WO2005084915A1

WO2005084915A1 - Device for conditioning plastic objects and respective conditioning method

Info

Publication number: WO2005084915A1
Application number: PCT/EP2005/050893
Authority: WO
Inventors: Matteo Zoppas; Massimo Coran
Original assignee: S.I.P.A. Società Industrializzazione Progettazione E Automazione S.P.A.
Priority date: 2004-03-02
Filing date: 2005-03-01
Publication date: 2005-09-15
Also published as: ITRM20040108A1

Abstract

A rotating turret (20) for extracting and cooling preforms, for an injection mould, is composed of a box-like structure, hollow on the inside, in the form of a parallelepiped, with two opposing faces (A) and (B), with a plurality of cooling cups (22), for inserting the preforms, in which the cups are completely contained inside the box-like structure of the turret and the cooling circuit is obtained in the structure itself.

Description

DEVICE FOR CONDITIONING PLASTIC OBJECTS AND RESPECTIVE CONDITIONING METHOD Field of the invention The invention refers to a rotating conditioning device for plastic objects, for conditioning them outside the mould. These plastic objects may be in particular «pre-forms» or «parisons» which are later transformed into containers, especially bottles or plastic pots, by means of a further blowing operation. Prior art In the field of the production of containers, in particular for liquid foodstuffs or fluids, plastics such as PET (polyethylene terephthalate) are widely used. Though these containers may be of various types, for example bottles, pots, phials, they will be indicated here generally with the name bottles, which represents the containers most used.

There are two main types of processes for producing plastic bottles, known as the «single-stage process» and the «two-stage process», in both of which an intermediate product is made, the so-called preform.

The preforms are obtained with different processes, for example by injection moulding, by extrusion combined with other hot-moulding operations, etc.

In the two-stage process the preforms obtained for example by injection moulding, generally using moulds with a large number of moulding cavities, are cooled and kept in an intermediate storage place at environment temperature. The blowing operation is performed later, after heating to make the preforms sufficiently plastic.

Generally much the longest phase of the injection moulding processes is the phase of cooling the moulded preform inside the mould, until it is sufficiently rigid to be taken out of the mould and handled. So, to increase the production rate of the moulding station, various devices have been developed for carrying out part of the cooling of the preforms outside the injection mould. Some examples of these devices are described in the patent EP-A-1252007 and in the Italian patent application RM2003A000459 . Such a device of the prior art is provided with a first sliding plate which, moving horizontally, is inserted between the two open halves of the injection mould. A plurality of preforms is let fall into the housings in the sliding plate. The sliding plate is extracted from the mould and positioned vertically on a rotating turret, on each of the two faces of which is arranged a plurality of cooling cups, of the type described for example in the application for patent WO02/074518. The preforms are let fall into the cooling cups of one of the two faces of the rotating turret, when they can continue cooling, outside the injection mould, until the desired temperature is reached.

An important aim of the present invention is to provide a rotating device for conditioning plastic objects and a respective conditioning method, for increasing the cycle time of a moulding station by carrying out part of the cooling of the moulded objects outside the extraction mould, which are an improvement on the methods of the prior art, in particular with respect to the devices and methods described in patent EP 1252007.

Another aim of the present invention is to provide an alternative rotating conditioning device which has a simpler and more economic construction and which maintains a characteristic of modularity that allows it to be used also on existing moulding systems.

A further aim of the present invention is to provide a conditioning device which produces preforms of better quality, eliminating an element of additional handling, and which achieves a better production efficiency. Summary of the invention

These aims are achieved, according to a first aspect of the present invention, by means of a rotating device for conditioning plastic objects having the characteristics of claim 1 and, according to a second aspect of the present invention, with an appliance for moulding plastic objects comprising the rotating conditioning device according to claim 6.

In a third aspect of the present invention, the aims described above are achieved with a conditioning method for plastic objects having the characteristics according to claim 8. Thanks to the configuration of the device in the invention, preforms may be produced in shorter sequences, of better quality because the amount of handling to which they are subjected is reduced, handling which often causes scratching or other types of damage. Moreover the greater compactness of the cooling cups, which may be arranged on a rotating turret, allows preforms to be made with a larger diameter while the overall bulk of the turret remains the same. List of Figures The advantages that may be obtained with the present invention will be more clear, to the technician in the sector, from the following detailed description of an embodiment, given by way of non limiting example, with reference to the following Figures in which: Figure 1 shows an overhead view of a device according to the invention; Figure 2 shows a side view of the device in Figure 1 ; Figure 3 shows another side view of the device in Figure 1 ; Figure 4 shows a section along the plain A-A of the device in Figure 1 ; Figure 5 shows an enlargement of detail B in Figure 4. Detailed description of embodiments Figure 1 shows a rotating device for conditioning plastic objects that are substantially oblong, in particular preforms of PET with which to obtain, in a subsequent blow-moulding operation, bottles, jars, phials or other types of containers, in a preferred embodiment of the present invention. This rotating conditioning device, referred to below in the description also as rotating turret, is indicated globally with the reference 20. Generally, but not necessarily, it is used for cooling preforms. It provides a box-shaped element, substantially in the form of a parallelepiped with two faces A and B opposed to each other, with a surface area greater than that of other faces, and comprises a plurality of housing bodies 21 , more or less tubular in shape, or anyway hollow, and indicated also, in this description, as «cooling cups» 21.

The cooling cups 21 are fixed onto a suitable frame or supporting body 10, forming a box-like structure, aligned in two spatial directions, horizontal and vertical, and arranged in rows and in columns so as to form a grid of square links. The inside of the cups forms a suitable seat 22 for housing the preforms, in which they are inserted through the opening 23.

According to the present invention, the conditioning cups 22 are arranged in such a way that each cup with opening on face B is coaxial with a cup with opening on face A, thus defining coaxial pairs of cups. The bottom of the cups in each coaxial pair is arranged facing and adjacent so as not to leave any spaces between them, or to leave only the minimum space indispensable to arrange the elements that are indispensable to perform determined functions. In alternative embodiments of the turret, pairs of cups on the opposite faces may also be slightly offset, though remaining with the bottoms of the cups, of each pair, very close to each other.

Moreover the overall external height of the rotating turret is smaller, so that the turret may be introduced directly between the two open halves of a mould, mounted on a press for moulding preforms, instead of having to use an intermediate sliding support thin enough to be inserted between the two open half- moulds. The cooling cycle time may therefore be reduced, since the transfer operation from an intermediate support to the cooling turret is avoided, and this also avoids leaving the preforms for a determined period on a non-conditioned intermediate support.

The elimination of this passage onto an intermediate mechanical handling element also avoids possible knocks, scratches or other damage which lead to undesirable production losses. Moreover, in this way it is possible to realise preform conditioning and/or extraction stations with a mechanical structure, and respective electric/electronic or pneumatic circuits, simpler than the extraction and/or conditioning stations of the prior art.

Advantageously, to reduce the width and length of the rotating turret 20, the cooling seats 22 are made in housing cups 21 with a relatively simple geometry, for example without shells, cavities or internal cooling ducts, and all the housing bodies 21 are placed in a casing composed of two metal front plates 24, 25 and of side plates 26, welded and/or screwed together so as to form a caisson; only the open ends of the cups 21 protrude from this caisson, just enough for the cups to be gripped by known extraction devices, not illustrated in the Figures. The space inside the caisson, between the outside walls 24, 25, 26 and the cooling cups, may be filled or passed through by a cooling liquid so as to cool the preforms inserted in the various cooling seats 22. A plurality of internal dividing walls 27, advantageously but not necessarily perforated or drained, form flowing ducts 32 for the cooling liquid and allow the liquid to follow a suitable path inside the caisson so as to lap and cool the various cups 21 in the desired way. This avoids making complex cooling structures which require jackets that enclose cooling circuits, for example coils.

The rotating turret 20 is also provided with suitable means for holding the preforms, suited for blocking the preforms and holding them in their cooling seats 22 when the seats are facing downwards. In the embodiment in Figures 4 and 5, this preform holding system is achieved with a system of ducts 29 connected to a pneumatic circuit: to hold a preform in a cooling seat 22 in the ducts 29, a pneumatic vacuum is generated, while to command or at least facilitate the expulsion of the preform, compressed air is blown into the ducts 29. A manifold 30 is provided in the central area of the turret, the function of which is to allow the circulation of compressed air or to produce a vacuum inside the cups. Without going outside the scope of the present invention, the rotating support 20 may be provided with holding and extraction systems of a different type, for example mechanical blocking systems, which may or may not be combined with pneumatic means, not shown in the Figures. A first preferred example of operation of the rotating turret 20 described above will now be presented, together with further characteristics of the construction and operation of a cooling station, or more generally a conditioning station, indicated globally with the reference 100, on which the turret is mounted. The rotating turret is mounted on a suitable metal frame so as to be able to slide horizontally and to rotate - substantially by about 180° - around an axis of rotation X, also horizontal, so as to tip and turn alternatively the first or the second face A, B upwards or downwards or, in other embodiments, towards another predetermined direction.

In a first instant of the operating sequence the rotating turret 20 assumes a first preform loading position, between the open halves of a mould, mounted on an injection moulding press, so as to be under the upper half-mould. A predefined group of N preforms, obtained with one moulding operation, is dropped from the half-mould into N cooling seats 22. Both the support 20 and the mould are made in such a way that on the vertical plane of a moulding shell of the mould there is a seat 22 of the support. The group of N preforms is let fall into the seats 22 of the rotating turret 20, filling rows of cups 21 according to a predetermined filling sequence which depends on the production rate chosen for the moulding system. Next the turret is extracted from the mould, by means of a traverse movement, so as to be able to close the mould and perform another moulding cycle of N preforms as soon as the space between the half-moulds is freed from the turret. After another moulding cycle of preforms has been performed, the turret 20 is again inserted between the two open half-moulds under the top half-mould, and the second group of N moulded preforms is let fall onto the support 20 so as to fill other rows of empty cups 21. When necessary the turret is rotated around its own axis of rotation. The process of receiving the preforms is repeated until all the cups on the turret have been filled, or until the moment predetermined for starting to extract the preforms which have concluded the conditioning cycle.

At this point the turret 20 is put into an unloading position, and a first group of N preforms is released by the rotating turret 22, letting it fall, with the aid of mechanical extraction means, possibly combined with a jet of compressed air supplied by the ducts 29, 30, onto another unloading support, for example a conveyor belt or a crate for collecting the cooled preforms. The extraction moulds are of the prior art and are not described in detail.

The cooling station can then repeat the operating cycle described above, at steady operating speed unloading at each cycle a group of N cooled preforms, generally corresponding to the number of preforms moulded in a moulding cycle. In alternative embodiments it is possible to provide shifting of the turret 20 orthogonal to the axis of rotation AR.

The examples of embodiments of the rotating turret 20, of the cooling station and of the respective operating sequences described above, can undergo numerous modifications and variations without going outside the scope of the present invention.

For example the turret may be made not only as a set of metal plates welded or screwed together to form a caisson, but more generally as a casing defining one or more internal cavities in which there are placed the substantially tubular bodies 22, and suited to contain a cooling fluid; the cooling cups may also present internal cooling ducts; the cooling seats 22 may be located on two faces A, B of the rotating turret, not only aligned according to two directions in one plane peφendicular to each other, but also according to two directions simply not parallel, or even in a more irregular way; or not only according to a grid of square mesh, but also with other arrangements, such as grids with rectangular or rhomboid mesh. A further advantage achieved with the device in the invention is the saving of space obtained between the various cups in realising a structure with the cups entirely immersed in the body of the turret and with the cooling circuit made in the structure of the turret itself, and also being able to make cups with seats for holding preforms with a larger diameter. In fact the walls of cups, without associated cooling circuits, are thinner than those with cups of the prior art.

Claims

CLAIMS 1. Device for conditioning plastic objects, comprising a rotating turret (20) defining a box-like structure, hollow on the inside, substantially ^" in the form of a parallelepiped, defining a first face (A) and a second face (B) reciprocally opposed, the device comprising a plurality of conditioning cavities (22), provided with a respective opening for inserting said objects, each cavity (22) defining a respective axis, the plurality of cavities being subdivided into a group of first cavities with opening on the first face (A) and a group of second cavities with opening on the second face (B), characterised in that each cavity is substantially totally contained inside the hollow box-like structure.

2. Device according to claim 2, wherein each of the first conditioning cavities (22) is axially aligned, with respect to its own axis, with the axis of each respective second cavity.

3. Device according to claim 1, wherein the hollow box-like structure contains at least one circuit for the circulation of conditioning fluid acting functionally on the conditioning cavities (22).

4. Device according to claim 3, wherein the conditioning cavities are arranged at a reciprocal distance at predetermined regular intervals.

5. Device according to one or more previous claims, wherein there are provided means of movement suited for rotating the turret (20) at least around an axis of rotation (X), so as to turn said first face (A) or said second face (B) alternatively towards a predetermined reference direction.

6. Appliance for moulding plastic objects, comprising the conditioning device according to claim 1.

7. Appliance according to claim 6, wherein there are provided motor means suited for tipping said rotating device so as to turn said first face (A) or second face (B) from time to time upwards or downwards.

8. Method for conditioning a plurality of moulded plastic objects, performed by means of the device according to claim 1, characterised in that it comprises the following stages:

- arranging a first face (A) of the rotating conditioning device (20) according to one or more claims from 1 to 7 facing upwards; - inserting the rotating device between two open half-moulds (S) of a mould;

- transferring at least one first set of moulded objects, obtained in a moulding cycle, from said mould to the rotating device, so as to fill at least a part of the conditioning cavities of the first face (A); - extracting the rotating device from the two open halves of the mould;

- tipping the rotating device so that a second face (B) is facing upwards; -reinserting said rotating device (20) again between two open halves of said mould;

- transferring at least a second set of moulded objects, obtained in a subsequent moulding cycle, from said mould, in which they were moulded, to said rotating device, so as to fill at least another part of said cooling cavities of said second face (B) of the rotating conditioning device.

9. Method according to claim 8, wherein there is provided the extraction stage of sets of moulded objects from the rotating conditioning device after the conclusion of a respective conditioning cycle.