DE102013000086A1 - Leak tightness testing device for flexible packages, particularly food packages or pharmaceutical product packages, has test chamber for introducing flexible package, where device adjusts defined high pressure level in test chamber - Google Patents

Abstract

The leak tightness testing device (1) has a test chamber (9) for introducing a flexible package (3) to be-tested, particularly a package formed by a film (5). The package contains a test gas, particularly in the form of carbon dioxide. The leak tightness testing device adjusts a defined high pressure level in the test chamber by a pressure gas and subsequently senses and evaluates a test gas concentration in test chamber over a time duration. The high pressure level acts on the package. An independent claim is included for a method for leak tightness testing of flexible packages.

Description

The present invention relates to a leak testing device according to the preamble of claim 1. Furthermore, the invention relates to a method of execution with such a leak testing device. The leak test device and the method are particularly suitable for a leak test on packaging, which are formed by means of film and flexible.

Various devices and methods for leak testing flexible packaging are known in the art. H. on packaging, which enclose each packaged goods, in particular gas-tight. Examples of such packaging, made for. Example by means of polymers are, for example, food packaging or packaging for pharmaceutical products.

A selection of such packages - as they are used in the present invention - contains a protective gas introduced by the manufacturer (in particular CO ₂ ), which is or can be used as a test gas in the context of a leak test. Such packaging or film packaging are z. B. for packaging perishable food, eg. As sausage, cheese, meat, or provided for medical or pharmaceutical products whose contamination should be avoided.

In generic methods, which make use of test gas for the detection of packaging leaks, an evacuation of a test room is usually provided. An apparatus for performing such a method shows z. B. the publication DE 196 42 099 A1 in which two films form an evacuable test space in which the packaged article is receivable. A test gas-sensitive detector is connected to the evacuable test space. A disadvantage of such systems for carrying out the leak test is the considerable construction costs for the evacuation, in particular for vacuum pumps and piping and to ensure the tightness of the test room. Furthermore, such systems, eg. B. when using multiple vacuum pumps to promote the gas to the sensor, error prone. A further disadvantage is that, in particular in the case of larger packaging leaks, there is the danger that test gas will already be drawn off during the evacuation, which is thus no longer detectable in the actual measurement. Leaks can not be reliably detected. In addition, for a reliable measurement mostly pressure levels in the range of 600 mbar to 700 mbar below atmospheric pressure are necessary, so that a considerable time has to wait until the pressure level in the test chamber is reached.

Next to it is from the publication DE 691 10 706 T2 a leak detection device for on-line measurement of the tightness of packaging known which mechanically applies pressure to the top of a package, including hydraulic cylinder and a plate device, which is accommodated in a hood, are provided. The gas surrounding the packaging is drawn off via the hood and test gas (helium) is detected. Also, this device is expensive to manufacture, woneben the risk of damage to packaging with inaccurate adjustment of recorded in the hood plate device consists. Furthermore, the use of helium as a test gas in the packaging process can lead to an increase in the concentration of helium in the environment, which in turn leads to a high level of noise on the regularly extremely sensitive helium sensors, so that no meaningful test results are available without further measures. This device is also subject to a high error rate.

Proceeding from this, the present invention seeks to overcome the above-described disadvantages of the prior art and to propose a Dichtigkeitsprüfvorrichtung which is error-resistant and robust executable with continued low construction costs, in particular always reliable test results. Furthermore, it is an object of the invention to provide a method of execution with such a Dichtigkeitsprüfvorrichtung.

This object is achieved by the features of claim 1.

According to the invention, a leakage test device or a leak detector with a test chamber for introducing a flexible packaging to be tested, in particular a packaging formed by means of (gas-tight) foil, which contains packaging test gas, is proposed. The test gas is z. B. component of a contained in the packaging inert gas, which protective gas in the food industry, for example, a mixture of carbon dioxide (CO ₂ ) and nitrogen. The packaging generally encompasses a packaged product, for example foodstuffs as mentioned at the outset, a pharmaceutical product or the like, in particular sealingly sealing the latter from the atmosphere or sealing it from the medium. The leak testing device is preferably designed for the test gas test in the form of CO ₂ .

The leak testing device is characterized in that the leak testing device is set up to set a defined overpressure level acting on the packaging in the test chamber by means of a compressed gas, and subsequently to sense and evaluate a test gas concentration in the test chamber gas over a period of time.

By means of this embodiment of the leak-tightness test device, it is possible to provide a fault-tolerant, robust and reliable testing device with advantageously low constructional outlay. The gas pressure acting on the packaging causes - advantageously without potentially damaging mechanical intervention - to release test gas from the packaging in the case of existing packaging leaks, so that a leak test is made possible. Here, as the inventor found out, an advantageous only low pressure, d. H. only a small amount of compressed gas required for a given test.

Preferably, the invention uses a compressed gas which has only a small (eg 0.01% to 0.05%) or no test gas content, at least one proportion of test gas substantially less than that in the package to be tested (usually between 20% to 100%). Thus, a leak detection is further simplified and also shortened, as far as a significant and rapid increase in the test gas concentration can be observed with adjacent positive pressure. In preferred embodiments of the Dichtigkeitsprüfvorrichtung, in which test gas is used in the form of CO ₂ , can be provided, low-pressure industrial compressed air with a low CO ₂ content, z. B. in the range less than 0.1% to use.

For the adjustment of the defined overpressure level in the test chamber, the leak testing device preferably has a pressure gas source and a pressure measuring device, wherein the pressure gas source can be switched in dependence on a pressure measured in the test chamber via the pressure measuring device. The compressed gas source can advantageously be inexpensively a commercially available compressed gas cylinder, for example a compressed air cylinder, alternatively, for example, a different compressed gas supply.

The pressure measuring device can be embodied by means of a manometer, in particular a fine manometer (or otherwise), which can advantageously be provided reliably and robustly and, in particular, inexpensively. The compressed gas source may preferably via at least one valve, for. B. a solenoid valve (2/2-way valve), which is arranged in a flow path from the compressed gas source to the test chamber, are connected in response to the measured pressure to the test chamber. For controlling the valve, a control device of the leak test device can be provided, to which the signals of the pressure measuring device are supplied. The control device may be part of a control and evaluation unit of the leak testing device.

The leak testing device preferably has a gas sensor, in particular a CO ₂ sensor, for determining the test gas concentration, in particular an NDIR (non-dispersive infrared) or a ceramic sensor. The sensor is z. B. connected via a sensor interface with the controller. Provided within the scope of the invention is preferable to detect an increase in the test gas concentration in the test chamber gas over a (predetermined) period by means of the sensor (and the controller).

In a preferred embodiment of the leak test device, the gas sensor is accommodated in the test chamber. As a result, the component complexity for the production of the leak testing device can be minimized. However, a pressure equalization time with respect to the sensor may be required if the overpressure in the test chamber is adjusted prior to testing.

In a further preferred embodiment of the leak testing device, the gas sensor is arranged outside the test chamber, wherein the gas sensor communicates with the test chamber via a gas guide. In this case, the dead volume of the test chamber can be kept advantageously small and pressure compensation times can be advantageously eliminated. In this embodiment of the leak test device, a throttle device is preferably provided between the test chamber and the gas sensor, which can be introduced into the gas guide. By means of the throttle device, a gas flow rate from the test chamber to the gas sensor can be set at the defined overpressure, using a commercially available CO ₂ sensor (eg NDIR), in particular to a value in the range from 50 ml to 80 ml per minute. A preferred embodiment provides, for example, advantageously a simple tube as a gas guide and also as a throttling device, especially a Teflon tube, which allows the formation of very fine diameter and thus the desired throttle effect.

Noteworthy in the solution shown, which provides the arrangement of the sensor outside the test chamber is that due to the set pressure in the test chamber advantageously no separate suction device for conveying the chamber gas through the gas guide to the sensor is required. Also in the other solution, in which the sensor is arranged in the test chamber, a Prüfkammergasabsaugung is advantageously not necessary.

Provided it may be preferred that the Dichtigkeitsprüfvorrichtung comprises a device for circulating the Prüfkammergases, in particular one or a plurality of fans. The fans can be simple axial or radial fans, which are available at low cost. The circulating air can contribute to improved test gas detection due to a uniform test gas concentration in the test chamber gas.

In a preferred embodiment of the leak test device, this is designed for purging the test chamber. For this purpose, the test chamber z. B. to a gas outlet, which leads to a flushing of the test chamber with compressed gas, i. e. preferably on the part of the compressed gas source, is openly controllable. The gas outlet may be formed with a valve which is accessible via the controller, z. B. as before a solenoid valve. The flushing by means of compressed gas, which is provided before the beginning of a measuring operation after the introduction of the packaging into the test chamber, advantageously makes it easy to provide a defined measuring environment.

In the context of the present invention, it is advantageously sufficient to set the defined overpressure level in the test chamber, i. e. for the test, essentially to set a value in the range of 100 mbar to 200 mbar above atmospheric pressure, in particular to substantially 1100 mbar to 1200 mbar. As a result, a pressurized gas supply can advantageously last long, while the waiting time for a test start compared with conventional evacuation methods is also shortened.

Also proposed within the scope of the present invention is a method for leak testing flexible packages, in particular packagings formed by means of foil, which have a test gas filling, wherein the method can be carried out with a leak test device as described above. The method provides that in a first step, a package is introduced into the test chamber, wherein in a second step by means of Druckgasbeaufschlagung a predetermined overpressure level is set in the test chamber, and wherein in a third step over a (predetermined) duration, the test gas concentration in the test chamber gas is determined and evaluated, in particular by means of a gas sensor. Advantageously, the method simply provides reliable test results.

Preferably, in the proposed method, a flushing of the test chamber may be provided by means of compressed gas, which preferably takes place after the first and before the second step, i. e. with the packaging placed in the test chamber and the test chamber closed. Here defined test conditions are generated.

Furthermore, it is preferred that the evaluation in the third step takes place by threshold value comparison, wherein the threshold value can be predetermined in particular as a function of the packaging to be tested on the leak-tightness test device. At the threshold setting, which preferably takes place before the third step, a previously determined test gas content of the respective packaging can be used as a basis.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawings, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. Show it:

1 exemplary and schematically a leak testing device, wherein the gas sensor is arranged in the test chamber; and

2 exemplary and schematically a Dichtigkeitsprüfvorrichtung, wherein the gas sensor is arranged outside the test chamber.

In the following description of the figures, the same elements or functions are provided with the same reference numerals.

The 1 and 2 each exemplify a leak detector or a Dichtigkeitsprüfvorrichtung 1 for a leak test on packaging 3 (with gutten in it), which flexibly by means of foil 5 are formed, in particular gas-tight film 5 , for example all or alternatively partial, and contain a proportion of a test gas in the form of CO ₂ . The test gas is part of a protective gas, for example, in a food packaging, eg. As a sausage or cheese packaging, or alternatively introduced as a test gas specifically for this purpose in the packaging, for example in a pharmaceutical packaging.

The leak tester 1 includes a housing 7 for receiving components of the leak tester 1 , In the case 7 is a test chamber 9 arranged, which is openable and closable, in particular sealingly closable. In the test chamber 9 are the packages to be tested 3 recoverable. For introducing the packaging 3 becomes the test chamber 9 opened, for example via a cover element (not shown), closed for further examination.

To support the packaging to be tested 3 can be a grid element 11 , For example, be provided a perforated plate, which preferably with Distance to the bottom of the test chamber 9 is arranged. Due to the gas permeable support 11 can also be at the bottom of a packaging 3 in case of leakage test gas in the volume of the chamber 9 be isolated, ie be detected. In addition, for example, at least one in the chamber 9 introduced (or communicating with the chamber) fan 13 , a uniform gas mixing in the chamber 9 be achieved, so that a reliable leak test is guaranteed without fluctuations on the sensor. An accumulation of CO ₂ at the bottom of the chamber 9 This is advantageously counteracted.

According to the invention, the leak testing device 1 furnished, a defined and on the packaging 3 acting overpressure level in the test chamber 9 , in particular in the range between 1100 mbar and 1200 mbar, to be adjusted by means of a compressed gas and subsequently a test gas concentration in the test chamber gas 15 (Gas in volume 17 the test chamber 9 ) to sense and evaluate over a duration.

For setting the defined overpressure level in the test chamber 9 has the leak tester 1 a compressed gas source 19 on, which via an external compressed gas connection or (alternatively or additionally) as compressed gas cylinder 19 is provided. The compressed gas source 19 can in the case 7 be included 1 , or outside the case 7 be arranged 2 , for example, via a separate connection to the housing 7 be guided. As compressed gas, the source of compressed gas 19 preferably pure compressed air (industrial compressed air) with a low CO ₂ content, for example, provide 0.1% CO ₂ .

Furthermore, to set the defined overpressure level in the test chamber 9 and thus for the production of defined test conditions, has the Dichtigkeitsprüfvorrichtung 1 a pressure measuring device 21 on, by means of which the pressure in the volume 17 is measurable. The pressure measuring device 21 is preferred by means of a fine gauge 21 educated.

Also continue to adjust the defined overpressure level in the test chamber 9 has the leak tester 1 a control and evaluation unit 23 on, about which and a (solenoid) valve 25 the compressed gas source 19 in communication with the test chamber 9 is switchable (control line 25a ), in particular as a function of a pressure measuring signal which also with the control and evaluation 23 connected pressure measuring device 21 (Signal line 21a ). For pressurized gas admission of the test chamber 9 , In particular, until reaching the predetermined pressure level, the valve 25 via the control and evaluation unit 23 be controlled open, so that compressed gas from the compressed gas source 19 into the chamber volume 17 flows (over an inlet 27 ). Is the intended pressure level in the chamber 9 reached (measurement signal from the pressure measuring device 21 ), controls the control and evaluation unit 23 the valve 25 closed.

After generating the predetermined overpressure level, a test gas concentration in the test chamber gas 15 to sense and evaluate a duration, that is to obtain a statement about the tightness of a package, has the Dichtigkeitsprüfvorrichtung 1 a gas sensor 29 which is preferably designed as an NDIR sensor (non-dispersive infrared sensor), alternatively, for example, as a ceramic sensor. The sensor 29 continuously provides a measurement signal, so that a test gas increase in the test chamber gas can be detected reliably in a simple manner over a period of time.

In the preferred embodiment of the leak tester 1 to 1 , is the NDIR sensor 29 within the test chamber 9 arranged, ie for sensing in communication with the volume 17 , One with the sensor 29 connected measuring signal line 29a is to the control and evaluation unit 23 guided, ie for the evaluation of the measurement signal. This solution requires advantageous only low structural complexity.

In the further preferred embodiment of the Dichtigkeitsprüfvorrichtung 1 according to 2 is the NDIR sensor 29 outside the test chamber 9 arranged and is over a gas guide 31 , for example in the form of a tube, with the inclusion of a throttle device 33 in communication with the volume 17 the test chamber 9 , The gas guide 31 with throttle function 33 is next to the actual guidance of the test chamber gas 15 adapted to a gas flow rate to the sensor 29 adjust, which allows a reliable sensing, ie without affecting the sensor in its sensing properties (cooling). At the same time, the throttle device 33 , for example in the form of a throttle valve, ensures that the leak test in the chamber 9 generated pressure level remains sufficiently stable for a long time, so that the leak test via the sensor 29 is easily possible. The gas guide is preferred 31 with throttle function 33 formed by a Teflon hose having a flow-through cross section of a diameter in the range of, for example, 0.5 mm to 1.5 mm. Preferably, the gas flow rate at the defined pressure level is set to a value in the range of 50 to 80 ml per minute. This solution in which both the sensor 29 as well as the test chamber gas 15 after exiting the chamber 9 are exposed to atmospheric pressure, is advantageously almost without measuring Dead time off. In addition, an optional arrangement of the sensor is advantageous 29 in the case 7 allows.

In order to continue to achieve improved and in particular defined test conditions before the start of a leak test is provided by means of compressed gas from the compressed gas source 19 the test chamber 9 to be able to rinse, leaving air with a relatively high proportion of test gas from the test chamber 9 displaced and replaced by compressed gas, ie preferably by compressed gas with a relatively low and further preferably known test gas content. For rinsing has the Dichtigkeitsprüfvorrichtung 1 an outlet 35 from the test chamber 9 on, which via another (solenoid) valve 37 open to the atmosphere. The valve 37 is this with the control and evaluation 23 connected (control line 37a ) and controllable over the same.

The text below deals with the method according to the invention for leak testing, which with the above-described leak test device 1 is feasible.

In the method, in a first step, the package to be tested 3 into the test chamber 9 brought in. For this purpose, the test chamber 9 opened and after insertion of the packaging 3 closed tightly.

Preferably, the test chamber is provided below 9 flush with compressed gas. This is the valve 25 on the part of the control and evaluation unit 23 openly controlled, allowing pressurized gas into the test chamber 9 over the inlet 27 arrives. Furthermore, the valve is also 37 openly controlled, allowing air out of the test chamber 9 over the valve 37 or the outlet 35 can be displaced. Subsequently, the valve 37 be controlled again in closed position.

After closing the second valve 37 can in a second step by means of Druckgasbeaufschlagung the (predetermined) pressure level in the test chamber 9 be set. With a measuring signal from the pressure measuring device 21 , which indicates the reaching of the predetermined pressure level, controls the control and evaluation unit 23 the valve 25 closed. Due to the overpressure in the test chamber 9 can test gas from the introduced packaging via a respective leak to a discharge into the chamber volume 17 be urged. A recirculation ventilation 13 , which via the control and evaluation unit 23 is switchable, line 13a , ensures a uniform concentration of the test gas in the test chamber 9 ,

In a third step, the test gas concentration in the test chamber gas 15 determined and evaluated over a (predetermined) duration. For this purpose, the test chamber gas is detected 15 exposed sensor 29 the gas concentration continuously, so that an increase in the gas concentration, which indicates a leak in the package, easily identifiable. The predetermined sensing duration can, in particular in dependence on the dead volume in the chamber 9 , the (expected) test gas content in the packaging 3 and / or the test gas content in the compressed gas, be between a few seconds to, for example, 1 min.

The evaluation in the third step is carried out by threshold value comparison, the threshold THRES depending on the package to be tested 3 at the leak tester 1 is specifiable in particular. Exceeds the determined test gas content in the test chamber gas 15 the threshold THRES, this is signaled and the packaging 3 can be rejected as faulty or leaking. For example, the THRES threshold may be based on packaging samples prior to a test or series of tests based on the determined proportion of test gas in a sample 3 be set.

For setting the threshold value THRES and / or for displaying the test result, the control and evaluation unit 23 or the leak tester 1 an input and output device 39 exhibit.

LIST OF REFERENCE NUMBERS

1

Dichtigkeitsprüfvorrichtung

3

packaging

5

foil

7

casing

9

test chamber

11

support element

13

Fan

13a

management

15

Prüfkammergas

17

volume 9

19

Compressed gas source

21

Pressure measuring device

21a

signal line

23

Control and evaluation unit

25

Valve

25a

control line

27

inlet 9

29

sensor

29a

signal line

31

gas guide

33

throttle

35

outlet

37

Valve

37a

control line

39

Input / output device

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19642099 A1 [0004]
• DE 69110706 T2 [0005]

Claims (12)

Tightness tester ( 1 ) with a test chamber ( 9 ) for introducing a flexible packaging to be tested ( 3 ), in particular by means of a film ( 5 ) formed packaging ( 3 ), which packaging ( 3 ) Test gas, in particular in the form of CO ₂ , characterized in that the Dichtigkeitsprüfvorrichtung ( 1 ), a defined one and on the packaging ( 3 ) acting overpressure level in the test chamber ( 9 ) by means of a compressed gas and subsequently a test gas concentration in the test chamber gas ( 15 ) to sense and evaluate over a duration. Tightness tester ( 1 ) according to claim 1, characterized in that the leak test device ( 1 ) for setting the defined overpressure level, a compressed gas source ( 19 ) and a pressure measuring device ( 21 ), wherein the compressed gas source ( 19 ) depending on a via the pressure measuring device ( 21 ) measured pressure in the test chamber ( 9 ) is switchable. Tightness tester ( 1 ) according to one of the preceding claims, characterized in that the tightness test device ( 1 ) a gas sensor ( 29 ), in particular a CO ₂ sensor, for determining the test gas concentration, in particular an NDIR or a ceramic sensor ( 29 ). Tightness tester ( 1 ) according to claim 3, characterized in that the gas sensor ( 29 ) in the test chamber ( 9 ) is recorded. Tightness tester ( 1 ) according to claim 3, characterized in that the gas sensor ( 29 ) outside the test chamber ( 9 ), wherein the gas sensor ( 29 ) with the test chamber ( 9 ) via a gas guide ( 31 ) communicates. Tightness tester ( 1 ) according to claim 5, characterized in that the Dichtigkeitsprüfvorrichtung ( 1 ) between the test chamber ( 9 ) and the gas sensor ( 29 ) a throttle device ( 33 ), in particular a hose, by means of which a gas flow rate from the test chamber ( 9 ) to the gas sensor ( 29 ) is adjusted at the defined overpressure, in particular to a value in the range of 50 ml to 80 ml per minute. Tightness tester ( 1 ) according to one of the preceding claims, characterized in that the tightness test device ( 1 ) a device ( 13 ) for circulating the test chamber gas, in particular at least one fan ( 13 ). Tightness tester ( 1 ) according to claim 2 with one of claims 3 to 7, characterized in that the test chamber ( 9 ) a gas outlet ( 35 ), which leads to a flushing of the test chamber ( 9 ) by means of the compressed gas source ( 19 ) is openly controllable. Leakage tester according to one of the preceding claims, characterized in that the defined overpressure level is set substantially to a value in the range of 100 mbar above atmospheric pressure, in particular to substantially 1100 mbar. Method for testing the tightness of flexible packaging ( 3 ), in particular packages which are formed by means of film and which contain a test gas portion, in particular in the form of CO ₂ , the method being provided with a leak-tightness test apparatus ( 1 ) is executable according to one of the preceding claims, wherein in a first step, a package ( 3 ) into the test chamber ( 9 ) is introduced, wherein in a second step by means of pressurized gas, a predetermined pressure level in the test chamber ( 9 ) and wherein in a third step over a period of time the test gas concentration in the test chamber gas ( 15 ) is determined and evaluated, in particular by means of a gas sensor ( 29 ). A method according to claim 10, characterized in that after the first and before the second step, a flushing of the test chamber ( 9 ) by means of compressed gas. Method according to one of claims 10 and 11, characterized in that the evaluation in the third step takes place by threshold value comparison, the threshold value (THRES) depending on the package to be tested ( 3 ) at the leak test device ( 1 ) is specifiable in particular.

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