SECTIONS ANCHORED TO EACH OTHER IN A FORM-FITTING MANNER

The invention concerns a process for manufacturing a cosmetic applicator according to the generic term of claim 1.

TECHNICAL BACKGROUND

The vast majority of cosmetic applicators, which are not designed as wire core applicators, consist of a single plastic material. In order to modify the properties of the respective applicator, several plastic materials are occasionally used. A typical process is two-component injection moulding or overmoulding. However, the plastic materials used for this normally must be matched to each other. Only then can a sufficiently strong bond be achieved. An alternative is the complex moltrusion® process. In said moltrusion processes, the plastic of a first applicator section is penetrated by fine threads of the still molten plastic mass of the second plastic section. This results in an intimate positive connection. In this case, it is not necessary to match the plastic materials to each other.

However, there is an increasing need for building applicators from different plastics that do not allow fixation by glueing or welding together. Nevertheless, one section of the applicator should be made of one plastic and the other section of the applicator of another plastic. Even in such a case, a sufficiently firm hold between the two plastics is required.

So far, this need (apart from the moltrusion process described above) can only be satisfied without any problems when the two applicator sections made of the different plastics are large enough to be mechanically firmly connected to each other - for example by snapping them together.

OBJECT OF THE INVENTION

Against this background, the invention is based on the task of creating an innovative method of manufacture. With the help of this new method, it will also be possible to connect those sections of the applicator that were previously considered to be unconnectable or at least not to be connectable without costly mechanical assembly or expensive moltrusion.

THE INVENTIVE SOLUTION

The problem is solved by a method according to the first main claim.

The method for manufacturing a cosmetic applicator uses a first applicator section made of a first material. This first applicator section can be prefabricated by a suitable procedure. Injection moulding or 3D printing can also be used. Said first applicator section has a cavity. This is preferably undercut .

According to the invention, a second applicator section is connected to the first applicator section. This second applicator section is generated in situ from a fluidic material. The material can be cured by electromagnetic radiation .

According to the invention, the first step of the inventive method is to fill or flood the cavity of the first applicator section with the second fluidic material. The filling is carried out without or predominantly without the second material hardening in layers during the filling process. This way, the second material is first filled into the cavity as a "bulk", so to speak.

In the next process step, a first layer is produced by curing, which spans the entire or substantially entire mouth of the cavity. As a rule, curing takes place pixel by pixel or point by point. This layer is part of the upcoming second applicator section. The curing of this layer is complete or essentially complete. In the latter case, a final heat treatment for complete curing may follow.

Then, in a subsequent step, several further layers are applied to the first layer one after the other. These layers are also cured in the same way. They also serve to form the second applicator section.

The electromagnetic radiation applied to the first and at least some subsequent layers is selected and/or adjusted and/or applied in such a way that it also cures the material located deeper in the cavity. This is usually done before the second applicator section is completed. At this point,

"curing" is understood to mean complete curing or in any case predominant curing.

The basis of the invention is the insight that for this special compound one has to leave the dogma of 3D printing, that one layer has to be hardened before the next layer is applied. Once this has been understood, a form-fit connection can be produced very efficiently using a 3D printing process. This also applies if the applicator sections to be connected are extremely small in size and therefore elude the methods known so far for connecting applicator sections.

The invention is surprising. Until now it has been assumed that 3D printing fails where a substrate with a cavity several millimeters deep is to be printed. A cavity that has a mouth on only one side, or even a noticeable undercut, or a cavity that is narrow because its mouth diameter is only as large or smaller than its depth. This is what the invention is all about. The problem now overcome was that in such a narrow or undercut cavity it was not possible to cure material layer by layer. In such cases there is no or almost no possibility to apply the bundled electromagnetic radiation within the cavity in such a way that a defined layer by layer curing takes place.

According to the invention, this supposed problem is overcome by filling the cavity first with fluidic material.

This material, which remains fluid at first, forms a support in the cavity, which is still movable within itself. This support carries a top layer or film which is reached by the bundled electromagnetic radiation and can thus be cured.

In this way, after filling the cavity, a first cap-like layer can be cured. The material which normally lies above this layer and fills the cavity is enclosed, although it is still fluid.

The decisive point here is that when the first layer and all or some of the subsequent layers harden, at least some of the electromagnetic radiation applied radiates through said layers. The radiation thus penetrates into the cavity and the uncured material trapped there. This triggers the curing process of the second plastic material, which is enclosed in the cavity and is initially fluidic. It may then continue to run by itself until complete curing. Alternatively, the material enclosed in the cavity is even completely cured. In this way, the content of the cavity finally becomes an integral part of the second stage of the applicator.

A particularly strong bond is achieved when the second material is chosen in such a way that it expands in the cavity permanently during curing.

Either way, there is usually a positive connection between the first and second applicator sections. As a rule, the electromagnetic radiation is adjusted and applied in such a way that the complete positive connection occurs before the second applicator section is completed. If this is not the case, then the electromagnetic radiation is at least adjusted and applied in such a way that a temporary positive connection occurs. This is a connection that is at least so resilient that the applicator can be handled for subjecting it to a subsequent heat treatment, such as tempering. This then leads to complete curing.

For the sake of good order, it should be noted that the first and the second fluidic material are usually different. In exceptional cases, however, they can also be identical. This may be the case if it is only a matter of creating a joint.

It should also be noted that a strict layered structure is particularly advantageous for the invention. In a broader sense, however, this term also refers to a „fuzzy" structure. This can be a structure that also leads to a de facto layered structure in the end. Such a construction can take place, where a layer or a foundation already exists, according to the divise "here a pixel on the foundation is hardened, at a distance from it another pixel on the foundation is hardened, and finally - again at a distance from it - a third pixel on the foundation is hardened."

POSSIBILITIES FOR FURTHER DEVELOPMENT OF THE INVENTION

It is particularly advantageous if a first applicator section is used as substrate for carrying out the process according to the invention, which provides a build-up surface next to the mouth of the cavity. The production of said first layer is started at the side of the build-up surface next to the mouth of the cavity. This is where the first layer, which is in the process of being created, is attached to the build-up surface to produce the second applicator section. Temporary attachment can also be sufficient instead of a final attachment. This will be the case, for example, if the second applicator section is later to be detached from the first applicator section because a joint is to be formed between the two applicator sections around which the two applicator sections can move relative to each other.

Then, in the course of ongoing production, said first layer is extended laterally so that it spans the cavity in the end.

In other cases it is particularly advantageous to carry out the procedure in such a way that the second fluidic material is initially exposed to electromagnetic radiation only or essentially only in the area of the mouth in such a way that it hardens. Then there is no need for said build-up surface next to the cavity. Instead, the soffit or inner boundary edge of the cavity holds the first layer, which closes the cavity, in position so that further layers can be built up. Where an undercut cavity is used, it is particularly advantageous to make the mouth of said cavity narrower in the first applicator section than the rest of the cavity. Ideally, the mouth is so narrow that the part of the second applicator section located in the cavity and firmly connected to the external rest of the second applicator section cannot be pulled out of the cavity non-destructively.

In many cases it is particularly advantageous if the first material and the second material are chosen in such a way that they do not stick or weld together significantly even during the hardening of the second material.

In most cases, the design of the substrate and the process control are chosen in such a way that the first applicator section holds the second applicator section in a positive fit after it has cured.

In some cases it is better if the first section of the applicator forms a socket in which a ball of the second section of the applicator can slide.

The Shore D hardness of the first and second material is different. This applies to ready-to-use applicators, i.e. after curing. It is particularly favourable if said Shore hardnesses differ by at least 10 %, better by at least 25 %.

Ideally, the first applicator section, which serves as substrate for the process, has an undercut cavity. Optimally, this shape has a hollow sphere, a hollow cone section or a hollow triangle that widens inwards from said mouth. Further possibilities of design, modes of action and advantages result from the following description of the invention on the basis of the preferred embodiments in the light of the associated figures.

LIST OF FIGURES

Figure 1 shows the first applicator section forming the substrate with its cavity at a stage where the inventive process begins.

Figure 2 shows the applicator section as shown in Figure 1 at a stage of the process in which the first layer is being formed, which becomes part of the second applicator section.

Figure 3 shows the development process of the second applicator section in an advanced process stage.

Figure 4 shows the same process stage as Figure 2, but an alternative approach is used to create the first layer.

Figure 5 shows the same process stage and procedure as Figure 4, but on an alternative substrate.

Figure 6 shows the same procedural stage as Figure 3, but here a ball joint applicator is produced. PREFERRED EMBODIMENTS

Figures 1 to 3 show a first preferred embodiment of the invention .

In this embodiment, a flowable, preferably liquid plastic material is used for the additive, layerwise or pixelwise production of the second applicator section 8.

As a rule, this plastic material or „plastic" is photosensitive. This means that the plastic in question can be cured by electromagnetic radiation in such a way that it no longer remains a flowable liqiud. Electromagnetic radiation can be at least predominantly thermal radiation, optically perceptible light or UV radiation, or a mixture thereof. In all this it is advantageous, but not absolutely necessary, that the flowable, photosensitive plastic is completely or solely cured with the aid of electromagnetic radiation. In some cases, the photosensitive plastic may be such that (at least if it is exposed to a sufficiently warm environment) it cures by itself once the curing process has been triggered by the exposure to electromagnetic radiation.

Figure 1 shows the first step of the inventive process.

Accordingly, a first applicator section 1 is used to perform this procedure. This first applicator section 1 may have been manufactured in an appropriate manner. If necessary, it is produced externally before the start of the process described here. For example, an injection moulding process can be used to produce the first applicator section 1. Alternatively, the first applicator section 1 may already have been produced by an additive process, such as 3D printing. This first applicator section 1 consists of a first plastic.

It is important that the first applicator section 1 has an undercut cavity 2. In this design example, the undercut cavity 2 is preferably formed by a hollow sphere or a hollow body essentially corresponding to a hollow sphere. The hollow sphere or hollow body can change into a tapered section towards the mouth 5. If necessary, the tapered section can almost be omitted. This will be the case if, for example, a hollow sphere is used which is open towards the outside due to its mouth which forms a section through the sphere.

In the course of the first step of the procedure according to the invention, the undercut cavity 2 is completely filled with a fluidic second plastic. It is the second plastic thatis used to manufacture the second applicator section 8. It is easy to see that this filling should take place without the second plastic penetrating into the cavity or undercut cavity 2 being cured layer by layer. Instead, the second plastic initially remains fluidic in the entire interior of the cavity 2. This is because it is usually not possible or too costly to insert the fluidic second plastic layer by layer into the undercut cavity 2 and immediately cure it layer by layer or pixel by pixel.

Figure 2 shows the next step carried out within the framework of this preferred embodiment of the inventive process.

As you can see here - coming from the side - a first layer 6 is applied. The application of the first layer is preferably carried out in such a way that the beginning of the first layer is attached or at least temporarily attached or tacked to the build-up surface 4 laterally adjoining the cavity 2 of the first applicator section 1. It goes without asying that an appropriate beam guidance is provided for.

This ensures that the first layer 6, which is currently under construction, is positioned sufficiently securely for the production period. The positioning continues at least until layer 6 is anchored to the cavity elsewhere. In the area above the mouth 5, the layer 6 is build step by step by the fact that on its lateral flank further fluidic material is attached by local curing. Thus, layer 6 grows beyond the mouth 5 of the cavity until it rests on the other side of the cavity again on the build-up surface 4 there. It may also be reattached there or temporarily attached.

In such a process, the end result is a hardened layer 6, which lies like a kind of lid or foil over the mouth 5 of cavity 2. The cured layer 6 then closes the mouth 5 of the cavity 2.

The decisive point is that the hardening effect of the laser beam used here, for example, is not strictly limited to the area of layer 6 shown in Figure 2. Instead, the effect of the laser beam in the direction of the incident beam extends beyond layer 6. The laser beam preferably used here also cures a certain area of the second plastic, which is hold in a fluidal state in the cavity 2 above layer 6. At least, the laser beam triggers the curing process here.

The second step described above is now repeated several times in order to build up the second applicator section 8 layer by layer from the second plastic, by stepwise curing.

A part of the energy introduced by the laser beam repeatedly crosses the several layers 6 (or the superimposed pixels) and penetrates in the beam direction, preferably scattered into cavity 2. As the inventors found out, in this way the second plastic in cavity 2 can be cured completely or essentially completely. This is usually achieved before the second applicator section 8 is completely finished.

At least, it is possible to trigger the curing process of the second plastic, which is initially still fluidly enclosed in cavity 2.

In cases where it has not yet been possible to achieve complete curing by the time the second applicator section is completed, heat can be introduced into the cavity area if necessary. For this purpose, the finished applicator is stored in an environment with a sufficiently high temperature for a period of time if required. As a result, the curing process - which has been already triggered by the effect of the electromagnetic radiation before - runs to its end.

Figure 3 illustrates this. One can see well how a good part of the second applicator section 8 has already been created, which here has the shape of a core 9 of a bristle-carrying applicator. It is also easy to see that at least a major part of the second plastic material filling cavity 2 has already been cured. The initially still fluidic second plastic in cavity 2 has thus become an integral solid component of the second applicator section 8 or core 9. This ensures that the second applicator section 8 is securely and positively anchored to the first applicator section 1. It therefore no longer matters if the mere attachment or tacking of the first layer 6 to the build-up surface 4 is loosened again.

It can also be seen well from Figure 3 that the core 9 in this preferred but not obligatory case carries bristles 10 for application purposes. In this design example, L is the longitudinal axis of the applicator.

It is easy to see from Figure 3 that the gradual curing of the second plastic material filling the cavity 2, which becomes an integral part of the applicator section 8, in this preferred embodiment provides a strong and generally immovable positive connection between the first applicator section 1 and the second applicator section 8.

Figure 4 illustrates a second preferred embodiment, which is ultimately a variant of the procedure described above. With the exception of the difference in the conduct of proceedings described below, the above applies mutatis mutandis to this embodiment.

The difference to the first version is that the layer structure is started differently. The first layer 6 produced by curing is not started over the build-up surface 4. It is therefore not temporarily secured in its position by itself being attached or stapled to the build-up surface 4. Instead, the first layer 6, which is in the process of being produced, is supported or attached at the soffit or inner boundary edge of its mouth 5, i.e. at the embrasure of the mouth 5 inside the cavity 2. Starting from this, layer 6 is continuously expanded. This expansion takes place "pixel by pixel", attaching more and more second plastic to its lateral edge by curing. This is continued until the mouth 5 is finally completely closed by the first layer 6 produced in this way.

Figure 5 illustrates a third preferred embodiment, which is ultimately a variant of the procedure described above. With the exception of the difference in the conduct of proceedings described below, what has been said previously in regard to the first and second embodiments applies mutatis mutandis.

The embodiment in Figure 5 differs from that in Figure 4 only in that a first applicator section 1 with a more skilful design has been used to carry out the procedure. With this applicator section 1, the cavity has its smallest diameter or narrowest area directly at the level of its mouth 5 and not (as with Fig. 4) only in the area of the interior of cavity 2 and thus above the mouth 5.

This results in the first hardened layer 6 being firmly fixed immediately after its completion in the construction according to Figure 5, at least as soon as it essentially spans the entire mouth 5.

This can be clearly seen from Figure 5. As the spherical cavity 2, which is preferably continuous here, becomes narrower and narrower up to its mouth 5, the solidified layer 6 cannot sink downwards. However, it cannot float towards the inside of the cavity either, as it would first have to displace the second fluidic plastic enclosed in cavity 2. That is not easily possible.

Figures 5 and 6 show a variant of the first embodiment of the inventive process, which has just been described. Accordingly, what is said there also applies here, unless otherwise stated in the following explanations.

The embodiment according to Figure 5 is for that reason particularly interesting, as it can form the preferred basis for a fourth, particularly practical embodiment according to Figure 6. For this fourth embodiment, what has been said before for the other embodiments applies mutatis mutandis, unless something else results from what is explained below.

As one can see here, on the first layer 6, shown in Figure 5, further layers (or pixel clusters) have been applied which form an applicator core 9. The assembly was carried out in such a way that the applicator core 9 is hold apart through the joint gap 12 from the build-up surfaces 4, which are no longer used for the layer assembly. The applicator core 9 is integrally connected in one piece with the meanwhile completely or largely cured second plastic, which flooded cavity 2 and which was initially trapped there - still in a fluidic state.

In this way, the second plastic in cavity 2 now forms a fixed joint ball. As long as the first and the second plastic are chosen in such a way that they do not permanently bond with each other, cavity 2 now forms a joint socket which holds the joint ball of the second applicator section 8 rotatably.

For completeness we have to say that the inventive method can also be used for manufacturing a single pivotably anchored bristle or bristles. Hence a second applicator section in the sense of the invention can also be a single bristle having a foot or root portion that forms a ball joint like portion as shown by the figures of this application. The same kind of pivotable joint can be used for a hedge-hog like bristled crown which may be carried by the forehead, (tree and face) of the bristle carrying rod or core of the applicator. REFERENCE SIGN LIST

1 first applicator section

2 cavity

3 second plastic filling the cavity, initially fluidic

4 build-up surface

5 mouth

6 layer of the initially fluidic second plastic material applied in a subsequent step

7 bundled beam of electromagnetic radiation, e.g. laser

8 second applicator section

9 core of a bristle-carrying applicator

10 bristle

11 surrounding fluidic plastic material (second plastic)

12 joint gap

L longitudinal axis of the applicator