Spreading device for spreading out fiber filament bundles and spreading method carried out using the same

1. A spreading device for spreading a fiber filament bundle to form a flat fiber band, the device comprising:

a first rotary shaft;

a plurality of first wings disposed about a circumference of the first rotary shaft and configured to rotate on the first rotary shaft, each of the first wings extending in an axial direction of the first rotary shaft and at least one of the first wings forming a first radial projection, the first radial projection having a first convexly bent spreading edge formed thereon, the first convexly bent spreading edge having at least one direction component perpendicular to a longitudinal extension of the fiber filament bundle including fibers to be spread apart relative to the first convexly bent spreading edge, the fiber filament bundle being configured to be placed under tension onto the first convexly bent spreading edge and thereafter being configured to be moved again with the at least one direction component such that the fiber filament bundle is released from the first convexly bent spreading edge;

a second rotary shaft; and

a plurality of second wings disposed about a circumference of the second rotary shaft and configured to rotate on the second rotary shaft, each of the second wings extending in an axial direction of the second rotary shaft and at least one of the second wings forming a second radial projection, the second radial projection having at least one second convexly bent spreading edge formed thereon;

the first and second rotary shafts being configured to rotate in mutually opposite directions such that the first and second convexly bent spreading edges are movable from opposite directions toward the fiber filament bundle with one of the second wings extending between two of the first wings in a path of rotation of the first wings during rotation of the first and second rotary shafts to clamp the fiber filament bundle under tension with an alternating force between the first and second convexly bent spreading edges.

2. The spreading device according claim 1 , further comprising a gear transmission, wherein the first and second rotary shafts are mutually oppositely driven by the gear transmission.

3. The spreading device according to claim 1 , wherein

each of a group of the first wings forms a respective first radial projection having a first convexly bent spreading edge formed thereon, and each of a group of the second wings forms a respective second radial projection having a second convexly bent spreading edge formed thereon, the first and second convexly bent spreading edges having edge portions that are configured to be placed successively onto the fiber filament bundle such that the fibers are respectively spread apart between the first and second convexly bent spreading edges.

4. The spreading device according to claim 1 , further comprising a loosening device that is provided in the conveying direction of the fiber filament downstream of a spreading device that includes the first and second convexly bent spreading edges, the loosening device being configured to loosen the fiber filament bundle whose fibers have been spread by the first and second convexly bent spreading edges.

5. The spreading device according to claim 4 , wherein the loosening device includes a suction chamber.

6. The spreading device according to claim 1 , further comprising a plurality of downstream spreading devices that increases the spreading ratio.

7. The spreading device according to claim 1 , wherein the first and second convexly bent spreading edges are formed on radially outermost regions of the respective first and second radial projections.

8. The spreading device according to claim 1 , wherein

each of a group of the first wings form a first radial projection having a first straight spreading edge formed thereon; and

each of a group of the second wings form a second radial projection having a second straight spreading edge formed thereon.

9. A spreading method for spreading a fiber filament bundle to form a flat fiber strand, comprising:

providing a first rotary shaft comprising a plurality of first wings disposed about a circumference of a first rotary shaft and configured to rotate on the first rotary shaft, each of the first wings extending in an axial direction of the first rotary shaft and at least one of the first wings forming a first radial projection, the first radial projection having a first convexly bent spreading edge formed thereon;

providing a plurality of second wings disposed about a circumference of a second rotary shaft and configured to rotate on the second rotary shaft, each of the second wings extending in an axial direction of the second rotary shaft and at least one of the second wings forming a second radial projection, the second radial projection having at least one second convexly bent spreading edge formed thereon; and

rotating the first and second rotary shafts in mutually opposite directions such that the first and second convexly bent spreading edges are movable from opposite directions toward the fiber filament bundle with one of the second wings extending between two of the first wings in a path of rotation of the first wings during rotation of the first and second rotary shafts to clamp the fiber filament bundle under tension with an alternating force between the first and second convexly bent spreading edges.