Patent ID: 6260708
Filing Date: 2001-07-17
Classification: B07B,G03G

Abstract:
A method for air classification of toner used to develop electrostatic images, whereby a toner product consisting of a powder with a wide particle size distribution is converted into a higher-quality toner product with a narrow particle size distribution, the improvement comprising:distributing the toner product uniformly across the extent of a classifying wheel by means of a centrifugal plate; androuting the toner product by means of a controlled material feed section in a gravitational direction through a classifying chamber; andcontrolling the residence time of the toner product by components in the classifying chamber, wherein said componentsin the upper section of the classifying chamber quickly introduce the toner product in a homogeneous state into the classifying chamber,in the central section of the classifying chamber permit a longer residence time of the toner product than in the upper section, andin the bottom section of the classifying chamber permit rapid discharge of the toner product;routing the classifying air with an average flow rate of between 3 and 7 m/s past an outer edge of the classifying wheel; andkeeping a ratio of the toner product mass flow rate to the classifying air volume flow rate between 0.05 kg/m.sup.3 and 0.3 kg/m.sup.3.