GB2081438A - Non-contact volumetric monitoring device - Google Patents

Abstract

A device for measurement and/or control of the volumetric flow in a mass (6) of material is characterised in that it includes comprises a non-contact speed measuring means (1) in combination with a non-contact measuring means (2), such as a visual angle measuring means or a width measuring means, where the measurement takes place directly on the object, for example for measuring diameter, edge, width, and the like, the output signals of said two measuring means being supplied to a computing device (3) for the volumetric flow, the output signals of which are a measure of this flow and may be supplied to a control device (5) for regulating the volumetric flow which the device is especially adapted for use in connection with materials which are difficult to handle, such as molten glass, corrosive fluids or bar material in a plastic state. <IMAGE>

Description

SPECIFICATION Non-contact volumetric monitoring device Technical Field This invention relates to an improved non-contact device for monitoring the volumetric flow, past a measuring station, of a coherent mass of material.

The invention finds particular utility in the determination of volumetric flow of materials which because of their temperature, their corrosive properties, their frangibility or their ready deformability, prevent the use of sensing devices which contact the material.

In a number of industrial processes, the need arises to determine the volumetric flow of a material past a measuring station. Such a determination could be used to meter desired volumes into containers orto control some processing condition upstream of the measuring station to ensure that a product produced directly from the stream of material has a uniform cross-section. Examples of the latter case would be extrusion of a strand of molten glass from a nozzle or the rolling of bar or strip material in a plastic state. However, no such contactless volumetric monitoring device is known which can make such a determination.

BackgroundArt It is known to provide contactless measurement of the longitudinal speed of advance of a moving strand during manufacture, but the changes in the area of the strand are not then taken into consider~ tion.

It is also known to measure a transverse dimension of an object by an optical system, but in this case the speed of the object has not been taken into consideration.

Disclosure ofthe Invention According to the present invention there is provided a device for monitoring volumetric flow, past a measuring station, of a coherent mass of material, which device comprises, a first sensing means adapted to sense the speed of advance of the coherent mass of material past the station without making contact with the said mass and to produce an output signal related to the sensed speed, a second sensing means adapted to sense a dimension of the mass transverse to the direction of advance without making contact with the said mass and to produce an output signal related to the sensed dimension, and a computing means adapted to receive the said output signals and to generate therefrom a further output signal which is a measure of the volumetric flow of the said material past the station.

The second sensing means can be a visual angle measuring means or some other optical width measuring means, where measurement takes place directly on the object, for example for measuring the diameter, the position of the edges or the width. The cross-sectional geometry of the coherent mass to be measured would normally be known (e.g. a rectangular or circular cross-section), so a measure of the cross-sectional area of the mass is obtained by means of the second sensing means. The further output signal from the computing means can be used as a regulating input signal for regulating the cross-sectional area of the mass.

Brief Description of Drawing The invention will be exemplified in greater detail with reference to the accompanying drawing, in which: Figure 1 is a schematic representation of a device according to the invention which is adapted to generate a signal proportional to volumetric flow of a moving strand, Figure 2 is a modification of Figure 1 showing how the output from the device controls the strand, and Figure 3 and 4 are schematic representations of how the measuring means used in the devices of Figures 1 and 2 operate.

Description of Preferred Embodiments In Figures 1 and 2, 6 represents a moving coherent mass of material which is forming a strand whose speed and width are sensed in a speed measuring means 1 and a width measuring means 2.

The strand 6 may have a natural radiation, for example glass with a temperature exceeding 750"C or a hot-rolled rod, but the invention can also be applied to illuminated objects with the aid of separate sources of illumination.

Molten glass, for example, is obtained in the form of a strand coming from a nozzle with heating means (induction coil, resistance heater, gas or oil heater).

The heater is controlled by means of the measure of the volumetric flowwith a view to obtaining a constant volumetric flow and/or area for the object.

In Figures 1 and 2, the numeral 1 designates a non-contact speed measuring means, for example a correlation speed measuring means of the kind QGLK 100 available from ASEA AB of Västerås, Sweden, which produces a signal vfrom a signal a which is proportional to the speed of the strand 6.

The unit 1 is shown in greater detail in Figure 3.

The numeral 2 of Figures 1 and 2 represents a non-contact visual angle measuring means, of the kind QGLF 106 also available from ASEAAB of Västerås, Sweden and this gives an output signal which is a measure of the width b or the diameter d, of the strand 6 and from these measures, with knowledge of the cross-section of the strand 6, the cross-sectional area is obtained. The unit 2 is shown in greater detail in Figure 4, but it is also possible to use a different width measuring means.

The transducer means 2 measures the positions of the two edges of the strand 6 and the time delay between detecting these edges during the sweeping of the measuring means provides a measure of the angle a which is related to the width of the strand. It may be the natural radiation emitted by the strand which is used or the strand may be illuminated. A high accuracy of the measured value may be obtained.

The signals vand dib from the means 1 and 2 are supplied to a computing means 3, the output signal of which is a measure of the volumetric flow .

Figure 2 shows the same measuring means 1,2 as in Figure 1. The signal (p for volumetric flow is compared with a reference 4)ref and the error signal AX is supplied to a power unit 4 (e.g. thyristorised), which is used for controlling an adjusting device 5 for the strand 6, for example for setting the temperature of the material as it reaches the extrusion nozzle to obtain a constant volumetric flow past the measuring station defined by the units 1,2 and 3.

The flow rate and the angle of vision or the width, or some other measure of the cross-sectional area of a flowing stream of liquid can be measured in a similar contactless manner, to monitor, for example, the flow of a corrosive fluid into a vessel. A similar device can be used when advancing a strand or wire or rod, for example during rolling or drawing.

Control of the volumetric flow in the case of a flowing liquid can be carried out by means of valve members or by means of feeding pumps. During rolling or drawing, the control can be performed through normal roll parameters, and, for example during glass manufacture, by variation of the heat at the extrusion nozzle, and during paper manufacture the control of pulp slurry flow is performed at the inlet box, valve members or pumps.

Figure 3 shows how the device 1 senses the surface structure visible on the strand 6 at two points spaced apart a distance L. The surface structure, in the case of a red hot rod will vary from moment to moment in a random manner but a particular structure will persist for long enough to enable it to be used for speed determination. Figure 3 also shows the plots of light intensity against time for the signal Si received at the first point and the signal S2 received at the second point. It will be seen that the patterns of the two signals are similar enough to be able to identify the time shift T between a characteristic feature in the two signals.

Knowing L, the speed V of the strand 6 can be computed as V = LIT.

Figure 4 shows how the device 2 senses the width from a measure of a. A photosensitive detector 12 located in the center of a rotating lens drum 11 periodically receives an image of the strand 6, as the four lenses 10 in the drum pass between the detector 12 and the strand 6. A synchronous motor 13 drives the drum, so that the pulses emitted from an amplifier 14 connected to the detector 12 have a width which is related to the angle a subtended by the strand 6 and the leading and trailing edge of each pulse have phase positions, relative to the synchronising signal feeding the motor 13, which indicate their position in the field of view of the device 2.

The devices described above may be varied in many ways within the scope of the following claims.

Claims (9)

1. A device for monitoring volumetric flow, past a measuring station, of a coherent mass of material, which device comprises, a first sensing means adapted to sense the speed of advance of the coherent mass of material past the station without making contact with the said mass and to produce an output signal related to the sensed speed, a second sensing means adapted to sense a dimension of the mass transverse to the direction of advance without making contact with thq said mass and to produce an output signal related to the sensed dimension, and a computing means adapted to receive the said output signals and to generate therefrom a further output signal which is a measure of the volumetric flow of the said material past the station.

2. A device as claimed in claim 1, in which the further output feeds a visual display to give a direct indication of the flow.

3. A device as claimed in claim 1, in which the - further output is fed to a control device acting to regulate the volumetric flow upstream of the station.

4. A device as claimed in any of claims 1,2 or 3, in which the first sensing means comprises a sensor optically scanning the mass of material and generating a signal reflecting variations in surface-structure of the coherent mass, and an electronic circuit correlating the surface structure signals observed at two different times to determine the advance of a surface feature in the time interval between said two times.

5. A device as claimed in any preceding claim, in which the second sensing means comprises a photoelectric detector across which detector is periodically swept an image of the mass of material and electronic circuitry to generate an output voltage proportional to the time taken in sweeping the image past the detector.

6. A device as claimed in claim 5, in which the detector is located in the center of a rotating lens drum.

7. A device as claimed in any preceding claim, in which the first and second sensing means are adapted to be sensitive to the natural electromagnetic radiation emitted by the mass of material.

8. A device for monitoring volumetric flow substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawing.

9. A device for monitoring volumetric flow substantially as hereinbefore described with reference to Figure 1 or Figure 2 incorporating a sensing means as shown in Figure 3 and/or Figure 4.