Laval nozzle with central feed tube and particle comminution processes thereof

A method of grinding particles comprising:

• a) introducing unground particles into a grinding chamber of a fluidized bed jet mill;
• b) injecting gas from a plurality of sources of high velocity gas into the grinding chamber through a nozzle or nozzles comprising:
• a first hollow cylindrical body with a first diameter and a first end, wherein one end of the body is directed towards a center of the jet mill and the other end traverses an outer wall of the jet mill;
• and a hollow cylindrical curvilinear body with a diameter which is less than said first diameter, wherein the first end of the hollow cylindrical curvilinear body is collinear with a long axis of said first hollow cylindrical body, wherein the first end of the hollow cylindrical curvilinear body is at a point approximately equal to the end of the first hollow cylindrical body, wherein a second end of the curvilinear body passes through an opening in the side wall of said first hollow cylindrical body, and wherein said side wall opening is leak free and resides within the grinding chamber of the fluid bed mill;
• wherein the nozzle communicates the gas stream from the nozzle to the grinding chamber thereby forming at least two particulate gas streams in the jet mill;
• c) forming a fluidized bed of said unground particles within the grinding chamber;
• d) entraining and accelerating a portion of said unground particles with said high velocity gas to form a high velocity particle gas stream;
• e) fracturing said portion of said entrained particles into smaller particles by projecting the particle gas stream against opposing particle gas streams;
• g) separating from said unground particles and said smaller particles a portion of said smaller particles smaller than a selected size;
• h) discharging said portion of said smaller particles from said grinding chamber;
• and
• i) continuing to grind remaining said smaller particles and said unground particles by reentrainment until said smaller particles, smaller than a selected size, are obtained thereby, wherein said high velocity gas stream has a high surface area periphery or profile, and wherein the relative throughput grinding efficiency is improved from about 1 percent to about 30 percent compared to a mill without said curvilinear body.

A method for grinding particles of electrostatographic developer material comprising:

• a) introducing unground particles of electrostatographic developer material into a grinding chamber of a fluidized bed jet mill;
• b) injecting gas from a plurality of sources of high velocity gas attached to an injecting nozzle comprising:
• a first hollow cylindrical body with a first diameter and a first end, wherein one end of the body is directed towards a center of the jet mill and the other end traverses an outer wall of the jet mill;
• and a hollow cylindrical curvilinear body with a diameter which is less than said first diameter, wherein the first end of the hollow cylindrical curvilinear body is collinear with a long axis of said first hollow cylindrical body, wherein the first end of the hollow cylindrical curvilinear body is at a point approximately equal to the end of the first hollow cylindrical body, wherein a second end of the curvilinear body passes through an opening in the side wall of said first hollow cylindrical body, and wherein said side wall opening is leak free and resides within the grinding chamber of the fluid bed mill;
• wherein the nozzle communicates the gas stream from the nozzle to the grinding chamber thereby forming at least two particulate gas streams in the jet mill;
• c) forming a fluidized bed of said unground particles;
• d) accelerating a portion of said unground particles with said high velocity gas stream to form a high velocity particle gas stream;
• e) fracturing a portion of the accelerated particles into smaller particles by projecting at least two particle streams in partial or complete opposition so that substantially all of the particles accelerated by the gas stream impact particles contained in an opposing stream;
• f) entraining and accelerating a portion of said unground particles and smaller partially ground particles into and through said second end of the hollow cylindrical curvilinear body with said high velocity gas to form a second high velocity particle gas stream;
• g) separating from said unground particles and said smaller particles a portion of said smaller particles smaller than a selected size;
• h) discharging said portion of said smaller particles from said grinding chamber;
• and
• i) continuing to grind the remainder of said smaller particles and said unground particles through reentrainment of particles in accordance with step d) and f) until said smaller particles smaller than a selected size are obtained thereby.