EP0238587A1

EP0238587A1 - Low or medium frequency induction furnace

Info

Publication number: EP0238587A1
Application number: EP19860905844
Authority: EP
Inventors: Christian Allemann; Rémi MINERY
Original assignee: Aces; Aces Electronics Co Ltd
Current assignee: Aces; Aces Electronics Co Ltd
Priority date: 1985-09-26
Filing date: 1986-09-25
Publication date: 1987-09-30
Also published as: WO1987002211A1; FR2587794B1; FR2587794A1

Abstract

Four à induction à basse ou moyenne fréquence, dans lequel l'inducteur est fixé d'une manière qui empêche des vibrations et des détériorations par chocs. L'inducteur (1) est fixé dans un bâti de support (2) entre deux bandes de calage (26, 27) en feutre, solidaires respectivement d'un élément supérieur (11) et d'un élément inférieur (22) du bâti. Ledit élément inférieur est un longeron (22) reposant sur des traverses (20) qui sont équipées de moyens de serrage (21). En complément, l'inducteur (1) peut être appuyé par des cales latérales (31). Le four selon l'invention est utilisable pour chauffer par induction des pièces métalliques.Low or medium frequency induction furnace, in which the inductor is fixed in a way which prevents vibrations and damage by shocks. The inductor (1) is fixed in a support frame (2) between two wedging strips (26, 27) of felt, secured respectively to an upper element (11) and a lower element (22) of the frame . Said lower element is a beam (22) resting on crosspieces (20) which are equipped with clamping means (21). In addition, the inductor (1) can be supported by lateral shims (31). The oven according to the invention can be used for induction heating of metal parts.

Description

LOW OR MEDIUM FREQUENCY INDUCTION OVEN

The present invention relates to a low or medium frequency induction furnace, comprising at least one coil-shaped inductor, arranged horizontally around a passage for the parts to be treated, and a substantially parallelepiped support frame surrounding this inductor.

The inductors of low or medium frequency induction furnaces are generally cylindrical or square coils, formed by turns of a conductor of large section, for example an insulated copper tube in which circulates a cooling fluid, these turns surrounding a refractory element inside which are introduced metal parts to be heated by induction. According to a known arrangement, these coils are held in position in the furnace by the support of four longitudinal members fixed to the frame of the furnace and applied against the top, the bottom and the two sides of the coil. However, as these coils are essentially manufactured by hand, their peripheral surface is always somewhat irregular and certain turns are therefore poorly supported by the side members. This results in vibrations of the coil, which produce repeated shocks and which lead, in combination with the very strong thermal gradients inherent in this type of device, to a deterioration of the inductor and a reduction in its service life.

On the other hand, the fixing of each of the four longitudinal members on the frame must include adjustment screws making it possible to correctly position the inductor and to exert a clamping force. These devices are relatively complicated and do not allow easy adjustment.

Consequently, the object of the present invention is to provide an induction furnace of the type indicated in the preamble, arranged so as to remedy the abovementioned drawbacks.

This object is achieved by the induction furnace according to the present invention, characterized in that it comprises at least one strip of upper wedging and at least one lower wedging strip, these wedging strips being parallel to the inductor and being respectively secured to an upper member and a lower member of the frame, in that said wedging strips are made of felt, and in that the oven comprises clamping means arranged to vary the spacing between said upper element and said lower element of the frame, so as to fix the inductor by clamping between the two wedging strips.

According to a particularly advantageous embodiment, said lower element of the frame is a rigid spar which extends over at least part of the length of the inductor. This spar rests on cross members which are adjustable in height relative to the rest of the frame. The clamping means may include screws connected to the ends of said crosspieces.

Preferably, one of the wedging strips is fixed against a closure plate constituting the upper face of the frame. According to a particular embodiment, said clamping means can include means for adjusting the spacing between said closure plate and the rest of the frame.

Preferably, the frame has side walls which are fixed to said lower and upper elements of the frame, and side wedges' are arranged between the inductor and these side walls, on either side of the inductor, so as to maintain it laterally with respect to the frame. These lateral shims can include adjustment screws making it possible to adjust the length of each shim.

The felt constituting the wedging strips can advantageously be made of an electrically insulating material, in particular of fibers of thermosetting synthetic material.

The present invention and its advantages will be better understood with the aid of the description of a preferred embodiment, given below with reference to the appended drawings, in which: FIG. 1 is a schematic view in cross section of an induction furnace according to the present invention,

FIG. 2 shows the lower structure of the oven frame of FIG. 1, seen from below,

FIG. 3 is a schematic perspective view of a lateral element of the oven frame, and

Figure * "is a schematic cross-sectional view of a variant of an oven according to the invention.

With reference to the figures, the furnace shown comprises an inductor 1 which is arranged longitudinally inside a support frame 2. The inductor 1 is constituted in known manner, by windings of a rectangular copper tube 3 to the interior of which circulates cooling water. These windings are coated with an insulator and form a coil which is provided with a refractory lining 4 surrounding a passage 5 into which the parts which are to be heated are introduced by means of the induction furnace. The respective sections of this passage and of the coil are matched to the dimensions of said parts.

The other constructive details of the inductor 1, in particular its connections for the supply of electricity and water, are of the conventional type and therefore need not be described here. The same applies to the organs ensuring the circulation and the maintenance of the parts inside the passage 5.

The frame 2 which surrounds and supports the inductor has the shape of a parallelepipedic box. In the example shown, it is closed on both sides and on top, but open at the bottom. However, it is obvious that this frame could also be provided with a closure on its underside, with the openings necessary for the connections. These connections could also be arranged laterally. The frame illustrated in figs. 1 to 3 comprises two rigid side walls 10 which support an upper closure plate 11 and two end flanges (not shown). The side walls 10 rest directly or by an intermediate frame allowing adjustment of the position of the oven, on a bench which supports the weight of the oven and which in particular contains the control members. In the example described here, the walls 10 are made of aluminum, but they can also be made of another non-magnetic material.

Fig. 3 shows in more detail one of the side walls 10, which comprises along its edges perpendicular cheeks 12 to 15 provided with oblong holes 16 which allow the wall to be fixed

10 in a laterally adjustable position relative to the rest of the frame. The wall 10 can obviously also include vertical stiffeners, in order to be more rigid. The top closing plate

11 (fig. 1), consisting for example of an asbestos-cement insulating plate, is bolted to the upper cheeks 13 of the side walls 10. Similarly, the two end flanges are bolted to the respective cheeks 11 and 15 of the side walls.

The lower elements of the frame 2 are visible in Figures 1 and 2. A series of crosspieces 20 is fixed to the lower flaps 12 of the side walls 10, by means of adjustment screws 21 which are supported on the cheeks 12 and which are engaged in threaded elements integral respectively with the ends of the crosspieces 20, to allow the positioning in height of these crosspieces relative to the rest of the frame, so as to adjust the spacing between the crosspieces 20 and the upper plate 11. The crosspieces 20 can be metal or insulating profiles, solid or hollow. A rigid spar 22, arranged parallel to the inductor 1, rests freely on the crosspieces 20. In the present case, this spar is a hollow rectangular metal profile which is coated with an insulating layer and which is preferably positioned by relative to the sleepers by means of ta¬ 23 fixed to the sleepers. In fact, in the example described here, the oven comprises two successive beams 22 and 24 (fig. 2) which are arranged respectively in the intervals separating three water connection points 25 of the inductor 1. It will be noted that the side members 22 and 2H can be full or hollow, and on the other hand insulating or not. They could also be integral with the sleepers. As seen in fig. 1, the inductor 1 is positioned inside the frame 2 between an upper wedging strip 26, fixed against the underside of the closure plate 11, and a lower wedging strip 27 which is fixed on the spar 22. Of course, an identical strip is provided on the spar 24. These wedging strips are made of a felt which is preferably, but not necessarily, made of fibers of a thermosetting and insulating synthetic material. However, it is also possible to use other fibers, animal, mineral or organic, insofar as they withstand the operating temperatures of the conductor 3. The felt wedging strips 26, 27 have an initial thickness of the order several millimeters, which allows them to adapt thanks to their compressibility to the irregularities of the outer surface of the coil 1, resulting in particular from small misalignments of the turns, as well as from the concavity appearing on the outer surface. rectangular copper tubes when rolled up. The inductor 1 is positioned, then fixed inside the frame 2 by tightening between the felt wedging strips 26 and 27. To do this, the cross members 20 are brought closer to the upper plate 11 by acting on the tightening screws. 21, which compresses the wedging strips 26 and. 27 and thus ensures positioning of each turn over the entire length of the inductor 1. In this way, the appearance of local vibrations is prevented, which can cause shocks and damage. It will be noted that the tightening force introduced by the screws 21 is transmitted to the upper plate 11 directly by the side walls 10, which tends to stiffen these walls.

It is obvious that the upper closure plate 11 could also be fixed to the side walls 10 by clamping means similar to the screws 21, in replacement or in addition to these clamping screws, or else be replaced by a system of crosspieces and spars. similar to the lower elements described above.

Fig. 1 also shows means of lateral setting of the inductor 1, which are not compulsory but which allow the inductor to be positioned more securely. In known manner, the inductor 1 has laterally studs 30 which are welded to the conductor to allow it to be grasped, during manufacture, when it must be immersed in a bath to form its insulating coating. The oven according to the invention can advantageously be fitted with insulating side shims, for example screw shims 31, which bear against the studs 30 and against the side walls 10 by means of pads 32 made of insulating material. This very simple device makes it possible to adjust the lateral position of the inductor 1 and to keep it in a safe manner in this position.

Fig. 4 shows an alternative embodiment of the oven described above, comprising side walls 10a which have substantially the same shape as the side walls 10, but are placed in an opposite position, their concavity being turned towards the outside. This arrangement allows a reduction in the interior volume of the box and a reduction in the length of the side shims, as well as easier access to the means for fixing and tightening the frame. In this variant, the lateral shims can advantageously also be formed by wedging strips 33 of felt.

The foregoing description shows that an oven according to the invention can be produced with a particularly simple frame, allowing inexpensive manufacture, as well as great assembly and disassembly facilities. By tightening the inductor 1 between the felt wedging strips 26 and 27, the drawbacks inherent in the prior art are essentially avoided.

The present invention is not limited to the embodiments described above by way of examples, but it extends to any modification or variant obvious to a person skilled in the art. In particular, the lower beam 22, 24 could be replaced by a pair of parallel beams wedged on the crosspieces 20 so as to hold the inductor both laterally and vertically, which makes the lateral wedges 31 or 33 superfluous or allows easy adaptation to a square or rectangular coil.

Claims

claims

1. Low or medium frequency induction furnace, comprising at least one inductor in the form of a coil, arranged horizontally around a passage for the parts to be treated, and a substantially parallelepiped support frame surrounding this inductor, characterized in that it comprises at least one upper wedging strip (26) and at least one lower wedging strip (27), these wedging strips being parallel to the inductor (1) and being respectively secured to an upper element (11) and of a lower element (22, 24) of the frame (2), in that said wedging strips (26, 27) are made of felt, and in that the oven comprises clamping means (21) arranged to vary the spacing between said upper element and said lower element of the frame, so as to fix the inductor by clamping between the two wedging strips.

2. Induction oven according to claim 1, characterized in that said lower element of the frame is a rigid spar (22, 24) which extends over at least part of the length of the inductor (1).

3. Induction oven according to claim 2, characterized in that said beam (22, 24) rests on crosspieces (20) which are adjustable in height relative to the rest of the frame.

4. Induction oven according to claim 3, characterized in that said clamping means comprise screws (21) connected to the ends of said crosspieces (20).

5. Induction furnace according to claim 1, characterized in that one (26) of said wedging strips is fixed against a closing plate (11) constituting a face of the frame.

6. Induction furnace according to claim 5, characterized in that said clamping means comprise means for adjusting the spacing between said closure plate (11) and the rest of the frame.

7. Induction furnace according to claim 1, characterized in that the frame has side walls (10, 10a) which are connected to said lower and upper elements of the frame, and in that side shims (31, 33) are arranged between the inductor and these side walls, on either side of the inductor, so as to maintain it laterally with respect to the frame.

8. Induction oven according to claim 7, characterized in that the lateral shims (31) comprise adjustment screws making it possible to adjust the length of each shim.

9. Induction oven according to any one of the preceding claims, characterized in that said felt is made of an electrically insulating material.