Patent Publication Number: US-2009236445-A1

Title: Fluid dispenser

Description:
RELATED APPLICATION 
     The present application claims priority from UK patent application No. 0 610 666.0, filed 30 May 2006, the entire content of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a fluid dispenser, for example for a nasal spray, and is particularly, but not exclusively, concerned with a fluid dispenser for drug administration. 
     BACKGROUND OF THE INVENTION 
     Prior art fluid dispensers, e.g. for dispensing fluids into a nasal cavity, are known from US-A-2005/0236434 and WO-A-2005/075103, the entire original disclosures of which (as well as their patent family members) are incorporated herein by way of reference. These dispensers comprise a fluid reservoir, an outlet and a pump for pumping fluid from the reservoir through the outlet. The outlet is provided in a nozzle, which nozzle may be shaped and sized for positioning in a nostril. As the dispensers are for dispensing a metered volume of the fluid, they further comprise a metering chamber which is selectively placed in fluid communication with the reservoir, through at least one metering chamber inlet, and the outlet. The pump reciprocates to move the metering chamber between an expanded state, in which the metering chamber has a first volume greater than the metered volume, and a contracted state. The dispensers further comprise a one-way valve between the metering chamber and the outlet which is biased to a ‘valve-closed’ position. When the metering chamber moves from its contracted state to its expanded state, the metering chamber and reservoir are placed in fluid communication through the at least one inlet and fluid is drawn from the reservoir into the metering chamber to fill the metering chamber with an excess volume of fluid. When the metering chamber moves from the expanded state towards the contracted state, there is an initial bleed phase in which the surplus volume of fluid in the metering chamber is pumped back into the reservoir through the at least one inlet to leave a metered volume of fluid in the metering chamber. In a final dispensing phase of movement of the metering chamber back to its contracted state, the metered volume of fluid in the metering chamber is pumped towards the one-way valve whereby the increasing pressure produced in the fluid causes the one-way valve to temporarily open to enable the metered volume to be pumped from the outlet. 
     An aim of the present invention is to provide a novel fluid dispenser, optionally incorporating the pumping principle disclosed in US-A-2005/0236434 and WO-A-2005/075103. 
     SUMMARY OF THE INVENTION 
     According to first aspect of the present invention there is provided a fluid dispenser comprising a dosing chamber, a piston member, a fluid outlet through which fluid will be dispensed, a fluid conduit for conveying fluid from the dosing chamber towards the fluid outlet, and a seal for sealing the fluid outlet; wherein:
         the piston member has a first end that acts as a piston within the dosing chamber for:   a) pumping fluid from the dosing chamber through the fluid conduit towards the fluid outlet when moved in a first manner relative to the dosing chamber, and   b) filling the dosing chamber with fluid from a supply of fluid when moved in a second manner relative to the dosing chamber;   the piston member has a second end positioned outside the dosing chamber and forming at least a part of the seal;   the seal is movable from a normal closed state, in which the seal prevents fluid communication between the fluid conduit and the fluid outlet, to an open state, in which the seal provides for fluid communication between the fluid conduit and the fluid outlet; and   the dispenser is adapted such that movement of the first end of the piston member in the first manner causes fluid in the fluid conduit to be pressurised to an extent sufficient to move the seal from its normal closed state to its open state thereby enabling fluid to be pumped through the fluid outlet.       

     Preferably the second manner is opposite to the first manner. 
     Preferably the first manner is movement in a first direction and the second manner is movement in a second direction. 
     Preferably movement of the first end of the piston member in the first and second manners is produced by movement of the piston member in the first and second manners. 
     Preferably the piston member is mounted to reciprocate between the first and second manners, for example by being mounted for stroking in the dosing chamber in the opposing first and second directions. 
     Preferably said movement of the first end of the piston member in the second manner is such as to draw fluid into the dosing chamber from the fluid supply. 
     Preferably the seal is biased to its normal closed state by a biasing force and the pressurisation of the fluid in the fluid conduit is sufficient to overcome the biasing force. Preferably the seal is biased to its normal closed state by a biasing member, typically a spring. 
     Preferably the normal closed state of the seal is provided by the second end of the piston member being configured as a plug to sealingly plug the fluid outlet. 
     Preferably the seal comprises a seal member with which the second end of the piston member is co-operable to form the seal. 
     The seal member may be, or form, a perimeter of the fluid outlet, in which case the second end of the piston member preferably sealingly engages the perimeter. The seal member may be annular (e.g. an O-ring). 
     Preferably the seal is a seal for opening or closing the fluid outlet. It might alternatively be for opening or closing an opening or port in the piston member. 
     Preferably the seal member has an aperture extending through it. Preferably fluid flows through that aperture when the seal is opened. Preferably the aperture is aligned with the fluid outlet. More preferably the aperture is both aligned and in contact with the fluid outlet. The aperture may be an integral part of the fluid outlet. 
     Preferably the second end of the piston member and the seal member are biased into a sealing relationship, for example to close and seal the aperture in the seal member. The bias may be provided by a biasing member, e.g. a spring, for instance acting on the piston member and/or the seal member. 
     Preferably the dispenser is adapted such that, in the normal closed state of the seal the seal member is disposed in a sealing position which seals the fluid outlet, in the open state of the seal the seal member is disposed in an unsealing position which unseals the fluid outlet, and movement of the seal member between the sealing and unsealing positions is controlled by the second end of the piston member. 
     Preferably the seal member is an O-ring, a resilient tube or a resilient pad. 
     Preferably the dispenser has a component in which the fluid outlet is formed. 
     Preferably the dispenser is adapted such that when the first end of the piston member moves in the first manner the fluid pressure created in the fluid conduit is such as to cause relative separatory movement between the component and the piston member which results in the seal moving from the normal closed state to the open state. 
     Preferably the second end of the piston member is mounted in the component for movement relative to the component between a sealing position, in which the second end of the piston maintains the seal in the normal closed state, and an unsealing position, in which the second end of the piston enables the seal to adopt its open state. 
     Preferably the second end of the piston member and the component are biased relative to one another to locate the second end in the sealing position. The bias may be provided by one or more biasing members, by way of example one or more springs. The biasing member(s) may act on the piston member and/or the component. 
     Preferably the second end of the piston member is spaced farther from the fluid outlet when in the unsealing position compared to the sealing position. 
     Preferably the second end of the piston member is mounted in the component to form an auxiliary chamber therebetween, the fluid conduit comprises the auxiliary chamber, and the auxiliary chamber is adapted so that when the first end of the piston member moves in the first manner a fluid pressure is created in the auxiliary chamber which moves the second end of the piston member from its sealing position to its unsealing position. The fluid pressure may forcibly move the piston member and/or the component. 
     Preferably during movement of the first end of the piston member in the first manner the component moves relative to the dosing chamber. 
     Preferably the second end of the piston member remains in the sealing position in the component in a first phase of said movement in the first manner and is movable to the unsealing position by the fluid pressure during a second subsequent phase of movement in the first manner. 
     Preferably the fluid dispenser is adapted so that the seal member is in the sealing position during a first phase of movement of the first end of the piston member in the first manner and moves to the unsealing position during a second subsequent phase of movement of the first end of the piston member in the first manner. Preferably during the first phase the fluid outlet and the second end of the piston move in unison relative to the dosing chamber and during the second phase the fluid pressure causes a relative separatory movement between the fluid outlet and the second end of the piston member. 
     Preferably the fluid conduit extends from the dosing chamber to a fluid dispensement chamber, which may be the afore-mentioned auxiliary chamber. The seal may be provided to open and close the fluid communication path between that fluid dispensement chamber and the dosing chamber. In a preferred arrangement, however, it is provided to open and close the fluid communication path between that fluid dispensement chamber and the fluid outlet. 
     Preferably the fluid conduit passes through the body of the piston member. Preferably it passes through the middle of the piston member. 
     Preferably the piston member is a tube having a longitudinal axis. 
     Preferably the first end of the piston member has an entrance hole in it. Preferably that entrance hole faces substantially towards the middle of the dosing chamber. The entrance hole is for receiving fluid from the dosing chamber for pumping towards the fluid outlet. 
     Preferably the entrance hole is provided in an end surface of the first end of the piston member (the bottom end). Most preferably the entrance hole is in the centre of that end. 
     Preferably the second end of the piston member has an exit hole in it through which fluid, in use, will exit the piston member. Preferably that exit hole is permanently open. 
     Preferably the exit hole leads directly into the fluid dispensement chamber. 
     The exit hole may be associated with the seal member such that the seal, when closed, seals the exit hole. 
     Preferably the piston member is elongated, with the fluid conduit passing along substantially the full length of the piston member. 
     Preferably a surface of the second end of the piston member (the top end) is closed. The exit hole, however, is still preferably positioned at that top end, for example it extends sideways out of the top end, i.e. it is a side port. 
     There may be more than one exit hole or side port. 
     Preferably there is a nipple at the second end of the piston member, for instance disposed in the fluid dispensement chamber. Preferably the exit hole(s) is provided in that nipple. Most preferably the nipple is disposed in the middle of the fluid dispensement chamber. A swirl chamber may surround that nipple. The swirl chamber may cause fluid, as it is dispensed, to swirl around the nipple, thereby being dispensed at a higher velocity, whereupon it will dispense in a finer mist, or with reduced size, spray particles. 
     Preferably the fluid dispensement chamber is in fluid communication with the dosing chamber through the fluid conduit in the piston member. As previously indicated, that fluid communication may be permanently open, or closeable by the seal. 
     Preferably the second end of the piston member has a region that acts as a piston within the fluid dispensement chamber. The region of the piston member second end may be disposed in a portion of the fluid dispensement chamber, which portion may be cylindrical and/or of constant cross-section. 
     Preferably the first end of the piston member has a region that acts as the piston in the dosing chamber. The region of the first end of the piston member may be disposed in a portion of the dosing chamber, which portion may be of constant cross-section and/or cylindrical. 
     A seal member is preferably provided to enable the first end of the piston member to sealing slide against the side wall of the dosing chamber and/or the second end of the piston member to sealingly slide against the side wall of the fluid dispensement chamber, more especially against the respective portions thereof. Preferably the seal member(s) is an O-ring fitted in a groove in the outer surface of the piston member. The seal member(s) may, however, be an integral seal(s) formed on the outside of the piston member, or a separate seal(s) welded, glued or otherwise attached to the piston member. 
     Preferably the piston member is biased in the second manner, for example to pull out of the dosing chamber, for resetting the fluid dispenser and refilling the dosing chamber with fluid after each dispensement. Preferably that bias is provided by a spring. That bias may also provide a biasing force that provides engagement between the second end of the piston member and the seal member for closing the seal. The biasing force that provides the engagement between the second end of the piston member and the seal member for closing the seal may alternatively be provided by a separate spring. 
     Preferably the first and second manners are linear movements of the piston member relative to the dosing chamber. 
     Preferably the fluid dispenser comprises a nozzle for inserting into a nostril of a user. The nozzle may be removable from the fluid dispenser, for example with a push fit or a snap fit. This is so the nozzle can be cleaned and/or replaced for hygiene purposes. 
     Preferably the fluid outlet is formed in a nozzle. Most preferably it is formed at an outer end of the nozzle. That nozzle might also be adapted to receive a replaceable nozzle over it, again to allow improved hygiene. 
     The nozzle may be formed as a one-piece part, or as a multi-component part. 
     The fluid outlet may be in a component (the “nozzle component”) of the nozzle. Preferably the nozzle component defines the fluid dispensement chamber. Preferably the nozzle component receives the second end of the piston member. Preferably engagement between the second end of the piston member and the seal member for closing the seal is provided by a biasing force on the nozzle component. Then, pressurising the fluid by movement of the first end of the piston member in the first manner results in the nozzle component being forced away from the second end of the piston member to bring the seal to its open state. In this instance, the seal may be formed by engagement of the second end of the piston member, e.g. the nipple at the second end, in the fluid outlet. 
     Preferably the biasing force on the nozzle component is less than the biasing force on the piston member which biases the first end thereof in the second manner. 
     Preferably there is a second fluid conduit for passage of fluid from the supply of fluid into the dosing chamber. The source of fluid might be mounted next to the dosing chamber, whereby the second fluid conduit is either unnecessary or very short. 
     Preferably at least one inlet to the dosing chamber is provided for the fluid in the supply to enter the dosing chamber. 
     Preferably the fluid dispenser comprises a supply of fluid, for example in the form of a fluid reservoir. The supply may be contained in a receptacle. The receptacle may be vented, or may be non-vented, e.g. of a variable internal volume, for instance contractible in response to fluid being removed therefrom, for example by having a moveable plunger. 
     Preferably the second fluid conduit is adapted to be selectively placed in and out of fluid communication with the dosing chamber by the motion of the first end of the piston member within the dosing chamber. This may be achieved with a valve, for instance fitted to the piston member. 
     Preferably the dosing chamber is a metering chamber for providing a metered dose of the fluid for dispensement through the fluid outlet. 
     Preferably the fluid dispenser is adapted to be repeatedly operated to dispense on each operation a dose of the fluid though the fluid outlet. To this end, the supply is preferably a supply containing multiple doses of the fluid. 
     Preferably the fluid dispenser is adapted such that the movement of the first end of the piston member in the first manner ends when the first end contacts an end wall of the dosing chamber. 
     Preferably at the end of the movement of the first end of the piston member in the first manner the seal member moves relative to the second end of the piston member for re-engagement therewith to restore the seal in the closed state. 
     Preferably the fluid dispenser is configured and arranged so that movement of the first end of the piston member in the second manner causes the dosing chamber to fill with a first volume of fluid from the supply, movement of the first end of the piston member in the first manner comprises a first phase and a second, subsequent phase, movement in the first phase causing a portion of the first volume to be pumped from the dosing chamber back into the supply until a second volume of fluid, which is less than the first volume, is left in the dosing chamber and movement in the second phase pumping the second volume of fluid from the dosing chamber through the fluid conduit towards the fluid outlet. 
     Preferably the at least one inlet to the dosing chamber is open in the first phase and closed in the second phase. 
     When the dosing chamber is a metering chamber, the second volume is the metered volume. 
     In accordance with a second aspect of the present invention, there is provided a fluid dispenser comprising a dosing chamber, a piston member, a fluid outlet through which fluid will be dispensed, and a fluid conduit for carrying fluid from the dosing chamber towards the fluid outlet; wherein:
         the piston member has a first end that acts as a piston within the dosing chamber for:   a) pumping fluid from the dosing chamber through the fluid conduit towards the fluid outlet when the first end is moved in a first manner relative to the dosing chamber, and   b) for filling the dosing chamber with fluid from a supply of fluid when the first end moves in a second manner relative to the dosing chamber;   wherein a one-way valve is fitted to the piston member for controlling the filling of the dosing chamber, the one-way valve adapted to be closed when the piston member is moved in the first manner and to be open when the piston is moved in the second manner.       

     Preferably the one-way valve is fitted to the first end of the piston member. 
     Preferably the one-way valve comprises a fluid flow chamber and a moveable sealing element for opening and closing the fluid flow chamber, the moveable sealing element adapted to move to close the fluid flow chamber when the first end of the piston member is moved in the first manner and to move to open the fluid flow chamber when the first end of the piston member is moved in the second manner. 
     Preferably the sealing element is movably mounted in the fluid flow chamber. The sealing element may then move between opening and closing positions in the chamber depending on the manner of movement of the first end of the piston member in the dosing chamber. 
     Preferably the sealing element forms a seal between the piston member and the dosing chamber. 
     Preferably the sealing element is a sealing ring, optionally mounted in a groove surrounding the piston member. 
     Preferably the fluid flow chamber has first and second regions between which the sealing element is moveable, the sealing element being adapted to fit within the first region to close the valve and to fit within the second region to open the valve. 
     Preferably, the sealing element seals against a sidewall of the dosing chamber and the piston member when the first end of the piston member moves in the first manner, whereby no fluid is able to pass about the sealing element, and leaves a gap between the dosing chamber sidewall and the piston member when the first end of the piston member moves in the second manner, thereby allowing fluid to pass about the sealing element. 
     Preferably, the sealing element seals against the fluid flow chamber (e.g. the first region thereof) when the first end moves in the first manner and leaves a gap between the fluid flow chamber (e.g. the second region thereof) and the dosing chamber sidewall when the first end moves in the second manner. 
     Preferably the gap is formed between at least one of (i) the sealing element and the piston member (e.g. the fluid flow chamber, in particular the second region thereof) and (ii) the sealing element and the dosing chamber sidewall. 
     Preferably the fluid flow chamber is a groove surrounding the first end of the piston member. 
     Preferably the sealing element is a sealing ring, e.g. mounted in the groove. 
     Preferably that groove is a circumferential annular groove, further preferably provided with the first and second regions, which may be annular regions of that groove. 
     Preferably the sealing ring is an O-ring. 
     Preferably the sealing element is adapted to move by the motion of the piston member relative to a sidewall of the dosing chamber. 
     Preferably the sealing element is adapted such that (i) movement of the piston member in the first manner relative to the dosing chamber, for pumping fluid from the dosing chamber, causes the sealing element to move in the second manner relative to the piston member to close the one-way valve, and (ii) movement of the piston member in the second manner relative to the dosing chamber, for filling the dosing chamber, causes the sealing element to move in the first manner relative to the piston member to open the one-way valve. 
     Preferably the one-way valve is carried by the piston member for movement therewith in the first and second manners. 
     Preferably there is provided at least one inlet to the dosing chamber for filling thereof, the at least one inlet provided in a wall of the dosing chamber such that a first area of the dosing chamber is disposed to one side of the at least one inlet and a second area of the dosing chamber is disposed to another side of the at least one inlet, the piston member is mounted in the dispenser such that the first end of the piston member moves past the at least one inlet (i) from the first area into the second area on movement in the first manner and (ii) from the second area into the first area on movement in the second manner, and the one-way valve is adapted to open as the first end of the piston member moves in the second manner before passing the at least one inlet into the first area to enable fluid to pass into the second area of the dosing chamber from the at least one inlet through the one-way valve. 
     Preferably the one-way valve is adapted to be kept closed after the first end of the piston member passes the at least one inlet when moving in the first manner from the first area into the second area, whereby fluid in the dosing chamber is unable to exit the dosing chamber through the at least one inlet. 
     Preferably the sealing element operates to open and close the one-way valve. 
     Preferably the sealing element engages the dosing chamber, for instance on the wall of the dosing chamber. Preferably for sealing element is arranged for sliding movement on the dosing chamber, for example sealing sliding movement, especially on movement of the first end of the piston member in the first manner. 
     Preferably the dispenser is configured and arranged such that:—
         the first end of the piston member is movable (i) in the first manner from a first position located in the dosing chamber to a second position in the dosing chamber and (ii) in the second manner from the second position to the first position,   when the first end moves in the first manner from the first position towards the second position fluid in the dosing chamber is pumped out of the dosing chamber through the at least one inlet until the first end moves to a third position at which the one-way valve closes fluid communication between the dosing chamber and the at least one inlet,   when the first end moves in the first manner from the third position to the second position, the fluid left in the dosing chamber is pumped through the fluid conduit towards the fluid outlet, and   when the first end of the piston member moves from the second position to the first position fluid fills the dosing chamber through the at least one inlet.       

     Preferably in the second position the first end of the piston member meets an end wall of the dosing chamber. 
     The one-way valve may additionally comprise a second groove at the first end of the piston member which is in fluid communication with the first groove and which opens into the dosing chamber. Preferably that second groove is an annular groove that is not circumferential, i.e. it is in the end surface of the first end of the piston member rather than in the side wall at the first end of the piston member. Preferably the fluid communication between the first and second grooves is achieved with intermittent slots or holes between the two grooves. A single hole may be sufficient. Alternatively the first and second grooves may form a unitary groove. 
     Preferably the movement of the moveable sealing element is in a direction that is generally parallel to the axis of the piston member. 
     Preferably the first region has a first depth and the second region has a second depth which is greater than the first depth. 
     Preferably the first region is spaced farther from the first end of the piston member than the second region. 
     Preferably the first and second regions are circumferentially oriented on the piston member. 
     Preferably a ramp provides a depth transition between the two regions. The ramp may be a straight ramp. As an alternative, the ramp can be convexly curved. Another alternative arrangement would be for one of the two regions to have a flat base with a ramp creating either a deeper or a shallower base (as required for the other one of the two regions). 
     In a third aspect of the present invention there is provided a fluid dispenser comprising a dosing chamber, a piston member, a fluid outlet through which fluid will be dispensed, and a fluid conduit for conveying fluid from the dosing chamber towards the fluid outlet; wherein:
         the piston member has a first end that acts as a piston within the dosing chamber for:   a) pumping fluid from the dosing chamber through the fluid conduit towards the fluid outlet when moved in a first manner relative to the dosing chamber, and   b) filling the dosing chamber with fluid from a supply of fluid when moved in a second manner relative to the dosing chamber; and   the fluid conduit has an extent through the piston member from an inlet in the first end to an outlet in the piston member at a position spaced from the first end.       

     Each aspect of the invention may also comprise any of the additional features of (i) the other aspects of the invention, (ii) the appended claims or (iii) the exemplary embodiments described with reference to the accompanying Figures. 
     These and other aspects and features of the present invention will be understood from the exemplary embodiments which will now be described with reference to the accompanying Figures of drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES OF DRAWINGS 
         FIGS. 1 to 4  schematically illustrate a sequence of operational steps carried out on a fluid dispenser embodying various aspects of the present invention; 
         FIGS. 5 to 8  illustrate an alternative seal arrangement for the fluid dispenser of the present invention; 
         FIGS. 9 to 14  illustrate how to assemble a preferred embodiment of the present invention; 
         FIGS. 15 and 16  show another alternative seal arrangement for the present invention; 
         FIGS. 17 to 20  illustrate a sequence of operational steps carried out on another embodiment of the present invention featuring another alternative seal arrangement; 
         FIG. 21  shows yet another alternative seal arrangement for the present invention; 
         FIGS. 22A to 22C  are perspective side views of a further fluid dispenser, 
       where  FIG. 22A  shows the fluid dispenser in a fully extended (open) position and  FIGS. 22B and 22C  respectively show the fluid dispenser in its rest and fired positions; 
         FIGS. 23A to 23C  illustrate the assembly of the fluid dispenser of  FIGS. 22A-C ; 
         FIGS. 24A to 24C  are cross-sectional side views of the fluid dispenser of  FIGS. 22A-C  in its fully extended, rest and fired positions; 
         FIG. 25  is an enlarged cross-sectional view of the nozzle area of the fluid dispenser of  FIGS. 22 to 24  showing a tip seal arrangement; 
         FIGS. 26A and 26B  are respectively side views and cross-sectional side views of a piston member of the fluid dispenser of  FIGS. 22 to 25 ; 
         FIGS. 27A and 27B  are respectively perspective and cross-sectional side views of a rear sealing element of the fluid dispenser of  FIGS. 22 to 25  which mounts on the piston member of  FIGS. 26A-B ; 
         FIGS. 28A and 28B  are respectively perspective and cross-sectional side views of a forward sealing element of the fluid dispenser of  FIGS. 22 to 25  which slidably mounts on the piston member of  FIGS. 26A-B  to form a one-way valve; 
         FIGS. 29A and 29B  are respectively perspective and cross-sectional side views of a main housing of the fluid dispenser of  FIGS. 22 to 25  which slidingly receives the piston member of  FIGS. 26A-B ; 
         FIGS. 30A and 30B  are respectively perspective and cross-sectional side views of a stopper portion of the fluid dispenser of  FIGS. 22 to 25  which mounts on a fluid supply and to which mounts the piston member of  FIGS. 26A-B ; 
         FIGS. 31A and 31B  are respectively perspective and cross-sectional side views of a nozzle of the fluid dispenser of  FIGS. 22 to 25  which slidingly mounts on the stopper portion of  FIGS. 30A-B ; 
         FIG. 32  is a perspective rear view of the nozzle of  FIGS. 31A and 31B  showing a swirl chamber formed in the end face thereof; 
         FIGS. 33A and 33B  are respectively perspective and cross-sectional side views of a carrier member of the fluid dispenser of  FIGS. 22 to 25  which slidingly mounts on the nozzle of  FIGS. 31A-B  and  32 ; 
         FIGS. 34A and 34B  are perspective views of a valve element of a valve mechanism of the fluid dispenser of  FIGS. 22 to 25  which mounts in the main housing of  FIGS. 29A-B ; 
         FIGS. 35A and 35B  are respectively perspective and cross-sectional side views of a nozzle insert of the fluid dispenser of  FIGS. 22 to 25  which inserts in the nozzle of  FIGS. 31A-B  and  32 ; 
         FIGS. 36A and 36B  are respectively perspective and cross-sectional side views of a cap of the fluid dispenser of  FIGS. 22 to 25  which mounts on the main housing of  FIGS. 29A-B ; 
         FIGS. 37A to 37J  are cross-sectional side views of a modified version of the fluid dispenser of  FIGS. 22 to 36  showing the sequential advancement of liquid therewithin during priming of the dispenser; 
         FIG. 38  corresponds to  FIG. 32  showing an modification to the swirl chamber; 
         FIG. 39  corresponds to  FIG. 25 , but shows an alternative tip seal arrangement for the fluid dispenser of  FIGS. 22 to 36 ; 
         FIG. 40  corresponds to  FIG. 25 , but shows a further alternative tip seal arrangement; 
         FIGS. 41A and 41B  are respectively perspective and cross-sectional side views of the nozzle insert in  FIG. 40 ; 
         FIG. 42  corresponds to  FIG. 25 , but shows an alternative sealing arrangement for the fluid dispenser of  FIGS. 22 to 36 ; 
         FIGS. 43A and 43B  are respectively perspective and cross-sectional side views of the sealing pin in  FIG. 42 ; 
         FIGS. 44A and 44B  are respectively perspective and cross-sectional side views of the backing plate in  FIG. 42 ; 
         FIGS. 45A and 45B  are respectively perspective and cross-sectional side views of the nozzle insert in  FIG. 42 ; and 
         FIGS. 46A and 46B  are respectively perspective and cross-sectional side views of the forward sealing element in  FIG. 42 . 
     
    
    
     DETAILED DESCRIPTION OF THE FIGURES OF DRAWINGS 
     Referring first of all to  FIGS. 1 to 4 , there is shown a schematic representation of the sequence of operation of a fluid dispenser  10  embodying the present invention, in this instance for dispensing a liquid containing a medicament, for example suspended or dissolved in the liquid. The underlying principle of operation of the fluid dispenser  10  is as described in US-A-2005/0236434 and WO-A-2005/075103 supra. 
     The fluid dispenser  10  comprises a main housing  12 , a piston member  14 , a nozzle  16  and a spring  18 . The spring  18  is for biasing the nozzle  16  away from, and piston member  14  out of, the main housing  12 . The skilled reader will appreciate that the nozzle  16  could form an internal component of the fluid dispenser  10 , e.g. housed within a dispenser casing (not shown). 
     The main housing  12  has an internal cavity that defines a dosing chamber  20 . That dosing chamber  20 , in this preferred embodiment, has a cylindrical cross-section. The dosing chamber  20  in this particular embodiment forms a metering chamber which meters a volume of the fluid for dispensement from the dispenser  10 , as in US-A-2005/0236434 and WO-A-2005/075103 supra. 
     A first end  22  of the piston member  14  also has a generally cylindrical cross-section. The diameter of that first end  22 , however, is smaller than the diameter of the dosing chamber  20 . As a result, that first end  22  of the piston member  14  will freely slide within the dosing chamber  20 . However, to stop that, that first end  22  of the piston member  14  is also provided with two annular grooves  24 ,  26  around its circumference, with each annular groove  24 ,  26  having an O-ring  28 ,  30  positioned in it. Those O-rings  28 ,  30  extend above the surface of the first end  22  of the piston member  14  so as to seal the gap between the piston member  14  and the wall of the dosing chamber  20 . As a result, the first end  22  of the piston member  14  can act as a piston within the dosing chamber  20 . As a piston, it will impose a pumping force onto fluid within the dosing chamber  20  as the piston member  14  moves within the dosing chamber  20 . 
     The end wall of the first end  22  (i.e. the bottom end) of the piston member  14  faces into the dosing chamber  20 . A hole  32  is provided in the middle of that end wall. That hole is an entrance hole for a fluid conduit  34  that extends along almost the full length of the piston member  14 . That fluid conduit  34  is for feeding fluid from the dosing chamber  20  into a fluid dispensement chamber  46  in the nozzle  16  upon actuation of the fluid dispenser  10  for dispensement of fluid out of the nozzle  16 . 
     Spaced around the entrance hole  32  in the bottom end  22  of the piston member  14  is a further annular groove. This further annular groove is provided as a circular groove  36  in that bottom wall, rather than extending around the side wall of the piston member  14 . This circular groove  36  is in fluid communication with the second annular groove  26 , i.e. the groove that is otherwise closest to the bottom end  22  of the piston member  14 . The fluid communication between these two annular grooves  26 ,  36  may be achieved with intermittent slots or holes between the two grooves  26 ,  36 . A single slot or hole would function however. 
     The combination of the circular groove  36 , the second annular groove  26  and the second O-ring  30  provides a non-return valve  31  at the first end  22  of the piston member  14 , as will now be described. 
     The width of the annular groove  26  is greater than the width dimension taken by its O-ring  30  when that O-ring  30  is compressed against the side wall of the dosing chamber  20 . As a result, that O-ring  30  can move within the annular groove  26  between two positions—a forward, sealing position (farther away from the bottom end  22 ) and a backward, non-sealing position (closer to the bottom end  22 ).  FIGS. 3 and 4 , respectively, show these two positions. As can be seen, the movement is in a direction that is generally parallel to the axis of the piston member  14 . 
     The second annular groove  26  also has a ramped base, whereby it has a varying depth. That varying depth allows the groove  26  to define two annular regions, the first annular region being for receiving the O-ring  30  at its forward, sealing position, and being spaced farthest from the circular groove  36 , and the second annular region being for receiving the O-ring  30  at its backward, non-sealing position, and being spaced closer to the circular groove  36  than the first annular region. 
     The ramped base is arranged such that the first annular region is less deep than the second annular region. The depth transition may be created by a straight ramp, or it may be created by either a curved ramp (usually a convex curve) or a ramp with one or more landings, or flat (non-depth-varying) regions. In the embodiment illustrated in  FIG. 1 , there is a convexly curved base. 
     The non-return valve  31  functions as follows:
         a) When the O-ring  30  is positioned in the first annular region, the O-ring  30  seals or closes the non-return valve  31  by being pressed both against the side wall of the dosing chamber  20  and against the base of the first annular region. This occurs because the first annular region has a diameter that is equal to, or more typically, greater than the inside diameter of the O-ring  30 , and also because the outside diameter of the O-ring  30  is equal to, or more typically, slightly larger than, the diameter of the dosing chamber  20 . When sealed like this, fluid will not pass around the O-ring  30  and thus not through the valve  31 .   b) When the O-ring  30  has moved into the second annular region, due to the piston member  14  moving relative to the dosing chamber  20 , the O-ring  30  becomes loose within the annular groove  26 . That is because the ramp, in effect, retracts the base of the groove  26  away from the O-ring&#39;s innermost surface, whereupon it will no longer be pressed against the base of the annular groove  26  as well as the side wall of the dosing chamber  20 —that second annular region, as explained above, is deeper than the first annular region and has a diameter that is smaller than the inside diameter of the O-ring  30 . The non-return valve  31  is then open, as fluid can pass around the O-ring  30 , whereupon fluid can pass through the valve  31  into the dosing chamber  20  from a source of fluid (e.g. a bottle  70 —see  FIGS. 5 ,  6  and  14 ) via a second fluid conduit  38 . As will be seen from  FIG. 4 , for example, the inherent bias in the O-ring  30  maintains the outer surface of the O-ring  30  in contact with the sidewall of the dosing chamber  20 , thereby creating a gap between the inner diametric surface of the O-ring  30  and the base of the second annular region. Accordingly, the fluid flows through this gap into the dosing chamber  20 .       

     When the piston member  14  moves downward relative to the dosing chamber  20 , the O-ring  30  is disposed in its forward, sealing position, as shown in  FIGS. 2 and 3 . Conversely, when the piston member  14  moves upwardly relative to the dosing chamber  20 , the O-ring  30  is disposed in its backward, non-sealing position, as shown in  FIGS. 1 and 4 . As will be understood by the skilled reader, the O-ring  30  is moved between its forward and backward positions in the groove  26  simply by the movement of the piston member  14  relative to the dosing chamber  20 . 
     The second fluid conduit  38  introduces fluid into the dosing chamber  20  through the side wall of the dosing chamber  20 . That entrance point is located a fixed distance D from the bottom wall  40  of the dosing chamber  20  (see  FIG. 1 ). That distance D sets the metered volume of fluid to be dispensed by the dispenser upon each full actuation i.e. the metered volume is the volume of the dosing chamber below that point, for example 50 μl (microlitres). It should be noted, however, that by varying that distance D, different dispensement volumes can be provided. That variation might be achieved by moulding the entrance point in a different location, e.g. in the factory, or by providing a moveable/variable position for the entrance point. 
     As shown in  FIG. 1  (the fully extended, rest position), the piston member&#39;s bottom end  22  is located above the entrance point for the second fluid conduit  38 . The dosing chamber is overfilled at that time—the dosing chamber is full and has, in this rest position, a volume greater than that which is to be dosed from the dispenser  10 . However, this overfilling will not result in an overdose to a user. As will be understood from  FIGS. 2 and 3 , this is because upon compressing the piston member  14  back down into the dosing chamber  20 , the excess volume of fluid (i.e. the fluid above the entrance point) will be forced/pumped back out of the dosing chamber  20  through the entrance point and down through second fluid conduit  38  and back into the bottle, until the O-ring  30  (which is in its forward, sealing position) closes the entrance point. Thereafter the fluid volume in the dosing chamber  20  is fixed by the non-return valve  31 , i.e. the metered volume is defined. 
     The above described overfilling upon each actuation cycle serves a useful function. It ensures that a complete and accurate metered dosage is provided upon each actuation. 
     Although only one entrance point to the dosage chamber  20  is shown, more than one entrance point may be provided, e.g. as shown in WO-A-2005/075103 supra. This reduces flow resistance between the dosing chamber  20  and the source of fluid. 
     In  FIG. 4 , the downward arrow shows that the main housing  12  is being moved away relative to the nozzle  16  and the piston  14 . This may be achieved by moving the housing  12  downwardly whilst the piston  14  and nozzle  16  are static or by simultaneously moving the piston  14  and nozzle  16  upwardly with the housing  12  being static, or by simultaneously moving the housing  12  downwards and the piston  14  and nozzle  16  upwards. Irrespective, the upward arrow indicates the resulting drawing up of fluid into the second fluid conduit  38  for filling the dosing chamber  20  through the open non-return valve  31  due to the O-ring  30  being in the backward, non-sealing position. 
     In  FIG. 2 , a dispensement is occurring—the non-return valve  31  is closed and the upward arrow is indicating that the main housing  12  is being moved towards the nozzle to force/pump the fluid out of the dosing chamber  20  up through the first fluid conduit  34 . Of course, the piston  14  and nozzle  16  could be moved towards the housing  12  which is held static, or by simultaneously moving the piston  14 —nozzle  16  arrangement and the housing  12  towards each other. 
     In  FIG. 3 , the arrow indicates the final moment of relative upward force against the main housing  12 , whereupon the dispensement is completed—the piston member  14  has been fully displaced into the dosing chamber  20  so as to abut with the bottom wall  40  of the dosing chamber  20 . 
     As the first annular groove  24  is spaced farther from the circular groove  36  than the second annular groove  26 , it seals the top end of the gap between the side wall of the piston member  14  and the side wall of the dosing chamber  20 . This stops fluid from leaking out of the dosing chamber  20  down the side of the piston member  14 , and also prevents outside air from entering the device. The first O-ring  28  does not move significantly in the first annular groove  24 . Indeed, the first annular groove  24  is less wide than the second annular groove  26 . This will mean that the first O-ring  28  fits tightly within that first groove  24  once it is being compressed against both the side wall of the dosing chamber  20  and the base of the first annular groove  24 . It will therefore provide a good, constant, seal between the piston member  14  and the side wall of the dosing chamber  20 . 
     It is preferred that the source of fluid will be a bottle or receptacle onto which the main housing  14  is attached. It might be screwed onto the bottle. Alternatively, the arrangement of  FIGS. 5 and 9  to  14  might be used. 
     The bottle may be vented, or may have some other configuration to prevent a back-pressure airlock as the fluid supply is used. For example the dispenser disclosed in WO-A-2005/075103 or WO-A-2004/014566 use a bottle which incorporates a piston in their bottles. 
     Preferably, the bottle is non-venting. 
     Referring to  FIG. 1  and the second end  42  of the piston member  14 , the first fluid conduit  34  extends up through the piston member  14  and exits out of a side port  44  in a nipple  60  at the second end  42 . The side port  44  is open to allow fluid within the dosing chamber  20  to be pumped from the dosing chamber  20 , up through the first fluid conduit  34  and then into the fluid dispensement chamber  46  formed in the nozzle  16 . The fluid dispensement chamber  46  occupies the entire upper internal space of the nozzle  16  and comprises two cylindrical portions. The first portion—the upper cylindrical portion—is sized to loosely receive the nipple  60  of the piston member  14 . The second portion—the lower cylindrical portion—serves to receive a piston arrangement provided at the second end  42  of the piston member (much like the previously described piston arrangement at the first end  22  of the piston member  14 ). 
     The diameter of the lower cylindrical portion is larger than the diameter of the dosing chamber  20 . The diameter of the piston arrangement at the second end  42  of the piston member  14  is therefore larger than the piston arrangement at the first end  22  of the piston member  14 . 
     The lower cylindrical portion has a constant cross-section, and that cross-section continues down to the bottom of the nozzle  16 . 
     The piston arrangement at the second end  42  of the piston member  14  is located within the lower cylindrical portion. The piston arrangement comprises a substantially cylindrical portion having a groove with an O-ring  48  in it. The O-ring  48  seals that piston against the side wall of that lower cylindrical portion. 
     In place of the O-ring  48 , an integral resilient member might be provided, for example one that is moulded onto the piston member  14 . Some other known sealing means might alternatively be used. 
     This second piston (within the lower cylindrical portion of the nozzle  16 ) serves to pressurise fluid in the fluid dispensement chamber  46 . 
     The nipple  60  of the piston member  14  extends away from the lower cylindrical portion, to be located, in use, in the upper cylindrical portion of the nozzle  16  and has a generally loose fit whereby fluid can pass around its outer surface. 
     The upper cylindrical portion of the nozzle  16  has an end wall defining the top of the fluid dispensement chamber  46 . A fluid outlet  52  is provided in that top, through which the pressurised fluid from the fluid dispensement chamber  46  can exit the nozzle  16  for dispensement to a user, e.g. in the form of a spray as shown in  FIG. 2 . The dispensement may be for delivery to a nostril of the user. 
     The fluid outlet  52  is associated with a sealing member  54  in the form of a further O-ring  54 . The O-ring  54  is significantly smaller than the previous O-rings and it forms part of a seal for closing the fluid outlet  52 . The other part of that seal is an end wall  50  of the nipple  60 . 
     The end wall  50  of the nipple  60  has a rounded tip. When the end wall  50  is pushed against the sealing member  54 , i.e. with the rounded tip in the middle of the O-ring  54 , the seal will be closed. This occurs in the default or rest position of the dispenser  10 , as shown in  FIG. 1 . It occurs because the end wall  50  is biased into engagement with the sealing member  54  by virtue of the spring  18  biasing the piston member  14  into a position spaced from the bottom wall  40  of the dosing chamber  20  ( FIG. 1 ). It will be appreciated that the nozzle  16  is restrained from moving beyond the position shown in  FIG. 1  to ensure that the biasing force has this desired effect. For example, there are clips  86  and grooves in the embodiment of  FIG. 5 . However, the restraining mechanism might be some known mechanism, such as an outer casing against an inside surface of which a flange  58  (see  FIG. 15 ) of the nozzle  16  may bear. 
     To dispense fluid from the dispenser  10 , the nozzle  16  needs to be compressed relative to the main housing  14 , as shown in  FIGS. 1 and 2 . The compression of the nozzle  16  will drive the piston member  14  into the dosing chamber  20  through the interengaging surfaces of the nozzle  16  and the piston member  14 . This causes compression of the spring  18 . During an initial phase of this movement, the end wall  50  of the piston member  14  will stay engaged to the sealing member  54  to keep the outlet  52  closed. During this initial bleed phase, the piston  14  pumps the surplus volume of fluid in the dosing chamber  20  through the entrance hole back into the second fluid conduit  38 , as described above. However, once the closed non-return valve  31  on the piston member  14  passes the entrance point for the second fluid conduit  38 , to therefore define the metered volume of fluid in the dosing chamber  20 , continued downward movement of the piston member  14  relative to the dosing chamber  20  causes pressure to build up within the fluid in front of the first end  22  of the piston member  14 , since the fluid will no longer be able to bleed through the entrance point due to the non-return valve  31  being closed, nor exit through the outlet  52  as the seal member  54  still sealingly co-operates with the nipple end wall  50 . 
     Once the build-up of fluid pressure is enough, there will be a force on the piston member  14  that is sufficient to overcome the biasing force provided by the spring  18  against the piston member  14 . As shown in  FIG. 1 , that force causes the piston member  14 , and hence the end wall  50  of the nipple  60 , to move away from the sealing member  54 , thereby opening the fluid outlet  52 . The pressurised fluid will then be free to escape out of the fluid dispenser  10  through the fluid outlet  52 , and since it is pressurised by the pumping action of the piston member  14 , it will exit the fluid dispenser  10  as an atomised spray. Further, that spraying will continue while the relative compression of the piston member  14  and dosing chamber  20  is continued until a) the piston member  14  is completely pressed into the dosing chamber  20  to abut the end wall  40 , and b) the piston member&#39;s end wall  50  has re-sealed the fluid outlet  52  by re-engaging the sealing member  54  due to the nozzle  16  continuing to move relatively downwardly, which movement is now also relative to the piston member  14  due to its abutment with the dosing chamber end wall  40 . The fluid dispenser  10  has then been fully compressed, as shown in  FIG. 3 . 
     As will be understood, the piston configuration at the second end  42  of the piston member  14  and the fluid dispensement chamber  46  are configured and arranged so that, when the fluid in front of the first end  22  of the piston member  14  is pressurised once the non-return valve  31  closes the entrance point to the dosing chamber  20 , the pressurised fluid acts to separate the nozzle  16  and the piston member  14  to open the fluid outlet  52 . 
     Once fully compressed, the fluid dispenser  10  can be released, whereupon the spring  18  will apply a return force against the interengaging nozzle  16  and the piston member  14  for resetting the fluid dispenser  10  to the configuration shown in  FIG. 1 , during which resetting the nozzle  16  and the piston member  14  will again be separated from the main housing  12 . During that motion, the one-way valve  31  will open, as described hereinabove, whereupon fluid will be drawn into the dosing chamber  20  from the source of fluid until the default position of  FIG. 1  is reached. In more detail, as the piston member  14  moves from the  FIG. 3  configuration back to the  FIG. 1  configuration, as illustrated in  FIG. 4 , a negative pressure is created in the dosing chamber  20  which draws fluid from the fluid source along the conduit  38 , through the entrance point and into the dosing chamber  20  through the open non-return valve  31 . Once the open non-return valve  31  passes the entrance point, the fluid continues to fill the expanding dosing chamber  20  directly. That then completes the product&#39;s use cycle, ready for its next dispensement, with the dosing chamber  20  once more overfilled with fluid. 
     Referring now to  FIGS. 17 to 20 , a similar arrangement for a fluid dispenser  10  to that of  FIGS. 1 to 4  is shown. However, in this embodiment, predefined fluid flow paths are provided between the side wall of the upper cylindrical portion of the nozzle  16  and the side wall of the nipple  60  by a screw thread on the side wall of the nipple  60 . Flow paths for fluid past the nipple  60  in the embodiment of  FIGS. 1 to 4  were instead provided just by a thin space between the side wall of the nipple  60  and the side wall of the upper cylindrical portion. 
     It will be appreciated that longitudinal grooves might instead be provided. 
     The operation of the fluid dispenser  10  of  FIGS. 17 to 20  is substantially identical to the operation of the device of  FIGS. 1 to 4 . However, a further structural difference exists in that the ramp in the second annular groove  26  is angular in this alternative embodiment. It has a single landing, as before. However, it has a straight ramp, rather than a curved ramp. 
     Referring now to  FIGS. 5 to 8 , another alternative arrangement for the present invention is disclosed which operates to the same principle as the embodiment of  FIGS. 1 to 4 . This arrangement again comprises the non-return valve  31  at the first end  22  of the piston member  14 , a spring  18  and a nozzle  16 . However, a nozzle cap  62  surrounds the nozzle  16 . 
     The nozzle cap  62  is press-fitted onto the nozzle  16 , and is removable for hygiene reasons. It can grip onto the nozzle  16  since the nozzle  16  has a flat shoulder  64  and a neck at its top end, which shoulder  64  and neck is adapted to fit with a corresponding shoulder  66  and hole in the top of the nozzle cap  62 . 
     The nozzle cap  62  has flanges  58  for allowing the nozzle cap  62 , and hence also the nozzle  16 , to be compressed down relative to the main housing  12 . That, as before, will cause the dispensement of fluid from the dosing chamber  20 , up through the fluid conduit  34 , out of a side port  44 , into a fluid dispensement chamber  46  and out of a fluid outlet  52  after passing through an open seal. However, in this embodiment there are two side ports  44 —one on either side of the nipple  60 . Further, the sealing member  54  is now a resilient or flexible tab or plate (e.g. made of rubber or silicone). That plate  54  is for closing over the hole of the fluid outlet  52  when pressed into a sealing position by the end wall  50  of the nipple  60 . 
     The sealing member  54  is shown in more detail in  FIGS. 7 and 8 . It can be flexed by the end wall  50  into a sealing position by the pressing or engagement of that end wall  50  against an underside of the sealing member  54 . That sealed position is the default or rest position—see  FIG. 7 . However, as before, the piston configuration at the second end  42  of the piston member  14  and the fluid dispensement chamber  46  are configured and arranged so that, when the fluid in front of the first end  22  of the piston member  14  is pressurised once the closed non-return valve  31  closes the entrance point to the dosing chamber  20 , the end wall  50  disengages from the sealing member  54  whereupon the sealing member  54  will be free to relax into a substantially flat shape—see  FIG. 8 . In that flat state, fluid can exit the fluid dispensement chamber  46  by escaping over the top surface of the sealing member  54 , thereby reaching and exiting through the fluid outlet  52 . Alternatively, the pressurised fluid itself flattens the sealing member  54  after the end wall  50  disengages therefrom. 
     The sealing member  54  comprises on an underside of it a spacer and centralising member  88 . That member  88  is a ring of material and it can be either stiff or flexible. The tip of the nipple  60  fits within the middle of that ring of material to ensure that the end wall  50  pushes against the middle of the sealing member  54  so as properly to close the seal. 
     The main housing  12  takes the form of a thin-walled, U-shaped cylindrical element having two opposing holes  68  through its side wall. Those holes  68  are the entrance points for the second fluid conduit  38  of this embodiment. 
     The dosing chamber  20  is defined by the interior of the thin-walled, U-shaped cylindrical element  12 . The second fluid conduit  38  is the annular gap surrounding the main housing  12 , between that main housing  12  and a stopper portion  76 . It is capped by an outwardly extending flange provided around the circumference of the main housing  12 . That flange is preferably welded onto the stopper portion  76  for that purpose, although some other seal might be provided. 
     The second fluid conduit  38 , as before, allows fluid to be fed from a bottle  70  into the dosing chamber  20 . In this embodiment, however, a supply or dip tube  72  is provided, which supply tube  72  extends from the end of the fluid conduit  38  to adjacent the bottom of the bottle  70 , whereby an upright bottle  70  can still supply the fluid even when the bottle is nearly empty. 
     In this embodiment, a lesser degree of overfill occurs (compare FIGS.  1  and  5 —in  FIG. 5 , the non-return valve  31  only slightly rises above the entrance point  68  for the second fluid conduit  38 ). More overfill might, however, be provided, if desired, by moving the opposing holes  68  down. 
     The stopper portion  76  is adapted to be pushed inside the neck  78  of the bottle  70  like a cork. That arrangement is then secured in place on the bottle  70  by a sealing cap or ferrule  74 . That sealing cap  74  tightly grips the stopper portion  76  onto the neck  78  by overlying a flange  80  of the neck  78 . 
     The stopper portion  76  additionally comprises its own neck portion  82 . That neck portion  82  has two opposed grooves  84  in it. Those grooves  84  extend generally axially, i.e. parallel to the piston member  14 , along a portion of the neck portion  82 . 
     The side walls of the nozzle  16  fit into the neck portion  82 . However, to lock it in place, i.e. to prevent the nozzle  16  from extending away from the main housing  12  beyond the position shown in  FIG. 5 , two clips  86  are provided on the outside wall of the nozzle  16 . They engage into the grooves  84 . 
     In use, as in the embodiment of  FIGS. 1 to 4 , the spring  18  causes the fluid dispenser  10  to take a fully extended default/rest position, as shown in  FIG. 5 . Then, upon relative compressing of the nozzle  16  towards the main housing  12 , the biasing force of the spring  18  maintains the piston member  14  against the sealing member  54  until such time that the O-ring  30  of the non-return valve  31  passes the two entrance holes  68  in the side walls of the dosing chamber  20 . Thereafter, the fluid (hydraulic) pressure will start to build-up in the fluid dispensement chamber  46 , as before. That pressure will then eventually cause the piston member&#39;s end wall  50  to separate from the sealing member  54 . That will allow the seal  54  to open, whereafter the metered dose of pressurised fluid will start to dispense out of the fluid dispenser  10  through the fluid outlet  52  (see  FIG. 6 ). 
     That dispensement will then continue until the piston member  14  hits the bottom wall  40  of the dosing chamber  20  and the nozzle  16  then moves relative to the piston member  14  until the piston member  14  re-engages with the sealing member  54  to close the seal  54  for the fluid outlet  52 . 
     After the dispensement, the mechanism can be released to return itself to the start position (as in  FIG. 5 ), during which time the dosing chamber  20  will be recharged with a surplus of fresh fluid from the bottle  70  via the second fluid conduit  38  and the supply tube  72 . 
     Referring now to  FIGS. 9 to 14 , a method of assembling the fluid dispenser of  FIGS. 5 to 8  is illustrated. 
     The fluid dispenser  10  comprises, from left to right in  FIG. 9 , the nozzle cap  62 , the nozzle  16 , the sealing member  54 , the spacer and centralising member  88 , the piston member  14  (with its three O-rings  28 ,  30 ,  48 ), the spring  18 , the main housing  12  and the stopper portion  76 . 
     The stopper portion  76  has the two grooves  84  and the neck portion  82 . 
     The main body  12  has its dosing chamber  20  inside it and the holes  68  in the side wall of that dosing chamber  20  (only one of those holes  68  is visible). 
     The two ends  22 ,  42  of the piston member  14  each have a fixed O-ring  28 ,  48  positioned in its appropriate groove  24 . Further, the O-ring  30  for the one-way valve  31  is located in its groove  26 . 
     The piston member  14  has its nipple  60  facing away from the dosing chamber  20  (just one of the two side ports  44  is visible in that nipple  60 ). 
     The preferred order for assembly requires the main housing  12  to be slotted into the stopper portion  76 . It may then be ultrasonically welded in position to form a hermetic seal between the two elements, whereby the second fluid conduit  38  is formed. Then the spring  18  and the piston member  14 , with its three O-rings  28 ,  30 ,  48 , are inserted into the main housing  12 , as shown in  FIG. 10 . Then the sealing member  54 , with its attached spacer and centralising member  88 , is put onto the nipple  60  of the piston member  14 . Then the nozzle  16  is snapped over that arrangement, engaging its two clips  86  (one shown) into the grooves  84  of the neck portion  82  of the stopper portion  76 . This assembly step is shown in  FIG. 11 . The resulting arrangement is shown in  FIG. 12 . 
     The nipple  60  in  FIG. 11  has an larger outer diameter than as shown in  FIGS. 5 to 8 , indicating a possible modification of the nipple  60 . 
     Returning back to  FIG. 11 , both the sealing member  54  and its attached spacer and centralising member  88  have a fluid flow groove  90  on at least one side thereof. That groove  90  is provided to improve fluid flow past them during fluid dispensement. 
     Referring again to  FIG. 12 , two further seals  92  are then positioned onto the resulting arrangement. Those seals  92  are for sealing with the sealing cap  74  and the bottle neck  78 , respectively, i.e. once that arrangement is finally mounted and secured onto the neck  78  of the bottle  70 . The lower seal  92  is positioned on an annular flange extending outwardly from the stopper portion  76 . The seals  92  and the annular flange are not shown in  FIGS. 5 and 6 , but their intended location in  FIGS. 5 and 6  will be understood. 
     Once assembled onto the bottle, the nozzle cap  62  is pushed onto the nozzle  16  to complete the assembly, although that could have been done earlier. 
     The completed assembly is shown in  FIG. 14 , with  FIGS. 5 and 6  showing the completed assembly in section. 
     Referring now to  FIGS. 15 and 16 , a further alternative sealing arrangement for the present invention is shown. In this embodiment, in place of a sealing member at the fluid outlet, the sealing member  54  seals the side port  44  for the fluid conduit  34  that is provided in the nipple  60  of the piston member  14 . 
     The sealing member  54  is a resilient tube that is held onto the nipple  60  by the resilience of the tube. In this preferred arrangement, that securement is assisted by two clips  94 . 
     As in the previous embodiments, a non-return valve  31  is provided at the first end  22  of the piston member  14 . Further, the general principle of refilling of the dosing chamber  20  is no different to before. The arrangement of the fluid conduit  34  in the piston member  14  is also unchanged. However, whereas before a large fluid dispensement chamber  46  was provided, in this embodiment a significantly smaller fluid dispensement chamber  46  is provided—the larger cross-sectional area is no longer required. 
     In order to dispense fluid from this device, the fluid pressure again needs to be raised in order to open the seal  54 . In this case, however, it is the hoop stress within the resilient tube that needs to be overcome. That is achieved, as before, by relative compressing of the nozzle  16  towards the main housing  12 . That compression, once the non-return valve  31  has passed the entrance point for the second fluid conduit  38 , still causes the fluid pressure to build up and that built-up pressure will eventually overcome the hoop stress in the resilient tube  54 , whereupon the tube  54  will expand away from the nipple  60 . Only then will pressurised fluid escape into the fluid dispensement chamber  46  for dispensement out through the fluid outlet  52 . 
     In order for there to be space for that expansion of the resilient tube, a narrow gap  96  (see  FIG. 16 ) is provided between the sealing member  54  (the resilient tube) and an internal wall of the fluid dispensement chamber  46 . By keeping the gap narrow, the fluid will have a greater tendency to spray out through the fluid outlet  52 . 
     A spring  18  may again be provided in this embodiment, as shown. However, it just serves to bias the nozzle  16  away from the main body  12 . 
     As previously described, flanges  58  are provided in this embodiment. They additionally, however, allow the nozzle  16  to be grasped by the user for relative compressing of the nozzle  16  down against the main housing  12 . 
     Finally, referring to  FIG. 21 , a further embodiment of the present invention is disclosed having the same general operating principle on the embodiment of  FIGS. 1 to 4 . In this embodiment, the non-return valve  31  is again provided at the first end  22  of the piston member  14 . Further, the spring  18  is provided to bias the piston member  14  and nozzle  16  away from the main housing  12  for the purpose of filling the dosing chamber  20 . However, this embodiment has a different nozzle arrangement. 
     The nozzle  16  comprises a hollow main body and a separate nozzle component  100  fitted therein. The hollow of the main body is cylindrical, but with a shoulder  98  approximately half way along it, which shoulder  98  separates a first and larger cylindrical portion from a smaller cylindrical portion. The smaller cylindrical portion is positioned towards the top of that main body, i.e. spaced farther from the main housing  12  of the fluid dispenser  10 . The separate nozzle component  100  is located within that smaller cylindrical portion. 
     A flange extends around the circumference of the piston member  14  below the piston of the second end  42 . That flange engages the underside of the shoulder  98  within the main body of the nozzle  16 . Further, the spring  18  acts upon the underside of that flange, and also upon the top of the main housing  12 , to bias that flange of the piston member  14  into engagement with that shoulder  98 . That force holds the nozzle&#39;s main body and the piston member  14  together such that they will move in unison throughout the use cycle of the fluid dispenser  10 , i.e. both during compression and release operations carried out on the fluid dispenser  10 . 
     The separate nozzle component  100  of the nozzle  16  slidingly fits within the smaller cylindrical portion of the main body of the nozzle  16 . It is also hollow. The hollow defines a) the upper cylindrical portion for the nipple  60  of the piston member  14  and b) the lower cylindrical portion for the piston at the second end  42  of the piston member  14 . 
     The fluid outlet  52  is provided in the top of the hollow of the nozzle component  100 . Further, the end wall  50  of the nipple  60  is adapted to seal that fluid outlet  52 . In this embodiment, the end wall  50  of the nipple  60  is rubberised for sealing that fluid outlet. However, the previously disclosed O-ring or sealing plate from the earlier embodiments would also work. 
     In a similar fashion to the embodiment of  FIG. 17 , the upper cylindrical portion of the separate nozzle component  100  has predefined fluid flow paths around the nipple  60 . They are again spiral channels, but this time are provided as a separate, folded or coiled member. However, it could also be formed integrally with the nozzle component  100 , for instance as a screw thread profile. 
     The piston at the second end  42  of the piston member  14 , as before, includes an O-ring  48 . It now, however, provides a sealing fit within the lower cylindrical portion of the separate nozzle component  100 . That sealing fit closes the bottom of the fluid dispensement chamber  46 , which is now within the separate nozzle component  100 . That fluid dispensement chamber  46 , however, can be fed pressurised fluid from the dosing chamber  20  in much the same way as in the previous embodiments, i.e. via a fluid conduit  34  that extends through the piston member  14  and out through a side port in the nipple  60 . 
     In this embodiment, the lower cylindrical portion has the same diameter as the dosing chamber  20 . A different mechanism for opening the seal for dispensement through the fluid outlet  52  is therefore needed. In this embodiment it is provided by the provision of a biasing means (a spring  102 ) between the nozzle&#39;s main body and the separate nozzle component  100 . That spring  102  fits between the nozzle&#39;s main body and the separate nozzle component  100 . It engages both a flange provided around the bottom perimeter of the separate nozzle component  100  and a second flange provided around the inside of the top of the smaller cylindrical portion of the nozzle&#39;s main body. The spring  102  therefore biases the separate nozzle component  100  downwards relative to the main body of the nozzle  16 , i.e. onto the end wall  50  of the piston member  14 . It therefore causes the fluid outlet  52  to be sealed closed by default. However, pressure build-up in the fluid of the fluid dispenser  10  during the dispensing part of the actuation cycle will eventually overcome the biasing force of the spring  102  and separate the nozzle component  100  from the nipple  60 , in this particular embodiment by moving the nozzle component  100  upwardly, away from the nipple  60 . By overcoming the biasing force of the return spring  102 , the seal will be opened, whereupon fluid dispensement can occur through the fluid outlet  52 . 
     By varying the return force of the spring  102 , i.e. by using weaker or stronger springs, different pressures will be required to open the seal. If a large force is required, the fluid will be under a greater pressure at the time of dispensement. That may be advantageous for forming a powerful spray. However, the compression force necessary to overcome that spring force must be within the abilities of a user. 
     Each of the afore-described fluid dispensers may be provided with a swirl chamber at the fluid outlet, as will be understood by the skilled person in the art. For instance, the swirl chamber  153  illustrated in  FIGS. 32 and 38  could be employed. 
       FIGS. 22 to 36  show an additional fluid dispenser with those features which are like features in the previously described fluid dispensers of  FIGS. 1 to 21  being indicated by like reference numerals. 
     Referring to  FIGS. 24B ,  26 A and  26 B, the piston member  114  of the additional fluid dispenser has a generally cylindrical form and is mounted to stroke in reciprocal fashion along a longitudinal axis L-L of the fluid dispenser  110  inside the dosing chamber  120  defined by the main housing  112 . The piston member  114  is mounted to stroke between forward and rear positions relative to the dosing chamber  120 . 
     The piston member  114  in this embodiment is injection moulded from polypropylene (PP), but other functionally equivalent plastics materials could be used. 
     Referring to  FIGS. 24B ,  24 C,  29 A and  29 B, the dosing chamber  120  is cylindrical and co-axially arranged with the longitudinal axis L-L. The dosing chamber  120  has forward and rear sections  120   a ,  120   b . As can be seen, the forward section  120   a  is narrower than the rear section  120   b . A step  120   c  tapers inwardly in the forward direction F (see  FIG. 24B ) to connect the rear section  120   b  to the forward section  120   a.    
     Turning back to  FIGS. 26A and 26B , the piston member  114  has a forward section  114   a , a rear section  114   b  and a central section  114   c . These are arranged co-axially. 
     The rear section  114   b  presents the open rear end  114   d  of the piston member  114 . The rear section  114   b  is cup-shaped having an annular outer peripheral wall  114   e  which defines an internal cavity  114   f  having a mouth  114   g  which opens in the rear end  114   d.    
     The forward section  114   a  is solid and presents the forward end  114   h  of the piston member  114 . The forward section  114   a  comprises an annular flange  114   i  rearwardly of the forward end  114   h.    
     The central section  114   c  connects to the forward and rear ends  114   a ,  114   b  and comprises an internal bore network  114   j  to place the rear section  120   b  of the dosing chamber  120  in fluid communication with the fluid supply  170  (a bottle—see  FIGS. 22A to 22C ), as will be described in more detail hereinafter. The bore network  114   j  consists of an axial section  114   k  and plural transverse sections  114   l . The axial bore section  114   k  extends forwardly from a rear opening  114   m  in a forward face  114   n  of the internal cavity  114   f  to a junction  114   p . The transverse bore sections  114   l  extend transversely, inwardly from respective forward openings  114   q  in the outer circumferential surface of the central section  114   c  to the junction  114   p  to connect with the axial bore section  114   k . The forward openings  114   q  are arranged equi-angularly about the central section  114   c . In this particular embodiment, there are two transverse bore sections  114   l , but one or greater than two transverse bore sections could be used. The forward openings  114   q  are also recessed in the central section  114   c.    
     The piston member  114  is provided with a plurality of axially-oriented grooves  114   r  about the outer periphery. The grooves  114   r  extend rearwardly from a rear surface  114   s  of the annular flange  114   i  in the forward section  114   a  to an annular rib  114   t  on the central section  114   c  rearward of the forward openings  114   q  of the internal bore network  114   j . The grooves  114   r  are arranged so that at least a portion of the forward openings  114   q  are within the grooves  114   r.    
     The tip part  114   u  of the forward section  114   a  of the piston member  114 , which extends forwardly from the flange  114   i  to the forward end  114   h , has a triangular cross-sectional shape, with the apexes being rounded. 
     Referring to  FIGS. 24B ,  24 C,  27 A and  27 B, the piston member  114  carries on its central section  114   c  a tubular rear sealing element  128  which provides a permanent dynamic (sliding) seal between the piston member  114  and the rear section  120   b  of the dosing chamber  120 . The rear sealing element  128  is fixed to the piston member  114  to move in unison therewith so that there is no relative axial movement therebetween as the piston member  114  strokes in the dosing chamber  120 . 
     The rear sealing element  128  is of the lip-seal type, being provided with resilient, annular sealing lips  128   a ,  128   b  at its forward and rear ends, respectively. The material of the rear sealing element  128  provides the sealing lips  128   a ,  128   b  with an inherent outwardly-directed bias. The sealing lips  128   a ,  128   b  have an outer diameter which is greater than the inner diameter of the rear dosing chamber section  120   b , whereby the sealing lips  128   a ,  128   b  are compressed inwardly by the inner surface of the rear dosing chamber section  120   b . As a result, the bias in the sealing lips  128   a ,  128   b  means they sealingly engage the inner surface of the rear dosing chamber section  120   b.    
     The rear sealing element  128  further comprises a tubular body  128   c  from which the sealing lips  128   a ,  128   b  depend and which fits on the outer surface of the piston member central section  114   c  by engagement of an inner circumferential bead  128   d  of the rear sealing element  128  in a recessed portion  114   w  of the central section  114   c  of the piston member  114 . The tubular body  128   c  has a length such that, when fitted on the piston member  114 , it covers substantially the entire axial extent of the central section  114   c  of the piston member  114 . 
     Now referring additionally to  FIGS. 28A and 28B , the piston member  114  further carries on its forward section  114   a  a tubular forward sealing element  148  to form a dynamic (sliding) seal between the piston member  114  and the forward section  120   a  of the dosing chamber  120 , but only during a particular phase of the piston member stroke, as will be described in more detail hereinafter. 
     The forward sealing element  148  is also of the lip-seal type, but this time only being provided with a resilient, annular sealing lip  148   a  at its forward end. The outer diameter of the forward lip seal  148   a  is less than the inner diameter of the rear dosing chamber section  120   b , but greater than the inner diameter of the forward dosing chamber section  120   a . Consequently, the forward sealing lip  148   a  is able to be biased into sealing engagement with the inner surface of the forward dosing chamber section  120   a.    
     As will be observed, the forward sealing element  148  is slidably mounted on the forward section  114   a  of the piston member  114 . In more detail, the forward sealing element  148  comprises a tubular body  148   b , from which the sealing lip  148   a  depends, and provides an axial, open-ended bore  149  through the forward sealing element  148  in which the forward section  114   a  of the piston member  114  is slidably mounted. The bore  149  comprises forward and rear bore sections  149   a ,  149   b  and an enlarged, central chamber  149   c . The forward and rear bore sections  149   a ,  149   b  respectively extend from the central chamber  149  to openings in the forward and rear ends  148   c ,  148   d  of the forward sealing element  148 . The forward end  148   c  is provided with grooves  148   g  which intersect the forward bore opening therein. The central bore chamber  149   c  is provided with a pair of diametrically opposed windows  149   f  through the tubular body  148   b.    
     The annular flange  114   i  of the piston member  114  is located inside of the central bore chamber  149   c . The central bore chamber  149   c  has transversely-oriented forward and rear end walls  149   d ,  149   e  which selectively engage the annular flange  114   i  of the piston member  114  to delimit the sliding movement of the forward sealing element  148  on the piston member  114 . Specifically, the forwardmost position of the forward sealing element  148  relative to the piston member  114  is delimited by the rear end wall  149   e  abutting the annular flange  114   i , and conversely the rearmost position of the forward sealing element  148  relative to the piston member  114  is delimited by abutment of the forward end wall  149   d  with the annular flange  114   i.    
     The sliding movement of the forward piston member section  114   a  in the forward sealing element bore  149  forms a one-way valve. The one-way valve is closed when the forward sealing element  148  is in its rearmost position relative to the piston member  114  and open as the forward sealing element  149  moves towards its forwardmost position relative to the piston member  114 , as will be discussed in more detail hereinafter. 
     To this end, it will be understood that the annular flange  114   i  forms a fluid-tight seal against the forward end  149   d  of the central bore chamber  149   c  when the forward sealing element  148  is in its rearmost position. 
     In operation, as the piston member  114  strokes forwardly relative to the dosing chamber  120 , the forward sealing element  148  moves forwardly with the piston member  114  through engagement of the annular flange  114   i  with the forward end wall  149   d  of the central bore chamber  149   c . Thus, the one-way valve is closed in the forward stroke of the piston member  114 . The forward stroke also brings the forward sealing element  148  into sliding sealing engagement with the forward section  120   a  of the dosing chamber  120 . 
     Once the piston member  114  reaches its forward position at the end of its forward stroke, as delimited by abutment of the forward end  148   c  of the forward sealing element  148  with a forward end wall  120   c  of the dosing chamber  120 , the piston member  114  starts its return, rearward stroke towards its rearward position. In an initial phase of the rearward stroke, the piston member  114  moves rearwardly relative to the forward sealing element  148  so that the one-way valve is moved to its open position for the rearward stroke. The rearward stroke of the piston member  114  ends with the piston member  114  being disposed in its rearward position, where the forward sealing element  148  is disposed in the rear dosing chamber section  120   b  so that the forward and rear dosing chamber sections  120   a ,  120   b  are in flow communication about the forward sealing element  148 . 
     It will thus be appreciated that in an initial phase of the forward stroke of the piston member  114  in the dosing chamber  120 , the piston member  114  moves forwardly relative to the forward sealing element  148  to (re)close the one-way valve. 
     The rear and forward sealing elements  128 ,  148  in this embodiment are injection moulded from low density polyethylene (LDPE), but other functionally equivalent plastics materials could be used. 
     The return, compression spring  118  in the fluid dispenser  110  is provided to bias the piston member  114  to its rearward (resting) position relative to the dosing chamber  120 , which is shown in  FIGS. 22B and 24B . The spring  118  may be made from a metal or a plastics material. 
     As shown in  FIGS. 29A and 29B , the main housing  112  is formed by a tubular body  112   a  from which an annular flange  112   b  projects. The tubular body  112   a  has an open-ended axial bore  112   c  into which an annular shoulder  112   d  projects to create a restricted bore section  112   e  relative to the forward and rear bore sections  112   f ,  112   g  disposed on either side of the annular shoulder  112   d . The rear bore section  112   g  defines the dosing chamber  120 . The forward section  112   h  of the tubular body  112   a  is provided with a pair of circumferential beads  112   i.    
     The main housing  112  in this embodiment is injection moulded from polypropylene (PP), but other plastics materials could be used. 
     The biasing force of the return spring  118  acts to reset the piston member  114  in its rear position relative to the dosing chamber  120  defined in the main housing  112  by acting on the main housing annular flange  112   b  to bias the main housing  112  forwardly to its relative position shown in  FIGS. 22B and 24B . 
     As shown in  FIGS. 36A and 36B , the nipple  160  is comprised in a separate cylindrical cap  165 . The cap  165  is of cup-form, having an annular side skirt  165   a  and a forward end wall  165   b  which form the boundary walls of an internal cylindrical chamber  165   c  which is open at the rear end  165   d  of the cap  165 . Moreover, the nipple  160  is in the form of a central sealing tip which projects forwardly from the forward end wall  165   b.    
     A plurality of apertures  165   e  are also formed in the forward end wall  165   b , about the base of the sealing tip  160 , to communicate with the internal chamber  165   c . In this embodiment, there are three equi-angularly spaced apart apertures  165   e , but alternatively there may be less or more in number than three apertures. 
     The inner circumferential side surface  165   f  of the internal chamber  165  is provided with a pair of circumferential beads  165   g . The outer circumferential edge of the forward end wall  165   b  presents a resilient, annular sealing lip  165   h.    
     In this embodiment, the cap  165  is formed from LDPE, but again other plastics materials could be used. 
     As shown in  FIGS. 24B and 24C , for instance, the cap  165  is mounted over the forward section  112   h  of the main housing  112  to enclose the forward bore section  112   f  of the main housing  112 . The cap  165  is secured to the main housing  112  by the respective internal and external beads  165   g ,  112   i  clipping or interlocking together such that they move in unison. 
     As further shown in  FIGS. 24B and 24C , a valve mechanism  189  is located in the forward bore section  112   f  of the main housing  112 . The valve mechanism  189  comprises a cylindrical, elongate valve element  191  mounted for axial movement in the forward bore section  112   f.    
     As shown in  FIGS. 34A and 34B , the valve element  191  has a cylindrical forward section  191   a  and a coaxial, enlarged rear section  191   b . The rear section  191   b  has a forward portion  191   c  and a frusto-conical rear portion  191   d  sized to sealingly fit in the restricted bore section  112   e  of the main housing  112  for closure thereof. A plurality of axial grooves  191   e  are formed in the outer peripheral surface of the rear section  191   b  to extend through the forward portion  191   c  and partially into the rear portion  191   d.    
     Turning back to  FIGS. 24B and 24C , the valve mechanism  189  further comprises a return, compression spring  193  which extends rearwardly from the inner surface of the forward end wall  165   b  of the cap  165  onto an annular flange  191  at the forward end of the rear section  191   b  of the valve element  191 . The return spring  193  acts to bias the valve element  191  rearwardly to dispose the frusto-conical rear portion  191   d  in the restricted bore section  112   e  for sealing closure thereof. 
     The valve element  191  in this embodiment is injection moulded from low density polyethylene (LDPE), but other functionally equivalent plastics materials could be used. The return spring  193  may be of metal or a plastics material. 
       FIGS. 24B and 24C  also show that the cylindrical stopper portion  176  has a cap form for fitting on the bottle neck  178 . In this embodiment, the stopper portion  176  is injection moulded from polypropylene (PP). However, other plastics materials could be used. 
     Referring also to  FIGS. 30A and 30B , the stopper portion  176  has an outer annular skirt  176   a , which surrounds the outer peripheral surface of the flange  180  of the bottle neck  178 , and a concentrically arranged inner annular skirt  176   b , which plugs the bottle neck  178 . The inner peripheral surface of the outer annular skirt  176   a  is provided with circumferentially-oriented bead  176   q  to engage underneath the flange  180  of the bottle neck  178  to give a snap-fit connection of the stopper portion  176  to the bottle  170 . The bead  176   q  may be continuous, or segmented to simplify the moulding of the stopper portion  176 . 
     The stopper portion  176  has a roof  176   c  at its forward end extending radially inwardly from the outer skirt  176   a  to the inner skirt  176   b . The inner skirt  176   b  encloses an internal cavity  176   d  which extends rearwardly from a opening  176   e  in the roof  176   c . The cavity  176   d  has a floor  176   f  at its rear end from which upstands an elongate tubular projection  176   g.    
     The tubular projection  176   g  has an open rear end  176   h , a forward end wall  176   i , an internal cavity  176   j  which extends forwardly from the open rear end  176   h  to the forward end wall  176   i , and a forward opening  176   k  in the forward end wall  176   i  to place the internal cavities  176   d ,  176   j  in flow communication. 
     As shown in  FIG. 24B , for example, the supply tube  172  inserts into the internal cavity  176   j  of the tubular projection  176   g  as an interference fit, with the supply tube  176  abutting the forward end wall  176   i  of the tubular projection  176   g . Likewise, the tubular projection  176   g  inserts into the internal cavity  114   f  of the rear section  114   b  of the piston member  114  so that the forward end wall  176   i  of the tubular projection  176   g  abuts the forward face  114   n  of the internal cavity  114   f . In this way, the bore network  114   j  in the piston member  114  is placed in flow communication with the fluid supply  170  through the supply tube  172 . 
     The tubular projection  176   g  is secured in the internal cavity  114   f  of the piston member  114  by the internal cavity  114   f  of the piston member  114  presenting a plurality of circumferential beads  114   v  on its inner circumferential surface to which clip or interlock circumferential beads  176   s  provided on the outer circumferential surface of the tubular projection  176   g.    
     As further shown in  FIG. 24B , for example, the tubular body  112   a  of the main housing  112  is also mounted in the internal cavity  176   d  of the stopper portion  176  for relative sliding motion therebetween. The relative sliding motion between the stopper portion  176  and the main housing  112  effects the relative sliding motion between the piston member  114  and the dosing chamber  120  because the piston member  114  is carried on the tubular projection  176   g  of the stopper portion  176 . The relative sliding motion is achievable by having the main housing  112  move rearwardly and maintaining the fluid supply  170  stationary, or vice-versa, or by having the main housing  112  and fluid supply  170  move towards one another at the same time. 
     It will be seen from  FIG. 24B , for example, that a sealing ring  171  is interposed between the stopper portion  176  and the fluid supply  170  to prevent leaks therebetween. 
     The fluid dispenser  110  further comprises a cylindrical carrier member  195  which surrounds the tubular body  112   a  of the main housing  112 . As shown in  FIGS. 33A and 33B , the carrier member  195  has an annular body  195   a  which is spaced radially outwardly of the tubular body  112   a  of the main housing  112  to define an annular space  187  therebetween (see  FIG. 24A ). The annular body  195   a  has an inwardly projecting, annular flange  195   b  at its rear end  195   c , and a plurality of outwardly projecting clips  195   d  disposed on tongues  195   f  defined by the castellated profile at its forward end  195   e.    
     As shown in  FIG. 24B , the return spring  118  extends rearwardly from the rear face  112   j  of the main housing annular flange  112   b  into the annular space  187  between the carrier member  195  and the main housing  112  and onto the carrier member annular flange  195   b  for carriage thereon. 
     In normal use of the fluid dispenser  110 , the carrier member  195  seats on the roof  176   c  of the stopper portion  176 , both in the rest and fired positions of the fluid dispenser  110  to be discussed hereinafter. This normal position for the carrier member  195  is shown in  FIGS. 24B  (rest) and  24 C (fired). 
     The carrier member  195  in this embodiment is also injection moulded from polypropylene (PP), but other plastics materials may be used. 
     Referring back to  FIGS. 30A and 30B  which show the stopper portion  176 , it will be seen that the roof  176   c  carries a pair of diametrically opposed main protrusions  176   n  and a series of minor protrusions  176   p  arranged equi-angularly about the roof opening  176   e . The main protrusions  176   n  are adapted in use to act on the outer circumference of the carrier member  195  to centralise it with respect to the stopper portion  176  as the carrier member  195  is seated on the roof  176   c . The minor protrusions  176   p  fit into complementary grooves (not shown) in the annular flange  195   b  of the carrier member  195  to correctly orient the carrier member  195  on the roof  176   c  so that the clips  195   d  will clip into T-shaped tracks  116   g  in the nozzle  116  to be described hereinafter. In a modification, not shown, there may be provided just two minor protrusions, each forming a radial extension from one of the main protrusions. 
     The fluid dispenser  110  also comprises a tubular nozzle insert  197  surrounding the cap  165  mounted on the forward section  112   h  of the main housing  112 .  FIGS. 35A and 35B  show the nozzle insert  197  has a hollow body  197   a  which at its forward end  197   b  has an end wall  197   c  through which is provided a central aperture  197   d . The body  197   a  comprises a first annular section  197   e  which extends rearwardly from the forward end wall  197   c  and has, about it rear end, an outer circumferential bead  197   p . The rear end  197   f  of the nozzle insert body  197   a  is presented by a plurality of spaced-apart, rearwardly extending legs  197   g . There are four legs  197   g  in this embodiment. The legs  197   g  are arranged circumferentially on the body  197   a  about a rear opening  197   h  to the body  197   a . Each leg  197   g  comprises an outwardly extending foot  197   i.    
     The nozzle insert body  197   a  further comprises a second annular section  197   j  spaced rearwardly of the first annular section  197   e  and from which the legs  197   g  depend. The first and second annular sections  197   e ,  197   j  are joined together by a plurality of spaced-apart, resilient ribs  197   k  which are disposed on the outer circumference of the body  197   a  and extend on a diagonal path between the first and second annular sections  197   e ,  197   j.    
     The second annular section  197   j  presents a pair of diametrically opposed, forwardly oriented, resilient tongues  197   l . The tongues  197   l  are disposed between the ribs  197 . 
     On the forward face of the forward end wall  197   c  there is provided an annular lip  197   m  about the central aperture  197   d . The forward end wall  197   c  is further provided with apertures  197   n  therethrough. 
     The nozzle insert  197  in this embodiment is injection moulded from polypropylene (PP), but could be made from other plastics materials, as will be appreciated by those skilled in the art. 
       FIGS. 24B and 24C  show the nozzle insert  197  is arranged in the fluid dispenser  110  about the cap  165  so that the sealing tip  160  of the cap  165  projects through the central aperture  197   d  in the forward end wall  197   c  of the nozzle insert  197 . Moreover, the sealing lip  165   h  of the cap  165  is slidingly sealingly engaged with the inner circumferential surface of the first annular section  197   e  of the nozzle insert  197 . 
     The annular space between the nozzle insert  197  and the cap  165  defines the fluid dispensement chamber  146 . 
     It will be seen from  FIGS. 36A-B  that the cap  165  is provided with an outwardly projecting, annular flange  165   i . As will be appreciated by additional reference to  FIGS. 35A-B  and  FIG. 24B , as the cap  165  is inserted into the nozzle insert  197  during assembly, the flange  165   i  pushes past the resilient tongues  197   l  of the nozzle insert  197  to be retained in the space between the first and second annular sections  197   e ,  197   j  of the nozzle insert  197 . 
     Mounted on the sealing tip  160  of the cap  165  is the sealing member  154 . The sealing member  154  is slidably, sealingly mounted on the sealing tip  160  and seated in the annular lip  197   m  of the nozzle insert  197 . The seal formed between the longitudinal surfaces of the sealing member  154  and the sealing tip  160  is such that fluid cannot pass therebetween. 
     The sealing member  154  is made from natural rubber or a thermoplastic elastomer (TPE), but other elastic materials may be used which have a ‘memory’ to return the sealing member  154  to its original state. 
     As illustrated by  FIGS. 22 and 23 , the nozzle  116  is slidably connected to the stopper portion  176  through engagement of a pair of rearwardly directed runners  116   a  of the nozzle  116  in complementary tracks  176   m  on the outer circumference of the stopper portion  176 . The runners  116   a  are provided with outwardly extending clips  116   b  to secure the runners  116   a  in the tracks  176   m  and to delimit the maximum sliding separation between the nozzle  116  and the stopper portion  176 . 
     As further illustrated in  FIGS. 31A and 31B , the nozzle  116  has a nozzle section  116   c , sized and shaped for insertion into a nostril of a human being, in which is formed the fluid outlet  152 , and shoulders  116   d  at the rear end of the nozzle section  116   c  from which depend the runners  116   a.    
     The nozzle section  116   c  encloses an internal cavity  116   e  having a rear open end  116   f . The inner surface of the internal cavity  116   e  also has a pair of T-shaped tracks  116   g  on opposite sides of the internal cavity  116   e  in the longitudinal section of which the clips  195   d  of the carrier member  195  are clipped to secure the carrier member  195  to the nozzle  116  and to provide for sliding movement therebetween. Moreover, in each corner of the crossbar section of the T-shaped tracks  116   g  is clipped one of the feet  197   i  of the nozzle insert  197  to fix the nozzle insert  197  in the internal cavity of the nozzle  116 . These connections are best seen in  FIGS. 22A-C . 
     The resilient ribs  197   k  of the nozzle insert  197  act as springs to enable the nozzle insert  197  to be inserted into the nozzle  116  and then the second annular section  197   j  compressed so that the feet  197   i  fix in the T-shaped tracks  116   g . The nozzle insert  197  is then held captive in the nozzle  116 . Moreover, the first annular section  197   a  forms a fluid-tight seal against the adjacent inner surface of the nozzle internal cavity  116   e  to prevent liquid leaking out of the fluid dispensement chamber  146 . 
     As shown in  FIG. 32 , a swirl chamber  153  is formed in the forward end wall  116   i  of the nozzle internal cavity  116   e . The swirl chamber  153  comprises a central cylindrical chamber  153   a  and a plurality of feed channels  153   b  which are equi-spaced about the central chamber  153   a  in tangential relationship thereto. At the centre of the central chamber  153   a  is a passageway  153   c  (exit) connecting the swirl chamber  153  to the fluid outlet  152 . The feed channels  153   b  may have a depth in the range of 100 to 250 microns, for instance in the range of 150 to 225 microns (inclusive). 
     As will be understood from  FIG. 25 , a gap exists between the side face  154   d  of the sealing member  154  and the adjacent surfaces of the internal cavity  116   e  of the nozzle  116  so as to be in flow communication with the fluid dispensement chamber  146  via the apertures  197   n  and the gaps between the sealing member  154  and the forward opening  197   d  of the nozzle insert  197 . 
     However, as shown most clearly in  FIG. 25 , the forward face  154   c  of the flexible sealing member  154  is held by the nozzle insert  197  in sealing engagement with the forward end wall  116   i  of the nozzle  116 . This means that the sealing member  154  seals over the swirl chamber feed channels  153   b  and that any liquid travelling up the gap between the side face  154   d  of the sealing member  154  and the nozzle  116  has to pass into the swirl chamber feed channels  153   b.    
     Moreover, the return spring  118  acts to bias the main housing  112  forwardly in the nozzle  116  whereby the sealing tip  160 , on the cap  165  fixed on the forward section  112   h  of the main housing  112 , pushes a central part of the forward face  154   c  of the sealing member  154  into the central chamber  153   a  of the swirl chamber  153  to sealingly close the passageway  153   c  to the fluid outlet  152 . In this way, no fluid can enter or exit the fluid outlet  152  until the sealing tip  160  releases the central part of the elastic sealing member  154 , to be described in more detail hereinafter. 
     In a modification, the straight walls of the central chamber  153   a  of the swirl chamber  153  may be chamfered to facilitate pushing the central part of the sealing member  154  thereinto. This is shown in  FIG. 38 , with the chamfered surface denoted by reference number  153   d.    
     The nozzle  116  in this embodiment is injection moulded from polypropylene (PP), but other plastics materials could be used. 
     To operate the fluid dispenser  110 , it is first necessary to prime the device to fill all the fluid pathways between the fluid outlet  152  and the fluid supply  170 . To prime, the fluid dispenser  110  is operated in exactly the same manner as for later dispensing operations. As shown in  FIGS. 22B-C  and  24 B-C, this is done by (i) sliding the nozzle  116  relatively towards the fluid supply  170 , by acting on the nozzle  116 , or the fluid supply  170 , while keeping the other stationary, or acting on both, to move the fluid dispenser from its rest position ( FIGS. 22B and 24B ) to its fired position ( FIGS. 22C and 24C ); and (ii) allowing the return spring  118  to return the nozzle  116  to its separated position relative to the fluid supply  170  to return the fluid dispenser  110  to its rest position. The relative sliding movement of the nozzle  116  and the fluid supply  170  is effected by the runners  116   a  of the nozzle  116  sliding in the tracks  176   m  of the stopper portion  176  fixed in the neck  178  of the fluid supply  170 . 
       FIGS. 37A to 37J  show the priming process, and the liquid flow during priming, albeit for a fluid dispenser  310  which is a subtle modification (but functional equivalent) of the fluid dispenser  110  of  FIGS. 22 to 36 , with like features being assigned like reference numbers. While the fluid dispenser  310  of  FIGS. 37A to 37J  will be discussed in more detail after the description of the fluid dispenser  110 ,  FIGS. 37A to 37J  are a useful reference to the detailed description of priming of the fluid dispenser  110  which now follows. 
     Each complete (reciprocal) cycle of the afore-mentioned sliding movement (a “pumping cycle”) between the nozzle  116  and the fluid supply  170  creates a negative pressure in the dosing chamber  120  which draws liquid from the fluid supply  170  up the supply tube  172  until liquid fills up all the fluid pathways from the fluid supply  170  to the fluid outlet  152 . 
     In more detail, the liquid flows forwardly through the supply tube  172 , into the bore network  114   j  of the piston member  114  via the rear opening  114   m  thereof, and out of the forward openings  114   q  of the bore network  114   j  into the rear section  120   b  of the dosing chamber  120  via the axial grooves  114   r  in the outer periphery of the piston member  114  (see  FIGS. 37A to 37C ). 
     As a result of the nozzle  116  and the fluid supply  170  respectively carrying the main housing  112  and the piston member  114 , as described above, each reciprocal cycle of relative movement of the nozzle  116  and the fluid supply  170  causes the piston member  114  to stroke in corresponding reciprocating fashion inside the dosing chamber  120  defined by the main housing  112  from the rear (rest) position. 
     As the piston member  114  returns from its forward position to its resting, rear position, in the second half of each cycle, a negative pressure is created in the dosing chamber  120  to draw the liquid further forwardly. Moreover, the piston member  114  moves rearwardly relative to the forward sealing element  148  to open the one-way valve, as described hereinabove, and therefore allows the liquid to flow forwardly into the forward dosing chamber section  120   a  through the one-way valve (see  FIGS. 37D to 37G ). 
     Specifically, as the annular flange  114   i  of the piston member  114  disengages from the forward end wall  149   d  of the central bore section  149   c  of the bore  149  in the forward sealing element  148 , the liquid to the rear of the one-way valve is able to flow around the flange  114   i  of the piston member  114  via the windows  149   f  in the forward sealing element  148 , over the tip part  114   u  of the piston member  114  and through the forward bore section  149   a  of the forward sealing element  148  into the forward section  120   a  of the dosing chamber  120 . 
     After the dosing chamber  120  (including the forward section  120   a ) is filled with liquid by priming the fluid dispenser with enough pumping cycles, each cycle thereafter results in the same amount (a metered volume) of the liquid being pumped forward from the dosing chamber  120  through the restricted bore section  112   e  in the main housing  112 . 
     In more detail, in the forward stroke of the piston member  114  to its forward position in the dosing chamber  120 , the valve mechanism  189  in the forward bore section  112   f  keeps the restricted bore section  112   e  shut until after the forward sealing element  148  comes into sealing engagement with the inner surface of the forward dosing chamber section  120   a . This is because the biasing force of the valve return spring  193  is not overcome by the hydraulic pressure of the liquid produced on the initial (first) phase of the forward stroke of the piston member  114  prior to the forward sealing element  148  sliding into sealing engagement in the forward dosing chamber section  120   a  to sealingly separate the forward and rear dosing chamber sections  120   a ,  120   b.    
     This first phase may be referred to as the “bleed phase” because it results in liquid being pumped rearwardly from the dosing chamber  120  back into the fluid supply  170  (i.e. bled) until the piston member  114  locates the forward sealing element  148  in the forward dosing chamber  120   a.    
     Once the forward sealing element  148  is located in the forward dosing chamber  120   a , the forward dosing chamber  120   a , and the liquid which fills it, is sealed. 
     In the next (second) phase of the continuous forward stroke of the piston member  114 , the piston member  114  increases the hydraulic pressure of the liquid in the forward dosing chamber section  120   a  as it moves relatively towards the forward end wall  120   c  of the forward dosing chamber section  120   a  presented by the annular shoulder  112   d  of the main housing  112 . In other words, the liquid is compressed as the distance between the piston member  114  and the forward end wall  120   c  of the dosing chamber  120  decreases. Again, this is because the biasing force of the return spring  193  of the valve mechanism  189  resists the increasing hydraulic pressure exerted by the liquid on the frusto-conical rear portion  191   d  of the valve element  191 . 
     However, at a certain point in the forward stoke of the piston member  114 , the hydraulic pressure of the liquid in the forward dosing chamber section  120   a  is at a level which is greater than the biasing force in the return spring  193  of the valve mechanism  189 , whereby the valve element  191  is forced out of sealing engagement with the restricted bore section  112   e  (which functions as a “valve seat”). This is the start of the final (third) phase of the forward stroke of the piston member  114  which ends when the piston member  114  reaches its forward position, as delimited by abutment of the forward end  148   c  of the forward sealing element  148  with the forward end wall  120   c  of the dosing chamber  120 . In this final phase, the metered volume of the liquid is dispensed through the restricted bore section  112   e , being conveyed along the grooves  191   e  in the valve member  191  into the forward bore section  112   f  of the main housing  112 , before the valve mechanism  189  is re-closed by the return spring  193  returning the valve member  191  into sealing engagement in the restricted bore section  112   e  (see  FIG. 37H ). 
     The valve mechanism  189  only opens in this final (third) phase, remaining closed at all other times. 
     The second and third phases can collectively be considered as a “dispensing phase”. 
     In an initial (first) phase of the return, rearward stroke of the piston member  114  in the dosing chamber  120 , the piston member  114  not only moves rearwardly with respect to the dosing chamber  120 , but also to the forward sealing element  148  so as to open the one-way valve, as discussed hereinabove. Moreover, a negative pressure (or vacuum) is generated in the headspace being formed in the forward dosing chamber section  120   a  in front of the rearwardly moving piston member  114 . This negative pressure draws more liquid out of the fluid supply  170  and through the open one-way valve into the forward dosing chamber section  120   a  until the forward sealing element  148  disengages from the forward dosing chamber  120   a  to enter the rear dosing chamber section  120   b  (see  FIG. 37I ). The provision of the one-way valve which opens in the initial phase of the return stroke avoids the creation of any hydraulic lock in front of the piston member  114  which could otherwise prevent or inhibit the return stroke. 
     In a final (second) phase of the rearward stroke of the piston member  114 , the piston member  114  moves from an intermediate position, at which the forward sealing element  148  has just been disposed in the rear dosing chamber section  120   b , to its rearward position. In this final phase, the liquid is able to be drawn from the rear dosing chamber section  120   b  directly into the forward dosing chamber section  120   a  around the outside of the forward sealing element  148 , in addition to via the open one-way valve. 
     At the end of the return, rearward stroke, the dosing chamber  120  is refilled with liquid. The return stroke may thus be referred to as the “filling phase”. 
     In each subsequent cycle of movement of the piston member  114 , the forward stroke results in another metered volume of the liquid being discharged through the restricted bore section  112   e  while the rearward stroke results in another metered volume of liquid being drawn from the fluid supply  170  to refill the forward section  120   a  of the dosing chamber  120 . 
     During priming, such subsequent pumping cycles continue until the liquid fills the fluid flow path from the dosing chamber  120  to the fluid outlet  152  (see  FIG. 37I ). In this regard, the liquid passing through the restricted bore section  112   e  flows through the forward bore section  112   f  of the main housing  112 , into the fluid dispensement chamber  146  via the apertures  165   e  in the forward end wall  165   b  of the cap  165  mounted over the forward end of the main housing  112 , and then into the space around the sealing member  154  by passing through the apertures  197   n  in the nozzle insert  197  fitted inside the nozzle  116  to enclose the cap  165 . 
     When liquid fills the fluid pathway from the fluid supply  170  to the fluid outlet  152 , the forward stroke of the piston member  114  relative to the dosing chamber  120  in the next pumping cycle results in another metered volume of liquid being pumped through the restricted bore section  112   e  thereby pressurising the liquid pending downstream of the restricted bore section  112   e . This pressure in the fluid dispensement chamber  146  results in rearward sliding movement of the cap  165  (and the main housing  112 ) in the nozzle insert  197  against the return force of the return spring  118  whereby the sealing tip  160  sealingly slides rearwardly in the sealing member  154 . As a result, the elasticity of the sealing member  154  flattens the central part of the forward face  154   c  of the sealing member  154  back to its original state to open the central chamber  153   a  and passageway  153   c  of the swirl chamber  153 . Consequently, a metered volume of the liquid is pumped through the fluid outlet  152  via the swirl chamber  153  for atomisation thereof to make space for the metered volume pumped through the restricted bore section  112   e  in that forward stroke (see  FIG. 37J ). 
     The seal between the opposing longitudinal sides of the sealing tip  160  and the sealing member  154  prevents liquid under the hydraulic pressure entering the sealing member cavity  154   e  ( FIG. 25 ) in which the sealing tip  160  is disposed and acting to oppose the central part of the forward face  154   c  of the sealing member  154  moving back to its original state when released by the sealing tip  160 . 
     The return force of the return spring  118  moves the main housing  112  back (forwardly) to its normal, rest position in the nozzle insert  197  once the return force is greater than the hydraulic pressure in the fluid dispensement chamber  146  so that the sealing tip  160  deflects the sealing member  154  to (re)close the fluid outlet  152 . 
     The sealing member  154  thus protects the liquid inside the fluid dispenser  110  from contamination by contaminants outside of the device  110  entering through the fluid outlet  152  as it only opens during dispensing (i.e. when the fluid dispenser  110  is fired). 
     The rearward stroke of the same pumping cycle draws another metered volume of liquid from the liquid supply  170  to fill the dosing chamber  120 , ready for the next pump cycle. 
     The device is now fully primed, and each pump cycle thereafter results in a constant metered volume of the liquid being pumped from the fluid outlet  152  until the fluid supply  170  is exhausted. 
     It will be appreciated that the fluid dispenser  110  configuration is such that there will be no drain-back of the liquid pending in the path between the dosing chamber  120  and the fluid outlet  152  as the restricted bore section  112   e  is sealed shut by the valve mechanism  189  except in the dispensing phase of the forward stroke. Thus, the need to re-prime the device is avoided or substantially alleviated. Moreover, the tip seal arrangement, formed by the sealing member  154  and the sealing tip  160 , and the valve mechanism  189  prevent ambient air being drawn into the fluid dispenser  110  through the fluid outlet  152  by the negative pressure (e.g. vacuum) created in the dosing chamber  120  in the filling phase. 
     It is also notable that during priming of the fluid dispenser  110 , air (and any other gas) in the headspace above the liquid is pumped out of the fluid outlet  152  by the same mechanism as described above for the liquid. 
       FIGS. 22A and 24A  show the fluid dispenser  110  in an open (fully extended) position, where the nozzle  116  (and its attached components) is spaced farther from the bottle  170  (and its attached components) than in the rest position shown in  FIGS. 22B and 24B . More particularly, in the rest position, the carrier member  195  rests on, or in close proximity to, the roof  176   c  of the stopper portion  176 , whereas in the open position the carrier member  195  is spaced from the stopper portion roof  176   c . In the open position, the clips  116   b  on the runners  116   a  of the nozzle  116  are at the forwardmost position with respect to the tracks  176   m  on the stopper portion  176 , as shown in  FIG. 24A . In the rest position, by contrast, the clips  116   b  are spaced rearwardly of the forwardmost position, as also shown in  FIG. 24B . The ability for the nozzle  116  and bottle  170  to be further separated from the normal rest position provides protection of the fluid dispenser against breakage in the event it is dropped or suffers an impact. 
     There now follows descriptions of alternative sealing arrangements that could be used in the fluid dispenser  110 , with like reference numerals being used to indicate like parts and features with the sealing arrangement in  FIGS. 22 to 36 . 
     In  FIG. 39  there is shown a first alternative tip seal arrangement that could be used in the fluid dispenser  110 . In  FIG. 39 , the sealing tip  160 ′ and sealing member  154 ′ are of different shape compared to their counterparts in the fluid dispenser  110  of  FIGS. 22 to 36 , but function in the same way as their counterparts. The cap  160  and sealing member  154 ′ are of the same materials as described for the fluid dispenser  110  of  FIGS. 22 to 36 . 
     In FIGS.  40  and  41 A-B there is shown a second alternative tip seal arrangement that could be used in the fluid dispenser  110 . In this alternative, the cap  165 ″, sealing member  154 ″ and nozzle insert  197 ″ are of different shape to their counterparts in the fluid dispenser  110  of  FIGS. 22 to 36 , but again function in the same way, and are made from the same materials, as those counterparts. However, in this version of the tip seal arrangement, the return spring  118  biases the cap  165 ″ into abutment with the nozzle insert  197 ″ to control the position of the sealing tip  160 ″ relative to the sealing member  154 ″, thereby protecting the sealing member  154 ″ from excessive force being applied to it by the sealing tip  160 ″. 
     In  FIG. 42  there is shown a different type of sealing arrangement for the fluid dispenser  110 , with  FIGS. 43 to 46  showing the components for this sealing arrangement. 
     In place of the elastic sealing member  154  there is provided an annular backing plate  254  ( FIGS. 44A-B ), made from a plastics material. In this embodiment, the backing plate is injection moulded from polypropylene (PP). The forward face  254   c  of the backing plate  254  is held by a modified nozzle insert  297  ( FIGS. 45A-B ) in sealing engagement with the forward end wall  116   i  of the nozzle  116  so as to seal over the swirl chamber feed channels  153   b  whereby any liquid travelling up the gap between the side face  254   d  of the backing plate  254  and the nozzle  116  has to pass into the swirl chamber feed channels  153   b.    
     A sealing pin  255  ( FIGS. 43A-B ) is seated on the nozzle insert  297  so that a forward sealing section  255   a  of the sealing pin  255  protrudes through the through-hole  254   n  in the backing plate  254  and into the central chamber  153   a  of the swirl chamber  153  to sealing close the passageway  153   c . Thus, the sealing pin  255  functions similarly to the elastic sealing member  154 . 
     As shown in  FIG. 42 , the sealing pin  255  has an enlarged, rear end  255   b  of tapering profile which is held captive in a through-hole  265   n  in the forward end wall  265   b  of a modified cap  265  ( FIGS. 46A-B ) so that the sealing pin  255  moves in unison with the main housing  112  to which the cap  265  is fixed. 
     It will therefore be appreciated that the return spring  118  acts on the main housing  112  to bias the sealing pin  255  into sealing engagement over the swirl chamber passageway  153   c . Moreover, during the dispensing phase of the forward stroke of the piston member  114  in the dosing chamber  120 , the hydraulic pressure produced in the fluid dispensement chamber  146  results in the cap  265  moving rearwardly against the return spring force, and in do doing moves the sealing pin  255  rearwardly so as to open the swirl chamber passageway  153   c  for release of the metered volume of liquid. 
     It will be observed that the sealing pin  255  is provided with forward and rear annular flanges  255   c ,  255   d . The rear flange  255   d  delimits the insertion of the sealing pin  255  into the cap through-hole  265   n . The forward flange  255   c  seals against the rear side of the backing plate  254 . 
     It will further be observed that the valve element  191  of the valve mechanism  189  in the main housing  112  is provided with an abbreviated length to accommodate the sealing pin  255 . 
     The sealing pin  255  in this embodiment is injection moulded from low density polyethylene (LDPE) or high density polyethylene (HDPE), but other functionally equivalent plastics materials could be used. 
     The modified cap  265  and modified nozzle insert  297  are made from the same materials are described for the corresponding parts in the fluid dispenser  110  of  FIGS. 22 to 36 . The modified nozzle insert  297  may also have a castellated forward end wall  297   c , as in the other illustrated nozzle inserts  197 ;  197 ′;  197 ′. 
     Referring now to the fluid dispenser  310  shown in  FIGS. 37A-J , this functions in the same way as the fluid dispenser  110  of  FIGS. 22 to 36 . The sealing tip  360 , sealing member  354 , forward sealing element  328  and stopper portion  376  are of a slightly different structure to the corresponding components in the fluid dispenser  110 . Most notably, however, is the absence of a carrier member for the return spring  318  in the fluid dispenser  310 . It will be seen from  FIG. 37A  that an annular retaining wall  376   t  projects forwardly from the roof  376   c  of the stopper portion  376 . As further shown in  FIG. 37A , the return spring  318  is carried on the stopper portion roof  376   c  and extends forwardly to the annular flange  312   b  of the main housing  312  through the gap formed between the annular retaining wall  376   t  and the main housing  312 . It will therefore be appreciated that the fluid dispenser  310  does not have an open position, like the fluid dispenser  110 , for improving protection against damage if dropped or otherwise impacted. 
     In the exemplary embodiments the sealing arrangement at the fluid outlet  52 ; 152 ; etc of the fluid dispenser  10 ;  110 ; etc acts to prevent or inhibit the ingress of microbials and other contaminants into the dispenser  10 ;  110 ; etc through the fluid outlet  52 ;  152 ; etc, and hence into the dosing chamber  20 ;  120 ; etc and ultimately the bottle/reservoir of the fluid. Where the fluid is a liquid medicament formulation, e.g. for nasal administration, this enables the formulation to be free of preservatives or, perhaps more likely, to be a preservative-sparing formulation. In addition, the seal acts to prevent the pending dose of the fluid in the dosing chamber from draining back into the supply or reservoir when the dispenser  10 ;  110 ; etc is in its rest configuration between actuations. This avoids or reduces the need for the dispenser  10  to be primed for its next usage (priming then only effectively being required for the very first usage of the fluid dispenser so as to fill the dosing chamber  20 ;  120 ; etc, but not after the first usage). 
     The fluid dispenser of the invention may be used to dispense a liquid medicament formulation for the treatment of mild, moderate or severe acute or chronic symptoms or for prophylactic treatment. The precise dose administered will depend on the age and condition of the patient, the particular medicament used and the frequency of administration and will ultimately be at the discretion of the attendant physician. When combinations of medicaments are employed the dose of each component of the combination will in general be that employed for each component when used alone. 
     Appropriate medicaments for the formulation may be selected from, for example, analgesics, e.g., codeine, dihydromorphine, ergotamine, fentanyl or morphine; anginal preparations, e.g., diltiazem; antiallergics, e.g., cromoglycate (eg as the sodium salt), ketotifen or nedocromil (eg as the sodium salt); antiinfectives e.g., cephalosporins, penicillins, streptomycin, sulphonamides, tetracyclines and pentamidine; antihistamines, e.g., methapyrilene; anti-inflammatories, e.g., beclomethasone (eg as the dipropionate ester), fluticasone (eg as the propionate ester), flunisolide, budesonide, rofleponide, mometasone (eg as the furoate ester), ciclesonide, triamcinolone (eg as the acetonide), 6α,9α-difluoro-11β-hydroxy-16α-methyl-3-oxo-17α-propionyloxy-androsta-1,4-diene-17β-carbothioic acid S-(2-oxo-tetrahydro-furan-3-yl)ester or 6α,9α-Difluoro-17α-[(2-furanylcarbonyl)oxy]-11β-hydroxy-16α-methyl-3-oxo-androsta-1,4-diene-17β-carbothioic acid S-fluoromethyl ester; antitussives, e.g., noscapine; bronchodilators, e.g., albuterol (eg as free base or sulphate), salmeterol (eg as xinafoate), ephedrine, adrenaline, fenoterol (eg as hydrobromide), formoterol (eg as fumarate), isoprenaline, metaproterenol, phenylephrine, phenylpropanolamine, pirbuterol (eg as acetate), reproterol (eg as hydrochloride), rimiterol, terbutaline (eg as sulphate), isoetharine, tulobuterol or 4-hydroxy-7-[2-[[2-[[3-(2-phenylethoxy)propyl]sulfonyl]ethyl]amino]ethyl-2(3H)-benzothiazolone; PDE4 inhibitors eg cilomilast or roflumilast; leukotriene antagonists eg montelukast, pranlukast and zafirlukast; [adenosine 2a agonists, eg 2R,3R,4S,5R)-2-[6-Amino-2-(1S-hydroxymethyl-2-phenyl-ethylamino)-purin-9-yl]-5-(2-ethyl-2H-tetrazol-5-yl)-tetrahydro-furan-3,4-diol (e.g. as maleate)]*; [α4 integrin inhibitors eg (2S)-3-[4-({[4-(aminocarbonyl)-1-piperidinyl]carbonyl}oxy)phenyl]-2-[((2S)-4-methyl-2-{[2-(2-methylphenoxy)acetyl]amino}pentanoyl)amino]propanoic acid (e.g as free acid or potassium salt)]*, diuretics, e.g., amiloride; anticholinergics, e.g., ipratropium (eg as bromide), tiotropium, atropine or oxitropium; hormones, e.g., cortisone, hydrocortisone or prednisolone; xanthines, e.g., aminophylline, choline theophyllinate, lysine theophyllinate or theophylline; therapeutic proteins and peptides, e.g., insulin or glucagons. It will be clear to a person skilled in the art that, where appropriate, the medicaments may be used in the form of salts, (e.g., as alkali metal or amine salts or as acid addition salts) or as esters (e.g., lower alkyl esters) or as solvates (e.g., hydrates) to optimise the activity and/or stability of the medicament and/or to minimise the solubility of the medicament in the propellant. 
     Preferably, the medicament is an anti-inflammatory compound for the treatment of inflammatory disorders or diseases such as asthma and rhinitis. 
     In one aspect, the medicament is a glucocorticoid compound, which has anti-inflammatory properties. One suitable glucocorticoid compound has the chemical name: 6α,9α-Difluoro-17α-(1-oxopropoxy)-11β-hydroxy-16α-methyl-3-oxo-androsta-1,4-diene-17β-carbothioic acid S-fluoromethyl ester (fluticasone propionate). Another suitable glucocorticoid compound has the chemical name: 6α,9α-difluoro-17α-[(2-furanylcarbonyl)oxy]-11β-hydroxy-16α-methyl-3-oxo-androsta-1,4-diene-17β-carbothioic acid S-fluoromethyl ester. A further suitable glucocorticoid compound has the chemical name: 6α,9α-Difluoro-11β-hydroxy-16α-methyl-17β-[(4-methyl-1,3-thiazole-5-carbonyl)oxy]-3-oxo-androsta-1,4-diene-17β-carbothioic acid S-fluoromethyl ester. 
     Other suitable anti-inflammatory compounds include NSAIDs e.g. PDE4 inhibitors, leukotriene antagonists, iNOS inhibitors, tryptase and elastase inhibitors, beta-2 integrin antagonists and adenosine 2a agonists. 
     Other medicaments which may be comprised in the formulation are 6-({3-[(Dimethylamino)carbonyl]phenyl}sulfonyl)-8-methyl-4-{[3-(methyloxy) phenyl]amino}-3-quinolinecarboxamide; 6a,9a-Difluoro-11b-hydroxy-16a-methyl-17a-(1-methycyclopropylcarbonyl)oxy-3-oxo-androsta-1,4-diene-17b-carbothioic acid S-fluoromethyl ester; 6a,9a-Difluoro-11i-hydroxy-16a-methyl-3-oxo-17a-(2,2,3,3-tetramethycyclopropylcarbonyl)oxy-androsta-1,4-diene-17i-carbothioic acid S-cyanomethyl ester; 1-{[3-(4-{[4-[5-fluoro-2-(methyloxy)phenyl]-2-hydroxy-4-methyl-2-(trifluoromethyl)pentyl]amino-6-methyl-1H-indazol-1-yl)phenyl]carbonyl}-D-prolinamide; and the compound disclosed in International patent application No. PCT/EP2007/053773, filed 18 Apr. 2007, in Example 24, and in particular the form which is 24C therein. 
     The fluid dispenser herein is suitable for dispensing fluid medicament formulations for the treatment of inflammatory and/or allergic conditions of the nasal passages such as rhinitis e.g. seasonal and perennial rhinitis as well as other local inflammatory conditions such as asthma, COPD and dermatitis. 
     A suitable dosing regime would be for the patient to inhale slowly through the nose subsequent to the nasal cavity being cleared. During inhalation the formulation would be applied to one nostril while the other is manually compressed. This procedure would then be repeated for the other nostril. Typically, one or two inhalations per nostril would be administered by the above procedure up to three times each day, ideally once daily. Each dose, for example, may deliver 5 μg, 50 μg, 100 μg, 200 μg or 250 μg of active medicament. The precise dosage is either known or readily ascertainable by those skilled in the art. 
     All usage herein of terms such as “about”, “approximately”, “substantially” and the like in relation to a parameter or property is meant to include the exact parameter or property as well as immaterial deviations therefrom. 
     The embodiments of the present invention described above are purely illustrative. Modifications in detail may be made within the scope of the invention as defined in the claims and the Summary of the Invention.