DE2719497C2

DE2719497C2 - Print head and non-return valve on a rotatable and axially displaceable screw of a plastic plasticizing unit

Info

Publication number: DE2719497C2
Application number: DE19772719497
Authority: DE
Inventors: Horst 3012 Langenhagen Gienapp; Friedrich Ing.(grad.) 3000 Hannover Theysohn
Original assignee: FA FRIEDRICH THEYSOHN 3012 LANGENHAGEN DE; FA FRIEDRICH THEYSOHN 3012 LANGENHAGEN
Current assignee: Friedrich Theysohn GmbH
Priority date: 1977-05-02
Filing date: 1977-05-02
Publication date: 1984-06-28
Also published as: DE2719497A1

Description

verschlissene Bauteil fortgeworfen wird Mit geringen Einschränkungen gilt das gleiche für den mit der Schnecke verbundenen Teil des bekannten Druckkopfes, welcher Teil der Schnecke ist und daher aus dem gleichen Material wie die Schnecke besteht Dieser Teil 5 wird zwar selber nicht auf Verschleiß beansprucht, er ist jedoch an das Schicksal der Schnecke gebunden und nur mit derselben verwendbar.worn component is thrown away with low Restrictions, the same applies to the part of the known print head connected to the screw, which part is the screw and therefore consists of the same material as the screw This part 5 is not subject to wear and tear itself, it is but tied to the fate of the snail and can only be used with the snail.

Der Erfindung Hegt die Aufgabe zugrunde, eine Plastifiziereinheit mit Rückstromsperre anzugeben, bei der die Teile des an der Spitze der Schnecke angeordneten Druckkopfs keinem Verschleiß unterworfen sind.The invention is based on the object of a plasticizing unit indicate with non-return valve, in which the parts of the arranged at the tip of the screw Printhead are not subject to wear and tear.

Diese Aufgabe wird bei einer Plastifiziereinheit der eingangs geschilderten Art gemäß der Erfindung dadurch gelöst,This object is achieved in a plasticizing unit of the type described at the outset according to the invention solved,

— daß zwischen den beiden Teilen des Druckkopfs ein auswechselbarer Dichtring aus einem harten, abriebfesten Material angeordnet ist der auf dem der Schnecke zugewandten Teil gehalten ist und dessen Durchmesser geringfügig größer als der größte Durchmesser der beiden Teile des Druckkopfs ist, und- That between the two parts of the print head a replaceable sealing ring made of a hard, abrasion-resistant Material is arranged that is held on the part facing the screw and its The diameter is slightly larger than the largest diameter of the two parts of the printhead, and

— daß der Druckkopf in an sich bekannter Weise mittels eines an dem der Schnecke zugewandten Teil angebrachten Gewindebolzens an der Spitze der Schnecke anschraubbar ist.- That the print head in a known manner by means of a part facing the screw attached threaded bolt can be screwed to the tip of the worm.

Die beiden miteinander zu verschraubenden Teile dieses Druckkopfs haben eine nahezu unbegrenzte Lebensdauer. Beide Teile können aus dem gleichen Material hergestellt werden, wobei die Abriebfestigkeit desselben ohne Bedeutung ist. Die Abdichtung des Druckkopfes gegenüber dem Schneckengehäuse erfolgt nur durch den aus abriebfestem Material bestehenden Dichtring, der ein von den beiden Teilen des Druckkopfes an sich unabhängiges Bauteil darstellt. Der Dichtring kann sehr einfach gestaltet und daher auch einfach hergestellt werden. Er kann ebenso einfach im Druckkopf angeordnet und ausgetauscht werden. Der Aufwand an teurem, verschleißfestem Material ist gering und die kompliziert geformten Teile mit den Kanälen brauchen für eine Spritzgießmaschine bzw. Plastifiziereinheit nur einmal hergestellt zu werden.The two parts of this printhead that are to be screwed together have an almost unlimited service life. Both parts can be made of the same material, the abrasion resistance being the same is irrelevant. The print head is only sealed against the worm housing by the sealing ring made of abrasion-resistant material, which is one of the two parts of the printhead represents an independent component in itself. The sealing ring can be designed very simply and therefore also easily manufactured will. It can just as easily be arranged in the printhead and exchanged. The effort at expensive, wear-resistant material is low and need the intricately shaped parts with the channels to be produced only once for an injection molding machine or plasticizing unit.

Ein weiterer, durch die US-PS 30 07 202 im Prinzip bekannter Vorteil dieses Druckkopfs besteht darin, daß er durch den Gewindebolzen insgesamt austauschbar ist. Er wird dadurch unabhängig von der Schnecke und ist für unterschiedliche Schnecken einsetzbar, auch für solche mit unterschiedlichen Durchmessern. Eine Anpassung an unterschiedliche Durchmesser ist durch den Einsatz von unterschiedlichen verschleißfesten Ringen leicht möglich.Another, from US-PS 30 07 202 in principle known advantage of this print head is that it is completely replaceable due to the threaded bolt. This makes it independent of the screw and can be used for different screws, including those with different diameters. An adjustment to different diameters is due to the use of different wear-resistant rings easily possible.

Ein Ausführungsbeispiel des Erfindungsgegenstandes ist in den Zeichnungen dargestellt. Es zeigtAn exemplary embodiment of the subject matter of the invention is shown in the drawings. It shows

F i g. 1 schematisch eine Darstellung einer Plastifiziereinheit teilweise im Schnitt,F i g. 1 schematically shows a representation of a plasticizing unit partially in section,

F i g. 2 in vergrößerter Darstellung eine Ansicht eines Druckkopfes der Plastifiziereinheit,F i g. 2 shows an enlarged view of a The printhead of the plasticizing unit,

F i g. 3 und 4 zwei Schnitte durch F i g. 2 längs den eo Linien HI-III bzw. IV-IV.F i g. 3 and 4 two sections through F i g. 2 along the eo Lines HI-III and IV-IV.

Mit 1 ist allgemein eine Spritzgießmaschine bezeichnet, die aus dem Spritzgießwerkzeug 2 und der Plastifiziereinheit 3 besteht. Das Spritzgießwerkzeug 2 selber ist beliebig gestaltet und daher nur in Form eines Blökkes dargestellt. Innerhalb der Plastifiziereinheit 3 ist eine Schnecke 4 angeordnet, die bei Drehung um ihre Achse in der Lage ist, Kunststoff in Richtung auf das Spritzgießwerkzeug 2 hin zu fördern, welcher durch einen Trichter 5 in die Plastifiziereinheit 3 eingeführt worden ist Im Bereich der Schnecke 4 wird der Kunststoff gleichzeitig noch erwärmt und dabei in einen geschmolzenen bzw. dünnflüssigen Zustand überführt An der Spitze der Schnecke 4 ist ein Druckkopf 6 angebracht dessen genauere Darstellung aus den F i g. 2 bis 4 hervorgeht. 1 with an injection molding machine is generally designated, which consists of the injection molding tool 2 and the plasticizing unit 3 consists. The injection molding tool 2 itself is designed as desired and therefore only in the form of a block shown. Within the plasticizing unit 3, a screw 4 is arranged, which when rotated around their Axis is able to promote plastic in the direction of the injection molding tool 2, which by a Funnel 5 has been introduced into the plasticizing unit 3 In the area of the screw 4, the plastic at the same time still heated and thereby converted into a molten or thin liquid state Attached to the tip of the screw 4 is a print head 6, the more detailed illustration of which is shown in FIGS. 2 to 4 can be seen.

Der Druckkopf 6 kann über einen Gewindebolzen 7 auf die Spitze der Schnecke 4 aufgeschraubt werden. Um den von der Schnecke 4 geförderten Kunststoff nach vorne in Richtung des Spritzgießwerkzeugs 2 gelangen zu lassen, sind in dem Druckkopf 6 Kanäle 8 und 9 angebracht, die entsprechend den eingezeichneten Pfeilen in einer zentralen Bohrung 10 münden, durch welche der Kunststoff beim Fördern durch die Schnekke 4 vorne aus dem Druckkopf 6 austreten kann. Auf dem Wege bis zur Spitze des Druckkopfes 6 tritt der Kunststoff durch eine Kammer 11 hindurch, welche eine Erweiterung der zentralen Bohrung 10 ist und in welcher eine in axialer Richtung frei bewegliche Kugel 12 angeordnet ist. Der Druckkopf 6 besteht aus zwei Teilen 13 und 14, die miteinander verschraubt werden können und in einer Ebene geteilt sind, die quer zur Achsrichtung der Schnecke 4 liegt. Vor dem Zusammenschrauben der beiden Teile 13 und 14 werden die Kugel 12 in die Kammer 11 hineingelegt und ein Dichtring 15 auf den Teil 14 aufgesetzt. Der Dichtring 15 besteht aus einem harten und abriebfesten Metall. Sein Durchmesser ist geringfügig größer als der Durchmesser der Teile 13 und 14. Der Dichtring 15 ist auswechselbar. Er dient zur Abdichtung des Druckkopfes 6 gegenüber dem Schneckengehäuse der Plastifiziereinheit 3.The print head 6 can be screwed onto the tip of the worm 4 via a threaded bolt 7. To get the plastic conveyed by the screw 4 forward in the direction of the injection molding tool 2 to let, 6 channels 8 and 9 are attached in the print head, which correspond to those shown Arrows open into a central bore 10 through which the plastic when conveyed by the screw 4 can emerge from the front of the print head 6. On the way to the tip of the print head 6 occurs Plastic through a chamber 11, which is a Expansion of the central bore 10 and in which a freely movable ball 12 in the axial direction is arranged. The print head 6 consists of two parts 13 and 14 which can be screwed together and are divided in a plane which is transverse to the axial direction of the screw 4. Before screwing together of the two parts 13 and 14, the ball 12 is placed in the chamber 11 and a sealing ring 15 is placed on it the part 14 put on. The sealing ring 15 consists of a hard and wear-resistant metal. Its diameter is slightly larger than the diameter of parts 13 and 14. The sealing ring 15 is exchangeable. He serves for sealing the print head 6 against the screw housing of the plasticizing unit 3.

Die Kugel 12 ist innerhalb der Kammer 11 durch mindestens drei Stege 16 geführt, die in radialer Richtung nach innen ragen und sich nahezu über die gesamte axiale Länge der Kammer 11 erstrecken. Für die einwandfreie Führung der Kugel 11 reichen drei Stege 16 aus, es können jedoch auch mehr als drei Stege angebracht werden. Durch die Stege 16 verbleiben zwischen der Wandung der Kammer 11 und der Kugel 12 jeweils Durchtrittskanäle 17, durch welche der Kunststoff hindurchtreten kann, wenn er von der Schnecke 4 gefördert wird. Um sicherzustellen, daß diese Kanäle von der Kugel 12 nicht verschlossen werden können, sind im vorderen Teil 13 des Druckkopfes 6 Abkröpfungen 18 vor der zentralen Bohrung 10 angebracht, die den Weg der Kugel 12 begrenzen, so daß der Eintritt der Kanäle 17 in den vorderen Teil der zentralen Bohrung 10 durch die Kugel 12 nicht verschlossen werden kann.The ball 12 is guided within the chamber 11 by at least three webs 16, which in the radial direction protrude inward and extend over almost the entire axial length of the chamber 11. For the flawless To guide the ball 11, three webs 16 are sufficient, but more than three webs can also be attached will. The webs 16 each remain between the wall of the chamber 11 and the ball 12 Passage channels 17 through which the plastic can pass when it is conveyed by the screw 4 will. To ensure that these channels can not be closed by the ball 12, are im front part 13 of the print head 6 bends 18 attached in front of the central bore 10, which the way limit the ball 12, so that the entry of the channels 17 in the front part of the central bore 10 through the ball 12 cannot be closed.

Nachdem der Druckkopf 6 auf die Spitze einer Schnecke 4 aufgeschraubt worden ist, kann die Schnekke 4 in Drehung versetzt werden. Es wird dann Kunststoff in Richtung auf das Spritzgießwerkzeug 2 zu bewegt. Während des Förderns des Kunststoffs nimmt die Kugel 12 die in F i g. 2 strichpunktiert dargestellte Position ein, so daß der Kunststoff frei durch die Kanäle 8 und 9, die Durchtrittskanäle 17 und die zentrale Bohrung 10 des Druckkopfes 6 hindurchtreten kann. Der Kunststoff nimmt dabei die Wege entsprechend den eingezeichneten Pfeilen. Nach Beendigung des Fördervorganps wird die Schnecke 4 stillgesetzt und beispielsweise hydraulisch oder pneumatisch in Richtung des Pfeiles 19 auf das Spritzgießwerkzeug 2 zubewegt. Diese Bewegung erfolgt schlagartig. Dabei tritt der vor dem Druckkopf 6 befindliche Kunststoff durch die zentrale Bohrung 10 wieder in den Druckkopf 6 ein und drückt die Kugel 12 in die in Fig. 2 dargestellte Position. DieAfter the print head 6 has been screwed onto the tip of a screw 4, the screw can 4 can be set in rotation. Plastic is then moved in the direction of the injection molding tool 2. While the plastic is being conveyed, the ball 12 takes the action shown in FIG. 2 position shown in phantom a, so that the plastic freely through the channels 8 and 9, the passage channels 17 and the central bore 10 of the print head 6 can pass. The plastic takes the path as shown Arrows. After the end of the conveyor, the screw 4 is stopped and, for example moved hydraulically or pneumatically towards the injection molding tool 2 in the direction of arrow 19. This movement occurs suddenly. The plastic located in front of the print head 6 passes through the central one Bore 10 back into the printhead 6 and presses the ball 12 into the position shown in FIG. the

Kugel 12 verschließt dann den hinteren Teil der zentralen Bohrung 10, so daß der Kunststoff nicht mehr in die Kanäle 8 und 9 gelangen kann. Auf diese Weise ist ein in sehr kurzer Zeit druckfest verschlossener Druckkopf 6 geschaffen, der eine wirksame Rückstromsperre darstellt, so daß die Füllung des Spritzgießwerkzeugs 2 ermöglicht wird.Ball 12 then closes the rear part of the central bore 10 so that the plastic is no longer in the Channels 8 and 9 can reach. In this way, a print head 6 which is closed pressure-tight in a very short time created, which represents an effective non-return valve, so that the filling of the injection mold 2 is made possible.

Hierzu 2 Blatt ZeichnungenFor this purpose 2 sheets of drawings

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Claims

Claim:

Plasticizing unit with a rotatable and axially displaceable screw for conveying and pressing of plasticized plastic in an injection mold, with one at the tip of the screw arranged, of two separated in a plane perpendicular to the axial direction of the screw, with each other screwable parts existing printhead, with inclined to the screw axis Channels for the passage of the plastic and with a non-return valve, designed as one central bore in the print head in the axial direction of the screw, in which the channels open out, with an expansion of the bore inside the printhead to a chamber with at least three inward-facing, extending over almost the entire axial length of the chamber Bars in which a ball, guided through the bars and freely movable in the axial direction, is arranged whose diameter is greater than the diameter of the bore and its displacement path in the chamber is limited by bend formed on the front part of the printhead, thereby marked,

- That between the two parts (13, 14) of the print head (6) a replaceable sealing ring (15) made of a hard, wear-resistant metal is arranged on the screw (4) facing Part (14) is held, and its diameter is slightly larger than the largest Diameter of the two parts (13, 14) of the printhead (6) is, and

- That the print head (6) in a known manner by means of a threaded bolt attached to the part (14) facing the screw (4) (7) can be screwed to the tip of the screw (4).

The invention relates to a plasticizing unit with a rotatable and axially displaceable screw, according to the preamble of the claim.

Injection molding machines with a plasticizing unit and injection molding tool have been known for a long time and are available on the market in a wide variety of shapes. Such machines can be used to produce moldings of all kinds, which can consist entirely of plastic or also serve as enclosures for any parts. These injection molding machines are equipped with injection molding tools in which the molded bodies to be produced are molded. They also have the upstream plasticizing unit in which a screw conveyor - hereinafter referred to as "screw" - is attached. During the rotation of the screw, with which plastic is conveyed to the injection molding tool, the same is heated and becomes plastic or even molten. When enough plastic has been conveyed to fill the injection mold, the screw stops turning. It is then moved axially in the direction of the injection molding tool. This movement takes place abruptly, so that the amount of plastic conveyed is also suddenly pressed into the injection molding tool. A significant problem with this press-in or push-in process is that the channels of the screw must be sealed for this process so that the required pressure can be built up. The channels must be present when the plastic is being conveyed (rotating screw), but they must be closed during the printing process.
From US-PS 30 07 202 an injection molding machine has become known in which a so-called print head is attached to the tip of the screw, in which the channels of the screw are continued. These channels are closed when pressing or when pressing by a ring, which is axially movably mounted at the tip of the screw on a bolt screwed into the screw releases in the printhead In the case of pressing, the ring is then carried along in the opposite direction by the plastic flowing back or by the forward movement of the worm. It should then close the channels in the second end position so that the print head is tight and the required pressure can be built up. This known construction of a non-return valve works properly when all parts are very precisely matched to one another, which is only possible with considerable effort. However, the ring is a wear part which, when it moves into both end positions, strikes against fixed parts of the print head and also performs a sliding movement on the bolt. The ring is therefore subject to constant wear. It must therefore usually be replaced after the machine has been in operation for a relatively short time. A decisive disadvantage of this known device, however, is that the ring cannot easily be guided properly, but is slightly tilted during its back and forth movement, thereby jammed and can then no longer perform its function. The print head with non-return valve is then entirely unusable and must be replaced.

A plasticizing unit, as described at the beginning, emerges from GB-PS 9 31 902. With this well-known Device is the gap between the print head and the screw housing, which is used to Build up a high pressure very tight «, a must, through the printhead itself sealed a radial extension that protrudes in diameter over the other parts of the printhead and inside rests against the worm housing. This front part of the print head is thus in its function as The non-return valve is not exposed to mechanical abrasion, but is caused by the rotation of the screw on the outer circumferential surface of its extension permanently mechanically stressed. Necessarily must this Part of the printhead is made entirely of expensive, abrasion-resistant material, which means that it can be manufactured with the channels and the thread for screwing on the other part is made more difficult. Nevertheless this one has to Part of the print head in the known arrangement must be replaced from time to time, since the same - even if it is made of abrasion-resistant material - the outer surface of its extension is subject to wear. A component that is complex to manufacture and made of expensive material must then be newly inserted while the equally elaborately manufactured,