Apparatus and method for straightening filaments

1. A filament straightening apparatus, comprising:

a filament conveyor configured for transporting filaments;

a heating device comprising a heating channel forming a transport path for the filaments; and

a cooling device arranged downstream of the heating device in a direction of transport, comprising a cooling channel that continues the transport path for the filaments,

wherein cross-sectional areas of the heating channel and the cooling channel at least partially overlap,

wherein the heating device further comprises a first gas supply device structured and arranged to admit a hot gas flow to the heating channel, and

wherein the heating device further comprises a bypass and a switchover device structured and arranged to switch the hot gas flow from the heating channel to the bypass.

2. The apparatus according to claim 1 , wherein the filaments are plastic filaments.

3. The apparatus according to claim 1 , wherein the heating device further comprises a second gas supply device structured and arranged to admit a cold gas flow to the heating channel.

4. The apparatus according to claim 3 , wherein the cooling device further comprises a third gas supply device structured and arranged to admit a cold gas flow to the cooling channel.

5. The apparatus according to claim 4 , wherein at least one of the first gas supply device, the second gas supply device and the third gas supply device is structured and arranged to admit its respective gas under pressure in an axial direction of its respective channel.

6. The apparatus according to claim 1 , wherein the heating channel is formed from a material having a specific heat capacity and a coefficient of thermal conductivity so that a further heating the filament after the hot gas has been diverted to the bypass.

7. The apparatus according to claim 6 , wherein the material comprises fiberglass-reinforced plastic or silicate foam.

8. The apparatus according to claim 1 , wherein the heating channel has drag coefficients matched to drag coefficients of the bypass.

9. The apparatus according to claim 1 , further comprising a recess, which is arranged between the heating device and the cooling device, and through which the transport path for the filament extends.

10. The apparatus according to claim 9 , further comprising at least one of:

a first noise reducing device, which is located at an end of the heating channel facing the recess, and which is structured to continue the transport path for the filament, and

a second noise reducing device, which is located at an end of the cooling device opposite the recess, and which is structured to continue the transport path for the filament.

11. The apparatus according to claim 1 , wherein the filament conveyor comprises a transport roller pair.

12. A method for producing straightened filaments in a filament straightening apparatus, wherein the filament straightening apparatus comprises:

a filament conveyor configured for transporting filaments;

a heating device comprising a heating channel forming a transport path for the filaments; and

a cooling device arranged downstream of the heating device in a direction of transport, comprising a cooling channel that continues the transport path for the filaments,

wherein the cross-sectional areas of the heating channel and the cooling channel at least partially overlap,

wherein the heating device further comprises a first gas supply device structured and arranged to admit a hot gas flow to the heating channel, and

wherein the heating device further comprises a bypass and a switchover device structured and arranged to switch the hot gas flow from the heating channel to the bypass, the method comprising:

transporting, in a direction of transport, a filament through the heating channel of the heating device via the filament conveyor;

heating, via the hot gas flow from the first gas supply, the heating channel during the transporting of the filament through the heating channel;

transporting, in the direction of transport, the heated filament through the cooling channel of the cooled cooling device; and

switching, via the switchover device, the hot gas flow from the heating channel to the bypass.