FR3160861A1 - Applicator device for liquid product - Google Patents

Abstract

The invention relates to an applicator device for a liquid product, such as a cosmetic product, comprising a rod extending along a longitudinal axis (X) and having a free end, said rod being characterized in that it comprises a longitudinal capillary channel delimited by a closed side wall, said capillary channel comprising a first end opening onto the free end of the rod and a second end inside the rod, and a vent channel fluidly connecting the capillary channel to an opening made on an outer wall of the rod. The invention also relates to a bottle containing the liquid product and comprising such an applicator device. figure for abstract: figure 1

Description

Applicator device for liquid product TECHNICAL FIELD OF THE INVENTION

The field of the invention is that of devices for dispensing a cosmetic product. More specifically, the technical field is that of applicators for dispensing a liquid product onto the skin or appendages.

STATE OF THE ART

Product formulation, the development of new application devices, and packaging are constantly evolving elements in the cosmetics industry. Cosmetic products encompass a wide range of compositions applied to the skin, hair, lips, and nails. Furthermore, consumers have become increasingly demanding regarding the quality, functionality, and aesthetics of cosmetic products.

In this regard, patent application WO 2014/191678 discloses a device for containing and dispensing a cosmetic product, which, due to its improved appearance, is attractive to the consumer. Indeed, the bottle, the product and the applicator have refractive indices close enough that the applicator is, through the bottle, almost invisible when immersed in the product. Thus, removing the applicator from the bottle creates a surprise effect for the user. However, this device can still be improved. More precisely, the application tip is formed from a glass or plastic-based rod, and the liquid or oily product can sometimes flow from the tip unexpectedly.

Aside from the aesthetic aspect of the product, solutions have been considered to improve the handling and transfer of liquids from the container to the application area. In fact, patent FR2 157 770 describes a dropper made from a single piece of plastic and which comprises a cylindrical support rod with one end having recesses between fork-shaped branches. These recesses, in the form of slots, have a capillary effect, allowing the liquid to adhere by the forces manifested in a narrow hollow space, at the molecular level between the liquid and the walls of the small tube. In addition, for better handling, the dropper is equipped at the end opposite the capillary recesses with a handle. However, since the low-viscosity liquid formula is trapped in a slot, it can sometimes flow out the sides. There is a risk of unwanted drops being delivered. In addition, even after wringing, the rod will be dirty along the entire length of the rod and the height of the slots. Additionally, the applicator area for dispensing product is imprecise, with slits potentially releasing product from the sides of the applicator. Finally, these slits can trap air bubbles, which is considered unsightly when the applicator is submerged in the liquid product.

In order to control the quantity of product applied and to avoid any excess that could lead to unwanted flows, the device described in patent EP3277121 relates to an applicator for liquid cosmetic products. This applicator is composed of at least one application element attached to at least one gripping element. It is distinguished by the fact that the application element has at least one application surface made of a non-compressible porous material with open cells. The objective is to provide a solution allowing controlled application of a limited quantity of cosmetic product, in particular by facilitating the application of quantities less than 0.1 ml. In addition, this document proposes a dispensing and application device for liquid cosmetic products, comprising a reservoir provided with a removable closure. However, this device has various drawbacks. The applicator is associated with a control mechanism of the flexible bulb or piston type, capable of generating a suction force to draw the product into the rod, then a pressure force to expel the product from the rod. These systems require specific handling by the user, who must squeeze the bulb when the stem is immersed in the formula, release to create a vacuum to raise the product up the stem, and then press again to remove the air and expel the product. Furthermore, these devices fail to make the stem invisible due to the presence of air in it. Furthermore, the use of bulbs made of elastomeric or plastic compounds can lead to potential compatibility issues, particularly at the olfactory level, by bringing the oil into contact with these compounds.

There is therefore a need to propose a device for taking a liquid cosmetic product from a bottle and retaining it by capillary action in capillary channels, then dispensing it in contact with the skin, while avoiding the presence of air, for example air bubbles, in the capillary channels.

The invention aims to remedy at least in part the drawbacks of the prior art, and more particularly to propose an applicator device for liquid cosmetic product which resolves all or part of the problems mentioned above.

To this end, the subject of the invention is an applicator device for a liquid product, comprising a rod extending along a longitudinal axis (X) and having a free end. The rod comprises a longitudinal capillary channel delimited by a closed side wall and a vent channel. This capillary channel has a first end which opens onto the free end of the rod and a second end inside the rod. This vent channel fluidically connects the capillary channel to an opening made on an outer wall of the rod.

This device allows the capillary channels to be loaded with a controlled, optimal and maximized dose, identical each time with simplified gestures. This recovery of the product and its release are carried out without any external actuation. In fact, a simple immersion of the applicator in the product and a simple contact of the tip of the applicator with the skin are enough to distribute the product.

Providing a vent channel allows, by positioning it low enough, i.e. close enough to the end of the stem, that the entire capillary channel is completely filled with liquid by level balance (when the stem is immersed in a liquid deeper than the level of the vent channel) or by capillarity. Conversely , if the stem were provided with capillary channels extending along the entire length of the stem, part of these channels would never be filled with liquid. The air present in the channels would give the stem a non-uniform appearance, due to the presence of air, which is what we want to avoid.

Advantageously, the vent channel connects the second end of the capillary channel to the opening made on the outer wall of the rod.

The free end of the rod forming the bottom of the rod and a longitudinally opposite end forming the top of the rod, the vent channel can then have an upper wall having an angle α of between 30° and 90° with respect to the longitudinal direction (X), and preferably 45°, and said upper wall can open onto the outer wall at the same level as the second end of the capillary channel or higher.

The vent channel may be of a flared shape having a flare angle β measured between the longitudinal direction (X) and a lower wall of the vent channel between the value of the angle α and 90°.

At least one longitudinal capillary channel of the device may have a circular, or oval, or rectangular, or square cross-section.

Alternatively, at least one longitudinal capillary channel may have an annular cross-section, or a letter-shaped or letter-shaped cross-section, for example a cross-section consisting of an intertwined "C" and an inverted "C".

The free end of the applicator device rod may be rounded.

The applicator device may have a stem made of glass, such as quartz or borosilicate glass, or of a plastic material, such as polyolefin plastic.

Each capillary channel can have a constant cross-section and the largest circle inscribed in this cross-section can have a diameter between 0.2 mm and 1.5 mm.

The total number of longitudinal capillary channels of the applicator device can for example be between 1 and 10.

When the applicator device comprises several capillary channels, said capillary channels can be arranged, seen in cross section, in a circle, or in concentric circles.

The invention also relates to a bottle comprising an applicator device as previously described, the bottle containing a liquid, in which said opening made on the outer wall of the rod is positioned longitudinally, relative to the free end of the rod, at a distance less than the maximum capillary rise height of the liquid in the capillary channel.

The bottle may have a transparent reservoir that contains the liquid, and the stem may be made of a material whose refractive index is equal to that of the liquid with a maximum difference of 0.1.

In this bottle, the liquid can, for example, be a very low viscosity oil, an alcoholic solution, or an aqueous solution.

BRIEF DESCRIPTION OF THE FIGURES

• laFIG. 1est une vue schématique d’un applicateur de produit liquide conforme à un mode de réalisation de l’invention ;
• laFIG. 2est une vue de principe d’un applicateur de produit liquide conforme à un mode de réalisation de l’invention ;
• LaFIG. 3est une vue schématique en coupe d’un applicateur de produit liquide, montrant des canaux capillaires et des canaux de mise à l’air libre formés dans un mode de réalisation de l’invention ;
• LaFIG. 4est une vue schématique en trois dimensions des canaux capillaires et des canaux de mise à l’air libre formés dans un mode de réalisation de l’invention ;
• laFIG. 5illustre, selon une vue en coupe schématique, un dispositif applicateur de produit liquide selon un autre mode de réalisation de l’invention ;
• laFIG. 6illustre, selon une vue schématique en trois dimensions les canaux capillaires et les canaux de mise à l’air libre formés dans un autre mode de réalisation de l’invention,
• laFIG. 7illustre, selon une vue schématique en trois dimensions un dispositif applicateur conforme à encore un autre mode de réalisation de l’invention.

Other advantages, aims and particular characteristics of the present invention will emerge from the following non-limiting description of at least one particular embodiment of the devices and methods which are the subject of the present invention, with reference to the appended drawings, in which:

• there FIG. 1 is a schematic view of a liquid product applicator according to one embodiment of the invention;
• there FIG. 2 is a principle view of a liquid product applicator according to one embodiment of the invention;
• There FIG. 3 is a schematic sectional view of a liquid product applicator, showing capillary channels and vent channels formed in one embodiment of the invention;
• There FIG. 4 is a three-dimensional schematic view of the capillary channels and vent channels formed in one embodiment of the invention;
• there FIG. 5 illustrates, in a schematic sectional view, a liquid product applicator device according to another embodiment of the invention;
• there FIG. 6 illustrates, in a three-dimensional schematic view, the capillary channels and the vent channels formed in another embodiment of the invention,
• there FIG. 7 illustrates, in a three-dimensional schematic view, an applicator device in accordance with yet another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the figures and in the remainder of the description, presenting non-limiting examples, the same references represent identical or similar elements. In addition, the different elements are not represented to scale so as to favor the clarity of the figures. Furthermore, the different embodiments and variants are not mutually exclusive and can be combined with each other. Unless otherwise indicated, the terms “substantially”, “approximately”, “of the order of” mean to within 10%. Furthermore, the terms “between … and …” and equivalents mean that the limits are included, unless otherwise indicated.

The invention relates to an applicator 10 comprising a rod 101 having the function of taking up and/or evacuating a cosmetic product via one end 121, as well as to a method of manufacturing such an applicator 10. The rod 101 is straight and extends in a direction called the longitudinal direction (X). This rod 101 comprises longitudinal capillary channels 12 opening at this end 121, and vent channels 13 connected to holes 131 present on the wall of the rod 101. The end 121 of the rod forms a dispensing tip.

The terms "lower", "upper", "up" and "down" refer to an increasing positioning along the X direction defined on the FIG. 2 In other words, the bottom of the rod corresponds to its end 121 forming the dispensing tip and the top of the rod corresponds to the opposite end of the rod.

The end 121 of the rod forming the tip is adapted, thanks to the capillary channels 12, to collect the formula by capillarity. In order for the fluid to rise freely along a capillary 12, the air must be able to easily escape from the second end 122 of the capillary channel. A vent channel 13 is thus connected to this second end 122 to facilitate the circulation of air. The capillary channels are sufficiently close to the external surface of the rod, so that the vent channels 13 are not too long. This characteristic makes it possible to avoid a significant quantity of product being present in said vent channels 13, and also limits the risk of an air bubble being trapped in these channels.

In practice, the rod 101 is immersed in a liquid, so that all the capillary channels 12 and the vent channels 13 are below the level of the liquid, the channels fill with liquid by hydrostatic equilibrium. When only the end 121 is immersed in the liquid, the capillary channels 12 fill by capillarity. The capillary rise is a consequence of the intermolecular forces between the liquid and the wall solid of the capillary channel 12.

When the end of the rod 121 is in contact with the skin, the capillary channels 12 are designed to evacuate the liquid product, and air can enter the capillary tubes 12 in compensation through the vent channel 13.

The evacuation of air from the capillary channel 12 is necessary to fill the capillary channel either by hydrostatic equilibrium or by capillary rise of the product. Furthermore, it is necessary to evacuate air for various reasons. For example, the presence of air bubbles in the capillary channel 12 may prevent the liquid from rising efficiently and uniformly along the capillary channel 12. But also, when the rod 101 is formed of a transparent material, an air bubble would be visible to the user and is considered unsightly.

Additionally, by removing the air, we ensure that the liquid can rise to an optimal and maximum capillary height, without being hindered by air pockets.

Once the capillary channels 12 are loaded with liquid product, the user can remove the applicator 10 from the cosmetic liquid. The capillary channel 12 is thin enough so that the column of liquid in the tube is maintained by surface tension and the capillary effect. The height at which the liquid can be maintained by capillarity is limited by the balance between surface tension and the force of gravity acting on the column of liquid.

The rounded tip of the applicator optimizes the contact of the blocked fluid with the skin at the various angles the rod can take during use. It is then possible to recover the fluid from the capillary(s). When the liquid comes out, the air refills the channel.

Thanks to the capillary effect, this process of retention and distribution of a controlled and regular dose of the product takes place without requiring the activation of a mechanism, and without additional components.

The applicator may be intended to be used for low viscosity liquids with strong adhesion to the rod material, for example a low viscosity oil. For example, an oil with a viscosity of between 10 mPa s and 600 mPa s, preferably between 10 mPa.s and 50 mPa.s and more preferably between 10 mPa.s and 20 mPa.s may be used. Good results have been obtained with a product having a viscosity of 17 mPa.s.

The above ranges and values have been validated by measurements carried out at a rate of 100 s-1 at 25°C.

The rod is for example made of glass (preferably), or plastic. It is neutral with respect to the formula. A glass such as quartz glass, borosilicate glass, polyolefin type plastic having a refractive index close to the cosmetic solution. For example, the solution envisaged could be oil with a refractive index equal to 1.46 or an alcoholic formula. The rod, when it is circular cylindrical, can have for example a diameter between 3 mm and 20 mm. Its refractive index is between 1 and 2, preferably between 1.45 and 2. In particular, the use of quartz glass, or borosilicate glass, whose refractive index is between 1.45 and 1.47 makes it possible to make the rod invisible or almost invisible when it is immersed in the aforementioned solution. The same is true when using polyolefin plastic, which has a refractive index of 1.50 or around 1.50. The material used can therefore be advantageously selected according to the liquid product in question, in order to have the same refractive index. Furthermore, the rod has a rounded or slightly convex tip so that the fluid can be distributed during application to the skin with different inclinations of the applicator.

Particular embodiments will be described relating to a cosmetic product applicator comprising longitudinal capillary channels intended to be connected by one end to free ventilation channels linked to the outer wall of the applicator. However, these embodiments can be adapted to other types of products, such as for example.

There FIG. 2 schematically illustrates an application rod according to a first variant of the embodiment of the invention.

There FIG. 2 represents in particular an applicator 10, comprising an external wall 11, longitudinal capillary channels 12 and vent channels 13.

The capillary channel 12 is formed in the rod 101 and extends along the longitudinal axis X.

The longitudinal capillary channel 12 may, for example, have a round, rectangular, or square cross-section. When it is cylindrical in revolution, the channel may, for example, have a diameter of 1 mm. Generally, the cross-section of the capillary channel (or of each capillary channel) is such that the largest circle inscribed in this section, i.e. the largest circle that can be included in this section without exceeding its contour, has a diameter of between 0.2 mm and 1.5 mm.

Several capillary canals can be formed in the stem. For example, the capillary canals can be arranged in one or more circles, seen in cross-section.

The longitudinal capillary channel 12 may have an annular cross-section. In this case, the difference between its inner diameter and its outer diameter may be between 0.2 mm and 1.5 mm, for example 1 mm. The rod may comprise several concentric channels having annular sections.

The dose is calibrated according to the number of channels and their shapes (section and height). As a guide, the dose, which corresponds to the cumulative volumes of the capillary channels, can be between 0.05 mL and 1 mL, for example between 0.1 mL and 0.5 mL.

The maximum height that can be reached by the liquid rising up the channel by capillarity (or that can be retained in the channel by capillarity, when the rod is no longer in contact with the liquid product) is determined by Jurin's law. Jurin's law links this maximum height Hmaxi (meter) to the radius r inside the tube (meter), to the density of the liquid ρ (kg.m-3 ), to the connection angle θ (°), to the surface tension (Nm-1 ) and the gravitational constant g (9.81 ms-2).

More precisely, Jurin's law is described by the formula: .

The connection angle is formed where the liquid meets the solid surface of the capillary tube. If this angle is acute (less than 90°), the liquid will rise in the capillary tube. On the other hand, if the angle is greater than 90°, the liquid will not rise in the tube. This maximum height Hmaxi is always calculated relative to the height of the liquid outside the stem. If we want to reduce the dose, or if we want the capillary to be full at all times when it is in contact with the formula, we can limit the height of the capillary tube so as not to exceed Hmaxi. Capillary tubes are generally cylindrical in shape with a constant inside diameter. The circular symmetry of a cylindrical tube ensures an equal rise of the liquid around the tube wall, which allows for a more uniform rise of the liquid. The inside radius of the capillary tube must be small enough so that surface tension can overcome the forces of gravity acting on the fluid. The narrower the tube, the stronger the capillary effects. The smooth and homogeneous interior surface promotes better adhesion of the liquid and therefore facilitates capillary rise.

As illustrated in the FIG. 2 , the longitudinal capillary channel 12 is connected to the vent channel 13 by the second end 122. Indeed, for the fluid to rise freely along a capillary, the air must be able to easily escape from the other end of the capillary. A vent channel 13 is thus fluidically connected to this end to facilitate the circulation of air. However, if the opening 131 is higher than Hmax, and the rod 101 is no longer immersed, part of the liquid empties even before contact with the skin. This is the case, for example, if we take a long hollow cylinder whose height is greater than the ''H max''. As soon as the rod is removed from the liquid, part comes out spontaneously. Only the equivalent of H Max of liquid will remain in this rod. The vent channel comprises an upper wall 132 and a lower wall 133. The vent channel 13 is advantageously oriented upwards, that is to say that its mouth on the side wall of the stem is higher than the level at which the vent channel 13 is connected to the capillary channel 12. The angle α between the longitudinal capillary channel 12 and the vent channel 13 is between 30° and 90°, for example 45°. More precisely, this angle α is located between the upper wall 132 and the longitudinal axis X. This angle α makes it easier to evacuate the air during the rise of the liquid in the capillary channels. This prevents an air bubble from being trapped at the top of the capillary channels or in the vent channel(s). An angle α equal to 45° gives the best results. The vent channel 13 connects the capillary channel 12 to an opening 131 formed on the outer wall 11 of the rod 101. This opening is lower than the Hmaxi to ensure that the capillary channel 12 fills completely. Hmaxi is here shown just above the opening 131, but this opening could of course be placed further below Hmaxi.

The vent channel 13 may be of flared shape with a flare angle β, measured between the longitudinal axis X and the lower wall 133 which is at most 90°. Thus the vent channel 13 is advantageously never oriented downwards. More precisely the angle α is never greater than 90°. If this were the case, the liquid present in the vent channel could flow from the rod, along the side wall.

The flare angle β is thus between the value of the angle α (in this case the lower wall 133 is parallel to the upper wall 132) and 90°.

An appropriate flaring angle β thus makes it possible to promote the exit of air from the capillary channel via the vent channel (and the entry of air as a replacement during product dispensing) while avoiding the risk of the cosmetic liquid leaking through the vent channel 13.

The similarities in the refractive indices between the formula or cosmetic product, the applicator, and the channels ensure invisibility of the applicator extending into the formula. This is because light does not undergo a change in direction at the interfaces between the two objects. More precisely, there is no difference in the behavior of light when passing from one to the other, and no additional refraction occurs at the interfaces. Therefore, there is no distortion or change in the image seen through these materials, rendering one or both objects invisible. For example, the refractive index of the rod can be equal to that of the liquid with a maximum difference of 0.1. In addition, the height of the capillary channels cannot be higher than this Hmax value to allow complete filling of the channels; this improves the invisibility effect. Air bubbles present during channel filling can interfere with the invisibility effect. An angle value α other than 90° improves this aspect, ensuring that any air bubbles will be easily evacuated from the capillary channel.

There FIG. 3 illustrates an embodiment according to the invention. Each longitudinal capillary channel 12 is connected to its own vent channel 13.

On the contrary, the FIG. 4 illustrates the channels within an applicator device according to another embodiment. Thus, at the FIG. 4 , it is the shape of the channels that is shown and the stem is omitted. In this embodiment, the vent channels join, so that each longitudinal capillary channel 12 is fluidically connected to each of the vent channels.

In the example of the FIG. 5 , the capillary channel 12 is connected to several vent channels 13. Increasing the number of vent channels 13 for each capillary channel 12 makes it possible to limit the risk of trapping air bubbles.

There FIG. 6 corresponds to a variant of the present invention, represented in the same way as the FIG. 4 , in which an annular capillary channel 12 is formed around a central capillary channel 12 which is cylindrical in revolution. The capillary channels thus formed are fluidically connected to several vent channels 13.

There FIG. 7 illustrates the stem of an applicator device according to an embodiment of the present invention in which a capillary channel 12 has a cross-section forming a logo (such as a design, a letter, or a set of several letters). In the example shown, the capillary channel has a cross-section formed of a C and an inverted C (seen in mirror image), the two Cs being intertwined.

The present invention can be made by an additive manufacturing process (3D printing), by sintering or by injection. A glass injection process, for example, involves several steps. First, the glass powder is mixed with the plastic resin, for example a water-soluble resin. This mixture is heated and then introduced into a mold until hardened. Then, a washing process to dissolve and remove the water-soluble resin is carried out. A homogenization step can be provided to standardize the structure. Alternatively, it is possible to form the capillary channels by a laser etching process or "etching".

Other techniques known to those skilled in the art such as welding or gluing may be incorporated into the process, for example by forming two plastic half-shells to form the stem which are then assembled.

The applicator proposed within the framework of the present invention makes it possible, thanks to its configuration comprising at least one capillary channel and at least one vent channel, to ensure complete filling and without air bubbles of the channels when the tip is immersed in the product. This gives a homogeneous appearance to the emerged part of the applicator, and possibly an invisible appearance to the immersed part of the applicator. In addition, the product dose taken and delivered is controlled. The application gesture is simple, without any mechanism to activate.

Claims (14)

Applicator device (10) for liquid product, comprising a rod (101) extending along a longitudinal axis (X) and having a free end (121), said rod (101) being characterized in that it comprises:

• a longitudinal capillary channel (12) delimited by a closed side wall, said capillary channel (12) comprising a first end opening onto the free end (121) of the rod (101) and a second end (122) inside the rod (101), and
• a vent channel (13) fluidly connecting the capillary channel (12) to an opening (131) made on an outer wall (11) of the rod (101).

Applicator device according to claim 1, in which the vent channel (13) connects the second end (122) of the capillary channel (12) to the opening (131) made on the outer wall (11) of the rod (101). Applicator device according to claim 1 or claim 2, the free end (121) of the rod forming the bottom of the rod (101) and a longitudinally opposite end forming the top of the rod (101),
the vent channel (13) having an upper wall (132) having an angle α of between 30° and 90° with respect to the longitudinal direction (X), and preferably 45°,
said upper wall (132) opening onto the outer wall (11) at the same level as the second end (122) of the capillary channel (12) or higher. Applicator device according to claim 3, in which the vent channel (13) is of flared shape having a flare angle β measured between the longitudinal direction (X) and a lower wall of the vent channel between the value of the angle α and 90°. Applicator device according to any one of the preceding claims, in which at least one longitudinal capillary channel (12) has a circular, or oval, or rectangular, or square cross-section. Applicator device according to any one of claims 1 to 4, in which at least one longitudinal capillary channel (12) has an annular cross-section, or in the shape of a letter or a shape composed of letters, for example in the shape composed of an intertwined "C" and an inverted "C". Applicator device according to any one of the preceding claims, wherein the free end (121) is rounded. An applicator device according to any preceding claim, wherein the rod (101) is made of glass, such as quartz or borosilicate glass, or of plastic material, such as polyolefin plastic. Applicator device according to any one of the preceding claims, wherein each capillary channel (12) has a constant cross-section and wherein the largest circle inscribed in this cross-section has a diameter of between 0.2 mm and 1.5 mm. Applicator device according to any one of the preceding claims, comprising a total number of capillary channels (12) of between 1 and 10. Applicator device according to any one of the preceding claims, wherein, the applicator device comprising several capillary channels (12), said capillary channels are arranged, seen in cross section, in a circle, or in concentric circles. Bottle comprising an applicator device according to any one of the preceding claims, the bottle containing a liquid,
wherein said opening (131) made on the outer wall (11) of the rod (101) is positioned longitudinally, relative to the free end (121) of the rod, at a distance less than the maximum height (Hmaxi) of capillary rise of the liquid in the capillary channel. Bottle according to claim 12, comprising a transparent reservoir which contains the liquid, in which the stem (101) is made of a material whose refractive index is equal to that of the liquid with a maximum difference of 0.1. A bottle according to claim 12 or claim 13, wherein the liquid is a very low viscosity oil, an alcoholic solution, or an aqueous solution.