Injection molding machine, silicone injection molding adapter and method for injection molding silicone workpieces

Abstract

The present invention relates to an injection molding machine (1) comprising a machine frame (3), a clamping unit (4) with two clamping plates (8r, 8l), an injection unit (5), an injection unit actuator (6) by means of which the injection unit (5) can be moved along the machine frame (3), a mold (7), and a silicone injection molding adapter (2) arranged between a mold half (14r) and a clamping plate (8r) for injecting silicone into the mold (7). The silicone injection molding adapter (2) has an adapter body (22) and an adapter piston (23). The adapter body (22) comprises a silicone transfer chamber (29), a closable inlet channel (31) through which silicone can be fed to the silicone transfer chamber (29), and an injection channel (33) through which silicone can be injected from the silicone transfer chamber (29) into the mold (7).The adapter piston (23) is slidably mounted in the silicone transfer chamber (29), and by moving the adapter piston (22), silicone can be injected from the silicone transfer chamber (29) via the injection channel (33) into the mold (7). The adapter piston (23) can be pushed into the silicone transfer chamber (29) of the adapter body (22) by moving the injection unit (5) using the injection unit actuator (6).

Description

[0001] The present invention relates generally to an injection molding machine with a machine frame, a clamping unit arranged on the machine frame with two clamping plates, an injection unit with a cylinder housing, a screw shaft movable in the cylinder housing and a plasticizing volume extending between the cylinder housing and the screw shaft and a mold with two mold halves, each of which is assigned to one of the clamping plates, and in particular, to a silicone injection molding adapter and a method for injection molding silicone workpieces

[0002] Such injection molding machines are typically used for injection molding conventional plastics such as elastomers, thermosets or thermoplastics.

[0003] Typically, plastic granules are filled into the (screw) flights of the rotating screw shaft of the injection unit and heated to melting temperature and melted in the injection unit by rotating the screw shaft in the cylinder housing and the resulting frictional heat, and if necessary by additional heating of the cylinder housing. The volume extending between the cylinder housing and the screw shaft is referred to as the plasticizing volume.

[0004] The flowable plastic melt now collects within the plasticizing volume in an area that extends between the screw tip and the tool mold, since at this point an outlet through which the melt could escape from the cylinder housing is typically still closed.

[0005] Since the screw shaft is typically mounted so that it can move axially, it retreats due to the pressure building up in the area of ​​the screw tip and screws itself out of the plastic melt like a corkscrew, so that the flowable plastic melt accumulates between the screw tip and the tool mold.

[0006] The backward movement of the screw shaft is specifically slowed down in order to build up the desired back pressure in the plastic melt.

[0007] As soon as a sufficient volume of plastic melt has accumulated in the plasticizing volume in front of the screw tip for the workpiece to be injected, the screw shaft is moved axially in the direction of the clamping plates by means of a screw shaft actuator.

[0008] As a result, the plastic melt located in front of the screw tip in the plasticizing volume is sprayed (pressed out) from the injection unit through a nozzle and injected through the mold half facing the injection unit into a cavity of the adjacent mold.

[0009] The plastic melt then solidifies into a solid in the mold. For thermoplastics, this typically occurs through cooling, while for thermosets and elastomers, it typically occurs through heating.

[0010] The two molds, each located on one of the two clamping plates, are then lifted apart by the clamping unit, and the solidified plastic body, the workpiece, is removed from the mold. After this demolding, the mold closes again, and the (injection molding) cycle begins again.

[0011] The injection unit, including the cylinder housing and screw shaft, is typically movable along the machine frame relative to the clamping unit by means of an injection unit actuator. The injection unit actuator serves to press the injection unit (more precisely, the nozzle of the injection unit) against the mold half located on the clamping platen facing the injection unit.

[0012] The contact force transmitted from the injection unit actuator via the injection unit to the mold half must be sufficiently large to ensure that no plastic melt escapes between the injection unit and the mold half during the injection process.

[0013] The injection unit can be removed (lifted) from the clamping unit by means of the injection unit actuator by moving the injection unit away from the clamping unit.

[0014] Such injection molding machines are typically designed to process specific materials and material quantities by adapting the geometry of the screw shaft and the cylinder housing.

[0015] In recent times, the production of workpieces made of silicone (silicone workpiece) using the injection molding process has become more and more important.

[0016] However, the injection molding process for silicones differs fundamentally from the injection molding process for conventional plastics such as thermoplastics, thermosets and elastomers.

[0017] A key difference is that silicone is already fed into the injection molding machine in a flowable (liquid) form, meaning it no longer needs to be melted, and that conveying the liquid silicone through an injection unit with a screw shaft, which would heat and shear the silicone, would lead to an undesirable deterioration of the material properties.

[0018] US patent application US 2019 210 260 A1 describes an injection molding machine with an injection system and a clamping system, wherein the injection system includes a removable injection module. The injection module comprises all parts that come into contact with the injection molding material and contains a valve arrangement that can switch between a filling position for loading the injection module with material and an injection position for ejecting material from the injection module into the mold.

[0019] DE 11 2021 007 370 T5 describes an injection device that is capable of injecting a certain amount of a resin material during each injection process, while preventing air from entering a cylinder.

[0020] Against this background, injection molding machines designed for processing thermoplastics, thermosets and / or elastomers (conventional injection molding machines) are generally not or only very poorly suited for processing silicone and the production of silicone workpieces.

[0021] And even if it might theoretically be possible to inject silicone into a mold like conventional plastic melt using a conventional injection molding machine, the downstream cleaning effort would at least be very high, which would make the use of a conventional injection molding machine for the production of small quantities of silicone workpieces even less attractive.

[0022] For the processing of silicone by injection molding, additional silicone injection molding machines designed specifically for this application are typically purchased, which is associated with relatively high costs and additional space requirements.

[0023] Against this background, the object of the present invention is to provide an injection molding machine of the type described above with improved practical suitability, which on the one hand is designed and suitable for the processing of conventional plastics such as thermosets, thermoplastics and elastomers, but on the other hand can also be quickly and easily converted and used for the processing of silicone.

[0024] This object is achieved by the injection molding machine according to claim 1, the silicone injection molding adapter according to claim 9 and the method for injection molding silicone workpieces according to claim 10.

[0025] Particularly advantageous embodiments of the invention are described in the subclaims. The characterizing features of the advantageous embodiments described in connection with the injection molding machine according to the invention can, of course, also be used in the silicone injection molding adapter according to the invention and in the method according to the invention.

[0026] The injection molding machine according to the invention comprises - a machine frame, - a clamping unit arranged on the machine frame with two clamping plates, - an injection unit with a cylinder housing, a screw shaft movable in the cylinder housing and a plasticising volume extending between the cylinder housing and the screw shaft, - an injection unit actuator, by means of which the injection unit together with the cylinder housing and the screw shaft can be moved along the machine frame relative to the clamping unit, - a tool mould with two tool mould halves, each of which is assigned to one of the two clamping plates, - a silicone injection molding adapter arranged between one of the two mold halves and one of the two clamping plates for injecting silicone into the mold, where - the silicone injection molding adapter has an adapter body and an adapter piston, - the adapter body comprises a silicone transfer chamber, a closable inlet channel through which silicone can be fed into the silicone transfer chamber, and an injection channel through which silicone can be injected from the silicone transfer chamber into the tool mold, - the silicone transfer chamber is fluidically separated from the plasticizing volume of the injection unit, - the adapter piston is mounted displaceably in the silicone transfer chamber and by moving the adapter piston, silicone can be injected from the silicone transfer chamber via the injection channel into the tool mould, and - the adapter piston can be inserted into the silicone transfer chamber of the adapter body by moving the injection unit using the injection unit actuator.

[0027] The invention is based on the finding that by using a silicone injection molding adapter according to the invention, which is arranged between one mold half and one of the two clamping plates, a conventional injection molding machine, which has a screw shaft for plasticizing conventional plastics, such as thermoplastics, thermosets and elastomers, and is thus specifically designed for processing such plastics, can be quickly and easily converted to process silicone in the injection molding process.

[0028] The conversion is just as easy as inserting a new tool shape into the clamping unit.

[0029] To inject the silicone into the mold (more precisely, into the cavity of the mold), the injection unit actuator already present in the conventional injection molding machine is used according to the invention.

[0030] The injection unit actuator, which is used in the processing of conventional plastics to press the nozzle of the injection unit against one half of the mold, is used in a somewhat "mispurposed" way in the processing of silicone to push the adapter piston into the adapter body and in this way to inject silicone from the silicone transfer chamber into the mold.

[0031] By moving the injection unit towards the adapter body using the injection unit actuator, the adapter piston can be pushed further into the adapter body and thus silicone located in the silicone transfer chamber can be injected into the tool mold via the injection channel.

[0032] If the injection unit is moved away from the adapter body again at a later point in time by the injection unit actuator, the injection unit lifts off the adapter piston again (lifting of the injection unit from the adapter piston).

[0033] When processing silicone, the injection of silicone into the tool mold is expressly not carried out by an axial movement of the screw shaft within the cylinder housing (by means of a screw shaft actuator), but by a movement of the entire injection unit including the cylinder housing by means of the injection unit actuator.

[0034] The processed silicone never enters the plasticizing chamber of the injection unit. The silicone transfer chamber of the adapter body is fluidically separated from the plasticizing chamber of the injection unit.

[0035] The processed silicone is therefore never in direct contact with the screw shaft or the inner wall of the cylinder housing during the injection process. Cleaning the injection unit after silicone processing is therefore not necessary. This represents an extreme simplification, as cleaning the screw shaft and cylinder housing typically requires the laborious disassembly and cleaning of the entire injection unit.

[0036] Furthermore, this method can significantly reduce silicone consumption, especially the silicone waste generated during production. Because the silicone does not come into contact with the screw shaft and the relatively large plasticizing volume, the amount of waste silicone—that is, the silicone that remains in the injection molding machine after silicone processing and must be removed during cleaning—can be significantly reduced.

[0037] In the following, some aspects and features of the injection molding machine according to the invention are explained and defined in more detail: The clamping unit has two clamping plates that can be moved toward and away from each other using a clamping actuator. The two mold halves are each assigned to one of the two clamping plates and can be moved together with this clamping plate.

[0038] By moving the two clamping platens toward each other, the mold can be closed with the two mold halves. By moving the two clamping platens apart, the two mold halves can be lifted apart, allowing the mold to be reopened for the removal of a workpiece. Removing a workpiece from an open mold is also known as demolding.

[0039] The adapter body and the adapter piston define a piston chamber, the volume of which varies depending on how far the adapter piston is inserted into the adapter body. By inserting the adapter piston into the adapter body, the piston chamber volume can be reduced and any silicone contained in the piston chamber can be forced out of the piston chamber through the injection channel.

[0040] Filling the silicone transfer chamber with silicone via the inlet channel means feeding silicone into the silicone transfer chamber via the inlet channel. When the silicone transfer chamber is filled with silicone, the volume of the silicone in the silicone transfer chamber increases, causing the adapter piston to be at least partially pushed out of the adapter body (displacing the adapter piston from the adapter body).

[0041] Because the adapter piston is displaced by the silicone flowing into the transfer chamber, (virtually) no air enters the silicone transfer chamber. This is a major advantage for the quality and reproducibility of the silicone injection molding process, as it prevents air pockets in the silicone workpiece.

[0042] The formulation that the silicone transfer chamber is fluidically separated from the plasticizing volume of the injection unit expresses that, within the scope of the invention, there is no fluidic connection between the silicone transfer chamber and the plasticizing volume, i.e., within the scope of the invention, no fluid flows from the plasticizing volume into the silicone transfer chamber (or vice versa).

[0043] In particular, a 2-component silicone is used, the two components of which are mixed into a homogeneous silicone by means of a static mixing tube immediately before being fed into the silicone transfer chamber (via the inlet channel).

[0044] According to a particularly preferred embodiment - the silicone injection molding adapter includes a shut-off valve, and - the shut-off valve is arranged in the inlet channel and the inlet channel can be closed using the shut-off valve.

[0045] By opening the shut-off valve in the inlet channel, the shut-off valve is switched so that silicone can flow through the shut-off valve.

[0046] To fill the silicone transfer chamber with the silicone to be processed and injected into the mold, the shut-off valve in the inlet channel is opened. The silicone to be processed is poured into the inlet channel using a hand press or an (electrically, pneumatically, or hydraulically driven) feeder, for example, passes through the open shut-off valve, and enters the piston chamber or silicone transfer chamber through the inlet channel. The silicone flowing into the silicone transfer chamber displaces the adapter piston from the adapter body, thus pushing the adapter piston out of the adapter body.

[0047] As soon as the desired amount of silicone has flowed into the silicone transfer chamber, the shut-off valve in the inlet channel is closed. This prevents any further flow of silicone through the inlet channel and also prevents silicone from escaping from the silicone transfer chamber via the inlet channel during injection into the mold.

[0048] If the mold is still closed during this phase of filling the silicone transfer chamber through the inlet channel and the workpiece manufactured in the previous injection molding cycle is still in the mold, it is possible to prevent silicone from undesirably entering the mold during this phase without using an additional valve in the injection channel.

[0049] When the silicone transfer chamber is filled, no more silicone is supplied. This can be done, for example, by closing the inlet channel using the shut-off valve.

[0050] Furthermore, it can be advantageously provided that the silicone injection molding adapter has a heat insulation plate which is arranged between the adapter body and the mold half closest to the adapter body.

[0051] In this way, the intensity of heat exchange between the tool mold and the adapter body can be reduced.

[0052] The silicones used in injection molding typically cure by heating. For this reason, cooling channels (or cooling elements) are sensibly provided in the adapter body to prevent premature curing of the silicone contained in the adapter body and thus ensure its flowability. Heating channels (or heating elements) are sensibly provided in the mold to properly cure the injected silicone into a workpiece. The thermal insulation plate impedes heat exchange between the adapter body and the mold. This prevents silicone from undesirably curing within the adapter body or from curing too slowly or not at all within the mold. This is beneficial to the quality of the manufactured component and process stability.

[0053] In this context, the adapter body has particularly advantageous coolant channels.

[0054] The undesirable heat exchange between the adapter body and the tool shape can be further reduced by - the silicone injection molding adapter has an injection nozzle, - the injection channel extends at least partially through the injection nozzle, - the injection nozzle is arranged in a corresponding recess of the adapter body and / or a corresponding recess of the adjacent tool mold half, and - an annular space (particularly one filled with air) extends between the injection sleeve and the recess of the adapter body and / or the recess of the tool mould half.

[0055] In particular, the (air-filled) annular space between the relatively cold injection nozzle and the relatively warm mold half acts as an insulator and prevents unwanted heat exchange.

[0056] It is particularly advantageous if - the injection nozzle has an external thread and the corresponding recess of the adapter body has a corresponding internal thread, so that the injection nozzle can be screwed into the corresponding recess of the adapter body, and / or - the injection nozzle is tapered towards its end face facing the mold half (in order to further reduce the thermal conductivity between the mold half and the injection nozzle).

[0057] In this way, the desired heat exchange between the injection nozzle and the adapter body can be improved, and consequently, the temperature of the injection sleeve (with appropriate cooling of the adapter body) can be further reduced. This prevents unwanted curing of the silicone in the injection channel (or in the injection sleeve), which can lead to blockage of the injection channel and require time-consuming cleaning.

[0058] According to a particularly preferred embodiment of the invention, the geometry of the injection nozzle and the intensity of the cooling of the adapter body or the placement of cooling channels / cooling elements provided there (and / or the intensity of the heating of the tool mold or the placement of heating channels / heating elements provided there) are adjusted so that when the silicone hardens in the tool mold, the silicone in the injection channel hardens to form a sprue plug only in a small channel section that borders the mold cavity, while the silicone in the remaining area of ​​the injection channel is sufficiently cooled so that it remains liquid or flowable.

[0059] When the cured workpiece is removed from the open mold during demolding, the silicone that has cured to form the sprue plug is pulled out of the injection channel along with the workpiece. This allows flowable silicone to be injected into the mold again in the subsequent injection molding cycle.

[0060] However, removing the (complete) sprue plug along with the workpiece during demolding is only possible if the sprue plug does not exceed a certain maximum length, i.e., if it does not extend too far into the injection channel. Otherwise, the sprue plug will tear during demolding of the workpiece, leaving a residual plug in the injection channel. If sufficiently long, this plug will prevent flowable silicone from flowing through during the next injection molding cycle, thus necessitating cleaning of the injection channel.

[0061] The geometry of the injection nozzle, the design of the cooling of the adapter body and the heating of the tool mold as well as the other process parameters must therefore be selected in such a way that the sprue plug does not exceed a permissible maximum length.

[0062] According to a further advantageous embodiment of the invention, the inlet channel does not penetrate either of the two clamping plates.

[0063] In this way, a silicone injection molding adapter can be realized with which an existing injection molding machine can be retrofitted particularly easily, since the structurally complex routing of the inlet channel through a possibly already existing opening in a clamping plate can be omitted.

[0064] In order to be able to adapt the amount of silicone to be injected and / or the injection pressure to be applied simply and quickly to the respective application, according to a further advantageous embodiment of the invention it can be provided that - the silicone injection molding adapter has a piston sleeve arranged in the adapter body, which at least partially delimits the silicone transfer chamber, and - the adapter piston is slidably mounted in the piston sleeve, and optionally - the piston sleeve is fixed in the adapter body by means of a quick-release fastener and can be replaced.

[0065] The piston sleeve and the associated adapter piston are matched to each other in such a way that the adapter piston can be moved within the piston sleeve and both components seal against each other with regard to the silicone to be processed.

[0066] By using an adapter piston with a smaller (effective) piston cross-section, the injection pressure with which silicone is injected from the silicone transfer chamber through the injection channel into the tool mold can be increased - with the same force exerted by the injection unit actuator via the injection unit onto the adapter piston.

[0067] The maximum injection pressure can thus be influenced by the diameter of the adapter piston or the (effective) piston cross-section. The effective piston cross-section refers to the cross-sectional area of ​​the area of ​​the adapter piston that can be inserted into the piston sleeve.

[0068] A smaller effective piston cross-section leads to a higher maximum injection pressure, a larger effective piston cross-section leads to a lower maximum injection pressure.

[0069] Different piston sleeve-adapter piston pairings can be kept in stock and used to achieve different effective piston cross-sections and thus different maximum injection pressures.

[0070] The quick release allows for easy and quick replacement of a piston sleeve-adapter piston pairing.

[0071] The present invention further manifests itself in a silicone injection molding adapter according to the invention, which is suitable for use in an injection molding machine according to the invention.

[0072] Furthermore, the invention manifests itself in a method according to the invention for injection molding silicone workpieces with an injection molding machine according to the invention with the following steps: A) Closing the tool mold by the clamping unit, B) Lifting the injection unit off the adapter piston by moving the injection unit away from the clamping unit using the injection unit actuator, C) Filling the silicone transfer chamber with silicone via the inlet channel, whereby the silicone entering the silicone transfer chamber causes an increasing displacement of the adapter piston from the adapter body, D) Finish filling the silicone transfer chamber, E) Opening the mold by the clamping unit and removing the silicone workpiece located in the mold, F) Closing the tool mould by the clamping unit, and G) Injecting silicone from the silicone transfer chamber through the injection channel into the tool mold by moving the injection unit using the injection unit actuator and thereby inserting the adapter piston into the adapter body.

[0073] The process steps A) to G) (or B) to G) of the process according to the invention form a complete cycle or injection cycle, which can be repeated as often as desired.

[0074] When running through an injection cycle, one silicone workpiece (or a large number of silicone workpieces) can be produced at a time.

[0075] For clarity, the terms "silicone workpiece" and "workpiece" will be referred to in the singular below. However, it is clear to the skilled person, even without further explanation, that with an appropriate mold design, several silicone workpieces can be manufactured simultaneously in one injection cycle.

[0076] In step E), the silicone workpiece produced in the previous injection cycle is removed from the mold.

[0077] By removing the silicone workpiece only after the silicone transfer chamber has been refilled, it can be ensured that no silicone flows into the mold while the silicone transfer chamber is being filled with silicone, since the workpiece from the previous injection cycle still fills the cavity of the mold and thus prevents further silicone from flowing in.

[0078] There is therefore no need to actively close the injection channel using a separate valve.

[0079] When the silicone workpiece is removed, the silicone that has hardened into a sprue in the injection channel is also removed. The injection channel is thus reopened, allowing flowable silicone to be injected into the mold again.

[0080] It is in the nature of things that during the first injection cycle, there is no silicone workpiece from the previous injection cycle present in the mold, which would close the injection channel while the silicone transfer chamber is being filled. Therefore, the following steps should be followed when running the first injection cycle: - Closing the tool mold by the clamping unit, - Lifting the injection unit off the adapter piston by moving the injection unit away from the clamping unit using the injection unit actuator, - Filling the silicone transfer chamber with silicone via the inlet channel, whereby the silicone entering the silicone transfer chamber causes an increasing displacement of the adapter piston from the adapter body, - Finish filling the silicone transfer chamber, - Injecting silicone from the silicone transfer chamber through the injection channel into the tool mold by moving the injection unit using the injection unit actuator and thereby pushing the adapter piston into the adapter body. - Curing of the workpiece in the tool mold, especially for about 1 to 5 minutes.

[0081] The method according to the invention for injection molding silicone workpieces with its steps A) to G) can then be carried out in any number of cycles.

[0082] When the silicone transfer chamber is first filled, a portion of the silicone will already flow into the mold. This effect can be taken into account when determining the amount of silicone to be added via the feed channel during the initial filling of the silicone transfer chamber.

[0083] According to a preferred embodiment of the method according to the invention - the method comprises a step B1) in which the shut-off valve in the inlet channel is opened before the silicone transfer chamber is filled with silicone via the inlet channel in accordance with step C), and - according to step D), the completion of filling of the silicone transfer chamber comprises closing the shut-off valve in the inlet channel.

[0084] Some embodiments of the invention are explained in more detail below with reference to the drawings. Fig. 1 a schematic side view of an injection molding machine according to the invention with a silicone injection molding adapter shown in a sectional view, Fig. 2 an enlarged sectional view of the silicone injection molding adapter according to Fig. 1, Fig. 3 the silicone injection molding adapter according to Fig. 2 in an exploded view, and Fig. 4 a flow diagram of a method according to the invention for injection molding silicone workpieces with an injection molding machine according to the invention.

[0085] Fig. 1 shows a schematic side view of an injection molding machine 1 according to the invention with a silicone injection molding adapter 2 shown in sectional view. Fig. 2 and Fig. 3 shows the silicone injection molding adapter 2 again enlarged or in an exploded view.

[0086] The injection molding machine 1 comprises a machine frame 3, a clamping unit 4 arranged on the machine frame 3, an injection unit 5, an injection unit actuator 6, a mold 7 and the silicone injection molding adapter 2.

[0087] The clamping unit 4 has two clamping plates 81, 8r and a closing actuator 9, by means of which the two clamping plates 81, 8r can be moved towards each other and away from each other. The right of the two in Fig. The clamping plate shown in Figure 1 (right clamping plate 8r) is immovably attached to the machine frame 3 (by means of a fixed bearing FL), while the left of the two clamping plates (left clamping plate 81) is mounted (by means of a loose bearing LL) so that it can move linearly along the x-axis x relative to the machine frame 3. The right clamping plate 8r has an opening 36 into which an annular cover 43 is inserted.

[0088] The injection unit 5 is mounted by means of a loose bearing LL along the x-axis x relative to the machine frame 3 and comprises a cylinder housing 10 with a nozzle 11, a screw shaft 12 movable in the cylinder housing 10 and a plasticizing volume 13 extending between the cylinder housing 10 and the screw shaft 12.

[0089] The injection unit actuator 6 allows the injection unit 5 together with the cylinder housing 10 and the screw shaft 12 to be moved linearly along the x-axis relative to the machine frame 3.

[0090] The mold 7 has two mold halves 141, 14r, each assigned to one of the two clamping plates 81, 8r, and between which a cavity 15 extends, into which silicone can be supplied via a mold channel 16. The silicone curing in the mold 7 forms a (silicone) workpiece 17, which can be removed from the mold 7 when it is opened.

[0091] The left of the two mold halves (left mold half 141) is attached to the left clamping plate 81, the right of the two mold halves (right mold half 14r) is attached to the silicone injection molding adapter 2.

[0092] The right mold half 14r has an insert 19 inserted into a corresponding receptacle 18, through which the mold channel 16 extends. However, the insert 19 and the right mold half 14r could also be constructed as a single piece.

[0093] Furthermore, heating channels 20 for heating the silicone located in the tool mold 7 and release pins 21 for ejecting a solidified workpiece 17 from the tool mold 7 are provided in the right tool mold half 141, 14r.

[0094] The silicone injection molding adapter 2 comprises an adapter body 22, an adapter piston 23, a piston sleeve 24, a shut-off valve 25, a heat insulation plate 26 and an injection nozzle 27.

[0095] The adapter body 22 is arranged between the right clamping plate 8r and the right mold half 14r and has a recess 28 into which the piston sleeve 24 is received, within which a silicone transfer chamber 29 extends. The adapter body 22 is penetrated by several coolant channels 30 through which a coolant can be circulated.

[0096] Silicone can be supplied to the silicone transfer chamber 29 via an inlet channel 31. The shut-off valve 25 is located in the inlet channel 31. By turning the shut-off valve 25, the inlet channel 31 can be closed or opened (unlocked).

[0097] Silicone can be injected from the silicone transfer chamber 29 into the cavity 15 of the tool mold 7 (i.e., into the tool mold) via an injection channel 33 (and the tool mold channel 16).

[0098] The silicone transfer comb 29 is fluidically separated from the plasticizing volume 13 of the injection unit 5.

[0099] The piston sleeve 24 is fixed in the recess 28 of the adapter body in the x-direction by means of a sleeve collar 34 and two easy-to-open quick-release fasteners 35.

[0100] The adapter piston 23 penetrates the opening 36 of the right clamping plate 8r, is slidably mounted in the piston sleeve 24 or in the silicone transfer chamber 29, and can be partially inserted into the piston sleeve 24. A piston collar 37 limits the maximum insertion depth of the adapter piston 23 into the piston sleeve 24 when it abuts the end face of the piston sleeve 24.

[0101] The injection nozzle 27 has a through-bore 38 through which the injection channel 33 extends. In a part facing the adapter body 22, the injection nozzle 27 has an external thread 39, by means of which the injection nozzle 27 is screwed into a corresponding recess 40 of the adapter body 22, provided with an internal thread. A part of the injection nozzle 27 facing the tool mold 7 projects into a corresponding recess 41 of the adjacent right-hand tool mold half 14r (or into the corresponding recess 41 of the insert 19 of the right-hand tool mold half 14r). Air-filled annular spaces 42 extend between the recess 40 of the right-hand tool mold half 14r and the injection nozzle 27.

[0102] The heat insulation plate 26 is arranged between the adapter body 22 and the right mold half 14r and has an opening through which the injection nozzle 27 extends.

[0103] The injection molding machine 1 according to the invention is shown in Fig. 4 as a flow chart and described below, is used for the injection molding of silicone workpieces (17): First, in step A (110), the mold 7 is closed by the closing unit 4 by moving the two mold halves 141, 14r towards each other and pressing them together by the closing actuator 9.

[0104] According to step B (120), the injection unit 5 is lifted from the adapter piston 23 of the silicone injection molding adapter 2 by moving the injection unit 5 away from the clamping unit 4 by the injection unit actuator 6. The injection unit 5 is shown in accordance with Fig. 1 move to the right.

[0105] According to step B1 (125), the shut-off valve 25 in the inlet channel is opened.

[0106] Subsequently, in step C (130), the silicone transfer chamber 29 is filled with flowable silicone via the inlet channel 31. The silicone entering the silicone transfer chamber 29 causes a partial displacement of the adapter piston 23 from the adapter body 22. The adapter piston 23 is thereby shown in the illustration according to Fig. 1 partially pushed out of the adapter body 22 to the right.

[0107] When the intended amount of silicone has flowed into the silicone transfer chamber 29, the filling of the silicone transfer chamber 29 is terminated according to step D (140) by closing the shut-off valve 25 in the inlet channel 31.

[0108] Subsequently, in step E (150), the mold 7 is opened by the clamping unit 4 using the closing actuator 9, and the silicone workpiece 17 located in the mold 7 is removed from the opened mold 7 (using the release pins 21). The silicone, which solidified into the silicone workpiece 17, was injected into the mold 7 in the previous injection molding cycle.

[0109] Subsequently, according to step F (160), the tool mold 7 is closed again by the closing unit 4 by means of the closing actuator 9.

[0110] Subsequently, in step G (170), the silicone is injected from the silicone transfer chamber 29 through the injection channel 33 (and the tool mold channel 16) into the (initially still) empty cavity 15 of the tool mold 7 by moving the injection unit 5 in the direction of the tool mold 7 by the injection unit actuator 6, so that first the nozzle 11 of the cylinder housing 10 of the injection unit 5 rests against the adapter piston 23 and then the adapter piston 23 is pushed into the piston sleeve 24, whereby the silicone is pressed out of the silicone transfer chamber 29.

[0111] The silicone injected into the mold 7 then solidifies into a silicone workpiece 17 and can be removed in the next injection molding cycle in step E. Reference symbol 1 injection molding machine 2 silicone injection molding adapters 3 machine frames 4 locking unit 5 Injection unit 6 Injection unit actuator 7 Tool shape 8r right clamping plate 81 left clamping plate 9 Closing actuator 10 cylinder housings 11 Nozzle 12 Worm shaft 13 Plasticizing volume 141 left tool mold half 14r right tool mold half 15 cavity 16 tool mold channel 17 (silicone) workpiece 18 recording 19 deployment 20 heating channels 21 release pins FL fixed bearing LL loose bearing 22 adapter body 23 adapter pistons 24 piston sleeve 25 Shut-off valve 26 Thermal insulation board 27 Injection nozzle 28 recess 29 Silicone transfer chamber 30 coolant channels 31 Inlet channel 33 Injection channel 34 sleeve collar 35 quick release 36 Breakthrough 37 piston collar 38 bore 39 external thread 40, 41 recess 42 annular space 43 annular aperture

Claims

[1] Injection molding machine (1) comprising - a machine frame (3), - a clamping unit (4) arranged on the machine frame (3) with two clamping plates (8r, 81), - an injection unit (5) with a cylinder housing (10), a screw shaft (12) movable in the cylinder housing (10) and a plasticising volume (13) extending between the cylinder housing (10) and the screw shaft (12), - an injection unit actuator (6), by means of which the injection unit (5) together with the cylinder housing (10) and the screw shaft (12) can be moved along the machine frame (3) relative to the clamping unit (4), - a tool mould (7) with two tool mould halves (14r, 141), each of which is assigned to one of the two clamping plates (8r, 81), - a silicone injection molding adapter (2) arranged between one of the two mold halves (14r) and one of the two clamping plates (8r) for injecting silicone into the mold (7), wherein - the silicone injection molding adapter (2) has an adapter body (22) and an adapter piston (23), - the adapter body (22) comprising a silicone transfer chamber (29), a closable inlet channel (31) through which silicone can be fed to the silicone transfer chamber (29), and an injection channel (33) through which silicone can be injected from the silicone transfer chamber (29) into the tool mold (7), - the silicone transfer chamber (29) is fluidically separated from the plasticizing volume (13) of the injection unit (5), - the adapter piston (23) is mounted displaceably in the silicone transfer chamber (29) and by moving the adapter piston (22) silicone can be injected from the silicone transfer chamber (29) via the injection channel (33) into the tool mould (7), and - the adapter piston (23) can be inserted into the silicone transfer chamber (29) of the adapter body (22) by moving the injection unit (5) by means of the injection unit actuator (6). [2] Injection molding machine (1) according to claim 1, wherein - the silicone injection molding adapter (2) comprises a shut-off valve (25), and - the shut-off valve (25) is arranged in the inlet channel (31) and the inlet channel (31) can be closed by means of the shut-off valve (25). [3] Injection molding machine (1) according to one of the preceding claims, wherein the silicone injection molding adapter (2) has a heat insulation plate (26) arranged between the adapter body (22) and the mold half (14r) closest to the adapter body. [4] Injection molding machine (1) according to one of the preceding claims, wherein the adapter body (22) has coolant channels (30). [5] Injection molding machine (1) according to one of the preceding claims, wherein - the silicone injection molding adapter (2) has an injection nozzle (27), - the injection channel (33) extends at least partially through the injection nozzle (27), - the injection nozzle (27) is arranged in a corresponding recess (40) of the adapter body and / or a corresponding recess (41) of the adjacent tool mold half (14r), and - an annular space (42), in particular filled with air, extends between the injection sleeve (27) and the recess (40) of the adapter body and / or the recess (41) of the tool mold half. [6] Injection molding machine (1) according to claim 5, wherein - the injection nozzle (27) has an external thread (39) and the corresponding recess (40) of the adapter body has a corresponding internal thread, so that the injection nozzle (27) can be screwed into the corresponding recess (40) of the adapter body, and / or - the injection nozzle (27) is tapered towards its end face facing the tool mould half (14r) [7] Injection molding machine (1) according to one of the preceding claims, wherein the inlet channel (31) does not penetrate either of the two clamping plates (8r, 81). [8] Injection molding machine (1) according to one of the preceding claims, wherein - the silicone injection-moulding adapter (2) has a piston sleeve (24) arranged in the adapter body (22), which at least partially delimits the silicone transfer chamber (29), and - the adapter piston (23) is slidably mounted in the piston sleeve (24), and optionally - the piston sleeve (24) is fixed in the adapter body (22) by means of a quick-release fastener (35) in an exchangeable manner. [9] Silicone injection molding adapter (2) suitable for use in an injection molding machine (1) according to one of the preceding claims. [10] Method (100) for injection molding silicone workpieces (17) with an injection molding machine (1) according to one of claims 1 to 8, comprising the following steps: A) Closing (100) of the tool mould (7) by the closing unit (4), B) Lifting (110) the injection unit (5) from the adapter piston (23) by moving the injection unit (5) away from the clamping unit (4) by means of the injection unit actuator (6), C) filling (120) the silicone transfer chamber (29) with silicone via the inlet channel (31), whereby the silicone entering the silicone transfer chamber (29) causes an increasing displacement of the adapter piston (23) from the adapter body (22), D) Completion (130) of filling the silicone transfer chamber (29), E) Opening (140) of the tool mould (7) by the closing unit (4) and removing the silicone workpiece (17) located in the tool mould (7), F) closing (150) the tool mold (7) by the closing unit (4), and G) Injecting (160) silicone from the silicone transfer chamber (29) through the injection channel (33) into the tool mold (7) by moving the injection unit (5) by means of the injection unit actuator (6) and thereby inserting the adapter piston (23) into the adapter body (22). [11] Method according to claim 10, wherein - the method comprises a step B1 in which the shut-off valve (25) in the inlet channel (31) is opened (125) before the silicone transfer chamber (29) is filled with silicone via the inlet channel (31) according to step C), and - according to step D), the termination of the filling of the silicone transfer chamber (29) comprises closing the shut-off valve (25) in the inlet channel (31).

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