WO2007137648A1

WO2007137648A1 - Injection molding device with needle closing jet and drool channel

Info

Publication number: WO2007137648A1
Application number: PCT/EP2007/003088
Authority: WO
Inventors: Herbert Günther
Original assignee: Günther Heisskanaltechnik Gmbh
Priority date: 2006-05-31
Filing date: 2007-04-05
Publication date: 2007-12-06
Also published as: DE202006008744U1; TW200804057A

Abstract

The invention relates to an injection molding device (10) with a clamping plate (12) and a distributor plate (14), in which there is at least one flow channel (16) for free-flowing material, which has at least one shut-off needle (20) passing through it at least in sections that can be shifted lengthwise into open or closed position by means of a drive. In addition, the injection molding device (10) has at least one needle closing jet, through which the free-flowing material can be fed to a separable mold insert with continuation of the flow channel (16), and a guide bush (38) to guide and seal the shut-off needle (20). An improved injection molding device alternative to the prior art is provided by a drool channel to receive and/or dispose of fluid escaping from the flow channel (16), which is provided for between the distributor plate (14) and the clamping plate (12).

Description

INJECTION MOLDING DEVICE WITH NEEDLE LOCK AND SUCTION CHANNEL

The invention relates to an injection molding apparatus according to the preamble of claim 1.

Needle valve nozzles are used in injection molding apparatus to supply a flowable mass to a separable mold insert at a prescribable temperature under high pressure. They usually have pneumatically or hydraulically driven shut-off needles that periodically open and close the gate openings in the mold insert. This allows for the most accurate material dosages, especially with a fast shot sequence. However, the flowable mass can also be injected segmented, e.g. when cascading.

Each closure needle is axially displaceable in the tool-side region of the injection molding device and preferably guided in the nozzle-side region centrally through a flow channel for the mass to be processed (see for example DE 32 49 486 C3 or DE 34 03 603 A1). The flow channel ends in a nozzle mouthpiece which forms a nozzle outlet opening at the end. In the closed position, the lower end of the locking needle engages in a sealing seat, which is formed in the nozzle mouthpiece or in the mold insert.

For tight guidance of the closure needle usually a guide or sealing bush is used in the distributor plate of the injection molding, hereinafter referred to uniformly as a guide bush which receives the cylindrical shaft of the locking needle (see, for example, DE 39 26 357 A1 or EP 1 223 020 B1). Between the locking needle and the guide bush remains a cylindrical space into which flows during the operation of the injection molding flowable material, so that the locking needle is sealed against the flow channel. At the same time creates a lubricating effect, which reduces the friction between the locking needle and the guide bushing.

Despite optimal design of such a sealing system, it can not be avoided due to the relatively high pressures within the tool and due to the lifting movements of the locking needle that the mass to be processed penetrates through the guide bushing to the outside. Material losses are the result. Moreover, the scraps contaminate both the sealing needle and the tool, which not only affects the sealing effect, but can permanently hinder the opening and closing movement of the locking needle. Elaborate cleaning or maintenance work is inevitable. In addition, due to the high frictional forces between the locking needle and the flowable material, gases and acids can form, which also seep outward and can attack the tool surfaces.

In order to counteract this, DE 100 25 341 A1 proposes collecting the material which flows out of the flow channels and / or the guide bushing in a seepage system and discharging it to the outside. To form the seepage system, the distributor plate is subdivided into two surface-abutting, preferably plate-shaped sections. In the abutting surface of one section seep channel forming grooves are milled, the openings of which are closed by the corresponding abutment surface of the other section. Each seepage channel is fluidly connected to a seepage bore formed concentrically with the closure needle so that the excess material taken up in the seepage bores can be removed through the corresponding seepage channels. The individual seepage channels are in turn fluidly connected to a central seepage passage which, like the seepage channels, is designed as a milled groove between the distributor plate sections and via which the excess material is discharged to the outside.

The disadvantage of this is that such a structure is very complicated and complicated, whereby the production is made more difficult and expensive. Furthermore, there are sealing problems within the distributor plate, which can lead to further material losses and impurities. The aim of the invention is to avoid these and other disadvantages of the prior art and to provide an alternative and improved injection molding apparatus.

Main features of the invention are specified in the characterizing part of claim 1. Embodiments are the subject of claims 2 to 15.

The injection molding apparatus according to the present invention comprises a platen, a distributor plate in which at least one flow channel for a flowable material is formed, at least one needle valve nozzle through which the flowable material can be fed to a separable mold insert, continuing the flow channel, at least one sealing needle, the Flow channel at least partially longitudinally interspersed and which can be brought by means of a drive in an open and a closed position, and a guide bush for the implementation and sealing of the locking needle. According to the invention, a seepage channel for receiving and / or discharging fluid emerging from the flow channel is provided between the distributor plate and the clamping plate, wherein the infiltration channel is preferably formed in the region of the guide bush to directly receive material or fluid exiting therefrom, for which purpose it is advantageously fluid - Technically connected to this. This also contributes when the guide bush ends in the seepage channel.

Characterized in that the seepage channel is provided between the distributor plate and the clamping plate, the distributor plate can be formed in one piece, in contrast to the distributor plate described in DE 100 25 341 A1, which is advantageous in view of the prevailing high system pressures. In addition, the seepage channel can be retrofitted in existing injection molding in a simple manner, because the manufacturing effort is low overall.

According to a preferred embodiment of the injection molding device according to the invention, the guide bush ends directly in the seepage channel, so that no further intermediate lines or the like are required to form the fluidic connection between the guide bush and the seepage channel.

Structurally, it is advantageous if the seepage channel is formed by a ring-shaped or cylindrical element which lies between the clamping plate and the distributor plate and which preferably has a bush, a sleeve or the like. which is concentric with the guide bush is arranged. In this way, results in a very simple and inexpensive construction.

If a plurality of drainage channels are provided correspondingly for a plurality of guide bushes, these advantageously lead to a central seepage passage, via which the excess material or the resulting gas is discharged. The seepage passage is preferably formed as a groove in an outer surface of the platen facing the distribution plate and covered, for example, with a cover plate as a cover element, which is penetrated by the individual seepage channels, which is described in more detail with reference to the drawing.

According to a further embodiment of the injection molding device according to the invention a cleaning device for cleaning the sealing needle is provided in the platen, which is arranged in the region of the seepage passage and fluidly connected to the seepage channel and / or the central seepage passage. In this way, the contaminants removed by the cleaning device can also be removed via the seepage channel and / or the central seepage passage.

A further embodiment provides that the guide bushing comprises a seal, in particular in the form of a sealing ring, for further sealing of the locking needle within the guide bushing. Accordingly, only a slight amount of flowable material can inadvertently penetrate the guide bush, thereby further reducing the amount of scrap.

Furthermore, the guide bushing preferably has at least one region which comprises the closure needle with little play and which lies at least in sections in the flow channel. As a result, an area of the guide bush is always in direct contact with the flowable material, which exerts pressure on the guide bush with each injection. This results in that the contact area is pressed while overcoming the small amount of play sealing against the locking needle, so that during the high pressure phase hardly more material can penetrate through the guide bushing out of the injection molding device to the outside. At the same time the locking needle is fixed by the guide bush in its central position, so that during the injection pressure phase no deflection movements of the locking needle can occur. If the injection pressure drops, the guide bush releases the needle again, which can be brought immediately into its closed position. Advantageously, the region has or forms at least one contact surface for the flowable material, which likewise lies at least in sections in the flow channel. The material to be processed can therefore act directly on the contact surface and actuate the guide bush in this area as a check valve.

In terms of construction, it is advantageous if the region with the contact surface projects radially or axially into the flow channel. This not only simplifies the structure of the guide bush, but also their installation, which has a favorable overall effect on the manufacturing and assembly costs.

Particular advantages arise when the area and / or the contact surface are surrounded on all sides by flowable material. The latter can thereby act evenly on the guide bushing or on the contact surface, so that the region projecting into the flow region is pressed uniformly over the entire circumference of the closure needle. The locking needle is sealed on all sides and centered in its central position. This also contributes, if the area has a cylindrical inner circumference, which is aligned coaxially to the closure needle. This inner circumference thus forms not only a sealing surface between the locking needle and the guide bush, but also a centering element for the locking needle.

In order for the pressure to act directly on the sealing surface or centering element, the cylindrical inner circumference and the contact surface lie substantially axially at a height, i. the cylindrical inner circumference is also directly in the flow channel.

An advantageous development provides that the region projecting into the flow channel forms an end region of the guide bush, wherein the contact surface is formed by the outer circumference of the region. This also allows a simple and inexpensive design of the guide bush, which can be preferably manufactured as a turned part.

In order to ensure a uniform pressing of the guide bush, the outer circumference of the end region is preferably a contact surface, preferably a sloping conical surface. This not only improves the contact with the flowable material. At the same time, the wall thickness of the end region, which can always be reliably compressed radially, is reduced. It may be advantageous if the conical surface is concave or convex. According to a further aspect of the present invention, the guide bush at an axial distance to the projecting into the flow channel area at least one further area having a coaxial with the locking needle aligned cylindrical inner circumference, wherein the preferably superposed end portions receive the locking needle with the least possible movement play. As a result, the locking needle is always held and guided exactly in a central position, so that deflections from the central position are effectively avoided, at least in the guide area.

A space formed between the end portions, the inner diameter of which is slightly larger than the outer diameter of the locking needle, provides lubrication of the guide sleeve slidably guided in the locking needle by the material to be processed, which reduces the frictional forces in the guide bushing.

The end regions and the free space preferably form a central through-bore.

Another embodiment of the present invention provides that the guide bushing is arranged in the distributor plate. Preferably, the guide bush is seated in a recess formed in the distributor plate, wherein the guide bush is fixable in the recess.

So that substantially no material can escape from the tool through the recess, the guide bushing is sealed within the recess via at least one surface perpendicular to the longitudinal axis, wherein the surface preferably forms the bottom of the recess.

For handling and fixing the guide bush, it is advantageous if this has a flange which sits centrally in the recess. On the flange, a neck portion is formed, which carries or forms the ends projecting into the flow channel area.

If the wall thickness of the end region as a whole selected smaller than the wall thickness of the neck portion, the end portion is extremely uniformly radially compressed during each injection process. The inner circumference of the end portion defines like a valve positively around the outer periphery of the locking needle, so that no material more of the flow channel in the guide bush penetrate and thus can escape to the outside.

Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of embodiments with reference to the drawing, which shows a schematic partial sectional view of an injection molding with a seepage system.

The generally designated 10 in the drawing injection molding device is used for the production of moldings from a flowable mass, such as a plastic melt. It comprises a clamping plate 12 and, in parallel thereto, a distributor plate 14 in which a system of flow channels 16 is formed. These each open in a needle valve nozzle, not shown, which is mounted on the underside 18 of the distributor plate 14.

Each needle valve nozzle comprises a nozzle body, not shown, preferably externally heated, in which a material tube for the continuation of the flow channel 16 is formed concentrically to the longitudinal axis L of a closure needle 20. The latter ends in a nozzle mouthpiece which forms a nozzle outlet opening at the end, via which the material to be processed is fed through a gate opening through a separable mold insert, also not shown.

To open and close the gate preferably formed in the mold insert, the closure needle 20 is provided which passes through the flow channel in the needle valve and a portion of the flow channel 16 in the distributor plate 14 longitudinally displaceable by a mechanical, electric, pneumatic or hydraulic drive, not shown a closed and open position can be brought. In the closed position, the closure needle 20 engages with a closure member formed end (not shown) through the nozzle outlet opening sealingly into the gate opening.

In the tool-side area, the closure needle 20 is connected through the distributor plate 14 and the clamping plate 12 above the platen 12 to the drive, which is not shown in detail in Fig. 1. To carry out the closure needle 20, a through-bore 22 is introduced into the clamping plate 12, the inner diameter of which is greater than the outer diameter of the closure needle 20.

In the platen 12, a cleaning device 24 is preferably formed for each locking needle 20. This has a housing 26 with a substantially cylindrical wall and an end formed, radially inwardly projecting flange rim 28. This carries axially a plurality of disc-shaped cleaning elements 30, which are peripherally held by annular spacers 32 at equal intervals. To secure the trained as a flat body cleaning elements 30 and the intermediate spacers 32 within the cleaning device 24 is a locking ring 34, which is preferably screwed into the housing 26.

Each cleaning element 30 is provided centrally with an opening, not shown, for carrying out the sealing needle 20. The inner diameter of the opening is chosen so that the edge formed by the opening with the outer periphery 36 of the locking needle 20 is form and frictionally in contact. On the outer circumference 36 of the locking needle 20 adhering material residues that emerge, for example, from the guide bush 38 described in more detail below, are thus always reliably detected by the shape-matched edges of the cleaning elements 30 and removed from the locking needle 20, i. the closure needle 20 guided through the cleaning device 24 or through the cleaning elements 30 is kept clean during the operation of the injection molding apparatus 10 with each reciprocation of the closure needle 20.

The upper bushing 40 and the lower bushing 42 are arranged one above the other according to the drawing in the extension direction of the locking needle 20 and engage positively with each other, wherein between the two bushing parts 40 and 42, a sealing ring 44 is provided which prevents the passage of liquid material between the socket parts. The sealing ring 44 is preferably made of a resilient steel or made of a resilient high temperature resistant plastic. Through the guide bushing 38 extends a central through hole 45, whose inner diameter in end regions 46, 48 of the guide bushing 38 to a small movement play the outer diameter of the Locking needle 20 corresponds. The latter is thus within the guide bushing 38 a central guide and support.

Between the end or guide regions 46, 48, a cylindrical free space 50 is axially formed, the inner diameter of which is slightly larger than the outer diameter of the closure needle 20. During operation of the injection molding apparatus 10, it selectively receives a small amount of flowable material from the flow channel 16, resulting in the sealing of the sealing needle 20 with respect to the flow channel 16 and the tool environment. At the same time the flowable mass within the space 50 acts as a lubricant, so that the friction between the locking needle 20 and the guide bushing 38 is reduced. The latter is - as well as the through hole 22 in the platen 12 - coaxial with the locking needle 20 and to its longitudinal axis L.

The guide bushing 38 has a widened flange portion 52, which sits centrally in a recess 54 in the distributor plate 14. About the flange portion 52, the guide bush 38 in the direction of the platen 12 has a smaller main outer portion 56 in the outer diameter, the end forms the upper end or guide portion 46. This encloses the locking needle 20 with its cylindrical inner circumference 58 except for a small movement play. At the same time he limited the cylindrical space 50 upwards, so that the material contained therein can not penetrate to the outside.

The main area 56 is coaxially enclosed by a threaded bushing 60. This has an external thread 62 which engages in a corresponding internal thread 64 of the recess 54. Turning the screw 60 in the recess 54 and thus in the distributor plate 14, the guide bush 38 is set in the tool. The bottom 66 of the recess 54 and the unspecified underside of the flange portion 52 lie positively against one another, so that the guide bushing 38 not only fixed in the distributor plate 14, but at the same time is sealed over a surface perpendicular to the longitudinal axis L of the closure needle 20.

Under the flange portion 52, the guide bushing 38 in the direction of the needle valve nozzle, not shown, on a neck portion 68 whose outer diameter is also smaller than the outer diameter of the flange portion 52. The lower end of the neck portion 68 forms the lower end or guide portion 48, with its cylindrical inner circumference 70, the locking needle 20 except for a encloses slight movement play and the cylindrical space 50 is limited accordingly downwards. In this case, the wall thickness of the end or guide region 48 is preferably smaller than the wall thickness of the neck section 68. In addition, the outer circumference 72 of the end region 48 at the level of the inner circumference 70 forms a contact surface 74 for the flowable mass, preferably a sloping or conical surface , so that the wall thickness of the end portion 48 decreases even further towards the Nadelverschlußdüse.

For receiving the neck portion 68 in the distributor plate 14, a through hole 76 is introduced between the recess 54 and the flow channel 16, the inner diameter of which substantially corresponds to the outer diameter of the neck portion 68. This extends as far as the flow channel 16, wherein the end region 48 with its locking needle 20 enclosing inner circumference 70 and its contact surface 74 projects radially and concentrically to the longitudinal axis L in the flow channel 16 in. The end portion 48 for the sealing needle 20 is thus completely in the mass flow, wherein the contact surface 74 contacts the material and - as well as the sealing needle 20 - is flushed in the flow channel 16 on all sides of the material to be processed.

The function of the needle seal or the guide bushing 38 is based essentially on the elastically deformable wall of the end portion 48 located in the flow channel 16. When the closure nozzle 20 is opened, it first slides freely within the guide bush 38 from the closed position to the open position, the end portions 46 and slide 48 with little play on the outer periphery 36 of the locking needle 20 along. If this has reached its end or open position, the injection pressure is built up, that is, the melt to be processed is pressed at high pressure through the flow channel 16 into the mold cavity. In this case, the flowable mass flows around the closure needle 20 and also the contact surface 74 of the end portion 48 uniformly from all sides, wherein the end portion 48 is radially compressed due to its relatively small wall thickness. The cylindrical inner periphery 70 defines like a closing or valve member positively and sealingly against the outer periphery 36 of the locking needle 20 so that no material can penetrate from the flow channel 16 into the free space 50 of the guide bushing 38 during the injection process. At the time of high pressure load in the flow channel 16 so no material can penetrate through the guide bush 38 through out of the tool to the outside. A supplementary or additional sealing is achieved via the sealing ring 44. Furthermore, the locking needle 20 is fixed concentrically to the longitudinal axis L in position. It can no longer be deflected by the flowing material from its central position, which has a favorable effect on the flow conditions in the flow channel 16.

Once the injection cycle has ended, the pressure in the flow channel 16 is reduced again. The end portion 48 resumes its original shape due to its elasticity and the inner periphery 70 of the end portion 48 detaches from the outer periphery 36 of the locking needle 20. This can be moved freely in the closed position.

It can be seen that the wall thickness of the preferably made of a steel material end portion 48 is selected so that it is deformable in the elastic range of the material and that the slight movement between the locking needle 20 and the inner circumference 70 is overcome by the material pressure, so that during the high pressure phase in the tool, the locking needle 20 is locked in the middle and no material can penetrate to the outside. Nevertheless, the locking needle 20 between the individual printing cycles within the spaced end portions 46 and 48 is precisely guided.

For receiving and discharging flowable material, gases and / or vapors, which optionally emerge between the locking needle 20 and the guide bush 38 at the top of the guide bushing 38 in the direction of the clamping plate 12 is between the platen 12 and the distributor plate 14 according to the invention a seepage channel 78 in the form of an annular sleeve or bush 79 is provided, which surrounds the over the distributor plate 14 projecting end of the guide bush 38 concentrically. The seepage channel 78 opens at its end facing the clamping plate 12 into a central seepage passage 80, which is milled below the recess 82 serving to receive the cleaning device 24 into the outer surface of the clamping plate 12. The open side of the central seepage passage 80 is covered with a plate-shaped cover member 84 which is fixed to the platen 12 by screws 86. The transition between the seepage channel 78 and the central seepage passage 80 is formed fluid-tight, so that no material and / or gas can escape to the outside. If the injection molding device 10 comprises a plurality of seepage channels 78, these preferably all open into a common central seepage passage 80. By the seepage channels 78 and the central seepage passage 80 having seeping system ensures that all flowable materials and / or gases that exit through guide bushings 38 from the distributor plate 14, are absorbed and properly discharged. Accordingly, such fluids can not damage the injection molding apparatus 10 or the sealing needles 20. Furthermore, the cleaning and maintenance times of the injection molding apparatus 10 are further reduced.

The invention is not limited to the previously described embodiment of the injection molding apparatus according to the invention. Rather, changes and modifications are possible without departing from the scope defined by the appended claims.

Thus, the guide bush, for example, be formed in one piece. Furthermore, if necessary, the sealing ring 44 can be dispensed with.

The wall thickness of the end or guide region 48 need not necessarily be smaller than the wall thickness of the neck portion 68. Both may also have approximately the same wall thickness. Important for the sealing effect is only that the flowing around the flowable material end 48 during the high pressure phase can elastically deform so far that the inner periphery 70 sealingly around the outer periphery of the locking needle 20 sets. The optionally formed at the end of the end portion 48 contact surface 74 may also be concave or convex, which also can be easily and precisely finished. The surface course has a favorable effect on the printing effect.

To fix the guide bushing 38, a flange ring or the like can be used instead of the screw bushing 60, which is fixed by means of screws to the distributor plate 14. It is important here that the guide bushing 38 is sealed within the receiving recess over at least one surface 42 perpendicular to the longitudinal axis L.

Further, the seepage channel 78 and the central seepage passageway 80 may be formed in other ways. Thus, the sleeve 79 and provided with a corresponding hole or opening cover plate 84 can be welded, soldered or glued together. But you can also form the sleeve 79 and the cover plate 84 in one piece. Essential for the simple construction, however, is that the seepage channel 78 is arranged between the clamping plate 12 and the distributor plate 14, so that the seepage system can also be retrofitted at any time. Another advantage is that the distributor plate 14 is formed in one piece, which has a very favorable effect on the production costs.

All of the claims, the description and the drawings resulting features and advantages, including design details and spatial arrangements may be essential to the invention both in itself and in various combinations.

Reference number list

Injection molding device 50 free space

Clamping plate 52 flange area

Distributor plate 54 recess

Flow channels 56 main area

Bottom 60 screw socket

Locking pin 62 external thread

Through hole 64 internal thread

Cleaning device 66 bottom

Housing 68 neck section

Flange edge 70 inner circumference

Cleaning elements 72 outer circumference

Spacers 74 contact surface

Circlip 76 Through hole

Outer circumference 78 seepage channel

Guide bushing 79 annular element upper bushing part 80 central seepage passage lower bushing part 82 recess

Sealing ring 84 cover element

Through hole 86 screws

end

Claims

claims

1. Injection molding apparatus (10) with a clamping plate (12), with a distributor plate (14) in which at least one flow channel (16) is formed for a flowable material, with at least one needle valve nozzle through which the flowable material with continuation of the flow channel ( 16) can be fed to a separable mold insert, with at least one closure needle (20) which passes through the flow channel (16) at least in sections and which can be brought into an open position and a closed position by means of a drive, and with a guide bush (38). for guiding and sealing the closure needle (20), characterized in that between the distributor plate (14) and the clamping plate (12) is provided a seepage channel for receiving and / or discharging fluid emerging from the flow channel (16).

2. Injection molding apparatus according to claim 1, characterized in that the seepage channel (78) in the region of the guide bush (38) is formed.

3. Injection molding apparatus according to claim 1 or 2, characterized in that the seepage channel (78) with the guide bush (38) is fluidly connected.

4. Injection molding apparatus according to one of claims 1 to 3, characterized in that the guide bushing (38) ends in the seepage channel (78).

5. Injection molding apparatus according to one of claims 1 to 4, characterized in that the seepage channel (78) is formed by a ring-shaped or cylindrical element (79).

6. Injection molding apparatus according to claim 5, characterized in that the annular element (79) or a socket, a sleeve or the like. is, which is arranged concentrically to the guide bush (38).

7. Injection molding apparatus according to one of claims 1 to 6, characterized in that the seepage channel (78) in a central seepage passage (80) opens.

8. Injection molding apparatus according to claim 7, characterized in that the seepage passage (80) in the clamping plate (12) is formed.

9. Injection molding apparatus according to claim 7 or 8, characterized in that the seepage passage (80) is at least partially covered by a cover (84).

10. Injection molding apparatus according to one of claims 1 to 9, characterized in that in the clamping plate (12) a cleaning device (24) for cleaning the locking needle (20) is provided.

11. Injection molding apparatus according to claim 10, characterized in that the cleaning device (24) in the region of the seepage passage (80) is arranged.

12. Injection molding apparatus according to one of claims 1 to 11, characterized in that within the guide bush (38) a ring element (44) is provided, which comprises the locking needle (20) in a form-fitting manner.

13. Injection molding apparatus (10) according to any one of claims 1 to 12, characterized in that the guide bush (38) has at least one region (48) which comprises the closure needle (20) with little play and the at least partially in the flow channel (16). lies.

14. Injection molding apparatus (10) according to claim 13, characterized in that the region (48) has at least one contact surface (74) for the flowable material or forms, which is at least partially in the flow channel (16).

15. Injection molding apparatus according to claim 13 or 14, characterized in that the region (48) protrudes radially or axially into the flow channel (16).