Dispensing – With discharge assistant – Fluid pressure
Reexamination Certificate
1999-12-22
2001-11-20
Derakshani, Philippe (Department: 3754)
Dispensing
With discharge assistant
Fluid pressure
C277S945000
Reexamination Certificate
active
06318603
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a valve for an aerosol container with the aid of which a quantity of the contents thereof can be dispensed. The invention has particular application to the dispensing of metered doses of medicaments, though it is applicable to the dispensing of aerosols generally.
The continuing use of aerosol formulations comprising conventional chlorofluorocarbon propellants is being debated due to the suspected role of such propellants in atmospheric depletion of ozone. Accordingly, formulations based on alternative propellants such as HFA-134a (1,1,1,2-tetrafluoroethane) and HFA-227 (1,1,1,2,3,3,3-heptafluropropane) are being developed to replace those conventional propellants thought to contribute to atmospheric ozone depletion.
Containers for aerosol formulations commonly comprise a vial body coupled to a valve. The valve comprises a valve stem through which the formulations is dispensed. Generally the valve includes a rubber valve seal intended to allow reciprocal movement of the valve stem while preventing leakage of propellant from the container.
It has been found that some conventional devices for delivering aerosols suffer impaired performance when used in connection with HRA-134a or HFA-227. Selection of suitable materials for use in valves to contain aerosol formulations based on these alternative propellants is complicated by interactions between the valve component materials and the formulation components, including the propellant. In conventional devices, particularly with some drug formulations the valve stem tends to stick, pause, or drag during the actuation cycle with the result that the user perceives a ‘notchiness’ as the valve stem is depressed and released. This may be partly caused by the drug to be dispensed from the container sedimenting or precipitating out of the drug-propellant suspension or solution formulation and depositing on the internal valve components, the presence of drug on the sliding interface creating increased friction during operation.
SUMMARY OF THE INVENTION
International Patent Application No. PCT/US94/06900 describes an aerosol valve wherein the rubber valve seal is made of a composition specially selected to minimize leakage of the propellant through the interface between the valve seal and valve stem upon firing. Smoothness of operation is also improved with some formulations compared to devices involving conventional thermoset rubber seals. However, although such seal compositions may improve valve performance, they do not prevent build up of deposit on the valve components, and the problem of notchiness may persist.
It is an object to provide a valve with improved smoothness of operation which alleviates the problem of valve sticking.
According to one aspect of the present invention there is provided a valve for an aerosol container for dispensing a suspension of a substance in a liquid propellant contained therein, the valve comprising a valve body defining an aperture, a seal mounted at the aperture, and a valve stem having and dispensing passage, the valve stem being slidably moveable through the seal such that in a first position the valve is closed to prevent the substance to be dispensed from entering the dispensing passage, and a in a second position the valve is open to allow the substance to be dispensed through the dispensing passage, characterised in that the valve stem is made from a material comprising lubricant.
According to another aspect of the present invention there is provided a valve stem made from a material comprising lubricant. According to a further aspect of the present invention there is provided an aerosol container comprising a valve as described herein.
REFERENCES:
patent: 5450989 (1995-09-01), Gilroy
patent: 0 634 166 A (1995-01-01), None
patent: 0 642 992 A (1995-03-01), None
patent: 2713299 A (1995-06-01), None
patent: 2740527 A (1997-04-01), None
Derakshani Philippe
Rogers Christopher P.
SmithKline Beecham Corporation
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