Method for covering a plastic part by a sheet cut during the method and part so obtained

The invention relates to a dressing process by at least one non-rigid decorative sheet essentially a visible face of a support piece material (s) plastic (s), into a mold essentially comprising a first and second portions reserving therebetween a molding cavity.

Is meant by non-rigid sheet, a flexible material (PVC, woven or nonwoven fabric material, ...) can comprise a layer of foam or the like, but is deformable. The sheet may be formed only in the mold during the molding process of the entire part or to have been already previously preformed so that it has before the implementation of this process a first shape similar to that of the part the mold with which it will come into contact.

The invention relates more particularly to the implementation of a finite-piece comprising a decorative medallion covering only part of the visible face. The problems inherent in this type of construction generally consist in properly position the sheet, to let appear on the finished part that a certain portion of the sheet while allowing satisfactory cohesion between the covered portion of the sheet appearance and uncoated portion.

In the following, the visible part of the sheet on the finished part and belonging to the visible face will be referred medallion. Part of the uncoated-support part by the sheet will be called "non-molded" or "uncovered", while the portion located "under" the medallion will be called "molded" or "covered".

To solve the aforementioned problems, the invention provides a method comprising the steps of:<ul><li>a) introducing said sheet into the mold, which comprises a decorative area for constituting the medallion and another zone, </li><li>b) at least partially closing the mold by bringing its two parts, so that the foil creates a continuous separation of the molding cavity into a first and a second volume,</li><li>c) cutting inside the molding cavity at least one aperture in the sheet at the location of the other region, so that the first and second volumes of the cavity are placed in fluid communication by this aperture which breaks their separation from that moment, to allow the passage therethrough of the material,</li><li>d) prior and / or after steps b) and / or c), introducing plastics material into the mold cavity,</li><li>e) after step c), divide the material into the mold cavity by passing through the opening, for the appearance of supporting locally coated with said piece medallion</li><li>f) cooling the room,</li><li>g) opening the mold and ejecting the finished part.</li></ul>

Thus, the problems wicking and cohesion between the molded parts and molded not be largely resolved. Indeed, the number and distribution of the material passes through the sheet structure can be controlled since they correspond to locations where the cut is made. Moreover, the cutting of the sheet being formed in the mold cavity and putting in fluid communication the two volumes as soon as it is formed, the opening can be accurately positioned relative to the mold.

We point out that it is commonly referred to as "wicking", a phenomenon consisting of a moisture spread by capillary action along the sheet, particularly along the fibers when the sheet is made of fiber-based.

While it is described in EP-A-0724942 advocating a method for passing the material through the sheet, cut the sheet in the vicinity of the mold cavity with a blade attached to the one of the mold parts, but no opening is created in the cavity providing communication between the two volumes from realization of the cut.

Furthermore, EP-A-684,120 calls in turn, to achieve cohesion between the covered portion and uncovered portion of the soft sheet over cavities. Since no cutting of the sheet is provided, the structure of this sheet then breaks under the pressure of the material injected into the molding cavity.

But when the material begins to flow through the structure of the sheet in some places, a pressure drop is observed, or at least the pressure mark a landing, so that the crossings remain local. material passages can then multiply or at least exist in sufficient numbers. Therefore, this solution is complex, while allowing only limited cohesion between the covered and uncovered parts and remains without a significant reduction "wicking".

It should be noted that the invention aims to solve the aforementioned problems whatever the relative position of the covered part and the uncovered part. In particular, the two parties will be side by side, the covered portion will surround the uncovered part or vice versa. They may also be in a pattern corresponding to a combination of these possibilities.

Furthermore, in order to obtain a satisfactory appearance of the finished piece, particularly in the uncoated portion, the invention proposes that, during step d) and preferably also during step e), is injected under pressure plastic material into the mold cavity.

The finished part is then obtained directly without the need to take the part in a further molding operation to produce the uncoated portion with a satisfactory appearance.

To reduce the risk of blemishes on the finished part, the invention provides even that advantageously:<ul><li>during step d), a first injection is made the plastic under pressure opposite one side of said decorative area, is such that the decorative area of ​​the foil is brought to bear against one of said parts of mold intended to receive it,</li><li>during step e), the first injection of plastic material is continued for passing the plastic material through the openings and a further injection is carried plastic under pressure outside the decorative area.</li></ul>

The injection of the first material "under" (that is to say opposite) the decorative area, allows to set up the sheet in the shaping in the mold cavity. The second injection is a return flow from the first injection. This improves the appearance of the uncoated portion and to perform non-coated larger parts. In addition, the second injection may be performed at a higher pressure (preferably 20 to 40 MPa depending on the material) in the uncoated portion where the medallion is not present, while the pressure of the first injection is more moderate (preferably several MPa to 20 MPa).

According to another characteristic of the invention, the decorative area is of said injection side, almost entirely topped with plastic prior to cutting of the sheet during step c). Therefore, before cutting the decorative area will be maintained through the other zone, particularly its voltage can be controlled, which will get a good layout of the decorative area. Almost complete lapping the decorative area will freeze this shaping, while avoiding that the decorative area of ​​the foil is deformed after cutting.

In order to achieve an uncoated section surrounded by a covered portion, the invention proposes that: <ul><li>the first mold part comprises at least two elements,</li><li>a recess is carried out (hole contour closed) in the sheet,</li><li>we introduce in step a) a region of the sheet defining the periphery of this recess between the two elements of the first mold part where the foil is maintained.</li></ul>

To further improve the process of obtaining the component, in particular the positioning of the opening into the molding cavity, the invention provides that advantageously:<ul><li>the first mold part comprises at least two elements,</li><li>we introduce in step a) a region of the outer sheet to the decorative area between the two elements of the first mold part,</li><li>closing the mold in step b) is only partial, the total closing of the mold being carried out in step c) and generating the cutting of the sheet by pressure between the first and the second element of the first part the mold.</li></ul>

The opening is then achieved when the shaped of the sheet and in particular setting of the setting area during the mold closing is completed. Consequently, the risk that the opening moves into the mold cavity and is found on the visible face is greatly reduced.

To further improve the implementation of the opening in the sheet, the invention provides that it has the sheet in step b) between two components of a punch device and in step c) , it instantly puts a sheet through the opening by bringing into contact with one another the two elements of the punch apparatus.

The opening is so easily achieved with accurate positioning, reliably and quickly, shortening the time for obtaining the room.

In order to increase the diversity of pieces made, the invention provides for the retention of the two components of the punch device into contact with each other until step f). This produces a finished part with a passage which is determined from the shape of the punch.

To prevent portions of the sheet appear on the visible face of the finished part in its part not molded, the invention proposes that, after step c) the injection is controlled with reference to decorative area and outside said decorative area so that during said first and second injection stages, opposing efforts are applied by material on either side of the other zone, thus avoiding that it appears on the visible face of the finished part. By controlling the (s) material stream (s) can be avoided that the opening moves towards the visible face.

The invention proposes as an additional or alternative solution after step c), in close proximity to one creates the opening cut in the sheet, a whirlpool effect or restraint of the flow of material injected into the first volume against its natural movement to the periphery of the second volume to prevent another area of ​​the sheet appears on the visible face.

The two abovementioned solutions will be even more interesting that, to avoid wicking of the sheet being retained on the mold in a retaining region of the outer sheet in the zone prior to the setting step c) is cut the sheet continuously in step c) to separate the decorative area and the retention area. While these areas are completely separated, while wicking becomes impossible.

If the wick of the problem is not critical, the invention proposes that from step b), we retain the sheet on the mold in a holding area of ​​the outer sheet at decorative area and during step c) discontinuously sheet is cut so that the sheet is retained at least until step f). The control of movement of the sheet and thus the quality aspect of the medallion on the finished part are thus improved. This solution also makes it possible to prevent the cut is found on the visible face.

In particular, according to an advantageous characteristic of the invention, after step c) is completely retains the retaining region of the sheet so that its movement is prohibited.

The invention further relates to a finished part obtained by the implementation of the method. According to the invention, it comprises a covered portion where a non-rigid decorative sheet overlies a visible face of a support piece plastics material and an uncoated portion where the decor sheet is absent from the visible face, and the overlapped part completely surrounds the uncovered part.

This configuration allows those with previously known to produce parts with almost all possible provisions between the covered and uncovered parts.

The invention will emerge more clearly in the description which follows, with reference to the accompanying drawings:<ul><li>Figure 1 shows in section a mold according to the invention during a first process step,</li><li>2 shows in section a mold according to the invention in a second method step,</li><li>3 shows in section a mold according to the invention in a third process step,</li><li>Figure 4 shows on a larger scale the detail indicated IV in Figure 3, at a stage prior to that of Figure 3,</li><li>5 shows at the same scale the detail indicated IV in Figure 3 at the same stage as that of Figure 3, </li><li>Figure 6 still shows at the same scale the detail indicated IV in Figure 3, in a subsequent process step,</li><li>Figure 7 is a sectional view along the line VII-VII of Figure 6,</li><li>Figures 8 and 9 show the mold embodiments in detail the portion marked IV in Figure 3,</li><li>10 shows in plan the sheet used in Figures 11 to 13,</li><li>11 shows a variant of mold in a first method step,</li><li>Figure 12 shows the mold of Figure 11 in a second process step,</li><li>13 shows in enlarged scale the detail marked XIII in Figure 12, in a third process step,</li><li>Figures 14 and 15 illustrate another variant mold in two successive steps of the method,</li><li>16 illustrates in enlarged scale the detail marked XVI in Figure 15, in a third process step,</li><li>Figures 17-22 in different parts illustent plane obtained by the process of the invention.</li></ul>

Figures 1 to 3, a mold 4 shown illustrated comprising a first moving part 4a and a second part consisting of a fixed part 4b and 4c of a bezel (frame-shaped block). Here, the bezel 4c is connected to the fixed part 4b by cylinders 5. The bezel could however alternatively be structurally linked to the movable portion 4a of the mold by means of jacks or the like.

In Figure 1, the mold 4 is in the open position - the movable part 4a and the fixed part 4b are widely spaced from each other - and the bezel is output - not supported on the fixed part -.

A sheet 2 is placed between the fixed part 4b and 4c the bezel by a first arm 6a of a robot 6. The sheet is then fixed on nails 8 in the upper part or by any other holding means. The remainder of the sheet is then positioned by gravity, it being understood that the cutting plane is vertical.

In Figure 2, the bezel is partially closed. A distance<u>d</u> nonetheless remains between the window 4c and the fixed part 4b of the mold. The means for holding the sheet constituted in particular by nails 8 and the pinch the sheet between the seat 4c and the fixed part 4b of the mold are then enabled, that is to say they retain a peripheral edge region of maintaining 2a of the sheet 2. However, the closure of the window being only partial, the sheet is not completely stopped, that is to say that it is slidable relative to the holding means. The tension of the sheet 2 is thus controlled.

Of thermoplastic material 1, intended to serve as support for the finished part is then injected from the fixed part 4b of the mold in an inner space 16 located beneath the sheet 2. During the filling of the volume 16, the mold 4 is gradually closed by bringing the two parts 4a, 4b, so as to obtain an injection-compression of the material 1.

At the end of the injection-compression phase, the movable portion 4a of the mold abuts against the seat 4c. In Figure 4, we see that the mold 4 and in particular the bezel 4c is then not completely closed - the distance<u>d</u> always separate the bezel 4c of the fixed part 4b -. There remains a space 20 around the sheet 2 between the seat 4c and the fixed part 4b. Thus, although the sheet is maintained, controlled slip thereof is still possible between the bezel and the part 4b.

When the volume 16 is completely or nearly completely filled, as shown in Figure 5, a central area 2c of the sheet 2 intended to appear on the visible face of the finished part to be there the medallion is applied by matter thermoplastic 1 against the movable part 4a next to the first volume 16. the central zone 2c is surrounded by a connection zone 2b, itself surrounded by the peripheral zone 2a of maintenance, the whole constituting the sheet 2.

The mold has a cavity 17 including the volume 16 and outer volume 18 surrounding the volume 16. Both volumes are here separated by the connection area 2b of the decor sheet.

Filling the volume 16 can be detected by measurement of the injected volume of material, opening the mold or with the aid of event sensors (pressure sensor, heat flow, temperature, optical or the like). When the volume 16 is nearly filled, the mold is closed is then controlled and the fixed and movable parts 4a 4b approach still one of the other.

Figures 3 and 5, the mold is completely closed, the reconciliation between the parties 4a and 4b which led to the closure of the window 4c is now in contact with the fixed part 4b. The shapes of the mold parts, as well as those of the frame 4c are in fact designed to that during its approach movement toward the fixed part 4b, the movable portion 4a abuts against the bezel 4c to push it until that it comes into contact with the portion 4b.

The bezel 4c has a protrusion 12 forming a sharp edge such as a "parrot's beak". This parrot's beak is cut at the boundary of the connecting region 2b and the peripheral zone 2a of maintaining the sheet 2 in the total closure of the pressure effect of the mold 4. The important thing is to achieve a cutting of the sheet 2 at least at the connection area 2b, that is to say, inside or outside the mold cavity to establish communication between volumes 16 and 18.

Figures 6 and 7, the cutting of the sheet 2 is only partial. The connection area 2b, and therefore the central region, are thus maintained since still bound by the sections 2a 2d to the holding zone. Total closing of the mold prevents slippage of the holding region 2a between the window 4c and the fixed part 4b of the mold. The connection area 2b is therefore no risk of come to bear against the movable portion 4a of the mold and appear on the visible face of the finished part.

The second cut-outs for their help to port the volume 16 and the outer volume 18, as soon as they are made. The flow of material can thus continue the volume covered 16 of the medallion to the volume 18 where the visible face of the finished part will not be covered.

The one material injection is carried out through nozzles 10a, 10b, 10c, 10d and 10e and gradually from the center of the 2c central area to the periphery thereof and then to the periphery of the uncovered part of the room after making the second cut in the sheet. The volume 16 is thus filled first with the nozzles 10a and 10b and 10c while the volume 18 is filled subsequently with the nozzles 10d and 10e.

This sequential injection is obtained using previously mentioned sensors-such as particular event sensors -, injection from a nozzle being controlled when the injected material front reaches his level. This flow front is controlled to be continuously in movement towards the periphery of the cavity 17 and thus avoid the presence of weld lines visible on the finished part.

Moreover, the injection pressure of the material 1 is preferably higher at the end of filling, particularly when it does not go out by the nozzles 10c and 10d located in the volume 18. Thus, it improves the qualities of aspect of the uncovered face - more pressure is higher the better the appearance quality of the finished part, including less visible are the weld lines - without risk of damaging the medallion by too high injection pressure.

The finished part 40 is illustrated in Figure 1 gripped by a second arm 6b of the crawler 6. The support 42 made by the thermoplastic material 1 is cured, the finished piece 40 is removed from the mold by moving the two mold parts. In this figure, the final means for cutting the sheet 2 for separating the holding region 2a of the finished part 40 have not been represented.

8 shows a variant in which the cutting of the connecting zone 2b performed using the "parrot's beak" 22 is complete. (However, this cut may be partial - as illustrated in Figures 6 and 7.)

The risk that the central zone 2c moves is reduced by the fact that the material 1 being injected - in particular by sequential injection - first under the medallion, it has already cooled in this zone and "cured" when the sheet is cut, that is to say substantially when the melt front reaches the volume 18. this contributes to the medallion and prevent it from shifting.

For against, the connecting region 2b no longer maintained by means of the holding zone 2a must then prevent it may appear on the visible face of the finished part. To do this, the movable part 14a of the mold has a rib 28 against which the edge of the central zone 2c rests in the space 16, this rib creating a recess 30 in the volume 18. The boundary between the volumes 16 and 18 will now be defined by an imaginary line connecting the rib 28 and the parrot's beak 22.

The fixed part 4b has, too, a recess 26 such that the volume 18 has an enlarged area 34 bounded by the recesses 26 and 28. The enlarged area 34 is of a length slightly greater than length of the connection area 2b leaf.

With this, the connection region 2b will be prevented from coming on the visible face, and this for two reasons:

On the one hand, material 1 from the space 16 abuts against the step 26 and takes a swirling motion illustrated by FLE che 32 so that it passes behind the connection area 2b for the cover and the walnut, until at the level of the groove 28. This groove 28 prevents the material 1 to interfere between the medallion 2c and the movable part 14a of the mold.

On the other hand, if injecting the material 1 in volume 18 external to the enlarged area 34, when the mold is fully closed (that is to say as soon as the sheet is cut), the flow of material derived from volume 18 will move in the direction of the arrow 36 until the recess 30 and be positioned between the movable portion 14a of the mold and the connection area 2b. This connection area 2b will be embedded in the plastic material between 1 flows from volumes 16 and 18. The seam formed by the meeting of two streams will not be troublesome here since it does not appear on the opposite side.

Moreover, the resulting material flow volumes 16 and 18 and apply to the sheet of the efforts that are opposed. The stresses in the sheet and tends to move it to the visible face are thus reduced.

9 shows a secondary cavity 38 communicating with the general molding cavity and formed in the fixed part 24b of the mold. The movable part of the mold 24a and the window 24c can be those illustrated previously. Cutting the sheet may be partial or complete.

This cavity 38 is made along the space 16 and serves as a "feeder", that is to say tank from "overflow" of material. During injection of the material 1 in the volume 16, said material extends around the injection points 10a, 10b, 10c. Thus, the connection area 2b may be impregnated material at some locations before others. Now it must wait for the central area 2c almost entirely topped with thermoplastic material to cut the sheet. Then, the accumulation of material leads to an increase of the pressure producing material of the material passes through the connection area.

The secondary cavity 38 creates a clearance for the material pending cutting the sheet and thus prevents the passage of material preventing that the latter is compressed by accumulation in a portion of the injection volume. It therefore allows to weigh the filling of gaps in the volume 16. In the end of injection, the cavity 38 is completely filled with material.

Figures 10 to 13 show a variant for carrying out a non-covered with a decor sheet entirely surrounded partly by a portion covered with a decor sheet. On these figures, the elements corresponding to those of the previous figures were spotted by an increased number of 50.

In Figure 11, mold 54 essentially differs from the mold 4 in that the fixed part 54b 54d comprises a movable core actuated by a jack (not shown). The robot 56 introduces a sheet 53 in the mold between the movable part 54b and 54c bezel.

This sheet 53 is further illustrated in Figure 10. It has a recess 53a so that it forms a sort of crown between an inner edge 53b defining the recess and an outer edge 53c. Around the recess of the sheet 53 has slits 53b extending radially in the sheet from the edge 53b.

The robot fixed in the upper sheet over the studs 58. The core 54d is then inserted through the recess 53a of the sheet 53. The core 54d is then closed by the closer to the fixed portion 54b of the mold, so an inner peripheral area 53f of retention and in particular of the sheet 53a inner edge 54d is disposed between the core and the fixed portion 54b of the mold.

As shown in Figure 12, during the closure of the core 54d, one retains the 53f inner area relative to the core 54d, the inner region 53f then moves substantially according to the movement of the core 54d. Thus, the notches 53d will be found between the core 54d and the fixed portion 54b of the mold. Therefore, the notches 53d facilitate the introduction of the sheet, they avoid that the sheet 53 crease when placed between the core 54d and the fixed part 54b, and is not likely to be visible on the finished part.

Closing the window 54c is performed as previously described in relation to the bezel 4c, substantially simultaneously with the closing of the core 54d. A surrounding outer region 53 of maintenance and in particular the outer edge 53c are arranged between the window 54c and the fixed portion 54b. We can retain more or less the 53rd outer area from the window 54c, as described in relation to the core 54d, in order to apply the desired tension to the sheet 53.

The core 54d is then partially closed, and for the window 54c, there remains a distance of (substantially equal to d) between itself and the fixed part 54b.

The mold cavity 67 then has three volumes 66, 68 and 69 continuously separated by the sheet 53, as shown in Figure 13. The plastic 51 is then injected into the space 66 causing a decorative area 53g of the sheet support against the movable portion 54b of the mold. It will be understood that the situation in the areas marked A and D correspond to what has been described above in connection with the detail IV. It is also understood that the marked areas B and C are similar to respectively marked areas D and A, the core 54d then playing a role similar to that of 54c bezel. Subsequent steps for obtaining the finished part 90 is therefore to those already described, they will not be explained again.

As shown in Figure 11, the finished part 90 has a visible face 94 and comprises a support piece 92 in plastqiue material covered with the decorative sheet 53 in the part 90b of the part, which surrounds the uncovered portion 90a and is surrounded by the uncoated portion 90c.

Figures 14 to 16 illustrate a variant to make an opening in a sheet. In these figures, a mold 104 has a fixed part 104b and a movable part 104a, between which is formed a mold cavity 117. The two mold parts are at least partially closed. A sheet 102 is arranged between these two parts of the mold and in particular in the molding cavity 117.

An anvil 107a is disposed within the movable portion 104a and the limit of the mold cavity 117. A hammer 107b having a cutting portion 107d is disposed inside the fixed part 104b, the limit of the cavity molding 117 and 107a facing the anvil. 107b hammer slides relative to the fixed part 104b. To reduce the wear of the fixed part 104b, a slider 107c is interposed between the fixed portion 104b and the hammer 107b. The assembly formed by the hammer and the anvil 107b 107a form a punch device, that is to say the rapprochement of the hammer 107b and the anvil 107a causes the cutting of the sheet 102 when disposed therebetween.

The sheet continuously separates the molding cavity 117 into a first cavity 116 on the edge of which is arranged the hammer 107b and a second cavity 118 in which is disposed to limit the anvil 107a.

In Figure 15, the contacting of the protrusion 107d 107b of the hammer and anvil 107a causes an opening 102a (shown in Figure 16) in the sheet 102 immediately putting in fluid communication the volumes 16 and 18. This opening surrounds a cropped area 102b of the sheet. The contact between the hammer and the anvil is advantageously carried out following the dotted line. Thus, cutting is discontinuous and forms an opening 102a formed by a plurality of passing through the sheet 102. The cut-out could however be continuous.

As shown in Figure 16, the hammer 107b and the anvil 107a are then maintained in contact with one another during plastic injection 101 in the volumes 116 and 118 and to the cooling the room. Thus, the plastic material 101 is not present opposite and on either side of the trimmed area 102b of the sheet.

After cooling, it is then easy to remove the cropped area 102b of the foil creating an opening (hole) 146 passing right through from the finished part 140, shown in Figure 17. The edge of this passage presents a beautiful appearance side of the face aspect 144, since present the appearance of a collar 148 of plastic masking the cutting of the sheet.

Alternatively, one could provide shift or move anvil 107a and 107b hammer after cutting the sheet, so that they allow to drown the cropped area 102b in the plastic. This would provide a finished piece consists of a molded part and a molded part and not devoid passageway therethrough.

It is easily understood that the invention allows to obtain the finished workpiece shown in Figure 18, since it differs from that illustrated in Figure 17 only in that the passageway 146 is formed at the edge of the finished part.

19 shows the visible face of the part 40 of Figure 1, the decorative sheet 2 being completely surrounded by the uncoated portion of the support 42.

Figure 20 illustrates a variant of Figure 19 that also provides the method of the invention. Parts coated and uncoated are then side by side.

Figure 21 shows a part comprising a support portion 42 is not covered and a portion covered with a decor sheet 2. The covered portion includes a passage 146 surrounded by a flange 148 of plastics material formed on the opposite side 144. this is somewhat of a combination of what is shown in figures 17 and 20.

Figure 22 shows the visible face 94 of the finished part 90 of Figure 11. Foil 53 surrounds an uncovered portion of support 42 and is surrounded by another uncoated portion of the support.

Of course, the invention is not limited to the embodiments described above. Thus, there could be structurally bind the bezel to the movable part of the mold, without altering the process for obtaining the finished part. In particular, it may be considered that the seat and the fixed part of the mold are operably linked.

It could also be preformed sheet to give it greater rigidity and / or preform facilitating the implementation of the sheet in the mold - see in particular GB-A-2271956 - for example by fitting.