Injection molds for tubular plastic parts

Abstract

An injection mold (1) for manufacturing at least one tubular plastic part comprises a first mold half (2) and a second mold half (4), the first mold half (2) comprising a first mold plate (3), the second mold half (4) comprising a second mold plate (5), the first mold half (2) and the second mold half (4) being arranged to be displaceable relative to each other in an axial direction (Z) between an open position and a closed position. The injection mold further comprises at least one core (6) protruding from the first mold plate (3), and the second mold plate (4) comprising at least one cavity (7) adapted to receive the core (6) of the first mold half (2) to form a molding cavity (8) in the closed position of the injection mold (1), the molding cavity (8) being used to receive molten plastic material in the molding cavity (8) to form the tubular plastic part. The bushing (9) is advantageously arranged in the second mold half (4), adjacent to the dorsal end (10) of the cavity (7), the bushing (9) being at least partially displaceable relative to the second mold plate (4), the bushing (9) comprising a hole (11) adapted to receive the end (12) of the core (6) in the closed position of the injection mold (1).

Description

Technical Field

[0001] The present disclosure is directed to the field of injection molds, and in particular to injection molds for injection molding tubular members made of plastic materials and other thermoplastic materials. Background Art

[0002] Injection molds for making elongated tubular plastic parts such as straws or, in particular, ends require high precision in their construction and operation. These injection molds typically include two mold halves, a first mold half with a core and a second mold half with an associated cavity that together form a molding cavity to receive molten plastic material to form the elongated tubular plastic part. In order to form the tubular plastic part, the end of the core must extend beyond the molding cavity and must be received in the second mold half in a precise manner so that the molten plastic is not injected beyond the mold cavity. Thermal expansion of the various components of the injection mold during operation complicates receiving the core end in a precise manner, and the core end is therefore often subject to wear.

[0003] Attempts to solve the above-mentioned problems known from the prior art are briefly described below.

[0004] EP2397301A1, first published in December 2011 in the name of Mold Masters, relates to an injection molding system and an edge gate nozzle that delivers plastic material to a cavity from substantially opposite sides. The core of a first mold half of the described injection molding system has a narrower portion that is received in a second mold half of the injection molding system to form a tubular member. Summary of the invention

[0005] In a preferred variant, an injection mold for manufacturing at least one tubular plastic part comprises a first mold half and a second mold half, the first mold half comprising a first mold plate, the second mold half comprising a second mold plate, the first mold half and the second mold half being arranged to be displaceable relative to each other in an axial direction between an open position and a closed position. In the closed position, the mold halves are substantially in direct contact, and the tubular plastic part can be removed from the injection mold in the open position. The injection mold also includes at least one core, which protrudes from the first mold plate. The second mold plate includes at least one cavity adapted to receive the core of the first mold half to form a molding cavity in the closed position of the injection mold, the molding cavity being used to receive molten plastic material in the molding cavity to form the tubular plastic part. Typically, the second mold plate includes a plurality of cavities, and preferably, the associated plurality of cores are arranged at the first mold plate. A bushing is arranged in the second mold half, adjacent to the back end of the cavity, and the bushing can be at least partially displaced relative to the second mold plate. The bushing includes a hole, which is adapted to receive the end of the core in the closed position of the injection mold. Depending on the field of application, the core may have a circular cross section, however other geometries are possible.To form the tubular plastic part, in the closed position of the injection mould, the end of the core usually protrudes from the back side end of the cavity into the bore of the bushing.

[0006] In order to reduce the influence of wear on the performance of the injection mold, preferably, the bushing is at least partially arranged in a floating manner in the lateral direction. In this way, the end of the core can be received by the hole of the bushing in a wear-minimizing manner, because the bushing can at least partially adjust the lateral positioning of the hole so that the hole is coaxial with the end of the core. The lateral direction is orthogonal to the axial direction. In addition, the bushing can be arranged in a displaceable manner in the axial direction. This allows the distance between the bushing and the end of the cavity to be changed by shifting the bushing in the axial direction. The end of the core may include a cylindrical portion, which can be accommodated in the substantially cylindrical hole of the bushing in the closed position. This allows compensation for the thermal expansion of the core in the axial direction during the operation of the injection mold, because the expansion of the core in the axial direction causes the end of the core to further protrude into the hole. Alternatively or additionally, a tapered portion at the end of the core is also possible.

[0007] In an advantageous variant, the bushing comprises a conical first surface which is arranged coaxially on the outside of the bushing relative to the hole. The conical first surface can cooperate with a conical second surface arranged in the second mold half in the closed position of the injection mold so that the end of the core is centered relative to the hole. In a preferred variant, conical means angled or tapered relative to the axial direction and / or generally the direction of the hole. The conical second surface can be formed as part of the second mold plate and is arranged between the cavity and the bushing in the axial direction and is essentially immobile relative to the cavity.

[0008] In order to tightly seal the molten plastic between the core and the hole, the bushing can include a plurality of clamping segments in the circumferential direction, which are arranged to be displaceable relative to each other in the radial direction relative to the hole, so that the end of the core can be accommodated in the hole in a manner that tightly seals the molten plastic in the closed position of the injection mold. In other words, when the clamping segments are displaced inwardly in the radial direction relative to the hole, thereby causing the diameter of the hole to decrease, the end of the core can be received in the hole of the bushing in a force-locked manner. In the open position of the injection molding machine, the diameter of the hole is greater than or equal to the diameter of the end of the core.

[0009] The clamping segments may be separated by one or more slits in the bushing, the one or more slits extending at least partially in the axial direction.Preferably, the clamping segments are interconnected to each other via a common base.

[0010] In a preferred variant, the bushing comprises a front section which is arranged between the back end of the cavity and the clamping section during operation. The front section comprises an uninterrupted entrance opening of the hole to receive the core. In the case of a flat or smooth contact surface of the bushing arranged relative to the cavity, this allows the end of the core to be received in a low-friction manner so as to produce a high-quality part without burrs. An uninterrupted entrance opening in the context can be understood as a continuous and circumferential entrance opening, in particular a smooth entrance opening. The front section can be formed as a separate part. In the case where the front section is formed as a washer-type part, good results can be achieved so that the end of the core can pass through the front section to be partially accommodated by the clamping section and partially accommodated by the front section. This allows further minimizing the friction-based wear of the end of the core during operation. Alternatively or additionally, the bushing can be formed as a washer-type element.

[0011] Preferably, in the closed position of the injection mold, the bushing can be at least partially displaced and / or clamped relative to the second mold plate by an actuator, which is arranged to be at least partially displaceable relative to the second mold plate. Therefore, the bushing is usually arranged between the dorsal end of the cavity and the actuator in the axial direction. The actuator is generally configured to generate a relative force in the axial direction between the conical first surface and the conical second surface. This in turn leads to an alignment of the conical first surface and the conical second surface and a resultant force in the radial direction. The clamping section is preferably mechanically interconnected with the conical first surface, and thus the resultant force in the radial direction can displace the clamping section.

[0012] In the case where the actuator includes at least one displaceable hydraulic piston and / or pneumatic piston, good results can be achieved. In a preferred variant, the second die plate includes a plurality of cavities arranged in a circular manner. When the piston is annular, a simple design can be achieved so that the shape of the piston can follow the circular arrangement of the cavity. Preferably, the annular piston allows simultaneous displacement of a plurality of bushings associated with the cavity in the axial direction. Alternatively or additionally, the actuator may include a push insert, which is arranged between the bushing and the piston of the actuator in the axial direction to mechanically interconnect the piston and the bushing. In a preferred variant, the conical second surface may be formed as a part of the actuator, in particular as a part of the push insert, and the conical second surface may be displaced relative to the cavity in the axial direction. Alternatively or additionally, the actuator includes a spring-loaded actuation plate. The actuation plate may be annular, and the actuation plate may also include a through hole to at least partially accommodate the push insert. This allows the actuation plate to keep the push insert relative to the piston in the axial direction. This also allows a restoring force to be applied to the piston.

[0013] Alternatively, or in addition to the piston, the actuator may include a rod-shaped pusher which is mechanically interconnected with the first mold half and a spring-loaded actuation plate arranged in the second mold half in the closed position of the injection mold, so that the actuation plate can be displaced relative to the second mold plate by the rod-shaped pusher.

[0014] In order to monitor the production of the tubular plastic part, at least one sensor may be arranged in the bushing or adjacent to the bushing. The sensor may be a pressure sensor and / or a temperature sensor.

[0015] The bushing may be held relative to the second mold plate or the actuator by a holding mechanism, wherein the holding mechanism comprises at least one of the following elements: a circlip, a ring of elastic material, a stop screw or a stop bolt, or the like.

[0016] Good results can be achieved if the bushing comprises at least one cutout, which is arranged laterally and connects the hole with the outside of the bushing. Preferably, the cutout is arranged between the clamping segment and the base to allow displacement of the clamping segment in radial direction with less force.

[0017] Another aspect of the present disclosure is directed to a method of manufacturing at least one tubular plastic part using the injection mold as described above. The method generally comprises the following steps:

[0018] - Closing the injection mould by displacing the mould halves relative to each other from an open position to a closed position. The core of the first mould plate is thus received in the cavity of the second mould plate and the end of the core protrudes from the dorsal end of the cavity in the axial direction. The end of the core is also received by the hole of the bushing which is arranged adjacent to the dorsal end of the cavity.

[0019] - Injecting molten plastic material into the molding cavity to form a tubular plastic part.

[0020] - After the plastic material has been sufficiently cured, the injection mold is opened and the tubular plastic part is removed.

[0021] In a preferred variant, the described method may additionally comprise the steps of:

[0022] - clamping the end of the core in the bore of the bushing in the closed position of the injection mould by displacing the piston in the axial direction towards the dorsal end of the cavity and thereby displacing the clamping segment in the radial direction inwardly via the conical second surface cooperating with the conical first surface.

[0023] - The end of the core is released from the grip of the bore in the closed position of the injection mould by displacing the piston in the axial direction away from the back end of the cavity.

[0024] It should be understood that both the foregoing general description and the following detailed description present embodiments and are intended to provide an overview or framework for understanding the nature and character of the present disclosure. The accompanying drawings are included to provide a further understanding and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments and, together with the description, serve to explain the principles and operation of the disclosed concepts. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The disclosure described herein will be more fully understood through the detailed description given herein below and the accompanying drawings, which should not be considered as limiting the disclosure described in the appended claims. The drawings show:

[0026] Figure 1 is a cross-sectional view of a first variation of an injection mold according to the present disclosure;

[0027] Figure 2 yes Figure 1 As shown in Figure 1 A detailed view of the first variant indicated by the letter E;

[0028] Figure 3 is a cross-sectional view of a second variation of an injection mold according to the present disclosure;

[0029] Figure 4 yes Figure 3 As shown in Figure 3 A detailed view of the second variant indicated by the letter D;

[0030] Figure 5 Yes Figure 1 and Figure 2 A perspective view of a bushing of a first variation shown in ;

[0031] Figure 6 Yes Figure 3 and Figure 4 A perspective view of a bushing of a second variation shown in ;

[0032] Figure 7 Yes Figure 8 A perspective view of a bushing of a third variation shown in FIG.

[0033] Figure 8 is a (partial) cross-sectional view of a third variant of an injection mold according to the present disclosure. DETAILED DESCRIPTION

[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, the embodiments disclosed herein may be implemented in many different forms 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, the same reference numerals will be used to refer to the same components or parts.

[0035] Figure 1 A cross-sectional view of a first variant of an injection mold 1 according to the present disclosure is shown. Figure 2 Shows Figure 1 As shown in Figure 1 Detailed view of the first variant indicated by the letter E in FIG. Figure 3 A cross-sectional view showing a second variant of the injection mold 1 according to the present disclosure, and Figure 4 Shows Figure 3 As shown in Figure 3 Detailed view of the second variant indicated by the letter D. Figure 5 In the Figure 1 and Figure 2 A perspective view of a bushing 9 of a first variant is shown in FIG. Figure 6 Shown as Figure 3 and Figure 4 A perspective view of a bushing 9 of a second variant is shown in FIG. Figure 8 shows a cross-sectional view of a third variant of the injection mold 1 according to the present disclosure, and Figure 7 The exploded view shows Figure 8 A third variant of the bushing 9.

[0036] Figure 1 and Figure 3The variant of the injection mold 1 shown in is shown in the closed position and comprises a first mold half 2 and a second mold half 4. To reach the closed position, the two mold halves 2 and 4 are displaced from the open position in the axial direction Z towards each other until they are in direct contact. The first mold half 2 comprises a first mold plate 3 and the second mold half 4 comprises a second mold plate 5. The injection mold 1 further comprises at least one core 6 protruding from the first mold plate 3, in the variant shown a plurality of cores 6 protruding from the first mold plate 3. As in Figure 2 , Figure 4 and Figure 8 As best seen in FIG. 1 , the second mold plate 5 comprises at least one cavity 7 for receiving the core 6 of the first mold plate 3, thereby forming a molding cavity 8 in the closed position of the injection mold 1. A bushing 9 is arranged in the second mold half 4 adjacent to the back end 10 of the cavity 7, and the bushing 9 can be at least partially displaced relative to the second mold plate 5. The bushing 9 comprises a hole 11 for receiving the end 12 of the core 6 in the closed position of the injection mold 1. As shown in FIG. Figure 2 , Figure 4 and Figure 8 As can be seen in the figure, the sleeve is joined to the end 12 of the core 6, closing the molding cavity 8 at the back end 10 of the cavity 7 in a manner that is sealed against the molten plastic material.

[0037] Figure 2 , Figure 4 and Figure 8 It is also shown that the bushing 9 is arranged in a floating manner in the lateral direction L. This can be achieved by means of a retaining mechanism 22 .

[0038] In order to center the bushing 9 relative to the cavity 7, the bushing 9 comprises a conical first surface 13 which is arranged coaxially on the outside of the bushing 9 relative to the hole 11. The conical first surface 13 cooperates with a conical second surface 14 arranged on the second mold half 4 in the closed position of the injection mold 1 so that the end 12 of the core 6 is centered relative to the hole 11. Figure 2 In a first variant, which can be seen in FIG. 4 , the conical second surface 14 is formed as part of the second mould plate 5 and is arranged in the axial direction Z between the cavity 7 and the bushing 9 in a manner immovable relative to the cavity 7 .

[0039] exist Figure 4 In a second variant, which can be seen in FIG. 1 , the bushing 9 comprises in the circumferential direction a plurality of clamping segments 15 which are arranged so as to be displaceable in the radial direction R relative to the bore 11, so that the end 12 of the core 6 is received in the bore 11 in the closed position of the injection mold 1 and is preferably clamped in the bore 11. The clamping segments 15 are mechanically interconnected with the conical first surface 13 of the outer side of the bushing 9. This variant of the bushing 9 can best be seen in FIG. Figure 6In this case, the bushing is held substantially immobile relative to the cavity 7 in the axial direction Z by means of a retaining means 22 formed as a circlip 24. The clamping segments 15 are separated by a plurality of slits 26 in the bushing 9, which extend at least partially in the axial direction Z. In the variant shown, the clamping segments 15 are interconnected with each other via a common base 16. Furthermore, the bushing comprises a plurality of laterally arranged cutouts 23, each of which connects the bore 11 and the outside of the bushing 9, respectively. The cutouts 23 are each arranged between two clamping segments 15 and the common base 16. Each of the slits 26 ends in the axial direction at a respective cutout 23.

[0040] As in Figure 8 The third variant shown in FIG. 1 differs from the second variant in that the bushing 9 comprises a dedicated front section 27 which is formed here as a separate part. Figure 7 As can be best seen in FIG. 1 , the front section 27 is formed as a washer-type part. During operation, the front section 27 is arranged between the back end 10 of the cavity 7 and the plurality of clamping segments 15, extending substantially perpendicularly to the axial direction Z. The bore 11 is partially arranged in the front section 27, which comprises an uninterrupted inlet opening 28 of the bore 11 in order to receive the core 6 in a low-friction manner. As shown in FIG. Figure 8 It can be seen that in the closed position, the core 6 is received in the hole 11, and the core extends through the front section 27 via the inlet opening 28, so that the end 12 of the core 6 can be accommodated in the hole 11 in the closed position of the injection mold 1 and is preferably clamped in the hole 11, in particular clamped in the hole 11 by the clamping section 15.

[0041] As in Figure 2 , Figure 4 and Figure 8 As can best be seen in FIG, in the closed position of the injection mold 1, the bushing 9 can be displaced and clamped relative to the second mold plate 5 by means of an actuator 17 which is arranged to be displaceable relative to the second mold plate 5. The bushing 9 is therefore arranged between the actuator 17 and the back end 10 of the cavity 7 in the axial direction Z. The actuator 17 comprises an annular pneumatic piston 18 which can be displaced in the axial direction Z to generate a relative force between the conical first surface 13 and the conical second surface 14. Figure 2 In the first variant shown, this relative force guides the alignment between the bushing 9 and the cavity 7, and therefore the alignment between the core 6 and the cavity 7, because the core 6 is guided into this alignment by the bushing 9 with the end 12 of the core 6 in the hole 11 of the bushing 9. Figure 4 The second variant shown and Figure 8In the third variant shown, the actuator comprises a push insert 25, and alignment is achieved in a similar manner. Here, the conical second surface 14 is formed as part of the actuator 17, in particular as part of the push insert 25, and can be displaced relative to the cavity 7 in the axial direction Z. The actuator 17 also comprises a spring-loaded actuation plate 19, which is configured to exert a restoring force in the axial direction Z. In the variant shown, the actuation plate 19 is annular similar to the shape of the piston 18, and the actuation plate 19 also comprises a through hole to partially accommodate the push insert 25.

[0042] In order to monitor the production of the tubular plastic part, at least one sensor 21 is arranged in the bushing 9 or adjacent to the bushing 9 .

[0043] Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the scope of the disclosure.

[0044] Reference numerals list

[0045] 1Injection mold

[0046] 2 First mold half

[0047] 3. First mold plate

[0048] 4 Second mold half

[0049] 5. Second mold plate

[0050] 6 core

[0051] 7 chambers

[0052] 8 Molding Cavity

[0053] 9 Bushing

[0054] 10 Dorsal end (cavity)

[0055] 11 holes

[0056] 12 terminal (core)

[0057] 13 Conical first surface

[0058] 14 Conical second surface

[0059] 15 Clamping section

[0060] 16 Base

[0061] 17 Actuator

[0062] 18 Piston

[0063] 19 Actuator Plate

[0064] 21 Sensors

[0065] 22 Holding mechanism

[0066] 23 incisions

[0067] 24 Circlip

[0068] 25 Push insert

[0069] 26 Slits

[0070] 27 front section (bushing)

[0071] 28 inlet openings (holes)

[0072] Z-axis direction

[0073] L Lateral direction

[0074] R radial direction

Claims

1. An injection mold (1) for producing at least one tubular plastic part, comprising: a. a first mold half (2) and a second mold half (4), the first mold half (2) comprising a first mold plate (3), the second mold half (4) comprising a second mold plate (5), the first mold half (2) and the second mold half (4) being arranged to be displaceable relative to each other in an axial direction (Z) between an open position and a closed position; and b. at least one core (6), the at least one core (6) protruding from the first mold plate (3); and c. the second mold plate (5) comprising at least one cavity (7) adapted to receive the core (6) of the first mold half (2) to form a molding cavity (8) in the closed position of the injection mold (1), the molding cavity (8) being used to receive molten plastic material in the molding cavity (8) to form the tubular plastic part; and d. a bushing (9) arranged in the second mold half (4) adjacent to the back end (10) of the cavity (7), the bushing (9) being at least partially displaceable relative to the second mold plate (5), the bushing (9) comprising a hole (11) adapted to receive an end (12) of the core (6) in a closed position of the injection mold (1); e. wherein the bushing (9) comprises a conical first surface (13), which is arranged coaxially on the outside of the bushing (9) relative to the hole (11), and the conical first surface (13) cooperates with a conical second surface (14) arranged on the second mold half (4) in the closed position of the injection mold (1) so that the end (12) of the core (6) is centered relative to the hole (11), Therein, the bushing (9) is arranged at least partially in a floating manner in a lateral direction (L).

2. The injection mold (1) according to claim 1, wherein: The bushing (9) is at least partially arranged in a displaceable manner in the axial direction (Z).

3. The injection mold (1) according to claim 1, wherein: The bushing (9) comprises a plurality of clamping segments (15) in the circumferential direction, the plurality of clamping segments (15) being arranged so as to be displaceable relative to each other in the radial direction relative to the hole (11) so that the end (12) of the core (6) is clamped in the hole (11) in the closed position of the injection mold (1).

4. The injection mold (1) according to claim 3, wherein: The clamping segments (15) are interconnected with each other via a common base (16).

5. The injection mold (1) according to claim 1, wherein: In the closed position of the injection mold (1), the bushing (9) can be at least partially displaced and / or clamped relative to the second mold plate (5) by an actuator (17), the actuator (17) being arranged to be at least partially displaceable relative to the second mold plate (5).

6. The injection mold (1) according to claim 5, wherein: The actuator (17) comprises at least one displaceable hydraulic piston and / or pneumatic piston (18).

7. The injection mold (1) according to claim 6, wherein: The piston (18) is annular.

8. The injection mold (1) according to claim 5, wherein: The actuator (17) comprises a spring-loaded actuation plate (19).

9. The injection mold (1) according to claim 8, wherein: The actuator (17) comprises a rod-shaped pusher which is mechanically interconnected with both the first mould half (2) and the spring-loaded actuation plate (19) in the closed position, so that the actuation plate (19) can be displaced relative to the second mould plate (5) by means of the rod-shaped pusher.

10. The injection mold (1) according to claim 1, wherein: At least one sensor (21) is arranged in the bushing (9) or adjacent to the bushing (9).

11. The injection mold (1) according to claim 5, wherein: The bushing (9) is held relative to the second mold plate (5) or the actuator (17) by a holding mechanism (22).

12. The injection mold (1) according to claim 1, wherein: The bushing (9) comprises at least one cutout (23) which is arranged laterally and connects the hole (11) with the outside of the bushing (9).

13. The injection mold (1) according to claim 3, wherein: The bushing (9) comprises a front section (27) which is arranged during operation between the dorsal end (10) of the cavity (7) and the clamping section (15), the front section (27) comprising an uninterrupted entrance opening (28) of the hole (11) in order to receive the end (12) of the core (6).

14. A method for manufacturing at least one tubular plastic part using the injection mold (1) according to claim 1, the method comprising the following steps: a. Closing the injection mold (1) by displacing the mold halves (2, 4) relative to each other from the open position to the closed position, wherein, i. the core of the first mould plate (3) is received in the cavity (7) of the second mould plate (5), and the tip (12) of the core (6) protrudes from the back end (10) of the cavity (7) in the axial direction (Z), and ii. the end (12) of the core (6) is received by the hole (11) of the bushing (9), the bushing (9) being arranged adjacent to the dorsal end (10) of the cavity (7); b. injecting molten plastic material into the molding cavity (8) to form the tubular plastic member; c. After the plastic material is sufficiently cured, opening the injection mold (1) and removing the tubular plastic part.

15. The method according to claim 14, comprising the steps of: a. clamping the end (12) of the core (6) in the hole (11) of the bushing (9) in the closed position of the injection mold (1) by displacing the piston (18) in the axial direction (Z) towards the back end (10) of the cavity (7) and thereby displacing the clamping section (15) inwardly in the radial direction (r) via the cooperation of the conical second surface (14) with the conical first surface (13); and b. releasing the end (12) of the core (6) from the grip of the hole (11) in the closed position of the injection mold (1) by displacing the piston (18) in the axial direction (z) away from the back end (10) of the cavity (7).

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