Method and installation producing preforms

Method for continuous production by injection-compression of preforms for the manufacture of synthetic material packaging, such as bottles, comprising the following steps:

• a) converting the raw material in an extruder and obtaining an extruded material at the optimum temperature,
• b) continuously filling with a predetermined quantity of the extruded material injection metering devices situated on the periphery of a continuously turning metering wheel and comprising a cylindrical body having an orifice and a piston,
• c) successively passing full injection metering devices onto a continuously turning injection-compression wheel having at its periphery a plurality of injection-compression modules,
• d) during one revolution of the injection-compression wheel, manufacture of a preform by each injection-compression module, recovery of the preform by take-up means and passage of each injection metering device onto the metering wheel for refilling,
• characterized in that wherein:
• the manufacture of each preform on the injection-compression wheel is effected by injecting the extruded material into an injection-compression module, displacing the piston of an injection metering device through an injection threshold of the mold of said module continuous with said orifice of the injection metering device until the end of said piston of the injection metering device shuts off the injection threshold and thereafter by advancing the punch of the injection-compression mold that was retracted during injection of the extruded material into the module to form the preform by compression, and
• the piston of the injection metering device remains in the position shutting off the injection threshold until the preform solidifies.