HK1084629B - A sprue apparatus and a method of controlling the temperature along a sprue apparatus - Google Patents

Description

Injection device and method for controlling temperature therein

Technical Field

More particularly, the present invention relates to an injection apparatus for use in an injection molding machine or a casting machine that is particularly, but not exclusively, useful for injecting a metallic material in a thixotropic state into a cavity of a mold.

Background

Injection sleeves for molding devices are well known in the art. For example, Herbert Rees, recognized injection Molding technique (1994 edition, ISBNI-56990-. In essence, an sprue bushing connects the machine nozzle with the runner system of the mold to inject at least partially molten molding material into the cavity of the mold. At least partially molten material (sometimes referred to as melt) is advanced from the machine nozzle into a conduit located within the sprue bushing and into the mold cavity of the mold. The direction of the bearing force (bearing force) is generally longitudinally through the sprue bushing, and during molding, the bearing force is used to seal the connection between the machine nozzle and the sprue bushing. The cold injection port is not heated. Any molten material that stops flowing in the cold sprue will solidify in the portion of the conduit within the sprue bushing. The solidified material must be removed from the injection cannula prior to a subsequent injection cycle. The cured material is discarded, which adds to the cost of the article by being a waste material.

The hot injection ports are typically electrically heated. Heat can be applied to the inside or outside of the injection port.

Generally, the hot sprue maintains the material in a molten state within a conduit through a sprue bushing of a single hot zone.

US5884687 to hotspot, published 23.3.1999, teaches a hot sprue with heating cavity for a molding machine. The feed sleeve includes an intermediate channel for receiving a melt of material. A heater providing a single hot zone surrounds the feed sleeve. One end of the feed sleeve is connected to a supply of liquid metal and the direction of the load bearing force is through a portion of the feed sleeve. A solid material check plug is formed near the gate and is pushed out by the injection force during the molding process.

US patent US6095789 to Polyshot corporation, published on 8/1/2000, teaches an adjustable heat injection sleeve. As described in that patent, a resistance heater surrounds the body of the sleeve. At the distal end of the sleeve, the number of turns of wire is increased, which provides more heat energy to the distal end of the sleeve, thereby compensating for the high thermal conductivity or loss at the distal end. This is to provide a constant temperature along the entire length of the sleeve within a single uniform thermal zone.

PCT application WO01/19552 by Hotflo casting company teaches an injection tip insert combined with a separate transition slot. It is apparent that the entire sprue is controlled in temperature along its entire length as a single uniform hot zone. The temperature of the material throughout the length of the injection port is high enough to ensure flow. A separate mating die includes a transition groove downstream of the sprue. The control of the transition groove is independent of the filling opening, so that the material in the transition groove can be frozen.

US6357511, published 3/19 2002 and assigned to the assignee of the present invention, teaches a spigot joint (injection joint) that provides an improved joint interface between melt channel components of an injection molding machine, particularly between a machine nozzle and other typical injection spigots used for thixomolding of metallic materials. The spigot joint includes a cylindrical portion of the first component located within a cylindrical bore of the second component. The fitting (fit) of the casing joint is characterized in that: there is a close radial fit between the outer surface of the cylindrical portion and the corresponding inner surface of the cylindrical bore, which may include a small annular gap for supporting initial melt exudate and a longitudinal engagement of sufficient length to allow limited relative axial movement without loss of sealing. The spigot joint provides a seal against melt leakage through this fit, which can be enhanced by a seal of solidified molding material exudate formed within the small gap.

European patent publication 0444748 to Boekel et al, published on 4.9.1991, describes a mold sprue bushing that includes a plurality of heat control regions disposed along the bushing.

Japanese patent publication 2002-059456 to Atsuki et al describes a machine nozzle for use with metal molding systems that includes a structure in which a controllable cold plug is formed.

The known sprue apparatus suffers from a number of problems due to poor thermal regulation along the sprue bushing, and only a single hot zone for maintaining the conditions of the molding material flowing through the sprue bushing. For example, with a single heat control zone for thermally regulating the molding material to ensure the molding process, it is not possible to independently thermally regulate the joint between mating melt channel components, whereas a spigot joint requires independent thermal regulation to ensure a reliable seal against leakage of molding material. In the processing of light alloys, such as magnesium alloys in the thixotropic state, particular attention is paid to leakage problems of the molding material, since rapid and uncontrolled oxidation can occur at high processing temperatures. In addition, there is a need for localized temperature control of the injection device along the length to overcome problems such as undesirable fluctuations in molding temperature, control the formation of injection plugs, or provide general processing flexibility. Another problem relates to the sensitivity of the known injection devices to permanent deformation when subjected to longitudinally applied load forces, in order to maintain a seal between the machine nozzle and the injection device, especially when the injection device is weakened at the high operating temperatures required for thixotropic magnesium. In particular, the injection means is constrained in use along a length between the machine nozzle and the moulding means, so that the injection means is compressed under the action of an applied load force through the machine nozzle. The infusion device is susceptible to permanent deformation due to compression, due to its slender construction; the elongated configuration of the injection device provides a short thermal conduction path and therefore a fast thermal response between the injection device and the heaters disposed along the length of the molding material in its melt conduit. Another problem relates to undesirable process fluctuations due to the formation and discharge of sprue plugs of variable length, which may be due to inadequate thermal regulation and the configuration of the melt channel.

Disclosure of Invention

A first aspect of the present invention provides an injection apparatus for connecting a melt conduit of a molding machine nozzle and a runner system of a molding apparatus. The injection device is mounted within the molding device and includes: a nozzle connection interface at the first end configured to form a joint with a complementary connection interface on a machine nozzle; a melt conduit passing through the injection device and extending from the first end to the second end; and a mold connecting interface at the second end configured to form a joint with a complementary connecting interface on a molding device for connecting the melt conduit with a runner system of the mold. The sprue apparatus also includes a plurality of thermal regulators disposed along the sprue apparatus that regulate the temperature of a plurality of hot zones dividing the sprue apparatus along its length for localized temperature control of molding material enclosed within the melt conduit portion. The injection device may be a set of parts connected together with a joint between the mating parts. Furthermore, any joints may be thermally regulated to ensure that the connection between the machine nozzle and the runner system of the molding apparatus is substantially leak-free.

The connection interface of the injection device may be configured as a sleeve joint as described in US 6357511.

Another aspect of the invention provides a method of controlling temperature along an injection device connecting a melt conduit of a machine nozzle with a runner system of a molding device, comprising the steps of: i) constructing a plurality of thermal zones dividing the injection device along the length; ii) configuring one or more thermal regulators for regulating the temperature within at least a portion of the plurality of thermal zones; iii) operating one or more controllers and driving at least a portion of the thermal regulators based on temperature feedback from the respective hot zones during the molding process.

Preferably, the method of controlling the temperature along the sprue apparatus further comprises the step of configuring one of the plurality of thermal zones as a nozzle sealing zone that surrounds the nozzle connection interface and a portion of the melt duct at the first end of the sprue apparatus, wherein the temperature at the nozzle connection interface is maintained below the melting point of the molding material while maintaining the molding material within the melt duct portion at any desired processing temperature. The method may further comprise the step of configuring one of the plurality of thermal zones as a conditioning zone located adjacent the nozzle sealing zone, wherein the molding material within the enclosed melt conduit portion is maintained at any desired processing temperature. The method may further include the step of configuring one of the plurality of thermal zones as a circulation zone at the second end of the sprue apparatus for controlled formation of a localized plug of solidified molding material within an enclosed melt duct portion.

An advantage of embodiments of the sprue apparatus of the present invention is that thermal regulation and control of multiple distinct thermal zones along the sprue apparatus is used to maintain the molding material within the melt duct at a desired temperature and physical state to ensure the molding process. The multiple hot zones also allow thermal regulation of the sleeve joint, ensuring a reliable sealing connection between the machine nozzle and the molding device.

Another advantage of embodiments of the injection device of the present invention is that the structure is durable even at the high operating temperatures required for thixomolding of magnesium. In particular, sensitive parts of the injection device may be substantially unaffected by the applied load bearing.

Another advantage of embodiments of the injection device of the present invention is that it provides a recirculation zone that controls the formation of a plug of molding material that is used for flow control. The circulation zone is configured and controlled to ensure that the size of the injection plug is constant and minimal so that there is little process variation between injections.

The present invention has been found to be particularly useful when molding in an injection molding system with a metal alloy, such as a magnesium-based alloy in a thixotropic state, although it will be understood that the concept is broadly applicable to any molding system, so long as the molding material has been plasticized or at least partially melted prior to being delivered to the mold.

Drawings

Exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a partial side sectional view of a molding system that may support the present invention, including a clamp unit and an injection unit;

FIG. 2A is a more detailed cross-sectional view of an injection device according to a preferred embodiment of the present invention, shown in a previous position within the molding system of FIG. 1;

FIG. 2B is another more detailed cross-sectional view of the injection device as described in the preferred embodiment of FIG. 2A;

FIG. 3 is an exploded view showing the components of the injection device according to the preferred embodiment of FIG. 2B;

FIGS. 4A and 4B are perspective views of the front housing of the injection device of FIG. 3;

FIG. 4C is an end view of the front housing of FIG. 4A;

FIG. 4D is a side cross-sectional view of the front housing taken along line 4D-4D of FIG. 4C;

FIG. 4E is a view of the other end of the front housing of FIG. 4A;

FIG. 5A is a perspective view of an alternative embodiment of the front housing of FIG. 3;

FIG. 5B is a cross-sectional view of the housing of FIG. 5A;

FIG. 6 is a cross-sectional view of the sprue bushing taken along line 6-6 of FIG. 3;

FIG. 7 is a perspective view of a cooling insert of the injection device of FIG. 3;

FIG. 8 is an end view of the cooling insert of FIG. 7 facing the injection unit;

FIG. 9 is another end view of the cooling core of FIG. 7 facing the mold;

FIG. 10 is a cross-sectional view of the cooling core taken along line 10-10 of FIG. 9;

FIG. 11 is a bottom side view of the cooling insert of FIG. 7;

FIG. 12 is a cross-sectional view of the insert taken along line 12-12 of FIG. 11;

fig. 13 is a cross-sectional view of the insert taken along line 13-13 in fig. 11.

Detailed Description

As shown in FIG. 1, an embodiment of the present invention will be described below with respect to (and in an initial position within) a typical injection molding system 10.

The injection molding system 10 includes an injection unit 14 and a clamp molding unit 12. The injection unit 14 processes the molding material to inject it into the mold. The injection unit 14 includes a frame 32, and the frame 32 typically supports a housing for controlling and operating the electrical components (not shown) of the machine and a housing for a power pack (not shown). A bracket (not shown) supports the barrel assembly 34 including the barrel 42. The carriage is movable relative to the frame 32 by a pair of carriage rollers (not shown). A screw 40 is positioned within the bore of a barrel 42. In operation, the screw 40 is rotated, and generally translated axially within the barrel 42, by the screw drive 36 in a manner well known in the art. The screw drive 36 may be a combination of a motor that rotates the screw 40 and a hydraulic component that translates the screw 40 for injection. Those skilled in the art will appreciate that either a complete hydraulic drive system or a complete electric motor drive system may be used with the injection unit 14. Additionally, while a single stage reciprocating screw injection unit is shown, it will be understood by those skilled in the art that a two stage injection unit may be used.

The clamping unit 12 opens and closes the mold, and applies a mold clamping force to the mold. The clamp die unit 12 includes a static plate 16 and a movable platen 20 mounted on a frame 18, and a clamp die actuator (not shown) that impacts the movable platen 20 against the static plate 16. The static plate 16 and the actuator are typically interconnected by four tie rods 38, only two of which are shown. The first mold half 24 is attached to the movable platen 20 and the second mold half 26 is attached to the static plate 16.

It will be understood by those skilled in the art that the clamp unit 12 may be driven by a hydraulic drive unit, a fully electric motor clamp drive, or a combination of electric motor and hydraulic components.

For a typical thixomolding system, magnesium flakes 178 or other suitable material is fed into a hopper 180 and metered through the feed throat 132 of the barrel 42. The screw 40 is rotated to transport molding material from the feed throat 132 along the barrel 42 through the shut-off valve 46 at the end of the screw 40 to the accumulation zone 82 at the head of the barrel and forward of the nozzle 48. As the screw conveys material to the accumulation zone 82 and the nozzle 48, the screw 40 moves back within the barrel 42, thereby accumulating a shot of material. When sufficient material is delivered into the accumulation zone 82, a shot of material is injected into the mold 24, 26 by the injection device. To complete this injection, a hydraulic actuator within the screw drive 36 advances the screw 40 toward the mold, thereby injecting material from the accumulation zone 82 into the mold through the nozzle 48. The shut-off valve 46 prevents backflow of material into the barrel 42 as the screw 40 moves forward. A heater 44 is positioned along the barrel 42 and nozzle 48 (see fig. 2A) to achieve and maintain the desired processing temperature and physical conditions of the molding material.

The injection device of the present invention is illustrated below with reference to the embodiments of fig. 2A and 2B. The sprue apparatus 51 connects the melt conduit of the machine nozzle 48 of the injection unit 14 with the runner system (not shown) of the second mold half 26. The injection device 51 is configured to be received within the second mold half 26 and includes a nozzle connection interface 94 at a first end that is configured to engage a complementary connection interface of the machine nozzle 48. Melt conduit 89 extends from a first end to a second end through injection fitting 51. A mold connecting interface 93 at the second end is configured to engage a complementary connecting interface on the second mold half 26 to connect the melt conduit 89 with the mold runner system. The sprue apparatus 51 also includes a plurality of thermal regulators disposed along the sprue apparatus 51 that regulate the temperature of a plurality of hot zones on the sprue apparatus 51 dividing the sprue apparatus 51 along its length for the purpose of locally controlling the temperature of the molding material within the enclosed melt duct portion. The injection device may be a combination of components that join the mating components together. In addition, the temperature of any joint may be adjusted so that the machine nozzle 48 and the runner system of the second mold half 26 may be connected substantially leak-free.

The attachment interface of the machine nozzle 48 is provided by the longitudinal surface of the extended end 92 of the sleeve in the shape of a cylinder. The joint between the nozzle connection interface 94 and the connection interface of the machine nozzle 48 contains a small gap into which the molding material is allowed to seep and cure to seal the gap, which is a typical spigot joint. The heat regulation maintains the temperature of the joint below the freezing point of the molding material. With this solution, the injection device 51 can expand and contract without losing sealing contact with the nozzle 48 or the second mold half 26.

Preferably, the injection device further comprises an injection sleeve 52 located within the isolating coupler 53. The sprue bushing 52 includes a nozzle connection interface 94 at a first end, and the first isolating coupler connection interface 72 is proximate the nozzle connection interface 94. Melt conduit 89 extends through sprue bushing 52 from the first end to the second end. A second isolating coupler connection interface 74 is located at the second end. The first and second isolating coupler connection interfaces 72 and 74 are configured to form a joint with complementary first and second sprue bushing connection interfaces 76 and 78 provided on the isolating coupler 53. The isolating coupler 53 is configured to be at least partially received within the second mold half 26 and is also configured to interconnect the melt conduit 89 of the sprue bushing 52 with the runner system of the second mold half 26. The isolating coupler 53 is preferably coupled to the sprue bushing 52 so as to distribute longitudinally applied load forces acting from the first end of the sprue bushing 52 all the way to the second mold half 26, thereby isolating the body portion of the sprue bushing 52 from the load forces. In particular, isolating coupler 53 longitudinally constrains a first end of sprue bushing 52, while allowing the remainder thereof to move longitudinally unrestrained. The isolating coupler also facilitates thermal conditioning of at least one of the plurality of thermal zones that divide the sprue apparatus 51 along its length by providing one or more thermal conditioners to increase or decrease the temperature of one or more of the plurality of thermal zones.

Isolating coupler 53 is preferably an assembly that includes a front housing 54 connected to a cooling insert 56.

The front housing 54 is fitted into the second mold half 26 and the cooling insert 56 is held in place by a retaining ring 84. Bolts 130 (see fig. 3) pass through retaining ring 58 and extend into threaded bores 136 to retain sprue bushing 52 within isolating coupler 53. The extended inner edge (on retaining ring 58) retains the sprue bushing 52 within the isolating coupler as long as the nozzle 48 is out of contact with the sprue bushing 52.

Preferably, front housing 54 provides a heat pipe for heat transfer between cooled second mold half 26 and the second end of sprue bushing 52, which acts as a heat regulator for controlling the temperature of the joint between second isolating coupler connection interface 74 and second sprue bushing connection interface 78, which is located near the second end of the front housing. Preferably, the joint is a sleeve joint, wherein the heat regulation is prepared for the formation of the seal of the above-mentioned cured moulding material.

The cooling insert 56 also acts as a thermal regulator. The cooling tube 66 and the connector 70 with the sleeve 168 provide a cooling fluid (preferably oil) to the cooling insert 56 to selectively cool the sprue bushing 52, as will be explained in more detail below.

Thermal regulators such as heaters 96a, 96b, 96c, and 96d are also positioned along the longitudinal axis of sprue bushing 52 and are shaped to ensure and maintain thermal contact. The heater can be selectively controlled as desired to adjust the temperature of the molding material. The heater 96d may surround a narrow portion of the sprue bushing 52. In the present example, the narrowed portion of sprue bushing 52 provides a shorter thermal conduction path between heater 96d and the molding material in melt duct portion 89d, thereby providing a rapid thermal response. It should be noted that the number of heaters and the locations of the heaters may vary. In addition, the diameter of the main body portion of the sprue bushing 52 can be unique from end to end, so that the inner circumference of all heaters is the same.

Thermocouples located along the length of sprue bushing 52 provide temperature feedback for each hot zone to at least one controller (not shown) that controls the thermal adjustment of at least a portion of the thermal regulators.

In a manner known in the art, the platen positioning ring 30 cooperates with the mold positioning ring 84 to position the second mold half 26 so that the second mold half 26 is properly aligned with the injection unit 14.

The nozzle 48 is attached to the collar head 50 by a screw 60. The barrel head 50 is connected to the return barrel 42 by a screw 188.

Turning now to fig. 3, there is shown an exploded view of the components of the injection device 51 in the preferred embodiment. The front housing 54 includes a passage slot 100 that allows the heaters 96b, 96c, and 96d and the wires of the thermocouples to pass through. The screw 68 extends through the enlarged ring 102 of the front housing 54 to couple the housing 54 to the cooling insert 56. The cooling insert 56 includes a slot 104 for receiving the electrical wires of the heater 96a and a second slot 106 for receiving the cooling circuit "(see fig. 7).

Heater elements 96b, 96c, and 96d fit within housing 54, while heating element 96a fits within cooling insert 56. Four heater elements are shown by way of example in the embodiment shown in fig. 3, so it will be understood that the number and location of the heater elements may be varied as desired or necessary. Furthermore, the type of heater used may all be selected at will and may include, without limitation, any combination of resistive, inductive resistance, and may also include thin or thick film heaters.

As described above, the sprue bushing 52 fits within the heating element and is retained within the heating element and between the front housing 54 and the cooling insert 56 by the retaining ring 58, with the retaining ring 58 being secured to the cooling insert 56 by the threaded fastener 130. The position ring 84 rests on a shoulder 108 of the cooling insert 56 and is secured by the bolts 62 to the mold support plate 64 (see fig. ZA). The second mold half 26 may include an insulating plate 110 (see fig. ZA) between the backing plate "and the retaining ring 84 to provide thermal isolation between the static plate 16 and the second mold half 26.

Fig. 4A, 4B, 4C, 4D and 4E show the front housing 54 in more detail. As shown here, the front housing includes an outer surface that is configured to be received within the second mold half 26. The portion of the front housing 54 near the second end provides a mold-attachment interface 93 that ensures a sealed connection with the second mold half 26. A bore 90 extends through the front housing from the first end to the second end. The bore 90 provides a pocket around the length of the body of the sprue bushing 52 between the first and second isolating coupler connection interfaces 72 and 74. The interstitial space within the bore between sprue bushing 52 and isolating coupler 53 provides a space for the sprue bushing to be isolated from the relatively cold second mold half 26 and provides a space for the heater and thermocouple wires 95 to pass through. The bore 90 also includes a cylindrical surface proximate the second end of the front housing 54 that provides a second sprue bushing connection interface 78 for receiving a complementary second isolating coupler connection interface of the sprue bushing 52. An outward taper proximate the second end extends the melt conduit 89 and functions to allow a plug of molding material to be formed, as will be explained below. Slots 114 on the inner wall of front housing 54 provide space for clips used with heaters 96b, 96c, and 96 d. The holes 118 and alignment pins together allow the housing 54 to be properly oriented with respect to the cooling insert 56. A shoulder 112 is provided that mates with a corresponding ridge 120 (see fig. 9) on the cooling insert 56 to provide a sealed connection between the housing 54 and the cooling insert 56. Screw holes 116 receive bolts 68 to connect housing 54 to cooling insert 56.

Fig. 5A and 5B illustrate another embodiment of the front housing 54. In this embodiment, the main body portion of the housing 154 along its entire length is a substantially uniform cylindrical body 184, the end adjacent the mold 26 having a reduced diameter so that it can fit within the second mold half 26. Cutouts 182 are provided on each side of cylinder 184, which provide access to threaded holes 186 to enable attachment of housing 54 to cooling insert 56.

Fig. 6 illustrates the sprue bushing 52 of fig. 3 in more detail. Located at the first end of the sprue bushing 52 is a recessed cylindrical bore 87, the inner surface of which provides a nozzle connection interface 94. A cylindrical flange 86 is also located at the first end of the sprue bushing 52 and the first isolating coupler connection interface 72 is located on an outer diameter of the flange 86. A shoulder 138 on the inner face of the cylindrical flange 86 provides a mating surface for mating with the cooling insert 56. A heat choke 124 is formed as a groove on the inner face of flange 86. The heating choke 124 provides a degree of thermal isolation between the portion of the sprue bushing 52 in contact with the cooling insert 56 and the remainder of the sprue bushing 52, thereby reducing heat transfer from the melt duct 89 to the cooling insert 56.

Melt conduit 89 extends through sprue bushing 52 from the first end to the second end and may include an inwardly converging tapered portion adjacent bore 87 that tapers the diameter of melt conduit 89 to match the nozzle melt conduit with the sprue bushing melt conduit. The melt conduit may also include a stepped transition 170 between the main melt conduit portion and the outwardly expanding tapered portion and proximate the second end of the sprue bushing 52. The stepped transition 170 shears a plug of constant length under applied injection pressure from one injection cycle to the next, while the outwardly expanding tapered melt conduit portion 89d also aids in the formation and ease of ejection of the injection plug under applied injection pressure at the beginning of each injection cycle. The ability to eject a plug of constant length allows the proper sizing of the injection collector (not shown) in the second mold half 26 and the configuration of the molding device runner system to optimize melt flow to stabilize the molding process.

Located at the second end of the sprue bushing 52 is an elongated circular bushing ring section 88, the outer surface of which provides the second isolating coupler connection interface 74. Thermocouple mounting points (e.g., 122a, 122b, and 122c) are distributed along the length of the sprue bushing 52 and provide temperature feedback in specific control zones, as will be described in more detail below.

Fig. 7 is an enlarged perspective view of the cooling insert 56. The thermocouple mounting point 128 is located at the bottom of the slot 106, and the slot 106 is a slot in the side wall of the cooling core through which the thermocouple mounting point is accessible through the slot 106 at the bottom of the cooling core. The thermocouple mounting points 128 are preferably located as shown in fig. 10. A slot 104 extending longitudinally through the side wall of the cooling insert allows electrical access to the heater 96a (not shown). A longitudinally extending slot 114b passes through an internal bore in the cooling insert 56 and provides a space for a screw clamp (not shown) that retains the heater 96a around the sprue bushing 52 in a manner known in the art.

FIG. 8 illustrates an end view of the cooling insert 56 facing the retaining ring 84 and the retaining ring 58. Bolts 130 (see fig. 3) pass through retaining ring 58 and extend into threaded holes 136 in cooling insert 56 to retain sprue bushing 52. Referring to fig. 2B and 6, a shoulder 138 (see fig. 6) on the inner face of flange 86 of sprue bushing 52 engages a surface 140 on the inner face of a recessed bore 91 formed in cooling insert 56 and is retained by retaining ring 58. The surface of the inner diameter of the cylindrical bore 91 provides a first sprue bushing connection interface 76 for receiving a first isolating coupler interface of the sprue bushing 52.

Fig. 9 shows an end view of the cooling insert 56 facing the front housing 54. Bolts 68 pass through slots 116 (see fig. 3) in front housing 54 and extend into threaded slots 134 in cooling insert 56, thereby holding front housing 54 in connection with cooling insert 56. The shoulder 112 (see FIG. 4A) of the front housing 54 receives the annular portion 120 of the cooling insert 56 to ensure that the cooling insert 56 and the housing 54 are tightly coupled. The retention slots 172 are formed during the creation of the cooling slot and contain plugs to close the cooling slot, as will be apparent from the description that follows.

FIG. 10 is a cross-sectional view of the cooling insert 56 taken along section line 10-10 in FIG. 9. The cooling channels circulate a cooling fluid, preferably oil, through the cooling insert 56. Thermocouple mounting points 128 are located near the interface region between the cooling insert 56 and the sprue bushing 52 (see FIG. 2B), as the temperature at this point is critical to proper operation of the injection molding process, as will be described below. The apertures 174 receive pins 176 (see FIG. 3) that engage corresponding apertures (not shown) on the sprue bushing 52 to ensure that the sprue bushing 52 is aligned with the cooling insert 56.

Fig. 11, 12 and 13 illustrate a particularly suitable arrangement of cooling channels of the cooling insert 56. The cooling insert 56 has cooling slots in two separate planes that are connected by vertical slot connections. Slots 144, 146 and 148 are shown in cross-section in fig. 13, while slots 150 and 152 are shown in cross-section in fig. 12. Vertical slot connectors 154, 156, 158, 160, 162, and 164 connect slots 144, 146, and 148 to slots 150 and 152 and cooling tubes 66.

The cooling pipe and the groove are connected to each other in the following manner. One cooling tube 66 is connected to a vertical slot connector 164. Vertical slot connector 164 is then connected to slot 144. The coolant flows through the slot 144 to the vertical slot connector 162. Vertical slot connector 162 carries coolant to slot 150. The coolant flows through the slots 150 to the vertical slot connector 160. Vertical slot connection 160 carries coolant to slot 146. The coolant flows through the slot 146 to the vertical slot connector 158. Vertical channel connector 158 carries coolant to channel 152. The coolant flows through the slot 152 to the vertical slot connector 156. Vertical slot connection 156 carries coolant to slot 148. The coolant flows through the slot 148 to the vertical slot connector 154, from where it is transported through the other cooling tubes 66. In this manner, the cooling fluid flows longitudinally through the cooling insert 56 and around the periphery of the cooling insert 56, thereby providing effective and useful cooling for the cooling insert 56 and the associated front housing 54.

In an alternative example, the thermal regulator of the isolating coupler may include a tubular coil for circulating the fluid, the tubular coil being disposed about the nozzle connection interface. Another alternative example may provide a shroud (wrap) disposed about the nozzle connection interface for circulating the fluid. The thermal regulator may comprise a hollow jacket (hollow socket) disposed about the nozzle connection interface for circulating the fluid, or may provide a plurality of fins for convective heat transfer. The present invention is not limited to regulating the temperature within the thermal regulator in a particular manner.

For a better understanding of the invention, the preferred operation of the injection molding apparatus, and in particular the injection apparatus 51, will be described below with particular reference to fig. 1 and 2A, and taking as an example the thixotropic molding operation of magnesium alloys.

As described above, the molding material is conveyed through the feed throat 132 where it is received by the screw 40. The screw 40 shears the molding material within the barrel 42 while it is also heated to a thixotropic state for thixotropic molding of light metal alloys. Thixotropic material is delivered to the accumulation zone 82 described above through the shut-off valve 46. The thixotropic melt material is maintained in a thixotropic state by the nozzle 48 and heater 44 within the barrel 42 and by the heaters 96a, 96b, 96c and 96d on the sprue bushing 52. When sufficient material is delivered into the accumulation zone 82, the screw drive 36 applies a bearing force and drives the screw forward, thereby injecting a shot of material into the mold 24, 26 through the injection device 51. After injection, the small plug at the end of sprue bushing 52 is driven into a plug collector (not shown) of the mold in a manner well known to those skilled in the injection molding art. During the previous injection cycle, the plug is formed by allowing the melt in the melt conduit adjacent to the ring portion 88 to solidify and plug the conduit, thereby preventing further escape of the melt material.

The bearing force counteracts the separation force generated by the injection, thereby maintaining the injection nozzle 48 in sealing connection with the injection device 51. In various embodiments, the load bearing force is applied through the machine nozzle 48 to the portion of the sprue bushing 52 defined between the shoulder of the nozzle 48 and the cooling insert 56, then through the cooling insert 56 to the front housing 54 and into the second mold half 26. This arrangement isolates a portion of the sprue bushing 52 adjacent the portion of the sprue bushing defined between the nozzle 48 and the cooling insert 56 from load bearing forces. Furthermore, because the injection sleeve 52 may move laterally within the borehole 90, any pressure transmitted into the sleeve 52 may be reduced. The force-isolating portion of sprue bushing 52 may thus be relatively thin in construction, which may correspondingly improve thermal response characteristics regardless of the effect of applied bearing forces, and is particularly important at the high operating temperatures typical of thixotropic molding of magnesium.

The sprue apparatus 51 of fig. 2B includes demarcations for a plurality of hot zones in a typical process. The present invention is not limited to a particular number or configuration of the plurality of thermal zones that may be required in further processes.

The plurality of thermal zones includes a nozzle seal zone Z1 at the first end of sprue apparatus 51 that includes a nozzle connecting interface 94 and a melt duct portion 89 a. The temperature in nozzle sealing zone Z1 is adjusted to maintain nozzle connection interface 94 and the junction between sprue bushing 52 and machine injection nozzle 48 at the desired sealing temperature while maintaining the molding material in melt duct portion 89a at any desired temperature to ensure the molding process. Thermal regulation of the sleeve joint forming the joint between the sprue bushing 52 and the machine nozzle 48 requires that the temperature at the connection interface 94 be kept low enough to cure any molding material that may seep into the joint, thereby forming a seal. Thus, to achieve the thermal conditioning needs within nozzle seal zone Z1, a balanced conductive heat flow needs to be established between the adjacent sprue bushing conditioning zone Z2 and the thermal conditioner of cooling insert 56, wherein sprue bushing conditioning zone Z2 is itself conditioned by thermal conditioning heaters 96b and 96 c. Providing sprue bushing 52 with a heating choke (124 in fig. 6) between the first isolating coupler connection interface and the nozzle connection interface so that heating flow from adjacent regulation zone Z2 preferentially flows into melt duct portion 89a and heating flow from the nozzle junction preferentially flows to cooling insert 56 helps balance the establishment of heating flow. The cooling insert 56 includes a flow path for circulating a coolant flow, and the thermostat thermally conditions the coolant using temperature feedback from thermocouples embedded in mounting points 128 on the cooling insert 56 and 122c on the sprue bushing flange 86.

As described above, the plurality of thermal zones includes conditioning zone Z2 disposed along a central portion of sprue apparatus 51 and adjacent to nozzle sealing zone Z1, wherein the molding material within encompassed melt duct portion 89b is maintained at a desired processing temperature to ensure the molding process. Thermal regulation within the hot zone is performed by thermal regulators/heaters 96a, 96b and 96c based on feedback from thermocouples installed in mounting points 122b (see fig. 6).

The plurality of thermal zones includes conditioning zone Z3 disposed along a reduced diameter portion of sprue apparatus 51 adjacent conditioning zone Z2 wherein the molding material within the encompassed melt duct portion 89c is maintained at a desired processing temperature to ensure the molding process. As described above, the shorter heat conduction path provided by the reduced diameter portion provides a relatively faster thermal response to temperature regulation of the molding material within melt conduit portion 89d by thermal regulator/heater 96d based on feedback from a thermocouple mounted within mounting point 122a (see FIG. 6). The rapid thermal response compensates for frequent temperature changes in the adjacent circulation zone Z4.

The plurality of thermal zones further includes a circulation zone Z4 at the second end of sprue apparatus 51 for controlled formation of a localized plug of solidified molding material within the enclosed melt duct portion 89 d. The plug may be used to prevent leakage of molding material during intervals of a molding process cycle and may eliminate the need for a mechanical melt shut-off. The thermal conditioning provided for the recirculation zone is the flow of heat transfer between the adjacent sprue bushing conditioning zone Z3, which is itself conditioned by the thermal conditioning heater 96d, and the thermal conditioner/heat conduit of the front housing 54. Although the heat conduit of the front housing 54 is not effectively controlled, it again provides a heat conduction path between the cooled second mold half 26 and the sprue bushing. In an alternative example, the circulation zone Z4 may be temperature regulated to at least partially re-melt the molding material, and other thermal regulators may assist it.

The plurality of thermal zones further includes a second sealing zone (not shown) that is integrated with the joint between the second isolating coupler connection interface 74 and the second sprue bushing connection interface 78 proximate the second end of the front housing 54. In this embodiment, the second sealing zone is located within the recirculation zone Z4. The joint is a spigot joint which is temperature regulated in use so that any moulding material which may penetrate into the joint cures to form a seal.

Thus, the sprue apparatus described above is a novel sprue apparatus that can be used in molding apparatus that require temperature regulation and control of multiple different hot zones. The invention finds particular utility when injecting metal alloys, such as magnesium-based alloys in a thixotropic state.

All U.S. and foreign patent documents and articles mentioned above are hereby incorporated by reference into the detailed description of the preferred embodiment.

The individual components shown in outline or designated by blocks in the attached drawings are all well-known in the injection molding arts, and their specific construction or operation is not critical to the operation or best mode for carrying out the invention.

Claims (29)

1. An injection apparatus (51) located within a molding apparatus for connecting a melt conduit (89) of a molding machine nozzle (48) to a runner system of the molding apparatus, the injection apparatus (51) comprising:

an infusion sleeve (52) for cooperating with an isolating coupler (53);

the infusion cannula (52) comprises:

a tubular body having first and second ends;

a nozzle connection interface (94) on an interior surface of the body at the first end of the body for connection to a complementary connection interface on a machine nozzle (48);

an outer surface of the tube for receiving a plurality of thermal regulators, the thermal regulators defining a plurality of thermal zones;

a first isolating coupler connection interface (72) on an outer surface of the body at the first end of the body substantially adjacent the nozzle connection interface (94);

a second isolating coupler connection interface (74) on an outer surface of the pipe body at the second end of the pipe body;

a melt conduit (89) passing through the tube body from the first end to the second end and located on an inner surface of the tube body;

the isolating coupler (53) includes:

a tubular body having first and second ends;

a first sprue bushing connection interface (76) on an interior surface of the tubular body at the first end of the tubular body for receiving a first isolating coupler connection interface (72) on a sprue bushing (52);

a second sprue bushing connection interface (78) on the interior surface of the tubular body proximate the second end of the tubular body for receiving a second isolating coupler connection interface (74) on the sprue bushing (52);

a mold attachment interface (93) at the second end of the body for engaging a complementary attachment interface on a molding apparatus;

the first isolating coupler connection interface (72) and the first sprue bushing connection interface (76) cooperate to substantially isolate the sprue bushing (52) from a load bearing force exerted by the machine nozzle (48).

2. The injection device (51) as set forth in claim 1, characterized in that the nozzle connection interface (94) is configured as a cylindrical sleeve interface.

3. The sprue apparatus (51) according to claim 2 wherein at least one of the plurality of hot zones is a heat-regulated seal that maintains the temperature at the nozzle connection interface (94) below the liquidus temperature of the molding material so that it connects to the machine nozzle (48) substantially leak free.

4. An injection device (51) as claimed in claim 1 or 2, wherein the mould attachment interface (93) is configured as a cylindrical sleeve interface.

5. Sprue apparatus (51) according to claim 4 characterised in that at least one of the plurality of hot zones is a heat-regulated sealing zone which maintains the temperature at the mould connection interface (93) below the liquidus temperature of the moulding material so that it connects to the moulding apparatus substantially leak-free.

6. Injection device (51) according to claim 4, wherein the isolating coupler (53) comprises a melt duct extension arranged along the inner surface of the tubular element and at the second end of the tubular element, said melt duct extension interconnecting the melt duct (89) of the sprue bushing (52) with the runner system of the molding device.

7. The infusion device (51) as claimed in claim 6, characterized in that the connection between the second isolating coupler connection interface (74) of the infusion sleeve (52) and the second infusion sleeve connection interface (78) of the isolating coupler (53) is a sleeve joint.

8. Sprue apparatus (51) according to claim 7 wherein at least one of the plurality of hot zones is a heat-regulated sealing zone which maintains the temperature at the mould connection interface (93) below the liquidus temperature of the moulding material so that it connects to the moulding apparatus substantially leak-free.

9. The injector device (51) of claim 7, wherein the isolating coupler (53) further comprises a front housing (54) coupled to the cooling insert (56), the cooling insert (56) serving as a thermal regulator adjacent the nozzle interface (94).

10. The injector device (51) according to claim 9, wherein the cooling insert (56) comprises a cooling channel (142) for circulating a cooling fluid.

11. The sprue apparatus (51) according to claim 10 wherein the cooling insert (56) includes a thermocouple located in a mounting point (128), the mounting point (128) being located adjacent an interface region between the cooling insert (56) and the sprue bushing (52).

12. An injection device (51) as claimed in claim 9, wherein the front housing (54) provides a heat pipe for heat conduction between the cooled molding device in a second sealing area and the second end of the sprue bushing (52), said heat pipe serving as a heat regulator in the vicinity of the connection between the second isolating coupler connection interface (74) of the sprue bushing (52) and the second sprue bushing connection interface (78) of the isolating coupler (53).

13. The sprue apparatus (51) according to claim 12 wherein the front housing (54) includes a bore (90) extending through the front housing (54) from the first end to the second end of the front housing, the bore (90) providing a bore longitudinally around the main section of the sprue bushing.

14. The sprue apparatus (51) according to claim 13 wherein the bore (90) further includes a cylindrical surface proximate the second end of the front housing (54) and an outward taper proximate the second end wherein the cylindrical surface provides the second sprue bushing connection interface (78) and the outward taper provides the melt duct extension.

15. The sprue apparatus (51) according to claim 14 wherein the front housing (54) includes an outer surface configured to provide a mold attachment interface (93).

16. An injector device (51) as claimed in claim 1, wherein the nozzle connection interface (94) is provided by an inner surface of a recessed cylindrical bore (87) at the first end of the injector sleeve (52).

17. The sprue apparatus (51) according to claim 16 wherein the first isolating coupler connection interface (72) is provided by a surface on an outer diameter of a cylindrical flange (86) at the first end of the sprue bushing (52).

18. The sprue apparatus (51) according to claim 17 further including a heat choke (124) formed as a groove on the inner surface of the flange (86).

19. Injection device (51) as claimed in claim 18 wherein the melt duct (89) further comprises an inwardly converging conical portion adjacent the bore (87) and a stepped transition (170) between the main melt duct portion and the outwardly expanding conical portion adjacent the second end of the sprue bushing (52).

20. The sprue apparatus (51) according to claim 19 wherein the sprue bushing (52) further includes an elongated glob bushing ring portion (88) at the second end having an outer surface providing the second isolating coupler connection interface (74).

21. The sprue apparatus (51) according to claim 20 wherein the sprue bushing (52) includes heaters (96a, 96b, 96c, 96d) disposed along a longitudinal axis of the sprue bushing (52) and wherein the sprue bushing (52) is selectively controllable, the heaters acting as heat regulators for selectively heating at least one conditioning zone between the sealing zones.

22. The sprue apparatus (51) according to claim 21 wherein the sprue bushing (52) further includes thermocouples mounted in mounting points (122a, 122b, 122c) disposed along its length for housing thermocouples that, in use, provide temperature feedback to at least one controller regarding thermal conditions along the length of the sprue bushing (52), the at least one controller controlling the heat settings of the heat regulators.

23. An injection device (51) as claimed in claim 22, characterised in that the injection sleeve (52) comprises a narrow section near its second end to enable rapid changes in the temperature of the moulding material.

24. A method of controlling the temperature along an injection device (51) according to claim 1, said injection device (51) connecting a melt conduit of a machine nozzle (48) with a runner system of a molding device, the method comprising the steps of:

constructing a plurality of thermal zones (Z1, Z2, Z3, Z4) dividing the injection device (51) along the length direction;

the plurality of thermal zones including a nozzle sealing zone (Z1) enclosing a nozzle connection interface (94) and a melt conduit portion (89a) of the first end of the sprue apparatus (51);

configuring one or more thermal regulators (54, 56, 96a, 96b, 96c, 96d) for regulating temperatures in the plurality of thermal zones;

operating a controller to drive at least a portion of the thermal regulators in accordance with temperature feedback from the respective thermal zones and the desired temperature setting;

the controller actuates the thermal regulator within the nozzle sealing zone (Z1) to maintain the temperature at the mold connection interface (93) below the liquidus temperature of the molding material so that a substantially leak-free connection with the machine nozzle (48) is provided.

25. The method of controlling temperature along a sprue apparatus (51) according to claim 24 further including the step of configuring at least one of the plurality of thermal zones as a conditioning zone (Z2, Z3) located adjacent the nozzle sealing zone (Z1) wherein the molding material within the enclosed melt duct portion (89b, 89c) is maintained at any desired processing temperature.

26. The method of controlling temperature along a sprue apparatus (51) according to claim 25 further including the step of configuring one of the plurality of thermal zones as a circulation zone (Z4) at a second end of the sprue apparatus (51) for controlled formation of a localized plug of solidified molding material within an enclosed melt duct portion (89 d).

27. A method of controlling the temperature along an injector (51) as claimed in claim 26 characterised in that the injector (51) includes an injector sleeve (52) located within an isolating coupler (53), the isolating coupler (53) itself including a front housing (54) connected to a cooling insert (56), the cooling insert (56) acting as a heat regulator for selectively cooling the nozzle seal zone (Z1).

28. Method of controlling the temperature along an infusion device (51) according to claim 27, characterized in that the infusion sleeve (52) comprises heaters (96a, 96b, 96c, 96d) arranged along the longitudinal axis of the infusion sleeve (52) and the infusion sleeve (52) can be selectively controlled, the heaters acting as heat regulators for selectively heating at least one regulation zone (Z2, Z3).

29. A method of controlling the temperature along an injection means (51) as claimed in claim 28, characterised in that the isolating coupling (53) provides a heat pipe for the conduction of heat between the cooling mould means contained in the second sealing zone in the circulation zone (Z4) and the second end of the injection sleeve (52), said heat pipe acting as a heat regulator.