Container leak detection

Description

Field of the Invention

[0001] The present invention relates to systems, methods and devices for detecting breaches in sealed containers, and in particular sealed, modified atmosphere food containers, such as trays and packets.Background to the Invention

[0002] Modified atmosphere packaging (MAP) is widely practiced in the food packaging industry as a way of reducing spoilage of produce and increasing shelf life. MAP typically comprises modifying the composition of the gas that is present alongside food product in a food container so that it is different from the standard atmospheric composition in a way which maximises the longevity of the food product. This will typically involve increases and decreases of the proportion of oxygen, nitrogen and / or carbon dioxide in the atmosphere within food packages.

[0003] When food is packaged using modified atmosphere packaging, any incomplete sealing of the packaging reduces or nullifies entirely the increased shelf life provided by the MAP process as the atmosphere within the package is allowed to return to standard atmospheric composition.

[0004] In order to try to identify containers which have a breach, i.e. an opening into the package which renders them incompletely sealed, packages are mechanically tested, typically in-line. Mechanical testing typically comprises mechanically squeezing the container and identifying an expected response as the pressure within the sealed package increases and the package resists the mechanically squeezing. Such methods of mechanically testing packages are typically very slow, which can limit the maximum production speed, or require many separate lanes to keep up with faster packaging systems. Such methods may also have limited sensitivity, leading to false negatives.

[0005] Alternative off-line systems are available, which use vacuum to urge gases out of the pack via the any breach. However, these are also typically very slow and so, to maintain production speeds, it is necessary to test multiple packs at a time. This has numerous limitations; there is no way to identify the fault pack when a leak is detected, all packs tested must be rejected. Therefore many "good" packs are lost, increasing operation costs. These systems are often placed later in the packing process, typically when the packs have been collated into large multi-pack cases. This causes further delay in feedback of failures and an error in the packing process may continue to produce "bad" packs for some time. The system size is also much larger and requires more factory space for its operation.

[0006] Laser technology has recently been developed which, when provided with an air sample, can accurately and precisely identify, for example, its carbon dioxide content. It has been identified as desirable to incorporate such technology within food packaging production lines as a means of identifying sealed food containers which have breaches by taking a sample of the air surrounding the container after packaging and identifying raised levels of one of the relevant gases relative to standard atmospheric composition. Such laser technology is based on a principle called tunable diode laser absorption spectroscopy (TDLAS), which measures the concentration of species in gaseous mixtures using tunable diode lasers and laser absorption spectrometry. Compared to other measurement techniques, such as paramagnetic detectors ("PMD") and Chemi-luminescence, TDLAS offers multielement detection capabilities, high accuracy with a wide dynamic range, low maintenance requirements, and a long life cycle. The use of lasers as spectroscopic light sources allows for high resolution spectroscopy (HRS), with quantum cascade lasers (QCLs) offering access to the valuable mid infrared (MIR) part of the electromagnetic spectrum. An example of a QCL system may be found in WO 03087787 A1.

[0007] Other leak detection systems known in the prior art are disclosed in JP2007108101A, JP2005257577A, JP2014215070A.Summary of the Invention

[0008] The present inventors have found, in trying to implement gas-detecting laser technology into systems and methods for detecting breaches in sealed food containers, that the sensitivity required to detect breaches in food containers is such that normal fluctuations that occur in real-world packaging facilities prevent consistent, reliable identification of a change in gas levels which would be associated with a breach in a modified atmosphere package. The present invention has therefore been developed to make the implementation of this technology feasible.

[0009] In accordance with a first aspect of the invention, there is provided a leak detection system according to claim 1.

[0010] The present inventors have found that a pressing member that applies pressure to the food container causes gas within a breached container to be forced out and into the region surrounding the container. This increases the amount of gas from within the container in the air-sampling region, i.e. the region surrounding the container and proximate to the air-sampling port, which therefore increases the likelihood of the change in proportionality of gases resulting from a breach being detectable by the air-sample testing equipment over normal background fluctuations.

[0011] In order to most conveniently integrate into existing production lines, and to maximise throughput, in preferable embodiments, the pressing member is configured to apply pressure to the sealed food container while the sealed food container moves relative to the pressing member.

[0012] The plurality of air-sampling ports are located in the pressing member. Providing an air-sampling port in the pressing member can improve the performance of the system by allowing the air sample to be taken very close to the point of contact between the pressing member and the sealed food container.

[0013] The pressing member comprises a porous material configured to contact the sealed food container, in use. This can prevent the pressing member itself from temporarily obstructing a breach in the food container as it applies pressure to the food container. Further, the porous material may cover at least one air-sampling port. Embodiments in which a porous material covers at least one air-sampling port advantageously allow for an air sample to be taken through the porous material by an air-sampling port on or in the pressing member.

[0014] The system further comprises at least a first conveyor, preferably a first conveyor belt, for conveying the sealed food container to, through and / or away from the air-sampling region.

[0015] The at least one pressing member comprises a conveyor belt configured to apply pressure to the sealed food container as it is conveyed through the air-sampling region. Like a roller or a wheel, a conveyor is able to maintain contact with the surface of a sealed food container as it moves through the air-sampling region.

[0016] The conveyor belt of the pressing member opposes the first conveyor such that the sealed food container is conveyed through the air-sampling region between the conveyor belt of the pressing member and the first conveyor. That is to say that the sealed food container will be sandwiched between the conveyor as it passes through the air-sampling region.

[0017] The material that forms one or both of the belts of the conveyors described above is porous by way of perforations in the surface of the conveyor belts. Further preferably, a surface of one or both of the first conveyor and the conveyor belt of the pressing member comprises an array of protrusions for contacting the sealed food container in use. The array of protrusions may take the forms of bumps or ridges. Such protrusions will prevent the surface of the conveyor from blocking any breaches in the sealed food container.

[0018] The air-sampling ports are arranged inside one or both of the first conveyor and the conveyor belt of the pressing member. An-air sampling port may be arranged inside a conveyor belt by providing the air-sampling port between the opposing halves of a conveyor belt assembly. A plurality of air sampling ports are arranged on an air-sampling port head located within the conveyor belt of the pressing member and / or a plurality of air sampling ports are arranged on an air-sampling port head located within the first conveyor.

[0019] Preferably, the system further comprises a vacuum pump connected to the air sample conduit for communicating vacuum suction to the at least one air-sampling port.

[0020] It will be appreciated that, when the sealed food container is a film-topped tray, leaks are most likely to be found in the top of the container. However, leaks may also be found in the other surfaces, for example the sides and bottom of a container, which is particularly true when the sealed food container is, for example, a sealed bag. Therefore, some embodiments comprise a plurality of air sampling ports, wherein a first subset of air-sampling ports take an air sample from a first side of a sealed food container and a second subset of air-sampling ports take an air sample from a second side of the sealed food container.

[0021] In accordance with a second aspect of the invention, there is provided a method according to claim 5.

[0022] This method of detecting breaches in sealed containers is suitable for implementation using a system according to the first aspect of the invention, and is particularly suited for detecting breaches in sealed food containers. The method provides the same advantages as the system according to the first aspect of the invention.

[0023] The method according to the second aspect of the invention is particularly suited to detecting breaches in sealed, modified atmosphere containers. However, it will be appreciated that the method could also be used for detecting breaches in containers with no modified atmosphere by performing the method in a controlled atmosphere, different from the atmosphere within the container.

[0024] In preferable embodiments, the pressing member applies pressure to the sealed container while the sealed container moves relative to the pressing member.

[0025] In preferable embodiments, taking an air sample from the air-sampling region comprises taking an air sample through a porous material forming a part of the pressing member used to contact the sealed container when applying the pressure to the sealed container.

[0026] In some embodiments, taking an air sample from the air-sampling region during and / or after applying the pressure to the sealed container comprises taking an air sample from a first side of a sealed container and taking an air sample from a second side of the sealed container. Preferably the first and second sides are opposite one another.

[0027] The above preferable features of the method according to the second aspect of the invention provide the same advantages as the equivalent features in the system according to the first aspect of the present invention.

[0028] Additionally, it is preferable in methods according to the invention that testing the composition of the air sample using the air-sample testing equipment comprises testing the carbon dioxide, oxygen and / or nitrogen content of the air sample, and it is determined that there is a breach in the sealed container when the carbon dioxide, oxygen and / or nitrogen content of the air sample meets pre-set criteria. Preferably, the pre-set criteria include that the rate of change in the carbon dioxide, oxygen and / or nitrogen content of the air sample is greater than a threshold value. This threshold value may be, for example, at least two to three times that of the average rate of change caused by background noise.Brief Description of the Drawings

[0029] Examples of systems, methods and devices in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a first comparative example of a leak detection system and leak detection head according to the invention; Figures 2A to 2C show a leak detection head according to the first comparative example in cross-sectional, perspective and bottom views respectively; Figures 3A to 3C show a leak detection head according to a second comparative example in perspective, cross-sectional and longitudinal section views respectively; Figures 4A and 4B show the leak detection head according to the second comparative example in upper and lower perspective views respectively, and in first and second states of disassembly respectively; Figures 5A to 5C show a leak detection head according to a third comparative example in a perspective view, in a perspective view with an external housing removed, and in zoomed view with an external housing removed; Figure 6 shows a cross-sectional view of the air-sampling head of the third comparative example; Figures 7A to 7F show a leak detection head according to a fourth comparative example in perspective, side, rear, bottom, front and cross-sectional views respectively; Figure 8A to 8D show a leak detection head according to a fifth comparative example in first and second perspective views, front view and bottom view respectively; Figure 9 shows, schematically, a leak detection system according to a sixth comparative example; Figure 10 is a flow diagram showing a method of detecting breaches in sealed containers; and Figures 11A to 11D show a leak detection system according to a first embodiment of the invention in perspective, top, side and front views respectively. Detailed Description

[0030] Figure 1 shows a first comparative example of a system 1 for detecting breaches in sealed food containers. The system comprises a conveyor 10 for conveying the sealed food containers through an air-sampling region 5. A leak detection head 100 is adjustably positioned above the conveyor 10 at the air-sampling region. The leak detection head 100 is supported over the conveyor by a mounting arm 60 coupled to the exterior of an equipment housing 50 that is positioned adjacent to the conveyor 10. An air sample tube (air sample conduit) 51 and compressed air tubes 52 extend from the equipment housing 50 to the leak detection head 100, as will be described in greater detail below.

[0031] The leak detection head 100 comprises a pressing member, in this case a roller 101, which has an axis of rotation parallel to the surface of the conveyor and perpendicular to the direction of conveyance of the conveyor. The roller 101 has a radius such that it projects down from the leak detection head 100 towards the conveyor 10, leaving a gap between the roller 101 and the conveyor which is configured, by adjusting the height of the leak detection head 100, to be slightly smaller than the height of the type of sealed food container to be tested.

[0032] As a sealed food container is conveyed along the conveyor 10, through the air-sampling region 5, it passes beneath the leak detection head 100. The roller 101, projecting down from the leak detection head 100 towards the conveyor 10, contacts an upper surface of the container and rotates as the container passes through the air-sampling region 5. Since the gap between the roller 101 and the conveyor 10 is slightly smaller than the height of the food container, a force is applied to the surface of the container across the contact area between the container and the roller. This pressure applied to the container acts to force an amount of gas out of the container through any breaches in the container. If there is no breach in the container, no gas will be forced out of the package.

[0033] Any gas forced through breaches in the container is then sampled by air-sampling ports 102 located on the leak detection head 100, and transferred through the air sample tube 51 into the equipment housing 50. The sample is drawn into the air-sampling ports 102 and along the air sample tube 51 by a vacuum pump (not shown) located inside the housing 50 in fluid communication with the air-sampling ports 102 via the air sample tube 51. Inside the housing is further located test equipment (not shown) which comprises a quantum cascade laser. The sample is provided to the test equipment for testing by the air sample tube 51. In this comparative example, the test equipment measures the rate of change in carbon dioxide levels and displays these in a graphical format.

[0034] The construction of the leak detection head 100 will now be described in more detail with reference to Figure 2.

[0035] The leak detection head 100 comprises a generally cuboidal housing 110 whose long axis lies across the width of the conveyor 10 in use. The housing 110 extends across the full width of the conveyor, and is open at its lower surface (i.e. the surface that faces the conveyor in use). Rotatably mounted within the housing 110 is the cylindrical roller 101. The axis of rotation of the roller is along the long axis of the housing, and the radius of the roller is such that it protrudes through the opening in the lower surface of the housing. The roller is mounted on bearings 101a, 101b located in respective end plates of the housing 110. In this comparative example, the roller is driven by means well known in the art. In other comparative examples, the roller may be made to rotate about its axis through contact with a tray, which is moved beneath the leak detection head by the conveyor 10.

[0036] The leak detection head 100 comprises a plurality of air-sampling ports 102. The air-sampling ports are small circular openings into the leak detection head that are provided in two rows running along the long axis of the housing 110, in the lower surface of the housing, with one row on either side of the opening in which the roller 101 is located. Each row of air-sampling ports 102 has a respective manifold 102a, 102b. The air-sampling ports 102 of each row are in fluid communication with their respective manifold through a respective conduit. The manifolds 102a, 102b feed into additional air sample conduits, which meet in the upper portion of the housing 110, and communicate with a test equipment port 104 through the upper surface of the housing 110. When incorporated into the system 1 of Figure 1, the test equipment port 104 is connected to the air-sample tube 51. In use, vacuum suction is communicated through the air-sample tube 51, and via the test equipment port to the manifolds and individual air-sampling ports 102 so that the air-sampling ports 102 each draw air into them, thereby collecting a sample from the air-sampling region. The air sample is then conveyed up to and along the air-sample tube 51 to the testing equipment.

[0037] The leak detection head 100 further comprises a plurality of gas-output ports 108. The gas-output ports 108 are small circular openings into the leak detection head that are provided around the periphery of the lower surface of the housing. The gas-output ports 108 define a rectangle on the lower surface of the housing, within which are located the air-sampling ports 102 and the roller 101. The gas-output ports 108 connect via respective conduits into one of two manifolds 108a, 108b in the leak detection head 100. Those gas-output ports 108 on a first side of the axis of the roller connect to the first manifold 108a and those on a second side of the axis of the roller connect to the second manifold 108b. Each manifold 108a, 108b is connected by a respect conduit 107a, 107b to a respective compressed-gas port 106a, 106b through a respective sidewall in the housing 110. In use, each compressed-gas port 106a, 106b communicates compressed gas from a compressed gas source (not shown) through the conduits and manifolds to the plurality of gas-output ports 108. The compressed gas source will typically comprise gas of standard atmospheric composition, such that it does not affect the testing performed by the testing equipment. In use, the compressed gas is directed by each gas-output port 108 diagonally down and away from the leak detection head 100, the plurality of gas-output ports 108 in combination generating an air curtain extending down and outward from the periphery of the lower surface of the leak detection head 100 (as shown by arrows A in Figure 2A). The air curtain acts to isolate the atmosphere beneath the leak detection head 100 from turbulence and other environmental factors that may cause fluctuations in atmospheric composition. As a container is moved beneath the leak detection head 100, it enters within the air curtain. Any carbon dioxide from the packaging process that is encouraged towards the sampling region by the motion of the food packages travel along the conveyor is displaced by the air curtain, and an air sample can be obtained from the region around the container within the controlled environment inside the air curtain. As a leaking container exits the air-sampling region, the air curtain helps in purging the elevated levels of carbon dioxide, stabilising the environment in the sampling region ready for the next package to be inspected.

[0038] The system described with reference to Figure 1 can be implemented with a number of different types of leak detection head. A second leak detection head will now be described with reference to Figures 3 and 4.

[0039] The leak detection head 200 according to the second comparative example comprises a single roller 201. The roller comprises a cylindrical sleeve 202 formed of a porous material, for example, an open cell foam or laser printed open structure roller. The cylindrical sleeve 202 is closed at either end by endplates 203, which are rotatably mounted to a fixed shaft 210 that runs coaxially through the sleeve and extends beyond either endplate 203. The rotatable endplates 203 allow the sleeve 202 to rotate about the shaft 210 while the shaft remains fixed. In use, rotation of the sleeve 202 is driven using a belt 251 and a motor 250, mounted adjacent to the roller, which cooperate with one of the end plates 203. Within the rotatable sleeve 202 is a roller core coupled to or formed integrally with the fixed shaft such that it does not rotate with the sleeve 202. The roller core comprises an air purge system 216 and air-sampling system 211, which will be described in more detail below.

[0040] The air-sampling system 211 comprises a sampling head 213 which extends downwardly from the fixed shaft 210. The lower surface of the sampling head is proximate the inner surface of the sleeve 202 and extends along the full length of the roller, within the sleeve 202. The lower surface of the sampling head has a line of air-sampling ports 212 therethrough, which face the inner surface of the sleeve 202 of porous material along the length of the roller, and are in fluid communication within a manifold 213a within the sampling head 213. The manifold 213a opens into a hollow interior of the fixed shaft 210. The hollow interior of the fixed shaft extends with the shaft out of both ends of the roller 201 and continues with the shaft, which turns to face generally upwardly, where it ceases. Both ends of the shaft are connected in use to a respective tube 210a, 210b. The tubes 210a, 210b meet at an inverted Y connector, and provide fluid communication with a single test equipment port 204. In use, the test equipment port 204 is connected to an air-sample tube (51 in figure 1) through which vacuum suction is communicated. The vacuum suction is transmitted through the test equipment port, tubes 210a, 210b, hollow shaft interior 210, and manifold to the individual air-sampling ports 212 so that the air-sampling ports 212 each draw air into them for communication back to the test equipment. In this comparative example the air drawn into the sampling ports has been drawn through the porous material of the sleeve 202.

[0041] The air purge system 216 comprises a gas-output sleeve 217 that is mounted on the fixed shaft 210. The outer surface of the gas-output sleeve 217 is proximate the inner surface of the sleeve 202 of porous material. The gas-output sleeve 217 extends along the full length of the roller, within the sleeve 202, and extends around beneath approximately three quarters of the circumference of the inner surface of the sleeve 202 of porous material. The gap in the gas-output sleeve 217, i.e. the approximately one quarter of the circumference in which the gas-output sleeve 217 is not provided, permits the sampling head 213 to extend to the inner surface of the sleeve of porous material. The gas-output sleeve 217 has a surface that is covered in small, slot shaped gas-output ports 217a. The gas-output ports are connected to one of two compressed gas sources, in use, by one of two tubes 217a, 217b each extending from the inner surface of the gas-output sleeve 217 to the fixed shaft. Each tube 217a, 217b connects to a respective conduit within the fixed shaft, separate from the hollow interior for communicating an air sample, which extends along the fixed shaft, in opposite directions, and past the respective end plate 203 which form the ends of the roller 201. Each conduit then connects to a respective compressed gas input port 218a, 218b in the fixed shaft, which can be connected to a respective compressed gas source, in use, by means that will be apparent to the skilled person.

[0042] Operation of the leak detection head 200 will now be described. In use, the leak detection head 200 is located over a conveyor such that a gap between the roller 201 and the conveyor is slightly smaller than the height of the type of sealed food container to be tested. The end plates 203 and sleeve 202 of the roller 201 are driven by the belt 251 and motor 250 to rotate such that the surface of the sleeve 202 moves at the same speed as the conveyor. A container is conveyed along the conveyor, and passes beneath the roller 201. Since the gap between the roller 201 and the conveyor is slightly smaller than the height of the food container, a force is applied to the surface of the container across the contact area between the container and the roller 201. This pressure applied to the container acts to force an amount of gas out of the container through any breaches in the container. While the roller 201 applies a pressure to the container, the air-sampling ports 212 continuously draw air into the air-sampling system 211, through the porous material where it contacts the container. The porous material, which lies between the air-sampling ports 212 and the container, acts to provide some protection from turbulence and other environmental changes which would affect the composition of the sampled air. An air sample is continuously provided via the air-sampling ports 212, manifold 213a, shaft 210, tubes 210a, 210b, test equipment port 204 and air-sample tube 51 to the test equipment for composition testing. As the roller 201 rotates, the area of the sleeve through which a sample was drawn rotates around the shaft so it is over the gas-output sleeve 217. Compressed gas is exhausted by the gas-output ports 217a and forced through the porous material, purging the porous material of any gas trapped therein. The sleeve 202 continues to rotate until the now purged area of porous material passes the end of the gas-output sleeve 217, and arrives again at the air-sampling location, i.e. between the air-sampling ports 212 and a container (if present).

[0043] A third leak detection head 300 will now be described with reference to Figures 5 and 6.

[0044] The leak detection head 300, as shown in Figure 5A, is partially enclosed within an external housing 360. Two side walls 361 and 362, in combination with an upper surface of the leak detection head and the conveyor 10, define a partially enclosed, generally cuboidal region, with openings at the front and rear ends of the conveyor into which containers may enter. The partially enclosed region helps to shield the air-sampling region within from the wider system environment, and reduce fluctuations in atmospheric composition therewithin. As mentioned above, the front and rear entrances could also, optionally, be closed by an air curtain to further isolate the air-sampling region.

[0045] Figure 5B shows the leak detection head 300 with the side walls 361 and 362 of the external housing removed. The leak detection head comprises leak detection head housing 310, which is defined by an upper surface, from which two sidewalls project downward. An array of rollers or wheels 301 form a pressing surface of the leak detection head at a lower surface of the leak detection head, facing the upper surface of the conveyor 10. The wheels 301 are mounted in closely packed repeating rows, each row having a spindle (not shown) about which the wheels of that row rotate. Each spindle is positioned parallel with the surface of the conveyor beneath 10, and perpendicular to the direction of conveyance of the conveyor 10. All of the spindles, and wheels 301 thereon, are mounted between sidewalls of a leak detection head housing 310, at the lower edge of the sidewalls.

[0046] The first three rows of wheels 301 on the leak detection head 300 are positioned at a progressively lower position, such that, when the leak detection head 300 is positioned above the conveyor 10, the second row is closer to the conveyor than the first, and the third row closer to the conveyor than the second. The remaining rows of wheels 301 are positioned at the same height above the conveyor in use as the third row of wheels. This configuration of the wheels 301 allows the pressure applied to the container to be gradually increased as the container enters underneath the leak detection head, before a relatively steady pressure is reached and maintained.

[0047] In approximately the centre of the leak detection head 300, in a gap between two rows of wheels 301, is an air-sampling head 311. The air-sampling head is also shown in cross-section in Figure 6. The air-sampling head extends in the same direction as the rows of wheels, across the direction of conveyance of the conveyor 10. The air-sampling head 311 comprises, in a lower surface, facing the conveyor in use, a plurality of air-sampling ports 312, lined in a row extending across the conveyor. Each air-sampling port 312 is connected via a respective conduit to a manifold 313 in the air-sampling head 311. At either lateral end of the air-sampling head 311, is a test equipment port 314, which, in use, is connected so as to be in fluid communication with an air sample tube (51 in Figure 1), which connects to the test equipment, and provides the vacuum suction to the air-sampling head 311.

[0048] In use, a container is provided to the conveyor 10, and conveyed into the external housing 360 and beneath the leak detection head 300. The height of the array of wheels 301 above the conveyor is configured to be smaller than the height of a container to be tested so that as the container enters beneath the leak detection head 300 it is pressed by the leak detection head. The container is conveyed along and past the air-sampling head 311. As it passes the air-sampling head 311, air, which is being continuously drawn into the air-sampling head 311 via the air-sampling ports 312, is sampled from a region above the container, and communicated through to the test equipment. The container continues and exits from beneath the leak detection head 300 at the rear of the conveyor 10.

[0049] A fourth leak detection head 400 will now be described by reference to Figure 7. The leak detection 400 comprises a housing 410, which accommodates first and second rotatably mounted rollers 401a, 401b. The first and second rollers are mounted horizontally between the opposing side walls 411, 412 of the housing 410. The axes of the first and second rollers are parallel, and in use the axes lie across the width of the conveyor 10 in a plane above and parallel to the conveyor 10. Each roller 401a, 401b has an internal drum motor for rotating the rollers in use. The internal drum motors are powered via respective cables 411a, 411b which extends through the side wall 411 of the housing 410.

[0050] The housing is open at its lower surface to permit the rollers to protrude through the opening for contact with containers being conveyed along the conveyor. The housing is also open at its front (upstream end with respect to the conveyor), as shown in Figure 7E, to expose the front surface of the front roller 401a. Exposure of the front surface of the front roller helps guide sealed bags underneath the leak detection head 400.

[0051] The first and second rollers 401a, 401b are spaced from one another in the housing 410 along the direction of conveyance of the conveyor 10. In between the rollers 401a, 401b is located a wall 405 inside the housing. The wall 405 extends from one side of the housing 410 to the other and extends from the top of the housing 410 to the opening in the bottom. At its lowest point, the wall 405 is slightly higher than the lowermost point of the rollers 401a, 401b, which protrude through the lower opening for contact with food containers. In the lower surface of the wall 405 is a plurality of air-sampling ports 402, as shown in Figure 7D. The air-sampling ports are arranged in a single row located in a groove 465 running along the lower surface of the wall 405, such that the air-sampling ports 402 extend across substantially the full width of the leak detection head 400. The air-sampling ports 402 are each in fluid communication with a central manifold (not shown) inside the wall via a respective conduit. The manifold communicates with a test equipment port 404 through the upper surface of the housing 410. When incorporated into the system 1 of Figure 1, the test equipment port 404 is connected to the air-sample tube 51. In use, vacuum suction is communicated through the air-sample tube 51, and via the test equipment port to the manifold and individual air-sampling ports 402 so that the air-sampling ports 402 each draw air into them, thereby collecting a sample from the air-sampling region, in between the two rollers 401a, 401b.

[0052] Running along either side of the row of air-sampling ports 402 are first and second sets of gas-output ports 408a, 408b. Each gas-output port connects via a respective conduit to one of two gas-output manifolds (not shown) in the central wall 405 of the housing 410. The two gas-output manifolds are in fluid communication with a respective compressed-gas port 406a, 406b in the upper surface of the housing 410. The sets of gas-output ports 408a, 408b are configured to generate respective first and second air curtains on either side of the row of air-sampling ports 402. The gas-output ports 408a, 408b are pointed diagonally down and away from the row of air-sampling ports such that the air curtains are directed down and away from the central wall 405 of the housing 410.

[0053] The leak detection head 400 also features first and second arms 421, 422 located on either side of the leak detection head and extending forward, beyond the front roller 401a, so as to be upstream of leak detection head 400 in use. Each arm is adjustably coupled to the upper side of the housing 410 via a respective thumbscrew. On the end of each arm 421, 422 are first and second sensors 423, 424. The sensors are photo optic sensors and are configured to detect an approaching food container. The first sensor 423 transmits a light source, which is detected by the second sensor 424 in the absence of any food container. The sensors, together, act as a light gate, which is broken when a food container passes between the sensors, allowing for detection and timing of the passage of the food container through the system. A control system has knowledge of the conveyor speed, and so can calculate the position of each individual food container for both sampling and reject actions. The first and second sensors 423, 424 detect an oncoming food container, in use, so that readings by the test equipment can be associated with the correct food container.

[0054] A fifth leak detection head will now be described with respect to Figure 8. The fifth comparative example is substantially identical to the fourth, and further comprises first and second side-sampling attachments 460, 470.

[0055] Each side-sampling attachment 460, 470 has an inverted T-shaped construction. The upper end of the side-sampling attachment 460, 470 features a projection (not shown) which cooperates with the groove 465 in the lower surface of the wall 405, and allows the side-sampling attachments 460, 470 to each be mounted on the lower surface of the sampling head in a laterally adjustable fashion.

[0056] Once mounted to the lower surface of the wall 405 of the sampling head 400, the arms of each side-sampling attachment 460, 470, which give it the inverted T-shaped appearance, extend in the upstream and downstream directions, parallel to the direction of conveyance of the conveyor 10 in use. In use, a container to be tested passes between these side-sampling attachments, underneath the air-sampling head 400.

[0057] Each side-sampling attachment 460, 470 features, on its inner surface, i.e. the surface facing the opposing side-sampling attachment, a row of air-sampling ports 462, 472. The row of air-sampling ports extends along the arms of their respective side-sampling attachment 460, 470, parallel to the direction of conveyance in use. The air-sampling ports 462, 472 of each side-sampling attachment 460, 470 are in fluid communication with a respective manifold internal to the side-sampling attachment. Each manifold connects to a conduit, which extends up through the side-sampling attachment 460, 470, through an opening in the upper surface of the projection that sits in the groove 465 of the air-sampling head 400. The opening in the upper surface of each side-sampling attachment 460, 470 cooperates with at least one of the air-sampling ports 402 to communicate the vacuum suction to the air-sampling ports 462, 472, and to allow the air sample collected by the air-sampling ports 462, 472 to be communicated to the air sample testing equipment in use.

[0058] While side-sampling attachments are used in this comparative example, it will be appreciated that separate and distinct side-sampling heads could alternatively be used.

[0059] A sixth comparative example will now be described with respect to Figure 9. This comparative example shows an underneath sampling device 600, which may be incorporated into an air-sampling system and used with any of the air-sampling heads described above.

[0060] Figure 9 shows, schematically, first and second conveyors 10a, 10b, which, for example, may replace the conveyor 10 of the system of the first comparative example. The conveyors are arranged adjacent another, with the downstream end of the first conveyor 10a being spaced from the upstream end of the second conveyor 10b by a narrow gap. Over the gap is located an air-sampling head, which in this case is the air-sampling head of the fourth comparative example. Located in the gap between the conveyors is an underneath-sampling device 600.

[0061] The underneath-sampling device 600 is a long, narrow, generally trapezoidal-prism shaped head. The underneath sampling device 600 comprises, in an upper surface, facing the leak detection head in use, a plurality of air-sampling ports 602, arranged in a row extending along the gap between the conveyors. Each air-sampling port 602 is connected via a respective conduit to a manifold 603 in the underneath sampling device 600. At either lateral end of the underneath sampling device 600, is a test equipment port 604, which, in use, is connected so as to be in fluid communication with an air sample tube for connecting to the test equipment and providing the vacuum suction to the underneath sampling device 600.

[0062] In use, as a container is conveyed by the first conveyor 10a beneath the air-sampling head 400 and across the gap onto the second conveyor. The air-sampling head presses on the upper surface of the container and obtains an air sample from the upper side of the container substantially as described above. The underneath-sampling device 600 simultaneously obtains an air sample from the bottom of the container as it is being pressed by the air-sampling head 400.

[0063] While the underneath-sampling device of this comparative example is separate from the leak detection head, it will be appreciated that it could alternatively be incorporated into a leak detection head, which would define a portal through which a container is conveyed in use.

[0064] A method of detecting breaches in containers, suitable for implementation using the above systems and devices, will now be described with reference to the flow diagram of Figure 10.

[0065] An embodiment of the method comprises the step S100 of applying a pressure to a sealed container located in an air-sampling region using a pressing member. This step acts to force air out of any breaches in the container, which improves the detectability of gases within the container. Optionally, this step may be performed while the sealed container moves relative to the pressing member.

[0066] Next, in step S200 an air sample is taken from the air-sampling region during and / or after applying the pressure to the sealed container. The air sample taken in step S200 will include at least some of the gas forced out of breaches (if any) in the container. Optionally, this sample may be taken through a porous material forming a part of the pressing member used to contact the sealed container. Further, the quality of the air sample obtained may be improved by performing this step with a step (not shown) of exhausting gas, either in the form of an air curtain, preferably surrounding the location at which the sample is taken, or in the form of gas exhausted through an area of the porous material before the air sample is taken, or both.

[0067] Next, in step S300, the air sample is communicated to air-sample testing equipment. In this step, the air sample, potentially including gas forced from a breach in a container, is provided to air-sample testing equipment.

[0068] Finally, in step S400, the composition of the air sample is tested using the air-sample testing equipment to determine whether there is a breach in the sealed container. If the composition of the air sample is found to meet user defined criteria, then the container from which the sample was taken is identified as having a breach. In particular, the carbon dioxide, oxygen and / or nitrogen content of the air sample may be tested, and a breach be identified when the carbon dioxide, oxygen and / or nitrogen content of the air sample meets pre-set criteria. These criteria may include the rate of change in carbon dioxide, oxygen and / or nitrogen being greater than a threshold value.

[0069] If, in step S400, it is determined that a container has a breach, this container may be identified for disposal or repackaging. When implemented as part of a production line, a breached container may be diverted off the production line at a point downstream of the air-sampling region for reprocessing.

[0070] A first embodiment will now be described with reference to Figures 11A to 11D. This example comprises a first conveyor belt 701, which acts as a pressing member, opposite a second conveyor belt 702. The conveyor belts are entrained about a plurality of rollers (not shown) for holding the conveyor belts in the desired arrangement and for powering the conveyor belts, as is generally known in the art. A sealed food container T is provided into the gap between the first and second conveyor belts. The sealed food container rests on the lower conveyor belt 702 and the upper conveyor belt 701 contacts the upper surface of the sealed food container T to apply a pressure to the sealed food container. In use, both conveyor belts 701, 702 rotate at the same speed such that the sealed food container moves through the system.

[0071] Within both the upper and lower conveyor belts 701, 702 are respective upper and lower air-sampling heads 711, 712. These may be constructed similarly to the underneath-sampling device 600 described above. Both air-sampling heads 711, 712 extend across the entire width of the conveyor belts and have a plurality of air sampling ports that face towards a sealed food container passing between the conveyor belts. As shown, in particular in Figure 11B, each of the conveyor belts 701, 702 comprise an array of perforations 703 such that the conveyor belts are air permeable. In use, vacuum suction is communicated through air-sample tubes (not shown) to the air-sampling heads and the individual air-sampling ports so that the air-sampling ports each draw air into them. The air-sampling heads 711, 712 are thereby able to sample air proximate the sealed food container T passing between the conveyor belts, i.e. in the air-sampling region. In use, any gas forced through breaches in the sealed food container by the sandwiching action of the upper and lower conveyors 701, 702 will be sampled by the air-sampling heads 711, 712 and communicated to testing means, described above, for detection of the breach.

Claims

1. A leak detection system for detecting breaches in sealed food containers, the leak detection system comprising: air-sample testing equipment (50) configured to test the composition of an air sample provided to the air-sample testing equipment; a first conveyor (702) for conveying the sealed food container to, through and / or away from the air-sampling region; at least one pressing member configured to, in use, apply pressure to the sealed food container (T) located in an air-sampling region, wherein the at least one pressing member comprises a conveyor belt (701) configured to apply pressure to the sealed food container (T) as it is conveyed through the air-sampling region, wherein the conveyor belt of the pressing member (701) opposes the first conveyor (702) such that the sealed food container is conveyed through the air-sampling region between the conveyor belt of the pressing member (701) and the first conveyor (702), and wherein a surface of one or both of the first conveyor and the conveyor belt of the pressing member is perforated (703); characterised by a plurality of air-sampling ports located in the air-sampling region, wherein the plurality of air-sampling ports are located on an air-sampling head (711, 712) arranged inside one of the first conveyor and the conveyor belt of the pressing member (701, 702); an air sample conduit extending between the plurality of air-sampling ports and the air-sample testing equipment (50); wherein, in use, the plurality of air-sampling ports takes an air sample from the air-sampling region at least during or after the at least one pressing member (701) applies pressure to the sealed food container (T) in the air-sampling region and communicates said air sample through the air sample conduit to the air-sample testing equipment (50).

2. A leak detection system according to claim 1, wherein a surface of one or both of the first conveyor (702) and the conveyor belt of the pressing member (701) comprises an array of protrusions for contacting the sealed food container in use.

3. A leak detection system according to any of the preceding claims, further comprising a vacuum pump connected to the air sample conduit for communicating vacuum suction to the plurality of air-sampling ports.

4. A leak detection system according to any of the preceding claims, comprising a plurality of air sampling ports located on a second air-sampling head (711, 712) arranged inside the other of the first conveyor (702) and the conveyor belt of the pressing member (701), such that a first subset of air-sampling ports take an air sample from a first side of a sealed food container (T) and a second subset of air-sampling ports take an air sample from a second side of the sealed food container (T) opposite the first side.

5. A method of detecting breaches in sealed containers comprising: conveying a sealed food container (T) through an air-sampling region using a first conveyor (702); applying a pressure to the sealed container located in the air-sampling region using a pressing member, wherein the at least one pressing member comprises a conveyor belt (701) configured to apply pressure to the sealed food container as it is conveyed through the air-sampling region, wherein the conveyor belt of the pressing member (701) opposes the first conveyor (702) such that the sealed food container (T) is conveyed through the air-sampling region between the conveyor belt of the pressing member (701) and the first conveyor (702), and wherein a surface of one or both of the first conveyor and the conveyor belt of the pressing member is perforated (703); taking an air sample from the air-sampling region during and / or after applying the pressure to the sealed container (T); communicating the air sample to air-sample testing equipment (50); testing the composition of the air sample using the air-sample testing equipment to determine whether there is a breach in the sealed container (T); characterised in that the air sample is taken using a plurality of air-sampling ports, wherein the plurality of air-sampling ports are located on an air-sampling head (711, 712) arranged inside one of the first conveyor (702) and the conveyor belt of the pressing member (701).

6. A method according to claim 5, wherein testing the composition of the air sample using the air-sample testing equipment comprises testing the carbon dioxide, oxygen and / or nitrogen content of the air sample, and it is determined that there is a breach in the sealed container when the carbon dioxide, oxygen and / or nitrogen content of the air sample meets pre-set criteria.

7. A method according to claim 6, wherein the pre-set criteria include a rate of change in the carbon dioxide, oxygen and / or nitrogen content of the air sample that is greater than a threshold value.

8. A method according to any of claims 5 to 7, wherein taking an air sample from the air-sampling region during and / or after applying the pressure to the sealed container comprises taking an air sample from a first side of a sealed container using the plurality of air-sampling ports on the air-sampling head (711, 712) and taking an air sample from a second side of the sealed container opposite the first side using a plurality of air-sampling ports located on a second air-sampling head (711, 712) arranged inside the other of the first conveyor (702) and the conveyor belt of the pressing member (701).