Aerosol generator and methods of making and using an aerosol generator

An aerosol generator includes a flow passage having an inlet and an outlet, a heater arranged relative to the flow passage for heating the flow passage, a source of material to be volatilized in communication with the inlet of the flow passage, a valve to open and close communication between the source of material and the inlet of the flow passage, and a pressurization arrangement for causing material in the source of material to be introduced into the flow passage when the valve is in an open position. The aerosol generator further includes a source of power for operating the heater and the valve, and a control device for controlling supply of power from the source of power to the heater and the valve. A metering device in an inhaler includes a pressurized source of medicated fluid and a metering chamber configured to deliver a predetermined volume of fluid to a heated flow passage in the inhaler. The metering chamber can be part of a rotary valve having a bore and a displacement member moveable within the bore from a first position where the fluid is loaded into the bore to a second position where the predetermined volume is ejected out of the bore. Another metering chamber has an elastic portion of a delivery passage in fluid communication with the pressurized source of liquid and the elastic portion of the delivery passage is deformed to eject the predetermined volume.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to aerosol generators and, more particularly, to aerosol generators able to generate aerosols without compressed gas propellants and methods of making and using such aerosol generators. The present invention also relates generally to metering valves in inhalers and, more particularly, to metering valves which deliver a predetermined volume in inhalers including aerosol generators able to generate aerosols without compressed gas propellants.

Aerosols are useful in a wide variety of applications. For example, it is often desirable to treat respiratory ailments with, or deliver drugs by means of, aerosol sprays of finely divided particles of liquid and/or solid, e.g., powder, medicaments, etc., which are inhaled into a patient's lungs. Aerosols are also used for purposes such as providing desired scents to rooms, applying scents on the skin, and delivering paint and lubricant.

Various techniques are known for generating aerosols. For example, U.S. Pat. Nos. 4,811,731 and 4,627,432 both disclose devices for administering medicaments to patients in which a capsule is pierced by a pin to release a medicament in powder form. A user then inhales the released medicament through an opening in the device. While such devices may be acceptable for use in delivering medicaments in powder form, they are not suited to delivering medicaments in liquid form. The devices are also, of course, not well-suited to delivery of medicaments to persons who might have difficulty in generating a sufficient flow of air through the device to properly inhale the medicaments, such as asthma sufferers. The devices are also not suited for delivery of materials in applications other than medicament delivery.

Another well-known technique for generating an aerosol involves the use of a manually operated pump which draws liquid from a reservoir and forces it through a small nozzle opening to form a fine spray. A disadvantage of such aerosol generators, at least in medicament delivery applications, is the difficulty of properly synchronizing inhalation with pumping. More importantly, however, because such aerosol generators tend to produce particles of large size, their use as inhalers is compromised because large particles tend to not penetrate deep into the lungs.

One of the more popular techniques for generating an aerosol including liquid or powder particles involves the use of a compressed propellant, often containing a chloro-fluoro-carbon (CFC) or methylchloroform, to entrain a material, usually by the Venturi principle. For example, inhalers containing compressed propellants such as compressed gas for entraining a medicament are often operated by depressing a button to release a short charge of the compressed propellant. The propellant entrains the medicament as the propellant flows over a reservoir of the medicament so that the propellant and the medicament can be inhaled by the user. Since the medicament is propelled by the propellant, such propellant-based arrangements are well-suited for those who might have difficulty inhaling. Nonetheless, aerosols generated by propellant-based arrangements have particles that are too large to ensure deep lung penetration.

In propellant-based arrangements, however, a medicament may not be properly delivered to the patient's lungs when it is necessary for the user to time the depression of an actuator such as a button with inhalation. Moreover, such arrangements tend to be poorly suited for delivery of materials in large quantities. Although propellant-based aerosol generators have wide application for uses such as antiperspirant and deodorant sprays and spray paint, their use is often limited because of the well-known adverse environmental effects of CFC's and methylchloroform, which are among the most popular propellants used in aerosol generators of this type.

In drug delivery applications, it is typically desirable to provide an aerosol having average mass median particle diameters of less than 2 microns to facilitate deep lung penetration. Most known aerosol generators are incapable of generating aerosols having average mass median particle diameters less than 2 to 4 microns. It is also desirable, in certain drug delivery applications, to deliver medicaments at high flow rates, e.g., above 1 milligram per second. Most known aerosol generators suited for drug delivery are incapable of delivering such high flow rates in the 0.2 to 2.0 micron size range.

U.S. Pat. No. 5,743,251, which is hereby incorporated by reference in its entirety, discloses an aerosol generator, along with certain principles of operation and materials used in an aerosol generator, as well as a method of producing an aerosol, and an aerosol. The aerosol generator disclosed according to the '251 patent is a significant improvement over earlier aerosol generators, such as those used as inhaler devices. It is desirable to produce an aerosol generator that is portable and easy to use.

According to one aspect of the present invention, an aerosol generator includes a flow passage such as a tube having an inlet and an outlet, a heater arranged relative to the flow passage for heating at least a portion of the flow passage, a source of material to be volatilized, the inlet of the flow passage being in communication with the source of material, and a valve operatively located between the source of material and the flow passage, the valve being openable and closeable to open and close communication between the source and the outlet of the flow passage. A pressurization arrangement is provided for causing material in the source of material to be introduced into the flow passage from the source of material when the valve is in an open position. A source of power is provided for operating the heater and for the valve, and a control device is provided for controlling supply of power from the source of power to the heater and the valve.

According to a further aspect of the present invention, a method of making an aerosol generator is disclosed. According to the method, a heater is arranged relative to a flow passage for heating of the flow passage, the flow passage having an inlet and an outlet. The inlet of the flow passage is connected to a source of material to be volatilized. An openable and closeable valve is provided between the source of material and the flow passage. A pressurization arrangement is provided for causing material in the source of material to be introduced into the flow passage from the source of material when the valve is in an open position. The valve is connected to a source of power for opening and closing the valve. The heater is connected to the source of power. The source of power is connected to a control device for controlling a supply of power from the source of power to the heater and the valve.

According to yet another aspect of the present invention, a method of generating an aerosol is disclosed. According to the method, a first signal indicative of a user's intention to generate an aerosol, is generated and sent to a control device. With the control device and responsive to the first signal, a second signal is sent to a source of power to cause the source of power to open an openable and closeable valve, the valve being disposed between a source of material to be volatilized and a flow passage, opening of the valve permitting material from the source of material to flow from the source of material and into the flow passage. Material from the source of material is thus caused to flow from the source of material and into the flow passage. With the control device and responsive to the first signal, a third signal is sent to the source of power to supply power to a heater disposed relative to the flow passage to heat the flow passage. Material from the source of material is heated in the flow passage with the heater to a vaporization temperature such that the material volatilizes and expands out of an outlet of the flow passage.

The present invention also provides a metering device in an inhaler having a pressurized source of medicated fluid and a metering chamber in fluid communication with the pressurized source of fluid. The metering chamber is configured to deliver a predetermined volume of fluid to a heated flow passage in an inhaler.

In accordance with one embodiment of the metering device, the metering chamber is a rotary valve including a bore and a displacement member located within the bore. The displacement member is movable from a first position where the fluid is loaded into a load portion of the bore to a second position where the predetermined volume of fluid is ejected out of the bore.

In accordance with another embodiment of the metering device, the metering device includes a delivery passage including an elastic portion. The metering chamber is located in the elastic portion of the delivery passage. The elastic portion of the delivery passage is compressed to eject a predetermined volume of liquid.

In accordance with another aspect of the invention, the inhaler preferably includes an aerosol generator wherein a flow passage has an inlet and an outlet and a pressurized source of fluid, a heater is arranged relative to the flow passage for heating at least a portion of the flow passage; and a metering chamber is in fluid communication with the pressurized source of fluid and is configured to deliver a predetermined volume to the flow passage.

In accordance with another aspect of the invention, a method of dispensing a predetermined volume of medicated fluid in an inhaler is provided wherein the inhaler includes a metering device having a pressurized source of fluid which is in fluid communication with a metering chamber. According to the method, the metering chamber is filled with fluid from the pressurized source and a predetermined volume of the fluid is ejected from the metering chamber into a heated flow passage.

DETAILED DESCRIPTION

An aerosol generator21according to the present invention is shown inFIG. 1. The principles of operation of the aerosol generator21and, where applicable, materials used in the aerosol generator are preferably similar to the principles of operation and materials used in the aerosol generator disclosed in U.S. Pat. No. 5,743,251, which is hereby incorporated by reference in its entirety.

A preferred application for the aerosol generator21is as an inhaler device, such as an inhaler for medicaments, such as asthma medication and pain killers or any other therapeutic agents for treatment of a bodily condition. The aerosol generator21preferably includes a first component23, which preferably includes, for example, the material to be turned into an aerosol and which is preferably disposable after one or a predetermined plurality of uses, removably attached to a second component25, which preferably includes, for example, power source and logic circuitry structures and which is preferably permanent in the sense that it is reusable with successive ones of the first components. The first and second components23and25can be, attachable to one another in end to end or side by side relationships. If desired or necessary, however, the aerosol generator can be a one-piece device.

The first component23preferably includes a flow passage in the form of a tube27having a first and a second end29,31, and a heater33arranged relative to the tube for heating the tube. A valve35is provided either on the tube27or between the second end31of the tube and a source37of material, the valve preferably being openable and closeable to open and close communication between the first end29of the tube and the source of material. The valve35may define the second end31of the tube. The valve35is preferably electronically openable and closeable, preferably a solenoid-type valve. The first component23preferably further includes the source37of material to be volatilized. The first component23preferably also includes a pressurization arrangement39for causing material in the source37of material to be introduced into the tube27from the source of material when the valve35is in an open position.

The second component25is preferably attachable and detachable to the first component23and includes a source41of power for the heater33and for the valve35, and a control device43, such as a microchip, for controlling supply of power from the source of power to the heater and the valve. The source41of power is preferably a battery, more preferably a rechargeable battery, however, the source of power may, if desired or necessary, be a non-depleting source of power, such as a conventional power line. International Publication No. WO 98/17131 discloses a power controller and a method of operating an electrical smoking system that discloses a power source and a control device, particularly for heaters, the principles of operation and features of which are transferrable to the present invention, and is hereby incorporated by reference.

In WO 98/17131 power is applied to a heater element in accordance with a predetermined series of phases with each phase assigned different target total energies per phase and predetermined time periods for each phase such that a heat treatment event is achieved. In WO 98/17131 the controller is configured to modulate power in each phase so that the target energies are maintained irrespective of externalities such as battery voltage or the like. Preferably all liquid entering the flow passage formed by the tube27is volatilized before being discharged from the tube27. Power modulation within one or more phases of a power cycle as described above can optionally be used to assure that such volatilization occurs consistently over a broad range of battery voltages such as those encountered along a battery discharge cycle.

General operation of the aerosol generator21involves a user providing a signal, such as by compressing a button or performing some other action such as inhaling near the first end29of the tube27to actuate a flow sensing detector or a pressure drop sensing detector, which is received by the control device43. In response to the signal, the control device43preferably controls the supply of power from the power source41such that the valve35is opened and power is supplied to the heater33to cause it to heat up to its desired operating temperature. It may be desired or necessary, depending upon the application and the equipment employed, to open the valve35before or after supplying power to the heater33.

Upon opening the valve35, the pressurization arrangement39causes material in the source37of material to be introduced into the tube27. The material in the tube27is heated to a vaporization temperature in the tube, volatilizes, and expands out of the free first end29of the tube. Upon exiting the tube27, the volatilized material contacts cooler air and condenses to form an aerosol. Preferably, after a predetermined period of time, the control device43automatically closes the valve35and shuts off the supply of power to the heater33. After one or a plurality of uses, the first component23is preferably separated from the second component25and is disposed of, and a new first component is attached to the second component for further use.

Because presently preferred applications for the aerosol generator21include use as an inhaler, the aerosol generator is preferably as small as possible. The valve35is preferably a microvalve. More preferably, the valve35, the heater33, and the tube27are a single microelectronic machine formed on a single chip. To the extent that other components of the aerosol generator21disclosed in the present application are subject to production as microelectronic devices, they may also be formed on a single chip with the valve35, the heater33, and the tube27, or on another chip.

According to the preferred embodiment, the source37of material includes a flexible container45, and the pressurization arrangement39includes a chamber47in which the flexible container is disposed. A pressurized gas G is preferably sealed in the chamber47and surrounds the flexible container45. The pressurization arrangement39is preferably a so-called sepra container of the type used for dispensing, for example, gel shaving creams, caulking compounds, and depilatories, although other pressurization arrangements for delivering the material, such as propellants and manual or automatic pumps, may be used if desired or necessary. The sepra container pressurization system is particularly preferred, however, particularly due to its capacity for resistance to surrounding temperature variations, as well as to variations in pressure of the gas G because the gas is not depleted. When it is desired to dispense material from the source37of material, and the valve35is opened, the pressure of the gas G, which is preferably about two atmospheres (about 30 psi) greater than ambient pressure, compresses the flexible container45, causing material to enter the tube27through the second end31of the tube in communication with the source of material. A preferred gas G is nitrogen because of its ready availability and comparatively low cost, although various other gases are also suitable and may be preferred for particular applications.

Displacement of material from the flexible container45means that there is more room in the chamber47, which means that the gas G enclosed in the chamber occupies a greater volume. Preferably, the size of the flexible container45relative to the size of the chamber47is selected such that pressure of the gas G is about ten percent lower when the flexible container is empty than when the flexible container is full.

A pressure sensor48may be provided to sense the pressure of the gas G in the chamber47. As seen inFIG. 2, the pressure sensor48is preferably arranged to send a signal representative of the pressure in the chamber47to the control device43. The control device43, in turn, is preferably arranged to control the power source41to adjust a length of time that power is supplied to the valve35, and if desired or necessary, to the heater33, in response to the signal from the pressure sensor. In this way, pressure drops in the chamber47, which may result in a decrease in the rate at which material in the flexible container45is dispensed, can be compensated for by dispensing material for somewhat longer periods of time, i.e., by keeping the valve35open longer and, if desired or necessary, maintaining a supply of power to the heater33.

A signal to the control device43to supply power to the valve35and the heater33and, where provided, other features of the aerosol generator21, is preferably provided by a user of the aerosol generator. While the signal may be provided by, for example, pressing a button, turning a knob, or switching a switch, a preferred arrangement for providing a signal is based on a user causing some manner of air flow in the proximity of the free first end29of the tube27, such as by inhaling on a mouthpiece section49of the aerosol generator. The aerosol generator21preferably includes an air flow detecting device51for determining when a predetermined air flow rate exists proximate the first end29of the tube27. The air flow detecting device51is preferably arranged to send a signal to the control device43to indicate that the predetermined air flow rate exists, which may be indicative that a user is drawing on the open end53of the mouthpiece49section, and the controller is preferably arranged to control the power source to supply power to the valve35and the heater33, and any other components, in response to the signal from the air flow detecting device. As seen inFIG. 1, the air flow detecting device51is preferably disposed transversely to and upstream of the first end29of the tube27so that the air flow detecting device will assist in ensuring that an adequate supply of air flow exists to produce and effectively deliver an aerosol from the volatilized material as it expands out of the first end of the tube.

Where the aerosol generator21is a multi-piece device, the air flow detecting device51is preferably permanently attached to the second component25and is, thus, preferably a permanent component, i.e., it is not disposed of. If desired or necessary, however, the air flow detecting device51can be a disposable component forming part of the first component23and can be removably connected, such as through an electrical connection, to the control device43.

The mouthpiece section49preferably has an open end53. The tube27is preferably disposed in the mouthpiece section49and the first end29of the tube is preferably disposed inside of the mouthpiece section at a distance from the open end53to permit complete mixing of volatilized material expanding out of the first end of the tube with surrounding air to form an aerosol. To ensure an adequate supply of air for mixing with the volatilized material, as well as to ensure an adequate supply of air for permitting a user to draw on the mouthpiece section and actuate the air flow detecting device51, the mouthpiece section49preferably has a plurality of vent holes55. To facilitate the flow of air past the first end29of the tube27and thereby facilitate formation of an aerosol, the first end of the tube is preferably disposed in the mouthpiece section49between the vent holes55and the open end53of the mouthpiece section. The vent holes55are preferably located relative to the tube27, preferably close to the end29, such that air passing through the vent holes has no or minimal cooling effect on the tube. The tube27may, of course, be insulated from air flowing through the vent holes55, such as by providing insulation material or a concentric tube56(shown in phantom) or the like around the tube to channel air away from the tube.

As an alternative to, or in addition to, using an air flow detecting device51to send a signal to the control device43, as seen inFIG. 2in phantom, a pressure drop detecting device57for determining when a predetermined pressure drop occurs proximate the first end29of the tube27may be used. The pressure drop detecting device57is preferably arranged to send a signal to the control device43to indicate that the predetermined pressure drop is occurring, which may be indicative of a user drawing on the open end53of the mouthpiece section49, and the control device is arranged to control the power source41to supply power to the valve35and the heater33, and any other electrically powered components, in response to the signal from the pressure drop detecting device.

A suitable pressure drop detecting device is a puff-actuated sensor in the form of a Model 163PC01D35 silicon sensor, manufactured by MicroSwitch division of Honeywell, Inc., Freeport, Ill., or an SLP004D 0–4″ H2O Basic Sensor Element, manufactured by SenSym, Inc., Milpitas, Calif. Other known flow-sensing devices, such as those using hot-wire anemometry principles, are also believed to be suited for use with the aerosol generator21. The use of an air flow detecting device51, as compared to a pressure drop detecting device, is presently preferred for inhaler-type applications because it is anticipated that an air flow detecting device will be easier for users to actuate as compared to a pressure drop detecting device.

Presently anticipated applications for the aerosol generating device21include drug delivery applications. For such applications, as well as in other applications to which the aerosol generating device21might be applied, the control device43may include a timer59for controlling a frequency with which the control device controls the power supply41to supply power to the valve35and the heater33and other components. In this way, the aerosol generating device21can automatically limit the frequency with which a user can operate the aerosol generating device, thereby facilitating in preventing accidental misuse and overdosages. Moreover, to assist caregivers in treating their patients, the aerosol generator21can be associated with a remote control device61remote from the control device43. The remote control device61is preferably capable of adjusting the timer59to adjust the frequency with which the control device43controls the power supply41to supply power to the valve35and the heater33, and other components. In this way, when a caregiver desires to increase or decrease the frequency with which the user is able to operate the aerosol generator, the caregiver can do so in situations where the caregiver and the user are separated by some distance. In this way, users who might otherwise be required to personally see their caregivers to have their treatment schedules adjusted have greater mobility.

The control device43and, if provided, the remote control device61, may also be configured to permit adjustment or remote adjustment of other powered components of the aerosol generator21, such as the length of time that the valve35is open, and the length of time that power is supplied to the heater from the power source41. In this manner, it is possible to adjust dosages up or down, as well as to adjust operating conditions of the aerosol generator21to maintain the same operation where, for example, pressure of the gas G in the chamber47drops or the rate at which power is supplied from the power source41reduces, such as where the aerosol generator is used in different temperatures, material in the flexible container45is used up, or the charge of a battery forming the power source diminishes.

The timer59of the control device preferably is associated with an indicator63, such as a beeper or light forming part of the timer or, for example, electrically connected to the timer, for indicating that the control device43is available to control the power supply41to supply power to the valve35and the heater33and other components. Where, for example, the aerosol generator21is used to dispense medication, the indicator63serves to remind the user that it is time for the medication. The indicator63may also, if desired or necessary, be operable by the remote control device61. The indicator63may also be used to indicate to a user a length of time since the aerosol generator21was actuated, such as where the aerosol generator is used as an inhaler, and the user is supposed to hold his or her breath for a length of time after inhaling, with the indicator63indicating when a period of time has elapsed.

The aerosol generator21may also include a display device65, such as an LCD display, for displaying information such as a number of times that the control device43controls the power supply41to supply power to the valve and the heater. The display device65may display, for example, a number of times that the aerosol generator21has been operated, e.g., 1 or 2 or 3, or a number of operations remaining, which may be based on, for example, the size of the source37of material and the amount of material dispensed each time that the valve35is opened and closed, or the life of the power supply41, such as the remaining life of a battery. The same or additional display devices can be provided to display other information, such as pressure in the pressure chamber47and power level of the power source41. Further, the aerosol generator21may be equipped with various sensors and displays to provide feedback to be displayed in a display device65to, for example, assist a user in learning how to use the aerosol generator properly as an inhaler, such as sensors to measure the volume and duration of an inhalation after completion of an inhalation, and even to provide feedback during an inhalation to assist the user in employing an optimum inhalation profile. The display device65is preferably controlled by the control device43and powered by the power supply41.

The control device43may be individually programmable, such as by a pharmacist, to control the aerosol generator21to dispense medications according to a prescription, i.e., quantity of medication, frequency, etc., as well as programming in the information that would prevent improper use of the aerosol generator. In this manner, fewer types of aerosol generators21may be useful for a wide range of medications. The particular aerosol generator21would preferably be optimized for different classes of medications and then “fine tuned” by, for example, the pharmacist, for a specific drug or prescription.

The aerosol generator21may also be programmed to permanently prevent use after a set period of time. In this way, it would be possible to prevent the use of expired medications. This may be accomplished by, for example, having a battery power source41be non-replaceable, or by incorporating a battery and/or control device that keeps track of date and time and prevents operation past a particular date and time.

While not wishing to be bound by theory, depending upon selection of factors presently understood to primarily include a rate of power supplied from the source of power41to the heater33, a diameter of the tube27, and the material to be volatilized and delivered as an aerosol, the aerosol generator21is preferably specifically designed to generate an aerosol having certain desired characteristics. For many applications, particularly for medication delivery applications, the aerosol generator21according to the present invention is preferably designed to produce an aerosol having a mass median particle diameter of less than 3 microns, more preferably less than 2 microns, still more preferably between 0.2 and 2 microns, and still more preferably between 0.5 and 1 microns. While not wishing to be bound by theory, depending upon selection of factors presently understood to primarily include a length of the tube27, a pressure with which the pressurization arrangement39supplies the material from the source37of material, and a rate at which power is supplied from the source41of power, the rate at which the material is supplied and volatilized in the tube is established. The aerosol generator21is preferably designed to supply and volatilize material at a rate greater than 1 milligram per second.

It may be desirable to produce an aerosol formed from different liquid components that, for a variety of reasons, may be best kept separated until the moment that it is desired to form the aerosol. As seen inFIG. 3, another embodiment of the aerosol generator121may, in addition to the features described with respect to the aerosol generator21, include, preferably as part of a modified first component123, a source137of a second material in liquid form that is supplied to the tube27together with the material from the first source of material37. The source137of second material preferably communicates with the tube27at a point171before the heater33. A separate valve135is preferably powered by the power source41and controlled by the control device43to permit the pressurization arrangement39to cause material in the source137of second material to be introduced into tube27from the source of second material when the valve35is in an open position. If desired or necessary, the valve35and the valve135can be opened and closed at different times.

The source137of second material preferably includes a second flexible container145. The pressurization arrangement39preferably includes a second chamber147in which the second flexible container145is disposed, and a second pressurized gas G2sealed in the second chamber and surrounding the second flexible container. The pressurized gas G and the second pressurized gas G2may be pressurized to different pressures to facilitate delivery of the material and the second material to the tube27at different rates. If desired or necessary, the flexible container45and the second flexible container145may be disposed in the same pressurized chamber. Additional sources of material and other components may be provided to produce an aerosol having still further components.

As seen with respect toFIG. 4, a third embodiment of the aerosol generator221may include, preferably as part of a modified first component223, a structure, or several structures, that is substantially entirely parallel to the structure of the first component to permit generation of an aerosol formed from two or more components. The aerosol generator221preferably includes a second tube227having a first and a second end229,231. A second heater233is preferably arranged relative to the second tube227for heating the second tube. A second valve235is preferably provided on the second tube227and is openable and closeable to open and close communication between the first and the second ends229and231of the second tube. A source237of second material to be volatilized is provided and the second end231of the second tube227communicates with the source of second material. A second pressurization arrangement239is provided for causing material in the source237of second material to be introduced into the second tube227from the source of second material when the second valve235is in an open position. If desired or necessary, the pressurization arrangement39can be used to cause material in the source237of second material to be introduced into the second tube227. Preferably, the source41of power supplies power for the second heater233and for the second valve235, as well as to any other electrically powered components of the aerosol generator, and the control device43controls supply of power from the source of power to the second heater and the second valve.

The aerosol generator221preferably includes a chamber249, such as a mouthpiece section. The first ends29and229of the tube27and the second tube227are preferably disposed in the chamber249proximate each other. The chamber249is preferably of sufficient size and configuration to permit mixture of volatilized material and volatilized second material that expands out of the tube27and the second tube227together with ambient air such that the volatilized material and the volatilized second material form first and second aerosols, respectively, the first and second aerosols being mixed with each other to form a combination aerosol including the first and second aerosols.

In the embodiment described with reference toFIG. 1, a combination aerosol can be formed by providing material in the source37of material that includes two or more components mixed together before the material is volatilized. While the components in the source37of material may be two or more liquids, it is also possible to suspend solid particles in solution in a liquid material, or to dissolve solid particles in a liquid material. If desired or necessary, the solid particles, when suspended in solution, may be of a larger average diameter than particles of the material in aerosol form. The solid particles, when they form a part of the aerosol, may be of a larger average diameter than particles of the material in aerosol form. Solid particles can, of course, also be suspended in solution in liquid materials in the embodiments described with reference toFIGS. 3 and 4.

As noted, a preferred pressurization arrangement39for the aerosol generator21includes a sepra container type of arrangement. An aerosol generator321having an alternative pressurization arrangement339is shown inFIG. 5. In this embodiment, the source337of material preferably includes a second tube345having first and second ends345a,345b.The first end345aof the second tube345is connected to the second end31of the tube27. The pressurization arrangement339includes a chamber347filled with a pressurized gas G. The second end345bof the second tube345is disposed in the chamber347and is open to the chamber. The source337of material, the second tube345, and the tube27preferably form part of a modified first component323.

As seen inFIGS. 6A–6C, the source337of material is preferably filled with material by first opening the valve35in the tube27, then immersing the open second end345bof the second tube345in liquid material L (FIG. 6A). After the liquid material in which the second tube345is immersed fills the second tube, the valve35is then shut. The second tube345is withdrawn from the liquid material, with the liquid material that filled the second tube remaining in the second tube due to closure of the valve (FIG. 6B), i.e., air is unable to get behind the liquid material in the second tube. The second tube345is then positioned in the chamber347and the chamber is pressurized (FIG. 6C). When the valve35is opened, the pressure in the chamber forces the liquid material in the second tube345to enter the tube27where it can be volatilized by the heater27.

In a method of making the aerosol generator21described with reference to the embodiment shown inFIG. 1, the heater33is arranged relative to the tube27to permit heating of the tube. The second end31of the tube27is connected to the source37of material to be volatilized. The openable and closeable valve35is provided to allow and stop communication between the source37of material and the tube27.

The pressurization arrangement39for causing material in the source37of material to be introduced into the tube27from the source of material when the valve35is in an open position is provided. The valve35is connected to the source41of power for opening and closing the valve. The heater35is connected to the source41of power. The source41of power is connected to the control device43for controlling the supply of power from the source of power to the heater33and the valve35, as well as to any other components of the aerosol generator.

The step of providing the pressurization arrangement39preferably includes positioning the source37of material in a chamber47and pressurizing the chamber, preferably to about two atmospheres. The source37of material preferably includes a flexible container45. However, other embodiments are also possible. For example, as described with reference to FIGS.5and6A–6B, the source337of material may include a second tube345having first and second ends345a,345b,the first end of the second tube being connected to the second end31of the tube27and the second end345bof the second tube being positioned in the chamber345.

In making the aerosol generator21according to the present invention, it is particularly preferred that the heater33, the tube27, the valve35, the source37of material, and the pressurization arrangement39are arranged relative to each other to form a first component23, and that the source41of power and the control device43are arranged relative to each other to form a second component25, and that the second component is attachable to and detachable from the first component. In this way, the second component25can be made as a permanent device, with most or all of the more expensive features of the aerosol generator being associated with the second component, and the first component23, which preferably includes the depletable or less expensive components of the aerosol generator, can be disposable. The different features of the aerosol generator21can be provided on whichever one of the components23and25seems appropriate for a particular application. However, according to the presently envisioned preferred application of the aerosol generator as a medical inhaler device, it is believed that the arrangement of features on the components23and25properly distributes the more and less disposable features.

The aerosol generator21is preferably used by a user providing a first signal, indicative of a user's intention to use the aerosol generator, to the control device43. The first signal may be provided by the user pressing a button58(FIG. 2, in phantom) but, particularly where the aerosol generator21is intended to be used as an inhaler device, it is preferred that the first signal be provided by some form of draw-actuated device, such as a pressure drop detecting sensor53or, more preferably, an air flow detecting sensor51.

The control device43, in response to the first signal, sends a second signal to the source of power41to cause the source of power to open the openable and closeable valve35. The valve35is preferably disposed between the tube27and the source37of material. Opening of the valve35permits material from the source37of material to flow from the source of material and into the tube27.

Material from the source37of material is caused to flow from the source of material and into the tube27, preferably by means of the pressurization arrangement. The source37of material preferably includes the flexible container45, and material in container is caused to flow from the source of material by a pressurization arrangement39. The pressurization arrangement39preferably includes the chamber47filled with gas G under pressure and in which the flexible container45is disposed. In an alternative embodiment, as described with reference to FIGS.5and6A–6C, the source337of material includes the second tube345having first and second ends345a,345b.The first end345aof the second tube345is connected to the second end31of the tube27, and material in the source337of material is caused to flow from the source of material by the pressurization arrangement339. The pressurization arrangement339includes a chamber347filled with gas G under pressure and in which the second end345bof the second tube345is disposed.

A third signal is sent by the control device43and in response to the first signal to the source41of power to supply power to the heater33disposed relative to the tube27to heat the tube. Material from the source37of material is heated in the tube27with the heater35to a vaporization temperature such that the material volatilizes and expands out of the first end29of the tube.

The aerosol generator according to the present invention is preferably constructed in accordance with certain design principles that the inventors have recognized. These design relationships permit design of the aerosol generator with a certain robustness, particularly with respect to ambient temperature and container pressure variations, such that it is possible to ensure that the rate of aerosol delivery is substantially constant. While not wishing to be bound by theory, one relationship involves the rate at which aerosol is delivered (D), which is understood to be substantially linearly related to the pressure delivered to the liquid to be volatilized, i.e., the pressure (P), according to the relationship: D=k1P, where k1is substantially constant and depends upon design factors peculiar to the particular aerosol generator.

The control device43can be programmed to ensure that as the pressure of the gas G drops certain changes in operation to accommodate these changes will take place. For example, as the pressure of the gas G drops, delivery of the same amount of material will take a longer time. Accordingly, the control device43can be programmed to, for example, keep the valve35open for a longer time. While not wishing to be bound by theory, in the case where the flow passage comprises a circular bore of capillary tube, for a given aerosol delivery rate D, tube diameter d could be chosen taking into account the effect of tube diameter upon particle size.

It is desirable that an inhaler deliver an accurately repeatable volume of medication to a user. In developing an inhaler which operates by volatilizing a fluid delivered to a heated flow passage such as a tube, it is desirable to deliver a repeatable and precise volume to the heated tube. Thus, a metering device for use in an inhaler according to the invention is preferably capable of reliably delivering a known volume of fluid to an aerosolizing portion of an inhaler (e.g., a heated tube).

According to one embodiment of the invention, an inhaler is provided wherein one or more parts contacted by medicated fluid are disposable after a particular number of delivered inhalation doses (e.g., 200). As such, it would be desirable for a metering device of such an inhaler to have a simple and cost-efficient design including a minimum number of wetted parts.

A metering device in accordance with a preferred embodiment of the present invention includes a pressurized source of medicated fluid and a metering chamber which provides precise and repeatable volumetric dispensing of the fluid. The metering device preferably includes a small number of wetted parts and is simple to manufacture.

For a better understanding of the invention, the following detailed description refers to the accompanying drawings, wherein exemplary embodiments of the present invention are illustrated and described.

An inhaler401including an exemplary metering device403is shown schematically inFIG. 7. In this example, a rotary valve405in a housing406contains a metering chamber407. The rotary valve405is located between a pressurized source of fluid408and a heated flow passage comprising a tube409in which the fluid is volatilized to produce an aerosol for inhalation by a user. The tube409can be heated by any suitable arrangement. For example, a power source411and electrical connections413for heating the tube409via a heater (not shown) are also shown schematically inFIG. 7.

In this example the metering chamber407in the rotary valve includes a bore415containing a sliding or “floating” piston417. First and second openings419,421at each end of the bore415can have diameters smaller than the diameter of the piston417so that the piston417is contained within the bore415. However, the piston417can be maintained in the bore415by any suitable arrangement such as by providing suitably sized flow passages in housing406which contain the piston in the bore. A predetermined volume is defined as the difference between the volume of the bore415and the volume of the piston417.

According to this arrangement the predetermined volume is delivered with each stroke of the piston417. For example, pressurized fluid enters the first opening419in the rotary valve and moves the sliding piston417from a first position where the sliding piston417is adjacent the first opening419in the bore to a second position where the sliding piston417is adjacent to the second opening421, thereby loading the predetermined volume of fluid into the rotary valve405. When the rotary valve405is rotated to bring the second opening421of the bore into fluid communication with the pressurized source of fluid408, the sliding piston417moves under pressure of the fluid from the first position to the second position to eject the predetermined volume out of the first opening419into a heated tube409and load a new predetermined volume through the second opening421in the rotary valve405. Thus, in the example shown inFIG. 7, each 180° turn of the rotary valve405simultaneously ejects a predetermined volume of fluid and loads the next predetermined volume of the fluid. The rotary valve can be rotated by any suitable technique, e.g., manually such as by actuation of a push button connected to suitable gears or linkage or electronically such as by actuation of a switch which operates a motor connected to the valve. A push button actuator is discussed in more detail in connection with the dose metering device shown inFIGS. 9 and 10.

Preferably, to prevent fluid leakage, the piston417includes one or more sliding seals such as O-rings425which also separate a load side of the piston from an ejection side of the piston417. Other means of sealing the load side of the piston417from the ejection side of the piston417are also within the scope of the invention. For example, the piston417can be designed in a manner and/or made of a material which provides one or more sections which matingly engage the bore to slidingly seal the ejection side of the load side.

The predetermined volume is determined by the difference between the volume of the sliding piston417and the volume of the bore415. For example a 5 μl volume can be delivered by a piston having a 0.093 inch diameter and a stroke of 0.048 inches within the bore415. The predetermined volume can be modified simply by changing a single dimension of the metering chamber407. For example the predetermined volume can be increased by shortening the piston417or increasing the length of the bore415, thereby increasing the stroke of the piston417. Accordingly, the predetermined volume can be easily and inexpensively modified to accommodate children's inhalation doses and adult inhalation doses, as well as the varying delivered volumes required for a range of medications.

According to a modified embodiment, the piston can be replaced with a flexible diaphragm427secured within the bore415. An example of a rotary valve of this sort is shown schematically inFIG. 8wherein the volume in one side of the bore is ejected when the diaphragm427is displaced by fluid from the pressurized source of fluid408filling the other side of the bore. The predetermined volume is determined by the volume of the bore415on an ejection side of the diaphragm427displaced by the diaphragm427. An advantage of the displacement member being a diaphragm is that there is less chance of the pressurized fluid bypassing the displacement member or of the displacement member malfunctioning as a result of incomplete movement along the bore.

It is desirable that the pressurized source of fluid408maintain a substantially constant pressure as fluid is depleted from the pressurized source408. That is, it is preferred that there be an insignificant change in pressure of the fluid delivered by the source408between delivery of the first delivered volume and the last delivered volume. The source of fluid408can be pressurized in any suitable manner. For instance, as shown inFIGS. 7 and 8, an elastic member such as a spring429can be used to bias a piston431against the fluid. Alternately, a pressurized gas can bias a piston against the fluid or fluid contained in a sealed collapsible bag. When a spring and piston mechanism is used to pressurize the source of fluid, the stroke of the piston is preferably small relative to the volume of fluid contained in the source to minimize the change in pressure as the fluid is depleted.

An example of a mechanism for actuating the rotary valve405is shown schematically inFIGS. 9 and 10wherein the rotary valve405can be actuated by a spring-loaded pushbutton435. Each time the spring-loaded pushbutton435is depressed, the rotary valve405is rotated approximately 180° thereby ejecting the predetermined volume of fluid out of the bore415. The pushbutton mechanism includes a spring-loaded pushbutton435pivotable connected to a ratchet arm437. A proximal end439of the ratchet arm437is pivotably attached to the pushbutton435and the distal end441of the ratchet arm437engages a pin443on a first gear445with a notch447at the distal end441of the ratchet arm437. The first gear includes six pins443spaced 60° apart. As the button435is depressed, the ratchet arm437exerts force on one of the six pins443pushing the first gear445in a clockwise direction. A spring449is attached at one end to a part of the inhaler which is stationary with respect to the movement of the ratchet arm437. Another end of the spring449is attached to the ratchet arm437and pulls the ratchet arm437back to a start position after the button435has been depressed. The notch447at the distal end441of the ratchet arm437is then positioned adjacent a next pin of the first gear445.

The first gear445engages a second gear451which is on a shaft452connected to the rotary valve405. As the shaft452is rotated, the bore415is rotated relative to the source of fluid408. For example, the first gear445can include 60 teeth and the second gear451can include 20 teeth such that when the first gear is rotated 60° the second gear451rotates 180°.

It is desirable to time heating of the flow passage in a capillary aerosol type inhaler with the ejection of the predetermined volume of fluid so that the fluid is efficiently volatilized in the flow passage. An exemplary timing device includes a pair of contacts or cam surfaces453on the second gear451to provide exposed ends455spaced about 180° from one another. A spring-loaded electrical contact or switch457is connected to a heating mechanism (not shown) for the flow passage. The spring loaded electrical contact or switch457is triggered each time it makes contact with an end of the surface457. Thus, according to this embodiment, each 180° rotation of the shaft452containing the rotary valve405ejects a predetermined volume, loads a predetermined volume and triggers the heating mechanism to heat the attached flow passage.

As mentioned in the embodiment described inFIG. 7, it is desirable to maintain a constant pressure in the pressurized source of fluid. An example of a mechanism minimizing the pressure loss as the fluid source is depleted is shown inFIG. 9. In this example, the metering chamber407is in fluid communication with a source408including two reservoirs459of pressurized fluid. Each reservoir459has a spring-loaded piston461which travels a shorter distance over the dispensing of the entire source volume than a single spring and piston arrangement having the same cross-sectional area as one of the two piston and reservoir arrangements. In this way, the difference in pressure exerted against the fluid in the initial filled condition and a later depleted condition can be minimized.

Another example of a metering device463according to the present invention is shown schematically inFIGS. 11–13. In this example, a metering chamber464is part of a delivery passage465having an elastic portion467. A source of medicated fluid469is in fluid communication with the delivery passage465. The elastic portion467of the delivery passage465is deformed to eject a predetermined volume of fluid out of the delivery passage469.

FIGS. 11A–11Cschematically show an embodiment of a metering device463according to the present invention. In this example, the delivery passage465is formed out of an elastic tube471. The elastic tube471can be formed of silicone or other known elastic materials. A first deforming member such as a pinch roller473deforms the elastic tube471such that fluid is prevented from flowing through the tube downstream of the roller473. Upstream of the first deforming member473is a second deforming member such as a metering roller475. The metering roller475is configured to travel a predetermined path477. In at least a portion of the path477, the metering roller475acts as a displacement member when it comes into contact with the elastic tube471to deform a portion of the elastic tube471and exert pressure on the fluid contained therein. Simultaneously, the pinch roller473is moved sufficiently to allow predetermined volume of fluid to be ejected from the tube471. The pinch roller473may be withdrawn or raised by the pressure generated by the metering roller475or by a suitable mechanical arrangement like the arrangements shown inFIGS. 12 and 13.

The predetermined volume is determined by an inner diameter of the elastic tube471and the length of the tube471which is sealed off and emptied by the metering roller475. As in the other examples illustrating the present invention, the predetermined volume can be varied by changing a single dimension of the metering device. For example, to increase the predetermined volume, an inner diameter of the elastic tube471or path of roller475can be increased.

An advantage of this example of a metering device463is that the fluid can be isolated in the elastic tube thus avoiding direct contact with moving parts. Also, in a reusable inhaler, the liquid source can be designed to be replaced with a cartridge having the delivery passage465attached thereto after a predescribed number of metered volumes have been delivered by a depleted liquid source.

Another example of a metering device463according to present invention is shown schematically inFIGS. 12 and 13. In this example, the source of fluid469is pressurized by a spring479connected to a piston481. A metering chamber483is part of a delivery passage485which includes an elastic portion487. The elastic portion487of the delivery passage485is formed by an elastic sheet489(FIG. 13) sealed over a portion of the delivery passage485. The elastic sheet489can be formed of silicone or other suitable elastic material.

In the example shown, a wheel491including five rollers493is located adjacent the elastic portion487of the delivery passage485. Each roller493is separated from adjacent rollers by 72°. The wheel491is arranged adjacent the elastic portion487of the delivery passage485so that as the wheel491is rotated the convex surfaces of the rollers493deform the elastic sheet489into and against the convex surface of the delivery passage485.

As shown inFIGS. 12 and 13, the portion of the delivery passage between the rollers493in contact with the sheet489defines a metered volume of liquid to be delivered to the inhaler. As the wheel491rotates 72°, the rollers493in contact with the elastic sheet489move the fluid contained in the delivery passage485between the rollers in a downstream direction for delivery to a spray mechanism of the inhaler. The pressurized source of fluid469fills the passage485as the rollers493pass inlet484of the metering chamber483. In this way, a predetermined volume of the fluid can be urged through the delivery passage into a heated flow passage of an inhaler which ejects the volatilized fluid to form an aerosol spray. The volume of the delivery channel contained between two adjacent rollers determines the predetermined volume and is dependent on the distance between the adjacent rollers493on the wheel491. In the embodiment shown inFIGS. 12 and 13, a metered volume is ejected each time the wheel491is rotated 72°.

The wheel491rotates on a shaft495which can be turned manually or with a mechanical, or electromechanical mechanism. For example, the shaft495can be turned by a conventional spring driven clock motor497. According to this arrangement the flow rate of fluid ejected can be controlled in addition to the predetermined volume. The clock motor497controls the time period and rate at which the wheel491rotates the predetermined distance. In this way, the predetermined volume can be metered at a predetermined rate.

The components of the metering chamber according to the present invention can be manufactured using conventional injection molding techniques. The components can be molded out of plastic resins or other materials known to be appropriate for inhaler applications.

According to the present invention a metering device can be provided which delivers a repeatable, precise volume of a medicated fluid in an inhaler. In addition, the metering device according to the present invention has few wetted parts and is simple to manufacture. Accordingly, the metering device according to the present invention is well suited for use in inhalers and in particular heated capillary aerosol inhalers.

While this invention has been illustrated and described in accordance with a preferred embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims. For instance, the aerosol generator could include arrangements for manually operating the valve35, i.e., instead of actuation by detection of air flow or pressure drop, with the controller43being configured to execute a scheduled heating cycle upon receipt of a signal indicating actuation of the valve. Such arrangements might further include devices (electrical or mechanical) to maintain the valve35in an opened position for a predetermined amount of time once it is mechanically actuated. Further, the mouthpiece is optional and need not be incorporated in inhalers or other devices utilizing the aerosol generator according to the invention.