Patent ID: 11104506

Abstract:
A pressure pack dispenser (100) for dispensing a product comprises a cylindrical container (401) with a product outlet through which the product is dispensed, a composite piston (408) movably mounted within the container, and a pressurised propellant. The composite piston comprises a first upper piston (409A) coupled to a second lower piston (409B) to permit limited relative axial movement and a viscous sealant material (410) located between the first and second pistons. The propellant comprises a compressed gas which remains in the gaseous phase as the piston (408) moves from a first full position to a second exhausted position, or a mixture of a liquid propellant and a compressed gas selected such that in the full position the mixture is at a pressure greater than the vapour pressure of the liquid propellant. A clearance is provided between the second lower piston (409B) and the container wall (401A) which is filled with the sealant (410) as the composite piston moves to expel product. The viscosity of the sealant and clearance are selected such that a thin film of viscous sealant material (410A) is left on the container wall of the propellant chamber, thereby reducing friction between the composite piston (408) and the container wall (401A). The sealant (410) preferably comprises a mixture of glycerine and starch, and has a viscosity of less than 100 poise and less than 4000 poise at 20° C.