System for detecting leaks in containers

Abstract

A system (100) for detecting leaks in a sealed container comprises a conveyor belt (10) positioned to transport a container along a forward direction (F), a pressurizing system (20) configured to apply a compressive mechanical load to a container by pressing it against the conveyor belt (10), a suction and measuring system (40) comprising suction units (41, 42, 43) configured to draw gas from an area adjacent to the container under compression, and one or more sensors for measuring the concentration of one or more gases in the drawn gas, and a processing unit configured to compare the gas concentration measured by the suction and measuring system (40) with a reference gas concentration to determine whether the container under test is leaking. The pressurizing system (20) comprises a plurality of rollers (21, 22, 23, 24) connected to a moving member (25) controlled by a control unit.

Description

Technical Field

[0001] The present invention relates to a system for detecting leaks in containers, which is configured to detect leaks in sealed containers, and more particularly, food containers used for packaging within a protective atmosphere.

Background Art

[0002] Detecting leaks in sealed food containers used for packaging within a protective atmosphere typically involves the following steps: a) Applying mechanical stress to the sealed container by a squeezing technique to promote the outflow of gas from the inside to the outside of the container when there is a leak. This mechanical stress is typically necessary because the internal pressure within the food container is equal to atmospheric pressure. b) Measuring the concentration of one or more gases in the external environment immediately adjacent to the container using one or more gas sensors. The aim of this step is to detect the outflow of gas from the container, which is part of the gas mixture forming the protective atmosphere inside the container but normally exists inside the container at a much higher concentration than the normal concentration of the same gas outside the container. The area typically inspected is the entire outer surface of the container where there may be minute leaks. Furthermore, optionally, the lower part of the container is also inspected by using a suction hood that conveys gas to a measurement zone where the gas sensor measures the concentration by extracting the gas present in the area adjacent to the lower part of the container. When the container is a tray, the inspection is typically limited to the upper part of the tray, particularly the welding area between the tray and the film that seals the tray. c) Comparing the measured concentration of the gas with a reference concentration of the gas measured for a leak - free container to determine whether the inspected container is leaking.

[0003] Known leak detection systems that perform the above functions, however, typically cannot apply the appropriate pressure to the container, for example, to allow gas to escape from the container without damaging it.

[0004] For example, document US2022228944A1 in the applicant's name describes a leak detection system which performs the above function, in which a mechanical stress is applied to a container by a pair of rotatable rollers, each of which is suspended from a corresponding floating arm hinged to its own hinge axis and connected to a corresponding pneumatic cylinder capable of applying a specific pressure to each arm, and consequently to the roller suspended from the arm. Thus the pneumatic cylinder operates passively, thereby causing the roller to move in the height direction displaced by the container passing beneath it. The assembly, consisting of the arms, the corresponding pneumatic cylinders, and the rollers connected to the arms, as a whole, defines a third-class lever, thereby the motion of each roller at a given height is of the type that pivots around the hinge axis of its respective floating arm. In particular, the first roller performs a counterclockwise upward rotational motion upon encountering a container, and the second roller performs a clockwise upward rotational motion upon encountering a container. These roller movements often cause container jamming, not only due to the vertical rotation of the rollers but also due to the clockwise upward rotational motion of the second roller.

[0005] The object of the present invention is to overcome the limitations of the prior art by providing a leak detection system that can appropriately pressurize a container to improve measurement sensitivity, i.e., the ability to detect smaller leaks than in the prior art.

[0006] A further objective of the present invention is to provide a leak detection system that can be adapted to a wide variety of containers.

[0007] These and other objectives are achieved by the detection system claimed in the attached claims. [Overview of the Initiative]

[0008] The system for detecting leaks in sealed containers according to the present invention is: - A conveyor belt arranged to transport containers along the forward direction, - A pressurization system configured to apply a compressive mechanical load (compression) to a container by pressing it against a conveyor belt, - A suction and measurement system comprising a suction unit configured to draw gas from an area adjacent to a container under compression, and one or more sensors for measuring the concentration of one or more gases in the drawn gas, - A processing unit configured to compare the gas concentration measured by a suction and measurement system with a reference gas concentration in order to determine whether or not the container under test is leaking.

[0009] Preferably, the leak detection system according to the present invention is a system included in a container transport line, that is, it is a so-called "inline" detection system.

[0010] The pressurizing system comprises a plurality of rollers (two or more, preferably four) connected to a moving member controlled by a control unit.

[0011] The moving members include height transition members, which are configured to move the rollers vertically, each roller independently of the other, and such that the rollers in motion follow the shape of the container under test, while applying the maximum possible pressure to the container without damaging it. These height transition members include, for example, a set of pistons, one piston for each roller.

[0012] According to the present invention, the movement of the rollers thus has a wave-like pattern: as the container passes through the detection system, the rollers lift and lower while pressurizing the container and adapting to the shape of the container. In this way, the container and the food contents inside the container are not damaged.

[0013] The rollers of the pressurizing system have a rotation axis (coinciding with the vertical axis of the roller) that is parallel to the conveyor belt and perpendicular to the forward direction of the conveyor belt, and are arranged in a sequential alignment along the aforementioned forward direction of the conveyor belt.

[0014] Preferably, the moving members of the pressurizing system are configured to rotate in accordance with the conveyor belt and to drive the rollers such that the rollers have a peripheral speed equal to the forward speed of the conveyor belt. The rotation of the rollers with a peripheral speed equal to the forward speed of the conveyor belt makes it possible to prevent damage to the containers, in particular to the sealing film of containers made as trays.

[0015] The piston of the height transition member, for example, operates actively, causing the roller to move upward or downward. The operation of the piston is controlled by the passage of a container on the conveyor belt, which is detected by a photocell and encoder on the conveyor belt.

[0016] Alternatively, the piston of the height transition member operates passively, preloaded with a predetermined force.

[0017] Preferably, the multiple suction units of the suction and measurement system include at least one upper suction unit, at least one first lateral suction unit, and at least one second lateral suction unit.

[0018] The upper suction unit is positioned between two of the multiple rollers and is mounted to move vertically in conjunction with one of the rollers, thereby minimizing the distance between the suction portion of the upper suction unit and the test container passing in close proximity to the upper suction unit.

[0019] The first side suction unit and the second side suction unit are arranged on the side opposite to the roller, laterally with respect to the roller, and fixedly attached at a specific height and distance from the roller, and the height and the distance are selected according to the test container so that the distance between the suction portion of the side suction unit and the test container passing close to the side suction unit is minimized.

[0020] Optionally, the conveyor belt comprises a first section and a second section which are arranged continuously with respect to each other and spaced apart from each other. In this case, preferably, the suction and measurement system comprises at least one lower suction unit arranged on the same plane as the surface of the conveyor belt on which the container is arranged, between the first section and the second section of the conveyor belt, whereby the suction portion of the lower suction unit is in contact with the test container when the container passes from the first section to the second section of the conveyor belt.

[0021] These and other features and advantages of the present invention will become apparent from the following description of the preferred embodiments given as non-limiting examples with reference to the accompanying drawings, in which parts denoted by the same or similar reference numerals denote parts having the same or similar functions and configurations.

Brief Description of the Drawings

[0022] [Figure 1] It is a perspective view of a system for detecting leaks in a container according to the present invention. [Figure 2] It is a side view of a system for detecting leaks in the container of FIG. 1. [Figure 3a] It is a schematic view of a system for detecting leaks in a container in one of the different steps of the first operating mode. [Figure 3b] [[ID=*27]]It is a schematic view of a system for detecting leaks in a container in one of the different steps of the first operating mode.* [Figure 3c]Schematic diagram of a system for detecting leakage of a container in one of the different steps of the first operating mode. [Figure 3d] Schematic diagram of a system for detecting leakage of a container in one of the different steps of the first operating mode. [Figure 3e] Schematic diagram of a system for detecting leakage of a container in one of the different steps of the first operating mode. [Figure 3f] Schematic diagram of a system for detecting leakage of a container in one of the different steps of the first operating mode. [Figure 3g] Schematic diagram of a system for detecting leakage of a container in one of the different steps of the first operating mode. [Figure 4a] Schematic diagram of a system for detecting leakage of a container in one of the different steps of the second operating mode. [Figure 4b] Schematic diagram of a system for detecting leakage of a container in one of the different steps of the second operating mode. [Figure 4c] Schematic diagram of a system for detecting leakage of a container in one of the different steps of the second operating mode. [Figure 4d] Schematic diagram of a system for detecting leakage of a container in one of the different steps of the second operating mode.

Embodiments for Carrying Out the Invention

[0023] A leakage detection system 100 according to an embodiment of the present invention, particularly for a food container, will be described below with reference to FIGS. 1 and 2.

[0024] The leakage detection system 100 is - a conveyor belt 10 arranged to transport the container, the conveyor belt 10 comprising a first section 11 and a second section 12 arranged continuously and spaced apart from each other. - A pressurizing system 20 is configured to apply a compressive mechanical load (compression) to a container by pressing it against a conveyor belt 10, - A suction and measurement system 40 configured to draw gas from an area adjacent to a container under compression and measure the concentration of one or more gases in the drawn gas, - The system includes a processing unit (not shown) configured to compare the gas concentration measured by the suction and measurement system 40 with a reference gas concentration in order to determine whether or not the container under test is leaking.

[0025] The pressurizing system 20 comprises four rollers, namely a first roller 21, a second roller 22, a third roller 23, and a fourth roller 24, connected to a moving member 25 controlled by a control unit (not shown).

[0026] Rollers 21 to 24 have a rotation axis (which coincides with the vertical axis of the roller) that is parallel to the conveyor belt 10 and perpendicular to the forward direction F of the conveyor belt 10, and are arranged in succession along the forward direction F.

[0027] The moving member 25 includes a rotating member, such as a belt (not shown), configured to drive rollers 21-24 to rotate in accordance with the conveyor belt (in the figure, the forward direction F of the conveyor belt 10 is from right to left, and therefore the rollers 21-24 rotate in a clockwise direction). Similarly, the rotating member is configured to drive rollers 21-24 such that the rollers preferably have a circumferential velocity (i.e., tangential velocity) equal to the forward speed of the conveyor belt 10.

[0028] The moving member 25 further includes a height transition member configured to move the rollers 21 to 24 vertically, with each roller moving independently of the other rollers. In particular, the height transition member includes a first piston 27 connected to the first roller 21, a second piston (not shown in Figures 1 and 2) connected to the second roller 22, a third piston 29 connected to the third roller 23, and a fourth piston (not visible in Figures 1 and 2) connected to the fourth roller 24.

[0029] Thanks to the independent movement of rollers 21-24, rollers 21-24 move in a predetermined height direction to follow the shape of the container under test while applying the maximum possible pressure to the container without damaging it. Thus, the movement of the four rollers 21-24 has a wave-like pattern: as the container passes the detection system 10, rollers 21-24 lift and lower while pressurizing the container and adapting to its shape. In this way, the container and the food contents inside the container are not damaged. Furthermore, the rotation of rollers 21-24 at a peripheral speed equal to the forward speed of the conveyor belt 10 makes it possible to prevent damage to the container, in particular to the sealing film of containers made as trays.

[0030] Therefore, the pressurization system 20 can be adapted to test containers of different sizes, shapes, and hardnesses, such as small and large bags, trays, tray storage bags, flat containers (packaging for so-called "piadines"), plastic-laminated paper films, plastic films, or trays sealed with thermoformed films.

[0031] According to the first embodiment, the pistons 27 and 29 of the height transition members operate in active mode, and the operation of the pistons, which bring about the upward or downward movement of the rollers 21-24, is controlled by the passage of the container 200 on the conveyor belt 10, which is detected by the photocell and encoder of the conveyor belt 10. In this mode of operation, the rollers thus begin from a starting position where the rollers are at a height relative to the conveyor belt 10 that is higher than the height of the container 200 under test, and the rollers descend in accordance with the forward movement of the container 200 on the conveyor belt 10 until the rollers reach a height suitable for pressurizing the container 200 with the maximum possible force without damaging the container. The height of the rollers at the starting position and the height of the rollers at the lowered position are set according to the shape and size of the container under test. This mode of operation of the pistons 27 and 29 is particularly advantageous in the case of containers made as trays sealed at the top with a sealing film. In such cases, the control unit of the pressurizing system 20 is actually configured to drive pistons 27, 29 such that rollers 21-24 only impact the top of the tray 200 and not the front or rear portion of the tray, as pressurizing by the rollers could cause damage to the tray (especially to the weld between the film and the tray). The above operating modes of the leak detection system 10 are schematically shown in Figures 3a-3g, where the forward movement of the container 200 occurs from right to left.

[0032] In a further embodiment, the pistons 27 and 29 of the height transition member operate in a passive mode, preloaded with a predetermined force. In this configuration, the rollers 21-24 start from a starting position where the rollers are at a height relative to the conveyor belt 10 that is lower than the height of the container 300. As the container 300 passes, each roller 21-24 applies a specific pressure to the container (by the preloading force of each roller), displaces as a result of the resistance provided by the container 300, performs an upward transition motion, and is then pushed back downward by the respective pistons. The height of the rollers at the starting position is set according to the shape and size of the container under test. Furthermore, in this mode of operation, adjustments to the pistons are only useful for determining the applied pressure, while the lifting / lowering moments are determined by the interaction between the container 300 and the rollers 21-24. This mode of operation of the leak detection system 10 is schematically shown in Figures 4a-4d, where the forward movement of the container 200 occurs from right to left.

[0033] The suction and measurement system 40 comprises a plurality of suction units, namely an upper suction unit 41, a first lateral suction unit 42 and a second lateral suction unit (not visible in Figures 1 and 2), and a lower suction unit 43.

[0034] The upper suction unit 41 is positioned between the second roller 22 and the third roller 23 and preferably comprises a plurality of downward-facing suction ports (not shown in the figure). The upper suction unit 41 is mounted to move vertically in conjunction with one of the rollers, for example, the second roller 22, so that the distance between the suction portion and the test container passing close to the upper suction unit 41 is minimized (for example, to less than 5 millimeters). The upper suction unit 41 can extend substantially along the entire length of the roller. Alternatively, a plurality of upper suction units 41 may be arranged successively along a direction parallel to the longitudinal axis of the roller, preferably so as to substantially cover the entire length of the roller.

[0035] The first and second lateral suction units are positioned laterally to the rollers 21-25: specifically, the first lateral suction unit 42 is positioned on the first side of the rollers 21-24, and the second lateral suction unit is positioned on the second side opposite the first side of the rollers 21-24. Both lateral suction units are positioned so that they appear between the second roller 22 and the third roller 23 when the system is observed from the side. Each lateral suction unit has one or more suction ports (not shown in the figure) facing the rollers 21-24. The lateral suction units are fixedly mounted at a specific height and distance from the rollers, the height and distance being selected according to the container under test so as to minimize the distance between the suction portion of the lateral suction unit and the container under test passing in close proximity to the lateral suction unit.

[0036] The lower suction unit 43 is positioned between the first section 11 and the second section 12 of the conveyor belt 10 and comprises a plurality of downward-facing suction ports (not shown in the figure). Preferably, the lower suction unit 43 is positioned coplanar with the surface 10a of the conveyor belt 10 on which the container is placed, so that its suction ports are in contact with the container under test as the container passes from the first section 11 to the second section 12 of the conveyor belt 10. Preferably, the lower suction unit 43 extends substantially along the entire length of the rollers 21-24. The presence of the lower suction unit 43 allows for the suction of gas from the zone below the container under test, thereby enabling the detection of leaks present at the bottom of the container.

[0037] The suction and measurement system 40 includes a gas sensor, which is connected to the suction unit by a suitable duct 45 such that the aspirated gas reaches the sensor 46 in order to measure the concentration of one or more gases. In particular, the sensor 46 measures the concentration of gas in a gas mixture that forms a protective atmosphere present inside the container, and the gas in the protective atmosphere is present inside the container at a much higher concentration than the gas concentration in the environment outside the container. In general, multiple sensors may be used to measure the concentration of a single gas; in fact, the more sensors used, the more accurate the measurement of the gas concentration becomes. Furthermore, a single sensor may be configured to measure the concentrations of several different gases. Preferably, the sensor 46 is located under the conveyor belt 10.

Claims

1. In a system (100) for detecting leaks in a sealed container, - A conveyor belt (10) arranged to transport containers along the forward direction (F), - A pressurizing system (20) configured to apply a compressive mechanical load to the container by pressing it against the conveyor belt (10), - A suction and measurement system (40) comprising suction units (41, 42, 43) configured to draw gas from an area adjacent to the container under compression, and one or more sensors for measuring the concentration of one or more gases in the drawn gas, - A processing unit configured to compare the gas concentration measured by the suction and measurement system (40) with a reference gas concentration in order to determine whether or not the container under test is leaking, The pressurizing system (20) comprises a plurality of rollers (21, 22, 23, 24) connected to a moving member (25) controlled by a control unit, The system is characterized in that the moving member (25) includes a height transition member, and the height transition member is configured to move the rollers (21, 22, 23, 24) vertically such that each roller moves independently of the other rollers and that the rollers in motion follow the shape of the container under test.

2. The system according to claim 1, wherein the rollers (21, 22, 23, 24) have a rotation axis parallel to the conveyor belt (10) and perpendicular to the forward direction (F) of the conveyor belt (10), and are arranged in succession in alignment along the forward direction (F).

3. The system according to claim 1 or 2, wherein the plurality of rollers consist of a first roller (21), a second roller (22), a third roller (23), and a fourth roller (24).

4. The system according to any one of claims 1 to 3, wherein the moving member (25) is further configured to rotate in accordance with the conveyor belt (10) and to drive the rollers (21, 22, 23, 24) such that the rollers (21, 22, 23, 24) have a peripheral speed equal to the forward speed of the conveyor belt (10).

5. The system according to any one of claims 1 to 4, wherein the height transition member comprises pistons (27, 29) that operate in active mode, and the operation of the pistons that cause the rollers (21, 22, 23, 24) to move upward or downward is controlled by the passage of a container on the conveyor belt (10), and the passage is detected by a photocell and encoder on the conveyor belt (10).

6. The system according to claim 5, wherein the rollers (21, 22, 23, 24) begin from a starting position where the rollers (21, 22, 23, 24) are at a height relative to the conveyor belt (10) that is higher than the height of the container under test (200), and the rollers (21, 22, 23, 24) move down as the container (200) moves forward on the conveyor belt (10) until the rollers reach a height suitable for pressurizing the container (200) with the maximum force that can be applied without damaging the container (200).

7. The system according to claim 6, wherein the control unit of the pressurizing system (20) is configured to drive the pistons (27, 29) such that the rollers (21, 22, 23, 24) only strike the top of the container (200) and not strike the front or rear portion of the container (200).

8. The system according to any one of claims 1 to 4, wherein the height transition member comprises pistons (27, 29) that operate in a passive mode and are pre-pressurized with a predetermined force.

9. The system according to any one of claims 1 to 8, wherein the suction unit of the suction and measurement system (40) comprises at least one upper suction unit (41), the at least one upper suction unit (41) is positioned between two rollers (22, 23) of the plurality of rollers (21, 22, 23, 24) and is mounted to move in the height direction integrally with one roller (22) of the plurality of rollers.

10. The suction unit of the suction and measurement system (40) comprises at least one first lateral suction unit (42) and at least one second lateral suction unit, wherein the at least one first lateral suction unit (42) and the at least one second lateral suction unit are positioned laterally to the rollers (21, 22, 23, 24) on opposing sides and are fixedly mounted at a specific height and distance from the rollers, according to any one of claims 1 to 9.

11. The system according to any one of claims 1 to 10, wherein the conveyor belt (10) comprises a first section (11) and a second section (12) arranged continuously and spaced apart from each other.

12. The system according to claim 11, wherein the suction unit of the suction and measurement system (40) further comprises at least one lower suction unit (43) located between the first section (11) and the second section (12) of the conveyor belt (10), on the same plane as the surface (10a) of the conveyor belt (10) on which the container is placed.

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