WO2025021601A1

WO2025021601A1 - One-size-fits-all personal care device comprising auxetic components

Info

Publication number: WO2025021601A1
Application number: PCT/EP2024/070207
Authority: WO
Inventors: Guido Antonius Theodorus ADRIAENSEN
Original assignee: Koninklijke Philips NV
Current assignee: Koninklijke Philips NV
Priority date: 2023-07-26
Filing date: 2024-07-17
Publication date: 2025-01-30
Anticipated expiration: 2026-01-26

Abstract

A personal care device (10), comprising a structure (16) having an inner wall (42) and an outer wall (40), the inner wall and outer wall connected to a base (44), wherein the base, inner wall, and outer wall define a cavity (60) configured to receive a plurality of teeth of a user, and wherein at least a portion of the base is composed of an auxetic material.

Description

ONE-SIZE-FITS-ALL PERSONAL CARE DEVICE COMPRISING AUXETIC COMPONENTS

Field of the Invention

[0001] The present disclosure is directed generally to a personal care device comprising auxetic components configured to enable a one-size-fits-all system.

Background

[0002] Proper tooth brushing technique, including length and coverage of brushing, helps ensure long-term dental health. Many dental problems are experienced by individuals who either do not regularly brush their teeth or who do so inadequately. Among individuals who do regularly brush, improper brushing habits can result in poor coverage of brushing and thus surfaces that are not adequately cleaned.

[0003] To facilitate proper brushing or mouth care technique, some personal care devices are designed to be one-size-fits-all mouth care devices or systems. There are many reasons to offer one-size-fits-all mouth care devices or systems such as toothbrushes, teeth whitening devices, and mouthguards, among other such devices. For example, this simplifies the manufacturing process and reduces costs. Additionally, one-size-fits-all mouth care devices or systems prevent customers from purchasing a device that many not properly fit their mouth.

[0004] However, one of the many difficulties in creating a one-size-fits-all solution is the fact that there is a very large variability in jaw lengths and teeth sizes within the intended user population. It has been observed that a minimum user stroke of roughly one tooth width is preferred for all jaw lengths. Another challenge is to ensure proper cleaning using a one-size-fits-all solution. It has been observed that the cleaning performance of a mouthpiece is significantly influenced by the amount of clamping (i.e., compression) of the bristles. When a mouthpiece is designed for the average jaw or tooth size, the amount of clamping could be too small for small-sized jaws, with the risk of consistently missing spots during a brushing session thus resulting in poor cleaning and bad oral health. Similarly, for large-sized jaws, the amount of clamping could become too large, which over-compresses the bristles and results in damage to the brush head and possibly discomfort for the user due to the amount of force exerted on the gums.

[0005] In contrast, when the mouthpiece is designed for the smallest jaw in the intended population, users with a medium or large jaw must apply a very large user motion to reach all teeth, and the amount of clamping for average and large jaw or tooth size would be too large. This introduces new challenges, since the brushing time on each tooth is reduced which reduces the cleaning, and the performance becomes highly dependent on the user technique which reduces one of the main benefits of a one-size-fits-all mouthpiece. Yet another challenge for one-size-fits-all mouthpieces is that sections of the mouthpiece designed to clean the user’s front teeth might be positioned more towards canine or even premolars in large jaws, for which they are not designed, leading to improper cleaning.

Summary of the Invention

[0006] Accordingly, there is a continued need in the art for one-size-fits-all personal care devices and systems that enable high performance cleaning, whitening, or protection of the teeth while overcoming the many problems of existing one-size-fits-all personal care devices and systems.

[0007] The present disclosure is directed to inventive methods and systems for a personal care device comprising auxetic components. Applied to a mouth care device, for example, the inventive methods and systems enable a one-size-fits-all system for high performance cleaning, whitening, or protection of the teeth. The device includes a structure having an inner wall and an outer wall connected to a base and defining a channel that fits the user’s teeth. For example, the structure may be U-shaped or curved for an entirety of the user’s upper or lower teeth, or for only a portion of the user’s upper or lower teeth. At least some of the base, and optionally more of the device, is composed of an auxetic material.

[0008] Generally in one aspect, a personal care device is provided. The device includes a structure having an inner wall and an outer wall, the inner wall and outer wall connected to a base, wherein the base, inner wall, and outer wall define a cavity configured to receive a plurality of teeth of a user, and wherein at least a portion of the base is composed of an auxetic material. [0009] According to an embodiment, the structure is U-shaped.

[0010] According to an embodiment, at least a portion of the structure is curved.

[0011] According to an embodiment, wherein the inner wall and the outer wall comprise a plurality of bristles extending into the cavity, the plurality of bristles configured to interact with the plurality of teeth of the user and/or gums of the user.

[0012] According to an embodiment, the inner wall and/or the outer wall comprises a plurality of spaced panels.

[0013] According to an embodiment, the inner wall and outer wall are perpendicular to the base.

[0014] According to an embodiment, the inner wall and outer wall are connected to the base with a small angle.

[0015] According to an embodiment, the personal care device is a one-size-fits-all device.

[0016] According to an embodiment, the personal care device is a toothbrush, a flossing device, or a tooth whitening device.

[0017] According to an embodiment, the personal care device is a mouthguard.

[0018] According to another aspect of the invention is a toothbrush. The toothbrush includes a brush head member comprising a care component, the care component comprising a structure having an inner wall and an outer wall, the inner wall and outer wall connected to a base, wherein the base, inner wall, and outer wall define a cavity configured to receive a plurality of teeth of a user, and wherein at least a portion of the base is composed of an auxetic material; wherein at least a portion of the structure is curved; and wherein the inner wall and the outer wall comprise a plurality of bristles extending into the cavity, the plurality of bristles configured to interact with the plurality of teeth of the user and/or gums of the user.

[0019] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. [0020] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

Brief Description of the Drawings

[0021] In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0022] FIG. 1 is a schematic representation of a personal care device, in accordance with an embodiment.

[0023] FIG. 2 is a schematic representation of a mouthguard, in accordance with an embodiment.

[0024] FIG. 3 is a schematic representation of a care component of a personal care device, in accordance with an embodiment.

[0025] FIG. 4A is a schematic representation of a non-auxetic material, in accordance with an embodiment.

[0026] FIG. 4B is a schematic representation of an auxetic material, in accordance with an embodiment.

[0027] FIG. 5 is a schematic representation of a care component of a personal care device, in accordance with an embodiment.

[0028] FIG. 6 schematic representation of a care component of a personal care device, in accordance with an embodiment.

[0029] FIG. 7 schematic representation of a care component of a personal care device, in accordance with an embodiment.

[0030] FIG. 8 is a graph of force applied by a non-auxetic material-based device versus an auxetic material-based device, in accordance with an embodiment. Detailed Description of Embodiments

[0031] The present disclosure describes various embodiments of a one-size-fits-all mouth care device and system. More generally, Applicant has recognized and appreciated that it would be beneficial to provide a one-size-fits-all device or system for high performance cleaning, whitening, or protection of the teeth. Accordingly, the devices and systems described or otherwise envisioned herein provide a one-size-fits-all personal care device. The device includes a structure having an inner wall and an outer wall connected to a base and defining a channel that fits the user’s teeth. For example, the structure may be U-shaped or curved for an entirety of the user’s upper or lower teeth, or for only a portion of the user’s upper or lower teeth. At least some of the base, and optionally more of the device, is composed of an auxetic material.

[0032] The embodiments and implementations disclosed or otherwise envisioned herein can be utilized with any personal care device. Examples of suitable personal care devices include a toothbrush such as a Philips Sonicare® toothbrush or other toothbrush device or system (manufactured by Koninklijke Philips Electronics, N. V.), a tooth whitening device, a mouthguard, or other personal care device. However, the disclosure is not limited to these enumerated devices, and thus the disclosure and embodiments disclosed herein can encompass any personal care device.

[0033] Referring to FIG. 1, in one embodiment, a personal care device 10 is provided that includes a handle or body portion 12 and a brush head member 14. Head member 14 includes at its end remote from the body portion a care component 16. In this embodiment, care component 16 is a U-shaped device configured to fit around the top and/or bottom portion of the user’s teeth or the user’s teeth and gums. The body portion 12 typically comprises a housing, at least a portion of which is hollow, to contain components of the personal care device. The personal care device 10 can be a manual toothbrush or other personal care device such as a tooth whitening device.

[0034] According to another embodiment, head member 14 is mounted so as to be able to move relative to the body portion 12. The movement can be any of a variety of different movements, including vibrations or rotation, among others. Alternatively, the personal care device 10 is a manual device with electrical components, but the brush head is not mechanically actuated by an electrical component.

[0035] According to an embodiment, the body portion 12 can comprise a drivetrain assembly with a motor 22 for generating movement, and a transmission component or drivetrain shaft 24, for transmitting the generated movements to brush head member 14. For example, the drivetrain comprises a motor or electromagnet(s) 22 that generates movement of a drivetrain shaft 24, which is subsequently transmitted to the brush head member 14. The drivetrain can include components such as a power supply, an oscillator, and one or more electromagnets, among other components. In this embodiment the power supply comprises one or more rechargeable batteries, not shown, which can, for example, be electrically charged in a charging holder in which personal care device 10 is placed when not in use. According to another embodiment, body portion 12 comprises a pneumatic drivetrain assembly with a motor 22 for generating the movement, and a transmission component 24, such as a tube. Many other embodiments are possible.

[0036] According to one embodiment, brush head member 14 is mounted to the drivetrain shaft 24 so as to be able to vibrate relative to body portion 12. The brush head member 14 can be fixedly mounted onto drivetrain shaft 24, or it may alternatively be detachably mounted so that brush head member 14 can be replaced with a different brush head member for different operating features, or when the bristles or another component of the brush head are worn out and require replacement. Body portion 12 is further provided with a user input 26 to activate and de-activate the drivetrain. The user input 26 allows a user to operate the personal care device 10, for example to turn the device on and off. The user input 26 may, for example, be a button, touch screen, or switch.

[0037] Care component 16 can be a variety of different personal care components, such as a teeth cleaning or tooth whitening component. For example, care component 16 may be a brush head (as shown in FIG. 1), it may be a tooth whitening component, it may be a water jetting or flossing component, or it may be another extension for a personal care device. The care component may be a removable or interchangeable member utilized with a personal care device. Although described herein in conjunction with a brush head member, the disclosure and embodiments disclosed herein can encompass any personal care device. The head member can also be associated with a specific user. For example, a household comprising multiple people may comprise a different head member for each person.

[0038] Referring to FIG. 2, according to another embodiment, the personal care device 10 may be a mouthguard that is designed to fit over at least a portion of the user’s teeth. The portion may be a portion of the user’s upper teeth, a portion of the user’s lower teeth, a portion of both the user’s upper teeth and lower teeth, or all of the user’s teeth. The mouth guard may be utilized for a variety of purposes including protection during sports, preventing teeth grinding, and alleviating snoring or sleep apnea. As described or otherwise envisioned herein, the mouthguard is a one-size- fits-all mouthguard. According to another embodiment, the mouthguard can be shaped to the plurality of teeth of the user.

[0039] Referring to FIG. 3, in one embodiment, is a three-dimensional representation of the boxed region from FIG. 1, showing a portion of the care component 16 of the personal care device. The care component may be U-shaped as shown in FIG. 1. However, the component may be less than an entire U, and thus may be only half of a U, less than half (i.e., curved), or more than half.

[0040] According to an embodiment, the care component 16 comprises an outer wall 40 which is positioned between (i) the user’s teeth or the user’s teeth and gums and (ii) the user’s cheek. The care component 16 also comprises an inner wall 42 which is positioned between (i) the user’s teeth or the user’s teeth and gums and (ii) the inner portion of the user’s mouth, including but not limited to the tongue.

[0041] The care component also comprises a base 44 which is positioned between the user’s upper and lower teeth. The base 44 is connected on one side to the outer wall 40 and on another side to the inner wall 42. According to an embodiment, the outer wall 40 and/or the inner wall 42 are connected to the base 44 with a right angle such that the walls are perpendicular to the flat plane of the base. Alternatively, one or more of the outer wall 40 and the inner wall 42 may be connected to the base at an angle, either greater than or less than 90 degrees. For example, according to one embodiment, the outer wall 40 and/or the inner wall 42 are connected to the base 44 with a small angle of approximately 10 degrees, although smaller and larger angles are possible. For example, the outer wall 40 and/or the inner wall 42 can be connected to the base 44 with an angle of 5 degrees, 10 degrees, 15 degrees, 20 degrees, and variations thereof as well as smaller and larger angles. The angling of the outer wall 40 and/or the inner wall 42 can be inward relative to the base 44, or outward relative to the base 44.

[0042] The outer wall 40, inner wall 42, and base 44 define a cavity 60 which is configured to receive at least a portion of the user’s teeth. The portion may be a portion of the user’s upper teeth, a portion of the user’s lower teeth, a portion of both the user’s upper teeth and lower teeth, or all of the user’s teeth. [0043] The base 44 is composed in whole or in part of an auxetic material. An auxetic material is a structure or material that has a negative Poisson’s ratio, meaning that when stretched, the material becomes thicker in the axis perpendicular to the applied force. The internal structure of an auxetic material deforms in a specific way when a force is uniaxially loaded (such as stretching), resulting in the perpendicular thickening. According to another embodiment, a portion or the entirety of the outer wall 40 and/or the inner wall 42 may also be composed of an auxetic material.

[0044] Referring to FIG. 4A, in one embodiment, is a schematic representation of a non-auxetic material or structure 70. When the non-auxetic material is pulled or stretched (or any other force is applied) along the X-X axis, the non-auxetic material becomes thinner in the perpendicular axis, as shown by the arrows.

[0045] In contrast, referring to FIG. 4B, in one embodiment, is a schematic representation of an auxetic material or structure 72. When the auxetic material is pulled or stretched (or any other force is applied) along the X-X axis, the auxetic material becomes thicker in the perpendicular axis, as shown by the arrows.

[0046] The auxetic material can be any material that exhibits this behavior. There are a wide variety of known auxetic materials. For example, the auxetic material may be a natural material, such as a mineral or biological, or may be a two-dimensional or three-dimensional synthetic or man-made material. Examples of natural materials including iron pyrites, a-cristobalite, tendons, graphene, certain minerals, and many other naturally occurring materials. Examples of synthetic or man-made materials including auxetic polyurethane foam, polytetrafluorethylene polymers, and many other synthetic materials. According to one embodiment, the auxetic material is a 2D reentrant or a chiral-type structure, although again many other structures and materials are possible.

[0047] Referring again to FIG. 3, in one embodiment, the outer wall 40 and/or the inner wall 42 may be segmented, thus comprising a plurality of panels or segments 45 each separated by a space 46. According to an embodiment, the base 44 may be segmented as well, with neighboring segments connected to each other. According to an embodiment, the segments of the base may be configured such that they can move relative to one another. However, according to other embodiments, the outer wall, inner wall 42, and base 44 are not segmented but are instead a nonsegmented structure without spacing, although the non-segmented structure may optionally be a flexible structure. [0048] Referring to FIG. 5, in one embodiment, is a three-dimensional representation of the boxed region from FIG. 1, showing a portion of the care component 16 of the personal care device. The care component may be U-shaped as shown in FIG. 1. However, the component may be less than an entire U, and thus may be only half of a U, less than half (i.e., curved), or more than half.

[0049] According to an embodiment, the care component 16 comprises an outer wall 40 which is positioned between (i) the user’s teeth or the user’s teeth and gums and (ii) the user’s cheek, and comprises an inner wall 42 which is positioned between (i) the user’s teeth or the user’s teeth and gums and (ii) the inner portion of the user’s mouth, including but not limited to the tongue. The care component also comprises a base 44 which is positioned between the user’s upper and lower teeth. The base 44 is connected on one side to the outer wall 40 and on another side to the inner wall 42. The base 44 is composed in whole or in part of an auxetic material. The outer wall 40, inner wall 42, and base 44 define a cavity 60 which is configured to receive at least a portion of the user’s teeth.

[0050] According to an embodiment as shown in FIG. 5, the cavity comprises a plurality of bristles 48 which are arranged to interact with the user’s teeth 50 or the user’s teeth 50 and gums 52. The bristles can extend into the cavity from the inner face of the inner wall 42, the inner face of the outer wall 40, and/or the inner face of the base 44. The bristles may be composed of any material suitable to clean or otherwise interact with the user’s teeth or the user’s teeth and gums. Alternatively, instead of bristles 48 the elements extending from the inner face of the inner wall 42, the inner face of the outer wall 40, and/or the inner face of the base 44 into the cavity may be any other shape, cleaning element, or other element configured to clean, whiten, or otherwise interact with the user’s teeth or the user’s teeth and gums.

[0051] Referring to FIG. 6, in one embodiment, is a three-dimensional representation of the boxed region from FIG. 1, showing a portion of the care component 16 of the personal care device. The care component 16 comprises an outer wall 40 which is positioned between (i) the user’s teeth or the user’s teeth and gums and (ii) the user’s cheek, and an inner wall 42 which is positioned between (i) the user’s teeth or the user’s teeth and gums and (ii) the inner portion of the user’s mouth, including but not limited to the tongue. Although shown as segmented, the outer wall 40 and/or the inner wall 42 can be a non-segmented structure. [0052] The care component also comprises a base 44 which is positioned between the user’s upper and lower teeth. The base 44 is connected on one side to the outer wall 40 and on another side to the inner wall 42. In this embodiment, the auxetic structure is incorporated in the base 44. Although shown with the complete base being made from the auxetic material, only a portion or region of the base may be made from the auxetic material. The cavity between the outer wall 40 and the inner wall 42 becomes wider and longer when it is inserted on a jaw with large teeth, due to the auxetic material. Also due to the flexibility of the auxetic structure, the bristles or other structure 60 (if present) fingers align with the teeth and/or gum surfaces regardless of the size of the user’s jaw or teeth.

[0053] Accordingly, the auxetic structure improves the contact between bristles and teeth, and reduces over compression of the bristles to improve alignment on the tooth surfaces. Accordingly, the auxetic structure improves tooth cleaning, when utilized as a component of a tooth cleaning device. Alternatively, the auxetic structure improves tooth engagement when utilized as a component of a tooth whitening device.

[0054] Referring to FIG. 7 is the embodiment depicted in FIG. 6, upon a force being applied to the structure to interact with the user’s teeth and/or gums. The force causes the auxetic structure to deform, which causes the auxetic structure to elongate along an axis perpendicular to the direction or axis of force.

[0055] According to an embodiment, one particular application of the care component 16 of the personal care device with an auxetic structure reduces the total force on the system reduces due to the reduction of over compressed bristles (as shown in FIG. 8 comparing a measurement of force of a prior art non-auxetic device with an auxetic device), and was shown to increase overall cleaning performance -20%.

[0056] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

[0057] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” [0058] The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified.

[0059] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.”

[0060] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified.

[0061] It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.

[0062] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively.

[0063] While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

Claims

Claims What is claimed is:

1. A personal care device (10), comprising: a structure (16) having an inner wall (42) and an outer wall (40), the inner wall and outer wall connected to a base (44), wherein the base, inner wall, and outer wall define a cavity (60) configured to receive a plurality of teeth of a user, and wherein at least a portion of the base is composed of an auxetic material.

2. The personal care device of claim 1, wherein the structure is U-shaped.

3. The personal care device of claim 1, wherein at least a portion of the structure is curved.

4. The personal care device of claim 1, wherein the inner wall and the outer wall comprise a plurality of bristles (48) extending into the cavity, the plurality of bristles configured to interact with the plurality of teeth of the user and/or gums of the user.

5. The personal care device of claim 1, wherein the inner wall and/or the outer wall comprises a plurality of spaced panels (45).

6. The personal care device of claim 1, wherein the inner wall and outer wall are perpendicular to the base.

7. The personal care device of claim 1, wherein the inner wall and outer wall are connected to the base with a small angle.

8. The personal care device of claim 1, wherein the personal care device is a one-size- fits-all device.

9. The personal care device of claim 1, wherein the personal care device is a toothbrush, a flossing device, or a tooth whitening device.

10. The personal care device of claim 1, wherein the personal care device is a mouthguard.

11. A toothbrush (10), comprising: a brush head member (14) comprising a care component (16), the care component comprising a structure (16) having an inner wall (42) and an outer wall (40), the inner wall and outer wall connected to a base (44), wherein the base, inner wall, and outer wall define a cavity (60) configured to receive a plurality of teeth of a user, and wherein at least a portion of the base is composed of an auxetic material; wherein at least a portion of the structure is curved; and wherein the inner wall and the outer wall comprise a plurality of bristles (48) extending into the cavity, the plurality of bristles configured to interact with the plurality of teeth of the user and/or gums of the user.

12. The toothbrush of claim 11, wherein the structure is U-shaped.

13. The toothbrush of claim 11, wherein the inner wall and/or the outer wall comprises a plurality of spaced panels.

14. The toothbrush of claim 11, wherein the inner wall and outer wall are perpendicular to the base.

15. The toothbrush of claim 11 , wherein the inner wall and outer wall are connected to the base with a small angle.