Process and device for the extrusion-moulding of hollow bodies made of a thermoplastic

1. A process for the extrusion-molding of hollow bodies made of a thermoplastic, comprising the cycle of the following steps:

a) a tubular parison is extruded in a vertical direction and flows downwardly under the effect of its own weight;

b) the parison is gripped by a mechanical handling device;

c) the parison is transferred and deposited in a preforming tool by the device;

d) the preformed parison is transferred to above a lower part of a mold by means of this preforming tool;

e) the parison is deposited from the preforming tool in the lower part of the mold;

f) the mold is closed and the parison is molded;

g) the mold is opened; and

h) the hollow body is removed from the mold,

wherein:

the preforming tool is separate from the mechanical handling device and comprises a portion that comes into direct contact with the parison, said portion being of a shape corresponding to the final shape of the hollow body molded by the process,

before the parison is gripped by the mechanical handling device, said parison is taken away over a certain length, and

the gripping of the parison and the deposition in the preforming tool are performed by means of an arm of the mechanical handling device acting as a robot.

2. Process according to claim 1 , wherein steps b and c of a further cycle immediately following a given cycle are carried out, at least in part, simultaneously with at least one of the steps of the given cycle.

3. Process according to claim 2 , wherein steps b and c of the cycle immediately following a given cycle are carried out, at least in part, simultaneously with step f of this given cycle.

4. Process according to claim 1 , wherein step h of a given cycle is carried out, at least in part, simultaneously with step e of the cycle immediately following this given cycle.

5. Process according to claim 4 , wherein a device for extracting the hollow body is actuated in order to make the hollow body drop under gravity into a recovery device.

6. A device for the extrusion molding of hollow bodies, comprising at least one extruder capable of delivering, in a vertical direction, a tubular parison made of a thermoplastic, flowing downwards under the effect of its own weight, a mechanical handling device, a preforming tool and a two-part mold intended for receiving such a parison and for molding it, wherein the handling device is a robot equipped with an arm capable of taking away a certain length of the parison after it leaves the extruder, of gripping it, of transferring it and of depositing it in a preforming tool which is separate from the robot, said preforming tool comprising a portion that comes into direct contact with the parison, and said portion having a shape corresponding to the final shape of the hollow body molded by the device.

7. Device according to claim 6 , wherein the preforming tool is provided with means for transferring the preformed parison into part of the open mould.

8. Device according to claim 6 wherein the robot, the preforming tool and the mold part may move simultaneously.

9. Device according to claim 6 , wherein the preforming tool is temperature conditioned.

10. Device according to claim 6 , wherein the hollow bodies which are extruded and molded are tubings for fuel.