MOWING THREAD

Abstract

A mowing thread comprises a core comprising a bast fiber or a bio-degradable chemical fiber, and a shell around the core comprising a bio-degradable synthetic material.

Claims

1. Mowing thread, comprising a core comprising a bast fiber or a bio-degradable chemical fiber, and a shell around the core comprising a bio-degradable synthetic material.

2. Mowing thread according to claim 1, wherein the bast fiber is a hemp fiber or a flax fiber.

3. Mowing thread according to claim 1, wherein the bio-degradable chemical fiber is a Lyocell fiber.

4. Mowing thread according to claim 1, wherein the core comprises a fiber made from a bio-degradable synthetic material in addition to the bast fiber or in addition to the bio-degradable chemical fiber.

5. Mowing thread according to claim 4, wherein the additional fiber is manufactured from a different bio-degradable synthetic material than the bio-degradable chemical fiber.

6. Mowing thread according to claim 4, wherein the additional fiber is manufactured from the bio-degradable synthetic material the shell consists of or that is comprised in the shell.

7. Mowing thread according to claim 1, wherein the shell comprises a bio-degradable polymer material.

8. Mowing thread according to claim 7, wherein the shell comprises two or more of the following materials: polylactid acid (PLA), polybutylene succinate (PBS), thermoplastic starch (TPS), polybutylene adipate terephthalate (PBAT), polyhydroxyalknaoate (PHA), polyhydroxybutyrate (PHB), polycaprolactone (PCL), and Lignin.

9. Mowing thread according to claim 1, wherein the shell comprises biopolymers, preferably polylactide.

10. Mowing thread according to claim 1, wherein the bast fiber or the bio-degradable chemical fiber has a tensile strength exceeding a tensile strength of the shell.

11. Mowing thread according to claim 1, wherein the shell has a flexural stiffness and/or a shear stiffness exceeding the flexural stiffness and/or shear stiffness of the bast fiber or the bio-degradable chemical fiber.

12. Mowing thread according to claim 1, wherein the shell is manufactured from an extrudable synthetic material.

13. Mowing thread according to claim 1, wherein the shell is manufactured from a synthetic material having a melting temperature of more than 100 C.

14. Mowing thread according to claim 1, wherein the mowing thread has a diameter between 1 mm and 4 mm.

15. String trimmer, comprising a mowing thread according to claim 1.

16. Method for manufacturing a mowing thread, comprising providing a core, the core comprising at least a bast fiber or a bio-degradable chemical fiber, heating and extruding a bio-degradable synthetic material, and supplying the extrudate to the core for shaping a shell around the core.

17. Method according to claim 16, comprising conveying the core, supplying the extrudate to the core at a stationary position, the core passing the stationary position, wherein shaping means effect a uniform forming of the extrudate to the core, and wherein the shell is built by hardening the extrudate.

18. Method according to claim 16, wherein providing the core includes twisting or interweaving or interlacing of an additional fiber made from a bio-degradable synthetic material with the bast fiber or with the bio-degradable chemical fiber.

19. Method according to claim 18, wherein the additional fiber is manufactured from the same bio-degradable synthetic material the shell consists of or that is comprised in the shell.

20. Method according to claim 18, wherein a ratio of the additional fiber and the portion of the bast fiber or the bio-degradable chemical fiber is less than or equal to 1:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Consideration is given to the following detailed description of embodiments of the present invention. Such description makes reference to the annexed drawings, wherein:

[0059] FIG. 1 illustrates a mowing thread according to an embodiment of the present invention;

[0060] FIG. 2 illustrates a mowing thread according to a further embodiment of the present invention; and

[0061] FIG. 3 illustrates a method for manufacturing a mowing thread, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0062] FIG. 1 illustrates a mowing thread according to an embodiment of the present invention. The mowing thread 10 comprises a core 1 and a shell 2 around the core 1. Presently, core 1 and shell 2 are of circular cross section. However, different shapes of cross sections are possible.

[0063] It is schematically indicated that the core 1 comprises a bast fiber or a bio-degradable chemical fiber 11, respectively a multitude of such fibers 11. The individual fibers may twist around each other in a helical shape or are interwoven. The number of the individual fibers 11 is not representative. Presently, the mowing thread 10 comprises a Lyocell fiber as bio-degradable chemical fiber. The shell 2 around the core 1 is made from a bio-degradable synthetic material.

[0064] FIG. 2 illustrates a mowing thread according to a further embodiment of the present invention. The mowing thread 10 of FIG. 2 differs from the mowing thread of FIG. 1 in that the core 1 comprises additional fibers 12 of the same material the shell 2 is made from. It is schematically shown, that owing to the melting of the additional fiber 12 which is based on thermal conditions while applying the shell 2 to the core 1, these additional fibers 12 melt or fuse with the shell 2, and, hence, build a unity together with the shell 2. This effect increases bonds between the shell 2 and the core 1.

[0065] FIG. 3 schematically illustrates a method for manufacturing a mowing thread, according to an embodiment of the present invention. Reference sign 3 shows an extruder, such as a screw extruder or a ram extruder, wherein a screw or a ram serve for conveying the extrudate. Other than the heating 31, details such as screw or ram are not explicitly illustrated in FIG. 3. The extruder 3 is filled with an extrudable material, presently with a bio-degradable synthetic material 21. This synthetic material 21 is heated by means of the heater 31 beyond its melting point, and is conveyed by way of a conveyor of the extruder, i.e. the screw or the ram, in its soft of liquid state as extrudate to a shaping means 4.

[0066] The shaping means 4 presently is represented by a tube which comprises an inlet for the extrudate 22 at a stationary location x. At this location x, the extrudate 22 flows into the interior of the tube. The later core of the mowing thread is supplied into the tube by means of a not illustrated conveyor. The core 1 preferably is a bast fiber or a bio-degradable chemical fiber. Its supply into the tube/into the shaping means 4 is processed constantly, e.g. from an unwinding roll provided for the bast or chemical fiber. Electric motors, rolls, guides, alone or in combination may contribute to the conveyor, in particular draw rolls such as indicated by reference sign 6. It is preferred that the mowing thread 10 is conveyed by a tensioning force in direction F. Hereby, the core 1 is unwound from the not illustrated roll and is supplied to the shaping means 4. The shaping means 4 preferably comprises guides holding the core 1 centered in the tube. The flow of the extrudate 22 is schematically indicated by way of the bows at the outlet of the extruder 3, which flow adapts within the shaping means 4 to the core 1 owing to space limitations. In view of the shape of the tube, the extrudate 22 takes a circular circumference. The extrudate 22 hardens in a subsequent cooling 5, e.g. a water cooling, and, hence, forms a solid shell 2 around the core 1, resulting in a mowing thread 10 with a core 1 and a shell 2. The mowing thread 10 manufactured and conveyed by this method can be cut into the desired length by means of a cutting tool 7, or may be coiled onto a reel and only will later be cut into the desired length from the reel, e.g. in retail or elsewhere.

[0067] While there are shown and described presently preferred embodiments of the invention, it is to be dis-tinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practised within the scope of the following claims.