INJECTION MOLDING DEVICE

Abstract

An injection molding device and related method includes a mold plate with at least one pocket having at least one discharge opening to discharge melted plastic from the pocket into at least one mold cavity interconnected to the pocket and a nozzle including a housing, which during operation is interconnected to the pocket. Per discharge opening a needle is arranged displaceable in an axial direction in the housing between a closed position and an open position. In the closed position the needle closes the thereto related discharge opening and is thereby preventing melted plastic from flowing from the pocket into the at least one mold cavity. In the open position, the needle releases the discharge opening such that melted plastic flows from the pocket into the at least one mold cavity. Furthermore, a melt channel is discharging into the pocket to supply melted plastic into the pocket.

Claims

1. A method to inject melted plastic into a mold cavity, comprising: supplying melted plastic into a pocket formed between a housing of a nozzle and a mold plate via a melt channel ending in said pocket; opening at least one discharge opening by axial displacement of at least one of a plurality of needles, each needle arranged in a corresponding discharge opening, wherein each needle is arranged displaceable in said axial direction in a corresponding needle bore in said housing; injecting melted plastic from the pocket into a thereto interconnected mold cavity through the at least one discharge opening; and closing the at least one discharge opening by moving at least one of the plurality of needles in an opposite direction.

2. The method of claim 1 wherein during operation one or more of the plurality of needles displaces in a radial direction with respect to its corresponding discharge opening to compensate mismatch.

3. The method of claim 2 wherein one or more of the plurality of needles displaces in a gap formed between each needle and its corresponding discharge opening and/or a gap between each needle and the housing.

4. An injection molding device, comprising: a mold plate with at least one pocket having at least one discharge opening arranged to discharge melted plastic from said pocket into at least one mold cavity interconnected to said pocket during an injection molding operation; at least one nozzle having a housing, which during the injection molding operation is interconnected to said pocket, and a plurality of discharge openings; a plurality of needles, each needle corresponding to one of the plurality of discharge openings, and each needle arranged displaceable in an axial direction in said housing in a corresponding needle bore between: a closed position in which the needle closes its thereto related discharge opening thereby preventing melted plastic from flowing from the pocket into the at least one mold cavity; and an open position in which the needle releases its discharge opening such that melted plastic flows from the pocket into the at least one mold cavity; and a melt channel alignable with the pocket and arranged to supply melted plastic into the pocket during the injection molding operation, wherein the melt channel is arranged to supply the melted plastic into the pocket independently of the plurality of needles arranged in the corresponding needle bores, and wherein the melt channel is oriented centralized between the plurality of needles in the housing.

5. The injection molding device of claim 4, further comprising: a spacer arranged between the housing of the nozzle and the mold plate, the spacer arranged as one or both of a thermal isolator between the housing and the mold plate and a seal between the housing and the mold plate.

6. The injection molding device of claim 5 wherein the housing includes a shoulder arranged to support the spacer in the axial direction.

7. The injection molding device of claim 5 wherein the spacer includes a sealing lip extending in the axial direction with a first side facing the pocket and a second side, opposite of the first side, abutting against the mold-plate and forming a sealing surface.

8. The injection molding device of claim 4 wherein at least one melt channel is arranged at least partially in the housing of the nozzle.

9. The injection molding device of claim 4 wherein at least two needles are arranged offset to the melt channel.

10. The injection molding device of claim 4 wherein at least two needles are actuated by a common actuator.

11. The injection molding device of claim 4 wherein each discharge opening is arranged in a dimple.

12. The injection molding device of claim 11 wherein each dimple is at least partially shaped conical.

13. The injection molding device of claim 11 wherein the housing includes a bump arranged to cooperate with each dimple of the thereto related discharge opening.

14. The injection molding device of claim 13 wherein each bump is at least partially shaped conical.

15. The injection molding device of claim 11 wherein two neighboring dimples are spaced apart by a ridge.

16. The injection molding device of claim 15 wherein the melt channel is arranged aligned with at least one ridge, said ridge arranged to support distribution of the melted plastic between at least two discharge openings.

17. The injection molding device of claim 4 wherein at least one discharge opening, in an area where it interacts with its thereto related needle, has a diameter that is 0.02 mm to 0.5 mm larger than a diameter of its thereto related needle.

18. The injection molding device of claim 4 wherein more than one needle has a needle tip with a reduced diameter to interact with the discharge opening.

19. The injection molding device of claim 4, further comprising: a distribution point is located on the mold plate opposite of the melt channel opening to the pocket.

20. The injection molding device of claim 19, further comprising: a stream trough arranged to direct melted plastic from the distribution point towards at least one discharge opening in the pocket.

Description

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0024] The herein described invention will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the invention described in the claims.

[0025] The drawings are showing:

[0026] FIG. 1 is a first variation of an injection molding device according to invention in a perspective view, partly sectionized;

[0027] FIG. 2 is a second variation of an injection molding device in a disassembled state in a sectionized, perspective view;

[0028] FIG. 3 is a detailed view of a closed position of the injection molding device according to FIG. 2 in a sectionized, perspective view;

[0029] FIG. 4 is a detailed view of an open position of the injection molding device according to FIG. 2 in a sectionized, perspective view;

[0030] FIG. 5 is a detailed view on a spacer according to FIG. 2-4;

[0031] FIG. 6 is a top view from an axial direction in a pocket of to the injection molding device according to FIG. 2-4;

[0032] FIG. 7 is a further variation of the injection molding device according to invention in a perspective view, partly sectionized;

[0033] FIG. 8 is a detailed view of FIG. 6 on the pocket.

DETAILED DESCRIPTION OF THE INVENTION

[0034] Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all features are shown. Indeed, embodiments disclosed herein may be embodied in many different forms and should not be understood as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, reference numbers will be used to refer to like components or parts.

[0035] FIG. 1 shows a first variation of an injection molding device 1 according to invention in a perspective view and partly sectionized. The illustrated injection molding device 1 comprises multiple nozzles 6 interacting with one mold plate 2. Each nozzle 6 is interconnected to a pocket 3 of the mold plate 2 with at least one discharge opening 4 to discharge melt in a further mold cavity (not shown). Each nozzle 6 is further interconnected to an actuator 19, which actuates multiple needles of one nozzle through an actuator plate 20 to open and close the respective discharge openings 4 arranged in the pocket 3. In the shown variation, the injection molding device 1 features in total eight nozzles 6. However, according to the invention, the injection molding device 1 may also feature only one nozzle, one mold plate etc. Such a variation is illustrated in FIG. 2.

[0036] FIG. 2 illustrates a second variation of the invention, where the injection molding device 1 comprises a mold plate 2 with a pocket 3 having multiple discharge openings 4 to discharge melted plastic from said pocket 3 into at least one mold cavity 5 (shown only schematically) interconnected to said pocket 3. The nozzle 6 comprises a housing 7, which during operation is interconnected to the pocket 3. In FIG. 2 the nozzle 5 and the mold plate 2 are shown in a separated manner, such that the inside becomes better apparent. Per discharge opening 4 a needle 8 is arranged displaceable in an axial direction (z-direction) in said housing 7 between an open and a closed position. The needles 8 are arranged in the housing 7 in corresponding needle bores 18 which are arranged coaxially with a thereto related discharge opening 4. Each discharge opening 4 is arranged at a lower end of a dimple 21 which in the shown variation is at least partially conically shaped such that a funnel towards the discharge opening 4 is formed. During operation the needles 8 extend between the housing 7 and the related discharge opening 4 over a free length at least in the closed position. In the open position they may be retracted in the housing 7 or remain extended over a reduced free length over said housing 7.

[0037] A detailed view of the injection molding device in the closed position is shown in FIG. 3, meanwhile the open position is shown in FIG. 4—both Figures are according to the variation of the invention of FIG. 2. In the closed position (FIG. 3) the multiple needles 8 close the thereto related discharge openings 4 thereby preventing melted plastic from flowing from the pocket 3 into the at least one mold cavity 5 (not shown here). In the open position as shown in FIG. 4 the needles 8 are displaced upwards (positive z-direction) by the actuator 19 and hence the needles 8 release the discharge openings 4 such that melted plastic can flow from the pocket 3 into the at least one mold cavity 5. As visible in FIG. 4, the melted plastic is supplied through a single melt channel 9, arranged at least partially in the housing 7. The melt channel 9 is discharging melt into the pocket 3, as illustrated by the arrows 27 indicating the direction of the melt flow. In the shown variation, the opening of the melt channel 9 into the pocket 3 is arranged symmetrically with respect to the discharge openings 4. The melt channel 9 is thus centralized between the multiple needles 8 such that the needles 8 are arranged around the melt channel 9 on a circle. To open, respectively to close the discharge openings 4 the needles are displaced in the axial direction (z) by means of the common actuator 19 (compare FIG. 2). Therefore, the needles 8 are each interconnected to an actuator plate 20 that is displaced by the actuator 19.

[0038] During closing of the discharge openings 4 with the needles 8, it is advantageous, that the needles 8 are displaceable in a lateral direction(x, y), perpendicular to the axial direction (z), such that the needles may be guided in the correct position to close the discharge opening 4. Preferably, a tip 28 of each needle comprises at its end (facing the pocket 3) a first tip section 29 with a reduced diameter, which is smaller than the diameter of the discharge opening 4. Preferably, the reduced diameter is about 0.05-0.5 mm smaller than the diameter of the discharge opening 4. Behind this first tip section 29 a second tip section 30 is arranged in which the diameter of the needle 8 is enlarged such that the second tip section 30 is tapered. Even through a gap remains between the first tip section 29 of the needles 8 and the discharge openings 4, the discharge openings 4 are closed due to residuals of the plastic that is at least party solidified due do the fact that the mold plate 2 is cooled. Alternatively, a sealing may also be formed between the tapered second section 30 and the tapered dimple 21 of the discharge opening 4 in order to close the discharge openings 4.

[0039] A spacer 10 is arranged between the housing 7 of the nozzle 6 and the mold plate 2, as it can be seen in the open and in the closed position. The spacer 10 seals the pocket 3 formed between the mold plate 2 and the nozzle 6 off with respect to the environment such that melted plastic supplied by the melt channel 9 into the pocket 3 can be discharged into the mold cavity 5 when the discharge openings 4 are opened by actuating the actuator 19.

[0040] A detailed view of the spacer 10 is given in FIG. 5. The spacer 10 acts further as a thermal isolator between the heated nozzle 6 and the cooled mold plate 2. Preferably, the spacer is therefore made at least partly of a thermally isolating material. The nozzle is heated by means of a spiral shaped heating element 16, that is arranged around the housing 7 and between said housing 7 and a sheath 26. The cooling element 17 is placed in the mold plate 2, circumventing at least partially the pocket 3. The spacer 10 may act additionally as a seal between the housing 7 and the mold plate 2, sealing the part of the pocket 3 that is filled during operation with the melt. In the shown case, the housing 7 comprises a shoulder 11 which supports the spacer 10 in the axial direction (z). The spacer 10 comprises a sealing lip 12 which is extending in the axial direction (z). The sealing lip 12 has a first side 13 facing the pocket 3 filled with melt and a second side 14, opposite of the first side 13, abutting against the mold plate 2 and forming a sealing surface 15.

[0041] FIG. 6 depicts a view from the top inside a pocket 3 of to the injection molding device according to FIG. 2-FIG. 4. From this perspective, it can be seen that in the center of the pocket 3 on the mold plate 2 a distribution point 24 is placed. The distribution point 24 is opposite of the opening of the melt channel 9 into the pocket 3 in the axial direction (not shown). From said distribution point, multiple stream troughs 25 guide the liquid melt in elongated depressions in the surface of the mold plate towards a dimple 21 in which each a discharge opening 4 is arranged. Two neighboring dimples 21 are spaced apart by a ridge 23. The dimples 21 are designed in such a way, that corresponding bumps 22 of the housing 7 of the nozzle follow the outline of said dimple, however leaving space between the two in order to allow the melt to flow towards the discharge opening 4, as indicated by the arrows 27.

[0042] FIG. 7 and FIG. 8 illustrate a further variation of the injection molding device 1 according to the invention. FIG. 7 shows the injection molding device 1 in a perspective view, partly sectionized. FIG. 8 depicts a detailed view on the pocket 3 of FIG. 7. The variation shown comprises an injection molding device with one nozzle 6 and one mold plate 5. The nozzle 6 comprises two needles 8 which open and close two respective discharge openings 4 that are arranged in line with the needles 8. The mold plate 2 comprises a pocket 3 in which the nozzle 6 is at least partly arranged. Each discharge openings 4 is arranged in a dimple 21. The two dimples 21 are overlapping each other and are thus divided by a ridge 23 between them that is varying in height. The melt channel 9 is located in the housing 7 of the nozzle 6. The opening of the melt channel 9 has the same distance to each opening of the needle bore 18 of the respective needles 8. Therefore, in the axial direction, the openings of the needle bores 18 and the melt channel 9 in the pocket 3 are arranged in a way that they define the corners of a hypothetic triangle. The opening of the melt channel 9 in the pocket 3 may be placed over the ridge 23 in the axial direction (z)—such that the distribution point 24, which is the point under the melt channel 9 opening in axial direction, is placed on the ridge 23. Thus the dimples 21 itself act as stream toughs 25. Alternatively, if the melt channel 9 opens in the pocket 3 but not above a dimple 21 and/or a ridge 23, a distribution point 24 may be used from which multiple stream troughs 25 emerge that guide the melted plastic towards the dimples 21.