Injection molding apparatus, injection molding method, and preheating assembly of injection molding apparatus

Abstract

The invention relates to an injection molding device, an injection molding method and a preheating assembly of the injection molding device. An injection molding device (1) for manufacturing an elastomeric part comprises: an injection assembly (2) for injecting an elastomeric molding material (4) having a nozzle (18); the injection assembly (2) is designed to heat the molding material (4) to a material temperature, and the cross-linking tool (3) is designed to heat the molding material (4) to a cross-linking temperature. The injection molding device (1) is characterized in that the injection molding device (1) comprises a preheating assembly (5) designed to heat the molding compound (4) to a preheating temperature, the preheating temperature in the preheating assembly (5) being higher than the material temperature in the injection assembly (2) and lower than the crosslinking temperature in the crosslinking tool (3).

Description

Technical Field

[0001] The invention relates to an injection molding device for producing an elastomeric component. The invention also relates to a preheating assembly. The invention also relates to a corresponding method. Background Art

[0002] In the following, the terms "heating", "preheating" and "heating up" are used interchangeably, unless the context indicates otherwise. Likewise, the terms "crosslinking" and "vulcanization" are used interchangeably, unless the context indicates otherwise. Furthermore, the terms "unit", "component" and "tool" are also used interchangeably, unless the context indicates otherwise. Finally, the terms "elastomer" and "rubber" are also used interchangeably, unless the context indicates otherwise.

[0003] Elastomer parts are usually manufactured in the injection molding process using injection molding devices. In this process, the elastomer is plasticized in a standard process, for example, it is fed into a piston injection molding machine. The temperature of the piston is significantly lower than the crosslinking temperature in the vulcanization tool. Therefore, additional thermal energy must be supplied to the elastomer before the crosslinking reaction can take place. This is usually achieved by friction heat in the nozzle of the piston assembly, by further friction in the sprue bushing or finally in the tool by heat transfer from the heated tool to the elastomer in the injection molding mold.

[0004] Such machines are known in the art, for example from EP 1 771 290 B1 or DE 1 9 17 975 A1. In order to shorten the cycle time, the temperature of the elastomer when it reaches the tool is increased there. This can be achieved, for example, by increasing the friction, for example by reducing the injection cross section. However, this has the disadvantage that the elastomer may be damaged by the additional friction, so that this measure can only be used to a limited extent. Alternatively, it is known from the prior art to use special piston assemblies in which the elastomer can be preheated faster. For this purpose, a large surface area is required to achieve a faster heat transfer in the piston assembly. For example, DE 10 154 676 B4 proposes to use an annular gap piston instead of a cylindrical piston in order to increase the contact area of ​​the assembly and the elastomer. However, this requires the purchase of a special machine, because it is very laborious to convert a standard machine with such an annular piston assembly.

[0005] Thus, known injection molding devices, in which the elastomer reaches the cavity in the vulcanization tool at a higher temperature, tend on the one hand to pre-damage the elastomer due to the high friction when injecting the elastomer into the vulcanization tool, which can lead to a shortened service life of the vulcanized part. On the other hand, other solutions require the purchase of special machines, which contradicts standardized machine equipment and can lead to economic disadvantages. Summary of the invention

[0006] The object of the present invention is therefore to provide an injection molding device as well as a preheating assembly and a method for producing elastomeric parts, by means of which the disadvantages of the prior art can be eliminated and by means of which, in particular, the crosslinking time during injection molding can be shortened.

[0007] To solve this problem, the present invention provides an injection molding device according to the first aspect of the present invention, a preheating assembly according to the fifteenth aspect of the present invention, and a method according to the sixteenth aspect of the present invention. Specific embodiments of the injection molding device are the subject of the second to fourteenth aspects of the present invention.

[0008] The injection molding device for manufacturing elastomeric parts of the present invention is also called a vulcanizing press, and includes an injection component for injecting elastomeric molding material and a cross-linking tool for cross-linking the molding material, wherein the injection component is designed to heat the molding material to a material temperature, and wherein the cross-linking tool is designed to heat the molding material to a cross-linking temperature, characterized in that the injection molding device includes a preheating component, which is designed to heat the molding material to a preheating temperature, wherein the preheating temperature in the preheating component is higher than the material temperature in the injection component and lower than the cross-linking temperature in the cross-linking tool.

[0009] By means of such an injection molding device, the entry temperature of the elastomer into the mold cavity (i.e. into the injection molding mold of the crosslinking tool) can be increased, thereby shortening the vulcanization or crosslinking time of the elastomeric part to be produced, i.e. the time required for the molding material to be completely crosslinked. The crosslinking time of the elastomeric part depends, in addition to the volume or thickness of the part, primarily on the temperature at which the molding material is injected into the crosslinking tool.

[0010] Typically, in elastomer injection molding, the molding material is first plasticized by means of an extruder and transferred to an injection assembly, such as a piston injection assembly. In the extruder and the injection assembly, the molding material is preheated to the material temperature by friction and contact heat. The injection assembly then injects the preheated molding material into a cross-linking tool through a nozzle, wherein the temperature of the molding material is additionally heated to the exit temperature due to further friction in the nozzle. In some cases, a so-called cold runner is also connected behind the nozzle, which ensures that the molding material is distributed into the cavity without significantly further increasing the temperature of the molding material. According to solutions known in the prior art, the molding material heated to the material temperature is then injected into the cross-linking tool for vulcanization. With the help of the preheating assembly of the present invention, the molding material to be injected in the next vulcanization step is first heated to the preheating temperature.

[0011] The advantage of preheating the molding material in the preheating component is that the crosslinking temperature of the molding material is reached particularly quickly in the crosslinking tool, so that the cycle time can be shortened significantly. The cycle time is the time required for each production cycle, wherein a production cycle comprises the steps of injecting the molding material into the mold cavity, subsequently crosslinking the molding material, opening the tool, removing the component and filling the mold again. The cycle time thus corresponds to the time required for producing each component or for producing each group of components produced simultaneously. In parallel with the described cycle, the steps of plasticizing in the extruder, filling the injection component and preheating to the material temperature in the injection component are also carried out.

[0012] When the molding material is injected into the cross-linking unit, it is already heated to the preheating temperature, which is why only a slight additional heating to the cross-linking temperature is necessary to initiate the vulcanization process. As a result, a uniform temperature distribution can be achieved over the entire component blank despite the relatively poor thermal conductivity of the molding material to be cross-linked. In this context, it is particularly envisaged to select a preheating temperature that is as high as possible, i.e. a preheating temperature that is as close as possible to the cross-linking temperature of the molding material, but does not lead to undesired cross-linking of the molding material already in the preheated component. In other words: cross-linking should not start before the molding material is injected into the cross-linking tool.

[0013] Advantageously, it is conceivable that the preheating temperature is selected from a temperature range in which the molding material in the preheating assembly reaches its minimum value of shear viscosity at the earliest after a preheating time of 5 minutes, and on the other hand the shear viscosity of the molding material increases by 20% relative to its minimum value at the latest after 20 minutes. During preheating, a preferred maximum temperature should be selected so that the minimum value of the shear viscosity of the molding material in the preheating assembly is reached at the earliest after a preheating time of 5 minutes, so that the molding material can still be injected in the preheating assembly and no significant crosslinking occurs. On the other hand, during preheating, a preferred minimum temperature should be selected so that the shear viscosity of the molding material in the preheating assembly increases by 20% relative to the minimum value at the latest after a preheating time of 20 minutes, i.e. crosslinking does not start until 20 minutes at the latest. Thus, due to the preheating of the molding material, the crosslinking time in the crosslinking tool can be significantly reduced. Here, the shear viscosity of the molding material is in particular the Mooney viscosity. Mooney viscosity refers to the shear viscosity or flow properties of an elastomeric material, which is determined by the method of the same name (Mooney method). In this method, the elastomeric material is preheated for a period of time and then loaded at a constant shear rate (the so-called deformation phase). The Mooney viscosity refers to the shear viscosity of the material starting from the end of the deformation phase.

[0014] Typically, the molding material is injected from the piston assembly directly into the crosslinking tool without additional preheating. For further preheating of the molding material, the friction heat in the nozzle of the piston assembly and, if necessary, a downstream gate distributor can be used. However, every strong friction of the molding material leads to preliminary damage to the elastomer. With the aid of the preheating assembly according to the invention, the elastomer can be transferred to the preheating assembly particularly gently, since the elastomer stays in the preheating assembly for the time of one cycle during the crosslinking of the component and can absorb additional heat from the preheating assembly there by heat transfer. As a result, there is no need to apply significant friction to the elastomer in the nozzle in order to further preheat the elastomer, so that the risk of preliminary damage to the elastomer due to friction can be minimized and the cycle time can be shortened.

[0015] It is also conceivable that the preheating assembly comprises at least one preheating block and at least one preheating base tool, wherein the at least one preheating block can be inserted into the at least one preheating base tool. Thus, the preheating base tool and the preheating block are independent components of the preheating assembly. Due to this modular structure, the preheating base tool can be combined with different preheating blocks. Thus, the geometry of the preheating block can be individually adapted to the corresponding cavity or cavities of the cross-linking assembly without also having to individually adjust the preheating base tool. In this way, tool costs can be saved and manufacturing time can be shortened.

[0016] It is also conceivable that the injection molding device comprises at least one heat shield. With the aid of the heat shield, optimal heat insulation of all units involved in the casting process from one another and / or from the environment is ensured, which leads to an increase in the efficiency of the device and thus saves energy. According to a further development, it is conceivable that the injection molding device comprises at least two heat shields, wherein a first heat shield is arranged between the injection assembly and the preheating assembly or between the distributor and the preheating assembly, and wherein a second heat shield is arranged between the preheating assembly and the cross-linking tool.

[0017] According to an advantageous embodiment, it is envisaged that the injection molding device comprises at least one distributor. At least one distributor may be part of the preheating assembly, or may be designed as a component separate from the preheating assembly. In addition, at least one distributor may be at least partially thermally isolated from the preheating assembly or the preheating block of the preheating assembly by a heat shield. If the distributor is separated from the preheating block by a heat shield, the distribution of the molding material can be carried out outside the preheating assembly, wherein the distributor has a lower temperature than the preheating block of the preheating assembly. By means of the heat shield between the distributor and the preheating block, the heat transfer from the preheating block at a higher temperature to the distributor at a lower temperature is minimized. Therefore, the mass of the tool steel that must be heated to the preheating temperature can be reduced to reduce the weight of the distributor, which reduces the total energy requirement for tempering. On the other hand, if the distributor is part of the preheating assembly, the number of tool parts can be reduced. In addition, this results in the molding material already being heated to the preheating temperature in the distributor, so that the volume of the distributor can be added to the total preheating volume. In this case, the total preheating volume is the sum of the volumes of at least one distributor and at least one preheating block (and any sub-distributors). Since the distributor provides additional volume for preheating, the preheat block itself can be smaller, or larger parts (with a larger rubber volume) can be manufactured in the crosslinking tool if the block size remains the same. The volumes in the preheat block can be designed smaller and therefore cheaper, or parts with an overall larger elastomer volume can be manufactured. At least one distributor can be designed as a cold runner distributor, i.e. the distributor is part of the injection assembly.

[0018] According to an advantageous embodiment, it is envisaged that the injection molding device comprises at least one needle valve nozzle (Nadelverschlussdüse). The needle valve nozzle can be arranged between the injection assembly and the preheating assembly or between the preheating assembly and the cross-linking tool. In other words: the needle valve nozzle can be arranged in front of or behind the preheating assembly, where "in front of" or "behind" refers to the path of the molding material through the injection molding device. In particular, the needle valve nozzle can be arranged between the distributor and the preheating assembly. In addition, the needle valve nozzle can be arranged directly behind the preheating assembly or directly behind each preheating block. In principle, the preheating assembly can also include a sub-distributor. In this case, the needle valve can be arranged behind the preheating assembly and a downstream sub-distributor, or the needle valve can be arranged behind a sub-distributor of the preheating assembly and in front of the cross-linking tool.

[0019] Preferably, the preheating temperature in the preheating assembly is higher than the exit temperature of the molding material flowing out of the nozzle of the injection assembly and lower than the crosslinking temperature in the crosslinking tool, wherein the exit temperature is the temperature of the molding material generated by the shear force generated when the molding material flows out of the nozzle of the injection assembly. The exit temperature is higher than the material temperature because additional friction heat is generated in the nozzle. This can reduce the energy input in the preheating assembly.

[0020] Preferably, the preheating component of the injection molding device can be designed to specifically heat the molding material from the material temperature or the exit temperature to the preheating temperature, wherein the preheating temperature is selected from a temperature range in which the shear viscosity of the molding material reaches a minimum value at the earliest after a preheating time of 5 minutes, wherein the shear viscosity of the molding material increases by 20% relative to its minimum value at the latest after 20 minutes.

[0021] According to another embodiment, it is envisaged that the injection assembly, the preheating assembly and the crosslinking tool are respectively independent building blocks, which can be assembled into an injection molding device. Due to this modular structure, different preheating assemblies and crosslinking tools can be easily combined with the injection assembly, while a standard machine for elastomer injection molding can still be used as the injection assembly. Therefore, there is no need for expensive special machine manufacturing for the injection assembly.

[0022] Furthermore, it is conceivable that the injection assembly is in fluid communication with the preheating assembly, and that the preheating assembly is in fluid communication with the crosslinking tool, wherein the injection assembly, the crosslinking tool and the preheating assembly are each designed to be individually temperature-controllable. This ensures that the molding material is in a closed system throughout the injection molding process, wherein it can be heated to the desired temperature in each of the three modules.

[0023] It is also conceivable that the preheating assembly is heated by means of a heating coil and / or by means of a heating plate and / or by means of a heating rod and / or by means of a fluid heating medium. With the aid of these heating systems, the preheating base tool and the preheating block are heated to the desired preheating temperature. In this case, it is particularly economically advantageous if one or more individual preheating blocks do not comprise an individual heating system, but rather absorb the preheating temperature by means of contact heat from the heated preheating base tool. Thus, the heating system does not have to be adapted to an individual preheating block which is inserted as precisely as possible into the preheating base tool, but rather to a more universal preheating base tool.

[0024] According to a further improvement, the preheating assembly may include at least one preheating channel, wherein each preheating channel is preferably integrated in a corresponding preheating block. In other words: each preheating block preferably includes a preheating channel. At least one preheating channel is designed so that the molding material contained therein has a surface area as large as possible relative to its volume. This can shorten the preheating time in the preheating assembly, that is, the time required to heat the molding material to the preheating temperature, and best match the vulcanization time in the cross-linking tool. Finally, the large surface area relative to the volume ensures a particularly effective heat transfer from the preheating assembly or preheating block to the molding material located in the preheating channel. In this way, the energy demand required for preheating the molding material can be reduced. Another advantage produced by the preferably designed preheating channel is that the molding material can be heated particularly gently while minimizing friction. This can avoid damage that may occur during the heating process due to friction or shearing.

[0025] Furthermore, it is conceivable that the crosslinking tool comprises at least one cavity in which the molding material is formed into the elastomeric component at the crosslinking temperature. The cavity here is essentially an injection mold in which the elastomeric molding material is injected and subsequently crosslinked into the final component. In particular, it is conceivable that the volume of at least one preheating channel is less than or equal to the volume of the cavity to which it corresponds. In this way, it can be ensured that the entire elastomeric molding material contained in the preheating channel is present for the maximum duration of the preceding component crosslinking before the molding material itself is transferred to the cavity of the crosslinking unit. In other words: before the molding material itself crosslinks, it never stays in the preheating channel for more than exactly one crosslinking cycle of the device. This makes it possible to avoid partial vulcanization of the molding material due to a too long residence time in the preheating channel. In this way, it can be ensured that the molding material is heated in the preheating assembly to a preheating temperature that is as close as possible to the crosslinking temperature. If the preheating assembly also includes distributors, sub-distributors or other volumes filled with molding material that are heated to the preheating temperature, so that these volumes add up to form a total preheating volume, it is advantageous for the reasons stated above if the total preheating volume is less than or equal to the volume of all cavities associated with the preheating assembly.

[0026] According to a further development, it is envisaged that at least one preheating channel is designed in an S-shaped and / or serpentine and / or meandering and / or spiral and / or zigzag and / or ramped and / or in the form of planar areas arranged in an overlapping manner. This configuration allows the preheating block and thus the preheating unit as a whole to remain compact while maintaining the same efficiency, since the at least one preheating channel optimally utilizes the available space in the preheating block. Preferably, the maximum possible surface area is advantageously adjusted to allow a good heat transfer by contact heat.

[0027] Advantageously, the preheating block can be designed such that the preheating channel is at least partially open along the periphery in the preheating block and is closed by the preheating base tool at least on one side of the preheating channel after the preheating block has been inserted into the preheating base tool. Alternatively, one side of the preheating channel can be closed by a separate component. Such a preheating channel that is open at the side or at the top and bottom is particularly easy to clean after the preheating block has been removed from the preheating base tool. It is also conceivable that the preheating base tool forms the preheating channel together with the preheating block; this design is particularly suitable in particular in the case where the preheating channel is open at the side in the preheating block. It is particularly advantageous that such complex preheating channel geometries can be manufactured in the preheating block using 3D metal printing technology.

[0028] Furthermore, it is conceivable that different component groups with different volumes can be manufactured in the same cross-linking tool. Thus, for example, a first preheating channel can be connected to "component group A" and a second preheating channel can be connected to "component group B", wherein component A of component group A has a different volume than component B of component group B. Accordingly, it is conceivable that the cross-linking tool comprises different types of cavities. Thus, a large number of different components can be manufactured using only one preheating assembly, but at the same time each preheating block can be optimally adapted to the downstream cavity.

[0029] It is also conceivable that the injection molding device includes a distributor, wherein the distributor is preferably in fluid communication with the injection assembly and with at least one preheating block of the preheating assembly. With the aid of the distributor, multiple parts can be manufactured simultaneously in one injection molding process. According to an embodiment, the distributor can be a part of the injection assembly ("cold runner principle"), a part of the preheating assembly or a part of the cross-linking tool ("hot runner principle"), and is designed to generate or maintain the expected temperature of these modules, respectively. Therefore, the distributor can be designed as a so-called cold runner distributor with or without a needle valve nozzle and is arranged downstream of the injection assembly. In this case, the cold runner can have a temperature between the leaving temperature and the preheating assembly.

[0030] It is also conceivable that at least one preheating block includes a sub-distributor, which is designed to distribute the molding material from the preheating channel to the cavity of the cross-linking tool. The sub-distributor (or multiple sub-distributors in the case of multiple preheating blocks) can replace the distributor or be provided as a supplement to the distributor. Therefore, for example, it is conceivable that the distributor first distributes the molding material from the injection assembly to multiple preheating blocks. This upstream distributor is advantageously designed as a cold runner, whereby the molding material has not yet begun to vulcanize in the pre-distribution area. Particularly advantageously, at least one needle valve nozzle is provided between the cold runner distributor and the preheating assembly to effectively prevent the molding material from flowing back due to the volume expansion in the preheating assembly. Then, the molding material preheated by means of the preheating block can be further distributed to multiple cavities using a sub-distributor arranged behind the preheating block. The sub-distributor can also be used to cast the parts to be manufactured at multiple injection points, which enables faster filling of the cavity and / or optimization of flow when filling the parts.

[0031] Furthermore, it is conceivable that the injection molding device comprises at least one nonreturn valve, which is arranged between the preheating channel and the crosslinking tool. This ensures that a sufficiently high pressure is built up in the individual cavities during the crosslinking process. Furthermore, a backflow of the molding material from the crosslinking tool into the preheating base tool due to the volume expansion during crosslinking is effectively prevented. The high pressure during the crosslinking process leads to particularly high-quality and durable elastomer components. In this case, the nonreturn valve can be embedded in a recess provided for this purpose in one of the heat shields. Instead of the nonreturn valve, a needle valve nozzle can also be used.

[0032] According to another embodiment, it is envisaged that the injection molding device includes at least one cooling plug-in, wherein the cooling plug-in is particularly arranged in the cross-linking tool, and each cooling plug-in at least partially surrounds and / or is at least partially thermally decoupled from the cross-linking tool there. It is also conceivable that the cooling plug-in at least partially surrounds the needle valve nozzle instead of the check valve and / or is at least partially thermally decoupled from the cross-linking tool. Here, it is conceivable that the cooling plug-in surrounds the part of the cavity facing the preheating base tool, such as the flow hole. With the help of the cooling plug-in, the risk of cross-linked material residues appearing at the transition between the preheating component and the cavity can be reduced, which material residues are usually retained on the component during the injection molding process and are called "sprues (Angussnippel)". Such cross-linked material residues may represent quality problems. In addition, this prevents active parts (such as check valves or needle valve nozzles) that are in contact with the molding material from being blocked or no longer functioning unrestrictedly and smoothly due to the cross-linking of the elastomer in the gate.

[0033] Another aspect of the present invention is directed to a preheating assembly for use with an injection molding apparatus for making elastomeric parts.

[0034] The preheating assembly of the present invention comprises at least one preheating block and at least one preheating base tool, wherein the at least one preheating block can be inserted into the at least one preheating base tool. Therefore, the preheating base tool and the preheating block should be understood as independent components of the preheating assembly. Preferably, at least one preheating block has one or more heating coils and / or one or more heating plates and / or one or more heating rods and / or a fluid heating medium. With the help of at least one of these heating systems, the preheating block is heated to the preheating temperature.

[0035] It is particularly envisaged here that the preheating assembly according to the invention can be connected to the crosslinking tools known from the prior art without requiring major structural changes to the crosslinking tools. Typically, the preheating base tool and the distributor matched thereto replace the gating system. In particular, however, standard machines can be used as injection assemblies (also called "vulcanizing presses"), since the design of the machine up to the nozzle of the piston-type injection assembly can be used unchanged. Therefore, the preheating assembly should be able to be used with almost all commercially available vulcanizing presses.

[0036] According to a further improvement, the preheating block of the preheating assembly comprises at least one preheating channel. At least one preheating channel is designed so that the molding material contained therein has a surface area that is as large as possible relative to its volume. This can shorten the time required to heat the molding material to the preheating temperature ("preheating time"), and finally, the large surface area relative to the volume ensures a particularly effective heat transfer from the preheating assembly to the molding material. In this way, the total energy requirement of the process cycle can be reduced by reducing the cycle time. Another advantage resulting from the preheating channel is that the molding material can be heated particularly gently while minimizing friction. This can prevent molecular degradation in the elastomer of the molding material that may occur during the heating process due to friction or shearing.

[0037] According to a further development, it is envisaged that at least one preheating channel is designed in the form of a meander and / or spiral and / or zigzag and / or ramp and / or S-shaped and / or serpentine and / or in the form of planar areas arranged in an overlapping manner. Due to this structure, the preheating assembly can be kept compact while maintaining efficiency, because the at least one preheating channel optimally utilizes the space available in the preheating assembly.

[0038] According to another aspect of the present invention, there is provided a method for manufacturing an elastomeric component using the injection molding apparatus described herein, wherein the injection molding apparatus comprises a cross-linking tool, an injection assembly, and a preheating assembly, wherein the method comprises the following steps:

[0039] a) filling the injection component tempered to the material temperature with the elastomeric molding material,

[0040] b) heating the molding material to the material temperature by means of heat input from the injection assembly by contact heat input and / or heat transfer,

[0041] c) transferring the molding material from the injection assembly to the preheating assembly,

[0042] d) heating the molding material to a preheating temperature in a preheating assembly,

[0043] e) injecting the molding material from the preheated assembly into the cross-linking tool,

[0044] f) Heating the molding material in a crosslinking tool from a preheating temperature to a crosslinking temperature.

[0045] The preheating temperature is selected from a temperature range in which the shear viscosity of the molding material reaches a minimum value at the earliest after a preheating time of 5 minutes, wherein the shear viscosity of the molding material increases by 20% relative to its minimum value at the latest after a preheating time of 20 minutes.

[0046] Preferably, when the molding material is transferred from the injection assembly to the preheating assembly, the molding material is heated from the material temperature to the exit temperature by shearing the molding material in the nozzle of the injection assembly. Accordingly, in the preheating assembly, the molding material is not heated from the material temperature to the preheating temperature, but from the exit temperature higher than the material temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Further features, details and advantages of the invention are apparent from the wording of the claims and from the following description of exemplary embodiments with the aid of the accompanying drawings.

[0048] Figure 1 A longitudinal sectional view showing an injection molding apparatus of the present invention according to a first embodiment;

[0049] Figure 2 shows a longitudinal sectional view of an injection molding apparatus of the present invention according to another embodiment;

[0050] Figure 3 shows a longitudinal sectional view of an injection molding apparatus of the present invention according to another embodiment;

[0051] Figure 4 shows a longitudinal sectional view of an injection molding apparatus of the present invention according to another embodiment;

[0052] Figure 5 shows a longitudinal sectional view of an injection molding apparatus of the present invention according to another embodiment;

[0053] Figure 6 shows a longitudinal sectional view of an injection molding apparatus of the present invention according to another embodiment;

[0054] Figure 7 A diagram is shown in which the time viscosity curve of an elastomeric molding material is plotted in relation to different test temperatures.

[0055] Reference numerals list

[0056] 1Injection molding device

[0057] 2 Injection components

[0058] 3 Cross-linking tools

[0059] 4 Molding material

[0060] 5. Preheat components

[0061] 6-needle valve nozzle

[0062] 7 Preheating block

[0063] 8 needle valve

[0064] 9 preheating channels

[0065] 10 Distributor

[0066] 11 Cavity

[0067] 12 Check valve

[0068] 13 Cooling plug-in

[0069] 14 Heat insulation board

[0070] 14a First heat insulation board

[0071] 14b Second heat shield

[0072] 15 Notch

[0073] 16-sub-distributor

[0074] 17 Upper part

[0075] 18 Nozzles

[0076] 19 Preheat the base tool

[0077] 20 Total preheat volume

[0078] t v Warm-up time

[0079] V m Mooney viscosity

[0080] T1 first test temperature

[0081] T2 Second test temperature

[0082] T3 The third test temperature

[0083] M minimum DETAILED DESCRIPTION

[0084] Figure 1 The injection molding device 1 according to the invention is shown in a longitudinal section according to a first embodiment. The injection molding device 1 comprises an injection assembly 2 for injecting an elastomeric molding material 4 into a cross-linking tool 3. The injection assembly 2 is shown in a very simplified and schematic manner. Usually, a plasticizing extruder is also connected upstream of the injection assembly 2 shown, here a piston assembly, which is filled with a piston injection assembly and has preheated the molding material 4. The plasticizing extruder is connected upstream of the injection assembly 2, here a piston assembly. Figure 1 A preheating assembly 5 is provided between the injection assembly 2 and the crosslinking tool 3. The three modules, namely, the injection assembly 2, the preheating assembly 5 and the crosslinking tool 3 are fluidly connected in such a way that the molding material 4 is located in a closed system throughout the injection molding process.

[0085] The injection assembly 2 of the device according to the invention now heats the molding material 4 to a starting temperature, referred to as the material temperature, due to the temperature of the injection assembly 2. Usually, the molding material 4 heated to the material temperature is then injected into the crosslinking tool 3 through the nozzle 18 for vulcanization. Figure 1 In the device 1 shown, it is envisaged that the molding material 4 is first transferred to a preheating assembly 5 through a nozzle 18, which is designed to heat the molding material 4 to a preheating temperature. At the preheating temperature, the molding material 4 is ideally heated to the maximum extent without already crosslinking.

[0086] according to Figure 1 In the embodiment shown, the injection molding device 1 comprises two heat shields 14a, 14b, wherein the first heat shield 14a is arranged between the preheating assembly 5 and the injection assembly 2, and wherein the second heat shield 14b is arranged between the preheating assembly 5 and the cross-linking tool 3. By means of the heat shields 14a, 14b, undesirable heat exchange between the modules is prevented or at least reduced. Here, the first heat shield 14a ensures the heat insulation of the preheating assembly 5 relative to the injection assembly 2 and the environment. The second heat shield 14b ensures the heat insulation of the preheating assembly 5 relative to the cross-linking tool 3 and the environment. As a result, the temperature required for preheating the molding material 4 in the preheating assembly 5 is neither reduced by the relatively low temperature of the injection assembly 2 or the environment, nor increased by the relatively high temperature of the cross-linking tool 3. This optimizes the efficiency of the preheating assembly 5.

[0087] Figure 1The shown injection molding device 1 also includes a distributor 10, wherein the distributor 10 is here distributed to the preheating component 5 ("hot distributor principle"), because the distributor and the preheating component 5 are heated to approximately the same temperature. This means that the distributor 10 is designed to generate and / or maintain the preheating temperature without crosslinking occurring in the distributor 10 ("hot runner principle"). In order to prevent an undesired heat exchange between the distributor 10 and the injection component 2 arranged in the preheating component 5 or the distributor 10 from dissipating its heat to its environment, the distributor 10 is covered by a first thermal insulation plate 14a. The distributor 10 is in fluid communication with the injection component 2 and with the preheating blocks 7 of the preheating component 5, so that the molding material 4 can be distributed to the individual preheating blocks 7 (in Figure 1 ). In this case, the preheating blocks 7 are designed as separately manufactured components, which are inserted into the preheating base tool 19. The distributor 10, the preheating base tool 19 and the preheating blocks 7 form the main components of the preheating assembly 5. Distributing the molding material 4 in the preheating assembly 5, which has a temperature below the crosslinking temperature, as is otherwise the case in conventional hot runner distributors, helps to minimize the amount of rubber waste that is usually generated when injection molding elastomeric parts using hot runner distributors.

[0088] Each preheating block 7 is heated indirectly by contact heat from the preheating base tool 19. However, each preheating block 7 may also be heated directly in addition to the contact heat from the preheating base tool 19, or exclusively, for example, by a heating rod or a heating coil. Figure 1 As shown, each preheating block 7 may include a meandering preheating channel 9. The preheating channel 9 is designed so that each molding material 4 contained therein has a surface area as large as possible relative to its volume. In this way, the energy requirement required for preheating the molding material can be reduced because the heat transfer from the preheating block 7 to the molding material 4 is optimized.

[0089] according to Figure 1 The embodiment shown is provided between the first insulation board 14a and the second insulation board 14b. The preheating assembly 5 advantageously comprises a plurality of (in the cross-sectional view) meandering preheating channels 10, of which two are shown in the longitudinal cross-sectional view. For example, such a structure can be easily manufactured using 3D printing. The preheating channels 10 are fluidically connected to the distributor 10 and are designed so that the contained molding material 4 has a surface area as large as possible relative to its volume.

[0090] Figure 1 The crosslinking tool 3 shown comprises a plurality of cavities 11, of which only two are shown in the longitudinal section. According to the invention, the preheated molding material 4 is injected from a preheating channel 10 into the cavity 11 and molded there into an elastomer component at the crosslinking temperature, wherein according to Figure 1, each preheating channel 9 is assigned to a cavity 11. Figure 1 As shown, the volume of each preheating channel 9 is smaller than the cavity 11 of the cross-linking tool 3 associated therewith. In this way, it is ensured that the entire elastomeric material 4 still located in the preheating channel 9 during each cross-linking step remains in the channel 9 for the maximum duration of the cross-linking step of the preceding component before being transferred to the cavity 11 of the cross-linking tool 5. If the total preheating volume of the molding material 4 in the preheating assembly 5, i.e. the volume in the distributor 10 and in the preheating channels 9 of the preheating block 7 is taken into account, then in the best case this volume is at most as large as the volume of the molding material 4 in the cross-linking tool 3, and therefore at most as large as the sum of the volumes of the molding material 4 in all cavities 11. Here, the cooling volume in the cooling insert 13 is still included in the total preheating volume.

[0091] Figure 1 The device 1 shown also has non-return valves 12, which are arranged between the preheating channel 10 and the cavity 11. In the case of the embodiment shown, the non-return valves 12 are arranged in recesses 15 provided for this purpose in the second thermal insulation plate 14b. The non-return valves 12 ensure that a sufficiently high pressure can be built up in the cavity 11 during the crosslinking process and that the elastomer that has not been crosslinked is pressed back into the preheating component 5 due to thermal expansion.

[0092] like Figure 1 As shown, the injection molding device 1 may also include a cooling insert 13, wherein Figure 1 Only two cooling inserts 13 are shown. Each cooling insert 13 is preferably arranged in the cross-linking tool and at least partially surrounds the cavity 11. Figure 1 Here, it is conceivable that the cooling insert 13 surrounds the upper channel-shaped part 17 of the cavity 11, ie the part of the cavity 11 facing the preheating channel 9. The cooling insert 13 prevents the molding material 4 from completely crosslinking in the nonreturn valve 12, thereby limiting the function of the nonreturn valve 12.

[0093] Figure 2 FIG. 2 shows a longitudinal sectional view of an injection molding device 1 according to another embodiment of the present invention. Figure 2 The difference between the implementation methods is that according to Figure 2, the distributor 10 is distributed to the injection assembly 2 ("cold runner principle"). This means that the distributor 10 is designed to maintain the material temperature. In order to prevent undesirable heat exchange between the preheating assembly 5 and the distributor 10 arranged in the injection assembly 2, the distributor 10 of the injection assembly 2 and the preheating assembly 5 are separated by a first insulation board 14a. The distributor 10 is fluidly connected to the preheating block 7 of the preheating assembly 5, so that the molding material 4 can be distributed to each preheating block 7. The molding material 4 transferred from the injection assembly to the distributor 10 at the material temperature can already be heated in the distributor 10 to a temperature slightly lower than the required preheating temperature. The molding material 4 is then actually heated to the preheating temperature in the preheating block 7 of the preheating assembly 5. Therefore, the total preheating volume 20 consists only of the volume of the preheating channel 9 in the preheating block 7. In theory, the preheating channel 9 can also be partially formed by the preheating base tool 19, but this is not shown here.

[0094] As in Figure 1 In the case of an embodiment, according to Figure 2 It is also conceivable to distribute the molding material 4 to a plurality of preheating blocks 7, wherein each preheating block 7 is fluidically connected to one cavity 11. In other words: each cavity 11 has its "own" preheating block 7. Figure 2 As shown, the volume of each preheating channel 9 is smaller than the associated cavity 11 of the cross-linking tool 3. The total preheating volume 20 is also smaller than the sum of the volumes of the molding material 4 in all cavities 11.

[0095] Figure 3 A longitudinal sectional view of an injection molding device 1 according to the invention is shown according to another embodiment. The injection molding device 1 shown comprises an injection assembly 2, a preheating assembly 5 and a cross-linking tool 3, which are connected to one another in such a way that they form a fluid-tight system through which a molding material 4 can flow. Figure 3 The embodiment shown is an injection molding device 1 according to the "hot runner principle". This means that the distributor 10 is arranged in the crosslinking tool 3 and is designed to generate and / or maintain the crosslinking temperature. Therefore, the distribution of the molding material 4 to the cavity 11 only takes place after the molding material has been heated to the preheating temperature in the preheating assembly.

[0096] The injection molding device 1 designed according to the hot runner principle enables a cost-effective tool to be realized because the preheating assembly 5 includes only one preheating block 7, by means of which the entire molding material 4 is heated to the preheating temperature. Therefore, the backflow stop device (such as the needle valve nozzle 6 or the check valve 12) that may be required can be reduced to a single sample (Exemplar) (in Figure 2 The distribution of the molding material 4 is performed only after the step of heating the molding material 4 to the preheating temperature, wherein the preheated molding material 4 is distributed to the mold cavity 11 instead of Figure 1 or Figure 2 As in the embodiment of the present invention, the plurality of preheating blocks 7 provided there are first distributed there. Since only one preheating block 7 is operated instead of a plurality of preheating blocks 7, the tool cost can be saved by using the hot runner principle.

[0097] Similar to Figure 1 and Figure 2 An embodiment of Figure 3 The injection molding device 1 shown in FIG. 1 comprises a first heat insulating plate 14 a and a second heat insulating plate 14 b , wherein the preheating assembly 5 is disposed between the first heat insulating plate 14 a and the second heat insulating plate 14 b .

[0098] exist Figure 4 , a longitudinal sectional view of an injection molding device 1 of the present invention according to another embodiment is shown. Figure 4 The injection molding device 1 basically corresponds to Figure 2 The injection molding device 1 shown is different in that Figure 4 The injection molding device 1 comprises a needle valve nozzle 6 with a needle valve 8. By means of the needle valve 8, the rubber is prevented from undesirably flowing back from the preheating component 5 into the distributor 10 due to thermal expansion in the preheating component 5 and / or the crosslinking tool 3 (here the "cold runner principle").

[0099] exist Figure 4 In the embodiment shown, it is envisaged that the needle valve nozzle 6 is arranged between the injection assembly 2 and the preheating assembly 5, respectively, and thus in front of the preheating block 7 (with respect to the path of the molding material 4 through the injection molding device 1). This arrangement may be advantageous because the needle valve nozzle 6 only needs to be guided through the distributor 10, which is simple to manufacture and therefore cost-effective and robust.

[0100] Figure 5 FIG. 2 shows a longitudinal sectional view of an injection molding device 1 according to another embodiment of the present invention. The injection molding device 1 basically corresponds to Figure 4 The injection molding device 1 is different in that Figure 5 In the embodiment shown, the needle valve nozzle 6 with the needle valve 8 is respectively arranged between the preheating assembly 5 and the cross-linking tool 3, and is therefore arranged behind the preheating block 7 (with respect to the path of the molding material 4 through the injection molding device 1). Therefore, the needle valve 8 is directly located at the channel-shaped part of the cavity 11 in the cross-linking tool 3. This can more effectively prevent the rubber backflow that occurs during the injection process.

[0101] exist Figure 6 , a longitudinal sectional view of an injection molding device 1 of the present invention according to another embodiment is shown. Figure 6 The injection molding device 1 basically corresponds to Figure 4 The injection molding device 1 is different in that, according to Figure 6 In the embodiment of the present invention, the preheating blocks 7 each have a sub-distributor 16. With the help of the sub-distributor 16, the molding material 4 can be distributed from the preheating channel to a plurality of injection points of the cavities 11 of the cross-linking tool. The sub-distributor 16 can also be part of the preheating base tool 19 or can be designed as a separate component within the preheating assembly 5. In principle, it is also conceivable to arrange the sub-distributor 16 within the cross-linking tool ("hot runner sub-distribution"; not shown).

[0102] Figure 7 The time-viscosity curve of the elastomeric molding material 4 in relation to the test temperatures T1, T2, T3 is shown. Here, the Mooney viscosity V of the molding material 4 is plotted along the ordinate. m Time t is represented by the horizontal axis. Finally, the vertical line t v represents the preheating time for preheating the molding material 4. Here, the preheating time t v The total cycle time should not be extended; therefore, the warm-up time t v The time is mainly determined by the time required to achieve the optimal crosslinking degree of the component in the crosslinking tool 3. Under the first test temperature T1, it can be seen from the graph that the measured viscosity V m Its minimum value is not reached. Therefore, no crosslinking of the molding material 4 occurs during the observation period. Therefore, the selected first test temperature T1 is low enough to be used as a preheating temperature, because the molding material 4 is prevented from crosslinking in the preheating assembly 5. However, the test temperature T1 is not suitable as a preferred preheating temperature in the sense of the present invention, because the crosslinking of the molding material that occurs after the preheating of the molding material is hardly accelerated.

[0103] In contrast, at the test temperature T3, during the preheating time t v Before the end, the viscosity V of the molding material 4 has been reached m Therefore, the test temperature T3 is also not suitable as a preheating temperature in the sense of the present invention, because at this preheating temperature, the molding material 4 has already (at least partially) crosslinked or vulcanized in the preheating component.

[0104] on the other hand, Figure 7 The test temperature T2 in the graph is very suitable as the preheating temperature. Finally, T2 is selected so that the molding material v Crosslinking has just not started or has only started slightly, while the viscosity has not increased significantly relative to the minimum value M, i.e. not more than 20%. m The minimum value M is only during the warm-up period t vThe viscosity of the crosslinking tool 3 is not increased by more than 20% compared to the minimum value M. The crosslinking temperature T2 is reached shortly before the end of the preheating time and increases significantly again only after the end of the preheating time. In other words: At a preheating temperature corresponding essentially to T2, the molding material 4 is heated in the preheating component 5 as close as possible to the desired crosslinking temperature without vulcanizing in the preheating component 5 or, if crosslinking has just begun, the degree of crosslinking is still so low that the viscosity does not increase by more than 20% relative to the minimum value M. Accordingly, the actual vulcanization of the molding material 4 can take place at maximum speed in the crosslinking tool 3, since the molding material is already injected into the crosslinking tool 3 at the highest temperature.

[0105] The present invention is not limited to any one of the above-described embodiments but may be modified in various ways.

[0106] All features and advantages arising from the description and the drawings, including construction details, spatial arrangements and method steps, either alone or in any combination, may be the subject matter of the invention.

Claims

1. An injection molding device (1) for manufacturing an elastomeric component, wherein: The injection molding device (1) comprises an injection component (2) having a nozzle (18) and a cross-linking tool (3) for cross-linking a molding material (4), wherein the injection component (2) is used to inject the molding material (4) of an elastomer, wherein the injection component (2) is designed to heat the molding material (4) to a material temperature, and wherein the cross-linking tool (3) is designed to heat the molding material (4) to a cross-linking temperature, and is characterized in that the injection molding device (1) comprises a preheating component (5), wherein the preheating component (5) is designed to heat the molding material (4) to a preheating temperature, wherein the preheating temperature in the preheating component (5) is higher than the material temperature in the injection component (2) and lower than the cross-linking temperature in the cross-linking tool (3).

2. The injection molding device (1) according to claim 1, characterized in that The preheating assembly (5) comprises at least one needle valve nozzle (6) having a needle valve (8).

3. The injection molding device (1) according to claim 1 or 2, characterized in that: The preheating temperature in the preheating component (5) is higher than the exit temperature of the molding material and lower than the cross-linking temperature in the cross-linking tool (3), wherein the exit temperature is the temperature of the molding material (4) generated by shear force when the molding material leaves the nozzle (18) of the injection component (2).

4. Injection molding device (1) according to any one of the preceding claims, characterized in that The injection component (2), the preheating component (5) and the cross-linking tool (3) are respectively independent building blocks, and these building blocks can be assembled into the injection molding device (1).

5. Injection molding device (1) according to any one of the preceding claims, characterized in that The cross-linking tool (3) comprises at least one cavity (11) in which the molding material (4) is formed into an elastomeric component at the cross-linking temperature.

6. Injection molding device (1) according to any one of the preceding claims, characterized in that The preheating assembly (5) comprises at least one preheating block (7) and at least one preheating base tool (19), wherein the at least one preheating block (7) can be inserted into the at least one preheating base tool (19).

7. The injection molding device (1) according to claim 6, characterized in that The at least one preheating block (5) comprises a preheating channel (9).

8. The injection molding device (1) according to claim 7, characterized in that The volume of the at least one preheating channel (9) is less than or equal to the volume of the at least one cavity (13) of the cross-linking tool (3) associated therewith.

9. The injection molding device (1) according to any one of claims 1 to 5, characterized in that: The at least one preheating channel (9) is designed in an S-shape and / or a serpentine shape, a meander shape and / or a spiral shape and / or a zigzag shape and / or a ramp shape and / or in the form of a stacked flat area.

10. The injection molding device (1) according to any one of claims 6 to 9, characterized in that The injection molding device (1) comprises a distributor (10) designed to distribute the molding material (4) to two or more preheating blocks (7) or two or more cavities (11).

11. The injection molding device (1) according to any one of claims 7 to 10, characterized in that The preheating block, the at least one preheating base tool (19), comprises a sub-distributor (16) designed to distribute the molding material (4) from the preheating channel (9) to two or more cavities (11).

12. The injection molding device (1) according to any one of claims 7 to 11, characterized in that The injection molding device (1) comprises at least one non-return valve (12), which is arranged between the preheating channel (9) and the cross-linking tool (3).

13. The injection molding device (1) according to claim 12, characterized in that The injection molding device (1) comprises at least one cooling insert (13), wherein the cooling insert (13) is arranged in particular in the cross-linking tool (5) and wherein each cooling insert (13) at least partially surrounds one of the non-return valves (12) and / or is at least partially thermally decoupled from the cross-linking tool (3).

14. Injection molding device (1) according to any one of the preceding claims, characterized in that The preheating temperature is selected from a temperature range within which the shear viscosity of the molding material (4) reaches a minimum value (M) at the earliest after a preheating time of 5 minutes, wherein the shear viscosity of the molding material (4) increases by 20% relative to its minimum value (M) at the latest after 20 minutes.

15. A preheating assembly (5) of an injection molding device (1) for manufacturing an elastomeric part, characterized in that The preheating component (5) heats the molding material (4) to a preheating temperature, wherein the preheating temperature is selected from a temperature range within which the shear viscosity of the molding material (4) reaches a minimum value (A) at the earliest after a preheating time of 5 minutes, wherein the shear viscosity of the molding material (4) increases by 20% relative to its minimum value (A) at the latest after 20 minutes.

16. A method for producing an elastomeric component using an injection molding device (1) according to any one of claims 1 to 14, wherein: The injection molding device (1) comprises a cross-linking tool (3), an injection assembly (2) for injecting a molding material (4) into the cross-linking tool (3), and a preheating assembly (5), wherein the method comprises the following steps: a) filling the injection component (2) tempered to the material temperature with the molding material (4); b) heating the molding material (4) to the material temperature by means of heat input from the injection assembly (2) by heat transfer; c) transferring the molding material (4) heated to the material temperature from the injection assembly (2) to the preheating assembly (5); d) heating the molding material (4) to the preheating temperature in the preheating assembly (5); e) transferring the molding material (4) from the preheating assembly (5) to the cross-linking tool (3); f) heating the molding material (4) in the crosslinking tool (3) from the preheating temperature to the crosslinking temperature, The preheating temperature is selected from a temperature range within which the shear viscosity of the molding material (4) reaches a minimum value (M) at the earliest after a preheating time of 5 minutes, and the shear viscosity of the molding material (4) increases by 20% relative to its minimum value (M) at the latest after 20 minutes.

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