AT511617A4 - RETURN LOCK FOR A PLASTIC NUCLEAR OF AN INJECTION MOLDING MACHINE - Google Patents

Abstract

Backflow lock (1) for a plasticizing screw (2) of an injection molding machine, with a tip (3), a pressure ring (4) and a relative to the tip (3) and the pressure ring (4) slidably mounted locking ring (5), wherein in the top (3) or on the locking ring (5) at least one guide track (6) for at least one on the locking ring (5) or at the top (3) arranged driver (7) is arranged, wherein the at least one guide track (6) parallel to Displacement direction (V) of the locking ring (5) arranged wall (8) and an obliquely to the displacement direction (V) of the locking ring (5) arranged wall (9) and the at least one driver (7) corresponding parallel extending portions (10,11) wherein the tip (3) in addition to all existing guide tracks (6) has at least one flow passage (12,12 ') for plastic melt.

Description

09/09/2011 10:43 + 43-512-5Β34Θ8 TORGGLER & HOFINGER p. 05/21

70926 31/31 1

The invention relates to a non-return valve for a plasticizing screw of an injection molding machine, with a tip, a pressure ring and a locking ring slidably disposed relative to the tip and the pressure ring, wherein arranged in the tip or on the spider at least one guideway for at least one of the locking ring and at the top Driver is arranged, wherein the at least one guide rail has a parallel to the direction of displacement of the locking ring arranged wall and an obliquely arranged to the direction of displacement of the locking ring wall and the at least one driver has corresponding parallel sections. Furthermore, a use of the non-return valve according to the invention in a method for injecting plastic melt into a cavity of a Sprit2gießmaschine be specified. Backflow valves have a decisive influence on the quality of an injection molded part. The more accurately, for example, the closure of the return flow lock can be controlled after reaching the end of the dosing, the higher the shot weight consistency.

It should be noted in advance that it is the backflow lock of the type mentioned in the reverse flow lock with a co-rotating locking ring. Technically, the co-rotation of the locking ring is realized in that at least one guideway is arranged for at least one on the locking ring or, arranged at the top driver in the top or on the locking ring. The fact that the at least one guideway furthermore has a wall arranged parallel to the direction of displacement of the blocking ring and a wall arranged obliquely to the direction of displacement of the blocking ring and the at least one driver has corresponding parallel sections has the following additional effect: it makes it possible to force-lock the return flow lock after reaching the end of the dosing by a short-term rotational movement of the plasticizing screw in the direction of rotation during the dosing opposite direction of rotation to bring about. How this compulsory closure proceeds in detail will be described below with reference to the drawings. 09/09/2011 11:50

No. R436 P.005 / 021 09/09/2011 10:43 + 43-512-583408 TORGGLER & HOFINGER p. 06/21 Backflow barriers of the type mentioned in the introduction are already known and are described, for example, in DE 10 2004 059 610 A1 described. A disadvantage of their design, however, is that the plastic melt is squeezed during the dosing through openings and gaps between the locking ring and the tip of Pla $ tifi2ierschnecke, which have very small cross-sections. This results in high pressures and a very high shear heat, which adversely affects the quality of the plastic melt and thus of the subsequent injection-molded part.

Object of the present invention is to avoid these disadvantages and to provide a comparison with the prior art improved return flow block.

This object is achieved in that the tip in addition to all existing guideways has at least one flow passage for plastic melt. This allows the plastic melt to flow unhindered from the area in which the plasticizing screw is located in the screw antechamber.

Protection is also desired for the use of the RDckstromsperre invention in a method for injecting plastic melt in a cavity of an injection molding machine, wherein the return flow lock is arranged at the top of a rotatably and slidably mounted in a plasticizer plasticizing screw of the injection molding machine.

Further advantageous embodiments of the invention are defined in the dependent claims and will be explained in detail in the context of the following description of the figures with reference to FIGS. Showing:

1 shows a first advantageous embodiment of the non-return valve according to the invention during the dosing together with a section of the plasticizing cylinder and the flange in a schematic cross-sectional view, 09/09/2011 11:50

No .: R436 P.006 / 021 09/89/2011 10:43 + 43-512-58340B TORGGLER & HDFINGER p. 07/21

3

Fig. 2, the backflow valve according to the first advantageous

Embodiment after reaching the end of the dosing together with a section of the plasticizing cylinder and the flange in a schematic cross-sectional view,

Fig. 3, the backflow valve according to the first advantageous Ausführungsbeispie! in a schematically illustrated perspective view,

4 shows the blocking ring of the non-return valve in a schematically illustrated side view,

Figure 5a shows the front portion of the plasticizing screw without blocking in a diagrammatically illustrated frontal view, i. viewed from the cavity along the direction of displacement of the locking ring,

Fig. 5b shows the front portion of the plasticizing screw with locking ring in a schematically illustrated frontal view, i. viewed from the cavity along the direction of displacement of the locking ring,

Fig. 5c shows the front portion of the plasticizing screw without locking ring in a schematically illustrated rear view, i. considered in the direction of the cavity and along the direction of displacement of the locking ring,

6a shows a second advantageous embodiment of the non-return valve according to the invention during the metering process together with a section of the plasticizing cylinder and the flange in a schematic cross-sectional representation,

6b shows a third advantageous embodiment of the non-return valve according to the invention during the dosing together with a section of the plasticizing cylinder and the flange in a schematic cross-sectional view, and Fig. 7 is a flow chart illustrating the use of the backflow lock according to the invention in a method for injecting plastic melt into a cavity an injection molding machine.

FIG. 1 is a schematic of a 09/09/2011 11:51 relevant to illustrating a first advantageous embodiment of the non-return valve 1 according to the invention

No .: R436 P.007 / 021 09/09/2011 10:43 + 43-512-583408 TORGGLER & HQFINGER p. 08/21 4

Section of an injection molding machine shown. On display is a part of a plasticizing screw 2, which is arranged rotatably and displaceably in a plasticizing cylinder 13. At the top 3 of this plasticizing screw 2, the return flow lock 1 is arranged, which comprises a pressure ring 4 and a locking ring 5 displaceably arranged relative to the tip 3 and to the pressure ring 4. The direction of displacement of the locking ring 5 or, the plasticizing screw 2 is provided with the reference symbol V. The tip 3 has two guideways 6 for two arranged on the locking ring 5 driver 7 and in addition to the two guideways 6 four flow passages 12 and 12 'for the plastic melt, in this illustration, only one of the two guideways 6 and two of the four flow passages 12 and 12 'can be seen. One of the visible flow passages, which is provided with the reference numeral 12, is seconded in an angular range in which none of the guideways 6 is arranged for the driver 7. The other visible flow passage, indicated by reference numeral 12 ', is located in the angular range of the visible track 6, more specifically below it. The term "angular range" refers to a viewing direction from the displacement direction V (see FIGS. 5a to 5c).

In Fig. 1 shows a position of the backflow lock 1 during a dosing dargstelit. In this position, the left in the figure left side surface of the locking ring 5 abuts against a contact surface 17 of the tip 3, and it can the plasticized plastic melt - starting from the channels 15 in the plasticizing screw 2 - to the left via the sealing ring 4 and through the locking ring 5 and the additional flow passages 12 and 12 'flow into the screw antechamber 14. In this case, a larger part of the plastic melt flows through the lower flow passage 12 in the figure and a smaller part of the plastic melt through the flow passage 12 ', which is arranged below the guide track 6. This situation should be indicated by means of the two arrows of different strengths. In the screw antechamber 14, the plastic melt collects during the dosing and pushes the plasticizing screw 2 to the right. Frequently, the channel extending from the antechamber 14 to a cavity of the injection molding machine through the flange 09/09/2011 11:51

No .: R436 P.008 / 021 09/09/2011 10:43 + 43-512-583408 T ORGGLER & HGFINGER p. 09/21 09/09/2011 10:43 + 43-512-583408 T ORGGLER & HGFINGER P. 09/21

passes through a closure nozzle during this dosing process.

When enough plastic melt has accumulated in the screw antechamber 14, i. the end of the dosing process is reached, the locking ring 5 is shifted relative to the plasticizing screw 2 to the right, so that it rests against the sealing ring 4 and no plastic melt can flow more into the screw antechamber 14 (see Fig. 2). This has been achieved in earlier embodiments - not shown here - of the non-return valve in that the outer wall 16 of the locking ring 5 adhered to the inner wall of the plasticizing cylinder 13 (by frictional forces) and the shank of the plasticizing screw 2 was pushed a little to the left until the right side surface the locking ring 5 on the sealing ring 4 struck. However, this closure method was subject to fluctuations, which were expressed in a relatively poor shot weight consistency. This disadvantage is avoided in the backflow lock 1 according to the invention characterized in that the two guideways 6 for the two arranged on the locking ring 5 drivers 7 each have a parallel to the direction of displacement V arranged wall 8 and an oblique to the direction V arranged wall 9 and the two drivers 7 respectively have corresponding parallel sections 10 and 11 (see Figures 3, 4 and 5a to 5c). This fact allows namely a forced closure of the locking ring 5 by a short-term rotational movement of the plasticizing screw 2 in the dosing rotational direction D during the metering opposite blocking direction S. Here, the obliquely to the direction of displacement V arranged wall 9 comes into contact with the parallel extending section 11 on Driver 7, subsequently exerts on this contact surface a force on the driver 7 and the entire locking ring 5, the characterized - eg considered in the figure 3 - is moved to the right rear.

The term "obliquely to the displacement direction V" corresponds in the embodiment shown, the backflow preventer 1 approximately at an angle of 45 °. This can be seen very well in the Fig, 4, in which the locking ring 5 is shown from the side. In this view you can also see that the locking ring 5 has two drivers 7. 09/09/2011 11:52

No .: R436 P.009 / 021 09/09/2011 10:43 + 43-512-563408 TORGGLER & HOFINGER p. 10/21

«* A · 6

In FIGS. 5 a to 5 c, the front region of the plasticizing screw 2 is shown, in FIG. 5 a without a locking ring 5 in a frontal view, i. 5b in the same view with locking ring 5 and in Fig. 5c without locking ring in a rear view, i. considered in the direction of the cavity and along the direction of displacement of the locking ring. In these views, it can be seen well that in this embodiment of the return flow block - are arranged in the top 3 two guideways 6 for two arranged on the locking ring 5 driver 7, - the two guide tracks 6 each arranged parallel to the direction of the locking ring 5 wall 8 and have a wall 9 arranged at an angle to the displacement direction of the locking ring 5, the two drivers 7 have corresponding parallel sections 10 and 11, the tip 3 has four flow passages 12 and 12 'in addition to the two existing guide tracks 6, two of the four flow passages 12 are arranged in angular ranges <x, in which none of the two existing guideways 6 are arranged, - two of the four flow passages 12 'are arranged in angular ranges .beta., In each of which one of the existing guideways 6 is arranged, - that the two latter flow passages 12 'each below the b eiden existing guideways 6 are arranged and - allow the two flow passages 12 a significantly higher flow of plastic melt, as the flow passages 12 '.

FIGS. 6a and 6b show two further advantageous embodiments of the non-return valve 1 according to the invention. They differ in the form of the two additional flow passages 12 in comparison with the exemplary embodiment illustrated in the preceding figures. In the case of FIG. 6 a, the flow passage 12 is differently inclined, in the case of FIG. 6 b cut deeper. 09/09/2011 11:52

No.; R436 P.010 / 021 09/09/2011 10:43 + 43-512-5834ΘΒ TOR6GLER & HOFINGER 5. 11/21

FIG. 7 is a flow chart intended to illustrate the use of the backflow arrestor according to the invention in a method of injecting plastic melt into a cavity of a sputtering machine. The starting point is the metering process, which serves to plasticize the plastic granulate and to transport it into the resulting plastic melt in the screw antechamber. During this dosing process, the plasticizing screw is rotated in a metering direction. After reaching the end of the metering process, you have the options to move the plasticizing screw (a small piece) in the direction of displacement of the locking ring from the cavity or on the cavity or perform neither of the two sliding movements and leave the plasticizing screw in the position at the it is at the end of the dosing process,

By a displacement of the plasticizing screw in the direction of displacement of the Sperrhngs away from the cavity, a so-called compression relief takes place. Performing the compression detent before a reverse rotation of the plasticizing screw in the reverse direction S, it is somewhat degraded by the pressure before the locking ring and optionally in the hot runner. In addition, the locking ring position is thereby reproducibly set to the "open" position. Performing the compression relief at least during part of the time period At the reverse rotation in blocking direction S, so the pressure level can be reduced faster before and behind the locking ring.

By a displacement of the plasticizing screw in the direction of displacement of the locking ring on the cavity to the locking ring can be closed faster with simultaneous reverse rotation of the plasticizing in the reverse direction S. However, a shut-off nozzle is absolutely necessary for this procedure in order to ensure a high shot weight consistency.

A rotation of the plasticizing screw in the direction opposite to the dosing direction locking direction S causes the above-described forced closing the backflow valve. It may be advantageous in some cases, the plasticizing screw with a predetermined or predeterminable 09/09/2011 11:52

No .: R436 P.011 / 021 09/09/2011 10:43 + 43-512-583408 TORGGLER & HOFINGER p. 12/21 8

Circumferential rotational speed in the blocking direction S to rotate, wherein in the case of a predetermined circumferential rotational speed, a value of 0.6 m / s is favorable.

But how long does it take to reverse the plasticizing screw in the blocking direction S? On the one hand, one can measure the pressure of the plastic melt in the screw antechamber and rotate the plasticizing screw in the reverse direction until a pressure is measured which is less than or equal to a predetermined pressure p (in the screw antechamber It should be noted, however, that the pressure can not be measured directly but also indirectly via a measured variable proportional to the pressure, such as the degree of deformation of a component in the area of the plasticizing cylinder However, this time span should in no case exceed a value of 1 second, as otherwise bridging in the feeder or material discharge via the shaft area may occur. in which case the value of 1 sec For example, it can be used as an additional safety criterion.

Finally, the plastic melt is injected into a cavity of the injection molding machine by moving the plasticizing cylinder in the direction of the cavity.

Innsbruck, September 9, 2011 09/09/2011 11:53

No. R436 P.012 / 021

Claims (12)

09/09/2011 10:43 + 43-512-583408 TORGGLER & HOFINGER p. 13/21 1. Claims 1. A backflow barrier (1) for a plasticizing screw (2) of an injection molding machine, with a tip (1). 3), a pressure ring (4) and a relative to the tip (3) and the pressure ring (4) slidably mounted locking ring (5), wherein in the tip <3) or on the locking ring (5) at least one guide track (6) for at least one on the locking ring (5) or at the top (3) arranged driver (7) is arranged, wherein the at least one guide track (6) parallel to the displacement direction (V) of the locking ring (5) arranged wall (8) and a Has inclined to the direction of displacement (V) of the locking ring (5) arranged wall (9) and the at least one driver (7) corresponding parallel extending portions (10,11), characterized in that the tip (3) in addition to all existing guideways (6) at least one flow passage (12, 12 ') for plastic masterpieces aufwei st. Second return valve (1) according to claim 1, characterized in that the at least one additional flow passage (12) - seen from the displacement direction (V) of the locking ring (5) on the tip (3) - in an angular range (a) is arranged , in which none of the existing guideways (6) is arranged. 3. backflow valve (1) according to claim 1, characterized in that the at least one additional flow passage (12 ') - seen from the displacement direction (V) of the locking ring (5) on the tip (3) - in the angular range (ß) a the existing guideways (6) is arranged. 4. backflow valve (1) according to claim 1, wherein the tip (3) has at least two additional flow passages (12,12 '), characterized in that - from the displacement direction (V) of the locking ring (5) on the tip (3) one of the at least two additional flow passages (12 ') in the angular range (β) of one of the existing guideways (6) and the 09/09/2011 11:53 no.: R436 P. 013/021 14/21 09/09 / 2011 10:43 + 43-512-563408 TORGGLER & HGFINGER S. • * * * ** * »* * * * * * · · ···« * 1 f * · * ».» · »· * Another of the at least two additional flow passages (12) is arranged in an angular range (a) in which none of the existing guideways (6) is arranged. *** " 5. Use of a non-return valve (1) according to one of claims 1 to 4 in a method for injecting plastic melt into a cavity of an injection molding machine, wherein the return flow lock (1) at the top (3) of a rotatable and displaceable in a plasticizing cylinder (13). mounted plasticizing screw (2) of the injection molding machine is arranged. 6. Use according to claim 5, wherein the plasticizing screw (2) is rotated during a preceding metering operation in a metering rotational direction (D), characterized in that the plasticizing screw (2) after reaching the end of the metering operation for a predetermined period of time (At) in one of the Dosierdrehrichtung (D) opposite locking direction of rotation (S) is rotated. 7. Use according to claim 6, characterized in that the predetermined period of time (At) is less than or equal to 1 second. 8. Use according to claim 6 or 7, wherein between the cavity and the tip (3) a screw antechamber (14) is arranged, characterized in that the pressure of the plastic melt in the screw antechamber (14) is measured and the plasticizing screw (2) while in the reverse rotation (S) is rotated until a pressure less than or equal to a predetermined pressure (ps) is measured, wherein the predetermined pressure (p,) is preferably 10 bar. 9. Use according to claim 8, characterized in that the pressure of the plastic melt in the screw antechamber (14) is measured via a proportional to this pressure measurement. 09/09/2011 11:53 No .: R436 P.014 / 021 09/09/2011 10:43 + 43-512-583408 TORGGLER & HCF INGER p. 15/21 3 10. Use according to one of claims 6 to 9, characterized in that the plasticizing screw (2) is rotated at a predetermined or predeterminable circumferential rotational speed in the blocking direction of rotation (S). 11. Use according to claim 10, characterized in that the plasticizing screw (2) is rotated at a peripheral rotational speed of 0.6 m / s. 12. Use according to one of claims 6 to 11, characterized in that the plasticizing screw (2) before the beginning of the rotational movement in the blocking direction (S) in the direction of displacement (V) of the locking ring (5) is moved. 13. Use according to one of claims 6 to 11, characterized in that the plasticizing screw (2) is displaced in the displacement direction (V) of the locking ring (5) at least during a part of the period of time (At) of the rotational movement in blocking direction of rotation (S). 14. Use according to claim 12 or 13, characterized in that the plasticizing screw (2) in the direction of displacement (V) of the locking ring (5) is moved to the cavity. 15. Use according to claim 12 or 13, characterized in that the plasticizing screw (2) in the displacement direction (V) of the locking ring (5) is displaced away from the cavity. Innsbruck, 9th September 2011 09/09/2011 11:54 no .: R436 P. 015/021