INJECTION NOZZLE

Abstract

The disclosure relates to an injection nozzle (1) suitable for injection molding of thermoplastic materials, in particular polyolefin materials, the injection nozzle (1) comprising a housing (2) comprising a sleeve-shaped rear section (3) and a thereto coaxially arranged sleeve-shaped front section (4) surrounding a central passage (5) extending in an axial direction (z) forming part of a melt channel (6). In the central passage (5) a needle (7) is arranged movable in the axial direction (z) between a retracted open position and an extended closed position in which a gate (8) at a tip (9) of the front section (4) is closed by a front end (10) of the needle (7) in a sealing manner. A spacer (11) is arranged between the rear section (3) and the front section (4) defining a total length of the housing (2) in the axial direction (z).

Claims

1. An injection nozzle suitable for injection molding of thermoplastic materials, in particular polyolefin materials, the injection nozzle comprising: a. a housing comprising a sleeve-shaped rear section and a thereto coaxially arranged sleeve-shaped front section surrounding a central passage extending in an axial direction (z) faulting part of a melt channel in which a needle is arranged movable in the axial direction (z) between a retracted open position and an extended closed position in which a gate at a tip of the front section is closed by a front end of the needle in a sealing manner; wherein b. a spacer is arranged between the rear section and the front section defining a total length of the housing in the axial direction (z).

2. The injection nozzle according to claim 1, wherein the spacer comprises at least one of a ring, a bushing, and a washer.

3. The injection nozzle according to claim 1, wherein the injection nozzle comprises a needle centering means, being arranged in the axial direction (z) between the spacer and the gate for centering the needle in a radial direction during operation when moved between the open and the closed position.

4. The injection nozzle according to claim 3, wherein the needle centering means is designed as a separate element inserted into the front section of the housing opposite to the gate.

5. The injection nozzle according to claim 3, wherein the needle centering means is arranged in a pocket of the front section.

6. The injection nozzle according to claim 5, wherein the needle centering means is clamped between a shoulder of the pocket and the spacer.

7. The injection nozzle according to claim 4, wherein the needle centering means is ring shaped.

8. The injection nozzle according to claim 3, wherein the needle centering means comprises at least one fin extending in radial direction and comprising on the inside a guiding surface during operation centering the needle in the radial direction.

9. The injection nozzle according to claim 5, wherein the needle centering means comprises at least two fins in a circumferential direction spaced apart from each other.

10. The injection nozzle according to claim 1, wherein the tip of the front section in combination with the front end of the needle form a molding contour configured to embed into a molding cavity contour during operation.

11. The injection nozzle according to claim 10, wherein a length of the spacer in the axial direction (z) is configurable to compensate thermal expansion of the housing in the axial direction (z), such that with respect to a thermoplastic material specific operating temperature the molding contour is embedded into a molding cavity contour in an adjustable and/or flush manner.

12. The injection nozzle according to claim 1, wherein the spacer comprises a rear sealing surface and a front sealing surface in a mounted position interacting with the front section and the rear section preventing leakage of melted thermoplastic material from the central passage.

13. The injection nozzle according to claim 1, wherein the rear section comprises an outer thread and the front section comprises an inner thread engaging in a mounted position with the outer thread for interconnecting the front section to the rear section.

14. The injection nozzle according to claim 1, wherein the spacer is arranged in the central passage and forms part of the melt channel.

15. The injection nozzle according to claim 1, wherein the spacer and/or the needle centering means comprises an engagement contour for engaging with a corresponding tool for removal or re-placement.

16. The injection nozzle according to claim 1, wherein the front section comprises an outer part and a tip element.

17. The injection nozzle according to claim 16, wherein the tip element is interconnected from the inside or from the outside to the outer part.

18. An injection molding tool for injection molding of thermoplastic materials, in particular polyolefin materials, the injection molding tool comprising: a. at least one cavity having a molding cavity contour at least partially defining plastic part formed therein from melted thermoplastic material; and b. at least one injection nozzle according to claim 1 arranged adjoining the cavity for supplying melted thermoplastic material to the cavity, the injection nozzle forming at least part of the molding cavity contour.

Description

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0022] The herein described disclosure will be more fully understood from the detailed description given herein below and the accompanying drawings which should not be considered limiting to the disclosure described in the appended claims. The drawings are showing:

[0023] FIG. 1 shows a partially sectioned and perspective view of a first variation of an injection nozzle according to the disclosure;

[0024] FIG. 2 shows a detailed view of the first variation of FIG. 1 indicated by box K;

[0025] FIG. 3 shows an exploded view of the first variation;

[0026] FIG. 4 shows a section view of a first variation of an injection molding tool according to the disclosure comprising a second variation of an injection nozzle according to the disclosure;

[0027] FIG. 5 shows a detailed view of FIG. 4 indicated by box T;

[0028] FIG. 6 shows a second variation of an injection nozzle according to the disclosure; and

[0029] FIG. 7 shows a section view of the second variation of FIG. 6 along section line UU.

DETAILED DESCRIPTION OF THE INVENTION

[0030] 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 foul's and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

[0031] FIG. 1 shows a partially sectioned and perspective view of aa first variation of an injection nozzle 1 according to the disclosure and FIG. 2 shows a detailed view of the first variation of FIG. 1 indicated by box K. FIG. 3 is sowing an exploded view of the first variation of the injection nozzle 1. FIG. 4 illustrates a section view of a first variation of an injection molding tool 23 according to the disclosure comprising a second variation of an injection nozzle 1 according to the disclosure and FIG. 5 shows a detailed view of FIG. 4 indicated by box P. FIG. 6 shows a second variation of an injection nozzle 1 according to the disclosure and FIG. 7 shows a section view of the second variation of FIG. 6 along section line UU.

[0032] The first variation of the injection nozzle 1 comprises a housing 1, suitable to be installed in a corresponding injection molding tool 23 adjacent to a cavity 24, as visible in FIG. 4. As best visible in FIGS. 1 to 3, the housing typically comprises a sleeve-shaped rear section 3 and a thereto coaxially arranged sleeve-shaped front section 4 surrounding a central passage 5 extending in an axial direction z and forming part of a melt channel 6. The central passage 5 is fluidly interconnected to a melt channel 6 of the injection molding tool preferably at the rear section 3.

[0033] In the central passage 5 a needle 7 is arranged movable in the axial direction z between a retracted open position and an extended closed position in which a gate 8 at a tip 9 of the front section 4 is closed by a front end 10 of the needle 7 in a sealing manner. This is best visible in FIGS. 1 and 2. Here the tip is integrally formed with the front section 4 of the nozzle allowing a good distribution of heat from the heating element 25 arranged at least partially surrounding the housing 2, to the tip 9.

[0034] A spacer 11 is typically arranged between the rear section 3 and the front section 4 defining a total length of the nozzle 1 in the axial direction z. In the first variation of the nozzle 1, as shown in FIG. 3, the spacer 11 is formed as a bushing arranged in the central passage 5 of the housing 2. The spacer 11 is made at least partially from tool steel. The spacer 11 typically comprises a rear sealing surface 19 and a front sealing surface 20 in a mounted position interacting with the front section 4 and respectively the rear section 3 preventing leakage of melted thermoplastic material from the central passage 5. As visible in FIG. 5, in the variation of a bushing-type spacer 11, the front and rear sealing surfaces 19, 20 are arranged at end faces of the bushing 11. During operation the front sealing surface 20 is pressed against a corresponding surface of the front section 4 in the axial direction z. Analogously, the rear sealing surface 19 is pressed against a corresponding surface of the rear section 3. The spacer 11 is preferably arranged in the central passage 5 extending in the axial direction z between a needle centering means 14 and the rear section 3 and forms part of the melt channel 6.

[0035] As best visible in FIG. 2, the tip 9 of the front section 4 in combination with the front end 10 of the needle 7 form a molding contour 12 embedded during operation into a molding cavity contour 13. This is shown in FIG. 5. The length of the spacer 11 in the axial direction z is adjustable, in particular, as the spacer 11 is designed exchangeable for a spacer 11 of different length.

[0036] As indicated above, injection nozzle 1 preferably comprises a needle centering means 14 comprising at least one passage for the melt to pass the needle centering means 14. The needle centering means 14 is arranged between the gate 8 at the front section 4 and the spacer 11, for centering the needle 7 in radial direction during operation when moved between the open and the closed position. This is best illustrated in FIG. 5. In the shown variations, the needle centering means 14 is formed as a separate, ring-shaped part, comprising three fins 17, each extending in a radially inward direction. Each fin typically comprises a guiding surface 18 for axially guiding the needle 7 and thereby centering the needle 7 in radial direction. As visible in FIGS. 2 and 5, the needle centering means 14 is preferably arranged in a pocket 15 of the front section 4 in the central passage 5, adjacent to the tip 9 of the nozzle 1. The pocket 15 comprises a circular shoulder 16 for supporting the needle centering means 14 in the axial direction z, when it is pressed during operation by the spacer 11 in the axial direction.

[0037] As shown in FIG. 3, the rear section 3 may comprise an outer thread 21 and the front section 4 may comprise a corresponding inner thread 22 for engaging with the outer thread 21 to interconnect the front section 4 to the rear section 3. Typically, the front section 4 is detachably interconnected to the rear section 3, however a fixed interconnection is thinkable as well.

[0038] FIG. 4 shows a section view of an injection molding tool 23, comprising an injection nozzle 1 according to the disclosure. The injection molding tool 23 comprises at least one cavity 24 having a molding cavity contour 13 defining the shape of a plastic part formed therein from melted thermoplastic material. The injection molding tool 23 further comprises at least one injection nozzle 1, as described before, arranged adjoining the cavity 24 for supplying melted thermoplastic material to the cavity, via the melt channel 6. The injection nozzle 1 forms at least part of the molding cavity contour 13, as visible in FIG. 5.

[0039] Optionally, a bushing 26 is arranged at least partially surrounding the tip 9 of the nozzle 1. The bushing comprises on its outside an indentation forming part of a cooling channel 27, for cooling the busing 26. The cooling channel is usually interconnected to a cooling circuit (not shown) of the injection molding tool 23.

[0040] The second variation of the nozzle 1 as visible in FIGS. 6 and 7 has a multipart front section 4. The front section 4 comprises an outer part 30 and a separate tip element 28 being removably coupled to the outer part 30. The Tip element 28 is in the shown second variation coupled to the outer part 30 by a retaining means 29 formed as a flange 29. The flange 29 is arranged in the axial direction z between the outer part 30 and the needle centering means 14. In addition, the flange 29 acts as the shoulder 15, forming in combination with the outer part 30 the pocket 15 to accommodate and support the needle centering means 14 with respect to the spacer 11 and thereby to the rear part 3. To remove the tip element 28 from the outer part 30, the outer part in unscrewed from the rear section 3.

[0041] Rather, the words used in the specification are words of description rather than limitation, and it is understood that changes may be made without departing from the scope of the disclosure.