FR3099401A1 - ADJUSTABLE CLOSED INJECTION NOZZLE - Google Patents

Abstract

The invention relates to an injection nozzle (B) of a material to be injected of the type comprising: - a hollow body (100) - a nozzle tip (200), - a movable shutter needle (300) along its longitudinal axis, - a needle guide (400) guiding said needle (300) in translation, - an elastic member (500) associated with the needle (300) for sealing purposes and to allow passage of the material through inject. This nozzle is remarkable in that said elastic member (500) is formed by at least one leaf spring arranged transversely to the axis of movement of said needle (300) and housed in a transverse housing (430) transversely crossing the needle guide ( 400) and said body (100). Figure to be published with the abstract: Fig. 1

Description

ADJUSTABLE CLOGGED NOZZLE

FIELD OF APPLICATION OF THE INVENTION

The invention relates to the field of the injection of materials such as plastic and silicone and in particular to the adaptations allowing an injection nozzle to modulate its closure and its opening.

DESCRIPTION OF PRIOR ART

A plastic injection nozzle is one of the sub-assemblies constituting the devices known as an injection press, injection press or machine, injection machine.

The plastic injection molding machine is the device which, using a mould, makes it possible to produce more or less complex plastic parts.

The injection nozzle is located at the outlet end of the injection screw (sometimes called plasticizing screw) and notably provides the mechanical interface with the mould.

There are so-called closed nozzles which include a shutter valve for the injection channel which is controlled upon contact with the mould.

It is also known to use a spring to control the return to position of said valve.

The presence of a spring-controlled valve allows automatic closing of the nozzle at the end of the injection process when the pressure exerted by the material in the nozzle decreases, which avoids the presence of cold drops of material likely to clog the nozzle. .

There are also nozzles equipped with an integrated heater ensuring the temperature maintenance of the heated plastic material.

However, conventional coil springs do not allow the closing and opening of the nozzle to be modulated according to the needs of the process. It is not currently possible to trigger the opening according to a defined pressure or at least to change this threshold pressure on the same nozzle.

Indeed, the adjustment of the stiffness of a coil spring accompanying a stroke of fixed value requires the possibility of producing springs of different diameter or length, which is not easy in current geometric configurations. It is also possible to change the material of the spring but this leads to high manufacturing costs.

If new springs could be proposed, it is also difficult in the current geometries to change said spring

In addition, coil springs also require a geometry of the nozzle body which makes the integration of a heating medium and cleaning difficult.

Finally, modifications to the spring cannot be made without reducing its service life.

Some solutions propose placing the spring outside the nozzle. Nevertheless, these solutions not only increase the external bulk of the device but also make it more difficult to heat the nozzle.

BRIEF DESCRIPTION OF THE INVENTION

Based on this state of affairs, the applicant conducted research aimed at obtaining an injection nozzle with adjustable shutter.

This research resulted in the design and construction of a nozzle with an original design to solve the problems of the prior art nozzle art.

The injection nozzle of a material to be injected of the invention is of the type comprising:

- a hollow body with a hollow core having an inlet orifice for the material to be injected and an outlet orifice of said material,

- a nozzle tip fitted to the outlet orifice and having an outer surface and an inner surface,

- a shutter needle movable along its longitudinal axis,

- a needle guide guiding said needle in translation,

- an elastic member associated with the needle to keep it in contact with the inner surface of the nozzle tip for sealing purposes and to allow the needle to move away from said inner surface under the effect of the constraining the material for material passage purposes.

It is remarkable in that said elastic member consists of at least one leaf spring arranged transversely to the axis of movement of said needle and housed in a housing passing transversely through the needle guide and said body.

By facilitating access to the spring, the innovation consists of offering a shutter solution (shutter and self-opening) that can be modulated according to the needs of the process, and therefore an opening trigger from a defined process pressure. Indeed, the use of a leaf spring makes it possible to require a lower reception volume for the elastic member in comparison with a coil spring. The transverse orientation facilitates access to the housing of the blade which will facilitate the change of the spring according to the process and the injected material. This change can be made without requiring the total dismantling of the nozzle.

This “removable spring blade” solution allows a range of hardnesses and therefore greater possibilities (low pressure when opening, or very strong when opening).

Thus, for example, for certain more loaded material (in fibers), the leaf spring used may have a greater hardness than for less loaded materials. This parameter could not be modulated with solutions using prior art springs.

In addition, the use of a leaf-shaped spring allows the characteristics of the spring to be changed without reducing its lifespan.

Another advantage of using such a spring geometry is the ease of cleaning, which is particularly important when the blades have to be interchanged.

According to another particularly advantageous characteristic of the invention, said leaf spring is curved towards the inner surface of said nozzle tip. Thus, the stress of the material on the end of the obturation needle causes the leaf spring to return to a flattened shape.

According to a preferred embodiment, the blade is pre-loaded to be calibrated on the effort required on opening. Thus the force exerted by the plastic material on the shutter needle (end of the shutter needle) deforms the blade within the limit of its elasticity and releases the injection flow.

According to another particularly advantageous characteristic of the invention, the rear end of the needle comes into contact with said leaf spring, the surface portion with which the end comes into contact is preformed with a concave volume to accommodate said end .

The positioning of the various elements is facilitated.

According to another particularly advantageous characteristic of the invention, said body adopts a cylindrical outer surface on which a removable cylindrical hollow sleeve fits closing the transverse housing. The accessibility and closing of the housing housing the leaf spring are therefore made easier.

More specifically, according to another particularly advantageous feature, said body is externally preformed with grooves for receiving annular seals coming into contact with the inner surface of said sleeve to implement sealing. In addition, said nozzle body is equipped with a collar on which one end of said sleeve comes to rest, a solution screwed directly between the sleeve and the body or indirectly by means of a screw and/or a nut ensures the maintaining said sleeve in position.

According to another particularly advantageous characteristic of the invention, said leaf spring is made of one of the following materials:

- stainless steel,

– Inconel-type metal alloy.

The choice of blade and its hardness, and therefore the opening trigger force, are defined by the need to keep it "closed" during the dosing phase preceding the actual injection. Indeed, during dosing, the material pressure at the end of the screw increases (especially when working with counter-pressure). It is therefore necessary to choose the hardness of this blade according to this process data.

The nozzle of the invention makes it possible to envisage different packaging in the form of a set where the same nozzle is sold associated with a plurality of leaf springs of different hardnesses and corresponding to different materials to be injected.

The fundamental concepts of the invention having just been explained above in their most elementary form, other details and characteristics will emerge more clearly on reading the description which follows and with regard to the appended drawings, giving by way of illustration non-limiting example, an embodiment of an injection nozzle according to the invention.

There is a schematic drawing of a sectional front view of a nozzle according to the invention;

There is a schematic drawing of a sectional top view of the nozzle of [Fig.1];

There is a schematic drawing of an exterior left view of the nozzle of [Fig.1];

There is a schematic drawing of an exterior front view of a leaf spring according to the invention;

There is a schematic drawing of an exterior bottom view of the leaf spring of [Fig.4];

There is a schematic drawing of an exterior left view of the leaf spring of Fig.4].

DESCRIPTION OF A PREFERRED EMBODIMENT

As illustrated in Figures 1, 2 and 3, the nozzle for injecting a material to be injected (not shown) is referenced B as a whole and is of the type comprising a hollow body 100 with a hollow core 110 having a inlet 120 of the material to be injected and an outlet 130 of said material. This nozzle B is placed at the end of a plasticizing screw (not shown) which brings the material like hot plastic.

The nozzle B comprises a nozzle tip 200 screwing onto the outlet orifice 130 and having an outer surface 210 and an inner surface 220. This nozzle tip 200 controls axial access to the hollow core 110 of the nozzle. The outer surface 220 contacts the mold (not shown).

A shutter needle 300 movable along its longitudinal axis (double arrow F1) comes to bear on the inner surface 220 for the purpose of sealing the nozzle tip 200 and therefore the nozzle B. This needle 300 comprises a tip (or needle) 310 and a rod 320. It is the head 310 which bears on the inner surface 220 of the nozzle tip 200 and which is preformed with a surface cooperating with the tip 200 and surfaces on which comes support the material to be injected during its passage through the nozzle B to cause the tip 310 to move back and therefore move away from the inner surface 220. This head 310 is substantially conical but has a plurality of successive conical or frustoconical portions of angles different.

When the needle 300 deviates the material to be injected can pass through the nozzle tip 200 and fill the mold (not shown).

A needle guide 400 guides in translation (double arrow F1) said needle 300 by guiding its rod 320. To do this, the needle guide 400 is preformed with a longitudinal bore 410 in which the rod 320 slides.

According to the illustrated embodiment, the rod 320 is in several parts, which makes it possible to adapt the material of each part (steel alloy, insulating alloy), its treatment, its shape according to the need.

This needle guide 400 is housed in the hollow core 110 of the nozzle body 100 which forms a shoulder 111 on which the needle guide 400 comes to bear. During assembly, this needle guide 400 is introduced through the orifice 130 into the hollow core 110. The nozzle tip 300 cooperating by screwing with said orifice 130 holds the needle guide 130 in position against the shoulder 111.

As illustrated in Figure 2, the needle guide 400 further comprises a plurality of channels 420 drilled around the longitudinal axis (occupied by the bore 410) parallel to the latter for the passage of the material to be injected.

In accordance with the principles of automatic sealing, an elastic member 500 is associated with the needle 300 to maintain it in contact with the inner surface 220 of the nozzle tip 200 for purposes of sealing and to allow the needle 300 to deviate from said inner surface 220 under the effect of the stress of the material for the purpose of passage of the material. Thus, when the pressure of the material to be injected ceases, the elastic member 500 returns the needle 300 to the closed position.

In order to allow the behavior of the needle to be modulated as a function of the pressure and the type of material injected, the nozzle B of the invention has been designed in such a way as to facilitate the interchangeability of the elastic member 500 without requiring the total dismantling of the nozzle.

Thus, in accordance with the invention, said elastic member 500 is constituted by a leaf spring arranged transversely to the axis of movement of said needle 300 according to the double arrow F1 and housed in a housing passing transversely through the needle guide 400 and said body 100.

The needle guide 400 is therefore provided with a through and transverse housing 430 in which the blade spring 500 evolves during its deformation. As illustrated in FIG. 2, the housing 430 has a depth allowing the deformation of the blade 500 but a width only allowing sliding according to the double arrow F1.

This transverse housing 430 is extended in the body 100 of the nozzle B by housings 140 and 150 arranged in opposition with respect to the axis which accommodate the ends of the leaf spring 500. These housings 140 and 150 constitute the ends of a hole drilled transversely in the body 100. This hole is open at both ends and thus allows access to the leaf spring 500 to ensure the change. However, it must be plugged to allow nozzle B to operate.

To achieve this, said body 100 adopts a cylindrical outer surface on which a removable hollow cylindrical sleeve 600 is fitted, closing the transverse housing by covering the openings defined in the body by the housings 140 and 150.

Said body 100 is also preformed externally with grooves for receiving annular seals 700 coming into contact with the inner surface of said sleeve 600 to implement sealing.

Said body 100 is preformed with a collar 160 on which bears one end of said sleeve 600, a solution screwed by means of a nut 610 screwing onto body 100 ensures that said sleeve 600 is held in position on collar 160.

Access to the transverse housing of the spring 500 is therefore facilitated without affecting the sealing of the nozzle B.

According to the illustrated embodiment, the nozzle B also accommodates in the thickness of its body a heating means 800 making it possible to maintain the material to be injected at the right temperature.

As illustrated in Figures 4, 5 and 6, the leaf spring 500 is curved at rest towards the inner surface of said nozzle. It is the constraint of the material to be injected on the surface of the tip 310 of the needle 300 which will lead the leaf spring 500 to a more rectilinear shape. Nevertheless, the blade is mounted with a pre-load to achieve the required trigger value.

This is the rear end of the rod 320 of the needle 300 comes into contact with said leaf spring 500, the surface portion with which the end comes into contact is preformed with a concave volume 510 to accommodate said end.

It is understood that the nozzle which has just been described and represented above, was for the purpose of disclosure rather than limitation. Of course, various arrangements, modifications and improvements may be made to the above example, without departing from the scope of the invention.

Claims (7)

Injection nozzle (B) for a material to be injected of the type comprising:
- a hollow body (100) with a hollow core (110) having an inlet orifice (120) for the material to be injected and an outlet orifice (130) of said material,
- a nozzle tip (200) fitted to the outlet orifice (130) and having an outer surface and an inner surface,
- a shutter needle (300) movable along its longitudinal axis,
- a needle guide (400) guiding said needle (300) in translation,
- an elastic member (500) associated with the needle (300) to keep it in contact with the inner surface of the nozzle tip (200) for sealing purposes and to allow the needle (300) to s 'move away from said inner surface under the effect of the stress of the material for the purpose of passing the material,
CHARACTERIZED BY THE FACT THAT
said elastic member (500) consists of at least one leaf spring arranged transversely to the axis of movement of said needle (300) and housed in a transverse housing (430) passing transversely through the needle guide (400) and said body (100 ). Nozzle (B) according to claim 1, CHARACTERIZED IN THAT said leaf spring (500) is curved towards the inner surface of said nozzle tip (200). Nozzle (B) according to claim 1, CHARACTERIZED IN THAT the rear end of the needle (300) comes into contact with the said leaf spring (500), the surface portion with which the end comes into contact is preformed of a concave volume to accommodate said end. Nozzle (B) according to claim 1, CHARACTERIZED BY THE FACT THAT said body (100) adopts a cylindrical outer surface on which a removable hollow cylindrical sleeve (600) fits closing the transverse housing (430). Nozzle (B) according to claim 4, CHARACTERIZED BY THE FACT THAT said body (100) is externally preformed with grooves for receiving annular seals (700) coming into contact with the inner surface of said sleeve (600) to implement a sealing. Nozzle (B) according to claim 4, CHARACTERIZED BY THE FACT THAT said nozzle body (100) is equipped with a collar (160) against which one end of said sleeve (600) comes to rest, a direct screwed solution between the sleeve (600) and the body (100) or indirectly by means of a screw and/or a nut maintains said sleeve (600) in position. Nozzle (B) according to claim 1, CHARACTERIZED IN THAT said leaf spring (500) is made of one of the following materials:
- stainless steel,
– Inconel-type metal alloy.