Patent Description:
The invention relates to a brush for applying a formulation as defined in claim <NUM>. Further embodiments of the invention are recited in the dependent claims.

In one aspect, the present disclosure provides a brush for applying a formulation, the brush having a core having an outer surface and a longitudinal axis, a plurality of bristle rings protruding from the core and spaced apart along the longitudinal axis, each bristle ring having at least <NUM> bristles spaced radially apart around the outer surface of the core, and a high density zone that covers at least a portion of the outer surface of the core, the high density zone having an equivalent <NUM> degree linear bristle density of <NUM> to <NUM> whole bristles per <NUM> of length along the outer surface of the core measured along the longitudinal axis, and a surface bristle density of <NUM> to <NUM> bristles per square millimeter of area of the outer surface of the core.

In one aspect, a first bristle ring and a second bristle ring may be spaced apart by <NUM> to <NUM>, as measured along the longitudinal axis, between the nearest surfaces of the first bristle ring and the second bristle ring. The first bristle ring and the second bristle ring may be spaced apart by <NUM> to <NUM>. Each bristle in one of the first and second bristle rings may have a diameter of <NUM> to <NUM>.

In one aspect, no part of the brush may have a surface bristle density that exceeds <NUM> whole bristles per square millimeter of area of the outer surface of the core.

In one aspect, the high density zone may extend across a <NUM>-<NUM> degree sector of the outer surface of the core, about the longitudinal axis.

In one aspect, the high density zone may extend along a <NUM> - <NUM> axial length of the outer surface of the core.

In one aspect, at least one bristle ring in the high density zone may include a first bristle length and a second bristle length. The at least one bristle ring may further include a third bristle length.

In one aspect, within a single bristle ring, no more than four bristles may have the same bristle length.

In one aspect, a difference between the first bristle length and the second bristle length may be at least <NUM>.

In one aspect, the core may have a cross sectional shape that results in, within at least one ring of the plurality of bristle rings, a first bristle length and a second bristle length. In one aspect, the cross sectional shape of the core may result in a third bristle length.

The core comprises a first recess formed in an outer surface of the core, the first recess being configured to hold a formulation. The first recess may extend along the core in a direction substantially parallel to the longitudinal axis. The core may include a second recess located on an opposite side of the core from the first recess. The core may have an hourglass cross sectional shape.

In one aspect, the present disclosure provides a system for optimally applying a formulation, the system comprising a formulation stored within a container, a wiper secured within the container, and a brush as described above that is removably secured within the container.

In one aspect, the present disclosure provides a brush for holding a formulation, comprising a core having an outer surface, a longitudinal axis, a non-cylindrical cross sectional shape, and a first recess formed in or by the outer surface, the first recess being configured to hold a formulation, and a plurality of bristle rings protruding from the core and spaced apart along the longitudinal axis, each bristle ring having a plurality of bristles spaced radially apart around the outer surface of the core, wherein the cross sectional shape of the core results in, within at least one ring of the plurality of bristle rings, a first bristle length, a second bristle length, and a third bristle length.

The plurality of bristle rings has an equivalent <NUM> degree bristle density of <NUM> to <NUM> whole bristles per <NUM> of length along the outer surface of the core measured along the longitudinal axis and a surface bristle density of <NUM> to <NUM> bristles per square millimeter of area of the outer surface of the core.

No two consecutive bristles in a single bristle ring have the same bristle length.

In one aspect, the first recess may extend along the core in a direction substantially parallel to the longitudinal axis.

In one aspect, the core may include a second recess located on an opposite side of the core from the first recess.

In one aspect, the core may have an hourglass-shape.

The foregoing aspects and many of the attendant advantages of disclosed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings. It shall be appreciated that the figures below are not necessarily to scale, and are intended to facilitate understanding of the inventive concepts discussed herein:.

The following description provides several examples of brushes that include bristle configurations designed to effectively apply formulations, e.g., cosmetic formulations, to fine hairs having a diameter of <NUM> to <NUM>, for example, eyelashes. In practice, brushes often carry a formulation on and around the bristles, and in gaps between bristles. A subject then applies the formulation by stroking the brush against the hairs. One challenge in applying formulations to such fine hairs is that the hairs often have a relatively small diameter as compared to gaps between brush bristles, such that formulation stored on the bristles cannot effectively transfer to the hairs. To an extent, this challenge can be mitigated by reducing the gap between adjacent bristles, which tends to increase bristle density on the brush. However, if bristles are too dense, then it becomes difficult for even fine hairs to enter the gap between adjacent bristles. Also, if the bristles are too dense, then it becomes difficult for the formulation to break up between the bristles, a condition that negatively affects how well the formulation transfers to the hairs. The foregoing problems are particularly acute for "gummy" formulations, which have a relatively high viscosity and tend to form clumps.

The inventive systems and brushes disclosed herein include one or more high density zones that are configured to efficiently and uniformly apply formulations - including gummy formulations - to fine hairs. Within the high density zone, both the linear bristle density relative to a core length and the overall bristle density relative to the surface area of the core contribute to this efficiency and uniformity. Some embodiments may include one or more reservoirs configured to hold formulation, to further improve brush performance. Various aspects discussed below generally relate to the high density zones of a brush. It is contemplated that the inventive brushes disclosed herein may have areas other than high density zones without deviating from the spirit of this disclosure.

Referring now to <FIG>, a representative system <NUM> is shown for storing and applying a formulation <NUM>. In the embodiment shown, the system <NUM> includes a container <NUM> and a brush <NUM> having a plurality of bristles. The container <NUM> includes an internal chamber <NUM> for storing a formulation, e.g., mascara. A rigid or semi-rigid wiper <NUM> is affixed within the internal chamber <NUM>, or formed integrally with the internal chamber <NUM> of the container <NUM>, and is configured to "wipe" excess formulation <NUM> off the bristles of the brush <NUM> as the brush <NUM> is removed from the container <NUM>. In the embodiment shown, the wiper <NUM> includes an internal opening <NUM> having a shape that may approximate a cross sectional shape of the brush <NUM>. In some embodiments, such as embodiments having brushes with non-cylindrical cores, the wiper may have an internal opening that is not circular in order to approximate the cross section shape of the core. In some embodiments, the opening <NUM> may be somewhat smaller than the cross sectional shape of the brush <NUM>.

The brush <NUM> may be releasably securable to the container <NUM>, for example via a threaded coupling or other closure structure (not shown). The brush <NUM> is generally elongated, and includes a bristle section <NUM> and a handle <NUM>. When the brush <NUM> is secured to the container <NUM>, the bristle section <NUM> is inserted into the internal chamber <NUM> of the container <NUM> such that a distal end <NUM> extends through the internal opening <NUM> of the wiper <NUM> such that the bristle section <NUM> may contact the formulation <NUM> stored within the internal chamber <NUM>. Once the bristle section <NUM> is removed, formulation <NUM> that has adhered to the brush <NUM> may then be applied to an object, such as hairs, by stroking the formulation-laden brush <NUM> against the object. The subject may occasionally reload the brush <NUM> by again inserting the distal end <NUM> into the internal chamber <NUM>, optionally rotating the brush <NUM> within the chamber and/or shaking the container <NUM> to distribute formulation <NUM> around the brush <NUM>, and then removing the brush <NUM>.

Generally, the formulation may have a wide range of properties and compositions depending on the application. Gummy formulations, for example mascara, generally include water as well as a water-soluble or water-dispersible polymer. The gummy formulations generally are shear-thinning (pseudoplastic) and may have a viscosity of less than about <NUM> Pascal-seconds when measured at moderate/high shear rate of <NUM>-<NUM>. The concentration of polymer is generally less than about <NUM>% by weight, such as less than about <NUM>% by weight, such as <NUM>%-<NUM>%. Any of the brushes described herein may be made, used, and/or sold as part of a system that includes a formulation, for example gummy formulations as described above.

Referring now to <FIG>, the brush <NUM> of <FIG> is shown without the container <NUM>. It is contemplated that any of the brushes described herein may be sold as part of a system (such as system <NUM>) that also includes a container having a wiper <NUM> and a formulation <NUM> contained within the internal chamber <NUM>, or may be distributed or sold separately from the container.

As shown in <FIG>, the bristle section <NUM> of the brush <NUM> includes a core <NUM> having a radial outer surface <NUM> and a plurality of bristles <NUM> projecting outwardly therefrom. The bristle section <NUM> of brush <NUM> extends longitudinally from the distal end <NUM> a distance L towards proximal end <NUM>. The core may be formed from a variety of materials, including plastics, and in some embodiments the core may be non-metallic. The outer surface <NUM> of the core <NUM> has a surface area that corresponds directly with the volume of formulation that the brush <NUM> can hold. In particular, and with reference to <FIG>, a formulation layer <NUM> may tend to form around the core <NUM>. Such a formulation layer <NUM> advantageously enables transfer of the formulation to the hairs of a subject. That is, the larger the surface area of the core <NUM>, the more formulation the brush <NUM> can hold, all else equal. The ability to hold more formulation may be advantageous. In addition to influencing how much formulation can be stored on the brush <NUM>, the surface area of the core <NUM> is also a key factor in bristle density. As will be discussed in more detail below, the bristle density of a given brush can greatly affect its ability to efficiently and uniformly transfer formulation to hairs of a subject. Namely, when bristle density is too high relative to the surface area of the core, fine hairs may not be able to enter gaps between adjacent bristles, and formulation may tend to clump together.

Returning to <FIG>, a longitudinal axis <NUM> is shown extending parallel to the core <NUM> through its center in order to facilitate visualization of the various features of the brush <NUM>. The length of the core may vary between embodiments, but generally is about <NUM> to about <NUM>. In the embodiment of <FIG>, the length L of core <NUM> is <NUM>. In other embodiments, the core may have a length L of <NUM>, <NUM>, <NUM>, or other length, although these core lengths are merely exemplary.

Generally, the core <NUM> has a cross sectional shape when viewed in a two-dimensional plane that is normal to the longitudinal axis <NUM>. In some embodiments, the cross sectional shape is constant along the longitudinal axis. For example, referring to <FIG>, the brush <NUM> has a cylindrical core <NUM> with a circular cross sectional shape when viewed in a plane that is normal to any point along the longitudinal axis <NUM>. In some embodiments, the core <NUM> has an outside diameter D of <NUM>, which equates to a circumference of <NUM>. In embodiments where the bristled section of the core <NUM> has a length L of <NUM>, the total nominal bristled surface area is approximately <NUM><NUM>, not considering the surface area occupied by the bristles themselves. In other embodiments, the cross sectional shape is not constant along the longitudinal axis <NUM>, but instead varies along the length L of core, or sections thereof. In yet other embodiments, the cross sectional shape remains constant along the longitudinal axis <NUM> but can vary in cross sectional area along the length L of core, or sections thereof. One example of such an embodiment is discussed below with respect to <FIG>.

Brushes of the present disclosure include one or more high density zones having a plurality of bristles <NUM> that protrude radially outward from the core <NUM>. The bristles conform to certain bristle density criteria that enable efficient and uniform transfer of formulations to fine hairs, such as eyelashes. The brush may include a single high density zone or a plurality of high density zones. In some embodiments, one or more high density zones may substantially make up the entire brush. For example, the brush <NUM> of <FIG> includes a single high density zone <NUM> that has a length equal to the length L of the bristle section <NUM>. The following discussion concerns such high density zones. Generally, the high density zone may include between about <NUM> to about <NUM>,<NUM> total bristles, for example about <NUM> to about <NUM>,<NUM> total bristles, or between about <NUM> and about <NUM> total bristles. It is contemplated that brushes of the present disclosure may have one or more zones that are not high density zones as described herein in addition to at least one high density zone.

The bristles serve several important functions, for example storing formulation, breaking up formulation into smaller amounts, separating hairs of the subject, and transferring the formulation to the hairs of the subject. In the brush <NUM> of <FIG>, the high density <NUM> zone includes bristles <NUM> arranged in a plurality of bristle rings <NUM> that are spaced apart along the core <NUM>, with each successive bristle ring <NUM>a, c staggered relative to each adjacent bristle ring <NUM>b, d about the longitudinal axis by an angle β of <NUM> degrees. In some embodiments, the brush <NUM> includes <NUM> bristle rings <NUM>, although different embodiments may include a different number of rings. When viewed from both the side as in <FIG> and from the end as in <FIG>, it can be seen that each bristle ring <NUM> is oriented substantially normally to the longitudinal axis <NUM> of the core <NUM>. In other embodiments however, bristle rings may have one or more orientations that are not perpendicular to the longitudinal axis of the core. For example, a bristle ring may have an oblique orientation relative to the longitudinal axis, and may intersect with other bristle rings, subject to the limits of bristle density discussed below. In still other alternative embodiments, the bristles may not form discrete rings, but rather one or more continuous helixes around the core for example. As noted above with respect to angle β, bristle rings may have different angular orientations with respect to the longitudinal axis when viewed in a two-dimensional plane that is normal to the longitudinal axis. For example, in other embodiments, bristle rings may be offset from each other about the longitudinal axis by about <NUM> to about <NUM> degrees, for example about <NUM> degrees, about <NUM> degrees, about <NUM> degrees, about <NUM> degrees, about <NUM> degrees, or another angle, etc. It is contemplated that bristle rings may have any orientation disclosed in <CIT>.

Each bristle ring <NUM> typically, but not always, extends all the way around the core <NUM>. Referring to <FIG>, each bristle ring <NUM> extends entirely around the outer surface <NUM> of the core <NUM>, i.e., <NUM> degrees around the longitudinal axis <NUM>. These "full" bristle rings <NUM> are preferred for applying formulation to fine hairs. However, it is contemplated that in other embodiments, a high density zone may include one or more bristle rings that only partially extend around the outer surface of the core, i.e., partially around the longitudinal axis, for example about <NUM> degrees, about <NUM> degrees, about <NUM> degrees, or another value that is less than <NUM> degrees.

Each bristle may generally be formed from any thermoplastic material that is optionally relatively rigid, e.g.: styrene-ethylene-butylene-styrene (SEBS); a silicone rubber; latex rubber; a material having good slip; butyl rubber; ethylene-propylene terpolymer rubber (EPDM); a nitrile rubber; a thermoplastic elastomer; a polyester, polyamide polyethylene, or vinyl elastomer; a polyolefin such as polyethylene (PE) or polypropylene (PP); polyvinyl chloride (PVC); ethyl vinyl acetate (EVA); polystyrene (PS); SEBS; styrene-isoprene-styrene (SIS); polyethylene terephthalate (PET); polyoxymethylene (POM): polyurethane (PU); styrene acrylonitrile (SAN); polyamide (PA); or polymethyl methacrylate (PMMA). It is also possible to use a ceramic, e.g. an alumina-based ceramic, a resin, e.g. a urea formaldehyde type resin, possibly a material filled with graphite. In particular, it is possible to use materials known under the trade names Teflon, Hytrel®, Cariflex®, Alixin®, Santoprene®, Pebax®, Pollobas®, this list not being limiting. Preferably, each bristle is formed from at least one thermoplastic elastomer.

The dimensions of individual bristles may vary between embodiments. In particular, the bristle length and bristle diameter can greatly influence brush performance. As used herein, bristle length is measured as the exposed length of a bristle that projects radially outwardly beyond the outer surface <NUM> of the core <NUM> - not the length considering any additional bristle length below the outer surface of the core. It has been discovered that in high density zones, bristle lengths of about <NUM> to about <NUM> are preferred for applying formulations to fine hairs, for example bristle lengths of about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, and about <NUM>. Referring to <FIG>, each bristle <NUM> of the brush <NUM> has a length λ, of <NUM>, which reflects the length of each bristle <NUM> that extends beyond the outer surface <NUM> of the core <NUM>. The range of appropriate bristle lengths for a given application may depend on the bristle material. For example, bristles may have lengths ranging from about <NUM> to about <NUM>, e.g., about <NUM> to about <NUM>, or about <NUM>. Further, a single brush, and even a single bristle ring, may include bristles of more than one length. The lengths of successive bristles may vary, for example in a continuously increasing or decreasing pattern, an alternating pattern, or another pattern, such that the different bristle lengths provide targeted advantages. It is contemplated that bristle rings may have bristle lengths as disclosed in <CIT>. In some embodiments, no more than, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> bristles may have the same bristle length. In some embodiments, a single bristle ring may include one or more bristles with a first bristle length and one or more bristles with a second bristle length, which may differ by about <NUM> to about <NUM>, e.g., about <NUM>, about <NUM>, or about <NUM>. In some embodiments, for example, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more consecutive bristles within the same bristle ring of the high density zone may have the same bristle length. In some embodiments, no two consecutive bristle rings may include bristles of the same bristle length. These features may advantageously provide bristles best suited for different fine hair diameters on a single brush (and even within a single high density zone). Such examples are discussed below with respect to the brushes of <FIG>.

Bristle diameter, measured where the bristle meets the outer surface of the core, should generally be about <NUM> to about <NUM>, e.g., about <NUM>, about <NUM>, about <NUM>, about <NUM>, and about <NUM>, subject to the bristle density limits discussed below. Bristles having diameters in this range generally exhibit sufficient stiffness while also permitting the brush to have bristle density within the limits discussed below. For example, the brush <NUM> of <FIG> has bristles with a diameter Δ, of about <NUM>.

The number of bristles per bristle ring may vary between embodiments. "Full" bristle rings, i.e., bristle rings that extend completely around the outer surface of the core (i.e., <NUM> degrees about the longitudinal axis), may each include <NUM> to <NUM> bristles in high density zones, and preferably <NUM> to <NUM> bristles per ring, for example <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or any other number of bristles in that range. In full rings, the number of bristles is the "full ring bristle count. " For example, each bristle ring <NUM> of the brush <NUM> of <FIG> includes <NUM> bristles, which are spaced apart about the longitudinal axis <NUM> by an angle α of about <NUM> degrees. Therefore, each bristle ring <NUM> has a full ring bristle count of <NUM> bristles.

In other embodiments, a partial bristle ring, i.e., a ring sector that does not extend completely around the outer surface of the core (i.e., that does not extend <NUM> degrees about the longitudinal axis of the core), may also include <NUM> to <NUM> bristles. For example, a partial bristle ring may include a sector that extends only <NUM> degrees about the longitudinal axis and includes <NUM> bristles in that <NUM> degree sector, each bristle being spaced apart from the adjacent bristles by an angle α of <NUM> degrees. Similarly, a single bristle ring may include bristles that have different angular spacing α about longitudinal axis of the core. For example, a single bristle ring may include a first <NUM> degree sector with <NUM> bristles spaced apart by <NUM> degrees, a second <NUM> degree first sector with <NUM> bristles spaced apart by <NUM> degrees, and a third <NUM> degree sector with <NUM> bristles spaced apart by <NUM> degrees. These configurations are merely exemplary. Other embodiments may include partial or full bristle rings having a different number of bristles and different angular spacing, within the limits of bristle density discussed below.

In embodiments with partial bristle rings or bristle rings with heterogeneous angular spacing, it can be useful to think of such partial or heterogeneous bristle rings by reference to an equivalent "full-ring bristle count," which may be calculated by multiplying a) the number of bristles in the densest angular sector of the partial ring and b) the number of such angular sectors that would fit within a <NUM> degree ring. For example, in the first example from the previous paragraph, the partial bristle ring that extends <NUM> degrees around the core and includes <NUM> bristles would have a full-ring bristle count of <NUM> bristles * (<NUM>/<NUM>) = <NUM> bristles. In the second example from the previous paragraph, the <NUM>-sector heterogeneous bristle ring has a full-ring bristle count based upon its densest sector, i.e., <NUM> bristles * (<NUM>/<NUM>) = <NUM> bristles.

The spacing between adjacent bristle rings is another important variable within high density zones. As noted above, fine hairs generally have diameters ranging from about <NUM> to about <NUM>. Adjacent bristle rings should be sufficiently spaced apart along the longitudinal axis such that fine hairs may enter that space - generally at least <NUM>. Insufficient spacing (e.g., less than <NUM>) not only makes it difficult for individual hairs to enter the spacing between bristles, but may also lead to undesirable clumping because the formulation does not have space to break apart. On the other hand, excessive spacing between adjacent bristles may result in inadequate transfer of formulation to the hairs of a subject because individual hairs pass between bristles without making contact with formulation stored on and around the bristles. This condition leads to inefficient formula transfer. Excessive spacing may also result in inadequate separation of the hairs, which can lead to irregular clumping of formulation on the hairs. To overcome these challenges, adjacent bristle rings of the inventive brushes disclosed herein may be spaced apart by a gap of between about <NUM> and about <NUM>, subject to the bristle density limitations discussed below. The aforementioned gap refers to the distance, measured along the longitudinal axis, between the nearest surfaces of adjacent bristle rings when viewed in a two-dimensional plane parallel to the longitudinal axis, and is not affected by an axial offset between adjacent bristle rings. For example, referring to <FIG>, adjacent bristle rings <NUM>c, <NUM>d are spaced apart by a gap G of about <NUM>.

Bristle density is a key variable in high density zones configured to efficiently and uniformly transfer formulations - especially gummy formulations - to fine hairs. More than one measure of bristle density impacts brush performance. One key measure of bristle density is the number of bristles relative to the core length, i.e., "linear bristle density. " It has been discovered that in order to optimally transfer gummy formulations to fine hairs, a high density zone should have a linear bristle density of <NUM> to <NUM> whole bristles per <NUM> of length along the outer surface of the core measured parallel to the longitudinal axis. For example, linear bristle densities of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> whole bristles per <NUM> of core length may be suitable. In the inventive brushes disclosed herein, <NUM> to <NUM> "full" bristle rings will fit within each <NUM> of core length within the high density zone, measured along the longitudinal axis. As a metric, the linear bristle density captures several specifications that impact brush performance, including bristle diameter (Δ), angular bristle spacing within a bristle ring (α), as well as spacing between bristles of adjacent bristle rings (G). When linear bristle density exceeds <NUM> bristles per <NUM> of core length, the bristles tend to not allow fine hairs to enter the gaps between bristles and tend to clump the formulation. The "full-ring linear bristle density" is calculated by first converting all bristle rings within the high density zone to their "full-ring bristle count," then measuring a <NUM> length parallel to the longitudinal axis of the core, and counting the number of "full-ring" bristles within the high density zone that would be encompassed by the <NUM> length. For example, referring again to <FIG>, the high density zone <NUM> of the brush <NUM> has <NUM> full bristle rings <NUM>, each with <NUM> bristles (and therefore each bristle ring <NUM> has a "full ring" bristle count of <NUM> bristles). Each bristle <NUM> has a <NUM> diameter, and adjacent bristle rings <NUM> are spaced apart by gap G of <NUM>. Thus, two full bristle rings <NUM>c,<NUM>d "fit" within a <NUM> length <NUM> measured along the core <NUM> (e.g., <NUM> + <NUM> + <NUM> = <NUM>). Because each bristle ring <NUM> has a full ring bristle count of <NUM> bristles, the high density zone <NUM> has a full ring linear bristle density of <NUM> bristles * <NUM> rings = <NUM> bristles per <NUM> length along the core <NUM>. It is important to note that other brushes having different bristle counts, bristle diameters, gaps, and angular spacing could achieve the same <NUM> bristle full-ring bristle density per <NUM> of core length. For example, a hypothetical brush with <NUM> bristles per full ring, each bristle having a <NUM> diameter, and adjacent rings spaced apart by <NUM>, would also have a full ring bristle density of <NUM> bristles per <NUM> of core length because three full bristle rings would fit within a <NUM> core length.

Another key measure of bristle density is the number of bristles relative to the core surface area, or "surface bristle density. " It has been discovered that in order to efficiently and uniformly transfer formulation to fine hairs, a high density zone should have a surface bristle density of <NUM>-<NUM> whole bristles per square millimeter of surface area of the core (i.e., the nominal core surface area, not considering the surface area occupied by the bristles themselves), as brushes with a surface bristle density that exceeds <NUM> whole bristles per square millimeter of surface area (i.e., <NUM>/mm<NUM> or greater) tend to not allow fine hairs to enter the gaps between bristles and tend to clump the formulation. As a metric, the surface bristle density captures several specifications that influence brush performance, including bristle diameter (Δ), angular bristle spacing (α), spacing between bristles of adjacent bristle rings along the longitudinal axis (G), and the amount of core surface area that is available to store formulation. The surface bristle density of a high density zone is the greater of a local measurement and an average measurement - neither should exceed <NUM> whole bristles per square millimeter of surface area. To determine the local surface bristle density within a high density zone, a <NUM> by <NUM> square in a plane that is tangential to the surface of the core is drawn, and then the number of whole bristles that fit within that <NUM> x <NUM> square is counted. For example, referring to the detail view of <FIG>, <FIG> whole bristles fit within the <NUM> x <NUM> box <NUM> that is tangential to core <NUM>, i.e., a local surface bristle density of <NUM> whole bristles / mm<NUM>. By comparison with the local surface bristle density, the average surface bristle density is determined by dividing the total number of bristles covering the core surface area corresponding to the high density zone, by the radial outer surface area of the high density zone itself. Referring again to <FIG>, the brush <NUM> has <NUM>,<NUM> bristles within the high density zone <NUM> (<NUM> bristle rings, each with <NUM> bristles), and the cylindrical core <NUM> has a <NUM> outer diameter D, and a <NUM> length L, which equates to a <NUM><NUM> surface area (<NUM>π mm x <NUM>). Therefore, the brush <NUM> has an average surface bristle density of <NUM>,<NUM> bristles / <NUM><NUM> = <NUM> bristles/ mm<NUM> (i.e., <NUM> whole bristles). From this, it is evident that the local and average surface bristle densities are the same: <NUM> whole bristles per square millimeter.

To clarify, inventive brushes of the present disclosure have (<NUM>) a high density zone with a linear surface bristle density <NUM> to <NUM> whole bristles per <NUM> of length along the outer surface of the core measured parallel to the longitudinal axis and (<NUM>) a surface bristle density of <NUM> to <NUM> whole bristles per square millimeter of core surface area (taken as the greater of the local or average surface bristle density measurements described above).

Referring now to <FIG>, another non-limiting example of a brush <NUM> is shown having a single high density zone <NUM> that includes <NUM> bristle rings <NUM>, each having <NUM> bristles with a <NUM> diameter Δ. Whereas each bristle ring of the brush of <FIG> has <NUM> bristles spaced apart by an angle α of <NUM> degrees, each bristle ring <NUM> of the brush <NUM> of <FIG> has <NUM> bristles <NUM> spaced evenly about the longitudinal axis <NUM> at an angle α of <NUM> degrees. In other words, each bristle ring <NUM> as a full ring bristle count of <NUM>. Adjacent bristle rings <NUM>a, <NUM>b are offset about the longitudinal axis <NUM> by angle β, which is <NUM> degrees. Adjacent bristle rings <NUM> are evenly spaced along the longitudinal axis by a gap G of <NUM> along a cylindrical core <NUM> having a length L of <NUM>, a diameter D of <NUM>, the core <NUM> having a constant cross sectional shape and dimensions along a longitudinal axis <NUM>. In this embodiment, the high density zone extends the entire length of the core <NUM>, and therefore has the same length. As shown in <FIG>, two full bristle rings <NUM>c, d fit within a <NUM> length <NUM> along the core; therefore, the brush has a linear bristle density of <NUM> bristles per <NUM> of core length. <FIG> also shows that the brush <NUM> has a local surface bristle density of <NUM> bristles, since whole bristles <NUM>a, <NUM>b, <NUM>c, and <NUM>d fit within the <NUM> x <NUM> area box <NUM>. The average surface bristle density is approximately <NUM> bristles per mm<NUM> (i.e., <NUM> whole bristles), calculated as the total number of bristles <NUM> within the high density zone (<NUM> rings x <NUM> bristles per ring = <NUM> bristles) divided by the surface area of the high density zone <NUM> (<NUM>. 5π mm x <NUM> = <NUM><NUM>). Thus, the high density zone <NUM> has a linear bristle density of <NUM> to <NUM> whole bristles per <NUM> of core length, and a surface bristle density of <NUM> to <NUM> whole bristles per mm<NUM>.

The brush <NUM> of <FIG> provides an additional advantage because each bristle ring <NUM> includes bristles <NUM> having different lengths. Referring to <FIG>, when the brush <NUM> is viewed in a plane that is normal to the longitudinal axis <NUM>, it can be seen that the bristle <NUM>e has a first length L<NUM>, while the bristle <NUM>f has second length L<NUM>. Moving clockwise from bristle <NUM>e to bristle <NUM>f, successive pairs of bristles <NUM> have shorter lengths than the preceding pairs of bristles <NUM>. Similarly, moving clockwise from bristle <NUM>g to bristle <NUM>h, successive bristle pairs have a longer length than the preceding bristle pair. Advantageously, this aspect enables the brush <NUM> to efficiently and uniformly transfer formulation to a wide variety of fine hairs, thus making the brush <NUM> suitable for a greater number of potential subjects. The brush <NUM> of <FIG> is a non-limiting example of this concept. Other brushes may include bristles having different lengths.

Brushes of the present disclosure may provide additional advantages by including at least one external recess for holding formulation. Such recesses are formed within, or by, the outer surface of the core, which recesses then hold formulation by surface tension. By storing formulation, the recesses reduce the frequency with which a brush must be reloaded with formulation, and also provides more formulation to transfer to the hairs of a subject in a single stroke. Such recesses may cooperate with other structure(s) designed to store formulation, e.g., cavities formed with the core of the brush, but are described herein as distinct from such "internal" cavities. The recesses may be formed by molding the core to a particular shape that inherently includes recesses, and/or by removing material from the core in a separate processing step. Cores having recesses may have organic or geometric cross-sectional shapes, which shapes and dimensions may be constant or may vary along a longitudinal axis. Such recesses may have a depth ranging from about <NUM> to about <NUM>, e.g., about <NUM> to about <NUM>, and may have a length ranging from about <NUM> to the entire length of the core. It is contemplated that the cores of brushes may have cross sectional shapes as disclosed in <CIT>.

Referring now to <FIG>, a brush <NUM> is shown having a high density zone <NUM> and embodies several advantages disclosed herein. Rather than a cylindrical core, the brush <NUM> includes a core <NUM> having an hourglass cross sectional shape. The hourglass shape is evident when the brush <NUM> is viewed along a longitudinal axis <NUM> as in <FIG>. A spline <NUM> defines the hourglass shape of an outer surface <NUM> of the core <NUM>. The spline <NUM> in an embodiment has a spline length of about <NUM>. The high density zone <NUM> extends along a length L of about <NUM> in some embodiments. Therefore, the outer surface area of the hourglass-shaped core <NUM> within the high density zone <NUM> is <NUM> x <NUM> = <NUM><NUM> in this embodiment.

Referring still to <FIG>, the core <NUM> advantageously includes a channel-shaped or groove-shaped first recess <NUM> and an identical second recess <NUM> located on an opposite side of the core <NUM>. The recesses <NUM>, <NUM> enable the brush <NUM> to hold more formulation, which is represented as layer <NUM> in <FIG>. Each recess <NUM>, <NUM> has a depth δ that is measured relative to a plane that is tangential to two radial-outermost points of the core <NUM>. The depth δ of recess <NUM> is about <NUM>, but in some embodiments may range from about <NUM> to about <NUM>. The first and second recesses <NUM>, <NUM> extend along the entire length L of the high density zone <NUM> or sections thereof. The depth δ and length L both correspond directly to a volume of the recesses <NUM>, <NUM>.

Many variations in the quantity, shape, and size of recesses are contemplated, and any brush of the present disclosure may include one or more such recesses - not just the embodiment of <FIG>. For example, in some embodiments, the core may have a tri-lobe cross-sectional shape that creates three recesses, a cloverleaf shape that creates four recesses, or a geometric shape that includes one or more recesses, such as a star shape. Other embodiments (not shown) may include only a single recess, or a greater number of recesses about the core, e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more recesses. Whereas the recesses <NUM>, <NUM> of <FIG> form channels or grooves in the core <NUM>, recesses in other embodiments may form divots, helixes, axially-spaced rings, and other shapes. In embodiments having a plurality of recesses, it is not essential that all recesses are identical; rather, the recesses may differ relative to each other in length, depth, shape, and other characteristics.

In use, the formulation layer <NUM> surrounds the core <NUM> and occupies the recesses <NUM>, <NUM>. As is evident from <FIG>, the formulation layer <NUM> has greater depth in the location of the recesses <NUM>, <NUM>. This additional formulation stored around the core <NUM> enables the brush <NUM> to transfer more formulation to the hairs of a subject without reloading the brush <NUM>.

The high density zone <NUM> of the brush <NUM> of <FIG> includes sixty-seven bristle rings spaced apart by about <NUM> to about <NUM>, e.g., about <NUM>. The number of bristles per ring varies - each odd bristle ring <NUM> has <NUM> bristles (designated <NUM>) and each even bristle ring <NUM> has <NUM> bristles (designated <NUM>), for a total bristle count of <NUM> bristles. Each successive bristle ring <NUM>, <NUM> is offset from each preceding and succeeding bristle ring <NUM>, <NUM> by an angle β of about fifteen degrees, such that when viewed along the longitudinal axis <NUM> as in <FIG>, <NUM> distinct bristles <NUM>, <NUM> are visible. Each bristle <NUM>, <NUM> has a base diameter of about <NUM>.

The bristle density of the brush <NUM> falls within the parameters outlined above. As shown in <FIG>, two bristle rings <NUM>a, <NUM>a fit within a <NUM> length <NUM> measured along the core <NUM>. Given that alternating bristle rings <NUM>, <NUM> have <NUM> and <NUM> bristles <NUM>, <NUM>, respectively, this equates to a linear bristle density of <NUM> bristles per <NUM> of core length. The local surface bristle density is <NUM> whole bristles per square millimeter of core surface area, as visualized by the <NUM> x <NUM> box <NUM> in <FIG>. The average surface bristle density is calculated by dividing <NUM> bristles by the <NUM><NUM> surface are of the high density zone, or <NUM> bristles per square millimeter (<NUM> whole bristles).

As yet another advantage, the hourglass-shaped core <NUM> advantageously causes the bristles <NUM>, <NUM> to have a plurality of bristle lengths. Referring again to <FIG>, it is evident that the bristles <NUM>a and <NUM>g have the longest bristle length, as they project radially outwardly from the lowest point in the first and second recesses, <NUM>, <NUM>, respectively. Moving clockwise from the bristle <NUM>a,.

the next visible bristle <NUM>b has a second bristle length, which is less than the first bristle length because the bristle <NUM>b does not extend from the lowest point in the first recess <NUM>. Moving clockwise again, the bristle <NUM>c has a third bristle length, which is less than the first and second bristle lengths because it is a shorter bristle and also because it projects from a relatively higher point on the core <NUM>. Likewise, the bristle <NUM>d has a fourth bristle length, the bristle <NUM>e has a fifth bristle length, and the bristle <NUM>f has a sixth bristle length. From this, it is apparent that shape of the core <NUM> causes bristles <NUM>, <NUM> to have different bristle lengths.

In use, a subject may use any of the brushes described herein to apply formulation to hair, such as eyelashes. With reference to the brush <NUM> of <FIG>, a subject may first load the brush <NUM> with formulation by inserting one end into a formulation-storing container (such as is shown in <FIG>), withdrawing the brush <NUM>, and stroking the brush <NUM> against one or more hairs <NUM>. Optionally, before stroking the brush <NUM> against the hairs <NUM>, the subject may selectively rotate the brush <NUM> about its longitudinal axis <NUM> before stroking the brush <NUM> such that hairs of the subject will pass through bristles <NUM>, <NUM> extending from either recess <NUM>, <NUM> during a stroke. In other words, the subject may rotate the brush <NUM> to align the first or second recess <NUM>, <NUM> with the hairs <NUM>. This step may advantageously increase the amount of formulation that is transferred to the hairs during a subsequent stroke. Optionally, the subject may selectively rotate the brush <NUM> before stroking such that bristles <NUM>, <NUM> having a particular bristle length (e.g., a first, second, third, fourth, fifth, or sixth bristle length) will contact the hairs. This step may advantageously position bristles <NUM>, <NUM> that are best-suited for the hair type of a subject to make contact with the hairs <NUM> during a stroke. The subject may then perform one or more strokes (preferably outward strokes) with the brush <NUM> against the hairs <NUM> in order to transfer formulation to the hairs <NUM>, performing any of the steps described above in between strokes. Optionally, the subject may rotate the brush <NUM> during a stroke or otherwise while the brush is in contact with the hairs <NUM>, in order to separate the hairs <NUM> and/or increase the amount of formulation transferred to the hairs <NUM>.

In summary, inventive brushes of the present disclosure are configured to efficiently and uniformly transfer formulations, especially gummy formulations, to fine hairs. Such brushes include at least one high density zone having a linear bristle density of <NUM> to <NUM> whole bristles per <NUM> of core length and a surface bristle density of <NUM> to <NUM> whole bristles per square millimeter of core surface area. This configuration enables fine hairs to enter gaps between bristles and also enables formulation to break apart between the bristles, contrary to known dense brushes. In addition, brushes may have more than one bristle length, which advantageously enables a single brush to efficiently and uniformly transfer formulation to different hair sizes. In addition, brushes may include one or more recesses formed on or in the core, which enable the brushes to store a greater amount of formulation, which advantageously reduces the frequency with which a brush must be reloaded with formulation, and also provides more formulation to transfer to the hairs of a subject in a single stroke.

The detailed description set forth above in connection with the appended drawings is intended as a description of exemplary embodiments of the disclosed subject matter and is not intended to represent the only embodiments. The exemplary embodiments described in this disclosure are provided merely as examples or illustrations of a cosmetic applicator and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Similarly, any features and/or process steps described herein may be interchangeable with other features and/or process steps, or combinations of features and/or process steps, in order to achieve the same or substantially similar result.

In the foregoing description, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiment of the present disclosure. It will be apparent to one skilled in the art, however, that many embodiments of the present disclosure may be practiced without some or all of the specific details. In some instances, well-known features, subassemblies, and/or process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein. For instance, any feature or configuration described above with respect to one wiping assembly may be adapted for use with any other wiping assembly.

Although certain descriptive terms have been used to illustrate or describe certain aspects or benefits of the present invention, they should not be seen as limiting. For instance, the present disclosure also includes references to directions, such as "distal," "proximal," "upward," "downward," "top," "bottom," "first," "second," etc. These references and other similar references in the present disclosure are only to assist in helping describe and understand the exemplary embodiments and are not intended to limit the claimed subject matter to these directions. The term "cosmetic formulation" or "cosmetic" should be interpreted broadly to include any cosmetic formulation, beauty product, lotion, lacquer, etc., generally applied to the skin, eyes, nails, or other body part of a person. Moreover, it should be appreciated that the cosmetic applicators may also be adapted for other non-cosmetic uses, such as applying medicine, paint, etc., to a desired body part or surface.

The present disclosure may also reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present disclosure. Also in this regard, the present disclosure may use the term "plurality" to reference a quantity or number. In this regard, the term "plurality" is meant to be any number that is more than one, for example, two, three, four, five, etc. The terms "substantially," "about," "approximately," etc., mean plus or minus <NUM>%. For the purposes of the present disclosure, the phrase "at least one of A, B, and C," for example, means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when greater than three elements are listed.

Claim 1:
A brush (<NUM>) for applying a formulation (<NUM>), comprising:
a core (<NUM>) having an outer surface (<NUM>) and a longitudinal axis (<NUM>);
a plurality of bristle rings (<NUM>, <NUM>) protruding from the core (<NUM>) and spaced apart along the longitudinal axis, each bristle ring (<NUM>, <NUM>) having at least <NUM> bristles spaced radially apart around the outer surface (<NUM>) of the core (<NUM>); and
a high density zone (<NUM>) that covers at least a portion of the outer surface (<NUM>) of the core (<NUM>), the high density zone (<NUM>) having an equivalent <NUM> degree linear bristle density (<NUM>) of <NUM> to <NUM> whole bristles per <NUM> of length along the outer surface (<NUM>) of the core (<NUM>) measured along the longitudinal axis, and a surface bristle density (<NUM>) of <NUM> to <NUM> bristles (<NUM>) per square millimeter of area of the outer surface (<NUM>) of the core (<NUM>),
characterized in that
the core (<NUM>) comprises a first recess formed in an outer surface (<NUM>) of the core (<NUM>), the first recess being configured to hold a formulation (<NUM>),
wherein no two consecutive bristles in a single bristle ring (<NUM>, <NUM>) have the same bristle length.