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 Foil essentially a visible face of a support piece material (s) plastic (s), in a mold comprising essentially a first and a second portions reserving them a mold cavity.

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

The invention relates more particularly to the production of a finished-part comprising a decorative medallion covering only part of the opposite side. The problems inherent in this type of embodiment consist generally to properly position the sheet, to let appear on the finished part than a specified portion of the sheet while permitting satisfactory cohesion between the covered portion of the trim sheet 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 support piece uncoated by the sheet will be called "non-molded" or "not covered ", while the portion located" under "the medallion will be called "Molded" or "covered".

To solve the aforementioned problems, the invention provides a method according to claim 1 comprising the steps of:<sl><li>a) introducing the sheet into the mold, between two elements mobile, said sheet comprising a decoration zone intended to constitute 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 mold cavity into first and second volumes,</li><li>c) bringing into contact one another, said two elements for cut inside the molding cavity at least one opening in the sheet at the location of the other region, so that the first and second the cavity volumes are in fluid communication with the opening which breaks their separation from that moment, to allow passage therethrough of the material,</li><li>d) prior and / or after steps b) and / or c), introducing the plastic material into the mold cavity,</li><li>e) after step c), distributing the material in the cavity molding by passing through the opening, for the support piece locally coated with said inset aspect,</li><li>f) cooling the room,</li><li>g) opening the mold and ejecting the finished part.</li></sl>

Thus, the problems wicking and cohesion between overmolded and not molded parts will be largely resolved. Indeed, the number and distribution of the material passes through the structure sheet can then be controlled as they are where the cut is made, in other words where the two elements are brought into contact with one another. Moreover, the cutting of the sheet being formed in the mold cavity and putting in fluid communication the two volumes from it is made, the opening can be positioned precisely relative to the mold.

We point out that it is commonly referred to as "effect wick ", a phenomenon consisting of a moisture propagation capillarity along the sheet, particularly along the fibers when the sheet is performed based on fibers.

While it is described in EP-A-0724942 a calling process for passing the material through the sheet, cut the sheet adjacent the mold cavity using a blade fixed on one of the parts of the mold, but no opening is created in the cavity putting communication between the two volumes from realization of the cut.

It is also described in EP-A-0724942, another method comprising the steps a), b), d), e), f) and g) above and for advocating achieve cohesion between the covered portion and the uncovered portion of tender leaf above cavities. Under the pressure exerted by the material plastic, sheet breaks and passes tavers the opening thus created in the leaf.

EP-A-0684120 discloses a relatively close process also of tensioning the sheet over the cavities. from when 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, as with regard to EP-A-0724942 that EP-A-0 684 120, when the material begins to flow through the structure of the sheet some places, a pressure drop is observed, or at least the pressure mark a landing, so that the crossings remain local. The passages material can then be multiplied or at least exist in numbers sufficiently important. Therefore, this solution is complex, while allowing only a limited cohesion between the parties and covered not covered, and without a significant reduction "wicking".

Furthermore, EP-A-0636464 teaches passing the material plastic through the pores of the decorative sheet. This solution requires use a decorative sheet of high porosity, which may among other problem to create material passes through the sheet at locations unwanted, especially reveal the injected plastic where only the Foil should be visible.

It should be noted that the invention aims to solve the aforementioned problems regardless of the relative position of the covered portion and the portion not covered. In particular, the two parties will be side by side, the part covered may surround the uncoated portion or vice versa. They will also be in a configuration corresponding to a combination of these possibilities.

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

The finished part is then obtained directly, without requiring resume the workpiece in a further molding operation to realize the uncovered part 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 carried out under pressure of plastic material facing a side of said decorative area, is so that the decorative area of ​​the foil is brought to bear against one of said the mold parts intended to receive it,</li><li>during step e), the first injection of material is continued plastic for passing the plastic material through the openings and sends another injection of plastic material under pressure outside the decorative area.</li></ul>

The injection of the first material "under" (that is to say opposite) the decorative area enables to set up the sheet in the shaping in the mold cavity. The second injection is a renewed flow from the first injection. This improves the appearance of the part uncovered and achieve broader uncoated parts. Of Moreover, 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 will be more moderate (preferably several MPa to 20 MPa).

According to another characteristic of the invention, the decorative area is, said injection side, almost entirely topped with plastic before the cutting of the film during stage c). Therefore, before cutting the decorative area will be maintained through the other area, in particular its voltage can be controlled, which will get a good setting shape of the decorative area. The almost complete topping the decorative area will freeze the shaping, while avoiding that the decorative area of ​​the sheet deforms after cutting.

In order to achieve uncoated portion surrounded by a part covered, 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 the recess between the two elements of the first part of the mold where the sheet is held.</li></ul>

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

The opening is then achieved when the shaping of the sheet and in particular the decorative area during closure of the mold is completed. Consequently, the risk that the opening moves in the cavity molding 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) is carried out instantly through the sheet an opening by bringing into contact with one the other two elements of the punch apparatus.

The opening is so easily achieved with a positioning accurate, reliable and timely manner, shortening the time for obtaining the room.

To increase the diversity of parts produced, the invention provides for the retention of the two elements of the cutter device in contact with each other until step f). This produces a finished part having a passage of which is determined shape from that of the punch.

To avoid that portions of the sheet appear on the face appearance of the finished piece in its portion not molded, the invention provides after step c) the control injection is opposite the decorative area and outside said decorative area so that during said first and second injection step, opposed efforts are applied by the 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) stream of material (s), are will prevent the opening from moving towards the visible face.

The invention as a complementary solution or Alternatively, after step c) is created in the immediate vicinity of the opening cut in the sheet, a whirlpool effect or restraint of the flow of material injected into the first volume against its movement natural to the periphery of the second volume to avoid the other area of the sheet to appear on the visible face.

The two solutions mentioned above will be more interesting that, to avoid wicking, the sheet being retained on the mold in a retaining region of the outer sheet to the decorative area prior to step c), continuously cutting the sheet 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), one retains the sheet on the mold in a retaining region of the outer sheet to the decorative area and in step c) is cut out discontinuously sheet so that the sheet is retained at least until step f). The control of movement of the sheet and therefore the appearance quality of the locket on the finished part are thus improved. This solution also makes it possible to prevent the cut is found on the face aspect.

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 portion which covered a non-rigid Foil covers an aspect of a face Plastic-support piece and an uncovered portion where the sheet decor is absent from the visible face, and the covered portion surrounds completely uncoated portion.

This con figuration allows those with previously known produce parts with almost all provisions possible between the coated and uncoated parts.

The invention will become more clear in the following description with reference to the accompanying drawings which:<ul><li>Figure 1 shows in section a mold according to the invention in a first method step,</li><li>Figure 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 method step,</li><li>Figure 4 shows on a larger scale the detail indicated IV Figure 3, at a stage prior to that of Figure 3,</li><li>5 shows at the same scale the detail indicated IV in FIG 3 in the same step as that of FIG 3, </li><li>Figure 6 shows still on the same scale the detail marked 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 alternative embodiments of the mold in the detail portion marked IV in Figure 3,</li><li>10 shows in plan the sheet used in Figures 11 to 13</li><li>Figure 11 shows a mold in a first alternative process 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 XIII spotted on Figure 12, in a third process step,</li><li>Figures 14 and 15 illustrate another variant in mold two successive steps of the method,</li><li>16 illustrates in enlarged scale the detail marked XVI on the Figure 15, in a third process step,</li><li>Figures 17-22 illustent in different parts obtained map according to the method of the invention.</li></ul>

Figures 1 to 3, we see illustrated a mold 4 comprising a first moving part 4a and a second part consisting of a fixed part 4b and 4c a bezel (frame-shaped block). Here, the bezel 4c is linked to the fixed part 4b by actuators 5. The telescope, however, could alternatively be related structurally to the movable portion 4a of the mold through cylinders 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 the bezel 4c 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 rest 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 pinching the sheet between the seat 4c and the fixed part 4b of the mold are then active, 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 part, the sheet is not completely stopped, that is to say, it is slidable relative to the holding means. The tension of the sheet 2 is well under control.

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 a interior space 16 located below the sheet 2. During the filling of the volume 16, the mold 4 is gradually closed by approximation of two parts 4a, 4b, so that the compression-injection is obtained of the material 1.

At the end of the injection-compression stage, the movable part 4a of mold bears against the bezel 4c. In Figure 4, we see that the mold 4 and in particular the bezel 4c is then not fully closed it 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. So, although the sheet is maintained, controlled sliding of the latter is always possible between the bezel and the part 4b.

When the volume 16 is completely or almost completely filled as shown in Figure 5, a central zone 2c of the sheet 2 for to appear on the visible face of the finished part to be there the medallion is applied by the thermoplastic material against the part 1 mobile 4a next to the first volume 16. The central zone 2c is surrounded by a connection zone 2b, itself surrounded by the area holding device 2a, the whole constituting the sheet 2.

The mold has a cavity 17 having the space 16 and a volume 18 surrounding the exterior volume 16. These two volumes are here separated by the connection area 2b of the decor sheet.

Filling the volume 16 can be detected by measuring the injected volume of material, opening the mold or using sensors event (pressure sensor, heat flow, temperature, optical or the like). When the volume 16 is nearly filled, closure the mold is then controlled and fixed mobile parts 4b and 4a still closer to each other.

Figures 3 and 5, the mold is completely closed, the rapprochement between the parties 4a and 4b which led to the closure of the bezel 4c which is now in contact with the fixed part 4b. Forms 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 moving part 4a abuts against the window 4c to push up it comes into contact with the portion 4b.

The bezel 4c has a projection 12 forming a ridge RAM such as a "parrot's beak". This parrot's beak is cut, the outside the connection area 2b and the retaining surrounding area 2a, the sheet 2 under the effect of the total closing pressure of the mold 4. The important thing is to achieve a cut of the film 2 at least at the connection area 2b, that is to say, inside or outside the cavity molding in order 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 as always linked by sections 2d 2a holding area. The total closing of the mold prevents slippage of the holding region 2a 4c between the bezel and the fixed part 4b of the mold. The connection area 2b therefore unlikely to be applied against the movable part 4a of the mold, and appear on the visible face of the finished part.

The second for their cuts make it possible to communication volume 16 and the outer volume 18, as they are performed. material flow may well continue Volume 16 covered the medallion to the volume 18 in which the visible face of the finished part will not be covered.

1 for injection is carried out through nozzles 10a, 10b, 10c, 10d and 10e and gradually from the center of the area Central 2c to the periphery thereof and to the periphery of the uncoated portion of the piece after making the second cut-outs in the leaf. The volume 16 is thus filled first with the nozzles 10a, then 10b and 10c while the volume 18 is filled subsequently with the nozzles 10d and 10e.

This sequential injection is obtained using sensors mentioned above-such as particular event sensors - injection from a nozzle being controlled when the melt front injected reaches its level. This flow front is controlled to be in continuously moving 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 will preferably higher at the end of filling, particularly when it does not go out only by 10c and 10d nozzles in the volume 18. Thus, it improves the appearance qualities of the uncovered face - the more pressure is high the better the appearance quality of the finished part, and in particular are less visible weld lines - without risking deteriorate the medallion by too high injection pressure.

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

8 shows a variant in which the cutting area of ​​the 2b connection carried out 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 the material being injected 1 - including 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 arrives in Volume 18. This helps to keep the medallion prevent it from shifting.

For against, the connecting region 2b being no longer held by 2a through the retaining zone, it is then necessary to prevent it may appear on the visible face of the finished part. To do this, the portion mobile 14a of the mold has a rib 28 against which the edge of the 2c central area bears in the volume 16, this rib creating a recess 30 in the volume 18. The boundary between the volumes 16 and 18 will now defined by an imaginary line connecting the rib 28 and the spout 22 parrot.

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 30. The expanded area 34 is of a length slightly greater than length of the connection area 2b of the sheet.

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

On the one hand, material 1 from the volume 16 abuts against the step 26 and takes an illustrated swirling movement by arrow 32 so that it passes behind the connection area 2b to encompass and walnut, to the level of the rib 28. The groove 28 1 prevents the material from interfering between the medallion and the movable portion 2c 14a of the mold.

On the other hand, if the material is injected in volume 18 1 outwardly to the enlarged area 34, as soon as the mold is completely closed (that is to say as soon as the sheet is cut), the flow of material from the Volume 18 will move in the direction of the arrow 36 to recess 30 and be positioned between the movable part 14a of the mold and connection area 2b. This connecting region 2b will be embedded in the plastic material, between the material 1 flows from the volumes 16 and 18. The seam created by the meeting of two streams will not be troublesome here since it does not appear on the visible face.

In addition, material flows from volumes 16 and 18 apply and on the sheet of efforts that are opposed. The strain on the sheet and tending to move it to the visible face are reduced.

9 shows a secondary cavity 38 communicating with General molding cavity and formed in the fixed part 24b of the mold. The moving part of the mold 24a and 24c telescope will be those shown previously. Cutting the sheet may be partial or complete.

This cavity 38 is made along the space 16 and serves "Feeder", that is to say tank from "overflow" of material. when the injection of the material 1 in the volume 16, said material extends around the injection points 10a, 10b, 10c. Thus, the connection area 2b risk being impregnated material in some places before others. However, it must wait for the central area 2c almost entirely topped material to cut the thermoplastic sheet. So matter accumulation generates an increase in the pressure of the material producing material passes through the connection area.

The secondary cavity 38 creates a clearance for material Meanwhile the cutting of the sheet and thus prevents the passage of material in preventing that the latter is compressed by accumulation in a portion of injection volume. It therefore allows to weigh the filling spreads volume 16. At 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 sheet setting surrounded entirely by a portion partly covered with a decorative sheet. In these figures the elements corresponding to those of the previous figures have been spotted by a number up 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 cylinder (not shown). The robot 56 introduces a sheet 53 in the mold between the movable portion 54b and 54c bezel.

This sheet 53 is further illustrated in Figure 10. It has a recess 53a so that it forms a kind of ring between an inner edge 53b defining the recess and an edge exterior 53c. Around the recess of the sheet 53 has notches 53d. extending radially into the sheet from the edge 53b.

The robot sets the upper sheet on nails 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 such so that an inner peripheral area 53f of maintenance and particularly the inner edge 53a of the sheet is disposed between the core 54d and the part fixed mold 54b.

As shown in Figure 12, during the ring closure 54d, one retains the 53f inner area relative to the core 54d, the area inner 53f then moves substantially according to the movement of 54d core. Thus, the notches 53d will find themselves between the core and the 54d fixed portion 54b of the mold. Therefore, the notches 53d facilitate the placing in place of the sheet, they avoid the sheet 53 when placed crease 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 described above with the bezel 4c, substantially simultaneously closing the core 54d. An outdoor area holding device 53 and in particular the outer edge 53c are arranged between the bezel and 54c the fixed part 54b. We can retain more or less the 53rd outer zone 54c relative to the window, as it has been described in connection with the core 54d, to apply the desired tension to the sheet 53.

The core 54d is then only partially closed, as well as 54c for the telescope, there remains a distance <u>of</u> (Substantially equal to d) between it 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 material plastic 51 is then injected into the space 66 causing a decorative area 53g the supporting sheet against the movable portion 54a of the mold. We understand whereas the situation in the areas marked A and D correspond to what has previously described in connection with the detail IV. We understand also that the marked areas B and C are similar to the marked areas D and A respectively, the core 54d then playing a role similar to that of 54c bezel. The subsequent steps to obtain the finished part 90 by being Therefore to those already described, they will not be explained again.

As shown in Figure 11, the finished part 90 has a front Aspect 94 and includes a support piece 92 plastic covered with the decorative sheet 53 in the part 90b of the room, wherein surrounds the uncovered portion 90a and is surrounded by the portion not 90c covered.

Figures 14 to 16 illustrate a variant to perform a opening in a sheet. In these figures, a mold 104 has a portion 104b fixed and a movable part 104a, between which is formed a cavity molding 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 inside 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, in boundary of the molding cavity 117 and 107a facing the anvil. The hammer 107b slides relative to the fixed part 104b. To reduce wear fixed part 104b, a slider 107c is interposed between the fixed portion 104b and the 107b hammer. The assembly formed by the hammer and the anvil 107b 107a form a punch device, that is to say the rapprochement hammer 107b and 107a of the anvil causes the cutting of the sheet 102 when it is disposed therebetween.

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

In Figure 15, the contacting of the protrusion 107d of the hammer 107b and the anvil 107a causes an opening 102a (shown Figure 16) in the sheet 102 by immediately communicating fluid volumes 16 and 18. This opening surrounds a cropped area 102b of the sheet. The contact between the hammer and the anvil is made advantageously following a broken line. Thus, the blank is discontinuous and forms a opening 102a formed by a multitude 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 the injection of material plastic 101 in the volumes 116 and 118 and until cooled piece. 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 sheet thus creating a passage (hole) 146 crossing from side to side the finished workpiece 140, illustrated in Figure 17. The edge of this passage present a Beautiful appearance side of the face Aspect 144, since it presents the appearance of a flange 148 of plastic masking the cutting of the sheet.

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

It is easily understood that the invention provides the room finite illustrated in FIG 18, since it differs from that illustrated in Figure 17 only in that the passage 146 is directed along the finished piece.

19 shows the visible face of the part 40 of Figure 1, the decorative film 2 is entirely surrounded by the uncoated portion of the support 42.

Figure 20 illustrates a variant of Figure 19 that allows also to obtain the method of the invention. The parts not covered are then covered together.

Figure 21 shows a part comprising a support portion 42 uncovered and part covered with a Foil 2. Part covered 146 includes a passage surrounded by a collar 148 plastic made on the visible face 144. It is somehow a combination of what is shown in Figures 17 and 20.

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

Of course, the invention is not limited to the embodiments embodiments described above. Thus, there could be link structurally the bezel to the movable part of the mold, without affecting the process for obtaining the finished part. In particular, we can consider that the seat and the fixed part of the mold are operably linked.

It could also preform the sheet to give it a higher stiffness and / or a preform facilitating the introduction of the sheet into the mold - see for example GB-A-2271956 -, for example by casing.