Device for inspecting molded parts

Abstract

The invention relates to a device (1) for inspecting beverage closure caps (2) for processing errors, having an electrode assembly (3) which is made of two electrodes (4, 5) that face each other, a transport device (6) for transporting the beverage closure caps (2) through the electrode assembly (3), a voltage source which is solely connected to one of the two electrodes (4, 5) and generates a high voltage in a pulsed manner, and an analysis unit (8) which measures the current at the other electrode of the two electrodes (4, 5). The invention is characterized in that the other electrode of the two electrodes (4, 5) is grounded, and the voltage source is provided by a capacitor discharge ignition (7).

Description

[0001] Device for testing molded parts

[0002] The present invention relates to a device for testing, in particular, individual molded parts for defects.

[0003] In the production of plastic parts such as beverage caps or coffee capsules, it is common practice to monitor their flawless production close to the process. However, the following will focus on beverage caps, although other (plastic) molded parts are also encompassed by the invention.

[0004] Until now, beverage caps typically have a base body with a shell, a lid surface, and an internal thread, as well as a tamper-evident strip. This strip is perforated and separated from the base body when the bottle is first unscrewed. However, due to a new EU regulation designed to prevent individual beverage caps separated from bottles from being illegally disposed of in the environment, beverage caps are no longer separated from the tamper-evident strip when first opened, but rather folded away from it, so that the entire beverage cap remains attached to the bottle neck even when the beverage is consumed.In order to be able to easily place the base body back onto the bottle neck, such so-called tethered caps are provided with corresponding guides on the inside of the lid surface, protruding from the lid surface, to simplify the centered placement of the beverage closure caps on the bottle opening.

[0005] Beverage caps are typically injection-molded parts, and during their production, defects such as holes, cracks, hairline fractures, or material weaknesses can occur, particularly in the injection point area, causing the caps to leak. To date, beverage caps have primarily been inspected for such defects using automated optical inspection. However, at product-related processing speeds of well over 2,000 to 4,000 products per minute, the previously described guides inside the tethered caps potentially lead to difficulties during inspection, as the angular position of the guide relative to the camera lens or an immersed electrode is uncertain, thus disrupting or even preventing defect detection via automatic image recognition or the immersion of the electrode.The entire separation, inspection and sorting process of the beverage cap therefore represents a major bottleneck in the production of beverage caps and must be carried out quickly and reliably.

[0006] For this reason, testing devices have already been developed which enable reliable testing even of beverage closure caps with incorporated elevations or guides. EP 3 204 762 B1, for example, discloses a device in which the beverage closure caps are passed between two electrodes, each provided with a voltage source and operated with such a high voltage difference that a discharge occurs if a beverage closure cap has a hole. A disadvantage of this prior art is the load on the switching elements for switching the voltage sources on and off, which already had to be reduced by using two voltage sources. Another disadvantage is that the voltage between the electrodes has to be switched off as soon as there is no beverage closure between them.The present invention is therefore based on the object of proposing a device which avoids the disadvantages of the prior art and yet enables efficient testing of beverage closure caps.

[0007] This object is achieved by a device for checking beverage closure caps for processing defects, comprising an electrode arrangement formed from two mutually facing electrodes, a transport device for transporting the beverage closure caps through the electrode arrangement, a voltage source which is connected to only one of the two electrodes and generates a high voltage in a pulse-like manner, and an evaluation unit which measures the current at 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.

[0008] Beverage closure caps are understood to mean, in particular, those manufactured by injection molding, as is customary in the prior art. However, this is not a prerequisite for the device to function according to the invention. Rather, according to the invention, the beverage closure caps are made of a plastic or other material that has an electrically insulating effect, so that the discharge of the electrode arrangement does not penetrate the material of the beverage closure caps, but can penetrate through any holes or cracks. For this purpose, the electrode arrangement, through which the beverage closure caps are transported through the transport device for testing, is formed of two facing electrodes, between which the beverage closure cap is located at the moment of testing.In principle, it is preferred that the beverage caps be placed in the electrode array in the same orientation, with the lid surface facing the current-receiving electrode, to enable proper inspection of the beverage caps. The electrodes are preferably each rotationally symmetrical to prevent discharge in a direction other than the direction of the second electrode, thus preventing uncontrolled discharges. For better control and reproducibility, the electrodes are also centered relative to one another in a plane perpendicular to their rotation axes, in particular coaxially. One of the electrodes is connected to a voltage source provided by a high-voltage capacitor ignition.This electrode is supplied with a voltage from the high-voltage capacitor ignition, while the other electrode is not supplied with a voltage and is preferably also grounded. Alternatively, a potential difference between the electrodes can be created by other means. This discharges the electrode supplied with the voltage, creating a voltage breakdown to the other electrode. When such a voltage breakdown occurs, a current can be measured and detected by the evaluation unit. A voltage breakdown thus indicates a hole or crack in a beverage closure cap positioned in the electrode arrangement. At the same time, the beverage closure cap acts as an electrical insulator, so that in the absence of a hole, partial discharges can occur. However, due to the low incoming current, these are not detected by the evaluation unit, and the beverage closure cap can therefore be assessed as defect-free.For the functioning of the device, it is fundamentally irrelevant whether the beverage caps are guided into the electrode array individually or in contact with each other. According to the invention, the high-voltage capacitor ignition is a commercially available high-voltage capacitor ignition. In addition to a capacitor, it comprises an ignition transformer with an open iron core. Compared to other ignition systems, the high-voltage capacitor ignition has the advantage that the ignition coils of the ignition transformer are not used as energy storage devices and therefore have a longer service life. Likewise, the high-voltage capacitor ignition is less susceptible to short circuits and environmental influences.Regardless of whether a voltage breakdown to the grounded electrode occurs or not, the stored charge in the capacitor of the high-voltage capacitor ignition is completely discharged into the ignition coils during each charging process and thus also during each ignition, so that the components of the high-voltage capacitor ignition are only minimally stressed. Due to the high voltage generated by the high-voltage capacitor ignition, the test speed is limited only by the capacitor's charging process. A high-voltage pulse generated by a high-voltage capacitor ignition is therefore determined by the energy in the capacitor and the winding ratio of the ignition transformer. The high-voltage pulse is preferably available within approximately 50 ps after ignition. A pulse width of 10 ps is sufficient to detect a defect such as a hole in a beverage cap.The flattening of this high-voltage pulse requires approximately another 25 ps, regardless of whether a voltage breakdown has occurred. High-voltage capacitor ignitions typically generate up to 100 high-voltage pulses per second, although larger numbers of high-voltage pulses per second are also possible. This allows up to 4,000 beverage caps to be tested per minute, even with a small buffer between the high-voltage pulses. According to the invention, the polarity of the high-voltage pulses can be switched so that positive or negative high-voltage pulses are generated as needed, particularly depending on the product. The high-voltage pulses are inverted on the primary side of the transformer via a relay with two changeover contacts. Furthermore, it is advantageous for the evaluation unit to be a current measuring transformer.A current transformer is particularly suitable for high voltage applications and generates higher quality signals that are easier to process than simple shunt resistors.

[0009] In one embodiment of the invention, the transformation ratio of an ignition transformer of the high-voltage capacitor ignition system is greater than 1:80, in particular greater than 1:100, preferably 1:135. Due to such a high transformation ratio, a relatively low charging voltage is required on the primary side to generate a high voltage through the high-voltage capacitor ignition system. If the high-voltage pulse is to be 50 kV, for example, only a charging voltage of approximately 325 V is required.

[0010] In a further development of the invention, the electrodes each have a conical tip, in particular with an opening angle of the cone less than or equal to 45°, particularly preferably equal to 40°. At opening angles of the cone greater than 45°, there is a risk of voltage breakdown in an undesired direction, for example, to the edge of a beverage cap and / or past the beverage cap. An opening angle of 40° has proven particularly advantageous and less prone to failure.

[0011] In one embodiment of the invention, at least one of the two electrodes is mounted so that it can be axially displaced relative to the other. By configuring the distance between the two electrodes, the device can be easily adapted to a changing application. This allows the device to be used with beverage caps of different sizes almost during ongoing operation. Furthermore, the device can be easily adapted to changing environmental parameters such as the size or temperature of the beverage caps or the ionization or humidity of the ambient air. The distance between the two electrodes can be determined using conventional sensors such as light barriers or similar.

[0012] In a further development of the invention, the distance between the electrodes is selected such that, in use, a creepage distance along a wall of the beverage closure cap is at least twice as long as a clearance distance that results in the event of a manufacturing defect in the beverage closure cap. For the purposes of the invention, a clearance distance is the most direct distance between the two electrodes that a breakdown would take in the event of a lack of resistance, i.e. due to a manufacturing defect, without creeping along a surface of the beverage closure cap. A creepage distance within the meaning of the invention, on the other hand, is the distance that the breakdown would take in the case of a beverage closure cap without a hole 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 that is not subject to voltage.The upper limit of twice the creepage distance compared to the clearance distance defines the limit for the ratio of the diameter to the height of the beverage caps. For example, a beverage cap with a small diameter and a large height may not be testable with the device, as a discharge could occur in undesired directions, while a discharge through the holes in the beverage cap could be prevented. In principle, a larger ratio is therefore more advantageous and promotes the desired breakdowns in the case of defects in the beverage caps being tested. A minimum ratio of twice the creepage distance to one clearance distance has proven to be sufficient to maintain quality.An upper limit for the ratio between creepage distance and clearance is indirectly defined by the upper edge of the beverage caps, but a distance of approximately 1 mm or more from the upper edge is preferably defined. This ensures that the beverage caps can always be guided through the electrode arrangement without collision. However, if the ratio between creepage distance and clearance is so disadvantageous that testing of the beverage caps is not readily possible, the invention provides for supplementing the device with a mechanism for immersing the electrodes into the interior of the beverage cap to be tested.

[0013] In one embodiment of the invention, the transport device is formed from an electrically insulating sliding surface and transport means. The sliding surface is understood according to the invention as a surface on which the beverage closure caps can slide with as little friction as possible. Transport means according to the invention are means that drive the beverage closure caps located on the sliding surface in a desired flow direction. Suitable transport means can in particular be mechanical pushing devices or air nozzles. Alternatively, a transport device according to the invention in which the beverage closure caps slide down an inclined sliding surface due to gravity is also according to the invention. One of the electrodes, in particular the electrode not subjected to voltage, is inserted flush at the top or countersunk by at most approximately 2 mm into the electrically insulating sliding surface.This has the advantage that, due to the electrical insulation of the sliding surface, the breakdown always ends in the electrode inserted therein and breakdowns at undesired locations are avoided.

[0014] In a further development of the invention, the transport means are designed as a conveyor belt, in particular as a perforated conveyor belt, wherein the conveyor belt is guided on the sliding surface, wherein the device further comprises, in particular, a separating device, in particular a rocker separating device. For the safe transport of beverage caps during the manufacturing process, in which 2,000–4,000 beverage caps are often processed per minute, it is advantageous to convey the beverage caps via a conveyor belt, to which they are held by a vacuum. For this purpose, the conveyor belt is perforated, while a vacuum is created by a device in the sliding surface.It is also advantageous to use a separating device that separates the beverage caps from one another and ideally positions each one over a hole in the conveyor belt. At the same time, the time of triggering the high-voltage pulse is synchronized with the beverage caps and the hole in the conveyor belt below them between the two electrodes. This ensures that each beverage cap is held securely on the conveyor belt by the vacuum, and that the voltage passing through a hole in the beverage cap also reaches the non-voltage-loaded electrode unhindered through the hole in the conveyor belt, preventing damage to the conveyor belt. In addition, a separating device can always maintain the same distance between the beverage caps, so that the high-voltage pulse can be a homogeneous, appropriately timed high-voltage pulse.A rocker separating device is particularly advantageous because it separates the beverage closure caps particularly gently, as force is only introduced via the less sensitive outer surface of the beverage closure caps. A rocker separating device according to the invention comprises rocker-like locking elements arranged on both sides of the transport path, which can be actuated synchronously by one or more actuators. The two pivoting elements act like a pair of pliers, which remain closed for a following beverage closure cap as long as the following beverage closure cap needs to be held back. According to the invention, this position can be actively switched by an actuator or purely mechanically without an actuator, and in particular can be released. In a further position of the locking elements, the following beverage closure cap is within the effective range of the locking elements.The use of an actuator to switch the position of the locking elements is particularly advantageous compared to a purely mechanical switching system, since the active switching of the actuator allows the holding time of these positions to be defined and adjusted via the control unit via the actuator's switching. This allows the distance between the beverage caps to be artificially extended or controlled, and their transport speed to be individually adjusted. If the locking elements are pivoted into a further position, i.e., a release position, through interaction with the actuator, the beverage cap located within the effective range of the locking elements is released.

[0015] In one embodiment of the invention, the transport means is designed as a star wheel, with the beverage closure caps accommodated in the star wheel resting on the sliding surface. According to the invention, such a star wheel has radial recesses on its outer surface in which the beverage closure caps are received and through which they are moved when the star wheel rotates about its axis of rotation. According to the invention, the electrode arrangement is arranged on the radial outer surface of the star wheel, so that the beverage closure caps are moved into the electrode arrangement by the star wheel. To enable the beverage closure caps to be transported with as little friction as possible, the beverage closure caps rest on the sliding surface.

[0016] In an embodiment of the invention, the device further comprises at least one sensor which measures the temperature of the beverage caps in front of the area between the two electrodes and / or the ambient air in the area between the two electrodes and / or the humidity of the ambient air in the area between the two electrodes. The temperature is measured in front of the area between the electrodes so that the voltage is already known at the time the capacitor is charging and a corresponding response can be made to the measured temperature. In addition, a measurement between the electrodes is disadvantageous because breakdowns occur in the electrode arrangement and as a result the air in the electrode arrangement is higher than the wider ambient air. Depending on the temperature of the beverage caps, a trigger voltage which is necessary for a discharge can be influenced.The trigger voltage decreases with increasing temperature because there are more and more free charge carriers in the air at higher temperatures. It has been found that with high voltages the required trigger voltage decreases particularly when the temperature of the beverage closure cap is above 40°C. The same applies to the humidity of the ambient air, with the required trigger voltage increasing with increasing humidity. In a further development of the invention it is provided that it has means for measuring an acoustic signal generated by a breakdown. In the event of a breakdown or spark strike, a noise is generated which has a different signal curve and / or a different spectrum depending on the length of the breakdown. By evaluating this acoustic signal more precisely, it is possible to distinguish whether the breakdown was caused directly by the manufacturing error in the beverage closure cap, i.e. the shortest path or the longest path.the air gap or along the wall of the beverage closure cap, i.e., across the creepage distance. According to the invention, such an evaluation is carried out by comparing the measured signal curve or spectrum with a database containing known acoustic signals from beverage closure caps with and / or without manufacturing defects. If the evaluation results in a particularly long breakdown, i.e., across a creepage distance, it can be assumed that there is no manufacturing defect and that the nearby air gap was not exposed, meaning that the beverage closure cap was free of defects. Such a signal curve can also be compared based on the current measurement signal.

[0017] In a further development of the invention, the device comprises a control unit with which the voltage generated by the voltage source can be regulated. Regulating the voltage is particularly advantageous when environmental parameters change, for example, the temperature of the beverage caps or the humidity, or when the distance between the electrodes is changed, which may be necessary, in particular, when the shape of the beverage caps to be tested changes.

[0018] In an embodiment of the invention it is provided that the

[0019] The voltage generated by the voltage source is up to 50 kV, particularly 35-45 kV. Such voltage values ​​have proven to be particularly advantageous and reliable trigger voltages, given the typical ambient parameters, the commercially available beverage cap shapes, and the desired timing of the high-voltage pulse.

[0020] In a further development of the invention, the device further comprises a high-voltage feedback device comprising a voltage divider and a feedback evaluation unit. Occasionally, it may be appropriate to check the device for its functionality. This can be achieved, particularly when the beverage caps are separated, by deliberately triggering the high-voltage pulse at a time when no beverage cap is positioned between the electrodes. In this case, the check is carried out via the evaluation unit, which can be used to determine whether the set high voltage is sufficient to bridge the distance between the two electrodes. However, if the beverage caps are not separated, it is advantageous if the device comprises a high-voltage feedback device.According to the invention, this device features an integrated high-voltage feedback signal, which allows the function of the high-voltage source to be monitored during operation. The high voltage is divided by a voltage divider and then evaluated by a comparator. This allows it to be verified whether the high voltage was actually as high as set or whether it deviates from this target value.

[0021] In an embodiment of the invention, the device further comprises means for influencing the ionization of the air in the area between the two electrodes. By changing the ionization of the air in the test area, the triggering of a voltage breakdown can be promoted or, conversely, prevented. This allows lower voltages to be applied to the high-voltage capacitor ignition.

[0022] According to the invention, it is also provided that the previously described device is used in a method for inspecting individual beverage closure caps for manufacturing defects. The method comprises the following steps, which are carried out for each beverage closure cap: a) placing the beverage closure caps between the two electrodes using the transport device, b) generating a high-voltage pulse using the voltage source and applying this voltage to the connected electrode, c) measuring the current arriving at the other electrode. Steps a) to c) are carried out for each beverage closure cap and take place in a few fractions of a second.

[0023] In a further development of this process, in a further step d) following step c), those beverage caps can be sorted out for which a current flowing from the voltage-applied electrode was measurable in step c). If a current flowing through the electrode not subjected to voltage is measurable during a breakdown, this indicates a hole in the beverage cap, making it unsuitable for normal use and must be sorted out. Sorting can be performed using mechanical means or air jets.

[0024] In one embodiment of the method, it is inventive that, after performing step c) with a beverage cap, steps b) and c) are performed without a beverage cap between the electrodes. This allows the functionality of the device to be monitored. If a current is measured at the electrode without voltage applied, it is clear that the high-voltage pulse is sufficient for voltage breakdown at the set distance between the electrodes.

[0025] Furthermore, it is advantageous to supplement the method with a step in which the temperature of the beverage caps and / or the ambient air in the region of the electrode arrangement and / or the air humidity in the region of the electrode arrangement is measured, since the trigger voltage for a breakdown is influenced by these environmental parameters. It is also advantageous to adjust the high voltage generated by the high-voltage capacitor ignition and / or the distance between the two electrodes according to the measured environmental parameters. For example, a higher voltage is required at higher air humidity, while a lower voltage is sufficient at temperatures above 40°C.

[0026] The invention is described by way of example in a preferred embodiment with reference to a drawing, wherein further advantageous details can be taken from the figures of the drawing.

[0027] Functionally identical parts are provided with the same reference symbols.

[0028] The figures in the drawing show in detail:

[0029] Fig. 1 : schematic sectional view of a device according to the invention in a first embodiment,

[0030] Fig. 2: schematic sectional view of a device according to the invention in a first embodiment with discharge lines drawn in, Fig. 3: schematic view of a device according to the invention in a second embodiment.

[0031] Fig. 4: schematic view of a device according to the invention in a third embodiment.

[0032] Fig. 1 shows a schematic sectional view of a device 1 according to the invention in a first embodiment. Also shown are three beverage closure caps 2, which are conveyed through the device 1 by a transport device 6. The middle of the three beverage closure caps 2 shown has a hole in its lid surface, which is detected by the device 1. In addition to the transport device 6, which in the illustrated embodiment is designed as a sliding surface 11 on which the beverage closure caps 2 are moved, the device 1 further has an electrode arrangement 3. The electrode arrangement 3 comprises two electrodes 4, 5, wherein in the illustrated embodiment the upper electrode 4 is connected to a voltage source provided by a high-voltage capacitor ignition 7.In contrast, the lower electrode 5 is incorporated flush with the sliding surface 11 at the top and is not connected to a voltage source, but is grounded. The high-voltage capacitor ignition 7 generates a high-voltage pulse with 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, especially if the beverage closure cap 2 has a hole in the lid surface. If such a breakdown occurs, the current arriving at the lower electrode 5 can be measured by an evaluation unit 8, and a hole or defect in the beverage closure cap 2 between the two electrodes 4, 5 can thus be detected.The high-voltage pulse generated by the high-voltage capacitor ignition 7 is a very short pulse with a pulse width of a few microseconds, which is sufficient for measurement by the evaluation unit 8 and enables a high processing rate of the beverage caps 2 per minute. To prevent breakdowns at the edge of the beverage caps 2 or past the outside of the beverage caps 2, the tips of the electrodes 4, 5 are designed in a rotationally symmetrical conical shape, with the opening angle of the cone tip being less than 45°. Furthermore, the electrical insulation of the sliding surface 11 ensures that a breakdown from the upper electrode 4 is discharged to the tip of the lower electrode 5.Since the trigger voltage for a breakdown depends on various environmental parameters, but also on the distance between the two electrodes 4, 5, at least one electrode, in particular the upper electrode 4 in the illustrated embodiment, is mounted so as to be movable in the axial direction, i.e., toward or away from the lower electrode 5. With regard to the environmental parameters, the device 1 has a sensor 14 that measures the temperature in front of the area of ​​the electrode arrangement 3 and / or the humidity of the ambient air in the area of ​​the electrode arrangement 3. In order to be able to react appropriately to the environmental parameters measured by the sensor 14, the device 1 further has a control unit 15 that controls the high-voltage capacitor ignition 7. Thus, the trigger voltage is lower at higher temperatures and higher at higher air humidity. This can be specifically compensated for by the control unit 15.In addition, the device 1 has means for influencing the ionization of the air 17, which changes the ionization of the air in the electrode arrangement 3 to a predetermined extent and thereby influences a breakdown. In order to be able to check whether the device 1 is functioning correctly, the device has a high-voltage feedback device 16, which, like the control unit 15, is connected to the high-voltage capacitor ignition 7. The voltage generated by the high-voltage capacitor ignition 7 is measured and evaluated during operation via the high-voltage feedback device 16. Alternatively, a high-voltage pulse could be triggered at a time when no beverage cap 2 is located between the two electrodes 4, 5, so that a breakdown occurs unhindered from the upper electrode 4 to the lower electrode 5 and the incoming current can be evaluated in the evaluation unit 8.

[0033] Fig. 2 shows a schematic sectional view of a device 1 according to the invention in a first embodiment with discharge lines drawn in. The embodiment shown here corresponds to the one shown in Fig. 1. In order to avoid a discharge past the beverage closure cap 2, i.e. along the creepage distance 9, it is advantageous according to the invention that the distance between the electrodes 4, 5 of the electrode arrangement 3 is selected such that the creepage distance 9 is at least twice as long as the air gap 10, which results between the electrodes 4, 5 directly from a processing error in the beverage closure cap 2. In contrast, the creepage distance 9 is the shortest distance along the wall of the beverage closure cap 2, which can be slightly shortened by perforations such as the perforation of a tamper-evident strip shown here.If the distance between the electrodes 4, 5 is so large that the ratio of the distances falls below this limit, the required trigger voltage for a discharge is too high and there is a risk of a discharge in unwanted directions. At the same time, the upper edge of the outer surface of the beverage closure caps 2 represents a further limit. The distance between the electrodes 4, 5 should therefore still be large enough that the tip of the upper electrode 4 does not have to immerse the beverage closure caps 2 and the beverage closure caps 2 can be guided through the electrode arrangement 3 without obstructions. To determine whether the breakdown occurred via the air gap 10 or the creepage distance 9, a means 19 for measuring an acoustic signal is provided, which records and evaluates the acoustic signals generated by the breakdown.The distance traveled by the breakdown can be determined based on the signal curve and / or the spectrum of the acoustic signal of the breakdown.

[0034] Fig. 3 shows a schematic view of a device 1 according to the invention in a second embodiment. This embodiment differs from the embodiment of the first two figures in particular in that the transport device has a conveyor belt 12 in addition to the sliding surface 11, which is guided on the sliding surface 11. The conveyor belt 12 is perforated so that a vacuum is drawn through the holes and the beverage closure caps 2 are thus held on the conveyor belt 12. In addition, the device 1 has a separating device 13, which in the embodiment shown is designed as a rocker separating device. The separating device 13 always separates the beverage closure caps 2 at a constant distance from one another. This makes it possible for the high-voltage pulse in the electrode arrangement 3, of which only one electrode is shown here, to be generated at the same time.In addition, the discharge can be timed according to the holes in the conveyor belt 12, so that the discharge can always occur unhindered via the electrode arrangement 3 when there is a hole in the beverage closure cap 2. Fig. 4 shows a schematic view of a device 1 according to the invention in a third embodiment. This embodiment, like the one shown in Fig. 3, has a transport device, which, in addition to a sliding surface (not shown here), has a star wheel 18. Its radial recesses are suitable for...

[0035] To separate beverage caps at a predefined distance from one another and transport them along the radial outer surface of the star wheel 18 around its rotational axis. For this purpose, the electrode arrangement 3 is arranged such that the beverage caps moved by the star wheel 18 are placed between the electrodes 4, 5.

[0036] LIST OF REFERENCE SYMBOLS

[0037] device

[0038] Beverage cap

[0039] Electrode arrangement

[0040] First electrode

[0041] Second electrode

[0042] T ransport device

[0043] High-voltage capacitor ignition

[0044] Evaluation unit

[0045] Creepage distance

[0046] Air distance

[0047] Slide surface

[0048] Means of transport

[0049] Separation device

[0050] sensor

[0051] Control unit

[0052] High-voltage feedback device

[0053] Means for influencing the ionization of the air Star wheel

[0054] Means for measuring an acoustic signal

Claims

PATENT CLAIMS 1. Device (1) for checking molded parts, in particular beverage closure caps (2) for processing defects, comprising an electrode arrangement (3) formed from two mutually facing electrodes (4, 5), a transport device (6) for transporting the beverage closure caps (2) through the electrode arrangement (3), a voltage source which is connected to only 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 at 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 a high-voltage capacitor ignition (7).

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

135.

3. Device (1) according to claim 1 or 2, characterized in that the electrodes (4, 5) each have a conical tip, in particular with an opening angle of the cone less than 45°, particularly preferably equal to 40°.

4. Device (1) according to claim 1, 2 or 3, characterized in that at least one of the two electrodes (4, 5) is mounted so as to be axially displaceable.

5. Device (1) according to one of the preceding claims, characterized in that the distance between the electrodes (4, 5) is selected such that, in use, a creepage distance (9) along a wall of the beverage closure cap (2) is at least twice as long as an air gap (10) which results in the presence of a processing defect in the beverage closure cap (2).

6. Device (1) according to one of the preceding claims, characterized in that the transport device (6) is formed from an electrically insulating sliding surface (11) and transport means (12).

7. Device (1) according to claim 5, characterized in that the transport means (12) are designed as a conveyor belt, in particular as a perforated conveyor belt, wherein the conveyor belt is guided on the sliding surface (11), wherein the device (1) in particular further comprises a separating device (13), in particular a rocker separating device.

8. Device (1) according to claim 5, characterized in that the transport means (12) are designed as a star wheel (18), wherein the beverage closure caps (2) accommodated in the star wheel (18) rest on the sliding surface (11).

9. Device (1) according to one of the preceding claims, characterized in that the device (1) further comprises at least one sensor (14) which measures the temperature of the beverage closure caps in front of the area between the two electrodes (4, 5) and / or 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. Device (1) according to one of the preceding claims, characterized in that it comprises means (19) for measuring an acoustic signal generated by a breakdown.

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

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

13. Device (1) according to one of the preceding claims, characterized in that the device (1) further comprises a high-voltage feedback device (16) comprising a voltage divider and a feedback evaluation unit.

14. Device (1) according to one of the preceding claims, characterized in that the device (1) further comprises means (17) for ionizing the air in the region between the two electrodes (4, 5).

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