PLASTIC CONTAINER INJECTION-MOULDING MACHINE EQUIPPED WITH QUICK MOULD-CHANGE ARRANGEMENT

Abstract: Injection-moulding machine for producing plastic containers, comprising an upper platen (1), a moving mould-carrying platen (2), a support bar (3) for lips constituted by two respective separable members (15a, 15b), a plurality of male members (6) applied to said upper platen (1), a cavity-carrying platen (4) in which there are provided removable means (16) adapted to delimitate the travel of said moving mould-carrying platen (2) towards the cavity-carrying platen (4), so that the moving mould-carrying platen (2) can be positioned at a pre-selectable distance with respect to the cavity-carrying platen (4). Said removable means (16) are preferably constituted substantially by a number of resting cylinders, or parallelepipeds, arranged parallel with respect to each other and having the same height, the axis of which is parallel to the moving direction of the moving mould-carrying platen (2).

Description: PLASTIC CONTAINER INJECTION-MOULDING MACHINE EQUIPPED WITH QUICK MOULD-CHANGE ARRANGEMENT DESCRIPTION The present invention refers to a specifically intended arrangement and a related utilization process, which are adapted to enable moulds to be changed in a very short time in injection moulding machines in which the half-moulds move in an either vertical or horizontal direction relative to each other. In particular, the present invention applies in a preferred manner to machines adapted for moulding at the same time a plurality of plastic articles, ie. the so-called "preforms", that are intended for subsequent processing by blow moulding into appropriate final containers, especially plastic bottles. Although reference will be made in the following description, mainly for reasons of greater descriptive convenience, to a machine for moulding preforms of plastic material of the vertical-drive type, as this is used in combination with the preliminary steps of melting and extrusion of said plastic material, it will be appreciated that the present invention shall be understood as applying also to horizontal- drive injection moulding machines or even other kinds of uses or applications, as far as these fall within the scope of the appended claims. It is generally known in the art that, during the preform moulding operation, use is generally made of a moulding machine comprising a stationary half-mould, which is firmly joined to the structure of the same machine, and a moving half-mould, which moves in a vertical direction and is selectively closable into an appropriate clamped position against said stationary half-mould. With reference to Figures 1, 2, 2A, 2B and 2C, which illustrate the state of the art, the upper platen 1, whose particular features shall not be described here since already generally known in the art, is associated externally to a moving mould-carrying platen 2, which is in turn connected to the bar 3 that supports the lips 15. The task performed by these lips 15 is to form the neck of a respective bottle and, therefore, they are constituted by two separable members 15a, 15b in consideration of the fact that, during the removal of the preform from the mould, the neck portion thereof shall be released from its own mould which is constituted exactly by said lips. Owing to said neck portion being actually provided with a number of undercut- like elements, a selected means for effectively releasing said neck portion from its own mould or lip 15 consists in making it out of two separable members 15a and 15b, as illustrated in Figure 7. To said upper platen there are removably secured, through the use of appropriate fastening means 5, a plurality of male members 6; furthermore, to this same upper platen 1 there are firmly associated, in a coaxial arrangement with respect to said male members, respective internal cooling tubes 7. The mould is completed downwards, ie. on the bottom, by a cavity- carrying platen 4, in which there can be noticed a plurality of cavities 8 adapted to be filled with the material that is injected through respective nozzles 9. The coupling of said upper platen 1 with said cavity-carrying platen 8 is brought about by means of a plurality of guide columns 13, which are firmly joined on top with said upper platen 1 and are adapted to slide into insertion in respective through-holes 10 appropriately provided in said cavity-carrying platen. Furthermore, in view of ensuring the required alignments and the parallelism of the movements, even said moving platen 2 is provided with appropriate through-holes 11 adapted to be slidably engaged by said same guide columns 13. During the practical operation of the injection moulding machine, it frequently occurs that such operational conditions arise as to make it necessary for access to be gained to said male members in order to replace and/ or repair them. As it can most easily be inferred from the illustration in Figures 2, 2 A and 2B, when such a need arises for said male members 6 to be so replaced and/ or repaired, the first thing that must be done is to start by separating the moving mould-carrying platen 2 from the upper platen 1, in such a manner as to create a gap between said platens and, therefore, to be able to gain proper access manually to said fastening means 5 and so be able to act on these so as to release and remove said male members 6. Now, such an operation can actually be carried out in a quite easy and convenient manner if there are just a few (ie. not many) of said male members and these are further arranged in a single row. If on the contrary said male members are arranged on several rows, as illustrated in the Figures, then it becomes much more difficult and awkward for anyone to gain access to said male members due to the scanty space that is available to such a purpose, so that the removal and re-assembly operation generally turns out to require a much longer time to be completed. If the fact is finally taken into due account that, owing to production- related or market-driven reasons, the need may actually arise for such male members to be replaced even as frequently as once a day, it can be readily appreciated how each such operation for the replacement of the male members, which may typically last as many as four hours, may on the whole turn out as being extremely expensive and time-wasting. All these circumstances are anyway largely known to all those skilled in the art, and are recalled here to the sole purpose of more effectively introduce and illustrate the technical context to which the present invention relates. Based on the above considerations, it is therefore a main purpose of the present invention to provide an injection moulding machine which comprises the moving platen, the lip-carrying platen and the cavity- carrying platen, and is equipped with an arrangement that enables the cavity-carrying platen to be undamped and moved away from the moving platen by such an extent as to allow access to be gained to the male members in a much more convenient and easy manner, so as to drastically cut down the time required to remove and subsequently reassemble said male members. The above arrangement shall furthermore be capable of being easily implemented using readily available and, therefore, cost-effective materials and techniques, and is further easy, reliable and safe to use. Such an aim of the present invention, along with further features thereof, is reached in an injection moulding machine that is made and operates as recited in the appended claims. The present invention may take the form of a preferred, although not sole embodiment such as the one that is described in detail and illustrated below by way of non-limiting example with reference to the accompanying drawings, in which: - Figure 1 is a perspective view of some basic parts of an injection moulding machine according to the state of the art, in a first operating state thereof; - Figure 1A is an enlarged view, from a different perspective, of a detail of Figure 1; - Figure 2 is a perspective view of the same parts as the ones illustrated in Figure 1 , however in a different operating state thereof; - Figure 2A is a perspective view of two of the machine parts illustrated in Figure 2, as seen from a different perspective point; - Figure 2B is a vertical cross- sectional view (A- A) of the injection moulding machine illustrated in Figure 1 ; - Figure 3 is a perspective view of the same parts of the injection moulding machine illustrated in Figure 1, in which said machine is however provided with the arrangement according to the present invention; - Figure 4 is a perspective view of the same parts of the injection moulding machine illustrated in Figure 3, in which the various parts thereof are however coupled with each other in a first operating phase according to the present invention; - Figure 5 is a perspective view of the same parts of the injection moulding machine illustrated in Figure 4, in which they are however arranged in a second operating phase according to the present invention; - Figure 5A is a different perspective view of the same parts of the injection moulding machine illustrated in Figure 5; - Figure 6 is a side view, along the direction "B", of the injection moulding machine illustrated in Figure 5A; - Figure 7 is an enlarged cross-sectional view of a portion of an injection moulding machine provided with an arrangement according to the present invention. With reference to the above listed Figures, a vertical-drive type of injection moulding machine provided with an upper half-mould adapted to produce preforms of plastic material comprises an upper platen 1, a moving platen 2, a plurality of lips, or neck- rings as they are also called in the art, which are the mould portions that are intended to form the neck portion of the preform during the injection of the thermoplastic resin, and are constituted by two respective separable members 15a and 15b, a support bar 3 carrying said plurality of lips, a plurality of male members 3 secured at their bottom or foot portion to said upper platen 1 by means of appropriate fastening means as they are commonly known and used in the art. Furthermore, inside said male members there are preferably provided respective cooling tubes 7, whose task and structure are generally known in the art, and which are applied on to the lower face of said upper platen 1. The injection moulding machine further comprises also a cavity- carrying platen 4, in which there are provided a plurality of cavities 8 associated to respective gates or nozzles 9 through which the molten resin is actually injected. The described injection moulding machine is provided also with a plurality of guide columns 13, which are firmly joined on top to said upper platen 1 and are adapted to slidably move into both respective appropriate through-holes 10 provided in said cavity-carrying platen and respective appropriate through-holes 11 provided in said moving mould-carrying platen 2. The task assigned to said guide columns and said through-holes is to ensure the correct alignment of upper platen, moving mould-carrying platen and cavity-carrying platen among each other when they move with respect to each other; on the other hand, these parts are solely illustrated by way of more effective, thorough exemplification, although not strictly necessary to the purposes of the present invention and are not anyway a part thereof. It is largely known that, according to prior-art solutions, in order to replace the male members in an injection moulding machine of the type described here by way of example, a procedure is usually followed including, among other things, the steps of: - releasing the safety pins 21 and clearing the knock-out pins 20; - raising the upper platen up to the highest opening position allowed for by the injection moulding machine itself; - separating the moving platen from the upper platen and lowering it down to a level corresponding to the downward stroke or travel covered to clamp, ie. close the mould and, anyway, limited by the length of said columns or pins. As this has already been said earlier in this description, in such a state of the injection moulding machine it is certainly possible for the male members to be reached for their removal. Under certain circumstances, however, this may well turn out as being quite awkward and complicated. The presence of the cooling tubes inserted in said male members, and which anyhow remain in their position inside said male members, needs to be furthermore taken into due account, since it becomes necessary for said male members to be appropriately lowered so as to be able to slip them off downwards from the respective attachments in the upper platen, ie. an operation that makes it still more complicated, awkward and demanding to disengage and subsequently re-assemble the male members. In view of doing away with such a drawback, the present invention consists in enabling the moving platen 2 to be lowered down to well beyond the usual level, without the constraint of having to retain it anyway engaged to said guide columns 13. As a matter of fact, the ability of lowering the moving platen to a significantly greater extent would enable the gap that is so obtained between said upper platen, which maintains its raised position, and the moving platen 2 to be increased accordingly. According to the present invention, such a greater extent of lowering is obtained by providing appropriate removable means between said moving platen and the cavity-carrying platen 4, wherein the task assigned to these removable means lies in constituting appropriate resting means for the moving mould -carrying platen which can in this way be fully disengaged from the upper platen 1. The need for the utilization of said resting means and an adequately large separation of the moving platen from the cavity-carrying platen 4 depends on the circumstance that there is provided a cam-operated mechanism 22 which, when the upper platen 1 is raised or, anyway, when said upper platen 1 is moved apart from the moving platen, automatically provides for the two portions 15a and 15b forming said lips to be separated and widened out. Now, if said portions are widened out (in order to allow for the neck portion of the preform to be knocked out), it would be practically impossible to simply bring the moving platen 2 into resting on to the cavity-carrying platen 4, since said lip portions 15a and 15b would interfere violently against the upper edge of the respective cavities, thereby getting damaged and/ or damaging the cavities themselves. An obvious solution lies therefore in providing appropriate removable means between said platens in such a manner as to adequately move and keep said platens apart from each other at a desired distance "Z" that is effective in doing away with the above described drawback. In a preferred manner, these removable means are constituted by a multiplicity of resting cylinders 16, or parallelepipeds, arranged parallel to each other and having the same height, the axis of which is parallel to the direction of movement of said moving mould -carrying platen, as this is illustrated in the Figures. With reference to Figure 7, it furthermore turns out to be of particular advantage if said removable means are applied to rest upon said cavity- carrying platen 4, while in view of a safer, more reliable engagement and centering of said means 16 with and relative to said moving platen 2 when the mould is clamped into its closed position, the moving platen 2 itself is provided, in correspondence of the resting zones of the lower surface 18 thereof, with appropriate recessed seats 17 adapted to get coupled with the upper portions 19 of respective ones of said removable means. Similarly, the cavity- carrying platen 4 is provided, on the upper surface thereof, with corresponding recessed seats 17A adapted to get coupled with the lower portions 19A of respective ones of said removable means. Those skilled in the art will at this point be fully capable of seeing clearly into the method involved in the implementation and utilization of the present invention, wherein such a method can be shortly set forth as including the steps of: - separating a moving mould-carrying platen 2, associated to and joined with a respective upper platen 1, from the lower cavity-carrying platen; - placing said removable means 16 between said moving mould- carrying platen 2 and said cavity-carrying platen, by preferably using said recessed seats 17 and 17A to this purpose; - lowering said moving platen 2 towards said cavity-carrying platen 4 down to the point at which said moving platen 2 eventually comes to rest upon said removable means; - separating and raising said upper platen 1 from said moving mould- carrying platen 2, which remains resting on said removable means 16.

Claims: CLAIMS 1. Injection moulding machine for forming preforms intended for the production of plastic containers, comprising: - an upper platen (1), - a moving platen (2), - a support bar (3) carrying a plurality of lips, or neck-rings, constituted by two respective separable members (15a, 15b) each, - a plurality of male members (6) applied on to said upper platen (1) by means of appropriate fastening means (5), - possible cooling tubes (7) inserted in respective ones of said male members, - a cavity-carrying platen (4) provided with a plurality of cavities (8) associated to respective nozzles (9), - a plurality of guide columns (13), firmly associated on top to said upper platen (1) and adapted to be slidably inserted into appropriate respective through-holes (10) provided in said cavity- carrying platen, - in which said moving platen (2) is provided with appropriate through- holes (11) adapted to be slidably engaged by said guide columns (13), characterized i that there are provided removable means (16) adapted to delimitate the travel of said moving platen (2) towards said cavity- carrying platen (4), so that said moving mould- carrying platen can be positioned at a pre-selectable distance (Z) with respect to said cavity- carrying platen. 2. Injection moulding machine for forming preforms for the production of plastic containers according to claim 1, characterized in that said removable means (16) are substantially constituted by a multiplicity of resting cylinders or parallelepipeds, arranged parallel to each other and having the same height, the axis of which is parallel to the direction of movement of said moving mould-carrying platen (2). 3. Injection moulding machine for forming preforms for the production of plastic containers according to claim 1 or 2, characterized in that said removable means are so applied as to rest upon said cavity- carrying platen (4). 4. Injection moulding machine for forming preforms for the production of plastic containers according to claim 3, characterized in that said moving platen is provided, on the lower surface (18) thereof, with appropriate recessed seats (17) adapted to get coupled with the upper portions (19) of respective ones of said removable means, and said cavity- carrying platen (4) is provided on top with corresponding recessed seats (17A) adapted to get coupled with the lower portions (19A) of respective ones of said removable means. 5. Method for removing and re-assembling male members in an injection moulding machine for forming plastic preforms, provided with an arrangement in accordance with the preceding claims, characterized in that it comprises the following steps of: a) - separating a moving (2), associated to and joined with a respective upper platen (1), from the cavity- carrying platen (4) provided thereunder; b) - placing a plurality of removable means (16) between said moving mould-carrying platen (2) and said cavity-carrying platen, said means being adapted to delimitate the travel of said moving platen towards said cavity-carrying platen (4), so that said moving platen can be positioned at a pre-selectable distance (Z) from said cavity- carrying platen; c) - lowering said moving platen (2) towards said cavity-carrying platen down to a position corresponding to said pre- selectable distance (Z), at which said moving platen (2) eventually comes to rest upon said removable means; d) - separating and raising said upper platen (1) from said moving mould-carrying platen (2), which remains resting on said removable means (16).

Inventors: BISCHER LUIGINO, FUGOLO PAOLO, ZOPPAS MATTEO, BISCHER, LUIGINO, FUGOLO, PAOLO, ZOPPAS, MATTEO
Applicants: BISCHER LUIGINO, FUGOLO PAOLO, SIPA SPA, ZOPPAS MATTEO, BISCHER, LUIGINO, FUGOLO, PAOLO, SIPA S.P.A., ZOPPAS, MATTEO
Application year: 2001
Main classification: B29C45
IPC codes: B29C45