DE2422701A1 - RESERVOIR PRESSURE TESTING - Google Patents

Description

The invention relates to a method and an apparatus to check the Dimckes in an airtight one Container that has at least one flexible wall on it, e.g. a can, a can or a jar füx · Food or beverages with a metal lid.

It is known that the natural frequency of a vibrating membrane depends on the surface tension applied to the membrane depends. This voltage can be introduced by applying a static force, its direction of action runs perpendicular to the surface of the membrane and in the case of an airtight, evacuated can or can by the difference between the atmospheric pressure and the level of vacuum created in the can or can. If the

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Vacuum is also the tension and thus the Change the natural frequency of the lid of the can or jar. A rigid vessel with a sheet metal lid was found to have a linear natural frequency of the lid Relation to the extent of the vacuum in the vessel, whereby the natural frequency increases with increasing vacuum. The extent of the vacuum is not the only parameter that influences the natural frequency. Other influencing factors include the size of the lid, its thickness, the material from which it is made and the contents of the Can or vessel.

So far one has to determine the extent of the vacuum in a container, bumped into the flexible wall of the container and determined with the ear whether the oscillation frequency indicates an acceptable or unacceptable container. Often times, "the container after the final." Stored capping for a few weeks before vacuum checking is carried out. This ensures that small, slow leaks are detected. The manual The method, although it is simple in itself, has the disadvantage that an inspection of containers at great speed is practically impossible and that no containers can be checked, which in turn are packed.

The invention has for its object to provide a method and a device with which the Pressure in containers can be checked quickly and easily. The method and the device should also be particularly suitable for checking containers that are arranged in individual sections, E.g. standing in batches on a packaging pallet and covered with a plastic shrink film.

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The method according to the invention which solves this problem is characterized in claim 1. Here the two, given values must be the same. It was determined, that when the wall is excited at a certain frequency, vibrations in a wide frequency range arise, whereby a pronounced aplitude maximum is assigned to the natural frequency of the wall. Most containers with a leak, when checked, show a vacuum of the value zero, in particular according to the one explained above Waiting period. Therefore, one of the two test frequencies is expediently chosen so that it mulls the vacuum in the container. The second test frequency is then, higher than the first, being the value to be chosen of the lower limit of the acceptable vacuum in the container. If the two frequencies selected in this way are very far apart, there can be a dead space between them set in which container with a vacuum level, which lies between zero xmd of the lower limit mentioned, cannot be displayed. In this case, three or also more test frequencies are used with the container the individual frequencies are separated and exposed one after the other.

It can therefore be seen with the display whether the oscillation amplitude exceeds a predetermined value or not, a distinction between "good" containers, i.e. those that have an acceptable degree of vacuum and "bad" containers, i.e. those that have don't do that, be effected. The specified amplitude value will after an investigation of each one. testing container r.o established that a reliable distinction is ensured between good and bad containers. For example, an examination of

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Glass vessels with bones disgusting a sound difference from 3> O dB between bad vessels (with zero vacuum) and good vessels. This difference becomes smaller to the extent that indeia the vacuum level of bad vessels the good vessels increased. Correspondingly, the reliability of the method according to the invention is all the lower the more you look at the "turning point" between good and bad Vessels approaching. This loss of reliability can be compensated by the fact that the "turning point" vacuum, i.e. the lowest acceptable vacuum level, higher than usual, so that a small number of containers that would otherwise be acceptable actually are displayed as unacceptable. The inventive The method is not only suitable for checking evacuated containers for possible leaks, but can also be used quite generally to test an overpressure or underpressure in the container.

A preferred development of the invention The method is characterized in claim 2. Under rejection is both physical or distance Removal of an unacceptable container from a group or series of acceptable containers as well as the marking of unacceptable containers to be used simultaneously or alternatively, for example by stamping, to understand.

The subject matter of the invention is also the device for checking the pressure as characterized in the claim airtight container with at least one flexible metallic wall. The two values given here can be the same.

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Many containers can with the specified in claim 4, "Appropriate development of the new / device checked v: grounding multiple containers in one grater arranged on the conveyor and thereby individually under the two electromagnets can be passed ": In practice, containers are often in several rows packaged, e.g. in the aforementioned shrink film packs; for checking containers packed in this way the preferred embodiment outlined in claim 5 of the invention ;; reeigneb, in each case a pair of electromagnets interacts with a number of containers. Prevents the preferably used displacement of the electromagnet pairs in the direction of travel of the conveyor a mutual influence of the electromagnet pairs.

The measures according to claim 6 and / or claim can be used to reject containers recognized as unacceptable be applied. When checking packages with several containers each, the rejecting device segregate and / or mark any package containing at least one unacceptable container. Preferably the rejection device is designed in such a way that that packages with multiple checked containers are marked so that unacceptable containers are within the Package are identifiable.

By applying the measures according to claim 8, the reliability of the new device is due the fact that every bandpass filter interferes with noise and other scatter maxima in the response behavior of the container, which do not correspond to the natural frequency, reduced or suppressed. The bandwidth of the filter must be be big enough so that there is no dead space between

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the two response ranges corresponding to the excitation frequencies results.

According to claim 9, the filter can be an acoustic one Filters include which sound is on its way to corresponding microphone happens. A suitably sized pipe is suitable for this purpose. Alternatively or An electronic bandpass filter can also be used at the same time according to claim 10 are used / ended.

The alternating currents fed to the electromagnets can have any waveform. According to claim 11, however, a rectangular shape is preferred, since this results in a maximum response level also found that for a container wall made of ferromagnetic Material with regard to the best response behavior a square wave is most suitable, the frequency of which half the natural frequency of the wall.

Although the testing of containers is specified as a preferred field of application of the invention, in which the flexible wall is made of ferromagnetic material, there is no reason why not also containers checked with a wall of non-magnetic metals according to the invention. Naturally some of the above-mentioned principles did not apply due to the different modes of action.

In the following, the invention is further advantageous Details are explained in more detail with reference to an exemplary embodiment shown schematically. In the drawing demonstrate:

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Fig. 1 is a greatly simplified plan view of a Vessel sorting device that is a pressure testing device comprises according to the invention;

l ^: 'ig. 2 shows a plan view of the pressure testing device according to FIG. 1 with the cover partially removed;

3 shows a section along the line IH-III in FIG. 2; i'ig. Λ a section along the line IV-IV in Fig. 3;

Fig. 5 is a block diagram of the electrical control circuit for the device according to Figs. 1-4-,

In Fig. 1 eirs Drackprüfvorrichtung 1 is shown according to the invention, which is assigned to the conveying strand of a conveyor 2. Parcels 3 with containers to be tested move on the conveyor in the direction of arrow A. An entrance gate M- represents a physical barrier against possible objects which are too large to be able to enter the device -1 and would therefore cause damage. The input gate 4- comprises a horizontal beam which ^{extends 1} across the conveyor at a height adjustable to three fixed positions depending on the height of the vessels to be tested.

The pressure testing device 1 checks all the vessels in the package Z> for leaks and rejects all packages, at least one. embrace bad vessel. Packages rejected in this way are repelled from the conveyor 2 by an oil device, specifically in FIG. 1 in the direction of the underside of the sheet. On the output side of the device 1, a conventional labeling device 5 is provided, which applies a label to all rejected packages. The Efcikcttiervorrichtung 5 is operated by a micro switch 6, which extends into the conveying wave of the packages 3 on the conveyor. Of actuation

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arm of the micro switch protrudes so far outwards, that the microswitch has been displaced or repelled Packets 5 is actuated, but not by undisplaced packets that contain only good vessels.

The vessels to be tested are made of glass and have sheet metal lids made of ferromagnetic material. Experiments have shown that the majority of certain vessels used to hold baby food the bad vessels create a vacuum in the area of ü Lis 12.5 cm of mercury at the time of review, i.e. after the waiting period explained above. The rest of the bad vessels fall in the 12.5 range and 25 cm of mercury, with a few above this Values are, up to the beginning, the range of an acceptable vacuum, namely 45 cm of mercury. In the During production, an initial vacuum of approximately 58 cm of mercury is created in the vessels, so that vessels with a vacuum between 45 and 58 cm mercury as "good" Vessels are viewed.

Further investigations are carried out with the vessels in order to determine the natural frequency of the lid. This varies only slightly from vessel to vessel and when checking vessels of different sizes from Size to size. However, as explained above, it is expedient to use at least approximately the natural frequency of the To be able to determine covers for different vacuum levels, i'ür the special one to be checked by the device The most reliable results were obtained by selecting the natural frequency of the vacuum Zero and achieved at a vacuum of 25 cm of mercury. These natural frequencies were 1.0 and 1.6 kHz, respectively.

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It must be emphasized that the values given above fluctuate depending on the containers checked and that the parameters of the respective container to be examined must be determined in the manner described above before the invention Device can be used reliably.

-O

For the further explanation of the pressure testing device, reference is made to the Ι'άρ. 2 to 5 referred to. The apparatus comprises six separate test stations 7 "to 12 which are fixedly attached to the frame 13 of the conveyor 2 and extend above the conveyor. As shown in Fig. 3, the conveyor is mounted on rollers _{v, one} of which is shown at Vv and is on top of it The underside is provided with a V-shaped cross section which interacts with a V-shaped groove 15 in each roller 14. This interaction between the groove and the rib counteracts a lateral displacement of the conveyor, which has the effect of the Pressure testing device.

The construction of the test station 10 is detailed shown in Figs. 3 and 4-. The station 10 comprises a metallic frame 16 which supports the conveyor bridged. A platform 17 is suspended from the frame 16 by means of four coil springs 18 which form the platform pretension upwards. A rod 19 extends from the top of the platform through a collar 20 in the frame 16 through and ends in a button 21. The rod 19 is slidable in the collar so that the height of the platform 17 can be adjusted. From the frame 16 extend four columns 22 on which a further platform 23 is supported. The platform 23 carries a slidable Pair of parallel plates 24, between which a rod 25

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is firmly attached. The rod 25 is provided with a button 26 at its free end. One of the two plates 24 has a cutout, the shape of which is shown in FIG. In this cutout a pin 27 extending away from the rod 19 is received, by means of which the upwardly directed Yorspanriungsbewegung of the rod 19 due to the helical springs 18 is limited. The shape of the cutout defines three positions for the pin 27 and thus three different heights for the platform 17 on the ax: ^ three different vessels. A change in height takes place simply by pressing down the button 21 until the pin 27 enters the common bleach C ', 1 cutout in the plate 24. The knob 26 is subsequently moved to the left or right depending on the gevünechten height adjustment of the platform 17 and then äcv Kaopf freigegebeil 21, so that the pin can move to a new rest position 27th

A microphone and electromagnet assembly suspended above the conveyor is attached to the platform 17. The arrangement comprises a plate 28 made of non-magnetic material on which a fused electromagnet 29 with pole pieces 30 νχιδ. a microphone assembly 3 ^ is attached. The microphone arrangement comprises a tube 32 made of stainless Staiii, which is extending through the platform 17 and secured thereto, sov / ie a Kondensatox'icikrophon 33 · mounted on the upper end of the tube. The tube 32 acts as an acoustic filter and greatly improves the noise suppression of the device. If necessary, the microphone can be attached to the tube 32 so that it can be displaced so that its length can be optimized in adaptation to special operating conditions. A condensate oxy microphone is used because of its high insensitivity to magnetic

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ti see fields used; However, others can too Pükrophone can be used with this property.

The plate 28 is supported by the platform 17 and the pipe 32 held in such a position that the magnetic Field between the pole pieces 30 through the cover which runs along the transported vessels. In practice there is a distance of approximately 3 mm between the lid and the pole pieces 30 for adequate equilibrium Approaches identified as appropriate. However, abSvands up to 12.5 mm have also been used, with however the output signal decreased. It is important that the magnet is pretty much in a position above the center of the lid is brought and therefore a precise lateral alignment of the packages or pallets 3 on the conveyor must be adhered to. As can be seen from Fig. 3, the station 10 checks only the middle of the three over the Width of the containers arranged by the conveyor; the other two vessels are checked by other stations. Indeed is according to the drawing, the microphone and magnet arrangement assigned to station 8 opposite that the station 10 is offset to the right and is used to check the information on the right-hand side in pack 3 arranged vessels.

Actuated when a defective vessel is detected a still to be described control circuit an ink roller 34 for stamping the package 3, which the defective Contains vessel. The roles assigned to the individual stations each stamp with a different color, see above that the faulty vessel in the pack quickly "recognized can be. The ink roller is attached to the end of a piston rod 35 of a pneumatic working cylinder 36,

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The working cylinder 56 is via an air pressure line 37, which leads to a compressed air source, not shown, Kittel.s a solenoid valve, also not shown actuated. l / enii a vessel is recognized as defective, actuates the control circuit that of the respective station associated roll of ink. In the figures it is not shown df iß the role of taking the response time into account the circuit of the associated microphone and electromagnets arranged slightly offset to the rear is. Therefore, the defective vessel can be found in the package 3 leaving the device on the basis of the color and the position of its marking can be identified. The hell also has the effect that the package 3 with the defective vessel in Fig. 3 shifts to the left and therefore the microslialter 6 is actuated when leaving the pressure testing device.

A cover 38, only partially shown in FIG. 2, serves to reduce the influence of ambient noise, which could lead to false tripping. The lid can optionally be coated on the inside to eliminate acoustic resonances.

All stations 7 to 12 have the same construction like station 10, of course, with the important exception that is the position of the microphone and electromagnet arrangement is different in the transverse direction from station to station. In detail, see Fig. 1 and 2, the stations in pairs, namely as pairs 7 and 8, 9 and 10 as well 11 and 12 arranged. At the stations 7 and 8, the electromagnets are arranged so that the cover of the upper Row of vessels excited v / ground. At stations 9 and 10, the electromagnets are used to excite the lid

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arranged in the middle row of vessels. At the stations 11 IUKl 12 are the electromagnets for excitation the LecJol eggs "lower row of vessels arranged. The ' Positions of the Eiekt.magnete are with the reference numerals 59, - '! O -and 4-1 for-the station pairs 7/8, 9/10 or 11/12 g ok enn draws.

A square-wave voltage is constantly applied to each of the electromagnets. The output of the microphones is a control circuit augofv'ln.'t, polygamy the roles. 34 and also a 'horn to display the Vorbciwonäerns a defective vessel controls. The electromagnets of stations 7i "9 urtd_11 receive a waveform with a frequency of 500 Hz, while the electromagnets of stations 8, 10 and 12 receive a waveform with a frequency of 800 Hz. These frequencies correspond to half the natural frequency of the covers to be tested at a vacuum of 0 or 25 cm mercury. The packages with the vessels to be tested move one after the other through the device from left to right according to FIG. 2. Each vessel is individually tested first at 500 Hz and then at 800 Hz The microphone assigned to the respective electromagnet receives the sound which the cover generates when responding to the magnetic field. This is processed in the control circuit. The control circuit intended for use with the pressure testing device according to FIGS. 2 to 4 is shown in FIG Circuit comprises two square wave generators 42 and 43 which generate output voltages with a frequency of 500 Hz and 800 Hz, respectively is used to monitor the output of the generator 42 or 43, depending on the position of a switch y \. The generators 42 and 43 are connected to connecting lines 44 and 45, respectively, to which power amplifiers 46 to 51 are connected, which

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the electromagnets 39, 40 and 41 feed. The microphones assigned to the stations 7 to 12 are denoted by the reference symbols Ύιί to 5? and are connected to respective amplifiers 58 to 63 which are contained in a comprehensive unit 64. The individual amplifiers are followed by Baodpass filters 65 to 70 of 1/3 octave, the Ilittenfrequenzen are set so that they correspond to the natural frequencies picked up by the two microphone groups. Filters 65, 67 and 69 are tuned to 1 kHz and filters 66, 68 and 70 are tuned to 1.6 kHz. Connected to the outputs of the bandpass filter sira AmpIitudeeiidiskriminatoren 71 to ¹ JG . The amplitude discriminators only allow an output signal to pass if the amplitude of the input sign exceeds a predetermined value. If this predetermined value is exceeded, a signal from the respective amplitude discriminator to one of several solenoid air valves 77 to 82 controls the supply of compressed air to one of the aforementioned working cylinders 36 . At the same time, the signal from the discriminator reaches an alarm switch 83, which actuates an alarm horn and / or a light display.

The operation of the system is such that a suitable excitation frequency is constantly supplied to each electromagnet and that when a vessel passes under an electromagnet, the ferromagnetic lid is under caused by the action of the electromagnets in vibration will. If, when excited by one of the first electromagnets in stations 7, 9 or 11, the lid of a vessel responds significantly at a frequency of 1 kHz? the respective microphone 52, 54 or 56 the voia lid generated sound at this frequency.

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If the vibration amplitude is sufficiently large, the respective amplitude discriminator 71> TO or 75 responds, which triggers the alarm and the respective Knerietventil 77, 79 or 81 is actuated. This also activates the assigned working cylinder $ 6 and stamps the examined pack on the side. The position of the stamp mark on the pack is next to the corresponding column of vessels within the pack. The stamp colors of the different Hollen JA- are each different, so that both the »column and the line of a faulty container can be easily identified. The movement of the roller also shifts the pack on the side of the conveyor.

A similar rejection occurs when the lid of a vessel is sufficiently at one frequency of 1.6 kHz responds after being triggered at a frequency of 800 Hz by an electromagnet in one of the stations 8, 10 or 12 was suggested.

It was previously mentioned that the device can be adjusted to accommodate vessels with three different heights. The height of the platform must of course 17 can be set in all stations 7 to 12. The danger here is obvious that of the operator is occasionally forgotten to adjust the platform of a station \ tfas the risk of that the microphone and electromagnet assembly of this station can be damaged if the error is not detected before vessels pass through the device be transported. It is therefore desirable to have a warning system that responds when the height of the platforms 17 is not the same in all stations.

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■ Such an electoral system can be carried out in a simple manner Arrangement of three microphones in each of the Stations 7 "to 12 are realized. The microswitches are attached to the inner side of the frame 16, corresponding operating levers of the microscope holder in the path of movement of the platform 17 within the frame 16 reach into it. Corresponds to every microscope holder a certain amount. The microscope holders in all stations, which correspond to a certain height are connected in series, so that when not actuated one of the Microswitch due to incorrect height setting a platform 17, an electrical circuit is interrupted, which triggers an acoustic alarm. Alternatively, the drive of the conveyor can also be stopped if the height setting is incorrect.

In addition, the gate 4-, see Fig. 1, can be provided with a corresponding arrangement of three microswitches ^ many are connected to the other microswitches in the same way. Then, the acoustic alarm is triggered odez ^1, the conveyor is stopped or both actions carried out if the height of the horizontal bar of the door 4 or the height of one of the platforms 17 are set differently from each other.

claims 69XXV

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Claims (11)

- 17 - 1A-44 866 Patent claims ti J Ver.fali.roji kuii Check the pressure in an airtight closed container with at least one flexible, metal wall, thus marked, that the flexible wall of the container is on electromagnetic Paths "to. Vibrations first with an i'x'-sequence and then with a second frequency that is different from the first, stimulates that one can be heard by means of a microphone determines the amplitude of the sound emitted by the wall and that an output signal is automatically generated generated when the sound amplitude corresponding to each excitation frequency is given a respective one Value exceeds. 2. The method according to claim 1, characterized in that the output signal for rejection "Every container is used, which produces a sound answer corresponds to one of the 'test frequencies above of the predetermined value is generated. 3. Device for checking the pressure in an airtight container with at least one flexible, metallic wall, preferably for carrying out the method according to claim 1 or 2, characterized by a pair of electromagnets (29), each of which is supplied with an alternating current of different frequency, by a device (2) to move the flexible wall of a test 40984 8/0869 44 Container in the magnetic field first of one and then the other electromagnet, by two microphones (33), which are each assigned to one of the electromagnets, to determine the sound generated by the flexible wall when excited by the electromagnetic fields of the j ex-sacred electromagnet , and by an output device (64) for generating an output signal when the amplitude of the sound signals received by each microphone exceeds a respective predetermined vert. 4. Apparatus according to claim 5 _; characterized geke η η is characterized in that a conveyor (2) is provided for transporting the container to be tested and that the electromagnets (29) are arranged above the conveyor so that a container to be tested first under one and then under the other electromagnet wanders. 5- device according to claim 4, characterized in that several pairs of electromagnets (39, 40, 41) are each provided with an associated microphone (33), and that each pair of electromagnets is a different one Position.in transverse direction over the conveyor (2) and corresponding pairs of electromagnets in The direction of travel of the conveyor are offset from one another. 6. Apparatus according to claim 4 or 5 _? characterized in that a return device (34 to 36) responding to the output signal is provided which rejects any container which generates sound above the predetermined value corresponding to one or the other test frequency. 409848/0869 44 7. Apparatus according to claim 4, 5 or. 6, thereby £ ~ eke ω η τ. ο i η et that one on the Ausßc'jji ^ .cGigüal oacpx'cchenda device for marking jcii es Bchü.3 i; ors "" is provided, which of the one or anät-rci. PreΓfrequency corresponding sound above the value, generated « O. Device according to claim 4, 5, 6 or 7> characterized in that in each sound path zxvi ^ chen the container ervrand and the output device (64y a bandpass filter (32; 65 to? O) is provided, that on a corresponding natural frequency of the excited Behalterv / arrä. abstii: r.at is. 9. Device "according to claim 8, characterized in that an elcustisch.es as a bandpass filter Filter (32) is provided, "which in the acoustic path is arranged between the container wall and the corresponding microphone (33) «. 10. The apparatus of claim 8 or 9, characterized GEK h η η is characterized in that is provided as a band-pass filter elec tronischep filter (up to 70 ^ 6), which influences the AußgaTigssignal Vora respective microphone (33). 11. Device · according to one of claims 4 to 10, characterized in that the electromagnets. (39) charged with triangular alternating currents ν, ¹ earth. 69JQCV 409848/0869 Blank page