Sealing test method, test specimen and test bench

Abstract

Method for testing the sealing of a test specimen (21) comprising a sealing film and two fibrous reinforcing layers, one on each side of the said sealing film, the said method comprising the steps of: connecting the said test specimen to a test bench (22),conducting a first test of behaviour under pressure,subjecting the said test specimen to at least a first thermal shock, andconducting at least a second test of behaviour under pressure,

Description

The invention will be made more comprehensible and other objects, details, features and advantages thereof will be clarified by the following description of a specific embodiment of the invention, provided solely for guidance and without restrictive intent, with reference to the attached drawings. In these drawings:

FIG. 1 is a schematic view of a test bench and of a test specimen according to an embodiment of the prior art,

FIG. 2 shows a detail of FIG. 1,

FIG. 3 is a schematic view of a test bench and of a test specimen according to one embodiment of the invention,

FIG. 4 shows a detail of FIG. 3,

FIG. 5 is a view, similar to that of FIG. 4, of a variant embodiment, and

FIG. 6 shows the test bench of FIG. 1, to which a prior art test specimen is fixed, in a variant.

FIGS. 3 to 5 show a test bench and a test specimen for the application of a sealing test method according to one embodiment of the invention. Elements which are identical or similar to elements of the embodiment of FIGS. 1 and 2 are indicated by the same reference numerals, increased by 20, and are not described in greater detail.

The test specimen 21 comprises a sealing film and two reinforcing layers, one on each side of the said sealing film. The sealing film can be made from metal, for example aluminium, or from any other sealing material. The reinforcing layers are fibrous; for example, they may be glass fibre textiles. In the remainder of this description, the assembly formed by the sealing foil and the reinforcing layers is called the “sheet”. The sheet is preferably of circular shape and has a central area 24 to be tested. The test specimen 21 also comprises an annular sealing gasket 31 which surrounds the said area to be tested 24. Alternatively, the sheet could have another shape, being square for example. In this case, the sealing gasket is also square and is adjacent to each edge of the sheet.

As shown in FIG. 4, the sealing gasket 31 has three portions: a contact portion 33 covers a connecting surface 25 of the sheet which surrounds the area to be tested 24, a thickness portion 34 extends parallel to the thickness of the sheet and surrounds its periphery, and a cover portion 35 covers the edge of the sheet opposite the contact portion 33. In a variant shown in FIG. 5, only the contact portion 33 is provided.

The sealing gasket 31 is, for example, overmoulded, in other words moulded around the sheet, or bonded to the sheet. It is made from a material which withstands cryogenic temperatures, in other words one which does not suffer damage in the form of hairline cracks or fragility when subjected to thermal shock, and which has a coefficient of deformation and an acceptable cold deformation which are compatible with those of the sheet, in other words of the same order of magnitude, to prevent the thermal shock from damaging the test specimen 21. For example, the sealing gasket 31 is made from polymerized polyurethane adhesive or rubber. In one embodiment, the sealing gasket 31 impregnates the fibres of the reinforcing layers.

In a variant which is not shown, the sheet of the test specimen 21 has an opening in the area to be tested 24, in a similar way to what was described with reference to FIG. 6. The opening is covered by a membrane composed of three layers similar to those of the sheet. The membrane is bonded to the sheet all round the opening. This makes it possible to test the quality of the sealing of the bond between the membrane and the sheet.

The test bench 22 also has its own sealing gasket 32, fixed for example by bonding to a connecting surface 26 which surrounds the opening 30 of the vacuum chamber 23. As explained below, the sealing gasket 32 is not subjected to thermal shocks. It can be made, for example, from rubber, from closed cell foam, or from vacuum sealing resin. In the illustrated embodiment, the test bench 22 also comprises a press 36. In another embodiment, the press 36 is omitted.

The test method according to one embodiment of the invention comprises the fixing of the test specimen 21 to the test bench 22 by placing the contact portion 33 of the sealing gasket 31 in contact with the sealing gasket 32, the area to be tested 24 covering the opening 30. The press 36 is operated so as to press the sealing gasket 31 against the sealing gasket 32 so as to form a substantially sealed connection by contact. In the variant in which the press 36 is omitted, the contact between the sealing gasket 31 and the sealing gasket 32 and the vacuum created in the vacuum chamber 23 are sufficient to connect the test specimen 21 to the test bench 22.

A first test of behaviour under pressure is then conducted, by a similar procedure to what is described above with reference to the prior art method, but this procedure is not essential to the application of the invention.

The test specimen 21 is then separated from the test bench 22. This separation is carried out without destruction of the test specimen 21 or of the test bench 22: the sealing gasket 31 remains fixed to the sheet and is separated from the sealing gasket 32 which remains fixed to the rest of the test bench 22.

A first thermal shock is then imparted to the test specimen 21, remotely from the test bench which is therefore not subjected to thermal shock. During this time, the test bench 22 can be used to conduct a test of behaviour under pressure with another test specimen. The thermal shock can be produced by pouring liquid nitrogen on to the test specimen 21, or in any other suitable way.

The test specimen 21 is then refixed to the test bench 22, and a second test of behaviour under pressure is conducted. By subsequently alternating thermal shocks and tests of pressure behaviour, it is possible to evaluate the initial degree of sealing of the test specimen 21 and the variation of this degree of sealing under the effect of a cycle of thermal shocks.

Clearly, although the invention has been described with reference to a particular embodiment, it is not limited in any way by this, and comprises all the technical equivalents of the means described and their combinations where these fall within the scope of the invention.

Claims

1. Method for testing the sealing of a test specimen (21) comprising a sealing film and at least one fibrous reinforcing layer adjacent to the said sealing film, the said method comprising the steps of: fixing the said test specimen to a test bench (22) comprising a vacuum chamber (23) in such a way that an area (24) of the said test specimen to be tested covers an opening (30) of the said vacuum chamber, a connecting surface (25) of the said test specimen surrounding the said area to be tested being connected by sealing means (31, 32) to a connecting surface (26) of the said test bench which surrounds the said opening,conducting a first test of behaviour under pressure, comprising the reduction of pressure in the said vacuum chamber, and the measurement of the pressure in the said vacuum chamber,subjecting the said test specimen to at least a first thermal shock, andconducting at least a second test of behaviour under pressure,characterized in that the said sealing means enable the said test specimen to be separated from the said test bench in a non-destructive way, the said method comprising at least the steps of: removing the said test specimen from the said test bench after the said first test of behaviour under pressure, and subjecting the said test specimen to the said first thermal shock remotely from the said test bench, andrefixing the said test specimen to the said test bench to conduct the said second test of behaviour under pressure.

2. Sealing test method according to claim 1, characterized in that the said sealing means comprise a first sealing gasket (31) fixed to the said test specimen, and a second sealing gasket (32) fixed to the said test bench.

3. Sealing test method according to claim 1, characterized in that, when the said test specimen is removed from the said test bench to be subjected to a thermal shock, the said method comprises fixing a second test specimen to the said test bench and conducting a test of behaviour under pressure with the said second test specimen.

4. Test specimen (21) comprising a sealing film and at least one fibrous reinforcing layer adjacent to the said sealing film, the said test specimen having an area to be tested (24), characterized in that it comprises a sealing gasket (31) which surrounds the said area to be tested.

5. Test specimen according to claim 4, characterized in that the said sealing gasket is adjacent to at least one edge of the said test specimen.

6. Test specimen according to claim 4, characterized in that the said sealing gasket covers a portion of the surface of the said reinforcing layer, the thickness of the said test specimen at its periphery not being covered by the sealing gasket.

7. Test specimen according to claim 4, characterized in that the said sealing gasket covers a portion of the surface of the said reinforcing layer and the thickness of the said test specimen at its periphery.

8. Test specimen according to claim 7, characterized in that it comprises two fibrous reinforcing layers, one on each side of the said sealing film, the said sealing gasket covering a portion of the surface of the other of the said reinforcing layers.

9. Test specimen according to claim 4, characterized in that it has a substantially circular shape, the said sealing gasket having a substantially annular shape.

10. Test specimen according to claim 4, characterized in that the said sealing gasket is overmoulded on or bonded to the assembly formed by the said sealing film and the said reinforcing layer.

11. Test specimen according to claim 4, characterized in that the said sealing gasket is made from a material which has a coefficient of expansion and an acceptable cold deformation which are compatible with those of the assembly formed by the said sealing film and the said reinforcing layer.

12. Test specimen according to claim 11, characterized in that the said sealing gasket is made from polyurethane adhesive or rubber.

13. Test specimen according to claim 4, in which the said sealing gasket impregnates the fibres of the said at least one reinforcing layer.

14. Sealing test method according to claim 2, characterized in that, when the said test specimen is removed from the said test bench to be subjected to a thermal shock, the said method comprises fixing a second test specimen to the said test bench and conducting a test of behaviour under pressure with the said second test specimen.

15. Test specimen according to claim 5, characterized in that the said sealing gasket covers a portion of the surface of the said reinforcing layer, the thickness of the said test specimen at its periphery not being covered by the sealing gasket.

16. Test specimen according to claim 5, characterized in that the said sealing gasket covers a portion of the surface of the said reinforcing layer and the thickness of the said test specimen at its periphery.

17. Test specimen according to claim 5, characterized in that it has a substantially circular shape, the said sealing gasket having a substantially annular shape.

18. Test specimen according to claim 5, characterized in that the said sealing gasket is overmoulded on or bonded to the assembly formed by the said sealing film and the said reinforcing layer.

19. Test specimen according to claim 5, characterized in that the said sealing gasket is made from a material which has a coefficient of expansion and an acceptable cold deformation which are compatible with those of the assembly formed by the said sealing film and the said reinforcing layer.

20. Test specimen according to claim 5, in which the said sealing gasket impregnates the fibres of the said at least one reinforcing layer.