HOT CHANNEL DEVICE

Abstract

A hot channel device for guiding an incoming hot melt, in particular a plastic melt, to a gate opening of a mould insert of a tool, which gate opening can be opened and closed again by a movable needle, wherein the hot channel device has a first hot channel region, with a coolable melt transfer region, and a second hot channel region, which are arranged one behind the other in the flow direction of the melt toward the mould insert, wherein the coolable melt transfer region has a melt transfer chamber, which is penetrated by the needle, said needle being guided displaceably in a needle channel so as to be sealed by a needle seal, and the needle channel continues in an aligned manner in a melt channel of the second hot channel region.

Claims

1. Hot channel device for conveying incoming hot melt to a gate opening of a mold insert of a mold, which gate opening can be opened and reclosed by a movable needle, wherein the hot channel device has a first hot channel region with a coolable melt transfer region and a second hot channel region, which are arranged one behind the other in the flow direction of the melt in the direction of the mold insert, characterized in that the coolable melt transfer region has a melt transfer chamber through which the needle passes, which is displaceably guided in a needle channel in a sealed manner with a needle seal, and the needle channel is continued in alignment in a melt channel of the second hot channel region.

2. Hot channel device according to claim 1, wherein the melt transfer chamber has an inlet for the melt and an outlet channel for the melt which is not parallel thereto but is arranged at an angle, in particular at a right angle, thereto, wherein the melt transfer chamber is penetrated by the needle, wherein the needle channel opens into the melt transfer chamber at an angle to the inlet and is continued in alignment in the outlet channel and in the melt channel of the second hot channel region up to the gate opening.

3. Hot channel device according to claim 1, wherein the melt in the first hot channel region is deflected from a first direction and fed into the melt transfer chamber, wherein the melt in the first hot channel region leaves said chamber again deflected by the angle a in the direction of the second hot channel region.

4. Hot channel device according to claim 3, characterized in that the first direction is the mold opening direction.

5. Hot channel device according to claim 1, wherein a melt conducting element of the first hot channel region projects into the melt transfer chamber without touching the melt transfer chamber.

6. Hot channel device according to claim 1, wherein the melt conducting element of the first hot channel region is configured to be exchangeable.

7. Hot channel device according to claim 1, wherein the melt transfer chamber is configured to be temperature-controlled in such a way that on the inner wall of the melt transfer chamber and in the transition to the sealing gap on the needle seal towards the needle and towards the needle channel, no liquid melt in particular no liquid plastic, is present during operation, but that a solidifying plastic layer is formed from the melt.

8. Hot channel device according to claim 1, cha wherein the melt transfer chamber can be temperature-controlled such that the temperature in the sealing gaps of the needle seal is below the glass transition temperature or below the crystallite melting temperature of the melt.

9. Hot channel device according to claim 1, wherein in the first hot channel region and in the second hot channel region the temperature is controlled or regulated in such a way that the respective incoming melt remains liquid and does not solidify on any walls, whereas in the melt transfer region the temperatures are kept lower in the edge region of the melt transfer chamber, so that melt can also solidify in the edge region of the melt transfer chamber, wherein a flow passage for the melt into the second hot channel region remains.

10. Hot channel device according to claim 1, wherein the first and second hot channel regions each have at least one or more hot channel elements each provided with a melt channel for the melt.

11. Hot channel device according to claim 10, wherein the hot channel elements comprise at least one or more of the following elements: one or more manifold plates and one or more hot channel nozzles.

12. Hot channel device according to claim 10, wherein one or more of the hot channel elements of the first hot channel region and the second hot channel region are designed to be heatable.

13. Hot channel device according to claim 1, wherein a melt channel element of the melt transfer region has at least one or more cooling channels for a fluid flowing through.

14. Hot channel device according to claim 1, wherein the melt channel element of the melt transfer region is configured as a mold insert.

15. Hot channel device according to claim 1, wherein a hot channel nozzle designed for lateral gating projects into the melt channel element of the melt transfer region.

16. Hot channel device according to claim 1, wherein the design of the melt transfer chamber and the entire melt transfer region is controllable in such a way that only temperatures which are more than 15 C., for example, more than 40 C., and for example, more than 60 C. below the glass transition temperature or below the crystallite melting temperature of the melt occur at the needle seal in the sealing gaps thereof.

17. Hot channel device according to claim 1, wherein the discharge of the melt from the melt transfer chamber into the second hot channel region is effected by a rear hot channel nozzle sealingly immersed in this chamber with a sleeve.

18. Hot channel device according to claim 1, wherein the rear hot channel nozzle has a heat conducting sleeve.

19. Hot channel device according to claim 1, wherein the rear hot channel nozzle is confogured in the direction of the mold insert as a nest nozzle.

20. Hot channel device according to claim 1, wherein a sliding seal is provided between the melt transfer chamber and the rear hot channel nozzle.

21. Hot channel device according to claim 1, wherein the second hot channel region has a hot channel nozzle with a rear seal to the melt transfer chamber and a front seal to the mold insert.

22. Method for operating a hot channel device, wherein the hot channel device comprises a mold with a first heated hot channel region with a melt channel, with an adjoining cooled melt transfer region with a needle seal with a melt channel and with an adjoining second heated hot channel region with a melt channel, which are arranged one behind the other in the direction of flow of the melt in the direction of a mold insert, wherein an injection molding melt is fed into the hot channel device and through this to the mold insert, a) the first hot channel region is temperature-controlled above the glass transition temperature or above the crystallite melting temperature of the melt, b) and the subsequent melt transfer region is temperature-controlled below the glass transition temperature or below the crystallite melting temperature of the melt, wherein a flow passage for the melt is maintained in the melt channel, c) and the subsequent second hot channel region is temperature-controlled above the glass transition temperature or above the crystallite melting temperature of the melt.

23. Method according claim 22, wherein the melt transfer region is temperature-controlled in such a way that a temperature prevails in the sealing gaps of the needle seal which is more than 15 C., for example, more than 40 C. and for example more than 60 C. below the glass transition temperature or below the crystallite melting temperature.

24. Method according to claim 22, wherein the melt transfer region is tempered in such a way that a solidifying plastic layer forms on an inner wall of a melt transfer chamber and in the transition to the sealing gap at the needle seal towards a needle and towards a needle channel during operation.

25. Hot channel device according to claim 1, wherein a melt conducting element of the first hot channel region projects into the melt transfer chamber, which temperature-controls a temperature in the melt channel for the melt to flow through the melt transfer chamber.

26. Method according to the preceding claim 22, wherein the first and the second hot channel regions as well as the melt transfer region are each operated to transfer the melt, wherein the temperature in the first hot channel region and in the second hot channel region are controlled or regulated such that the respective incoming melt remains well fluid and does not solidify on walls, whereas in the melt transfer region the temperatures are kept so low, at least in some areas, especially in the edge region of the melt transfer chamber, that melt can also solidify in the edge region thereof, wherein a flow passage remains for the melt into the second hot channel region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 shows a section of a first hot channel device according to the present disclosure with three hot channel regions;

[0028] FIG. 2 shows a section of a second hot channel device according to the present disclosure;

[0029] FIG. 3 shows an enlarged section of a variant of the hot channel device from FIG. 1;

[0030] FIG. 4a shows a section of another hot channel device according to the present disclosure; and

[0031] FIG. 4b shows a detail enlargement from FIG. 4a.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032] FIGS. 1 to 4a and 4b show different hot channel devices 1. The hot channel devices 1 shown are each used to direct incoming hot melt to a gate opening 401 of a mold insert 400. This meltwhich may be a plastic meltis fed from an injection-molding machine (not shown here) directly or, optionally, via further hot channel components (not shown here) upstream of the hot channel device shown, to hot channel device 1 shown in FIG. 1, 2, 3 or 4.

[0033] The hot channel device 1 has a first hot channel region 100, a melt transfer region 200 and a second hot channel region 300. These areas 100, 200, 300 are arranged one behind the other in the direction of flow of the melt towards the mold insert 400. The elements of the regions 100, 200, 300 are held together by one or more plates 501, 502, 503, 504, 505, 506 of mold 500.

[0034] The first and second hot channel regions 100 and 300 as well as the melt transfer region 200 each serve to transfer the melt. They differ, however, among other things in their operating temperature, i.e. the wall temperature.

[0035] In the hot channel regions 100 and 300, this is usually above 200 C., for example at a pressure of 200 MPa or more.

[0036] In the first hot channel region 100 and in the second hot channel region 300, the temperature is selected in such a way that the respective incoming melt remains well fluid and does not cool and solidify on any walls.

[0037] In the melt transfer region 200, on the other hand, the temperatures can be lower in certain areas, especially in the peripheral area of a melt transfer chamber, as will be discussed further below, on whose walls the melt can cool and solidify, as long as a sufficiently large flow passage for the melt remains in it.

[0038] The first hot channel region 100 has at least one or more hot channel element(s), each provided with a melt channel 101 for the melt.

[0039] These hot channel elements may include at least one or more of the following elements: one or more manifold plates 102 (FIGS. 1, 2, 3, 4) and/or one or more hot channel nozzles 103 (FIGS. 1, 3, 4). The melt channels 101 of these elements then form the melt channel 101 of the first hot channel region 100 when connected in series. In particular, it is also conceivable to provide several hot channel nozzles 103 directly or through manifold plates 102 spaced apart one behind the other.

[0040] The hot channel elements of the first hot channel region 100 are each designed to be heatable, as otherwise the temperature drop of the melt in the first hot channel region 100 would be so great that the temperature of the melt at the end of the first hot channel region 100 would be too low for the respective application or the subsequent transfer through the subsequent melt transfer sections 200 or hot channel regions 300 and material would solidify in the melt channel 101.

[0041] The first hot channel region caneven with only one manifoldespecially have a manifold plate 102 with a melt channel 101.

[0042] Here the melt channel 101 first extends in a direction X and then shows a deflection from this direction X into a direction Y which is at an angle to ithere at right angles (see also FIG. 2 or FIG. 3).

[0043] The second hot channel region 200 has one or more melt channel element(s) 202, each equipped with a melt conducting channel 201 for the melt. These are not called hot channel elements here, as the temperature can be so low, at least in sections, that melt can solidify and settle on the walls of this area.

[0044] The melt channel elements 202 can be designed to be heatable, coolable or temperature-controllableprovided the above-mentioned requirements are met.

[0045] A plate 202 which is provided with the melt conducting channel 201 is especially suitable as the at least one melt channel element 202 of the melt transfer region 200, especially a coolable or temperature-controlled mold insert 270 (FIG. 2, FIG. 3).

[0046] An inlet of the melt transfer chamber 240 of the melt transfer region 200 is angled, especially at right angles, to the outlet of the melt channel 101 of the first hot channel region 100.

[0047] The inlet of the melt conducting channel 201 is also preferably designed as an unheated melt transfer chamber 240 (see also FIG. 4b). A melt conducting element 105 of the first hot channel region 100 can extend into the melt transfer chamber 240. This does not necessarily touch the melt channel elements 202. The melt conducting element 105 may be hot enough to keep a flow passage free for melt in the melt transfer chamber. The melt conducting element 105 can be designed as a kind of tip insert of the hot channel nozzle 103 or 104.

[0048] The melt transfer chamber 240 has an inlet 241 for the melt and an outlet 242 for the melt (FIG. 4b). The melt conducting element 105 can extend into inlet 241.

[0049] The inlet 241 for the melt and the outlet 242 for the melt are not parallel, but are oriented at an incline to each other or at an angle to each other. This angle is not zero. The angle is preferably between 15 and 160, especially at 90. Here the inlet extends in direction Y. The outlet, however, extends in direction X.

[0050] The melt transfer chamber 240 is penetrated by a needle 250. This needle 250 is slidingly guided in a needle channel 251, which opens into the melt transfer chamber 240 and is continued in alignment in the outlet channel 242. Since the needle is formed in a straight way, this means here that the needle channel 251, the needle 250 and the outlet channel 242 extend in direction X.

[0051] A needle seal 252 is arranged in an annular space between the needle 250 and the inner wall of the needle channel 251. This needle seal 252 can be made of various materials, e.g. a steel alloy. It can be designed as a sleeve.

[0052] Melt material can collect in the annular gaps inside and outside the needle seal 252. As this can remain there for a relatively long time, it is important to prevent carbonization of this material, as this can lead to sluggishness or blockage of needle 250.

[0053] The melt transfer chamber 240 is or will be penetratedin particular by cooling bores or cooling channels 218 (FIG. 4a and b), through which a cold or tempered fluid can be passed, so that on the inner wall of the melt transfer chamber 240 and in the sealing gap of the seal 252 towards the needle 250 and towards the needle channel 251, no liquid melt, in particular no liquid plastic, is present during operation of the hot channel device, but that a solidifying thin plastic layer is formed from the melt.

[0054] In this way, the annular gaps are sealed at the needle seal 252. Due to the lower temperature, it is ensured that no further melt deposits can occur in the sealing gaps during operationapart from a short period after initial start-upand that no carbonizations can occur. This ensures that the needle remains easily movable and generally does not jam.

[0055] The needle is driven by a needle drive 260 and is held in a drive plate 261 which moves parallel to the mold opening direction X.

[0056] The needle drive 260 is embodied here as a hydraulic or pneumatic drive and can actuate several needles 250 simultaneously via the drive plate 261. This needle drive can be electrically driven in a different embodiment. Each needle can have its own needle drive 260, which can be driven electrically, hydraulically or pneumatically. The needle drive 260, especially the electrically driven needle drive 260, can be embodied in such a way that different needle positions can be approached besides the fully closed and fully open position.

[0057] The intermediate positions of the needle can be used, for example, to regulate the melt flow during the injection process. The needle can also be moved at different speeds. Here, different speeds from one needle position to the next needle position are possible. It is possible to control or regulate an acceleration curve between one needle position and the next needle position. It is also possible to readjust the needle end positions between the injection processes. The regulation of the needle position is made possible by a control loop. Various prior-art sensors can be used for regulation so that the needle position is known.

[0058] The outlet 242 of the melt transfer chamber 240 opens into the second hot channel section 300, which in turn has at least one or more hot channel element(s) which is/are each provided with a melt channel 301 for the melt.

[0059] These hot channel elements can comprise one or more of the following elements: one or more manifold plates (not shown here) and/or one or more hot channel nozzle(s) 303, 304 connected in series. The hot channel bores of these elements then form the melt channel 301 (not shown here) of the second hot channel region 300 in interaction when connected in series. This melt channel 301 is penetrated by the needle 250in this case up to the mold insert 400. The outlet of this melt channel 301 opens into the gate opening 401 of the mold insert 400.

[0060] The needle channel 251, the melt transfer chamber 240 and the melt channel 301 are penetrated by the needle 250, which can be moved within them to a limited extent to open or close the gate opening 401.

[0061] In embodiments, the needle seal 252 is or can be cleverly arranged by the selected arrangement in an area of the hot channel device 1 which is cooler than the areas in which liquid melt is present and that the needle movement direction can still be the same as the mold opening direction.

[0062] The hot channel elements 102, 103, 104 as well as 303, 304, 307 of the first and second hot channel region 100, 300 can each be formed in a heatable manner. This applies in particular if the temperature drop of the melt in the first or second hot channel region 100, 300 would otherwise be so great that it would solidify at the edge of the hot channel 100, 200. In the second hot channel region 300 in particular, a heating devicepreferably one or more hot channel nozzles 303, 304is usually necessary to supply the melt with heat after it has flowed through the melt transfer chamber 240, in order to heat it up again or at least to prevent it from cooling down further.

[0063] Due to the selected arrangement in the area of the needle seal 252, lower temperatures, in particular a considerably lower temperature, can prevail during operation and also prevails than in the melt channel 101, 301.

[0064] The melt transfer chamber 240 and the entire melt transfer region 200 can be configured in such a way that during operation only temperatures below the glass transition temperature or below the crystallite melting temperature of the melt occur at the needle seal 252. In embodiments, the temperatures are more than 40 C., and in some embodiments, more than 60 C., below this temperature. In this way, deposits on the needle 250 can be avoided very reliably.

[0065] In this way, the needle 250 is easily protected in the area of the needle seal 252 against deposits that can occur due to excessive temperatures in the sealing gaps and the resulting carbonization of the melt.

[0066] The melt can be discharged from the melt transfer chamber 240, for example, by means of a rear hot channel nozzle 303 which is sealingly immersed in the chamber 240 with a sleeve 306 (FIGS. 1, 2, 3, 4). To improve temperature control, this can also have a heat conducting sleeve 307. By means of this arrangement, the needle 250 can be guided through the needle seal 252 mounted in the temperature-controlled (cold) area of the mold structure and the adjacent hot channel components or hot channel elements in the axis of the mold opening movement X to the gate opening 401. How the further melt guidance is to be configured generally depends on the individual application. For example, the rear-immersing, melt-diverting nozzle 303 can be designed both in the direction of the mold insert 400 (cavity 413) and as a so-called nest nozzle, so that only one hot channel component is present in the melt-diverting strand.

[0067] In an embodiment, it may be provided to design a region of the melt transfer chamber 240 as a mold insert 270 in the manner of a ring-shaped melt conducting plate 202, since all relevant dimensional adjustments of the sealing passages in a component of the melt transfer region 200 can be made with it (FIG. 3).

[0068] The present disclosureexemplified in FIGS. 1 to 4makes it possible to guide the needle 250 movably in melt channel 301, which is usually under high pressure and high temperature (200 MPa and more as well as >200 C.).

[0069] This concept of the cold needle seal has the advantage that no carbonization takes place and a practically leakage-free sealing situation is created in which the polymer entering during initial start-up acts as an additional gap filling and the thin polymer layer acts as a sealing and sliding film. This also minimizes wear between needle seal 252 and needle 250.

[0070] According to the present disclosure, the needle seal 252 can be mounted in any area of the mold 500, since it is used for lateral melt transfer into a hot channel component that carries the melt away, for example the rear hot channel nozzle 303, wherein a melt transfer region 200 with the melt transfer chamber 240 is installed at a suitable location in a plate 202 of the mold construction 500, into which both the heat conducting element 105 of the hot channel nozzle 103 to be fed and the hot channel component 303 which carries away the melt and in particular the needle seal 252 open.

[0071] Following the hot channel component which carries the melt away, for example rear hot channel nozzle 303, a second hot channel nozzle 304 can be installed, with which the mold insert 400 can be reached in the usual way. The needle 250 guided through the cold needle seal 252 can thus be guided unhindered through the hot channel component 303, which carries the melt away, and the second hot channel nozzle 304 up to the gate opening 401, and the needle movement can thus take place without restriction in mold opening direction X.

[0072] This makes the principle of the cold needle seal universal, since with the additional second hot channel nozzle 303, 304, every cavity 413 can be reached in the usual way.

[0073] In a simpler version of the embodiment of FIG. 1, as shown in FIG. 2, the feeding nozzle 103 or 104 can also be dispensed with and the lateral melt outlet can be a direct component of the heated manifold or a corresponding heated manifold plate 102.

[0074] In a further embodiment according to FIGS. 4a and b, the lateral melt outlet from manifold 102 can be extended by a heated third hot channel nozzle 104, here aligned perpendicular (or at a certain angle ) to direction X.

[0075] The nozzle 103 or the nozzle 104 or the manifold 102 each feed into the laterally accessible, preferably unheated melt transfer chamber 240 in the mold 500, into which the needle 250 is immersed in the axis of the mold opening movement X. The melt transfer chamber 240 as well as the needle seal 252 are temperature-controlled through cooling holes or cooling channels 218 in such a way that no liquid plastic is present on the inner wall of the melt transfer chamber 240 and in the sealing gap of the seal 252, but that a thin, still soft but not liquid plastic layer is formed.

[0076] Appropriately temperature-controlled here means a temperature level well below the glass transition temperature or the crystallite melting temperature. Examples: Polystyrene (amorphous): hot channel temperature 180 C. to 260 C., mold temperature of the melt transfer region 200 10 C. to 60 C., glass transition temperature approx. 100 C. or polyamide (semi-crystalline): hot channel temperature 280 C. to 300 C., mold temperature of the melt transfer region 200 60 C. to 80 C., crystallite melting temperature 260 C. to 275 C. or polyacetal (POM) (semi-crystalline): hot channel temperature 190 C. to 210 C., mold temperature of the melt transfer region 200 80 C. to 100 C., crystallite melting temperature 175 C. to 178 C.

[0077] In embodiments, the temperature of the needle seal 252 is below the softening range, i.e., as described above, below the glass transition or crystallization range.

[0078] In this case, the needle seal 252 is located in a relatively cold area of the mold, so that the polymer that has entered the gap of the seal during the initial filling of the system is not exposed to any temperature that would cause significant degradation.

[0079] The needle seal 252 only experiences a certain temperature increase through the heat conduction of the needle 250 and through the melt in the melt transfer chamber 240, but this is so low that no cracking occurs. Rather, this temperature increase (below the softening point) leads to better sliding behavior of the needle in the seal.

[0080] In contrast to conventional sealing concepts (seal in the hot manifold), the needle seal does not determine the maintenance interval of a mold in any of the applications illustrated with the valve gate technology.