Method and device for producing particle foam part, and method for calibrating production process

Abstract

The invention relates to a method for producing a particle foam part for sportswear, sports equipment or balls from foam particles using electromagnetic waves, comprising the following steps: filling a mold cavity, heating the foam particles with electromagnetic waves to weld them, demolding, in which parameters characterizing the absorption of the electromagnetic waves are monitored during the heating of the foam particles, and terminating the heating of the foam particles if the parameter changes by a predetermined amount. The method ensures that correct heat is supplied to the foam particles in a simple manner.

Description

Technical Field

[0001] The invention relates to a method and a device for producing particle foam parts for sportswear, sports equipment or balls from foam particles, a method for calibrating a process for producing particle foam parts for sportswear, sports equipment or balls from foam particles, a method for producing particle foam parts for sportswear, sports equipment or balls from foam particles, and a shoe. Background Art

[0002] WO 2013 / 05081A1 discloses a method for manufacturing a particle foam component, wherein a mixture of foam particles and a dielectric transfer liquid is heated by electromagnetic waves to fuse the foam particles to form a particle foam component. Radio waves or microwaves are used as electromagnetic waves. The material of the foam particles is formed of polypropylene (PP).

[0003] US 3,060,513 A discloses a method for sintering moist thermoplastic foam particles. The particles are dielectrically heated and simultaneously compressed in a mold. Electromagnetic waves are applied at a frequency of about 2 to 1000 MHz.

[0004] A similar process is described in US Pat. No. 3,242,238 A, in which foam particles are moistened with an aqueous solution and exposed to an electromagnetic field with a frequency of about 5 to 100 MHz.

[0005] GB 1,403,326 A describes a method for welding expandable polystyrene foam particles, wherein the particles are moistened with an aqueous solution and exposed to an electromagnetic field in the range of 5 to 2000 MHz.

[0006] WO 01 / 64414A1 discloses another method in which electromagnetic waves, particularly microwaves, are used to heat polyolefin polymer particles wetted by a liquid medium. In this case, the temperature in the molding tool is regulated by controlling the pressure present therein.

[0007] In the methods described above, in each case, moist foam particles are heated using electromagnetic waves, the electromagnetic energy being absorbed by the liquid and transferred to the particles.

[0008] US 5,128,073A discloses thermoplastic particles coated with a material that absorbs high frequency energy. These particles can be heated with electromagnetic waves, and the coating releases the electromagnetic energy and releases it to foam particles. Electromagnetic waves of 40 MHz to 2450 MHz are used to weld the foam particles.

[0009] These methods have been known for decades. However, they have not been successful in practice. There are various reasons for this. In laboratory samples, these methods work very well.

[0010] Therefore, in practice, foam particles are almost only welded by saturated dry steam, as is known, for example, from WO 2014 / 128214A1. Compared with welding with steam, welding with electromagnetic waves has never been successful in practice in recent decades, although electromagnetic wave welding will have considerable advantages due to the principle. In the case of electromagnetic waves, energy can be transmitted in a more targeted manner, whereby heating auxiliary bodies will not be required. When steam is used, steam must first be generated in a steam generator. Then, the steam must be supplied to the tool via a pipeline. All these components must be heated to a sufficiently high temperature so that the steam does not condense therein. This results in considerable heat losses. In addition, the device for steam generation and the steam pipeline occupy the largest installation space on the device for producing particle foam parts. If steam is not required to weld the foam particles, the entire device can be formed in a more compact manner.

[0011] The applicant of this patent application has only recently succeeded in achieving the transition to industrial production. He first realized that the main reason why the attempts to weld foam particles with electromagnetic waves have been unsuccessful for decades is that heat cannot be introduced uniformly into the foam particles. As a result, uniform welding cannot be obtained in the particle foam parts.

[0012] WO 2017 / 125410 A1, WO 2017 / 125412 A1, WO 2018 / 100154 A2, WO 2021 / 073924 A1 and WO 2022 / 229030 A1 disclose methods and devices for producing particle foam parts with a uniform heat distribution in the mold space.

[0013] In particular, WO 2018 / 100154A2 discloses a device for producing a particle foam part, comprising a molding tool defining a molding space, wherein at least two capacitor plates are arranged adjacent to the molding space, the capacitor plates being connected to a radiation source of electromagnetic radiation, wherein the radiation source of electromagnetic radiation is designed to emit electromagnetic radiation. The device is provided with a voltage measuring device, with which the voltage applied to the capacitor can be measured. The voltage measuring device is used to tune an oscillating circuit, which is designed to have a generator for electromagnetic waves and therefore has electrical power for supplying to the capacitor.

[0014] The object of the present invention is to provide a method and a device for manufacturing particle foam components made of foam particles for sportswear, sports equipment or balls, as well as a method for calibrating a process for producing particle foam components for sportswear, sports equipment or balls from foam particles, by means of which particle foam components made of foam particles for sportswear, sports equipment or balls and shoes can be reliably industrially manufactured by welding foam particles with the aid of electromagnetic waves, wherein the particle foam components made of foam particles for sportswear, sports equipment or balls are obtained with high quality. Summary of the invention

[0015] This object is achieved through several embodiments described herein.

[0016] According to a first aspect, the invention relates to a method for producing a particle foam component for sportswear, sports equipment or a ball from foam particles, in particular also for use, the method comprising the following steps:

[0017] - filling the moulding space,

[0018] - heating the foam particles with electromagnetic waves to fuse them together,

[0019] - Demoulding.

[0020] The method is characterized in that a parameter characterizing the absorption of electromagnetic waves is monitored during the heating of the foam particles and that the heating of the foam particles is terminated if the parameter changes by a predetermined amount.

[0021] The present invention is based on the recognition that the absorption capacity of the material increases sharply with the melting of the foamed particle material to be welded. It has long been known that polar molecules or polar functional groups absorb electromagnetic waves by being excited by electromagnetic waves and vibrating. During the melting of the material, the connection between the molecules becomes separated, making it easier for individual molecules or their functional groups to move. In the case where the material (such as PEEK) has polar functional groups but is firmly bound in the molecular structure, the polar functional groups cannot move, and the material hardly absorbs electromagnetic waves. Therefore, in order to absorb electromagnetic waves, the polar functional groups must be movable so that they can vibrate. In the case of very high mobility of polar functional groups, they do not cause friction or only cause slight friction, so that electromagnetic waves can only be slightly absorbed. Therefore, there is usually a peak area in which the corresponding material can absorb electromagnetic waves well. Since the mobility of the functional group is temperature-dependent, the absorption capacity of electromagnetic waves is usually also temperature-dependent.

[0022] Furthermore, the inventors of the present invention have recognized that the problem when welding foam particles for sportswear, sports equipment or balls with electromagnetic waves is that the heat must not only be evenly distributed in the molding space, but also must be accurately metered. When welding foam particles with steam, in the case of insufficient welding, steam can be supplied over a relatively long period of time so that all areas of the particle foam part are fully welded. Since the temperature of the steam is limited, overheating does not occur. This is also one reason why welding foam particles with electromagnetic waves has been less successful in the past than welding with steam.

[0023] Therefore, during welding, when the material to be welded has melted, the heat supply of the electromagnetic waves should be interrupted. Once the foam particles are melted, they combine during the cooling process to form the particle foam part, which is called welding. Further heating is not necessary, but harmful, because the material is then heated to a relatively high temperature and may burn.

[0024] According to the invention, during melting, the fact that the material's ability to absorb electromagnetic waves changes, which usually occurs suddenly, is used to adjust the duration of heating. Thus, in a very simple way, an exact metering of the heat to be supplied is achieved, which leads to a good weld and reliably prevents burning of the material.

[0025] The foam particles which are welded by the method to form the particle foam component (which comprises sportswear, sports equipment or a ball) are preferably foam particles from a thermoplastic material. The thermoplastic material can be, in particular, expanded polyurethane (ePU), polyether block amide (PEBA) or expanded polyethylene (ePE). These are polar plastics that absorb electromagnetic waves and, during melting, show a very strong change in the electromagnetic wave absorption capacity.

[0026] Foam particles from non-polar plastics, for example based on expandable polypropylene (ePP) or expandable polystyrene (ePS), can also be welded to form particle foam parts. Since these materials have no polar groups, they absorb electromagnetic radiation only to a very small extent. Therefore, it is advantageous to add a dielectric heat transfer medium, such as water. A small amount of water that wets the surface is sufficient. Water can be added in liquid form or as steam. Water molecules form dipoles, so that they absorb electromagnetic waves well and quickly heat up when radiating electromagnetic waves. Even if water is added to the foam particles in the form of steam, at least some of the water condenses on the surface of the foam particles and forms a liquid film. If water is added in liquid form, the water exists in liquid form before the foam particles are heated with electromagnetic waves, and a film is usually formed on the surface of the foam particles. When the foam particles are heated with electromagnetic waves, the water is heated and evaporated. The phase change from liquid water to steam causes a considerable change in the electromagnetic wave absorption capacity. If the water is completely converted into steam, this means that there is hot steam suitable for welding the foam particles in the mold space. Since the individual water molecules are free to move in the steam, they absorb almost no electromagnetic waves compared to liquid water. No further heating is required. The heating process can end.

[0027] The foam particles may also be formed from biological material, such as industrial popcorn from corn, which is provided with or coated with a binder such that the binder bonds the popcorn upon heating.

[0028] The term "popcorn" in the sense of the present invention includes in particular all materials, such as puffed corn (Zea mays, convar. Microsperma), which are exploded to high temperatures, if appropriate after corresponding fattening, by rapid heating, the water present in the seeds evaporates suddenly, thereby converting the starch contained in the seeds into a foamy consistency. This behavior is known in particular from quinoa seeds, amaranth, rice or also wheat, and materials based on these basic materials are also explicitly called "popcorn" and are included as "popcorn" in the sense of the present invention, the term "popcorn" not being intended to be limited to corn, but being selected in particular for reasons of simplicity, clarity and readability.

[0029] The binder may comprise a thermoplastic that melts when heated and solidifies when cooled, thereby bonding the popcorn grains to each other. The binder may also comprise a glue that chemically reacts when heated, thereby bonding the popcorn grains to each other.

[0030] Suitable binders are, in particular, thermoplastics, thermosetting plastics, amino resins, phenolic resins, isocyanates, proteins, tannic acid, starch, synthetic binders or natural binders, or mixtures of binders, for example urea-formaldehyde resins, melamine-formaldehyde resins, melamine-reinforced urea-formaldehyde resins, tannic acid-formaldehyde resins, phenolic resins, polymeric diphenylmethane diisocyanate or mixtures thereof.

[0031] The proportion of binder in the molded part (in % based on the weight of the molded part) is preferably <10%, preferably <5%.

[0032] Biomaterials usually contain a certain amount of moisture. The water contained in the biomaterial absorbs electromagnetic waves and heats the popcorn particles and the binder. When the binder evaporates, the absorption capacity of water for electromagnetic waves changes in the same way as above, which can again be determined by characteristic parameters. This also shows that the material is heated and combined in the molding space to form a particle foam part.

[0033] Therefore, there are different physical mechanisms of action, which cause changes in the electromagnetic wave absorption capacity. Since electromagnetic waves heat the material present in the molding space, strong changes in the electromagnetic wave absorption capacity always represent a reproducible phase of the heating process. Therefore, a characteristic parameter is a physical variable, which is characteristic of the foam particles to be welded and changes due to the radiation of electromagnetic waves, so that a specific process state or processing state of the foam particles to be welded can be determined based on this change.

[0034] The heating process can then be terminated depending on the change in the characteristic parameter. If the characteristic parameter changes, the heating process can be terminated directly or it can also be conveniently terminated at a predetermined time period after the change in the characteristic parameter (delayed termination of the heating process). The delay period is material-specific and the value of the delay period can be determined empirically. It has been found that in the case of most polar plastic materials, which melt due to the effect of electromagnetic forces, very short delay periods or delay periods of "0" are advantageous. In the case of other materials, in particular materials in which connections are formed between the foam particles due to chemical reactions, delay periods greater than "0" are also advantageous.

[0035] The electromagnetic wave can be generated by means of a capacitor in which the molding space is located. In this case, the electromagnetic wave can be applied to the capacitor with a predetermined voltage amplitude, and the power introduced into the molding space or its first or second order derivative over time can be measured as a characteristic parameter. It is also possible to apply the electromagnetic wave to the capacitor with a predetermined power and measure the voltage drop across the capacitor or its first or second order derivative over time as a characteristic parameter.

[0036] If the characteristic parameter is monitored directly, then in order to determine the change of the predetermined amount, it is checked whether the characteristic parameter changes by a predetermined threshold value within a predetermined time interval. This means a sudden change of the characteristic parameter.

[0037] If the first time derivative of the characteristic parameter is monitored, then in order to determine the change of the predetermined amount, it is checked whether the first time derivative of the characteristic parameter exceeds a predetermined threshold value. This in turn means a sudden change of the characteristic parameter.

[0038] If the second time derivative of the characteristic parameter is monitored, in order to determine the change of the predetermined amount, it is checked whether the second time derivative exceeds a predetermined threshold value. This means that the profile change of the characteristic parameter itself changes very strongly. If the profile of the characteristic parameter is entered in a diagram, a second time derivative exceeding a certain threshold value means a strong bending of the profile of the characteristic parameter over time. This also indicates a strong change of the characteristic parameter.

[0039] Therefore, there are different ways in which a strong change in a characteristic parameter can be detected. In order to obtain a signal for ending the heating of the foam particles by electromagnetic waves, it is important that the signal is characteristic and reproducible for the respective heating state of the foam particles. This is given in all the methods explained above.

[0040] Preferably, after heating and before demoulding, the particle foam part produced in the mold space is cooled in the mold space. This cooling process is also called stabilization.

[0041] The electromagnetic waves are preferably RF radiation. RF radiation has a frequency range of 30 kHz to 300 MHz. In many countries, a frequency of 27.12 MHz is available for industrial applications. This is a suitable frequency for heating the foam particles.

[0042] The amplitude of the high frequency voltage applied to the capacitor is preferably within 10 3 V to 10 5 V, and in particular in the range of 5×10 3 V to 1.5×10 4 within the range of V.

[0043] According to another aspect, the invention relates to a method for calibrating the manufacture of particle foam parts for sportswear, sports equipment or balls from foam particles using electromagnetic waves. In this method, at least one particle foam part for sportswear, sports equipment or balls is manufactured using a mold defining a specific molding space and foam particles of a specific material type according to one of the above methods, wherein the heating of the foam particles is controlled or terminated based on characteristic parameters. Then, other particle foam parts for sportswear, sports equipment or balls are produced by heating the foam particles with the same settings, the same settings being used to provide electromagnetic waves in each case with a production heating interval corresponding to the duration determined with the calibration process. These settings are mainly the applied electrical power or the applied voltage.

[0044] As a result, a production heating interval is determined during the calibration process, which defines the duration for which the foam particles are heated by the electromagnetic waves.

[0045] Since the suitable duration for heating the foam particles depends on the molding tool and the material type of the respective foam particles, it is possible to easily and quickly determine the individual production heating intervals for this purpose in order to produce high-quality particle foam parts therewith in a simple and reliable manner.

[0046] In the calibration process, a plurality of particle foam parts for sportswear, sports equipment or balls can also be produced and the duration of heating can be measured in each case. The production time interval can then be determined based on the plurality of durations measured during the calibration process. The average or median value of the individual durations can be determined as the production time interval.

[0047] Furthermore, when determining the production time interval, only durations that are within a predetermined multiple of a standard deviation around a mean value or around a median value of the measured durations are taken into account.

[0048] The duration of the measurement can be statistically evaluated to determine a quality factor for the production process. If the quality factor indicates that the stability of the production process is too low, the production process can be optimized based on this quality factor by changing certain parameters of the production process.

[0049] At least one of the following parameters may be changed and then the production time interval may be determined again according to the calibration process described above:

[0050] - the applied power of the electromagnetic wave,

[0051] - applied voltage for generating electromagnetic waves,

[0052] - the amount of heat transfer medium supplied to the moulding space,

[0053] - the amount of foam particles supplied to the molding space,

[0054] - The pressure exerted on the foam particles by the molding tool before heating the foam particles.

[0055] The at least one parameter to be changed and the degree of change can be determined automatically by means of an expert system.

[0056] According to another aspect, the invention relates to a device for producing granular foam parts for sportswear, sports equipment or balls from foam particles, the device comprising a molding tool delimiting a molding space, wherein at least two capacitor plates are arranged adjacent to the molding space, the capacitor plates being connected to a radiation source for electromagnetic radiation, wherein the radiation source for electromagnetic radiation is designed to emit electromagnetic radiation, and the device has a control device designed so that the device automatically performs the above-mentioned method.

[0057] According to a further aspect, the invention relates to a particle foam component made of foam particles for sportswear, sports equipment or a ball, which is produced according to one of the above methods. The particle foam component can be a sole or a part of a sole, in particular a midsole or a part of a midsole.

[0058] According to another aspect, the invention relates to a shoe, in particular a sports shoe, comprising a sole or midsole made of the above-described particle foam component, the particle foam component being made of foam particles for sportswear. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Possible embodiments of the present invention are further described below with reference to the following drawings:

[0060] Figure 1 An exemplary embodiment of a device for producing a particle foam component for sportswear, sports equipment or a ball from foam particles is shown,

[0061] Figure 2a , 2b The partially opened position ( Figure 2a ) and closed position ( Figure 2b ),

[0062] Figure 3 An electromagnetic radiation generator and a molding tool forming an adjustable oscillating circuit are shown in a circuit diagram, and

[0063] Figure 4 A control device for controlling the power supply is shown in a circuit diagram. DETAILED DESCRIPTION

[0064] In the following detailed description, possible embodiments of various aspects of the invention are described mainly with respect to methods and devices for producing particle foam parts for sportswear from foam particles, the sportswear including sports footwear, such as shoes and soles. However, it is emphasized that the invention is not limited to these embodiments. On the contrary, it can also be used for various types of sportswear, sports articles and sports equipment and sports equipment or balls, respectively, wherein at least one component comprises a particle foam part, such as any type of ball or racket, such as tennis rackets, golf clubs, baseball bats, badminton rackets, cricket rackets, ice hockey sticks, hockey sticks, squash rackets, table tennis rackets, or any type of protective clothing used in sports applications, such as shin guards, knee pads or elbow pads, etc.

[0065] Figure 1 The basic structure of a device 1 for producing particle foam parts for sportswear, sports equipment or balls from foam particles is shown. The device 1 comprises a material container 2, a molding tool 3 and a line 4 leading from the material container 2 to the molding tool 3. The particle foam parts are made of foam particles and are used for sportswear, sports equipment or balls.

[0066] The material container 2 is used to receive the loose foam particles. The material container 2 has a bottom 5, wherein the material container is connected to a compressed air source 7 in the bottom region via a compressed air line 6. The compressed air line 6 is connected to a plurality of nozzles (not shown) arranged in the bottom 5, so that a plurality of air streams (=fluidizing air) can be introduced into the material container 2, which swirl the foam particles present therein and thereby separate them.

[0067] An opening is formed in the region of the bottom 5 of the material container 2, to which opening the conveying line 4 is connected. The opening can be closed by a slide (not shown).

[0068] A driving nozzle 8 is located in the conveying line 4, adjacent to the material container. The driving nozzle 8 is connected to the compressed air source 7 via another compressed air line 9. The compressed air supplied to this driving nozzle 8 serves as driving air because it enters the conveying line 4 through the driving nozzle 8 and flows in the direction of the molding tool 3. As a result, a negative pressure is generated on the driving nozzle 8 on the side facing the material container 2, which sucks the foam particles out of the material container.

[0069] The conveying line 4 opens into a filling ejector 10 coupled to the molding tool 3. The filling ejector 10 is connected to a compressed air source 7 via a further compressed air line 11. The compressed air supplied to the filling ejector 10 is used, on the one hand, for filling the molding tool 3, wherein the foam particle flow is applied in the direction of the molding tool 3 by the compressed air. On the other hand, the compressed air supplied to the filling ejector 10 can also be used to blow the foam particles from the conveying line 4 back into the material container 2 at the end of the filling process of the molding tool 3.

[0070] The molding tool 3 consists of two mold halves 12, 13. At least one molding space 14 is defined between the two mold halves, into which a filling injector 10 for introducing foam particles is directed. By moving the two mold halves 12, 13 together, the volume of the molding space 14 can be reduced. When the mold halves 12, 13 are separated, a gap called a crack gap is formed between the mold halves 12, 13. Therefore, such a molding tool 3 is also called a crack gap molding tool.

[0071] The device 1 has no steam generator and no steam supply to the molding space 14, which are common in conventional devices for producing particle foam parts. In the molding space 14, moisture can be present through residual moisture contained in the material of the foam particles and moisture contained in the compressed air. However, the device 1 can also be formed with a steam generator and a steam supply to the molding space 14 and / or the conveying line 4 to supply saturated dry steam to the molding space 14 for additional heating or preheating of the foam particles and / or in order to wet the foam particles during their transport from the material container 2 to the molding space 14. The foam particles located in the material container 2 can also be wetted with water in liquid form, wherein for this purpose, corresponding nozzles for atomizing the water are arranged in the material container 2.

[0072] Capacitor plates 15, 16 are arranged on the half-molds 12, 13, respectively. These capacitor plates each contain a highly conductive material, such as copper or aluminum. A filling jet 10 is arranged on the half-mold 13. The filling jet 10 extends through a groove in the capacitor plate 16, which is attached to the half-mold 13.

[0073] The capacitor plates 15, 16 are connected to a generator 18 (e.g. an alternating voltage source) via electrical wires 17 for transmitting a high frequency voltage. These electrical wires 17 are usually waveguides. In the exemplary embodiment, the waveguide is formed by a hollow tube having, for example, a rectangular cross section and containing a conductive material. However, there are also other types of waveguides, such as coaxial cables, which are basically suitable for connecting the generator 18 to the capacitor plates 15, 16.

[0074] The mold halves 12, 13 each have a body which can be formed from a non-conductive material which is in particular substantially transparent to electromagnetic RF radiation, such as polytetrafluoroethylene (PTFE), polyethylene (in particular UHMWPE), polyetherketone (PEEK). Only the capacitor plates 15, 16 are formed to be conductive. A "material which is substantially transparent to" is a material which can be penetrated by electromagnetic radiation, in particular RF radiation. However, this material can be formed in a targeted manner which has certain absorption properties for electromagnetic RF radiation in order to convert part of the electrical RF radiation into heat and in order to heat the mold halves 12, 13 themselves. This will be explained in more detail below.

[0075] Alternatively, one or both mold halves may also form capacitor plates if they comprise an electrically conductive material such as aluminum or steel. However, the two mold halves are substantially electrically insulated from each other. Preferably, one of the two mold halves is formed to be electrically conductive and the other mold half is formed to be non-conductive. The conductive mold half may be three-dimensionally contoured so that it forms a corresponding three-dimensionally contoured surface on the particle foam part. The conductive mold half produces a smooth or predetermined precise surface texture and is therefore preferably used to produce a visible surface on the particle foam part.

[0076] The molding tool can be selectively connected to a negative pressure pump 19 so that negative pressure or vacuum can be applied to the molding space 14. This negative pressure causes moisture contained in the molding space 14 to be discharged.

[0077] The capacitor plates 15, 16 are preferably provided with cooling means. In the present exemplary embodiment, the cooling means are formed by a fan 20 which directs cooling air onto the side of the capacitor plates 15, 16 facing away from the molding space 14. To increase the cooling action, cooling fins 21 may be provided on the capacitor plates 15, 16.

[0078] Alternatively or additionally, a temperature control line can also be arranged on the capacitor plates 15, 16, through which a temperature control medium is conducted. Preferably, a liquid, such as water or oil, is used as the temperature control medium.

[0079] The method for producing a particle foam component for sportswear, sports equipment or a ball from foam particles using the above-described device is explained below:

[0080] The method includes the following basic steps:

[0081] -Filling the mold space 14

[0082] - Welding foam particles

[0083] - Stabilization (optional)

[0084] --Demolding

[0085] -Cleaning tools (optional)

[0086] To fill the molding space 14, air is blown into the region of the bottom 5 of the material container via the compressed air line 6, so that the foam particles present therein are swirled and separated. At the same time, drive air is also supplied to the drive nozzle, so that the foam particles are sucked out of the material container 2 into the conveying line 4 and conveyed together with the drive air in the direction of the molding tool 3. The molding space 14 is closed, wherein the half molds 12, 13 can be completely moved together or spaced apart from each other by a crack gap.

[0087] The slide of the material container 2 can be opened and closed continuously. The opening and closing time is usually in the range of 500 ms to 1 s. By this cyclic opening and closing of the slide, the foam particles from the material container 2 are intermittently fed to the conveying line 4. As a result, the bridges of the foam particles in the material container 2 can be opened and the foam particles are separated. This is particularly advantageous in the case of foam particles with an adhesive surface (e.g. eTPU foam particles).

[0088] Intermittent suction can alternatively also take place by means of an intermittent supply of drive air, which is supplied from a compressed air line 9 to a drive nozzle 8 arranged directly adjacent to the material container 2 .

[0089] The molding tools 12, 13 are provided with at least one valve (not shown) which opens when the foam particles are supplied so that the compressed air flowing into the molding space 14 can escape. The valve can be arranged in such a way that a counterpressure is formed in the molding space 14 during the filling of the molding space 14. As a result, the pressure in the delivery line and the molding space 14 can be kept high, so that the foam particles are kept in a small volume. This makes it possible to supply more foam particles to the molding space 14 than if no counterpressure was applied. After the counterpressure has been removed, the foam particles expand in the molding space 14.

[0090] Another parameter for setting the filling amount is the crack gap, ie the gap between the two mold halves 12, 13 arranged at a distance from one another during filling. Using the crack gap during filling first increases the density in the thin regions of the particle foam component to be produced.

[0091] Once it is determined that the mold space 14 is filled with foam particles, the filling ejector 10 is closed. The foam particles present in the line are blown back into the material container 2 by the compressed air supplied to the filling ejector 10.

[0092] The filling of the mould space 14 with foam particles is described in detail in the German patent application DE 10 2014 117 332 A1, to which reference is made for this reason.

[0093] After the mold space 14 is filled with foam particles, they are heated by applying electromagnetic RF radiation. The RF radiation is applied by injecting about 10 4 A high frequency voltage of V is applied to capacitor plates 15 and 16.

[0094] The electromagnetic RF radiation preferably has a frequency of at least 30 kHz or at least 0.1 MHz, in particular at least 1 MHz or at least 2 MHz, preferably at least 10 MHz.

[0095] The electromagnetic RF radiation preferably has a frequency of at most 300 MHz.

[0096] The foam particles for sportswear, sports equipment or balls can be formed on the basis of polyurethane (eTPU). In the case of electromagnetic radiation with a frequency of 1 MHz, the dielectric loss factor D of polyurethane is 0.2. In contrast, the dielectric loss factor of polypropylene (PP) is only 0.00035 in the case of electromagnetic radiation with a frequency of 1 MHz. Therefore, the absorption of polyurethane is significantly higher than that of polypropylene. Therefore, the heat required for welding the foam particles can be introduced into the mold space 14 without additional heat transfer substances, in particular without aqueous solutions, because the foam particles themselves absorb electromagnetic waves.

[0097] Instead of polyurethane-based foam particles, it is also possible to use foam particles based on polyether block amide (PEBA) or based on polyethylene (PE).

[0098] Foam particles based on ePP (expandable polypropylene) or ePS (expandable polystyrene) can also be welded to form particle foam parts. Since these materials absorb electromagnetic radiation only to a very small extent, it is advantageous to add a dielectric heat transfer medium, such as water. The foam particles can be wetted with the heat transfer medium in the material container 2 or during its transport from the material container 2 to the molding tool 3. The advantage of wetting in the line 4 is that the foam particles are wetted very evenly and the heat transfer medium is evenly distributed in the mold space 14. This leads to a correspondingly uniform heating of the foam particles in the mold space 14.

[0099] The molding tool 3 can also be connected to a steam source (not shown) by which saturated dry steam can be supplied to the molding space 14. This is advantageous when welding materials in which the dielectric loss factor is temperature-dependent. Such a material is, for example, ePES (expandable polyethersulfone) or expandable polyamide. At low temperatures, the absorption properties of electromagnetic waves are low. Therefore, these foam particles are first heated by steam to subsequently be heated from a specific temperature to an even higher temperature by electromagnetic radiation alone or in addition. Alternatively, the foam particles can be wetted with a dielectric heat transfer medium so that the dielectric heat transfer medium is heated by electromagnetic radiation to heat the foam particles to a predetermined temperature. Thereafter, direct heating of the foam particles can occur due to electromagnetic radiation, since the absorption properties of electromagnetic radiation increase with increasing temperature.

[0100] The molding tool 3 ( Figure 2a , Figure 2b ), which in each case have a first mold half 12 and a second mold half 13, and can be used in the above-described device 1. For a simpler illustration, in Figure 2a , 2b omits the moving device, the holding element, the thermometer for measuring the temperature in the mold space and other mechanical components for opening and closing the tool.

[0101] The moulding tool 3 is formed by two mould halves 12, 13, each having a body 24, 25 comprising an electrically conductive material. These bodies comprise, for example, aluminium, copper or a highly conductive alloy.

[0102] The two mold halves 12, 13 delimit the molding space 14 by means of inner delimiting surfaces 26, 27. The inner delimiting surfaces 26, 27 of the two mold halves 12, 13 are provided with an electrically insulating coating 28, 29.

[0103] The electrically insulating coatings can be formed of a material that is substantially transparent to electromagnetic radiation, in particular RF radiation, such as PTFE, PE, PEEK. However, they can also be formed of a plastic material whose dielectric loss factor is similar to that of the plastic material to be processed in the molding space 14 - in the case of applying electromagnetic radiation, so as to achieve uniform heating over the entire molding space 14 and at the edge areas of the molding space during the application of electromagnetic radiation. For this purpose, the coatings 28, 29 are preferably formed of a material with a medium loss factor, such as PET (polyethylene terephthalate), PEEK (polyether ketone), POM (polyoxymethylene), polyimide and PMMA (polymethyl methacrylate). Therefore, these coatings 28, 29 are substantially transparent to RF radiation because they absorb only a small part of the electromagnetic radiation and, due to the relatively low loss factor, can be formed to a specific thickness, such as at least 2 mm, in particular at least 2.5 mm or at least 5 mm. The coating is preferably not thicker than 20 mm, in particular not thicker than 15 mm, preferably not thicker than 10 mm, so that the coating absorbs a small proportion of the electromagnetic wave energy.

[0104] The conductive bodies 24, 25 form capacitor plates of the molding tool 3. They therefore have an electrical connection to enable connection to the generator 18 or to ground 30. The generator 18 represents a radiation source for generating electromagnetic radiation. Preferably, the generator is formed for generating RF radiation. The generator can also be formed for generating microwave radiation, wherein in the case of a larger molding space 14, a substantially more uniform heating can be achieved with RF radiation compared to microwave radiation. In addition, most plastic materials can absorb RF radiation better than microwave radiation. It is therefore preferred to use RF radiation.

[0105] Since both mold halves 12, 13 delimit the mold space 14 and simultaneously form capacitor plates, the distance between the "capacitor plates" and the mold space 14 is very small and is determined only by the electrically insulating coatings 28, 29. As a result, the losses of electromagnetic radiation are very low, whereby the proportion of power introduced as heat into the foam particles to be welded is very high. Thus, such a tool allows very efficient welding of foam particles to form particle foam parts for sportswear, sports equipment or balls.

[0106] In an embodiment of the molding tool 3 according to the invention, the first mold half 12 has a bottom wall 31 and a circumferential side wall 32. In an exemplary embodiment of the invention, both the bottom wall 31 and the side wall 32 are formed by an electrically conductive body 24 and a coating 28 arranged on the inside. The side wall 32 can also be made only of a non-conductive material, in particular a plastic material, or only partially by an electrically conductive body 24. The second mold half 13 forms a plunger which can be moved into the cavity formed by the first mold half 12 and thus tightly close the molding space 14. The tight closure between the two mold halves 12, 13 is at least so tight that the foam particles present therein cannot escape. The molding space 14 does not have to be closed in an airtight manner.

[0107] The two mold halves 12 , 13 can be moved relative to each other by a press (not shown) and a predetermined force can be applied.

[0108] A passage opening for supplying foam particles, hereinafter referred to as a filling opening 33, is arranged on the first half mold 12. The filling ejector 10 is connected to the filling opening 33. The filling ejector 10 is different from a conventional filling ejector in that it has no closing mechanism for closing the filling opening 33, which will be described in detail below.

[0109] The first mold half 12 has one or more passage openings for venting air, which are referred to below as ventilation openings 34 .

[0110] The filling opening 33 and the ventilation opening 34 are arranged on a part or region of the first half mold 12, in particular on an edge region, which is covered or covered by the second half mold 13 in the closed state of the molding tool 3 ( Figure 2b ). As a result, when the molding tool 3 is closed by introducing the second molding tool 13 into the cavity formed by the first molding tool 12, the filling opening 33 and the vent opening 34 are automatically closed. Therefore, the filling ejector 10 does not need to have a closing mechanism for closing the filling opening 33.

[0111] This portion or area is the area of ​​the first mold half 12 that is not covered by the second mold half 13 and is the area that is open when the mold halves are moved apart into the crack gap position.

[0112] Preferably, the first mold half 12 is connected to ground 30. The filling jet 10 is coupled to the conductive body 24 of the first mold half 12 so that the filling jet 10 is also electrically connected to ground 30. The generator 18 generates an electromagnetic wave or an alternating voltage relative to ground 30, which is applied to the body 25 of the second mold half 13. As a result, an electromagnetic alternating field, in particular RF radiation, is formed in the molding space 14.

[0113] In this embodiment of the molding tool 3, it is important that the electrically conductive bodies 24, 25 of the two mold halves 12, 13 are electrically insulated from one another. In the present exemplary embodiment, this is achieved by means of the coatings 28, 29.

[0114] Preferably, the inner delimiting surface 26, 27 of one of the two mold halves 12, 13 is formed in a contoured manner. Contoured in the sense of the present invention is any shape that deviates from a plane delimiting surface. In the present exemplary embodiment, the inner delimiting surface 27 of the second mold half 13 is contoured. The inner delimiting surface 26 of the first mold half 12 is not contoured in the region of the bottom wall 31.

[0115] Furthermore, this molding tool 3 differs from known molding tools for welding foam particles by means of electromagnetic waves in that the second molding tool 13 is constructed in the form of a plunger and is located with its electrical body 25 at least partially in the cavity defined by the first half mold 12, and the conductive body 25 which therefore acts as a capacitor plate is very close to the molding space 14 or very close to the foam particles to be welded.

[0116] Figure 3 Schematically shown is a generator 18, a tool capacitor formed by capacitor plates 15, 16 surrounding the half-molds 12, 13, and a line (hollow waveguide or coaxial line) 46 suitable for transmitting electromagnetic waves, through which the electromagnetic waves are transmitted from the generator 18 to the tool capacitors 15, 16. Preferably, the hollow waveguide forming the line 46 is formed as a coaxial air line with a conductive inner tube and a conductive outer tube. The dimensions of the coaxial air line are designed so that high-voltage signals can be reliably transmitted. The wave impedance is preferably set to about 50Ω.

[0117] In this line 46, a generator-side inductance 47 and a tool-side inductance 48 are symbolically shown. These inductances are generated by the line itself, wherein the length of the respective line segment determines the magnitude of the respective inductance. A tool-side capacitor 49 is connected in parallel with the tool capacitors 15, 16. This capacitor 49 represents the capacitance between the capacitor plate 15 and the housing 35 of the molding tool 3. The tool capacitors 15, 16, the capacitor 49 and the tool-side inductance 48 form a tool oscillating circuit 50.

[0118] The generator side capacitor 51 is connected in series with the generator 18 and the generator side inductor. The generator side capacitor 51 and the generator side inductor 47 form a generator oscillating circuit 52. At least the generator side capacitor 51 or the generator side inductor 47 is designed to be variable, for example, by a capacitor with capacitor plates with variable distances or by providing line sections of different lengths. It is also possible that both the generator side capacitor 51 and the generator side inductor 47 are designed to be variable. The generator side capacitor 51 can be provided with a servomotor, during the driving of which the distance between the two capacitor plates changes, the change of which distance is achieved by, for example, a linear movement of one of the two capacitor plates (wherein the two capacitor plates are always parallel to each other) or a pivoting of one of the two capacitor plates.

[0119] By changing the capacitance of the capacitor 51 or the inductor 47, the resonant frequency of the generator oscillating circuit 52 can be changed or tuned. If the resonant frequencies of the generator oscillating circuit and the tool oscillating circuit match, the maximum electrical power is transmitted from the generator 18 to the tool oscillating circuit 50 and thus to the tool capacitors 15, 16. By changing the resonant frequency of the generator oscillating circuit 52, the transmission of electrical power can be controlled in a targeted manner, wherein the stronger the resonant frequency of the two oscillating circuits 50, 52, the lower the transmitted power. Thus, the tuning of the generator oscillating circuit 52 can be used purposefully to set the electrical power introduced into the molding space 14.

[0120] In the present exemplary embodiment, the resonant frequency of the generator oscillating circuit 52 is changed. The resonant frequency of the tool oscillating circuit 50 can also be changed. This has the same effect on power transmission. However, it is more difficult to provide a variable capacitor or a variable inductor on the tool side than on the generator side.

[0121] Figure 4 The arrangement for controlling the electric power supplied to the tool capacitors 15, 16 is shown in a schematic simplified circuit diagram. A generator 18 is connected to the tool capacitors 15, 16. A measuring capacitor 53 is connected in parallel with the tool capacitors 15, 16, the capacitance of the measuring capacitor 53 being a fraction of the capacitance of the tool capacitors 15, 16. The measuring capacitor 53 is connected to a voltage measuring device (voltmeter) 55 via a coaxial line 54. Preferably, a diode 56 is connected in parallel with the measuring capacitor 53. The coaxial line 54 is connected in series with an inductor 58 for filtering high frequency signals.

[0122] The measuring unit formed by the measuring capacitor 53 and the diode 56 is separated from the tool capacitors 15, 16 by the isolating capacitor 59. The isolating capacitor has a high dielectric strength. The capacitance of the isolating capacitor 59 is smaller than the capacitance of the measuring capacitor 53. As a result, the voltage drop across the isolating capacitor is higher than the voltage drop across the measuring capacitor 53. The ratio of the capacitance of the isolating capacitor 59 to the capacitance of the measuring capacitor 53 is preferably 1:100 or 1:1,000 or 1:10,000. Therefore, the voltage applied to the tool capacitors 15, 16 in the measuring unit 53, 56 is reduced so that the voltage is in the measuring range of the voltage measuring device 55 and can be reliably detected by the voltage measuring device.

[0123] In this circuit, a voltage corresponding to the voltage applied to the tool capacitors 15, 16 and reduced according to the ratio of the capacitance of the measuring capacitor 53 relative to the capacitance of the isolation capacitor 59, thus drops across the measuring capacitor 53. Due to the provision of the diode 56, only half of the oscillation of a specific polarity occurs. The diode 56 thus forms a rectification of the voltage appearing across the measuring capacitor 53. This measurement voltage is measured by the voltage measuring device 55 and converted into a measurement signal. The measurement signal is forwarded to the control device 57, which automatically controls the generator 18 to output a predetermined electrical power in order to generate a specific voltage across the tool capacitor or a specific measurement voltage, which is a portion of the voltage of the tool capacitor across the measuring capacitor.

[0124] The control device 57 controls the power of the generator 18 based on the measured voltage. In this case, there may be different target values ​​for the predetermined power to be controlled. On the one hand, the power may be controlled to a certain constant amplitude, or on the other hand, the power may be varied so that the voltage drop across the measuring capacitor 53 and rectified by the voltage measuring device 55 is substantially constant. In other words, on the one hand, depending on the measured voltage, the electrical power output or the measured voltage may be kept constant.

[0125] As already explained at the outset, the absorption capacity of the material to be welded present in the tool capacitors 15, 16 changes depending on the temperature, and in certain processing situations a particularly strong change in the absorption capacity for electromagnetic waves occurs. Figure 4 In the equivalent circuit diagram shown, the change in electromagnetic wave absorption capacity can also be regarded as a change in the capacitance of the tool capacitors 15, 16. Depending on whether the control device 57 is designed to keep the electric power output or the voltage (= voltage amplitude) applied to the tool capacitors 15, 16 constant, the capacitance that changes at the tool capacitors 15, 16 either brings about a change in the voltage (= voltage amplitude) or brings about a change in the electric power output.

[0126] In principle, it is simpler to output a predetermined constant electric power by means of the generator 18, because then the tuning of the tool oscillating circuit 50 to the generator oscillating circuit 52 can be kept constant, so that the generator 18 outputs a constant electric power. In this embodiment, the measured voltage measured by the voltage measuring device 55 can represent a parameter characterizing the absorption capacity of the material to be welded, which parameter is monitored by the control device 57. If the measured voltage changes a predetermined threshold value within a predetermined time interval, this is established by the control device 57 and evaluated as a trigger point for ending the heating process. The heating process can end directly with the establishment of the trigger point, or it can also be delayed for a predetermined period of time. The heating process is ended by cutting off the power supply from the generator 18, wherein the cutting off of the generator 18 is controlled by the control device 57.

[0127] In a variant of this embodiment, the control device 57 can be designed such that it first derives the measured voltage as a function of time. If the signal after the first-order time derivative of the measured voltage exceeds a certain threshold value, this means a predetermined sudden change in the measured voltage present across the tool capacitors 15, 16, which in turn is evaluated by the control device 57 as a trigger point for ending the heating process.

[0128] In another variant of this embodiment, the control device 57 can also be designed so that the second time derivative of the measured voltage is determined. If the second time derivative of the measured voltage exceeds a certain threshold value, this means a predetermined curvature in the profile of the measured voltage and therefore a sudden change in the voltage signal. This can also be evaluated as a trigger point for ending the heating process.

[0129] If the control device 57 is designed such that the electric power output by the generator 18 is varied in such a way that a substantially constant voltage (=voltage amplitude) drops across the tool capacitors 15, 16, the entire system reacts to a sudden change in the electromagnetic wave absorption capacity of the material to be welded present in the tool capacitors 15, 16 by a corresponding change in the electric power. This power can essentially be determined by measuring the current output to the tool capacitors 15, 16, since the voltage present across the tool capacitors 15, 16 is known and measured by the voltage measuring device 55. The power can then be determined from the corresponding current value and the corresponding voltage value.

[0130] However, it is simpler to tap the control signal output by the control device 57 and use this control signal to control the power output of the generator 18. The control signal corresponds to the power to be output, and a predetermined strong change in the control signal can be evaluated as a trigger point for ending the heating process. Since the control signal is present in the control device 57, it can also be monitored here at the same time.

[0131] Here, different embodiments of how to establish the trigger point are also possible. The control signal can be monitored to determine whether it changes by a predetermined threshold within a predetermined time interval, and its first or second order derivative can also be monitored to determine whether it exceeds a predetermined threshold.

[0132] Likewise, when a trigger point is established (based on voltage or power; monitoring a directly measured signal or a first or second derivative), the heating process may end directly when the trigger point is established, or may be delayed for a predetermined period of time.

[0133] During each production process of producing a particle foam part for sportswear, sports equipment or a ball from foam particles, the method can be performed individually and again to automatically determine the duration of heating the foam particles (which are used for sportswear, sports equipment or a ball) using electromagnetic waves. However, within the scope of the present invention, the method can also be used to calibrate the duration of heating the foam particles (which are used for sportswear, sports equipment or a ball) using electromagnetic waves for a specific molding tool and for a specific type or a specific batch of foam particles (which are used for sportswear, sports equipment or a ball). The duration of the heating process (until all foam particles are completely welded to form the particle foam part) depends primarily on the molding tool used (which defines the molding space), as well as the type used or the batch of foam particles used.

[0134] A method for producing a particle foam component for sportswear, sports equipment or a ball from foam particles is called a calibration method, wherein the duration of heating the foam particles with electromagnetic waves is individually set according to the above method, and the duration of heating the foam particles with electromagnetic waves applied here is detected and stored using a clock or a clock generator. The duration of heating the foam particles with electromagnetic waves determined in this way is hereinafter referred to as a "production time interval".

[0135] Single or multiple calibration processes can be carried out, in which the duration of heating the foam particles (which are used for sportswear, sports equipment or balls) using electromagnetic waves is detected in each case. If multiple heating intervals are detected, they can be statistically evaluated and, for example, the average value or median of the detected heating intervals can be kept as a production time interval that can be used as a further production process. In the further production process, the characteristic parameters are no longer monitored, but the duration of heating the foam particles using electromagnetic waves is controlled only based on the production time interval. Therefore, the duration of heating the foam particles using electromagnetic waves has been calibrated. Therefore, further control is simplified and, if appropriate, can be transferred to further devices for producing particle foam parts using the same tool, in which the same type or the same batch of foam particles are used to produce particle foam parts. These other devices can be designed with a simple control device, which controls the heating process only based on the existing production time interval.

[0136] As described above, a plurality of production time intervals can be statistically evaluated, each of which is detected using a calibration process. This statistical evaluation also makes it possible to determine a quality factor of the production process. If different production time intervals deviate significantly from one another, this is a sign that the production process is unstable and that particle foam parts of different quality are produced. If, on the other hand, the production time intervals are essentially the same, this means that the production process is stable and that the particle foam parts are each produced with the same quality. Therefore, the standard deviation of the production time intervals of different calibration processes can be varied as a quality factor for evaluating the production process - if the quality factor indicates that the stability of the production process is too low.

[0137] To optimize the production process, one or more of the following parameters can be changed:

[0138] - the applied power of the electromagnetic wave,

[0139] - applied voltage for generating electromagnetic waves,

[0140] - the amount of heat transfer medium supplied to the moulding space,

[0141] - the amount of foam particles supplied to the molding space,

[0142] - The pressure exerted by the moulding tool on the foam particles before they are heated.

[0143] The lower the applied power or the applied voltage used to generate the electromagnetic waves, the slower the foam particles are heated. The slower they are heated, the better the thermal balance can be between the different areas of the mold space, and the more uniform the welding is generally. Therefore, stabilization of the production process can usually be achieved by reducing the power or voltage.

[0144] However, in the case of some molding tools, in particular molding tools with conductive half-molds, the heat can be dissipated very well at certain points, whereby certain points of the mold space cool more strongly than other points. On the contrary, in the case of such molding tools, it may be advantageous to heat the foam particles as quickly as possible and to operate the heating of the foam particles with the highest possible electromagnetic wave power or with the highest possible applied voltage. In this case, an increase in power or voltage can bring about a stabilization of the production process. The amount of foam particles located in the mold space and / or the amount of binder used to bind the foam particles can also have a considerable influence on the stability of the production process, so there are situations where an increase or decrease in the amount of foam particles or the amount of binder leads to a stabilization of the production process. This can be identified with the help of a statistical evaluation based on a quality factor and set accordingly.

[0145] This optimization can be performed automatically using an expert system. It can also be based on machine learning, where the quality of the produced particle foam parts is monitored manually or by suitable measurement methods using data technology and fed back into the system as feedback, based on which an optimization and learning process can be carried out.

[0146] It has been shown that the duration of the application of electromagnetic RF radiation depends on the volume of the molding space 14, the density of the foam particles and the applied electrical power or the applied voltage. In tests, it has been shown that, depending on the volume and the material forming the foam particles, about 30 seconds to about 2 minutes are required in order to reliably and completely weld the foam particles. In this case, a voltage (= voltage amplitude) of 3 kV to 20 kV is usually applied.

[0147] During the welding process, the temperature of the foam particles can be measured and the electrical power can be controlled accordingly. The electrical power is preferably controlled in such a way that the foam particles have a temperature slightly above their softening temperature.

[0148] The surface delimiting the molding space 14 can be additionally temperature controlled. To this end, a heating wire 22 can be arranged in the molding tool close to the surface delimiting the molding space 14. The heating wire 22 is connected to a power supply 23, by which a heating current can be supplied to the heating wire.

[0149] Instead of the heating wire, fluid channels can also be provided in the mold halves 12, 13, through which channels a corresponding temperature control fluid flows. Preferably, the fluid is water or steam.

[0150] After the application of the electromagnetic RF radiation, the molding space 14 remains closed for a stable time interval, whereby the heat introduced is evenly distributed in the particle foam part and a very uniform weld is formed between all the foam particles. This process step is called stabilization. During the stabilization process, a slight cooling of the particle foam part also occurs. Since the mold halves 12, 13 are formed from a material which is essentially transparent to the electromagnetic RF radiation and is generally a poorly thermally conductive plastic material, substantially only little heat is output to the outside in the closed molding space 14. Of course, this is different if one mold half is formed from an electrically conductive and therefore highly thermally conductive material.

[0151] The mold halves 12, 13 formed of plastic have advantages over mold halves formed of metal in that, on the one hand, they have substantially better thermal insulation and, on the other hand, have a lower thermal capacity. As a result, the required temperature cycles can be carried out substantially faster and with less energy, the heat provided being almost completely supplied to the foam particles.

[0152] During the stabilization period or part of the stabilization period, the capacitor plates 15 , 16 can be actively cooled by the cooling devices 20 , 21 , thereby extracting heat from the body of the mold halves 12 , 13 and thus also from the particle foam component.

[0153] After stabilization, the particle foam component is demoulded by separating the two mold halves 12, 13. For demoulding, a demoulding punch can be provided on the molding tool, with which the particle foam component is pushed out of one of the two mold halves 12, 13.

[0154] Stabilization is an optional method step. In the case of certain materials and molds, it can also be omitted. The larger the volume of the particle foam part to be produced, the more suitable it is to stabilize the particle foam part in the molding tool after welding.

[0155] In order to increase the yield, electromagnetic RF radiation can already be applied during the filling and / or during the closing of the crack gap.

[0156] Electromagnetic radiation, in particular RF radiation, can be applied during filling or only after filling the molding space 14 with foam particles first with low power or low voltage in order to preheat the material to a certain temperature and then gradually or suddenly increase the electrical power or voltage.

[0157] It is also advantageous to gradually increase the power or voltage of the electromagnetic RF radiation, as a result of which the ramping is performed over a duration of, for example, 30 seconds to 3 minutes, due to the gradual increase of the electrical power or voltage of the electromagnetic RF radiation. As a result, a very uniform heating of the foam particles is achieved.

[0158] Alternatively, negative pressure and / or vacuum may also be applied to the molding space 14. This is advantageous when the supplied foam particles and / or compressed air have a certain moisture content.

[0159] Compared to steam welding alone, the above-described method is a dry method. As a result, after the production process, the produced particle foam parts are dry or drier and can be supplied to further processing steps more quickly. It is also advantageous to demould the hot particle foam parts and supply them directly to further processing. As a result, a significant increase in production efficiency can be achieved, because on the one hand the pauses between the individual process steps can be shortened and on the other hand the heat introduced for welding the foam particles can also be used at least partially in subsequent method steps.

[0160] It is also advantageous to provide a water supply or steam supply line at the welding station, using which water and / or steam is supplied to the molding tool. This is particularly advantageous when foam particles that only have a low dielectric loss factor at low temperatures or foam particles that only have a low dielectric loss factor are to be welded. In this case, a small amount of water or steam is supplied. Due to electromagnetic radiation, water is heated to steam or steam is further heated. As a result, the foam particles are heated to a relatively high temperature, at which the dielectric loss factor is greater, so that they themselves absorb electromagnetic radiation and are further heated. It has been shown that for a molding space with a volume of 50 liters, several 100g of water are sufficient. If the foam particle material is, for example, ePS (expandable polystyrene), 300g or less of water is sufficient to heat and weld the foam particles in a molding space with a volume of 50 liters. In traditional welding, in which the foam particles are heated only by superheated steam, for a molding space with a volume of 50 liters, a steam amount of several kilograms of water is required.

[0161] Thus, if foam particles which absorb electromagnetic radiation only slightly are to be welded, it is basically the case that a single addition of 300 g of water is sufficient for a molding space with a volume of 50 liters. In the case of many materials which absorb electromagnetic radiation only slightly, even smaller amounts of water are sufficient. In the case of molding spaces with other volumes, the maximum necessary amount of water can be adapted to the volume in the same ratio.

[0162] If the water is heated in the molding space by electromagnetic radiation, it is advantageous to use a molding tool with a pressure sensor, with which the pressure prevailing in the molding space can be measured. This pressure is proportional to the temperature. The irradiation with electromagnetic radiation is then preferably controlled as a function of the measured pressure value, i.e. it is preferably set to a specific pressure value.

[0163] Reference numerals list

[0164] 1 device

[0165] 2Material Container

[0166] 3 Molding tools

[0167] 4 pipelines

[0168] 5Bottom

[0169] 6 Compressed air pipeline

[0170] 7. Compressed air source

[0171] 8 drive nozzles

[0172] 9 Compressed air pipeline

[0173] 10 Fill the injector

[0174] 11 Compressed air pipeline

[0175] 12 Half mold

[0176] 13 Half mold

[0177] 14 Molding Space

[0178] 15 Capacitor Plates

[0179] 16 capacitor plates

[0180] 17 Wire

[0181] 18 Generator (eg AC voltage source)

[0182] 19 Negative pressure pump

[0183] 20 Fan

[0184] 21 Cooling fins

[0185] 22 Heating wire

[0186] 23 Power Supply

[0187] 24 Main Body

[0188] 25 Main Body

[0189] 26 Internal defining surface

[0190] 27 Internal defining surface

[0191] 30 Land

[0192] 31 bottom wall

[0193] 32 Sidewall

[0194] 33 Filling opening

[0195] 34 Ventilation openings

[0196] 35 Shell

[0197] 46 lines

[0198] 47 Generator side inductance

[0199] 48 Tool side inductance

[0200] 49 Tool side capacitor

[0201] 50 Tool Oscillation Circuit

[0202] 51 Generator side capacitor

[0203] 52 Generator oscillation circuit

[0204] 53 Measuring capacitor

[0205] 54 Coaxial pipeline

[0206] 55 Voltmeter

[0207] 56 diode

[0208] 57 Control Device

[0209] 58 Inductor

[0210] 59 Isolation capacitor

Claims

1. A method for producing particle foam parts for sportswear, sports equipment or balls from foam particles using electromagnetic waves, comprising the following steps - filling the moulding space, - heating the foam particles with electromagnetic waves to fuse them together, - demoulding, A parameter characterizing electromagnetic wave absorption is monitored during heating of the foam particles, and if the parameter changes by a predetermined amount, heating of the foam particles is terminated.

2. The method according to claim 1, characterized in that The electromagnetic wave is generated by a capacitor, and the molding space is located in the capacitor, wherein applying an electromagnetic wave to the capacitor at a predetermined voltage amplitude, and measuring the power introduced into the molding space or its first or second order derivative with time as a characteristic parameter, or The electromagnetic wave is applied to the capacitor at a predetermined power, and a voltage drop across the capacitor or its first-order or second-order derivative with time is measured as a characteristic parameter.

3. The method according to example 1 or 2, characterized in that After heating and before demoulding, the particle foam component is cooled in the mold space.

4. The method according to any one of claims 1 to 3, characterized in that RF radiation is used as electromagnetic waves, in particular electromagnetic waves in the frequency range of 30 kHz to 300 MHz.

5. A method for calibrating a process for producing particle foam parts for sportswear, sports equipment or balls from foam particles using electromagnetic waves, in, Using a mold defining a specific molding space and foam particles of a specific material type, at least one particle foam component for sportswear, sports equipment or a ball is produced according to any one of claims 1 to 4 in a calibration process, and The duration of heating with electromagnetic waves is measured until the characteristic parameter changes by a certain threshold, and Further particle foam components for sportswear, sports equipment or balls are produced by heating the foam particles with the same settings for supplying electromagnetic waves in each case with production heating intervals corresponding to the duration determined by a calibration process.

6. The method according to claim 5, characterized in that A plurality of particle foam parts for sportswear, sports equipment or balls are produced according to the method according to any one of claims 1 to 4 during a calibration process, and The duration of heating was measured in each case, and A production time interval is determined based on a plurality of time durations measured during the calibration process.

7. The method according to claim 6, characterized in that The average or median value of the individual durations is determined as the production time interval.

8. The method according to example 6 or 7, characterized in that For determining the production time interval, only durations that are within a predetermined multiple of a standard deviation about a mean value or about a median value of the measured durations are taken into account.

9. The method according to any one of claims 6 to 8, characterized in that The measured durations are evaluated statistically to determine the quality factor of the production process.

10. The method according to claim 9, characterized in that If the figure of merit indicates that the stability of the production process is too low, the production process can be optimized based on the figure of merit by changing at least one specific parameter of the production process.

11. The method according to claim 10, characterized in that A plurality of particle foam components for sportswear, sports equipment or balls are produced by the method according to any one of claims 1 to 4, at least one of the following parameters is varied and then the production time interval is again determined: - the applied power of the electromagnetic wave, - an applied voltage for generating said electromagnetic wave, - the amount of heat transfer medium supplied to the moulding space, - the amount of the foam particles supplied to the molding space, - Pressure exerted by the moulding tool on the foam particles before heating them.

12. The method according to claim 11, characterized in that The at least one parameter to be changed and the degree of change are automatically determined by an expert system.

13. An apparatus for producing particle foam parts for sportswear, sports equipment or balls from foam particles, the apparatus comprising: a molding tool delimiting a molding space, wherein at least two capacitor plates are arranged adjacent to the molding space, the capacitor plates being connected to a radiation source of electromagnetic radiation, wherein the radiation source of electromagnetic radiation is designed to emit electromagnetic radiation, and A control device, the control device being designed to cause the device to automatically perform the method according to any one of claims 1 to 12.

14. A particle foam component from foam particles for sportswear, sports equipment or a ball, produced according to the method of any one of claims 1 to 4.

15. The particle foam component according to the preceding claim, wherein The particle foam component is a sole or a part of a sole, in particular a midsole or a part of a midsole.

16. A shoe, in particular a sports shoe, comprising a particle foam component according to the preceding claim.

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