Valve assembly for metered dose dispensers

Abstract

A valve assembly for a metered dose dispenser is described. A metering chamber and a pressurised storage reservoir have a boundary wall that includes a first vent. An opposing wall of the metering chamber includes a second vent. Each vent includes a seal. A valve stem 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 it is not. Movement of the valve stem through its extended positions to its depressed positions closes the first vent before the stem reaches the threshold between its extended and depressed positions. The limits of the metering chamber are accurately defined by the main body of the valve assembly. The first and second seals are positioned between the outer surface of the insert and the inner surfaces of the cavity. A compression spring that surrounds the valve stem acts between the outside of the metering chamber and the outside of the valve stem to bias the valve stem to its extended positions. Accordingly, product from the metering chamber does not come into contact with the spring as it is dispensed via the valve stem. A ferrule attaches the valve assembly to the storage reservoir and includes an opening for passage of the valve stem. The ferrule encapsulates the compression spring and helps reduce side-streaming.

1 . A valve assembly for a metered dose dispenser comprising: 
 a metering chamber having a 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 boundary wall includes a first vent that allows the metering chamber to communicate with the storage reservoir and an opposing wall of the metering chamber includes a second vent, the first and second vents including first and second seals respectively;    a valve stem that is movable via the second vent, in sealing contact with the second seal, 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 sealing contact with the first seal, thus closing the first vent, before the stem reaches the threshold between its extended and depressed positions; and    the limits of the metering chamber are defined by a hollow insert that lies between the first and second seals, both seals being positioned outside the metering chamber.    
     
     
         2 . A valve assembly according to  claim 1  in which the proportion of the surface area of the metering chamber provided by the seals is no greater than 10%.  
     
     
         3 . A valve assembly according to  claim 2  in which the proportion of the surface area of the metering chamber provided by the seals is no greater than 5%.  
     
     
         4 . A valve assembly according to  claim 3  in which the proportion of the surface area of the metering chamber provided by the seals is 2% or less.  
     
     
         5 . A valve assembly according to any one of claims  1 - 4  in which the insert is metallic.  
     
     
         6 . A valve assembly according to  claim 5  in which the insert is formed from stainless steel.  
     
     
         7 . A valve assembly according to any one of claims  1 - 6  comprising a main body having a cavity within which the insert is positioned and in which the first and second seals are positioned between the outer surface of the insert and the inner surfaces of the cavity.  
     
     
         8 . A valve assembly for a metered dose dispenser comprising: 
 a metering chamber having a 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 boundary wall includes a vent that allows the metering chamber to communicate with the storage reservoir; and    a valve stem that is movable between depressed positions in which the inside of the metering chamber is in communication with the outside to allow product to be dispensed from the metering chamber 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 closes the vent before the stem reaches the threshold between its extended and depressed positions; and    a spring is provided acting between the outside of the metering chamber and the outside of the valve stem to bias the valve stem to its extended positions, such that product from the metering chamber does not come into contact with the spring as it is dispensed via the valve stem.    
     
     
         9 . A valve assembly according to  claim 8  in which the spring is a compression spring.  
     
     
         10 . A valve assembly according to  claim 9  in which the spring is a helical compression spring that surrounds the valve stem.  
     
     
         11 . A valve assembly according to  claim 9  or  claim 10  further including a ferrule for attaching the valve assembly to the storage reservoir, the ferrule including an opening for passage of the valve stem and being adapted, with the walls of the metering chamber, to encapsulate the compression spring.  
     
     
         12 . A valve assembly according to  claim 11  in which the spring is a conical compression spring and in which movement of the valve stem through its extended positions to its depressed positions causes the coils of the spring to nest within one another as the spring is compressed.  
     
     
         13 . 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.  
     
     
         14 . 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.  
     
     
         15 . A valve assembly for a metered dose dispenser comprising: 
 a metering chamber having a 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 boundary wall includes a first vent that allows the metering chamber to communicate with the storage reservoir and an opposing wall of the metering chamber includes a second vent, the first and second vents including first and second seals respectively;    a valve stern that is movable via the second vent, in sealing contact with the second seal, 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 sealing contact with the first seal, thus closing the first vent, before the stem reaches the threshold between its extended and depressed positions; and    the valve stem includes a friction-reducing coating applied to at least those parts of it that contact the first and/or second seals.