WO2005023346A1 - Improvements relating to medical apparatus - Google Patents

Abstract

Medical apparatus having means for forming a jet of fluid is disclosed. The means for forming a jet of fluid comprises a fluid passageway (16) and a plug (30) closely received therewithin. The plug (30) provides an incomplete closure of the fluid passageway such that a fluid conduit (38) is formed between the plug (30) and a facing surface of the passageway (16). A nebuliser comprising a liquid entrainment jet is also disclosed. The liquid entrainment jet delivers, in use, a jet of gas and entrained liquid via an exit orifice (39) to a target (46) juxtaposed with the exit orifice (39). The target (46) is part of a component (40) that also defines, at least partly, the exit orifice (39).

Description

Title - Improvements relating to Medical Apparatus

This invention relates to medical apparatus and in particular to medical apparatus including means for forming a jet of fluid, such as nebulisers that produce a fine mist of liquid particles by impacting a jet of gas and liquid particles upon a fixed target.

Many forms of medical apparatus include means for forming a jet of fluid. For instance, a particular form of nebuliser currently in use includes means for forming a jet of gas mixed with particles of drug solution, with the jet impacting a target component so as to reduce the size of the particles of drug solution. Another example is a venturi device in which a jet of oxygen is mixed with atmospheric air before being supplied to a patient.

The means for forming a jet of fluid usually comprises a fluid passageway that terminates at an exit orifice of reduced dimension relative to the fluid passageway. Conventionally, such components are injection moulded in plastics material. The exit orifice is therefore usually formed using a moulding tool including a delicate core of small cross-sectional area. Such cores are highly prone to breakages. Tool breakages are highly undesirable due to the time and money wasted in stopping manufacture whilst the breakage is fixed.

A further problem associated with conventional medical apparatus is that the delicate core of the moulding tool used to form the exit orifice wears easily. There is therefore a relatively large variation in the size of the exit orifices formed during manufacture. Variation in the size of the exit orifice is highly undesirable because this leads to inconsistency in the performance of the apparatus.

Nebulisers are devices that produce a fine mist of liquid particles, usually a drug in solution, which is suitable for inhalation by a patient. Drugs typically used in nebulisers include bronchodilators, anticholinergics, anti- inflammatories including corticosteroids; and other anti-allergies. Different types of nebuliser utilise different techniques for producing a fine mist of liquid particles suitable for inhalation by a patient. One particular type of nebuliser produces a fine mist of liquid particles by impacting a jet of gas and entrained liquid particles upon a fixed target. The action of the jet striking the fixed target reduces the size of the liquid particles so as to form a fine mist of liquid particles suitable for inhalation.

The performance of such nebulisers is dependent upon many variables including the distance between the target and the exit orifice from which the jet is emitted. The construction of conventional nebulisers is such that this distance may vary considerably from one nebuliser to another. In particular, conventional nebulisers commonly comprise a target component attached to the nebuliser by a screw thread. This means that the distance between the target and the exit orifice from which the jet is emitted may vary between nebulisers and may also vary between uses of the same nebuliser, due to the nebuliser being disassembled and then reassembled between uses. Screw threads are particularly undesirable because they are difficult to tool and slow to mould.

There has now been devised improved medical apparatus, and an improved nebuliser, which overcome or substantially mitigate the above-mentioned and/or other disadvantages associated with the prior art.

According to a first aspect of the invention, there is provided medical apparatus having means for forming a jet of fluid, said means comprising a fluid passageway and a plug closely received therewithin, the plug providing an incomplete closure of the fluid passageway such that a fluid conduit is defined by a surface of the plug and a facing surface of the fluid passageway.

The medical apparatus according to the first aspect of the invention is advantageous principally because delicate apparatus is not required in order to form the fluid conduit for the jet of fluid. Tool breakages occurring during manufacture will therefore be significantly reduced, thereby reducing the cost of the manufacturing process. Furthermore, the fluid conduit of the medical apparatus according to the invention can be manufactured to a greater degree of accuracy compared to that of conventional medical apparatus.

A further significant advantage of medical apparatus according to the first aspect of the invention is that the plug may be replaced relatively easily in order to alter the form of the fluid conduit. This reduces the cost of manufacturing medical apparatus having a range of fluid conduit forms, and may also allow the user to alter the form of the fluid conduit between uses. This is particularly useful where the medical apparatus according to the first aspect of the invention is a nebuliser that produces a fine mist of liquid particles by impacting a jet of gas and drug solution particles upon a fixed target. The performance of such nebulisers is dependent to a large extent upon the form of the fluid conduit from which the jet is emitted, as well as the particular gas and drug solution combination used. Nebulisers according to the first aspect of the invention therefore allow the form of the fluid conduit to be easily optimised, either by the user or during manufacture, for a particular gas and drug solution combination.

The fluid conduit preferably extends along the length of the plug. Most preferably, the fluid passageway is of constant cross-section and the cross- sectional area of the plug increases from one end to the other, so that the cross-sectional area of the fluid conduit reduces from one end of the plug to the other.

The plug may be formed so as to be closely received within the fluid passageway save for a recess in the external surface of the plug which defines, along with an internal surface of the fluid passageway, the fluid conduit.

Alternatively, the cross-sectional shapes of the plug and the fluid passageway may be selected such that the fluid conduit is defined by an external surface of the plug and an internal surface of the passageway. For instance, the plug may have a particular cross-sectional shape, for example a circularly-shaped cross-section, and the fluid passageway may have a correspondingly shaped cross-section but including an enlarged portion within which the fluid conduit is defined. Most preferably, the fluid passageway has a teardrop-shaped cross- section and the plug has a correspondingly shaped cross-section save for the face of the plug that forms the tip of the teardrop cross-section being flattened. The fluid conduit is then generally triangular in cross-section.

The fluid passageway is preferably formed in a relatively rigid plastics material, such as polypropylene or acrylonitrile-butadiene-styrene (ABS), and the plug is preferably formed in a more compliant material, such as an elastomeric material.

A particularly suitable medical apparatus according to the first aspect of the invention is a nebuliser comprising a liquid entrainment jet that delivers, in use, a jet of gas and entrained liquid via an exit orifice to a target juxtaposed with the exit orifice. Most preferably, the target is part of a component that also defines, at least partly, the exit orifice.

In order for the nebuliser to emit a jet of gas containing particles of liquid from the exit orifice, a liquid conduit preferably converges with the fluid conduit at the exit orifice. Most preferably, the fluid conduit is in communication, in use, with a gas supply and the liquid conduit is in communication, in use, with a liquid supply. Most preferably, the nebuliser includes a liquid reservoir and the liquid conduit preferably extends between the liquid reservoir and the exit orifice.

The fluid conduit preferably reduces in cross-sectional area before terminating at the exit orifice. In this case, the velocity of the gas supplied to the fluid conduit increases towards the exit orifice so that a relatively high velocity jet of gas is emitted from the exit orifice. Where the liquid conduit converges with the fluid conduit at the exit orifice, the high velocity of the gas may be utilised to draw liquid along the liquid conduit towards the exit orifice. This occurs because of the drop in gas pressure caused by the increase in gas velocity according to Bernoulli's principle. Most preferably, therefore, the exit orifice is situated above the level of the liquid in the liquid reservoir during use. Liquid will therefore only be drawn to the exit orifice when gas is being emitted from the exit orifice above a critical velocity.

A preferred arrangement for the nebuliser according to the first aspect of the invention is a nebuliser comprising a liquid reservoir with an upstanding spigot including the fluid passageway, the plug being closely received within an open end of the fluid passageway and a sleeve being disposed around the upstanding spigot. The spigot, plug and sleeve are preferably arranged to together form the fluid conduit and exit orifice. The nebuliser preferably includes formations such that when the sleeve is positioned around the spigot, a void is formed between the sleeve and the external surface of the spigot, thereby forming a liquid conduit that extends from the liquid reservoir to the exit orifice.

The sleeve is preferably integrally formed with the target as a single target component. This component is preferably injection moulded in plastics material, such as polypropylene or acrylonitrile-butadiene-styrene (ABS). The target component preferably includes a planar support that joins the sleeve and the target so that the target faces the exit orifice. The normal of the planar support is preferably orientated perpendicularly to the direction of the jet and preferably also to the normal of the target surface. The surface of the target is preferably orientated with its normal parallel to the direction of the jet. The jet preferably strikes the centre of the target.

According to a second aspect of the invention, there is provided a nebuliser comprising a liquid entrainment jet that delivers, in use, a jet of gas and entrained liquid via an exit orifice to a target juxtaposed with the exit orifice, wherein the target is part of a component that also defines, at least partly, the exit orifice. The nebuliser according to the second aspect of the invention is advantageous principally because the distance between the exit orifice from which the jet of gas and liquid particles is emitted and the target is constant. Variability of performance between nebulisers and also between uses is therefore reduced considerably.

In order for the nebuliser to emit a jet of gas containing particles of liquid from the exit orifice, a liquid conduit and gas inlet preferably converge at the exit orifice. The gas inlet is preferably in communication, in use, with a gas supply and the liquid conduit is preferably in communication, in use, with a liquid supply. Most preferably, the nebuliser according to the invention includes a liquid reservoir and the liquid conduit preferably extends between the liquid reservoir and the exit orifice.

The gas inlet preferably reduces in cross-sectional area before terminating at the exit orifice. In this case, the velocity of the gas supplied to the gas inlet increases towards the exit orifice so that a relatively high velocity jet of gas is emitted from the exit orifice. Where the liquid conduit converges with the gas inlet at the exit orifice, the high velocity of the gas may be utilised to draw liquid along the liquid conduit towards the exit orifice. This occurs because of the drop in gas pressure caused by the increase in gas velocity according to Bernoulli's principle. Most preferably, therefore, the exit orifice is situated above the level of the liquid in the liquid reservoir during use. Liquid will therefore only be drawn to the exit orifice when gas is being emitted from the exit orifice above a critical velocity.

A preferred arrangement for the nebuliser according to the invention is a nebuliser comprising a liquid reservoir with an upstanding spigot including the gas inlet, and a sleeve received around the upstanding spigot and forming at least part of the exit orifice. The nebuliser preferably includes formations such that when the sleeve is positioned around the spigot, a void is formed between the sleeve and the external surface of the spigot, thereby forming a liquid conduit that extends from the liquid reservoir to the exit orifice.

The sleeve is integrally formed with the target as a single target component. This component is preferably injection moulded in plastics material, such as polypropylene or acrylonitrile-butadiene-styrene (ABS). The target component preferably includes a planar support that joins the sleeve and the target so that the target faces the exit orifice. The normal of the planar support is preferably orientated perpendicularly to the direction of the jet and preferably also to the normal of the target surface. The surface of the target is preferably orientated with its normal parallel to the direction of the jet. The jet preferably strikes the centre of the target surface.

In a preferred embodiment, the spigot includes a plug closely received within the gas inlet, the plug being adapted such that the exit orifice is defined by an external surface of the plug and a facing surface of the target component.

A gas conduit is preferably formed along the length of the plug from the end of the plug remote from the exit orifice to the exit orifice. Most preferably, the gas conduit is defined by an external surface of the plug and an internal surface of the gas inlet. In this case, the gas inlet is preferably of constant cross-section and the cross-sectional area of the gas conduit preferably reduces between the end of the plug remote from the exit orifice and the exit orifice.

The plug may be formed so as to be closely received within the gas inlet save for a recess in the external surface of the plug which defines, along with a surface of the target component, the exit orifice. Most preferably, such a recess extends along the length of the plug, thereby defining, along with a surface of the target component and an internal surface of the gas inlet, the exit orifice and the gas conduit respectively.

Alternatively, the cross-sectional shapes of the plug and the gas inlet may be selected such that the gas conduit is defined by an external surface of the plug and an internal surface of the gas inlet. For instance, the plug may have a particular cross-sectional shape, for example a circularly-shaped cross-section, and the gas inlet may have a correspondingly shaped cross-section but including an enlarged portion within which the gas conduit is defined. Most preferably, the gas inlet has a teardrop-shaped cross-section and the plug has a correspondingly shaped cross-section save for the face of the plug that forms the tip of the teardrop cross-section being flattened. The gas conduit is then generally triangular in cross-section.

The spigot is preferably formed in a relatively rigid plastics material, such as polypropylene or acrylonitrile-butadiene-styrene (ABS), and the plug is preferably formed in a more compliant material, such as an elastomeric material.

The invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawings, in which

Figure 1 is a cross-sectional view of a first embodiment of a nebuliser according to the invention;

Figure 2 is a perspective view of the nebuliser of Figure 1 , partly cut-away;

Figure 3 is a perspective view of the nebuliser of Figures 1 and 2 in a disassembled state;

Figure 4 is a diagrammatic cross-sectional view of part of the assembled nebuliser of Figures 1 to 3, showing hidden detail;

Figure 5 is a close-up perspective view, partly cut away, of that part of the nebuliser that is illustrated in Figure 4;

Figure 6 is a side view of a target component forming part of the nebuliser of Figures 1 to 5; Figure 7 is a perspective view of a second embodiment of a nebuliser according to the invention in a disassembled state;

Figure 8 is a perspective view of the nebuliser of Figure 7 in an assembled state;

Figure 9 is a cross-sectional view of the nebuliser of Figures 7 and 8; and

Figure 10 is a cross-sectional view of a third embodiment of a nebuliser according to the invention.

Figures 1 , 2 and 3 each show a first embodiment of a nebuliser according to the present invention. The nebuliser comprises an inlet component 10, an outlet component 20, a nozzle plug 30 and a target component 40. These four components 10,20,30,40 are formed separately by injection moulding plastics material and then assembling from a disassembled state, as shown in Figure 3, to an assembled state, as shown in Figures 1 and 2. The inlet component 10, outlet component 20 and target component 40 are formed in a relatively rigid plastics material, such as polypropylene or acrylonitrile- butadiene-styrene (ABS), whereas the nozzle plug 30 is formed in a more compliant material, such as an elastomeric material.

The inlet component 10 is generally cylindrical in form with an open upper end, an open lower end and an internal partition 12. The internal partition 12 includes a circular opening from which a generally cylindrical inlet port 14 extends downwards (as shown in Figures 1 , 2 and 3), with a slight taper, to a position approximately level with the lower end of the inlet component 10. The inlet port 14 has an axial bore that extends from the opening of the internal partition 12 to the lower end of the inlet port 14.

A tubular spigot 16 extends upwards from the internal partition 12, co-axially with the inlet port 14, such that the inlet port 14 communicates with the interior of the spigot 16 via the opening of the internal partition 12. The spigot 16 extends to a position just below the upper end of the inlet component 10, and has a constant teardrop-shaped cross-section (best visible in Figure 3) and an open upper end. The walls of the spigot 16 are of constant thickness, and so the internal bore of the spigot 16 is of similar teardrop-shaped cross-section.

The upper rim 18 of the inlet component 10 is bifurcated. The rim 18 comprises inner and outer rims, the latter being of slightly reduced height.

The outlet component 20 is generally cylindrical in form with open upper and lower ends and a double-walled structure. The space between the walls of the outlet component 20 is closed at its upper (as viewed in Figures 1 and 2) end and open at its lower end.

The lower rim 22 of the outer wall is bifurcated and adapted to engage with the upper rim 18 of the inlet component 10. The lower rim 22 comprises an inner rim that engages, with a snap-fit, the inner rim of the upper rim 18, and an outer rim that abuts the outer rim of upper rim 18 when the inlet component 10 and outlet component 20 are so engaged. The inlet and outlet components 10,20 may therefore be engaged and disengaged, with a snap fit, as required.

The nozzle plug 30 has a generally teardrop-shaped cross-section similar to (but smaller in dimension than) that of the spigot 16. The plug 30 has a circular rounded head 32 and an outwardly extending flange located a small distance below the head 32. The face of the plug 30 at the tip of its teardrop- shaped cross-section is flattened and tapered towards its lower end (as viewed in Figures 1 , 2 and 3). The plug 30 is formed so as to be closely received on all sides, save for the flattened face, by the spigot 16 with the flange abutting the top edge of the spigot 16. When the nozzle plug 30 and spigot 16 are engaged, a channel 38 is defined by the flattened face of the nozzle plug 30 and the internal surface of the spigot 16. Due to the taper of the nozzle plug 30, the channel 38 gradually reduces in cross-sectional area towards its upper end. The flattened face of the plug 30 also includes a recess 36 that is level with the flange. The recess 36 extends across the width of the flattened face of the plug 30, and has a flat lower surface and a curved upper surface.

The target component 40 comprises a sleeve 42, an outwardly projecting flange 44 at the lower end of the sleeve 42, and a target 46. The sleeve 42 and flange 44 are arranged so that the spigot 16, with the plug 30 engaged, is received within the sleeve 42 and the flange 44 is aligned alongside the upper surface of the internal partition 12. The upper end of the sleeve 42 has an inwardly projecting lip which rests upon the flange of the plug 30. The upper end of the sleeve 42 fits closely around the nozzle plug 30, save for an opening that constitutes a nozzle 39 and is in registration with the upper end of the channel 38.

The lower end of the sleeve 42 is formed with an arcuate spacer 43 that projects below the flange 44 and maintains the lower surface of the flange 44 a small distance away from the upper surface of the internal partition 12, as shown in Figure 1. The sleeve 42 has an enlarged portion adjacent the side of the spigot 16 that encloses the channel 38. The arcuate spacer 43 does not extend into the enlarged portion of the sleeve 42 so that a fluid conduit is formed that extends from the space between the flange 44 and the internal partition 12, up the side of the spigot 16 that is enclosed by the enlarged portion, between the upper end of the spigot 16 wall and the underside of the lip of the sleeve 42, and into the recess 36 and the part of the channel 38 that is adjacent the recess 36.

The enlarged portion of the sleeve 42 and the recess 36 are formed so that fluid can be drawn into the channel 38 from all directions. The arrangement of the recess 36, channel 38 and fluid conduit can be seen more clearly in Figures 4 and 5.

The target 46 has the form of a disc with a convex lower surface that is held a short distance above the nozzle 39 by a support 48. The support 48 comprises a pair of planar arms that extend from the sleeve 42 at diametrically opposite sides thereof, as shown in Figure 6. The support 48 is arranged with its normal orientated perpendicularly to the direction faced by the nozzle 39. The target 46 is formed on the lower edge of the support 48 and is arranged so that the nozzle 39 faces the centre of the lower surface of the target 46. By virtue of the fact that the nozzle 39 is defined partly by the upper end of the sleeve 42 and the position of the target 46 relative to the upper end of the sleeve 42 is fixed by the support 48, the separation of the nozzle 39 and target 46 is constant.

In use, the nebuliser is maintained in an upright position, as shown in Figures 1 , 2 and 3, and the volume defined by the upper surface of the internal partition 12, the exterior surface of the sleeve 42 and the interior surface of the inlet component 10 contains a reservoir of drug in solution. Drugs typically used in nebulisers include bronchodilators such as salbutamol or terbutaline; anticholinergics such as ipratropium bromide; anti-inflammatories including corticosteroids, such as budesonide; and other anti-allergies, such as sodium cromoglycate.

The upper end of the outlet component 20 is connected to a means for supplying gas to a patient, such as a face mask, and the inlet port 14 of the inlet component 10 is connected to a pressurised supply of a gas such as air or oxygen. In use, the pressurised gas passes through the inlet port 14, through the spigot 16 (indicated by arrow 50 in Figure 4), and along channel 38. Since channel 38 gradually reduces in cross-sectional area, the velocity of the gas will increase, thereby creating a region of low pressure. Drug solution will therefore be drawn up through the fluid conduit (indicated by arrow 52 in Figure 4) towards the channel 38 where it will be entrained by the gas, and a mixture of gas and drug solution will exit the nozzle 39 as a jet (indicated by arrow 54 in Figure 4). The jet typically contains drug solution particles with a diameter of between 10 and 10Oμm. The jet of gas and drug solution will then strike the centre of the target 46. This causes some of the drug solution particles to fragment into smaller particles of between 1 and 10μm diameter. These smaller particles will then be carried by the flow of air to the patient while the larger particles will strike the walls of the nebuliser and fall back into the reservoir of drug solution.

After use, the nebuliser can be separated from the face mask and the outlet component 20 removed from the inlet component 10 to permit replenishment of the drug solution held within, the latter. If necessary, the nebuliser can be completely disassembled for cleaning and/or sterilisation by removal of the target component 40 and nozzle plug 30. The nebuliser is reassembled by fitting of the plug 30 into the spigot 16, followed by the placement of the target component 40 over the spigot 16 until the lower end of the sleeve 42

(specifically the spacer 43) abuts the internal partition 12 and the upper end of the sleeve 42 seats around the upper part of the plug 30.

Figures 7, 8 and 9 show a second embodiment of a nebuliser according to the invention, which is generally designated 100. The second embodiment 100 is substantially similar to the first embodiment shown in Figures 1 to 6 and comprises an inlet component 110, an outlet component 120, a nozzle plug 130 and a target component 140. However, the second embodiment 100 includes a number of additional features that are described in detail below.

A hinge 119 extends between the upper rim 118 of the inlet component 110 and the lower rim 122 of the outlet component 120 (as viewed in Figures 8 and 9). The hinge 119 is arranged such that the inlet and outlet components 110,120 are rotatable relative to one another, through 180°, bringing the upper and lower rims 118,122 into, and out of, engagement with one another.

The inlet and outlet components 110,120 are formed as a single component in both a rigid plastics material, and a more compliant material, preferably by a two-shot injection moulding process. In particular, the upper rim 118 of the inlet component 110, the lower rim 122 of the outlet component 120 and the hinge 119 are formed in the more compliant material, and the remainder of the inlet and outlet components 110,120 are formed in the rigid plastics material. The rigid plastics material is preferably a material that bonds weakly with water molecules, and in particular a material for which the adhesive forces between the water molecules of the drug solution and the rigid plastics material are weak, so that larger particles of solution run down into the reservoir, rather than adhering to the walls.

The two-shot injection moulding process involves injection moulding the rigid plastics material and subsequently injection moulding the more compliant material onto the rigid plastics material so that the two materials are integrally bonded. Once the inlet and outlet components 110,120, the nozzle plug 130 and the target component 140 have been moulded, the second embodiment 100 is assembled from a disassembled state, as shown in Figure 7, to an assembled state, as shown in Figures 8 and 9, in a similar manner to the first embodiment save for the inlet and outlet components 110,120 being rotatable relative to one another about the hinge 119.

The hinge 119 comprises a rectangular and generally planar strip of material extending between the upper rim 118 and lower rim 122 of the inlet component 110 and outlet component 120 respectively. The hinge 119 includes a transverse region which is of greatly reduced thickness such that the inlet and outlet components 110,120 can hinge about this region. The hinge 119 is preferably adapted to provide a positive opening and shutting action.

The second embodiment 100 also includes a volume indicator 121 which extends downwards along the length of the inlet component from the upper rim 118. The volume indicator 121 includes a volume scale so that the volume of drug solution present in the upright nebuliser 100 is immediately identifiable.

A final additional feature of the second embodiment 100 is the baffle 127 that extends across the majority of the opening defined by the lower edge of the inner wall of the outlet component 120. The baffle 127 has a diametrically extending opening that accommodates the upper part of the support 148 of the target component 140, and allows gas and entrained drug solution to exit the nebuliser 100. The baffle 127 ensures that only drug solution particles small enough to be carried by the air stream within the nebuliser 100 and through the baffle opening can exit the nebuliser 100, thereby reducing the likelihood of any larger particles of drug solution exiting the nebuliser 100.

Figure 10 shows a third embodiment of a nebuliser according to the invention, which is generally designated 200. The third embodiment 200 is substantially similar to the second embodiment 100 shown in Figures 7 to 9 and comprises an inlet component 210, an outlet component 220, a nozzle plug 230 and a target component 240. However, the third embodiment 200 is adapted to have a lower residual volume of drug solution than the second embodiment 100. By "residual volume" is meant the volume of drug solution present in the reservoir below which the nebuliser will fail.

In particular, the internal partition 212 upon which the target component 240 rests has an inclined outer portion extending away from the target component 240. For this reason, the target component 240 of the third embodiment 200 has an elongated sleeve 242 and lacks the outwardly projecting flange 44 of the first embodiment. The internal partition 212 is arranged so that the target component 240 rests upon a near central flat portion and the inclined outer portion has the form of a funnel so that drug solution is directed towards the near central flat portion of the internal partition 212. The inclined outer portion has an inclination of approximately 45° to the longitudinal axis of the nebuliser 200. Since the sleeve 242 of the target component 240 is elongated, the inlet component 210 of the third embodiment 200 is of greater height than that of the second embodiment 100.

The third embodiment 200 has a residual volume of approximately 0.3ml which is lower than the residual volume of the second embodiment 100 of approximately 0.8ml. However, the third embodiment 200 is of greater height (approximately 72mm) than the second embodiment 100 (approximately

63mm). In addition, as is clear from Figures 9 and 10, the second embodiment 100 is able to work when inclined up to 90° from its upright position whereas the third embodiment 200 is only able to work when inclined up to 45° from its upright position.

The second and third embodiments 100,200 are used in a similar manner to the first embodiment, as outlined above.

Claims

Claims

1. Medical apparatus having means for forming a jet of fluid, said means comprising a fluid passageway and a plug closely received therewithin, the plug providing an incomplete closure of the fluid passageway such that a fluid conduit is defined by a surface of the plug and a facing surface of the fluid passageway.

2. Medical apparatus as claimed in Claim 1 , wherein the fluid conduit extends along the length of the plug.

3. Medical apparatus as claimed in Claim 1 or Claim 2, wherein the plug is formed so as to be closely received within the fluid passageway save for a recess in the external surface of the plug which defines, along with an internal surface of the fluid passageway, the fluid conduit.

4. Medical apparatus as claimed in Claim 1 or Claim 2, wherein the cross- sectional shapes of the plug and the fluid passageway are selected such that the fluid conduit is defined by an external surface of the plug and an internal surface of the passageway.

5. Medical apparatus as claimed in Claim 4, wherein the plug has a particular cross-sectional shape, and the fluid passageway has a correspondingly shaped cross-section but including an enlarged portion within which the fluid conduit is defined.

6. Medical apparatus as claimed in Claim 4 or Claim 5, wherein the fluid passageway has a teardrop-shaped cross-section and the plug has a correspondingly shaped cross-section save for the face of the plug that forms the tip of the teardrop cross-section being flattened.

7. Medical apparatus as claimed in any preceding claim, wherein the fluid passageway is formed in a relatively rigid plastics material and the plug is formed in a more compliant material.

8. Medical apparatus as claimed in any preceding claim, wherein the medical apparatus is a nebuliser comprising a liquid entrainment jet that delivers, in use, a jet of gas and entrained liquid via an exit orifice to a target juxtaposed with the exit orifice.

9. Medical apparatus as claimed in Claim 8, wherein the target is part of a component that also defines, at least partly, the exit orifice.

10. Medical apparatus as claimed in Claim 8 or Claim 9, wherein a liquid conduit converges with the fluid conduit at the exit orifice, the fluid conduit being in communication, in use, with a gas supply and the liquid conduit being in communication, in use, with a liquid supply.

11. Medical apparatus as claimed in Claim 10, wherein the nebuliser includes a liquid reservoir and the liquid conduit extends between the liquid reservoir and the exit orifice.

12. Medical apparatus as claimed in any one of Claims 8 to 11 , wherein the fluid conduit reduces in cross-sectional area before terminating at the exit orifice.

13. Medical apparatus as claimed in Claim 12, wherein the fluid passageway is of constant cross-section and the cross-sectional area of the plug increases from one end to the other.

14. Medical apparatus as claimed in Claim 12 or Claim 13, wherein the velocity of the gas supplied to the fluid conduit increases towards the exit orifice so that a relatively high velocity jet of gas is emitted from the exit orifice and the gas draws liquid along the liquid conduit towards the exit orifice when gas is being emitted from the exit orifice above a critical velocity.

15. Medical apparatus as claimed in any one of Claims 8 to 14, wherein the nebuliser comprises a liquid reservoir with an upstanding spigot including the fluid passageway, the plug being closely received within an open end of the fluid passageway, a sleeve being disposed around the upstanding spigot, and the spigot, plug and sleeve being arranged to together form the fluid conduit and exit orifice.

16. Medical apparatus as claimed in Claim 15, wherein the nebuliser includes formations such that when the sleeve is positioned around the spigot, a void is formed between the sleeve and the external surface of the spigot, thereby forming a liquid conduit that extends from the liquid reservoir to the exit orifice.

17. Medical apparatus as claimed in Claim 15 or Claim 16, wherein the sleeve is integrally formed with the target as a single target component.

18. Medical apparatus as claimed in Claim 17, wherein the target component is injection moulded in plastics material.

19. Medical apparatus as claimed in Claim 17 or Claim 18, wherein the target component includes a planar support that joins the sleeve and the target so that the target faces the exit orifice.

20. Medical apparatus as claimed in Claim 19, wherein the normal of the planar support is orientated perpendicularly to the direction of the jet.

21. Medical apparatus as claimed in any one of Claims 8 to 20, wherein the surface of the target is orientated with its normal parallel to the direction of the jet.

22. Medical apparatus as claimed in any one of Claims 8 to 21 , wherein the jet strikes the centre of the target.

23. A nebuliser comprising a liquid entrainment jet that delivers, in use, a jet of gas and entrained liquid via an exit orifice to a target juxtaposed with the exit orifice, wherein the target is part of a component that also defines, at least partly, the exit orifice.

24. A nebuliser as claimed in Claim 23, wherein the nebuliser comprises a liquid conduit and gas inlet that converge at the exit orifice, the gas inlet being in communication, in use, with a gas supply and the liquid conduit being in communication, in use, with a liquid supply.

25. A nebuliser as claimed in Claim 24, wherein the nebuliser according to the invention includes a liquid reservoir and the liquid conduit extends between the liquid reservoir and the exit orifice.

26. A nebuliser as claimed in Claim 24 or Claim 25, wherein the gas inlet reduces in cross-sectional area before terminating at the exit orifice.

27. A nebuliser as claimed in Claim 26, wherein the velocity of the gas supplied to the gas inlet increases towards the exit orifice so that a relatively high velocity jet of gas is emitted from the exit orifice and the gas draws liquid along the liquid conduit towards the exit orifice when gas is being emitted from the exit orifice above a critical velocity.

28. A nebuliser as claimed in any one of Claims 23 to 27, wherein the surface of the target is orientated with its normal parallel to the direction of the jet.

29. A nebuliser as claimed in any one of Claims 23 to 28, wherein the jet strikes the centre of the target.

30. A nebuliser as claimed in any one of Claims 23 to 29, wherein the nebuliser comprises a liquid reservoir with an upstanding spigot including the gas inlet, and a sleeve received around the upstanding spigot and forming at least part of the exit orifice.

31. A nebuliser as claimed in Claim 30, wherein the nebuliser includes formations such that when the sleeve is positioned around the spigot, a void is formed between the sleeve and the external surface of the spigot, thereby forming a liquid conduit that extends from the liquid reservoir to the exit orifice.

32. A nebuliser as claimed in Claim 30 or Claim 31 , wherein the sleeve is integrally formed with the target as a single target component.

33. A nebuliser as claimed in Claim 32, wherein the target component is injection moulded in plastics material.

34. A nebuliser as claimed in Claim 32 or Claim 33, wherein the target component includes a planar support that joins the sleeve and the target so that the target faces the exit orifice.

35. A nebuliser as claimed in Claim 34, wherein the normal of the planar support is orientated perpendicularly to the direction of the jet.

36. A nebuliser as claimed in any one of Claims 32 to 35, wherein the spigot includes a plug closely received within the gas inlet, the plug being adapted such that the exit orifice is defined by an external surface of the plug and a facing surface of the target component.

37. A nebuliser as claimed in Claim 36, wherein a gas conduit is formed along the length of the plug from the end of the plug remote from the exit orifice to the exit orifice, the gas conduit being defined by an external surface of the plug and an internal surface of the gas inlet.

38. A nebuliser as claimed in Claim 37, wherein the gas inlet is of constant cross-section and the cross-sectional area of the gas conduit reduces between the end of the plug remote from the exit orifice and the exit orifice.

39. A nebuliser as claimed in Claim 37 or Claim 38, wherein the plug is formed so as to be closely received within the gas inlet save for a recess in the external surface of the plug which defines, along with a surface of the target component, the exit orifice.

40. A nebuliser as claimed in Claim 39, wherein the recess extends along the length of the plug, thereby defining, along with a surface of the target component and an internal surface of the gas inlet, the exit orifice and the gas conduit respectively.

41. A nebuliser as claimed in Claim 37 or Claim 38, wherein the cross- sectional shapes of the plug and the gas inlet are selected such that the gas conduit is defined by an external surface of the plug and an internal surface of the gas inlet.

42. A nebuliser as claimed in Claim 41 , wherein the plug has a particular cross-sectional shape, and the gas inlet has a correspondingly shaped cross- section but including an enlarged portion within which the gas conduit is defined.

43. A nebuliser as claimed in Claim 41 or Claim 42, wherein the gas inlet has a teardrop-shaped cross-section and the plug has a correspondingly shaped cross-section save for the face of the plug that forms the tip of the teardrop cross-section being flattened.

44. A nebuliser as claimed in any one of Claims 30 to 43, wherein the spigot is formed in a relatively rigid plastics material and the plug is formed in a more compliant material.