Injection-molding apparatus

Claim 1

In an injection-molding apparatus, particularly for making green ceramic bodies, a combination comprising mold means having a mold cavity provided with a charging opening; passage-forming means having a passage which communicates with said mold cavity, including a chamber provided with an inlet port formed in a circumferential wall of said chamber and communicating with said passage and an outlet port formed in an end wall of said chamber and communicating with said charging opening; injecting means for injecting the molded material via said passage into said cavity and comprising a cylinder having a front end provided with an outlet which communicates with said passage, a material inlet rearwardly spaced from said outlet, a ram reciprocable in said cylinder between a first end position in which it is located rearwardly of said inlet and a second end position in which it is located forwardly of said inlet and close to said outlet, and a skirt projecting rearwardly from said ram and extending across said inlet when said ram is in said second end position so as to prevent molding material from entering said cylinder behind said ram; and blocking means in said chamber and movable, subsequent to reciprocation of said ram to said second end position thereof, from a rest position to a first operating position in which it interrupts communication between said chamber and said passage and charging opening, respectively, and beyond said first operating position in which it continues the interruption of said communication and additionally exerts compacting pressure upon the material in said mold cavity, said blocking means including a tubular element having an interior which communicates with said outlet port and a circumferential wall provided with an opening movable into and out of registry with said inlet port.