DE1062848B - Electric heating furnace for inductive heating of materials - Google Patents

Description

The invention relates to an electric heating furnace for the inductive heating of materials with a transformer primary part, the excitation of which is used to generate a magnetic field.

For the heat treatment of workpieces ovens are already known in which z. B. in a hollow heating chamber used a certain amount of a material to be heated and a certain time removed after heating for the purpose of introducing further material to be treated will. An elongated, hollow heating chamber through which the Material continuously fed through by means of automatic conveying means or by hand became.

However, both types of ovens have various disadvantages. Either material loads could only be carried out intermittently be treated, or it was inevitably long heating chambers with continuous operation required, so that the systems are very expensive due to the construction costs associated with their establishment and also took up a lot of space. These designs were also often complicated Control devices required to maintain a certain gas atmosphere. Through often Existing leaks resulted in considerable losses of expensive gas.

Electric heating ovens are also known in which the heating device for the purpose of heating a moving one Material is inductively coupled to a transformer or where through to a Outer jacket articulated drive means a movement, but not an alternating movement for advancing of the material is made possible.

According to the invention, in the electric heating furnace for inductive heating of materials the heating device has an outer jacket and a heating chamber mounted on bearings so that they are around their vertical axis brought relatively easily to a cylindrical pendulum motion on these bearings can be. This can be achieved e.g. B. by suitable actuating means which are hinged to the outer casing are; this mechanism can be in a hydraulic or air-driven cylinder or in a suitable electrical or mechanical device with which the heating device can be continuously rotated forwards and backwards in a controllable manner. In this way, the in the heating chamber materials introduced through the loading channel through them in the direction of the removal channel due to the continuous forward and backward movements of the heating device allocated jacks are advanced; the amount of their advance and thus the duration of the

Electric heater
for inductive heating of materials

Applicant:
Lindberg Engineering Company,
Chicago, III. (V.St.A.)

Representative: Dr.-Ing. H. Ruschke, Berlin-Friedenau,
and Dipl.-Ing. K. Grentzenberg,
Munich 27, Pienzenauerstr. 2, patent attorneys

Claimed priority:
V. St. v. America 3 October 1956

August W. Lillienberg, Chicago, III.,
and George V. Harris, Racine, Wis. (V. St. A.),
have been named as inventors

The heat treatment of the material is determined by the type and size of the oscillating movements.

The material is heated by a transformer core with a primary winding; here parts of the outer jacket are appropriately assigned in operative connection. In one embodiment of the invention, the transformer core encloses completely part of the outer jacket and the primary winding is applied to one leg of the core, so that it is inductively coupled to the heating chamber located in the outer jacket as soon as electrical Energy is supplied. The heating chamber thus serves as the secondary winding of the transformer, so that, when voltage is applied, it, as well as the material as it passes through the heating chambers is heated in the specified manner as a result of the oscillating movements.

From a business point of view, it is desirable that only the heating chamber be heated in the outer jacket. Therefore this is interrupted at one point and the ends are through an electrically insulating material connected together so that on the circumference of the outer jacket there is no closed electrical current path.

When the furnace is in operation, the material is continuously fed through the feed channel into the heating chamber introduced and on the circular path of the chamber after the outlet channel due to the Torsional vibrations of the heating device conveyed on. The diameter of the ring-shaped

* 909 580/3 «

The heating chamber is chosen so that the material to be heated prior to heating for a desired period of time is exposed to the exit from the extraction channel, with this dimensioning at the same time the available Floor space is taken into account. With this new design of the furnace you can easily create a heating surface create the size of a relatively elongated furnace of the previously known elongated construction equals; this can be achieved with a ring heating chamber of relatively reach small diameter. According to the invention, therefore, the construction costs as well as those for the space required by the new design of the heating chamber.

In another embodiment of the invention, one can still enlarge the Heating chamber surface without changing the dimensions of the heating furnace by forming the heating surface in the Reach the outer jacket in the form of a spiral with one or more turns. Here is again an inlet channel is provided on the uppermost part of the windings and an outlet channel is provided on the lower part thereof, so that the materials during the rocking or rotating pendulum movements from the upper to the lower part to wander on the spiral. Because the heating chamber forms a completely closed circuit is supposed to act as the secondary winding of the transformer, its loading and unloading ends electrically connected by a bracket or the like.

Since the heating chamber is practically completely closed in each of the specified designs, can one can easily maintain a gas atmosphere in it. Accordingly, in conjunction with her and passing through the outer jacket an inlet channel, e.g. B. a tube for the supply of a gas atmosphere to be ordered. This significantly increases the efficiency of the furnace operation.

Furthermore, the heating chamber can be designed for the purpose of local regulation of the heat generation, that the resistance is different along its extension. So you can see the cross-section of the Heating chamber at the points where more intense heating is required, such as B. at the inlet and outlet ends, keep it smaller and reduce the constriction along its remaining part to lower the heating temperature. In addition, you can see the heat development on the circumference of 360 ° of the heating chamber Means regulate the corresponding switching on and off of the primary winding of the transformer as required enable.

1 shows an electric furnace designed according to the invention in a perspective view,

Fig. 2 is a plan view of this furnace,

Fig. 3 is a partial section along the section line 3-3 of Fig. 2,

Fig. 4 is a vertical section along the section line 4-4 of the same figure,

5 shows a section similar to FIG. 4 for a modified embodiment according to the invention and

FIG. 6 is a perspective view of the furnace heating chamber used in FIG.

The furnace according to FIGS. 1 to 4 has an essentially circular body 10 through which the material to be subjected to the heat treatment runs. It is movably supported on a frame part provided with feet 11; they have support bearings, for example rollers 12, and support the body 10 . The support frame can, for. B. od on the floor. Like. Be set up, wherein the feet are isolated from each other by an insulating support plate 13 and at the same time

be kept at an appropriate distance from each other.

The annular body 10 (FIGS. 3 and 4) consists of an outer metal jacket 14 made of a suitable metallic material, e.g. B. steel of a weak profile, aluminum or the like. To prevent the formation of induction currents in the casing 14 (Fig. 2 and 3), this is interrupted by an interposed insulating strip 15 to prevent the flow of current in the circumference of the jacket.

In the casing 14 and isolated from it there is an annular heating chamber 16, which is made of a heat-resistant but electrically conductive material, such as. B. steel. This heating chamber 16 can be made of a difficult-to-melt material 17, such as. B. od a brick structure. The like., To be superimposed, while the space from it gets laterally and above a filling of heat insulating material 18 of any kind. This can be difficult to melt and is either poured in, poured in molten or loosely inserted.

The material to be treated with heat is introduced into the heating chamber (FIG. 3) through an inlet conduit 19 which extends through the outer jacket 14 and the insulating material 18 into the annular heating chamber 16 . As can be seen, the line 19 passes through an enlarged opening in the outer jacket 14 so that it is electrically isolated from the walls of the jacket at a distance from the latter. The materials or workpieces are discharged from the heating chamber 16 through a similar conduit 21 which extends downward from the heating chamber 16 through the heat insulating material and the outer jacket. During operation, the material introduced into the inlet line 19 migrates all around the heating chamber and, after the heat treatment has taken place, passes through the line 21 into a corresponding extinguishing tank or the like.

In order to subject the material to be treated to the intended effect of heat, a primary part of a transformer is provided which serves to inductively generate a flow of heating current in the heating chamber 16 and in the material located therein. This is achieved by a rectangular transformer core 22 which surrounds the ring body 10 and carries a primary winding 23 which is preferably accommodated in its free inner ring space. The core 22 is supported by plates 24 which are attached to the insulating washer 13 . If the winding 23 is excited by alternating current, advantageously such a high frequency, then a secondary heating current is induced in the annular heating chamber 16 , so that the chamber and the material in it is heated by conduction. Since this passes through the magnetic field generated by the winding 23 , a secondary current is also induced directly in it; this increases the heating effect. During the heating of the material passing through the heating chamber to the desired temperature, the desired degree of heating can be regulated by correspondingly varying the frequency and voltage of the primary current and the dwell time of the material in the heating chamber.

In many cases it may be desirable to have the heat applied to the material along the passage to change in the heating chamber. For this it is recommended to measure the cross-sectional area of the heating chamber walls to vary in order to increase the current intensity at the points of the cross-sectional

Claims (1)

to bring about the area of the walls where this is reduced; this allows the heat distribution to be regulated effectively. For example, a particularly high temperature may be desirable in the vicinity of the inlet opening in order to bring the material to the treatment temperature as quickly as possible. According to the invention, the material is conveyed forward through an alternating or oscillating movement of the heating chamber. The reciprocating or oscillating movements can be generated by any suitable means, for example (FIG. 2) by means of a liquid motor. In the embodiment according to FIG. 2, a cylinder 25 is articulated to one end of the support plates 24 or, if it appears expedient, articulated directly to the bobbin 22. The cylinder 25 contains a piston, the rod 26 of which is articulated to a block 27 of the body 10. A propellant is alternately supplied to the cylinder at its opposite ends by means of an automatically operating valve control (not shown). As a result, the body 10 executes a rotary pendulum movement with support on the rollers 12. This is done so that the body 10 is in the direction of the intended passage of material, i. H. in the direction from the inlet to the outlet side, moved relatively slowly, so that the material is carried along by the circulating movement of the heating chamber, while the return movement in the opposite direction is so fast that the material does not participate in this second movement. The amount of its advance through the heating chamber can be regulated by the size of the swinging of the body 10; so it is up to you to influence the dwell time of the material in the heating chamber in the desired way. The furnace according to the invention is particularly suitable for treating materials in a gas envelope. To make it suitable for these purposes, a conduit 28 can be provided which extends through the jacket into the heating chamber and which is connected to a gas generator by a movable hose. Since the heating chamber, apart from the inlet and outlet lines, is closed, only a relatively low consumption of the gas atmosphere will take place, so that the chamber can be kept perfectly filled at all times. The temperature in the heating chamber can be determined by a thermocouple 29 or the like, which extends through the jacket and is in contact with the chamber and either carries a suitable indicating instrument at its upper end or through movable lines with a remotely mounted indicating instrument connected is. If the furnace shown in FIGS. 1 to 4 is to be put into operation, then the primary winding 23 must be connected to voltage and the annular body 10 must be set in rotary pendulum movements to the desired extent. The material to be heated is introduced through the inlet line 19 into the heating chamber 16 and (for example according to FIG. 2) is moved forward in the reverse clockwise direction towards the outlet line on its rotation in the heating chamber. When passing through the heating chamber, the workpieces are heated by conduction from the walls of the heating chamber; Incidentally, they themselves also heat up due to the secondary current. In this way, the materials can be brought to any desired temperature and maintained at that temperature level for any desired prescribed heat treatment time. Because of the circular design of the heating chamber, the material can be given a relatively long flow path without requiring a correspondingly large amount of space. Furthermore, this ring construction results in a secondary current loop which is particularly favorable for the creation of the secondary heating current. If an even longer residence time of the material in the heating chamber or an even greater compactness of the furnace structure is required, then the construction according to FIGS. 5 and 6 can be taken into account. Here again the furnace has a circular body 30, which is similar to the ring body 10, but is deeper. The metal casing 31 of the body is interrupted at at least one point on its circumference so that current cannot flow through it. The spiral-shaped heating chamber 32 arranged in the casing 31 is kept at a distance by a heat-insulating material 33, the spiral chamber being supported on this material. The heating chamber 32 can have any desired number of turns, either in the form of a helix, as shown, or optionally in the form of a flat spiral. In the embodiment of Fig. 6 the heating chamber has two complete turns, one end pointing upwards and forming an inlet conduit 34 which passes through the jacket S1 and the opposite end pointing downwards so that an outlet conduit 35 is formed which also is to be passed through the casing 31. In order for the spiral chamber to form a completely closed secondary loop, a direct connection is made between the inlet and outlet parts of the body by means of an electrically conductive bracket so that the current can flow through the entire body. In this case, the secondary current is induced in the spiral body and the material contained therein with the aid of a transformer primary part, which has a magnetic core 37 encompassing the body 30, which (FIG. 5) is conveniently located inside the body and carries the primary winding 38. This type of furnace operates in exactly the same way as the embodiment shown in FIGS. In operation, the body is set in oscillatory or rotary movements in the same way as the body 10 in the embodiment shown in FIGS. 1 to 4; this causes the material to travel the spiral path from the inlet to the outlet end. During this process, the material or the workpieces are heated by conduction from the body in accordance with the secondary current generated in it; In addition, there is heating by the induction current generated in the workpieces themselves. In the embodiment according to FIG. 5, an extraordinarily large heating chamber length can be accommodated in a very compact space, so that a long residence time of the material in the furnace as well as a high degree of heating is made possible. Patent claims: 1.Electric heating furnace for inductive heating of materials, with a transformer primary part, whose excitation is used to generate a magnetic field, characterized by a ring-shaped transformer secondary winding of tubular, delimiting a heating chamber (16)