Film chamber having double film
The invention relates to a film chamber 10 which has a film chamber wall for testing the sealing tightness of a gas-filled test specimen 38 , which film chamber wall defines a chamber volume 32 for holding the test specimen 38 and has a first vacuum connection 28 for evacuating the chamber volume 32 by means of a first vacuum pump 30 connected to the first vacuum connection 28 , wherein at least a portion of the film chamber wall has a flexible film 12, 14 , characterized in that the film 12, 14 has two layers 20, 22 arranged adjacent to each other which surround an evacuable film interspace 26.
1. A film chamber comprising a film chamber wall provided for a tightness test on a gas-filled test specimen, said film chamber wall defining a chamber volume for accommodating said test specimen and being provided with a first vacuum connection for evacuating said chamber volume by means of a first vacuum pump connected to said first vacuum connection, wherein at least a portion of the film chamber wall comprises a flexible film and wherein said film comprises two layers arranged adjacent to each other and surrounding an evacuable film interspace,
wherein a second vacuum connection is provided to which a second vacuum pump is connected for evacuating the film interspace,
wherein the film chamber comprises two adjacent films between which the chamber volume is defined and which are respectively made up of two adjacent layers having respective film interspaces arranged between said two layers.
2. The film chamber according to claim 1 , wherein in the film interspace a gas-permeable material separating the two layers from each other is arranged.
3. The film chamber according to claim 2 , wherein the gas-permeable material is a nonwoven fabric.
4. The film chamber according to claim 1 , wherein the outer edge area of each film is provided with a frame holding said film and being sealingly connected with said film, wherein said two frames constitute or comprise the first and/or the second vacuum connection.
5. A method for leakage detection on a test specimen using a film chamber according to claim 1 , comprising the steps of:
introducing said test specimen into the chamber volume,
closing said chamber volume,
evacuating said chamber volume down to a predetermined vacuum pressure below atmospheric pressure,
measuring over time the pressure inside said film chamber in the area outside said test specimen,
detecting an increase of the measured pressure, and
evacuating at least one, and preferable each film interspace during the leakage detection,
wherein the film interspace is permanently kept below a limit vacuum pressure during the pressure measurement.