RU2344396C2 - Method of checking air-tightness of closed containers and device to this end - Google Patents

Abstract

FIELD: physics; test engineering.

SUBSTANCE: present invention pertains to test engineering and is meant for checking air-tightness of packets or containers with at least one flexible part of the walls. The invention is aimed at simplifying checking while retaining its accuracy. This is made possible by that, a loading element is moved towards and until in contact with part of the wall. Movement is stopped and the loading force acting on the container is monitored. A value of loading force, monitored in the initial instant in time, is selected, giving the initial signal of the measured force. That signal is stored in memory and the stored signal is generated. A differential signal, based on the signal corresponding to the initial signal of the measured force and the signal stored in memory is generated. When storing the signal in memory, a value of loading force is selected, monitored in at least one second subsequent time instant, and a second signal of the measured force is obtained. A second differential signal is generated corresponding to the stored signal, second signal of the measured force and first differential signal, as a signal indicating leakage.

EFFECT: simplification of testing while retaining accuracy.

21 cl, 17 dwg

Description

Technical field

The present invention relates to a method for leak testing of closed containers with at least one flexible wall section and a device for leak testing of a closed container with a flexible wall section, regardless of whether the container is filled with product or not.

State of the art

When testing closed containers, the known method provides for the location of the test container in the test cavity, which is then hermetically closed, pumping air from the inner space of the test cavity around the test container, and after the pumping of air is stopped at a given vacuum level, an assessment is made of the nature of changes in pressure time in the space surrounding the container. Although the specified technical solution provides very high accuracy, it requires very high care to achieve high accuracy. The volume of the test cavity and its configuration must strictly correspond to the external configuration of the test container. On the one hand, minimization of this volume leads to a correspondingly short time for pumping out air, and on the other hand, the degree of minimization largely determines the accuracy achieved in detecting leaks. A change in pressure in the space surrounding the container is detected as a sign of leak detection. Therefore, the smaller the volume at which the leak affects the pressure, the higher the accuracy of its detection.

In addition, the degree of vacuum, which is installed in the space surrounding the container, greatly affects accuracy, which makes it necessary to use relatively expensive vacuum pumps to obtain high accuracy. They even use multi-stage vacuum pumps if it is necessary to create a vacuum that reaches a level created only with the help of a vacuum turbopump.

Summary of the invention

The objective of the present invention is to provide a method and device that eliminates these disadvantages.

The problem is solved by creating a method for testing the tightness of closed containers, which includes the operation of the relative movement of the loading element in the direction of the flexible wall of the container and in contact with it, stopping the movement and tracking the loading force acting on the specified container. The value of the monitored loading force is taken at the first moment of time, which gives the first signal of measurement of force, and taken at least at the second subsequent moment of time, which gives the second signal of measurement of force. A difference signal is also generated based on two measurement signals, as a signal indicating a leak.

Thus, if the container under test is loaded, which results in either compression or expansion of the container, loading forces will be applied externally to the container wall as reaction forces of the expanded or compressed container. Such reaction forces can be easily tracked. If the application of the load is brought to a predetermined level and then stopped, the sealed container will provide tracking of a constant reaction force corresponding to the achieved level of application of the load. If the container is leaky, there will be an exchange between media located outside and inside the container, leading to a decrease in the reaction force, which is monitored over time.

Thus, the accuracy of the technique is largely independent of the volume surrounding the container under test, and, in addition, is mainly determined by the degree of application of the load and the surface for determining the force that the loaded container counteracts.

In a preferred embodiment of the method according to the invention, a load is applied until a predetermined loading force is achieved.

Upon reaching the set value of the loading force, it is proposed to hold the time before the corresponding first and second force measurement signals are generated by sampling, on the basis of which a difference signal is generated. Thus, during this period of time, the configuration of the loaded container is stabilized. In one embodiment of the invention, the application of load to the test container is controlled as a function of the generated differential signal in such a way as to maintain the specified differential signal at a predetermined level and use the action of the loading element as detecting leakage. Thus, a negative feedback loop is created where the loading element in a controlled manner counteracts the change in force generated due to leakage, and in the extreme case, there will not be a change in force due to the fact that the loading element maintains a constant reaction force.

In the most preferred embodiment of the invention, the application of load to the container is not created by the relative movement of the outer surfaces on the container wall, but by creating a pressure differential between the interior of the container and its surrounding space. Thus, the pressure differential in the most preferred embodiment of the invention is created by pumping air from the space surrounding the container. The flexible wall of the container in this case tends to bend outward, and if stationary surfaces outside the container prevent this bending outward, the container will act with corresponding force on such surfaces. This effort is being tracked.

In order to exclude the fact that due to the application of the load, the existing leak in the container will be blocked due to the fact that the wall with the leak is pressed against the outer surface, it is proposed to provide the sections that come into contact with the container wall when it is loaded with an additional structure. Such a structure can be formed by placing between the wall of the container and the outer surface of the mesh or lattice element, or preferably by roughening such a surface, for example, by etching or machining.

In another preferred embodiment, the first force measurement signal is stored in the memory, and a difference signal is generated based on the stored first force measurement signal and the second measurement signal.

In another preferred embodiment, already at the first moment of time, a difference signal is generated based on the first force measurement signal stored in the memory and the first force measurement signal not saved on the memory. The resulting difference signal, such as a zero offset signal, is stored in the memory, and the zero offset of the last generated differential signal is compensated for by the stored value of the zero offset signal.

In order to detect large leaks before smaller leaks, it is proposed to compare the monitored loading force with at least one predetermined threshold value at the latest when sampling at the first moment of time, which leads to the detection of very large leaks and in addition to comparing the difference signal with at least one preset threshold value.

The leakproofness testing device according to the present invention comprises a loading member for compressing or expanding the test container, as well as a force sensor pressed against the wall of the test container and generating an electrical output signal. The output of the force sensor during operation is connected to a storage device connected to the comparison unit. The second input of the comparison unit during operation is connected to the output of the force sensor.

The invention is particularly suitable for leak testing of bags or containers having a completely flexible wall, filled with, for example, a viscous substance.

Other preferred embodiments of the method and device according to the invention are described below.

Brief Description of the Drawings

The invention is further explained in the description of the preferred embodiments with reference to the accompanying drawings, in which

figure 1 depicts a first embodiment of the device in which the test container is loaded with compression, while the loading element and the force sensor are located on opposite sides of the container according to the invention;

figure 2 is an embodiment of the invention in which the container is located on the base, and the loading element, as well as the force sensor are located on the side opposite to this base, according to the invention;

FIG. 3 is a preferred embodiment of a device in which a load is applied to a container by pumping air from a medium surrounding a test container according to the invention;

4 is a diagram of the change in force over time according to the invention;

5 is a block diagram of a device according to the invention;

6 is a block diagram of a preferred embodiment of a storage device and a comparison unit according to the invention;

7 and 8 are general views of a test chamber according to the invention;

Fig.9 and 10 - elements of the test chamber according to the invention;

11a-11c are diagrams of the signal of the force in time according to the invention;

12 is a block diagram of a device according to the invention;

13 is a diagram of a force signal over time showing the statistical distribution of the loading force achieved after a predetermined time of application of a load to sealed containers of the same type, according to the invention;

FIG. 14 is a block diagram of an apparatus for generating an adaptive threshold value in the embodiment shown in FIG. 12, according to the invention;

15 is a diagram of adaptively variable threshold values according to the invention;

FIG. 16 is a block diagram of an embodiment of the invention for adaptively adjusting another reference or threshold value according to the invention; FIG.

17 is a section of a production line for in-line assembly and testing of containers.

Description of preferred embodiments of the invention

The container (figure 1), tested for leaks, has a flexible section 3 of the wall. To test the container 1 for leaks, the loading element 5 is moved by the actuator 7 in the direction of the wall of the container 1 and in contact with it. The force sensor 9 reads the reaction force F and generates an electric signal F _el corresponding to the force F. As shown in FIG. 2, the force sensor 9 is directly connected to the loading element 5, and they are jointly driven relative to the flexible portion 3 of the wall of the container 1 and contact with it, the latter being located on the base plate 11.

In another preferred embodiment of the invention (Fig. 3), the actuator 7, which moves either the load element 5, or the force sensor 9, or a unit of the combined force sensor and the load element relative to the flexible portion 3 of the wall of the container 1, is made in the form of a pneumatic drive. The force sensor 9 and the loading element 5 are stationary in the test chamber 13.

Using a vacuum pump 15, air is evacuated from the test chamber 13, creating a pressure differential Δp between the environment surrounding the container 1 and the internal environment, which is directed outward from the inside of the container. The flexible part 3 of the wall with a pressure differential bends outward, moves in the direction of the force sensor 9 and comes into contact with it. The force sensor in a preferred embodiment of the invention simultaneously acts as a loading element and as a force sensor. As shown by dashed lines, depending on the shape of the wall of the container 1, it is also possible to compress the container 1, for example, using a source of compressed gas 16 to bend the portion 3 out. Regardless of where the loading element 5 and the force sensor 9 are located and how the actuator 7 is made, that is, as a mechanical actuator (Fig. 1, 2) or as creating a pressure differential (Fig. 3), applying a load to the container 1 by means of relative movement loading element 5 to the container 1 and in contact with it leads to the fact that when the load is applied to the container 1 or when it expands, the force sensor 9 detects an increasing force F. When at time t ₀ (Fig. 4), the loading element 5 enters in contact with the wall of the container 1, with long By pressing the loading element on the wall of the container 1, the reaction force F increases. After a predetermined period of time t _{1, the} relative movement of the wall of the container 1 and the loading element 5 is stopped. If the container is tight and its wall does not create an additional reaction, reaching a balanced configuration, get a constant reaction force F ₀ .

If the container, being in a stressed state, shows a strong leakage LL, corresponding to line (b), the movement of the loading element will not lead to the formation of a reaction force F reaching the level F ₀ , but after a period of time corresponding to t ₁ -t ₀ , the sensor 9 force will be measured or recorded significantly less force F _LL .

Thus, a strong leakage LL will be detected if the loading element moves with a given pace or speed towards the container wall and in contact with it and after a specified period of time t ₁ -t _{0, the} specified force F _{0 is} not reached.

The behavior of the container is recorded after a period of time that is shorter than t ₁ -t ₀ , so that you can stop applying the load to the container early enough, until the product contained in the container is extruded or sucked into the surrounding space. Thus, a shorter period of time t _LL −t _{0 has been set} , and after this period of time, the increasing load checks whether the predetermined threshold force F _{LL has} been reached (FIG. 4). If it is not reached, as shown by load line (b), further application of the load is stopped and the container with a strong leakage is released from the load as soon as possible.

If the container 1 does not produce a strong leak, the monitored reaction force F will reach after a predetermined period of time t ₁ -t _{0 the} application of an increasing load of the threshold value F ₀ , and the leaky state of the container will be recorded later.

After the detection of a strong leakage LL and the termination of further application of load to the container at time t ₁ , a predetermined period of time t ₂ -t _{1 is set} up to time t ₂ , during which the system consisting of container 1, loading element 5 and force sensor 9 remains until equilibrium is reached, for example, the configuration of the container.

Thus, in a preferred embodiment, t _{2 is} set at the maximum value corresponding to t _max , indeed the equality t ₂ = t _max . This is true if the test container does not exhibit, for example, a change in volume under voltage from application of the load, which leads to a decrease in the reaction force in the transition phase, and this decrease is not a consequence of leakage.

When the moment t _{2 is} reached or after it, a sampling is made and the value of the monitored reaction force F is stored in the memory, in this case, the prevailing force F ₂ . After an additional period of time t ₃ −t _{2 has} elapsed until time t ₃ , the values of the monitored reaction force F are again sampled as the force F ₃ and compared with the reaction force F ₂ that has been stored. Thus, the difference ΔF of the forces F ₃ and F ₂ in most cases is estimated as a signal indicating a leak.

As shown in FIG. 4, it is also possible to sample and store the value of the force F ₂ in the ascending section of the load curve of the container 1 and wait until the monitored force F re-reaches this level in the downward section of the curve of force F after the termination of further load application at time t ₁ , that is, the value corresponding to F ₂ , which thus means that the system has actually stabilized. In this case, the moment in time t ₂ will be determined by the force F, registered as having again reached the predefined and stored in memory value of F ₂ .

Figure 5 shows a block diagram of a device for leak testing of closed containers.

In the test chamber 13, which is a vacuum, the test container 1 is disposed. The vacuum pump 15 is operated by a synchronization unit 17. The pump 15 pumps air from the chamber 13, preferably with a constant and adjustable capacity.

The combined loading element 5 and the force sensor 9 are rigidly mounted inside the chamber 13 and preferably opposite to the adjacent portion 3 of the flexible wall of the container 1. The force sensor 9 generates an electric signal S (F) as a function of the force acting between section 3 and the contact section of the assembly 9/5 of the loading element and the force sensor, which is shown as provided with a surface structure 19 to prevent this surface from blocking the leak from the section 3, if she accidentally finds herself where section 3 comes into contact with node 9/5. The same structure 19a is located on the bottom surface of the chamber 13.

The signal S (F) is supplied at time t _LL under the control of the synchronization unit 17 and through the switching unit SW ₁ to the comparison unit 21, where at time t _{LL the} output signal S (F) is compared with the threshold value S ₀ (F _LL ), denoting a strong leak, which is predefined in block 23.

Each time, at the time t _{LL, the} value S ₀ (F _LL ) is not reached by the force signal S (F), the switching unit SW ₂ , the input of which is connected to the signal transmission line S (F), opens, stopping further application of the load, for example, the pump 15 under the control of the control unit 25. If the threshold value S (F _LL ) is reached by the signal S (F) at time t _LL , then the signal S (F) is supplied to another switching unit SW ₃ , and under the control of the synchronization unit 17 at the time t _{2, the} prevailing signal is actually sampled and storing in the storage device 27. In the device 27, a value corresponding to the force F _{2 is} stored (FIG. 4). The output of the storage device 27 is connected to the comparison unit 28, to which, under the control of the synchronization unit 17, at the time t _3, an additional signal S (F) is supplied, corresponding, in this case, to the prevailing value of F ₃ . In block 28, the comparison compares the value of the force at time t ₂ with the value of the force that prevails at time t ₃ . The output signal ΔF of the comparison unit 28 displays the leakage state of the test container 1 in addition to the predominant strong leakage that was previously detected.

Instead of directly evaluating the output of the comparison unit 28, it is possible to control the application of the load as a function of the output of the comparison unit 28. A negative feedback control circuit (not shown) is formed in which the comparison unit 28 compares the nominal value corresponding to the signal stored in the memory 27 with the instantly prevailing signal S (F). As a control unit in a negative feedback control circuit, the loading element is controlled so as to minimize the output of the comparison unit 28. Thus, the control signal of the loading element 15 is used as a signal indicating leakage.

6 shows the most preferred embodiment of the storage device 27 and the comparison unit 28.

The output of the force sensor 9 at node 9/5 is output to a conversion unit 121, which comprises an analog-to-digital converter 121a as an input stage, followed by a digital-to-analog converter 121b. The output signal of the conversion unit 121 is supplied to a differential amplifier 123, which additionally directly receives the output signal from the force sensor 9. The output signal of the differential amplifier 123, corresponding to the comparison unit 28 (Fig. 5), is supplied to another amplifier 125, the output signal of which is superimposed at a point 128 on its input signal through the storage device 127. The input signal to the storage device is supplied from the output of the block 125. Block 129 synchronization, similar to block 17 synchronization (figure 5), controls the circuit. To save the signal corresponding to the value of the force F ₂ (Fig. 5) at time t ₂ , the synchronization block 129 starts the conversion cycle in block 121 so that the reconverted analog output signal el ₀ (F ₂ ) .

At the same time, the same signal S (F) from the force sensor 9 is supplied as a signal el (F ₂ ) to the second input of block 123. At the output of block 125, a zero signal should appear. However, typically a non-zero signal will appear at the output of block 125, which is stored in memory 127 by the signal of synchronization block 129. At time t ₃ (Fig. 5), the conversion in block 121 does not start and at the input of amplifier 123 a signal appears that comes directly from the force sensor 9, which corresponds to the value of force F ₃ prevailing at time t ₃ and is stored in block 121 in memory signal corresponding to the value of the force F ₂ prevailing at time t ₂ . In addition, a signal with an offset from zero, which was stored in block 127, is superimposed as an offset compensation signal on the output signal of block 123 so that the resulting signal at the output of amplifier 125 is a signal with a compensated offset from zero. This provides a very accurate measurement of the difference in forces ΔF (figure 4).

Even if a vacuum is applied to move the container wall to and in contact with the force sensor, the volume of the test chamber relative to the volume of the container under test is not a very critical parameter. In known leak testing devices, pressure is evaluated, and according to the present invention, force is evaluated. When evaluating the pressure, for example, the pressure prevailing in the volume surrounding the container under test, the accuracy of the measurement largely depends on the volume remaining between the wall of the test chamber and the wall of the container under test, since leakage will affect the pressure in the intermediate volume the more, the smaller the intermediate volume. According to the present invention, by applying a load to the container wall, the container wall comes into contact with a force sensor. Leakage into the environment of the container will affect this force regardless of the volume of the surrounding space and, therefore, the relative volume of the test chamber relative to the container under test.

From the point of view of reducing the duration of the test cycles, it is recommended to use test chambers that have a minimum volume relative to the containers tested in them, if the load is applied by means of evacuation (Fig. 3). By selecting the steady-state load corresponding to F ₀ and the force and the corresponding signal S (F), a measurement level can be selected and set. Since the flexible part of the wall, when it is bent, will come into contact with the force sensor and / or the loading element on a successively increasing contact area, in relation to the embodiment of the invention shown in FIG. 3, the establishment of a larger loading pressure differential Δp will lead to an over-proportional increase in the loading force F. This corresponds to the amplification of the used signal ΔF (figure 4). In turn, this significantly increases the accuracy of the entire measuring system and facilitates the establishment of a range of evaluated signals.

In a preferred embodiment of the invention, bags filled with product are tested. 7 and 8 show a simplified image of two halves of the test chamber or test cavity corresponding to the chamber 13 in figure 3, specially adapted for testing packages.

At the base 30 (FIG. 7) there is a recess 32 configured in accordance with the packet 34 tested therein (shown by a dashed line). For example, in the base 30, one or more suction lines 36 are used, connected to a vacuum pump corresponding to the pump 15.

The upper plate 37 (Fig. 8), which is similar to the lower plate 30, has a recess 38, which, when the upper plate 37 is located on the lower plate 30, together with the recess 32 forms a test chamber or test cavity. The lower surface 40b and the upper surface 40a of the two plates 30 and 37 are closely and vacuum adjacent to each other and, if necessary, provided with corresponding sealing elements located around the periphery around the recesses 32/38. In one, possibly in both of the plates 30, 37, there is a force sensor 42 with a large sensitive surface 44, exactly corresponding to the configuration of the test chamber. The force sensor 42 preferably operates on the principle of a resistance sensor, that is, pressing on the surface 44 will generate a force corresponding to the pressure multiplied by the area of the contact surface, which will slightly bend the resistance sensor, thereby generating an electrical signal S (F) corresponding to that shown in figure 5.

Obviously, other force sensors based on other physical principles may be used, with force sensors that operate with minimal mechanical movement being preferred. A piezoelectric force sensor can be used, for example.

When the test chamber formed by the two recesses 32 and 38 (Figs. 7 and 8) for testing the packages is made so that it exactly matches the configuration of the container 1 (package) being tested in it, additional information, especially about strong leaks, can be obtained by measuring the electrical leakage impedance outside the test container, which changes each time, for example, when the liquid contents of an unpressurized container are expelled or sucked out of the container. Only in the lower plate 30 (Fig. 7) (not shown in the upper plate 37 in Fig. 8) the inner surface of the test chamber may contain electrodes 44. Each second electrode 44 is connected by one input connector 46 to the impedance measuring unit 48, and each located between them the electrode is with an input connector 49. The impedance measuring unit 48 can measure the AC impedance and / or the DC impedance, preferably the DC impedance. Thus, each time a load is applied to a container, such as bag 34, and the liquid or viscous contents are squeezed into the test chamber, regardless of the measurement of strong leakage, a change in the impedance measured by unit 48 will indicate such leakage, and the output signal of unit 48 resistance will stop further application of load to the container.

To clean the test chamber when the contents of the leaky container spilled out into the test chamber, additional lines or pipes (not shown) connected to the test chamber and connected to a source of liquid and / or gaseous cleaning medium such as air or nitrogen may be used. , and / or flushing fluid under pressure. In addition, a heater may be included in the walls of the test chamber to dry and further clean the contaminated test chamber.

With reference to FIGS. 9 and 10, the most important feature is described, which is used regardless of whether the system operates in accordance with FIG. 1 or 2 or in accordance with FIG. 3.

Each time a load is applied to the test container 1, at least two parts of the container wall, which are opposed to each other and are indicated by numbers 51a and 51b in FIGS. 9 and 10, will be pressed strongly against the assembly of the loading element / force sensor or, generally to surfaces. Each time there is a leak in the wall of the container, it can be clogged by the surface. Thus, in all areas to which a wall portion will be pressed against the container during application, a surface structure is applied so that the surface comes into contact with the wall of the container 1 only in separate contact areas, leaving significant parts of the wall non-contacting. This can be done by positioning the mesh or grid element between the respective surfaces and parts of the wall of the container 1 or by roughening such surfaces by machining, for example pickling or sandblasting. The mechanical bearings 53 (FIGS. 9 and 10) that come into contact with the respective individual portions of the container wall are formed by microstructuring the corresponding surface. With respect to the embodiment of the invention shown in FIGS. 7 and 9, it is recommended that the surfaces of the respective plates 30 and 37, which form the recesses 32 and 38, be machined to produce a coarse microstructure. Thus, it is prevented that any leakage in the container wall can be blocked when a portion of the leaky container wall is pressed against the surface of the system, whether it is the surface of the loading element, the surface of the force sensor, or another part of the surface of the test chamber.

The force versus time diagrams are shown in FIG. 11a for very large and large VGL leaks, in FIG. 11b for small leaks, and in FIG. 11c for sealed containers.

Block 201 (Fig) synchronization initiates at time t _{10 the} application of the load to the test container 1. In the embodiment corresponding to figure 3, block synchronization 201 initiates the pumping of air from the test chamber 13.

This is shown in FIG. 12 as the start load signal BIST / t ₁₀ .

After a fixed predetermined period of time ΔT has elapsed, the output of the force sensor S (F) is compared with the first reference signal RFVGL predefined in the source 107 of the predefined signals. Block 201 synchronization at time t ₁₀ + ΔT starts block 102 comparison.

If after a period of time ΔT has elapsed, the actually monitored force corresponding to the electric signal S (F) in Fig. 12 does not reach the reference signal of a very strong leakage RFVGL (line I in Fig. 11a), this means that there is a very strong leakage VGL. This is detected by the comparator 109 generating an output signal of a very strong VGL leak. If, according to the characteristics shown in block 109 (Fig. 12), the output signal of the running comparison unit at time t ₁₁ = t ₁₀ + ΔT is still high, indicating the presence of a very strong leak VGL, the output signal is issued as the output signal of a very strong leak VGL. If the loading force F has reached and crossed the reference level of RFVGL according to line II (Fig. 11a), the output signal of a very strong leakage VGL is not generated.

A very strong VGL leakage signal stops the load cycle because it could squeeze the contents of the test container into the surrounding area.

As shown by line II (Fig. 11a), when a very strong VGL leak does not occur, the application of the load to the test container continues until the next time t ₁₃ . At time t _13, the synchronization unit 201 turns off the load application drive, which is either a mechanical drive 7 or a vacuum pump 15.

In addition, the position of the synchronization unit 201 starts the comparison unit 111, into which another reference RFGL strong leakage reference value generated by the reference signal source 113 is supplied. If at time t _{13 the} force monitored by the force sensor does not reach the reference value of the strong leakage RFGL, the comparison unit 111 generates an output signal of the strong leakage GL, indicating that the test container has a strong leakage GL. In this case, certain actions are also taken regarding the further operation of the test system.

If the signals of very strong leakage VGL or strong leakage GL are triggered by both comparison units 109, 111, the synchronization unit 201 in most cases restores its original position since the test is completed and the quality of the test container 1 is established. This is shown schematically in FIG. 12 with an RS ₂₀₁ signal. If the restoration of the initial position does not occur immediately after the time t ₁₃ , the value of the signal S (F) (t ₁₃ ) of the force monitored by the force sensor is stored in the storage or storage device 117. The output of the storage or storage device 117 is connected to one input of the forming unit 119 differences, while the second input of this block 119 is connected to the output S (F) of the force sensor. After the pre-set time T _T of the test cycle, which begins at time t ₁₃ or at the time of saving data in the memory 117, (shown schematically by block 121 in FIG. 12), the force difference signal ΔF is supplied to another comparison block 125, which is started by expiration of time T _T test.

Using an additional reference source 127, a reference value of the force difference ΔFREF is supplied to the comparison unit 125. As described below, the value of the reference signal of the force difference ΔFREF can be controlled in a controlled manner in time, and / or the reference value ϕ _R , to which the value of ΔFREF is associated, can also be controlled in a controlled manner.

If the signal of the force difference ΔF at time t ₁₃ + T _{T is} greater than the reference value of the difference of forces ΔFREF, then in block 125 a signal FL is generated, indicating a small leakage of the container under test. This corresponds to the situation shown in FIG. 11b. If the signal of the force difference ΔF does not reach the reference value of the difference of forces ΔFREF, then the container is considered leakproof, since none of the signals of very strong leakage VGL, strong leakage GL and small leakage FL were generated. This corresponds to FIG. 11c.

If a very strong VGL leak signal is generated in accordance with FIG. 12, then, regardless of the device variant (FIGS. 1, 2 and 3), further load application is immediately stopped. In the embodiment according to FIG. 3, the vacuum pump 15 is immediately disconnected from the test chamber 13. This is necessary because with a very strong leakage, the vacuum pump 15 may be contaminated with the leaking contents of the container 1.

In a test system with multiple chambers in a production line using the embodiment of the invention shown in FIG. 3, the appearance of a strong leakage signal GL and possibly even the appearance of a small leakage signal FL, indicating a small leakage, will disable or “ignore” this camera and stopping the supply of test containers to the chamber, while other chambers continue to operate and perform tests on newly supplied containers.

Ignoring the test chamber 13, in which the container was identified as having a strong or even small leakage, is carried out so as not to affect the results of further tests in this chamber and, in particular, not to contaminate the vacuum pump 15 connected to it due to the suction of the contents of the leaking container into such a pump. The normal functioning of this ignored chamber is restored during further test cycles in other chambers after removal of the leaky container.

The restoration of normal functioning can be carried out by heating the chamber 13, washing it with a liquid and / or gas, preferably nitrogen, especially a heated gas.

Looking at figa and 11b, you can find that setting the reference value of the strong leakage RFGL and, especially, setting the reference value of the difference in forces ΔFREF can be very critical and can greatly affect the accuracy of the system. Factors such as ambient temperature, manufacturing tolerances of the container, etc., can affect the prevailing line of force and lead to false results if the critical reference levels and, in particular, the reference value of the force difference ΔFREF are set with the highest accuracy.

On Fig shows a diagram of the loading force corresponding to the lines shown in figa-11b, but measured relative to containers of the same type, which are recognized as tight. This can be done through long-term experiments and / or using leak detection systems that are standard and highly accurate, but require a lot of time and / or are very expensive.

The force values measured at time t ₁₃ for the sealed containers are slightly different and form the statistical distribution shown in FIG. 13. They give an average value (RFGL) _m . The RFGL value used in the comparison unit 111 (FIG. 12), or used in accordance with FIGS. 11a-11c, is obtained by subtracting the offset value ΔRFGL from (RFGL) _m . During current operations with a large number of identical containers, the temperatures and manufacturing tolerances of such containers may vary. Such parameters may change slowly and may change (RFGL) _m .

при вычитании смещенного сигнала ΔRFGL, результатом этой операции является динамически изменяющееся опорное значение RFGL, которое подается в блок 111 сравнения (фиг.12). Динамически изменяющееся опорное значение RFGL показано на фиг.15, начиная от первоначальной установки, как было описано относительно измерений с испытываемыми герметичными контейнерами.Each time during numerous consecutive tests at the corresponding time t ₁₃ until the moment when the corresponding container is identified as having no strong leakage, the actual output signal of the force sensor enters the averaging unit 130 (Fig. 14), in which m last values of the actual force for containers without strong leakage averaged. The output average resulting signal corresponding to (RFGL) _m (Fig. 13) varies over time, for example, due to a change in production parameters for containers of the same type. To give an average result

when subtracting the offset signal ΔRFGL, the result of this operation is a dynamically changing reference RFGL value, which is supplied to the comparison unit 111 (Fig. 12). The dynamically changing RFGL reference value is shown in FIG. 15, starting from the initial installation, as described with respect to measurements with test sealed containers.

(t₁₃) является основой, к которой также привязано ΔFREF. Таким образом, опорное значение разности сил ΔFREF не привязано к абсолютному статическому значению, такому как ϕ_R, а привязано к

.Average Strength

(t ₁₃ ) is the basis to which ΔFREF is also attached. Thus, the reference value of the force difference ΔFREF is not tied to an absolute static value, such as ϕ _R , but tied to

.

, усредненному за последние m испытательных циклов, смещается на ΔΔF, и результат используется в качестве сигнала изменения времени ΔFREF, подаваемого в блок 127 (фиг.12).An even greater improvement in accuracy has been achieved, which can be obtained separately or in addition to obtaining dynamic RFGL and, based on it, a dynamic upper limit ΔFREF. Thus, according to FIG. 16, at the end of the time period T _{T, the} signal of the actual force difference ΔF is supplied to the averaging unit 135 each time that the small leakage output signal FL indicates that the container under test is sealed. The output signal of block 135, which corresponds to the average signal of the difference of forces

, averaged over the last m test cycles, is shifted by ΔΔF, and the result is used as a signal of a change in time ΔFREF supplied to block 127 (Fig. 12).

, с привязыванием (ΔFREF)_t к стабильному постоянному значению ϕ_R (показано на фиг.12 пунктирной линией) вместо привязывания к динамически изменяющемуся значению

.Returning to Fig. 15, which shows the application of the constant signal ΔFREF, it should be noted that the averaging technique ΔF leads, as schematically shown by the line (ΔFREF) _t , to a dynamic change in the value of ΔFREF, which changes in accordance with changes in the disturbing parameters influencing such a difference forces. It is clear that providing dynamic signal change (ΔFREF) _t according to that shown in FIG. 15 can be carried out without using a dynamically changing base value

, with snapping (ΔFREF) _t to a stable constant value ϕ _R (shown by a dashed line in Fig. 12) instead of snapping to a dynamically changing value

.

Preferably, the output signal S (F) of the one or more force sensors is evaluated digitally.

On Fig shows a production line on which the assembly and testing of containers is carried out in a continuous manner. For example, the bags are first brewed in step 60 of welding on the base plate 30 (Fig.7), used as a carrier and support for assembly. The base plate 30, after the package is assembled by welding, moves to the overlay point of the upper plate. The upper plate 37 (Fig. 8) is applied to the lower plate 30. After that, the hermetically sealed test chamber is moved to the test point 64, where the test is carried out. A system consisting of a weld point 60 and / or a top plate overlay point 62 and / or a test point 64 may be stationary relative to the conveyor 66 for the base plate 30. Depending on the time required for a particular operation, the test point 64 may move in conjunction with conveyor 66 so that it is independent of the speed of conveyor 66.

Using the method and device corresponding to the present invention, a test technique has been obtained that is much less critical when achieving the same accuracy as using leak test methods, according to which pressure measurement results are evaluated. Applying a load to the container according to the invention is much simpler than creating a proper vacuum around the container, and measuring the loading force is much simpler than accurately measuring the time variation of the negative pressure around the container. When measuring vacuum there is a much larger number of unknown and uncontrolled parameters that can affect the categories being measured, namely negative pressure, than when using the force measurement used in accordance with the present invention. While setting the measurement level when using the method of measuring vacuum significantly affects the cost of vacuum pumps, changing and setting the loading force requires a significantly smaller amount of work.

The method and apparatus of the present invention are suitable for testing bags, but they can be used to test all types of containers, up to large tanks, if part of their wall can elastically bend. The present invention can be carried out on production flow lines with many test points, for example, located on a rotary installation with a very high productivity.

Claims (21)

1. A method of manufacturing a sealed closed container with at least one flexible section of the wall, which consists in moving the loading element relative to the section of the wall, towards it and before contact with it, stop the specified movement, monitor the displacement force acting on the container, a bias force value being monitored at the first moment of time is sampled, which gives the first measured force signal, a signal corresponding to the first measured force signal is stored in memory, and generated protected signal, a bias force value is monitored at least at one second subsequent moment of time, and a second measured force signal is obtained, a differential signal is generated depending on the first and second measured force signals as a signal indicating the presence of leakage, the container is rejected , in which there is a leak detected by the difference of the signals of the measured force. 2. The method according to claim 1, characterized in that they further apply a bias force to the wall portion until a predetermined bias force is achieved. 3. The method according to claim 2, characterized in that a time interval is set between achieving a predetermined bias force and performing said sampling. 4. The method according to claim 1, characterized in that it further controls the bias force as a function of the difference signal in order to keep the difference signal at the set value level and use the relative action of the loading element as a leak. 5. The method according to claim 1, characterized in that the loading element is additionally moved by establishing a pressure differential between the interior of the container and the surrounding space. 6. The method according to claim 5, characterized in that it further sets the specified pressure difference by pumping air from the surrounding space. 7. The method according to any one of claims 1 to 6, characterized in that it further establishes surface areas in contact with the container wall when the device applies a bias force. 8. The method according to claim 7, characterized in that it further compares the indicated monitored bias force with at least one predetermined threshold value when sampling at the first time. 9. The method according to claim 1, characterized in that it further stores in memory the first signal of the measured force using an analog-to-digital Converter for conversion at the first time. 10. The method according to claim 9, characterized in that they perform the inverse conversion of the digital signal of the analog-to-digital converter into an analog signal and generate a difference signal using the inverse conversion of the analog signal. 11. The method according to claim 10, characterized in that the impedance is measured on the wall or at least near the container wall, the resistance being measured by direct current, and the further movement of the loading element to the wall section and in contact with the impedance measurement result is continued or stopped him. 12. The method according to claim 11, characterized in that it further monitors the bias force using a resistance sensor. 13. The method according to p. 12, characterized in that it further selects the value of the bias force, tracked at the third time, but no later than the first time, and receive the third signal of the force measurement, compare the third signal of the force measurement with a predetermined value threshold signal and a strong leakage signal is generated if the third force measurement signal does not reach the threshold signal value. 14. The method according to p. 13, characterized in that they use the test chamber for the container and clean the test chamber after the container is identified as having a leak, moreover, the cleaning is carried out by washing with a gas, preferably nitrogen, and / or washing with a liquid, and / or heating. 15. The method according to 14, characterized in that they test a series of containers in a stream in a plurality of test chambers and stop the tests in the test chamber for at least one test cycle if the container previously tested in it was leaking to a given degree. 16. The method according to clause 15, characterized in that the load element is additionally moved to the specified wall section and in contact with it at a given speed, a strong leak is detected by monitoring the loading force after a predetermined period of movement time and by monitoring whether the loading has reached the force of the first predetermined threshold value. 17. The method according to clause 16, characterized in that the load element is additionally moved at a constant speed to the specified section of the wall and in contact with it. 18. The method according to 17, characterized in that the first force measurement signal is averaged with the first force measurement signals that were sampled during previous container tests, and a difference is formed depending on the averaged first measurement signal. 19. The method according to p. 18, characterized in that the averaged signal is shifted by a predetermined value and the specified difference is formed depending on the biased averaged signal. 20. Device for testing the tightness of a closed container with at least one flexible section of the wall, containing a loading element for compressing or expanding the test container, a force sensor applied to the wall of the test container and generating an electrical output signal, while the output of the force sensor is operational connected to a storage device, the output of which in operational condition is connected to the comparison unit, the second input in operational condition being connected to the output of the force sensor. 21. The device according to claim 20, characterized in that the loading element contains a pair of spaced elements that are moved by the drive relative to each other, towards each other and from each other.

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