Patent ID: 6880732
Filing Date: 2005-04-19
Classification: B65D

Abstract:
1. A piston adapted to be used in a pressurized dispensing container for dispensing product that is loaded into the container under pressure and which product is substantially more flowable when loaded into the container than when dispensed, comprising: an annular sidewall having an upper end and a lower end, said upper end of said piston sidewall being substantially rigid and having a first outer diameter to provide a clearance with the wall of the container with which it is designed to be used, said first clearance being small enough to aid in maintaining an effective seal during loading of product into the container yet large enough to permit piston movement under pressure during dispensing, said lower end of said piston sidewall having a second outer diameter to provide an interference fit with the wall of the container, said interference fit being small enough to permit piston movement under pressure during dispensing, said first small clearance at said upper end and said interference fit at said lower end cooperating to minimize product leakage past said upper end during loading, said interference fit at said lower end being adequate to minimize by-pass during charging of propellant into the container, at least a major portion of said piston sidewall between said upper end and said lower end has an outer diameter less than said first and second outer diameters to provide a recess between said upper and lower ends, the primary component of frictional resistance to movement of the piston in the container during the dispensing of product is the degree of engagement between said upper and lower ends of said piston sidewall and the sidewall of the container.