Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
  • G01M3/32—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators
  • G01M3/3218—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators for flexible or elastic containers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/36—Investigating fluid-tightness of structures by using fluid or vacuum by detecting change in dimensions of the structure being tested
  • G01M3/363—Investigating fluid-tightness of structures by using fluid or vacuum by detecting change in dimensions of the structure being tested the structure being removably mounted in a test cell
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/38—Investigating fluid-tightness of structures by using light

Definitions

• the invention relates to a method for leak detection on a flexible, non-rigid test specimen.
• Non-rigid specimens have a flexible structure that yields when pressure changes. Such specimens are, for example, food packaging. If the pressure difference between the internal pressure of the test specimen and its ambient pressure is too great, there is a risk that the test specimen will burst or at least be damaged.
• test specimens are filled with a test gas and the test gas in the exhaust stream of the pumping system, which is used to produce the required pressure differences is used, measured.
• the use of a particular test gas can be omitted if the sensor is adapted to the filling gas inside the test object. In this measurement method, influences of the ambient gas can falsify the measurement result.
• DE 10 2012 200 063 A1 describes a method for leak detection on a non-rigid test specimen which is contained in a foil chamber. After introducing the test specimen into the film chamber, the pressure in the film chamber is lowered in the region outside the test specimen. A leak in the test specimen is detected by means of a spatial change of the foil of the foil chamber. In this case, the change in the film position or a change in volume of the film chamber is measured.
• This method has the advantage that the tightness of the film chamber affects the measurement only insignificantly. It is only to achieve such a tightness of the film chamber, which allows the desired lowering of the pressure within the film chamber.
• the measurement of the spatial change can be made by laser-optical measurement of the position of the film surface, by measuring the capacitance change of a metallized film surface or by measuring a contact with the film surface.
• the content of DE 10 2012 200 063 A1 is incorporated by reference into the present application.
• the spatial change of the film can not be detected in particular at several simultaneously contained in the film chamber specimens which of the samples is leaking.
• the measurement accuracy depends on the variance of the volume from test item to test item.
• the invention has for its object to provide an improved method for leak detection on a flexible specimen in a foil chamber.
• the pressure in the film chamber outside the test object is lowered in such a way that at least a portion of the film conforms to the outer contour of the test object contained in the film chamber or the test objects contained in the film chamber.
• the outer contour of the specimen or the specimens is thereby transferred to the film.
• An imaging system captures this contour of the film.
• the recorded images of the film contour are compared with previously recorded, stored reference images, which were recorded in the case of a dense test object with otherwise identical boundary conditions of the measuring arrangement.
• the image taken by the image acquisition system is thus subjected to a nominal-actual comparison in order to detect leaky specimens.
• the film surface is provided with a grid formed, for example, by dots arranged in a grid (lattice structure) or by intersecting lines. In the case of points, these are arranged at the crossing points of an imaginary grid.
• the grating may be projected onto the film surface, for example by means of a laser or other optical system which images the grating by light on the film surface.
• grid lines are projected onto the film surface with the aid of a laser.
• the grid is firmly applied to the film surface, for example by printing, embossing, painting, etc.
• the recorded images are analyzed and evaluated.
• the contours and grids of each captured image are compared with the corresponding contours and grids of the previously recorded reference images.
• the time profile of the contour change is a measure of the leak rate in order to determine the leak rate of a recognized leak.
• an empty pumped test specimen in the case of a massive leak can be seen on the basis of the changed contour.
• a detected leak can be assigned to one of the samples.
• FIG. 1 shows a measuring arrangement for the application of the invention
• Figure 2 shows the contour of the film surface in the case of a leaking test specimen
• Figure 3 shows the contour of the film surface of a dense test specimen
• the measuring arrangement consists of a film chamber 10, in which a plurality of flexible, that is not dimensionally rigid specimens 12 are introduced in the form of food packaging. After introduction of the specimens 12 in the film chamber 10, this is closed, in which the two films forming the film chamber 14, 16 with the intervening specimens 12 are superimposed and pressed in the edge regions by a clamping device 18 airtight to each other.
• the film chamber is evacuated by a vacuum pump 20, which is connected via a valve 22 to the interior of the film chamber.
• the valve 22 is opened and a likewise connected to the interior of the film chamber 10 ventilation valve 24 is closed to the atmosphere.
• the pressure in the volume surrounding the specimens 12 within the foil chamber 10 is lowered by at least 100 mbar relative to the ambient pressure of the foil chamber 10.
• the valve 22 is closed and the pump 20 is deactivated.
• a grid 28 formed from intersecting lines is projected onto the surface of the film 14.
• the optical camera of an image acquisition system 26 With the optical camera of an image acquisition system 26, the provided with the grid 28 surface of the film 14 is filmed.
• the pressure within the film chamber 10 in the region outside the specimens 12 is lowered in such a way that the films 14, 16 conform to the outer contour of the specimens 12.
• the outer contour of the specimens 12 is pressed into the films 14, 16 and thereby transferred to the films 14, 16.
• the contour of the film surfaces of the films 14, 16 changed because gas escapes from the leaking specimen 12 and thereby changes its contour.
• the change in the contour of the films 14, 16 changes the shape of the screen 28 projected onto the films 14, 16 Change in the shape of the grating 28 can be seen in the images 30, 32 taken by the image acquisition system 26.
• the recorded images 30 are compared with previously recorded reference images 32 in the case of a dense specimen 12 or in the case of corresponding multiple dense specimens 12. It is crucial that the reference images 32 were taken for the same number and arrangement of the samples 12 as in the case of the tightness measurement.
• a desired-actual comparison can be performed and closed, for example, when exceeding a predetermined deviation from the contours in the reference images 32 to a leak become.
• the image acquisition system 26 is provided with an image processing and image recognition software for this purpose. Based on known image recognition algorithms, the evaluation of the recorded images takes place. In particular, it is thus recognizable which of several specimens contained in the foil chamber 12 is leaky.
• FIG. 2 shows the image 30 of the grating 28 in the case of a leaky specimen 12 of a plurality of specimens 12.
• FIG. 3 shows the previously recorded reference image 32 of the grating 28 with itself the number and arrangement of the specimens 12 as in FIG. 2 for the case of dense specimens 12.
• the situation illustrated in FIG. 3 serves as a reference for dense specimens 12, that is to say for recording a reference image 32, which is compared for later comparison with the images 30 taken during leak detection.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Examining Or Testing Airtightness (AREA)

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Citations (5)

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• 2016
  • 2016-01-29 DE DE102016201359.9A patent/DE102016201359A1/de not_active Withdrawn
• 2017
  • 2017-01-30 WO PCT/EP2017/051883 patent/WO2017129809A1/de not_active Ceased
  • 2017-01-30 BR BR112018014939-0A patent/BR112018014939B1/pt active IP Right Grant
  • 2017-01-30 AU AU2017213162A patent/AU2017213162B2/en active Active
  • 2017-01-30 US US16/072,308 patent/US10852212B2/en active Active
  • 2017-01-30 EP EP17702835.4A patent/EP3408636B1/de active Active
  • 2017-01-30 CN CN201780008526.6A patent/CN108700489A/zh active Pending
  • 2017-01-30 JP JP2018539413A patent/JP2019507337A/ja active Pending

Patent Citations (5)

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