Brush, in particular toothbrush, and process for its manufacture

Abstract

The invention relates to a brush and a method for its production, which allows for more efficient use of the plastics used and, therefore, more cost-effective production. The brush comprises a head (28) with bristle filaments (6), a neck, and a handle, arranged one behind the other in the longitudinal direction of the brush. In this brush, a bristle support (32) that holds the bristle filaments (6) is formed from a rigid component (16), and the handle is formed from a foamed plastic material (24). In the method of the invention, to form the bristle support (32) that holds the bristle filaments (6), a first plastic component (16) is injected into a first mold cavity (14). The bristle support (32) is then transferred to another mold cavity (22), and in a subsequent molding cycle, a foamed plastic material (24) is introduced into the other mold cavity (22) and foamed within it.

Description

[0001] The present invention relates to a brush, in particular a toothbrush, and a method for its manufacture.

[0002] A brush, especially a toothbrush, has a brush body that holds bristle filaments. The brush body has a brush head to which the bristle filaments are attached, a handle for gripping the brush, and a brush neck in between.

[0003] Brushes of this type, in the form of toothbrushes, have been known for a long time.

[0004] EP 1 110 478 A1, filed by the applicant, relates to a method for manufacturing a toothbrush. In this method, an injection mold is first loaded with several bristle bundles, each consisting of a multitude of bristle filaments. The bristle bundles are first melted at the attachment point, creating a thickening. This thickening is then overmolded with a first plastic component in a first injection mold. The intermediate product is then transferred to a further, larger injection mold and overmolded with a second plastic component.

[0005] This process is intended to produce visually appealing brushes. Overmolding the attachment ends of the bristle filaments can typically only be done with a limited injection pressure, as the bristle filaments protrude through the mold cavity formed for overmolding. For this purpose, a perforated channel is formed in the injection mold to hold the respective bristle bundle. However, a complete seal is not achieved at this point. Therefore, a reduced injection pressure must be applied when overmolding the thickened section and the attachment end of the bristle bundle. This results in a surface finish on the resulting intermediate product that does not always meet the visual and design requirements for a hygiene product like a toothbrush. Therefore, the intermediate product is overmolded with another plastic component in the second mold cavity.The second mold cavity is sealed by surfaces of the intermediate product formed by the first plastic component, allowing higher injection pressures to act in the second mold cavity.

[0006] The present invention aims to provide a brush and a method for its manufacture which allows for more efficient use of the plastic employed. This should make it possible to manufacture brushes of the aforementioned type, in particular toothbrushes, more cost-effectively.

[0007] To solve this problem, the present invention proposes a brush having the features of claim 1.

[0008] This brush can be a toothbrush comprising, in a manner known per se, a brush head, a brush neck, and a handle, with the brush neck positioned between the brush head and the handle. These components are arranged one behind the other in the longitudinal direction of the toothbrush. They typically form the brush body of the toothbrush, which is an elongated brush body. According to the invention, a bristle carrier of the brush, which holds the bristle elements, is formed from a hard component. This hard component is a conventional plastic capable of holding the bristle filaments, regularly several bristle filaments bundled together, to the brush head with the necessary pull-out strength. The filaments can be held without anchors, as described above. For this purpose, the bristle filaments are embedded in the hard component forming the bristle carrier during its formation.The filaments can also be attached using an anchor. In this process, the bristle carrier is first manufactured, usually by injection molding, and then, typically after the brush body is completely finished, the bristle filaments are attached to the brush head.

[0009] In the brush according to the invention, the brush head can have several bristle carriers. The bristle carriers are designed as fastening elements for attaching the bristle filaments. Individual bristle carriers, each carrying at least one bristle filament or bristle bundle, can be articulated to another bristle carrier. The bristle carriers can be connected to one another via film hinges, so that all bristle carriers of the brush head can be formed in a single injection molding cycle.

[0010] The brush according to the invention has a handle made of a foamed plastic. The foamed plastic can also form the brush neck. The foamed plastic allows the production of a brush body in the usual and known dimensions, but using a reduced amount of plastic. The foaming process leads to improved utilization of the amount of plastic material introduced during injection molding for forming the brush body. The brush is lighter overall. It can be manufactured more cost-effectively, since a reduced amount of plastic is required to form the brush body without compromising the brush's dimensions.

[0011] Document US 5815874 A shows a toothbrush with a handle made of foamed plastic.

[0012] From the applicant's patent DE 100 34 839 A1, it is known to manufacture a thick-walled handle for a toothbrush by overmolding the handle several times with a cost-effective recycled material, so that the handle is formed by several ring-like layers around a core of a high-quality, virgin plastic component. Such a design cannot be produced economically for toothbrushes because available recycled materials regularly contain unspecified ingredients and additives, meaning that the recycled material does not meet the requirements for the chemical purity of hygiene products (FDA compliance).

[0013] The bristle carrier is preferably designed as a bristle carrier limited to the brush head. The handle and the brush neck are formed from the foamed plastic. The connection can be made, for example, according to EP 3 087 864 A1.

[0014] The foamed plastic can also form parts of the brush head. If there are multiple bristle carriers in the brush head area, the foamed plastic can connect or encase them. This also results in the brush head being formed into an aesthetically pleasing segment of the brush body with reduced plastic weight, thanks to its outer encasement in the foamed plastic.

[0015] In a preferred embodiment of the invention, the bristle carrier is therefore at least partially surrounded by the foamed plastic.

[0016] According to a preferred embodiment of the present invention, the brush head, handle, and neck consist of the foamed plastic and the hard component. In other words, the brush according to the invention is preferably formed solely by the brush body formed from these two components and the cleaning elements attached thereto. These cleaning elements can be bristle filaments or soft, elastic cleaning elements, for example, made of a TPE. Limiting the use to just two plastic materials forming the brush body simplifies manufacturing and increases cost-effectiveness.

[0017] In a preferred embodiment of the invention, the foamed plastic has essentially the same hardness as the hard component. Preferably, the hardness, in particular the tensile strength, of the foamed plastic is at least 50%, more preferably at least 80%, of that of the hard component. In this way, it is possible to produce a sufficiently stable handle while simultaneously reducing the amount of material used.

[0018] In another embodiment of the invention, the foamed plastic is sufficiently compressible on its own, so that the brush provides a pleasant feel. In this case, haptic elements molded from a separate material on the outer surface, particularly of the handle, can be omitted. The overmolding of the brush body with a soft, elastic plastic compound, as known from the prior art for creating haptic elements, is unnecessary.

[0019] A hard component within the meaning of the present invention is, in particular, an engineering plastic such as PA, PE, or PP. With regard to the desired pull-out strength of the bristle filaments relative to the brush body, the hard component preferably has a tensile strength of at least 80 MPa, more preferably at least 90 MPa, and most preferably at least 500 MPa.

[0020] The area of ​​the brush body formed by the foamed plastic is preferably shaped as an integral foam. With regard to hygiene requirements, the foamed plastic forms a closed, thick outer skin, so that even those surface areas of the brush body made of the foamed plastic cannot absorb moisture or dirt. The core of the foamed material, on the other hand, has a cellular structure, with the density of the foamed material typically decreasing from the outside to the inside. Such an integral foam can be the result of mechanical or physical foaming. The foamed plastic can also be shaped by chemical foaming.

[0021] Insofar as the foamed plastic extends into the brush head, the design should be such that the bristle filaments project through and away from an upper outer surface of the brush head formed by the hard component, whereas adjacent to this projected outer surface and in the same plane or extent, the surface is formed by the foamed plastic. This is usually achieved by the foamed plastic completely surrounding the upper outer surface. When viewed from the top of the brush head, the hard component is then visible in the area of ​​the bristle filaments, and the foamed plastic is visible where no bristle elements are present. This design offers further functional advantages.The foamed plastic in the brush head area provides a softness that protects the mucous membranes when the brush is used as a toothbrush in the oral cavity. This creates a synergistic effect: on the one hand, material is saved for shaping the brush body; on the other hand, the foamed plastic forms functional areas on the brush head.

[0022] The same applies to technical functional elements of the brush head, such as joints that are to be formed or created between individual bristle carriers. Due to the reduced stiffness of the foamed plastic compared to a conventional hard component, relative pivoting of the bristle carriers relative to each other on the brush body can be easily achieved.

[0023] By positioning the foamed plastic on the back surface of the brush head opposite the upper outer surface, a tongue scraper can be formed from the foamed plastic. Here, too, the inherent compressibility of the foamed plastic allows for a corresponding functionality, enabling the effective treatment of mucous membranes within the oral cavity, a feature not provided by a conventional hard component.

[0024] Insofar as the back surface is entirely formed from the foamed plastic, corresponding functional elements can be provided over a large area of ​​the back surface. This also allows for comprehensive impact protection for the sensitive oral mucosa, by which the bristle carrier(s) formed from the hard component are almost completely encased. Only the surface directly pierced by the bristle filaments, which, due to the spacing provided by the bristle filaments, cannot come into contact with the oral mucosa, is formed from the hard component in this design.

[0025] To increase the usability of the brush according to the invention, a preferred embodiment of the present invention proposes to provide the foamed plastic on the back surface of the brush head such that at least one functional surface formed by the hard component is completely surrounded by the foamed plastic. The functional surface can, for example, have ribs or bumps formed by the hard component, thus exhibiting higher mechanical effectiveness against the surface to be cleaned.

[0026] The connection between the rigid component and the solidified, foamed plastic material of the brush head can be either material-bonded or form-fit. A form-fit connection is created, in particular, by the solidified foamed plastic completely or almost completely encasing the rigid component. In the case of almost complete encasing, the rigid component only forms areas on the upper outer surface of the brush head that surround the bristle filaments. For example, each individual bristle bundle can be completely surrounded by a ring of the rigid component, forming a ring-shaped area on the upper outer surface, which is otherwise formed by the foamed plastic. The surface segments of the brush head typically merge seamlessly, preventing dirt and bacteria from accumulating on the brush head.

[0027] Individual support rings or a uniform grid of rings produced by injection molding, with connecting bridges acting as film hinges between them, can also serve as bristle carriers, with each individual ring typically supporting a single bristle bundle. The bristle bundle can be conventionally attached to a ring that is closed on the underside using an anchor, adhesive bond, or welding. Alternatively, a ring serving as a bristle carrier can be open on the underside, allowing the bristle bundle to protrude through the ring. On the ring surface opposite the upper outer surface, the bristle bundle is held securely in place by a thickening formed on the bristle bundle, providing a positive locking connection and good pull-out strength to the bristle carrier element.

[0028] With regard to the procedural aspect of the underlying problem, the present invention proposes a method for manufacturing a brush in which a first plastic component is injected into a first mold cavity to form a bristle carrier, and the intermediate product thus produced is then transferred to a further mold cavity, which is regularly larger than the first mold cavity, and in a further forming cycle a foaming plastic is introduced into the further mold cavity. This foaming plastic is foamed in the further mold cavity, resulting in a form-fit and / or material-fit connection between the hard component forming the bristle carrier and the solidified foamed plastic.

[0029] Further details and advantages of the present invention will become apparent from the following description of exemplary embodiments of a schematic process flow in conjunction with the drawing. This drawing shows: Figure 1 is a schematic sectional view to illustrate a first injection molding step for the production of the brush head; Figure 2 is a representation according to Figure 1 To illustrate the second injection molding step; Figure 3 is a representation according to Figure 2 for an alternative embodiment; Figure 4 a schematic sectional view to illustrate a first injection molding step for the production of a brush head according to an alternative embodiment; Figure 5 a representation according to Figure 4Figure 6 illustrates the second injection molding step for the production of the second embodiment; Figure 6 shows a schematic sectional view to illustrate the design of the second embodiment of a brush head; Figure 7 shows a schematic sectional view to illustrate the attachment of a bristle filament according to a first variant; and Figure 8 shows a schematic sectional view to illustrate the attachment of a bristle filament according to a second variant.

[0030] In the Figures 1 and 2 Two successive steps of the two-component injection molding of a brush body (not shown in detail) are illustrated. The brush body is designed as a toothbrush body and has a brush head shown in section in the figures, a brush neck extending longitudinally to it, and a handle adjoining the brush neck.

[0031] In the manufacturing process, a perforated plate 2 is first stuffed with at least one bristle bundle 4. For this purpose, the bristle filaments 6 forming the bristle bundle 4 are pushed through a hole 8 and melted at the end to form a thickening 10. The perforated plate 2 is then joined to an injection mold half 12a to form a first mold cavity 14 together with an injection mold half 12b. A hard component 16 is injected into this first mold cavity 14 as the first plastic component.

[0032] After the hard component 16 has solidified, a Figure 1 The intermediate product marked with reference numeral 18 is demolded. The demolding takes place together with the perforated plate 2, which is sealed against a second injection mold half 20a, which, together with another second injection mold half 20b and the perforated plate 2, forms a second mold cavity 22.

[0033] A foaming plastic 24 is introduced into this second mold cavity 22, which is then foamed or expanded physically and / or chemically and / or mechanically. Preferably, an integral foam is formed, such that the foamed plastic 24 solidifies with a closed, thicker outer skin against the perforated plate 2 surrounding the second mold cavity 22 and the second injection-molded halves 20a, 20b, while having a density that decreases towards the interior.

[0034] In this context, it is important to understand that the Figures 1 and 2The section through a brush according to the invention is shown only schematically. It is understood that the hard component 16 must be sufficiently thick around the thickening 10 to ensure the desired attachment of the bristle bundles 4, while, on the other hand, to achieve the desired material savings, the majority of the brush body to be produced must be formed from the foamed plastic 24.

[0035] The Figure 3 shows a contrast to the Figures 1 and 2 Modified embodiment after injection of the foaming plastic 24. Identical components are marked with the same reference numerals. The second embodiment according to Figure 3The main difference is that an upper outer surface of the brush head 28, shown in cross-section and pierced by the bristle bundles 4 and marked with reference numeral 26, is formed almost entirely by the foamed plastic 24. Only a circular ring surface 30 completely surrounds the bristle bundle 4, which in this case has a round cross-section.

[0036] Accordingly, the surface areas of the brush head 28 pierced by the bristle bundles 4 are formed by the hard component 16, while the upper outer surface 26 is otherwise predominantly made of the foamed plastic 24. The variant shown also results in a completely form-fitting seal of the bristle carrier formed by the hard component 16 and marked with reference numeral 32.

[0037] The Figures 4 to 6 illustrate the production of a second embodiment of a Figure 6Bristle carrier designated with reference numeral 32, which has a hard component designated with reference numeral 16, forming a core within the bristle carrier 32. This hard component 16 is described in accordance with Figure 4 in a first mold cavity 14. The mold cavity 14 is produced - as in Figure 2 - enclosed by two injection molded halves 12a, 12b and a pin plate 34 which carries a pin 36 which protrudes into the first mold cavity 14.

[0038] Figure 4 illustrates the design after the injection of the hard component 16, which surrounds the pin 36.

[0039] According to Figure 5This intermediate product 18 is transferred into the second mold cavity 22 by moving the pin plate 34. The second mold cavity is dimensioned such that a space remains between the outer surface of the intermediate product 18 and the mold cavity surface of the second mold cavity 22. In this case, this space is shaped to surround the hard component 16 in a trough-like form. Now, as in the first embodiment, foamed plastic 24 is introduced into the second mold cavity 22. The foam solidifies, forming a skin that adheres to the surfaces bounding the second mold cavity 22. Thus, a sealed surface is also present on the area penetrated by the pin 36, which is hereinafter referred to as the surface of the brush head 28.

[0040] After demolding the bristle carrier 32, the pin plate 34 is also removed. Instead of the pin 36, the bristle carrier 32 now has a base hole 38.

[0041] How Figure 7To illustrate, a bundle of bristles 4 can be driven into the borehole 38 and secured therein using a conventional anchor 40.

[0042] Figure 8 Figure 2 shows a second variant in contrast to the first, in which the bristle bundle 4 has a thickening 10 formed by melting, which is inserted into the shorter base hole 38. A ring-shaped area of ​​the surface surrounding the base hole 38 is then plastically deformed, so that the material initially bounding the cylindrical base hole 38 on the surface of the bristle carrier 32 is displaced radially towards the bristle bundle 4, and the thickening 10 is positively locked in the base hole 38.

[0043] In one variant, for example, the intermediate product 18 can also be arranged at a distance from the pin plate 34 by relative movement of the pin 36, so that the core formed by the hard component 16 is basically completely sealed by the foamed plastic 24.

[0044] A single core formed by the hard component 16 can be provided for each individual bristle bundle 4. The core can also be formed by a ring through which the bristle bundle extends, but which is otherwise contained within the foamed plastic 24, wherein the bristle bundle 4 is positively locked against the ring on the back side facing away from the front surface of the bristle carrier 32 by the thickening 10.

[0045] The fastening of the bristle bundle 4 formed by the hard component 16 can therefore have various specific configurations. Reference symbol list

[0046] 2 Perforated plate 4 Bristle bundle 6 Filament 8 Hole 10 Thickening 12 First injection molded half 12 Top injection molded half 14 First mold cavity 16 Hard component 18 Intermediate product 20 Second injection molded half 20 Second injection molded half 22 Second mold cavity 24 Foamed plastic 26 Upper outer surface 28 Brush head 30 Ring surface 32 Bristle carrier 34 Pin plate 36 Pin 38 Base hole 40 Anchor

Claims

1. Brush, in particular toothbrush, comprising a brush head (28) carrying bristle filaments (6), a brush neck and a handle stem, which are arranged one behind the other in the longitudinal direction of the brush, wherein a bristle carrier (32) holding the bristle filaments (6) is formed of a hard component (16) and the handle stem is formed of a foamed plastic (24), wherein the bristle carrier (32) is formed as a bristle carrier element restricting itself to the brush head (28), and in that the handle stem and the brush neck are formed from the foamed plastic (24), and wherein the bristle carrier (32) is at least partially surrounded by the foamed plastic.

2. Brush according to any one of the previous claims, characterized in that the brush head, the handle stem and the brush neck consist of the foamed plastic (24) and the hard component (16).

3. Brush according to any one of the preceding claims, characterized in that the brush head (28) has a plurality of bristle carrier elements connected to one another by the foamed plastic (24).

4. Brush according to any one of the preceding claims, characterized in that the bristle filaments (6) project from an upper outer surface (26) of the brush head (28) formed by the hard component and surrounded circumferentially by the foamed plastic (24).

5. Brush according to claim 4, characterized in that the foamed plastic (24) is provided on a rear surface of the brush head provided opposite to the upper outer surface.

6. Brush according to claim 5, characterized in that the rear surface is formed of the foamed plastic (24).

7. Brush according to claim 6, characterized in that the foamed plastic (24) circumferentially surrounds a functional surface formed by the hard component (16) and exposed at the rear surface.

8. Brush according to any one of the preceding claims, characterized in that the hard component has a tensile strength of at least 500 MPa.

9. Method of manufacturing a brush according to any one of the claims 1 to 8, in particular a toothbrush comprising a brush head provided with bristle filaments, a handle stem and a brush neck located therebetween, by injection molding, wherein a first plastic component (16) is injected into a first mold cavity (14) to form a bristle carrier (32) holding bristle filaments (6), characterized in that the bristle carrier (32) is transferred into a further mold cavity (22) and in a further molding cycle a foaming plastic (24) is introduced into the further mold cavity (22), which foams in the further mold cavity (22).

10. Method according to claim 9, characterized in that the bristle filaments (6) are embedded in the first plastic component (16) when forming the bristle carrier (32).

11. Method according to claim 9, characterized in that after ejecting the bristle carrier (32) the bristle filaments (6) are fixed to the bristle carrier (32).

12. Method according to any one of claims 11 to 12, characterized in that the foaming plastic (24) is physically or mechanically foamed.

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