WO2019145877A1

WO2019145877A1 - Injection nozzle

Info

Publication number: WO2019145877A1
Application number: PCT/IB2019/050575
Authority: WO
Inventors: Francisco Jose VESTIA MILHINHOS
Original assignee: Yudo Eu, S.A.
Priority date: 2018-01-25
Filing date: 2019-01-23
Publication date: 2019-08-01

Abstract

The present application describes an injection nozzle (2), to be used in a system for injecting material into a molding cavity. Said nozzle is designed to solve the technical problem associated to the color transition of the material to be injected into the molding cavity, so as to provide a fast and effective mixture between the material particles remaining in the injection channel, with a given color, with the new material to be injected having a different color, keeping the physical properties of the materials to be injected intact. The nozzle (2) comprises a tip (10) and a cone-shaped nipple (3) fitted with a coupling mechanism, wherein the tip (10) is inserted. The tip comprises at least five independent material-conducting channels, a central (6) one inside the tip (10) and at least four outer channels (7) embossed on the outer surface of the tip (10).

Description

DESCRIPTION

"INJECTION NOZZLE"

Technical field

The present application describes an injection nozzle to be used in a system for injecting material into a molding cavity .

Background art

It is currently noted that the injection systems used for injecting material into a molding cavity are not adapted to provide a fast and effective change of color of said material, when the resulting part comprises more than one color. In this context, it is usual to use insulation nipples at the front of the tip to fill this zone, in order to prevent the stoppage of traces of the preceding color, bearing in mind that these nipples are highly breakable.

Actually, it is verified that under these circumstances the color change is not immediate, a non-homogeneous transition between two colors along the part being noted as a result of the mixture of the new color with the previous one still remaining inside the injection system. Consequently, the final appearance of the part produced is impaired, failing to meet desirable quality standards, and thus is discarded. This means increased costs associated to wasted parts. As such, a mechanism that provides fast and effective color transition is, nowadays, of vital importance for injection systems in general, since the industry - especially the automotive industry - increasingly requires the same part to have different colors, which may range from black to white .

As a way of solving the technical problem associated to the color transition of the material to be injected into the molding cavity, the state of the art presents a series of techniques designed to solve said problem.

Document US5716651 A describes a nozzle for a non-valved injector system to be inserted at the front of the injection nozzle. This nozzle has two outer channels to where the material is routed to be injected into the molding cavity, comprising helical grooves along its surface. The helical characteristic of the grooves imparts a rotational movement to the material running along them, favoring the mixture between the remaining material and the new material .

The same principle underlies document US 20070065538 A1 , which discloses an injection nozzle comprising a central channel, fitted with helical slots, where the material is displaced by action of an injection needle which controls the flow to be injected into a molding cavity. The outer surface of the needle leads the material through the central channel by way of spiral contours along its longitudinal section.

Document US 20070077328 A1 discloses an injection molding device comprising several nipples to be introduced in the hot channel injection system, each of them from a redistribution element placed along the material-conducting channel. Said redistribution element is formed by a central channel fitted with helical depressions, whose entry is flatter than the rest, providing an increase in the pressure put on the material at the entry of the channel, which translates into a propagation thereof through the helical path, promoting the mixture with the remaining material .

Therefore, it is noted, in practice, that the known solutions are based on the development of injection nozzles, fitted with injector channels that impart a rotational movement to the material running along them, favoring the mixture thereof.

However, these solutions have proven themselves insufficient to cause a major turbulence, which promotes the effective mixture of materials. Furthermore, the heating by friction to which the material is subjected to along this path is not taken into consideration, and consequently its shear rate, which may adversely affect the physical properties of the material to be injected into the molding cavity.

Summary

The present application describes an injection nozzle comprising a tip to be installed into the injection nozzle of an injection system, and a nipple wherein the tip is inserted; said tip bush of injection nozzle characterized in that :

- the tip comprises:

- an inlet chamber which at one end connects to the injection nozzle and at the opposite end has a connection area for connection to at least five material-conducting channels;

- at least five material-conducting channels, which extend along the longitudinal shaft of the tip, from the connection area of the inlet chamber up to the outlet end of the tip; one of them being a central channel which extends inside of the tip; and at least four spiral channels embossed along the outer surface of the tip, whose surface is helical;

- the nipple is cone-shaped and comprises:

- a coupling mechanism, at the end in contact with the injection nozzle;

- an injector element at the opposite end to the one connecting to the injection nozzle;

wherein the coupling between tip and nipple is adapted to create a recess between the outer diameter of the tip and the inner diameter of the nipple.

In a particular embodiment of the nozzle, the recess existing between the outer diameter of the tip and the inner diameter of the nipple has a value varying between 0.5 mm and 3 mm.

In another particular embodiment of the nozzle, the coupling between tip and nipple is adapted to create an empty space, mixing chamber, between the outlet end of the tip and the injector element.

In a particular embodiment of the nozzle, the capacity of the mixing chamber has 1/8 of the total capacity of the conducting channels.

In a particular embodiment of the nozzle, the outer channels all have the same diameter. In a particular embodiment of the nozzle, the diameter of the central channel varies between 3/1 and 1/1 the diameter of an outer channel.

In a particular embodiment of the nozzle, the diameter of the central channel is equal to the diameter of the control needle of the injection nozzle of the injection system wherein the nozzle is installed.

In a particular embodiment of the nozzle, the inner surface of the central channel is linear.

In a particular embodiment of the nozzle, the inner surface of an outer channel is spherical.

In a particular embodiment of the nozzle, the inner surface of an outer channel is rectangular.

In a particular embodiment of the nozzle, the coupling mechanism of the nipple is of the threaded type.

In a particular embodiment of the nozzle, the tip and the nipple are made of a metallic material.

In a particular embodiment of the nozzle, the metallic material is TZM or carbide.

General description

The present application describes an injection nozzle to be used in a system for injecting material (polymer) into a molding cavity. Said nozzle is designed to solve the technical problem associated to the color transition of the material to be injected into the molding cavity, so as to provide a fast and effective mixture between the material particles remaining in the injection channel, with a given color, with the new material to be injected having a different color, keeping the physical properties of the materials to be injected intact.

The injection nozzle comprises a tip which is installed into the injection nozzle of an injection system, its fastening being guaranteed by a nipple fitted with a coupling mechanism. The tip and nipple assembly that makes up the developed nozzle is made of a metallic material. The tip comprises an inlet chamber and at least five independent material-conducting channels, one of them being central, and at least four outer channels placed around the central one. The inlet chamber, at one end connects to the injection nozzle, having an inner diameter equal to that of the injection nozzle, and always greater than any of the conducting channels of the opposite side. At said opposite end of the inlet chamber there is a connection area that causes the narrowing of the inner diameter of the chamber to establish the connection to the central channel, and respective adaptation between both diameters - inlet chamber and central channel. The connection area is where the inlets to the outer channels are arranged symmetrically to each other, and around the entrance of the central channel .

The at least four outer conducting channels are embossed on the outer surface of the tip, having a spherical or rectangular shape, extending spirally along its longitudinal shaft. The inner surface of the channels presents helical slots that enable the forward flow of the material in a rotational movement, favoring the agglutination of particles of a prior material still remaining in the conducting channel. The arrangement of said channels along this surface conforms to a particular scheme of balance and stability of the material flow to be mixed, where the termination of a given outer channel will have to exceed the entry of the subsequent channel by at least an additional 10%, its reference being the longitudinal shaft of the nozzle. In practical terms, an outer channel has its entrance in the connection area of the inlet chamber, and this entrance is from the inside to the outside of the tip, which is where the channel begins its progress along the tip, implying that the channel terminates downstream of the entrance to the following outer channel. The effect achieved by this configuration is one of a more effective mixing between the material leaving contiguous channels.

In turn, the inner conducting channel has a linear inner surface, its diameter being greater than the diameter of an outer channel, typically at a ratio of 3/1. However, this ratio may vary between 1/1 and 3/1, ensuring that the flow of material running through the outer channels is always greater than the one running through the inner channel, enhancing the mixture operation.

The developed nozzle additionally comprises a cone-shaped nipple which envelops the tip and enables the correct installation and fastening thereof to the injection nozzle, by way of a coupling mechanism, typically threaded. Furthermore, the coupling mechanism promotes the sealing of the nozzle, preventing the spillage of material at the junction of the tip with the injection nozzle. The coupling between nipple and tip enables the creation of a recess between the outer diameter of the tip and the inner diameter of the nipple, which favors the mixing operation and continuous homogenization of the material. Actually, the cone-shaped geometry conferred by the nipple to the nozzle represents a profile which, together with the helical slots present on the surface of the outer conducting channels, favors an increased rotation speed of the material particles running therethrough, improving the mixing operation of the materials running through the outer conducting channels. The nipple further comprises an injector element where all the conducting channels are connected, agglutinating the material leaving them, and providing the contact with the molding cavity for injection of same. In an alternative embodiment, the coupling between nipple and tip enables the creation of a mixing chamber at the front of the tip, next to the outlets of the conducting channels. The empty space existing between the tip and the nipple, where the materials coming from the conducting channels come together, before entering the injector element, favors the agglutination of all the materials, causing a new mixing operation, before the material is injected into the molding cavity. This empty space may have different capacities according to requirements, at the expense of using different sized nipples. The capacity of the mixing chamber is based on the total capacity of the conducting channels.

The material is guided through the central and outer conducting channels and the injection into the molding cavity is operated by way of a control needle, belonging to the injection nozzle of the system, where the developed nozzle is installed. The forward and backward displacements of this needle along the inlet chamber of the central conducting channel and of the mixing chamber are controlled by the pneumatic or hydraulic cylinder of the injection system. It is these displacements of the needle that cause the constriction of the material in the entrance of the central channel, directing the material to the outer conducting channels forcing them to move. The cone shape of the nipple implies, subsequently, that the material running through the outer channels will be pushed against its inner wall which, because of its angular profile, will promote the movement thereof to the respective outlets, thus preventing the permanence and adherence of particles to the surface of the inner wall of the nipple.

The mixing operation between materials was devised so as to guarantee that the physical properties of the materials are not adversely affected in the injection process, namely its shear rate which, in a worst-case scenario, will imply the degradation thereof. This fact is achieved through balance and stability between the material running through the central channel and the outer channels, guaranteeing that the material outflow through the latter is always higher than that running through the former. This fact is guaranteed by the ratio between the diameters of the conducting channels and by adjusting the control needle, which promotes the displacement of the material through said channels.

With this structure, the developed nozzle forces the material to run through multiple conducting channels before a final mixture that precedes injection thereof into the molding cavity. Actually, the characteristics of the outer channels that impart a rotational movement to the material enable the combination of the remaining particles of a previous material - with a given color - to occur in a fast and effective manner in the new material, whereby achieving the desired homogenization in the material transition process .

Brief description of the drawings

For an easier understanding of the present application, the accompanying drawings represent preferred embodiments, though they are not intended to limit the art here disclosed .

Figure 1 illustrates the installation of the injection nozzle developed into a hot channel injection system, wherein the numerical reference signs have the following meaning :

1 - Injector system;

2 - Injection nozzle;

4 - Control needle;

5 - Inlet chamber.

Figure 2 illustrates the developed injection nozzle, wherein the numerical reference signs have the following meaning :

2 - Injection nozzle;

3 - Nipple;

6 - Central channel;

7 - Outer channel;

13 Recess .

Figure 3 illustrates the injection nozzle developed, wherein the numerical reference signs have the following meaning :

2 - Injection nozzle;

3 - Nipple;

4 - Control needle.

Figure 4 illustrates the tip of the injection nozzle developed, wherein the numerical reference signs have the following meaning:

7 - Outer channel;

10 - Tip;

11 - Holes linking to the outer channel;

12 - Spacing between outer channels.

Figure 5 illustrates the injection nozzle developed, wherein the numerical reference signs have the following meaning :

2 - Injection nozzle;

3 - Nipple;

4 - Control needle;

5 - Inlet chamber;

6 - Central channel;

7 - Outer channel;

8 - Mixing chamber;

9 - Injector element;

10 - Tip.

Description of the embodiments

With reference to the drawings, some embodiments will now be described in greater detail, but are not intended to limit the scope of the present application.

In a particular embodiment, the injection nozzle (2), is applied in a hot channel valve injection system, comprising the tip (10) and nipple (3) combination made of titanium zirconium molybdenum alloy (TZM) or carbide. Alternative manufacturing materials for the nozzle (2) include copper- beryl, steel or tungsten carbide. The coupling between the tip (10) and the injection nozzle of the injector system (1) is provided by the nipple (3) with steel thread fitting .

In a particular embodiment, the tip comprises an inlet chamber (5) and at least five independent material conducting channels, one being central (6), and at least four outer channels (7) placed around the central one. The inlet chamber (5) has an initial diameter higher than any of the conducting channels, having a final narrowing zone for connection to the central channel (6), and which promotes the adaptation between both diameters - inlet chamber (5) and central channel (6) . It is in this narrowing zone where the inlets to the outer channels (7) are arranged symmetrically to each other, and around the entrance of the central channel (6) .

In a particular embodiment of the injection nozzle (2), the central channel (6) is inside the tip (10), extending along its longitudinal shaft, and whose inner surface is linear. In turn, the four outer channels (7) are embossed in spherical form on the outer surface of the tip, along its longitudinal shaft, extending from the narrowing zone of the inlet chamber (5) to the opposite end of the tip (8) . The inner surface of said channels (7) presents helical slots throughout its length. In a particular embodiment, the outer channels all have the same diameter and the diameter ratio between the outer channels (7) and the central channel (6) is 1/3.

The nipple (3) is cone-shaped, envelops the tip (10) and enables the correct installation and fastening thereof to the injection nozzle, through a coupling mechanism, typically threaded. The coupling between the nipple (3) and tip (10) enables the creation of a constant recess between the outer diameter of the tip (10) and the inner diameter of the nipple (3), typically between 0.5 mm and 3 mm. In a particular embodiment, the coupling between nipple (3) and tip (10) creates an empty space, a mixing chamber (8), at the front of the tip, next to the outlets of the conducting channels, into where the material running therethrough flows. The capacity of the chamber represents, typically, approximately 1/8 of the total capacity of the conducting channels. In a particular embodiment, the total capacity of the inlet channels is 2234 mm³ and the capacity of the mixing chamber (8) is 299 mm³.

The cone-shaped geometry that the nipple (3) confers to the nozzle (2), represents a profile that, together with the helical slots present on the surface of the outer conducting channels (7) and the opening defined by the control needle in the central channel, favors the increase in rotation speed of the material particles running therethrough, improving the mixing operation in the chamber (8) between the materials coming from the various conducting channels. The nipple (3) further comprises an injector element (9) which provides the contact with the molding cavity, injecting the material that is in the mixing chamber into the molding zone.

The guiding of the material through the conducting channels and the injection into the molding cavity are operated by way of a control needle (4), belonging to the injection nozzle of the system (1), where the developed nozzle (2) is installed. The forward and backward displacements of this needle (4), along the inlet chamber (5) of the central conducting channel (6) and of the mixing chamber (8) are controlled by the pneumatic or hydraulic cylinder of the injection system (1), causing constriction and flow control of the material at the entrance to the conducting channels which forces the displacement thereof. Accordingly, the diameter of the central channel (6) will have to be at least equal to the diameter of the needle (4) . The inner geometry of the central channel of said tip (10) is designed to guide the needle when it reaches the injection zone and may seal without damaging the nipple.

Naturally, the present description is not restricted in any way to the embodiments presented in this document and a person with average knowledge in the field may envisage many possibilities of modifying it without straying from the general idea, as defined in the claims. The preferred embodiments described above are obviously combinable with each other. The accompanying claims additionally define preferred embodiments.

Claims

1. An injection nozzle comprising a tip for installing onto the injection nozzle of an injection system and a nipple wherein the tip is inserted; said tip bush of injection nozzle characterized in that:

- the tip is comprised of:

- at least five material-conducting channels, which extend along the longitudinal shaft of the tip, from the connection area of the inlet chamber up to the outlet end of the tip; one being a central channel which extends through the inside of the tip; and at least four channels embossed in spiral form along the outer surface of the tip, whose surface is helical;

- the nipple is cone-shaped and comprises:

- a coupling mechanism, at the end in contact with the injection nozzle;

- an injector element at the opposite end to the one that connects to the injection nozzle; wherein, the coupling between tip and nipple is adapted to create a recess between the outer diameter of the tip and the inner diameter of the nipple.

2. The nozzle according to claim 1, wherein the recess existing between the outer diameter of the tip and the inner diameter of the nipple is a value varying between 0.5 mm and 3 mm.

3. The nozzle according to either of the preceding claims, wherein the coupling between tip and nipple is adapted to create an empty space, mixing chamber, between the outlet end of the tip and the injector element.

4. The nozzle according to claim 3, wherein the capacity of the mixing chamber has 1/8 of the total capacity of the conducting channels.

5. The nozzle according to any of the preceding claims, wherein the outer channels all have the same diameter.

6. The nozzle according to claims 1 or 5, wherein the diameter of the central channel varies between 3/1 and 1/1 the diameter of an outer channel.

7. The nozzle according to any of the preceding claims, wherein the diameter of the central channel is equal to the diameter of the control needle of the injection nozzle of the injection system where the nozzle is installed.

8. The nozzle according to any of the preceding claims, wherein the inner surface of the central channel is linear.

9. The nozzle according to any of the preceding claims, wherein the inner surface of an outer channel is spherical.

10. The nozzle according to any of the preceding claims, wherein the inner surface of an outer channel is rectangular .

11. The nozzle according to any of the preceding claims, wherein the coupling mechanism of the nipple is of the threaded type.

12. The nozzle according to claim 1, wherein the tip and the nipple are made of a metallic material.

13. The nozzle according to claim 12, wherein the metallic material is titanium zirconium molybdenum alloy or carbide.