Apparatus for blow-molding plastic containers

An apparatus for blow-molding plastic containers includes at least one blow-molding station which defines at least one molding cavity which extends around a main axis of extension and further includes at least two lateral bodies and a respective bottom for each molding cavity that is defined by the blow-molding station. The bottom defines a recessed central portion, which is arranged around the main axis of extension, and a lateral containment portion, which has petal-shaped regions which have a substantially radial extension.

TECHNICAL FIELD

The present disclosure relates to an apparatus for blow-molding plastic containers.

BACKGROUND

Typically, such apparatuses for blow-molding plastic containers comprise blow-molding stations that define one or more molding cavities for forming the containers.

In particular, the blow-molding stations comprise two lateral bodies, and a respective bottom for each forming cavity defined by the blow-molding station.

At least one of the lateral bodies is movable on command by way of cyclic opening and closing means, as is the bottom, so as to allow the transition of the molding station from an open condition, in which the is preform or preforms can be fed in and the blow-molded container can be ejected, and a closed condition, in which the blow-molding of the preform is performed in order to obtain the container.

During blow-molding operations, it is necessary to evacuate the air from the mold, as this air hampers the correct forming of the container.

Such evacuation is usually achieved by providing air evacuation ducts that connect the inside of the mold with the outside.

In many cases, apparatuses for blow-molding containers operate under highly variable working conditions that depend on many factors such as, for example, the pressure of blow-molding, the weight of the preforms, the material of the preforms, and the temperature of the preforms.

With the varying of the above mentioned working conditions, in many cases the result is a certain variability of the molded containers which sometimes are non-compliant or in any case at the limit of the tolerances required.

In particular, in some cases, problems are encountered which are linked to the eversion of the bottom, which are accentuated if it is desired to perform blow-molding at pressures that are not excessively high (for example equal to about 20 bar).

SUMMARY

The aim of the present disclosure is to provide an apparatus for blow-molding plastic containers which is capable of improving the known art in one or more of the above mentioned aspects.

Within this aim, the disclosure provides an apparatus for blow-molding plastic containers that makes it possible to obtain containers that meet the required requirements even with the variation of the active working conditions and of the characteristics of the preforms used.

The disclosure also provides an apparatus for blow-molding plastic containers that is highly reliable, easy to implement and of low cost.

This aim and these and other advantages which will become better apparent hereinafter are achieved by providing an apparatus for blow-molding plastic containers according to claim1, optionally provided with one or more of the characteristics of the dependent claims.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to the figures, the apparatus for blow-molding plastic containers according to the disclosure comprises at least one blow-molding station, generally designated by the reference numeral1, which defines at least one molding cavity10which extends about a respective main axis of extension100.

Typically, the blow-molding stations10are supported at the peripheral region of a carousel, which is able to rotate about a rotation axis of the carousel, and the longitudinal main axes100of the blow-molding stations1are arranged substantially parallel to the rotation axis of the carousel.

The or each molding station1comprises at least two lateral bodies2a,2b, and a respective bottom20for each forming cavity10that is defined by the blow-molding station1.

In particular, at least one of the lateral bodies2a,2band the bottom20are movable on command by way of cyclic opening and closing means in order to allow the transition of the molding station1from an open condition, in which the preform or preforms can be fed in and the blow-molded container can be ejected, and a closed condition, in which the blow-molding is performed of the preform in order to obtain the container.

The bottom20defines a recessed central portion21, which is arranged around the main axis of extension100, and a lateral containment portion22.

Advantageously, the lateral containment portion22comprises a plurality of petal-shaped regions23which have a substantially radial extension.

According to the present disclosure, the bottom20comprises a central abutment body30which defines a head portion31which is arranged inside the cavity10.

The central abutment body30is, in particular, adjustable in position, via adjustment means40, along an adjustment direction that is substantially parallel to the main axis of extension100in order to vary the distance between the abutment head31and the respective recessed central portion21of the bottom20.

In practice, by acting on the adjustment means40, it is possible to vary the base clearance BDBC.

Conveniently, the abutment head31comprises a lateral containment body31a, inside which there is a seat31bwhich has a concavity which is directed toward the cavity10.

Conveniently, the adjustment axis corresponds substantially to the main axis of extension100.

According to a preferred embodiment, the bottom20comprises a circumferential venting groove24which is defined in the above mentioned bottom20at the lateral containment portion22and extends around the main axis of extension100.

Naturally there is no reason not to use classic bottoms, including bottoms made in a single piece, and bottoms adapted for molding at higher pressures.

Conveniently, the adjustment means40are provided with an adjustment portion41which is associated with the bottom20and is arranged at the external surface of the bottom20that is arranged on the opposite side with respect to the cavity10.

Advantageously, sealing means32are arranged between the external surface of the bottom20and the central abutment body30.

Preferably, the central abutment body30has an elongated body which defines, at a first longitudinal end, the abutment head31and, at the second longitudinal end, which is opposite to the first one, the adjustment portion41.

The adjustment means41comprise, for example, a screw-and-nut coupling between the central abutment body30and the bottom20.

The bottom therefore defines, substantially at the adjustment axis, a threaded hole which can engage with a male threading defined on the lateral surface of the elongated body.

At the second longitudinal end, the elongated body has a maneuvering portion on which the user can intervene in order to displace, along the adjustment axis, the elongated body so as to be able to vary the distance between the abutment head31and the respective recessed central portion21of the bottom20.

The bottom20is functionally associated with a cooling circuit.

Advantageously, the blow-molding station is adapted to perform the blow-molding of the containers at a pressure of less than 25 bar, and more preferably at 20 bar.

Conveniently, the blow-molding station is adapted to perform the blow-molding of the containers at a pressure of less than 15 bar.

Use of the apparatus according to the disclosure is the following.

Before beginning operations to mold via blow molding, the central abutment body30is positioned so that the abutment head31is positioned so as to define a base clearance BC that is deemed ideal for the operating characteristics for the process and for the product.

If analysis of the containers produced by the blow-molding station is exhibit problems or defects (for example incorrect manufacture of the bottom of the container, or problems of eversion), it is possible to intervene, via the adjustment means, on the position of the abutment head31so as to increase and/or reduce the base clearance BC until containers are obtained that are capable of meeting the specific requirements.

In this manner it is possible to furthermore appreciably reduce the average pressure of blow-molding, so as to reduce the production costs.

In practice it has been found that the disclosure fully achieves the intended aim and advantages by providing an apparatus that is capable of rendering the process of molding containers extremely practical, even with the variation of the process parameters.

The disclosure, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.

In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements and to the state of the art.

The disclosures in Italian Patent Application No. 102018000009880 from which this application claims priority are incorporated herein by reference.