Patent Application
20250050560
The present invention relates to the field of molding hollow plastic articles, such as bottle preforms, for example.
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.
The Applicant has developed an injection apparatus comprising two injectors, which to date has not been disclosed, i.e., is currently secret. 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, in particular PET, into a mold for molding bottle preforms;
The invention also relates to a molding apparatus, in particular according to claim 14.
The invention also relates to a molding process, in particular according to claim 15.
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, or in other words, it 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 100 or injection machine, according to the invention are described.
In particular, the injection apparatus 100 is for molding hollow articles, in particular preforms, more in particular bottle preforms.
In fact, the injection apparatus 100 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 100 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 100 comprises
In particular, the injector 1 and the injector 2 are adapted to inject molten plastic into the mold, in particular into the same mold, through the same nozzle 54.
The injection apparatus 100 is in particular configured so that, if a condition occurs in which the molten plastic is prevented from entering into both the injector 1 and the injector 2 (simultaneously), the molten plastic from the conduit 8 is received by the injector 3 (i.e., in the injector 3) and then, when the molten plastic is allowed to enter into the injector 1 or the injector 2, the injector 3 injects the molten plastic present inside the injector 3 into the conduit 8.
Each of the injectors 1, 2 comprises a body 11, 21 adapted to receive the molten plastic, a piston 12, 22 adapted to slide in the body 11, 21, and actuation means 14, 24, constrained to the piston 12, 22. The actuation means 14, 24 are adapted to move the piston 12, 22. The actuation means 14, 24 preferably comprise or consist of an actuation cylinder, preferably a hydraulic cylinder. In particular, each piston 12, 22 is adapted to slide along a respective axis X′, X″ which preferably is the longitudinal axis of the respective injector 1, 2.
The injector 3 comprises a body 31 adapted to receive the molten plastic, a piston 32 adapted to slide in the body 31, and actuation means 34 constrained to the piston 32. The actuation means 34 are adapted to move the piston 32. The actuation means 34 preferably comprise or consist of an actuation cylinder, preferably a hydraulic cylinder. In particular, each piston 32 is adapted to slide along an axis X′″, which is preferably the longitudinal axis of the injector 3.
Each injector 1, 2, 3, in particular the respective body 11, 21, 31, is provided with a respective opening through which the molten plastic can pass for entering and exiting the injector 1, 2, 3.
The molten plastic is received in the space delimited, in particular, by the body 11, 21, 31 and by the piston 12, 22, 32 of each injector 1, 2, 3.
In particular, the actuation means 34 of the injector 3, are adapted to cause the piston 32 to move forward (towards the opening for the passage of the molten plastic of the body 31), in particular at a controlled speed, to inject the molten plastic into the conduit 8. Furthermore, advantageously, the actuation means 34 are adapted to control the backward movement of the piston 32 of the injector 3 while it receives the molten plastic from the conduit 8.
Preferably, there is provided at least one transducer 341 (shown diagrammatically in
It is preferable that the injection apparatus 100 is configured to control the backward movement of the piston 32, in particular the backward movement speed, of the injector 3 while it receives the molten plastic, so that the pressure of the molten plastic in the injector 3 is constant, or substantially constant, during the backward movement of the piston 32.
For example, said at least one transducer 341 can be arranged so as to be adapted to detect the hydraulic pressure of the hydraulic cylinder and thus the transducer 341 is adapted to detect the pressure of the molten plastic in the injector 3.
The injection apparatus 100 preferably comprises an electronic control unit configured to control the displacement of the piston 32 as a function of the pressure values detected by said at least one transducer 341, in particular so as to keep the pressure of the molten plastic in the injector 3 constant, or substantially constant.
Preferably, the third injector 3 has a lower molten plastic loading capacity than the loading capacity of the injector 1 and than the loading capacity of the injector 2; preferably from 5 to 50 times, e.g., from 20 to 25 times, or from 10 to 60 times, e.g., from 25 to 30 times lower than the injector 1 and the injector 2.
In other words, the injector 3 is configured to receive a maximum amount of molten plastic therein (in particular, when the piston 32 is in the fully back position), which is lower than the maximum amount of molten plastic that the injector 1 can receive and lower than the maximum amount of molten plastic that the injector 2 can receive, in particular when the respective piston 12, 22 is in the fully back position.
Preferably, the injector 1 and the injector 2 have the same loading capacity, or substantially the same loading capacity.
Preferably, the injection apparatus 100, in particular the injector 3, is configured to inject molten plastic at a lower injection speed than the injection speed of the injector 1 and the injector 2, i.e., the injector 3 is configured to inject molten plastic at a lower injection speed than the injection speed of each of the injectors 1, 2, preferably from 4 to 10 times lower.
The injector 3 thus injects the molten plastic slowly and therefore undesired pressure peaks are avoided.
The injectors 1, 2 are preferably configured to inject molten plastic at the same injection speed.
The injection apparatus 100 is configured so that the two injectors 1, 2 can receive the molten plastic and inject it into the mold alternately to each other.
In particular, the apparatus 100 is configured so that while one of the injectors 1 receives the molten plastic (i.e., it is filled, loading step), the other injector 2 injects the molten plastic (and is therefore emptied, injection step).
Preferably, the injection apparatus 100 comprises two valves 41, 42, in particular one valve 41, 42 for each injector 1, 2. Preferably, the valves 41, 42 are spool valves.
The valves 41, 42 are used to allow loading one of the injectors 1, 2 with molten plastic and injecting the molten plastic which exits from another injector 1, 2 in an alternate manner.
In particular, the injection apparatus 100 comprises:
In particular, the injector 3 is connected to the conduit 8 upstream, in particular fluidly upstream, of the valve 41 and the valve 42.
In particular, each valve 41, 42 is adapted to take a first position, in which it allows the passage of molten plastic from the conduit 8 to the respective injector 1, 2 (loading step) and prevents the passage of molten plastic from the respective injector 1, 2 towards the mold; and a second position, in which it allows the passage of molten plastic from the respective injector 1, 2 towards the mold (injection step) and prevents the passage of molten plastic from the conduit 8 to the respective injector 1, 2.
The injection apparatus 100 is configured to control the valve 41 and the valve 42 so that while the valve 41 is in the first position thereof, the valve 42 is in the second position thereof, and vice versa. In fact, the injection apparatus 100 is configured to cause the valve 41 to move from the first position to the second position, and vice versa; and to cause the valve 42 to move from the first position to the second position, and vice versa.
For the injectors 1, 2 to inject the molten plastic into the mold alternately, the two valves 41, 42 need to switch the position thereof.
It may happen that a condition occurs, in which both valves 41, 42 prevent the passage of molten plastic from the conduit 8 to the respective injector 1, 2, as shown for example in
This condition may occur, for example, in an initial (transitory) step of the position change of the two valves 41, 42; or for example, due to a delay in the position change of the valves 41, 42.
Advantageously, in this condition, the molten plastic from the conduit 8 can be received in the injector 3. In particular, the piston 32 moves backward so that the molten plastic can enter the injector 3. Therefore, a fluid hammer is avoided from occurring, in particular in the conduit 8. The molten plastic inside the injector 3 can then be injected into the conduit 8 when one of the two valves 41, 42 allows the molten plastic to enter into the respective injector 1, 2.
In particular, the aforesaid conduit 8 has an inlet section or opening 86 (
Preferably, the conduit 8 has only one inlet opening 86 and only three outlet openings 85, 87, 88.
In particular, the inlet opening 86 is adapted to be connected to the plasticization apparatus 102.
An end portion 89 of the conduit 8 is provided with said inlet opening 86.
The conduit 8 comprises a stretch 80 and two branches 81, 82. The two branches 81, 82 are connected to the stretch 80 so as to receive the molten plastic from the stretch 80. The two branches 81, 82 are preferably transverse to the stretch 80. The stretch 80 is provided with the inlet opening 86, and each branch 81, 82 is provided with a respective outlet opening 87, 88. The branch 81 is adapted to carry the molten plastic towards the injector 1 and the branch 82 is adapted to carry the molten plastic towards the second injector 2.
The valve 41 is connected to the branch 81 so as to receive molten plastic therefrom; and the valve 42 is connected to the branch 82 so as to receive molten plastic therefrom.
In particular, the body 411, 421 of each valve 41, 42 is connected to a respective branch 81, 82.
The injector 3 is preferably connected to the conduit 8 so as to receive molten plastic from said stretch 80 of the conduit 8, preferably directly from stretch 80. The body 31 of the injector 3 is preferably fixed to the conduit 8, in particular to a wall delimiting the conduit 8.
The injection apparatus 100 is in particular configured so that the molten plastic from the plasticization apparatus 102 is introduced into the conduit 8, in particular into the stretch 80 and then into the branches 81, 82.
The conduit 8, preferably extends from the inlet opening 86 for the molten plastic to the three outlet sections or openings 85, 87, 88; in particular to the outlet opening 87 (in particular to the valve 41), to the outlet opening 88 (in particular to the valve 42) and to the outlet opening 85.
In some variants, not shown, the number of valves for controlling the molten plastic flow towards the injectors 1, 2 can be greater than two, e.g., three.
For the actuation of each valve 41, 42, in particular to cause each valve 41, 42 to move from the first position to the second position and vice versa, actuation means 413, 423 are provided (
The body 411, 421 of each valve 41, 42 is preferably fixed to the respective injector 1, 2. In particular, the body 411, 421 of each valve 41, 42 is fixed to the end portion of the respective injector 1, 2 where the opening for the entry and exit of molten plastic of the respective injector 1, 2, is present.
Inside the body 411, 421 of each valve 41, 42 there is a respective movable element 412, 422. Each movable element 412, 422 preferably defines a conduit which, in a position of the respective valve 41, 42, can (fluidly) communicate with the conduit 8 and the opening of the respective injector 1, 2. Each movable element 412, 422 also defines another conduit which, in another position of the respective valve 41, 42, can (fluidly) communicate with the opening of the respective injector 1, 2 and the tubing 5, in particular with a respective branch 51, 52 of the tubing 5.
Each of the aforesaid actuation means 413, 423 is adapted to move a respective movable element 412, 422.
The length of said conduit 8 is preferably shorter than the length Ltot, in particular than the total length, of each of the two injectors 1, 2 along the respective longitudinal axis X′, X″.
In particular, the “length” of the conduit 8 means the length of the path traveled by the molten plastic when crossing the whole conduit 8, i.e., when crossing the conduit 8 from the beginning to the end thereof, in particular from the inlet opening 86 to the three outlet sections or openings 85, 87, 88.
The length of the conduit 8 comprises the length of the stretch 80, and the length of each of the two branches 81, 82; in particular, the length of the conduit 8 is preferably equal to the sum of the length of the stretch 80, and of the length of each of the two branches 81, 82.
The aforesaid stretch 80 preferably comprises a stretch 801 (
Stretch 801 preferably has the aforesaid inlet opening 86.
The aforesaid stretch 80 preferably comprises two stretches 801, 802 (or sub-stretches or portions) which are transverse to each other, e.g., orthogonal to each other. The first stretch 80 can have, for example, a substantially L shape. The two stretches 801, 802 are joined to each other by a connection stretch 803. In particular, the connection stretch 803 is substantially an elbow (i.e., it is curved).
Part of the conduit 8 is preferably delimited by a component, e.g., a T-shaped- or Y-shaped tube, comprising said two branches 81, 82. In particular, said T- or Y-shaped component also comprises part of the stretch 80 of conduit 8, in particular part of stretch 802.
Said length Ltot of each injector 1, 2 comprises the length Lcm of said body 11, 21 and the length Lhc of said actuation means 14, 24 (the length Lhc is also measured along the longitudinal axis X′, X″).
In particular, each injector 1, 2 has a first axial end 19′ (
The actuation means 14, 24 are preferably connected to the respective body 11, 21 by a respective connection body 13, 23, extending between the body 11, 21 and the actuation means 14, 24.
In this case, said length Ltot of each injector 1, 2 comprises the length Lcm of said body 11, 21, the length Lmb (along the longitudinal axis X′, X″) of the connection body 13, 23 and the length Lhc of said actuation means 14, 24.
A valve 15, 25, in particular a proportional valve, can be connected to the actuation means 14, 24.
Preferably, said length Ltot of each injector 1, 2 does not comprise the length of the valve 15, 25.
Preferably, but not exclusively, the two injectors 1, 2 are parallel to each other; in particular, the longitudinal axes thereof are parallel to each other. Alternatively, the two injectors 1, 2 can be transverse to or aligned with each other.
In particular, the two injectors 1, 2 have the same length Ltot.
The two injectors 1, 2 are preferably equal to each other.
The length Ltot of each injector 1, 2 is preferably from 2500 mm to 3300 mm; and/or the length Lcm of each body 11, 21 is from 700 mm to 1200 mm; and/or the length Lhc of the actuation means 14, 24 is from 800 mm to 1300 mm; and/or the length Lmb of the connection body 13, 23 is from 600 mm to 1100 mm.
Preferably, but not exclusively, the injection apparatus 100 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 1, 2.
In any case (in all embodiments), the inner diameter of the conduit 8, in particular of stretch 80 and branches 81, 82 is preferably from 30 mm to 50 mm. In particular, the inner diameter of the conduit 8 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 89 of the conduit 8, in particular the inlet opening 86, adapted to be connected to the plasticization apparatus 102 is preferably arranged in the space below, in particular below and at, or above, in particular above and at, the two injectors 1, 2.
Said end portion 89 preferably comprises a flange for the connection with the plasticization apparatus 102.
The apparatus 100, as already mentioned, also comprises a tubing 5 or channel, used to carry the molten plastic injected by the injectors 1, 2 towards the mold.
The tubing 5 comprises a stretch 50 adapted to receive the molten plastic from the injectors 1, 2. In particular, the stretch 50 can receive both the molten plastic injected by the injector 1 and the molten plastic injected by the injector 2.
The tubing 5 also comprises two branches 51, 52 or stretches. Each branch 51, 52 is adapted to receive the molten plastic from a respective injector 1, 2; i.e., each stretch 51, 52 is adapted to receive a respective molten plastic flow from a respective injector 1, 2. In particular, each branch 51, 52 is connected to an outlet of a respective valve 41, 42.
Stretch 50 is connected to the two branches 51, 52. In particular, the two branches 51, 52 converge in stretch 50, i.e., the molten plastic flow exiting each branch 51, 52, is introduced into stretch 50. In particular, stretch 50 is fluidly downstream of the branches 51, 52.
A valve 6 is preferably provided along said stretch 50 of the tubing 5.
Stretch 50 preferably comprises a first stretch 53 and a second stretch 54 (or sub-stretches), both connected to the valve 6. In particular, stretch 53 is upstream of the valve 6 and stretch 54 is downstream of the valve 6. Stretch 54 is substantially a nozzle.
In particular, as a function of its position, the valve 6 is adapted to allow or prevent the passage of molten plastic towards the mold.
The valve 6, 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 50 (preventing the molten plastic from reaching the mold), in particular for carrying out a purging operation.
Actuation means 61, e.g., an actuation cylinder, are provided for actuating the valve 6.
In particular, the valve 6 is only used during the purging step. In particular, the purging step is the step of starting the molding apparatus 101 (which comprises the injection apparatus 100 and the plasticization apparatus 102). Basically, instead of injecting the first loads of molten plastic (e.g., molten PET) of each injector 1, 2 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 5. This is because the first material can be highly degraded having spent a long time inside the plasticization apparatus 102 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 100 preferably comprises a body 79 to which the tubing 5 is connected, in particular to stretch 50, more in particular to stretch 54. The body 79 is configured to be connected to the mold.
Two actuation cylinders, preferably two hydraulic cylinders 71, 72 are preferably provided to allow operations of maintenance and special cleaning, e.g., the removal of stretch 54 (or nozzle). The hydraulic cylinders 71, 72 allow the injectors 1, 2 to move backward, i.e., they allow displacing them away from the mold, and they allow the injectors 1, 2 to move forward, i.e., they allow displacing them towards the mold. In particular, the two hydraulic cylinders 71, 72 comprise a respective part 711, 721 adapted to push against the body 79. During normal operation (i.e., full operation), after the injection apparatus 100 has been moved forward towards the mold to the working position, the two hydraulic cylinders 71, 72 serve the function of keeping the injection apparatus 100 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 54 from the mold.
The conduit 8 (in particular stretch 801) is preferably delimited by two parts 91, 92 (
The telescopic system is particularly advantageous when the plasticization apparatus 102 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 100), i.e., it is fixed in position. In fact, it allows horizontally translating the injectors 1, 2, 3 and the components integral therewith, including the valves 41, 42, the tubing 5, and the conduit 8, except for part 91 (in fact, part 91 is integral with the plasticization apparatus 102, which is preferably fixed in position).
Preferably, but not exclusively, the two injectors 1, 2 are tilted, preferably by an angle α from 10° to 45°, with respect to a horizontal plane H, parallel to the support surface of the injection apparatus 100.
In particular, the two injectors 1, 2 are preferably tilted so that the end portion 19′, where there is provided the opening for the entry and exit of molten plastic from the injector 1, 2 (in particular from the body 11, 21), is further down (i.e., closer to the support surface of the injection apparatus 100) with respect to the end portion 19″ which is axially opposite to the end portion 19′.
One of the advantages associated with the tilting of the injectors 1, 2 consists in the optimization of the volumes. In fact, it is thus possible to reduce the horizontal volume of the injection apparatus 100, and it is further possible to arrange at least part of the plasticization apparatus 102 in the space below the injectors 1, 2. The tilting of the injectors 1, 2 allows reducing the length of the conduit 8 and thus it allows reducing the residence time of the molten plastic inside the conduit 8.
The feature related to the tilting of the injectors 1, 2 is thus preferably, but not exclusively, associated with the arrangement of the end portion 89 of the conduit 8 in the space below the injectors 1, 2.
The injection apparatus 100 preferably comprises a support structure 7, adapted to support, in particular, the injectors 1, 2. The injectors 1, 2 are preferably constrained to the support structure 7 so as to slide with respect thereto. To this end, for example, two sliding guides 73, 74 are provided.
The injection apparatus 100 is particularly adapted to be connected and operate with a plasticization apparatus 102 configured to plasticize PET in the form of flakes. In particular, the plasticization apparatus 102 is preferably configured to generate a substantially continuous molten plastic flow.
The plasticization apparatus 102 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 102 can comprise other components downstream of the extruder.
The conduit 8, in particular the inlet opening 86 of the conduit 8, is connected in particular to the last component of the plasticization apparatus 102. Preferably, the conduit 8 is the only conduit adapted to carry the molten plastic from the plasticization apparatus 102 towards the two injectors 1, 2 (or to the two injectors 1, 2), i.e., between the plasticization apparatus 102 and the conduit 8 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 3, 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 102 is fixed in position, in particular it is integral with the ground. In fact, the plasticization apparatus 102 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 101 for producing one or more hollow articles, comprising an injection apparatus 100 and a plasticization apparatus 102 connected to the conduit 8, so that the molten plastic can move from the plasticization apparatus 102 to the conduit 8.
The invention is also directed to a process for molding one or more hollow articles, in particular bottle preforms, by an injection apparatus 100, or by a molding apparatus 101, in which if a condition occurs, in which the molten plastic is prevented from entering into both the injector 1 and the injector 2 (in particular simultaneously), the molten plastic from the conduit 8 is received by the injector 3 and then, when the molten plastic is allowed to enter into the injector 1 or the injector 2, the injector 3 injects the molten plastic present inside the injector 3 into the conduit 8.
Preferably, in order to inject the molten plastic into the mold, the injector 1 and the injector 2 inject molten plastic at a first injection speed; and when the injector 3 injects the molten plastic contained therein, the injector 3 injects the molten plastic at a second injection speed which is lower than said first injection speed; preferably from 4 to 10 times lower. The injector 3 thus injects the molten plastic slowly, and therefore undesired pressure peaks are avoided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021000028796 | Nov 2021 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/060874 | 11/11/2022 | WO |
