Patent Publication Number: US-2023149960-A1

Title: Fluid product dispenser

Description:
The present invention relates to a fluid product dispenser comprising a fluid product vessel provided with an externally threaded neck and internally defining an opening communicating with the inside of the vessel. The dispenser further comprises a dispensing head that is mounted on the neck of the vessel, the head comprising a dispensing member, such as a pump or a valve, a pusher for actuating the dispensing member and a fastening member engaging both with the threaded neck of the vessel and with the dispensing member. Such dispensers are frequently used in the fields of perfumery, cosmetics, or also pharmacy. 
     In the prior art, document WO 2009/150351 is known, which describes a dispenser comprising a vessel provided with a threaded neck and a fastening member comprising a deformable and malleable skirt intended to engage with the threaded neck, and a rigid collar engaged around the skirt to push the skirt radially against the threaded neck in such a way as to deform the skirt against the thread of the neck so as to create a thread imprint in the skirt. The skirt of the fastening member is thus brought into engagement with the threaded neck by an inwardly-directed radial movement, and not by an axial turning movement, as with conventional threaded skirts. Before the skirt is mounted for the first time on a threaded neck, the skirt does not include any thread imprint: it is only while radial thrust is being applied by means of the collar, that the thread imprint is created by plastic deformation of the deformable and malleable skirt. The material constituting the deformable and malleable skirt creeps plastically around the threads of the neck of the vessel in order to achieve a final state with a satisfactory thread imprint. 
     This dispenser of the prior art thus allows to mount the skirt around the neck without rotation and then allows to remove the skirt from the neck by simple unscrewing. This dispenser therefore meets a recycling requirement by allowing the separation of these constituent elements. However, it has been found empirically that it is not possible to rescrew the skirt onto the neck for several reasons. The first is that the contact between the skirt and the neck is extremely close and tight, such that there is absolutely no clearance. The second results from the skirt relaxes slightly when it is removed from the neck as a result of its malleability. The third reason is associated with the fact that the skirt is formed of flexible tabs that are separated by slots: when it is desired to rescrew the skirt, its tabs hook the thread of the neck and come across, thus making it impossible to rescrew. It is therefore not possible to reuse this dispenser, which does not meet the current requirement of durability. 
     An object of the present invention is to remedy the above-mentioned drawbacks of the prior art by defining a fluid product dispenser, the fastening member of which can be rescrewed onto the neck after unscrewing. The user should not have to make several attempts to engage the imprints of the skirt on the threads of the neck. 
     To do this, the present invention proposes that the helical thread(s) of the neck comprise(s) an upper screw start, a lower thread end and an intermediate portion that has a cross-section that decreases in the unscrewing direction and/or increases in the screwing direction, such that the unscrewing torque decreases and/or the rescrewing torque increases. Thus, the imprints of the skirt which first engage with the threads of the neck during rescrewing are greater than the thread starts, which create a clearance between the imprints and the threads. This clearance will facilitate engagement of the skirt on the threads during rescrewing. Naturally, this clearance decreases as the rescrewing takes place and disappears at the end of the rescrewing. The interleaving of the threads in the imprints can be likened to a cone-in-cone contact, given that the threads and the imprints both have a “conical” or “tapered” configuration, if their helical curvature is ignored. The rescrewing therefore requires an increasing torque, which gives the user a justified feeling of sufficiency and quality. 
     It should be observed that this particular configuration of the threads of the neck finds a very particular advantage with the dispenser of document WO 2009/150351. Indeed, it is the “conical” or “tapered” configuration of the threads that provides the same negative configuration to the imprints of the skirt, which makes it possible to create this advantageous clearance between the imprints and the threads at the beginning of rescrewing. 
     Advantageously, at least half of the length of the intermediate portion has a cross-section which decreases in the unscrewing direction and increases in the screwing direction, such that the unscrewing torque decreases and the rescrewing torque increases. On the other hand, the helical thread, at the junction between the lower thread end and the intermediate portion, may present a maximum cross-section. According to an embodiment, the intermediate portion may include a constant maximum cross-section lower part ( 12 MC). This means that the cross-section does not necessarily increase over the entire length of the intermediate portion. A constant end section range may be used to indicate to the user that rescrewing is sufficient. 
     Advantageously, the intermediate portion presents an axial height and a radial thickness, at least one of these two sizes decreases in the unscrewing direction and increases in the screwing direction. It is therefore possible to act on these two sizes, or only on one, in order to vary the cross-section of the thread(s). By way of indication, the axial height may vary by at least 20%, advantageously between 1 mm and 1.5 mm. Alternatively or cumulatively, the radial thickness may vary by at least 30% and preferably by 50%, advantageously between 0.4 mm and 0.6 mm. The ratio of the axial height to the radial thickness may be of the order of 2 to 3. 
     According to an advantageous embodiment, the neck comprises at least two helical threads, advantageously three or four. The docking of the skirt on the neck is all the more stable the greater the number of threads, since the number of bearing points is multiplied. 
     According to another interesting characteristic, the helical threads may overlap. 
     Advantageously, said at least one helical thread includes two inclined lateral flanks and a substantially flat and cylindrical top, such that the helical thread presents a cross-section of generally short configuration. This increases the stiffness of the threads, which will have to withstand various uncalibrated torques, since they are exerted by the users. 
     According to an advantageous practical embodiment, the skirt is made of a plastic material and the helical threads are made of glass, the skirt comprising flexible tabs separated by slots, each flexible tab being internally provided with at least one bead intended to be deformed by the helical thread of the neck, the beads being elongate and extending transversely to the helical thread. 
     The spirit of the present invention resides in the tapered shape over a significant part of the length of the neck threads, which makes it possible to produce corresponding imprints, which enables to create a clearance at the start of rescrewing which is used to advantage for starting the rescrewing easily without trial. 
    
    
     
       The invention will now be described in more detail with reference to the accompanying drawings, which show several embodiments of the invention as non-limiting examples. 
       In the figures: 
         FIGS.  1  to  4    are views showing a fluid product dispenser of document WO 2009/150351, during various successive mounting and removal steps; 
         FIG.  5    is a lateral plan view of a threaded neck of the invention; 
         FIG.  6    is a vertical cross-sectional view through the threaded neck of  FIG.  5   ; 
         FIGS.  7   a  and  7   b    are larger-scale views of surrounded details A and B of  FIG.  6   , 
         FIGS.  8   a  and  8   b    are perspective views showing the engagement of the skirt with the threaded neck respectively in the context of document WO 2009/150351 and the present invention, and 
         FIGS.  9   a ,  9   b  and  9   c    respectively illustrate three other embodiments for neck threads of the invention. 
     
    
    
     The fluid product dispenser shown in the  FIGS.  1  to  4    in order to illustrate the prior art corresponding to document WO 2009/150351 comprises two distinct parts or sub-assemblies, namely a fluid product vessel  1  and a dispensing head  2  for mounting on the vessel so as to co-operate with each other to constitute the dispenser. 
     The fluid product vessel  1  is shown in part only in the  FIGS.  1  to  4   . Only the neck  11  and a portion of the shoulder  14  of the vessel  1  are shown in the figures. The neck  11  projects axially upwards from the shoulder  14  that already forms a portion of the vessel body (not shown). The neck  11  internally defines an opening  10  that puts the inside of the vessel into communication with the outside. The opening  10  is defined by an annular top edge  13  of the neck  11 . Externally, the neck  11  forms one or more helical threads  12   a  that are in the form of one or more projecting ribs disposed in helical manner. The threads  12   a  can extend over all or part of the periphery of the neck  11 . The threads  12   a  may be continuous, or, on the contrary, they may be interrupted. The purpose of the threads  12   a  is to enable a turning movement to be combined conventionally with an axial movement. This may be referred to as screwing/unscrewing movement. The vessel  1  can be made of any material that makes it possible to obtain a neck that is rigid and not deformable. In particular, the vessel may be made of glass, of metal, or even of a rigid plastic material. 
     The dispensing head  2  essentially comprises three component members, namely: a dispensing member  3  that can be a pump or a valve; a pusher  4  that is mounted on the dispensing member  3  so as to actuate it; and a fastening member  5 . 6  engaging both with the threaded neck  11  of the vessel and the dispensing member  3 . Reference is made below to all of the figures while describing the structure of the dispensing head  2 . 
     The dispensing member  3  includes a body  30  that defines, at one of its ends, an inlet  31  for the fluid product coming from the vessel. The body  30  forms a fastening rim  37  that projects radially outwards. The dispensing member  3  also includes an actuation rod  32  that projects upwards, out from the body  30 , and that is axially movable down and up relative to the body. A return spring  33  urges the actuation rod  32  into the position in which it is extended to its maximum out from the body. The actuation rod  32  internally defines a flow channel for the fluid product put under pressure inside the body  30 . This design is entirely conventional for a pump or a valve in the fields of perfumery, cosmetics, and even pharmacy. Given that the internal structure of the dispensing member  3  is not critical for the present invention, it is not described in greater detail below. 
     The pusher  4  is mounted on the free end of the actuation rod  32  of the dispensing member  3 . The fluid coming from the actuation rod  32  is conveyed via an internal channel to the dispensing orifice  42  formed by the pusher. In addition, the pusher includes a bearing surface  41  on which the user can press using one or more fingers so as to move the pusher  4  axially down and up. In this way, fluid product is dispensed through the dispensing orifice  42 , optionally in metered manner. Here again, this design is entirely conventional for a fluid product dispenser. 
     The fastening member comprises two distinct component elements, namely a fastening ring  5  and a blocking collar  6 . The collar  6  is engaged around the ring  5  in such a manner as to mask all or part of it. One purpose of the collar  6  is to deform the ring  5  radially inwards and to hold it in that state. 
     The ring  5  is advantageously made of a plastic material that is deformable and malleable making it possible to create both zones that deform easily, and other zones that are more rigid. The ring  5  presents an overall configuration that is substantially circularly cylindrical about the axis of the dispenser. The ring  5  is preferably made as a single piece, but it is possible to distinguish three portions, each performing a distinct function. 
     The ring thus includes a skirt  51  intended to engage about the threaded neck  11  of the vessel. Consequently, in the mounted position, the skirt  51  extends around the neck  11  down to below threads  12   a , as shown in  FIGS.  4  and  5   . The skirt  51  may be continuous over its entire periphery in such a manner as to form a complete cylinder. In a preferred variant, as shown in the figures, the skirt  51  forms flexible tabs  52  that are separated by radial slots  54 . This can clearly be seen in  FIG.  1   . The number of tabs  52  can lie in the range three to more than ten. In the figures, the skirt  51  forms six flexible tabs  52  that are separated by six radial slots  54 . The slots  54  can extend over all or part of the height of the skirt  51 . In other words, a portion of the skirt can remain continuous, while another portion that is lower down is slotted to form the tabs. In the figures, the skirt  51  is slotted over its entire height. As a result of the skirt  51  being slotted, the tabs  52  present great flexibility, in particular in the radial direction. It can thus be deformed freely outwards and inwards without risk of damaging the tabs. The inside walls of the tabs (or of the skirt) can be completely smooth, or, on the contrary, in a preferred variant, the tabs are formed with beads  53  that project radially inwards. The beads  53  are situated in the proximity of the free bottom end of the tabs  52 . The beads  53  are preferably thin and elongate in the axial direction. They are thus in the form of separate small vertical splines or bars. The beads  53  may present beveled leading edges so as to make it easier to put the ring into place on the neck of the vessel. By way of example, it is possible to provide two or three beads per tab. It can also be envisaged to provide only a single bead per tab, which bead extends over all or part of the radial width of the tab. In the figures, there are two beads per tab and six tabs, making a total of twelve beads for the skirt  51 . The beads  53  are disposed on the skirt  51  in such a manner as to come to be positioned on the threads  12   a , as can be seen in  FIGS.  2  to  5   . The beads  53  are for being plastically deformed against the threads  12   a  of the neck  11 , as described below. 
     In addition to the skirt  51 , the ring  5  also forms a guide and preassembly bushing  55  that extends upwards in register with the skirt  51 . The bushing  55  presents a configuration that is substantially cylindrical, with a diameter that is appropriate for receiving the collar  6 , as described below. 
     At the junction between the bushing  55  and the skirt  51 , the ring  5  forms a bearing flange  56  that projects radially inwards. This flange  56 , that can be continuous over the entire periphery, or, on the contrary, that can be interrupted, is intended to engage with the rim  37  of the body  30  of the dispensing member  3 , so as to push it towards the top edge  13  of the neck  11 , with a neck gasket  7  possibly being interposed therebetween. Thrusting the flange  56  against the collar  37  thus causes the neck gasket  7  to be compressed against the annular edge  13  of the neck  11 . Good sealing is thus provided between the dispensing member  3  and the neck  11 . The compressed state of the gasket  7  is provided solely by the press used to mount the dispensing head, and not by the deformation of the skirt  51 , as occurs with prior-art fastening members. 
     The blocking collar  6  may be a visible collar that is attractive, or, on the contrary, it may be an internal collar that is not visible. In the figures, the collar  6  is a visible covering collar that may be made of metal, for example. The collar  6  is generally cylindrical with an inwardly-directed top flap  61  for coming into abutment against the free top end of the bushing  55 . The inside diameter of the collar  6  is slightly smaller than or equal to the outside diameter of the ring  5 . The collar  6  thus constrains and holds the ring  5  in a substantially-cylindrical and blocked configuration. 
     Reference is made below consecutively and in order to the various figures, so as to describe a cycle for mounting a dispensing head on a threaded vessel-neck and for removing it therefrom. In  FIG.  1   , the dispensing head  2  is not yet in engagement with the neck  11 . The tabs  52  of the skirt  51  thus extend in completely cylindrical manner, without being subject to any deformation. The collar  6  is pre-engaged around the ring  5  at the bushing  55 . The ring  5  and the collar  6  thus constitute a single sub-unit that is inseparable, and that is therefore held captive. In addition, the bushing  55  makes it possible to hold and to guide the collar  6  accurately axially. It should be observed that the collar  6  is not yet engaged around the skirt  51 . The first mounting step consists in engaging the skirt  51  around the threaded neck  11 . This is shown in  FIG.  2   . The dispensing member  3  thus being engaged inside the opening  10  of the neck. The gasket  7  disposed under the collar  37  is thus in contact with the top edge  13  of the neck  11 . The beads  53  formed at the tabs  52  are disposed on the threads  12   a . It should be observed that the tabs  52  are slightly deformed outwards, as a result of the beads  53  coming into contact with the threads  12   a . The beads  53  are not yet deformed against the threads  12   a . The third mounting step consists in lowering the collar  6  around the ring  5 . This is performed by exerting pressure on the inwardly-directed flap  61  of the collar  6 . The pressure makes it possible to flatten the neck gasket  7  so as to provide sealing. The collar  6  thus begins to be engaged around the skirt  51 . The beads  53  begin to be pressed hard against the threads  12   a . The operation of lowering or engaging the collar  6  around the ring  5  continues until the collar  6  surrounds the ring  5  completely, as shown in  FIG.  3   . This corresponds to the final mounted position in which the beads  53  of the tabs  52  are deformed against the threads  12   a  in such a manner as to create thread imprints  530   a  in the material constituting the beads  53 . In this final mounted position, the inwardly-directed flap  61  is in abutment against the top end of the bushing  55 . It is also possible to determine the final mounted position when the bottom end of the collar  6  comes into abutment contact with the shoulder of the vessel. To do this, it suffices to provide a collar that is slightly taller. As a result of the threads  12   a  extending in helical manner, the thread imprints  530   a  are formed at different axial levels on the various beads  53 . For example, in  FIG.  3   , the thread  12   a  in the right-hand portion forms an imprint  530   a  that is in the proximity of the bottom end of the bead  53 , whereas in the left-hand portion, the imprint  530   a  is formed towards the top of the bead  53 . The threads advantageously come into contact with the skirt  51  only at the beads  53 . Thus, contact between the skirt and the neck occupies only part of the periphery, and preferably extends over less than half the periphery of the neck. This applies when there are only twelve beads  53  distributed around the periphery. This interrupted contact makes it possible to reduce the friction forces between the skirt and the neck considerably, thereby making it possible to loosen the dispensing head manually. The torque is applied directly on the collar  6  that is in clamping contact with the ring  5 . Contact between the collar and the ring extends over the entire periphery and advantageously over almost the entire height of the ring. The friction between the ring and the collar is therefore considerably greater than the friction between the beads  53  and the threads  12   a . Loosening is thus made possible. Once the loosening operation has been completed, the dispenser is in the configuration shown in  FIG.  4   . The thread imprints  530   a  that have been created in the beads  53  can thus clearly be seen. Each imprint  530   a  comprises an imprint bottom wall  531  that is bordered by two opposite imprint flanks  532  and  533 . This demonstrates that the thread imprints  530   a  are formed without generating traction on the tabs  52 . In other words, the inwardly-directed radial thrust created by the collar  6  is not transformed into thrust with an axial component while the beads  53  are making contact with the threads  12   a . The compression of the neck gasket  7  is thus obtained and controlled entirely by the force exerted by the mounting press. Such imprints  530   a  can be obtained merely as a result of the beads extending on either side of the threads  12   a . There is therefore no cam effect or force-direction transformation effect while the beads  53  are being deformed. The deformation of the beads  53  is plastic deformation by instantaneous and/or subsequent movement of material, in particular by creep. It is known that plastics materials tend to creep over time in order to achieve a final deformed state. In the context of the present invention, the creep phenomenon is used to advantage, given that a relatively lengthy period of time passes between the dispenser being mounted and the dispensing head being loosened when the vessel is empty. Once the dispensing head has been loosened, the thread imprints  530  remain in this state so as to form a permanent complementary thread. The plastic material constituting the beads  51  does not deform back again by shape memory, given that the material has been subject to creep over a lengthy period. 
     By means of the fastening member of document WO 2009/150351, it is possible to fasten a dispensing head on a vessel with a threaded neck without performing a screwing operation, while making it possible to unscrewing the head so as to enable the dispenser to be recycled by separating the vessel from its dispensing head. 
     The rescrewing of the dispensing head onto the threaded neck was not a purpose of document WO 2009/150351: it was sufficient for the head to be able to be removed by unscrewing. Rescrewing is a new requirement that meets the objectives of durability, since it allows the user to fill the vessel and replace the dispensing head. It has been found that the rescrewing is not possible with the fastening member and the threaded neck of document WO 2009/150351, because the thread imprints  530   a  formed by the threaded neck in the skirt  51  are in “too” intimate contact with the threads  12   a  of the neck. 
     The present invention provides an enhancement or improvement to the device of the document WO 2009/150351, which is intended to allow easy rescrewing, but also to facilitate unscrewing, without, however, changing anything in the method of assembly and in the fastening member of the document WO 2009/150351. The modification only relates to the threads  12   a  of the threaded neck  11 : this implies that the ring of the invention is identical to that of the document WO 2009/150351, except concerning the thread imprints which are created by the thread of the neck. While the threads  12   a  of document WO 2009/150351 are constant over their entire length, that is to say that their vertical cross-section is unchanged over their length, the threads  12  of the invention have a cross-section which decreases in the unscrewing direction or increases in the screwing direction, so that the unscrewing torque decreases and the rescrewing torque increases. This can already be seen in  FIGS.  5  and  6   , where it can be seen that the threads are “thinner” or “narrower” as they approach the upper annular edge  13 . Conversely, it can be said that the threads  12  are “larger” or “wider” as they approach the shoulder  14 . It can also be said that the threads  12  taper or thin from the bottom upwards, or from the shoulder  14  towards the upper annular edge  13 . Their cross section decreases upwards. This reduction in section may be due to a reduction in their axial height and/or in their radial thickness. This reduction may be continuous over the entire length of the threads. It could also be discontinuous and have segments or portions of thread of constant cross-section. But overall, it can be said that the threads  12  reduce in the unscrewing direction or increase in the screwing direction. 
     In the embodiment in  FIGS.  5  and  6   , the neck  11  comprises two threads  12  which extend substantially over a little more than half of the periphery of the neck: it can be seen that they overlap each other over a short distance. Each thread  12  defines an upper thread start  12   m  located in the proximity of the edge  13  and a lower thread end  12 M located in the proximity of the shoulder  14 . The start  12   m  and the end  12 M can be defined as the end portions of the thread  12  whose cross section increases/decreases rapidly. The thread start  12   m  has a minimum cross-section and the thread end  12 M has a maximum cross-section. Between these two points, the thread  12  forms an intermediate portion  12   i  of increasing cross-section, going from the thread start  12   m  towards the thread end  12 M. The length of the intermediate portion  12   i  is much greater than the length of the start  12   m  or the end  12 M. In this embodiment, the variation in cross-section is constant and progressive over the entire length of the intermediate portion  12   i . Thus, the helical thread  12 , at the junction between the bottom thread end  12 M and the intermediate portion  12   i , has a maximum cross-section. 
     In  FIG.  7   a   , it can be seen that the thread start  12   m  defines an axial height Hmin and a radial thickness Emin with respect to the remainder of the neck  11  which is generally cylindrical. The thread start  12   m  has a substantially trapezoidal shape, with two inclined lateral flanks  121   m  and  123   m  and a substantially flat and cylindrical top  122   m , such that the helical thread  12  has a cross-section of generally short configuration. As a purely indicative example, Hmin may be about 1.2 mm and Emin may be from about 0.3 mm to 0.5 mm. 
       FIG.  7   b    shows that the thread end  12 M defines an axial height Hmax and a radial thickness Emax. The thread end  12 M also has a substantially trapezoidal shape, with two inclined lateral flanks  121 M and  123 M, and a substantially flat and cylindrical top  122 M, such that the helical thread  12  also has a cross-section of generally short configuration. By way of indication, Hmax may be about 1.5 mm and Emax may be 0.2 mm greater than Emin, i.e., between 0.5 and 0.7 mm. 
     Thus, the axial height may vary by at least 20%, and the radial thickness may vary by at least 30%, and preferably by 50%. 
       FIG.  8   a    is in the context of document WO 2009/150351, with constant threads  12   a  and corresponding thread imprints  530   a . During the rescrewing, the imprints  530   a  will come directly into intimate and pressed contact C with the threads  12   a : it can even be said that the skirt  51  will come into abutment against the threads  12   a  and make the initiation of the rescrewing almost impossible. In practice, it is very laborious, or even impossible, to achieve the engagement of the threads  12   a  in the imprints  530   a . After several unsuccessful attempts, most users give up rescrewing the dispensing head onto the threaded neck. 
       FIG.  8   b    shows the context of the invention, with increasing threads  12  and corresponding thread imprints  530 . During rescrewing, the imprints  530  will engage easily around the threads  12   a  because of the clearance G existing between them: this clearance G results from the fact that the imprints  530  of maximum section engage around the thread starts  12   m  of minimum section. In practice, it is very easy to achieve the engagement of the threads  12  in the imprints  530  of the skirt  51 . The screwing torque is then almost zero, but it will increase progressively as the rescrewing takes place. At the end of rescrewing, the torque will be maximum, since the imprints  530  will come into intimate contact with the threads  12  which have formed them. The mutual engagement of the threads  12  in the imprints  530  may be similar to a cone-in-cone contact, given that they are both conical or tapered. 
       FIGS.  9   a ,  9   b  and  9   c    illustrate different necks that have been unrolled flat to see all of the threads  12 . 
     The neck  11  of  FIG.  9   a    comprises three threads  12  which overlap a little. Each thread defines a thread start  12   m  of reduced section and a thread end  12 M of increased section. The variation in section of the intermediate portion  12   i  is constant, continuous and progressive over its entire length. 
     The neck  11  of  FIG.  9   b    comprises four threads  12  which overlap a little. Each thread defines a thread start  12   m  of reduced section and a thread end  12 M of increased section. The variation in section of the intermediate portion  12   i  is constant, continuous and progressive over its entire length. 
     The neck  11  of  FIG.  9   c    comprises three threads  12  which do not overlap. Each thread defines a thread start  12   m  of reduced section and a thread end  12 M of increased section. The variation in section of the intermediate portion  12   i  is constant, continuous and progressive up to a constant section portion  12 MC, the end of which defines the thread end  12 M. 
     Thus, it can be said that the intermediate portion  12   i  has, over at least part of its length, a cross-section which decreases in the unscrewing direction and increases in the screwing direction, so that the unscrewing torque decreases and the rescrewing torque increases. 
     Although several threads are preferred, it is still possible to produce a neck of the invention with a single thread. 
     By means of the invention defining neck threads of increasing section in the screwing direction, a dispensing head that has been previously unscrewed and that was initially mounted on the threaded neck by radial clamping to form the thread imprints can easily be rescrewed. The invention, from a structural point of view, relates essentially to the configuration of the threads of the neck, and consequently to the vessel, but the advantages induced by this particular configuration of the neck threads are manifested essentially relative to the cooperation between this threaded neck and the skirt, which allows not only the initial axial assembly and the disassembly by unscrewing, but above all an easy and effective reassembly by rescrewing. Although the vessel is the essential structural means, it is the dispensing head which makes it possible to carry out the invention in association with the vessel.