HK1120242B - An injection nozzle for introducing the melt material into a plastic die-casting mould - Google Patents

Description

Injection nozzle for introducing melt into plastic injection mold

Technical Field

The invention relates to an injection nozzle for introducing a melt material into a plastic injection mold.

Background

Such an injection nozzle is known from DE 19608676C 1. The plastic material of the plasticized melt stream is fed to a central melt channel via an inlet opening in the injection nozzle. A short inclined bore branches off from the central melt channel and opens into a spherical-crown-shaped cavity in the vicinity of the pouring opening. When the nozzle needle is lifted in the opening direction, material is discharged from the cavity through the released nozzle opening into the mold cavity.

The cavity between the nozzle tip and the mold plate described in DE 19608676C1 is used in particular for insulation purposes, i.e. to prevent heat transfer between the injection nozzle and the mold plate. Heat transfer from the injection nozzle to the mold plate is thus minimized.

From US 4781572, an injection nozzle is known in which the melt is fed via a central melt channel to an inclined bore which is located in the nozzle tip and opens into a spherical-crown-shaped cavity. The melt is supplied to a pouring opening of the cavity via the cavity, which pouring opening can be closed by means of a nozzle needle. In the region adjacent to the gate-side end of the nozzle needle, the nozzle needle is annularly grooved over the entire circumference, so that the nozzle needle has a smaller diameter in this region. By means of the axial displacement, both the region of smaller diameter and the region of larger diameter can be arranged in the inner flat surface (laibang) of the pouring opening.

If the end region of larger diameter corresponds to the inner flat surface of the pouring opening, the pouring opening is closed so that no melt can enter the mold cavity. If, on the other hand, the region of smaller diameter is arranged in the inner side plane of the gate, an annular space is formed between the inner side plane of the gate and the outer diameter of the nozzle needle, through which annular space the melt can pass through the gate in the direction of the mold cavity. In this prior art, the angled bore of the nozzle tip also opens into the cavity in the vicinity of the pouring opening of the nozzle.

In practice, it has been found that, in the injection molding of plastics, a number of injection processes are generally required after a color change until the mold parts no longer have the old-colored components. Many attempts have therefore been made to produce defect-free components more quickly, for example after a colour change or material change.

Disclosure of Invention

Proceeding from DE 19608676C1, the object of the present invention is to provide an injection nozzle for introducing a melt into a plastic injection mold, which is further improved with regard to operational safety and economy. In particular, diecasting machines should produce defect-free parts after a color change with as few injection processes as possible.

To this end, the invention provides an injection nozzle for introducing a melt material into a plastic injection mold, comprising a nozzle core body and a central melt channel, which downstream merges into at least one outlet channel extending obliquely to the melt channel and which is provided with an outlet opening for the plastic melt, wherein the outlet opening opens into a cavity formed as a spherical cap-shaped annular space, which cavity is connected to a gate of a mold cavity, wherein the gate is arranged in the region of the apex of the spherical cap-shaped cavity, and a nozzle needle is provided, which nozzle needle can be moved between a position closing the gate and a position releasing the gate, characterized in that the outlet opening of the outlet channel is arranged in the region of the bottom of the cavity at a position which is as far away as possible from the region of the apex of the cavity.

The principle of the invention is essentially that the outlet opening of the outlet channel is arranged in the spherical-crown-shaped cavity at a position as far away as possible from the pouring opening of the cavity. It is important here that the outlet opening is arranged such that the melt located in the cavity during an injection process is completely forced into the nozzle by the melt flowing out of the outlet opening. The outlet opening is located in a spherical-crown-shaped bottom part, which is formed, for example, by a sealing ring and delimits a spherical-crown-shaped cavity. If a plurality of holes of the nozzle tip open into the cavity, all the outlet openings are arranged in the region described above.

The "spherical crown shape" in the present invention may be any shape of the shell in a broad sense. The hollow space can be designed, for example, as a sphere or in the shape of a ball cage. The cavity may be parabolic in cross-section, for example. The designations "spherical cap base" and "spherical cap apex" in the present invention refer accordingly to the base or apex region of the shell-shaped cavity.

The "sprue" is in the present invention an opening which communicates the spherical-crown-shaped cavity directly with the mould cavity. The gate may, for example, be an opening to a channel which indirectly connects the cavity to the mold cavity.

The "apex region" may be a region where a gate is provided in the present invention, for example.

The "bottom region" is in the present invention the region which is as far away as possible from the apex region of the cavity, in which the pouring opening is located, with respect to the flow path of the plastic melt. "as far as possible" is understood here with respect to the flow path. The bottom region can be formed, for example, by an annular shoulder of the nozzle core or nozzle tip or, for example, by the end face of a sealing ring.

The advantage of the invention is that the plastic located in the cavity is completely pushed out of the cavity by the plastic flowing in later when the color changes. If the material used before the change in material or colour or the material with the pigment is still located in the cavity, it is completely possible for the new material to be extruded from the cavity by a single injection process. Less residues are produced here, which still contain residues with previously used pigments or previously used materials. The nozzle is quickly released from the previously used material or material with the previously used paint and the tool is quickly ready for producing a flawless component.

According to a first embodiment, the outlet channel widens conically in the flow direction. The outlet opening of the outlet channel is larger than the inlet opening of the outlet channel. In this way, a melt flow is produced at the outlet opening over a large surface cross section, which extrudes the plastic material located in the cavity. Due to the conical expansion, the flow speed of the plastic melt in the outlet channel is reduced. The slower flow speed produces an improved expansion flow which expands as the plastic melt flows out of the outlet channel in all directions and at the same time also extrudes the plastic melt located in the cavity out of the space between the outlet openings of the outlet channel.

According to another configuration of the invention, the bottom region of the cavity is delimited by an outer surface of the sealing ring. The cavity may for example be delimited by an end face of the sealing ring.

According to a further embodiment of the invention, the base surface merges into a concave annular surface of the nozzle tip. Thus, for example, a wedge or a back cut is prevented. Plastic can reach into this type of space, which is not or only partially punched out of the cavity during the die-casting cycle. By means of the configuration according to the invention, spaces are avoided in the region of the cavity in which no or only a small exchange of the plastic located in the cavity takes place.

According to a further embodiment of the invention, the sealing ring is made of a material having a low heat conductivity. The sealing ring may for example be made of titanium, so that the heat transfer from the injection nozzle to the mold plate is reduced. But for example also high-grade steel or other suitable materials with a low heat conductivity are considered.

According to a further embodiment of the invention, the clear width of the cavity is widened in the region of the outlet opening. This has the result that the melt can expand out of the outlet opening of the outlet channel without hindrance and the melt in the cavity is thereby extruded out of the cavity.

According to a further embodiment, at least two outlet channels are arranged distributed over the circumference. A plurality of outlet channels may also be distributed over the circumference of the nozzle tip. When two or more outlet openings are pointed out of the nozzle, the gap between the outlet openings is so small that the melt material located there is completely extruded in the next injection cycle. In this case, defect-free components can be produced particularly quickly when a color or material change occurs. According to one advantageous configuration, as many outlet channels as possible are distributed over the circumference of the nozzle tip.

According to a further embodiment, the outlet openings are distributed uniformly over the circumference of the nozzle tip. By the fact that the outlet openings are distributed uniformly over the circumference of the nozzle tip, it is likewise prevented, for example, that a position is formed between two outlet openings, at which a material exchange only takes place after a relatively large number of injection cycles.

According to a further embodiment, a nozzle needle which is movable back and forth in the axial direction is provided for opening and closing the pouring opening, wherein the central melt channel at least partially surrounds the nozzle needle concentrically. The nozzle needle is thus arranged partially in the central melt channel. The production of the injection nozzle is simplified in this embodiment, since no separate receiving space for the nozzle needle is provided. The lift of the nozzle needle can be, for example, 1 to 4mm, in particular 2 mm. The free nozzle needle length protruding from the nozzle tip can be smaller due to the smaller needle lift. Thus preventing movement of the free end of the nozzle needle transversely to the longitudinal axis of the injection nozzle.

According to a further embodiment of the invention, the nozzle needle has a front region by means of which the gate of the mold cavity can be closed, wherein the nozzle needle is centered by means of a guide in the vicinity of the front region. "centering by means of the guide" in the sense of the present invention means that the needle valve is guided in each position and never comes out of contact with the guide, in particular due to the small needle lift. The needle tip protruding from the nozzle tip is smaller due to the smaller lift of the nozzle needle and the guiding and centering near the pouring opening. The guiding and centering of the nozzle needle in the vicinity of the gate has the further consequence that lateral movements of the nozzle needle transversely to the longitudinal axis of the injection nozzle are prevented or minimized. Lateral movements of the nozzle needle should be avoided, since the contact of the front region of the nozzle needle with a region of the mold plate adjacent to the gate results in increased wear of the nozzle needle.

According to a further embodiment of the invention, the guide is designed as a sliding bearing. The sliding bearing can be formed, for example, by the wall of the nozzle body.

According to a further embodiment of the invention, the guide is formed by the inner wall of the bore in the nozzle tip. The nozzle needle may be received within the bore with a close clearance fit such that movement of the nozzle needle transverse to the longitudinal axis is prevented. The inner surface of the through-hole may be subjected to a surface treatment. In addition, the inner surface of the hole may be plated.

Drawings

Further advantages are obtained by means of a description of an embodiment shown in the drawing. Wherein:

FIG. 1 is a cross-sectional view of an injection nozzle of the present invention;

FIG. 2 is an enlarged cross-sectional view of the section indicated by II in FIG. 1, wherein the temperature sensor ring and the nozzle heater are not shown;

FIG. 3 is a cross-sectional view of the nozzle tip according to FIG. 2, with the nozzle needle not shown;

fig. 4 is a view of the injection nozzle of the present invention.

Detailed Description

According to fig. 1, the injection nozzle 10 essentially comprises a nozzle core 11 with a central melt channel 12, a nozzle needle 13 and a drive a for the nozzle needle 13.

The plastic melt coming out of the hot channel 21 is fed to a not shown mold cavity via a gate 22 in the mold plate F by means of the injection nozzle 10.

The nozzle needle 13 is used to open and close the pouring gate 22. To open and close the pouring opening 22, the nozzle needle 13 can be moved in directions x1, x2 along the longitudinal axis l of the injection nozzle 10. According to fig. 1 and 2, the nozzle needle 13 is shown in a closed position, in which a front region 23 of the nozzle needle 13 is arranged in the gate 22 and closes it. The pouring opening 22 is provided with a centering ramp 34 for the nozzle needle 13 (see fig. 2).

By moving the nozzle needle 13 in the direction x2 from the position shown in fig. 1 and 2, the nozzle needle 13 can be moved into an open position, not shown, in which the front region 23 is removed from the pouring opening 22. If the nozzle needle 13 is in the open position, the plastic melt can flow into the mold cavity via the gate 22. The needle lift is about 2mm when the nozzle needle 13 moves between the open position and the closed position and is therefore relatively small.

According to fig. 1, the nozzle needle 13 is driven by a piston K of the drive a, which is guided in a recess of the fastening plate P. For fastening to the piston K, the nozzle needle 13 has an end region 27 provided with an external thread 38. The external thread 38 is screwed into the internal thread 39 of the piston K of the drive a. If the piston K is moved in one of the directions x1, x2 in a manner not shown in detail here, the nozzle needle 13 is also moved in the respective direction x1, x 2.

According to fig. 1, the nozzle needle 13 extends through an intermediate plate Z, the bore 32 in the hot channel 21, the sliding bearing shell 28 fixed in the nozzle core 11, the central melt channel 12 of the nozzle core 11 and the bore 15 in the nozzle tip 14 of the nozzle core 11. The front region 23 of the nozzle needle 13 projects from the nozzle tip 14.

The nozzle needle 13 is mounted in an intermediate region in the slide bearing bush 28, while a region 33 (see fig. 2) of the nozzle needle 13 is guided in a sliding manner and centered by an inner wall 37 of the bore 15. The guidance of the nozzle needle 13 in the vicinity of the gate 22 has the advantage that the needle tip 23 projecting from the nozzle tip 14 has a smaller length. Due to the smaller length, the movement of the region 23 of the nozzle needle 13 transversely to the longitudinal axis l of the injection nozzle 10 is minimized and thus the wear of the nozzle needle 13, which occurs as a result of contact with the mold plate F, is reduced.

The melt flowing out of the hot channel 21 during the die casting process is fed to the central melt channel 12 via an inclined opening 26 according to fig. 1. A plurality of outlet channels 16, which open out into a spherical-cap-shaped cavity 17 according to fig. 1 to 4, are delimited by the central melt channel 12. The spherical cap-shaped cavity 17 has the purpose of avoiding direct contact between the mold plate F and the injection nozzle 10 and thus avoiding heat transfer. The cavity 17 furthermore serves as a melt-guiding channel for guiding the plastic melt to the pouring opening 22.

In this embodiment five output channels 16 are formed. The number of output channels may also differ from this number, i.e. there may be more or less than five output channels 16. The outlet openings 25 of the outlet channel 16 are arranged distributed uniformly over the circumference of the nozzle tip 14. Since the nozzle needle 13 is guided in the bore 15, the melt does not pass through the bore 15 into the cavity 17.

In the bottom region 18 (see fig. 2), the cavity 17 is sealed by means of a sealing ring 20. A sealing ring 20 is fixed to the nozzle core 11 and extends radially between the nozzle core 11 and the die plate F. The end face 29 of the sealing ring 20 thus delimits the spherical-cap-shaped cavity 17 in the base region 18. The spherical cap tip of the cavity 17 is indicated by reference numeral 19. The sealing ring 20 is made of an insulating material, such as titanium. Heat transfer from the injection nozzle 10 to the mold plate F is thus prevented as much as possible.

The pouring opening 22 is arranged in the region of the spherical cap tip 19 of the cavity 17. The cavity 17 communicates with a not shown mould cavity via a pouring opening 22.

The outlet channels 16 extend conically downstream (see fig. 2 and 3), so that each outlet channel 16 has a smaller diameter at the inlet opening 24 than at the outlet opening 25. This increased flow cross section leads to a reduction in the flow velocity of the outlet channel 16. Since the flow velocity at the discharge opening 25 is lower than the flow velocity at the inlet opening 24, a favorable expansion flow of the plastic melt results.

The expanding flow has the consequence that the plastic melt expands into the cavity 17 in all directions when leaving the outlet channel 16 and presses the plastic material present there. The increased diameter of the outlet openings 25 at the same time leads to a better scavenging effect, since the gap 35 between the outlet openings 25 is reduced. The expansion flow is also supported by the enlarged net width W of the cavity 17 in the bottom region 18 of the cavity 17.

The discharge opening 25 directly adjoins the seal 20. The end face 29 of the sealing ring 20, which delimits the cavity 17 in the base region 18, merges into a concave annular face 36 of the nozzle tip 14. In this way, spaces are prevented in which the plastic melt can collect, but which are not completely pushed out of the cavity 17 by the plastic melt flowing in after the next injection molding cycle.

According to the invention, for example, during a color change, the melt material located in the cavity 17 is completely removed by the melt material flowing in later, so that no more undesired melt residue with the previously used other pigments or other materials is present in the mold after one or a few injection processes.

It is also to be noted that the injection nozzle 10 is heated by means of a heating device 30 embodied as a tubular heating body and that a temperature sensor ring 31 is arranged on the nozzle core 11, on which temperature sensor ring 31 the temperature can be measured and set by means of a control and regulating device, not shown.

It should also be mentioned that, as an alternative to the above-described embodiment, the nozzle tip can also be formed as a separate component and screwed to the nozzle core 11.

Claims (14)

1. Injection nozzle for introducing a melt material into a plastic injection mold, comprising a nozzle core body (11) and a central melt channel (12), wherein the melt channel (12) merges downstream into at least one outlet channel (16) running obliquely to the melt channel (12) and provided with an outlet opening (25) for the plastic melt, wherein the outlet opening (25) opens into a cavity (17) which is designed as a spherical annular space and which is connected to a gate (22) of a mold cavity, wherein the gate (22) is arranged in the apex region (19) of the spherical cavity (17) and a nozzle needle (13) is provided which can be moved between a position for closing the gate (22) and a position for releasing the gate (22), characterized in that the outlet opening (25) of the outlet channel (16) is arranged at a position which is as far away as possible from the apex region (19) of the cavity (17) Is arranged in a bottom region (18) of the cavity (17).

2. An injection nozzle according to claim 1, characterized in that the outlet channel (16) widens conically in the flow direction of the plastic melt.

3. Injection nozzle according to claim 1 or 2, characterised in that the bottom area (18) of the cavity (17) is defined by a bottom surface (29) which is formed by the end surface of a sealing ring (20).

4. Injection nozzle according to claim 3, characterised in that the discharge opening (25) adjoins the bottom surface (29).

5. An injection nozzle according to claim 3, characterized in that the bottom surface (29) merges into a concave annular surface (36) of the nozzle tip (14).

6. Injection nozzle according to claim 3, characterised in that the sealing ring (20) is made of an insulating material.

7. Injection nozzle according to claim 1, characterised in that the clear width (W) of the cavity (17) widens in relation to the nozzle tip (14) in the region of the discharge opening (25).

8. Injection nozzle according to claim 1, characterised in that at least two outlet channels (16) are provided.

9. Injection nozzle according to claim 1, characterised in that the outlet openings (25) of the outlet channel (16) are arranged evenly distributed over the circumference of the nozzle tip (14).

10. An injection nozzle according to claim 1, characterized in that the central melt channel (12) at least partially concentrically surrounds the nozzle needle (13).

11. Injection nozzle according to claim 1, characterised in that the nozzle needle (13) has a needle lift of 2 to 4 mm.

12. Injection nozzle according to claim 1, characterised in that a front region (23) of the nozzle needle (13) can be moved at least partially into the pouring opening (22) to close the pouring opening (22), and in that the nozzle needle (13) is centred in the vicinity of the front region (23) by means of a guide (37).

13. Injection nozzle according to claim 12, characterised in that the guide (37) is formed by the inner wall of the hole (15) in the nozzle tip (14).

14. Injection nozzle according to claim 12, characterised in that the guide part (37) is constructed as a slide bearing.