METHOD FOR INJECTING PREFORMS FOR CONVERSION INTO CONTAINERS AND DEVICE FOR THEM

Description

Field of the invention

[0001] The invention relates to overmoulding consisting of a technique for use in injection moulding, wherein in a 1 st< phase an injection moulded plastics material is inserted into a cavity of an injection mould, which is mounted on a core thereof, and wherein in a 2 nd< phase another material is injected over or around the first inserted product.

[0002] It is started herein with a method for producing plastics preforms by injection moulding, intended for working into plastics containers. Primary raw material for the production of a preform is injected into a mould having a cavity side and a core side, between which the preform is formed. After this, the mould is opened into its two halves -cavity side and core side- wherein each core of the core side bears a preform.Background of the invention

[0003] For preforms, overmoulding constitutes an interesting technique to be adopted when the preform needs a very high light barrier, such as in containers for dairy products. In this case, an inner preform is made of a material which is light-tight or opaque, whilst a corresponding outer preform is made which is transparent or has a colour. As described in PCT / BE2007 / 000040, when blowing the preform into a milk bottle, it is white on the outer side, whilst on the inner side, there is a black or grey layer of plastic which produces the light barrier. An extrusion coating process of overmoulding could be used here, consisting in producing preforms to begin with the injection moulding of the grey inner layer, over which a 2 nd< white layer is further sprayed. This guarantees the light barrier which is required with ultra-high temperature (UHT) milk bottles.

[0004] The overmoulding preform and the bottle blown therefrom can also be used however for other fields of application, such as in case of gas-tight, moisture-tight or chemical barriers requirements.

[0005] A method exists in which the inner preform, as the first injected product, is transferred to the cavity / core of the outer preform, as the product yet to be injected, by means of a transport and transfer system incorporated in the mould. Although this system offers an advantage as regards cycle time, it also has many drawbacks.

[0006] US 2005 / 0249902 A1 concerns the compression of overmoulded preforms for containers, in which a compression injection moulding production method for a two-layer preform is disclosed. This technique is unrelated, however, to an overmoulding injection moulding process involving a stretching and blowing technique.

[0007] In EP 1970181 of Minera Catalano-Aragonesa, a two-layer preform produced by an overmoulding technique is described. The preform comprises two layers, which each consist of a composition of polyethylene terephthalate (PET), titanium dioxide (TiO 2 ) and a dye with light-absorbing capacity in the visible light spectrum. However, neither a specific preparation method nor an elaborate overmoulding technique is proposed.

[0008] US 2010 / 0092711 of MOLMASA APLICACIONES TECNICAS, S.L. discloses a method and mould for producing a two-layer preform by overmoulding which differ considerably from the invention below, however, both in terms of mould design and of the course of the production method. Firstly, the technique and the mould which are described therein use the same core for injection into both the primary and secondary mould cavities, which calls for a vertical displacement of both the cavity side and the core side of the mould.

[0009] Secondly, this technique uses alternate primary and secondary cavities. Although this reduces the amount of vertical movement which is necessary to effect the transfer of the primary preforms, this also implies, however, a more complex hot runner system having alternate nozzles for the primary and secondary material, respectively. A drawback of this known system is that an investment needs to be made in a new non-standard machine, a special mould using an as yet unknown technology, and a good deal of peripheral equipment.

[0010] It is further known that there are currently limits on the output of the production system, notably no higher than 24-fold, which, in itself, is a limitation for the output, so that an increase in this is eagerly awaited. In case the requested number of products to be made is large, several such systems must be purchased, which entails additional costs. This system also operates with moving parts in a mould which is particularly complex, so that this is very prone to wear as a result of these moving parts.Prior art

[0011] Document JP-HO4-296520-A describes the manufacturing of composite materials, wherein as a first step an injection moulding part is formed in a first cavity, in a second step another material is pressed over this injection moulding part with a press, and in a third step a next injection moulding part is added thereto. In this method, a pressing technique is thus adopted, which by no means fits into the process which is referred to here.

[0012] Document WO 94 / 16871-A1 describes only the use of two robot arms for the production of PET preforms, which is simply regarded here as a specific application in the production of overmoulding preforms, without any contribution being made to the overmoulding technique which is aimed at here, per se.

[0013] In document DE-198 56 356-A1, a method is also described for the production of overmoulding preforms, for which, however, a mould with rotating core side is utilized, and wherein the injected product remains constantly on the same core and is placed into another cavity. However, this is completely opposite to the system meant here, wherein it is precisely intended to make the mould components move as little as possible, especially in a rotary direction, for the sake of preventing wearing thereof.

[0014] Document US2004 / 151937-A1 discloses a mould for the injection moulding of PET preforms, wherein the neck and cavity consist of a material having a different thermal conductivity in order to obtain a different cooling. This falls completely outside the application to the method which is referred to here.

[0015] Document JP-2004 082622-A has no relation to preforms, which constitutes though the basic intermediate product whose production is specifically meant here, in particular for the production of containers, with its thereto associated specifies.

[0016] Finally, document JP-H04296520 of MITSUBISHI Heavy IND neither discloses a process for manufacturing preforms nor does it mention the injection moulding technique therein, in contrast with the present invention wherein no other technique is presently envisaged. Moreover, according to this document, an initial injection is made and that so injected product is brought to the bottom, and only then a second injection is made, in contrast to the present intention from now on to proceed to inject both simultaneously. Furthermore, the process is conducted from top to bottom here. There is a priori only one cavity and core visible on the drawings, wherein the whole system as described appears geared to one single cavity, resp. core.

[0017] US 2005 / 170113 A1 discloses a process for making preforms made of two different materials wherein the first and second materials are injected with nozzles having center axis that are not coaxial. Said preforms may comprise an inclusion of the second material within the lateral wall of the first material, further comprising a bottom region and a lateral wall region, wherein the bottom region is entirely made of the first material and the lateral wall region is generally made of the first material except for at least one volume which is filled by the second material.

[0018] US 2008 / 241447 A1 is directed to polyester containers that are produced from polyester preforms having a thermoplastic overmould layer on at least a part of their exterior surface. The preform is made by overmoulding the thermoplastic layer onto the preform surface in one or more overmoulding operations. In a single overmoulding embodiment, the preform has a body layer of a first color and the overmould layer of a second color. The overmould layer can have a thickness gradient varying in thickness from one end of the preform to adjacent another end thereof. This gives the blow molded container an appearance wherein the container is transparent or of a first color and the overmould layers of different colors. Said overmould layers can have a thickness and color gradient. A third color results from the blending of the first color and the differing colors of the overmould layers where the first color and the differing colors can both be perceived. There can result only a first color at one end and a second color at another end with a third color varying blend intermediate between both ends.Aim of the invention

[0019] The object of this invention consists of providing another overmoulding method, with which a solution is brought to the aforementioned problems, and the aforementioned drawbacks and / or deficiencies are remedied to.Summary of the invention

[0020] To this end, an insert overmoulding method of the abovementioned type is proposed according to the invention, for manufacturing plastic hollow articles by injection moulding consisting of plastics preforms. According to a basic embodiment of the method of the invention, it is remarkable in that composite preforms are made as said hollow articles, which consist of sub-preforms and which are intended to be worked into plastics containers, wherein secondary raw material for producing a secondary preform conjugated to each preform is injected into the injection mould, which is equipped with multicavities with an even number of at least 2 of cavities and cores, wherein both sub-preforms are injected at the same time.

[0021] In a 1 st< step the injection mould containing the injected composite preform and secondary sub-preform is closed, and a gripping member provided with a set of receiving members is set in a standby position A aside from the mould.

[0022] In a 2 nd< step the forming mould is opened in its cavity side and core side, which are driven apart from each other, wherein each primary core bears an injected composite preform, and respectively the secondary core bears a secondary inner preform.

[0023] In a 3 rd< step, the gripping member is set in motion under the drive of a driving unit according to a preset direction of movement between the set-aside standby position A and an active take-over operating position B, which is directed to the core side of the mould. The injected composite preform and the secondary sub-preform are cooled and are taken over from the core side by the gripping member by means of suction means, wherein the composite preform and the secondary sub-preform are received in the corresponding receiving members.

[0024] In a 4 th< step, the gripping member is further moved into a further operating position C, in which it places the received secondary inner preforms onto the respective primary cores and continues to hold said preforms in place. Then the integrated preform composed of the primary preform and its added secondary inner preform is formed. Hereafter the gripping member is then moved back into the set-aside standby position A in order to expel the so produced integrated composite preforms to a discharge unit for further treatment. One full cycle is thus completed and the forming mould is then closed again.

[0025] In this case, only the injection moulding technique is adopted, limited to plastics preforms as hollow articles. Both primary and secondary preforms are injected simultaneously, with the incorporation of a suitable hot runner system.

[0026] The mould which is used in the method according to the invention is of relatively simple construction, like existing moulds which are readily available, thus yielding less complexity. After all, there are no moving parts, and thus no displacements, in the mould, thereby causing less wear herein. As a result, the whole system becomes cheaper, whilst machinery and peripheral equipment can be used for the standard preforms.

[0027] All these characteristics according to the invention constitute valuable advantages thereof.

[0028] It is also endeavoured according to this invention to shift this complexity from the mould to the deployed robot which cooperates therewith, bearing in mind that the robot is visible from the outside and is directly accessible - which is also more manageable in the event of maintenance or repair- in contrast to the mould. By virtue thereof, the production process can be better controlled, especially visually, so that this readily also becomes more reliable, at least for the applications intended here. By virtue of the use of existing standard machines, this results in greater flexibility as a result of maintained standardization.

[0029] According to a particular embodiment of the present invention, in said 3 rd< step, the one gripper arm is moved up to between both mould halves from which it receives the composite and secondary preforms for producing in said 4 th< step the integrated composite preform by means of one overmoulding sequence Φ1, Φ2, Φ3, Φ4 thereby accomplishing one cycle O, yet starting again with a new set of simultaneously injected preforms, wherein the production process is restarted in loop O for a new cycle O' in this prescribed order.

[0030] According to a further embodiment of the present invention, the injection moulded composite and secondary preforms are received in a vacuum plate provided on the gripper arm. The core side forms the movable mould plate with a predetermined number of primary cores, and a corresponding number of secondary cores for the secondary inner preforms, each occupying substantially one half of the core side. The opposite cavity side forms the fixed side with a corresponding number of primary cavities and a further set with a corresponding number of secondary cavities for the secondary inner preforms, which occupy the other half of said cavity side.

[0031] Both primary resp. secondary sub-fields of each mould side may be divided into an even number of equally occupied sub-fields, notably 2, of both mould plates being organized in a matrix pattern in an even number of rows and a predetermined number of columns respectively containing an equal number of elements, not less than 32 pieces as a power of 2 of at least 5 th< order exponent, up to 64 and more. So, the primary and secondary sub-fields of each mould side are thus organized in a matrix pattern in a predefined number of rows and columns respectively containing an equal number of elements, just as for the thereto corresponding primary and secondary sub-fields of the gripping member. This subtends a higher number of cavities, in particular 32-fold, even extending up to 64 and above.

[0032] Furthermore, no use is made in this invention of alternate primary and secondary cavities, which implies a more complex hot runner system indeed having alternate nozzles for the primary and secondary material, respectively. In the proposed invention, on the contrary, all primary cavities and cores can advantageously be grouped together in a dedicated subfield of the mould, namely a secondary field, in particular the bottommost part thereof, and all secondary cavities and cores in another sub-field of the mould, namely a primary field, in particular the topmost part, or possibly vice versa.

[0033] Said gripping arm is thus provided with a vacuum plate as the receiving member for the take-up of injection moulded products consisting of said preforms, wherein the relevant mould plate constitutes the movable side having a predefined number of cores, intended for a set of primary resp. secondary preforms, and a corresponding number of cores for the secondary preforms alone, which each occupy virtually their dedicated half of the plate surface on the core side of the mould, more particularly on the top half and the bottom half. The mould plate constituting the fixed side has a corresponding number of cavities for the primary preforms and a further set having a still corresponding number of cavities intended for the secondary preforms, which occupy the other half of the plate surface, in particular the remaining bottom half.

[0034] According to a more particular embodiment of the method of the invention, in the 2 nd< step, the mould is opened, and the movable mould half is removed in parallel respective the fixed mould half. The top products in the top half constitute the outer preforms, and the inner preforms are received therein. A finished product is then formed by the combination in each case of a top and bottom product, possibly with a positive connection, wherein the bottom products in the bottom half form the inner preforms.

[0035] In the third step, the gripping arm is moved downward vertically with its vacuum plate, from the standby position A or deflected idle mode, into the active take-up working position B between both mould halves aligned therewith and in which the integrated composite preforms and the secondary preforms are transferred from the resp. primary and secondary cores to the vacuum plate.

[0036] In the fourth step, the gripping arm is moved back in the opposite direction, vertically upward into alignment with the composite preforms and the secondary preforms, wherein the secondary bottom preforms are transferred on the primary top cores at the primary top half.

[0037] The gripping arm may then be moved further upward vertically, thereby containing said integrated composite preforms, wherein the latter preforms are expelled from the vacuum plate and are thus ready to be further discharged to said discharge means.

[0038] As soon as the gripping arm is removed from between both mould halves, the mould is closed again.

[0039] In a sequential representation of overmoulding, the injection mould is closed in step 1, in step 2 the mould is opened, in step 3 the gripping member is displaced between both mould halves in which said products are received, and in step 4 the bottommost products are placed onto topmost cores by this one grab arm. As soon as the gripping member disappears from between the mould, the mould is closed again as in step 1 and it is thus made ready to injection-mould a following series of products, being the integrated composite preforms at the top and a corresponding number of inner preforms at the bottom. The plastics preform is thus made with an integrated added inner preform. In step 1, the one mould half thus serves as the movable side with the cores thereon, opposite to the other mould half, which serves as the fixed side, in which the cavities also are, wherein the finished products are injected and are located between the relevant cores and cavities.

[0040] Besides, the primary core, with which injection is made into the primary cavity, is also used, whilst the secondary core is used for injection into the secondary cavity. Following the first injection step, the secondary preform is removed from the secondary cavity by an advantageously robotized grab arm, it is transported vertically and it is placed onto the primary core. This means that the vertical movement which is necessary to displace the secondary preform from the secondary core to the primary core takes place without movement of the cavity side or core side of the mould. This precludes any movements of the heavy and complex mould sides, which simplifies the process, prevents excessive wearing of the mould and allows the use of standard machines.

[0041] Advantageously, the gripping member is further displaced vertically upwards, with the aforementioned number of top products therein, wherein these are then expelled from the vacuum plate and are hence finally ready for packing.

[0042] The procedure is conducted from bottom to top here, i.e. the other way round compared to the known procedure.

[0043] According to a privileged embodiment of a method according to the invention, at least one second gripping member is operated, which is moved under drive from a second, resp. additional driving unit, wherein said gripping means are matched to each other for taking over and discharging the moulded preforms mutually sequentially, possibly alternately; or in mutual overlap, possibly in parallel. The latter may thus be coordinated with the first drive unit, between the aforementioned position B and the operating position C, wherein these gripping members are coordinated with one another for the mutual successive takeover and discharge of the shaped preforms. In a parallel operation of overmoulding, several cycles O, O' may thus be proceeded at the same time, notably under the action of yet one gripping element per cycle, which are matched to each other with a mutual phase shift τ, wherein an integrated composite preform is performed which consists of a primary preform and secondary inner preform resp., with actually one overmoulding sequence loop per cycle O i .

[0044] According to a specific embodiment of a method according to the invention, the gripping members are moved in a to-and-fro motion in the direction of their respective longitudinal axes Y1, Y2, wherein the gripping members are initially arranged on top of the mould and wherein their respective movement ΔX1, ΔX2 relative to one another is shifted in time over τ, the time shift may be adjustable, particularly as a function of the number of rows of cores and cavities respectively.

[0045] According to a yet more particular embodiment of the method according to the invention, a first cooling time is set for cooling the injected preforms in the cavity side. Following expiry of the set first cooling time, at the end of the set first cooling time, the cavity side and the core side of the mould are separated from each other, to a distance between them which is sufficient for the insertion of one of said gripping members into a space thus formed between cavity side and core side, wherein the reception side of said one gripper element is directed towards the core side, said one gripper element is moved from the disconnected position B to said space, and said one gripper element is thus taken into said working position C relative to the core side. The preforms are cooled there in the yet corresponding reception elements during a second set cooling time. After expiry of said cooling time the preforms are passed from the core side to said one gripper element each into a reception element corresponding to each core. After this, said one gripper element is moved back into the disconnected position B, both gripper elements are shifted crosswise until the further gripper element is driven in the disconnected position B and the one gripper element in said standby position A. Subsequently, the movement executed by said one gripper element during the completed cycle is then carried out in the same way by the further gripper element, and a further set of preforms is thus taken over by the latter from the core side of the mould, and said further gripper element is then driven back to the disconnected position B.

[0046] According to a still more particular embodiment of a method according to the invention, during a first cycle O1 said mould opens at the end of a first cooling period, i.e. after expiry of a first cooling time, wherein injected preforms are resting on said core side. Once a space is formed between core side and cavity side, which is large enough to place therein the first gripper element, with a reliable transfer of the preforms, said first gripper element is moved by being driven by a motor constituting said drive unit along the longitudinal axis Y1 of said first gripper element between said core side and cavity side until it is in the working position C. Said first gripper element then takes over a complete first set of preforms from the core side. After the preforms have been transferred, said first gripper element is driven back along said longitudinal axis Y1 to the disconnected position B in which the preforms are held in respective sleeves forming said reception elements of said first gripper element during a subsequent cycle O2 which starts from the moment that said first gripper element is driven into said disconnected position B. The preforms are accommodated in their respective sleeves, where they are subjected to an appropriate cooling, whereby in the meantime the preforms of said first cycle O1 are still present in said second gripper element. Shortly before the end of the subsequent cycle O2, said second gripper element is moved from the standby position A into the disconnected position B, while said first gripper element is moved to a standby position A' with a similar takeover process being carried out with the second gripper element. After said first gripper element has reached the disconnected position, its preforms are removed, and the abovementioned steps are repeated for the next cycle On in a repeated process.

[0047] In a still more particular embodiment of the method according to the invention, the primary and inner secondary outer preform are injected in a different color. Particularly, at least one selective recess is made in the inner preform, through which certain specific aspects and variations in colours of the final preform are carried out, more particularly wherein a complete longitudinal recess is carried out in the longitudinal axis ℓ of said inner preform, which is combined with a transparent outer preform, thereby yielding a transparent window over the entire length of the preform which is to be blown into a bottle, whereby the fill level thereof becomes observable.

[0048] In a specific embodiment of the method according to the invention, for the manufacture of overmoulding preforms, two different materials are added, wherein the inner and the outer preforms are injected in a different material, through which a blocking barrier, a gas barrier, moisture barrier or light barrier is incorporated in the final preform.

[0049] In a yet more particular embodiment of the method according to the invention, the overmoulding process hereby used when intended for containers for dairy products with a high light barrier, consists of producing preforms, which begins with the injection moulding of a gray inner layer, on which a 2 nd< white layer is further overmoulded, which ensures the light barrier which is required for ultra-high temperature UHT milk bottles, wherein the inner preform is made from a material that is light-tight, or opaque, and a corresponding outer preform which is transparent or has a color, wherein the relevant milk bottle becomes white outside after blowing the combined overmoulding preform, while being with a black or gray layer of plastic carried out as a light barrier at the inside.

[0050] In a more specific embodiment of the method according to the invention, a primary preform is coated by a secondary preform being applied as a coating on at least a portion of the primary plastic preform in which the latter preform consists of at least one coating layer; a primary preform made of plastic from a biaxially stretchable material for use in the manufacture of a plastic container is coated, wherein it is partly covered with a secondary preform as coating, with at least one coating layer consisting of a polymer coating applied to at least a portion of the primary plastic preform; the coating has a glass transition temperature value T G which is lower or equal to that of the abovementioned stretchable material; particularly PET is selected as said stretchable material, wherein the coating has a glass transition temperature value T G which is thus lower or equal to that of PET; more particularly, a barrier coating is applied on the preform; said at least one coating layer may be provided on the outside of the preform, notably in order to avoid contact of the coating with foodstuffs.

[0051] This invention also relates to an apparatus which is especially intended for the implementation of a method as set out above, the apparatus comprising a mould to form preforms, which has mutually releasable cavity and core sides. Protruding cores are provided therein for holding the preforms. A gripping member is provided with a pair of receiving members which can be directed at the cores for cooling and receiving the preforms. The gripping member is movable under the drive of a driving unit between a waiting position B and an operation mode C, wherein the gripping member is connected with the core side. This device is remarkable in that at least one hot-runner system is included in one injection mould. In particular two independent hot runner systems are provided in one injection mould, wherein the two hot runners for the primary and secondary materials are completely separated, wherein both hot runners are adjustable at mutually independent processing temperatures T a , T b .

[0052] In an even more particular embodiment of the apparatus according to the invention, an insert overmoulding machine is composed of a 2K multicavities PET injection machine, in particular two cavities, wherein the hot-runner is mounted so that both materials are sprayable individually in the upper cavity and in the lower cavity respectively, wherein the cavities are mounted so that in the lower cavity an inner preform is producible without a screw thread, and in the upper cavity an outer preform with PCO screw-thread resp., wherein in the upper cavity a core can be placed with a slightly smaller diameter than the core in the lower cavity, esp. of about 0,6 mm less, wherein the take-off robot is programmable so that, after one cycle the preform of the lower core is removable and displaceable on the upper core, while the finished preform of the upper core is removable and recoolable.

[0053] According to a further embodiment of the apparatus according to the invention, at least one second gripping member is provided with a further set of receiving means with which the cores of the core side of the mould can be aligned, wherein said at least second gripper means is displaceable under the drive of a further drive unit between the disconnected position B and the operating position C, wherein the latter gripping member is connected to the core side, and the latter movement is adjustable to the one of the first gripping member.

[0054] Each gripping member is formed by a gripper arm, wherein the receiving elements are formed by sleeves, wherein the cavity side of the mould is located on a fixed machine platform, wherein the core side is fixed on a movable platform of the machine, and wherein a core puller is provided having a retaining action on the preforms which remain on the respective cores of the core side by way of a topically fitted clamping connection. More particularly two bearing plates or support tables are provided, each having a gripping member with separate control.

[0055] In summary, by virtue of the special set-up of standard elements according to the invention, which are used according to defined method steps, it is possible to operate in a simplified, and all in all, less complex manner. The system according to the invention consists in dividing a standard mould, in particular 64-fold, into two fairly equal halves, i.e. 32 bottom parts for the inner preforms and 32 top parts for the outer preforms, or possibly vice versa.

[0056] It will be clear that the robot arm, apart from the above-described vertical movement for displacing the injection moulding parts, can also make a horizontal movement in order to place the secondary injection moulding part into the primary cavity.

[0057] A preform for blow moulding of a container, as specific hollow article manufactured according to a method as set out above, particularly with an apparatus as set out above, comprises a neck portion, a wall portion adjacent thereto and a bottom portion extending along an axis ℓ, wherein the preform is composed of a primary plastic base material and at least one additional secondary material, at least in a sub-area thereof, wherein it consists of an overmoulding preform comprising two different materials, with the inner and the outer preform made of another moulding material comprising a barrier, such as a gas barrier, moisture barrier or light barrier; particularly wherein the inner preform is made of a polyolefin, and the outer preform of PET, wherein it combines the mechanical and gas barrier properties of PET with the chemical barrier, moisture barrier and thermal properties of polyolefins.

[0058] The method and apparatus of the invention are further illustrated by the appended drawings, wherein further details are explained in more detail in the following description in some embodiments of the invention with reference to the attached drawings.Brief description of the drawings

[0059] Fig. 1 is a general sequential representation of an overmoulding cycle of a main embodiment of the method according to the invention. Fig. 2 shows step 1 of the method, wherein the mould is closed and the grab arm is in a standby position. Fig. 3 is a cross section along the line D-D of the device represented in the previous Fig. 2. Fig. 4 is an analogous representation to the previous Fig. 3, consisting in a cross-sectional view through the line A-A, though in this case with regard to the inner preform as the finished product. Fig. 5 represents the following phase or step 2, wherein the mould is opened. Fig. 6 represents a section along the line E-E in the previous Fig. 5, on which the topmost 32 products constitute the composite preforms, with inner preforms. Fig. 7 is an analogous representation to the previous Fig. 6, though of a section along the line B-B, with representation of the bottommost 32 products, which only represent the 32 inner preforms. Fig. 8 is a schematic representation of the thus formed finished product, consisting of the aforementioned composite preforms, in which the inner preform is accommodated. In addition, Fig. 9 shows the third phase of the method according to the invention, wherein the grab arm with the vacuum plate, which was in the standby position, now receives all products from the cores. Fig. 10 is a sectional representation along the line C-C in the previous Fig. 9, showing a cross section, wherein the bottommost 32 products, being the inner preforms, are transferred into the vacuum plate. Fig. 11 schematically represents the fourth step of the method according to the invention, wherein the grab arm moves upwards with the vacuum plate with the injection moulded products. In addition, Fig. 12 shows a cross section along the line G-G in the previous Fig. 11, wherein the injection moulded inner preforms are on the topmost cores. Fig. 13 represents a 3D perspective view of a detail of the mould components. Fig. 14 represents a front view of a detail of the mould components according to the previous Fig. 13. Fig. 15 represents a detail in enlarged view from Figs. 1 & 2 respectively. Figs. 16-23 each represent a view of the robot components. Figs. 24 and 25 are a mixed representation of a composite preform as a semi-finished product, especially obtained by applying the method as represented in Fig. 1. Figs. 26 and 27 show a combined application of overmoulding and coating on a preform, resp. the wall section thereof. Fig. 28 et seq. show a combined application of overmoulding and coating on a preform, thereby including zebra states. Description

[0060] Fig. 1 shows in partial views a to d a general sequential representation of overmoulding with, in Φ1, an injection mould 3 which is closed; in Φ2, the mould which is opened into its 2 mould halves, 31 as the core side and 32 as the cavity side; in Φ3, a grab arm 4, which arrives therebetween and receives products 11, 12, and finally, in Φ4, the grab arm 4, which places bottommost products 12 onto topmost cores 31'.

[0061] Fig. 2 shows said one grab arm 4, which is provided with a vacuum plate 40 for the reception of injection moulded products 11, 12. Opposite thereto, the relevant mould plate 31, constituting the movable side, is depicted, having for example 32 cores intended for the composite preforms 10 and 32 cores for the inner preforms 12, which each occupy virtually half of the plate surface, in this case on the top half. The mould plate 32, constituting the fixed side, correspondingly has 32 cavities for the composite preform and a further set of 32 cavities intended for the inner preform, which occupy the other half of the plate surface, in this case the bottom half.

[0062] Fig. 3 shows the mould 3, closed in step 1 of the method, in the closed state, and the grab arm 4 in a standby position.

[0063] In Fig. 4, the mould plate is represented as the movable side 31 opposite the mould plate represented as the fixed side 32, in which the cavities for the composite preform 10 are also depicted, in which the core is incorporated therefor, with therebetween the finished composite preform 10 with injected inner preform 12.

[0064] Fig. 5 is an analogous representation to the previous Fig. 4, consisting in a cross-sectional view through the line A-A, though in this case with regard to the inner preform 12 as the finished product.

[0065] Fig. 6 represents the following phase 2, wherein the mould 3 is opened, in particular with a section along the line E-E in the previous Fig., on which the topmost 32 products constitute the composite preforms 10, with inner preforms.

[0066] Fig. 7 is an analogous representation to the previous Fig., though of a section along the line B-B, with representation of the bottommost 32 products, which represent only the 32 inner preforms.

[0067] Fig. 8 is a schematic reproduction of the so formed finished product consisting of the aforementioned composite preform, in which the inner preform is accommodated.

[0068] In addition, Fig. 9 shows the third phase of the method, wherein the grab arm 4 with the vacuum plate 40, which was in the standby position, now receives all products from the cores 33.

[0069] Fig. 10 is a sectional representation along the line C-C in the previous Fig. showing a cross section, wherein the bottommost 32 products, being the inner preforms, have been transferred into the vacuum plate 40.

[0070] Fig. 11 schematically represents the fourth step of the method according to the invention, wherein the grab arm moves upwards with the vacuum plate with the injection moulded products. Here, the 32 bottommost products, being the inner preforms, are transferred onto the cores 33 of the 32 topmost composite preforms 10. Next, the topmost finished products are deposited onto a discharge conveyor 100.

[0071] In addition, Fig. 12 shows a cross section along the line G-G in the previous Fig., wherein the injection moulded inner preforms 12 are seated on the topmost cores 33.

[0072] The robot arm then moves further vertically, with the 32 topmost products, being the composite preforms, therein, wherein these are further expelled from the vacuum plate 40 and are thus ready for packing.

[0073] Once the robot arm 41 has disappeared from between the mould 3, the mould can reclose, just as in step 1. This is then ready to injection mould the following products, being 32 integrated preforms 10 at the top and 32 inner preforms 12 at the bottom.

[0074] The overmoulding method can be used to produce bicolour preforms. For this, the inner and outer preform 11 are sprayed a different colour, or only the inner or outer preform is coloured. As a result of selective recesses in the inner preform 12, certain specific designs and variations in colours can be obtained.

[0075] For example, an opaquely coloured inner preform, wherein in the longitudinal axis of the preform a complete recess is provided, and a transparent outer preform 11. This gives rise to a transparent window over the full length of the preform and bottle, whereby the fill level of the bottle can be observed.

[0076] As far as the addition of two different materials is concerned, the described method for the production of overmoulding preforms likewise allows the inner and the outer preform 11 to be injection moulded in another material. This can have special advantages for, for example, gas barrier, moisture barrier or hot-fill applications. The outer preform 11 can be produced from standard PET here, and the inner preform 12 can be produced from a high barrier or hot-fill material. If so desired, this allows the use of a higher share of secondary material for barrier applications compared with known multilayer preforms.

[0077] For hot-fill applications, wherein the complete bottle must standardly be made of expensive hot-fill material, the inner preform alone may consist of secondary material. For further applications, the inner preform could consist, for example, of a polyolefin, and the outer preform of PET. This bottle combines the mechanical and gas barrier properties of PET with the chemical barrier, moisture barrier and thermal properties of polyolefins.

[0078] Even though this can call for a longer vertical movement between the primary and secondary injection step, it does however ensure two completely separate hot runners for the primary and secondary material a, b. In addition to an extreme simplification of the hot runner systems, this ensures greater flexibility for the material, since the two hot runners can be set at mutually independent processing temperatures.Examples of insert-overmoulding with unitized machine:

[0079] Insert-overmoulding preforms were produced on a dual-cavity 2K PET injection machine. The hot runner was mounted such that the A material can be injected individually into the topmost cavity and the B material can be injected individually into the bottommost cavity.

[0080] The cavities were mounted such that in the bottommost cavity an inner preform has been produced without screw thread, and in the topmost cavity an outer preform has been produced with PCO screw thread. In the topmost cavity a core having a diameter of 0,6 mm less than the core in the bottommost cavity has been placed.

[0081] The take-off robot was programmed such that, after one cycle, the preform has been taken off the bottommost core and placed on the topmost core, whilst the finished preform has been removed from the topmost core and subsequently cooled.Materials

[0082] Test 1: In a first test, an overmoulding preform was produced, the inner layer was coloured blue in order to be able to visually evaluate both layers. Weight of inner preform 6,2 g; total weight 25,8 g A material (outer preform): PET, colourless. B material (inner preform): PET, coloured blue.

[0083] From the produced preforms, bottles were blown and evaluated. Both layers were present in the expected ratio and there was good adhesion between the layers.

[0084] Test 2: In a second test, a milk preform having a highest possible light barrier was produced with overmoulding.

[0085] Weight of inner preform 6,5 g; total weight 26,3 g A material (outer preform): coloured with 5% white dye. B material (inner preform): coloured with 1% black dye.

[0086] From the produced preforms, bottles were blown and evaluated for light barrier with a spectrophotometer. The results indicated a markedly improved light barrier compared with only white coloured bottles.

Claims

1. Method for manufacturing plastic hollow articles by injection moulding, wherein primary raw material is injected into a mould (3) having a core side (31) and a cavity side (32), between which hollow articles (10) are formed, after which the mould (3) is opened into its two halves (31, 32), the cores (33) whereof each bear a hollow article, characterized in that composite preforms (10) are made as said hollow articles, which consist of sub-preforms (11, 12) and which are intended to be worked into plastics containers, in that secondary raw material for producing a secondary preform (12) conjugated to each preform (10) is injected into the injection mould (3), which is equipped with multicavities with an even number of at least 2 of cavities and cores (33, 34), and in that both sub-preforms (11) and (12) are injected at the same time, wherein in a 1st step (Φ1) the injection mould (3) containing the injected composite preform (10) and secondary sub-preform (12) is closed, and a gripping member (4) provided with a set of receiving members (16) is set in a standby position (A) aside from the mould (3); in a 2nd step (Φ2) the forming mould (3) is opened in its cavity side (32) and core side (31), which are driven apart from each other, wherein each primary core (33) bears an injected composite preform (10), and respectively the secondary core (33') bears a secondary inner preform (12) in a 3rd step (Φ3), the gripping member (4) is set in motion, under the drive of a driving unit (5) according to a preset direction of movement between the set-aside standby position (A) and an active take-over operating position (B), which is directed to the core side (31) of the mould (3), wherein the injected composite preform (10) and the secondary sub-preform (12) are cooled and are taken over from the core side (31) by the gripping member (4) by means of suction means (6), wherein the composite preform (10) and the secondary sub-preform (12) are received in the corresponding receiving members (16); in a 4th step (Φ4), the gripping member (4) is further moved into a further operating position (C), in which it places the received secondary inner preforms (12) onto the respective primary cores (33) and continues to hold said preforms (11) in place, with the formation of the integrated preform (10) composed of the primary preform (11) and its added secondary inner preform (12), after which the gripping member (4) is moved back into the set-aside standby position (A) in order to expel the so produced integrated composite preforms (10) to a discharge unit for further treatment, whereby one full cycle (O) is thus completed and whereupon the forming mould (3) is then closed again.

2. Method according to claim 1, characterized in that in said 3rd step (Φ3), the one gripper arm (4) is moved up (H) to between both mould halves (31, 32) from which it receives the composite and secondary preforms (10, 12) for producing in said 4th step (Φ4) the integrated composite preform (10) by means of one overmoulding sequence (Φ1, Φ2, Φ3, Φ4) thereby accomplishing one cycle (O), yet starting again with a new set of simultaneously injected preforms (11, 12), wherein the production process is restarted in loop (O) for a new cycle (O') (Φ1', Φ2', Φ3', Φ4') in this prescribed order.

3. Method according to claim 1 or 2, characterized in that the injection moulded composite and secondary preforms (11, 12) are received in a vacuum plate (40) provided on the gripper arm (4), wherein the core side (31) forms the movable mould plate with a predetermined number of primary cores (33), and a corresponding number of secondary cores for the secondary inner preforms (12), each occupying substantially one half of the core side (31), wherein the opposite cavity side (32) forms the fixed side with a corresponding number of primary cavities (34) and a further set with a corresponding number of secondary cavities (34') for the secondary inner preforms (12), which occupy the other half of said cavity side (32), and / or in that both primary resp. secondary sub-fields (I, II, III, IV) of each mould side (31, 32) are divided into an even number of equally occupied sub-fields, in particular 2, of both mould plates (31; 32) being organized in a matrix pattern in an even number of rows and a predetermined number of columns respectively containing an equal number of elements, more particularly an even number of at least two cores (33) resp. cavities (34) not less than 32 pieces as a power of 2 of at least 5th order exponent, up to 64 and more.

4. Method according to any one of the preceding claims, characterized in that in the 2nd step (Φ2) the mould is opened, wherein the movable mould half (31) is removed in parallel respective the fixed mould half (32), wherein the top products (11) in the top half (101) form the outer preforms (11), and the inner preforms (12) are received therein, with the formation of a finished product (10) by the combination in each case of a top (11) and bottom product (12), possibly with a positive connection, wherein the bottom products (12) in the bottom half (102) form the inner preforms; and / or in that in the third step (Φ3) the gripping arm (4) is moved downward vertically with its vacuum plate (40), from the standby position (A) or deflected idle mode, into the active take-up working position (B) between both mould halves (31, 32) aligned therewith and in which the integrated composite preforms (10) and the secondary preforms (11,12) are transferred from the resp. primary and secondary cores (33, 33') to the vacuum plate (40), in that in the 4th step (Φ4) the gripping arm (4) is moved back in the opposite direction (-H), vertically upward into alignment with the composite preforms (10) and the secondary preforms (12), wherein the secondary bottom preforms (12) are transferred on the primary top cores (33) at the primary top half; and / or in that the gripping arm (4) is then moved further upward vertically, thereby containing said integrated composite preforms (10), wherein the latter preforms (10) are expelled from the vacuum plate (40) and are thus ready to be further discharged to said discharge means; and / or in that as soon as the gripping arm (4) is removed from between both mould halves (31, 32), the mould (3) is closed again.

5. Method according to any one of the preceding claims, characterized in that at least one second gripping member (42,...) is operated, which is moved under drive from a second, resp. additional driving unit (52), wherein said gripping means (41), (42) are matched to each other for taking over and discharging the moulded preforms mutually sequentially, possibly alternately; or in mutual overlap, possibly in parallel.

6. Method according to claim 4 5, characterized in that the gripping members (41, 42) are moved in a to-and-fro motion (G, -G) in the direction of their respective longitudinal axes (Y1, Y2), wherein the gripping members (41, 42,... 4i) are initially arranged on top of the mould (3), and wherein their respective movement (ΔX1, ΔX2) relative to one another is shifted in time over (τ).

7. Method according to any one of the claims 5 or 6, characterized in that a first cooling time is set for cooling the injected preforms (11) in the cavity side (32), in that at the end of the set first cooling time the cavity side (32) and the core side (31) of the mould (3) are separated from each other, to a distance between them which is sufficient for the insertion of one of said gripping members (41, 42) into a space (39) thus formed between cavity side and core side, wherein the reception side (44) of said one gripper element is directed towards the core side (31), said one gripper element is moved from the disconnected position (B) to said space (34), and said one gripper element is thus taken into said working position (C) relative to the core side, and the preforms (11) are cooled there in the yet corresponding reception elements (16) during a second set cooling time, wherein after expiry of said cooling time the preforms are passed from the core side to said one gripper element each into a reception element (16) corresponding to each core (33), following which said one gripper element is moved back into the disconnected position (B), both gripper elements are shifted crosswise until the further gripper element is driven in the disconnected position (B) and the one gripper element in said standby position (A), after which the movement executed by said one gripper element during the completed cycle is then carried out in the same way by the further gripper element, and a further set of preforms (11) is thus taken over by the latter (42) from the core side of the mould (3), and said further gripper element is then driven back to the disconnected position (B).

8. Method according to any one of the claims 5 to 7, characterized in that during a first cycle (O1) said mould opens at the end of a first cooling period, wherein injected preforms (11) are resting on said core side (31), wherein as soon as a space (34) is formed between core side (31) and cavity side (32) which is large enough to place therein the first gripper element (41), with a reliable transfer of the preforms, said first gripper element (41) is moved by being driven by a motor forming said drive unit (5) along the longitudinal axis (Y1) of said first gripper element (41) between said core side and cavity side until it is in the working position (C), wherein said first gripper element (41) then takes over a complete first set of preforms (81) from the core side (31), wherein after the preforms have been transferred, said first gripper element (41) is driven back along said longitudinal axis (Y1) to the disconnected position (B) in which the preforms (11) are held in respective sleeves forming said reception elements (16) of said first gripper element (41) during a subsequent cycle (O2) which starts from the moment that said first gripper element (41) is driven into said disconnected position (B), wherein the preforms (11) are accommodated in their respective sleeves (34'), where they are subjected to an appropriate cooling, whereby in the meantime the preforms of said first cycle (O1) are still present in said second gripper element (42), wherein shortly before the end of the subsequent cycle (O2) said second gripper element (42) is moved from the standby position (A) into the disconnected position (B), while said first gripper element (41) is moved to a standby position (A') with a similar takeover process being carried out with the second gripper element (42), wherein after said first gripper element (41) has reached the disconnected position, its preforms (11) are removed, and wherein the abovementioned steps are repeated for the next cycle (On) in a repeated process.

9. Method of overmoulding according to any one of the preceding claims, characterized in that the primary and inner secondary outer preform (11, 12) are injected in a mutually different color, particularly wherein at least one selective recess (77) is made in the inner preform (12), through which certain specific aspects and variations (76) in colours of the final preform (10) are carried out, more particularly wherein a complete longitudinal recess (77) is carried out in the longitudinal axis (f) of said inner preform (12), which is combined with a transparent outer preform (11), thereby yielding a transparent window (79) over the entire length of the preform (10) which is to be blown into a bottle (1), whereby the fill level (78) thereof becomes observable.

10. Method according to any one of the claims 7 to 9, characterized in that for the manufacture of overmoulding preforms, two different materials (a, b) are added, wherein the inner and the outer preforms (12, 11) are injected in a different material, through which a blocking barrier (75), a gas barrier, moisture barrier or light barrier is incorporated in the final preform (10).

11. Method according to claim 10, characterized in that it is intended for containers for dairy products with a high light barrier, wherein the overmoulding process used herein consists of producing preforms that begins with the injection moulding of a gray inner layer, on which a 2nd white layer is further overmoulded, which ensures the light barrier which is required for ultra-high temperature (UHT) milk bottles, wherein the inner preform is made from a material that is light-tight, or opaque, and a corresponding outer preform which is transparent or has a color, wherein the relevant milk bottle becomes white outside after blowing the combined overmoulding preform (10), while being with a black or gray layer of plastic carried out as a light barrier at the inside.

12. Method according to any one of the preceding claims, characterized in that a primary preform (11) is coated by a secondary preform being applied as a coating on at least a portion of the primary plastic preform in which the latter preform (12) consists of at least one coating layer; wherein a primary preform made of plastic, from a biaxially stretchable material, for use in the manufacture of a plastic container, is coated, wherein it is partly covered with a secondary preform as coating, with at least one coating layer consisting of a polymer coating applied to at least a portion of the primary plastic preform (11); wherein the coating (98) has a glass transition temperature value TG which is lower or equal to that of the abovementioned stretchable material; particularly wherein PET is selected as said stretchable material; more particularly wherein a barrier coating (99) is applied on the preform (11); and / or wherein said at least one coating layer (98) is provided on the outside of the preform.

13. Apparatus for carrying out a method according to any one of the preceding claims for manufacturing plastic preforms by injection moulding means, comprising a mould (3) to form said preforms (11,12), wherein primary raw material is injected into said mould (3) having mutually releasable cavity (32) and core sides (31) for forming said preforms, in which a number of protruding cores (33) are provided for holding the preforms, by means whereof composite preforms (10) are made which consist of sub-preforms (11, 12) intended to be worked into plastic containers, wherein injecting means are provided for producing a secondary preform (12) conjugated to each preform (10) by injecting secondary raw material into said injection mould (3), which is equipped with multicavities with an even number of at least 2 of cavities and cores (33, 34), wherein closing means are provided for closing the injection mould (3) containing the injected composite preform (10) and secondary sub-preform (12), and wherein setting means are provided for setting a gripping member (4) provided with a pair of receiving members (16) to be directed along the cores (33) for cooling and receiving the preforms, wherein opening means are provided for opening the forming mould (3), wherein each primary core (33) bears an injected composite preform (10), and respectively the secondary core (33') bears a secondary inner preform (12), wherein the gripping member (4) is movable under the drive of a driving unit (5) between a standby position (A) and an active take-over operating position (B), which is directed to said core side (31), wherein the gripping member (4) is connected with the core side (31), in which the injected composite preform (10) and the secondary sub-preform (12) are taken over from the core side (31) by the gripping member (4) by means of suction means (6), wherein the composite preform (10) and the secondary sub-preform (12) are received in the corresponding receiving members (16); whereby the received secondary inner preforms (12) stand onto the respective primary cores (33) yielding the formation of the integrated preform (10) composed of the primary preform (11) and its added secondary inner preform (12), for being expelled to a discharge unit for further treatment, characterized in that at least one hot-runner system is included in one injection mould (3), particularly two independent hot runner systems wherein the two hot runners for the primary and secondary materials (a, b) are completely separated, wherein both hot runners are adjustable at mutually independent processing temperatures (Ta,Tb).

14. Apparatus according to the preceding claim, characterised in that an insert overmoulding device is composed of a 2K multicavities PET injection machine, in particular two cavities, wherein the hot-runner is mounted so that the material (a) and the material (b) are sprayed individually in the upper cavity and in the lower cavity respectively, wherein the cavities (32) are mounted so that in the lower cavity (32') an inner preform (12) is produced without a screw thread, and in the upper cavity (32) an outer preform (11) with PCO screw-thread resp., wherein in the upper cavity a core (33) is placed with a slightly smaller diameter than the core (33') in the lower cavity, esp. of about 0,6 mm less, wherein the take-off robot (4) is programmed so that, after one cycle the preform of the lower core (33') is removed and displaced on the upper core (33), while the finished preform (10) of the upper core is removed and recooled.

15. Apparatus according to claim 13 or 14, characterized in that at least one second gripping member (42) is provided with a further set of receiving means (16) with which the cores (33) of the core side (31) of the mould (3) can be aligned, wherein said at least second gripper means (42) is displaceable under the drive of a further drive unit (52) between the disconnected position (B) and the operating position (C), wherein the latter gripping member (42) is connected to the core side (31), and the latter movement is adjustable to the one of the first gripping member (41); wherein each gripping member (41, 42) is formed by a gripper arm, wherein the receiving elements (16) are formed by sleeves, wherein the cavity side (32) of the mould (30) is located on a fixed machine platform, wherein the core side (31) is fixed on a movable platform (37') of the machine, and wherein a core puller (38') is provided having a retaining action on the preforms (11) which remain on the respective cores (33) of the core side (31) by way of a topically fitted clamping connection (39'); particularly wherein two bearing plates or support tables are provided, each having a gripping member with separate control.