Air leak test apparatus and method

Abstract

To provide a new type of air leak test apparatus.SOLUTION: An air leak test apparatus comprises a pressure source 1, a main passage 2 connected to the pressure source 1, a work capsule 10 connected to a distal end of the main passage 2, a supply valve 20 provided in the main passage 2, an absolute pressure sensor 30 connected to the main passage 2, and a controller 50. In a large-leak inspection process, the supply valve 20 is opened to supply pressure from the pressure source 1 to the work capsule 10. When pressure inside the work capsule 10 detected by the absolute pressure sensor 30 reaches a test pressure by a set time elapse time point tx from a pressure supply start time point, it is determined that there is no large leak in an inspection target 100. When the pressure does not reach the test pressure by the set time elapse time point tx, it is determined that there is a large leak in the inspection target. Following this large-leak inspection process, a small-leak inspection is performed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a new type of air leak test device and method. [Background technology]

[0002] Air leak test equipment that applies test pressure to a hollow product (test object) is known as a device for evaluating the airtightness of the product. Here, we will explain the case where the test pressure is positive for a product without a pressurized port (hereinafter referred to as a sealed product). If the test object has a minute defect such as a pinhole, compressed air will gradually enter the test object over time. This will be referred to as a small leak below. If the test object has a large defect, compressed air will enter the test object in a short period of time. This will be referred to as a large leak below. If the test pressure is negative, the flow of air through the defect will be reversed.

[0003] Air leak test equipment for sealed products is generally equipped with a tank and is capable of detecting both small and large leaks from the test object. There are two types of test methods: Method 1, in which a small leak test is performed after a large leak test, and Method 2, in which a small leak test is performed after a large leak test. Patent Document 1 discloses an air leak test device that allows the user to select which of the two methods to perform, and also describes the advantages and disadvantages of the two methods. A brief explanation will be given below.

[0004] In the first method, pressure from a pressure source is supplied to a tank of known volume in advance to accumulate pressure, and then the tank pressure is released to the closed main circuit at atmospheric pressure, and the pressure in the main circuit is detected, and the presence or absence of a large leak in the test object connected to the main circuit is determined based on this detected pressure.In this case, the subsequent small leak test is performed using a test pressure that is intermediate between the pressure from the pressure source and atmospheric pressure, so the test accuracy cannot be high.

[0005] In the second method, the pressure from the pressure source is used as the test pressure in the small leak test, which improves the accuracy of the small leak test. However, this reduces the accuracy of the subsequent large leak test, because leakage from the test object during the small leak test affects the large leak test. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-117103 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, in the method of testing for large leaks using a tank, it is not possible to accurately determine whether or not a large leak has occurred in a test object that has variations in volume due to manufacturing errors or the like. Furthermore, when a large leak test and a small leak test are performed, it is not possible to perform both tests with high accuracy. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides an air leak test device comprising a pressure source, a main passage connected to a base end of the pressure source and to a terminal end of the main passage to which an object to be tested or a work capsule for sealing the object to be tested is connected, valve means provided in the main passage for controlling communication between the pressure source and the object to be tested or the work capsule, pressure detection means connected to a passage portion in the main passage between the valve means and the object to be tested or the work capsule and for detecting the pressure inside the object to be tested or the work capsule, and control and calculation means, The control and calculation means executes a large leak inspection process, in which the valve means is opened to supply pressure from the pressure source to the inspection object or work capsule, and when the pressure detected by the pressure detection means reaches a test pressure within a set time from the start of pressure supply, it is determined that there is no large leak in the inspection object, and when the test pressure is not reached within the set time, it is determined that there is a large leak in the inspection object. According to this configuration, the pressure from the pressure source is used to perform the large leak test based on the time it takes for the test object or work capsule to reach the test pressure, so that even if there is variation in the volume of the test object, it is possible to determine with high accuracy whether or not there is a large leak.

[0009] The main circuit may be provided with an orifice to limit the flow rate of air. With this configuration, even if the variation in the volume of the test object is relatively small, the time axis for reaching the test pressure can be extended, thereby maintaining high accuracy in determining whether or not there is a large leak.

[0010] Preferably, following the large leak inspection process, the control and calculation means executes a small leak inspection process for at least the test object determined to have no large leak, and in the small leak inspection process, closes the valve means, and determines that there is no small leak when the change in pressure over time within the test object or work capsule detected by the pressure detection means is smaller than a threshold value, and determines that there is a small leak when it is greater than the threshold value. According to this configuration, the small leak test is performed using the test pressure after the large leak test or a pressure close to the test pressure, so that the presence or absence of a small leak can be determined with high accuracy.

[0011] In one embodiment, even when the control / calculation means determines that there is a large leak in the test object, it executes an inspection process similar to the small leak inspection process, and if the change in pressure over time in the test object or work capsule detected by the pressure detection means in this inspection process is greater than a threshold value, it determines that there is a medium leak.

[0012] In one embodiment, the pressure detection means comprises an absolute pressure sensor, and the control and calculation means, in the large leak inspection process, determines whether the detected pressure from the absolute pressure sensor has reached a test pressure by the time the set time has elapsed, and in the small leak inspection process, compares the change in the detected pressure from the absolute pressure sensor over time with the threshold value. According to this configuration, the absolute pressure sensor is used for both large leak testing and small leak testing, so that a simple circuit configuration can be achieved.

[0013] In another embodiment, the pressure detection means includes an absolute pressure sensor and a differential pressure sensor, one port of the differential pressure sensor is connected to the test object or work capsule via the main passage, and the other port is connected to a pressure accumulation means that accumulates the test pressure from the main passage, and the control / calculation means determines whether the detected pressure from the absolute pressure sensor has reached the test pressure by the time the set time has elapsed in the large leak inspection process, and compares the detected differential pressure from the differential pressure sensor with the threshold value in the small leak inspection process. According to this configuration, since a differential pressure sensor is used in the small leak test, the accuracy of the small leak test can be further improved.

[0014] In one embodiment, the test object has a flexible package enclosing contents, the test object is contained in a work capsule, and the pressure source is a negative pressure source.

[0015] In another aspect of the present invention, in an air leak test method, a large leak inspection process is carried out using an air leak test device that includes a pressure source, a main passage having a base end connected to the pressure source and a terminal end connected to an object to be inspected or a work capsule that seals the object to be inspected, a valve means provided in the main passage for controlling communication between the pressure source and the object to be inspected or the work capsule, and a pressure detection means connected to a passage portion in the main passage between the valve means and the object to be inspected or the work capsule and detecting the pressure inside the object to be inspected or the work capsule, and in the large leak inspection process, the valve means is opened to supply pressure from the pressure source to the object to be inspected or the work capsule, and if the pressure detected by the pressure detection means reaches a test pressure within a set time from the start of pressure supply, it is determined that there is no large leak in the object to be inspected, and if the test pressure is not reached within the set time, it is determined that there is a large leak in the object to be inspected. [Effects of the Invention]

[0016] According to the present invention, even if the test objects have variations in volume, it is possible to determine with high accuracy whether or not there is a large leak in the test objects. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a circuit diagram of an air leak test device according to a first embodiment of the present invention. [Figure 2] 10 is a graph showing pressure changes inside the work capsule during a large leak inspection process and a small leak inspection process performed by the air leak test device. [Figure 3] FIG. 4 is a circuit diagram of an air leak test device according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a circuit diagram of an air leak test device according to a third embodiment of the present invention. [Figure 5] FIG. 10 is a circuit diagram of an air leak test device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] <Air leak test device configuration> An air leak test device according to a first embodiment of the present invention will be described below with reference to Fig. 1. The air leak test device includes a pressure source 1, a main passage 2 having a base end 2a connected to the pressure source 1, a work capsule 10 connected to an end 2b of the main passage 2, a supply valve 20 (valve means) provided in the main passage 2, an absolute pressure sensor 30 (pressure detection means) connected in the main passage 2 between the supply valve 20 and the work capsule 10 (end 2b of the main passage 2), a pressure release valve 40 connected in the main passage 2 between the supply valve 20 and the work capsule 10, and a controller 50 (control and calculation means).

[0019] The work capsule 10 includes a container-shaped capsule body 11 that is open at the top and accommodates the inspection object 100, and a lid 12. The capsule body 11 is movable between a carry-in / carry-out position (not shown) and an inspection position below the lid 12. When the capsule body 11 is in the inspection position, the capsule body 11 and the lid 12 are clamped by a clamping mechanism, and the inspection object 100 is sealed in the accommodation space 13.

[0020] The controller 50 controls the work capsule 10 , the supply valve 20 , and the shutoff valve 40 , and determines whether or not the test object 100 is leaking based on the detected pressure from the absolute pressure sensor 30 .

[0021] In this embodiment, the inspection object 100 is, for example, a bag 102 (flexible packaging) having a content 101, such as bread, sealed therein. The volume of the bag 102 varies due to manufacturing errors, etc. When the inspection object 100 includes the flexible bag 102, a negative pressure source including a vacuum pump is used as the pressure source 1.

[0022] <Large leak inspection process> The controller 50 executes the large leak inspection process described below in a state where the work capsule 20 in which the inspection object 100 is sealed is connected to the end 2b of the main passage 2. In the initial state, the supply valve 20 is closed and the pressure release valve 40 is open, so that the work capsule 10 and the main passage 2 communicating with this work capsule 10 are at atmospheric pressure. From this state, the pressure release valve 40 is closed, and then the supply valve 20 is opened. When the supply valve 20 is opened, negative pressure from the pressure source 1 is supplied to the main passage 2 and the work capsule 10. That is, the air inside the main passage 2 and the work capsule 10 is vacuum-sucked. The internal passage of the supply valve 20 is narrow and serves to limit the amount of air flow to a certain level.

[0023] In FIG. 2, the pressure changes in the work capsule 10 from the pressure supply start time t0 for three test objects 100 are shown by curves A, B, and C. The controller 50 reads the detected pressure of the absolute pressure sensor 30 over a time period from t1 to t2 after the pressure supply start time (time t0) and detects the elapsed time until the test pressure is reached. The test objects 100 shown by curves A and B reach the test pressure earlier than the set time tx from the pressure supply start time t0, and in this case, it is determined that the test object 100 does not have a large leak (i.e., it is a non-defective product with no leaks or only a small leak). The test object 100 shown by curve C is delayed in reaching the test pressure and does not reach the test pressure even after the set time tx has passed. In this case, it is determined that the test object 100 has a large leak.

[0024] The principle of the large leak detection will now be explained. The air in the bag 102 is sealed, and if there are no defects, the air in the bag 102 does not leak into the work capsule 10. Therefore, the air in the work capsule 10 and the main passage 2 is vacuum-suctioned normally, and the test pressure is reached approximately at the scheduled time. In contrast, if there is a large defect in the bag 102, the air in the bag 102 leaks into the work capsule 10, and the amount of air suctioned by the negative pressure source 1 increases accordingly, so it takes longer to reach the test pressure. Note that if there is only a small defect in the bag 100, there will be only a small amount of air leaking from the bag 102 to the work capsule 10, and the test pressure will be reached in approximately the same time as a non-defective product without a leak, making it difficult to distinguish. Detection of such small defects in the inspection object 100 is left to the small leak inspection process described below.

[0025] The volume of the bag 102 varies within an allowable range due to manufacturing errors, etc. Therefore, even for non-defective products without leakage, a non-defective product with a large volume of the bag 102 will change as shown by curve A in Figure 2 and reach the test pressure sooner. On the other hand, a non-defective product with a small volume of the bag 102 will change as shown by curve B and reach the test pressure later. The set time elapsed point tx is set to be slightly beyond the point at which a non-defective product within the allowable range will reach the test pressure latest.

[0026] <Small leak inspection process> After the large leak inspection process is completed, the process moves to the small leak inspection process. That is, for the inspection object 100 that has reached the test pressure by the set time tx, as shown by curves A and B in Figure 2, the supply valve 20 is closed at or immediately after the time ta and tb at which the test pressure is reached, respectively, to isolate the work capsule 10 and the main passage 2 (the passage between the supply valve 20 and the work capsule 10) from the pressure source 1, and the change in the detected pressure from the absolute pressure sensor 30 over time (shown schematically by a dashed line in Figure 2) is compared with a threshold value. Specifically, the difference between the detected pressure a certain time after isolation and the test pressure (or the detected pressure immediately after isolation of the main passage) is compared with the threshold value. If the difference is smaller than the threshold value, the product is determined to be non-defective with no small leaks, and if it is greater than the threshold value, it is determined to have a small leak. The comparison of the change in the detected pressure with the threshold value can be performed in various ways. For example, the difference between the reference pressure at a certain time after the interruption, which is obtained from data of a non-defective sample acquired in advance, and the detected pressure at the same time may be calculated, and this difference may be compared with the threshold value.

[0027] As described above, the small leak inspection process can be performed at a test pressure where the work capsule 10 has a high degree of vacuum or at a pressure close to the test pressure, thereby improving the accuracy of the small leak inspection. After the small leak inspection process is completed, the pressure release valve 40 is opened to open the work capsule 10 and the main passage 2 (the passage portion between the supply valve 20 and the work capsule 10) to the atmosphere.

[0028] The timing of transition from the large leak inspection process to the small leak inspection process (i.e., the timing of the closing operation of the supply valve 20) may be, for example, after the time ta or tb at which the test pressure is reached. For example, it may be the time t2 at which pressure monitoring ends. In this case, the change in the detected pressure over time for the inspection object 100 shown by curve C may be compared with a threshold value in the same manner as in the small leak inspection process. If the detected pressure is smaller than the threshold value, it is determined that there is a large leak, and if the detected pressure is larger than the threshold value, it is determined that there is a medium leak (the defect is not large enough to be determined as a large leak, but the defect is larger than the level acceptable for a small leak).

[0029] Second Embodiment Figure 3 shows an air leak test device according to the second embodiment. In Figure 3, components corresponding to those in the first embodiment are given the same numbers, and detailed descriptions thereof will be omitted. An intermediate valve 21 (valve means) is provided between the absolute pressure sensor 30 and the work capsule 10 in the main passage 2, and one port 60a of a differential pressure sensor 60 is connected between the intermediate valve 21 and the work capsule 10 in the main passage 2, and is connected to the work capsule 10 via the main passage 2.

[0030] The other port 60b of the differential pressure sensor 60 is connected to the main passage 2 via a pressure detection passage 66. A pressure detection valve 67 is provided in the pressure detection passage 66. As will be described later, the pressure detection valve 67 closes after a test pressure is applied to the other port 60b, thereby allowing a reference pressure close to the test pressure to be stored in the passage portion of the detection circuit 66 between the pressure detection valve 67 and port 60b. In this way, the pressure detection circuit 66 and the pressure detection valve 67 constitute a pressure accumulating means 65.

[0031] <Large leak inspection process> When the supply valve 20 and intermediate valve 21 serving as valve means are opened, pressure from the pressure source 1 is supplied to the main passage 2 and the work capsule 10. The subsequent determination of whether or not there is a large leak is the same as in the first embodiment.

[0032] <Small leak inspection process> After the large leak inspection process is performed, the supply valve 20 and the intermediate valve 21 are closed to isolate the work capsule 100 and the main passage 2 (the passage portion between the intermediate valve 21 and the work capsule 10) from the pressure source 1. At the same time, the pressure detection valve 67 is closed after the pressure equilibration time has elapsed, and the differential pressure sensor 60 detects the pressure change 60b over time in the work capsule 10. Specifically, the difference between the pressure at port 60a and the reference pressure at port 60b after a predetermined time has elapsed is detected, and this detected differential pressure is compared with a threshold value to determine the presence or absence of a small leak, as in the first embodiment. In this embodiment, the use of the differential pressure sensor 60 allows for highly accurate small leak inspection.

[0033] <Third embodiment> The third embodiment shown in Fig. 4 has a more complex circuit configuration than the second embodiment, but the main configuration is the same as the second embodiment, and the basic operation is also the same as the second embodiment, so detailed explanation will be omitted. The controller is not shown in Fig. 4. In the third embodiment, a positive pressure source 70 is connected to the pressure release valve 40. In the second embodiment, the inside of the work capsule 10 is in a near-vacuum state when the inspection is completed, so it takes time to separate the capsule body 11 and the lid 12 just by opening the pressure release valve 40 and releasing it to the atmosphere. However, in this embodiment, the pressure release valve 40 is opened to send pressurized air from the positive pressure source 70 to the work capsule 10, creating a positive pressure in the work capsule 10, so the work capsule 10 can be separated in a short time.

[0034] In the third embodiment, a calibrator 80 (volume changer) is also connected to the circuit. Calibration can be performed according to the pressure change when the volume of this calibrator 80 is changed. In the third embodiment, a tank 90 and a tank valve 95 that controls communication between this tank 90 and the main passage 2 are installed as options, and a leak test different from the method of the present invention can also be performed. When this tank valve 90 is used, the presence or absence of a small leak is checked at the test pressure, and then the tank valve 95 is opened to release the test pressure into the tank 90 to check for a large leak.

[0035] <Fourth embodiment> The fourth embodiment shown in Fig. 5 has the same configuration as the second embodiment, but an orifice 3 is provided in the main passage 2. The position of the orifice 3 may be on either the pressure source 1 side or the opposite side of the pressure source 1 as viewed from the supply valve 20. With this configuration, the orifice 3 further restricts the amount of air flow in the large leak inspection process, thereby lengthening the time axis for reaching the test pressure. Therefore, even when there is relatively little variation in the volume of the object to be inspected, it is possible to maintain high accuracy in determining whether or not there is a large leak.

[0036] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. In the case of leak testing of objects other than flexible packaging, the pressure source may be a positive pressure source. The pressure of the pressure source may be the same as the test pressure or may be higher in absolute value than the test pressure. A hollow test object may be directly connected to the end of the main passage without using a workpiece. For example, when performing a leak test on a hollow test object with an opening, such as a fuel tank or a plastic bottle, the opening is directly connected to the end of the main passage. [Industrial Applicability]

[0037] The present invention can be applied to an air leak test device. [Explanation of symbols]

[0038] 1. Pressure source 2 Main passage 3 Orifice 10 Work Capsules 20 Supply valve (valve means) 21 Intermediate valve (valve means) 30 Absolute pressure sensor (pressure detection means) 50 Controller (control and calculation means) 60 Differential pressure sensor (pressure detection means) 100 Inspection subjects

Claims

1. a pressure source; a main passage having a base end connected to the pressure source and a distal end connected to an object to be inspected or a work capsule that seals the object to be inspected; a valve means provided in the main passage for controlling communication between the pressure source and the inspection object or the work capsule; a pressure detecting means connected to a passage portion between the valve means and the inspection object or work capsule in the main passage, the pressure detecting means detecting a pressure inside the inspection object or work capsule; a control and calculation means; In an air leak test device comprising: The control / calculation means executes a large leak inspection process, and in this large leak inspection process, the valve means is opened to supply pressure from the pressure source to the inspection object or the work capsule, and if the pressure detected by the pressure detection means reaches a test pressure within a set time from the start of pressure supply, it is determined that there is no large leak in the inspection object, and if the test pressure is not reached by the set time, it is determined that there is a large leak in the inspection object.

2. 2. The air leak test device according to claim 1, wherein an orifice for restricting the flow rate of air is provided in the main circuit.

3. the control and calculation means executes a small leak inspection process for at least the inspection object determined not to have a large leak following the large leak inspection process; 2. The air leak test device according to claim 1, wherein in the small leak inspection process, the valve means is closed, and when the change in pressure over time in the inspection object or work capsule detected by the pressure detection means is smaller than a threshold value, it is determined that there is no small leak, and when the change is larger than the threshold value, it is determined that there is a small leak.

4. The leak test device according to claim 3, characterized in that the control / calculation means executes an inspection process similar to the small leak inspection process even when it determines that there is a large leak in the test object, and in this inspection process, when the change in pressure over time in the test object or work capsule detected by the pressure detection means is greater than a threshold value, it determines that there is a medium leak.

5. the pressure detection means comprises an absolute pressure sensor, 4. The air leak testing device according to claim 3, wherein the control / calculation means determines whether the pressure detected by the absolute pressure sensor has reached the test pressure by the time the set time has elapsed in the large leak testing step, and compares a change in the pressure detected by the absolute pressure sensor over time with the threshold value in the small leak testing step.

6. The pressure detection means includes an absolute pressure sensor and a differential pressure sensor, one port of the differential pressure sensor is connected to the test object or the work capsule via the main passage, and the other port is connected to a pressure accumulating means that accumulates the test pressure from the main passage, 4. The air leak testing device according to claim 3, wherein the control / calculation means, in the large leak testing step, determines whether the pressure detected by the absolute pressure sensor has reached the test pressure before the set time has elapsed, and, in the small leak testing step, compares the detected differential pressure from the differential pressure sensor with the threshold value.

7. 2. The air leak test device according to claim 1, wherein the test object has a soft package enclosing contents, the test object is contained in a work capsule, and the pressure source is a negative pressure source.

8. A large leak inspection process is carried out using an air leak test device that includes a pressure source, a main passage connected to a base end of the pressure source and to a distal end of the main passage to which an inspection object or a work capsule that seals the inspection object is connected, valve means that is provided in the main passage and controls communication between the pressure source and the inspection object or the work capsule, and pressure detection means that is connected to a passage portion in the main passage between the valve means and the inspection object or the work capsule and detects the pressure inside the inspection object or the work capsule, In the large leak inspection step, the valve means is opened to supply pressure from the pressure source to the inspection object or the work capsule, and if the pressure detected by the pressure detection means reaches a test pressure within a set time from the start of pressure supply, it is determined that there is no large leak in the inspection object, and if the test pressure is not reached within the set time, it is determined that there is a large leak in the inspection object.

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