METHOD AND APPARATUS FOR FORMING PARTICLES INTO SHAPED ARTICLES
Method and apparatus for forming fine, relatively dry particles into shaped refractory, ceramic and porcelain preforms or similar compacted articles by confining the loose particles in a shaped enclosure having at least one movable, preloaded side to maintain the particles in a loose but contiguous mass, accelerating the mass of particles and at least a portion of the mold in such a manner as to induce a positive or negative acceleration of the mass of a magnitude at least 25 to 50 g"s, depending upon the particle composition, and preferably in the range of 500 g"s, or greater, again depending on the particle composition, in order that each particle undergoes a force generating impact with adjacent particles to homogenously compact and fuse the adjacent particles one to the other in a nonbridging manner. A preferred apparatus (20) for accomplishing the abrupt acceleration and deceleration of the particles comprises a mold (10) having fixed sidewalls (11) and at least one movable end wall (13) positioned on a vertically oscillating table (21) and confined above the table (21) by an underdamped system tuned to a frequency corresponding to the frequency of oscillation of the table (21), and preferably including a pneumatic cylinder (30) and a punch member (12) to provide the desired preload to the mass. In operation, the pneumatic cylinder (30) and overload structure are tuned to reciprocate with the mold (10) approximately 180o out of phase with the table (21) such that the mold (10) is accelerated upward by the table (21) upon impact of the mold (10), descending pneumatic cylinder (30) and punch (12) with the table (21) in order that the particles are abruptly accelerated and/or decelerated thereby generating compacting and fusing forces at each particle throughout the particle mass.