WO1990010223A1

WO1990010223A1 - Process for detecting faults in containers made of electrically non-conductive material and device for implementing it

Info

Publication number: WO1990010223A1
Application number: PCT/DE1990/000117
Authority: WO
Inventors: Rainer Berthold
Original assignee: Texpa - Arbter Maschinenbaugesellschaft Mbh
Priority date: 1989-02-23
Filing date: 1990-02-21
Publication date: 1990-09-07
Also published as: DE3905530A1

Abstract

In a processs for detecting faults in a container, preferably a bottle, made of electrically insulating material, e.g. metal, plastic or mineral material, especially glass, the wall of the container is taken into a high-voltage field, the strength and frequency of which are such that partial discharges which can be detected occur at the locations of the faults.

Description

description

Method for detecting defects in containers made of electrically non-conductive material and device for carrying out the method

The invention relates to a method for detecting defects in material made of electrically non-conductive or insulating material, e.g. Containers made of plastic or mineral material, preferably glass. The invention relates in particular to a method for detecting defects in glass bottles. Furthermore, it relates to a device for performing the method.

Before bottles are filled or shortly after they are manufactured, they are fed to a bottle sorting machine in which they are aligned. So that defective bottles cannot get to a filling station or to the shipping department, so-called empty bottle inspectors are installed in the area of the transport device in front of the sorting station the mouth of the bottles is checked or examined to determine whether there are foreign bodies in the bottle, such as residual liquor liquid and the like.

A device has become known with which the interior or the mouth of the bottles can be examined with infrared light for foreign bodies or defects. However, this optical method can only be used if the foreign bodies or defects have a diameter of greater than 2 mm.

In the past, studies have been carried out to determine whether defects in bottles can be detected using ultrasound methods known from material science. However, it has been found that the known ultrasound methods cannot be used in bottle transport systems mainly because the ultrasound interference level cannot be depressed far enough there; Defects whose diameter is less than 2 mm are therefore not recognized.

In addition, it has also become known to apply excess pressure to the interior of the bottle, so that the bottle is destroyed if a defect is present. So-called automatic error statistics are not possible due to the destruction of the bottles.

The object of the invention is therefore to provide a method of the type mentioned in the introduction, in which all types of errors can be detected even if they are smaller than 2 mm in diameter. It is also an object to specify a device for carrying out the method.

This object is achieved according to the invention in a method of the type mentioned at the outset by introducing the container wall into a voltage field, the size and frequency of which are dimensioned such that partial discharges are formed in the defects which are detected. The voltage field is preferably a high voltage field.

The invention makes use of the fact that when the containers, in particular the bottles, are brought into a suitably shaped electromagnetic high-voltage field, the high voltage, depending on its height, in the defect in the glass of the bottle, for example in the case of ceramic, stone, metal or Inclusions of sand, cracks, air bubbles etc. produce a partial discharge which, in addition to the immediately occurring charge equalization, also has some other manifestations of an electrical or non-electrical type. These secondary effects, which are physical processes that start immediately with the discharge, can be used for the measurement of a partial discharge in bottles.

During such a partial discharge, very small currents flow up to the breakdown voltage. The charges transported thereby move, for example, between 5 pC and 70,000 pC, which, depending on the insulating ability of the glass and the shape of the electrode in the area of the defect, leads to partial discharge currents in the milliampere range. This current can be measured and used for the detection of partial discharges. In addition, the partial discharge emits high-frequency energy in the form of electromagnetic waves, the frequencies of which are similar to those which are generated in air in the event of discharges. Conclusions from the measured high-frequency spectra of spark discharge and corona in air, specified in VDE 0434, cannot, however, be easily transferred to the discharge in glass, since the discharge process in air is different. Nevertheless, the high-frequency radiation can be detected.

Another secondary effect is the emission of ultrasound. Within the defect, the discharge acts like a small explosion on the surrounding medium, glass or air, as a result of which sound waves are emitted, the frequency spectrum of which extends from a few kHz to the MHz range. A generally valid relationship between the partial discharge intensity in pC and the emitted sound energy cannot, however, be specified here, since the sound at the point of origin can only be measured via the coupling to the transducer. The coupling factor is e.g. with discharges in gas bubbles, much smaller than in glass.

In addition to the so-called secondary effects described above, the discharge results in a more or less strong light emission, depending on the partial discharge intensity. Evaluations with the help of photographs showed an approximate proportionality between the emitted light flux and the discharge current. There was always a relatively long afterglow, even when there was no current. This suggests stable excitation states that arise during discharge. With stronger partial discharges, the discharge is always good visible. It can be assumed that part of the converted energy is always radiated during ionization at the discharge point, since in addition to ionization, there is always an excitation of molecules.

The secondary effects described here can be advantageously used for the method according to the invention. All known devices, sensors and the like can be used with which high-frequency radiation, ultrasound or light can be detected.

A particularly advantageous embodiment of the invention can be such that the spectrum of the partial discharges is recorded; From this spectrum, conclusions can be drawn about the individual types and sizes of the defects.

A device in which the method according to the invention can be used in a particularly advantageous manner is characterized in that a vessel with an electrically conductive liquid is provided, into which the container, which is preferably filled with the same liquid, can be immersed, and that in the liquid in the Container an inner electrode and outside of the container an outer electrode are provided, between which the high voltage field is generated. Since the vessel is made of electrically insulating material, an outer electrode will be immersed in the liquid, in the same way as an inner electrode is inserted in the container.

Accordingly, the container to be examined, possibly with defects, is placed in the vessel filled with the conductive liquid, in particular the bottle, which itself has the same conductive one Liquid is filled. Of course, there must be no electrically conductive connection between the liquid parts inside and outside the container, for example the bottle. The connection to the actual measuring device is made via the high-voltage electrodes, which are immersed in the vessel and in the container, preferably the bottle. The connection to this partial discharge measuring device is made via a known field cutoff in order to avoid any undesired disturbances.

A further advantageous embodiment can be such that a layer of electrically conductive material is applied tightly to the outer and inner surface of the container, which layer serves as an inner and outer electrode and between which the high-voltage field is applied. In a particularly advantageous manner, the layers consist of electrically conductive and elastic material, for example soot-filled rubber, and are pressed against the inside or outside surface of the container by means of air, similarly to an airbag, for example.

First of all, the partial discharge signals are not evaluated with regard to frequency spectrum, pulse height and shape, etc., but only act as an indication as to whether there is a container with a defect at all. In this case, the partial discharge current and / or the emitted high-frequency power and / or the emitted light emission and / or the ultrasound pressure is preferably detected. The latter arises (according to Harrold, the relationship between Ultra sonic and electrical measurements of under-oil-corona sources, IEEE Transactions on Electrical Insulation Vol. EL-11 (1976) 1, pp. 8-11) from:

ö for partial discharge between 5 and 230 pC and off

for partial discharge charges between 2,000 and 70,000 pC. At values between 230 and 2,000 pC there is an unstable range in which an unambiguous assignment to the sound pressure cannot be determined.

Detection of any partial discharge signal is sufficient for the indication. If you change the high voltage applied, you can infer the type, size and shape of the defects in the containers. For example, long cracks compared to short, metal inclusions compared to ceramic inclusions, large air bubbles compared to small ones with constant high voltage each result in larger partial discharge signals. On the basis of the spectrum of the partial discharge signals, conclusions can also be drawn regarding the type, size and shape of the defects.

If, in particular, glass bottles are subjected to a partial discharge investigation, then it can be seen that - above a certain value of the high voltage, a certain size of the defect causes an electrical breakdown, which causes the bottle to burst. This is the case if, for a certain voltage, the defect is, for example, larger than 0.5 mm in diameter. For a sorting machine to be developed, a switch in the bottle conveyor is no longer necessary to sort out the bottles with defects because the bottle splinters simply fall out of the bottle holder alone. However, this sorting method is only suitable if no automatic quality statistics are necessary. A combination would be possible. The destruction voltage, that is the voltage at which a bottle is destroyed, must be determined beforehand for each bottle shape. Further advantageous refinements and improvements of the invention can be found in the further subclaims.

On the basis of the drawing, in which some exemplary embodiments of the invention are shown, the invention and further advantageous refinements and improvements and further advantages are to be explained and described in more detail.

It shows:

1 shows a schematic representation of a device according to the invention for carrying out the method according to the invention,

2 shows a schematic circuit arrangement of a partial discharge measuring device,

3 shows a further embodiment of the invention,

4 shows a further embodiment of a device for testing bottles, in a schematic representation and

5 shows a plan view of a bottle transport device, likewise in a schematic representation.

The device for detecting imperfections within a container is shown schematically in FIG. 1. An electrically conductive liquid is filled into a conductive vessel 1, into which a container 3 to be checked, here preferably a bottle, is immersed. The bottle 3 is filled with a likewise conductive liquid 4, the two liquids 2 and 4 not being electrically connected to one another; both liquids can be identical.

An inner electrode 5 is inserted into the bottle 3, the vessel 1 serving as an outer electrode. A measuring device 6 is connected to the inner and outer electrodes 5, 1, as shown for example in FIG. 2. If the vessel 1 consists of insulating plastic, then an outer electrode 5 '(as shown in FIG. 1) must be inserted into the liquid 2 and connected to the measuring device 6. There is a defect 7 in the bottle 3 which can produce a partial discharge.

2 shows a measuring device, which can be the measuring device 6, for example. The measuring electrode arrangement shown in FIG. 1 is shown in FIG. 2 with the reference number 10; only the inner electrode 5 and the outer electrode 5 'are shown in FIG. 2; the outer electrode 5 'can also be the housing 1 at the same time. The partial discharge in the defect 7 of the bottle is indicated by the Z-shaped arrow 11. The high voltage between the two high voltage electrodes 5, 5 '/ lr is generated by means of a high voltage generator 12 which is electrically conductively connected to the electrodes 5, 5' / l. A measuring resistor 13 is switched on in the line between the high voltage generator 12 and the electrode 5 '/ 1, from which a measuring voltage U can be taken; A measuring current I then flows through the measuring resistor 13, represented by the arrow I. The measuring voltage U is fed to a measuring amplifier 14, which is connected to a display device 15 and with which a coil 16 of a relay 17 is connected in series, with which a device 18 for sorting out the bottles is connected with defects.

The mode of operation of the measuring device according to FIG. 2 is per se clear from the circuit arrangement:

If a partial discharge 11 occurs at the defect 7, then a current I flows, which generates a voltage U at the measuring resistor 13, which is read from an indicator 15 by means of an amplifier and a control device for sorting out by means of a relay 16/17 Bottles, labeled 18 in total, controls.

FIG. 3 shows a further embodiment of the circuit arrangement according to FIG. 2.

It is mentioned above that the partial discharge 11 generates high-frequency radiation 20 which can be received in a high-frequency detector 21. It can be measured there and used for a control signal to control a device (not shown) corresponding to the device 18.

4 shows a further embodiment of the device for detecting defects. A bottle 41 with an opening 42 is shown schematically within a vessel 40. The vessel 40 is preferably a steel container into which the bottle 41 is inserted, with either the bottle or the container being moved. In the area of Free edge of the vessel 41 is attached to the inside of a bag 43 made of electrically conductive material, which defines an airtight space 44 between itself and the inner surface of the vessel 40, into which a tube 45 opens, in which a valve arrangement 46 is located, which is connected to a compressor (not shown).

A pressure line tube 47 is inserted into the interior of the bottle 41, which ends in the interior of the bottle and is connected outside the bottle 41 via a valve 48 to the compressor (not shown in more detail). A sack 49 made of electrically conductive, elastic material is attached to the pressure tube 47 in a gas-tight manner, specifically in such a way that the sack 49 surrounds the region of the tube which will be located entirely within the bottle.

If the bottle 41 is to be examined for defects, then air is pumped into the space 44 via the pipeline 45 and into the sack 49 via the pipeline 47, in such a way that the sack 43 is completely and tightly sealed onto the outer surface of the Press bottle 41 and sack 49 completely tight against the inside surface of bottle 41. Care must be taken to ensure that the air between the contact surfaces of the sacks and the bottle is completely pushed out, similarly to when a film is smoothed on a smooth surface. The two bags 43 and 49, which bear against the inner and outer wall of the bottle 41, form high-voltage electrodes which are connected to the measuring device 50 in an electrically conductive manner. This version 50 can, for example, the measuring device according. Fig. 2 be. The facilities acc. 1 to 4, as indicated in Fig. 5, can be used in a bottle conveyor. Bottles 52 are conveyed in the direction of arrow P on such a bottle conveyor track 51. A defect detection device 53, ie one according to FIG. 4, through which the bottles 52 pass on their way over the bottle conveyor belt 51. A conveyor track 54 for vessels 40 with sacks 43 runs parallel to the bottle conveyor belt 51 in such a way that such vessels 40 are fed to the bottle conveyor track 51 at point A and transported away from the conveyor track at point B. As a result, the vessels 40 move in the direction of the arrow P-. Parallel to the bottle conveyor track 51 is a conveyor track 55 for the tubes 47 with the bags 49, which are fed to the bottle conveyor track in the area of the defect detection device 53 and are removed from it again.

The bottle 52, which is located at the point 52, reaches the area of the point A and is received there as a bottle 52_ by the vessel 40 with the sack 43. Both move on the bottle conveyor belt 51 to point C; there the inflation process of the space 44 is then completed. The tube 47 with the bag 49 is then inserted into the bottle 52 ₂ in the area of the defect detection device and the bag 49 is inflated therein. The measurement is carried out within the detection device 53, and after the end of the measurement, the tube 47 with the sack 49 is removed from the bottle and the vessel 40 is pulled downward away from the bottle; the latter process is completed in the area D / B and the vessel 40 can be transported back to the starting point A via the web 54. If the measurement in the defect detection device 53 has revealed a defect in the bottle, then the switch 56 in the bottle conveyor track 51 is activated and the bottle 52, which is located just in front of the switch 56, is transported to a disposal device according to the direction of the arrow P_. If the bottle is not affected by defects, the switch 56 is not activated and the bottle 52 moves, for example, to a bottle filling system or to the dispatch according to the direction of the arrow P.

Claims

1. Method for detecting defects in an electrically insulating material, e.g. made of metal, plastic or mineral material, in particular glass, existing container, preferably a bottle, characterized in that the container wall is introduced into a high-voltage field, the size and frequency of which are dimensioned such that partial discharges are formed in the defects which are detected become.

2. The method according to claim 1, characterized gekennzeich¬ net that the currents generated by the partial discharges and / or ultrasonic emissions and / or light emissions and / or high-frequency beams are detected.

3. The method according to any one of the preceding claims, characterized in that the high voltage applied, in particular 'in containers made of ceramic material or glass, is chosen so high that the partial discharge leads to destruction of the container.

4. The method according to any one of the preceding claims, characterized in that the spectrum of the partial discharge signals is recorded and conclusions are drawn on the type, size and shape of the defects from this spectrum.

5. Device for performing the method according to one of the preceding claims, characterized in that a vessel (1) with an electrically conductive liquid (2) is provided, in which the preferably filled with the same liquid (4) container can be immersed, and that an internal electrode is provided in the liquid in the container and an external electrode is provided in the liquid in the vessel, between which the high-voltage field is generated.

6. Device for performing the method according to claim 5, characterized in that the vessel (1) consists of electrically conductive material and serves as an outer electrode.

7. Device for performing the ^' method according to any one of claims 5 and 6, characterized in that on the outer and inner surface of the container (41) each have a layer (43, 49) of electrically conductive material is applied tightly, which as the inside - Serve and outer electrode and between which the high voltage field is applied.

8. Device for performing the method according to claim 7, characterized in that the layers of electrically conductive material are formed like a bag and are pressed by means of air against the inner or outer surface of the container (41).

, Device for carrying out the method according to claim 8, characterized in that the layer (43) is designed as a sack made of electrically conductive material and is attached in a gas-tight manner in the region of the free end of the vessel (40) such that there is between the outer surface of the sack (43) and the inner surface of the vessel (40) forms a space (44) into which air can be pumped.

10. Device for performing the method according to one of claims 5 to 9, characterized gekennzeich¬ net that a conduit for pressure fluid (47) is provided, which is surrounded by a bag (49) made of electrically conductive and elastic material so that it is gastight a space is formed between the inner surface of the sack (49) and the outer surface of the conduit (47), into which pressure fluid can be pumped via the conduit (47).

11. Device for performing the method according to one of claims 5 to 10, characterized gekennzeich¬ net that it has a measuring device with a sensor (13, 21) on which signals (U) are removable, the partial discharge current and / or Ultrasonic emission of the partial discharge and / or the high-frequency emission of the partial discharge and / or the light emission of the partial discharge correspond to those which can be fed to an amplifier and can be displayed in a display device.

12. A device for performing the method according to claim 11 for installation in a bottle transport device, characterized in that the measurement signals traceable to the partial discharge serve to control a switch (56) on a conveyor belt (51), via which bottles with defects are sorted out ¬ are bar.