WO2011142658A2

WO2011142658A2 - A method and a system for producing a mat of fibrous material

Info

Publication number: WO2011142658A2
Application number: PCT/NL2011/000039
Authority: WO
Inventors: Willem Frans Van Der Mast
Original assignee: Willem Frans Van Der Mast
Priority date: 2010-05-12
Filing date: 2011-05-11
Publication date: 2011-11-17
Also published as: WO2011142658A3; NL1037958C2

Abstract

A method and a system for producing a mat (30) of fibrous material, whereby at least one fibre supply unit (10) supplies a fibre (8,9) to a moving surface (19) located underneath the fibre supply unit (10). The fibre supply unit (10) makes a reciprocating rotating movement around an axis (22). The distance between the center of gravity of the fibre supply unit (10) and said axis (22) is less than half the distance between the fibre supply unit (10) and the moving surface (19).

Description

A method and a system for producing a mat of fibrous material

The invention is related to a method for producing a mat of fibrous material, whereby at least one fibre supply unit supplies a fibre to a moving surface located underneath the fibre supply unit. In this specification a "fibre" is defined as a continuous fibre or filament, or an assembly of a number of such fibres or filaments that may stick to each other, or a fibre or fibres having a limited length. The moving surface can be flat or curved depending on the desired shape of the mat to be produced. It can be the flat surface of a moving belt of a conveyor or, for example, it can be the outer surface of a tube or pipe rotating and/or translating underneath the fibre supply unit. In such way the tube or pipe can be reinforced by the fibres during its manufacturing.

In general, a fibre mat can be used to reinforce a plastic object, whereby the fibre mat is embedded in the plastic material, in order to form a plastic composite construction. The fibre can be a glass fibre or a fibre of other material, such as basalt, quartz, silica, carbon, nylon, polypropylene, polyester or other materials or combination of materials. The stiffness and strength of a composite construction is mainly determined by the presence of the reinforcing fibres. The fibres in the composite construction may be continuous fibres or may be cut into predetermined lengths.

For the production of a mat fibres may be used that have to be "opened", which means to fall apart into separate fibres, in order to make a fine mat composition of fibres, providing more strength and a nicer surface in the composite material that is to be reinforced by the mat.

In general, the distribution of the fibres in the mat has to be homogeneous. The "homogeneity", or uniformity of the density, of the fibres in the mat is defined by the variation of its weight per unit of surface, for example plus or minus 10% around the average weight of the mat layer per square decimetre.

Publication EP-A-0428063 describes a method for producing a continuous fibre mat, whereby one or more fibre supply units are positioned above a moving surface. The fibre supply units are traversed back and forth above the moving surface parallel to one another and in a direction perpendicular to the direction of motion of the moving surface. Fibres are pulled by the fibre supply units from a fibre supply source, such as a plurality of spools with fibres or strands, or just one spool with fibre. Each fibre supply unit provides the pulling force necessary to advance the fibres from the fibre supply source and eventually deposits the fibre upon the moving surface. In the operation of this system, the configuration of the equipment has inherent limitations on its performance. In general, a fibre supply unit has a weight of usually 5 to 15 kg. This weight limits the variations of the applicable traversing speed, and the impact forces at each reversal of direction must be overcome or absorbed somehow. These mechanical limitations on the traverse speed also limit the rate of mat production.

According to EP-A-0428063, mechanical vibrations and wear of the system caused by the movement of the fibre supply units are decreased by means of an improved control of the speed variations of the fibre supply units.

An object of the invention is a method for producing a mat of fibrous material, whereby at least one fibre supply unit supplies a fibre to a moving surface located underneath the fibre supply unit, and whereby relatively low mechanical forces are required to move the fibre supply units.

Another object of the invention is a method for producing a mat of fibrous material, whereby the control of depositing fibres on the moving surface can be improved, so that a more uniform fibre density of the mat can be achieved.

In order to accomplish with one or both these objects, the fibre supply unit makes a reciprocating rotating movement around an axis, whereby the distance between the center of gravity of the fibre supply unit and said axis is less than half the distance between the fibre supply unit and the moving surface. By rotating the fibre supply unit around an axis located relatively near the center of gravity of the fibre supply unit, the mechanical forces required for moving the fibre supply unit are much lower than the forces being required to move the unit along a straight line. Furthermore is has been found that the location where a fibre is dropped on the moving surface is more precisely controllable in case of a rotating movement of the fibre supply unit in stead of a movement of the unit in a straight line.

In a preferred embodiment, the fibre supply unit comprises rollers rotating in opposite directions and forming a pinch whereby the fibre passes the pinch, and whereby, preferably, the circumferential surface of each roller is provided with ribs in axial direction so that said circumferential surfaces engage each other, so that the fibre passing through the pinch is zigzag bended. The pair of rotating rollers pulls the fibre from the fibre supply source and supplies the fibre towards the moving surface. Preferably, each fibre supply unit is provided with a drive motor. The ribs of each rollers engage like the teeth of two cooperating gear wheels, so that only one roller has to be driven by the drive motor. Thereby, the fibre is bent over the ribs and forced into a zigzag shape between the rollers. This zigzag movement may cause the fibre to be opened into separate fibres. After having passed the fibre supply unit fibres tend to stay in bends or curl on their way from to the moving surface, and shapes randomly curls in the mat on said surface.

In a preferred embodiment, the fibre supply unit supplies a substantially continuous fibre to the moving surface, and in another preferred embodiment, the fibre supply unit cuts a continuous fibre into pieces, so that fibres of limited length are dropped on the moving surface. Thereby, the rollers are provided with knives in order to cut the passing fibre into pieces. A device for applying such method is described in EP-A-1723272.

Preferably, the distance between the center of gravity of the fibre supply unit and said axis is less than 0.3, more preferably less than 0.1 times the distance between the fibre supply unit and the moving surface. In a preferred embodiment, said axis is located through the fibre supply unit. The lowest mechanical force to rotate the fibre supply unit is achieved when the axis around which the fibre supply unit rotates is located through said center of gravity, but the forces are relatively low when said axis is located near said center of gravity.

In a preferred embodiment, the angle between the plane of said moving surface at the location where the fibre is dropped and said axis is less than 45°, preferably less than 10°, whereby the fibre supply unit preferably directs the supplied fibres in a plane perpendicular with respect to said axis. Thereby, the fibres are moving towards the moving surface in a substantially straight path.

Preferably, the velocity of the fibre leaving the fibre supply unit is larger than

200m/min, preferably larger than 300m/min, and more preferably larger than 400m/min, which speed appeared to result in a satisfactory movement of the fibres towards the moving surface.

The invention is also related to a system for applying the method as described above, comprising at least one fibre supply unit and a moving surface being located underneath said fibre supply unit, wherein the fibre supply unit can make a reciprocating rotating movement around an axis, whereby the distance between the center of gravity of the fibre supply unit and said axis is less than half the distance between the fibre supply unit and the moving surface.

The invention will now be further elucidated by means of a description of a system for producing a mat of fibrous material comprising four fibre supply units above the moving surface of a conveyor, whereby reference is made to the drawing, comprising four figures, whereby: Fig. 1 is a front view of a fibre supply unit;

Fig. 2 is a side view of the fibre supply unit;

Fig. 3 shows a part of the pair of rollers in more detail, and

Fig. 4 is a perspective view of the mat producing system.

The figures are merely schematic representations, only showing parts that contribute to the elucidation of the method applied when operating the system, and whereby like parts are indicated by the same numerals.

Figure 1 shows a fibre supply 10 unit in front view. Roller 1 is mounted on shaft 3, which shaft is the motor shaft of the motor 11 (figure 2) driving roller 1. the circumferential surface 5 of roller 1 is provided with ribs 13 in axial direction, which ribs 13 engage with corresponding ribs 14 on the circumferential surface 6 of roller 2, which roller 2 is driven by the engagement with roller 1. The two rollers 1 ,2 rotate in directions indicated by arrows 15,16 around the centrelines of there respective shafts 3 and 4. A fibre 8 is guided by means of a guiding pipe 12 into the pinch 7 between the two rollers 1,2. The fibre 8 is an assembly of continuous fibres and is bended zigzag in the pinch 7 by means of the ribs 13,14, so that the fibre 8 is opened into a number of separate fibres 9. A usual diameter of the rollers 1,2 is between 40mm and 150mm, and the two rollers 1,2 may have a different diameter.

Figure 2 is a side view of the fibre supply unit 10 of figure 1 , showing motor 1 1 and its shaft 3, on which shaft 3 roller 1 is mounted.

Figure 3 shows a detail of the pair of rollers 1 ,2. Preferably, at least one of the rollers

1,2 is provided with an elastic material 15 around its circumference to ensure smooth running and clamping of the fibre 8. It is also preferred to make the outward top of the ribs 13,14 of a hard material 17 to prevent wear of the tips, whereby the grooves 18 between the top of the ribs 13,14 of an elastic material. The hard material 17 in the drawing is extended inwards to the core of the rollers 1,2.

Fig 4 is a general view of a mat producing machine, showing the assembly of four fibre supply units 10 and a horizontal surface 19 of a conveyor. Conveyor surface 19 is moving in a direction indicated by arrow 20 at a controlled velocity. Each of the four fibre supply units 10 is individually mounted at a shaft 21, which shaft 21 is supported by bearings 32 to enable them to rotate or pivot around axis 22. Axis 22 is situated preferably through or close to the center of gravity of the fibre supply unit 10. The fibre supply unit 10 is pivoting and wagging by shaft 21 over an arc-sector 23. The wagging movement is driven by rod 24 connected to levers 25, that are fixed to shaft 21. Arc-sectors 23 are equal to arc-sectors 26, both showing the area over which the fibre supply units 10 are wagging. Motor 27 is mounted on the support frame 29 and moves rod 28 in a reciprocating linear movement as indicated by the double sided arrow shown along rod 28. Rod 28 is connected with rod 24 in order to drive rod 24 in its reciprocating movement. Preferably, the arc-sectors 23 and 26 are smaller than 60°. In an alternative embodiment, each fibre supply unit is driven by a separate motor 27, so that the wagging movements of the fibre supply units 10 have different arc-sectors 23,26.

Conveyor surface 19 passes underneath the fibre supply units 10. Preferably, the distance between the fibre supply units 10 and the conveyor surface 19 is 50cm or more.

Each fibre supply units 10 is pulling one or more fibres 8, via one or more inlet guides 12 that are fixed at the fibre supply unit 10. The fibre bundle 9 exits the fibre supply unit 10 in a direction preferably substantially perpendicular to the pivoting axis 22 and is projected towards the conveyor surface 19, in order to form a mat 30. By the wagging movement over arc-sector 26 and the conveyor surface movement 20 the fibre is projected in bands 31 on the conveyor surface 19 forming mat 30. In figure 4 the mat 30 is only represented schematically to show the pattern of the deposited fibres. In the system of figure 4, the wagging speed is relatively high compared to the conveyor surface speed, so that the bands 31 will overlap each other and form a mat 30 with a homogeneous weight distribution. A wagging frequency of 2Hz has been found to work satisfactory.

While the invention has been illustrated in the drawing and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Any reference signs in the claims should not be construed as limiting the scope of the invention.

Claims

1. A method for producing a mat (30) of fibrous material, whereby at least one fibre supply unit (10) supplies a fibre (8,9) to a moving surface (19) located underneath the fibre supply unit (10), characterized in that the fibre supply unit (10) makes a reciprocating rotating movement around an axis (22), whereby the distance between the center of gravity of the fibre supply unit (10) and said axis (22) is less than half the distance between the fibre supply unit (10) and the moving surface (19). 2. A method as claimed in claim 1, characterized in that the fibre supply unit (10) comprises rollers (1,

2) rotating in opposite directions and forming a pinch (7), whereby the fibre (8,9) passes the pinch (7).

3. A method as claimed in claim 2, characterized in that the circumferential surface (5,6) of each roller (1,2) is provided with ribs (13,14) in axial direction so that said circumferential surfaces (5,6) engage each other, whereby the fibre (8,9) passing the pinch (7) is zigzag bended.

4. A method as claimed in any one of the preceding claims, characterized in that the fibre supply unit (10) supplies a substantially continuous fibre (8) to the moving surface (19).

5. A method as claimed in any one of claims 1-3, characterized in that the fibre supply unit (10) cuts a continuous fibre (8) into pieces, so that fibres (9) of limited length are dropped on the moving surface (19).

6. A method as claimed in any one of the preceding claims, characterized in that the distance between the center of gravity of the fibre supply unit (10) and said axis (22) is less than 0.3, preferably less than 0.1 times the distance between the fibre supply unit (10) and the moving surface (19).

7. A method as claimed in any one of the preceding claims, characterized in that said axis (22) is located through the fibre supply unit (10).

8. A method as claimed in any one of the preceding claims, characterized in that the angle between the plane of said moving surface (19) at the location where the fibre is dropped and said axis (22) is less than 45°, preferably less than 10°.

9. A method as claimed in any one of the preceding claims, characterized in that the velocity of the fibre (9) leaving the fibre supply unit (10) is larger than 200m/min, preferably larger than 300m/min, and more preferably larger than 400m/min.

10. A system for producing a mat (30) of fibrous material comprising at least one fibre supply unit (10) and a conveyor having a moving surface (19) being located underneath said fibre supply unit (10), characterized in that the fibre supply unit (10) can make a reciprocating rotating movement around an axis (22), whereby the distance between the center of gravity of the fibre supply unit (10) and said axis (22) is less than half the distance between the fibre supply unit (10) and the moving surface (19).