Overmoulding method for preforms to be converted into containers and device therefor

Abstract

Method for manufacturing plastic preforms (10) by injection moulding, consisting of sub-preforms (11, 12) injected at the same time, wherein (1) the injection mould (3) containing the injected composite preform (10) and secondary sub-preform (12) is 1 st closed, and a gripper (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 (2) the mould (3) is opened, wherein each primary core (33) bears an injected composite preform (10), and the secondary core (33) a secondary inner preform (12); the gripper (4) is then driven (3) in motion between the standby position (A) and a take-over position (B), wherein the injected preforms (10, 12) are cooled and taken over from the core side (31) by the gripper (4) by means of suction means (6); wherein the gripper (4) is further moved (4) 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), with formation of integrated preforms (10) which are expelled to a discharge unit.

Claims

1. Method for manufacturing plastic hollow articles by injection moulding, comprising the following steps: providing 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), said mould (3) comprising multicavities with an even number of at least two sets of cavities (34) and cores (33), and wherein both sub-preforms (11) and (12) are injected at the same time, primary raw material is injected into a first area comprising one of the two sets of cavities and cores (33) of the mould (3) forming primary sub-preforms, secondary raw material is injected into a second area comprising another of the two sets of cavities and cores of the mould (3) forming secondary sub-preforms, the mould (3) is opened into its two halves (31, 32), and each of the cores (33) in the first area is a primary core adapted to bear a primary hollow article and each of the cores in the second area is a secondary core adapted to bear a secondary hollow article, composite preforms (10) are made as hollow articles comprising the primary and secondary sub-preforms (11, 12) and to be worked into plastic containers, wherein in a 1.sup.st step (1) 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 aside from the mould; in a 2.sup.nd step (2) the forming mould (3) is opened and its cavity side (32) and core side (31), which are driven apart from each other, wherein each core in the first area (33) bears an injected composite preform (10), and respectively the secondary core in the second area (33) bears a secondary inner preform (12); in a 3.sup.rd step (3), 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 each composite preform (10) and each secondary inner 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 inner preform (12) are received in the corresponding receiving members (16); in a 4.sup.th step (4), the gripping member (4) is further moved into a further operating position, in which it places the received secondary inner preforms (12) onto the respective primary cores (33) and continues to hold said primary preforms (11) in place, the mold is closed with the formation of each integrated composite preform (10) composed of the primary preform (11) on the secondary inner preform (12), the mold is opened, 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, wherein insert overmoulding preforms (10) are produced on a dual cavity injection machine, wherein a hot-runner is mounted such that a first material (a) is injected individually in one of both cavities, notably an upper one (34) and a second material (b) is injected individually into the other cavity notably a lower one (34), wherein the cavities are mounted such that in the lower cavity, an inner preform (12) is produced without a screw thread, and in said other cavity, an outer preform (11) is produced with a screw thread, wherein a core (33) is further disposed in the upper cavity with a diameter that is slightly smaller than the core (33) in the lower cavity, wherein the take-off robot gripping member (4) is programmed such that, after one cycle, the preform (11) is taken off from the lower core (33) and is placed on the upper core (33), while the finished preform (10) of the upper core (33) is removed and is recooled, wherein the primary and inner, secondary outer preform (11, 12) are injected in a different color, wherein only the inner or outer preform (11) or (12) is colored, 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, in particular by means of an opaquely coloured inner preform (12), more particularly wherein a complete longitudinal recess (77) is carried out along the longitudinal axis (l) 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.

2. Method according to claim 1, wherein in said 3.sup.rd step (3) the one gripping member (4) is moved (H) up to between both mould halves (31, 32) from which it receives the composite and secondary preforms (10, 12) for producing in said 4.sup.th step (4) the integrated composite preform (10) by means of one overmoulding sequence of said 1.sup.st step followed by said 2.sup.nd step, said 3.sup.rd step and said 4.sup.th step, respectively (1, 2, 3, 4), thereby accomplishing one cycle (O), yet starting again with a new set of simultaneously injected outer and inner preforms (11, 12), wherein the production process is restarted in loop (O) for a new cycle (O) of said 1.sup.st step followed by said 2.sup.nd step, said 3.sup.rd step and said 4.sup.th step respectively (1, 2, 3, 4) in this prescribed order.

3. Method according to claim 1, wherein the injection molded composite and secondary inner preforms (11, 12) are received in a vacuum plate (40) provided on the gripping member (4), wherein the core side (31) forms the movable mould plate with a predetermined number of 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 wherein both primary respectively secondary sub-fields (I, II, III, IV) of each mould side (31, 32) are divided into an even number of equally occupied sub-fields 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, according to a regular quadratic arrangement grid of the elements (33, 34), an even number of cores (33) and cavities (34), wherein each said half (101, 101) of the core side (31) and side (32) is split according to a staggered occupancy per row (110, 111), column (120, 121), grouped plural in pairs or more.

4. Method according to claim 1, wherein in said 2.sup.nd step (.sub.2) 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 said secondary 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, with a positive connection, wherein said bottom products in the bottom half (102) form said inner preforms, and/or wherein in said third step (.sub.3) said gripping member (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 said integrated composite preforms (10) and said secondary preforms (11, 12) are transferred from the respectively primary and secondary cores (33, 33) to said vacuum plate (40), wherein in said fourth step (.sub.4) said gripping member (4) is moved back in the opposite direction (-H), vertically upward into alignment with said composite preforms (10) and said secondary inner preforms (12), wherein the secondary inner preforms (12) are transferred on the primary top cores (33) at the primary top half; and/or wherein said gripping member (4) is then moved further upward vertically, thereby containing said integrated composite preforms (10), wherein the latter preforms (10) are expelled from said vacuum plate (40) and are thus ready to be further discharged to said discharge means; and/or wherein as soon as said gripping arm (4) is removed from between both mould halves (31, 32), said mould (3) is closed again.

5. Method according to claim 1, wherein at least one second gripping member (42, . . . ) is operated, which is moved under drive from a second or additional driving unit (52), wherein said gripping members (41, 42) are matched to each other for taking over and discharging the molded preforms mutually sequentially, alternately, or in mutual overlap, in parallel, wherein in a parallel operation of overmolding, several cycles (0, 0) are proceeded at the same time, under the action of yet one gripping member (41,42) per cycle, which are matched to each other with a mutual phase shift (), wherein an integrated composite preform (10) is performed which consists of a primary preform (11) and secondary inner preform (12) respectively, with actually one overmolding sequence loop (1, 2, 3, 4) per cycle (Oi).

6. Method according to claim 5, wherein the gripping members (41, 42) are moved in a to-and-fro motion (G, -G) in a first 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 (X1, X2) relative to one another is shifted in time over (), wherein said at least two gripping members (41, 42) are arranged on a carrier (9), in a set-up plane which is substantially perpendicular relative to the ground of the supporting surface and are shifted in said set-up plane in accordance with a second direction under the drive of a further driving unit (5i), between a standby position (A) in idle mode and a take-over position (B) in operation mode, wherein said at least two gripping members (41, 42) are moved successively in accordance with two mutually substantially orthogonal directions, wherein said first direction of movement is selected substantially vertically relative to the ground, and both of the gripping means are moved between said take-over position (B) and operation mode (C); wherein the latter movement of the two gripping members (41, 42) is proceeded simultaneously in said second direction (X) in which said carrier plate (9) is moved under the drive of a further motor that forms the further driving unit (5i).

7. Method according to claim 5, wherein 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 mold (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 claim 5, wherein during a first cycle (O1) said mould opens at the end of a first cooling time, 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 gripping member (41) during a subsequent cycle (O2) which starts from the moment that said first gripping member (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 gripping member (42), wherein shortly before the end of the subsequent cycle (O2) said second gripping member (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 gripping member (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 according to claim 7, wherein for the manufacture of overmolding 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), especially a gas barrier, moisture barrier or light barrier is incorporated in the final preform (10), wherein the outer preform (11) is made from standard PET, and the inner preform (12) from a high barrier or hotfill material, in the case of use for hotfill applications, when intended for containers for dairy products with a high light barrier, wherein the overmolding process hereby used consists of producing preforms, which begins with the injection molding of a gray inner layer, on which a 2.sup.nd white layer is further overmoulded, which perform 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 overmolding preform (10), while being with a black or gray layer of plastic carried out as a light barrier at the inside.

10. Method according to claim 1, wherein 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 consists of at least one coating layer, wherein a primary preform made of plastic, more specifically from a particularly 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 T.sub.G which is lower or equal to that of said stretchable material, wherein PET is selected as said stretchable material, wherein the coating has a glass transition temperature value T.sub.G which is lower or equal to that of PET, wherein a barrier coating (99) is applied on the preform (11), wherein said at least one coating layer (98) is provided on the outside of the preform, in particular in order to avoid contact of the coating (98) with foodstuffs.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A, 1B, 1C and 1D are general sequential representations of an overmoulding cycle of a main embodiment of the method according to the invention.

(2) FIG. 2 shows step 1 of the method, wherein the mould is closed and the grab arm is in a standby position.

(3) FIG. 3 is a cross section along the line D-D of the device represented in the previous FIG. 2.

(4) 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.

(5) FIG. 5 represents the following phase or step 2, wherein the mould is opened.

(6) 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.

(7) 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.

(8) 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.

(9) 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.

(10) 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.

(11) 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.

(12) 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.

(13) FIGS. 13A and 13B represent 3D perspective views of a detail of the mould components.

(14) FIG. 14 represents a front view of a detail of the mould components according to the previous FIG. 13.

(15) FIG. 15 represents a detail in enlarged view from FIGS. 1 & 2 respectively.

(16) FIGS. 16-21, 22A, 22B, 23A and 23B each represent a view of the robot components.

(17) FIGS. 24 and 25 are a mixed representation of a composite preform according to the invention as a semi-finished product, especially obtained by applying the method as represented in FIG. 1.

(18) FIGS. 26 and 27 show a combined application of overmoulding and coating on a preform, resp. the wall section thereof.

(19) FIGS. 28A and 28B to 35 show a combined application of overmoulding and coating on a preform, thereby including zebra states.

DESCRIPTION

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

(21) 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.

(22) 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.

(23) 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.

(24) 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.

(25) 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.

(26) 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.

(27) 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.

(28) 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.

(29) 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.

(30) 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.

(31) 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.

(32) 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.

(33) 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.

(34) 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.

(35) 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.

(36) 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.

(37) 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.

(38) 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.

(39) Examples of Insert-Overmoulding with Unitized Machine:

(40) 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.

(41) 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.

(42) 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.

(43) Materials

(44) 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.

(45) Weight of inner preform 6.2 g; total weight 25.8 g

(46) A material (outer preform): PET, colourless.

(47) B material (inner preform): PET, coloured blue.

(48) 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.

(49) Test 2: In a second test, a milk preform having a highest possible light barrier was produced with overmoulding.

(50) Weight of inner preform 6.5 g; total weight 26.3 g

(51) A material (outer preform): coloured with 5% white dye.

(52) B material (inner preform): coloured with 1% black dye.

(53) 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.