WO2022053158A1

WO2022053158A1 - Foam dispenser

Info

Publication number: WO2022053158A1
Application number: PCT/EP2020/075621
Authority: WO
Inventors: Frank Zeiter
Original assignee: Kao Corp
Current assignee: Kao Corp
Priority date: 2020-09-14
Filing date: 2020-09-14
Publication date: 2022-03-17
Anticipated expiration: 2023-03-14

Abstract

The invention refers to a foam dispenser, which is in particular suitable for dispensing foam produced by mixing a foaming liquid and gas, in particular air. The invention also refers to a foam dispenser assembly, a vessel for storing a foamable aqueous composition and a method for forming foam using the foam dispenser.

Description

Foam dispenser

Technical field

The invention refers to a foam dispenser, which is in particular suitable for dispensing foam produced by mixing a foaming liquid and gas , in particular air . The invention also refers to a foam dispenser assembly, a vessel for storing a foamable aqueous composition and a method for forming foam using the foam dispenser .

Background art

In the technical field of foam dispensers , it is known to create non-aerosol foam using meshes . Meshes , however, have the drawback that the liquid may clogg the openings of the mesh, which again leads to the problem that the foam cannot be dispensed to its full amount or that the foam quality i s low .

JP 2011-251691 A refers to a foam discharge container having a container body with flexibility, the foamer cap attached to the mouth part of the container body, and the dip tube extending from the foamer can into the container body . An inner cylindrical portion has a first mesh at an opening end opposite to a dip tube and is connected to a bubble discharge path and a discharge port . A second mesh is further provided in the bubble discharge path between the first mesh and the discharge port .

Summary of the invention

The present invention provides a foam dispenser, comprising : a base portion, a first insert portion and a second insert portion, a plurality of mixing sections comprising an upstream mixing section and at least a further mixing section, wherein the mixing sections are at least partially formed by at least one of the base portion, the first insert portion and the second insert portion, respectively, and the mixing sections are in fluid communication with each other . The foam dispenser further comprises at least one liquid supply channel arranged to introduce a liquid in the upstream mixing section, and at least one gas supply channel , the gas supply channel being in fluid communication with the upstream mixing section and the at least one further mixing section via one or more through holes formed in the base portion and the second insert portion, respectively .

The foam dispenser of the present invention comprises a plurality of mixing sections wherein the liquid supply is provided from the base portion of the foam dispenser . Therefore , the liquid stream subsequently passes through the mixing sections with each of them having air supply . By using this configuration, meshes for foam development or foam dispersing can be avoided, and compositions comprising scrub particles can be dispensed without clogging .

Air supply can, for example , be provided by holes in the side walls . Air supply holes in the side walls can improve the dispensing operation, as they create air turbulences for dispersing the liquid stream .

According to a further aspect , a foam dispenser assembly is provided, which comprises the foam dispenser as defined above or in any of the claims referring to the foam dispenser, and liquid container, wherein the foam dispenser assembly i s preferably selected from a propellant foamer assembly, a pump foamer assembly and a squeeze foamer assembly, and more preferably is a pump foamer assembly .

According to a third aspect , a vessel for storing a foamable aqueous composition having attached to it a cap comprising the foam dispenser as defined above or in any of the claims referring to the foam dispenser .

As a fourth aspect , a method for forming foam using the foam dispenser as defined above or in any of the claims referring to the foam dispenser, or the foam dispenser assembly as defined above is provided, which method comprises the steps of : introducing liquid in the upstream mixing section and mixing the liquid with gas , in particular pressuri zed gas , wherein the liquid is forwarded to the at least one further mixing section and mixed with gas , in particular pressuri zed gas .

Brief description of the drawings

The drawings illustrate embodiments of the invention, and, together with the description, explain various embodiments of the disclosed subj ect matter . The drawings have not necessarily been drawn to scale , and the dimensions in the accompanying drawings are for illustration purposes .

Fig . 1 is a perspective of a foam dispenser according to a first embodiment of the invention .

Fig . 2a shows a configuration of a base portion of the foam dispenser according to the first embodiment .

Fig . 2b shows a modi fication of a base portion .

Fig . 3 shows a first insert portion of the foam dispenser according to the first embodiment .

Fig . 4 is a perspective of a foam dispenser according to a second embodiment of the invention .

Fig . 5 shows a first insert portion of the foam dispenser according to the second embodiment . Fig . 6 is a perspective of a foam dispenser according to a third embodiment of the invention .

Fig . 7 is a cross-sectional view of a foam dispenser assembly comprising a foam dispenser according to the invention .

Detailed description of the invention

The invention aims to a device for creating foam with improved foam quality while avoiding clogging problems .

With the foam dispenser of the invention, foam with high foam quality can be provided, while avoiding clogging of the foam dispenser or parts thereof . In particular, a mesh for creating foam can be avoided .

Hereafter, embodiments and variations of the present invention are described as illustrative examples . Variations and modi fications of speci fic aspects of the embodiments can be combined so as to provide further embodiments . Although the embodiments , modi fications and variations are not to be understood as limiting, but rather as examples to enhance the understanding of the invention, single features of the embodiments , modi fications and variations or a combination thereof can be used to speci fy the invention as defined in the appended claims .

Foam dispenser

The invention provides a foam dispenser, comprising : a base portion, a first insert portion and a second insert portion, a plurality of mixing sections comprising an upstream mixing section and at least a further mixing section, wherein the mixing sections are at least partially formed by at least one of the base portion, the first insert portion and the second insert portion, respectively, and the mixing sections are in fluid communication with each other . The foam dispenser further comprises at least one liquid supply channel arranged to introduce a liquid in the upstream mixing section, and at least one gas supply channel , the gas supply channel being in fluid communication with the upstream mixing section and the at least one further mixing section via one or more through holes formed in the base portion and the second insert portion, respectively .

According to an embodiment , the foam dispenser can provide an air-liquid ratio in the range o f 13-40 , preferably in the range of 13-32 .

The foam dispenser can, for example , be attached to a handheld container or bottle . The liquid is preferably charged in a container . The foam dispenser may preferably be a nonaerosol device .

First embodiment

The foam dispenser 10 comprises a base portion 20 , a first insert portion 30 and a second insert portion 40 .

The first insert portion 30 is adj acent to or supported by the base portion 20 , and the second insert portion 40 is adj acent to or supported by the first insert portion 30 . The base portion 20 , the first insert portion 30 and the second insert portion 40 are separate components which are assembled to form the foam dispenser 10 , and the base portion 20 , the first insert portion 30 and the second insert portion 40 can for example be formed by inj ection molding or by 3D-printing .

The foam dispenser 10 provides a plurality of mixing sections M1-M3 , each being configured to create foam or to further enhance partially foamed liquid . An upstream mixing section Ml is arranged at an upstream side where liquid to be foamed is introduced . Further downstream, a middle mixing section M2 is provided, followed by a downstream mixing section M3 . In the mixing sections M1-M3 , a liquid is mixed with gas , in particular air, to establish a foam, which can be dispensed from the foam dispenser 10 .

The mixing sections M1-M3 are at least partially foamed by at least one of the base portion 20 , the first insert portion 30 , and the second insert portion 40 , respectively, and the mixing portions M1-M3 are in fluid communication with each other .

The foam dispenser 10 further comprises a liquid supply channel 11 which is configured to introduce the liquid in the upstream mixing section Ml which is provided by a supply portion 24 of the base portion 20 and a lower side of the first insert portion 30 . Further , at least one gas supply channel (not shown) is provided, wherein the gas supply channel is in fluid communication with the upstream mixing section Ml and the downstream mixing section M3 via corresponding holes in the base portion 20 and the second insert portion 40 , respectively .

Fig . 2a provides a detailed view of the base portion 20 according to the first embodiment . The base portion 20 comprises a first portion 21 and a second portion 22 , which are distant to each other by distancing elements 23 . The first portion 21 is plate-shaped and has an outer circular circumferential face . The second portion 22 is ring-shaped and has an inner and outer circular circumferential face .

Between the distancing elements 22 , the supply portion 24 i s provided . The supply portion 24 is tubular-shaped, extends in an axial direction of the foam di spenser 10 and is in fluid communication with the liquid supply channel 11 so that the liquid can be introduced into the supply portion 24 . A space on an inner side of the supply portion 24 provides the upstream mixing section Ml .

The gas supply channel (not shown) is arranged so that gas , in particular air, is introduced in the space between the distancing elements 23 and the supply portion 24 .

The supply portion 24 comprises a plurality of first through holes 25 providing a fluid communication between an exterior side of the supply portion 24 and the inner side of the supply portion 24 . In the present embodiment , four first through holes 25 are provided in the supply portion 24 at equidistant distances in a circumferential direction . According to modi fications , les s than four first through holes or more than four first through holes are provided in the supply portion . According to further modi fications , the distances between the first through holes 25 may vary .

The first through holes 25 allow gas to be introduced into the supply portion 24 , thereby mixing the liquid supplied to the supply portion 24 via the liquid supply channel 11 with gas introduced through the first through holes 25 . Since the liquid is guided by the tubular-shaped supply portion 24 in the axial direction, gas introduced into the supply portion 24 interacts with the liquid on a radially outer side of the liquid stream . An impact of the gas with the liquid creates bubbles in the liquid .

According to the first embodiment , the first through holes 25 extend as twisted through holes , which have a rectangular cross-section . Consequently, the first through holes 25 allow entry of the gas in a direction which has a radial and a circumferential component , thereby leading to a swirl motion of the liquid stream .

According to a modi fication shown in Fig . 2b, a base portion 20a of the modi fication comprises , similar to the first embodiment , a first portion 21 a, a second portion 22a , distancing elements 23a and a supply portion 24a . Di f ferent to the first embodiment , the supply portion 24a comprises first through holes 25a which are formed as straight through holes having a rectangular cros s-section . Since the first through holes 25a extend as straight through holes through the supply portion 24a, the first through holes 25a allow entry of the gas in a radial direction .

Apart from the configuration of the first through holes 25a , the configuration of the base portion 20a of the modi fication is similar to the configuration of the base portion 20 of the first embodiment . Further, the base portion 20a can be arranged in a similar way in a foam dispenser, like the foam dispenser 10 of the first embodiment .

Although the first through holes 25 , 25a of the first embodiment and the modi fication have a rectangular crosssection, the through holes with round or oval cross sections provide further modi fications .

The first insert portion 30 is cup-shaped and is , in the assembled state , partially introduced into the supply portion 24 of the base portion 20 . In a bottom portion of the first insert portion 30 , an inlet opening 31 is provided which allows the liquid to pass from the supply portion 24 providing the upstream mixing section Ml to the inner side of the first insert portion 30 providing the middle mixing section M2 .

The first insert portion 30 comprises a body portion 33 , protruding portions 32 extending from the body portion 33 , and a rim 34 on a side of the body portion opposite to the protruding portions 32 . The protruding portions 32 are spaced in a circumferential direction so as to provide a gap between the adj acent protruding portions 32 . Further, the first insert portion 30 comprises channels 36 on an exterior side which are formed in the body portion 33 and extend in the axial direction of the foam dispenser 10 through the rim 34 . In use , gas is guided through the channels 36 to a space extending about the second insert portion 40 .

In the first insert portion 30 , the liquid which is already in a state in which the liquid is , at least in portions , foamed, is further mixed by turbulences created when introducing the liquid in the first insert portion 30 . Consequently, the liquid is further mixed in the middle mixing section M2 to enhance the foam properties and to create additional bubbles in the liquid . Thereby, the foam characteristic is enhanced .

The second insert portion 40 is in contact with the rim 34 of the first insert portion 30 and extends as a tubular member in the axial direction of the foam dispenser 10 . At a portion arranged in a distance from the first insert portion 30 , the second insert portion 40 comprises third through holes 45 , which are provided in a circumferential wall of the second insert portion 40 . The third through holes 45 have , according to the present embodiment , a rectangular shape ; however , according to further modi fications , the third through holes 45 may also have a round or oval cross-section .

The third through holes 45 are arranged to introduce gas , in particular air, from the space extending about the second insert portion 40 in the downstream mixing section M3 of the foam dispenser .

The tubular wall of the second insert portion 40 circumferentially encloses a space providing the downstream mixing section M3 . The liquid already foamed in the upstream mixing section Ml and the middle mixing section M2 is further mixed by introducing gas through the third through holes 45 . Consequently, the liquid is further foamed in the downstream mixing section M3 to enhance the foam properties .

Second embodiment

Fig . 4 shows a foam dispenser 10 ' according to a second embodiment . Parts or elements of the foam dispenser 10 ' of the second embodiment which are similar to corresponding parts or elements of the foam dispenser 10 of the first embodiment are marked with corresponding reference signs . In addition to the following explanations , reference is also made to the description of the first embodiment .

The foam dispenser 10 ' comprises a base portion 20 ' , a first insert portion 30 ' and a second insert portion 40 ' . The foam dispenser 10 ' according to the second embodiment di f fers from the foam dispenser 10 of the first embodiment in that the first insert portion 30 ' comprises second through holes 35 ' . Further, the second insert portion 40 ' comprises third through holes 45 ' which are arranged closer to the first insert portion 30 ' as compared to the third through holes 45 of the first embodiment .

Similar to the foam dispenser of the first embodiment , the foam dispenser 10 ' of the second embodiment comprises a plurality of mixing sections M1-M3 , namely an upstream mixing section Ml , a middle mixing section M2 and a downstream mixing section M3 . The mixing sections are in fluid communication with each other .

At an upstream side , the foam dispenser 10 ' comprises a liquid supply channel 11 ' configured to introduce a liquid in the upstream mixing section Ml , which is provided by a supply portion 24 ' of the base portion 20 ' and a lower side of the first insert portion 30 ' . Further, at least one gas supply channel (not shown) is provided, wherein the gas supply channel is in fluid communication with the upstream mixing section Ml, the middle mixing section M2 and the downstream mixing section M3 via corresponding holes in the base portion 20' , the first insert portion 30' and the second insert portion 40' , respectively.

The base portion 20' comprises first through holes 25' which extend through the supply portion 24' of the base portion 20' circumferentially surrounding a part of the first insert portion 30' . Similar to the first embodiment or the modification of the base portion of the first embodiment, the first through holes 25' can be twisted through holes or straight through holes. Further, the first through holes 25' may have a rectangular, round or oval cross section.

The first through holes 25' allow gas to be introduced into the supply portion 24' , thereby mixing the liquid supplied to the supply portion 24' via the liquid supply channel 11' with gas introduced through the first through holes 25' . Since the liquid is guided by the tubular-shaped supply portion 24' in the axial direction, gas introduced into the supply portion 24' interacts with the liquid on a radially outer side of the liquid stream. An impact of the gas with the liquid creates bubbles in the liquid.

The first insert portion 30' is cup-shaped and is, in the assembled state, partially introduced into the supply portion 24' of the base portion 20' . In a bottom portion of the first insert portion 30' , an inlet opening 31' is provided which allows the liquid to pass from the supply portion 24' providing the upstream mixing section Ml to the inner side of the first insert portion 30' providing the middle mixing section M2.

The first insert portion 30' comprises a body portion 33' , protruding portions 32' extending from the body portion 33' , and a rim 34' on a side of the body portion opposite to the protruding portions 32' . The protruding portions 32' are spaced in a circumferential direction so as to provide a gap between the adjacent protruding portions 32' .

Further, the first insert portion 30' comprises channels 36' on an exterior side which are formed in the body portion 33' and extend in the axial direction of the foam dispenser 10' through the rim 34' . In use, gas is guided through the channels 36' to a space extending about the second insert portion 40' .

Different to the first insert portion 30 of the first embodiment, the first insert portion 30' of the second embodiment additionally comprises second through holes 35' which are arranged so that gas is introduced in the middle mixing section M2. The second through holes 35' are in particular in fluid communication with the channels 36' so that a portion of the gas guided to the space extending about the second insert portion 40' is branched off. The second through holes 35' are arranged in an upper section of the first insert portion 30' , in particular adjacent to a rim of the first insert portion 30' . The second through holes 35' have a round shape in cross-section and are arranged in equidistant positions in a circumferential direction of the first insert portion 30' .

The liquid which is, when introduced in the middle mixing section M2, already in a state in which the liquid is, at least in portions, foamed, further mixed with gas introduced via the second through holes 35' , thereby creating additional bubbles in the liquid and enhancing the foam characteristic.

In addition, the foam dispenser 10' comprises third through holes 45' which are provided in a circumferential wall of the second insert portion 40' . The third through holes 45' may have a rectangular, round or oval cross section. The third through holes 45' are arranged to introduce gas, in particular air, from the space extending about the second insert portion 40 ' in the downstream mixing section M3 of the foam dispenser .

As compared to the third through holes 45 of the first embodiment , the third through holes 45 ' of the second embodiment are arranged relatively close to the rim 34 ' of the first insert portion 30 ' .

Consequently, during operation of the foam dispenser 10 ' , a liquid is introduced from the liquid supply channel 11 ' to the upstream mixing section Ml and mixed in this section with gas , the gas being introduced via the first through holes 25 ' . The liquid, which is already in parts in a foamed state , is further introduced through the opening 31 ' to the first insert portion 30 ' which provides the middle mixing section M2 . In the middle mixing section M2 , further gas i s introduced and mixed with the liquid introduced into the middle mixing section M2 . At a downstream side of the middle mixing section M2 , additional gas is introduced in the downstream mixing section M3 , thereby adding further gas to the liquid .

Third embodiment

A foam dispenser 10 ' ' according to a third embodiment is shown in Fig . 6 . Parts or elements of the foam dispenser 10 ' ’ of the third embodiment which are similar to corresponding parts or elements of the foam dispenser 10 of the first embodiment and/or the foam dispenser 10 ' of the second embodiment are marked with corresponding reference signs . In addition to the following explanations , reference is also made to the description of the first and second embodiment .

The foam dispenser 10 ' ’ compri ses , similar to the foam dispenser of the first and second embodiment , a base portion 20 ' ’ , a first insert portion 30 ' ’ and a second insert portion 40' ' . The base portion 20' ' , the first insert portion 30' ' and the second insert portion 40' ’ are separate components which are assembled to form the foam dispenser 10' ’ .

A plurality of mixing sections M1-M3 are formed in the foam dispenser 10' ’ , in particular an upstream mixing section Ml, a middle mixing section M2, and a downstream mixing section M3. These mixing sections are in fluid communication with each other. Further, a liquid supply channel 11' ' is provided, which is configured to introduce a liquid in the upstream mixing section Ml . At least one gas supply channel (not shown) is provided, wherein the gas supply channel is in fluid communication with the upstream mixing section Ml, the middle mixing section M2 and the downstream mixing section M3 via corresponding holes in the base portion 20' ’ , the first insert portion 30' ’ and the second insert portion 40' ’ , respectively .

The base portion 20' ' is similar to the base portion of the first and second embodiment. The base portion 20' ’ comprises a first portion 21' ’ and a second portion 22’ ’ , which are distant to each other by distancing elements 23' ’ . The first portion 21' ’ is plate-shaped and has an outer circular circumferential face. The second portion 22’ ’ is ring-shaped and has an inner and outer circular circumferential face.

Between the distancing elements 22' ' , a supply portion 24' ' is provided. The supply portion 24' ’ is tubular-shaped, extends in an axial direction of the foam dispenser 10' ’ and is in fluid communication with the liquid supply channel 11' ' so that the liquid can be introduced into the supply portion 24' ' . A space on an inner side of the supply portion 24' ’ provides the upstream mixing section Ml .

The supply portion 24' ’ comprises a plurality of first through holes (not shown) providing a fluid communication between an exterior side of the supply portion 24' ' and the inner side of the supply portion 24' ’ .

The first insert portion 30' ’ is cup-shaped and is, in the assembled state, partially introduced into the supply portion 24' ’ of the base portion 20. In a bottom portion of the first insert portion 30' ’ , an inlet opening 31' ’ is provided which allows the liquid to pass from the supply portion 24' ’ providing the upstream mixing section Ml to the inner side of the first insert portion 30 providing the middle mixing section M2.

The first insert portion 30' ’ comprises a body portion 33' ’ , protruding portions 32' ’ extending from the body portion 33' ’ , and a rim 34' ’ on a side of the body portion opposite to the protruding portions 32. The protruding portions 32' ’ are spaced in a circumferential direction so as to provide a gap between the adjacent protruding portions 32' ' . Similar to the second embodiment, the first insert portion 30' ’ comprises second through holes 35' ’ .

Further, the first insert portion 30' ' comprises channels 36' ' on an exterior side which are formed in the body portion 33' ' and extend in the axial direction of the foam dispenser 10' ’ through the rim 34' ’ . In use, gas is guided through the channels 36' ’ to a space extending about the second insert portion 40' ’ . The second through holes 35' ’ are in fluid communication with the channels 36' ’ so that a portion of the gas guided to the space extending about the second insert portion 40' ’ is branched off.

The second insert portion 40' ’ is similar to the second insert portion 40 according to the second embodiment. The second insert portion 40' ’ comprises third through holes 45' ’ , which are arranged in a distance from the first insert portion 30' ’ . During operation of the foam dispenser 10' ' , a liquid is introduced from the liquid supply channel 11' ' to the upstream mixing section Ml and gas is introduced via the first through holes 25' ’ to the upstream mixing section Ml. The liquid, which is already in parts in a foamed state, is further introduced to the middle mixing section M2. In the middle mixing section M2, further gas is introduced and mixed with the liquid introduced into the middle mixing section M2. The liquid is further guided to the downstream mixing section M3, where additional gas is added to the liquid.

Foam dispenser assembly

In another aspect, a foam dispenser assembly 100' ’ ’ with a foam dispenser 10' ’ ’ is provided. A container with liquid can be attached to the foam dispenser assembly 100' ’ ’ . Although the foam dispenser assembly 100' ’ ’ is, according to the present embodiment a pump foamer assembly, the foam dispenser assembly can be selected from a propellant foamer assembly and a squeeze foamer assembly.

The foam dispenser assembly 100' ’ ’ can comprise an aqueous composition for cleansing of skin and/or hair, comprising

- one or more foaming surf actant ( s ) ,

- one or more particles insoluble in water at 25°C and under atmospheric pressure having a number of average particle size in the range of 1pm to 250pm determined by static light scattering. With this configuration, the foam produced by the foam dispenser has in addition an enhanced cleaning effect.

The foam dispenser 10' ’ ’ comprises, similar to the first to third embodiment, a first insert portion 30' ’ ’ adjacent to or supported by a base portion 20' ’ ’ and a second insert portion 40' ’ ’ adjacent to or supported by the first insert portion 30. The base portion 20' ’ ’ and the first insert portion 30' ’ ’ are similar to the first embodiment. With respect to details of the base portion 20' ’ ’ and the first insert portion 30' ’ ’ , reference is made to the explanations of the first embodiment .

The second insert portion 40 ' ’ ’ is in contact with the first insert portion 30 ' ’ ’ and extends as a tubular member in the axial direction of the foam dispenser 10 ' ’ ’ . The second insert portion 40 ' ’ ’ comprises third through holes 45 ' ’ ’ in various distances from the first insert portion 30 ' ’ ’ , which are provided in a circumferential wall of the second insert portion 40 ' ’ ’ . Stating it di f ferently, the second insert portion 40 ' ’ ’ comprises third through holes 45 ' ’ ’ at various levels . The third through holes 45 ' ’ ’ have a rectangular shape , but may also have a round or oval cross-section .

With this configuration, the foam dispenser 10 ' ' ' provides a plurality of mixing sections M1-M3 , each being configured to create foam or to further enhance partially foamed liquid .

According to a further aspect of the invention, a vessel for storing a foamable aqueous composition is provided, which comprises a cap with the foam dispenser according to one or more of the previously mentioned aspects .

Method for forming foam

As another embodiment , the invention provides a method for forming foam . According to the method, a liquid is introduced in the upstream mixing section Ml , where the liquid is mixed with gas , in particular pressuri zed gas . Further, the liquid is forwarded to the at least one further mixing section M2 , M3 and mixed with gas , in particular pressuri zed gas .

According to an embodiment , the liquid, which is already in parts in a foamed state , is further introduced to the middle mixing section M2 providing a further mixing section . In the middle mixing section M2 , the liquid is further mixed . At a downstream side of the middle mixing section M2 , additional gas is introduced in the downstream mixing section M3 , thereby adding further gas to the liquid .

In another embodiment , the liquid, which is already in parts in a foamed state , is further introduced to the middle mixing section M2 providing a further mixing section . In the middle mixing section M2 , further gas is introduced and mixed with the liquid introduced into the middle mixing section M2 . The liquid is further guided to the downstream mixing section M3 as a yet further mixing section, where additional gas is added to the liquid .

Claims

Foam dispenser ( 10 — 10 ' ' ' ) , comprising: a base portion (20-20' ' ' ) , a first insert portion (30-

30" ' ) and a second insert portion (40-40'" ) , a plurality of mixing sections (M1-M3) comprising an upstream mixing section (Ml) and at least a further mixing section (M2, M3) , wherein the mixing sections (M1-M3) are at least partially formed by at least one of the base portion (20-20'" ) , the first insert portion (30-30'" ) and the second insert portion (40-40'" ) , respectively, and the mixing sections (M1-M3) are in fluid communication with each other, at least one liquid supply channel (11-11'" ) arranged to introduce a liquid in the upstream mixing section (Ml ) , and at least one gas supply channel, the gas supply channel being in fluid communication with the upstream mixing section (Ml) and the at least one further mixing section (M2, M3) via one or more through holes formed in the base portion (20-20' ' ' ) and the second insert portion (40-40'" ) , respectively. Foam dispenser (10-10'" ) according to claim 1, wherein the first insert portion (30-30'" ) and the second insert portion (40-40'" ) are separate components, wherein it is preferred that the first insert portion (30-30' ’ ’ ) and the second insert portion (40-40' ' ' ) are formed by injection molding or by 3D-printing. Foam dispenser according to any of the preceding claims, wherein the first insert portion (30-30' ' ' ) is adjacent or in contact with the base portion (20-20' ' ' ) , and the second insert portion (40-40' ' ' ) is adjacent or in contact with the first insert portion (30-30' ' ' ) . Foam dispenser according to any of the preceding claims, wherein the further mixing section (M2, M3) comprises a middle mixing section (M2) and a downstream mixing section (M3 ) , the middle mixing section (M2) being formed by a circumferential wall of the first insert portion (30— 30' ' ' ) and the downstream mixing section (M3) being formed by a circumferential wall of the second insert portion (40-40' ' ' ) . Foam dispenser according to any of the preceding claims, wherein the through holes formed in the base portion (20-20' ' ' ) and the second insert portion (40-40' ' ' ) , respectively, are distanced in an axial direction. Foam dispenser (10-10' ' ' ) according to any of the preceding claims, wherein the first insert portion (SOSO' ' ' ) is arranged between the upstream mixing section (Ml) and the further mixing section (M2, MS) . Foam dispenser (10-10' ' ' ) according to any of the preceding claims, wherein the one or more through holes are arranged so that air, preferably pressurized air, passes through the one or more through holes from a radial outer portion to a radial inner portion. Foam dispenser (10-10' ' ' ) according to any of the preceding claims, wherein the one or more through holes comprise one or more first through holes (25-25' ' ' ;

25a) , wherein the one or more first through holes (ISIS' ' ' ; 25a) are formed in the base portion (20-20' ' ' ) . Foam dispenser (10' ' ' ) according to claim 8, wherein the first through holes (25-25' ' ' , 25a) extend as twisted through holes or straight through holes through a portion of the base portion (20-20' ' ' ) circumferentially surrounding a part of the first insert portion (30-30' ' ' ) . Foam dispenser (10' ' ' ) according to claim 8 or 9, wherein the one or more first through holes (25-25' ' ' ; 25a) have a rectangular, round or oval cross-section. Foam dispenser (10' -10' ' ' ) according to any of the preceding claims, wherein the one or more through holes comprise one or more second through holes (35' -35' ' ' ) , wherein the second through holes (35' -35' ' ' ) are formed in the first insert portion (30'— 30' ' ' ) . Foam dispenser (10-10' ' ' ) according to any of the preceding claims, wherein the one or more through holes comprise one or more third through holes (45-45' ' ' ) , wherein the one or more third through holes (45-45' ' ' ) are provided in a circumferential wall of the second insert portion (40-40' ' ' ) .

Foam dispenser (10' ' ' ) according to claim 12, wherein the one or more third through holes (45-45' ' ' ) have a rectangular, round or oval cross-section. Foam dispenser (10' ' ' ) according to claim 12 or 13, comprising a plurality of groups of the third through holes (45' ' ' ) which are arranged in a circumferential wall of the second insert portion (40-40' ' ' ) , wherein 22 the groups of third through holes ( 45 ' ' ' ) are spaced apart in an axial direction of the second insert portion (40-40' " ) . Foam dispenser (10-10' ' ' ) according of the preceding claims, wherein the foam dispenser is configured to provide an air-liquid ratio in the range of 13-40, preferably in the range of 13-32. Foam dispenser (10-10' ' ' ) according to any of the preceding claims, wherein the first insert portion (30— 30' ' ' ) is cup-shaped (30-30' ' ' ) , wherein it is preferred that a cross-sectional area of the first insert portion (30-30' ' ' ) increases in a downstream direction. Foam dispenser (10-10' ' ' ) according to any of the preceding claims, wherein the second insert portion (40— 40' ' ' ) is tubular-shaped, wherein it is preferred that a cross-sectional area of the second insert portion (40— 40' ' ' ) is constant in a downstream direction. Foam dispenser assembly, comprising the foam dispenser (10-10' ' ' ) according to any of the preceding claims and liquid container, wherein the foam dispenser assembly is preferably selected from a propellant foamer assembly, a pump foamer assembly and a squeeze foamer assembly, and more preferably is a pump foamer assembly. A vessel for storing a foamable aqueous composition having attached to it a cap comprising the foam dispenser (10-10' ' ' ) as defined in claims 1 to 17. Method for forming foam using the foam dispenser (10— 10' ' ' ) according to any one of claims 1 to 17 or the foam dispenser assembly according to claim 18, 23 introducing liquid in the upstream mixing section (Ml) and mixing the liquid with gas, in particular pressurized gas, wherein the liquid is forwarded to the at least one further mixing section (M2, M3) and mixed with gas, in particular pressurized gas.