CA2619440A1

CA2619440A1 - Injection molding device with needle shutoff nozzle and guide bush

Info

Publication number: CA2619440A1
Application number: CA 2619440
Authority: CA
Inventors: Herbert Guenther
Original assignee: Individual
Current assignee: Guenther Heisskanaltechnik GmbH
Priority date: 2005-08-10
Filing date: 2006-08-04
Publication date: 2007-02-15
Also published as: TW200722264A; BRPI0616555A2; EP1922202A1; DE202005012705U1; KR20080041642A; WO2007017187A1; CN101237980A; JP2009504433A

Abstract

Injection-moulding device (1) with a feed plate (3), in which at least one flow channel (4) for a flowable material is formed, with at least one needle valve nozzle, through which the flowable material can be fed in continuation of the flow channel to a separable mould insert, with at least one shut-off needle (20), at least a portion of which passes through the flow channel in a longitudinally displaceable manner and which can be brought by means of a drive into an open position and a closed position, and with a guide bush (30) for leading the shut-off needle (20) through and sealing it. The guide bush has a region which encloses the shut-off needle with a small amount of play and at least a portion of which lies in the flow channel. The region thereby has a contact surface for the flowable material, at least a portion of which lies in the flow channel. The region and the contact surface (44) are flowed around by flowable material on all sides.

Description

INJECTION MOLDING DEVICE WITH NEEDLE SHUTOFF NOZZLE AND GUIDE BUSH
The present invention relates to injection mold device fitted with needle shutoff noz-zles as defined in the preamble of claim 1.

Needle shutoff nozzles are used in injection molding devices to feed a flowable, here-after fluid material at high pressure and predetermined temperature to a separable mold in-sert. These nozzles in general are fitted with pneumatically or hydraulically driven needles periodically opening and closing gate apertures in the mold insert. This feature allows very precisely metering the applied material, in particular are used at high operational rates.
However the fluid material also may be injected segment-wise, for instance in cascade mold-ing.

Each shutoff needle is axially displaceable in the mold-side region of the injection molding device and is made to pass preferably centrally through a flow duct for the material being processed in the nozzle-side region (see for instance DE 32 49 486 C3 or 603 Al). The flow duct terminates in a nozzle mouth element constituting at its end a nozzle discharge aperture. In its closed position, the lower end of the shutoff needle enters a seal-ing seat constituted in the nozzle mouth or in the mold insert.

Typically a guide bush or a sealing sleeve is inserted into the manifold plate of the injection molding equipoment to guide the shutoff needle in sealing manner and receives the cylindrical shank of the shutoff valve (see for instance DE 39 26 357 Al or EP

B1). During operation, fluid material enters a cylindrical clear space is subtended between the shutoff needle and the bush and thereby seals the needle from the flow duct. Lubrication is attained thereby and reduces the friction between the shutoff needle and the bush.

In spite of optimal designs of such sealing systems, the high pressures within the mold and the excursions of the needle inevitably cause the material being processed to leak to the outside through the guide or sealing bush. Accordingly material will be lost. The mate-rial residues contaminate both the shutoff needle and the mold, thereby not only degrading sealing, but in the long run also hampering the opening and closing motion of the shutoff needle. Cumbersome cleaning or maintenance work is inevitable.

The objective of the present invention is to avoid these and other drawbacks of the state of the art and to further improve the guidance and sealing of shutoff needles in injection molding devices. A particular objective is a sealing system which is manufactured economi-cally using simple means and which is easily operated.

The main features of the present invention are defined in claim 1. Embodiment modes of the present invention are defined in claims 2 through 23.

As regards an injection molding device comprising a manifold plate fitted with at least one flow duct for a fluid material, further with at least one needle shutoff nozzle allowing feeding the fluid material while extending the flow duct into a separable mold insert, with at least one shutoff needle running in the flow duct in at least portion-wise displaceable manner and actuated by a drive into an open position and into a closed position, and with a guide bush guiding and sealing the shutoff needle, the present invention provides that the guide bush comprises at least one zone encompassing the shutoff needle at little play of displace-ment and being configured at least portion-wise in the flow duct.

In such a design, a zone of the guide bush is constantly in direct contact with the fluid material which during any injection molding procedure applies pressure to the guide bush.

As a result, the contact zone is forced at in sealing manner, while overcoming the slight play of displacement against the shutoff needle, and consequently no material can leak out through the guide bush of the injection molding device during the high pressure stage. At the same time the shutoff needle is affixed by the guide bush into its center position, and thereby needle deviations are precluded during the injection molding stage. If the injection pressure drops, the guide bush once again releases the needle which can be moved at once into its closed position.

Said zone advantageously comprises or subtends a contact surface for the fluid ma-terial, this surface also being configured at least segment-wise in the flow duct. Therefore the material being processed can directly act on the contact surface and drive the guide bush in this zone as a check valve.

In one advantageous design, said zone enters by the contact surface the flow duct radially or axially. This feature not only simplifies the design of the guide bush, but also its assembly, positively affecting manufacturing and assembly costs.

Particular advantages are attained when the fluid material the said zone and/or the fluid material flows omnidirectionally around said zone and/or contact surface. As a result this material is able to uniformly act on the guide bush respectively the contact surface whereby the zone entering the flow is compressed uniformly over the full circumference of the shutoff needle. The needle then is sealed off omnidirectionally and kept in a center posi-tion. This feature is also attained when said zone comprises an internal, cylindrical periph-ery coaxial with the shutoff needle. As a result said inner periphery not only constitutes a sealing surface between the needle and the guide bush, but also acts as a centering ele-ment for the needle.

In order to allow the pressure to act directly on the sealing surface respectively on the centering element, the cylindrical periphery and the contact surface are configured axi-ally at the same height, that is, the cylindrical inner periphery also is configured directly in the flow duct.

In a further embodiment mode of the present invention, the zone entering the flow duct constitutes an end portion of the guide bush, the contact surface being constituted by the zone's outer periphery. This feature too allows economically manufacturing the guide bush that preferably shall be made on a lathe.

To assure uniform compression of the guide bush, the end position's outer periphery preferably is oblique, preferably a conical surface. Not only does this feature improve contact with the fluid material, but at the same time the end portion's wall thickness is reduced, said end portion always being reliably compressible in the axial direction. It may be advanta-geous too to make the conical surface concave or convex.

In a further embodiment mode of the present invention, the guide bush furthermore comprises, at an axial distance from said zone entering the flow duct, at least one further zone which is fitted with a cylindrical inner periphery coaxial with the shutoff needle, the preferably superposed end zones receiving the shutoff needle with a minimal play of dis-placement. In this manner the shutoff needle always is kept and guided in a center position, whereby deviations from the center position are effectively precluded at least in the guide zone.

A free space subtended between the end zones and of an inside diameter slightly exceeding the shutoff needle outside diameter assures that the material being processed lubricates the shutoff needle made to glide through the guide bush and thus reduces friction in the guide bush.

Preferably the end zones and the free space subtend a central and continuous bore-hole.

In a further significant embodiment mode of the present invention, the guide bush is configured in the manifold plate. However, in alternative or complementing manner, the guide bush also may be mounted in the needle shutoff nozzle. In any case, the guide bush shall preferably be seated in a recess in the manifold plate and/or in the needle shutoff noz-zle, the guide bush being affixable in said recess.

To preclude material from leaking through the recess out of the mold, the guide bush is sealed off within the recess over at lest one surface perpendicular to the longitudinal axis, said surface preferably forming the base of the recess.

Advantageously as regards operating and affixing the guide bush, this bush is advan-tageously fitted with a flange seated centrally in said recess. A neck segment is constituted at the flange and is fitted terminally or is constituted by the zone entering the flow duct.

If the wall thickness of the end zone is selected less than that of the neck segment, then the end zone is compressed radially in very uniform manner during each injection. The inner periphery of the end zone hugs physically and in locking manner the outer periphery of the shutoff needle, as a result of which material from the flow duct no longer can penetrate the bush 30 and from there leak to the outside.

Preferably the flange and the neck segment are integral. However these compo-nents also may be separate and made of different substances.

Further features, particulars, and advantages of the invention are given in the claims and in the description below in relation to the appended drawings.

Fig. I is a partial, schematic view of an injection molding device comprising a sealing system for a shutoff needle, partly shown in section, and Fig. 2 is a separate sectional view of the sealing system of Fig. 1.

The injection molding device denoted overall by 1 in Fig. 1 is used to make molded parts from a fluid material such as a plastic melt. It comprises a clamping plate 2 and paral-lel to it a manifold plate 3 into which is fitted a system of flow ducts 4.
These ducts each is-sue into an omitted needle shutoff nozzle assembled to the lower side 5 of the manifold plate 3.

Each needle shutoff nozzle comprises a preferably externally nozzle casing (also omitted) into which is fitted a material duct which is concentric with the longitudinal axis L
and which extends the flow duct 4. The flow duct 4 terminates into a nozzle mouth element which subtends a nozzle discharge aperture at the end side by means of which the material to be processed is guided through a sprue aperture into a separable (omitted) mold insert.

A shutoff needle 20 is used to open and close the sprue aperture preferably fitted into the mold insert and displaceably passes through the flow duct into the needle shutoff nozzle and a portion of the flow duct 4 in the manifold plate 3, said needle being displaceable by an omitted mechanical, electrical, pneumatic or hydraulic drive into a closed or open position.

In the closed position. In the closed position the shutoff needle 20 enters by its terminal (omitted) sealing element the nozzle discharge aperture and seals off the sprue aperture.

In its mold-side region, the shutoff needle 20 is connected by the manifold plate 3 and the clamping plate 2 to the drive, the needle 20 being fitted at its end with an adapter 22 fitted at its tip 23 with a polygonal cross-section. Said tip is to be driven by an omitted tool with which to assemble the needle 20 and to adjust it longitudinally. An omitted locknut is used to irrotationally affix the needle 20.

A borehole 6 of which the inside diameter is larger than the outside diameter of the shutoff needle 20 is fitted into the clamping plate 2 to pass this shutoff needle 20.

The clamp plate 2 also comprises a cleaning element 10 cleaning the shutoff needle 20. Said cleaning element comprises a housing 11 having a substantially cylindrical wall and a terminal, radially inward flange rim 13. This rim is fitted with several planar cleaning elements 40 kept equidistant by annular spacers 14 at the side of the rim. T A
securing ring preferably axially threaded into the housing 11 secures the planar cleaning elements 40 15 and the spacers 14 in-between within the cleaning element 10.

Each cleaning element 40 is fitted centrally with an omitted aperture passing the shutoff needle 20. The inside aperture diameter is selected in a manner the rim's aperture edge makes mechanically as well as frictional locking contact with the outer periphery 24 of the shutoff needle 20. Material residues illustratively leaking through the guide bush 30 and adhering to the outer periphery 24 of the shutoff needle 20 therefore are always reliable gripped by the rims of the cleaning elements 40 and removed from the needle 20, in other words, the shutoff needle 20 guided through the cleaning device 10 respectively the cleaning elements 40 is kept clean during each reciprocating motion of the injection molding device 1.
A guide bush 30 fitted with a central borehole passage 31 having an inside diameter in the end zones 32, 33 matches except for a slight play the outside diameter of said needle 20 is received in the manifold plate 3 and acts as a needle seal. In this manner said needle 20 is both centrally guided and supported within the bush 30.

A cylindrical free space 34 is subtended by the end and guide zones 32, and 33 of which the inside diameter is slightly larger than the outside diameter of the shutoff needle 20.
During operation of the injection molding device, said free space receives from the flow duct 4 in controlled manner a slight amount of the fluid material, thereby causing sealing between the shutoff needle 20 and the flow duct 4 and the mold environment. At the same time the fluid material within the free space 34 acts as a lubricant reducing the friction between the shutoff needle 20 and the guide bush 30. Just as does the passage borehole 6 in the clamp plate, said guide bush 30 is configured coaxially with the shutoff needle 20, i.e. its longitudi-nal axis L.

The guide bush 30 comprises an enlarged flange 35 centrally configured in a recess 36 in the manifold plate 3. Above the flange 35 as seen in the direction of the clamp plate 2, the bush 30 comprises a main part 38 of lesser outer diameter constituting the (upper) guide zone 32. By its cylindrical inside periphery 42, this guide zone 32 encloses the shutoff nee-dle 20 while leaving a slight play of displacement. At the same time said guide zone bounds the cylindrical free space 34 in the upward direction to preclude the material contained in said free space from leaking outward.

The main part 38 is coaxially enclosed by a threaded bush 37. Said bush is fitted with an external thread 47 engaging a matching inside thread 56 of the recess 38. When the threaded bush 37 is rotated inside the recess 36 and hence is screwed into the manifold plate 3, the bush 30 is affixed to the mold. In the process, the bottom 41 of the recess 36 and the lower side (not shown in further detail) of the flange 35 are locked in mechanical manner against each other, as a result of which the guide bush 30 is affixed not only in the manifold plate 3 but at the same time is also sealed by a surface perpendicular to the longi-tudinal axis L.

Underneath the flange 35, the bush 30 (as seen in the direction of the needle shutoff nozzle), is fitted with a neck segment 39 of which the outside diameter also is less than that of the flange 35. The lower end of the neck segment 39 constitutes the (lower) guide zone 33 enclosing by its cylindrical, inner periphery 43 the shutoff needle 20 except for a slight play of displacement and correspondingly bounding downward the cylindrical free space 34.
As elucidated in Fig. 2, the wall thickness W of the end/guide zone 33 preferably shall be less than the wall thickness U of the neck segment 39. The outer periphery 44 of the zone 33 is fitted with an oblique surface 44 at the level of the inner periphery 43, preferably a coni-cal surface, whereby the wall thickness W tapers further toward the needle shutoff valve.

A passage borehole 46 is configured between the recess 36 and the flow duct 4 to receive the neck segment 39 in the manifold plate 3, said borehole's inside diameter sub-stantially matching the outside diameter of the neck segment 39. This neck segment extends the flow duct 4, where the end zone 33 by its inside periphery 43 encloses the shutoff needle 20 and by its conical surface 44 enters the flow duct 4 radially and concentrically with the longitudinal axis L. The guide zone 33 for the shutoff needle 20 thereby is immersed fully in the flow of material, the oblique/conical surface 44 constituting a contact surface for said ma-terial, this contact surface -- just as does the shutoff needle 20 -- being totally and omnidi-rectionally immersed within the flow duct 4 into the material to be processed.

The operation of the needle seal respectively of the guide bush 30 is substantially based on the elastically deforming wall of the end zone 33 configured in the flow duct 4.
When the shutoff needle 20 is moved into the open position, it first slides unhampered within the guide bush 30 from the closed position into the open position, the end zones 32, 33 slid-ing at little play of displacement along the outer periphery 24 of the needle 20. Once this end or opening position has been reached, the injection molding pressure builds up, that is the melt to be processed is forced at high pressure through the melt duct 4 into the mold cavity. In the process the fluid material flows evenly and omnidirectionally around and along the shutoff needle 20 and the contact surface 44 of the end zone 33, the latter on account of its relative thin wall then being radially deformed. Like a closing or valve element, the cylin-drical inside periphery 43 rests in geometrically locking and sealing manner against the outer periphery 24 of the shutoff needle 20 so that, during injection molding, material no longer can enter from the flow duct 4 into the free space 34 of the guide bush 30. As a result there is a clearly improved sealing of the shutoff needle 20 relative to conventional designs be-cause when high pressure stresses prevail in the flow duct 4, material no longer can flow outward from the mold through the guide bush 30. At the same time the needle 20 is affixed concentrically with the longitudinal axis L. Therefore the material no longer is able to deviate the needle 20 out of its centered position, and the flow conditions in the flow duct 4 are ad-vantageously affected by this feature.

At the end of the injection cycle, the pressure in the flow duct 4 will drop back. Be-cause of its elasticity, the end zone is restored to its initial shape and the inner periphery 43 of the end zone 33 detaches off the outer periphery 24 of the shutoff needle 20. This needle then can be moved in unhampered manner into its closed position.

Therefore the wall thickness W of the preferably steel end zone 33 is selected in a manner that said zone is deformable within its elastic limits in order that the slight play of dis-placement between the shutoff needle 20 and the inside periphery 43 can be overcome by the material's pressure, whereby the needle 20 shall be centrally affixed in the mold during the high pressure stage and said material is prevented from leaking outward.
Nevertheless the needle 20 is accurately guided within the mutually spaced end zones 32, 33.

The present invention is not restricted to one of the above discussed embodiment modes, rather it may be modified in versatile manner. Illustratively the guide bush 30 is not mandatorily configured in the manifold plate 3. Instead it may also be mounted in the needle shut off nozzle, for instance in the nozzle case that is assembled to the lower side 5 of the manifold plate 3. For that purpose said plate 3 is fitted with a simple passage borehole allow-ing the shutoff needle 20 to pass through it in friction-free manner to the drive, whereas the nozzle head is fitted at its end face with the recess 36 receiving the guide bush 30 and the threaded bush 37. The neck segment 39 of the bush 30 projects axially into the material pipe whereas the flow duct 5 issues directly below into the material pipe. In this manner the end zone 33 -- which preferably has an outside diameter lesser than that of the neck seg-ment 39 -- is configured axially in the flow zone. Its contact surface 44 --just as that of shutoff needle 20 -- is immersed in all directions in the material to be processed, whereby the pressure generated in the flow duct 4 can compress, in elastically and in sealing manner, the end zone 33 acting as a kind of check valve against the outer periphery 24 of the shutoff needle 20. As a result the flow duct 4 is completely sealed from the ambience during injec-tion molding. The needle 20 is centrally affixed.

The wall thickness W of the end/guide zone 33 is not mandatorily smaller than the wall thickness U of the neck segment 39. Both wall thicknesses may be approximately the same. The significant feature remains that the end zone 33 immersed in the fluid material may be elastically deformed to such an extent during the high pressure stage that the inside periphery 43 is able to elastically hug the outside periphery 24 of the shutoff needle 20.

The contact surface 44 optionally subtended at the end of the end zone 33 also may be concave or convex, a design also allowing simple and accurate manufacture.
This sur-face design positively affects the pressure distribution.

Instead of the threaded bush 37, an omitted flange annulus also may be used to affix the guide bush 30 in the mold 1, said ring being affixed by screws to the manifold plate 3 or to the needle shutoff nozzle. What is significant in this respect is that the guide bush 30 be sealed off within the recess 36 across a surface 41 perpendicular to the longitudinal axis L.

Preferably the flange 35, the main part 38 and the neck segment 39 are integral.
However the main part 38 and/or the neck segment 39 also may be made separately and be connected for instance by screws to the flange 35. In this manner the neck segment 39 with the end zone 33 and the remaining components of the guide bush 30 may be made of differ-ent materials. Or, when processing abrasive materials, the neck segment 39 might be ex-changed at any desired time against a new element without having to exchange the entire guide bush 30.

All features and advantages expressly stated or implicit in the claims, specification and drawings, including manufacturing details, spatial arrangements and process proce-dures, may be deemed inventive per se or also in arbitrary combinations.

LIST OF REFERENCES
L longitudinal axis 36 recess U wall thickness 37 threaded bush W wall thickness 38 main part 39 neck segment 1 injection molding device 2 clampdown plate 40 cleaning element 3 manifold plate 4 flow duct 41 bottom underside 42 inner periphery 6 passage borehole 43 inner periphery 44 contact surface/outer periph-cleaning element eral/oblique surface 11 housing 46 passage borehole 14 spacer 47 outer thread securing ring 56 inner thread.
shutoff needle 22 adapter 23 tip 24 outer periphery guide bush 31 passage borehole 32 end/guide zone 33 end/guide zone 34 free space flange 13a

Claims

1. Mold injection device (1) comprising a manifold plate (3) into which is config-ured at least one flow duct (4) for a flowable, hereafter fluid material, further at least one needle shutoff nozzle through which the fluid material can be applied through an extension of the flow duct (4) into a separable mold insert, further at least one shutoff needle (20) which runs through the flow duct (4) in at least segment-wise, displaceable manner and which can be moved by a drive into an open and a closed position, and a guide bush (30) passing and sealing the shutoff needle (20).

characterized in that the guide bush (30) comprises at least one zone (33) enclosing the shutoff needle (20) at little play of displacement and situated at least portion-wise in the flow duct (4).

2. Injection molding device as claimed in claim 1, characterized in that the zone (33) is fitted with or constitutes a fluid-material contact surface (44) situated at least portion-wise in the flow duct (4).

3. Injection molding device as claimed in either of claims 1 and 2, characterized in that the zone (33) enters the flow duct (4) radially or axially,

4. Injection molding device as claimed in one of claims 1 through 3, character-ized in that the zone (33) comprises a cylindrical inner periphery (43) coaxial with the shutoff needle (20).

5. Injection molding device as claimed in claim 4, characterized in that the cylin-drical inner periphery (43) and the contact surface (44) are configured axially substantially at the same height.

6. Injection molding device as claimed in one of claims 1 through 5, character-ized in that the zone (33) constitutes a tip of the guide bush (30).

7. Injection molding device as claimed in one of claims 1 through 6, character-ized in that the contact surface (44) is subtended by the outer periphery of the zone (33).

8. Injection molding device as claimed in claim 7, characterized in that the outer periphery (44) is an oblique, preferably a conical surface.

9. Injection molding device as claimed in claim 8, characterized in that the coni-cal surface (44) is concave or convex.

10. Injection molding device as claimed in one of claims 1 through 9, character-ized in that the guide bush (30) configured an axial distance from the zone (33) and entering the flow duct (4) comprises at least one further zone (32) fitted with a cylindrical periphery (42) coaxial with the shutoff needle (20).

11. Injection molding device as claimed in claim 10, characterized in that the end zones (32, 33) receive the shutoff needle (20) with the least possible play of displacement.

12. Injection molding device as claimed in either of claims 10 and 11, character-ized in that a free space (34) is subtended between the end zones (32, 33) and exhibits an inside diameter slightly larger than the outside diameter of the shutoff needle (20).

13. Injection molding device as claimed in one of claims 10 through 12, character-ized in that the end zones (32, 33) and the free space (34) constitute a central passage borehole (31).

14. Injection molding device as claimed in one of claims 1 through 13, character-ized in that the guide bush (30) is configured in the manifold plate (3).

15. Injection molding device as claimed in one of claims 1 through 13, character-ized in that the guide bush (30) is configured in the needle shutoff nozzle.

16. Injection molding device as claimed in one of claims 1 through 15, character-ized in that the guide bush (30) is received in a recess (36) in the manifold plate (3) and/or in the needle shutoff nozzle.

17. Injection molding device as claimed in claim 16, characterized in that the guide bush (30) can be affixed in the recess (36).

18. Injection molding as claimed in either of claims 16 and 7, characterized the guide bush (30) is sealed within the recesses (36) by means of at least one surface (41) perpendicular to the longitudinal axis (L).

19. Injection molding device as claimed in claim 18, characterized in that the sur-face (41) is constituted by the bottom of the recess (36).

20. Injection molding device as claimed in one of claims 16 through 19, character-ized in that the guide bush (30) is fitted with a flange (35) centrally received in the recess (36).

21. Injection molding device as claimed in one of claims 16 through 20, character-ized in that the guide bush (30) comprises a neck segment (39) which supports or consti-tutes at its end the zone (33).

22. Injection molding device as claimed in claim 21, characterized in that the wall thickness (W) of the end zone (33) is less than the wall thickness (U) of the neck segment (39).

23. Injection molding device as claimed in either of claims 21 and 22, character-ized in that the flange (35) and the neck segment (39) are integral.