Leak detection device

Abstract

A leak detection device is disclosed. The leak detection device comprises an inspection zone and a conveyor device, configured to be able to transport a product or test candidate to and through said inspection zone along a conveying direction. The leak detection device further comprises in said inspection zone a first brush arrangement and a second brush arrangement, wherein the first and second brush arrangements are offset from each other in a direction transverse to the conveying direction such that they are not opposite to each other in a referential of said product or test candidate. The leak detection device further comprises a DC-source, wherein the two brush arrangements are connected with said DC-source such that they are set at different electrical potential, preferably one of the brush arrangements is set to ground level. A detection unit is configured to detect current charging the product or test candidate and outputting a signal when a peak representing the detection of a pinhole or other defect occurs.

Description

DescriptionTitle: _ Leak detection device

[0001] This application claims priority of Luxembourg patent application LU507445, filed on 10 June 2024. The entire disclosure of the Luxembourg patent application LU507445 is hereby incorporated herein by reference.TECHNICAL FIELD

[0002] The invention relates to the technical field of leak detection, specifically to a high-voltage leak detection device for use in detecting and signaling leaks, tears, breaks, or other imperfections in packaging containers, including, but not limited to, vials, syringes, ampoules, pouches, and I V. bags for sensitive sterilizable or non-sterilizable goods.BACKGROUND OF INVENTION

[0003] There are two established techniques for using high-voltage leak detection (HVLD) in the field of leak detection. AC high-voltage leak detection, referred to as conventional HVLD, uses a pure AC current at high voltage values. DC high- voltage leak detection, referred to as DC HVLD, uses a pure DC voltage at high voltage values. While both conventional HVLD and DC HVLD employ high voltage to ultimately detect leaks, the two methods utilize very different techniques based on the inherent differences in AC and DC voltage. Because of these different techniques used by conventional HVLD and DC HVLD, each method has different advantages and disadvantages when it comes to testing certain packaging containers and products contained therein.

[0004] For conventional HVLD, AC high voltage is applied to a container to break the resistance of the product and container. The presence of a leak is then determined by detecting the difference of the current through a control container versus the current through the tested container. If the difference is great enough, a leak is determined to be present.

[0005] Conventional HVLD testing involves placing a container between two electrodes and applying AC high voltage to the circuit, with one electrode being an inspection electrode and the other electrode being a detection electrode. The two electrodes are oriented such that the container to be tested is oriented between the two electrodes without making physical contact with either electrode. The container would then have two specific impedances and a specific resistance: a specific impedance at the container wall across from the inspection electrode, a specific impedance at the container wall across from the detection electrode, and a specific resistance of the product inside the container. The resulting current through the nondefective container can be monitored.

[0006] However, if the container should have a leak, a discharge current will flow through a pinhole, crack, or defective seal into the container. A leak in the container will result in the loss of one of the impedances. The resulting current through a defective container will result in a current with different value due to the loss of the specific impedance. A signal through the product is then detected by the detection electrode. Detecting the change in this current enables to recognize the presence of a defect.

[0007] When a leak is present one of the impedances will be missing. The current through the defective container can be found.

[0008] A defective container will have a larger electric current present than a container without defect. The difference between the electric currents determines whether the container is defective.

[0009] It is important to note that the testing parameters are variables and change depending on the amplitude of the applied AC high voltage, material characteristics (such as dielectric strength of the container and liquid product), and the conductivity of the liquid product. The higher the applied voltage, the ozon is created. The risk of applying too large of a voltage is that applied high voltage may create an arc or spark over the impedances listed above and cause what appears as a false leak. Therefore, it is necessary in conventional HVLD technology to reach the highest possible voltage, in order to get better sensitivity of the leak detection, without sparking around the container to break down the insulation of the container and the liquid product inside the container. The risk of detecting false leaks using the con-ventional HVLD is especially high with low-conductivity products. Humidity in the air and more particularly wet products often result in erroneous results, as with AC small droplets can jeopardize the measurement and result in erroneous detection of a defect, though the product did not have a defect but only presented a droplet on the outside.

[0010] Beyond the risk of false-positives when used with leak detection, use of conventional HVLD also poses risks to the integrity of the products held within tested containers. The applied pure AC high voltage used in conventional HVLD is able to penetrate through the capacitive impedance of a good container without high attenuation and expose the product within the container to the AC high- voltage directly. This results in potentially harmful and unwanted exposure of the product inside of a good container to high-voltage with unknown side effects. This problem is especially important to the pharmaceutical field, where exposure to high voltage during testing could potentially denature or otherwise harm pharmaceutical products.

[0011] Conventional HVLD thus needs specific adaptation also with respect to the frequency of the AC and also faces mechanical disadvantages, as the components necessary to create a testing device employing conventional HVLD are heavy and unwieldy. This makes a conventional HVLD benchtop tool impractical.

[0012] Another drawbacks of the conventional HVLD is that it produces excessive ozone during an inspection since AC high voltage creates ozone effectively and adjusting the device to proper parameters both with respect to frequency and voltage depending on the product to be tested is most cumbersome.

[0013] In DC HVLD, a container to be tested for leaks is instead charged purely with DC high voltage. The presence of leaks is determined through the detection of charging and neutralizing currents. A DC HVLD system of Takeda Chemical Industries, as described in US patent no. 4,125,805 , hereinafter Takeda, is representative of a typical DC HVLD system.

[0014] Takeda uses DC high voltage to charge a container. The container with fluid product contained within is placed between an anode rod, an auxiliary electrode rod, and a cathode plate. The anode rod is connected to positive side of the DC high voltage source. The cathode plate and the auxiliary rod are connected to a negativeside of the DC high voltage source through a measuring resistance and a switch respectively.

[0015] When the switch is turned off, the auxiliary electrode is not connected to the negative side of the DC high voltage source then neither electrical charging nor discharging takes place. However, if the switch is turned on, the auxiliary electrode is connected to the negative side of the DC high voltage source, and a spark discharge occurs between the auxiliary electrode and anode rod which simultaneously causes the electrical charge at the neck portion of the ampoule to be discharged. Meanwhile, a discrimination circuit is used across resistor to detect the potential developed across it.

[0016] A neutralizing current is caused to flow from the auxiliary electrode rod to the cathode plate, and is detected by the discrimination circuit. The neutralizing current normally reaches its maximum value immediately after initiation of the discharge by the auxiliary electrode, and subsequently decreases rapidly, In the state as described, if the ampoule is a good sample (i.e., free from any defects such as pin holes, etc.), with a predetermined amount of fluid contained therein, the neutralizing current caused to flow obtains a peak value of one unit.

[0017] On the other hand, when the ampoule has a defect, such as a pin hole larger than 2 microns, a neutralizing current of about two units or more is caused to flow. In principle all known DC HVLD systems rely on analyzing the discharge current.

[0018] A major disadvantage of the DC HVLD method and system is the lack of continuity and consistency in testing. In Takeda, the DC HVLD system is a discontinuous test since it is a discontinuous signal which is discretely created and sampled. Each package tested must be charged before being discharged through the discrimination circuit for a single measurement. The charging and discharging of the packages takes place one after another. This makes using the DC HVLD system for an online inspection in a production line almost impossible due to its slow speed and discontinuous nature.

[0019] Another disadvantage of the DC HVLD system is the discontinuous nature of the signal applied during testing due to the charging and discharging required. The high voltage discharge used in the DC HVLD system of Takeda can be very stochastic. Since its detected signal is a discrete waveform, the signal in the DCHVLD does not have a certain frequency, phase, or amplitude. The amplitude can vary strongly dependent on the amount of charging and discharging which occurs, and can vary based on the distance between the electrodes and the defect.

[0020] Further, the DC HVLD method requires that the anode rod is stationary at top of the package. This technology can be used only for inspection of ampoules. Containers like IV bags are more difficult to handle and thus there is a prejudice against using DC HVLD systems.

[0021] DC HVLD also requires that the cathode plate is in contact with the package. Contact with packages during testing is undesirable for online testing using rigid electrodes, as such contact is considered to be a destructive method of on-line testing.

[0022] US Patent No. 6,634,216 Bl , also describes a DC HVLD system and discloses an inspection method for inspecting a hermetically sealed package for pinholes, According to the method, when a hermetically sealed package whose contents such as electrically conductive fluid or food are covered with an electrically insulating film is inspected for pinholes by using a high voltage, the inspection can be achieved with an extremely simple procedure while fully preventing occurrence of misoperations due to the atmosphere such as humidity during the inspection. In particular, in the hermetically sealed package in which contents, such as electrically conductive fluid, are covered with an electrically insulating film, an electrical conductor derived from a voltage output terminal of a DC high voltage power supply is put into contact with or proximity to a side face portion of the hermetically sealed package, by which the contents in the hermetically sealed package are electrified. Next, a lead wire is connected to a connecting terminal of an electrode put into close contact with or opposed proximity to an inspection-object portion of the package where pinholes are most likely to occur, and the lead wire is grounded. Then, a discharge current derived from the inspection-object portion that flows only when a pinhole is present is detected by a discharge current detector, by which the presence or absence of a pinhole is detected depending on the presence or absence of the discharge current. In this procedure, the inspection can be made by placing the package on a support electrode derived from an AC high voltage power supply and electrifying the contents.

[0023] Publication US 4 125 805 A relates to a similar defect inspection apparatus and to a method of electrically inspecting for the presence of faulty sealed spots such as pin-holes and cracks in a sealed container of insulating material containing an electrically conductive electrolyte or nonelectrolyte fluid based on the discharging current after having charged the product.

[0024] One attempt to alleviate the drawbacks in the prior art has been proposed in EP 3 411 685 Bl, suggesting to provide in addition to the AC-Voltage a DC-offset voltage, but the results, though being promising remains unsatisfactory, as the need to adjust the parameters and in particular the correct frequency persists. Additionally, the testing is still as with all AC testing prone to result in a discharge likely to bum up the defect. Humidity also remains a major issue as with all prior AC leak detection devices. In an attempt to provide for a continuous operation a conveyor has been suggested with brushes to create the opposing electrodes, but the creation of noise in the data used for measurements and identifying defects and the risk of sparking introduces further limitations due to the proximity of opposing electrodes exhibiting a high difference in electrical potential.

[0025] As can be seen there is a need for an easy operable leak detection device, overcoming the drawbacks of the known devices. Intense research about the use of suitable frequencies for AC HVLD has shown that a universal leak detection device without sophisticated setting of parameters appear to be a bar for industrial use. The discontinuous operation needed for DC inspection also appeared to be a hurdle impossible to overcome.

[0026] According to a first aspect of the present invention there is provided for a device having the features as recited in claim 1. Preferred embodiments are defined in the dependent claims.

[0027] In particular, the present invention provides according to the first aspect for a device for leak detection that comprises a conveyor device, configured to be able to transport a product or test candidate to and through an inspection zone along a conveying direction. The inspection zone comprises a first brush arrangement and a second brush arrangement, wherein the first and second brush arrangements are offset from each other in a direction transverse to the conveying direction such that they are not opposite to each other, though each bruch arrangement can compriseopposing brushes. The two brush arrangements are connected with a DC-source such that they are set at different electrical potential, preferably one of the brush arrangements is set to ground level. The brush arrangements are positioned such that they can touch the product to be tested upon said product being conveyed along the brush arrangements or preferably between opposing brushes of the respective brush arrangements. As such different areas of the product or test candidate will be in contact with one of the brush arrangements respectively. Thus, an electrical field will build up.

[0028] In a most surprising way it was found that instead of monitoring a discharge current on a static product as was done in the prior art when using DC HVLD a different behavior can be detected directly upon conveying the test candidate or product along the brush arrangements between a test candidate or product not having any leakage and one having a leakage, provided that the leakage is within the area of the test candidate or product that is swiped by either of the brush arrangements. Against all expectations moving parts within an electrical field created in this way is not impaired too much by noise. In positioning brush arrangements so as to contact the test candidate or product has the benefit that there is no need for complex setting of the device such as for choosing an adequate frequency nor does the testing alter the defect as the Voltage can be set in a very preferred manner at a level that in conjunction with small amperage is not prone to burn the test candidate or product once a defect such as a pinhole is detected. When a peak representing the detection of a pinhole or other defect occurs, which means that when a current excursion is measured that coincides with a leak the system can reliably provide for leak detection without considering noise or other small variations in the current flow by mistake.

[0029] Additionally, it is possible to keep ozone creation at low level. Since the voltage only needs to be set such that any possible air gap can be overcome the voltage level can be set to a relatively low level, though we are of course still in an area of several kilovolts (kV). Indeed, when detecting pinholes the detection is very difficult as the size of such pinholes can result in the hole not filling up with the content of the test candidate or product and the pinhole thus could be filled with air. It is thus important that the brush arrangements are in rather constant contact withthe test candidate or product at least when the location of the defect is swiped by either of the brush arrangements. In Such a situation the applied voltage can bridge the defect, such as the pinhole, irrespective as to whether filled with liquid or air and the set potential difference between the two brush arrangements will fluctuate in a measurable way. Indeed, if the brush arrangements are in contact with the object there will be flowing a small current because the object has an electronic capacitance which is charged. If there is a pinhole or other defect between the conductive material in the object to be tested and one of the brush arrangements there will be a much higher current, which is caused by a much higher capacitance. This extra current is measured and with a peak detector it is possible to distinguish between a normal part without pinholes, and a part with one or more pinholes. Small air gaps between the pinhole and the contacting brush can be overcome by setting the voltage at adequate level.

[0030] Furthermore, it has been surprisingly found that humidity or even droplets of liquid on the product or test candidate do not jeopardize the testing. Contrary to AC-Testing only if a conductive liquid film would be present between the brush arrangements would be capable of resulting in misinterpretation of the test result as even if such humidity would be charged the level of current flowing would still be easily differentiable from current flowing in case of a pinhole or other defect.

[0031] According to an aspect of the invention at least one of the brush arrangements comprises a pair of opposing brushes, preferably said opposing brushes touch each other in the absence of a product or test candidate and / or are arranged to be at the same electrical potential.

[0032] The advantage of such a set up is that contact with the product or test candidate can be obtained in a straight forward way. The product or test candidate will be guided by the brushes and the risk of harming can be reduced. Should the brushes be placed with a gap it is possible that a thin part of the product or test candidate e.g. a medical pouch is not touched by the brush which makes detection of a leak more difficult. Furthermore, the occurrence of static charging of either brush can be advantageously avoided as the brushes having same electrical level will electrically balance. Finally, the risk of contamination of the brushes can be reduced.

[0033] According to an aspect of the invention at least one brush of at least one brush arrangement is mounted on a flexible spring blade, preferably a conductive flexible spring blade, more preferably said conductive flexible spring blade is made of a springy metal band such as made of stainless-steel and is dimensioned such that its size is much smaller compared to the brush(es) to reduce possible touching of the product or test candidate. The length is preferably adjustable to be able to adjust the elasticity that should be lower than the elasticity provided fo by the brushes themselves. On the other hand the elasticity allows to be set in accordance with the product or test candidate to avoid any excessive impact or deformation on it while guaranteeing that the swiping is ascertained.

[0034] According to an aspect of the invention at least one brush of at least one brush arrangement is arranged and / or configured such that filaments of said brush are oriented to be perpendicular to the conveying direction.

[0035] With this setup the contact surface between the brush and the material can be minimized. Having a brush with a large extension perpendicular and a small extension in the conveying direction allows to determine a position on the bag where the leak is situated more precisely. It should also be mentioned that the leak test device is intended for many candidates to be tested so wear and deterioration of brush filaments over time should also be contemplated. Finally the minimization of contact always will also need to consider the nature of tested product, in particular the vulnerability may provide for limits in the minimization. For redundancy reasons the brush should comprise at least 10 filaments in any extension direction in a particularly preferred embodiment.

[0036] According to an aspect of the invention at least one brush of at least one brush arrangement is arranged and / or configured such that filaments of said brush satisfy to one or more among the following conditions:- are having conductivity of 1 Mega Ohm or less- are made of carbon coated nylon filaments- are having a diameter of between 0,02mm and 2mm- are having a length 1mm or more, preferably the length is about 4 cm.

[0037] A conductivity of about 1 Mega Ohm has proven to be particularly useful in providing an adequate compromise in avoiding noise and in charging the candidateboth when having no defect and when having a defect, while providing optimum differentiability of the resulting signals. Filaments can also be hollow filaments in case needed and the dimensioning and material choice of the filaments in the indicated ranges have proven to be suitable to avoid risk of damaging the candidate while maintaining certainty to properly contact the candidate, still avoiding the risk of broken filaments, that can result in wrong detection results or at worst case even in a short-circuiting of the device.

[0038] According to an aspect of the invention at least one brush of at least one brush arrangement is elongated in a direction transverse to the extension of filaments and extends in a direction transvers to the conveying direction.

[0039] In such a configuration more surface of the brush is in contact with the product or candidate and the contacting can be maintained over a desired longer timespan. This will increase the chance of a detection of a leak or pinhole.

[0040] According to an aspect of the invention at least one brush of at least one brush arrangement is configured and / or arranged to define an area in a direction transverse to the extension of filaments, said area extending in a direction transvers to the conveying direction, preferably said area being dimensioned to be about 0,5 cm in the conveying direction and about 5 cm in the direction transverse to it.

[0041] Choosing the proper dimension will b depending on the nature and the size of the test candidate. Since too much friction is also to be avoided the area of one brush should not be more than 10% of the total area of surface of the product or test candidate.

[0042] According to an aspect of the invention at least one brush of at least one brush arrangement is arranged and / or configured so as to be aligned with the surface to be contacted of the product or test candidate.

[0043] In this case the friction between the brush and the device under test is minimal. This can lead to a longer lifetime of the brush, and when the surface area in contact with the bag can be made relatively small with the possibility to give an indication of the position of the pinhole / leak. Obviously the smaller a brush is the more precisely the location of the defect can be identified.

[0044] According to an aspect of the invention at least one brush of at least one brush arrangement is arranged and / or configured such that ends of filaments are parallel to the conveying direction.

[0045] Parallel brush arrangements lead to a longer contact with the product under test so a bigger chance of detecting a hole can be obtained. Furthermore, wear of a brush is easy to detect such that replacing a worn-out brush can be made more easily.

[0046] According to an aspect of the invention at least one brush of at least one brush arrangement is arranged and / or configured to create a funnel.

[0047] A funnel configuration of the brushes will give a good contact with the product or candidate under test, with a minimum of friction. Additionally, a funnel configuration can correct any possible misalignment of the product or candidate and may also assist in providing a controlled deformation should this be intended. In other words, the device may either be configured such that only the brushes and eventually the support thereof deforms or that a certain amount of deformation of the candidate or product to be tested can also be provided for.

[0048] According to an aspect of the invention at least one of the brush arrangements comprises a roller brush.

[0049] The use of a roller brush can be a superior solution for making contact and reducing friction. One draw back of a roller brush is mechanical complexity.

[0050] According to an aspect of the invention the leak detection device further comprises at least one additional pair of brush arrangements, offset in the conveying direction and preferably arranged such that when said product or test candidate is subsequently swiped by all of the present brush arrangements the entire surface to be tested has been contacted by at least one brush of all present brush arrangements.

[0051] With such an embodiment it is possible to arrange two or more brush arrangements such that the entire surface can be swiped in one single pass. The larger the number of arrangements the more precise the localization of the defect will be as the respective swiped area can be reduced. It is further possible to more easily adapt the setting for safety purposes or for avoiding electrical interferences with metallic parts when arranging the subsequent arrangements such that the groundedbrushes are respectively arranged in the areas prone to be accessed by a user or repairing engineer and in areas closer to metallic parts whereas the high voltage brushes can be arranged mor remotely from metallic parts and or access areas.

[0052] According to an aspect of the invention the leak detection device further comprises a deformation unit, configured to deform the product or test candidate.

[0053] If one wants to detect holes e.g. in medical bags, a problem is that most such bags have a so called “head space”. In the head space a gas or air is found on top of the fluid inside the bag. This gas or air acts as an insulator, which makes the measurement difficult or impossible. To accommodate for this issue the deformation unit will shake the fluid in the device under test, so that the material inside the bag will be temporarily wetted by the fluid, and becomes a conductive path to the bulk of the fluid inside of the bag. In this case it is possible to measure leaks / pinholes, also in the area where the air / bas bubble resides. A further application of the deformation unit can also provide for a compression of the test candidate to improve the detectability of leaks. Indeed, defects in medical bags can be very small and such pinholes may be obstructed and would thus not be detected. Deforming the test candidate or increasing temporarily the internal pressure can effectively prevent such obstructions and will thus result in a even mor reliable leak testing. Using a deformation unit can also allow to use a reduced high voltage as the risk that the pinhole is filled with air instead of fluid can be viably reduced.

[0054] According to an aspect of the invention the leak detection device further comprises an orientation changing unit, configured to change the orientation of the product or test candidate.

[0055] In this case the problem with the gas / air bubble in the product under test is solved by measuring in the first orientation, and by moving the device under test is another orientation changing the position of the air / gas bubble. The provision of an orientation changing unit also allows swiping the complete surface of the product under test using e.g. only one pair of brush arrangements or brush arrangements not having opposing brushes, provided the / an orientation changing unit is arranged and configured such that the changed orientation will result in a different area of the product or test candidate being swiped in a subsequent passage. The person skilled in the art will realize that the handling of the product or test candidate can be inloops or with back and forth movements in such a configuration to ascertain that the entire surface has been swiped at least once by filaments of at least one brush. The result will be that it is possible to properly analyze also areas for defects that would, when using only one single orientation could be masked through the effect of an air bubble.BRIEF DESCRIPTION OF THE FIGURES

[0056] Fig 1 is an illustration of an example of an inspection zone of a leak detection device according to an embodiment, such device also being referred to as DC HVLD device, using a pair of opposing brushes at the same electrical potential in each brush arrangement;

[0057] Fig 2 is a conceptual side view of an example of a leak detection device according to an embodiment;

[0058] Fig 3 is a conceptual sectional view taken along the plane A illustrated in Fig. 2;

[0059] Fig 4 is a conceptual sectional view taken along the plane B illustrated in Fig. 2;

[0060] Fig 5 is a conceptual sectional view taken along the plane C illustrated in Fig. 2 in a situation where the test candidate arrives in the inspection zone;

[0061] Fig 6 is a conceptual sectional view taken along the plane C illustrated in Fig. 2 in a situation where the test candidate is being tested in the inspection zone;

[0062] Fig 7 is an illustration similar to Fig 5 of an alternative configuration;

[0063] Fig 8 is an illustration similar to Fig 5 of another alternative configuration;

[0064] Fig 9 is an illustration similar to Fig 5 of an alternative configuration including a test candidate deformation unit;

[0065] Fig 10 is a conceptual side and top view of another example of a leak detection device according to an embodiment using a conveyor belt on which test candidates are resting and an orientation changing device, wherein each brush arrangement is arranged for using a single brush instead of opposing brushes for contacting the test candidate;

[0066] Fig. 11 shows an example of an alternative brush configuration

[0067] Fig 12 shows an example of a test result without defect and with defect.DETAILED DESCRIPTION

[0068] Fig 1 shows the working principle according to the present invention and is an illustration of an example of an inspection zone of a leak detection device according to an embodiment, such device also being referred to as DC HVLD device, using a pair of opposing brushes at the same electrical potential in each brush arrangement.

[0069] The device as shown comprises an upper brush arrangement that is foreseen for example at ground potential, having pair of brushes to be at the same electrical potential and comprising in the illustrated embodiment a first brush 2a 1 and a second brush 2a3. The device as shown comprises a lower brush arrangement that is foreseen for example at high voltage potential such as for example 4 kV, having another pair of brushes to be at the same electrical potential and comprising in the illustrated embodiment a third brush 2a2 and a fourth brush 2a4.

[0070] Between both brush arrangements 2al, 2a3 and 2a2, 2a4 that are provided to contact with a product or test candidate 1 as illustrated, in order to be subjected to leak detection, there is a high voltage DC provided for by a suitable HVDC source 10 and the voltage is existing between both brush arrangements. If the respective brushes come into contact with the product or test candidate 1, which is here in the illustrated case a flexible medical bag 1 having a liquid content there will be flowing a small current because the product or test candidate 1 has an electronic capacitance which is charged due to the fact that the medical bag itself is made of isolating material. Typically a medical bag will be made of PET or PVC foils that have been welded at the other periphery, and will be filled with some kind of aqueous solution.

[0071] If there is a pinhole or other defect through the isolating foil of the medical bag the conductive material in the product or test candidate can be more rapidly charged if any of the brushes contacts the area where the pinhole or defect is located and thus there will be a much higher current, which is caused by a much higher capacitance. The current is measured and with a peak detector it is possible to dis-tinguish between a normal part of the medical bag without pinholes, and a part of the medical bag with one or more pinholes. Small air gaps between the pinhole and the contacting brush can be overcome if the voltage is high enough.

[0072] It is to be noted that the current density in both cases, when no defect is detected or when a defect is detected is verry little.

[0073] A most suitable HVDC source 10 will have the following particulars: A Voltage adjustable from OkV to 20kV, and capable of delivering a few milliamperes (e.g. 2mA). The device should also preferably be current limited with an adjustable maximum current value.

[0074] The current measurement device 20 can comprise electronic circuitry to filter noise and to offset for the charging that is occurring in case of a non-defective product. The current measurement device 20 can be provided with a discriminator such that upon detection of a peak a light can be switched on to indicate that leakage has been detected. Alternatively or in addition, the current measurement device 20 can also be provided with a display, configured to show the measurements in real time.

[0075] Fig 2 shows a conceptual side view of an example of a leak detection device according to an embodiment. The device is having a conveying device allowing to convey medical bags 1, as examples of products or test candidates 1, along a conveying direction CD. In the shown example the medical bags 1 are made of an isolating material and are filled with a fluid being at least more conductive than the material the medical bag is made of. In the illustrated embodiment the medical bags are hung via port sections with which these medical bags are most often provided with.

[0076] As shown, the medical bags can thus be conveyed towards and through a testing or an inspection zone, where brush arrangements are foreseen as will be detailed herein. The brush arrangements are in the present example comprising a total of eight brushes, however the person skilled in the art will realize that other figures are conceivable for instance to increase the capability to not only provide for a leak detection in general, but to also indicate the location where the leak is occurring.

[0077] In the shown embodiment there are provided 4 pairs of brushes, that are arranged such that filaments of each pair of brushes substantially extends in the direc-tion of the opposite brush belonging to the same pair of brushes. In other words the embodiment shown comprises two sets of two brush arrangements, one arrangement of each set being at ground level and the other one at high voltage, wherein each brush comprises two opposing brushes. In the illustration of the conceptual side view only one of each pair of brushes can be seen, as the respective opposite brush will be located behind of it. The medical bag thus is conveyed towards the inspection zone and will be contacted by two brush arrangements that are provided at different height and at different electric potential. Basically, a first brush arrangement comprises the here shown first brush 2al that will be the upper brush that contacts the medical bag at the same time as brush 2a2 of the lower brush arrangement provided a high voltage potential. For further details the brush arrangements will be described later using the sectional view as illustrated by the dotted line A of Fig. 2.

[0078] As shown, the first upper brush arrangement 2al, 2a3 and the first lower brush arrangement 2a2, 2a4 are mutually offset in a direction transverse to the conveying direction, such that an electrical field can be build up between them through the medical bag 1. For the avoidance of doubts it is indicated that brushes belonging to the same brush arrangement can touch each other but brushes from different brush arrangements should not touch, most importantly when they are not at the same electrical potential, such that an electrical field can be build up between two respective brush arrangements. The conception is totally different from previously known testing with AC where the electrodes are provided to be facing each other. In the here illustrated embodiment, a pair of brushes is arranged in a way to oppose each other (see figures 3 and 4), but they are not forming different electrodes but are part of the same electrical potential. The configuration is also in full contrast to previously used DC-testing, as DC testing was previously not usable in a continuous way not only as the product or test candidate was charged and then the discharge was measured, but also as the electrodes used to rather be a kind of a place and a connector to one end of the test candidate. Indeed, it was expected that moving parts within a DC field would result in high noise such that any differences in current measurement could not be safely differentiated from noise. In the illustrated embodiment the two first brush arrangements 2al, 2a3 and 2a2, 2a4 are spacedapart from each other by almost the extension of one brush in the vertical direction. It is to be noted that preferably the brushes are always at a certain distance from any metallic part and in the illustrated embodiment the upper brush arrangement 2al, 2a3 is the grounded one as it is less affected by noise that could be induced by the conveying device, often including metal parts. In addition, arranging the ground level at the upper brush arrangement 2a 1, 2a3 can improve user security as in case of maintenance or the like the user or operator will most likely need to access from above.

[0079] As further shown in Fig 2 in the downstream direction along the conveying direction CD a further set of brush arrangement is provided for in a plane that is indicated by a doted line B. Again, the set of brush arrangements is having an upper brush arrangement at ground potential and a lower brush arrangement at high voltage potential. As for the first set the brush arrangements are vertically offset such that a vertical electrical field can build up within the medical bag 1. In the illustration a third brush 2b 1 and a fourth brush 2b2 can be seen. As can be further seen the further set is offset versus the first set such that the brushes of the further set can swipe the area of the test candidate void of having been swiped by the first set. It is to be noted that the sets are arranged and configured such that the entire surface can be swiped with a little overlap to avoid that any part of the medical bag would never be contacted by any filament of the entire set of brushes.

[0080] As further illustrated in Fig 2 the offset between the first set and the further set can be such that both sets can be in contact with the medical bag simultaneously or in an alternative not shown they can be spaced by more than the extension of the medical bag in the conveying direction. It is to be noted that the spacing should at least be such that brush filaments, even when deflected can never interfere or contact with each other. In case of a spacing between the respective sets to be smaller than the extension of the medical bag in the conveying direction it is possible that the electrical field that is build up is not strictly vertical but rather diagonally, however this will not hinder proper leak detection. It is however to be noted that if the spacing is more than the extension of the medical bag 1 in the conveying direction it would be possible to localize the defect, provided that each set of brush arrangements has its own circuitry as will be detailed later.

[0081] Fig 3 is a conceptual sectional view taken along the plane A illustrated in Fig. 2. As seen in Fig 3, an upper brush arrangement is built up by a pair of opposing brushes, namely a first brush 2al and a second brush 2a3. These two brushes are connected via circuitry to the ground section of a high voltage DC source 10. The view of Figure 3 is what the medical bag 1 would see just prior to arriving at the inspection zone (the subsequent set of brush arrangements as illustrated in Fig 4 has been omitted for clarity of the illustration. Indeed, in real the view of the medical bag would also include the second set of brush arrangements, but farther away. The view would be a continuous, even verry slightly overlapping array of brush filaments.

[0082] As shown in Fig 3 each brush is supported by a metallic spring blade 4 allowing for the brush to be deflected in the conveying direction. As illustrated, the connection of the circuitry is also performed via said metaling spring blades. It is to be noted that other means for providing the capacity to deflect could be envisaged as well such as a mounting using hinges or the like, but it is important to consider that a biasing is preferred to ascertain proper and constant touching of the filaments versus the medical bag. As also shown in Fig 3, the opposing brushes can contact each other by the respective ends of the filaments or even be arranged such that they would intermesh. This is particularly interesting as the opposing brushes are at the same electrical potential.

[0083] Fig 4 is a conceptual sectional view taken along the plane B illustrated in Fig. 2, showing the further set of brush arrangements as previously described. In view of the similarity of the set illustrated in Fig 3 a very detailed description will be omitted here for brevity reasons. It is however important to note again that the sets are offset such that the entire surface to be tested of the medical bag can be contacted filaments of at least one of the brushes illustrated in Fig 3 and Fig 4. As already indicated it is possible to localize a pinhole or defect at least roughly, provided the sets are having own dedicated circuitries. As illustrated in figures 3 and 4, each set is having an own circuitry. It is however to be noted that a highly economic device can also be provided for by using a common circuitry for both sets, though one would lose the option to know whether any specific set of brushes resulted in the leak detection. The person skilled in the art will also realize that theconcept would easily work as well with only a first set such as illustrated in Fig 3, wherein only the swiped area would be analyzed or by providing an orientation changing device and to have the medical bag e.g. be passed through the set of brushes at a first height adjustment and a second time at a second height adjustment such that in the second run the area not having been swiped in the first run can be tested. Obviously if the brushes have smaller vertical extension more then two passages might be required. At the same time the person skilled in the art will realize that the invention is not limited to embodiments having two sets of brush arrangements but rather there can be a multitude of subsequent sets. The smaller the brushes are the more sets or passages will be needed. The larger the number of sets or passages is the more precise the localization of the defect can be as each time a defect is detected actual brush contacting area can identify the area where the defect is. Thus, using brushes with smaller area will allow to make a more precise localization.

[0084] Figures 5 and 6 are illustrations of the medical bag arriving at or being between opposing brushes of the first set of brush arrangements, mor particularly the lower brush arrangement comprising brushes 2a2 and 2a4, corresponding to the plane as illustrated in Figure 2 by a doted line C. As can be seen in particular in Figure 6, once the medical bag has been conveyed to be in between of the brushes 2a2 and 2a4 filaments 2f attached to brush head 2h will deflect and swipe over a defined area of the medical bag such that if that area is void of any defect or pinhole the electrical field will build up slowly, corresponding to a very small amount of current flowing, or if the defect or pinhole is swiped by filaments the reduced isolation of the missing product or test candidate such as the here illustrated medical bag will result in a sudden increase of current flow. The biasing of the spring blade and or the elasticity of the brush filaments will ensure close contact, such that even a small amount of air, such as when the pinhole is not filled with liquid but only comprises air can be disregarded, provided the voltage setting is also adequate.

[0085] Although various configuration of brushes can be considered it is preferable to use one single type of brushes to allow easy maintenance and repair or replacement of any of the brushes as needed. A particularly well-suited brush will have the following details, which are however indicted as a purely illustrative example:

[0086] A carbon coated nylon brush with hair length of 4cm, embedded in a metal holder to keep the hairs in position. The conductive hairs should be flexible, but there is a very wide optimal window formed by: to flexible and the hairs do not stay in position and can miss parts of the product under test, not flexible enough which leads to friction and possible damage of the product under test. An example of a brush that has proven to work well will be in rectangular shape of 0,5 cm by 5 cm.

[0087] The testing process using the preferred embodiment illustrated in Figures 2 to 6 will now be described in detail. At first medical bags 1 will be hung to the conveyor system such that each medical bag can be conveyed along a conveying direction CD to and through the inspection zone. The DC voltage is then set on and the conveyor system started. Obviously safety mechanisms can be installed such that e.g. the DC power is conditioned with the closed situation of a housing, such that no access is possible to the DC high voltage area when switched on. Upon the medical bag arriving at the brushes these will contact the medical bag and due to the potential difference between the two brush arrangements an electrical field will build up in the vertical direction. While the bag continues to move horizontally the filaments of the brushes will deflect and intimately contact the medical bag, such that the medical bag will be swiped or brushed in the area corresponding to the first set of brush arrangements. After the medical bag has left the first set of brush arrangements the bag will be for a small amount of time without contact of any filaments before arriving at the second set of brush arrangements, basically configured in a similar way, but arranged such that the area that has previously not been swiped or brushed is now involved. To make sure that no area is not swiped or brushed there can be provided a small overlap in the positioning of the brushes. During the entire conveying movement, the flow of current is monitored. If the bag is void of any defects such as pinholes the current flow will be constant during the brushes contacting the medical bag but will show a dedicated peak if a defect or pinhole is present. It should be noted, that the brush arrangements can also be positioned such that the bag, once he has come into contact with the first brushes will be constantly in contact, without a need that the bag leaves the contact from the first set of brush arrangements before getting into contact with the second set, provided that the brushes are arranged such that even deflected there is no chance ofmutual contacting of two brushes other than the one of an opposed pair of brushes. In this case it is possible, that the build up electrical field is not strictly vertical, but this will not jeopardize the leak detection function, if a simple circuitry is used that mainly aims at detecting a defect at all. In a more sophisticated set up, using independent circuitry, at least when it comes to detection allows to deduce from the detection result, if a defect has been detected where the defect is. For example, if a medical bag of a length of about 12 centimeters would be analyzed using three sets of brush arrangements with each brush having an extension of 2 centimeters in the vertical direction would provide for a swiped area corresponding to the uppermost two centimeters plus the fourth one. The next set would swipe the second and the fifth one. The third set would swipe the third and the sixth one. Hence the entire bag is swiped and in case a pinhole would be present in the area of the second lowest portion of the medical bag then the detection provided with the second set would allow to exclude for the presence of the defect such as a pinhole the areas swept by the first and the third set. Obviously, there is a multitude of possible settings with independent, partly combined of fully combined detection. Furthermore the person skilled in the art will understand that alternatively to several sets of brush arrangements it is also possible to use a multi-pass arrangement where the medical bag is passed several times through the same set of brush arrangements but at a modified height, obtained by an orientation change unit that can either change the orientation of the medical bag or of the brushes, though it would appear that changing the position of the medical bag is more easy to realize.

[0088] Figures 7 and 8 show optional features that can be used in the present invention. In order to ease the entrance of the medical bag in the area between opposing brushes the brushes can be arranged and / or configured to provide for a funnel.

[0089] Figure 9 is a schematic representation showing an optional add on unit 40 configured to deform the product or test candidate, such as for example a medical bag filled with liquid. The unit 40 as illustrated comprises two actuators 46. Each actuator is configured to expand a piston 44 to displace a plate member 42 forth and back. Usually, a medical bag is having a head space void of liquid. Hence if the filaments are in contact with the medical bag where there is no liquid a pinhole or defect might not be properly detected as the air of the head space will not allow thesudden increase in current flowing. By deforming quickly, the medical bag just prior to entering the inspection zone can provide for at least wetting the entire inner surface of the bag such that detection still can be provided for a viable way. As shown the deformation unit is provided upstream of the upper pair of brushes, but it could also be provided at any other location, suitable to deform the medical bag in such a manner that the entire inner surface is covered by at least a continuous wet film. In an alternative or in addition it is also possible to change the orientation of the bag prior to performing a second run or pass through the inspection zone such that the part of the bag that is occupied by the head space in the first run will be filled with liquid in the second run.

[0090] Figure 10 shows an alternative embodiment, wherein again medical bags are to be tested for the presence of leaks such as due to one or more pinholes. In this embodiment the medical bags are conveyed lying on a conveyor belt. In this embodiment the brush arrangements are not comprising opposing brushes, but rather single brushes. Here the brushes of one brush set having a difference in the electrical potential are offset and spaced in the horizontal direction, rather than vertically as in the previous embodiments. Basically the same brushes as previously can be used and the use of two or more staggered brush sets is contemplated as well , again arranged such that the entire surface can be swiped by filaments. Contrary to the previous embodiments it is however only possible to test the here upper surface of the bag. Once the upper surface of the bag has been tested an orientation changing unit 50 can intervene to turn the medical bag 1 upside down for a second inspection run to test the then upper surface that was the lower non-inspected surface before. In this embodiment a deformation unit might be used as well, in particular as the head space in such a configuration is more prone to result in incorrect detection.

[0091] Fig 11 shows an alternative configuration for a brush, that can be used in the inventive device. Rather than having a brush head 2h from witch the filaments extend linearly a brush head can be provided for in cylindrical form, wherein the filaments extend radially. Such a roller like brush has the advantage of being less prone to wear and at the same time an easy access as with a funnel configuration in inherent to the roller shape. If the roller brush is used it is however more difficult tosupply the DC voltage and the possible rotational movement might induce additional noise.

[0092] Fig 12 shows typical detection results, on the left side for a medical bag not having any defects and on the right side for a medical bag having at least one defect such as a pinhole. As can be seen the medical bag enters into contact with at least one filament at ground level and one filament at high voltage level at the time ta. In both cases the charge will slowly increase resulting in a small amount of current flowing. The current will flow until the bag has exited the inspection zone or is not contacting any filament anymore. At the time where one or more filaments contact the medical bag at a location presenting a defect such as a pinhole the current can flow more easily and the liquid will be charged faster. Hence, there will be a peak in the current flowing allowing to identify the presence of a leak. Obviously the circuitry can be provided with adequate noise filtering and a display that can be a simple lamp or LED or a more complex display such as a video screen.

[0093] Although the invention has been previously described taking reference to the appendaged drawings, which are part of the disclosure the person skilled in the art will realize that every feature described can be combined with other features described whether such features have been described alone or in conjunction with other features.

Claims

Claims1. Leak detection device, comprising an inspection zone and a conveyor device, configured to be able to transport a product or test candidate (1) to and through said inspection zone along a conveying direction (CD), wherein the leak detection device further comprises: in said inspection zone a first brush arrangement (2al, 2a3) and a second brush arrangement (2a2, 2a4) forming a brush arrangement set, wherein the first and second brush arrangements are offset from each other in a direction transverse to the conveying direction (CD) such that they are not mutually opposite to each other in a referential of said product or test candidate, a DC-source (10), wherein the two brush arrangements are connected with said DC-source such that they are set at different electrical potential, preferably one of the brush arrangements is set to ground level, a detection unit (20), configured to detect current charging the product or test candidate and outputting a signal when a peak representing the detection of a pinhole or other defect occurs.

2. Leak detection device, according to claim 1, wherein at least one of the brush arrangements comprises a pair of opposing brushes, preferably said opposing brushes touch each other in the absence of a product or test candidate and / or are arranged to be at the same electrical potential.

3. Leak detection device, according to claim 1 or 2, wherein at least one brush of at least one brush arrangement is mounted on a flexible spring blade (4), preferably a conductive flexible spring blade, more preferably said conductive flexible spring blade is made of spring steel or stainless steel and has dimensions of about five millimeters in thickness, about three centimeters in with and a length of about five centimeters, more preferably the length being adjustable.

4. Leak detection device, according to any one of the preceding claims, wherein at least one brush of at least one brush arrangement is arranged and / or configuredsuch that filaments (2f) of said brush are oriented to be perpendicular to the conveying direction (CD).

5. Leak detection device, according to any one of the preceding claims, wherein at least one brush of at least one brush arrangement is arranged and / or configured such that filaments (2f) of said brush satisfy to one or more among the following conditions:- are having conductivity of 1 Mega Ohm or less;- are made of carbon coated nylon filaments;- are having a diameter of between 0,02mm and 2mm;- are having a length 1mm or more, preferably the length is about 4 cm.

6. Leak detection device, according to any one of the preceding claims, wherein at least one brush of the at least one brush arrangement is elongated in a direction transverse to the extension of filaments and extends in a direction transvers to the conveying direction.

7. Leak detection device, according to any one of the preceding claims, wherein at least one brush of at least one brush arrangement is configured and / or arranged to define an area in a direction transverse to the extension of filaments, said area extending in a direction transvers to the conveying direction, preferably said area being dimensioned to be 0,5 cm by 5 cm.

8. Leak detection device, according to any one of the preceding claims, wherein at least one brush of at least one brush arrangement is arranged and / or configured so as to be aligned with the surface to be contacted of the product or test candidate (1).

9. Leak detection device, according to any one of the preceding claims, wherein at least one brush of at least one brush arrangement is arranged and / or configured such that ends of filaments are in a plane parallel to the conveying direction.

10. Leak detection device, according to any one of the preceding claims, wherein at least one brush of at least one brush arrangement is arranged and / or configured to create a funnel.

11. Leak detection device, according to any one of the preceding claims, wherein at least one of the brush arrangements comprises a roller brush.

12. Leak detection device, according to any one of the preceding claims, further comprising at least one additional set of brush arrangements, offset in the conveying direction and preferably arranged such that when said product or test candidate is subsequently swiped by all of the present brush arrangements the entire surface to be tested has been contacted by at least one brush of all present brush arrangements.

13. Leak detection device, according to any one of the preceding claims, further comprising a deformation unit (40), configured to deform the product or test candidate.

14. Leak detection device, according to any one of the preceding claims, further comprising an orientation changing unit (50), configured to change the orientation of the product or test candidate.

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