WO2022118203A1

WO2022118203A1 - Machine for the compression moulding of a parison and for the blow moulding of a parison

Info

Publication number: WO2022118203A1
Application number: PCT/IB2021/061159
Authority: WO
Inventors: Davide BALDISSERRI; Stefano Bergami; Marcello ZAMA
Original assignee: Sacmi Cooperativa Meccanici Imola Societa' Cooperativa
Priority date: 2020-12-04
Filing date: 2021-12-01
Publication date: 2022-06-09
Also published as: TW202228986A

Abstract

A machine (1) for the compression moulding of a parison from a charge (20) of thermoplastic material and for the blow moulding of the parison comprises: a carousel (10); a plurality of moulds (11) positioned on the carousel (10), where each mould (11) includes a female element (111), a male element (112) and a blow moulding cavity associable with the male element (112) in place of the female element (111); a conveyor system (3) for transporting the charges (20) and including a wheel (30), a plurality of conveyor elements (31) associated with the wheel (30) and each including a gripper hand (32), one or more doors (331, 332) and a shutter (34); a forming device (4) for forming the charges (20) and including an extruder (41), configured to produce a flow of fluid plastic, and a knife (42), configured to cut individual charges (20) from the flow of fluid plastic.

Description

DESCRIPTION

MACHINE FOR THE COMPRESSION MOULDING OF A PARISON AND FOR THE BLOW MOULDING OF A PARISON

Technical field

This invention relates to a machine for the compression moulding of a parison and for the blow moulding of the parison. This invention also relates to a method for the compression moulding and blow moulding of a parison.

Background art

Generally speaking, this invention addresses the technical sector of rotary machines for individually forming plastic objects by compression moulding in a continuous cycle. More in general, this invention addresses the technical sector of rotary machines for forming plastic containers by the combined action, in succession in the same machine, of compression moulding to form parisons and blow moulding to form the containers from the parisons; thus, these machines are fed with a succession of charges of plastic material and return a corresponding succession of blow moulded containers.

Examples of machines of this kind are described in patent documents W008110887A2 and WO07107822A2 in the name of the present Applicant. These documents describe a machine comprising a plurality of moulds associated with a carousel; each mould comprises a male element and a female element, configured to form the parison by compression moulding from a charge of plastic material placed in the female element of the mould; after moulding the parison, the female element is moved away from the male element and the parison remains hanging from the male element; next, the parison is stretched with a stretching rod, which is extractable from the male element, and then blown into a blow moulding i cavity to obtain the container. Usually, the charges are made by a knife which cuts the individual charges from a rod of continuously extruded material; the charges are then conveyed one by one to the cavity of the female element of each respective mould.

Rotary compression moulding machines and, more specifically, forming and blow moulding machines, present several problems. One of these problems is connected with the way the charges are transferred into the moulds.

This problem is made particularly critical by two factors: the high rotation speed of the carousel which the moulds are mounted on and the fact that the charges, consisting of hot, viscous plastic, are sticky, especially if the plastic used is PET.

For transferring the charges, several solutions have been developed in the context of rotary machines for forming plastic objects by compression moulding.

Examples of conveying systems for transporting charges for rotary plastic compression moulding machines without the blow moulding feature are provided by the following patent documents: EP2195147B1 , W0201850740A1 , WO0745577A2, WO0995753A2, WO05102642A1 , W02005102640A1 , W020051 02643A1 , W020051 02641 A2,

EP1868787B1 , EP2125317B1 , W02005102646A1 , WO201084470A2 and EP2054205B1 in the name of the present Applicant. Other examples of conveying systems for transporting charges for rotary plastic compression moulding machines without the blow moulding feature are provided by the following patent documents: EP1579979B1 and EP1849573A.

In all these examples, the conveying system comprises a rotary carousel, associated with a plurality of conveyor elements which are moved by the carousel and which pick up the charges from a pick-up zone, where the charges are made, and transport them to a release zone, where one of the conveyor elements is vertically aligned with a corresponding mould female element underneath it, into which the charge is dropped. The conveyor elements that transport the charges comprise an upper wall, having the shape of a C, to form a concavity adapted to impact the charge in the pickup zone, and a guide tube (or funnel) placed under the upper wall, to guide the charge as it drops vertically towards the mould.

To reduce the risk of the charge sticking to the walls of the guide tube as it moves down along the guide tube, diverse measures have been devised. For example, in document EP2195147B1 , the inside wall of the guide tube is provided with rolling elements; in document EP2125317B1 , the rolling elements are applied on the upper wall. In document WO200995753A2, the guide tube is movable axially to facilitate detachment of the charge when it stops in the lowered position. In document W0201850740A1 , the guide tube is provided with perforations or is porous to allow air to flow into the guide tube. In document WO200745577A2, the guide tube is cooled.

Documents W005102642A1 , W005102640A1 , WO05102641 A2,

EP1868787B1 , W005102646A1 and W0201084470A2 concentrate on the mechanism by which the charges are delivered by opening and closing the outlet opening of the guide tube.

Document EP2054205B1 concentrates on the mechanism for moving the conveyor elements.

In the conveyor elements described in documents W02005102643A1 and EP1849573B1 , the upper wall over the guide tube is provided with one or two doors which, when the charge impacts the concave surface of the upper wall, prevents the charge from bouncing and thus helps to channel it correctly into the passage formed by the guide tube. In this regard, attention is drawn to Figure 5 of document W02005102643A1 and Figures 7 and 8 of document EP1849573B1. Document EP1849573B1 (at paragraph 30) also mentions the possibility of making the guide tube vibrate, again for the purpose of reducing the risk of the charge adhering to the wall of the tube.

Nevertheless, in the solutions described above, the risk of the charge sticking to the wall of the guide tube remains high. A different approach is described in patent document EP1652645A1 , according to which (with reference to Figure 3, for example) the conveyor elements are each provided with a respective knife for cutting off the charge and with a gripper, made up of a supporting element and a pushing element, which holds the charge while it is being conveyed and then releases it when it moves away from the supporting element; in this solution, each conveyor element is mounted on a carriage to move vertically from a raised position, which it adopts in the charge pick-up zone, to a lowered position, which it adopts in the charge release zone.

This solution, too, however, does not entirely solve the problem of the charge sticking to the conveyor element, especially if the plastic used is PET, because the pressure which the grippers apply on the charge tends to make the charge rather more liable to adhere to the walls of the supporting element or of the pushing element. Moreover, this solution is particularly complicated and fragile because each of the conveyor elements must be provided with a movable knife and must itself be movable vertically.

The general need therefore remains for rotary machines for the compression moulding of objects from charges of plastic to have a conveying system for transporting the charges which reduces the risk of the charges sticking to the conveyor elements themselves, so that the machines can operate at high speeds and with any kind of plastic, including PET. This need is felt in particular for rotary machines which not only form the parisons by the compression moulding of the charges but which also form the containers by the blow moulding of the parisons.

Moreover, there are other solutions of machines for forming a parison by compression moulding and for blow moulding the parison, which are disclosed in the following documents: US2012100241 A1 , US2011280981 , EP 3512679A1 and EP2324917A1. However, these documents disclose solutions wherein the production speed is limited. Disclosure of the invention

The aim of this disclosure is to provide a machine for forming a parison by compression moulding and for blow moulding the parison, and a method for the compression moulding and blow moulding of a parison to overcome the above mentioned disadvantages of the prior art.

This aim is fully achieved by the machine and method of this disclosure as characterized in the appended claims.

This disclosure relates to a machine for the compression moulding of a parison from a charge of thermoplastic material; the machine is preferably also configured for blow moulding the parison. The thermoplastic material may be, for example, polyethylene or polypropylene.

The machine comprises a carousel which rotates about a first, longitudinal axis of rotation in a first rotation direction. The first, longitudinal axis of rotation is parallel to a longitudinal direction; preferably, the longitudinal direction is parallel to the weight force.

The machine comprises a plurality of moulds, positioned on the carousel. Each mould includes a female element which defines a hollow designed to receive the charge. Each mould includes a male element, associable with the female element to delimit a forming cavity; the male element is configured to compress the charge, thereby forcing it to occupy the forming cavity so as to form the parison. More specifically, the male element is movable relative to the female element between a spaced-apart position, corresponding to an open configuration of the mould, and a close together position, corresponding to a closed (or forming) configuration of the mould. The charge is inserted into the female element in the open configuration of the mould; the mould is then closed to delimit the forming cavity in which the parison is formed.

Preferably, each mould also comprises a blow moulding cavity (or element), associable with the male element in place of the female element to delimit a blow moulding cavity in which a container is formed from the parison. Thus, the mould has a forming configuration in which the male element is associated with the female element; in the forming configuration, the parison is formed from the charge. The mould also has a blow moulding configuration in which the male element is associated with the blow moulding cavity; in the blow moulding configuration, the container is formed from the parison.

The machine comprises a conveying system for transporting the charges from a pick-up zone to a release zone. Preferably, the pick-up zone and the release zone are stationary.

The charge conveying system comprises a wheel which rotates about a second, longitudinal axis of rotation in a second rotation direction, opposite to the first rotation direction. The second, longitudinal axis of rotation is parallel to the first, longitudinal axis of rotation, hence to the longitudinal direction.

The charge conveying system comprises a plurality of conveyor elements, associated with the wheel to move along a trajectory which intercepts the pick-up zone and the release zone. The trajectory may be circular, in the case where the conveyor elements have a stationary radial position, or partly elliptic (or oval), in the case where the conveyor elements are movable radially relative to the wheel. In effect, a radial movement of the conveyor elements is imaginable in the proximity of the release zone to enable the conveyor elements to follow the female elements in order to increase the length of time each conveyor element is at a position close to the female element into which it must insert the charge.

The charge conveying system comprises a forming device, configured to form the charges. The forming device is located in the pick-up zone. The forming device is outside relative to the wheel and the carousel (that is to say, it does not rotate on the wheel or on the carousel). The forming device includes an extruder, configured to produce a flow of fluid plastic. The forming device includes a knife, configured to cut off individual charges from the flow of fluid plastic.

The extruder has a stationary position (or at least, a stationary longitudinal level) relative to the wheel and/or the carousel.

Preferably, the knife oscillates (or rotates) relative to the extruder to periodically intercept the flow of fluid plastic; the movement of the knife is synchronized with the rotation of the wheel which the conveyor elements are mounted on; that way, when a conveyor element is in the pick-up zone, the knife cuts off a charge from the flow of fluid plastic and the charge is received by the conveyor element. Thus, the knife cuts the charges in a cutting zone, which is stationary relative to the wheel and/or the carousel. Preferably, the knife and the extruder are located at a longitudinal level that is stationary relative to the wheel and the carousel.

Each conveyor element of the charge conveying system includes a gripper hand. The gripper hand extends longitudinally between a first end, located at a first level, and a second end, located at a second level, lower than the first level. It should be noted that by first and second level are meant a first and a second longitudinal, or vertical, level. The gripper hand has a transverse cross section (perpendicular to the longitudinal direction) that is C-shaped, so as to define a concavity responsible for intercepting the charge in the pick-up zone.

It is observed that the gripper hand is provided with the C-shaped transverse cross section along the entire (longitudinal) length of the gripper hand, from the first end to the second end. The gripper hand has a lower opening, provided at the second end. The gripper hand may also be provided with an upper opening, provided at the first end. Moreover, the gripper hand has a lateral opening, wherein the lateral opening extends for the entire (longitudinal) length of the gripper hand (between the first end and the second end). The lateral opening defines the C-shape and has the function to allow the gripper hand to receive the charge on the concave surface, during the movement of the gripper hand. The lower opening has the function to allow the charge to be discharged longitudinally downwards.

Each conveyor element of the charge conveying system includes one or more doors (preferably a first and a second door) which are movable between an open position of non-interference with the trajectory of the gripper hand moving towards the charge in the pick-up zone, and a closed position where they are close to the gripper hand; at the closed position, the one or more doors act in conjunction with the gripper hand to define a containing surface extending around a longitudinal axis of the gripper element so as to surround the charge that is operatively interposed therebetween. The longitudinal axis of the gripper element is parallel to the longitudinal direction. In the closed position, the doors close the lateral aperture, whereas in the open position the door leave the lateral opening at least partly open, to allow the gripper hand to intercept the charge.

Each conveyor element of the charge conveying system includes a shutter, positioned at the second end of the gripper hand; the shutter is movable to open and close an outlet for the passage of the charge; the passage is formed by the gripper hand and by the one or more doors at the closed position.

Thus, the charge is received by the gripper hand in the pick-up zone when the one or more doors are at the open position. Once the charge has been placed in the concavity of the gripper hand, the one or more doors are moved to the closed position, where they define the containing surface that surrounds the charge. It should be noted that the one or more doors must be closed as promptly as possible after the charge has been received from the gripper hand to prevent the charge from bouncing on the concavity of the gripper hand so the conveyor element is unable to catch it. Once the doors are closed, the charge moves down by gravity along the containing surface towards the second end of the gripper hand; thus, the containing surface also defines a passage for the charge. The shutter is located at the second end of the gripper hand and, until it opens, it prevents the charge from leaving the containing surface (or passage). In the meantime, the wheel turns and the conveyor element moves from the pick-up zone to the release zone. When the pick-up element is at the release zone, the shutter opens the passage for the charge to allow the charge to be released. The charge released by the conveyor element is received by the female element of the mould.

Operatively, the charge is received by the gripper hand at the concavity of the gripper hand, through the lateral aperture (with the doors opened); the charge is discharged through the lower opening (with the shutter opened). When the charge is received by the gripper hand at the concavity thereof, the relative movement between the charge and the gripper hand is transverse (orthogonal) with respect to the longitudinal direction; when the charge is discharged from the gripper hand (through the lower aperture), the relative movement between the charge and the gripper hand is along the longitudinal direction (in a downward direction).

Preferably, the passage formed by the gripper hand and the one or more doors is larger in cross section at the first end of the gripper element and smaller in cross section at the second end of the gripper element; that way, the charge is received more easily by the gripper hand and fed with greater precision to the female element of the mould.

In one example, said one or more doors extend longitudinally between the first end of the gripper hand and the second end of the gripper hand. In fact, the passage which is closed or open by the shutter is defined by the gripper hand and by said one or more doors, which thus extend along all the longitudinally extension of the gripper hand.

This embodiment makes the machine more compact and, as a consequence, allows the machine to work faster.

In an embodiment, the passage includes at least one portion whose cross section is convergent (for example, frustoconical) towards the outlet of the passage.

Preferably, the passage formed by the gripper hand and the one or more doors at the closed position has a first stretch and a second stretch, the second stretch being longitudinally consecutive with the first stretch. Preferably, the second stretch defines the outlet of the passage (and is thus partly delimited by the second end of the gripper hand). Preferably, the first stretch is partly delimited by the first end of the gripper hand. Preferably, the passage has, in its second stretch, a cylindrical shape with a second passage area and, in its first stretch, a wide cross section with a first passage area that is greater than the second passage area. The first passage area may vary along the longitudinal axis of the gripper element but in any case remaining greater than the second passage area. This shape is useful for limiting the problem of bouncing when the charge is received and the problem of guiding and aligning the charge relative to the female element when the charge is released.

Preferably, the first stretch of the passage has at least one portion that is frustoconical in shape. More specifically, the frustoconical portion may be defined longitudinally (for example, the first stretch may include a frustoconical portion and a cylindrical portion). In addition or alternatively, the frustoconical portion may be defined in an arc-shaped portion partly surrounding the longitudinal axis of the gripper element; more specifically, the concavity of the gripper hand might have a frustoconical shape, whilst the one or more doors might be parallel to the longitudinal axis of the gripper element. The frustoconical shape is tapered towards the second portion, to which it is connected.

Preferably, for each conveyor element, the gripper hand has a receiving surface, defining the concavity that receives the charge; the receiving surface has at least one portion that is inclined relative to the longitudinal axis of the gripper element, tapered towards the outlet of the passage for the charge. It should be noted that this shape is useful for limiting the problem of bouncing when the charge is received and the problem of guiding and aligning the charge relative to the female element when the charge is released. In an embodiment, the inclined portion may be defined by the frustoconical shape in the first stretch of the passage. In another embodiment, the inclined portion may extend from the first to the second end of the gripper hand; in this embodiment, the concavity thus has a frustocomcal shape from the first to the second end.

Preferably, the one or more doors rotate about respective longitudinal axes of oscillation; the longitudinal axes of oscillation are parallel to the longitudinal direction, the longitudinal axes of oscillation are disposed laterally of the gripper hand (on the outside of it). More specifically, the longitudinal axes of oscillation are located at a position behind the gripper hand relative to the trajectory of the gripper hand moving towards the charge in the pick-up zone; that way, the doors do not interfere with the trajectory of the gripper hand that receives the charge.

Preferably, for each conveyor element, the one or more doors are operatively in contact with the lateral ends of the gripper hand, at the closed position. More specifically, a first door might be in contact with a first lateral end of the gripper hand, a second door might be in contact with a second lateral end of the gripper hand, opposite to the first lateral end, and the first door might be in contact with the second door, at the closed position.

It should be noted that the knife is positioned at a third (longitudinal) level; the third level is preferably situated just above the first level at which the first end of the gripper hand is situated; for example, the third level may be located at a distance of 1 -3 mm from the first level. That way, the gripper hand receives the charge that has just been cut off by the knife. In other words, the knife is positioned, along the longitudinal direction, between the extruder and the first end of the gripper hand, to receive the charge that has just been cut off by the knife. The knife is longitudinally spaced from the first end of the gripper hand of a distance which is included in an interval between 0,5-6 mm, preferably 1 -3 mm.

It should be noted that the shutter is positioned at a fourth (longitudinal) level. The fourth level is situated just below the second level at which the second end of the gripper hand is situated; for example, the fourth level may be located at a distance of 1 -3 mm from the second level.

It should be noted that the top of the female element of the mould is ii positioned at a fifth (longitudinal) level. The fifth level is situated just below the fourth level. Preferably, the fifth level is spaced from the second level by a length of less than 10 mm.

The difference between the first level (where the first end is situated) and the second level (where the second end is situated) corresponds to the longitudinal extension of the gripper hand (that is, of the passage). Preferably, the longitudinal extension of the gripper hand is just a little greater than the longitudinal extension of the charge; for example, it may be 1 to 10 mm greater than the longitudinal extension of the charge.

In an embodiment, the apparatus includes an opposing element. The opposing element is positioned at the pick-up zone. The opposing element is interposed, longitudinally, between the gripper hand and the knife. The opposing element is located at a position behind the longitudinal axis of the gripper hand, with reference to the trajectory of the gripper hand towards the charge; in effect, it is located at a rear wall of the gripper hand that defines the concavity. Thus, the opposing element is located at a position behind the charge. The opposing element is useful for preventing a top part of the charge from settling outside the gripper hand after being cut off. The opposing element is between 8 and 10 mm high along the longitudinal axis; preferably, the opposing element has an upper end that is approximately 1 mm away from the knife and a lower end that is approximately 1 mm away from the gripper hand. Consequently, where the opposing element is provided, the third level may be located between 10 and 12 mm away from the first level.

Preferably, for each conveyor element, the conveying system comprises a nozzle, configured to generate an air jet. The nozzle is associated with the respective conveyor element. The nozzle is movable transversely to the longitudinal axis of the gripper element between a retracted position, where it is spaced from the longitudinal axis of the gripper element, and an advanced position, where it is advanced towards the longitudinal axis of the gripper element (preferably intercepting it) to blow the air jet along the longitudinal axis of the gripper element, the air jet being oriented towards the outlet of the passage (that is, towards the second end of the gripper hand). More specifically, when the conveyor element is in the pick-up zone, the nozzle is at the retracted position so as not to interfere with the extruder, and when the conveyor element is in the release zone, the nozzle is at the advanced position. The emission of the air jet is preferably synchronized with the opening of the shutter: that way, when the shutter opens, the air jet facilitates detachment of the charge from the conveyor element so that it drops into the female element of the mould.

In an embodiment, for each conveyor element, the conveying system comprises a vibrator and a switch. The vibrator and the switch are associated with the respective conveyor element. The vibrator is operable in an activated configuration, in which it makes the gripper hand vibrate, and in a deactivated configuration. The switch is configured to change the configuration of the vibrator from activated to deactivated and vice versa, responsive to the position of the conveyor element along its trajectory. More specifically, the vibrator is in the activated configuration when the conveyor element is at the release position; that way, vibration facilitates detachment of the charge from the conveyor element so that it drops into the female element of the mould. Further, the vibrator may also be in the activated configuration when the conveyor element is moving along its trajectory from the pick-up zone to the release zone, so as to prevent the charge from sticking to the conveyor element. More specifically, the switch might set the vibrator to a first vibration frequency when the conveyor element is moving along its trajectory from the pick-up zone to the release zone and to a second vibration frequency, different from the first, when the shutter opens. The second vibration frequency is preferably greater than the first.

Preferably, for each conveyor element, the gripper hand is provided with a rough surface covering or, more generally speaking, a rough surface. Preferably, the one or more doors also have a rough surface covering or, more generally speaking, a rough surface. The roughness helps to prevent the charge from sticking to the conveyor element. For example, the surface is characterized by a roughness value higher than 0,05 pm, preferably higher than 0,1 pm. In one embodiment, the roughness value is between 3 and 50 pm.

Preferably, the conveying system includes a thermal conditioning device to cool the gripper hands. The thermal conditioning device includes one or more channels formed inside each gripper hand. Preferably, the one or more channels include one or more longitudinal ducts. The purpose of cooling the gripper hand is to prevent the charge from sticking to the gripper hand.

This disclosure also provides a method for forming a parison by compression moulding and for blow moulding the parison.

The method comprises a step of forming charges in succession from a flow of fluid plastic by means of a knife located in a pick-up zone. The pickup zone is preferably stationary. The knife is movable between a pick-up position, where it cuts the flow of fluid plastic, and a rest position, where it does not interfere with the flow of fluid plastic.

The method comprises a step of transporting each charge individually from the pick-up zone to a release zone by means of a plurality of conveyor elements which are movable along a trajectory. More specifically, the plurality of conveyor elements is associated with a wheel.

The method comprises a step of receiving the charges of thermoplastic material in respective moulds, associated with a rotary carousel, in the release zone.

The method comprises a step of forming the parison from the charge in a forming cavity delimited by a male element and a female element of the mould.

Preferably, the method comprises a step of stretching and blow moulding the parison to form a container; blow moulding is carried out in a blow moulding cavity associated with the male element in place of the female element.

Each conveyor element includes a gripper hand defining a concavity that intercepts the charge in the pick-up zone. Each conveyor element also includes one or more doors which are movable between a closed position, where they act in conjunction with the gripper hand to surround the charge that is interposed therebetween, and an open position of non-interference with the trajectory of the gripper hand moving towards the charge in the pick-up zone. Each conveyor element also includes a shutter, positioned at the second end of the gripper hand and movable to open and close an outlet of a passage for the charge, the passage being formed by the gripper hand and by the one or more doors at the closed position. When the charge is intercepted by the gripper hand (or just after it has been intercepted), the one or more doors (initially open) are closed; the shutter is also closed, so as to form a passage that is closed at the bottom to surround the charge, without squeezing it, in order to move the charge from the pick-up zone to the release zone. At the release zone, the shutter is opened but the one or more doors remain closed so that the passage formed by the gripper hand and the one or more closed doors can guide the charge moving downwards, after which the one or more doors are opened before the gripper element intercepts another charge in the pickup zone.

Preferably, the passage formed by the gripper hand and the one or more closed doors is larger in diameter, along its entire longitudinal length, than the charge and, in a first, upper stretch of it, is larger in diameter than in a second, lower stretch of it.

In an embodiment, the gripper hand is made to vibrate during the step of releasing the charge. This makes it easier for the charge to drop into the female element.

Brief description of drawings

These and other features will become more apparent from the following description of a preferred embodiment, illustrated by way of non-limiting example in the accompanying drawings, in which:

- Figure 1 illustrates a machine for forming a parison by compression moulding according to one or more aspects of this disclosure;

- Figures 2 and 3 are, respectively, a perspective view and a side view illustrating a charge forming system and a charge conveying system of the machine of Figure 1 during a step in which the conveying system picks up a charge;

- Figure 4 illustrates a charge conveying system and a female element associated therewith, of the machine of Figure 1 , during a step of releasing the charge into the female element;

- Figure 5 shows a cross section of a detail from Figure 4;

- Figure 6 is a bottom view of a conveyor element of the charge conveying system of the machine of Figure 1 ;

- Figures 7 and 8 are longitudinal cross sections of a conveyor element of the charge conveying system of the machine of Figure 1 ;

- Figures 9 and 10 are further longitudinal cross sections of a conveyor element of the charge conveying system of the machine of Figure 1 ;

- Figure 11 illustrates a mould of the machine of Figure 1 during a step of moulding the parison;

- Figure 12 illustrates the male element of the mould of Figure 11 during a step of stretching the parison;

- Figure 13 schematically illustrates an embodiment comprising an opposing element for the charge.

Detailed description of preferred embodiments of the invention

With reference to the accompanying drawings, the numeral 1 denotes a machine for the compression moulding and blow moulding of a parison (or a plurality of parisons).

The machine 1 comprises a forming device 4, configured to form charges 20 of thermoplastic material. The machine 1 comprises a plurality of moulds 11 configured to receive the charges 20 and to form the parisons by compression moulding.

The machine 1 comprises a conveying system 3 for the charges 20, configured to transport the charges 20 from the forming device 4 to the moulds 11 . More specifically, the conveying system 3 picks up the charges 20 from the forming system 4 in a pick-up zone Z1 , which is stationary, and releases the charges 20 to the corresponding moulds 11 in a release zone Z2, which is also stationary.

The machine 1 comprises a carousel 10 on which the moulds 11 are mounted at equal angular intervals. The carousel 10 rotates about a first, longitudinal axis of rotation A1 in a first rotation direction R1 .

The conveying system 3 for the charges 20 comprises a plurality of conveyor elements 31 and a wheel 30 on which the conveyor elements 31 are mounted. Preferably, the conveyor elements 31 are angularly equispaced on the wheel 30. It should be noted that for simplicity the wheel 30 is illustrated with only one conveyor element 31 mounted on it, although it is provided with a plurality of conveyor elements 31 .

The wheel 30 rotates about a second, longitudinal axis of rotation A2 in a second rotation direction R2. The second rotation direction R2 is opposite to the first rotation direction R1 ; that way, each conveyor element 31 can remain close to a corresponding mould 11 mounted on the carousel 10 for a longer time: that is to say, it can follow the corresponding mould 11 mounted on the carousel 10. To allow following for an even longer time, the conveyor elements 31 might be made movable radially on the wheel 30 at the release zone Z2 so that its trajectory T1 in proximity to the carousel 10 is modified.

The forming device 4 includes an extruder 41 , configured to produce a flow of fluid plastic. The forming device 4 also comprises a knife 42, configured to cut off the individual charges 20. The extruder 41 is stationary. The knife 42 rotates about an axis of rotation A4, oriented longitudinally to periodically intercept the flow of fluid plastic. The knife 42 rotates in a rotation direction R4 which is opposite to the second rotation direction R2 in which the wheel 30 of the conveying system 3 rotates and which is thus the same as the first rotation direction R1 in which the carousel 10 rotates. The knife 42 therefore intercepts the flow of plastic on the side opposite to that from which the conveyor element 31 arrives; this makes it easier for the charge 20 to be picked up by the conveyor element 31. The forming device 4 comprises a rotation actuator 420 configured to drive the knife 42 rotationally about its axis of rotation A4.

Each conveyor element 31 includes a gripper hand 32. The gripper hand 32 extends longitudinally between a first end 32A and a second end 32B. The gripper hand 32 has a C-shaped transverse cross section that defines a concavity 32C that encloses a longitudinal axis A3 of the gripper element.

Each conveyor element 31 includes a first door 331 and a second door 332. The first door 331 and the second door 332 are rotatable about respective longitudinal axes of rotation A331 , A332. More specifically, the first door 331 and the second door 332 are rotatable between an open position, where they are spaced apart, and a closed position, where they are close together and act in conjunction with the gripper hand 32 to define a passage 35 for the charge 20; the passage 35 is elongated along the longitudinal axis A3 of the gripper element 32 between the first end 32A and the second end 32B. The conveyor element 31 moves by the effect of the rotation of the wheel 30; thus, the longitudinal axis A3 of the conveyor element 31 moves around the axis of rotation A2 of the wheel 30. More specifically, the conveyor element 31 moves in a direction such that the gripper hand 32 advances with the concavity 32C facing forward. When the gripper element 31 passes near the pick-up zone Z1 , the doors 331 and 332 are at the open position so as not to interfere with the trajectory of the concavity 32C of the gripper hand 32 moving towards the charge 20; as soon as the concavity 32C of the gripper hand 32 grips the charge 20, the doors 331 and 332 close and thereby define, with the gripper hand 32, a containing surface surrounding the charge 20.

Preferably, the conveying system 3 comprises a first and a second supporting element 3310, 3320. The first supporting element 3310 is connected to the first door 331 ; the second supporting element 3320 is connected to the second door 332. The first supporting element 3310 rotates about the axis of oscillation A331 so as to cause the first door 331 to rotate; the second supporting element 3320 rotates about the axis of oscillation A332 so as to cause the second door 332 to rotate. The axes of oscillation A331 and A332 are located behind the gripper hand 32 with reference to the trajectory of the gripper hand 32 (that is, of the conveyor element 31 ); thus, considered in their entirety, the supporting elements 3310, 3320 and the doors 331 , 332 enclose the gripper hand 32.

It should be noted that the passage 35 (that is, the containing surface) for the charge 20 includes a first stretch 351 and a second stretch 352. The first stretch 351 extends longitudinally from the first end 32A of the gripper hand 32 to a zone of connection to the second stretch 352. The second stretch 352 extends longitudinally from the zone of connection to the second end 32B of the gripper hand 32. The first stretch 351 has a cross section that is convergent towards the zone of connection to the second stretch 352; the second stretch 352 has a constant cross section, equal to the cross section of the zone of connection to the first stretch 351. More specifically, at the first end 32A, the first stretch 351 has a first diameter D1 and, proceeding towards the zone of connection, the diameter is progressively reduced until reaching a second diameter D2, smaller than the first diameter D1 , of the zone of connection. The second diameter D2 is constant along the second stretch 352. Thus, the first stretch 351 has a frustoconical shape and the second stretch 352 a cylindrical shape.

It should be noted that both the gripper hand 32 and the doors 331 and 332 contribute to defining the shape of the passage 35. In effect, both the gripper hand 32 and the doors 331 and 332 have a wall that is inclined to the longitudinal axis A3 along the first stretch 351 of the passage 35, and a wall that is parallel to the longitudinal axis A3 along the second stretch 352 of the passage 35.

Each conveyor element 31 also comprises a shutter 34, positioned at the second end 32B of the gripper hand 32; more specifically, the shutter 35 is located just below the second end 32B of the gripper hand 32. The shutter 34 is movable between a closed configuration, in which it obstructs an outlet of the passage 35 to prevent the charge 20 from coming out of the passage 35, and an open configuration, where it does not interfere with the outlet of the passage 35 to enable the charge 20 to come out of the passage 35. The shutter 34 is in the closed configuration when the conveyor element 31 is in the pick-up zone Z1 and switches to the open configuration when the conveyor element 31 reaches the release zone Z2. More specifically, the shutter 34 comprises a first claw 341 and a second claw 342. movable relative to each other between a position where they are close together, defining the closed configuration of the shutter 34, and a position where they are spaced apart, defining the open configuration of the shutter 34.

The conveying system 3 comprises a nozzle 36 for each conveyor element 31 ; the nozzle 36 is configured to blow a jet of air into the passage 35. The nozzle 36 is movable transversely to the longitudinal axis A3 of the gripper element between a retracted position, where it is spaced from the longitudinal axis A3 of the gripper element (and close to the axis A2 of the wheel 30), and an advanced position, where it is close to the longitudinal axis A3 of the gripper element (and spaced from the axis A2 of the wheel 30); when the nozzle is at the advanced position, it is configured to blow the jet of air into the passage 35 in parallel with the longitudinal axis A3 of the gripper element. The nozzle 36 is positioned at a vertical level greater than the level of the first end 32A of the gripper hand (that is, above the inlet of the passage 35); thus, at its advanced position, the nozzle 36 is configured to blow the air jet in a direction towards the second end of the passage 35; in other words, the air jet is directed from the top down. Preferably, ducts 37 formed in the gripper hand 32 are configured to enable a cooling fluid to circulate. Preferably, ducts 37 configured to enable a cooling fluid to circulate are also formed inside the doors 331 , 332. The ducts 37 constitute a thermal conditioning device configured to cool the walls of the passage 35, hence to cool the charge 20 inserted therein. More specifically, the flow of cooling fluid in one or more of the ducts 37 formed in the gripper hand 32 and/or in the doors 331 , 332 is controllable independently of the flow in the other ducts 37; that way, thermal conditioning may be selective in certain zones of the passage 35. Each mould 11 comprises a female element 111 , defining a cavity, and a male element 112. The conveyor element 31 is configured to insert the charge 20 into the cavity of the female element 111. The male element 112 is associable with the female element 111 of the mould 11 to delimit a forming cavity 110 that forms the parison from the charge 20.

More specifically, the male element 112 comprises a die 1121 extending along a longitudinal axis A11 and including a body.

In an embodiment, the body has, inside it, a longitudinal cavity extending along the longitudinal axis A11 and, at one end of it, a socket 1123 which is in communication with the longitudinal cavity. In this embodiment, the male element also comprises a stretching rod 1122 which is slidably inserted in the longitudinal cavity and which, at one end of it, includes a terminal portion 1122A; the stretching rod 1122 is movable relative to the die 1121 between a retracted position, in which the terminal portion 1122A is housed inside the socket to contribute, together with the die 1121 , to delimiting the forming cavity 110, and an extracted position, in which the terminal portion 1122A is extracted from the socket so it stretches the parison. There is also a passage for an air flow to blow mould the parison to form a container; the passage for the air flow to blow mould the parison may be defined between an inside wall of the longitudinal cavity and the stretching rod 1122. Preferably, inside it, the die 1121 includes a cooling circuit 1124 configured to allow a cooling fluid to flow through it. More specifically, the die 1121 includes a liner which surrounds the body and the cooling circuit 1124 includes ducting defined between the liner and the body; the ducting is preferably has a helical shape, surrounding the axis A11.

In another embodiment (not illustrated), the die 1121 is retractile relative to a support structure of the male element 112 so it can move between a retracted position where, together with the support structure, it contributes to delimiting the forming cavity 110, and an extracted position, where it is configured for stretching the parison. In this embodiment, therefore, the stretching function is performed by the die.

In an embodiment, the machine 1 includes an opposing element 5. The opposing element 5 is interposed longitudinally between the gripper hand 32 and the knife 42 and is configured to come into abutment against the charge 20 to channel it into the passage 35. The opposing element 5 is positioned at the pick-up zone Z1 .

This disclosure also provides a machine for forming a parison by compression moulding (and not necessarily also configured for blow moulding the parison); similarly, this disclosure also provides a method for forming a parison by compression moulding (and not necessarily including a step of blow moulding). Furthermore, this disclosure also provides a conveying system for transporting charges of thermoplastic material from a pick-up zone to a release zone, for a machine for the compression moulding of parisons from corresponding charges. It should be noted that one or more of the aspects described in this disclosure are applicable to the machine for forming a parison by compression moulding, the method for forming a parison by compression moulding and the charge conveying system. In this context, the following paragraphs, listed in alphanumeric order for reference, are non-limiting example modes of describing this invention.

A. A machine for the compression moulding of a parison from a charge of thermoplastic material, comprising: - a carousel rotating in a first rotation direction;

- a plurality of moulds positioned on the rotary carousel, wherein each mould includes a female element, defining a cavity designed to receive the charge, and a male element, associable with the female element and configured for compressing the charge and forcing it to occupy the forming cavity so as to form the parison;

- a conveying system for transporting the charges from a pick-up zone to a release zone and including a wheel which rotates about longitudinal axis of rotation in a second rotation direction, opposite to the first rotation direction, a plurality of conveyor elements, associated with the wheel to move along a trajectory which intercepts the pick-up zone and the release zone;

- a forming device for forming the charges, located at the pick-up position, outside relative to the wheel and the carousel, and including an extruder, configured to produce a flow of fluid plastic, a knife, configured to cut off individual charges from the flow of fluid plastic, characterized in that each conveyor element of the charge conveying system includes a gripper hand which extends longitudinally between a first end, located at a first level, and a second end, located at a second level, lower than the first level, and whose transverse cross section is C-shaped so as to define a concavity responsible for intercepting the charge in the pick-up zone, one or more doors which are movable between an open position of non-interference with the trajectory of the gripper hand moving towards the charge in the pick-up zone and a closed position, where they are close to the gripper hand and act in conjunction with the gripper hand to define a containing surface extending around a longitudinal axis of the gripper element so as to surround the charge that is operatively interposed therebetween, and a shutter, positioned at the second end of the gripper hand and movable to open and close an outlet of a passage for the charge, the passage being formed by the gripper hand and by the one or more doors at the closed position.

B. A conveying system for transporting charges of thermoplastic material from a pick-up zone to a release zone, for a machine for the compression moulding of parisons from corresponding charges by means of a plurality of moulds, positioned on a carousel, and a knife, positioned in the pick-up zone on the outside of the carousel to cut individual charges from a flow of fluid plastic, the system comprising:

- a wheel, rotating about a longitudinal axis of rotation;

- a plurality of conveyor elements, associated with the wheel to move along a trajectory which intercepts the pick-up zone and the release zone, each conveyor element including a gripper hand which extends longitudinally between a first end, located at a first level, and a second end, located at a second level, lower than the first level, and whose transverse cross section is C-shaped so as to define a concavity responsible for intercepting the charge in the pick-up zone, and a shutter, movable to open and close an outlet for the passage of the charge leaving the conveyor element, characterized in that each conveyor element includes one or more doors which are movable between an open position of non-interference with the trajectory of the gripper hand moving towards the charge in the pick-up zone and a closed position, where they are close to the gripper hand and act in conjunction with the gripper hand to define a containing surface extending around a longitudinal axis of the gripper element so as to surround the charge that is operatively interposed therebetween, and in that the shutter is positioned at the second end of the gripper hand to open and close an outlet of a passage for the charge, the passage being formed by the gripper hand and by the one or more doors at the closed position.

Claims

1. A machine (1 ) for the compression moulding of a parison from a charge (20) of thermoplastic material and for the blow moulding of the parison, comprising:

- a carousel (10), rotating about a first, longitudinal axis of rotation (A1 ) in a first rotation direction;

- a plurality of moulds (11 ), positioned on the carousel (10), wherein each mould (11 ) includes a female element (111) which defines a hollow designed to receive the charge (20), a male element (112), associable with the female element (111 ) to delimit a forming cavity (110) and configured to compress the charge (20), thereby forcing it to occupy the forming cavity (110) so as to form the parison, a blow moulding cavity, associable with the male element (112) in place of the female element (111 ) to form a container from the parison, the mould (11 ) having a forming configuration in which the male element (112) is associated with the female element (111 ) and a stretching and blow moulding configuration in which the male element (112) is associated with the blow moulding cavity;

- a conveying system (3) for transporting the charges (20) from a pick-up zone (Z1 ) to a release zone (Z2) and including a wheel (30), rotating about a second, longitudinal axis of rotation (A2) in a second rotation direction (R2), opposite to the first rotation direction (R1), a plurality of conveyor elements (31 ), associated with the wheel (30) to move along a trajectory which intercepts the pick-up zone (Z1 ) and the release zone (Z2);

- a forming device (4) for forming the charges (20), located in the pick-up zone (Z1 ), outside relative to the wheel (30) and the carousel (10), and including

25 an extruder (41), configured to produce a flow of fluid plastic, a knife (42), configured to cut off individual charges (20) from the flow of fluid plastic, characterized in that each conveyor element (31 ) of the conveying system (3) for transporting the charges (20) includes a gripper hand (32) which extends longitudinally between a first end (32A), located at a first level, and a second end (32B), located at a second level, lower than the first level, and whose transverse cross section is C- shaped so as to define a concavity (32C) responsible for intercepting the charge (20) in the pick-up zone (Z1), one or more doors (331 , 332) which are movable between an open position of non-interference with the trajectory of the gripper hand (32) moving towards the charge (20) in the pick-up zone (Z1 ) and a closed position, where they are close to the gripper hand (32) and act in conjunction with the gripper hand to define a containing surface extending around a longitudinal axis (A3) of the gripper element so as to surround the charge (20) that is operatively interposed therebetween, a shutter (34), positioned at the second end (32B) of the gripper hand (32) and movable to open and close an outlet of a passage (35) for the charge (20), the passage (35) being formed by the gripper hand (32) and by the one or more doors (331 , 332) at the closed position.

2. The machine (1 ) according to claim 1 , wherein the passage formed by the gripper hand (32) and by the one or more doors (331 , 332) at the closed position has a first stretch (351 ) and a second stretch (352), the second stretch (352) being longitudinally consecutive with the first stretch (351 ) and defining the outlet of the passage, and has, in the second stretch (352) of it, has, a cylindrical shape with a second passage area and, in its first stretch (351 ), a wide cross section with a first passage area that is greater than the second passage area.

3. The machine (1) according to claim 2, wherein the first stretch (351 ) of the passage (35) has at least one portion that is frustoconical in shape.

4. The machine (1 ) according to any of the preceding claims, wherein the gripper hand (32) has, for each conveyor element (31 ), a receiving surface defining the concavity (32C) that receives the charge (20), wherein the receiving surface has at least one portion that is inclined relative to the longitudinal axis (A3) of the gripper element, tapered towards the outlet of the passage (35) for the charge (20).

5. The machine (1 ) according to any of the preceding claims, wherein, for each conveyor element (31 ), the one or more doors (331 , 332) are rotating about respective longitudinal axes of oscillation (A331 , A332), disposed laterally of the gripper hand (32).

6. The machine (1 ) according to claim 5, wherein the longitudinal axes of oscillation (A331 , A332) are located at a position behind the gripper hand (32) relative to the trajectory of the gripper hand (32) moving towards the charge (20) in the pick-up zone (Z1 ).

7. The machine (1 ) according to any of the preceding claims, wherein, for each conveyor element (31 ), the one or more doors (331 , 332) are operatively in contact with lateral ends of the gripper hand (32) at the closed position.

8. The machine (1 ) according any of the preceding claims, wherein one or more of the following conditions is true: i) the knife (42) is positioned at a third level, just above the first level; ii) the shutter (34) is positioned at a fourth level, just below the second level; iii) the top of the female element (111 ) of the mould (11 ) is positioned at a fifth level, spaced from the second level by a length less than 10 mm.

9. The machine (1 ) according to any of the preceding claims, wherein the conveying system (3) comprises, for each conveyor element (31 ), a nozzle (36) configured to generate an air jet, the nozzle (36) being movable transversely to the longitudinal axis (A3) of the gripper element between a retracted position, where it is spaced from the longitudinal axis (A3) of the gripper element, and an advanced position, where it intercepts the longitudinal axis (A3) of the gripper element, to blow the jet of air along the longitudinal axis (A3) of the gripper element in the direction of the outlet of the passage (35).

10. The machine (1 ) according to any of the preceding claims, wherein the conveying system (3) comprises, for each conveyor element (31 ), a vibrator, operable in an activated configuration, in which it makes the gripper hand (32) vibrate, and in a deactivated configuration, and a switch, configured to change the configuration of the vibrator from activated to deactivated and vice versa, responsive to the position of the conveyor element (31 ) along its trajectory.

11 . The machine (1 ) according to any of the preceding claims, wherein, for each conveyor element (31 ), the gripper hand (32) has a rough surface covering.

12. The machine (1 ) according to any of the preceding claims, wherein the conveying system (3) includes a thermal conditioning device to cool the gripper hands (32).

13. The machine (1 ) according to any of the preceding claims, wherein said one or more doors (331 , 332) extend longitudinally between the first end (32A) of the gripper hand (32) and the second end (32B) of the

28 gripper hand (32).

14. The machine (1 ) according to any of the preceding claims, wherein the gripper hand is provided with the C-shaped transverse cross section along its entire longitudinal length, between the first end and the second end.

15. A method for the compression moulding and blow moulding of a parison, the method comprising the following steps:

- forming charges (20) in succession from a flow of fluid plastic by means of a knife located in a pick-up zone (Z1 );

- transporting each charge (20) individually from the pick-up zone (Z1 ) to a release zone (Z2) by means of a plurality of conveyor elements (31) which are movable along a trajectory;

- receiving the charges (20) of thermoplastic material in respective moulds (11 ), associated with a rotary carousel (10), in the release zone (Z2);

- forming the parison from the charge in a forming cavity (110) delimited by a male element (112) and a female element (111 ) of the mould (11 );

- stretching and blow moulding the parison to form a container, characterized in that each conveyor element (31 ) includes a gripper hand (32), defining a concavity that intercepts the charge (20) in the pick-up zone (Z1 ), one or more doors (331 , 332) which are movable between a closed position, where they act in conjunction with the gripper hand (32) to surround the charge (20) that is interposed therebetween, and an open position of non-interference with the trajectory of the gripper hand (32) moving towards the charge (20) in the pick-up zone (Z1), and a shutter (34), positioned at a second end (32B) of the gripper hand (32) and movable to open and close an outlet of a passage (35) for the charge (20), the passage being formed by the gripper hand (32) and by the one or more doors (331 , 332) at the closed position, wherein, when the charge (20) is intercepted by the gripper hand (32), the

29 one or more doors (331 , 332) are closed and the shutter (34) is closed so as to form a passage (35) that is closed at the bottom to surround the charge (20) without squeezing it, in order to move the charge (20) from the pick-up zone (Z1 ) to the release zone (Z2) and wherein, at the release zone (Z2), the shutter (34) is opened but the one or more doors (331 , 332) remain closed so that the passage (35) formed by the gripper hand (32) and the one or more closed doors (331 , 332) can guide the charge (20) moving downwards, after which the one or more doors (331 , 332) are opened before the gripper hand (32) intercepts another charge (20) in the pick-up zone (Z1 ).

16. The method according to claim 15, wherein the passage (35) formed by the gripper hand (32) and the one or more closed doors (331 , 332) is, along its full longitudinal length, has a larger area relative to the width of the charge (20) and, in its first, upper stretch (351 ), has a passage area that is larger than the passage area than a second, lower stretch (352).

17. The method according to claim 15 or 16, wherein the gripper hand (32) is made to vibrate during the step of releasing the charge (20).

30