DE102004063403B4 - Method and device for producing a thin-walled molded part made of foam - Google Patents

Abstract

Apparatus for producing a thin-walled molded part made of foam, comprising a hollow mold (3) with a filling opening (2) and / or a passage opening (11) for the reaction mixture and a mixing head (1) sealingly connected to the filling opening (2) or the passage opening (11) is connectable, wherein the filling opening (2) or the passage opening (11) independently of the mixing head (1) is closed by a valve, wherein the mixing head (1) and the valve are separable from each other and wherein the valve Part of the mold (3) forms, wherein the valve comprises a closing piston (7) which from the mixing head (1) facing away from the direction of the filling opening (2) and / or the passage opening (11) is engageable, wherein the Filling opening (2) and / or the passage opening (11) with a ring seal (8, 9) for the closing piston (7) and / or the mixing head (1) is provided, wherein the ring seal (8, 9) at least teilteili g is formed by a carrier (5) and / or by a cover film (4) and by the closing piston (7) with the filling opening (2) or the passage opening (11) is engageable, wherein the carrier (5) and / or the cover film (4) is deformable at least in the region of the annular seal (8, 9), consists of an injection molded part of polymeric material and the filling opening (2) on the inside with a passage opening (11) having a smaller passage than the filling opening ( 2), in such a way that the passage opening (11) is surrounded by a first annular seal (8) which can be brought into engagement with the mixing head (1) and by a second annular seal (9) which can be brought directly or indirectly into engagement with the closing piston (7) is, and the carrier (5) by at least one of the reaction mixture umspülbares support member (6) sealingly against the mixing head (1) can be pressed.

Description

The invention relates to a method and an apparatus for producing a thin-walled molding of foam.

Technical area

Methods and apparatuses of this type are used, in particular, in relation to the production of large-sized structural components provided with a foam, for example in the manufacture of dashboards and of side and interior trim for motor vehicles. In addition to specific strength properties, a tasteful appearance, an easy and safe way of anchoring and the lowest possible weight is required. In order to achieve these objectives, a core consisting of a reaction foam is generally covered with a decorative film in the area of the visible side of the structural part and provided in the region of the back with a flat stiffening part, which can be made of plastic or metal.

State of the art

In order to reduce the weight of such construction parts, it is already known to evacuate the mold during the introduction of the reaction mixture and to keep it closed until the end of the reaction time. For this purpose, the mixing head, from which the reaction mixture is fed into the mold, until the end of the reaction time sealingly connected to the filling opening of the mold. However, this may require a few minutes each, which significantly inhibits the production process.

From the DE 600 05 736 T2 is a method for vacuum-foaming of thermally insulating insulation boards, for example, insulation boards for cold rooms or other applications known. Furthermore, an apparatus for the discontinuous production of thermally insulating insulation boards by the vacuum Aufschäumverfahren is disclosed.

From the EP 0 289 764 A2 a method for foaming the cavity in the walls of trough-shaped containers is known in which the inner wall placed on the core of a molding box, the outer walls are inserted into the molding box and aligned with each other and to the inner wall. The molding box is then closed. The components of the foaming plastic are injected into the cavity through at least one closable opening in the outer wall parts.

The DE 195 05 937 C2 describes a valve for the closure of foamable cavities after introduction of a foamable, consisting of at least two components reactive mixture. The valve is disposed within the cavity and is in contact with at least one of the boundary walls of the cavity. The valve has two substantially rotationally symmetrical coaxial cages, wherein the inner cage has an axial opening for introducing the reactive mixture and at least two radial openings for the passage of the reactive mixture in the annulus formed between the inner and outer cage.

From the DE 22 06 406 A is a device for interrupting the inflow of foamable plastic reactive material between foaming machine and foam known. A closure member for the filling opening slidably interrupts the inflow line and seals the mold. The closure member is designed as a pivotally arranged closure displaceable with a guide for the inlet hose of the mixing device.

From the EP 0 226 105 B1 For example, there is known a method of making foam molded articles in which an expandable film is inserted between cavity walls of halves of a composite mold, thereby delimiting a foaming chamber. By filling a foamable resin into the foaming chamber and foaming it, the film is expanded against at least one of the cavity walls and into conformance with its shape. Before filling the foamable resin in the Verschäumungskammer air is removed from the Verschäumungskammer.

The DE 35 07 523 C1 relates to a foaming support mold for the production of motor vehicle interior trim parts, such as instrument panels, consisting of a film cover, foam backing and on and / or foamed support parts. The support mold comprises an upper and a lower support mold half. When folded, the mold halves enclose the mold cavity. In one support mold half, at least one injection channel is provided, which opens into the mold cavity. In the other support mold half with respect to the opening of the injection channel, a valve plunger which can be moved back and forth in the direction of the opening and which presses the film cover sealingly against the opening is inserted.

Presentation of the invention

The invention is based on the object to further develop such a method that results in a better quality and faster work progress, and a device for To provide such an improved method.

This object is achieved by a device according to claim 1 and a method according to claim 4. In advantageous embodiments, the dependent claims relate.

In the method according to the invention for producing a thin-walled molded part made of foam, it is provided to enter the reaction mixture of polymeric material leaving a mixing head through a filling opening or a passage opening into a mold, to expand it by filling in the hollow mold by a chemical reaction, to cure and subsequently using a device according to the invention as a solid molding to remove from the mold, wherein it is provided to insert before the introduction of the reaction mixture optionally deep-drawn, flexible cover and to glue the cover parallel to the formation of the foam with this.

Such surface fabrics, z. B. cover films, are generally made of PVC, EPDM, TPU, PU or similar, elastically deformable materials. They are often provided in the area of the visible side with a decorative leather grain and / or tastefully colored.

Alternatively or additionally, prior to the introduction of the reaction mixture, it is also possible to introduce into the mold a support which has been deep-drawn, injection-molded or produced according to another relevant method which bonds to the foam in parallel with the foam. Such carriers have primarily static and / or dynamic tasks. If an injection-molded carrier made of polymeric material is used, for example one made of cost-effective polypropylene, then it is also possible to embed in the cross-section during the manufacture of the carrier reinforcing fibers, for example in the form of uniformly distributed short fibers or in the form of fiber mats or fiber strands synthetic or mineral materials. As a result, advantages in terms of strength of the wearer can be achieved while reducing the weight.

The carrier may also be produced by a thermoforming process of polymeric or metallic materials.

If a cover film and a carrier are inserted into the mold, it has proved to be expedient if the foam is introduced only into the space between the cover film and the carrier in order to glue the cover film and the carrier together in parallel with the formation of the foam. Such a molding may be limited to the outside overall by the carrier and the cover sheet. Appropriately, the carrier for such a purpose on the cover sheet side facing optionally provided with spacers, which are soft elastic deformable and flow around the reaction mixture. In particular, in the production of injection-molded plastic carriers, the integral molding of such spacers is associated with no particular effort. They may for example consist of inclined, columnar projections of a small diameter of the carrier, which are easily demoulded and are not noticeable in the visible side of the ready-to-use molding. The visible side can thus have balanced, soft-elastic properties in all partial areas including these locations.

In order to obtain foam moldings of particularly low density, it has proven to be advantageous if the mold is evacuated prior to introduction of the reaction mixture and if the vacuum is maintained during the introduction of the reaction mixture on. The expansion of the reaction mixture is thereby promoted, which at the same blowing agent content has relatively reduced volume weights of foam moldings result and at the same time facilitates penetration of the foam during its formation into narrow gaps and undercuts.

In the case of a hollow mold which has a filling opening and / or a passage opening for the reaction mixture, which can be brought into sealing contact with the mixing head, it has proven advantageous if the filling opening and / or the passage opening can be closed by a valve independently of the mixing head is and when the mixing head of the closed filling opening and / or the passage opening is separable.

The valve in this case comprises a closing piston, which can be brought into engagement directly or indirectly with the filling opening and / or the passage opening from the direction away from the mixing head. In order to achieve a good sealing result, it has proven to be useful if the filling opening and / or the passage opening are provided with a ring seal for the closing piston and / or the mixing head. Since the mixing head and the sealing piston preferably engage from the opposite directions with the filling opening and / or the passage opening, the two ring seals are arranged in a corresponding embodiment on the opposite sides of the filling opening and / or the passage opening. You can see the figure of Have lip seals or integrally molded annular projections of preferably semi-circular profile, which surround the filling opening and the passage opening concentrically. Similarly designed ring seals, which can be brought into engagement with the filling opening or the passage opening, can additionally or additionally also be provided on the mixing head.

The ring seals may be made of any known sealing material, such as a polymeric material, steel, copper or brass.

The ring seal is at least partially formed by the carrier and / or by the cover. A one-piece design with the carrier or the use of a cover made of soft elastic covering as an intermediate layer for sealing the closing piston against the filling opening or the passage opening is particularly easy to implement and ensures safe operation, because such intermediate layers only temporarily loaded and again for each working cycle New condition are available.

A particularly good sealing result is achieved if the carrier and / or the cover film are elastically deformable at least in the region of the seal. A particularly high resistance to deformation is generally not required because in the present case it is only about the sealing of a pressure of 3 bar maximum within a few minutes. The sealing effects required for this can be achieved with conventional, soft-elastic polymer materials and also with thermoplastic materials for a sufficiently long time, for example with polypropylene.

The carrier is expediently provided with a passage opening which covers the filling opening and which has a smaller passage than the filling opening, the passage opening being accessible from a first ring seal which can be brought into engagement with the mixing head and directly or indirectly engageable with the closing piston. second ring seal is enclosed. Both ring seals may have sealing lips and in such an embodiment form an integral part of the carrier. They come together with this only once, namely in the production of a molding, for use. A occurring during the sealing, permanent deformation of the ring seals is therefore irrelevant. The use of polypropylene or ABS with 10 to 20% glass fiber content for the production of the carrier is therefore almost always sufficient.

The carrier can be pressed against the mixing head in a sealing manner by at least one support element which can be flushed around by the reaction mixture, in order to ensure its reliable backfoaming. The support element can thereby enclose the second annular seal as a crown-shaped crown gate, whose projections are cut through by radially extending passages for the reaction mixture, in order to facilitate the passage of the reaction mixture into the cavity to be filled with the foam. The projections are, based on the center of the filling or passage opening, expediently of trapezoidal profile in order to obtain a particularly good static support of the ring seal through the mold. The base facing the carrier should overlap with the mixing head its end face and at the same time the edge of the filling opening. The support member, the carrier and the ring seals may be integrally formed merge into each other, which reduces the cost of manufacturing.

Brief description of the drawing

The invention will be further clarified below with reference to the accompanying drawings. Show it:

1 the region of a filling opening of a hollow mold according to the invention in longitudinal section,

2 similar to the area of a filling opening 1 in which an O-ring seal made of rubber is provided for the sealing of the mixing head with respect to the carrier,

3 similar to the area of a filling opening 1 , in which a hollow-conical flat gasket is provided for the sealing of the mixing head with respect to the mold.

Embodiment of the invention

The in 1 reproduced section of a mold illustrates an inventive method for producing a thin-walled molding of foam, in which one of a mixing head 1 along the arrow exiting reaction mixture of polymeric material, for example, a polyurethane composition, through a filling opening 2 and a passage opening 11 in an evacuated mold 3 entered, filling in the mold 3 expanded by a chemical reaction to a foam, cured and subsequently from the mold 3 is removed. The filling opening 2 and the passage opening 11 are closed vacuum-tight after filling of the reaction mixture by a valve and the mixing head 1 then from the filling opening 2 and the passage opening 11 away. The valve forms an integral part the mold 3 , In this, a deep-drawn cover sheet was before introducing the reaction mixture 4 made of EPDM, which has a thickness of 0.6 to 2.0 mm, preferably from 1.3 to 1.7 mm, which is elastically deformable and which has a leather-like grain on the visible side. The cover foil 4 covers the entire underside of the mold 3 ,

Further, before the introduction of the reaction mixture, a carrier 5 in the mold 3 placed and on the top of the cover 4 arranged. The carrier 5 consists of an injection molded part made of polypropylene with a glass fiber content of 15% and a thickness of 2 to 4 mm, preferably 2.5 mm. The passage opening 11 is circular and limited by a ring seal 8th and immediately adjacent thereto of tooth-like distributed and the center of the passage opening radially associated spacers 6 enclosed, which have a trapezoidal in the direction of the carrier extended cross-section and are thus suitable, the pressure forces of the mixing head 1 and on the cover sheet on the lower wall of the mold 3 to transfer, without causing a gap formation between the carrier and the wall resting on the mold 3 comes. Other, not reproduced in the drawing, spacers 6 are over the entire surface of the carrier 5 distributed. They consist of elastically deformable, inclined projections of the carrier 5 Keep him at a distance from the cover 4 hold. Further, the carrier with molded beads 10 provided that increase its rigidity. The reproduced in the drawing bead 10 is ringfömig trained and the passage opening 11 assigned concentrically. Their average distance from the passage opening is approximately equal to the average distance of the spacers 6 match.

The carrier 5 can additionally or alternatively also in the edge region of the mold 3 be temporarily attached. All spacers 6 also have a distance from each other in the transverse direction, to ensure that the distance from the cover 4 formed cavity is completely and uniformly filled by the expanding reaction foam to obtain a consistent and clearly predictable deformation behavior of the molding in all sub-areas. This is of considerable importance for later use.

The liquid state in the space between the cover 4 and the carrier 5 introduced reaction foam bonded during its formation and curing with the cover 4 and the carrier 5 and connects them together. The case at the same time involved in the foam body spacers 6 of the carrier 5 ensure a particularly strong connection of the carrier 5 to the foam body. For a secure anchoring of the molding in a motor vehicle, this is a great advantage.

Of course, it is basically possible for the wearer 5 and / or the cover sheet 4 in the production of moldings if necessary also omit. The closing piston and the mixing head act in such a design directly with the mold and / or the filling opening together and then be sealed with respect to this.

In the hollow mold is thus preferably a valve containing a closing piston 7 comprises, which is directly or indirectly engageable from the direction away from the mixing head with the direction of the filling opening and / or the passage opening. In the embodiment shown, the closing piston 7 from the elastically deformable cover film 4 About Covers. He is in the drawing in a lowered state below the cover 4 , which brings the valve in the open position. The mixing head is sealed to the passage opening 11 applied and the mold 3 optionally evacuated. From the mixing head 1 This allows reaction mixture in the mold 3 be fed. From the in the mold 3 optionally contained vacuum results in a particularly rapid filling and a particularly low density of the foam. The required sealing to the outside is by direct investment and contact pressure of the mixing head 1 to a ring seal 8th causes, in this design in one piece with the carrier 5 is formed and encloses the passage opening. The passage opening 11 of the carrier 5 Thus, in this training functionally takes the place of the filling opening 2 the mold 3 ,

2 shows a design in which the ring seal 8th according to 1 through an O-ring seal 13 is replaced by rubber, in a downwardly open groove of the end face of the mixing head 1 is arranged. The groove is expediently reduced in the region of its mouth to a width which is slightly smaller than the cross section of the rubber O-ring seal to prevent it from falling out of the groove when lifting the mixing head.

3 shows a design in which the ring seal 8th according to 1 through a ring protrusion 14 is replaced, the one integrally molded part of the mold 3 forms and the filling opening 2 radially outside immediately encloses. The ring protrusion 14 may consist of an insert part of the mold 3 and be made of copper, to provide a favorable sealing effect in connection with the hardened state of the mixing head 1 achieved during the filling process with a force is pressed directly to it.

In all versions, the closing piston will follow the filling process 7 together with the immediately adjacent area of the cover 4 raised from the reproduced in the drawing, lowered open position in a sealing position in which the cover 4 sealing to the second ring seal 9 applies, the filling opening 2 or the passage opening 11 encloses on its underside. The closing piston 7 thus does not reach directly, but through the cover sheet forming an intermediate layer 4 from the ring seal 9 separated, only indirectly engaged with this. Nevertheless, there is a complete valve function and a secure completion of the filled mold, which prevents leakage of reaction foam as well as the effect of the atmospheric pressure on the interior when it is evacuated during the filling process.

When the valve is actuated, a certain residual volume of reaction mixture through the motor-driven stroke of the closing piston 7 promoted back into the mixing head, which is not disadvantageous, if this is subsequently transferred quickly to a new filling position. The mixing head 1 can therefore from the closed mold 3 be lifted without the atmospheric pressure can connect with the interior. The newly formed foam can thereby chemically react in the mold until a mechanically stable state is reached and the resulting molded part can be removed after opening the mold. The mixing head can be used again during this time to further molds 3 similar type to fill. In draughty operation, a self-cleaning is observed, which reduces the number of defective parts and saves costs.

For the basic function, it is therefore of no importance whether the filling opening after the filling of the reaction mixture and before removing the mixing head hollow mold side by a valve directly or indirectly, using the cover as an engageable with the carrier or the mold interposer liner , is closed. It is important that the uncontrolled escape of freshly formed reaction foam is prevented as well as the uncontrolled effect of the atmospheric pressure on the interior of the mold, the terms filling 2 and passage opening 11 are therefore to be understood in the context of the present invention as a synonym for access to the filling mold.

Nevertheless, a design is preferred in the invention, in which the ring seals 8th . 9 on the carrier 5 are provided. You get in such a design only once in function, which allows you to choose a particularly low-cost design and still have the guarantee that each part has the same quality.

It is not always necessary to evacuate the mold during its filling with the reaction mixture, but quite possible to allow the air contained therein at the beginning of the filling to escape parallel to the filling of the space with the reaction mixture. For this purpose, serve outlet openings, which are positioned at time-delayed points of the mold so that always a complete filling of the space with the reaction mixture is guaranteed. Even in such cases, a pressure can be generated by the ausreagierenden foam mixture, which can be collected in the inventive method in the mold to achieve a homogenization of the foam structure.

The advantages achieved by the invention consist in a significantly improved efficiency in the production of foam-lined trim parts, the z. B. In motor vehicles can be used.

Claims (7)

Device for producing a thin-walled molded part made of foam, comprising a hollow mold ( 3 ) with a filling opening ( 2 ) and / or a passage opening ( 11 ) for the reaction mixture and a mixing head ( 1 ), sealing with the filling opening ( 2 ) or the passage opening ( 11 ), wherein the filling opening ( 2 ) or the passage opening ( 11 ) independent of the mixing head ( 1 ) is closable by a valve, wherein the mixing head ( 1 ) and the valve are separable from each other and wherein the valve is a part of the mold ( 3 ), the valve having a closing piston ( 7 ), which from that of the mixing head ( 1 ) facing away with the filling opening ( 2 ) and / or the passage opening ( 11 ) is engageable, wherein the filling opening ( 2 ) and / or the passage opening ( 11 ) with a ring seal ( 8th . 9 ) for the closing piston ( 7 ) and / or the mixing head ( 1 ), wherein the ring seal ( 8th . 9 ) at least proportionally by a carrier ( 5 ) and / or through a cover ( 4 ) is formed and by the closing piston ( 7 ) with the filling opening ( 2 ) or the passage opening ( 11 ) is engageable, wherein the carrier ( 5 ) and / or the cover ( 4 ) at least in the area of the ring seal ( 8th . 9 ) is deformable, consists of an injection molded part of polymeric material and the filling opening ( 2 ) on the inside with a passage opening ( 11 ), which has a smaller passage than the filling opening ( 2 ), such that the passage opening ( 11 ) of one with the mixing head ( 1 ), first Ring seal ( 8th ) and one with the closing piston ( 7 ) directly or indirectly engageable, second ring seal ( 9 ) and the carrier ( 5 ) by at least one of the reaction mixture umspülbares support element ( 6 ) sealingly to the mixing head ( 1 ) can be pressed. Device according to claim 1, characterized in that the support element ( 6 ) the second ring seal ( 9 ) surrounds as a dental cast-like crown sprue, which of radially extending passages ( 12 ) is separated for the reaction mixture. Device according to claim 1 or 2, characterized in that the supporting element ( 6 ), the carrier ( 5 ) and the ring seals ( 8th . 9 ) are integrally formed. Process for producing a thin-walled molded part of foam, in which one of a mixing head ( 1 ) exiting reaction mixture of polymeric material through a filling opening ( 2 ) or a passage opening ( 11 ) in a mold ( 3 ), filling in the mold ( 3 ) is expanded by a chemical reaction, cured and subsequently removed from the mold ( 3 ), using a device according to one of the preceding claims, characterized in that in the mold ( 3 ) before the introduction of the reaction mixture is an optionally deep-drawn, flexible cover film ( 4 ) is inserted and that the cover ( 4 ) is glued parallel to the formation of the foam with this. A method according to claim 4, characterized in that in the mold ( 3 ), before introduction of the reaction mixture, an optionally deep-drawn support ( 5 ) and that the carrier ( 5 ) is glued parallel to the formation of the foam with this. Method according to claims 4 and 5, in which in the mold ( 3 ) a cover sheet ( 4 ) and a carrier ( 5 ) are inserted, characterized in that the foam in the space between the cover ( 4 ) and the carrier ( 5 ) and parallel to the formation of the foam, the cover ( 4 ) and the carrier ( 5 ) glued together. Method according to one of claims 4 to 6, characterized in that the hollow mold is evacuated before introducing the reaction mixture.

Images