of forming a cover element of upholstery of an element of a motor vehicle seat, comprising at least one layer of foam and a cap made at least of a covering material, wherein the forming of the cover element comprises the steps of: 
         [0009]    placing said cap against a matrix defining the visible shape of the cover element, with the covering material on the matrix side; 
         [0010]    maintaining the cap pressed against the matrix by suction; 
         [0011]    placing said foam layer against the back of said covering material; and 
         [0012]    applying a forming punch defining a rear surface of the cover element. 
         [0013]    According to an embodiment, said foam layer is obtained by spraying foam on a substrate supported by a suction plate. 
         [0014]    According to an embodiment, said substrate is a polyethylene film. 
         [0015]    According to an embodiment, said substrate comprises a slit foam layer. 
         [0016]    According to an embodiment, said substrate comprises a woven or nonwoven textile. 
         [0017]    According to an embodiment, the cap has a permeability to air smaller than 300 liters/m 2  per second. 
         [0018]    According to an embodiment, the cap comprises said covering material and a barrier layer, preferably made of polyurethane. 
         [0019]    According to an embodiment, the covering material is assembled with the barrier layer by sewing along style feature lines. 
         [0020]    According to an embodiment, the covering material is skin. 
         [0021]    According to an embodiment, the thickness of the cover element is in the range from 5 to 40 mm. 
         [0022]    According to an embodiment, elements for attaching the covering element to the support block are embedded in the foam layer. 
         [0023]    An embodiment also provides a cover element for motor vehicle seat upholstery. 
         [0024]    An embodiment also provides motor vehicle seat upholstery comprising a foam support block and a cover element. 
         [0025]    An embodiment also provides a motor vehicle seat comprising at least one piece of upholstery. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The foregoing and other features and advantages of the present invention will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings, among which: 
           [0027]      FIG. 1  is a simplified lateral view of a motor vehicle seat; 
           [0028]      FIGS. 2A, 2B, and 2C  are perspective views of upholstery of a seat element; 
           [0029]      FIG. 3  is a simplified representation of an example of a cap; 
           [0030]      FIG. 4  is a simplified representation of another example of a cap; 
           [0031]      FIGS. 5A, 5B, and 5C  are perspective cross-section views illustrating an embodiment of a cover element; 
           [0032]      FIG. 6  is a perspective cross-section view of an embodiment of a cover element obtained by the implementation of the method of  FIGS. 5A to 5C ; and 
           [0033]      FIG. 7  is a perspective cross-section view of seat upholstery obtained with the cover element of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    The same elements have been designated with the same reference numerals in the different drawings, which have been drawn out of scale. For clarity, only those steps and elements which are useful to the understanding of the present invention have been shown and will be described. In particular, the forming of other seat portions than the upholstery has not been detailed, the invention being compatible with any usual forming of upholstery placed on a frame. 
         [0035]    In the following description, when reference is made to terms qualifying absolute positions such as “front”, “rear”, “top”, “bottom”, “left”, “right”, etc., or relative positions, such as “above”, “under”, “upper”, “lower”, etc., or to terms qualifying directions, it is referred to a seat in a normal position of use in the usual vehicle motion direction. Unless otherwise specified, expressions approximately, substantially, and in the order of mean to within 10%. 
         [0036]      FIG. 1  is a simplified lateral view of a motor vehicle seat  1 . 
         [0037]    Such a seat comprises a seat bottom piece  12  having a backrest  13 , most often topped with a headrest  14 , jointed thereto. Seat bottom piece  12 , backrest  13 , and headrest  14  each comprise upholstery fastened to their frame, generally made of metal. Frame  16  of seat bottom piece  12  may be connected to floor  15  of the vehicle by a slide rail mechanism. Seat  1  may also comprise one or several armrests (not shown). 
         [0038]    Motor vehicle seat upholstery generally appears in the form of a padding coated with a cap comprising, at the lower surface (not shown), a foam thickness under the cover material (made of textile material, of skin, of a synthetic material, etc.). 
         [0039]      FIGS. 2A, 2B, and 2C  are perspective views illustrating the forming of upholstery of a seat element (for example, of seat bottom piece  12 ). 
         [0040]    A foam support block  21  ( FIG. 2A ) is formed with no style feature, and upper surface  211  of the foam block does not define the final visible shape of the seat bottom piece. 
         [0041]    Support block  21  is intended to receive a cover element  22  ( FIG. 2B ) defining the final shape (imitating style feature lines  36 ) of the seat element. 
         [0042]    Cover element  22  is intended to be placed ( FIG. 2C ) on block  21  to obtain the final upholstery of element  12 . The fastening of element  22  to block  21  is performed, for example, by self-adhesive bands (not shown) applied by gluing or overmolding at the surface of elements  22  and  21 , which eases the replacing of the cover element in case it is worn off or defective. As a variation, element  22  is glued or snapped to block  21  or simply maintained in position by the upholstery stretching forces. 
         [0043]    Lateral tucked panels or skirts (not shown in  FIGS. 2A to 2C ) taking part in the holding of element  22  on block  21  may also be provided. Such tucked panels are generally sewn to the edges of element  22 . 
         [0044]      FIG. 3  is a perspective cross-section view of an embodiment of a cap  3 , intended to form part of cover element  22 . 
         [0045]    It is started by forming an apparent layer (cover material) of cap  3  in the form of a covering  32  made of textile, plastic-coated textile (vinyl), leather, split leather, various skins, or any other type of covering capable of forming the apparent surface of seat upholstery. As an example, pieces of covering material  32  (for example, leather pieces) are assembled by sewing  37  along style feature lines  36 . In the example of  FIG. 3 , optional lateral tucked panels or skirts  38  are provided. 
         [0046]      FIG. 4  is a simplified representation of another embodiment of a cap  3 . 
         [0047]    According to this embodiment, a layer  34 , forming, in a way, a barrier and which is assembled to covering  32  for example by gluing, by peripheral sewing of covering pieces  32 , by flame treatment, etc., are provided. 
         [0048]    Preferably, particularly for a skin covering  32 , layer  34  is assembled only at the periphery of the skin pieces (at the level of style feature lines  36 ) so that skin  32  does not adhere to layer  34 , which improves the aspect and the comfort. In  FIG. 4 , this phenomenon has been exaggerated by showing a space “v” free of material between covering  32  and layer  34 , outside of seams  37 . In practice, covering  32  is not simply fastened to layer  34  outside of the seams. 
         [0049]    Another function of layer  34 , which will better appear from the description of the subsequent drawings, is to avoid for the foam which will be deposited (sprayed) at the rear surface of the cap to adhere to covering material  32 , which preserves the flexibility and the feel of the covering material. 
         [0050]    Cap  3 , preferably including a barrier layer  34 , has the feature of having a limited permeability to air (smaller than 300 liters per m 2  and per second under a 100-Pa pressure). Layer  34  is provided, for example, if covering  32  is too permeable. 
         [0051]    As a specific example, layer  34  may be slit polyurethane foam, having a thickness between approximately 1 mm and 20 mm and having a density in the range from 20 to 70 kg/m 3 . A polyurethane film having a thickness between 15 microns and 80 microns, microperforated or not, may also be used. 
         [0052]    In the presence of lateral tucked panels  38 , said panels preferably comprise no barrier layer  34 , as illustrated in  FIG. 4 . 
         [0053]    The mechanical resistance of barrier layer  34  and/or of covering  32  may be improved by means of a knitted or woven textile grid (not shown) having a relatively low weight per unit area (for example, between 20 and 150 g/m 2 ). 
         [0054]    The function of the low permeability to air of cap  3  thus formed is to allow an accurate positioning of the cover in a mold matrix at the next manufacturing steps. A shifting out of its position of the cap during the pressing which follows its installation in the mold is thus avoided. 
         [0055]      FIGS. 5A, 5B, and 5C  are views, respectively in perspective for  FIG. 5A  and in cross-section for  FIGS. 5B and 5C , illustrating steps of the forming of cover element  22  from a cap  3 . 
         [0056]    A substrate  42 , for example, made of a polyethylene film, of a slit foam layer, of a woven or nonwoven textile, or of a stack of a plurality of these components, is placed on a suction plate  52  and is held in place by suction (symbolized by a suction arm  5  of a robotized element of the installation). Different embodiments of the substrate will be illustrated hereafter. 
         [0057]    In this embodiment illustrated in  FIG. 5A , it is provided to position, against substrate  42  and before spraying a foam layer  4 , catching elements, for example, hook-and-loop straps  56  intended to subsequently cooperate with the support block to fasten the cover element. Foam  53  is sprayed (spray head  54 ) on a surface of substrate  42 . 
         [0058]    As illustrated in  FIG. 5B , cap  3 , resulting from the embodiment illustrated in  FIG. 3  or  FIG. 4 , is positioned against a first portion or matrix  62  of a mold for forming the cover element. Matrix  62  defines, by its surface or upper plate  621 , the final shape desired for cover element  22  and has the specificity of applying a suction (openings  622 ). Thus, cap  3  takes the shape of upper portion  621  of matrix  62  due to the suction, the cap being positioned with its visible surface (skin or textile) against plate  621 . A peripheral holding (not shown) of cap  3  may be provided at the level of matrix  62 , but preferably with no tension. 
         [0059]    Plate  52  supporting, on substrate  42 , layer  4  of sprayed foam is then placed, with foam  4  on the side of cap  3 , against matrix  62 . Then, plate  52  is removed and a punch  64  closes the mold ( FIG. 5C ). 
         [0060]      FIG. 5B  illustrates the presence of suction channels  522  at the level of plate  52 . In practice, when the plate is flipped before its transfer onto matrix  62 , substrate  42  is pinched at the periphery by means of a frame  55 , which eases handling operations. Once the plate has been flipped and positioned vertically above matrix  62 , the suction is stopped, so that substrate  42  is no longer held. Thus, the assembly formed of substrate  42  and foam  4  is laid on matrix  62 . Plate  52  is then removed and punch  64  may close the mold. 
         [0061]    On closing of the mold ( FIG. 5C ), foam  4  is compressed by means of punch  64 . In practice, the foam is compressed before being dried, that is, while it is in its sticky phase. According to the nature of the foam, this pressing is performed between approximately 15 seconds and 60 seconds after the end of the spraying. The time period for which mold  6  remains closed depends on the time period necessary to dry the foam. Typically, this time period is in the range from 50 to 90 seconds to be able to easily unmold the part. 
         [0062]    Once the cover element has been unmolded, polyethylene film  42  is preferably removed, particularly to make optional strips  56  accessible, before placing cover element  22  on support block  21 . 
         [0063]    The shape of punch  64  defines the surface of the cover element, intended to bear against the support block ( 21 ,  FIG. 2A ). Thus, matrix  62  defines the visible surface of cover element  22  while punch  64  defines the rear surface thereof. The space between matrix  62  and punch  64  defines the final thickness of cover element  22  and, in particular, of its foam layer  4 . 
         [0064]      FIG. 6  illustrates, in a perspective cross-section view, an example of a cover element  22  obtained after coming out of mold  6  of  FIG. 5C . 
         [0065]    This embodiment takes the example of cap  3  of  FIG. 4  (presence of a barrier layer  34 ) and illustrates the presence of hook-and-loop straps  56  at the rear surface of the cover element. 
         [0066]    Once this cover element has been obtained, it is associated with a support block which may for example be formed as described in above-mentioned document WO-A-2010/010281. 
         [0067]      FIG. 7  is a simplified perspective view of a seat bottom piece  12  provided with cover element  22  of  FIG. 6 , at the end of its manufacturing. 
         [0068]    The seating cushion, formed of support block  21  and of cover element  22 , is shown to be assembled on a slide rail mechanism  16 . Lateral tucked panels  38  cover, preferably with the covering material, the edges of the seat bottom piece. 
         [0069]    An advantage of the described embodiments is that the foam thickness may be different according to the areas of the padding, the thickness adaptation being performed by means of mold  6 . As a specific embodiment, the foam may have a thickness in the range from 5 to 40 mm according to regions. 
         [0070]    Various embodiments have been described. Various alterations and modifications will occur to those skilled in the art. In particular, although the embodiments have been described in relation with an example of upholstery for a seat bottom piece, they more generally apply to any seat element. Further, the distribution between the thickness provided to foam support block  21  and that of cover element  22  may vary according to seat ranges. Further, the practical implementation of the described embodiments is within the abilities of those skilled in the art based on the functional indications given hereabove.