Patent Description:
In particular, the invention relates to an injection apparatus particularly adapted to inject molten plastic from a plasticization apparatus which can generate a substantially continuous flow of molten plastic. The molten plastic can be produced from plastic, such as PET, for example, in the form of flakes.

In order to produce bottle preforms, an apparatus comprising an extruder and only one injector is usually used.

The forward and backward movements of the screw of the extruder and the piston of the injector are asynchronous.

In fact, while the screw rotates and moves backward along the longitudinal axis thereof while melting the granules, typically of PET, and accumulating the volume of molten plastic needed for the subsequent injection (plasticization step), the piston moves forward to inject the molten plastic into the mold (injection step); and vice versa, while the screw rotates and moves forward along the longitudinal axis thereof to transfer the molten plastic produced in the plasticization step (transfer step), the piston moves backward so that the injector is filled with molten plastic (loading step). Thus, the flow of molten plastic produced by the extruder is discontinuous.

This is the standard process carried out when the raw material to be melted by the extruder is in the form of pellets or granules, in particular when the raw material is virgin PET or, in case of recycled and recast material, rPET.

The use of material in the form of flakes is increasingly requested, the flakes being obtained by grinding preforms and bottles, without melting them.

In order to produce preforms from PET flakes, a plasticization apparatus is required, comprising the extruder designed to have a different operation from that previously described.

Unlike PET pellets, the PET flakes, due to the smaller apparent density thereof, can require a particular plasticization process, where the screw does not move forward/backward as described above, but operates in a mode referred to as a pure extruding mode. Basically, the screw rotates at a constant speed without moving forward/backward along the longitudinal axis thereof.

This results in a flow of molten plastic exiting the plasticization apparatus being substantially continuous and constant, and no longer discontinuous as in the previously described process.

Thus, as the flow exiting the extruder is continuous, two injectors are needed.

In particular, downstream of the extruder, two injectors alternatively receive the molten plastic from the extruder. More in particular, the apparatus is designed so that while a first injector is injecting the molten plastic into the mold, a second injector receives the molten plastic from the extruder, and vice versa.

However, disadvantageously, there can be conditions such that the molten plastic is prevented from entering into both injectors simultaneously.

<CIT> discloses an injection apparatus for injecting molten plastic into a mold, a first injector and a second injector adapted to receive molten plastic and inject it into a mold, a conduit adapted to carry molten plastic from a plasticizing apparatus towards the first injector and towards the second injector and a third injector provided with a piston, the third injector being connected to the conduit so as to receive molten plastic from the conduit and then inject it into the conduit. <CIT> discloses an injection molding apparatus comprising two injectors which are adapted to inject molten plastic into the same mold through the same nozzle. The apparatus of D4 is configured so that after the injection of molten plastic into the mold with the first injector, the mold is opened and closed again, so that the second injector can inject molten plastic.

The Applicant has developed an injection apparatus comprising two injectors.

Such an apparatus comprises a conduit adapted to carry the molten plastic from the plasticization apparatus towards the two injectors.

Furthermore, such an injection apparatus comprises two valves, in particular a valve for each injector.

Each valve is adapted to allow or prevent the entry of molten plastic into the respective injector as a function of the position or configuration thereof.

The apparatus is designed so that while one of the two valves allows the molten plastic to enter into the respective injector, the other valve prevents the molten plastic from entering into the respective injector.

However, disadvantageously, there can be conditions such that both valves simultaneously prevent the molten plastic from entering into the respective injector, e.g., during the switching of the valve position.

It is possible that, when both valves prevent the molten plastic from entering into the respective injector, a hydraulic shock or fluid hammer occurs in the conduit connecting the injection apparatus to the plasticization apparatus.

The occurring pressure peak can damage one or more components of the plasticization apparatus, in particular the molten plastic pump arranged fluidly downstream of the extruder and upstream of the aforesaid conduit. Therefore, the molten plastic pump, which should operate with constant pressure downstream, can be damaged or in any case the operating life thereof is reduced.

The need is felt to avoid hydraulic shocks occurring in the conduit adapted to connect the injection apparatus to the plasticization apparatus when the molten plastic is prevented from entering into both injectors adapted to operate alternately to each other.

It is also desirable to be able to avoid hydraulic shocks from occurring, and also to be able to avoid the molten plastic from degrading.

In fact, the degradation of the molten plastic can lead to the formation of undesired volatile compounds, such as acetaldehyde and benzene.

Being able to avoid the degradation of molten plastic is not trivial, especially when carrying out a preform production process from PET in the form of flakes.

It is an object of the present invention to provide an injection apparatus for producing hollow articles, e.g., bottle preforms, in particular from plastic to be melted in the form of flakes, which allows avoiding hydraulic shocks from occurring in the conduit adapted to connect the injection apparatus to the plasticization apparatus.

In particular, it is an object of the present invention to avoid hydraulic shocks from occurring in the conduit adapted to connect the injection apparatus to the plasticization apparatus if a condition occurs, in which the molten plastic is prevented from entering into both injectors adapted to operate alternately to each other.

It is another object of the present invention to also be able to avoid the degradation of the molten plastic, in particular of the molten PET.

The present invention achieves at least one of the aforesaid objects, and other objects which will become apparent in light of the present description, by an injection apparatus for injecting molten plastic according to claim <NUM>.

The invention also relates to a molding apparatus, in particular according to claim <NUM>.

The invention also relates to a molding process, in particular according to claim <NUM>.

Advantageously, an injection apparatus according to the invention allows avoiding hydraulic shocks from occurring in the conduit adapted to connect the injection apparatus to the plasticization apparatus.

In fact, the third injector is capable of receiving, an amount of molten plastic from the plasticization apparatus to avoid a fluid hammer from occurring.

Advantageously, an injection apparatus according to the invention allows avoiding hydraulic shocks also when the plasticization apparatus is configured to dispense a continuous or substantially continuous flow of molten plastic, such as a plasticization apparatus loaded with plastic flakes, for example.

The injection apparatus preferably comprises two valves, in particular a valve for each injector; and each valve is adapted to allow or prevent the entry of molten plastic into the respective injector as a function of the position or configuration thereof.

Advantageously, the third injector can receive the molten plastic for the time strictly required for one of the two valves to be in a condition in which it allows the molten plastic to enter into the respective injector, in particular for the time strictly required for one of the two valves to be completely switched to the position allowing the molten plastic to enter into the respective injector.

In particular, the third injector is not destined to have a loading amount, referred to as shot size, equal to that of the first injector and the second injector, but only a fraction with respect to the loading amount of each of them.

The first injector and the second injector can be referred to as main injectors, and the third injector can be referred to as auxiliary injector.

Advantageously, an apparatus according to the invention allows reducing the harmful pressure fluctuations inside the conduit adapted to be connected to the plasticization apparatus to receive the molten plastic.

It is particularly preferable that actuation means are provided, e.g., a hydraulic cylinder, adapted to cause the piston of the third injector to move forward, to inject the molten plastic into the conduit adapted to receive the molten plastic from the plasticization apparatus. The residence time of the molten plastic in the third injector is thus minimized. Thus, the risk that the molten plastic at high temperature degrades is avoided, the degradation causing the generation of spots of burnt material which would circulate and contaminate the molded articles.

It is particularly preferable that said actuation means are adapted to control the backward movement of the piston of the third injector while it receives the molten plastic from the conduit. In fact, controlling the backward movement of the piston of the third injector allows avoiding or in any case minimizing the formation of bubbles in the molten plastic. For the production of bottle preforms, in particular made of PET, the formation of bubbles is particularly undesired. Instead, it is desired that the molten plastic remains as compact as possible. An uncontrolled speed of the piston of the third injector can lead to the formation of air bubbles in the molten plastic.

In order to avoid the formation of bubbles optimally, it is particularly preferable that the injection apparatus is configured to control the backward movement of the piston of the third injector while it receives the molten plastic, so that the pressure of the molten plastic in the third injector is constant or substantially constant during the backward movement of the piston of the third injector.

An injection apparatus according to the invention allows avoiding or minimizing the degradation of the molten plastic, in particular of the molten PET.

The inventors have found that the length of the conduit carrying the molten plastic from the plasticization apparatus to the injectors significantly affects the degradation of the molten plastic.

In particular, the inventors have found that a too long conduit increases the residence time of the molten plastic at high temperature, leading to a degradation of the molten plastic.

Therefore, it is preferable to select the length of the aforesaid conduit so that it is lower than the length of each of the main injectors, so as to reduce the residence time of the molten plastic at high temperature in the conduit. Therefore, it is possible to minimize the degradation of the molten plastic.

The aforesaid third injector is particularly advantageous in the optional variants in which the length of the aforesaid conduit is shorter than the length of each of the main injectors. In fact, without the third injector, when the conduit is short, the aforesaid problem of the fluid hammer can be accentuated with respect to a longer conduit.

Further features and advantages of the invention will become more apparent in light of the detailed description of exemplary, but non-exclusive embodiments.

The dependent claims describe particular embodiments of the invention.

In the description of the invention, reference is made to the accompanying drawings, which are provided by way of a non-limiting example, in which:.

The same elements or components have the same reference numeral.

With reference to the Figures, exemplary embodiments of an injection apparatus <NUM> or injection machine, according to the invention are described.

In particular, the injection apparatus <NUM> is for molding hollow articles, in particular preforms, more in particular bottle preforms.

In fact, the injection apparatus <NUM> is adapted to inject molten plastic, in particular molten PET, into a mold (not shown) of one or more hollow articles, such as bottle preforms. The mold can be provided, for example, with a plurality of molding cavities, each for a respective hollow article, e.g., each for a respective preform.

The injection apparatus <NUM> is suitable for injecting the molten plastic (or molten polymer) produced from the plasticization of polymer material, e.g., PET (Polyethylene terephthalate), in particular in the form of flakes.

In all embodiments, the injection apparatus <NUM> comprises.

In particular, the injector <NUM> and the injector <NUM> are adapted to inject molten plastic into the mold, in particular into the same mold, through the same nozzle <NUM>.

The injection apparatus <NUM> is in particular configured so that, if a condition occurs in which the molten plastic is prevented from entering into both the injector <NUM> and the injector <NUM> (simultaneously), the molten plastic from the conduit <NUM> is received by the injector <NUM> (i.e., in the injector <NUM>) and then, when the molten plastic is allowed to enter into the injector <NUM> or the injector <NUM>, the injector <NUM> injects the molten plastic present inside the injector <NUM> into the conduit <NUM>.

Each of the injectors <NUM>, <NUM> comprises a body <NUM>, <NUM> adapted to receive the molten plastic, a piston <NUM>, <NUM> adapted to slide in the body <NUM>, <NUM>, and actuation means <NUM>, <NUM>, constrained to the piston <NUM>, <NUM>. The actuation means <NUM>, <NUM> are adapted to move the piston <NUM>, <NUM>. The actuation means <NUM>, <NUM> preferably comprise or consist of an actuation cylinder, preferably a hydraulic cylinder. In particular, each piston <NUM>, <NUM> is adapted to slide along a respective axis X', X" which preferably is the longitudinal axis of the respective injector <NUM>, <NUM>.

The injector <NUM> comprises a body <NUM> adapted to receive the molten plastic, a piston <NUM> adapted to slide in the body <NUM>, and actuation means <NUM> constrained to the piston <NUM>. The actuation means <NUM> are adapted to move the piston <NUM>. The actuation means <NUM> preferably comprise or consist of an actuation cylinder, preferably a hydraulic cylinder. In particular, each piston <NUM> is adapted to slide along an axis X‴, which is preferably the longitudinal axis of the injector <NUM>.

Each injector <NUM>, <NUM>, <NUM>, in particular the respective body <NUM>, <NUM>, <NUM>, is provided with a respective opening through which the molten plastic can pass for entering and exiting the injector <NUM>, <NUM>, <NUM>.

The molten plastic is received in the space delimited, in particular, by the body <NUM>, <NUM>, <NUM> and by the piston <NUM>, <NUM>, <NUM> of each injector <NUM>, <NUM>, <NUM>.

In particular, the actuation means <NUM> of the injector <NUM>, are adapted to cause the piston <NUM> to move forward (towards the opening for the passage of the molten plastic of the body <NUM>), in particular at a controlled speed, to inject the molten plastic into the conduit <NUM>. Furthermore, advantageously, the actuation means <NUM> are adapted to control the backward movement of the piston <NUM> of the injector <NUM> while it receives the molten plastic from the conduit <NUM>.

Preferably, there is provided at least one transducer <NUM> (shown diagrammatically in <FIG>) adapted to detect the pressure of the molten plastic which is inside the injector <NUM>, in particular during the backward movement of the piston <NUM>.

It is preferable that the injection apparatus <NUM> is configured to control the backward movement of the piston <NUM>, in particular the backward movement speed, of the injector <NUM> while it receives the molten plastic, so that the pressure of the molten plastic in the injector <NUM> is constant, or substantially constant, during the backward movement of the piston <NUM>.

For example, said at least one transducer <NUM> can be arranged so as to be adapted to detect the hydraulic pressure of the hydraulic cylinder and thus the transducer <NUM> is adapted to detect the pressure of the molten plastic in the injector <NUM>.

The injection apparatus <NUM> preferably comprises an electronic control unit configured to control the displacement of the piston <NUM> as a function of the pressure values detected by said at least one transducer <NUM>, in particular so as to keep the pressure of the molten plastic in the injector <NUM> constant, or substantially constant. Preferably, the third injector <NUM> has a lower molten plastic loading capacity than the loading capacity of the injector <NUM> and than the loading capacity of the injector <NUM>; preferably from <NUM> to <NUM> times, e.g., from <NUM> to <NUM> times, or from <NUM> to <NUM> times, e.g., from <NUM> to <NUM> times lower than the injector <NUM> and the injector <NUM>.

In other words, the injector <NUM> is configured to receive a maximum amount of molten plastic therein (in particular, when the piston <NUM> is in the fully back position), which is lower than the maximum amount of molten plastic that the injector <NUM> can receive and lower than the maximum amount of molten plastic that the injector <NUM> can receive, in particular when the respective piston <NUM>, <NUM> is in the fully back position. Preferably, the injector <NUM> and the injector <NUM> have the same loading capacity, or substantially the same loading capacity.

Preferably, the injection apparatus <NUM>, in particular the injector <NUM>, is configured to inject molten plastic at a lower injection speed than the injection speed of the injector <NUM> and the injector <NUM>, i.e., the injector <NUM> is configured to inject molten plastic at a lower injection speed than the injection speed of each of the injectors <NUM>, <NUM>, preferably from <NUM> to <NUM> times lower.

The injector <NUM> thus injects the molten plastic slowly and therefore undesired pressure peaks are avoided.

The injectors <NUM>, <NUM> are preferably configured to inject molten plastic at the same injection speed.

The injection apparatus <NUM> is configured so that the two injectors <NUM>, <NUM> can receive the molten plastic and inject it into the mold alternately to each other.

In particular, the apparatus <NUM> is configured so that while one of the injectors <NUM> receives the molten plastic (i.e., it is filled, loading step), the other injector <NUM> injects the molten plastic (and is therefore emptied, injection step).

Preferably, the injection apparatus <NUM> comprises two valves <NUM>, <NUM>, in particular one valve <NUM>, <NUM> for each injector <NUM>, <NUM>. Preferably, the valves <NUM>, <NUM> are spool valves. The valves <NUM>, <NUM> are used to allow loading one of the injectors <NUM>, <NUM> with molten plastic and injecting the molten plastic which exits from another injector <NUM>, <NUM> in an alternate manner.

In particular, the injection apparatus <NUM> comprises:.

In particular, the injector <NUM> is connected to the conduit <NUM> upstream, in particular fluidly upstream, of the valve <NUM> and the valve <NUM>.

In particular, each valve <NUM>, <NUM> is adapted to take a first position, in which it allows the passage of molten plastic from the conduit <NUM> to the respective injector <NUM>, <NUM> (loading step) and prevents the passage of molten plastic from the respective injector <NUM>, <NUM> towards the mold; and a second position, in which it allows the passage of molten plastic from the respective injector <NUM>, <NUM> towards the mold (injection step) and prevents the passage of molten plastic from the conduit <NUM> to the respective injector <NUM>, <NUM>.

The injection apparatus <NUM> is configured to control the valve <NUM> and the valve <NUM> so that while the valve <NUM> is in the first position thereof, the valve <NUM> is in the second position thereof, and vice versa. In fact, the injection apparatus <NUM> is configured to cause the valve <NUM> to move from the first position to the second position, and vice versa; and to cause the valve <NUM> to move from the first position to the second position, and vice versa.

<FIG> shows, by way of a non-limiting example, a moment in which the injector <NUM> is about to start the loading step and the injector <NUM> has completed the injection step. The valve <NUM> is in the second position thereof and the valve <NUM> is in the first position thereof. Preferably, in this condition, the piston <NUM> of the injector <NUM> substantially remains still, preferably in a forward position, e.g., fully or almost fully forward position.

For the injectors <NUM>, <NUM> to inject the molten plastic into the mold alternately, the two valves <NUM>, <NUM> need to switch the position thereof.

It may happen that a condition occurs, in which both valves <NUM>, <NUM> prevent the passage of molten plastic from the conduit <NUM> to the respective injector <NUM>, <NUM>, as shown for example in <FIG>.

This condition may occur, for example, in an initial (transitory) step of the position change of the two valves <NUM>, <NUM>; or for example, due to a delay in the position change of the valves <NUM>, <NUM>.

Advantageously, in this condition, the molten plastic from the conduit <NUM> can be received in the injector <NUM>. In particular, the piston <NUM> moves backward so that the molten plastic can enter the injector <NUM>. Therefore, a fluid hammer is avoided from occurring, in particular in the conduit <NUM>. The molten plastic inside the injector <NUM> can then be injected into the conduit <NUM> when one of the two valves <NUM>, <NUM> allows the molten plastic to enter into the respective injector <NUM>, <NUM>.

In particular, the aforesaid conduit <NUM> has an inlet section or opening <NUM> (<FIG>) for the entry of the molten plastic, and three outlet sections or openings <NUM>, <NUM>, <NUM> (<FIG>) for the exit of the molten plastic from the conduit <NUM>. The three outlet openings <NUM>, <NUM>, <NUM> are distinct from one another and distinct from the inlet opening <NUM>. The molten plastic exiting the outlet opening <NUM> is introduced into the injector <NUM> (in particular first into the valve <NUM> and then into the injector <NUM>); the molten plastic exiting the outlet opening <NUM> is introduced into the injector <NUM> (in particular first into the valve <NUM> and then into the injector <NUM>); the molten plastic exiting the outlet opening <NUM> is introduced into the injector <NUM>.

Preferably, the conduit <NUM> has only one inlet opening <NUM> and only three outlet openings <NUM>, <NUM>, <NUM>.

In particular, the inlet opening <NUM> is adapted to be connected to the plasticization apparatus <NUM>.

An end portion <NUM> of the conduit <NUM> is provided with said inlet opening <NUM>.

The conduit <NUM> comprises a stretch <NUM> and two branches <NUM>, <NUM>. The two branches <NUM>, <NUM> are connected to the stretch <NUM> so as to receive the molten plastic from the stretch <NUM>. The two branches <NUM>, <NUM> are preferably transverse to the stretch <NUM>. The stretch <NUM> is provided with the inlet opening <NUM>, and each branch <NUM>, <NUM> is provided with a respective outlet opening <NUM>, <NUM>. The branch <NUM> is adapted to carry the molten plastic towards the injector <NUM> and the branch <NUM> is adapted to carry the molten plastic towards the second injector <NUM>.

The valve <NUM> is connected to the branch <NUM> so as to receive molten plastic therefrom; and the valve <NUM> is connected to the branch <NUM> so as to receive molten plastic therefrom.

In particular, the body <NUM>, <NUM> of each valve <NUM>, <NUM> is connected to a respective branch <NUM>, <NUM>.

The injector <NUM> is preferably connected to the conduit <NUM> so as to receive molten plastic from said stretch <NUM> of the conduit <NUM>, preferably directly from stretch <NUM>. The body <NUM> of the injector <NUM> is preferably fixed to the conduit <NUM>, in particular to a wall delimiting the conduit <NUM>.

The injection apparatus <NUM> is in particular configured so that the molten plastic from the plasticization apparatus <NUM> is introduced into the conduit <NUM>, in particular into the stretch <NUM> and then into the branches <NUM>, <NUM>.

The conduit <NUM>, preferably extends from the inlet opening <NUM> for the molten plastic to the three outlet sections or openings <NUM>, <NUM>, <NUM>; in particular to the outlet opening <NUM> (in particular to the valve <NUM>), to the outlet opening <NUM> (in particular to the valve <NUM>) and to the outlet opening <NUM>.

In some variants, not shown, the number of valves for controlling the molten plastic flow towards the injectors <NUM>, <NUM> can be greater than two, e.g., three.

For the actuation of each valve <NUM>, <NUM>, in particular to cause each valve <NUM>, <NUM> to move from the first position to the second position and vice versa, actuation means <NUM>, <NUM> are provided (<FIG>) for each valve <NUM>, <NUM>. For example, there is provided a respective actuation cylinder for each valve <NUM>, <NUM>.

The body <NUM>, <NUM> of each valve <NUM>, <NUM> is preferably fixed to the respective injector <NUM>, <NUM>. In particular, the body <NUM>, <NUM> of each valve <NUM>, <NUM> is fixed to the end portion of the respective injector <NUM>, <NUM> where the opening for the entry and exit of molten plastic of the respective injector <NUM>, <NUM>, is present.

Inside the body <NUM>, <NUM> of each valve <NUM>, <NUM> there is a respective movable element <NUM>, <NUM>. Each movable element <NUM>, <NUM> preferably defines a conduit which, in a position of the respective valve <NUM>, <NUM>, can (fluidly) communicate with the conduit <NUM> and the opening of the respective injector <NUM>, <NUM>. Each movable element <NUM>, <NUM> also defines another conduit which, in another position of the respective valve <NUM>, <NUM>, can (fluidly) communicate with the opening of the respective injector <NUM>, <NUM> and the tubing <NUM>, in particular with a respective branch <NUM>, <NUM> of the tubing <NUM>.

Each of the aforesaid actuation means <NUM>, <NUM> is adapted to move a respective movable element <NUM>, <NUM>.

The length of said conduit <NUM> is preferably shorter than the length Ltot, in particular than the total length, of each of the two injectors <NUM>, <NUM> along the respective longitudinal axis X', X".

In particular, the "length" of the conduit <NUM> means the length of the path traveled by the molten plastic when crossing the whole conduit <NUM>, i.e., when crossing the conduit <NUM> from the beginning to the end thereof, in particular from the inlet opening <NUM> to the three outlet sections or openings <NUM>, <NUM>, <NUM>.

The length of the conduit <NUM> comprises the length of the stretch <NUM>, and the length of each of the two branches <NUM>, <NUM>; in particular, the length of the conduit <NUM> is preferably equal to the sum of the length of the stretch <NUM>, and of the length of each of the two branches <NUM>, <NUM>.

The aforesaid stretch <NUM> preferably comprises a stretch <NUM> (<FIG>) which is substantially horizontal, or in any case parallel to the support surface of the injection apparatus <NUM>.

Stretch <NUM> preferably has the aforesaid inlet opening <NUM>.

The aforesaid stretch <NUM> preferably comprises two stretches <NUM>, <NUM> (or sub-stretches or portions) which are transverse to each other, e.g., orthogonal to each other. The first stretch <NUM> can have, for example, a substantially L shape. The two stretches <NUM>, <NUM> are joined to each other by a connection stretch <NUM>. In particular, the connection stretch <NUM> is substantially an elbow (i.e., it is curved).

Part of the conduit <NUM> is preferably delimited by a component, e.g., a T-shaped- or Y-shaped tube, comprising said two branches <NUM>, <NUM>. In particular, said T- or Y-shaped component also comprises part of the stretch <NUM> of conduit <NUM>, in particular part of stretch <NUM>.

Said length Ltot of each injector <NUM>, <NUM> comprises the length Lcm of said body <NUM>, <NUM> and the length Lhc of said actuation means <NUM>, <NUM> (the length Lhc is also measured along the longitudinal axis X', X").

In particular, each injector <NUM>, <NUM> has a first axial end <NUM>' (<FIG>) and a second axial end <NUM>"; the first axial end <NUM>' delimits the opening of said body <NUM>, <NUM> through which the molten plastic can pass, in particular to enter and exit the body <NUM>, <NUM>; the second axial end <NUM>' 'is an end of said actuation means <NUM>, <NUM>, in particular the distal end from the opening of the body <NUM>, <NUM>; and said length Ltot of each injector <NUM>, <NUM> is the distance, in particular along the respective longitudinal axis X', X", from the first axial end <NUM>' to the second axial end <NUM>".

The actuation means <NUM>, <NUM> are preferably connected to the respective body <NUM>, <NUM> by a respective connection body <NUM>, <NUM>, extending between the body <NUM>, <NUM> and the actuation means <NUM>, <NUM>.

In this case, said length Ltot of each injector <NUM>, <NUM> comprises the length Lcm of said body <NUM>, <NUM>, the length Lmb (along the longitudinal axis X', X") of the connection body <NUM>, <NUM> and the length Lhc of said actuation means <NUM>, <NUM>.

A valve <NUM>, <NUM>, in particular a proportional valve, can be connected to the actuation means <NUM>, <NUM>.

Preferably, said length Ltot of each injector <NUM>, <NUM> does not comprise the length of the valve <NUM>, <NUM>.

Preferably, but not exclusively, the two injectors <NUM>, <NUM> are parallel to each other; in particular, the longitudinal axes thereof are parallel to each other. Alternatively, the two injectors <NUM>, <NUM> can be transverse to or aligned with each other.

In particular, the two injectors <NUM>, <NUM> have the same length Ltot.

The two injectors <NUM>, <NUM> are preferably equal to each other.

The length Ltot of each injector <NUM>, <NUM> is preferably from <NUM> to <NUM>; and/or the length Lcm of each body <NUM>, <NUM> is from <NUM> to <NUM>; and/or the length Lhc of the actuation means <NUM>, <NUM> is from <NUM> to <NUM>; and/or the length Lmb of the connection body <NUM>, <NUM> is from <NUM> to <NUM>.

Preferably, but not exclusively, the injection apparatus <NUM> has one or more of the following features (also combined together):.

Each of the aforesaid features allows obtaining a better optimization, in particular a greater reduction, in the volume that the molten plastic must cross to reach the injectors <NUM>, <NUM>.

In any case (in all embodiments), the inner diameter of the conduit <NUM>, in particular of stretch <NUM> and branches <NUM>, <NUM> is preferably from <NUM> to <NUM>. In particular, the inner diameter of the conduit <NUM> is selected in this range so as to minimize the undesired effects on the molten plastic, including the formation of undesired substances, e.g., due to excessive sheer stress.

The end portion <NUM> of the conduit <NUM>, in particular the inlet opening <NUM>, adapted to be connected to the plasticization apparatus <NUM> is preferably arranged in the space below, in particular below and at, or above, in particular above and at, the two injectors <NUM>, <NUM>.

Said end portion <NUM> preferably comprises a flange for the connection with the plasticization apparatus <NUM>.

The apparatus <NUM>, as already mentioned, also comprises a tubing <NUM> or channel, used to carry the molten plastic injected by the injectors <NUM>, <NUM> towards the mold.

The tubing <NUM> comprises a stretch <NUM> adapted to receive the molten plastic from the injectors <NUM>, <NUM>. In particular, the stretch <NUM> can receive both the molten plastic injected by the injector <NUM> and the molten plastic injected by the injector <NUM>.

The tubing <NUM> also comprises two branches <NUM>, <NUM> or stretches. Each branch <NUM>, <NUM> is adapted to receive the molten plastic from a respective injector <NUM>, <NUM>; i.e., each stretch <NUM>, <NUM> is adapted to receive a respective molten plastic flow from a respective injector <NUM>, <NUM>. In particular, each branch <NUM>, <NUM> is connected to an outlet of a respective valve <NUM>, <NUM>.

Stretch <NUM> is connected to the two branches <NUM>, <NUM>. In particular, the two branches <NUM>, <NUM> converge in stretch <NUM>, i.e., the molten plastic flow exiting each branch <NUM>, <NUM>, is introduced into stretch <NUM>. In particular, stretch <NUM> is fluidly downstream of the branches <NUM>, <NUM>.

A valve <NUM> is preferably provided along said stretch <NUM> of the tubing <NUM>.

Stretch <NUM> preferably comprises a first stretch <NUM> and a second stretch <NUM> (or sub-stretches), both connected to the valve <NUM>. In particular, stretch <NUM> is upstream of the valve <NUM> and stretch <NUM> is downstream of the valve <NUM>. Stretch <NUM> is substantially a nozzle.

In particular, as a function of its position, the valve <NUM> is adapted to allow or prevent the passage of molten plastic towards the mold.

The valve <NUM>, in a first position, allows the passage of molten plastic towards the mold, and in a second position, allows the molten plastic to exit the stretch <NUM> (preventing the molten plastic from reaching the mold), in particular for carrying out a purging operation.

Actuation means <NUM>, e.g., an actuation cylinder, are provided for actuating the valve <NUM>.

In particular, the valve <NUM> is only used during the purging step. In particular, the purging step is the step of starting the molding apparatus <NUM> (which comprises the injection apparatus <NUM> and the plasticization apparatus <NUM>). Basically, instead of injecting the first loads of molten plastic (e.g., molten PET) of each injector <NUM>, <NUM> directly into the mold, it is preferable to discard such a material into a collection tray (not shown), which in particular is outside the tubing <NUM>. This is because the first material can be highly degraded having spent a long time inside the plasticization apparatus <NUM> during the heating step, before the starting at full operation. Injecting it into the mold would result in filling it with highly degraded material which is then also difficult to remove.

The injection apparatus <NUM> preferably comprises a body <NUM> to which the tubing <NUM> is connected, in particular to stretch <NUM>, more in particular to stretch <NUM>. The body <NUM> is configured to be connected to the mold.

Two actuation cylinders, preferably two hydraulic cylinders <NUM>, <NUM> are preferably provided to allow operations of maintenance and special cleaning, e.g., the removal of stretch <NUM> (or nozzle). The hydraulic cylinders <NUM>, <NUM> allow the injectors <NUM>, <NUM> to move backward, i.e., they allow displacing them away from the mold, and they allow the injectors <NUM>, <NUM> to move forward, i.e., they allow displacing them towards the mold. In particular, the two hydraulic cylinders <NUM>, <NUM> comprise a respective part <NUM>, <NUM> adapted to push against the body <NUM>. During normal operation (i.e., full operation), after the injection apparatus <NUM> has been moved forward towards the mold to the working position, the two hydraulic cylinders <NUM>, <NUM> serve the function of keeping the injection apparatus <NUM> in contact with the mold as they are adapted to apply a sufficient force to oppose the separation force given by the injection pressure which would tend to separate the nozzle <NUM> from the mold.

The conduit <NUM> (in particular stretch <NUM>) is preferably delimited by two parts <NUM>, <NUM> (<FIG>) adapted to mutually slide, so as to form a telescopic system. In particular, part <NUM> is preferably inserted into part <NUM>. Part <NUM> delimits the inlet opening <NUM> of the conduit <NUM> and is adapted to be fixed, in particular integrally fixed, to the plasticization apparatus <NUM>. During the aforesaid backward and forward movement of the injectors <NUM>, <NUM>, the part <NUM> can slide with respect to part <NUM>. In particular, the sliding can occur along an axis substantially horizontal, or in any case parallel to the support surface of the injection apparatus <NUM>. The injection apparatus <NUM> is preferably configured so that the variation in length of the conduit <NUM> due to the aforesaid optional telescopic system is at most <NUM> or <NUM>. When the telescopic system is provided, the aforesaid length of the conduit <NUM> preferably refers to the maximum length obtained when the injectors <NUM>, <NUM> are in the proximal position with respect to the mold - the position in which the conduit <NUM> is in the maximum extension thereof (the distal position is obtained when the injectors <NUM>, <NUM> are translated to the furthest position from the mold by the hydraulic cylinders <NUM>, <NUM>).

The telescopic system is particularly advantageous when the plasticization apparatus <NUM> is of the type that must be fixed, in particular integrally, to the ground (or in any case to the support surface of the injection apparatus <NUM>), i.e., it is fixed in position. In fact, it allows horizontally translating the injectors <NUM>, <NUM>, <NUM> and the components integral therewith, including the valves <NUM>, <NUM>, the tubing <NUM>, and the conduit <NUM>, except for part <NUM> (in fact, part <NUM> is integral with the plasticization apparatus <NUM>, which is preferably fixed in position).

Preferably, but not exclusively, the two injectors <NUM>, <NUM> are tilted, preferably by an angle α from <NUM>° to <NUM>°, with respect to a horizontal plane H, parallel to the support surface of the injection apparatus <NUM>.

In particular, the two injectors <NUM>, <NUM> are preferably tilted so that the end portion <NUM>', where there is provided the opening for the entry and exit of molten plastic from the injector <NUM>, <NUM> (in particular from the body <NUM>, <NUM>), is further down (i.e., closer to the support surface of the injection apparatus <NUM>) with respect to the end portion <NUM>" which is axially opposite to the end portion <NUM>'.

One of the advantages associated with the tilting of the injectors <NUM>, <NUM> consists in the optimization of the volumes. In fact, it is thus possible to reduce the horizontal volume of the injection apparatus <NUM>, and it is further possible to arrange at least part of the plasticization apparatus <NUM> in the space below the injectors <NUM>, <NUM>. The tilting of the injectors <NUM>, <NUM> allows reducing the length of the conduit <NUM> and thus it allows reducing the residence time of the molten plastic inside the conduit <NUM>.

The feature related to the tilting of the injectors <NUM>, <NUM> is thus preferably, but not exclusively, associated with the arrangement of the end portion <NUM> of the conduit <NUM> in the space below the injectors <NUM>, <NUM>.

The injection apparatus <NUM> preferably comprises a support structure <NUM>, adapted to support, in particular, the injectors <NUM>, <NUM>. The injectors <NUM>, <NUM> are preferably constrained to the support structure <NUM> so as to slide with respect thereto. To this end, for example, two sliding guides <NUM>, <NUM> are provided.

The injection apparatus <NUM> is particularly adapted to be connected and operate with a plasticization apparatus <NUM> configured to plasticize PET in the form of flakes. In particular, the plasticization apparatus <NUM> is preferably configured to generate a substantially continuous molten plastic flow.

The plasticization apparatus <NUM> comprises an extruder. In particular, the extruder is configured to generate a substantially continuous molten plastic flow. Preferably, to this end, the screw of the extruder rotates about the longitudinal axis thereof, preferably at a substantially constant speed, and in particular, it does not move along the longitudinal axis thereof. The plasticization apparatus <NUM> can comprise other components downstream of the extruder.

The conduit <NUM>, in particular the inlet opening <NUM> of the conduit <NUM>, is connected in particular to the last component of the plasticization apparatus <NUM>. Preferably, the conduit <NUM> is the only conduit adapted to carry the molten plastic from the plasticization apparatus <NUM> towards the two injectors <NUM>, <NUM> (or to the two injectors <NUM>, <NUM>), i.e., between the plasticization apparatus <NUM> and the conduit <NUM> there are not provided other conduits for the molten plastic.

By way of a non-limiting example, a molten plastic pump can optionally be provided, in particular downstream of the extruder. The aforesaid injector <NUM>, which allows avoiding the hydraulic shocks, is particularly advantageous for protecting such a pump. A filter, and optionally a viscometer, is preferably provided upstream of the pump, and a purging valve can be provided downstream of the pump. One or more reactors can also be provided upstream of the extruder, for treating, in particular pretreating, the PET flakes.

Preferably, as already mentioned, the plasticization apparatus <NUM> is fixed in position, in particular it is integral with the ground. In fact, the plasticization apparatus <NUM> can have such a weight and volume that it needs to be fixed to the ground, e.g., due to the aforesaid reactors.

The invention is also directed to a molding apparatus <NUM> for producing one or more hollow articles, comprising an injection apparatus <NUM> and a plasticization apparatus <NUM> connected to the conduit <NUM>, so that the molten plastic can move from the plasticization apparatus <NUM> to the conduit <NUM>.

The invention is also directed to a process for molding one or more hollow articles, in particular bottle preforms, by an injection apparatus <NUM>, or by a molding apparatus <NUM>, in which if a condition occurs, in which the molten plastic is prevented from entering into both the injector <NUM> and the injector <NUM> (in particular simultaneously), the molten plastic from the conduit <NUM> is received by the injector <NUM> and then, when the molten plastic is allowed to enter into the injector <NUM> or the injector <NUM>, the injector <NUM> injects the molten plastic present inside the injector <NUM> into the conduit <NUM>.

Claim 1:
An injection apparatus (<NUM>) for injecting molten plastic, in particular PET, into a mold for molding bottle preforms;
the injection apparatus (<NUM>) comprising
- a first injector (<NUM>) and a second injector (<NUM>) adapted to receive molten plastic and inject it into the mold alternately to each other;
- a conduit (<NUM>) adapted to carry molten plastic from a plasticization apparatus (<NUM>) towards the first injector (<NUM>) and towards the second injector (<NUM>);
- a third injector (<NUM>) provided with a piston (<NUM>), the third injector (<NUM>) being connected to the conduit (<NUM>) so as to receive molten plastic from the conduit (<NUM>) and then inject it into the conduit (<NUM>);
- actuation means (<NUM>) adapted to cause the piston (<NUM>) of the third injector (<NUM>) to move forward to inject the molten plastic into the conduit (<NUM>);
wherein the first injector (<NUM>) and the second injector (<NUM>) are adapted to inject molten plastic into the mold, in particular into the same mold, through the same nozzle (<NUM>);
wherein said actuation means (<NUM>) are adapted to control the backward movement of the piston (<NUM>) of the third injector (<NUM>) while it receives the molten plastic from the conduit (<NUM>).