Finely divided powder and process and apparatus for treating the same

Claim 2

A process for eliminating undesirably large particles in powders of brittle materials capable of sintering or injection molding, comprising the steps of placing the powder particles into a suspension having a concentration of solid particles in a liquid solvent with which it does not chemically react such that the average distance between the particles in the suspension lies within the range up to 100 times the average particle size of the powder, conducting the suspension through at least one roller pair which includes therebetween a predetermined fixedly adjusted gap that corresponds to the desired maximum size of the powder particles, a minor portion of said powder particles being greater in size than the gap and a major portion of said powder particles being substantially smaller in size than said gap, matching the through-put thereof to the roller movement, and thereafter separating the powder particles from the liquid in the suspension.

Claim 3

A process for treating finely divided powders of brittle materials according to claim 1, wherein the materials are ceramics or intermetallic phases.

Claim 4

A process for treating finely divided powders according to claim 1, in which the particles are obtained by atomization or rotary comminution of fused droplets or by other comminution such a fine grinding with subsequent classification of the collected powder particles.

Claim 7

An apparatus according to claim 4, wherein the gap between the roller means is sealed off against the outside.

Claim 8

An apparatus according to claim 5, wherein the gap can be preliminarily adjusted.

Claim 9

An apparatus according to claim 5, wherein the gap includes a circumferential groove between the roller means for discharging liquid.

Claim 10

An apparatus according to claim 7, wherein the roller means are so driven that the centrifugal forces serve for the discharge of the liquid.

Claim 11

An apparatus according to claim 8, further comprising wiping means coordinated to the roller means.

Claim 12

An apparatus according to claim 9, wherein the wiping means is arranged at a distance of about 10% of the roller gap relative to the roller means for purposes of microsedimentation.

Claim 13

An apparatus according to claim 10, wherein the roller means consist at least superficially of a material similar to the powder to be processed.

Claim 14

An apparatus according to claim 10, wherein the roller means consist at least superficially of a material identical to the material to be processed.

Claim 15

An apparatus according to claim 10, wherein the roller means consist partly of a material at least similar to the material to be processed.

Claim 16

An apparatus according to claim 10, wherein the roller means consist completely of a material similar to the material to be treated.

Claim 17

An apparatus according to claim 1, wherein the roller means are so driven that the centrifugal forces serve for the discharge of the liquid.

Claim 18

An apparatus according to claim 1, further comprising wiping means coordinated to the roller means.

Claim 19

An apparatus according to claim 16, wherein the wiping means is arranged at a distance of about 10% of the roller gap relative to the roller means for purposes of microsedimentation.

Claim 20

An apparatus according to claim 1, wherein the roller means consist at least superficially of a material similar to the powder to be processed.

Claim 21

An apparatus according to claim 1, wherein the roller means consist at least superficially of a material identical to the material to be processed.

Claim 22

An apparatus according to claim 1, wherein the roller means consist partly of a material at least similar to the material to be processed.

Claim 23

An apparatus according to claim 1, wherein the roller means consist completely of a material similar to the material to be treated.

Claim 24

A process according to claim 1, wherein the conducting of the suspension through at least one roller pair includes a gap therebetween having a width less than 50 μm.

Claim 25

An apparatus as in claim 4, wherein the gap has a width less than 50 μm.

Claim 26

A process for eliminating undesirably large particles in powders of brittle materials capable of sintering or injection molding, comprising the steps of placing the powder particles into a suspension having a concentration of solid particles in a liquid solvent with which it does not chemically react such that the average distance between the particles in the suspension lies within the range up to 100 times the average particle size of the powder, conducting the suspension through at least one roller pair which includes therebetween a predetermined fixedly adjusted gap that corresponds to the desired maximum size of the powder particles, a portion of said powder particles being greater in size than the gap, matching the through-put thereof to the roller movement, and thereafter separating the powder particles from the liquid in the suspension, and maintaining said gap by including contact surface areas oppositely disposed on outer ends of each roller of said at least one roller pair having a first diameter at which each said roller of each at least one roller pair are pressed against one another, said gap being disposed in between said contact surfaces of each outer end in a central area of each said at least one roller pair, at least one roller of said at least one roller pair having a second diameter in said central area less than said first diameter.

Claim 27

A process for eliminating undesirably large particles in powders of brittle materials capable of sintering or injection molding, comprising the steps of placing the powder particles into a suspension having a concentration of solid particles in a liquid solvent with which it does not chemically react such that the average distance between the particles in the suspension lies within the range up to 100 times the average particle size of the powder, conducting the suspension through at least one roller pair which includes therebetween a predetermined fixedly adjusted gap that corresponds to the desired maximum size of the powder particles, a portion of said powder particles being greater in size than the gap, matching the through-put thereof to the roller movement, and thereafter separating the powder particles from the liquid in the suspension, and maintaining said gap by including contact surface areas oppositely disposed on outer ends of each roller of said at least one roller pair having a first diameter at which each said roller of each at least one roller pair are pressed against one another, said gap being disposed in between said contact surfaces of each outer end in a central area of each said at least one roller pair, at least one roller of said at least one roller pair having a second diameter in said central area less than said first diameter.

Claim 28

A process according to claim 1, wherein said conducting of the suspension through said gap includes a gap having a width five times greater than an average size of said powder.