Pre-chamber assembly with wear insert

Abstract

The present invention relates to a pre-chamber assembly (1) for an injection moulding nozzle, in particular an injection moulding nozzle having a needle closure, comprising a pre-chamber body (3) and a wear insert (4), wherein the pre-chamber body (3) has a pre-chamber side (31) and a cavity side (32), wherein the wear insert (4) is received in a recess (33) in the pre-chamber body (3) and forms a sprue bore (5) connecting the pre-chamber side (31) and the cavity side (32). According to the invention the wear insert (4) is connected to the pre-chamber body (3) and is secured in the axial direction.

Description

[0001] Prechamber arrangement with wear insert

[0002] Technical field

[0003] The invention relates to a pre-chamber arrangement for an injection molding nozzle, in particular an injection molding nozzle with needle valve, comprising a pre-chamber body and a wear insert.

[0004] Technical background

[0005] Wear inserts are used in injection molds to extend the tool's service life and improve the quality of the manufactured parts. The wear insert is integrated into the gate pre-chamber geometry of a pre-chamber assembly and includes the gate bore through which molten plastic is injected into a cavity.

[0006] The pre-chamber assembly houses the nozzle body and, via a sprue bore / gate opening located within it, establishes the connection between the nozzle and the mold cavity. To ensure the most precise material metering, even with rapid shot sequences, hot runner nozzles are often designed as needle valve nozzles. In these nozzles, a generally conical tip of a usually piston-driven needle serves to periodically open and close a gate opening, with the needle coming into contact with the pre-chamber assembly. Due to the high pressures involved, a precise seal in the closed position is just as essential as accurate needle guidance.

[0007] The injection process, and in some cases the opening and closing of the sprue bore using a nozzle needle, places particularly high stress on the sprue bore. Worn sprue bores can negatively impact component quality. The wear insert allows for easy and cost-effective replacement of a worn sprue bore without the need for mechanical reworking.

[0008] EP4241958 describes an insert for an injection mold nozzle, which is attached to the nozzle tip and, in its installed position, rests against a mold plate. The insert encompasses the sprue bore and simultaneously forms the pre-chamber of the injection mold nozzle. A disadvantage of this solution is that the insert is relatively large and requires considerable effort to remove from the nozzle for replacement. W02005108044 discloses a pre-chamber arrangement consisting of a highly thermally conductive material and a mechanically high-strength material, with the mechanically high-strength material located in the area of ​​the sprue opening of the pre-chamber arrangement. This pre-chamber arrangement is designed in three parts.It features an outer and inner copper base body, separated by tempering fluid channels and joined by electron beam welding along a cylindrical contact surface. The mechanically high-strength material consists of tool steel, which is also attached to the first two base bodies by electron beam welding. A disadvantage is the lack of replaceability of the welded material in the area of ​​the gate opening.

[0009] DE202007006060 discloses a pre-chamber arrangement for injection molds, particularly those with hot runner systems, consisting of a material with high thermal conductivity. At mechanically stressed locations, especially in the area of ​​a sprue bore, a material layer resistant to thermal and / or mechanical stresses is provided. This layer is applied to a base body of the pre-chamber arrangement by laser cladding. A disadvantage is the lack of replaceability of the welded material in the area of ​​the sprue opening.

[0010] Furthermore, a funnel-shaped wear insert is known which is pressed into a recess in the gate area of ​​a pre-chamber assembly. The wear insert has a larger surface area on the pre-chamber side than on the cavity side. Accordingly, a greater force acts on the wear insert on the pre-chamber side, which further secures the wear insert in the recess during the injection molding process. Although such wear inserts are small and easily replaceable, there is a risk that they may become dislodged from the recess or shift slightly over several injection molding cycles, leading to increased wear and defective injection-molded products.

[0011] Description of the invention

[0012] One task is to specify a pre-chamber arrangement for an injection molding nozzle that avoids or at least reduces the disadvantages of the prior art.

[0013] This problem is solved by a prechamber arrangement with the features of claim 1 and an injection mold with the features of claim 1. The prechamber arrangement for an injection molding nozzle, in particular an injection molding nozzle with a needle valve, comprises a prechamber body and a wear insert. The prechamber body has a prechamber side and a cavity side. The wear insert is received in a recess—generally central—in the prechamber body and forms a gate bore connecting the prechamber side and the cavity side. The wear insert is axially secured to the prechamber body.

[0014] The axial locking mechanism is preferably a positive-locking connection or a releasable positive-locking connection. In other words, the recess in the pre-chamber body can have at least one undercut in the axial direction of the pre-chamber assembly, into which the wear insert engages, thus preventing axial displacement of the pre-chamber body. A wear insert secured in this way will not loosen even under increased pressure or due to differing thermal expansion rates between the pre-chamber body and the wear insert. Furthermore, in addition to the funnel-shaped design, other shapes are also possible.

[0015] Preferred embodiments of the invention are specified in the dependent claims.

[0016] In some embodiments, the wear insert can have an external thread and be screwed into an internal thread of the recess in the pre-chamber body. This prevents it from being pushed out axially by the pre-chamber assembly. The external thread can be located in the pre-chamber-side area of ​​the wear insert.

[0017] In some embodiments, the wear insert and the pre-chamber body can be connected by means of a bayonet fitting. This prevents the pre-chamber assembly from being pushed out axially. The wear insert can have at least two bayonet arms that engage in the corresponding recess of the pre-chamber body. The recess can be provided with complementary bayonet arms. The bayonet arms of the wear insert can be chamfered on one side. The bayonet arms of the wear insert and / or the pre-chamber body are generally located in the pre-chamber-side area of ​​the wear insert.

[0018] In some embodiments, the wear insert can be provided with several mounting recesses on the pre-chamber side. To facilitate the installation and removal of a wear insert, a suitable mounting tool can engage in the mounting recesses to transmit torque.

[0019] In some embodiments, the recess of the pre-chamber body can have a circumferential snap groove into which the wear insert engages with a pre-chamber-side edge region. This prevents the pre-chamber assembly from being pushed out axially. The recess of the pre-chamber body can be provided with at least one recess on the pre-chamber side for removing the wear insert. The wear insert can be gripped with a suitable tool via these recesses, and the snap connection to the pre-chamber body can be released. Preferably, two opposing recesses are provided.

[0020] In some embodiments, the wear insert may have a cylindrical cavity-side section and a centering cone. The cylindrical section may be precisely fitted into the cavity-side section of the recess.

[0021] In some embodiments, the wear insert can be connected to the pre-chamber body by means of a shrink-fit connection and secured axially. This also provides a detachable, axially secure connection. The pre-chamber body and the wear insert can be made of different materials, with the material of the wear insert having a lower coefficient of thermal expansion than that of the pre-chamber body. This allows the shrink-fit connection to be disassembled.

[0022] The invention further relates to an injection mold comprising a pre-chamber arrangement as described above, and an injection molding nozzle with a shut-off needle.

[0023] Brief explanation of the characters

[0024] The invention will be explained in more detail below with reference to exemplary embodiments in connection with the drawing(s). The drawing(s) show:

[0025] Fig. 1 shows a sectional view of a first variant of a pre-chamber arrangement with a wear insert;

[0026] Fig. 2 shows the wear insert from Fig. 1, (a) in a side view, (b) in a cavity-side top view, and (c) in a perspective view; Fig. 3 shows a sectional view of a second variant of a prechamber arrangement with a wear insert;

[0027] Fig. 4 shows the wear insert from Fig. 3, shown in (a) a side view, (b) a cavity-side top view, and (c) a perspective view;

[0028] Fig. 5 shows a top view of the pre-chamber arrangement from Fig. 3;

[0029] Fig. 6 shows a third variant of a pre-chamber arrangement with a wear insert, with (b) a detailed enlargement thereof;

[0030] Fig. 7 shows a top view of the pre-chamber arrangement from Fig. 6, taken from the pre-chamber side.

[0031] Ways to implement the invention

[0032] Figures 1 and 2 show a first variant of a pre-chamber arrangement 1 with a wear insert 4. Figure 1 is a sectional view of the pre-chamber arrangement 1, which also shows a closing pin 2. Figure 2 shows several views of the wear insert 4.

[0033] The prechamber assembly 1 comprises a prechamber body 3 and a wear insert 4. The prechamber body 3 has a prechamber side 31 and a cavity side 32. In the installed state, the injection molding nozzle is received in the prechamber side of the prechamber assembly 1. The cavity side 32 of the prechamber assembly closes off a cavity of the injection mold. Furthermore, the prechamber body 3 has a central recess 33 in which the wear insert 4 is received.

[0034] The wear insert 4 is funnel-shaped with a cylindrical cavity-side area 42 and a centering cone 43. Furthermore, the wear insert 4 has a gate bore 5 connecting the pre-chamber side 31 and the cavity side 32. This bore can be closed with a shut-off needle 2 of the injection molding nozzle.

[0035] The wear insert 4 has an external thread 44 on the pre-chamber side, by means of which the wear insert 4 is screwed into an internal thread 34 of the recess 33 of the pre-chamber body 3. The cylindrical cavity-side area 42 fits precisely into the recess 33 and seals the cavity of the injection mold.

[0036] To facilitate the insertion, screwing in or removal of the wear insert 4, the wear insert 4 is provided with mounting recesses 41 (in the variant shown there are three mounting recesses 41) into which a suitable mounting tool can engage to transmit a torque.

[0037] Figures 3 to 5 show a second variant of the pre-chamber arrangement 1. In contrast to the first variant, the wear insert 4 is connected to the pre-chamber body 3 via a bayonet fitting. For this purpose, the wear insert 4 has several bayonet arms 45 on the pre-chamber side. In the variant shown, there are three bayonet arms 45. The bayonet arms 45 of the wear insert 4 are chamfered on one side and engage with complementary bayonet arms 35 of the pre-chamber body 3, which are also arranged on the pre-chamber side. Figure 4 shows several views of the wear insert 4. In Figures 3 and 5, the pre-chamber body 3 is shown with the wear insert 4 inserted. To facilitate insertion, screwing in, or removal of the wear insert 4, it is also provided with mounting recesses 41.

[0038] Figures 6 and 7 show a third variant of the prechamber arrangement 1. In contrast to the preceding variants, the wear insert 4 is connected to the prechamber body 3 via a snap connection. For this purpose, the recess 33 of the prechamber body 3 has a circumferential snap groove 36 on the prechamber side, into which the wear insert 4 engages with a prechamber-side edge region 46. The snap groove 36 is clearly visible in the detailed view of Figure 6. The recess 33 also has two opposing recesses 37 (see Figure 7), into which a suitable tool for disassembling the wear insert 4 can engage. The recesses 37 allow the wear insert 4 to be gripped with a suitable tool and the snap connection to the prechamber body 3 to be released.

[0039] List of designations

[0040] 1 Prechamber arrangement

[0041] 2 locking pins

[0042] 3. Prechamber bodies

[0043] 31 Prechamber side

[0044] 32 Cavity side

[0045] 33 recess

[0046] 34 Internal thread 35 Bayonet arm

[0047] 36 Snap groove

[0048] 37 Exclusion

[0049] 4 Wear insert 41 Mounting recess

[0050] 42 cylindrical cavity-side area

[0051] 43 Centering cone

[0052] 44 external threads

[0053] 45 Bayonet arm 46 Pre-chamber side edge area

[0054] 5 Gate bore

Claims

Patent claims 1. Prechamber arrangement (1) for an injection molding nozzle, in particular an injection molding nozzle with needle valve, comprising a prechamber body (3) and a wear insert (4), wherein the prechamber body (3) has a prechamber side (31) and a cavity side (32), wherein the wear insert (4) is received in a recess (33) in the prechamber body (3) and forms a gate bore (5) connecting the prechamber side (31) and the cavity side (32), characterized in that the wear insert (4) is connected to the prechamber body (3) and secured in the axial direction.

2. Pre-chamber arrangement according to claim 1, characterized in that the wear insert (4) has an external thread (44) and is screwed into an internal thread (34) of the recess (33) of the pre-chamber body (3).

3. Pre-chamber arrangement according to claim 1, characterized in that the wear insert and the pre-chamber body are connected by means of a bayonet fitting.

4. Pre-chamber arrangement according to claim 3, characterized in that the wear insert (4) has at least two bayonet arms (45) which engage in the corresponding recess (33) of the pre-chamber body (3).

5. Pre-chamber arrangement according to claim 4, characterized in that the bayonet arms (45) are chamfered on one side.

6. Pre-chamber arrangement according to one of claims 2 to 5, characterized in that the wear insert (4) is provided with several mounting recesses (41) on the pre-chamber side.

7. Prechamber arrangement according to claim 1, characterized in that the recess (33) of the prechamber body (3) has a circumferential snap groove (36) exhibits, into which the wear insert engages with a pre-chamber-side edge area.

8. Pre-chamber arrangement according to claim 7, characterized in that the recess (33) is provided on the pre-chamber side with at least one recess (37) for dismantling the wear insert (4).

9. Pre-chamber arrangement according to one of claims 1 to 8, characterized in that the wear insert (4) has a cylindrical cavity-side area (42) and a centering cone (43).

10. Prechamber arrangement according to claim 1, characterized in that the wear insert (4) is connected to the prechamber body by means of a shrink connection. (3) is connected and secured in the axial direction.

11. Prechamber arrangement according to claim 10, characterized in that the prechamber body (3) and the wear insert (4) are made of different materials, wherein preferably the material of the wear insert (4) has a lower coefficient of thermal expansion than the material of the has an ante-chamber body (3).

12. Injection mold comprising a pre-chamber arrangement (1) according to one of the preceding claims, and an injection molding nozzle with a shut-off needle (2).

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