Mold clamping device having a half nut and injection molding apparatus

An injection molding apparatus comprising:

• a mold clamping device;
• and an injection device arranged vertically on the mold clamping device;
• wherein the mold clamping device comprises:
• a bed;
• a pressure-receiving platen supported by and fixed to the bed;
• a traction platen disposed beneath the pressure-receiving platen;
• a movable platen disposed above the pressure-receiving platen and configured to be moved up and down by a mold opening and closing mechanism;
• one or more tie bars connected to and extending downward from the movable platen and penetrating the pressure-receiving platen and the traction platen, each tie bar having a tooth portion at its lower end portion engageable with a tooth portion of a half nut connected to an underside of the traction plate;
• the mold clamping device being configured to clamp molds disposed between the pressure-receiving platen and the movable platen by lowering the traction platen thereby lowering the one or more tie bars and the movable platen together as a unit with the traction platen while each half nut is engaged with the tooth portion of one of the tie bars;
• a strong mold opening mechanism disposed beneath the pressure-receiving platen for opening the molds at an initial stage of a mold opening process, the strong mold opening mechanism having a larger axial force and a shorter stroke than the mold opening and closing mechanism;
• and
• a control unit configured to control a position of the traction platen, the mold opening and closing mechanism, opening and closing of each half nut and the strong mold opening mechanism, and adjust a position of each half nut such that the half nut is synchronized with the tooth portion of one of the tie bars by the strong mold opening mechanism;
• and
• wherein the injection device comprises:
• a heating cylinder arranged on the movable platen and containing a rotationally driven screw for feeding resin material downward through the heating cylinder and injecting the resin material through a nozzle into an upper one of the molds when the molds are opened;
• an injection device moving mechanism for moving the heating cylinder upward and downward;
• and
• a purging cover mounted on the movable platen and enclosing a space between the lower end portion of the heating cylinder and the movable platen.