Patent Publication Number: US-8534509-B2

Title: Fluid dispenser head and a dispenser including such a dispenser head

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. §119(e) of pending U.S. provisional patent application Ser. No. 61/425,096, filed Dec. 20, 2010, and priority under 35 U.S.C. §119(a)-(d) of French patent application No. FR-10 59093, filed Nov. 4, 2010. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a dispenser head for dispensing a fluid, preferably a viscous fluid or a paste, and for mounting on, or associating with, a variable-volume fluid reservoir having a movable wall. By way of example, the reservoir may be constituted by a tube having a flexible wall on which the user may exert pressure in such a manner as to squeeze the tube. The combination of this type of reservoir with a dispenser head of the invention constitutes a fluid dispenser that also forms the subject of the present invention. Such a dispenser head, or such a fluid dispenser, may find an advantageous application in the field of cosmetics, pharmacy, or even food. The purpose of the dispenser head is to close the fluid reservoir in sealed manner, so that the fluid stored inside the reservoir does not come into contact with the outside air, or with any contaminating element situated outside the container. 
     BACKGROUND OF THE INVENTION 
     In general, the dispenser head includes a dispenser orifice where the user may recover the dispensed fluid. The head also includes a sealing closure member, e.g. in the form of a pin, that closes the dispenser orifice when the fluid present in the head is at a pressure that is lower than a predetermined threshold, and opens the orifice when the fluid present in the head is at a pressure that is higher than the predetermined threshold. The closure pin is thus controlled directly by the pressure exerted by the fluid that is put under pressure in the head by actuating the movable wall of the fluid reservoir. In order to ensure closure that is completely sealed, the dispenser head also includes resilient means for urging the closure pin against the dispenser orifice. The harder the resilient means are urged against the pin in sealing contact with the dispenser orifice, the better the sealing. In addition, the dispenser head also includes a fluid inlet in communication with the reservoir. 
     Thus, when the movable wall of the fluid reservoir is squeezed, the pressure of the fluid inside the dispenser head must overcome the force exerted by the resilient means in order to remove the pin from the dispenser orifice. The minimum pressure for removing the pin corresponds to the predetermined threshold. The pressure exerted by the fluid inside the reservoir and the head is identical, but varies as a function of the force exerted by the user on the movable wall of the reservoir. In contrast, the pressure forces exerted on the inner walls of the dispenser head vary as a function of the surface area on which the pressure is exerted, since a pressure force is directly proportional to the surface area on which the pressure is exerted. 
     A well known problem of dispenser heads mounted on reservoirs having squeezable walls is that it is necessary to squeeze the reservoir hard in order to remove the closure pin from the dispenser orifice. As a result, the fluid is then dispensed very quickly and often in uncontrollable manner. Even by squeezing the reservoir very progressively, the dispenser orifice nevertheless opens suddenly, and the fluid thus dispensed tends to be squirted out or even sprayed, which is not the desired result when dispensing cream or a paste. On the contrary, it is necessary for the fluid to be dispensed in the form of a glob or a bead. 
     Naturally, a solution that may be envisaged in order to solve the problem of sudden and quick dispensing is to decrease the stiffness of the resilient means that urge the pin against the orifice. That achieves dispensing that conforms more to the desired result, namely dispensing in the form of a glob or a bead. However, decreasing the stiffness of the resilient means naturally decreases the force with which the closure pin bears against the dispenser orifice so as to close it in sealed manner. As a result, the dispenser orifice is not closed in completely sealed manner, and the composition present inside the head is subject to attacks from the outside air, or from any contaminating element situated outside the container. This is unacceptable for certain fluids that are particularly fragile and/or that do not include any preservatives. 
     It thus turns out that it is difficult to make agreeable and appropriate dispensing compatible with closing the dispenser orifice in completely sealed manner. The force exerted by the resilient means does indeed contribute to obtaining sealed closure, but prevents the fluid from being dispensed in suitable manner. Nevertheless, it is increasingly required to combine these two requirements, particularly when it is desired to dispense a fluid that is fragile and/or that does not include any preservatives. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to combine these two apparently-incompatible requirements as much as possible. The dispenser head of the present invention must ensure both that the dispenser orifice is closed in completely sealed manner, and that the fluid is dispensed in agreeable and controlled manner. 
     To do this, the head of the present invention further comprises a flexible differential membrane defining a bottom face facing towards the inlet and a top face facing towards the dispenser orifice, and at least one passage connecting the two faces of the membrane, the bottom and top faces respectively defining bottom and top surface areas that are simultaneously subjected to opposite pressure forces that are exerted by the fluid under pressure on both faces of the membrane, the bottom surface area being substantially smaller than the top surface area, the pin or closure member being formed by the flexible membrane. The flexible membrane is a “differential membrane”, since both of its faces are simultaneously subjected to the pressure exerted by the fluid. Its movement inside the head is thus directly dependent on the surface areas on which the pressure of the fluid acts on each face of the membrane, given that the pressure is identical on both sides of the membrane. The difference between the surface areas that are subjected to the pressure makes it possible to create a differential or a multiplying effect that, in this embodiment, is used advantageously to overcome the forces exerted by the resilient means. Advantageously, the ratio of the top surface area to the bottom surface area is greater than 3, advantageously greater than 4. Thus, the force exerted on the top surface area is 3 or 4 times greater than the force exerted on the bottom surface area. This gives the user the impression of squeezing the reservoir with only light or medium effort in order to dispense the fluid. However, this makes it possible to implement strong resilient means for urging the pin against the orifice, and thus ensuring complete sealing. The resilient means are easily overcome by the force resulting from the pressure exerted on the top surface area, as a result of the 3 or 4 multiplying effect. The flexible membrane thus fulfils a genuine function of multiplying force, thereby making it possible to have both strong resilient means, and easy and controlled dispensing. 
     In a practical embodiment, the dispenser head defines a fluid chamber on either side of the flexible membrane, namely an inlet chamber defined between the inlet and the membrane, and an outlet chamber defined between the membrane and the dispenser orifice, the two chambers communicating with each other via at least one through hole, so that both chambers are simultaneously subjected to the same pressure. However, given that the surface areas against which the pressure acts are not identical on both sides of the membrane, said membrane moves inside the head, in such a manner as to open the dispenser orifice. 
     In another practical aspect of the invention, the dispenser head comprises a base forming the inlet, a cover forming the dispenser orifice, and a flexible part forming the membrane, the flexible part being disposed between the base and the cover and defining seals. Advantageously, the base and the cover are rigid. According to an advantageous characteristic of the invention, the base may form resilient means, advantageously in the form of flexible oblique tabs, for urging the closure member or pin against the orifice. In a variant or in addition, the flexible part may form resilient means for urging the closure member or pin against the orifice, the resilient means connecting the membrane to the base. In a variant or in addition, the dispenser head may further include a spring that acts between the base and the membrane for urging the closure member or pin against the orifice. Thus, the resilient means may come from various locations, namely from the base, from the flexible part, or even from a separate spring. Naturally, the flexible membrane intrinsically incorporates resilient means resulting from its reversible deformability. 
     In a practical embodiment, the flexible part may form: the flexible membrane that is provided with a plurality of through holes that are disposed around the pin (closure member); a sealing fastener ring that surrounds the flexible membrane and that comes into sealing engagement with the cover; and a sleeve connecting the membrane to the base, the sleeve being axially deformable so as to enable the flexible membrane to move relative to the base, the sleeve forming a sealing anchor stub that comes into sealing engagement with the base, the sleeve extending around the inlet. 
     In another advantageous aspect of the invention, the inlet chamber is defined between the base and the flexible part, and the outlet chamber is defined between the membrane and the cover. Advantageously, the base is received by snap-fastening in the cover. The flexible part is thus jammed in sealed manner between the base and the cover. 
     The present invention also defines a fluid dispenser comprising a variable-volume fluid reservoir having a movable wall, and on which there is mounted a dispenser head as defined above. 
     The principle of the invention is to use a flexible differential membrane inside a dispenser head, the membrane acting as a sealing shutter member for a fluid reservoir. The differential characteristic of the flexible membrane is thus used advantageously to create a force-multiplying effect, making it possible to overcome strong resilient means while providing agreeable and controlled actuation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described more fully below with reference to the accompanying drawings that show two embodiments of the invention by way of non-limiting example. 
       In the figures: 
         FIG. 1  is an exploded vertical section view through a fluid dispenser incorporating a dispenser head in a first embodiment of the invention; 
         FIG. 2  is a vertical section view through the  FIG. 1  dispenser head in its assembled state; 
         FIGS. 3   a  and  3   b  are very greatly enlarged views of details of  FIG. 2 ; 
         FIG. 4  is an exploded vertical section view through a dispenser head in a second embodiment of the invention; and 
         FIG. 5  is a view of the  FIG. 4  dispenser head in its assembled state. 
     
    
    
     DETAILED DESCRIPTION 
     Reference is made firstly to  FIGS. 1 and 2  in order to describe in detail the structure of a fluid dispenser incorporating a dispenser head of the invention. The dispenser head is for associating with, or mounting on, a fluid reservoir R of variable capacity. For this purpose, the reservoir R includes a movable wall P on which the user may act by exerting a pressure force. The movable wall P may be rigid, or, on the contrary, may be flexible: either way, moving it reduces the working volume of the reservoir R. In an extremely simple embodiment, the reservoir is a flexible tube provided with a neck N. The user may take hold of the tube and press against its flexible wall P in such a manner as to squeeze it. In the field of cosmetics, this type of reservoir is often designated by the term “squeeze bottle”. Instead of this type of reservoir, it is also possible to use a reservoir comprising a cylinder in which a scraper piston is slidably mounted and on which the user may bear so as to move it inside the cylinder. 
     The dispenser head in  FIGS. 1 and 2  comprises three essential component elements, namely a cover  1 , a flexible part  2 , and a base  3 . The elements may be made by injection-molding appropriate plastics material. They all present more or less perfect circular symmetry around the axis X. In a variant, the cover  1 , or even the base  3 , may be made out of metal, ceramic, composite material, etc. The cover  1  and the base  3  are substantially rigid, while the flexible part  2  is elastically deformable, by definition. In another embodiment, the flexible part  2  may advantageously be made by bi-injection. The cover  1  and the associated base  3  co-operate with each other to form a kind of casing in which the flexible part  2  is housed, as described below. The flexible part  2  defines seals both with the cover  1  and with the base  3 , as described below. In this particular embodiment, the cover  1  is in the form of a lid including a top wall  11  that is substantially plane, and in the shape of a disk, at the center of which there is formed a dispenser orifice  12  that is placed on the axis X in this embodiment. Naturally, a configuration other than plane, and a shape other than disk-shaped, could be envisaged for the top wall  11 . It is also possible to envisage placing the dispenser orifice  12  off the axis X. On its bottom face, the top wall  11  is provided with a lip  14  of annular shape that projects axially downwards. On its outer periphery, the top wall  11  is extended by a substantially-cylindrical skirt  13  that, in the proximity of its bottom end, defines an internal annular housing  16  having a function that is explained below. In addition, between the skirt  13  and the lip  14 , the cover  1  defines an annular housing  15  having a function that is explained below. In this embodiment, the cover  1  presents a cross-section that is circular, but it is also possible to envisage some other cross-section shape for the cover  1 . 
     The flexible part  2  constitutes a kind of motor of the dispenser head, since it defines the dynamic portion of the head. The flexible part  2  initially defines a flexible membrane  21  in the shape of a disk. The membrane  21  defines a top face  2   s  and a bottom face  2   i . A passage is defined in order to connect both faces of the membrane. This passage may have a plurality of through holes  23  passing through the membrane, which through holes are disposed in a circle around the axis X, in this embodiment. At its center, on the axis X, the membrane  21  defines a closure member in the form of a sealing closure pin  22  that projects upwards. The pin  22  is situated on the top face  2   s . The through holes  23  make it possible to communicate directly from the top face  2   s  to the bottom face  2   i . It should be observed that the top face  2   s  is substantially or completely plane, interrupted only at the through holes  23  and at the closure pin  22 . In this embodiment, the bottom face  2   i  is stepped, thereby defining a thin portion at its outer periphery. The through holes  23  and the pin  22  are defined at its thick portion. Thus, the membrane  21  deforms more easily at its outer portion. Its thick inner portion is also deformable, but to a lesser extent. The thin peripheral portion thus fulfils a role of resilient means, making it possible to return the membrane to its rest state. The flexible part  2  also defines a sleeve  26  that extends downwards from the bottom face  2   i . The sleeve extends around the axis X. The sleeve  26  defines a bellows segment  27 , enabling the sleeve  26  to be contracted axially. At its bottom end, the sleeve  26  forms a sealing anchor stub  28 , as described below. On its outer periphery, the flexible membrane  21  is connected to a sealing fastener ring  25  that defines an axial annular groove  24 . The ring is made with increased wall thickness, so as to impart a certain amount of strength thereto. In another embodiment, the flexible part  2  may advantageously be heat-sealed on the cover  1  at the lip  14 , so as to guarantee sealing from the outside. 
     The base  3  includes a fastener cylinder  31  for coming into engagement with the neck N of the reservoir R. In the embodiment in the figures, the cylinder  31  is internally-threaded so as to be capable of being screw-fastened on the threaded neck N of the reservoir. In a variant, the base  3  may equally well be fastened by snap-fastening on the neck of the reservoir. The cylinder  31  defines a fluid inlet  32  for the dispenser head. Around the cylinder  31 , the base  3  defines a sealing reception groove  33  for receiving the anchor stub  28  of the sleeve  26  of the flexible part  2 . The base  3  further defines an annular disk  34  that extends radially outwards and that is for coming into contact with the reservoir R, for example. The disk  34  is provided with a plurality of sloping resilient tabs  35  that extend in oblique manner towards the axis X from the disk  34 . In order to enable the tabs  35  to be molded, the disk  34  is perforated with windows  36  through which mold cores can pass. The free top ends of the resilient tabs  35  are for coming into contact with the bottom face  2   i  of the membrane  21 . Finally, on its outer periphery, the base  3  defines a bushing  37  that is provided with a snap-fastener bead  38  that projects radially outwards. 
     Reference is made more particularly to  FIG. 2  in order to describe how the various elements  1 ,  2 , and  3  are assembled together and how they interact. As can be seen, the flexible part  2  is engaged inside the cover  1  in such a manner that the lip  14  penetrates into the annular groove  24  formed by the ring  25  of the flexible part  2 . The ring  25  is thus engaged inside the housing  15 . An annular gap is thus defined between the top wall  11  of the cover  1  and the top face  2   s  of the membrane  21 . The gap constitutes an upper chamber Cs for the fluid, as described below. The upper chamber Cs is not defined by the entire top face  2   s , but merely by a fraction of the top face that is referred to herein as the top surface area Ss. The top surface area Ss may be defined as the top face  2   s  of the membrane  21  minus the combined section area of the through holes  23  and the section area of the closure pin  22 . The upper chamber Cs is extremely thin axially, but presents a considerable radial extent. The top surface area Ss is practically equal to the top face  2   s , since the combined section area of the through holes  23  and of the pin  22  is negligible. The upper chamber Cs communicates with a lower chamber Ci via the through holes  23 . The lower chamber Ci is defined between the bottom face  2   i  of the membrane  21 , the sleeve  26 , and the cylinder  31  of the base  3 . In this embodiment, the chamber Ci presents the general shape of an upsidedown cup. It can be seen that the fluid inlet  32  communicates directly with the through holes  23  via the lower chamber Ci. 
     In  FIG. 2 , it can also be seen that the sealing anchor stub  28  of the sleeve  26  is engaged in permanent and sealed manner in the groove  33  of the base  3 . In addition, the sloping flexible tabs  35  come to bear with their free top ends against the bottom face  2   i  of the membrane  21 . The bushing  37  is engaged in the skirt  13 . More precisely, the snap-fastener bead  38  of the bushing  37  is housed permanently in the snap-fastener groove  16  of the skirt  13 . The top end of the bushing  37  pushes the fastener ring  25  against the lip  14  and into the housing  15 . Two seals are thus created, a first between the ring  25  and the cover  1 , and a second between the stub  28  and the base  3 , so as to isolate the top and bottom chambers Cs and Ci from the outside at the inlet  32 . In a variant, the anchor stub  28  of the sleeve  26  may be heat-sealed in the groove  33  of the base  3 , so as to guarantee sealing from the outside. 
     When the fluid under pressure coming from the reservoir R reaches the dispenser head, it fills the bottom and top chambers Ci and Cs that communicate easily with each other via the through holes  23 . In the lower chamber Ci, the pressure is exerted on a fraction of the bottom face  2   i  of the membrane  21 , which fraction is referred to herein as the bottom surface area Si. On the other side of the membrane  21 , the pressure is exerted on a fraction of the top face  2   s  of the membrane  21 , which fraction is referred to herein as the top surface area Ss. It should easily be observed that the bottom surface area Si is much smaller than the top surface area Ss. The surface area ratio Ss/Si is about 3 or 4 for the embodiment shown in the figures. It is even possible to envisage increasing this ratio by extending the top surface area Ss even more until it reaches the lip  14 , and by decreasing the bottom surface area Si by decreasing the diameter of the sleeve  26  and possibly also of the cylinder  31 . In all circumstances, the top surface area Ss is greater than the bottom surface area Si, and as a result the force exerted by the pressure of the fluid on the surface area Ss is much greater than the force exerted by the pressure of the fluid on the bottom surface area Si. In response to pressure, the flexible membrane  22  moves relative to the cover  1  and to the base  3  in such a manner as to remove the closure pin  22  from the dispenser orifice  12 . In other words, the membrane  22  moves away from the top wall  11 , towards the cylinder  31 . The movement of the membrane  22  is generated merely by the pressure of the fluid, such that the membrane may be referred to as a differential membrane since it reacts to the difference between the pressure forces exerted on the two faces. The volume of the upper chamber Cs increases while the volume of the chamber Ci decreases as the pressure increases. However, given that the flexible membrane  21  is urged resiliently towards the top wall  11  of the cover  1  by the resilient means, it is necessary for the pressure inside the chambers to reach a predetermined pressure threshold making it possible to overcome the resilient means. The resilient means are the result of combining a plurality of individual means, namely the elasticity proper of the membrane  21 , the elasticity provided by the bellows segment  27  of the sleeve  26 , and the elasticity of the oblique flexible tabs  5  of the base  1 . Naturally, it is possible to vary the various resilient means that act on the flexible membrane  21 . For example, it is possible to envisage eliminating the flexible tabs  35 . It is also possible to envisage having more of them so as to increase the resilient means. It is possible to envisage making the bellows segment more flexible, or, on the contrary, increasing its stiffness. It is also possible to vary the local thicknesses of the flexible membrane  21 . All of these factors co-operate in creating resilient means of greater or lesser strength, and that tend to urge the closure pin  22  against the dispenser orifice  12 , so as to close it in sealed manner. 
     At rest, as shown in  FIG. 3   a , the annular edge of the orifice  12  comes into sealing contact with a frustoconical wall formed by the closure pin  22 . Thus, the upper chamber Cs is isolated in completely sealed manner from the outside. However, during the dispensing stages, as shown in  FIG. 3   b , the frustoconical wall of the pin  22  lifts off from the edge of the opening  12 , thereby opening up an outlet passage for the fluid by putting the upper chamber Cs into communication with the outside. 
     Because of the flexible differential membrane  21  of the present invention, strong resilient means may be implemented, but without needing to squeeze the flexible wall P of the reservoir R very hard. As a result of the multiplying effect created by the pressure surface area differential, a reasonable manual force suffices to cause the membrane  21  to move. As described above, the multiplying ratio is about 3 or 4, so that medium pressure exerted on the reservoir suffices to overcome resilient means that present considerable stiffness. As a result, both completely sealed closure at rest and agreeable and controlled handling during dispensing are obtained in combination. These two apparently-opposing objectives are associated in judicious manner in the dispenser head of the present invention. 
     Reference may be made to  FIGS. 4 and 5  which show a second embodiment that is in fact a variant of the dispenser head in  FIGS. 1 to 3   b . In this second embodiment, the cover  1  and the flexible part  2  may be identical or similar to those of the first embodiment. The base  3  differs from that of the first embodiment only by the absence of the sloping resilient tabs  35 . The sloping resilient tabs are replaced by a conventional coil spring  4  that acts between the base  3  and the flexible part  2 . The spring  4  is disposed around the groove  33  and around the sleeve  26 , bearing against the bottom face  2   i  of the flexible membrane  21 . 
     By means of the invention, the force multiplying properties of a flexible differential membrane are used advantageously to overcome the stiffness of strong resilient means that make it possible to close a dispenser orifice in very effective manner, but without needing to squeeze the fluid reservoir excessively.