HK1051511B - Injection nozzle for guiding melt in a plastic injection mould or the like - Google Patents

Description

The invention relates to an injection nozzle as defined in the general concept of claim 1.

Although the well-known injection nozzle of this type has proved itself in practice many times, improvements are desirable for certain applications. In particular, in the case of the well-known injection nozzle in conjunction with flame-resistant plastics, the leakage of gases may lead to corrosion on the back face of the nozzle core, e.g. made of beryllium or a beryllium alloy.

The invention is based on the injection nozzle according to DE 34 31 173 C2 and the aim is to develop the known nozzle in such a way that it is as insensitive as possible to leaks in the rear sealing area, in particular by avoiding the deficiencies described.

This task is solved according to the totality of the characteristics of claim 1.

In particular, by placing a protective cap of corrosion-resistant material between the rear face of the nozzle core and the rear backing surface, with a front seal on the rear face of the nozzle chamber and a rear seal on the rear backing surface, the rear face of nozzle cores, e.g. of beryllium or beryllium alloy, is protected to the greatest extent from the direct attack of aggressive plastic melting, so that corrosion and also annoying melt leaks can be avoided as far as possible.

Although a seal between the rear back surface and the rear seal surface of the hood is sufficient in itself to protect the rear face of the jet core from corrosion, a particularly advantageous embodiment of the invention is that the front face of the hood is completely attached to the rear face of the jet core.

The sealing zone shall be suitably designed so that the rear front face of the jet core, the front face of the hood, the rear face of the hood and the rear face of the backrest each form corresponding circular surfaces.

In particular, it has been found appropriate that the rear front face of the jet core and the front face of the hood form circular surfaces radially extending with respect to the melting channel, while the rear face of the hood and the rear rear rear rear cover each have a cone-shaped cover.

In a further development of the invention, the rear seal surface of the protective cap and the rear back cover surface adjacent to the melting channel each form a radially extending circular surface and, subsequently, an outer cone-stump cover.

The protective cap may be made of steel, such as stainless steel, molybdenum or a molybdenum alloy, as described in the invention.

In a further development of the invention, a circular melting tube is contained within a cylindrical receptacle of the nozzle between the nozzle tip and the cap, which is known by DE 34 31 173 C2 as a closed loop.

A particularly desirable design according to the invention is, however, that the protective cap is securely connected to the melting tube, thus achieving complete sealing of the rear face of the jet core in relation to the rear backing surface. This advantageous design also avoids the formation of a ring gap between the melting tube and the cylindrical absorption of the jet core, as such a ring gap can fill with molten mass and thus cause problems with colour change or leakage with further mass buildup.

Another advantage of the invention is that the nozzle tip is connected to the melting pipe in a material-tight manner.

It has also been found appropriate that the protective cap and the melting tube are made of the same material as the nozzle tip and the melting tube.

In order to achieve a high mechanical resistance to plastic melting with abrasive adhesives, it has been found to be useful to chemically nickel the inner surface of the melt pipe and the inner surface of the protective cap. Such chemical nickel coating allows very large surface hardness. However, in order to allow a precise axial adjustment, which may require a work on the back seal surface of the protective cap, for example a certain abrasion dimension, it has been found to be useful to exclude the back seal surface of the protective cap from the possibility of chemical nickel coating. This is done accordingly by providing the invention of a better protection against chemical coating, i.e. a better protection against chemical coating.

A further design of the invention is characterised by the fact that the largest outer diameter of the nozzle tip is equal to or less than the largest outer diameter of the melting tube. These features, in particular, in conjunction with the preferred embodiment in which the protective cap and the nozzle tip are connected to the melting tube, allow a through-mount from the back to the front through the nozzle core through the nozzle tip, the melting tube and the protective cap.

The drawing shows a preferred embodiment of the invention.

Figure 1 shows a radial section through an injection nozzle.

The nozzle, marked with 10 in total, for the control of a plastic melting-pot, has a nozzle casing 11 consisting of a front nozzle 12 and a rear nozzle cover 13.

The inner part of the nozzle housing 14 is equipped with a nozzle core 15 made of beryllium or an alloy of beryllium; the nozzle core 15 has an electric heating cuff 17 on its outer surface 16 and a thermal element for heat regulation 18; the electrical supply to the heating cuff 17 and the control of the thermal element 18 are provided by a cable arrangement numbering 19.

A pipe-shaped body, inserted in a screw-like outer nut into the outer shell 16 of the jet core 15, may also be known to be used instead of the heating cuff 17.

The flow direction of the plastic melt is indicated by x. With respect to the flow direction x of the plastic melt from, a nozzle tip 20 is assigned to the nozzle core 15. The nozzle tip 20 is permeated by two or more flow channels 21 for the plastic melt, which then flow into a nozzle chamber 22 and from there through a nozzle opening 23 into an unmarked hollow of a plastic injection mold.

The nozzle tip 20 also forms a very small frontal support surface 24 for the nozzle core 15 which is supported by the frontal support surface designated by 25 which is formed internally by the frontal housing part 12 of the nozzle housing 11.

To avoid any unacceptable heat transfer between the actual beryllium or beryllium alloy core 15 and the nozzle casing 11, a ring gap 26 is formed between the inner surface of the front of the housing 12 and the front of the nozzle core 15.

The nozzle tip 20 is connected uniformly and continuously to a circular melting tube 27 which is thermally shrunk in a corresponding circular nozzle 28 of the nozzle core 15.

Also uniformly and solidly connected to the melting tube 27 is a protective cap 29 on the rear side of the jet core 15 which is closely connected with a front seal 30 to a rear face surface 31 of the jet core 15 and the protective cap 29 with a rear seal designated with a total of 32 to a back cover 33 formed by the housing cover 13.

The rear seal surface 32 of the hood 29 consists of a radial circular surface 34 adjacent to the melt channel K and a cone-stump cover surface 35 adjacent to it.

The housing cover 13 is securely screwed to the front housing 12 by means of several screws. The nozzle housing 11 is made of steel, while - as mentioned above - the nozzle core 15 is made of a high-temperature conductive metal, in particular beryllium or a beryllium alloy (e.g. copper-cobalt-beryllium). Due to the greater thermal linear expansion coefficient of its material compared to steel, the heated nozzle core 15 with its front installation surface 14 - and conveyable via the rear seal surface 32 of the protective cap 29 - tightly stretches between the front nozzle side air gaps 25 and the rear nozzle side air gaps 33.

A possible cleavage between the jet core 15 and the jet core 29 and the jet core 29 and the retrofit surface 33 due to the different thermal expansion of the different materials of the jet core 15 and the cap 29 and, where applicable, the melting tube 27 is completely avoided by the greater thermal expansion of the jet core 15.

A correspondingly tight system is formed between the front seal 30 of the hood 29 and the rear face surface 31 of the jet core 15 on the one hand and the rear bumper 33 and the rear seal 32 of the hood 29 on the other.

A complete seal in the rear transition area between the housing lid 13 and the nozzle core 15 is achieved by the material-tight and material-uniform connection of the protective cap 29 to the melting pipe 27.

To achieve greater mechanical resistance to abrasive components of the plastic melt, the inner shell 37 of the melting tube 27 and the inner shell 38 of the protective cap 29 are covered with a chemically formed layer of nickel of high surface hardness.

The present invention relates to injection nozzles which have a nozzle casing 11 as in the present case, as well as to nozzles without casing.

Claims (16)

1. An injection nozzle (10) for guiding hot melt compound in a plastics injection mould or the like, having a nozzle core (15) which is made from a material with high thermal conductivity, such as beryllium, a beryllium alloy or the like, which surrounds a melt flow-way (K) and whereof the outer surface (16) carries a heating device (17) and which carries at its front end (at 24) located downstream in respect of flow of the melt a nozzle point (20) which is adjacent to the mould cavity of a mould, this nozzle core being supported in sealing manner by means of its front end (at 24) against a front abutment face (25) and being supported in sealing manner by means of its rear end face (31) remote from the nozzle point (20) at least indirectly against a rear abutment face (33), and this nozzle core being clamped axially between the two abutment faces (25, 33), characterised in that between the rear end face (31) of the nozzle core (15) and the rear abutment face (33) there is arranged a protective cap (29) which is made from a corrosion-resistant material and which abuts by means of a front sealing face (30) against the rear end face (31) of the nozzle core (15) and abuts by means of a rear sealing face (32) against the rear abutment face (33).
2. An injection nozzle according to Claim 1, characterised in that the front sealing face (30) of the protective cap (29) abuts over its full surface against the rear end face (31) of the nozzle core (15).
3. An injection nozzle according to Claim 1 or Claim 2, characterised in that the rear end face (31) of the nozzle core (15), the front sealing face (30) of the protective cap (29), the rear sealing face (32) of the protective cap (29) and the rear abutment face (33) form in each case mutually corresponding annular faces.
4. An injection nozzle according to one of Claims 1 to 3, characterised in that the rear end face (31) of the nozzle core (15) and the front sealing face (30) of the protective cap (27) form annular faces which extend radially in respect of the melt flow-way (K).
5. An injection nozzle according to one of Claims 1 to 4, characterised in that the rear sealing face (32) of the protective cap (29) and the rear abutment face (31) each have an outer surface (at 35) in the shape of a truncated cone.
6. An injection nozzle according to Claim 5, characterised in that the rear sealing face (32) of the protective cap (29) and the rear abutment face (33) each form adjacent to the melt flow-way (K) a radially extending annular face (at 34) and, outwardly adjoining the latter, an outer surface (at 35) in the shape of a truncated cone.
7. An injection nozzle according to one of Claims 1 to 6, characterised in that the protective cap (29) is made from steel, for example stainless steel.
8. An injection nozzle according to one of Claims 1 to 6, characterised in that the protective cap (29) is made from molybdenum or a molybdenum alloy.
9. An injection nozzle according to one of Claims 1 to 8, characterised in that within a cylindrical receiver (28) in the nozzle core (15) between the nozzle point (20) and the protective cap (29) there is a cylindrical melt flow-way tube (27) which is arranged in sealing manner both in respect of the nozzle point (20) and in respect of the protective cap (29).
10. An injection nozzle according to Claim 9, characterised in that the protective cap (29) is materially connected to the melt flow-way tube (27).
11. An injection nozzle according to one of Claims 1 to 10, characterised in that the nozzle point (20) is materially connected to the melt flow-way tube (27).
12. An injection nozzle according to one of Claims 1 to 11, characterised in that the protective cap (29) and the melt flow-way tube (27) are made from the same material.
13. An injection nozzle according to one of Claims 9 to 11, characterised in that the nozzle point (20) and the melt flow-way tube (27) are made from the same material.
14. An injection nozzle according to one of Claims 9 to 13, characterised in that the inner surface (37) of the melt flow-way tube (27) and the inner surface (38) of the protective cap (29) are nickel-plated.
15. An injection nozzle according to Claim 14, characterised in that the rear sealing face (32) of the protective cap (29) is provided with a protective layer, such as a coated layer or the like, before the nickel-plating.
16. An injection nozzle according to one of Claims 9 to 15, characterised in that the largest external diameter of the nozzle point (20) is equal to or smaller than the largest external diameter of the melt flow-way tube (27).