SHOE, SHOE PRODUCTION SYSTEMS AND METHOD FOR PRODUCING A SHOE

A shoe, a shoe production system and a method for producing a shoe including the steps: a. providing an upper assembly (2), wherein the upper assembly includes an upper (3) being mounted on a carrier (4), wherein the upper (3) includes a bottom section (5) being made from a thermoplastic polymer upper material; b. providing a sole molding unit (6), wherein the sole molding unit defines a cavity; c. inserting the upper assembly (2) at least partially into the cavity; introducing a midsole polymer composition comprising a molten thermoplastic polymer midsole material which has a melting temperature being equal or higher than the melting temperature of the thermoplastic polymer upper material into the cavity and foaming the molten thermoplastic polymer midsole material inside the cavity to provide a foamed midsole and to establish a material-bonded connection between the upper (3) and the foamed midsole (8).

CROSS-REFERENCE TO RELATED APPLICATIONS

Swiss Patent Application Nos. CH 000937/2023, filed 31 Aug. 2023, the priority document, corresponding to this invention, to which a foreign priority benefit is claimed under Title 35, United States Code, Section 119, and its entire teachings are incorporated, by reference, into this specification.

FIELD OF THE DISCLOSURE

The present invention lies in the field of shoe manufacturing technology and relates in particular to a method for producing a shoe, a shoe and a shoe production system.

BACKGROUND OF THE DISCLOSURE

Sports shoes, in particular running shoes, consist typically of a sole and an upper. The upper is usually a textile, such as a knit or a woven fabric. Commonly, the upper is produced as a flat textile material, e.g. a flat knit or a flat woven fabric. Such flat textile materials are sometimes referred to as 2D structures. The flat textile material is typically produced with a knitting or weaving machine and is then mounted on a last. Alternatively, circular knits are commonly used. The sole of common running shoes comprises a midsole, which is typically foamed to effect cushioning, and a wear resistant outsole to protect the midsole. Furthermore, the sole may comprise an insole which is in contact with the wearer's foot. In the prior art, the sole and often even the midsole and the outsole, and the upper are produced separately and with different machines. Depending on the production method it may even be necessary to use multiple machines only for sole production. During production, the lasted upper is connected to the sole typically by using an adhesive to establish a material-bonding connection between upper and sole. In addition, stitching can be used to support the connection between upper and sole. For such a process, human workforce is required and the produced intermediate parts have to be transported from one machine to another. For example, midsole foam molding is typically done by inserting a granulated polymer manually into a mold, closing the mold and foaming, manually removing the midsole and manually removing offcut material. Then the produced soles are taken to another workstation where they are adhered to a lasted upper. This separation of steps and relatively large demand of human workforce makes the production process laborious and inefficient.

Classic foam molding further suffers from various drawbacks. For example, the soles often expand after deforming and thus an accurate size control is difficult. Furthermore, the molds must be heated which increases the energy consumption of the process. From an environmental point of view, traditional foam molding emits a large amount of volatile organic compounds (VOCs).

SUMMARY OF THE DISCLOSURE

It is the general object of the present invention to advance the state of the art in shoes and shoe manufacturing and preferably to overcome the disadvantages of the prior art fully or partly. In advantageous embodiments, a method and a shoe production system is provided which is more efficient and/or reduces the required human workforce and/or reduces the demand of resources and/or waste, and/or is less harmful to the environment. In further advantageous embodiments, a shoe is provided which has been produced by such a method or with such a shoe production system. Such a shoe has a smaller ecological footprint and is cheaper in production costs.

The general object is achieved by the subject matter of the independent claims. Further advantageous embodiments follow from the dependent claims and the overall disclosure.

A first aspect of the invention relates to a method for producing a shoe. The method comprises steps a. to d. as discussed further below. It should be noted however, that as used herein, designations of steps such as a., b., or d. are not to be understood as defining a specific order of steps, but serve to unambiguously identify a specific step. Therefore, while it may be the case in some embodiments that step a. is followed by step b., which is followed by step c., which is followed by step d., it may well be possible in some other embodiments that for example step b. is performed before and/or during step a.

Step a. comprises: providing an upper assembly. The upper assembly comprises an upper which is mounted on a carrier. The upper comprises a bottom section which is made from a thermoplastic polymer upper material. It should be noted that it is also possible that the rest of the upper, or another portion thereof may be made from the same thermoplastic polymer upper material or from a different material. Typically, however, at least the bottom section is made from the thermoplastic polymer upper material. Preferably, the majority of the upper (i.e. more than 50 wt. %) or even all of the upper may be made from the same thermoplastic polymer upper material.

Step b. comprises: providing a sole molding unit which defines a cavity. The cavity is typically configured for producing a sole of a shoe, particularly a midsole. In preferred embodiments, the cavity is delimited by one or more sidewalls which circumferentially surround the cavity and a bottom wall which delimits the bottom of the cavity. In some embodiments, the cavity is however open at the top portion, i.e. the portion being oppositely arranged to the bottom portion. This opening and the upper assembly may preferably be configured such that upon inserting the upper assembly at least partially into the cavity, the top portion of the cavity is closed by the upper assembly, in particular hermetically closed.

Step c. comprises: at least partially, or fully, inserting the upper assembly provided in step a. into the cavity defined by the sole molding unit. Typically, step c. is performed such that at least a part, or all, of the bottom section of the upper is inserted into the cavity of the sole molding unit. By inserting the upper assembly at least partially, or fully, into the cavity a sole molding compartment is preferably formed. This sole molding compartment may be delimited, in particular only delimited, by the sole molding unit and the inserted upper assembly. It is understood that the sole molding compartment is configured such that by introducing and foaming a midsole polymer composition, a midsole can be formed therein. The sole molding compartment may typically be part of or arranged inside the cavity.

Step d. comprises: introducing, in particular injecting, a midsole polymer composition comprising a molten thermoplastic polymer midsole material into the cavity and foaming the molten thermoplastic polymer midsole material inside the cavity. By introducing and foaming the molten thermoplastic polymer midsole material, a foamed midsole is provided and a material-bonded connection, in particular a direct material-bonded connection, more particular a fused connection, between the upper, in particular the bottom section of the upper, and the foamed midsole is established. The molten thermoplastic polymer midsole material has a melting temperature which is equal to or higher than the melting temperature of the thermoplastic polymer upper material. This has the effect that upon introduction of the molten thermoplastic polymer midsole material into the cavity and its foaming in the cavity, the molten thermoplastic polymer midsole material contacts and melts the bottom section of the upper being inserted into the cavity. In other words, upon introducing, particularly injecting, the midsole polymer composition into the cavity, the thermoplastic polymer midsole material contacts and melts at least parts of or the whole bottom section of the upper. Thus, a direct material-bonded connection between upper and midsole is formed which is free of any additional external adhesive, but may be considered as a fused connection between upper and foamed midsole. This allows not only to avoid additional process steps or materials, but it also establishes a much firmer and more reliable connection between upper and midsole. The midsole polymer composition may for example be introduced into the sole molding compartment being delimited by the upper assembly and the sole molding unit. In such embodiments, the shape of the sole molding compartment defines the shape of the foamed midsole. Typically, the molten thermoplastic polymer upper material is introduced into the cavity and directly foamed therein.

As used herein, it is understood that the term “melting temperature” may for example refer to a specific melting point, e.g. in case a single or pure material is used as thermoplastic polymer upper material or thermoplastic polymer midsole material, or can also relate to a melting temperature range, for example when a mixture of different base materials is used as thermoplastic polymer upper material or thermoplastic polymer midsole material.

The bottom section of the upper is typically arranged at the bottom of the carrier and may preferably be the section forming the peripheral lower delimitation of the upper in the produced shoe at the transition to the foamed midsole. The bottom section may typically circumferentially surround the foot of the wearer. The bottom section may also be the region of the upper being in the worn state arranged underneath the foot of the wearer, respectively during production between the carrier and the foamed midsole. For example, the bottom section may extend up to 3 cm in the vertical direction of the upper.

As used herein, the term “thermoplastic polymer upper material” is used to indicate that this material is the thermoplastic polymer material which is present in the upper of the formed shoe. Accordingly, the term “thermoplastic polymer midsole material” is used to indicate that this material is the thermoplastic polymer material which is present in the midsole of the formed shoe. The thermoplastic polymer upper material and the thermoplastic polymer midsole material may in some embodiments be the same material or they may also be different materials. Accordingly, the term “thermoplastic polymer outsole material” is used to indicate that this material is the thermoplastic polymer material which is present in the outsole of the formed shoe. The thermoplastic polymer upper material, the thermoplastic polymer midsole material and the thermoplastic polymer outsole material may in some embodiments be the same material or they may also be different materials.

As used herein, a direct material-bonded connection of two elements means that they are connected with each other without an additional adhesive. For example, a direct material-bonded connection may be a fused connection in which the two elements are fused to each other.

It is generally understood herein that the term “comprising” is interpreted as meaning that it includes those features following this term, but that it does not exclude the presence of other features, as long as they do not render the claim unworkable. On the other hand, if the wording “consist of” is used, then no further features are present in the corresponding apart from the ones following said wording.

The abbreviation “SCIF” as used herein is an abbreviation for supercritical injection foaming.

Generally, the molten thermoplastic polymer midsole material can be provided by melting a thermoplastic polymer midsole material, for example in a melting unit or in an extruder, e.g. inside a screw and barrel extruder. For example, the thermoplastic polymer midsole material can be provided as a granulate which can be melted.

In some embodiments, the carrier is removed from the upper after step d.

The carrier may preferably be a last, e.g. a shoe last, or at least a portion of a last. Such a last may for example be a standardized last for a particular shoe size or it may also be a customized last, e.g. a last which has been produced based on a preceding scan of the foot of a wearer. A last may be provided by molding, additive manufacturing or by subtractive manufacturing, such as milling.

In some embodiments, the foamed midsole is cooled after step d.. This may be done either in the cavity or after removal of the foamed midsole and the thereto material-bonded, in particular fused, upper from the cavity.

It is understood that the sole molding unit typically comprises, respectively defines, one or more injection openings being configured for introducing the midsole polymer composition into the cavity, respectively into the sole molding compartment.

In some embodiments, step d. is performed by, respectively comprises or consists of, supercritical injection foaming (SCIF). SCIF has the advantage that the volatile organic compound emissions are significantly reduced as compared to conventional foaming. Furthermore, in contrast to other foaming techniques, it is not necessary to use nucleating agents and/or to coat the mold with chemical agents for facilitating demolding. Therefore, SCIF is more environmentally friendly and easier to perform.

SCIF as used in some embodiments of the invention, may comprise the injection of the midsole polymer composition into the cavity, preferably by an injection unit, for example an extruder, such as a screw and barrel extruder. The midsole polymer composition may in such embodiments comprise, or consist of, a molten thermoplastic polymer midsole material and a supercritical fluid, e.g. N2or CO2.

The midsole polymer composition used in SCIF in some embodiments of the invention may be injected in step d. into the cavity as a single phase, i.e. as a homogenous single phase.

In some embodiments using SCIF, the midsole polymer composition is injected into the cavity, wherein the pressure in the cavity is lower than the pressure in the injection unit, in particular in the barrel of the extruder. This has the effect that foaming occurs directly upon injection and ceases when the cavity, in particular the sole molding compartment, is filled at the maximum filling capacity under the applied conditions. These conditions may in particular comprise the pressure in the cavity and the injection unit. Due to the lower pressure in the cavity and the SCIF method in general, the foamed midsole does not expand after deforming. Thus, the cavity dictates directly and accurately the size of the foamed midsole. For example, the pressure in the cavity may be between 800 bar to 1200 bar, in particular 900 bar to 1000 bar, lower than the pressure in the injection unit.

In some embodiments, the cavity is pressurized to a first cavity pressure above atmospheric pressure, prior and/or during injection of the midsole polymer composition. The first cavity pressure may be provided as a gas counter pressure to the cavity.

In some embodiments, foaming the molten thermoplastic polymer midsole material can generally be achieved by decreasing the first cavity pressure to a second cavity pressure being lower than the first cavity pressure. Thereby, formation of gas bubbles of the physical blowing agent occurs which effects foaming of the molten thermoplastic polymer midsole material. The second cavity pressure may in some embodiments be atmospheric pressure.

Decreasing the pressure in the cavity from the first cavity pressure to the second cavity pressure may be achieved by venting of the cavity, by a continuous pressure decrease at a predefined rate (e.g. by a valve or by decreasing a counter gas pressure being applied to the cavity) or by a stepwise decrease. The predefined rate may for example be between 0.5 bar/s to 50 bar/s, in particular 1 bar/s to 20 bar/s, more particular 1 bar/s to 10 bar/s.

In some embodiments, the pressure in the cavity, i.e. the first cavity pressure, may be between 10 bar to 200 bar, in particular 40 bar to 100 bar. In some embodiments, the pressure in the injection unit, e.g. in the barrel of the extruder, may be between 900 bar to 1200 bar, in particular 1000 to 1100 bar.

In some embodiments, the polymer composition in step d. comprises a physical blowing agent. Typically, the physical blowing agent may be mixed together with the thermoplastic polymer midsole material prior to introducing the midsole polymer composition into the cavity. It may in certain embodiments be for example possible to mix the physical blowing agent with the thermoplastic polymer midsole material in the injection unit, e.g. in the barrel of the screw and barrel extruder. It may also be possible to infuse the physical blowing agent into the thermoplastic polymer midsole material prior to or during melting of the thermoplastic polymer midsole material.

The blowing agent may preferably be a physical blowing agent, such as N2or CO2. As understood by the skilled person, a physical blowing agent is a blowing agent which can induce foaming upon changing the physical state of the blowing agent or the physical conditions, such as pressure and/or temperature to induce foaming. In contrast, a chemical blowing agent is a blowing agent which releases a gas upon a chemical reaction, for example the release of N2from a diazo moiety. Although it is in some embodiments possible to employ a chemical blowing agent, physical blowing agents are generally preferred. In particular embodiments, the physical blowing agent is in a supercritical state, e.g. in the injection unit, respectively in the screw and barrel extruder. This may for example be the case in embodiments in which step d. is performed by SCIF.

In some embodiments, the bottom section of the upper is during step d. at least partially or completely melted. In certain embodiments, the bottom section is at least partially or completely melted by the thermal energy of the molten thermoplastic polymer midsole material. This means, the thermal energy provided by the molten thermoplastic polymer midsole material is transferred to the bottom section upper upon which the latter melts. In particular embodiments, the bottom section is at least partially or completely melted only by the thermal energy of the molten thermoplastic polymer midsole material. This means, no additional thermal energy must be provided.

In certain embodiments, the bottom section of the upper is covered prior to step d. and in particular prior to step c., by a thermoplastic film being preferably made from the thermoplastic polymer midsole material.

In some embodiments, the sole molding unit is free of heating and/or cooling elements. This not only makes the sole molding unit less complex, but also improves production efficiency and the ecological footprint of the production process. In some embodiments, the sole molding unit is not heated or cooled during step d. and/or any of steps a. to d..

In some embodiments the upper assembly is inserted in step c. in such a manner into the sole molding unit that a closed sole molding compartment is formed which is defined by the sole molding unit and the upper assembly, in particular only by the sole molding unit and the upper assembly. It is understood that also in such embodiments, the sole molding unit may preferably comprise, respectively define, one or more injection inlets for introducing the midsole polymer composition into cavity, respectively into the sole molding compartment. The sole molding compartment formed is typically arranged within the cavity of the sole molding unit. Upon insertion of the upper assembly into the cavity, the upper, in particular the bottom section of the upper is inserted into the cavity of the sole molding unit.

In particular embodiments, the upper assembly is inserted in step c. in such a manner into the sole molding unit that a closed and sealed sole molding compartment is formed being defined by the sole molding unit and the upper assembly. In certain embodiments, the upper assembly is configured such that it forms a sealing element, such as a sealing lip which provides for a fluid tight connection between the sole molding unit and the upper assembly. The sealing element may for example be a part of the upper, particularly an integral part of the upper. Alternatively, the sealing element may be releasably connected to the upper and/or the carrier. As understood by the skilled person, a releasable connection as used herein is a connection which can be released without destroying the structural integrity of the connected elements. Optionally, a releasable connection can be released and reconnected multiple times. Thus, a form-locking and/or force locking connection may be considered a releasable connection, while a material-bonding connection is not.

In some embodiments, an outsole polymer composition, which comprises a molten polymer outsole material, in particular a molten thermoplastic outsole material, is introduced into the cavity after step d. to provide an outsole being material-bonded to the foamed midsole. Preferably, the outsole provided is directly material-bonded to the foamed midsole. As used herein, a direct material-bonded connection of two elements means that they are connected with each other without an additional adhesive. For example, a direct material-bonded connection may be a fused connection in which the two elements are fused to each other. The outsole polymer material may in some embodiments be the same material than the thermoplastic polymer upper material and/or than the molten thermoplastic polymer midsole material. Providing an outsole in such a manner allows to generate a foamed midsole being material-bonded to the upper and an outsole being material-bonded to the foamed midsole in a single unit without having to move the parts and intermediate products between different locations.

In some embodiments, the upper assembly is held by a movable robotic arm, in particular during step c. and d. and/or during step a.. For example, step c. i.e. the insertion of the upper assembly into the cavity may be performed by the robotic arm. The robotic arm may for example be a cantilever. Preferably, the robotic arm is movable in the 3-dimensional space. The robotic arm may for example comprise one or more beams being connected with each other via joints thereby allowing the movement of the arm in the 3-dimensional space. In some embodiments, the robotic arm, particularly its movement in the 3-dimensional space, may be controlled by a control unit. The control unit may preferably comprise a circuit, e.g. a microprocessor. For example, a movement path may be stored in a memory unit which can be accessed by the control unit to move the robotic arm along this movement path. For step c. it may be possible that the robotic arm either holds the carrier of the upper assembly already before step c. or that the robotic arm first grips the carrier and then inserts it upper assembly at least partially into the cavity of the sole molding unit.

In some embodiments, the robotic arm can be used to remove the carrier after step d. to separate the produced shoe from the carrier.

In certain embodiments, the robotic arm may hold the upper assembly by holding the carrier. In particular, the robotic arm holds the upper assembly in a form-locking or force-locking manner. For example, the robotic arm and the carrier may be connected by a snap fit engagement or the robotic arms may comprise gripping elements with which it can grip the carrier of the upper assembly.

In some embodiments, the upper assembly is provided in step a. by producing the upper on the carrier. This may be done by applying the thermoplastic molten upper material which is comprised in at least the bottom section of the upper or from which the upper is made, onto the carrier by means of a nozzle in the form of at least one filament, particularly at least one continuous filament, to provide the upper being mounted on the carrier. In particular, the nozzle only applies one filament at the time onto the carrier. That is, if more than one filament is applied, the filaments are sequentially applied to the carrier.

In some embodiments, the at least one filament is applied in such a manner on the carrier that it forms a plurality of crossings with itself on the carrier and/or that it forms a plurality of loops on the carrier. In preferred embodiments, a material-bonded connection is established at at least one crossing between different sections of the at least one filament. For example, the filament may form a loop and thereby one section of the filament is laid on another section of the same filament. In typical embodiments, the filament is applied such that it is still in the molten state, and/or in a softened state as compared to the aggregate state of the thermoplastic polymer upper material after being stored for 24 h at 23° C. and at atmospheric pressure. Thus, when two sections of the same filament form a crossing, a direct material-bonding connection is formed at the crossing. This significantly improves the durability of the provided upper.

A loop as used herein is a section formed by the filament which starts at a crossing, extends along the thermoplastic filament and arrives again at the same crossing. For example a loop may have a round shape, in particular a circular or oval shape. It may also be possible that the loops have an irregular shape.

In some embodiments, the nozzle comprises a material outlet and a plurality of air openings being circumferentially arranged around the material outlet. In such embodiments, pressurized air is applied in such a manner onto the molten polymer upper material which exits the material outlet of the nozzle that it is applied on or to the carrier as a helical filament. This does not mean that the helical filament must necessarily extend completely between the nozzle and the carrier during application, although this may be the case in some embodiments. In some embodiments, the pressurized air being applied onto the molten polymer upper material has a temperature of more than 150° C., in particular of more than 200° C. In some embodiments, the pressurized air being applied onto the molten polymer upper material has a temperature at most 600° C., in particular of at most 400° C. In some embodiments, the pressurized air being applied onto the molten polymer upper material has a temperature of between 150° C. to 600° C., in particular of 200° C. to 400° C.

In certain embodiments, the nozzle is part of a depositing unit as described herein. It is in certain embodiments possible that the depositing unit, or at least the nozzle, is movable in the 3-dimensional space. The depositing unit may for example in some embodiments be controlled by a depositing unit control unit. The depositing unit control unit may preferably comprise a circuit, e.g. a microprocessor. For example, a movement path may be stored in a depositing memory unit which can be accessed by the depositing control unit to move the nozzle along this movement path. Furthermore, the pressure of pressurized air being applied onto the exiting molten thermoplastic polymer upper material can be controlled by the control unit. It may also be possible that the depositing rate or pressure of the molten thermoplastic polymer upper material on or to the carrier may be controlled by the control unit.

Embodiments in which a molten thermoplastic polymer upper material is applied onto the carrier by a nozzle as at least one filament are preferred, since the whole process from producing the upper on the carrier, generating the foamed midsole and connecting it to the upper in a direct material-bonding manner, e.g. by fusing upper and the foamed midsole together, and optionally also producing an connecting an outsole to the foamed midsole can be done at a single location and/or fully automatic. Thus, in preferred embodiments, the method for producing a shoe is fully automatic.

In some embodiments, during applying the thermoplastic polymer upper material onto the carrier, the upper assembly and the nozzle are moved relative to each other in the 3-dimensional space by moving the robotic arm holding the carrier and/or by moving the depositing unit, respectively the nozzle.

In some embodiments, the thermoplastic polymer midsole material is selected from polyolefins, such as polyethylene or polypropylene, polyester, such as PET or PBT, polyamide, polyether block amide (PEBAX), polyurethane, ethylene vinyl acetate (EVA) or mixtures thereof.

In some embodiments, the thermoplastic polymer upper material is selected from polyolefins, such as polyethylene or polypropylene, polyester, such as PET or PBT, polyamide, polyether block amide (PEBAX), polyurethane, ethylene vinyl acetate (EVA) or mixtures thereof.

In some embodiments, the polymer outsole material, in particular the thermoplastic polymer outsole material is selected from rubber, polyolefins, such as polyethylene or polypropylene, polyester, such as PET or PBT, polyamide, polyether block amide (PEBAX), polyurethane, ethylene vinyl acetate (EVA) or mixtures thereof.

The method according to any of the embodiments of the first aspect of the invention may in particular be performed by a shoe production system according to any of the embodiments described herein, in particular with respect to the third aspect of the invention.

According to a second aspect of the invention, a shoe is provided. In particular, the shoe has been obtained by the method according to any of the embodiments described with respect to the first aspect of the invention. The shoe comprises an upper, which comprises, or consists of, a thermoplastic polymer upper material. Furthermore, the shoe comprises a foamed midsole, which comprises a thermoplastic polymer midsole material. The upper and the foamed midsole are directly material-bonded to each other. In particular, the upper and the foamed midsole are fused to each other. Preferably, the connection of upper and foamed midsole is devoid of an external adhesive.

In some embodiments, the shoe further comprises an intermediate material zone. In the intermediate material zone, upper and foamed midsole are directly material-bonded to each other, in particular fused to each other.

Preferably, the intermediate material zone comprises the thermoplastic polymer upper material and the thermoplastic polymer midsole material. While it may in some embodiments be the case that the thermoplastic polymer upper material and the thermoplastic polymer midsole material are different materials, they may in some embodiments also be the same.

The intermediate material zone has preferably a certain thickness in the vertical direction. The vertical direction extends from the midsole towards the upper, or in the operative state from the midsole or the ground to the foot of the wearer. The thickness of the intermediate material zone in which both thermoplastic polymer upper material and thermoplastic polymer midsole material are present and/or in which upper and foamed midsole form a material-bonded connection, particularly are fused together, may be between 0.01 mm to 1 mm, in particular between 0.05 mm to 0.5 mm. In certain embodiments, the thermoplastic polymer midsole material and the thermoplastic polymer upper material are intermingled with each other in the intermediate material zone.

The intermediate material zone thus consists partly of thermoplastic polymer upper material and thermoplastic polymer midsole material and upper and midsole are therein directly material-bonded to each other. This results in a significantly durable and strong connection and thus improved stability of the shoe. Furthermore, the structure of the intermediate material zone may be different from the structure of the rest of the upper and/or the rest of the foamed midsole. For example, the intermediate material zone may have a different density and/or a different hardness than the rest of the upper and/or the rest of the foamed midsole. In some embodiments, the rest of the upper may have a loop structure, while preferably the intermediate material zone may be a massive material layer.

Typically, the rest of the upper, e.g. the part which is not part of the intermediate material zone (e.g. the upper section of the shoe) is preferably free of the thermoplastic polymer midsole material. Vice versa, the rest of the midsole, e.g. the part which is not part of the intermediate material zone (e.g. the midsole section of the shoe), is preferably free of the thermoplastic polymer upper material.

In some embodiments, the intermediate zone extends in a plane along the longitudinal direction and the transversal direction completely over the foamed midsole and/or completely over the upper. The longitudinal direction extends from a heel edge of the shoe to the shoe tip and is perpendicular to the vertical direction. The transversal direction extends perpendicular to the longitudinal and the vertical direction and extends from the lateral area to the medial area of the shoe.

The intermediate material zone may in some embodiments form an insole.

If the upper and the foamed midsole form a direct material-bonded connection with each other, i.e. if upper and foamed midsole are fused to each other, upper and foamed midsole are integral with each other.

In some embodiments, the intermediate material zone is arranged between a midsole section being devoid of the thermoplastic polymer upper material and an upper section being devoid of the thermoplastic polymer midsole material. In certain embodiments, the intermediate material zone is a layer separating the midsole section being devoid of the thermoplastic polymer upper material and the upper section being devoid of the thermoplastic polymer midsole material.

In some embodiments, the intermediate material zone comprises a gradient of the thermoplastic polymer upper material. This gradient preferably extends from the upper section to the midsole section. In other words, the gradient extends against the vertical direction of the shoe. This means the amount (in wt. %) of thermoplastic polymer upper material in the intermediate material zone decreases against the vertical direction, i.e. towards the foamed midsole.

In some embodiments, the intermediate material zone comprises a gradient of the thermoplastic polymer midsole material. This gradient preferably extends from the midsole section to the upper section. In other words, the gradient extends along the vertical direction of the shoe. This means the amount (in wt. %) of thermoplastic polymer midsole material in the intermediate material zone decreases along the vertical direction, i.e. towards the upper.

In some embodiments, the melting temperature of the thermoplastic polymer midsole material is equal or higher than the melting temperature of the thermoplastic polymer upper material. The thermoplastic polymer upper material may in some embodiments be the same or different than the thermoplastic polymer midsole material.

In some embodiments, the thermoplastic polymer midsole material is selected from polyolefins, such as polyethylene or polypropylene, polyester, such as PET or PBT, polyamide, polyether block amide (PEBAX), polyurethane, ethylene vinyl acetate (EVA) or mixtures thereof.

In some embodiments, the thermoplastic polymer upper material is selected from polyolefins, such as polyethylene or polypropylene, polyester, such as PET or PBT, polyamide, polyether block amide (PEBAX), polyurethane, ethylene vinyl acetate (EVA) or mixtures thereof.

A third aspect of the invention relates to a shoe production system, in particular an automated shoe production system. Such a shoe production system is preferably configured to perform the method described herein, in particular with respect to the embodiments of the first aspect of the invention. The shoe production system may also be used to produce a shoe as described herein, in particular with respect to the embodiments of the second aspect of the invention.

The shoe production system comprises a sole molding unit, in particular a sole molding unit as described herein, e.g. with respect to the first aspect of the invention. The sole molding unit defines a cavity. The shoe production system further comprises a movable robotic arm which is configured to hold a carrier of an upper assembly, i.e. an upper assembly as described herein.

In some embodiments, the cavity defined by the sole molding unit is delimited by one or more sidewalls which circumferentially surround the cavity and further a bottom wall which delimits, respectively defines, the bottom of the cavity. In some embodiments, the cavity is however open at the top portion, i.e. the portion being oppositely arranged to the bottom portion. This opening and the upper assembly may preferably be configured such that upon inserting the upper assembly at least partially into the cavity, the top portion of the cavity is closed by the upper assembly, in particular hermetically closed.

The robotic arm may for example be a cantilever. Preferably, the robotic arm is movable in the 3-dimensional space. The robotic arm may for example comprise one or more beams being preferably connected with each other via joints thereby allowing the movement of the arm in the 3-dimensional space.

In some embodiments, the robotic arm may be controlled by a control unit which may also be part of the shoe production system. The control unit may preferably comprise a circuit, e.g. a microprocessor. For example, a movement path may be stored in a memory unit which can be accessed by the control unit to move the robotic arm along this movement path. The memory unit may also be part of the shoe production system.

In some embodiments, the shoe production system comprises a depositing unit which is configured for depositing a thermoplastic polymer upper material on the carrier being held by the movable robotic arm. The depositing unit may be a depositing unit as described herein above, in particular with respect to embodiments described in the first aspect of the invention.

In some embodiments, the depositing unit comprises a nozzle. The nozzle may in certain embodiments comprise a material outlet and a plurality of air openings which are circumferentially arranged around the material outlet. The air openings are further configured to apply pressure in such a manner on the molten thermoplastic polymer upper material exiting the material outlet that the exiting molten thermoplastic polymer upper material is applied, respectively deposited, on or to the carrier as a helical filament.

In some embodiments, the depositing unit comprises further a melting unit. The melting unit is configured to transform a thermoplastic polymer upper material, in particular in solid form, into the molten thermoplastic polymer upper material, in particular by energy transfer, such as heating. For example, the melting unit may be an extruder or be part of an extruder, in particular an extruder with screw and barrel. The melting unit is preferably in fluid communication with the material outlet of the nozzle. Thus, the thermoplastic polymer upper material can be melted in the melting unit and can then be transported to the nozzle and applied through the material outlet of the nozzle on the carrier.

In certain embodiments, the depositing unit further comprises a pump, such as a dosing pump, which is configured to transport the molten thermoplastic polymer upper material out of nozzle and on the carrier.

It is in some embodiments possible that the depositing unit is movable in the 3-dimensional space. The depositing unit may for example in some embodiments be controlled by a depositing unit control unit. The depositing unit control unit may preferably comprise a circuit, e.g. a microprocessor. For example, a movement path may be stored in a depositing memory unit which can be accessed by the depositing control unit to move the robotic arm depositing along this movement path. In some embodiments, in which both the depositing unit is movable in the 3-dimensional space and in which the carrier is held by a movable robotic arm, the depositing unit control unit may also be part of or being equal to the control unit controlling the robotic arm holding the carrier.

In some embodiments, the depositing unit further comprises a motor being configured to drive the pump.

The control unit of the shoe production system may be configured to control the movement path of the robotic arm holding the carrier, and/or the movement path of the depositing unit as described below, and/or the pressure of the air being applied through the air openings of the nozzle onto the molten thermoplastic upper material exiting the material outlet of the nozzle, and/or the pump. The depositing control unit may for example be part of the control unit as such.

In some embodiments, the memory unit stores one or more of movement paths for the robotic arm being configured to hold the carrier and/or for the depositing unit, respectively its nozzle.

In some embodiments, the control unit may determine the movement path, in particular an ideal movement path, based on training data stored in the memory unit. Preferably, the determination of the movement path may be performed by machine learning.

Particularly, it may generally be possible that the robotic arm is configured to move the carrier and/or the upper assembly along three space axes, such as a vertical axis, a longitudinal axis and a transversal axis. Additionally, or alternatively, it may generally be possible that the movable robotic arm is configured for rotating the carrier and/or the upper assembly around a rotation axis.

DESCRIPTION OF THE EMBODIMENTS

FIG.1shows an upper assembly2which comprises a carrier4and an upper3being mounted on carrier4. Carrier4can in this embodiment or any other embodiment described herein for example be a last, i.e. a shoe last. Upper3further comprises bottom section5which is made from a thermoplastic polymer upper material. In this embodiment, the boundary of bottom section5is indicated by the dashed line. However, it may in some embodiments well be the case that the bottom section and the rest of the upper are identical, e.g. they may be made from the same material and/or have the same structure, such as a non-woven, knit or woven structure. Upper assembly2is partially inserted into cavity7(seeFIG.3) defined by sole molding unit6. Thereby, the upper assembly2and the sole molding unit6define together sole molding compartment9. Sole molding compartment9is a part of the cavity defined by sole molding unit6. The upper assembly, in particular upper3, respectively its bottom section5, and the sole molding unit6form together a fluid tight connection. Typically, when upper assembly2is inserted into cavity7, cavity7and therefore also sole molding compartment9is filled with air, e.g. ambient air. It may also in this or any other embodiment as described herein be possible to apply a sub-atmospheric pressure to sole molding compartment9after partially inserting upper assembly2into cavity7of sole molding unit6.

As a next step, a midsole polymer composition comprising a molten thermoplastic polymer midsole material is introduced into the cavity and thus also into sole molding compartment9. This introduction may for example occur via injection inlet24which opens into cavity7, respectively sole molding compartment9. Since upper assembly2is partially introduced into cavity7and/or the sole molding compartment9is defined by upper assembly2and sole molding unit6, the introduced molten thermoplastic polymer composition is provided onto bottom section5of upper3being introduced into cavity7. As the molten thermoplastic polymer midsole material has an equal or higher melting temperature than the thermoplastic polymer upper material of bottom section5(and optionally of complete upper3), the bottom section5partially or fully melts and a material-bonded connection being a fused connection between upper and the formed foamed midsole occurs without any additional adhesive. Furthermore, during introduction, foaming of the molten thermoplastic polymer midsole material is performed during step d. which provides the foamed midsole. This results in a produced shoe with a foamed midsole being directly material-bonded, i.e. fused, to an upper3. Subsequently, cooling and/or curing can be performed and the produced shoe can be removed from sole molding unit6and carrier4can be removed from the produced shoe.

FIG.2shows a shoe1which can be obtained by the method according to the invention. Shoe1comprises upper3and foamed midsole8. Upper3comprises a thermoplastic polymer upper material and foamed midsole8comprises a thermoplastic polymer midsole material. In addition, shoe1comprises outsole10being material-bonded to foamed midsole8. Outsole10can for example be obtained in that after step d. of the method according to the invention, i.e. after foamed midsole8is produced and material-bonded to upper3, a molten polymer outsole material, preferably a molten thermoplastic outsole material is introduced into cavity7defined by sole molding unit6, respectively sole molding compartment9onto foamed midsole8. Introduction of the molten polymer outsole material may for example occur via injection inlet24or via an additional separate injection inlet. Only thereafter the thus produced shoe is typically removed from sole molding unit6and carrier4is removed from upper3.

FIG.2shows a view of shoe1on its heel edge, i.e. as indicated by the coordinate system along longitudinal direction L towards the sole tip of shoe1. Vertical direction V extends perpendicularly thereto from foamed midsole8towards upper3, respectively in the worn or operative state from the ground to the foot of the wearer. Transversal direction T is perpendicular to both longitudinal direction L and vertical direction V. Shoe1further comprises intermediate material zone16which is indicated by the two parallel extending dashed lines. When the molten thermoplastic polymer midsole material is introduced, e.g. injected, onto bottom section5of upper3, bottom section5at least partially or fully melts and therefore forms upon cooling/and or curing a material-bonded, e.g. fused, connection between foamed midsole8and upper3. Thereby intermediate material zone16can be formed, which comprises both the thermoplastic polymer upper material of the upper, respectively bottom section5and also the thermoplastic polymer midsole material. In contrast, midsole section17, i.e. the rest of foamed midsole8is devoid of the thermoplastic polymer upper material. Vice versa, upper section18of upper3, i.e. the rest of upper18, is devoid of the thermoplastic polymer midsole material. Against vertical direction V there is a gradient of the thermoplastic polymer upper material in intermediate material zone16extending from upper section18to midsole section17. This gradient is decreasing, i.e. the amount, such as the mass percentage, of the thermoplastic polymer upper material decreases from the intermediate material zone16extending from upper section18to midsole section17. Furthermore, there is an opposite gradient in intermediate material zone16of the thermoplastic polymer midsole material extending along or in vertical direction V, i.e. from midsole section17to upper section18. The gradient of the thermoplastic polymer midsole material decreases in intermediate material zone16from midsole section17to upper section18. The gradient may also in this case be represented by a decreasing amount, e.g. mass percentage, of the thermoplastic polymer midsole material. In some embodiments, the intermediate material zone16may extend completely along the transverse direction T and the longitudinal direction L of shoe1and for example completely separate midsole section17from upper section18. However, it may generally also be possible that intermediate material zone16may extend only along a certain portion of the transverse direction T and/or the longitudinal direction L of shoe1. For example, the intermediate material zone may only be arranged at the periphery of shoe1and thus not in its center.

FIG.3shows a shoe production system100when being used to produce a shoe, e.g. for producing a shoe in the method according to the invention. Shoe production system100comprises sole molding unit6, such as sole molding unit6as described with respect toFIG.1, which defines cavity7being configured for molding a shoe sole, such as foamed midsole8. Cavity7is defined by sidewalls circumferentially surrounding the cavity and bottom wall delimiting the bottom of the cavity (not visible). As can be seen, the cavity is open at the top portion, which allows to insert upper assembly2directly into cavity7. Furthermore, shoe production system100comprises movable robotic arm11which holds carrier4. For example, robotic arm11may form a form-locking and/or force-locking engagement with carrier4. It may for example be possible that robotic arm11forms a snap fitting engagement with carrier4. Robotic arm11is configured for moving carrier4in the 3-dimensional space. Particularly, it may generally be possible that robotic arm11is configured to move carrier4along three space axes, such as a vertical axis, a longitudinal axis and a transversal axis. Additionally, or alternatively, it may generally be possible that the movable robotic arm11is configured for rotating carrier4around a rotation axis. Shoe production system100further comprises control unit23which is configured to control the movement of robotic arm11, particularly with respect to nozzle12being further comprised in the shown shoe production system100. Nozzle12which may be part of depositing unit (seeFIG.6).

FIG.3depicts how upper assembly2can be provided in step a of the method according to the invention. In this embodiment, the molten thermoplastic polymer upper material is applied by nozzle12onto carrier4. The robotic arm moves carrier4in the 3 dimensional space with respect to nozzle4. As can be seen, molten thermoplastic polymer upper material is applied as a filament onto carrier4as a helical filament. After the application of the molten thermoplastic polymer upper material is finished, the upper assembly2comprising carrier4and upper3being mounted on carrier4is provided. As a next step in the method according to the invention, the upper assembly2is at least partially inserted into cavity7of sole molding unit6, for example in the manner as shown inFIG.1. The insertion may for example be done by movable robotic arm11being preferably controlled by control unit23. After the upper assembly2has been inserted into cavity7, step d. of the method according to the invention is performed, i.e. the midsole polymer composition is introduced into cavity7and foaming of the molten thermoplastic polymer midsole material is performed to establish a direct fused connection between upper3, respectively its bottom section5, and foamed midsole8to produce shoe1. Thus, the complete shoe can be produced at a single location with a single system and fully automatically.

FIG.4shows a top view of nozzle12as it can be used in some embodiments of the invention. Nozzle12comprises centrally arranged material outlet13. Furthermore, nozzle12comprises a plurality of air openings14,15(only two openings are referenced for clarity purposes) being circumferentially arranged around material outlet13. As can be seen, each air opening is arranged such that air being guided through it is guided inwardly, i.e. in the direction of the filament of molten thermoplastic upper material exiting material outlet13. However, each air opening is also arranged such that pressurized air being guided through the air openings is applied in such a manner on the molten polymer upper material exiting the material outlet (i.e. the filament) that it is applied to the carrier as a helical filament. This is achieved by directing the pressurized air offset to the axis being perpendicular to material outlet13and extending through its center along the application direction in which the molten thermoplastic polymer material is applied to the carrier (i.e. in the direction the viewer views onto the nozzle inFIG.4). This allows to effect a movement of the exiting molten thermoplastic polymer material such that it is applied onto the carrier as a helical filament.FIG.5shows a perspective view of nozzle12shown inFIG.4, which further clarifies the configuration of air openings14and15.

FIG.6shows a detailed view of a depositing unit19as it can be used in some embodiments of the invention. Depositing unit19comprises melting unit20which may be an extruder, such as a screw and barrel extruder having screw21and barrel22. Melting unit20comprises material inlet26through which the thermoplastic polymer upper material can be inserted into melting unit20for example as solid granulate. This material is then melted inside melting unit20and transported towards nozzle12which may be a nozzle as shown inFIGS.4and5. The molten thermoplastic polymer upper material is then applied via material outlet13out of nozzle12. By means of pressurized air being applied through air inlet openings14,15(seeFIGS.4and5), the molten thermoplastic polymer upper material is applied to carrier4as a helical filament. By moving carrier4in the 3-dimensional space, for example by a movable robotic arm (not shown here, seeFIG.3), an upper assembly2can be provided. The depositing unit can be controlled by depositing unit control unit25. It may be possible that depositing unit control unit25is in some embodiments included into control unit23which controls the movement of movable robotic arm11(seeFIG.3).