Dispensing – Resilient wall – Supply container delivering to receiving chamber
Patent
1996-04-24
1998-07-07
Derakshani, Philippe
Dispensing
Resilient wall
Supply container delivering to receiving chamber
2224022, 22240224, B65D 8314
Patent
active
057755450
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates to a metering valve for aerosols.
Valves are known which are affixed to aerosol cans and are designed to release one measured dose of product/propellant mixture per actuation. These valves are typically used with medicinal aerosols, such as Metered Dose Inhalers for treating asthma and other conditions, where the product is a powdered drug suspended in a liquid propellant. There is a present need for a design of metering valve which does not employ any sliding sealing faces because some products or powders can migrate past this type of seal and cause leakage or incorrect dosage. Examples of aerosols utilising sliding seal type metering valves are shown in U.S. Pat. No. 3,301,444.
U.S. Pat. No. 2,835,417 describes a metered dosage valve for a container of fluid under pressure. The valve has a tubular measuring chamber having a resilient sealing gasket at one end with a central opening through which a hollow valve stem extends into the measuring chamber. The stem is depressable to close a normally open discharge passage from the measuring chamber and then supply fluid to the measuring chamber. When the valve stem is moved downwardly from its normal position, the centre portion of the gasket is bent downwardly so that when the downward force on the stem is released, the resilient gasket acts to urge the valve stem upwardly to its initial position.
Although this seal does not involve a sliding action, after repeated deformation resulting from operation of the stem the gasket is likely to deteriorate and become less resilient which would lead to less efficiency in the sealing of the valve and allow migration of products or powders past it. Furthermore, it could lead to less effective sealing against the valve stem which would lead to the same problems mentioned above in that some products or powders could migrate past the seal and cause leakage or incorrect dosage.
Therefore according to the invention, there is provided a metering valve to be fitted to an aerosol container for dispensing a product, said valve comprising a housing, a metering chamber located within said housing and a hollow actuator stem extending into the chamber and axially slidable relative thereto, the metering chamber and actuator stem being moveable into and out of positive sealing contact with oppositely facing valve seats provided on the valve housing and the metering chamber respectively, and sealing means being provided between the actuator stem and the housing and fixed to the housing such that relative movement between the stem and housing is permitted, characterised in that the sealing means consist of a flexible web or membrane fixed to the actuator stem.
The provision of oppositely facing valve seats with a fixed flexible membrane or web averts the use of sliding or deforming seals resulting in a considerably improved metering valve.
In each of the metering valves described in U.S. Pat. No. 3,301,444, a further problem arises in that the metering chamber which receives aerosol prior to dispensing is refilled with a fresh dose of aerosol immediately after the previous dose of aerosol has been dispensed therefrom. The fresh dose then remains in the metering chamber until the valve is subsequently operated to dispense the next dose. Such an arrangement is disadvantageous in that the fresh does of aerosol can tend to drain from the metering chamber at least to some extent over a period of time. When that happens, the next dispensed dose will be incomplete and can have undesirable consequences for a person suffering, for example, from asthma where the correctness of the initial dose is important. Moreover, where a fresh charge of aerosol remains in the metering chamber for a long period of time, the suspended drug can settle in the chamber and will not be properly discharged from the dispensing chamber when the next dose is dispensed.
The invention further provides that the metering chamber receives aerosol for dispensing by the actuator stem and the sealing contact of the
REFERENCES:
patent: 2835417 (1958-05-01), Kiraly
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