Injection molding one-piece insert having cooling chamber with radial rib portions

In an injection molding one-piece gate and cavity insert to be mounted in a mold between a heated nozzle and the cavity, the gate and cavity insert having a rear surface with a recessed portion, a front surface which partially forms a cavity, and a gate extending centrally therethrough from the rear surface to the front surface to convey melt from the nozzle to the cavity, the gate and cavity insert having an outer surface, a cooling fluid inlet, a cooling fluid outlet, and a circular cooling fluid chamber, the outer surface of the gate and cavity insert having a generally cylindrical portion with the cooling fluid inlet and the cooling fluid outlet extending inwardly therefrom opposite to each other, the generally circular cooling fluid chamber extending in the gate and cavity insert to convey cooling fluid from the cooling fluid inlet both ways around the gate to the cooling fluid outlet, the improvement wherein;

• the front surface of the gate and cavity insert has a recessed portion to partially form a convex portion of the cavity, the gate and cavity insert having a cavity wall portion with a predetermined thickness extending between the cooling fluid chamber and the cavity,
• the gate and cavity insert having a plurality of first radially extending rib portions projecting frontwardly into the cooling fluid chamber, and a plurality of second radially extending rib portions projecting rearwardly from the cavity wall portion into the cooling fluid chamber, the first frontwardly extending rib portions alternating with and being sufficiently spaced from the second rearwardly extending rib portions to provide a pair of tortuous passages through the cooling fluid chamber for the cooling fluid flowing from the cooling fluid inlet to the cooling fluid outlet.