Device for manufacturing a molded part

Abstract

Device (1) for producing a molded part, comprising an upper tool (2) which can be placed on or connected to a corresponding lower tool (3), wherein a cavity (4) forming the molded part to be produced is located between the upper tool (2) and the lower tool (3), into which a mold skin (5) and a carrier (6) are inserted on the one hand, wherein the molded part is formed from a material-bonded connection between the carrier (6), the mold skin (5) and a foam (7) introduced into the cavity (4) between the carrier (6) and the mold skin (5), which is initially liquid and foams up and solidifies through a chemical reaction, and wherein a labyrinth seal (10) formed by several channels (9) for the air extraction of the foam spreading during its reaction is introduced at least partially into the edge region (8) of the cavity (4) of the device (1), characterized in thatthat on the side opposite the channels (9) of the labyrinth seal (10), below the mold skin (5), a deformable, soft-elastic seal (11) is inserted into a receiving groove (12) of the tool part (2 or 3) receiving the mold skin (5), the receiving groove being designed in a complementary manner to the seal geometry.

Description

[0001] The invention relates to a device for producing a molded part, wherein the device comprises an upper tool that can be placed on or connected to a corresponding lower tool, wherein a cavity forming the molded part to be produced is located between the upper tool and the lower tool, into which a mold skin and a carrier are inserted on the one hand. The molded part is formed from a material-bonded connection between the carrier, the mold skin, and a foam material that is initially liquid and foaming up through a chemical reaction, subsequently solidifying, and introduced into the cavity between the carrier and the mold skin. Furthermore, a labyrinth seal formed by several channels is incorporated, at least partially, into the edge region of the device's cavity to vent air from the foam material as it expands during its reaction.Such devices with labyrinth seals are known, for example, from DE 10 2015 113 027 A1 or from EP 3 130 440 A1. Furthermore, the publications also describe methods for manufacturing such a molded part with such a device.

[0002] The term "molded parts" generally refers to composite components consisting of at least two different parts and possessing a predetermined geometric shape. Examples of such molded parts include trim panels for motor vehicles, such as instrument panels, door panels, or glove box lids. A significant manufacturing challenge with these aforementioned trim panels is their complex geometry, and they often require cutouts to accommodate the later installation of fittings or instruments.Such molded parts typically consist of a substrate, a molded skin, and a foam layer sandwiched between the substrate and the molded skin. The foam in this layer is composed of a reaction mixture that was initially liquid, usually foamed polyurethane (PU) or polyethylene (PE). Polyurethanes are plastics or synthetic resins produced by the polyaddition reaction of dialcohols or polyols with polyisocyanates. Carbon dioxide (CO2) is released during this chemical reaction. The foam of the molded part bonds the substrate to the molded skin, creating a cohesive material once it has fully reacted and thus foamed up. In the aforementioned automotive trim parts, the molded skin can be a colored decorative layer, a leather covering, or a plastic layer that, for example, forms the visible surface of a dashboard.When the term "molded skin" is used in this context, it should not be interpreted restrictively. Rather, the components to be connected to the substrate can also be other structural elements, such as another substrate or similar components. Besides inserting the foam layer between two components, it is also known to apply a foam layer to only a single component. This process is often referred to as "back-foaming" and can also be used for the molded parts described above or similar ones.

[0003] During the chemical reaction, which causes the reaction mixture to foam, it expands progressively, displacing the air or gas present in the cavity of the components to be joined. Therefore, a controlled venting of this air or gas is essential. Another crucial aspect in the production of a molded part with a foam layer is that the device used to manufacture such a part, for example, a foaming tool, must be capable of ensuring this air venting and, furthermore, withstanding the resulting reaction pressure.This requires special sealing systems because insufficiently effective seals can lead to so-called "pulling voids," which form greatly enlarged or deformed CO2 cells within the foam layer, resulting in the foam layer not meeting the required quality. In some cases, this can even render the entire molded part unusable.

[0004] The sealing systems described above in a device for manufacturing a molded part currently require, disadvantageously, a circumferential component edge that must be removed as waste in a subsequent process. This, in turn, entails additional manufacturing effort as well as considerable material and process costs. The sealing systems used to date are often so-called "contour seals" that are filled with air to perform their sealing function. The contour seals of the foaming tool remain filled, at least in sections, until the foam approaches. Following this, the contour seal must perform its sealing function within a very short time, which requires a correspondingly complex control or switching system. Pneumatic systems are typically used to operate the contour seals.However, when using these contour seals, it is almost unavoidable that a certain part of the foam passes through the sealing area, otherwise the air or gas cannot completely escape from the cavity between the carrier and the molded skin.

[0005] DE 698 27 178 T2, for example, describes a contour seal for a foaming tool that has an expandable hose element whose wall can be elastically deformed by increasing the internal pressure within the hose element. The reference to the internal pressure within the hose element is made to normal atmospheric pressure, so that an increase in the internal pressure means raising the pressure above normal atmospheric pressure. According to DE 698 27 178 T2, a sealing component of the contour seal consists of a solid body made of elastic material. This component of the contour seal is received in a guide groove of the foaming tool and is thus movable like a piston. Since the seal and the hose element are manufactured as a single unit in the known solution, the contour seal is a very complex and costly component to produce.Such contour seals for foaming tools are also subject to considerable wear, as they are subjected to high thermal and mechanical stresses. For this reason, the contour seals must be serviced and replaced at regular intervals. This also results in high manufacturing costs for the molded parts produced in this way.

[0006] From DE 10 2012 219 107 A1, a molded part is known in which a vent channel is present in the contact area between a carrier and a mold skin. This vent channel, which has a square cross-section, is formed by two circumferential, rib-shaped protrusions formed on the carrier, with interruptions incorporated therein that are offset from one another. The rib-shaped protrusions of this solution represent a linear contact between the carrier and the mold surface.

[0007] A similar design is also described in DE 10 2007 025 884 A1. Here, the inherently unstable decorative layer, also referred to as the "molded skin," is provided with V-shaped grooves, preferably extending over the entire edge of the decorative piece. Due to their inherent instability, these grooves must be stabilized by additional support ribs within the mold. This results in increased manufacturing effort during the production of the device and therefore presents a disadvantage.

[0008] The invention is based on the objective of providing a device for the production of a molded part in which an improvement in the sealing effect is achieved with a simple design by using a labyrinth seal in the edge area of ​​the cavity.

[0009] The invention solves this problem with the features of claim 1. Further embodiments of the invention are the subject of the following dependent claims.

[0010] A device for producing a molded part, comprising an upper tool that can be placed on or connected to a corresponding lower tool, wherein a cavity forming the molded part to be produced is located between the upper tool and the lower tool, into which a mold skin and a carrier are inserted on the one hand, wherein the molded part is formed from a material-bonded connection between the carrier, the mold skin and a foam material that is initially liquid and foams up and solidifies through a chemical reaction, and wherein a labyrinth seal formed by several channels for air extraction from the foam material that expands during its reaction is introduced at least partially into the edge region of the cavity of the device, was further developed according to the invention in such a way that on the side opposite the channels of the labyrinth seal,Below the mold skin, a deformable, soft-elastic seal is inserted into a receiving groove of the tool part receiving the mold skin, the receiving groove being designed complementary to the seal geometry.

[0011] The seal, made of an elastically deformable material and inserted beneath the mold skin, exerts a compressive force on the mold skin and thus on the labyrinth seal. This causes the foam front spreading within the channels of the labyrinth seal to solidify more quickly due to the smaller cross-section of the channels compared to previously used labyrinth seals. This results in a significant improvement, leading to a substantial reduction in unwanted waste, which in turn means less material requiring recycling. Furthermore, the seal according to the invention effectively compensates for tolerance variations in the substrate or the mold skin. The fact that the seal is inserted into the receiving groove according to the invention also allows for easy replacement if the seal becomes damaged.This provides a very simple solution for significantly improving the seal between the carrier and the mold skin of a device for manufacturing a molded part. Reliable degassing and venting functions, a reliable seal, and considerable cost reductions can be achieved. The labyrinth seal used is also low-wear and low-maintenance.

[0012] According to a first embodiment of the invention, it is proposed that the seal is inserted into the receiving groove by forming a positive fit. This connection between the receiving groove and the seal enables a precise fit between the two. Furthermore, the geometry of the seal and the corresponding receiving groove allows for easy assembly. For example, the seal can be inserted into the receiving groove by applying slight pressure and is thus fixed in place without any additional tools.

[0013] Furthermore, a particularly advantageous design of the connection between the seal and the receiving groove is characterized by the fact that the receiving groove has an undercut into which at least one section of the seal is precisely fitted. The undercut secures the seal and thus represents a special form of positive locking.

[0014] A further development of the proposed use of an undercut is that the seal, viewed in cross-section, has a dovetail-shaped or convex section inserted into the undercut of the receiving groove, which transitions into a rib-like area with a smaller cross-section than the dovetail-shaped or convex section. A seal profile with a convex section could also be described as a "lollipop profile." This is particularly easy to insert into the corresponding receptacle.

[0015] To achieve an optimal contact surface beneath the mold skin, it is also advantageous if the seal has a flat section on the side opposite the convex section that rests directly against the underside of the mold skin and exerts a uniform pressure force on the labyrinth seal through the elastic deformation of the seal when the device is closed. Preferably, the cross-section of this flat section should correspond to the full width of the labyrinth seal. This has the advantage that all channels of the labyrinth seal are covered by the surface of this flat section.

[0016] The seal is preferably manufactured in one piece. The flat section, viewed in cross-section, extends on both sides and at right angles from the rib-like transition area. Thus, in cross-section, it forms an approximately rectangular shape, although the transition area between the rib-like transition area and the flat section may also have rounded edges to facilitate demolding.

[0017] Silicone has proven to be a particularly suitable material for manufacturing a seal according to the invention. It is highly elastic, easy to shape, and simple to process. Furthermore, silicone is a cost-effective material. This allows the seal to be injected directly into the receiving groove, thus immediately assuming the desired shape of the groove.

[0018] Depending on the requirements or desired properties of the seal and its contact pressure on the labyrinth seal, a silicone material with varying degrees of hardness can be used. However, a simple alternative for increasing the sealing force is to incorporate an insert. For example, a metallic or plastic wire can be used as an insert in the convex section of the seal. This is incorporated or inserted directly into the convex section of the seal during manufacturing.

[0019] As an alternative to this proposed solution, the seal could also have at least one cavity to increase its flexibility. Such a cavity can also be provided in the convex section of the seal. This significantly influences the properties of the seal, resulting in a seal with a cavity that is very soft overall.

[0020] According to a further proposal of the invention, the individual channels of the labyrinth seal can, for example, have a wave-shaped, preferably sinusoidal, cross-section. Furthermore, other geometries, such as a V-shape or a U-shape, are also possible. The wave shape, particularly a sinusoidal geometry, has proven especially advantageous because it facilitates demolding the carrier from a mold used to manufacture it, thus representing a manufacturing-friendly option. It also provides a relatively large contact area between the mold skin and the surfaces formed by the channels of the labyrinth seal. The foam simultaneously acts as a kind of adhesive between the mold skin and the carrier, creating a material-bonded connection between these components.

[0021] The geometric design of the labyrinth seal and the arrangement of the individual channels allow for a very precise assessment of the seal's behavior and are crucial for the quality of the molded part to be produced. For this reason, a further aspect of the invention proposes arranging the channels of the labyrinth seal equidistant from one another.

[0022] An alternative solution is to have the channels of the labyrinth seal, viewed in the direction of flow, have a curved, meandering or zigzag pattern.

[0023] For the geometric design of the cross-section of a single channel of the labyrinth seal, a cross-sectional area between 0.15 mm² was used, depending on the viscosity of the foam material to be processed. 2 and 0.4 mm 2The results show that the channels of the labyrinth seal have a relatively small overall area and are therefore relatively narrow. This ensures optimal venting and allows the frictional heat generated in the channels by the foam as it enters to be used effectively to accelerate the process.

[0024] Furthermore, depending on the viscosity of the foam, channel lengths between 30 mm and 60 mm have proven particularly advantageous for the labyrinth seal. As a general rule of thumb, a shorter channel length is sufficient for high-viscosity foam, while a longer channel length is required for low-viscosity foam. Since the overall length of the labyrinth seal channels is relatively short, this also means that the edge area on the substrate or molded skin can be made narrow, which further reduces waste.

[0025] To ensure the smoothest possible drainage of air or gases from the space between the carrier and the molded skin, one embodiment of the invention provides that the labyrinth seal has an air outlet open to the environment. In the simplest case, this air outlet can be a single opening, with each channel of the labyrinth seal having its own opening, or a common opening for several channels being provided. The only important factor here is that the escaping volume of air or gas is not subjected to any significant resistance, so as not to impede its drainage.

[0026] A method for manufacturing a molded part using such a device is characterized by the following process steps: - Inserting the seal into the designated receiving groove, - Insertion of a molded skin into the part of the cavity of the device containing the seal, - Arrangement of a carrier in the corresponding, other part of the cavity formed in the device, - Closing the device while simultaneously creating the necessary reaction conditions for the foaming process of the reaction mixture, - Introduction of the liquid reaction mixture, which later forms the foam, into the cavity between the carrier and the mold skin, whereby the foaming process removes the air, followed by the foaming reaction mixture expanding in volume, from the cavity via a labyrinth seal consisting of several channels located on the carrier and / or on the mold skin, until the reaction mixture fills the labyrinth seal and closes it by hardening. - complete curing of the reaction mixture, forming the foam layer that bonds the carrier and the molded skin together in a materially bonded manner, - Opening the device and removing the produced molded part.

[0027] Alternatively, the device can also be closed only after the liquid reaction mixture, which later forms the foam, has been introduced into a space between the carrier and the molded skin.

[0028] In this context, if the necessary reaction conditions for the foaming process of the reaction mixture are created, this leads to the air, followed by the foaming reaction mixture expanding in volume, being carried out of the cavity via the labyrinth seal present on the carrier and / or on the mold skin, until the reaction mixture fills the labyrinth seal and closes it through its hardening.

[0029] Creating the necessary reaction conditions for the foaming process of the reaction mixture includes, for example, heating the upper or lower mold, which can be done conventionally by a heating device or by supplying heated water. According to the invention, it is important that the labyrinth seal can be formed either on the carrier or on the mold skin, or on both components.The reacting mixture, which later forms the foam, pushes the air present in the space between the substrate and the mold skin ahead of it. This is due to the different viscosities of air and foam, allowing the subsequent foam front to expand into even the smallest corners of the molded part being produced. This ensures complete filling of the space between the mold skin and the substrate, resulting in a molded part free of defects, air inclusions, or voids. Therefore, the inventive method guarantees a high level of manufacturing quality.

[0030] One embodiment of the process is that the mold skin is placed in the lower tool and the carrier in the corresponding upper tool.

[0031] Alternatively, it is also possible to insert the mold skin into the upper tool and the carrier into the corresponding lower tool.

[0032] The invention is explained in more detail below with reference to the accompanying drawings. The exemplary embodiments shown do not represent a limitation to the variants shown, but serve merely to explain a principle of the invention.

[0033] Identical or similar components are always designated by the same reference numerals. To illustrate the functionality of the invention, the figures show only highly simplified schematic diagrams, omitting components that are not essential to the invention. However, this does not mean that such components are not present in a solution according to the invention.

[0034] It shows: Fig. 1: a section of a labyrinth seal of a device for manufacturing a molded part, Fig. 2: a partial section through a previously known embodiment of a device 1 for producing a molded part, Fig. 3: the section line III-III from Fig. 2, Fig. 4: A seal as an isolated individual part in a perspective view, Fig. 5: a view of a first version of a seal from the front side, Fig. 6: a look at a second version of a seal, viewed from the front side and Fig. 7: a look at a third version of a seal, viewed from the front.

[0035] From the Fig. Figure 1 shows a section of a labyrinth seal 10 of a device 1 for manufacturing a molded part. The labyrinth seal 10 consists of several parallel channels 9, which in the illustrated example are Fig. 1 are incorporated into a carrier 6. The carrier 6 is in turn received in an upper tool 2. Corresponding to the upper tool 2, the device 1 has a lower tool 3, wherein the upper tool 2 and the lower tool 3 are coupled to each other, i.e., can be opened and closed, for example. In the illustrated example, the lower tool 3 receives a mold skin 5, which comes into contact with adjacent channels 8 of a labyrinth seal 10 in an edge region 8 of a cavity 4. Of course, the reverse case is also possible, namely that the mold skin 5 is arranged in the region of the cavity 4 of the upper tool 2 and the carrier 6 in the lower tool 3.Between the carrier 6 and the mold skin 5, the aforementioned cavity 4 is formed, so that the molded part is created from a material-bonded connection between the carrier 6, the mold skin 5, and a foam material that is initially liquid and foamed up and solidified through a chemical reaction between the carrier 6 and the mold skin 5, and which is introduced into the cavity 4. The special feature according to the invention is that a seal 11, made of an elastically deformable material such as silicone, is incorporated into the lower tool 3 and below the mold skin 5 in the area of ​​the labyrinth seal 10.The seal 11 itself consists of a convex section 14 and an adjoining, rib-like transition area 15, wherein the rib-like transition area 15 merges into a surface section 16, projecting at right angles to it on both sides in cross-section, the width of which corresponds approximately to the width of the labyrinth seal 10. Thus, when the device 1 is closed, the seal 11 exerts an elastically effective compressive force on the labyrinth seal 10 and therefore on the individual channels 9 via the molded skin 5, which accelerates the curing of the spreading reaction mixture of the foam. Furthermore, such a solution allows for optimal tolerance compensation between the molded skin 5 and the carrier 6. The seal 11 is inserted into a complementarily shaped receiving groove 12, forming a positive fit, with the convex section 14 located in a kind of undercut 13.

[0036] The Fig. Figure 2 shows a partial section through a previously known embodiment of a device 1 for producing a molded part. The illustration, like the Fig. 3, merely to explain the functioning of a previously known labyrinth seal 10. A portion of the upper tool 2 and the lower tool 3 is shown in an indicative manner. From the Fig. Figure 2 clearly shows the special feature that a labyrinth seal 10 is formed not in the device 1, but directly on the molded part to be produced, more precisely, on the carrier 6 of the molded part. However, the labyrinth seal 10 can also be formed on the mold skin 5, as shown in the illustration of the Fig. 2, however, this is not the case. The labyrinth seal 10 consists of a plurality of individual, preferably labyrinthine, channels 9, which serve to drain the air present in the cavity 4 and the gas produced during the foaming process, which is predominantly carbon dioxide (CO2). The incoming foam hardens in these channels, thus closing the labyrinth seal 10 only when the entire volume of air present in the cavity 4 has completely escaped from the molded part being produced. The foaming foam therefore creates a material-bonded connection between the carrier 6 and the molded skin 5, forming a foam layer 7.

[0037] As can be seen from the section line III-III Fig. 2, the subject of the Fig. As is clearly evident in Figure 3, air or gas escapes from air outlet openings 21 of the labyrinth seal 10 and is released into the environment. The expanding foam in the cavity 4 forms a foam layer 7 and, through its expansion, displaces the existing air across the labyrinth seal 10. Subsequently, the foam also enters the labyrinth seal 10 through the inlet openings 19 to harden both in the cavity 4 and within the labyrinth seal 10. The hardening foam ends at the foam front, designated 20, within the labyrinth seal 10. Unrestricted venting is possible up to the point where the foam enters the channels 9 of the labyrinth seal 10. Tests have shown that it is advantageous to arrange the inlet openings 19 relatively close together; in other words, for example, to provide an inlet opening 19 every 20 mm.This allows for optimal ventilation.

[0038] As can be seen from the presentation in the Fig. As shown in Figure 4, which depicts a seal 11 as an isolated component in a perspective view, the seal 11 is an elongated component that is inserted or injected into a corresponding receiving groove 12 of the device 1. The surface section 16 can, for example, have a height of 3 mm and a width of 12 mm. Furthermore, a special embodiment allows the rib-like transition area 15 to have a width of 5 mm. The convex section 14 has a radius of 3 mm. As can be seen from the specified dimensions, which are of course not binding but merely exemplary, the seal 11 is a relatively slender component whose essential properties derive from the elasticity of the material.

[0039] As exemplified by the presentation in Fig. Figure 5, which shows a view of a first embodiment of a seal 11 from the end face, the entire seal 11 can in a particularly preferred manner consist of a one-piece component, which is made, for example, of silicone.

[0040] An alternative design variant is shown in the representation in Fig. 6. It can be seen from this that, for example, an insert 17 can be inserted into the convex section 14 to increase the stiffness of the seal 11. The insert 17 can, for example, consist of a metallic or plastic wire and reinforces the seal 11 overall, so that the elastic properties of the seal 11 can be influenced in any desired way.

[0041] Another version shows the Fig.7, in which the seal 11 is also shown viewed from the front side and has a cavity 18 in the convex section 14 of the seal 11 to reduce the strength. REFERENCE MARK LIST: 1 device 2 Upper tool 3 lower tools 4 Cavity 5. Molded skin 6 carriers 7 Foam 8. Rim area (of the cavity) 9 channels 10 Labyrinth seal 11 Seal 12 recordings 13 Undercut 14 convex section 15 stair-like transition area 16 Area section 17 deposit 18 Cavity 19 entrances 20 Foam front (end) 21 air outlet openings QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2015 113 027 A1

[0001] EP 3 130 440 A1

[0001] DE 698 27 178 T2

[0005] DE 10 2012 219 107 A1

[0006] DE 10 2007 025 884 A1

[0007]

Claims

[1] A device (1) for producing a molded part, comprising an upper tool (2) which can be placed on or connected to a corresponding lower tool (3), wherein a cavity (4) forming the molded part to be produced is present between the upper tool (2) and the lower tool (3), into which cavity a molded skin (5) and a carrier (6) are inserted, wherein the molded part is formed from a material-to-material connection between the carrier (6), the molded skin (5) and a foam (7) introduced into the cavity (4) between the carrier (6) and the molded skin (5), which is originally liquid and foams and solidifies as a result of a chemical reaction, and wherein a labyrinth seal (10) formed by a plurality of channels (9) is introduced at least in sections into the edge region (8) of the cavity (4) of the device (1) for the purpose of discharging air from the foam expanding during its reaction, characterized bythat on the side opposite the channels (9) of the labyrinth seal (10), below the molded skin (5), a deformable, soft-elastic seal (11) is inserted into a receiving groove (12) of the tool part (2 or 3) receiving the molded skin (5), said receiving groove being designed complementarily to the seal geometry. [2] Device according to claim 1, characterized by that the seal (11) is inserted into the receiving groove (12) to form a positive fit. [3] Device according to one of the preceding claims, characterized by that the receiving groove (12) has an undercut (13) into which at least a portion of the seal (11) is inserted with a precise fit. [4] Device according to claim 3, characterized bythat the seal (11), viewed in cross-section, has a dovetail-shaped or spherical section (14) inserted into the undercut (13) of the receiving groove (12), which section merges into a web-like transition region (15) which in turn has a smaller cross-section than the dovetail-shaped or spherical section (14). [5] Device according to one of the preceding claims, characterized by that the seal (11) has, on the side opposite the spherical section (14), a surface section (16) which lies directly against the underside of the molded skin (5) and exerts a compressive force on the labyrinth seal (10) due to the elastic deformation of the seal (11) when the device (1) is closed. [6] Device according to claim 5, characterized by that the surface section (16) extends on both sides and at right angles from the web-like transition area (15). [7] Device according to one of the preceding claims, characterized by that the seal is made entirely of one piece. [8] Device according to one of the preceding claims, characterized by that the seal (11) is made of silicone material. [9] Device according to one of claims 1 to 8, characterized by that the seal (11) has an insert (17) to increase its compressive force. [10] Device according to one of claims 1 to 8, characterized by that the seal (11) has at least one cavity (18) to increase its flexibility. [11] Device according to one of the preceding claims, characterized by that the cross-section of the adjacent channels (9) of the labyrinth seal (10) has a wave shape, a sinusoidal wave shape, a V-shape or a U-shape. [12] Device according to one of the preceding claims, characterized bythat the channels (9) of the labyrinth seal (10) are equidistant from each other. [13] Device according to one of the preceding claims, characterized by that the channels (9) of the labyrinth seal (10), viewed in the direction of flow, have a straight, curved, meandering or zigzag-like course. [14] Device according to one of the preceding claims, characterized by that the cross-section of each channel (9) of the labyrinth seal (10) is between 0.15 mm 2 and 0.4 mm 2 amounts. [15] Device according to one of the preceding claims, characterized by that the length of each channel (9) of the labyrinth seal (10) is between 30 mm and 60 mm, depending on the viscosity of the foam material. [16] Device according to one of the preceding claims, characterized bythat the labyrinth seal (10) has an air discharge that is open to the environment.

Images