MXPA99000290A - Molding apparatus by injection of multiple layers that has a three-position valve member - Google Patents

Abstract

The present invention relates to an injection molding apparatus with a valve gate for multi-layer molding having at least one manifold and at least one heated nozzle mounted in a mold, at least one heated nozzle having a rear end, a front end, a central molten material channel extending to the front end, and at least one channel of annular fused material extending around the central molten material channel to the front end of the nozzle, at least one heated nozzle extending from at least one manifold with the central molten material channel in alignment with, and adjacent to, a gate leading to a cavity in the mold, a first passage of molten material from a first source of molten material extending through at least one manifold and at least one of the channels of molten material in at least one heated nozzle until the lined gate, a second passage of molten material from a second source of molten material extending through at least one manifold and at least one of the channels of molten material in at least one heated nozzle to the lined gate , an elongated valve member having a rear end and a front end extending through the central molten material channel in at least one heated nozzle, the improvement further comprising: a rack and pinion drive mechanism for alternating each elongate valve member between a first closed position, a second partially open position and a third fully open position, the actuating mechanism comprising: (a) a rack member slidably received in at least one manifold meshing with the rear end of the elongated valve member, the rack member having a row of teeth facing towards outside, (b) a pivotally mounted pinion member with an outer end and an inner end having a plurality of teeth meshing with the teeth of the rack member, and (c) a front cylinder, a rear cylinder adjacent to, and aligned with, the front cylinder, a front piston seated in the front cylinder and connected to the outer end of the pinion member, a rear piston seated in the rear cylinder, the rear piston having a rod projecting from the rear cylinder into the cylinder front to maintain at least a predetermined minimum distance between the front and rear pistons, first and second fluid pressure media lines connected to the front cylinder on opposite sides of the front piston, and a third pressure media fluid line of fluid connected to the rear cylinder on the rear side of the rear piston, whereby applying fluid pressure to Through the first, second and third fluid pressure lines, the elongate valve member is alternated between the first closed position, the second partially open position and the third fully open position in accordance with a continuous injection cycle, wherein the Fluid pressure is first released from the first fluid line, and fluid pressure is applied from the third fluid line to drive the rear piston to a fully forward position, whereby the piston rod drives the frontal piston towards an intermediate position urging the elongate valve member backwardly from the first closed position to the second partially open position, wherein the front end of the elongate valve member is sufficiently retracted to allow material flow from the first source of material melted through an outer channel of at least one channel of material gone annular through at least one heated nozzle and the gate, after a short predetermined period fluid pressure is applied from the second fluid line to propel the frontal piston to a fully forward position which urges the elongate valve member back to the third fully open position, where the front end of the elongated valve member is sufficiently retracted to allow the simultaneous flow of molten material from the second source of molten material through the central molten material channel and the gate, when the cavity is almost full, the fluid pressure is released from the second fluid line and fluid pressure is applied from the first fluid line to return the front piston to the intermediate position returning the elongate valve member to the second partially open position until the cavity is filled, and then pressure is released from the fluid. fluid from the third fluid line to drive the front pistons at and back to fully retracted positions urging the elongate valve member to the first closed position, wherein the front end of the elongated valve member is seated in the gate to allow ejection of the molded part.

Description

MULTI-LAYER INJECTION MOLDING APPARATUS THAT HAS A THREE-POSITION VALVE MEMBER BACKGROUND OF THE INVENTION This invention relates generally to an injection molding apparatus with a valve gate, and more particularly to said apparatus having a three-position valve member drive mechanism for molding multiple layers. Injection molding apparatuses with valve gate for manufacturing multi-layer food protective containers, or preforms for beverage bottles, are well known. Frequently, the inner and outer layers are made of a material of the type of polyethylene terephthalate (PET) with one or more barrier layers made of a material such as ethylene-vinyl alcohol copolymer (EVOH) or nylon. For example, the patent of E.U.A. No. 4,657,496 by Ozeki et al., Issued April 14, 1987, shows a drive mechanism having an outer piston alternating in an outer cylinder, and an inner piston alternating in an inner cylinder. The inner piston drives the elongated valve member, and the outer piston drives a rod surrounding the elongated valve member, and operates in a controlled injection cycle to sequentially inject first the PET and then the barrier material to mold products of three hats. Although this is satisfactory for some applications, sequential molding has the disadvantage of a relatively long cycle. As seen in the patent of E.U.A. No. 4,919,606 by Gellert, issued April 24, 1990, the rack and pinion valve member drive mechanism is also known. However, previously it had the disadvantage of only providing open and closed positions, which is not sufficient for the molding of multiple layers.

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 an injection molding apparatus with valve gate having three-position rack and pinion valve member drive mechanism for the molding of multiple layers. For this purpose, in one of its aspects, the present invention provides an injection molding apparatus with valve gate for multi-layer molding, having one or more manifolds and one or more heated nozzles mounted in a mold. The heated nozzle has a trailing end, a front end, a central molten material channel extending to the front end, and one or more channels of annular molten material extending around the central molten material channel to the front end of the molten material. the mouthpiece The heated nozzle extends from the manifold with the central molten material channel in alignment with, and adjacent to, a gate leading to a cavity in the mold. A first passage of molten material from a first source of molten material extends through the manifold and one of the channels of molten material in the heated nozzle to the aligned gate. A second passage of molten material from a second source of molten material extends through the manifold and one of the channels of molten material in the heated nozzle to the aligned gate. An elongated valve member having a rear end and a front end extends through the central molten material channel in the heated nozzle. A rack and pinion drive mechanism alternates each elongated valve member between a first closed position, a second partially open position and a third fully open position. The drive mechanism comprises a rack member slidably received in the manifold meshing with the rear end of the elongated valve member having a row of teeth facing outwards. A pivotally mounted pinion member with an outer end and an inner end has a plurality of teeth meshing with the teeth of the rack member. The drive mechanism also includes a front cylinder, a rear cylinder adjacent to, and aligned with, the front cylinder, a front piston seated in the front cylinder and connected to the outer end of the pinion member, and a rear piston seated in the rear cylinder. The rear piston has a rod projecting from the rear cylinder into the front cylinder to maintain at least a predetermined minimum distance between the front and rear pistons. The first and second fluid lines of a fluid pressure supply are connected to the front cylinder on opposite sides of the front piston, and a third fluid line of the fluid pressure supply is connected to the rear cylinder on the rear side of the rear piston . The application of fluid pressure through the first, second and third fluid pressure lines alternates the elongate valve member between the first closed position, the second partially open position and the third fully open position in accordance with a cycle of continuous injection. The fluid pressure is released first from the first fluid line, and the fluid pressure is applied from the third fluid line to drive the rear piston to a fully forward position, whereby the rod drives the front piston to an intermediate position. This urges the elongate valve member back from the first closed position to the second partially open position, where the front end of the elongated valve member is retracted sufficiently to allow the flow of molten material from the first source of molten material through of the outer annular molten material channel through at least one heated nozzle and the gate. After a short period, fluid pressure is applied from the second fluid line to propel the frontal piston to a fully forward position. This urges the elongate valve member back to the third fully open position, where the front end of the elongate valve member is sufficiently retracted to allow the simultaneous flow of molten material from the second source of molten material through the material channel. central melt and gate. When the cavity is almost full, the fluid pressure is released from the second fluid line and fluid pressure is applied from the first fluid line to return the front piston to the intermediate position that returns to the elongate valve member to the second partially open position until the cavity fills. Then, fluid pressure is released from the third fluid line to drive the front and rear pistons to fully retracted positions. This urges the elongate valve member to the first closed position, wherein the front end of the elongated valve member is seated in the gate to allow ejection of the molded part. Other objects and advantages of the invention will be apparent from the following description considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view of a portion of an injection molding apparatus with valve gate according to a preferred embodiment of the invention; Figure 2 is a sectional view taken along line 2-2 of Figure 1 showing the elongated valve member in the first closed position; Figure 3 is a similar view showing the elongate valve member in the second partially open position; and Figure 4 is a similar view showing the elongated valve member in the third fully open position.

DETAILED DESCRIPTION OF THE INVENTION Reference is first made to Figures 1 and 2, which show a portion of an individual cavity injection molding apparatus and with a valve gate for the molding of three layer preforms or other products by a combination of sequential coinjection molding. and simultaneous. A heated steel nozzle 10 is seated in an opening 12 in a nozzle retainer plate 14 that forms part of the mold 16. Although the mold 16 may have a larger number of plates depending on the application, in this embodiment they are only shown to facilitate the illustration the nozzle retainer plate 14 and a manifold retainer plate 18, which are secured together by bolts 20, as well as a cavity retainer plate 22. The heated nozzle 10 has an integral electric heating element 24 and a channel of annular fused material 26 which extends around a central molten material channel 28. The heated nozzle 10 has a collar portion 30 which is received in a circular seat 32 that extends around the opening 12. This locates the nozzle heated with its central molten material channel 28 extending in alignment with a gate 34 extending through a composite insert. rta cooled 36 to a cavity 38. It also provides an insulating air space 40 between the heated nozzle 10 and the surrounding mold 16 which is cooled by pumping cooling water through cooling ducts 42. The cavity 38 for manufacturing preforms of bottles of The beverage extends between a cavity insert 44 and a mold core 46 in a conventional manner. The heated nozzle 10 has a front end 48 and a rear end 50 that abuts against the front face 52 of a heated steel manifold 54. In this single-cavity embodiment it is often used as an assay before manufacturing a complete system multiple cavities, the heated manifold 54 has a front plate portion 56 and a rear cylindrical portion 58 secured by bolts 60. In other embodiments for molding individual cavities, the manifold 54 consists of a single piece. In other embodiments for molding multiple cavities of two materials having different temperature characteristics, there are two manifolds, one extending in front of the other. The manifold 54 is heated by an integral electrical heating element 62. The manifold 54 is secured in place by a mold positioning ring 64 fixed to the manifold retainer plate 18 by screws 65. The heated manifold 54 is precisely located by a locating pin 68, and has an insulating air gap 70 between it and the adjacent cooled mold 16. An elongated steel valve member 72 extends from the central molten material channel 28 rearwardly in a slot 74 in the portion rear 58 of the manifold 54. The elongate valve member 72 has a front end 76 that fits into the gate 34 and a rear end 78 that is engaged by a rack and pinion drive mechanism 80 described below. The elongated valve member 72 fits through a central hole 82 in a valve bushing 84 that extends from the heated nozzle 10 backward in an assembly seat 86 in the faceplate portion 56 of the manifold 54. A filtration hole 88 extends from the seat 86 to vent the molten material or the corrosive gases that can be generated by friction from the elongate valve member 72 alternating in the hole 82. The elongated valve member 72 also extends rearwardly through an aligned hole 90 in the front plate portion 56 of the manifold 54 and an aligned central hole 92 in another bushing 94 securely seated in the multiple 54. In this modality, a first passage of molten material 96 receives molten material through a first inlet 98 and extends through the heated manifold 54 and the heated nozzle 10 as shown to join the annular melt channel 26 in front of the valve bushing 84. A second passage of molten material 100 receives molten material through a second inlet 102, and extends through the front plate portion 56 of the heated manifold 54 and the heated nozzle 10 as shown to join the channel of molten material. central 28 in front of valve bushing 84 and extends around elongated valve member 72 to gate 34. Said insulating and elastic separator 66 compensates for the machine pressure of second inlet 102. Thus, as described in more detail below , the molten material of the first inlet 98 flows towards the gate 34 through the annular molten material channel 26 around the molten material of the second the inlet 102 flowing through the central molten material channel 28. Also in relation to FIG. 2, the valve member actuating mechanism 80 includes a rack member 104 that fits into the slot 74 in the rear portion 58 of the manifold 54, and a pinion member 106 extending into the slot 74. The rack member 104 has a T-shaped space 108 that meshes with the head 110 of the elongated valve member 72. The rack member 104 has also two sliding flat surfaces 112 that look inwardly and that rest against the sliding surfaces 114 that look outwardly on the valve member bushing 94, and a row of teeth 116 that look outwardly. The pinion member 106 is pivotally mounted on a pin 118, and has an outer end 120 extending out of the slot 74 and an inner end 122 with teeth 124 that mesh with the teeth 116 on the rack member 104. The mechanism valve member actuator 80 also includes a front cylinder 126, a rear cylinder 128 aligned with the front cylinder 126, a front piston 130 seated in the front cylinder 126 and a rear piston 132 seated in the rear cylinder 128. As can be Note, the aligned cylinders 126, 128 are fixed to a fixed mounting bracket 134 by a pin 136 which allows them to pivot during the operation. The front cylinder 126 has first and second air lines 138, 140 connected on opposite sides of the front piston 130. The rear cylinder 128 has a vent hole 142 that extends over the front side of the rear piston 132, and a third line of air 144 connected on the rear side of the rear piston 132. Although a pneumatic drive mechanism 80 is shown, in other embodiments a hydraulic drive mechanism may be used. The front piston 130 is connected by a connecting rod 146 to the outer end 120 of the pinion member 106. The rear cylinder 128 is shorter in length than the front cylinder 126, and the rear piston 132 has a rod 148 projecting to through a hole 150 in the wall 152 in the front cylinder 126 to maintain at least a predetermined minimum distance between the front and rear pistons 130, 132. The use, the injection molding system is assembled as shown in the figures 1 and 2, and functions to form 3-layer preforms and other products with a barrier layer of a material such as EVOH or nylon between two layers of a PET-type material in the following manner. Electric power is applied to the heating element 24 in the nozzle 10 and to the heating element 62 in the manifold 54 to heat them to a suitable operating temperature. Water is supplied to the cooling ducts 42 and the mold core 46 to cool the mold 16, the gate insert 36 and the cavity 38. A first injection cylinder (not shown) mounted on the first inlet 98 injects molten material subjected under pressure such as a polyethylene terephthalate (PET) type material in the first passage of molten material 96, and a second injection cylinder (not shown) mounted on the second inlet 102 injects another molten material under pressure, which is a suitable barrier material such as an ethylene-vinyl alcohol copolymer (EVOH) or special nylon in the second passage of molten material 100 in accordance with a predetermined injection cycle. As mentioned above, when molding materials such as these having different melting points, two multiples mounted opposite each other are heated at different temperatures. Controlled pneumatic pressure is also applied from a supply of pressure to the air lines 138, 140, 144 to alternate the elongated valve member 72 in accordance with the injection cycle. First, air pressure is released from the first air line 138, and air pressure is applied through the third air line 144 which drives the rear piston 132 to a fully forward position. The rod 148 projecting into the front cylinder 126 urges the front piston 130 to an intermediate position which, in turn, drives the elongate valve member 72 backward from a first closed position shown in Figure 2 to a second partially positioned position. shown in Figure 3. In this second position, the front end 76 of the elongated valve member 72 is sufficiently retracted to allow the PET of the first passage of molten material 96 to flow through the annular melt channel 26 in the nozzle. heated 10. After a small amount of PET has been injected into the cavity 38, air pressure is applied through the second air line 140 to drive the front piston 130 to a fully forward position. This urges the elongated valve member 72 back to a third fully open position shown in Figure 4, in which the front end 76 of the elongate valve member 72 is sufficiently retracted to allow the barrier material of the second passage of material 100 melt flows through the central molten material channel 28 and the gate 34 simultaneously with the PET of the first passage of molten material 96 flowing through the annular molten material channel 26. The barrier material flowing simultaneously with the PET separates the flow of PET in two, and provides a central layer of the barrier material between two outer layers of PET. When the cavity 38 is almost full, air pressure is released from the second air line 140, and air pressure is applied from the first air line 138 to return the front piston 130 to the intermediate position that returns the air limb. elongated valve 72 to the second partially open position. This closes the flow of the barrier material through the central molten material channel 28, and allows only the PET of the first passage of molten material 96 to flow through the annular molten material channel 26 until the cavity 38 is filled. After a brief packing period, the air pressure is released from the third air line 144 to drive both pistons 130, 132 to their fully retracted positions. This, in turn, urges the elongate valve member 72 to the first closed position shown in Figure 2, with its front end 76 seated in the gate 34 to allow the mold to open for ejection. After ejection, the mold 16 is closed, and the cycle is repeated continuously every 15 to 30 seconds, with a frequency that depends on the wall thickness and the number and size of the cavities 38 and the exact materials being molded. Although the description of the valve gate injection molding apparatus having three-position rack and pinion valve member drive mechanism has been given with respect to a preferred embodiment, it will be evident that several other modifications are possible without departing of the scope of the invention, as understood by those skilled in the art and as defined in the following claims. For example, the description of the three-position drive mechanism has been given for the molding of three layers with an individual manifold, but it can also be used with apparatuses having separate front and rear manifolds. It can also be used for five layer molding, having two passages of PET melt material with a valve in one of them, as shown in the applicant's Canadian patent application serial number 2,219,257, filed October 23, 1997 , and titled "Sprue Gated Five Layer Injection Molding Apparatus". In addition, this three-position drive mechanism can be used in a multi-cavity application, providing a separate drive mechanism for each heated nozzle 10. The embodiments of the invention, in which a unique property or privilege is claimed, are defined in the following way:

Claims (4)

NOVELTY OF THE INVENTION CLAIMS

1. - In an injection molding apparatus with valve gate for multi-layer molding having at least one manifold and at least one heated nozzle mounted in a mold, at least one heated nozzle having a rear end, one end front, a channel of central molten material extending to the front end, and at least one channel of annular fused material extending around the central molten material channel to the front end of the nozzle, at least one heated nozzle which extends from at least one manifold with the central molten material channel in alignment with, and adjacent to, a gate leading to a cavity in the mold, a first passage of molten material from a first source of molten material that is extends through at least one manifold and at least one of the channels of molten material in at least one heated nozzle to the aligned gate, one second passage of molten material from a second source of molten material extending through at least one manifold and at least one of the channels of molten material in at least one heated nozzle to the aligned gate, an elongated valve member having a rear end and a front end extending through the central molten material channel in at least one heated nozzle, the improvement further comprising: a rack and pinion drive mechanism for alternating each elongated valve member between a first closed position, a second partially open position and a third fully open position, the driving mechanism comprising: (a) a rack member slidably received in at least one manifold meshing with the rear end of the elongate valve member, rack member having a row of teeth facing outward, (b) a pinion member pivotally mounted with an outer end and an inner end having a plurality of teeth meshing with the teeth of the rack member, and (c) a front cylinder, a rear cylinder adjacent to, and aligned with, the front cylinder, a piston front seated in the front cylinder and connected to the outer end of the pinion member, a rear piston seated in the rear cylinder, the rear piston having a rod projecting from the rear cylinder into the front cylinder to maintain at least a minimum distance predetermined between the front and rear pistons, first and second fluid pressure fluid means lines connected to the front cylinder on opposite sides of the front piston, and a third fluid pressure means fluid line connected to the rear cylinder on the side of the posterior piston, by means of which by applying fluid pressure through the first, second and third fluid pressure lines, the elongate valve member is alternated between the first closed position, the second partially open position and the third fully open position in accordance with a continuous injection cycle, wherein the fluid pressure is released first of the first fluid line, and the fluid pressure is applied from the third fluid line to drive the rear piston to a fully forward position, whereby the rod drives the frontal piston toward an intermediate position that urges toward the valve member elongated backwardly from the first closed position to the second partially open position, wherein the front end of the elongated valve member is sufficiently retracted to allow the flow of molten material from the first source of molten material through a outer channel of at least one annular molten material channel through at least one heated nozzle and the gate, after a short predetermined period fluid pressure is applied from the second fluid line to propel the frontal piston to a fully forward position which urges the elongate valve member back to the third fully open position, where the front end of the elongate valve member is sufficiently retracted to allow the simultaneous flow of molten material from the second source of molten material through the central molten material channel and the gate, when the cavity is almost full, the fluid pressure is released from the second fluid line and fluid pressure is applied from the first fluid line to return the front piston to the intermediate position that returns the elongate valve member to the second partially open position until the cavity is filled, and then pressure is released of fluid from the third fluid line to drive the pistons fr Ontal and posterior to fully retracted positions urging the elongated valve member to the first closed position, wherein the front end of the elongate valve member is seated in the gate, to allow ejection of the molded part.

2. The injection molding apparatus according to claim 1, character by the molding of three layers, wherein at least one heated nozzle has a channel of annular fused material that extends around the central molten material channel, the first passage of molten material from the first source of molten material extends through the annular channel, the second passage of molten material from the second source of molten material extends through central molten material channel, the molten material from the first source of molten material flows through the annular molten material channel when the elongate valve member is in the second partially open position, and the molten material of the second source of molten material flows simultaneously through the central molten material channel when the elongated valve member is in the third fully open position.

3. - The injection molding apparatus according to claim 1 for molding an individual cavity, further character in that it comprises only one manifold and only one heated nozzle extending therefrom.

4. - The injection molding apparatus according to claim 1, further character in that it has a valve member bushing seated in at least one nozzle, the valve member bushing having a rearward extending portion projecting into at least one manifold, a valve member hole extending therethrough in alignment with the central molten material channel through at least one heated nozzle to receive the elongated valve member therethrough , and at least one outward facing surface, wherein the rack member has at least one inwardly facing surface slidably supported against at least one surface facing outwardly of the valve member bushing. SUMMARY OF THE INVENTION Injection molding apparatus with valve gate having a three position valve member drive mechanism for multiple layer molding; a first passage of molten material extends to the gate through an annular channel in a heated nozzle, while a second passage of molten material extends around an elongated valve member in a channel of central molten material; a rack member meshing with the rear end of the valve member is driven by a pinion member connected to a front piston in a front cylinder; a rear piston in a shorter rear cylinder aligned with the front cylinder has a rod that extends forward in the front cylinder; first, the air pressure applied behind the rear piston retracts the valve member from a first closed position to a second partially open position, wherein the molten material flows only through the annular channel; then, the air pressure applied behind the front piston retracts the valve member to a third fully open position, wherein the molten material flows simultaneously through both channels of molten material to provide the three layers; when the cavity is almost full, the air pressure is released behind, and applied opposite, the front piston to return the valve member to the second position, until the cavity is filled; the air pressure is then released behind the third piston to advance the valve member to the first closed position, in which its front end is seated in the ejector gate. MG / amm * lpm * xma. P98-1396.