GB2470188A

GB2470188A - Dispensing apparatus dose counters

Info

Publication number: GB2470188A
Application number: GB0908058A
Authority: GB
Inventors: Richard Warby
Original assignee: Consort Medical Ltd
Current assignee: Consort Medical Ltd
Priority date: 2009-05-11
Filing date: 2009-05-11
Publication date: 2010-11-17
Anticipated expiration: 2029-05-11
Also published as: GB0908058D0; GB2470188B

Abstract

A dispensing apparatus comprising an actuator and a metered dose inhaler; the actuator comprising a housing with a valve stem receiving block with an outlet duct27and a flexible wall portion35; the metered dose inhaler comprising a container and a metering valve, the metering valve comprising a valve stem having a valve stem outlet, the container containing a product, the metered dose inhaler being receivable in the housing part such that the valve stem is received in the valve stem receiving block, such that, in use, actuation of the metering valve causes a metered dose of the product to be dispensed from the valve stem outlet into the valve stem receiving block from where it is directed to be dispensed out of the outlet duct27; wherein the dispensing apparatus further comprises a dose counter comprising a switch with first and second switch elements31,32, a display40for displaying an indication of the number of doses remaining or number of doses dispensed from the metered dose inhaler and a power source for providing power to the display; wherein the flexible wall portion35of the valve stem receiving block comprises the first switch element.

Description

Improvements in or relating to dispensing apparatus and dose counters The present invention relates to improvements in dispensing apparatus and dose counters. In particular it relates to dispensing apparatus for dispensing metered doses of product where the number of doses dispensed from a dispensing container or remaining within the dispensing container must be monitored.

It is known to provide dispensing apparatus with a dose counter in order to provide an indication of the number of doses dispensed from or remaining in a dispensing container.

For example, in the field of medicament dispensers it is known to provide metered dose inhalers (MDIs) with a dose counter to monitor the number of doses dispensed or remaining. The dose counter may be a mechanical counter which relies on the movement of a mechanism (driven by movement of the dispensing container) to incrementally move a dose indicator such as one or more annular counter rings.

A disadvantage with mechanical dose counters is that the mechanisms can be complicated to design and manufacture and tolerances must be kept under tight control to ensure consistent and accurate operation throughout the lifetime of the dispensing apparatus.

As an alternative to purely mechanical dose counters it has been proposed to provide an electro-mechanical dose counter for I4DIs. In one type of electro-mechanical counter described in EP0684047 a mechanical arm, driven in sync with the dispensing apparatus, is used to actuate a switch of an electronic counter. A disadvantage with such a design is that actuation of the counter is not directly linked to dispensation of a metered dose. Variation in the dimensions of the manufactured valves can lead to a situation where the mechanical arm actuates the counter before the metering valve valve stem is actuated or vice versa. This can lead to over or under counting which is undesirable.

Another design described in US5676129 utilises a miniature pressure sensor mounted to the valve stem receiving block of an MDI to detect when the actual dose of product is dispensed. A disadvantage with this design is the need to incorporate a microprocessor and use of sophisticated software to correctly analyse the detected signals to determine when a dose has been discharged.

It is an object of the present invention to provide an improved means for counting dispensation of doses of product, in particular counting of metered doses of product from medicament dispensers such as MDIs.

Accordingly, the present invention provides dispensing apparatus comprising an actuator and a metered dose inhaler; the actuator comprising a housing part, a valve stem receiving block and an outlet duct; the metered dose inhaler comprising a container and a metering valve, the metering valve comprising a valve stem having a valve stem outlet, the container containing a product, the metered dose inhaler being receivable in the housing part such that the valve stem is received in the valve stem receiving block, such that, in use, actuation of the metering valve causes a metered dose of the product to be dispensed from the valve stem outlet into the valve stem receiving block from where it is directed to be dispensed out of the outlet duct; wherein the dispensing apparatus further comprises a dose counter comprising a switch, a display for displaying an indication of the number of doses remaining or number of doses dispensed from the metered dose inhaler and a power source for providing power to the display; wherein actuation, in use, of the switch causes the indication of the number of doses of the display to be updated; characterised in that the switch is actuatable by the pneumatic force produced by each metered dose of product as it is dispensed.

Advantageously, the dose counter is actuated by the force of the dispensed dose itself. Thus, a direct count of dispensed doses is achieved which avoids the problems of over-or under-counting. The manufacturing tolerances of the valve stem of the metering valve or of the valve stem receiving block are not critical to correct operation. This makes the manufacture of these parts much simpler.

Typically, the product dispensed by the dispensing apparatus will be a product that prior to dispensation is in a liquefied form and comprises a volatile propellant and an active ingredient which may be, for example, in solution or suspension within the propellant. On actuation of the metering valve the propellant boils off and is discharged through the valve stem receiving block in the form of a gas stream. The gas stream carries with it the previously solubilised or suspended active ingredient. Thus it will be understood that the pneumatic force used to actuate the switch of the present invention is mainly derived from the passage of the still relatively pressurised gas stream (including the active ingredient particles) In one embodiment the switch is a proximity switch comprising a first element and a second element which are moveable relative to one another to actuate the switch, wherein the movement of the first and/or second element is by the pneumatic force produced by each metered dose of product as it is dispensed. For example, the proximity switch may be a Hall effect switch. This embodiment provides a simple arrangement that does not require complicated sensing arrangements or sophisticated signal processing.

In another embodiment, the switch may comprise a first element and a second element which are movable between an open position in which the first and second elements are separated and a closed position in which the first and second elements contact one another to actuate the switch, wherein the first and second elements are movable into the closed position by the pneumatic force produced by each metered dose of product as it is dispensed.

This embodiment thus provides a mechanically simple mechanism for counting dose dispensations that does not require expensive or complicated sensor arrangements nor sophisticated processor control.

The first element may be movable by the pneumatic force produced by each metered dose of product as it is dispensed.

In this case, preferably the second element is static.

The first element is preferably mounted in a flexible mounting.

In one aspect the valve stem receiving block comprises an inlet aperture, an outlet aperture and a transfer duct connecting the inlet aperture to the outlet aperture, wherein the inlet aperture receives, in use, the valve stem of the metered dose inhaler and the outlet aperture directs the dispensed product into the outlet duct, wherein the flexible mounting comprises at least a portion of an internal wall of the transfer duct.

The valve stem receiving block may contains a portion of the switch.

The valve stem receiving block may contain the first element and the second element of the switch.

The valve stem receiving block may be formed separately from the housing part of the actuator and assembled thereto.

This option can simplify assembly of the dispensing apparatus.

Preferably the flexible mounting comprises an element formed from a thermoplastic or thermoplastic elastomer. A non-exhaustive list of suitable elastomers include low density polyethylene, Santoprene� TPE, Hytrel� TPE, Thermoflex� TPE and Kraton� TPE.

The present invention also provides an actuator comprising a housing part, a valve stem receiving block and an outlet duct; wherein the actuator further comprises a dose counter comprising a switch, a display for displaying an indication of the number of doses remaining or number of doses dispensed from a metered dose inhaler and a power source for providing power to the display; wherein actuation, in use, of the switch causes the indication of the number of doses of the display to be updated; characterised in that the switch is actuatable by a pneumatic force.

The switch may be a proximity switch comprising a first element and a second element which are moveable relative to one another to actuate the switch, wherein the movement of the first and/or second element is by the pneumatic force.

An example is a Hall effect switch.

Alternatively, the switch may comprise a first element and a second element which are movable between an open position in which the first and second elements are separated and a closed position in which the first and second elements contact one another to actuate the switch, wherein the first and second elements are movable into the closed position by the pneumatic force.

For both the embodiments described above, the display may be an LCD and the power source may be a battery.

However, other sources of power such as electro-mechanical generators and solar cells may be utilised.

The present invention further provides a dose counter mechanism comprising a duct having an inlet, an outlet and a conduit connecting the inlet to the outlet, the conduit being predominantly formed from a rigid material and additionally comprising a flexible wall portion formed from a flexible material; wherein said flexible wall portion comprises a first switch element; wherein a second switch element is provided outside the conduit; wherein, in use, a metered dose of pressurised gas received through the inlet is conveyed to the outlet whilst causing flexure of the flexible wall portion of the conduit to move the first switch element relative to the second switch element in order to actuate a switch.

The first and second elements may form a proximity switch such as a Hall effect switch.

Alternatively, the first and second elements may be brought into contact with each other by flexure of the flexible wall portion in order to actuate the switch.

The flexible wall portion may be formed from a element made of a thermoplastic or thermoplastic elastomer of the types described above.

The first switch element may be mounted to an outer face of the flexible wall portion such that an inner face of the flexible wall portion exposed to product passing through the conduit is free of obstructions.

Advantageously, the absence of any obstructions avoids the likelihood of additional product deposition on the surfaces of the conduit. In addition, the flow characteristics of the product through the conduit are unaffected by the presence of the flexible portion of wall.

The conduit may comprise a transfer duct of a valve stem receiving block of an actuator.

The flexible wall portion may be located at a base of a sump of the transfer duct. Alternatively, the flexible wall portion may be located in a side wall of the transfer duct located opposite the outlet of the conduit.

The present invention further provides a method of counting doses dispensed from a dispensing apparatus of the type comprising an actuator and a metered dose inhaler, comprising the steps of: providing the actuator with a conduit for receiving product dispensed by the metered dose inhaler, the conduit comprising a flexible element; actuating the metered dose inhaler to dispense a metered dose of product into the conduit of the actuator thereby causing flexure of the flexible element; detecting flexure of the flexible element; on detection of flexure of the flexible element updating a display indicative of a count of doses.

The method may further comprise use of a switch to detect flexure of the flexible element.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a part of a dose counter mechanism according to the present invention; Figure 2 is a cross-sectional view of a first embodiment of dispensing apparatus incorporating a dose counter according to the present invention; Figure 2A is an enlarged cross-sectional view of a part of the switch of the dispensing apparatus of Figure 2; Figure 3 is a cross-sectional view of a second embodiment of dispensing apparatus incorporating a dose counter according to the present invention; and Figure 4 is a cross-sectional view of a third embodiment of dispensing apparatus incorporating a dose counter according to the present invention.

As shown in Figure 1, the dose counter mechanism of the present invention comprises in part a duct 1 having an inlet 2 and an outlet 3 at opposed ends. The duct 1 defines a conduit for pressurised gas that is input at the inlet 2 and is output at the outlet 3.

The duct 1 is predominantly formed from a tubular portion 11 formed of a rigid material having an internal surface 10. However, a portion of the duct 1 is formed from a flexible member 5 which defines a portion of the wall of the duct 1. The flexible member 5 is for example a block of thermoplastic elastomer having an inner face 9 and an outer face 8. The inner face 9 is formed flush with the internal surface 10 of the tubular portion 11.

The flexible member 5 is bonded to, or otherwise coupled in a fluid-tight manner to the tubular portion 11 50 that the overall conduit is fluid tight such that all fluid entering the inlet 2 is conveyed to the outlet 3.

The thickness of the flexible member 5 in the radial dimension is relatively thin.

The outer face 8 of the flexible member 5 has bonded or coupled thereto a first switch element or contact 6 formed from a metallic material such as copper or a magnetic material depending on the type of switch to be utilised as will be described below.

In use, pressurised fluid, in the form of a pressurised gas carrying therein an active ingredient passes through the conduit from inlet 2 to outlet 3. The increase in pressure within the conduit that results causes the flexible member 5 to flex radially outwardly causing the first switch element 6 to move in a direction perpendicular to the conduit as depicted by arrow 7 in Figure 1. This movement of the first switch element 6 can be utilised as part of a switching circuit as will be described below in more detail. Once the gas stream has passed through the duct the pressure therein will fall and the flexible member 5 will recover to its original state due to its inherent elasticity.

As shown in Figure 2, a first embodiment incorporating a dose counter according to the present invention comprises an actuator 20 which comprises a cylindrical housing part 21, a valve stem receiving block 22 and a mouthpiece 23.

The cylindrical housing part 21 is provided with an open upper end 24 through which in use can be received a pressurised dispensing container. The valve stem receiving -10 -block 22 is located at a lower end of the cylindrical housing part 21. The mouthpiece 23 depends off the lower end of the cylindrical housing part 21 and forms an outlet duct of the actuator 20. The valve stem receiving block 22 as is well known in the art comprises a generally cylindrical rigid body 25. An upper part of the body 25 is provided with a bore 26 which is aligned with the longitudinal axis of the cylindrical housing part 21. An outlet orifice 27 is provided in a side wall of the body 25 directed towards the mouthpiece 23. In use, a pressurised dispensing container (not shown) is received in the cylindrical housing part 21 of the actuator 20 such that a valve stem of the pressurised dispensing container is received as an interference fit in the bore 26 of the valve stem receiving block 22.

Also, as known in the art, actuation of the pressurised dispensing container results in a metered dose of product being dispensed from the valve stem into the cylindrical bore 26 of the valve stem receiving block 22. The product, which at this stage is still pressurised relative to atmosphere, is discharged through the outlet orifice 27 into the outlet duct of the mouthpiece 23. Preferably the shape and size of the outlet orifice 27 are chosen to provide the necessary spray pattern to the discharged product.

Typically, this will result in aerosolisation of the product which is desirable for subsequent inhalation of the product by a user.

According to the present invention the actuator of Figure 2 is provided with a dose counter mechanism. The dose counter mechanism comprises a switch 30, a display in the form of a liquid crystal display (LCD) 40 and a battery acting as a power source for the dose counter mechanism.

-11 -The switch 30 comprises a switch housing 33 which is received in a recess 28 in a lower part of the body 25 of the valve stem receiving block 22. The body 25 of the valve stem receiving block comprises a bore 38 extending between the recess 28 and the bore 26.

The switch housing 33 comprises a cylindrical body 34 formed from a rigid material such as acetal or polyester and having an aperture 39 in a lower end thereof. A second switch element in the form of a contact 32 is received in the aperture 39. The second switch contact 32 remains static in use relative to the switch housing 33. An upper end of the switch housing body 34 is open and is closed in use by a flexible part 35 formed from a thermoplastic or thermoplastic elastomer such as low density polyethylene, Santoprene� TPE, Hytrel� TPE, Thermoflex� TPE and Kraton� TPE. The flexible part 35 is affixed around its periphery to the upper rim of the switch housing body 34 as most clearly shown in the enlarged Figure 2A. The flexible part is in the form of a disc-shaped member having an upwardly projecting central projection 36. In addition, a centrally-located recess 37 is formed on an under side face of the disc-shaped part. A first switch element in the form of a contact 31 is mounted in the recess 37. The first switch contact 31 may be mounted or affixed to the flexible part 35 by any suitable means such as co-moulding, adhesive or simply an interference friction fit. As can be seen most clearly from Figure 2A, when the switch housing 33 is assembled with the valve stem receiving block 22 the upstanding projection 36 is received as a sliding fit within bore 38 of the valve stem receiving block housing 25. As such, an upper face 29 of the upstanding projection 36 is exposed to the interior of the bore 26 of the valve stem -12 -receiving block 22. In the rest position of Figure 2 the upper face 29 is flush with the inner surface of the bore 26.

As can be seen from Figure 2, with the first switch contact 31 mounted in the flexible part 35 and the second switch contact 32 mounted in the bore 39, the first and second switch contacts 31 and 32 are aligned along a common axis. Figure 2 shows the switch 30 in the rest position wherein there exists a small air gap between the distal ends of the first switch contact 31 and second switch contact 32.

The dose counter mechanism further comprises a housing 51 which may be mounted or affixed to the exterior of the actuator housing or may form an integral part therewith.

The housing 51 contains the battery 50, the LCD display 40 and any other parts of the dose counter mechanism that may be required. The first and second switch contacts 31, 32 are interconnected with the battery 50 and LCD display 40 in a manner well known in the art. Thus, the dose counter mechanism comprises an electrical switching circuit comprising the essential elements of a switch 30, a power source 50 and a display means 40. The display means 40 may be an LCD unit such as the SUB-CUB 1 unit manufactured by Red Lion Controls Inc. of York, PA, USA. Preferably the apparatus includes a 555 monostable circuit to prevent bounce or chatter of the switching signal.

In use, a pressurised dispensing container such as a metered dose inhaler is received in the actuator 20 with the valve stem of the MDI received in the bore 26 of the valve stem receiving block 22. Each actuation of the pressurised dispensing container results in the discharge of a single metered dose of product into the bore 26 and out of the discharge outlet 27 of the valve stem receiving block 22.

-13 -During passage of the pressurised gas (containing active ingredient) through the bore 26, the pressure within the bore 26 will rise. As shown in Figure 2A, as a result of the pressure rise, the upstanding projection 36 of the flexible member 35 will be displaced downwardly within bore 38 due to the increased pressure acting on upper face 29.

Downward movement of the upstanding projection 36 is accommodated by flexure of the disc-shaped part of the flexible part 35 as shown in Figure 2A. Consequently, the first switch contact 31 is brought into electrical contact with the second switch contact 32 closing the switching circuit of the dose counter mechanism. At this point the dose count indication displayed on the LCD display 40 is updated.

The dose indication on the LCD display 40 may be a numerical count of the doses remaining in the pressurised dispensing container or the number of doses dispensed from the pressured dispensing container. Where the dose indication is a numerical count then each closure of the switching circuit results in the count being incremented or decremented. However the dose indication of the LCD display may be of another type, for example a graphical indication may be provided such as a plurality of bars which may all be displayed when the dispensing container is full and may be gradually reduced in number as the dispensing container is emptied. The skilled person will understand that any such method of displaying the dose count information to the user is applicable in the present invention.

Once the pressurised gas of the metered dose of product has been discharged through the outlet orifice 27 of the valve stem receiving block 22, the pressure within the bore -14 - 26 returns to atmospheric at which point the upstanding projection 36 resiliently recovers its position due to the inherent elasticity of the thermoplastic elastomer forming the flexible part 35. Thus, the electrical contact between the first switch contact 31 and the second switch contact 32 is broken.

The dose counter mechanism may incorporate means for preventing false multiple counts on each closure of the switch, known as contact bounce' or chatter' such as the 555 monostable circuit mentioned above.

Figure 3 shows a second embodiment of actuator incorporating a dose counter mechanism according to the present invention with many similarities to the embodiment shown in Figures 2 and 2A. Similar components have been referenced with the same reference numerals. In this embodiment the switch 30 is similar to the switch 30 of Figure 2 and again comprises a static second switch contact 32 and a movable first switch contact 31. As before the static second switch contact 32 is mounted in an aperture of a switch housing 33 formed from a relatively rigid material.

Again, the movable first switch contact 31 is mounted in a flexible member 35 formed from a thermoplastic or thermoplastic elastomer. Unlike the embodiment of Figure 2, in this embodiment the switch housing 33 is located in a lower part of the cylindrical housing part 21 of the actuator 20 and is orientated generally horizontally such that the flexible member 35 forms a part of the side wall of the bore 26 opposite the outlet orifice 27. Also in this case, the flexible part 35 is not provided with an upstanding projection 36. Rather, the upper face 29 of the flexible part 35 is substantially free of obstructions and is mounted in the body 25 of the valve stem receiving block -15 - 22 to be flush with the inner surface of the bore 26. An advantage of this arrangement is that the upper face 29 of the flexible part 35 may form a relatively large part of the internal surface area of the bore 26 resulting in increased flexure during operation.

Operation of the switch 30 is substantially the same as that of the embodiment of Figure 2 in that discharge of pressurised gas through the bore 26 results in flexure of the flexible part 35 which brings the first switch contact 31 into contact with the second switch contact 32.

An advantage of the arrangement of Figure 3 is that it is easier to provide a larger surface area of the flexible part 35 in contact with the pressurised gas contained in the bore 26. Thus, for a particular pressure within the bore 26, a greater degree of flexure can be produced in the flexible part 35.

It can also be seen from Figure 3 that in this embodiment the body 25 of the valve stem receiving block 22 is formed as a separate component from the remainder of the housing part 21 and mouthpiece 23. The actuator 20 is provided with an aperture 60 through which the separately moulded valve stem receiving block 22 can be inserted and affixed by any suitable means such as ultrasonic welding, adhesive or snap fit projections. This arrangement can ease assembly of the apparatus and in particular moulding of the valve stem receiving block 22 which in this embodiment requires moulding of the bore 26, outlet orifice 27 and an aperture for receiving the flexible part 35.

Figure 4 illustrates a third embodiment of dispensing apparatus according to the invention. This embodiment has many similarities to the embodiments described above.

-16 -Similar components have been referenced with the same reference numerals.

In the third embodiment the physically contacting elements of the switching means of the above embodiments is replaced by a Hall effect sensor which is contactiess. As shown, the Hall effect sensor comprises a magnetic element which is mounted to the flexible part 35 and a transducer 81 which remains static. The output from the transducer 81 is connected to the counting circuit. (The positions of the magnetic element 80 and transducer 81 could be reversed if required) A specific advantage of this embodiment is that no electrical connection is required to be made to the switching element (in the form of the magnetic element) that is carried on the flexible part 35.

In use, as described above passage of a dose of product through the bore 26 causes flexure of the flexible part 35 which causes relative movement between the magnetic element and the transducer 81. This movement is detected by the Hall effect sensor and triggers the LCD display to update.

Whilst the Hall effect sensor has been shown in the horizontal orientation in Figure 4, it could also be mounted in the vertical orientation akin to that illustrated in Figure 2 for the embodiment described above.

In the above embodiments the power for the counting mechanism has been described as a battery. However, other sources of electrical power can be utilised, such as a dynamo, wind-up mechanism or piezo-electrical crystal device which converts mechanical energy into electrical energy.

Claims

-17 -Claims: 1. Dispensing apparatus comprising an actuator and a metered dose inhaler; the actuator comprising a housing part, a valve stem receiving block and an outlet duct; the metered dose inhaler comprising a container and a metering valve, the metering valve comprising a valve stem having a valve stem outlet, the container containing a product, the metered dose inhaler being receivable in the housing part such that the valve stem is received in the valve stem receiving block, such that, in use, actuation of the metering valve causes a metered dose of the product to be dispensed from the valve stem outlet into the valve stem receiving block from where it is directed to be dispensed out of the outlet duct; wherein the dispensing apparatus further comprises a dose counter comprising a switch, a display for displaying an indication of the number of doses remaining or number of doses dispensed from the metered dose inhaler and a power source for providing power to the display; wherein actuation, in use, of the switch causes the indication of the number of doses of the display to be updated; characterised in that the switch is actuatable by the pneumatic force produced by each metered dose of product as it is dispensed.
2. Dispensing apparatus as claimed in claim 1 wherein the switch is a proximity switch comprising a first element and a second element which are moveable relative to one another -18 -to actuate the switch, wherein the movement of the first and/or second element is by the pneumatic force produced by each metered dose of product as it is dispensed.
3. Dispensing apparatus as claimed in claim 2 wherein the proximity switch is a Hall effect switch.
4. Dispensing apparatus as claimed in claim 1 wherein the switch comprises a first element and a second element which are movable between an open position in which the first and second elements are separated and a closed position in which the first and second elements contact one another to actuate the switch, wherein the first and second elements are movable into the closed position by the pneumatic force produced by each metered dose of product as it is dispensed.
5. Dispensing apparatus as claimed in claim 4 wherein the first element is movable by the pneumatic force produced by each metered dose of product as it is dispensed.
6. Dispensing apparatus as claimed in claim 4 or claim 5 wherein the second element is static.
7. Dispensing apparatus as claimed in any of claims 2 to 6 wherein the first element is mounted in a flexible mounting.
8. Dispensing apparatus as claimed in claim 7 wherein the valve stem receiving block comprises an inlet aperture, an outlet aperture and a transfer duct connecting the inlet aperture to the outlet aperture, -19 -wherein the inlet aperture receives, in use, the valve stem of the metered dose inhaler and the outlet aperture directs the dispensed product into the outlet duct, wherein the flexible mounting comprises at least a portion of an internal wall of the transfer duct.
9. Dispensing apparatus as claimed in claim 8 wherein the valve stem receiving block contains a portion of the switch.
10. Dispensing apparatus as claimed in claim 8 wherein the valve stem receiving block contains the first element and the second element of the switch.
11. Dispensing apparatus as claimed in preceding claim wherein the valve stem receiving block is formed separately from the housing part of the actuator and assembled thereto.
12. Dispensing apparatus as claimed in any of claims 7 to 11 wherein the flexible mounting comprises an element formed from a thermoplastic or thermoplastic elastomer.
13. An actuator for use in a dispensing apparatus as claimed in any preceding claim comprising a housing part, a valve stem receiving block and an outlet duct; wherein the actuator further comprises a dose counter comprising a switch, a display for displaying an indication of the number of doses remaining or number of doses dispensed from a metered dose inhaler and a power source for providing power to the display; wherein actuation, in use, of the switch causes the indication of the number of doses of the display to be updated; -20 -characterised in that the switch is actuatable by a pneumatic force.
14. Actuator as claimed in claim 13 wherein the switch is a proximity switch comprising a first element and a second element which are moveable relative to one another to actuate the switch, wherein the movement of the first and/or second element is by the pneumatic force.
15. Actuator as claimed in claim 14 wherein the proximity switch is a Hall effect switch.
16. Actuator as claimed in claim 13 wherein the switch comprises a first element and a second element which are movable between an open position in which the first and second elements are separated and a closed position in which the first and second elements contact one another to actuate the switch, wherein the first and second elements are movable into the closed position by the pneumatic force.
17. Dispensing apparatus or actuator as claimed in any preceding claim wherein the display is an LCD.
18. Dispensing apparatus or actuator as claimed in any preceding claim wherein the power source is a battery.
19. A dose counter mechanism comprising a duct having an inlet, an outlet and a conduit connecting the inlet to the outlet, -21 -the conduit being predominantly formed from a rigid material and additionally comprising a flexible wall portion formed from a flexible material; wherein said flexible wall portion comprises a first switch element; wherein a second switch element is provided outside the conduit; wherein, in use, a metered dose of pressurised gas received through the inlet is conveyed to the outlet whilst causing flexure of the flexible wall portion of the conduit to move the first switch element relative to the second switch element in order to actuate a switch.
20. A dose counter mechanism as claimed in claim 19 wherein first and second elements form a proximity switch such as a Hall effect switch.
21. A dose counter mechanism as claimed in claim 19 wherein the first and second elements are brought into contact with each other by flexure of the flexible wall portion in order to actuate the switch.
22. A dose counter mechanism as claimed in any of claims 19 to 21 wherein the flexible wall portion is formed from a element made of a thermoplastic or thermoplastic elastorner.
23. A dose counter mechanism as claimed in any of claims 19 to 22 wherein the first switch element is mounted to an outer face of the flexible wall portion such that an inner face of the flexible wall portion exposed to product passing through the conduit is free of obstructions.

-22 -
24. A dose counter mechanism as claimed in any of claims 19 to 23 wherein the conduit comprises a transfer duct of a valve stem receiving block of an actuator.
25. A dose counter mechanism as claimed in claim 24 wherein the flexible wall portion is located at a base of a sump of the transfer duct.
26. A dose counter mechanism as claimed in claim 24 wherein the flexible wall portion is located in a side wall of the transfer duct located opposite the outlet of the conduit.
27. A method of counting doses dispensed from a dispensing apparatus of the type comprising an actuator and a metered dose inhaler, comprising the steps of: providing the actuator with a conduit for receiving product dispensed by the metered dose inhaler, the conduit comprising a flexible element; actuating the metered dose inhaler to dispense a metered dose of product into the conduit of the actuator thereby causing flexure of the flexible element; detecting flexure of the flexible element; on detection of flexure of the flexible element updating a display indicative of a count of doses.
28. The method of claim 27 comprising use of a switch to detect flexure of the flexible element.Amendments to the Claims have been filed as follows.Claims: 1. Dispensing apparatus comprising an actuator and a metered dose inhaler; the actuator comprising a housing part, a valve stem receiving block and an outlet duct; the valve stem receiving block comprising a flexible wall portion formed from a flexible material; the metered dose inhaler comprising a container and a metering valve, the metering valve comprising a valve stem having a valve stem outlet, the container containing a product, the metered dose inhaler being receivable in the housing part such that the valve stem is received in the valve stem receiving block, such that, in use, actuation of the metering valve causes a metered dose of the product to be dispensed from the valve stem outlet into the valve stem receiving block from where it is directed to be dispensed out of the outlet duct; wherein the dispensing apparatus further comprises a dose counter comprising a switch with first and second S. : switch elements, a display for displaying an indication of the number of doses remaining or number of doses dispensed from the metered dose inhaler and a power source forSproviding power to the display; S..... * .wherein the flexible wall portion of the valve stem *.... receiving block comprises the first switch element; wherein actuation, in use, of the switch causes the indication of the number of doses of the display to be updated; wherein the switch is actuatable by the pneumatic force produced by each metered dose of product as it is dispensed, in that conveyance of the metered dose of product through the valve stem receiving block causes flexure of the flexible wall portion to move the first switch element relative to the second switch element.2. Dispensing apparatus as claimed in claim 1 wherein the switch is a proximity switch comprising the first switch element and the second switch element which are moveable relative to one another.3. Dispensing apparatus as claimed in claim 2 wherein the proximity switch is a Hall effect switch.4. Dispensing apparatus as claimed in claim 1 wherein the first switch element and the second switch element which are movable between an open position in which the first and second switch elements are separated and a closed position in which the first and second switch elements contact one another to actuate the switch, wherein the first and second switch elements are movable into the closed position by the flexure of the flexible wall portion. S. * * . ** * ***. * *5. Dispensing apparatus as claimed in claim 4 wherein the * *S** second switch element is static.**.*.S * * 6. Dispensing apparatus as claimed in any preceding claim wherein the first switch element is mounted in the flexible wall portion.7. Dispensing apparatus as claimed in any preceding claim wherein the valve stem receiving block comprises an inlet aperture, an outlet aperture and a transfer duct connecting the inlet aperture to the outlet aperture, wherein the inlet aperture receives, in use, the valve stem of the metered dose inhaler and the outlet aperture directs the dispensed product into the outlet duct, wherein the flexible wall portion comprises at least a portion of an internal wall of the transfer duct.8. Dispensing apparatus as claimed in any preceding claim wherein the valve stem receiving block contains the first switch element and the second switch element of the switch.9. Dispensing apparatus as claimed in preceding claim wherein the valve stem receiving block is formed separately from the housing part of the actuator and assembled thereto.10.Dispensing apparatus as claimed in any preceding claim wherein the flexible wall portion comprises an element formed from a thermoplastic or thermoplastic elastomer. ****S... 11.Dispensing apparatus as claimed in any preceding claim S...wherein the first switch element is mounted to an outer face of the flexible wall portion such that an inner face of the flexible wall portion exposed to product passing through the * . ..S' * valve stem receiving block is free of obstructions.*5SS** S * 12. An actuator for use in a dispensing apparatus as claimed in any preceding claim comprising a housing part, a valve stem receiving block and an outlet duct; the valve stem receiving block comprising a flexible wall portion formed from a flexible material; wherein the actuator further comprises a dose counter comprising a switch with first and second switch elements, a display for displaying an indication of the number of doses remaining or number of doses dispensed from a metered dose inhaler and a power source for providing power to the display; wherein the flexible wall portion of the valve stem receiving block comprises the first switch element; wherein actuation, in use, of the switch causes the indication of the number of doses of the display to be updated; wherein the switch is actuatable by a pneumatic force, in that conveyance of a metered dose of product through the valve stem receiving block causes flexure of the flexible wall portion to move the first switch element relative to the second switch element.13. Actuator as claimed in claim 12 wherein the switch is a proximity switch comprising the first switch element and the second switch element which are moveable relative to one another to actuate the switch. S.. * SS ** * S.* **,. 14. Actuator as claimed in claim 13 wherein the proximity switch is a Hall effect switch. , 25* U S* * 15. Actuator as claimed in claim 12 wherein the first switch element and the second switch element are movable * 4 between an open position in which the first and second elements are separated and a closed position in which the first and second elements contact one another to actuate the switch.16. Dispensing apparatus or actuator as claimed in any preceding claim wherein the display is an LCD.17. Dispensing apparatus or actuator as claimed in any preceding claim wherein the power source is a battery.18. A dose counter mechanism comprising a duct having an inlet, an outlet and a conduit connecting the inlet to the outlet, the conduit being predominantly formed from a rigid material and additionally comprising a flexible wall portion formed from a flexible material; wherein said flexible wall portion comprises a first switch element; wherein a second switch element is provided outside the conduit; wherein, in use, a metered dose of pressurised gas received through the inlet is conveyed to the outlet whilst causing flexure of the flexible wall portion of the conduit to move the first switch element relative to the second switch element in order to actuate a switch. e. ** *S19. A dose counter mechanism as claimed in claim 18 wherein first and second elements form a proximity switch such as a S * *S..Hall effect switch. *55*S20. A dose counter mechanism as claimed in claim 18 wherein the first and second elements are brought into contact with each other by flexure of the flexible wall portion in order to actuate the switch.21. A dose counter mechanism as claimed in any of claims 18 to 20 wherein the flexible wall portion is formed from a element made of a thermoplastic or thermoplastic elastomer.22. A dose counter mechanism as claimed in any of claims 18 to 21 wherein the first switch element is mounted to an outer face of the flexible wall portion such that an inner face of the flexible wall portion exposed to product passing through the conduit is free of obstructions.23. A dose counter mechanism as claimed in any of claims 18 to 22 wherein the conduit comprises a transfer duct of a valve stem receiving block of an actuator.24. A dose counter mechanism as claimed in claim 23 wherein the flexible wall portion is located at a base of a sump of the transfer duct.25. A dose counter mechanism as claimed in claim 23 wherein the flexible wall portion is located in a side wall of the transfer duct located opposite the outlet of the conduit. * S * S. * *..*26. A method of counting doses dispensed from a dispensing apparatus of the type comprising an actuator and a meteredS S...* 25 dose inhaler, comprising the steps of: S***S * S providing the actuator with a conduit for receiving product dispensed by the metered dose inhaler, the conduit *. comprising a flexible wall portion; actuating the metered dose inhaler to dispense a metered dose of product into the conduit of the actuator thereby causing flexure of the flexible wall portion; detecting flexure of the flexible wall portion; on detection of flexure of the flexible wall portion updating a display indicative of a count of doses.27. The method of claim 26 comprising use of a switch to detect flexure of the flexible wall portion. * I I I. I I... * I 0III I.. * I S...SSIIIII * SI*S..*S * . I..