Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D83/00—Containers or packages with special means for dispensing contents
  • B65D83/14—Containers or packages with special means for dispensing contents for delivery of liquid or semi-liquid contents by internal gaseous pressure, i.e. aerosol containers comprising propellant for a product delivered by a propellant
  • B65D83/44—Valves specially adapted therefor; Regulating devices
  • B65D83/52—Valves specially adapted therefor; Regulating devices for metering
  • B65D83/54—Metering valves ; Metering valve assemblies

Definitions

• the present invention relates to a metered dose dis- an.
• Metered dose dispensers find many practical applications.
• the me- tered dose dispenser is typically used to dispense a measured dose of a pharmaceutically active substance from a pressurised aerosol canister into an airway through which inhalation takes place.
• a valve assembly for a typical metered dose inhaler is illustrated in figure 1. It is designed for attachment to a pressurised canister within which is contained a drug product and a propellant.
• the valve assembly constitutes a metered dose dispenser, or metering valve, the purpose of which is to allow doses of the drug product, of a controlled size, to be dispensed into the inhalation airway via a metering chamber 10.
• the boundary wall 12 between the metering chamber 10 and the pressurised canister, forming the lower wall of the metering chamber 10, includes a first vent 14 that allows the metering chamber 10 to communicate with the pressurised canister.
• a second vent 16 is provided in the opposite, upper wall 18 of the metering chamber 10 and both vents 14, 16 are occupied by a valve stem 20 which bears against a circu- lar elastomeric seal in each 22, 24.
• the valve stem 20 is in the form of a tube that is closed at its lower, inner- most end 26 and open at its upper, outermost end 28 and includes a side hole 30 communicating between the inside and the outside of the valve stem 20 and an indented channel 32 towards its lower end 26 that interrupts its normally circular cross-section.
• the valve stem 20 is normally in an elevated or extended position, in which the channel 32 is located within the first vent 14 and allows the canister to communicate with the metering chamber 10. This primes the metering chamber 10.
• the valve stem 20 is depressed against the bias of a spring 34, firstly the channel 32 moves below the seal 22 in the first vent 14, isolating the canister from the metering chamber 10. This is the situation as illustrated in figure 1.
• the side hole 30 moves below the seal 24 in the second vent 16, allowing the metering chamber 10 to communicate with the outside via the side hole 30 and the open end 28 of the valve stem 20.
• the open end 28 of the valve stem 20 is located in a rebate in an inhaler body that acts as a bearing surface for depression of the valve stem 20 and also provides a conduit for the drug to be dispensed into the inhalation airway.
• CFC chlorofluorocarbon
• the drug product may be more inclined to agglomerate, particularly if it is stored in the canister as an emulsion or suspension, or to stick to the surfaces of the inhaler with which it makes contact, such as the inside of the canister.
• the latter problem has been addressed with some measure of success by coating the inside of the canister with PTFE or other non-stick compounds.
• the former problem has been addressed by including in the formulation of drug and propellant a surfactant of an appropriate kind.
• the surfactant can help to keep the droplets of an emulsion stable, to prevent droplets of the drug from adhering to the walls of the canister or to one another and can also act as a lubricant .
• the US FDA will in due course discourage the use of surfactants in drug formulations for metered dose inhalers. This brings to the foreground the deficiencies in conventional dose metering systems that are caused or exacerbated by the switch from CFC propellants. These deficiencies include inconsistent dose sizes, a rate of leakage of product from the canister, usually via a path different from the dispensing path, that is higher than is desirable and friction between the moving parts of the inhaler causing inconsistent dosing, or poor perception of quality on the part of the user.
• Metered dose inhalers conventionally require a spring to bias the valve stem back to its extended positions once it has been depressed to dispense a dose of drug product.
• the conventional positioning of such springs has left them prone to promote deposition of the drug product. This can lead to poor quality of operation of the valve stem, which may result in incomplete dosing. Uniformity of dosing is compromised when the active drug is deposited, than later released. It can also interfere with the free flow of drug product out of the device.
• figure 1 show just such an arrangement, in which the spring 34 acts between a cup 36, in which the closed end 26 of the valve stem 20 is received, and the base 38 of a perforated cage 40. It is permanently exposed to drug product within the pressurised canister.
• valve assembly in which the common boundary wall between the metering chamber and the pressurised storage reservoir is elastic. Depression of the valve stem flexes the boundary wall, thus closing a vent in it that would otherwise allow the metering chamber to communicate with the storage reservoir.
• a first aspect of the present invention provides a valve assembly for a metered dose dispenser comprising: a metering chamber having a elastic wall that is adapted to form a common boundary between the metering chamber and a pressurised storage reservoir to which it is to be attached and in which the elastic wall includes a vent that allows the metering chamber to communicate with the storage reservoir and an opposing wall of the metering chamber includes a second vent; and a valve stem that is movable via the second vent between depressed positions in which the inside of the metering chamber is in communication with the outside via the valve stem and extended positions in which the inside of the metering chamber is isolated from the outside; in which movement of the valve stem through its extended positions to its depressed positions causes the boundary wall to flex, thus closing the vent before the stem reaches the threshold between its extended and depressed positions.
• valve stem when extended by the pressure within the metering chamber and/or the elastic recovery of the valve body, to remain within the second vent, so that no separate sealing arrangement for the second vent is required.
• a stop of an appropriate form might be used to ensure that this hap- pens, but it any case it is preferred that in all extended and depressed positions of the valve stem, an innermost end of the valve stem lies within the metering chamber and an outermost end of the valve stem lies outside it.
• a valve stem of essentially conventional construction can be used, in the form of a tube that is closed at its innermost end and open at its outermost end and including a side hole communicating between the inside and the outside of the valve stem.
• the inside of the metering chamber is in communication with the outside via the side hole and the open end of the valve stem.
• the valve stem is no need for the valve stem to include an indented channel towards its lower end. This makes it easier to manufacture.
• the pressure difference between the canister and the outside can be used to extend the valve stem once a dose has been delivered. If the valve assem- bly is so arranged that the flexing of the boundary wall caused by movement of the valve stem through its extended positions to its depressed positions is brought about by the innermost end of the valve stem bearing against the boundary wall, then a further benefit arises.
• This bene- fit is that the pressure within the canister will act against the flexing of the boundary wall and provide an additional restoring force counteracting that flexing. Therefore, the initial return of the boundary wall to its rest configuration is assisted by the pressure differ- ence, in this case between the canister and the metering chamber.
• a second aspect of the present invention provides a valve assembly for a metered dose dispenser comprising: a metering chamber having a flexible wall that is adapted to form a common boundary between the metering chamber and a pressurised storage reservoir to which it is to be attached and in which the flexible wall includes a vent that allows the metering chamber to communicate with the storage reservoir and an opposing wall of the metering chamber includes a second vent; and a valve stem that is movable via the second vent between depressed positions in which the inside of the metering chamber is in communication with the outside via the valve stem and extended positions in which the inside of the metering chamber is isolated from the outside; in which movement of the valve stem through its ex- tended positions to its depressed positions causes an innermost end of the valve stem to bear against the boundary wall, in turn causing the boundary wall to flex, thus closing the vent before the stem reaches the threshold between its extended and depressed positions.
• the vent is a simple hole in the boundary wall that forms a seat for and is closed by the innermost end of the valve stem.
• the vent could include a check valve, such as a flap overlying it, that is operated by the innermost end of the valve stem.
• the sealing surface no longer lies perpendicular to the direction of ' the lateral forces; it lies parallel or substantially parallel.
• the flexible wall include a hole that is smaller than the diameter of the valve stem that receives and forms a seal with a projection on the innermost end of the valve stem.
• the present invention also provides a metered dose dispenser comprising a pressurised storage reservoir and a valve assembly according to the present invention attached to it so that the common boundary wall is a common boundary of the metering chamber and the storage reser- voir.
• Figure 1 is a conventional valve assembly for a metered dose inhaler,-
• Figures 2-4 show essentially similar metered dose inhalers according to the present invention, of different nominal dosing volumes.
• Figure 2 shows a metered dose inhaler accord- ing to the present invention having a nominal dose size of 100 ⁇ £ .
• the inhaler consists of a pressurised stainless steel or aluminium alloy canister 40 that acts as a reservoir for a drug product, upon which is mounted a valve assembly that acts as a metered dose dispenser, or metering valve.
• An engineered elastomer main body 42 of the valve assembly is located over the open end of the canister 40 and provides an annular seal at 46.
• the main body 42 is secured to the end of the canister 40 by an aluminium ferrule 48.
• the ferrule 48 shown in figure 2 has been partially formed, but requires a further forming operation to conform to the exterior shape of the end of the canister 40, so as to secure the main body 42 in place .
• the main body 42 is made of a suitably engineered elas- tomer or rubber, designed for long-term dimensional stability, low release of organic or inorganic compounds, low permeability, low swell, high strength and low drug adhesion.
• the main body 42 includes a central cavity 70 that extends neither to the top of the main body 42, nor to its base.
• the central cavity 70 forms a metering chamber.
• a flexible, elastic wall 72 Between the bottom of the cavity 70 and the base of the main body 42 is formed a flexible, elastic wall 72. Holes 50 in the elastic wall 72 are provided to form a first vent between the metering chamber 70 and the canister 40 and the material surrounding the holes 50 is designed to provide a first seal as will be described later.
• the flexible wall 72 provides a boundary wall between the metering chamber 70 and the pressurised canister 40.
• the material of the main body 42 gives way to a second vent, the exposed sides of which provide a second seal 74.
• the second vent is occupied by a valve stem 20 which bears against the second seal 74.
• the valve stem 20 is formed from deep-drawn stainless steel into the form of a tube that is closed at its lower, innermost end 26 and open at its upper, outermost end (not shown) and includes a side hole 30 communicating between the inside and the outside of the valve stem 20.
• a projection 76 is formed on the lower end 26 and passes through and seals with a central hole 78 of the flexible wall 72. This substantially reduces the likelihood of side-streaming whist the valve stem 20 is depressed as described above, because the relevant seal- ing surface is substantially horizontal and the valve stem is centred by the central hole 78 and the projection 76.
• the valve stem includes a crimped waist 60 that forms an abutment for the upper wall of the cavity 70.
• the valve stem 20 is normally in an elevated or extended position as shown in figure 2, in which the innermost end 26 of the valve stem 20 is clear of the first vent 50 and allows the canister 40 to communicate with the metering chamber 70. This primes the metering chamber 70.
• the valve stem 20 As the valve stem 20 is depressed, it bears against the flexible wall 72, causing the wall to flex and wrap around the innermost end 26 of the valve stem 20, until the first vent 50 is sealed off by the innermost end 26 of the valve stem 20, isolating the canister 40 from the meter- ing chamber 70.
• the elastic, flexible wall 72 resists the movement of the valve stem, providing a bias or tangible feedback.
• the elastic, flexible wall 72 tends to return to its rest configuration as shown in figure 2 owing firstly to its own elasticity and secondly to the pressure difference that now exists between the canister 40 and the metering chamber 70.
• the seal of the first vent 50 is lifted and the metering chamber 70 is primed once more.
• Figure 3 shows an inhaler similar to that of figure 2, but is designed to a nominal dose size of 50 ⁇ £ . Many of the same components are used in figure 3 as are used in figure 2 and the only real difference is the use of a main body 42 with a smaller central cavity 70.
• Figure 4 shows an inhaler essentially similar to that of figure 3, but with a nominal dose size of 25 ⁇ l . It has a yet smaller central cavity 72 in the main body 42.

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• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Containers And Packaging Bodies Having A Special Means To Remove Contents (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 2000
  • 2000-04-14 GB GB0009138A patent/GB2361228A/en not_active Withdrawn
• 2001
  • 2001-04-17 AU AU48558/01A patent/AU4855801A/en not_active Abandoned
  • 2001-04-17 EP EP01921585A patent/EP1272400A1/de not_active Withdrawn
  • 2001-04-17 WO PCT/GB2001/001691 patent/WO2001079078A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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