MXPA98008713A - Injection molding apparatus that has transfer bushings of bath fused between multip - Google Patents

Abstract

The present invention relates to a multiple-cavity hot-melt injection molding apparatus for multi-layer molding having a front molten bath distribution manifold and a subsequent molten bath distribution manifold mounted in a mold that it extends substantially parallel to each with an insulating air space therebetween, a plurality of heated nozzles, each heated nozzle having a rear end, a front end, a central molten bath channel extending through it from the trailing end to the front end, an annular molten bath channel extending to the front end around the central molten bath channel with first molten bath hole extending from the rear end of the heated nozzle to the annular molten bath channel interior and an annular molten bath channel extending to the front end around the ca The central molten bath channel and the inner annular molten bath channel with at least one second molten bath hole extending from the rear end of the heated nozzle to the outer annular molten bath channel, the heated nozzles being mounted on the mold with the rear end of each heated nozzle spliced against the front molten bath distribution manifold, a first molten bath passage from a first molten bath source branches into the front molten bath distribution manifold and divides again to extending through the central molten bath channel and the at least one second molten bath hole extends from the rear end of the heated nozzle to the outer annular molten bath channel and the outer annular molten bath channel in each heated nozzle to an injection hole adjacent to the front end of the heated nozzle leading to a cavity in the mold, and a second passage of molten bath from a second source of molten bath which branches into the subsequent molten bath distribution manifold and extends through the first molten bath hole and the inner annular molten bath channel in each nozzle heated to the injection port, the enhancement further comprising: a plurality of molten bath transfer bushings, each molten bath transparency bushing having a rear end, a front end and a central molten bath hole extending through them from the trailing end to the front end, each molten bath transfer bushing being in a position to extend from the subsequent molten bath distribution manifold forward through the insulating air gap between the manifold manifold of the molten back bath and the distribution manifold of the front molten bath and inside a hole that extends through the front cast bath distribution manifold to the first molten bath hole extending from the rear end of one of the heated nozzles to the inner annular fused bath channel, whereby the central hole through each molten bath transfer bushing forms a part of the second bath passage

Description

INJECTION MOLDING APPARATUS THAT HAS TRANSFER BUBBLES CASED BETWEEN MULTIPLE BACKGROUND OF THE INVENTION This invention relates generally to multi-layer injection molding apparatus and more particularly to such apparatus having molten bath transfer bushes extending from a subsequent molten bath distribution manifold through an insulating air gap in holes. that extend through a distribution manifold of front molten bath. Injection molding apparatuses are well known for making multi-layer protective containers for food or preforms for beverage bottles. Commonly the inner and outer layers are made of a polyethylene terephthalate type material (PET) with one or more barrier layers made of a material such as ethylene-vinyl alcohol copolymer (EVOH) or nylon. In some multi-cavity apparatuses, the two different molten baths are distributed through a single molten bath distribution manifold having different passages. However, preferably for materials such as those having different injection temperatures of about 296 and 204 ° C respectively, the two molten baths are distributed through two different molten bath distribution manifolds. In some cases, the two molten baths are injected sequentially, while in other cases both co-injection and sequential injection are used. The two materials are injected through heated nozzles, each with a central molten bath channel and one or more annular molten bath channels that extend around the central molten bath channel to an injection orifice leading to the cavity. As seen in the patent of E.U.A. Do not. ,223,275 to Gellert, which was issued on June 29, 1993, it is also known to separate the distribution manifolds of the front and rear molten bath by an insulating air gap, the molten bath flowing from the subsequent molten bath distribution manifold flowing. through a flat spacer washer mounted between the two manifolds. Although this is suitable for some applications, it has the disadvantage that there is not sufficient thermal separation between the front molten bath distribution manifold and the molten bath that comes from the subsequent molten bath distribution manifold flowing therethrough.

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 multi-layered injection molding apparatus having molten bath transfer bushings extending forward from the manifold manifold. rear molten bath in holes extending through the front molten bath distribution manifold. Up to this point, in one of its aspects, the invention provides a multi-cavity hot channel injection molding apparatus for multi-layer molding having a front molten bath distribution manifold and a subsequent molten bath distribution manifold. mounted in a mold extending substantially parallel to each with an insulating air gap therebetween. There are a number of heated nozzles, each with a rear end, a front end and a central molten bath channel extending therethrough from the trailing end to the front end. Each heated nozzle has an inner annular fused bath channel extending to the front end around the central molten bath channel with molten bath hole extending from the rear end of the heated nozzle to the inner annular fused bath channel. It also has an outer annular fused bath channel extending to the front end around the central molten bath channel and the inner annular molten bath channel, with one or more molten bath holes extending from the rear end of the heated nozzle to the outer annular fused bath channel. The heated nozzles are mounted in the mold with the rear end of each heated nozzle abutting against the front molten bath distribution manifold. A first molten bath passage from a first molten bath source branches into the front molten bath distribution manifold and divides again to extend through the central molten bath channel and the one or more molten bath holes that are fused. extend from the rear end of the heated nozzle to the outer annular fused bath channel, and the outer annular fused bath channel in each heated nozzle to an injection orifice adjacent the front end of the heated nozzle leading to a cavity in the mold. A second molten bath passage from a second molten bath source branches into the subsequent molten bath distribution manifold and extends through the first molten bath hole and the inner annular molten bath channel in each nozzle heated to the injection hole. There are a number of molten bath transfer bushings, each with a rear end, a front end and a central molten bath hole extending therethrough from the trailing end to the front end. Each molten bath transfer bushing is mounted in a position to extend from the rear molten bath distribution manifold forward through the insulating air gap between the subsequent molten bath distribution manifold and the bath manifold and into a hole extending through the front molten bath distribution manifold to the first molten bath hole extending from the rear end - from one of the heated nozzles to the inner annular fused bath channel. In this way, the central hole through each molten bath transfer bushing forms a part of the second molten bath passage. In another of its aspects, the invention further provides a multiple-cavity hot-runner injection molding apparatus for multi-layer molding, having a front molten bath distribution manifold and a subsequent molten bath distribution manifold mounted in a mold extending substantially parallel to each with an insulating air gap therebetween. There are a number of heated nozzles, each with a rear end, a front end and a central molten bath channel extending therethrough from the trailing end to the front end. Each heated nozzle has an annular molten bath channel extending around the central molten bath channel to the front end, with one or more molten bath holes extending from the rear end of the heated nozzle to the annular molten bath channel. The heated nozzles are mounted in the mold with the rear end of each heated nozzle abutting against the front molten bath distribution manifold. A first molten bath passage from a first molten bath source branches in the front molten bath distribution manifold and extends through the one or more molten bath holes and the annular molten bath channel in each heated nozzle to a injection port adjacent the front end of the heated nozzle leading to a cavity in the mold. A second molten bath passage coming from a second molten bath source branches into the subsequent molten bath distribution manifold and extends through the central molten bath channel in each heated nozzle to the injection port. There are a number of molten bath transfer bushings, each with a head portion at the rear end, an elongated rod portion extending from the head portion forward towards a front end and a central hole extending therethrough from the trailing end to the front end. Each molten bath transfer bushing is mounted in alignment with the central molten bath channel of one of the heated nozzles. The head portion extends between the posterior molten bath distribution manifold and the front molten bath distribution manifold to be a spacer that provides the insulating air space therebetween. The elongate rod portion extends from the head portion forward in a hole extending through the front molten bath distribution manifold in alignment with the central molten bath channel through a heated and aligned nozzle. In this manner, the central hole through each molten bath transfer bushing receives an elongated pin extending forward therefrom in the central molten bath channel in the heated and aligned nozzle, the second molten bath passage extending. which comes from the second source of molten bath along the elongated pin. Additional objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a partial sectional view of a portion of a multi-layer injection molding apparatus having molten bath transfer bushings in accordance with one embodiment of the invention, Figure 2 is an isometric view of one of the bushings of molten bath transfer shown in Fig. 1, Fig. 3 is a sectional view showing a molten bath transfer bushing according to another embodiment of the invention, Fig. 4 is a partial sectional view of a portion of an apparatus of multi-layer injection molding having molten bath transfer bushings according to a further embodiment of the invention, Figure 5 is an isometric view of the molten bath transfer bushing shown in Figure 3, Figure 6 is a partial sectional view of a portion of an injection molding apparatus with multi-layer valve having molten bath transfer bushings in accordance with a further embodiment of the present invention, Figure 7 is an isometric view of the molten bath transfer bushing shown in Figure 6, Figure 8 is an elongated sectional view showing the valve pin shown in Figure 5 in the position partially open, Figure 9 is a similar view showing the valve pin in the fully open position, and Figure 10 is a partial sectional view of a portion of a multi-layer injection molding apparatus having molten bath transfer bushings according to a further embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Reference is first made to Figure 1 which shows a portion of an injection molding apparatus with multiple cavity opening for molding three layer preforms or other products by coinjection molding. A number of heated nozzles 10 are mounted in a mold 12 with a rear end 14 abutting against the front face 16 of u? multiple distribution of cast steel frontal bath 18. Although the mold may have a greater number of plates depending on the application, in this case, only a heated nozzle retention plate 20, a manifold retention plate 22 and a back plate 24, secured together by bolts 26, as well as a cavity retention plate 28 to facilitate illustration. The front end 30 of each heated nozzle 10 is aligned with an injection port 32 extending through a cooled injection port insert 34 to a cavity 36. This cavity 36 for manufacturing beverage bottle preforms extends between a cavity insert 38 and a mold center 40 in a conventional manner. Each heated nozzle 10 is heated by an integral electric heating element 42 having a terminal 44. Each heated nozzle 10 is seated in an opening 46 in the nozzle retaining plate 20 with a rear collar portion 48 of each heated nozzle 10. received in a circular locating seat 50 extending 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 bath channel 56 extending from its rear end 14 to its front end 30. Each heated nozzle 10 has an insert portion 58 made of several pieces 60 that fit together to form a channel inner annular fused bath 62 extending around the central molten bath channel 56 to the front end 30 and a channel outer annular fused bath 64 extending around the inner annular fused bath channel 62 and the central molten bath channel 56 to the front end 30. In this configuration, the nozzle heated 10 has a single molten bath bore 66 extending from its rear end 14 to connect to the inner annular melt bath channel 67 and four separate molten bath holes 68 extending from the rear end 14 of the heated nozzle 10 to the outer annular molten bath channel 64. The front molten bath distribution manifold 18 is heated by an integral electrical heating element 70. This is located by a central location ring 72 and screws 74 that extend into each heated nozzle 10 to have an insulating air space 76 extending therebetween and the surrounding cooled mold 12. A rear steel cast bath distribution manifold 78 is mounted in the mold 12 extending parallel to the front cast bath distribution manifold 18 with a number of insulating and elastic spacers 80 extending between it and the back plate 24. As can be observe, the front and rear manifolds 18, 78 are separated by spacers 82 to provide an insulating air space 84 therebetween. As described in more detail below, the rear molten bath distribution manifold 78 is heated by an integral electric heating element 86 to a lower operating temperature than that of the front molten bath distribution manifold 18, and the space of Insulating air 84 between these provides enough thermal separation to allow this difference in temperature to be maintained. A first molten bath passage 88 extends from a central inlet 90 through a cylindrical manifold extension 92 and branches into the front molten bath manifold 18 to extend through a molten bath partition bushing 94 seated on the front face 16 of the front molten bath distribution manifold 18 in alignment with each heated nozzle 10. The molten bath division bushing 94 is made of three steel layers integrally welded as described in the co-pending Canadian application serial number. 2,219,054, entitled "Injection Molding Apparatus Having Melt Dividing Bushings", presented concurrently with the present. In this configuration, the first molten bath passage 88 is divided into the molten bath partition bushing 94 to extend to the central molten bath channel 56 and the four separate molten bath holes 68 that extend to the molten bath channel outer annular 64 in the heated and aligned nozzle 10. An elongated molten bath transfer bushing 96 according to the invention extends from the rear molten bath distribution manifold 78 through the insulating air space 84 and into a hole 98 that extends through the manifold of distribution of front fade bath 18 and each die split bath bushing 94. Although the transfer bushes 96 can be made in one piece, in this embodiment, as best seen in Figure 2 , each molten bath transfer bushing 96 has an elongated cylindrical body portion 100 with a connector bushing 102 extending forwardly therefrom. The elongated body portion 100 has a threaded rear end 104, a front end 106, a central molten bath hole 108 extending therethrough from the rear end 104 to the front end 106, and an integral electric heating element. 110 extending around the central molten bath hole 108. The threaded rear end of the elongated body portion 100 fits into a threaded seat 112 of the rear molten bath distribution manifold 78. The connector bushing 102 also has a rear end threaded 114, a front end 116 and a central molten bath hole 118 extending therethrough, which coincides with the central molten bath hole 108 through the elongate body portion 100 of the molten bath transfer bushing 96 The threaded rear end 114 of the connector bushing 102 fits into a threaded seat 120 at the front end 106 of the elongated body portion. 100, and the front end 116 of the connector bushing 102 fits into a matching seat 121 at the rear end 14 of the heated nozzle 100. This allows the length of the molten bath transfer bushing 96 to be adjusted to match the width of the bushing. air space 84 between the front molten bath distribution manifold 18 and the rear molten bath distribution manifold 78. The diameter of the elongate body portion 100 of the molten bath transfer bushing 96 is sufficiently smaller than the diameter of the molten bath. hole 98 through the front molten bath distribution manifold 18 to provide an insulating air space 124 that extends around the molten bath transfer bushing 96.

A second molten bath passage 126 extends from a second inlet 128 and branches into the rear molten bath distribution manifold 78 to extend through the aligned molten-bath holes 108, 118 through each bath transfer bushing. molten 96 to the aligned molten bath hole 66 extending from the rear end 14 of each heated nozzle 10 to the inner annular molten bath channel 62. Although only a single heated nozzle 10 is shown to simplify the illustration, it is understood that in a typical configuration there will be many heated nozzles 10 (e.g., 32, 48 or 64) seated in the mold 12 to receive molten bath through the two molten bath passages 88, 126, which will have more complex configurations than those shown. During use, the injection molding system is assembled as shown in Figure 1 and operates as follows to create three-layer preforms or other products with a barrier layer of a material such as EVOH or nylon between two layers of a PET type material. Electric power is applied to the heating element 70 in the front molten bath distribution manifold 18 and the heating elements 42 in the heated nozzles 10 to heat them to a temperature of about 296 ° C. Electric power is also applied to the heating element 86 in the rear molten bath distribution manifold 78 and the heating elements 110 in the molten bath transfer manifolds 96 to heat them to an operating temperature of about 204 ° C. Water is applied to the cooling ducts 54 to cool the molds 12 and the injection orifice inserts 34. Pressurized and hot molten bath is then injected into the central inlet 90 of the front molten bath distribution manifold 18 and the second inlet 128. of the rear cast bath distribution manifold 78 according to a predetermined injection cycle. First, an injection cylinder (not shown) injects pressurized molten bath such as a polyethylene terephthalate (PET) type material through the first molten bath passage 88 which is separated in each molten bath partition bushing 94 to extend through of the central molten bath channel 56 and the outer annular fused bath channel 64 of each heated nozzle 10 to the injection port 32. After a small amount of PET has been injected into the cavities 36, another pressurized molten bath which is a suitable barrier material such as ethylene alcohol vinyl copolymer (EVOH) or nylon is then co-injected simultaneously by another injection cylinder (not shown) through the second molten bath passage 126 extending through the insulating air space 84 through the molten bath transfer bushes 96 and through the inner annular fused bath channel 62 of each heated nozzle 10 towards the ori injection chamber 32. When the cavities 36 are almost full, the injection pressure of the barrier material is released, which stops its flow, but the flow of the PET continues until the cavities 36 are completely filled. The injection pressure of the PET is then released and, after a cooling period, the mold is opened for ejection. After ejection, the mold is closed and the cycle is repeated continuously with a frequency that depends on the wall thickness and the number and size of the cavities 36, as well as the exact type of materials being molded. In this way, as can be seen, in addition to transporting the barrier material through the insulating air space 84 between the two manifolds 18, 78, the molten bath transfer bushes 96 provide thermal separation for the barrier and heat material. additional control if the barrier material is nylon while flowing through the front molten bath distribution manifold 18, which is at a higher temperature. Reference is now made to Figure 3 which shows an injection molding apparatus according to another embodiment of the invention. As many of the elements of the different modalities are the same as those described above, not all common elements are described again and those that are described again have the same reference numbers as before. In this case, the rear end 104 of the elongate body portion 100 of each molten bath transfer bushing 96 is not threaded. Instead, the molten bath transfer bushing 96 is secured to the rear molten bath distribution manifold 78 by screws 130 which extend in the rear molten bath distribution manifold 78 through holes 132 in a portion of flange 134 of elongate body portion 100. Otherwise, the structure and use of molten bath transfer bushings 96 are the same as those described above and do not need to be repeated. . Reference is now made to Figures 4 and 5 which show injection molding apparatuses according to a further embodiment of the invention. In this case, each molten bath transfer bushing 96 has a central molten bath hole 136 that extends through a rear head portion 138 and an elongated rod portion 140 that extends forward from the head portion. rear 138. The head portion 138 of each molten bath transfer bushing 96 forms a spacer to provide the insulating air space 84 between the front and rear molten bath distribution manifolds 18, 78. The elongated rod portion 140 is extends forward through the hole 98 through the front molten bath distribution manifold 18 in contact with the rear end 14 of the heated and aligned nozzle 10. Although the molten bath transfer bushing 96 may be made in one piece, in the embodiment shown the elongate rod portion 140 has a threaded rear end 142 which is screwed into a threaded seat 144 in the head portion. at 138. This allows the elongated rod portion 140 to be made of a wear resistant steel and the rear head portion 138 to be made of a less thermally conductive titanium alloy. As can be seen, the rear head portion 138 has a number of concentric grooves 146 on both the front and rear faces 148, 150 to reduce thermal conduction from the front faucet distribution manifold 18 to the molten bath distribution manifold. posterior 78 of lower temperature. The elongated rod portion 140 has a smaller outer diameter portion 152 that extends between two larger outer diameter portions 154 at its ends, which forms the insulating air space 124 around the molten bath transfer bushing 96 while extends through the hole 98 in the front molten bath distribution manifold 18. As mentioned above, this insulating air space 124 provides thermal separation for the barrier material as it flows through the front molten bath distribution manifold. 18 which is at a higher temperature.

Reference is now made to Figures 6 to 9 which show an injection molding apparatus according to a different embodiment of the invention for molding three-layer preforms or other products by simultaneous molding or co-injection. In this case, the apparatus has injection orifice valves 32 provided by elongated valve pins 156 that extend through the central hole 136 through each molten bath transfer bushing 96 and the aligned central molten bath channel 156 in each heated nozzle 10. Each valve pin 156 has a front end 158 and a rear end or head 159. As best seen in FIGS. 8 and 9, each valve pin 156 has a central hole 160 that extends rearward from its front end 158 to four side molten bath holes 161 that extend diagonally outwardly toward the outer surface 162 of the valve pin 156. In this embodiment, each valve pin 156 has a reduced diameter portion 163 that fits in a reduced diameter portion 134 of the central molten bath channel 56 through the heated nozzle 10. The reduced diameter portion 163 d the valve pin 156 is longer than the reduced diameter portion 164 of the central molten bath channel 56 which thus forms a space 165 around the reduced diameter portion 163 of the valve pin 156. As described below, the elongate valve pins 156 are reciprocally moved by means of a hydraulic actuating mechanism 166 according to a predetermined cycle between three different positions. In this embodiment, each molten bath transfer bushing 96 also has a cylindrical neck portion 167 that extends rearwardly in an opening 168 through the rear molten bath distribution manifold 78, and the central hole 136 extends through of this posterior neck portion 167 also. As can be seen in this embodiment, the insert portion 58 of each heated nozzle guide 10 only forms a single annular molten bath channel 169 that extends around the central molten bath channel 56 with four separate molten bath holes 170 extending backwardly. from the annular molten bath channel 169 to the rear end 14 of the heated nozzle 10. The first cast bath passage 88 for the PET is divided into the molten bath partition bushing 94 to extend to the four molten bath holes 170 which lead to the annular fused bath channel 169 in the heated and aligned nozzle 10. The second fused bath passage 126 for the barrier material branches into the rear molten bath distribution manifold 78 and extends through a passage 172 L-shaped drilled in the head portion 138 of each molten bath transfer bushing 96 to a longitudinal slot 174 machined to extend a predetermined distance backwardly on the valve pin 156 from the space 165 around the reduced diameter portion 163 of the valve pin 156. In other embodiments, the slot 174 may extend helically about the valve pin 156, or the pin valve 156 may be small enough to allow the barrier material to flow therethrough. However, in view of the relatively low volume and low viscosity of the barrier material, it is preferable to flow it through the slot 174. The valve pin 156 fits into the central hole 136 of the molten bath transfer bushing 96. tight enough to prevent leakage of molten bath by reciprocally moving the elongate valve pin 156. Each molten bath transfer bushing 96 is retained in proper alignment by a small pin 176 extending therebetween and the manifold manifold. Frontal molten bath 18. The portion of insert 58 of each heated nozzle 10 also has an annular insulating air space 178 which extends between the central molten bath channel 56 and the surrounding annular fused bath channel 168 to provide some thermal separation therebetween. Additional thermal separation is provided around the central molten bath channel 56 by means of a circle of separate holes 180 drilled in the rear end 14 of each heated nozzle 10. Combined with the insulating air space 124 around the stem portion 140 of each molten bath transfer bushing 96, this provides a continuous thermal separation for the barrier material as it flows through the upper temperature molten bath distribution manifold 18 and the heated nozzles 10. The front surface 148 of the head portion 138 of each bushing molten bath transfer 96 has an outer rib 182 that forms an insulating air space 184 between the head portion 138 and the front molten bath distribution manifold 18 to provide thermal separation between the front and rear molten bath distribution manifolds 18 , 78. The rear end or head 159 of the valve pin 156 is connected to a front piston 186 seated in a cylinder 188 in the rear plate or cylinder 24. The activation mechanism 166 also includes a rear piston 190, and both pistons 186, 190 are driven by controlled hydraulic pressure applied through ducts 192 to reciprocally move the valve actuator 156 between three different positions. Although the hydraulic activation mechanisms 166 are shown to simplify the illustration, other types of activation mechanisms such as electromechanical mechanisms may of course be used for other applications.

During use, each valve pin 156 is initially retracted only far enough to a first partially open position to allow the PET to flow through the annular molten bath channel 169. In this embodiment, there is a double blockage of the flow of the barrier in this intermediate position. As seen in Figure 8, the side molten bath holes 161 in the valve pin 156 are very forward to connect with the space 165 around the reduced diameter portion 163 of the valve pin 156. Furthermore, as In Figure 6, the longitudinal or helical groove 174 in the valve pin 156 does not extend far enough backward to connect to the L-shaped passage 172 in the molten bath transfer bushing 96 in this position. In other embodiments, it may only be necessary to use one or the other of these ways of blocking the flow of the barrier material. Subsequently, each valve pin 156 is further retracted to a second position or open position shown in Figure 9. In this position, the side molten bath holes 161 in the valve pin 156 are connected to the space 165 around the portion of reduced diameter 163 of each valve pin 156 and longitudinal slot 174 in the valve pin 156 is connected to the L-shaped passage 172 in the melt bath transfer bushing 96, which allows the barrier material flow through the molten bath passage 126 in the cavities 36. As mentioned above, the central location of the hole 160 in the front end 158 of the valve pin 156 and the relatively small size of the slot 174 and the central hole 160 is They combine with the relatively low volume and low viscosity of the barrier material to ensure that the flow of the barrier material is reliable to provide a reliable Even and very thin material of barrier material that is quite expensive. As seen in Figure 9, the barrier material flowing simultaneously with the PET separates the PET flow in two and provides a central layer 194 of the barrier material between two outer layers 196 of PET. When the cavities 36 are almost full, the front end of each valve member 156 is returned to the first position by closing the flow of the barrier material through the central hole 160. The flow of PET through the annular molten bath channel 169 it continues until the cavities 36 are completely full. Each valve pin 156 is then urged to the third or fourth closed position where its front end 158 is seated in the injection hole 32 tied with the cavity 36. After a short cooling period, the mold is opened for ejection . After ejection, the mold is closed and the cycle repeated continuously every 15 to 30 seconds with a frequency that depends on the wall thickness and number and size of the cavities 36 and the exact materials being molded. Reference is now made to Figure 10 which shows an injection molding apparatus according to another embodiment of the invention. In this case, each molten bath transfer bushing 96 again has the central hole 136 extending through an elongated rod portion 140 and a rear head portion 138 that forms a separator between the two melt bath distribution manifolds. 18, 78. An elongated pin 198 is fixed in place with its head 200 seated on the rear face 202 of the head portion 138 of each molten bath transfer bushing 96 and its partially tapered front end 204 adjacent to and in alignment with one of the injection holes 32. Although not seen in Figure 10 due to the scale of the pattern, the elongated pin has a central hole 160 extending to its front end 204 and side holes 161 equal to those seen in FIG. Figure 9. During each cycle, PET is first injected through the first molten bath passage 88 and flows through the annular molten bath channel 168 in each heated nozzle 10 to the injection orifices 32 leading to the cavities 36. Just after the start of the injection PET, a predetermined amount of the less viscous barrier material is then injected simultaneously through the second molten bath passage 126 which forms a central layer 194 of the barrier material between two outer layers of PET 196. When the cavities 36 are almost full, the injection pressure of the barrier material is released by stopping its flow, and the PET injection is continued to completely fill the cavities 36. The injection pressure of the PET is then released and, after a short period of quenching, the mold is open for expulsion. After ejection, the mold 12 is closed and the cycle is repeated continuously every 15 to 30 seconds with a frequency that depends on the wall thickness and number and size of the cavities 36 and on the exact materials being molded. Although the description of the injection molding apparatus having molten bath transfer bushings extending through the air space 84 between the front and rear manifolds 18, 78 has been given with respect to various embodiments, it will be evident that other different modifications are possible without departing from the scope of the invention as understood by those skilled in the art and defined in the following claims. For example, the description of the invention has been given for an injection molding apparatus for a three layer molding, but it can also be used with injection molding apparatus for five layer molding.

The methods of the invention in which a property or exclusive privilege is claimed are defined below.

Claims (24)

NOVELTY OF THE INVENTION CLAIMS

1. - In an injection molding apparatus of "multi-cavity hot runner for multi-layered molding having a fade-bath faucet manifold manifold and a fade-bath float manifold manifold mounted in a mold extending substantially parallel to each with an insulating air space between them, a plurality of heated nozzles, each heated nozzle has a rear end, a front end, a central molten bath channel extending therethrough from the rear end to the front end, a molten bath channel annular interior extending to the front end around the central molten bath channel with a first molten bath hole extending from the rear end of the heated nozzle to the inner annular molten bath channel and an exterior annular molten bath channel -extending to the front end around the central molten bath channel and the molten bath channel or inner annular with at least a second molten bath hole extending from the rear end of the heated nozzle to the outer annular fused bath channel, the heated nozzles being mounted in the mold with the rear end of each heated nozzle being joined against the front molten bath distribution manifold, a first molten bath passage from a first molten bath source branches into the front molten bath distribution manifold and splits again to extend through the central molten bath channel and the at least one second molten bath hole extends from the rear end of the heated nozzle to the outer annular fused bath channel and the outer annular fused bath channel in each heated nozzle to an injection orifice adjacent to the front end of the molten bath. the heated nozzle leading to a cavity in the mold, and a second passage of molten bath desd a second source of molten bath branching into the subsequent molten bath distribution manifold and extending through the first molten bath hole and the inner annular molten bath channel in each heated nozzle to the injection orifice, the improvement that also comprises; a plurality of molten bath transfer bushings, each molten bath transfer bushing having a trailing end, a front end and a central molten bath hole extending therethrough from the trailing end to the front end, each molten bath transfer bushing being mounted in a position to extend from the rear molten bath distribution manifold forward through the insulating air space between the subsequent molten bath distribution manifold and the front molten bath distribution manifold and in a hole that extends through the distribution manifold of front melt-bath to the first molten bath hole extending from the rear end of one of the heated nozzles to the inner annular fused bath channel, whereby the central hole through each molten bath transfer bushing forms a part of the second molten bath passage.

2. - An injection molding apparatus according to claim 1, further characterized in that each molten bath transfer bushing extends through the hole through the front molten bath distribution manifold in sealing contact with the rear end of the molten bath. said one of the heated nozzles.

3. An injection molding apparatus according to claim 2, further characterized in that there is an insulating air gap between each molten bath transfer bushing and the surrounding front molten bath distribution manifold.

4. An injection molding apparatus according to claim 3, further characterized in that each molten bath transfer bushing has an integral electrical heating element, the electric heating element has a helical portion extending around at least part of the central molten bath hole extending through the bushing transfer of molten bath.

5. An injection molding apparatus according to claim 2, further characterized in that each molten bath transfer bushing comprises an elongate body portion and a connector bushing, the elongated body portion having a rear end, a front end and a central molten bath hole extending therethrough from the rear end to the front end, the connector hub having a rear end, a front end and a central molten bath hole extending therethrough, which coincides with the central molten bath hole extending through the elongate body portion, the connector hub extends forwardly from the elongated body portion.

6. An injection molding apparatus according to claim 5, further characterized in that the rear end of the elongate body portion of each molten bath transfer bushing is threaded to screw into a threaded seat extending around the second molten bath passage in the rear cast bath distribution manifold.

7. - An injection molding apparatus according to claim 6, further characterized by one of the central molten bath hole in the front end of the elongated body portion of each molten bath transfer bushing and the first bath hole fused extending from the rear end of the heated and aligned nozzle has a threaded seat around it, and one of the front and rear ends of the connector bushing is threaded, the threaded end of the connector bushing being screwed into said threaded seat in one of the central molten bath hole in the front end of the elongated body portion of each molten bath transfer bushing and the first molten bath hole extending from the rear end of the heated nozzle.

8. An injection molding apparatus according to claim 2, further characterized in that each molten bath transfer bushing has a head portion and an elongated stem portion.; the head portion extends between the posterior molten bath distribution manifold and the front molten bath distribution manifold to be a spacer that provides the insulating air space therebetween, the elongated rod portion extends "from the portion head forward through the hole that extends through the manifold of the front molten bath distribution.

9. In a multi-cavity hot-runner injection molding apparatus for multi-layer molding having a front molten bath distribution manifold and a subsequent melt bath distribution manifold mounted in a substantially extending mold parallel to each with an insulating air gap therebetween, a plurality of heated nozzles, each heated nozzle has a rear end, a front end, a central molten bath channel extending therethrough from the rear end to the front end and an annular molten bath channel extending around the central molten bath channel to the front end with at least one molten bath hole extending from the rear end of the heated nozzle to the annular molten bath channel , the heated nozzles being mounted in the mold with the rear end of each heated nozzle splicing c On the front molten bath distribution manifold, a first molten bath passage from a first molten bath source branches into the front molten bath distribution manifold and extends through the at least one molten bath hole and the annular molten bath channel in each heated nozzle to an injection orifice adjacent the front end of the heated nozzle leading to a cavity in the mold, and a second molten bath passage from a second molten bath source branches in the multiple of subsequent molten bath distribution and extends through the central molten bath channel in each heated nozzle to the injection orifice, the improvement further comprising; a plurality of molten bath transfer bushings, each molten bath transfer bushing has a head portion at a rear end, an elongated rod portion extending from the head portion forward towards a front end and a central hole extending therethrough from the trailing end to the front end, each molten bath transfer bushing being mounted in alignment with the central molten bath channel of one of the heated nozzles, the head portion extends between the posterior molten bath distribution manifold and the front molten bath distribution manifold to be a separator that provides the insulating air space therebetween, in the elongated rod portion extends from the head portion forward into a hole that extends through the front molten bath distribution manifold in alignment with the channel d the central molten bath through the aligned heated nozzle, whereby the central hole through each molten bath transfer bushing receives an elongated pin extending forward therefrom in the central molten bath channel in the nozzle heated and aligned, with the second molten bath passage from the second molten bath source extending along the elongate pin.

10. - An injection molding apparatus according to claim 9, further characterized in that the elongated rod portion of each molten bath transfer bushing extends through the hole through the front molten bath distribution manifold with the front end of each molten bath transfer bushing by abutting against the rear end of the heated and aligned nozzle.

11. An injection molding apparatus according to claim 10, further characterized in that there is an insulating air space between the elongated rod portion of each molten bath transfer manifold and the surrounding front molten bath distribution manifold.

12. An injection molding apparatus according to claim 11, further characterized in that the head portion of each molten bath transfer bushing has a molten bath channel out of the center extending from an inlet on the rear end to join the central molten bath channel and form part of the second molten bath passage.

13. An injection molding apparatus according to claim 12, further characterized in that the molten bath passage outside the center is L-shaped.

14. An injection molding apparatus according to claim 12, further characterized because the elongated pin is a. valve pin and further includes an activation mechanism for reciprocally moving the valve member between a retracted open position and a front closed position.

15. An injection molding apparatus according to claim 14, further characterized in that each molten bath transfer bushing comprises a neck portion extending rearwardly from the head portion within an opening in the manifold manifold of molten back bath, and the elongate valve pin fits into the central hole in the neck portion sufficiently tightly to prevent spillage of molten bath while the elongated valve pin reciprocates.

16. An injection molding apparatus according to claim 12, further characterized in that the elongated pin is a fixed pin with a molten bath groove therein extending longitudinally.

17. The injection molding apparatus according to claim 1, further characterized in that there is an insulating air space between each heated nozzle and the surrounding mold.

18. The injection molding apparatus according to claim 1, further characterized in that the insulating air gap between the posterior molten bath distribution manifold and the front molten bath distribution manifold is formed by placing a plurality of spacers between the same.

19. The injection molding apparatus according to claim 1, further characterized in that there is an insulating air space between the front molten bath distribution manifold and the surrounding cooled mold.

20. The injection molding apparatus according to claim 19, further characterized in that the insulating air space between the front molten bath distribution manifold and the surrounding cooled mold is formed by placing a central location ring therebetween.

21. The injection molding apparatus according to claim 1, further characterized in that there is an insulating air space located between the rear molten bath distribution manifold and a rear plate.

22. The injection molding apparatus according to claim 19, further characterized in that there is an insulating air gap located between the rear molten bath distribution manifold and a rear plate.

23. The injection molding apparatus according to claim 22, further characterized in that there is an insulating air gap between each heated nozzle and the surrounding mold.

24. The injection molding apparatus according to claim 1, characterized, further, because said insulating air spaces provide sufficient thermal separation to allow a difference in temperature to be maintained between a first molten bath passing through the subsequent molten bath distribution manifold and a second molten bath passing to the molten bath. through the front distribution manifold upon passing said molten bath into said nozzles.