Abstract
Method for injection moulding one or more parts using an injection moulding machine and tool (12, 13) comprising at least one mould cavity (17), and a feed system comprising at least one gate (18) and at least one runner (19, 20, 21) that is located upstream of the at least one gate (18). The at least one runner (19, 20, 21) comprises a at least one moveable wall and the method comprises the step of changing at least one cross-sectional dimension (T, B, H, S or S+S) of the at least one runner (19, 20, 21) by moving the at least one moveable wall in order achieve at least one of the following: a) to vary a flow rate of material in the at least one runner (19, 20, 21), b) to apply a holding pressure to material in the at least one runner (19, 20, 21) and consequently to the at least one mould cavity (17), c) to compress residue in the at least one runner (19, 20, 21).
Claims
1-11. (canceled)
12. Method for injection moulding two or more parts with a different size, shape and/or volume simultaneously using an injection moulding machine and tool (12, 13) comprising two or more mould cavities (17), and a feed system comprising at least one gate (18) a plurality of runners (19, 20, 21) located upstream of said at least one gate (18), characterized in that said plurality of runners (19, 20, 21) comprises at least one moveable wall and said method comprises the step of changing at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) by moving said movable wall in order to achieve at least one of the following: a) to apply a holding pressure to material in said plurality of runners (19, 20, 21) and consequently to said two or more mould cavities (17), b) to compress residue in said plurality of runners (19, 20, 21), whereby said at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) is individually variable.
13. Method according to claim 12, characterized in that it comprises the step of heating said plurality of runners (19, 20, 21) to a temperature less than a melting point or melting interval of the material in said plurality of runners (19, 20, 21).
14. Method according to claim 12, characterized in that said movable wall is arranged to be mechanically, hydraulically or electrically controlled.
15. Method according to claim 13, characterized in that said movable wall is arranged to be mechanically, hydraulically or electrically controlled.
16. Injection moulding tool (12,13) for performing a method for simultaneously injection moulding two or more parts with a different size, shape and/or volume using an injection moulding machine, according to claim 12, which comprises two or more mould cavities (17) and a feed system comprising at least one gate (18) and a plurality of runners (19, 20, 21) that is arranged to be located upstream of said at least one gate (18), characterized in that said plurality of runners (19, 20, 21) comprises at least one movable wall that is arranged to enable at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) to be changed in order achieve at least one of the following: a) to apply a holding pressure to material in said plurality of runners (19, 20, 21) and consequently to said two or more mould cavities (17), b) to compress residue in said plurality of runners (19, 20, 21), whereby said tool comprises means to change said at least one cross-sectional dimension of said a plurality of runners, and whereby said at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) is individually variable.
17. Tool (12, 13) according to claim 16, characterized in that it comprises a plurality of adjacently arranged gate inserts (16, 26) that are adapted to change said at least one cross-sectional dimension (T) of said plurality of runners (19) automatically in a stepless or gradual manner by means of mechanics or hydraulics or an electric circuit including a drive unit and a control system.
18. Tool (12, 13) according to claim 16, characterized in that it comprises heating means to heat said plurality of runners (19, 20, 21) to a temperature less than a melting point or melting interval of the material in said plurality of runners (19, 20, 21).
19. Tool (12, 13) according to claim 17, characterized in that it comprises heating means to heat said plurality of runners (19, 20, 21) to a temperature less than a melting point or melting interval of the material in said plurality of runners (19, 20, 21).
20. Tool according to claim 16, characterized in that said movable wall is arranged to be mechanically, hydraulically or electrically controlled by said means to change said at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) automatically in a stepless or gradual manner by means of mechanics or hydraulics or an electric circuit including a drive unit and a control system.
21. Tool according to claim 18, characterized in that said movable wall is arranged to be mechanically, hydraulically or electrically controlled by said means to change said at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) automatically in a stepless or gradual manner by means of mechanics or hydraulics or an electric circuit including a drive unit and a control system.
22. Tool (12, 13) according to claim 16, characterized in that at least part of said means to change said at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) constitutes an exchangeable cassette that is arranged to be removably attached to said tool.
23. Tool (12, 13) according to claim 17, characterized in that at least part of said means to change said at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) constitutes an exchangeable cassette that is arranged to be removably attached to said tool.
24. Tool (12, 13) according to claim 18, characterized in that at least part of said means to change said at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) constitutes an exchangeable cassette that is arranged to be removably attached to said tool.
25. Tool (12, 13) according to claim 20, characterized in that at least part of said means to change said at least one cross-sectional dimension (T, B, H, S or S+S) of said plurality of runners (19, 20, 21) constitutes an exchangeable cassette that is arranged to be removably attached to said tool.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0090] The present invention will hereinafter be further explained by means of non-limiting examples with reference to the appended schematic figures where;
[0091] FIGS. 1a-c show the Mono Sandwich method according to the prior art,
[0092] FIGS. 2 & 3 illustrate some of the problems that can occur when injection moulding a part having a complex form using any co-injection method according to the prior art,
[0093] FIG. 4 shows the part illustrated in FIGS. 2 and 3 that has been injection moulded using the over-moulding method according to the prior art,
[0094] FIGS. 5a-b illustrates a part incorporating an upper portion which is co-injection-moulded and at least one connection integrated therewith which is filled only with core material using a method according to the prior art,
[0095] FIGS. 6 & 7 show features of a tool according to an embodiment of the invention,
[0096] FIG. 8 shows a feed system according to an embodiment of the invention,
[0097] FIG. 9 shows a plurality of runners,
[0098] FIGS. 10a-d shows means for changing a cross-sectional dimension and for applying a pressure in the melt in a plurality of runners according to an embodiment of the invention,
[0099] FIGS. 11a-c shows means for changing a cross-sectional dimension and for applying a pressure in the melt in a plurality of runners according to an embodiment of the invention,
[0100] FIG. 12 is a flow diagram showing the steps of a method according to an embodiment of the invention.
[0101] It should be noted that the drawings have not necessarily been drawn to scale and that the dimensions of certain features may have been exaggerated for the sake of clarity.
DETAILED DESCRIPTION OF EMBODIMENTS
[0102] FIGS. 6 and 7 show the two halves of an injection moulding tool, one half 12 on the stationary side and the other half 13 on the moving side of the clamp unit of the injection moulding machine in which the tool is housed, and which tool may be used in a method according to the present invention, such as any co-injection method and the method to mould family parts. The illustrated tool halves 12 and 13 comprise a three-plate mould in which a stripper plate 14 constitutes the third plate. A beam 15 mounted on the stripper plate 14 comprises side gate inserts 16 or 26, and which beam 15 and side gate inserts 16 or 26 are detachable from the stripper plate 14.
[0103] The tool halves 12 and 13 comprise two mould cavities 17 in which the parts are to be formed and each mould cavity has a side gate 18. The tool halves 12 and 13 also comprise tool inserts 25 where a plurality of side gate runners 19 and a plurality of two branch runners 20 and a main runner 21 are positioned.
[0104] In the illustrated tool halves 12 and 13 of FIGS. 6 and 7, said runners 20 and 21 have rectangular cross sections and are completely positioned in tool inserts 25 mounted on the moving side tool half 13 and the top surface of the moving cores (40 in FIG. 11c) is located at the bottom of the runners 20 and 21, the walls of the through-hole for the moving cores 40 are the side surfaces of said runners and the flat or curved surface of the mould plate 12, opposite inserts 25, in the stationary tool half is located at the top surface of said runners.
[0105] FIG. 11c shows that, according to an embodiment of the invention, the plurality of branch runners 20 and main runners 21 may have a substantially circular cross-section, a substantially oval cross-section or any other geometry. By setting the height Sx on the axis of symmetry of the cross-section of the runners 20 or 21 as shown in FIG. 11c the cross-section could, if desired, become substantially oval. Features of said runners 20 or 21 with a substantially circular or an oval cross section are firstly that the plastic residue in the runners 20 and/or 21 will have a smaller volume at the same flow resistance than corresponding runners with rectangular or square cross sections, secondly that the groove 43 together with the radially shaped surface on top of the core 40 forms a flange 44 that will press against the surface of the through-hole for the cores 40, and, especially when a high pressure is built up in the melt or an extreme low-viscosity plastic melt is used, this design of the top of the core will contribute to an improved tightening in order prevent leakage of melt between the core 40 and its through-hole in the tool insert 25.
[0106] The tool halves 12 and 13 in the FIGS. 6 and 7 are merely an example of an injection moulding tool which may be used with the method according to the present invention. Generally, a tool does not necessarily have to comprise a stripper plate 14 and a beam 15. Side gate inserts 16 and 26 or cores 40 associated with a plurality of runners 19, 20 and 21, as shown in FIGS. 9, 10a-d and 11a-c, no matter if they are coupled to drive mechanics according to the invention or not, can be positioned directly in the stationary half 12 as well as in the moving half 13 of the tool. A tool according to the present invention may also comprise any number of mould cavities 17, such as one, two, three, four, five, or more mould cavities, where, in the case of a plurality of mould cavities their shapes, sizes and/or volumes may be the same or different.
[0107] FIG. 8 shows features of a feed system according to an embodiment of the invention which is used to feed plastic melt into one or more mould cavities 17 (not shown in FIG. 8) when the injection moulding tool is in use. When the injection moulding tool is in use, there is namely plastic material in the main runner 21, the two branch runners 20 and the plurality of five or two streamlined side gate runners 19. The side gate 18 supplies the melt to the cavities 17. FIG. 8 thus illustrates an exemplary shape and geometry of said side gate 18 and said runners 19, 20 and 21. The feed system is situated in the parting line of the tool in between the moving half 13 and the stationary half 12 and the beam 15. The plastic material in the feed system shown in FIG. 8 has no compressed portions or any other deformations, so the shape/geometry of the plastic material fully corresponds to the surfaces/geometry of the runners and side gate of the feed system in the tool.
[0108] The term gate means an opening connecting at least one runner to a mould cavity. A side gate is an example of such a gate. A side gate may be located to let in the melt at a lateral edge, or close to such an edge, of either a single-curved or a double-curved wall of the moulded part. A side gate is of course also possible to locate at a straight edge of a flat wall of the part such as the side gate 18 into the larger cavity 17 shown in FIGS. 7 and 8. A gate is dimensioned to allow for sufficient flow of melt to fill a mould cavity without causing too high shear and degradation of the material. Only one gate 18 per mould cavity is preferable to avoid weld lines, when the melt is spreading out in the mould cavity 17, and other defects in the final part. A plurality of runners 19 according to the invention can be arranged to feed melt through a side gate 18. A branch runner 20 with its extension alongside the inlets to the plurality of side gate runners 19, has to be arranged to feed the melt into this plurality of runners 19, whereby means, such as the wedge-like tip 52, to axially split the melt flow front at the inlet of each runner 19, and then deflect the split portion of the melt into each runner of the plurality of runners 19, which deflection can be facilitated by machining a cross section enlargement 53 partly at the inlet of each runner.
[0109] The main runner 21 and the two branch runners 20, shown in FIG. 8, both have a rectangular cross section, with heights Hx and widths Bx. In corresponding runners with substantially circular or oval cross sections, the diameter is Sx for a circular cross section as shown in FIG. 11c and the width and height for an oval cross section is Sx respective Sx+Sx. The plurality of runners 19 have a thickness Tx in their cross section across the melt flow direction. The index x means that the dimensions Hx, Bx, Sx and Tx belong to more than one of the plurality of runners and thereby may have different, fixed or adjustable sizes. In the illustrated tool, H.sub.1, H.sub.2 and H.sub.3 are the heights of the main runner 21 and of each of the two branch runners 20 respectively, and these heights may have been set by moving the cores 40 either to a fixed position in each runner before the injection moulding operations starts or to be changed gradually or stepless for each cycle during the injection moulding operations. The dimensions Tx for the thickness of respective runners in the plurality of runners 19 are T.sub.1, T.sub.2, T.sub.3, T.sub.4 and T.sub.5 for the large cavity 17 and T.sub.6 and T.sub.7 for the small cavity 17 and each of the runners 19 may be set at different thicknesses by moving the side gate inserts 16 with the set screws 35, see FIGS. 9 and 10a.
[0110] The tool according to an embodiment of the invention is arranged to carry out the one or more of the following functions: [0111] to infinitely variably adjust the melt flow rate, cm.sup.3 s.sup.1, to fill either a single mould cavity 17 or to fill each mould cavity of a plurality of mould cavities 17 using individual melt flow rates, and/or [0112] to apply a holding pressure in the melt in a single mould cavity 17 or individually in each mould cavity of a plurality of mould cavities 17, and/or [0113] to apply a pressure in the melt to compress the plastic residue in the plurality of runners 19, 20 and 21 of the feed system so that a minimum volume of plastic is left inside the runners 19, 20 and 21.
[0114] These means are: [0115] a plurality of side gate runners 19 located upstream of a gate 18, (see FIG. 8 for example), whereby the runners 19 according to the invention are associated with a plurality of infinitely adjustable gate inserts 16 or 26 in one of the tool halves and a fixed gate insert 34 in the other tool half (as shown in FIG. 9), or adjustable gate inserts 26 in the other tool half (as shown in FIG. 10d), which plurality of runners 19 can be coupled to [0116] drive mechanics (as shown in FIG. 10a), where one or more of the gate inserts 16 (or inserts 26 in FIG. 10d) are coupled via set screws 35 to an upper wedge 22 and a lower wedge 23 with a connection 45 to a drive unit (not shown). [0117] a plurality of branch runners 20 and main runners 21 (as shown in FIG. 8), where a moveable wall of each of the runners 20 and 21 is constituted by the top of the cores 40 that are moving in through-holes in the inserts 25 (as is illustrated in the example in FIGS. 11a and 11b), a portion of the surface of the through-holes and a usually single-curved surface in the tool half on the opposite side, and mechanics according to the invention for the plurality of branch runners 20 and/or main runners 21 (see FIGS. 11a and 11b) [0118] which mechanics for each runner of the plurality of runners 20 and 21 may be either infinitely adjustable to set the cores 40 in an optional fixed position, before the injection moulding operations starts, with a height Hx (as shown in FIG. 8) or Sx (as shown in in FIG. 11c) or Sx+Sx in an oval cross section, giving a cross section area in each of the plurality of runners 20 and/or 21 so that a desired melt flow rate through each of said runners is obtained, or [0119] which mechanics for each runner of the plurality of runners 20 and 21 is used for varying the melt flow rate individually in each of said runners during each cycle of the injection operations, or for applying a holding pressure operation in the melt individually in each of said runners, or applying a pressure in the melt to compress the plastic material to a minimum volume individually in said runners corresponding to the heights Hrx or Srx, or for sequentially combining said melt flow adjusting operations and holding pressure operations during the same moulding cycle. The index r means residue, i.e. the plastic material remaining in the plurality of runners 19, 20 and 21 after the, or each mould cavity has been filled (see FIGS. 10d and 11c).
[0120] FIG. 11c illustrates a holding pressure operation where a substantially circular cross section of a runner 20 and/or 21 expands from a height Sx to Sx+Sex in order to accumulate a melt cushion that is necessary for the holding pressure operation. At the end of the holding pressure operation, (see the drawing on the right in FIG. 11c), the melt residue in the runners is compressed to a height Srx=about 0.6 Sx provided that the initial cross section is substantially circular with a diameter Sx.
[0121] The plurality of runners 19 upstream of the gate 18 may be used merely to adjust the melt flow individually in each runner 19 and thereby the profile of the melt flow front can be formed to spread in the cavity(-ies) 17 in such a way that optimum filling is obtained. The dimension Tx is, by successive trials, individually set in each runner of the plurality of runners 19 until the melt flow front in the mould cavity has obtained a desired profile and the entire flow front will reach the farthest contour of the mould cavity at practically the same time. FIG. 9 shows a plurality of gate inserts 16 mounted in a recess 32 of a cassette 33, which inserts 16 together with the fixed insert 34 in the tool half on the opposite side form a plurality of runners where each runner can be adjusted individually by the set screws 35 to a dimension Tx in the plurality of runners 19. The cover screws 36 have to be unscrewed before the set screws 35 can be turned. The cassette 33 and the fixed insert 34 are easy to mount and dismount in the stationary or moving mould plates of the tool.
[0122] The embodiment exemplified in FIG. 9 can be used in tools where there is a need of [0123] an optimum flow front profile for the spread of melt in the mould cavity, for example at co-injection or conventional single-material injection moulding of parts with complex design, [0124] optimum spread of the melt in a mould cavity combined with balancing the melt flow among mould cavities with equal shape, size and volume in a multi-cavity tool.
[0125] The embodiment shown in FIG. 9 can be supplemented with drive mechanics to apply a force on the gate inserts 16, (see FIGS. 10a-c) to perform a holding pressure operation in the melt in the plurality of gate runners 19 upstream of the side gate 18 and consequently a holding pressure in the melt that has been fed into the mould cavity 17.
[0126] In the embodiment shown in FIG. 10a there is also a cassette 33 with a recess 32 where the side gate inserts 16 are mounted and which together with the fixed insert 34 form a plurality of runners 19 upstream of the side gate 18. The set screws 35 are connected to the upper wedge 22 and the dimension Tx can be adjusted individually by the set screw 35 in each gate insert 16 in the plurality of runners 19 so that the melt flow, when having passed the plurality of runners 19, will form a desired flow front in the mould cavity 17.
[0127] FIGS. 10a-c show an example of holding pressure operational steps, where a plurality of side gate inserts 16 are coupled to an upper wedge 22 that via a lower wedge 23 has a connection 24 to a drive unit that may be a double-acting hydraulic cylinder or a hydraulic motor or an electric servo motor. The holding pressure operation is activated to start at the same point of time as the melt filling operation into the mould cavity 17 has ceased, or at a point of time shortly before the filling operation has ceased, meaning that the plurality of side gate runners 19 that has been set to different dimensions Tx (see FIG. 10a) in the next step (shown in FIG. 10b) the package/row of side gate inserts 16 is controlled to expand a distance Te which distance is the same for all runners in the plurality of runners 19 as the side gate inserts 16 are in fixed positions in relation to each other after being set to dimension Tx. The expanding movement Te is carried out by pulling the lower wedge 23 a corresponding distance backwards in the cassette 33. Thereby plastic melt is accumulated in the plurality of runners 19 to a so-called melt cushion, which will accomplish a volume, as a result of an appropriately chosen expansion Te, which volume is as large as, or slightly larger than, the volume of plastic melt needed for maintaining a desired holding pressure in the mould cavity 17 during the whole holding pressure operation. The compression of the plastic material terminates with different dimensions Trx/See FIG. 10c) of the plastic residue in the plurality of runners 19 and which dimensions Trx usually are slightly larger than Tx.
[0128] With this embodiment a holding pressure operation can be performed in the plurality of runners 19, and consequently in the mould cavity 17, provided that there is a device in one of the runners of the plurality of runners 20 or 21 upstream of the plurality of runners 19 for shutting off the melt flow to said mould cavity in order to prevent the melt being pressed backwards whereby a desired holding pressure in the melt that has been supplied to the cavity would not be possible to build up. The shut off device may be positioned in a way that the melt flow can be shut off either in one of the plurality of branch runners 20 or in a main runner 21. FIG. 7 shows two shut off devices 30 that each comprise a mini hydraulic cylinder driving a shut off core that closes and opens the two branch runners 20. Such a shut off device may be designed in different ways.
[0129] The embodiment according to the invention that is exemplified in FIGS. 10a-c can be used in tools where there is a need of: [0130] applying an individual holding pressure and an individual time for the holding pressure operation in each of the mould cavities in tools with a plurality of mould cavities 17, for example in a tool for the injection moulding of family parts, [0131] applying a holding pressure in a tool comprising a single mould cavity or a plurality of mould cavities with equal shape, size and volume in order to achieve the shortest possible cycle time in cases where a too long time for plasticizing and metering in the injection unit of the injection moulding machine would cause a lengthened cycle time when using the holding pressure function in a conventional injection moulding machine. Injection moulding using the sequential co-injection method Mono Sandwich could be mentioned as such a case where the total time for injection, holding pressure and cooling operations may be so short that the total time for plasticizing and metering of the core layer material and docking of the extruder to the nozzle of the injection unit, followed by metering of the surface layer material will cause a lengthened cycle time. With a cavity-specific holding pressure, the metering of core material can start as soon as the cavity(-ies) has/have been completely (volumetrically) filled as the holding pressure operation in the injection unit of the machine and the corresponding time for said operation is not used.
[0132] The embodiment comprising a plurality of side gate runners 19 and cassette 37 which is shown in FIG. 10a, comprising the mechanics to apply a holding pressure in the melt, is possible, even without taking down the tool from the injection moulding machine, by mounting and dismounting the tool in the following way: [0133] Mounting starts with pushing the cassette 37 into the recess in between the mould plates 39 with the wedge 23 in the rear position, (see FIG. 10b) and then connecting the coupling 45 to said wedge. The wedge 23 is then pushed forward until it reaches its end position, (see FIG. 10a) and at the same time the wedge 23 is pushing the wedge 22 within the clearance 50 towards the parting line between the tool halves 12 and 13. After having mounted the cassette 33 in the mould plate 39, set screws 35 together with the side gate inserts 16 or 26 (FIG. 10d) can be screwed through the inserts 16 or 26 from the parting line and tightened into the wedge 22. All dimensions Tx of the plurality of runners 19 are thereby set in their start positions Tmax, such as 3 mm. Finally the cover screws 36 should be screwed into each of the side gate inserts 16 or 26. [0134] Dismounting is carried out in the opposite way starting with unscrewing the cover screws 36 from the side gate inserts 16 or 26.
[0135] The embodiment shown in FIGS. 10a-c can be combined with a plurality of side gate inserts 26 including drive mechanics, (see FIG. 10d), which replaces the fixed insert 34 shown in FIGS. 10a-c. The purpose of supplementing said embodiment with a plurality of runners 19 including driven side gate inserts 26 is to compress the plastic material residue in the plurality of runners 19 to a minimum volume, corresponding to a dimension Trx, which dimension may be different from side gate runner to side gate runner, in order to get smallest possible amount of residual material when recycling the residue directly into the injection unit of the machine or when recycling the residue separately. The compression operation may be carried out simultaneously from both sides of the plurality of runners 19 (see FIG. 10d). The plurality of side gate inserts 26 and its drive mechanics according to FIG. 10d, is designed just for performing a compression operation on the plastic residue in the plurality of side gate runners 19 and thereby has to be combined either with the embodiment for applying a holding pressure to the melt in said runners 19 according to FIGS. 10a-c or combined with a holding pressure operation in the injection unit of the machine. Usually the dimension Tx could be compressed by at least 50%, i.e. the compressed dimension Trx0.5 Tx.
[0136] The mechanics of the embodiment for the compression operation of the plastic residue in the plurality of runners 19 as shown in FIG. 10d is identical to the mechanics of the embodiment in FIGS. 10a-c for carrying out the holding pressure operation, apart from the side gate inserts 26, the set nuts 27, the screws 28 and the coil springs 29. As the cross sections of the plurality of runners 19 in FIGS. 10a-c have been set to a dimension Tx and the desired dimension of the compressed plastic residue is Trx the set nuts 27 should be turned to move the side gate inserts 26 to be set at a dimension TxTrx from their initial position where they are fully tightened to the screws 28 which screws are permanently fully tightened to the wedge 22. The coil springs 29 will ensure that the inserts 26, which are connected to a dowel of the set nuts, are returning together with the set nuts 27 when the drive unit is pulling back the wedges 22 and 23. An example of the plurality of branched runners 20 and main runners 21 according to the invention, all of them being so-called cold runners are shown in FIGS. 7 and 8 in the form of corresponding plastic residues of the feed system. In the tool consisting of the tool halves 12 and 13, FIGS. 6 and 7, said runners have rectangular cross sections and are completely positioned in tool inserts 25 mounted on the moving side tool half 13 where the top surface of the moving cores 40 constitutes the bottom of the runners 20 and 21, the walls of the through-hole for the moving cores 40 are the side surfaces of said runners and the flat or curved surface of the mould plate 12, opposite inserts 25, in the stationary tool half constitutes the top surface of said runners.
[0137] The mechanics according to the invention for the plurality of side gate runners 19 is constituted by an upper wedge 22 and a lower wedge 23 connected to a coupling rod 45, which all are mounted in a cassette 37 that is pushed into a recess in between the mould plates 39. The upper wedge 22 is, via the set screws 35, connected to the plurality of side gate inserts 16 or 26, see FIGS. 10a and 10d. The mechanics for the plurality of runners 20 and 21, see FIG. 11a, is also constituted by an upper wedge 22 and a lower wedge 23 connected to a coupling rod 45, which are all mounted in a cassette 37 that is pushed into a recess in between the mould plates 39 and the upper wedge 22 via inclined hooks 42 and notches 24 coupled to the moving cores 40.
[0138] FIG. 11a shows the mounting of the moving cores 40 in the through-holes in a tool insert 25. Mounting of the mechanics starts by positioning the cassette 37, wherein the upper and lower wedges 22 and 23 are in a fixed position as shown in FIG. 11a, a short distance backwards from the very front of the recess whereupon the cores 40, including the bridging pieces 41, are pushed into their through-holes so that the hooks 42 will be situated on the upper surface of the wedge 22 a short distance to the left of the notches 24. Then the cassette 37 is pushed said short distance forward to its very front position whereby the hooks 42 will slide down into the notches 24 and thus the cores 40 are thereby connected to the upper wedge 22 as shown in FIG. 11b. Then, in case the operation of the cores so requires, the coupling 45 can connect the lower wedge 23 to a drive unit for the purpose of either adjusting the melt flow rate or applying a holding pressure in the plurality of runners 20 and/or 21 or the coupling 45 can be connected to a screw device (such a device 24 can be seen in FIG. 10a) for setting the heights Hx or Sx or Sx+Sx in fixed but optional positions in said runners with substantially rectangular or circular or oval cross sections. The cores 40 have a flat surface on both sides of their lower part which surfaces glide against support pieces 47 to ensure that the hooks 42 are fully kept down in the notches 24 during use of the tool. Demounting is carried out in the opposite order, with the upper and lower wedges 22 and 23 in a fixed position (as shown in FIG. 11a), and pulling the cassette 37 a short distance backwards etc. The cores 40 can, when unfastened, be pulled out from their through-holes.
[0139] The functions and operations according to the invention, such as start and stop times and speeds/forces for the drive means coupled to the mechanics for the plurality of runners 19, 20 and 21, have to be co-ordinated and controlled in such a manner that this new injection moulding technology can be adapted to specific and different methods that can utilize the invention. Typical operations of the injection moulding machine and the tool according to the invention, are the start of injection and changing injection speed at different positions for the reciprocating motion of the screw piston in the machine, changing the cross section and closing/opening of one or more of the plurality of branch runners 20 or main runners 21, switch-over to holding pressure either in the injection unit of the machine or in the plurality of runners 19, 20 and 21 in the tool and performing the holding pressure and compression operations in one or more of said runners.
[0140] The drive means connected via a coupling rod 45 to the mechanics connected to side gate inserts 16 and/or 26 and moving cores 40, which inserts and cores are associated with the plurality of runners 19, 20 and 21, may be hydraulic cylinders. Electric servomotors or hydraulic motors may also be used. The drive means in a tool according to the present invention, may be connected to an electronic control system in such a way that the moulding process in each mould cavity in a tool with a plurality of mould cavities and a plurality of runners, can to a great extent be individually and variably controlled regarding melt flow rate and operations for holding pressure and/or compression of plastic residue in the gating system. The start and end positions for moving the plurality of side gate inserts 16 and 26 and the cores 40 during the injection and holding pressure operations may be set with the screw device 51. The control system may either be stationary and integrated in the injection moulding machine or located externally to the injection moulding machine, i.e. the control equipment may be transportable between different injection moulding machines.
[0141] The tool inserts 25, shown in FIGS. 7 and 10, may be designed in such a way that two functions of the new injection moulding technology according to the present invention will be accomplished, which functions are [0142] heating the tool inserts 25 to reach a temperature on the walls of the plurality of runners 19, 20 and 21 that might be chosen to be substantially higher than conventionally used mould temperatures recommended by plastic material producers, and said heating of the inserts 25 may be performed so that the least possible amount of heat is conducted or radiated to other parts of the tool such as mould plates, cavity inserts etc, and [0143] wear properties of the tool inserts 25 should be sufficient to ensure the lowest possible wear in through-holes for moving cores 40 and in recesses for moving side gate inserts 16 and 26 in the inserts 25 so that the duration of the inserts 25 will be equal to at least the life time of the tool.
[0144] Heating of the tool inserts 25 is performed by using a heating unit that is separate from the heating unit that tempers the rest of the tool to achieve and maintain a mould temperature recommended by the plastic producer. The inserts 25 must be thermally insulated to prevent heat from being conducted or radiated to other parts of the tool, which is achieved in several ways such as: [0145] selection of a steel grade with very low heat conductivity such as stainless steel, and [0146] designing the inserts 25 with outer and inner recesses whereby the air in the recesses will decrease heat conduction through the material of said inserts.
[0147] Moving cores 40 or side gate inserts 16 or 22 perform a reciprocating movement under high pressure and high temperature in the plastic melt at each process cycle and mostly during a long period of time. These process conditions will cause a fairly high pressure between cores 40 and their through-holes and between side gate inserts 16 and/or 26 and their recesses. When injection moulding certain types of plastic material, a mixture of air and volatiles from the melt will to some extent force its way out along the moving surfaces of cores/side gate inserts and/or through-holes/recesses. So there might be both mechanical and corrosive wear on these surfaces. Minor wear could be acceptable on the moving cores 40 and side gate inserts 16 and 22 as they are cheaper to manufacture and easy to exchange in the tool, but said process conditions require that the tool inserts 25 have to be manufactured from an extremely high hardened and corrosion resistant steel grade such as stainless steel hardened to at least 60 HRC. Moving cores 40 and side gate inserts 16 or 22 may be manufactured from a material that is somewhat softer but still corrosion resistant. The tool inserts 25 can be manufactured conventionally or using a 3D printing additive method using steel powder.
[0148] Further modifications of the invention within the scope of the claims would be apparent to a skilled person.
