Nozzle assembly for an injection mold

Abstract

A nozzle assembly (1) for an injection mold suitable to supply melted plastic material into a cavity of the injection mold. The nozzle assembly (1) comprises a nozzle housing (2) comprising a melt channel (5) arranged therein having a valve opening (3). A valve needle (4) being arranged in the melt channel (5) displaceable in an axial direction (z) relative to the nozzle housing (2) between a closed position and an open position. An actuator (6) comprises an actuator housing (7) interconnected to the nozzle housing (2) and a drive shaft (8) interconnected to the valve needle (4) to displace the valve needle (4) between the closed position and the open position. A first force sensor (9) interconnecting the actuator housing (7) and the nozzle housing (2) is foreseen to determine the forces acting on the valve needle (4) via the actuator housing (7).

Description

NOZZLE ASSEMBLY FOR AN INJECTION MOLDCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to German Patent Application No. 102024111872.5, filed April 26. 2024, the contents of which are incorporated by reference herein in their entirety.FIELD OF THE DISCLOSURE

[0002] The present disclosure relates to nozzle assemblies for injection molds and hot runners for injections molds comprising one or more of such nozzle assemblies.BACKGROUND OF THE DISCLOSURE

[0003] Over the years, numerous advancements have been made in hot runner systems comprising one or more injection nozzles and cavity sensors, which provide enhanced productivity and capabilities for molders. The manner in which a mold cavity fills has a significant impact on the quality of the injection-molded part. Even minor alterations to the timing, temperature and pressure as the melted plastic material fills the cavity can influence the dimensions, aesthetics and functional strength of the part. Cavity sensors have played a crucial role in monitoring the injection molding process, providing valuable data on timing, temperature, and pressure as the melted plastic material fills the mold cavity.

[0004] As an example, for larger injection-molded part, often more than one injection nozzle is used to inject melted plastic material into the cavity in which the injection-molded part is formed. Typically valve gated nozzles are installed to fill the cavity in a cascade manner (i.e. sequentially) to achieve high part quality. The implementation of automatic cascade control, can be achieved through the utilization of sensors positioned within the cavity.

[0005] Know n approaches typically involve the arrangement of cavity sensors in the mold cavity in proximity to the respective injection point (i.e. next to the gate of therespective injection nozzle). However, this approach necessitates additional efforts on the part of the mold maker to install sensors in the cavity of the mold.

[0006] US2014210119A1 published in 2014 in the name of Synventive Molding Solutions relates to an apparatus for performing an injection molding cycle, comprising: a manifold routing injection fluid to two or more gates, an actuator associated with each gate, each gate having a downstream sensor that senses a selected condition of the injection fluid material, a controller, the downstream sensors establishing a standard elapsed time, the controller including instructions that compares the standard elapsed time with a calculated amount of elapsed time associated with each of the gates and that adjust the velocity or position of each of the actuators.

[0007] US2021078226A1 published in 2021 in the name of Synventive Molding Solutions relates to an injection molding system comprising: a first selected valve, one or more downstream valves, delivering a fluid to a mold cavity, at least one fluid property sensor, each valve associated with a position sensor that detects opening of a gate at an actual open gate time to the controller, the controller automatically adjusting time of instruction to open the gates on a subsequent injection cycle by an adjustment time equal to any delay in time between a predetermined open gate target time and an actual open gate time, wherein the system forms a first one or more parts or obj ects, the user inspecting or measuring the first one or more parts or objects and manually adjusts the predetermined open gate target time.SUMMARY OF THE DISCLOSURE

[0008] One of the primary challenges associated with the known injection molding systems is the necessity of placing sensors directly within the cavity. Firstly, the installation of cavity7sensors requires additional efforts and resources during the setup of the inj ection molding system. Integrating sensors within the cavity7requires intricate machining processes to ensure proper positioning and alignment. This not only increases the complexity of manufacturing the mold but also extends the setup time, thereby impacting production efficiency. Secondly, the complex installation of cavity7sensors poses a significant risk of damage to the sensors.

[0009] To address at least some of the limitations of traditional injection molding systems, a first aspect of the disclosure relates to a nozzle assembly for an injection mold suitable to supply melted plastic material into a cavity of the injection mold.

[0010] In a preferred variation the nozzle assembly comprises a nozzle housing comprising a melt channel arranged therein having a valve opening. Depending on the design, the valve opening is formed as a valve gate at a downstream end of the nozzle housing. However the valve opening can also be arranged upstream of the downstream end of the nozzle housing (i.e. within the melt channel at an intermediate position). A valve needle is arranged in the melt channel displaceable in an axial direction relative to the nozzle housing between a closed position in which the valve needle closes the valve opening and thereby blocks the passage of molten plastic material from the melt channel through the valve opening and an open position in which the valve needle allows passage of molten plastic material from the melt channel through the valve opening. If appropriate, the needle can be brought to intermediate positions between the fully open and the fully closed position to regulate the flow of the material. An actuator comprising an actuator housing is arranged interconnected to the nozzle housing. A drive shaft of the actuator is interconnected to the valve needle to displace the valve needle between the closed position and the open position.

[0011] Preferably a first force sensor is interconnecting the actuator housing and the nozzle housing to determine during operation the forces acting on the valve needle via the actuator housing.

[0012] In an assembled state and / or during operation, the first force sensor mechanically interconnects the actuator housing and the nozzle housing. In other words, the first force sensor forms part of the load path of the needle when the actuator displaces the valve needle during operation relative to the nozzle housing between the closed and the open position.

[0013] If appropriate, the signal of the first force sensor is indicative of the forces acting on the valve needle in axial direction during operation. In particular the signal ofthe first force sensor is indicative for a pressure (or a change thereof) on the valve needle (i.e. a front face of the valve needle).

[0014] Forces acting upon the valve needle can be distinguished as follows: The force, which acts upon the front face of the valve needle, when during operation the injection mold and the valve needle are in a closed position, after the melt has been injected into the cavity, in particular in the holding pressure phase. Forces from shear stress resulting from melt flowing along the valve needle in the melt channel. Dynamic forces resulting from mass inertia during opening and closing of the valve opening by the valve needle driven by the actuator.

[0015] The nozzle assembly according to the disclosure provides a solution for plug and play nozzle assemblies, which can e.g. be used in pre-installed hot runner assemblies. The nozzle assemblies according to the disclosure eliminate the need to place sensors adjacent to or within the cavity of the injection mold. This reduces manufacturing costs and minimizes the risk of damage to (cavity) sensors. In addition, this allows to retrofit nozzle assemblies according to the disclosure in existing injection molds previously not having any sensors, without the need to retrofit any sensors into the existing cavity (cavities respectively).

[0016] Depending on the field of application, the actuator housing is arranged in a floating manner linearly displaceable in the axial direction with respect to the nozzle housing by a linear bearing. The actuator can be a hydraulic actuator or a pneumatic actuator or an electric actuator, depending on the requirements of the application. In case of an hydraulic or pneumatic actuator, the drive shaft is mechanically coupled to a piston of the actuator. Preferably the drive shaft is integrally formed with the piston. A rotation stop can be arranged between the drive shaft and the actuator housing to prevent rotation of the drive shaft with respect to the actuator housing. In particular, when a position sensor configured to detect the axial position of the piston is attached to the actuator housing.

[0017] In case of an electric actuator, the drive shaft can be of a multi-part design, allowing an electric motor of the electric actuator to be arranged offset from a central axis of the needle.

[0018] In some variations, the linear bearing comprises at least one pillar against which the actuator housing is arranged displaceable. For a stable linear bearing typically more than two, preferably four pillars are foreseen. This arrangement enhances the overall stability of the linear bearing.

[0019] Preferably the actuator housing comprises a recess in which the at least one pillar extends. Typically the actuator housing comprises an individual recess for each pillar respectively. The recess can be formed as a through-bore, wherein in an assembled state the pillar extends through the through-bore such that the linear bearing is provided between the recess and the pillar being arranged displaceable relative to each other.

[0020] In some variations the actuator housing is interconnected to an adjustment arrangement for adjusting the actuator housing with respect to the nozzle housing in axial direction to adjust axial position of the valve needle.

[0021] If appropriate the at least one pillar is fixedly attached to the adjustment arrangement. When four pillars are foreseen, these may form in combination with the adjustment arrangement a mounting cage for the actuator housing. The actuator housing being in the assembled state arranged in a mounting cage in a floating manner. The adjustment arrangement supporting the actuator housing in the axial direction and being configured to adjust the position of the actuator housing in axial direction relative to the mounting cage.

[0022] Good results can be achieved when the first force sensor is arranged between the actuator housing and adj ustment arrangement. In particular the first force sensor can be arranged between the actuator housing and the mounting cage.

[0023] Depending on the design, the adjustment arrangement comprises a set screw for adjusting the axial position of the actuator housing with respect to the nozzle housing. The adjustment arrangement may comprises a plate with an opening having an inner thread to receive in an assembled state the set screw. Said plate may act as a top plate of the mounting cage. Preferably the pillars are attached to said top plate.

[0024] The mounting cage may comprise a mounting plate arranged in the assembled state in axial direction opposite to the top plate, wherein the pillars connect the top plate and the mounting plate. The actuator housing being arranged between the top plate and the mounting plate linearly guided by the pillars extending through respective recesses of the actuator housing.

[0025] In a preferred variation, the first force sensor is arranged concentric around a fixing screw fixedly connecting the actuator housing to the adjustment arrangement. If appropriate, the fixing screw connects the set screw and the actuator housing.

[0026] Alternatively or in addition, the first force sensor may be arranged concentric around a fixing protrusion of the actuator housing, which fixedly connects the actuator housing to the adjustment arrangement. Said fixing protrusion may comprise an inner and / or outer thread to connect to the adjustment arrangement. The actuator housing can be integrally formed with the fixing protrusion.

[0027] Said fixing screw or fixing protrusion may form a single-point suspension for the actuator housing. Accordingly, forces acting on the actuator housing in axial direction e.g. induced by forces acting on a front face of the valve needle are transmitted to the adjustment arrangement via said single-point suspension. For good results, the mounting cage is during operation arranged fixed in position relative to the nozzle housing.

[0028] Preferably the first force sensor is arranged coaxially with the valve needle. However an off-axis positioning is thinkable as well, wherein ty pically two or more first force sensors are arranged symmetrically with respect to a center axis of the needle and / or the drive shaft respectively.

[0029] Alternatively or in addition, to the first force sensor, a second force sensor can be arranged between the drive shaft of the actuator and a rear end of the valve needle to determine the forces acting on the valve needle, in particular in axial direction. Alternatively or in addition, the second force sensor can be integrated into the drive shaft of the actuator.

[0030] Good results can be accomplished when first force sensor is a piezoelectric sensor. Preferably the first force sensor being preloaded by the fixing screw in an assembled state. This allows to measure both, tension and compression forces in an axial direction of the valve needle. Alternatively or in addition, the first force sensor may comprise a strain gauge. The same is applicable for the second force sensor, if present.

[0031] Depending on field of application the first force sensor is implemented as a load cell comprising a strain gauge. In some variations the set screw of the adjustment arrangement may act as a load cell.

[0032] In another aspect of the disclosure the valve needle comprises a front face at which a first temperature sensor is arranged. In combination with the first and / or second force sensor great technical advantages can be achieved by determining both, the temperature of the melted plastic material injected into the cavity, as well as the pressure hereof on the front face of the needle. However a first temperature sensor being arranged at a front face of the valve needle is in principle independent of the disclosure relating to the first (and / or second) force sensor. This aspect therefore forms an independent inventive concept.

[0033] Forces determined by the first and / or the second force sensor can be dynamic and / or static loads during operation, such as forces resulting from mass of inertia during displacement of the valve needle in axial direction by the actuator and / or forces resulting from pressure inside the cavity and / or inside the melt channel acting onto the valve needle, in particular a front face of the valve needle arranged e.g. adjacent to a cavity wall of a mold cavity in an injection mold.

[0034] Good results are possible, when the first temperature sensor element being arranged for direct thermal contact with the melted plastic material inj ected into the cavity during operation.

[0035] Preferably the first temperature sensor is crimped from the front and welded to the front face of the valve needle. Depending on the desired application, the front end of the valve needle is then manufactured (ground) to match the final geometry of the valve needle.

[0036] The first temperature sensor is preferably a type N thermocouple. The positive leg of the first temperature sensor can be made from NiCroSil and another nickel alloy, NiSil, can be used for the negative leg. The legs of the first temperature sensor may extend through a sleeve partially encapsulating the first temperature sensor. Said sleeve preferably forms part of the front face of the valve needle, allowing direct contact of the first temperature sensor with the melted plastic material injected into the cavity during operation.

[0037] For connecting the first temperature sensor, the valve needle comprises a bore extending in longitudinal direction and in which a cable is arranged interconnected to the first temperature sensor arranged at the front face of the valve needle. The bore is preferably a through-bore in axial direction having the first temperature sensor inset into a front-end of the through-bore. The cable exits the valve needle at a rear end arranged opposite to the front-end of the valve needle.

[0038] The drive shaft preferably comprises a recess extending in axial direction for partially accommodating the cable of the first temperature sensor allowing the cable to not bend beyond its minimal bending radius when being routed laterally away from the drive shaft.

[0039] To support the cable of the first temperature sensor, in particular when the drive shaft displaces the thereto connected valve needle during operation between the closed and the open position, a cable support element is arranged at the drive shaft for guiding the cable in a lateral direction away from the drive shaft. The support element preferably comprises a guide surface having a curvature equal or greater to a minimal bending radius of the cable. This prevents damage to the cable, as bending the cable beyond its minimal bending radius is prevented.

[0040] For easy installation the drive shaft is interconnected to a rear end of the valve needle by a quick release coupling.

[0041] Alternatively or in addition, to the first temperature sensor, a second temperature sensor is arranged at a front end of the nozzle housing. Preferably the nozzle housing comprises a front face at which the second temperature sensor is arranged.

[0042] For connecting the second temperature sensor, the nozzle housing comprises a channel extending at least partially along the outer surface of the nozzle housing in which a cable interconnected to the second temperature sensor is arranged.

[0043] Depending on the design, the nozzle housing is of a multi -part design comprising an essentially tubular body and a tip bushing. The tip bushing may be attached to the body by a threaded connection. The second temperature sensor element can be arranged in the tip bushing. Preferably a front face of the tip bushing is configured to be embedded into a cavity of an injection mold. Good results are possible, when the second temperature sensor is inset into the front face of the tip bushing to directly determine the temperature of melted plastic material injected into the cavity.

[0044] In some variations a third temperature sensor is arranged in the valve needle in axial direction spaced apart from the first temperature sensor. One advantage of this arrangement is that the temperature difference between the first and third temperature sensor allows detection of shear heat at the valve opening. Shear heat may be understood as heat generated due to frictional forces arising from the relative movement between layers of melted plastic matenal in particular at rejuvenating sections of the melt channel such as at the valve gate or at the front face of the valve needle. By accurately detecting shear heat, this arrangement enables precise monitoring and control of the injection molding process. Furthermore, adhesion of melt to the needle tip due to shear heat can be predicted and / or consequently avoided.

[0045] Good results can be achieved when the third temperature sensor is arranged for thermal contact with the melted plastic material in the melt channel during operation, wherein thermal contact may be understood as a configuration enabling efficient heat transfer between the sensor and the melted plastic material. This enables accurate and immediate temperature measurements of the melted plastic material.

[0046] An easy assembly and / or maintenance of the nozzle assembly is possible, when a first connector part is arranged at a rear end of the valve needle for connecting a sensor arranged in the valve needle. Alternatively, or in addition, the first connector part is arranged at the actuator housing interconnected to the first force sensor. Preferably theelectric first connector part is arranged at a top end of the drive shaft for electronically connecting the first and / or the second force sensor.

[0047] A connector part may be understood as a mechanical, electrical or optical interface designed to establish a detachable connection between two components, facilitating signal transmission. One advantage of this arrangement is that it eliminates the need for cables fixedly attached to the valve needle, thereby significantly reducing the risk of cable damage during installation or maintenance procedures. If appropriate, an electric first connector part is arranged at a rear end of the valve needle for electronically connecting the first and / or the third temperature sensor.

[0048] Preferably a second connector part is coupled to the first connector part for connecting the sensor to the connector box in a detachable manner.

[0049] Good results are possible, when the drive shaft comprises a cable channel, wherein a cable channel may be understood as a dedicated passage or conduit arranged within the drive shaft to accommodate and guide a cable, in particular for feeding a cable in axial direction across the actuator housing. One advantage of this arrangement is easy access to the cable. By integrating the cable channel directly into the drive shaft, the cable can be conveniently routed through the actuator housing without requiring additional external cable guides or protective elements. This arrangement simplifies assembly and maintenance procedures, in particular in case the second connector part is arranged at the top side.

[0050] Depending on the field of application, the valve needle comprises in axial direction two or more segments. Preferably the valve needle comprises a tip segment accommodating the first and / or the third temperature sensor and a stem. A tip segment may be understood as the forward-most portion of the valve needle, positioned closest to the injection mold cavity. A stem may be understood as an elongated shaft portion of the valve needle, extending rearward from the tip segment. This allows simplified manufacturing, particularly when producing valve needles of different lengths, as the stem can be cut to size independently from the tip segment. Another advantage is that the tip segmentcan be manufactured separately with high precision, ensuring accurate positioning of the first temperature sensor within the tip segment.

[0051] In a preferred variation the first and / or the third temperature sensor elements are inserted into the tip segment having a blind hole in axial direction. A blind hole may be understood as a hole that is drilled or machined into the tip segment along its axial direction, which does not pass completely through the segment. An advantage of this arrangement is that the first temperature sensor has indirect thermal contact with the melt injected into the canty, thereby protecting the sensor from direct exposure to the melt while still enabling accurate temperature measurement. This further allows the front face of the tip segment to be machined to match the contour of an injection mold cavity. By providing a blind hole for sensor insertion, the first temperature sensor is not damaged when the front face is machined.

[0052] If appropriate, the stem and the tip segment are connected by a thread and / or by a welded connection. One advantage of a threaded connection is the ease of assembly and disassembly. An advantage of a welded connection is the provision of a robust and permanent joint between the stem and tip segment, ensuring reliable operation under demanding injection molding conditions.

[0053] The valve needle can be essentially tubular. The front end of the valve needle can. depending on the application, have different geometries, such as cylindrical or conical.

[0054] In some variations centering means are arranged in the nozzle housing for centering the valve needle in a radial direction during operation when moved between the open and the closed position. The needle centering means preferably comprise at least one fin extending in radial direction which has on the inside a guiding surface during operation centering the needle in radial direction.

[0055] Another aspect of the disclosure relates to a hot runner assembly for an injection mold. The hot runner assembly comprises typically at least one, preferably two or more, nozzle assemblies according to the disclosure attached to a common manifold distributing during operation melted plastic material into the respective melt channels.

[0056] Such hot runner assemblies can be installed in an injection mold without requiring the installation of additional sensors in the cavity. As a result no additional wiring for cavity sensors is required leading to a reduction cost to the mold maker and reduced risk of damage to (cavity) sensors. A hot runner assembly according to the disclosure can be considered to be “plug and play”, since the hot runner assembly can be inserted into a prepared injection mold without additionally installing sensors in the cavity (or cavities), while providing the same level of process control (i.e. cascade opening of nozzles).

[0057] Preferably the hot runner assembly comprises a junction box being connected to the sensors of the at least one nozzle assembly for receiving signals therefrom. Typically the junction box is connected to the sensors of two or more nozzle assemblies. The junction box preferably provides an interface such as one or more electrical connectors to connect to a controller (e.g. a cascade controller configured to control the actuators). The interface is configured to transmit the sensor signals to said controller.

[0058] It is to be understood that both the foregoing general description and the following detailed description present embodiments, and are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to provide a further understanding, and are incorporated into and constitute a part of this specification. The draw ings illustrate various embodiments. and together with the description serve to explain the principles and operation of the concepts disclosed.BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The herein described disclosure will be more fully understood from the detailed description given herein below7and the accompanying drawings which should not be considered limiting to the disclosure described in the appended claims. The draw ings are showing:

[0060] Fig. l a perspective view7of a partially sectioned hot runner assembly comprising a first variation of a nozzle assembly according to the disclosure;

[0061] Fig. 2 an exploded view of the first variation of Fig. 1;

[0062] Fig. 3 a perspective view of a partially sectioned hot runner assembly comprising a second variation of a nozzle assembly according to the disclosure;

[0063] Fig. 4 a perspective view of a partially sectioned hot runner assembly comprising a third variation of a nozzle assembly according to the disclosure;

[0064] Fig. 5 a perspective view of a partially sectioned drive shaft of a nozzle assembly according to the disclosure;

[0065] Fig. 6 the drive shaft of Fig 5 in another perspective and sectioned view;

[0066] Fig. 7 a perspective view of a front end of a first variation of a valve needle according to the disclosure, as well as a section view indicated by section line BB;

[0067] Fig. 8 a perspective view of a front end of a second variation of a valve needle according to the disclosure, as well as a section view indicated by section line CC;

[0068] Fig. 9 a partially sectioned and perspective view of a first variation of a drive shaft according to the disclosure having a force sensor integrated;

[0069] Fig. 10 a partially sectioned and perspective view of an actuator according to the disclosure comprising a second variation of a drive shaft according to the disclosure having a force sensor integrated;

[0070] Fig. I l a perspective view of a partially sectioned second variation of a nozzle assembly comprising a variation of an actuator similar to Fig. 10; and

[0071] Fig. 12 a perspective view of a partially sectioned hot runner assembly of Figure 1 comprising a third variation of a nozzle assembly according to the disclosure.DESCRIPTION OF THE EMBODIMENTS

[0072] Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

[0073] Figure 1 shows a hot runner assembly 26 comprising a first variation of a nozzle assembly 1 according to the disclosure. Figure 2 shows the first variation of the nozzle assembly 1 of Figure 1 in an exploded view.

[0074] The nozzle assembly 1 comprises a nozzle housing 2 attached to a manifold 27. In the shown variation, the nozzle housing 2 is attached to the manifold 27 by a threaded connection in a sealing manner. The nozzle housing 2 comprises a melt channel 5 receiving during operation melted plastic material from the manifold 27. A valve needle 4 is arranged in the melt channel 5 displaceable between a closed position and an open position. In the closed position the valve needle closes a valve opening 3. such that no melted plastic material can flow through. In the open position the valve needle 4 allows melted plastic material to flow through. In the first variation, the valve opening 3 is arranged at a front end 23 of the nozzle housing 2.

[0075] Opposite of the nozzle housing 2 relative to the manifold 27 an actuator 6 is arranged. The actuator 6 comprises an actuator housing 7 and a drive shaft 8. Said drive shaft 8 is in an assembled state detachably connected to a rear end 17 of the valve needle 4, to displace the valve needle 4 during operation between the open and the closed position. The shown actuator 6 is e.g. a pneumatic or a hydraulic actuator comprising a piston 37 displaceable in the actuator housing 7 in the axial direction z . A rotation stop 31 is arranged between the piston 37 and the actuator housing 7 to prevent rotation of the drive shaft 8 with respect to the actuator housing 7.

[0076] A first force sensor 9 is arranged on an upper side of the actuator housing 7. Said first force sensor 9 arranged in a load path from the valve needle 4 via the drive shaft 8, the piston 37 and the actuator housing 7 to the nozzle housing 2 to determine the forces acting on the valve needle 4.

[0077] In the shown variations the actuator housing 7 is arranged in a mounting cage comprising a top plate 28. a mounting plate 29 and four pillars 11 extending in axial direction z between the top plate 28 and the mounting plate 28. The actuator housing 7 comprises four recesses for respectively receiving each a pillar tor form a linear bearing 9 of the actuator housing 7 in the mounting cage in axial direction z. The actuator housing 7 is attached to the top plate 28 of the mounting cage. The mounting plate 29 of the mounting cage is attached to the manifold 27 and therefore fixed in position relative to the nozzle housing 2 completing the load path.

[0078] The first force sensor 9 is in the first variation arranged in axial direction z between the upper side of the actuator housing 7 and the top plate 28 of the mounting cage. This first variation comprises an adjustment arrangement 13 arranged at the top plate 28. The adjustment arrangement 13 comprises a set screw 14 and a fixing screw 15. The set screw 14 comprises an outer thread and is arranged in an opening of the top plate 28 having an inner thread to engage with the set screw' 14, such that the axial position of the set screw 14 is adjustable by turning said set screw 14. The fixing screw 15 fixedly connects the set screw 14 and the actuator housing 7. As can be seen in Figure 2, the first force sensor 9 is essentially ring shaped and arranged concentric around the fixing screw 15. In this arrangement, the first force sensor 9 is also coaxial with the valve needle 4.

[0079] In the first variation, as shown in Figure 1. the first force sensor 9 is a piezoelectric force sensor, wherein the fixing screw 15 clamps the first force sensor 9 between the actuator housing 7 and the set screw 14 thereby pre-loading the sensor.

[0080] In addition to the first force sensor 9 a first temperature sensor 19 is foreseen. The valve needle 4 comprises a front face 19 at which the first temperature sensor 19 is arranged. As best visible in Figures 7 and 8, the first temperature sensor 19 is arranged in a bore 20 (through-bore) extending in axial direction z. The first temperaturesensor 19 comprises two legs 35 (a positive and a negative) which extend in axial direction z to the front face 18 of the valve needle 4. The front face 18 of the valve needle 4 is partially formed by a sleeve 36 of the first temperature sensor 19, being inset into the bore 20. A cable 21 of the first temperature sensor 19 extends along the bore 20 and exits the bore 20 at a rear end 17 of the valve needle 4. The first variation of the valve needle 4, as shown in Figure 7 has a conical front section. In difference thereto the second variation of the valve needle 4 has, as shown in Figure 8, a cylindrical front section.

[0081] The rear end 17 of the needle is attached to the drive shaft 8 of the actuator 6. This is shown in Figures 5 and 6. The drive shaft comprises a quick release coupling 25 for detachably connecting to the read end 17 of the valve needle 4. The insertion of the rear end 17 into the quick release coupling 25 is indicated in Figure 6 with dashed lines. The drive shaft 8 comprises a recess 30 extending in axial direction z for partially accommodating the cable 21. In addition a cable support element 32 is arranged at the drive shaft 8 to guide the cable 21 from the recess 30 laterally away from the drive shaft 8. The cable 21 is guided by a guide surface 38 of the cable support element 32 having a curvature greater or equal to a minimal bending radius of the cable 21.

[0082] In Figure 3 a second variation of a nozzle assembly 1 according to the disclosure is shown. The second variation differs from the first variation, in that a second temperature sensor 22 is arranged at a front end 23 of the nozzle housing 2 and a second force sensor 16 is arranged at the drive shaft 8. The second temperature sensor 22 is inset into a front face of a tip bushing 39 of the nozzle housing 2. The second force sensor 16 is resting against the rear end 17 of the valve needle.

[0083] In Figure 4 a third variation of a nozzle assembly 1 according to the disclosure is shown. The third variation differs from the first and the second variation, in that the first force sensor 9 is formed as a load cell 33 comprising a strain gauge 34. In the shown variation, the load cell 33 acts as the set screw' 14 of the first and the second variation by which the axial position of the actuator housing 7 relative to the manifold 27 and consequently to the nozzle housing 2 can be adjusted.

[0084] Figure 9 shows a partially sectioned and perspective view of a first variation of a drive shaft 8 according to the disclosure having a force sensor 16 integrated. In this variation, the drive shaft 8 comprises aside from the force sensor 16 an upper part and a lower part connected through the force sensor 16 by a threaded connection. The upper part comprises a cable channel 43 for routing a cable form the force sensor 16 to a top end 47 of the drive shaft 8 for easy access during assembly and / during maintenance.

[0085] In Figure 10 a partially sectioned and perspective view of an actuator 6 according to the disclosure comprising a second variation of a drive shaft 8 according to the disclosure is shown having a force sensor 16 integrated. In difference to the first variation of a drive shaft 8 of Figure 9, the second variation comprises a coaxial cable channel 43 with a first connector part 41 being arranged at an exit of the cable channel 43 at a top end 47 of the drive shaft 8. A second connector part 42 is shown configured to couple to the first connector part 41 and to establish in particular an electrical connection therebetween. A cable (not shown) connects the second connector part 42 to a connector box (also not shown).

[0086] In Figure I l a perspective view of a partially sectioned second variation of a nozzle assembly 1 is shown. This second variation of a nozzle assembly 1 differs from the first variation in that a double chambered pneumatic actuator 6 is used. Furthermore, the first force sensor 9 is integrated into the drive shaft 8. The cable 20 of the first temperature sensor 19 exits the bore 21 at a rear end 17 of the valve needle 4. Instead of extending laterally away from a bottom end of the drive shaft 8, the cable 21 extends through a cable channel 43 of the drive shaft 8 to a top end of the drive shaft, thereby crossing the actuator housing 7. The cable ends in a first electrical connector part 41, coupled to a second electrical connector part 42. For disassembly, the second electrical connector 42 can be disconnected and the drive shaft 8 can be loosened and pulled in axial direction z from the actuator 6. Optionally a further detachable electrical connection is arranged at the rear end 17 of the valve needle 4, such that the valve needle 4 may stay in position while the drive shaft 8 is pulled out.

[0087] Figure 12 shows a perspective view of a partially sectioned hot runner assembly of Figure 1 comprising a third variation of a nozzle assembly according to thedisclosure similar to the first variation in its actuator 6 design and similar to the second variation regarding the detachable electrical connection of the sensors 19, 40 in the valve needle 4.

[0088] Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the scope of the disclosure.LIST OF DESIGNATIONS1 Nozzle assembly 23 Front end (nozzle housing)2 Nozzle housing 24 Front face (nozzle housing)3 Valve opening 25 Quick release coupling4 Valve needle 26 Hot runner assembly5 Melt channel 27 Manifold6 Actuator 28 Top plate7 Actuator housing 29 Mounting plate8 Drive shaft (actuator) 30 Recess (drive shaft)9 First force sensor 31 Rotation stop10 Linear bearing 32 Cable support element11 Pillar (linear bearing) 33 Load cell12 Recess (actuator housing) 34 Strain gauge13 Adjustment arrangement 35 Leg (temperature sensor)14 Set screw (adjustment ar36 Sleeve (temperature sensor) rangement) 37 Piston (actuator)15 Fixing screw (adjustment ar38 Guide surface (cable support rangement) element)16 Second force sensor 39 Tip bushing (nozzle housing)17 Rear end (valve needle) 40 Third temperature sensor18 Front face (valve needle) 41 First connector part19 First temperature sensor 42 Second connector part20 Bore (valve needle) 43 Cable channel21 Cable (first temperature sen44 Tip segment (valve needle) sor) 45 Stem (valve needle)22 Second temperature sensor 46 ThreadTop end (drive shaft)

Claims

PATENT CLAIMS1. A nozzle assembly (1) for an injection mold suitable to supply melted plastic material into a cavity of the injection mold, the nozzle assembly (1) comprising: a. a nozzle housing (2) comprising a melt channel (5) arranged therein having a valve opening (3); b. a valve needle (4) being arranged in the melt channel (5) displaceable in an axial direction (z) relative to the nozzle housing (2) between i. a closed position in which the valve needle (4) closes the valve opening (3) and thereby blocks the passage of molten plastic material from the melt channel (5) through the valve opening (3) and ii. an open position in which the valve needle (4) allows passage of molten plastic material from the melt channel (5) through the valve opening (3); c. an actuator (6) comprising i. an actuator housing (7) interconnected to the nozzle housing (2) and ii. a drive shaft (8) interconnected to the valve needle (4) to displace the valve needle (4) between the closed position and the open position;d. a first force sensor (9) interconnecting the actuator housing (7) and the nozzle housing (2) to determine during operation the force acting on the valve needle (4) via the actuator housing (7).

2. The nozzle assembly (1) according to claim 1, wherein the actuator housing (7) is arranged in a floating manner linear displaceable in axial direction (z) with respect to the nozzle housing (2) by a linear bearing (10).

3. The nozzle assembly (1) according to claim 2, wherein the linear bearing (10) comprises at least one pillar (11) against which the actuator housing is arranged displaceable.

4. The nozzle assembly (1) according to claim 3, wherein the actuator housing (7) comprises a recess (12) in which the pillar (11) extends.

5. The nozzle assembly (1) according to any of the previous claims, wherein the actuator housing (7) is interconnected to an adjustment arrangement (13) for adjusting the actuator housing (7) with respect to the nozzle housing (2) in axial direction (z) to adjust axial position of the valve needle (4), in particular by a set screw (14) of the adjustment arrangement (13).

6. The nozzle assembly (1) according to claim 5, wherein the first force sensor (9) is arranged between the actuator housing (7) and adjustment arrangement (13).

7. The nozzle assembly (1) according to claim 5 or 6, wherein the first force sensor (9) is arranged concentric around a fixing screw (15) fixedly connecting the actuator housing (7) to the adjustment arrangement (13).

8. The nozzle assembly (1) according to at least one of the previous claims, wherein the first force sensor (9) is arranged coaxially with the valve needle (4).

9. The nozzle assembly (1) according to any of the preceding claims, wherein alternatively or in addition to the first force sensor (9), a second force sensor (16) is arranged between the drive shaft (8) of the actuator (6) and a rear end (17) of the valve needle (4) to determine the forces acting on the valve needle (4).

10. The nozzle assembly (1) according to any of the preceding claims, wherein alternatively or in addition to the first force sensor (9), a second force sensor (16) is integrated into the drive shaft (8) of the actuator (6) to determine the forces acting on the valve needle (4).

11. The nozzle assembly (1) according to any of the preceding claims, wherein first force sensor (9) being a piezoelectric sensor, in particular preloaded by the fixing screw (15) in an assembled state.

12. The nozzle assembly (1) according to any of the preceding claims, wherein the valve needle (4) comprises a front face (18) at which a first temperature sensor (19) is arranged.

13. The nozzle assembly (1) according to claim 12, wherein the valve needle (4) comprises a bore (10) extending in longitudinal direction (z) and in which a cable (21) is arranged interconnected to the first temperature sensor (19) arranged at the front face (18) of the valve needle (4).

14. The nozzle assembly (1) according to any of the preceding claims, wherein a second temperature sensor (22) is arranged at a front end (23) of the nozzle housing (2).

15. The nozzle assembly (1) according to claim 14, wherein the nozzle housing (2) comprises a front face (24) at which the second temperature sensor (22) is arranged.

16. The nozzle assembly (1) according to claim 14 or 15, wherein the nozzle housing (2) comprises a channel (5) extending at least partially along the outer surface of the nozzle housing (2) in which a cable interconnected to the second temperature sensor (22) is arranged.

17. The nozzle assembly (1) according to any of the preceding claims, wherein the drive shaft (8) is interconnected to a rear end (17) of the valve needle (4) by a quick release coupling (25).

18. The nozzle assembly (1) according to any of the preceding claims, wherein a first connector part (42) is arranged at the actuator housing (7) interconnected to the first force sensor (9), in particular an electric first connector part (42) is arranged at a top end (27) of the drive shaft (8) for electronically connecting the first force sensor (9).

19. The nozzle assembly (1) according to any of the preceding claims, wherein the drive shaft (8) of the actuator (6) comprises a cable channel (43). in particular for feeding a cable in axial direction (z) across the actuator housing (7).

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