Pressurized dispensing containers are widely used in the pharmaceutical industry for storing medications and other products to be dispensed in aerosol form.

Such containers usually contain a propellant, such-as HFC134a, in which the product is suspended or dissolved. Solvents, such as ethanol, may also be present in the formulation. Other dispensers are used for dispensing drugs stored in bulk powder form.

Such dispensing containers are commonly used with pressurized dispensing apparatus capable of dispensing metered doses of the product from the containers upon each actuation of the container valve, for example, metered dose inhalers. The reliability and consistency of the metered dose is especially important where the product comprises or includes a medication. Inconsistent or unreliable dispensation could result in a user of the dispensing apparatus receiving too great or too little medication.

A problem found by many users of such apparatus is the inability to determine the quantity of product remaining in the container. Many types of apparatus continue to allow the dispensing of quantities of propellant and/or solvent when the container is near empty, even though the dose of product contained in the propellant is below the required level, thereby exacerbating the problem. Thus, users are often unaware that the dispensing apparatus operating

inadequately. This has potentially dangerous consequences where the product or medication dispensed is required urgently and no time is available to locate a replacement dispenser, such as in the treatment of asthmatic conditions. Sufferers of asthma often carry dispensers with them for extended periods of time, which may only be used on an occasional basis. Therefore, there is a danger that, where the user is unable to determine the contents of the pressurized dispensing container and the device is required in an emergency situation, the contents of the container may be inadequate.

Existing arrangements used in drug dispensers utilising mechanical components to count the number of actuations or level indication have inherent complexities and product challenges. For example the life of the product, i. e. the available number of doses, may differ depending on temperature or other ambient conditions. Furthermore, if the dispensing device is held in a manner which allows only gas to be released or misfired, the dose count or level indication becomes invalid in relation to the actual drug level. It is particularly challenging in large scale production to ensure that the dose count occurs precisely when the valve opens, given additive tolerances of the valve and counting mechanism.

Failure to align the count with the valve opening during the actuation sequence leaves the possibility for either a count without the correct dose being dispensed or vice versa, resulting in an inaccurate count level indication.

It is therefore an objection of the present invention to provide a level indicator for quickly and reliably determining the level of liquid or powder in a reservoir, which is suitable for use in, say, a

pressurised dispensing container for dispensing drugs, although the invention is equally applicable to non- pressurised dispensation systems.

According to the invention there is therefore provided a liquid level indicating system comprising a magnetic float of sufficient buoyancy to float on the surface of a liquid to be measured, and a measuring device, said device comprising a strip of magnetic material of a lower magnetic field strength than the magnetic float and magnetically sensitive media contained within the device, wherein when the measuring device is remote from the magnetic float or other independent magnetic field, the magnetically sensitive media is attracted to and aligned with the magnetic strip, and when the measuring device is in the vicinity of the magnetic float a quantity of the magnetic sensitive media falling within a magnetic field generated by the float is attracted towards and realigns to form a pointer in the direction of the magnetic float.

The invention also provides a level indicating system comprising a magnetic float which is significantly light to rest on the surface of a bulk powder to be measured, and a measuring device, said device comprising a strip of magnetic material of a lower magnetic field strength than the magnetic float and magnetically sensitive media contained within the device, wherein when the measuring device is remote from the magnetic float or other independent magnetic field, the magnetically sensitive media is attracted to and aligned with the magnetic strip, and when the measuring device is in the vicinity of the magnetic float a quantity of-the magnetic sensitive media falling within a magnetic field generated by the float is attracted towards and realigns to form a pointer in

the direction of the magnetic float.

The present invention further provides a level indicating system comprising a magnetic float of sufficient buoyancy to float on the surface of a liquid to be measured, and a measuring device, said device comprising an array of magnetically-activated sensors, a microprocessing means operatively linked to the array of sensors, and an indication means linked to the microprocessing means for displaying to a user an indicator of the level to be measured, wherein the sensors of the array are activatable when the magnetic float is in the vicinity of said sensors to send a signal to the microprocessing means indicative of the level to be measured wherein the microprocessing means is operatable to operate the indication means to display the indicator of the level to be measured.

The present invention further provides a level indicating system comprising a magnetic float which is significantly light to rest on the surface of a bulk powder to be measured, and a measuring device, said device comprising an array of magnetically-activated sensors, a microprocessing means operatively linked to the array of sensors, and an indication means linked to the microprocessing means for displaying to a user an indicator of the level to be measured, wherein the sensors of the array are activatable when the magnetic float is in the vicinity of said sensors to send a signal to the microprocessing means indicative of the level to be measured wherein the microprocessing means is operatable to operate the indication means to display the indicator of the level to be measured.

The present invention further provides an indicating system comprising a reservoir of a liquid or powder having a magnetic element associated

therewith and a housing in which the reservoir is received in use, said housing comprising a measuring device, said measuring device comprising a magnetically-activated sensor, a microprocessing means operatively linked to the sensor, and an indication means linked to the microprocessing means for displaying to a user an indicator of the number of activations of the reservoir, wherein the sensor of the measuring device is activatable when the magnetic element transits the sensor to send a signal to the microprocessing means wherein the microprocessing means is operatable to operate the indication means to update the display of the number of activations of the reservoir remaining.

Preferred embodiments of the present invention will now be described by way of example only, with reference to the following drawings, in which: Figure 1 is a cross-sectional side elevation of a first embodiment of pressurised dispensing container and magnetic level indicator according to the present invention; Figure 2 is a perspective view of a second embodiment of pressurised dispensing container and magnetic level indicator according to the present invention, with certain parts cut-away to show internal features ; and Figure 3 is a perspective view of a third embodiment of pressurised dispensing container and magnetic level indicator according to the present invention, with certain parts cut-away to show internal features.

Referring to Figure 1 there is illustrated the use of the present invention in conjunction with a first embodiment of the pressurised dispensing

container 10. The dispensing container 10 comprises a can 11, which defines a reservoir 12. The dispensing container 15 further comprises a metering valve 13 attached to the can 11 by means of a ferrule 14 which is placed over the metering valve 13 and crimped to the open mouth of the can 11. A valve stem 15 extends actually from the metering valve 13 and defines an outlet through which the product is dispensed.

Where the contents of the reservoir 12 in such a dispensing container 10 are partially gas 16 and partially liquid 17, and it is the liquid level that is crucial for the user to know. A first part of the level indicator comprises magnetic float 18, 19, which is formed by combining a magnet 18 with a low specific weight element 19, which reduces the combined weight of the magnet 18 plus element 19 to less than that of the drug, or other product for dispensing, which is suspended or disclosed in the liquid 17. The low specific weight element 19 may be a blow-moulded plastic component. Another option would be to use thin walled injection moulded components, in which case the magnets 18 which are either heat-swaged, ultrasonic or laser-welded together. The materials used can be anything suitable, for example, LDPE or Topas (Ticona-cyclic olefin copolymer). The main intent is to encapsulate the magnet 18 and completely isolate it from the drug, in an element 19 incorporating an air pocket.

As a result the magnetic float 18,19 floats on the surface of the liquid 17. In the embodiment shown, the magnet 18 is provided in an annular form and embedded within the low specific weight element 19, which is provided in the form of an annular jacket. It should be noted, however, that other variations in form can be used.

In a bulk powder dispenser, the contents of the reservoir 12 comprise a dry powder. In this case, the magnetic float needs to be sufficiently lightweight to enable to rest on the surface of the powder since it may therefore still incorporate a low specific weight element similar to the liquid indicator.

Alternatively, the magnet may be provided in a thin plate-like form which in itself is sufficiently lightweight to rest on the surface of the powder.

Such a magnet would need to be coated in an appropriate material to prevent contamination of the powder drug. In the same way as the buoyant magnetic float 18, 19 in the liquid indicator, the magnetic float of the powder indicator would remain resting on top of the powder and lower as the powder is consumed.

In the example shown, the container 10 further comprises an elongate guide stem 20, which is secured to the can 11 by means of an annular flange 21 and held in position by the ferrule 14. Where an annular float magnetic float 18,19 is used, this can be conveniently located around the guide stem 20 and constrained to move downwards along the stem 20, so that it remains centrally within the can 11 as the liquid level drops.

The second part of the level indicator comprises an elongate measuring device 21. The measuring device 21 is preferably flat, with a wide, but thin cavity defined between its front and rear surfaces. Contained within the cavity is a magnetically sensitive media 22, which may be a ferrous fluid, comprised of a liquid such as a hydrocarbon, ester, perfluoropolyether or water, and magnetic particles.

Another option for the magnetically sensitive media 22 would be"the green film" (TM) which is a micro- encapsulated film. This is a highly flexible film

supplied by Magne-Rite, Inc which enables a static magnetic field to be viewed. Such a film is generally made from two layers of filmic materials with magnetic particles captured in between. The particles have sufficient space between the film layers to reposition when a magnetic field is applied.

The magnetic particles may, if preferred, be coloured to provide a pleasing visual effect. The magnetic particles may also be luminous, which enables the level to be detected in the dark. Alternatively, the magnetic particles may be non-luminous and held against a luminous film background.

Along one edge of the measuring device 21 is a strip of low power magnetic material 23. When the measuring device 21 is held remote from any independent magnetic influence, the magnetically sensitive media 22 is attracted towards the magnetic material 23, and forms a substantially straight line along the length of the measuring device 21 adjacent to the magnetic material 23.

To measure the level of liquid within the dispensing container reservoir 12, the measuring device 21 is held adjacent to the container 10. As the higher power magnetic field emanating from the magnetic float 18,19 is stronger than the magnetic field emanating from the magnetic strip 23, the media 22 in the magnetic field emanating from the magnetic float 18,19 realigns and is caused to shift towards the magnetic float 18,19 to essentially reform to provide a pointer 24 at the liquid level.

Thus, when held vertically, a visual indication of the liquid, and therefore drug, level will be given to the user from the pointer 24 created in the media

22, which gives an indication of remaining doses available, and will alert the user as to when to acquire a replacement container 10.

A printed or other form of graduated scale may be placed along the opposite edge of the measuring device 21 to the magnetic strip 23, which gives either an indication of the number of doses remaining in the container 10, or that the container is full/half full or empty, or the specific volume of the contents.

The elongate measuring device 21 may be a separate component from the container 10, but may advantageously be integrated with the container 10 or an actuator in which the container 10 is received in use. For example, the measuring device 21 can be adhered to the outside of the container 10 using an adhesive such as an epoxy resin.

A second embodiment of the invention is shown in Figure 2. The pressurised container 10 and magnetic float 18, 19 are the same as in the first embodiment and will not be described further. In the second embodiment, the second part of the magnetic level indicator is provided, not on the can 11 but as part of a housing 30 in which the pressurised container 10 is received in use.

The housing 30 comprises a hollow longitudinal section 31 and a laterally directed mouthpiece 32 depending from one end. The opposite end 33 of the longitudinal section 31 is open to receive the pressurised container 10 as a sliding fit therethrough. The valve stem 15 is received as a push fit in a stem block 34 which is provided with a conduit terminating in an outlet orifice 35 through which the product contained in the container 10 is

dispensed. The orifice 35 is directed towards an outlet 36 of the mouthpiece 32.

According to the present invention, the housing 30 is provided with the second part of the magnetic level indicator in the form of an elongate array of electronic sensors 40 aligned along the axis of the longitudinal section 31. The electronic sensors 40 are responsive to magnetic fields. The sensors 40, which may be magnetic reed switches, are linked to a microprocessor (not shown) which receives signals from the sensors 40 and processes the signals to output a signal indicative of the level of the fluid or powder in the container 10. The output signal from the microprocessor is used to control a display (not shown) which provides a visual indication to a user of the device of the remaining number of doses. The visual indication can be in the form of a number, word, colour or combination of these elements.

In use, as the quantity of fluid or powder in the reservoir decreases, the magnetic float 18,19 will be brought into alignment with successively lower sensors in the sensor array. This change is detected by the microprocessor which changes the visual display accordingly. The number of sensors 40 in the array can be varied to vary the number of doses required to be dispensed between changes in the visual display.

A third embodiment is shown in Figure 3. The container 10 is generally as described before.

However, the container 10 is provided with a magnetic ring 50 on the front face of the ferrule 14 rather than a magnetic float inside the reservoir. A housing 30 is again provided in which the container 10 is received in use. The container comprises a longitudinal section 31, mouthpiece 32 and stem block

34. The housing 30 is further provided with a magnetically-activated reed switch 51 aligned near the vicinity of the ferrule 14 when the container 10 is in its at rest position within the housing 30. The reed switch 51 is linked to a microprocessor (not shown) which receives signals from the reed switch 51 and processes the signals to output a signal indicative of the number of activations of the container 10. The output signal from the microprocessor is used to control a display (not shown) which provides a visual indication to a user of the device of the remaining number of doses. The visual indication can be in the form of a number, word, colour or combination of these elements.

In use, activation of the container 10 causes the magnetic ring 50 on the ferrule 14 to pass the position of the reed switch 51. In so doing the magnetic ring 50 causes a signal to be sent from the reed switch 51 to the microprocessor which updates the visual display accordingly.

Although the invention has been described for us with a pressurised dispensing container, this system for liquid or powder level indication can be used in any containment system, whether pressurised or not.

Whilst it is particularly useful for medicament and drug dispensing apparatus, it can of course be used in other fields. It is especially useful in applications that require an opaque container for the reservoir due to necessary material properties to withstand pressure or stability with the liquid or powder formulation.

It can also be used, however, in transparent or semi- transparent reservoirs for improved visibility of liquid or powder level.