Film chamber with carrier gas supply unit and leak test method

Abstract

An improved film chamber for carrier gas leak testing of a specimen containing a test fluid, and a method using the same, are provided. A film chamber 10 used for a sealability test of a specimen containing a test fluid includes at least one vacuum port 20 connected to a vacuum pump 32 and a gas detector 36, at least one flexible wall 14 forming a film chamber space, and a frame 12 surrounding the wall 14 from the outside and sealing the film chamber space. The vacuum port 20 and at least one gas inlet 22, 30 for supplying a carrier gas are arranged in an area central to the frame 12 and surrounded by the frame 12, and the other is arranged in an area of ​​the outer frame, so that the carrier gas flowing in from the gas inlet flows radially along the wall 14 within the film chamber space to the vacuum port 20.

Description

Technical Field

[0001] The present invention relates to a film chamber used for leak testing a subject containing a test fluid (test gas or test liquid).

Background Art

[0002] A film chamber is used, for example, as a test chamber for testing the airtightness of a subject such as food packaging with a gas. At this time, the subject is filled with a test gas and placed in the film chamber. Next, the film chamber is closed, evacuated, and the test gas leaking from the subject into the film chamber is detected by a gas detector. In a method alternative to the detection of the test gas, the total pressure increment in the film chamber is measured. According to this, the leak of the subject is detected regardless of the type of the test gas leaking from the subject.

[0003] A method is known in which a rigid test chamber is used and a carrier gas different from the test gas is circulated in a continuous flow in the test chamber, and the test gas leaked from the subject is supplied to a detector together with the carrier gas. Such a carrier gas method is described in, for example, Patent Document 1.

[0004] A method using a carrier gas is also known in a test chamber having a flexible wall or wall portion, that is, a so-called film chamber, as described in, for example, Patent Document 2.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In particular, in the case of film chambers equipped with flexible test chamber walls, if the walls of the film chamber adhere to the sample when the chamber is evacuated, it becomes difficult to generate a uniform carrier gas flow. If the carrier gas flow distributed on the film surface is not uniform, the leak rate signal will change depending on the location of the sample or leak point within the film chamber.

[0007] The present invention aims to provide an improved film chamber for performing a leak test of a test subject containing a test fluid using a carrier gas method, and a method using the same. [Means for solving the problem]

[0008] One configuration of the film chamber according to the present invention is defined by claim 1.

[0009] The film chamber according to the present invention is equipped with a vacuum port connected to a vacuum pump and a gas detector for drawing gas from inside the film chamber. The film chamber is equipped with at least one flexible wall that forms the film chamber space. Specifically, the design may be such that at least one entire wall of the film chamber is flexible. Preferably, all walls of the film chamber are flexible. In this case, the film chamber may be formed from two flexible films that are butted against each other. A frame surrounding the outside of the flexible wall is provided to close the film chamber space. This frame may sandwich the films together and press them against each other. Specifically, a configuration can be envisioned in which each film wall is equipped with its own frame, and the film chamber space is closed by hermetically pressing the frames of the film walls against each other.

[0010] In a specific configuration of the present invention, the vacuum port is centrally located relative to the frame, with its outer periphery surrounded by the frame, while at least one gas inlet for supplying carrier gas to the film chamber space is located in the outer frame region. The carrier gas flowing in through this gas inlet is configured to flow from the outside to the inside along the flexible wall within the film chamber space, up to the vacuum port. This makes it possible to make the flow uniform in the region of the flexible wall within the film chamber space. During a leak test, the film chamber space is small, and when the film chamber is evacuated, the gas is distributed along the surface of the flexible wall.

[0011] "Centered relative to the frame and surrounded by the frame" means, for example, in a plan view of the film chamber, as shown in Figure 1, that the vacuum port is approximately equidistant from the frame in all directions, and that the frame surrounds the vacuum port in a ring shape (however, the frame itself does not need to be ring-shaped). For example, the vacuum port may be located at or near the geometric center or centroid of the frame in a plan view of the film chamber.

[0012] In a second embodiment of the present invention, the vacuum port and the gas inlet are replaced with kinematically inverted positions. That is, the gas inlet is centrally located relative to the frame and surrounded on its outer periphery by the frame, while at least one vacuum port is located in the outer region of the frame, and the carrier gas flowing in from the gas inlet flows through the film chamber space from the inside to the outside along the flexible wall to the at least one vacuum port.

[0013] The test fluid may be a test gas and / or a test liquid, or a mixture of gas and liquid.

[0014] In the present invention, it is preferable that the carrier gas after it has flowed into the film chamber from the gas inlet, or before it flows out of the film chamber from the vacuum port, flows with a circumferential conductance value higher than the radial conductance value to the vacuum port. As a result, in the first configuration of the present invention, after the gas flows into the film chamber, it first spreads outward in the circumferential direction along the outer edge of the film chamber wall, and then flows radially from the outside to the inside towards the vacuum port between the film chamber walls. In the second configuration of the present invention, the gas flows radially from the inside to the outside towards at least one of the vacuum ports between the film chamber walls, then spreads outward in the circumferential direction along the outer edge of the film chamber wall, and then flows out of the film chamber.

[0015] In both configurations, a gas flow is generated that is uniformly distributed circumferentially and directed radially toward the vacuum port. Specifically, for this purpose, the distance d2 between the inner surfaces of the frames that are in contact with each other and facing the film chamber space can be set to be greater than the distance d1 between the inner film surfaces of the film chamber in the exhaust state when no specimen is contained or in areas where the contained specimen has not pulled the films apart. As a result, when carrier gas flows in from the gas inlet, because the distance d2 is set to be large, the gas first disperses circumferentially along the frame, and then flows radially from the outside to the inside toward the vacuum port between the film layers that are attracted to each other.

[0016] In one embodiment of the present invention, a plurality of gas inlets or vacuum ports are distributed along the circumference of the frame. Specifically, the film chamber may be designed in a radially symmetric (axially symmetric) configuration in which the vacuum ports are concentric with respect to the circumferentially annular frame. This makes it possible to flow a uniformly distributed carrier gas within the film chamber, radially from the outside to the inside along the surface of the film.

[0017] If the film chamber comprises two film chamber walls that abut against each other, a vacuum port or gas inlet may be provided in each of these two walls, concentrically positioned in the center with respect to the frame.

[0018] At least on the film chamber space side, it is preferable that the flexible wall portion contains or consists solely of a material that does not absorb the test fluid and / or carrier gas. This material may be, for example, silicone, butyl rubber, EPDM (ethylene propylene diene monomer) rubber, etc.

[0019] A layer of material having a structurally high gas conductance ratio may be further provided on the inside of the film chamber wall or the flexible wall portion, for example, in the form of a thin net or mesh, to promote gas flow from the outer frame to the vacuum port, or from the inner gas inlet to the outer frame, between the walls that are attracted to each other. Alternatively, or in addition to this, a certain amount of gas conductance value may be added by roughening, non-smoothing, or other processing, and / or providing a number of protrusions and / or depressions on the film chamber space side of at least one of the walls or flexible wall portions.

[0020] The method according to the present invention is defined by the configuration of claim 13. According to this, first, a specimen is introduced into the film chamber, and then the film chamber is closed, and the pre-film chamber is evacuated by a vacuum pump connected to the vacuum port. In the evacuated state where the film chamber space is reduced, carrier gas is supplied from the gas inlet to the film chamber. If there is a leak in the specimen, the test fluid leaks from the inside of the specimen into the film chamber and mixes with the carrier gas. The gas mixture of the carrier gas and the test fluid thus generated is sucked from the vacuum port by the vacuum pump, and the gas mixture is supplied to a gas detector also connected to the vacuum port for analysis. The carrier gas flowing in from the gas inlet flows from the outside to the inside along the flexible wall portion in the film chamber space and is supplied to the vacuum port (first configuration), or flows from the inside to the outside along the flexible wall portion and is supplied to the vacuum port (second configuration). Thereby, a carrier gas flow uniformly distributed along the flexible wall portion is generated.

[0021] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic view of the first embodiment. [Figure 2] It is a schematic view of the second embodiment. [Figure 3] It is a perspective view of the third embodiment.

Modes for Carrying Out the Invention

[0023] The film chambers 10 of the first two embodiments include an annular outer peripheral frame 12. In the third embodiment, although it is an annular (loop-shaped) outer peripheral frame 12, its shape is not annular but a substantially rectangular parallelepiped shape with rounded corners. Other annular geometric shape frames 12 may be adopted.

[0024] The frame 12 may consist of two parts of complementary shapes, with each frame part 12a and 12b supporting the film chamber wall 14. As shown in Figure 2, the two frame parts 12a and 12b are airtightly connected to each other via two annular seals 16 and 18.

[0025] Two films 14 are each sandwiched between two frame portions 12a and 12b, and at least one of the films 14 is provided with a vacuum port 20 located in the center, concentric with respect to the outer frame 12. The frame 12 has a gas inlet 22 for supplying carrier gas from the frame 12 into the film chamber, and in the embodiment of Figure 1, gas inlets 22 and 30 are provided. In the embodiments of Figure 2 and Figure 3, two gas inlets 22 and 30 for the carrier gas are formed on opposite sides of the frame 12. In Figure 1, a flushing gas source and a carrier gas source are connected to the gas inlet 22 via valves V1 and V2. The frame 12 further has another gas port 24. The gap 26 formed between the two seals 16 and 18 can be evacuated through the gas port 24 by a vacuum pump 28 connected to this gas port 24. In the embodiment of Figure 1, the vacuum pump 28 is connected to the gas port 24 via valve V3.

[0026] Each of the two frame sections 12a and 12b has an inner frame surface 13, which is adjacent to the film chamber space on one side and faces each other. The inner frame surfaces 13 of the two frame sections 12a and 12b are spaced apart from each other by a distance d2. This distance d2 remains unchanged even when the frame 12 is closed and the film chamber is closed, or even when the film chamber is evacuated.

[0027] Both films 14 each have an inner film surface 15 on the side facing the film chamber space. In the closed film chamber shown in Figure 2, the two inner film surfaces 15 are separated by a distance d1, both before and after exhaustion. The films 14 deform and the distance can increase in the area of ​​the subject only when the subject is placed between the films 14 and taken into the films 14. Since the distance d2 is greater than the distance d1, especially when the vacuum pump is exhausted, the carrier gas flowing into the film chamber space from the gas inlets 22 and 30 first spreads circumferentially between the two frame sections 12a and 12b, and then flows radially from the entire circumference, from outside to inside, towards the central vacuum port 20. This generates a gas flow of carrier gas that is uniformly distributed circumferentially, from outside to inside.

[0028] As shown in Figure 1, a vacuum pump 32 is connected to the vacuum port 20. In the embodiment shown in Figure 1, the vacuum pump 32 is connected to the vacuum port 20 via valves V4 and V6. A gas detector 36 is connected to a gas conduit 34 that connects the vacuum pump 32 and the vacuum port 20, allowing the gas exhausted from the film chamber 10 to be analyzed for the presence or absence of the test fluid. Here, the gas detector 36 is connected to a detection gas conduit 38 having two ends, which are connected to the gas conduit 34 via valves V7 and V8, respectively.

[0029] As a result, after introducing the sample, the film chamber space can be evacuated by opening valves V4 and V6 while operating the vacuum pump 32. Once a sufficient vacuum is reached, valve V5 can be immediately closed, and valve V2 can be opened to supply a continuous flow of carrier gas regulated by the throttle from the gas inlet 22 into the film chamber space. This continuous flow flows radially from the outside to the inside along the inside of the film chamber wall 14 within the flow chamber space, towards the vacuum port 20. When valve V6 is closed and valves V7 and V8 are opened, the gas mixture drawn from the film chamber space is supplied to the gas detector 36 through the opened valves V4 and V7, and finally reaches the vacuum pump 32 through the opened valve V8, from where it dissipates into the surrounding outside air.

[0030] After the leak test is complete, closing valve V2 and opening valve V1 allows a flushing gas flow to be supplied from the gas inlet 22 into the film chamber space, thereby flushing the film chamber space. Here, the supply of the flushing gas through valve V1 is either not diaphragmatically adjusted, or at least diaphragmatically adjusted less than the supply of the carrier gas by opening valve V2.

[0031] By opening valve V3 and operating the vacuum pump 28, the gap between the two seals 16 and 18 in the frame (also called the ring-shaped chamber gap) is evacuated. As a result, the two frame sections 12a and 12b press against each other, allowing the film chamber 12 to be closed.

[0032] Preferably, the carrier gas flow flows radially symmetrically through the space between the walls of the test chamber, from the outer edge of the chamber frame inward to the vacuum port in the center of the wall (film). This makes it possible to detect leaked gas at any point in the specimen with the same sensitivity and rate (response time).

[0033] The uniformity of the gas flow is greatly influenced not only by the conductance value along the film space, but also by the pressure difference between the inlet (which is each transition point from the chambering to the film space) and the vacuum port in the center of the film.

[0034] Therefore, it is desirable that the pressure within the ring-shaped chamber gap be uniform. For this reason, the gas conductance value in the circumferential direction along the ring-shaped chamber gap, from the position of the carrier gas inlet 22 to the position furthest from the gas inlet 22 in the ring-shaped chamber gap, needs to be set to 10 times or more the radial gas conductance value from the ring-shaped chamber gap to the center of each film chamber wall along the space formed between the film chamber walls (film chamber space).

[0035] The second embodiment of the present invention is basically identical to the embodiment shown in Figures 1 to 3, except that the vacuum port and gas inlet are replaced. The present invention also includes the following embodiments. [Aspect 1] A film chamber (10) used for leak testing of a test subject containing a test fluid, At least one vacuum port (20) connectable to a vacuum pump (32) and a gas detector (36), At least one flexible wall portion (14) forming a film chamber space, The flexible wall portion (14) is surrounded from the outside by a frame (12) that closes the film chamber space, The at least one vacuum port (20) is located in a central region relative to the frame (12) and its radial outer circumference is surrounded by the frame (12), A film chamber (10) is characterized in that at least one gas inlet (22, 30) for supplying a carrier gas is located in the outer region of the frame, and the carrier gas flowing in from the gas inlet is configured to flow within the film chamber space along the flexible wall (14) from the radial outside to the inside toward the vacuum port (20). [Aspect 2] A film chamber (10) used for leak testing of a test subject containing a test fluid, At least one vacuum port (20) connectable to a vacuum pump (32) and a gas detector (36), At least one flexible wall portion (14) forming a film chamber space, The flexible wall portion (14) is surrounded from the outside by a frame (12) that closes the film chamber space, At least one gas inlet (22, 30) for carrier gas supply is located in a central region relative to the frame (12), and its radial outer circumference is surrounded by the frame (12), A film chamber (10) characterized in that at least one vacuum port (20) is located in the outer region of the frame, and the carrier gas flowing in from the gas inlets (22, 30) flows through the film chamber space along the flexible wall portion (14) from the radial inside to the outside towards the vacuum port (20). [Aspect 3] A film chamber (10) according to embodiment 1 or 2, characterized in that the frame (12) is configured to extend in an annular manner around the flexible wall portion (14) and borders the flexible wall portion (14). [Aspect 4] A film chamber (10) according to any one of embodiments 1 to 3, wherein the film chamber space is characterized in that the circumferential gas conductance value in the region of the frame (12) is higher than the radial gas conductance value from the gas inlet (22, 30) to the vacuum port (20). [Aspect 5] A film chamber (10) according to any one of embodiments 1 to 4, characterized in that the vacuum port (20) or the gas inlet is arranged concentrically with respect to the frame (12). [Aspect 6] A film chamber (10) according to any one of embodiments 1 to 5, characterized in that the walls of the film chamber are made to be flexible as a whole and are held in place by the frame. [Aspect 7] A film chamber (10) according to any one of embodiments 1 to 6, characterized in that the gas inlet (22, 30) or the vacuum port (20) is formed in the frame (12) or in the vicinity of the frame (12). [Aspect 8] A film chamber (10) according to any one of embodiments 1 to 7, characterized in that the frame (12) has a plurality, preferably two, gas inlets (22, 30) or vacuum ports (20). [Aspect 9] A film chamber (10) according to embodiment 8, characterized in that the gas inlets (22, 30) or vacuum ports (20) are uniformly distributed at equal intervals from one another along the circumference of the frame (12). [Aspect 10] A film chamber (10) according to any one of embodiments 1 to 9, characterized in that two vacuum ports (20) or gas inlets (22, 30) are formed on opposite sides of the film chamber space. [Aspect 11] A film chamber (10) according to any one of embodiments 1 to 10, wherein the frame (12) has two inner frame surfaces (13) that are in contact with the film chamber space and facing each other, and the two films (14) have inner film surfaces (15) that are in contact with the film chamber space and facing each other, and the distance (d2) between the inner frame surfaces (13) is greater than the distance between the inner film surfaces (15) in the exhaust state when no test specimen is contained in the film chamber (10). [Aspect 12] A film chamber (10) according to any one of embodiments 1 to 11, characterized in that the flexible wall portion (14) is made of a material that does not absorb the test fluid and / or carrier gas, particularly silicone, butyl rubber, or EPDM. [Aspect 13] A method for performing a leak test on a test subject containing a test fluid using a film chamber described in any one of embodiments 1 to 12, The steps include introducing the subject into the film chamber (10), The steps include: evacuating the film chamber (10) using a vacuum pump connected to the vacuum port (20); The steps include supplying a carrier gas from the gas inlets (22, 30) to the film chamber (10), The steps include: drawing a gas mixture consisting of the test fluid leaked from the leak point of the subject and the carrier gas through the vacuum port (20) and supplying the drawn gas mixture to the gas detector (36); The gas detector (36) is used to analyze the gas mixture for the presence or absence of a test fluid. A method characterized in that the carrier gas flowing in from the gas inlets (22, 30) flows through the film chamber space along the flexible wall portion (14) from the radial outside to the inside, or from the outside to the inside, toward the vacuum port (20). [Aspect 14] The method according to Embodiment 13, characterized in that the carrier gas flows with a circumferential gas conductance value higher than the radial gas conductance value toward the vacuum port (20) or the gas inlet (22, 30) after it has entered the film chamber space from the gas inlet (22, 30) or before it has flowed out of the film chamber space from the vacuum port (20). [Explanation of symbols]

[0036] 22 Carrier gas inlet 10 Film Chamber 12 Outer frame 12a, 12b Frame section 13 Inner frame surface 14. Film (chamber wall) 15. Inner film surface 16, 18 Seals 20, 28 Vacuum Ports 22, 30 Gas Inlet 32 Vacuum pump 34 Gas conduit 36 Gas detectors

Claims

1. A leak test apparatus used for leak testing of a test specimen containing a test fluid, comprising a film chamber (10), a vacuum pump (32), a carrier gas source, and a gas detector (36), The aforementioned film chamber is At least one vacuum port (20) connected to the vacuum pump (32) and gas detector (36), At least one flexible wall portion (14) that forms the film chamber space, The flexible wall portion (14) is surrounded from the outside by a frame (12) that closes the film chamber space, The at least one vacuum port (20) is located in a central region relative to the frame (12) and its radial outer circumference is surrounded by the frame (12), A leak test apparatus characterized in that at least one gas inlet (22, 30) connected to the carrier gas source for supplying carrier gas is located in the outer region of the frame, and the carrier gas flowing in from the gas inlet is configured to flow through the film chamber space along the flexible wall portion (14) from the radial outside to the inside toward the vacuum port (20).

2. A leak test apparatus used for leak testing of a test specimen containing a test fluid, comprising a film chamber (10), a vacuum pump (32), a carrier gas source, and a gas detector (36), The aforementioned film chamber is At least one vacuum port (20) connected to the vacuum pump (32) and gas detector (36), At least one flexible wall portion (14) that forms the film chamber space, The flexible wall portion (14) is surrounded from the outside by a frame (12) that closes the film chamber space, At least one gas inlet (22, 30) connected to the carrier gas source for carrier gas supply is located in a central region relative to the frame (12) and its radial outer circumference is surrounded by the frame (12), A leak test apparatus characterized in that at least one vacuum port (20) is located in the outer region of the frame, and the carrier gas flowing in from the gas inlets (22, 30) flows through the film chamber space along the flexible wall portion (14) from the radial inside to the outside towards the vacuum port (20).

3. A leak test apparatus according to claim 1 or 2, characterized in that the frame (12) is configured to extend in an annular shape around the flexible wall portion (14) and borders the flexible wall portion (14).

4. A leak test apparatus according to any one of claims 1 to 3, characterized in that the circumferential gas conductance value in the region of the frame (12) of the film chamber space is higher than the radial gas conductance value from the gas inlet (22, 30) to the vacuum port (20).

5. A leak test apparatus according to any one of claims 1 to 4, characterized in that the vacuum port (20) or the gas inlet is arranged concentrically with respect to the frame (12).

6. A leak test apparatus according to any one of claims 1 to 5, characterized in that the wall of the film chamber is made entirely of flexible material and is held in place by the frame.

7. A leak test apparatus according to any one of claims 1 to 6, characterized in that the gas inlet (22, 30) or the vacuum port (20) is formed in the frame (12) or in the vicinity of the frame (12).

8. A leak test apparatus according to any one of claims 1 to 7, characterized in that the frame (12) has a plurality, preferably two, gas inlets (22, 30) or vacuum ports (20).

9. A leak test apparatus according to claim 8, characterized in that the gas inlets (22, 30) or vacuum ports (20) are uniformly distributed at equal intervals from one another along the circumference of the frame (12).

10. A leak test apparatus according to any one of claims 1 to 9, characterized in that two vacuum ports (20) or gas inlets (22, 30) are formed on opposite sides of the film chamber space.

11. A leak test apparatus according to any one of claims 1 to 10, wherein the frame (12) has two inner frame surfaces (13) that are in contact with the film chamber space and facing each other, and the two films (14) have inner film surfaces (15) that are in contact with the film chamber space and facing each other, and the distance between the inner frame surfaces (13) is (d ２ A leak test apparatus characterized in that the distance between the inner film surfaces (15) is greater than the distance between the inner film surfaces (15) in the exhaust state when no test specimen is contained in the film chamber (10).

12. A leak test apparatus according to any one of claims 1 to 11, characterized in that the flexible wall portion (14) is made of a material that does not absorb the test fluid and / or carrier gas, particularly silicone, butyl rubber, or EPDM.

13. At least one vacuum port (20) connectable to a vacuum pump (32) and a gas detector (36), At least one flexible wall portion (14) that forms the film chamber space, The flexible wall portion (14) is surrounded from the outside by a frame (12) that closes the film chamber space, The at least one vacuum port (20) is located in a central region relative to the frame (12) and its radial outer circumference is surrounded by the frame (12), A method for performing a leak test on a test subject containing a test fluid, using a film chamber (10) wherein at least one gas inlet (22, 30) for supplying a carrier gas is located in the outer region of the frame, and the carrier gas flowing in from the gas inlet is configured to flow within the film chamber space along the flexible wall (14) from the radial outside to the inside toward the vacuum port (20), The steps include introducing the subject into the film chamber (10), The steps include: evacuating the film chamber (10) using a vacuum pump connected to the vacuum port (20); The steps include supplying a carrier gas from the gas inlets (22, 30) to the film chamber (10), The steps include: drawing a gas mixture consisting of the test fluid leaked from the leak point of the subject and the carrier gas through the vacuum port (20) and supplying the drawn gas mixture to the gas detector (36); The gas detector (36) is used to analyze the gas mixture for the presence or absence of a test fluid. A method characterized in that the carrier gas flowing in from the gas inlets (22, 30) flows through the film chamber space along the flexible wall portion (14) from the radial outside to the inside toward the vacuum port (20).

14. At least one vacuum port (20) connectable to a vacuum pump (32) and a gas detector (36), At least one flexible wall portion (14) that forms the film chamber space, The flexible wall portion (14) is surrounded from the outside by a frame (12) that closes the film chamber space, At least one gas inlet (22, 30) for carrier gas supply is located in a central region relative to the frame (12) and its radial outer circumference is surrounded by the frame (12), A method for performing a leak test on a test subject containing a test fluid, using a film chamber (10) wherein at least one vacuum port (20) is located in the outer peripheral region of the frame, and the carrier gas flowing in from the gas inlets (22, 30) flows within the film chamber space along the flexible wall portion (14) from the radial inside to the outside towards the vacuum port (20), The steps include introducing the subject into the film chamber (10), The steps include: evacuating the film chamber (10) using a vacuum pump connected to the vacuum port (20); The steps include supplying a carrier gas from the gas inlets (22, 30) to the film chamber (10), The steps include: drawing a gas mixture consisting of the test fluid leaked from the leak point of the subject and the carrier gas through the vacuum port (20) and supplying the drawn gas mixture to the gas detector (36); The gas detector (36) is used to analyze the gas mixture for the presence or absence of a test fluid. A method characterized in that the carrier gas flowing in from the gas inlets (22, 30) flows through the film chamber space along the flexible wall portion (14) from the radial inside to the outside towards the vacuum port (20).

15. A method according to claim 13 or 14, characterized in that the carrier gas flows in a state in which the circumferential gas conductance value is higher than the radial gas conductance value toward the vacuum port (20) or the gas inlet (22, 30) after it has entered the film chamber space from the gas inlet (22, 30) or before it has flowed out of the film chamber space from the vacuum port (20).

Images