WO2023115293A1

WO2023115293A1 - Actuator arrangement with adjustable stroke length

Info

Publication number: WO2023115293A1
Application number: PCT/CN2021/139873
Authority: WO
Inventors: Liqiao LI; Feng Ling
Original assignee: Synventive Molding Solutions (Suzhou) Co. Ltd.
Priority date: 2021-12-21
Filing date: 2021-12-21
Publication date: 2023-06-29

Abstract

The present disclosure relates to a fluidically driven actuator arrangement (10, 110, 210, 310) comprising a piston (16) and a valve pin (28) being drivable along a reciprocal path of axial travel having an adjustable stroke length that extends between a downstream gate closed position and an adjustable final upstream gate open position. The actuator arrangement (10, 110, 210, 310) comprises a counteracting means (30, 130, 230, 330) configured to apply a counteracting force to the piston (16) that counteracts an upstream movement force applied to the piston (16). The adjustable final upstream gate open position is defined by a position where the counteracting force equals the upstream movement force and is thus adjustable by selectively setting the pressurization of the arrangement.

Description

Actuator arrangement with adjustable stroke length

The present invention relates to a nozzle actuator arrangement for a hot runner system of an injection mold. The nozzle actuator arrangement is particularly suitable for use in multi cavity hot runner systems.

Background of the invention

A common task in the context of injection molding is the modification of a maximum flow cross section of injection fluid material in nozzle actuator arrangements in order to influence the injection molding process. Namely, modifications of the maximum flow cross section of injection fluid material can be necessary to influence process parameters, such as process time, as well as quality and/or consistency of injection-molded objects. In particular, in multi cavity hot runner systems with multiple nozzle arrangements and mul-tiple valve pins, where flow cross sections of various valve pins might need to be adapted relative to each other, the modification can be very elaborately and time-consuming.

In fluidically operated actuator arrangements known from practice, the maximum flow cross section of indi-vidual valve pins is modified by manually mounting spacers inside the arrangement, which spacers limit the stroke length of the valve pins. However, for mounting the spacers, the actuator arrangement has to be disassembled, the spacer/shas/have to be installed and the actuator arrangement has to be reassembled. Then the result of the modification is tested and in many cases additional spacers have to be added or pre-viously added spacers have to be removed, which again requires a disassembling and reassembling of the arrangement. Specifically, but not only, in multi cavity hot runner systems this is very elaborately and time-consuming.

It is an object of the present invention to provide an actuator arrangement which has improved characteris-tics and overcomes at least some of the disadvantages of the prior art.

In particular, it is an object of the present invention to provide an actuator arrangement that overcomes at least one of the above disadvantages.

In particular, it is an object of the present invention to provide a, preferably inexpensive, actuator arrange-ment that enables an easy modification of the flow cross section of injection fluid material.

These objects are achieved by the subject-matter of the independent claims. Preferred embodiments and preferred features are specified in the dependent claims and the following description.

Summary of the invention

According to a first aspect, the invention relates to an actuator arrangement, also called nozzle actuator arrangement, for a hot runner system of an injection mold. The actuator arrangement is a fluidically driven actuator arrangement and comprises a fluid sealed chamber, and a piston slidably mounted in the fluid sealed chamber and forming a first drive chamber and a second drive chamber within the fluid sealed chamber. Each drive chamber has a respective fluid flow port for selective pressurization of the drive chamber.

The fluidically driven actuator arrangement comprises a valve pin interconnected to and moveable with the piston. Interconnected to can mean that the valve pin is directly or indirectly attached or mounted to the piston.

The piston and the valve pin are drivable along a reciprocal path of axial travel by selective pressurization of the first drive chamber or of the second drive chamber. The reciprocal path of axial travel has an adjust-able stroke length that extends between a downstream gate closed position of the valve pin and the piston, where the valve pin blocks flow of injection fluid material through a gate of the system to a mold, and an adjustable final upstream gate open position of the valve pin and the piston, where injection fluid material is enabled through the gate to the mold.

The fluidically driven actuator arrangement comprises at least one counteracting means configured to apply a counteracting force to the piston that counteracts a constant upstream movement force applied to the piston. The counteracting means can apply the counteracting force directly to the piston or indirectly to the piston, e.g. via the valve pin or an additional component of the arrangement. In particular, the counteracting force can be a spring force or an elastic force or a variable force. The counteracting force can be depend-ing on or varying according to an at least partial deformation and/or deflection of the counteracting means or at least a portion thereof. The counteracting means can be an at least partially elastic counteracting means.

The adjustable final upstream gate open position is defined, or in other words determined, by a position of the piston and the valve pin, where the counteracting force applied to the piston equals the upstream movement force caused by pressurization of the second drive chamber. The adjustable final upstream gate open position is thus adjustable by selectively setting the pressurization of the second drive chamber.

The adjustable final upstream gate open position can also be described as the upstream gate open position that constitutes the respective fully upstream gate open position in the respectively considered configura-tion (including the structural arrangement and the applied pressurization) . When in a certain configuration the counteracting force applied to the piston equals the upstream movement force, the piston upstream movement is blocked and the then fully (or then maximum) upstream gate open position is reached. How-ever, when the upstream movement force is increased (by increasing the pressurization) the final upstream gate open position is altered, which constitutes the then fully upstream gate open position for this respec-tive configuration. In other words, the final upstream gate open position can constitute the fully upstream gate open position for a certain overall configuration (including structural arrangement and applied pressur-ization) , even though there different fully upstream gate open positions can be reached with the same structural configuration of the actuator arrangement when changing the pressurization.

In contrast to known prior art fluidically driven actuator arrangements, which merely have a fixed fully up-stream gate open position and thus a fixed stroke length that can only be altered by reconfiguration and structural adaption of the arrangement, the actuator arrangement of the present invention has an adjustable final upstream gate open position and thus an adjustable stroke length that is adjustable already in the ar-rangement’s present structural configuration. In other words, according to the present invention the adjust-able final upstream gate open position and thus the adjustable stroke length is adjustable without modifica-tion of the structural configuration.

Adjusting the stroke length results in an adjustment of the flow path through the nozzle, i.e. the flow cross section of injection fluid material. Increasing the maximum stroke length results in an increase of the flow path’s annular surface at the tip insert, between an inner surface of the tip insert and an outer surface of the valve pin. Respectively, the maximum stroke length results in a decrease of the flow path’s annular surface at the tip insert.

Thus, the invention provides a simple and inexpensive solution for adjusting stroke lengths of actuator ar-rangements and thereby setting the injection molding process. In particular in view of multi cavity hot runner systems that have high balance requirements with regard to the multiple valve pins, the present invention enables a simple and quick adjustment solution.

Since the actuator arrangement does not need to be disassembled, an adjustment of stroke length is even possible during mold dry.

The actuator arrangement can comprise a single counteracting means (single counteracting component) or more than one counteracting means. In particular, the actuator arrangement can comprise more than one counteracting means of the same kind or of a different kind.

The actuator arrangement can be configured so that pressurizing the first drive chamber causes the piston and the valve pin to move to the downstream gate closed position. This can be called a downstream movement. The actuator arrangement can be configured so that pressurizing the second drive chamber causes the piston and the valve pin to move to the adjustable final upstream gate open position, i.e. in a direction away from the downstream gate closed position. This can be called an upstream movement. Mov-ing the piston and the valve pin towards the adjustable final upstream gate open position, i.e. upstream, can cause, at least along a part of the stroke length, the counteracting means to exert the counteracting force that counteracts the upstream movement force caused by pressurization of the second drive chamber. More precisely, moving the piston and the valve pin towards the adjustable final upstream gate open posi-tion, i.e. upstream, can cause, at least along a part of the stroke length, the counteracting means to build up a continuously increasing counteracting force.

In an embodiment, the counteracting means can be interconnected to and moveable with the piston, and thus with the valve pin. Interconnected to can mean that the counteracting means is directly or indirectly attached or mounted to the piston. The counteracting means can preferably be arranged in the region of an upper side of the piston, thus at least partially extending into the first drive chamber. In this embodiment, moving the piston and the counteracting means upstream or downstream by means of pressurizing the respective drive chambers consequently also moves the interconnected counteracting means, respectively. Moving the piston, the valve pin and the counteracting means towards the adjustable final upstream gate open position, i.e. upstream, can at least along a part of the stroke length, at least partially compress the counteracting means which causes the counteracting means to exert the counteracting force that counter-acts the constant upstream movement force caused by pressurization of the second drive chamber. Thus, upon an upstream movement of the piston, the counteracting means can apply a compressive force to the piston. Preferably, in some embodiments, after an initial free upstream movement moving the piston, the valve pin and the counteracting means upstream can cause a free end of the counteracting means to abut an abutment surface of the fluid sealed chamber.

In an alternative embodiment, the counteracting means (or at least a base body thereof) can be arranged stationary, preferably inside the fluid sealed chamber, in particular in the first drive chamber. The counter-acting means can be arranged inside and at a top side of the fluid sealed chamber at an opposite inner surface opposing the piston. In this embodiment, moving the piston and the valve pin upstream or down-stream by means of pressurizing the respective drive chambers moves the piston and the valve pin towards or away from the counteracting means, respectively. More precisely, moving the piston upstream or down-stream by means of pressurizing the respective drive chambers moves the piston towards or away from a free end of the counteracting means, respectively. Moving the piston towards the counteracting means, preferably by an upstream movement, can at least along a part of the stroke length at least partially com-press the counteracting means, which causes the counteracting means to exert the counteracting force that counteracts the upstream movement force caused by pressurization of the second drive chamber. Thus, upon an upstream movement of the piston, the counteracting means can apply a compressive force to the piston. Preferably, in some embodiments, after an initial free upstream movement moving the piston, the valve pin and the counteracting means upstream can lead to an abutment of the piston with the free end of the counteracting means.

In an alternative embodiment, the counteracting means can be arranged inside the second drive chamber and can be attached to the piston and to a housing of the fluid sealed chamber (both directly or indirectly) . Thus, upon an upstream movement of the piston, the counteracting means can be at least partially de-formed or deflected and can thus apply a tensile force to the piston that counteracts the upstream move-ment force caused by pressurization of the second drive chamber.

The pressurization of each of the drive chambers can be manually adjustable so as to manually adjust the maximum upstream movement force (by manually adjusting the pressurization of the second drive chamber) and the maximum downstream movement force (by manually adjusting the pressurization of the first drive chamber) . Thus, in a manually adjustable embodiment provision of a controller is not needed.

However, it is understood that in optional embodiments a controller can be implemented that allows auto-matic adjustment of the stroke length in addition or alternative to manual adjustment. In particular in auto- mated or semi-automated embodiments, one or more sensors can be provided in order to control and/or visualize various parameters of the actuator arrangement, such as the stroke length, the pressurization of the drive chambers, etc.

In an embodiment, the counteracting means can be a spring, preferably a gas spring, such as a nitrogen gas spring, a tension spring, a compression spring, etc. The counteracting means can be a compressible, elastic material, preferably formed as a cushion.

In an embodiment, the fluid flow port of at least the second drive chamber can be fluidically connected with a pressure relief valve. Thus, a simple manual pressurization adjustment, and consequently stroke adjust-ment, can be realized as by means of the pressure relief valve the maximum pressure applicable to the second drive chamber can be easily adjusted. Thereby, the upstream movement force can be reduced or increased and a position in which the counteracting force equals the upstream movement force can thus be reached earlier or later.

The fluidically operated actuator arrangement can be configured for hydraulic or pneumatic pressurization of the drive chambers. Preferably, the drive chambers can be pressurized by means of hydraulic oil.

In an embodiment, when the valve pin and piston are at a fully downstream gate closed position, a free end of the counteracting means can be spaced from an opposite surface, preferably an inner top surface of the fluid sealed chamber or a surface of the piston, by a predefined gap or a predefined gap length in order to allow free upstream movement of the piston and the valve pin at least along an initial part of the adjustable stroke length, wherein the distance of the initial part equals the gap length. Free movement here means an unhindered movement, which is not affected by any counteracting force of the counteracting means. Hence, a sufficiently fast opening of the gate can be guaranteed by means of the gap.

Namely, in one embodiment, when the valve pin and piston are at a fully downstream gate closed position, a free end of the counteracting means mounted to the piston can be spaced from an opposite inner top surface of the fluid sealed chamber by a predefined gap in order to allow free upstream movement of the piston and the valve pin at least along an initial part of the adjustable stroke length, wherein the distance of the initial part equals the gap length.

Namely, in an alternative embodiment, when the valve pin and piston are at a fully downstream gate closed position, a free end of the counteracting means stationary arranged at an inner top surface of the fluid sealed chamber can be spaced from an opposite surface of the piston, by a predefined gap in order to al-low free upstream movement of the piston and the valve pin at least along an initial part of the adjustable stroke length, wherein the distance of the initial part equals the gap length.

Preferably, the gap can be between 1 mm and 10 mm, preferably between 2 mm and 8 mm, more prefera-bly between 3 mm and 6 mm.

In an embodiment, the stroke length can be adjustable between 2 mm and 25 mm, preferably between 4 mm and 22 mm, more preferably between 5 mm and 18 mm.

In an embodiment, the maximum stroke length can be between 3 mm and 25 mm, preferably between 5 mm and 22 mm, more preferably between 8 mm and 18 mm.

In an embodiment, the minimum stroke length can be between 2 mm and 12 mm, preferably between 3 mm and 10 mm, more preferably between 4 mm and 8 mm.

In an embodiment, the counteracting means can be configured to exert a varying force, depending on the load applied to the counteracting means. The counteracting means can have a start force between 500 N and 2300 N, preferably between 1000 N and 2000 N, more preferably between 1400 N and 1800 N and/or can have a maximum force between //1500 N and 5000 N, preferably between 3100 N and 3700 N, more preferably between 3400 N and 3600 N//.

Another aspect relates to a hot runner system of an injection mold for conveying molten injection fluid mate-rial from a machine nozzle into a cavity. The hot runner system comprises a heated manifold having a dis-tribution channel for distributing the molten injection fluid material. The hot runner system further comprises a nozzle having a gate and a fluid delivery channel. The fluid delivery channel being fluidically connected to the distribution channel and configured to receive the molten injection fluid material from the distribution channel. The hot runner system comprises an actuator arrangement of the type described above.

In particular, the actuator arrangement is a fluidically driven actuator arrangement and comprises:

a fluid sealed chamber,

a piston slidably mounted in the fluid sealed chamber and forming a first and a second drive chamber within the fluid sealed chamber, each drive chamber having a respective fluid flow port for selective pres-surization of the drive chamber,

a valve pin interconnected to and moveable with the piston,

the piston and the valve pin being drivable along a reciprocal path of axial travel by selective pressuri-zation of the first drive chamber or of the second drive chamber, the reciprocal path of axial travel having an adjustable stroke length that extends between a downstream gate closed position where the valve pin blocks flow of injection fluid material through a gate of the system to a mold and an adjustable final up-stream gate open position where injection fluid material is enabled through the gate to the mold, and

at least one counteracting means configured to apply a counteracting force to the piston that counter-acts an upstream movement force applied to the piston,

wherein the adjustable final upstream gate open position is defined by a position where the counteract-ing force equals the upstream movement force and is thus adjustable by selectively setting the pressuriza-tion of the second drive chamber.

In a preferred embodiment, the hot runner system is a multi-cavity hot runner system with multiple nozzle arrangements and multiple valve pins. The hot runner system can thus comprise a plurality of nozzles and a plurality of actuator arrangements.

Another aspect relates to a method for adjusting a stroke length of an actuator arrangement, in particular an actuator arrangement of the type described above. The actuator arrangement comprises

a fluid sealed chamber,

a valve pin interconnected to and moveable with the piston,

a counteracting means.

The method comprises the step of pressurizing the second drive chamber with a selected upstream move-ment pressure that applies an upstream movement force to the piston and thus moves the piston upstream, wherein upstream movement of the piston causes the counteracting means to apply a counteracting force to the piston that counteracts the upstream movement force. The piston reaches the adjustable final up-stream gate open position when the counteracting force equals the upstream movement force.

In an embodiment of the method, the second drive chamber is pressurized with a selected upstream movement pressure between 10 and 70 bar, preferably between 20 bar and 60 bar, more preferably be-tween 30 bar and 50 bar.

In an embodiment of the method, the pressurization of the second drive chamber is set by adjusting a pres-sure relief valve arranged within a fluidic connection between the second drive chamber and a pressure source.

Even though some of the features, functions, embodiments, technical effects and advantages have been described with regard to one aspect, it will be understood that these features, functions, embodiments, technical effects and advantages can be combined with one another also applying to other embodiments and aspects.

Brief description of the drawings

For a better understanding of embodiments of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which like numer-als designate corresponding elements or sections throughout.

In the accompanying drawings:

Fig. 1 shows a schematic drawing of an actuator arrangement according to a first embodi-ment of the invention;

Fig. 2 shows a schematic drawing of an actuator arrangement according to a second em-bodiment of the invention;

Fig. 3 shows a schematic drawing of an actuator arrangement according to a third embodi-ment of the invention;

Fig. 4 shows a schematic drawing of an actuator arrangement according to a fourth embod-iment of the invention;

Figs. 5A to 5E show a sequence of the actuator arrangement of Fig. 1 at different stages.

Detailed description of the drawings

Fig. 1 shows a schematic drawing of a fluidically operated actuator arrangement 10 according to a first em-bodiment of the invention. The actuator arrangement 10 comprises a fluid sealed chamber 12 arranged inside an actuator housing 14.

A piston 16 is slidably arranged inside the fluid sealed chamber 12 for reciprocal upstream and downstream movement. The piston 16 divides the fluid sealed chamber 12 into a first drive chamber 18 and a second drive chamber 20. The first drive chamber 18 is provided with a first fluid port 22 and the second drive chamber 20 is provided with a second fluid port 24. The first and the

second drive chambers

18, 20 can be selectively pressurized via the

fluid ports

22, 24. The arrows shown in Fig. 1 (as well as in Figs. 2 to 4) indi-cate a fluid flow direction for pressurizing the second fluid chamber 20 in order to cause an upstream movement of the piston 16. However, it is understood that the fluid flow direction can be switched in order to pressurize the first drive chamber 18 in order to cause a downstream movement of the piston 16 (in this case the shown arrows in the fluid paths would be reverse) .

At least the fluid path of the second drive chamber 20 is provided with a pressure relief valve 26 that can be manually adjusted in order to set a maximum pressurization of the second drive chamber 20, and conse-quently a maximum upstream movement force applied to the piston 16.

A valve pin 28 is fixedly mounted to the piston 16 in a region at a lower end of the piston 16. Thus, the valve pin 28 is moveable together with the piston 16 and is thus configured for the same reciprocal up-stream and downstream movement as the piston 16. The piston 16 and the valve pin 28 are moveable be-tween a downstream gate closed position where the valve pin 28 blocks flow of injection fluid material through a gate of the system to a mold and an adjustable final upstream gate open position where injection fluid material is enabled through the gate to the mold (see Fig. 5A to 5E) .

The actuator arrangement 10 further comprises a counteracting means 30. In the embodiment of Fig. 1, the actuator arrangement 10 is a gas spring, preferably a nitrogen gas spring, that is mounted to the piston 16. Here, the counteracting means 30 is arranged in a region at an upper end of the piston 16. The counteract-ing means 30 at least at least partially protrudes upwardly over the upper end of the piston.

In order to move the piston 16 and valve pin 28 upstream, from a downstream gate closed position towards a final upstream gate open position, the second drive chamber 20 is pressurized via the corresponding fluid flow port 24 with maximum pressurization.

By pressurizing the second drive chamber 20 an upstream movement force is applied to the piston 16 which moves the piston 16 (and the interconnected valve pin 28 and interconnected counteracting means 30)upstream. The counteracting means 30 thus approaches an opposing inner top surface 34 of the fluid sealed chamber 12 /the actuator housing 14. This brings an upper free end 32 of the counteracting means 30, here the gas spring, into abutment with the opposing inner top surface 34. Further upstream movement of the piston 16, the valve pin 28 and the counteracting means 30 caused by the pressure applied to the second drive chamber 20 leads to compression of the counteracting means 30, i.e. the gas spring. Conse-quently, the counteracting means 30 applies a counteracting force to the piston that counteracts the up-stream movement force. The counteracting force increases in accordance with the increasing compression of the counteracting means 30 and in accordance with the gas spring characteristics. It is understood that a gas spring with suitable characteristics can be chosen depending on the overall structural configuration of the actuator assembly and the requirements of the respective application. The piston 16, the valve pin 28 and the counteracting means 30 keep moving upstream as long as the constant upstream movement force exceeds the counteracting force. When the increasing counteracting force equals the upstream movement force, further upstream movement is blocked and a final upstream gate open position is reached.

When the maximum pressurization of the second drive chamber 20 is reduced or increased by manually setting the pressure relief valve 26, the upstream movement force (for the present or a subsequent stroke) is respectively adjusted. In case of a reduced upstream movement force, the balance between the up-stream movement force and the counteracting force is reached earlier during upstream movement. Hence, the final upstream gate open position is reached earlier and the stroke length of the actuator arrangement is reduced. In case of an increased upstream movement force, the balance between the upstream move-ment force and the counteracting force is reached later during upstream movement. Hence, the final up-stream gate open position is reached later and the stroke length of the actuator arrangement is increased.

By means of the counteracting means 30 the present actuator arrangement 10 has an easily adjustable stroke length, since a final upstream gate open position of the piston 16 and valve pin 28 can be manually modified by setting the pressurization of the second drive chamber 20. Hence, the actuator arrangement 10 does not need to be disassembled and reassembled in order to adapt its stroke length.

Fig. 2 shows a schematic drawing of an actuator arrangement 110 according to a second embodiment of the invention. The functioning principle and most of the basic configuration of the actuator arrangement 110 of the second embodiment are analog to the functioning principle and most of the basic configuration of the actuator arrangement 10 of the first embodiment. The same features are provided with the same reference sings.

In contrast to the embodiment of Fig. 2, the actuator arrangement 110 of Fig. 2 has a different configuration of the counteracting means 130. The counteracting means 130 is a stationary component. It is mounted to the actuator housing 14 in the region of the inner top surface of the fluid sealed chamber 12. As in the em-bodiment of Fig. 1, the counteracting means 130 of Fig. 2 is a gas spring. The counteracting means 130, here a free end 132 of the counteracting means 130, extends inside the fluid sealed chamber 12 towards the piston 16.

When the piston 16 and the valve pin 28 interconnected therewith are moved upstream by pressurization of the second drive chamber 20, an upper surface of the piston approaches and at a certain position abuts the free end 132 of the counteracting means 130. Upon further upstream movement of the piston 16, the coun-teracting means 130 is compressed and applies a counteracting force to the piston 16 that counteracts up-stream movement. The counteracting force increases in accordance with the increasing compression of the counteracting means 130 and in accordance with the gas spring characteristics. The piston 16 and the valve pin 28 keep moving upstream as long as the constant upstream movement force exceeds the coun-teracting force. When the increasing counteracting force equals the upstream movement force, further up-stream movement is blocked and a final upstream gate open position is reached.

The adjustable final upstream gate open position and thus the adjustable stroke length can in this embodi-ment be adjusted analog to the adjustment in the embodiment of Fig. 1, i.e. by manually setting the pres-sure relief valve.

Fig. 3 shows a schematic drawing of an actuator arrangement 210 according to a third embodiment of the invention. The functioning principle and most of the basic configuration of the actuator arrangement 210 of the third embodiment are analog to the functioning principle and most of the basic configuration of the ac-tuator arrangement 110 of the second embodiment. The same features are provided with the same refer-ence sings.

In contrast to the embodiment of Fig. 2, the actuator arrangement 210 of Fig. 3 has a different configuration of the counteracting means 230. Like in the second embodiment, the counteracting means 230 of the third embodiment is also a stationary component. It is mounted to the actuator housing 14 in the region of the inner top surface of the fluid sealed chamber 12. Different than in the embodiments of Figs. 1 and 2, the counteracting means 230 of Fig. 3 is a cushion formed of a compressible material. The counteracting means 230 extends inside the fluid sealed chamber 12 towards the piston 16.

When the piston 16 and the valve pin 28 interconnected therewith are moved upstream by pressurization of the second drive chamber 20, an upper surface of the piston 16 approaches and at a certain position abuts a lower surface 232 of the counteracting means 230. Upon further upstream movement of the piston 16, the counteracting means 230 is compressed and applies a counteracting force to the piston 16 that coun-teracts upstream movement. The counteracting force increases in accordance with the increasing com-pression of the counteracting means 230 and in accordance with the material characteristics. The piston 16 and the valve pin 28 keep moving upstream as long as the constant upstream movement force exceeds the counteracting force. When the increasing counteracting force equals the upstream movement force, further upstream movement is blocked and a final upstream gate open position is reached.

The adjustable final upstream gate open position and thus the adjustable stroke length can in this embodi-ment be adjusted analog to the adjustment in the embodiments of Figs. 1 and 2, i.e. by manually setting the pressure relief valve.

It is understood that in another embodiment according to the invention, the gas spring shown in the embod-iment of Fig. 1 can be replaced by a compressible material as shown in the embodiment of Fig. 3.

Fig. 4 shows a schematic drawing of an actuator arrangement 310 according to a fourth embodiment of the invention. The functioning principle and most of the basic configuration of the actuator arrangement 310 of the fourth embodiment are analog to the functioning principle and most of the basic configuration of the actuator arrangement 210 of the third embodiment. The same features are provided with the same refer-ence sings.

In contrast to the embodiment of Fig. 3, the actuator arrangement 310 of Fig. 4 has a different configuration of the counteracting means 330. Namely, the actuator arrangement 310 comprises two counteracting means 330. It is understood that in alternative embodiments only one or more than two counteracting means 330 can be provided. Each of the counteracting means 330 is attached at one end to the actuator housing 14 in a region of an inner bottom surface of the fluid sealed chamber 12 and is attached on an op-posite end to the piston 16. Different than in the embodiments of Figs. 1 to 3, the counteracting means 330 of Fig. 4 is elastically stretched by an upstream movement of the piston 16. The counteracting means 330 is a spring, e.g. a coil spring.

In the embodiment of Fig. 4, when the piston 16 and the valve pin 28 interconnected therewith are moved upstream by pressurization of the second drive chamber 20, the counteracting means 330 are elastically stretched and thus apply a tensile counteracting force to the piston 16 that counteracts upstream move-ment (pulls the piston in a downstream direction) . The counteracting force increases in accordance with the increasing stretching of the counteracting means 330 and in accordance with the spring characteristics.

The piston 16 and the valve pin 28 keep moving upstream as long as the constant upstream movement force exceeds the counteracting force. When the increasing counteracting force equals the upstream movement force, further upstream movement is blocked and a final upstream gate open position is reached.

The adjustable final upstream gate open position and thus the adjustable stroke length can in this embodi-ment be adjusted analog to the adjustment in the embodiments of Figs. 1 to 3, i.e. by manually setting the pressure relief valve.

Similar according to all embodiments is that all counteracting means are elastically deformed by an up-stream movement of the piston, i.e. by an upstream movement force, and thereby apply a counteracting force to the piston.

It is understood that in further embodiments of the invention, features of the embodiments shown in Figs. 1 to 4 can be combined and exchanged. For example, a spring as shown in Fig. 4 can be used in the embod-iment of Figs. 1 and 2 that is compressed when moving the piston upstream and thus excerpts a counter-acting compressive force. As another example, an elastically deformable material can be used in the em-bodiment of Fig. 4 instead of the coil spring, which elastically deformable material can be attached to the piston and to the housing and is stretched by an upstream movement of the piston.

Figs. 5A to 5E show a sequence of the actuator arrangement 10 of Fig. 1 at different stages, e.g. different stages during an injection molding cycle. In order to provide a clear overview, only some of the components of the actuator assembly are provided with reference signs. Components and features of which the refer-ence signs are not repeated in Figs. 5A to 5E resemble the components and features in Fig. 1.

The actuator arrangement is shown in its assembled configuration installed in a partly shown hot runner system 50, the hot runner system 50 comprising a heated manifold 52 having a distribution channel 54 for distributing the molten injection fluid material, and a nozzle 56 having a gate 58 and a fluid delivery channel 60 fluidically connected to the distribution channel 54 and configured to receive the molten injection fluid material from the distribution channel 54. The valve pin 28 of the actuator arrangement 10 is arranged co-axial with the fluid delivery channel 60 and extends into the nozzle 56.

Fig. 5A shows the actuator arrangement 10 in a downstream gate closed stage. Namely, the piston 16 and the valve pin 28 are at a downstream gate closed position where the valve pin 28 blocks flow of injection fluid material through the gate 58 of the system to a mold (not shown) . In this stage, the first drive chamber 18 is or at least has previously been pressurized in order to urge the piston 16 and valve pin 28 to the downstream gate closed position.

As can be seen in Fig. 5A, the counteracting means 30 is arranged such that there is a defined gap 36 be-tween the counteracting means 30, more precisely the free end 32 of the counteracting means 30, and the opposing component (here the inner top surface 34 of the fluid sealed chamber 12 /the actuator housing 14) . Provision of the gap 36 allows free, unhindered upstream movement of the piston 16, the valve pin 28 and here the counteracting means 30 at least along an initial part of the adjustable stroke length, which free initial movement is not affected by any counteracting force of the counteracting means 30. The distance of the free initial part of the adjustable stroke length equals the gap length. Hence, a sufficiently fast opening of the gate 58 can be guaranteed. In the shown example, the gap 36, i.e. a minimum distance between the counteracting means 30 and the inner top surface 34, has a length x of 6.5 mm.

It is understood that in other embodiments, the preferred gap can be provided between the counteracting means and an opposing surface of the piston, namely in embodiments in which the counteracting means is stationary.

Fig. 5B shows the actuator arrangement 10 in a stage during an initial gate opening phase. As can be seen, piston 16 and valve pin 28 have already been withdrawn from the fully gate closed position to a certain ex-tent, i.e. moved slightly upstream towards an upstream gate open position. However, in the shown stage, the flow path through the gate is still just barely blocked.

Upstream movement of the piston 16 by a distance A, here 4 mm, causes a respective upstream move-ment of the valve pin 28 by the same distance A, here 4 mm, and reduces the gap 36 by the distance A (here to 2 mm) . Hence, in the shown stage, the piston 16, valve pin 28 and counteracting means 30 can still be moved freely upstream for a further distance of 2.5 mm, i.e. until the gap 36 is closed. During the initial free upstream movement, enabled by means of the gap 36, the counteracting means 30 is inactive and does not apply any counteracting force.

Fig. 5C shows the actuator arrangement 10 in a subsequent upstream movement stage, exactly at the end of the initial gate opening phase, in which the piston 16, valve pin 28 and counteracting means 30 can be freely moved upstream. At the shown end of the initial gate opening phase, the free end 32 of the counter-acting means 30 abuts the opposing inner top surface 34 of the fluid sealed chamber 12 /the housing 14. From this moment on, the counteracting means 30 starts working upon further upstream movement of the piston 16, i.e. applies a counteracting force to the piston 16 that counteracts the upstream movement of the piston 16.

As can be seen in Fig. 5C, at the end of the initial gate opening phase, when the counteracting means 30 firstly abuts the opposing surface 34 a deformable portion 38 of the counteracting means 30 protrudes up-wardly from the piston 16 by a length B, here in the shown example 11.5 mm. Here, the deformable portion 38, i.e. the counteracting means 30, is still in an uncompressed (non-deformed) state.

In this stage, the piston 16 and the valve pin 28 have been moved upstream by the same distance A, here 6.5 mm. Consequently, the gap 36 is 0 mm in the shown stage.

Figs. 5D and 5E show the actuator arrangement 10 in alternative final upstream gate open positions that have been set by adapting the pressure applied to the second drive chamber 20. The pressure 1 applied to the second drive chamber is lower in the embodiment of Fig. 5D compared to the pressure 2 applied to the second drive chamber in the embodiment of Fig. 5E. Besides the different pressures applied to the second drive chamber 20, there is no difference between the configuration of the actuator arrangement of Fig. 5D and the actuator arrangement of Fig. 5E. In fact, Figs. 5A to 5E all show the same structural actuator ar-rangement 10.

Here, pressure 1 can be for example 30 bar. Pressure 2 can be for example 40 bar. In both Figs. the sec-ond drive chamber 20 can be fluidically connected with a pressure source that provides a constant pressur-ization. The change in the pressure actually applied to the second drive chamber 20 can be adjusted by setting the pressure relief valve 26 (not shown in Figs. 5A to 5E, but see Figs. 1 to 4) .

Fig. 5D shows the actuator arrangement 10 in a further subsequent upstream movement stage compared to Fig. 5C, here at a final upstream gate open position of the piston 16 and the valve pin 28. The piston 16 and the valve pin 28 have been moved upstream by a total distance A of here 9.5 mm. Hence, compared to the stage shown in Fig. 5C, the piston 16 and the valve pin 28 have been further moved upstream by an-other 3 mm. Thus, in this stage the counteracting means 30, more precisely the deformable portion 38, has been compressed by 3 mm. Hence, the compressed length B of the deformable portion (and thus of the length of the counteracting means 30) has been reduced by 3 mm, i.e. to 8.5 mm. This compression of the counteracting means 30 has led to a counteracting force that the counteracting means applies to the piston 16. Further upstream movement and thus compression of the counteracting means 30 would further in-crease the counteracting force. However, in the shown stage and with the applied pressure 1 the counter-acting force at this compression stage equals the upstream movement force caused by the pressurization of the second drive chamber 20 with pressure 1. Hence, in this stage, a balance between the counteracting force and the upstream movement force is reached so that substantially no further upstream movement of the piston 16 and the valve pin 28 is caused and no further compression of the counteracting means 30 is caused.

Thus, a final upstream gate open position has been reached and with the given configuration, including the given pressurization by pressure 1, the stroke length of the actuator arrangement 10 has been adjusted to 9.5 mm.

As the valve pin 28 has been withdrawn upstream from the gate closed position, here by the stroke length of 9.5 mm, gate 58 has been opened to a certain extent so that injection fluid material is enabled through the gate 58 to the mold. As can be seen, in this stage the smallest distance C between the tip of the valve pin 28 and the inner circumferential surface of the nozzle 56 is 1.4 mm so that the flow path section is ra-ther small in this stage.

Fig. 5E shows the actuator arrangement 10 in a further subsequent upstream movement stage compared to Fig. 5C, here at an alternative final upstream gate open position of the piston 16 and the valve pin 28. The piston 16 and the valve pin 28 have been moved upstream by a total distance A of here 14.5 mm. Hence, compared to the stage shown in Fig. 5D, the piston 16 and the valve pin 28 have been further moved upstream by another 5 mm, and compared to the stage shown in Fig. 5C, the piston 16 and the valve pin 28 have been further moved upstream by another 8 mm. Thus, in this stage the counteracting means 30, more precisely the deformable portion 38, has been compressed by 8 mm. Hence, the com- pressed length B of the deformable portion (and thus of the length of the counteracting means 30) has been reduced by 8 mm, i.e. to 3.5 mm. This compression of the counteracting means 30 has led to an in-creased counteracting force that the counteracting means applies to the piston 16. Further upstream movement and thus compression of the counteracting means 30 would further increase the counteracting force. However, in the shown stage and with the applied pressure 2, this increased counteracting force equals the upstream movement force caused by the pressurization of the second drive chamber 20 with pressure 2. Hence, in this stage, a balance between the increased counteracting force and the upstream movement force is reached so that substantially no further upstream movement of the piston 16 and the valve pin 28 is caused and no further compression of the counteracting means 30 is caused.

Thus, an alternative final upstream gate open position has been reached and with the given configuration, including the given pressurization by pressure 2, the stroke length of the actuator arrangement 10 has been adjusted to 14.5 mm.

As the valve pin 28 has been further withdrawn upstream, here by the distance A of 14.5 mm, gate 58 has been opened to an increased extent so that more injection fluid material is enabled through the gate 58 to the mold. As can be seen, in this stage the smallest distance C between the tip of the valve pin 28 and the inner circumferential surface of the nozzle 56 is 2.7 mm so that the flow path section is greater in the stage of Fig. 5E than in the stage of Fig. 5D.

It is understood that the specified mm values are only exemplary. In other embodiments, different lengths /distances can be provided and the stroke length and thus the flow path section can be adjusted in arbitrarily small steps as necessary by simply setting the pressurization.

Claims

Actuator arrangement (10, 110, 210, 310) for a hot runner system of an injection mold, the actuator arrangement (10, 110, 210, 310) being a fluidically driven actuator arrangement (10, 110, 210, 310) and comprising:

a fluid sealed chamber (12) ,

a piston (16) slidably mounted in the fluid sealed chamber (12) and forming a first and a second drive chamber (18, 20) within the fluid sealed chamber (12) , each drive chamber (18, 20) having a respective fluid flow port (22, 24) for selective pressurization of the drive chamber (18, 20) ,

a valve pin (28) interconnected to and moveable with the piston (16) ,

the piston (16) and the valve pin (28) being drivable along a reciprocal path of axial travel by selective pressurization of the first drive chamber (18) or of the second drive chamber (20) , the reciprocal path of axial travel having an adjustable stroke length that extends between a downstream gate closed position where the valve pin (28) blocks flow of injection fluid material through a gate (58) of the system to a mold and an adjustable final upstream gate open position where injection fluid material is enabled through the gate (58) to the mold, and

a counteracting means (30, 130, 230, 330) configured to apply a counteracting force to the piston (16) that counteracts an upstream movement force applied to the piston (16) ,

wherein the adjustable final upstream gate open position is defined by a position where the counteract-ing force equals the upstream movement force and is thus adjustable by selectively setting the pressuriza-tion of the second drive chamber (20) .
Actuator arrangement (10, 110, 210, 310) according to claim 1, wherein the actuator arrangement (10, 110, 210, 310) is configured so that pressurizing the first drive chamber (18) causes the piston (16) and the valve pin (28) to move to the downstream gate closed position, and being configured so that pressurizing the second drive chamber (20) causes the piston (16) and the valve pin (28) to move to the adjustable final upstream gate open position,

wherein the actuator arrangement (10, 110, 210, 310) is configured so that moving the piston (16) and the valve pin (28) towards the adjustable final upstream gate open position causes, at least along a part of the stroke length, the counteracting means (30, 130, 230, 330) to exert the counteracting force that coun-teracts the upstream movement force caused by pressurization of the second drive chamber (20) .
Actuator arrangement (10) according to claim 1 or 2, wherein the counteracting means (30, 130) is interconnected to and moveable with the piston (16) .
Actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims, wherein the counteracting means (30, 130, 230, 330) is arranged inside the fluid sealed chamber (12) .
Actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims, wherein the pressurization of each of the drive chambers (18, 20) is manually adjustable so as to manually adjust the maximum upstream movement force and the maximum downstream movement force.
Actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims, wherein the counteracting means (30, 130, 230, 330) is a spring, preferably a gas spring, and/or a compressible material.
Actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims, wherein the fluid flow port (24) of the second drive chamber (20) is fluidically connected with a pressure relief valve.
Actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims, wherein the actuator arrangement (10, 110, 210, 310) is configured for hydraulic or pneumatic pressurization of the drive chambers (18, 20) .
Actuator arrangement (10, 110, 210) according to at least one of the preceding claims, wherein at a downstream gate closed position, a free end of the counteracting means (30, 130, 230) is spaced from an opposite surface (34) , preferably an inner top surface of the fluid sealed chamber (12) or a surface of the piston (16) , by a predefined gap (36) in order to allow free upstream movement of the piston (16) and the valve pin (28) at least along an initial part of the adjustable stroke length.
Actuator arrangement (10, 110, 210, 310) according to claim 9, wherein the gap (36) is between 1 mm and 10 mm, preferably between 2 mm and 8 mm, more preferably between 3 mm and 6 mm.
Actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims, wherein the stroke length is adjustable between 2 mm and 25 mm, preferably between 4 mm and 22 mm, more preferably between 5 mm and 18 mm.
Actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims, wherein the maximum stroke length is between 3 mm and 25 mm, preferably between 5 mm and 22 mm, more preferably between 8 mm and 18 mm.
Actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims, wherein the minimum stroke length is between 2 mm and 12 mm, preferably between 3 mm and 10 mm, more pref-erably between 4 mm and 8 mm.
Actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims, wherein the counteracting means (30, 130, 230, 330) has a maximum force between //1500 N and 5000 N, prefera-bly between 3100 N and 3700 N, more preferably between 3400 N and 3600 N//.
Hot runner system (50) of an injection mold for conveying molten injection fluid material from a ma-chine nozzle into a cavity, the hot runner system (50) comprising

a heated manifold (52) having a distribution channel (54) for distributing the molten injection fluid mate-rial,

a nozzle (56) having a gate (58) and a fluid delivery channel (60) fluidically connected to the distribu-tion channel (54) and configured to receive the molten injection fluid material from the distribution channel (54) , and

an actuator arrangement (10, 110, 210, 310) according to at least one of the preceding claims.
Hot runner system (50) according to claim 15, comprising a plurality of nozzles (56) and a plurality of actuator arrangements (10, 110, 210, 310) .
Method for adjusting a stroke length of an actuator arrangement (10, 110, 210, 310) , in particular an actuator arrangement (10, 110, 210, 310) according to at least one of claims 1 to 14, which actuator ar-rangement (10, 110, 210, 310) comprises

a fluid sealed chamber (12) ,

a piston (16) slidably mounted in the fluid sealed chamber (12) and forming a first and a second drive chamber (20) within the fluid sealed chamber (12) , each drive chamber (18, 20) having a respective fluid flow port (22, 24) for selective pressurization of the drive chamber (18, 20) ,

a valve pin (28) interconnected to and moveable with the piston (16) ,

the piston (16) and the valve pin (28) being drivable along a reciprocal path of axial travel by selective pressurization of the first drive chamber (18) or of the second drive chamber (20) , the reciprocal path of axial travel having an adjustable stroke length that extends between a downstream gate closed position where the valve pin (28) blocks flow of injection fluid material through a gate (58) of the system to a mold and an adjustable final upstream gate open position where injection fluid material is enabled through the gate (58) to the mold, and

a counteracting means (30, 130, 230, 330) ,

the method comprising the steps of

pressurizing the second drive chamber (20) with a selected upstream movement pressure that applies an upstream movement force to the piston (16) and thus moves the piston (16) upstream, wherein up-stream movement of the piston (16) causes the counteracting means (30, 130, 230, 330) to apply a coun-teracting force to the piston (16) that counteracts the upstream movement force,

wherein the piston (16) reaches the adjustable final upstream gate open position when the counteract-ing force equals the upstream movement force.
Method according to claim 17, wherein the second drive chamber (20) is pressurized with a selected upstream movement pressure between 10 and 70 bar, preferably between 20 bar and 60 bar, more prefer-ably between 30 bar and 50 bar.
Method according to claim 17 or 18, wherein the pressurization of the second drive chamber (20) is set by adjusting a pressure relief valve arranged within a fluidic connection between the second drive chamber (20) and a pressure source.