Internal mold gating method and apparatus

Abstract

A process and apparatus for the internal gating of molds used to make a shaped article of aggregate filler infiltrated with a curable binder, including preparing a mold having a cavity and having gating tubes extending through the mold cavity and spaced from its surfaces, and the gating tubes having walls with multiple openings therethrough which are located inside the mold cavity, the cavity being dry-packed outside of the tubes with aggregate filler and the interstitial spaces therebetween being pumped full of liquid binder to form a matrix, the binder entering through the tubes and their openings and progressively expanding through the interstices while expelling air from breather holes, the binder then being cured in the mold either with the tubes still in place or with the tubes removed and the spaces filled with similar aggregate and binder before curing is completed. To prevent aggregate from entering the tubes before pumping of the binder begins, a snug fitting rod can be inserted in each tube at one end, and then the pump can be started to inject liquid binder into the other end of the tube while withdrawing the rod from said one end of the tube at a rate proportional to the rate at which the mold fills with binder. The tubes can be bent to follow curved contours of the mold, and the mold can be evacuated of air while the binder is being infiltrated.