Device for inspecting molded parts

Abstract

The invention relates to a device (1) for checking beverage closures (2) for processing errors. The invention relates to a beverage closure device (1), comprising an electrode arrangement (3) consisting of two electrodes (4, 5) which are directed towards each other, a transport device (6) for transporting a beverage closure (2) through the electrode arrangement (3), a voltage source which is connected only to one of the two electrodes (4, 5) and generates a high voltage in a pulsed manner, and an evaluation unit (8) which measures the current across the other of the two electrodes (4, 5). The other of the two electrodes (4, 5) is grounded, and the voltage source is provided by a high-voltage capacitive ignition device (7).

Description

TECHNICAL FIELD

[0001] The present invention relates to an apparatus for inspecting, in particular separating, shaped parts. BACKGROUND

[0002] In the manufacture of plastic parts, such as beverage closure caps or coffee capsules, it is common to monitor their faultless manufacture in-line. The example will be dealt with below in particular of a beverage closure cap, although other (plastic) shaped parts are also covered by the invention.

[0003] To date, beverage closure caps usually have, in addition to a base body with a sheath face, a cap face and an internal thread, an original band which is connected perforatedly to the base body and which is separated from the base body upon the first unscrewing of the bottle. Due to a new EU regulation which aims to prevent the improper disposal of separated beverage closure caps from the bottle in the environment, the beverage closure cap is no longer separated from the original band upon the first opening, but is instead folded away from it, so that the entire beverage closure cap remains on the bottle neck also upon the consumption of the beverage. In order to be able to place the base body onto the bottle neck again without problems, such so-called tethered caps are provided on the inner side of the cap face with corresponding guide means which protrude from the cap face for the simplified centring placement of the beverage closure cap onto the bottle mouth. Beverage closure caps are usually injection-moulded parts, in the manufacture of which defects such as, for example, holes, cracks, micro-cracks or material weakening can occur, in particular in the region of the injection point, as a result of which the beverage closure cap is not leak-tight. To date, beverage closure caps have been checked for such defects mainly by means of automated optical inspection. However, in the case of product-related processing speeds which significantly exceed 2000 up to 4000 products / minute, the guide means described previously in the interior of the tethered cap potentially lead to difficulties in inspection, since the angular position of the guide means relative to the camera lens or the inserted electrode is not determined and thus interferes with or even prevents defect recognition by automated image recognition or the insertion of the electrode. The entire separation, inspection and sorting process of the beverage closure cap thus constitutes a fundamental bottleneck in beverage closure cap manufacture and must be carried out correspondingly quickly and reliably.

[0004] An inspection apparatus has therefore been developed which enables reliable inspection even for beverage closure caps with protrusions or guide means moulded therein. Such an apparatus is known from EP 3 204 762 B1, in which the beverage closure cap is guided between two electrodes, which are each provided with a voltage source and which are operated with such a high voltage difference that an electrical discharge occurs as soon as the beverage closure cap has a hole. The disadvantage of this prior art is the load on the switching elements for switching on and off the voltage sources, which has had to be reduced by using two voltage sources. Also disadvantageous is the fact that the voltage between the electrodes has to be switched off as soon as there is no beverage closure cap between the electrodes. SUMMARY The invention is therefore based on the task of proposing a device which avoids the disadvantages of the prior art and still enables an efficient inspection of beverage closure lids.

[0005] The task is solved by a device for inspecting beverage closure lids for processing errors, having an electrode arrangement consisting of two mutually pointing electrodes, a transport device for transporting beverage closure lids through the electrode arrangement, a voltage source which is connected only to one of the two electrodes and which generates a high voltage in pulses, and an evaluation unit which measures the current on the other of the two electrodes, wherein the other of the two electrodes is grounded, and the voltage source is provided by a high-voltage capacitor ignition device.

[0006] Here, a beverage closure lid is understood in particular to be one which is manufactured by the injection-molding method as is common in the prior art, but this is not a prerequisite for the device to function according to the invention. Rather, a beverage closure lid according to the invention is formed from a plastic or other material which is electrically insulating, so that the discharge of the electrode arrangement does not penetrate the material of the beverage closure lid, but is able to pass through any holes or cracks which can be present. For this purpose, the beverage closure lid is transported through the electrode arrangement consisting of two mutually pointing electrodes by means of the transport device for the purpose of the inspection, at the time of which the beverage closure lid is located between the two electrodes. In principle, it is preferred to feed the beverage closure lid into the electrode arrangement in the same orientation, in which the beverage closure lid is oriented with the lid face in the direction of the electrode which receives the current breakdown, in order to enable a compliant inspection of the beverage closure lid. The electrodes are preferably each constructed rotationally symmetrically, in order to avoid a discharge in a direction other than that of the second electrode and thus an uncontrolled discharge. For better controllability and reproducibility, the electrodes are furthermore centered on one another in a plane perpendicular to their rotational axis, in particular coaxially. Here, one of the electrodes is connected to the voltage source, which is provided by a high-voltage capacitor ignition device. This electrode is applied with a voltage from the high-voltage capacitor ignition device, while the other electrode is not provided with a voltage and is furthermore preferably grounded. Alternatively, the potential difference between the electrodes can also be established by other means. Thereby, the electrode which is applied with a voltage discharges, and a voltage breakdown to the other electrode occurs. At such a voltage breakdown, a current becomes measurable, which can be detected by the evaluation unit. The voltage breakdown thus indicates a hole or crack in the beverage closure lid which is positioned in the electrode arrangement. At the same time, the beverage closure lid is electrically insulating, so that in the absence of a hole, although a partial discharge can occur, this is not perceived by the evaluation unit due to the low current which reaches it, and the beverage closure lid can thus be assessed as being defect-free. It is not important in principle for the mode of action of the device whether the beverage closure lids are guided into the electrode arrangement separately or in contact with one another.

[0007] According to the application, the high-voltage capacitor ignition device is a commercially available high-voltage capacitor ignition device. In addition to the capacitor, the high-voltage capacitor ignition device has an ignition transformer with an open-circuit core. The high-voltage capacitor ignition device has the advantage over other ignition devices that the ignition coil of the ignition transformer is not used as an energy store and therefore has a higher service life. Also, the high-voltage capacitor ignition device is less sensitive to short circuits and environmental influences. Regardless of whether a voltage breakdown to the grounded electrode occurs, the charge stored in the capacitor of the high-voltage capacitor ignition device is completely discharged into the ignition coil during each charging process and thus also during each ignition, so that even here the components of the high-voltage capacitor ignition device are only lightly loaded. Due to the high voltage generated by the high-voltage capacitor ignition device, the inspection speed is limited only by the charging process of the capacitor. The high-voltage pulse generated by the high-voltage capacitor ignition device is thus determined by the energy in the capacitor and the winding ratio of the ignition transformer. The high-voltage pulse is provided preferably within about 50 µs after ignition. A pulse width of 10 µs is sufficient for identifying defects such as holes in beverage closure lids. The flattening of this high-voltage pulse requires about a further 25 µs, regardless of whether a voltage breakdown has occurred. Typically, the high-voltage capacitor ignition device generates up to 100 high-voltage pulses per second here, with a greater number of high-voltage pulses per second also being possible. Thus, even with a short buffer time between the high-voltage pulses, up to 4000 beverage closure lids can be inspected per minute. Here, the polarity of the high-voltage pulse is switchable according to the application, so that positive or negative high-voltage pulses are generated as required, in particular in relation to the product. The reversal of the high-voltage pulse takes place on the primary side of the transformer via a relay with two switching contacts. It is further advantageously provided that the evaluation unit is a current transformer. Current transformers are particularly suitable in the high-voltage field and generate a signal of higher quality and thus easier to process than a simple shunt resistor. It is provided in the design of the application that the transformation ratio of the ignition transformer of the high-voltage capacitor ignition device is greater than 1:80, in particular greater than 1:100, preferably 1:135. Due to this high transformation ratio, a relatively low charging voltage is required on the primary side in order to generate a high voltage by means of the high-voltage capacitor ignition device. If the high-voltage pulse is to be, for example, 50 kV, only a charging voltage of about 325 V is required.

[0008] It is provided in the improvement of the application that the electrodes each have a conical tip, in particular with a cone opening angle of less than or equal to 45°, particularly preferably equal to 40°. With a cone opening angle greater than 45°, there is a risk of a voltage breakdown in an undesirable direction, for example to the edge of the beverage closure lid and / or around the beverage closure lid. A cone opening angle of 40° has proven to be particularly advantageous and foolproof here.

[0009] In a design variant of the application it is provided that at least one of the two electrodes is supported so as to be axially movable relative to the other. By the configuration of the distance between the two electrodes the device can be simply adapted to changing application situations. In this way, in the case of beverage closure caps of different sizes, the device can almost be used in continuous operation. Furthermore, in this way the device can be simply adapted to changing environmental parameters such as the size or temperature of the beverage closure cap or the ionization or humidity of the ambient air. The distance between the two electrodes can here be determined by means of conventional sensors such as optical gratings or the like.

[0010] In a refinement of the application it is provided that the distance between the electrodes is selected in such a way that, in the case of use, the creepage distance along the wall of the beverage closure cap is at least twice as long as the air distance which arises in the case of a processing error of the beverage closure cap. The application understands the air distance to be the shortest distance between the two electrodes, which the breakdown will pass in the case of a missing resistance, i.e. due to a processing error, without creeping along the surface of the beverage closure cap. In contrast, the creepage distance in the sense of the application is the distance which the breakdown will pass when a beverage closure cap without a hole is located between the two electrodes. Since the beverage closure cap is electrically insulating, the breakdown seeks a path along the beverage closure cap to the electrode to which no voltage is applied. By the upper limit of twice the length of the creepage distance relative to the air distance, a limit is defined for the ratio of the diameter to the height of the beverage closure cap. In this way, beverage closure caps with a small diameter and a large height can not be able to be checked by the device in certain cases, since a discharge in the undesired direction can occur, while a discharge through the hole of the beverage closure cap can be prevented. In principle, a larger ratio is therefore advantageous and promotes the desired breakdown in the case of a defect in the beverage closure cap to be checked, for which a minimum ratio of twice the creepage distance to the single air distance has proved to be sufficient to maintain quality. The upper limit of the ratio between the creepage distance and the air distance is here indirectly defined by the upper edge of the beverage closure cap, however preferably a distance of approximately 1 mm or more from the upper edge. In this way, the beverage closure cap can always be guided without collision through the electrode device. However, if the ratio between the creepage distance and the air distance is so unfavorable that the beverage closure cap cannot be easily checked, the device is supplemented according to the application with an insertion mechanism which extends the electrodes into the interior space of the beverage closure cap to be checked.

[0011] In the design of the application it is provided that the transport device consists of an electrically insulating slide surface and a transport mechanism. The slide surface is understood according to the application as a surface on which the beverage closure can slide with as little friction as possible. The transport mechanism according to the application is a mechanism which drives the beverage closure located on the slide surface into the desired flow direction. A suitable transport mechanism can be in particular a mechanical push device or an air jet. Alternatively, a transport device is also in accordance with the application in which the beverage closure slides along its downward direction on an inclined slide surface due to gravity. One of the electrodes, in particular the electrode which is not applied with voltage, is flush or at most sunk by about 2 mm into the electrically insulating slide surface. This has the advantage that due to the electrical insulation of the slide surface the breakdown always ends in the electrode which is placed in the slide surface and a breakdown at an undesired location is avoided.

[0012] In a refinement of the application, it is provided that the transport mechanism is configured as a transport belt, in particular as a perforated transport belt, wherein the transport belt is guided on a sliding surface, wherein the device in particular also has a separating device, in particular a rocker separating device. In order to safely transport beverage closure lids during the manufacturing process, in which typically 2000-4000 beverage closure lids are processed per minute, it is advantageous to transport the beverage closure lids via a transport belt on which the beverage closure lids are held by means of a negative pressure. For this purpose, the transport belt is perforated and the negative pressure is generated by means of a device in the sliding surface. It is likewise advantageous here to apply a separating device, which separates the beverage closure lids from one another and ideally positions them onto the holes in the transport belt, wherein the moment at which the high-voltage pulse is triggered is synchronized with the beverage closure lid between the two electrodes and the hole in the transport belt located thereunder. In this way, it is ensured that not only is each beverage closure lid reliably held on the transport belt by means of the negative pressure, but also the breakdown through the hole in the beverage closure lid reaches the electrode, which is not applied with voltage, unhindered through the hole in the transport belt, and the transport belt is not damaged. Furthermore, by means of the separating device, it is possible to establish a constant spacing between the beverage closure lids, so that the high-voltage pulse can be a uniform, correspondingly metronomic high-voltage pulse. A rocker separating device is particularly advantageous here, since it separates the beverage closure lids particularly gently, since the introduction of force takes place at most via the less sensitive peripheral surface of the beverage closure lid. A rocker separating device in the sense of the application here comprises blocking members configured as rockers arranged on both sides of the transport path, which can be synchronously manipulated by means of one or more actuators. The two swing members act like forceps, which remain closed on the subsequent beverage closure lid as long as the latter needs to be blocked. This position can be actively switched by means of the actuators according to the application, or also purely mechanically without actuators, and in particular can be released. In the other position of the blocking members, the subsequent beverage closure lid is located in the action area of the blocking members. The use of actuators for switching the position of the blocking members is particularly advantageous over purely mechanical switching, since by means of the active switching of the actuators, the duration of the holding of these positions is definable and adjustable by means of a control unit via the circuit of the actuators. In this way, the spacing between the beverage closure lids can be artificially lengthened or controlled, and their transport speed can be individually adapted. If the blocking members are pivoted into the further position, i.e. the release position, by means of the interaction with the actuators, the beverage closure lid located in the action area of the blocking members is released.

[0013] In an embodiment of the application it is provided that the transport mechanism is configured as a star wheel, in which the beverage closure received in the star wheel rests on a sliding surface. According to the application, such a star wheel has radial recesses on its outer surface, in which the beverage closure is received and moved by these radial recesses when the star wheel is rotated about its axis of rotation. According to the application, the electrode arrangement is arranged here on the radially outer surface of the star wheel, so that the beverage closure is transported by the star wheel into the electrode arrangement. In order to achieve a transport of the beverage closure with as little friction as possible, the beverage closure rests on a sliding surface.

[0014] In an embodiment of the application it is provided that the device also has at least one sensor which measures the temperature of the beverage closure before the region between the two electrodes and / or the temperature of the ambient air in the region between the two electrodes and / or the air humidity of the ambient air in the region between the two electrodes. The temperature measurement takes place before the region between the electrodes in order to already know the voltage at the time of the capacitor charging process and to be able to react to the measured temperature accordingly. Furthermore, a measurement between the electrodes is not advantageous, since a breakdown occurs in the electrode arrangement and the air in the electrode arrangement is thereby heated compared to the rest of the ambient air. Depending on the temperature of the beverage closure, the trigger voltage required for the discharge can be influenced. The trigger voltage thus decreases with increasing temperature, since there are more and more free charge carriers in the air at higher temperatures. It has been shown here under high voltage that, in particular at beverage closure temperatures of more than 40°C, the required trigger voltage decreases. The same applies to the air humidity of the ambient air, wherein the required trigger voltage increases with increasing air humidity.

[0015] In an improvement of the application it is provided that it has a mechanism for measuring the acoustic signal produced by the breakdown. A noise is produced at the breakdown or spark strike, which has a different signal curve and / or different frequency spectrum depending on the length of the breakdown. Through a more precise evaluation of this acoustic signal it can be distinguished whether the breakdown has occurred directly through the processing error of the beverage closure, i.e. the shortest path or air distance, or along the wall of the beverage closure, i.e. via a creeping distance. According to the application, this evaluation takes place by comparing the measured signal curve or frequency spectrum with a database in which known acoustic signals of beverage closures with and / or without processing errors are stored. If the result of the evaluation is that the breakdown is particularly long, i.e. via a creeping distance, it should be assumed that there is no processing error and the adjacent air distance is not exposed, i.e. the beverage closure is defect-free. This comparison of signal curves can likewise be carried out on the basis of current measurement signals.

[0016] In an embodiment of the application it is provided that the device has a control unit with which the voltage generated by the voltage source can be adjusted. The adjustment of the voltage is advantageous in particular when the environmental parameters change, for example the temperature or the air humidity of the beverage closure, or when the distance between the electrodes is changed, which can be necessary in particular when the shape of the beverage closure to be checked changes.

[0017] In an embodiment of the application it is provided that the voltage generated by the voltage source is up to 50 kV, in particular 35 - 45 kV. Such voltage values have proven to be particularly advantageous and reliable trigger voltages with regard to the usual environmental parameters, the shape of the beverage closure common on the market and the beat to be reached by the high-voltage pulse.

[0018] In an embodiment of the application it is provided that the device further has a high-voltage feedback device which has a voltage divider and a feedback evaluation unit. It can be expedient to check the functionality of the device. This can be achieved in particular when the beverage closure is separated by consciously triggering a high-voltage pulse at the moment when no beverage closure is positioned between the electrodes. In this case, the check takes place via the evaluation unit with the aid of which it can be determined whether the set high voltage is sufficient to span the distance between the two electrodes. However, if the beverage closure is not separated, it is advantageous for the device to have a high-voltage feedback device. According to the application, the high-voltage feedback device has an integrated high-voltage feedback signal with the aid of which the functionality of the high-voltage source can be monitored during operation. Here the high voltage is divided via the voltage divider and then evaluated by the comparator. In this way it can be checked whether the high voltage is actually as high as set or it deviates from the rated value.

[0019] In an embodiment of the application it is provided that the device further has a mechanism for influencing the air ionization in the region between the two electrodes. By changing the air ionization in the examination region, it can be facilitated or, on the contrary, prevented that the trigger voltage breaks down. Thereby, a lower voltage on the high-voltage capacitor ignition device is sufficient.

[0020] It is also provided according to the application that the previously described device is applied in a method for checking separated beverage closures for processing errors. According to the application, the method here has the following steps, which are carried out for each beverage closure: a) feeding the beverage closure with the aid of a conveying device between two electrodes, b) generating a high-voltage pulse with the aid of a voltage source and applying the voltage to the electrodes connected thereto, c) measuring the arrival current on the other electrode. Here steps a) to c) are carried out for each beverage closure and take place within fractions of a second.

[0021] In a refinement of the method, those beverage closures which in step c) have a measurable arrival current from the electrode to which the voltage is applied can be sorted out in a further step d) following step c). If a current is measurable at the time of the breakdown on the electrode to which no voltage is applied, this is an indication of a hole in the beverage closure, which makes it unsuitable for regular use and it has to be sorted out. The sorting out can here be carried out by mechanical means or air nozzles.

[0022] In a design variant of the method, it is in accordance with the application that steps b) and c) are carried out without a beverage closure between the electrodes after step c) has been carried out for a beverage closure. In this way the functionality of the device can be checked. If a current is thus measured on the electrode to which no voltage is applied, it is clear that the high-voltage pulse is sufficient to produce a voltage breakdown at the set distance between the electrodes.

[0023] It is furthermore advantageous to supplement the method with a step in which the temperature of the beverage closure and / or the ambient air in the region of the electrode device and / or the air humidity in the region of the electrode device is measured, since the triggering voltage for the breakdown is influenced by these environmental parameters. It is likewise advantageous to adapt the high voltage produced by the high-voltage capacitor ignition device and / or the distance between the two electrodes to the measured environmental parameters. A higher voltage is thus required at higher air humidity, while a lower voltage is sufficient at temperatures warmer than 40°C.

[0024] The application is described in a preferred embodiment with reference to the drawings, in which further advantageous details can be gathered from the figures.

[0025] Functionally identical components are provided here with the same reference numerals. BRIEF DESCRIPTION OF DRAWINGS

[0026] The drawings show in detail: Figure 1 : schematic sectional view of the device according to the application in the first embodiment, Figure 2 : schematic sectional view of the device according to the application in the first embodiment with the drawn discharge lines, Figure 3 : schematic view of the device according to the application in the second embodiment, Figure 4 : schematic view of the device according to the application in the third embodiment. DETAILED DESCRIPTION Figure 1A schematic cross-sectional view of the device 1 according to the application in a first embodiment is shown. Also shown are three beverage closure caps 2, which are conveyed through the device 1 by a conveying device 6. The middle one of the three shown beverage closure caps 2 has a hole in its cap face, which is detected by the device 1. In addition to the conveying device 6, which in the shown embodiment is configured as a slide surface 11 on which the beverage closure caps 2 are moved, the device 1 also has an electrode device 3. The electrode device 3 comprises two electrodes 4, 5, wherein in the shown embodiment the upper electrode 4 is connected to a voltage source provided by a high-voltage capacitor ignition device 7. In contrast, the lower electrode 5 is machined flush upwards in the slide surface 11 and is not connected to a voltage source, but is earthed. The high-voltage capacitor ignition device 7 generates a high-voltage pulse, which has such a high voltage that a breakdown from the tip of the upper electrode 4 to the tip of the lower electrode 5 is possible, in particular when the beverage closure cap 2 has a hole in the cap face. If such a breakdown occurs, the current reaching in the lower electrode 5 can be measured by an evaluation unit 8 and from this the hole or defect in the beverage closure cap 2 between the two electrodes 4, 5 can be determined. The high-voltage pulse generated by the high-voltage capacitor ignition device 7 is a very short pulse with a pulse width of a few microseconds, which is sufficient for the measurement by the evaluation unit 8 and enables a high number of beverage closure caps 2 per minute. In order to avoid a breakdown at the edge of the beverage closure cap 2 or outside the beverage closure cap 2, the tips of the electrodes 4, 5 are configured as rotationally symmetrical conical, wherein the opening angle of the conical tip is less than 45°. Furthermore, due to the electrical insulation of the slide surface 11, it is ensured that the breakdown from the upper electrode 4 is discharged into the tip of the lower electrode 5. Since the trigger voltage for the breakdown depends on different environmental parameters, but also on the distance between the two electrodes 4, 5, at least one electrode, in the shown embodiment in particular the upper electrode 4, is movably supported in the axial direction, that is to say towards or away from the lower electrode 5. With regard to the environmental parameters, the device 1 has a sensor 14, which measures the temperature before the area of the electrode device 3 and / or the air humidity of the ambient air in the area of the electrode device 3. In order to be able to react appropriately to the environmental parameters measured by the sensor 14, the device 1 also has a control unit 15, which controls the high-voltage capacitor ignition device 7. In this way, the trigger voltage is lower at higher temperatures and greater at higher air humidity. This can be compensated by the control unit 15 in a targeted manner. Furthermore, the device 1 has a mechanism for influencing the ionization of the air 17, which changes the ionization of the air in the electrode device 3 to a predetermined extent and thereby influences the breakdown. In order to be able to check whether the device 1 is working correctly, the device has a high-voltage feedback device 16, which, like the control unit 15, is connected to the high-voltage capacitor ignition device 7. Via the high-voltage feedback device 16, the voltage generated by the high-voltage capacitor ignition device 7 is measured and evaluated in operation.Alternatively, the high-voltage pulse can be triggered at the moment when the beverage closure 2 is not located between the two electrodes 4, 5, so that the breakdown proceeds unhindered from the upper electrode 4 into the lower electrode 5, and the arriving current can be evaluated in the evaluation unit 8.

[0027] Figure 2 A schematic sectional view of the device 1 according to the application in the first embodiment with the drawn discharge lines is shown. The embodiment shown here corresponds to that shown in Figure 1 To avoid a discharge through the beverage closure 2, i.e. along the creepage distance 9, it is advantageous according to the application for the distance between the electrodes 4, 5 of the electrode arrangement 3 to be chosen so that the creepage distance 9 is at least twice as long as the air distance 10, which is produced directly between the electrodes 4, 5 by a manufacturing error in the beverage closure 2. In contrast to this, the creepage distance 9 is the shortest distance along the wall of the beverage closure 2, which can be shortened slightly by perforations, for example the perforations of the original band shown here. If the distance between the electrodes 4, 5 is so great that the ratio of the distances falls below this limit, the triggering voltage required for the discharge is too great and there is a risk of a discharge in an undesired direction. At the same time, the upper edge of the jacket surface of the beverage closure 2 forms another limit. The distance between the electrodes 4, 5 should therefore still be great enough so that the tip of the upper electrode 4 does not have to protrude into the beverage closure 2 and the beverage closure 2 can be guided unhindered through the electrode arrangement 3. To determine whether the breakdown is a breakdown via the air distance 10 or the creepage distance 9, a mechanism 19 for measuring acoustic signals is also provided, which receives and evaluates the acoustic signals produced by the breakdown. As a result, the distance travelled by the breakdown can be determined from the signal curve and / or the spectrum of the acoustic signals of the breakdown.

[0028] Figure 3 A schematic view of the device 1 according to the application in the second embodiment is shown. The embodiment differs from the embodiments of the previous two figures in particular in that the transport arrangement has, in addition to the sliding surface 11, a transport belt 12, which is guided on the sliding surface 11. The transport belt 12 is perforated here so that a negative pressure is drawn through the holes and the beverage closures 2 are thereby held on the transport belt 12. Furthermore, the device 1 has a separating device 13, which is designed as a rocker separating device in the embodiment shown. By means of the separating device 13, the beverage closures 2 are separated from one another at always the same distance. As a result, the high-voltage pulses in the electrode arrangement 3, only one electrode of which is shown here, can be produced at the same rhythm. Furthermore, the discharges can correspond to the rhythm of the holes in the transport belt 12, so that a discharge through the holes for the beverage closures 2 can always take place unhindered via the electrode arrangement 3.

[0029] Figure 4 A schematic view of the device 1 according to the application in the third embodiment is shown. The embodiment is like that in theFigure 3 The transport device shown in the middle is likewise provided with a star wheel 18, in addition to a slide surface, which is not shown here. The radial recesses of the star wheel 18 are suitable for separating the beverage closure caps from one another at a predefined distance and transporting them along the radial outer surface of the star wheel 18 about the axis of rotation of the star wheel 18. For this purpose, the electrode device 3 is arranged in such a way that the beverage closure caps moved by the star wheel 18 are fed between the electrodes 4, 5.

[0030] List of reference signs 1 device 2 beverage closure cap 3 electrode device 4 first electrode 5 second electrode 6 transport device 7 high-voltage capacitor ignition device 8 evaluation unit 9 creepage distance 10 air distance 11 slide surface 12 transport mechanism 13 separating device 14 sensor 15 control unit 16 high-voltage feedback device 17 mechanism for influencing air ionization 18 star wheel 19 mechanism for measuring acoustic signals.

Claims

1. An apparatus (1) for inspecting molded parts for processing errors, particularly beverage caps (2), comprising an electrode assembly (3) consisting of two mutually pointing electrodes (4, 5), a conveying device (6) for conveying the beverage cap (2) through the electrode assembly (3), a voltage source connected only to one of the two electrodes (4, 5) and generating a high voltage in a pulsed manner, and an evaluation unit (8) for measuring the current on the other of the two electrodes (4, 5), characterized in that, The other of the two electrodes (4, 5) is grounded, and the voltage source is provided by the high-voltage capacitor ignition device (7).

2. The apparatus (1) according to claim 1, characterized in that, The transformation ratio of the ignition transformer in the high-voltage capacitor ignition device (7) is approximately 1:

135.

3. The apparatus (1) according to claim 1 or 2, characterized in that, Electrodes (4, 5) each have a conical tip, particularly having a cone angle of less than 45°, and especially preferably equal to 40°.

4. The apparatus (1) according to claim 1, 2 or 3, characterized in that, At least one of the two electrodes (4, 5) is supported to be axially movable.

5. The apparatus (1) according to any one of the preceding claims, characterized in that, The distance between the electrodes (4, 5) is chosen such that, in use, the creepage distance (9) along the wall of the beverage cap (2) is at least twice the length of the air distance (10), which is generated in the presence of a manufacturing error in the beverage cap (2).

6. The apparatus (1) according to any one of the preceding claims, characterized in that, The conveying device (6) consists of an electrically insulated sliding surface (11) and a conveying mechanism (12).

7. The apparatus (1) according to claim 5, characterized in that, The conveying mechanism (12) is constructed as a conveyor belt, particularly as a perforated conveyor belt, wherein the conveyor belt is guided on a sliding surface (11), wherein the device (1) also has a separation device (13), particularly a rocker-type separation device.

8. The apparatus (1) according to claim 5, characterized in that, The delivery mechanism (12) is constructed as a star wheel (18), in which the beverage sealing cap (2) received in the star wheel (18) is abutted against the sliding surface (11).

9. The apparatus (1) according to any one of the preceding claims, characterized in that, The device (1) also has at least one sensor (14) that measures the temperature of the beverage cap before the area between the two electrodes (4, 5) and / or the temperature of the ambient air in the area between the two electrodes (4, 5) and / or the humidity of the ambient air in the area between the two electrodes (4, 5).

10. The apparatus (1) according to any one of the preceding claims, characterized in that, The device (1) has a mechanism (19) for measuring the acoustic signal generated by the breakdown.

11. The apparatus (1) according to any one of the preceding claims, characterized in that, The device (1) has a control unit (15) which can regulate the voltage generated by the high-voltage capacitor ignition device (7).

12. The apparatus (1) according to any one of the preceding claims, characterized in that, The voltage generated by the high-voltage capacitor ignition device (7) is as high as 50 kV, especially 35-45 kV.

13. The apparatus (1) according to any one of the preceding claims, characterized in that, The device (1) also has a high-voltage feedback device (16) which has a voltage divider and a feedback evaluation unit.

14. The apparatus (1) according to any one of the preceding claims, characterized in that, The device (1) also has a mechanism (17) for ionizing air in the region between the two electrodes (4, 5).

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