INJECTION MOLD WITH CENTERING DEVICE

Abstract

An injection mold with a centering device includes a die-holding plate with a cavity-forming die unit, a core-holding plate with a core unit, and a stripping plate between the core-holding and die-holding plates. The centering device has a insert and a mount with a clearance, which is rotationally symmetrical about a center axis and is for receiving the insert. The insert has an opening for receiving the core unit and the insert and the clearance of the mount are insertable in a torsion-free manner in the clearance of the mount in at least three positions rotatable about a center axis of the insert, and the center axis of the clearance and the center axis of the insert overlie one another. A center axis of the opening of the insert is arranged eccentrically in relation to the center axis of the insert by an offset. The centering unit is arranged in the stripping plate.

Claims

1-15. (canceled)

16. An injection mold with a centering device, the injection mold comprising a die holding plate having a cavity-forming die unit, a core holding plate having a core unit, which is introduced into the die unit in the closed state of the mold, and a stripping plate between the core holding plate and the die holding plate, wherein the centering device comprises a centering insert and a centering insert holder having a recess, which is rotationally symmetrical about a central axis, for mounting of the centering insert; wherein the centering insert has an opening for mounting the core unit; wherein the centering insert and the recess of the centering insert holder are configured in such a manner that the centering insert is insertable in the recess of the centering insert holder in a manner secured against rotation in at least three positions that are rotatable about a central axis of the centering insert with the central axis of the recess and the central axis of the centering insert superposed; wherein a central axis of the opening of the centering insert is arranged eccentrically by an offset with respect to the central axis of the centering insert; and wherein the at least one centering unit is arranged in the stripping plate.

17. The injection mold according to claim 16, wherein the centering insert is formed by a stripping element mounted in the stripping plate.

18. The injection mold according to claim 16, wherein the core unit is held in the core holding plate in a floating manner.

19. The injection mold according to claim 16, wherein the outer contour of the centering insert has the shape of a regular polygon, wherein the inner contour of the recess of the centering insert holder is constructed to be complementary to the outer contour of the centering insert, and wherein the central axis of the opening of the centering insert is aligned eccentrically by an offset towards the direction of a polygon side or a polygon corner.

20. The injection mold according to claim 20, wherein the regular polygon has three to twelve side surfaces.

21. The injection mold according to claim 16, wherein the centering insert comprises a circular cylindrical base body, on the cylindrical surface of which a projection standing perpendicular to the central axis of the centering insert is arranged; and wherein the recess of the centering insert holder has a shape complementary to the base body, which has at least three rotationally symmetrically arranged slots running parallel to the central axis of the recess for accommodating the projection of the centering insert.

22. The injection mold according to claim 21, wherein the central axis of the opening of the centering insert is aligned eccentrically by an offset in the direction towards the projection.

23. The injection mold according to claim 16, wherein the core unit is mountable in the opening in such a manner that a displacement in the longitudinal direction of the core unit is possible.

24. The injection mold according to claim 16, wherein the opening is a through hole or a blind hole or in that the opening is formed cylindrically or conically.

25. The injection mold according to claim 16, wherein the centering insert has a cylindrical shape.

26. The injection mold according to claim 16, wherein the offset is 0.01 mm to 0.1 mm.

27. The injection mold according to claim 16, wherein the injection mold has a plurality of cavities, with each of the plurality having a centering unit.

28. The injection mold according to claim 16, wherein a further centering unit is arranged in the core holding plate and/or the die unit.

29. The injection mold according to claim 16, wherein the centering insert holder is constructed as a separate part which is mounted in the die unit, the stripping plate and/or the core holding plate.

30. The injection mold according to claim 16, wherein the centering insert holder is formed by the die unit, the stripping plate and/or the core holding plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention shall be explained in more detail in the following on the basis of exemplary embodiments in connection with the drawing(s). In the figures:

[0027] FIG. 1 shows a sectional illustration of a cutout of an injection mold with a centering device;

[0028] FIG. 2 shows a centering device in the shape of a regular 8-gon;

[0029] FIG. 3 shows a plurality of centering devices arranged in a circle;

[0030] FIGS. 4A-4C show a further variant of a centering device, a plan view onto the end face of the centering insert with pin under FIG. 4A, a sectional illustration of the centering holder under FIG. 4B, a perspective view of the centering insert under FIG. 4C; and

[0031] FIG. 5 shows a sectional illustration of a cutout of an injection mold with a stripping element constructed as a centering device.

DETAILED DESCRIPTION OF EMBODIMENTS

[0032] FIG. 1 shows a sectional illustration of a cutout of an injection mold with at least one cavity 1 for a thin-walled, elongated injection-molded article. The injection mold comprises a core holding plate 4, in which at least one cavity-forming core unit 5 is held, and a die holding plate 2, in which at least one cavity-forming die unit or die 3 is held. Furthermore, between the core holding plate 4 and the die holding plate 2, the injection mold comprises a stripping plate 12, in which a stripping element or stripping ring 13 is held. In the injection mold shown, the injection takes place via an injection channel 14 arranged laterally with respect to the core unit 5.

[0033] FIG. 2 shows a centering device for centering a core unit in a mold. The centering device comprises a centering insert 6 and a centering insert holder 7. The centering insert holder 7 forms a recess 8 for precise mounting of the centering insert 6. The recess 8 is formed rotationally symmetrically to a central axis MA. In the embodiment shown, the recess 8 has an inner contour 11 in the shape of a regular 8-gon. The centering insert 6 is rotationally symmetrical to a central axis MB and in cross section (sectional plane perpendicular to the longitudinal axis of the core unit or to the central axis MB) has a complementary outer contour 10 to the inner contour 11 of the recess 8, in the shape of a regular 8-gon. Furthermore, an opening 9 for the core unit (not illustrated) is formed in the centering insert 6, in which the core unit is held in a precisely fitting manner so as to be displaceable or non-displaceable in the longitudinal direction. In the illustration shown, the central axis MC of the opening 9 is formed exactly centrally to the outer contour without offset, i.e. the central axis MC of the opening 9 overlays the central axis MB of the centering unit 6. In the inserted state of the centering unit 6 in the centering insert holder 7, the central axis MB of the centering unit 6 overlays the central axis MA of the recess 8 of the centering insert holder 7.

[0034] A core unit, which is not exactly centered in the cavity or the die unit owing to production tolerances, can be centered using a correcting centering insert 6. To this end, the central axis MC of the opening 9 of the centering insert 6 is constructed to be offset by an offset V, usually in the range of a few hundredths of a millimetre, in the direction R towards a side surface (or a corner) of the 8-gon. Using a centering insert 6 with eccentric opening 9, the position of the core unit with respect to the die/cavity can then be corrected by the offset V in eight different directions. Should the size of the offset or the direction of the offset not be correct in the inserted state (which can be determined by means of a trial run of the mold), the centering insert 6 can simply be rotated or replaced by a centering insert 6 with larger or smaller offset V.

[0035] FIG. 3 shows a plurality of centering devices of an injection mold, which are arranged on a circle (only a semicircle is shown) in the illustration shown. The very space-saving and simple configuration of the centering device with a centering insert in the shape of a regular polygon allows a very close packing of cavities for thin-walled, elongated injection-molded articles. In the illustration shown, eight cavities are arranged in the shape of a circle (only a semicircle is shown), which are injection-molded on centrally. In molds of this type, the core must often be arranged slightly eccentrically in the cavity towards the injection point owing to the injection pressure, so that the core comes to lie in its correct central position during the injection process. Such a close packing is possible using the described centering device and the position of each core unit can be set in a simple manner and individually.

[0036] Depending on the requirement, the centering unit is formed in one or more regions (A, B, C) of the core unit, as illustrated in FIG. 1. The centering unit can be arranged in the core holding plate 4 at the foot of the core unit 5, in the stripping plate 12 and in the die holding plate 2 in the region of the tip of the core 15.

[0037] In the region of the tip of the core 15 (region C), the opening 9 of the centering insert 6 is usually formed as a slightly conical blind hole, into which the tip of the core 15 dips and is held during the closing of the mold. A lateral displacement transverse to the longitudinal direction of the core unit is not possible when the mold is closed and the position of the tip of the core can be set as desired using the correct centering insert 6. The centering insert 6 is held secured against rotation in the centering insert holder 7.

[0038] A centering insert of a centering device in the region of the stripping plate (region B, centering unit not illustrated) has a continuous opening, in which the core unit is held in a displaceable manner in its longitudinal direction during the operation of the mold.

[0039] A centering insert of a centering device in the region of the core holding plate (region A, centering unit not illustrated) or the foot of the core unit has a continuous opening, in which the core unit is held in a displaceable manner in its longitudinal direction. The core unit is fixed after setting in the core holding plate has taken place.

[0040] FIGS. 4A to 4C show a further variant of a centering device, the centering insert 6 of which comprises a base body 6a in the shape of a circular cylinder with central axis MB and a projection 6b arranged laterally on the cylindrical surface of the base body 6a. In the embodiment illustrated, the projection 6a is constructed as a pin 6a standing perpendicular to the central axis MB. Furthermore, the centering insert 6 has the opening 9 for mounting the core unit (not illustrated). The central axis MC of the opening 9 is offset by the offset V in the direction of the pin 6a with respect to the central axis MB of the centering insert.

[0041] The substantially circular cylindrical recess 8 of the centering insert holder 7, which is complementary to the centering insert 6, has a plurality of slots 8a running in the longitudinal direction for accommodating the projection or pin 6b of the centering insert 6. These slots 8a are arranged rotationally symmetrically around the central axis MA of the recess 8. Eight such slots 8a are shown in the embodiment shown. In the inserted state of the centering insert 6, the same is held in the centering insert holder 7 aligned in the desired direction and secured against rotation using the pin 6b. An additional securing against rotation is not required.

[0042] Using the centering device from FIGS. 4A-4C, a core unit can be centered analogously to the previously described 8-gon centering device.

[0043] FIG. 5 shows a sectional illustration of a cutout of an injection mold with centering device, analogously to FIG. 1. The injection mold comprises a die holding plate 2 having at least one cavity-forming die unit 3, a core holding plate 4 having at least one core unit 5, which is introduced into the die unit 3 in the closed state of the mold and forms a cavity 1, and a stripping plate 12, which is arranged between the core holding plate 4 and the die holding plate 2. A stripping element or a stripping ring 13 is arranged in the stripping plate 12. The stripping element 13 is used for ejecting an injection-molded article during the opening of the mold following the injection molding process, in that the stripping plate 12 with the stripping element or the stripping ring 13 is moved forwards relatively to the core unit 5 towards the tip of the core 15.

[0044] The stripping element 13 is the centering insert 6 of the centering device at the same time. The stripping plate 12 forms the centering insert holder 7. In the embodiment shown, the centering device is constructed according to the variant of FIGS. 4A-4C. The centering insert 6 has a base body 6a with a pin 6b, which can be brought into the desired rotational position by means of slots 8a in the centering insert holder 7. The opening 9 of the centering insert 6 is formed conically, so that the stripping element 13 or the centering insert 6 can be displaced slightly forwards relatively to the core unit 5. The core unit is correspondingly likewise conically constructed.

[0045] The stripping element 13 constructed as centering insert 6 extends substantially over the entire thickness of the stripping plate 12. In this manner, the core unit guided in the opening 9 of the centering insert 6 can be supported and stabilized over a long region or at two regions. The core unit 5 is then correspondingly likewise conically constructed. In order to reduce possible friction and thus wear of the individual parts, the core unit 5 in the design shown has a circumferential taper 16 in a central region of a section, which is held in the opening 9 in the closed mold. There is no contact with the centering unit 5 in this central region in the closed state. The regions adjoining the central region on both sides contact the centering unit 5 however and fix the core unit at the desired position in the closed state of the mold.

[0046] The core unit 5 is mounted in the core holding plate 4 in a floating manner in the embodiment shown. When the mold is closed, the core unit 5 is centered and fixed in the correct position by means of the centering insert 6 or the stripping element 13.

LIST OF REFERENCE NUMBERS

[0047] 1 Cavity

[0048] 2 Die holding plate

[0049] 3 Die unit/die

[0050] 4 Core holding plate

[0051] 5 Core unit/core

[0052] 6 Centering insert

[0053] 6a Base body

[0054] 6b Projection, pin

[0055] 7 Centering insert holder

[0056] 8 Recess

[0057] 8a Slot

[0058] 9 Opening

[0059] 10 Outer contour

[0060] 11 Inner contour

[0061] 12 Stripping plate

[0062] 13 Stripping ring

[0063] 14 Injection channel

[0064] 15 Tip of the core

[0065] 16 Circumferential taper

[0066] A, B, C Region of arrangement of a centering device

[0067] MA Central axis of the recess 8

[0068] MB Central axis of the centering insert 6

[0069] MC, MC′ Central axis of the opening 9

[0070] R Offset direction

[0071] V Offset