EP1968355B1 - Induction coil and device for inductive heating of workpieces - Google Patents

Description

The present invention relates to an induction coil for inductive heating of workpieces, which has a plurality of turns, wherein at least one of the turns is at least partially flat, according to the preamble of patent claim 1.

Furthermore, the invention relates to a device for inductive heating of workpieces, comprising a high-frequency generator (HF generator) in signal-operative connection with at least one induction coil, according to the preamble of patent claim 11.

Such devices are used for inductive heating of workpieces containing electrically conductive components, and are used for example for the hardening of workpieces, for joining (welding, gluing) of workpieces or for sealing containers.

Devices for inductive heating basically consist of a high-frequency generator and an induction coil (or in short: coil), which is usually arranged in a processing head. The coil is either flat in a plane or three-dimensional, in particular helical or tunnel-shaped, wound. It usually consists either of copper pipe, which is flowed through with water for cooling, or of stranded wire. Coils made of stranded wire can be cooled by air. It is also known to surround the coil with a Ferrritumhüllung that focuses the electromagnetic field in the direction of application. The coil is typically incorporated in a series or parallel resonant circuit that is driven near the resonant frequency to produce current spikes in the coil. Due to the electromagnetic field of the induction coil eddy currents are generated in the electrically conductive components of the workpieces, which lead to a warming.

The machining head, which contains the induction coil, is often arranged above a conveying device, with the aid of which the workpieces to be heated under the coil or through it. It is also possible to immerse the workpieces in the coil or coil in the workpieces.

From the DE 918158 B and the DE 1132671 A It is known to arrange in a helical induction coil a so-called "concentrator", which consists of copper, is arranged at a small, finite distance from the turns of the coil and has a close to the body to be heated zooming flange to the magnetic field to concentrate the heating station.

From the US 5,048,260 is an inductively-sealing machine known in which longitudinally parallel portions of a single-winding tunnel coil straight portions of the material of the tunnel coil by soldering are connected thereto to homogenize the magnetic field of the coil and concentrate.

An induction coil for inductive heating of workpieces having a plurality of turns is known from US 5,156,237 DE 23 31 004 known. In the case of the coil described there, a planar winding is surrounded in a radially inner region by a single, radially outer winding, wherein both windings are arranged concentrically in a common plane.

In the DE 23 57 688 are like in the DE 23 31 004 the two windings are also arranged concentrically in a common plane, wherein the outer winding is arranged in a groove of the inner winding.

The invention has for its object to further develop an induction coil or a device of the type mentioned in each case that a high concentration and gain effect on the magnetic field generated and thus the heating effect and energy efficiency can be improved.

The object is achieved by an induction coil having the features of patent claim 1 and by a device having the features of patent claim 11.

Efindungsgemäß is an induction coil for inductive heating of workpieces, which has a plurality of turns, characterized in that the planar winding extends at least over a covered area of the other turns, wherein either the induction coil flat and with a substantially annular, flat Winding under the other, spirally extending turns is formed, wherein the flat winding is parallel to the coil plane of the remaining turns; or the induction coil has helically extending turns, wherein the two-dimensional turn is substantially cylindrical and arranged within the helically extending turns.

In addition, a device according to the invention for the inductive heating of workpieces, comprising a high-frequency generator in operative signal connection with at least one induction coil, characterized in that the induction coil is designed as an induction coil according to the invention.

Advantageous developments of the invention are the subject matter of subclaims, the wording of which is hereby incorporated by express reference into the present description in order to avoid unnecessary text repetitions.

It has surprisingly been recognized that the effect of a concentrator can be increased many times when the concentrator is designed as an additional, at least partially or sectionally planar winding of the induction coil, that is, connected in series with a number of the remaining coil turns. In an apparatus according to the invention for induction heating, therefore, the induction coil consists of several turns, wherein at least one of the turns is at least partially flat, and wherein this planar turn or partial turn of at least a portion of the remaining turns inductively, ie by the electromagnetic field of the other turns being affected. The inductive influencing is preferably carried out in that at least a portion of the remaining turns is arranged directly adjacent, parallel or enveloping to the flat (partial) winding, ie, characterized in that the flat winding at least one of the supernatant turns covered area extends. With such a coil form according to the invention, a significantly better energy input into the workpieces can be achieved with significantly lower output power of the HF generator than with the induction coils described in the prior art. Not only a concentration, but also a significant amplification of the magnetic field of the induction coil at the location of the workpiece is achieved.

In the following, the at least one planar (partial) winding is referred to as a "planar winding" in places, without expressing that this winding is completely, in accordance with the invention. must be formed flat in a whole.

The concentration of the magnetic field of an induction coil according to the invention is preferably further improved by the fact that the flat winding of the coil has a shape, e.g. has a recess or bulge with smaller dimensions than the flat turn itself, which extends in the direction of the workpiece. The effect of the magnetic field is focused in this way in the area of the molding on the workpiece.

Induction coils with such integrated concentrator, which forms one of the coil turns, can have different geometric embodiments:

According to a first embodiment, the induction coil is planar and formed with a substantially annular, flat winding under the other, spirally extending turns, wherein the planar winding is parallel to the coil plane of the other turns. As a result, the magnetic field is amplified and homogenized under the turns and in the region of a possibly existing recess of the flat turn.

According to a second alternative embodiment, the induction coil is designed as a helical coil with a cylindrical concentrator winding, ie, the planar winding is substantially cylindrical and formed within the arranged helically extending turns, wherein the two-dimensional turn inside for concentration purposes may have a rectangular or conical shape in cross-section.

According to a further development, the two-dimensional turn extends inwards beyond the remaining turns, so that only a relatively small-scale recess in the form of a small hole for receiving a workpiece remains inside the flat turn. This causes a strong concentration of energy input at this point in the workpiece.

In an embodiment not according to the invention, the induction coil is designed as a tunnel coil, each having a flat partial turn on the two parallel sides of the coil (coil halves), wherein the planar winding for concentrating the field without limiting the generality has a rectangular in cross section molding inward.

Generally, the structure of an induction coil in development of the invention is either designed so that one of the remaining turns is soldered to the flat winding, so that these two windings act as a common turn, so are effective, in particular electrically connected. Alternatively, the flat winding is contacted only at its two ends by one of the remaining turns and thus acts as an additional turn of the coil, which is connected in series with all other windings. Between the further turns and the flat turn, an insulating layer can be arranged in a further development of the invention, preferably in the form of a Teflon foil.

Preferably, at least the flat winding and particularly preferably all turns of the induction coil according to the invention consist of copper.

The formations of the flat winding can be flowed through in the invention as well as the other windings for cooling with water or another cooling medium.

To concentrate the effect of the magnetic coil field even more at the location of the workpiece, the coil on its side facing away from the workpiece with a sheath of magnetically good and electrically poorly conductive material, preferably ferrite, be surrounded, which limits the magnetic field of the coil and focused in application direction.

Fig. 1

eine grundlegende schematische Darstellung einer erfindungsgemäßen Vorrichtung zum induktiven Erwärmen von Werkstücken;

Fig. 2a, b

verschiedene Ansichten einer ersten Ausführungsform der erfindungsgemäßen Induktionsspule;

Fig. 3

eine zweite Ausführungsform der erfindungsgemäßen Induktionsspule;

Fig. 4a, b

verschiedene Ansichten einer dritten Ausführungsform der erfindungsgemäßen Induktionsspule;

Fig. 5

eine vierte Ausführungsform der erfindungsgemäßen Induktionsspule; und

Fig. 6

eine Ausgestaltung einer Induktionsspule als Tunnelspule.

Further advantages and features of the present invention will become apparent from the following description of exemplary embodiments with reference to the drawing. Features to be taken from the individual embodiments may be implemented individually or in combination in embodiments of the present invention. It shows / shows:

Fig. 1

a basic schematic representation of an inventive device for inductive heating of workpieces;

Fig. 2a, b

different views of a first embodiment of the induction coil according to the invention;

Fig. 3

a second embodiment of the induction coil according to the invention;

Fig. 4a, b

different views of a third embodiment of the induction coil according to the invention;

Fig. 5

a fourth embodiment of the induction coil according to the invention; and

Fig. 6

an embodiment of an induction coil as a tunnel coil.

Fig. 1 shows a basic schematic representation of an inventive device 1 for inductive heating of workpieces, For example, for sealing containers or containers 2. The device 1 has a high-frequency generator (HF generator) 3 in conjunction with a resonant circuit 4. The oscillating circuit 4 comprises a capacitor 5 which is connected in series with an induction coil (inductance) 6 in order to achieve a current increase. The capacitance can also be arranged parallel to the inductance and then together with this form a parallel resonant circuit. At least the induction coil 6 is arranged in a movable or fixed machining head 1a of the device 1. The movable machining head 1a is movable as a whole in the direction of the double arrows A, A 'in order to adapt the device 1 to different dimensions of the workpieces to be heated, in this case the container 2 to be sealed. It is alternatively also possible that the workpiece 2 moves and the machining head 1 is fixed. In the current-carrying state, the induction coil 6 generates an (electro) magnetic field H, in the region of which a container 2 to be sealed is arranged with a container opening or a sealing film 7 present on the container opening. The container 2 is typically moved by means of a conveyor 8, such as a conveyor belt, through the area of the magnetic field H. Thereby, the sealing film 7 is heated and fused with the material of the container 2, so that it is sealed.

As those skilled in the art will appreciate, the scope of the device 1 is by no means limited to the sealing of containers or containers, but can be extended to any type of induction heating of workpieces.

As an alternative to the embodiment shown by way of example, it is also possible, depending on the field of application, to place the workpieces 2 by means suitable for this purpose, e.g. by suitable design of the conveyor 8 and the machining head 1a, to immerse in the induction coil 6 or the induction coil 6 itself in the workpieces 2.

Fig. 2a shows an overall perspective view of a first embodiment of the inventive induction coil 6. The induction coil 6 has connection jaws 6a, 6b, which are connected to a conductor 6c in the form of a copper tube. The conductor 6c or the copper tube are in the operation of the induction coil 6 for cooling purposes by a cooling medium, in particular water, flows through.

Starting from the connecting jaw 6a, the conductor 6c initially has a straight course, is then angled downwards and then arranged in the form of a planar spiral, that is to say in the form of helical spiral windings 6c ', 6c "with decreasing diameter or winding radius 6c 'of the conductor 6c is then returned to the connection jaw 6b essentially parallel to the initial course of the conductor 6c from the connection jaw 6a. Below the spiral turns of the conductor 6c, a further turn of the induction coil 6 is arranged, which is referred to as a planar winding 6d is formed with a relative to the other conductor 6c enlarged (top) surface is formed.The flat winding 6d is formed in the form of an open ring made of copper and has corresponding at 6e a slot and an inner space 6f (recess), the Recording of workpieces to be heated (not shown here) serve According to the invention, when current flows through the induction coil 6, a considerable concentration and amplification of the magnetic field generated by the induction coil 6 takes place in the region of the free space 6f and below the coil turns. Depending on their geometry, the workpieces to be heated are arranged either below the induction coil 6 or within the free space 6f. Further details of the induction coil 6 according to Fig. 2a are in Fig. 2b shown.

Fig. 2b shows a sectional view of the induction coil 6 according to Fig. 2a along the line II in Fig. 2a , As can be seen from this illustration, the inner spiral turn 6c 'abuts against the flat turn 6d and is preferably soldered to it. The remaining spiral windings 6c "are arranged elevated in relation to the inner spiral windings 6c 'by a dimension d and do not touch the flat windings 6d, but can influence them inductively.An insulating layer, not shown, can continue to flow between the flat windings 6d and the remaining spiral windings 6c" Form of a Teflon film may be arranged. As with renewed reference to the Fig. 2a As is clear, even the inner spiral turn 6c 'does not contact the two-dimensional turn 6d over the slit 6e, so that the two-dimensional turn 6d effectively cooperates with the inner spiral turn 6c' as one turn of the induction coil 6. In addition, as already mentioned, it functions as a concentrator, through which the magnetic field of the induction coil 6 concentrates on the region below the spiral turns as well as within the free space 6f and noticeably strengthened in this area. The inner spiral turn 6c 'also serves to cool the flat turn 6d, which itself is not flowed through by water. It is also possible not to solder the inner spiral turn 6c ', but one of the remaining spiral turns 6c "to the flat turn 6d Advantageously, that of the spiral turns 6c', 6c" is connected to the flat turn 6d, which is the location of greatest heat development is closest, so the spiral winding 6c ', when the workpieces to be heated in the free space 6f of the induction coil to be arranged.

Fig. 3 shows an overall perspective view of another embodiment of the induction coil 6 according to the invention substantially corresponds to the embodiment according to the FIGS. 2a . b , so that in this case only on relevant differences will be discussed in more detail. While the flat turn 6d in the embodiment according to the FIGS. 2a . b is formed limited by one of the remaining (spiral) turns 6c ', 6c "covered area, the embodiment according to Fig. 3 In that the planar winding 6d extends beyond an area covered by the remaining (spiral) windings 6c ', 6c " Fig. 3 the flat winding 6d extends inwardly over the course of the inner spiral turn 6c ', so that at an inner end of the slit 6e only one opposite to the embodiment of FIG FIGS. 2a . b in its dimensions greatly reduced space 6f remains in the form of a hole. This serves to accommodate workpieces of smaller dimensions, with a correspondingly increased concentration of the magnetic field of the induction coil 6 takes place in this area.

Fig. 4a shows a perspective view of a further embodiment of the induction coil 6 according to the invention. In conjunction with the connection jaws 6a, 6b, this has an angle-shaped holding part 6g, on which the conductor 6c is guided in isolation. The windings 6c ', 6c "of the induction coil 6 extend in a helical manner, the two-dimensional turn 6d being substantially cylindrical and arranged within the helically extending remaining windings 6c', 6c" of the induction coil 6. As the annular planar winding of the embodiments according to the FIGS. 2a . b and 3 also indicates the two-dimensional turn 6d of the embodiment Fig. 4a a slot 6e. Opposite them The two-dimensional turn 6d is electrically insulated by an insulating layer 6h in the form of a Teflon foil, the latter having openings at 6i and 6j at which the two inner of the remaining coil turns 6c 'are electrically conductive with the flat turn 6d connected to both sides of the slot 6 e, preferably soldered, are, so that the flat winding 6 d effectively acts as an additional turn of the induction coil 6.

Fig. 4b shows the induction coil 6 according to Fig. 4a according to a section along the line II-II in Fig. 4a , As can be seen from this illustration, the planar winding 6d has an encircling hollow formation 6k that extends inwards, that is to say in the region of the free space 6f, with respect to the remaining windings 6c ', 6c ", which is rectangular in cross section Formations 6k is thus again provided with an area of lesser dimension (smaller diameter) so that a magnetic field generated by the induction coil 6 is concentrated and amplified in the free space 6f, in particular between the formations 6k of the planar coil 6d Fig. 4a and Fig. 4b can be seen, the inner, hollow coil turns 6c 'connected to the openings 6i and 6j with the hollow shape 6k, so that during operation of the induction coil 6, the cooling medium, preferably water, both the coil turns 6', 6c "and the formation 6k and the conductor 6c flows through in a common cooling circuit.

Fig. 5 shows by means of a representation, the perspective of those in Fig. 4b corresponds to a further embodiment of the induction coil 6 according to the invention. In the present case, reference is only made to the essential differences between the induction coil 6 Fig. 5 and the induction coil according to Fig. 4b received. According to Fig. 5 The flat winding 6d of the induction coil 6 has an inwardly extending hollow formation 6k, which is cone-shaped in cross-section. This way is opposite to in Fig. 4b shown embodiment of the induction coil 6 reaches a reinforced cooling effect on the flat turn 6d. In Fig. 5 In addition, a cylindrical Ferrritumhüllung 9 is shown with a U-shaped inner profile, which surrounds the induction coil 6 and additionally focuses the magnetic field of the coil on the coil interior. Analogously designed ferrite cladding can also be used in all other induction coils according to the invention shown.

As one skilled in the art will appreciate, the internal formation of the flat turn 6d or its shape 6k is not based on the embodiments according to FIGS FIGS. 4b and 5 limited. Various further shaping geometries for generating correspondingly concentrated magnetic fields in the free space 6f of the induction coil 6 are possible without departing from the scope of the present invention.

Fig. 6 shows an induction coil 6, which is formed as a tunnel coil with two substantially parallel coil halves 6 ', 6 ". (Coil) conductor 6c consists of stranded wire and forms in the region of the two coil halves 6', 6" in each case a number of parallel conductor sections which are connected to coil windings via conductor loops 6I, 6I '. Furthermore, in each of the two coil halves 6 ', 6 ", a planar partial turn 6d, 6d' is arranged, which is contacted at points 6i 'and 6j' (and analogously for the coil half 6", not visible here) through the conductor 6c (eg screwed or soldered to it) so as to act as an additional partial turn of the corresponding coil half 6 ', 6 ".The two planar partial turns 6d, 6d' have on their inner side, that is to say, their side facing the respective other coil half hollow shape 6k, 6k ', which according to the present example is rectangular in cross-section, deviating configurations of the formations 6k, 6k' are of course possible, in particular a conical configuration according to FIG Fig. 5 What the expert readily recognizes. The formation 6k, 6k 'is in the operation of the induction coil 6 by a cooling medium, preferably of water, flows through.

Claims (12)

1. An induction coil (6) for inductive heating of workpieces (2), which comprises a plurality of turns (6c', 6c", 6d), wherein at least one of the turns (6d) has an at least partially flat configuration,
   characterised in that
   the flat turn extends at least over a region overlapped by the remaining turns (6c', 6c"), wherein
   either the induction coil (6) has a planar configuration with a substantially annularly configured flat turn (6d) under the remaining spirally running turns (6c', 6c"), wherein the flat turn (6d) runs parallel to the coil plane of the remaining turns (6c', 6c"),
   or the induction coil (6) comprises helically running turns (6c', 6c"), wherein the flat turn (6d) has a substantially cylindrical configuration and is arranged inside the helically running turns (6c', 6c").
2. An induction coil (6) according to the preceding claim, characterised in that for the inductive effect at least a part of the remaining turns (6c', 6c") is arranged directly adjacent to, parallel to and/or enclosing the flat turn (6d, 6d').
3. An induction coil (6) according to the claim 1 or 2, characterised in that the flat turn (6d, 6d') comprises a region (6f) having smaller dimensions than an overall dimension of the flat turn, said region being designed for receiving a workpiece to be heated.
4. An induction coil (6) according to any one of the preceding claims, characterised in that the annular flat turn (6d) is opened by means of a slot (6e).
5. An induction coil (6) according to any one of the preceding claims, characterised in that the flat turn (6d) is configured so as to be restricted substantially to a region overlapped by the remaining turns (6c', 6c").
6. An induction coil (6) according to any one of claims 1 to 4, characterised in that the flat turn (6d) is of configured to extend beyond a region overlapped by the remaining turns (6c', 6c").
7. An induction coil (6) according to any one of the preceding claims, characterised in that one of the remaining turns (6c') is operatively connected, in particular soldered, to the flat (partial) turn (6d).
8. An induction coil (6) according to any one of the preceding claims, characterised in that an insulating layer, in particular in the form of a Teflon film, is arranged between the flat (partial) turn (6d) and the remaining turns (6c', 6c").
9. An induction coil (6) according to any one of the preceding claims, characterised in that at least the flat (partial) turn (6d) and in particular all turns (6c', 6c"; 6d) consist of copper.
10. An induction coil (6) according to any one of the preceding claims, characterised in that the remaining turns (6c', 6c") are of hollow, in particular tubular, construction and during operation a coolant flows therethrough.
11. A device (1) for inductive heating ofworkpieces (2), comprising a high frequency generator (3) operatively connected in terms of signalling to at least one induction coil (6), characterised in that the induction coil (6) is configured according to one of the preceding claims.
12. A device (1) for inductive heating of workpieces (2) according to the preceding claim, characterised in that the induction coil (6), on the face thereof facing away from the workpiece (2), is enclosed with a covering (9) made of material, in particular of ferrite, that is magnetically highly conductive and electrically poorly conductive.

Images