Method and apparatus for leak detection

Abstract

A leak detection device (1) arranged to detect a leak in a seal (23) of a pipe (2), comprising: a first pipe pressure device (3) and a second pipe pressure device (4) arranged to provide a predetermined pressure to the pipe; a detection means arranged to detect a pressure change in the tube after a predetermined pressure has been applied to the tube; an electronic control unit arranged to compare an initially applied pressure value with a second pressure value to determine if a pressure change has occurred and to issue a fault signal if a pressure change has occurred, in which the leak detection device (1) comprises a first sealing pressure device (16) and a second sealing pressure device (17), the first and second sealing pressure means are arranged to be positioned at a seal (23) of the tube (2) when the sealing pressure means (3, 4) apply pressure to the tube (2).

Description

Technical Field

[0001] The present invention relates to a method and apparatus for high speed detection of leaks in containers, such as tubes or other flexible containers. Applications of this type are frequently used in the packaging industry and the invention is intended for full production speed detection of containers or seals in sealed packages containing perishable products in the form of cosmetics, chemicals or pharmaceutical products, toothpaste, food or the like. The arrangement according to the invention allows high speed, in-line testing of the quality of the seals on such packages as well as the tightness of the packages themselves. Background Art

[0002] It is known to extend and protect the shelf life of perishable products by modifying the atmosphere in the free space remaining in the package after the product has been filled. The gases most commonly used in modified atmosphere packaging (MAP) are nitrogen, CO2 and oxygen or mixtures thereof. Oxygen is mainly used to maintain the red color of fresh meat or to control the ripening rate of fruits and vegetables, while nitrogen and CO2 are used to reduce the aging effects of oxygen and to reduce the aerobic growth of microorganisms in a variety of products.

[0003] The packaging material in a MAP can be any substantially airtight material including plastic films or coatings, coated papers and thin metal foils.

[0004] Leaks in the packaging due to production errors or subsequent damage will result in at least a partial loss of the improved atmosphere and may shorten the expected shelf life.Another disadvantage of leaks is that the product may escape from the packaging and contaminate the surroundings.

[0005] A common cause of leakage in plastic tubes is product residues or splashes deposited on the sealing surface before closure by welding. Therefore, the seals are usually tested for leakage before the tubes are delivered. Various leak testing arrangements have been proposed and, in some cases, are also used to prevent leaking packages from reaching store shelves.

[0006] A common limitation in many known methods is that they cannot perform 100% leak testing on individual packages at full line speeds of more than 30 packages per minute or more, i.e. with a cycle time of less than 2 seconds. This problem can be addressed by limiting testing to off-line point tests or by batch testing an appropriate number of packages in the same test cycle.

[0007] One possible way to increase the test capacity is to set up multiple parallel test arrangements, each operating at a lower speed but together matching the cycle time of the fill line.

[0008] EP 0894252 B1 discloses a leak testing method which is said to be able to perform a single package test "very quickly, typically in about 1 second", indicating a testing capacity of up to 60 packages per minute.

[0009] The method disclosed in EP 0894252 B1 uses diluted hydrogen as tracer gas. Hydrogen and helium are commonly used as tracer gases for leak testing. A problem with these gases is their relatively high diffusion rate through thin polymer films and other packaging materials used as gas barriers in packaging materials. If the tracer gas diffuses through the non-leaking walls of the package, there is a risk that the leak test arrangement will detect a diffusion leak that is not a package integrity problem. This problem can be overcome if the time between filling gas and testing for leaks is short enough so that a leak test is performed before the gas has penetrated through the barrier material. Depending on the material used and on the thickness of the film, this penetration time is on the order of a few seconds to a few minutes.

[0010] EP 0894252 B1 uses a chamber in which the package is placed. The chamber is then closed and a limited negative pressure is drawn. The document states that this limited vacuum level can be achieved quickly and at a low cost compared to the levels used in previous arrangements for gas testing. The package should remain in the chamber for a required residence time in the range of 0.5 seconds to 60 seconds.

[0011] By having these steps performed in parallel, the time required for some of these steps can be partially reduced. For example, it is obvious that the loading of the next package can be carried out in the same order as the unloading of the package just tested. Another example of this optimization is to allow some sensor recovery time to occur during the unloading / loading steps.

[0012] However, even with best practices, additional time is required to reduce the pressure in the chamber and, most importantly, additional time is required for the actual sensor recovery. Sensor recovery time is long and often not fully predictable. This places a significant limitation on automated systems, as the process cannot be run at a constant speed.

[0013] Therefore, the invention disclosed in EP 0894252 B1 cannot meet production speeds faster than the production speed of 60 packages per minute required in today's industry. It is even doubtful whether a speed of 30 packages per second can be achieved.

[0014] Even though such testing systems can detect small leaks in tubes etc., they cannot test the quality of the seal. In these systems, a low pressure is applied to the tube wall so that if there is a leak in the seal, the test gas used can escape. However, such systems cannot test the quality of the seal, i.e. whether the seal is strong enough for normal handling. If a higher pressure is applied to the tube, e.g. in a shopping basket with other goods carried on the tube, it is important that the seal remains tight and does not break. Therefore, it is advantageous to test the tube by applying a higher pressure to the tube wall.

[0015] EP 2959282 B1 discloses a method in which external pressure is applied to a tubular package, and wherein the deformation of the weld seal of the tubular package is detected. The deformation of the weld seam is detected by measuring the thickness of the seal. In one example, the thickness of the seal is measured at one point of the seal using a laser distance sensor. Using this method, if the entire seal is defective and peels off, a defective seal can be detected. If only one side of the seal is defective, a defective seal cannot be detected. In addition, this method only detects defective weld seams. Another defect of the tubular package, such as a defect in the wall material or a defect at the end area between the package wall and the seal will not be detected. In addition, it is said that this method requires more than 10 seconds to perform a leak test, and is therefore not suitable for online testing with a cycle time lower than 1 second.

[0016] In another known leakage system, a tube is pressed between two pressure members at a relatively high pressure, such as 8 bar or more. The test pressure is a predetermined pressure set by the manufacturer or the customer. If the quality of the seal and the tube is acceptable, the seal and the tube will withstand this pressure. If the seal or the tube fails, the seal or the tube will suddenly break and the contents will escape from the tube. This will simultaneously contaminate the production line with the product, so that the production line must be stopped for cleaning. One method of detecting that the contents have escaped from the tube is to use electrodes arranged above the seal and around the tube, wherein when the contents touch the electrodes, the contents will close the circuit.

[0017] Such a system will detect a defective seal or tube, but requires the production line to be stopped when a defective seal or tube is detected.There is therefore room for improvement in leak detection systems. Summary of the invention

[0018] It is an object of the present invention to provide an improved device for leak detection. Another object is to provide an improved method for leak detection.

[0019] The solution to the problem according to the invention is defined by the features of the independent claims relating to the leak detection device and the method for detecting leaks. The other claims contain advantageous further developments of the leak detection device and the method for detecting leaks.

[0020] In a leakage detection device arranged to detect leakage in a seal of a tube, the device comprises: a first tube pressure device and a second tube pressure device, the first tube pressure device and the second tube pressure device are arranged to apply a predetermined pressure to the tube; a first sealing pressure device and a second sealing pressure device, the first sealing pressure device and the second sealing pressure device are arranged to be positioned at the seal of the tube before the tube pressure device applies pressure to the tube, the purpose of the present invention is achieved due to the following: the leakage detection device comprises a sensor device, the sensor device is arranged to measure a signal indicating the pressure in the tube when the first tube pressure device and the second tube pressure device apply a predetermined pressure to the tube; and the leakage detection device comprises an electronic control unit, the electronic control unit is arranged to determine whether a pressure change has occurred in the tube based on input from the sensor device.

[0021] By means of a first embodiment of the leak detection device according to the invention, a leak detection device is provided which can detect leaks in the seal of a tube without the risk of substances escaping from the tube. If the seal is defective, the pressure applied to the tube will cause the seal to rupture. By positioning the sealing pressure device at the seal, the sealing pressure device will prevent substances from ejecting from the tube in the event of a defective seal, which would otherwise lead to contamination of the test equipment with substances. The leak detection device is arranged as an in-line test device, otherwise the entire production line would have to be stopped for cleaning of the test equipment. The leak detection device will also be able to detect defects in the tube itself, for example defects in the tube wall material.

[0022] The first tube pressure device and the second tube pressure device are arranged to apply a predetermined pressure to the tube by displacing the first tube pressure device and the second tube pressure device toward each other when the tube is positioned between the first tube pressure device and the second tube pressure device.

[0023] In one example, the sealing pressure device is arranged to be pressed on the seal so that the sealing pressure device is supported on the seal before the tube pressure device applies a predetermined pressure to the tube. In this example, the sealing pressure device is arranged to be pressed on the outer part or upper part of the seal, for example, on the upper half of the seal. In this way, a part of the seal will not be supported by the sealing pressure device. The upper part pressed by the sealing pressure device is, for example, 30% to 60% of the seal. This will make the lower part of the seal, that is, the part of the seal closest to the tube, unsupported, and if the seal is defective, the lower part of the seal will open when the tube pressure device applies pressure to the side of the tube. When the seal opens, a pressure change in the tube will be detected and if the pressure change is greater than a predetermined value, a fault signal indicating that the seal or tube is defective is issued. The pressure of the tube pressure device is released, the pressure of the sealing pressure device is released, and the tube is discarded from the product flow. By releasing pressure from the tube pressure device before the sealing pressure device is released, there will be no pressure in the tube to cause the remainder of the defective seal to rupture when the sealing pressure device is released.

[0024] In another example, the sealing pressure device is arranged to approach the seal at a distance between 0.1mm and 1mm from the seal before the tube pressure device applies a predetermined pressure to the tube. In this example, the sealing pressure device is arranged at a small distance from the seal. This small distance will allow the defective seal to open a little, so that a part of the side of the seal is supported on the sealing pressure device and a small amount of air can escape from the tube through the opened seal. Another advantage of this method is that the bad seal may have been partially opened before it arrives at the sealing pressure test station, for example, due to previous treatment or a bad sealing process. If the sealing pressure device is used to press such a bad seal, no pressure change will occur because only the sealing pressure device holds the seal together. By keeping the sealing pressure device at a small distance from the seal, such a bad seal can also be detected. This will cause a pressure change in the tube. In this example, the sealing pressure device can be arranged on the entire seal, or at least on 60% of the seal. When the seal is opened, the pressure change is detected by a sensor device, which measures a signal representing the pressure in the tube. At the same time, the small distance between the seal and the seal pressure device will prevent the material from being ejected from the tube in the event of a defective seal. When the seal opens, a pressure change in the tube will be detected and if this pressure change is greater than a predetermined value, a fault signal indicating a defective seal is emitted. At the same time, the seal pressure device can be moved towards the seal in order to directly prevent the material from escaping from the tube, and the pressure applied by the tube pressure device is released. The seal pressure device is then extracted from the seal and the tube is discarded from the product flow.

[0025] The tube pressure device and the sealing pressure device are arranged in one example to move towards and away from the tube in a horizontal straight direction when the tube is upright, but other directions of movement, such as rotational movement, are also possible. It is also possible to detect leaks of tubes laid on a conveyor belt, in which case the tube pressure device and the sealing pressure device move in a direction perpendicular to the central axis of the tube. Because the movement must be relatively fast and because the movement can be advantageously adjusted depending on the tube used, an electric movement device is preferred. An electric drive device with a position sensor is fast and easy to control and position in a predetermined position.

[0026] In one example, the predetermined pressure applied to the tube is between 1.5 bar and 4 bar.

[0027] In various embodiments, the first tube pressure device and the second tube pressure device are arranged on a first drive belt driven by a first drive unit, and / or the first sealing pressure device and the second sealing pressure device are arranged on a second drive belt driven by a second drive unit. The drive belt and the drive unit enable the tube pressure device and / or the sealing pressure device to move effectively.

[0028] In various embodiments, the first drive unit includes a first motor and a first transmission, and / or the second drive unit includes a second motor and a second transmission.

[0029] In one example, the sealing pressure device is arranged on a first drive belt driven by a first rotary motor and the tube pressure device is arranged on a second drive belt driven by a second rotary motor. Each motor is controlled independently of the other motor. By arranging one sealing pressure device on a first portion of the first drive belt and arranging another sealing pressure device on a second portion of the first drive belt, the rotation of the motor will move the two sealing pressure devices toward each other or away from each other. In this way, the sealing pressure device can apply pressure to the tube in less than one second, and for example in 0.1 to 0.2 seconds. The release of the sealing pressure device is also fast. This also applies to the tube pressure device.

[0030] In other embodiments, the first tube pressure device is arranged on the linear actuator and the second tube pressure device is arranged on the linear actuator, and / or the first sealing pressure device is arranged on the linear actuator and the second sealing pressure device is arranged on the linear actuator.

[0031] In another example, the seal pressure device is arranged on two linear actuators and the tube pressure device is arranged on two linear actuators. The linear actuators will allow the two seal pressure devices to move towards or away from each other in a short time. In this way, the seal pressure device can move towards the seal in less than one second and for example in 0.1 to 0.2 seconds. The release of the tube pressure device is also fast. The same applies to the tube pressure device.

[0032] In other embodiments, the first tube pressure device is arranged on the pivotable support and the second tube pressure device is arranged on the pivotable support, and / or the first sealing pressure device is arranged on the pivotable support and the second sealing pressure device is arranged on the pivotable support.

[0033] In another example, the sealing pressure device is arranged on two pivotable supports and the tube pressure device is arranged on two pivotable supports. The pivotable supports are preferably driven directly by an electric motor or by some type of transmission device, which will allow the two sealing pressure devices to move towards each other or away from each other in a short time. In this way, the sealing pressure device can move towards the seal in less than one second, and for example in 0.1 to 0.2 seconds. The release of the tube pressure device is also fast. The same applies to the tube pressure device.

[0034] In various embodiments, the sensor device is arranged to measure the drive current of the first drive unit and / or the sensor device is arranged to measure the drive current of the second drive unit. The drive current of the first drive unit measured by the sensor device can be used to provide a measurement signal indicating the pressure in the pipe when the pipe pressure device applies a predetermined pressure to the pipe. The electronic control unit determines whether a pressure change has occurred in the pipe based on the input signal from the sensor device, and the measured drive current of the first drive unit is used to estimate the pressure in the pipe.

[0035] In one example, the drive current of the first drive unit is continuously measured by the sensor device during the movement of the first tube pressure device and the second tube pressure device from the idle position to the pressure position, in which a predetermined pressure is applied to the tube during a specific time before returning to the idle position. If the drive current does not reach the predetermined value, the tube is considered to be faulty. If the drive current decreases rapidly during the movement of the first tube pressure device and the second tube pressure device to the pressure position or during a specific time in the pressure position, the tube is considered to be faulty. When detecting a faulty tube, the first tube pressure device and the second tube pressure device can be returned directly to the idle position.

[0036] In various embodiments, the sensor device is arranged to measure the movement of the first drive unit and / or the sensor device is arranged to measure the movement of the second drive unit. In this way, when the tube pressure device applies a predetermined pressure to the tube. The movement of the first drive unit measured by the sensor device can be used to provide a measurement signal indicating the pressure in the tube. In one example, a predetermined pressure is applied to the tube by the tube pressure device and the exact position of the first tube pressure device and the second tube pressure device is detected. If the seal is correct, the position of the tube pressure device will not change. If the seal is incorrect, the position of the tube pressure device will change slightly and this change is detected by the sensor device.

[0037] The present invention also relates to a method for detecting a leak in a seal of a tube by means of a leak detection device. The leak detection device comprises: a first tube pressure device and a second tube pressure device, a first sealing pressure device and a second sealing pressure device, and a sensor device. The method comprises the following steps: positioning the tube between the first tube pressure device and the second tube pressure device, and positioning the seal between the first sealing pressure device and the second sealing pressure device; applying a predetermined pressure to the tube by means of the first tube pressure device and the second tube pressure device; measuring a signal indicating the pressure in the tube by means of the sensor device when the first tube pressure device and the second tube pressure device apply the predetermined pressure to the tube; determining by means of an electronic control unit whether a pressure change has occurred in the tube based on an input signal from the sensor device.

[0038] In one embodiment, the method further comprises the step of applying a predetermined pressure to the tube by displacing the first tube pressure device and the second tube pressure device towards each other.

[0039] In one embodiment, the method further comprises the step of issuing a fault signal if a pressure change is determined by the electronic control unit.

[0040] In one embodiment, the method further comprises the step of positioning the first sealing pressure means and the second sealing pressure means such that the first sealing pressure means and the second sealing pressure means bear on a seal of the tube.

[0041] In one embodiment, the method further comprises the step of positioning the first sealing pressure means and the second sealing pressure means at a distance of 0.1 mm to 1.0 mm from the seal of the tube.

[0042] In one embodiment, the method further comprises the step of applying a predetermined pressure in the range between 1.5 bar and 4 bar to the tube.

[0043] In one example, a method for detecting leakage in a flexible pipe having a welded seal includes the following steps: placing a seal pressure device at the seal of the pipe; applying a predetermined pressure to the pipe using the pipe pressure device; measuring a signal indicating the pressure in the pipe using a sensor device; determining whether there is a pressure change in the pipe using a control unit after the predetermined pressure has been applied to the pipe; and issuing a fault signal if a pressure change is detected.

[0044] By means of the method of the invention, leaks in pipes with welded seals can be detected without completely destroying the seals, which will prevent substances from the pipe from contaminating the surroundings of the pipe by being ejected from the pipe. In this way, each individual seal of a pipe can be tested in the normal production flow, and pipes with defective seals can be immediately discarded either by directly stopping the production flow or without having to stop the production flow to clean the test equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The invention will now be described in more detail with reference to the embodiments shown in the accompanying drawings, in which:

[0046] Figure 1 A view showing a leakage detection device according to the present invention,

[0047] Figure 2 shows details of the leak detection device before pressure is applied to the tube,

[0048] Figure 3 Details of the leak detection device are shown when pressure is applied to the tube.

[0049] Figure 4 shows details of the leak detection device when pressure is applied to the tube, and

[0050] Figure 5 A flow chart of a method for detecting leakage of a flexible pipe having a welded seal according to the present invention is shown. DETAILED DESCRIPTION

[0051] The embodiments of the invention described below with further improvements are to be regarded as examples only and in no way limit the scope of protection offered by the patent claims.

[0052] Figure 1 A view showing a leak detection device, Figures 2 to 4 shows the details of the leak detection device, and Figure 5A flow chart of a method for leak detection is shown. A leak detection device 1 according to the present invention comprises a first tube pressure device 3 and a second tube pressure device 4 arranged to apply pressure to a tube 2. The pressure can be applied to any position of the tube, but in the example shown, the pressure is applied to the upper half of the tube. Applying pressure to the tube close to the seal will allow a compact leak detection device that does not interfere with the tube flow. The first tube pressure device 3 comprises a first pressure pad 5, and the second tube pressure device 4 comprises a second pressure pad 6. The pressure pads are provided with a smooth surface and shape so that the pressure pads will apply pressure to the tube without damaging the tube surface. In the example shown, the pressure pads are semicircular pads made of a rigid material that does not bend when pressure is applied to the tube, but other shapes are also possible. The material may be plastic, rubber or metal.

[0053] The first pressure pad 5 is mounted to a first holding bracket 7 and the second pressure pad 6 is mounted to a second holding bracket 8. The holding brackets are removably attached to the tube pressure device so that the pressure pads can be easily replaced or exchanged so that the pressure pads can be replaced to match the size of the tube being used.

[0054] In the example shown, each tube pressure device is provided with a locking arrangement which releases the retaining bracket of the pressure pad when the tube pressure device is positioned in the release position. The locking arrangement comprises a pivotable bracket 9 having a locking nose 10 arranged on one side of the retaining bracket and an adjustable support member 11 which bears on an end stop 12 in the release position. In the release position, the pivotable bracket will pivot so that the locking nose releases the retaining bracket and the pressure pad can be removed. The retaining bracket may be provided with a magnet which holds the retaining bracket in place when the tube pressure device is in the release position. A spring holds the locking arrangement in the locked position.

[0055] The first tube pressure device and the second tube pressure device are provided with an idle position 14 and a pressure position 13. In the idle position 14, the distance between the pressure pads is greater than the width of the tube so that the tube can be positioned between the pressure pads without interfering with the pressure pads. In the pressure position 13, the pressure pads apply a predetermined pressure to the tube so that the pressure inside the tube increases. The pressure is applied perpendicular to the central axis 15 of the tube 2. The applied pressure must be high enough to detect defective welds of the tube 2 or defects in the tube. Suitable pressures are, for example, between 1.5 bar and 4 bar or between 2 bar and 3 bar, depending on the size of the tube. The exact applied pressure is not important, because the suitable pressure is the detected pressure change that indicates whether the weld is defective. However, too low a pressure will not adequately test the seal and will further deform the defective weld too slowly.

[0056] The leakage detection device is also provided with a first sealing pressure device 16 and a second sealing pressure device 17. The first sealing pressure device is mounted on the first arm 18 and the second sealing pressure device is mounted on the second arm 19. Each sealing pressure device can be provided with a slightly elastic surface, such as soft plastic or rubber, so that when the sealing pressure device 25 is supported on the weld, the weld will not be damaged. The sealing pressure device is provided with a sealing support position 20, a sealing pressure position 21 and a sealing idle position 22. In the sealing support position, the sealing pressure device is supported on the weld with a lower force. In the sealing pressure position, the sealing pressure device is positioned close to the weld at a small distance. In the sealing idle position, the sealing pressure devices are positioned separately from each other so that the pipe can be positioned between the sealing pressure devices without interfering with the sealing pressure devices.

[0057] exist Figure 3 In the first example shown in , the first sealing pressure device 16 and the second sealing pressure device 17 are positioned at the sealing support position 20, so that the first sealing pressure device 16 and the second sealing pressure device 17 are supported on the seal 23 of the tube 2. In this example, the sealing pressure device is supported on the upper half of the seal, so that at least 40% of the seal is free. When the sealing pressure device is supported on the seal, the first tube pressure device 3 and the second tube pressure device 4 are positioned at the tube pressure position 13, so that the first tube pressure device 3 and the second tube pressure device 4 apply pressure to the tube. When the pressure pad is supported on the tube, the sensor device measures the signal indicating the pressure in the tube, and the electronic control unit (ECU) 36 is used to determine whether there is a pressure change in the tube based on the measured signal. In one example, a signal indicating the pressure in the tube or the pressure applied to the tube is measured. The estimated pressure value can be determined, for example, by measuring the force applied to the tube, by measuring the drive current used to apply the force to the tube, or by measuring the position of the drive unit. The system will measure several values ​​representing the pressure in the tube, and will use two or more values ​​to determine whether there is a pressure change in the tube.

[0058] In one example, a first value is measured and the first value is compared to a second value. If the difference between the first value and the second value is greater than a predetermined amount, it is determined that a pressure change has occurred. In another example, several values ​​are measured and the slope of the curve is used to determine if a pressure change has occurred. If the slope is steeper than a predetermined value, it is determined that a pressure change has occurred.

[0059] If the seal is correct, the pressure in the tube will remain the same and the ECU will determine that the pressure has not changed. In this case, the seal of the tube is acceptable. The tube pressure device moves to the tube idle position and the seal pressure device moves to the seal idle position, the tube is advanced in the tube flow and the new tube is positioned for leak testing.

[0060] If the seal is defective, the lower half of the seal will break open, which will slightly reduce the pressure in the tube because the total internal volume of the tube will increase slightly. This pressure change is detected by the ECU and the tube is rejected. The tube pressure device moves to the tube idle position, after which the seal pressure device moves to the seal idle position and the tube is discarded from the tube flow. By applying pressure to the seal during the leak test, the entire seal will not be able to snap open, which prevents the contents of the tube from being ejected.

[0061] exist Figure 4 In the second example shown in , the first sealing pressure device 16 and the second sealing pressure device 17 are positioned at the sealing pressure position 21. In this example, the sealing pressure device will not contact the seal but will be positioned close to the seal at a distance between 0.1mm and 1.0mm from the seal 23 of the tube 2. In this example, the sealing pressure device can be arranged at the same height as the seal so that the sealing pressure device covers most of the seal or the entire seal. When the sealing pressure device is positioned at the sealing pressure position 21, the first tube pressure device 3 and the second tube pressure device 4 are positioned at the tube pressure position 13 so that the first tube pressure device 3 and the second tube pressure device 4 apply pressure to the tube. When the pressure pad is supported on the tube, the initial pressure in the tube can be estimated and the initial pressure can be used as a default pressure value. The system will measure at least one of the following values ​​representing the pressure in the tube in order to determine whether there is a pressure change in the tube.

[0062] If the seal is correct, the pressure in the tube will remain the same and the ECU will not detect a pressure change. In this case, the seal of the tube is acceptable. The tube pressure device moves to the tube idle position and the seal pressure device moves to the seal idle position, the tube is advanced in the tube flow and the new tube is positioned for leak testing.

[0063] If the seal is defective, part of the seal will open so that some air can escape from the seal and the pressure in the tube is reduced. Since the seal pressure device is located close to the seal, the seal will not be completely broken open. Instead, a small opening will be formed through which the pressure can escape slowly, but this will prevent the substance in the tube from escaping. When the opening releases some of the gas in the tube, the pressure will be slightly reduced. This pressure change is detected by the ECU, a fault signal is issued and the tube is unqualified. At the same time, the seal pressure device is preferably moved toward the seal to directly prevent the substance from escaping from the tube and the tube pressure device moves to the tube idle position to release the pressure applied to the tube. Thereafter, the seal pressure device moves to the seal idle position and the tube is discarded from the tube flow. By allowing the seal to open slightly so that a small amount of gas in the tube can escape, the entire seal will not be able to break open, which prevents the substance in the tube from spraying out. If the seal is very poor, for example, if the seal is partially opened before it reaches the seal pressure test station, a defective seal can also be detected by this method. For such a poor seal, when pressing directly on the seal with the seal pressure device, no pressure change will be detected because only the seal pressure device is holding the seal together. By allowing some air to escape the tube when pressure is applied to the tube, such a poor seal will also be detected and can be discarded.

[0064] In one example, the first tube pressure device 3 and the second tube pressure device 4 are arranged on a first drive belt 24 driven by a first drive unit 30. The first drive unit comprises a first motor 32 and a first transmission 33. The drive belt is preferably provided with teeth so that the belt does not slip on the drive wheel. The first drive belt runs on a drive wheel driven by the first motor through the first transmission and an idler wheel arranged at the second transmission. The first tube pressure device 3 is arranged on a first portion 25 of the first drive belt arranged in the example shown in the front area, and the second tube pressure device 4 is arranged on a second portion 26 of the first drive belt arranged in the example shown in the rear area. In this way, when the drive motors rotate, the tube pressure devices will move in opposite directions. When the first drive motor rotates in one direction, both tube pressure devices will move inwards towards the tube pressure position 13. When the first drive motor rotates in the other direction, both tube pressure devices will move outwards towards the tube idle position 14 or the tube release position.

[0065] The first sealing pressure device 16 and the second sealing pressure device 17 are arranged on the second drive belt 27 driven by the second drive unit 31. The second drive unit includes a second motor 34 and a second transmission device 35. The drive belt is preferably provided with teeth so that the belt does not slip on the drive wheel. The second drive belt runs on the drive wheel driven by the second motor through the second transmission device and the idle wheel arranged at the first transmission device. The first sealing pressure device 16 is arranged on the first part 28 of the second drive belt arranged in the front area in the example shown, and the second sealing pressure device 17 is arranged on the second part 29 of the second drive belt arranged in the rear area in the example shown. In this way, when the drive motor rotates, the sealing pressure device will move in opposite directions. When the second drive motor rotates in one direction, both sealing pressure devices will move inward toward the sealing support position 20 or the sealing pressure position 21. When the second drive motor rotates in the other direction, both sealing pressure devices will move outward toward the sealing idle position 22.

[0066] The first and second tube pressure devices and the first and second sealing pressure devices may also be moved in other ways. In one example, each pressure device is arranged on a separate linear actuator. In another example, each pressure device is arranged on a pivotable support, and the pivotable support is arranged on a separate rotating shaft driven by a motor. Other ways of moving the pressure devices between the sealing support position or the sealing pressure position and the sealing idle position are also possible.

[0067] The drive motor may be provided with some position sensing means, such as an optical rotation sensor, which will detect the rotational position of the motor and thus the position of the pressure device. Linear position sensors or other types of position detection means may also be used to provide feedback signals for the first and second drive units. The drive current of the drive units may also be measured to estimate the pressure in the pipe.

[0068] The signal indicating the pressure in the tube can be measured in several different ways. In one example, a predetermined pressure is applied to the tube by a tube pressure device and the exact position of the first tube pressure device and the second tube pressure device is detected. If the seal is correct, the position of the tube pressure device will not change. If the seal is incorrect, the position of the tube pressure device will change slightly and this position change is detected by the detection device. The position sensor can be a rotation sensor arranged in, for example, a drive motor, or can be a linear position sensor, such as an optical linear sensor.

[0069] In one example, as the pressure in the pipe changes, the motor drive current used to hold the pipe pressure device in place will change. The drive current applied to the motor can be measured and changes in the motor current can be detected, indicating changes in pressure in the pipe. In another example, the rotational position of the motor is measured and changes in the rotational position are detected, indicating changes in pressure in the pipe.

[0070] Rapid detection of pressure changes in the tube is important. In one example, the throughput of the system is 100 tubes per minute, which gives a tube cycle time of 0.6 seconds. Therefore, positioning of the seal pressure device and application of pressure to the tube by the tube pressure device may take 0.1 to 0.2 seconds, determination of the pressure change may take 0.2 to 0.4 seconds, and release of the seal pressure device and tube pressure device may take 0.1 to 0.2 seconds. If the seal is defective, the tube is discarded from the tube flow.

[0071] The determination of the pressure change is performed by an electronic control unit (ECU) which controls the movement of the tube pressure device and the seal pressure device and receives measurement values ​​from a sensor device which measures a signal representative of the pressure in the tube.

[0072] In the inventive method for detecting leaks in flexible pipes with welded seals, the leak detection device will be able to detect defective seals without contaminating the production equipment, such as a pipe filling machine, or surrounding components with material from the pipe.

[0073] In step 100, a sealing pressure device is positioned at the seal of the pipe, either bearing directly on the seal or at a small distance from the seal. The sealing pressure device can be positioned to cover the entire seal, or to cover the upper part of the seal.

[0074] In step 110, a predetermined pressure is applied to the pipe using a pipe pressure device. The predetermined pressure is high enough to break a defective seal and may be, for example, between 1.5 bar and 4 bar.

[0075] A signal indicative of the pressure in the pipe is measured using the sensor device in step 120. This signal can be measured in different ways, for example by measuring the motor drive current of the pipe pressure device or by measuring the rotational position of the motor of the pipe pressure device.

[0076] In step 130, it is determined whether there is a pressure change in the pipe after a predetermined pressure has been applied to the pipe. The determination of the pressure change is performed by the ECU based on the measured signal.

[0077] If it is determined that there is no pressure change, the tube is released and the method continues with a new tube in step 100 .

[0078] In step 140, if a pressure change in the tube is determined, a fault signal is issued. The pressure change in the tube indicates a faulty seal or a faulty tube. The fault signal can be used to control a device that discards the faulty tube from the tube flow. The fault signal can also be used to stop the tube filling system and to signal an operator of the tube filling system. After the defective tube is discarded or the tube filling system is restarted, the method can continue with step 100.

[0079] The invention should not be considered limited to the above-described embodiments, but many additional variations and modifications are possible within the scope of the appended patent claims.

[0080] Reference numerals

[0081] 1: Leak detection device

[0082] 2: Tube

[0083] 3: First pipe pressure device

[0084] 4: Second pipe pressure device

[0085] 5: First pressure pad

[0086] 6: Second pressure pad

[0087] 7: First holding bracket

[0088] 8: Second holding bracket

[0089] 9: Pivotable bracket

[0090] 10: Lock the nose

[0091] 11: Supporting member

[0092] 12: End stop

[0093] 13: Pipe pressure position

[0094] 14: Tube idle position

[0095] 15: Central axis

[0096] 16: The first sealing pressure device

[0097] 17: Second sealing pressure device

[0098] 18: First Arm

[0099] 19: Second Arm

[0100] 20: Seal support position

[0101] 21: Sealing pressure position

[0102] 22: Seal idle position

[0103] 23: Seals

[0104] 24: First drive belt

[0105] 25: First section of first drive belt

[0106] 26: Second section of the first drive belt

[0107] 27: Second drive belt

[0108] 28: First section of the second drive belt

[0109] 29: Second section of the second drive belt

[0110] 30: First drive unit

[0111] 31: Second drive unit

[0112] 32: First Motor

[0113] 33: First transmission device

[0114] 34: Second Motor

[0115] 35: Second transmission

[0116] 36: Electronic Control Unit

Claims

1. A leak detection device (1), arranged to detect a leak in a seal (23) of a tube (2), the leak detection device (1) comprising: a first tube pressure device (3) and a second tube pressure device (4), wherein the first tube pressure device (3) and the second tube pressure device (4) are arranged to apply a predetermined pressure to the tube (2); a first sealing pressure device (16) and a second sealing pressure device (17), wherein the first sealing pressure device (16) and the second sealing pressure device (17) are arranged to be positioned at the sealing member (23) of the tube (2) before the first tube pressure device (3) and the second tube pressure device (4) apply the predetermined pressure to the tube (2), The invention is characterized in that the leakage detection device (1) comprises a sensor device, which is arranged to measure a signal indicating the pressure in the pipe (2) when the first pipe pressure device (3) and the second pipe pressure device (4) apply the predetermined pressure to the pipe (2), wherein the leakage detection device (1) comprises an electronic control unit (36), which is arranged to determine whether a pressure change has occurred in the pipe (2) based on an input from the sensor device.

2. The leakage detection device (1) according to claim 1, in, The first tube pressure device (3) and the second tube pressure device (4) are configured to apply the predetermined pressure to the tube (2) by shifting the first tube pressure device (3) and the second tube pressure device (4) toward each other when the tube (2) is positioned between the first tube pressure device (3) and the second tube pressure device (4).

3. The leakage detection device (1) according to claim 1 or 2, in, The first sealing pressure means (16) and the second sealing pressure means (17) are arranged to bear on the sealing member (23) before the first tube pressure means (3) and the second tube pressure means (4) apply the predetermined pressure to the tube (2).

4. The leakage detection device (1) according to claim 3, in, The first sealing pressure means (16) and the second sealing pressure means (17) are arranged to bear on the outer part of the seal (23) before the first tube pressure means (3) and the second tube pressure means (4) apply the predetermined pressure to the tube (2).

5. The leakage detection device (1) according to claim 1 or 2, in, The first sealing pressure device (16) and the second sealing pressure device (17) are arranged to be positioned at a distance between 0.1 mm and 1.0 mm from the sealing member (23) before the first tube pressure device (3) and the second tube pressure device (4) apply the predetermined pressure to the tube (2).

6. Leak detection device (1) according to any of the preceding claims, in, The predetermined pressure applied to the tube (2) is between 1.5 bar and 4 bar.

7. Leak detection device (1) according to any of the preceding claims, in, The first tube pressing device (3) and the second tube pressing device (4) are arranged on a first drive belt (24) driven by a first drive unit (30).

8. The leakage detection device (1) according to claim 7, in, The first driving unit (30) comprises a first motor (32) and a first transmission device (33).

9. The leakage detection device (1) according to claim 7 or 8, in, The sensor device is arranged to measure a drive current of the first drive unit (30).

10. The leakage detection device (1) according to claim 7 or 8, in, The sensor arrangement is arranged to measure the movement of the first drive unit (30).

11. The leakage detection device (1) according to any one of claims 1 to 6, in, The first tube pressure device (3) is arranged on a linear actuator and the second tube pressure device (4) is arranged on a linear actuator, or Therein, the first tube pressing device (3) is arranged on a pivotable support and the second tube pressing device (4) is arranged on a pivotable support.

12. Leak detection device (1) according to any of the preceding claims, in, The first sealing pressure device (16) and the second sealing pressure device (17) are arranged on a second driving belt (27) driven by a second driving unit (31).

13. The leakage detection device (1) according to claim 12, in, The second driving unit (31) comprises a second motor (34) and a second transmission device (35).

14. The leakage detection device (1) according to claim 12 or 13, in, The sensor device is arranged to measure a drive current of the second drive unit (31).

15. The leakage detection device (1) according to claim 12 or 13, in, The sensor device is arranged to measure the movement of the second drive unit (31).

16. The leakage detection device (1) according to any one of claims 1 to 11, in, The first sealing pressure device (16) is arranged on the linear actuator and the second sealing pressure device (17) is arranged on the linear actuator, or Therein, the first sealing pressure device (16) is arranged on a pivotable bracket and the second sealing pressure device (17) is arranged on a pivotable bracket.

17. A method for detecting a leak in a seal (23) of a pipe (2) by means of a leak detection device (1), in, The leakage detection device (1) comprises: a first pipe pressure device (3) and a second pipe pressure device (4), a first sealing pressure device (16) and a second sealing pressure device (17), and a sensor device, wherein the method comprises the following steps: Positioning the tube (2) between the first tube pressure device (3) and the second tube pressure device (4), and positioning the seal (23) between the first seal pressure device (16) and the second seal pressure device (17); Applying a predetermined pressure to the tube (2) by means of the first tube pressure device (3) and the second tube pressure device (4); When the first tube pressure device (3) and the second tube pressure device (4) apply the predetermined pressure to the tube (2), a signal indicating the pressure in the tube (2) is measured by the sensor device; It is determined by an electronic control unit (36) based on input from the sensor device whether a pressure change has occurred in the tube (2).

18. The method according to claim 17, in, The method further comprises the step of applying the predetermined pressure to the tube (2) by displacing the first tube pressure device (3) and the second tube pressure device (4) towards each other.

19. The method according to claim 17 or 18, in, The method further comprises the step of issuing a fault signal if a pressure change is determined by the electronic control unit (36).

20. The method according to any one of claims 17 to 19, in, The method further comprises the step of positioning the first sealing pressure means (16) and the second sealing pressure means (17) such that the first sealing pressure means (16) and the second sealing pressure means (17) bear on the seal (23) of the tube (2).

21. The method according to any one of claims 17 to 19, in, The method further comprises the step of positioning the first sealing pressure means (16) and the second sealing pressure means (17) at a distance of 0.1 mm to 1.0 mm from the seal (23) of the tube (2).

22. The method according to any one of claims 17 to 21, in, The method further comprises the step of applying said predetermined pressure in the range between 1.5 bar and 4 bar to said tube (2).

23. The method according to any one of claims 17 to 22, in, The first tube pressure device (3) and the second tube pressure device (4) are arranged on a first drive belt (24) driven by a first drive unit (30), wherein the method comprises the following steps: When the first tube pressure device (3) and the second tube pressure device (4) apply the predetermined pressure to the tube (2), the driving current of the first driving unit (30) is measured by the sensor device, wherein the measured driving current indicates the pressure in the tube (2), or When the first tube pressure device (3) and the second tube pressure device (4) apply the predetermined pressure to the tube (2), the movement of the first drive unit (30) is measured by the sensor device, wherein the measured movement is indicative of the pressure in the tube (2).

24. The method according to any one of claims 17 to 23, in, The method steps are performed in less than 1 second.

Images