The present invention relates to a device for producing hollow bodies of thermoplastic material, of the type comprising a multi-part hollow mold mounted in a movable closure assembly on movable mold platens which are carried by two supporting bars extending below the hollow mold.
In a known device of this kind, the supporting bars necessary for guiding the mold platens are mounted on the lower part of the closure assembly. Consequently, with the mold open, the intermediate space between the mold platens, in which the multi-part hollow mold is located, is freely accessible so that larger molded bodies can be removed immediately after the opening of the hollow mold, without hindrence by the bars. This is not possible in other known devices since in these, at least one supporting bar is provided in the upper part of the closure assembly.
However, when the supporting bars are provided only in the lower part of the closure assembly, a risk is run that, during the blowing, the mold halves spread apart at the ends of the mold platens which are remote from the bars. In this connection, it is to be considered that the mold halves may be exposed to pressures up to 15 Mp (15 metric tons) and more. To absorb the forces thereby produced and thrusting the mold halves apart during the blowing, in the known device, the mold platens are strongly reinforced by thick plates and ribs. In addition, the supporting bars have a very large diameter since they have to support the large mass of the heavy mold platens. In consequence, the closure assembly comprises a huge mass which can be moved only with a high energy supply, wherefor the device becomes uneconomical in operation. Also in the known device, the mold halves are pivotally mounted on the mold platens and bear against them through accumulators. This measure makes the known device still more expensive and relatively susceptible to trouble.