Abstract:
A metering valve for dispensing an aerosol, includes a metering chamber and a valve stem. The valve stem is equipped with one end disposed on the side of a container and a dispensing end mounted in the metering chamber such that it can slide under the force of a spring between a first high position, known as the rest position, and a second position, known as the intermediate position for filing the metering chamber. The final low position is defined when a shoulder provided on the valve stem abuts against a shoulder provided inside the metering chamber.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to the technical field of metering valves for dispensing an aerosol, and more particularly, but not exclusively, retention valves for dispensing pharmaceutical products. 
       BACKGROUND OF THE INVENTION 
       [0002]    The fluid product dispensing valves, notably the metering valves for dispensing pharmaceutical products in the form of aerosol sprays are known. They generally comprise a cylindrical valve body containing a metering chamber extending between two seals, a top seal and a bottom seal, a valve stem sliding in a seal-tight manner in the metering chamber between a rest position, a dispensing position and a final bottom position, The valve body is generally fixed to the neck of a vessel containing the product to be dispensed by means of a capsule crimped onto the neck. By way of example, the application EP 0 803 449 can be cited, which describes a valve known from the prior art. 
         [0003]    One problem that this type of valve poses relates to the volume or the quantity of the dose to be dispensed. In effect, such valves are generally used to dispense doses of pharmaceutical products, in which t e doses have to be particularly accurate and dispensed constantly. These doses have to be all the more accurate since the metering valve generally contains powder in suspension in a liquid phase comprising a liquefied propellant gas. Also, the valve has to both deliver a volume of a liquid and powder that can be repeated each time it is administered, the liquid being the vector of the powder, but also a very even quantity of powder (dry mass). It is therefore important for the valve to be able to dispense a strictly identical dose of the product throughout its use. 
       SUMMARY OF THE INVENTION 
       [0004]    The aim of the present invention is notably to propose a metering valve that makes it possible to limit the variations of the doses dispensed during the use of the metering device, 
         [0005]    To this end, the invention relates to a metering valve for dispensing an aerosol, comprising a metering chamber and a valve stem provided with an end positioned on the side of a tank and a dispensing end and mounted to slide in the metering chamber under the effect of a spring, between a first top position, called rest position, a second position, called intermediate metering chamber filling position, and a third position, called final bottom position, in which the spring is compressed, the valve stem comprising an expulsion orifice linking the metering chamber to the dispensing end when the stem is in the final bottom position, and a filling passage linking a tank to the metering chamber when the valve stem is in the intermediate filling position, a valve in which the final bottom position is defined by the abutting of a shoulder formed on the valve stem with a shoulder formed inside the metering chamber. 
         [0006]    Thus, a valve is proposed in which the stem is provided with an abutment making it possible to define the final bottom position of the pump, by an abutment occurring in the metering chamber. The result thereof is that the valve stem is more centered relative to the metering chamber, that is to say that it does not risk being offset. In fact, since the abutment is located in the metering chamber, the axial orientation of the valve stem is more guaranteed than in the valves of the prior art, where the final bottom position is generally defined by an abutting of the valve stem against the spring which is in a totally compressed state, with its turns abutting. In effect, the fact that the final bottom position is defined by the spring at the end of its travel, that is to say when the spring arrives in its maximum compression state, presents a risk of slightly offsetting the end of the valve stem, because of a possible slight offsetting or overlapping of the turns of the spring when they are abutting. Now, the slightest offsetting of the end of the stem risks creating a slight loss of seal-tightness between the stem and a top seal and/or a bottom seal of the metering chamber. This loss of seal-tightness can cause the dose of liquid and/or powder dispensed to vary. 
         [0007]    Furthermore, in the case where the metering valve is equipped with a dose metering system, the position of the valve stem has to be particularly accurate because it is the position of the stem relative to the valve body or to a ferrule which enables the meter to consider that a dose has been delivered or not. Thus, the efficiency of the dose meter depends on the accuracy of the position of the valve stem. Now, when the valve stem is stopped by the spring at the end of its travel, it is stopped at a distance which can vary from one dose to another, and even more from one metering valve to another, on the one hand because the compressed configuration of a spring can depend on the force exerted by the user or even on the plastic deformation of the spring over time, and on the other hand because the spring can have a tendency, during its compression, to be positioned askew in its housing, such that this can slightly offset the height of the valve stem in the final bottom position. 
         [0008]    In the present description, the expressions “top” and “bottom” refer to the position of the valve stem in relation to the tank to which the metering valve is added. Thus, a bottom position of the stem corresponds to a position in which the stem is closer to the tank than in the case of a top position of the stem. 
         [0009]    “The spring is compressed” should be understood to mean that the spring is in a configuration of maximum compression in the valve, but this does not necessarily mean that the turns of the spring are abutting. 
         [0010]    The metering valve is generally intended to be fitted onto the neck of a tank containing a fluid product to be dispensed in the form of an aerosol, more particularly a pharmaceutical product. It is intended to be used in the inverted position, also called “head down”. 
         [0011]    The metering valve can further comprise one or more of the following features, taken alone or in combination.
       The shoulder formed on the valve stem is arranged in such a way that the abutment surface extends in a plane at right angles to the axis of the valve stem. It preferably comprises a protuberance formed on the valve stem, the protuberance being able to be annular or semi-annular, for example an annular flute. The shoulder formed inside the metering chamber can also furthermore comprise an annular or semi-annular protuberance.   The shoulder formed on the valve stem is arranged in such a way that the abutment surface extends in a plane not at right angles to the axis of the valve stem. For example, it comprises an annular or semi-annular protuberance cooperating by a tapered or spherical bearing with the metering chamber, or else a tapered or spherical surface cooperating with an annular or semi-annular protuberance formed in the metering chamber.   The shoulder formed on the valve stem is borne by a protuberance also providing a function of abutment of the valve stem with a top wall of the metering chamber when the valve stem is in the rest position. Thus, a same protuberance is used to ensure both the abutment function defining the final bottom position and that defining the rest position. This shows how more accurate doses can be obtained, since the valve has only the production tolerances of this protuberance, whereas, in the case where the abutments were provided by two distinct parts separate from one another, the valve would have the production tolerances of each of these parts.   The metering chamber comprises a top cylindrical compartment and a bottom cylindrical compartment, the diameter of the top compartment being greater than the diameter of the bottom compartment, the shoulder being formed at the interface between the two compartments.   In the final bottom position of the stem, the spring is not completely compressed.   The end of the valve stem comprises a first bearing surface against an net seal of the metering chamber ensuring a first sealing of the metering chamber with respect to a tank when the stem is in the rest position. Preferably, this end of the valve stem comprises a part added on, forming a cap, the first bearing surface against the inlet seal being formed on this cap.   The first sealing between the end of the stem and the seal is produced in the axial direction of the device.   The valve stem comprises a second bearing surface against an inlet seal of the metering chamber ensuring a second sealing of the metering chamber with respect to a tank when he stem is in the final bottom position.   The second sealing between the stem and the seal is produced in the radial direction of the device.   The valve comprises an annular, or semi-annular, aperture, for the inlet of the aerosol into the metering chamber, the aperture being defined by the space between an inlet seal and the valve stem when the stem is in the intermediate position.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The invention will be better understood on reading the following description, given solely as an example and with reference to the drawings in which: 
           [0023]      FIG. 1  is a view in longitudinal cross section of a metering valve according to one embodiment, in the top rest position, the metering chamber being isolated from the outside of the dispensing device and from the inside of the tank. 
           [0024]      FIG. 2  is a view similar to  FIG. 1 , in which the valve is in the intermediate position, in which the metering chamber communicates with the inside of the tank and is isolated from the outside of the device. 
           [0025]      FIG. 3  is a view similar to  FIG. 1 , in which the valve is in the final bottom position, in which the metering chamber communicates with the outside of the device and is isolated from the inside of the tank. 
           [0026]      FIGS. 4A  and B are two different views in longitudinal cross section of the stem of the valve of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    With reference in particular to  FIG. 1 , a valve  1  is represented of the metering valve type for dispensing a fluid product, notably medicinal, in aerosol form, by means of propellant gas, notably of HFA type. Of course, the present invention can also be applied to valves of another type or used in different fields, such as perfumery or cosmetics, and with other propellant gases, for example CFC or compressed air, 
         [0028]    The valve is suitable for operating, or designed to operate, in the inverted position, that is to say in the position as represented in the drawings. In other words, the valve of the invention is intended to be used in a position in which the valve is situated under the tank containing the product to be dispensed, taking the direction of gravity as reference. 
         [0029]    The valve  1  represented in  FIG. 1  comprises a valve body  7  in which is added notably a ring  8 , delimiting a metering chamber  10 , or dose chamber. A valve stem  13  is fitted to slide in the metering chamber  10 , between a first top position, called rest position, represented in  FIG. 1 , and a third dispensing position, or final bottom position, represented in  FIG. 3 , in which the valve stem is depressed axially toward the interior, or toward the bottom, of the valve  1 , by being placed in abutment. The valve stem  13  is stressed toward its rest position by a spring  11 , or return means, which is compressed when a user actuates the valve and pushes the valve stem axially inside the valve. When the user relaxes his or her actuation force, the compressed spring  11  returns the valve stem  13  from its dispensing position to its rest position. 
         [0030]    During the actuation of the valve stem  13 , from the top position to the bottom position, or when the valve stem  13  is returned from its final bottom position to its top rest position, the valve stem  13  assumes a second position, called intermediate position, allowing the metering chamber  10  to communicate with the tank on which the valve is fitted. It will be noted that the first, second and third positions of the stem correspond to distinct positions. 
         [0031]    The valve stem comprises, in its top part, a central axial channel  12  emerging on one side on an axial outlet orifice  33 , intended to be connected to a dispensing end fitting, for example a spraying end fitting, and on the other side on a radial channel  14 , which emerges in the metering chamber  10  when the valve stem  13  is in the dispensing position. The metering chamber  10  communicates with a tank and with the outlet orifice  33  respectively by virtue of a filling passage  15  and the channel  14 , also called expulsion orifice. To this end, the valve  1  comprises a top seal  21 , or outlet seal, forming a sealing between the metering chamber and the outside, and a bottom seal  23 , or inlet seal, forming a sealing between the tank and the metering chamber. It will be understood that when the passage  15 , respectively  14 , is closed, the valve stem  13  slides in a seal-tight manner against the bottom seal  23 , respectively against the top seal  21 , such that liquid cannot infiltrate between the stem  13  and the seal  23 , respectively between the stem  13  and the seal  21 . 
         [0032]    The valve, and more specifically the valve body  7 , is joined to the tank by means of a fitting member  100 , which is advantageously a ferrule or capsule to be crimped as represented in  FIGS. 1 to 3 . It should be noted here that the fitting member  100  could be of a different type, for example a screwing, snap-fitting or similar means. 
         [0033]    The metering chamber  10  consists, in this example, of a top cylindrical compartment  50  and a bottom cylindrical compartment  51 , the diameter of the top compartment being greater than the diameter of the bottom compartment. A shoulder  17  is formed at the interface between the two compartments. In other words, the metering chamber  10  of the valve is constructed as follows:
       the top part  50  of the metering chamber  10  is essentially cylindrical of circular section, of a first determined diameter, and   the bottom part  51  of the metering chamber is essentially cylindrical of circular section, of a second determined diameter; the second diameter of the bottom part of the metering chamber being smaller than that of the top part of the metering chamber,
 
the two cylinders being coaxial and juxtaposed in the axial direction, one being in the extension of the other,
 
the sum of the volumes of the two cylinders, from which the volume of the valve stem  13  in this area is subtracted, defining the volume of the dose dispensed by the valve  1 , upon its actuation.
       
 
         [0036]    The bottom wail of the metering chamber  10  is delimited notably by the bottom seal  21 , and the top wall  10  of the metering chamber is delimited notably by the seal  23 . 
         [0037]    The interface between the bottom part and the top part of the metering chamber  10  forms the shoulder  17 . 
         [0038]    Here the position assumed by the valve stem  13  when the latter is actuated and the valve stem comes into abutment with the shoulder  17  formed in the metering chamber is defined by the final bottom position. This final bottom position is also called aerosol dispensing position, since the dispensing orifice  14  is then in communication with the metering chamber  10  and allows the release of the aerosol through the dispensing end  12 . It will be noted that the orifice  14  is in communication with the outside before the final bottom position is reached, and that the final bottom position corresponds to one dispensing position out of several successive dispensing positions. This position is represented in  FIG. 3 . It will be noted, in the final bottom position, that the two parts  50  and  51  of the chamber communicate with one another. In other words, there is never any sealing between these two parts  50 ,  51 . 
         [0039]    The top rest position corresponds to the position in which the spring is most relaxed and exerts a minimum thrust on the valve stem. The metering chamber  10 , in the rest position, is isolated both from the outside of the device and from the inside of the tank to which the valve is fixed. This position is represented in  FIG. 1 , By virtue of this double isolation of the metering chamber in the rest position, the valve  1  is a so-called “retention” valve, because the chamber is normally filled and the liquid that it contains communicates neither with the tank nor with the outside. It will be noted that the valve delivers the dose a little before reaching the final rest position. 
         [0040]    An intermediate position is also defined, which corresponds to a position assumed by the valve stem  13 , between its top and bottom positions described above. In this intermediate position, the metering chamber  10  communicates only with the inside of the tank onto which the valve  1  is fitted. This position is represented in  FIG. 2 . 
         [0041]      FIG. 1  shows the valve  1  in the top position, or rest position. 
         [0042]    In this position, the metering chamber  10  is isolated in a seal-tight manner from the outside of the device and from the inside of the tank on which the valve is fitted. 
         [0043]    The sealing of the metering chamber  10  is ensured:
       in the top part of the metering chamber  10 , by radial cooperation between the seal  21  and the valve stem  13 , as well as by axial cooperation between the protuberance  14  and the seal  21 , and   in the bottom part of the metering chamber  10 , by axial cooperation between the seal  23  and a part of the valve stem  13 . More specifically, the valve stem comprises a part  22 , added onto its bottom end  40 , here forming a cap.       
 
         [0046]    In the rest position, the bottom end  40  of the valve stem  13  oriented toward the bottom of the valve, more specifically the cap  22 , cooperates with the spring  11 . The cap  22  has an essentially planar and horizontal surface  24 , opposite the surface cooperating with the spring  11  and represented in the  FIGS. 4 . This planar surface  24 , which serves as bearing surface against the bottom seal  23 , abuts with the bottom seal  23  in the rest position of the valve stem  13 . The cooperation between the cap  22  and the seal  23  ensures the sealing of the bottom part of the metering chamber  10  in this position. Also, in the rest position, the seal  23  and the planar surface cooperate axially, by crushing seal  23 , in order to ensure the sealing of the metering chamber  10 . If the device to which the valve is fixed is in the “head up” position (the valve being in the reverse position to that represented in the figures), the aerosol contained in the metering chamber cannot escape to the tank. Moreover, the axial sealing has the effect of limiting the wear of the seal  23  during the sliding of the stem  10 , as would be the case in the case of a radial mobilization of the seal  23 . It will be noted that this radial mobilization of the seal  23  can take place slightly when the valve stem comprises ribs interfering with the seal  23 . Thus, it is particularly advantageous to provide a stem  13  without ribs cooperating with the seal  23 . 
         [0047]    Still in the rest position, the top part of the valve chamber  10  is hermetically sealed by two means:
       a first means consisting of the radial cooperation between the valve stem  13  and the top seal  21  to ensure the sealing of the metering chamber  10 , and   an auxiliary means consisting of an axial cooperation between a protuberance  16  of the valve stem  13  and the top seal  21 .       
 
         [0050]    Thus, by virtue of the auxiliary means, the sealing of the top part of the metering chamber is increased by the crushing of the seal  21  by the annular protuberance  16  of the valve stem. The aerosol contained in the metering chamber  10 , when the valve is in the overturned position as indicated in the figures, cannot therefore escape to the outside. 
         [0051]    Advantageously, the protuberance  16  of the valve stem  13  forms a shoulder  31  defining an essentially planar and horizontal surface which abuts with the shoulder  17  of the metering chamber  10 . The protuberance  16  of the valve stem  13  also forms a second shoulder  32  opposite the shoulder  31 , the second shoulder  32  also forming an essentially planar surface which abuts with the top seal  21 , when the valve stem is in the top position, or rest position. 
         [0052]    The abutment of the second surface of the protuberance of the valve stem  13  with the top seal  21  serves to hermetically block the outlet end  12  of the metering chamber  10  when the valve stem is in a top rest position. 
         [0053]    The protuberance  16  of the valve stem  13 , through its two shoulders borne by a single protuberance, makes it possible to reduce the manufacturing tolerances of the stem. Moreover, the presence of a single protuberance  16  having two shoulders makes it possible to reduce the volume occupied by the valve stem  13  in the metering chamber  10 , and improve the accuracy of a dose metering system when it is coupled to the metering valve. 
         [0054]    When the valve stem  13  is stressed into its dispensing position, as indicated in  FIG. 3 , by compression of the spring  11 , the shoulder  16  formed on the valve stem abuts with the shoulder  17  of the metering chamber. This shoulder  16  of the valve stem  13  is advantageously an annular protuberance, having the effect of increasing the solidity of the shoulder  16  in the case of an excessively strong abutment against the shoulder  17  of the metering chamber. It is, however, possible to provide other forms of shoulders, notably in the form of partially annular protuberance(s). It will be understood that the spring  11  acts as a member for returning the valve stem  13  to its rest position. It is understood that any elastic member applying the same effect to the valve stem is also suitable and can be called spring. 
         [0055]    The valve stem  13  cannot be stressed axially beyond the shoulder  17  of the metering chamber, so this is its final bottom position or dispensing position. 
         [0056]    The abutment of the valve stem  13  has the effect of reducing the stress of the spring  11 , because it is not necessarily fully compressed, and of ensuring its longevity. 
         [0057]    it is found in fact that, in the field of metering valves, the springs stressed to their maximum, called springs operating at end of travel, have a tendency to be skewed, that is to say to be displaced in such a way that they are no longer positioned axially relative to the valve stem (the outer jacket of the spring is no longer strictly a cylinder). In such a position, the spring can exert a radial force in addition to the axial force, this radial component being able to displace the valve stem. Such a change of position of the spring  11 , not only is likely to modify the end-of-travel position of the stem  13 , but can also provoke sealing losses between the valve stem  13  and the seals  21  or  23 . 
         [0058]    It is understood that, in the rest position in the present retention valve, the bearing surface  24  of the cap and the surface  32  of the protuberance  16  simultaneously bear on seals  21 ,  23 , which guarantees the isolation of the metering chamber with respect to the tank and to the outside. It is also understood that the seals  21 ,  23  are made of elastomer material, without which the sealing would be theoretically impossible because there would then be non-deformable materials. 
         [0059]    Referring in particular to  FIG. 2 , the valve stem  13  can slide in the metering chamber  10 , between the top  23  and bottom  21  seals, in a so-called intermediate filling position. 
         [0060]    When the valve stem  13  is mobilized toward the bottom of the valve, exerting a thrust on the spring  11 , the valve in its intermediate position as defined previously makes it possible for the aerosol to enter from the tank to the metering chamber  10 , through the bottom part of the metering chamber. 
         [0061]    The aperture in the bottom part of the metering chamber  10  corresponds to an annular aperture  15  defined between the bottom seal  23  and the bottom part  40  of the valve stem  13 . This aperture  15  could be semi-annular, in the form of ring segments. On the bottom part  40  of the valve stem  13 , the valve stem does not cooperate radially, at least partly, with the bottom seal  23 , thus creating a free space through which the aerosol contained in the tank on which the valve is fitted can penetrate into the metering chamber  10 . 
         [0062]    Advantageously, the bottom part  40  of the valve stem  13  which does not cooperate at least partially with the top seal  23  is of semi-annular form interrupted by one or more, notably two to six, preferentially three to six, axial ribs  30 . Such a valve stem  13  is represented in  FIG. 4A . The presence of ribs  30  makes it possible to increase the bore section through the aperture without weakening the end of the valve stem  13 . 
         [0063]    A valve stem  13  without any axial ribs  30 , and therefore having an annular bottom part  40 , is represented in  FIG. 4B . 
         [0064]    The valve stem  13  can finally assume a fourth position in which the metering chamber  10  is isolated from the outside and from the inside of the tank. In this fourth position, the valve stem has slid axially between the bottom  23  and top  21  seals, but the shoulder  31  has not yet abutted with the shoulder  17  of the metering chamber  10 . 
         [0065]    The top part of the metering chamber is still sealed by the part of the valve stem  13  included above the protuberance  16 , but without the orifice  14 , or a radial channel  14 , being in contact with the inside of the metering chamber  10 . 
         [0066]    The bottom part of the metering chamber  10  is blocked by the cooperation of the part  41  of the valve stem  13  immediately above the bottom part  40  of the valve stem  13 . 
         [0067]    Since the diameter of the part  41  of the valve stem  13  is greater than the internal diameter of the seal  23 , the part  41  cooperates radially with the seal  23 , thus blocking the bottom part of the metering chamber  10 . 
         [0068]    Such blocking of the bottom part of the metering chamber  10  has the effect of preventing the communication between the tank and the outside of the device when the valve stem  13  is in the final bottom position. Thus, only the content of the metering chamber  10  can be dispensed. 
         [0069]    It will be noted that the invention is not limited to the embodiments described above.