Injection molding machine for making a worm wheel

A machine for forming a worm wheel made by an injection molding process, said wheel comprising a tooth having a tooth crest, and a bottom land formed at a bottom of a tooth space between adjoining teeth, the bottom land including a recessed surface,

• at least the teeth being formed by injection molding a synthetic resin,
• the tooth crest including a trace formed along a parting line as a result of the injection molding process, the forming machine comprising:
• a stationary mold;
• a movable mold movably provided relative to the stationary mold;
• a stationary mold plate disposed on the stationary mold;
• a movable mold plate disposed on the movable mold;
• recesses formed in opposite surfaces of the stationary mold plate and the movable mold plate;
• a core disposed in the recess of the movable mold plate;
• a plurality of slide cores allowed to move radially of the core as arranged radially about the core;
• diameter decreasing means for simultaneously moving the slide cores radially inwardly relative to the core at closure of the movable mold;
• and
• diameter increasing means for simultaneously moving the slide cores radially outwardly relative to the core at opening of the movable mold,
• wherein each slide core includes a block shaped like a fan,
• wherein each block includes a tooth crest forming face and a tooth-space forming projection formed centrally of a width of the tooth crest forming face, and
• wherein, during the closure of the mold, adjoining slide cores are in intimate contact at a respective lateral side of their blocks while defining the parting line between their tooth crest forming faces.