MXPA98008716A - Injection molding apparatus with injection hole for multip five layer molding - Google Patents

Abstract

The present invention relates to an injection molding apparatus with multiple cavity injection orifice having a plurality of melt distribution manifolds and a plurality of heated nozzles mounted in a mold, each heated nozzle having a rear end that is supports against one of the manifolds of distribution of molten material and a front end adjacent an orifice leading to a cavity in the mold, each heated nozzle having first, second and third channels of molten material which extend therethrough from the back end to the front end, a first passage of molten material for transporting molten material from a first source of molten material which branches into one of the manifolds of distribution of molten material and which extends through the first channel of molten material in each heated nozzle to the hole, a second passage of molten material or to transport molten material from a second of molten material that branches into one of the manifolds of distribution of molten material and that extends through the second of molten material in each heated nozzle to the orifice, and a third passage of molten material for transporting molten material from the first source of molten material that branches into one of the manifolds of distribution of molten material and which extends through the third channel of molten material in each heated nozzle to the orifice, characterized in that it comprises a bushing orifice extending to one of the manifolds of distribution of molten material with the first and third channels of molten material extending through the orifice bushing and one of the aforementioned manifolds of molten material distribution, valve means mounted in the orifice bushing and activation means to activate the valve means between open positions Closed and closed to control the flow of molten material through the first channel of molten material in each heated nozzle in accordance with a predetermined cycle

Description

MOLDING APPARATUS BY INJECTION WITH INJECTION HOLE FOR MOLDING OF MULTIPLE LAYERS BACKGROUND OF THE INVENTION This invention relates generally to an injection molding apparatus with injection orifice for five layer molding, and more particularly to said apparatus having two passages of molten material extending from a source of common molten material to one of the passages of molten material having a control valve to control the flow of molten material to a central molten material channel in each heated nozzle. Multiple cavity injection molding apparatuses are known for making five-layer protective containers for food or preforms for beverage bottles. Two layers of a barrier material such as ethylene-vinyl alcohol copolymer (EVOH) or nylon are molded between two outer layers and a core layer of a material of the polyethylene terephthalate (PET) type. For example, the patent of E.U.A. No. 4,717,324 by Schad et al., Issued January 5, 1988, shows an apparatus for sequentially injecting first the PET, then the barrier material, and finally the PET again through two channels of different molten material. While this is satisfactory for some applications, sequential molding has the disadvantage of a relatively long cycle time. As seen in the patents of E.U.A. Us. 4,990,301 by Krishnakumar et al., Issued on February 5, 1991, 5,131,830 by Orimoto et al., Issued July 21, 1992, and 5,141,695 by Nakamura, issued on August 25, 1992, injection molding devices are also known for simultaneously injecting multi-layered products, but these apparatuses have the disadvantage of requiring a separate source of molten material and a separate valve for each passage of molten material.

BRIEF DESCRIPTION OF THE INVENTION Accordingly, an object of the present invention is to overcome at least partially the disadvantages of the prior art, by providing a multiple cavity injection molding apparatus for five layer molding, having only two sources of molten material and only one control valve. For this purpose, in one of its aspects, the invention provides an injection molding apparatus with multiple cavity injection hole for five layer molding having one or more manifolds of distribution of molten material with a front face and a plurality of heated nozzles mounted in a mold. Each heated nozzle has a rear end that bears against the manifold for distributing molten material and a front end adjacent an orifice leading to a cavity in the mold. Each heated nozzle has first, second and third channels of molten material that extend therethrough from the trailing end to the front end. A first passage of molten material for transporting molten material from a first source of molten material branches in the molten material distribution manifold and extends through the first channel of molten material in each heated nozzle to the orifice. A second passage of molten material for transporting molten material from a second source of molten material branches into the molten material distribution manifold and extends through the second channel of molten material in each heated nozzle to the orifice. A third passage of molten material for transporting molten material from the first source of molten material branches into the molten material distribution manifold and extends through the third channel of molten material in each heated nozzle to the orifice. The first passage of molten material has a valve in the same upstream of the branch to control the flow of the molten material towards the first channel of molten material in each heated nozzle in accordance with a predetermined cycle. In another of its aspects, the invention provides a method for continuously molding five-layer products in a multi-cavity injection molding apparatus having a melt distribution manifold and a plurality of heated nozzles mounted in a mold. Each heated nozzle has a rear end that abuts against the manifold of distribution of molten material, and a front end adjacent to a hole leading to a cavity in the mold. Each heated nozzle has a central molten material channel extending therethrough from the trailing end to the front end, a channel of inner annular molten material extending around the center molten material channel to the front end and a channel of outer annular fused material extending around the inner annular fused material channel to the front end. A first passage of molten material extending from a common inlet in the molten material distribution manifold and having valve means activated therein, branches into the molten material distribution manifold and extends through the manifold channel. central molten material in each nozzle heated up to the hole. A second passage of molten material branches into the melt distribution manifold and extends through the inner annular melt channel in each heated nozzle to the orifice. A third passage of molten material that also extends from the common inlet in the molten material distribution manifold branches into the molten material distribution manifold, and extends through the outer annular molten material channel in each heated nozzle to the hole. The method comprises the steps, the valve means being in the first passage of molten material in the closed position, of injecting a first molten material from a first source of molten material through the common inlet, to the first and third passages of material melted, by means of which the first molten material flows in the third passage of molten material through the outer annular channel in each heated nozzle and the orifice aligned in the cavities. After a predetermined amount of the first molten material has been injected into the cavities, simultaneously inject a second molten material from a second source of molten material into the cavities through the second passage of molten material, whereby the second material of molten material flows through the interior annular molten material channel in each heated nozzle and the aligned orifice, and separates the first molten material flowing from the outer annular channel in each heated nozzle to form two outer layers of the first material in each of the cavities. Then, after the flow of the second molten material into the cavities has been established, the activation of the valve means in the first passage of molten material to the open position simultaneously injects the first molten material of the first source of molten material. in the cavities through the first passage of molten material, by means of which the first molten material flows through the central molten material channel in each heated nozzle and the aligned craft, and separates the second molten material flowing from the channel inner annular in each heated nozzle to form a central layer of the first material between two intermediate layers of the second material in each of the cavities. When the cavities are almost full, the injection of the second material through the second passage of molten material is discontinued, while the injection of the first material continues until the cavities are filled. After a period of cooling, the mold opens to eject the molded products. Finally, the mold closes after ejecting the molded products.

Other objects and advantages of the invention will become apparent from the following description, considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view of a portion of the multiple cavity injection molding apparatus for five layer molding in accordance with one embodiment of the invention; Figures 2 to 5 are sectional views of a portion of Figure 1 showing the injection sequence of a five-layer preform; and Figure 6 is a sectional view of a portion of a multiple cavity injection molding apparatus for five layer molding according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION First reference is made to Figure 1, which shows a portion of the injection molding apparatus with multiple cavity injection hole for molding five layer preforms or other products by a combination of sequential and simultaneous co-injection. Several heated nozzles 10 are mounted in a mold 12 with a rear end 14 leaning against the front face 16 of a front steel manifold for distributing molten material 18. While the mold may have a larger number of plates, depending on the application In this case, only a nozzle retainer plate 20, a manifold retainer plate 22 and a cylinder plate 24 secured together by bolts 26, as well as a cavity retainer plate 28, are shown for illustrative purposes. front 30 of each heated nozzle 10 is aligned with a hole 32 that extends through a cooled orifice insert 34 to a cavity 36. This cavity 36 for manufacturing beverage bottle preforms extends between a cavity insert 38 and the mold core 40 in a conventional manner. Each nozzle 10 is heated, preferably by an integral electrical heating element 42 having a terminal 44. Each heated nozzle 10 is seated in an opening 46 in the nozzle retainer plate 20, a rear collar portion 48 of each nozzle being received. heated 10 in a circular locating seat 50 which extends around the opening 46. This provides an insulating air space 52 between the heated nozzle 10 and the surrounding mold 12, which is cooled by pumping cooling water through cooling ducts. 54. Each heated nozzle 10 has a central molten material channel 56 extending from its rear end 14 to its front end 30. In the configuration shown, each heated nozzle 10 has an insert portion 58 which is secured in a seat 60. by a threaded nozzle seal 61 that is screwed into place and forms the front end end 30 of the nozzle 10. As can be seen, the insertion portion 50 is made of several pieces 62 that fit together to form the central molten material channel, an inner annular melt channel 64 extending around the molten material channel. central 56 to the front end 30, and an outer annular melt channel 66 extending around the inner annular melt channel 64 and the central molten material channel 56 to the front end 30. In this configuration, the heated nozzle 10 has a single molten material hole 68 extending from its rear end 14 to connect to the inner annular melt channel 64. A separate hole circle 70 is open at the rear end 14 of the heated nozzle 10 around the hole of molten material 68 to provide thermal separation for the molten material flowing through the molten material bore 68. The configuration The ion shown also has four separate molten holes 72 extending from the rear end 14 of the heated nozzle 10., up to the outer annular melt channel 66. The front manifold for distributing molten material 18 is heated by an electric heating element 74. It is preferably located by a central locating ring 76 and screws 78 that extend into each heated nozzle. 10 to have an insulating air space 80 extending therebetween and the surrounding cooled mold 12. A rear steel manifold for distributing molten material 82 is mounted to the mold 12 by several insulating and elastic spacers 84 extending between the same and the cylinder plate 24 to extend parallel to the front distribution manifold of molten material 18. As can be seen, the two manifolds 18, 82 are separated by heat insulating molten material transfer bushings 86 positioned therebetween. As described in more detail below, the subsequent manifold for distributing molten material 82 is heated by an integral electric heating element 88 to a lower operating temperature than the front manifold for distributing molten material 18, and the air space 9Q provided by thermal insulator bushes of molten material transfer 86 between the two manifolds 18, 82 provides thermal separation therebetween. A first passage of molten material 92 and a third passage of molten material 94 extend from a common inlet 96 through a multiple cylindrical extension or orifice bushing 98, and both branch into the front manifold of molten material distribution 18. , and, in this configuration, they extend through a molten material division bushing 100 seated on the front face 16 of the molten material distribution front manifold 18 in alignment with each heated nozzle 10. The molten material division bushing 100 is made of three steel layers integrally welded together as described in co-pending Canadian application No. 2,219,054, entitled "Injection Molding Apparatus Having Melt Dividing Bushings", presented concurrently with the present. In this configuration, the first passage of molten material 92 extends through an L-shaped conduit 102 in the molten material dividing bushing 100 in alignment with the central molten material channel 56 through each heated nozzle 10 and the third passage of molten material 94 branches into the melt-splitting bushing 100 to four holes 104, each aligned with one of the four holes of molten material 72 extending from the rear end 14 of each heated nozzle 10 to the outer annular melt channel 66. In this configuration, each melt transfer thermal insulating bushing 86 has an elongated rod portion 106 extending forwardly from a rear head portion 107 through a hole 108 in the front manifold of distribution of molten material 18 and an eccentric hole 110 in molten material division bushing 100. A second passage of m molten material 112 extends from a second inlet 114 and branches into the subsequent molten material distribution manifold 82 to extend through a central hole 116 in each molten material transfer bushing 86 to the aligned molten material bore 68 that extends from the rear end 14 of each heated nozzle 10 to the inner annular melt channel 64. According to the invention, a control valve 118 is mounted in the first passage of molten material 92 in the cylindrical extension or bushing orifice 98 leading to the front distribution manifold of molten material 18. A hinge 120 extending from the control valve 118 is attached to a connecting rod 122 which extends from a piston 124 in a die cylinder 126 on the plate cylinder 24. Piston 124 is driven by pneumatic pressure applied through inlets 128130 to drive the control valve 118 between open and closed positions in accordance with a predetermined cycle. In fact, in other embodiments, the control valve 118 can be operated in any of the techniques known in the art, for example, hydraulically activated rather than pneumatically activated, or other types of valves can be used. During use, the injection molding system is assembled as shown in Figure 1, and functions to form five layer preforms or other products with two layers of barrier material alternating between three layers of a material of the terephthalate type of polyethylene (PET) as indicated below. The barrier material is a material such as ethylene-vinyl alcohol copolymer (EVOH) or nylon. First, electric power is applied to the heating element 74 in the front distribution manifold of molten material 18 and the heating elements 42 in the heated nozzles 10 to heat them to an operating temperature in which the material is injected into the first and third passages of molten material 92, 94, which is preferably PET that requires an operating temperature of about 296.1 ° C. Electric power is also applied to the heating element 88 in the subsequent melt distribution manifold 82 to heat it to an operating temperature of the material to be injected into the second passage of molten material 112 of about 204.4 ° C. Water is applied to the cooling ducts 54 to cool the molds 12 and the orifice inserts 34. Hot melted material is then injected under pressure into the common inlet 96 in the front manifold of molten material distribution 18 and the second inlet 114 in the subsequent distribution manifold of molten material 82 in accordance with a predetermined injection cycle. Reference is now also made to Figures 2 to 5 to describe the operation sequence of the injection cycle. First, pneumatic pressure is applied to the cylinder 126 to rotate the control valve 118 to the closed position. A molten material subjected to pressure, such as a material of the type of polyethylene terephthalate (PET) is injected through the common inlet 96 into the cylindrical extension or orifice bushing 98 of the molten material distribution front manifold 18 by a cylinder of injection (not shown). With the control valve 118 in the first passage of molten material 92 in the closed position, the molten material flows through the third passage of molten material 94 which branches into the front manifold of the molten material 18 and extends through the molten material. the outer annular melt channels 66 in each heated nozzle 10 to the aligned orifice 32 leading to a cavity 36. After a predetermined amount of PET has been injected into the cavity 36, and while the PET continues to be injected through of the outer annular melt channel 66, another melt material subjected to pressure which is a barrier material, such as ethylene-vinyl alcohol copolymer (EVOH) or nylon, is co-injected by another injection cylinder (not shown) through the second inlet 114, and flows through to the second passage of molten material 112 which branches into the subsequent distribution manifold of molten material 82. and extends through the inner annular melt channel 64 in each heated nozzle 10 to the aligned orifice 32 leading to the cavity 36. As seen in Figure 3, the flow of the barrier material separates the PET flow in two outer layers 132. After the simultaneous flow of PET through the outer annular melt channels 66 and the barrier material through the inner melt channels 64 is reversed, the pneumatic pressure is reversed to the cylinder 126 for rotating the control valve 118 to the open position. Then, the pressurized PET also flows through the first passage of molten material 92 which branches into the front manifold of molten material distribution 18 and extends through the central melt channel 56 in each heated nozzle 10 to the aligned hole 32 and in the cavity 36. As seen in Figure 4, this flow of PET through the first passage of molten material 92, in turn separates the flow of the barrier material into two intermediate layers 134 of the barrier material on both sides of a central PET layer 136. When the cavities 36 are almost full, the pneumatic pressure is reversed back to the cylinder 126 to rotate the control valve 118 back to the closed position. This closes the PET flow through the central molten material channel 56, thereby terminating the flow separation of the barrier material and allowing it to establish a continuous sealed flow. Then, the injection pressure of the barrier material is released to stop its flow through the inner annular melt channels 76 in the heated nozzles 10, and another small amount of PET is injected to complete the filling of the cavities 36. The injection pressure of the PET is then released and, after a short cooling period, the mold 12 is opened for ejection. After ejection, the mold 12 is closed and the cycle repeats continuously every 15 to 30 seconds, with a frequency that depends on the wall thickness and the number and size of cavities 36 and the exact materials being molded. Thus, as can be seen, the provision of the control valve 118 mounted on the first passage of molten material 92 before it branches into the front manifold of molten material distribution 18 allows separate control of the flow of molten material through of each of the three passages of molten material during the injection cycle. Reference is now made to Figure 6, which shows the injection molding apparatus according to another embodiment of the invention for molding five-layer preforms or other products by a combination of sequential and simultaneous co-injection. Although many of the elements are the same or similar to those described above, not all the elements common to both modalities are described again and those that are described again have the same reference numbers as before. In this case, the subsequent manifold of distribution of molten material 82 more than the front manifold of distribution of molten material 18 has the manifold extension or orifice bushing 98. Thus, the first and third passages of molten material 92, 94 which extending from the common inlet 96 in the manifold extension or orifice bushing 98 extend through the subsequent manifold of molten material distribution 82 more than the manifold front distribution of molten material 18. In addition, the second passage of molten material 112 extends from the second inlet 114 through the front manifold of molten material distribution 18 more than the subsequent manifold of distribution of molten material 82. As can be seen, a splitting and transfer of molten material bushing 138 is seated behind each heated nozzle 10 in a cylindrical opening 140 through the front distribution manifold of molten material 18, where its rear end 142 bears against the rear distribution manifold. of molten material 82. The first passage of molten material 92 branches into the subsequent molten material distribution manifold 82, and extends through an eccentric hole 114 extending through each molten material dividing and transferring bushing. 138 in alignment with the central molten material channel 56 in the adjacent heated nozzle 10. The split and molten material transfer bushing 138 is made of two steel layers integrally welded together, and the third passage of molten material 94 of the manifold Subsection of distribution of molten material 82 branches into the splitting hub and transfer of material 138 is disposed from a single inlet 146 at its rear end 142 to four separate outlets 148 at its front end 150. A small spike 152 extends from the split and molten material transfer hub 138 outward in the front manifold material distribution casting 18, for locating the splitting bushing and melt transfer 138 with the four separate outlets 148 in alignment with the four holes of molten material 72 extending from the rear end 14 of the heated nozzle 10, to the material channel outer annular die 66. From the second passage of molten material 112 which branches into the molten material distribution front manifold 118, it extends through the individual molten material bore 68 extending from the rear end 14 of the heated nozzle 10. , up to the internal annular melt channel 64. The operation of this embodiment of the invention is the same to that described above, and does not need to be repeated. While the description of injection molding apparatus with injection hole for five layer molding has been given with respect to preferred embodiments, it will be apparent that various modifications are possible without departing from the scope of the invention, as understood by the inventors. skilled in the art and as defined in the following claims. For example, other materials having suitable characteristics may be used, more than PET, EVOH and nylon.

The embodiments of the invention, in which a unique property or privilege is claimed, are defined as follows:

Claims (24)

NOVELTY OF THE INVENTION CLAIMS

1. - An injection molding apparatus with multiple cavity injection orifice having a plurality of molten material distribution manifolds and a plurality of heated nozzles mounted in a mold, each heated nozzle having a rear end that abuts against one of the manifolds of distribution of molten material and a front end adjacent an orifice leading to a cavity in the mold, each heated nozzle having first, second and third channels of molten material extending therethrough from the trailing end to the front end, a first passage of molten material for transporting molten material from a first source of molten material which branches into one of the manifolds of distribution of molten material and which extends through the first channel of molten material in each heated nozzle to the hole, a second passage of molten material to transport molten material or from a second source of molten material that branches into one of the manifolds of distribution of molten material and that extends through the second channel of molten material in each heated nozzle to the orifice, and a third passage of molten material to transport molten material from the first source of molten material which branches into one of the manifolds of distribution of molten material and which extends through the third channel of molten material in each heated nozzle to the orifice, characterized in that it comprises; an orifice bushing extending to one of the manifolds of distribution of molten material with the first and third channels of molten material that extend through the orifice bushing and one of the aforementioned manifolds of molten material distribution, means of valve mounted in the orifice bushing and activation means for activating the valve means between open and closed positions to control the flow of the molten material through the first channel of molten material in each heated nozzle in accordance with a predetermined cycle.

2. The injection molding apparatus according to claim 1, further characterized in that the first channel of molten material through each heated nozzle is a channel of central molten material, the second channel of molten material through each nozzle. heated includes an inner annular melt channel extending around the central molten material channel to the front end, and the third molten material channel through each heated nozzle includes an outer annular molten material channel extending around the channel of inner annular fused material to the front end.

3. The injection molding apparatus according to claim 2, further characterized in that the molten material of the first source is polyethylene terephthalate (PET).

4. The injection molding apparatus according to claim 3, further characterized in that the molten material of the second source is ethylene-vinyl alcohol copolymer (EVOH).

5. The injection molding apparatus according to claim 3, further characterized in that the molten material of the second source is nylon.

6. The injection molding apparatus according to claim 2, further characterized in that the first and third passages of molten material of the first source of molten material are branched into a front manifold of distribution of molten material mounted on the mold and the second passage of molten material from the second source of molten material branches into a subsequent manifold of distribution of molten material mounted in the mold.

7. The injection molding apparatus according to claim 6, further characterized in that the first and third passages of molten material extend from a common entry in the orifice bushing.

8. The injection molding apparatus according to claim 7, further characterized in that the front manifold of molten material distribution extends substantially parallel to, and is separated by a predetermined distance from the subsequent manifold of molten material distribution, and the second passage of molten material from the second source of molten material is branched in the subsequent manifold of distribution of molten material and then extends through holes of molten material in the front manifold of distribution of molten material.

9. The injection molding apparatus according to claim 8, further characterized in that each heated nozzle has at least one hole of molten material extending from the rear end to the interior annular molten material channel and at least a hole of molten material extending from the trailing end to the channel of outer annular melt material, wherein the second passage of molten material of the second source of molten material branches into the subsequent manifold of molten material distribution, and extends through the holes of molten material in the front manifold of molten material distribution which extends through at least one hole of molten material extending from the trailing end to the channel of inner annular molten material at each heated nozzle.

10. The injection molding apparatus according to claim 9, further characterized in that the third passage of molten material that branches into the front manifold of molten material distribution extends through at least one hole of molten material extending from the trailing end to the channel of outer annular fused material in each heated nozzle.

11. The injection molding apparatus according to claim 10, further characterized in that the valve means comprises a control valve mounted in the first passage of molten material in the orifice bushing with activation mechanism to drive the valve of control between open and closed positions in accordance with the predetermined cycle.

12. The injection molding apparatus according to claim 2, further characterized in that the first and third passages of molten material of the first source of molten material are branched into a subsequent manifold of distribution of molten material mounted in the mold, and the second passage of molten material from the second source of molten material branches into a front manifold of distribution of molten material mounted in the mold.

13. The injection molding apparatus according to claim 12, further characterized in that the first and third passages of molten material extend from a common entry in the orifice bushing.

14. The injection molding apparatus according to claim 13, further characterized in that the front manifold of molten material distribution extends substantially parallel to and is separated by a predetermined distance from the rear manifold of molten material distribution and the first and third passages of molten material from the first source of molten material branches into the subsequent manifold of molten material distribution and then extends through holes of molten material in the front manifold of molten material distribution.

15. The injection molding apparatus according to claim 14, further characterized in that each heated nozzle has at least one hole of molten material extending from the trailing end to the interior annular molten material channel and at least a hole of molten material extending from the trailing end to the outer annular melt channel, wherein the second passage of molten material from the second source of molten material branching into the front manifold of molten material distribution extends through at least one hole of molten material extending from the trailing end to the inner annular melt channel in each heated nozzle.

16. The injection molding apparatus according to claim 15, further characterized in that the third passage of molten material which branches into the subsequent manifold of molten material distribution and which extends through the holes of molten material in the front manifold of molten material distribution extends through the minus one hole of molten material extending from the trailing end to the channel of outer annular molten material in each heated nozzle.

17. The injection molding apparatus according to claim 16, further characterized in that the valve means comprises a control valve mounted in the first passage of molten material in the orifice bushing with activation mechanism to drive the valve of control between open and closed positions in accordance with the predetermined cycle.

18. A method for continuously molding five-layer products in a multi-cavity injection molding apparatus having at least one manifold for distributing molten material and a plurality of heated nozzles mounted in a mold, each heated nozzle having a rear end that bears against at least one manifold of distribution of molten material and a front end adjacent to an orifice leading to a cavity in the mold, each heated nozzle having a channel of central molten material extending through therein from the rear end to the front end, an inner annular melt channel extending around the central molten material channel to the front end, an outer annular melt channel extending around the annular molten material channel interior to the front end, a first passage of molten material that extends from common entry in at least one melt distribution manifold and having valve means activated therein which branches into at least one molten material distribution manifold and extends through the central melt channel in each nozzle heated to the orifice, a second passage of molten material branching into at least one molten material distribution manifold and extending through the interior annular molten material channel in each heated nozzle to the orifice, and a third passage of molten material also extending from the common inlet into at least one manifold of distribution of molten material which branches into at least one manifold of distribution of molten material and which extends through the channel of annular fused material outside in each mouthpiece heated to the orifice, characterized in that it comprises the steps of: (a) the valve means being in the first passage of molten material in closed position, injecting a first molten material from a first source of molten material through the common inlet, to the first and third passages of molten material, whereby the first molten material flows in the third passage of molten material through the outer annular channel in each heated nozzle and the aligned orifice in the cavities; (b) after a predetermined quantity of the first molten material has been injected into the cavities, simultaneously injecting a second molten material from a second source of molten material into the cavities through the second passage of molten material, by means of which the second molten material flows through the inner annular melt channel in each heated nozzle and the aligned orifice, and separates the first molten material flowing from the outer annular channel in each heated nozzle to form two outer layers of the first material in each one of the cavities; (c) after the flow of the second molten material has been established in the cavities, activating the valve means in the first passage of molten material to the open position to simultaneously inject the first molten material of the first source of molten material into the cavities through the first passage of molten material, by means of which the first molten material flows through the central molten material channel in each heated nozzle and the office aligned and separates the second molten material flowing from the inner annular channel in each heated nozzle to form a central layer of the first material between two intermediate layers of the second material in each of the cavities; (d) the cavities being filled and after a cooling period, opening the mold and ejecting the molded products; and (e) closing the mold after ejecting the molded products.

19. An injection molding method according to claim 18, further characterized in that it comprises the passage when the cavities are almost full of disinfecting the injection of the second material through the second passage of molten material, while the injection of the first material until the cavities are filled.

20. An injection molding method according to claim 19, further characterized in that the first material is polyethylene terephthalate (PET).

21. An injection molding method according to claim 20, further characterized in that the second material is ethylene-vinyl alcohol copolymer (EVOH).

22. An injection molding method according to claim 20, further characterized in that the second material is nylon.

23. An injection molding apparatus comprising a first manifold for distributing molten material mounted in a mold between an orifice bushing and a plurality of heated nozzles, first and third passages of molten material extending through the first manifold for dispensing molten material for transporting a first molten material from a first source of molten material to a plurality of holes and a second passage of molten material for transporting a second molten material from a second source of molten material to said orifices, said bushing orifice having valve means for controlling the flow of said first molten material through one of said first and third passages of molten material.

24. An injection molding apparatus according to claim 23, further characterized in that it comprises a second distribution manifold of molten material through which the second passage of molten material extends. SUMMARY OF THE INVENTION Injection molding apparatus with injection orifice for molding preforms or other products, having two layers of a barrier material such as EVOH or nylon alternating between three layers of another thermal plastic material such as PET; the PET is injected by an injection cylinder in the first and third passages of molten material that branch in a front manifold of distribution of molten material to extend to several heated nozzles; the first passage of molten material extends through a central molten material channel in each heated nozzle, and the third passage of molten material extends through a channel of outer annular molten material surrounding the passage of central molten material to a aligned hole leading to a cavity; the barrier material is injected by another injection cylinder into a second passage of molten material which branches into a subsequent distribution manifold of molten material to extend into a channel of inner annular fused material extending between the passage of central molten material and the outer annular melt channel in each nozzle, heated; an individual control valve mounted on the first passage of molten material before it branches into the front manifold of molten material distribution, allows separate control of the flow of molten material through each of the three passages of molten material during the injection cycle. EAM / rvs / hlp / fch. P98-1116.