Patent Publication Number: US-2023147318-A1

Title: Self-cleaning case for powder cosmetic product

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is related to and claims priority benefits from French Application No. 2111871, filed Nov. 9, 2021 and titled NOM ET ADRESSE DU DEMANDEUR OU DU MANDATAIRE À QUI LA CORRESPONDANCE DOIT ÊTRE ADRESSÉE, the entire content of which is incorporated herein by this reference. 
     TECHNICAL FIELD OF THE INVENTION 
     The invention relates to a case for a powder cosmetic product comprising:
         a base comprising a cavity for receiving said product, the cavity opening axially through an opening;
           a sifter arranged in the opening;   a closing cover which is intended to be screwed onto the base between a fully unscrewed position and a fully screwed position in which it is axially brought closer to the opening to allow its sealed closing;   a seal attached to the cover by an upper end which comprises:
               a lateral section elastically deformable in an axial direction;   a membrane which is attached to a lower end of the deformable section and which comprises a contact face intended to rest on the entire surface of the sifter;   a chamber delimited between the cover and the membrane.   
               
               

     TECHNICAL BACKGROUND 
     Various examples of case designs are known from the prior art for receiving a powder cosmetic product, such as loose powder or similar products used for make-up. 
     In a known design, the case comprises a base comprising a cavity for containing a powder cosmetic product, a sifter which is arranged at the level of the opening of the cavity and through orifices of which the cosmetic product is discharged for use. 
     One disadvantage of such a case is in particular that the powder cosmetic product is dispersed through the multiple orifices of the sifter, in other words uncontrolled discharge of said product from the cavity forming reservoir. 
     The dispersion of the cosmetic product through the sifter is likely to occur on the one hand during the transport of the case in the closed position and on the other hand during the use of the case in open position. During the transport, the dispersion of the cosmetic product is limited by a cover that covers the sifter in closed position. 
     To limit such a dispersion during the transport, it is in particular known to place an applicator—typically a sponge—above the sifter so that at least one portion of the cosmetic product dispersed through the orifices is captured by the sponge. 
     However, the sponge does not completely prevent the dispersion of the powder cosmetic product out of the cavity, which poses a problem for the cleanliness of the case. 
     In order to achieve a sealed closure of the case, the sponge is therefore pressed tightly against the walls of the case. However, when the sponge is removed, the powder cosmetic product is sucked through the sifter by the suction-cup effect. Thus, it is impossible to open the case without spilling the powder cosmetic product outside its cavity. 
     In addition, the sponge often comprises an excessive amount of cosmetic product on its face in contact with the grid, making it difficult to use the saturated sponge for make-up. 
     In an attempt to overcome the problem of dispersion during the transport, it is also known to use a plug, for example secured to the cover of the case. Such a plug is configured to cover the sifter in the closed position of the case so as to isolate it and thus prevent the powder cosmetic product from being dispersed. 
     However, after using the case, the sifter is covered with powder cosmetic product. However, such a plug does not allow the sifter to be cleaned by reintroducing the powder cosmetic product into the cavity. 
     As a result, the powder cosmetic product is found in the space between the sifter and the plug, said cosmetic product covers the surface of the plug, in the same way that the face of a sponge in the previous example. However, the cosmetic product on the surface of the plug is then likely to disperse everywhere after the opening of the cover, in particular to come to dirty the case, the hands of the user, etc. 
     One of the consequences of this dispersion of the powder cosmetic product in use, as well as during the transport, is finally the lack of cleanliness of the case. However, such a defect of cleanliness of the case is particularly badly perceived on the qualitative level, i.e. disappointing for a user. 
     It is understandable that the handling of a case soiled with powder cosmetic product thus dispersed risks dirtying the hands or even the inside of a bag in which such a case would be conveyed. 
     To solve this problem, it has already been proposed to use a rigid plug attached to the cover and equipped with fins that scrape the sifter when the cover is screwed. The sifter used is a rigid sifter. 
     However, such a rigid plug does not allow for satisfactory cleaning of the sifter because once the fins are in close contact with the sifter, they form a stop which prevents the cover from being tightened further. 
     In addition, such an arrangement requires very precise dimensioning and positioning of the parts in relation to each other to allow the cover to be attached correctly while benefiting from the scraping effect of the fins. 
     Such a solution is therefore complex and expensive to implement. 
     SUMMARY OF THE INVENTION 
     The invention proposes a case for powder cosmetic product comprising:
         a base comprising a cavity for receiving said product, the cavity opening out axially through an opening;   a sifter arranged in the opening;   a closing cover which is intended to be screwed onto the base between a fully unscrewed position and a fully screwed position in which it is axially brought closer to the opening to allow its sealed closure;   a seal attached to the cover by an upper end which comprises:
           a lateral section elastically deformable in an axial direction;   a membrane which is attached to a lower end of the deformable section and which comprises a contact face intended to rest on the entire surface of the sifter;   a chamber delimited between the cover and the membrane.   
               

     According to the teachings of the invention, the case is characterised in that the contact face of the membrane is elastically deformable in flexion so that the contact face conforms to the shape of the sifter when the cover is screwed on, the contact face having relief elements. 
     According to another aspect of the invention, the contact face has a different shape between the fully unscrewed position of the cover and the fully screwed position of the cover. 
     According to another aspect of the invention, the membrane is elastically deformable in flexion when the cover is screwed on between a state of partial contact of the contact face with the sifter when the cover occupies a first position and a state of total axial abutment of the contact face against the entire surface of the sifter when the cover occupies a second position. 
     According to another aspect of the invention, during screwing on, the contact face reaches its state of total axial abutment before the cover reaches its fully screwed position, the deformation of the deformable section allowing an axial sliding of the cover towards the sifter up to its fully screwed position. 
     According to another aspect of the invention, an annular sealing segment of the membrane, which surrounds the contact face, is intended to come into sealed contact with an annular face of the bowl in the fully screwed position. 
     According to another aspect of the invention, the seal is configured so that, upon unscrewing, a periphery of the contact face begins to move axially away from the sifter to release a peripheral area of the sifter, with a complementary inner area of said peripheral area remaining entirely in contact with the contact face. 
     According to another aspect of the invention, the seal is configured so that the sealing segment is moved away from its bearing face prior to or simultaneously with the initiation of moving away from the periphery of the contact face of the peripheral area of the sifter to create an interstice for the passage of the air into the cavity through said peripheral area. 
     According to another aspect of the invention, the contact face of the seal has, in a resting state of the membrane, a periphery of convex shape. 
     According to another aspect of the invention, in a resting state of the membrane, the contact face has a convex shape over its entire surface from a central point arranged substantially at the level of a central axis of the sifter. 
     According to another aspect of the invention, the elastically deformable section is formed by an annular bellow that surrounds the chamber. 
     According to another aspect of the invention, the deformable section has a lower flexibility than that of the membrane so that the contact face begins to deform in flexion before the attachment section. 
     According to another aspect of the invention, the seal is made in one part. 
     According to another aspect of the invention, the seal and the cover are made of the same material. 
     According to another aspect of the invention, the relief elements are evenly distributed over the entire surface of the contact face. 
     According to another aspect of the invention, the relief elements are pimples. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Further characteristics and advantages of the invention will become apparent from the following detailed description, for the understanding of which reference is made to the attached drawings briefly described below. 
         FIG.  1    is a perspective view of a case produced according to the teachings of the invention, the case occupying a closed position. 
         FIG.  2    is a perspective view of the case in  FIG.  1   , the case occupying an open position. 
         FIG.  3    is an exploded perspective view showing the various components of a base of the case in  FIG.  1   . 
         FIG.  4    is a perspective view showing the cover of the case in  FIG.  1   . 
         FIG.  5    is an exploded view of the cover in  FIG.  4    and a seal equipping it. 
         FIG.  6    is a similar view to  FIG.  5   , which shows the cover and the seal from a different angle. 
         FIG.  7    is a cross-sectional view along the cutting plane  7 - 7  of  FIG.  5    that shows the seal of the cover on a larger scale. 
         FIG.  8    is an axial cross-sectional view showing the case of  FIG.  1    when the cover occupies a fully unscrewed position in which it is laid on its base. 
         FIG.  9    is a similar view to  FIG.  8    in which the cover occupies a first position in which it is partially screwed. 
         FIG.  10    is a similar view to  FIG.  8    in which the cover occupies a second position in which it is partially screwed. 
         FIG.  11    is a similar view to  FIG.  8    in which the cover is in a fully screwed position on the base. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, elements with identical structure or similar functions will be referred to by the same reference. 
     In the remainder of the description, an axial orientation parallel to a main axis of the case, and indicated by the arrow “A” which is directed from bottom to top, will be adopted. Radial orientations extending radially with respect to the main axis of the case from the inside to the outside will also be adopted. Tangential orientations that are orthogonal to the axial and radial orientations will also be adopted. 
     In the embodiments of the case shown in the figures, said main axis constitutes an axis of rotation for screwing the cover onto a base of the case. 
     The terms “top” and “bottom”, “above” and “below”, “upper” and “lower” are used as geometric reference frame in relation to the axial orientation as shown in the figures and independently of the direction of the gravity of the earth. 
       FIG.  1    shows a case  10  for a powder cosmetic product in closed position, and  FIG.  2    shows the same case  10  in open position. 
     A powder cosmetic product is for example loose powder to be used for make-up. For example, it is a powder cosmetic product applied to the face with an applicator (not shown), in particular by means of a brush or a sponge (or any other equivalent means). 
     Preferably, the powder cosmetic product is intended to be applied by means of a brush which is here separate from said case  10 . 
     The case  10  of powder cosmetic product comprises at least one cover  12  and a base  14  that are movably mounted relative to each other between at least one closed position, shown in  FIG.  1   , and an open position of the case  10 , shown in  FIG.  2   , in which the cover  12  is removed from the base  14 . 
     The cover  12  is intended to be screwed onto an associated thread  34  of the base  14 . The case  10  has a main axis O determining the axial direction. The base  14  is located at the bottom and the cover  12  at the top. The cover  12  is more particularly intended to be screwed by rotation about the main axis O on the base  14 . 
     The cover  12  and the base  14  have a complementary shape that gives the case  10  its aesthetic appearance, in particular in closed position. 
     In a non-limiting way, the case  10  has a general cylindrical shape of revolution centred on said main axis O. 
     Alternatively, the case could have another general shape, in particular a parallelepiped shape, in particular a square or rectangular shape. 
     Advantageously, the case  10  is a “compact” type case, i.e. sized so that it can be conveyed, in particular but not exclusively in a bag, for example a handbag of a user. 
     Preferably, the cover  12  is removable from the base  14 , i.e., the cover  12  is separate from the base  14  in the open position of the case  10  as shown in  FIG.  2   . 
     Alternatively, the cover could be connected to the base by means of a flexible attachment allowing it to be screwed and unscrewed from the base. 
     The base  14  comprises a cavity  16  for receiving said product, visible for example in  FIG.  8   . The cavity  16  opens axially upwards through an opening  18  into an axially upwardly open bowl  20  outside the base. 
     A sifter  22  equipped with passage orifices of the product is arranged in the opening  18  to form a delimitation between the cavity  16  and the bowl  20 . 
     Thus, the invention is applicable to a case  10  comprising mainly the cavity  16  for receiving the cosmetic product delimited upwardly by the sifter  22  and which opens into a bowl  20 . 
     As shown in more detail in  FIG.  3   , in the example embodiment shown in the figures, the base  14  comprises, in a non-limiting way, several components assembled. 
     Here, the base  14  comprises a pedestal  24 , a container  26  and a ring  28  for attaching the container  26  in the pedestal  24 . This configuration allows the container  26  to be replaced when it is empty or when a cosmetic product is desired to be changed in a clean and quick manner, while retaining the rest of the case  10 . This configuration is therefore both economical and ecological. 
     For this purpose, the pedestal  24  comprises a housing  29 . The housing  29  is divided into two portions. A lower portion  30  of the housing  29  is intended to receive the container  26 , while the upper portion of the housing  29  is intended to remain free to receive the bowl  20  allowing to collect powder cosmetic product present on the sifter  22  by means of an applicator without risk of spilling it everywhere. 
     The upper portion of the housing  29  is radially delimited by a cylindrical wall  32 . The cylindrical wall  32  comprises on its external face the thread  34  for screwing the cover  12 . The cylindrical wall  32  comprises a free upper end edge  35 . 
     The upper portion of the housing  29  is delimited from the lower portion  30  by a face  36  with an annular bearing surface which is turned axially upwards. 
     The container  26  here comprises the cavity  16  which is delimited radially by a peripheral wall  38  and axially downward by a bottom  40 , visible for example in  FIG.  8   . The sifter  22  is intended to be attached to an upper end edge  42  of the peripheral wall  38 . 
     In the embodiment shown in the figures, at least one of the peripheral wall  38  and the bottom  40  is made of a material sufficiently flexible that a user can lift the bottom  40  to bring it into contact with the sifter  22  by simply pressing on the bottom  40  with a finger of the hand. For this purpose, the housing  29  of the pedestal  24  is closed downwards by a bottom  41  which is perforated with a window  43  for access to the bottom  40  of the container  26 . 
     Such an arrangement thus allows the cosmetic product to be passed over the sifter  22  by lifting the bottom  40 , without having to tip the container  26  to drop the cosmetic product. 
     The sifter  22  is a flexible sifter which is made, for example, in the form of a grid, of nylon or other material, consisting of a set of meshes each delimiting one of the orifices for the passage of the powder cosmetic product out of the cavity. 
     To allow to keep the sifter  22  stretched across the opening  18 , the sifter  22  is carried by a frame  44  of complementary shape to that of the outline of the opening  18 , here of circular shape, centred on the main axis O. The frame  44  is made of a much more rigid material than the peripheral wall  38  and/or the bottom  40  of the container  26 . 
     The frame  44  is for example made of a plastic material over-moulded on the periphery of the sifter  22 . 
     The frame  44  is mounted by snap fitting on the upper edge  42  of the container  26 . Thus, the container  26  and the sifter  22  are attached to each other to form a single component that is easy to house in the pedestal  24  and replace. The frame  44  allows the upper end of the peripheral wall  38  to be made more rigid. The container  26  thus maintains an opening  18  of same shape, in this case circular, at all times during the use of the housing  10 . 
     The container  26  further comprises a rim  46  that surrounds the opening  18 . The rim  46  projects radially outwardly from the peripheral wall  38 . When the container  26  is positioned in its housing  29 , it rests by means of its rim  46  which rests on the bearing face  36  of the pedestal  24 , as shown in  FIG.  8   . 
     Since the container  26  is very flexible, it would be complicated to extract it from the top of the housing  29  by exerting a pressure through the window  43  without spilling the remaining powder it contains to the outside. It is therefore preferable to be able to grip it by a more rigid portion, namely by the rim  46 , made more rigid by the frame  44 . To allow the container  26  to be easily grasped by the frame  44  and/or the rim  46 , the cylindrical wall  32  of the pedestal  24  comprises at least two radially opposed indentations  48  that provide access to at least the rim  46  of the container  26 . The indentations  48  are made in the upper edge  35  of the cylindrical wall  32 . They extend downwards up to the face  36  of the bearing surface. Each indentation  48  allows a user to grasp the rim  46  with the pad of two fingers. 
     The ring  28  for attaching the container  26  is attached by dismountable attachment means in the housing  29  by tightening the rim  46  of the container  26  against the bearing face  36 . The ring  28  will thus hold the container  26  firmly in its housing  29 . 
     The attachment ring  28  comprises a peripheral wall  50  which has an external diameter slightly smaller than the internal diameter of the cylindrical wall  32  of the pedestal  24  so that the ring  28  is received in the upper portion of the housing  29  with a radial clearance allowing the mounting and the dismounting. 
     The attachment ring  28  also comprises an annular upper wall  52  inclined in the direction of the opening  18  of the container  26  that radially delimits the bowl  20 . The upper wall  52  thus forms a funnel that allows the cosmetic product to slide towards the sifter  22 . For this purpose, the upper wall  52  has an inner diameter that is approximately equal to the diameter of the sifter  22 . 
     As illustrated in  FIG.  8   , the upper wall  52  has a lower annular face  54  that is intended to press against the rim  46  of the container  26  when the attachment ring  28  is mounted in the pedestal  24 . Here, the annular face  54  presses against the rim  26  by means of the frame  44  of the sifter  22 . Thus, the attachment ring  28  holds the container  26  firmly in position in its housing  29 . The rim  46  is tightened axially between the attachment ring  28  and the bearing face  36 . 
     The attachment ring  28  is mounted in a sealing manner around the container  26 . To this end, the frame  44  has a flexible lip  56  that extends radially outward from the circumference of the frame  44 . An annular bead  57  on the upper wall  52  of the attachment ring  28  is intended to come into tight axial contact with the lip  54  to ensure a good sealing preventing the cosmetic product from passing between the container  26  and the attachment ring  28 . 
     The attachment ring  28  is attached to the pedestal  24  by snap fitting in an axial direction. For this purpose, the attachment ring  28  comprises two axially extending attachment tabs  58  which are elastically deformable in flexion. Each attachment tab  58  is equipped at its free lower end with a crampon  60  which is intended to be fitted, here radially outwards, into a notch  62  of the pedestal  24 . Thus, each attachment tab  58  is flexible between a fitting state of the crampon  60  in its notch  62 , towards which it is elastically biased, and a disengaged state, in which it is flexed radially inward and is stressed against the elastic biasing force. 
     An upper portion of the attachment tabs  58 , ensuring the connection with the rest of the ring  28 , is formed by a portion of the peripheral wall  50  delimited, along the circumference of the ring  28 , by two axial slits  64  which are made in the peripheral wall  50  and which open downwards. These two slits  64  thus promote the flexibility of each attachment tab  58 . 
     The attachment tabs  58  are here two in number and they are arranged diametrically opposite to the main axis O of the case  10 . 
     The notches  62  are here arranged in line with the indentations  48 . The notches  62  are more particularly arranged below the bearing face  36 . This arrangement allows a user to bias the attachment tabs  58  towards their constrained state by biasing them directly with their fingers through the indentations  48 . Thus, the attachment ring  28  can be easily removed. 
     To allow the attachment ring  28  to be properly positioned relative to the pedestal  24 , the upper portion of each attachment tab  58 , formed in the peripheral wall  50 , comprises a radially outwardly extending projection  66  that is axially nested with the indentation  48 . These projections  66  come in abutment against the upper edge  35  of the cylindrical wall  32  of the pedestal  24  when they are not aligned with an indentation  48 . 
     The projections  66  also allow the ring  28  to be immobilized in rotation about the main axis O with respect to the pedestal  24 . 
     The cover  12  for closing the housing  29  is intended to be screwed onto the thread  34  of the pedestal  24  between a fully unscrewed position, as shown in  FIG.  8   , and a fully screwed position, as shown in  FIG.  11   , in which it is brought axially closer to the sifter  22  to allow the cavity  16  to be sealed. The screwing is done by rotating the cover  12  around the main axis O of the case  10 . 
     As shown in  FIGS.  4  and  5   , the cover  12  comprises an upper wall  68  from which a cylindrical wall  70  extends downward. An internal face of the cylindrical wall  70  comprises a thread  71  complementary to that of the pedestal  24  so that the cover  12  can be screwed to the pedestal  24 . 
     The cover  12  is equipped with a seal  72  which is intended to seal the opening  18  in the fully screwed position of the cover to prevent the cosmetic product from exiting its cavity  16 . 
     As shown in  FIGS.  4  to  7   , the seal  72  comprises a sealed membrane  74  that extends generally parallel to the sifter  22 . The membrane  74  comprises a lower face which forms a contact face  76  intended to rest on the entire surface of the sifter  22  when the cover  12  is in its fully screwed position. The membrane  74  has a circular outline with a diameter at least equal to that of the sifter  22 . 
     The contact face  76  is made of a material that has substantially no porosity capable of retaining or storing grains of cosmetic products. In particular, the contact face  76  does not have the structure of a sponge. The seal  72  is made of an elastomeric material. Here, the seal  72  is made in one part, for example by moulding. 
     When the seal  72  is attached to the cover  12 , the membrane  74  is arranged away from the upper wall  50  so that a chamber  78  is axially delimited between the cover  12  and the membrane  74 . The chamber  78  extends over substantially the entire surface of the sifter  22 . 
     The membrane  74  is made of a flexible material. This chamber  78  allows the membrane to deform in flexion under the effect of a pressure applied upwardly on the contact face  76 . The contact face has, at rest, a different shape than that of the sifter  22 . The membrane  74  is thus elastically deformable in flexion so that the contact face  76  conforms to the shape of the sifter  22  during the screwing of the cover  12  as will be explained in more detail later. 
     The seal  72  comprises a section  80  that is elastically deformable in an axial direction and is attached to the interior of the cover  12  by an upper end. The membrane  74  is attached to a lower end of the deformable section. The elastically deformable section  80  radially delimits the chamber  78 . The membrane  74  is thus secured in rotation with the cover  12  around the main axis O. 
     The deformable section  80  is here formed by an annular bellow that surrounds the chamber  78 . An upper edge  82  of the bellow forming the deformable section  80  is intended to axially abut against a lower face of the upper wall  68  of the cover  12 . 
     To allow the seal  72  to be attached to the cover  12 , the upper edge  82  of the deformable section  80  has radially outwardly projecting teeth  84 . These teeth  84  are intended to be radially embedded in notches  86  made in a circular partition  88  that extends axially downward from the lower face of the upper wall  68  of the cover  12 . The circular partition  88  is here adapted to internally receive the upper edge  82  of the deformable section  80 , with or without clearance. The deformable section  80  is made of sufficiently flexible material to allow the teeth  84  to snap fit into the notches  86 . 
     During the screwing and the unscrewing of the cover  12 , the volume of the chamber  78  is intended to vary as a function of the deformations of the deformable section  80 , on the one hand, and the deformations in flexion of the membrane  74 , on the other hand. To allow the air to enter and exit the chamber  78  to promote these deformations, at least one vent  90  of air passage is provided between the chamber  78  and the exterior of the seal  72 . The vents  90  are here made in the form of grooves made in the upper edge  82  of the deformable section  80 . The vents  90  are arranged in correspondence with reserved passages  92  in the circular partition  88 . 
     As will be explained later, the contact face  76  is intended to rub against the sifter  22  during the rotation of the cover  12 . This rubbing allows to push the grains of cosmetic product through the orifices in the sifter  22  back into the cavity  16 . Thus, the sifter  22  and the contact face  76  are cleaned and do not comprise cosmetic product when the cover  12  is opened again. 
     In order to achieve this rubbing effect, the contact face  76  comprises relief elements. The relief elements form a multitude of roughnesses on the contact face  76 . More particularly, these relief elements are formed here by a multitude of pimples  94 , visible in more detail in  FIG.  4   . 
     The pimples  94  are evenly distributed over the entire contact face  76 . In a variant of the invention not shown, the pimples are distributed with a greater density in the centre of the contact face  76  than at its periphery. 
     Here, the pimples  94  protrude axially by a height much less than the thickness of the membrane  74 , for example by a tenth of millimetre. 
     The pimples  94  are all the same height. 
     Alternatively, the pimples can have different heights depending on their location. 
     Moreover, the pimples have dimensions much smaller than the diameter of the contact face, for example in the order of millimetre or even tenth of millimetre. The pimples  94  are distributed with a high density. For example, the space between the summit of two adjacent pimples  94  is between one and two times the width of the base of a pimples  94 . 
     Preferably, but not necessarily, the compressive flexibility of the membrane  74  is much less than its flexural flexibility. Similarly, the compressive flexibility of the membrane  74  is much less than the axial deformation flexibility of the deformable section  80 . This means that when the membrane  74  is pressed against the sifter  22 , the pimples  94  are not deformed by crushing. The pimples  94  thus remain in relief even when the membrane  74  is pressed against the sifter  22 . When the cover  12  is pressed downwards, it is the deformation in flexion of the membrane  74  and the axial deformation of the deformable section  80  that absorb these forces. 
     This allows to ensure an optimal cleaning of the sifter  22  while avoiding creating a suction of the cosmetic product when removing the membrane  74 , as will be explained in more detail later. 
     In addition, the membrane  74  comprises an annular sealing segment  96  at its periphery that surrounds the contact face  76 . 
     This annular sealing segment  96  is here formed by two superimposed and parallel annular beads that project radially outward from a peripheral edge of the membrane  74 . The sealing segment  96  is intended to come into sealed contact with an annular face  98  of the base  14  in fully screwed position of the cover  12 . 
     As shown in  FIG.  11   , when pressed against the sifter  22 , the membrane  74  has an outer diameter that is substantially equal to the inner diameter of the upper wall  52  of the attachment ring  28 . More particularly, the diameter of the membrane  74  is selected so that the sealing segment  96  is in radial abutment outwardly against the internal edge of the upper wall  52 , which thus forms the annular face  98 , when the contact face  76  is pressed against the sifter  22 . 
     As is particularly apparent in  FIGS.  8  and  9   , the contact face  76  of the membrane  74  has, at rest, a convexly shaped periphery so that the sealing segment  96  is arranged axially above the level of the remainder of the contact face  76 . 
     More particularly, the contact face  76  here has a convex shape over its entire surface from a central point arranged substantially at the level of the main axis O of the case  12 . 
     Because of this convex shape, the membrane  74  is elastically deformable when the cover  12  is screwed on between a state of partial contact with the sifter  22  when the cover  12  occupies a first position, as shown in  FIG.  9   , and a state of total axial abutment against the entire surface of the sifter when the cover occupies a second position, as shown in  FIG.  10   . 
     The second partial screwed position is between the first position and the fully screwed position of the cover  12 . Thus, the contact face  76  is in contact with the entire sifter  22  before the cover  12  is completely screwed on. Thus, as the cover  12  continues to be rotated to complete the closing operation by screwing, the membrane  74  is driven in rotation by the cover  12 . This provides an effective cleaning of the entire surface of the sifter  22  and the contact face  76  of the membrane  74 . 
     To promote a proper cleaning of the sifter  22  and of the membrane  74 , the deformable section  80  has a lower flexibility than the flexibility in flexion of the membrane  74  so that the contact face  76  begins to deform before the deformable section  80 . Therefore, when the cover is screwed on, the membrane  74  will first reach its full contact state, and then the deformation of the deformable section  80  will absorb the axial displacements of the cover  12 . 
     The first position is preferably intermediate between the fully unscrewed position and the second position. This means that in its fully unscrewed position, i.e., when the cover  12  is placed on the base  14  without that the screwing having begun, as shown in  FIG.  8   , the contact face  76  of the membrane  74  is located at a distance above the sifter  22 . This allows, for example, a user to use the case  10  by discharging cosmetic product onto the sifter  22 , and then placing the cover  12  on the base  14 , for example, to prevent an air stream from carrying away the cosmetic product, without the cosmetic product gluing to the membrane  74 . 
     To facilitate the recycling of the case  10 , the seal  72  and the cover are made of one or more materials that can be treated by the same recycling stream. The cover and the seal  72  are made of polypropylene (PP), for example. 
     The operation of the invention is now described with reference to  FIGS.  8  to  11   . 
     As shown in  FIG.  8   , the cover  12  is first placed on the base  14  without being screwed on. In this fully unscrewed position, the membrane  74  of the seal  72  is arranged at a distance above the sifter  22 . The deformable section  80  and the membrane  74  are in a resting state. 
     Then, the cover  12  begins to be screwed on by rotation about the main axis O with respect to the base  14 . By cooperation between the threads  34  and  71 , the cover  12  moves axially in the direction of the base  14  until it reaches the first position in which the membrane  74  comes into contact with the sifter  22 , as shown in  FIG.  9   . In this first position, and due to its convex shape, the contact face  76  is in contact with the sifter  22  through a central point  100  located along the main axis O. In this first position, the sealing segment  96  of the membrane  74  is not yet in sealed contact with the annular face  98  of the base  14 . Thus, the air is still able to pass between the cavity  16  and the outside. 
     As the cover  12  continues to be screwed on, and due to the greater flexibility in flexion of the membrane  74 , the latter deforms in flexion as it abuts against the sifter  22 . Due to this deformation in flexion of the membrane  74 , the contact surface area between the contact face  76  and the sifter  22  gradually increases. The contact surface area here has a disc shape, the diameter of which increases as the cover  12  moves closer to the sifter  22 . Thus, an annular area of the sifter  22 , which surrounds the contact surface area, remains free. Air is therefore still likely to flow between the inside and the outside of the cavity  16  through this free annular area. The volume of the chamber  78  decreases as the membrane  74  deforms in flexion. 
     During the screwing, the cover  12  reaches its second position, as shown in  FIG.  10   . The contact face  76  then reaches its fully axially supported state before the cover  12  reaches its fully screwed position. In this position, the sealing segment  96  is then in sealed contact with the annular face  98  of the base  14 . The cavity  16  is thus sealed by the membrane  74 . The contact face  76  is then pressed axially against the entire surface of the sifter  22 . The deformable section  80  is only slightly, if at all, axially deformed. 
     As the cover  12  continues to be screwed on, the contact face  76  rotates, rubbing against the entire surface of the sifter  22 . This forces the cosmetic product grains back into the cavity  16  through the sifter  22 . Thus, the surface of the sifter  22  and the contact face  76  are simultaneously cleaned of cosmetic product residue. The cover  12  is thus rotated about its main axis O until it reaches its fully screwed position on the base  14 , as shown in  FIG.  11   . Between the second position, shown in  FIG.  10   , and the fully screwed position, shown in  FIG.  11   , the cover  12  can be rotated, for example, through an angle of rotation of between a quarter turn and two turns. Of course, the greater the angle of rotation, the more effective the cleaning. 
     Between its second position and its fully screwed position, the cover  12  moves even closer to the sifter  22 . To prevent the membrane  74  from pressing too hard against the sifter  22 , which could damage the latter, the deformation of the deformable section  80  allows the cover  12  to slide axially towards the sifter  22  up to its fully screwed position without the pressure of the contact face  76  against the sifter  22  being substantially augmented. The volume of the chamber  78  then becomes minimal, but not zero, with the membrane  74  still spaced from the upper wall  68  of the cover  12  in this fully screwed position. 
     The fully screwed position is stopped, for example, when a lug  102  carried by one of the cover  12  or the pedestal  24  is snap fitted into a notch  104  carried by the other of the cover  12  or the pedestal  24 . The lug  102  is here made in relief at the bottom of the internal face of the cylindrical wall  70  of the cover  12 , below the thread  71  as shown in  FIG.  4   . The notch  104  is here made at the bottom of the external face of the cylindrical wall of the pedestal, below the thread  34 , as shown in  FIG.  3   . 
     The case  10  is then sealed. 
     When the case  10  is opened again, the cover  12  is rotated in an unscrewing direction about the main axis O relative to the base  14 . The seal  71  is configured so that, upon unscrewing, the periphery of the contact face  76  begins to move axially away from the sifter  22  to release a peripheral area of the sifter  22 . A complementary inner area of the sifter  22  of said peripheral area remains in full contact with the contact face  76 . 
     The sealing segment  96  is moved away from its bearing face prior to or simultaneously with the initiation of the movement away from the periphery of the contact face  76  of the peripheral area of the sifter  22  to create an interstice for air to pass into the interior of the cavity  16  through said peripheral area. 
     This avoids a suction-cup effect that would oppose the opening of the cover  12 . This also prevents the suction of cosmetic product over the sifter  22  that could occur if the contact face had the same shape as the sifter  22 . 
     On the contrary, the fact that the contact face  76  progressively moves away from the sifter  22 , regaining its convex shape as the cover  12  is unscrewed, allows the surface of the sifter  22  to be progressively released from the outside inwards, thus avoiding the air streams above the sifter  22 . 
     Thus, when the user opens the case  10  again, not only the sifter  22  but also the contact face  76  of the seal  72  is cleaned. This allows to avoid spilling cosmetic product everywhere. In order to use the cosmetic product, the user must therefore voluntarily move the bottom  40  of the container  26  upwards by finger pressure to make the desired amount of cosmetic product pass over the sifter  22 .