Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
  • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material

Definitions

• the present invention relates to a device and to a method for non-destructive and continuous measurement and / or control of the thickness of a profile.
• the present invention provides a method and a device for non-destructive and continuous measurement and / or control of the thickness of a profile overcoming the drawbacks of the methods of the prior art.
• the method and the device according to the invention easily apply to the case of corrugated profiles whatever the shape and amplitude of the corrugations.
• the method of the invention is based on the measurement of the radiation emitted by the profile during a heating phase or a cooling phase.
• a material of substantially homogeneous density cools, or heats up, the more quickly the less its thickness.
• the radiation emitted by the profile during a thermal transient regime that is to say during its heating or at during its cooling, it is possible to observe or measure continuously thicknesses or variations in thickness.
• a material of substantially homogeneous density emits radiation, in particular infrared, whose power is proportional to the fourth power of its surface temperature.
• the evolution of the surface temperature depends on the thickness of the profile.
• each variation in thickness corresponds to different surface temperatures, therefore radiation emissions, in particular infrared radiation of different powers.
• This phenomenon is more marked for materials having a low thermal conductivity, and for which the cooling or the heating is generally faster than the homogenization of the temperature within the material.
• the present invention makes it possible in particular, but not exclusively, to carry out a continuous, non-destructive control, by infrared camera, of the thickness of thermoplastic corrugated tubes constituting for example the core of reinforced corrugated tubes.
• the device for non-destructive and continuous measurement and / or control of the thickness of a profile, according to the present invention uses this physical phenomenon.
• the device according to the invention comprises in combination:
• the means for detecting and measuring the radiation emitted is connected to a means for recording the measurement of this radiation.
• the means for detecting and measuring the emitted radiation comprises an infrared camera connected to a display screen and / or to a computer system comprising image processing software.
• the computer system will preferably include means for storing the images. provided by the infrared camera and / or results provided by the image processing software.
• the device will comprise at least one means allowing the profile to travel, for example tracks, and at least one means allowing the synchronization of this travel with the scanning movement of the detection and measurement means. of the radiation emitted, so that the entire surface of the profile is scanned by said detection and measurement means.
• the device of the present invention can be used for non-destructive and continuous measurement and / or control of the thickness of a profile during its manufacture.
• the profile heating means consists of the device for shaping said profile.
• This shaping device can for example be an extruder, a pultruder machine die or any other device well known to those skilled in the art.
• the device of the present invention can be used for non-destructive and continuous measurement and / or control of the thickness of a profile before its use, for example at the time of its manufacture, but also after its manufacture or in a remote site. from its place of manufacture.
• the means of heating or reheating said profile is usually chosen from the group formed by electrical resistances, gaseous fluids or hot liquids and sources of heat by radiation (for example ramps of infrared lamps). .
• the heating may for example be obtained by circulation of a hot fluid, such as for example air, water, a mineral or organic oil, around said profile or in the case of a profile having the form of 'a tube, inside of it.
• the profile is most often heated so that its temperature is at least 50 ° C higher than ambient temperature in the area located at the level of the radiation detection and measurement means.
• the maximum heating temperature depends on the material or materials constituting said profile; it is most often at most equal to the profile formation temperature, for example the extrusion temperature of the thermoplastic material used which is most often about 160 to about 280 ° C.
• the position of the radiation detection and measurement means relative to that of the heating means depends both on the material of which the profile is made, on the temperature at which it is heated and on its average thickness.
• This detection and measurement means is preferably positioned at a point where the temperature of said profile is from about 50 ° C to about 140 ° C.
• the distance between this means and the profile itself is not critical and can be easily chosen by a person skilled in the art according to the characteristics of this detection and measurement means, and in particular according to its detection sensitivity.
• an alarm system may for example be controlled by the computer system, the image processing software of which can, after calibration, convert the measured temperatures into thicknesses. It is thus possible to set one or more thresholds or alarm levels. We could for example consider setting an alarm threshold for a thickness greater than a previously chosen value and an alarm threshold for a thickness less than a previously chosen value, or choose only one alarm threshold, for example for a thickness less than a previously chosen value.
• the means allowing the detection and measurement means to scan the entire surface of the profile can include a guide system such as for example a rail on which said detection and measurement means can be fixed so as to be mobile.
• the present invention also relates to a method of non-destructive and continuous measurement and / or control of the thickness of a profile, characterized in that it comprises in combination: the creation of a temperature variation of said profile up to at a temperature sufficient for said profile to emit radiation, and the detection and measurement, over the entire surface of said profile, of the radiation emitted by said profile.
• said profile is heated to a temperature such that it emits infrared radiation having a wavelength substantially between 2 and 25 micrometers and preferably between 2 and 5 micrometers.
• the method of the present invention comprises recording the radiation emitted by the profile, viewing and / or processing it using a computer system comprising image processing software.
• the method of the invention comprises scrolling the profile and recording the radiation emitted by synchronized scanning of the entire surface of the profile by the radiation detector.
• thermoplastic materials such as those made of polyethylene (PE), polypropylene (PP), polyamide (PA), polyvinyl chloride.
• thermoplastic materials may or may not be reinforced with fibers such as for example glass fibers, carbon fibers, or aromatic polyamides such as for example Kevlar (registered trademark). These materials all have a relatively low thermal conductivity and a high emissivity, especially in the range of wavelengths corresponding to infrared.
• the present method can be. applied to the control and measurement of the thickness of flat or tubular profiles having a substantially circular, oval, elliptical, rectangular section or any other shape defined by a closed curve. It is particularly well suited for checking or measuring the thickness of tubes or corrugated sheets.
• the undulations can have any shape and a very variable amplitude. These undulations are for example undulations of sinusoidal, square or rectangular section.
• the profiles usually have an average thickness of about 0.1 millimeter to about 20 millimeters and most often about 0.2 millimeter to about 10 millimeters.
• the device of the present invention is illustrated diagrammatically in FIG. 1 while FIG. 2 is a simplified visualization of a corrugated tube.
• the device according to the invention shown diagrammatically in FIG. 1, comprises an extrusion device 2 allowing the continuous extrusion of a tube 1, for example of substantially circular section and having undulations of sinusoidal section.
• the heating means 2e is in this case the extrusion apparatus itself.
• the tube moves along its longitudinal axis YY ', for example at substantially constant speed, and its surface is scanned by an infrared camera 3 positioned on a mobile carriage moving simultaneously on a rail 4 perpendicular to the axis YY' of the tube.
• the infrared camera is connected to a computer system 5 comprising a display screen 6.
• FIG. 2 is a visualization of a thickness control of a PVDF tube of average thickness equal to 1 millimeter.
• the device used to carry out this control is that shown diagrammatically in FIG. 1.
• the infrared camera used can be a camera known per se, for example a camera of the registered trademark THERMOVISION sold by the French company AGEMA, this camera is cooled to liquid nitrogen, and has a spectral band of 2 to 5 micrometers.
• the associated computer system can be a system marketed by the company AGEMA, referenced TIC-8000, comprising an IBM PC-AT computer and a program such as CATS-E developed by the company AGEMA for thermal analysis purposes.
• the screen printing reproduced in FIG. 2 is carried out using an inkjet printer known per se.
• the invention therefore consists in scanning the entire surface of the profile to be examined using an infrared camera 3, the profile then being in thermal transient, that is to say either during the heating period, or in cooling period, anyway emitting radiation capable of being detected by said camera.
• the computer system associated with the infrared camera 3 comprises in particular a means of recording the emitted radiation, a means of storing the images supplied by the camera, a means of processing said images, a means of storing the results supplied by the means image processing.
• each variation in thickness results in the appearance of a spot on the image of the profile viewed on the screen, a spot corresponding to a variation in color or in a variation grayscale for black and white screens.
• FIG. 2 shows a simplified screen display according to which one can see three spots A, B, C corresponding respectively to three faults.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Investigating Or Analyzing Materials Using Thermal Means (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Radiation Pyrometers (AREA)
• Length-Measuring Devices Using Wave Or Particle Radiation (AREA)
• Analysing Materials By The Use Of Radiation (AREA)
• Length Measuring Devices With Unspecified Measuring Means (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9418159

Family Applications (1)

Country Status (7)

Families Citing this family (21)

Citations (3)

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• 1991
  • 1991-10-21 FR FR9112989A patent/FR2682757A1/fr active Granted
• 1992
  • 1992-09-30 WO PCT/FR1992/000922 patent/WO1993008446A1/fr not_active Ceased
  • 1992-09-30 ES ES92921797T patent/ES2092132T3/es not_active Expired - Lifetime
  • 1992-09-30 US US08/078,310 patent/US5399016A/en not_active Expired - Fee Related
  • 1992-09-30 JP JP5507477A patent/JPH06503650A/ja active Pending
  • 1992-09-30 EP EP92921797A patent/EP0563356B1/fr not_active Expired - Lifetime
  • 1992-09-30 DE DE69212299T patent/DE69212299T2/de not_active Expired - Fee Related

Patent Citations (3)

Non-Patent Citations (1)

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