A molding die has a lower holder, an intermediate holder, an upper holder, a lock member, an upper link bar, a lower link bar, a restriction member, and a drive part. A movement of the lock member in a molding die opening direction or a molding die closing direction is restricted by the intermediate holder. The upper link bar has a first retaining groove in which the lock member fits when being located at a molding die closing position. The lower link bar has a second retaining groove in which the lock member fits and a release portion that enables the lock member to be released from the first retaining groove. The restriction member is movable between a restriction position that prevents the lock member from fitting in the second retaining groove and a free position that enables the lock member to fit in the second retaining groove.

A clamp assembly for an injection molding machine includes (a) a clamp cylinder housing and (b) a clamp piston affixed to an end portion of a tie bar and slidable within the housing among a clamping position, a mold break position, and a meshing position disposed axially intermediate the clamping and the mold break positions. The clamp assembly further includes (c) a clamp chamber for urging the clamp piston towards the clamping position when pressurized; (d) a return device for urging the clamp piston towards the meshing position when pressure in the clamp chamber is relieved; and (e) a mold break chamber for urging the clamp piston towards the mold break position when pressurized. The mold break chamber is bounded axially by opposed surfaces of the tie bar and the return device.

A clamp assembly for an injection molding machine includes (a) a clamp cylinder housing and (b) a clamp piston affixed to an end portion of a tie bar and slidable within the housing among a clamping position, a mold break position, and a meshing position disposed axially intermediate the clamping and the mold break positions. The clamp assembly further includes (c) a clamp chamber for urging the clamp piston towards the clamping position when pressurized; (d) a return device for urging the clamp piston towards the meshing position when pressure in the clamp chamber is relieved; and (e) a mold break chamber for urging the clamp piston towards the mold break position when pressurized. The mold break chamber is bounded axially by opposed surfaces of the tie bar and the return device.

A molding die has a lower holder, an intermediate holder, an upper holder, a lock member, an upper link bar, a lower link bar, a restriction member, and a drive part. A movement of the lock member in a molding die opening direction or a molding die closing direction is restricted by the intermediate holder. The upper link bar has a first retaining groove in which the lock member fits when being located at a molding die closing position. The lower link bar has a second retaining groove in which the lock member fits and a release portion that enables the lock member to be released from the first retaining groove. The restriction member is movable between a restriction position that prevents the lock member from fitting in the second retaining groove and a free position that enables the lock member to fit in the second retaining groove.