Test chamber and method for locating leaks in test pieces

Abstract

In a test chamber device (10) for locating a gas leak (24) in a test sample (20) filled with a test gas, the test chamber device (10) comprises a test chamber, whose test chamber walls (14, 16) enclose a test volume (22) for accommodating the test sample (20), which test volume is hermetically closable from the outside atmosphere, and a vacuum pump (26) connected to the test chamber (12) for evacuating it, characterized in that the test chamber device (10) comprises a locating device (30) configured to determine the temperature of the test chamber walls (14, 16) or of a structure (15) adjacent to the test chamber, and to deduce the location of the leak (24) in the test sample (20) from the determined temperature.

Description

Technical Field

[0001] This invention relates to a test chamber apparatus and a method for locating leaks in a specimen containing a test gas. Background Technology

[0002] A known method involves filling a test specimen (such as food packaging) with a test gas and placing it in a film chamber. The chamber is then evacuated to detect any leakage of the test gas from the specimen into the film chamber. In many cases, a gas already present in the test specimen itself can be used as the test gas, such as the gas in the packaging bag. This gas can be a protective gas or a component of air, such as nitrogen, oxygen, or carbon dioxide. Aromatic substances from the food inside the packaging, such as the aroma emitted by coffee, can also be used as a test gas. Furthermore, gases produced within the packaged food can also be used as the test gas, such as the carbon dioxide produced by coffee packaging after several hours.

[0003] Because the pressure outside the specimen within the membrane chamber is lower than the internal pressure, test gas can escape through any potential leaks in the specimen. Known methods monitor the pressure rise within the membrane chamber to determine if a leak exists. If the pressure rises above a certain level, it can be considered an indication of a leak in the specimen.

[0004] In addition, known practices also include performing a sealing test on a specimen containing a test gas in a test chamber with rigid chamber walls.

[0005] Regardless of whether the test chamber has rigid walls or is designed as a thin chamber with flexible test chamber walls, a leak sensor is traditionally connected to the test chamber. After the test chamber is evacuated, leaks in the test sample can be detected at the atmospheric pressure inside the test sample. The leak sensor can be, for example, a pressure sensor that measures the pressure inside the test chamber. In this case, a known method is to measure the total pressure in the test chamber, or to measure and monitor the change in total pressure over time (“pressure rise rate”). Another alternative is to measure the partial pressure of the test gas in the test chamber, i.e., the proportion of the test gas in the gas mixture inside the test chamber. Partial pressure measurements can be performed using membrane and pressure sensors or mass spectrometers that are selective to the test gas. In test chambers with rigid test chamber walls, gas detectors are typically used as leak sensors capable of detecting the test gas.

[0006] In this specification, all these types of sensors, namely gas detectors, pressure sensors, mass spectrometers, etc., are referred to as "leak sensors".

[0007] Traditional leak sensors using test chambers typically cannot pinpoint the location of a leak in a test sample; they can only detect its presence. To detect leaks, an alternative leak detection device, such as a sniffing leak detector, must be used. This traditional leak detection requires an additional measurement process, independent of the actual leak detection. In this process, independent of the test chamber, the test sample is pressurized relative to the outside atmosphere, and an alternative location-based leak detection device is used to search the outer surface of the test sample. For example, a sniffing leak detector is used to sniff the surface of the test sample. A common feature of these location-based leak detection methods is that the operator must manually guide the alternative leak detection device to the surface of the test sample, and there is a risk that some areas of the test sample surface will not be inspected or will be insufficiently inspected. Summary of the Invention

[0008] Against this backdrop, the object of the present invention is to provide an improved test chamber device and an improved method for locating leaks in test samples.

[0009] The apparatus according to the invention is defined by the features of claim 1. The test chamber apparatus has a test chamber wall that forms the test chamber and surrounds the test volume, and in the closed state, it is gas-tightly sealed from the external environment. The test chamber wall can be opened to place a test sample into the test chamber. Here, the test sample is filled with a test gas that is already present in the test sample, such as gas present in food packaging, or is actively added to the test sample before it is placed into the test chamber. In the "pressure rise rate" method, the test gas used can also be air, and the total pressure increase during measurement is detected by a total pressure sensor independent of the test gas.

[0010] A test chamber is connected to a vacuum pump that evacuates the test volume when the test chamber is closed. A leak sensor (not strictly necessary for this invention) may be connected to the test volume and configured to detect leaks in the test sample, for example, by detecting whether the gas extracted from the test chamber contains the test gas. A distinctive feature of this invention is that the test chamber device is equipped with a positioning device configured to detect the temperature in at least one region of the test chamber wall or in at least one structure adjacent to at least one test chamber wall, for example, by measuring the temperature or detecting a parameter from which the temperature can be inferred. The positioning device is further configured to infer the location of a leak in the test sample based on the detected temperature.

[0011] This is based on the principle that test gas (such as air or helium) leaking from the test sample expands as it escapes from the leak and cools due to the expansion. The expanded, cooled test gas reaches the test chamber wall and / or adjacent structures, cooling the corresponding area. By detecting the temperature or temperature change of the test chamber wall or adjacent structures in this area, it can be determined that the temperature of the test chamber wall or structure in this area is lower than that in other areas. The positioning device can then identify this area as the vicinity (Nähe) of the leak in the test sample.

[0012] Here, the positioning device may include a temperature sensor. The temperature sensor may be connected to the test chamber wall or an adjacent structure, or form a structure adjacent to the test chamber wall, contacting the test chamber wall, or positioned outside the test chamber at a certain distance from the test chamber wall, detecting thermal radiation emitted from the test chamber wall. For example, the temperature sensor may be a thermal imager used to detect thermal radiation from the outer surface of the test chamber wall. Alternatively or additionally, other types of temperature sensors may be considered, such as sensors in contact with the test chamber wall.

[0013] In this regard, a thermally sensitive membrane is particularly suitable, placed on the inner or outer side of the test chamber wall as an adjacent structure to facilitate heat conduction from the test chamber wall to the membrane. The membrane's color changes in areas where the temperature of adjacent test chamber walls varies (e.g., when leaking gas impacts the test chamber wall). Alternatively or additionally, at least one, preferably multiple, uniformly distributed temperature sensors can be disposed on the test chamber wall as temperature components in contact with the test chamber wall, generating a temperature-dependent voltage that can be detected and evaluated to determine the temperature.

[0014] Specifically, the positioning device may include multiple temperature sensors, for example, different temperature sensors may be arranged on opposite sides of the test chamber. Specifically, thermal imagers, thermal films, and / or thermoelectric components may be arranged on opposite sides.

[0015] Furthermore, the positioning device may include an analysis unit connected to a temperature sensor. This analysis unit is configured to evaluate the determined temperature value and, based on the temperature value, determine a region on the test chamber wall near which a leak exists in the test sample. This determined region can be the projection of the leak location in the test sample onto the adjacent test chamber wall. Once the position and orientation of the test sample within the test chamber are known, the location of the leak in the test sample can be inferred from the determined region on the test chamber wall.

[0016] Therefore, a determined temperature threshold can be used to infer the presence of a leak near the corresponding location on the test chamber wall when the temperature exceeds or falls below the threshold. Thus, when test gas leaking from the test sample cools the test chamber wall region adjacent to the leak, the region can be detected when the test chamber wall temperature is below the corresponding threshold.

[0017] The determined temperature of the test chamber wall is preferably displayed to the operator via the display device of the test chamber apparatus. During leak detection, the operator can simultaneously detect potential leak locations in the test sample without performing separate measurements independent of the actual leak detection to locate the leak. For example, with a thermal imager, the images captured by the thermal imager can be displayed on the display device. Attached Figure Description

[0018] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. In the drawings: Figure 1 A schematic diagram of the first embodiment is shown. Figure 2 A schematic diagram of the second embodiment is shown. Figure 3 A schematic diagram of the third embodiment is shown. Figure 4 A schematic diagram of the fourth embodiment is shown. Detailed Implementation

[0019] The test chamber device 10 of the illustrated embodiment includes a test chamber 12, which is in the form of a conventional thin-film chamber. The test chamber walls 14 and 16 are composed of membrane layers with overlapping edges. The test chamber walls 14 and 16 are hermetically connected at their edges by a surrounding fixing frame 18, thereby hermetically sealing the test chamber 12. In order to remove and replace the test sample 20, the fixing frame 18 can be opened, allowing the test chamber walls 14 and 16 to unfold, thereby opening the test chamber 12.

[0020] The attached diagram shows the test chamber 12 in the closed state. The test volume 22, surrounded by the test chamber walls 14 and 16, contains the test sample 20, which may be, for example, food packaging.

[0021] Test chamber 12 is connected to vacuum pump 26, which evacuates it to a pressure below atmospheric pressure. During this process, the distance between the test chamber walls 14, 16 and the test sample 20 decreases. In the case of a thin-film chamber, the membrane of the test chamber walls 14, 16 adheres closely to and contacts the outer contour of the test sample 20. The large distance between the test sample 20 and the test chamber walls 14, 16 shown in the accompanying drawings is for illustrative purposes only and should not be construed as a scale drawing. For thin-film chambers, the actual distance under vacuum is much smaller.

[0022] exist Figure 1 In this configuration, a leak sensor 28, in the form of a gas detector, is connected to the outlet of the vacuum pump 26. This sensor analyzes the gas extracted by the vacuum pump 26 from the test chamber 12. If the gas extracted by the vacuum pump 26 contains the test gas, it can be detected by the leak sensor 28. This confirms the presence of a leak 24 in the test sample 20, but does not allow for its location.

[0023] As Figure 1 An alternative to the leakage sensor 28 is to place the leakage sensor 28 upstream of the vacuum pump 26 (i.e., between the test chamber 12 and the vacuum pump 26), such as... Figure 4 As shown. Figure 4 The leak detector 28 is a total pressure sensor. After the test chamber 12 is evacuated, the valve between the leak sensor 28 and the vacuum pump 26 can be closed to measure and monitor the total pressure of the gas inside the test chamber 12. Here, for example, a measurement method based on the principle of "pressure rise rate" can be implemented. Figure 4 The type 28 leakage sensor shown is also suitable for... Figure 2 and Figure 3 The embodiments shown are alternatives to using the leakage sensor 28.

[0024] In order to locate the leak, each embodiment of the test chamber device 10 is provided with a positioning device 30, which includes two temperature sensors 32 and 34 on opposite sides of the test chamber 12. Figure 1 In the illustrated embodiment, temperature sensors 32 and 34 are thermal imagers. The thermal imager corresponding to temperature sensor 32 captures images of the test chamber wall 14, while the thermal imager corresponding to temperature sensor 34 captures images of the test chamber wall 16. In this way, thermal radiation 36 emitted from the test chamber walls 14 and 16 is captured by temperature sensors 32 and 34.

[0025] Two temperature sensors 32 and 34 are electrically connected to the analysis unit 38. In this embodiment, the analysis unit 38 is designed as part of the leakage sensor 28. This means that the analysis unit 38 and the leakage sensor 28 are installed in the same housing.

[0026] The analysis unit 38 receives electronic measurement data generated by temperature sensors 32 and 34, and calculates corresponding thermal images of the outer surfaces of the test chamber walls 14 and 16 from this measurement data. These thermal images are displayed visually on the display device 40. In the illustrated embodiment, the display device 40 is mounted on the housing of the leak sensor 28 and the analysis unit 38, allowing the user of the leak sensor 28 to view the display device 40.

[0027] The analysis unit 38 is configured to correlate the measurement data received from the temperature sensors 32 and 34 with the spatial positions on the surfaces of the test chamber walls 14 and 16. Thus, the analysis unit 38 can determine that the temperature in a certain region 42 of the surface of the test chamber wall 14 is lower than the temperature in another region 43 and the temperature of the other test chamber wall 16.

[0028] The temperature of the test chamber wall 14 is lower in region 42 because there is a leak 24 in the test sample 20 near region 42. The test gas flows from this leak into region 42 and cools as it expands upon escaping from the test sample 20, thus cooling region 42 when it impacts the test chamber wall 14. Therefore, region 42 can be interpreted as the projection of the location of the leak 24 onto the adjacent test chamber wall 14. Thus, the location of the leak 24 in the underlying test sample 20 can be inferred from the location of region 42 on the surface of the test chamber wall 14.

[0029] exist Figure 2 In this embodiment, temperature sensors 32 and 34 are not thermal imagers, but cameras that capture images of the outer surfaces of the test chamber walls 14 and 16 (especially the adjacent thermal film 15). Figure 2 In this embodiment, the thermal membrane 15 is tightly adhered to the outer side of each test chamber wall 14, 16, allowing heat to be conducted from the test chamber walls 14, 16 to the membrane 15. The membrane 15 changes color in region 42 because the gas escaping from the leak 24 cools the test chamber wall 14 in that region, causing a temperature drop in the membrane 15, resulting in a color change in region 42, which is captured by the camera 32. The thermal membrane thus forms a structure that is tightly adhered to the outer side of the test chamber walls 14, 16.

[0030] Figure 3 An alternative is shown in which a structure 15 in the form of multiple thermoelectric components is arranged inside and adjacent to the test chamber walls 14, 16, with each thermoelectric component contacting the test chamber walls 14, 16 from the inside. The thermoelectric components in region 42 are cooled by the gas escaping from leak 24, thereby sending a voltage signal to the evaluation unit 38 that is different from that of the other thermoelectric components. The thermoelectric components thus form temperature sensors 32, 34 for detecting the temperature of the test chamber walls 14, 16.

Claims

1. A test chamber device (10) for locating gas leakage (24) in a test specimen filled with test gas, the test chamber device (10) comprising a test chamber having a plurality of test chamber walls (14, 16) surrounding a test volume (22) for accommodating the test specimen (20) and being hermetically isolated from the external atmosphere, and a vacuum pump (26) connected to the test chamber (12) for evacuating the test chamber. Its features are, The test chamber device (10) includes a positioning device (30) for determining multiple temperatures of the test chamber walls (14, 16) or multiple structures (15) adjacent to the test chamber, and for inferring the location of a leak (24) in the test specimen (20) based on the determined temperatures.

2. The test chamber device (10) according to claim 1, characterized in that, The positioning device (30) includes a temperature sensor.

3. The test chamber device (10) according to claim 1 or 2, characterized in that, The positioning device (30) includes an analysis unit (38) that associates the location of the measured temperature value with the location on the test chamber wall.

4. The test chamber device (10) according to claim 3, characterized in that, When the leak sensor (28) has detected a leak (24) in the specimen (20), the analysis unit (38) is used to associate the location of the measured temperature with the leak location when the threshold of the measured temperature is exceeded or not reached.

5. The test chamber device (10) according to claim 1, characterized in that, The test chamber device (10) includes a leak sensor (28) for detecting possible leaks (24) in the test piece (20).

6. The test chamber device (10) according to claim 1, characterized in that, The test chamber device (10) is a thin film chamber, and at least one region of the test chamber walls (14, 16) is formed by a flexible membrane attached to the specimen (20) in the vacuum state of the test chamber device (10).

7. A method for locating a leak (24) in a test specimen (20), the test specimen (20) comprising a test cavity device (10) according to any one of claims 1 to 6, characterized by the following steps: The specimen (20) was placed in the test chamber (12). The test chamber (12) was evacuated. The positioning device (30) determines multiple temperatures of at least one structure of the test chamber walls (14, 16) or adjacent to a test chamber wall (14, 16). Based on these determined temperatures, a leak (24) is determined in the specimen (20).

8. The method for locating a leak (24) in a test specimen (20) according to claim 7, characterized in that, The location (42) where the temperature exceeds or does not reach the threshold is considered as the projection of the location of the leak (24) in the test specimen (20) onto the test chamber wall (14).

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