EP0486472B1 - Device for heating a length of electrically conductive material - Google Patents

Device for heating a length of electrically conductive material Download PDF

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Publication number
EP0486472B1
EP0486472B1 EP92101680A EP92101680A EP0486472B1 EP 0486472 B1 EP0486472 B1 EP 0486472B1 EP 92101680 A EP92101680 A EP 92101680A EP 92101680 A EP92101680 A EP 92101680A EP 0486472 B1 EP0486472 B1 EP 0486472B1
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EP
European Patent Office
Prior art keywords
strand
capacitor plates
capacitor
high frequency
opposite
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 - Lifetime
Application number
EP92101680A
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German (de)
French (fr)
Other versions
EP0486472A3 (en
EP0486472A2 (en
Inventor
Eckhard Schulz
Georg Zimmermann
Franz Wosnitza
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Sicowa Verfahrenstechnik fuer Baustoffe GmbH and Co KG
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Sicowa Verfahrenstechnik fuer Baustoffe GmbH and Co KG
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Publication of EP0486472A3 publication Critical patent/EP0486472A3/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B3/00—Producing shaped articles from the material by using presses; Presses specially adapted therefor
    • B28B3/20—Producing shaped articles from the material by using presses; Presses specially adapted therefor wherein the material is extruded
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B11/00—Apparatus or processes for treating or working the shaped or preshaped articles
    • B28B11/24—Apparatus or processes for treating or working the shaped or preshaped articles for curing, setting or hardening
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B7/00—Moulds; Cores; Mandrels
    • B28B7/40—Moulds; Cores; Mandrels characterised by means for modifying the properties of the moulding material
    • B28B7/42—Moulds; Cores; Mandrels characterised by means for modifying the properties of the moulding material for heating or cooling, e.g. steam jackets, by means of treating agents acting directly on the moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
    • B30B15/0088—Lubricating means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
    • B30B15/34—Heating or cooling presses or parts thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B5/00—Presses characterised by the use of pressing means other than those mentioned in the preceding groups
    • B30B5/04—Presses characterised by the use of pressing means other than those mentioned in the preceding groups wherein the pressing means is in the form of an endless band
    • B30B5/06—Presses characterised by the use of pressing means other than those mentioned in the preceding groups wherein the pressing means is in the form of an endless band co-operating with another endless band
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/46—Dielectric heating
    • H05B6/60—Arrangements for continuous movement of material

Definitions

  • the invention relates to a device for heating a strand guided in a channel from an electrically conductive material, a capacitor plate arrangement which is connected to a high-frequency generator being arranged in an electrically insulated manner from the strand, and the capacitor plate arrangement being two pairs of opposing first ones which are adjacent in the longitudinal direction of the strand Has capacitor plates, on the two outer sides of which two further pairs of second capacitor plates are arranged in the longitudinal direction of the strand, which are connected to a connection of the high-frequency generator which is at zero potential.
  • Such a device is known from EP-A-0 085 318, in which two capacitor plates are arranged on two opposite sides of the channel offset by approximately their length from one another, which are connected to a non-potential-free connection of the high-frequency generator, while adjacent on both sides to the two capacitor plates are each arranged two further capacitor plates, which are connected to the potential-free connection of the high-frequency generator and extend along the channel to such an extent that the strand is no longer at potential outside the heating range.
  • the heating of the strand is not sufficiently uniform and, as a result, it can lead to the formation of shells within the strand, which affects the homogeneity of the end product and thus its strength, if, for example, building materials to be hardened are heated.
  • a high-frequency heating of workpieces is known from AT-B-184 997, the workpieces being conveyed by a device which comprises an impedance arrangement in the form of carriages, slides or other moving devices.
  • Each device is equipped with a capacitor plate which is moved for operation parallel to one or more stationary capacitor plates of the device for energy coupling which are subjected to voltage with one or more high-frequency generators against ground.
  • the high-frequency energy is transferred capacitively from the fixed to the moving capacitor plate and thus to the respective device, which has a capacitive impedance, i.e. comprises a capacitor which represents the impedance generating heat in the workpiece.
  • an inductive impedance is then shunted in the respective device to form a tunable resonant circuit.
  • the workpiece to be heated is at rest relative to the capacitor plates of the device.
  • the device is unsuitable for heating a strand of conductive material.
  • the object of the invention is therefore to provide a device of the type mentioned at the outset which enables more uniform heating of the strand and prevents the formation of shells within the strand.
  • the object is achieved in that a further high-frequency generator which is not correlated with the first high-frequency generator is provided and a pair of opposing first capacitor plates is connected to the outputs of one of the two high-frequency generators.
  • the distance between the floating outer capacitor plates is and to select the adjacent, middle, non-potential-free capacitor plates at least equal to the distance of the capacitor plates opposite each other with respect to the strand, while the distance between the middle neighboring capacitor plates can be narrower.
  • the skin effect in heating devices using high-frequency electrical energy is normally a second-order disturbance, it can become a dominant effect depending on the size of the capacitor plate.
  • the capacitor plates each from several, preferably two, partial plates which are at the same potential and whose adjacent edges are separated by a slot which is preferably kept as small as possible.
  • Fig. 1 shows essentially schematically and in perspective a strip strand system with a device for heating the strand.
  • the 1 comprises four belts 10, 11, 12 and 13, which are arranged such that they form a rectangular channel 14 between them.
  • the belts 10 to 13 are guided around rollers 15 and driven synchronously by means of a drive, not shown.
  • the tapes 10 to 13 are, if necessary, also supported adjacent to the channel 14 by support gratings, not shown, while the vertical tapes 12 and 13 can additionally be guided at their edges via slide rails.
  • the lower horizontal belt 10 is extended beyond the outlet end of the channel 14 and guided to the belt running control via a dancer roller 16.
  • a filling device e.g. a filling funnel 17, which is expediently arranged such that it can be moved out of the inlet region of the channel 14 by means of a piston-cylinder unit for cleaning.
  • the outlet opening of the filling funnel 17 is located in the inlet area of the channel 14.
  • a cutting device 18 is provided, which can be moved in the feed direction of the strip 10 from an initial position synchronously with the feed speed of the strip 10 and can be returned to the initial position after the cutting process has been carried out.
  • the cutting device 18 has a bracket 19, which receives a cutting wire 19a to and fro and is adjustable in the vertical direction in accordance with the cutting progress and can be moved with a slide 20.
  • a belt weighing line can follow the cutting device 18 be provided.
  • the tapes 10 to 13 consist of an electrically non-conductive plastic, while adjacent to the tapes 12 and 13, namely on the outside of the tape parts, which form the entrance area of the channel 14, a schematically illustrated capacitor plate arrangement 21 is provided, which via corresponding lines 22 High-frequency generators 23 are connected.
  • a raw mixture for example consisting of quartz sand, lime, water, cement with an accelerator / retarder system and foam for the production of lime silicate stones
  • the raw mixture passes into the channel 14 and is conveyed through the belts 10 to 13 on the predetermined channel cross section kept.
  • the raw mixture in the duct 14 is heated, for example, to a temperature of 50 ° C. via the capacitor plate arrangement 21, so that the raw mixture solidifies due to the strengthening reactions of the cement that are set in motion.
  • the solidifying strand of raw mixture in channel 14 is conveyed through belts 10 to 13 to the outlet end of channel 14. A relative movement between the strand and the belts 10 to 13 and between the belts 10 to 13 does not take place here, so that the wear problems are minimal.
  • the tapes 10 to 13 are sprayed with a separating agent by spray devices 24 before they are deflected to the channel 14.
  • wipers 25 are provided, which remove any adhering material from the belts 10 to 13.
  • the solidified strand After the solidified strand exits the channel 14, it is transported further through the lower belt 10 and divided into individual stone blanks 26 by means of the cutting device 18.
  • the isolated stone blanks 26 can then optionally be weighed on a belt weighing line in order to be able to readjust the composition of the raw mixture in this way in order to ensure the most uniform possible To achieve cullet bulk density of the stone blanks 26.
  • the waste heat from the high-frequency generators 23 can be used by blowing warm air generated by the generator cooling, for example by means of a hood, onto the stone blanks 26 in order to harden them, so that these have a sufficiently high strength for subsequent transport to an autoclave, but they do not must be fully generated by the heating in the region of the capacitor plate assembly 21.
  • the length of the channel 14 is dimensioned such that the emerging strand has a desired strength, which may be increased to the necessary value by reheating with warm air from the generator cooling or another heat source.
  • the area of the channel 14 is expediently accommodated in a housing (not shown) which is at ground potential and which extends from the filling funnel 17 to the cutting device 18.
  • the belts 10 to 13 with their rollers 15 as well as support grids and sliding guides can be adjusted with respect to their belt levels so that the cross section of the channel 14 can be changed.
  • the length of the blanks 26 can be changed by the cycle of the cutting device 18.
  • the feed speed of the belts 10 to 13 is expediently adjustable, in particular continuously variable, in order to be able to adapt the feed speed to the heating speed and the size of the capacitor plate arrangement 21 accordingly.
  • the belt strand system is suitable, for example, for the production of blanks for wall blocks, in particular lightweight blocks, for example based on lime silicate, gas or foam concrete or made of coarse-ceramic material, the raw mixture containing large amounts of foam and water, so that body density down to 0.2 g / cm3 can be achieved.
  • two pairs of opposing capacitor plates 30 are provided adjacent to the belts 12 and 13 at a distance from one another, between which two further pairs of opposing capacitor plates 31 are arranged, so that in the longitudinal direction of the channel 14 a capacitor plate 30, two capacitor plates 31 and a capacitor plate 30 follow one another in the longitudinal direction of the channel 14 on the two opposite sides.
  • Two high-frequency generators 23 of half the total power are provided, which are uncorrelated.
  • the outer pairs of capacitor plates 30 are each connected to the potential-free connection (0) of one of the two high-frequency generators 23 and extend along the channel 14 to such an extent that the stray fields emanating from the inner capacitor plates 31 are picked up by the capacitor plates 30 on both sides, so that the strand inside the channel 14 is free of contact voltage outside the heating area.
  • the capacitor plates 31 are shorter than the capacitor plates 30 and each connected to the other non-potential-free connection (+) of one of the two high-frequency generators 23, which applies a zero potential to the capacitor plates 30 which are adjacent to the capacitor plates 31 in the longitudinal direction of the channel 14.
  • auxiliary capacitor plates 32 which are each connected to the non-potential-free connection (+) of the two high-frequency generators 23, are provided adjacent to the bands 10 and 11 opposite one another approximately in the middle between the four middle capacitor plates 31.
  • the auxiliary capacitor plates 32 can be approximately as long as the capacitor plates 31, but are narrow in relation to the distance d between the capacitor plates 30 and 31 and are directed with their longitudinal axis in the direction of the longitudinal axis of the channel 14.
  • the auxiliary capacitor plates 32 together with the same-polarized capacitor plates 31 lead between the outer, differently polarized capacitor plates 30 to a field line distribution which, in addition to the entire heating of the strand, particularly supports surface heating, which contributes to a shortening of the heating path, the auxiliary capacitor plates 32 providing additional heating in the area of cause neighboring strand. In the above-mentioned applications, this leads to an additional hardening in this area and thus also to a better detachment of the hardened strand from the belts 10, 11.
  • two high-frequency generators 23 of half the total power are provided, which are uncorrelated are.
  • a pair of mutually opposite middle capacitor plates 31 is connected to the potential-free and to the potential-free connection of one of the two high-frequency generators 23 (potential-free supply to the capacitor plates), the adjacent capacitor plates 31 being of opposite polarity, but in each case in the longitudinal direction of the strand other high frequency generator 23 are connected.
  • a distance between the capacitor plates 30, 31 in the longitudinal direction of the strand is at least approximately equal to the distance d between capacitor plates 30 or 31 located opposite one another.
  • the polarity of the capacitor plates 30, 31 is the same as in FIG. 3, but only one high-frequency generator 23 is used.
  • Auxiliary capacitor plates 32 can be provided in the middle between the four middle capacitor plates 31 as in FIG. 2, but in such a way that they are also approximately at a distance d from the adjacent capacitor plates 31.
  • the auxiliary capacitor plates 32 can also be round or oval.
  • the distance between adjacent capacitor plates 30, 31 lying at zero potential can be chosen to be smaller than d, as shown in FIG. 5.
  • the auxiliary capacitor plates 32 of the embodiment of FIG. 4 can also be connected to a further uncorrelated high-frequency generator 23, in which case the distance between the capacitor plates 31 and 32 can be chosen to be correspondingly small.
  • the capacitor plate arrangement is as in FIG. 5, but the opposite pairs of capacitor plates 31 are each subjected to voltage symmetrically to the zero potential by connecting a capacitor plate 31 to an output terminal of the respective high-frequency generator 23 and the opposite capacitor plate 31 to the latter is connected via a phase shifting lambda / 2 bypass line 34 or a phase shifter network which causes a phase shift by half a period.
  • a high-frequency generator 23 with a symmetrical output can also be used.
  • the opposing pairs of capacitor plates 31 are subjected to voltage symmetrically to the zero potential by connecting a capacitor plate 31 to one output connection of the high-frequency generator 23 and the capacitor plate 31 opposite with respect to the string to the other output connection of the high-frequency generator 23, which causes the opposite electrodes to be driven in phase .
  • the capacitor plates 30 are then connected to the zero potential of the high-frequency generator 23.
  • the capacitor plate 31 connected to the ungrounded connection of the high-frequency generator overlaps a small piece across the bands 10, 11 at both ends transversely to the longitudinal direction of the strand, either through a bend 35 or through its own narrow auxiliary capacitor plate 36 realized, whereby the field in the upper and lower region of the strand is slightly compressed for local surface heating. If this is followed by a further pair of capacitor plates 31 of reversed polarity, the more inhomogeneous field is located on the other side of the strand, so that overall a good homogeneous surface heating results.
  • the capacitor plates 31 can consist of a plurality of sub-plates 31a, 31b arranged adjacent to one another in order to keep the skin effect in the strand material as low as possible.
  • the partial plates 31a, 31b are at the same potential and their adjacent edges are separated by a slot 37, which can be as narrow as possible due to the same potential.
  • the concavity of the capacitor plate 30, 31 can be filled with a material 38 with the highest possible dielectric constant, so that its surface facing the corresponding band 10, 11, 12 or 13 is flat and abuts against it.
  • plastics have a dielectric constant of the order of about 2 to 4 (with a loss factor tg ⁇ , which is extremely low, so that the plastic practically does not heat up)
  • materials such as calcium titanate are provided here, whose dielectric constant is very much greater than 1 is. Also show these materials have high dimensional stability and a low coefficient of thermal expansion.
  • the extrudate has a dielectric constant of approximately 40 to 80 and a noteworthy loss factor tg ⁇ , ie the extrudate can be heated particularly well by means of a high-frequency field.
  • the capacitor plates on the sides facing the strips with a plastic layer or to embed the capacitor plates in plastic in order to keep the wear of the strips moving along the capacitor plates low.
  • this plastic coating should be as thin as possible so as not to influence the stress profile too much.
  • the material 41 can be ground and polished on the side facing the belt.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Structural Engineering (AREA)
  • Electromagnetism (AREA)
  • Constitution Of High-Frequency Heating (AREA)
  • Resistance Heating (AREA)
  • General Induction Heating (AREA)
  • Control Of Resistance Heating (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Drying Of Solid Materials (AREA)

Abstract

The pairs of electrodes (30,31) are coupled to a high frequency generator (23) to provide the heating effect. The elecrodes form capacitor plates, electrically insulated from the strip material. Smaller plates (32) are positioned on the sides of the strip where there are no main and are similarly linked to the generator. The overall heating effect from the different paris of electrodes an even heating pattern without forming any localised discontinuities, especially for heat setting materials.

Description

Die Erfindung betrifft eine Vorrichtung zum Erwärmen eines in einem Kanal geführten Strangs aus einem elektrisch leitfähigen Material, wobei eine Kondensatorplattenanordnung, die an einen Hochfrequenzgenerator angeschlossen ist, elektrisch isoliert gegenüber dem Strang angeordnet ist und wobei die Kondensatorplattenanordnung zwei in Stranglängsrichtung benachbarte Paare von einander gegenüberliegenden ersten Kondensatorplatten aufweist, zu deren beiden äußeren Seiten in Stranglängsrichtung zwei weitere Paare von zweiten Kondensatorplatten angeordnet sind, die mit einem auf Nullpotential liegenden Anschluß des Hochfrequenzgenerators verbunden sind.The invention relates to a device for heating a strand guided in a channel from an electrically conductive material, a capacitor plate arrangement which is connected to a high-frequency generator being arranged in an electrically insulated manner from the strand, and the capacitor plate arrangement being two pairs of opposing first ones which are adjacent in the longitudinal direction of the strand Has capacitor plates, on the two outer sides of which two further pairs of second capacitor plates are arranged in the longitudinal direction of the strand, which are connected to a connection of the high-frequency generator which is at zero potential.

Eine derartige Vorrichtung ist aus der EP-A-0 085 318 bekannt, bei der auf zwei gegenüberliegenden Seiten des Kanals um etwa ihre Länge zueinander versetzt zwei Kondensatorplatten angeordnet sind, die mit einem nicht potentialfreien Anschluß des Hochfrequenzgenerators verbunden sind, während beidseitig benachbart zu den beiden Kondensatorplatten jeweils zwei weitere Kondensatorplatten angeordnet sind, die mit dem potentialfreien Anschluß des Hochfrequenzgenerators verbunden sind und sich soweit entlang des Kanals erstrecken, daß der Strang außerhalb des Erwärmungsbereichs nicht mehr auf Potential liegt. Wie sich jedoch gezeigt hat, ist die Erwärmung des Strangs nicht genügend gleichmäßig und kann infolgedessen zu einer Schalenbildung innerhalb des Strangs führen, wodurch die Homogenität des Endprodukts und damit dessen Festigkeit, wenn es sich beispielsweise um durch Erwärmung zu erhärtende Baustoffe handelt, beeinträchtigt wird. Dies dürfte darauf zurückzuführen sein, daß sich die Felder in der Mitte des Strangs in etwa kompensieren können, während zwischen nebeneinander befindlichen Kondensatorplatten unterschiedlicher Polarität im Randbereich des Strangs sehr starke Felder auftreten, so daß die Feldverteilung zur Symmetrieachse in Längsrichtung des Strangs stark unsymmetrisch ist. Wegen der relativ ungleichmäßigen Erwärmung ist außerdem eine sehr große Erwärmungsstrecke erforderlich.Such a device is known from EP-A-0 085 318, in which two capacitor plates are arranged on two opposite sides of the channel offset by approximately their length from one another, which are connected to a non-potential-free connection of the high-frequency generator, while adjacent on both sides to the two capacitor plates are each arranged two further capacitor plates, which are connected to the potential-free connection of the high-frequency generator and extend along the channel to such an extent that the strand is no longer at potential outside the heating range. However, as has been shown, the heating of the strand is not sufficiently uniform and, as a result, it can lead to the formation of shells within the strand, which affects the homogeneity of the end product and thus its strength, if, for example, building materials to be hardened are heated. This may be due to the fact that the fields in the middle of the strand can approximately compensate each other, while very strong fields occur between adjacent capacitor plates of different polarity in the edge region of the strand, so that the field distribution in the longitudinal direction with respect to the axis of symmetry of the strand is very asymmetrical. Because of the relatively uneven heating, a very large heating section is also required.

Aus der AT-B-184 997 ist ein Hochfrequenzerwärmen von Werkstücken bekannt, wobei die Werkstücke durch eine Vorrichtung befördert werden, die eine Impedanzanordnung in Form von Wagen, Schiebern oder anderen bewegten Geräten umfaßt. Jedes Gerät ist mit einer Kondensatorplatte ausgerüstet, die zum Betrieb parallel zu einer oder mehreren feststehenden, mit einem oder mehreren Hochfrequenzgeneratoren gegen Masse spannungsbeaufschlagten Kondensatorplatten der Vorrichtung zur Energieankopplung bewegt wird. Die Hochfrequenzenergie wird kapazitiv von der feststehenden auf die bewegte Kondensatorplatte und damit auf das jeweilige Gerät übertragen, das eine kapazitive Impedanz, d.h. einen Kondensator umfaßt, der die im Werkstück wärmeerzeugende Impedanz darstellt. Zu letzterer ist dann im jeweiligen Gerät eine induktive Impedanz im Nebenschluß zur Bildung eines abstimmbaren Schwingkreises geschaltet. Das zu erwärmende Werkstück ist relativ zu den Kondensatorplatten des Gerätes in Ruhe. Zum Erwärmen eines Strangs aus leitfähigem Material ist die Vorrichtung ungeeignet.A high-frequency heating of workpieces is known from AT-B-184 997, the workpieces being conveyed by a device which comprises an impedance arrangement in the form of carriages, slides or other moving devices. Each device is equipped with a capacitor plate which is moved for operation parallel to one or more stationary capacitor plates of the device for energy coupling which are subjected to voltage with one or more high-frequency generators against ground. The high-frequency energy is transferred capacitively from the fixed to the moving capacitor plate and thus to the respective device, which has a capacitive impedance, i.e. comprises a capacitor which represents the impedance generating heat in the workpiece. To the latter, an inductive impedance is then shunted in the respective device to form a tunable resonant circuit. The workpiece to be heated is at rest relative to the capacitor plates of the device. The device is unsuitable for heating a strand of conductive material.

Aufgabe der Erfindung ist es daher, eine Vorrichtung der eingangs genannten Art zu schaffen, die eine gleichmäßigere Erwärmung des Strangs ermöglicht und eine Schalenbildung innerhalb des Strangs verhindert.The object of the invention is therefore to provide a device of the type mentioned at the outset which enables more uniform heating of the strand and prevents the formation of shells within the strand.

Die Aufgabe wird dadurch gelöst, daß ein weiterer mit dem ersten Hochfrequenzgenerator nicht korrelierter Hochfrequenzgenerator vorgesehen und jeweils ein Paar von gegenüberliegenden ersten Kondensatorplatten mit den Ausgänge jeweils einer der beiden Hochfrequenzgeneratoren verbunden ist.The object is achieved in that a further high-frequency generator which is not correlated with the first high-frequency generator is provided and a pair of opposing first capacitor plates is connected to the outputs of one of the two high-frequency generators.

Hierdurch wird erreicht, daß das Feld im Inneren des Strangs homogener und konzentrierter wird.This ensures that the field inside the strand becomes more homogeneous and concentrated.

Wenn man zwei unkorrelierte Hochfrequenzgeneratoren verwendet, ist der Abstand zwischen den potentialfreien äußeren Kondensatorplatten und den benachbarten, mittleren, nicht potentialfreien Kondensatorplatten mindestens gleich dem Abstand der sich bezüglich des Strangs gegenüberliegenden Kondensatorplatten zu wählen, während der Abstand zwischen den mittleren benachbarten Kondensatorplatten enger sein kann.If you use two uncorrelated high frequency generators, the distance between the floating outer capacitor plates is and to select the adjacent, middle, non-potential-free capacitor plates at least equal to the distance of the capacitor plates opposite each other with respect to the strand, while the distance between the middle neighboring capacitor plates can be narrower.

Zwar ist der Skin-Effekt bei Erwärmungsvorrichtungen mittels hochfrequenter elektrischer Energie normalerweise eine Störung 2. Ordnung, jedoch kann er in Abhängigkeit von der Kondensatorplattengrösse zu einem dominanten Effekt werden. Um seine Auswirkung möglichst gering zu halten, ist es daher zweckmäßig, die Kondensatorplatten jeweils aus mehreren, vorzugsweise zwei Teilplatten aufzubauen, die auf gleichem Potential liegen und deren benachbarte Kanten durch einen Schlitz getrennt sind, der vorzugsweise so klein wie möglich gehalten ist.Although the skin effect in heating devices using high-frequency electrical energy is normally a second-order disturbance, it can become a dominant effect depending on the size of the capacitor plate. In order to keep its impact as low as possible, it is therefore expedient to construct the capacitor plates each from several, preferably two, partial plates which are at the same potential and whose adjacent edges are separated by a slot which is preferably kept as small as possible.

Weitere Ausgestaltungen der Erfindung sind der nachfolgenden Beschreibung und den Ansprüchen zu entnehmen.Further embodiments of the invention can be found in the following description and the claims.

Die Erfindung wird nachstehend anhand der in den beigefügten Abbildungen dargestellten Ausführungsbeispiele näher erläutert.The invention is explained in more detail below on the basis of the exemplary embodiments illustrated in the attached figures.

Fig. 1 zeigt im wesentlichen schematisch und perspektivisch eine Bandstranganlage mit einer Vorrichtung zum Erwärmen des Strangs.Fig. 1 shows essentially schematically and in perspective a strip strand system with a device for heating the strand.

Fig. 2 bis 10 zeigen im wesentlichen schematisch Ausführungsformen von Kondensatoranordnungen.2 to 10 show essentially schematic embodiments of capacitor arrangements.

Die in Fig. 1 dargestellte Bandstranganlage umfaßt vier Bänder 10, 11, 12 und 13, die derart angeordnet sind, daß sie zwischen sich einen rechteckigen Kanal 14 bilden. Die Bänder 10 bis 13 sind um Rollen 15 geführt und mittels eines nicht darstellten Antriebs synchron angetrieben. Die Bänder 10 bis 13 werden, soweit erforderlich, ferner benachbart zum Kanal 14 durch nicht dargestellte Tragroste abgestützt, während die vertikalen Bänder 12 und 13 zusätzlich über Gleitschienen an ihren Kanten geführt sein können. Das untere horizontale Band 10 ist über das Austrittsende des Kanals 14 hinaus verlängert und über eine Tänzerwalze 16 zur Bandlaufregelung geführt.1 comprises four belts 10, 11, 12 and 13, which are arranged such that they form a rectangular channel 14 between them. The belts 10 to 13 are guided around rollers 15 and driven synchronously by means of a drive, not shown. The tapes 10 to 13 are, if necessary, also supported adjacent to the channel 14 by support gratings, not shown, while the vertical tapes 12 and 13 can additionally be guided at their edges via slide rails. The lower horizontal belt 10 is extended beyond the outlet end of the channel 14 and guided to the belt running control via a dancer roller 16.

Zwischen den Bändern 10 bis 13 mündet im Eintrittsbereich des Kanals 14 eine Befüllungseinrichtung, z.B. ein Fülltrichter 17, der zweckmäßigerweise etwa mittels einer Kolben-Zylinder-Einheit zwecks Reinigung aus dem Eintrittsbereich des Kanals 14 herausfahrbar angeordnet ist. Die Austrittsöffnung des Fülltrichters 17 befindet sich im Eintrittsbereich des Kanals 14.Between the belts 10 to 13, a filling device, e.g. a filling funnel 17, which is expediently arranged such that it can be moved out of the inlet region of the channel 14 by means of a piston-cylinder unit for cleaning. The outlet opening of the filling funnel 17 is located in the inlet area of the channel 14.

Am Austrittsende des Kanals 14 ist eine Schneideeinrichtung 18 vorgesehen, die in Vorschubrichtung des Bandes 10 aus einer Ausgangsstellung synchron mit der Vorschubgeschwindigkeit des Bandes 10 verfahrbar und nach Durchführung des Schneidvorgangs in die Ausgangsstellung zurückfahrbar ist. Die Schneideeinrichtung 18 besitzt in der dargestellten Ausführungsform einen Bügel 19, der einen Schneidedraht 19a hin- und herbeweglich sowie in vertikaler Richtung entsprechend dem Schneidfortgang verstellbar aufnimmt und mit einem Schlitten 20 verfahrbar ist.At the exit end of the channel 14, a cutting device 18 is provided, which can be moved in the feed direction of the strip 10 from an initial position synchronously with the feed speed of the strip 10 and can be returned to the initial position after the cutting process has been carried out. In the embodiment shown, the cutting device 18 has a bracket 19, which receives a cutting wire 19a to and fro and is adjustable in the vertical direction in accordance with the cutting progress and can be moved with a slide 20.

Nachfolgend zur Schneideeinrichtung 18 kann eine Bandwiegestrecke vorgesehen sein.A belt weighing line can follow the cutting device 18 be provided.

Die Bänder 10 bis 13 bestehen aus einem elektrisch nichtleitenden Kunststoff, während benachbart zu den Bändern 12 und 13, und zwar auf Außenseiten der Bandteile, die den Eingangsbereich des Kanals 14 bilden, eine schematisch dargestellte Kondensatorplattenanordnung 21 vorgesehen ist, die über entsprechende Leitungen 22 mit Hochfrequenzgeneratoren 23 verbunden sind.The tapes 10 to 13 consist of an electrically non-conductive plastic, while adjacent to the tapes 12 and 13, namely on the outside of the tape parts, which form the entrance area of the channel 14, a schematically illustrated capacitor plate arrangement 21 is provided, which via corresponding lines 22 High-frequency generators 23 are connected.

Wird eine Rohmischung, beispielsweise bestehend aus Quarzsand, Kalk, Wasser, Zement mit einem Beschleuniger/Verzögerer-System und Schaum zur Herstellung von Kalksilikatsteinen in den Fülltrichter 17 eingefüllt, gelangt die Rohmischung in den Kanal 14 und wird durch die Bänder 10 bis 13 auf dem vorbestimmten Kanalquerschnitt gehalten. Über die Kondensatorplattenanordnung 21 erfolgt die Erwärmung der Rohmischung im Kanal 14 beispielsweise auf eine Temperatur von 50°C, so daß sich die Rohmischung aufgrund der dadurch in Gang gesetzten festigkeitsbildenden Reaktionen des Zements verfestigt.If a raw mixture, for example consisting of quartz sand, lime, water, cement with an accelerator / retarder system and foam for the production of lime silicate stones, is filled into the filling funnel 17, the raw mixture passes into the channel 14 and is conveyed through the belts 10 to 13 on the predetermined channel cross section kept. The raw mixture in the duct 14 is heated, for example, to a temperature of 50 ° C. via the capacitor plate arrangement 21, so that the raw mixture solidifies due to the strengthening reactions of the cement that are set in motion.

Der sich verfestigende Strang aus Rohmischung im Kanal 14 wird durch die Bänder 10 bis 13 zum Austrittsende des Kanals 14 gefördert. Eine Relativbewegung zwischen dem Strang und den Bändern 10 bis 13 sowie unter den Bändern 10 bis 13 untereinander findet hierbei nicht statt, so daß auch die Verschleißprobleme minimal sind.The solidifying strand of raw mixture in channel 14 is conveyed through belts 10 to 13 to the outlet end of channel 14. A relative movement between the strand and the belts 10 to 13 and between the belts 10 to 13 does not take place here, so that the wear problems are minimal.

Um am Austrittsende des Kanals 14 ein leichtes Lösen der Bänder 10 bis 13 von dem verfestigten Strang zu erreichen, werden die Bänder 10 bis 13, bevor sie zum Kanal 14 umgelenkt werden, durch Sprüheinrichtungen 24 mit einem Trennmittel besprüht. Außerdem sind Abstreifer 25 vorgesehen, die eventuell anhaftendes Material von den Bändern 10 bis 13 entfernen.In order to achieve a slight detachment of the tapes 10 to 13 from the solidified strand at the outlet end of the channel 14, the tapes 10 to 13 are sprayed with a separating agent by spray devices 24 before they are deflected to the channel 14. In addition, wipers 25 are provided, which remove any adhering material from the belts 10 to 13.

Nach Austritt des verfestigten Strangs aus dem Kanal 14 wird dieser durch das untere Band 10 weitertransportiert und mittels der Schneideeinrichtung 18 in einzelne Steinrohlinge 26 zerteilt. Die vereinzelten Steinrohlinge 26 können dann gegebenenfalls auf einer Bandwiegestrecke gewogen werden, um auf diese Weise die Zusammensetzung der Rohmischung nachregeln zu können, um eine möglichst gleichmäßige Scherbenrohdichte der Steinrohlinge 26 zu erzielen.After the solidified strand exits the channel 14, it is transported further through the lower belt 10 and divided into individual stone blanks 26 by means of the cutting device 18. The isolated stone blanks 26 can then optionally be weighed on a belt weighing line in order to be able to readjust the composition of the raw mixture in this way in order to ensure the most uniform possible To achieve cullet bulk density of the stone blanks 26.

Ferner läßt sich die Abwärme der Hochfrequenzgeneratoren 23 nutzen, indem durch die Generatorkühlung erzeugte Warmluft etwa mittels einer Haube auf die Steinrohlinge 26 geblasen wird, um diese nachzuhärten, so daß diese eine für einen nachfolgenden Transport zu einem Autoklaven ausreichend hohe Festigkeit besitzen, die jedoch nicht voll durch die Erwärmung im Bereich der Kondensatorplattenanordnung 21 erzeugt werden muß. Die Länge des Kanals 14 ist derart bemessen, daß der austretende Strang eine gewünschte Festigkeit aufweist, die gegebenenfalls durch die Nachwärmung mit Warmluft von der Generatorkühlung oder auch einer sonstigen Wärmequelle auf den notwendigen Wert erhöht wird.Furthermore, the waste heat from the high-frequency generators 23 can be used by blowing warm air generated by the generator cooling, for example by means of a hood, onto the stone blanks 26 in order to harden them, so that these have a sufficiently high strength for subsequent transport to an autoclave, but they do not must be fully generated by the heating in the region of the capacitor plate assembly 21. The length of the channel 14 is dimensioned such that the emerging strand has a desired strength, which may be increased to the necessary value by reheating with warm air from the generator cooling or another heat source.

Der Bereich des Kanals 14 wird zweckmäßigerweise in einem nicht dargestellten auf Erdpotential befindlichen Gehäuse untergebracht, das vom Fülltrichter 17 bis zur Schneideeinrichtung 18 reicht.The area of the channel 14 is expediently accommodated in a housing (not shown) which is at ground potential and which extends from the filling funnel 17 to the cutting device 18.

Um andere Formate herstellen zu können, ist es zweckmäßig, wenn die Bänder 10 bis 13 mit ihren Rollen 15 sowie Tragrosten und Gleitführungen in bezug auf ihre Bandebenen verstellbar sind, um so den Querschnitt des Kanals 14 ändern zu können. Die Länge der Rohlinge 26 kann durch den Takt der Schneideeinrichtung 18 verändert werden.In order to be able to produce other formats, it is expedient if the belts 10 to 13 with their rollers 15 as well as support grids and sliding guides can be adjusted with respect to their belt levels so that the cross section of the channel 14 can be changed. The length of the blanks 26 can be changed by the cycle of the cutting device 18.

Zweckmäßigerweise ist die Vorschubgeschwindigkeit der Bänder 10 bis 13 regelbar, und zwar insbesondere stufenlos regelbar, um die Vorschubgeschwindigkeit an die Aufheizgeschwindigkeit und die Größe der Kondensatorplattenanordnung 21 entsprechend anpassen zu können.The feed speed of the belts 10 to 13 is expediently adjustable, in particular continuously variable, in order to be able to adapt the feed speed to the heating speed and the size of the capacitor plate arrangement 21 accordingly.

Die Bandstranganlage eignet sich beispielsweise zur Herstellung von Rohlingen für Wandbausteine, insbesondere Leichtbausteine, etwa auf Basis von Kalksilikat, Gas- oder Schaumbeton oder aus grobkeramischem Material, wobei die Rohmischung große Anteile Schaum und Wasser enthält, so daß Scherbenrohdichten bis herab zu 0,2 g/cm³ erzielt werden.The belt strand system is suitable, for example, for the production of blanks for wall blocks, in particular lightweight blocks, for example based on lime silicate, gas or foam concrete or made of coarse-ceramic material, the raw mixture containing large amounts of foam and water, so that body density down to 0.2 g / cm³ can be achieved.

Bei der in Fig. 2 dargestellten Kondensatorplattenanordnung 21 sind an den Bändern 12 bzw. 13 anliegend mit Abstand zueinander zwei Paare von einander gegenüberliegenden Kondensatorplatten 30 vorgesehen, zwischen denen zwei weitere Paare von einander gegenüberliegenden Kondensatorplatten 31 angeordnet sind, so daß in Längsrichtung des Kanals 14 auf den beiden gegenüberliegenden Seiten jeweils eine Kondensatorplatte 30, zwei Kondensatorplatten 31 und eine Kondensatorplatte 30 aufeinander in Längsrichtung des Kanals 14 folgen. Es sind zwei Hochfrequenzgeneratoren 23 der halben Gesamtleistung vorgesehen, die unkorreliert sind. Die äußeren Paare von Kondensatorplatten 30 sind jeweils an den potentialfreien Anschluß (0) eines der beiden Hochfrequenzgeneratoren 23 angeschlossen und erstrecken sich dabei soweit entlang des Kanals 14, daß die von den inneren Kondensatorplatten 31 ausgehenden Streufelder von den Kondensatorplatten 30 auf beiden Seiten aufgenommen werden, so daß der Strang innerhalb des Kanals 14 außerhalb des Erwärmungsbereichs berührungsspannungsfrei ist. Die Kondensatorplatten 31 sind kürzer als die Kondensatorplatten 30 und jeweils an den anderen nicht potentialfreien Anschluß (+) eines der beiden Hochfrequenzgeneratoren 23 angeschlossen, der die bezüglich der Kondensatorplatten 31 in Längsrichtung des Kanals 14 benachbarten Kondensatorplatten 30 mit einem Nullpotential beaufschlagt. Außerdem sind zwei Hilfskondensatorplatten 32, die jeweils an den nicht potentialfreien Anschluß (+) der beiden Hochfrequenzgeneratoren 23 angeschlossen sind, benachbart zu den Bändern 10 und 11 einander gegenüberliegend etwa in der Mitte zwischen den vier mittleren Kondensatorplatten 31 vorgesehen. Die Hilfskondensatorplatten 32 können etwa so lang wie die Kondensatorplatten 31 sein, sind jedoch im Verhältnis zum Abstand d zwischen den Kondensatorplatten 30 bzw. 31 schmal und mit ihrer Längsachse in Richtung der Längsachse des Kanals 14 gerichtet. Die Hilfskondensatorplatten 32 führen zusammen mit den gleichgepolten Kondensatorplatten 31 zwischen den äußeren anders gepolten Kondensatorplatten 30 zu einer Feldlinienverteilung, die neben der gesamten Erwärmung des Strangs besonders die Oberflächenerwärmung unterstützt, was zu einer Verkürzung der Erwärmungsstrecke beiträgt, wobei die Hilfskondensatorplatten 32 eine zusätzliche Erwärmung im Bereich des hierzu benachbarten Strangs bewirken. Dies führt bei den vorstehend erwähnten Anwendungsfällen zu einer zusätzlichen Verfestigung in diesem Bereich und damit auch zu einem besseren Lösen des verfestigten Strangs von den Bändern 10, 11.In the capacitor plate arrangement 21 shown in FIG. 2, two pairs of opposing capacitor plates 30 are provided adjacent to the belts 12 and 13 at a distance from one another, between which two further pairs of opposing capacitor plates 31 are arranged, so that in the longitudinal direction of the channel 14 a capacitor plate 30, two capacitor plates 31 and a capacitor plate 30 follow one another in the longitudinal direction of the channel 14 on the two opposite sides. Two high-frequency generators 23 of half the total power are provided, which are uncorrelated. The outer pairs of capacitor plates 30 are each connected to the potential-free connection (0) of one of the two high-frequency generators 23 and extend along the channel 14 to such an extent that the stray fields emanating from the inner capacitor plates 31 are picked up by the capacitor plates 30 on both sides, so that the strand inside the channel 14 is free of contact voltage outside the heating area. The capacitor plates 31 are shorter than the capacitor plates 30 and each connected to the other non-potential-free connection (+) of one of the two high-frequency generators 23, which applies a zero potential to the capacitor plates 30 which are adjacent to the capacitor plates 31 in the longitudinal direction of the channel 14. In addition, two auxiliary capacitor plates 32, which are each connected to the non-potential-free connection (+) of the two high-frequency generators 23, are provided adjacent to the bands 10 and 11 opposite one another approximately in the middle between the four middle capacitor plates 31. The auxiliary capacitor plates 32 can be approximately as long as the capacitor plates 31, but are narrow in relation to the distance d between the capacitor plates 30 and 31 and are directed with their longitudinal axis in the direction of the longitudinal axis of the channel 14. The auxiliary capacitor plates 32 together with the same-polarized capacitor plates 31 lead between the outer, differently polarized capacitor plates 30 to a field line distribution which, in addition to the entire heating of the strand, particularly supports surface heating, which contributes to a shortening of the heating path, the auxiliary capacitor plates 32 providing additional heating in the area of cause neighboring strand. In the above-mentioned applications, this leads to an additional hardening in this area and thus also to a better detachment of the hardened strand from the belts 10, 11.

Bei der in Fig. 3 dargestellten Ausführungsform sind zwei Hochfrequenzgeneratoren 23 der halben Gesamtleistung vorgesehen, die unkorreliert sind. Jeweils ein Paar von einander gegenüberliegenden mittleren Kondensatorplatten 31 ist an den potentialfreien und an den nicht potentialfreien Anschluß eines der beiden Hochfrequenzgeneratoren 23 angeschlossen (potentialfreie Zuführung zu den Kondensatorplatten), wobei in Längsrichtung des Strangs die benachbarten Kondensatorplatten 31 von entgegengesetzter Polarität, jedoch an jeweils einen anderen Hochfrequenzgenerator 23 angeschlossen sind. Hierdurch wird ein insgesamt bezüglich des Strangquerschnitts recht homogenes Feld erzeugt, so daß auch das Stranginnere gut erwärmt und Schalenbildung vermieden wird.In the embodiment shown in FIG. 3, two high-frequency generators 23 of half the total power are provided, which are uncorrelated are. A pair of mutually opposite middle capacitor plates 31 is connected to the potential-free and to the potential-free connection of one of the two high-frequency generators 23 (potential-free supply to the capacitor plates), the adjacent capacitor plates 31 being of opposite polarity, but in each case in the longitudinal direction of the strand other high frequency generator 23 are connected. As a result, a field which is quite homogeneous overall with respect to the strand cross section is generated, so that the interior of the strand is also warmed well and shell formation is avoided.

Bei der in Fig. 4 dargestellten Ausführungsform ist zur Erzeugung eines homogeneren Feldes vorgesehen, daß zwischen den Kondensatorplatten 30, 31 in Längsrichtung des Strangs jeweils ein Abstand mindestens etwa gleich dem Abstand d zwischen einander gegenüberliegenden Kondensatorplatten 30 oder 31 ist. Die Polung der Kondensatorplatten 30, 31 ist wie bei Fig. 3, jedoch wird nur ein Hochfrequenzgenerator 23 verwendet.In the embodiment shown in FIG. 4, in order to generate a more homogeneous field, it is provided that a distance between the capacitor plates 30, 31 in the longitudinal direction of the strand is at least approximately equal to the distance d between capacitor plates 30 or 31 located opposite one another. The polarity of the capacitor plates 30, 31 is the same as in FIG. 3, but only one high-frequency generator 23 is used.

In der Mitte zwischen den vier mittleren Kondensatorplatten 31 können wie bei Fig. 2 Hilfskondensatorplatten 32 vorgesehen sein, jedoch derart, daß sie sich ebenfalls etwa im Abstand d von den benachbarten Kondensatorplatten 31 befinden. Die Hilfkondensatorplatten 32 können auch rund oder oval sein.Auxiliary capacitor plates 32 can be provided in the middle between the four middle capacitor plates 31 as in FIG. 2, but in such a way that they are also approximately at a distance d from the adjacent capacitor plates 31. The auxiliary capacitor plates 32 can also be round or oval.

Wenn man bei der in Fig. 4 dargestellten Ausführungsform zwei Hochfrequenzgeneratoren 23 verwendet, die unkorreliert sind, genügt es, wenn nur der Abstand zwischen den auf unterschiedlichem Potential befindlichen Kondensatorplatten 30 und 31 mindestens etwa gleich d ist, wie in Fig. 5 dargestellt. Die Kondensatorplatten 30 sind hierbei jeweils mit dem potentialfreien Ausgangs des Hochfrequenzgenerators 23 verbunden, der auch mit der benachbarten potentialfreien Kondensatorplatte 31 verbunden ist.If two high-frequency generators 23 which are uncorrelated are used in the embodiment shown in FIG. 4, it is sufficient if only the distance between the capacitor plates 30 and 31, which are at different potential, is at least approximately equal to d, as shown in FIG. 5. The capacitor plates 30 are each connected to the floating output of the high-frequency generator 23, which is also connected to the adjacent floating capacitor plate 31.

Werden zwei Hochfrequenzgeneratoren 23 verwendet, deren Ausgänge symmetrisch zum Nullpotential sind, sind die dem an ein Paar von Kondensatorplatten 31 benachbarten Kondensatorplatten 30 auf das Nullpotential des jeweiligen Hochfrequenzgenerators 23 zu legen, damit Berührungsspannungsfreiheit gewährleistet ist.If two high-frequency generators 23 are used, the outputs of which are symmetrical to the zero potential, the capacitor plates 30 adjacent to a pair of capacitor plates 31 are to be connected to the zero potential of the respective high-frequency generator 23 No contact voltage is guaranteed.

Zwischen benachbarten auf Nullpotential liegenden Kondensatorplatten 30, 31 kann der Abstand kleiner als d gewählt werden, wie in Fig. 5 dargestellt ist.The distance between adjacent capacitor plates 30, 31 lying at zero potential can be chosen to be smaller than d, as shown in FIG. 5.

Man kann auch die Hilfkondensatorplatten 32 der Ausführungsform von Fig. 4 an einen weiteren nichtkorrelierten Hochfrequenzgenerator 23 anschließen, wobei dann der Abstand zwischen den Kondensatorplatten 31 und 32 entsprechend gering gewählt werden kann.The auxiliary capacitor plates 32 of the embodiment of FIG. 4 can also be connected to a further uncorrelated high-frequency generator 23, in which case the distance between the capacitor plates 31 and 32 can be chosen to be correspondingly small.

Bei der in Fig. 6 dargestellten Ausführungsform ist die Kondensatorplattenanordnung wie in Fig. 5, aber die einander gegenüberliegenden Paare von Kondensatorplatten 31 werden jeweils symmetrisch zum Nullpotential spannungsbeaufschlagt, indem eine Kondensatorplatte 31 mit einem Ausgangsanschluß des jeweiligen Hochfrequenzgenerators 23 verbunden und die gegenüberliegende Kondensatorplatte 31 mit letzterer über eine phasenverschiebende lambda/2-Umwegleitung 34 oder ein Phasenschiebernetzwerk verbunden ist, das eine Phasenverschiebung um eine halbe Periode bewirkt.In the embodiment shown in FIG. 6, the capacitor plate arrangement is as in FIG. 5, but the opposite pairs of capacitor plates 31 are each subjected to voltage symmetrically to the zero potential by connecting a capacitor plate 31 to an output terminal of the respective high-frequency generator 23 and the opposite capacitor plate 31 to the latter is connected via a phase shifting lambda / 2 bypass line 34 or a phase shifter network which causes a phase shift by half a period.

Stattdessen kann aber auch ein Hochfrequenzgenerator 23 mit symmetrischem Ausgang verwendet werden. Die einander gegenüberliegenden Paare von Kondensatorplatten 31 werden dabei symmetrisch zum Nullpotential spannungsbeaufschlagt, indem eine Kondensatorplatte 31 mit einem Ausgangsanschluß des Hochfrequenzgenerators 23 und die bezüglich des Strangs gegenüberliegende Kondensatorplatte 31 mit dem anderen Ausgangsanschluß des Hochfrequenzgenerators 23 verbunden wird, was eine gegenphasige Ansteuerung der gegenüberliegenden Elektroden bewirkt. Die Kondensatorplatten 30 sind dann mit dem Nullpotential des Hochfrequenzgenerators 23 verbunden.Instead, a high-frequency generator 23 with a symmetrical output can also be used. The opposing pairs of capacitor plates 31 are subjected to voltage symmetrically to the zero potential by connecting a capacitor plate 31 to one output connection of the high-frequency generator 23 and the capacitor plate 31 opposite with respect to the string to the other output connection of the high-frequency generator 23, which causes the opposite electrodes to be driven in phase . The capacitor plates 30 are then connected to the zero potential of the high-frequency generator 23.

Gemäß Fig. 7 kann vorgesehen sein, daß die an den nicht geerdeten Anschluß des Hochfrequenzgenerators angeschlossene Kondensatorplatte 31 an beiden Enden quer zur Längsrichtung des Strangs eine kleines Stück über die Bänder 10, 11 übergreift, entweder durch eine Abwinkelung 35 oder durch eine eigene schmale Hilfskondensatorplatte 36 realisiert, wodurch das Feld im Ober- und Unterbereich des Strangs zur lokalen Oberflächenerwärmung leicht komprimiert wird. Wenn sich daran ein weiteres Kondensatorplattenpaar 31 umgekehrter Polung anschließt, befindet sich dort das inhomogenere Feld auf der anderen Seite des Strangs, so daß sich insgesamt eine gute homogene Oberflächenerwärmung ergibt. Hierbei kann man mit einem oder mit zwei unkorrelierten Hochfrequenzgeneratoren 23 oder mit symmetrischen oder unsymmetrischen Potential (bezüglich des Nullpotentials) arbeiten.7, it can be provided that the capacitor plate 31 connected to the ungrounded connection of the high-frequency generator overlaps a small piece across the bands 10, 11 at both ends transversely to the longitudinal direction of the strand, either through a bend 35 or through its own narrow auxiliary capacitor plate 36 realized, whereby the field in the upper and lower region of the strand is slightly compressed for local surface heating. If this is followed by a further pair of capacitor plates 31 of reversed polarity, the more inhomogeneous field is located on the other side of the strand, so that overall a good homogeneous surface heating results. Here, one can work with one or two uncorrelated high-frequency generators 23 or with symmetrical or asymmetrical potential (with respect to the zero potential).

Gemäß Fig. 8 können die Kondensatorplatten 31 (und eventuell auch 30) aus mehreren, benachbart zueinander angeordneten Teilplatten 31a, 31b bestehen, um den Skin-Effekt im Strangmaterial so gering wie möglich zu halten. Die Teilplatten 31a, 31b liegen auf gleichen Potential und ihre benachbarten Kanten sind durch einen Schlitz 37 getrennt, der infolge gleichen Potentials so eng wie möglich sein kann.According to FIG. 8, the capacitor plates 31 (and possibly also 30) can consist of a plurality of sub-plates 31a, 31b arranged adjacent to one another in order to keep the skin effect in the strand material as low as possible. The partial plates 31a, 31b are at the same potential and their adjacent edges are separated by a slot 37, which can be as narrow as possible due to the same potential.

Wie in Fig. 9 dargestellt, ist es zweckmäßig, in Bezug auf den Strang etwas konkav ausgebildete Kondensatorplatten 30, 31 zu verwenden, wodurch ebenfalls ein Beitrag zur Homogenisierung des Feldes erhalten wird. Außerdem kann die Konkavität der Kondensatorplatte 30, 31 mit einem Material 38 mit möglichst hoher Dielektrizitätskonstante ausgefüllt sein, so daß ihre dem entsprechenden Band 10, 11, 12 oder 13 zugewandte Fläche plan ist und an diesem anliegt. Während Kunststoffe eine Dielektrizitätskonstante in der Größenordnung von etwa 2 bis 4 aufweisen (bei einem Verlustfaktor tg δ, der extrem niedrig ist, so daß sich der Kunststoff praktisch auch nicht erwärmt), sind hier Materialien wie Calciumtitanat vorgesehen, deren Dielektrizitätskonstante sehr viel größer als 1 ist. Außerdem zeigen diese Materialien hohe Formstabilität und einen geringen Temperaturausdehnungskoeffizienten. Fig. 10 zeigt den normierten Potentialverlauf zwischen zwei gegenüberliegenden Kondensatorplatten für eine Kunststoffschicht zwischen Strang und Kondensatorplatte (gestrichelt) und für ein Material 38 mit hoher Dielektrizitätskonstante zwischen Strang und Kondensatorplatte (durchgezogen). Ersichtlich ergibt sich im letzteren Falle ein sehr viel kleinerer Spannungsabfall über den Kondensatorplatten, was die Betriebssicherheit deutlich erhöht. Das Stranggut hat zumindestens bei den vorstehend angesprochenen Anwendungsfällen eine Dielektrizitätskonstante von ca. 40 bis 80 und einen nennenswerten Verlustfaktor tg δ, d.h. das Stranggut ist mittels eines Hochfrequenzfeldes besonders gut erwärmbar.As shown in FIG. 9, it is advantageous to use somewhat concave capacitor plates 30, 31 with respect to the strand, which also contributes to the homogenization of the field. In addition, the concavity of the capacitor plate 30, 31 can be filled with a material 38 with the highest possible dielectric constant, so that its surface facing the corresponding band 10, 11, 12 or 13 is flat and abuts against it. While plastics have a dielectric constant of the order of about 2 to 4 (with a loss factor tg δ, which is extremely low, so that the plastic practically does not heat up), materials such as calcium titanate are provided here, whose dielectric constant is very much greater than 1 is. Also show these materials have high dimensional stability and a low coefficient of thermal expansion. 10 shows the normalized potential curve between two opposite capacitor plates for a plastic layer between the strand and the capacitor plate (dashed) and for a material 38 with a high dielectric constant between the strand and the capacitor plate (solid). Obviously, there is a much smaller voltage drop across the capacitor plates in the latter case, which significantly increases operational reliability. At least in the above-mentioned applications, the extrudate has a dielectric constant of approximately 40 to 80 and a noteworthy loss factor tg δ, ie the extrudate can be heated particularly well by means of a high-frequency field.

Außerdem ist es zweckmäßig, die Kondensatorplatten an der den Bändern zugewandten Seiten mit einer Kunststoffschicht zu versehen bzw. die Kondensatorplatten in Kunststoff einzubetten, um den Verschleiß der sich an den Kondensatorplatten entlang bewegenden Bänder gering zu halten. Diese Kunststoffbeschichtung sollte jedoch so dünn wie möglich sein, um das Spannungsprofil nicht zu stark zu beeinflussen. Zum selben Zweck kann das Material 41 an der dem Band zugekehrten Seite geschliffen und poliert sein.In addition, it is expedient to provide the capacitor plates on the sides facing the strips with a plastic layer or to embed the capacitor plates in plastic in order to keep the wear of the strips moving along the capacitor plates low. However, this plastic coating should be as thin as possible so as not to influence the stress profile too much. For the same purpose, the material 41 can be ground and polished on the side facing the belt.

Claims (10)

  1. An apparatus for heating a continuous electrically conductive body of material, hereinafter called a strand, guided in a channel (14), a capacitor plate arrangement (21) which is connected to a high frequency generator (23) being electrically insulated from the strand, the capacitor plate arrangement (21) having two pairs of opposite first capacitor plates (31), such pairs being adjacent one another lengthwise of the strand, two further pairs of second capacitor plates (30) being disposed lengthwise of the strand in association with the two outer sides of the first capacitor plates (31), the second capacitor plates (30) being connected to a zero-potential terminal of the high frequency generator (23), characterised in that a further high frequency generator (23) uncorrelated with the first high frequency generator (23) is provided and a pair of opposite first capacitor plates (31) are connected to the respective outputs of one of the two high frequency generators (23).
  2. An apparatus according to claim 1, characterised in that two of the diagonally opposite first capacitor plates (31) are connected to the zero potential terminals of the high frequency generators (23).
  3. An apparatus according to claim 1 or 2, characterised in that between capacitor plates (30, 31) which are adjacent one another lengthwise of the strand there is a gap which is at least substantially equal to the gap (d) between the capacitor plates (30, 31 respectively) which are opposite one another in relation to the strand.
  4. An apparatus according to any of claims 1 to 3, characterised in that the first capacitor plates (31) which are disposed on opposite sides relatively to the strand are energised symmetrically of the zero potential.
  5. An apparatus according to claim 4, characterised in that a first capacitor plate (31) is connected to the first capacitor plate (31) opposite it relatively to the strand by way of a half-wave bypass (34) or of a phase shift network.
  6. An apparatus according to claim 4, characterised in that the high frequency generator (23) has symmetrical output terminals in respect of zero potential.
  7. An apparatus according to any of claims 1 to 6, characterised in that the first and possibly second capacitor plates (31, 30) each consist of at least two subplates (31a, 31b) separated by a gap (37).
  8. An apparatus according to any of claims 1 to 7, characterised in that the first and possibly second capacitor plates (31, 30) are concave towards the strand, the concavity being filled with an electrical insulant (41).
  9. An apparatus according to claim 8, characterised in that the electrical insulant (41) has a dielectric constant which is very much greater than unity, preferably greater than 100.
  10. An apparatus according to any of claims 1 to 9, characterised in that in the case of a strand having longitudinal edges the first capacitor plates (31) engage the strand over a short distance in comparison with strand width on the two adjacent edges on opposite sides of the strand, where the first capacitor plates (31) do not engage, by means of a bent part (35) or a separate auxiliary capacitor plate (36).
EP92101680A 1985-12-10 1986-12-09 Device for heating a length of electrically conductive material Expired - Lifetime EP0486472B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE3543569 1985-12-10
DE19853543569 DE3543569A1 (en) 1985-12-10 1985-12-10 DEVICE FOR HEATING A STRAND OF ELECTRICALLY CONDUCTIVE MATERIAL
EP86117107A EP0228615B1 (en) 1985-12-10 1986-12-09 Arrangement for heating a billet of electrically conductive material

Related Parent Applications (2)

Application Number Title Priority Date Filing Date
EP86117107A Division EP0228615B1 (en) 1985-12-10 1986-12-09 Arrangement for heating a billet of electrically conductive material
EP86117107.2 Division 1986-12-09

Publications (3)

Publication Number Publication Date
EP0486472A2 EP0486472A2 (en) 1992-05-20
EP0486472A3 EP0486472A3 (en) 1992-05-27
EP0486472B1 true EP0486472B1 (en) 1994-09-21

Family

ID=6288080

Family Applications (4)

Application Number Title Priority Date Filing Date
EP92101679A Expired - Lifetime EP0487504B1 (en) 1985-12-10 1986-12-09 Arrangement for heating an elongated piece of electrically conductive material
EP86117107A Expired - Lifetime EP0228615B1 (en) 1985-12-10 1986-12-09 Arrangement for heating a billet of electrically conductive material
EP92101680A Expired - Lifetime EP0486472B1 (en) 1985-12-10 1986-12-09 Device for heating a length of electrically conductive material
EP92101681A Expired - Lifetime EP0485363B1 (en) 1985-12-10 1986-12-09 Device for heating a long product of electrical conductive material

Family Applications Before (2)

Application Number Title Priority Date Filing Date
EP92101679A Expired - Lifetime EP0487504B1 (en) 1985-12-10 1986-12-09 Arrangement for heating an elongated piece of electrically conductive material
EP86117107A Expired - Lifetime EP0228615B1 (en) 1985-12-10 1986-12-09 Arrangement for heating a billet of electrically conductive material

Family Applications After (1)

Application Number Title Priority Date Filing Date
EP92101681A Expired - Lifetime EP0485363B1 (en) 1985-12-10 1986-12-09 Device for heating a long product of electrical conductive material

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EP (4) EP0487504B1 (en)
AT (4) ATE113434T1 (en)
DE (5) DE3543569A1 (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3817831A1 (en) * 1988-05-26 1989-11-30 Sicowa Verfahrenstech Process for producing blocks
EP0413975B1 (en) * 1989-08-21 1995-04-26 General Electric Company High dielectric constant material to shape electric fields for heating plastics
DE102021121013A1 (en) 2021-08-12 2023-02-16 KB Engineering GmbH Process for the production of single or multi-layer shaped elements, in particular wall or stone elements, and associated plant

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2288269A (en) * 1941-06-04 1942-06-30 Compo Shoe Machinery Corp Electrostatic heating apparatus
DE858868C (en) * 1951-02-18 1952-12-11 Siemens Ag Method for treating a e.g. B. piece-shaped goods by the action of an alternating field
US2712586A (en) * 1952-05-23 1955-07-05 Bostadsforskning Ab High frequency heating system
DE933046C (en) * 1953-04-19 1955-09-15 Siemens Ag Device for treating particularly grainy bulk material by means of a high-frequency field
AT184997B (en) * 1954-08-09 1956-03-10 Bostadsforskning Ab Device for high-frequency heating of workpieces that are transported in carriages, slides or the like through a heating system
EP0085318B1 (en) * 1982-01-30 1987-09-09 SICOWA Verfahrenstechnik für Baustoffe GmbH & Co. KG Device for heating an extrusion moulding track of electrically conductive material, and the use thereof

Also Published As

Publication number Publication date
EP0487504B1 (en) 1994-10-26
EP0485363A3 (en) 1992-05-27
EP0485363B1 (en) 1994-11-17
ATE113434T1 (en) 1994-11-15
EP0228615B1 (en) 1992-10-07
DE3650076D1 (en) 1994-10-27
EP0487504A1 (en) 1992-05-27
EP0228615A2 (en) 1987-07-15
DE3543569A1 (en) 1987-06-11
ATE114212T1 (en) 1994-12-15
EP0486472A3 (en) 1992-05-27
DE3650115D1 (en) 1994-12-01
EP0485363A2 (en) 1992-05-13
DE3686938D1 (en) 1992-11-12
ATE112129T1 (en) 1994-10-15
EP0228615A3 (en) 1988-06-08
ATE81434T1 (en) 1992-10-15
EP0486472A2 (en) 1992-05-20
DE3650141D1 (en) 1994-12-22

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