Free flow aerosol valves

#This invention relates to a metered dose dispensing valve for dispensing metered volumes of a pressurised aerosol formulation from an aerosol container. In particular, the invention relates to an aerosol valve suitable for dispensing metered doses of medicament for administration to the respiratory system of a patient.

#The use of aerosol devices to administer drug or other therapeutically active compounds by inhalation therapy is common, particularly for the treatment of respiratory disorders, such as, asthma. Aerosol containers are charged with a self-propelling liquid composition comprising an aerosol propellant having medicament dispersed or dissolved therein and the container is equipped with a valve capable of discharging a metered amount of the self-propelling composition.

#Metered dose valves which have been used on commercially available aerosol inhalers comprise a fixed metering chamber having a movable valve stem extending therethrough. When the valve stem is in its closed position, there is a path for pressurised aerosol formulation in the aerosol container to pass into the metering chamber. As the valve stem is moved to its dispensing position, communication between the metering chamber and aerosol container is blocked thereby defining a fixed volume of pressurised aerosol formulation within the metering chamber. Further movement of the valve stem causes a discharge orifice in the valve stem to enter the metering chamber thereby allowing the contents of the chamber to be expelled through the valve stem under the influence of the aerosol propellant. Thus, in this type of metering valve, the metered volume of the aerosol formulation remains effectively stationary and the valve stem is moved into the metered volume of formulation until a discharge orifice in the valve stem communicates with the metering chamber.

#The invention will now be described with reference to the accompanying drawings in which:

#FIGS. 1a and 1b represent a longitudinal cross-section through a valve in accordance with the invention in its priming and dispensing positions respectively,

#FIGS. 2a to 2i represent diametric cross-sections through sealing elements suitable for use in the invention,

#Referring to FIGS. 1a and 1b a valve of the invention comprises a body (2) having an annular seal or gasket (4) for engaging the neck of an aerosol container (not shown) to facilitate a gas-tight seal. The body (2) may be secured to the aerosol container by any suitable means e.g. a conventional outer casing or ferrule (not shown) which is crimped around the neck of the aerosol container.

#The body (2) defines a chamber (6) having an inlet passage (8) and an outlet passage (10) for dispensing pressurised aerosol formulation. A valve stem (12) extends through the chamber (6) and is movable between a closed or priming position shown in FIG. 1a and a dispensing position as shown in FIG. 1b. The valve stem (12) is biased to its dispensing position by means of a spring (14). The valve stem (12) is fitted with an inner seal (16) and outer seal (18) which provide gas-tight seals between the valve stem and the inner wall of the chamber (6). The chamber (6), external dimensions of the valve stem (12) and position of the seals (16 and 18) are arranged to define a pre-determined volume within the chamber (6) between the seals (16 and 18).

#In operation the valve stem (12) is moved inwardly against the bias of the spring (14) to the priming position shown in FIG. 1a. In the closed or priming position, aerosol formulation contained in the aerosol can or vial may freely enter or leave the chamber via the annular inlet between the seal (16) and the open end of the chamber as depicted by the arrow. With the aerosol unit held in this valve-down orientation, the design of the valve readily allows satisfactory doses to be obtained even when the aerosol vial is nearly empty, thereby preventing significant wastage of formulation. The inlet (8) is positioned at a level allowing substantially complete emptying of the aerosol container.