Patent Description:
Within the art of paperboard-based liquid packaging, it is known to produce a blank and fold and assemble the blank to produce a container. The container may then be utilised to hold a liquid, e.g. dairy products, such as milk or yoghurt, or juices.

The blank is typically produced from a laminate packaging material, which typically comprises a multi-ply paperboard sheet on which is laminated one or a plurality of barrier layers for holding the liquid and/or prevent migration of air and flavours through the paperboard. A barrier layer may typically comprise a polyethylene or an aluminium layer.

A method of producing the blank from the laminate packaging material typically comprises the steps of cutting the laminate packaging material to a predefined shape and providing crease lines in the laminate packaging material, and a method of producing the container from the blank typically comprises the step of folding the blank along crease lines to produce the container.

A crease line, or crease, may be defined as an embossed or impressed depression on one side of the laminate packaging material with a corresponding raised ridge or welt, also referred to as the bead, on the other side forming a line along which the laminate packaging material is structurally weakened and along which the laminate packaging material will bend or fold when pressure is applied. After folding, parts of the blank are glued or welded together to form a sealed container.

As is known in the art, paperboard-based containers may alternatively be made in a roll-fed process in which a web of paperboard-material is continuously folded to form a tube, filled with the food product, sealed to form so called pouches, and finally cut to form individual containers.

Generally, there is a need to control or verify the integrity of the container, e.g. to control the container's susceptibility to leakage and also to control the strength of the container, in particular the strength of sealed seams. Also, as part of a development program the integrity level of a new container must be tested before launching it in the market, and in the serial production phase the integrity level of the packages must be ensured. Typically, in the production phase, container samples are continuously taken from the production and tested to monitor their integrity level.

The standard method of testing the integrity of produced containers is the so-called Blue Die Test (BDT). In this test, leakage is detected by means of coloured die. The die is provided on the inside of the container. If the die leaks through the package, the die will be easily visible on the outside of the package when inspected by an operator.

A drawback of the BDT is that it is a subjective method which is unsuitable for automation. Furthermore, the test is relatively time-consuming. Yet another drawback is that the test requires the use of unwanted chemicals.

<CIT> discloses a method and a system for measuring leak tightness (i.e. pressure testing) of sealed packages. The method includes providing a sealed package having a first deformable volume and providing a second deformable volume containing a fluid. The method includes clamping the second deformable volume against the sealed package and determining a first pressure in the second deformable volume at a first moment and a second pressure at a second moment spaced in time. The method includes determining leak tightness of the sealed package on the basis of the first and second pressures.

With this method and system, the package to be tested does not need to be pierced. The method and system are thus directed to non-destructive testing. Further this method and system measure the pressure in the package indirectly via the second deformable volume. The method and system require that the package to be tested is deformable, which limits the scope of use. gable top cartons may not be suitable for use with this method and system, as the forces applied from the second deformable volume may be partly or fully absorbed by the structural integrity of the gable top carton, thus making the indirect pressure readings from the second volume inaccurate. The method is also sensitive for relative movement between the two volumes.

<CIT> discloses a seal testing apparatus for testing the integrity of a seal in the packaging of vacuum packed product and a method of testing seal integrity. The apparatus includes a mechanical gripper that grips a portion of the packaging and is urged away from the packaging. A sensor monitors the movement of the gripper relative to the vacuum-packed product and an evaluator compares the sensed movement of the gripper with an acceptable profile and accepts or rejects the product based on the comparison.

Leaks are thus detected by means of a gripper pulling in the packaging and a distance sensor measuring how far the gripper can pull the packaging relative to the packed product. This means that the apparatus and method will only work with a flexible packaging (e.g. made of plastic) and that the packed product must be in a solid state.

ASTM F2095- 07e1 "<NPL> discloses a test method for measurements of leaks in non-porous film, foil or laminate flexible pouches and foil-sealed trays. The testing apparatus comprises a means to enter a package so that an inflation pressure can be applied to the package and changes in internal pressure can be sensed. However, it is essential that said means provides a sufficiently leak-tight seal to the package.

<CIT> discloses a method of testing for leaks in containers. A nozzle seals to the bung hole and air under pressure is introduced. The rate of increase of internal pressure during the testing operation is sensed by supporting members and compared to a preprogrammed rate of pressure increase, and if the rate of increase does not come up to a pre-set level, within a pre-set time, a leak is indicated, and the container can be rejected.

<CIT> discloses a pressure testing apparatus has a probe with a piercing tip. The probe sealingly engages a special entry port having a mating pressure-coupling body which establishes a sealing connection with the probe before the tip pierces the package. An adhesive sheet flange extends about the body of the entry port and sealingly secures the body to the package.

The present invention is directed to a method and a system that may solve or at least reduce at least one of the aforementioned problems or challenges.

According to one aspect, the present invention brings forward a method of testing leakage and/or strength of paperboard-based according to appended claim <NUM>.

Said first pressure value may be within the range of <NUM> mbar to <NUM> mbar.

Said predetermined period of time may be within the range of <NUM> seconds to <NUM> seconds.

The step of attaching the nozzle to the through-opening comprises the sub-steps of:.

The step of attaching the nozzle to the through-opening may comprise the sub-steps of:.

The step of performing the first series of steps may comprise:.

The method may comprise the step of supporting side panels of the container. Thus, the container can be prevented from flexing or bulging during said first series of steps.

The method of producing the through-opening in the container may comprise the sub-steps of:.

The method may comprise the step of removing a food product from the container via the through-opening prior to performing said at least one of the first series of steps and the second series of steps.

According to yet a further aspect, the present invention brings forward a pressure testing apparatus for testing leakage and/or strength of a paperboard-based according to appended claim <NUM>.

The pressure testing apparatus may further comprise a housing in which the nozzle is arranged, wherein the housing is adapted for receiving the container and attaching the nozzle to the container.

The housing may comprise a support surface configured to be brought into engagement with an outer surface section of the container encircling the through-opening, and the support surface and the sealing disk may be configured to engage the container in a clamping motion, thus allowing the container to be clamped between the support surface and the sealing disk.

The nozzle may be arranged to the support surface and configured to stroking relative to the support surface.

The housing may comprise a support structure for supporting side wall panels of the received container during testing.

The pressure testing apparatus may comprise a portable power source for powering the pressure testing apparatus.

The pressure testing apparatus may comprise a computer program comprising instructions which, when the program is executed by a computer, cause the computer to instruct the pressure testing apparatus to carry out said first series of steps and/or said second series of steps.

According to a further aspect, the present invention brings forward a computer program comprising instructions which, when the program is executed by a computer installed in said pressure testing apparatus, cause the computer to instruct the pressure testing apparatus to carry out said first series of steps and/or said second series of steps.

According to yet a further aspect, the present invention brings forward a system for testing leakage and/or strength of a paperboard-based container, wherein the system comprises:.

wherein the drilling and cutting apparatus comprises a receptacle for receiving a container and a drilling or cutting device for producing a through-opening, for attachment of the nozzle, in the received container.

Above-discussed preferred and/or optional features of each aspect of the invention may be used, alone or in appropriate combination, in the other aspects of the invention.

Following drawings are appended to facilitate the understanding of the invention:.

In the drawings, like reference numerals have been used to indicate common parts, elements or features unless otherwise explicitly stated or implicitly understood by the context.

In the following, one or more specific embodiments of the invention will be described in more detail with reference to the drawings. However, it is specifically intended that the invention is not limited to the embodiments and illustrations contained herein but includes modified forms of the embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.

<FIG> shows a paperboard-based container <NUM> for a pourable food-product. As is known in the art, such containers are produced from a laminate packaging material, which typically comprises a multi-ply paperboard sheet on which is laminated one or a plurality of barrier layers for holding the food product and/or prevent migration of air and flavours through the paperboard. A barrier layer may typically comprise a polyethylene or an aluminium layer.

As is known in the art, paperboard-based container can have many forms. Generally, however, such containers have a substantially flat bottom panel <NUM>, forming a bottom of the container, a top panel <NUM>, forming a top of the container and sometimes comprising a closure device <NUM> sealing an opening for dispensing the food product, and side panels <NUM> extending between the bottom panel <NUM> and the top panel <NUM>. The number and shape of the side panels may vary depending on container type. In the disclosed embodiment, the container <NUM> has a substantially quadrangular cross-section and the side panels comprise a front panel 18a, a rear panel 18b and two lateral panels 18c, 18d (see also <FIG>).

The container <NUM> is a gable-top container. As is known in the art, such a container is produced from a carton blank that is folded and filled with the food product in a filling machine. As is also known in the art, paperboard-based containers may alternatively be made in a roll-fed process.

Irrespective of the process by which containers are produced, there is a need to verify that the produced containers are capable of holding the food product in an intended manner. This can be done by sampling produced containers and verifying the food product holding capability of the sampled containers. As is known in the art, in particular the top and bottom panels of the container may be prone to leakage.

In the following, an embodiment of method for verifying the food product holding capability of the gable-top container <NUM> disclosed in <FIG> will be discussed. It is to be understood, however, that the method can be used also for verifying the food product holding capability of roll-fed containers. Also, it is to be understood that the method can be applied also to containers, gable-top or roll-fed, having shapes and forms other than the container <NUM> disclosed in <FIG>.

The first step according to the present embodiment of the method is to obtain a sample of a sealed container <NUM>. This can be done by taking a sample from the stream of containers produced in a filling machine. In such a case, the sampled container will be filled with the food product. Alternatively, a container sample can be obtained by running the filling machine without filling the container with the food product, in which case a sealed but empty container is obtained.

Consequently, with reference also to <FIG> which is a flowchart schematically illustrating the present embodiment of the method, the first step <NUM> of the method is to produce a sealed container. The produced container may be empty or filled with a food product.

The next step <NUM> is to produce a through-opening in the container <NUM>. This may be effectuated using a drilling or cutting apparatus, e.g. the apparatus <NUM> illustrated in <FIG>. The apparatus <NUM> comprises a receptacle or cavity <NUM> having a cross-section with dimensions that substantially correspond to the dimensions of the cross-section of the container <NUM>. The receptacle <NUM> has a back-stop (not visible) ensuring that the container <NUM> can be inserted into the receptacle <NUM> to a precise depth.

The back-stop and the receptacle, by virtue of having a cross-section substantially corresponding to the cross-section of the container <NUM>, allow containers to be positioned in the apparatus <NUM> in a precise and repeatable manner, thus allowing containers having the same form to be positioned in the apparatus <NUM> in a common cutting or drilling position.

The apparatus <NUM> also comprises a drilling or cutting device <NUM> arranged to drill or cut a through-opening or hole in the container <NUM> when it is positioned in the apparatus <NUM> in a drilling or cutting position. In the present embodiment of the apparatus <NUM>, the drilling or cutting device <NUM> is positioned above the receptacle <NUM>, thereby allowing a drilling or cutting bit (not visible in <FIG>) of the device <NUM> to be brought down into the receptacle <NUM> from above.

When producing a through-opening in the container <NUM>, the container <NUM> is introduced in the receptacle <NUM> and brought to a drilling or cutting position, in which the bottom panel <NUM> of the container <NUM> is in contact with the back-stop. In the present example embodiment, the container <NUM> is positioned in the apparatus <NUM> with the front panel 18a facing upwards.

When the container <NUM> is in the drilling or cutting position, the drilling or cutting device <NUM> is activated and the drilling or cutting bit is brought downwards to drill or cut the through-opening in the container. By virtue of the through-opening being drilled or cut in a side panel of the container facing upwards in the apparatus <NUM>, spillage of any food product in the container <NUM> can be minimized.

The drilling or cutting device <NUM> may comprise an electric motor configured to rotate the drilling or cutting bit in a drilling or cutting motion during the drilling or cutting operation. The device <NUM> may also comprise actuators, e.g. electric or pneumatic actuators, configured to actuate the drilling or cutting bit vertically during the drilling or cutting operation. Alternatively, the vertical actuation of the drilling or cutting bit may be effectuated manually.

After the through-opening has been drilled or cut, the drilling or cutting bit is raised and the container <NUM> is removed from the apparatus <NUM>. If the container <NUM> contains a food product, the food product may then be removed from the container <NUM> via the through-opening, as is illustrated in step <NUM> in <FIG>.

In the example container <NUM>, the through-opening <NUM> (see <FIG>) is drilled or cut substantially centrally in the front panel 18a, i.e. substantially equidistant from the bottom <NUM> and top panel <NUM>, and/or substantially equidistant from corner edges 28a and 28b of the container <NUM>. Whereas this may be a suitable position for the through-opening <NUM> in the present example container <NUM>, it is to be understood that the position of the through-opening in containers having other forms and/or shapes may be different. Generally, however, the through-opening should advantageously be positioned at a distance from crease lines, embossing patterns or other indentations in the side panel surface. For example, the through-opening may be positioned at least <NUM>, and more preferable at least <NUM>, from such crease lines, embossing patterns and indentations. Also, the region of the through-opening should preferably be substantially flat.

In the example container <NUM>, the through-opening <NUM> is circular and has a diameter D that is within the range of <NUM> to <NUM>. It is to be understood, however, that the through-opening may have other dimensions and/or shapes, in particular in containers having side panels with shapes and/or forms differing from the shape and form of the front panel 18a of container <NUM>.

When the through-opening <NUM> has been produced in the container <NUM> and any food product in the container has been removed, the container is positioned in a pressure testing apparatus <NUM> (see <FIG>) and a nozzle <NUM> is attached to the through-opening <NUM> in a gas-tight manner (see <FIG>), i.e. in a manner that sealingly connects the nozzle <NUM> to the through-opening and prevents leakage of a gaseous fluid between the nozzle <NUM> and the container <NUM>. In <FIG>, this step is illustrated as <NUM>. Attachment of the nozzle <NUM> to the through-opening <NUM> in a gas-tight manner may be effectuated in many ways. However, the nozzle <NUM> may advantageously have a distal end <NUM> and an annular, flexible sealing disk <NUM> sealingly attached to and arranged circumferentially about the distal end <NUM>. The distal end <NUM> may have a lateral extension allowing the distal end <NUM> to fit within the through-opening <NUM>, and the disk <NUM> may have a lateral extension that is sufficiently large to allow the disk <NUM> to cover the through-opening. The distal end <NUM> may for example have a substantially circular cross-section having a diameter that is less than the diameter D of the through-opening <NUM>, and the sealing disk <NUM> may have a circular, outer border having a diameter that is larger than the diameter D of the through-opening <NUM>.

This allows the distal end <NUM> and the disk <NUM> to be inserted through the through-opening <NUM>, as is illustrated in <FIG> and <FIG>, and the disk <NUM> to be brought into sealing engagement with a section <NUM> of the inside surface of the container <NUM> surrounding the through-opening <NUM>, as is illustrated in <FIG>. Since the sealing disk <NUM> has a diameter that is larger than the diameter of the through-opening <NUM>, a lubricant, e.g. silicon oil, may be applied on a section of the outside surface of the container <NUM> surrounding the through-opening, such that insertion of the disk <NUM> through the through-opening <NUM> is facilitated.

Once the disk <NUM> has been brought through the through-opening <NUM>, the movement of the tube/disk assembly is reversed such that the disk <NUM> is brought into contact with the inside surface of the carton <NUM>, covering the through-opening <NUM>. In order to be able to provide a gas-tight seal against the inside surface of the container in this position, the disk <NUM> should have a lateral extent allowing the disk to overlap the through-opening in all directions. At the same time, the lateral extent of the disk <NUM> must not prohibit the insertion of the disk through the through-opening <NUM>. In embodiments where the through-opening <NUM> and the disk <NUM> are circular, it has been found that a gas-tight seal can be achieved while allowing the disk to be inserted into the through-opening if the disk has a radius that is approximately <NUM> larger than the radius of the through-opening <NUM>.

The pressure testing apparatus <NUM> may have a housing <NUM> configured to hold the container during pressure test procedure. As illustrated in <FIG>, the apparatus <NUM> may comprise wall sections and the nozzle <NUM> may be arranged in one of the wall sections. Like the apparatus <NUM>, the housing <NUM> may have a cross-section with internal dimensions that substantially correspond to the dimensions of the cross-section of the container <NUM>.

In the embodiment shown in <FIG>, the housing <NUM> comprises parallel side walls 50a and 50b, a lid section 50c and a base section 50d. The nozzle <NUM> is arranged in the lid section 50c and this section 50c is hinged to side wall 50b. In other embodiments, the nozzle may be arranged stationary in one of the side walls, in which case the opposite side wall may be detachably connected or hinged to the rest of the housing in order to allow the container to be placed in the common testing position. In such an embodiment, it is the container that is brought over the nozzle instead of the nozzle being brought through the through-opening.

The housing <NUM> can be operated between an open position and a closed position. In the open position, the lid section 50c is separated from wall sections 50a and 50b allowing a container to be positioned in the housing, as is illustrated in <FIG>. In the closed position, the side wall of the housing <NUM> supports the outer side walls <NUM> of the container <NUM>. As illustrated in <FIG>, a locking device <NUM> can be provided to keep the housing <NUM> closed.

When the housing <NUM> is in the open position (see <FIG>), the container <NUM> can be placed in the housing <NUM> and positioned so that the through-opening <NUM> is aligned with the nozzle <NUM>. The housing <NUM> may comprise alignment means, e.g. alignment markings (not illustrated), ensuring that the container <NUM> is properly aligned in the housing. The alignment means and the housing <NUM>, by virtue of having a cross-section substantially corresponding to the cross-section of the container <NUM>, allow containers to be positioned in the housing <NUM> in a precise and repeatable manner, thus allowing containers having the same form to be positioned in the housing <NUM> in a common testing position.

With the container <NUM> placed into the housing <NUM>, the housing is closed. During the pivotal travel of the lid section 50c from the open position to the closed position (see <FIG>), the nozzle <NUM> will enter the through-opening <NUM>. The longitudinal extension of the nozzle <NUM> is adapted to allow the distal end <NUM> of the nozzle <NUM> to enter the through-opening <NUM>. The distal end <NUM> of nozzle <NUM> has a smaller diameter than the through-opening <NUM> and will thus easily enter the through-opening. As stated above, the disc <NUM> has a larger diameter than the through-opening <NUM> in the container <NUM> and will therefore elastically deform during entry through said through-opening <NUM>. The force required to bring the disk <NUM> through the through-opening will depend on the diameter, thickness and material of the disc <NUM>. The required force should not jeopardize damaging of the container <NUM>, e.g. tearing the edge of the through-opening <NUM>. The disk may advantageously be made from silicon and may advantageously have a Shore A hardness of <NUM>. A lubricant, e.g. silicon oil, may be applied on the section of the outside surface of the container <NUM> surrounding the through-opening to facilitate the insertion of the disk <NUM> through the through-opening <NUM>. Alternatively, or in addition, the disk <NUM> may have a frustoconical shape in order to facilitate the insertion of the disk <NUM>. The frustoconical shape will also contribute to centre the nozzle <NUM> in the through-opening <NUM> during said insertion.

When the housing <NUM> is closed, the distal end <NUM> of the nozzle <NUM> and the disc <NUM> is located inside the container <NUM> (see <FIG>). Since the disc <NUM> will elastically deform during entry through the through-opening <NUM>, it must be brought a certain distance past side panel 18a, i.e. the side panel comprising the through-opening <NUM>. It will therefore typically be located at a distance from the inner surface of the side panel 18a immediately after entry through the through-opening <NUM>. At this stage the disc <NUM> is not necessarily sealing against the inner surface of side panel 18a. Once the disk <NUM> has entered through the through-opening <NUM>, the movement of the nozzle <NUM> is therefore reversed, bringing the disk <NUM> into gas-tight engagement with the inner annular surface section <NUM> of the panel 18a encircling the through-opening <NUM>. When the disc <NUM> is brought into gas-tight engagement with the annular surface section <NUM>, the inner surface of the lid section 50c provides a support surface or an abutment surface <NUM> for the disc <NUM>. Consequently, when the disc <NUM> is brought into engagement with the inner surface of the panel 18a the panel 18a becomes sandwiched between the disc <NUM> and the support surface <NUM> formed by the lid section 50c. In particular, the sealing disk <NUM> is brought into gas-tight engagement with the inner surface section <NUM> of the container <NUM> encircling the through-opening <NUM> and the support surface <NUM> is brought into engagement with an outer surface section <NUM> of the container <NUM> encircling the through-opening <NUM> (se <FIG>).

In order to ensure the gas-tight engagement between the surface section <NUM> and the disk <NUM>, the disk <NUM> should advantageously overlap the through-opening <NUM>, i.e. extend beyond the lateral extent of the through-opening, by at least <NUM>. However, in order to facilitate insertion of the disk <NUM> through the through-opening <NUM> preferably the overlap should not be more than <NUM>.

The nozzle <NUM> comprises a conduit <NUM> which, at one end, is connected to a pressure unit <NUM>. At the other end the conduit <NUM> opens into apertures <NUM> in the distal end <NUM> of the nozzle <NUM> (see <FIG> and <FIG>).

Once the nozzle <NUM> has been attached to the through-opening <NUM>, the container can be pressure tested, e.g. tested for leakage and strength.

<FIG> shows a container <NUM> positioned in the housing <NUM> and ready for testing. In the following, two examples of pressure testing of the container will be discussed, namely leakage testing and strength testing.

When performing a leakage test, a gaseous fluid is injected into the container <NUM>. The gaseous fluid is supplied to the inside of the container <NUM> through the apertures <NUM> which is in fluid communication with the pressure unit via the conduit <NUM>. The pressure unit may comprise a pump or a pressure tank. The pressure unit may be supplied with ambient air, nitrogen or any other gaseous fluid.

A pressure sensor is used to measure the pressure inside the container <NUM>. The pressure sensor <NUM> may be arranged at the distal end of the nozzle (see <FIG>).

In the leakage test, the pressure in the container <NUM> is increased by injecting the gaseous fluid into the container <NUM> until a predetermined, first pressure value p<NUM> is obtained in the container. In <FIG> this step is illustrated as <NUM>. The first pressure value p<NUM> may be within the range of <NUM> mbar to <NUM> mbar.

When the first pressure value p<NUM> is obtained in the container <NUM>, the gaseous fluid is prevented from entering or exiting the container <NUM> via the nozzle <NUM>, as is indicated in step <NUM> in <FIG>. This can be achieved by isolating the pressure source from the inner volume of the container <NUM>. A valve (not shown) may be used to isolate the container <NUM> from the pressure source. The valve may preferably be arranged at the nozzle <NUM> but may alternatively be arranged in the pressure tank or anywhere along the conduit <NUM>.

Consequently, according to one embodiment of the method a valve (not shown) in the nozzle <NUM> is closed to prevent gaseous fluid from entering or exiting the container <NUM> via the nozzle <NUM> when the first pressure value p<NUM> has been obtained in the container <NUM>.

At a predetermined time twait after the gaseous fluid has been prevented from entering or exiting the container <NUM> via the nozzle <NUM>, a second pressure value p<NUM> is measured in the container <NUM> and the difference in pressure between the first pressure value p<NUM> and the second pressure value p<NUM>, i.e. pdrop = p<NUM> - p<NUM>, is used as a measure of leakage of the container. In <FIG> this step is illustrated at <NUM>.

The predetermined time twait may typically be within the range of <NUM> to <NUM>.

Throughout the test, the pressure inside the container <NUM> may be continuously measured and logged and at twait the difference in pressure pdrop = p<NUM> - p<NUM> may be calculated.

The measured leakage is evaluated based on comparison with target values. If the container <NUM> has a leakage below a given target value, the container is considered to have passed the test.

If no further test is required, the test procedure may then be terminated, as is illustrated in step <NUM>.

When performing the strength test, the pressure in the container <NUM> is increased by injecting a gaseous fluid into the container <NUM>. This is performed in the same manner as for the leakage test. The equipment and test setup of the leakage test is typically used also for the strength test. While pressurizing the container <NUM>, the pressure inside the container <NUM> can be continuously measured. Unlike the leakage test, however, the pressurizing of the container <NUM> is not stopped at a given first pressure value. Instead the pressure is increased until the container <NUM> fails and the pressure value at failure, i.e. the maximum pressure value pmax obtained in the container <NUM> prior to the container <NUM> failing, is measured, as is indicated in steps <NUM> and <NUM> in <FIG>. The maximum pressure value pmax is then used a measure of the strength of the container <NUM> and of corresponding containers having the same design. The test procedure may then be terminated, as is illustrated in step <NUM>.

The strength test may follow the leakage test in a combined leakage-strength test sequence, as is indicated by dashed line <NUM> in <FIG>. Alternatively, a strength test may be performed on a container without the container previously having been subjected to a leakage test, as is indicated by line <NUM> in <FIG>.

In order to prevent or at least minimize that bulging or flexing of the container <NUM> results in erroneous pressure value readings, especially during the leakage test, it may be advantageous that the side panels <NUM> of the container <NUM> are supported at least during steps <NUM> to <NUM>. In the apparatus shown in <FIG>, a substantial section of each side panel 18a-18d is supported (by side walls 50a, 50b, lid portion 50c and base portion 50d). However, in other embodiments only a minor portion of the container side panels may be supported or, depending on the container design, only some but not all side panels.

The bottom panel <NUM> and the top panel <NUM> are usually sufficiently stiff to prevent bulging or flexing during the leakage test. Therefore, there is no need to support these panels during steps <NUM> to <NUM>. Also, since it is the bottom and top panels that are most susceptible to breakage, these panels should preferably not be supported during the breakage test (steps <NUM> and <NUM>). Supporting the bottom and top panels will risk giving too high a pressure value at failure of the container.

<FIG> schematically illustrates a container testing system <NUM> according to one embodiment of the present invention.

The system <NUM> comprises a drilling or cutting apparatus <NUM> having a drilling or cutting device <NUM> configured for drilling or cutting a through-opening in a paperboard-based container. The drilling or cutting apparatus <NUM> may be of the same type as is disclosed in <FIG>.

The system <NUM> further comprises pressure testing apparatus <NUM> having a nozzle <NUM> configured to be attached to the through-opening of the container in a gas-tight manner. The pressure testing apparatus <NUM> may be of the same type as is disclosed in <FIG>.

The pressure testing apparatus <NUM> may comprises a pressure sensor <NUM> configured to measure the pressure inside a container arranged in the apparatus <NUM> and a pressure unit <NUM> configured to supply a pressurised gaseous fluid to the nozzle <NUM>.

The pressure testing apparatus <NUM> may also comprise a control system <NUM> communicating with the pressure sensor <NUM> and the pressure unit, for controlling the pressure applied to the inside of the container. The control system <NUM> typically comprises a computer <NUM> having a central processing unit configured to run a computer program. The computer program may comprise instructions which, when the program is executed by the control system <NUM>, cause the control system to carry out the steps of the above-described leakage test and/or the strength test.

The control system <NUM> may be operated by an input/output terminal <NUM>, e.g. comprising push buttons and/or a touch screen.

All the components of the pressure testing apparatus <NUM> and optionally also the drilling or cutting apparatus <NUM> may be assembled in one cabinet and provided with wheels for portability. If the pressure testing apparatus <NUM> and/or the drilling or cutting apparatus <NUM> is configured for portability, the container testing system <NUM> may preferably comprise a portable power source <NUM>, such as a battery.

Claim 1:
A method of testing leakage and/or strength of paperboard-based containers,
characterised by the steps of:
- producing a sealed paperboard-based container (<NUM>);
- producing a through-opening (<NUM>) in a panel (<NUM>, <NUM>, <NUM>) of the container (<NUM>); and
- attaching a nozzle (<NUM>) to the through-opening (<NUM>);
which method further comprises performing at least one of a first series of steps and a second series of steps, wherein the first series of steps comprises:
- increasing pressure in the container (<NUM>) by injecting a gaseous fluid into the container (<NUM>) via the nozzle (<NUM>) until a predetermined, first pressure value (p<NUM>) is obtained in the container (<NUM>);
- when the first pressure value (p<NUM>) is obtained in the container (<NUM>), closing the nozzle (<NUM>) preventing gaseous fluid from entering or exiting the container (<NUM>) via the nozzle (<NUM>);
- at a predetermined period of time (twait) after closure of the nozzle (<NUM>), measuring a second pressure value (p<NUM>) in the container (<NUM>); and
- using a difference in pressure (pdrop) between the first pressure value (p<NUM>) and the second pressure value (p<NUM>) as a measure of leakage of the container (<NUM>),
and wherein the second series of steps comprises:
- increasing pressure in the container (<NUM>) by injecting a gaseous fluid into the container (<NUM>) via the nozzle (<NUM>) until the container (<NUM>) fails;
- measuring the maximum pressure value (pmax) obtained in the container (<NUM>) prior to the container (<NUM>) failing; and
- using the maximum pressure value (pmax) as a measure of the strength of the container (<NUM>),
wherein the step of attaching the nozzle (<NUM>) to the through-opening (<NUM>) comprises the sub-steps of:
- inserting a flexible sealing disk (<NUM>) encircling a distal end (<NUM>) of the nozzle (<NUM>) into the container (<NUM>) via the through-opening (<NUM>); and
- bringing the sealing disk (<NUM>) into gas-tight engagement with an inner surface section (<NUM>) of the container (<NUM>) encircling the through-opening (<NUM>).