The present invention relates to a device for the injection molding of preforms.

Devices for the injection molding of preforms, and in particular of preforms intended for providing plastic containers, are constituted by a first portion associated with a plurality of cavities, or female half mold parts, and a second portion supporting respective mold cores, or male half mold parts.

To produce a preform, the mold cores are inserted into the respective cavities. The cavity and the mold core are configured and arranged so that after the mold core has been inserted into the cavity an interspace is formed between the internal surface of the cavity and the surface of the mold core, the shape of the interspace corresponding to the shape of the preform to be obtained.

The interspace is delimited on the outside by the cavity and on the inside by the mold core.

In order to obtain the preform, liquid polymer, typically PET, is injected at high pressure into the interspace between the cavity and the mold core.

As soon as the melted mass has cooled sufficiently and therefore solidified sufficiently, the mold is opened and the solidified melted mass is removed from the cavity as a preform.

In order to reduce cycle times, i.e., the time between one injection process and the next, it is common practice to remove the preform from the cavity at a very early step and thus detach it from the mold core.

To do this, it is necessary to cool the preform effectively as soon as it has formed.

The preform is cooled by the mold core and by the cavity, which consequently also serve as a cooling body. Typically, the mold core is cooled with a cooling system, which usually incorporates a cooling circuit built into the mold core. Typically, the mold core is configured as an elongated body that is closed at the end designed to be inserted into the respective cavity; a duct for feeding the cooling fluid is arranged internally and coaxially to the mold core and leads out at the closed end and then advances, through an interspace, toward the opposite end.

A system for cooling the mold core is known from EP3666493 Al which provides for using a cooling duct, which also has a longitudinal extension and is open at its end, wherein the outer surface is provided with spiral raised portions which allow on the one hand to facilitate the flow of the cooling fluid and on the other hand to ensure sufficient overall rigidity of the mold core structure.

Known solutions, although widely used, are however not without drawbacks.

In particular, when the diameter of the preform is particularly small, it is extremely complex to obtain a supply duct in which the diameter of the coaxial channel and the thickness of the interspace are able to ensure efficient cooling.

The aim of the present invention is to provide a device for the injection molding of preforms that is capable of improving the background art in one or more of the aspects mentioned above.

Within this aim, an object of the invention is to provide a device for the injection molding of preforms that has an extremely high performance in cooling preforms, even extremely small ones.

This aim and this and other objects that will become better apparent hereinafter are achieved by a device for the injection molding of preforms according to claim 1, optionally provided with one or more of the characteristics of the dependent claims.

Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of the device for the injection molding of preforms according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figures 1 and 2 are two perspective views of the cooling body of the mold core;

Figures 3 to 5 are respective side views of the cooling body of the mold core;

Figure 6 is a longitudinal sectional view of the cooling body of the mold core;

Figure 7 is a front view of the mold core supporting block and of the respective cavity;

Figure 8 is a sectional view of the mold core accommodated in the respective cavity taken along the plane of arrangement indicated by the line VIII- VIII of Figure 7;

Figure 9 is a perspective view of the molding device in the open position;

Figure 10 is a perspective view of the molding device in the closure position.

With reference to the above figures, the device for the injection molding of preforms according to the invention, generally designated by the reference numeral 1, comprises a first half mold part la which supports a plurality of cavities 2 and a second half mold part lb which supports a plurality of mold cores 3.

Conveniently, the first half mold part la comprises a plurality of mold elements designed to form respective cavities 2; conveniently, the mold elements are provided in two bodies: a first body 21 designed to form the inlet of the preform and constituted by two members 21, 21b usually known in the jargon as “neck rings”, which can be moved mutually closer and further apart, and a second body 22, which is generally monolithic and is designed to form the substantially cylindrical part of the cavity and its bottom wall. The first and second half mold parts la, lb are movable on command with respect to each other between a mold closure position (shown in the perspective view of Figure 10), in which at least one mold core 3 is arranged, with a longitudinal forming end 3 a thereof, inside a respective cavity 2 in order to form a molding interspace which has a shape that corresponds to the preform 10 to be molded, and an open position (shown in Figure 9), in which the mold core 3 is arranged outside the respective cavity 2 so as to allow the removal of the molded preform 10 from the device 1.

The mold core 3 comprises a cooling body 11, which is accommodated within a recess 9 which extends at the axis of longitudinal extension 100 of the mold core 3.

The cooling body 11 comprises at least one duct 12 for feeding the cooling fluid which has at least one outlet 13 which communicates with the recess 9.

In particular, the outlet 13 is arranged so as to be spaced from the end Ila of the cooling body 11 that is located at the forming end 3a of the mold core 3.

At least one communication channel 14 is formed between the surface 3b of the mold core 3 that forms the recess 9 and the outer surface 11 c of the cooling body 11 and connects the outlet 13 to a channel 15 for discharging the cooling fluid.

Typically, the cooling fluid is a liquid.

According to a particularly important aspect of the present invention, the cooling body 11 comprises its terminal portion 11b which is accommodated at the longitudinal forming end 3 a of the mold core 3, which has a shape with a solid cross-section.

Conveniently, the terminal portion 11b extends starting from the outlet 13 toward the end Ila of the cooling body 11.

This allows to combine excellent cooling capacity with the rigidity of the cooling body 11 , even in the case of mold cores 3 designed for molding preforms 10 of extremely small diameter.

Conveniently, the cooling body 11 comprises a shoulder 16 arranged at the outlet 13, which extends on the opposite side with respect to the terminal portion 11b.

The shoulder 16 is configured to convey the cooling fluid that exits from the outlet 13 toward the communication channel 14, so as to bring the cooling fluid to skim the terminal portion 11b.

Conveniently, the cooling body 11 has at least one spacing and centering body 17 which protrudes from the outer surface in order to make contact with the surface directed toward the inside of the recess 9.

In particular, at least one spacing and centering body 17 is formed at the outer surface of the terminal portion 11b.

The operation of the device 1 for the injection molding of preforms, according to the invention, is as follows.

The cooling body 11 is accommodated inside the recess 9 and has its terminal portion 11b, which has a solid cross-section, arranged at the longitudinal forming end 3a of the mold core 3.

Cooling of the mold core 3 is performed by means of the cooling fluid that flows out at the outlet 13, which is located so as to be spaced with respect to the end of the terminal portion 11b that is accommodated at the longitudinal forming end 3a.

The cooling fluid therefore passes through the communication channel 14 (which is formed at the interspace formed between the terminal portion Ila of the cooling body 11 and the recess 9).

The fluid, after cooling the mold core 3 and therefore the preform 10, moves toward the discharging channel 15.

In practice it has been found that the invention achieves the intended aim and objects, providing a molding device provided with a cooling body 11 which has an extremely high performance, even if it is designed to cool preforms of reduced diameter. The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may furthermore be replaced with other technically equivalent elements. In practice, the materials used, so long as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to the requirements and the state of the art.

The disclosures in Italian Patent Application No. 102022000005306 from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.