Pneumatic mill for extra-fine powder

Claim 1

A pneumatic pulverizer to reduce pregranulated material into substantially fine and uniform powder continuously, comprising an annular chamber to swirl supersonic pneumatic fluid therein to pulverize pregranulated material, another annular chamber mounted on said annular pulverization chamber to swirl pneumatic fluid therein to separate pulverized fine powder from coarse powder, a cylinder extending downward from the center of said annular separation chamber through said annular pulverization chamber to deliver separated fine powder, nozzle means arranged around said annular pulverization chamber to jet supersonic pneumatic fluid into said pulverization chamber, conduit means arranged around said annular separation chamber to return coarse powder from said separation chamber to said pulverization chamber, means connected to said jet nozzle means to distribute pneumatic fluid to said jet nozzle means, means arranged around said pulverization chamber to feed pregranulated material into said pulverization chamber, means connected to said delivery cylinder to guide delivered fine powder out of said delivery cylinder, and means connected to said guide means to exhaust a gas from said guide means; said annular pulverization chamber being provided with an annular passage in the center thereof communicating with said annular separation chamber, said annular passage surrounding a portion intermediate the upper and lower ends of said delivery cylinder, said annular pulverization chamber being provided with a plurality of ports through an annular sidewall thereof to introduce supersonic pneumatic fluid therethrough, said ports in said pulverization chamber being spaced equally around the circumference of said annular pulverization chamber and directed in an eccentric relation to the center of said pulverization chamber to swirl supersonic pneumatic fluid satisfactorily therein, said separation chamber being provided with a plurality of ports through an annular sidewall thereof to withdraw pneumatic fluid therethrough, said ports in said separation chamber being spaced equally around the circumference of said separation chamber and directed in an eccentric relation to the center of said separation chamber to withdraw swirling fluid, said pulverization chamber provided with at least one radial port through an annular sidewall thereof to introduce pneumatic fluid therethrough, said delivery cylinder being provided with an annular flange extending from the upper end thereof into said separation chamber to shelter said annular passage sufficiently to keep separated fine powder from being mixed with material in process entering said separation chamber through said annular passage, said jet nozzle means being connected to said eccentric ports in said pulverization chamber, said return conduit means connected to said eccentric ports in said separation chamber, and said feed means being connected to said radial port in said pulverization chamber.