Electromagnetic foaming

Abstract

Aspects herein relate to systems and methods for manipulating the distribution of microwave and / or thermal energy within a mold cavity holding a part to be foamed. The cavity can be constructed from a combination of materials having one or more dielectric properties that allow different microwave frequencies to be absorbed, transmitted, or reflected in order to achieve a desired distribution of microwave and thermal energy within the cavity. A solid-state microwave energy source is combined with a frequency synthesizer to tailor the microwave energy that is transmitted, and a press can be used to apply pressure to the material within the mold during the manufacturing process. A thermoplastic polymer can be introduced into the mold cavity in the form of a plurality of pellets, granules, beads, or other discrete elements, or in the form of a preform.

Description

Background Technology

[0001] Shoes and similar items are typically constructed from smaller parts or components made of various materials, including rubber, foam, or other materials that require foaming. Often, these parts are irregularly shaped, which presents challenges for proper foaming. For example, a typical shoe sole is shaped in an uneven manner, as the heel portion of the sole can have a shorter width and a higher height than the ball of the foot portion. Furthermore, as described below, the volume of the sole material can vary from the heel portion to the ball of the foot during the foaming process. Summary of the Invention

[0002] The present invention generally relates to systems and methods for uniformly foaming non-uniform workpieces (such as shoe parts) using a combination of microwave energy and pressure.

[0003] The systems and methods described in this paper provide various ways to manipulate the distribution of microwave and / or thermal energy within a mold cavity holding a part to be foamed. The cavity can be constructed from a combination of materials having one or more dielectric properties that allow different microwave frequencies to be absorbed, transmitted, or reflected as needed to achieve a desired distribution of microwave and thermal energy within the cavity, either alone or in combination with other features consistent with the aspects described herein. In some aspects, a solid-state microwave energy source is combined with a frequency synthesizer to customize and vary the frequency and intensity / amplitude of the transmitted microwave energy. In some aspects, a press or other device can be used to apply pressure to the material within the mold during the manufacturing process. In some aspects, the press is part of an overall system or apparatus for heating and foaming a shoe part.

[0004] In various aspects, thermoplastic polymers are used to form shoe parts. This material can be in the form of multiple granules, pellets, beads, or other discrete elements that can be introduced into a mold cavity. In various aspects, the discrete elements have a foaming agent injected or otherwise incorporated therein. In various aspects, the discrete elements include thermoplastic polyester elastomer (r-TPEE) and a foaming agent. In other aspects, the discrete elements can be processed in a preliminary step to form a preform with a desired shape and material distribution. The preform is then introduced into the mold cavity.

[0005] Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon review of the brochure, or may be learned by practice of the invention. Attached Figure Description

[0006] Examples of various aspects of this article are described in detail below with reference to the accompanying drawings, in which:

[0007] Figure 1 The figure illustrates a schematic cross-sectional side view of the system decomposed according to one aspect of this paper;

[0008] Figures 2A to 2D The diagram illustrates the various steps in the manufacturing process according to the aspects described in this article. Figure 1 A cross-sectional view of the assembled system;

[0009] Figure 3 This is a flowchart of a manufacturing method according to one aspect of the present invention;

[0010] Figures 4A to 4B The illustration shows schematic side views of several aspects of a preform formed according to another aspect of this article;

[0011] Figure 5 yes Figure 3 A flowchart of an optional preliminary process for the manufacturing method; and

[0012] Figure 6 A schematic cross-sectional side view of the system components according to the second aspect of this document is illustrated. Detailed Implementation

[0013] A footwear article, such as a shoe, can be formed from various components. For example, a shoe includes a sole portion, which divides the shoe into parts that provide a variety of functional benefits. Therefore, from the perspective of process and material selection, the formation of the sole is fundamental to obtaining the advantages of the sole. Soles are traditionally formed from foamed polymer compositions, but conventional methods for forming foamed soles have limitations, thus limiting the ability to achieve the desired properties of the sole. As will be described in detail below, aspects of this paper envision a customized distribution of electromagnetic energy (e.g., microwave energy) and a system for such distribution to tune the formation of polymer foamed components (such as those forming the sole). In addition to providing a tuned electromagnetic energy distribution and the tools for achieving such distribution, the concepts envisioned herein also tune the process and the resulting article through material selection. As an example of material selection factors considered in the envisioned manner to achieve the desired foamed article, a tuned dielectric microwave dielectric constant characteristic is considered for the material to which electromagnetic energy is applied.

[0014] As used herein, foam is a material formed by trapping air bubbles or cavities within a solid matrix. In conventional foaming techniques, a quantity of material to be foamed (called a “load”) is contained in the cavity of a mold and heated under pressure until a blowing agent is activated. The load can initially be in solid form before heating and can be in liquid form during the activation of the blowing agent. The mold can then be held under pressure until the load cools, after which the mold is opened; upon opening, the foaming reaction occurs, and the foamed part expands and ejects from the mold cavity. Conventional heat sources used for this process include ovens or hot presses that rely on resistance heating.

[0015] The characteristics of the load can affect the uniformity of the resulting part formed by the load during the foaming process. These characteristics can include profile, volume, mass, length, width, height, material type, the position of the load relative to the heat or energy source used, and / or the position of the load relative to a portion of the mold cavity. Therefore, to achieve a desired temperature, one portion of the load within the cavity may require a different amount of energy than another portion of the load within the same cavity. For example, the heel portion of a shoe sole can have a larger mass than the ball of the foot portion, and thus the sole can be foamed using a tunable electromagnetic energy distribution and associated tools.

[0016] Customizing the energy distribution throughout the cavity allows parts (such as shoe soles) to be foamed uniformly, even if the part has a non-uniform shape or other non-uniform properties. However, achieving this customized energy distribution throughout a small volume (such as the mold cavity of a shoe part) using conventional heat sources such as ovens or hot presses can be difficult, as these conventional heat sources are typically designed to heat large volumes in a non-discrete manner. Furthermore, these conventional heating methods require heating not only the load but also the mold, oven, or press itself, as well as the medium used to transfer heat to the mold (e.g., the air within the oven), resulting in a significant amount of energy being wasted as excess heat.

[0017] Recently, the use of electromagnetic radiation, such as microwave energy, for foaming shoe parts has been explored. Microwave energy is a form of electromagnetic radiation. Microwaves can have wavelengths ranging from one meter to one millimeter, corresponding to frequencies between 300 MHz (1-meter wavelength) and 300 GHz (1-millimeter wavelength). Microwave energy can interact with materials based on various factors, such as power, frequency, proximity, and beam shape, to generate heat energy known as dielectric heating. In many cases, dielectric heating is often more efficient than heating via conventional heat sources such as ovens or hot presses, which rely on traditional heating elements such as resistance heating, because microwave energy can be directly absorbed and converted into heat by the target, rather than having to be conducted through physical conduits (e.g., air inside an oven chamber or metal on a hot press plate).

[0018] However, efforts to use microwave heating technology in foam manufacturing processes have encountered several problems. These problems include the "blowtorch effect" (overheating at the initial point of contact between microwave energy and the load) and the difficulty in properly "tuning" the chamber to uniformly heat the material in the mold.

[0019] It has been demonstrated that utilizing microwave energy from conventional microwave energy sources (e.g., magnetrons) for small cavities the size required for typical shoe parts is particularly challenging. A fixed-frequency microwave signal emitted within the microwave cavity is reflected multiple times, eventually establishing a modal distribution of energy. The overall distribution of electromagnetic energy throughout the microwave cavity is non-uniform, resulting in both high-energy field regions and low-energy field regions—hot spots and cold spots.

[0020] Another challenge is that many typical materials used to form shoe parts, such as ethylene vinyl acetate (EVA), are not particularly well-suited for heating via microwave energy. A large part of dielectric heating occurs through a phenomenon known as orientation polarization (also called dipole polarization), in which polar molecules in the material rotate to align themselves with the electric field of the microwaves. As the microwave electric field oscillates continuously, the molecules move accordingly, leading to molecular friction and collisions that result in rapid heating of the material. However, some materials do not undergo significant orientation polarization when exposed to microwave energy. In particular, it has been observed that EVA (a material widely used in shoe manufacturing) may not be efficiently heated via microwave energy due to the length of its molecules.

[0021] To address these issues, various methods are provided based on the systems and approaches described in this paper to manipulate the distribution of microwave and / or thermal energy within the cavity holding the part to be foamed.

[0022] Some aspects described herein generally relate to systems and methods for customizing the distribution of microwave energy within a cavity to uniformly process non-uniform workpieces. These aspects of the invention can utilize microwave energy sources including solid-state transistors and frequency synthesizers. Compared to conventional sources such as magnetrons, such microwave energy sources allow for more precise tuning of the amplitude and frequency of the microwave energy being utilized by the system, while also generating microwaves more efficiently, thereby reducing the amount of power required. A computing device can be coupled to the microwave energy source to adjust the application of microwave energy based on parameters such as the elapsed time during a manufacturing cycle and / or temperature measured by one or more sensors. Additionally, aspects of the system (which may include molds and presses) include one or more components formed of materials with different dielectric properties, selected to selectively configure the energy and heat distribution of the load being applied within the mold. By selecting the locations of different materials that can absorb, reflect, or transmit the microwave energy used, additional energy can be directed to different portions of the mold cavity as needed. For example, some portions of the mold may be formed of a material that absorbs microwave energy and is heated, which in turn can transfer heat to adjacent portions of the load within the cavity via conduction. This provides the system with an additional mechanism for transferring energy (in the form of microwaves or heat) to the load inside the mold cavity in a discrete manner.

[0023] Additionally, blends comprising recycled polyethylene terephthalate (PET) and a foaming agent have been found to be sufficiently responsive to microwave energy and expand well even under suboptimal conditions. In particular, materials known as recycled thermoplastic polyester elastomers (recycled TPEE or r-TPEE) have been found to readily absorb microwave energy and heat rapidly, thus aiding in foaming. r-TPEE can be produced using post-consumer recycled (PCR) and / or PET bottles as feedstock. A specific r-TPEE envisioned herein has a relatively low carbon impact, manufactured from post-consumer recycled PET bottles, and has an estimated total CO2e of approximately 1.3 kg / kg r-TPEE, where CO2e represents the metric tons of CO2 emissions with the same global warming potential as one metric tonne of another greenhouse gas, and is calculated using Equation A-1 in Part 98 of 40 CFR. Besides being a suitable material for dielectric heating, r-TPEE exhibits acceptable properties (e.g., resilience, durability) and remains recyclable when introduced into the waste stream. Therefore, using r-TPEE to form shoe parts using the systems and methods described herein provides significant progress in sustainability by reusing waste as raw materials, reducing the energy used in manufacturing shoe parts, and minimizing waste at the end of their lifespan. However, it should be understood that non-renewable materials, such as TPEE that does not contain any recycled content, can also be used according to this disclosure.

[0024] In some aspects, r-TPEE (or other materials to be foamed) is introduced into a mold (i.e., a cavity formed within the mold) in the form of granules or other discrete elements. In others, the material can be preformed into different shapes. For example, discrete elements containing r-TPEE can be introduced into a preforming mold having a volume that is the same as or different from the volume of the mold cavity in at least one aspect. The preforming mold is then heated to a temperature that allows the discrete elements to adhere to each other, but not to a temperature at which the foaming agent is substantially activated and foaming of the composition substantially begins. The preform can be heated via conventional methods (e.g., convection, conduction) and / or by applying microwave energy (referred to herein as microwave for convenience). The preform can then be removed from the preforming mold and introduced into the mold. An optional cooling step can be performed before removing the preform from the preforming mold.

[0025] Using preforms allows for a more precise distribution of material within specific areas of the mold, which can then lead to different properties in corresponding portions of the foamed part. For example, preforms can be used in conjunction with the formation of a shoe sole component with a non-uniform volume along the part, where the application of loose granules may not result in proper material distribution to fill the mold volume forming the non-uniform part shape. Using preforms can help ensure that a sufficient volume of material is positioned appropriately within the mold volume to adequately fill and form the resulting part, or alternatively, distribute additional or less material in one or more portions of the mold volume, such that the formed part exhibits different properties in those portions.

[0026] Dielectric properties such as dielectric constant and dielectric loss factor affect the intensity and rate of heating a material experiences when exposed to microwave energy. At high levels, a material's relative permittivity (also known as dielectric constant) indicates its ability to absorb microwave energy, while the dielectric loss factor explains its ability to convert absorbed microwave energy into heat. Materials with a higher relative permittivity mean that more microwave energy can be stored in the material compared to materials with a lower relative permittivity. The relative permittivity of vacuum is 1, and all other materials have a relative permittivity greater than 1. Materials with a higher dielectric loss factor will dissipate more energy as heat compared to materials with a lower dielectric loss factor.

[0027] The response of a material to microwave energy can also depend on factors such as temperature or phase, and can be specific to a particular wavelength. For example, regarding radio frequency (RF) energy in the microwave band, liquid water will absorb energy and heat up rapidly, while ice is largely transparent to microwave energy.

[0028] A material's response to microwave energy also depends on its ability to penetrate or pass through the material. For materials with essentially zero penetration, such as metals, microwave energy will be reflected. At the other end of the spectrum are materials with infinite penetration (i.e., microwaves pass through without any loss); these materials are considered transparent to microwave energy. For materials between these two ends of the spectrum, the outer layers will absorb some microwave energy, while the rest will penetrate deeper into the material until it is gradually absorbed or passed through.

[0029] Now for reference Figure 1 and Figures 2A to 2D , Figure 1 and Figures 2A to 2D A schematic cross-sectional view of a system 10 for molding articles using microwave energy, according to various aspects thereof, is provided. A general description of the components of system 10 is now given. System 10 includes a mold base 100 having one or more mold chambers 110 and a mold cover 200 configured to fit over the mold base 100 and seal the mold chambers 110. The mold base 100 and mold cover 200 are configured to fit within a press including a press base 300 and a top pressure plate 500. A microwave energy source 400 is coupled to the press base 300 via a transmission line 410. A computing device 600 is connected to system 10 and is capable of controlling the operation of the system.

[0030] Turning now to a more detailed description of the various components of system 10 according to one aspect of this document, mold base 100 has a top surface 102, a bottom surface 104, and at least one mold chamber 110. Each mold chamber 110 has a mold chamber bottom 112 and a mold chamber sidewall 114. In one aspect, mold base 100 may be formed of a material that is effectively transparent to the microwave frequency used; examples of such materials include certain ceramic materials (such as alumina, magnesium oxide, and silicon dioxide), Teflon, quartz, and glass. In another aspect, mold chamber sidewalls 114 may comprise a variety of materials, each having one or more dielectric properties with respect to the microwave frequency used, and thus different responses and interactions with microwaves. For example, some or all of the mold chamber sidewalls 114 may comprise or be lined with a material such as silicon carbide, which absorbs at least some of the frequencies emitted from microwave energy source 400 and undergoes dielectric heating; the heated mold chamber sidewalls 114 then transfer heat to a load via conduction. In another example, at least a portion of the mold cavity sidewall 114 may be lined with a material (e.g., a metal) that reflects at least some of the frequencies being utilized, in which case microwaves are reflected back into the load material. As used herein, having a surface “lined” with a certain material may mean having a surface coated with that material or having discrete layers of that material bonded to that surface; the bonding of the lining to the surface can be achieved by a number of suitable methods, such as using adhesives, bonding agents, and / or using mechanical connectors.

[0031] like Figure 1 and Figures 2A to 2CAs shown, the mold cover 200 includes an upper mold plate 210 corresponding to the number of mold chambers 110 in the mold base 100, and effectively forms a sealed mold chamber when in a closed configuration with the mold base 100. The mold cover 200 is configured such that it can be inserted into the pressing surface 510 of the top pressure plate 500. The mold cover 200 and the upper mold plate 210 may comprise materials that are microwave-reflective, microwave-transparent, or microwave-absorbing, depending on the desired characteristics. In one aspect, some or all of the upper mold plate 210 is formed, lined, or otherwise associated with a material that absorbs at least some of the microwave frequencies being utilized. For example, if it is desired that the load be heated by a combination of direct microwave energy absorption and heat transfer via conduction from the upper mold plate 210, a lining of material may be used to form or line the surface of the upper mold plate 210 such that the lining absorbs certain microwave frequencies that pass through the load material (or are otherwise reflected within the mold). In other respects, some or all of the upper mold plate 210 is formed of or lined with a material of at least some of the microwave frequencies used for reflection. This alternative configuration allows microwave frequencies that are absorbed by the material but have managed to pass through the mold cavity 110 on their first attempt to be reflected back into the mold cavity 110, thus allowing these microwave frequencies to have another opportunity to be absorbed by the load material.

[0032] The upper mold plate 210, the bottom 112 of the mold cavity, and the sidewalls 114 of the mold cavity can be formed to provide shape, texture, pattern, or design to one or more surfaces of the foamed part. Figure 1 In the aspects shown, the mold base 100 is a component separate from the press base 300, and the mold cover 200 is a component separate from the top pressure plate 500. In other aspects, one or both of the mold base 100 and the mold cover 200 may be integrated into the press base 300 and / or the top pressure plate 500, respectively.

[0033] The press base 300 of system 10 includes a bottom pressure plate 310 and a bed 320 into which a mold base 100 can be inserted. The top surface 322 of the bed 320 has one or more windows 324, each window coupled to a corresponding conduit 326. As used herein, a "window" is a portion of a component that is more transparent or more permeable to microwave energy than the surrounding portion. The window 324 is formed of a material that is effectively transparent to the microwave frequencies emitted by the microwave energy source 400. In one aspect, suitable materials for the window 324 may include ceramics, fused silica / quartz, polytetrafluoroethylene, or polyetheretherketone. In another aspect, the window 324 is a physical aperture in the top surface 322 of the bed 320, since air is largely transparent to microwave energy. In various aspects, the window 324 may have one or more portions made of different materials having a different set of dielectric properties; this configuration allows for a greater degree of customization of the microwave energy and heat distribution supplied to the load 700 within the mold chamber 110.

[0034] A microwave energy source 400 (including a power supply, solid-state components, and at least one frequency synthesizer) provides the microwave energy used by system 10. In one aspect, the microwave energy source 400 is coupled to a window 324 in a press base 300 via a combination of a transmission line 410 and a conduit 326. As used herein, a “transmission line” refers to a structure that propagates microwave energy from the microwave energy source to the press base 300, and a “conduit” refers to a structure that propagates microwave energy through the press base 300 to the window 324. In one aspect, the transmission line 410 and the conduit 326 include one or more combinations of RF coaxial cables and waveguides, which are selected to be compatible with the microwave wavelength being utilized. In one aspect, the coaxial cable allows for flexible installation and accommodates potential movement of different components of the system, including molds. In one aspect, an antenna device can be used to transfer energy from the coaxial cable to the waveguide. Systems using only waveguides, or only coaxial cables, or other suitable transmission structures for propagating microwave energy are contemplated within the scope of this disclosure. In one aspect, a waveguide comprising a steel or aluminum channel having a rectangular cross-section with specified dimensions related to the wavelength can be used. In another aspect, the waveguide may have a rectangular cross-section with internal dimensions of approximately 86 mm wide and approximately 43 mm high.

[0035] In an exemplary aspect, it is conceivable that the microwave energy used herein may be within a specific frequency range. For example, the energy range may be within a frequency band between 2400 MHz and 2500 MHz, one of two bands permitted by currently applicable broadcast regulations and the band in which many widely available commercial microwave ovens operate. However, despite any regulatory limitations, it is conceivable that any microwave or even radio frequency (RF) energy, as further described herein, can be implemented in the exemplary aspects herein, depending on the materials of the load and the nature of the system components. In one aspect, the microwave energy source 400 changes frequency serially. That is, the microwave energy source 400 provides microwaves of a first frequency during a first time period, then switches to a second frequency during a second time period, and so on. Thus, multiple frequencies can coexist within the mold cavity. In another aspect, more than one microwave energy source may be used to deliver microwave energy of the same or different frequencies to the same mold cavity.

[0036] In one aspect, computing device 600 includes a processor communicatively coupled to a memory device, wherein the memory device is capable of storing instructions, and the processor is capable of processing the instructions stored in the memory. Computing device 600 is communicatively coupled to one or more sensor components 610, which may include one or more sensors (e.g., thermocouples, pressure sensors) for measuring parameters (such as temperature, pressure) within mold chamber 110 and / or other system components. In one aspect, computing device 600 is also communicatively coupled to a press. In these aspects, computing device 600 may also be used to control the opening and closing of the press and the amount of pressure applied to the mold. For example, computing device 600 may adjust the transmission of microwave energy from microwave energy source 400 and / or the amount of pressure applied by the press based on parameters such as the elapsed time during a manufacturing cycle and / or the temperature measured by sensor component 610. Although Figure 1 Figure 2 shows a single sensor component 610, but it should be understood that this is a schematic representation and that those skilled in the art will readily understand that one or more sensor components (each sensor component having one or more types of sensors) located within or adjacent to the system 10 may be used.

[0037] exist Figures 2A to 2D The diagram illustrates one aspect of practicing this concept, with a corresponding block diagram for the process 1000 used to foam a part. Figure 3 The diagram shows that in the first step 1010, system 10 is in an open and ready position (e.g., as shown in the diagram). Figure 2AAs shown in the figure, the mold cover 200 is inserted into the pressing surface 510 of the top pressure plate 500, and the mold base 100 is inserted into the bed 320 of the press base 300.

[0038] In step 1020 and as Figure 2B As illustrated, a desired amount of material to be foamed (load 700) is loaded into each of the mold chambers 110. In one aspect, the load 700 r-TPEE is in the form of granules or other discrete elements, such as beads or particles. In another aspect, the diameter of the granules can be from about 2 mm to 4 mm, or from about 1 mm to 10 mm. In other aspects, r-TPEE or other polymeric materials can be introduced into the mold chambers in other forms of discrete elements. For example, the material can be in the form of strands or blocks of material, which can be formed by extrusion or other suitable manufacturing methods. The ability to provide different forms of material can reduce costs (e.g., by reducing the amount of processing required to prepare the material) or provide greater control over the amount of material introduced into the mold chambers 110.

[0039] In one aspect, discrete elements of different shapes and sizes can also be used together. This can have the advantage of reducing the amount of unoccupied space in the mold by fitting smaller discrete elements into the gaps between larger discrete elements. In aspects using r-TPEE discrete elements (e.g., granules), the material to be foamed and the foaming agent are integrated into the granules (e.g., by soaking the granules in the foaming agent), which can provide the additional convenience of simplifying the steps of loading the material into the mold during the manufacturing process. In other aspects, the material to be foamed and the foaming agent can be added separately to the mold cavity 110, which can facilitate greater flexibility in allowing for tuning the material-to-foaming agent ratio for a specific application.

[0040] In one aspect, the mold is then slightly agitated to distribute the discrete elements more evenly within the mold cavity. Other methods for redistributing the discrete elements can also be used, such as, for example, agitating the granules within the cavity using mechanical equipment. In other aspects, foaming agents or other additives are omitted when they are not required to achieve the desired results.

[0041] A load 700 can be introduced into the mold cavity 110. In one aspect, the temperature of both the mold and the discrete component is at ambient temperature (approximately 5°C to 27°C). In another aspect, the mold is preheated while maintaining the discrete component at a lower temperature until the discrete component is introduced into the mold. In one aspect, the mold is preheated to approximately 170°C, and the discrete component is maintained at a temperature below 50°C until it is introduced into the mold.

[0042] In step 1030, the press is activated, and the top pressure plate 500 and the bottom pressure plate 310 come together to close the mold cover 200 onto the mold base 100, and optionally, continuous pressure is applied, such as... Figure 2C As shown in the diagram. Figure 2B In the example shown, the load 700, after being introduced into the mold cavity 110 but before the mold cover 200 is closed, occupies a larger volume in the mold cavity 110 than the volume after the mold cover 200 is closed on the mold base 100. Therefore, as Figure 2C As shown, when the mold chamber 110 is closed, the load 700 is compressed by the bottom 112 of the mold chamber, the sidewalls 114 of the mold chamber, and the upper mold plate 210. In other respects, the load 700 may occupy a volume equal to or smaller than the closed mold chamber 110. This flexibility allows the system 10 to form a wider variety of parts with different desired characteristics. For example, by being able to accommodate a load that would otherwise exceed the volume of the mold chamber 110, the system 10 can form parts with higher densities than achievable otherwise.

[0043] In step 1040, the computing device 600 activates the microwave energy source 400 to emit microwave energy of a desired frequency, intensity, and duration. The computing device 600 may adjust the frequency and intensity of the microwave energy based on input from the sensor component 610, or it may follow a preset procedure. In one aspect, microwave energy is applied to the load 700 until a first temperature is reached sufficient to activate the foaming agent and initiate foaming of the r-TPEE.

[0044] The microwave frequency to be used is selected so that heat can be distributed according to the desired profile. For example, the microwave frequency most readily absorbed by the load (e.g., r-TPEE) should not be used alone, as this would cause all energy to be trapped at the outer surface of the load at the point where the microwave energy enters the mold cavity 110 (e.g., along the bottom 112 of the mold cavity adjacent to window 324), resulting in overheating of that portion of the load 700. Instead, one or more frequencies should be selected such that the desired portion of the microwaves can penetrate into the internal portion of the load 700 within the mold cavity 110. Alternatively and / or additionally, frequencies transparent to the load 700 but absorbed by the material in the upper mold plate 210 can be used such that the top pressure plate is heated and heat is transferred via conduction to the portion of the mold cavity furthest from the point where the microwave energy enters adjacent to window 324. In this way, the system 10 can be tuned to optimize energy and heat transfer to the load as needed to achieve the desired result for the final foamed part. In other aspects, the configuration of the materials used to form the various components, along with the selection and configuration of the microwave energy introduced into the mold chamber 110, results in multiple partitions within the mold chamber 110, wherein the microwave energy applied to one partition has at least one different characteristic compared to the microwave energy applied to at least one other partition. This partitioning technique can be used in conjunction with other techniques described herein to further adjust the energy directed into different portions of the load 700 within the mold chamber 110.

[0045] Various materials can be used to form various parts of the assembly, depending on the desired dielectric properties. Each material has one or more dielectric properties that provide an indication of the degree / type of response that will be identified based on factors such as microwave energy. For example, a first material may substantially reflect microwave energy under a first set of factors, a second material may be substantially transparent to microwave energy under the same first set of factors, and a third material may convert microwave energy into heat energy using dielectric heating. In other words, a first material may reflect microwave energy of a certain frequency, intensity, and orientation; a second material may allow microwave energy with those same properties to pass through the material; and a third material may absorb the same microwave energy and thus become hot.

[0046] Materials that are effectively transparent to frequencies most readily absorbed by r-TPEE include alumina ceramics, fused silica or quartz, polytetrafluoroethylene (PTFE), and polyetheretherketone (PEEK). Materials that are effectively reflective to frequencies most readily absorbed by r-TPEE include silicon carbide ceramics. It should be understood that other properties, such as durability, response to temperature and pressure, cost, availability, and sustainability, should also be considered when selecting materials for system components. Furthermore, it may be desirable to use sheaths, coatings, or deflectors to shield certain parts or components of system 10 (e.g., computing device 600, power cables, other electronic devices) from microwave energy. Although not explicitly described herein, it should also be understood that those skilled in the art can combine known techniques (such as the use of waveguides, deflectors, distribution plates, conductive rods) with the teachings herein to further customize the microwave energy distribution within the microwave cavity.

[0047] The load 700 and the mold cavity 110 are brought to a peak temperature ranging from approximately 170°C over a period of approximately 30 seconds to approximately 300 seconds. Various variables are selected in all aspects to ensure that all parts of the load 700 are heated uniformly.

[0048] The desired skin thickness of the finished part can be achieved by selecting a maximum heating temperature within a temperature range. The skin thickness can be selected to alter the cushioning and feel, such as in molded insoles used in footwear. The skin thickness on the molded part can be at least about 60 micrometers. In various aspects, a peak temperature is selected to produce a skin thickness from about 50 micrometers to about 300 micrometers. The computing device 600 can then be used to instruct the microwave energy source 400 to stop supplying microwave energy to the system 10, and then cool the mold from about 170°C to about 20°C over a period from about 300 seconds to about 900 seconds.

[0049] In step 1050, during the heating and cooling process, the load 700 is maintained under pressure until sufficient time has elapsed for the foaming agent process to complete. Although not always necessary, pressure is typically required during this process to achieve the desired results. The level of this pressure depends on the material properties and the desired characteristics of the finished part, such as specific gravity, and other relevant factors. Figure 1 In the example shown in Figure 2, the pressure on the mold can come from a conventional press that applies pressure via a top pressure plate 500 and a bottom pressure plate 310.

[0050] In step 1060, and as Figure 2DAs illustrated, once the load 700 has been sufficiently cooled, the computing device 600 instructs the press to release pressure, and the top pressure plate 500 and the bottom pressure plate 310 retract relative to each other, opening the mold cover 200 away from the mold base 100. Once the pressure is released, the load 700 will undergo a foaming process to form a foamed part 710. In one aspect of using r-TPEE, the mold can be opened once the load has cooled to approximately 25°C or lower.

[0051] In one aspect, the foamed part 710 will want to expand to a volume larger than that of the mold cavity 110, which may cause the foamed part 710 to spontaneously pop out of the mold cavity 110 when the mold cover 200 is removed.

[0052] In an alternative approach, the load 700 may be introduced into the mold cavity 110 in the form of a preform 720, rather than as granules or other discrete components, which is formed from granules in an initial step. For example, using a preform 720 may be advantageous if it is desired to concentrate the added material more precisely in one or more areas of the foamed part 710. Figure 4A As shown, the preform 720 can have a wedge shape, with the thicker portion of the wedge at the heel end 724. Other more complex preform shapes are also possible. For example, Figure 4B The preform is thicker in both the toe tip 722 and the heel tip 724 than in the middle 726. This allows for greater density of the foamed part 710 in those areas, even if the corresponding portion of the finished part (e.g., the toe area) is thinner than the middle. The preform can be used regardless of whether its volume in any area is less than, equal to, or greater than the corresponding volume of the mold cavity 110, as long as the mold can still be completely closed.

[0053] In such Figure 5In one aspect of the illustrated preforming process 1100, in a first step 1110, a preforming load, which may be in the form of granules or other discrete elements, is introduced into a preforming mold chamber. In a second step 1120, the preforming load is then heated until it reaches a temperature at which the granules begin to melt and fuse together, but below the temperature at which the foaming agent can be activated. Heating of the preforming load during the preforming process can use conventional heat sources (e.g., ovens or hot plates), microwaves, or a combination of both. For example, if the shape of the preform is not complex and many preforming molds can be heated in the same oven, an oven may be the best option. Alternatively, if the shape of the preform itself is complex and more discrete heating of the individual parts is desired, microwave heating may be preferred. In a third step 1130, the preforming load is then cooled and removed from the preforming mold, subsequently used in place of loose granules in the foaming manufacturing process of the present invention as described above.

[0054] Within the scope of this invention, many variations of various aspects of system 10 are possible. For example, Figure 6 The illustration shows a system 10 with a separate microwave energy source 400 for each of the two mold chambers 110. The microwave energy source 400 is integrated within the press base 300 and adjacent to the window 324, thereby eliminating the need for conduits and / or transmission lines for propagating microwave energy from the microwave energy source 400 to the mold chamber 110. Other methods of applying, maintaining, and releasing pressure, such as via vacuum sealing, can also be used.

[0055] Other changes in the system may include the direction relative to the pressure applied by the press, or the directional axis of the microwave energy initially propagated into the mold, altering the orientation of the mold chamber 110.

[0056] The following clauses represent exemplary aspects of the concepts envisioned herein. Any of the following clauses may be combined in a dependent manner to depend on one or more other clauses. Furthermore, any combination of dependent clauses (clauses that explicitly depend on preceding clauses) may be combined while remaining within the scope of the aspects envisioned herein. The following clauses are illustrative and not restrictive.

[0057] Clause 1. A system for foaming components of footwear articles, the system comprising: a solid-state microwave energy source including a frequency synthesizer; a footwear component mold having a mold chamber configured to form the component from a polymeric material reactive to microwave energy from the solid-state microwave energy source, the footwear component mold including a first material having a first value of a first microwave dielectric property; and a press capable of compressing one or more portions of the footwear component mold.

[0058] Clause 2. The system according to Clause 1, wherein the solid-state microwave energy source includes a transmitter capable of changing the electromagnetic wavelength, field configuration or intensity on the transmitter.

[0059] Clause 3. The system according to Clause 1 or 2, wherein the solid-state microwave energy source is coupled to the footwear component mold via a microwave energy conduit.

[0060] Clause 4. The system according to any one of Clauses 1 to 3, wherein the solid-state microwave energy source generates electromagnetic radiation with a frequency between about 2.4 GHz and about 2.5 GHz.

[0061] Clause 5. The system according to any one of Clauses 1 to 4, wherein the footwear component mold comprises a second material having a second value of the first microwave dielectric property.

[0062] Clause 6. A system according to any one of Clauses 1 to 5, wherein the first microwave dielectric property is a relative permittivity, and wherein the first value is less than the second value for a first frequency of microwave energy from the solid-state microwave energy source.

[0063] Clause 7. A system according to any one of Clauses 1 to 6, wherein the first value of the first microwave dielectric property is different from the second value of the first microwave dielectric property of the polymer material.

[0064] Clause 8. The system according to any one of Clauses 1 to 7, wherein the polymer material is a thermoplastic polyester elastomer.

[0065] Clause 9. The system according to any one of Clauses 1 to 8 further includes a computing system logically coupled to the solid-state microwave energy source and the press, wherein the computing system is configured to coordinate the application of microwave energy from the solid-state microwave energy source and the application of force by the press to the footwear component mold.

[0066] Clause 10. A method of manufacturing a foam component for footwear articles, the method comprising: introducing a polymer material into a mold chamber of a footwear component mold; closing the footwear component mold to a closed state having a substantially fixed mold volume; applying microwave energy across multiple frequencies to the polymer material in the footwear component mold until the polymer material begins to undergo a foaming process; after applying the microwave energy, holding the footwear component mold in the closed state for a first time, such that the foam component is formed; and after the first time, opening the footwear component mold from the closed state.

[0067] Clause 11. The method according to Clause 10 further includes forming a preform from the polymer material, wherein introducing the polymer material into the mold cavity includes introducing the preform into the mold cavity.

[0068] Clause 12. The method according to Clause 11, wherein the preform has a volume greater than the volume of the mold cavity in the closed state before the application of microwave energy.

[0069] Clause 13. The method according to Clause 11, wherein the preform has a volume smaller than the volume of the mold cavity in the closed state before the application of microwave energy.

[0070] Clause 14. The method according to any one of Clauses 11 to 13, wherein forming the preform comprises: introducing the polymer material into a preforming mold; applying heat to the polymer material in the preforming mold to form the preform; and removing the preform from the preforming mold.

[0071] Clause 15. The method according to any one of Clauses 10 to 14, wherein the footwear component mold comprises a plurality of partitions, and the microwave energy applied to one partition has at least one different characteristic compared to the microwave energy applied to at least one other partition.

[0072] Clause 16. The method according to any one of Clauses 10 to 15, wherein the polymer material is introduced as a plurality of discrete elements.

[0073] Clause 17. The method according to Clause 16, wherein the plurality of discrete elements are in a granular configuration.

[0074] Clause 18. A method of manufacturing a foam component for footwear articles, the method comprising: introducing a polymer material comprising a thermoplastic polyester elastomer into a molding chamber of a preform mold; heating the polymer material to a first temperature; after heating the polymer material to the first temperature, retaining the polymer material in the preform mold until the polymer material is below the first temperature; removing the polymer material from the preform mold, wherein the polymer material forms a preform having a first volume; inserting the preform into a molding chamber of a footwear component mold; closing the footwear component mold to a closed state having a second volume; heating the preform to a second temperature by applying microwave energy from a solid-state microwave energy source, the solid-state microwave energy source comprising a frequency synthesizer that changes the frequency of emitted electromagnetic radiation, wherein the second temperature is higher than the first temperature; after applying the microwave energy, retaining the footwear component mold in the closed state for a first time until the polymer material of the preform cools to a third temperature; and after the first time, opening the footwear component mold from the closed state.

[0075] Clause 19. The method according to Clause 18 further includes, after heating the preform and before opening the footwear component mold from the closed state, decoupling the footwear component mold from the solid-state microwave energy source and transferring the footwear component mold relative to the solid-state microwave energy source.

[0076] Clause 20. The method according to Clause 19 further includes, after decoupling the footwear component mold from the solid-state microwave energy source and transferring the footwear component mold relative to the solid-state microwave energy source: inserting a second preform into a molding chamber of the second footwear component mold; closing the second footwear component mold to a closed state; positioning the solid-state microwave energy source relative to the second footwear component mold; and applying microwave energy from the solid-state microwave energy source to the second preform within the second footwear component mold.

[0077] The subject matter of this invention has been specifically described herein to satisfy legal requirements. However, this description itself is not intended to limit the scope of this disclosure. Rather, the inventors envision that the claimed or disclosed subject matter may also be embodied in other ways in combination with other current or future techniques to include different steps or combinations of steps similar to those described in this document. Furthermore, although the terms “step” and / or “box” may be used herein to refer to different elements of the method employed, these terms should not be construed as implying any particular order among or between the various steps disclosed herein, unless and only if the order of individual steps is explicitly stated.

[0078] Various aspects of this disclosure have been described in an illustrative rather than restrictive manner. Alternative aspects will become apparent to those skilled in the art without departing from its scope. Those skilled in the art can develop alternative means to implement the above-described improvements without departing from the scope of this disclosure.

Claims

1. A system for foaming components of footwear articles, the system comprising: A solid-state microwave energy source, wherein the solid-state microwave energy source includes a frequency synthesizer; A footwear component mold having a mold chamber configured to form the component from a polymer material reactive to microwave energy from a solid-state microwave energy source, the footwear component mold including a first material having a first value of a first microwave dielectric property; and a press capable of compressing one or more portions of the footwear component mold.

2. The system of claim 1, wherein the solid-state microwave energy source includes a transmitter capable of changing the electromagnetic wavelength, field configuration, or intensity on the transmitter.

3. The system according to claim 1, wherein the solid-state microwave energy source is coupled to the shoe component mold via a microwave energy conduit.

4. The system of claim 1, wherein the solid-state microwave energy source generates electromagnetic radiation with a frequency between about 2.4 GHz and about 2.5 GHz.

5. The system of claim 1, wherein the footwear component mold comprises a second material having a second value of the first microwave dielectric property.

6. The system of claim 5, wherein the first microwave dielectric property is a relative permittivity, and wherein the first value is less than the second value for a first frequency of microwave energy from the solid-state microwave energy source.

7. The system of claim 1, wherein the first value of the first microwave dielectric property is different from the second value of the first microwave dielectric property of the polymer material.

8. The system of claim 1, wherein the polymer material is a thermoplastic polyester elastomer.

9. The system of claim 1, further comprising a computing system logically coupled to the solid-state microwave energy source and the press, wherein the computing system is configured to coordinate the application of microwave energy from the solid-state microwave energy source and the application of force by the press to the shoe component mold.

10. A method for manufacturing a foam component for footwear articles, the method comprising: Polymer materials are introduced into the mold cavity of footwear component molds; The footwear component mold is closed to a closed state having a substantially fixed mold volume; Microwave energy across multiple frequencies is applied to the polymer material in the footwear component mold until the polymer material begins to undergo a foaming process; after the microwave energy is applied, the footwear component mold is held in the closed state for a first time, allowing the foam component to form; and after the first time, the footwear component mold is opened from the closed state.

11. The method of claim 10, further comprising forming a preform from the polymer material, wherein introducing the polymer material into the mold cavity includes introducing the preform into the mold cavity.

12. The method of claim 11, wherein the preform has a volume greater than the volume of the mold cavity in the closed state before the microwave energy is applied.

13. The method of claim 11, wherein the preform has a volume smaller than the volume of the mold cavity in the closed state before the microwave energy is applied.

14. The method of claim 11, wherein forming the preform comprises: The polymer material is introduced into a preforming mold; heat is applied to the polymer material in the preforming mold to form the preform; And remove the preform from the preform mold.

15. The method of claim 10, wherein the footwear component mold comprises a plurality of partitions, and the microwave energy applied to one partition has at least one different characteristic compared to the microwave energy applied to at least one other partition.

16. The method of claim 10, wherein the polymer material is introduced as a plurality of discrete elements.

17. The method of claim 16, wherein the plurality of discrete elements are in a granular configuration.

18. A method for manufacturing a foam component for footwear articles, the method comprising: A polymer material, including a thermoplastic polyester elastomer, is introduced into the molding cavity of a preform mold; The polymer material is heated to a first temperature; after heating the polymer material to the first temperature, the polymer material is held in the preform mold until the polymer material is below the first temperature; the polymer material is removed from the preform mold, wherein the polymer material forms a preform having a first volume; the preform is inserted into a molding chamber of a footwear component mold; the footwear component mold is closed to a closed state having a second volume; the preform is heated to a second temperature by applying microwave energy from a solid-state microwave energy source, the solid-state microwave energy source including a frequency synthesizer that changes the frequency of emitted electromagnetic radiation, wherein the second temperature is higher than the first temperature; after applying the microwave energy, the footwear component mold is held in the closed state for a first time until the polymer material of the preform cools to a third temperature; and after the first time, the footwear component mold is opened from the closed state.

19. The method of claim 18, further comprising, after heating the preform and before opening the footwear component mold from the closed state, decoupling the footwear component mold from the solid-state microwave energy source and transferring the footwear component mold relative to the solid-state microwave energy source.

20. The method of claim 19, further comprising, after decoupling the footwear component mold from the solid-state microwave energy source and transferring the footwear component mold relative to the solid-state microwave energy source: inserting a second preform into a molding chamber of a second footwear component mold; closing the second footwear component mold to a closed state; positioning the solid-state microwave energy source relative to the second footwear component mold; and applying microwave energy from the solid-state microwave energy source to the second preform within the second footwear component mold.

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