Method and device for producing particle foam parts from foam particles for sports clothing, sports equipment, or balls; method for calibrating process for producing particle foam parts from foam particles for sports clothing, sports equipment, or balls; particle foam parts from foam particles for sports clothing, sports equipment, or balls; and shoes

Abstract

To provide a method for using electromagnetic waves to produce particle foam parts from foam particles for sports clothing, sports equipment, or balls.SOLUTION: The method includes the steps of filling the mold cavity, heating the foam particles with electromagnetic waves to weld them together, and demolding the mold, and monitoring a parameter characteristic of electromagnetic wave absorption during heating of the foam particles, and terminating heating of the foam particles when this parameter changes by a predetermined amount . This method ensures that a reliable and accurate amount of heat is delivered to the foam particles in a simple manner.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls, a method for calibrating a process for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls, particle foam parts from expanded particles for sports clothing, sports equipment or balls, and shoes. [Background technology]

[0002] WO 2013 / 05081 discloses a method for producing a particle foam part, in which a mixture of foam particles and a dielectric transmission liquid is heated by electromagnetic waves to melt the foam particles and form a particle foam part. The electromagnetic waves can be radio waves or microwaves. The material of the foam particles is made of polypropylene (PP).

[0003] US Patent No. 3,060,513 discloses a method for sintering moistened thermoplastic foam particles. The particles are simultaneously dielectrically heated and compressed in a mold. Electromagnetic waves are applied at frequencies between about 2 and 1000 MHz.

[0004] A similar method is described in US Pat. No. 3,242,238, in which expanded particles are wetted with an aqueous solution and exposed to an electromagnetic field at frequencies between about 5 and 100 MHz.

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

[0006] WO 01 / 64414 discloses a further method in which polymer particles of polyolefin moistened with a liquid medium are heated by electromagnetic waves, in particular by microwaves, in which the temperature in the moulding tool is regulated by controlling the pressure present in the moulding tool.

[0007] In each of the methods described above, moistened foam particles are heated with electromagnetic waves, the electromagnetic energy being absorbed by the liquid and transferred to the particles.

[0008] US Patent No. 5,128,073 discloses thermoplastic particles coated with a material that absorbs radio frequency energy. These particles can be heated with electromagnetic waves, causing the coating to emit electromagnetic energy, which is then transferred onto the expanded particles. Electromagnetic waves in the range of 40 MHz to 2450 MHz are used to fuse the expanded particles.

[0009] These methods have been known for several decades. Nevertheless, they have not been successful in practice. There are various reasons for this. On laboratory samples, these methods work quite well.

[0010] Thus, in practice, foam particles are almost exclusively welded by saturated dry steam, as is known, for example, from WO 2014 / 128214. Compared to welding with steam, electromagnetic wave welding has considerable advantages in principle, but welding with electromagnetic waves has not been successful in practice for the last few decades. With electromagnetic waves, the energy can be transferred more targetedly, so that the auxiliary objects do not need to be heated. If steam is used, it must first be generated in a steam generator. Then, via a pipe, the steam must be fed to the fixture. All these parts must be heated to a sufficiently high temperature so that the steam does not condense inside the part. This results in considerable heat losses. In addition, in an apparatus for producing particle foam parts, the apparatus for steam generation and the steam pipes take up the most installation space. If steam was not required for welding the foam particles, the entire apparatus could be made much more compact.

[0011] For the applicant of the present patent application, the successful transition to industrial production has only recently been made. The applicant first realized that the main reason why attempts to weld foam particles with electromagnetic waves have been unsuccessful for decades is due to the inability to introduce heat uniformly into the foam particles. As a result, uniform welding of the particle foam parts is not achieved.

[0012] WO 2017 / 125410, WO 2017 / 125412, WO 2018 / 100154, WO 2021 / 073924, and WO 2022 / 229030 disclose methods and apparatus for producing particle foamed parts that provide uniform heat distribution in the mold space.

[0013] In particular, WO 2018 / 100154 discloses an apparatus for producing particle foam parts, comprising a moulding fixture that defines a moulding space, in which at least two capacitor plates are arranged adjacent to the moulding space, which capacitor plates are connected to a source of electromagnetic radiation that is designed to emit electromagnetic radiation. The apparatus is provided with a voltage measuring device that can measure the voltage applied to the capacitor. The voltage measuring device is used to adjust an oscillating circuit designed with a generator of electromagnetic waves and thus to adjust the power supplied to the capacitor.

[0014] The invention is based on the object of providing a method and an apparatus for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls, as well as a method for calibrating a process for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls, which makes it possible to reliably industrially produce particle foam parts from expanded particles for sports clothing, sports equipment or balls and shoes by welding the expanded particles with the aid of electromagnetic waves, such that particle foam parts from expanded particles for sports clothing, sports equipment or balls are obtained with high quality. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] International Publication No. 2013 / 05081 [Patent Document 2] U.S. Patent No. 3,060,513 [Patent Document 3] U.S. Patent No. 3,242,238 [Patent Document 4] British Patent No. 1,403,326 [Patent Document 5] WO 01 / 64414 [Patent Document 6] U.S. Patent No. 5,128,073 [Patent Document 7] International Publication No. 2014 / 128214 [Patent Document 8] International Publication No. 2017 / 125410 [Patent Document 9] International Publication No. 2017 / 125412 [Patent Document 10] International Publication No. 2018 / 100154 [Patent Document 11] International Publication No. 2021 / 073924 [Patent Document 12] International Publication No. 2022 / 229030 [Patent Document 13] German Patent Application Publication No. 102014117332 Summary of the Invention

[0016] This object is achieved by the subject matter of the independent claims. Advantageous embodiments are set forth in the respective dependent claims.

[0017] According to a first aspect, the present invention relates to a method for producing a particle foam part from expanded particles for a sports garment, a sports equipment or a ball, in particular comprising: Filling the mold cavity; A step of heating and fusing the foamed particles with electromagnetic waves; A demolding step; The present invention relates to a method comprising the steps of:

[0018] The method comprises monitoring a parameter characteristic of the absorption of electromagnetic waves during heating of the expanded beads and terminating the heating of the expanded beads when the parameter changes by a predetermined amount.

[0019] The present invention is based on the finding that the absorption capacity of a material increases rapidly as the material of the foamed beads to be welded melts. It has long been known that polar molecules and polar functional groups absorb electromagnetic waves by being excited by electromagnetic waves and vibrating. During the melting of a material, the bonds between molecules are broken, so that individual molecules or their functional groups can move more easily. For example, in the case of a material that has polar functional groups but is firmly incorporated in the molecular structure, such as PEEK, the polar functional groups cannot move and the material absorbs very little electromagnetic waves. Therefore, in order to absorb electromagnetic waves, it is necessary that the polar functional groups are mobile so that they can vibrate. If the mobility of the polar functional groups is very high, they will not cause friction or only little friction, so only a little electromagnetic wave can be absorbed. Therefore, there is generally a peak region in which each material can absorb electromagnetic waves well. Since the mobility of functional groups is temperature dependent, the absorption capacity of electromagnetic waves is generally temperature dependent as well.

[0020] Furthermore, the inventors of the present invention have realized that the problem with welding foam particles for sports clothing, sports equipment, or balls with electromagnetic waves is that the heat must not only be distributed uniformly in the molded space, but also must be metered accurately. When welding foam particles with steam, if the welding is insufficient, the steam can be supplied for a relatively long time so that all areas of the particle foam part are sufficiently welded. The temperature of the steam is limited, so that overheating can never occur. This is also one reason why welding foam particles with electromagnetic waves has not been as successful in the past as welding with steam.

[0021] Therefore, the supply of heat should be interrupted during electromagnetic welding when the material to be welded has melted. When the foam particles melt, they bond during cooling to form a particle foam part, which is called welding. Further heating is not necessary and is even harmful, as the material would be heated to a relatively high temperature and could burn.

[0022] According to the invention, the fact that the material's electromagnetic wave absorption capacity changes during melting, and this change generally occurs rapidly, is utilized to adjust the heating time, so that an accurate metering of the heat delivered is achieved in a very simple manner, which results in a good weld and ensures that the material is not burned out.

[0023] The expanded particles for sports clothing, sports equipment or balls that are welded by the method for forming particle foam parts are preferably expanded particles from a thermoplastic material, which may be, inter alia, 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 their ability to absorb electromagnetic waves.

[0024] Foam particles from non-polar plastics, such as those based on expandable polypropylene (ePP) or expandable polystyrene (ePS), can also be welded to form particle foam parts. These materials have no polar groups and therefore only very little absorb electromagnetic radiation. It is therefore advantageous to add a dielectric heat transfer medium, for example water. A small amount of water to wet the surface is sufficient. Water can be added in liquid form or as steam. Water molecules form dipoles, so they absorb electromagnetic waves well and heat up quickly when radiated with electromagnetic waves. Even if water is added to the foam particles in steam form, at least a part 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 is present in liquid form before the heating of the foam particles by electromagnetic waves and generally also forms a film on the surface of the foam particles. When the foam particles are heated by electromagnetic waves, the water is heated and evaporated. The phase transition from liquid water to steam causes a considerable change in the absorption capacity of electromagnetic waves. When the water has been completely converted to steam, this means that there is hot steam in the mould space suitable for welding the foam particles. The individual water molecules are free to move in steam, so they absorb very little electromagnetic radiation compared to liquid water. Further heating is no longer necessary. The heating process can be terminated.

[0025] The expanded particles can also be formed from biological materials, such as, for example, industrial popcorn derived from corn, which is provided with or coated with a binder such that the binder holds the popcorn together after heating.

[0026] The term "popcorn" in the sense of the present invention includes all materials that explode at high temperatures by rapid heating, in particular puffed corn (maize, convar. Microsperma), due to the rapid evaporation of the water present in the seeds and the conversion of the starch contained in the seeds into a foamy consistency, if applicable after corresponding fattification. Such a property is also known, inter alia, from quinoa grain, amaranth, rice or wheat, and materials based on these base materials are also explicitly called "popcorn" in the sense of the present invention and are included in "popcorn", the term "popcorn" being chosen in particular for reasons of simplicity, clarity and readability, without intending to be limited to maize only.

[0027] The binder may comprise a thermoplastic material that melts when exposed to heat and solidifies when cooled, thus bonding the popcorn particles together. The binder may also include an adhesive that chemically reacts when heated to bond the popcorn particles together.

[0028] Suitable binders are, in particular, thermoplastic resins, thermosetting resins, amino resins, phenolic resins, isocyanates, proteins, tannins, starches, synthetic or natural binders or mixtures of binders, such as, for example, urea-formaldehyde resins, melamine-formaldehyde resins, melamine-reinforced urea-formaldehyde resins, tannin-formaldehyde resins, phenol-formaldehyde resins, polymeric diphenylmethane-diisocyanates or mixtures thereof.

[0029] The proportion of binder in the moulded part (% by weight based on the weight of the moulded part) is preferably <10%, preferably <5%.

[0030] Biological materials generally contain a certain amount of moisture. This water contained in the biological material absorbs electromagnetic waves and heats the popcorn grains and the binder. When the binder evaporates, the water's absorption ability for electromagnetic waves changes in the same manner as described above, and this change can be determined by the characteristic parameter. The characteristic parameter is also an indicator of the material being heated in the molding space and bonding to form the particle foam part.

[0031] Thus, there are various physical mechanisms of action that cause changes in the absorption capacity of the electromagnetic waves. Since the electromagnetic waves heat the material present in the forming space, strong changes in the absorption capacity of the electromagnetic waves always indicate reproducible stages of the heating process. Thus, the characteristic parameters are physical variables characteristic of the foamed particles to be welded, which change due to the radiation of electromagnetic waves, and based on this change, it is possible to determine the specific process or treatment state of the foamed particles to be welded.

[0032] The heating process can then be terminated depending on the change in the characteristic parameter. Termination of the heating process can be done immediately if the characteristic parameter changes, or it may also be advantageous to terminate the heating process by a predefined period of time 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 empirically determined. For most polar plastic materials that melt as a result of the action of electromagnetic waves, very short delay periods or a delay period of "0" have been found to be advantageous. Delay periods greater than "0" may also be advantageous, especially for other materials that form bonds between the foam particles as a result of a chemical reaction.

[0033] The electromagnetic wave can be generated by a capacitor in which the forming space is arranged. In this case, the electromagnetic wave can be applied to the capacitor with a predetermined voltage amplitude, and the power introduced into the forming space or the first or second derivative of the power with respect to time can be measured as the 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 the first or second derivative of the voltage drop with respect to time as the characteristic parameter.

[0034] When the characteristic parameter is directly monitored, a check is made to see if the characteristic parameter changes by a predetermined threshold within a predetermined time interval to determine a predetermined amount of change, which means an abrupt change in the characteristic parameter.

[0035] When monitoring the first time derivative of the characteristic parameter, it is checked whether the first time derivative of the characteristic parameter exceeds a predetermined threshold value to determine a predetermined amount of change, which means an abrupt change of the characteristic parameter.

[0036] When monitoring the second time derivative of the characteristic parameter, it is again determined whether the second time derivative exceeds a certain threshold value in order to determine a predetermined amount of change. This means that the change in the characteristic parameter profile itself changes very strongly. If the characteristic parameter profile is entered into a diagram, a second time derivative exceeding a certain threshold value means that the curvature of the characteristic parameter profile becomes stronger over time. This also indicates a strong change in the characteristic parameter.

[0037] There are therefore various methods by which strong changes in the characteristic parameters can be detected. In order to obtain a signal intended to terminate the heating of the expanded beads by electromagnetic waves, it is important that this signal is characteristic and reproducible for each heating state of the expanded beads. This is given in all the methods described above.

[0038] Preferably, the particle foam part produced in the molding space is cooled in the molding space after heating and before demolding, such a cooling process is also called stabilization.

[0039] The electromagnetic waves are preferably RF radiation. RF radiation has a frequency range of 30 kHz to 300 MHz. In many states, a frequency of 27.12 MHz is available for industrial use. This is a suitable frequency for heating the foam particles.

[0040] The magnitude of the high frequency voltage applied to the capacitor is preferably 10 3 V~10 5 V range, especially 5×10 3 V~1.5×10 4 V range.

[0041] According to a further aspect, the invention relates to a method for calibrating a process for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls using electromagnetic waves, comprising producing at least one particle foam part for sports clothing, sports equipment or balls according to one of the above-mentioned methods using a mold defining a specific molding space and expanded particles of a specific material type, and controlling or terminating the heating of the expanded particles based on characteristic parameters. Further particle foam parts for sports clothing, sports equipment or balls are then produced by heating the expanded particles with the same settings for supplying electromagnetic waves in each case for a production heating interval corresponding to a period determined in the calibration process. These settings are mainly the applied power or the applied voltage.

[0042] As a result, a production heating interval, which defines the period of time during which the expanded particles are heated with electromagnetic waves, is determined in a calibration process.

[0043] Since the appropriate period for heating the expanded beads depends on the molding tool and the material type of the respective expanded beads, the individual production heating intervals therefor can be easily and quickly determined, thereby allowing high-quality particle foam parts to be produced simply and reliably.

[0044] A number of foamed parts for sports clothing, sports equipment or balls can also be produced during the calibration process, and in each case the heating periods can be measured. The production time interval is thus determined based on the number of periods measured during the calibration process. The average or median value of the individual periods can be determined as the production time interval.

[0045] Furthermore, only periods that are within a predetermined multiple of a standard deviation around the mean or median of the measured periods may be considered when determining the production time interval.

[0046] A statistical evaluation of the measured time period can be performed to determine the quality factor of the manufacturing process. If the quality factor indicates that the stability of the manufacturing process is too low, the manufacturing process can be optimized based on this quality factor by modifying certain parameters of the manufacturing process.

[0047] 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. - the applied power of the electromagnetic waves, - an applied voltage to generate electromagnetic waves; - the amount of heat transfer medium supplied to the forming space, - the amount of foam particles fed into the moulding space; - The pressure exerted by the forming tool on the foam particles before they are heated.

[0048] The at least one parameter to be altered and the degree of alteration may be determined automatically by an expert system.

[0049] According to a further aspect, the present invention relates to an apparatus for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls, comprising a moulding tool defining a moulding space, at least two capacitor plates arranged adjacent to the moulding space, said capacitor plates being connected to a source of electromagnetic radiation, said source of electromagnetic radiation being designed to emit electromagnetic radiation, and having a control device designed to automatically carry out the method described above.

[0050] According to a further aspect, the present invention relates to a particle foam part from expanded particles for sports clothing, sports equipment or balls, manufactured according to one of the above-mentioned methods. The particle foam part may be a shoe sole or part of a shoe sole, in particular an insole or part of an insole.

[0051] According to a further aspect, the present invention relates to a shoe, in particular a sports shoe, comprising a sole or insole from the above-mentioned particle foam part from foamed particles for sports clothing.

[0052] The present invention includes the following embodiments.

[0053] [Embodiment 1] A method for producing particle foam parts from foam particles for sports clothing, sports equipment or balls using electromagnetic waves, comprising: - filling the moulding space; - heating and fusing the foam particles with electromagnetic waves; - demolding, monitoring a parameter characteristic of the absorption of electromagnetic waves during heating of the foamed beads, and terminating the heating of the foamed beads when the parameter changes by a predetermined amount; method.

[0054] [Embodiment 2] Electromagnetic waves are generated by a capacitor within which the forming space is disposed; An electromagnetic wave is applied to the capacitor with a predetermined voltage amplitude and the power introduced into the forming space or the first or second derivative of the power with respect to time is measured as the characteristic parameter; or An electromagnetic wave is applied to a capacitor with a given power, and the voltage drop across the capacitor or the first or second derivative of the voltage drop with respect to time is measured as a characteristic parameter. 2. The method of embodiment 1,

[0055] [Embodiment 3] After heating, the particle foam part is cooled in the molding cavity before demolding. 3. The method according to embodiment 1 or 2, characterized in that

[0056] [Embodiment 4] RF radiation is used as electromagnetic waves, especially in the frequency range from 30 kHz to 300 MHz. 4. The method according to any one of embodiments 1 to 3, characterized in that

[0057] [Embodiment 5] 1. A method for calibrating a process for producing particle foam parts from foam particles for sports clothing, sports equipment or balls using electromagnetic waves, comprising: A method, wherein at least one particle foam part for a sports garment, sports equipment or ball according to any one of the preceding embodiments is manufactured in a calibration process using a mold defining a specific molding space and expanded particles of a specific material type, the duration of heating by electromagnetic waves is measured until a characteristic parameter changes by a specific threshold value, and further particle foam parts for a sports garment, sports equipment or ball are manufactured by heating the expanded particles with in each case the same settings for supplying electromagnetic waves, during a manufacturing heating interval corresponding to the duration determined in the calibration process.

[0058] [Embodiment 6] A plurality of particle foam parts for sports clothing, sports equipment or balls are manufactured according to one of the methods according to embodiments 1 to 4 during a calibration process, the heating periods in each case are measured, and the manufacturing time interval is determined based on the plurality of periods measured during the calibration process; 6. The method of embodiment 5,

[0059] [Embodiment 7] The mean or median value of each period is determined as the production time interval; 7. The method of embodiment 6,

[0060] [Embodiment 8] Only those periods that are within a predetermined multiple of the standard deviation around the mean or median of the measured periods are considered for determining the production time interval; 8. The method according to embodiment 6 or 7,

[0061] [Embodiment 9] A statistical evaluation of the measured periods is carried out to determine the quality factor of the manufacturing process; 9. The method according to any one of embodiments 6 to 8, characterized in that

[0062] [Embodiment 10] If the quality factor indicates that the stability of the manufacturing process is too low, the manufacturing process is optimized based on the quality factor by changing at least one specific parameter of the manufacturing process; 10. The method of embodiment 9,

[0063] [Embodiment 11] The following parameters: - the applied power of the electromagnetic waves, - an applied voltage to generate electromagnetic waves; - the amount of heat transfer medium supplied to the forming space, - the amount of foam particles fed into the moulding space; - the pressure exerted by the molding tool on the foam particles before the foam particles are heated; and then producing a plurality of particle foam parts for sports clothing, sports equipment or balls according to the method according to any one of embodiments 1 to 4, the production time interval is determined again; 11. The method of embodiment 10,

[0064] [Embodiment 12] At least one parameter to be modified and the degree of modification are automatically determined by an expert system; 12. The method of embodiment 11,

[0065] [Embodiment 13] An apparatus for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls, comprising: a molding tool defining a molding space, the molding tool having at least two capacitor plates disposed adjacent the molding space, the capacitor plates connected to a source of electromagnetic radiation, the source of electromagnetic radiation configured to emit electromagnetic radiation; Equipped with A control device designed to automatically carry out the method according to any one of claims 1 to 12, Device.

[0066] [Embodiment 14] A particle foam part made from expanded particles for sports clothing, sports equipment or balls, produced according to the method according to any one of embodiments 1 to 4.

[0067] [Embodiment 15] 15. The particle foam part according to embodiment 1 to 14, wherein the particle foam part is a sole or part of a sole, in particular an insole or part of an insole.

[0068] [Embodiment 16] A shoe, in particular a sports shoe, comprising a sole or insole according to any of the preceding embodiments.

[0069] Possible embodiments of the invention are further explained below with reference to the following drawings: [Brief description of the drawings]

[0070] [Figure 1] 1 shows an exemplary embodiment of an apparatus for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls. [Figure 2a] FIG. 2 is a cross-sectional view of a forming tool in a partially open position. [Figure 2b] FIG. 2 is a cross-sectional view of a forming tool in a partially closed position. [Diagram 3] FIG. 1 is an electrical diagram showing a generator for electromagnetic radiation forming a tunable oscillator circuit and a forming fixture. [Figure 4] FIG. 2 is a circuit diagram showing a control device for controlling a power supply. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0071] Possible embodiments of the various aspects of the invention are described in the following detailed description, mainly with respect to a method and an apparatus for producing particle foam parts from expanded particles for sports clothing, including sports footwear such as shoes and soles. However, it is emphasized that the invention is not limited to these embodiments. Rather, the invention can be used for various types of sports clothing, sports articles as well as sports equipment and sports goods, respectively, or balls, at least one part of which includes a particle foam part, for example any type of ball, or for any type of protective clothing, such as rackets, such as tennis rackets, golf clubs, baseball bats, badminton rackets, cricket bats, ice hockey sticks, hockey sticks, squash rackets, table tennis rackets, or shin guards, knee pads, or elbow pads for use in sports.

[0072] The basic structure of an apparatus 1 for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls is shown in Figure 1. The apparatus 1 includes a material container 2, a molding tool 3 and a pipeline 4 leading from the material container 2 to the molding tool 3. The particle foam parts are produced from expanded particles and are used for sports clothing, sports equipment or balls.

[0073] The material container 2 serves to accommodate the loose foam particles. It has a bottom 5 and is connected in the bottom region via a compressed air line 6 to a compressed air source 7. The compressed air line 6 is connected to a number of nozzles (not shown) arranged in the bottom 5, by means of which a number of air streams (=fluidizing air) can be introduced into the material container 2, which air streams cause the foam particles present in the material container 2 to swirl and thereby separate the foam particles.

[0074] In the region of the bottom 5 of the material container 2 an opening is formed, to which the conveying line 4 is connected. The opening can be closed by a slide (not shown).

[0075] The drive nozzle 8 is arranged in the conveying line 4 adjacent to the material container. The drive nozzle 8 is connected to the compressed air source 7 by a further compressed air line 9. The compressed air supplied to the drive nozzle 8 enters the conveying line 4 through the drive nozzle 8 and flows in the direction of the forming tool 3, thus acting as drive air. As a result, a negative pressure is generated on the side of the drive nozzle 8 facing the material container 2, which sucks out the foamed particles from the material container.

[0076] The conveying line 4 opens into a filling injector 10 which is connected to the moulding tool 3. The filling injector 10 is connected to a compressed air source 7 via a further compressed air line 11. The compressed air supplied to the filling injector 10 is used on the one hand for filling the moulding tool 3, by means of which a flow of foamed particles is exerted in the direction of the moulding tool 3. On the other hand, the compressed air supplied to the filling injector 10 can also be used for blowing the foamed particles back from the conveying line 4 into the material container 2 when the operation of filling the moulding tool 3 is completed.

[0077] The moulding tool 3 is formed from two mould halves 12, 13. At least one moulding space 14, into which a filling injector 10 for introducing the foamed particles opens, is delimited between the two mould halves. The volume of the moulding space 14 can be reduced by moving the two mould halves 12, 13 together. When the mould halves 12, 13 are moved apart, a gap called a crack gap is formed between the mould halves 12, 13. Such a moulding tool 3 is therefore also called a crack gap moulding tool.

[0078] The device 1 does not have a steam generator or a steam supply to the moulding space 14, as is customary in conventional devices for producing particle foam parts. In the moulding space 14, moisture can pass through the residual moisture contained in the material of the foamed particles and the moisture contained in the compressed air. However, the device 1 can also be formed with a steam generator and a steam supply to the moulding space 14 and / or the conveying line 4 in order to supply saturated dry steam to the moulding space 14 for additional or pre-heating of the foamed particles and / or to moisten the foamed particles during transport from the material container 2 to the moulding space 14. The foamed particles located in the material container 2 can also be moistened with liquid water, and for this purpose corresponding nozzles for atomising water are arranged in the material container 2.

[0079] Capacitor plates 15, 16 are arranged in each case in the mould halves 12, 13. These capacitor plates consist in each case of a highly conductive material, for example copper or aluminium. The filling injector 10 is arranged in the mould half 13. It passes through a recess in the capacitor plate 16, which is attached to the mould half 13.

[0080] The capacitor plates 15, 16 are connected to the generator 18 via electric wires 17 for transmitting a high-frequency voltage. These electric wires 17 are generally waveguides. In the present exemplary embodiment, the waveguides are formed from hollow tubes, for example of rectangular cross section and made of a conductive material. However, there are also other types of waveguides, such as for example coaxial cables, that are fundamentally suitable for connecting the generator 18 to the capacitor plates 15, 16.

[0081] Each of the mould halves 12, 13 has a body which may be made of a non-conductive material, in particular substantially transparent to electromagnetic RF radiation, such as, for example, polytetrafluoroethylene (PTFE), polyethylene, in particular UHMWPE, polyetherketone (PEEK). Only the capacitor plates 15, 16 are made to be conductive. A "substantially transparent material" is a material through which electromagnetic radiation, in particular RF radiation, can pass. However, this material may be made in a targeted manner to have certain absorption properties for electromagnetic RF radiation, in order to convert a part of the electrical RF radiation into heat and to heat the mould halves 12, 13 themselves. This will be explained in more detail below.

[0082] Alternatively, if one or both mold halves comprise a conductive material, such as aluminum or steel, they can also form a capacitor plate. However, the two mold halves are essentially electrically insulated from each other. Preferably, one of the two mold halves is formed to be conductive and the other mold half is formed to be non-conductive. The conductive mold half can be three-dimensionally contoured so that a corresponding three-dimensionally contoured surface is formed on the particle foam part. The conductive mold half provides a smooth or predetermined precise surface texture and is therefore preferably used to generate a visible surface on the particle foam part.

[0083] The moulding tool may optionally be connected to a negative pressure pump 19 so that a negative pressure or vacuum can be applied to the moulding space 14. This negative pressure removes any moisture contained in the moulding space 14.

[0084] The condenser plates 15, 16 are preferably provided with a cooling device. In the present exemplary embodiment, the cooling device is formed by a fan 20 which directs cooling air towards the side of the condenser plates 15, 16 facing away from the moulding space 14. To enhance the cooling effect, cooling fins 21 can be provided on the condenser plates 15, 16.

[0085] Alternatively or additionally, a temperature control conduit can also be arranged in the capacitor plates 15, 16, through which a temperature control medium is guided. As temperature control medium, a liquid, such as, for example, water or oil, is preferably used.

[0086] A method for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls using the above-mentioned apparatus is described below.

[0087] The method comprises the following basic steps: - filling the moulding space 14; - welding the foam particles; - a stabilization step (optional); - demolding; - cleaning the fixture (optional); Includes.

[0088] To fill the molding space 14, air is blown via the compressed air line 6 into the region of the bottom 5 of the material container, which causes the foamed particles present therein to swirl and separate. At the same time, drive air is also fed to the drive nozzle, so that the foamed particles are sucked out of the material container 2 into the conveying line 4 and transported together with the drive air in the direction of the molding tool 3. The molding space 14 is closed, and the mold halves 12, 13 can move completely together or can be separated from each other by a crack gap.

[0089] The slide of the material container 2 can be opened and closed continuously. The opening and closing time is typically in the range of 500 milliseconds to 1 second. This cyclical opening and closing of the slide causes the expanded particles from the material container 2 to be intermittently fed to the conveying pipe 4. As a result, the cross-linking of the expanded particles in the material container 2 can be broken, and the expanded particles are separated. This is particularly advantageous in the case of expanded particles having an adhesive surface, such as, for example, eTPU expanded particles.

[0090] The intermittent suction can alternatively also be achieved by intermittent supply of drive air from a compressed air line 9 to a drive nozzle 8 arranged immediately next to the material container 2 .

[0091] The moulding jigs 12, 13 are provided with at least one valve (not shown) which is opened during the feeding of the foamed beads so as to allow the escape of the compressed air entering the moulding space 14. This valve can be set during the filling of the moulding space 14 so that a counter pressure is created in the moulding space 14. As a result, the pressure in the conveying lines and in the moulding space 14 can be kept high, whereby the volume of the foamed beads is kept small. This allows more foamed beads to be fed into the moulding space 14 than would be the case without the application of the counter pressure. After the counter pressure is removed, the foamed beads expand in the moulding space 14.

[0092] A further parameter for setting the filling amount is the crack gap, i.e. the gap with which the two mould halves 12, 13 are spaced apart from each other during filling. The use of the crack gap during filling results, among other things, in a higher density of the thin areas of the produced particulate foam part.

[0093] As soon as it is determined that the molding space 14 has been filled with the foamed particles, the filling injector 10 is closed. The foamed particles present in the line are blown back into the material container 2 by compressed air supplied to the filling injector 10.

[0094] The filling of the moulding space 14 with expanded particles is described in detail in DE 10 2014 117 332 A1, to which patent application reference is made in this regard.

[0095] After filling the molding space 14 with the foam particles, the foam particles are heated by application of electromagnetic RF radiation. The RF radiation has a frequency of 27.12 MHz and a frequency of about 10 4 It is generated by applying a high frequency voltage of V to the capacitor plates 15, 16.

[0096] 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.

[0097] The electromagnetic RF radiation preferably has a frequency of up to 300 MHz.

[0098] Expanded particles for sports clothing, sports equipment or balls can be formed on the basis of polyurethane (eTPU). Polyurethane has a dielectric loss factor D of 0.2 for electromagnetic radiation with a frequency of 1 MHz. In contrast, the dielectric loss factor of polypropylene (PP) is only 0.00035 for electromagnetic radiation with a frequency of 1 MHz. The absorption factor of polyurethane is therefore substantially higher than that of polypropylene. As a result, it is possible to introduce the heat required for welding the expanded particles into the mould space 14 without additional heat transfer substances, in particular without aqueous solutions, since the expanded particles themselves absorb the electromagnetic waves.

[0099] Instead of polyurethane-based expanded particles, polyether block amide (PEBA)-based or polyethylene (PE)-based expanded particles can also be used.

[0100] Foam particles based on ePP (expandable polypropylene) or ePS (expandable polystyrene) can also be welded to form particle foam parts. Since these materials only slightly absorb electromagnetic radiation, it is expedient to add a dielectric heat transfer medium, for example water. The foam particles can be moistened with the heat transfer medium in the material container 2 or during transport from the material container 2 to the moulding tool 3. Wetting in the lines 4 has the advantage that the foam particles are very uniformly moistened and the heat transfer medium is distributed uniformly in the mould space 14. Correspondingly, the foam particles in the mould space 14 are heated uniformly.

[0101] The moulding tool 3 can also be connected to a steam source (not shown), by means of which saturated dry steam can be supplied to the moulding space 14. This is advantageous when welding materials whose dielectric loss factor is temperature dependent. Such materials are, for example, ePES (expandable polyethersulfone) or expandable polyamide. At low temperatures, they have low absorption properties for electromagnetic waves. These foam particles are therefore first heated by steam and then heated from a certain temperature to a higher temperature, either alone or additionally by electromagnetic radiation. Alternatively, the foam particles can be moistened with a dielectric heat transfer medium and heated to a predefined set temperature, as an electric heat transfer medium is heated by electromagnetic radiation. The foam particles can then be heated directly by electromagnetic radiation, as the absorption properties of electromagnetic radiation increase with increasing temperature.

[0102] A moulding tool 3 (Figures 2a, 2b) is described below, which in each case has a first mould half 12 and a second mould half 13 and can be used in the above-mentioned apparatus 1. The transfer devices, holding elements, a thermometer for measuring the temperature in the mould space and further machine parts for opening and closing the tool are omitted in Figures 2a, 2b for a simpler diagrammatic representation.

[0103] The mold fixture 3 is formed from two mold halves 12, 13, each having a body 24, 25 constructed from a conductive material, for example aluminum, copper, or a highly conductive alloy.

[0104] The two mould halves 12, 13 delimit the moulding space 14 by inner boundary surfaces 26, 27. The inner boundary surfaces 26, 27 of the two mould halves 12, 13 are provided with electrically insulating coatings 28, 29.

[0105] The electrically insulating coatings can be made of materials that are substantially transparent to electromagnetic radiation, in particular RF radiation, such as PTFE, PE, PEEK, etc. However, these coatings can also be made of plastic materials that have a dielectric loss factor similar to that of the plastic material that is processed in the molding space 14 when electromagnetic radiation is applied, in order to achieve uniform heating throughout the molding space 14 and in the edge regions of the molding space during the application of electromagnetic radiation. For this purpose, the coatings 28, 29 are preferably made of materials with a moderate loss factor, such as, for example, PET (polyethylene terephthalate), PEEK (polyetherketone), POM (polyoxymethylene), polyimide, and PMMA (polymethyl methacrylate). These coatings 28, 29 are therefore substantially transparent to RF radiation, since they absorb only a small portion of the electromagnetic radiation, and can be made with a specific thickness, for example at least 2 mm, in particular at least 2.5 mm or at least 5 mm, due to their relatively low loss factor. The coating is preferably no more than 20 mm, especially no more than 15 mm, preferably no more than 10 mm thick, so that a small proportion of the electromagnetic energy is absorbed by the coating.

[0106] The conductive bodies 24, 25 form the capacitor plates of the moulding tool 3. They therefore have electrical connections so that they can be connected 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, with RF radiation allowing substantially more uniform heating than microwave radiation for larger mould spaces 14. In addition, most plastic materials can absorb RF radiation substantially better than microwave radiation. Therefore, the use of RF radiation is preferred.

[0107] Since the mould halves 12, 13 delimit the moulding space 14 and at the same time form the capacitor plates, the distance between the "capacitor plates" and the moulding 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, which results in a very high proportion of the power being introduced as heat into the foam particles to be welded. Such a tool therefore allows a very efficient welding of foam particles to form particle foam parts for sports clothing, sports equipment or balls.

[0108] In this exemplary embodiment of the moulding tool 3, the first mould half 12 has a bottom wall 31 and a circumferential side wall 32. In this exemplary embodiment, the bottom wall 31 and the side wall 32 are both formed from a conductive body 24 and a coating 28 arranged on the inside. The side wall 32 can also be formed only from a non-conductive material, in particular a plastic material, or only partially by the conductive body 24. The second mould half 13 forms a movable plunger in the cavity formed by the first mould half 12, thereby sealing the moulding space 14. The seal between the two mould halves 12, 13 is at least so tight that the foam particles present therein cannot escape. The moulding space 14 does not necessarily have to be closed airtight.

[0109] The two mould halves 12, 13 can be moved relative to one another by a press (not shown) and a predetermined force can be applied.

[0110] A passage opening for feeding the foamed particles, hereinafter referred to as the fill opening 33, is arranged in the first mould half 12. A fill injector 10 is connected to the fill opening 33. This fill injector 10 differs from conventional fill injectors because there is no closing mechanism for closing the fill opening 33, as will be explained in more detail below.

[0111] First mold half 12 has one or more passage openings for allowing air to escape, hereinafter referred to as vent openings 34 .

[0112] The fill opening 33 and the vent opening 34 are located in parts or areas, particularly edge areas, of the first mould half 12 that are covered or covered by the second mould half 13 in the closed state of the mould tool 3 (Figure 2b). As a result, closing of the mould tool 3 by introducing the second mould tool 13 into the cavity formed by the first mould tool 12 automatically closes the fill opening 33 and the vent opening 34. As a result, the fill injector 10 does not need to have a closing mechanism for closing the fill opening 33.

[0113] This portion or area is the area of ​​the first mold half 12 that is not covered by the second mold half 13 and that is open when the mold halves are moved apart to the crack gap location.

[0114] Preferably, the first mould half 12 is connected to ground 30. The fill injector 10 is coupled to the conductive body 24 of the first mould half 12 such that the fill injector 10 is also electrically connected to ground 30. The generator 18 generates an electromagnetic wave or AC voltage with respect to ground 30, which is applied to the body 25 of the second mould half 13. As a result, an alternating electromagnetic field, in particular RF radiation, is formed in the moulding space 14.

[0115] In such an embodiment of the moulding tool 3, it is important that the conductive bodies 24, 25 of the two mould halves 12, 13 are electrically insulated from one another. In the present exemplary embodiment, this insulation is achieved by coatings 28, 29.

[0116] Preferably, the inner boundary surface 26, 27 of one of the two mould halves 12, 13 is formed so as to be contoured. Contoured in the sense of the present invention means any shape deviating from a flat boundary surface. In the present exemplary embodiment, the inner boundary surface 27 of the second mould half 13 is contoured. The inner boundary surface 26 of the first mould half 12 is not contoured in the area of ​​the bottom wall 31.

[0117] Furthermore, such a moulding tool 3 differs from known moulding tools for welding foamed particles by means of electromagnetic waves in that the second moulding tool 13 is formed like a plunger, with its electrical body 25 being at least partially arranged within the cavity delimited by the first mould half 12, and thus the conductive body 25 acting as a capacitor plate is arranged very close to the moulding space 14 or to the foamed particles to be welded.

[0118] 3 shows, in an electrical circuit diagram, a generator 18, a fixture capacitor formed by capacitor plates 15, 16 surrounding the mould halves 12, 13, and a line (hollow waveguide or coaxial line) 46 suitable for transmitting electromagnetic waves, which transmits the electromagnetic waves from the generator 18 to the fixture capacitor 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 coaxial air line is dimensioned so that it can reliably transmit high voltage signals. The wave impedance is preferably set to about 50 Ω.

[0119] The line 46 is symbolically shown with a generator-side inductance 47 and a fixture-side inductance 48. These inductances are provided by the line itself, with the length of each line section determining the magnitude of each inductance. A fixture-side capacitor 49 is connected in parallel with the fixture capacitors 15, 16. This capacitor 49 represents the capacitance between the capacitor plate 15 and the housing 35 of the forming fixture 3. The fixture capacitors 15, 16, the capacitor 49 and the fixture-side inductance 48 form a fixture oscillator circuit 50.

[0120] The generator-side capacitor 51 is connected in series with the generator 18 and the generator-side inductance. The generator-side capacitor 51 and the generator-side inductance 47 form a generator oscillator circuit 52. At least the generator-side capacitor 51 or the generator-side inductance 47 is of variable design, for example by providing a capacitor with a variable distance between the capacitor plates or line sections of different lengths. It is also possible for both the generator-side capacitor 51 and the generator-side inductance 47 to be of variable design. The generator-side capacitor 51 can be provided with a servo motor, during its operation the distance between the two capacitor plates is changed, for example by linearly moving one of the two capacitor plates (in which case both capacitor plates are always parallel to each other) or by pivoting one of the two capacitor plates.

[0121] By varying the capacitance of the capacitor 51 or the inductance 47, the resonant frequency of the generator oscillator circuit 52 can be changed or adjusted. If the resonant frequency of the generator oscillator circuit and the resonant frequency of the fixture oscillator circuit coincide, the maximum power is transferred from the generator 18 to the fixture oscillator circuit 50 and thus to the fixture capacitors 15, 16. By varying the resonant frequency of the generator oscillator circuit 52, the transfer of power can be controlled in a targeted manner; the greater the difference between the resonant frequencies of the two oscillator circuits 50, 52, the lower the transferred power. Adjustment of the generator oscillator circuit 52 can therefore be used in a targeted manner to set the power introduced into the forming space 14.

[0122] In this exemplary embodiment, the resonant frequency of the generator oscillator circuit 52 is changed. It is equally possible to change the resonant frequency of the fixture oscillator circuit 50. This has the same effect on the power transfer. However, it is more difficult to provide a variable capacitor or variable inductance on the fixture side than on the generator side.

[0123] 4 shows in a schematic simplified circuit diagram an arrangement for controlling the power supplied to the fixture capacitors 15, 16. A generator 18 is connected to the fixture capacitors 15, 16. A measuring capacitor 53, the capacitance of which is a fraction of the capacitance of the fixture capacitors 15, 16, is connected in parallel with the fixture capacitors 15, 16. The measuring capacitor 53 is connected to a voltage measuring device (voltmeter) 55 via a coaxial line 54. A diode 56 is preferably connected in parallel with the measuring capacitor 53. The coaxial line 54 is connected in series with an inductance 58, which serves to filter high-frequency signals.

[0124] The measuring unit formed by the measuring capacitor 53 and the diode 56 is separated from the fixture capacitors 15, 16 by an isolation capacitor 59. The isolation capacitor has a high dielectric strength. The capacitance of the isolation capacitor 59 is smaller than the capacitance of the measuring capacitor 53. As a result, the voltage drop across the isolation capacitor is higher than across the measuring capacitor 53. The ratio of the capacitance of the isolation capacitor 59 to the capacitance of the measuring capacitor 53 is preferably 1:100 or 1:1,000 or 1:10,000. As a result, the voltage applied to the fixture capacitors 15, 16 in the measuring unit 53, 56 is reduced so that it is within the measuring range of the voltage measuring device 55 and can be reliably detected by the voltage measuring device.

[0125] In this circuit, a voltage corresponding to the voltage applied to the fixture capacitors 15, 16 and decreasing depending on the ratio of the capacitance of the measurement capacitor 53 to the capacitance of the isolation capacitor 59 is dropped across the measurement capacitor 53. As a result of the provision of the diode 56, only half of the oscillations of a certain polarity occur. The diode 56 therefore forms a rectification of the voltage developed across the measurement capacitor 53. This measurement voltage is measured by the voltage measuring device 55 and converted into a measurement signal. The measurement signal is transferred to the control device 57, which automatically controls the generator 18 to output a predetermined power in order to generate a certain measurement voltage across the measurement capacitor, which is a certain voltage across the fixture capacitor or a fraction of the voltage across the fixture capacitor.

[0126] The control device 57 controls the power of the generator 18 on the basis of the measured voltage. In this case, the setpoint value of the predetermined controlled power may be different. On the one hand, the power can be controlled to a certain constant magnitude, on the other hand, the power can be varied in such a way that the voltage dropped across the measuring capacitor 53 and rectified in the voltage measuring device 55 is substantially constant. In other words, depending on the measured voltage, on the one hand, the power output or the measured voltage can be kept constant.

[0127] As explained at the beginning, the absorption capacity of the material to be welded present in the fixture capacitors 15, 16 changes depending on the temperature, and particularly strong changes in the absorption capacity of the electromagnetic waves occur in certain process situations. In the equivalent circuit diagram shown in Figure 4, the change in the absorption capacity of the electromagnetic waves can also be considered as a change in the capacitance of the fixture capacitors 15, 16. This change in capacitance in the fixture capacitors 15, 16 leads either to a change in the voltage (= voltage amplitude) or to a change in the power output, depending on whether the control device 57 is designed to keep the power output or the voltage (= voltage amplitude) applied to the fixture capacitors 15, 16 constant.

[0128] In principle, it is easier to output a predefined constant power by the generator 18, since in that case the adjustment of the fixture oscillator circuit 50 to the generator oscillator circuit 52 can be kept constant, resulting in a constant power being output by the generator 18. In this embodiment, the measured voltage measured by the voltage measuring device 55 can represent a parameter characteristic of the absorption capacity of the material to be welded, which parameter is monitored by the control device 57. If the measured voltage changes by a predefined threshold within a predefined time interval, this change is determined by the control device 57 and evaluated as a trigger point for terminating the heating process. The heating process can be terminated simultaneously with the determination of the trigger point or with a delay of a predefined period. The heating process is terminated by switching off the supply of power from the generator 18, the switching off of the generator 18 being controlled by the control device 57.

[0129] In a modification of this embodiment, the control device 57 can be designed to first derive the measured voltage as a function of time. If the signal after the first time derivative of the measured voltage exceeds a certain threshold, this means a predefined abrupt change in the measured voltage present across the fixture capacitors 15, 16, which is then evaluated by the control device 57 as a trigger point for terminating the heating process.

[0130] In a further modification of this embodiment, the control device 57 can also be designed in such a way 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 certain curvature of the profile of the measured voltage and thus an abrupt change in the voltage signal. This change can also be evaluated as a trigger point for terminating the heating process.

[0131] If the control device 57 is designed such that the power output by the generator 18 is changed so that a substantially constant voltage (=voltage amplitude) drops across the fixture capacitors 15, 16, the entire system reacts to a sudden change in the electromagnetic wave absorption capacity of the material present in the fixture capacitors 15, 16, which is welded by a corresponding change in power. This power can basically be determined by measuring the current output to the fixture capacitors 15, 16, since the voltage present across the fixture capacitors 15, 16 is already 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.

[0132] However, it is easier to tap the control signal output by the controller 57, which controls the power output of the generator 18. This control signal corresponds to the power to be output, and a predefined strong change in the control signal can be evaluated as a trigger point for terminating the heating process. Since this control signal is present within the controller 57, it can also be monitored here at the same time.

[0133] Here, various embodiments are also possible as to how the trigger point is determined: It can be monitored whether the control signal changes by a predefined threshold within a predefined time interval, as well as whether the first or second derivative exceeds a predefined threshold.

[0134] Similarly, once a trigger point is determined (based on voltage or power, either by monitoring a directly measured signal or a first or second derivative), the heating process can be terminated immediately upon determination of the trigger point or delayed for a predetermined period of time.

[0135] This method for automatically determining the heating period of the expanded particles for sports clothing, sports equipment, or balls using electromagnetic waves can be carried out again individually during each manufacturing process for manufacturing a particle foam part from expanded particles for sports clothing, sports equipment, or balls. However, within the scope of the present invention, it is also possible to use this method to calibrate the heating period of the expanded particles for sports clothing, sports equipment, or balls using electromagnetic waves for a specific molding tool and a specific type or a specific batch of expanded particles for sports clothing, sports equipment, or balls. The duration of the heating process until all the expanded particles are completely fused to form the particle foam part mainly depends on the molding tool used, which defines the molding space, and the type or batch of expanded particles used.

[0136] The manufacturing process for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls is called a calibration process, in which the period for heating the expanded particles using electromagnetic waves is set individually according to the method described above, in which the period for heating the expanded particles using electromagnetic waves is detected and stored using a clock or clock generator. The period determined in this way for heating the expanded particles using electromagnetic waves is called "production time interval" below.

[0137] A single calibration process or multiple calibration processes can be carried out, in each case the duration of heating the expanded particles for sports clothing, sports equipment or balls using electromagnetic waves is detected. If multiple heating intervals are detected, these intervals can be statistically evaluated, for example the average or median of the detected heating intervals can be made available as production time interval for the further production process. In the further production process, the characteristic parameter is no longer monitored, but rather the duration of heating the expanded particles using electromagnetic waves is controlled solely on the basis of this production time interval. The duration of heating the expanded particles using electromagnetic waves is thus calibrated. As a result, the further control can be simplified and transferred, if appropriate, to further devices for producing particle foam parts, which use the same fixture and produce particle foam parts using the same type or the same batch of expanded particles. These further devices can be designed with simple control devices that control the heating process solely on the basis of the existing production time interval.

[0138] As explained above, a number of manufacturing time intervals, each of which is detected using a calibration process, can be statistically evaluated. By such statistical evaluation, it is also possible to determine the quality factor of the manufacturing process. If the different manufacturing time intervals deviate significantly from each other, this is a sign that the manufacturing process is unstable and produces particle foam parts with different qualities. In contrast, if the manufacturing time intervals are substantially the same, this means that the manufacturing process is stable and produces particle foam parts with the same quality, respectively. Therefore, if the quality factor indicates that the stability of the manufacturing process is too low, the standard deviation of the manufacturing time intervals of the different calibration processes can be modified as the quality factor for evaluating the quality of the manufacturing process.

[0139] To optimize the manufacturing process, one or more of the following parameters can be varied: - the applied power of the electromagnetic waves, - an applied voltage to generate electromagnetic waves; - the amount of heat transfer medium supplied to the forming space, - the amount of foam particles fed into the moulding space; - The pressure exerted by the forming tool on the foam particles before they are heated.

[0140] The lower the applied power or voltage to generate the electromagnetic waves, the slower the foaming particles will heat up. The slower the foaming particles heat up, the better the thermal equalization between different areas of the mold space can be achieved, and the more uniform the overall welding will be. Therefore, the stabilization of the manufacturing process can often be achieved by lowering the power or voltage.

[0141] However, in the case of some moulding tools, especially those with electrically conductive mould halves, the heat can be dissipated very well at certain points, so that certain points of the mould space are cooled more strongly than others. In contrast, in the case of such moulding tools, it may be advantageous to heat the foam particles as quickly as possible and to operate the heating of the foam particles with as high an electromagnetic power or as high an applied voltage as possible. In this situation, increasing the power or voltage can lead to a stabilisation of the production process. The amount of foam particles located in the mould space and / or the amount of binder for binding the foam particles can also have a considerable influence on the stability of the production process, and it is equally the case that increasing or decreasing the amount of foam particles or the amount of binder leads to a stabilisation of the production process. These amounts can be recognised by statistical evaluation based on quality factors and set accordingly.

[0142] This optimization can be performed automatically using an expert system. This optimization can also be based on machine learning, where the quality of the manufactured particle foam parts is detected manually or by suitable measurement methods using data technology and entered as feedback into the system, on the basis of which the optimization and learning process can be performed.

[0143] It has been shown that the period during which the electromagnetic RF radiation is applied depends on the volume of the molding space 14, the density of the foamed particles and the applied power or applied voltage. Tests have shown that to ensure and completely weld the foamed particles, between about 30 seconds and about 2 minutes are required, depending on the volume and the material from which the foamed particles are made. In this case, a voltage (= voltage amplitude) of between 3 kV and 20 kV is generally applied.

[0144] During welding, the temperature of the expanded beads can be measured and the power controlled accordingly. The power is preferably controlled so that the expanded beads have a temperature slightly above their softening temperature.

[0145] The surfaces that bound the moulding space 14 may furthermore be temperature controlled. For this purpose, a heating wire 22 may be arranged in the moulding fixture adjacent to the surfaces that bound the moulding space 14. The heating wire 22 is connected to a current source 23, by means of which a heating current can be supplied to the heating wire.

[0146] Instead of heating wires, fluid channels can also be provided in the mould halves 12, 13 through which a corresponding temperature controlled fluid flows. Preferably, the fluid is water or steam.

[0147] After the application of the electromagnetic RF radiation, the molding space 14 is kept closed for a stabilization time interval, whereby the introduced heat is distributed homogeneously in the particle foam part and a very uniform weld is formed between all the foam particles. This process step is called stabilization. During stabilization, a slight cooling of the particle foam part also takes place. Since the mold halves 12, 13 are made of a material that is practically transparent to the electromagnetic RF radiation and is usually a plastic material with low thermal conductivity, essentially no heat is output to the outside in the closed molding space 14. Of course, this is not the case if one of the mold halves is made of an electrically conductive and thus highly thermally conductive material.

[0148] The mould halves 12, 13 made from plastic have the advantage over mould halves made from metal on the one hand of significantly better thermal insulation and on the other hand of a lower heat capacity, so that the desired temperature cycle can be carried out substantially faster and with less energy, and the supplied heat is delivered almost entirely to the expanded particles.

[0149] During the stabilization period, or during a portion of the stabilization period, the capacitor plates 15, 16 are actively cooled by cooling devices 32, 33, thereby extracting heat from the body of the mold halves 12, 13 and thus from the particle foam part.

[0150] After stabilization, the particle foam part is demolded by separating the two mold halves 12, 13. For demolding, a demolding plunger can be provided in the mold fixture, which pushes the particle foam part out of one of the two mold halves 12, 13.

[0151] Stabilization is an optional method step. For certain materials and molds, stabilization can also be omitted. The larger the volume of the particle foam parts to be produced, the more expedient it is to stabilize the particle foam parts in the mold fixture after welding.

[0152] To increase throughput, electromagnetic RF radiation can already be applied during filling and / or closing of the crack gap.

[0153] The electromagnetic radiation, in particular RF radiation, can be applied already during the filling of the molding space 14 with the foamed particles or else only after filling, first at low power or low voltage to preheat the material to a certain temperature and then the power or voltage is gradually or suddenly increased.

[0154] It may also be expedient to gradually increase the power or voltage of the electromagnetic RF radiation, so that the ramp is carried out over a period of, for example, 30 seconds to 3 minutes, as a result of which a very uniform heating of the foam particles is achieved.

[0155] Optionally, negative pressure and / or vacuum can also be applied to the moulding space 14. This is advantageous when the supplied expanded particles and / or compressed air have a certain moisture content.

[0156] The above-described method is a dry method compared to the sole welding with steam. As a result, the produced particle foam part is dry or drier after the production process and can be fed to further processing steps more quickly. It may also be advantageous to demold the warm particle foam part and feed it immediately to further processing. As a result, on the one hand, the pauses between the individual process steps can be shortened and, on the other hand, a significant efficiency increase can be achieved in production, since the heat introduced for welding the foam particles can also be used at least partially for the subsequent method steps.

[0157] It may be advantageous to provide the welding station with a water or steam supply line to supply water and / or steam to the molding tool. This is particularly advantageous when welding foamed particles that have only a low dielectric loss factor at low temperatures or that generally have a low dielectric loss factor. In such cases, small amounts of water or steam are supplied. As a result of the electromagnetic radiation, the water is heated to steam or the steam is further heated. As a result, the foamed particles are heated to a relatively high temperature at which the dielectric loss factor is greater, whereby the foamed particles themselves absorb the electromagnetic radiation and are further heated. It has been shown that a few hundred grams of water are sufficient for a molding space with a volume of 50 liters. If the foamed particle material is, for example, ePS (expandable polystyrene), not more than 300 grams of water are sufficient to heat and weld the foamed particles in a molding space with a volume of 50 liters. In the case of conventional welding, where the foamed particles are heated only by superheated steam, a large amount of steam containing several kilograms of water is required for a molding space with a volume of 50 liters.

[0158] Therefore, when welding foam particles that only slightly absorb electromagnetic radiation, a single addition of 300 g of water for a moulding space with a volume of 50 litres is basically sufficient. For many materials that only slightly absorb electromagnetic radiation, even smaller amounts of water may be sufficient. For moulding spaces with other volumes, the maximum required amount of water can be adapted to the volume in the same proportions.

[0159] When heating the water in the moulding space by means of electromagnetic radiation, it is advantageous to use a moulding tool having a pressure sensor capable of measuring the pressure present in the moulding space, this pressure being proportional to the temperature. The application of electromagnetic radiation is then preferably controlled depending on the measured pressure value, i.e. is preferably set to a specific pressure value. [Explanation of symbols]

[0160] 1 device 2 Material container 3. Forming tool 4 conduit 5 Bottom 6 Compressed air pipeline 7 Compressed Air Source 8 Driving Nozzle 9 Compressed Air Pipeline 10 Filling injector 11 Compressed air pipeline 12 Mold half 13 Mold half 14 Molding space 15 Capacitor Plate 16 Capacitor Plate 17 Electrical Lines 18 AC voltage source 19 Negative pressure pump 20 Fans 21 Cooling fin 22 Heating Wire 23 Current source 24 Main Unit 25 Main Unit 26 Inner boundary surface 27 Inner boundary surface 30 Grounding 31 Bottom wall 32 Side wall 33 Filling opening 34 Ventilation opening 35 Housing 46 Pipeline 47 Generator side inductance 48 Fixture side inductance 49 Jig side capacitor 50 Jig Oscillator Circuit 51 Generator side capacitor 52 Generator Oscillator Circuit 53 Measuring capacitor 54 coaxial line 55 Voltmeter 56 Diode 57 Control device 58 Inductance 59 Isolation Capacitor

Claims

1. A method for producing particle foam parts from foam particles for sports clothing, sports equipment or balls using electromagnetic waves, comprising: - filling the moulding space, - heating and fusing the foamed particles with electromagnetic waves; - demolding, monitoring a parameter characteristic of the absorption of electromagnetic waves during the heating of the expanded beads, and terminating the heating of the expanded beads when the parameter changes by a predetermined amount. method.

2. the electromagnetic waves are generated by a capacitor within which the molding space is disposed, The electromagnetic wave is applied to the capacitor with a predetermined voltage amplitude and the power introduced into the forming space or the first or second derivative of said power with respect to time is measured as a characteristic parameter; or The electromagnetic wave is applied to the capacitor with a predetermined power, and a voltage drop across the capacitor or a first or second derivative of the voltage drop with respect to time is measured as a characteristic parameter.

2. The method according to claim 1 .

3. After heating, the bead foam part is cooled in the molding space before demolding.

2. The method according to claim 1 .

4. RF radiation is used as the electromagnetic wave; 2. The method according to claim 1 .

5. 1. A method for calibrating a process for producing particle foam parts from foam particles for sports clothing, sports equipment or balls using electromagnetic waves, comprising:

2. A method according to claim 1, in which at least one particle foam part for a sports garment, sports equipment or ball is manufactured in a calibration process using a mold defining a specific molding space and expanded particles of a specific material type, the duration of said heating by electromagnetic waves is measured until said characteristic parameter changes by a specific threshold value, and further particle foam parts for a sports garment, sports equipment or ball are manufactured by heating said expanded particles with in each case the same settings for supplying said electromagnetic waves, during a production heating interval corresponding to said duration determined in said calibration process.

6. A plurality of particle foam parts for sports clothing, sports equipment or balls are manufactured according to the method of claim 1 during a calibration process, the durations of the heating being measured in each case, and a manufacturing time interval is determined based on the durations measured during the calibration process.

6. The method according to claim 5 .

7. The average or median value of each of the periods is determined as the production time interval; 7. The method according to claim 6 .

8. only those periods within a predetermined multiple of a standard deviation around the mean or median of the measured periods are considered for determining the production time interval; 7. The method according to claim 6 .

9. a statistical evaluation of the measured time periods is performed to determine a quality factor of the manufacturing process.

7. The method according to claim 6 .

10. if the quality factor indicates that the stability of the manufacturing process is too low, the manufacturing process is optimized based on the quality factor by modifying at least one specific parameter of the manufacturing process.

10. The method according to claim 9.

11. The following parameters: - the applied power of said electromagnetic waves, - an applied voltage for generating said electromagnetic waves; the amount of heat transfer medium supplied to the forming space, the amount of the expanded particles fed into the moulding space, the pressure exerted on the expanded beads by the molding tool before the expanded beads are heated; and then producing a plurality of particle foam parts for sports clothing, sports equipment or balls according to the method of claim 1, the production time interval is determined again.

11. The method according to claim 10.

12. the at least one parameter to be altered and the extent of alteration are determined automatically by an expert system; 12. The method according to claim 11 .

13. An apparatus for producing particle foam parts from expanded particles for sports clothing, sports equipment or balls, comprising: a moulding tool defining a moulding space, at least two capacitor plates being arranged adjacent to said moulding space, said capacitor plates being connected to a source of electromagnetic radiation, said source of electromagnetic radiation being designed to emit electromagnetic radiation; Equipped with A control device designed to automatically carry out the method according to claim 1. Device.

14. 13. A particle foam part made from expanded particles for sports clothing, sports equipment or balls, produced according to the method of claim 1.

15. The particle foam part of claim 1 , wherein the particle foam part is a shoe sole or a part of a shoe sole.

16. A shoe comprising the sole or insole according to claim 1.

Images