Patent ID: 12257116

DETAILED DESCRIPTION OF THE INVENTION

The method for manufacturing a handle for an electrically operated personal care implement comprises the provision of a metal tube housing, the housing having a metal wall with an opening therein and an inner surface, the inner surface defining an inner cavity for accommodating an energy source for operating the personal care implement. The opening, e.g. a cut-out which may be provided by laser cutting, to accommodate a switch assembly for activating the energy source, i.e. for switching the electronically operated personal care implement to an ON/OFF status. Said switch assembly for operating the implement comprises a hard switch component and a soft switch component; the hard switch component comprises a frame with a recess.

In order to provide the metal tube housing with the switch assembly, the method according to the present disclosure comprises: providing a hard switch component comprising a frame with a recess, and attaching the frame of the hard switch component to the inner surface of the metal wall, the frame surrounding the opening and providing an undercut between the recess and the inner surface, the undercut being open towards the opening. The frame of the hard switch component surrounding the opening provides an undercut which is open towards the opening so that a portion of the soft switch component can be accommodated therein. The soft switch component is provided by at least partially over-molding the opening from the outside of the housing, thereby forming the switch assembly. The switch assembly seals the opening from the inner surface of the metal wall, preferably in a substantially waterproof manner.

In the method according to the present disclosure, the metal tube housing with the hard switch component attached thereto may be inserted into an injection mold before the soft switch component will be over-molded. Said injection mold may comprise a mold insert having a hardness being lower than the hardness of the metal tube material itself to avoid any damage to the metal tube housing during the closure of the mold. For example, the mold insert may be made from brass or from a soft elastic material. The insert may be provided at least in the area where the mold touches the metal tube.

Typical housings for electrical, handheld devices according to the art are usually made from plastic materials. While the housing itself is molded out of hard-plastic material, like PP or ABS, such devices often comprise a switch area molded out of soft elastomeric material, e.g. TPE to form a membrane that allows the actuation of a switch located inside the housing. By overholding the soft component on the hard-plastic housing a waterproof housing assembly can only be achieved, if the right material combination and geometry is selected; sufficient bonding properties between the hard and the soft component are crucial.

However, if a slim overall product design with a housing made from metal having small wall dimensions including a let-in flush switch element is to be provided, a waterproof assembly cannot be ensured by simply over-molding the soft component onto the metal housing as the bonding area would not be sufficiently large (due to the low wall thickness and reduced freedom to design such metal tube housing vs. freeformed plastic parts). The bonding force between the soft switch component and the metal tube housing would not be sufficiently strong to resist peeling stress. Further, no counterforce is provided to hold the soft switch component in place. If a force is applied onto the switch to activate the electrically operated implement, peel stress occurs in the bonding area which significantly weakens the bonding connection. A weakened bonding connection may cause fine cracks or crevices allowing water to enter the inner cavity of the handle metal tube housing.

To enable the provision of a waterproof switch assembly (i.e. a durable and waterproof sealing/bonding between the switch assembly and the metal material) in connection with a metal tube housing having small wall dimensions (e.g. between 0.4 mm and about 1.2 mm) without the need of using separate sealing elements, the present disclosure suggests the use of a switch assembly assembled of a hard switch component and a soft switch component. As the soft switch component is injection molded into the undercut provided between the recess of the hard switch component and the inner wall of the housing, the soft switch component is securely locked and supported from three sides (seeFIG.8and description provided below). Neither a force applied from the outside of the housing onto the switch component, nor a force applied from the inside of the housing results in significant peel stress on the bonding area as the frame provides a counterforce and holds the soft switch component in place. A switch assembly according to the present disclosure can be seamlessly integrated into the opening in the metal tube housing and can seal the opening in a substantially waterproof manner. Such design prevents water, toothpaste and saliva from entering the housing; a hygienic electrically operated toothbrush can be provided.

The metal wall circumferencing the opening in the housing accommodating the switch assembly may define an angle α between its outer surface and the neighboring surface/side wall of 90° or less. If angle α is less than 90°, the bonding area between the metal wall and the soft switch component is slightly increases which results in improved bonding properties.

For example, the personal care implement may be battery-operated and may comprise a battery to be located in the inner cavity of the handle housing. The electrically operated personal care implement comprising such handle and a head may be an electrically operated toothbrush. The head may be repeatedly attachable to and detachable from the handle. In order to allow for an exchange of the head, the handle may be provided—in a further method step—with a connector comprising a snap-fit locking mechanism. The connector may be inserted into a hollow portion in the head, or the head may comprise a connector insertable into a hollow portion in the handle. Alternatively, a connector may be provided as a further, i.e. separate part of the oral care implement. Such connector may be insertable into a hollow portion in the handle and into a hollow portion the head, respectively, thereby providing sufficiently strong connection and stability between the head and the handle to enable a user to perform a brushing action.

While the high-quality handle of the personal care implement is adapted for use over a longer period of time as compared to common implements, like manual toothbrushes which are discarded after about three months of use, the relatively cheap head/brush refill can be exchanged on a regular basis, e.g. after about three months. This provides a cost-efficient and environmentally sustainable personal care implement providing both, high quality handle solutions as well as cost saving opportunities as only the head has to be exchanged/re-purchased and not the handle.

The metal tube housing may provide an electrically operated personal care product with improved premium consumer delight in contrast to housings made from plastic materials. While the use of metal material drives premium consumer perception and high durability, the handle can be sustainably used over a long period of time. For example, the metal tube housing may be made from stainless steel and/or aluminum. Such materials are highly durable and allow for slim product designs. Beside higher value impression and comfortable haptic, the use of metal material also allows for relatively low wall thicknesses of the housing to enable an overall slim product design. Such slim product design drives premium consumer perception and improved handling properties. A wall thickness of about 0.4 mm to about 1 mm may create a durable metal wall handle, while ensuring high product perception. The thickness of the metal wall may be about 0.4 mm to about 1.2 mm, preferably of about 0.5 mm to about 1 mm. Such slim housing enables users to perform a well-coordinated brushing technique and also improves sensory feeling during brushing.

The frame of the hard switch component may comprise at least two protrusions for precisely positioning/centering the hard switch component onto the inner surface of the metal wall during assembling. Such protrusions to be received by respective recesses provided in the metal tube housing may help to define the position of the hard switch component in respect to the metal tube housing thereby facilitating manufacturing. To this end, the method for manufacturing the handle may comprise the step of positioning the frame of the hard switch component on the inner surface of the metal tube housing by means of at least two protrusions provided on a surface of the frame facing the inner surface and being adapted to be inserted into respective recesses provided in the metal tube housing.

The hard switch component may comprise a lever arm which may extend into the opening provided in the metal wall. The lever arm may comprise a button element, also positioned within the opening. At least a portion of the button element may not be over-molded by the soft switch component. The material of the hard switch component may be provided in a color different from the color of the soft switch component to precisely indicate where the user shall put/rest his finger to activate the switch assembly of the personal care implement.

While the soft switch component may be overmolded and may be made from a soft elastomeric material, preferably from thermoplastic elastomers (TPE), the hard switch component may be manufactured by injection molding from a hard-plastic material, preferably from acrylonitrile butadiene styrene (ABS) and/or acrylonitrile styrene acrylate (ASA).

The hard switch component may be fixed within the housing by means of gluing and/or by other means, including but not limited to substance-to-substance bonds, mechanically interlocking or frictional connections.

To facilitate improved bonding of the glue (if gluing is used for fixing the switch assembly within the housing), the method for manufacturing the handle may further comprise the step of pre-treating the inner surface of the metal tube housing by any of the following methods: laser treatment, plasma treatment, ultraviolet (UV) irradiation treatment, corona treatment, flame treatment and/or by activating the inner surface by removing oxide layers by a blasting process and/or by a sandblast coating process. Further, to provide an even better bonding, a curable resin layer, a coating material layer, and/or a pressure-sensitive non-curable adhesive may be applied onto the surface of the frame of the hard switch component facing the inner surface of the housing.

A method for treating the surface may comprise the following steps: selecting a material of interest to be processed comprising a target surface of interest; determining a surface adhesion transformation of said target surface of interest based on said material's properties, a shape of said target surface of interest, an adhesion material, and required degree of adhesion between said target surface of interest and the others object surface, wherein said material's properties comprise mechanical or chemical interfacial material properties required after application of said method. Studies have shown that such object can be achieved by applying any of the above-mentioned pre-treatment methods.

If the hard switch component is fixed within the housing by means of gluing, the hard switch component may be pressed onto the inner surface of the metal tube housing over a pre-defined period of time depending on the glue used.

The hard switch component can be further supported by a chassis inserted into the inner cavity of the housing. The chassis may comprise a carrier holding components for electrically operating the personal care implement, e.g. a motor, electronics and an energy source, for example a battery.

Further, a metal sheet having magnetic properties may be inserted into the inner cavity of the metal tube housing in a further manufacturing step. Said metal sheet may be formed as a part of the carrier.

Said metal sheet may provide the handle with magnetic/ferromagnetic properties which may allow for hygienic storage of the oral care implement by magnetically attaching the handle to a magnetic holder, e.g. provided at a wall. If the personal care implement is a toothbrush, remaining water, toothpaste slurry and saliva can drain off from the brush. The oral care implement can dry relatively quickly. Consequently, bacteria growth can significantly be reduced, thereby rendering the oral care implement more hygienic. In contrast to a common toothbrush being stored in a toothbrush beaker where drained fluids get collected and accumulated at the bottom of the beaker, the brush according to the present disclosure is exposed to wet conditions over a significantly shorter period of time.

The magnetic holder may have the form of a flat disk attachable to a wall. Such flat disk may represent an easy to clean surface. Further, a user just needs to bring the oral care implement in close proximity to the magnetic holder, and then the oral care implement gets attached automatically. No precise positioning or threading as with common toothbrush holders is required. If the magnetic properties are merely provided in the handle, and not in the head, the head portion cannot accidentally be attached to the magnetic holder, thereby reducing the risk that the magnetic holder gets soiled.

The handle for the electrically operated personal care implement may be provided with pressure compensation means, e.g. a pressure compensation membrane covering a small hole provided e.g. at a distal end of the handle, to prevent any potential explosions. The membrane may be glued onto the inner wall of the housing. Air can exit the inner cavity of the metal tube housing through the membrane, but water cannot enter the inner cavity from the outside.

The handle or part of the handle may get additional decoration in a further manufacturing step, e.g. by brushing, electroplating and/or by physical vapor deposition (PVD) to add improved appearance and a pleasant feel. Thermoplastic elastomers are well suited for electroplating as they allow for the creation of both hard and soft composite components to be electroplated selectively in one operation.

For example, the handle may be provided with a thumb rest being made from a thermoplastic elastomer material and/or from a polypropylene material. These materials can be easily injection molded over the metal tube housing. Such thumb rest may provide the handle with improved handling properties, e.g. with anti-slip properties to improve maneuverability of the personal care implement under wet conditions, e.g. when the user brushes his teeth. The thumb rest may be made from thermoplastic elastomer material having a Shore A hardness from about 30 to about 60, or about 40 to prevent the oral care implement from being too slippery when used in wet conditions. At least a portion of the thumb rest may have a concave shape with an angle α with respect to the area of the remaining portion of the thumb rest from about 20° to about 25°, or about 24°. The thumb rest or a gripping region may be attached onto the front surface of the handle in the region close to the proximal end, i.e. closest to the head. The thumb rest may comprise a plurality of ribs, e.g. extending substantially perpendicular, parallel or diagonal to the longitudinal axis of the oral care implement. Such ribs may allow users/consumers to use the oral care implement with even more control. The user/consumer can better grasp and manipulate the handle of the oral care implement during brushing. Such handle may provide improved control and greater comfort during brushing, in particular under wet conditions.

Thermoplastic elastomer material may form the thumb rest on the front surface of the oral care implement and/or a palm grip on the back surface being opposite the front surface to be gripped by the user's/consumer's fingers and thumb. Such handle configuration may even further resist slippage during use.

If the personal care implement is a toothbrush, tooth cleaning elements, e.g. bundle of filaments forming one or a plurality of tufts, may be attached to the toothbrush head by means of a hot tufting process. One method of manufacturing the head with tufts of filaments embedded in the head may comprise the following steps: In a first step, tufts are formed by providing a desired amount of filaments. In a second step, the tufts are placed into a mold cavity so that ends of the filaments which are supposed to be attached to the head extend into said cavity. The opposite ends of the filaments not extending into said cavity may be either end-rounded or non-end-rounded. For example, the filaments may be not end-rounded in case the filaments are tapered filaments having a pointed tip. In a third step the head is formed around the ends of the filaments extending into the mold cavity by an injection molding process, thereby anchoring the tufts in the head. Alternatively, the tufts may be anchored by forming a first part of the head—a so called “sealplate”—around the ends of the filaments extending into the mold cavity by an injection molding process before the remaining part of the oral care implement is formed. Before starting the injection molding process the ends of the tufts extending into the mold cavity may be optionally melted or fusion-bonded to join the filaments together in a fused mass or ball so that the fused masses or balls are located within the cavity. The tufts may be held in the mold cavity by a mold bar having blind holes that correspond to the desired position of the tufts on the finished head of the oral care implement. In other words, the tufts attached to the head by means of a hot tufting process are not doubled over a middle portion along their length and are not mounted in the head by using an anchor/staple. The tufts are mounted on the head by means of an anchor-free tufting process.

Alternatively, the head for the oral care implement may be provided with a bristle carrier having at least one tuft hole, e.g. a blind-end bore. A tuft comprising a plurality of filaments may be fixed/anchored in said tuft hole by a stapling process/anchor tufting method. This means, that the filaments of the tuft are bent/folded around an anchor, e.g. an anchor wire or anchor plate, for example made of metal, in a substantially U-shaped manner. The filaments together with the anchor are pushed into the tuft hole so that the anchor penetrates into opposing side walls of the tuft hole thereby anchoring/fixing/fastening the filaments to the bristle carrier. The anchor may be fixed in opposing side walls by positive and frictional engagement. In case the tuft hole is a blind-end bore, the anchor holds the filaments against a bottom of the bore. In other words, the anchor may lie over the U-shaped bend in a substantially perpendicular manner. Since the filaments of the tuft are bent around the anchor in a substantially U-shaped configuration, a first limb and a second limb of each filament extend from the bristle carrier in a filament direction. Filament types which can be used/are suitable for usage in a stapling process are also called “two-sided filaments”. Heads for oral care implements which are manufactured by a stapling process can be provided in a relatively low-cost and time-efficient manner.

The following is a non-limiting discussion of example embodiments of oral care implements and parts thereof in accordance with the present disclosure, where reference to the Figures is made.

FIG.1shows a personal care implement10, in this specific embodiment an electrically operated oral care implement, i.e. toothbrush10. Toothbrush10comprises a handle12and a head14, the head14being repeatedly attachable to and detachable from the handle12, e.g. by means of connector16. The connector16may be made from stainless steel and/or plastic material with or without glass-fibers. The connector16may comprise a spring-loaded ball element comprising a ball and a spring, the spring applying a radial force onto the ball in a direction towards an outer lateral surface of the connector. The ball may be received by a recess provided within a cavity of the head14. The connector may be inserted into in the inner cavity of the handle and fixed therein e.g. by gluing, welding and/or press-fitting. Alternatively, the connector16may be inserted into the inner cavity mounted to the handle thereby providing some degree of movement of the connector in relation to the housing to allow the use of a pressure sensor.

The handle comprises a switch assembly24located in the housing for activating an energy source accommodated within the handle12so that the electrical toothbrush10is operational. Electrical toothbrush10can be switched in an ON/OFF status by actuating the switch assembly24.

The housing of the handle12comprises substantially three parts as shown inFIGS.2,3and4, respectively: a metal tube housing18(FIG.2), a hard switch component20(FIG.3), and a soft switch component22(FIG.4).FIG.5shows the metal tube housing18, the hard and the soft switch component20,22in an assembled state.

As derivable fromFIG.2, the metal tube housing18is made from a metal wall26provided with an opening28for receiving the switch assembly24. The metal wall26has an inner surface30which defines an inner cavity32for accommodating the energy source, e.g. a battery. The metal tube housing18may be made from stainless steel and/or aluminum to provide high durability as well as high quality perception and appearance of the overall product. The metal wall26may have a thickness54(extending from the inner surface30and an outer surface31) of about 0.4 mm to about 1.2 mm, or of about 0.5 mm to about 1 mm to provide an overall slim product design.

The switch assembly24for activating the energy source comprises hard switch component20(FIG.3) and soft switch component22(FIG.4). Both, the hard and the soft switch components20,22are located within the opening28provided in the metal wall26of the housing18. The hard and soft switch components20,22are arranged in a manner that the switch assembly24seals the opening28in a substantially waterproof manner.

While hard switch component20may be molded from hard-plastic material, e.g. from acrylonitrile butadiene styrene (ABS) and/or acrylonitrile styrene acrylate (ASA), soft switch component22may be made from soft elastomeric material, e.g. from thermoplastic elastomers (TPE). TPE adheres well to metal material as well as to ABS and ASA.

As shown inFIG.3, the hard switch component20comprises a frame34with a recess36, the frame34being attached to the inner surface30of the metal wall26thereby surrounding/circumferencing the opening28in the metal tube housing18(seeFIGS.7and8).

The recess36creates an undercut38in which the soft switch component22is positioned and securely fixed (seeFIG.8). The hard switch component20may be connected to the inner surface30of the housing18by gluing, i.e. glue may be applied onto area40of the frame34, and then the frame gets connected to the inner surface30of housing18. Fixation of the hard switch component20on the inner surface may alternatively be provided by means of substance-to-substance bonds, mechanically interlocking or frictional connections. The frame34of the hard switch component20may comprise at least two protrusions42,43that help positioning the hard switch component20onto the inner surface30of the metal wall26; to this end the inner surface30may comprise respective recesses to receive said protrusions42,43.

The hard switch component20may further comprise a lever arm44comprising a button element46at the distal end of the lever arm44. The lever arm44and the button element46may extend into the opening28of the metal wall26.

The material forming the softs witch component22may be overmolded over the lever arm44and partially over the button element46thereby keeping a portion of the button element46exposed to provide an indication where a user should place his finger to activate switch assembly24. To this end, the color of the material of the hard switch component20and the color of the material of the soft switch component22may be different to provide a clear and easily visible indication. The material of the soft switch component22covers any remaining open area of the opening28and is fixed in the undercut38provided between recess36and inner surface30of metal wall26.

To further strengthen the bonding properties between the material of the soft switch component22and the metal wall26by slightly increasing the bonding area, the metal wall26surrounding the opening28may define an angle α between the outer surface31and the neighboring surface33of 90° or less.

The housing assembly comprising the metal tube housing18, the hard and soft switch components20,22allows for solid anchoring of the soft switch component22. The recess36of the hard switch component20together with the inner surface30creates a defined undercut, i.e. cavity that can be filled with the material of the soft switch component22during a molding process. The recess facilitates bonding of the soft switch component22on three sides48,50,52. Neither a force applied from the outside of the handle, nor a force applied from the inside onto the soft switch component22results in peel stress as the frame of the hard switch component20holds the softs witch component22in place. By over-molding the soft switch component22, a substantially waterproof and durable seal can be provided which may prevent water, toothpaste and/or saliva from entering the inside/inner cavity32of the housing18.

FIG.11shows the method steps for manufacturing the handle12for the electrically operated personal care implement10according toFIG.1.

In a first step100, a metal tube housing18according toFIG.2is provided, the housing18having a metal wall26with an opening28and an inner surface30, the inner surface30defining an inner cavity for accommodating an energy source. The opening28may be provided by laser cutting.

In a second step200, a hard switch component20according toFIG.3is provided by means of injection molding, the hard switch component comprising a frame34with a recess.

In a third step300, the inner surface30of the metal tube housing18is pre-treating by any of the following methods: laser treatment, plasma treatment, ultraviolet (UV) irradiation treatment, corona treatment, flame treatment and/or by activating the inner surface by removing oxide layers by a blasting process and/or by a sandblast coating process.

In a fourth step400, a curable resin layer, a coating material layer, and/or a pressure-sensitive non-curable adhesive is applied onto the surface of the frame34facing the inner surface30of the housing18.

In a fifth step500, the frame34of the hard switch component20is attached to the inner surface30of the metal wall26by gluing, the frame34surrounding the opening28and providing an undercut38between the recess36and the inner surface30the undercut38being open towards the opening28. The frame34of the hard switch component20gets positioned on the inner surface30of the metal tube housing18by means of at least two protrusions42,43provided on a surface of the frame34facing the inner surface30and being adapted to be inserted into respective recesses provided in the metal tube housing18.

In a sixth step600, the hard switch component20is pressed onto the inner surface30of the metal tube housing18over a pre-defined period of time.

In a seventh step700, the metal tube housing18with the hard switch component20attached thereto is inserted into an injection mold80, the injection mold80comprising a mold insert82to prevent any damage to the housing18when the mold is getting closed. The mold insert has a hardness being lower than the hardness of the metal tube material. For example, the mold insert may be made from brass or from a soft elastic material. The insert may be provided at least in the area where the mold touches the metal tube.FIG.9shows a perspective view of the mold80for over-molding the soft switch component22to form the switch assembly24.FIG.10shows a cross sectional view of the mold80ofFIG.9with the soft switch component22being overmolded and injection nozzle insert84.

In an eighth step800, the opening28is at least partially over-molding to form a soft switch component22according toFIG.4, the soft switch component22being accommodated in the undercut38thereby forming with the hard switch component20a switch assembly24for activating the energy source, the switch assembly24sealing the opening28from the inner surface30of the metal wall26.

In a ninth step900, a metal sheet having magnetic properties is inserted into the inner cavity of the metal tube housing18to provide the handle12with magnetic properties.

In the context of this disclosure, the term “substantially” refers to an arrangement of elements or features that, while in theory would be expected to exhibit exact correspondence or behavior, may, in practice embody something slightly less than exact. As such, the term denotes the degree by which a quantitative value, measurement or other related representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

The dimensions and values disclosed herein are not to 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”.

Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.