EP2305869B1 - Device and method for manufacturing moulded parts from fibrous material - Google Patents

Description

The invention relates to a device for producing three-dimensional molded parts made of fiber material, in particular according to the preamble of patent claim 1.

Such moldings are preferably used in vehicle construction, in particular as a sound insulation mat, such as under the hood, as a lining mat in the footwell or in the trunk or in the seat upholstery or floor carpets, etc.

Such a device is for example from the WO 2009/062646 has become known and discloses an apparatus for producing three-dimensional molded parts made of fiber material. For this purpose, a two-part form consisting of upper and lower mold is used. The respective inner sides of the upper and lower molds partially determine the contour of the molded part. In the space between the upper and lower mold fibers are injected by an air flow through several nozzles. The air flow escapes through openings in the upper and lower molds so that the fibers attach to the insides of the upper and lower molds. Subsequently, the fibers are optionally still locally compacted, and then to glue together in another step by supplying heat. After cooling of the fibers then finally the finished molded part can be removed from the mold. The fibers form in the form of a so-called random fiber fleece, that is, the fibers of the fleece are arranged arbitrarily with respect to their respective orientation.

It is also through the DE 24 05 994 in the production of moldings known to align the fibers in the direction of their main load in order to increase the load capacity of the molded part. This alignment takes place in that the shape after the introduction of the fiber material of a directed shaking movement is suspended. In addition, an electrostatic field is applied, whereby the fibers undergo an alignment in the direction of the electric field lines.

Finally it is through the DE 976 870 in the manufacture of wood chipboard from elongated wood shavings with binders known to turn them during their Fallweges by a mechanical guiding and straightening device and an electrostatic field in a desired direction.

The invention is based on the recognition that such molded parts should be better adapted to the later applications with regard to product-specific properties.

The object of the present invention is therefore to provide a method and an apparatus for producing three-dimensional molded parts made of fiber material, in order to improve the possible uses and properties of molded parts.

The object is achieved in a device according to the preamble of claim 1 by its characterizing features.

By means of the device according to the invention it is achieved that the fibers in the interior of the mold align themselves better in accordance with the electric field or along the respective field lines of the electric fields. Subsequently, the fibers then deposit in a preselectable preferred direction on the inside of the mold. If the mold is completely filled with fibers oriented in this way, the fibers are glued together and retain the orientation of the respective electric field during bonding. This results in a molded part whose fibers are aligned in certain areas or in the entire molded part. The directions of the electric fields or the field lines are chosen so that the respective directions of the fibers coincide with one or more preferred directions for certain properties. Thereby, the possible uses of molded parts are increased, so that they can now also in other areas, which were unsuitable for example because of the loads occurring there for moldings, can be used. Subject to the molding, for example, when used as intended a certain load direction, the direction of the electric field is chosen so that the fibers are oriented parallel to this loading direction. In this way it is achieved that their restoring force will increase counter to an externally acting force. The effectiveness and the life of the molded part thereby extended considerably.

It is particularly expedient if the pre-alignment of the fibers causing conveying element is designed as a cylinder.

Advantageously, the fibers are provided with an electrical charge before and / or during the blowing in and / or the charging of already charged fibers is intensified. The fibers then align with the one or more electric fields to form a molded article having one or more desired fiber preferred directions. For already charged fibers their charge can be increased so that they align faster and more reliable according to the field lines of the electric fields in the interior and finally aligned in the manufactured molded part.

In order to produce the electric fields easily and inexpensively, it is expedient that the electric fields by means of conductive portions of the

Form be generated. The conductive sections of the mold are arranged so that the directions of the electric fields or the field lines correspond to the desired preferred directions of the fibers. Conductive portions of the mold can each be isolated from each other. As a result, additional means for generating the electric fields are unnecessary and the process can be carried out more cheaply.

In order to increase the homogeneity of the electric fields and at the same time to facilitate the simplest possible maintenance, the at least one electric field can also be generated by electrodes which are arranged offset on the outer sides of the multi-part mold or outwardly. This ensures easy accessibility of the electrodes and maintenance of the electrodes. In addition, in the positioning of the electrodes less boundary conditions, for example. Projections, etc., to pay attention, so that the electrodes can be made larger, which favors the homogeneity of the field between the respective electrodes, because edge effects of the fields at the respective edges of the electrodes play a minor role.

In order to provide as little additional means for the generation of electric fields, it is expedient that the blowing of fiber material into the interior takes place by at least one nozzle, which is itself formed as an electrode for at least one electric field. In this case, the nozzle may consist of sections isolated from one another, in order to produce individual partial fields in different directions. Of course, however, a plurality of nozzles may be formed as an electrode.

The corresponding corresponding second electrode for the electric field need not necessarily also be present in the form of a nozzle, but may for example also have any other expedient shape, in particular, this can also be formed by conductive portions of the mold, which are optionally electrically isolated from each other.

It is particularly advantageous if the means for electrical charging are arranged on the at least one nozzle and / or on one of the nozzle supply lines. If the charging means are arranged on the nozzle, a compact construction of the device is thus achieved. If the means are arranged on a supply line for at least one nozzle, the fibers are given the desired charge even before they are blown into the interior space. In this way, the nozzle can be produced relatively simply and inexpensively, at the same time influencing the electric fields in the interior of the Form by the means for electrical charging, if they are arranged on the nozzle itself, avoided and thus achieves a reliable alignment of the fibers in the interior by the one or the electric fields.

Advantageously, the means for electrically charging the fibers comprise a ring electrode. In this way, the means can be particularly easily integrated into existing feed lines for the nozzles or in the nozzles themselves, for example by the annular electrode is formed directly as a portion of the feed line or simply arranged around the feed line on the outside thereof.

For the most cost-effective production and a simple arrangement of the means for generating electric fields are also plate and / or rod-shaped electrodes into consideration. In this case, the two types of electrodes can also be used together for the generation of an electric field, for example by a stick electrode being arranged on one side of the mold and a plate-shaped electrode on the opposite side. In this case, the field lines are perpendicular to the rod-shaped electrode to the surface thereof and terminate in parallel on the surface of the plate-shaped electrode.

So that the device can be made as compact as possible, it is expedient that at least part of the multi-part mold is at least partially formed as an electrode. This "embedding" of the electrode in the mold allows for a more compact design of the form, on the other hand, the fields are largely homogeneous, because no disturbing additional leads in the field of electric fields must be arranged, which would disturb the homogeneity of the electric fields.

In order to also allow easier accessibility for the maintenance of the device, it is advantageous that electrodes are arranged on the outer sides of the multi-part mold and in particular the multi-part mold is made partly of non-conductive material. If the electrodes are arranged on the outside, they are easily accessible from the outside. At the same time, in particular, the multi-part mold is partially made of non-conductive material in order to avoid partial shielding of the electric fields by the Faraday effect. It can also serve a corresponding design of the form by means of conductive and non-conductive materials that the Faraday effect is exploited to selectively influence the or the electric fields in the field strength and geometric orientation.

When the electrodes are arranged on the outer sides of the multi-part mold, it is not necessary that they are connected to the multi-part mold. For example, by positioning electrodes farther away from the multi-part mold, they can be made much larger than the mold or at least portions of the mold. At the same time, this also avoids edge effects in the electric field (bulges of the field lines at the edge of the electrode, plate-shaped electrodes directly opposite have only a homogeneous field substantially in the interior space between the plates).

So that the device can be made even more compact, it is expedient that at least one nozzle is designed as an electrode. In this case, both a nozzle with a differently shaped electrode can form means for generating electric fields and two corresponding nozzles.

In order to ensure the most error-free production of the molded part and to avoid short circuits etc. between the means for generating electric fields, it is expedient that means for electrical insulation, in particular between parts of the multi-part mold are arranged. As a result, conductive regions are isolated from each other, so that an error-free production of the molded part is made possible.

Figur 1

eine perspektivische Darstellung einer erfindungsgemäßen mehrteiligen Form vor dem Einblasen von Fasern;

Figur 2

eine erfindungsgemäße Form gemäß Figur 1 während des Einblasens von Fasern mit angelegtem elektrischem Feld;

Figur 3

eine Form gemäß Figur 2 ohne angelegtes elektrisches Feld;

Figur 4a,4b

Querschnitt durch ein Formteil mit ausgerichteten Fasern bzw. hergestellt ohne ausgerichtete Fasern;

Figur 5

eine erfindungsgemäße mehrteilige Form;

Figur 6a - c

perspektivische Darstellungen einer Ober- bzw. Unterform;

Figur 7

perspektivische Darstellung eines Ausschnitts einer Zuführleitung mit Elektrode; und

Figur 8

einen Vertikalschnitt durch ein Faser-Ausrichtgerät.

Further features and advantages of the invention will become apparent from the dependent claims and the following description of exemplary embodiments and from the drawing. It shows

FIG. 1

a perspective view of a multi-part mold according to the invention prior to the blowing of fibers;

FIG. 2

a mold according to the invention FIG. 1 during the blowing of fibers with applied electric field;

FIG. 3

a form according to FIG. 2 without applied electric field;

Figure 4a, 4b

Cross section through a molded part with aligned fibers or produced without aligned fibers;

FIG. 5

a multi-part mold according to the invention;

FIG. 6a-c

perspective views of a top or bottom mold;

FIG. 7

perspective view of a section of a supply line with electrode; and

FIG. 8

a vertical section through a fiber alignment device.

In FIG. 1 is a multi-part mold 1 shown for a device according to the invention. The mold 1 consists of two perforated, shell-like parts, upper mold O and lower mold U, which form between them an interior I, which has the shape of the molded part to be produced. On the outer sides of the upper or lower mold O, U, two plate-shaped electrodes 2a, 2b are arranged, which serve to generate an electric field E, which acts in the inner space I. On the right side of the lower mold U in FIG. 1 is a nozzle D arranged for blowing fibers F ₁ , F ₂ in the interior I. Furthermore, an electrode 2c attached to the nozzle D in the interior I, which for static charging of the fibers F ₁ , F ₂ during their injection into the interior I serves. The interior is acted upon before, but at the latest during the blowing of the fibers F ₁ , F ₂ with the electric field E.

In FIG. 2 now the situation is shown, are injected at the fibers 1 by means of the nozzle D in the direction 4 in the interior I between upper mold O and lower mold U. When blowing and the resulting turbulence, the fibers F _{1 are} initially not aligned despite effective electric field E in the interior I. By slowing down the air flow, the fibers F ₁ , F ₂ lose kinetic energy on further penetration into the interior I and are now due to the force of the electric field E corresponding to the field lines, that is here in FIG. 2 approximately perpendicular to the mold top and bottom extending field lines of the plate-shaped electrode 2a to the plate-shaped electrode 2b aligned parallel to each other (fibers F ₂ ).

In a next step (not shown), the fibers F ₂ are now deposited in their corresponding orientation on the inner sides of the upper or lower mold O, U, while the injected air escapes through the perforated upper and lower molds. If the interior I completely filled with (aligned) fibers F ₂ , the fibers F ₂ are connected together, such as by heat sealing. Thereafter, if necessary, the mold or the bonded fibers F _{2 are} cooled. The result is a solid molding that can be removed after opening the mold 1.

In FIG. 3 In particular, the alignment of the fibers F _{1 is} shown, which assume the fibers F ₁ in the interior I, when no electric field E in the interior I acts. The fibers F ₁ are arbitrarily oriented to one another and form a so-called random fiber fleece with non-rectified fibers F ₁ .

In FIG. 4a 4b and 4b show cross-sections of molded parts 5, which were once made by means of fibers F _2, which were aligned by an electric field E ( FIG. 4a ) and once a molded part 5 with non-directional fibers F ₁ , which were prepared in the absence of an electric field E in the interior I. Furthermore, a force F acting from above on the molded parts 5 produced in this way is shown. In FIG. 4a the fibers F _{2 are} aligned parallel to this acting force F, whereas in FIG. 4b assume no definite orientation, ie a random orientation with respect to the force F acting from above. Since the fibers F ₂ in FIG. 4a are aligned parallel to the forces acting on the mold part 5 force F, the molding of the FIG. 4a a much larger restoring force R under load by the force F on compared with the restoring force R of the molding 5 of FIG. 4b in that the restoring force, that is to say the force acting counter to the force F, is greatest when the fibers F ₂ are oriented parallel to the force F acting on the shaped part 5. By aligning the fibers F ₂ in one or more preferred directions, here parallel to a force acting on the molding force according to FIG. 4a , the fatigue-free resilience of the molded part and thus its life is significantly improved.

In FIG. 5 a mold 1 according to the invention is shown, consisting of upper mold O and lower mold U. Both forms are made in known manner from perforated wall parts which are detachably connected to each other. When the fibers are blown in, the upper mold and lower mold form a closed box. After bonding the injected fibers, this box is then opened as known.

On the right side wall of the lower mold U, a nozzle D for injecting fiber material into the inner space I of the mold 1 is arranged approximately perpendicular to this side wall. The nozzle D carries an electrode 2c for static charging of the fibers F ₁ , F ₂ during the blowing. Furthermore, a part of the upper mold O is formed as an electrode 2a and, accordingly, also a part of the lower mold U as an electrode 2b. Between the electrodes 2a and 2b, optionally also in combination with the electrode 2c, an electric field E can be generated by applying a voltage. The voltage at the electrodes is selected such that an electric field strength of 5 kV / cm to 10 kV / cm, in particular 6 kV / cm to 8 kV / cm is formed.

The upper mold O and the lower mold U have sieve-like arranged holes 5, which serve that the air flow from the inner space I can escape again. As a result of the escape of the air, the fibers F ₁ , F _{2 are transported} to the insides of the upper mold O and lower mold U and are deposited thereon, so that after completely filling the inner space I with fibers F ₁ , F ₂ by gluing the fibers F ₁ , F ₂ can be made to each other a molding. The upper mold O and the lower mold U can not partially be made of conductive material, wherein the respective electrodes 2a, 2b are of course made of conductive material.

In FIG. 6a a lower tool U of a mold 1 is shown. The lower mold U has a perforated plate 5 and usually forms the negative pole. Furthermore, the lower mold U is substantially cup-shaped, wherein the edges of the lower mold U have a total of a substantially rectangular cross-section.

In the Figures 6b, 6c is the subform U of FIG. 6a corresponding upper mold O shown, which has substantially the same structure and forms the positive pole. The upper mold O is either made of a non-conductive material, on the outside of which there is an electrode 2a directly ( FIG. 6b ) or the upper mold O is itself completely formed as an electrode 2a ( FIG. 6c ) and therefore has a peripheral electrical insulation 6 disposed at the edges of the upper mold O, so that when the upper mold O is placed on the lower mold U to form an inner space I, the upper mold O and the lower mold U are electrically insulated from each other ,

In FIG. 7 a feed line Z for a nozzle D is shown, in which the fiber material is transported in the direction R by means of air flow, in order subsequently to be transported via the nozzle D into the interior I. For electrostatic charging, a ring electrode 2d is arranged on the outside of the supply line Z, which charges uncharged fibers F ₁ , F ₂ and further strengthens already charged fibers F ₁ , F ₂ with respect to their charge, so that these fibers F ₁ later after blowing , F ₂ are aligned under the action of an electric field E in the interior I. In this case, the electrode 2d is mounted directly in front of the nozzle D or an injection opening and comprises either a pipe section 2d made of metal, which is arranged in the supply line Z or the ring electrode 2d shown, which is arranged on the outside of a feed line hose Z made of plastic. Of course, it is within the scope of the invention to provide other forms of electrodes.

A particularly advantageous development of the invention is in FIG. 8 shown. It shows the vertical section through a device 10 for pre-alignment of the fibers before the fibers enter the nozzle.

The alignment device consists of a circulating cover tape 11, which conveys the fibers thrown from the top - possibly after a certain separation, so that they are connected only in small flakes - to the left to a pair of feed rollers 12a, 12b. These are two rollers rotating in opposite directions and arranged with a small gap parallel to one another, which are roughened on their outer circumferential surface, in particular slightly toothed. They pick up the fibers coming from the cover belt 11 and convey them further through their intermediate gap to the left. In order to avoid clogging, at least one of the two rollers can be mounted displaceably in the vertical direction against spring force.

It is essential that the fibers are carried along by a relatively large rotating cylinder 13. This cylinder is surrounded by a small distance from approximately semi-cylindrical outer walls 14. Due to its rough, in particular toothed outer cylindrical surface, it pulls the fibers through the gap located between the cylinder 13 and the outer wall 14. The fibers are gradually aligned by their friction on the outer wall 14 more or less in the rotational direction of the cylinder 13, so preferably oriented in the circumferential direction. In this orientation, the fibers then - after a half, sometimes even after one and a half revolutions of the cylinder 13 - to an output gap 15, from where the fibers are then transported to the one or more nozzles, ie in the mold 1.

In order to improve the detachment of the fibers from the cylinder 13 and their transfer in the discharge gap 15 to the downwardly outgoing line 16, it is recommended to apply an approximately tangential air flow to the transition region. This air flow then also takes over the further transport of the fibers through the conduit 16 into the mold 1.

By the frictional forces acting on the fibers during the entrainment of the fibers through the cylinder 13, they receive a preferred orientation in the transport direction. This mechanical pre-alignment facilitates later alignment within the mold by means of one or more electric fields.

The pre-alignment of the fibers prior to their delivery to the nozzle (s) has been described above by means of a mechanical drum in which frictional forces in a gap create the alignment forces. Of course, it is also within the scope of the invention to bring about the pre-alignment of the fibers by other mechanical means.

In summary, the present invention has the advantage that in a simple manner, the fibers for the production of the molding can be aligned in one or more preferred directions, so that the fibers are arranged in a certain direction in the finished molding to desired properties of the molding in its intended use to reinforce. In particular, this allows the strength, the elasticity and, as a result, the service life of the molded part to be specifically influenced.

Claims (8)

1. Device for producing three-dimensional mouldings from fibres (F₁, F₂), especially suitable for carrying out a process for producing mouldings from fibre material,
   comprising

   • a multi-component mould (1) having at least one cavity (I), the inner side of the mould (1) at least to some extent determining the contours of the moulding to be produced,

   • one or more nozzles (D) for blowing the fibres (F₁, F₂) into the cavity (I),

   • air openings (5) in the mould (1) for enabling the air to escape from the cavity (I) and for depositing the fibres (F₁, F₂) on the inner side of the mould (1) and

   • means for bonding the fibres (F₁, F₂) to produce the moulding,

   • means (2a, 2b) for generating one or more electric fields (E) which expose at least part of the cavity (I) to one or more electric fields (E), with the result that at least some of the fibres (F₁, F₂), on being blown into the mould (1), become aligned along the directions of the electric fields (E) which correspond at least approximately to one or more desired preferred directions of the fibres (F₁, F₂) in the moulding,

   characterised in that
   upstream of the nozzle(s) (D) there is arranged a fibre alignment device (10) having a movable conveyor element (13) which conducts the fibres (F₁, F₂) under friction along an oppositely located wall (14).
2. Device according to claim 1,
   characterised in that
   the movable conveyor element (13) is in the form of a rotating cylinder.
3. Device according to at least one of claims 1 and 2,
   characterised in that
   electrical charging means (2d) are arranged on the at least one nozzle (D) and/or on a supply line (Z) for the at least one nozzle (D).
4. Device according to at least one of claims 1 to 3,
   characterised in that
   the means (2a, 2b) for generating electric fields (E) comprise annular, plate-like and/or rod-like electrodes (2a, 2b).
5. Device according to at least one of claims 1 to 4,
   characterised in that
   at least one component of the multi-component mould (1) is at least in part in the form of an electrode (2a, 2b).
6. Device according to at least one of claims 1 to 5,
   characterised in that
   electrodes (2a, 2b) are arranged on the outer sides of the multi-component mould (1) and particularly the multi-component mould (1) is at least in part made from non-conductive material.
7. Device according to at least one of claims 1 to 6,
   characterised in that
   at least one nozzle (D) is in the form of an electrode (2a, 2b).
8. Device according to at least one of claims 1 to 7,
   characterised in that
   electrical insulation means (6) are arranged, particularly between components of the multi-component mould (1).

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