midsole

Abstract

Disclosed herein is a midsole (1) for a shoe and a production method for such a midsole. The midsole (1) comprises an inner foamed core (2) and an outer sheathing layer (3) circumferentially encompassing the inner foamed core (2). The midsole (1) further comprises a plurality of channels (4a, 4b, 4c). In addition, the outer sheathing layer (3) has a greater density than the inner foamed core (2).

Description

[0001] Midsole

[0002] Field of disclosure

[0003] The present invention lies in the field of footwear technology and relates in particular to a midsole for shoe, such as a sports shoe or leisure shoe, and to a method of producing a midsole.

[0004] Background, prior art

[0005] Cushioning soles are prominently used in different sports shoes to prevent injuries, such as knee, ankle, hip and back injuries. This is particularly important in sports in which repeating high impact forces occur, such as running. To prevent these injuries, many different cushioning systems have been developed over time. They comprise for example gas filled chambers, resilient elements, advanced polymer foams, shock absorbing buffer structures and channel cushioning. The latter typically envisions channels in the sole structure which extend from the medial side to the lateral side of the sole. Typically the channels are filled with ambient air. By means of the medial and lateral openings, the channels are in fluidic connection with the environment. If the sole is loaded with a force, the sole can deform, which leads to a decreasing channel open area, because the air inside the channels is vented out of the channel through the medial and lateral opening, and the channel wall sections which delimit the channel are moved towards each other. Thus, in such soles, the channels are used as cushioning elements and decrease the rigidity and / or hardness in the areas of the sole where the channels are located. When designing a channel cushioning sole, channels are therefore used as softening elements which locally soften the midsole and are placed in areas where enhanced cushioning is required.

[0006] An important advantage of such channel cushioning over many other systems is that the soles are relatively easy to manufacture, because the channels can directly be introduced during molding or foam molding by suitable molding pins. Further, these soles can be manufactured as single pieces, because the cushioning system is operationally simple to produce and does not require multiple different parts which have to be assembled together as it is the case for other cushioning systems. For example, in gas filled bladder cushioning systems, the bladder shell is often made from different material than the rest of the sole as it must be gas tight. Also shock absorbing buffer structures often require different materials for the buffer structures as compared to the rest of the sole. Therefore, channel cushioning has advantages in view of ease of production, material demand, cost and recyclability, because it requires a lower number of different materials.

[0007] A problem with such channel cushioning is however that the channels can cause instabilities, in particular during tread (i.e. when the foot contacts the ground). This is particularly problematic if treading is not neutral (i.e. such that the sole extends in parallel to the ground), but if it occurs under pronation or supination of the runner’s foot. This may either be caused by the anatomic prerequisites of the runner or by an uneven ground, such as a step, a stone, a tree branch or the like. Although channel cushioning as described above achieves good cushioning, it may cause such instabilities which may lead to both immediate injuries or to long term issues for the wearer. Such instabilities also occur for soles without channels if they can for example easily tilt or are otherwise unstable towards undesired pronation or supination.

[0008] Summary of disclosure

[0009] It is the general object of the present invention to advance the state of the art in the field of footwear technology and preferably to overcome the disadvantages of the prior art fully or partly. In advantageous embodiments, a midsole and a production method is provided which provides both sufficient cushioning and additionally a stable stand particularly avoiding lateral and medial instabilities and therefore undesired pronation or supination of the wearer’s foot. In further advantageous embodiments, such midsoles are provided in economically and environmentally more efficient manner.

[0010] 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 midsole for a shoe. The shoe can be any sports shoe of leisure shoe. Another aspect may relate to a shoe including such a midsole.

[0011] The midsole may comprise an inner foamed core and an outer sheathing layer. The outer sheathing layer may encompass, in particular circumferentially encompasses, the inner foamed core. In particular embodiments, the outer sheathing layer completely circumferentially encompasses the inner foamed core, for example such that at least 90%, or at least 95%, or at least 99% or even 100% (i.e. the entire surface) of the surface of the inner foamed core is covered by the outer sheathing layer. Therefore, in such embodiments, the inner foamed core may not be exposed to the outer environment of the midsole and / or only the outer sheathing layer may be exposed to the outer environment of the midsole. The outer sheathing layer may in some embodiments be considered as an outer jacket. The terms “inner” and “outer” refer to the fact that the outer sheathing layer encompasses the foamed core and therefore the sheathing layer is an outer sheathing layer or outer jacket and the foamed core is an inner foamed core.

[0012] In some embodiments, the outer sheathing layer is configured to increase the hardness of the midsole and / or to decrease the deformability of the midsole. In certain embodiments, the outer sheathing layer is a support layer which is configured to decrease the deformability of the midsole as compared to a midsole without the outer sheathing layer, in particular consisting of the inner foamed core.

[0013] In some embodiments, the outer sheathing layer has a greater density and / or greater hardness and / or greater rigidity, than the inner foamed core. Having such an outer sheathing layer provides support, in particular laterally and medially and prevents instabilities in particular undesired pronation and supination. The inner foamed core on the other hand is typically softer and / or less dense than the outer sheathing layer and is therefore responsible for the cushioning. The outer sheathing layer may act as support jacket, which circumferentially encompasses the inner foamed core. The higher the amount (e.g. volume % or surface area %) of the outer sheathing layer, the more stability is provided. A sufficiently large inner foamed core provides at the same time for sufficient cushioning. Since the outer sheathing layer may in some embodiments cover the entire surface of the inner foamed core, it becomes clear that increasing the surface area of the inner foamed core (and thus the amount of the outer sheathing layer covering this surface), provides for a better support and a higher stability.

[0014] In some embodiments, the outer sheathing layer has a greater density than the inner foamed core. Optionally, the outer sheathing layer as additionally a hardness and / or greater rigidity, than the inner foamed core.

[0015] In some embodiments, the outer sheathing layer has a greater hardness than the inner foamed core. Optionally, the outer sheathing layer as additionally a greater density and / or greater rigidity, than the inner foamed core.

[0016] In some embodiments, the outer sheathing layer has a greater rigidity than the inner foamed core. Optionally, the outer sheathing layer as additionally a greater density and / or greater hardness than the inner foamed core.

[0017] In some embodiments, the midsole further comprises, respectively delimits or defines, a plurality of channels.

[0018] As used herein, a channel is a tubular structure being delimited, respectively defined by a channel wall which is part of the midsole. The channels may preferably be filled with air and may be in fluid communication with the outer environment. Thus, the channels are in such embodiments not pressurized but the air inside the channels has the same pressure as the outside environment pressure. Fluid communication with the outer environment may for example be achieved by channel openings. In some embodiments, the channels may therefore have an opening, such as one or even two openings. For example, each channel may have a lateral opening being arranged on the lateral side of the midsole and / or a medial opening being arranged on the medial side of the midsole. Channels which have only one opening, such as a lateral or a medial opening, are considered as blind holes or blind hole channels. In contrast, channels which have two openings, such as a lateral and a medial opening are considered as through-going or penetrating channels, i.e. channels which completely penetrate the midsole, such as from the lateral to the medial side. In certain embodiments, the channels may also be filled with a material, such as a solid material, for example a foam material. It may also be possible that the channels are hermetically closed and contain a gas, such as pressurized gas, e.g. air. In some embodiments, the channels are completely delimited by the midsole. This does not mean that the channels cannot have openings, such as lateral or medial openings, but that the channels are only defined by the midsole and not by any other component, for example an outsole or an insole or a plate element.

[0019] 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.

[0020] The “hardness” as used herein for an element such as the midsole or regions thereof can be determined as a Shore A or Shore D hardness, preferably Shore A. The cushioning and / or peak loading force and / or energy return can be determined by the ASTM F 1976-13 standard test for impact attenuation of athletic shoe cushioning systems and materials.

[0021] The midsole can in some embodiments have a peak loading force, in particular in the heel area and / or in the forefoot area, as determined by ASTM F 1976-13 of 300 g to 400 g, in particular 333 g to 385 g.

[0022] In some embodiments, the midsole can have an energy loss, in particular in the heel area and / or in the forefoot area, as determined by ASTM F 1976-13 of 1.0 to 22.0 %, in particular of 3.0 to 16.0 %. The energy loss is the surface area between the curve of loading phase and the curve of unloading phase (see Fig. 6 as well as the description of Fig. 6). In general, for the ASTM F 1976-13, a mass of 8.5 kg is used, the drop height is 50 mm and the nominal value of the total energy input is 5 J.

[0023] Directional indications as used in the present disclosure are to be understood as follows: The longitudinal direction LO of the midsole is described by an axis from the heel area, respectively from the heel edge, to the forefoot region, respectively to the midsole tip, and thus extends along the longitudinal axis of the midsole. Thus the term “extending along / in the longitudinal direction” typically refers to extending towards the midsole tip and the term “extending against the longitudinal direction” typically refers to extending towards the heel edge. The transverse direction TR of the midsole extends transversely to the longitudinal axis and substantially parallel to the base layer of the midsole, or substantially parallel to the ground in the operative state. Thus, the transverse direction runs along a transverse axis of the midsole. In the context of the present invention, the vertical direction V denotes a direction from the base layer to the top layer of the midsole, or in the operative state in the direction of the foot of the wearer, and thus runs along a vertical axis of the midsole respectively the shoe sole. Thus the term “extending along / in the vertical direction” typically refers to extending towards the top layer of the midsole and the term “extending against the vertical direction” typically refers to extending towards the base layer of the midsole. The longitudinal direction, the vertical direction and the transverse direction may all be perpendicular to each other. The lateral side of the midsole is the outer perimeter of the midsole between the heel edge and the sole tip, which in the worn state rests against the outer instep of the wearer's foot. The indication “horizontal” refers to a plane extending in the longitudinal and the transverse direction and being perpendicular to the vertical direction. The medial side of the midsole, refers to the inner perimeter of the midsole between the heel edge and the sole tip, which is located opposite the lateral side. Thus, in a pair of worn shoes, the medial sides of the two running shoes face each other and the lateral sides face away from each other. The midsole may comprise a top layer and a base layer being oppositely arranged to the top layer. The top and base layer form typically the vertically outer delimitations of the midsole. Furthermore, the midsole may typically along the longitudinal direction be divided into a forefoot area, a heel area and a midfoot area being arranged between the forefoot area and the heel area. For example, the forefoot area extends from the midsole tip against, i.e. opposite, the longitudinal direction to 30-45% of the total length of the midsole in the longitudinal direction. The heel area extends, for example, from the heel edge in the longitudinal direction to 20-30% of the total length of the midsole in the longitudinal direction. The midfoot area extends directly between the heel area and the forefoot area, such that the length in the longitudinal direction of the midfoot area makes up the remaining portion of the total length, particularly from 15-50% of the total length.

[0024] In some embodiments, the density and / or rigidity and / or hardness, in particular the density, of the outer sheathing layer is at least 1.05x, in particular 1 .1x, more particular at least 1.2x, more particular at least 1 ,5x that of the inner foamed core.

[0025] In some embodiments, the density of the inner foamed core is between 50 to 500 kg / m3, in particular between 100 and 400 kg / m3, more particular between 130 and 300 kg / m3.

[0026] In some embodiments, the density of the outer sheathing layer is between 800 kg / m3to 1500 kg / m3, in particular 900 kg / m3to 1500 kg / m3, more particular 1000 kg / m3to 1300 kg / m3.

[0027] In some embodiments, a density ratio between the density of the outer sheathing layer to the density of the inner foamed core is 2:1 to 8: 1 , in particular 3:1 to 7: 1. The higher density of the outer sheathing layer improves the stability of the midsole.

[0028] In some embodiments, the inner foamed core and the outer sheathing layer are made from the same material. This does however not mean that they have the same properties, such as the same physical properties. As noted above, the outer sheathing layer may have a greater density and / or greater rigidity and / or greater hardness than the inner foamed core but still be made from the same material. Such embodiments have the advantage that the midsole can be easily recycled and be easier manufactured because only one material can be used, which is particularly advantageous if the midsole is produced according to any of the embodiments of the method according to the invention as described herein. In some embodiments, the inner foamed core is made from a thermoplastic polymer. Examples for suitable thermoplastic polymers are selected from one or more of: polyolefin, such as polyethylene or polypropylene, polyester, such as polyethylene terephthalate or polybutylene terephthalate, polyamide, such as PA-6 or PA-11 , polyurethane, polyvinyl polymer, such as polyvinyl acetate, and copolymers thereof, such a polyether block amide (PEBA) or ethylene vinyl acetate (EVA).

[0029] In some embodiments, the outer sheathing layer is made from a thermoplastic polymer. Examples for suitable thermoplastic polymers are selected from one or more of: polyolefin, such as polyethylene or polypropylene, polyester, such as polyethylene terephthalate or polybutylene terephthalate, polyamide, such as PA-6 or PA-11 , polyurethane, polyvinyl polymer, such as polyvinyl acetate, and copolymers thereof, such a polyether block amide (PEBA) or ethylene vinyl acetate (EVA).

[0030] In some embodiments, the inner foamed core and the outer sheathing layer are made from the same thermoplastic polymer. Examples for suitable thermoplastic polymers are selected from one or more of: polyolefin, such as polyethylene or polypropylene, polyester, such as polyethylene terephthalate or polybutylene terephthalate, polyamide, such as PA-6 or PA- 11 , polyurethane, polyvinyl polymer, such as polyvinyl acetate, and copolymers thereof, such a polyether block amide (PEBA or PEBAX) or ethylene vinyl acetate (EVA).

[0031] In some embodiments, the inner foamed core and the outer sheathing layer form a material bonding connection with each other, in particular a direct and / or inherent material bonding connection with each other. An inherent material bonding connection is a connection which is devoid of an external adhesive. This can for example be formed if the material forming the inner foamed core and the material forming the outer sheathing layer are provided in a molten form in contact with each other and are then cooled below their melting temperature such that they solidify and form a material bonding connection with each other.

[0032] In some embodiments, the inner foamed core and the outer sheathing layer are integrally formed with each other, respectively are formed from a single piece. For example, the inner foamed core and the outer sheathing layer may be produced by curing, e.g. cooling, a molten thermoplastic polymer below its melting temperature. Particularly, the inner foamed core and the outer sheathing layer may be produced by curing, e.g. cooling, a molten thermoplastic polymer, i.e. below its melting point. The curing conditions may in some embodiments be different for the material forming the outer sheathing layer and the material forming the inner foamed core. For example, an applied cooling gradient may be different.

[0033] In some embodiments, the channels are each delimited by a channel wall. In certain embodiments, the channel wall is made of, e.g. consists of, the outer sheathing layer. That is, the channel wall may be part of the outer sheathing layer. Thus, the channel is part of the foamed inner core or made of it. Such embodiments have an advantageous effect on the stability of the midsole. As noted above, channels are commonly used as cushioning elements, i.e. elements which soften the midsole in certain areas. However, since in these embodiments, the channel walls are made of, respectively are part of, the outer sheathing layer which has a greater density and / or greater rigidity and / or greater hardness than the inner foamed core, the channels actually act as supporting and / or rigidifying elements. Thus, the areas in which the channels are positioned show less cushioning properties as compared to areas without such channels, because such other areas have a correspondingly larger portion of the inner foamed core, which provides for cushioning and less of the outer sheathing layer which provides more support and thus more stability. In conclusion, in contrast to standard channel cushioning, removing material from the midsole by channel formation actually increases the stability, e.g. rigidity and / or hardness, of the midsole. The channel wall of each channel may comprise multiple channel wall sections. Such channel wall sections may in particular have a planar and particularly an even planer structure, and may be angled with respect to each other.

[0034] In some general embodiments, the midsole with channels as described in any of the embodiments herein, may have a higher hardness and / or higher rigidity as midsole being devoid of channels but being otherwise identical. In some general embodiments, the midsole with channels as described in any of the embodiments herein, may have a less pronounced cushioning as midsole being devoid of channels but being otherwise identical.

[0035] In some embodiments, the plurality of channels comprises, or consists of, a plurality of channels extending completely through the midsole. For example, at least one, or the majority (i.e. more than 50%) of the channels of the midsole may be such channels, i.e. channels extending, respectively penetrating, completely through the midsole. In specific embodiments, all channels of the midsole may be such channels, i.e. channels extending completely through the midsole. As noted above, in contrast to channels being commonly used as cushioning elements, such channels decrease the cushioning effect and increase stability. Thus, such channels may for example be beneficial in the forefoot area, because stability in this area is advantageous for providing an efficient push-off. The more stable the forefoot area, the less energy is lost during push-off, because the wearer’s energy is not lost by deforming a cushioning system, but is almost completely used for the push-off process.

[0036] In particular embodiments, these channels have a channel wall being part of the outer sheathing layer.

[0037] In particular, these channels may extend from the lateral to the medial side of the midsole. In certain embodiments, each of these channels may have a lateral opening on the lateral side of the midsole and a medial opening on the medial side of the midsole. In some embodiments, the channels may extend along and in particular in parallel to the transverse direction of the midsole. For example, the channels may extend in parallel to the base layer of top layer of the midsole.

[0038] In some embodiments, the plurality of channels comprises, or consists of, a plurality of channels being configured as blind holes. Such channels may be considered as “blind hole channels”. As noted above, a blind hole channel has only one opening. It extends from there partially through the midsole up to a dead end of the blind hole channel. In some embodiments, the channels being configured as blind holes, may extend along, respectively in parallel to the transverse direction. Further, at their dead end they may be delimited by a corresponding vertical channel wall section. In general, also the channels being configured as blind holes may particularly be delimited by a channel wall being part of the outer sheathing layer.

[0039] For example, at least one, or the majority (i.e. more than 50%) of the channels of the midsole may be such blind hole channels, i.e. channels being configured as blind holes. In specific embodiments, all channels of the midsole may be such blind hole channels, i.e. channels being configured as blind holes.

[0040] Blind hole channels offer specific advantages. For example, as they do not penetrate completely through the midsole, they allow to provide section with increased stability (i.e. sections in which they actually extend) and section with increased cushioning (i.e. the section behind their dead end, respectively sections in which they do not extend).

[0041] In some embodiments, the channels being configured as blind holes (i.e. the blind hole channels) have a depth of 15% to 60%, in particular 15% to 45%, of the width of the midsole. The width of the midsole refers to the distance between the lateral and the medial side of the midsole along the transverse direction at the position at which the corresponding channel is arranged.

[0042] In some embodiments, the channels being configured as blind holes (i.e. the blind hole channels) have a depth of 10 mm to 60 mm, in particular 15 mm to 50 mm. As used herein, the depth of the channel refers to the channel extension from its opening to its corresponding dead end. As noted above, a blind hole channel extends between its opening and its dead end.

[0043] In some embodiments, the midsole defines a central clear space being open towards the base layer. In certain embodiments, the blind hole channels open towards the central clear space and extend in the direction of the medial or later side of the midsole. However, since they have a dead end before they reach the medial or lateral side of the midsole, they enhance central stability of the midsole, while the midsole may still provide a peripheral cushioning portion.

[0044] In some embodiments, some of the blind hole channels are lateral channels and / or some of the blind hole channels are medial channels. In other words, in some embodiments, the midsole comprises a plurality of lateral channels being configured as blind holes. In some embodiments, the midsole comprises a plurality of medial channels being configured as blind holes.

[0045] The lateral channels may have an opening on the lateral side and extend from the opening on the lateral side of the midsole towards a central region of the midsole. In particular, the lateral channels may extend along the transverse direction and particularly in parallel to the top layer or bottom layer of the midsole.

[0046] The medial channels may have an opening on the medial side and extend from the opening on the medial side of the midsole towards a central region of the midsole. In particular, the medial channels may extend along the transverse direction and particularly in parallel to the top layer or bottom layer of the midsole. The central region of the midsole is typically arranged between a lateral outer region and a medial outer region of the midsole. The lateral outer region extends generally from the lateral side to the central region and the medial outer region from the medial side to the central region. Thus along the transverse direction, the central region is arranged between the lateral outer region and the medial outer region of the midsole.

[0047] In some embodiments, also the medial and lateral channels are delimited by a channel wall which is part of the outer sheathing layer.

[0048] Embodiments of a midsole with both such lateral and medial channels (which are both blind hole channels) are particularly advantageous. Since the channels increase the stability due to the increased density and / or rigidity and / or hardness, and since the channels extend from a lateral sided or medial sided opening towards the central region, the central region is less rigid and provides therefore for a satisfying cushioning effect, while the lateral and medial outer region have a greater stability and therefore, both good cushioning and stability is achieved. The lateral and medial stability prevents injuries from undesired supination or pronation.

[0049] In some embodiments, the central region comprises, or consists of, a portion of the inner foamed core. In some embodiments, a portion of the inner foamed core is arranged between one or more of the lateral channels and one or more of the medial channels. In particular, a portion of the inner foamed core is arranged between dead ends of opposing lateral and medial channels being configured as blind holes. Preferably, this portion of the foamed core is in contact with the channel wall, in particular the vertical channel wall delimiting the corresponding opposing medial and / or lateral channels.

[0050] In some embodiments, the plurality of lateral channels are aligned with the plurality of medial channels. In particular, the plurality of lateral channels are aligned such with the plurality of medial channels that the lateral channels and medial channels extend towards each other, in particular along the transverse direction, and / or are facing each other.

[0051] Aligned channels may be in flush with each other and are therefore not offset to each other.

[0052] In some embodiments, the plurality of lateral channels and the plurality of medial channels are offset to each other, in particular completely offset to each other (i.e. without overlap).

[0053] In particular, the medial and lateral channels may be arranged such that when travelling from the heel edge to the midsole tip along the longitudinal direction, the lateral channels and medial channels are alternatingly arranged (and thus offset to each other).

[0054] In some embodiments, the midsole comprises a lateral outer region and a medial outer region. The midsole may further comprise a central region being arranged between the lateral outer region and the medial outer region. As noted above, the lateral outer region may extend between the lateral side (i.e. the lateral outer periphery of the midsole) and the central region and the medial outer region may extend between the medial side (i.e. the medial outer periphery of the midsole) and the central region. In certain embodiments, the lateral outer region comprises the lateral channels being configured as blind holes. Particularly, the lateral channels are only arranged in the lateral outer region. In certain embodiments the medial outer region comprises the medial channels being configured as blind holes. Particularly, the medial channels are only arranged in the medial outer region.

[0055] In certain embodiments, the central region is devoid of any channels. Such embodiments are especially advantageous because as noted above, the channels increase rigidity, density and / or hardness and therefore decrease the cushioning effect. Since however, most of the weight force acts on the central region during running, avoiding channels in the central region improves the cushioning of the midsole. Further, if combined with medial and lateral channels as described herein, the medial outer region and the lateral outer region may comprise channels as described herein and have therefore a greater density, hardness and / or rigidity and therefore the midsole as an increased peripheral stability while having a central cushioning effect.

[0056] It may also be possible in some alternative embodiments, that the central region is not devoid of channels. In particular, the central region may comprise a smaller number of channels than each of the medial or lateral outer region. This may for example be achieved in that some of the channels are lateral channels or medial channels being configured as blind holes as described above, and other channels of the plurality of channels of the midsole extend completely through the midsole form the medial side to the lateral side and thus extend also through the central region.

[0057] In some embodiments, the lateral outer region and the medial outer region each have a greater rigidity and / or greater hardness than the central region.

[0058] In some embodiments, the midsole comprises at least one area being devoid of channels.

[0059] In particular, such an area may be one in which there are no channels between the base layer and the top layer of the midsole. Such areas may be 3-dimensional areas and extend in the transverse, longitudinal and vertical direction. In particular embodiments, such an area being devoid of channels may have a smaller rigidity and / or a smaller hardness than areas in which a channel is arranged, for example in which a channel is arranged between the base layer and the top layer of the midsole. As the skilled person understands, the differences in hardness may for example be determined by a Shore A or Shore D test in that the loading pin is in one measurement arranged in a first region, such as above a channels, and in a second measurement arranged in a second region being devoid of channels.

[0060] In some embodiments, at least one channel, or the majority (i.e. more than 50%), or even all of the channels, has in cross-section perpendicular to the transverse direction of the midsole (e.g. a cross-sectional plane being defined by the vertical and longitudinal direction) a cross-sectional shape with rounded edges. In particular embodiments, each rounded edge may have a minimum curve radius of at least 2.0 mm, particularly at least 1.5 mm, more particular at least 1.0 mm. Such rounded edges are beneficial for manufacturing a high quality midsole. As described herein, channels are typically produced by providing pins extending into a mold cavity. When the molten polymer composition is injected into the mold, it flows around the pins and thereby generates the channels. However, edges being defined by two angled planes often lead to stalling and thus undesired loss of quality during polymer injection and foaming. The rounded edges as described herein prevent or at least decrease stalling.

[0061] In some embodiments, at least one channel, or the majority (i.e. more than 50%), or even all of the channels, has in cross-section perpendicular to the transverse direction of the midsole (e.g. a cross-sectional plane being defined by the vertical and longitudinal direction) a shape of an ellipse or a polygon, such as hexagon, pentagon, tetragon or triangle, in particular tetragon. Preferably, the tetragon is an irregular tetragon. In certain embodiments, the irregular tetragon has two, in particular only two, parallel sides. These two parallel sides are typically the two longest sides of the tetragon and / or extend along the longitudinal direction. It may for example be possible that the two parallel sides are parallel to the top layer or bottom layer of the midsole. In some embodiments, at least one channel or the majority (i.e. more than 50%), or even all of the channels, has in cross section along longitudinal direction and perpendicular to transverse direction the shape of a parallelogram. Such a parallelogram may in particular have four sides, such as a first pair of opposing, in particular parallel, sides and a second pair of opposing, in particular parallel, sides. In certain embodiments, the inner angles between the sides of the parallelogram are different from 90°. That is, two of the inner angles are >90°, in particular > 95° or even >100° and two inner angles are <90°, in particular < 85°, or even < 80°. Thus, the channel has a shape of an oblique parallelogram.

[0062] In some embodiments, at least one channel, or the majority (i.e. more than 50%), or even all of the channels, has in cross-section along the transverse direction and perpendicular to the longitudinal direction a shape which comprises one or more steps and / or which comprises or is being made of a plurality of adjacent cylinder portions whit different diameters. In particular the diameter of the adjacent cylinders may decrease from the opening of the channel on the lateral or medial side towards the central region of the midsole.

[0063] In some embodiments, the channels each have a channel height, i.e. extension in the vertical direction, of 2 to 16 mm, in particular 4 to 8 mm.

[0064] In some embodiments, the channels each have a channel width, i.e. extension in the longitudinal direction, of 4 to 24 mm, in particular 8 to 16 mm.

[0065] In some embodiments, the channel width is greater than the channel height. For example, the ratio of the channel width : channel height may be between 1 :1 to 5:1 , in particular 1 :1 to 2:1.

[0066] In some embodiments, the total open area being defined as the sum of the open area on the medial and lateral side of the channel openings is smaller, in particular at least 1.5x, more particular at least 2x, even more particular at least 5x, smaller, than the total closed area of the midsole on the lateral and medial side. In some embodiments, the total channel wall surface being defined as the sum of the total surface area of the channel walls of all channels (or in other words the sum of the surface area exposed in the channels) is between 10 cm2to 310 cm2, in particular 110 cm2to 210 cm2. These values may for example apply for a men size LIS10 midsole. Since the channel walls are part of the outer sheathing layer, such a high total channel wall surface is beneficial as it significantly increases the lateral and medial stability of the midsole.

[0067] In some embodiments, the outer sheathing layer has a thickness (that is for example the distance between the outer environment of the midsole and the inner foamed core) of between 0.1 mm to 5 mm, in particular 0.1 mm to 2 mm.

[0068] In some embodiments, the outer sheathing layer has a thickness which is between 0.1% and 6.8%, in particular 0.1 % to 2.7% of the minimum total width of the midsole. The minimum total width of the midsole refers to the smallest distance between the lateral and the medial side of the midsole along the transverse direction. Typically, the minimum total width is arranged in the midfoot area of the midsole.

[0069] In some embodiments, the total volume of the outer sheathing layer may be between 1% to 25%, in particular between 2% to 20%, more particular 2% to 15%, of the volume of the inner foamed core.

[0070] In some embodiments, the inner foamed core may have an average cell size of 50 to 300 pm, in particular 50 to 200 pm, more particular 80 to 200 pm.

[0071] In some embodiments, the midsole is produced by supercritical injection foaming.

[0072] A second aspect of the invention refers to a method of producing a midsole, in particular a midsole as described herein, such as with respect to any of the embodiments of the first aspect of the invention.

[0073] The method may comprise forming a mixture of a supercritical fluid dissolved in a molten thermoplastic polymer. Typically, the supercritical fluid and the molten thermoplastic polymer form a single phase. For example, the supercritical fluid may be CO2 or N2 or mixtures thereof. It is understood that such supercritical fluids can act as blowing agents. For this purpose, the conditions, such as temperature and pressure, may for example be changed such that they transform from the supercritical state into the gaseous state which induces foaming upon pressure release. Typically, the mixture and preferably the whole method are devoid of chemical blowing agents. In certain embodiments, the mixture consists only of the supercritical fluid and the molten thermoplastic polymer.

[0074] The method may further comprise the step of injecting and foaming the mixture of supercritical fluid being dissolved in the molten thermoplastic material. For example, the formed mixture of the supercritical fluid being dissolved in the molten thermoplastic polymer is injected into a cavity of a mold via one or more injection gates of the mold.

[0075] The mold which may be used in any of the embodiments of the method described herein may for example comprise a peripheral mold portion which delimits, respectively defines the cavity. Further, the mold may comprise a plurality of pins which extend into the mold cavity. The pins may correspond to the channels being formed in the midsole. That is, their surface defines the shape of the channels, respectively, the pins serve as “negative” for the channels of the produced midsole.

[0076] Injecting the mixture into the cavity and foaming the mixture may be performed such that a midsole is obtained. This midsole may be the midsole according to any of the embodiments of the first aspect and may comprise an inner foamed core and an outer sheathing layer, which encompasses, in particular circumferentially encompasses the inner foamed core. In particular embodiments, the outer sheathing layer completely circumferentially encompasses the inner foamed core, for example such that the entire surface of the inner foamed core is covered by the outer sheathing layer. The midsole may further comprise a plurality of channels being defined by the plurality of pins that extend into the cavity. The outer sheathing layer of the midsole has greater density and / or greater rigidity and / or greater hardness than the inner foamed core. Optionally, the obtained midsole may then be removed from the cavity, i.e. after injecting and foaming the mixture.

[0077] The pins may for example be retractable pins. Thus, after foaming, the pins can be retracted from the obtained midsole. Alternatively, the pins may be removed together with the foamed midsole from the mold and only thereafter be removed from the midsole. In the latter embodiments, the pins are releasably arranged in the mold, respectively releasably connected to the peripheral mold portion.

[0078] In some embodiments, the pins and / or the peripheral mold portion comprise temperature control elements being configured to heat and / or cool the pins and / or the peripheral mold portion.

[0079] In certain embodiments, the pins and / or the peripheral mold portion are actively cooled during or after injecting the mixture of the supercritical fluid being dissolved in a molten thermoplastic polymer.

[0080] In some embodiments, the one or more injection gates are positioned such that they are perpendicular to the longitudinal direction of the midsole being obtained and / or perpendicular to the transversal direction of the midsole being obtained during injecting and foaming the mixture. Thus, the one or more injection gates are perpendicular to a horizontal plane being defined by the longitudinal and transversal direction.

[0081] In some embodiments, the pins have a cross-sectional shape with rounded edges. In particular embodiments, each rounded edge may have a minimum curve radius of at least 2.0 mm, particularly at least 1.5 mm, more particular at least 1.0 mm.

[0082] In some embodiments, the pins have in cross-section a shape of an ellipse or a polygon, in particular hexagon, pentagon, tetragon or triangle, in particular tetragon. Preferably, the tetragon is an irregular tetragon. In certain embodiments, the irregular tetragon has two, in particular only two parallel sides. These two parallel sides are typically the tow longest sides of the tetragon.

[0083] In some embodiments, the pins have in cross section a shape of a parallelogram. Such a parallelogram may in particular have four sides, such as a first pair of opposing, in particular parallel, sides and a second pair of opposing, in particular parallel, sides. In certain embodiments, the inner angles between the sides of the parallelogram are different from 90°. That is, two of the inner angles are >90°, in particular > 95° or even >100° and two inner angles are <90°, in particular < 85°, or even < 80°. Thus, the pins have a shape of an oblique parallelogram.

[0084] In some embodiments, injecting the mixture into the cavity comprises injecting the mixture into a pressurized cavity having a pressure being greater than atmospheric pressure. Typically, the pressure in the pressurized cavity may be between 10 to 200 bar, in particular 40 to 100 bar. For foaming, the pressure may then be at least partially released, for example via a pressure releasing valve of the mold.

[0085] In some embodiments, injecting and foaming the formed mixture is performed such that the midsole obtained has 0.9 to 1.1 times the weight, in particular the same weight, as a midsole being produced in the same cavity being devoid of any pins under otherwise identical conditions. Since a midsole with channels has a larger amount, e.g. surface area, of the outer sheathing layer having a greater density, the weight loss of the channels is essentially compensated by the generated additional outer sheathing layer of which the channel walls are part of.

[0086] In some embodiments, the outer sheathing is formed by contacting of the molten thermoplastic polymer with a surface of the peripheral mold portion and a surface of the plurality of pins.

[0087] In certain embodiments, the temperature of the surface of peripheral mold portion and the surface of the pins is smaller than the melting temperature of the thermoplastic polymer. For example, it may be at least 50 K to 200 K, more particular 100 K to 150 K lower than the melting temperature of the thermoplastic polymer. It certain embodiments, the temperature of the surface of peripheral mold portion and the surface of the pins is before injection between 0 °C and 40 °C, in particular 10 °C to 30 °C. In embodiments in which the pins and / or the peripheral mold portion comprise temperature control elements, this temperature may be actively maintained during injecting and foaming of the mixture. It may however also be possible to dispense with the temperature control elements. In such embodiments, thermal energy is transmitted from the mixture to the pins and / or peripheral mold portion, upon which their surface temperature rises. Thus in such embodiments, the pins and / or peripheral mold portion and / or the mold is / are devoid of temperature control elements.

[0088] Brief description of the figures

[0089] The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the invention described in the appended claims. The drawings are showing:

[0090] Fig. 1 a schematic cross-sectional view of a midsole according to an embodiment of the disclosure;

[0091] Fig. 2 a perspective view of a sectioned midsole according to another embodiment of the disclosure;

[0092] Fig. 3 a cross-sectional CT scan of a midsole according to another embodiment of the disclosure;

[0093] Fig. 4 a cross-sectional CT scan of a midsole according to another embodiment of the disclosure;

[0094] Fig. 5 a schematic cross sectional view of a channel as it can be realized in certain embodiments of the disclosure; Fig. 6 a force-deformation diagram obtained during an ASTM F 1976-13 standard test for impact attenuation of athletic shoe cushioning systems and materials;

[0095] Fig. 7a a chart illustrating the measured peak loads in multiples of g (9.81 m / s2) depending on the energy loss in the heel area according to the ASTM F 1976- 13 standard test for different midsoles;

[0096] Fig. 7b a schematic representation of the heel sections of midsoles VO, V1 and V2 tested in Fig. 7a;

[0097] Fig. 8a a chart illustrating the measured peak loads in multiples of g (9.81 m / s2) depending on the energy loss in the forefoot area according to the ASTM F 1976-13 standard test for different midsoles;

[0098] Fig. 8b a schematic representation of the forefoot sections of midsoles VO, V1 and V2 tested in Fig. 8a.

[0099] Exemplary embodiments

[0100] Fig. 1 shows a cross-sectional view of a midsole 1. It can be seen that midsole 1 comprises an inner foamed core 2 with a cell structure being visualized in Fig. 1. Inner foamed core 2 is encompassed and surrounded by outer sheathing layer 3. Outer sheathing layer may sheath, respectively cover, in this or any other embodiment described herein, the majority (i.e. more than 50%) or even all of the surface of the inner foamed core. Inner foamed core 2 and outer sheathing layer 3 form together an inherent material bonding connection without any additional or external adhesive, Thus, outer sheathing layer 3 and inner foamed core are integrally formed. Furthermore, outer sheathing layer 3 has a higher density than the inner foamed core 2 and is therefore stiffer and more rigid than inner foamed core 2. The thickness t of outer sheathing layer is also illustrated in Fig. 1.

[0101] Midsole 1 further comprises a top layer 7 and an oppositely arranged bottom layer 6.

[0102] Midsole 1 along the transverse direction T divided into a lateral outer region LR, medial outer region MR and central region CR arranged between lateral outer region and medial outer region. The midsole further comprises channels 4a and 4b which are both configured as blind-holes and do therefore not completely penetrate through the midsole. Channel 4a is a lateral channel which extends from an opening on the lateral side of midsole 1 against transverse direction T towards the central region CR. In contrast, channel 4b is a medial channel extending from an opening on the medial side of midsole 1 along transverse direction T towards central region CR. The channels 4a and 4b are delimited by channel walls 5a and 5b, which are part of outer sheathing layer 3.

[0103] It can be seen that due to these two channels 4a and 4b the amount of outer sheathing layer 3 in the lateral outer region and the medial outer region is higher as compared to the central region CR as the latter is devoid of channels. Since the outer sheathing layer 3 has a higher density and thus a higher rigidity, midsole 1 is softer in the central region where no channels are arranged and more stable in the lateral outer region and the medial outer region.

[0104] Channel 4a as in the shown cross-section along transverse direction T and perpendicular to the longitudinal direction a shape which is made from 3 adjacent cylinder portions. It can be seen that the outer cylinder portion commencing at the channel opening on the lateral side has a larger diameter than the next adjacent second cylinder portion, which has a larger diameter than the third (e.g. innermost) cylinder portion. Medial channel 4b comprises two such cylinder portions.

[0105] Fig. 2 shows a midsole 1 according to the invention in a partially sectioned perspective view. Midsole 1 comprises inner foamed core 2 being completely encompassed by outer sheathing layer 3, which has a greater density as compared to the inner foamed core 2. It can be seen that midsole 1 further comprises a plurality of channels 4a-c (only 3 channels are referenced for clarity purposes). As can be seen from the sectional view, at least some of the channels, such as channels 4a and 4b are configured as blind holes. Lateral channel 4a extends from its opening on the lateral side of midsole 1 towards the central region of the midsole, but does not extend into the central region and also not penetrate through the midsole. Vice versa, medial channel 4b extends from the medial side of midsole 1 towards the central region but does also not extend into the central region. The central region is devoid of channels. It can further be seen that also the channel walls are part of the outer sheathing layer 3. Since the outer sheathing layer has a higher density as the inner foamed core, the presence of such blind hole channels 4a and 4b provides for a reduced cushioning and increased stability in the lateral and medial region as compared to the central region, because a higher amount of the outer sheathing layer is present in the lateral and medial region due to the blind hole channels.

[0106] Fig. 3 shows a sectional X-ray view taken from a midsole according to the invention. The section is provided in a plane being defined by the transverse direction T and vertical direction V and being perpendicular to longitudinal direction L. The section is further taken through a channel 4c which is not a blind hole channel, but as can be seen, penetrates from the medial side to the lateral side of the midsole. The light area at the outer periphery of the midsole indicates the high density outer sheathing layer 3 which encompasses inner foamed core 2.

[0107] Fig. 4 shows also a sectional X-ray view similar to Fig. 3, however the section is taken in a plane being defined by the longitudinal direction L and vertical direction V and being perpendicular to transversal direction T. The section is taken in a forefoot area of a midsole according to another embodiment of the invention. In this embodiment, at least the section shown and / or the forefoot area is devoid of channels. Again, the lighter outer periphery indicates outer sheathing layer 3 having a higher density as inner foamed core 2.

[0108] Fig. 5 shows schematically a channel 4a as it can be embodied in some embodiments of the invention. Channel 4a has in cross section along longitudinal direction L (and vertical direction V) and perpendicular to transverse direction T the shape of a tetragon. In this particular embodiment, channel 4a has the shape of a parallelogram. Channel 4a has in the shown cross section a first pair of parallel sides 8 and 9 and a second pair of parallel sides 10 and 11 . Furthermore, the inner angles between the four sides, e.g. the four sides of the parallelogram are different from 90°. That is, two of the inner angles are >90°, in particular > 95° or even >100° and two inner angles are <90°, in particular < 85°, or even < 80°. Thus, the channel has a shape of an oblique parallelogram. Such channels are advantageous in terms of cushioning but also during production by injection foaming. The pins being used for producing such a channel have a shape being the negative of the shape of channel 4a. Due to the uneven parallelogram shape, stalling of the material during injection is avoided or at least reduced. This leads to a more uniformly foamed midsole.

[0109] Fig. 6 shows a force-deformation diagram obtained during an ASTM F 1976-13 standard test for attenuation of athletic shoe cushioning systems and materials. The test was performed using a mass of 8.5 kg and a nominal value of the total energy input of 5 J with a drop height of 50 mm. The upper curve shows the loading phase I and the lower curve the unloading phase u. Encircled is the peak loading force, meaning the point in the force deformation diagram at which the highest force and largest deformation is measured. The surface area EL between the curve of loading phase I and the curve of unloading phase u represents the energy loss, i.e. energy which does not push against the dropped mass during unloading, but which is lost. The surface area underneath the curve of the unloading phase u indicates the energy returned.

[0110] Fig. 7a shows a chart illustrating the measured peak loads depending on the energy loss in the heel area according to the ASTM F 1976-13 standard test for different midsoles V0, V1 and V2. Midsole V0 is devoid of channels, midsole V1 comprises one horizontal layer of channels and midsole V2 comprises two horizontal layers of channels (see Fig. 7b). The channels are all configured as through-going channels (that is they penetrate from the lateral side to the medial side of the midsole). The designation “a” (VO-a, V1-a, V2-a) refers to a midsole being made from the a first Pebax (polyether block amide) material, the designation “b” refers to a midsole being made from a second Pebax material (which is different than the Pebax materials used for the a-series and c-series), the designation “c” refers to a midsole being made from the a third Pebax material (which is different than the Pebax materials used for the a-series and b-series). It can be seen that the sole V2 having a two horizontal layers of channels show the highest peak load and thus are the most rigid midsoles, respectively have the least pronounced cushioning. In contrast, midsoles V0 having no channels at all have the lowest peak loads and therefore show the most pronounced cushioning of the midsoles tested. Thus, it is shown that channels increase the rigidity which is the opposite of how channels are normally used in channel cushioning systems.

[0111] Fig. 8a shows a chart illustrating the measured peak loads depending on the energy loss in the forefoot area according to the ASTM F 1976-13 standard test for different midsoles VO, V1 and V2. Midsoles VO, V1 and V2 are the same soles discussed with reference to Fig. 7a and b above. Fig. 8b shows the forefoot sections of the midsole VO, V1 and V2 as used for the tests shown in Fig. 8a. It can be seen from Fig. 8a that also in the forefoot area the VO midsoles have the lowest peak force. This illustrates that midsoles without channels have a more pronounced cushioning as compared to midsoles having channels. Without wishing to be bound to a theory, applicant surmises that this is due to the increased density of the outer sheathing layer. Since more channels result in higher amounts of outer sheathing layer, midsoles VO are softer as midsoles V1 , which are softer as midsoles V2. Again the double layer channel configuration of midsoles V2 shows a less pronounced cushioning as compared to the single layer channel configuration of midsoles V1.

[0112] List of designations

[0113] 1 midsole

[0114] 2 inner foamed core

[0115] 3 outer sheathing layer

[0116] 4a-c channels

[0117] 5a-c channel walls

[0118] 6 base layer

[0119] 7 top layer

[0120] 8 first side

[0121] 9 second side

[0122] 10 third side

[0123] 11 fourth side CR central region

[0124] L longitudinal direction

[0125] LR lateral outer region

[0126] MR medial outer region T transverse direction t thickness (of outer sheathing layer)

[0127] V vertical direction

Claims

Claims1. A midsole (1) for a shoe, the midsole (1) comprising an inner foamed core (2) and an outer sheathing layer (3) circumferentially encompassing the inner foamed core (2), wherein the midsole (1) further comprises a plurality of channels (4a, 4b, 4c), and wherein the outer sheathing layer (3) has a greater density than the inner foamed core (2).

2. The midsole (1) according to claim 1 , wherein the inner foamed core (2) and the outer sheathing layer (3) are made from the same material.

3. The midsole (1) according to claim 1 or 2, wherein the inner foamed core (2) and the outer sheathing layer (3) form a material bonding connection with each other.

4. The midsole (1) according to any of the previous claims, wherein the inner foamed core (2) and the outer sheathing layer (3) are integrally formed.

5. The midsole (1) according to any of the previous claims, wherein the channels (4a, 4b, 4c) are each delimited by a channel wall (5a, 5b, 5c) being part of the outer sheathing layer (3).

6. The midsole (1) according to any of the previous claims, wherein the plurality of channels (4a, 4b, 4c) comprises a plurality of channels (4c) extending completely through the midsole (1), in particular from a lateral to a medial side of the midsole (1).

7. The midsole (1) according to any of the previous claims, wherein the plurality of channels (4a, 4b, 4c) comprises a plurality of channels (4a, 4b) being configured as blind holes.

8. The midsole (1) according to claim 7, wherein the channels (4a, 4b) being configured as blind holes extend from an opening on the lateral side or from an opening on themedial side of the midsole (1) towards a central region (CR) of the midsole (1), in particular along a transverse direction (T) of the midsole (1).

9. The midsole (1) according to any of the previous claims, wherein the plurality of channels (4a, 4b, 4c) comprises a plurality of lateral channels (4a) being configured as blind holes and extending from an opening on the lateral side of the midsole (1) towards a central region (CR) of the midsole (1); and wherein the plurality of channels (4a, 4b, 4c) further comprises a plurality of medial channels (4b) being configured as blind holes and extending from an opening on the medial side of the midsole (1) towards a central region (CR) of the midsole (1).

10. The midsole (1) according to claim 9, wherein a portion of the inner foamed core (2) is arranged between one or more of the lateral channels (4a) and one or more of the medial channels (4b).

11. The midsole (1) according to claim 9 or 10, wherein the plurality of lateral channels (4a) are aligned with the plurality of medial channels (4b), in particular such that the lateral channels (4a) and medial channels (4b) extend towards each other.

12. The midsole (1) according to claim 9 or 10, wherein the plurality of lateral channels (4a) and the plurality of medial channels (4b) are offset to each other, in particular in a longitudinal direction (L) of the midsole (1) .

13. The midsole (1) according to any of claims 9 to 12, wherein the midsole (1) comprises a lateral outer region (LR), a medial outer region (MR) and a central region (CR) being arranged there between, wherein the lateral outer region (LR) extends between the lateral side of the midsole (19) and the central region (CR) and comprises the lateral channels (4a), and wherein the medial outer region (MR) extends between the medial side of the midsole (1) and the central region (CR) and comprises the medial channels (4b).

14. The midsole (1) according to claim 13, wherein the central region (CR) is devoid of channels.

15. The midsole (1) according to claim 13 or 14, wherein the lateral outer region (LR) and the medial outer region (MR) each have a greater rigidity and / or greater hardness than the central region (CR).

16. The midsole (1) according to any of the previous claims, wherein the midsole (1) comprises at least one area being devoid of channels, in particular at least one area in which there is no channel between a base layer (6) and a top layer (7) of the midsole (1), which has a smaller rigidity and / or smaller hardness than areas in which a channel is arranged between the base layer (6) and the top layer (7) of the midsole (1).

17. The midsole (1) according to any of the previous claims, wherein at least one channel (4a, 4b, 4c) has in cross-section perpendicular to the transverse direction (T) of the midsole (1) a cross-sectional shape with rounded edges.

18. The midsole (1) according to any of the previous claims, wherein at least one channel (4a, 4b, 4c) has in cross-section perpendicular to the transverse direction (T) of the midsole (1) a shape of a tetragon, in particular of an irregular tetragon, such as an irregular tetragon with two parallel sides.

19. The midsole (1) according to any of the previous claims, wherein the outer sheathing layer (3) has a thickness of 0.1 mm to 5 mm, in particular 0.1 mm to 2 mm.

20. The midsole (1) according to any of the previous claims, wherein the outer sheathing layer (3) has a thickness (t) which is between 0.1% and 6.8%, in particular 0.1 % to 2.7% of the minimum total width of the midsole (1).

21. The midsole (1) according to any of the previous claims, wherein the midsole (1) is produced by supercritical injection foaming.

22. A method for producing a midsole (1), in particular a midsole (1) according to any of the previous claims, the method comprising the steps: a. Forming a mixture of a supercritical fluid dissolved in a molten thermoplastic polymer; b. Injecting the mixture into a cavity of a mold via one or more injection gates, the mold comprising a peripheral mold portion delimiting the cavity, the mold further comprising a plurality of pins extending into the mold cavity; and foaming the mixture, wherein injecting and foaming is performed such that a midsole (1) is obtained which comprises an inner foamed core (2) and an outer sheathing layer (3) completely circumferentially encompassing the inner foamed core (2), the midsole (1) further comprising a plurality of channels (4a, 4b, 4c) being defined by the plurality of pins, and wherein the outer sheathing layer (3) has a greater density than the inner foamed core (2); c. Removing the obtained midsole (1) from the cavity.

23. The method according to claim 22, wherein the one or more injection gates are positioned such that they are perpendicular to the longitudinal direction (L) and / or the transversal direction (T) of the midsole (1) obtained in step b.

24. The method according to claim 22 or 23, wherein injecting the mixture into the cavity comprises injecting the mixture into a pressurized cavity having a pressure being greater than atmospheric pressure.

25. The method according to any of claims 22 to 24, wherein step b. is performed such that the midsole (1) obtained has 0.9 to 1.1 times the weight, in particular the same weight, as a midsole (1) being produced in the same cavity being devoid of any pins under otherwise identical conditions.

26. The method (1) according to any of claims 22 to 25, wherein the outer sheathing layer (3) is formed by contacting of the molten thermoplastic polymer with a surface of the peripheral mold portion and a surface of the plurality of pins.

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