INJECTION MOULDING TOOL

Abstract

An injection moulding tool for producing at least one injection-moulded part with an outer shape and an inner shape includes at least one cavity and, for every cavity, one hot-runner nozzle connected thereto, which has an annular nozzle mouth for injecting at least one melt into the cavity. The at least one cavity is formed by a cooled die, which forms the outer form for the outer shape of the injection-moulded part to be produced, and by a core, which forms the inner form for the inner shape of the injection-moulded part to be produced. The hot-runner nozzle has a nozzle core and a hollow needle, which can be moved along the nozzle core for opening and closing the annular nozzle mouth. The nozzle core protrudes beyond the annular nozzle mouth of the hot-runner nozzle and the nozzle core forms the core of the cavity of the injection mould.

Claims

1. An injection moulding tool for producing an injection-moulded part with an outer shape and an inner shape comprising a cavity and a hot-runner nozzle connected to the cavity having an annular nozzle mouth for injecting at least one melt into the cavity; wherein the cavity is formed by a cooled die which forms an outer form for an outer shape of the injection-moulded part to be produced and by a core which forms an inner form for an inner shape of the injection-moulded part to be produced; and wherein the hot-runner nozzle has a nozzle core and a hollow needle which is displaceable along the nozzle core for opening and closing the annular nozzle mouth, wherein the nozzle core protrudes beyond the annular nozzle mouth of the hot-runner nozzle and that wherein the nozzle core forms the core of the cavity of the injection moulding tool.

2. The injection moulding tool according to claim 1, wherein the nozzle core comprises an inner cooling core and an outer core.

3. The injection moulding tool according to claim 1, wherein upstream of the nozzle mouth of the hot-runner nozzle, the nozzle core comprises an insulating jacket along which the hollow needle is guided.

4. The injection moulding tool according to claim 3, wherein the insulating jacket is made of ceramic, a low heat-conducting metal or a low heat-conducting metal alloy.

5. The injection moulding tool according to claim 2, wherein the outer core has a circumferential shoulder or a circumferential flange in the region of the nozzle mouth, which forms one side of the nozzle mouth.

6. The injection moulding tool according to claim 2, wherein upstream of the nozzle mouth the outer core has a circumferential recess.

7. The injection moulding tool according to claim 1, wherein the hot-runner nozzle is a co-injection nozzle for injection of a concentrically layered melt flow into the cavity.

8. The injection moulding tool according to claim 1, wherein a cooled die plate forms the die.

9. The injection moulding tool according to claim 1, wherein the core is cooled and is arranged in a cooled core plate.

10. The injection moulding tool according to claim 1, wherein the hot-runner nozzle is mounted in the cooled core plate by a sealing ring.

11. A hot-runner nozzle for an injection moulding tool, wherein the hot-runner nozzle has an annular nozzle mouth, a nozzle core and a hollow needle displaceable along the nozzle core for opening and closing the annular nozzle mouth, wherein the nozzle core protrudes beyond the annular nozzle mouth of the hot-runner nozzle and wherein the nozzle core in the installed state of the hot-runner nozzle forms a core of a cavity of the injection moulding tool.

12. The hot-runner nozzle according to claim 11, wherein the nozzle core comprises an inner cooling core and an outer core.

13. The hot-runner nozzle according to claim 11, wherein upstream of the nozzle mouth of the hot-runner nozzle, the nozzle core comprises at least one insulating jacket along which the hollow needle is guided.

14. (canceled)

15. A method for producing an injection-moulded part using the injection moulding tool according to claim 1, comprising the following steps: a) closing the injection moulding tool to form a cooled cavity for the injection-moulded part to be injected by introducing the nozzle core of the hot-runner nozzle into the cooled die; b) injecting at least one melt into the cooled cavity through an annular nozzle mouth running around the nozzle core; and c) opening the injection moulding tool and ejecting the injection-moulded part.

Description

BRIEF EXPLANATION OF THE FIGURES

[0032] The invention will be explained in detail hereinafter with reference to exemplary embodiments in connection with the drawing(s). In the figures:

[0033] FIG. 1 shows a sectional view of an injection moulding tool;

[0034] FIG. 2 shows a side view of a melt distributor insert;

[0035] FIG. 3 shows a side view of a melt distributor insert with dividing sleeve; and

[0036] FIG. 4 shows a detailed view of a hot-runner nozzle in the area of the nozzle mouth.

WAYS FOR IMPLEMENTING THE INVENTION

[0037] The injection moulding tool comprises a die plate 1 which forms the die 1a for the cavity 3 and a core plate 2 which receives a hot-runner nozzle 4. The hot-runner nozzle 4 has an annular nozzle mouth 5 and a hollow needle, wherein the nozzle mouth 5 can be opened and closed by the hollow needle 6. To this end, the hollow needle 6 is guided movably along an axially non-movable nozzle core 7. The nozzle core 7 protrudes beyond the annular nozzle mouth and forms the core 2a of the cavity 3.

[0038] In the embodiment shown the nozzle core 7 comprises an inner cooling core 8 which is actively cooled with a cooling medium, in particular water, and an outer core 9. The downstream-directed end of the outer core 9 and the downstream-directed front face 10 of the cooling core 8 form the core 2a of the cavity 3, i.e. they correspond to the negative of the inner shape of the injection-moulded part to be produced. The outer core could also form the entire front face of the core 2a. In the embodiment shown, upstream of the nozzle mouth, the nozzle core 7 has an insulating jacket 11 which is made of ceramic or a less heat-conducting metal alloy (e.g. a chromium steel) than the metal alloy for the heated parts of the hot-runner nozzle 4. The insulating jacket 11 reduces the heat transfer between the hot parts of the hot-runner nozzle 4 and the cooled nozzle core 8 or outer core 9. This heat transfer is additionally reduced by a circumferential recess 12 on the jacket surface of the outer core 9 and upstream of the nozzle mouth 5. The insulating jacket 11 extends as far as the nozzle mouth 5. The hollow needle 6 is guided along the insulating jacket 11 of the nozzle core 7. The hot-runner nozzle can have more than one insulating jacket.

[0039] In the embodiment shown in FIG. 1, the insulating jacket 11 extends as far as the cavity 3. FIG. 4 shows a detailed view of the hot-runner nozzle in the area of the nozzle mouth (circle A in FIG. 1). Unlike the hot-runner nozzle in FIG. 1, the outer core 9 of the hot-runner nozzle from FIG. 4 has a circumferential flange 13 in the area of the nozzle mouth 5. The circumferential flange 13 forms a part of the cavity 3 so that the cavity 3 is completely formed by the cooled die plate 1, the cooled core plate 2 and the cooled nozzle core 7 of the hot-runner nozzle 4. The insulating jacket 11 in this case extends only as far as the circumferential flange 13 and insulates the cooled nozzle core with respect to the heated parts of the hot-runner nozzle 4. In the co-injection nozzle shown, as will be described in detail hereinafter, these are a nozzle body 30, a melt distributor insert 31, a dividing sleeve 32 and a retaining and sealing sleeve 33. Depending on the configuration of the cavity, the circumferential flange can also be configured as a shoulder on which the insulating jacket rests.

[0040] The hot-runner nozzle can be designed for one melt or for several melts as a co-injection nozzle. In the embodiment of FIG. 1 which is shown, the hot-runner nozzle is configured as a co-injection nozzle for a triply layered melt flow having two outer layers of a first melt A and an inner layer, e.g. a so-called barrier layer, of a second melt B. In the front region upstream of the annular nozzle mouth, the co-injection nozzle has an annular inner melt channel 20, an annular central melt channel 21 and an annular outer melt channel 22. The annular inner 20 and the annular outer melt channel 22 are fluidically connected to at least one melt supply channel 23a, 23b for the first melt A. The annular central melt channel 21 is fluidically connected to at least one melt supply channel 25 for the second melt B (cannot be identified in FIG. 1 because it is arranged in front of and behind the plane of intersection).

[0041] The co-injection nozzle 4 shown in FIG. 1 comprises a nozzle body 30, a melt distributor insert 31, a dividing sleeve 32, and a retaining and sealing sleeve 33 (or sealing ring). The nozzle body 30 is provided with a heating element 34. FIG. 2 shows a side view of the melt distributor insert from FIG. 1. FIG. 3 shows a side view of the melt distributor insert 21 and the dividing sleeve 22 from FIG. 1.

[0042] The co-injection nozzle 4 has a central bore which extends axially through the melt distributor insert 31 and in which the hollow needle 6 is movably received. The central bore has a larger diameter in a central to lower region (i.e. downstream) than in the upper region (i.e. upstream) so that the annular inner melt channel 20 is formed along the hollow needle 6. The hollow needle 6 can also be tapered in this region in order to enlarge the cross-section of the annular inner melt channel 20. Also only the hollow needle can be configured to be tapered and the central bore can have the same diameter over the entire length. A non-movable nozzle core is arranged inside the hollow needle 6. This can be configured as the previously described cooled nozzle core 7, protrude beyond the nozzle mouth 5 of the hot-runner nozzle 4 in the flow direction of the melt and form a cooled core 2a in the core plate 2 of the injection moulding tool which forms the inner form for the inner shape of the injection-moulded part to be produced.

[0043] The annular central melt channel 21 is formed by an outer surface of the distributor insert 31 and an inner surface of the dividing sleeve 32. The annular outer melt channel 22 is formed by an outer surface of the dividing sleeve 32 and an inner surface of the retaining and sealing sleeve 33.

[0044] In the embodiment shown the annular inner melt channel 20 is connected upstream fluidically to two first melt supply channels 23a, 23b for the first melt A. Downstream it is connected fludically to a nozzle mouth 5. The first two melt supply channels 23a, 23b for the melt A each lead from a first melt supply opening on the upper side of the melt distributor insert 31 partially through the nozzle body to the annular inner melt channel 20. Furthermore, in each case at least one melt distributor channel 24a (in FIG. 1 only the upper end can be identified) for the melt A is connected fluidically to the first two melt supply channels 23a, 23b and conducts the respective melt A into the common annular outer melt channel 22.

[0045] The melt A is therefore guided via the two melt supply channels and the respective melt distributor channels into the common annular inner melt channel 20 and the common annular outer melt channel 22.

[0046] Furthermore, in the embodiment shown the co-injection nozzle 4 comprises two second melt supply channels for the second melt B (cannot be identified in FIG. 1). In FIGS. 2 and 3 one of the two melt supply channels 25a is indicated by an arrow and its end can be identified on the outer surface of the melt distributor insert 31. The two melt supply channels for the second melt B lead like the first two melt supply channels 24a, 24b for the melt A from respective melt supply openings on the upper side of the melt distributor insert 31 partially through the nozzle body 30 to respectively at least one melt distributor channel for the second melt B. The melt distributor channels for the second melt B are fluidically connected downstream to the common annular central melt channel 21.

[0047] Both the melt distributor channels for the first melt A and also the melt distributor channels for the second melt B are formed on the outer surface of the distributor insert (e.g. by milling) and are delimited in the direction radially outwards by the inner surface of the nozzle body 30 or the dividing sleeve 32.

[0048] The melt distributor channels 24a for the first melt A end above the annular central melt channel 21. Via a through-opening 27 in the dividing sleeve 32 they are each connected to melt distributor channels 28 formed on the outer surface of the dividing sleeve 32, which are finally fluidically connected to the annular outer melt channel 22. Alternatively the bores can also lead directly into the annular outer melt distributor channel 22.

[0049] In order in particular in the case of a large diameter of the annular nozzle opening 5 to distribute the melts A, B uniformly on the annular outer and central melt channel 21, 22, the respective melt distributor channels on the outer surface of the distributor insert 31 can have a branching or bifurcations, as shown for example in FIGS. 2 and 3. The melt distributor channels on the dividing sleeve 32 can also have a branching or bifurcation. After each branching or bifurcation the cross-section of the channels can be reduced in order to achieve an approximately uniform flow rate over the entire flow section.

[0050] The annular melt flows from the annular inner, central and outer melt channels 20, 21, 22 are combined shortly before the outlet through the nozzle mouth 5 to form a concentrically layered melt flow which finally passes through the nozzle mouth 5 into the cavity 3.

REFERENCE LIST

[0051] 1 Die plate [0052] 1a Die [0053] 2 Core plate [0054] 2a Core [0055] 3 Cavity [0056] 4 Hot-runner nozzle [0057] 5 Annular nozzle mouth [0058] 6 Hollow needle [0059] 7 Nozzle core [0060] 8 Cooling core [0061] 9 Outer core [0062] 10 Front face [0063] 11 Insulating jacket [0064] 12 Circumferential recess [0065] 13 Circumferential flange [0066] 20 Annular inner melt channel [0067] 21 Annular central melt channel [0068] 22 Annular outer melt channel [0069] 23a, 23b Melt supply channel for melt A [0070] 24a Melt distributor channel [0071] 25a Melt supply channel for melt B [0072] 26a Melt distributor channel for melt B [0073] 27 Through opening [0074] 28 Melt distributor channel on dividing sleeve for melt A [0075] 30 Nozzle body [0076] 31 Melt distributor insert [0077] 32 Dividing sleeve [0078] 33 Retaining and sealing sleeve/sealing ring [0079] 34 Heating element