CROSS REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. application Ser. No. 11/629,634, filed Aug. 7, 2007, now U.S. Pat. No. 8,142,696, which is the U.S. National Stage completion of International Application No. PCT/EP2005/006360 filed Jun. 14, 2005 (published as WO 2005/123360 on Dec. 29, 2005) designating the U.S., and which claims priority to German Patent Application Serial Number DE 10 2004 028 803.8, filed Jun. 15, 2004, the teachings of which are incorporated herein by reference.
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OF THE INVENTION
1. Field of the Invention
The invention relates to a method and a device for producing back-foamed air-permeable textile products such as back-foamed mats as a floor covering for motor vehicles, seat upholstery, head rests and the like, and to a back-foamed air-permeable textile product of this type.
2. Related Technology
The above-mentioned products are typical representatives of such air-permeable textile products which can be back-foamed on the back turned away from a useful or visible face.
In the case of floor coverings for a motor vehicle, the back-foamed mat has the function not only of compensating for unevenness in a vehicle floor relative to the desired planar configuration in the vehicle interior but also of receiving cables and of insulating and damping undesirable noises. The mat is an air-permeable textile product, generally a carpet web, which is tufted in a textile air-permeable carpet substrate.
In the case of seat upholstery, head rests and the like, back-foaming of the textile product, generally a fabric, in turn has the function of giving the seat upholstery or the head rest a desired form which improves the sitting posture. Acoustic effects here are relatively insignificant, it being more important additionally to achieve very good climatic comfort. Climatic comfort refers to the property whereby air can circulate through the textile product, even when it is back-foamed, so that atmospheric moisture can be transported and air can also circulate easily, leading to rapid compensation in terms of ambient temperature and ambient humidity, in particular also when a person is using the seat upholstery or the head rest.
Conventionally the air-permeable textile product, for example a mat blank, etc., is inserted into a mold with the useful or visible face resting on one mold half for typical manufacture. The mold is then closed and the reaction product is introduced to form the back-foaming foam such as polyurethane foam. A relatively high pressure is produced during the reaction of the reaction products. Since the textile product is air-permeable, usually being a hosiery or knitted fabric or the like with high porosity, and due to the action of capillary forces, at least one of the reaction products, possibly all of them, can pass through these pores or openings in the fabric to the visible face of the textile product, where they adhere to any parts provided there. Any foam which is being formed can also pass through these pores. This is highly undesirable. Back-foamed textile products in which the visible face has adhesive regions or in which the foam has passed to the visible face cannot be sold.
To overcome this problem, a film is provided on the back of the mat as an acoustically effective component (DE 38 09 980 C2) with a known method for manufacturing floor coverings. Closed-cell thin foam layers have also been proposed. The known provision of a film is counter-productive to the achievement of climatic comfort as it prevents the circulation of air. A film of this type, which is impermeable to air, is also undesirable with respect to the acoustic properties.
It is known from DE 691 13 137 T2 to destroy such a film, at least in part, after manufacture of the back-foamed product by additional methods, the effect of heat combined with the production of a reduced pressure. The additional process steps required here are obviously very expensive and complex, and the complete or uniform removal or perforation of the film cannot be reproducibly ensured. Residues of the film adversely affect the flow resistance at the respective positions. Therefore, this procedure is not particularly suitable, especially for mass production.
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OF THE INVENTION
Accordingly the invention provides a method and a device for the production of back-foamed air-permeable textile products, with which the penetration of reaction products or foam to the visible face can be reliably avoided, without necessitating the provision of films or the like.
The invention provides a method for producing back-foamed air-permeable textile products, including the steps of inserting the textile product into a mold, closing the mold and introducing reactants to form the foam, allowing reactants to react, with a simultaneous decrease in the pressure created during the reaction via at least one expansion orifice in the mold half turned away from the inserted textile product, and controlling the decrease in pressure in such a way that none of the reactants nor the foam created by the reaction penetrates the textile product.
The invention also provides a back-foamed air-permeable textile product such as a back-foamed mat as a floor covering for a motor vehicle, seat upholstery, head rest or the like, in which the cells of the foam adhere tightly to the back of the textile product without the interposition of a film or the like and without the foam penetrating the textile product.
The invention also provides a device for carrying out the inventive method, including a mold and with an upper region, a suction orifice for evacuation and a system for ventilating the mold, and at least one expansion orifice at a predetermined position in an upper portion of the upper mold region, wherein the expansion orifice is associated with a control valve which can be activated in such a way that, as a function of product parameters and detected actual values, a decrease in the pressure produced during the reaction of the reactants takes place in the mold in such a way that none of the reactants themselves nor the foam produced by the reaction thereof can penetrate an air-permeable textile product inserted into the mold.
The invention starts from the surprising finding that the measure described in the earlier patent application 102 58 546.6, with which void-free parts can be achieved in short cycle times during the manufacture of foamed polyurethane shaped articles, can be developed in such a way that the decrease in the pressure created during the reaction of the reaction products can be regulated in such a way that, despite the achievement of the desired back-foaming, none of the reaction products nor created foam can penetrate to the visible face of the textile product.
The pressure created inside the mold during the reaction of the reaction products and also the capillary action inherent in the textile product or its make-up are important parameters. Both parameters can be sufficiently determined via the time characteristic thereof, beginning with the introduction of the reaction products, to determine the time characteristic of the penetration-preventing decrease in pressure in the mold. A valve associated with at least one expansion orifice and opening toward the reduced pressure chamber is regulated accordingly. Toward the end of the back-foaming process, there is a smooth transition to the method according to the earlier application, in such a way that the backs of the back-foamed products are at least substantially void-free. The device according to the earlier application can basically also be employed since the four-way valve described therein is an arrangement in which a valve with a controllable degree of opening can be opened in a controlled manner to a reduced pressure source such as a reduced pressure chamber. The needle valve mentioned in the earlier application, which prevents the admission of foam into the expansion orifice and therefore the production of voids, can be retained without change.
BRIEF DESCRIPTION OF THE DRAWINGS
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The invention will be described in more detail by the embodiment shown in the drawings, in which
FIG. 1 is a schematic view and longitudinal section of a device for controlling the sequence in a mold according to an embodiment of the invention,
FIG. 2 is a schematic view and longitudinal section of a device equipped with a plurality of expansion orifices and a common reduced pressure and excess pressure supply according to a further embodiment of the invention,
FIG. 3 is a schematic section of a needle valve which can be activated via a pressure sensor for use in the invention,
FIG. 4 shows the typical characteristic of pressure and degree of opening of the valve over time.
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FIG. 1 shows a preferred embodiment of a device for carrying out the method according to the invention. A mold 10 with an upper mold half 10a and a lower mold half 10b can be seen. The two mold halves 10a, 10b are separated from one another by a mold parting plane 10c. The mold plane 10c preferably has a vacuum seal. In the case of elastically deformed textile products, the sealing effect can also be achieved by the textile product which is to be back-foamed itself. An expansion orifice 5 formed in the upper mold half 10a and having a needle valve 1 arranged therein is also provided. The needle valve 1 is connected via a valve arrangement designated schematically as a four-way valve 11 to a source of reduced pressure and excess pressure (not shown in detail) and to the atmosphere. This arrangement allows not only the extraction via the needle valve 1 of gases released during the expansion process but also the evacuation or ventilation of the mold 10 and the application of excess pressure. The output signal of a pressure sensor 6 serves to control the valve drive 7 of the needle valve 1 and preferably to regulate in accordance with the invention the internal pressure in the mold 10 during the expansion process, as will be explained hereinafter. If a drop in pressure is triggered by polyurethane which is penetrating the needle valve 1, the valve needle 3 is driven out downwards and the valve 1 closed, any polyurethane which has already penetrated being expelled again.
FIG. 2 is a schematic view of the connection of a plurality of valves 1 of this type to a common media supply. The arrangement of a plurality of valves may be appropriate or even necessary in the case of molds covering a very great area, to compensate the pressure loss over long flow paths by means of reduced pressure adjustment at the individual valves 1. Molds with a complex geometric configuration, in particular with a plurality of peaks, are a further possible application, void formation being avoided herein. Other possible applications are conceivable.
According to FIG. 2, a plurality of needle valves 1 with respective pressure sensors 6 are arranged in the upper mold half 10a of the mold 10. The needle valves 1 are each connected via a four-way valve 11 to common supply lines to a reduced pressure source or to an excess pressure source 14. The reduced pressure source in this case consists of a vacuum tank 12 which may be evacuated by means of a vacuum pump 13. In addition, each four-way valve 11 also comprises an outlet 15 to the atmosphere. The four-way valve 11 is advantageously formed by an arrangement (cf. FIG. 1) of a two-position valve 25 to the excess pressure source 14, a two-position valve 26 to the atmosphere 15 and a control valve 27 to the reduced pressure source 12, 13. The control valve 27 is preferably a proportional valve which also allows individual adjustment of the reduced pressure to each single valve 1 or each expansion orifice 5, despite having a common media supply.
FIG. 3 is a schematic view of a needle valve 1. The needle valve 1 essentially comprises a housing 2, a valve needle 3 and a valve seat 4 as well as a capillary as the expansion orifice 5 of the mold. A pressure sensor 6 is also directly allocated. As soon as a foam front penetrates into the valve capillary or the expansion orifice 5, the pressure in the capillary drops abruptly. This pressure drop is detected by the pressure sensor 6 and converted via a control unit not shown in the figures into a control signal for a valve drive 7. This control signal causes the valve needle 3 (in the figure) to travel downwards and close the valve 1. The polyurethane which has already penetrated into the capillary 5 is thus expelled by the valve needle 3. The end face of this valve needle 3 is expediently constructed in such a way that it scrapes off this polyurethane completely and, when driven out, closes the expansion orifice 5 flush with the mold.