Injection molding device

Abstract

Injection molding device (10), the device comprising: - a feed channel (22) for the molten material, - an injection channel (24) equipped with an inlet for the molten material and configured to direct the molten material to an injection nozzle (14) for injection into a mold cavity (28), - a nozzle closure (12) which is mounted coaxially transversely to the injection channel (24), where a component (30) comprises: - a connecting channel (60, 80, 48, 50) with an angled profile, equipped with a connecting inlet (62) and a connecting outlet (44), - a through-cavity (40) which is in fluid communication with the connecting channel (60, 80, 48, 50) and is designed for the slidable reception of the closure (12), wherein the component (30) is arranged such that the connection inlet (62) is connected to the feed channel (22) to receive molten material, and the connection outlet (44) is connected to the inlet of the injection channel (24) to direct molten material therein, - an element (70) for diverting a material flow that has entered the component (30) from the connection inlet (62) in a direction opposite to or contrary to the direction of the connection outlet (44) in order to push at least a part of the material entering the connection channel (60, 80, 48, 50) towards a target area (84) of the connection channel (60, 80, 48, 50) arranged behind the closure.

Description

[0001] The present invention relates to an injection molding device.

[0002] For example, WO 2021 / 19850 A1 describes the problem that a velocity difference or gradient occurs in the melt at the transition from the feed channel (CA) to the injection channel (CI), see p. 2, lines 3-27. Essentially, in the connecting channel between the CA and the CI, the flow coming from the CA collides with the valve and is forced to take two paths: a direct path along the "front" of the valve and a path along the "back" of the same. The paths have different geometries, so they are characterized by different pressure drops and consequently by different feed velocities along the CI.

[0003] The portion of the flow that encounters the occlusion and is deflected downwards into the concave oblique (CI) before reaching it experiences a smaller pressure drop and is therefore faster. The portion of the flow that encounters the occlusion and bypasses it is forced to take a longer path and is thus slowed down.

[0004] Because the liquid flows more slowly on the back side of the closure, stagnant areas of the material form there, where the material remains for several molding cycles. This stagnation leads to defects in the molded parts during color change processes, i.e., when the color of the injected polymer is changed.

[0005] Since the waste pieces can be very numerous, leading to increased consumption of raw materials, especially for large molded parts, energy and time, it is then necessary to clean the connecting channel promptly and quickly in order to limit the contamination of the molded parts by residues of the previous material.

[0006] The purpose of the invention is to improve upon this state of the art.

[0007] This task is fulfilled by the subject matter of the independent claim.

[0008] The dependent claims define preferred embodiments of the invention.

[0009] One advantage of the invention is the improvement of casting efficiency, in particular by reducing the number of required disposable injection shots needed to perform a color change in injection molding systems.

[0010] Another advantage is the standardization of the speed and thermal field of the liquid material injected into the injector, which ensures greater radial uniformity at the exit of the injection point or injector.

[0011] The invention is applied to an injection molding device comprising a distributor provided with • a feed channel for molten material with an outlet for the molten material, • an injection channel which is provided with an inlet for molten material and is configured to direct the molten material from the inlet to a nozzle for injection into a mold cavity, wherein the inlet of the injection channel and the outlet of the supply channel are connected to each other by an angled connecting channel; • a nozzle closure that is positioned so that it coaxially crosses the connecting channel in front of the outlet and the injection channel.

[0012] The behavior of the plastic material in the device is improved by the following steps: Guiding a flow of molten material from the outlet of the feed channel to the inlet of the injection channel. Redirecting the material flow while it is in the feed channel and before it enters the connecting channel, in the opposite or counter-clockwise direction to the inlet of the injection channel, to push at least part of the material entering the connecting channel towards a target zone of the connecting channel located behind the closure.

[0013] According to the convention used in this text, the relative term ‘behind’ (and synonyms) in relation to the closure is to be understood in relation to the direction in which the material enters the connecting channel.

[0014] The deflection causes part of the material entering the connecting channel to be aligned in the direction of the target zone and / or generates a displacement / velocity component in the material entering the connecting channel in the direction of the target zone.

[0015] The redirected material flow thus puts a strain on the material that is stagnating in the target zone and reduces the residues remaining there.

[0016] Another beneficial effect of the deflection is that the material entering the connecting channel can more easily bypass the closure, thus limiting the slowdown caused by the size of the closure.

[0017] In a preferred embodiment, in the aforementioned step the flow is deflected at or near the outlet or exit of the feed channel into the connecting channel, in particular only at or near the outlet or exit of the feed channel into the connecting channel, with the advantage of maximizing the said displacement / velocity component.

[0018] In a preferred embodiment that is easy to implement, the material flow is redirected in this step by gradually or abruptly reducing the cross-section of the feed channel, in particular by narrowing the feed channel.

[0019] In a preferred embodiment, the feed channel at the outlet or exit within the connecting channel has a cross-section (for example, as a cross-section with respect to a section plane orthogonal to the axis of the feed channel) with a profile composed of • a first end section adjacent to the inlet of the injection channel, and • a second end section that is diametrically opposite the first and further away from the inlet of the injection channel.

[0020] In a more preferred embodiment, to achieve the aforementioned deflection, the cross-section of the feed channel is reduced or narrowed by progressively narrowing the cross-section of the feed channel only at the section leading to the first end section, while the cross-section of the feed channel remains constant at the section leading to the second end section.

[0021] The first end section is located relative to the outlet of the feed channel, where the radius of curvature of the connecting channel is smaller.

[0022] In a preferred embodiment that is easy to implement, the material flow is redirected by placing an obstacle in the feed channel.

[0023] In a preferred embodiment, as the material flows through the feed channel and before it enters the connecting channel, two flows are generated in the material flow, which diverge and are directed towards opposite sides of the closure located within the connecting channel.

[0024] This facilitates the flow of material around the closure, thereby limiting the portion of the material flow that impacts the closure head-on from the feed channel. This reduces material buildup in the connecting channel. Therefore, it is possible to limit the velocity of the material flow in the front area of ​​the closure (the area facing the outlet of the feed channel), where the material meets the closure, while simultaneously increasing the flow velocity at the sides of the closure. A larger quantity of liquid material, which has maintained its velocity because it bypassed the closure almost without contact, then reaches the rear of the closure.This means that part of the liquid, which in the prior art impacted the closure, is now deflected and reaches the back of the closure at a higher speed, where a washing and dragging effect develops, removing material residues because the local speed of the material is increased.

[0025] In a preferred embodiment, the material flow is redirected and these flows are generated simultaneously in the same section of the feed channel.

[0026] In a preferred embodiment that is easy to implement, these flows are generated by a flow obstruction.

[0027] A component of such an injection molding device may include: • a connecting channel with an angled shape, which is provided with a connecting inlet and a connecting outlet, • a through-cavity that is connected to the connecting channel and is designed to accommodate the sliding closure, the component is attached in such a way that the connecting inlet is connected to the feed channel to receive molten material from it, and the connecting outlet is connected to the inlet of the injection channel in order to direct molten material there, • Means or an element for redirecting a material flow that has entered the component from the connection inlet in the opposite or counter-clockwise direction to the connection outlet, in order to push at least some of the material entering the connection channel towards a target zone of the connection channel located behind the closure.

[0028] In a preferred embodiment, the connecting channel comprises, with respect to the flow direction of the material, an initial section which • extends from the connection inlet to the inside of the component, • is designed in such a way that it guides a portion of the material linearly along a central longitudinal axis of the initial section, and • is connected via a curved, angle-shaped section.

[0029] Preferably, the means or element is arranged at or near the initial section, or only at or near the initial section.

[0030] In a preferred embodiment, the means or element comprises or consists of a barrier to the material flow, wherein the barrier is designed to deflect the material as defined above.

[0031] In a preferred embodiment, the means or elements comprise or consist of a reduction in the cross-section of the initial section towards the inside of the component.

[0032] In a preferred embodiment, an inner wall of the initial section comprises an inclined plane or ramp inclined with respect to the central longitudinal axis, wherein the inclined plane or ramp is designed to taper the cross-section of the initial section as the initial section extends towards the inside of the component in order to redirect material flow to an opposite curved wall of the connecting channel.

[0033] In a preferred embodiment, the initial section has a cross-section (for example, as a cross-section with respect to a cross-sectional plane orthogonal to the central longitudinal axis) with a profile consisting of the following: - a first end section adjacent to the inlet of the injection channel, and - a second end section that is diametrically opposite the first and further away from the inlet of the injection channel.

[0034] Preferably, the means or element comprises or consists of a reduction in the cross-section of the initial section only at the section leading to the first end section, wherein the cross-section of the connecting channel for the section leading to the second end section remains constant.

[0035] To facilitate construction, the obstacle or an interior wall of the initial section may include an inclined plane or ramp inclined with respect to a central longitudinal axis of the initial section, wherein the inclined plane or ramp is designed to narrow the cross-section of the initial section when the initial section runs towards the inside of the component, and to divert the material flow to the outside of the connecting channel or to an opposite curved wall of the connecting channel that extends in front of the outlet of the initial section into the connecting channel, and / or to the target zone.

[0036] In particular, the inclined plane or ramp is located at the first end section.

[0037] In a preferred embodiment, the means or element is configured to generate two flows in the material that diverge and are directed to opposite sides of the closure arranged within the connecting channel or to opposite zones of the connecting channel.

[0038] In particular, the means or element comprises two substantially diverging grooves or slots extending within the initial section from the connection opening to the inside of the component. More precisely, the grooves or slots are formed on the sides of the inclined surface or ramp.

[0039] Another aspect of the invention is such a casting device for injecting molten material, in which the connecting channel has an angled shape and - is equipped with a connecting inlet and a connecting outlet and - is connected to a through-cavity designed to accommodate the sliding closure, wherein the connecting inlet is connected to the feed channel to receive molten material, and the connecting outlet is connected to the inlet of the injection channel to direct molten material there, wherein the device further comprises means or an element for redirecting a material flow coming from the feed channel and before it has entered the connecting channel in the opposite or counter-clockwise direction to the connecting outlet in order to push at least a portion of the material entering the connecting channel towards a target zone of the connecting channel located behind the closure.

[0040] The device exhibits all embodiments defined for the component.

[0041] In a preferred embodiment of the various aspects of the invention: - Are the cross-sectional areas of the material in the connecting channel the same before and after the closure? - the connecting channel is curved by 90 degrees and / or the material entering the injection channel from the feed channel is subjected to a 90-degree change in direction; and / or - the obstacle has the shape of a lamella, a tab, a prism, a pyramid, a cone, a ramp, a part thereof, or a combination thereof; and / or - the target zone is a curved wall of the connecting channel in front of the outlet of the feed channel and / or a volume of the connecting channel in front of the curved wall and behind the closure.

[0042] The injection channel usually runs inside an injector.

[0043] The invention can be used in hot or cold runner systems.

[0044] Further features and advantages of the invention are best made clear by reference to the following description of preferred embodiments of an injection molding device, in which: Fig. Figure 1 shows a schematic section of an injection device; Fig. Figure 2 shows a three-dimensional view of a component of the device. Fig. 1; Fig. Figure 3 shows a sectional view along plane III-III from Fig. 2; Fig. 4 shows a three-dimensional view of the in Fig. 3 of the component shown; Fig. Figure 5 shows a side view of the component. Fig. 2; Fig. Figures 6-9 each show a sectional view along planes VI-VI, VII-VII, VIII-VIII and IX-IX. Fig. 5.

[0045] In the figures, identical elements are marked with the same numbers, and to keep the drawings clear, sometimes only a few numbers are given.

[0046] Fig. Figure 1 shows a very general and essential scheme of an injection molding device 10, which includes a distributor or hot runner 20, which is provided internally along the X-axis with one or more feed channels 22 into which the molten plastic material is pressed by a press (indicated by an arrow M).

[0047] Each feed channel 22 is connected to an injection channel 24 via a connecting channel 26.

[0048] In particular, the initial part of the injection channel 24 is designed such that it extends into an injector 20a attached to the distributor 20. The end of the injection channel 24 can have suitable nozzle tips 23.

[0049] For the sake of simplicity, only two channels of distributor 20 are shown in the figures.

[0050] The injection channel 24 along the Y-axis is coaxially crossed by a known closure 12 (shown only schematically), which serves to open or close an injection nozzle 14 provided at the end of the injection channel 24. The closure 12 can be moved from an open position of the nozzle 14 to a closed position and vice versa by means of a known drive 27 in order to regulate the material flow to a cavity 28 of the mold.

[0051] A preferred embodiment of a flow deflector component configured to redirect the material flow is described in Fig. 2 is shown and labelled 30.

[0052] Component 30 has a substantially cylindrical shape with a Y2 axis and is provided with an internal connecting channel. The connecting channel comprises: a first channel 40, which runs axially through its thickness and crosses it, and a second channel 60 with an X2 axis, which is connected to the first channel 40 at a connection zone 80 approximately in the middle of the component 30.

[0053] The first channel 40 has an inlet 42 at the upper base of the component 30 and an outlet 44 at the lower base of the component 30, while the second channel 60 has an inlet 62 on the side surface of the component 30.

[0054] Component 30 is installed in distributor 20 in such a way that it fills connection channel 26 and that the X2-axis coincides with the X-axis, the Y2-axis coincides with the Y-axis, the inlet 62 is aligned with the feed channel 22 and The outlet 44 is aligned with the injection channel 24.

[0055] For manufacturing and assembly reasons, the X2 and Y2 axes are preferably orthogonal to each other. The X and Y axes are also preferably orthogonal to each other. The closure 12 is slidably inserted coaxially with the Y2 axis in the first channel 40.

[0056] Therefore, the material coming from the feed channel 22 generally enters the inlet 62, flows through the second channel 60, reaches the connecting zone 80, flows through the first channel 40, exits from the outlet 44 and enters the injection channel 24.

[0057] More precisely, when the material leaves the connecting zone 80 to reach the outlet 44, it only occupies a part 46 of the first channel 40, namely the part 46 that extends between the connecting zone 80 and the outlet 44, and flows through this part 46.

[0058] Near the connection zone 80, section 46 preferably comprises a channel 48 with a linearly increasing cross-section, which opens into a channel 50 with a cross-section that is approximately constant and larger than the maximum cross-section of the channel 48. The channel 50 forms a seat into which an injector can be screwed.

[0059] To improve the dynamic behavior of the material, a flow deflection element 70 is provided in the second channel 60.

[0060] Element 70 is configured to generate a displacement / velocity component in the material – see arrow Q – directed towards a curved wall 84 of connection zone 80, which is diametrically opposite the inlet of connection zone 80 (in front of cross-section S2). That is, the curved wall 84 is the part of connection zone 80 located directly in front of the outlet of channel 60 within connection zone 80.

[0061] In this way, the material flow exiting the second channel 60 is diverted to the center of the second channel 60, thereby deflecting the material towards the curved wall 84 and the zone behind the closure 12. Within the volume of the connecting zone 80 near the curved wall 84, the material then flows faster and with a lower risk of residue formation.

[0062] In other words, element 70 not only prevents some of the material coming from the second channel 60 from colliding with the shutter 12, thus forcing the material to bypass the shutter 12 more gently with a lower pressure drop, but also maintains a more uniform velocity of the material in the zone in front of and behind the shutter 12. Furthermore, element 70 directs a larger quantity of material towards the curved wall 84, thereby facilitating its rapid and effective cleaning.

[0063] To simplify the construction, the element 70 preferably comprises or consists of a reduction in the cross-section of the second channel 60 in the direction of the connection zone 80.

[0064] In particular, the second channel 60 has a cross-section (for example, as a cross-section in relation to a cross-sectional plane orthogonal to the axis X2) with a profile at its connection with the connecting zone 80 (see Fig. 8) up, which is made of • a first end section 61, which adjoins section 46, and • a second end section 63, which is diametrically opposite the first section 61 and further away from section 46.

[0065] According to a preferred embodiment, the second channel 60 has a progressively reduced cross-section only in the section leading to the first end section 61, with the cross-section of the channel 60 remaining constant for the section leading to the second end section 63.

[0066] To simplify the construction, the means or element 70 is preferably designed in the form of a ramp 72, which is configured to taper the cross-section of the second channel 60 in the direction of the connection zone 80.

[0067] The ramp 72 extends cantilevered from a front face P of the inner surface of the second channel 60 in the direction of the Y2 axis with an inclination relative to the Y2 axis and extends towards the connection zone 80 to terminate at an edge or tip 82 that delimits the beginning of the connection zone 80. Thus, the second channel 60 has a cross-section S1 at the inlet 62 and a cross-section S2 < S1 at the inlet of the connection zone 80 at the edge 82 (i.e., at the end of the second channel 60).

[0068] In particular, ramp 72 allows a narrowing of the cross-section of channel 60 only for the section of the channel leading to the final section 61.

[0069] Although ramp 72 ensures a smooth transition between cross-sections S1, S2 (without stagnation), it is possible to use a different flow deflection element, e.g. a stepped structure or a ramp with a concave curved profile.

[0070] Preferably, the flow deflection element 70 also has the function of branching the material flow while it flows through the second channel 60 and before it enters the connection zone 80, i.e., before the material encounters the closure 12.

[0071] The flow deflection element 70 is configured to separate the material flow in the second channel 60 into two diverging flows, each directed towards opposite sides of the closure 12. For this purpose, the ramp 72 along the transition channel from cross-section S1 to cross-section S2 does not have a uniform slope; instead, at its sides, the inclined surface of the ramp 72 slopes radially away from the Y2 axis to form two lateral channels or grooves 74, 76. The surface of the ramp 72 on which the material flows thus consists of a central channel 78 (see Fig. 6), which is nearly flat or almost flat or has the shape of a tooth, and the two lateral channels 74, 76, which are designed as a recess or depression of the central channel. The lateral channels 74, 76 define preferred flow channels for the fluid and are preferably of the same size and / or symmetrical to the central channel 78.

[0072] In this configuration, the lateral channels 74, 76 facilitate the bypass of the closure 12 by reducing / limiting the material flow that impacts the closure 12 head-on. Consequently, the less the material velocity decreases and the more material flows around the sides of the closure 12, the less material impacts the closure 12. This allows more material to reach the rear of the closure 12, in front of the curved wall 84, i.e., the accumulation zone. Since the material velocity also increases at the rear of the closure 12 (zone or curvature 84), the probability of residues / stagnation forming there decreases.

[0073] The cross-sectional areas of the material in front of and behind the closure are preferably the same, but can also be different.

[0074] The fluid dynamic behavior described above can also be achieved by directly shaping the interior of the feed channel 22 like that of the second channel 60, without incorporating a component 30. For this purpose, the distributor 20 can, for example, be manufactured using SLM technology (Selective Laser Melting) or another technology that allows for the creation of arbitrary internal shapes. Alternatively, the distributor 20 can be formed from two sandwich-like, superimposed plates, with one half of the channel 22 being produced by removing material from the surface of one plate and the second half by removing material from the surface of the second plate. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2021 / 19850 A1

[0002]

Claims

[1] Injection molding device (10), the device comprising: - a feed channel (22) for the molten material, - an injection channel (24) equipped with an inlet for the molten material and configured to direct the molten material to an injection nozzle (14) for injection into a mold cavity (28), - a nozzle closure (12) which is mounted coaxially transversely to the injection channel (24), where a component (30) comprises: - a connecting channel (60, 80, 48, 50) with an angled profile, equipped with a connecting inlet (62) and a connecting outlet (44), - a through-cavity (40) which is in fluid communication with the connecting channel (60, 80, 48, 50) and is designed for the slidable reception of the closure (12), wherein the component (30) is arranged such that the connection inlet (62) is connected to the feed channel (22) to receive molten material, and the connection outlet (44) is connected to the inlet of the injection channel (24) to direct molten material therein, - an element (70) for diverting a material flow that has entered the component (30) from the connection inlet (62) in a direction opposite to or contrary to the direction of the connection outlet (44) in order to push at least a part of the material entering the connection channel (60, 80, 48, 50) towards a target area (84) of the connection channel (60, 80, 48, 50) arranged behind the closure. [2] Injection molding device (10) according to claim 1, wherein the connecting channel (60, 80, 48, 50) comprises an initial section (60) with respect to the flow direction of the material, which - extends from the connection inlet (62) to the inside of the component (30), - is configured to guide the material linearly along a central longitudinal axis of the initial section, and - is connected by means of an angle-cut curved section (80); wherein the element (70) is located at or near the initial section (60). [3] Injection molding device (10) according to claim 2, wherein the element (70) comprises or consists of a reduction of the cross-section of the initial section towards the interior of the component (30). [4] Injection molding device (10) according to claim 3, wherein an inner wall of the initial section comprises a ramp (72) inclined with respect to the central longitudinal axis (X2), wherein the ramp (72) is designed to taper the cross-section of the initial section, while the initial section within the component (84) is designed to redirect the material flow to an opposite curved wall of the connecting channel (80). [5] Injection molding device (10) according to one of claims 2 to 4, wherein the initial section, in accordance with the connection to the connecting channel (60, 80, 48, 50), has a cross-section consisting of a first end section (61) adjacent to a section (46) extending between the angle-curved section (80) and the connecting outlet (44), and a second terminal section (63) which is diametrically opposite the first terminal section (61) and further away from section (46), wherein the element (70) comprises or consists of a reduction in the cross-section of the initial section only for the section leading to the first end section (61), wherein the cross-section of the connecting channel (60, 80, 48, 50) remains constant for the section leading to the second end section (63).

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