DE8330000U1 - Hot runner system for injection molding devices - Google Patents

Description

PH 417 Ot / Qr Ddpl.-Ing. Herbert Günther, 3559 Allendorf / Eder

HeiÖkanaleyetem Mr injection molding devices

B e a ο h r e i b u η e

The present invention relates to a Heiekanaleyetein for

according to the preamble of claim 1.

Bin device for hot runner injection molding with a heating tube, tfu is surrounded by a Xeolienuieee, goes out of the

5 091 Θ12. £ ine over the length of the used «Oirie de · associated distributor and iitunbee special up to DUMnapitxe reaching even tea temperature control is included 4ItMr SpritagießvorriohtunÄ but not possible * Sa is missing aa Regeleinriohtungeni the directly heated inner tube can therefore «Jaindeet accept quite a few overtemperature, especially in «• ine« middle area.

In U.S. Patent No. 3,520,026, another hot runner injection molding apparatus eats described, the resistance heating for the Outer skin of torpedoes or quills has * sine inner electrc niÄdrigea specific resistance and clearer cross-section

The outer thin electrode of higher "specific resistance" results in an external heating with which the melting of the plastic can be carried out. Un without shorting by the lOtift (s) to, for example, also made of stainless steel or a €% ftmaickel - to use alloy existing runner itself to "lektrlschen heating, insulator AtHttendestüCke and air gaps are provided. The system enables SMT construction energy savings, but in no way guarantees an even temperature distribution. In the case of the previously known heating elements, the electrical conductors iron in the area of one

Nozzle tip differences in diameter, cross-section and in Distance to the housing. Especially at the conical tip of the torpedo and at the transition to the distributor but a higher one occurs Temperature drop compared to the middle piece of the canal. For processing highly viscous thermoplastics with high injection speeds and high drifts, the well-known direction only with very short torpedo training «

Due to the newer temperature-sensitive thermoplastics, the requirements for a hot runner system with regard to temperature management are higher still grown «At every place of flowing plastic should the same adjustable temperature be available simply by touching the hot canister system with the cold mold However, the temperature equilibrium of the hot runner system is disturbed. This results in the need to prevent the unwanted heat dissipation in d «o area where the heating element and manifold are in contact with the tool, to correct through sensible structural measures · moreover let < low energy consumption is not only economically desirable but also technically necessary for the heat balance of the tools not to burden unnecessarily.

The object of the invention is accordingly to use simple and economical means to improve a hot runner system of the type mentioned at the beginning in such a way that it can be operated in an energy-saving manner and without additional heating in production operations, so that heating energy is essentially only required for the start-up phase will. In addition, the temperature influence on the tool or the injection mold should be as small as possible, so that the external components of the tool have almost tool temperature during operation, in order to avoid thermal expansion problems and make Ism * controllable. Furthermore, an equalization of the theater level should be achieved at every point of the hot runner system in order to be able to conduct temperature-sensitive thermoplastics in a molten state through the hot runner system.

, Il It ·· ··

1: 1 * tit

"I"

• · Il

Basic features of the invention are specified in the characterizing part of claim 1. Refinements are the subject of Claims 2 to 11.

The principle of the invention is based on the fact that the supplied Hei power to a thermal concentration at the ends of the heater; is brought, while in the area in between measures for dosed heat dissipation or for insulation to the outside and / or sum temperature compensation inside can be carried out · The additional provided gradation is designed so that in an Axialberei see the ends of the stimulus elements create a concentration of heat, while in between there is a dosed temperature equalization by taking various measures to reduce the heating output is distributed as required over the length of the nozzle, whereby eic la operation through the heat dissipation of the flowing plastic melt sets a steady state *

Zmr is prepared in DE-OS 28 24 971 (on p. 8, Abe. 2 to St 9 " Aba" 1) that in a hot runner nozzle in addition to a cross-sectional reduction for the purpose of concentrated heat generation a and in the tip la connection to the latter The component is arranged with a considerably larger surface, which transfers sufficient heat to the melt through it an inner u • Ines separated from this outer electrical conductor by insulation; it cannot therefore be directly compared with the hot runner system according to the invention. Rather, the heating element according to DE-OS 28 Zh 971 suffered from an outer casing and concentrically to it inside a heating rod. This is shaped at the front or lower end to the point that is welded to the outer nax & tel webs in such a way that laterally angularly offset outflow openings result. The structure differs fundamentally from the system according to the invention.

•• 4> it

case

Further features, details and advantages of the invention emerge from the wording of the patent claims and also from the following description of exemplary embodiments based on the drawing. Show barin %

Fig.

Fig. 3

Fir, Aa and 4b

Flg. Flg.

an axial section approximates a heating element in

a distributor »

a partial axial flow of a modified Heating elements similar to FIG. 1, tine partly side-by-side, partly in section a »more expensive ι

One rare or one axial harmony Another embodiment of a heating element bit Stutsringen in a distributor »an axial section is related to a further heating element embodiment,

an axial view of a modified one Heating elements and

an aacial section like another Helselejient-AuafUhrungaform «

The generally old 10 denoted prefix shown in Hg »1

We have a tool 12 and a distributor 14 on "Oieaer a cavity 16, which can be designed in the form of bores ia a housing 18. Heating elements 20 ftareheetzeft the Kohl-16. La distributor 14 let a heat conductor 22 across atu Heizeleüen arranged that a cavity boundary or shell 24 den

26 of the heating elements 20 touched. The Heixleitt .. '22 know or tube and, if necessary, be stepped

Aa * erial * entrance or enema 28 leads to an »internal 50 »that consists of stepped sections 30a, 30b, 30c, 30d From upper Saide 52, e ± äe fii closes

A thermally conductive pin 38 is provided at the end 36 ** a end piece 48 on heating pipe 30 is stimulating. The end piece 48 is tend and cohesive with the lower end 46 of one Hei * tube 40 connected, which is also made of gwtuftwa

J®a * 40b, 40c, 4Od consists. At the upper end 42 deft Heating tube 40 is connected to an electrode 44.

«I» 111 * SfIt (I.

Device is designed so that the supplied heating power is distributed over the length of the heating element 20 as required. The stepped sections of the heating column 30, 40 change the current-carrying cross-section A so that immediately ^ Bu end piece 48 and at the material inlet or inlet 28 a Heat concentrate is available, but otherwise - before especially on the central part 26 of the heating element - a sea temperature distribution that is as uniform as possible is given. In operation it gets through HtIe generated heating power on the one hand and through the heat dissipation of the flowing plastic melt, on the other hand, in the space between the heating element 20 and the outer wall of the tool 12 Steady state a.

It can be seen that the temperature control according to the invention also through the choice of the outer diameter D of the heating element 20 ; can be optimized, furthermore by the diameter of the hollow .4NMaS 16 In the tool 12 and through a suitable choice of material for the pickling tubes 30, 40. In addition, a support ring 50, the ■ "has at least two, preferably three or more radial webs 52, at selected points along the heating element 20 either cause a metered heat dissipation or extensive heat dissipation Isolation practically prevent heat dissipation. At the same time we "the end piece 48 centered towards the sprue hole and at a shoulder" b »w. a collar 58 which melts from the flowing plastic resulting force on the support ring 50 excepted. With a larger diameter on the heating element 20, an unintentional! Prevents slipping of the filled hot runner,

They electrically conductive heating pipes 30, 40 are advantageous «Us resistance material based on nickel alloys. The pin 38 as well as consists of materials that conduct heat well the Sndstüok 48, which is used in particular for the processing of fiberglass-reinforced thermoplastics wear-resistant design DW flirtitxring 50 and changes supports are preferred sue kersitiaohen material old tiledriger thermal conductivity for example zirconium oxide.

»Ι · Ι · | · ■ I I 1 1 1

ι '"' · ι * it in

/ ι O

. ■ " ⁸ ~

" ⁸

Etching ring 50 can be designed so that webs 52 from conductive material with insulating interlayers either radially «« Ben or inside are provided. Such non-conductive interim obligations indulge in enamel or ceramic glue, an .lttefrteaperatur glue or the like. confess. Each other plant ,; However, the radial webs 52 can and should be axially moved to allow expansion compensation

Preferably, the support ring 50 is located at a distance of two to ~~ 'ft & sfmal Torpedo diameter D of the Bndstück 48 · removed by i' aSßpto support is a metered heat dissipation after mice,

so 4aS «Ine temperature increase in the area (in the direction of flow) . TBfr a * m support ring 50 despite the increased heating power in the bottom piece ^ _t , is veapeieden.

Overall, the heating power over the length (J, _t Fig. 4a) of the heating element 20 can easily be in a ratio of 1 t 1.1 to 1 t 3 *

Twelve of the outer heating tube 40 and the inner heating tube 30 are present (see, for example, FIG. 2). As can be seen from the embodiment according to FIGS. 4a and 4b, a thermal sensor 72 can be provided with which the temperature at the end piece 48 can be determined. In addition, the thermal sensor 72 can be designed and arranged in such a way that the temperature profile along the heating element 20 can also be detected. During production, the thermocouple 72 with its measuring tip remains in the position shown: “The thermal conductive © pin JjS, which is made of copper, provides teapera-ture in the area of the measuring point at the end piece 48.

FIG. 2 shows a section from a heating element 20, since the structure according to FIG. 1 corresponds globally. In this case, however, a single section 30a ₁ 30b, 30c of the inner heating pipe 30 is not a part 40a, 40b (40c) of the outer heating pipe 40

((Kt ^ ttickig, but made of different parts, which by • la · connection V, for example brazing, electrically conductive • are connected to each other.

Different dimensions and / or materials can be used according to The embodiment of FIG. 3 can also be used on the distributor 12 and its heating conductor 22. Here, for example, the Subareas of the heating conductor 22 immediately adjacent to the heating element 20 have a higher electrical resistance. In the same zone, the manifold 14 can have a cavity 24 of have a larger diameter than laterally adjoining bores on the left and right. The ratio of the electrical Resistances at the partial areas of the heating conductor 22 (voc. Right to the left) can, for example, be about 1: 1.25: (0.1 ·· .0.2) and the diameter ratio of the bore 24 to the adjoining, narrower cavities are approximately (1.1 ... 1.4): 1.

Also in the Auaführungsform according to Fig. 4a and 4b, a uniform temperature distribution is obtained over the length £ of the heating element 20 through the mentioned measures. This in turn has an outer heating tube 40 and an inner heating element which is arranged at a radial distance therefrom and which is designed here as a heating rod 30 '. An insulating compound M electrically separates the heating rod 30 * and the outer heating tube; a conductive connection is only provided at the top and bottom end pieces (48). In the lower part of section 30b * the heating rod has a lateral recess or groove for the electrically insulated embedding of the thermal sensor 72. The heating element 20 can expand axially to both sides from ribs 74, so that practically no thermal expansion stresses occur as a result of temperature differences . Compared to webs as they are known from the prior art, twice the axial force can be absorbed with the support 50, which makes a significant contribution to operational safety.

The same construction principle is also used in the embodiment according to FIG. 5 applied. The heating element 20 is designed here as a double heating tube. For this purpose, rings or sleeves 60 are used electrical insulation from the heating tubes 30, 40 is provided. Kit the double heating tube significant advantages are achieved because

* I Ii Il ti
• · I it · Il

• It It ti * I

• · · Il Il Il It

# Ti ti Il ti I

the heat dissipation resulting spans present and the flowing electric current to the way there as well as on the way back the Koneteiioff In; Heating pipe 30. To the outside is that! Toppelheiirofer insulating Surrounding mass H, which Bruc & kxifte "Mn inside the heating element balances and

It should be mentioned here that the heating rod 30 'or the inner HetxroBcP Outer heating pipe 40 from each other with an insulating gap | 8 $ true to one another are, the width of which a (Fig. 2) is about a tenth of 4 ***. Sweeter heating pipe diameter D (Flg. 1) difference Vöa inner to outer heating conductor half past 10

Xn area of the heating element 20, in particular its * middle part,

are heat-conducting supports 62 in the form of Obergm iftMjl Wi lYeii or support ribs attached. You serve n * better the and axial force transmission at the ¥ ttra * iit * o'clock

Heating element area, as described, is «ttr

in the area of the material inlets 2S and there the heating power is concentrated «Heat conduction

Heating elements could therefore not be used in the old age

let rise «The radial support causes

Heat dissipation and also enables centering Piece 48 at the sprue hole of the tool 12 · ", * m

Flg. 6 shows an exemplary embodiment for optimizing temperature control through the use of insulating materials with different thermal conductivity values and / or with the insulating layer dioke. In this case, the heating conductor is also designed as a short double heating tube in a sub-area of the Bndstüoke 4β tttd de "material inlets 28. Receives at the ends of the heating element 20 ma doing this Wels · the desired high heat output, while dl "by the insulating or supporting element bO *" 62 "64 takes place in the borrowed Warfflekonzentration and Teis ^ eraturfUhrung area. The central portions 4Ob ₁ 40% heat pipe 40 may conveniently be made of electrically well material.

09 * 4 suffered * I

• ϊ! ': ί ί

HItIIl · ί · ·. «., ...

- 11 -

SU · Supports 62 are at least »once on a heating element 20 eo auegebilden that a seal from the sweeter heating pipe 40 mm Oehäuse 'is achieved. The liquid plastic can under Enter the pressure equalization on the outside of the heating tube in the capillaries. A Fe conventionally possible unwanted flow process on the outside of the heating pipe Thus there is no washing out of the insulating material door consequences and could render the heating element unusable «

The examples in FIGS. 4b and 7 show further possible solutions dÄJSauß it can be seen that the principle of at least one sowing dt · Pliefiriohtung to redirect, also applied to the thermal sensor 72 is.

B ·! the execution according to Flg. 7 throws the axial force on the inner Bvfterrohr 30 received via a closed screen 74. the JMftiHUung does not take place directly, sondona with an external> helically placed around the tube 30 heating coil 76. The power tupaesung takes place in a well-known way through the density of the dei Wioklung 76. The heated pipe can also face each other here expand the housing. The increased output at the material inlet SS and at the end piece 48 is achieved by the outer pipe sections 40a, 40t and the supports 62 are removed so that no excess temperatures occur in the central area of the inner heating tube 30.

For the concentration of heat at the ends of the heating element 20, it is important that the heat transfer there is reduced compared to the central part 26, for example by increased distances, low thermal conductivity values or the like. Thus, according to the invention, it is possible to obtain the required “WÖHBe m the narrow or narrower gaps at the material inlet 28 on the one hand and on the end piece 48 on the other hand with little loss. It may be useful to design the area of the end piece 48 in a special way. According to FIGS. 6 and 7, inclined supports 64 create a shoulder at the more rigid end of the heating element 20, which contributes to the desired heat concentration.

• f III »

• I I

• · 14 «

Legend

contraption A cross section Cavity / bore (s) 44 58 66 thermally conductive pen outer heating conductor / tool D diameter casing (Nozzle) ⁴⁶ 60 68 Heating pipe Distributor e distance Heating element 48 Material entry ₆₂ 70 , d sections i length Heating conductor 50 inner heating conductor / _AZl
Heating pipe 72 top end M Ißolierinasae Covering/ Cavity (limitation) 52 d sections 74, electrode s gap width Middle part Heating rod Ii lower end Enema/ , d ¹ sections 88 End piece 10 top end Support ring 12th electrode Most radial ^ 14th lower end Waistband / shoulder 16 Rings / sleeves 18th conductive supports 20th V connection (soldering) conductive transition piece 22nd ΛΛ Insulating layer breakthrough 24 40a, b, c connections 26th Thermocouple umbrella Heating coil 30th Insulating gap 304.1J ₁ C * 30 * 30 * t _f; V * o * 52 36 38

Claims (11)

tti r «ta ··· Dipl.-Phys.Karl H.Ulbricht "" Patent attorney At the vineyard 15 D-355 ^ Niederweimar Telephone (06421) 78627 PH 417 Ot / Gr Dipl.-Ing. Herbert Günther, 3559 Allendorf / Eder Hot runner system for injection molding devices Protection claims 1 · Hot runner system in a plastic injection mold for Melt guiding of temperature-sensitive thermoplastics in at least one hot runner, each with a longitudinally arranged heating element that consists of a concentric arrangement an inner and an outer electrical conductor separated from this by an insulation, of which has at least one section that is different in diameter, in cross section and in distance from the housing, thereby characterized in that the heating element (20) is consecutive in the longitudinal direction between the ends of the hot runner Has sections that ia diameter (D) and / or in cross section (A) and / or in the electrical material conductance of at least one heating conductor (30; 40) and / or in thickness and / or The conductivity of the insulation for targeted temperature control of the hot runner are coordinated. 2. System according to Claim 1, with a heating pipe as the inner heating conductor, characterized in that selected sections (30a, 30dj 40a, 40d) of both heating conductors (30, 40) are designed as a double heating tube. 3. System according to claim 2, characterized in that that the inner heating conductor as a heating tube (30) from a heating coil (76) enclosed 1st * - ι> ι j · ■ t ■ «··· 4. System according to claim 2 or 3 _f characterized zeicl net that at least one Endaußenab section (40d) of the double heating tube with a conductive transition piece (64) connects to a central section of the outer tube. 5. System according to one of claims 2 to 4, characterized g e k e η r indicates that the double heating tube has an end piece (48) a material with different electrical and thermal conductivity properties is designed as the heating tubes (30, 40). 6. System according to claim 5, characterized in that that the end piece (48) has a thermally conductive pin (38) is connected to the inner heating pipe (30). 7. System according to at least one of claims 1 to 6, characterized in that the outer heating pipe (40) is interrupted with respect to a central section (e.g. 30b, 30c) of the inner heating conductor (30). 8 · System according to at least one of claims 1 to 7§ thereby characterized in that the cross-sectional changes (. Of the sections of at least one heating pipe (30 or 40) over the length of the heating element should be in the range of 1 χ 4. 9. System according to at least one of claims 1 Me 8, characterized in that the diameter of the surrounding housing boring sections are in the range of about 1 t 1.5. Seee eee that changes in the electrical resistance of sections (92-94) of the heating conductors (22, 30, 1) over their length in the range of about 1 second in the area of their electrical connections (70) 10 lying « 11. System according to at least one of claims 1 to 10, characterized g e k ejj-tTz e it is worth making changes in sections trttrmeleitwertee the Isollermasse (M) in a range of ■ s e ■ ■ «- • ο ο υ υ υ υ