Method and apparatus for detecting leaks from sealed containers

Abstract

A method for detecting fluid leakage from a sealed container, comprising the steps of: defining a detection area (13) in which the sealed container (CT) is placed; communicating the detection area (13) with at least one gas sensor (19; 219a, 219b) via at least one duct (21); introducing flushing gas into the detection area (13) through the at least one duct (21); placing the container (CT) within the detection area (13); drawing gas from the detection area (13) via the duct (21) and transmitting the gas to sensors (19; 219a, 219b) that determine the presence of a gas leak in the container (CT).

Description

[Technical field]

[0001] The present invention relates to a method and device for detecting leakage from a sealed container. The method and device according to the invention are capable of detecting leakage of a fluid from a sealed container. More specifically, but not exclusively, the fluid may be in a gaseous or vapor state, may consist of a gas or a gas mixture, or may consist of a vapor or a vapor mixture, or may consist of a gas and a vapor mixture. The container may be both a rigid container, such as, for example, a glass jar or bottle, and a container having at least one flexible wall, such as, for example, various kinds of plastic tubs, bags, and flexible packages. [Background technology]

[0002] Currently, many beverages, and other products intended for use as food, are preserved primarily by using one of the following packaging methods:

[0003] According to the first way, which is mainly used to store liquids, a rigid or semi-rigid container is filled with the substance to be stored through a suitable opening provided in the container. The opening is then sealed by a suitable closure element, for example a cap. In other cases, the product to be stored is wound by a ribbon or film or introduced into a tube of flexible plastic material, and the package thus obtained is then sealed by welding along one or more seam lines. In yet another case, it is known to use a preformed tub of plastic material. The tub is filled through an opening provided therein, which is then sealed by a plastic film welded to the tub wall.

[0004] More commonly, but not exclusively, food products are stored in sealed packages with the objective of preserving as little change over time as possible the chemical and physical properties that the product possesses at the time of packaging.

[0005] Thus, one of the main problems encountered when applying the aforementioned methods is how to obtain an optimal seal of the package to avoid contamination with the external environment. In many applications, an optimal seal results in a closure that must be substantially airtight at the external pressure at which the package is maintained, or in any case at the pressure to which the package is subjected during normal use, transport and storage. For example, in the case of food products, the package must be substantially airtight when at atmospheric pressure, in order to communicate the environment inside the package with the external environment, thereby preventing the passage of substances and air from one environment to the other, thus preventing the risk of contaminating the packaged product and the deterioration of its organoleptic properties.

[0006] In the case of containers sealed by welding, the hermetic seal of the package may be compromised, for example, by an incorrect execution of the welding process, for example by an incomplete weld. Incorrect setting of the welding temperature, incorrect selection of the adhesive weld material, imperfect planarity of the contact surfaces in the weld area, and the presence of impurities or foreign bodies in the weld area are all factors that may impair the achievement of a hermetic seal of the container.

[0007] In the case of rigid or semi-rigid containers, such as bottles, which are closed by caps, it is well known that the airtight seal may be compromised, for example, by imperfect shape of the cap or bottle in the area to be capped, or by operational problems of the capping machine, for example alignment problems during the capping step.

[0008] Generally, losses of material from a container resulting from obvious imperfections in the container closure can be easily detected by a careful worker, even by visual inspection. Such losses generally entail obvious spills of material from the container. Thus, under such circumstances, a careful worker in charge of supervising the packaging line can easily identify the defective container immediately downstream of the filling and sealing steps and remove it if necessary, primarily to dispose of it and prevent it from being offered to consumers, or to submit it for further inspection or repair.

[0009] As can be easily understood, detection of leaks from containers becomes more difficult for workers as the leaks become smaller, as in the case of leaks due to microcracks and microholes. These leaks are defined as microleaks, i.e. very small leaks from containers, which are not immediately detectable because they do not necessarily involve obvious leakage of liquid or other substances, and in the long run they can impair the quality of the product. Generally, such microleaks are caused by cracks of the order of tens of microns, and even by cracks of a few microns, e.g., 3 to 7 μm.

[0010] To solve the problem of how to effectively detect the presence of microleaks from sealed containers, several solutions have been proposed in the past.

[0011] The first known solution to the problem of how to detect leaks from heat-sealed containers is disclosed, for example, in US Pat. No. 3,708,949 (A), which discloses a method and an apparatus for forming an airtight seal of a heat-sealed envelope and subsequently inspecting it. The method disclosed in such document essentially comprises the steps of sealing the container after the introduction of a conditioned atmosphere, subjecting the container to a mechanical stress that reduces the volume enclosed by the container's walls and increases the pressure of the gas enclosed within the container, thereby facilitating the escape of the gas in the presence of microcracks, detecting outside the container the presence of a tracer gas present in the conditioned atmosphere with a gas detector, and removing the containers that fail to pass the inspection.

[0012] Another known method for testing the tightness of a heat-sealed container is disclosed in WO2013 / 011329(A2). According to the teachings of this document, the container is filled with a tracer gas and subjected to compression in order to promote gas escape through microcracks possibly present in the sealed area. A suitable detector including a pair of electrodes is positioned close to the area of ​​the container where gas microleaks are likely to occur. A change in voltage at the detector electrodes detects the presence of the tracer gas.

[0013] WO2017125386(A2) discloses a method in which a chemical, typically in the form of strips, is applied to a container. The substance is such that its physical and / or chemical properties change depending on the concentration of a gas, e.g. oxygen, in contact with the substance. The change in the substance's properties causes a change in the frequency, wavelength or phase of the emitted electromagnetic radiation that is detectable by a detector located outside the container.

[0014] DK201570808(A1) discloses an apparatus for detecting gas leakage from a sealed container into which a tracer gas has been introduced. The apparatus includes an analysis chamber in which the container is received during a hermeticity test, and a device capable of creating a vacuum inside the chamber. A gas detector is disposed in communication with the chamber to detect the presence of the tracer gas.

[0015] Thus, according to the teachings of the prior art, the step of detecting microleaks generally involves the use of a tracer gas, typically carbon dioxide (CO), which is introduced into the container before it is sealed. 2 ), helium (He), or hydrogen (H 2 ) is carried out with the help of CO 2 To detect leaks, the presence of the tracer gas outside the container is generally detected, usually by a detector, e.g., an electrode or a detector operating based on non-dispersive infrared (NDIR) or other techniques, when the liquid or tracer gas (e.g., He) is detected.

[0016] In the field of detection of gas leaks from squeezable sealed containers, the problem of how to clean the area in which the sample to be examined is placed from possible traces of undesirable gases, for example due to contamination caused by the passage of previous samples or by gases coming from the external environment surrounding the detection area, is also known.

[0017] EP 2 755 015 (A1) teaches the use of so-called compressed air curtains to clean the detection area. This document also teaches the use of external gases, more specifically CO, which may contaminate the detection area and thereby alter the leak detection. 2 It also teaches the use of multiple air curtains to screen the detection area from possible flows of air. According to the specification of this document, the air coming from a compressed air source is delivered to the device through a dedicated duct circuit and, when diffused by appropriately shaped openings or slots, is arranged to spread substantially over a plane and exit the detection area through a set of nozzles arranged to define corresponding air curtains or blades, i.e. air flows, which, thanks to the flow velocity, maintain such a configuration for a certain distance from the diffuser.

[0018] Air curtains are used for cleaning (also called flushing) of the detection area. However, they are located at the beginning and end of the measurement tunnel and for clearly evident reasons related to functional interference, they cannot be located in the immediate vicinity of the intake fan. Therefore, the effectiveness of the air curtain is only partial and even if we assume that the air curtain can be located in the immediate vicinity of the intake fan, which is only a theoretical hypothesis, the air curtain cannot flush inside the intake duct. Thus, the flushing performed by the air curtain according to the currently known technology is limited to the detection area, whereas other parts of the device, such as the ducts communicating with the detectors, which are generally present in this type of device, do not undergo any air changes and therefore can still be contaminated by foreign gases that can be detrimental to the correct detection of leaks from sample containers, especially when the leak volume is small or very small and the test must be performed very quickly, for example in order not to slow down the product progression line in an industrial plant.

[0019] FR2522820(A1) discloses a method and device for detecting gas leakage from a container in which a bell surrounds a detection area near the container. During the gas leakage measurement step, the bell is connected in a closed circuit including a detector capable of measuring the concentration of the gas to be detected. More specifically, the closed circuit comprises a first duct connecting the detector outlet to the bell inlet and a second duct connecting the bell outlet to the detector inlet. A circulator connected in the first duct between the detector and the bell causes gas circulation inside the circuit. The container is kept under the bell for a long period of time, thus accumulating an increasing amount of the gas to be measured, whereby such gas can circulate several times in the circuit, thus through the detector. To allow cleaning of the detector and the bell before a new measurement, the closed circuit is opened and a gas different from the gas to be measured in the first duct is made to flow. But such gas is not made to flow in the second duct, which can therefore still be contaminated by the gas of a previous measurement.

[0020] The above method thus results in homogenization of the gas being examined by repeated passage of the same gas in a closed circuit. The method taught also has the drawback of not allowing efficient and rapid cleaning of the entire device, thereby slowing down operation between measurements of gas leakage from one container and the next. Summary of the Invention [Problem to be solved by the invention]

[0021] It is a primary object of the present invention to provide a method and apparatus for detecting leakage from a sealed container that does not suffer from the limitations and drawbacks discussed above with respect to the prior art.

[0022] Another object of the invention is to provide a method and device of the above kind that makes it possible to detect leaks from various kinds of containers, of flexible and rigid type, mechanically squeezed or not mechanically squeezed, even when the leaks are small or very small, i.e. corresponding to microleakage and caused by openings of a few microns.

[0023] It is a further object of the present invention to provide a method and apparatus for detecting leaks from sealed containers that allows for improved operating speeds when compared to the prior art, a method and apparatus that allows for faster detection of leaks, if any, and therefore maximizing the operating speed of a production or container processing plant.

[0024] It is yet another object of the present invention to provide a method and apparatus of the above kind which allows for greater accuracy in leak detection even in the presence of disturbances or changes in the ambient environmental conditions.

[0025] A further, but not final, object of the present invention is to provide a method and apparatus which can be used in a reliable and inexpensive manner, such that the method and apparatus can have large-scale industrial application. [Means for solving the problem]

[0026] These and other objects are achieved by the methods and apparatus set out in the appended claims.

[0027] Description of the invention The method for detecting leakage from a sealed container mainly comprises the steps of placing the container, the tightness of which is to be checked, in the detection area and of sucking in the air present in the detection area through at least one suction duct communicating with the detection area. According to the invention, the suction step is preceded by a step of flushing the duct and the detection area, which is carried out by introducing a flushing gas into the detection area and by making it flow through the same duct mentioned above in a direction opposite to the direction in which the air sucked in during the suction step flows. Also, preferably, the detection area is in communication with the atmosphere.

[0028] In one embodiment of the present invention, the suction step and the flushing step are respectively performed by a suction fan having a suction port communicating with a duct and by a blower having an outlet port communicating with the same duct. An electromechanical valve, for example a three-way valve, is further provided to communicate the duct with the suction fan during the suction step and with the blower during the flushing step. The same three-way valve closes the communication between the duct and the blower during the suction step and closes the communication between the duct and the suction fan during the flushing step. Thus, according to this embodiment, the air suction from the detection area and the flushing is performed by two separate and independent units, namely the suction fan and the blower, which are exclusively communicated with the duct and the detection area, respectively, for example via a three-way valve. Preferably, in the introduction step, the flushing gas introduced into the detection area is taken from a controlled environment containing the flushing gas, and in the suction step, the gas sucked from the detection area is exhausted to an uncontrolled environment.

[0029] In an alternative embodiment of the invention, the air suction and flushing from the detection area is performed by a single unit, which therefore acts as a suction fan and as a blower. - (in the step of drawing air from the detection area) a duct communicating with the detection area with an inlet port of the unit and an outlet port of the unit with the outside environment, or alternatively, - (in the flushing step) connecting a duct communicating with the detection area to an outlet port of the unit and connecting an inlet port of the unit to a controlled environment containing a flushing gas or gas mixture. The valve is connected to a circuit that is adapted to provide communication therebetween.

[0030] In a further embodiment of the invention, air suction and flushing from the detection area is alternatively performed by a single reversible unit which can operate both as a suction fan and as a blower by reversing the motion of the blades of a single impeller, and preferably in this embodiment, in the suction step, the single reversible unit exhausts the suctioned gas to the external environment, while in the flushing step, the single reversible unit takes the flushing gas from the controlled environment which contains it.

[0031] According to a preferred embodiment of the invention, at least one gas sensor is provided along the suction and flushing duct between the detection area and the suction unit or blower, the sensor being positioned to generate an electrical signal indicative of the presence of a given gas or gas mixture in the airflow flowing through the duct coming from the detection area and passing by the sensor.

[0032] Therefore, according to the invention, a method for detecting a leak preferably comprises: - defining a detection area in which the sealed container is placed; - communicating the detection area with a gas sensor via a duct; - introducing a flushing gas or gas mixture into the detection area by flowing the flushing gas or gas mixture through a duct in a first direction; - placing a container within the detection zone; - drawing a gas sample from the detection area and transmitting the gas sample to a sensor that identifies the presence of a gas leak in the container, wherein the gas is transmitted from the detection area to the sensor by flowing the gas through a duct in a second direction opposite to the first direction.

[0033] According to the invention, the step of placing the container in the detection zone can be performed before or after the introduction of flushing gas. Preferably, however, the introduction of flushing gas into the detection zone is discontinued after the container to be inspected has been placed in the detection zone.

[0034] According to a particular aspect of the invention, the steps of defining a detection zone adapted to receive the sealed container to be inspected and the flushing step are carried out so as to generate a gas atmosphere with constant concentration and substantially free of turbulence in the detection zone. According to the invention, an atmosphere containing one or more gases with constant concentration and free of turbulence can be obtained by forming an environment with a mixture as similar as possible to the gas concentration in the atmosphere or by introducing into the detection zone, preferably by means of a diffuser, a gas or gas mixture preferably coming from a controlled environment in which the gas to be detected is absent or in which the gas is present in a limited and stable concentration. According to the invention, it is preferred that the flow of gas introduced into the detection zone should be as laminar and free of turbulence as possible.

[0035] According to a preferred embodiment of the invention, the containers are adapted to be displaced on a conveyor belt inside a tunnel in which one or more diffusers are provided, preferably arranged to analyze the entire contour of the sample as the belt progresses in order to monitor the presence of possible leaks in any part of the same container.

[0036] Also according to the invention, throttling means are preferably provided to encourage possible gas escape from the container when it is in the detection zone, and means for disposing of the container depending on the result of the carried out test may be provided downstream of the detection zone.

[0037] According to this first aspect, the invention makes it possible to detect microleaks of gas from a sealed container when the concentration of a tracer gas in the atmosphere inside the container differs from its concentration in the surrounding environment.

[0038] Optionally, the invention also provides the possibility to correct the concentration of the gas mixture present in the atmosphere near the container, thus allowing the detection of gas microleaks from the container when the tracer gas concentration in the atmosphere inside the container is the same as in the surrounding environment before conditioning.

[0039] An example of a tracer gas that is introduced into the vessel before sealing it is CO. 2 Referring to the above, the present invention relates to a method for producing a gas-permeable refrigerant gas (GPG) containing CO2 gas inside a container at a concentration exceeding that of atmospheric air (typically 400 ppm), according to a first embodiment described herein. 2 According to the second embodiment described, the presence of CO at a concentration approximately equal to that of atmospheric CO 2 In the second case, as previously mentioned, the present invention provides a modified atmosphere, i.e., CO 2 Low concentration of CO 2 This second aspect of the invention can be achieved, for example, by introducing a pure gas, such as nitrogen, into the detection area.

[0040] Below, CO 2 is often referred to as the tracer gas being detected, but the present invention is 2 , H 2 Any other tracer gas, such as, for example, 1000 cc or 1000 cc, and other gases or gas mixtures suitable for the purpose, may be used.

[0041] According to the invention, the sealed container to be inspected is positioned in the detection zone by a positioning assembly, preferably including at least one conveyor belt or carousel, or a conveyor or any other device capable of conveying the container to the detection zone. It is further preferred that the positioning assembly includes a pair of side guides for accurately positioning the container in the detection zone.

[0042] The positioning assembly preferably further includes a pair of conveyor belts for respectively introducing or entering the containers into the detection area and removing or withdrawing the containers from the detection area.

[0043] A throttle assembly may be suitably provided in the detection zone, capable of throttling the container to be inspected during sealing in order to encourage gas outflow in the event of the presence of micro-holes. Preferably, the throttle assembly comprises a pair of rotatable rollers, preferably arranged transversely to the direction of travel of the product to be inspected, and having an axis of rotation substantially parallel to the plane in which the product travels. When the product to be inspected travels on the conveyor belt, preferably the rotatable rollers are arranged in a plane parallel to the belt plane, with an axis of rotation transverse to the direction of travel of the belt. In a preferred embodiment, each roller is suspended on a pair of floating arms and connected to a corresponding pneumatic cylinder capable of exerting on the arms, and thus on the roller, a pressure suitable for throttling the container located in the detection zone. A motor is provided on the pivot axis of each arm, which rotates the roller via a drive belt. The pivot axis of the arm is fixed with respect to the structure of the detection device, while the spatial position of the rotation axis of the roller may vary depending on the pressure exerted by the pneumatic cylinder during the passage of the container in the detection zone. The described assembly with the arms, pneumatic cylinders and associated rollers of the throttle assembly collectively defines a third type lever. An angular potentiometer is mounted at the pivot axis of each arm to the stationary structure of the device, capable of generating an electrical signal indicative of the angular position of the arm, and therefore the position of the roller, relative to the sample container present in the detection area at that moment. Angular displacement indicates the presence of a sample container which is subject to detection. Angular displacement of the arms and rollers indicates that a sample is present and being throttled. If the sample is not throttled, for example if the sample has reached a highly throttled state, the sample is discarded.

[0044] According to a preferred embodiment of the invention, the roller of the squeeze assembly comprises a cylinder defining a central portion bounded by a pair of end plates for side protection, on the outside of one of the end plates is provided a grooved pulley engaged by a belt transmitting a motion imparted by a motor located corresponding to the pivot axis of one of the floating arms from which the roller is suspended.

[0045] Preferably, the central part of the roller, when viewed in cross section, comprises, starting from the inside and going radially outwards, a substantially rigid and hollow inner central sleeve, e.g. made of steel or aluminium, a soft layer, e.g. made of foam rubber, and an outer coating of a non-slip material, i.e. a material with a high grip, e.g. natural rubber, capable of exerting a strong friction against the surface of the passing sample vessels in order to advance the sample vessels without slipping. A shaft, the ends of which are integral with the end plates and the outer pulleys, is mounted inside the central sleeve.

[0046] In an alternative embodiment, the rollers of the squeezing assembly comprise hollow rubber sleeves, the outer surface of which has anti-slip properties and the cavity of which determines some softness and compressibility due to the external radial thrust caused by the resistance to squeezing that the sample container faces while passing under the rollers.

[0047] According to a preferred embodiment of the invention, a suction head with a number of slots for sucking gas is located in the detection area. Advantageously, the slots are arranged along a peripheral band that substantially surrounds the entire sample container during its passage through the detection area. Advantageously, the slots are distributed over the peripheral band in a plane that is approximately perpendicular to the direction of sample travel. Overall, the slots are therefore arranged along the top, two side and bottom surfaces of the peripheral band. For example, three top and three bottom slots may be provided, while a side slot is provided per side, totalling two side slots. Each slot also communicates with a respective duct and with a gas sensor.

[0048] The detection area may further comprise a diffuser through which an air curtain or blade is blown, helping to isolate the detection area from contamination by gases coming from the surrounding environment.

[0049] According to a preferred embodiment of the invention, taking into account that the detection head extends along a peripheral band that substantially surrounds the entire sample container passing through the detection zone, it is preferable to interrupt the conveyor belt so as to create an area of ​​slack at the time of the conveyor belt interruption to allow air flow from and to the slots in the underside of the slot band. Thus, preferably, the conveyor belt comprises an input section proceeding in a direction towards the detection zone to place the sample in the zone and to pass the sample inside the band of slots, and an output section proceeding in a direction away from the detection zone, thereby moving the sample from the zone towards its subsequent destination in the container processing plant. The slots in the underside of the peripheral band are located corresponding to the interruption of the conveyor belt between the end of the input section and the beginning of the output section. Alternatively, the conveyor belt may be made of a breathable material or other means allowing air flow from and to the detection zone may be used to transport the sample products.

[0050] Preferably, the slots located on the top surface and along the sides of the detector head are adjustable in height to accommodate the presence of containers having different sizes.

[0051] Preferably, the slots located along the upper surface are arranged obliquely relative to the periphery of the peripheral band and inclined at an angle ranging from about 15° to 30° relative to the plane of the band. Preferably, the slots located along the sides of the peripheral band are arranged approximately perpendicular to the respective sides and parallel to the direction of sample travel. Preferably, the slots located on the lower surface are parallel to the lower surface and perpendicular to the direction of sample travel. Preferably, the lower slots are defined in a suction assembly having, for example, three channels, one per slot. The lower suction assembly has an elongated body having a trapezoidal cross-sectional shape. Cavities communicating the corresponding slots with the respective gas outlet ports are defined inside the elongated body. In this case, three slots are provided overall, which have a length less than the length of the elongated body and are arranged on two parallel lines. Also, the slots are offset so as to ensure continuity of suction over the entire length of the elongated body. The interior cavity of the elongate body which defines the inlet ducts which carry the fluid drawn through the slots towards the respective outlet ports is configured to avoid sharp angles and to encourage laminar flow of the fluid flowing therethrough.

[0052] The slots located on the top surface are defined in an upper suction assembly having two channels, one for each slot. The upper suction assembly has an elongated body having a generally parallelepiped shape. Two cavities are defined inside the elongated body, communicating the corresponding slots with the respective gas outlet ports. The two slots are generally provided, have a length less than the length of the elongated body, and are obliquely arranged with an overlap of the projections of the slots on a plane perpendicular to the direction of sample travel, ensuring continuity of suction across the entire width of the elongated body. The internal cavities of the elongated body defining suction ducts for conveying the fluid suctioned through the slots towards the respective outlet ports are configured to avoid sharp angles and to encourage laminar flow of the fluid therethrough.

[0053] Preferably, the slots located on each side are defined in a respective side suction assembly having one channel, one assembly being provided on each side. The side suction assembly has a prismatic body having a generally parallelepiped shape. A cavity is defined inside the body, communicating the corresponding slot with each gas outlet port. There is a single slot having approximately the same length as the suction body and arranged parallel to the direction of sample travel. The internal cavity of the elongated body defining a suction duct conveying the fluid suctioned through the slot towards the respective outlet port is configured to avoid sharp angles and to encourage laminar flow of the fluid flowing therethrough.

[0054] A first advantage of the invention is that the flushing of the detection area is performed through the same duct through which the gas is sucked from the detection area. Thus, according to the invention, the duct is used in a bidirectional manner, both for the sucking of gas from the detection area and for the transport of gas towards the sensor, as well as for the introduction of a flushing gas or gas mixture into the detection area. Such an arrangement makes it possible to flush undesirable gases in a rapid manner both from the detection area and from the area through which the sample passes, more important with regard to the possible presence of undesirable gases defined by the ducts arranged between the detection area and the sensor, and between the sensor and the suction fan. This also makes it possible to speed up the work, without having to wait for the undesirable gases to leave the area by unforced diffusion to the external environment. Also, always thanks to such an arrangement, the space in which the sensor is located, as well as the internal space of the same sensor, are flushed by the action of the flushing gas or gas mixture. Thanks to such an arrangement, this minimizes the risk that the environment through which the sample passes and through which the duct carries the gas towards the sensor is contaminated by undesirable gas due to the previous passage of the sample, and therefore significantly improves the ability to detect leaks of microscopic quantities, i.e. micro-leaks.

[0055] Advantageously, the invention makes it possible to detect even small leaks, that is microleaks, of a gas or gas mixture through holes, even small in size, of the order of a few microns, for example 3 to 7 μm (microholes), which happen to be present in the flexible wall of the container.

[0056] The invention also advantageously provides the possibility of implementing a detection method that allows the detection sensitivity itself to be significantly increased, such that it is possible to advantageously increase the detection sensitivity and thus to detect the presence of minute tracer gas concentrations due to microleaks of tracer gas from a sample container in the atmosphere present in the detection zone.

[0057] The invention thus makes it possible to detect gas microleaks from containers in which the tracer gas concentration is not significantly different from that of the external environment. According to the invention, such a detection method can be carried out without or in combination with a function to modify the composition of the gas mixture in the vicinity of the container.

[0058] According to a further such embodiment of the invention, at least two sensors are provided, adapted to generate respective signals indicative of the presence of the tracer gas, both sensors being passed in series by the same gas flow drawn from the detection zone, with the second sensor, i.e., the one located downstream of the first sensor, generating a delayed signal relative to the first sensor.

[0059] In an alternative to such an embodiment, a single sensor is provided and the delay is obtained by passing the same gas flow coming from the detection area first in one direction through this sensor and then in the opposite direction.

[0060] Some preferred embodiments of the present invention are given below, by way of non-limiting example, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0061] [Figure 1A]1 is a schematic diagram of a number of embodiments of the present invention; [Figure 1B] 1 is a schematic diagram of a number of embodiments of the present invention; [Figure 1C] 1 is a schematic diagram of a number of embodiments of the present invention; [Figure 1D] 1 is a schematic diagram of a number of embodiments of the present invention; [Figure 1E] 1 is a schematic diagram of a number of embodiments of the present invention; [Figure 1F] 1 is a schematic diagram of a number of embodiments of the present invention; [Figure 2A] FIG. 1 is a side perspective view of an apparatus according to a preferred embodiment of the present invention. [Figure 2B] FIG. 2B is a side perspective view of the detection area of ​​the device shown in FIG. 2A. [Figure 2C] FIG. 2B is a side view of the detection area of ​​the device shown in FIG. 2A. [Figure 2D] FIG. 2B is a plan view of the detection area of ​​the device shown in FIG. 2A. [Figure 3A] FIG. 2 is a perspective view of a squeeze roller according to the first embodiment. [Figure 3B] FIG. 3B is a perspective view of the squeeze roller shown in FIG. 3A with the end plates removed. [Figure 4] FIG. 11 is a cross-sectional perspective view of a squeeze roller according to a modified embodiment. [Figure 5A] FIG. 2 is a top perspective view of the first diffuser. [Figure 5B] FIG. 5B is a perspective view of the diffuser shown in FIG. 5A. [Figure 6A] FIG. 2 is a side view of a second diffuser. [Figure 6B] FIG. 6B is a bottom view of the diffuser shown in FIG. 6A. [Figure 6C] FIG. 6B is a perspective view of the diffuser shown in FIG. 6A. [Figure 7A] FIG. 13 is a side view of the third diffuser. [Figure 7B] FIG. 7B is a bottom view of the diffuser shown in FIG. 7A. [Figure 8] FIG. 2 is a schematic diagram of a second embodiment of the device according to the invention. [Figure 9A] 1 is a graph of a tracer gas concentration signal. [Figure 9B] 1 is a graph of a tracer gas concentration signal. [Figure 9C] 1 is a graph of a tracer gas concentration signal. [Figure 9D] 1 is a graph of a tracer gas concentration signal. [Figure 9E] 1 is a graph of a tracer gas concentration signal. [Figure 10] 1 is a graph including two tracer gas concentration signals of different intensities. [Figure 11A] 1 is a graph of a gas concentration signal showing no leaks. [Figure 11B] 1 is a graph of a gas concentration signal showing no leaks. [Figure 11C] 1 is a graph of a gas concentration signal showing no leaks. [Figure 12] FIG. 4 is a diagram of a comparison circuit according to a second embodiment of the present invention. [Figure 13] 4 is a graph of a pair of gas concentration signals generated by a pair of sensors in a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] In all the figures, the same reference numbers are used to denote equal or functionally equivalent components.

[0063] With reference to Fig. 1A, a detection device 11 made according to a preferred embodiment of the invention and comprising a detection area 13 is shown diagrammatically. The detection area 13 is adapted to receive a sealed container CT to be inspected in order to ascertain the presence of possible leaks, i.e. with respect to openings that may communicate the contents of the container CT with the ambient environment outside the container. According to a preferred embodiment of the invention, the detection area 13 is defined by a support structure 15 including a frame 17, which communicates with the external environment.

[0064] The apparatus 11 further comprises a gas sensor device 19 adapted to generate an electrical signal indicative of the presence of a particular gas in a gas mixture passing through the sensor 19. In a particular embodiment of the invention, the gas is CO 2 and the sensor 19 is an infrared CO sensor including a measuring cell with an IR emitter and a corresponding photodetector. 2 The gas mixture to be analyzed, when passing through a measuring cell in the sensor 19, causes a change in at least one parameter of an electrical signal passing through an electrical circuit associated with a photodetector. The change is a function of the amount of CO present. 2 of the mixture passing through the sensor 19. 2 In other embodiments, different types of gas sensors measure CO in various modalities. 2 or various types of gases, e.g. He or H 2 Such sensors are known to those skilled in the art and therefore they will not be described in more detail.

[0065] The device 11 further comprises a duct 21 in communication with the detection area 13 and the gas sensor 19. According to the invention, as will become more apparent from the following description, gas flows through the duct 21 in a first direction (arrow f1) from the detection area 13 to the sensor 19 in a step of gas suction from the detection area 13, and in a second direction arrow (f2) opposite to the first direction from the sensor 19 to the detection area 13 in a gas flushing step.

[0066] According to the embodiment of the invention shown in Fig. 1A, the device 11 comprises a flushing gas blower 23 with an outlet port 23a communicating with the duct 21, from which the flushing gas leaves, and an inlet port 23b for the inlet of the drawn gas, connected to a controlled environment (not shown) containing the flushing gas. In the embodiment shown, the device 11 further comprises a suction fan 25 with an inlet port 25a, through which air is drawn, communicating with the duct 21, and an outlet port 25b for discharging the drawn air to an uncontrolled environment, for example the external environment. Always referring to the embodiment shown, the duct 21 comprises a first segment 21a connected between the detection area 13 and the sensor 19, a second segment 21b connected between the sensor 19 and a first port of the three-way switching valve 27, and two segments 21c and 21d connected between the second port 27b of the valve 27 and the blower 23 and between the third port 27c of the valve 27 and the suction fan 25, respectively.

[0067] In this preferred embodiment of the invention, the segment 21a communicates with the detection zone 13 through a diffuser 29. According to the invention, a single detection zone 13 may be provided with a plurality of diffusers 29. For example, the diffusers 29 may be provided surrounding the container CT passing through the zone 13 such that substantially the entire side of the container CT passing through the zone 13 is subject to air suction by the diffusers 29.

[0068] Referring to FIG. 1B, in a particular embodiment of the present invention, a diffuser 29 communicates with a single sensor 19 via respective segments 21a of a duct 21 arranged in parallel.

[0069] Referring to FIG. 1C, in another embodiment, multiple diffusers 29 are provided, each belonging to an independent and separate detection system with a respective sensor 19, blower 23, intake fan 25, and valve 27.

[0070] Referring to FIG. 1D, in yet another embodiment of the invention, an intermediate configuration between those described above is provided, where each diffuser 29 is provided with a dedicated sensor 19, each sensor 19 communicating via a respective segment 21b of duct 21 with a single valve 27 associated with a single blower 23 and a single suction fan 25.

[0071] Always according to the invention other embodiments are conceivable, for example resulting from combinations of the features described above.

[0072] Also preferably, each diffuser 29 may be configured and oriented to fit the geometry of the area 13 and the container CT to be inspected through that area 13 .

[0073] Preferably, the controlled environment into which the blower 23 draws gas contains a mixture of a particular gas, e.g. a gas different from the tracer gas present in the container being inspected, or a gas mixture in which the concentration of this type of gas present in the container being inspected is lower than the concentration of the same gas in the container.

[0074] 1A to 1D, an embodiment of the invention is shown in which a blower 23 and a suction fan 25 are provided for each duct 21. The blower 23 has an outlet port 23a communicating with the duct 21 through a segment 21c of the duct 21, and the suction fan 25 has an inlet or suction port 25a communicating with the duct 21 through a segment 21d of the same duct 21. A three-way valve 27 is further provided to communicate the duct 21 with the suction fan 25 during the suction step and with the blower 23 during the flushing step. The same three-way valve 27 closes the communication between the duct 21 and the blower 23 during the suction step and closes the communication between the duct 21 and the suction fan 25 during the flushing step. Thus, according to this embodiment of the invention, air suction and flushing from the detection area 13 is performed by two separate and independent units 23, 25 which are exclusively in communication with the duct 21 and the detection area 13 via a three-way valve 27.

[0075] With reference to Fig. 1E, an alternative embodiment of the device 11 according to the invention is shown, in a schematic and partial manner, in which the air suction from the detection area 13 and the flushing step are therefore performed by a single unit 31 acting as a suction fan and as a flushing gas blower. The unit 31 incorporates a valve 33 adapted to put the duct 21 into communication with the detection area 13, which alternatively communicates with the inlet / outlet port 31a or the outlet / inlet port 31b of the unit 31. The unit 31 may for example consist of a reversible blower unit or a compressor. Also, during the suction step, the single unit 31 exhausts the sucked gas to the external environment, while in the flushing step the single unit 31 takes the flushing gas from the controlled environment containing the flushing gas.

[0076] With reference to Fig. 1F, another alternative embodiment of the device 11 according to the invention is shown, diagrammatically and partially, in which the air suction from the detection area 13 and the flushing steps are performed by a single unit 31', which therefore acts both as a suction fan and as a flushing gas blower. - (during the step of air intake from the detection area 13) the segment 21b of the duct 21 to the inlet port 31'a of the unit 31' and to the outlet port 31'b of the unit 31' to the outside environment, or alternatively, - (during the flushing step) connecting the segment 21b of the duct 21 to the outlet port 31'b of the unit 31' and connecting the inlet port 31'a of the unit 31' to a controlled environment containing a flushing gas. It communicates with a valve 27' adapted to communicate therewith, preferably a five-way valve.

[0077] In a further embodiment of the invention, air suction and flushing from the detection area 13 is performed by a single reversible unit which can operate as a suction fan or as a blower by reversing the direction of its operating motion.

[0078] 2A to 2D, according to the illustrated embodiment of the invention, a sample container to be tested is positioned within a detection zone 13 defined within the apparatus 11 by a positioning assembly 51. According to this embodiment, the positioning assembly 51 comprises a pair of conveyor belts 53, 55 for respectively introducing or inserting the container into the detection zone 13 and removing or removing the container from the detection zone 13. Preferably, the positioning assembly 51 further comprises a pair of side guides 55a, 55b for accurately positioning the container within the detection zone 13, preferably in the center of the zone 13.

[0079] Always referring to the present embodiment, a throttle assembly 57 is further provided within the detection zone 13, the throttle assembly 57 comprising a pair of rotatable rollers 59a, 59b arranged transverse to the direction of travel "d" of the conveyor belts 53, 55 and having an axis of rotation "S1" substantially parallel to a plane defined by the belts 53, 55 in which the sample container to be inspected is placed. Each roller 59a, 59b is suspended relative to a pair of floating arms 61 and each connected to a respective pneumatic cylinder 63, capable of exerting a pressure on the arms 61, and thus on the rollers 59a, 59b, suitable for squeezing a container located within the detection zone 13 and, if an opening is present in the container, encouraging gas leakage from the interior of the container towards the surrounding environment within the zone 13.

[0080] A motor 65 is provided corresponding to the pivot axis "S2" of each arm 61 for rotating the rollers 59a, 59b via a drive belt 67. The position of the pivot axis "S2" of the arm 61 is fixed relative to the structure 15 of the device 11, whereas the position of the rotation axis "S1" of the rollers 59a, 59b can vary depending on the pressure exerted by the pneumatic cylinder 63 during the passage of a container through the detection area 13. The described assembly comprising the arm 61, the corresponding pneumatic cylinder 63 and the rollers 59a, 59b associated with the arm of the described throttle assembly 57 collectively defines a third type lever. An angular potentiometer 69 is provided corresponding to the pivot axis "S2" of each arm 61 on the frame 17 of the stationary structure 15 of the device 11, capable of generating an electrical signal indicative of the angular position of the associated arm 61 and, consequently, of the rollers 59a, 59b relative to the sample container present in the detection area 13 at that moment. The angular displacement indicates the presence of a sample container to be inspected within zone 13. The angular displacement of arm 61 and associated rollers 59a, 59b indicates that a sample is present within zone 13 and that the sample has been partially deformed by the squeeze assembly 57. If the sample is not squeezed, e.g., the container is already very flat, e.g., because the container has suffered a significant leak such that the container is floppy or deflated, the sample is discarded.

[0081] A number of diffusers 29a, 29b, 29c, 29d, each including a respective suction head 71a, 71b, 71c, 71d with a number of slots 73 for gas intake, are located within the detection area 13. The slots 73 are generally arranged along a peripheral band that substantially surrounds the sample container while it is moving within the detection area 13. The peripheral band is also located on a plane "P1" that is approximately perpendicular to the direction of travel "d" of the sample on the belts 53, 55. The slots 73 are generally arranged along the upper surface, a pair of side surfaces, and the lower surface of the peripheral band. Two slots 73 are located on the upper surface and belong to the upper diffusion head 71a, four slots 73 are located on the lower surface and belong to the lower diffusion head 71d, and one slot 73 is located on each side, for a total of two side slots 73, which belong to the side diffusion heads 71b and 71c, respectively. Each slot 73 also communicates with a respective duct formed in the corresponding slotted head, which in turn communicates with the gas sensor 19 via a port 75. In accordance with the configurations described and associated with this particular embodiment of the invention, each slot 73 along the peripheral band is associated with a respective port 75. The port 75 may be connected to a same number of sensors 19 or to a single sensor 19, according to one of the embodiments described above in connection with Figures 1A-1D.

[0082] The detection area 13 further comprises an auxiliary diffuser 77 through which an air curtain or blade is blown, which helps to isolate the detection area 13 from contamination by gases coming from the surrounding environment.

[0083] 3A and 3B, rollers 59a, 59b of aperture assembly 57 include a cylindrical body 81 defining a central portion 81a bounded by a pair of side end plates 81b, 81c. A grooved pulley 83 is provided on the outside of one such end plate for engagement by a belt 67 which transmits motion imparted by a motor 65 located corresponding to the pivot axis "S2" of one of the floating arms 61 from which the corresponding roller 59a, 59b is suspended.

[0084] The central part 81a of the rollers 59a, 59b, when seen in cross section, starting from the inside and going radially outwards, comprises a substantially rigid and hollow inner central sleeve 85a, for example made of steel or aluminium, an intermediate soft layer 85b, for example made of foam rubber, and an outer coating 85c of a non-slip material, i.e. a non-slip material with a high grip, for example natural rubber, capable of exerting strong friction against the surfaces of the sample containers through which they pass in order to advance without slipping while being squeezed in the detection zone 13. A shaft 87, the ends of which are integral with the side end plates 81b, 81c and the outer pulley 83, is mounted inside the central sleeve 85a.

[0085] In an alternative embodiment, see FIG. 4, the rollers 59a, 59b of the squeeze assembly 57 comprise a hollow rubber sleeve 91, the outer surface 91a of which has anti-slip properties thanks to the nature of the material of the sleeve, and the inner cavity 91b of which determines a certain softness and compressibility of the sleeve 91 by the external radial thrust due to the resistance to squeezing that the sample container faces while passing under the rollers 59a, 59b.

[0086] Returning from FIG. 2A to FIG. 2D, the need for interrupting the conveyor belt arises while the sample container passes through the detection zone 13, taking into account that the latter includes a peripheral band of suction slots 73 surrounding the sample container. That is, the conveyor belt 53, 55 includes an input section 53 proceeding in a direction towards the detection zone 13 so as to place the sample in the zone 13 and pass it inside the band of slots 73, and an output section 55 proceeding in a direction away from the detection zone 13, thereby moving the sample from the zone 13 towards a destination downstream of the zone 13 in the container processing plant. The destination can be either a preferential destination containing the container in a packaging plant, or an excluded destination where the container showing a defect in the hermetic seal is disposed of. The slot 73 in the lower surface of the peripheral band belonging to the lower diffusion head 71d is located at the break in the conveyor belt between the end of the input section 53 and the beginning of the output section 55. Thus, sections 53, 55 are spaced apart from one another longitudinally of the belt travel by a distance sufficient to allow air suction by the lower diffusion head 71d, but without compromising the smooth transport of the sample containers, i.e., such a discontinuity is not likely to cause jamming or changes in direction for the samples.

[0087] Slots 73 located on the top surface and along the sides of the peripheral band are adjustable in height to accommodate the presence of sample vessels having different sizes within the detection area 13 .

[0088] The slots 73 belonging to the upper head 71a are therefore located along the upper surface of the peripheral band and are arranged obliquely with respect to the plane of the band, inclined at an angle in the range of about 15° to 30° with respect to this plane. The slots 73 belonging to the side heads 71b, 71c are therefore located along the sides of the peripheral band and are arranged approximately perpendicular to the plane of the band and parallel to the direction of sample advancement "d". The slots 73 belonging to the lower head 71d are therefore located along the lower surface of the peripheral band and are parallel to the plane of the band and perpendicular to the direction of sample advancement "d".

[0089] As can be better seen from Figures 5A and 5B, the lower slots 73 are defined in the suction head or assembly 71d with four channels, one for each slot 73. The lower suction assembly 71d has an elongated body with a generally trapezoidal cross-sectional shape. Four separate cavities 101 are defined inside the elongated body that communicate the corresponding slots 73 with the respective gas outlet ports 75. The four slots 73 are generally provided in the lower suction head 71d, have a length less than the length of the elongated body, and are arranged on two parallel lines, with a pair of slots per line. Also, the slots 73 are offset so as to ensure continuity of suction over the entire length of the elongated body of the head 71d. The internal cavities 101 of the elongated body that define the suction ducts that carry the fluids sucked through the slots 73 towards the respective outlet ports 75 are configured to avoid sharp angles and to encourage laminar flow of the fluid flowing therethrough.

[0090] With reference to Figures 6A to 6C, the slots 73 located on the upper surface of the peripheral band are defined in the upper head 71a or upper suction assembly having two channels, one for each slot 73. The upper suction assembly 71a has an elongated body having a generally parallelepiped shape. Two cavities 105 are defined inside the body, which communicate the corresponding slots 73 with the respective gas outlet ports 75. The two slots 73 are provided generally, they have a length less than the length of the elongated body of the head 71a, and are obliquely arranged such that there is an overlap of the projections of the slots on a plane perpendicular to the direction of sample advancement "d", so as to ensure continuity of suction over the entire width of the elongated body of the upper head 71a. The internal cavities 105 of the elongated body, which define the suction ducts that carry the fluids sucked through the slots 73 towards the respective outlet ports 75, are configured to avoid sharp angles and to encourage laminar flow of the fluids flowing therethrough.

[0091] With reference to Figures 7A and 7B, the slots 73 located on each side are defined in the respective side heads 71b, 71c or side suction assemblies, one channel, one assembly per side. The side suction assemblies 71b, 71c have a prismatic body having a generally parallelepiped shape. A cavity 109 is defined inside the body, connecting the corresponding slots 73 with the respective gas outlet port 75. There is a single cavity 73 for each side head 71b, 71c, which has approximately the same length as the corresponding suction body and is disposed approximately parallel to the direction of sample travel "d". The internal cavity 109 of the elongated body, which defines the suction duct that conveys the suctioned fluid through the slots 73 towards the respective outlet port 75, is configured to avoid sharp angles and to encourage laminar flow of the fluid flowing therethrough.

[0092] Returning to FIG. 1A, a preferred embodiment of a method for detecting leakage from a sealed container according to the present invention will now be described.

[0093] The method mainly comprises the steps of placing the container whose tightness is to be checked in the detection area 13 and sucking the air present in the detection area 13 through at least one suction duct 21 communicating with the detection area 13. According to the invention, the suction step is preceded by a step in which the duct 21 and the detection area 13 are flushed, this step being carried out by reversing the flow through the same duct 21.

[0094] According to a first aspect, the invention preferably comprises the step of defining a predetermined gas atmosphere substantially free of turbulences in the detection zone 13, in which a tracer gas of the type enclosed in the container is present in a constant concentration. Advantageously, the shape and arrangement of the diffuser 29 described above makes it possible to achieve the desired result as long as turbulences in the zone 13 are not involved. According to such a first aspect, the invention makes it possible to detect microleaks of gas from a container when the concentration of the tracer gas inside the container differs from that of the surrounding environment.

[0095] The invention also provides the possibility to modify, if appropriate, the composition of the gas mixture by a flushing step near the container in the detection area 13, thereby modifying the concentration of the gas corresponding to the tracer gas enclosed in the sealed container. The invention therefore makes it possible to detect microleaks of gas from the container when the gas composition is approximately the same as the composition in the surrounding environment before the modification is carried out during the flushing step.

[0096] CO as a tracer gas introduced into the vessel before sealing it 2 By way of example, the present invention relates to a method for producing a gas-filled container having a CO concentration above that of atmospheric air (typically 400 ppm) according to the first aspect of the invention. 2 According to the second embodiment described, the presence of CO at a concentration approximately equal to that of atmospheric CO 2 In the second case, as mentioned above, the invention provides a method for flushing the detection area 13 with modified atmospheric air, i.e. CO 2 The concentration of CO 2 This second aspect of the invention can be achieved, for example, by introducing a pure gas, such as nitrogen, into the detection area.

[0097] In a preferred embodiment of the present invention, the suction step and the flushing step are respectively performed by a suction fan 25 having a suction port 25a communicating with the duct 21 and by a blower 23 having an outlet port 23a communicating with the same duct 21. A three-way valve 27 is further provided to communicate the duct 21 with the suction fan 25 during the suction step and with the blower 23 during the flushing step. The same three-way valve 27 closes the communication between the duct 21 and the blower 23 during the suction step and closes the communication between the duct 21 and the suction fan 25 during the flushing step.

[0098] According to the invention, the gas sensor 19 is provided along the suction and flushing duct 21 between the detection area 13 and the suction unit 25 or blower 23, and is adapted to generate an electric signal indicative of the presence of a given gas in the airflow flowing in the duct 21 coming from the detection area and passing the sensor 19. Advantageously, the arrangement of the gas sensor 19 adjacent to the detection area 13 makes it possible to increase the measurement sensitivity of the gas sensor. In fact, the gas sucked from the detection area 13 by the suction unit 25 arrives directly at the gas sensor 19 without having flowed previously through the suction unit 25, which causes homogenization of the gas to be detected in the sucked gas sample.

[0099] Thus, according to the invention, the method for detecting a leak mainly and preferably comprises: - defining a detection area 13 in which the sealed container is placed; - placing the detection area 13 in communication with a gas sensor 19 via a duct 21; - introducing a flushing gas or gas mixture into the detection area 13 by flowing the flushing gas or gas mixture through a duct 21 in a first direction; - placing a container within the detection area 13; - drawing a gas sample from the detection area 13 and transmitting the gas to a sensor 19 which detects the presence of a gas leak in the container, the gas being transmitted from the detection area 13 to the sensor 19 by flowing the gas through the same duct 21 in a second direction opposite to the first direction.

[0100] Also, preferably, the suction step is commenced immediately, i.e. in a substantially uninterrupted manner, after the flushing step has stopped.

[0101] Optionally, the method according to the invention includes a step in which the sample vessel is subjected to a compression or throttling step in order to encourage possible gas escape. Preferably, the throttling step is performed by the throttling assembly 57 described above.

[0102] Reference is now made to FIG. 8 to illustrate a preferred embodiment of an apparatus 11' adapted to implement a detection method according to a particular embodiment of the invention and which is capable of significantly increasing the sensitivity of detection itself.

[0103] In figure 8, reference numbers 219a and 219b indicate two gas sensors connected in series in the same duct 21. According to this embodiment of the invention, the duct segment 21e connecting the two sensors 219a, 219b causes a delay in the signalling by the sensor 219b of the presence of a tracer gas coming from the detection area 13 and mixed with the gas mixture flowing in the duct 21 with respect to the signal generated by the sensor 219a located downstream of the duct segment 21e.

[0104] The principle of operation of this variant of the detection method according to the invention will now be explained in more detail.

[0105] Referring to FIG. 9A, a CO 2 The CO measured by the signal generated by the sensor 19 2 A graph of the change in concentration against time is shown: the graph in Figure 9A relates to an operating cycle of the device 11 according to the invention when there is no sample to be examined or when the sample is completely airtight, i.e. without any leaks.

[0106] According to a preferred embodiment of the method according to the invention, the time T 0 At the detection area 13 of the device 11 made according to the invention, a flow of flushing gas coming from a blower 23 arrives. The flushing gas can be, for example, nitrogen or a gas mixture with a high nitrogen concentration. The flow of flushing gas is introduced into the detection area 13 via a diffuser 29. The flow of flushing gas flows through a duct 21 in the direction of the detection area 13 and brushes against the gas sensor 19, which gives a CO concentration of 0 ppm since nitrogen is substantially the only gas brushing against the sensor. 2 Detect.

[0107] Time T 1 Then the flow of flushing gas stops in an almost uninterrupted manner and a suction step is started to draw air from the detection area 13, always through the same diffuser 29 where the flushing of the area 13 was performed. The air drawn from the detection area 13 by the suction fan 25 flows further through the same duct 21 through which the flow of flushing gas had previously flowed, which is picked up by the sensor 19, thereby detecting a concentration of, for example, 400 ppm, i.e., CO 2 Detect typical atmospheric concentrations of

[0108] Time T 2 Then the suction step stops and the flushing step starts again in which nitrogen coming from the blower 23 is introduced into the detection area 13. The nitrogen flows again through the same duct 21 in the opposite direction to the air sucked in in the previous step, which means that the only gas that brushes against the sensor 19 is still nitrogen, resulting in a CO2 concentration of 0 ppm. 2 is again captured by the sensor 19 which detects the time T 3 And the cycle stops.

[0109] Referring to FIG. 9B, next, CO 2 Reference is made to the sample container to be inspected passing through the detection zone 13 of the device 11 which contains a tracer gas which is assumed to be

[0110] FIG. 9B shows CO 2 CO measured by the indicator signal generated by the sensor 19 2 1 shows a graph of the change in concentration versus time. The operating cycle is essentially the same as before, but at time T 1 So, CO 2 The sample container to be tested, which has a micro-hole through which the liquid leaks, is made to pass through the detection area 13 at a constant speed. 1 and T 2 In the interval between, as can be seen from FIG. 9B, the sensor 19 detects CO 2 Detect leaks. CO at sensor 19 2The concentration gradually increases to a maximum and then decreases as the passing sample, and therefore the micro-hole, moves away from the detection area 13. The time T during which the container is being inspected 2 has already passed the detection area 13, so the microleak has moved beyond the diffuser 29 into which the gas was drawn, and the drawing stops, and pure nitrogen, i.e., 0 ppm CO 2 The flushing step involving the introduction of a gas substantially containing 3 And the cycle stops.

[0111] The operating cycle of the device 11 described above with reference to Figures 9A and 9B can be performed using compressed air (400 ppm, dashed line in the graph of Figure 9B) as flushing gas instead of pure nitrogen (solid line in the graph of Figure 9B) or CO 2 This can also be achieved by using other gas mixtures where the concentrations are lower than those due to the detected microleak.

[0112] Referring to FIG. 9C, the CO measured by sensor 19 when two passing samples show different amounts of gas leakage, i.e., a small amount (dashed line) and a large amount (solid line). 2 A graph of the change in concentration versus time is shown. As can be seen, the tracer gas (CO 2 The shape of the curve of the signal showing the change in concentration of ) is almost always the same in the examples shown. As will become more clear from the following description, the experiments carried out were carried out at intervals T 1 ~T 2 This indeed enabled the determination that the appearance of the graph of the signal indicative of the gas concentration at has a Gaussian-like behavior. What is obviously different is the signal strength, which depends on the size of the opening causing the leak, if any, the tracer gas concentration in the gas mixture leaking from the vessel, and whether and how much the sample is mechanically stressed by the restrictor assembly 57 (the tighter the restrictor, the higher the strength of the leak detected by the sensor 19).

[0113] 9D and 9E, in the illustrated example, ambient CO 2 The concentration of the tracer gas is disturbed at intervals T 1 ~T 2 CO generated in section 13 when the sample passes through at high speed 2 A graph of the change in concentration versus time is shown.

[0114] With particular reference to FIG. 9D, the tracer gas (CO in certain cases) is injected with a variable offset. 2 ) with a very high and constant background value in the interval T 1 ~T 2 The CO measured by sensor 19 when the two passing samples show different amounts of gas leakage, i.e., a small (dashed line) and a large (solid line) gas leakage, when present in 2 A graph of the change in concentration versus time is shown.

[0115] With particular reference to FIG. 9E, the tracer gas (CO in this particular case) is injected into the plasma with strong turbulence and variable offsets. 2 ) very high and highly variable background values ​​in the interval T 1 ~T 2 The CO measured by sensor 19 when the two passing samples show different amounts of gas leakage, i.e., a small (dashed line) and a large (solid line) gas leakage, when present in 2 A graph of the change in concentration versus time is shown.

[0116] As can be seen from Fig. 10, a detection method based on a certain threshold for the tracer gas concentration has several limitations. Firstly, when the threshold is constant, such a detection method is very sensitive to background gas offsets. Secondly, the moment at which the signal indicative of the tracer gas concentration emitted by the sensor exceeds a certain threshold and thus causes the signaling of the occurrence of a leak varies depending on the tracer gas concentration, which in turn depends on the amount of leak. Always referring to Fig. 10, where signals indicative of a small (dashed line) and a large (solid line) leak are shown and where the threshold is identified by the horizontal solid line Th, the moment at which the occurrence of a leak is signaled actually has a time shift T → T' that varies as the tracer gas concentration changes.

[0117] Also, such an approach in which a certain threshold is set for the signal generated by the gas sensor does not perform well in the case of very small micro-leaks, giving rise to the problem of false positives, i.e., erroneous signaling of the occurrence of a leak. More specifically, referring to FIG. 11A, an example is shown in which a small change in the tracer gas concentration at the gas sensor due to a micro-opening in the container is not enough to allow the recognition that the container is not properly sealed and therefore possibly to be disposed of. FIG. 11B shows an example in which a fluctuation in the concentration of the same type of gas as the tracer gas introduced into the container, due to a source outside the container, is enough to generate a signal at the gas sensor having a value above a certain set threshold, and is therefore misinterpreted as a leak. FIG. 11C shows an example similar to the previous one in which background gas turbulence due to a source outside the container is misinterpreted as a leak.

[0118] A constant threshold that is too low therefore makes it practically impossible to distinguish transitions due to microleakage from those due to the bulk of the background noise. The presence of background noise therefore forces the threshold to be set at a value significantly different from zero, and in any case with an absolute value higher than the "peaks" of the noise. In certain cases, this therefore means that a leak will only be detected if its amount is much larger than the background fluctuations.

[0119] The detection method according to an alternative embodiment of the invention, which allows to significantly increase the sensitivity of the detection itself, makes use of a principle that allows to establish precisely the moment, i.e. the timing, when a leak occurs. By establishing a precise and repeatable timing of signaling the occurrence of a leak, it is possible to considerably narrow the analysis interval of measurements on samples moving close to the passage of the sample container affected by the leak to be detected. The precise timing section makes the detection method insensitive to ambient turbulences that may create signals that are very similar to the signal characteristics of a leak and therefore may be mistaken for a leak-indicative signal.

[0120] As previously described with reference to FIG. 10, by assuming a constant threshold Th, the exceeding of which triggers the signaling of the presence of tracer gas, and a change in the amplitude of the signal indicating the presence of gas produced by a leak, the delay of the moment T, T' at which the exceeding of the threshold signals the leak also changes. More precisely, such delay increases as the signal amplitude decreases. If we assume that the signal generated by the sensor 19 is fed to a comparator device adapted to generate a logic signal "0" when the strength of the comparator input signal is below a set threshold and to generate a logic signal "1" when the strength of the comparator input signal exceeds a set threshold, the time interval between the transitions from logic state "0" to "1" does not correspond to the correct time interval at which a change in the concentration of tracer gas at the sensor occurs due to the delays pointed out above. This effect of timing dependence on the signal amplitude is referred to in the scientific literature as the "walk" effect, and as pointed out above, timing techniques based on a constant threshold suffer from a significant "walk" effect.

[0121] Additionally, the signals generated by gas sensors are typically affected by significant background noise, which causes an equally significant "jitter" effect, ie, timing variations.

[0122] The substantial similarity of the curve shapes of the signals indicative of the tracer gas concentration in the gas mixture reaching the sensor, despite changes in signal amplitude, advantageously enabled the employment of a nearly walk-free timing technique that ideally matches a defined maximum percentage of the curve, for each signal, when the signal crosses a threshold, e.g., when the signal achieves half its final amplitude, by causing a transition in the timing logic signal.

[0123] Providing such a "floating" threshold is comparable to so-called "Constant Fraction Timing" or "Constant Fraction Discrimination" (CFD).

[0124] Reference is now made again to FIG. 8 to illustrate a preferred embodiment of a device 11' made in accordance with a particular embodiment of the invention adapted to implement a detection method which makes it possible to significantly increase the sensitivity of detection itself.

[0125] As disclosed above, the apparatus 11' includes a pair of sensors 219a and 219b connected to each other by a duct segment 21e, the internal volume of which is known, i.e., the length and cross-sectional size of the duct segment 21e are known and constant. Such a duct 21e separating the sensors 219a and 219b effectively forms a corresponding delay line in the gas propagation along the duct 21.

[0126] Referring again to FIG. 12, the corresponding signals M coming from the two sensors 219a and 219b are 1 and M. 2 is sent to the comparator 210, and the output signal M of the comparator 10 3 indicates the occurrence of a leak from the container passing when the signal of the second sensor 219b exceeds a floating threshold determined by the variable signal of the first sensor at the same time instant.

[0127] This technique is advantageous because it makes it possible to have an identification time that is independent of amplitude and insensitive to jitter and walk.

[0128] The CFD identification also makes the system more capable in the case of low strength leak signals and increases the measurement sensitivity. 2 The detection technique is less affected by background variations or turbulent effects in the flow field and makes it possible to avoid false positives, i.e. to prevent external fluctuations from being misinterpreted as a measurement of a leak.

[0129] In the example shown in Figure 13, two switches, i.e. two transitions of the comparator 0 → 1, occur at the correct measurement interval, but at different times from the moment the reading is made. If the switches occur too close together, they will be considered by the system as being due to background noise and will not be detected by the CO 2 is not considered an event determined by a leak of

[0130] In an alternative embodiment of the device made according to this particular embodiment of the invention, the signal of the second sensor is replaced by a second signal of the first sensor and the gas flow is made to flow in the opposite direction at a second time. In other words, according to such an alternative embodiment, the gas flow coming from the detection area 13 passes the first sensor 19 by flowing along the duct in a first direction towards the intake fan 25 and then in the opposite direction towards the sensor 19. Obviously in this embodiment a single and unique sensor may also be provided.

[0131] In the following, a particular signal processing modality is described that can be applied to an embodiment of the invention, in which at least two gas sensors, preferably six sensors connected in parallel, are provided, so as to impede the flow of gas coming from the detection area 13 along the corresponding duct 21. Such a signal processing modality can be applied, for example, to the embodiment of the device 11 shown in FIG. 1C. Such a particular processing modality results in correlating the signals of several sensors connected in parallel by a convolution method applied to the sensor pairs. If the degree of correlation exceeds a certain factor (for example >+0.8 or <-0.8), a preprocessing operation is performed on the signals, which makes it possible to subtract from each signal noise or disturbance signals that are common to several sensors and that appear as a constant offset or a linear (increasing or decreasing) signal.

[0132] The pre-processing step involves the determination of the signals of the two channels, and therefore the signal strengths SS of the two gas sensors. 1 and S.S. 2Each signal SS 1 Once it is digitized, it can be represented as an array of points with a length that depends on the duration of sampling and measurement. The Pearson correlation coefficient is defined as the covariance divided by the product of the standard deviations σ of the two variables, considered for each signal pair. ρ SS1 SS2 = σ SS1 SS2 / (σ SS1 ,σ SS2 ) Where, σ SS1 SS2 The two signals SS 1 and S.S. 2 is the covariance between SS1 and σ SS2 are two standard deviations.

[0133] A strong correlation exists when the Pearson coefficient is greater than +0.8 or less than -0.8. N The calculation is performed between all combinations of pairs of

[0134] The number of channels is denoted by N, and the independent combinations are given by (N·(Nl)) / 2.

[0135] For example, if N=6 (ie, 6 is the number of independent channels according to a preferred embodiment of the present invention), then 15 following pairs are obtained: (1 2)(1 3)(1 4)(1 5)(1 6) (2 3)(2 4)(2 5)(2 6) (3 4)(3 5)(3 6) (4 5)(4 6)

[0136] For all combinations, signals are cross-correlated where all Pearson coefficients are above +0.8 or below -0.8, indicating the presence of background changes.

[0137] In such a case, the average signal of all channels SS m The array of all signals SS nThe new value is *SS N teeth, *SS 1 :=SS 1 -SS m *SS 2 :=SS 2 -SS m …………… *SS n :=SS n -SS m It becomes.

[0138] According to the invention, such a detection method can be performed without or in combination with the function of modifying the gas mixture in the vicinity of the vessel as disclosed above and operated in a flushing step. [Industrial Applicability]

[0139] The invention finds industrial applications in several fields of detecting leaks and micro-leaks from almost any kind of container, compressible or rigid. The invention can also be applied to detect leakage of liquids (e.g. water or beverages) from pressurized rigid containers.

[0140] The invention as described and illustrated is susceptible to several variations and modifications which fall within the scope of the same inventive principles.

Claims

1. 1. A method for detecting a leak from a sealed container, comprising: - defining a detection area (13) in which a sealed container (CT) is placed; - communicating said detection area (13) with a first gas sensor (219a) and a second gas sensor (219b) through a duct (21), said first gas sensor (219a) and said second gas sensor (219b) being connected in series with each other by a segment (21a) of said duct (21), the internal volume of said segment (21a) being known and said segment (21e) determining a corresponding delay line in the gas propagation along said duct (21); - introducing a flushing gas into the detection area (13) by flowing said flushing gas through said one duct (21) in a first direction; - placing a container (CT) within said detection zone (13); - drawing gas from the detection area (13) and transmitting said gas to said first gas sensor (219a) and said second gas sensor (219b) for locating the presence of a gas leak in said container (CT), said gas being transmitted from said detection area (13) to said first gas sensor (219a) and said second gas sensor (219b) by making said gas flow through said one duct (21) in a second direction opposite to said first direction; - receiving a corresponding signal (M １ , M. ２ ) and each corresponding signal (M １ , M. ２ ) to a comparator; - the output signal (M ３ ), wherein the output signal (M ３ ) is the signal (M ２ ) at the same time, the variable signal (M １ indicating the presence of a leak from a container present in said detection zone (13) when the floating threshold determined by A method comprising:

2. The method of claim 1 , wherein the detection area (13) is in communication with the atmosphere of an external environment surrounding the detection area (13).

3. The method according to claim 1 or 2, further comprising the step of subjecting the container (CT) to a squeeze when placed in the detection area (13) in order to encourage possible outflow of fluid from the container (CT) through any openings that may be provided in the container.

4. 4. The method according to claim 1, 2 or 3, wherein the steps of introducing and sucking are respectively performed by a flushing gas blower (23) and a suction fan (25), both of which communicate with the detection area (13) via the one duct (21).

5. 5. The method of claim 4, wherein in the introducing step, the flushing gas introduced into the detection area (13) is taken from a controlled environment containing the flushing gas, and in the drawing step, the gas drawn from the detection area (13) is exhausted to an uncontrolled environment.

6. 4. The method according to claim 1, 2 or 3, wherein the steps of introducing and sucking are performed by a single unit (31) acting as a suction fan and as a flushing gas blower by means of a flow reversing circuit provided with a switching valve (33) and communicating with the detection area (13) through the one duct (21).

7. The steps of introducing and sucking are carried out by a single unit (31') acting as a suction fan and as a blower, the single unit (31') comprising: - during said drawing step, said duct (21) communicating with said detection area (13) is connected to an inlet port (31'a) of said single unit (31') and an outlet port (31'b) of said single unit (31') is connected to the outside environment, or said introducing step comprises connecting said duct (21) communicating with said detection area (13) to said outlet port (31'b) of said single unit (31') and connecting said inlet port (31'a) of said single unit (31') to a controlled environment containing a flushing gas; 4. The method according to claim 1, 2 or 3, wherein the circuit is provided with a valve (27') adapted to communicate with the circuit.

8. 1. An apparatus for detecting leakage from a sealed container, comprising: a detection area (13) adapted to receive a sealed container (CT), a first gas sensor (219a) and a second gas sensor (219b), a duct (21) communicating with said detection area (13) and with said first gas sensor (219a) and said second gas sensor (219b); a flushing gas blower (23) with an outlet port (23a) for flushing gas, said outlet port (23a) communicating with said duct (21), said blower (23) being configured to introduce said flushing gas into said detection area (13) by making it flow through said one duct (21) in a first direction; a suction fan (25) with an inlet port (25a) for drawing in air, said inlet port (25a) communicating with said one duct (21), said suction fan (25) being configured to draw in gas from said detection area (13) by making said gas flow through said one duct (21) in a second direction opposite to said first direction, The first gas sensor (219a) and the second gas sensor (219b) are connected in series with each other by a segment (21a) of the duct (21), the internal volume of which is known and which determines a corresponding delay line in gas propagation along the duct (21) communicating with the detection area (13) and a corresponding signal (M) coming from the first gas sensor (219a) and the second gas sensor (219b). １ , M. ２ ) is fed to a comparator (210), whereby the signal (M ３ ) is the signal (M ２ ) at the same time, the variable signal (M １ ) indicating the presence of a leak from a container present within said detection zone (13) when the floating threshold determined by Device.

9. 9. The apparatus according to claim 8, wherein the intake fan (25) is connected to an uncontrolled environment, the intake fan (25) exhausts the gas sucked from the detection area (13) to the uncontrolled environment, and the flushing gas blower (23) is connected to a controlled environment, the flushing gas blower (23) takes flushing gas from the controlled environment.

10. The blower and the suction fan are a single unit (31'), the single unit (31') being connected to a circuit with a valve (27'), the valve - said duct (21) with the inlet port (31'a) of said single unit (31') and with the outlet port (31'b) of said single unit (31') with the outside environment, or - connecting said duct (21) to said outlet port (31'b) of said single unit (31') and to said inlet port (31'a) of said single unit (31') with a controlled environment containing a flushing gas; The device of claim 8 configured to communicate.

11. An apparatus as described in any of claims 8 to 10, wherein the first gas sensor (219a) and the second gas sensor (219b) are located along the one duct (21) between the detection area (13) and the suction fan (25) or blower (23).

12. 12. Apparatus according to any one of claims 8 to 11, wherein the duct (21) communicates with the detection area (13) via at least one diffuser (29).

13. 13. Apparatus according to any of claims 8 to 12, wherein a suction head (71a...71d) comprising a plurality of slots (73) for sucking and introducing gas is arranged in the detection area (13).

14. 14. The device of claim 13, wherein the slots (73) are arranged along a peripheral band that entirely surrounds the sample vessel as it passes through the detection zone (13).

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