CA1159618A - Hot-duct system for feeding molten synthetic material to an injection-mould - Google Patents
Hot-duct system for feeding molten synthetic material to an injection-mouldInfo
- Publication number
- CA1159618A CA1159618A CA000361041A CA361041A CA1159618A CA 1159618 A CA1159618 A CA 1159618A CA 000361041 A CA000361041 A CA 000361041A CA 361041 A CA361041 A CA 361041A CA 1159618 A CA1159618 A CA 1159618A
- Authority
- CA
- Canada
- Prior art keywords
- hot
- duct
- section
- duct system
- sections
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Moulds For Moulding Plastics Or The Like (AREA)
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
ABSTRACT
A hot-duct system is equipped with heating conductors for feeding molten synthetic material to an injection-mould, preferably a multiple injection-mould with spot-injection for each moulding. A plurality of hot-duct sections are coupled together in unit-construction style and consist of a housing having at least one inlet- and one outlet-aperture and a heating conductor adapted to be connected to an electrical supply. The individual heating conductors in the hot-duct sections are adapted to be operated electrically independently of each other. The unit-construction design of the hot-duct system, in the form of individual hot-duct sections, makes it possible to use the same components, namely the same hot-duct sections, for injection-moulds of totally different designs. The individual hot-duct sections may also be used to build up a hot-duct system when the original injection-moulds have become worn and must be replaced. Thus full use may be made of the life of the hot-duct sections, independently of the service-life of the injection-mould. Since each hot-duct section has a heating conductor, which can be operated electrically independently of the adjacent, or some other, hot-duct sections the hot-duct system according to the invention makes it possible to heat up the individual hot-duct sections to different degrees.
This permits thermal control of the molten synthetic material in various parts of the hot-duct system.
A hot-duct system is equipped with heating conductors for feeding molten synthetic material to an injection-mould, preferably a multiple injection-mould with spot-injection for each moulding. A plurality of hot-duct sections are coupled together in unit-construction style and consist of a housing having at least one inlet- and one outlet-aperture and a heating conductor adapted to be connected to an electrical supply. The individual heating conductors in the hot-duct sections are adapted to be operated electrically independently of each other. The unit-construction design of the hot-duct system, in the form of individual hot-duct sections, makes it possible to use the same components, namely the same hot-duct sections, for injection-moulds of totally different designs. The individual hot-duct sections may also be used to build up a hot-duct system when the original injection-moulds have become worn and must be replaced. Thus full use may be made of the life of the hot-duct sections, independently of the service-life of the injection-mould. Since each hot-duct section has a heating conductor, which can be operated electrically independently of the adjacent, or some other, hot-duct sections the hot-duct system according to the invention makes it possible to heat up the individual hot-duct sections to different degrees.
This permits thermal control of the molten synthetic material in various parts of the hot-duct system.
Description
1 ~59~18 The invention relates to a hot-duct system equipped with an electrical heating conductor for feeding molten synthetic material to an injection-mould, preferably a multiple injection-mould with spot-injection for each moulding.
An apparatus of this kind is known (Austrian Patent 286 607). It consists of a distribution plate closely adjacent a moulding plate provided with moulding cavities. The distribution plate comprises horizontal distributing ducts from which vertical injection ducts branch, leading to spot-injection apertures in the moulding cavities. The distributing ducts are equipped with a central heater-wire which is of U-shaped configuration in the vicinity of the injection ductso The known apparatus, equipped with the hot-duct system, is designed with the injection-mould and is thus an integral part thereof. The parts of this apparatus cannot be used to build up a hot-duct system for an injection-mould of a totally different configuration. Moreover, differential heating of the various areas of the hot-duct system is not possible.
It is the purpose of the invention to design the apparatus located between the synthetic-material extruder and the injection-mould ca~ity in such a manner that different areas of the hot-duct `
system may be heated differently for thermal control of the molten synthetic material, and so that the pattern of the hot-duct system may easily be adapted to different injection-moulds.
The invention provides an electrically heated hot-duct system for feeding molten synthetic material to an injection mould, said system comprising a plurality of hot-duct sections adapted to be coupled together in unit-construction stvle, each hot-duct , ., ...~ ,, .. ~.~ ,. , :, . . .
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1 ~5~8 section defining a duct for the molten synthetic material and com-prising an outer housing provided with an inlet aperture and at least one outlet aperture and a rod-shaped heating conductor extend-ing over the entire length of the outer housing within said duct and secured to the end faces of the outer housing, the individual heating conductors of the hot-duct sections being adapted to be electrically heated independently of each other.
The unit-construction design of the hot-duct system, in the form of individual hot-duct sections, makes it possible to use the same components, namely the same hot-duct sections, for injection-moulds of totally different designs. The individual hot-duct sections may also be used to build up a hot-duct system when the original injection-moulds have become worn and must be replaced.
Thus full use may be made of the life of the hot-duct sections, independently of the service-life of the injection-mould.
Since each hot-duct section has a heating conductor, which can be operated electrically independently of other hot-duct sections the hot-duct system according to the invention makes it possible to heat the individual hot-duct sections to different degrees. This permits thermal control of the molten synthetic material in various parts of the hot-duct system.
Embodiments of the invention are described hereinafter in greater detail, in conjunction with the attached drawings wherein:
Figure 1 is a partial cross-sectional view of a hot-duct system and an injection-mould;
Figure 2 is a plan view of a four-way distributor to which hot-duct sections are coupled;
Figure 3 is a plan view of a hexagonal distributor to " ~ .'t~ ' ':
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which hot-duct sections are coupledi Figure 4 is a longitudinal section through a hot-duct section to be coupled to a polygonal distributor;
Figure 5 is a plan view of a distributor with a plurality of hot-- 2a -,, , , -- .. . . . . .
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duct sections, the hot-duct sections on one side of the distributor being parallel with each other;
Figure 6 is a section along the line VI - VX in Figure 5;
Figure 7 is a cross-section through a hot-duct section arranged in the form of an inverted U in a vertical plane;
Figure 8 is a longitudinal section through a hot-duct section, equipped at both ends with overflow-apertures for the molten synthetic ma-terial;
Figure g is a longitudinal section through another embodiment of hot-duct section;
Figure 10 is a view of point X in Figure 9 to an enlarged scale;
Pigure 11 shows another possible design for point X in Figure 9;
Figure 12 and 13 show cross-sections of heating conductors;
Figure 14 ~on the same sheet as Figure 8) is a cross-section through another emobidment of hot-duct section;
Figure 15 ~on the same sheet as Figure 8) is a cross-section through a design-detail of a hot-duct section;
Pigure 16 ~on the same sheet as Figure 8) is a longitudinal section through the housing of a hot-duct section, with a passage expanding conically 2Q from the central inlet-aperture out to the outlet-apertures;
Figure 17 is a perspective view of a hot-duct system prior to assembly of the functional parts;
Figure 18 is a variant of the hot-duct system according to Figure 17;
Pigure 19 shows the hot-duct system according to Figure 18 duly assembled;
Figure 20 is a section along the line XX - XX in Figure 19;
Figure 21 is a plan view, in part section, of an H-shaped hot-duct , :: :
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, l ~9~18 section;
Figure 22 is a view in the direction of arrol~ X~II in Figure 21;
Figure 23 is a plan vie~ of the heating conductor for the hot-duct section according to Figure 22;
Figure 24 shows a T-shaped hot-duct section in partial cross-section.
The apparatus illustrated in Figure 1 comprises a hot-duct section 1 fitted with an adapter bush 2 into which is inserted the machine-nozzle of a synthetic-material extruder. Bush 2 thus forms an input-aperture 3 for the molten synthetic material which is introduced into a duct 4 in hot-duct sec-tion 1. Duc* 4 is defined outwardly by a housing 5 and inwardly by an elec-trical heating conductor 6. The molten synthetic material passes through an outlet-aperture 7 into duct 8 of a second hot-duct section 9 which is equipped with nozzles 10 through which the molten synthetic material flows into mould-cavities 11 in the injection-mould. The central area of the hot-duct section 9 is also equipped with an electrical heating conductor 6.
The opening in the injection-mould for removal of the solidified injection-moulding is in plane 12, the moulding being stripped from the mould-cavities by ejectors 13.
Electrical heating conductor 6 is mounted in an insulating element 14 near the end of the housing, the end of the conductor being sealed from duct 4 by means of a packing gland 15 and a compression screw 16. Ends 17 of the heating conductor have a socket 18 into which the plug of the power-supply cable is inserted. This plug-and-socket connection is designed to carry high currents without substantial losses.
If the hot-duct section and the heating conductor are of consider-able length, the conductor may be provided with a support 19 in relation to the housing. Electrical insulation 20 is provided between support 19 and housing 5.
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~ 1~9~8 Since some of the heat produced in the heating conductor 6 is lost to atmosphere through the ends 17 emerging from housing 5, it is desirable, as shown in Figure 10, to provide the heating conductor with a constriction 21. This constriction of the conducting cross-section leads to an increase in electrical resistance, thus producing substantially more heat in this area.
Adjacent the insulating element 14, and the end-caps of the housing 5, the heating conductor 6 is provided with a collar 22 which pr0vents it from mov-ing inside the housing.
In the design according to Figure 11, the reduction in the conduct-ing cross-section, in the vicinity of the collar 22, is obtained by means of a bore filled with electrically non-conducting material 23.
The heating conductor may be of circular or other cross-section, for instance rectangular, cruciform as shown in Figure 12, or star-shaped as in Figure 13.
~ igure 2 is a plan view of a four-way distributor 24, the upper surface of which has an inlet-aperture 25, while the lateral surfaces have outlet-apertures for the molten synthetic material. The outlet-apertures are connected to an end-face inlet-aperture 26 in a hot-duct section 27. Each hot-duct section 27 has at least one outlet^aperture 28 for the molten syn-2Q thetic material, into which a nozzle 10 is inserted.
In the design according to Figure 3, the distributor 29 is hexagonalin plan view and is connected to six hot-duct sections 27. The molten syn-thetic material is fed to ~he distributor 29, from a machine nozzle, through inlet-aperture 25 Figure 3 shows, in dotted lines, that hot-duct sections 27 may be connected to further hot-duct sections running at right angles to sections 27.
The design of hot-duct section 27 is more clearly shown in Figure 4.
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~ 1~9~18 At ~he end ~acing the inlet-aperture 26 of the hot-duct section 27, the heat-ing conductor 6 is connected electrically to a retaining insert 30 made of electrically conducting material. This insert stabilized the end of the heat-ing conductor and constitutes an electrical connection between heating conduc-tor 6 and housing 31 which is also made of electrically conducting material.
Retaining insert 30 is provided with at least one flow-aperture 32 for the molten synthetic material.
End-inlet-aperture 26 is defined by an outwardly projecting hollow socket 33 which may be introduced into a recess in the distributor. It is preferably of circular cross-section. The hollow socket has a threaded flange 34 which is screwed into a threaded bore in housing 31 and secures the retaining insert 30 in the housing 31. In this design, the electrical current ~lows through heating conductor 6, retaining insert 30 and housing 31.
Whereas hot-duct sections 27 form, in Figure 2, a cruciform and, in Figure 3, a star-shaped hot duct system, it is also possible to produce, with hot-duct sections 27, the hot-duct system illustrated in Figures 5 and 6.
Molten synthetic material is fed to a distributor 35, or to a hot-duct section, through an inlet-aperture 36. From duct 37 in distributor 35, the molten synthetic material reaches hot-duct sections 27 and passes, thence, through nozzles 10, into the moulding cavities in the injection-mould. Ar-ranged on each side of distributor 35 are two hot-duct sections 27 parallel with each other.
Figure 7 illustrates, in dotted lines, a large-area moulding 38.
This moulding may be injected through nozzles 10 at almost any desired loca-tion. In this design, the hot-duct system consists of a hot-duct section 1 and two hot-duct sections 27 running at right angles thereto. Heating con-ductors 6 in the three hot-duct sections are wired in series to a power source.
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l 159~18 With a similar hot-duct system it ig also possible to feed molten synthetic material to the moulding cavities in a multi-stage injection-mould.
In this case, vertical hot-duct section 27 are fitted with a plurality of nozzles which are then arranged in the respective stages.
Figure 8 shows a longitudinal sèction through a hot-duct section 39 comprising flow-apertures 40 for the molten synthetic material at each end.
These apertures are located in retaining inserts 41 secured in housing 44 by threaded flanges 42 of hollow sockets 43. The retaining inserts, which are made of electrically conducting material, are connected conductingly with a heating conductor 45 and with housing 44. Heating conductor 45 has a central power-supply 46 insulated from the housing 44.
The molten synthetic material is fed to the hot-duct section 39 through an end-inlet-aperture, flows through the hot-duct section and, through the other end-aperture, to a coupled hot-duct section.
Figure 14 is a cross-section of a hot-duct section 57 equipped with a hollow heating conductor 48. This increases the heat-exchanging surface of the heating conductor in relation to the conducting cross-section thereof.
For the purpose of increasing mechanical stability, the interior of the heating conductor is filled with a non-conducting stabilizing material 49.
It may be gathered from Figure 14 that the heating conductor in the hot-duct section 47 may also be in two parts 50, 51 connected electrically in the central plane 52 of the hot-duct section. A support 53, in relation to housing 54, is arranged at the junction. The housing is provided with an adap-ter 2 defining the inlet-aperture for the molten synthetic material. The hous-ing also has outlet-apertures 55.
When the apparatus is in operation, the~molten synthetic material, which solidifies on the inside of the housing, forms an insulating layer.
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1 15g~8 The solidifled layer of synthetic material bears the refsrence numeral 56 in Figure 15. It may be gathered, from this figure, that the solidified synthetic material provides, in the area of the collar 22, satis-factory insulation and sealing in relation to the end-cap of housing 5. Thus the plasticized synthetic material flowing in nozzles 10 does not come into contact with the collar 22.
Figure 16 is a longitudinal section through the housing 57 of a hot-duct section having an inlet-aperture 58 and outlet-apertures 59 for the molten synthetic material. The housing is provided with a duct 60, the cross-section of which expands conically from the central inlet-aperture 58 outward-ly to the outlet-apertures 59. Although the hot-duct section loses more heat from the inlet-aperture for the molten synthetic material towards the end-faces, the conical design of the duct ensures that there will be no substan-tial pressure-drop, even with a long duct.
Figure 17 illustrates a hot-duct system in which hot-duct sections 1 and 60 lie in two different planes. The longitudinal axes of hot-duct sec-tions 60 are at right angles to those of hot-duct section 1.
Hot-duct sections 60 are fitted with a series of nozzles 10 through w~ch spot-injections are made into the cavities in the injection mould. The 2Q molten synthetic material is fed to adapter 2 and inlet-aperture 3, passes through the duct in hot-duct section 1, through inlet-apertures 51, into hot-duct sections 60, and thence to nozzles 10.
I~ it is desired to reduce the distance between the heating conduc-tor in hot-duct section 1 and the heating conductors in hot-duct sections 60, the hot-duct sections to be coupled together must be designed as shown in Figures 18, 19, 2a.
The housing 62 of the hot-duct section 63 is provided with recesses l 159618 64, while the housing 65 of the hot-duct sections 66 comprises recesses 67.
Section 63 is coupled to sections 66 as shown in Figures 19 and 20, the sections engaging positively with each other.
Electrical heating conductor 6 in the hot-duct section 63 is located ~as may be seen in Figure 20) at a short dlstance from conductors 6 in sec-tions 66. This short distance between the said heating conductors provides satisfactory thermal control of the molten synthetic material.
Figures 21 and 22 illustrate another design of hot-duct section 67, t~e latter being of H-shaped cross-section, and being fitted with an H-shaped la electrical heating conductor 68. Housing 69 is provided with an adapter 70 and also comprises outlet-apertures 71 for the molten synthetic material, which may be provided, for example, at each end of longitudinal ducts 72 which are connected together by a transverse duct 73.
Electrical heating conductor 68 consists of longitudinal conductors 74 and a transverse conductor 75. Electrical conductor 68 is heated by means o$ two transformers. Dotted lines 76, 77 indicate that a double current $10ws through transverse conductor 75, as compared with the other conductor sections. Since this would impart too much heat to the transverse conductor, lf the complete conductor 68 is made of the same material, transverse con-2U ductor 75 is made tubular, is filled with copper, and is welded to longitudi-nal conductors 74. Copper has a very low electrical resistance, so that the overall resistance of the transverse conductor is low and less heat is there-$ore produced in this area.
It may be seen from ~igure 21 that the inlet-apertures for the molten synthet~c material is located in the middle of the transverse duct 73.
Figure 2~ shows a hot-duct section 78 in the form of a T. The section has a central power-supply plug 79. The ends of heating conductor 80 _ g _ .:
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l 159B18 are grounded through contact angles 81 formed by housing 82.
The molten synthetic material is supplied from an injection-head 83, passes through T-shaped duct 84, and reaches outlet apertures 85. Nozzles 10 may be inserted into the outlet-apertures, or a connection may be made in this area to another hot-duct section.
The hot-duct sections described above provide a plurality of pos-sible combinations for building up a hot-duct system~ When the injection-mould is no longer needed, or must be replaced, the hot-duct sections may be re-used. The electrical heating conductors of an assembled hot-duct system may ~e wired in series or in parallel, but may also be operated through trans-formers.
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An apparatus of this kind is known (Austrian Patent 286 607). It consists of a distribution plate closely adjacent a moulding plate provided with moulding cavities. The distribution plate comprises horizontal distributing ducts from which vertical injection ducts branch, leading to spot-injection apertures in the moulding cavities. The distributing ducts are equipped with a central heater-wire which is of U-shaped configuration in the vicinity of the injection ductso The known apparatus, equipped with the hot-duct system, is designed with the injection-mould and is thus an integral part thereof. The parts of this apparatus cannot be used to build up a hot-duct system for an injection-mould of a totally different configuration. Moreover, differential heating of the various areas of the hot-duct system is not possible.
It is the purpose of the invention to design the apparatus located between the synthetic-material extruder and the injection-mould ca~ity in such a manner that different areas of the hot-duct `
system may be heated differently for thermal control of the molten synthetic material, and so that the pattern of the hot-duct system may easily be adapted to different injection-moulds.
The invention provides an electrically heated hot-duct system for feeding molten synthetic material to an injection mould, said system comprising a plurality of hot-duct sections adapted to be coupled together in unit-construction stvle, each hot-duct , ., ...~ ,, .. ~.~ ,. , :, . . .
.
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1 ~5~8 section defining a duct for the molten synthetic material and com-prising an outer housing provided with an inlet aperture and at least one outlet aperture and a rod-shaped heating conductor extend-ing over the entire length of the outer housing within said duct and secured to the end faces of the outer housing, the individual heating conductors of the hot-duct sections being adapted to be electrically heated independently of each other.
The unit-construction design of the hot-duct system, in the form of individual hot-duct sections, makes it possible to use the same components, namely the same hot-duct sections, for injection-moulds of totally different designs. The individual hot-duct sections may also be used to build up a hot-duct system when the original injection-moulds have become worn and must be replaced.
Thus full use may be made of the life of the hot-duct sections, independently of the service-life of the injection-mould.
Since each hot-duct section has a heating conductor, which can be operated electrically independently of other hot-duct sections the hot-duct system according to the invention makes it possible to heat the individual hot-duct sections to different degrees. This permits thermal control of the molten synthetic material in various parts of the hot-duct system.
Embodiments of the invention are described hereinafter in greater detail, in conjunction with the attached drawings wherein:
Figure 1 is a partial cross-sectional view of a hot-duct system and an injection-mould;
Figure 2 is a plan view of a four-way distributor to which hot-duct sections are coupled;
Figure 3 is a plan view of a hexagonal distributor to " ~ .'t~ ' ':
':
' " .
'. ' ' ~ ' .
:' ' ' "
1 15g~
which hot-duct sections are coupledi Figure 4 is a longitudinal section through a hot-duct section to be coupled to a polygonal distributor;
Figure 5 is a plan view of a distributor with a plurality of hot-- 2a -,, , , -- .. . . . . .
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duct sections, the hot-duct sections on one side of the distributor being parallel with each other;
Figure 6 is a section along the line VI - VX in Figure 5;
Figure 7 is a cross-section through a hot-duct section arranged in the form of an inverted U in a vertical plane;
Figure 8 is a longitudinal section through a hot-duct section, equipped at both ends with overflow-apertures for the molten synthetic ma-terial;
Figure g is a longitudinal section through another embodiment of hot-duct section;
Figure 10 is a view of point X in Figure 9 to an enlarged scale;
Pigure 11 shows another possible design for point X in Figure 9;
Figure 12 and 13 show cross-sections of heating conductors;
Figure 14 ~on the same sheet as Figure 8) is a cross-section through another emobidment of hot-duct section;
Figure 15 ~on the same sheet as Figure 8) is a cross-section through a design-detail of a hot-duct section;
Pigure 16 ~on the same sheet as Figure 8) is a longitudinal section through the housing of a hot-duct section, with a passage expanding conically 2Q from the central inlet-aperture out to the outlet-apertures;
Figure 17 is a perspective view of a hot-duct system prior to assembly of the functional parts;
Figure 18 is a variant of the hot-duct system according to Figure 17;
Pigure 19 shows the hot-duct system according to Figure 18 duly assembled;
Figure 20 is a section along the line XX - XX in Figure 19;
Figure 21 is a plan view, in part section, of an H-shaped hot-duct , :: :
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, l ~9~18 section;
Figure 22 is a view in the direction of arrol~ X~II in Figure 21;
Figure 23 is a plan vie~ of the heating conductor for the hot-duct section according to Figure 22;
Figure 24 shows a T-shaped hot-duct section in partial cross-section.
The apparatus illustrated in Figure 1 comprises a hot-duct section 1 fitted with an adapter bush 2 into which is inserted the machine-nozzle of a synthetic-material extruder. Bush 2 thus forms an input-aperture 3 for the molten synthetic material which is introduced into a duct 4 in hot-duct sec-tion 1. Duc* 4 is defined outwardly by a housing 5 and inwardly by an elec-trical heating conductor 6. The molten synthetic material passes through an outlet-aperture 7 into duct 8 of a second hot-duct section 9 which is equipped with nozzles 10 through which the molten synthetic material flows into mould-cavities 11 in the injection-mould. The central area of the hot-duct section 9 is also equipped with an electrical heating conductor 6.
The opening in the injection-mould for removal of the solidified injection-moulding is in plane 12, the moulding being stripped from the mould-cavities by ejectors 13.
Electrical heating conductor 6 is mounted in an insulating element 14 near the end of the housing, the end of the conductor being sealed from duct 4 by means of a packing gland 15 and a compression screw 16. Ends 17 of the heating conductor have a socket 18 into which the plug of the power-supply cable is inserted. This plug-and-socket connection is designed to carry high currents without substantial losses.
If the hot-duct section and the heating conductor are of consider-able length, the conductor may be provided with a support 19 in relation to the housing. Electrical insulation 20 is provided between support 19 and housing 5.
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~ 1~9~8 Since some of the heat produced in the heating conductor 6 is lost to atmosphere through the ends 17 emerging from housing 5, it is desirable, as shown in Figure 10, to provide the heating conductor with a constriction 21. This constriction of the conducting cross-section leads to an increase in electrical resistance, thus producing substantially more heat in this area.
Adjacent the insulating element 14, and the end-caps of the housing 5, the heating conductor 6 is provided with a collar 22 which pr0vents it from mov-ing inside the housing.
In the design according to Figure 11, the reduction in the conduct-ing cross-section, in the vicinity of the collar 22, is obtained by means of a bore filled with electrically non-conducting material 23.
The heating conductor may be of circular or other cross-section, for instance rectangular, cruciform as shown in Figure 12, or star-shaped as in Figure 13.
~ igure 2 is a plan view of a four-way distributor 24, the upper surface of which has an inlet-aperture 25, while the lateral surfaces have outlet-apertures for the molten synthetic material. The outlet-apertures are connected to an end-face inlet-aperture 26 in a hot-duct section 27. Each hot-duct section 27 has at least one outlet^aperture 28 for the molten syn-2Q thetic material, into which a nozzle 10 is inserted.
In the design according to Figure 3, the distributor 29 is hexagonalin plan view and is connected to six hot-duct sections 27. The molten syn-thetic material is fed to ~he distributor 29, from a machine nozzle, through inlet-aperture 25 Figure 3 shows, in dotted lines, that hot-duct sections 27 may be connected to further hot-duct sections running at right angles to sections 27.
The design of hot-duct section 27 is more clearly shown in Figure 4.
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~ 1~9~18 At ~he end ~acing the inlet-aperture 26 of the hot-duct section 27, the heat-ing conductor 6 is connected electrically to a retaining insert 30 made of electrically conducting material. This insert stabilized the end of the heat-ing conductor and constitutes an electrical connection between heating conduc-tor 6 and housing 31 which is also made of electrically conducting material.
Retaining insert 30 is provided with at least one flow-aperture 32 for the molten synthetic material.
End-inlet-aperture 26 is defined by an outwardly projecting hollow socket 33 which may be introduced into a recess in the distributor. It is preferably of circular cross-section. The hollow socket has a threaded flange 34 which is screwed into a threaded bore in housing 31 and secures the retaining insert 30 in the housing 31. In this design, the electrical current ~lows through heating conductor 6, retaining insert 30 and housing 31.
Whereas hot-duct sections 27 form, in Figure 2, a cruciform and, in Figure 3, a star-shaped hot duct system, it is also possible to produce, with hot-duct sections 27, the hot-duct system illustrated in Figures 5 and 6.
Molten synthetic material is fed to a distributor 35, or to a hot-duct section, through an inlet-aperture 36. From duct 37 in distributor 35, the molten synthetic material reaches hot-duct sections 27 and passes, thence, through nozzles 10, into the moulding cavities in the injection-mould. Ar-ranged on each side of distributor 35 are two hot-duct sections 27 parallel with each other.
Figure 7 illustrates, in dotted lines, a large-area moulding 38.
This moulding may be injected through nozzles 10 at almost any desired loca-tion. In this design, the hot-duct system consists of a hot-duct section 1 and two hot-duct sections 27 running at right angles thereto. Heating con-ductors 6 in the three hot-duct sections are wired in series to a power source.
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l 159~18 With a similar hot-duct system it ig also possible to feed molten synthetic material to the moulding cavities in a multi-stage injection-mould.
In this case, vertical hot-duct section 27 are fitted with a plurality of nozzles which are then arranged in the respective stages.
Figure 8 shows a longitudinal sèction through a hot-duct section 39 comprising flow-apertures 40 for the molten synthetic material at each end.
These apertures are located in retaining inserts 41 secured in housing 44 by threaded flanges 42 of hollow sockets 43. The retaining inserts, which are made of electrically conducting material, are connected conductingly with a heating conductor 45 and with housing 44. Heating conductor 45 has a central power-supply 46 insulated from the housing 44.
The molten synthetic material is fed to the hot-duct section 39 through an end-inlet-aperture, flows through the hot-duct section and, through the other end-aperture, to a coupled hot-duct section.
Figure 14 is a cross-section of a hot-duct section 57 equipped with a hollow heating conductor 48. This increases the heat-exchanging surface of the heating conductor in relation to the conducting cross-section thereof.
For the purpose of increasing mechanical stability, the interior of the heating conductor is filled with a non-conducting stabilizing material 49.
It may be gathered from Figure 14 that the heating conductor in the hot-duct section 47 may also be in two parts 50, 51 connected electrically in the central plane 52 of the hot-duct section. A support 53, in relation to housing 54, is arranged at the junction. The housing is provided with an adap-ter 2 defining the inlet-aperture for the molten synthetic material. The hous-ing also has outlet-apertures 55.
When the apparatus is in operation, the~molten synthetic material, which solidifies on the inside of the housing, forms an insulating layer.
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1 15g~8 The solidifled layer of synthetic material bears the refsrence numeral 56 in Figure 15. It may be gathered, from this figure, that the solidified synthetic material provides, in the area of the collar 22, satis-factory insulation and sealing in relation to the end-cap of housing 5. Thus the plasticized synthetic material flowing in nozzles 10 does not come into contact with the collar 22.
Figure 16 is a longitudinal section through the housing 57 of a hot-duct section having an inlet-aperture 58 and outlet-apertures 59 for the molten synthetic material. The housing is provided with a duct 60, the cross-section of which expands conically from the central inlet-aperture 58 outward-ly to the outlet-apertures 59. Although the hot-duct section loses more heat from the inlet-aperture for the molten synthetic material towards the end-faces, the conical design of the duct ensures that there will be no substan-tial pressure-drop, even with a long duct.
Figure 17 illustrates a hot-duct system in which hot-duct sections 1 and 60 lie in two different planes. The longitudinal axes of hot-duct sec-tions 60 are at right angles to those of hot-duct section 1.
Hot-duct sections 60 are fitted with a series of nozzles 10 through w~ch spot-injections are made into the cavities in the injection mould. The 2Q molten synthetic material is fed to adapter 2 and inlet-aperture 3, passes through the duct in hot-duct section 1, through inlet-apertures 51, into hot-duct sections 60, and thence to nozzles 10.
I~ it is desired to reduce the distance between the heating conduc-tor in hot-duct section 1 and the heating conductors in hot-duct sections 60, the hot-duct sections to be coupled together must be designed as shown in Figures 18, 19, 2a.
The housing 62 of the hot-duct section 63 is provided with recesses l 159618 64, while the housing 65 of the hot-duct sections 66 comprises recesses 67.
Section 63 is coupled to sections 66 as shown in Figures 19 and 20, the sections engaging positively with each other.
Electrical heating conductor 6 in the hot-duct section 63 is located ~as may be seen in Figure 20) at a short dlstance from conductors 6 in sec-tions 66. This short distance between the said heating conductors provides satisfactory thermal control of the molten synthetic material.
Figures 21 and 22 illustrate another design of hot-duct section 67, t~e latter being of H-shaped cross-section, and being fitted with an H-shaped la electrical heating conductor 68. Housing 69 is provided with an adapter 70 and also comprises outlet-apertures 71 for the molten synthetic material, which may be provided, for example, at each end of longitudinal ducts 72 which are connected together by a transverse duct 73.
Electrical heating conductor 68 consists of longitudinal conductors 74 and a transverse conductor 75. Electrical conductor 68 is heated by means o$ two transformers. Dotted lines 76, 77 indicate that a double current $10ws through transverse conductor 75, as compared with the other conductor sections. Since this would impart too much heat to the transverse conductor, lf the complete conductor 68 is made of the same material, transverse con-2U ductor 75 is made tubular, is filled with copper, and is welded to longitudi-nal conductors 74. Copper has a very low electrical resistance, so that the overall resistance of the transverse conductor is low and less heat is there-$ore produced in this area.
It may be seen from ~igure 21 that the inlet-apertures for the molten synthet~c material is located in the middle of the transverse duct 73.
Figure 2~ shows a hot-duct section 78 in the form of a T. The section has a central power-supply plug 79. The ends of heating conductor 80 _ g _ .:
- , - :, ., . - : .
., , ~ , , , : ,, . ;.: :
.
;, -, . . . . . .
, . . . . . .
l 159B18 are grounded through contact angles 81 formed by housing 82.
The molten synthetic material is supplied from an injection-head 83, passes through T-shaped duct 84, and reaches outlet apertures 85. Nozzles 10 may be inserted into the outlet-apertures, or a connection may be made in this area to another hot-duct section.
The hot-duct sections described above provide a plurality of pos-sible combinations for building up a hot-duct system~ When the injection-mould is no longer needed, or must be replaced, the hot-duct sections may be re-used. The electrical heating conductors of an assembled hot-duct system may ~e wired in series or in parallel, but may also be operated through trans-formers.
., . . . , ~ , . . ~
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::
Claims (24)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electrically heated hot-duct system for feeding molten synthetic material to an injection mould, said system comprising a plurality of hot-duct sections adapted to be coupled together in unit-construction style, each hot-duct section defining a duct for the molten synthetic material and comprising an outer housing having end faces and provided with an inlet aperture and at least one outlet aperture and a rod-shaped heating conductor extending over the entire length of the outer housing within said duct and secured to the end faces of the outer housing, the individual heating conductors of the hot-duct sections being adapted to be electrically heated independently of each other.
2. A hot-duct system according to claim 1, comprising a distributor which is polygonal in plan view, said distributor hav-ing an upper surface in which is located an inlet-aperture, and lateral surfaces defining outlet-apertures each for connection to the inlet-aperture of a hot-duct section.
3. A hot-duct system according to claim 2, wherein the inlet-aperture of the hot-duct section is defined by an outwardly pro-jecting hollow socket adapted to be introduced into a recess in the distributor.
4. A hot-duct system according to claim 3, wherein the hollow socket comprises a threaded flange adapted to be screwed in-to a threaded bore in the hot-duct section, said flange serving to secure the flange of a retaining insert for the heating conductor, said insert being made of electrically conducting material.
5. A hot-duct system according to claim 4, wherein the retaining insert is connected to one end of the electrical heating conductor and is provided with at least one flow-aperture for the molten synthetic material.
6. A hot-duct system according to claim 1, 2 or 3 wherein a first hot-duct section is connected to at least one other hot-duct section the centreline of which runs parallel with the centre-line of the first hot-duct section, or the centreline of which is in alignment with the centreline of the said first hot-duct section.
7. A hot-duct system according to claim 1 wherein in the vicinity of the outlet aperture of the hot-duct section the heating conductor is equipped with a collar.
8. A hot-duct system according to claim 7, wherein in the vicinity of the ends of the hot-duct section, the heating conductor is provided with a reduction in the conducting cross-section.
9. A hot-duct system according to claim 8, wherein the reduction in the conducting cross-section is in the form of a con-striction in the heating conductor.
10. A hot-duct system according to claim 8, wherein, in the vicinity of the reduction in the conducting cross-section, the heating conductor has a bore which is filled with electrically insulating material.
11. A hot-duct system according to claim 1, 2 or 3 wherein the individual heating conductors are in the form of hollow con-ductors, the interiors of which are filled with a non-conducting material.
12. A hot-duct system according to claim 1, 2 or 3 wherein the heating conductor is provided, in the central area, with a support in relation to the housing.
13. A hot-duct system according to claim 1, 2 or 3 wherein said inlet-aperture is located intermediate the ends of the housing of a hot-duct section the duct of which expands conically outwards from the inlet-aperture to the outlet-apertures.
14. A hot-duct system according to claim 1, 2 or 3 wherein the heating conductor is of circular, rectangular, cruciform, or star-shaped cross-section.
15. A hot-duct system according to claim 1, wherein the hot-duct section comprises flow-apertures for the molten synthetic material at each end.
16. A hot-duct system according to claim 15, wherein the flow-apertures are located in retaining inserts connected to the electrical heating conductor, the latter being equipped with a central power-supply.
17. A hot-duct system according to claim 1, wherein the hot-duct sections are connected to lie in two planes, the longitudinal axes of the sections in one plane running at right angles to those of the sections in the other plane.
18. A hot-duct system according to claim 17, wherein the housings of the hot-duct section in the one plane engage positively with the housings of the hot-duct sections in the other plane, the heating conductors in the two planes being at a short distance from each other.
19. A hot-duct system according to claim l, wherein hot-duct sections are coupled together in a vertical plane in the form of a U, the vertical hot-duct sections having injection nozzles located in a plurality of planes and associated with a multi-stage injec-tion-mould.
20. A hot-duct system according to claim l, wherein the hot-duct section is H-shaped in plan view and is equipped with an H-shaped electrical heating conductor.
21. A hot-duct system according to claim 20, wherein the central transverse conductor of the H-shape has a lower resistance value than the conductor-parts running at right-angles thereto.
22. A hot-duct system according to claim 21, wherein the transverse conductor is of tubular design, is filled with copper, and is welded to the other conductor-parts.
23. A hot-duct system according to claim 20, 21 or 22, where-in the inlet-aperture for the molten synthetic material is located centrally of the transverse conductor.
24. A hot-duct system according to claim 1, wherein the hot-duct section is T-shaped, forms the central vertical part of the injection head, and comprises a power-supply plug.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19782838832 DE2838832A1 (en) | 1977-09-06 | 1978-09-06 | DRUM BRAKE |
| DEP2838832.7 | 1979-09-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1159618A true CA1159618A (en) | 1984-01-03 |
Family
ID=6048813
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000361041A Expired CA1159618A (en) | 1978-09-06 | 1980-09-25 | Hot-duct system for feeding molten synthetic material to an injection-mould |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1159618A (en) |
-
1980
- 1980-09-25 CA CA000361041A patent/CA1159618A/en not_active Expired
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