| 摘要 |
A method and apparatus for classifying desirable particles of powder metal by size and removing particles of undesirable material of a different density than the metal particles. There is included a housing defining a closed flow path for a recirculated stream of protective gas different than ambient air. A particle supply device introduces particles into the housing at a controlled rate in a downwardly falling stream. A plurality of receptacle trays are disposed in the housing generally vertically below the particle supply device with each tray having a forward lip positioned forwardly in the direction of the gas flow of the trays thereabove. An electrostatic gas ionizer is disposed upstream of the particle supply device for ionizing the gas and a screen is disposed in the stream of gas between the ionizer and the particle supply device for attracting the ionized gas from the ionizer while allowing the passage of the gas through the screen for establishing the recirculated stream of gas to impinge the stream of falling particles to impart to each particle a horizontal component of velocity so that the trajectories of the particles will vary depending upon size and density thereof for falling into the various receptacle trays. Consequently, the desirable particles are classified by size, undesirable particles of a different density than the desirable particles are removed or separated out, undesirable hollow particles are also removed or separated out, and because of the charge placed thereon, clusters of particles are broken up, i.e., the particles in such a cluster repel one another and separate.
|
