Leak Detection Method and Device

Abstract

A leakage detection device (1) for detecting leakage in a sealing portion (23) of a pipe (2), comprising a first pipe pressurizing means (3) and a second pipe pressurizing means (4) configured to apply a predetermined pressure to the pipe, a detection means configured to detect a pressure change in the pipe after the predetermined pressure is applied to the pipe, and an electronic control unit configured to compare a first applied pressure value with a second pressure value to determine whether a pressure change has occurred, and to give a failure signal when a pressure change has occurred. The leakage detection device (1) includes a first sealing portion pressurizing means (16) and a second sealing portion pressurizing means (17) configured to be located at the sealing portion (23) of the pipe (2) when the sealing portion pressurizing means (3, 4) applies pressure to the pipe (2).

Description

Technical Field

[0001] The present invention relates to a method and apparatus for rapidly testing for leaks within a container such as a tube or other flexible container. This type of application is often used in the packaging industry, and the present invention is directed to detecting the integrity of seals at production speed in sealed packages containing perishable products in the form of cosmetics, chemicals or pharmaceuticals, toothpaste containers, or food products, etc. The configuration according to the present invention enables a high-speed in-line test of the quality of the seals on such packages and the airtightness 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 within the package after filling the product. The most common gases used in modified atmosphere packaging (MAP) are nitrogen, CO2 and oxygen or mixtures thereof. Oxygen is mainly used to keep fresh meat red or to control the ripening rate of fruits and vegetables, while nitrogen and CO2 are used to reduce the aging effect of oxygen and the aerobic growth of microorganisms in many products.

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

[0004] Leaks within the package due to manufacturing errors or subsequent damage result in at least a partial loss of the modified atmosphere and can shorten the predicted shelf life. A further drawback of leaks is that the product may leak from the package and contaminate the surroundings.

[0005] Common causes of leakage in plastic pipes are product residues or droplets deposited on the sealing surface before closing by welding. Therefore, it is common to test the sealability for leakage before the pipes are delivered. Various leakage test regulations have been presented and are also used in some cases to prevent leaking packages from reaching the store shelves.

[0006] A common limitation in many known methods is that it is not possible to perform a 100% test for leakage on individual packages at a full production line speed exceeding 30 packages per minute, i.e., having a cycle time of less than 2 seconds. This problem can be avoided by limiting the test to an offline spot test or by performing batch tests on an appropriate number of packages in the same test cycle.

[0007] One possible way to increase the test capacity is to provide a number of parallel test configurations, each operating at a lower speed but collectively matching the cycle time of the filling line.

[0008] Patent Document 1 discloses a leakage test method that can perform individual package tests "very quickly, typically in about 1 second", which shows a test capacity up to 60 packages per minute.

[0009] The method disclosed in Patent Document 1 uses diluted hydrogen as the tracer gas. Hydrogen and helium are commonly used as tracer gases for leakage tests. One problem with these gases is their relatively high diffusion rate through thin polymer films used as gas barriers in packaging materials and other packaging materials. When the tracer gas diffuses through the non-leaking walls of the package, there is a risk that the leakage test configuration will detect diffusion leakage, which is not a problem of the package integrity. This problem can be overcome if the time between gas filling and leakage test is short enough so that leakage detection is performed before the gas permeates the barrier material. This breakthrough time is on the order of seconds to minutes, depending on the materials and film thicknesses used.

[0010] Patent Document 1 uses a chamber in which packages are placed. Thereafter, the chamber is closed and a limited negative pressure is drawn. Patent Document 1 claims that this limited vacuum level can be achieved by a rapid and low-cost means as compared with the level used in the previous configuration for gas testing. The package needs to be held in the chamber for a dwell time ranging from 0.5 second to 60 seconds.

[0011] By performing these steps in parallel, it is possible to partially shorten the time required for some of these steps. For example, it is obvious that the loading of the next package can be performed in the same order as the unloading of the package that has just been tested. Another example of such optimization is to enable a part of the sensor recovery time to occur during the unloading / loading step.

[0012] However, even in the best implementation, additional time is required to reduce the pressure in the chamber and, above all, for the true sensor recovery. The sensor recovery time is often long and completely unpredictable. This poses a major constraint on the automation system in that the process cannot be run at a constant speed.

[0013] Therefore, the invention disclosed in Patent Document 1 cannot meet a production speed faster than 60 packages per minute required in today's industry. It is also doubtful whether a speed of 30 packages per second can be achieved.

[0014] Even if such a test system can detect small leaks in a tube or the like, it cannot detect the quality of the seal part. In these systems, a low pressure is applied to the wall of the tube so that the test gas used can escape if there is a leak in the seal part. However, such a system does not detect the quality of the seal part, that is, whether the seal part is strong enough for normal handling. For example, in a shopping basket where other goods are bearing against the tube, when a higher pressure is applied to the tube, it is important that the seal part remains tight and does not break. Therefore, it is advantageous to test the tube by applying a higher pressure to the wall of the tube.

[0015] Patent Document 2 discloses a method of applying an external pressure to a tubular package and detecting deformation of the welded seam of the tubular package. The deformation of the welded seam is detected by measuring the thickness of the seam. In one example, the thickness of the seam is measured at one point of the seam using a laser distance sensor. In this method, when there is a defect in the entire seam and it peels off, the defective seam can be detected. However, when there is a defect only on one side of the seam, the defective seam may not be detected. Furthermore, this method only detects defective welded seams. Other defects in the tubular package, such as defects in the wall material and defects in the end region between the package wall and the seam, are not detected. Furthermore, this method is said to take more than 10 seconds to perform a leak test and is therefore not suitable for in-line testing with a cycle time of less than 1 second.

[0016] In another known leakage system, the tube is pressed between two pressure members at a relatively high pressure of 8 bar or more. This test pressure is a pressure pre-set by the manufacturer or the customer. If the quality of the seal part and the tube is acceptable, the seal part and the tube can withstand this pressure. If there is a defect in the seal part or the tube, the seal part or the tube will burst and break, and the contents will leak from the tube. This will simultaneously contaminate the production line with the product and the production line must be stopped for cleaning. One way to detect that the contents have leaked from the tube is to use electrodes provided above the seal part and around the tube, where the contents close the circuit when they impinge on the electrodes.

[0017] Such a system detects a defective seal part or tube, but if a defective seal part or tube is detected, it requires the production line to be stopped. Therefore, there is room for improvement in the leakage detection system.

Prior Art Documents

Patent Documents

[0018]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0019] An object of the present invention is to provide an improved device for leakage detection. A further object is to provide an improved method for leakage detection.

Means for Solving the Problems

[0020] The solution to the problems according to the present invention is defined by the features of the independent claims regarding the leakage detection device and the leakage detection method. The other claims describe advantageous further developments of the leakage detection device and the leakage detection method.

[0021] An object of the present invention is a leakage detection device for detecting leakage in a seal portion of a pipe, the first pipe pressurizing means and the second pipe pressurizing means configured to apply a predetermined pressure to the pipe, and the pipe pressurizing means being configured to be located at the seal portion of the pipe before applying pressure to the pipe. The first seal portion pressurizing means and the second seal portion pressurizing means are provided, and the leakage detection device is configured to measure a signal indicating the pressure in the pipe when the first pipe pressurizing means and the second pipe pressurizing means apply the predetermined pressure to the pipe. The leakage detection device is achieved by including an electronic control unit configured to determine whether a pressure change has occurred in the pipe based on an input from the sensor means.

[0022] According to a first embodiment of the leakage detection device according to the present invention, there is provided a leakage detection device capable of detecting leakage in a seal portion of a pipe without leakage of a substance from the pipe. When there is a defect in the seal portion, the seal portion bursts due to the pressure applied to the pipe. By positioning the seal portion pressurizing means at the seal portion, the seal portion pressurizing means prevents the substance from jetting out of the pipe when there is a defect in the seal portion, otherwise the test device will be contaminated by the substance. When the leakage detection device is arranged as an in-line test device, it is not necessary to stop the entire production line for cleaning the test device. The leakage detection device can also detect defects in the pipe itself, for example, defects in the wall material of the pipe.

[0023] The first pipe pressurizing means and the second pipe pressurizing means are configured to apply a predetermined pressure to the pipe by displacing the first pipe pressurizing means and the second pipe pressurizing means toward each other when the pipe is located between the first pipe pressurizing means and the second pipe pressurizing means.

[0024] In one example, the seal portion pressing means is configured to press the seal portion such that the seal portion pressing means presses the seal portion before the pipe pressing means applies a predetermined pressure to the pipe. In this example, the seal portion pressing means is provided so as to press the outer portion or the upper portion of the seal portion, for example, the upper half of the seal portion. In this way, a part of the seal portion is not supported by the seal portion pressing means. The upper portion pressed by the seal portion pressing means is, for example, 30 to 60% of the seal portion. As a result, the lower portion of the seal portion, that is, the portion of the seal portion closest to the pipe remains unsupported. When there is a defect in the seal portion, when the pipe pressing means applies pressure to the side surface of the pipe, the lower portion of the seal portion opens. When the seal portion opens, a change in the pressure inside the pipe is detected, and when the pressure change is greater than a predetermined value, a failure signal indicating a defect in the seal portion or the pipe is issued. The pressure of the pipe pressing means is released, the pressure of the seal portion pressing means is released, and the pipe is discarded from the product flow. By releasing the pressure from the pipe pressing means before the seal portion pressing means is released, when the seal portion pressing means is released, no pressure is generated inside the pipe that would burst the remaining defective seal portion.

[0025] In another example, the seal portion pressing means is provided in proximity to the seal portion at a distance between 0.1 mm and 1 mm from the seal portion before the pipe pressing means applies a predetermined pressure to the pipe. In this example, the seal portion pressing means is provided at a small distance with respect to the seal portion. Due to this short distance, a part of the side surface of the seal portion abuts against the seal portion pressing means, and a small amount of air can escape from the pipe through the opened seal portion, enabling a defective seal portion to open somewhat. A further advantage of this method is that, for example, due to previous handling or an inappropriate seal portion process, there may be a possibility that a defective seal portion has already been partially opened before reaching the seal portion pressure test station. Even if such a defective seal portion is pressed by the seal portion pressing means, since only the seal portion pressing means holds the seal portion, no pressure change occurs. Also, by holding the seal portion pressing means slightly away from the seal portion, such a seal portion defect can also be detected. Thereby, the pressure inside the pipe changes. In this example, the seal portion pressing means may be provided over the entire seal portion or exceeding at least 60% of the seal portion. When the seal portion opens, the pressure change is detected by sensor means that measures a signal representing the pressure inside the pipe. At the same time, the small distance between the seal portion and the seal portion pressing means prevents a substance from jetting out of the pipe if there is a defect in the seal portion. When the seal portion opens, a pressure change inside the pipe is detected, and if the pressure change is greater than a predetermined value, a failure signal indicating a defect in the seal portion is issued. At the same time, the seal portion pressing means can be moved towards the seal portion to directly prevent a substance from leaking from the pipe and to release the pressure applied by the pipe pressing means. Next, the seal portion pressing means is withdrawn from the seal portion, and the pipe is discarded from the product flow.

[0026] The tube pressurizing means and the seal portion pressurizing means are configured, as an example, to move in a horizontal linear direction toward and away from the tube when the tube is upright, but other moving directions such as rotational movement are also possible. Also, it is possible to detect leakage of a tube placed on a conveyor belt, in which case the tube pressurizing means and the seal portion pressurizing means move in a direction perpendicular to the central axis of the tube. The movement has to be relatively fast and it is advantageous that the movement can be adjusted depending on the tube used, so electric moving means are preferred. An electric drive device equipped with a position sensor enables high-speed control and can be positioned at a predetermined position.

[0027] In one example, the predetermined pressure applied to the tube is between 1.5 and 4 bar.

[0028] In an embodiment, the first tube pressurizing means and the second tube pressurizing means are provided on a first drive belt driven by a first drive unit, and / or the first seal portion pressurizing means and the second seal portion pressurizing means are provided on a second drive belt driven by a second drive unit. The drive belts and the drive units enable efficient movement of the tube pressurizing means and / or the seal portion pressurizing means.

[0029] In an embodiment, 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.

[0030] In one example, the seal portion pressing means is provided on a first drive belt driven by a first rotary motor, and the tube pressing means is provided on a second drive belt driven by a second rotary motor. Each motor is controlled independently of the other motors. By arranging one seal portion pressing means on a first portion of the first drive belt and the other seal portion pressing means on a second portion of the first drive belt, the rotation of the motor moves the two seal portion pressing means towards or away from each other. In this way, the seal portion pressing means can apply pressure to the tube in less than 1 second, for example, in 0.1 to 0.2 seconds. The release of the seal portion pressing means is similarly rapid. The same applies to the tube pressing means.

[0031] In other embodiments, the first tube pressing means is provided on a linear actuator, the second tube pressing means is provided on a linear actuator, and / or the first seal portion pressing means is provided on a linear actuator, and the second seal portion pressing means is provided on a linear actuator.

[0032] In another example, the seal portion pressing means is provided on two linear actuators, and the tube pressing means is provided on two linear actuators. The linear actuators enable the two seal portion pressing means to move towards or away from each other in a short time. In this way, the seal portion pressing means can move towards the seal portion in less than 1 second, for example, in 0.1 to 0.2 seconds. The release of the tube pressing means is similarly rapid. The same applies to the tube pressing means.

[0033] In other embodiments, the first tube pressing means is provided on a pivotable bracket, the second tube pressing means is provided on a pivotable bracket, and / or the first seal portion pressing means is provided on a pivotable bracket, and the second seal portion pressing means is provided on a pivotable bracket.

[0034] In another example, the seal portion pressing means is provided on two pivotable brackets, and the tube pressing means is provided on two pivotable brackets. The pivotable brackets are preferably driven directly or via some type of transmission by an electric motor that enables the two seal portion pressing means to move towards or away from each other in a short time. In this way, the seal portion pressing means can move towards the seal portion in less than 1 second, for example, 0.1 to 0.2 seconds. The release of the tube pressing means is similarly rapid. The same applies to the tube pressing means.

[0035] In an embodiment, the sensor means is configured to measure the drive current to the first drive unit and / or the sensor means is configured to measure the drive current to the second drive unit. The drive current to the first drive unit measured by the sensor means may be used to provide a measurement signal indicating the pressure inside the tube when the tube pressing means applies a predetermined pressure to the tube. The electronic control unit determines whether a pressure change has occurred inside the tube based on the input from the sensor means, and the measured drive current to the first drive unit is used to estimate the pressure inside the tube.

[0036] In one example, the drive current to the first drive unit is continuously measured by the sensor means while the first tube pressing means and the second tube pressing means move from the idle position to the pressurizing position where a predetermined pressure is applied to the tube over a specific time, and then return to the idle position. If the drive current has not reached a predetermined value, the tube is considered to be faulty. If the drive current rapidly decreases during the movement of the first tube pressing means and the second tube pressing means to the pressurizing position or during a specific time at the pressurizing position, the tube is considered to be faulty. When a defective tube is detected, the first tube pressing means and the second tube pressing means can directly return to the idle position.

[0037] In an embodiment, the sensor means is configured to measure the movement of the first drive unit and / or the sensor means is configured to measure the movement of the second drive unit. In this way, the movement of the first drive unit measured by the sensor means can be used to provide a measurement signal indicating the pressure in the pipe when the pipe pressurizing means applies a predetermined pressure to the pipe. In one example, a predetermined pressure is applied to the pipe by the pipe pressurizing means, and the exact positions of the first pipe pressurizing means and the second pipe pressurizing means are detected. When the sealing part is correct, there is no change in the position of the pipe pressurizing means. When the sealing part is incorrect, the position of the pipe pressurizing means changes slightly, and this change in position is detected by the sensor means.

[0038] The present invention further relates to a method for detecting a leak in a sealing part of a pipe by means of a leak detection device. The leak detection device comprises a first pipe pressurizing means and a second pipe pressurizing means, a first sealing part pressurizing means and a second sealing part pressurizing means, and sensor means. This method includes the following steps. Position the pipe between the first pipe pressurizing means and the second pipe pressurizing means, position the sealing part between the first sealing part pressurizing means and the second sealing part pressurizing means, apply a predetermined pressure to the pipe by the first pipe pressurizing means and the second pipe pressurizing means, measure a signal indicating the pressure in the pipe by the sensor means when the first pipe pressurizing means and the second pipe pressurizing means apply the predetermined pressure to the pipe, and determine whether a pressure change has occurred in the pipe by an electronic control unit based on an input from the sensor means.

[0039] In one embodiment, the method further includes the step of applying a predetermined pressure to the pipe by displacing the first pipe pressurizing means and the second pipe pressurizing means towards each other.

[0040] In one embodiment, the method further includes the step of emitting a fault signal when a pressure change is determined by the electronic control unit.

[0041] In one embodiment, the method further includes positioning the first seal portion pressing means and the second seal portion pressing means so that they contact the seal portion of the pipe.

[0042] In one embodiment, the method further includes positioning the first seal portion pressing means and the second seal portion pressing means at a distance of 0.1 to 1.0 mm from the seal portion of the pipe.

[0043] In one embodiment, the method further includes applying a predetermined pressure to the pipe in the range of 1.5 to 4 bar.

[0044] In one example, a method for detecting leakage of a flexible pipe having a welded seal portion, the method including the steps of disposing seal portion pressing means on the seal portion of the pipe, applying a predetermined pressure to the pipe using pipe pressurizing means, measuring a signal indicating the pressure inside the pipe using sensor means, determining whether there is a pressure change inside the pipe using a control unit after the predetermined pressure has been applied to the pipe, and emitting a fault signal if a pressure change is detected.

[0045] According to the method of the present invention, it is possible to detect leakage of a pipe having a welded seal portion without completely destroying the seal portion, and prevent substances from the pipe from jetting out of the pipe and contaminating the surroundings of the pipe. In this way, the individual seal portions of the pipe can be tested in the normal manufacturing flow, and pipes having defective seal portions can be immediately discarded by directly stopping the manufacturing flow or stopping the manufacturing flow without cleaning the test apparatus.

Brief Description of the Drawings

[0046]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0047] The present invention will be described in more detail below with reference to the embodiments shown in the accompanying drawings.

[0048] Embodiments of the present invention with further developments described below should be regarded as merely examples and should in no way limit the scope of protection provided by the claims.

[0049] FIG. 1 shows a diagram of the leak detection device, FIGS. 2 to 4 show the details of the leak detection device, and FIG. 5 shows a flowchart of the leak detection method. The leak detection device 1 according to the present invention includes a first tube pressurizing means 3 and a second tube pressurizing means 4 provided to apply pressure to the tube 2. The pressure can be applied at any position of the tube, but in the illustrated example, the pressure is applied to the upper half of the tube. By applying pressure to the tube near the seal portion, a compact leak detection device that does not impede the flow of the tube becomes possible. The first tube pressurizing means 3 includes a first pressurizing pad 5, and the second tube pressurizing means 4 includes a second pressurizing pad 6. The pressurizing pad has a smooth surface and shape so as to apply pressure to the tube without damaging the tube surface. In the illustrated example, the pressurizing pad is a semi-circular pad made of a rigid material that does not bend when pressure is applied to the tube, but other shapes are also possible. The material can be plastic, rubber, or metal.

[0050] The first pressurizing pad 5 is attached to a first holding bracket 7, and the second pressurizing pad 6 is attached to a second holding bracket 8. Since the holding bracket is attached to the tube pressurizing means in a removable manner, the pressurizing pad can be easily replaced or exchanged, and the pressurizing pad can be exchanged to fit the size of the tube to be used.

[0051] In the illustrated example, each tube pressurizing means includes a locking mechanism that releases the holding bracket of the pressure pad when the tube pressurizing means is positioned at the release position. The locking mechanism includes a pivotable bracket 9 having a locking nose 10 provided on a side portion of the holding bracket, and an adjustable bearing member 11 that abuts against an end stop 12 at the release position. In the release position, the pivotable bracket pivots such that the locking nose releases the holding bracket and the pressure pad can be removed. The holding bracket can include a magnet that holds the holding bracket in a predetermined position when the tube pressurizing means is at the release position. A spring holds the locking mechanism in the locked position.

[0052] The first and second tube pressurizing means include an idle position 14 and a pressurizing position 13. In the idle position 14, the distance between the pressure pads is greater than the width of the tube, and the tube can be positioned between the pressure pads without interfering with the pressure pads. In the pressurizing position 13, the pressure pads apply a predetermined pressure to the tube, increasing the pressure inside the tube. The pressure is applied perpendicular to the central axis 15 of the tube 2. The applied pressure must be high enough to detect a welding defect or a defect inside the tube. An appropriate pressure is, for example, 1.5 to 4 bar, or 2 to 3 bar, depending on the size of the tube. Since it is the detected pressure change that indicates whether there is a defect in the welding, the exact applied pressure is not important. However, if the pressure is too low, the seal portion cannot be sufficiently tested, and a defective weld portion will be further deformed.

[0053] In addition, the leakage detection device includes a first seal portion pressing means 16 and a second seal portion pressing means 17. The first seal portion pressing means is attached to the first arm 18, and the second seal portion pressing means is attached to the second arm 19. Each seal portion pressing means can be provided with a somewhat elastic surface such as soft plastic or rubber so that the welded portion is not damaged when the seal portion pressing means presses the welded portion. The seal portion pressing means is provided with a seal bearing position 20, a seal portion pressing position 21, and a seal portion idle position 22. At the seal bearing position, the seal portion pressing means is in contact with the welded portion with a low force. At the seal portion pressing position, the seal portion pressing means is positioned close to the welded portion at a short distance. At the seal portion idle position, the seal portion pressing means are positioned apart from each other so that the pipe can be positioned between the seal portion pressing means without interfering with the seal portion pressing means.

[0054] In the first example shown in FIG. 3, the first and second seal portion pressing means 16, 17 are positioned at the seal bearing position 20 so as to contact the seal portion 23 of the pipe 2. In this example, the seal portion pressing means contacts the upper half of the seal portion so that at least 40% of the seal portion is free. When the seal portion pressing means contacts the seal portion, the first and second pipe pressing means 3, 4 are positioned at the pressing position 13 of the pipe and press the pipe. When the pressure pad contacts the pipe, the sensor means measures a signal indicating the pressure inside the pipe, and the electronic control unit (ECU) 36 is used to determine whether there is a pressure change inside the pipe based on the measured signal. In one example, a signal indicating the pressure inside the pipe or the pressure applied to the pipe is measured. The estimated pressure value can be determined, for example, by measuring the force applied to the pipe, by measuring the drive current used to apply force to the pipe, or by measuring the position of the drive unit. The system measures several values representing the pressure inside the pipe and uses two or more values to determine whether there is a pressure change inside the pipe.

[0055] In one example, a first value is measured and compared to a second value. If the difference between the first value and the second value is greater than a predetermined amount, a pressure change is determined to have occurred. In another example, several values are measured and the slope of a curve is used to determine if a pressure change has occurred. If the slope is steeper than a predetermined value, a pressure change is determined to have occurred.

[0056] If the seal part is correct, the pressure inside the pipe remains the same and the ECU determines that no pressure change has occurred. In this case, the seal part of the pipe is approved. The pipe pressurizing means is moved to the idle position of the pipe, the seal part pressurizing means is moved to the seal part idle position, the pipe is sent to the flow of the pipe, and a new pipe is positioned for the leak test.

[0057] If the seal part is incomplete, the lower half of the seal part bursts open, which slightly reduces the pressure inside the pipe because the total internal volume of the pipe increases somewhat. This pressure change is detected by the ECU and the pipe is not approved. The pipe pressurizing means is moved to the idle position of the pipe, and then the seal part pressurizing means is moved to the seal part idle position, and the pipe is discarded from the flow of the pipe. By applying pressure to the seal part during the leak test, the entire seal part does not burst open and the substance inside the pipe is prevented from jetting out.

[0058] In the second example shown in FIG. 4, the first and second seal portion pressing means 16, 17 are positioned at the seal portion pressing position 21. In this example, the seal portion pressing means does not contact the seal portion and is positioned close to the seal portion at a distance of 0.1 to 1.0 mm from the seal portion 23 of the pipe 2. In this example, the seal portion pressing means may be provided at the same height as the seal portion so as to cover most of the seal portion or the entire seal portion. When the seal portion pressing means is located at the seal portion pressing position 21, the first and second pipe pressing means 3, 4 are located at the pipe pressing position 13 and are pressing the pipe. When the pressure pad contacts the pipe, the initial pressure inside the pipe is estimated and may be used as the default pressure value. The system measures at least one next value representing the pressure inside the pipe to determine whether there is a pressure change inside the pipe.

[0059] If the seal portion is correct, the pressure inside the pipe remains the same and the ECU does not detect a change in pressure. In this case, the seal portion of the pipe is approved. The pipe pressing means is moved to the idle position of the pipe, the seal portion pressing means is moved to the idle position of the seal portion, the pipe is sent to the flow of the pipe, and a new pipe is positioned for the leak test.

[0060] If there is a defect in the seal part, a part of the seal part opens, and as a result, some air may escape from the seal part, causing the pressure inside the pipe to drop. Since the seal part pressurizing means is positioned close to the seal part, the seal part does not burst completely. Instead, a small opening is formed, from which the pressure may slowly escape, but it prevents the substance inside the pipe from escaping. When the opening releases a part of the gas inside the pipe, the pressure decreases slightly. This pressure change is detected by the ECU, a fault signal is issued, and the pipe is not approved. At the same time, the seal part pressurizing means is preferably moved towards the seal part to directly prevent the substance from escaping from the pipe, and the pipe pressurizing means is moved to the idle position of the pipe to release the pressure applied to the pipe. Then, the seal part pressurizing means is moved to the idle position of the seal part, and the pipe is discarded from the flow of the pipe. By slightly opening the seal part so that a small amount of gas inside the pipe can escape, the entire seal part does not burst open, preventing the substance inside the pipe from jetting out. If the seal part is very defective, for example, if the seal part is partially open before arriving at the seal part pressure test station, the defective seal part can also be detected by this method. For such a defective seal part, even if the seal part is directly pressed by the seal part pressurizing means, since only the seal part pressurizing means holds the seal part, the pressure change is not detected. By allowing some air to escape from the pipe when pressure is applied to the pipe, such defective seal parts can also be detected and discarded.

[0061] In one example, the first and second tube pressurizing means 3, 4 are provided on a first drive belt 24 driven by a first drive unit 30. The first drive unit includes a first motor 32 and a first transmission 33. The drive belt preferably has teeth so that the belt does not slip on the drive wheel. The first drive belt runs between a drive wheel driven by the first motor via the first transmission and an idle wheel provided on the second transmission. The first tube pressurizing means 3 is provided on a first portion 25 of the first drive belt provided in the front region in the illustrated example, and the second tube pressurizing means 4 is provided on a second portion 26 of the first drive belt provided in the rear region in the illustrated example. In this way, when the drive motor rotates, the tube pressurizing means moves in the opposite direction. When the first drive motor rotates in one direction, both tube pressurizing means move inward toward the pressurizing position 13 of the tube. When the first drive motor rotates in the other direction, both tube pressurizing means move outward toward the idle position 14 of the tube or the release position of the tube.

[0062] The first and second seal portion pressing means 16, 17 are provided on a second drive belt 27 driven by a second drive unit 31. The second drive unit includes a second motor 34 and a second transmission 35. The drive belt preferably has teeth so that the belt does not slip on the drive wheel. The second drive belt runs between a drive wheel driven by the second motor via the second transmission and an idler wheel provided on the first transmission. The first seal portion pressing means 16 is provided on a first portion 28 of the second drive belt provided in the front region in the illustrated example, and the second seal portion pressing means 17 is provided on a second portion 29 of the second drive belt provided in the rear region in the illustrated example. In this way, when the drive motor rotates, the seal portion pressing means moves in the opposite direction. When the second drive motor rotates in one direction, both seal portion pressing means move inward toward the seal portion support position 20 or the seal portion pressing position 21. When the second drive motor rotates in the other direction, both seal portion pressing means move outward toward the seal portion idle position 22.

[0063] The first and second tube pressing means and the first and second seal portion pressing means may be moved in other ways. In one example, each pressing means is provided on an individual linear actuator. In another example, each pressing means is provided on a pivotable bracket provided on an individual rotating shaft driven by a motor. Other ways of moving the pressing means between the seal portion support position or the seal portion pressing position and the seal portion idle position are also possible.

[0064] The drive motor can be provided with some kind of position detection means, such as an optical rotation sensor, for detecting the rotational position of the motor and thus the position of the pressing means. It is also possible to use a linear position sensor or other types of position detection means to provide a feedback signal to the first and second drive units. It is also possible to measure the drive current to the drive unit to estimate the pressure inside the tube.

[0065] Signals indicating the pressure inside the tube can be measured in several different ways. In one example, a predetermined pressure is applied to the tube by tube pressurizing means, and the exact positions of the first and second tube pressurizing means are detected. When the seal part is correct, there is no change in the position of the tube pressurizing means. When the seal part is incorrect, the position of the tube pressurizing means changes slightly, and this change in position is detected by the detection means. The position sensor may be, for example, a rotation sensor provided in a drive motor, or may be a linear position sensor such as an optical linear sensor, for example.

[0066] In one example, when the pressure inside the tube changes, the motor drive current used to hold the tube pressurizing means in a predetermined position changes. The drive current applied to the motor can be measured, the change in the motor current can be detected, and it indicates the change in the pressure inside the tube. In another example, the rotational position of the motor is measured, and the change in the rotational position indicating the change in the pressure inside the tube is detected.

[0067] It is important that the detection of the pressure change inside the tube is rapid. In one example, the throughput of the system is 100 tubes per minute, which gives a tube cycle time of 0.6 seconds. Therefore, it takes 0.1 - 0.2 seconds to position the seal part pressurizing means and apply pressure to the tube by the tube pressurizing means, 0.2 - 0.4 seconds to determine the pressure change, and 0.1 - 0.2 seconds to release the seal part pressurizing means and the tube pressurizing means. If there is a defect in the seal part, the tube is discarded from the flow of the tubes.

[0068] The determination of the pressure change is performed by an electronic control unit (ECU: electronic control unit) that controls the movement of the tube pressurizing means and the seal part pressurizing means and receives measurement values from sensor means that measures a signal representing the pressure inside the tube.

[0069] In the method of the present invention for detecting leakage of a flexible tube having a welded seal part, the leakage detection device can detect a defective seal part without contaminating the manufacturing apparatus, such as a tube filling machine, or surrounding components with substances from the tube.

[0070] In step 100, the seal portion pressing means is positioned at the seal portion of the tube and is in contact with the seal portion or supported at a slight distance from the seal portion. The seal portion pressing means may be positioned so as to cover the entire seal portion or may be positioned so as to cover the upper portion of the seal portion.

[0071] In step 110, a predetermined pressure is applied to the tube by the tube pressing means. The predetermined pressure is high enough to break a defective seal portion and may be, for example, 1.5 to 4 bar.

[0072] In step 120, a signal indicating the pressure inside the tube is measured by the sensor means. The signal can be measured in various ways, for example, by measuring the motor drive current of the tube pressing means or by measuring the rotational position of the motor of the tube pressing means.

[0073] In step 130, after the predetermined pressure is applied to the tube, it is determined whether there is a pressure change inside the tube. The determination of the pressure change is made by the ECU based on the measured signal.

[0074] If no pressure change is determined, the tube is released and the method continues with a new tube in step 100.

[0075] In step 140, if a pressure change inside the tube is determined, a failure signal is issued. The pressure change inside the tube indicates a defective seal portion or a defective tube. The failure signal can be used to control a device that discards the defective tube from the tube flow. Also, the failure signal may be used to stop the tube filling system and signal the operator of the tube filling system. After the defective tube is discarded or after the tube filling system is restarted, the method can proceed to step 100.

[0076] The present invention should not be regarded as limited to the above-described embodiments, and many additional variations and modifications are possible within the scope of the following claims.

Explanation of Symbols

[0077] 1: Leak detection device 2: Pipe 3: First pipe pressurizing means 4: Second pipe pressurizing means 5: First pressure pad 6: Second pressure pad 7: First holding bracket 8: Second holding bracket 9: Pivotable bracket 10: Lock nose 11: Support member 12: End stop 13: Pressurizing position 14: Idle position 15: Central axis 16: First seal portion pressurizing means 17: Second seal portion pressurizing means 18: First arm 19: Second arm 20: Seal portion support position 21: Seal portion pressurizing position 22: Seal portion idle position 23: Seal portion 24: First drive belt 25: First portion of the first drive belt 26: Second portion of the first drive belt 27: Second drive belt 28: First portion of the second drive belt 29: Second portion of the second drive belt 30: First drive unit 31: Second drive unit 32: First motor 33: First transmission 34: Second motor 35: Second transmission 36: Electronic control unit

Claims

1. A leakage detection device (1) for detecting leakage in a seal portion (23) of a pipe (2), comprising a first pipe pressurizing means (3) and a second pipe pressurizing means (4) configured to apply a predetermined pressure to the pipe (2), and a first seal portion pressurizing means (16) and a second seal portion pressurizing means (17) configured to be positioned at the seal portion (23) of the pipe (2) before the first pipe pressurizing means (3) and the second pipe pressurizing means (4) apply the predetermined pressure to the pipe (2). The leakage detection device (1) includes sensor means configured to measure a signal indicating the pressure inside the pipe (2) when the first pipe pressurizing means (3) and the second pipe pressurizing means (4) apply the predetermined pressure to the pipe (2), and an electronic control unit (36) configured to determine whether a pressure change has occurred inside the pipe (2) based on an input from the sensor means. A leakage detection device characterized by the above.

2. The leakage detection device (1) according to Claim 1, wherein the first pipe pressurizing means (3) and the second pipe pressurizing means (4) are configured to apply the predetermined pressure to the pipe (2) by displacing the first pipe pressurizing means (3) and the second pipe pressurizing means (4) toward each other when the pipe (2) is positioned between the first pipe pressurizing means (3) and the second pipe pressurizing means (4).

3. The leakage detection device (1) according to Claim 1 or 2, wherein the first seal portion pressurizing means (16) and the second seal portion pressurizing means (17) are configured to contact the seal portion (23) before the first pipe pressurizing means (3) and the second pipe pressurizing means (4) apply the predetermined pressure to the pipe (2).

4. The leakage detection device (1) according to Claim 3, wherein the first seal portion pressurizing means (16) and the second seal portion pressurizing means (17) are provided to contact an outer portion of the seal portion (23) before the first pipe pressurizing means (3) and the second pipe pressurizing means (4) apply the predetermined pressure to the pipe (2).

5. The leakage detection device (1) according to Claim 1 or 2, wherein The leakage detection device is configured such that the first seal portion pressing means (16) and the second seal portion pressing means (17) are positioned at a distance of 0.1 mm to 1.0 mm from the seal portion (23) before the first pipe pressing means (3) and the second pipe pressing means (4) apply the predetermined pressure to the pipe (2).

6. The leakage detection device (1) according to any one of Claims 1 to 5, wherein the predetermined pressure applied to the pipe (2) is 1.5 to 4 bar, the leakage detection device.

7. The leakage detection device (1) according to any one of Claims 1 to 6, wherein the first pipe pressing means (3) and the second pipe pressing means (4) are provided on a first drive belt (24) driven by a first drive unit (30), the leakage detection device.

8. The leakage detection device (1) according to Claim 7, wherein the first drive unit (30) includes a first motor (32) and a first transmission (33), the leakage detection device.

9. The leakage detection device (1) according to Claim 7 or 8, wherein the sensor means is configured to measure a drive current to the first drive unit (30), the leakage detection device.

10. The leakage detection device (1) according to Claim 7 or 8, wherein the sensor means is configured to measure the movement of the first drive unit (30), the leakage detection device.

11. The leakage detection device (1) according to any one of Claims 1 to 6, wherein the first pipe pressing means (3) is provided on a linear actuator, and the second pipe pressing means (4) is provided on a linear actuator or wherein the first pipe pressing means (3) is provided on a pivotable bracket, and the second pipe pressing means (4) is provided on a pivotable bracket, the leakage detection device.

12. The leakage detection device (1) according to any one of Claims 1 to 11, wherein the first seal portion pressing means (16) and the second seal portion pressing means (17) are provided on a second drive belt (27) driven by a second drive unit (31), the leakage detection device.

13. The leakage detection device (1) according to Claim 12, wherein the second drive unit (31) includes a second motor (34) and a second transmission (35), the leakage detection device.

14. The leak detection device (1) according to claim 12 or 13, wherein the sensor means is configured to measure a drive current to the second drive unit (31), the leak detection device.

15. The leak detection device (1) according to claim 12 or 13, wherein the sensor means is configured to measure the movement of the second drive unit (31), the leak detection device.

16. The leak detection device (1) according to any one of claims 1 to 11, wherein the first seal portion pressing means (16) is provided on a linear actuator, and the second seal portion pressing means (17) is provided on a linear actuator or the first seal portion pressing means (16) is provided on a pivotable bracket, and the second seal portion pressing means (17) is provided on a pivotable bracket, the leak detection device.

17. A method for detecting a leak in a seal portion (23) of a pipe (2) by a leak detection device (1), wherein the leak detection device (1) includes a first pipe pressurizing means (3) and a second pipe pressurizing means (4), a first seal portion pressurizing means (16) and a second seal portion pressurizing means (17), and sensor means, and the method includes positioning the pipe (2) between the first pipe pressurizing means (3) and the second pipe pressurizing means (4), and positioning the seal portion (23) between the first seal portion pressurizing means (16) and the second seal portion pressurizing means (17); applying a predetermined pressure to the pipe (2) by the first pipe pressurizing means (3) and the second pipe pressurizing means (4); measuring, by the sensor means, a signal indicating the pressure in the pipe (2) when the first pipe pressurizing means (3) and the second pipe pressurizing means (4) apply the predetermined pressure to the pipe (2); determining, by an electronic control unit (36) based on an input from the sensor means, whether a pressure change has occurred in the pipe (2).

18. The method according to claim 17, wherein the method further includes applying the predetermined pressure to the pipe (2) by displacing the first pipe pressurizing means (3) and the second pipe pressurizing means (4) toward each other.

19. The method according to claim 17 or 18, wherein A method further comprising the step of emitting a fault signal when a pressure change is determined by the electronic control unit (36).

20. The method according to any one of claims 17 to 19, further comprising the step of positioning the first seal portion pressurizing means (16) and the second seal portion pressurizing means (17) so as to contact the seal portion (23) of the pipe (2).

21. The method according to any one of claims 17 to 19, further comprising the step of positioning the first seal portion pressurizing means (16) and the second seal portion pressurizing means (17) at a distance of 0.1 to 1.0 mm from the seal portion (23) of the pipe (2).

22. The method according to any one of claims 17 to 21, further comprising the step of applying the predetermined pressure to the pipe (2) in the range of 1.5 to 4 bar.

23. The method according to any one of claims 17 to 22, wherein the first pipe pressurizing means (3) and the second pipe pressurizing means (4) are provided on a first drive belt (24) driven by a first drive unit (30), a step of measuring a drive current to the first drive unit (30) by the sensor means when the first pipe pressurizing means (3) and the second pipe pressurizing means (4) apply the predetermined pressure to the pipe (2), wherein the measured drive current indicates the pressure in the pipe (2), or a step of measuring the movement of the first drive unit (30) by the sensor means when the first pipe pressurizing means (3) and the second pipe pressurizing means (4) apply the predetermined pressure to the pipe (2), wherein the measured movement indicates the pressure in the pipe (2), the method comprising.

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

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