Method for determining the temperature of a strand

Abstract

A method for determining the temperature of a strand comprises disposing the strand along a background radiator of known temperature. Receiving the strand using a spatially resolving thermal imaging sensor in front of the background radiator while the strand is being disposed along its longitudinal axis. Forming an integral across a measuring value area, the integral configured to detect a complete strand portion located in front of the background radiator of the thermal imaging sensor. deducing the temperature of the strand by comparing the formed integral with a reference value.

Claims

1. A method for determining a temperature of a thin vibrating strand of known diameter, the method comprising: disposing the thin vibrating strand along a background radiator of known temperature, the strand being oriented along its longitudinal axis; receiving the strand using a spatially resolving thermal imaging sensor in front of the background radiator while the strand is being disposed along its longitudinal axis, the spatially resolving imaging sensor forming a measuring value area; detecting a complete width of the strand in the measuring value area that is in front of the background radiator and at least a portion of the background radiator behind the strand; forming an integral across the measuring value area; and deducing the temperature of the strand by comparing the formed integral with an integral of the measuring value area without the strand positioned in front of the background radiator.

2. The method according to claim 1, wherein the background radiator is a near black-body radiator.

3. The method according to claim 1, wherein a temperature of the background radiator is measured by means of a temperature-measuring apparatus.

4. The method according to claim 1, wherein the background radiator is heated to a predetermined temperature by means of a heating apparatus.

5. The method according to claim 1, wherein the temperature of the strand is further deduced by taking into account an assumed or measured diameter of the strand.

6. The method according to claim 1, wherein the temperature of the strand is further deduced by taking into account an assumed or measured emissivity of the strand.

7. The method according to claim 1, wherein the strand is substantially surrounded by the background radiator.

8. The method according to claim 7, wherein the background radiator is a cavity radiator with an inlet opening and an outlet opening, wherein the strand is disposed through the inlet opening and the outlet opening and through the cavity radiator, and wherein the cavity radiator comprises at least one measuring opening through which the spatially resolving thermal imaging sensor detects the strand in front of an inner wall of the background radiator.

9. The method according to claim 1, wherein a whole measuring area of the thermal imaging sensor is selected as the measuring value area.

10. The method according to claim 1, wherein the thermal imaging sensor is an infrared thermal imaging camera.

11. The method according to claim 1, wherein the strand comprises a glass fibre or a metal wire.

12. The method according to claim 1, wherein the strand comprises a diameter of less than 500 m.

13. The method according to claim 1, wherein the strand comprises a diameter of less than 150 m.

14. The method according to claim 1, wherein the strand is cooled in a cooling apparatus.

15. The method according to claim 14, wherein the strand is cooled before or after it is disposed along the background radiator.

16. The method according to claim 14, wherein the cooling apparatus is a helium cooling apparatus.

17. The method according to claim 1, wherein the strand is provided with a coating in a coating apparatus after being disposed along the background radiator.

18. A glass fibre drawing tower configured to carry out the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention is explained in greater detail in the following figures. The figures show schematically:

(2) FIG. 1 illustrates a top schematic view or an embodiment of a measuring arrangement;

(3) FIG. 2 illustrates a side schematic view of the embodiment of the measuring arrangement from FIG. 1;

(4) FIG. 3 illustrates two theoretical measuring results from the embodiment of the measuring arrangement of FIG. 1;

(5) FIG. 4 illustrates two integrals formed or taken from the theoretical measuring results from FIG. 3;

(6) FIG. 5 illustrates an example of two real strand temperature measurements from an embodiment of the measuring arrangement; and

(7) FIG. 6 illustrates a comparison between the disclosed strand temperature measuring method and a strand temperature measurement method according to the prior art.

(8) Unless otherwise stated, in the figures the same reference numbers denote the same objects.

DETAILED DESCRIPTION OF THE INVENTION

(9) FIGS. 1 and 2 show a measuring arrangement for carrying out the method according to the invention. A circular cylindrical strand, for example a metal wire or a glass fibre, guided through the measuring arrangement, is shown in sections next to reference number 10. A thermal imaging sensor 12 with a lens system 14, here a lens 14, detects the strand 10 in front of a background radiator 16, here a substantially black-body radiator. The temperature of the background radiator 16 is determined by a temperature sensor 18.

(10) During the conveying along the background radiator 16, the strand 10 is received in front of the background radiator 16 by the thermal imaging sensor 12, for example an infrared line sensor or surface sensor 12. An evaluation apparatus not shown in greater detail in the figures determines the integral across the whole of the measuring area of the thermal imaging sensor 12, for example as measuring value area, and forms the difference between this integral and a reference value. In the present example, the integral across the measuring value area can be selected as a reference value, without strand 10 guided through the measuring arrangement. Given the known diameter and emissivity of strand 10, based thereon and taking into account the temperature of the background radiator 16 measured using the temperature sensor 18, the temperature of the strand 10 can be reliably and accurately determined in the manner according to the invention.

(11) This is to be explained in even greater detail by means of the diagrams in FIGS. 3 to 6. Given the same strand and same temperature, FIG. 3 shows the theoretical progress of the measuring signal along the x direction in FIGS. 1 and 2 next to the reference number 20 for a stationary strand 10 on the one hand, and next to reference number 22 for an oscillating strand 10. The temperature measured by the thermal imaging sensor is applied over the entire area. It can be understood that the maximum values of both the curves applied in FIG. 3 differ considerably, although the strand has the same temperature in both cases. This means that the evaluation of the maximum value for a temperature determination entails a considerable measuring error.

(12) Next to the reference number 24, FIG. 4 shows the integral across the curve 20 from FIG. 3, and next to the reference number 26 the integral across the curve 22 from FIG. 3. The integral results in the area of each surface below the curves 24, 26. The fact that the surface content below the curves 24, 26 is practically identical is clear in FIG. 4, so that determining the temperature based on the integral is independent of the oscillation of the strand 10 or respectively a blurring due to movement.

(13) Real measuring values are applied in FIG. 5 by way of illustration. The progress of a measuring value for a good focusing and a stationary strand is shown next to the reference number 20. Given the same temperature and same strand 10, the progress of a measuring value for a poor focusing, or respectively a vibration of the strand 10, is shown next to reference number 22.

(14) Next to the reference number 28, the diagram in FIG. 6 shows the resulting temperature values according to the method of the prior art with an evaluation of the maximum of the measuring curve for the same strand and same strand temperature, but in FIG. 1 with the position of the strand 10 changing in z direction, that is, in the direction towards the thermal imaging sensor 12 or away from the thermal imaging sensor 12. It can be understood that the changing position of the strand 10 with respect to the focus of the thermal imaging sensor 12 and its lens 14 produces considerable deviations from the determined temperature value. In other words, the temperature value determined during an evaluation of the maximum of the measuring curves shown in FIG. 5 greatly depends on the position of the strand 10 with respect to the focusing level of the thermal imaging sensor 12 and its lens 14.

(15) The same progress of the temperature measuring value for the method according to the invention is shown next to the reference number 30. In this case it is clear that the position of the strand 10 in z direction with respect to the focusing level of the thermal imaging sensor 12 and its lens 14 has no appreciable influence on the result of the temperature determination according to the invention.