Device for the simultaneous actuation of a plurality of closure needles in a plastic injection molding machine

Abstract

Device (1) for the simultaneous actuation of a plurality of shut-off needles (32) in needle shut-off nozzles (42) of a plastic injection molding machine comprising a mounting plate, which extend from a hot runner manifold (10) through an intermediate plate (6) of the plastic injection molding machine to an injection mold (8), wherein the shut-off needles (32) are received at their end opposite the injection mold (8) together on a lifting plate (12), which, in the direction of movement of the shut-off needles (32), can be moved by an actuator (16) from a release position, in which liquefied plastic material from the hot runner manifold (10) is injected through the injection openings of the needle shut-off nozzles (42) into the injection mold (8), towards the injection mold (8) to a closing position, in which the flow of the plastic material through the injection openings of the needle shut-off nozzles (42) is interrupted, wherein the lifting plate (12) is supported on a frame (14) which is movable transversely to the direction of movement of the locking pins (32) and which is movable along a guide by the actuator (16), wherein the guide comprises two parallel guide grooves (22) which are formed in the mounting plate (2) of the injection molding machine in a plane perpendicular to the direction of movement of the locking needles (32), and in which the frame (14) is supported via guide rollers (20), characterized by that the lifting plate (12) is supported on the frame (14) via toggle levers (18), that the guide rollers (20) of the frame (14) are each received in a recess (60) within an arm (24) of the frame (14), and that between two recesses (60) a further recess (62) is provided in which one end of a toggle lever (18) is received.

Description

[0001] The invention relates to a device for the simultaneous actuation of a plurality of shut-off needles in a plastic injection molding machine according to the preamble of claim 1.

[0002] In the field of plastics processing, needle valve nozzles are used to produce plastic molded parts. These nozzles inject plastic, which has been liquefied by heating and fed via a melt distributor, through an intermediate plate into an injection mold, from which the molded part can be removed after the plastic has solidified.

[0003] The position of the shut-off needles, which are moved back and forth via an actuating device within a nozzle channel formed in the intermediate plate in order to open or close a corresponding injection opening in the injection mold, must be adjusted very precisely because, for example, if the needle penetration depth is too low, the liquid plastic material can enter the nozzle channel, which, after the plastic material has hardened, will impair the movement of the shut-off needle.

[0004] Furthermore, it is known, for example from EP 0 790 116 A1, to couple a plurality of synchronously actuated locking needles together with a plate or crossbar and to move this plate or crossbar with a drive from a closed position into a release position.

[0005] DE 29 48 624 A1 discloses a drive mechanism for injection molding valve needles, wherein the ends of the needles are accommodated in two opposite lifting plates, which are moved back and forth by means of toggle levers.

[0006] DE 199 07 116 A1 discloses a device for the simultaneous actuation of a plurality of shut-off needles in a plastic injection molding machine, wherein the shut-off needles are accommodated in lifting plates which can be moved up and down via an actuating mechanism in the form of a slotted guide.

[0007] DE 196 11 880 A1 discloses an injection mold with multiple hot runner valve gate nozzles, wherein several needles are actuated simultaneously with an actuating device. For this purpose, a mechanical drive transmission is provided between a lifting drive and needle carrier elements, with elastic intermediate elements provided between the needle carrier elements and the respective needle to compensate for dimensional tolerances.

[0008] As technology advances, ever smaller injection molded parts are produced simultaneously in a single operation in order to reduce manufacturing costs, for example, in a single, identical single cavities arranged side by side within a single injection mold. Therefore, the actuators for each individual cavities should have the smallest possible width, as this width limits the distance between the individual cavities—and thus the size of the injection mold. In other words, a smaller actuator width can reduce the distances between two adjacent individual cavities, which overall leads to a reduction in the size of the injection mold—and thus to lower manufacturing costs.

[0009] Furthermore, there is the problem that the adjustment means provided for adjusting the penetration depth of the shut-off needle on the actuating device are difficult to reach in the assembled state of the known actuating devices, so that a precise adjustment of the penetration depth of the shut-off needles is comparatively time-consuming.

[0010] Accordingly, it is an object of the present invention to provide a device for the simultaneous actuation of a plurality of shut-off needles in a plastic injection molding machine, which device enables a highly precise axial adjustment of the shut-off needle in a particularly simple and time-saving manner, and which at the same time has a more precise and faster reaction when actuating the needle shut-off nozzles compared to the known devices, which allows the production of higher quality products in larger quantities.

[0011] This object is achieved according to the invention by a device having the features of claim 1.

[0012] Further features of the invention are contained in the subclaims.

[0013] According to the invention, a device for the simultaneous actuation of a plurality of shut-off needles of needle valve nozzles in a plastic injection molding machine, which extend from a hot runner manifold through an intermediate plate of the plastic injection molding machine to an injection mold, comprises a lifting plate on which the shut-off needles are jointly received with their end facing away from the injection mold. The lifting plate is moved in the direction of movement of the shut-off needles by an actuator from a release position, in which plastic material liquefied by heating penetrates from the hot runner manifold through the injection openings of the needle valve nozzles into the injection mold, towards the

[0014] Injection mold can be moved into a closed position in which the flow of heated plastic material through the injection openings of the needle valve nozzles is prevented.

[0015] The device according to the invention is characterized in that the lifting plate is supported via toggle levers on a frame, in particular a fork-shaped frame, which is movable transversely to the direction of movement of the closure needles and which can be displaced along a guide by the actuator.

[0016] The actuator is in particular an electrically, pneumatically, or hydraulically actuated actuator, preferably an electric motor. Furthermore, the preferably four toggle levers, with a lifting plate with a length of, for example, 40 cm, have a length of preferably 8 cm and a width of preferably 1 cm, and are arranged at an angle in the range of 45 to 60 degrees to the plane of the lifting plate in the release position of the lifting plate. When the actuator moves the locking pins from the retracted release position into the closed position and in the process displaces the fork-shaped frame by approximately 3 cm into the corresponding end position, the toggle levers have an angle of approximately 90 degrees relative to the plane of the lifting plate.

[0017] It has proven particularly advantageous that the essentially almost parallel course of the toggle levers to the longitudinal axis of the shut-off needles causes a disproportionately strong increase in the thrust force generated by the actuator and transmitted to the lifting plate via the toggle levers when the end position of the closed position is reached, which advantageously leads to the shut-off needles being pressed into the needle seats of the needle valve nozzles after the injection process and shortly before complete closing with a force that is significantly higher than the force of the actuator, thereby pushing the liquefied plastic melt back into the injection mold.

[0018] It is also particularly advantageous that the actuator of the device according to the invention for moving the shut-off needles into the closed position and also from this into the release position has to apply considerably less power, since a disproportionate increase in the friction forces when moving the lifting plate into the closed position for closing the needle shut-off nozzles is avoided.

[0019] According to a further concept underlying the invention, the guide comprises two parallel guide grooves formed in the clamping plate of an injection molding machine in a plane perpendicular to the direction of movement of the valve pins. The fork-shaped frame is advantageously supported by guide rollers in the guide grooves, which significantly reduces frictional forces compared to pure sliding friction.

[0020] Due to the preferably pure rolling friction between the guide rollers, which are preferably mounted laterally on the fork-shaped frame, as well as the preferably roller-like bearing of the toggle levers, the friction forces can be reduced by a factor of approximately 2 to 20 compared to a pure plain bearing.

[0021] Furthermore, the reduced friction and the variable reduction ratio resulting from the use of toggle levers significantly reduce the adjustment time for actuating the shut-off pins. This is because, at the beginning of the closing movement, the adjustment travel of the lifting plate is disproportionately large relative to the adjustment travel of the fork-shaped frame, and the actuating force on the shut-off pins, which can be moved with only small forces in the release position, is comparatively small. In other words, a variable reduction ratio between the actuation travel of the actuator and the adjustment travel of the lifting plate is advantageously achieved.

[0022] Due to the reduction of the frictional forces and the associated lower power requirement when moving the fork-shaped frame by the actuator, the positioning accuracy of the shut-off needles in the aforementioned embodiment of the device according to the invention is also advantageously increased.

[0023] Likewise, due to the non-linear transmission ratio, a significantly reduced starting torque of the actuator is advantageously required to move the valve pins into the release position after an injection process. The breakaway torque required to move the lifting plate from the closed position, which is caused by the cooled residues of the plastic melt in the area of ​​the pin tips and the pressing of the pin tips into the pin seats of the needle valve nozzles, can be overcome much more easily by the actuator due to the variable reduction ratio of the toggle lever drive and the associated reduced actuation forces. This advantageously reduces the drive power—and thus the size and energy consumption—of the actuator.

[0024] It has also proven particularly advantageous if the toggle levers and the guide rollers, via which the fork-shaped frame is supported on the guide groove of the clamping plate, are arranged substantially along a central center line of each arm of the fork-shaped frame.

[0025] The previously described embodiment has the particular advantage that the arrangement of the guide rollers along a central center line within the outer edges of the arms of the fork-shaped frame provides particularly high stability of the lateral holding forces of the guide rollers, thereby counteracting any shear forces that may occur. It is also advantageous if the bearing axes of the guide rollers are arranged in the fork-shaped frame such that, viewed from the injection mold, the guide rollers protrude slightly, preferably by less than 1 mm, from the rear of the fork-shaped frame in order to limit the contact area with the wall of the guide groove in the clamping plate to the guide rollers and, furthermore, to advantageously further reduce the surface friction between the surfaces of the fork-shaped frame and the guide grooves.

[0026] According to a further embodiment of the invention, the guide rollers of the fork-shaped frame are each accommodated in a recess within an arm of the fork-shaped frame. In this embodiment of the invention, the end of each of the preferably four or more toggle levers is accommodated in a further recess of the fork-shaped frame, which is arranged between two recesses for the guide rollers. This results in a particularly compact design and a central introduction of the force applied by the actuator into the toggle levers and, via these, into the lifting plate.

[0027] Alternatively, however, it can also be provided that the ends of the toggle levers and the recess in which the guide rollers are accommodated via corresponding pins on the fork-shaped frame are arranged within a common recess in the fork-shaped frame. This advantageously increases the travel distance required for the toggle levers when moving the fork-shaped frame from the release position to the closed position, eliminating the need for material webs that would otherwise be located between two recesses.

[0028] According to a further embodiment of the device according to the invention, the toggle levers are rotatably supported by bearing bushes on the lifting plate and the fork-shaped frame, thereby further reducing frictional forces. It is also conceivable to use needle bearings or ball bearings instead of bearing bushes to reduce frictional forces. The material combination of the bearing bushes and the corresponding bearing journals for the toggle levers is preferably selected such that a self-lubricating, maintenance-free bearing arrangement is achieved, which does not require the use of externally supplied lubricant. Such a bearing arrangement can be achieved, for example, using steel journals or chrome-plated journals in combination with bearing bushes made of sintered metal or bronze.

[0029] According to a further embodiment of the invention, the lifting plate has guide bores which run parallel to the longitudinal axes of the locking needles and through which guide pins extend, on which the lifting plate is slidably guided.

[0030] This offers the advantage that the lifting plate is moved in a well-defined manner along several linear guides, with the forces applied by the actuator being symmetrically transmitted to the lifting plate via a total of four toggle levers. Because the linear guides act at multiple points, this results in a high degree of security against tilting of the lifting plate during its movement into and out of the closed position.

[0031] In the preferred embodiment of the invention, the guide pins are supported on the machine-side clamping plate of the plastic injection molding machine and extend through the otherwise unsupported cavity in the frame plate up to the underlying support plate for the hot runner manifold, to which the manifold is attached. This additionally spans the cavity in which the lifting plate moves up and down, thereby increasing the rigidity of the plate on which the hot runner manifold is located many times over. The significantly increased rigidity of the entire construction achieved in this way means that the sometimes considerable forces exerted on the housings of the needle valves and via these on the hot runner manifold due to the cross-sectional area of ​​the shut-off needles in conjunction with the high pressures of the plastic melt can be advantageously absorbed and transferred to the clamping plate.This allows the material thicknesses of the intermediate plate and the clamping plate, or the frame plate for the hot runner manifold, required to achieve the required deformation tolerances to be significantly reduced, thereby advantageously reducing the weight and also the manufacturing costs.

[0032] The invention is described below with reference to the drawings using a preferred embodiment.

[0033] The drawings show: Fig. 1 a schematic side view of the preferred embodiment of the actuating device according to the invention in the closed position, Fig. 2 a schematic side view of the preferred embodiment of the actuating device according to the invention in the release position, Fig. 3 a schematic cross-sectional view of the preferred embodiment of the actuating device according to the invention perpendicular to the plane of movement of the fork-shaped frame, and Fig. 4 a schematic cross-sectional view of the preferred embodiment of the actuating device according to the invention along the axis of the fork-shaped frame.

[0034] The representations of the Fig. 1 and Fig. 2 both show the device 1 according to the invention and differ only in the illustrated positions of the lifting plate 12 and the fork-shaped frame 14. In Fig. 1, the device 1 according to the invention is shown in the closed position, in which a flow of plastic material through the injection openings of the needle valve nozzles 42 into the cavities of the injection mold 8 is prevented, whereas in Fig. 2 shows the state of the device 1 according to the invention in the release position, in which liquefied plastic material can enter the injection mold 8. The following description of the representation of Fig. 1 essentially also refers to the representation of Fig. 2.

[0035] As in Fig. 1, a device 1 for the simultaneous actuation of a plurality of shut-off needles 32 of needle valve nozzles 42 in a plastic injection molding machine comprises a clamping plate 2, a frame plate 4 arranged adjacent to the clamping plate 2 as viewed in the direction of the injection mold 8, and an intermediate plate 6 adjacent to the clamping plate. The frame plate 4 has, on its side facing the intermediate plate 6, a recess 7 for receiving the hot runner manifold 10, which distributes the plastic melt introduced into the hot runner manifold 10 via a feed channel 44 to a plurality of needle valve nozzles 42.

[0036] According to the presentation of Fig. 1, the frame plate 4 has, on its side facing away from the intermediate plate 6, a further recess forming a cavity 9 for receiving the lifting plate 12, in which a plurality of needle receptacles 34 are arranged to hold the shut-off needles 32 of the needle shut-off nozzles 42, which pass through the hot runner manifold 10 and the frame plate 4, and to move them into a release position or a closed position following the movement of the lifting plate 12. The cavity 9 with the lifting plate 12 is in turn closed on the machine side by the clamping plate 2, in which a particularly fork-shaped frame 14 is slidably received perpendicular to the direction of movement of the shut-off needles 32.

[0037] In order to transmit the kinetic energy of the particularly fork-shaped frame 14 to the lifting plate 12 - and thus also to the locking needles 32 - the lifting plate 12 is supported on the fork-shaped frame 14 via toggle levers 18, wherein the toggle levers 18 are preferably pivotably mounted in bearing bushes 30 on the lifting plate 12 and on the fork-shaped frame 14.

[0038] As the representation of Fig. 1 can still be removed, the fork-shaped frame 14 is displaced by an actuator 16, which is preferably arranged laterally on the clamping plate 2 and on the frame plate 4, preferably linearly along a guide within the clamping plate 2 perpendicular to the direction of movement of the shut-off needles 32, in order to open or close the needle shut-off nozzles 42. The actuator 16 is preferably an electric motor with a corresponding gear, which is preferably fastened to the frame plate 4 and / or to the clamping plate 2 via screws (not shown in more detail). The guide comprises a guide groove 22 in the clamping plate 2 which receives the fork-shaped frame 14, as well as guide rollers 20, which are preferably arranged upstream and downstream of the bearing bushes 30 of the toggle levers 18 in the direction of movement of the fork-shaped frame 14.

[0039] The lifting plate 12 of the device 1 according to the invention further has a plurality of guide bores 26, through which respective guide pins 28 extend, which are received on the clamping plate 2, which is preferably constructed in two parts in order to mount the frame 14 in the guide groove or the guide grooves 22. The guide bores 26, together with the guide pins 28, form a sliding guide, for which purpose the guide bores 26 can be provided with inserts (not shown in more detail), for example made of bronze or a similar material with self-lubricating properties. The guide pins 28 are supported with their respective second ends on the inner surface of the frame plate 4 opposite the fork-shaped frame 14, which in the illustration of Fig. 1 and Fig. 2 limits the underside of the cavity 9 in which the lifting plate 12 moves up and down.

[0040] The one in the Fig. 1 and Fig. The actuator 16 of the device 1 according to the invention shown in Fig. 2 further comprises two connections 50 which can be connected, for example, to corresponding hydraulic or pneumatic lines (not shown) in order to control the hydraulic or pneumatic actuator accordingly when it is used.

[0041] The representation of Fig. 3 shows a cross-sectional view along the plane of the fork-shaped frame 14 in the direction of the injection mold 8. It can be seen in detail that the guide groove 22 in the clamping plate 2 has a shape corresponding to the shape of the fork-shaped frame 14, which is adapted to the shape of the fork-shaped frame 14 to ensure precise lateral guidance in width, particularly in the area of ​​the arms 24. In the longitudinal direction of the fork-shaped frame 14, the guide groove 22 has an expanded dimension, thereby defining a free space 57 in which the fork-shaped frame 14 can be displaced back and forth along the axis 58.

[0042] As the representation of Fig. 3 can still be removed, the feed channel 44 is preferably arranged centrally in the clamping plate 2 and the fork-shaped frame 14 is positioned in the clamping plate 2 such that the feed channel is also located at the center point of the preferably four toggle levers 18 when the fork-shaped frame 14 is in the closed position - not shown here. The guide pins 28 are preferably arranged point-symmetrically around the feed channel 44 in the plane of the fork-shaped frame 14 in order to distribute the pressure forces occurring when the needle valve nozzles 42 are closed or opened as evenly as possible across the fork-shaped frame 14.

[0043] According to the presentation of Fig. 4, the toggle levers 18 are pivotably mounted on the lifting plate 12 by means of retaining means 36 that are screwed or pressed laterally into the lifting plate 12. In the case of screw-in retaining means 36, lateral openings 38 are preferably provided in the frame plate 4, through which the screw-in retaining means 36 can be reached with a suitable tool for tightening or loosening the screw connection.

[0044] As the representation of Fig.4 can still be removed, the clamping plate 2 is preferably connected to the frame plate 4 by means of threaded bolts 64, whereby the latter can be easily dismantled in order to gain access to the needle receptacles 34 of the shut-off needles 32. After dismantling the frame plate 4, the shut-off needles 32 can be adjusted in the axial direction by adjusting a corresponding screw element 46, or in the case of a defective shut-off needle 32, they can be removed by removing a fixing element 40 (only indicated schematically) through the corresponding bore in the lifting plate 12 and replaced with a new shut-off needle 32. List of reference symbols 1 device 2 clamping plate 4 frame plate 6 Intermediate plate 7 Recess 8 Injection mold 9 Cavity 10 hot runner manifolds 12 Lifting plate 14 fork-shaped frame 16 Actuator 18 knee levers 20 Leadership role 22 guide groove 24 arms 26 Guide hole 28 guide pins 30 bearing bush 32 locking needle 34 needle holder 36 holding devices 38 Opening 40 Fixing element 42 Needle valve nozzle 44 supply channel 46 screw element 48 actuator 50 connections 52 support bearings 54 Axis of the locking needle 56 Axis of the guide pin 57 open space 58 Axle of the forked frame 60 recess 62 further recess 64 threaded bolts 66 central center line

Claims

[1] Device (1) for the simultaneous actuation of a plurality of shut-off needles (32) in needle valve nozzles (42) of a plastic injection molding machine comprising a clamping plate, which extend from a hot runner manifold (10) through an intermediate plate (6) of the plastic injection molding machine to an injection mold (8), wherein the shut-off needles (32) are received together at their end opposite the injection mold (8) on a lifting plate (12) which can be moved in the direction of movement of the shut-off needles (32) via an actuator (16) from a release position, in which plastic material liquefied by heating is injected from the hot runner manifold (10) through the injection openings of the needle valve nozzles (42) into the injection mold (8), in the direction of the injection mold (8) into a closed position, in which a flow of the plastic material through the injection openings of the needle valve nozzles (42) is interrupted,where, the lifting plate (12) is supported on a frame (14) which is displaceable transversely to the direction of movement of the locking needles (32) and which is displaceable along a guide by the actuator (16), wherein the guide comprises two guide grooves (22) running parallel to one another, which are formed in the clamping plate (2) of the injection moulding machine in a plane running perpendicular to the direction of movement of the shut-off needles (32), and in which the frame (14) is supported via guide rollers (20), characterized by , that the lifting plate (12) is supported on the frame (14) via knee levers (18), that the guide rollers (20) of the frame (14) are each received in a recess (60) within an arm (24) of the frame (14), and that between two recesses (60) a further recess (62) is provided, in which one end of a toggle lever (18) is received. [2] Device according to claim 1, characterized bythat the toggle levers (18) are supported rotatably via bearing bushes (30) on the lifting plate (12) and on the frame (14). [3] Device according to claim 1 or 2, characterized by that the lifting plate (12) is slidably guided via guide pins (28) which extend parallel to the axis (54) of the locking needles (32) through guide bores (26) in the lifting plate (12). [4] Device according to claim 3, characterized by that the guide pins (28) extend from the clamping plate (2) to the frame plate (4) and support it against the clamping plate (2). [5] Device according to one of claims 1 to 4, characterized by that the closure needles (32) are each held with their ends opposite the injection mold (8) on a needle holder (34) on the lifting plate (12), which is adjustable in the axial direction of the closure needles (32). [6] Device according to one of claims 1 to 5, characterized by that the toggle levers (18) and the guide rollers (20), via which the frame (14) is supported on the guide groove (22) of the clamping plate (2), are arranged along a central center line (66) of an arm (24) of the frame (14).

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