Abstract:
A trim element ( 1 ) includes a base element ( 2 ) of rigid plastic material, a supple skin ( 4 ), and a layer of foam ( 6 ), the trim element having a principle region ( 8 ) and a marginal region ( 10 ). The marginal region ( 10 ) includes an end region ( 16 ) in which the base element has a substantially constant thickness (e 16 ) and the layer of foam is absent, and a coupling region ( 18 ) at a distance from the edge ( 12 ) of the base element ( 2 ) and the edge ( 14 ) of the skin ( 4 ) and in which the base element ( 2 ) has a thickness (e 16 ) smaller than the thickness (e 16 ) in the end region ( 16 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a trim element, especially an interior trim element of a vehicle, and to a method for the manufacture thereof. 
   2. Description of the Related Art 
   Interior trim elements for vehicles are already known which comprise a base element of rigid plastics material, a supple skin covering the base element and having a practically constant thickness, and a layer of foam located between the base element and the skin. 
   It is already known to produce such a trim element by arranging the skin and the base element in a mould cavity and injecting foam between the skin and the base element. The foam thus fixedly joins the skin and the base element to each other. 
   The trim element therefore comprises a marginal region in which the skin extends as far as the edge of the base element and is not connected thereto owing to the absence of foam. This external portion formed by the marginal region of the base element and of the skin is to be inserted into a groove in order to be assembled, for example, in a dashboard of a motor vehicle. 
   In order for this assembly to be effected under satisfactory conditions, the marginal region of the trim element must have a thickness which is substantially constant and which is markedly smaller than that of the principal region. However, owing to the absence of foam between the base element and the skin in the marginal region, the skin may move away from the base element and it may be difficult to insert the trim element into a groove. It is therefore desirable, especially when the marginal region has a substantial width, for the skin to be held against the base element over at least a portion of the marginal region. 
   In order for the skin to be held against the base element, it is possible to use the foam which already ensures that the skin and the base element are fixedly joined to each other in the principal region of the trim element. However, problems may arise in the marginal region, either owing to excessive clamping (absence of foam) or owing to insufficient clamping (passing of foam to the outside and onto the skin which may be soiled). In addition, the air which is expelled by the foam during injection into a small space may not be properly evacuated and may prevent the foam from advancing as far as the site intended for holding the skin in position. 
   SUMMARY OF THE INVENTION 
   In order to solve the above-mentioned problems, the invention uses the introduction of foam between the base element and the skin in one portion only of the marginal region, under well-defined conditions. In addition, in order that the skin should be held in position as far as the vicinity of the edge of the base element and, at the same time, that the marginal portion should preserve a constant thickness over a great width, it is desirable for the base element to delimit projections between which the foam can advance to the vicinity of the edge of the trim element. 
   To be more precise, the invention relates to a trim element, of the type which comprises a base element of rigid plastics material, a supple skin covering the base element and having a substantially constant thickness, and a layer of foam arranged between the base element and the skin, the trim element having a principal region and a marginal region, the marginal region extending as far as the edges of the base element and of the skin, the thickness of the trim element in the marginal region being substantially constant and smaller than its thickness in the principal region; according to the invention, the marginal region comprises an end region which extends to the periphery of the trim element and in which the base element has a substantially constant thickness and the layer of foam is absent, and a coupling region which is sited at a distance from the edge of the base element and the edge of the skin and in which the layer of foam extends between the base element and the skin, the base element having in the coupling region a thickness smaller than its thickness in the end region. 
   Preferably, the end region has portions of substantially constant width. 
   Preferably, the end region has, locally, projections directed towards the principal region. The projections advantageously extend as far as the principal region. 
   Preferably, the coupling region extends over the majority of the marginal region. 
   In a variant, the trim element comprises at least one ventilation duct located in the base element in the end region, between the coupling region and the outside of the end region. Preferably, the at least one ventilation duct is at a site on the trim element at which the base element extends beyond the skin. 
   The invention relates also to a method for the manufacture of a trim element according to the preceding paragraphs, which method comprises the following steps: 
   the production of a base element of rigid plastics material, having a marginal region which comprises an end region extending to the periphery and having a substantially constant thickness, and a coupling region extending at a distance from the edge of the base element and having a thickness smaller than the thickness in the end region, 
   the production of a supple skin of substantially constant thickness, 
   the covering of the base element by the skin, and the arrangement of the skin and the base element in a cavity of a mould having a closure and a main body, in such a manner that, when the mould is closed, the closure and the main body are at a substantially constant distance from each other in the marginal region which comprises the end region and at least one portion of the coupling region, 
   the closing of the mould and the application of the skin, by pressure, against the base element in the end region, and 
   the injection of foam between the base element and the skin. 
   Preferably, the base element comprises at least one ventilation duct located in the end region between the coupling region and the outside of the end region, and the method comprises the stopping of the injection operation when foam escapes via the duct, beyond the skin. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention will be better understood on reading the following description of embodiments, which is given with reference to the appended drawings in which: 
       FIG. 1  is a perspective view of a trim element manufactured in accordance with the invention and comprising a base element; 
       FIG. 2  is a section through a portion of the trim element of  FIG. 1 , in accordance with the cutting plane marked by the reference II—II in  FIG. 1 ; 
       FIG. 3  is a perspective view of a portion of the base element, sectioned across the plane II—II in  FIG. 1 ; 
       FIG. 4  illustrates a step for carrying out the method according to the invention; and 
       FIG. 5  is similar to  FIG. 3  and illustrates a variant in which the moulding cavity is ventilated. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 to 3  represent an interior trim element of a vehicle in the form of a dashboard cover  1 . The cover  1  comprises a base element  2 , sometimes called an “insert”, a supple skin  4  covering the base element  2 , and a layer of foam  6  located between the base element  2  and the skin  4 . 
   The base element  2  is formed from rigid plastics material and imparts its mechanical strength to the cover  1 . It has the configuration of a plate of practically constant thickness e 2  fashioned in the necessary shape. The base element  2  therefore has two faces  2   a,    2   b  and terminates at an edge  12 . The face  2   a  is to be completely concealed by the supple skin  4  whose edge  14  advantageously terminates at the edge  12  of the base element  2 . 
   The skin  4  has a visible face  4   a,  which is to impart aesthetic characteristics to the cover  1 , and an opposite face  4   b.  It has a thickness e 4  which is practically constant over the entire cover  1 , between the two faces  4   a  and  4   b.    
   A layer of foam  6  is located between the face  2   a  of the base element  2  and the rear face  4   b  of the skin  4 . 
   The cover  1  comprises a principal region  8  in which the layer of foam  6  has a relatively great thickness, and a marginal region  10 . The marginal region  10  has a width L which is practically constant and it extends around the principal region  8 , as far as the edges  12 ,  14  of the base element  2  and of the skin  4 . The thickness E 10  of the cover  1  in the marginal region  10  is practically constant at the periphery of the cover  1 . 
   The marginal portion  10  is to cooperate with another interior trim element of the vehicle by docking against that element. The marginal region  10  is therefore concealed in the other element once the assembly of the vehicle has been completed. 
   The cover  1  has, in its principal region  8 , a thickness E 8  which is much greater than the thickness E 10  in the marginal region because the foam has a notable thickness in the principal region  8  so that it imparts a soft feel to the cover  1 . 
   The marginal region  10  has a coupling region  18  which is contained practically entirely within the marginal region  10  or which may extend slightly beyond it towards the principal region  8 . In this coupling region  18 , the base element  2  forms recesses  32  (see  FIG. 4 ). Therefore, in the coupling region  18 , the thickness e 18  of the base element is smaller than its thickness e 2  in the principal region. In the trim element, the recess  32  is almost completely filled with foam. 
   The marginal region  10  comprises, towards the outside of the coupling region  18 , an end region  16  which extends as far as the edge  12  of the base element. In this end region  16 , the base element  2  has a thickness e 16  which is practically constant and which is preferably equal to the thickness e 2  of the base element  2  in its principal portion. The end region is covered by the skin without the interposition of foam  6  between the base element  2  and the skin  4 . Therefore, the end region  16  has no foam. However, its width is relatively small compared with that of the marginal region  10 . 
   The end region  16  comprises a series of portions  20  of practically constant width  1 , and bridges  22  which project relative to the portions  20  towards the principal region  8 , it even being possible for the projections to penetrate slightly into the principal region. 
   The width  1  of the end region  16 , except for the bridges  22 , is preferably smaller than half the width L of the marginal region  10 . Consequently, the foam  6  is present in the majority of the marginal region  10 . The coupling region  18  is therefore present in the majority of the marginal region  10 . 
   It will be noted that, in the coupling region  18 , the foam has a small thickness. It will therefore be appreciated that, if the foam drives before it the air remaining in the cavity of the mould, it may have difficulty in reaching the end region.  FIG. 5  shows an improvement which enables this problem to be solved. To be more precise,  FIG. 5  indicates the presence of a ventilation duct  36  formed in the base element  2  between the coupling region  18  and the outside of the base element. Therefore, this ventilation duct  36  is formed solely in the end region. When the foam drives air before it, the air can escape via the duct  36  to the outside of the base element. 
   It may be advantageous to form one or more ventilation ducts  36  at sites on the base element  2  where the latter extends beyond the skin so that it can be secured to another element. Thus, any foam which might escape via the duct  36  is concealed. It is also possible to tear off the superfluous foam when the trim element has been removed from the mould. 
   The method for the manufacture of the trim element described above will now be considered with reference to  FIG. 4 . 
   After its manufacture, the supple skin  4  is placed in a main body  30  of a mould  24 , and it is then covered with the base element  2 . The mould is closed by arranging a closure  28  in such a manner that a cavity  26  is delimited between the closure  28  and the main body  30 . 
   The distance d separating the closure  28  from the main body  30  in the marginal region  10  is practically constant when the mould is in the closed position. This distance d is practically equal to the sum of the thickness e 16  of the base element  2  in the end region  16  and the thickness e 4  of the skin. Consequently, the skin  4  is applied against the base element  2  in the end region  16  when the mould is closed. 
   The foam can then be injected into the cavity  26  via a hole  34  formed for the purpose in the base element  2 . The foam  6  flows between the base element  2  and the skin  4 , but not into the end region  16  since, in that region, the skin is in contact with the base element  2 . The foam may optionally pass only via ventilation ducts  36  when the latter are present. Since the thickness of the base element  2  in the coupling region  18  is smaller than its thickness in the end region  16 , the recess  32  forms a space between the base element  2  and the skin in the coupling region  18 , and the foam  6  penetrates into that space. 
   In one embodiment, the thicknesses e 2 , e 16  of the base element  2 , except for the coupling region  18 , are of the order of from 3 to 5 mm, and the thickness of the recesses  32 , which corresponds to the difference between the thicknesses e 16  and e 18  of the end region and the coupling region, is of the order of from 1 to 3 mm. In that case, the width  1  of the portions  20 , that is to say, the minimum width of the end region  16 , is advantageously of the order of from 3 to 5 mm. The thickness e 4  of the skin is preferably less than 1 mm, and the thickness E 8  of the cover  1  in its principal region  8  is advantageously of the order of from 3 to 8 mm. 
   The base element  2  is advantageously produced from polyolefin, while the skin  4  may be formed by a composite assembly comprising a textile material, with a sheet of polyvinyl chloride or of polyolefin. The foam is advantageously formed by a polyurethane.