Textiles: fluid treating apparatus – Machines – Liquid applying
Reexamination Certificate
2000-08-11
2003-03-11
Stinson, Frankie L. (Department: 1746)
Textiles: fluid treating apparatus
Machines
Liquid applying
C068S202000, C118S419000
Reexamination Certificate
active
06530246
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a method and a device for impregnating fibrous material, wherein by fibrous material, fibre bundles or strands, woven textiles or also fibre matting is understood, wherein in the latter case the individual fibres or filaments are present in a random orientation. The fibrous material can be made of the most varied materials; glass, carbon or aramid fibres can be used, or natural fibres such as, for example, flax, jute, hemp or cotton fibres, or metal fibres such as steel, copper or aluminium fibres, or plastics fibres such as, for example, polyethylene, polypropylene or polyamide, or polyethylene terephthalate fibres can be used. The soaking or impregnating of such fibrous materials is an important step in the manufacturing of fibre-reinforced composite substances, in which a good cohesion between a matrix substance and the fibres is vital. This good cohesion is only made possible by as complete as possible wetting of the surface of the individual fibres.
In particular, the present invention relates to a method for impregnating fibrous material, in which an impregnating agent is introduced into the spaces in the fibrous material, and the individual fibres are coated and/or soaked through, wherein the impregnating agent is supplied via a supply body with one or more apertures, on which body the fibrous material is moved past in contact with the supply body or at a distance from it.
The corresponding device for impregnating fibrous material, upon which the present invention is based, is provided with a supply body with one or more apertures for the impregnating material and transport means for the fibrous material, by means of which the fibrous is moved through the device, or respectively on the supply apertures or respectively moved past the supply body.
Such a method and a corresponding device are known from DE 38 35 574, whereby in this an impregnating device is described in which a fibre bundle is conveyed via a nozzle, wherein a plastics flux is pressed through the fibre bundle, at a raised pressure, at right-angles to the direction of movement of the fibres, which fibre bundle is consequently soaked through. With this, impregnation is carried out substantially locally by bringing together the fibrous material and a nozzle in one place, where, because of the pressure of the impregnating material leaving the nozzle, the fibre bundle, or respectively the fibrous material, is interspersed relatively quickly by the impregnating agent.
In comparison, a method and a device are also known in which the supply is by means of a permeable supporting surface moved at the same speed along with the fibrous material. Such a method and a corresponding device are relatively complex because of the supporting surface also having to be moved and the matching of the speeds of the fibrous material and the supporting surface.
The method and device with local supply, even when the local supply of impregnating material is repeated on a plurality of occasions in a succession of positions, have the disadvantage that the soaking through of the fibrous material is often irregular and incomplete. For example, in the case of fibre bundles, it can happen that the fibre bundles are of different thicknesses when seen from right-angles to their longitudinal extent, and because of this the impregnating material penetrating in this direction of thickness can encounter a very different flow resistance. The impregnating material then flows preferentially through areas with low flow resistance, in certain conditions even separating the fibre bundle in this way, and only poorly soaks through the thicker areas of the bundle.
JP 984615 shows a device with a tube-shaped base body. A slit extending in a longitudinal direction is arranged in this tube-shaped base body. A sintered body is incorporated into this slit, through which sintered body the impregnating agent is supplied to the fibres.
Compared to this prior art, the object of the present invention is to provide a method and a device which achieve a more complete and uniform soaking through of the fibrous material.
With respect to the method, this object is solved in that a supply body of a permeable or porous material is used for the supply of the impregnating agent, over which body the fibrous material is moved along in a sliding manner.
Preferably, the permeable or respectively porous supply body has, when seen in the direction of flow of the impregnating material, a greater flow resistance than the fibrous material. It is clear that the flow resistance of the fibrous material is to be viewed as the same direction as that in which the impregnating material is pressed through the fibrous material, that is to say perpendicular to the contact surface of the permeable or respectively porous supply body.
A configuration of the method is preferred in which the supply of the impregnating agent is done under moderate pressure of, for example, at least 10 and at the most 500 bar in the case of thermoplastic impregnating agents, and 1 to 50 bar with duroplastic impregnating agents, measured on the side of the porous supply body opposite the fibrous material.
Furthermore, a configuration of the method according to the invention is preferred in which the dimensions of the supply body, that is to say in particular its porous surface, over which the fibrous material is passed, and the speed of movement of the fibrous material which is to be soaked through are matched with one another such that a given point of the fibrous material which is touching the contact surface of the supply body, remains touching this contact surface for at least 50 milliseconds (ms), thus actually requires at least 50 ms to be moved over the length of the contact surface, measured in the direction of movement of the fibrous material. In other words, when the fibrous material moves relative to the supply body at a speed of 50 mm per second, the length of the contact surface of the porous supply body would have to be at least 2.5 mm, and if the speed of the fibrous material is 500 mm per second, the corresponding length of the supply body would have to be 25 mm.
With the aid of the method according to the invention, duromer impregnating agents can be applied to fibres without any problems, which agents are then cured after impregnation of the fibres. Unexpectedly, it has been proved that even thermoplastic materials which have a substantially greater viscosity compared to duromers, can be applied very well through permeable or respectively porous supply bodies which have relatively small effective cross-section supply apertures, and possibly also relatively long supply channels to the fibres to be impregnated using the method according to the invention. Moreover, it has been established that the speed at which the fibrous material can move relative to the supply body can be increased substantially above the figures already described, as in many cases a contact time of 10 milliseconds is enough for sufficiently wetting the fibrous material to be impregnated or soaked through. The supply body can either be correspondingly shortened or the speed of supply of the fibrous material can be correspondingly increased, for example, to 1-5 m per second.
A particular application of the method according to the invention is disclosed in connection with the application of the impregnated fibres onto blank moulds. These can be, for example, rod or tube-shaped and the fibres can either be applied in the longitudinal direction of such a blank mould or be wound around it, at an angle which can in principle, be selected between 0° (corresponding to the longitudinal direction) and 90° (corresponding to wrapping in a plane perpendicular to the feed direction of the blank mould).
The blank mould can either be rotated or the supply means for the fibres is rotated together with a corresponding impregnating means around the blank mould, according to which variant proves more practically advantageous. In particular when the blank moulds are of a very gre
Killworth, Gottman Hagan & Schaeff, L.L.P.
Stinson Frankie L.
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