Personal care device and method for manufacturing such a personal care device

Abstract

The present invention relates to a personal care device such as an electric hair cutter like a shaver or a toothbrush, and a method of manufacturing such a personal care device. More specifically, the personal care device includes a handle and a functional head that supports at least one personal care tool, the functional head being attached to the handle, and at least one of the handle and the functional head having a ring-shaped or sleeve-shaped form with a closed annular cross-section and including an external metal shell formed in one part having an integral and homogeneous seamless structure. The external metal shell includes at least one undercut portion, and the undercut portion deforms the metal shell blank by applying hydraulic pressure to one side of the metal shell blank disposed in the mold and presses the opposite side of the metal shell blank against the mold to take the shape of the contour of the mold.

Description

Technical Field

[0001] The present invention relates to a personal care device and a method of manufacturing such a personal care device. More specifically, the present invention relates to a personal care device such as a hair cutter or a toothbrush, which may include a handle and a functional head such as a cutter head or a brush head attached to the handle, and at least one of the handle and the functional head includes the external metal shell, and the external metal shell may be a part of a housing that houses a functional component such as an electric drive unit including an electronic device, a motor, and a mechanical transmission device, or a power source such as a battery or a power storage component. The personal care device may also include a base station for loading and / or cleaning and / or parking the handheld device, and the base station may also include an external metal shell as described above, but the external metal shell may be a part of a housing that houses a functional component such as an electronic device, a power source, or a cleaning tool.

Background Art

[0002] A handheld personal care device can perform various personal care functions such as hair cutting, shaving, skin treatment, teeth brushing and cleaning, nail trimming, or other personal care procedures. Usually, the handle of such a personal care device has a dual function. On the one hand, the handle is a gripping part for gripping and holding the personal care device by hand. On the other hand, the handle houses or supports functional components such as an electric drive unit for driving personal care tools such as a hair cutting tool, a brush unit, a skin peeling or massage tool, a nail grinding tool, or other personal care tools. More specifically, the handle can form a housing that can accommodate an electric motor, a mechanical transmission device for transmitting the driving motion of the motor to the personal care tool, an electronic control device, a power supply device such as a battery, a net supply terminal, and an information device such as a display. The handle may be waterproof and / or sealed against moisture and / or dust to protect the functional components housed within the housing.

[0003] The functional head of such a personal care device usually supports one or more personal care tools such as a shear-type foil cutter, a long hair cutter, a trimmer, or one or more brush units, an interdental cleaner, etc. Such personal care tools may be movably supported with respect to the frame or shell of the functional head, and a mechanical transmission device may connect the movably supported tool to the drive unit within the handle.

[0004] The base station may receive or be connected to the handheld personal care device to load and / or clean and / or park the handheld device. The housing of the base station usually houses functional components such as an electronic device such as a data processor and a display for communicating with the handheld device, a power supply having an electrical connector for charging the handheld device, or a cleaning tool such as a cleaning machine for cleaning the functional head of the handheld device.

[0005] Generally, the outer shell of the handle, the outer shell of the functional head, and the outer shell of the base station are mainly made of plastic, and a plurality of plastic parts such as rigid plastic parts and soft plastic parts may be attached to each other to form the outer shell.

[0006] On the other hand, the handle and / or the functional head may include an external metal shell, and the external metal shell may form the outer surface of the handle that is gripped by the hand or finger, and / or at least a part of the housing that houses the aforementioned functional components, and / or may form a frame for supporting the personal care tool of the functional head. When such a metal shell forms the outer surface of the handle and / or the functional head, it can provide a cold feeling to the user, has high strength and rigidity, and further has high resistance to wear, tearing, scratching, and the chemical environment. In addition, the external metal shell provides a valuable aesthetic appearance and a clean appearance.

[0007] When attaching functional components inside and / or on such an external metal shell, it is very difficult to enable both the easy and accurate manufacturing of the metal shell on the one hand and the easy assembly of the personal care device including the attachment of the functional components on the other hand when the external metal shell has a precise fit and small dimensions. Furthermore, the openings and perforations in the metal shell used to insert functional components or to provide access to functional components such as displays, controllers, or switches, or connectors such as loading cable terminals may have sharp and burr-edged.

[0008] If the outer shell is to have a hollow shape and be made of a single piece with an integral and homogeneous seamless structure, it becomes even more difficult to meet such different requirements. Such a seamless structure without visible seams, such as welding seams between different shell parts, is not only desirable from an aesthetic point of view but also increases strength and rigidity and reduces the assembly process. However, such an integral structure having a hollow ring-shaped or sleeve-shaped configuration requires at least one opening through which the aforementioned functional components such as electronic devices, drive units, or batteries or mechanical transmission devices can be inserted or through which access to internal components can be obtained. Providing a large opening facilitates the attachment process but reduces strength, while a small opening does not allow for easy attachment. In any case, it is difficult to achieve a perfect fit between the metal shell and the functional components without compromising the ergonomic shape and aesthetically pleasing three-dimensional complex appearance.

[0009] Furthermore, it has been found that the edges of the metal shell can form edges that can impinge on the user's skin.

SUMMARY OF THE INVENTION

MEANS FOR SOLVING THE PROBLEM

[0010] The underlying object of the present invention is to provide an improved personal care device that avoids at least one of the drawbacks of the prior art and / or further develops existing solutions. Another underlying object of the present invention is to provide an improved method for manufacturing a personal care device as described above, including an external metal shell and / or a metal housing.

[0011] A further underlying object of the present invention is to provide a method for manufacturing a metal housing or an external metal shell without the risk of impinging on the user's skin at the edges of the metal shell or the metal housing.

[0012] A further object underlying the present invention is to combine a small installation area, a precise fit with functional components mounted within and / or on the metal shell, and easy attachment of the functional components, without sacrificing the functional shape of the external metal shell that provides rigidity and ergonomic handling, for such a personal care device.

[0013] A further object underlying the present invention is to provide an improved manufacturing method for an external metal shell of a personal care device that enables accurate formation of the metal shell despite its complex three-dimensional shape, without requiring a number of processing steps using complex and expensive tools.

[0014] To achieve at least one of the foregoing objects, a personal care device having the features of claim 1 is provided. A method of manufacturing a personal care device, including the features of claim 18, is provided to achieve at least one of the foregoing objects. Further advantageous aspects are constituted by the features of the dependent claims.

[0015] Preferably, a personal care device such as a hair cutter or a toothbrush is provided, the personal care device comprising a handle and a functional head supporting at least one personal care tool, the functional head being attached to the handle, at least one of the handle and the functional head including an external metal shell, the metal shell having at least one opening, at least one plastic chassis member being housed within the external metal shell, the plastic chassis member having a protrusion that penetrates the opening within the external metal shell and projects beyond the outer surface of a metal shell section surrounding the opening, and / or the plastic chassis member completely covering the outer edge of the opening. Thus, it is not necessarily required to add an additional manufacturing process for rounding the edges at the opening of the outer shell. This is because these edges are mounted within such an opening and are thus completely covered by a module or a plastic chassis part that covers the edges. Preferably, the mounted module or plastic chassis part is provided as a kind of skin bumper or skin protection material that projects beyond the outer surface of the outer shell and / or projects beyond the upper end of the outer shell.

[0016] More preferably, the external metal shell includes at least one lateral opening through which a functional component that at least partially extends to the outside of the external metal shell and / or is accessible from the outside of the external metal shell is connected to another functional component housed inside the external metal shell. Thus, the lateral opening of the metal shell houses a functional component or a plastic chassis part therein.

[0017] More preferably, the handle is provided with a front module and a back module on its opposing lateral sides, and each module is provided with the plastic chassis member that extends through a corresponding opening of the external metal shell.

[0018] More preferably, the handle includes a top module and a bottom module on its opposing longitudinal side portions, and each module includes the plastic chassis member extending through the corresponding opening of the external metal shell.

[0019] More preferably, the functional head is provided with the plastic chassis member extending through the bottom opening and the top opening of the functional head.

[0020] More preferably, the protrusion includes a collar seated on the outer surface of the metal shell section that overlaps and / or surrounds the opening.

[0021] More preferably, even when the contour of the opening does not extend in one plane, the protrusion protrudes beyond the outer surface of the metal shell substantially uniformly along the entire opening, by a certain amount, and / or by an amount in the range of 0.05 to 1 mm or 0.1 to 0.5 mm or 0.1 to 0.3 mm.

[0022] More preferably, the protrusion is made of soft plastic and / or hard plastic having an outer contour that conforms to the inner contour of the opening in terms of shape and dimensions, and provides sealing of the protrusion with the metal shell and / or engagement by fitting and / or snap-fitting engagement of the shape.

[0023] More preferably, the metal shell has opposing ends each defining a closed-ring-shaped cross-section, and an intermediate portion between the opposing ends includes at least one lateral opening and / or lateral perforation for accessing at least one functional component housed within the external metal shell.

[0024] More preferably, the external metal shell has a ring-shaped or sleeve-shaped configuration with a closed-ring cross-section, has an integral and homogeneous seamless structure, and is formed as a single part.

[0025] More preferably, the external metal shell is a hydraulically formed portion and / or a hydroformed portion that is deformed by hydraulic pressure.

[0026] More preferably, the external metal shell includes at least one undercut portion.

[0027] More preferably, the external metal shell includes an expanded intermediate portion that defines a maximum cross-sectional area and a pair of opposing end portions provided with a front opening having a cross-sectional area smaller than the maximum cross-sectional area of the expanded intermediate portion.

[0028] More preferably, the external metal shell includes at least one opening surrounded by a three-dimensional shaped metal shell section, and the opening has a three-dimensional shaped edge contour that extends substantially perpendicular to the surrounding metal shell section along the entire contour of the opening, and the surrounding shell portion adjacent to and surrounding the opening has various orientations that vary along the opening.

[0029] More preferably, the metal shell has opposing end portions that each define a closed ring-shaped cross-section, and an intermediate portion between the opposing end portions includes at least one lateral opening and / or lateral perforation for accessing at least one functional component housed within the external metal shell.

[0030] More preferably, the external metal shell has an elongated hollow shape with front openings at opposing axial end portions, and the axial end portions have a closed annular cross-section surrounding the openings.

[0031] The metal shell blank is made of stainless steel or steel containing chromium, nickel, and molybdenum, particularly 10 to 25% by mass of Cr, 5 to 20% by mass of Ni, and 1 to 5% by mass of Mo, or 16 to 18% by mass of Cr, 10 to 14% by mass of Ni, and 2 to 3% by mass of Mo.

[0032] A method of manufacturing a handheld personal care device such as a hair cutter or a toothbrush having an external metal shell, forming the external metal shell into a desired shape, including the step of attaching functional components for performing or assisting in performing personal care functions in and / or on the formed external metal shell, wherein the forming step includes a hydraulic forming step of applying hydraulic pressure to one side of a metal shell blank disposed in a mold to deform the metal shell blank, pressing the opposite side of the metal shell blank against the mold to take the shape of the contour of the mold, thereby forming an external metal shell having a desired shape, forming at least one opening in the external metal shell, a notching step is provided for attaching a plastic chassis part in the at least one opening, the outer edge of the opening being covered by the plastic chassis part and / or the plastic chassis part protruding beyond the external metal shell.

[0033] More preferably, the metal shell blank has a hollow, sleeve-like or pipe-like shape and is disposed in a cavity of the mold surrounding the outside of the metal shell blank, and hydraulic pressure is applied inside the hollow metal shell blank, thereby expanding the hollow metal shell blank and pressing the outside of the metal shell blank against the contour of the cavity of the mold, thereby causing the outside of the metal shell blank to take the shape of the contour of the mold.

[0034] More preferably, one or more undercut portions of the external metal shell are formed hydraulically in the hydraulic forming step.

[0035] It has been proposed to form the external metal shell as a single part having a ring-shaped or sleeve-shaped configuration with an annular closed cross-section and having a homogeneous and integral seamless structure, with one or more undercuts provided in the external metal shell. Combining such a seamless integral annular structure with one or more undercuts not only provides excellent strength and rigidity but also enables a precise fit and small size of the metal shell, while one or more functional components are to be mounted in and / or on the metal shell. This is because the shape of the metal shell can be adapted to conform to the contour of such functional components of the personal care device. For example, additional accommodation space for the bulky portions of the functional components can be provided by one or more undercut portions of the metal shell without the need to increase the dimensions over the entire length of the metal shell. At the same time, ergonomic needs can be met by an organic shape in the portion gripped by hand or in the portion contacting the skin. In addition, a valuable aesthetic appearance can be combined with the cold touch felt by the user. The seamless integral structure avoids the accumulation of dirt and can reduce irritation to the skin caused by edges that create scratches. Even if the outer shell is an integral structure, the handle or the functional head is referred to separately. The functional head is connected to the handle by a support structure that allows movement of the head relative to the handle, and thus two outer shells are provided for each of the head and the handle, at least one of which includes the above-mentioned metal shell. Alternatively, such separate metal outer shells are provided for both the head and the handle. Further alternatively, both the functional head and the handle together comprise a single metal outer shell structure as described above. Such a variant is particularly applicable when the outer head shell is immovable relative to the outer handle shell.

[0036] To combine the design freedom enabling complex shapes with an efficient formation of the shell, the external metal shell may be formed, at least in part, by a hydraulic pressure that deforms the metal shell into the desired shape. According to one aspect, the external metal shell includes at least one hydraulically formed portion.

[0037] More specifically, one or more of the aforementioned undercuts of the external metal shell are formed by hydraulic pressure applied to a shell portion desired to have such an undercut shape. Nevertheless, the external metal shell can be formed as a single part having a closed ring shape or a closed sleeve shape and having a homogeneous and integral seamless structure.

[0038] For example, a substantially tubular and elongated external metal shell of a handle, or a hollow sleeve-shaped outer shell of a functional head of a personal care device, or another hollow external metal shell of a personal care device accessory such as a loading station may have a hydraulically formed profile having an intermediate portion defining a maximum cross-sectional area and a pair of end portions disposed on both sides of the intermediate shell portion and having a cross-sectional area smaller than that of the bulged intermediate portion.

[0039] More specifically, the step of forming the external metal shell includes a hydroforming step of applying hydraulic pressure to one side of a metal shell blank disposed in a mold to deform the metal shell blank and pressing the opposite side of the metal shell blank against the mold to take the shape of the mold contour, thereby forming an external metal shell having a desired shape. Such a hydroforming step enables the metal shell blank to be deformed into a complex three-dimensional shape without the problem of mechanical forming tools such as punches, pushers, or movable core elements coming out of the recesses of the metal shell.

[0040] The hydroforming step may be a hydroforming process in which the metal shell blank and / or the mold in the mold are filled with a working fluid such as water or oil and pressure is applied to the working fluid from a pressure source outside the mold.

[0041] These and other advantages will become apparent from the following description with reference to the drawings and possible examples.

Brief Description of the Drawings

[0042]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

DETAILED DESCRIPTION OF THE INVENTION

[0043] According to one aspect, it is proposed to form an external metal shell with a part having a ring-shaped or sleeve-shaped configuration with an annular closed cross-section and having a homogeneous and integral seamless structure, and one or more undercuts are provided in the external metal shell. Combining such a seamless integral annular structure with one or more undercuts not only provides excellent strength and rigidity, but also enables a precise fit and small size of the metal shell, while one or more functional components will be attached within and / or on the metal shell. This is because the shape of the metal shell can be adapted to match the contour of such functional components of the personal care device. For example, without the need to increase the dimensions over the entire length of the metal shell, additional accommodation space for the bulky portions of the functional components can be provided by one or more undercut portions of the metal shell. At the same time, ergonomic needs can be met by an organic shape in the portion gripped by hand or in contact with the skin. In addition, a precious aesthetic appearance can be combined with the cold touch felt by the user. The seamless integral structure avoids the accumulation of dirt and can reduce the irritation to the skin caused by the edges that create scratches.

[0044] To combine the design freedom enabling complex shapes with the efficient formation of the shell, the external metal shell may be formed, at least in part, by a hydraulic pressure that deforms the metal shell into the desired shape. According to one aspect, the external metal shell includes at least one hydraulically formed portion.

[0045] More specifically, the aforementioned one or more undercuts of the external metal shell may be hydraulically formed portions, and nevertheless, the external metal shell can be formed as an integral part having a closed ring-shaped or closed sleeve-shaped configuration and having a homogeneous and integral seamless structure.

[0046] For example, a substantially tubular and elongated outer metal shell of a handle, or a hollow sleeve-shaped outer shell of a functional head of a personal care device, or another hollow outer metal shell of a personal care device accessory such as a loading station may have a hydraulically formed contour having an intermediate portion that defines a maximum cross-sectional area and a pair of end portions disposed on both sides of the intermediate shell portion and having a cross-sectional area smaller than that of the bulged intermediate portion.

[0047] More specifically, the step of forming the outer metal shell may include a hydroforming process in which hydraulic pressure is applied to one side of a metal shell blank disposed in a mold to deform the metal shell blank, and the opposite side of the metal shell blank is pressed against the mold to take the shape of the mold contour, thereby forming an outer metal shell having a desired shape. Such a hydroforming process enables the metal shell blank to be deformed into a complex three-dimensional shape without the problem of mechanical forming tools such as punches, pushers, or movable core elements disengaging from the indentation of the metal shell.

[0048] For example, the aforementioned outer metal shell having an intermediate bulged portion that defines a maximum cross-sectional area and a pair of end portions disposed on both sides of the intermediate shell portion and having a cross-sectional area smaller than that of the intermediate bulged portion may be hydroformed.

[0049] Another example of an undercut shape of the outer metal shell may include a substantially hemispherical concave or bowl-shaped spherical portion that is closed with respect to the outside of the shell and open with respect to the inside thereof. Also, for example, an outer platter-shaped raised portion forming a finger grip portion or a support portion for an additional element may also be formed in an open state inside the metal shell by an undercut method.

[0050] As described above, the external metal shell may have a one-piece structure. More specifically, the metal shell may be formed of a single one-piece component having a homogeneous seamless structure, and the external metal shell may have a ring-shaped or sleeve-shaped configuration having a closed-loop cross-section. That being said, the ring-shaped or sleeve-shaped external metal shell may have one or more lateral openings or transverse notches, and of course, a closed-loop cross-section does not exist in the area of such notches. However, the external metal shell may be formed to have an annular cross-section having a closed-ring shape at least at both ends of the external metal shell and / or on both sides of the lateral opening. These axial ends of the external metal shell, considering the external metal shell of the handle of the personal care device, on the one hand, can face and support the functional head of the personal care device, and on the other hand, can form the bottom end of the handle. Considering the functional head, the opposing ends of the external metal shell may, on the one hand, face the handle and, on the other hand, support the personal care treatment tool and / or may surround or be adjacent to the skin contact surface of the functional head.

[0051] Such a closed-loop cross-section at the end can provide strong and rigid support for the rigidity of the housing or frame, especially for the functional elements mounted in and on the external metal shell. Nevertheless, openings may be provided on the axial end side itself of the metal shell, and these openings may be surrounded by the annular portion having a closed-loop cross-section. For example, a support structure for supporting the functional head is usually attached to or supported on one of the axial ends of the handle, and thus, providing a closed-loop cross-section at such an end of the external metal shell helps to rigidly support the functional head.

[0052] By utilizing the formation of an external metal shell by hydraulic pressure, a substantially sleeve-shaped or ring-shaped external metal shell can be formed to have a laterally bulged portion with an increased diameter or an increased lateral spread, and various other portions of the external metal shell that form undercuts, without having the problem that known punching elements or movable core elements will fall out of the mechanical die system. Forming such undercuts by the hydraulic pressure applied to the inner surface of the sleeve-shaped external metal shell is not a problem because the working fluid can be easily discharged from the inside of the metal shell.

[0053] More specifically, the external metal shell may have the ends tapered at both axial ends of the external metal shell and / or have an intermediate shell section that bulges in the radial or lateral direction defining the maximum cross-sectional area of the external metal shell. In particular, the diameter, or the lateral spread in the case of a non-circular or substantially rectangular or other non-uniform cross-section, may decrease towards the axial ends and / or increase in one or more intermediate portions between the ends. For example, the external metal shell may form an elongated, streamlined bar with a maximum thickness at the central portion and tapering towards the ends, or may have a substantially oval configuration.

[0054] Other shapes with undercuts may also be desirable. For example, it may be desirable to have an inflated or raised terrace-like portion on one lateral side of the external metal shell, e.g., at the central portion, to have additional space inside the external metal shell to accommodate special functional elements, or, for example, to place an input switch or a touch display at a laterally raised position outside the metal shell. Another option is an elongated handle with an organic contour having an outer side ergonomically adapted to a closed hand's fingers and palm.

[0055] Regardless of the details of the shape of the outer metal shell, a metal shell blank having a hollow, sleeve-like, or pipe-like shape may be placed within a cavity of a mold that surrounds the outside of the hollow metal shell blank, where hydraulic pressure is applied inside the hollow metal shell blank, thereby expanding the hollow metal shell blank and pressing the outside of the metal shell blank against the contour of the mold cavity, and the outside of the metal shell blank may be made to conform to the contour of the mold cavity.

[0056] The hydraulic forming process may be a hydroforming process in which the metal shell blank and / or the mold within the mold is filled with a working fluid such as water or oil, and pressure is applied to the working fluid from a pressure source outside the mold.

[0057] In addition to or instead of such a hydroforming process, an electrohydraulic forming process may be provided in which the metal shell blank is placed within and / or immersed in a working fluid reservoir, and one or more pressure waves are generated by at least one pair of electrodes, and the one or more pressure waves form the metal shell blank into the desired shape of the outer metal shell. More specifically, such pressure waves may deform the metal shell blank within the mold, press the metal shell blank against the mold contour, and cause the metal shell blank to conform to the shape of such mold contour.

[0058] In addition to or instead of such hydroforming or electrohydraulic forming processes, the metal shell blank may also be deformed by electromagnetic forming, where a metal shell blank made of a magnetically responsive material may be used, and such metal shell blank may be subjected to a magnetic field that can be generated by an electromagnetic device. More specifically, a magnetic field may be applied to the metal shell blank to convert the metal sheet blank into a viscoplastic state and deform the metal shell blank to conform to the mold contour. Such electromagnetic forming enables the formation of complex shapes at high speed under low temperature conditions.

[0059] When forming such an expanded cross-sectional portion or radially raised portion by applying hydraulic pressure inside the metal shell, it may be helpful to apply an axial compressive force to the metal shell blank, and such an axial compressive force can be applied before, during, and / or after applying the hydraulic pressure. More specifically, such an axial compressive force helps to push the material of the metal shell blank axially into the mold, thereby facilitating the radial expansion of the metal shell blank, which axial expansion can be achieved mainly by hydraulic pressure. Nevertheless, when the metal shell blank expands radially, the axial compression helps the material to yield and provides a certain fresh supply of material to compensate for the material expanding radially.

[0060] To achieve such axial compression, an axial force may be applied to one or both axial ends of the metal shell blank, particularly at one or more ends where the hydraulic fluid or hydraulic pressure is supplied into the mold and / or into the sleeve-shaped or tubular metal shell blank. For example, a pair of pusher elements that can be coaxially arranged with each other can push both ends of the metal shell blank received in the mold in opposite directions so as to apply an axial compressive force. Such an axial compressive force may be applied to the metal shell blank particularly during the application of hydraulic pressure, which at least partially overlaps with the period of hydroforming.

[0061] The hydraulic forming process may be configured to produce two or more external metal shells simultaneously or in one hydraulic forming process. For example, a substantially tubular or sleeve-shaped metal shell blank having a length greater than the sum of the lengths of two or more metal shells may be used. Such a sufficiently long metal shell blank may be deformed in the hydraulic forming process to form two external metal shells having a desired shape that are still connected to each other, for example, immediately after the hydraulic forming process. The metal shell blank is deformed into a certain row of external metal shells that are connected to each other and arranged in a row one after another. The plurality of formed shells can be arranged with their main axes coaxial with each other. The metal shells formed by hydraulic pressure may be separated from each other in a subsequent cutting or separating process, for example, by cutting the connection portion between two adjacent metal shells.

[0062] In particular, a pair of external metal shells may be formed in one hydraulic forming process such that the metal shells have opposite orientations with respect to each other. For example, when the desired shape of the external metal shell is a substantially oval shape, the two eggs may be formed in the mold by hydraulic forming such that the thicker ends of the eggs face each other and the thinner ends of the eggs face away from each other. The formation of the pair of metal shells in such opposite orientations helps to achieve uniform deformation of the material and uniform yielding of the material in the section having a large radial expansion.

[0063] As described above, the hydraulic forming process may be a hydroforming process. Alternatively, the hydraulic forming process may include electrohydraulic forming, in which shock waves or pressure waves are generated in the working fluid by at least one pair of electrodes to which an electric current is applied, and thus a certain explosion in the working fluid is generated by the electric current. The pressure of such a hydraulic pressure wave hits the surface of the metal shell blank, thereby causing its deformation. In particular, the metal shell blank can be pressed against the wall of the mold in which the metal shell blank is received by such a pressure wave, substantially in the same manner as in the aforementioned hydroforming process.

[0064] Instead of hydroforming and electrohydraulic forming, the metal shell blank may be deformed into the desired shape of the metal shell by electromagnetic forming, sometimes known as EMF. For such an EMF forming process, a metal shell blank made of a metal that responds to magnetic forces is used. On the other hand, for hydroforming or electrohydraulic forming, other materials that do not respond to magnetic forces can also be used.

[0065] For example, an aluminum shell may be used, or other materials such as brass, low alloy steel, and stainless steel may be used as the metal shell blank.

[0066] A particularly advantageous material for the external metal shell is stainless steel, which can include chromium, nickel, and molybdenum. More specifically, the steel may contain 10 - 25 wt% Cr, 5 - 20 wt% Ni, and 1 - 5 wt% Mo, or it may contain 16 - 18 wt% Cr, 10 - 14 wt% Ni, and 2 - 3 wt% Mo.

[0067] For example, type 1.4301 stainless steel may be used, or stainless steel 1.4404 may be used, which provides further increased corrosion resistance.

[0068] As can be seen from FIGS. 1 and 2, the handheld personal care device 1 may be an electric shaver 2 comprising an elongated handle 3 and a functional head 4 attached to one end of the handle 3, and the functional head 4 may be a shaver head. The functional head may form a separate part having a separate housing shell with respect to the handle, and a support arm 42 is provided to connect the functional head to the handle so as to support the functional head movably (e.g., to enable swiveling and / or tilting movements) or non - movably with respect to the handle. Alternatively, the functional head may be an integral part of the handle forming the upper end of the device, and an outer shell integral with both may be provided.

[0069] The functional head 4 may include one or more functional components for performing or assisting in performing personal care treatments. In the case of a shaver head, the functional components of the functional head 4 may include one or more cutting tools 13, which may include one or more of a shear-type foil short hair cutter and / or a long hair cutter, and / or a trimmer. The treatment tool may project from one side of the body of the functional head 4 to define a skin contact surface.

[0070] As can be seen from FIG. 11, the cutting tool 13 may be replaceable and may thus be removably supported by the frame of the functional head 4.

[0071] A drive module may be received within the functional head 4 to actuate and / or drive the treatment tool, and such a drive module 27 may include an electric motor or, alternatively, a transmission or coupling for coupling to another part of the transmission device 12 coming from the handle 3.

[0072] The aforementioned functional components 9 of the functional head 4 may be at least partially housed within the housing 6 of the functional head 4, and the housing 6 may include a metal shell 8, which will be described in detail below.

[0073] The elongated handle 3 serves the purpose of gripping and holding the personal care device 1, and the outer peripheral surface of the handle 3 can be gripped by a hand or a finger of a hand. In addition to such a gripping function, the handle 3 also serves the purpose of housing further functional components 9 of the personal care device 1, and the functional components 9 of the handle 3 may include a drive unit 10 for driving the treatment tool 13 in the functional head 4. More specifically, the drive unit 10 may include a motor 11 that can be driven by electrical energy supplied by the battery 28 or via a network cable connected to a power terminal.

[0074] The elongated handle 3 comprises an upper end portion 17 adjacent to the functional head 4 and a lower end portion 18 on the opposite side. Each of these end portions may be provided with front openings 17, 18. In an alternative example, the outer shell 7 may not be provided with an opening at the bottom end portion 18. At least one lateral opening 21, 22 is provided in the lateral side surface of the outer shell 7 to accommodate the front module 32 and / or the back module 33 therein. Thus, during assembly, each opening in the outer shell 7 is preferably closed by a cap or modules 32, 33, 35, 40 made at least partially from plastic.

[0075] To control the operation of the motor 11, the handle 3 may include a control unit, which may include electronic components such as an electronic controller. More specifically, the control unit can include a printed circuit board (PCB) to which the motor 11 is connected. On the other hand, input / control means such as control switches, touchscreens, or other control elements can be connected to the PCB 30 or, more generally, to the electronic control unit.

[0076] As can be seen from FIGS. 3 to 5, the elongated handle 3 may comprise a substantially hollow housing 5, within which the aforementioned functional components 9 can be received and accommodated. The housing 5 of the handle 3 can include a metal shell 7 that at least partially forms the outer surface of the handle 3.

[0077] The functional components 9 received within the handle 3 may be pre-assembled to form a pre-assembled mounting unit. For example, the functional elements 9 may be pre-attached to a chassis element 31 that can be made at least partially, for example, from plastic. The aforementioned chassis element 31 may also include the aforementioned printed circuit board 30 to which other elements such as a motor, a battery, or a control switch, or a display can be mounted or connected.

[0078] As shown in FIGS. 3 to 5, the functional elements 9 may be grouped differently in a pre-assembled mounting module. According to an advantageous aspect, the personal care device 1 may be configured to have an elongated internal functional module 29 that can be inserted into the handle 3 through an opening at one of the axial ends of the housing 5. For example, a front opening 19 (see FIG. 6) may be provided at the axial upper end of the handle 3 facing the functional head 4, through which the elongated internal functional module 29 may be inserted into the handle 3. The elongated internal functional module 29 may include, for example, a motor 11, a battery 28, and an electronic control unit for controlling the motor 11, and the control unit may include a printed circuit board 30. The internal functional module 29 can have a sealed or sealed configuration that protects the electronic components as well as the motor and the battery from moisture and water.

[0079] The internal functional module 29 may also include a transmission device 12 for transmitting the driving motion of the motor 11 to the treatment tool 13 of the functional head 4, and a part of the transmission device 12 may protrude from the axial upper end of the handle 3 into or towards the functional head 4.

[0080] As can be seen from FIGS. 3 to 5, the front module 32 and / or the back module 33 may be attached to the lateral side surface of the handle 3, and such front module 32 and / or back module 33 may also be connected to the internal functional components 9 received inside the handle 3. In order to enable the connection of the front module 32 and the back module 33 to the internal components, the housing 5 of the handle 3, more specifically its external metal shell 7, may be provided with lateral notches or openings 21, 22 through which the front module 32 and the back module 33 may at least partially extend.

[0081] The front module 32 and the back module 33 may include electronic components and / or electrical components and / or mechanical components and / or tools, and the front module 32 and the back module 33 may include parts made of plastic and / or parts made of materials other than metal such as glass, but some other parts may be formed of metal. For example, the front module 32 can include a display such as a touch display for inputting control commands and / or for displaying control information such as, for example, treatment time or battery charge state. In addition or alternatively, the front module 32 can also include control elements such as control switches and / or output elements such as sound generators or speakers.

[0082] The back module 33 may include, for example, a battery module that can be configured to be replaceable. Such an additional battery module may be provided, for example, in addition to the battery 28 received in the handle 3 so as to have a range extender, or such an additional battery module may be replaced with the battery 28 in the handle 3. In addition or alternatively, the back module 33 may include other functional components 9 such as a special treatment tool 13. In the case of the shaver 2 or the hair clipper, such a special treatment tool 13 can include a long hair clipper.

[0083] As can be seen from FIGS. 3 to 5, the bottom module 35 may be attached to the handle 3 at the axial end opposite to the functional head 4. The handle 3, more specifically its housing 5, and more specifically the metal shell 7 of the handle housing 5 may be provided with a front opening 19 into which the bottom module 35 can be at least partially inserted. Such a bottom module 35 may be at least partially made of plastic and / or may include electronic components such as connection terminals for connecting a supply cable and / or for connecting a charger pin or charger connector of a charger station. The bottom module 35 may also include a data connection terminal for connecting the personal care device 1 to a data transmission / reception station.

[0084] The top module 34 may be formed by the aforementioned functional head 4. Such a top module 34 may be permanently or removably attached to the upper end of the handle 3. More specifically, the base of the top module 34, which can support the body of the functional head 4 and / or the functional components 9, may be at least partially inserted into the hollow housing 5 of the handle 3 and / or may be attached to the axial end of the handle 3. More specifically, the base portion of the top module 34 may be attached to the metal shell 6 of the handle 3 in order to connect the functional components 9 of the functional head 4 to the functional components 9 of the handle 3. The top module 34 may be firmly attached to the metal shell 7 of the handle 3. Such a firm attachment may be fixed or releasable (see FIGS. 3, 4, and 5).

[0085] As can be seen from FIG. 7, at least one of the aforementioned functional modules 29, 32 to 35 may be inserted into each notch or opening 19, 20 or 21 of the metal shell 7 or the handle 3, whereby at least one module 29, 32 to 35 may extend partially inside and partially outside the housing 5 of the handle 3, and more specifically may extend partially inside and partially outside the metal shell 7. More specifically, at least one of the modules 29, 32 to 35 may be configured to have a protrusion 25 extending through the corresponding openings 19, 20, 21 inside the metal shell 7, and the outer portion of the protrusion 25 protrudes towards the outside of the handle 3 beyond the outer surface of the metal shell 7 (see the partial view (b) of FIG. 7).

[0086] For example, at the interface between the metal shell 7 and the functional module, the protrusion 25 may protrude beyond the outer surface of the metal shell 7 by an amount in the range of 0.05 to 1 mm or 0.1 to 0.5 mm, or 0.1 to 0.3 mm. Such protrusions form a kind of protector that protects the skin and fingers from contacting the edges of the openings 19, 20 and 21.

[0087] However, alternatively, the functional modules 29, 32 to 35 may be inserted flush into the corresponding openings 19, 20, 21 such that the aforementioned protrusion amount is substantially 0, and for example, it is also possible to have a slight negative protrusion amount of -0.1 to -0.5 mm.

[0088] As can be seen from FIG. 7(b), at least one of the functional modules 29, 32 to 35 may fit precisely into the corresponding openings 19, 20 and 21, and the outer peripheral surfaces of the modules 32 to 35 may conform to the corresponding openings 19, 20, 21 in terms of shape and dimensions. More specifically, the aforementioned protrusions 25 extending through the openings have a peripheral shape adapted to the contours of the respective openings 19, 20, 21 to achieve a precise fit between them or to enable sealing between them.

[0089] As can be seen from FIG. 7(b), the protrusion 25 may basically have a cylindrical shape, and thus, the outer portion of the protrusion 25 may extend substantially perpendicular or transversely to the outer surface of the metal shell 7. Alternatively, the protrusion 25 may include a collar 26 having a diameter or dimension or extension that is slightly larger than the portion of the protrusion that seats within the openings 19, 20, 21. Such a collar 26 can be seated on the outer surface of the metal shell 7.

[0090] The aforementioned protrusions 25 of the corresponding functional modules 29, 32-35 seated within the respective openings 19, 20, and 21 may be at least partially formed from plastic, and such plastic may be, for example, rigid plastic or soft plastic or a mixture thereof so as to snap-fit each module into the corresponding opening and seal the interface between the module attached to the metal shell 7.

[0091] As can be seen from FIGS. 11-13, the functional head 4 may have a configuration similar to that of the functional head housing 6 and the functional modules or functional components 9 attached thereto. In particular, the functional component 9 or group of functional components 9 may be at least partially inserted inside the housing 6 of the functional head 4. More specifically, the functional component 9 may include a protrusion 25 that protrudes outside beyond the outer surface of the metal shell 8 of the head housing 6, and the amount of protrusion (see FIG. 13) may be in the range of 0.05-1 mm, 0.1-0.5 mm, or 0.1-0.3 mm. Also in this case, as described for the functional modules of the handle 3, there is no height difference or a negative height difference is basically possible to achieve a flush configuration.

[0092] The protrusion 25 of the chassis element attached to the functional head 4 may also be at least partially formed from plastic, and such plastic may be rigid plastic and / or soft plastic to achieve snap-fitting and / or sealing.

[0093] The metal shell 7 of the handle 3 and / or the metal shell 8 of the functional head 4 may be hydroformed. More specifically, the manufacture of the metal shells 7, 8 may include a hydroforming process that includes applying a high-pressure working fluid to the inner surface of the metal shell blank 14, as shown in more detail in FIGS. 8 and 9.

[0094] Referring to FIG. 8, first, a metal shell blank 14, which may initially have a tubular shape, is inserted into an open mold 15 that, when closed, may define a cavity corresponding to the desired shape on the outside of the metal shells 7, 8. As can be seen from FIG. 8a, the metal shell blank 14 may be inserted such that the opposing edges of the tubular blank 14 reach the opposing edges of the mold 15 at the interface of the two mold parts. The ends of the tubular metal shell blank 14 should be accessible from the outside of the mold 15 to enable the supply of the working fluid into the interior of the tubular metal shell blank 14. Further, a pusher element 37 should be in contact with both ends of the tubular metal shell blank 14 so as to be able to apply an axial compressive force.

[0095] When the mold 15 is closed (see FIG. 8b), a fluid supply connector is connected to the said end of the tubular metal shell blank 14 and / or the pusher element 37 is arranged at the end of the tubular metal shell blank 14, the working fluid is injected into the interior of the tubular metal shell blank 14 through the open axial end of the tubular metal shell blank 14 to completely fill the interior of the metal shell blank 14 (see FIG. 8c).

[0096] Next, the hydraulic pressure is increased to achieve a radial expansion of the metal shell blank 14, more specifically, to press the metal shell blank 14 against the mold surface that defines the cavity of the mold 15 so that the metal shell blank 14 can take the shape of the mold cavity (see FIG. 8d).

[0097] Before, during, and / or after the metal shell blank 14 expands radially by hydraulic pressure, the aforementioned pusher 37 can be actuated to apply an axial compressive force to the metal shell blank 14. More specifically, the pusher element 37 may be pressed against both ends of the tubular metal shell blank 14 (see FIG. 8d) to support the desired deformation of the material of the metal shell blank 14.

[0098] The axial compressive force may be applied when the metal shell blank 14 is within the mold 15.

[0099] FIGS. 9a and 9b show the transition and deformation of the metal shell blank 14 into the outer metal shells 7, 8 having the desired shape. According to an advantageous aspect, a pair of metal shells 7, 8 may be formed in one hydroforming or hydraulic forming process (see FIG. 9b), and the mold 15 may be configured to achieve the hydroforming or hydraulic forming of a pair of outer metal shells 7, 8 oriented opposite to each other. As can be seen from FIG. 9b, for example, the two metal shells 7, 8 may face each other at their thicker ends, while the thinner ends may face away from each other, and the two metal shells may be arranged substantially coaxially with each other about their main axes.

[0100] After the hydroforming process, the metal shell or pair of metal shells may be removed from the mold and one or more cutting processes may be performed. In particular, the axial ends of the formed metal shells 7, 8 may be cut (see FIG. 9c). Such cutting processes may include different cutting techniques such as laser cutting, sawing, and / or milling.

[0101] As is apparent from FIG. 9c, the aforementioned front openings 19, 20 at the axial ends of the metal shells 7, 8 are created by cutting the ends in this way.

[0102] As shown in FIG. 9d, one or more lateral openings 21 are also cut into the metal shells 7, 8, enabling attachment of the aforementioned front module 32 and back module 33. It should be noted that other lateral openings can also be cut into the lateral sides of the outer metal shells 7, 8. For example, the perforations may be cut or drilled so as to enable visual contact with components within the metal shell such as a display or LEDs.

[0103] As shown in FIG. 10, the creation of the openings 19, 20, 21 or notches can be carried out by different methods and different cutting techniques. For example, as shown by FIG. 10a, the opening can have a sharp edge and / or an edge profile with a substantially cylindrical configuration as a parallel extension of all sections of the cut edge. Such a configuration can be achieved, for example, by drilling a hole or by moving another cutting tool such as a saw or a milling tool in a fixed orientation with respect to the metal shells 7, 8. For example, the metal shells 7, 8 may be fixedly held in a horizontal orientation, while the milling tool is fixedly held in a vertical orientation and moved in the horizontal plane to machine the desired cutout profile.

[0104] Alternatively, as shown by FIG. 10b, the opening or notch may be manufactured by 3D cutting, and the orientation of the cutting tool is adjusted or changed along the displacement path of the cutting tool such that the edges of the resulting opening have different orientations in different sectors of the opening.

[0105] More specifically, such 3D cutting may be configured to adjust the orientation of the cutting tool relative to the inclination, orientation, and / or gradient of the outer surface of the metal shell section where the cutting is performed. More specifically, the orientation of the 3D cutting tool can be adjusted such that the edge of the resulting opening is substantially perpendicular to the outer surface of the metal shell adjacent to or surrounding the opening (see FIG. 10b), and such an outer surface adjacent to the opening can change its orientation along the opening and / or can have a curved shape such as a barrel shape or can have a multi-axis curved profile.

[0106] For example, such 3D cutting may include laser cutting by a laser cutter that can pivot about two or three axes, and the translational displacement of the laser relative to the metal shell may be achieved by the translation of the fixture holding the metal shell during the cutting process and / or the translation of the laser cutter. It is also possible to achieve 3D cutting by rotating the fixture holding the metal shell and adapting the orientation of the laser to the inclination or orientation of the metal shell surface.

[0107] Such 3D cutting may also use other cutting techniques such as milling or waterjet cutting.

[0108] As can be seen from FIG. 14, the hydroforming process for forming the metal shells 7, 8 may also include electrohydroforming, which is also sometimes known as EHF. Such electrohydroforming is based on the ultra-high-speed deformation of a metal shell blank using shock waves or pressure waves in a working fluid such as water. An electric arc can be generated in water between at least a pair of electrodes via a discharge current. Such an electric arc evaporates the surrounding water and / or working fluid and converts electrical energy into a high-pressure wave of mechanical energy. Such a shock wave simultaneously converts the metal shell blank 14 into a viscoplastic state and presses and / or accelerates the metal shell blank 14 onto the surface of the die cavity, thereby forming the desired shape at high speed under low-temperature conditions. Such electrohydroforming can form particularly complex shapes.

[0109] As shown in FIG. 15, for the forming process of forming the external metal shells 7 and 8 into a desired shape, electromagnetic forming known as EMF may be used. Such electromagnetic forming is based on the ultra-high speed deformation of metal using a magnetic field. For example, through the discharge current in a coil, a magnetic field is generated, which converts the metal shell blank into a viscoplastic state and at the same time presses / accelerates the metal shell blank onto the surface of the mold cavity, thereby forming the metal shell into the desired shape at high speed under low temperature conditions. Also, such electromagnetic forming can form complex shapes.

[0110] The dimensions and values disclosed in this specification should not be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 mm".

Claims

1. A personal care device, such as a hair cutter or a toothbrush, comprising a handle (3) and a functional head (4) that supports at least one personal care tool, wherein the functional head (4) is attached to the handle (3), and at least one of the handle (3) and the functional head (4) includes an external metal shell (7, 8), the metal shell (7, 8) has at least one opening (19, 20, 21), and at least one plastic chassis member (31, 32, 33, 35, 40) is housed within the external metal shell (7, 8), and the plastic chassis member (31, 32, 33, 35, 40) penetrates through the opening (19, 20, 21, 22) within the external metal shell (7, 8) and has a protrusion (25) that protrudes beyond the outer surface of the metal shell section surrounding the opening (19, 20, 21, 22), and / or the plastic chassis member completely covers the outer edge of the opening (19, 20, 21, 22).

2. The personal care device according to claim 1, wherein the external metal shell (7, 8) includes at least one lateral opening (21, 22), and a functional component (9) that extends at least partially outside the external metal shell (7, 8) and / or is accessible from outside the external metal shell (7, 8) is connected to another functional component (9) housed inside the external metal shell (7, 8) through the lateral opening (21, 22).

3. The personal care device according to claim 1 or 2, wherein the handle is provided with a front module and a back module on its opposing lateral sides, and each module is provided with the plastic chassis member that extends through the corresponding opening of the external metal shell (7).

4. The personal care device according to any one of claims 1 to 3, wherein the handle is provided with a top module and a bottom module on its opposing longitudinal sides, and each module is provided with the plastic chassis member that extends through the corresponding opening of the external metal shell (7).

5. The personal care device according to any one of claims 1 to 4, wherein the functional head (4) is provided with the plastic chassis member (31) extending through the bottom opening and the top opening of the functional head (4).

6. The personal care device according to any one of claims 1 to 5, wherein the protrusion (25) includes a collar (26) that overlaps the openings (19, 20, 21, 22) and / or seats on the outer surface of the metal shell section surrounding the openings (19, 20, 21, 22).

7. The personal care device according to any one of claims 1 to 6, wherein the protrusion (25) protrudes beyond the outer surface of the metal shell (7, 8) by a substantially constant amount along the entire opening and / or by an amount in the range of 0.05 to 1 mm or 0.1 to 0.5 mm or 0.1 to 0.3 mm, even when the contour of the opening (19, 20, 21, 22) does not extend in one plane.

8. The personal care device according to any one of claims 1 to 7, wherein the protrusion (25) is made of soft plastic and / or hard plastic having an outer contour that conforms to the inner contour of the opening (19, 20, 21, 22) in terms of shape and dimensions, and provides a sealing and / or engaging by fitting and / or snap-fitting engagement of the protrusion with the metal shell (7, 8).

9. The personal care device according to any one of claims 1 to 8, wherein the metal shell (7, 8) has opposing ends (17, 18) each defining a closed-ring-shaped cross-section, and an intermediate portion (16) between the opposing ends (17, 18) includes at least one lateral opening and / or lateral perforation for accessing at least one functional component (19) housed inside the external metal shell (7, 8).

10. The personal care device according to any one of claims 1 to 9, wherein the external metal shell (7, 8) has a ring-shaped or sleeve-shaped form with a closed-ring cross-section, and is formed in one piece with a homogeneous seamless structure.

11. The personal care device according to claim 10, wherein the external metal shell (7, 8) is a hydraulically formed portion and / or a hydroformed portion deformed by hydraulic pressure.

12. The personal care device according to any one of claims 1 to 11, wherein the external metal shell (7, 8) includes at least one undercut portion (23).

13. The external metal shell (7, 8) includes at least one opening (19, 20, 21) surrounded by a three-dimensional shaped metal shell section, and the opening (19, 20, 21) has a three-dimensional shaped edge contour (22) that extends substantially perpendicular to the surrounding metal shell section along the entire contour of the opening. The surrounding shell portion adjacent to and surrounding the opening (19, 20, 21) has various orientations that vary along the opening (19, 20, 21). The personal care device according to any one of claims 1 to 12.

14. The metal shell (7, 8) has opposing ends (17, 18) each defining a closed ring-shaped cross-section, and an intermediate portion (16) between the opposing ends (17, 18) includes at least one lateral opening and / or lateral perforation for accessing at least one functional component (19) housed inside the external metal shell (7, 8). The personal care device according to any one of claims 1 to 13.

15. The external metal shell (7, 8) has an elongated hollow shape with front openings (19, 20) at opposing axial ends, and the axial ends have a closed annular cross-section surrounding the openings (19, 20). The personal care device according to any one of claims 1 to 14.

16. The metal shell (7, 8) is made of stainless steel, or steel containing chromium, nickel, and molybdenum, particularly 10 to 25% by mass of Cr, 5 to 20% by mass of Ni, and 1 to 5% by mass of Mo, or 16 to 18% by mass of Cr, 10 to 14% by mass of Ni, and 2 to 3% by mass of Mo. The personal care device according to any one of claims 1 to 15.

17. A method of manufacturing a handheld personal care device such as a hair cutter or a toothbrush having an external metal shell, forming the external metal shell (7, 8) into a desired shape, and attaching a functional component (9) for performing or assisting in performing a personal care function on and / or in the formed external metal shell (7, 8). The forming step includes a hydroforming step of applying hydraulic pressure to one side of a metal shell blank (14) disposed in a mold (15) to deform the metal shell blank (14), pressing the opposite side of the metal shell blank (14) against the mold (15) to take the shape of the contour of the mold (15), thereby forming the external metal shell having the desired shape. forming at least one opening in the external metal shell; a notching step is provided for attaching a plastic chassis part in the at least one opening, wherein an outer edge of the opening is covered by the plastic chassis part and / or the plastic chassis part protrudes beyond the external metal shell. A method characterized by this.

18. The metal shell blank (14) has a hollow, sleeve-like or pipe-like shape and is disposed in a cavity of the mold (15) surrounding the outside of the metal shell blank (14), and the hydraulic pressure is applied inside the hollow metal shell blank, thereby expanding the hollow metal shell blank, pressing the outside of the metal shell blank (14) against the contour of the cavity of the mold (15), thereby causing the outside of the metal shell blank (14) to take the shape of the contour of the mold (15). The method according to claim 17.

19. The method according to any one of claims 1 to 18, wherein one or more undercut portions (23) of the external metal shell (7, 8) are hydroformed in the hydroforming step.

Images