US Patent 7871255 Injection molding machine

The injection molding machine has a fixed platen and a movable platen for fixing a pair of molds; a pair of clamp plates mounted to the fixed platen and the movable platen, respectively, and having a fixation surface for mold fixation, respectively; and magnetic force generation mechanisms for generating a magnetic force for fixing the molds to the fixation surfaces. An air-gap formation mechanism is provided at least in one of the clamp plates for automatically forming air-gaps between the fixation surfaces and the molds in association with the movement start of the movable platen while the magnetic force generation mechanisms are inactivated for detaching the molds from the fixation surfaces.