AU2008323609B2 - An injector nozzle and method of manufacture - Google Patents

Abstract

An injector tip (3.032) for an injection mould (1.010) includes a first and second conic sections (3.030, 3.028) intersecting in a plane and forming an undercut cavity (3.018) therebetween. The cavity (3.018) is connected by ducts to a water jacket (1.018) enclosing the cylindrical body of the injector (3.032).

Description

1 An Injector nozzle and method of manufacture Field of the invention [001] This invention relates to an injector nozzle and a method of manufacturing such a nozzle. [002] The invention is particularly applicable to nozzles for use in thermosetting moulding processes using thermosetting silicone or other thermosetting material. Background of the invention [003] W02007025331 describes an injection moulding apparatus including a number of water cooled injectors for moulding low viscosity materials such as liquid silicones and polyurethanes. [004] The process of moulding using thermosetting materials encounters problems when the parts of the injector become heated above the thermosetting temperature. This can cause the injector to become clogged as the injection material sets. In turn, this requires the disassembly of the mould to clean the injector. [005] Any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates, at the priority date of this application. Summary of the invention [006] The present invention provides a tapered injection tip and a mould injector, the injector having a coolant jacket adapted to remove heat from at least part of the injector proximate the mould, wherein the coolant jacket extends to at least a part of the tapered tip. [007] The present invention also provides an injector tip for an injection mould includes a first and second conic sections intersecting in a plane and forming an undercut cavity therebetween, the cavity being connectable by coolant ducts to a water jacket enclosing the cylindrical body of the injector. [008] The injector tip can include an extended coolant jacket, wherein the extended coolant jacket extends to at least a part of the tapered tip in an undercut cavity.

2 [009] The injector tip can include an inner conic section having a first taper angle, and a second conic section concentric with the first conic section and having a taper angle which is greater than the first taper angle so that the second conic section encompasses the first conic section and defines the undercut cavity therebetween, the first and second conic sections terminating at their respective tapered ends in a common plane, the undercut cavity being closed at the end proximate the common plane. [010] The injector tip can include a first cylindrical body extending from the first conic section. [011] The injector tip can include a second cylindrical body extending from the second conic section. [012] The second cylindrical body is concentric with the first cylindrical body. [013] The second cylindrical body can be connected to the first cylindrical body by a plurality of radial spokes defining coolant apertures therebetween, through which coolant can pass to the undercut cavity. [014] A thread can be formed on the distal end of the first cylindrical body. [015] A needle support can be located concentrically within the first cylindrical body. [016] The inner surface of the first conic section can include a valve seat for a valve needle. [017] The injector tip can be made of titanium, tungsten, stainless steel or other appropriate metal. In addition, polymers having high temperature stability can be used. [018] The invention also provides a method of manufacturing an injector tip including deposition a first series of concentric annuli having a progressively increasing inner and outer diameters, the inner diameter of each succeeding layer being less than the outer diameter of the preceding layer until a required first conic shape has been formed, and then depositing a further series of concentric annuli of having inner diameters and outer diameters equal to those of the preceding layer to form a first cylindrical body, and 3 depositing a second series of concentric annuli having a progressively increasing inner and outer diameters, the inner diameter of each succeeding layer being less than the outer diameter of the preceding layer until a required second conic shape has been formed, and then depositing a further series of concentric annuli of having inner diameters and outer diameters equal to those of the preceding layer to form a second cylindrical body have been formed, the second conic shape being attached at its root to the first conic shape and having a larger equivalent diameter over the majority of its length compared with the outer diameter of the first conic shape, to define an undercut cavity therebetween, the second cylindrical body having a greater inner diameter than the outer diameter of the first cylindrical body to define a coolant channel therebetween connected to the undercut cavity. [019] The layers can be formed using direct material deposition. [020] The material can be a depositable material having a suitable coefficient of thermal expansion. [021] The material can be stainless steel, titanium, tungsten, or a polymer. Brief description of the drawings [022] An embodiment or embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [023] Figure 1 is a schematic section view a mould and injector; [024] Figure 2 is a top view of the injector of Figure 1; [025] Figure 3 is a schematic section view of the end of an injector according top an embodiment of the invention; [026] Figure 4 is a section view of an injector according to an embodiment of the invention; [027] Figure 5 is an isometric rear view of an injector tip according to an embodiment of the invention; [028] Figure 6 is a first section view through an injector tip according to an embodiment of the invention; 4 [029] Figure 7 is a second section view through an injector tip according to an embodiment of the invention; [030] Figure 8 is a schematic view of the process of manufacturing an injector tip according to an embodiment of the invention; [031] Figure 9 is a schematic view of an idealized raster for use in manufacturing an injector tip according to an embodiment of the invention. [032] The convention used in the drawings is that the reference numbers include one or two digits in front of the decimal point corresponding to the drawing number, and three digits after the decimal point representing the feature of the drawing. Detailed description of the embodiment or embodiments [033] Embodiments of the invention will be described with reference to the accompanying figures, wherein the convention used in the drawings is: X.YY, XX.YY, X.YYY, XX.YYY where X or XX represents the figure number in which an item, feature or part is illustrated, while YY or YYY represents the item, feature or part. [034] Figure 1 shows a mould 1.010, 1.012, cavity 1.014, and injector 1.002, 1.004, having a tapered tip 1.006. A coolant jacket 1.018 extends over the majority of the length of the injector duct 1.002, but does not extend to the tapered tip 1.006 of the injector. Coolant can be circulated under pressure through the jacket, for example in the direction of arrows 1.020, 1,022. Baffles such as 1.024, 2.024, 2.026 can be used to direct the coolant to the bottom of the injector. The injection fluid is fed through the hollow core 1.002 of injection fluid duct 1.001. [035] Figure 3 shows the details of an injector tip according to an embodiment of the invention. The injector tip 3.004 includes a cylindrical body with a threaded end 3.032, and a tapered tip forming a nozzle 3.006. An O-ring seal 3.033 is provided between the injector tip 3.032 and the injector fluid duct 3.001. A seal groove 3.034 is provided to receive a seal between the outer edge of the tip and the outer wall of the injector 3.016. This seal can also be an O-ring. [036] The needle is shown in the withdrawn or open position to permit moulding material to flow to the mould cavity. The tapered tip can have an exit zone 3.029 defined by a 5 narrower taper angle and a pre-taper zone 3.028 defined by a somewhat larger taper angel, as indicated by angle P. The needle 3.004 has a tapered tip 3.008 adapted to match the angle of the exit zone 3.029. [037] Coolant jacket 3.016 and the outer surface of injection fluid duct 3.001 define the coolant cavity 3.018 adjacent to the cylindrical portion of the injector. An extension of the coolant cavity 3.030 extends to surround a substantial portion of the injector tip. The extension cavity 3.030 is in fluid communication with the coolant cavity 3.018 via coolant apertures best seen at 5.050 in Figure 5. Baffles as in Figure 1 can be used to direct the coolant to the tip of the injector. Preferably the baffles are spiralled to provide a more even heat distribution. [038] Figure 4 is an illustration of a section of an injector according to an embodiment of the invention showing the injection needle 4.004 in the closed position with the needle tip 4.008 protruding from the nozzle of the injector. Thus the mould material cannot enter the mould cavity from the feed duct 4.001 while the needle is in the closed position. The needle is operated via a pneumatic cylinder 4.042. The moulding material can be fed through a hollow cylinder 4.044 through the pneumatic cylinder to the feed duct 4.00 1. As shown in Figure 4, the extension of the water jacker 4.030 extends substantially to the tip of the nozzle 4.006. [039] Figure 5 is an isometric rear view of a nozzle tip according to an embodiment of the invention. The nozzle has a cylindrical main body 5.054 through which the moulding material duct 5.001 passes. A needle support 5.052 having three support legs is located in the body of the nozzle tip to stabilize the needle. The support arrangement can be streamlined to facilitate the flow of material around the support. The thread 5.032 is shown in this figure, while the tapered nozzle is not visible. A seat for an O-ring is shown at 5.033. A plurality of coolant apertures 5.050 formed by concentric outer cylinder 5.056 and connection radials 5.058 are shown. The coolant can flow through these apertures into the tapered portion of the coolant extension cavity to cool the tapered section of the nozzle. [040] A method of construction the nozzle tip will now be described. Figure 6 shows a section through the nozzle at line A-A of Figure 3 below the extension coolant cavity 3.030. The nozzle aperture 6.060 is shown surrounded by the section of the nozzle 6.o62 which, at the location A-A is a single annulus.

6 [041] Figure 7 shows the section B-B of Figure 3. At this location, the section is bifurcated into an inner annulus 7.064 and an outer annulus 7.066, while the space between the two rings 7.064, 7.066 defines the extension coolant cavity 7.030. [042] Figure 8 is a schematic view of a laser assisted direct material deposition process using a deposition head to deposit and fuse material on a substrate. A laser head 8.080 is surrounded by a material feed nozzle 8.082 for feeding powdered material, such as titanium, a titanium alloy such as Ti64 or tungsten to a nozzle supported on a substrate. Preferably the material has a differential expansion rate comparable with that of the mould material. Titanium has a coefficient of thermal expansion which makes it particularly suitable for this application. The system is adapted to permit three dimensional relative movement between the laser and feed nozzle on the one hand and the substrate on the other hand. The process is carried out in an inert or controlled atmosphere. The laser is programmably controlled, for example using computer aided manufacturing software, to move in a raster pattern to lay down successive layers of the fused material building up from the substrate, with each successive layer being deposited on top of the previous layer, the adjoining layers fusing to form a solid mass. In this example, the powdered material will be assumed to be titanium. [043] Initially, the laser is focussed on a substrate 8.068 which will support the nozzle during manufacture. The powdered titanium is fed into the focus zone of the laser and sintered or melted to form an amalgamated mass of the material. The deposit will have a predetermined depth as shown at 8.084, and a predetermined width (not shown). [044] The laser is moved in a "raster' to trace out the shape of the specific layer. Figure 9 illustrates an exemplary composite raster for laying down the injector nozzle aperture 9.060, and, after several intervening layers, indicated by dotted lines 9.092, the raster for the section B-B of Figure 8, being the concentric rings 9.064 (inner), and 9.066 (outer). The dot dash line 9.094 indicates that there is no deposition between ring 9.064 and ring 9.066. [045] Because the nozzle has a substantially circular section, a spiral or stepped circular raster is best suited for building such a device as this permits continuous deposition of a complete annulus. On completion of each layer, the deposit head (the laser and powder nozzles, index upward by an amount equal to the depth of the deposited layer, and deposition of the next layer commences when the laser is located at the registration point for that layer.

7 [046] The first layer 9.060 will thus correspond with the injector nozzle aperture 8.060. This may be one or more deposit lines wide and one deposit line deep. Each layer is thus built up on the preceding layer, and can extend a short distance beyond the outer edge of the previous layer. Preferably the overhang step between layers is less than half the thickness of the deposited metal to ensure a firm, positive physical contact. As can be seen in Figure 9, this permits the formation of an undercut structure. [047] The process continues after the sloping surfaces have been deposited in the formation of the double concentric cylinders and connecting spokes defining the coolant apertures, and finally the remaining cylindrical portion of the body of the nozzle is built up. [048] The thread 5.032 can be machined into the body of the nozzle after the deposition process is completed. [049] In this specification, reference to a document, disclosure, or other publication or use is not an admission that the document, disclosure, publication or use forms part of the common general knowledge of the skilled worker in the field of this invention at the priority date of this specification, unless otherwise stated. [050] Where ever it is used, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of'. A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear. [051] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. All of these different combinations constitute various alternative aspects of the invention. [052] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.

Claims (18)

1. An injector tip for a mould, the injector tip including an extended coolant jacket, wherein the extended coolant jacket extends to at least a part of the tapered tip in an undercut cavity.

2. An injector tip as claimed in claim 1, wherein the tip includes an inner conic section having a first taper angle, and a second conic section concentric with the first conic section and having a taper angle which is greater than the first taper angle so that the second conic section encompasses the first conic section and defines the undercut cavity therebetween, the first and second conic sections terminating at their respective tapered ends in a common plane, the undercut cavity being closed at the end proximate the common plane.

3. An injector tip as claimed in claim 2, including a first cylindrical body extending from the first conic section.

4. An injector tip as claimed in claim 2, including a second cylindrical body extending from the second conic section.

5. An injector tip as claimed in claim 4, wherein the second cylindrical body is concentric with the first cylindrical body.

6. An injector tip as claimed in claim 4 or claim 5, wherein the second cylindrical body is connected to the first cylindrical body by a plurality of radial spokes defining coolant apertures therebetween, through which coolant can pass to the undercut cavity.

7. An injector tip as claimed in any one of claims 3 to 6, including a thread on the distal end of the first cylindrical body.

8. An injector tip as claimed in any one of claims 3 to 7, including a needle support located concentrically within the first cylindrical body.

9. An injector tip as claimed in any one of claims 2 to 8, wherein the inner surface of the first conic section includes a valve seat for a valve needle.

10. An injector tip as claimed in any one of the preceding claims made of a depositable material having a suitable coefficient of thermal expansion. 9

11. An injector tip as claimed in claim 10, wherein the material is selected from titanium, tungsten, stainless steel, or polymer.

12. A method of manufacturing an injector tip including deposition a first series of concentric annuli having a progressively increasing inner and outer diameters, the inner diameter of each succeeding layer being less than the outer diameter of the preceding layer until a required first conic shape has been formed, and then depositing a further series of concentric annuli of having inner diameters and outer diameters equal to those of the preceding layer to form a first cylindrical body, and depositing a second series of concentric annuli having a progressively increasing inner and outer diameters, the inner diameter of each succeeding layer being less than the outer diameter of the preceding layer until a required second conic shape has been formed, and then depositing a further series of concentric annuli of having inner diameters and outer diameters equal to those of the preceding layer to form a second cylindrical body have been formed, the second conic shape being attached at its root to the first conic shape and having a larger equivalent diameter over the majority of its length compared with the outer diameter of the first conic shape, to define an undercut cavity therebetween, the second cylindrical body having a greater inner diameter than the outer diameter of the first cylindrical body to define a coolant channel therebetween connected to the undercut cavity.

13 A method as claimed in claim 12, wherein the layers are formed using direct material deposition.

14. A method as claimed in claim 12 or claim 13, wherein the deposit material is titanium or tungsten.

15. A method of manufacturing an injector tip, substantially as herein described with reference to figures 8 and 9 of the accompanying drawings.

16. An injector having a tip as claimed in any one of claims I to 11.

17. An injector substantially as herein described with reference to figures 1 to 7 of the accompanying drawings. 10

18. An injector having a tip made by the method of any one of claims 12 to 15.