Valve assembly for metered dose dispensers

Abstract

A valve assembly for a metered dose dispenser is described. A metering chamber ( 70 ) is formed as a cavity within an elastomeric main body ( 42 ) that also includes a flexible, elastic wall ( 72 ) as an integral part. That wall ( 72 ) forms a common boundary between the metering chamber and a pressurised storage reservoir ( 40 ) and includes a first vent ( 50 ). An opposing wall of main body ( 42 ) includes a second vent. A valve stem ( 20 ) is movable via the second vent between depressed positions in which the inside of the metering chamber ( 70 ) is in communication with the outside via the valve stem ( 20 ) and extended positions in which it is not. As the valve stem is depressed, it bears on the boundary wall ( 72 ), causing it to flex and wrap around the inner-most most end ( 26 ) of the valve stem ( 20 ). This seals off the first vent ( 50 ) before the stem ( 20 ) reaches the threshold between its extended and depressed positions. The pressure within the canister ( 40 ) returns the valve stem ( 20 ) to its extended position.

1 . 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.    
     
     
         2 . An assembly according to  claim 1  in which 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 an innermost end of the valve stem bearing against the boundary wall.  
     
     
         3 . 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 extended positions to its depressed positions causes an innermost end of the valve stem to hear 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.    
     
     
         4 . An assembly according to  claim 2  or  claim 3  in which 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.  
     
     
         5 . An assembly according to any one of claims  2 - 4  in which the flexible wall includes a hole that is smaller than the diameter of the valve stem and the innermost end of the valve stem includes a projection received by and forming a seal with that hole.  
     
     
         6 . An assembly according to any preceding claim in which 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.  
     
     
         7 . An assembly according to  claim 6  in which: 
 the valve stem is in the form of a tube that is closed at its innermost end and open at its outermost end and includes a side hole communicating between the inside and the outside of the valve stem; and  
 when the valve stem is in its depressed positions, the inside of the metering chamber is in communication with the outside via the side hole and the open end of the valve stem.  
 
     
     
         8 . An assembly according to any preceding claim in which the metering chamber is a cavity within a main body of the valve assembly, of which the flexible or elastic wall forms an integral part.  
     
     
         9 . An assembly according to  claim 8  in which the main body is adapted to provide sealing contact with the valve stem at the second vent and sealing contact with the canister.  
     
     
         10 . A valve assembly for a metered dose dispenser substantially as described herein with reference to any one of FIGS.  2 - 4  of the accompanying drawings.  
     
     
         11 . A metered dose dispenser comprising a pressurised storage reservoir and a valve assembly according to any preceding claim attached to it so that the common boundary wall is a common boundary of the metering chamber and the storage reservoir.  
     
     
         12 . A metered dose dispenser comprising a pressurized storage reservoir and a valve assembly according to  claim 9  or  claim 10  attached to it so that the common boundary wall is a common boundary of the metering chamber and the storage reservoir and the main body provides sealing contact with the valve stem at the second vent and sealing contact with the canister.