System for the injection moulding of plastic material, particularly suitable for being associated with a blowing unit of the moulded plastic material

Injection moulding system (10;

• 110;
• 210) for plastic material, comprising:
• a press (11;
• 111;
• 211) having a first (11a) and a second (11b) pressure plate associated respectively with a first side (13a) and a second side (13b), opposite to the first one, of a mould (13;
• 113;
• 213), said two pressure plates (11a, 11b) being suitable for moving (f1) the one with respect to the other in order to close, between them, said mould (13) during an injection and moulding step of a piece (P), so as to apply on said mould (13;
• 113;
• 213) a closing force (F), and
• a distribution and injection assembly (12;
• 112;
• 212) suitable for distributing and injecting, into said mould (13;
• 113;
• 213), a fluid plastic material (MP) during said injection and moulding step, said distribution and injection assembly (12;
• 112;
• 212) being arranged adjacently to and along a third side (13c) of said mould (13), different from said first and second side (13a, 13b), so that said distribution and injection assembly (12;
• 112;
• 212) is not associated with said first and second pressure plate (11a, 11b) and thereby it is not subject to the closing force (F) applied on said first and second side (13a, 13b), opposite each other, of said mould by the two pressure plates (11a, 11b) of said press (11;
• 111;
• 211),
• wherein said distribution and injection assembly (12;
• 112;
• 212) comprises:
• a first bottom plate (21);
• a second nozzle-bearing plate (22) bearing one or more injection nozzles (17;
• 117;
• 217) provided for cooperating with said mould (13), along the respective third side (13c), in order to inject into said mould (13) the fluid plastic material (MP);
• and
• a third intermediate hot distribution plate (23), which is interposed between said bottom plate (12a) and said nozzle-bearing plate (12b) and defines at its inside a network of flow hot channels (16) suitable for distributing to said one or more injection nozzles (17) the plastic material (MP) fluid to be injected in said mould (13), during said injection and moulding step, said third intermediate hot plate (23) being coupled and provided for cooperating in contact, along a respective sliding and contact surface (23a), with said one or more injection nozzles (17), in order to distribute the fluid plastic material (MP) to be injected into the mould, said third intermediate hot plate (23) being arranged between said bottom plate (21) and said nozzle-bearing plate (22) in such a way to be free, when it is heated during use, to expand thermally, in a longitudinal sense, with respect to said bottom plate (21) and to said nozzle-bearing plate (22), by sliding, in the zone of said sliding and contact surface (23a), relatively to said one or more injection nozzles (17), and
• wherein said distribution and injection assembly (12;
• 112;
• 212) is designed and the respective first, second and third plate (21, 22, 23) are bound and cooperate each with the other, in said distribution and injection assembly (12;
• 112;
• 212), in such a way to ensure the sealing against any outflow or leakage towards the outside of the fluid plastic material (MP) which passes through said sliding and contact surface (23a), from said third intermediate hot plate (23) to said one or more injection nozzles (17), despite said distribution and injection assembly (12;
• 112;
• 212) is not subject to the action of said closing force (F), applied by the pressure plates (11a, 11b) of said press (11) on said mould (13).