HK1035164B - Valve gating apparatus and method for injection molding - Google Patents

Description

Valve gating apparatus and method for injection molding

Technical Field

The present invention relates to a valve gating apparatus. More specifically, the present invention relates to an apparatus for laterally controlling the flow of molten material from an injection nozzle into a mold cavity.

Background

It is well known in the injection molding art that means must be provided to prevent the flow of molten material into the cavity of the mold so that the mold can be cooled and opened and the molded part removed. Basically, two main stopping techniques are known in the field of injection molding, namely: hot gating, in which a gate at the outlet of a nozzle rapidly cools upon completion of an injection operation, forms a solid or semi-solid plug of injected material and a valve gate at the gate, in which a mechanical device is used to prevent the injected material from flowing into a mold cavity, each having its own advantages and disadvantages over the other, and many devices for hot gating and for valve gating are well known.

While various devices of each type have been developed, valve gating systems are generally one of two types, namely a coaxial and lateral device in which a valve stem centered with a gate is moved to a direction parallel to the direction of movement of molten material (commonly referred to as "melt") and through the gate, between a position where the valve stem extends into the gate to block further flow into the gate and a position where the valve stem is retracted from the gate to allow flow therethrough into the mold cavity. To align the gate, a valve stem is positioned inside the nozzle and at least partially within the melt flow path.

For these or other reasons, coaxial valve gates have various problems. A common problem is valve stem wear due to contact with the nozzle and/or gate, which can lead to valve stem deflection and thus valve leakage or failure. Another common problem is the transition of the melt from a tubular flow into the nozzle to an annular (or other discontinuous) flow caused by a valve stem or other related component in the melt stream. Such a discontinuous flow can produce welds or ties in the molded article due to recombination of the melt streams in the gate or mold cavity, and this can result in a weakened or rejected molded article. Some examples of recent coaxial devices that have attempted to address these and/or other issues include: 4,412,807 of U.S. patent York, 4,925,384 of Manner, 5,254,305 of femandrez, and the like.

In a side-valve gating system, a valve element is moved through the melt stream before or after the gate to block or allow fluid to pass through the gate. The side gating system can avoid the problems of offset, reliability and melt shunting of the coaxial valve gating system. They have their own problems and disadvantages. For example, a side-gate valve gating system positioned too far from the mold cavity can result in unsatisfactory sprue marks on the molded part.

Another problem with gate systems is that, typically, in the melt channel of the mold cavity, the melt material near the gate is subjected to a different cooling pattern than the remaining melt in the cavity. In particular, the nozzle is heated to maintain the melt in a molten state, so that the melt material in the melt channel near the gate of the mold cavity cools less effectively than the remaining material in the mold cavity because of some heat transfer from the melt in the gate. Many melt materials degrade or otherwise produce undesirable characteristics when exposed to poor cooling conditions. For example, in the particular case of PTE, the material can exhibit crystallinity when in a poor cooling state and/or when the level of acetylaldehyde that can be produced increases.

Us patent 4,108,956 to Lee indicates that in the embodiment of figures 1, 2 and 3, the lateral gating mechanism comprises a valve gate in the form of a pair of slidable plates having through holes. When the holes in these plates are aligned with the gates, the melt material is able to flow from the nozzles into the mold cavities. When the injection operation is complete, laterally moving the plate moves the aperture away from alignment with the gate and prevents additional melt from flowing into the mold cavity. This patent teaches that the plates impart the advantage that they provide thermal insulation between the gate of the nozzle and the cooling mold to prevent unwanted heat transfer therebetween. Thereby, poor cooling of the melt in the mold cavity adjacent the gate is mitigated. Thus, the thickness and material of the plates are selected to provide the desired thermal insulation characteristics, and in fact, the patent teaches that a pair of plates, one above the other, use plates adjacent to the various plates formed of the thermally insulating material and the plates are adjacent to a mold formed of the thermally conductive material.

However, as with many other side gating mechanisms, the device taught by Lee also suffers from several disadvantages, particularly that as they move to a melt blocking position, some material, such as melt, is entrained in the bore of the plate and forms a cooling blockage therein, which results in two disadvantages, namely that some material is wasted in each mold closing operation and that the cooling blockage must be prepared for removal and disposal from the bore before the plate returns to a position that allows melt flow. The generation of waste is unacceptable in many applications, such as when forming PET preforms or in clean room environments. The additional means of removing and discarding cooling plugs is not satisfactory in multi-cavity molds. The Lee patent does not represent a viable approach.

Other examples of known side gating systems are shown in U.S. Pat. Nos. 3,288,903 to Hendry, 3,599,290 to Garner, 3,632,729 to Biefeldt and 3,809,519 to Ganer. Most of these patents are directed to controlling the flow of melt from an injection molding machine. Thus, the disadvantages of Lee '956', which is typically used only for mold in-gates, do not represent a major problem.

British patent 1,369,744, although not teaching a side gating system, shows in the embodiment shown with reference to figures 1 to 8a pair of valves positioned upstream from the gate and which contain a side shuttle. These shuttles are forced from a closed position (i.e., where melt flow is prevented) to an open position by the pressure exerted by the melt, which counteracts the applied hydraulic pressure. The valve is used to open and close the material to be injected rather than to control the flow of melt out of the gate and into the mold cavity. Moreover, when the gate is directly downstream of the shuttle, there is a significant amount of melt downstream of the shuttle and can create large, undesirable sprue marks on the molded part because the melt material remains in contact with the mold cavity. Also, the shuttles are driven by the pressure differential between the hydraulic cylinder and the melt stream. Such drive mechanisms do not provide precise control of the multiple nozzles and are not suitable for installation in injection molds due to the volume occupied by the mechanism and hydraulic leakage, which inevitably delays use and is not possible in molds.

Another problem with all drive gate systems is that the gates are of a constant size. The present inventors are now aware of all gating systems in which the cross-sectional area of the gate is constant and thereby limits the rate of melt flow into the mold cavity. In some cases, it is desirable to inject different materials and/or different amounts of those materials into the mold cavity, as in the case of co-injection molding. In this case, the mold designer must select a gate size that is a compromise between the optimum size for each material and/or quantity of material.

In other cases, it may be desirable to inject a material or materials at different rates. For example, cantilevered mold cores, such as those used in molding PET blow preforms, can be laterally displaced within the mold cavity by the melt material entering the mold cavity at the beginning of the injection operation. In conventional devices, the mold cavity is filled at a substantially constant rate because the cross-sectional area of the gate and the melt supply pressure from the injection molding machine are substantially constant. Thus, the molten material enters the mold cavity at a substantially constant pressure and velocity. If the mold gate size can be changed, the melt can begin to enter the mold cavity at a reduced pressure and/or velocity until some melt surrounds a portion of the mold core, and then the gate size is adjusted to allow the remainder of the melt to enter at a higher pressure and/or velocity.

Moreover, with prior art gating systems, as the mold cavity changes to mold different parts, the gates of the mold need to be changed to be larger or smaller to accommodate the new melt flow requirements. If the size of the mold gate can be changed in the mold, the time required to change the cavity can be reduced.

It would be desirable to have an apparatus and method for side gating for injection molding operations that provides the advantages of side gating without at least some of the drawbacks typically associated therewith. In addition, it is desirable to have an apparatus and method for a side gate that allows the cross-sectional area of the gate to be varied. This change in the cross-sectional area of the gate enables the melt to be injected under different conditions, such as different flow velocities and/or pressures.

Summary of The Invention

It is an object of the present invention to provide a novel valve gating apparatus for a valve gate used in an injection molding operation.

According to one aspect of the present invention there is provided a valve gating apparatus for an injection mold nozzle assembly, the assembly being disposed on a manifold plate and including a melt channel and a nozzle gate, the valve gating apparatus being located between the nozzle gate and a mold cavity, the valve gating apparatus comprising: at least one movable shuttle is disposed between the manifold plate and the mold cavity, the at least one movable shuttle being movable between a first position in which the gate is in fluid communication with the mold cavity and a second position in which the shuttle blocks the flow of melt material from the nozzle gate; means for moving said shuttle between said first and second positions in a direction substantially perpendicular to the flow of melt through said nozzle gate; the method is characterized in that: the shuttle includes a body having a through bore defining a melt flow path and a sealing rim, the through bore having a sealing post mounted therein proximate the nozzle gate, the sealing rim of the shuttle abutting the sealing post in the second position to prevent melt flow, and the sealing rim being spaced from the sealing post in the first position.

The present invention provides a novel side valve gating apparatus for operating an injection mold. The thermal insulation between the cooled melt in the mold cavity and the hot melt in the nozzle can be improved and sprue marks reduced or eliminated. The valve gate constructed according to the present invention has good reliability and no abnormal wear. Also, the gate of the nozzle can be adjusted to a reduced cross-sectional area to allow for the injection flow characteristics to be determined at will. In addition, each melt channel of the multi-material nozzle may be optionally gated.

The present invention also provides the ability to control a multi-mold nozzle with a single shuttle or a pair of shuttles, which can give the present invention a particular size and cost efficiency. In particular, a single shuttle or a pair of shuttles requires much less volume within the injection mold than many prior art valve gating systems that require separate actuators for each nozzle. This enables the mold or machine designer to place the nozzles in a narrower space and/or to use more nozzles than would otherwise be the case. Furthermore, the shuttle or shuttle pair, according to the present invention, is inexpensive to configure, since the shuttle is very simple to manufacture and reduces the number of drives required to operate the shuttle, as well as being able to reduce the cost of constructing such a machine or mold. Furthermore, by controlling multiple nozzles with one shuttle or a pair of shuttles, accurate and easy gate control of those multiple nozzles can be ensured.

Furthermore, an important benefit is that the present invention employs a single or multiple shuttle that does not carry melt material when the mold is closed, reducing or eliminating material waste at the valve gate, and eliminating the need to provide specialized equipment for removing and disposing of such waste material.

Brief description of the drawings:

preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings.

FIG. 1 shows a cross-section of a portion of a nozzle and a side gate member including a pair of shutters adjacent a mold cavity and with the shutters in an open position in accordance with a first embodiment of the present invention;

FIG. 2 shows a section along line 2-2 of FIG. 1 with a square cross-sectional gate;

FIG. 2a shows a section along line 2-2 of FIG. 1 with a round cross-sectional gate;

FIG. 3 shows the shuttle of FIG. 1 in a closed position;

FIG. 4 shows a cross-section along line 4-4 of FIG. 3;

FIGS. 5a-5d illustrate the construction of a shuttle according to the present invention;

FIG. 6 shows a cross-section of a portion of a nozzle and a shuttle proximate a mold cavity and wherein the shuttle is in an open position in accordance with another embodiment of the present invention;

FIG. 7 shows a cross-section taken along line 7-7 of FIG. 6;

FIG. 8 shows the shuttle of FIG. 6 in a closed position;

FIG. 9 shows a cross-section taken along line 9-9 of FIG. 8;

FIG. 10 shows a cross-section of two nozzles and a shuttle according to another embodiment of the present invention, and wherein the shuttle is in an open position;

FIG. 11 shows a cross-section taken along line 11-11 of FIG. 10;

FIG. 12 shows the shuttle of FIG. 10 in a closed position;

FIG. 13 shows a cross-section taken along line 13-13 of FIG. 12;

FIG. 14 shows a cross-section of a portion of a nozzle and a shuttle proximate a mold cavity with the shuttle in an open position in accordance with another embodiment of the present invention;

FIG. 15 shows the shuttle of FIG. 14 in a closed position;

FIG. 16 shows a cross-section of a portion of a nozzle and a pair of shuttles adjacent a mold cavity with the shuttles in an open position in accordance with another embodiment of the present invention;

FIG. 17 shows the shuttle of FIG. 16 in a closed position;

FIG. 18 is a diagrammatic, schematic view of one embodiment of a drive for moving a shuttle in accordance with the present invention;

FIG. 19 is a diagrammatic, schematic illustration of three shuttles mounted within a frame and a drive moving the frame in accordance with the present invention;

FIG. 20 shows a shuttle with a two-dimensional array of orifices for controlling an array of nozzles in accordance with an embodiment of the present invention;

FIG. 21 shows a cross-section of a structure similar to that of FIG. 10, but including a round gate and a suitable shuttle;

FIG. 22 shows the shuttle of FIG. 21 in a closed position;

FIG. 23 shows a pair of shuttles in a closed position controlling three melt channel nozzles;

FIG. 24 shows the shuttle of FIG. 23 in a position wherein one gate is open and two gates are closed in the nozzle of the three melt channel;

FIG. 25 shows a single shuttle of the nozzle for two melt channels in a closed position;

FIG. 26 shows the shuttle of FIG. 25 in a first open position; and

FIG. 27 shows the shuttle of FIG. 25 in a second open position.

Detailed description of the invention

A portion of an injection mold according to a first embodiment of the present invention is shown generally at 20 in fig. 1. FIG. 1 shows a hot runner nozzle assembly 24 for a mold 20 with a mold gate 28 adjacent a nozzle tip 32 of a nozzle 36. Nozzle 36 is in thermal contact with one or more heater elements 34, which may be wound, ribbon, ceramic or other suitable heater elements, and includes a melt channel 38 through which melt material from the injection molding machine flows. The flow of melt material out of the melt channel 38 in the nozzle through the gate 28 and the insulating member 39 help thermally insulate the melt from the mold plate 20.

The mold cavity 40 with the mold core 44 is connected to the mold gate 28 through an inlet 48 to the mold cavity 40. Between nozzle tip 32 and inlet 48 to mold cavity 40 is a valve, which, according to a first embodiment of the present invention, is formed by a pair of side gate shuttles 52a, 52 b.

In FIG. 1, the shuttle 52 is in an open position, whereby melt from the nozzle assembly 24 can be injected into the mold cavity 40 through the gate 28 and the inlet 48 to the mold cavity 40. Fig. 2 is a cross-section taken along line 2-2 of fig. 1 showing the relationship between gates 28 a-28N and shuttles 52a and 52b of an array of N nozzles. Also, the present invention may be employed with a single nozzle assembly 24, which is expected to be most conducive to multi-cavity or large single-cavity molds, wherein multiple nozzle assemblies 24 will be used, each manipulated by shuttle 52.

In the embodiment shown in fig. 2, each of the gates 28a, 28b, and 28n has a substantially square cross-section. Fig. 2a shows the system of fig. 2, but wherein the gate 28 is circular in cross-section. In fig. 2, a sealing element 56 is located between each pair of gates 28 and only the end sealing element 60 is disposed opposite the open sides of gates 28a and 28 n. In the illustrated embodiment, the end seal element 60 is a separate piece, but it is also contemplated that the seal element 60 is part of the shuttle 52a and/or the shuttle 52 b. As will be apparent to those skilled in the art, the periphery of gates 28a and 28n is sealed on one side by end seal element 60, on the next side by gate 52a, on the next side by seal element 56, and on the last side by shuttle 52 b. The periphery of gate 28 between adjacent nozzles, such as gate 28b, is sealed by sealing member 56 and shuttles 52a and 52 b.

In fig. 2a, the periphery of gate 28 and the "dead space" described below are sealed by end seal element 60, shuttle 52a, seal element 56, and shuttle 52 b. As shown in this figure, some melt will collect in the dead zone. By moving the two shuttles 52a and 52b, the material is pushed back into the mold or nozzle. Therefore, no waste will be generated. Any known means such as a pneumatic piston and an elastic resilient means can drive the shuttles 52a and 52 b.

Fig. 3 shows the nozzle of fig. 1 in a closed position with shuttles 52a and 52b, wherein melt from nozzle 36 is prevented from entering inlet 48 of mold cavity 40 and mold cavity 40. Fig. 4 shows a section taken along line 4-4 of fig. 3, which shows how gate 28 is blocked when shuttles 52a and 52b are in the closed position, as will be apparent to those skilled in the art, and as will be discussed further below, shuttles 52a and 52b may be set to various intermediate positions illustrating the open and closed positions to arbitrarily "tune" gate 28 and thereby effectively establish a gate of a desired cross-sectional size.

When a round gate 28 is used as shown in fig. 2a, shuttles 52a and 52b function substantially as they would if used in a gate of square cross-section. As will be apparent to those skilled in the art, when the shuttles 52a and 52b are in the open condition as shown in fig. 1 and 2, the molten material is able to enter the dead zone 54. However, it will also be apparent that when the shuttles 52a and 52b are moved to the closed position as shown in FIG. 4, the molten material is scraped from the dead space by the leading edge of the shuttle 52 into the gate 28 and inlet 48.

It is contemplated that shuttles 52a and 52b, seal 56 and end seal 60 can be made from a variety of materials and in a variety of configurations. One of the anticipated advantages of the present invention is the ability to obtain thermal insulation between the melt in the gate 28 and the melt in the inlet 48 to the mold cavity 40. Accordingly, the shuttle 52, seal 56 and end seal 60 may be fabricated from a suitable insulating material such as titanium or a ceramic such as zirconia and/or coated with a material having the desired heat transfer characteristics. For example, the surface of the shuttle 52 adjacent the gate 28 may be coated with a heat reflective material such as chromium or silver and the surface of the shuttle 52 proximate the inlet 48 to the mold cavity 40 may be coated with a heat transfer material such as copper or stainless steel.

Various factors influence the thickness selection of shuttle 52. It is generally desirable that shuttle 52 be relatively thin to minimize the displacement of melt into nozzle assembly 24 and/or mold cavity 40 as shuttle 52 moves from the open position to the closed position. It will be apparent to those skilled in the art that when shuttle 52 is closed, the melt therebetween will be expelled and that this expelled melt will create a back pressure of the melt entering nozzle assembly 24 and/or mold cavity 40. The thinner shuttle 52 that can be manufactured, the less melt that is expelled, whereas, when shuttle 52 is in the closed position, it must be in close proximity to one another to provide a reasonable seal against the flow of more melt from nozzle assembly 24 into mold cavity 40, and thus, shuttle 52 must be sufficiently rigid to ensure that a seal is created at the interface. Sufficient stiffness may be achieved in a variety of ways, including making the shuttle 52 of a material of sufficient dimension (thickness) to ensure stiffness and/or to support the side edges 64 of the shuttle 52 in additional grooves (not shown) in the seal 56 and/or seal 60, in any event, the thickness of the seal 56 and end seal 60 will generally be selected to correspond to the selected thickness of the shuttle 52.

In the embodiment of fig. 1-4, it is apparent that in fig. 1 and 3, the sealing edges 68 of the shuttles 52a and 52b are formed perpendicular to the plane of the shuttle 52 and this provides a relatively large contact area between the shuttles to achieve the desired seal. Fig. 5(a) to 5(d) show other contemplated configurations of the sealing edge 68 of the shuttle 52, one configuration shown in fig. 5(a) in which the sealing edge 68 of the shuttle 52 is wedge-shaped. It is contemplated that such a configuration will "cut" the melt in gate 28 and will direct any melt expelled upon closing shuttle 52 into mold cavity 40, but conversely, fig. 5(b) shows a similar configuration that will direct expelled melt into nozzle assembly 24 upon closing shuttle 52. Melt 5(c) represents a configuration in which the sealing edge 68 on each shuttle 52 complements the other shuttle 52. In this particular example, shuttle 52b includes a wedge-shaped sealing edge 68b having a complementary wedge-shaped groove in sealing edge 68a of shuttle 52 a. FIG. 5(d) shows a sealing edge 68 of shuttle 52 having a mirror image wedge-shaped edge, which embodiment may be preferred when it is desired to "tune" the size of gate 28.

One of the advantages perceived with the dual shuttle 52 is that they can be moved to the throttling gate 28 so that the resulting effective gate cross-sectional area remains coaxial below the tip 32.

Fig. 6 shows another embodiment of the invention, generally designated 80, in which components identical to those shown in fig. 1 are designated by the same reference numerals. In this embodiment, only a single shuttle 84 is employed. Fig. 7 is a cross-section taken along line 7-7 of fig. 6 showing the relationship between gates 28 a-28 n of an array of nozzles and shuttle 84. Moreover, while the present invention may be employed with a single nozzle assembly 24, it is contemplated that a multi-cavity mold or a large single-cavity mold in which multiple nozzle assemblies 24 are employed is most beneficial. As shown in fig. 6 and 7, a seal 88 is disposed on a side of gate 28 opposite shuttle 84.

As shown, shuttle 84 includes a sealing edge 92 and a pair of side edges 96 formed on a sealing finger 100. The seal 88 may be a separate element or formed directly in the multi-tube sheet 104, including a slot 108 into which a portion 112 of the seal finger 100 extends when in the open position shown.

In the closed position, as shown in fig. 8 and 9, shuttle 84 is moved such that sealing edge 92 abuts seal 88 and sealing finger 100 extends into slot 108 as shown. It is presently believed that this embodiment provides advantages over those shown in fig. 1-4 in that only a single shuttle 84 must move and the sealing edges 92 are well supported throughout their range of motion by the sealing fingers 100.

It will be apparent to those skilled in the art that as with the previous embodiments of the invention, the shuttle 84 is disposed at any intermediate position between the illustrated open position and the illustrated closed position if desired to provide gates 28 having different sizes, i.e., a "trim" gate. Further, shuttle 84 may be fabricated from a variety of materials and/or coatings to achieve the desired thermal properties and to enable a variety of suitable configurations for sealing edge 92.

It will be apparent to those skilled in the art that in the embodiment of figures 6 to 9, the gate 28 need not be square in cross-section in this embodiment and may instead be of generally circular or other cross-section.

Figures 10 to 13 show a further embodiment of the invention, generally designated 110, in which the same parts as those shown in figure 1 will be indicated by the same reference numerals. As shown in fig. 10 and 11, in this embodiment, two nozzle assemblies 24 and 24' are located in the manifold plate 120 and controlled by a single shuttle 128. For each nozzle 24 and 24', manifold plate 120 includes a sealing post 124 that may be integrally formed with plate 120 or secured thereto by any suitable means as will occur to those of skill in the art. Shuttle 128 includes a rectangular slot 132 for each nozzle 24, 24', sized to conform to the width of the illustrated post 124 and gate 28 and including a sealing edge 136. When it is desired to close the gates 28 and 28', the shuttle 128 moves to bring the sealing edge 136 into contact with the sealing post 124, as shown in fig. 12 and 13. As with other embodiments of the invention, shuttle 128 may be disposed at any desired position intermediate the open position of fig. 10 and the closed position of fig. 12 to vary the size of gates 28, 28 ', i.e., to adjust gates 28, 28'. If multiple shuttles 128 are used, each shuttle 128 controls one or more nozzles and may be coupled to a suitable frame for synchronous movement between positions by a single drive mechanism, as described below.

Fig. 14 and 15 illustrate another embodiment of the present invention, generally indicated at 160, in which components identical to those shown in fig. 1 are identified by the same reference numerals. In this embodiment, similar to that shown in fig. 6-8, on one side of gate 28, manifold plate 120 extends toward the mold cavity to form a surface having an edge 164 against which the shuttle in closed position shuttle 84 abuts.

Fig. 16 and 17 illustrate another embodiment of the present invention, generally indicated at 180, in which components identical to those shown in fig. 1 are identified by the same reference numerals. In this embodiment, similar to that shown in fig. 10-13, seal post 124 is disposed on manifold plate 120 and second seal post 184 is disposed on cavity plate 188, which is on the opposite side of gate 28 from seal post 124. With a pair of shuttles 128 and 192, each seal abuts a respective one of the sealing posts 124 and 184 in the closed position, as shown in FIG. 17. This embodiment positions the gate 28 over the center of the through-hole formed by the shuttle 128,192 as they are positioned intermediate the open and closed positions shown to accommodate the gate 28. Further, shuttle 128 may be fabricated from a material having good thermal insulation properties, such as titanium or a ceramic material, and shuttle 192 may be fabricated from a material having good heat transfer properties to provide the desired thermal properties for cooling the article in mold cavity 40.

It will be apparent to those skilled in the art that the possibility of controlling multiple nozzles with a single shuttle or with a shuttle gives the invention particular size and cost efficiencies. In particular, a shuttle or shuttle pair requires much less volume in an injection mold than many prior art valve gated nozzle systems that require separate actuators for each nozzle. Thus, the machine and/or mold designer can employ more nozzles and/or space the nozzles closer together, if desired.

Further, the configuration of multiple or dual shuttles according to the present invention is less expensive because the shuttles are simpler to manufacture and the number of drives required to operate the shuttles is reduced. Also, by controlling a plurality of nozzles with a single shuttle or with pairs of shuttles, accurate and consistent nozzle control can be achieved with relative ease, ensuring that an equal amount of melt material is supplied to each mold cavity.

It will be apparent to those skilled in the art that operation of the shuttle in embodiments of the present invention may be accomplished by a variety of means. For example, as shown in the schematic of fig. 18, shuttle 200 may be moved between open, regulated (neutral) and closed positions by a hydraulic driver 204 and a return spring 208. Any suitable method may be used to move the shuttle 200 in the direction of arrow 216 to supply the hydraulic fluid 212 to the hydraulic cylinder 204 and the return spring 208 is capable of moving the shuttle 200 in the direction indicated by arrow 220 when hydraulic pressure is removed from the hydraulic cylinder 204. If more precise positioning is required, such as to regulate melt flow in a very precise manner, a mechanical worm drive, stepper motor, or any other suitable method as would occur to those skilled in the art may be employed.

The present invention can be configured in various ways for multi-nozzle applications. As described above, a single shuttle or a pair of shuttles according to the present invention may function as a throttle or valve controlled multi-nozzle. It is contemplated that, as shown in FIG. 19, the shuttle 250 may be mounted on a frame 254 and then moved in the direction of arrow 256 by a drive 258. If pairs of shuttles 250 are employed, each shuttle has one or more apertures 252. One of each pair of shuttles 250 is mounted in a frame 254 and the corresponding other shuttle of each pair of shuttles 250 is mounted in a second frame 254, and the frames are free to move by a corresponding one of a pair of actuators 258.

FIG. 20 shows another embodiment of the present invention using a shuttle 275 wherein a series of nozzles to be controlled are aligned. As shown, shuttle 275 is a substantially rectangular plate or flap in which apertures 279 are formed in a layout that conforms to the configuration of the nozzles to be controlled. A drive (not shown) may be coupled to the shuttle 275 in any suitable manner.

Fig. 21 and 22 illustrate another embodiment of the present invention, which is similar to that discussed above with reference to fig. 10-14, but wherein the gate 28 is circular. As shown in fig. 21, wherein the shuttle 128 is in the open position, the sealing post 124 includes a semicircular edge 300 corresponding to the edge of the adjacent gate 28. The leading edge 304 of shuttle 128, which is a complementary semi-circle, fits into edge 300 to seal the gate 28 as shown in the closed position of FIG. 22. As will be apparent to those skilled in the art, the semi-circular edge 304 creates a dead zone 308 into which melt may enter when an injection operation is performed, but from which dead zone 304 such melt is scraped as the shuttle 128 moves to the closed position.

FIG. 23 shows a dual shuttle embodiment of the present invention, generally designated 400, having a nozzle 404 with three melt channels 408, 412 and 416. Each melt channel supplies one of the different melt materials to gates 420, 424, and 428, with two of the shuttles 432 and 436 in fig. 23 in a closed state, wherein all three of gates 420, 424, and 428 are closed. In fig. 24, shuttle 432 has moved to the left, and shuttle 436 has also moved to the left to a lesser extent, so that at this point gate 420 is open while gates 424 and 428 remain closed. It will be apparent to those skilled in the art that by appropriately positioning shuttles 432 and 436, gates 420, 424 and 428 can be closed or one, any adjacent two or all three of gates 420, 424 and 428 can be opened as desired. Also, shuttles 432 and 436 can be positioned to adjust one or more of gates 420, 424 and 428 if desired. This new design may be used to form a multilayer preform where one material may be virgin PET, a second material may be recycled PET and a third material may be a barrier layer such as EVOH. A multi-tube and injection molding machine capable of operating with these nozzles is described in U.S. patent No.4863665, incorporated herein by reference, and the same study can be applied to a nozzle having two melt channels for different materials.

Fig. 25, 26 and 27 illustrate another embodiment of the present invention, generally designated 500. One two-material nozzle 504 includes a first melt channel 508 and a second melt channel 512. This embodiment may be used for a valve-injection operation, where a first amount of melt material is injected in melt channel 508, and then an amount of both melt material in melt channel 508 and melt material in melt channel 512 are injected simultaneously. Fig. 25 shows the embodiment in a closed position, similar to that shown in fig. 10, with the shuttle 516 in the closed position and abutting against the sealing post 520. FIG. 26 shows this embodiment in a first injection operating position, wherein shuttle 516 has been moved to open between melt channel 508 and gate 28. FIG. 27 shows an embodiment of a second injection operating position wherein shuttle 516 has been moved to open between melt channels 508 and 512, where melt material is simultaneously injected, and gate 28. As will be apparent to those skilled in the art, shuttle 516 may be disposed in an intermediate position, if desired, in which (i) melt channel 508 is shut off and melt channel 512 is closed, and (ii) melt channel 508 is open and melt channel 512 is shut off.

However, the embodiment of fig. 25 to 27 shows one shuttle and one sealing post. It will be apparent to those skilled in the art that the other embodiments described above may optionally employ nozzles having two melt channels.

The present invention provides a novel valve gating apparatus and method for operating an injection mold. Thermal insulation between the cooled melt in the mold cavity and the hot melt in the nozzle can be improved and gate marks can be reduced and eliminated. Valves constructed in accordance with the present invention have good reliability and do not suffer from abnormal wear. Moreover, in rare cases where multiple nozzles require control, the present invention can be implemented in a smaller area and at a lower cost than prior art systems that require a valve stem for each nozzle.

The embodiments of the invention described above are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.

Claims (14)

1. A valve gating apparatus for an injection mold nozzle assembly (24, 24 ') disposed on a manifold plate and including a melt channel (38) and a nozzle gate (28, 28 '), said valve gating apparatus being positioned between the nozzle gate (28, 28 ') and a mold cavity (40), said valve gating apparatus comprising:

at least one movable shuttle (128, 192, 250, 275, 516) disposed between the manifold plate and the cross-cavity, the at least one movable shuttle being movable between a first position in which the gate (28, 28 ') is in fluid communication with the mold cavity (40) and a second position in which the shuttle (128, 192, 250, 275, 516) blocks the flow of melt material from the nozzle gate (28, 28');

means for moving said shuttle (128, 192, 250, 275, 516) between said first and second positions in a direction substantially perpendicular to the flow of melt through said nozzle gate (28, 28'); the method is characterized in that:

the shuttle (128, 192, 250, 275, 516) includes a body having a through bore (132, 252, 279) defining a melt flow path and a sealing rim (136, 304), the through bore (132, 252, 279) having mounted therein a sealing post (124, 184, 520) proximate the nozzle gate (28, 28'), the sealing rim (136, 304) of the shuttle abutting the sealing post (124, 184, 520) in the second position to inhibit melt flow, and the sealing rim (136, 304) being spaced from the sealing post (124, 184, 520) in the first position.

2. The valve gating apparatus as defined in claim 1 wherein said moving means is further operable to move said shuttle (128, 184, 250, 275, 520) to a position intermediate said first and second positions to regulate the flow of melt through said nozzle gate (28, 28').

3. The valve gating apparatus as defined in claim 1 or 2 wherein the bore (132, 252, 279) is substantially rectangular and the sealing edge (136, 304) is a straight edge.

4. The valve gating apparatus as defined in claim 1 or 2 wherein said sealing edge (304) of said bore is semi-circular and said sealing post includes a complementary semi-circular surface (300) against which said sealing surface abuts in said second position.

5. The valve gating apparatus as defined in claim 1 or 2 wherein said shuttle (128, 250, 275) includes at least two apertures (132, 252, 279) for controlling a corresponding number of nozzles, each of said apertures (132, 252, 279) receiving a respective sealing post associated with a corresponding nozzle, and said sealing edge of each of said apertures abutting each respective sealing post in said second position.

6. The valve gating apparatus as defined in claim 5 wherein the sealing edge of each of said bores is semi-circular and each of said sealing posts includes a complementary semi-circular surface against which said sealing surface abuts in said second position.

7. The valve gating apparatus as claimed in claim 1 or 2 wherein said nozzle gate is circular.

8. The valve gating apparatus as defined in claim 1 or 2 wherein said sealing edge includes a beveled portion to sever said melt material when said shuttle is moved into said second position.

9. The valve gating apparatus as defined in claim 1 or 2 wherein the nozzle includes two melt channels (508, 512), and wherein the moving means is capable of positioning the shuttle (516) intermediate the first and second positions to place the first melt channel (508) in fluid communication with the mold cavity (40) and to block the flow of the melt from the second melt channel (512).

10. The valve gating apparatus of claim 1 further comprising a second shuttle (192) having a through bore and a sealing post (184) on a mold cavity plate (188), the mold cavity plate (188) being adjacent the entrance to said mold cavity on the opposite side of said nozzle from said sealing post (124) adjacent said nozzle, said second shuttle including a sealing edge abutting said second sealing post in the second position, and said moving means being operable to move said shuttle and said second shuttle in a reciprocating direction between the first and second positions.

11. The valve gating apparatus as defined in claim 10 wherein said shuttle (128) is fabricated from a thermally insulative material and said second shuttle (192) is fabricated from a thermally conductive material.

12. The valve gating apparatus as defined in claim 1 or 2 wherein said sealing edge is tapered to sever molten material when said shuttle is moved into said second position.

13. The valve gating apparatus as defined in claim 12 wherein said wedge shaped sealing edge includes at least one beveled portion oriented to direct melt expelled through closure of said shuttle (52) into a mold cavity (40).

14. The valve gating apparatus as defined in claim 12 wherein said wedge shaped sealing edge includes at least one beveled portion oriented to direct melt discharged through closure of said shuttle (52) into a nozzle assembly (24).