MXPA98008714A - Injection molding device that has barrenode bath flooded through the front end of the ag - Google Patents

Abstract

Multiple cavity injection molding apparatus for three layer molding having elongated needles for needle arrangement or fixed valve arrangement. Each elongated needle has a central molten bath bore extending backward from its front end to the number of borehole extending laterally. A low viscosity clogging material such as EVOH or nylon flows through these holes to the gate leading to the cavity, this allows co-injection with fixed needles and provision of drinking fountains in one mode or by arrangement of valves in another modality.

Description

MOLDING APPARATUS BY INJECTION WHICH HAS CASTED BATH BREAK THROUGH THE FRONT END OF THE NEEDLE BACKGROUND OF THE INVENTION This invention relates generally to a multiple cavity injection molding apparatus for three layer molding and more particularly to such an apparatus wherein an elongated needle extending through a central molten bath channel in each heated nozzle has a central molten bath hole extending backwards from the front end. Multiple cavity injection molding apparatuses are known for making protective containers in three layers for food, or preforms or parisons for beverage bottles. A layer of clogging material, such as ethylene vinyl alcohol copolymer (EVOH) or nylon, is molded between two layers of the polyethylene terephthalate (TPE) type material. In some multi-cavity apparatuses, the two different molten baths are distributed through a single tubular distribution system of molten baths having two molten bath ducts, but preferably for materials such as these having different injection temperatures of about 200. . ° C to 296.1 ° C respectively, the two molten baths are distributed through two different tubular distribution systems of molten baths. In some cases, the two fused baths are injected sequentially, while in other cases both co-injection and sequential injection are used. The two molten baths are injected through a heated nozzle having a central molten bath channel and an annular molten bath channel extending around the central molten bath channel to a gate leading to the cavity. As seen in the patent of E.U.A. No. 4,717,324 of Schad et al., Issued on January 5, 1988, valve gate apparatus for three-layer molding has been used. However, this apparatus has the disadvantage that it does not disclose the devices with drinking arrangements and also that the apparatus with valve gate does not allow the simultaneous injection or co-injection of the two molten baths.

BRIEF DESCRIPTION OF THE INVENTION According to the above, it is an object of the present invention to overcome at least partially the disadvantages of the prior art by providing an injection molding apparatus for multiple cavities for three-layer molding that allows the provision of sprues with fixed needles of simultaneous injection or coinjection by arrangement of the valves. To that effect and in one of its aspects, the invention provides multiple cavity injection molding apparatus for three layer molding having one or more tubular distribution systems of molten baths with a front face and a plurality of heated nozzles mounted on a cast. Each heated nozzle has a rear end terminating in the tubular distribution system of molten baths and a front end adjacent to a gate leading to a cavity in the mold. Each heated nozzle has a central casting channel extending therethrough from the rear end to the front end and a molten annular bath channel ^ LO which extends around the central molten bath channel to the front end. An elongated needle having a rear end, a front end and an outer surface extends into the central molten bath channel in each heated nozzle in alignment with a gate leading to a cavity in the mold. A molten bath duct from the molten bath source branches to the tubular bath distribution system ^ Cast and extends through the single annular bath channel $ molten in each nozzle heated to the gate. Other The molten bath duct from another molten bath source branches into the tubular molten bath distribution system and extends along the elongate needle in the molten bath central channel in each nozzle heated in the gate. Each elongated needle has a central bath hole cast and one or more molten bath side holes. The central molten bath bore extends a predetermined distance backward from the front end of the elongated needle to a rear end of the molten bath central bore. The molten bath side bore extends outward from the rear end of the molten bath center bore to the outer surface of the elongated needle. In other aspects, the invention further provides a method for continuously injection molding products in three layers in a multi-cavity injection molding apparatus having a tubular front distribution system for molten bath.

The one separated from a rear tubular distribution system with a plurality of heated nozzles mounted in a mold. Each heated nozzle has a rear end that terminates the front tubular distribution system of molten bath has a frontal nozzle adjacent to a gate that leads to a cavity in the mold. Each heated nozzle also has 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. An elongated needle that has a rear end, a front end and an outer surface extending into the central molten bath channel in each heated nozzle in alignment with a gate leading to a cavity in the mold. The method comprises the steps of injecting a first molten material of a first source of molten bath to the cavities through a first molten bath duct that branches into the front tubular molten bath distribution system and extends through the annular molten bath channel in each nozzle heated through the gate aligned After a predetermined amount of the first molten material has been injected into the -cavities, simultaneously injecting a second molten material from a second source fused to the cavities through a second molten bath conduit branching into the rear tubular system of distribution of molten bath and extends along the elongated needle through a hole through a tubular front distribution system of molten bath and the molten bath central channel aligned through each of the heated nozzles and the gates aligned. This forms an inner layer of the second material between the two outer layers of the first material in each of the cavities. When the cavities are almost full, the injection of the second material is suspended through the second molten bath conduit, while the injection of the first material through the first molten bath conduit is continued until the cavities are full. After a cooling period the mold is opened and ejected into the molded products. Finally, the mold is closed after the expulsion of the molded products. In other aspects, the emission also provides an injection molding apparatus with multiple-cavity hot sprues for three-layer molding having a tubular front distribution system of the molten bath and a tubular rear distribution system of molten bath mounted on a mold extending substantially parallel to each other with an insulating air space therebetween. It includes the number of heated nozzles, each having a rear end, a front end, a central molten bath channel extending therethrough and an annular molten bath channel extending around the central molten bath channel front end, one or more molten bath holes extending at 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 terminating in the front tubular molten bath distribution system. An elongated needle that has a rear end, a front end and an outer surface extending into the central molten bath channel in each nozzle heated in alignment with a gate leading to a cavity in the mold. A number of molded bath split transfer bushings each having a rear end and a front end is mounted in the openings through the tubular front distribution system of molten bath with its rear ends terminating the tubular rear distribution system of molten bath and the front end of each transfer bushing division of molten bath ending at the rear end of one of the heated nozzles. Each elongated needle has a central molten bath bore and one or more molten bath side bores. The central molten bath bore extends a predetermined amount backward from the front end of the elongated needle to the rear end of the molten bath central bore. The molten bath side bore that extends outward from the rear end of the molten bath core bore to the outer surface of the elongated needle. In this way, a first molten bath conduit from a first molten bath source branches into the rear tubular molten bath distribution system and extends through each transfer bushing bath division.

The molten melt and the annular fused bath channel in each nozzle heated to a gate adjacent to the front end of the heated nozzle leading to the cavity in the mold. A second molten bath conductor of a second molten bath source branches into the front tubular system of distribution of molten bath and extends through the transfer bushing split molten bath and along the elongated needle in the central molten bath channel in each nozzle? heated to the gate. Other objects and advantages of the invention with the following description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view of a portion of a multiple cavity injection molding apparatus having sprue arrangement with fixed elongated needles according to one embodiment of the invention, Fig. 2 is an elongated section of a portion of Figure 1, Figure 3 is an elongated sectional view showing a flow of molten bath through the central molten bath bore at the front end of the elongated needle seen in Figure 1, Figure 4 is an isometric view that shows a front portion of the elongated needle seen in Figure 1, Figure 5 is a sectional view of a portion of the multi-cavity injection molding apparatus having elongated needles with valve arrangement according to another embodiment of the invention 6 is an enlarged sectional view showing the valve needle seen in FIG. 5 in the middle position, FIG. 7 is a view similar to that of FIG. shows the valve needle in the open position, Figure 8 is a sectional view of a portion of a multi-cavity injection molding apparatus having sprue arrangement with fixed elongated needles according to a further embodiment of the invention, Figure 9 is an exploded isometric view showing three layers of the molten bath transfer and division bushing seen in Figure 8 before being integrally joined together, Figure 10 is a similar bag showing the other faces of the three layers of the same transfer bushing and > - molten bath split, and Fig. 11 is an isometric sectional view of the molten bath passages in the same molten bath transfer and split bushing.

DETAILED DESCRIPTION OF THE INVENTION Reference is first made to Figures 1 and 2 which show a portion of the multi-cavity injection molding apparatus for molding preforms into three layers or other products by a combination of sequential or simultaneous co-injection through sprue orifices. A number of heated nozzles 10 are mounted in a mold 12 with its rear ends 14 ending in the front face 16 of a tubular front distribution system for molten bath 18. While the mold 12 may have a larger number of plates depending on the application, and in this case, for ease of illustration, only one nozzle retainer plate 20, one tubular retainer plate 22 and one rear plate 24 are fixed together with bolts 26, as well as the cavity retainer plate 28 The front end 30 of each heated nozzle 10 and is aligned with a sprue orifice 32 through the cooling orifice insert 34 to a cavity 36. This cavity 36 for making beverage bottle preforms extends between an insert of cavity 38 and a mold core 40 in a conventional manner. A molten bath conduit 42 for the TPE is assigned the inlet port 44 through a cylindrical station 46 of the tubular system and the front tubular molten bath distribution system 18 is branched to extend through a bath partition bushing. molten 48 received in a seat 50 on the front face 16 the tubular faucet distribution system 18 to each heated nozzle 10. The molten bath division bushings 48 are retained in proper alignment by small alignment pins 52 which extend to the front tubular distribution system of molten bath 18. Although only one heated nozzle 10 is shown for ease of illustration, it is understood that a typical configuration will be many heated nozzles 10 (eg 32, 48, 74) seated in the mold to receive molten bath through the melt conduit 42 which will have a more complex coloration than that shown. The heated nozzle 10 sits in an opening 54 in the nozzle retainer plate 20 with its rear end 14 the size of the front end 56 of the molten bath partition bushing 48. The heated nozzle 10 is heated by an integral electric heating element 58 having a terminal 60, A collar portion 62 of each heated nozzle 10 in a circular locator 64 that extends around the opening 54. This provides an insulating air space 66 between the heated nozzle 10 and still recirculating 12 that is cooled overflowing chiller water through the cooling ducts 68. In the configuration shown, each heated nozzle 10 has an insertion portion 70 which is fixed in a seat 72 by a threaded nozzle plug 73 which is threaded and forms a front end 30 of the heated nozzle 10. As can be seen, the insert portion 70 is made of several pieces of steel 74 that join together to provide a fused bath annular channel 76 extending around a molten bath central channel 78 to the front end 30. The insert portion 70 of the heated nozzle 10 also has an annular insulating air space 79 extending from the central channel molten bath 78 and surrounding annular fused bath channel 76 to provide some thermal separation therebetween. The central molten bath channel 78 extends from the rear end 14 of the heated nozzle 10, while the surrounding fused annular bath channel 76 extends from four separate molten bath bores 80 which reach the rear end 14 of the heated nozzle 10. A circle of spaced holes 82 is drilled in the rear end 14 of the heated nozzle 10 by extending between the molten bath channel 68 and the surrounding spaced molten bath bores 80 to provide some thermal separation therebetween. The molten bath partition bushing 48 is made of three steel layers integrally welded together as described in co-pending Canadian patent application Serial No. 2,219,054, entitled "Injection Molding Apparatus Having Melt Dividing Bushings" filed. concurrently with the present. As described therein, the melt bath conduit TPE 42 is divided between the molten bath partition bushing 48 and extends through the four spaced holes 84 which are in alignment with the four molten bath holes spaced 80 in the rear end 14 of the heated nozzle 10. The front tubular molten bath distribution system 18 is heated by the integral electric heating element 86. It is located by a central locator ring 88 and the rings 90 extending to each heated nozzle 10. to enter an insulating air space 92 extending therebetween and to a surrounding inlet 12. In this configuration, another tubular back-cast steel bath distribution system 94 is mounted to the mold 12 by a number of insulating spacers and elastics 96 that extend between it and the back plate 24 to extend parallel to the front tubular distribution system of the bath 18. As can be seen, the two tubular systems 18, 94 are separated by molten bath transfer bushing 98 thermal insulators placed therebetween. As described in more detail below, a back tubular molten bath distribution system 94 is heated by an integral electric heating element 100 to a lower operating temperature for the front tubular molten bath distribution system 18 and the air gap. 101 provided by the transfer bushing of molten insulating-thermal bath 98 between the two tubular systems 18, 94 provides that thermal pressure between them. In this configuration, each thermally insulating molten bath transfer bushing 98 has an elongated rod portion 102 that extends forward of a rear head portion 103 through a bore 104 in the front tubular molten bath distribution system 18. and a central bore 106 in the molten bath division bushing 48 and exactly holds in place the molten bath transfer bushing 98. The transfer bushing 98 also has a bore 108 extending through the rod portion 102. and receives an elongated needle 110 according to the invention. The elongate needle 110 also extends through the central molten bath channel 68 in the heated nozzle 10. As described in more detail below the elongated needle 110 is fixed in place with its head 112 seated on the rear face 114 of the rear head portion 103 of the molten bath transfer bushing 98 and its front end 116 partially used to the gate 32 and in alignment therewith. A separate molten bath duct 118 for the clogging material extends into inlet port 120 and the tubular molten bath distribution rear system 94 is ramped to extend through an L-shaped duct 122 drilled into the duct portion. rear head 103 of each molten bath transfer bushing 98 to a longitudinal slot 124 machined to extend a predetermined distance backward in each fixed water 110. In other embodiments, the slot 124 may extend heicoidally around a fixed needle 110 or needle fixed 110 may be small enough to allow the obstruction material to flow around it. However, in view of the relatively low volume and low viscosity of the clogging material, it is preferable to make the fixed needle 110 fit into the bore 108 of the molten bath transfer bushing 98 and the molten bath center channel 78 in the heated nozzle 10 and provides the elongated helical groove 124 in the fixed needle 110 to flow through the clogging material. Each molten bath transfer bushing 98 is mounted in proper alignment by a small pin 126 extending therebetween from the front tubular molten bath distribution system 18. Fixed needle 110 is similarly maintained in proper alignment by a small spigot 128 which extends from its head 112 to the rear head portion 103 of the molten bath of the molten bath transfer bushing 98. As best seen in FIGS. 3 and 4, each fixed water 110 has a central bore. molten bath 130 extending backward from its front end 116 to the four molten bath lateral bores 132 extending outward to the outer surface 134 of the fixed needle 110. The molten bath side bores 132 extend diagonally toward outside the rear end 136 of the molten bath central barrel 130 to the exterior surface 134. In this embodiment, each fixed needle 110 has a diametre portion. The reduced portion 138 that extends forward of the front end of the longitudinal slot 124 to its front end 116 and fits into a reduced diameter portion 139 of the molten bath central channel 78 through the heated nozzle 10. The diameter portion reduced 38 of the fixed needle 110 is longer than the reduced diameter portion 139 of the molten bath central channel 78 which thus forms a space 140 around the reduced diameter portion 138 of the fixed needle 110. In this way, the molten bath duct 118 of clogging material extends from the longitudinal slot 124 in each fixed needle 110 in this space 140 and then inward through the molten bath side bores 132 and forward through the central bath hole cast 130 to gate 32 leading to cavity 36. In other embodiments, the fixed needle 110 may have one or a different number of lateral holes extending inward from the front end of the longitudinal slot 124 to the rear end 136 of the molten bath central bore 130.

In use, the injection molding system is assembled as shown in Figures 1 and 2 and operates to reproduce preforms in three layers or other products as follows. First, the electric power is applied to the heating element 86 in the front tubular distribution system of the molten bath 18 and the heating elements 58 in the heated nozzles 10 to heat them to an operating temperature of approximately 296.1 ° C. Electric power is also applied to the heating element 100 in the rear tubular molten bath distribution element 94 to heat it to an operating temperature of about 204. ° C. Water is supplied to the cooling ducts 68 to cool the mold 12 and the gate inserts 34. The hot molten bath subjected to pressure is injected after the separate injection cylinders (not shown) to the first and the second molten bath product 42, 118 through the inlet orifices 44, 120 according to a predetermined cycle. molten bath injected into the first molten bath duct 42 is a material of the polyethylene terephthalate (TPE) type. The molten bath duct 42 branches in the front tubular molten bath distribution system 18 and extends to each molten bath partition hub 48 where the four separate holes 84 are aligned aligned with the four molten bath drill holes 80 in the rear end 14 of the heated nozzle. These spaced boreholes of molten bath 80 are then extended through the annular molten bath channel 76 to the gate. The molten bath injected into the second molten bath conduit 118 is a suitable clogging material such as ethylene-vinyl copolymer (EVOH) or nylon. The second molten bath conduit 118 branches to the rear tubular molten bath distribution system 94 and extends through the aligned conduit 122 in each molten bath transfer bushing 98 and the helical longitudinal groove 124 aligned in each fixed needle 110 that it extends through the central bore 108 in the molten bath transfer bushing 98, the central bore 106 in the molten bath partition bushing 48 and the molten bath center channel 78 in the heated nozzle 10 to the space 140 around the small diameter portion 138 of each fixed needle 110. The second molten bath conduit 118 then extends through the side holes 132 and the molten bath central bore 130 in each fixed needle 10 driving the aligned gate 32. During each cycle , a predetermined amount of TPE is injected behind the first molten bath conduit 42 and the outer layers 141 thereof adhere to the sides 142 in the cavity 36. A short time after the start of the TPE injection, a predetermined amount of the less viscous clogging material is then simultaneously injected through the second molten bath conduit 118 and forms a central layer 144 between the two outer layers 141 of TPE When the cavities 36 are almost full, the frictional pressure of the clogging material is released which stops its flow and the injection of TPE is continued to completely fill the cavities 36. It is then seen the injection appearance of the TPE and, after a short period of cooling, the mold 12 for injection is opened. After the injection, the mold 12 is closed and the cycle is repeated continuously every 15 to 30 seconds with a frequency that depends on the thickness of the wall and the size number of the cavities 36 and the exact materials being molded. The central location of the central molten bath bore 130 in the front end 30 of the fixed needle 110 and the relatively small size in the groove 124 and the molten bath central bore 130 is combined with the relatively low volume and low viscosity of the material of obstruction to ensure that the flow of the clogging material is reliable and a very thin layer of the clogging material can be provided. Reference is now made to Figures 5-7 showing the injection molding apparatus according to another embodiment of the invention for molding preforms into three layers or other products by a combination of sequential and simultaneous co-injection. Since many of the laments are the same as those described above, all the elements common to both modalities are not described and those that are described again have the same reference numbers as before. In this mode, the appliance has valve gates instead of sprue gates with fixed needles. Each elongated valve needle 110 has the same shape, except that its front end 116 is cylindrical instead of partially tapered. The elongated valve needle 110 is alternated in the molten bath center channel 78 in each heated nozzle 10 by the hydraulic actuating mechanism 146 according to a predetermined cycle. In this case, the thermally insulating molten bath transfer bushing 98 also has a neck portion 148 which extends rearwardly through an opening 150 in the rear tubular molten bath distribution system 94 of the central bore 108 extends to through this back neck portion 148. Each elongated valve needle 110 fits into the central bore 108 in the molten bath transfer bushing 98 that was insulated with the molten bath central channel 78 in the heated nozzle 10 with sufficient tightness to prevent leakage of molten bath around the elongated valve needle 110 with alternating form. The head 112 of the elongated valve needle 110 is connected to a front piston 152 seated in a cylinder 154 in the rear plate or cylinder 24. The drive mechanism 146 also includes a rear piston 156 and the two pistons 152, 156 are driven by controlled oil pressure that is applied through the conduits 158 for the valve needle channel 110 between the three different positions. Although the hydraulic drive mechanisms 146 are shown for ease of illustration, other types of drive mechanisms, such as electromechanical mechanisms for other applications, may be used. In the first or intermediate position shown in Figure 6, the front end 116 of each valve needle 110 retracts only far enough and sufficiently elongated to allow a small amount of TPE to flow through the annular molten bath channel 76. In this mode, there is a double blockage of the flow of the obstruction material in this intermediate position. As seen in Figure 6, the molten bath side holes 132 in the valve needle 110 are too far forward to connect with the space 140 around the reduced diameter position 138 of the valve needle 110. Furthermore, as shown in FIG. see in Figure 5, the longitudinal or helical groove 124 in the valve needle 110 does not have them sufficiently far back to connect with the L-shaped conduit 122 in the head position 103 of the molten bath transfer bushing 98 in this position. In other embodiments, it may be necessary to only use one or the other of these ways to block the flow of obstruction material. Then, the front end 116 of each valve needle 110 is retracted further to a second or open position shown in Figure 7. In this position, the molten bath side holes 132 in the valve needle 110 are connected to the space 140 around the reduced diameter portion 138 of each valve needle 110 and the slot 124 in the valve needle 110 does not connect with the L-shaped conduit 122 in the bath-molded transfer bushing 98 which allows the clogging material flows through the molten bath duct 118 to the cavities 136.

As mentioned above, the central location of the molten bath central bore 130 in the front end 30 of the fixed needle 110 and the relatively small size of the groove 124 and the molten bath bore 130 are combined with the relatively low volume and The viscosity sheet of the clogging material to ensure that the flow of the clogging material is reliable to provide a uniform and very thin layer of the clogging material, which is a considerably expensive material. As seen in Figure 7, the barrier material flowing simultaneously with the TPE divides the flow of TPE into two and provides a central layer 160 of the succession material between the two outer layers 162 of TPE. When the cavities 36 are almost full, the front pattern of each valve member 110 is returned to the first position by interrupting the flow of the clogging material through the molten bath central bore 130. The flow of TPE through the annular bath channel cast 76 continues until the cavities 36 are completely full. It is driven after the valve 110 has passed to the third or forward closed position in which its front end 116 is seated in the gate 32 at the level of the booth 36. After a period of pre-cooling, the mold is opened to your injection After the injection, the mold is closed and the cycle repeated continuously every 15 or 30 seconds with a frequency that depends on the thickness of the stop and the number and size of the cavities 36 and the exact materials being molded.

Reference is made to Figures 8-11 which show the injection molding apparatus according to another embodiment of the invention for molding preforms into three layers and other products by a combination of sequential and simultaneous co-injection to the drinking gate. In this case, the tubular rear distribution system of molten bath 94 instead of the front tubular distribution system of molten bath 18 has the extension of tubular system 46. In this way, the first molten bath conduit 42 for the TPE extends in the inlet orifice 44 common in the tubular system extension 46 extends through the tubular rear distribution system of molten bath 94 instead of the front tubular molten bath construction system 18. In addition, the second molten bath conduit 118 for the clogging material it extends into the second inlet 120 through the tubular faucet 18 front distribution system of cast bath 18 instead of the tubular back flushing bath distribution system 94.

As can be seen, a molten bath partition transfer bushing 164 is seated behind each heated nozzle 10 in a cylindrical opening 166 behind the front tubular molten bath distribution system 18 with its rear end 168 terminating in the tubular system. rear distribution of molten bath 94. The rear schematic 14 of each of the heated nozzles 10 terminates at the front end 169 of each of the molten bath transfer and direction bushes 164 as well as the tubular front distribution bath system cast 18. Each fixed needle 110 has a central molten bath bore 130 and four lateral holes of molten baths 132 as shown in Fig. 3.

Referring also to Figs. 9-11, each of the molten bath transfer and division hubs 164 is made by previously joining the first, second and third layers 170, 172, 174. The first layer 170 is machined to have a central hole 176 extending therethrough from its rear face 178 to its front face 180. The central hole 176 has a larger diameter portion 182 adjacent to the rear face 178 to receive the head 112 of the fixed needle 110. The first layer 170 is drilled to also have an out-of-center hole 184 extending therethrough. The second layer 172 is bored to have two holes 186 spaced on opposite sides of a central hole 188 extending therethrough. The front face 180 of the first layer 170 and the rear face 190 of the second layer 172 is machined to have corresponding slots 192., 194 which are joined when the three layers 170, 172, 174 are joined together to form a first curved molten bath duct 196 which branches from the center off hole 184 through the first layer 172 to the two spaced holes 186 through the second layer 172.

The third layer 174 is drilled to have four holes 198 spaced around a central hole 200 which is aligned with the central molten bath channel 78 in the heated nozzle 10 aligned. Each of the four spaced bores 198 is in alignment with one of the four spaced molten bath bores 80 which extends to the rear end 14 of the heated nozzle 10 to the molten annular bath channel 76. The third layer 174 is bored to have also a third radial hole 202 extending from the central hole 200 in alignment with the second molten bath conduit 118 in the front tubular molten bath distribution system 18. The front face 204 of the second layer 172 and the third face 206 of the third layer 174 is machined to each have a pair of matching slots 208, 210 which join when the three layers 170, 172, 174 are joined together to form a pair of second curved ducts of molten bath 212. Each of the second curved molten bath ducts 212 are branched from one of the two spaced holes 186 through the second layer 172 to two of the four spaced holes 198 through the third layer 174 and the alignment with the four molten bath holes 80 extending at the rear end 14 of the heated nozzle 10 to the molten annular bath channel 76. The three layers 170, 172, 174 are also bored. to have the holes 214 for receiving the alignment pins 216.

An amount of nickel ally (not shown) is applied to the face or the front faces 180 of the first layer 170 of the second face 204 of the second layer 172 and the three layers 170, 172, 174 are assembled together with the ears 216 keeping them in proper alignment. The assembled layers 170, 172, 174 are then introduced into a vacuum oven and gradually heated to a temperature of about 496.1 ° C which is higher than the melting temperature of the nickel ally. As the furnace is heated, it is evacuated to a relatively high vacuum to remove substantially all of the oxygen and then partially refilled with an inert gas such as argon or nitrogen. When the melting point of the nickel alliance is reached, the nickel alliance melts and flows by capillary action between the first layer 170, the second layer 172 and the third layer 174 to be integrally welded together to form a bushing of transfer and division of molten bath 164 integral.

The use of the injection molding system shown in Fig. 8 is essentially the same as that described above with respect to Figs. 1-4, except that the tubular rear distribution system of molten bath 94 and the heated nozzles 10 are heated to a pressure temperature of about 296.1 ° C of the front tubular molten bath distribution system is heated to an operating temperature of about 204.4 ° C. Also, the material of the TPE type is injected into the first conduit 42 which is unified in the rear tubular molten bath distribution system 94 and extends through each bushing to the transfer and division of the molten bath 164 to the annular channel of the molten bath. molten bath 76 in the heated nozzle 10 aligned. The clogging material is now heated to the second molten bath duct 118 which is modified to the front tubular molten bath distribution system and extends through the radial bore 202 and down the slot 124 in each fixed needle 110.

Although the description of the three-layer injection molding apparatus having elongated needles 110 with central boreholes of molten baths 130 at their front ends 116 is given with respect to the valve support and fixed gate modes, it will be evident that they are possible other various modifications are possible without departing from the scope of the invention as understood by those skilled in the art and how the following claims are defined. For example, materials having suitable characteristics can be used instead of TPE or EV0H or nylon.

Claims (21)

NOVELTY OF THE INVENTION CLAIMS

1. - Of a multiple cavity injection molding apparatus for three layer molding having at least one tubular distribution system of molten bath with a front face and a plurality of heated nozzles mounted in a mold, each nozzle having one heated end rear end terminating in at least one tubular molten bath distribution system and leading one end adjacent to a gate to a mold cavity, each heated nozzle having 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 central end, having an elongate needle, a trailing end, a front end and an outer surface extending into the central molten bath channel in each nozzle heated in alignment with a gate leading to a cavity in the mold, branching a first conduit of molten bath from a first molten bath source in at least one tubular molten bath distribution system and flowing out through the annular molten bath channel in each nozzle heated to the gate, branching a second molten bath conduit from a second source of molten bath in at least one tubular distribution system of molten bath and extending along the elongated needle in the central molten bath channel in each nozzle heated to the gate, improvement in which: each elongated needle has a borehole molten bath central and at least one central molten bath bore, the central molten bath bore extending a predetermined distance backward from the front end of the elongated needle to a rear end of the molten bath central bore, and igniting at least one a molten bath side hole back from the rear end of the molten bath central bore to the ext. erior of the elongated needle.

2.- Injection molding apparatus according to claim 1, further characterized in that the first molten bath duct of the first molten bath source is branched into a front tubular molten bath distribution system mounted on the mold and the second The molten bath duct of the second molten bath source is branched into a back tubular molten bath distribution system mounted in the mold.

3. An injection molding apparatus according to claim 2, further characterized in that the front tubular molten bath distribution system extends in a direction substantially parallel to the rear tubular molten bath distribution system and is spaced a predetermined distance from the molten bath. same, each elongated needle extends through a hole through the tubular front distribution system of molten bath the second molten bath conduit of the second molten bath source branches to the tubular rear distribution system of molten bath and is - then extends along each elongated needle in the holes of the tubular front distribution system of molten bath.

4.- Injection molding apparatus according to claim 1, further characterized in that each needle > 0 elongated has four molten bath side holes extending radially outwardly from the rear end of the molten bath central bore to the outer surface of the elongated needle.

5.- Injection molding apparatus according to claim 4, further characterized in that the molten bath lateral holes extend diagonally from the rear end of the molten bath central bore to the outer surface of the elongated needle.

6.- Injection molding apparatus in accordance with claim 4, further characterized in that each elongated needle is smaller in diameter than the bore through the tubular front distribution system of molten bath and the central bore aligned with molten bath to through the heated nozzle through which the elongated needle 5 extends, whereby the second molten bath duct extends along the elongate needle.

7. - Injection molding apparatus according to claim 6, further characterized in that each elongated needle is fixed in its position with the front end of the needle adjacent to the gate.

8.- Injection molding apparatus according to claim 6, further characterized in that the rear end of each elongated needle is connected to a mechanism of . actuation by means of which the elongated needle is alternated between several different positions according to the predetermined injection t0 cycle.

9.- Injection molding apparatus according to claim 4, further characterized in that each elongated needle has a groove extending therethrough whereby the second molten bath duct extends through the groove at the throat. side hole of molten bath at least unique.

10. An injection molding apparatus according to claim 9, further characterized in that each elongated needle is fixed in its position with the front end of the needle adjacent to the gate.

11.- Injection molding apparatus according to claim 9, further characterized in that the rear end of each elongated needle is connected to a driving mechanism whereby the elongated needle is alternated between several different positions according to the cycle of predetermined injection.

12. - Injection molding apparatus according to claim 9, further characterized in that the slot extends helically around the elongated needle.

13.- Injection molding apparatus according to claim 1, further characterized in that the slot extends a predetermined distance backwards whereby the slot is connected with the second molten bath duct to the second tubular molten bath distribution system only in a retracted open position.

14. In an injection molding apparatus with multiple cavities hot sprue for three-layer molding that has a front tubular distribution system for molten bath and a rear tubular distribution system for molten bath mounted in a mold that extends in the direction substantially parallel to each other with an insulating air gap 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 rear end to the front end and an annular molten bath channel extending around the central bath channel fused to the front end with at least one molten bath bore extending to the rear end of the heated nozzle to the annular molten bath channel, assembled nozzles heated in the mold with the rear end of each heated heated nozzle that terminates the tubing system The front distribution of molten bath, having an elongated needle having a rear end, a front end and an outer surface extending into the central channel of molten bath in each nozzle heated in alignment with a gate leading to a cavity in the mold , the improvement further comprising: a plurality of molded bath transfer and splitting bushings each having a rear end and a front end and being mounted in an aperture through the front tubular molten bath distribution system with the rear ends of the molten baths. transfer hubs and molten bath division terminating is tubular rear distribution system of molten bath of front end of each transfer bushing and molten bath division ending at the rear end of one of the heated nozzles, each elongated needle having a central molten bath hole and at least one central molten bath bore, extending the central molten bath bore a predetermined distance backward from the front end of the elongated needle to a rear end of the molten bath central borehole, the at least one external molten bath bore extending outward from the rear end of the molten bath central bore to the outer surface of the elongated needle, whereby the first molten bath duct from a first molten bath source branches off to the tubular rear distribution system of molten bath and extends through each molten bath division transfer bushing and the molten bath annular channel in each heated nozzle to a gate adjacent to the front end of the heated nozzle leading to a Mold cavity and a second molten bath duct from a second molten bath source branches to the front tubular molten bath distribution system and extends through the molten bath transfer and division bushing and along the elongated needle in the elongated channel in the central molten bath channel in each nozzle heated to the gate.

15.- Injection molding apparatus according to claim 14, further characterized in that each elongated needle is fixed in its position with the front end of the needle adjacent to the gate.

16.- Injection molding apparatus according to claim 14, further characterized in that the rear end of each elongated needle is connected to the drive mechanism whereby the elongated needle is alternated between the various different positions according to a cycle of Redefined injection.

17. A method for continuously injection molding products in three layers of a multi-cavity injection molding apparatus having a tubular faucet distribution system spaced apart from a rear distribution tubular system with a plurality of heated nozzles mounted in a mold, each heated nozzle having a rear end terminating the front tubular molten bath distribution system and the front end adjacent to a gate leading to a cavity in the mold, each heated nozzle having a central molten bath channel that extends therethrough from the rear end 5 to the front system in an annular molten bath channel extending around the central molten bath channel to the front end, with an elongated needle having a rear end, a front end and an outer surface which extends into the molten bath central channel in each heated nozzle AjlO in alin With a gate leading to a cavity in the mold comprising the steps of: (a) injecting a first melt material from a first source of molten bath into the cavities through a first molten bath conduit that branches to the system tubular front bathroom layout 15 melt extending through the annular molten bath channel in each heated nozzle through the aligned gate, (b) after the cavities have been injected a predetermined amount of the first molten material, simultaneously injecting a second molten material from a second 20 source of molten bath to the cavities through a second molten bath conduit that branch to the drawn tubular distribution system of molten bath that extends along the elongated needle through a borehole through the front tubular system of distribution of molten bath and the 25 aligned central channel of molten bath through each of the heated nozzles and aligned gates, whereby the inner layer of the second material is formed between the two outer layers of the first material in each of the cavities, (c) when the cavities are almost full, discontinue the injection of the second material through the second molten bath passage, while continuing to inject the first material through the first molten bath conduit until the cavities are full, (d) after a cooling period to open the mold and inject the molded products, and (e) to close the mold after the injection of the molded products.

18. An injection molding method according to claim 17, further characterized in that the elongated needle in the central molten bath channel in each nozzle is a valve needle and is first retracted to a partially open position to allow injection of the first material melted in step (a), is then retracted completely to a fully open position to allow simultaneous injection of the first and second material in step (b), then stirred to a partially open position to allow injection of the first molten material to continue until the cavities are complete, and finally alternates to a closed position where the front end of the valve needle sits in the aligned gate.

19. An injection molding method according to claim 17, further characterized in that the first polyethylene terephthalate (PET) material.

20. - An injection molding method according to claim 19, further characterized in that the second material is ethylene vinyl alcohol copolymer (EVOH).

21. An injection molding method according to claim 19, further characterized in that the second material is nylon.