GB2205220A

GB2205220A - Induction heating device

Info

Publication number: GB2205220A
Application number: GB08812157A
Authority: GB
Inventors: Eugen Nolle; Hugo-Werner Geschka
Original assignee: E Blum GmbH and Co
Current assignee: E Blum GmbH and Co
Priority date: 1987-05-26
Filing date: 1988-05-23
Publication date: 1988-11-30
Anticipated expiration: 2008-05-23
Also published as: IT1217714B; IT8820720A0; GB8812157D0; DE3717742A1; DE3717742C2; GB2205220B

Description

4 1 Induction heating device The invention relates to an induction heating

device for heating a material, especially a thermoplastic material, with a massive housing having a transit opening for the material to be heated, which housing is magnetically coupled with at least one laminated iron core carrying a winding.

In the previously proposed devices of this kind, the coils or windings are wound of copper or aluminium wire and special precautionary measures are necessary, such for example as thermal insulating materials between the coils and the housing to be heated and coverings which serve for contact protection. In order to prevent damage to the coil or winding which effects the heating of the massive housing, it is moreover necessary in many cases to provide a relatively expensive cooling device on or around the massive housing so as to prevent the thermal stability of, for example, the insulating varnish on the winding, from being impaired. Consequently the construction of the device is relatively expensive and costly.

22 0 5220 The basic object of the present invention is to provide a device of the kind initially referred to with which the desired high temperatures can be obtained in the massive housing without the precautionary measures that are necessary in the present state of the art. In particular, it will also be possible with the device according to the invention to cool the massive housing so as to keep the temperature of the material circulating through it between narrow limits. Moreover, the device according to the invention will be capable of being produced much more simply and economically and in addition it will be more efficient.

According to the invention this is achieved with a device of the kind initially referred to in that the winding or coil arranged on the laminated iron core which is magnetically coupled to the massive housing is composed of a hollow conductor. The use of such a hollow conductor enables the massive housing to be cooled as required in a X, particularly simple manner by causing a cooling medium to flow through the hollow conductor so that the heat transmitted from the massive housing to the winding can be removed by the said cooling medium. In order to obtain a particularly effective removal of the surplus heat, it may be advantageous if the winding is wound directly round the laminated iron core which is magnetically coupled with the massive housing. By means of the last-mentioned feature an optimum transfer of the surplus amount of heat from the housing to the winding is obtained via the laminated iron core.

According to a further development of the invention the winding provided on the laminated iron core is designed as a low voltage winding, so that the amount of insulation that has to be used can be considerably reduced and in some cases no coverings serving as protection against contact are necessary.

The invention can be used in a particularly advantageous manner in induction heated synthetic plastics extrusion housings provided internally with a rotary conveying or kneading screw. The invention may, however, also be used advantageously with spray nozzles, e.g. for synthetic plastics material.

When a low voltage winding is used for the laminated iron core which is magnetically coupled directly with the massive housing, it may be particularly suitable if this winding is electrically coupled with a secondary winding of a transormer. This secondary winding may also have the form of a low voltage winding.

When a low voltage winding is used for the secondary winding of the transformer and/or for the winding on the laminated iron core, which is directly couple with the massive housing, it may be particularly advantageous if the voltage of these windings is less than 60 volts, and it may preferably be between 6 and 48 volts. In a particularly advantageous manner the transformer and the winding on the iron core which is magnetically with the massive housing may be so arranged that the secondary winding of the transformer and/or the winding provided on the iron core which is magnetically coupled with the massive housing operate at a voltage which is less than 24 volts.

A i c 4 1 1 The last-mentioned constructional variant has the advantage that no special protective devices need be provided and furthermore an uninsulated material may be used for the production of the respective windings.

It may be particularly advantageous for the operation and construction of the device if the secondary winding of the transformer consists of a hollow conductor, which is so conected at at least one end with the hollow.conductor forming the winding on the laminated iron core that is magnetically coupled with the housing that the hollow spaces of the two conductors are interconnected. In the case of such a construction of the device, the medium which serves for the cooling of the massive housing can circulate both through the secondary winding of the transformer and also through the winding on the laminated iron core which is magnetically coupled with the housing.

It may moreover be particularly advantageous if the two hollow conductors are so coupled with each other that the hollow spaces within them form a closed circuit conduit system. The primary winding of the transformer may advantageously be formed by a high voltage primary winding which, for example, may be energized with the usual 220 volts supplied from the mains supply. The voltage may however be higher, e.g. 380 volts, or lower.

For the cooling of the device, a cooling medium, such as for example water or oil or another liquid may be caused to flow through the windings which may be made of tubular conductors of for example round or rectangular cross-section.

In order to achieve rapid removal of the excess amount of heat from the massive housing, it may be particularly advantageous if the medium that is circulated through the hollow conductors is displaced positively through the windings. For this purpose a feed pump may be provided in the conduit system formed by the hollow conductors, which feed pump may advantageously be located between the secondary winding of the transformer and the winding which is provided on the housing.

k Especially in the case of a closed circuit cooling system in which the same cooling medium is practically always used, it may be particularly advantageous for increasing the cooling effect if in addition a heat exchanger is provided in the system formed by the hollow conductors.

It may moreover be particularly suitable if a liquid-air heat exchanger is used through which the medium circulating In the hollow conductors can be caused to flow.

For many applications it may be advantageous if only the winding provided on the laminated iron core which is coupled with the massive housing is composed of hollow conductors and serves for cooling the massive housing. This winding is then - as already described - electrically coupled with the secondary winding of a transformer, in which case this secondary winding or coil may be wound from a solid wire. In such a construction it is also appropriate if both ends of the winding provided on the laminated iron core are connected together with the interposition of a pump and perhaps also a storage container for the cooling medium.

The invention will be explained in more detail with reference to the drawing.

The induction heating device 1 shown in the drawing for heating a material consists of a massive metal housing 2 with a transit opening 3 through which the material to be warmed or heated, such as a thermoplastic material is conveyed. The housing 2 may for example be used for extruders, in which case the opening 3 may be provided with a suitabley adapted conveyor screw.

The housing 2 has two flanges 4, 5 between which there is provided a housing portion 6 of reduced cross-section. The housing portion 6 as well as the two flanges are of parallelepiped shape, the rectangular end surfaces 7 of the housing 2 or of the flanges 4, 5 being disposed at right angles to the axial extent of the opening 3.

In the constructional embodiment shown, the device 1 is furthermore provided with a laminated iron core 8, composed of E-shaped metal sheets, on which is provided a coil 9. The outer limbs 8a, b as well as the middle limb 8c of the laminated iron core 8 have on their free ends abutment surfaces which are formed by the individual laminae and by means of which the iron core 8 is supported against one lateral surface 10 of the middle portion 6 of the housing, so that the iron core 8 is magnetically coupled with the massive metal housing 2, which may for example be made of steel.

The winding or coil 9 which is arranged on the middle limb 8c is electrically coupled with the secondary winding 11 of a transformer 12. The transformer 12 also has a primary coil on winding 13 which is, for example, energised by the mains supply with a voltage of 220 volts. The two windings 9 and 11 are so arranged with respect to the primary winding 13 of the transformer 12 that they form low voltage windings, the voltage in the windings 9 and 11 being advisably less than 24 volts.

The secondary winding 11 provided on the laminated core part 14 of the transformer 12 and the energising winding 9 provided on the middle limb 8c of the laminated iron core 8 are wound from a tubular conductor which may, for example, be of annular or rectangular cross-section and may be connected to each other in such a manner that the hollow spaces of the windings 9 and 11 form a closed-conduit or closed-circuit system. A cooling liquid is contained in the windings 9 and 11 and is positively forced to flow through these windings 9 and 11 by means of a circulating pump 15. The cooling medium provided in the hollow spaces within the windings 9 and 11 is utilized as required for the cooling of the nonlaminated metal housing 2. Moreover, the laminated iron core 8 is utilized as a heat conductor or heat transmitter between the metal housing 2 and the winding 9. In order to increase the cooling action a heat-exchanger 16 may also be provided which may be arranged in the region between the energising winding 9 and the secondary winding 1. This heat-exchanger may be either a liquid- or air-heat-exchanger. Moreover, a resevoir for the cooling fluid may be provided in the region between the two windings 9 and 11 that are each formed of a hollow conductor and this resevoir may be incorporated in the heat exchanger 16.

According to another possible constructional embodiment of the invention the secondary winding 11 may be made of a solid conductor, so that only the energizing winding 9 is then produced from hollow conductors. In such a form of the invention the end parts of the energizing winding 9 are then interconnected by means of an electrically non-conductive junctio:n, so that once again there is a closed flow circuit for the cooling medium. Such a junction is shown in broken lines in the drawing and indicated by the reference 17. Also, in this embodiment, the energizing winding 9 is coupled electrically with the secondary winding 11. Furthermore, in such a constructional embodiment, a cooling medium which is electrically nonconductive should be used.

Claims

1. Induction heating device for heating a material, especially thermoplastic material, with a massive housing having a transit opening for the material to be heated, which housing is magnetically coupled with at least one laminated iron core carrying a winding, characterised in that the winding consists of a hollow conductor.

2. Induction heating device especially according to claim 1, characterised in that the winding is a low voltage winding.

3. Induction heating device according to claim 1 or 2, characterised in that the winding on the iron core which is magnetically coupled with the housing is electrically coupled with a secondary winding of a transformer.

4. Induction heating device, especially according to one of claims 1 to 3, characterised in that the secondary winding consists of a low voltage winding.

5. Induction heating device according to one of claims 1 to 4, characterised in that the voltage of the winding of the iron core which is magnetically coupled to the housing and/or of the secondary winding of the transformer is less than 60 volts and is preferably between 6 and 48 volts.

6. Induction heating device according to one of claims 1 to 5, characterised in that the voltage of the winding of the iron core which is magnetically coupled to the housing andlor of the secondary winding of the transformer is less than 24 volts.

7. Induction heating device especially according to one of claims 1 to 6, characterised in that the secondary winding of the transformer consists of a hollow conductor which is so connected at at least one end with the hollow conductor forming the winding on the iron core that is magnetically coupled with the housing that the hollow spaces within the two wires are connected with each other.

b

8. Induction heating device according to one of claims 1 to 7, characterised in that the winding on the iron core which is magnetically coupled to the housing and the secondary winding of the transformer are so coupled with each other that the hollow spaces within them form a closed circuit conduit system.

9. Induction heating device according to one of claims 1 to 8, characterised in that a cooling medium, such as water or oil, can be caused to flow through the hollow conductor.

10. Induction heating device according to one of claims 1 to 9, characterised in that a feed pump is provided in the conduit system formed by the hollow conductors for the medium that can be caused to flow through the windings.

Induction heating device according to claim 10, characterised in that the pump is provided between the exciting winding and the secondary winding.

12. Induction heating device according to one of claims 1 to 11, characterised in that a heat-exchanger is provided in the system formed by the hollow conductors.

13. Induction heating device according to claim 12, characterised in that the heat-exchanger is a liquid-air heat-exchanger through which the medium circulating in the system can be caused to flow.

Q Published 1988 at The Patent Office, State House, 66'71 High Holborn. London WClR 4TP. Further copies may be obtained from The Patent Office, Sales Branch. St MaTry Cray. Orpington, Kent BR5 3RD- Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1/87