FI95156B - Method and plant for forming a mat containing various types of fibers - Google Patents

Description

95156

The invention relates to a method for forming a mat containing different fiber grades and to an apparatus for forming a mat containing different fiber grades as set out in the preamble of appended claim 5.

10

When making staple fiber mats, it is often necessary to form the mat from a fiber blend of two or more fiber grades in order to obtain, for example, optimal physical properties for the mat. 15 Different fiber grades in this case mean either fibers of different lengths or sizes of the same material or fibers of different materials, for example mineral fibers, glass fibers and synthetic fibers, which may be a polymer, such as polyethylene, polypropylene or polyester. .

Such a mat is generally formed by breaking up the staple fiber bales used as raw material and "opening" the fibers in a special opening unit so that they are as separate as possible and do not form bundles of fibers. The fibers are generally blended together during such an opening process. There is also a method in which the fibers are mixed together before opening or in a post-opening carding step. The disadvantage of all these methods is that • 9 the fibers are not allowed to mix evenly with each other and the finished mat product does not become uniform. Prior to forming the fibers into a mat by means of an air flow 35 on a suitable substrate, the fibers in the preceding processing steps tend to remain in bundles or to form them with fibers of substantially the same quality. The density values of the fibers also affect their settling during the carpet formation step. This is especially problematic for rigid fibers such as mineral and glass fibers.

The object of the invention is to provide a method by which the above-mentioned difficulties can be overcome and by which two or more fiber grades can be blended to produce a uniform matte product. To achieve this object, the method 10 according to the invention is mainly characterized by what is set forth in the characterizing part of the appended claim 1. By feeding the fibers sequentially into the same air flow with sufficient turbulence, the fibers can be mixed well and the mixing in the pretreatment step 15 does not have to be performed.

The appended dependent claims 2-4 further disclose some preferred embodiments of the method according to the invention.

20

It is also an object of the invention to provide an apparatus with which the above method can be implemented. This apparatus is characterized by what is set forth in the characterizing part of the appended claim 5. 25 The apparatus has an air duct into which two or more fiber supply points ♦ open in succession in the direction of air flow and which have means for providing sufficient turbulence.

In addition, there are some preferred embodiments of the apparatus. set out in the appended dependent claims 6-10.

The invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 shows the apparatus according to the invention in a side view, and Figure 5 shows two successive fiber feed points of the apparatus on a larger scale.

Figure 1 shows an apparatus for forming a mat from staple fibers. Such equipment can be used to form non-woven staple fiber mats of different basis weights. The raw material used is staple fibers, 10 in this case referring to fibers which are short enough to be transported by air flow.

The apparatus has a closed air duct 1 with a closed cross-section 15, into which the air flow F is led from one end thereof. The air duct opens at the opposite end to the carpet formation point D, which will be described in more detail later. In the longitudinal direction of the air duct, there are three separate fiber feed points in succession, feed points 20 A, B and C.

The fibers are fed in such a way that each feed point is fed its own fiber quality into the air flow F flowing at it. Thereafter, sufficient turbulence is caused for the air flow 25, which causes the fibers fed at the next feed point to mix with the fibers supplied at the previous feed point. Although three feed points are shown in the figure below, there may also be several or only two feed points, depending on the number of fiber grades to be blended.

In a long air duct at two consecutive feed points 35, the turbulence mixing the fibers can be caused after the first feed point by means sufficiently close to the second feed point, at the second 4 95156 feed points due to the feed point design or by special members after the second feed point.

In the example of Figure 1, for example, a suitable volume of mineral fiber can be fed to feed point A, a suitable volume of glass fiber to a subsequent feed point B and a suitable volume of synthetic fiber to a subsequent feed point C. The volume feeds are schematically indicated in Fig. 10 by the arrows AV, BV and CV. These feed rates can be used to adjust the percentage of different fiber grades in the finished product, and the total feed rate can be used to adjust the basis weight of the final product.

15

The fibers are preferably fed in such an order that the stiffer fibers are fed to the air flow F before the more flexible fibers. For example, in the case of Figure 1, the mineral fiber and the more rigid glass fiber 20 are fed into the air duct before the flexible and more easily intertwined synthetic fiber. In this case, no accumulation of synthetic fiber occurs, but there is already previously fed mineral and / or glass fiber around each synthetic fiber, whereby a homogeneous air / fiber mixture is achieved. In addition, the stiffer mineral fiber and fiberglass open easily in the air duct due to strong turbulence, which contributes to the homogeneity of the final product.

30 At the end of the air duct 1 there is a carpet formation point D.

,. At the point of formation of the mat, there is a diffuser 6 with an expanding cross-sectional area, at the narrower beginning of which the air duct 1 ends. Here, the velocity of the well-mixed fibers coming from the air duct decreases 35 and they are lowered to the substrate at the end of the diffuser 6, through which the air flow is passed. In Fig. 1, two air-permeable cylinders with opposite surfaces are used at this point, 5 95156 air screens 5, on the surfaces of which the fibers descend, and as the screens rotate in opposite directions, the finished carpet enters between them and goes to further processing. The air screens can, of course, be replaced by other forming elements, such as, for example, an air-permeable conveyor wire.

By the term carpet formation site is meant all such elements to which the fibers accompanying the air flow form a carpet on the forming substrate. This mat is not necessarily a final product, but can also be an intermediate product that is further processed in the process, and e.g. it can be re-disintegrated by air flow and re-counted as a rug, e.g. as described in 15 previous Finnish patent application 880755.

Sufficient turbulence to mix the fibers in the air duct 1 is provided by means 2 restricting the cross-sectional area 20 of the air duct, which are always located in the apparatus of Figure 1 between two successive feed points, the first between feed points A and B and the second between feed points B and C. In addition, it should be noted that turbulence is also produced 25 before the first supply point A at the beginning due to a reduction in the cross-sectional area of the wider air duct or at the supply point itself, as described below.

Figure 2 shows two successive feed points 30 A and B and the throttling element 2 between them on a larger scale. At the fiber feed point, a roller 3 with spikes or similar projections 3a is rotatably arranged, the jacket surface of which communicates with the inner part of the channel 1 at an opening in the upper wall 1a of the channel. The direction of rotation of the jacket surface at the opening is the same as the direction of air flow F, and. the roller 3 thus feeds the fibers to the opening by means of its spikes, where the air flowing in the duct draws them 6 95156 according to it. Also at this point it is possible to create turbulence in the air flow F due to the fact that the roller 3 extending at the opening into the inner part of the duct reduces the cross-sectional area of the duct. This causes a slight turbulence at the last feed point C just before the diffuser 6. This turbulence is completely sufficient for the flexible fibers fed at this point, and there is no need to use turbulence-inducing means thereafter.

10

Figure 1 further shows a feed roll 4 adjacent to the roll 3, the opposite rolls of which feed the fibers towards the surface of the roll 3 at a point in the direction of rotation of the roll before the point 15 connected to the channel 1.

Figure 2 also shows the structure of the chokes. The chokes are located in the lower wall Ib of the air duct 1 and comprise a projection 20 towards the central part of the duct, the side facing the air flow being at a sufficiently steep angle to the air flow to produce the desired turbulence. The throttling members 2 are arranged to be movable against the longitudinal direction of the channel in the transverse direction to change the cross-sectional area of the channel 25 and consequently: to change the turbulence. In addition, the side against the air flow of the chokes causes a pressure shock to the rigid fibers, which opens the fibers even better. In particular, after two successive feed points A, B of the rigid fiber 30 (e.g. mineral fiber and glass fiber), it is preferable to use such a separate throttling member which ensures sufficient turbulence for the rigid fibers fed at these feed points to mix with each other.

35

The air duct can be formed as a closed duct with a cross-section * corresponding to the width of the carpet to be made, in the upper wall 1a of which 95156 are provided with openings for rollers 3 at the feed points and in the opposite lower wall Ib for throttle members 2 extending to the width of the duct.

5 The air flow F can be obtained with known solutions and its speed can be, for example, in the order of 30-100 m / s for rollers 3, but always higher than the surface speed of the roll. The rotational speed of the rollers can be such that its surface speed exceeds 30 m / s.

Claims (10)

A method of forming a mat containing different fiber types, wherein a method of different fiber types containing blend is deposited in the form of a mat by means of an air flow, wherein, to the same air flow (F), fibers are measured at two or more successive feeding sites ( A, B), characterized in that turbulence is generated in the air flow after the first of two successive feed sites for uniform mixing of fibers with each other at the latter feed point and the air flow (F) is led to a mat formation site (D). 15 2. A method according to claim 1, characterized in that for causing turbulence the fibers containing the air flow are throttled after two successive feeding sites (A, B). 20 A method according to claim 1 or 2, characterized in that stiffer fibers are measured in the air flow (F) before flexible fibers. Method according to any one of claims 1 to 3, characterized in that the fibers are measured to the air flow (F) with a rotating spikes or corresponding projections comprising nozzle (3). 5. Apparatus for forming a mat containing 30 different fiber types, comprising an air duct and in the prefabrication; bonding to this existing means for depositing a variety of fiber types containing mixture from the duct in the form of a mat, wherein to the same air duct (1) successively opens in the air flow direction two or more feeding points (A, B) of fibers, characterized in that in the duct (1) exists after the first of two. successive feeding points means (2, 3) to generate <au l am 1 i in M i! <95156 turbulence required for uniform mixing of fibers at the latter feeding site. 6. Apparatus according to claim 5, characterized in that, after some feed place (A, B) of fibers, means (2, 3) are provided which obstruct the air flow in the duct (1). 7. Apparatus according to claim 6, characterized in that the means (2) for throttling the air flow in the duct are located after two successive feeding points (A, B), and they are separate from the means of the fiber feeding site. 8. Device according to claim 7, characterized in that the throttling means (2) are arranged movable in a transverse direction towards the longitudinal direction of the duct to change the transverse area of the duct for adjusting turbulence. 20 Device according to any one of claims 5 to 8, characterized in that at the feed point of the fibers there is a rotatable device, spikes or corresponding projections comprising roll (3), the casing surface of which is connected at one point to the channel (1). . 10. Device according to claim 9, characterized in that in the direction of rotation of the roll (3) before the place connected to the channel (1) there is a feeding roll system (4) for feeding fibers to the roll (3). • *